Late Paleocene- Early Eocene paleoenvironments in the Southwest Pacific (ODP Leg 189): Revised Stratigraphy of an Antarctic PETM Record.

NASA Astrophysics Data System (ADS)

Bijl, P. K.; Brinkhuis, H.; Sluijs, A.; Reichart, G.; Schouten, S.; Röhl, U.

2007-12-01

The Late Paleocene and Early Eocene (~60 ¡V 50 Ma) were characterized by globally warm climates. Superimposed on this general warmth, several episodes of further warming occurred (so-called hyperthermals), including the Paleocene-Eocene thermal maximum (PETM, ~55 Ma) and Eocene thermal maximum 2 (ETM2, ~53 Ma). While the PETM is by now well documented from Northern Hemisphere, and some equatorial locations, southern high-latitude records are still rare. Here we present high-resolution palynological, XRF, bulk organic stable carbon isotope (Ô13CTOC), and TEX86 palaeothermometry data across Upper Paleocene through Lower Eocene pro-deltaic deposits from the Southwest Pacific Ocean, at ~65¢XS palaeolatitude (ODP Site 1172). Based on a revised integrated biomagnetostratigraphic age model and Ô13CTOC stratigraphy, we identify the southernmost marginal marine PETM ever encountered. Moreover, there is every indication that ETM2 was recovered as well at Site 1172. Despite a high latitude source of the surface waters at this site, the PETM is marked by the characteristic acme of representatives of the (sub) tropical dinoflagellate cyst (dinocyst) Apectodinium, confirming the truly global nature of this PETM event. TEX86 values indicate that surface ocean temperatures rose from ~23¢XC to ~30¢XC during the PETM at Site 1172, hence by a similar magnitude as recorded in other PETM successions globally. Before and after the CIE, mass abundances of low salinity tolerant dinocysts are recorded, taken as indicative of increased runoff. These trends are analogous to those recorded at northern high latitudes, indicating a similar climate response at both polar regions during the PETM. Yet, some distinct differences are apparent, and are discussed.

The magnitude and phasing of variations in climate and ocean carbonate chemistry during Eocene Thermal Maximum 2: Insights into C cycle feedbacks

NASA Astrophysics Data System (ADS)

Harper, D. T.; Zeebe, R. E.; Hoenisch, B.; Zachos, J. C.

2016-12-01

The early Eocene features several large abrupt global warming events ("hyperthermals") that were characterized by negative δ13C excursions suggesting isotopically `light' carbon release to the atmosphere. The most prominent events, the Paleocene-Eocene Thermal Maximum (PETM) and Eocene Thermal Maximum 2 (ETM2), present an opportunity to study the operation of carbon cycle processes, and in particular negative feedbacks in the carbon cycle, such as silicate and carbonate weathering. Here we study sea surface temperature (SST) and ocean carbonate chemistry changes across ETM2, by measuring Mg/Ca, B/Ca, and δ13C in planktic foraminifera at two IODP sites (1209 in the Pacific and 1265 in the S. Atlantic). We observe a 2-3°C increase in SST in the Pacific and a 2°C increase in the Atlantic. The observed decrease in planktic B/Ca at both sites is consistent with increased atmospheric pCO2, and when scaled to the 0.3 pH unit decrease estimated for the PETM by Penman et al., 2014, the estimated pH decrease during the ETM2 is 0.15. However, reconstructions of the δ13C recovery during the ETM2 show that it is more rapid than models have been able to successfully simulate. We compare these new proxy data to LOSCAR model output, to assess whether the rapid δ13C recovery was a result of: 1) changes in the type and δ13C of weathered carbonates or δ13C of buried organic carbon during the recovery, 2) a one-time event of isotopically `light' carbon burial during the recovery phase, or 3) enhanced burial of `light' carbon due to background orbital eccentricity forcing during the recovery. Our preliminary results suggest that the phasing of the drop in the B/Ca relative to δ13C during recovery is due to the burial of organic carbon.

Transient dwarfism of soil fauna during the Paleocene–Eocene Thermal Maximum

PubMed Central

Smith, Jon J.; Hasiotis, Stephen T.; Kraus, Mary J.; Woody, Daniel T.

2009-01-01

Soil organisms, as recorded by trace fossils in paleosols of the Willwood Formation, Wyoming, show significant body-size reductions and increased abundances during the Paleocene–Eocene Thermal Maximum (PETM). Paleobotanical, paleopedologic, and oxygen isotope studies indicate high temperatures during the PETM and sharp declines in precipitation compared with late Paleocene estimates. Insect and oligochaete burrows increase in abundance during the PETM, suggesting longer periods of soil development and improved drainage conditions. Crayfish burrows and molluscan body fossils, abundant below and above the PETM interval, are significantly less abundant during the PETM, likely because of drier floodplain conditions and lower water tables. Burrow diameters of the most abundant ichnofossils are 30–46% smaller within the PETM interval. As burrow size is a proxy for body size, significant reductions in burrow diameter suggest that their tracemakers were smaller bodied. Smaller body sizes may have resulted from higher subsurface temperatures, lower soil moisture conditions, or nutritionally deficient vegetation in the high-CO2 atmosphere inferred for the PETM. Smaller soil fauna co-occur with dwarf mammal taxa during the PETM; thus, a common forcing mechanism may have selected for small size in both above- and below-ground terrestrial communities. We predict that soil fauna have already shown reductions in size over the last 150 years of increased atmospheric CO2 and surface temperatures or that they will exhibit this pattern over the next century. We retrodict also that soil fauna across the Permian-Triassic and Triassic-Jurassic boundary events show significant size decreases because of similar forcing mechanisms driven by rapid global warming. PMID:19805060

Transient dwarfism of soil fauna during the Paleocene-Eocene Thermal Maximum.

PubMed

Smith, Jon J; Hasiotis, Stephen T; Kraus, Mary J; Woody, Daniel T

2009-10-20

Soil organisms, as recorded by trace fossils in paleosols of the Willwood Formation, Wyoming, show significant body-size reductions and increased abundances during the Paleocene-Eocene Thermal Maximum (PETM). Paleobotanical, paleopedologic, and oxygen isotope studies indicate high temperatures during the PETM and sharp declines in precipitation compared with late Paleocene estimates. Insect and oligochaete burrows increase in abundance during the PETM, suggesting longer periods of soil development and improved drainage conditions. Crayfish burrows and molluscan body fossils, abundant below and above the PETM interval, are significantly less abundant during the PETM, likely because of drier floodplain conditions and lower water tables. Burrow diameters of the most abundant ichnofossils are 30-46% smaller within the PETM interval. As burrow size is a proxy for body size, significant reductions in burrow diameter suggest that their tracemakers were smaller bodied. Smaller body sizes may have resulted from higher subsurface temperatures, lower soil moisture conditions, or nutritionally deficient vegetation in the high-CO(2) atmosphere inferred for the PETM. Smaller soil fauna co-occur with dwarf mammal taxa during the PETM; thus, a common forcing mechanism may have selected for small size in both above- and below-ground terrestrial communities. We predict that soil fauna have already shown reductions in size over the last 150 years of increased atmospheric CO(2) and surface temperatures or that they will exhibit this pattern over the next century. We retrodict also that soil fauna across the Permian-Triassic and Triassic-Jurassic boundary events show significant size decreases because of similar forcing mechanisms driven by rapid global warming.

Transient dwarfism of soil fauna during the Paleocene-Eocene Thermal Maximum

USGS Publications Warehouse

Smith, J.J.; Hasiotis, S.T.; Kraus, M.J.; Woody, D.T.

2009-01-01

Soil organisms, as recorded by trace fossils in paleosols of the Willwood Formation, Wyoming, show significant body-size reductions and increased abundances during the Paleocene-Eocene Thermal Maximum (PETM). Paleobotanical, paleopedologic, and oxygen isotope studies indicate high temperatures during the PETM and sharp declines in precipitation compared with late Paleocene estimates. Insect and oligochaete burrows increase in abundance during the PETM, suggesting longer periods of soil development and improved drainage conditions. Crayfish burrows and molluscan body fossils, abundant below and above the PETM interval, are significantly less abundant during the PETM, likely because of drier floodplain conditions and lower water tables. Burrow diameters of the most abundant ichnofossils are 30-46% smaller within the PETM interval. As burrow size is a proxy for body size, significant reductions in burrow diameter suggest that their tracemakers were smaller bodied. Smaller body sizes may have resulted from higher subsurface temperatures, lower soil moisture conditions, or nutritionally deficient vegetation in the high-CO2 atmosphere inferred for the PETM. Smaller soil fauna co-occur with dwarf mammal taxa during the PETM; thus, a common forcing mechanism may have selected for small size in both above- and below-ground terrestrial communities. We predict that soil fauna have already shown reductions in size over the last 150 years of increased atmospheric CO2 and surface temperatures or that they will exhibit this pattern over the next century. We retrodict also that soil fauna across the Permian-Triassic and Triassic-Jurassic boundary events show significant size decreases because of similar forcing mechanisms driven by rapid global warming.

Revisiting carbonate chemistry controls on planktic foraminifera Mg / Ca: implications for sea surface temperature and hydrology shifts over the Paleocene-Eocene Thermal Maximum and Eocene-Oligocene transition

NASA Astrophysics Data System (ADS)

Evans, David; Wade, Bridget S.; Henehan, Michael; Erez, Jonathan; Müller, Wolfgang

2016-04-01

Much of our knowledge of past ocean temperatures comes from the foraminifera Mg / Ca palaeothermometer. Several nonthermal controls on foraminifera Mg incorporation have been identified, of which vital effects, salinity, and secular variation in seawater Mg / Ca are the most commonly considered. Ocean carbonate chemistry is also known to influence Mg / Ca, yet this is rarely examined as a source of uncertainty, either because (1) precise pH and [CO32-] reconstructions are sparse or (2) it is not clear from existing culture studies how a correction should be applied. We present new culture data of the relationship between carbonate chemistry and Mg / Ca for the surface-dwelling planktic species Globigerinoides ruber and compare our results to data compiled from existing studies. We find a coherent relationship between Mg / Ca and the carbonate system and argue that pH rather than [CO32-] is likely to be the dominant control. Applying these new calibrations to data sets for the Paleocene-Eocene Thermal Maximum (PETM) and Eocene-Oligocene transition (EOT) enables us to produce a more accurate picture of surface hydrology change for the former and a reassessment of the amount of subtropical precursor cooling for the latter. We show that pH-adjusted Mg / Ca and δ18O data sets for the PETM are within error of no salinity change and that the amount of precursor cooling over the EOT has been previously underestimated by ˜ 2 °C based on Mg / Ca. Finally, we present new laser-ablation data of EOT-age Turborotalia ampliapertura from St. Stephens Quarry (Alabama), for which a solution inductively coupled plasma mass spectrometry (ICPMS) Mg / Ca record is available (Wade et al., 2012). We show that the two data sets are in excellent agreement, demonstrating that fossil solution and laser-ablation data may be directly comparable. Together with an advancing understanding of the effect of Mg / Casw, the coherent picture of the relationship between Mg / Ca and pH that we outline here represents a step towards producing accurate and quantitative palaeotemperatures using this proxy.

Ferrimagnetic Iron Sulfide Formation and Methane Venting Across the Paleocene-Eocene Thermal Maximum in Shallow Marine Sediments, Ancient West Siberian Sea

NASA Astrophysics Data System (ADS)

Rudmin, Maxim; Roberts, Andrew P.; Horng, Chorng-Shern; Mazurov, Aleksey; Savinova, Olesya; Ruban, Aleksey; Kashapov, Roman; Veklich, Maxim

2018-01-01

Authigenesis of ferrimagnetic iron sulfide minerals (greigite and monoclinic pyrrhotite) occurred across the Paleocene-Eocene Thermal Maximum (PETM) within the Bakchar oolitic ironstone in southeastern Western Siberia. Co-occurrence of these minerals is associated with diagenetic environments that support anaerobic oxidation of methane, which has been validated by methane fluid inclusion analysis in the studied sediments. In modern settings, such ferrimagnetic iron sulfide formation is linked to upward methane diffusion in the presence of minor dissolved sulfide ions. The PETM was the most extreme Cenozoic global warming event and massive methane mobilization has been proposed as a major contributor to the globally observed warming and carbon isotope excursion associated with the PETM. The studied sediments provide rare direct evidence for methane mobilization during the PETM. Magnetic iron sulfide formation associated with methanogenesis in the studied sediments can be explained by enhanced local carbon burial across the PETM. While there is no strong evidence to link local methane venting with more widespread methane mobilization and global warming, the magnetic, petrographic, and geochemical approach used here is applicable to identifying authigenic minerals that provide telltale signatures of methane mobility that can be used to assess methane formation and mobilization through the PETM and other hyperthermal climatic events.

Sea Surface Warming and Increased Aridity at Mid-latitudes during Eocene Thermal Maximum 2

NASA Astrophysics Data System (ADS)

Harper, D. T.; Zeebe, R. E.; Hoenisch, B.; Schrader, C.; Lourens, L. J.; Zachos, J. C.

2017-12-01

Early Eocene hyperthermals, i.e. abrupt global warming events characterized by the release of isotopically light carbon to the atmosphere, can provide insight into the sensitivity of the Earth's climate system and hydrologic cycle to carbon emissions. Indeed, the largest Eocene hyperthermal, the Paleocene-Eocene Thermal Maximum (PETM), has provided one case study of extreme and abrupt global warming, with a mass of carbon release roughly equivalent to total modern fossil fuel reserves and a release rate 1/10 that of modern. Global sea surface temperatures (SST) increased by 5-8°C during the PETM and extensive evidence from marine and terrestrial records indicates significant shifts in the hydrologic cycle consistent with an increase in poleward moisture transport in response to surface warming. The second largest Eocene hyperthermal, Eocene Thermal Maximum 2 (ETM-2) provides an additional calibration point for determining the sensitivity of climate and the hydrologic cycle to massive carbon release. Marine carbon isotope excursions (CIE) and warming at the ETM-2 were roughly half as large as at the PETM, but reliable evidence for shifts in temperature and the hydrologic cycle are sparse for the ETM-2. Here, we utilize coupled planktic foraminiferal δ18O and Mg/Ca to determine ΔSST and ΔSSS (changes in sea surface temperature and salinity) for ETM-2 at ODP Sites 1209 (28°N paleolatitude in the Pacific) and 1265 (42°S paleolatitude in the S. Atlantic), accounting for potential pH influence on the two proxies by using LOSCAR climate-carbon cycle simulated ΔpH. Our results indicate a warming of 2-4°C at both mid-latitude sites and an increase in SSS of 1-3ppt, consistent with simulations of early Paleogene hydroclimate that suggest an increase in low- to mid-latitude aridity due to an intensification of moisture transport to high-latitudes. Furthermore, the magnitude of the CIE and warming for ETM-2 scales with the CIE and warming for the PETM, suggesting that the source of carbon was similar for both events.

Sharply increased insect herbivory during the Paleocene-Eocene Thermal Maximum.

PubMed

Currano, Ellen D; Wilf, Peter; Wing, Scott L; Labandeira, Conrad C; Lovelock, Elizabeth C; Royer, Dana L

2008-02-12

The Paleocene-Eocene Thermal Maximum (PETM, 55.8 Ma), an abrupt global warming event linked to a transient increase in pCO2, was comparable in rate and magnitude to modern anthropogenic climate change. Here we use plant fossils from the Bighorn Basin of Wyoming to document the combined effects of temperature and pCO2 on insect herbivory. We examined 5,062 fossil leaves from five sites positioned before, during, and after the PETM (59-55.2 Ma). The amount and diversity of insect damage on angiosperm leaves, as well as the relative abundance of specialized damage, correlate with rising and falling temperature. All reach distinct maxima during the PETM, and every PETM plant species is extensively damaged and colonized by specialized herbivores. Our study suggests that increased insect herbivory is likely to be a net long-term effect of anthropogenic pCO2 increase and warming temperatures.

Capturing the global signature of surface ocean acidification during the PETM

NASA Astrophysics Data System (ADS)

Babila, T. L.; Penman, D. E.; Hoenisch, B.; Kelly, D. C.; Bralower, T. J.; Rosenthal, Y.; Zachos, J. C.

2016-12-01

Anthropogenic greenhouse gas emissions over the last century have elevated atmospheric carbon dioxide concentrations while concomitantly acidifying the oceans. Instrumental records are sparse and limited in duration, making it difficult to separate regional from global trends of ocean acidification. Geologically rapid carbon perturbations such as the Paleocene-Eocene Thermal Maximum (PETM, 56 Ma) are arguably the closest paleo analogue to present climate change. Marine ecosystems experienced dynamic changes during the event, and parallel environmental changes, including acidification and warming. Here we present a synthesis of new and published geochemical reconstructions from various oceanographic settings to determine the magnitude and spatial extent of surface ocean acidification. In the deep ocean, acidification is inferred from widespread dissolution of seafloor carbonates, whereas evidence for surface ocean acidification has emerged from planktonic foraminifera boron proxy records (B/Ca and δ11B) (Penman et al. 2014; Babila et al. 2016). B/Ca and δ11B in surface and thermocline planktonic foraminifera suggest a simultaneous decrease at the PETM onset in all pelagic and shelf sites. Salinity, diagenesis and foraminiferal symbiont loss can complicate the interpretation of boron proxy records. Local salinity changes (based on paired Mg/Ca and δ18O) account for a relatively small component of total B/Ca change. The large range in environmental conditions between sites could explain the subtle differences in absolute values exhibited by the records. Shelf sites (ODP 174AX Bass River and Ancora, NJ) reveal similar absolute values and trends compared to pelagic sites (ODP 1209, N. Pacific), precluding a significant preservation bias on the geochemical records. Southern Ocean sites (ODP 689 and 690) are located in colder surface waters and exhibit a similar decrease in B/Ca, suggesting that temperature and symbiont loss are likely not major factors. We conclude that while the mass of released carbon is comparable to anthropogenic emissions, the rate is much slower, resulting in a less severe degree of undersaturation. Furthermore, the consistent latitudinal pattern of acidification suggests that thermal stress rather than acidification contributed to the observed biotic responses.

Extreme warming, photic zone euxinia and sea level rise during the Paleocene/Eocene Thermal Maximum on the Gulf of Mexico Coastal Plain; connecting marginal marine biotic signals, nutrient cycling and ocean deoxygenation

NASA Astrophysics Data System (ADS)

Sluijs, A.; van Roij, L.; Harrington, G. J.; Schouten, S.; Sessa, J. A.; LeVay, L. J.; Reichart, G.-J.; Slomp, C. P.

2013-12-01

The Paleocene/Eocene Thermal Maximum (PETM, ~56 Ma) was a ~200 kyr episode of global warming, associated with massive injections of 13C-depleted carbon into the ocean-atmosphere system. Although climate change during the PETM is relatively well constrained, effects on marine oxygen and nutrient cycling remain largely unclear. We identify the PETM in a sediment core from the US margin of the Gulf of Mexico. Biomarker-based paleotemperature proxies (MBT/CBT and TEX86) indicate that continental air and sea surface temperatures warmed from 27-29 °C to ~35 °C, although variations in the relative abundances of terrestrial and marine biomarkers may have influenced the record. Vegetation changes as recorded from pollen assemblages supports profound warming. Lithology, relative abundances of terrestrial vs. marine palynomorphs as well as dinoflagellate cyst and biomarker assemblages indicate sea level rise during the PETM, consistent with previously recognized eustatic rise. The recognition of a maximum flooding surface during the PETM changes regional sequence stratigraphic interpretations, which allows us to exclude the previously posed hypothesis that a nearby fossil found in PETM-deposits represents the first North American primate. Within the PETM we record the biomarker isorenieratane, diagnostic of euxinic photic zone conditions. A global data compilation indicates that deoxygenation occurred in large regions of the global ocean in response to warming, hydrological change, and carbon cycle feedbacks, particularly along continental margins, analogous to modern trends. Seafloor deoxygenation and widespread anoxia likely caused phosphorus regeneration from suboxic and anoxic sediments. We argue that this fuelled shelf eutrophication, as widely recorded from microfossil studies, increasing organic carbon burial along continental margins as a negative feedback to carbon input and global warming. If properly quantified with future work, the PETM offers the opportunity to assess the biogeochemical effects of enhanced phosphorus regeneration, as well as the time-scales on which this feedback operates in view of modern and future ocean deoxygenation.

Hydrological and associated biogeochemical consequences of rapid global warming during the Paleocene-Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Carmichael, Matthew J.; Inglis, Gordon N.; Badger, Marcus P. S.; Naafs, B. David A.; Behrooz, Leila; Remmelzwaal, Serginio; Monteiro, Fanny M.; Rohrssen, Megan; Farnsworth, Alexander; Buss, Heather L.; Dickson, Alexander J.; Valdes, Paul J.; Lunt, Daniel J.; Pancost, Richard D.

2017-10-01

The Paleocene-Eocene Thermal Maximum (PETM) hyperthermal, 56 million years ago (Ma), is the most dramatic example of abrupt Cenozoic global warming. During the PETM surface temperatures increased between 5 and 9 °C and the onset likely took < 20 kyr. The PETM provides a case study of the impacts of rapid global warming on the Earth system, including both hydrological and associated biogeochemical feedbacks, and proxy data from the PETM can provide constraints on changes in warm climate hydrology simulated by general circulation models (GCMs). In this paper, we provide a critical review of biological and geochemical signatures interpreted as direct or indirect indicators of hydrological change at the PETM, explore the importance of adopting multi-proxy approaches, and present a preliminary model-data comparison. Hydrological records complement those of temperature and indicate that the climatic response at the PETM was complex, with significant regional and temporal variability. This is further illustrated by the biogeochemical consequences of inferred changes in hydrology and, in fact, changes in precipitation and the biogeochemical consequences are often conflated in geochemical signatures. There is also strong evidence in many regions for changes in the episodic and/or intra-annual distribution of precipitation that has not widely been considered when comparing proxy data to GCM output. Crucially, GCM simulations indicate that the response of the hydrological cycle to the PETM was heterogeneous - some regions are associated with increased precipitation - evaporation (P - E), whilst others are characterised by a decrease. Interestingly, the majority of proxy data come from the regions where GCMs predict an increase in PETM precipitation. We propose that comparison of hydrological proxies to GCM output can be an important test of model skill, but this will be enhanced by further data from regions of model-simulated aridity and simulation of extreme precipitation events.

Tropical Atlantic climate and ecosystem regime shifts during the Paleocene-Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Frieling, Joost; Reichart, Gert-Jan; Middelburg, Jack J.; Röhl, Ursula; Westerhold, Thomas; Bohaty, Steven M.; Sluijs, Appy

2018-01-01

The Paleocene-Eocene Thermal Maximum (PETM, 56 Ma) was a phase of rapid global warming associated with massive carbon input into the ocean-atmosphere system from a 13C-depleted reservoir. Many midlatitude and high-latitude sections have been studied and document changes in salinity, hydrology and sedimentation, deoxygenation, biotic overturning, and migrations, but detailed records from tropical regions are lacking. Here, we study the PETM at Ocean Drilling Program (ODP) Site 959 in the equatorial Atlantic using a range of organic and inorganic proxies and couple these with dinoflagellate cyst (dinocyst) assemblage analysis. The PETM at Site 959 was previously found to be marked by a ˜ 3.8 ‰ negative carbon isotope excursion (CIE) and a ˜ 4 °C surface ocean warming from the uppermost Paleocene to peak PETM, of which ˜ 1 °C occurs before the onset of the CIE. We record upper Paleocene dinocyst assemblages that are similar to PETM assemblages as found in extratropical regions, confirming poleward migrations of ecosystems during the PETM. The early stages of the PETM are marked by a typical acme of the tropical genus Apectodinium, which reaches abundances of up to 95 %. Subsequently, dinocyst abundances diminish greatly, as do carbonate and pyritized silicate microfossils. The combined paleoenvironmental information from Site 959 and a close-by shelf site in Nigeria implies the general absence of eukaryotic surface-dwelling microplankton during peak PETM warmth in the eastern equatorial Atlantic, most likely caused by heat stress. We hypothesize, based on a literature survey, that heat stress might have reduced calcification in more tropical regions, potentially contributing to reduced deep sea carbonate accumulation rates, and, by buffering acidification, also to biological carbonate compensation of the injected carbon during the PETM. Crucially, abundant organic benthic foraminiferal linings imply sustained export production, likely driven by prokaryotes. In sharp contrast, the recovery of the CIE yields rapid (≪ 10 kyr) fluctuations in the abundance of several dinocyst groups, suggesting extreme ecosystem and environmental variability.

Evaluating Carbon and Climate Sensitivities of the NOAA/GFDL Earth System Model ESM2Mb to Forcing Perturbations during the Paleocene-Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Tandy, H.; Shevliakova, E.; Keller, G.

2017-12-01

The Paleocene-Eocene Thermal Maximum (PETM, 55.5 Myr) was a period of rapid warming resulting from major changes in the carbon cycle and has been cited as the closest historical analogue to anthropogenic carbon release. Up to now, modeling studies of the PETM used either a low-resolution coupled model of the ocean and atmosphere with prescribed CO2 or CH4, or coupled climate-carbon models of intermediate complexity (i.e. simplified ocean or atmosphere). In this study we carried a suit of numerical experiments with the NOAA/GFDL comprehensive atmosphere-ocean coupled model with integrated terrestrial and marine carbon cycle components, known as an Earth System Model (ESM2Mb). We analyzed the output from millennia-scale ESM2Mb simulations with different combinations of forcings from the pre-PETM and PETM, including greenhouse gas concentrations and solar intensity. In addition we explore sensitivities of climate and carbon cycling to changes in geology such as topography, continental positions, and the presence and absence of large land glaciers. Furthermore, we examine ESM2Mb climate and carbon sensitivities to PETM conditions with a focus on how alternate conditions and forcings relate to the uncertainty in the climate and carbon cycling estimates from paleo observations. We explore changes in atmosphere, land, and ocean temperatures and circulation patterns as well as vegetation distribution, permafrost, and carbon storage in terrestrial and marine ecosystems from pre-PETM to PETM conditions. We found that with the present day land/sea mask and land glaciers in ESM2Mb, changes in only greenhouse gas concentrations (CO2 and CH4) from pre-PETM to PETM conditions induce global warming of 3-5 °C, consistent with the lower range of estimates from paleo proxies. Changes in the carbon permafrost storage from warming cannot explain the rapid increase in the atmospheric CO2 concentration. Changes in the ocean circulation and carbon storage critically depend on geological conditions such as continental positions. The study illustrates how models designed for studying future climate change can capture past paleo events, such as the PETM, and how modern day geological conditions may affect climate and carbon cycle sensitivities.

Constraints on ocean circulation at the Paleocene-Eocene Thermal Maximum from neodymium isotopes

NASA Astrophysics Data System (ADS)

Abbott, April N.; Haley, Brian A.; Tripati, Aradhna K.; Frank, Martin

2016-04-01

Global warming during the Paleocene-Eocene Thermal Maximum (PETM) ˜ 55 million years ago (Ma) coincided with a massive release of carbon to the ocean-atmosphere system, as indicated by carbon isotopic data. Previous studies have argued for a role of changing ocean circulation, possibly as a trigger or response to climatic changes. We use neodymium (Nd) isotopic data to reconstruct short high-resolution records of deep-water circulation across the PETM. These records are derived by reductively leaching sediments from seven globally distributed sites to reconstruct past deep-ocean circulation across the PETM. The Nd data for the leachates are interpreted to be consistent with previous studies that have used fish teeth Nd isotopes and benthic foraminiferal δ13C to constrain regions of convection. There is some evidence from combining Nd isotope and δ13C records that the three major ocean basins may not have had substantial exchanges of deep waters. If the isotopic data are interpreted within this framework, then the observed pattern may be explained if the strength of overturning in each basin varied distinctly over the PETM, resulting in differences in deep-water aging gradients between basins. Results are consistent with published interpretations from proxy data and model simulations that suggest modulation of overturning circulation had an important role for initiation and recovery of the ocean-atmosphere system associated with the PETM.

Outpacing the Anthropocene: New Constraints for the Rate of Carbon Release at the Paleocene-Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Wright, J. D.; Schaller, M. F.

2012-12-01

The Paleocene/Eocene Thermal Maximum (PETM) Carbon Isotope Excursion (CIE) is linked to benthic foraminiferal extinction and excursion taxa in planktonic foraminifera and calcareous nannofossils. Previous studies have used integrated bio-magneto-stratigraphies, cycle counting, and extraterrestrial 3He accumulation rates to produce a range of estimates for the duration of the initial onset of the PETM CIE between 750 years to 30 kyr. Durations for the total release time (onset to initiation of recovery) range from 45 to 95 kyr. Uncertainty in the timing of the onset of the PETM CIE prevents the identification of a causal mechanism, and hence understanding the biological responses. Recent work on the Paleocene/Eocene Marlboro Clay has unveiled the presence of regular couplets (~2 cm) expressed in multiple cores and exposures throughout the Atlantic Coastal Plain. Specifically, the Millville and newly recovered Wilson Lake B cores contain 750 and 660 layers through the CIE, respectively. These couplets have corresponding oxygen stable isotope cycles, arguing for a climatic origin. Orbital and millennial periodicities are far too long to explain the ~750 layers identified in the Millville core. Seasonal insolation is the only regular climate cycle that can plausibly account for the observed δ18O amplitudes (~1‰, with some cycles up to 2‰) and layer counts. Seasonal freshwater input can also augment the cyclic oscillations in δ18O, but the majority of the variability is most plausibly ascribed to temperature. Wilson Lake B and Millville have total δ13C excursions of -5 and -4.5‰ respectively, as well as highly expanded sections of the PETM CIE. In the Millville core, high-resolution, bulk stable isotope records show a 3.5‰ δ13C decrease over 12 layers across the PETM CIE onset. Concomitant with this δ13C decrease is a sharp drop in CaCO3. Decreases in both proxies require a large, sudden release of isotopically light carbon. The couplet chronology indicates that the carbon released during the CIE consisted of a large, nearly instantaneous initial burst, followed by a protracted lower-level release lasting approximately 500 years. Such a scenario is most consistent with the release of thermogenic carbon due to LIP emplacement, or a comet impact. Under this release schedule, excursion planktonic foraminiferal and nannofossil taxa represent morphologic adaptation to the high CO2, low pH conditions rather than evolutionary changes.

Carbon Burn-Down in a Greenhouse World: Wildfires and Soil Carbon Loss across the Paleocene-Eocene Thermal Maximum (PETM)

NASA Astrophysics Data System (ADS)

Denis, E. H.; Foreman, B.; Maibauer, B.; Bowen, G. J.; Collinson, M. E.; Belcher, C.; Freeman, K. H.

2014-12-01

Projections for Earth's future suggest that wildfire activity will increase with global warming, but the factors controlling fire are complex. The Paleocene-Eocene Thermal Maximum (PETM) was a geologically abrupt global warming event that had profound effects on vegetation and hydrologic patterns and serves as an analog for modern climate change. Carbon burn-down (i.e., oxidation of organic matter) could amplify feedbacks with warming through release of carbon to the atmosphere. To assess relationships between climate, fire and soil respiration, we evaluated biomarkers, including polycyclic aromatic hydrocarbons (PAHs), charcoal and total organic carbon (TOC) for three paleo-floodplain depositional sites in the Western USA. Samples were selected from Bighorn Basin Coring Project cores in the Bighorn Basin, Wyoming (at Basin Substation and Polecat Bench) and from an outcrop section in the Piceance Basin, Colorado. In general, the Paleocene had higher PAH concentrations (μg/g TOC) than the Eocene, but there was no clear trend during the onset (~20 kyr) or through the PETM (~200 kyr). Median %TOC decreased through the PETM, then increased in the Eocene, but did not return to Paleocene values. At Basin Substation, PAH concentrations decreased by an order of magnitude during the PETM interval, concurrent with a decline in TOC and charcoal. High molecular weight (MW) PAHs tend to dominate, especially in low TOC samples; this suggests preferential loss of low MW PAHs, which are relatively more susceptible to post-depositional processes. Lithology, TOC and the relative proportion of PAHs help discern the signals of carbon oxidation, by fire and by soil respiration. Despite climate conditions that tend to promote fire, there is no evidence for increased fires at the onset or throughout the PETM. Biomarker and petrographic data suggest decreased organic carbon preservation, including loss of refractory carbon, at Basin Substation during the PETM. This suggests soil carbon loss, possibly due to higher rates of organic matter decay associated with a hotter and more seasonal climate during the PETM. We propose that higher carbon burn-down, due to accelerated decay rates, outpaced terrestrial productivity during the hyperthermal event, which hindered soil carbon sequestration and enhanced the atmospheric greenhouse.

Assessing the variation in mercury deposition around the North Atlantic during the Palaeocene-Eocene Thermal Maximum (PETM)

NASA Astrophysics Data System (ADS)

Jones, Morgan; Percival, Lawrence; Frieling, Joost; Mather, Tamsin; Svensen, Henrik

2017-04-01

The Palaeocene-Eocene Thermal Maximum (PETM) is a widely studied extreme global warming event that occurred 55.8 Ma. The PETM is marked by a sharp and sustained negative δ13C excursion, indicating a voluminous and rapid release of isotopically light carbon to the ocean-atmosphere system. The source(s) of carbon that instigated this global warming event remain heavily debated. The PETM is broadly contemporaneous with the second major pulse of activity (56-54 Ma) from the North Atlantic Igneous Province (NAIP), suggesting a possible causal relationship. This may have been driven by direct volcanic degassing of carbon dioxide (CO2) and/or thermogenic volatiles (e.g. CH4 and CO2) through contact metamorphism of organic-rich sedimentary layers affected by igneous intrusions. An emerging field in geochemistry that could shed light on the possible link between large igneous province emplacements and hyperthermal events is the use of mercury (Hg) preserved in the sedimentary record as a far field proxy for periods of major volcanic activity. Significant emissions of Hg could be sourced from both volcanic gases and from contact metamorphism, which are transported globally prior to deposition if released directly to the atmosphere. In marine settings, organic matter and clay minerals scavenge Hg and bury it in sediments; spikes in Hg/TOC (total organic carbon) ratios represent increases in Hg loading. Therefore, this method may be able to differentiate between magmatic and other sources as triggers for the PETM and the general activity through time. Here we present new Hg and C data from selected cores around Europe and North America to assess the variability of Hg deposition across the PETM with geographic location. The results indicate that while there is a slight background increase in Hg deposition during the PETM, there is significant variability between cores and extreme peaks within individual sections. This suggests that the behaviour of the Hg cycle during the PETM is a complex one, and that local factors such as core lithology and post-depositional mobility may be a factor.

Methane and Environmental Change during the Paleocene-Eocene Thermal Maximum (PETM): Modeling the PETM Onset as a Two-stage Event

NASA Technical Reports Server (NTRS)

Carozza, David A.; Mysak, Lawrence A.; Schmidt, Gavin A.

2011-01-01

An atmospheric CH4 box model coupled to a global carbon cycle box model is used to constrain the carbon emission associated with the PETM and assess the role of CH4 during this event. A range of atmospheric and oceanic emission scenarios representing different amounts, rates, and isotopic signatures of emitted carbon are used to model the PETM onset. The first 3 kyr of the onset, a pre-isotope excursion stage, is simulated by the atmospheric release of 900 to 1100 Pg C CH4 with a delta C-13 of -22 to - 30 %. For a global average warming of 3 deg C, a release of CO2 to the ocean and CH4 to the atmosphere totalling 900 to 1400 Pg C, with a delta C-13 of -50 to -60%, simulates the subsequent 1 -kyr isotope excursion stage. To explain the observations, the carbon must have been released over at most 500 years. The first stage results cannot be associated with any known PETM hypothesis. However, the second stage results are consistent with a methane hydrate source. More than a single source of carbon is required to explain the PETM onset.

Fluvial-system response to climate change: The Paleocene-Eocene Tremp Group, Pyrenees, Spain

NASA Astrophysics Data System (ADS)

Colombera, Luca; Arévalo, Oscar J.; Mountney, Nigel P.

2017-10-01

The Tremp Group of the Tremp-Graus Basin (Southern Pyrenees, Spain) is a succession of predominantly continental origin that records the Paleocene-Eocene Thermal Maximum (PETM), a transient episode of extreme global warming that occurred across the Paleocene-Eocene boundary. For this succession, the stratigraphic position of the PETM is accurately determined, and histories of tectonic and sea-level controls are well constrained. Building upon previous studies, this work assesses changes in sedimentary architecture through the PETM in the Tremp Group, based on quantitative sedimentological analyses documented over a km-scale strike-oriented transect in the Arén area, with the scope to better understand the response of this alluvial system to the hyperthermal event. The analysed features represent a partial record of the geomorphic organization and processes of the system at the time of deposition, and are therefore interpretable in terms of geomorphic change in alluvial landscapes caused by the PETM. The record of the PETM, as previously recognized, begins at a time when erosional palaeotopographic relief was developed and deposition was confined in valleys. A shift between valley back-filling and widespread aggradation is observed at the onset of the PETM interval, which demonstrates uniquely the impact of the hyperthermal on both depositional loci and interfluves. Compared to underlying strata, the interval that embodies the onset and main phase of the PETM is characterized by: (i) higher proportion of channel deposits; (ii) channel complexes of greater average thickness and width; (iii) barforms and channel fills that are slightly thicker; (iv) increased thickness of sets of cross-stratified sandstones; (v) similar values of maximum extraclast size, by architectural element. An evident change in the facies organization of channel deposits is also seen through the stratigraphy, though this appears to predate the PETM. Increased channel-body density in the PETM interval can be explained in terms of increased channel mobility, which itself can be related to changes in the stream catchments (e.g., greater bedload delivery, increased water discharge or discharge variability), or to changes in the nature of the depositional basin that would permit the channels to be more mobile (e.g., increased bank erodibility due to variations in vegetation type and density). Interfluve planation is inferred to have occurred immediately prior to, or penecontemporaneously with, accumulation of PETM deposits, which is in accord with inferences of increased erodibility of the interfluves or increased stream erosive power. These observations offer insight into the potential geomorphic metamorphosis of river systems in mid-latitude regions experiencing conditions of rapid global warming.

Resilient terrestrial ecosystems at the Paleocene-Eocene Thermal Maximum (Invited)

NASA Astrophysics Data System (ADS)

Wing, S.

2010-12-01

The Paleocene-Eocene Thermal Maximum (PETM) was an interval of global warming lasting ~200 ka that began ~56 Ma. Global temperature rose 5-8 °C in association with the emission of thousands of Pg of carbon into the ocean-atmosphere system. PETM rocks and fossils are extensively exposed in the SE Bighorn Basin of Wyoming, where the event is represented by ~40 m of fluvial rocks. Fossil plants demonstrate a rapid and nearly complete turnover in floral composition that also suggests a change in the structure of vegetation. Floras collected from the last ~50 ka of the Paleocene are composed of Platanaceae (sycamores), Betulaceae (birches), Fagaceae (oaks), Lauraceae (laurels), Juglandaceae (walnuts), Cercidiphyllaceae (katsura), Taxodiaceae (dawn redwood), and Arecaceae (palms), among others. Many of these families are most diverse and abundant today in temperate to subtropical, mid-latitude forests. During the body of the carbon isotope excursion (CIE) associated with the PETM fossil floras have a completely different composition. All of the latest Paleocene plant types are absent, except for palms, and instead the floras are dominated by Fabaceae (bean family). Other taxa include Sapindaceae (soapberry), Annonaceae (paw-paw), and Hernandiaceae. Where living relatives are known, they live in dry tropical forests of Central and South America. This floral composition is maintained through the ~30 m of section representing the ~110 ka-long body of the CIE, the same interval characterized by dwarfed mammalian faunas. During the recovery phase of the CIE most of the latest Paleocene plants returned to the area of study, although some new taxa appeared, apparently coming in from Europe or Asia. The distinctive PETM floral types are not seen after the recovery phase of the CIE. Change in floral composition during the PETM apparently represents regional extirpations of populations of plants that preferred warm, mesic conditions, and northward range extensions of plants that preferred dry tropical climates. This process was reversed at the end of the PETM. Although characteristics of PETM vegetation cannot be assessed directly, the distribution of living relatives is consistent with the idea that PETM vegetation was more water-stressed and more open than pre- and post-PETM vegetation. This is also matches inference from paleosol features. The radical change in composition and probable structure of vegetation across the PETM is particularly notable in light of the low extinction rates at this time. Although there is strong evidence of rapid range change and rapid evolution, the increase in temperature and decrease in precipitation do not appear to have exceeded the capacity of lineages to respond, even though the PETM is cited as an example of geologically rapid environmental change.

Changes in Nannoplankton Assemblages during the recovery of the Paleocene Eocene Thermal Maximum (PETM)

NASA Astrophysics Data System (ADS)

Grey, J. A.; Bralower, T. J.; Self-Trail, J. M.

2016-12-01

The recovery interval of the Paleocene Eocene Thermal Maximum (PETM) presents an opportunity to examine how organisms adapt to environmental change after a rapid global warming event. Calcareous nannoplankton survived the PETM, but we lack an understanding of how long it took for assemblages to adapt to a changing climate and the millennial-scale changes in their ecology. Here, we present the first high-resolution record of nannoplankton community change during the PETM recovery using a global data set (United States Geological Survey (USGS) Wilson Lake core, USGS Cam-Dor core, Ocean Drilling Program (ODP) Sites 690, 1265, and 1209) to assess millennial-scale assemblage change across space and time. Preliminary multivariate analyses on assemblage changes at Wilson Lake demonstrate that within 20,000 years after the onset, the structure of nannoplankton communities shifts from an assemblage dominated by warm eutrophic specialists to one dominated by eutrophic low salinity specialists. In the late recovery, ubiquitous taxa dominate assemblages, suggesting that the shelf environment became favorable for generalists. The latest part of the recovery is marked by a slight increase in oligotrophic specialists, indicating that the shelf became less eutrophic into the early Eocene. Overall, these analyses suggest that assemblages changed rapidly in response to cooling and changing ocean circulation during the early recovery of the PETM. Future analyses will build on these data by comparing assemblage change from other PETM coastal and open ocean sites. These analyses will help us better understand the spatial and temporal changes of nannoplankton communities on a global scale, lessons that can inform how nannoplankton will respond to future climate change.

Terrestrial floral change during the ETM2 hyperthermal

NASA Astrophysics Data System (ADS)

Wing, S. L.; Currano, E. D.

2017-12-01

Hyperthermal events during the Eocene are defined by negative shifts in carbon isotope composition, global temperature increase and carbonate dissolution in marine settings. These features suggest repeated releases of large amounts of carbon followed by increasing concentration of CO2in the atmosphere and ocean, climate change, and biotic responses such as rapid evolution and changes in geographic range and trophic relationships. The Paleocene-Eocene Thermal Maximum (PETM, 56.0 Ma) is the largest Eocene hyperthermal in terms of carbon cycle, climate and biotic effects, including dwarfing of mammalian lineages. Terrestrial floral turnover at the PETM documented in the Bighorn Basin, Wyoming, USA, is very high. Almost all late Paleocene species, most belonging to mesic, warm-temperate lineages, disappeared during the PETM. The PETM flora was composed of species belonging to dry tropical lineages present only during the body of the PETM. Most mesic, warm-temperate species returned to the area immediately after the PETM. Such extreme change in floral composition makes it difficult to assess how much floral turnover is associated with how much change in temperature. The ETM2 hyperthermal event ( 53.7 Ma) is characterized by a carbon isotope excursion and warming about half as great as during the PETM, and by half as much mammalian dwarfing. Here we report on a new fossil flora from ETM2 that demonstrates the magnitude of floral change was also less than during the PETM. Some characteristic PETM plant species reappeared in the Bighorn Basin during ETM2, including species of Fabaceae that dominate PETM assemblages but are less common during ETM2. Many stratigraphically long-ranging plant species that preferred mesic climates remain common in the ETM2 flora. We conclude that warm climate during ETM2 shifted ranges of plant species such that some PETM species returned to northern Wyoming, but was not so severe as to cause local extirpation of species preferring 'background' late Paleocene - early Eocene climate. In its effect on floral composition, as in other ways, ETM2 was less severe than the PETM.

Continental warming preceding the Palaeocene-Eocene thermal maximum.

PubMed

Secord, Ross; Gingerich, Philip D; Lohmann, Kyger C; Macleod, Kenneth G

2010-10-21

Marine and continental records show an abrupt negative shift in carbon isotope values at ∼55.8 Myr ago. This carbon isotope excursion (CIE) is consistent with the release of a massive amount of isotopically light carbon into the atmosphere and was associated with a dramatic rise in global temperatures termed the Palaeocene-Eocene thermal maximum (PETM). Greenhouse gases released during the CIE, probably including methane, have often been considered the main cause of PETM warming. However, some evidence from the marine record suggests that warming directly preceded the CIE, raising the possibility that the CIE and PETM may have been linked to earlier warming with different origins. Yet pre-CIE warming is still uncertain. Disentangling the sequence of events before and during the CIE and PETM is important for understanding the causes of, and Earth system responses to, abrupt climate change. Here we show that continental warming of about 5 °C preceded the CIE in the Bighorn Basin, Wyoming. Our evidence, based on oxygen isotopes in mammal teeth (which reflect temperature-sensitive fractionation processes) and other proxies, reveals a marked temperature increase directly below the CIE, and again in the CIE. Pre-CIE warming is also supported by a negative amplification of δ(13)C values in soil carbonates below the CIE. Our results suggest that at least two sources of warming-the earlier of which is unlikely to have been methane-contributed to the PETM.

Warming, euxinia and sea level rise during the Paleocene-Eocene Thermal Maximum on the Gulf Coastal Plain: implications for ocean oxygenation and nutrient cycling

NASA Astrophysics Data System (ADS)

Sluijs, A.; van Roij, L.; Harrington, G. J.; Schouten, S.; Sessa, J. A.; LeVay, L. J.; Reichart, G.-J.; Slomp, C. P.

2014-07-01

The Paleocene-Eocene Thermal Maximum (PETM, ~ 56 Ma) was a ~ 200 kyr episode of global warming, associated with massive injections of 13C-depleted carbon into the ocean-atmosphere system. Although climate change during the PETM is relatively well constrained, effects on marine oxygen concentrations and nutrient cycling remain largely unclear. We identify the PETM in a sediment core from the US margin of the Gulf of Mexico. Biomarker-based paleotemperature proxies (methylation of branched tetraether-cyclization of branched tetraether (MBT-CBT) and TEX86) indicate that continental air and sea surface temperatures warmed from 27-29 to ~ 35 °C, although variations in the relative abundances of terrestrial and marine biomarkers may have influenced these estimates. Vegetation changes, as recorded from pollen assemblages, support this warming. The PETM is bracketed by two unconformities. It overlies Paleocene silt- and mudstones and is rich in angular (thus in situ produced; autochthonous) glauconite grains, which indicate sedimentary condensation. A drop in the relative abundance of terrestrial organic matter and changes in the dinoflagellate cyst assemblages suggest that rising sea level shifted the deposition of terrigenous material landward. This is consistent with previous findings of eustatic sea level rise during the PETM. Regionally, the attribution of the glauconite-rich unit to the PETM implicates the dating of a primate fossil, argued to represent the oldest North American specimen on record. The biomarker isorenieratene within the PETM indicates that euxinic photic zone conditions developed, likely seasonally, along the Gulf Coastal Plain. A global data compilation indicates that O2 concentrations dropped in all ocean basins in response to warming, hydrological change, and carbon cycle feedbacks. This culminated in (seasonal) anoxia along many continental margins, analogous to modern trends. Seafloor deoxygenation and widespread (seasonal) anoxia likely caused phosphorus regeneration from suboxic and anoxic sediments. We argue that this fueled shelf eutrophication, as widely recorded from microfossil studies, increasing organic carbon burial along many continental margins as a negative feedback to carbon input and global warming. If properly quantified with future work, the PETM offers the opportunity to assess the biogeochemical effects of enhanced phosphorus regeneration, as well as the timescales on which this feedback operates in view of modern and future ocean deoxygenation.

Abrupt turnover in calcareous-nannoplankton assemblages across the Paleocene/Eocene Thermal Maximum: implications for surface-water oligotrophy over the Kerguelen Plateau, Southern Indian Ocean

USGS Publications Warehouse

Jiang, Shijun; Wise, Sherwood W.

2007-01-01

Ocean Drilling Program (ODP) Core Section 183-1135A-25R-4 from the Kerguelen Plateau in the Indian Ocean sector of the Southern Ocean represents only the second complete, expanded sequence through the Paleocene/Eocene Thermal Maximum (PETM; ~55 Ma) recovered from Antarctic waters. Calcareous nannoplankton at this site underwent an abrupt, fundamental turnover across the PETM as defined by a carbon isotope excursion. Although Chiasmolithus, Discoaster, and Fasciculithus exponentially increase in abundance at the onset, the former abruptly drops but then rapidly recovers, whereas the latter two taxa show opposite trends due to surface-water oligotrophy. These observations confirm previous results from ODP Site 690 on Maud Rise. The elevated pCO2 that accompanied the PETM caused a shoaling of the lysocline and carbonate compensation depth, leading to intensive dissolution of susceptible holococcoliths and poor preservation of the assemblages. Similarities and contrasts between the results of this study and previous work from open-ocean sites and shelf margins further demonstrate that the response to the PETM was consistent in open-ocean environments, but could be localized on continental shelves where nutrient regimes depend on the local geologic setting and oceanographic conditions.

The spread of marine anoxia on the northern Tethys margin during the Paleocene-Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Dickson, Alexander J.; Rees-Owen, Rhian L.; März, Christian; Coe, Angela L.; Cohen, Anthony S.; Pancost, Richard D.; Taylor, Kyle; Shcherbinina, Ekaterina

2014-06-01

Records of the paleoenvironmental changes that occurred during the Paleocene-Eocene Thermal Maximum (PETM) are preserved in sedimentary rocks along the margins of the former Tethys Ocean and Peri-Tethys. This paper presents new geochemical data that constrain paleoproductivity, sediment delivery, and seawater redox conditions, from three sites that were located in the Peri-Tethys region. Trace and major element, iron speciation, and biomarker data indicate that water column anoxia was established during episodes when inputs of land-derived higher plant organic carbon and highly weathered detrital clays and silts became relatively higher. Anoxic conditions are likely to have been initially caused by two primary processes: (i) oxygen consumption by high rates of marine productivity, initially stimulated by the rapid delivery of terrestrially derived organic matter and nutrients, and (ii) phosphorus regeneration from seafloor sediments. The role of the latter process requires further investigation before its influence on the spread of deoxygenated seawater during the PETM can be properly discerned. Other oxygen-forcing processes, such as temperature/salinity-driven water column stratification and/or methane oxidation, are considered to have been relatively less important in the study region. Organic carbon enrichments occur only during the initial stages of the PETM as defined by the negative carbon isotope excursions at each site. The lack of observed terminal stage organic carbon enrichment does not support a link between PETM climate recovery and the sequestration of excess atmospheric CO2 as organic carbon in this region; such a feedback may, however, have been important in the early stages of the PETM.

Fire and ecosystem change in the Arctic across the Paleocene-Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Denis, E. H.; Pedentchouk, N.; Schouten, S.; Pagani, M.; Freeman, K. H.

2016-12-01

Fire, an important component of ecosystems at a range of spatial and temporal scales, affects vegetation distribution, the carbon cycle, and climate. In turn, climate influences fuel composition (e.g., amount and type of vegetation), fuel availability (e.g., vegetation that can burn based on precipitation and temperature), and ignition sources (e.g., lightning). Climate studies predict increased wildfire activity in future decades, but mechanisms that control the relationship between climate and fire are complex. Reconstructing environmental conditions during past warming events (e.g., the Paleocene-Eocene Thermal Maximum (PETM)) will help elucidate climate-vegetation-fire relationships that are expressed over long durations (1,000 - 10,000 yrs). The abrupt global warming during the PETM dramatically altered vegetation and hydrologic patterns, and, possibly, fire occurrence. To investigate coincident changes in climate, vegetation, and fire occurrence, we studied biomarkers, including polycyclic aromatic hydrocarbons (PAHs), terpenoids, and alkanes from the PETM interval at IODP site 302 (the Lomonosov Ridge) in the Arctic Ocean. Both pollen and biomarker records indicate angiosperms abundance increased during the PETM relative to gymnosperms, reflecting a significant ecological shift to angiosperm-dominated vegetation. PAH abundances increased relative to plant biomarkers throughout the PETM, which suggests PAH production increased relative to plant productivity. Increased PAH production associated with the angiosperm vegetation shift indicates a greater prevalence of more fire-prone species. A time lag between increased moisture transport (based on published δD of n-alkanes data) to the Arctic and increased angiosperms and PAH production suggests wetter conditions, followed by increased air temperatures, favored angiosperms and combined to enhance fire occurrence.

Nannoplankton malformation during the Paleocene-Eocene Thermal Maximum and its paleoecological and paleoceanographic significance

USGS Publications Warehouse

Bralower, Timothy J.; Self-Trail, Jean

2016-01-01

The Paleocene-Eocene Thermal Maximum (PETM) is characterized by a transient group of nannoplankton, belonging to the genus Discoaster. Our investigation of expanded shelf sections provides unprecedented detail of the morphology and phylogeny of the transient Discoasterduring the PETM and their relationship with environmental change. We observe a much larger range of morphological variation than previously documented suggesting that the taxa belonged to a plexus of highly gradational morphotypes rather than individual species. We propose that the plexus represents malformed ecophenotypes of a single species that migrated to a deep photic zone refuge during the height of PETM warming and eutrophication. Anomalously, high rates of organic matter remineralization characterized these depths during the event and led to lower saturation levels, which caused malformation. The proposed mechanism explains the co-occurrence of malformed Discoaster with pristine species that grew in the upper photic zone; moreover, it illuminates why malformation is a rare phenomenon in the paleontological record.

Single Species Dinoflagellate Cyst Carbon Isotope Ecology across the Paleocene-Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Sluijs, A.; Roij, L. V.; Frieling, J.; Laks, J.; Reichart, G. J.

2017-12-01

We present the first ever species-specific records of fossil dinoflagellate cyst stable carbon isotope ratios (δ13C). These records across a Paleocene-Eocene Thermal Maximum section in New Jersey were established using a novel coupled laser ablation - isotope ratio mass spectrometer setup. The overall good correspondence with carbonate δ13C records across the characteristic PETM carbon isotope excursion indicates that the δ13C of dissolved inorganic carbon exerts a major control on dinocysts δ13C. Pronounced and consistent differences between species, however, reflect the differential physiological response to changing seawater carbonate chemistry following PETM carbon injection. Moreover, they reflect different habitats or life cycle processes, notably related to bloom intensity. Intriguingly, decreased inter-specimen variability during the PETM in a species that also drops in abundance suggests a more limited niche, either in time (seasonal) or space. This opens a new approach for ecological and evolutionary reconstructions based on organic microfossils.

Nannoplankton malformation during the Paleocene-Eocene Thermal Maximum and its paleoecological and paleoceanographic significance

NASA Astrophysics Data System (ADS)

Bralower, Timothy J.; Self-Trail, Jean M.

2016-10-01

The Paleocene-Eocene Thermal Maximum (PETM) is characterized by a transient group of nannoplankton, belonging to the genus Discoaster. Our investigation of expanded shelf sections provides unprecedented detail of the morphology and phylogeny of the transient Discoaster during the PETM and their relationship with environmental change. We observe a much larger range of morphological variation than previously documented suggesting that the taxa belonged to a plexus of highly gradational morphotypes rather than individual species. We propose that the plexus represents malformed ecophenotypes of a single species that migrated to a deep photic zone refuge during the height of PETM warming and eutrophication. Anomalously, high rates of organic matter remineralization characterized these depths during the event and led to lower saturation levels, which caused malformation. The proposed mechanism explains the co-occurrence of malformed Discoaster with pristine species that grew in the upper photic zone; moreover, it illuminates why malformation is a rare phenomenon in the paleontological record.

Paleocene-Eocene Thermal Maximum (PETM) and its Effects on Continental Biotas: Evidence from Polecat Bench in Northwestern Wyoming

NASA Astrophysics Data System (ADS)

Gingerich, P. D.

2012-12-01

Many important environmental events in the geological past were first recognized by their effects on the associated biota, and this is true for the Paleocene-Eocene Thermal Maximum or PETM global greenhouse warming event, which happened 55 million years before present. In the Southern Ocean, PETM carbon and oxygen isotope anomalies were found to coincide with a major terminal-Paleocene disappearance or extinction of benthic foraminiferans. On North America the PETM carbon isotope excursion (CIE) was found to coincide with mammalian dwarfing and a major initial-Eocene appearance or origination event of continental mammals. Linking the two records, marine and continental, resolved a long-standing disagreement over competing definitions of the Paleocene-Eocene epoch boundary, and more importantly indicated that the PETM greenhouse warming event was global. Dwarfing of herbivorous mammals can be interpreted as a response to elevated atmospheric CO2. The origin of modern orders of mammals including Artiodactyla, Perissodactyla, and Primates ('APP' taxa) is more complicated and difficult to explain but the origin of these orders may also be a response, directly or indirectly, to PETM warming. We now know from Polecat Bench and elsewhere in North America that the biotic response to PETM greenhouse warming involved the appearance of at least two new mammalian faunas distinct from previously known Clarkforkian mammals of the upper or late Paleocene and previously known Wasatchian mammals of the lower or early Eocene. Three stages and ages of the former are known (Cf-1 to Cf-3) and seven stages and ages of the latter are known (Wa-1 to Wa-7), each occupying about a hundred meters of strata representing a half-million years or so of time. Between the standard Clarkforkian and Wasatchian faunal zones is an initial 'Wa-M' faunal zone of only five or so meters in thickness and something on the order of 20 thousand years of geological time. The Wa-M fauna includes the first appearance of its namesake herbivorous condylarth, Meniscotherium, but Wa-M seemingly lacks APP taxa. Overlying Wa-M is the better known 'Wa-0' fauna in a zone spanning 30 meters of strata and about 120 thousand years of geological time. This has dwarfed mammals and APP taxa, and is overlain in turn by strata with a standard Wa-1 early Eocene fauna. Documentation is still in progress, but it appears that the change from a Cf-3 to a Wa-M fauna lagged behind the onset of the CIE, the Wa-M fauna coincided with maximum excursion of the CIE, and the Wa-0 fauna lagged behind this maximum excursion and filled the recovery phase of the CIE. It is possible that other short-lived faunas will be found in addition to those already known because the events of interest are so short in duration that they may not be preserved in every stratigraphic section. Biotic effects (e.g., dwarfing and other adaptive change, biotic extinction, and biotic origination) are compelling reasons to study global warming, and the PETM provides an opportunity to study warming and sustainability in an event free from human influence.;

Atmospheric pCO2 Reconstructed across the Early Eocene Hyperthermals

NASA Astrophysics Data System (ADS)

Cui, Y.; Schubert, B.

2015-12-01

Negative carbon isotope excursions (CIEs) are commonly associated with extreme global warming. The Early Eocene is punctuated by five such CIEs, the Paleocene-Eocene thermal maximum (PETM, ca. 55.8 Ma), H1 (ca. 53.6 Ma), H2 (ca. 53.5 Ma), I1 (ca. 53.3 Ma), and I2 (ca. 53.2 Ma), each characterized by global warming. The negative CIEs are recognized in both marine and terrestrial substrates, but the terrestrial substrates exhibit a larger absolute magnitude CIE than the marine substrates. Here we reconcile the difference in CIE magnitude between the terrestrial and marine substrates for each of these events by accounting for the additional carbon isotope fractionation by C3 land plants in response to increased atmospheric pCO2. Our analysis yields background and peak pCO2 values for each of the events. Assuming a common mechanism for each event, we calculate that background pCO2 was not static across the Early Eocene, with the highest background pCO2 immediately prior to I2, the last of the five CIEs. Background pCO2 is dependent on the source used in our analysis with values ranging from 300 to 720 ppmv provided an injection of 13C-depleted carbon with δ13C value of -60‰ (e.g. biogenic methane). The peak pCO2 during each event scales according to the magnitude of CIE, and is therefore greatest during the PETM and smallest during H2. Both background and peak pCO2 are higher if we assume a mechanism of permafrost thawing (δ13C = -25‰). Our reconstruction of pCO2 across these events is consistent with trends in the δ18O value of deep-sea benthic foraminifera, suggesting a strong link between pCO2 and temperature during the Early Eocene.

Changes in benthic ecosystems and ocean circulation in the Southeast Atlantic across Eocene Thermal Maximum 2

NASA Astrophysics Data System (ADS)

Jennions, S. M.; Thomas, E.; Schmidt, D. N.; Lunt, D.; Ridgwell, A.

2015-08-01

Eocene Thermal Maximum 2 (ETM2) occurred 1.8 Myr after the Paleocene-Eocene Thermal Maximum (PETM) and, like the PETM, was characterized by a negative carbon isotope excursion and warming. We combined benthic foraminiferal and sedimentological records for Southeast Atlantic Sites 1263 (1500 m paleodepth) and 1262 (3600 m paleodepth) to show that benthic foraminiferal diversity and accumulation rates declined more precipitously and severely at the shallower site during peak ETM2. As the sites are in close proximity, differences in surface productivity cannot have caused this differential effect. Instead, we infer that changes in ocean circulation across ETM2 may have produced more pronounced warming at intermediate depths (Site 1263). The effects of warming include increased metabolic rates, a decrease in effective food supply and increased deoxygenation, thus potentially explaining the more severe benthic impacts at Site 1263. In response, bioturbation may have decreased more at Site 1263 than at Site 1262, differentially affecting bulk carbonate records. We use a sediment-enabled Earth system model to test whether a reduction in bioturbation and/or the likely reduced carbonate saturation of more poorly ventilated waters can explain the more extreme excursion in bulk δ13C and sharper transition in wt % CaCO3 at Site 1263. We find that both enhanced acidification and reduced bioturbation during the ETM2 peak are needed to account for the observed features. Our combined ecological and modeling analysis illustrates the potential role of ocean circulation changes in amplifying local environmental changes and driving temporary, but drastic, loss of benthic biodiversity and abundance.

Ecological Impact of Climate Change on Leaf Economic Strategies Across the Paleocene- Eocene Thermal Maximum, Bighorn Basin, Wyoming

NASA Astrophysics Data System (ADS)

Royer, D. L.; Currano, E. D.; Wilf, P.; Wing, S. L.; Labandeira, C. C.; Lovelock, E. C.

2007-12-01

Deciphering the ecological impacts of climate change is a key priority for paleontologists and ecologists alike. An important ecological metric in vegetated settings is the leaf economics spectrum, which represents an adaptive continuum running from rapid resource acquisition to maximized resource retention. This spectrum is comprised of a large number of coordinated traits, including leaf mass per area (LMA), leaf lifespan, photosynthetic rate, nutrient concentration, and palatability to herbivores. Here we apply a recently developed technique for reconstructing LMA to a suite of four isotaphonomic fossil plant sites spanning the Paleocene-Eocene thermal maximum (PETM) in the Bighorn Basin, Wyoming, USA. This technique is based on the biomechanical scaling between petiole width and leaf mass, and it has been calibrated with 65 present-day sites from five continents and tested on two well-known Eocene fossil localities (Bonanza, Utah and Republic, Washington). There are no significant differences in LMA among plants across the PETM. This stasis is present despite a backdrop of extreme climate change during the PETM in this region, including a three-to-four-fold increase in atmospheric CO2, an ~5 °C rise in temperature, and possible drying. Moreover, quantitative measurements of insect herbivory show, on average, a two-fold increase during the PETM relative to before and after the event. We interpret our results to suggest that leaf-economic relationships can, in some situations, partially decouple. More specifically, our documented increase in insect herbivory during the PETM with no concomitant decrease in LMA implies that during this interval less carbon was being captured by plants per unit of investment. Because the rate and magnitude of climate change during the PETM is similar to present-day anthropogenic changes, our results may provide clues for predictions of ecological impacts in the near future.

A Smoking Gun for Methane Hydrate Release During the Paleocene-Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Frieling, J.; Peterse, F.; Lunt, D. J.; Bohaty, S. M.; S Sinninghe Damsté, J.; Reichart, G. J.; Sluijs, A.

2016-12-01

The Paleocene-Eocene Thermal Maximum (PETM; 56 Ma) was a period of rapid 4-5ºC global warming and a global negative carbon isotope excursion (CIE) of 3-4.5‰, signaling the input of at least 1500 Gt of δ13C-depleted carbon into the ocean-atmosphere system. Methane from submarine hydrates has long been proposed as a carbon source, but direct and indirect evidence is lacking. We generated a new high-resolution TEX86 and δ13C record from Ocean Drilling Program Site 959 in the eastern tropical Atlantic and find that initial warming preceded the PETM CIE by 10 kyr. Moreover, time-shifted cross-correlations on these new and published temperature-δ13C data imply that substantial (2-3 °C) warming lead 13C-depleted carbon injection by an average of 2-3 kyr globally. Finally, a data compilation shows that global burial fluxes of biogenic Ba approximately doubled across all depths of the ocean studied, which on PETM time scales can only be explained by significant Ba addition to the oceans. Submarine hydrates are Ba-rich and require warming to dissociate. The simplest explanation for the temperature lead and Ba addition to the ocean is that methane hydrate dissociated as a response to initial warming and acted as a positive carbon cycle feedback during the PETM.

Mo isotopes as redox indicators for the Southern Tethys during the PETM

NASA Astrophysics Data System (ADS)

Wouters, H.; Dickson, A.; Porcelli, D.; Hesselbo, S. P.; van den Boorn, S.; Gomez, V. G.; Mutterlose, J.

2014-12-01

As several ocean and climate models predict a decline in dissolved ocean oxygen concentrations associated with future global warming [1], recent research is increasingly focusing on past episodes of low ocean oxygen levels. Trace metals are generally enriched in organic-rich sediments deposited under such low oxygen conditions, and the concentration and isotopic signatures of several of these elements (e.g. Mo, U, Cr) may be applied as proxies to reconstruct the processes involved in these redox changes [2,3]. This project investigates the use of the molybdenum isotope system as a proxy for redox changes during an interval of abrupt environmental change spanning the Paleocene/Eocene boundary (the Paleocene/Eocene Thermal Maximum, PETM, ~56 Ma). The PETM is characterized by global warming and environmental and ecological changes including decreased ocean oxygen levels [4]. Study of the PETM can therefore offer us a valuable insight into how marine ecosystems and biogeochemical cycles may respond to future climate changes, and the predicted decrease of oxygen concentrations in seawater. The molybdenum concentrations and isotope compositions of organic-rich sediments spanning the PETM have been obtained from a Jordan oil shale drill core (OS-28). The obtained δ98/95Mo isotopic ratios range between -0.12‰ and 1.59‰ and coincide with significant fluctuations in trace metal abundances. The data together demonstrate that the global environmental changes associated with the PETM were manifest in the Jordanian basin as significant changes in basin hydrography and dissolved oxygen levels.

The PETM in the coastal ocean: changes in redox, productivity, and organic matter sources recorded in mid-Atlantic sediments

NASA Astrophysics Data System (ADS)

Lyons, S. L.; Baczynski, A. A.; Vornlocher, J.; Freeman, K. H.

2016-12-01

Climate events in the geologic record reveal the broad array of Earth's responses to carbon cycle perturbations, and provide valuable insights to the predicted impacts of future anthropogenic climate change. The Paleocene-Eocene Thermal Maximum (PETM) hyperthermal was linked to a rapid injection of isotopically light carbon into Earth's ocean-atmosphere system, and this event serves as the best-known analogue for anthropogenic climate change. The addition of 4500 Gt CO2 over < 20,000 years, estimated based on carbon isotope excursions of 3-5‰ in marine and terrestrial records, was accompanied by abrupt global warming of 5-9 oC. Changes in ocean redox chemistry, productivity, sediment accumulation, and organic matter sourcing often accompany climate and carbon cycle perturbations and have been implicated in PETM off-shore ocean records. Yet, despite numerous studies of biomarkers and organic matter in terrestrial and marine PETM records, we lack organic records from truly coastal environments, leaving a gap in our understanding of the land-ocean interface and how the shallow marine environments changed during the PETM. To better understand the effects of climate change on coastal sites and the marine sedimentary records during the PETM, we investigated the role of redox, productivity, and organic matter sourcing using recently collected cores from the paleo-Atlantic shelf. These new coastal PETM records provide needed datasets to understand biogeochemical changes in the shallow marine environment. Here, we present lipid biomarkers (pristane, phytane, n-alkanes, hopanoids, steranes, GDGTs) and compound-specific carbon isotope data along a transect from proximal coastal to more distal inner shelf. These molecular records help detail the intensity of water column stratification, productivity, and carbon source changes, as well as shifting terrestrial and marine inputs. Constraining the marine carbon isotope excursion, organic matter sourcing, and water column chemistry along the shallow shelf during the PETM reveals the impact of abrupt changes in the carbon cycle and global temperatures on the coastal ocean.

Paleoenvironmental changes during the Paleocene-Eocene recorded in the Yaxcopoil-1 borehole, Chicxulub impact crater.

NASA Astrophysics Data System (ADS)

Marca-Castillo, M.; Perez-Cruz, L. L.; Fucugauchi, J. U.

2017-12-01

The aim of this study is to investigate the paleoclimatic events along the Paleocene/Eocene (P/E) boundary based on stratigraphy, magnetic susceptibility logs and geochemical (major and trace elements) records. Data points were taken first each 10 cm and then each centimeter during the main interval of interest at the Yaxcopoil-1 (Yax-1) borehole in the Chicxulub impact crater, located in the northwestern part of the Yucatan Peninsula, Mexico. The Yax-1 was drilled at 20° 44' 38.45'' N, 89° 43' 6.70'' W, recovering a core of 1511 m depth. The interval between 750 and 700 m depth was selected to study the P/E boundary, with the knowledge from previous works that the K/Pg boundary is around 794 m depth in this core. At the interval between 750 and 700 m, the drop in Ca values, high MS logs and an abrupt increase in clay minerals suggested the location of the P/E boundary may be between 735 m to 722 m depth, therefore high resolution geochemical measurements were taken using an XRF scanner at the interval from 724.59 to 732.92 m to identify the hyperthermal events occurred during the Paleogene. In this study the lower Ca content along the P/E boundary is associated with a warm event called the Paleocene Eocene Thermal Maximum (PETM) also known as ETM1, due to carbonate dissolution as a result of the ocean acidification at the end of the Paleocene. On the other hand, ratios of Ca/Ti, K/Ti and Rb/Sr were used as paleoclimatic proxies to define the P/E boundary. The Ca/Ti ratio indicates the biogenic content in the sediments, mainly CaCO3 content; K/Ti ratios may record changes of the intensity of chemical weathering. Furthermore, based on the geochemical ratios and low Ca content was possible to recognize in the Yax-1 another hyperthermal events, occurred during the Paleogene, called ETM2 and ETM3, showing similar characteristics than the PETM. The results from analysis of power spectrums of the geochemical and magnetic susceptibility data also support the occurrence of these warming events.

Surviving rapid climate change in the deep sea during the Paleogene hyperthermals.

PubMed

Foster, Laura C; Schmidt, Daniela N; Thomas, Ellen; Arndt, Sandra; Ridgwell, Andy

2013-06-04

Predicting the impact of ongoing anthropogenic CO2 emissions on calcifying marine organisms is complex, owing to the synergy between direct changes (acidification) and indirect changes through climate change (e.g., warming, changes in ocean circulation, and deoxygenation). Laboratory experiments, particularly on longer-lived organisms, tend to be too short to reveal the potential of organisms to acclimatize, adapt, or evolve and usually do not incorporate multiple stressors. We studied two examples of rapid carbon release in the geological record, Eocene Thermal Maximum 2 (∼53.2 Ma) and the Paleocene Eocene Thermal Maximum (PETM, ∼55.5 Ma), the best analogs over the last 65 Ma for future ocean acidification related to high atmospheric CO2 levels. We use benthic foraminifers, which suffered severe extinction during the PETM, as a model group. Using synchrotron radiation X-ray tomographic microscopy, we reconstruct the calcification response of survivor species and find, contrary to expectations, that calcification significantly increased during the PETM. In contrast, there was no significant response to the smaller Eocene Thermal Maximum 2, which was associated with a minor change in diversity only. These observations suggest that there is a response threshold for extinction and calcification response, while highlighting the utility of the geological record in helping constrain the sensitivity of biotic response to environmental change.

Paleocene-Eocene Thermal Maximum triggered by Volcanism revealed by Mercury anomalies

NASA Astrophysics Data System (ADS)

Khozyem, Hassan; Adatte, Thierry; Mbabi Bitchong, André; Chevalier, Yoann; Keller, Gerta

2017-04-01

The Paleocene-Eocene Thermal Maximum (PETM, 55.8±0.2 Ma) is marked by a global drop of 2-6‰ in 13C values and rapid warming of 4-5°C in tropical surface waters and 4-8°C in high latitudes. Climate warming persisted for several tens of thousands of years and resulted in rapid diversification in terrestrial mammals and marine planktic foraminifera. Deep-water bathyal benthic foraminifera suffered a mass extinction ( 40% species) but no significant extinctions occurred shallow shelf environments. Benthic extinctions are commonly explained as the effects of the initial stage of climate warming due to North Atlantic Volcanic Province volcanism (NAVP), which triggered methane release from ocean sediments causing global warming and ocean acidification. But the relationship between NAPV and the PETM events are not clearly demonstrated. Several studies [1-4] demonstrated the relationship between Hg anomalies in sediments and LIP activity associated with mass extinctions. We investigated the mercury (Hg) content of several sections located in deep bathyal (Zumaya, Trabakua, N-Spain) and outer shelf environments (Dababiya GSSP, Duwi, Egypt). At Zumaya the PETM is marked by a red clayey and marly interval poor in organic matter and coincident with a pronounced ∂13C negative shift. A comparable clay interval with low TOC content is also present in the Dababyia section in the lower part of the negative ∂13C shift, whereas the upper part of is enriched in TOC, reflecting increased productivity. A significant but unique Hg enrichment is observed at the onset of the PETM just below the carbone isotope shift in Spain as well as in Egypt. This increase, which is not correlated with clay or total organic carbon contents, suggests the Hg anomaly resulted from higher atmospheric Hg input into the marine realm, rather than organic matter scavenging and/or increased run-off. This Hg anomaly at the onset of the PETM provides the first direct evidence that volcanism played a crucial role in triggering the PETM events by initiating the warming that likely released methane gases that accelerated greenhouse warming and ocean acidification.

Temperature and atmospheric CO2 concentration estimates through the PETM using triple oxygen isotope analysis of mammalian bioapatite

PubMed Central

Gehler, Alexander; Pack, Andreas

2016-01-01

The Paleocene–Eocene Thermal Maximum (PETM) is a remarkable climatic and environmental event that occurred 56 Ma ago and has importance for understanding possible future climate change. The Paleocene–Eocene transition is marked by a rapid temperature rise contemporaneous with a large negative carbon isotope excursion (CIE). Both the temperature and the isotopic excursion are well-documented by terrestrial and marine proxies. The CIE was the result of a massive release of carbon into the atmosphere. However, the carbon source and quantities of CO2 and CH4 greenhouse gases that contributed to global warming are poorly constrained and highly debated. Here we combine an established oxygen isotope paleothermometer with a newly developed triple oxygen isotope paleo-CO2 barometer. We attempt to quantify the source of greenhouse gases released during the Paleocene–Eocene transition by analyzing bioapatite of terrestrial mammals. Our results are consistent with previous estimates of PETM temperature change and suggest that not only CO2 but also massive release of seabed methane was the driver for CIE and PETM. PMID:27354522

Foraminiferal Stable Isotope Record at Millville, NJ: Implications for the onset of the PETM

NASA Astrophysics Data System (ADS)

Wright, J. D.; Miller, K. G.

2016-12-01

Traditional paleoceanographic tools (magneto-biostratigraphy, orbital cycles) are insufficient to assign rates to the initial release of carbon during the rapid onset of the PETM (<10 kyr). The ODP Leg 174AX Millville, NJ PETM section (70 m paleodepth) is >10 times more expanded relative to the thickest open ocean sites (e.g., Site 690). The onset interval at Millville is defined by a bulk carbonate δ13C of 3.5‰ across 25 cm interval. Two groups used the geochemical changes to constrain the timing for the initial pulse of carbon. Wright and Schaller (2013) focused on the differential responses in δ13C and %CaCO3 arguing that the release was fast (<1 year). Conversely, Zeebe et al. (2016) assumed the initial covariance in δ18O and δ13C represented equilibrium conditions, modeling a 4 kyr duration for the release. We generated planktonic and benthic foraminiferal stable isotope records across the onset of the PETM CIE at Millville. Most of the δ13C change recorded by foraminifera occurred over the 25 cm onset interval. However, foraminiferal δ18O values continue to decrease for another 1.5 m above the initial δ13C decrease contradicting Zeebe et al.'s assumption of equilibrium conditions. The foraminiferal stable isotope pattern is similar to the modeled response following a large, instantaneous release of light carbon to the atmosphere, that produces a rapid (decadal) scale warming in the surface air masses followed by continued warming but at a slower rate. Differential responses in δ13C, δ18O, and %CaCO3 at the onset of the PETM are consistent with an instantaneous initial release of carbon with centennial-scale warming that continued well after the initial carbon pulse similar to that predicted by climate models. Fitting the Millville isotope records to these models suggests that peak warmth followed the initial release by 100 to 200 years. The mid-shelf location of Millville a made it responsive to atmospheric changes unlike open ocean sites where thermal inertia dampens the larger atmosphere changes.

Towards a mechanistic understanding of the linkages between PETM climate modulation and stratigraphy, as discerned from the Piceance Basin, CO, USA

NASA Astrophysics Data System (ADS)

Barefoot, E. A.; Nittrouer, J. A.; Foreman, B.; Moodie, A. J.; Dickens, G. R.

2017-12-01

The Paleocene-Eocene Thermal Maximum (PETM) was a period of rapid climatic change when global temperatures increased by 5-8˚C in as little as 5 ka. It has been hypothesized that by drastically enhancing the hydrologic cycle, this temperature change significantly perturbed landscape dynamics over the ensuing 200 ka. Much of the evidence documenting hydrological variability derives from studies of the stratigraphic record, which is interpreted to encode a system-clearing event in fluvial systems worldwide during and after the PETM. For example, in the Piceance Basin of Western Colorado, it is hypothesized that intensification of monsoons due to PETM warming caused an increase in sediment flux to the basin. The resulting stratigraphy records a modulation of the sedimentation rate, where the PETM interval is represented by a laterally extensive sheet sand positioned between units dominated by floodplain muds. The temporal interval, the sediment provenance history, as well as the tectonic history of the PETM in the Piceance Basin are all well-constrained, leaving climate as the most significant allogenic forcing in the Piceance Basin during the PETM. However, the precise nature of landscape change that link climate forcing by the PETM to modulation of the sedimentation rate in this basin remains to be demonstrated. Here, we present a simple stratigraphic numerical model coupled with a conceptual source-to-sink framework to test the impact of a suite of changing upstream boundary conditions on the fluvial system. In the model, climate-related variables force changes in flow characteristics such as sediment transport, slope, and velocity, which determine the resultant floodplain stratigraphy. The model is based on mathematical relations that link bankfull geometry and water discharge, impacting the lateral migration rate of the channel, sediment transport rate, and avulsion frequency, thereby producing a cross-section of basin stratigraphy. In this way, we simulate a raft of plausible, and mutually exclusive, climate-change scenarios for the case study of the Piceance Basin during the PETM, which may be compared to the stratigraphic record through field observation. The method described here represents a step towards connecting the impacts of global climate change to fluvial systems and sedimentation dynamics.

A high-resolution sulfur isotope record of the Paleocene-Eocene Thermal Maximum (PETM)

NASA Astrophysics Data System (ADS)

Yao, W.; Paytan, A.; Wortmann, U.

2017-12-01

The Paleocene-Eocene Thermal Maximum (PETM) is a transient episode of extreme global warming lasting 10,000 to 40,000 years, characterized by the significant rise in deep-ocean and equatorial sea-surface temperatures. Our current understanding of the PETM is based on sedimentological evidence (short-term negative excursions of benthic δ13C and δ18O, widespread oceanic carbonate dissolution). Here we add to this body of research by presenting a high-resolution δ34S and δ18OSO4 data of seawater sulfate derived from marine barite (ODP Leg 199 Core 1221C-11X-3). Our results show that during the PETM, the δ34S of seawater sulfate increases from 17.26 permil to 18.31 permil between 55.30 and 55.19 Ma, and quickly returns to values around 17.60 permil at 55.15 Ma. Similarly, the δ18OSO4 value exhibits a positive excursion of 1.7 permil over the same time. The peak of δ18OSO4 appears coincident with the peak of δ34S within the PETM interval (55.21-55.17 Ma). While these numbers appear small, the long residence time of sulfate in the ocean implies rather large fluxes. We show that these changes require the removal of about 1.5e17 mol of 32S through microbial sulfate reduction. The quick return of the δ34S-signal necessitates that the reduced sulfur is stored in a transient reservoir, and released back into the ocean. The magnitude and reversibility of this process render pyrite burial unlikely. Rather, we suggest that large quantities of reduced sulfur are temporarily stored in an expanded oxygen minimum zone (OMZ). Depending on the assumed H2S concentrations, the OMZ must have increased somewhere between 100 and 1000 meters in thickness. The observed sulfate δ18OSO4 is consistent with this interpretation.

Sensitivity of the Palaeocene-Eocene Thermal Maximum climate to cloud properties.

PubMed

Kiehl, Jeffrey T; Shields, Christine A

2013-10-28

The Palaeocene-Eocene Thermal Maximum (PETM) was a significant global warming event in the Earth's history (approx. 55 Ma). The cause for this warming event has been linked to increases in greenhouse gases, specifically carbon dioxide and methane. This rapid warming took place in the presence of the existing Early Eocene warm climate. Given that projected business-as-usual levels of atmospheric carbon dioxide reach concentrations of 800-1100 ppmv by 2100, it is of interest to study past climates where atmospheric carbon dioxide was higher than present. This is especially the case given the difficulty of climate models in simulating past warm climates. This study explores the sensitivity of the simulated pre-PETM and PETM periods to change in cloud condensation nuclei (CCN) and microphysical properties of liquid water clouds. Assuming lower levels of CCN for both of these periods leads to significant warming, especially at high latitudes. The study indicates that past differences in cloud properties may be an important factor in accurately simulating past warm climates. Importantly, additional shortwave warming from such a mechanism would imply lower required atmospheric CO2 concentrations for simulated surface temperatures to be in reasonable agreement with proxy data for the Eocene.

Pollen and palynofacies analyses of Paleocene-Eocene Thermal Maximum sediments from the North American continental shelf

NASA Astrophysics Data System (ADS)

Willard, D. A.; Robinson, M. M.; Self-Trail, J. M.; Wandless, G. A.; Sluijs, A.

2014-12-01

Analyses of pollen and palynofacies from Paleocene-Eocene Thermal Maximum (PETM) sediments from three cores collected on the Atlantic Coastal Plain provide insights into the timing of vegetation and hydrologic changes associated with the PETM in eastern North America. The Mattawoman Creek-Billingsley Road (MCBR2), South Dover Bridge (SDB), and Bass River (ODP Site 1074AX) cores were collected at progressively greater distances from the paleoshoreline in continental shelf deposits in Maryland and New Jersey, USA. The PETM carbon isotope excursion (CIE) at each site is accompanied by sharp increases in pollen and spore concentrations, as well as changes in terrestrial palynomorph assemblage composition. In the two sites proximal to the paleoshoreline in Maryland, CIE fern spore abundance was two- to three times greater than in pre-CIE assemblages. At the distal site at Bass River, fern spores are present in CIE sediments and absent in pre-CIE sediments. Angiosperm pollen is most common in CIE sediments at all three sites. Palynofacies analyses, which quantify contributions of organic material from marine and non-marine sources, indicate that terrestrial influx increased sharply at the CIE onset. This observation is consistent with seasonally increased runoff from the continent.

Increased terrestrial methane cycling at the Palaeocene-Eocene thermal maximum.

PubMed

Pancost, Richard D; Steart, David S; Handley, Luke; Collinson, Margaret E; Hooker, Jerry J; Scott, Andrew C; Grassineau, Nathalie V; Glasspool, Ian J

2007-09-20

The Palaeocene-Eocene thermal maximum (PETM), a period of intense, global warming about 55 million years ago, has been attributed to a rapid rise in greenhouse gas levels, with dissociation of methane hydrates being the most commonly invoked explanation. It has been suggested previously that high-latitude methane emissions from terrestrial environments could have enhanced the warming effect, but direct evidence for an increased methane flux from wetlands is lacking. The Cobham Lignite, a recently characterized expanded lacustrine/mire deposit in England, spans the onset of the PETM and therefore provides an opportunity to examine the biogeochemical response of wetland-type ecosystems at that time. Here we report the occurrence of hopanoids, biomarkers derived from bacteria, in the mire sediments from Cobham. We measure a decrease in the carbon isotope values of the hopanoids at the onset of the PETM interval, which suggests an increase in the methanotroph population. We propose that this reflects an increase in methane production potentially driven by changes to a warmer and wetter climate. Our data suggest that the release of methane from the terrestrial biosphere increased and possibly acted as a positive feedback mechanism to global warming.

Coccolithophore calcification response to past ocean acidification and climate change

PubMed Central

O’Dea, Sarah A.; Gibbs, Samantha J.; Bown, Paul R.; Young, Jeremy R.; Poulton, Alex J.; Newsam, Cherry; Wilson, Paul A.

2014-01-01

Anthropogenic carbon dioxide emissions are forcing rapid ocean chemistry changes and causing ocean acidification (OA), which is of particular significance for calcifying organisms, including planktonic coccolithophores. Detailed analysis of coccolithophore skeletons enables comparison of calcite production in modern and fossil cells in order to investigate biomineralization response of ancient coccolithophores to climate change. Here we show that the two dominant coccolithophore taxa across the Paleocene–Eocene Thermal Maximum (PETM) OA global warming event (~56 million years ago) exhibited morphological response to environmental change and both showed reduced calcification rates. However, only Coccolithus pelagicus exhibits a transient thinning of coccoliths, immediately before the PETM, that may have been OA-induced. Changing coccolith thickness may affect calcite production more significantly in the dominant modern species Emiliania huxleyi, but, overall, these PETM records indicate that the environmental factors that govern taxonomic composition and growth rate will most strongly influence coccolithophore calcification response to anthropogenic change. PMID:25399967

Coccolithophore calcification response to past ocean acidification and climate change.

PubMed

O'Dea, Sarah A; Gibbs, Samantha J; Bown, Paul R; Young, Jeremy R; Poulton, Alex J; Newsam, Cherry; Wilson, Paul A

2014-11-17

Anthropogenic carbon dioxide emissions are forcing rapid ocean chemistry changes and causing ocean acidification (OA), which is of particular significance for calcifying organisms, including planktonic coccolithophores. Detailed analysis of coccolithophore skeletons enables comparison of calcite production in modern and fossil cells in order to investigate biomineralization response of ancient coccolithophores to climate change. Here we show that the two dominant coccolithophore taxa across the Paleocene-Eocene Thermal Maximum (PETM) OA global warming event (~56 million years ago) exhibited morphological response to environmental change and both showed reduced calcification rates. However, only Coccolithus pelagicus exhibits a transient thinning of coccoliths, immediately before the PETM, that may have been OA-induced. Changing coccolith thickness may affect calcite production more significantly in the dominant modern species Emiliania huxleyi, but, overall, these PETM records indicate that the environmental factors that govern taxonomic composition and growth rate will most strongly influence coccolithophore calcification response to anthropogenic change.

Thermogenic methane release as a cause for the long duration of the PETM

PubMed Central

Frieling, Joost; Svensen, Henrik H.; Planke, Sverre; Cramwinckel, Margot J.; Selnes, Haavard; Sluijs, Appy

2016-01-01

The Paleocene–Eocene Thermal Maximum (PETM) (∼56 Ma) was a ∼170,000-y (∼170-kyr) period of global warming associated with rapid and massive injections of 13C-depleted carbon into the ocean–atmosphere system, reflected in sedimentary components as a negative carbon isotope excursion (CIE). Carbon cycle modeling has indicated that the shape and magnitude of this CIE are generally explained by a large and rapid initial pulse, followed by ∼50 kyr of 13C-depleted carbon injection. Suggested sources include submarine methane hydrates, terrigenous organic matter, and thermogenic methane and CO2 from hydrothermal vent complexes. Here, we test for the contribution of carbon release associated with volcanic intrusions in the North Atlantic Igneous Province. We use dinoflagellate cyst and stable carbon isotope stratigraphy to date the active phase of a hydrothermal vent system and find it to postdate massive carbon release at the onset of the PETM. Crucially, however, it correlates to the period within the PETM of longer-term 13C-depleted carbon release. This finding represents actual proof of PETM carbon release from a particular reservoir. Based on carbon cycle box model [i.e., Long-Term Ocean–Atmosphere–Sediment Carbon Cycle Reservoir (LOSCAR) model] experiments, we show that 4–12 pulses of carbon input from vent systems over 60 kyr with a total mass of 1,500 Pg of C, consistent with the vent literature, match the shape of the CIE and pattern of deep ocean carbonate dissolution as recorded in sediment records. We therefore conclude that CH4 from the Norwegian Sea vent complexes was likely the main source of carbon during the PETM, following its dramatic onset. PMID:27790990

Enhanced terrestrial weathering/runoff and surface ocean carbonate production during the recovery stages of the Paleocene-Eocene thermal maximum

NASA Astrophysics Data System (ADS)

Kelly, D. Clay; Zachos, James C.; Bralower, Timothy J.; Schellenberg, Stephen A.

2005-12-01

The carbonate saturation profile of the oceans shoaled markedly during a transient global warming event known as the Paleocene-Eocene thermal maximum (PETM) (circa 55 Ma). The rapid release of large quantities of carbon into the ocean-atmosphere system is believed to have triggered this intense episode of dissolution along with a negative carbon isotope excursion (CIE). The brevity (120-220 kyr) of the PETM reflects the rapid enhancement of negative feedback mechanisms within Earth's exogenic carbon cycle that served the dual function of buffering ocean pH and reducing atmospheric greenhouse gas levels. Detailed study of the PETM stratigraphy from Ocean Drilling Program Site 690 (Weddell Sea) reveals that the CIE recovery period, which postdates the CIE onset by ˜80 kyr, is represented by an expanded (˜2.5 m thick) interval containing a unique planktic foraminiferal assemblage strongly diluted by coccolithophore carbonate. Collectively, the micropaleontological and sedimentological changes preserved within the CIE recovery interval reflect a transient state when ocean-atmosphere chemistry fostered prolific coccolithophore blooms that suppressed the local lysocline to relatively deeper depths. A prominent peak in the abundance of the clay mineral kaolinite is associated with the CIE recovery interval, indicating that continental weathering/runoff intensified at this time as well (Robert and Kennett, 1994). Such parallel stratigraphic changes are generally consonant with the hypothesis that enhanced continental weathering/runoff and carbonate precipitation helped sequester carbon during the PETM recovery period (e.g., Dickens et al., 1997; Zachos et al., 2005).

Deep-sea Benthic Foraminifera in the SE Atlantic across Eocene Hyperthermal Events

NASA Astrophysics Data System (ADS)

Thomas, E.

2016-12-01

Short-term episodes of global warming (hyperthermal events) were superimposed on the warming trend into the Early Eocene Climate Optimum (EECO). The Paleocene-Eocene Thermal Maximum (PETM; 56 Ma) was the most extreme, followed by Eocene Thermal Maximum-2 and -3 (ETM2: 1.8 myr, ETM3: 3.1 myr post-PETM). Hyperthermals are characterized by negative carbon isotope excursions (CIEs, emission of isotopically light carbon in the ocean-atmosphere), negative oxygen isotope excursions (global warming) and carbonate dissolution (ocean acidification). Sensitivity of biota to environmental changes due to carbon emissions can be evaluated by studying their response to hyperthermals of different magnitude. Deep-sea benthic foraminiferal records across PETM, ETM2 and -3 are available for Site 1262 (3600 m) and 1263 (1500m) on SE Atlantic Walvis Ridge. Benthic foraminifera (carbonate and agglutinated) are absent in the carbonate-free PETM clay-layer (Site 1262: 65 kyr; Site1263: 10 kyr). Deep-sea benthic foraminifera suffered extinction and diversity loss at the start of the PETM, as they did globally, with diversity recovering only partially. Stable isotope records show a larger PETM-CIE and amount of warming at Site 1263 than global average (McCarren et al., 2008), and warming was more pronounced at Site 1263 than at 1262 during ETM2 (Jennions et al., 2015) and ETM3 (Roehl et al., 2005). During ETM2 and -3, carbonate dissolution affected the sites, both remaining between CCD and lysocline. Assemblages were more severely affected (larger drop in benthic foraminiferal accumulation rates, BFAR) at the shallower site, opposite to expected if caused mainly by carbonate corrosivity. The large decrease in BFAR indicates a decline in food arrival at the sea floor, more pronounced at the shallower site, as supported by changes in relative and absolute abundance of species, and more pronounced at ETM2 than at ETM3. Greater warming at intermediate depths could have been caused by ocean circulation changes, with the greater warming more severely affecting metabolic rates of benthic foraminifera, thus patterns of effective food supply, species and diversity change. Roehl et al. 2005 GSA Abstr. 37: 264. McCarren et al. 2008 G3, 9 (10): Q10008. Jennions et al. 2015 Paleoceanogr. 30: 1059-1077

The record of Tethyan planktonic foraminifera at the early Paleogene hyperthermal events and Middle Eocene Climatic Optimum in northeastern Italy: are they comparable?

NASA Astrophysics Data System (ADS)

Luciani, Valeria; Giusberti, Luca; Agnini, Claudia; Fornaciari, Eliana; Rio, Domenico

2010-05-01

The early Paleogene is one of the more climatically and evolutionary dynamic periods in the Earth history that records a pronounced warming trend peaking in the Early Eocene, and a successive composite transition towards the modern icehouse world. Ever increasingly scientific attention is dedicated to definitely comprehend timing, nature and characters of the complex, non-linear evolution of the Paleogene climate. Several complete and expanded Paleogene successions (Forada, Possagno, Alano, Farra), with a sound magneto-biochronostratigraphic and stable isotope record crop out in the Venetian Southern Alps (Northeast Italy). Recent studies (Giusberti et. al., 2007; Luciani et al., 2007; Agnini et al., 2008) and unpublished data document the presence in these section of the main short-lived warming events (hyperthermals) of the Eocene (Paleocene-Eocene Thermal Maximum, PETM, ca 55 Ma, Eocene Layer of Mysterious Origin (ELMO, ca 53,6 Ma), X-event (ca 52.5 Ma), of the Early Eocene Climatic Optimum (EECO, ca 50-52 Ma) and of the Middle Eocene Climatic Optimum (MECO, ca 40 Ma; Zachos et al., 2001. 2008). All these events are typified by marked negative shifts in δ13C curves that correspond to carbonate decrease related to rise of the carbonate compensation depth in turn induced by large introduction in the ocean-atmosphere system of CO2. Common features to the warming events are pronounced and complex changes in planktonic foraminiferal assemblages, indicating strong environmental perturbations that perfectly parallel the variations of the stable isotope curves in all the examined events. These strict correspondences indicate close cause-effect relationships between changes in environmental conditions and modifications of the assemblages. Our analysis shows that the most striking variations are recorded by the PETM and MECO assemblages that reflect highly perturbed environments. The ELMO, X-event and EECO exhibit planktic foraminiferal responses that are similar to, though less intense than, those observed across the PETM and the MECO. In addition, sedimentological and quantitative micropaleontological data from the hyperthermal events from the Venetian Southern Alps essentially suggest as the main response to the pronounced warmth, increased weathering and runoff as well as sea surface eutrophication. A pronounced shift from relatively oligotrophic to eutrophic, opportunist planktonic foraminiferal assemblages was observed at the MECO as well, thus showing analogies with the hyperthermal events recorded in the same area. The taxa indicating eutrophic environmental conditions are however different at the MECO from the Alano section; on the other hand we can expect that the planktonic foraminiferal taxa indicating analogous scenarios might be different in different Eocene time-intervals. Remarkably, the PETM and MECO events record a significant occurrence of giant and malformed foraminifera, evidence of transient alteration in the ocean chemistry, including possible pH oscillations and increase in trace metal content. Our data suggests therefore that a major threshold in the photic zone ocean chemistry has been passed only for those prominent events. In conclusion, from the biotic response to the hyperthermal events, to the EECO and MECO we deduce that the most important effect of pronounced warming, that is the aspect common to all these events, has been the eutrophication of surface waters, as a consequence of modification in the hydrological cycle. The location adjacent to land masses of the studied Tethyan setting evidently facilitated the terrigenous input that was apparently the main responsible for the increase in nutrient availability during the cited Paleogene warming events. Finally, several lines of evidence indicate that PETM, EECO and MECO were linked to permanent changes in planktonic foraminiferal evolution beside the transient, ecologically controlled variations. Even though the true mechanisms forcing evolution of life on Earth are still unexplained, our record of the major climatic Paleogene events suggests a close interaction between global climate and biological evolution. REFERENCES Agnini et al., 2008. Rend. Soc. Geol. It. 4, 5-12. Giusberti et., 2007; Geol. Soc. Am. Bull. 119, 391-412. Luciani et al., 2007. Mar. Micopaleont. 64, 189-214. Zachos et al., 2001. Science 292, 686-693. Zachos et al 2008 Nature 451, 279-283.

Fluvial response to abrupt global warming at the Palaeocene/Eocene boundary.

PubMed

Foreman, Brady Z; Heller, Paul L; Clementz, Mark T

2012-11-01

Climate strongly affects the production of sediment from mountain catchments as well as its transport and deposition within adjacent sedimentary basins. However, identifying climatic influences on basin stratigraphy is complicated by nonlinearities, feedback loops, lag times, buffering and convergence among processes within the sediment routeing system. The Palaeocene/Eocene thermal maximum (PETM) arguably represents the most abrupt and dramatic instance of global warming in the Cenozoic era and has been proposed to be a geologic analogue for anthropogenic climate change. Here we evaluate the fluvial response in western Colorado to the PETM. Concomitant with the carbon isotope excursion marking the PETM we document a basin-wide shift to thick, multistoried, sheets of sandstone characterized by variable channel dimensions, dominance of upper flow regime sedimentary structures, and prevalent crevasse splay deposits. This progradation of coarse-grained lithofacies matches model predictions for rapid increases in sediment flux and discharge, instigated by regional vegetation overturn and enhanced monsoon precipitation. Yet the change in fluvial deposition persisted long after the approximately 200,000-year-long PETM with its increased carbon dioxide levels in the atmosphere, emphasizing the strong role the protracted transmission of catchment responses to distant depositional systems has in constructing large-scale basin stratigraphy. Our results, combined with evidence for increased dissolved loads and terrestrial clay export to world oceans, indicate that the transient hyper-greenhouse climate of the PETM may represent a major geomorphic 'system-clearing event', involving a global mobilization of dissolved and solid sediment loads on Earth's surface.

Impact of dissolution on the sedimentary record of the Paleocene-Eocene thermal maximum

NASA Astrophysics Data System (ADS)

Bralower, Timothy J.; Kelly, D. Clay; Gibbs, Samantha; Farley, Kenneth; Eccles, Laurie; Lindemann, T. Logan; Smith, Gregory J.

2014-09-01

The input of massive amounts of carbon to the atmosphere and ocean at the Paleocene-Eocene Thermal Maximum (PETM; ˜55.53 Ma) resulted in pervasive carbonate dissolution at the seafloor. At many sites this dissolution also penetrated into the underlying sediment column. The magnitude of dissolution at and below the seafloor, a process known as chemical erosion, and its effect on the stratigraphy of the PETM, are notoriously difficult to constrain. Here, we illuminate the impact of dissolution by analyzing the complete spectrum of sedimentological grain sizes across the PETM at three deep-sea sites characterized by a range of bottom water dissolution intensity. We show that the grain size spectrum provides a measure of the sediment fraction lost during dissolution. We compare these data with dissolution and other proxy records, electron micrograph observations of samples and lithology. The complete data set indicates that the two sites with slower carbonate accumulation, and less active bioturbation, are characterized by significant chemical erosion. At the third site, higher carbonate accumulation rates, more active bioturbation, and possibly winnowing have limited the impacts of dissolution. However, grain size data suggest that bioturbation and winnowing were not sufficiently intense to diminish the fidelity of isotopic and microfossil assemblage records.

Productivity and river flux variability in response to the PETM on Atlantic margin at Bass River, NJ.

NASA Astrophysics Data System (ADS)

Stoll, H.; Shimizu, N.; Savain, R.; Zachos, J.; Ziveri, P.

2009-04-01

While the dramatic climate warming of the Paleocene-Eocene Thermal Maximum has been well characterized, changes in the hydrological cycle and the broader biogeochemical feedbacks (weathering, nutrients, productivity) are less well constrained. Here we describe new geochemical results from a coastal section on the midlatitude Atlantic margin of the U.S. at Bass River, NJ. We measured the elemental geochemistry of coccoliths to probe the productivity of these algae in response to the changing nutrient dynamics on the shelf in the time interval preceding and during the PETM. Coccoliths extracted from the siliclastic coastal section at Bass River NJ exhibit exceptionally good preservation and negligible overgrowth compared to typical ocean carbonate-rich sediments. Analysis of individual coccoliths using secondary ion mass spectrometry (SIMS) facilitates reliable trace element measurements in this low-carbonate section. Published sequence stratigraphy and microfossil analysis have revealed several third order sea level cycles in the late Paleocene including a highstand during the PETM. Consequently we extend our paleoproductivity records far below the PETM to characterize this background variability. We recognize a pattern of generally maximum productivity during lowstands and minimal productivity during highstands. Because nutrient concentrations decrease significantly with distance from the coast, highstands reduce productivity by shifting the highest nutrient levels landward, away from the site. This is likely due to greater distance from river sources as well as reduced wave turbulence which mixes nutrients into the photic zone. This general pattern is broken during the PETM, which features high productivity despite a sea level highstand. This anomalous high productivity may reflect enhanced riverine nutrient delivery, and potentially changes in wind strength and mixing intensity. Riverine nutrient delivery could increase with higher precipitation or precipitation seasonality, and/or higher weathering intensity. In support of enhanced riverine flow, seawater d18O ratios, calculated from coccolith d18O and TEX86 temperatures, indicate a strong decrease characteristic of freshening during the PETM. The excellent preservation of coccoliths also enables us to examine interspecific vital effects on coccolith stable isotopes, with minimal diagenetic homogenization. In Bass River coccolith size fractions separated and measured from the same sediments, the vital effects among different size fractions are <0.5 permil in carbon and oxygen isotope ratios, with little change over the PETM, consistent with our earlier results from ODP 690. This contrasts with the large range of stable isotope vital effects in modern cultures and sediment traps, which correlate with cell size and carbonate ion. These results support our hypothesis that the range of interspecific vital effects may have been reduced in the high-CO2 Paleocene ocean when the modern diversity of carbon concentrating mechanisms was not required.

Reconstruction of the PETM onset from single specimen analyses of foraminiferal stable isotopes at Medford, NJ

NASA Astrophysics Data System (ADS)

Makarova, M.; Miller, K. G.; Wright, J. D.

2017-12-01

The Paleocene-Eocene transition ( 56 Ma) is marked by a global temperature increase of 4-8°C and the carbon isotope excursion (CIE) found ubiquitously in marine and terrestrial realms. However, the mechanisms of warming and overall changes in the ocean-atmosphere system during the Paleocene-Eocene thermal maximum (PETM) are uncertain. The timing of the PETM onset has been debated suggested by various studies between years to thousands of years and therefore is of particular interest to ascertain the trigger mechanism. One way to resolve this is to study thick cores on the continental margins that have higher sedimentation rates and thus resolution. Stratigraphically more complete in regard to the CIE onset marine PETM sections are found along the U.S. mid-Atlantic margin, New Jersey coastal plain (35-40°N paleolatitude). We present new carbon and oxygen isotopic data of planktonic and benthic foraminifera from the Medford 3A core, drilled on the New Jersey coastal plain in Summer 2016. Medford is the most proximal among the New Jersey coastal plain sites. The Medford 3A core has recovered 4 ft (1.2 m) of the Marlboro Formation, unit that contains the CIE "core" with low stable δ13C values and CIE recovery in other New Jersey cores. The top of the Marlboro Formation is truncated at Medford 3A, but the base is conformable with the underlaying Vincentown Formation. The sharp δ13C decrease appears within the Vincentown/Marlboro transitional lithological interval 1.5 ft (0.5 m) thick allowing a detailed study of the PETM onset. The Medford 3A core recovered sufficient well-preserved foraminifera to establish isotopic changes across the PETM onset. We measure δ13C and δ18O in single specimens of surface dwellers (Morozovella, Acarinina), thermocline dwellers (Subbotina), and benthic foraminifera (Anomalinoides, Cibicidoides) at high resolution to understand the nature of the PETM onset. We compliment previously published single specimen isotopic records from the deepest water Bass River core, NJ with newly generated lithologic and single specimen isotopic data at most proximal Medford. This allows high resolution reconstruction of the PETM onset at marginal depositional settings along the New Jersey paleoshelf: from 25 m at Medford to over 100 m at Bass River.

Release of Volatiles During North Atlantic Flood Basalt Volcanism and Correlation to the Paleocene-Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Pedersen, J. M.; Tegner, C.; Kent, A. J.; Ulrich, T.

2017-12-01

The opening of the North Atlantic Ocean between Greenland and Norway during the lower Tertiary led to intense flood basalt volcanism and the emplacement of the North Atlantic Igneous Province (NAIP). The volcanism is temporally overlapping with the Paleocene-Eocene Thermal Maximum (PETM), but ash stratigraphy and geochronology suggests that the main flood basalt sequence in East Greenland postdates the PETM. Significant environmental changes during the PETM have been attributed to the release of CO2 or methane gas due to either extensive melting of hydrates at the ocean floor or as a consequence of the interaction of mantle derived magmas with carbon rich sediments.Estimates suggest that a minimum of 1.8x106 km3 of basaltic lava erupted during North Atlantic flood basalt volcanism. Based on measurements of melt inclusions from the flood basalts our preliminary calculations suggest that approximately 2300 Gt of SO2 and 600 Gt of HCl were released into the atmosphere. Calculated yearly fluxes approach 23 Mt/y SO2 and 6 Mt/y HCl. These estimates are regarded as conservative.The S released into to the atmosphere during flood basalt volcanism can form acid aerosols that absorb and reflect solar radiation, causing an effective cooling effect. The climatic effects of the release of Cl into the atmosphere are not well constrained, but may be an important factor for extinction scenarios due to destruction of the ozone layer.The climatic changes due to the release of S and Cl in these amounts, and for periods extending for hundred thousand of years, although not yet fully constrained are likely to be significant. One consequence of the North Atlantic flood basalt volcanism may have been the initiation of global cooling to end the PETM.

Fire and ecosystem change in the Arctic across the Paleocene-Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Denis, Elizabeth H.; Pedentchouk, Nikolai; Schouten, Stefan; Pagani, Mark; Freeman, Katherine H.

2017-06-01

Fire has been an important component of ecosystems on a range of spatial and temporal scales. Fire can affect vegetation distribution, the carbon cycle, and climate. The relationship between climate and fire is complex, in large part because of a key role of vegetation type. Here, we evaluate regional scale fire-climate relationships during a past global warming event, the Paleocene-Eocene Thermal Maximum (PETM), in order to understand how vegetation influenced the links between climate and fire occurrence in the Arctic region. To document concurrent changes in climate, vegetation, and fire occurrence, we evaluated biomarkers, including polycyclic aromatic hydrocarbons (PAHs), terpenoids, and alkanes, from the PETM interval at a marine depositional site (IODP site 302, the Lomonosov Ridge) in the Arctic Ocean. Biomarker, fossil, and isotope evidence from site 302 indicates that terrestrial vegetation changed during the PETM. The abundance of the C29n-alkanes, pollen, and the ratio of leaf-wax n-alkanes relative to diterpenoids all indicate that proportional contributions from angiosperm vegetation increased relative to that from gymnosperms. These changes accompanied increased moisture transport to the Arctic and higher temperatures, as recorded by previously published proxy records. We find that PAH abundances were elevated relative to total plant biomarkers throughout the PETM, and suggest that fire occurrence increased relative to plant productivity. The fact that fire frequency or prevalence may have increased during wetter Arctic conditions suggests that changes in fire occurrence were not a simple function of aridity, as is commonly conceived. Instead, we suggest that the climate-driven ecological shift to angiosperm-dominated vegetation was what led to increased fire occurrence. Potential increases in terrestrial plant biomass that arose from warm, wet, and high CO2 conditions were possibly attenuated by biomass burning associated with compositional changes in the plant community.

Significance of a Shelf-wide Dissolution Event during the Paleocene-Eocene Thermal Maximum, Maryland and New Jersey, USA

NASA Astrophysics Data System (ADS)

Bralower, T. J.; Kump, L. R.; Robinson, M. M.; Self-Trail, J. M.; Zachos, J. C.

2016-12-01

Continental-shelf sediments of the US Atlantic margin experienced a brief episode of carbonate dissolution during the onset of the Paleocene-Eocene Thermal Maximum (PETM). Dissolution is represented by reduced percentages of carbonate, and calcareous microfossil distribution and preservation trends, in cores from Maryland and New Jersey. The base and the top of the dissolution zone are abrupt compared to the gradual nature of the onset of the carbon isotope excursion (CIE). The thickness of the dissolution zone varies from 9 cm in the Bass River core (outer paleoshelf) to 1.6 m in the CamDor core (middle paleoshelf). The decrease in %CaCO3 suggests dissolution locally removed 83 to 100% of the initial biogenic carbonate. Shelf-wide dissolution during the onset of the PETM may be a regional event, associated, for example, with eutrophication. Samples from across the paleoshelf contain abundant fine-grained framboidal pyrite, which suggests photic-zone euxinia occurred before, during, and after the dissolution event. Dissolution may also be associated with oxidation of this pyrite during later exposure to oxidizing groundwaters, although the restricted duration of the dissolution interval argues against this. Alternatively, the dissolution event may have global significance related to surface ocean-water acidification or shoaling of the calcite compensation depth (CCD) to shelf depths. The event began near the onset of the CIE on the shelf, whereas dissolution in deep-sea sections began later. Earlier shelf dissolution is consistent with surface ocean acidification while later deep-sea dissolution is thought to be associated with shoaling of the CCD. In our presentation, we weigh evidence for each of these possibilities and test them using the global dataset.

Mechanistic insights into a hydrate contribution to the Paleocene-Eocene carbon cycle perturbation from coupled thermohydraulic simulations

NASA Astrophysics Data System (ADS)

Minshull, T. A.; Marín-Moreno, H.; Armstrong McKay, D. I.; Wilson, P. A.

2016-08-01

During the Paleocene-Eocene Thermal Maximum (PETM), the carbon isotopic signature (δ13C) of surface carbon-bearing phases decreased abruptly by at least 2.5 to 3.0‰. This carbon isotope excursion (CIE) has been attributed to widespread methane hydrate dissociation in response to rapid ocean warming. We ran a thermohydraulic modeling code to simulate hydrate dissociation due to ocean warming for various PETM scenarios. Our results show that hydrate dissociation in response to such warming can be rapid but suggest that methane release to the ocean is modest and delayed by hundreds to thousands of years after the onset of dissociation, limiting the potential for positive feedback from emission-induced warming. In all of our simulations at least half of the dissociated hydrate methane remains beneath the seabed, suggesting that the pre-PETM hydrate inventory needed to account for all of the CIE is at least double that required for isotopic mass balance.

Reconstructing Atmospheric CO2 Through The Paleocene-Eocene Thermal Maximum Using Stomatal Index and Stomatal Density Values From Ginkgo adiantoides

NASA Astrophysics Data System (ADS)

Barclay, R. S.; Wing, S. L.

2013-12-01

The Paleocene-Eocene Thermal Maximum (PETM) was a geologically brief interval of intense global warming 56 million years ago. It is arguably the best geological analog for a worst-case scenario of anthropogenic carbon emissions. The PETM is marked by a ~4-6‰ negative carbon isotope excursion (CIE) and extensive marine carbonate dissolution, which together are powerful evidence for a massive addition of carbon to the oceans and atmosphere. In spite of broad agreement that the PETM reflects a large carbon cycle perturbation, atmospheric concentrations of CO2 (pCO2) during the event are not well constrained. The goal of this study is to produce a high resolution reconstruction of pCO2 using stomatal frequency proxies (both stomatal index and stomatal density) before, during, and after the PETM. These proxies rely upon a genetically controlled mechanism whereby plants decrease the proportion of gas-exchange pores (stomata) in response to increased pCO2. Terrestrial sections in the Bighorn Basin, Wyoming, contain macrofossil plants with cuticle immediately bracketing the PETM, as well as dispersed plant cuticle from within the body of the CIE. These fossils allow for the first stomatal-based reconstruction of pCO2 near the Paleocene-Eocene boundary; we also use them to determine the relative timing of pCO2 change in relation to the CIE that defines the PETM. Preliminary results come from macrofossil specimens of Ginkgo adiantoides, collected from an ~200ka interval prior to the onset of the CIE (~230-30ka before), and just after the 'recovery interval' of the CIE. Stomatal index values decreased by 37% within an ~70ka time interval at least 100ka prior to the onset of the CIE. The decrease in stomatal index is interpreted as a significant increase in pCO2, and has a magnitude equivalent to the entire range of stomatal index adjustment observed in modern Ginkgo biloba during the anthropogenic CO2 rise during the last 150 years. The inferred CO2 increase prior to the CIE coincides in part with the 'pre-warming' interval documented from δ18O in mammalian tooth enamel from the Bighorn Basin. Stomatal density values increase ~30ka prior to the CIE, suggesting a decrease in cell size from water stress, a change that closely matches the timing of a trend towards drier paleosols in the same region of the Bighorn Basin. All evidence collected to date suggests a long-term rise in pCO2 and temperature, and drying of soils prior to the prominent CIE. Presumably the source for CO2 released prior to the CIE did not significantly alter the isotopic value of atmospheric CO2. As suggested by previous authors, warming prior to the CIE may have triggered the release of carbon from a source depleted in 13C at the onset of the PETM. Well-preserved dispersed cuticle has been extracted from stratigraphic levels within the CIE, and may permit reconstruction of changes in pCO2 during the PETM.

Multiple Export Production and Sulfur Isotope Records over the Paleocene Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Gray, E.; Paytan, A.

2007-12-01

The Paleocene Eocene Thermal Maximum (PETM) was a global climatic event that occurred 55 million years ago. δ18O values from benthic foraminifera indicate that temperatures rose 4-5°C coeval with a precipitous drop in δ13C values that indicate a new source of carbon rapidly entered the global carbon cycle. Marine barite (BaSO4) was used to evaluate the 1) barite accumulation rate that serves a proxy for export production and 2) the sulfur isotopic composition of seawater that reflects the mass balance of oceanic sulfate (SO42-). Increased barite accumulation rates at the PETM suggest that increased export production and CO2 sequestration was in direct response to the carbon isotope excursion, although not all of the increases are accounted for. High resolution δ34S values are lower but within reasonable range of previously observed values and indicate a decrease in sulfate removal by pyrite deposition.

Re-assessing the role of plant community change and climate in the PETM n-alkane record

NASA Astrophysics Data System (ADS)

Bush, R. T.; Baczynski, A. A.; McInerney, F. A.; Chen, D.

2012-12-01

The terrestrial leaf wax n-alkane record of the Paleocene-Eocene Thermal Maximum (PETM) in the Bighorn Basin, Wyoming, shows large excursions in both carbon isotope (δ13C) values and n-alkane average chain length (ACL). At the onset of the PETM, ACL values increase from ~28.5 to ~30.1 while the negative carbon isotope excursion (CIE) is 4-6‰ in magnitude and larger than δ13C records from other materials. It has been hypothesized previously that both the ACL excursion and the large magnitude of the CIE were caused by a concurrent turnover in the local flora from a mixed conifer/angiosperm community before the PETM to a different suite of angiosperm species during the PETM. Here, we present the results of a meta-analysis of data (>2000 data from 89 sources, both published and unpublished) on n-alkane amounts and chain length distributions in modern plants from around the world. We applied the data in two sets of comparisons: 1) within and among plant groups such as herbs and graminoids, and 2) between plants and climate, using reported collection locations for outdoor plants and climate values generated via GIS extraction of WorldClim modeled data. We show that angiosperms, as group, produce more n-alkanes than do gymnosperms by 1-2 orders of magnitude, and this means that the gymnosperm contribution to a mixed soil n-alkane pool would be negligible, even in an ecosystem where gymnosperms dominated (i.e. the pre/post-PETM ecosystems). The modern plant data also demonstrate that turnover of the plant community during the PETM, even among only the angiosperm species, is likely not the source of the observed ACL excursion. First, we constructed "representative" groups of PETM and pre/post-PETM communities using living relative species at the Chicago Botanic Garden and find no significant difference in chain length distributions between the two groups. Second and moreover, the modern plant data reveal that n-alkane chain length distributions are tremendously variable within large vascular plant groups--both functional groups such as woody plants or graminoids as well as phylogenetic groups at the family level or higher. This variability makes it difficult at best to use n-alkane chain lengths to distinguish one vascular group from another, as was previously suggested. Instead, our results suggest that chain length distributions and ACL are driven more by climate, especially temperature. Longer chain lengths, with their increased hydrophobicity, would likely experience favorable selection under warmer or drier conditions where leaf water loss is likely to be a greater stress. Thus, it may be that we can interpret the increase in ACL during the PETM as a direct response by the flora to increased temperature during the hyperthermal event, and n-alkane chain length distributions, properly constrained, may possibly serve as a qualitative paleotemperature proxy.

Chromium Isotope Anomaly Scaling with Past Warming Episodes

NASA Astrophysics Data System (ADS)

Remmelzwaal, S.; O'Connor, L.; Preston, W.; Parkinson, I. J.; Schmidt, D. N.

2017-12-01

The recent expansion of oxygen minimum zones caused by anthropogenic global warming raises questions about the scale of this expansion with different emission scenarios. Ocean deoxygenation will impact marine ecosystems and fisheries demanding an assessment of the possible extent and intensity of deoxygenation. Here, we used past climate warming events to quantify a potential link between warming and the spread of oxygen minimum zones: including Ocean Anoxic Event (OAE) 1a, OAE 2 in the Cretaceous, the Palaeocene-Eocene Thermal Maximum (PETM), the Eocene Thermal Maximum 2 (ETM2), and Pleistocene glacial-interglacial cycles. We applied the emerging proxy of chromium isotopes in planktic foraminifera to assess redox changes during the PETM, ETM2, and Pleistocene and bulk carbonate for the OAEs. Both δ53Cr and chromium concentrations respond markedly during the PETM indicative of a reduction in dissolved oxygen concentrations caused by changes in ocean ventilation and associated warming [1]. A strong correlation between Δδ53Cr and benthic Δδ18O, a measure of the excursion size in both oxygen and chromium isotopes, suggest temperatures to be one of the main drivers of ocean deoxygenation in the past [1]. Chromium concentrations decrease during ETM2 and OAE1a, and, increase by 4.5 ppm over the Plenus Cold Event during OAE2, which suggests enhanced seafloor ventilation. [1] Remmelzwaal, S.R.C., Dixon, S., Parkinson, I.J., Schmidt, D.N., Monteiro, F.M., Sexton, P., Fehr, M., Peacock, C., Donnadieu, Y., James, R.H., in review. Ocean deoxygenation during the Palaeocene-Eocene Thermal Maximum. EPSL.

Very large release of mostly volcanic carbon during the Paleocene-Eocene Thermal Maximum

PubMed Central

Gutjahr, Marcus; Ridgwell, Andy; Sexton, Philip F.; Anagnostou, Eleni; Pearson, Paul N.; Pälike, Heiko; Norris, Richard D.; Thomas, Ellen; Foster, Gavin L.

2017-01-01

Global warming during the Palaeocene-Eocene Thermal Maximum1,2 (PETM, ~56 Ma) is commonly interpreted as being primarily driven by the destabilization of carbon from surficial sedimentary reservoirs such as methane hydrates3. However, the source(s) of carbon remain controversial1,3–5. Resolving this is key to understanding the proximal cause, as well as quantifying the roles of triggers versus feedbacks in driving the event. Here we present new boron isotope data – a proxy for seawater pH – that demonstrate the occurrence of persistently suppressed surface ocean pH across the PETM. Our pH data, alongside a paired carbon isotope record, are assimilated in an Earth system model to reconstruct the unfolding carbon cycle dynamics across the event6,7. We find strong evidence for a much larger (>10,000 PgC) and on average isotopically heavier carbon source than considered previously8,9. This leads us to identify volcanism associated with the North Atlantic Igneous Province, rather than carbon from a surficial reservoir, as the main driver of the PETM10,11. We also find that, although amplifying organic carbon feedbacks with climate likely played only a subordinate role in driving the event, enhanced organic matter burial was important in ultimately sequestering the released carbon and accelerating the recovery of the Earth system12. PMID:28858305

The Paleocene Eocene carbon isotope excursion in higher plant organic matter: Differential fractionation of angiosperms and conifers in the Arctic

NASA Astrophysics Data System (ADS)

Schouten, Stefan; Woltering, Martijn; Rijpstra, W. Irene C.; Sluijs, Appy; Brinkhuis, Henk; Sinninghe Damsté, Jaap S.

2007-06-01

A study of upper Paleocene-lower Eocene (P-E) sediments deposited on the Lomonosov Ridge in the central Arctic Ocean reveals relatively high abundances of terrestrial biomarkers. These include dehydroabietane and simonellite derived from conifers (gymnosperms) and a tetra-aromatic triterpenoid derived from angiosperms. The relative percentage of the angiosperm biomarker of the summed angiosperm + conifer biomarkers was increased at the end of the Paleocene-Eocene thermal maximum (PETM), different when observed with pollen counts which showed a relative decrease in angiosperm pollen. Stable carbon isotopic analysis of these biomarkers shows that the negative carbon isotope excursion (CIE) during the PETM amounts to 3‰ for both conifer biomarkers, dehydroabietane and simonellite, comparable to the magnitude of the CIE inferred from marine carbonates, but significantly lower than the 4.5‰ of the terrestrial C 29n-alkane [M. Pagani, N. Pedentchouk, M. Huber, A. Sluijs, S. Schouten, H. Brinkhuis, J.S. Sinninghe Damsté, G.R. Dickens, and the IODP Expedition 302 Expedition Scientists (2006), Arctic's hydrology during global warming at the Paleocene-Eocene thermal maximum. Nature, 442, 671-675.], which is a compound sourced by both conifers and angiosperms. Conspicuously, the angiosperm-sourced aromatic triterpane shows a much larger CIE of 6‰ and suggests that angiosperms increased in their carbon isotopic fractionation during the PETM. Our results thus indicate that the 4.5‰ C 29n-alkane CIE reported previously represents the average CIE of conifers and angiosperms at this site and suggest that the large and variable CIE observed in terrestrial records may be partly explained by the variable contributions of conifers and angiosperms. The differential response in isotopic fractionation of angiosperms and conifers points to different physiological responses of these vegetation types to the rise in temperature, humidity, and greenhouse gases during the PETM.

Model Simulations of the Global Carbon and Sulfur Cycles: Implications for the Paleocene-Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Higgins, J. A.; Schrag, D. P.

2004-12-01

Extreme global warmth and an abrupt negative carbon isotope excursion during the Paleocene-Eocene Thermal Maximum (PETM) have been attributed to a rapid addition of isotopically depleted carbon to the ocean-atmosphere system. Potential carbon sources include the abrupt release of 1000-2000 Gt C as methane hydrate (\\delta13C ~-60\\permil) from sediments on the continental slope (Dickens et al., 1995) and the oxidation of 8000-9000 Gt of organic carbon (\\delta13C ~-25\\permil) in rampant global wildfires (Kurtz et al., 2003). Using a simple geochemical model of the global carbon and sulfur cycles, we investigate whether these hypotheses are consistent with estimates of climate warming during the PETM by considering the effects of atmospheric composition and climate in the Paleocene and feedbacks driven by changes in sulfur cycling and seawater chemistry. Modest increases in atmospheric CO2 (70-150 ppm) associated with methane hydrate release cannot, without additional feedbacks in the climate system, account for a 5-6° C increase in global sea surface temperature during the PETM. In contrast, a significant increase in atmospheric CO2 (600-700 ppm) is observed following the oxidation of 8000-9000 Gt of organic carbon. However, constraints on the size and extent of the Paleocene terrestrial carbon pool and the absence of geologic evidence indicative of vast wildfires argue against a global conflagration as an important source of depleted carbon. Instead, we interpret the PETM and its associated negative carbon isotope excursion as representing the oxidation of 8000-9000 Gt C as organic matter in shallow marine and near shore terrestrial sediments following the retreat of major epicontinental seaways in the Paleocene. This hypothesis is also consistent with large changes in the sulfur cycle in the early Eocene inferred from the \\delta34S of seawater sulfate. References: Dickens G.R., et al., (1995) Paleoceanography, 10, 965-971. Kurtz, A.C., et al., (2003) Paleoceanography, 18, 1090-1104.

Repetitive mammalian dwarfing during ancient greenhouse warming events

PubMed Central

D’Ambrosia, Abigail R.; Clyde, William C.; Fricke, Henry C.; Gingerich, Philip D.; Abels, Hemmo A.

2017-01-01

Abrupt perturbations of the global carbon cycle during the early Eocene are associated with rapid global warming events, which are analogous in many ways to present greenhouse warming. Mammal dwarfing has been observed, along with other changes in community structure, during the largest of these ancient global warming events, known as the Paleocene-Eocene Thermal Maximum [PETM; ~56 million years ago (Ma)]. We show that mammalian dwarfing accompanied the subsequent, smaller-magnitude warming event known as Eocene Thermal Maximum 2 [ETM2 (~53 Ma)]. Statistically significant decrease in body size during ETM2 is observed in two of four taxonomic groups analyzed in this study and is most clearly observed in early equids (horses). During ETM2, the best-sampled lineage of equids decreased in size by ~14%, as opposed to ~30% during the PETM. Thus, dwarfing appears to be a common evolutionary response of some mammals during past global warming events, and the extent of dwarfing seems related to the magnitude of the event. PMID:28345031

Very large release of mostly volcanic carbon during the Palaeocene-Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Gutjahr, Marcus; Ridgwell, Andy; Sexton, Philip F.; Anagnostou, Eleni; Pearson, Paul N.; Pälike, Heiko; Norris, Richard D.; Thomas, Ellen; Foster, Gavin L.

2017-08-01

The Palaeocene-Eocene Thermal Maximum (PETM) was a global warming event that occurred about 56 million years ago, and is commonly thought to have been driven primarily by the destabilization of carbon from surface sedimentary reservoirs such as methane hydrates. However, it remains controversial whether such reservoirs were indeed the source of the carbon that drove the warming. Resolving this issue is key to understanding the proximal cause of the warming, and to quantifying the roles of triggers versus feedbacks. Here we present boron isotope data—a proxy for seawater pH—that show that the ocean surface pH was persistently low during the PETM. We combine our pH data with a paired carbon isotope record in an Earth system model in order to reconstruct the unfolding carbon-cycle dynamics during the event. We find strong evidence for a much larger (more than 10,000 petagrams)—and, on average, isotopically heavier—carbon source than considered previously. This leads us to identify volcanism associated with the North Atlantic Igneous Province, rather than carbon from a surface reservoir, as the main driver of the PETM. This finding implies that climate-driven amplification of organic carbon feedbacks probably played only a minor part in driving the event. However, we find that enhanced burial of organic matter seems to have been important in eventually sequestering the released carbon and accelerating the recovery of the Earth system.

Shallow marine ostracode turnover in response to environmental change during the Paleocene-Eocene thermal maximum in northwest Tunisia

NASA Astrophysics Data System (ADS)

Morsi, Abdel-Mohsen M.; Speijer, Robert P.; Stassen, Peter; Steurbaut, Etienne

2011-02-01

Two outcrop sections spanning the Paleocene-early Eocene boundary in the Sidi Nasseur-Wadi Mezaz area in northwest Tunisia provided rich ostracode assemblages, yielding 26 species of which three are newly described: Reymenticosta bassiounii, Reymenticosta nasseurensis and Buntonia? tunisiensis. The recorded ostracode fauna and associated foraminifera reflect deposition in a coastal to inner neritic environment. Many of the recorded taxa have a wide geographic distribution throughout the Middle East and North Africa. A correspondence is also observed with West African faunas, especially in the early Eocene fauna. These taxa seem to have originated in West Africa during the Paleocene and migrated northwards during the late Paleocene to early Eocene. Sea-level change and decrease in oxygenation associated with the Paleocene-Eocene thermal maximum (PETM) caused the local disappearance of the South Tethyan Paleocene fauna represented by Paracosta kefensis (morphotype-A), Paracosta aff. paleomokattamensis, Paracypris sp. B Esker, Loxoconcha saharaensis, Buntonia sp. 3 Donze et al., Protobuntonia nakkadii, and probably Reymenticosta bassiounii and R. nasseurensis. Simultaneously, a new but poorly diverse Afro-Tethyan fauna, mainly represented by Alocopocythere attitogonensis and Buntonia? tunisiensis, settled in the studied part of the basin. After the PETM, diversity increased again as various taxa (e.g. Bairdia aegyptiaca, Reticulina lamellata and Aegyptiana duwiensis) (re)appeared. Although detailed records across the P/E boundary are still sparse, it appears that the PETM exerted significant influence on the paleobiogeography and composition of Tethyan ostracode faunas.

Cerium Anomalies in Fossil Fish Teeth Reveal Changes in Bottom Water Oxygenation

NASA Astrophysics Data System (ADS)

Chun, C. O.; Scher, H. D.; Delaney, M. L.

2007-12-01

Shale-normalized rare earths and yttrium (REY) concentrations of fossil fish teeth in deep sea sediments display prominent negative cerium (Ce) anomalies and positive yttrium (Y) anomalies. These features are ultimately inherited from seawater and strongly indicate that fossil fish teeth preserve a seawater REY signature. In seawater, Ce+3 is oxidized to Ce+4, and Ce becomes depleted relative to the other REY's as it partitions into other phases (e.g., ferromanganese oxyhydroxides). The magnitude of Ce depletion in a water mass is thus related to its oxygen content. We hypothesize that changes in the oxygenation of bottom waters may be revealed by examining downcore variability in the magnitude of the Ce anomaly of fossil fish teeth. To test this hypothesis, REY concentrations were measured on samples of cleaned fossil fish teeth recovered from the late Paleogene to early Eocene sections of Ocean Drilling Program (ODP) Sites 1262 and 1263 (lower and upper Walvis Ridge, ODP Leg 208, South Atlantic Ocean). These sites are vertically offset (early Eocene paleodepths were 3700 and 1700 meters, respectively) and have been extensively studied to characterize the oceanic response to the Paleocene/Eocene Thermal Maximum (PETM). Manganese enrichment factors (Mn EF) determined from total digestions of samples from these sites reveal abrupt changes in the oxygenation of bottom waters across the PETM interval. Mn EF's decrease to crustal values (~1) during the PETM, which reflects the reduction of Mn oxides as bottom water oxygen levels were depleted. Mn EF's begin to increase to 6-8 during the 'recovery phase' following the PETM. The Ce anomaly for these samples, Ce/Ce*, was calculated according to the geometric approach reported by Lawrence et al. (2006, Aquatic Geochemistry 12, 39-72), where Ce* represents an interpolation of the expected shale-normalized Ce concentration from near neighbors. In this notation, when Ce/Ce* = 1 no Ce anomaly is present. At upper Walvis Ridge downcore Ce anomalies show a distinct excursion from pre-PETM values between 0.7-0.8 to values ~1.0 during the PETM event. The values return to pre-excursion levels during the recovery phase following the PETM. The results of this study closely follow the evolution of Mn EF's at Walvis Ridge sites. The smallest Ce anomalies (i.e., Ce/Ce* = 1) coincide with Mn EF's of 1, which provide independent evidence for low oxygen levels in the bottom waters bathing these locations. These results confirm the hypothesis that Ce anomalies in fossil fish teeth can be used to assess changes in the oxygenation of bottom waters.

Distributions of Benthic Foraminifera in the Salisbury Embayment before and after the PETM Onset

NASA Astrophysics Data System (ADS)

Range, M. M.; Robinson, M. M.

2017-12-01

Abrupt climatic perturbations associated with the onset of the Paleocene-Eocene Thermal Maximum (PETM) caused major disruptions to the shallow shelf ecology along the U.S. Atlantic Coastal Plain. Several studies examine the changes in benthic foraminiferal assemblages across the PETM in neritic sediments in New Jersey, Maryland, and Virginia and describe a hydrological and sedimentological paradigm shift that marks the Paleocene-Eocene boundary. In the Salisbury Embayment, a flexural low between the South Jersey High and the Norfolk Arch, this shift is seen in the transition between the upper Paleocene Aquia Formation and the lower Eocene Marlboro Clay. Here we map the abundance of seven benthic foraminifera species from five sites within the Salisbury Embayment from both the uppermost Aquia Formation and the lowermost Marlboro Clay. In addition to the benthic foraminiferal turnover at the PETM onset, we show a geographic distribution of species that highlights a past latitudinal biogeographic zonation not unlike what is found on the modern shelf in this region. Sites document a change in the abundance of species between the late Paleocene and early Eocene, showing a decrease in biodiversity of benthic species along the U.S. Atlantic Coast. Spatial extent of the different species also changed across the Paleocene-Eocene boundary. On the modern Atlantic shelf, a biogeographic zonation is due to the path of the Gulf Stream marking a boundary between relatively cold sea-surface temperatures to the north and warmer temperatures to the south, guided by the geomorphic expression of the mid-Atlantic coastline. During the Paleocene-Eocene transition, we suspect a similar boundary likely existed between the New Jersey sites and the Maryland and Virginia sites. We speculate that with the addition of more assemblage data, we will be able to partially reconstruct the geomorphic expression of the PETM coastline and/or the path of major coastal ocean currents.

Re-evaluating the isotopic divide between angiosperms and gymnosperms using n-alkane δ13C values

NASA Astrophysics Data System (ADS)

Bush, R. T.; McInerney, F. A.

2009-12-01

Angiosperm δ13C values are typically 1-3‰ more negative than those of co-occurring gymnosperms. This is known for both bulk leaf and compound-specific values from n-alkanes, which are stable, straight-chain hydrocarbons (C23-C35) found in the epicuticular leaf wax of vascular plants. For n-alkanes, there is a second distinction between the δ13C values of angiosperms and gymnosperms—δ13C values generally decrease with increasing chain-length in angiosperms, while in gymnosperms they increase. These two distinctions have been used to support the ‘plant community change hypothesis’ explaining the difference between the terrestrial and marine carbon isotope excursions during the Paleocene-Eocene Thermal Maximum (PETM.) Preserved n-alkanes from terrestrial paleosols in the Bighorn Basin, Wyoming reveal a negative carbon isotope excursion during the PETM of 4-5‰, which is 1-2‰ greater than the excursion recorded by marine carbonates. The local plant community, known from macrofossils as well as palynoflora, shifted from a deciduous, mixed angiosperm/gymnosperm flora to a suite of evergreen angiosperm species during the PETM. At the end of the PETM, the community returned to a mixed deciduous flora very similar to the original. This change in the plant community could thus magnify the terrestrial negative carbon isotope excursion to the degree necessary to explain its divergence from the marine record. However, the comparison between modern angiosperms and gymnosperms has been made mostly between broadleaf, deciduous angiosperms and evergreen, coniferous gymnosperms. New data analyzing deciduous, coniferous gymnosperms, including Metasequoia glyptostroboides and Taxodium distichum, suggests that the division previously ascribed to taxonomy may actually be based on leaf habit and physiology, specifically broadleaf, deciduous versus needle-leaf, evergreen plants. If differences in n-alkane δ13C values can be described not as angiosperms versus gymnosperms, but as deciduous versus evergreen plants, then a re-examination of the PETM terrestrial carbon isotope excursion and its causes may be necessary.

Fish production and diversity in the Paleocene-Eocene Thermal Maximum—Increased production but no novel faunas during a "Future Earth" analog

NASA Astrophysics Data System (ADS)

Tomczik, D. W.; Norris, R. D.; Gaskell, D. E.

2014-12-01

A partial analog for future global change is the Paleocene-Eocene Thermal Maximum—a transient episode of warming, acidification, and biogeographic change at ~55.5 Ma. The PETM is known to have triggered extinction in some deep sea biotas, extensive biogeographic range shifts, and the common occurrence of 'excursion biotas'—non-analog occurrences of species that are typically rare in the open ocean before or after the PETM. Here we report on the impact of the PETM on fish production and biodiversity. Our data include the mass accumulation rate of fish teeth and denticles as well as an analysis of tooth morphotypes for three PETM sites: ODP 1220 and 1209 in the Pacific, and ODP 1260 in the equatorial Atlantic. Tooth morphotypes hardly change through the PETM and consist of abundant midwater species (angler fish and flashlight fish) in addition to sharks and epipelagic fish. There is no evidence for a non-analog 'excursion biota' during the PETM, suggesting that fish experienced fewer geographic range shifts than the calcareous and organic-walled plankton where excursion biotas are commonplace. Fish mass accumulation rates are also relatively stable before and after the PETM although all sites show a transient rise in fish production at the onset of the PETM or within the later part of the "PETM Core". These results broadly match published estimates of PETM export production from biogenic barium fluxes. Our findings run counter to "Future Earth" models that use climate forecasts for the next century to predict the impact of global change on fish stocks. These models suggest that future warming and ocean stratification will decrease most tropical and subtropical ocean fish production, accentuate fish production in the boundary currents and generally shift production toward higher latitudes. A resolution of "Future Earth" models and PETM data may reflect the different timescales of observation and stages of ecological response to severe global change.

Characterizing the Response of Fluvial Systems to Extreme Global Warming During the Early Eocene Climatic Optimum: An Analysis of the Wasatch and Green River Formations, Uinta Basin, UT

NASA Astrophysics Data System (ADS)

Jones, E. R.; Plink-Bjorklund, P.

2013-12-01

The Wasatch and Green River Formations in the Uinta Basin, UT contain fluvial sandstones that record changes in terrestrial sedimentation coincident with Paleocene-Eocene Thermal Maximum (PETM) and at least six post-PETM hyperthermal climate change events. While proxies for chemical weathering rates during the PETM have been developed using the marine osmium isotope record, to date there has been little research on chemical weathering rates in proximal terrestrial depocenters. This work is one part of a multi-proxy research effort combining quantitative petrographic analysis, the stable carbon isotope record, and a high-resolution stratigraphic and sedimentologic framework across the southern margin of the Uinta Basin. Relative tectonic quiescence in the Uinta Basin during the Early Eocene suggests that climate is the forcing mechanism controlling fluvial architecture and composition, and gradual basin subsidence has preserved at least six pulses of greenhouse climate change during the Early Eocene Climatic Optimum (EECO). Terrestrial records of PETM climate do not support a humid climate with increased precipitation as previously suggested from marine proxies of climate change. Instead, terrestrial records of the PETM climate show evidence of prolonged drought punctuated by intense terrestrial flooding events in mid-latitude continental interiors. Increases in chemical weathering rates during the PETM due to increased temperature and average precipitation is cited as a key carbon sink to initiate a recovery phase where atmospheric CO2 returned to normal concentrations. If terrestrial records of chemical weathering rates differ substantially from marine proxies the carbon-cycle dynamics active during the EECO must be reconsidered. Initial results of this study show that these peak hyperthermal climate change conditions in the Uinta Basin preserve more compositionally and texturally immature sediments due to extremely high erosion and deposition rates, and subdued duration of transport. In particular the relative proportions of preserved potassium and especially plagioclase feldspar are sensitive to these pulses of greenhouse climate change. This dataset suggests that the seasonality of sediment dispersal and transport can play a more important role in the preservation potential of unstable mineral phases in the sedimentary record than just variations in global chemical weathering rates. Compositional variability in perenially wet and peaked seasonality facies in fluvial sandstones in the Wasatch Formation.

Evidence for a rapid release of carbon at the Paleocene-Eocene thermal maximum.

PubMed

Wright, James D; Schaller, Morgan F

2013-10-01

The Paleocene/Eocene thermal maximum (PETM) and associated carbon isotope excursion (CIE) are often touted as the best geologic analog for the current anthropogenic rise in pCO2. However, a causal mechanism for the PETM CIE remains unidentified because of large uncertainties in the duration of the CIE's onset. Here, we report on a sequence of rhythmic sedimentary couplets comprising the Paleocene/Eocene Marlboro Clay (Salisbury Embayment). These couplets have corresponding δ(18)O cycles that imply a climatic origin. Seasonal insolation is the only regular climate cycle that can plausibly account for δ(18)O amplitudes and layer counts. High-resolution stable isotope records show 3.5‰ δ(13)C decrease over 13 couplets defining the CIE onset, which requires a large, instantaneous release of (13)C-depleted carbon. During the CIE, a clear δ(13)C gradient developed on the shelf with the largest excursions in shallowest waters, indicating atmospheric δ(13)C decreased by ~20‰. Our observations and revised release rate are consistent with an atmospheric perturbation of 3,000-gigatons of carbon (GtC).

Evidence for a rapid release of carbon at the Paleocene-Eocene thermal maximum

PubMed Central

Wright, James D.; Schaller, Morgan F.

2013-01-01

The Paleocene/Eocene thermal maximum (PETM) and associated carbon isotope excursion (CIE) are often touted as the best geologic analog for the current anthropogenic rise in pCO2. However, a causal mechanism for the PETM CIE remains unidentified because of large uncertainties in the duration of the CIE’s onset. Here, we report on a sequence of rhythmic sedimentary couplets comprising the Paleocene/Eocene Marlboro Clay (Salisbury Embayment). These couplets have corresponding δ18O cycles that imply a climatic origin. Seasonal insolation is the only regular climate cycle that can plausibly account for δ18O amplitudes and layer counts. High-resolution stable isotope records show 3.5‰ δ13C decrease over 13 couplets defining the CIE onset, which requires a large, instantaneous release of 13C-depleted carbon. During the CIE, a clear δ13C gradient developed on the shelf with the largest excursions in shallowest waters, indicating atmospheric δ13C decreased by ∼20‰. Our observations and revised release rate are consistent with an atmospheric perturbation of 3,000-gigatons of carbon (GtC). PMID:24043840

Eocene Hyperthermal Event Offers Insight Into Greenhouse Warming

NASA Astrophysics Data System (ADS)

Bowen, Gabriel J.; Bralower, Timothy J.; Delaney, Margaret L.; Dickens, Gerald R.; Kelly, Daniel C.; Koch, Paul L.; Kump, Lee R.; Meng, Jin; Sloan, Lisa C.; Thomas, Ellen; Wing, Scott L.; Zachos, James C.

2006-04-01

What happens to the Earth's climate, environment, and biota when thousands of gigatons of greenhouse gases are rapidly added to the atmosphere? Modern anthropogenic forcing of atmospheric chemistry promises to provide an experiment in such change that has not been matched since the early Paleogene, more than 50 million years ago (Ma),when catastrophic release of carbon to the atmosphere drove abrupt, transient, hyperthermal events. Research on the Paleocene-Eocene Thermal Maximum (PETM)-the best documented of these events, which occurred about 55 Ma-has advanced significantly since its discovery 15 years ago. During the PETM, carbon addition to the oceans and atmosphere was of a magnitude similar to that which is anticipated through the 21st century. This event initiated global warming, biotic extinction and migration, and fundamental changes in the carbon and hydrological cycles that transformed the early Paleogene world.

Integrin-targeted pH-responsive micelles for enhanced efficiency of anticancer treatment in vitro and in vivo

NASA Astrophysics Data System (ADS)

Liu, Jinjian; Deng, Hongzhang; Liu, Qiang; Chu, Liping; Zhang, Yumin; Yang, Cuihong; Zhao, Xuefei; Huang, Pingsheng; Deng, Liandong; Dong, Anjie; Liu, Jianfeng

2015-02-01

The key to developing more nanocarriers for the delivery of drugs in clinical applications is to consider the route of the carrier from the administration site to the target tissue and to look for a simple design to complete this whole journey. We synthesized the amphiphilic copolymer cRGDfK-poly(ethylene glycol)-b-poly(2,4,6-trimethoxybenzylidene-1,1,1-tris(hydroxymethyl) ethane methacrylate) (cRGD-PETM) to construct multifunctional micelles. These micelles combined enhanced drug-loading efficiency with tumor-targeting properties, visual detection and controllable intracellular drug release, resulting in an improved chemotherapeutic effect in vivo. Doxorubicin (DOX) was encapsulated within the cRGD-PETM micelles as a model drug (termed as cRGD-PETM/DOX Ms). The size and morphology of the micelles were characterized systematically. As a result of the hydrophobic interaction and the π-π conjugation between the DOX molecules and the PTTMA copolymers, the cRGD-PETM/DOX Ms showed an excellent drug-loading capacity. The results of in vitro drug-release studies indicated that the cumulative release of DOX from cRGD-PETM/DOX Ms at pH 5.0 was twice that at pH 7.4. The results of fluorescent microscopic analysis showed that the cRGD-PETM/DOX Ms could be internalized by 4T1 and HepG2 cells via receptor-mediated endocytosis with rapid intracellular drug release, which resulted in increased cytotoxicity compared with free DOX. Ex vivo imaging studies showed that the cRGD-PETM/DOX Ms improved the accumulation and retention of the drug in tumor tissues. Studies of the in vivo anticancer effects showed that the cRGD-PETM/DOX Ms had a significantly higher therapeutic efficacy with lower side-effects than free DOX and PETM/DOX Ms. These results show that the multifunctional cRGD-PETM/DOX Ms have great potential as vehicles for the delivery of hydrophobic anticancer drugs.

Constraints on the duration of the Paleocene-Eocene Thermal Maximum by orbitally-influenced fluvial sediment records of the northern Bighorn Basin, Wyoming, USA

NASA Astrophysics Data System (ADS)

van der Meulen, Bas; Abels, Hemmo; Meijer, Niels; Gingerich, Philip; Lourens, Lucas

2016-04-01

The addition of major amounts of carbon to the exogenic carbon pool caused rapid climate change and faunal turnover during the Paleocene-Eocene Thermal Maximum (PETM) around 56 million years ago. Constraints are still needed on the duration of the onset, main body, and recovery of the event. The Bighorn Basin in Wyoming provides expanded terrestrial sections spanning the PETM and lacking the carbonate dissolution present in many marine records. Here we provide new carbon isotope records for the Polecat Bench and Head of Big Sand Coulee sections, two parallel sites in the northern Bighorn Basin, at unprecedented resolution. Cyclostratigraphic analysis of these fluvial sediment records using descriptive sedimentology and proxy records allows subdivision into intervals dominated by avulsion deposits and intervals dominated by overbank deposits. These sedimentary sequences alternate in a regular fashion and are related to climatic precession. Correlation of the two, 8-km-spaced sections shows that the avulsion-overbank cycles are laterally consistent. The presence of longer-period alternations, related to modulation by the 100-kyr eccentricity cycle, corroborates the precession influence on the sediments. Sedimentary cyclicity is then used to develop a floating precession-scale age model for the PETM carbon isotope excursion (CIE). We find a CIE body encompassing 95 kyrs aligning with marine cyclostratigraphic age models. The duration of the CIE onset is estimated at 5 kyrs, but difficult to determine because sedimentation rates vary at the sub-precession scale. The CIE recovery starts with a 2 to 4 per mille step and lasts 40 or 90 kyrs, depending on what is considered the carbon isotope background state.

Rethinking the global carbon cycle with a large, dynamic and microbially mediated gas hydrate capacitor

NASA Astrophysics Data System (ADS)

Dickens, Gerald R.

2003-08-01

Prominent negative δ13C excursions characterize several past intervals of abrupt (<100 kyr) environmental change. These anomalies, best exemplified by the >2.5‰ drop across the Paleocene/Eocene thermal maximum (PETM) ca. 55.5 Ma, command our attention because they lack explanation with conventional models for global carbon cycling. Increasingly, Earth scientists have argued that they signify massive release of CH4 from marine gas hydrates, although typically without considering the underlying process or the ensuing ramifications of such an interpretation. At the most basic level, a large, dynamic 'gas hydrate capacitor' stores and releases 13C-depleted carbon at rates linked to external conditions such as deep ocean temperature. The capacitor contains three internal reservoirs: dissolved gas, gas hydrate, and free gas. Carbon enters and leaves these reservoirs through microbial decomposition of organic matter, anaerobic oxidation of CH4 in shallow sediment, and seafloor gas venting; carbon cycles between these reservoirs through several processes, including fluid flow, precipitation and dissolution of gas hydrate, and burial. Numerical simulations show that simple gas hydrate capacitors driven by inferred changes in bottom water warming during the PETM can generate a global δ13C excursion that mimics observations. The same modeling extended over longer time demonstrates that variable CH4 fluxes to and from gas hydrates can partly explain other δ13C excursions, rapid and slow, large and small, negative and positive. Although such modeling is rudimentary (because processes and variables in modern and ancient gas hydrate systems remain poorly constrained), acceptance of a vast, externally regulated gas hydrate capacitor forces us to rethink δ13C records and the operation of the global carbon cycle throughout time.

Paleohydrologic change across the Paleocene-Eocene Thermal Maximum, Bighorn Basin, WY

NASA Astrophysics Data System (ADS)

Baczynski, A. A.; McInerney, F. A.; Wing, S. L.; Kraus, M. J.

2013-12-01

One of the uncertainties in accurately predicting future climate change involves how the hydrologic cycle will respond to increasing pCO2 and temperature. Quantifying the relationship between carbon cycle perturbations and the hydrologic cycle in the geologic past is crucial to understanding and accurately modeling how anthropogenic carbon emissions will affect future changes in the hydrologic cycle. Records of paleohydrologic response to global warming in the geologic past are rare, particularly for continental interiors, where climate model projections of precipitation are highly uncertain. Here we examine hydrogen isotope ratios of leaf waxes as a tool for reconstructing paleohydrologic change in the continental interior of North America across the Paleocene-Eocene Thermal Maximum (PETM), an abrupt, transient episode of extreme global warming ~56 Ma. New hydrogen isotope measurements of leaf-wax n-alkanes from the southeastern Bighorn Basin, Wyoming record two positive shifts during the PETM. n-Alkane δD values first shift to more positive values just after the onset of the carbon isotope excursion and then again higher up in the body of the carbon isotope excursion, with a return to slightly more negative δD values in between. Paleobotanical, paleopedologic, and isotope data from the same field area have suggested that the Bighorn Basin may have experienced a drier or more seasonally dry climate during the PETM. Mean annual precipitation estimates based on paleosol major oxides, soil wetness assessed using the soil morphology index, and an aridity proxy based on differences in δ18O values of tooth enamel in aridity-sensitive and aridity-insensitive mammals each independently suggest a potential two-phase drying within the PETM interval. Similarly, the hydrogen isotope record could reflect two periods of drying, with a return to slightly wetter conditions in between. However, leaf-wax hydrogen isotope ratios reflect not only source water hydrogen isotope values but also deuterium-enrichment resulting from soil evaporation and transpiration. Interpretation of hydrogen isotope records requires consideration of both of these factors. To examine the potential roles of changes in source water isotopic composition and transpirational D-enrichment, we compare the hydrogen isotope ratios of leaf waxes with the oxygen isotope ratios of tooth enamel from Coryphodon, a large herbivore and an obligate drinker. The Coryphodon tooth enamel δ18O record enables us to constrain shifts in surface water isotope values. Relative humidity of paleoenvironments can then be explored using a modified Craig-Gordon model for transpirational D-enrichment. Preliminary calculations suggest that relative humidity increased during the PETM, contrary to the drying suggested by all other aridity proxies. One possibility is that leaf waxes record only the relative humidity at the time of leaf formation. Therefore, the n-alkane δD record could reflect an increase in seasonality of precipitation, with greater relative humidity during the early growing season. To evaluate the validity of this approach, we will systematically examine the assumptions involved in using hydrogen isotope ratios of leaf waxes as a paleoaridity index to evaluate paleohydrologic changes in the Bighorn Basin during the PETM.

The extended Price equation quantifies species selection on mammalian body size across the Palaeocene/Eocene Thermal Maximum.

PubMed

Rankin, Brian D; Fox, Jeremy W; Barrón-Ortiz, Christian R; Chew, Amy E; Holroyd, Patricia A; Ludtke, Joshua A; Yang, Xingkai; Theodor, Jessica M

2015-08-07

Species selection, covariation of species' traits with their net diversification rates, is an important component of macroevolution. Most studies have relied on indirect evidence for its operation and have not quantified its strength relative to other macroevolutionary forces. We use an extension of the Price equation to quantify the mechanisms of body size macroevolution in mammals from the latest Palaeocene and earliest Eocene of the Bighorn and Clarks Fork Basins of Wyoming. Dwarfing of mammalian taxa across the Palaeocene/Eocene Thermal Maximum (PETM), an intense, brief warming event that occurred at approximately 56 Ma, has been suggested to reflect anagenetic change and the immigration of small bodied-mammals, but might also be attributable to species selection. Using previously reconstructed ancestor-descendant relationships, we partitioned change in mean mammalian body size into three distinct mechanisms: species selection operating on resident mammals, anagenetic change within resident mammalian lineages and change due to immigrants. The remarkable decrease in mean body size across the warming event occurred through anagenetic change and immigration. Species selection also was strong across the PETM but, intriguingly, favoured larger-bodied species, implying some unknown mechanism(s) by which warming events affect macroevolution. © 2015 The Author(s).

Changes in seasonality and productivity recorded at low latitudes in Tanzania during the PETM

NASA Astrophysics Data System (ADS)

O'Halloran, A.; Nicholas, C. J.; Goodhue, R.

2010-12-01

The Tanzanian Drilling Project (TDP) has been active since 2002 in recovering Cretaceous and Paleogene marine sediments from along a 150km piece of coast in southern Tanzania. Late Cretaceous and Paleogene sediments along this stretch of coast are part of the Kilwa Group (Nicholas et al., 2006). The sediments largely comprise organic-rich marine clays and claystones, with occasional interbedded limestones and sporadic carbonate-rich beds. Calcareous microfossils are generally very well preserved, due to the impermeability of the clays and claystones, and do not show the recrystallised microstructure typical of deep-sea oozes and chalks (Pearson et al., 2001). van Dongen et al. (2006) have shown that the Kilwa Group sediments contain well preserved terrestrial biomarkers, indicating a shallow maximum burial depth. The sediments are interpreted as having been deposited in a bathyal outer shelf to upper slope setting at an estimated depth of 300-500m. TDP Site 14 recovered sediments from the very latest Paleocene and the Paleocene-Eocene Thermal Maximum. These well preserved, organic-rich clays were analysed using three separate techniques designed to complement the standard paleoclimatic analyses of planktonic and benthic foraminifera and nannofossils carried out by other workers. Nitrogen isotope chemostratigraphy is used in this work as a proxy for past productivity and associated nutrient supply. In order to identify any other potential contributors to, or dilution of the nitrogen isotope signal, sedimentary mineralogy and elemental geochemistry techniques were also employed. The results from mineralogy and elemental geochemistry analyses indicate that terrigenous run-off increased during the PETM at this locaton. Kaolinite abundances, meanwhile, show that this region did not experience any major changes in humidity. Mineralogical investigation also found a large reduction in calcium carbonate in these sediments during the PETM interval. Finally, nitrogen isotope chemostratigraphy recorded an increase in its regular cyclicity recorded prior to the PETM. In conclusion, this data suggests that the southern coast of Tanzania was a place of extreme local climate with wetter and more intense precipitation in the rainy season. The rainy season may even have become longer, much like the effects of modern El Niño. The weathering in this region would have been intensified during the PETM, with older and deeper soils being eroded and washed out to sea in swollen rivers, where they were deposited as far out as the mid to outer shelf. These influxes of terrestrial sediment brought nutrients to the lightly acidified upper levels of the ocean allowing what planktonic life remained there to flourish for a time, driving down their nitrogen isotope signal, which was then recorded in the marine sediments as they died. Nicholas et al., 2006, Journal of African Earth Sciences, v. 45, p. 431. Pearson et al.., 2001, Nature, v. 413, p. 481-487. van Dongen, et al., 2006, Organic Geochemistry, v. 37, p. 539-557.

Large volcanic eruptions and the PETM: Geochemistry from the Fur Formation, Denmark

NASA Astrophysics Data System (ADS)

Jones, Morgan; Svensen, Henrik; Tegner, Christian; Planke, Sverre; Willumsen, Pi

2015-04-01

The opening of the North Atlantic Ocean during the early Cenozoic was accompanied by substantial volcanism that resulted in the deposition of numerous ash layers over much of northern Europe. This volcanism was contemporaneous with the extreme greenhouse climate of the Palaeocene-Eocene Thermal Maximum (PETM), and is therefore of particular interest for volcanism-climate interactions. The island of Fur, northern Denmark, contains abundant outcrops of volcanic ash layers deposited in a shallow marine environment. Over 179 distinct ash horizons (those greater than ~1 cm are numbered #-39 to #+140) are found within the ~60 m thick Fur Formation. The ash layers are predominantly black and composed of volcanic glass particles ranging from silt to sand in size. Each bed is normally graded and lacks any evidence of significant reworking. There were no volcanoes in the vicinity of Fur during this time, and the outcrops are >700 km from the break-up axis, indicating that at least some of the ash layers were formed during very large eruptions and transported a long way from the source volcanoes. A few thick grey ash layers (e.g. #-33 and #+19) are believed to have originated from volcanoes in East Greenland. Here we present geochemical data from two key sections within the Fur Formation, a beach section at Stolleklint where ashes #-34 to #-31 are exposed, and a quarry section at Jenshøj that covers ashes #+17 to #+35. The #-33 and #+19 ashes are both prominent marker horizons around 15-20 cm thick. The Stolleklint section is clay rich while the quarry section is dominated by diatomite. At Stolleklint, bulk rock total organic carbon (TOC) δ13C values throughout a 1.5 m section are relatively steady at -30.7 to -31.7 o typical of the carbon isotope excursion values of the PETM at Fur. Just above ash layer #-33, δ13C = -27.9 o characteristic of post-PETM values. The bulk rock TOC is high, 1.5 to 4 wt. %. The post-PETM quarry section is much poorer in organic material (0-0.5 wt. % TOC). Values of δ13C are more varied than at Stolleklint, scatter around -28.0 o in the lower 0.5 m. A small negative δ13C excursion occurs just above the thick #+19 ash layer, followed by a slow recovery to less negative values up section. This suggests a possible causal relation between the ash deposition and the carbon isotope record, as diminished primary productivity is typified by negative δ13C TOC values. These results indicate that North-Atlantic volcanism had significant repercussions and could have played a role in the termination of the PETM.

Beyond methane: Towards a theory for the Paleocene-Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Higgins, John A.; Schrag, Daniel P.

2006-05-01

Extreme global warmth and an abrupt negative carbon isotope excursion during the Paleocene-Eocene Thermal Maximum (PETM) have been attributed to a massive release of methane hydrate from sediments on the continental slope [1]. However, the magnitude of the warming (5 to 6 °C [2],[3]) and rise in the depth of the CCD (> 2 km; [4]) indicate that the size of the carbon addition was larger than can be accounted for by the methane hydrate hypothesis. Additional carbon sources associated with methane hydrate release (e.g. pore-water venting and turbidite oxidation) are also insufficient. We find that the oxidation of at least 5000 Gt C of organic carbon is the most likely explanation for the observed geochemical and climatic changes during the PETM, for which there are several potential mechanisms. Production of thermogenic CH4 and CO2 during contact metamorphism associated with the intrusion of a large igneous province into organic rich sediments [5] is capable of supplying large amounts of carbon, but is inconsistent with the lack of extensive carbon loss in metamorphosed sediments, as well as the abrupt onset and termination of carbon release during the PETM. A global conflagration of Paleocene peatlands [6] highlights a large terrestrial carbon source, but massive carbon release by fire seems unlikely as it would require that all peatlands burn at once and then for only 10 to 30 ky. In addition, this hypothesis requires an order of magnitude increase in the amount of carbon stored in peat. The isolation of a large epicontinental seaway by tectonic uplift associated with volcanism or continental collision, followed by desiccation and bacterial respiration of the aerated organic matter is another potential mechanism for the rapid release of large amounts of CO2. In addition to the oxidation of the underlying marine sediments, the desiccation of a major epicontinental seaway would remove a large source of moisture for the continental interior, resulting in the desiccation and bacterial oxidation of adjacent terrestrial wetlands.

Synchronizing early Eocene deep-sea and continental records - cyclostratigraphic age models for the Bighorn Basin Coring Project drill cores

NASA Astrophysics Data System (ADS)

Westerhold, Thomas; Röhl, Ursula; Wilkens, Roy H.; Gingerich, Philip D.; Clyde, William C.; Wing, Scott L.; Bowen, Gabriel J.; Kraus, Mary J.

2018-03-01

A consistent chronostratigraphic framework is required to understand the effect of major paleoclimate perturbations on both marine and terrestrial ecosystems. Transient global warming events in the early Eocene, at 56-54 Ma, show the impact of large-scale carbon input into the ocean-atmosphere system. Here we provide the first timescale synchronization of continental and marine deposits spanning the Paleocene-Eocene Thermal Maximum (PETM) and the interval just prior to the Eocene Thermal Maximum 2 (ETM-2). Cyclic variations in geochemical data come from continental drill cores of the Bighorn Basin Coring Project (BBCP, Wyoming, USA) and from marine deep-sea drilling deposits retrieved by the Ocean Drilling Program (ODP). Both are dominated by eccentricity-modulated precession cycles used to construct a common cyclostratigraphic framework. Integration of age models results in a revised astrochronology for the PETM in deep-sea records that is now generally consistent with independent 3He age models. The duration of the PETM is estimated at ˜ 200 kyr for the carbon isotope excursion and ˜ 120 kyr for the associated pelagic clay layer. A common terrestrial and marine age model shows a concurrent major change in marine and terrestrial biota ˜ 200 kyr before ETM-2. In the Bighorn Basin, the change is referred to as Biohorizon B and represents a period of significant mammalian turnover and immigration, separating the upper Haplomylus-Ectocion Range Zone from the Bunophorus Interval Zone and approximating the Wa-4-Wa-5 land mammal zone boundary. In sediments from ODP Site 1262 (Walvis Ridge), major changes in the biota at this time are documented by the radiation of a second generation of apical spine-bearing sphenolith species (e.g., S. radians and S. editus), the emergence of T. orthostylus, and the marked decline of D. multiradiatus.

Shallow marine response to global climate change during the Paleocene-Eocene Thermal Maximum, Salisbury Embayment, USA

USGS Publications Warehouse

Self-Trail, Jean; Robinson, Marci M.; Bralower, Timothy J.; Sessa, Jocelyn A.; Hajek, Elizabeth A.; Kump, Lee R.; Trampush, Sheila M.; Willard, Debra A.; Edwards, Lucy E.; Powars, David S.; Wandless, Gregory A.

2017-01-01

The Paleocene-Eocene Thermal Maximum (PETM) was an interval of extreme warmth that caused disruption of marine and terrestrial ecosystems on a global scale. Here we examine the sediments, flora, and fauna from an expanded section at Mattawoman Creek-Billingsley Road (MCBR) in Maryland and explore the impact of warming at a nearshore shallow marine (30–100 m water depth) site in the Salisbury Embayment. Observations indicate that at the onset of the PETM, the site abruptly shifted from an open marine to prodelta setting with increased terrestrial and fresh water input. Changes in microfossil biota suggest stratification of the water column and low-oxygen bottom water conditions in the earliest Eocene. Formation of authigenic carbonate through microbial diagenesis produced an unusually large bulk carbon isotope shift, while the magnitude of the corresponding signal from benthic foraminifera is similar to that at other marine sites. This proves that the landward increase in the magnitude of the carbon isotope excursion measured in bulk sediment is not due to a near instantaneous release of 12C-enriched CO2. We conclude that the MCBR site records nearshore marine response to global climate change that can be used as an analog for modern coastal response to global warming.

Shallow marine response to global climate change during the Paleocene-Eocene Thermal Maximum, Salisbury Embayment, USA

NASA Astrophysics Data System (ADS)

Self-Trail, Jean M.; Robinson, Marci M.; Bralower, Timothy J.; Sessa, Jocelyn A.; Hajek, Elizabeth A.; Kump, Lee R.; Trampush, Sheila M.; Willard, Debra A.; Edwards, Lucy E.; Powars, David S.; Wandless, Gregory A.

2017-07-01

The Paleocene-Eocene Thermal Maximum (PETM) was an interval of extreme warmth that caused disruption of marine and terrestrial ecosystems on a global scale. Here we examine the sediments, flora, and fauna from an expanded section at Mattawoman Creek-Billingsley Road (MCBR) in Maryland and explore the impact of warming at a nearshore shallow marine (30-100 m water depth) site in the Salisbury Embayment. Observations indicate that at the onset of the PETM, the site abruptly shifted from an open marine to prodelta setting with increased terrestrial and fresh water input. Changes in microfossil biota suggest stratification of the water column and low-oxygen bottom water conditions in the earliest Eocene. Formation of authigenic carbonate through microbial diagenesis produced an unusually large bulk carbon isotope shift, while the magnitude of the corresponding signal from benthic foraminifera is similar to that at other marine sites. This proves that the landward increase in the magnitude of the carbon isotope excursion measured in bulk sediment is not due to a near instantaneous release of 12C-enriched CO2. We conclude that the MCBR site records nearshore marine response to global climate change that can be used as an analog for modern coastal response to global warming.

Occurrence of gigantic biogenic magnetite during the Paleocene-Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Schumann, D.; Raub, T. D.; Kopp, R. E.; Guerquin-Kern, J. L.; Wu, T. D.; Rouiller, I.; Smirnov, A. V.; Sears, S. K.; Lücken, U.; Tikoo, S. M.; Hesse, R.; Kirschvink, J. L.; Vali, H.

2009-04-01

The Paleocene-Eocene Thermal Maximum (PETM) is one of the most severe climatic events of the Cenozoic Era. A massive injection of light carbon into the oceans and atmosphere over a few thousand of years triggered drastic perturbation of Earth's climate resulting in abrupt global warming of ~5-9oC [Sluijs et al., 2007] that persisted for ~180,000 years. This episode is marked by the diversification and radiation of terrestrial plants and mammals while in the marine realm numerous deep-sea benthic foraminifera species disappeared and new forms evolved. Sediments deposited during the PETM are clay-rich and contain distinct evidence of these climatic changes. Kopp et al., (2007) and Lippert & Zachos (2007) report an extraordinary magnetofossil ‘Lagerstätte' in lowermost Eocene kaolinite-rich clay sediments deposited at subtropical paleolatitude in the Atlantic Coastal Plain of New Jersey, USA. Magnetofossils are magnetic particles produced most abundantly by magnetotactic bacteria. Kopp et al. (2007) and Lippert & Zachos (2007) used ferromagnetic resonance (FMR) spectroscopy, other rock magnetic methods, and transmission electron microscopy (TEM) of magnetic separates to characterize sediments from boreholes at Ancora (ODP Leg 174AX) and Wilson Lake, NJ, respectively. These sediments contain abundant ~40- to 300-nm cuboidal, elongate-prismatic and bullet-shaped magnetofossils, sometimes arranged in short chains, resembling crystals in living magnetotactic bacteria. Despite the scarcity of intact magnetofossil chains, the asymmetry ratios of the FMR spectra reflects a profusion of elongate single domain (SD) crystals and/or chains. Here we address both conundrums by reporting the discovery from these same sediments of exceptionally large and novel biogenic magnetite crystals unlike any previously reported from living organisms or from sediments. Aside from abundant bacterial magnetofossils, electron microscopy reveals novel spearhead-like and spindle-like magnetite crystals up to 4 μm long (eight times larger than magnetite produced by magnetotactic bacteria) and elongated hexaoctahedra up to 1.4 μm long. Similar to magnetite produced by magnetotactic bacteria, these single-crystal particles exhibit chemical composition and lattice perfection consistent with a biogenic origin. The oxygen isotopic composition of indiviual particles supports a low temperature aquatic origin. Electron holography indicates single-domain magnetization despite the large crystal size. In a few cases, we observed apparently intact, tip-outward spherical assemblages of spearhead-like particles that possibly represent the preserved original biological arrangement of these crystals in a hitherto unknown magnetite producing organism. The discovery of these exceptionally large biogenic magnetite crystals that possibly represent the remains of a new microorganism that appeared and disappeared with the PETM sheds some light upon the ecological response to biogeochemical changes that occurred during this warming event. The abundance of fossil magnetotactic bacteria on the Atlantic Coastal Plain during the PETM could be explained by enhanced production, enhanced preservation, or both. The presence of novel magnetofossils, however, argues that changes in growth conditions are a major part of the explanation. Considering that other bacterial magnetofossils are present (although less abundant) and well-preserved in sediments below and above the PETM clay, as well as in a sand lens within the PETM clay [Kopp et al., 2007], suggests that the new magnetofossils are unlikely to be a preservation artefact. We conclude, therefore, that the development of a thick suboxic zone with high iron bioavailability - a product of dramatic changes in weathering and sedimentation patterns driven by severe global warming - resulted in diversification of magnetite-forming organisms, likely including eukaryotes. In this study we extended the search for these new magnetofossils [Schumann et al. 2008] to other PETM locations of the Atlantic margin and to a possible modern analog environment. High surface productivity with low-organic carbon density sediments and meter-scale sedimentary suboxic zones are provided by tropical shelves fed by energetic river systems, such as the Amazon. We inverstigated several magnetic extracts of samples taken from the meter-scale suboxic zones of the Amazone delta system. Sluijs A, Brinkhuis H, Schouten S, Bohaty SM, John CM, Zachos JC, Reichart GJ, Damste JSS, Crouch EM, Dickens GR. 2007. Environmental precursors to rapid light carbon injection at the Palaeocene/Eocene boundary. Nature 450:1218-1221. Kopp RE, Raub TD, Schumann D, Vali H, Smirnov AV, Kirschvink JL 2007. Magnetofossil spike during the Paleocene-Eocene thermal maximum: Ferromagnetic resonance, rock magnetic, and electron microscopy evidence from Ancora, New Jersey, United States. Paleoceanography, doi:10.1029/2007pa001473. Lipper PC, Zachos JC 2007. A biogenic origin for anomalous fine-grained magnetic material at the Paleocone-Eocene booundary at Wilson Lake, New Jesery. Paleoceanography, doi:10.1029/2007pa001471. Schumann D, Raub TD, Kopp RE, Guerquin-Kern JL, Wu TD, Rouiller I, Smirnov AV, Sears K, Lücken U, Tikoo SM, Hesse R, Kirschvink JL, Vali H 2008. Gigantism in unique biogenic magnetite at the Paleocene-Eocene Thermal Maximum. PNAS, 105:17648-17653.

Extreme Seasonality During Early Eocene Hyperthermals

NASA Astrophysics Data System (ADS)

Plink-Bjorklund, P.; Birgenheier, L.

2012-12-01

An outcrop multi-proxy dataset from the Uinta Basin, Utah, US indicates that extreme seasonality occurred repeatedly during the Early Eocene transient global warming events (hyperthermals), during the Palaeocene-Eocene Thermal Maximum (PETM) as well as during the six consequent younger hyperthermals. In this multi-proxy analysis we have investigated the precipitation distribution and peakedness changes during Early Eocene hyperthermals. This dataset is different from previously published terrestrial climate proxy analyses, in that we fully utilize the sedimentary record itself, and especially the hydrodynamic indicators within the river strata. We combine these high-resolution sedimentologic-stratigraphic analyses, with analyses of terrestrial burrowing traces, and the conventional palaeosol and stable carbon isotope analyses. With this approach, we are able to better document hydroclimatologic changes, and identify climate seasonality changes, rather than just long-term mean humidity/aridity and temperature trends. For this study we analyzed over 1000 m of Palaeocene and Early Eocene river and lake strata in the Uinta Basin, Utah, US (Figs. 1 and 2). The sedimentologic-stratigraphic analyses of outcrops included measuring detailed stratigraphic sections, analyzing photopanels, a spatial GPS survey, and lateral walk-out of stratigraphic packages across an area of 300 km2, with additional data across an area of ca 6000 km2 (Fig. 2). Continental burrowing traces and palaeosols were analyzed along the measured sections. For geochemical analysis 196 samples of mudrock facies were collected along the measured sections and analyzed for total organic carbon (Corg), total nitrogen (Ntot), and δ13C values of bulk organic matter. Biostratigraphy (25), radiometric dates, and carbon isotope stratigraphy, using bulk δ13C of organic matter in floodplain siltstones confirm the position of the PETM and the 6-8 post-PETM hyperthermals in the studied strata The seasonality intensification is seen as short intense rain seasons alternating with prolonged droughts. Such seasonality intensification had a profound effect on landscape morphology as well as on vegetation. River systems changed from braided streams to highly seasonal fluvial megafans with tens of meters deep channels. River channels staid dry through most of the prolonged droughts, as witnessed by intra-channel insect burrows and paleosols. The intense wet seasons caused extremely high water discharge in channels, resulting in high rates of erosion, sediment transport and deposition. As a result, the channels were filled locally by up to 10s of meters of sediment, causing rapid river course changes and terrestrial flooding. Particulate organic matter content is extremely low in these sediments. This is in contrast to river sediments that were deposited during less intense seasonality. The dataset was compared to other datasets from intermontane basins in the Western Interior and also Europe (Spain), where similar seasonality changes are indicated to have occurred during the PETM. This is in great contrast to intermontane Early Eocene river systems documented in Norwegian Arctic (e.g. Spitsbergen) and in tropics (e.g. Venezuela), where no seasonality intensification has been documented. Thus the seasonality intensification seems to have been confined to (northern) mid-latitudes and subtropics.

Tracking changes in ocean redox during the PETM using stable chromium isotopes

NASA Astrophysics Data System (ADS)

Dixon, S. K.; Parkinson, I. J.; Sexton, P.; Fehr, M.; James, R. H.; Peacock, C.

2012-12-01

Climate models predict a decline in oceanic dissolved oxygen under global warming conditions and observations suggest the expansion of tropical oxygen minimum zones is already underway1, with concern over the trend for future seawater oxygen levels. Therefore, previous deoxygenation events in the geological record may provide insight into the dynamics of changing oxygen levels in the Earth's oceans. One such event, is the Palaeocene-Eocene Thermal Maximum (PETM) at ~55Ma which represents a period of rapid global warming. Multiple lines of evidence suggest that at least on a local scale, near bottom anoxia occurred during the event2,3 and further understanding of changing redox conditions during this period may provide insight into future sea level oxygenation. To track seawater oxygenation during the PETM, we are utilising stable Cr isotope composition of marine carbonates, a new palaeo-redox proxy, which has shown potential when applied to modern and ancient carbonates 4,5. We present δ53Cr, trace element and REE data of foraminiferal ooze deposits over the PETM interval. Samples were taken from the North East Atlantic DSDP site 401, which preserves an exceptional and complete carbonate sequence over the interval, at a time when ocean acidification lead to massive sea floor carbonate dissolution6. Foraminifera were taken from the 63 - 150μm size fraction and planktic count data indicate that the relative proportions of dominant species do not change significantly over the event7. Systematic changes occur in REEs, Cr concentration and δ53Cr coincident with the onset of the negative δ13C excursion. The Cr concentrations of the carbonates decrease into the event, which suggests the sea level Cr concentration has fallen. We interpret this to reflect falling oxygen concentration in the seawater, leading to a decrease in aqueous Cr (VI) via precipitation of Cr out of the water column in the form of insoluble Cr (III) hydroxide. Additionally, we will demonstrate how stable Cr isotopes in carbonates respond to changes in ocean chemistry during the PETM. (1) Stramma et al. (2008). Science, 320, 655-658. (2) Dickson et al. (2012). Geology, 40, 639-642. (3) Dypvik et al. (2011). Palaeogeography, Palaeoclimatology, Palaeoecology, 302, 156-169. (4) Bonnand (2011). PhD thesis, The Open University ; (5) Frei et al. (2011). Earth and Planet. Sci. Lett., 312, 114-125. (6) Zachos et al. (2005). Science, 308, 1611-1615. (7) Pardo et al. (1997). Marine Micropaleontology, 29, 129-158.

Changes in the Occurrence and Distribution of Extreme Precipitation Events at the Paleocene-Eocene Thermal Maximum (PETM)

NASA Astrophysics Data System (ADS)

Carmichael, M.; Pancost, R. D.; Lunt, D. J.

2015-12-01

The study of the sensitivity of the hydrological cycle to episodes of global warmth in the geologic past is receiving increased attention, but knowledge of the occurrence of hydrological extremes remains limited. A range of geomorphological, microfossil and biomarker proxies indicate significant hydrological change accompanied the PETM hyperthermal at ~55.8 Ma, many of which have been interpreted to reflect changes to Mean Annual Precipitation (MAP) or runoff. Recently, changes in the occurrence of intense, episodic precipitation has been suggested at some sites, but it is currently unknown whether such regions were particularly susceptible to extremes, or whether proxies from other regions require further interpretation. In this work, we seek to understand whether a numerical climate model is capable of simulating changes in the frequency and global distribution of intense precipitation events by analysing GCM-simulated hourly precipitation rates. Our Eocene simulations are performed at x2 and x4 preindustrial CO2 using a coupled atmosphere-ocean GCM, HadCM3L. Climatological differences between high- and low-CO2 may be considered analogous to the PETM. We find that changes in storm characteristics and extremes are highly regionalised. In particular, our simulations support that extreme events occurred with a reduced return period at the PETM in tropical regions of Africa and South America, whilst in the mid-latitudes the importance of extremes varies significantly between sites in close proximity. We also identify regions where changes in extreme behaviour are decoupled from those of MAP, which may represent important proxy acquisition targets. Given that tropical precipitation distributions are highly sensitive to GCM parameterisation scheme and given biases in the representation of sub-daily precipitation within HadCM3L, there is a clear need for further modelling work to fully characterise the Eocene hydrological cycle. However, our results indicate that the interpretation of existing proxies must consider the influences of both changes in mean annual precipitation rate, but also the occurrence of intense, high impact events.

The hydrocarbon cycle and its role in hyperthermals, ocean anoxic events and mass extinctions

NASA Astrophysics Data System (ADS)

Dahlgren, Torbjørn

2016-04-01

Release of light isotopic carbon, ocean oxygen deficiency and extinction characterizes the Paleocene-Eocene Thermal Maximum (PETM). The PETM carbon isotope excursion (CIE) has been linked to gas hydrate decomposition and/or methane release due to igneous intrusions in sedimentary basins. In reviewing the published geological and geochemical data it became apparent that the majority of observations are in fact compatible with a different source(s) of the light isotopic carbon, namely, that of fluids trapped in sedimentary basins. Here I make a connection between the drilled paleo-accumulations of oil and gas in the Barents Sea, their burial and tectonic history, and published data of the PETM that may be reinterpreted as to reflect large scale leakage of oil and gas accumulations. I focus on oil, as leaked oil has a preservation potential in the sedimentary record. In contrast, gas from either leaked gas accumulations or exsolution from pore waters has little preservation potential other than contributing to the CIE. Sedimentary records compatible with leaked oil is present in the Arctic Ocean and Spitsbergen as fluorescent bitumen/amorphous organic matter (AOM) with carbon isotope ratios and biomarker signatures similar to those recorded in Barents Sea oil samples. Bitumen/AOM-rich immature sediments are also found in the North Sea and unresolved complex organic matter compatible with highly weathered oil has been found as far south as Walvis Ridge, offshore Namibia. Large scale fluid leakage from sedimentary basins can also explain the increase in radiogenic Osmium and Rhenium that mimic the CIE. Also biological evidence such as the extinction of North Atlantic benthic foraminifera lineages, the A. Augustum bloom and the occurrence of malformed micro/nanno-fossils may be linked to large scale leakage of oil and diagenetically altered porewaters. The leaked oil and gas was partially re-cycled into an organic rich shale (source rock) suggesting a 'hydrocarbon cycle' exists. Based on previously noted similarities between the PETM, the Toarcian OAE and the Triassic-Jurassic and Permian-Triassic events, it is inferred that also these may have been associated with catastrophic leakage of hydrocarbons trapped in sedimentary basins.

Mammal faunal response to the Paleogene hyperthermals ETM2 and H2

NASA Astrophysics Data System (ADS)

Chew, A. E.

2015-04-01

Scientists are increasingly turning to deep-time fossil records to decipher the long-term consequences of climate change in the race to preserve modern biotas from anthropogenically driven global warming. "Hyperthermals" are past intervals of geologically rapid global warming that provide the opportunity to study the effects of climate change on existing faunas over thousands of years. A series hyperthermals is known from the early Eocene (∼56-54 million years ago), including the Paleocene-Eocene Thermal Maximum (PETM) and two subsequent hyperthermals, Eocene Thermal Maximum 2 (ETM2) and H2. The later hyperthermals occurred following the onset of warming at the Early Eocene Climatic Optimum (EECO), the hottest sustained period of the Cenozoic. The PETM has been comprehensively studied in marine and terrestrial settings, but the terrestrial biotic effects of ETM2 and H2 are unknown. Their geochemical signatures have been located in the northern part of the Bighorn Basin, WY, USA, and their levels can be extrapolated to an extraordinarily dense, well-studied terrestrial mammal fossil record in the south-central part of the basin. High-resolution, multi-parameter paleoecological analysis reveals significant peaks in species diversity and turnover and changes in abundance and relative body size at the levels of ETM2 and H2 in the south-central Bighorn Basin record. In contrast with the PETM, faunal change at the later hyperthermals is less extreme, does not include immigration and involves a proliferation of body sizes, although abundance shifts tend to favor smaller congeners. Faunal response at ETM2 and H2 is distinctive in its high proportion of species losses potentially related to heightened species vulnerability in response to the changes already underway at the beginning of the EECO. Faunal response at ETM2 and H2 is also distinctive in high proportions of beta richness, suggestive of increased geographic dispersal related to transient increases in habitat (floral) complexity and/or precipitation or seasonality of precipitation. These results suggest that rapid ecological changes, increased heterogeneity in species incidence, and heightened species vulnerability and loss may be expected across most of North America in the near future in response to anthropogenically-driven climate change.

An Ecological Tipping Point Defined by Shallow Marine Foraminifera in the latest Paleocene

NASA Astrophysics Data System (ADS)

Robinson, M. M.; Spivey, W.

2016-12-01

The Paleocene-Eocene Thermal Maximum (PETM) is recognized in marine sediments by a carbonate dissolution zone, the extinction or turnover of benthic taxa, and a radiation of planktic excursion taxa, all accompanied by a rapid-onset, negative carbon isotope excursion (CIE). We present foraminiferal evidence from shallow marine sediments in southeastern Maryland, USA, where accumulation rates are high, for a minor ocean acidification event in the latest Paleocene that coincides with a relatively small (-2‰) CIE. This pre-onset excursion (POE) precedes the larger (-4‰) PETM CIE onset and dissolution event. During the POE, the benthic assemblage is reconfigured toward agglutinated species in order to adapt to increased acidity, and the planktic assemblage begins to speciate due to perturbed mixed layer conditions. The benthic assemblage returns to normal, without interruption, as the POE recovers, but planktic excursion taxa continue to appear in very low numbers. This is contrasted to the major ocean acidification event associated with the PETM CIE onset that results in a zone of complete dissolution followed by distinctive benthic and planktic foraminiferal assemblages. Our microfossil evidence documents a biotic response to bottom water and mixed layer perturbations that illustrates how coastal ecosystems react to both moderate and severe ocean acidification events, bracketing the ecological tipping point of shallow marine ecosystems. The POE, roughly half the magnitude of the CIE onset, provides insight into the nature of the initial effects of climate perturbation as well as an example of one that is fully recoverable. It is here that research aimed to better understand the long-term effects and reversibility of modern deteriorating oceanic conditions should focus. This study provides an initial metric by which to measure modern ecosystem disturbances and will help to define the tipping point for the shallow marine environment.

Facilitating Identification of Poorly Preserved Marine Microfossils through 3D Printing

NASA Astrophysics Data System (ADS)

Christensen, R. V.; Robinson, M. M.; Sessa, J.

2016-12-01

The Paleocene-Eocene Thermal Maximum (PETM) was a period of sudden and intense global warming that occurred 56 Myr, and is widely considered a possible analogue for future climatic changes. Marine microfossils are important proxies used in the reconstruction of PETM paleoenvironments and paleoclimate. The correct species-level identification of foraminifera and pteropod specimens is necessary to understand ocean temperature, chemistry, nutrient availability, and ecosystem structure during this hyperthermal event. During periods of extreme or rapid environmental perturbations foraminifera can be poorly preserved. Pteropod identification is equally challenging as aragonitic shells are vulnerable to changing ocean acidity and often only internal molds are left to be identified. The macroscopic rendering of the internal and external test morphology of marine microfossils via 3D printing allows for a more experiential species-recognition education, especially of difficult to identify specimens. A selected microfossil specimen is scanned using computerized tomography (CT), creating x-ray slices of the specimen that are then processed into a digital model. The digitized fossil can then be analyzed using 3D software and subsequently printed using a wide variety of materials. The magnified model can be easily manipulated in a student's hand, and thus can be studied in a more visible and tactile way than traditional methods allow. This invaluable teaching tool physically manifests what was previously limited to textbook images and illustrations or the view field of a microscope. We show the step-by-step 3-D printing process of several PETM marine microfossil specimens from CT scans and demonstrate their advantage over 2-D SEM images for learning to identify microfossils to the species level. In addition, we provide samples to demonstrate the utility of 3-D models in identifying poorly preserved foraminifer specimens and species of pteropods from internal molds.

A new record of the Paleocene Carbon Isotope Maximum from the Mississippi Embayment

NASA Astrophysics Data System (ADS)

Platt, B. F.; Gerweck, E. D.

2017-12-01

The Paleocene-Eocene interval is well known as a time of climatic transitions, especially hyperthermals associated with disturbances in the carbon cycle that are used as proxies for impacts of projected anthropogenic global climate change. A recent roadcut in Benton County, Mississippi exposes a disconformity between the Paleocene Naheola Formation and the Eocene Meridian Sand. The disconformity is developed on a thick, kaolinitic paleosol, which we interpret as a mature Oxisol that supported tropical rainforest vegetation (as evidenced by associated well preserved leaf fossils). The nature of the paleosol at the disconformity led us to hypothesize that the strata might contain evidence of the Paleocene Eocene Thermal Maximum (PETM). We sampled two Mississippi Mineral Resources Institute (MMRI) cores from the equivalent stratigraphic interval from Benton and Tippah Counties, Mississippi, for bulk organic carbon stable isotopes at 25-cm intervals. Results showed no evidence of the negative excursion characteristic of the PETM. Instead, we found a gradual upsection enrichment that we interpret as the positive trend characteristic of the lower Paleocene Carbon Isotope Maximum (PCIM). This is reasonable based on published biostratigraphy and absolute ages from elsewhere in the Naheola Formation. Further analyses will be performed to determine whether the PCIM trend continues throughout the remainder of the core. The identification of the PCIM in Mississippi Embayment (ME) sediments is important because stable carbon isotope data may be useful for improving chronostratigraphy in the ME. Also, the PCIM is associated with a gradual warming trend as indicated by previously published stable oxygen isotopes from benthic foraminifera. Studying successive ME paleosols throughout the PCIM may yield information about the impacts of gradual atmospheric warming on soils and associated terrestrial systems.

Mass extinction in tetraodontiform fishes linked to the Palaeocene-Eocene thermal maximum.

PubMed

Arcila, Dahiana; Tyler, James C

2017-11-15

Integrative evolutionary analyses based upon fossil and extant species provide a powerful approach for understanding past diversification events and for assessing the tempo of evolution across the Tree of Life. Herein, we demonstrate the importance of integrating fossil and extant species for inferring patterns of lineage diversification that would otherwise be masked in analyses that examine only one source of evidence. We infer the phylogeny and macroevolutionary history of the Tetraodontiformes (triggerfishes, pufferfishes and allies), a group with one of the most extensive fossil records among fishes. Our analyses combine molecular and morphological data, based on an expanded matrix that adds newly coded fossil species and character states. Beyond confidently resolving the relationships and divergence times of tetraodontiforms, our diversification analyses detect a major mass-extinction event during the Palaeocene-Eocene Thermal Maximum (PETM), followed by a marked increase in speciation rates. This pattern is consistently obtained when fossil and extant species are integrated, whereas examination of the fossil occurrences alone failed to detect major diversification changes during the PETM. When taking into account non-homogeneous models, our analyses also detect a rapid lineage diversification increase in one of the groups (tetraodontoids) during the middle Miocene, which is considered a key period in the evolution of reef fishes associated with trophic changes and ecological opportunity. In summary, our analyses show distinct diversification dynamics estimated from phylogenies and the fossil record, suggesting that different episodes shaped the evolution of tetraodontiforms during the Cenozoic. © 2017 The Author(s).

Calcareous nannofossil assemblage changes across the Paleocene-Eocene thermal maximum: Evidence from a shelf setting

USGS Publications Warehouse

Self-Trail, Jean M.; Powars, David S.; Watkins, David K.; Wandless, Gregory A.

2012-01-01

Biotic response of calcareous nannoplankton to abrupt warming across the Paleocene/Eocene boundary reflects a primary response to climatically induced parameters including increased continental runoff of freshwater, global acidification of seawater, high sedimentation rates, and calcareous nannoplankton assemblage turnover. We identify ecophenotypic nannofossil species adapted to low pH conditions (Discoaster anartios, D. araneus, Rhomboaster spp.), excursion taxa adapted to the extremely warm climatic conditions (Bomolithus supremus and Coccolithus bownii), three species of the genus Toweius (T. serotinus, T. callosus, T. occultatus) adapted to warm, rather than cool, water conditions, opportunists adapted to high productivity conditions (Coronocyclus bramlettei, Neochiastozygus junctus), and species adapted to oligotropic and/or cool‐water conditions that went into refugium during the PETM (Zygrablithus bijugatus, Calcidiscus? parvicrucis and Chiasmolithus bidens). Discoaster anartios was adapted to meso- to eutrophic, rather than oligotrophic, conditions. Comparison of these data to previous work on sediments deposited on shelf settings suggests that local conditions such as high precipitation rates and possible increase in major storms such as hurricanes resulted in increased continental runoff and high sedimentation rates that affected assemblage response to the PETM.

Mammal faunal change in the zone of the Paleogene hyperthermals ETM2 and H2

NASA Astrophysics Data System (ADS)

Chew, A. E.

2015-09-01

"Hyperthermals" are past intervals of geologically rapid global warming that provide the opportunity to study the effects of climate change on existing faunas over thousands of years. A series of hyperthermals is known from the early Eocene (~ 56-54 million years ago), including the Paleocene-Eocene Thermal Maximum (PETM) and two subsequent hyperthermals (Eocene Thermal Maximum 2 - ETM2 - and H2). The later hyperthermals occurred during warming that resulted in the Early Eocene Climatic Optimum (EECO), the hottest sustained period of the Cenozoic. The PETM has been comprehensively studied in marine and terrestrial settings, but the terrestrial biotic effects of ETM2 and H2 are relatively unknown. Two carbon isotope excursions (CIEs) have been described in the northern part of the Bighorn Basin, WY, USA, and related to ETM2 and H2. An ~ 80 m thick zone of stratigraphic section in the extraordinarily dense, well-studied terrestrial mammal fossil record along the Fifteenmile Creek (FC) in the south-central part of the basin spans the levels at which the CIEs occur in the northern Bighorn Basin. High-resolution, multiparameter paleoecological analysis of this part of the FC section reveals two episodes of significant faunal change - faunal events B-1 and B-2 - characterized by significant peaks in species diversity and turnover and changes in abundance and relative body size. Faunal events B-1 and B-2 are hypothesized to be related to the CIEs in the northern part of the basin and hence to the climatic and environmental change of ETM2 and H2. In contrast with the PETM, change at faunal events B-1 and B-2 is less extreme, is not driven by immigration and involves a proliferation of body sizes, although abundance shifts tend to favor smaller congeners. The response at faunal events B-1 and B-2 is distinctive in its high proportion of species losses, potentially related to heightened species vulnerability in response to changes already underway in the lead-up to the EECO. Faunal response at faunal events B-1 and B-2 is also distinctive in that it shows high proportions of beta richness, suggestive of increased geographic dispersal related to transient increases in habitat (floral) complexity and/or precipitation or seasonality of precipitation.

Evaluating the Effect of Autogenic Sedimentation on the Preservation of Climate Proxy Records: Modeling and Examples from the Paleocene Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Trampush, S. M.; Hajek, E. A.

2016-12-01

The stratigraphic record provides a vital opportunity to investigate how changes in climate can impact many different landscapes and seascapes. However, the inherent variability in sedimentation within many depositional environments may mask or remove the signature of climate change. A common solution is to use geochemical proxies - usually collected at regular stratigraphic intervals - to independently identify climate events. This approach doesn't account for the potentially significant variability in deposition and erosion time series resulting from autogenic landscape dynamics. In order to explore how geochemical proxy records could be overprinted by landscape dynamics, we use a 1D stochastic sedimentation model where we mimic fluvial, lacustrine, shallow marine, and deep marine environmental dynamics by varying the frequency-magnitude distributions of sedimentation rates. We find that even conservative estimates of the frequency and magnitude of stochastic sedimentation variability can heavily modify proxy records in characteristic ways by alternately removing, compressing, and expanding portions of the record, regardless of the magnitude or duration of the climatic event. Our model results are consistent with observations of the carbon isotope excursions of the Paleocene Eocene Thermal Maximum (PETM) preserved within both fluvial (e.g. the Bighorn Basin, Wyoming and the Piceance Basin, Colorado) and shallow marine (e.g. the New Jersey shelf) deposits. Our results suggest that we may be able to use existing geochemical proxy records within well studied, global climate events, such as the PETM, to constrain the variability in sedimentation present within different depositional environments.

Taking the pulse of the carbon release during the onset of the Paleocene-Eocene thermal maximum

NASA Astrophysics Data System (ADS)

Babila, T. L.; Bralower, T. J.; Robinson, M. M.; Self-Trail, J. M.; Zachos, J. C.

2015-12-01

The Paleocene-Eocene thermal maximum (PETM) (~55 Ma) is a warming event characterized by a negative carbon isotope excursion (CIE) representing a large and rapid injection of carbon into global reservoirs. Debate continues regarding the mechanism, magnitude, and tempo of the carbon released. A few terrestrial and marine sediment records document two distinct δ13C excursions a pre-onset excursion (POE) and CIE interpreted as evidence of multiple carbon injections. We generated geochemical records of ocean carbonate chemistry and temperature using cores drilled by the U.S Geological Survey (USGS) that recovered expanded sections of the PETM onset along the mid-Atlantic coastal plain. Our stable isotope (δ13C and δ18O) planktonic foraminifer records from South Dover Bridge (SDB), Maryland USA exhibit prominent anomalies across the Paleocene-Eocene boundary consistent to proximal coastal sites. δ13C records of mixed-layer (Acarinina spp.) and thermocline (Subbotina spp.) dwelling planktonic foraminifera show two negative carbon excursions that include a 2 ‰ POE and 3-4 ‰ CIE that return to baseline values between events in conjunction with bulk carbonate trends. Remarkably, contemporaneous foraminifer δ18O records exhibit only a minor response during the POE. This could be an artifact of preservation, or at face value, indicative of little to no warming. For the latter, this would require a rapid, but relatively small carbon release. To test the coupled link between atmosphere and surface ocean δ13C records we aim to integrate our geochemical results with model simulations to establish the duration and global extent of multiple carbon releases.

Long-Life and High-Power Binder-Free Cathode Based on One-Step Synthesis of Radical Polymers with Multi-Pendant Groups.

PubMed

Chen, Yaoguang; Zhang, Yangfan; Liu, Xiu; Fan, Xuliang; Bai, Bing; Yang, Kang; Liang, Zhongxin; Zhang, Zishou; Mai, Kancheng

2018-05-16

The main bottlenecks for the widespread application of radical polymers in organic radical batteries are poor cycling stability, due to the dissolution of radical polymers into the electrolyte, and the low efficiency of multi-step synthesis strategies. Herein, a kind of electrolyte-resistant radical polymer bearing multi-pendant groups (poly(ethylene-alt-TEMPO maleate) (PETM)) is designed and synthesized through a one-step esterification reaction to graft 4-hydroxy-2,2,6,6-teramethylpiperidinyl-1-oxy into the commercially available poly(ethylene-alt-maleic anhydride). Interestingly, PETM is hardly soluble in the ethylene carbonate/dimethyl carbonate/ethyl methyl carbonate-based electrolyte, showing an extremely low solubility of 0.59 mg mL -1 , but is easily soluble in tetrahydrofuran and N-Methyl pyrrolidone. The derived binder-free PETM cathode exhibits nearly 100% utilization of the grafted nitroxide radicals (88 mA h g -1 ) and excellent rate capability with almost invariant capacitance from 10 C to 40 C. Significantly, the PETM cathodes retain 94% of the initial capacity after 1000 cycles, outperforming most reported radical polymer-based cathodes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The DeepMIP Contribution to PMIP4: Experimental Design for Model Simulations of the EECO, PETM, and pre-PETM (version 1.0)

NASA Technical Reports Server (NTRS)

Lunt, Daniel J.; Huber, Matthew; Anagnostou, Eleni; Baatsen, Michiel L. J.; Caballero, Rodrigo; DeConto, Rob; Dijkstra, Henk A.; Donnadieu, Yannick; Evans, David; Feng, Ran;

Gigantism in unique biogenic magnetite at the Paleocene-Eocene Thermal Maximum.

PubMed

Schumann, Dirk; Raub, Timothy D; Kopp, Robert E; Guerquin-Kern, Jean-Luc; Wu, Ting-Di; Rouiller, Isabelle; Smirnov, Aleksey V; Sears, S Kelly; Lücken, Uwe; Tikoo, Sonia M; Hesse, Reinhard; Kirschvink, Joseph L; Vali, Hojatollah

2008-11-18

We report the discovery of exceptionally large biogenic magnetite crystals in clay-rich sediments spanning the Paleocene-Eocene Thermal Maximum (PETM) in a borehole at Ancora, NJ. Aside from previously described abundant bacterial magnetofossils, electron microscopy reveals novel spearhead-like and spindle-like magnetite up to 4 microm long and hexaoctahedral prisms up to 1.4 microm long. Similar to magnetite produced by magnetotactic bacteria, these single-crystal particles exhibit chemical composition, lattice perfection, and oxygen isotopes consistent with an aquatic origin. Electron holography indicates single-domain magnetization despite their large crystal size. We suggest that the development of a thick suboxic zone with high iron bioavailability--a product of dramatic changes in weathering and sedimentation patterns driven by severe global warming--drove diversification of magnetite-forming organisms, likely including eukaryotes.

High latitude hydrological changes during the Eocene Thermal Maximum 2

NASA Astrophysics Data System (ADS)

Krishnan, Srinath; Pagani, Mark; Huber, Matthew; Sluijs, Appy

2014-10-01

The Eocene hyperthermals, including the Paleocene-Eocene Thermal Maximum (PETM) and Eocene Thermal Maximum 2 (ETM2), represent extreme global warming events ∼56 and 54 million years ago associated with rapid increases in atmospheric greenhouse gas concentrations. An initial study on PETM characteristics in the Arctic region argued for intensification of the hydrological cycle and a substantial increase in poleward moisture transport during global warming based on compound-specific carbon and hydrogen isotopic (2H/1H) records from sedimentary leaf-wax lipids. In this study, we apply this isotopic and hydrological approach on sediments deposited during ETM2 from the Lomonosov Ridge (Integrated Ocean Drilling Program Expedition 302). Our results show similar 2H/1H changes during ETM2 as during the PETM, with a period of 2H-enrichment (∼ 20 ‰) relative to ;pre-event; values just prior to the negative carbon isotope shift (CIE) that is often taken as the onset of the hyperthermal, and more negative lipid δ2H values (∼ - 15 ‰) during peak warming. Notably, lipid 2H-enrichment at the base of the event is coeval with colder TEX86H temperatures. If 2H/1H values of leaf waxes primarily reflect the hydrogen isotopic composition of precipitation, the observed local relationship between temperature and 2H/1H values for the body of ETM2 is precisely the opposite of what would be predicted using a simple Rayleigh isotope distillation model, assuming a meridional vapor trajectory and a reduction in equator-pole temperature gradients. Overall, a negative correlation exists between the average chain length of n-alkanes and 2H/1H suggesting that local changes in ecology could have impacted the hydrogen isotopic compositions of leaf waxes. The negative correlation falls across three separate intervals - the base of the event, the initial CIE, and during the H2 hyperthermal (of which the assignment is not fully certain). Three possible mechanisms potentially explain 2H-enriched signals at the base of the event, including (1) intense local drying and cooling leading to evaporative 2H-enrichment; (2) changes in frequency/intensity of storm events and its impact on high latitude amount effects; and (3) changes in low-latitude temperatures. Evidence for hydrological shifts at the base of both hyperthermals suggests that hydrological change or the factors promoting hydrological change played a role in triggering the release of greenhouse gases. Generation of similar high-resolution isotopic- and temperature records at other latitudes is crucial for understanding the causal links between temperature and hydrological changes and may help constrain the source and mechanism of carbon release that triggered the early Eocene hyperthermals.

Biomarkers and their stable isotopes in Cenozoic sediments above the Chicxulub impact crater

NASA Astrophysics Data System (ADS)

Grice, K.; Schaefer, B.; Coolen, M.; Greenwood, P. F.; Scarlett, A. G.; Freeman, K.; Lyons, S. L.

2017-12-01

The most widely accepted hypothesis for the cause of the End-Cretaceous mass extinction (K/Pg event) 66 Ma ago is the impact of an extra-terrestrial body, which produced the 200 km wide Chicxulub impact structure. This event led to an extinction of 75% of all species on Earth. The massive extinction in the terrestrial realm is partly attributed to the intense heat pulse, the widespread wild fires caused by the impact and the ensuing darkness, as dust and sulfate aerosols blocked out the sun leading to photosynthesis shut off and productivity collapse in both the terrestrial and marine realms. The marine realm may additionally have experienced ocean acidification resulting in mass extinction of plankton (foraminifera and coccolithophorids) and marine reptiles. Samples from the Cenozoic marine sediments including the Paleocene-Eocene Thermal Maximum (PETM) have been extracted for hydrocarbons and analysed to investigate the molecular and isotopic organic record of biotic and environmental change after the K/Pg boundary event. Specific biomarker-precursor relationship has been established by the direct correlation of sedimentary biomarkers with the biochemicals (e.g. lipids) of extant biological systems. The structural characterisation of biomarkers as well as their stable isotopic compositions (C, H and N) are used to evaluate the source(s) of organic matter (OM) and to reconstruct paleoenvironmental depositional conditions. Throughout the Cenozoic sediments (including the PETM) the biomarker distribution suggests a variation in the source of organic matter from terrestrial to marine. Furthermore, the presence of sulfurised biomarkers indicates euxinic environmental conditions at the time of deposition. Biomarker distributions indicative of green sulfur bacteria reveal persistent photic zone euxinic conditions at several intervals in the Cenozoic. Further compound specific isotope analyses will provide insights into the long-term biogeochemical cycling of C, H and S after the K/Pg extinction including the PETM.

Early Eocene deep-sea benthic foraminiferal faunas: Recovery from the Paleocene Eocene Thermal Maximum extinction in a greenhouse world

PubMed Central

Thomas, Ellen; D’haenens, Simon; Speijer, Robert P.; Alegret, Laia

2018-01-01

The early Eocene greenhouse world was marked by multiple transient hyperthermal events. The most extreme was the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma), linked to the extinction of the globally recognised deep-sea benthic foraminiferal Velasco fauna, which led to the development of early Eocene assemblages. This turnover has been studied at high resolution, but faunal development into the later early Eocene is poorly documented. There is no widely accepted early Eocene equivalent of the Late Cretaceous-Paleocene Velasco fauna, mainly due to the use of different taxonomic concepts. We compiled Ypresian benthic foraminiferal data from 17 middle bathyal-lower abyssal ocean drilling sites in the Pacific, Atlantic and Indian Oceans, in order to characterise early Eocene deep-sea faunas by comparing assemblages across space, paleodepth and time. Nuttallides truempyi, Oridorsalis umbonatus, Bulimina trinitatensis, the Bulimina simplex group, the Anomalinoides spissiformis group, pleurostomellids, uniserial lagenids, stilostomellids and lenticulinids were ubiquitous during the early Eocene (lower-middle Ypresian). Aragonia aragonensis, the Globocassidulina subglobosa group, the Cibicidoides eocaenus group and polymorphinids became ubiquitous during the middle Ypresian. The most abundant early Ypresian taxa were tolerant to stressed or disturbed environments, either by opportunistic behavior (Quadrimorphina profunda, Tappanina selmensis, Siphogenerinoides brevispinosa) and/or the ability to calcify in carbonate-corrosive waters (N. truempyi). Nuttallides truempyi, T. selmensis and other buliminids (Bolivinoides cf. decoratus group, Bulimina virginiana) were markedly abundant during the middle Ypresian. Contrary to the long-lived, highly diverse and equitable Velasco fauna, common and abundant taxa reflect highly perturbed assemblages through the earliest Ypresian, with lower diversity and equitability following the PETM extinction. In contrast, the middle Ypresian assemblages may indicate a recovering fauna, though to some extent persistently disturbed by the lower-amplitude Eocene hyperthermals (e.g., Eocene Thermal Maximum 2 and 3). We propose the name ‘Walvis Ridge fauna’ for future reference to these Ypresian deep-sea benthic foraminiferal assemblages. PMID:29474429

Early Eocene deep-sea benthic foraminiferal faunas: Recovery from the Paleocene Eocene Thermal Maximum extinction in a greenhouse world.

PubMed

Arreguín-Rodríguez, Gabriela J; Thomas, Ellen; D'haenens, Simon; Speijer, Robert P; Alegret, Laia

2018-01-01

The early Eocene greenhouse world was marked by multiple transient hyperthermal events. The most extreme was the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma), linked to the extinction of the globally recognised deep-sea benthic foraminiferal Velasco fauna, which led to the development of early Eocene assemblages. This turnover has been studied at high resolution, but faunal development into the later early Eocene is poorly documented. There is no widely accepted early Eocene equivalent of the Late Cretaceous-Paleocene Velasco fauna, mainly due to the use of different taxonomic concepts. We compiled Ypresian benthic foraminiferal data from 17 middle bathyal-lower abyssal ocean drilling sites in the Pacific, Atlantic and Indian Oceans, in order to characterise early Eocene deep-sea faunas by comparing assemblages across space, paleodepth and time. Nuttallides truempyi, Oridorsalis umbonatus, Bulimina trinitatensis, the Bulimina simplex group, the Anomalinoides spissiformis group, pleurostomellids, uniserial lagenids, stilostomellids and lenticulinids were ubiquitous during the early Eocene (lower-middle Ypresian). Aragonia aragonensis, the Globocassidulina subglobosa group, the Cibicidoides eocaenus group and polymorphinids became ubiquitous during the middle Ypresian. The most abundant early Ypresian taxa were tolerant to stressed or disturbed environments, either by opportunistic behavior (Quadrimorphina profunda, Tappanina selmensis, Siphogenerinoides brevispinosa) and/or the ability to calcify in carbonate-corrosive waters (N. truempyi). Nuttallides truempyi, T. selmensis and other buliminids (Bolivinoides cf. decoratus group, Bulimina virginiana) were markedly abundant during the middle Ypresian. Contrary to the long-lived, highly diverse and equitable Velasco fauna, common and abundant taxa reflect highly perturbed assemblages through the earliest Ypresian, with lower diversity and equitability following the PETM extinction. In contrast, the middle Ypresian assemblages may indicate a recovering fauna, though to some extent persistently disturbed by the lower-amplitude Eocene hyperthermals (e.g., Eocene Thermal Maximum 2 and 3). We propose the name 'Walvis Ridge fauna' for future reference to these Ypresian deep-sea benthic foraminiferal assemblages.

Fidelity of fossil n-alkanes from leaf to paleosol and applications to the Paleocene-Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Bush, R. T.; McInerney, F. A.; Baczynski, A. A.; Wing, S. L.

2011-12-01

Long chain n-alkanes (C21-C35) are well-known as biomarkers of terrestrial plants. They can be preserved across a wide range of terrestrial and marine environments, survive in the sedimentary record for millions of years, and can serve as proxies for ancient environments. Most n-alkane records are derived from sediments rather than directly from fossil leaves. However, little is known about the fidelity of the n-alkane record: how and where leaf preservation relates to n-alkane preservation and how patterns of n-alkane carbon isotope ratios (δ13C) compare to living relatives. To examine these questions, we analyzed n-alkanes from fluvial sediments and individual leaf fossils collected in the Bighorn Basin, Wyoming, across the Paleocene-Eocene Thermal Maximum (PETM) carbon isotope excursion. We assessed the fidelity of the n-alkane signature from individual fossil leaves via three separate means. 1) Spatial variations were assessed by comparing n-alkane concentrations on a fossil leaf and in sediments both directly adjacent to the leaf and farther away. Absolute concentrations were greater within the compression fossil than in the directly adjacent sediment, which were in turn greater than in more distant sediment. 2) n-Alkane abundances and distributions were examined in fossil leaves having a range of preservational quality, from fossils with intact cuticle to carbonized fossils lacking cuticle and higher-order venation. The best preserved fossils preserved a higher concentration of n-alkanes and showed the most similar n-alkane distribution to living relatives. However, a strong odd over even predominance suggests a relatively unmodified plant source occurred in all samples regardless of preservation state. 3) n-Alkane δ13C values were measured for both fossil leaves and their living relatives. Both the saw-tooth pattern of δ13C values between odd and even chain lengths and the general decrease in δ13C values with increasing chain length are consistent with modern plant data. These results suggest that n-alkanes extracted directly from a fossil leaf provide a true signature of an individual leaf fossil rather than a mixture from the entire plant community. Therefore, comparisons between fossil morphotypes and between fossil and related modern taxa should be robust. Furthermore, by placing fossil leaf data within the context of the chemostratigraphy of Bighorn Basin sediments across the P-E boundary, fossil leaf n-alkanes can be used to bridge the gap between our understanding of modern plant lipids and bulk lipid data from sediments across the PETM. It has been hypothesized that changes in the both the molecular distribution and carbon isotope composition of n-alkanes across the PETM were due to changes in the local plant community, which included a large proportion of deciduous gymnosperms before and after-but not during-the PETM. Analysis of fossils such as Ginkgo and angiosperms provides the opportunity to compare and distinguish the molecular and isotopic signatures of gymnosperms and angiosperms. These comparisons shed light on the dynamics of climate and ecosystem changes as they are recorded in the signatures of lipid biomarkers.

Using n-alkane records to constrain carbon cycle - hydrological cycle coupling: Case study from the Northern Hemisphere mid-latitudes during the PETM

NASA Astrophysics Data System (ADS)

Krishnan, S.; Pagani, M.; Tipple, B. J.

2010-12-01

The early Eocene was a warmer world compared to the present and is characterized by rising temperatures interspersed with rapid hyperthermal events. During the largest of these rapid warming events; the Paleocene-Eocene Thermal Maximum (PETM), proxy records suggest that sea surface temperatures (SST) rose by 3-5 deg. C in the tropics (Zachos et al., 2003, Tripati and Elderfield, 2004), >5 deg. C in the Arctic (Sluijs et al., 2006) and perhaps has high as 9 deg. C in some sub-Antarctic regions (Kennett and Stott, 1991; Thomas et al., 1999). This warming is believed to be the result of massive input of 13C-depleted carbon into the ocean-atmosphere system, evidenced by the large negative carbon isotope excursion (CIE) and carbonate dissolution associated with the event. However, there are several questions regarding the exact mechanism of warming and feedbacks between the carbon cycle and climate. Did climate shift prior to the main event that led to the release of isotopically light carbon? Do we observe consistent leads or lags between changes in carbon isotopes and hydrological conditions during warm intervals? This study aims to reconstruct hydrological changes in the in the Northern Hemisphere mid-latitudes during the PETM using terrestrial biomarkers. Terrestrial biomarkers, such leaf-wax lipids stored in sediments, have the unique advantage of recording carbon and hydrogen isotopic compositions of atmospheric CO2 (modified by plant fractionation) and precipitation (modified by plant fractionation and evapotranspiration), allowing evaluation of the relative timing of carbon and hydrogen isotopic (i.e., climate) shifts. In this study, we compile and present three mid-latitude PETM records from the Northern Hemisphere, i.e. Alamedilla (Spain), Cicogna and Forada (Italy). The Cicogna and Forada sections are located in the Belluno basin (~12 km apart). Preliminary results do not indicate any significant pre-excursion hydrogen isotope changes at Cicogna, while at Forada we observe a pre-excursion shift toward more positive values. Comparison of the mean-weighted isotopic trends (to account for vegetation changes) indicates that the carbon and hydrogen isotopic compositions shift simultaneously at the start of the CIE at Cicogna and Forada and remain coupled during the latter part of the recovery. However, the most depleted values in δD do not coincide with the most negative δ13C values, suggesting that the response time of the hydrological cycle was slower than the carbon isotopic excursion. The δD trends appear to diverge from δ13C records during the initial recovery period. This difference in response and response times between the initial perturbation and recovery enable us to constrain the timing and mechanism of feedbacks. A third section (Alamedilla), located at lower latitude, will be used to test these hypotheses. The timing and average magnitudes of δD changes at these three sites will be extrapolated to infer precipitation trends during the late Paleocene, peak PETM, and early Eocene for this region and will be useful for future data-model comparisons.

An atmosphere-ocean GCM modelling study of the climate response to changing Arctic seaways in the early Cenozoic.

NASA Astrophysics Data System (ADS)

Roberts, C. D.; Legrande, A. N.; Tripati, A. K.

2008-12-01

The report of fossil Azolla (a freshwater aquatic fern) in sediments from the Lomonosov Ridge suggests low salinity conditions occurred in the Arctic Ocean in the early Eocene. Restricted passages between the Arctic Ocean and the surrounding oceans are hypothesized to have caused this Arctic freshening. We investigate this scenario using a water-isotope enabled atmosphere-ocean general circulation model with Eocene boundary conditions including 4xCO2, 7xCH4, altered bathymetry and topography, and an estimated distribution of Eocene vegetational types. In one experiment, oceanic exchange between the Arctic Ocean and other ocean basins was restricted to two shallow (~250 m) seaways, one in the North Atlantic, the Greenland-Norwegian seaway, and the second connecting the Arctic Ocean with the Tethys Ocean, the Turgai Straits. In the restricted configuration, the Greenland-Norwegian seaway was closed and exchange through the Turgai Straits was limited to a depth of ~60 m. The simulations suggest that the severe restriction of Arctic seaways in the early Eocene may have been sufficient to freshen Arctic Ocean surface waters, conducive to Azolla blooms. When exchange with the Arctic Ocean is limited, salinities in the upper several hundred meters of the water column decrease by ~10 psu. In some regions, surface salinity is within 2-3 psu of the reported maximum modern conditions tolerated by Azolla (~5 psu). In the restricted scenario, salt is stored preferentially in the North Atlantic and Tethys oceans, resulting in enhanced meridional overturning, increased poleward heat transport in the North Atlantic western boundary current, and warming of surface and intermediate waters in the North Atlantic by several degrees. Increased sensible and latent heat fluxes from the North Atlantic Ocean, combined with a reduction in cloud albedo, also lead to an increase in surface air temperature of over much of North America, Greenland and Eurasia. Our work is consistent with previous findings on the potential influence of Arctic gateways on ocean overturning and also suggests that Northern Hemisphere climate, particularly in the North Atlantic, was very sensitive to changes in Arctic seaways. This result is of particular significance when considered in the context of the Paleocene Eocene Thermal Maximum (PETM). Volcanic activity prior to the PETM may have been responsible for the formation of a sub-aerial barrier in the North Atlantic, and consequently may have driven warming of intermediate waters sufficient to destabilize methane clathrates. Evidence for freshening of Arctic ocean waters prior to the PETM would support this hypothesis.

New Biogeographic insight into Bauhinia s.l. (Leguminosae): integration from fossil records and molecular analyses

PubMed Central

2014-01-01

Background Given that most species that have ever existed on earth are extinct, it stands to reason that the evolutionary history can be better understood with fossil taxa. Bauhinia is a typical genus of pantropical intercontinental disjunction among the Asian, African, and American continents. Geographic distribution patterns are better recognized when fossil records and molecular sequences are combined in the analyses. Here, we describe a new macrofossil species of Bauhinia from the Upper Miocene Xiaolongtan Formation in Wenshan County, Southeast Yunnan, China, and elucidate the biogeographic significance through the analyses of molecules and fossils. Results Morphometric analysis demonstrates that the leaf shapes of B. acuminata, B. championii, B. chalcophylla, B. purpurea, and B. podopetala closely resemble the leaf shapes of the new finding fossil. Phylogenetic relationships among the Bauhinia species were reconstructed using maximum parsimony and Bayesian inference, which inferred that species in Bauhinia species are well-resolved into three main groups. Divergence times were estimated by the Bayesian Markov chain Monte Carlo (MCMC) method under a relaxed clock, and inferred that the stem diversification time of Bauhinia was ca. 62.7 Ma. The Asian lineage first diverged at ca. 59.8 Ma, followed by divergence of the Africa lineage starting during the late Eocene, whereas that of the neotropical lineage starting during the middle Miocene. Conclusions Hypotheses relying on vicariance or continental history to explain pantropical disjunct distributions are dismissed because they require mostly Palaeogene and older tectonic events. We suggest that Bauhinia originated in the middle Paleocene in Laurasia, probably in Asia, implying a possible Tethys Seaway origin or an “Out of Tropical Asia”, and dispersal of legumes. Its present pantropical disjunction resulted from disruption of the boreotropical flora by climatic cooling after the Paleocene-Eocene Thermal Maximum (PETM). North Atlantic land bridges (NALB) seem the most plausible route for migration of Bauhinia from Asia to America; and additional aspects of the Bauhinia species distribution are explained by migration and long distance dispersal (LDD) from Eurasia to the African and American continents. PMID:25288346

New Biogeographic insight into Bauhinia s.l. (Leguminosae): integration from fossil records and molecular analyses.

PubMed

Meng, Hong-Hu; Jacques, Frédéric Mb; Su, Tao; Huang, Yong-Jiang; Zhang, Shi-Tao; Ma, Hong-Jie; Zhou, Zhe-Kun

2014-08-10

Given that most species that have ever existed on earth are extinct, it stands to reason that the evolutionary history can be better understood with fossil taxa. Bauhinia is a typical genus of pantropical intercontinental disjunction among the Asian, African, and American continents. Geographic distribution patterns are better recognized when fossil records and molecular sequences are combined in the analyses. Here, we describe a new macrofossil species of Bauhinia from the Upper Miocene Xiaolongtan Formation in Wenshan County, Southeast Yunnan, China, and elucidate the biogeographic significance through the analyses of molecules and fossils. Morphometric analysis demonstrates that the leaf shapes of B. acuminata, B. championii, B. chalcophylla, B. purpurea, and B. podopetala closely resemble the leaf shapes of the new finding fossil. Phylogenetic relationships among the Bauhinia species were reconstructed using maximum parsimony and Bayesian inference, which inferred that species in Bauhinia species are well-resolved into three main groups. Divergence times were estimated by the Bayesian Markov chain Monte Carlo (MCMC) method under a relaxed clock, and inferred that the stem diversification time of Bauhinia was ca. 62.7 Ma. The Asian lineage first diverged at ca. 59.8 Ma, followed by divergence of the Africa lineage starting during the late Eocene, whereas that of the neotropical lineage starting during the middle Miocene. Hypotheses relying on vicariance or continental history to explain pantropical disjunct distributions are dismissed because they require mostly Palaeogene and older tectonic events. We suggest that Bauhinia originated in the middle Paleocene in Laurasia, probably in Asia, implying a possible Tethys Seaway origin or an "Out of Tropical Asia", and dispersal of legumes. Its present pantropical disjunction resulted from disruption of the boreotropical flora by climatic cooling after the Paleocene-Eocene Thermal Maximum (PETM). North Atlantic land bridges (NALB) seem the most plausible route for migration of Bauhinia from Asia to America; and additional aspects of the Bauhinia species distribution are explained by migration and long distance dispersal (LDD) from Eurasia to the African and American continents.

Benthic Foraminiferal Assemblages during ETM2: Variations by Geography and Depth

NASA Astrophysics Data System (ADS)

Thomas, E.

2017-12-01

Early Paleogene hyperthermal events were perturbations of the global carbon cycle of varying magnitude, characterized by global warming and ocean acidification. The most extreme was the Paleocene-Eocene Thermal Maximum (PETM; 55.9 Ma), with Eocene Thermal Event 2 (ETM2) 1.8 myr later. These events of different magnitude allow us to investigate whether the response of biota to hyperthermal events scales with the magnitude of the event (given by its carbon isotope excursion). During the PETM deep-sea benthic foraminifera suffered severe extinction; assemblages directly postdating the extinction have low diversity and high dominance of opportunistic taxa. Faunas had partially recovered before ETM2, but never recovered the full pre-PETM diversity. Across ETM2, assemblages at Walvis Ridge (SE Atlantic) Sites 1263 (paleodepth 1500m) and 1262 (paleodepth 3600m) (Jennions et al., 2015) and at Site 1209 (Shatsky Rise, subtropical Pacific, paleodepth 1900 m) and Site 1215 (tropical eastern Pacific Ocean) did not suffer extinction. All sites saw temporary declines in diversity and equity, increased abundance of low-food indicators, and declining benthic foraminiferal accumulation rates, possibly linked to increased remineralization in the water column (Lewis et al. 2017). ETM2 records for deep Pacific Site 1215 are incomplete, because the site was close to, and at times, below the CCD, but assemblages are similar to these at deeper Site 1262 (above the Atlantic CCD), with abundant oligotrophic taxa. ETM2 assemblages at Site 1209 and 1263 both have more rectilinear and buliminid taxa than the deeper sites, indicative of a higher food supply. Site 1263, the shallowest of the studied sites, saw a much more severe decline in diversity and abundance of benthic foraminifera than Site 1209, and than both deeper sites. Deep-sea benthic assemblages thus show no simple correlation between the magnitude of hyperthermal events and that of the global biotic response, but have strong geographic and bathymetric variability. Jennions, S. M., Thomas, E., Schmidt, D. N., Lunt, D., and Ridgwell, A., 2015, Paleoceanography, 30 1059-1077 Lewis, A., Griffith, E. M., Thomas, E., and Winguth, A., 2017. Marine Export Production and Remineralization during early Eocene hyperthermal events. AGU, this session.

Late Paleocene-middle Eocene benthic foraminifera on a Pacific seamount (Allison Guyot, ODP Site 865): Greenhouse climate and superimposed hyperthermal events

NASA Astrophysics Data System (ADS)

Arreguín-Rodríguez, Gabriela J.; Alegret, Laia; Thomas, Ellen

2016-03-01

We investigated the response of late Paleocene-middle Eocene (~60-37.5 Ma) benthic foraminiferal assemblages to long-term climate change and hyperthermal events including the Paleocene-Eocene Thermal Maximum (PETM) at Ocean Drilling Program (ODP) Site 865 on Allison Guyot, a seamount in the Mid-Pacific Mountains. Seamounts are isolated deep-sea environments where enhanced current systems interrupt bentho-pelagic coupling, and fossil assemblages from such settings have been little evaluated. Assemblages at Site 865 are diverse and dominated by cylindrical calcareous taxa with complex apertures, an extinct group which probably lived infaunally. Dominance of an infaunal morphogroup is unexpected in a highly oligotrophic setting, but these forms may have been shallow infaunal suspension feeders, which were ecologically successful on the current-swept seamount. The magnitude of the PETM extinction at Site 865 was similar to other sites globally, but lower diversity postextinction faunas at this location were affected by ocean acidification as well as changes in current regime, which might have led to increased nutrient supply through trophic focusing. A minor hyperthermal saw less severe effects of changes in current regime, with no evidence for carbonate dissolution. Although the relative abundance of infaunal benthic foraminifera has been used as a proxy for surface productivity through bentho-pelagic coupling, we argue that this proxy can be used only in the absence of changes in carbonate saturation and current-driven biophysical linking.

Coupled high-resolution marine and terrestrial records of carbon and hydrologic cycles variations during the Paleocene-Eocene Thermal Maximum (PETM)

NASA Astrophysics Data System (ADS)

Tipple, Brett J.; Pagani, Mark; Krishnan, Srinath; Dirghangi, Sitindra S.; Galeotti, Simone; Agnini, Claudia; Giusberti, Luca; Rio, Domenico

2011-11-01

The Paleocene-Eocene Thermal Maximum is characterized by a massive perturbation of the global carbon cycle reflected in a large, negative carbon isotope excursion associated with rapid global warming and changes in the hydrologic system. The magnitude of the carbon isotope excursion from terrestrial carbonates and organic carbon is generally larger relative to marine carbonates. However, high-resolution marine and terrestrial isotopic records from the same locality for direct comparison are limited. Here we present coupled carbon isotope records from terrestrial biomarkers (δ 13C n-alkane ), marine bulk carbonates (δ 13C carbonate), and bulk organic carbon (δ 13C organic) from the continuous sedimentary record of the Forada section in northern Italy in order to evaluate the magnitude and phase relationships between terrestrial and marine environments. Consistent with previous reports, we find that the carbon isotope excursion established from δ 13C n-alkane values is more negative than those established from δ 13C carbonate and δ 13C organic values. In contrast to the majority of PETM records, all Forada δ 13C records show a sharp 13C-enrichment immediately following the onset of the carbon isotope excursion. Further, the terrestrial δ 13C n-alkane record lags δ 13C carbonate/δ 13C organic trends by ~ 4-5 kyr—offsets that reflect the long residence time of soil organic carbon. Hydrogen isotope records from higher-plant leaf waxes (δD n-alkane ) and sea-surface temperatures (TEX 86) were established to assess hydrologic and ocean temperature trends. We find δD n-alkane values trend more positive, associated with higher temperatures prior to the onset of the carbon isotope excursion, and conclude that regional changes in the hydrologic cycle likely occurred before the onset of the carbon isotope anomaly.

An Ocean Acidification Pulse in the Pre-onset Carbon Isotope Excursion Preceding the Paleocene-Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Robinson, M. M.; Self-Trail, J. M.; Willard, D. A.; Stassen, P.; Spivey, W.

2015-12-01

The Paleocene-Eocene Thermal Maximum (PETM; ~55.5 Ma) is recognized globally in marine sediments by a carbonate dissolution zone, the extinction or turnover of benthic taxa, and a radiation of planktic excursion taxa, all accompanied by a rapid-onset, negative carbon isotope excursion (CIE). The cause and nature of the massive carbon release leading to this extreme climate event remains under debate. Regardless of cause, the environmental and ecosystem changes centered on the PETM are the subject of much study because they provide an analog to modern deteriorating conditions associated with the ongoing rise in atmospheric carbon dioxide. We present evidence from sediments of the South Dover Bridge core, deposited on the U.S. mid-Atlantic shelf, for an ocean acidification event in the latest Paleocene that coincides with a relatively small (-2‰) negative carbon isotope excursion (CIE) that precedes the larger (-4‰) Paleocene-Eocene CIE onset. Planktic foraminifers during this pre-onset event (POE) show post-deposition dissolution in which the coarsely cancellate and muricate wall textures characteristic of many Late Paleocene species have been dissolved away, leaving smooth, thin-walled specimens often with collapsed chambers. In addition, we document biotic responses in benthic, planktic, and terrestrial communities to the POE, including shifts in foraminifer and pollen assemblages and adaptations in calcareous nannofossil species in response to environmental perturbations. A complete recovery is evident between the POE and CIE in both the carbon isotopic signal and in the biotic response, providing additional evidence not only for a pulsed carbon release, but also for a more rapid rate of carbon release than is suggested by a single pulse over a longer period of time. The timing, nature and magnitude of ecological changes during the less extreme POE shallow water acidification event may help to define the ecological tipping point of shallow marine ecosystems.

A Possible Late Paleocene-Early Eocene Ocean Acidification Event Recoded in the Adriatic Carbonate Platform

NASA Astrophysics Data System (ADS)

Weiss, A.; Martindale, R. C.; Kosir, A.; Oefinger, J.

2017-12-01

The Paleocene-Eocene Thermal Maximum (PETM) event ( 56.3 Ma) was a period of massive carbon release into the Earth system, resulting in significant shifts in ocean chemistry. It has been proposed that ocean acidification - a decrease in the pH and carbonate saturation state of the water as a result of dissolved carbon dioxide in sea water - occurred in both the shallow and deep marine realms. Ocean acidification would have had a devastating impact on the benthic ecosystem, and has been proposed as the cause of decreased carbonate deposition in marine sections and coral reef collapse during the late Paleocene. To date, however, the only physical evidence of Paleocene-Eocene ocean acidification has been shown for offshore sites (i.e., a shallow carbonate compensation depth), but isotope analysis (i.e. B, I/Ca) suggests that acidification occurred in the shallow shelves as well. Several sites in the Kras region of Slovenia, has been found to contain apparent erosion surfaces coeval with the Paleocene-Eocene Boundary. We have investigated these potentially acidified horizons using petrography, stable carbon isotopes, cathodoluminescence, and elemental mapping. These datasets will inform whether the horizons formed by seafloor dissolution in an acidified ocean, or are due to subaerial exposure, or burial diagenesis (i.e. stylotization). Physical erosion and diagenesis can easily be ruled out based on field relationships and petrography, but the other potential causes must be analyzed more critically.

Dinocyst taphonomy, impact craters, cyst ghosts, and the Paleocene-Eocene thermal maximum (PETM)

USGS Publications Warehouse

Edwards, Lucy E.

2012-01-01

Dinocysts recovered from sediments related to the Chesapeake Bay impact structure in Virginia and the earliest Eocene suboxic environment in Maryland show strange and intriguing details of preservation. Features such as curled processes, opaque debris, breakage, microborings and cyst ghosts, among others, invite speculation about catastrophic depositional processes, rapid burial and biological and chemical decay. Selected specimens from seven cores taken in the coastal plain of Virginia and Maryland show abnormal preservation features in various combinations that merit illustration, description, discussion and further study. Although the depositional environments described are extreme, many of the features discussed are known from, or could be found in, other environments. These environments will show both similarities to and differences from the extreme environments here.

Interpreting the paleo-redox record: Mn enrichment factors

NASA Astrophysics Data System (ADS)

Chun, C. O.; Delaney, M. L.

2006-12-01

Redox-sensitive metal enrichment factors (EF), have the ability to describe the redox chemistry of the overlying water and marine sediments at time of burial. Manganese (Mn) precipitates as Mn-rich oxyhydroxides in oxic environments, leading to sedimentary EF > 1 calculated relative to average continental crust as the presumed detrital source. Mn EF can also occur from source changes that are unrelated to redox changes. We compared bulk sediment digestions to sample splits treated with a reductive cleaning step prior to sediment digestion, to test whether the Mn EF are from oxyhydroxides. We measured sedimentary Mn EF for the past 30 m.y. for a Nazca Ridge site in the southeast Pacific (ODP Site 1237). The site is marked by a pronounced color change at 162 mcd, within an interval dominated by calcareous-rich lithology, prompting questions of source versus paleo-redox changes. Mn EF were measured across the Paleocene-Eocene Thermal Maximum (PETM) at three sites on Walvis Ridge in the southeast Atlantic (ODP Sites 1262, 1266, and 1263). The PETM global warming event leads to questions of redox changes. At Nazca Ridge Mn EF range from 10-70 prior to the change with decrease to crustal averages after the boundary. After two reductive cleanings on sediments exhibiting Mn EF >1, Mn EF were at crustal averages. Mn EF prior to the color change are oxyhydroxides and not a major input of detrital material. We suggest the color change represents a paleo-redox boundary, more oxygenated depositional setting prior to the change and more reducing depositional setting afterwards. Walvis Ridge PETM sections exhibit Mn EF values ranging between 4 and 12 prior to the warming, values at crustal averages during the warming, return to pre-event values in the recovery period. After the reductive cleaning procedure the deep (1262) and intermediate (1266) sites with Mn EF >1 before and after the warming event reduced to crustal averages with no change to Mn EF during the event. Bottom waters at those two sites were most likely oxygenated prior to the event, reducing at the onset of the warming, and returned to pre-event conditions in the recovery. Future studies of Mn EF as a paleo-redox indicator should include the reductive cleaning procedure to verify Mn-oxyhydroxides.

Cenozoic mean greenhouse gases and temperature changes with reference to the Anthropocene.

PubMed

Glikson, Andrew

2016-12-01

Cenozoic greenhouse gases (GHG) variations and warming periods underscore the extreme rates of current climate change, with major implications for the adaptability and survivability of terrestrial and marine habitats. Current rise rate of greenhouse gases, reaching 3.3 ppm CO 2 per year during March 2015-2016, is the fastest recorded since the Paleocene-Eocene Thermal Event (PETM) when carbon release to the atmosphere was about an order of magnitude less than at present. The ice core evidence of concentration of (GHG) and temperatures in the atmosphere/ocean/cryosphere system over the last 740 kyr suggests that the rate of rise in GHG over the last ~260 years, CO 2 rates rising from 0.94 ppm yr -1 in 1959 (315.97 ppm) to 1.62 ppm yr -1 in 2000 (369.52 ppm) to 3.05 ppm yr -1 in 2015 (400.83 ppm), constitutes a unique spike in the history of the atmosphere. The reliance of pre-740 kyr paleoclimate estimates on multiple proxies, including benthic and plankton fossils, fossil plants, residual organic matter, major and trace elements in fossils, sediments and soils, place limits on the resolution of pre-upper Pleistocene paleoclimate estimates, rendering it likely recorded mean Cenozoic paleoclimate trends may conceal abrupt short-term climate fluctuations. However, as exemplified by the Paleocene-Eocene thermal maximum (PETM) and earlier GHG and temperature spikes associated with major volcanic and asteroid impact events, the long-term residence time of CO 2 in the atmosphere extends the signatures of abrupt warming events to within detection limits of multiple paleoproxies. The mean post-1750 temperature rise rate (approximately ~0.0034 °C per yr, or ~0.008 °C per yr where temperature is not masked by sulfur aerosols) exceeds those of the PETM (approximately ~0.0008-0.0015 °C per yr) by an order of magnitude and mean glacial termination warming rates (last glacial termination [LGT] ~ 0.00039; Eemian ~0.0004 °C per yr) by near to an order of magnitude. Consistent with previous interglacial peaks an increasing likelihood of collapse of the Atlantic Meridional Ocean Circulation is threatening a severe stadial event. © 2016 John Wiley & Sons Ltd.

Thermal evolution of the equatorial Pacific thermocline during Eocene Thermal Maximum 2 from foraminifera stable isotope and trace metal analysis

NASA Astrophysics Data System (ADS)

Strojie, W. M.; Harper, D. T.; Zachos, J. C.

2017-12-01

The late Paleocene and Early Eocene were characterized by a series of brief hyperthermal events, the largest of which is the Paleocene-Eocene Thermal Maximum (PETM, 55.5 Ma) followed by a lower magnitude Eocene Thermal Maximum 2 (ETM2, 53.7 Ma), also known as H1. These events are characterized by a global negative Carbon Isotope Excursion (CIE) coincident with a dissolution horizon in pelagic sediment cores indicative of Carbonate Compensation Depth (CCD) shoaling and significant ocean acidification. The S.E. Atlantic Walvis Ridge ETM2 CIE is a δ13CCarb 1.0‰ - 1.5‰ and δ13CBulk 3.5‰ with an estimated 3oC surface and benthic warming. The record of transient hyperthermals such as ETM2 is not as extensive in the Pacific as the Atlantic. Given the size of the Pacific, this represents a critical gap in our understanding of the overall carbon cycle and oceanographic response of this event. Our research investigates the evolution of ocean thermal structure in the equatorial Pacific preceding, during, and after ETM-2. We generated new data on thermocline temperature from ODP Site 1209 Shatsky Rise using planktonic foraminifera δ18O and Mg/Ca while inferring carbon cycle dynamics from δ13C. The data shows 3 CIE's from 53.7Ma - 53.6Ma (ETM2, H2, and I1). ETM2 is preceded by 40kyr of bulk and thermocline δ13C convergence with two transient warming steps. The CIE duration 90kyr with an 50kyr recovery phase. The total magnitude of peak thermocline warming 2.0oC to 2.2oC for ETM2. No thermocline warming is observed for H2. I1 peak magnitude of thermocline warming 3.0oC. Orbital pacing of the carbon cycle is also evident from 100kyr separation of ETM2 and H2, an 300kyr separation of ETM2 and I1, and an 40kyr pre-CIE convergence of δ13Ccarb & δ13Cbulk with an apparent two warming steps 15-20kyr apart.

The Eocene Thermal Maximum 2 (ETM-2) in a terrestrial section of the High Arctic: identification by U-Pb zircon ages of volcanic ashes and carbon isotope records of coal and amber (Stenkul Fiord, Ellesmere Island, Canada)

NASA Astrophysics Data System (ADS)

Reinhardt, Lutz; von Gosen, Werner; Piepjohn, Karsten; Lückge, Andreas; Schmitz, Mark

2017-04-01

The Stenkul Fiord section on southern Ellesmere Island reveals largely fluvial clastic sediments with intercalated coal seams of the Margaret Formation of Late Paleocene/Early Eocene age according to palynology and vertebrate remains. Field studies in recent years and interpretative mapping of a high-resolution satellite image of the area southeast of Stenkul Fiord revealed that the clastic deposits consist of at least four sedimentary units (Units 1 to 4) separated by unconformities. Several centimeter-thin volcanic ash layers, recognized within coal layers and preserved as crandallite group minerals (Ca-bearing goyazite), suggest an intense volcanic ash fall activity. Based on new U-Pb zircon ages (ID-TIMS) of three ash layers, the volcanic ash fall took place at 53.7 Ma in the Early Eocene, i.e. within the Eocene Thermal Maximum 2 (ETM-2) hyperthermal. The ETM-2 is bracketed further by discrete negative excursions of carbon isotope records of both bulk coal and amber droplets collected from individual coal layers of the section. The identification of the ETM-2 hyperthermal provides a stratigraphic tie-point in the terrestrial Margaret Formation sediments enabling assignment of the lowermost sedimentary Unit 1 to the Late Paleocene-earliest Eocene, Unit 2 to the Early Eocene, whereas Unit 3 and 4 might be Early to Middle Eocene in age. Thus the timing of syn-sedimentary movements of the Eurekan deformation causal for the observed unconformities in the section can be studied and the positions of further hyperthermals like the PETM or the ETM-3 in the section can be identified in the future. The integration of structural studies, new U-Pb zircon ages, and different carbon isotope records provides a new stratigraphic framework for further examination of the unique Early Eocene flora and fauna preserved in this high-latitude outcrop.

The PETM in the mid-Atlantic Coastal Plain: A widespread record of unique climate signatures in shallow-shelf Marlboro Clay

NASA Astrophysics Data System (ADS)

Powars, D. S.; Edwards, L. E.; Kopp, R. E.; Self-Trail, J.; Schultz, A.

2009-12-01

Abrupt sedimentary changes mark the Paleocene-Eocene Thermal Maximum (PETM) in the mid-Atlantic Coastal Plain. Across the tectonic downwarp known as the Salisbury Embayment (southeastern Virginia to central New Jersey), kaolinite-rich clay (the Marlboro Clay) abruptly replaces glauconite-rich quartz sand, silt, and illite-smectite clay of the late Paleocene. Dozens of cored boreholes obtained by the USGS and other Federal and State agencies, together with geophysical logs from more than 100 boreholes, allow us to document the widespread distribution and depositional, biostratigraphic, paleoecologic, taphonomic, and tectonic characteristics of the Marlboro Clay. In Maryland and Virginia, the Marlboro Clay is a silvery-gray to pale-red plastic clay and locally includes thin laminations and thicker beds of silt, concretions, pyrite nodules, and rare shell fragments (in downdip cores). The clay is unconformity bounded with highly burrowed contacts. The lower contact is locally so bioturbated that it has been reported as gradational. The upper contact in Virginia has glauconite-rich, sand-filled burrows from the overlying Nanjemoy Formation (lower Eocene) that penetrate as much as 8.5 m down into the Marlboro Clay (total thickness only 9 m). Biostratigraphically, the Marlboro Clay is placed in calcareous nannofossil Zone NP9 (and NP10 in downdip cores) and includes the PETM marker dinocyst species Apectodinium augustum (in downdip cores). In New Jersey, a similar clay deposit is described from the subsurface; and based on consistency in lithology, biostratigraphy, stratigraphic position, isotopic composition and its magnetic properties, we apply the name Marlboro Clay to this unique clay unit throughout the Salisbury Embayment. Structure-contour and isopach maps of the present configuration of the Marlboro Clay reveal a widespread deposit with localized truncation or thinning. Tectonic folding and faulting along the inner Coastal Plain and along the James River structural zone produced syn- and post-depositional erosional thinning on uplifted sides of faults and thickening in downdropped areas. The Chesapeake Bay Impact Structure (CBIS) removed the Marlboro Clay across a large area of southeastern Virginia. Faults and folds associated with the CBIS appear to deform the clay in an outer-fracture-zone that extends up to 25-km outside the crater’s outer rim. The Marlboro Clay thickens and is slightly finer-grained in the deeper part of the Marlboro basin in where structure contours on the top-of-basement generally mimic the tectonic downwarp. The apparent deepest (>200 m below sea level) and thickest (>14 m) part of the Marlboro depositional basin appears to extend from just south of the mouth of the Potomac River northward to the lower Choptank River valley, Maryland, then turns sharply northeastward to beneath the central part of Delaware Bay. The Marlboro Clay of the mid-Atlantic United States thus provides a widespread deposit that in its regional and tectonic setting records, in its unusual sedimentary properties, the severe regional environmental changes associated with global climate change during the PETM.

Paleo-Productivity across the Paleocene-Eocene Thermal Maximum, Walvis Ridge Transect (ODP Sites 1262, 1263, and 1266)

NASA Astrophysics Data System (ADS)

Chun, C. O.; Delaney, M. L.; Zachos, J. C.

2005-12-01

Walvis Ridge transect (Ocean Drilling Program (ODP) Leg 208) provides the first high-resolution depth-transect of deep-sea sediments recovered from the south Atlantic across the P/E boundary. A geographically restricted depth transect (~ 2.2 km, water depths between 2500 and 4770 m) allows us to constrain the surface waters by assuming marine productivity conditions in the overlying water column are similar across all sites. The sediment record will reveal variations for processes that are water-depth dependent. We use the geochemical tracers; biogenic barium, phosphorus, calcium carbonate, and the redox sensitive trace elements manganese and uranium, to reconstruct nutrient burial, paleoproductivity, and bottom water redox chemistry across the Paleocene-Eocene Thermal Maximum (PETM). We calculate our concentrations on a calcium carbonate-free basis to account for dilution by non-carbonate sediments. Trace metal enrichment factors (EFs) are calculated relative to bulk crustal averages. We chose three sites from the depth transect: the shallowest (Site 1263, 2717 m water depth), an intermediate site (Site 1266, 3798 m water depth), and the deepest site (Site 1262, 4755 m water depth). We sampled each site at a sample resolution of ~ 1-2 kyr for 5 m.y. centered at 55 Ma. Uranium EFs at the shallow site exhibits values ~ 5 pre-event and drop to values near crustal averages during and after the carbon isotope excursion (CIE). No dramatic changes in U EFs across the P/E boundary are recorded at the deep and intermediate sites. Mn EFs range between 2.9 -8.6 prior to the event across all three sites, suggesting an oxygenated depositional environment. At the boundary, Mn EFs drop to crustal averages at all sites, then gradually return to pre-event values, indicating more reducing environments during the CIE, a possible explanation for the benthic extinction event (BEE) observed across this transect. Ba excess and reactive phosphorus exhibit decreased concentrations during the CIE with gradual return to pre-event values at the shallowest and deepest sites. We will compare the paleo-productivity and redox chemistry response at the Walvis Ridge sites across the PETM.

Evaluating the provenance of Permian-Triassic and Palaeocene-Eocene ash beds by high precision U-Pb and Lu-Hf isotopic analyses of zircons: linking local sedimentary records to global events

NASA Astrophysics Data System (ADS)

Eivind Augland, Lars; Jones, Morgan; Planke, Sverre; Svensen, Henrik; Tegner, Christian

2016-04-01

Zircons are a powerful tool in geochronology and isotope geochemistry, as their affinity for U and Hf in the crystal structure and the low initial Pb and Lu allow for precise and accurate dating by U-Pb ID-TIMS and precise and accurate determination of initial Hf isotopic composition by solution MC-ICP-MS analysis. The U-Pb analyses provide accurate chronostratigraphic controls on the sedimentary successions and absolute age frames for the biotic evolution across geological boundaries. Moreover, the analyses of Lu-Hf by solution MC-ICP-MS after Hf-purification column chemistry provide a powerful and robust fingerprinting tool to test the provenance of individual ash beds. Here we focus on ash beds from Permian-Triassic and Palaeocene successions in Svalbard and from the Palaeocene-Eocene Thermal Maximum (PETM) in Fur, Denmark. Used in combination with whole rock geochemistry from the ash layers and the available geochemical and isotopic data from potential source volcanoes, these data are used to evaluate the provenance of the Permian-Triassic and Palaeocene ashes preserved in Svalbard and PETM ashes in Denmark. If explosive eruptions from volcanic centres such as the Siberian Traps and the North Atlantic Igneous Province (NAIP) can be traced to distal basins as ash layers, they provide robust tests of hypotheses of global synchronicity of environmental changes and biotic crises. In addition, the potential correlation of ash layers with source volcanoes will aid in constraining the extent of explosive volcanism in the respective volcanic centres. The new integrated data sets will also contribute to establish new reference sections for the study of these boundary events when combined with stable isotope data and biostratigraphy.

Effects of rapid global warming at the Paleocene-Eocene boundary on neotropical vegetation.

PubMed

Jaramillo, Carlos; Ochoa, Diana; Contreras, Lineth; Pagani, Mark; Carvajal-Ortiz, Humberto; Pratt, Lisa M; Krishnan, Srinath; Cardona, Agustin; Romero, Millerlandy; Quiroz, Luis; Rodriguez, Guillermo; Rueda, Milton J; de la Parra, Felipe; Morón, Sara; Green, Walton; Bayona, German; Montes, Camilo; Quintero, Oscar; Ramirez, Rafael; Mora, Germán; Schouten, Stefan; Bermudez, Hermann; Navarrete, Rosa; Parra, Francisco; Alvarán, Mauricio; Osorno, Jose; Crowley, James L; Valencia, Victor; Vervoort, Jeff

2010-11-12

Temperatures in tropical regions are estimated to have increased by 3° to 5°C, compared with Late Paleocene values, during the Paleocene-Eocene Thermal Maximum (PETM, 56.3 million years ago) event. We investigated the tropical forest response to this rapid warming by evaluating the palynological record of three stratigraphic sections in eastern Colombia and western Venezuela. We observed a rapid and distinct increase in plant diversity and origination rates, with a set of new taxa, mostly angiosperms, added to the existing stock of low-diversity Paleocene flora. There is no evidence for enhanced aridity in the northern Neotropics. The tropical rainforest was able to persist under elevated temperatures and high levels of atmospheric carbon dioxide, in contrast to speculations that tropical ecosystems were severely compromised by heat stress.

Palaeoclimate reconstruction within the upper Eocene in central Germany using fossil plants

NASA Astrophysics Data System (ADS)

Moraweck, Karolin; Kunzmann, Lutz; Uhl, Dieter; Kleber, Arno

2013-04-01

The Eocene has been commonly called "The world`s last greenhouse period" covering the Paleocene-Eocene Thermal Maximum (PETM) as well as the Eocene-Oligocene turnover. In the mid-latitudes of Europe this turnover was characterized by pronounced climatic changes from subtropical towards temperate conditions that were accompanied by significant vegetational changes on land. Fossil plants are regarded as excellent palaeoenvironmental proxies, because leaf physiognomy often reflects climate conditions. The study site, the Paleogene Weißelster basin in central Germany, including fluvial, estuarine and lacustrine deposits, provides several excellently preserved megafloras for reconstructions of terrestrial palaeoclimate. For our case study we used material from different stratigraphic horizons within the late Eocene Zeitz megafloral assemblage recovered from the open-cast mines of Profen and Schleenhain. These horizons cover a time interval of ca. 3 Ma. The Zeitz megafloral assemblage ("Florenkomplex") was characterized by mainly evergreen, notophyllous vegetation, consisting of warm-temperate to subtropical elements. Tropical species are present but very rare. To infer the regional climatic conditions and putative climate changes from these fossil plants we compare proxy data obtained by the application of standard methods for quantitative reconstruction of palaeoclimate data: the coexistence approach (CA), leaf margin analysis (LMA) and Climate Leaf Analysis Multivariate Program (CLAMP).Before the CA was applied to the material the list of putative nearest living relative species (NLR) was carefully revisited and partly revised. In case of the LMA approach information of so-called "silent taxa" (fossil species preserved by diaspores, leaf margin state is inferred from NLR data) were partly included in the data set. The four floras from the Zeitz megafloral assemblage show slightly different floral compositions caused by various taphonomic processes. An aim of the investigations was to test whether these differences lead to differences in calculated mean annual temperatures (MAT) or not. The MAT, calculated by LMA for the four sites, remarkably differ in dependency on the incorporation of "silent taxa" whenever present. MAT based on leaf remains only is often higher, because of the overrepresentation of laurophyllous entire-margined leaves in the respective taphocoenoses. Inclusion of "silent taxa" that often represents species with un-toothed leaves significantly decreases calculated MAT. It is expected that CLAMP and CA will render more reliable results, which will be part of the discussion. The contribution will also focus on problems in the use of leaf physiognomy as palaeoclimatic proxies and on the comparison of results obtained from a single plant taphocoenosis using different methods for quantitative reconstructions of MAT.

Hydrological cycle during the early Eocene: What can we learn from leaf waxes?

NASA Astrophysics Data System (ADS)

Krishnan, S.; Pagani, M.; Huber, M.

2012-12-01

Understanding how rapid warming modified global precipitation patterns during periods of global warming is essential to forecasting the impact of future climate change. The early Eocene (~55-52 Ma) represents a period of peak warmth for the past 65 million years with global temperatures ~10 degrees C warmer than present. This period is also known for at least three, greenhouse gas-induced episodes of rapid global warming (hyperthermals: PETM; ~55 Ma, ETM-2; ~53.7 Ma and ETM-3; 52.8 Ma), often considered extreme analogues to modern climate change. Hyperthermals are also characterized by negative carbon isotope excursions (CIE), which reflect the input of isotopically light carbon responsible for observed temperature increases. A novel proxy used for hydrological reconstructions uses the hydrogen isotopic composition of compound-specific biomarkers preserved in the sedimentary record. For terrestrial leaf-wax lipids (e.g., n-alkanes), the hydrogen isotopic composition primarily reflects the isotopic composition of meteoric waters, which is dependent on distance of vapor transport, number of rainout events, precipitation amount, and evapotranspiration. Isotopic compositions of PETM n-alkanes (δDalkanes) recovered from the Arctic Ocean show a substantial deuterium (D)-enrichment at the onset of the CIE which was argued to potentially reflect reduced rainout in the mid-latitudes, resulting in increased precipitation in the Arctic (Pagani et al., 2006). D-depleted values of n-alkanes during peak warmth of the PETM suggest either modification of local precipitation or a global change in the fraction of rainout. In this study, we evaluate the veracity of previous conclusions by compiling existing δDalkanes records (including from Mar-2X, Venezuela; Tawanui, New Zealand; Wilkes Land, Antarctica; and the Lomonsov Ridge, Arctic) with new records from the Pacific and Atlantic oceans and marginal marine sections (including Cicogna, Italy; Giraffe Core, Canadian High Arctic). To determine the background state of the hydrological cycle in a warmer world, we measured early Eocene δDalkanes at these sites. This compilation was then compared against results from the isotope-coupled National Center for Atmospheric Research (NCAR) Community Climate System Model v3.0 (CCSM) global climate model, with Eocene boundary conditions and two different pCO2 levels (2240 and 4480 ppm). Preliminary analyses suggest that the model is able to simulate the equator-pole trends in precipitation δD. However, predicted values are offset from the n-alkane data by up to 40‰. To study changes in the hydrological cycle with rapid warming, we analyze n-alkane δD and δ13C values for the PETM and ETM-2. Leads and lags between the carbon and hydrogen isotopic records help constrain the timing and type of hydrological shifts with respect to carbon input. Preliminary results from the ETM-2 recovered from the Arctic indicate similar hydrological changes during both hyperthermals. A pre-event increase in δD values (of 60‰ during the PETM and 25‰ during ETM-2) is observed, followed by a decrease in δD (~10-15‰ for both the events) during the peak of the CIE. A significant pre-PETM D-enrichment at mid-latitudes is not evident, however, more negative δD values during the CIE is observed in some sites. The reasons for these isotopic shifts and their implication for the local and global water cycles will be discussed.

Comparative analysis of marine paleogene sections and biota from West Siberia and the Arctic Region

NASA Astrophysics Data System (ADS)

Akhmet'ev, M. A.; Zaporozhets, N. I.; Iakovleva, A. I.; Aleksandrova, G. N.; Beniamovsky, V. N.; Oreshkina, T. V.; Gnibidenko, Z. N.; Dolya, Zh. A.

2010-12-01

The analysis of the main biospheric events that took place in West Siberia and the Arctic region during the Early Paleogene revealed the paleogeographic and paleobiogeographic unity of marine sedimentation basins and close biogeographic relations between their separate parts. Most biotic and abiotic events of the first half of the Paleogene in the Arctic region and West Siberia were synchronous, unidirectional, and interrelated. Shelf settings, sedimentation breaks, and microfaunal assemblages characteristic of these basins during the Paleogene are compared. The comparative analysis primarily concerned events of the Paleocene-Eocene thermal maximum (PETM) and beds with Azolla (aquatic fern). The formation of the Eocene Azolla Beds in the Arctic region and West Siberia was asynchronous, although it proceeded in line with a common scenario related to the development of a system of estuarine-type currents in a sea basin partly isolated from the World Ocean.

Recent changes to the Gulf Stream causing widespread gas hydrate destabilization.

PubMed

Phrampus, Benjamin J; Hornbach, Matthew J

2012-10-25

The Gulf Stream is an ocean current that modulates climate in the Northern Hemisphere by transporting warm waters from the Gulf of Mexico into the North Atlantic and Arctic oceans. A changing Gulf Stream has the potential to thaw and convert hundreds of gigatonnes of frozen methane hydrate trapped below the sea floor into methane gas, increasing the risk of slope failure and methane release. How the Gulf Stream changes with time and what effect these changes have on methane hydrate stability is unclear. Here, using seismic data combined with thermal models, we show that recent changes in intermediate-depth ocean temperature associated with the Gulf Stream are rapidly destabilizing methane hydrate along a broad swathe of the North American margin. The area of active hydrate destabilization covers at least 10,000 square kilometres of the United States eastern margin, and occurs in a region prone to kilometre-scale slope failures. Previous hypothetical studies postulated that an increase of five degrees Celsius in intermediate-depth ocean temperatures could release enough methane to explain extreme global warming events like the Palaeocene-Eocene thermal maximum (PETM) and trigger widespread ocean acidification. Our analysis suggests that changes in Gulf Stream flow or temperature within the past 5,000 years or so are warming the western North Atlantic margin by up to eight degrees Celsius and are now triggering the destabilization of 2.5 gigatonnes of methane hydrate (about 0.2 per cent of that required to cause the PETM). This destabilization extends along hundreds of kilometres of the margin and may continue for centuries. It is unlikely that the western North Atlantic margin is the only area experiencing changing ocean currents; our estimate of 2.5 gigatonnes of destabilizing methane hydrate may therefore represent only a fraction of the methane hydrate currently destabilizing globally. The transport from ocean to atmosphere of any methane released--and thus its impact on climate--remains uncertain.

Tempo and scale of late Paleocene and early Eocene carbon isotope cycles: Implications for the origin of hyperthermals

NASA Astrophysics Data System (ADS)

Zachos, James C.; McCarren, Heather; Murphy, Brandon; Röhl, Ursula; Westerhold, Thomas

2010-10-01

The upper Paleocene and lower Eocene are marked by several prominent (> 1‰) carbon isotope (δ 13C) excursions (CIE) that coincide with transient global warmings, or thermal maxima, including the Paleocene-Eocene Thermal Maximum (PETM). The CIE, which are recorded mainly in marine sedimentary sequences, have also been identified in continental sequences, occurred episodically, and yet appear to be paced or triggered by orbital forcing. To constrain the timing and scale of the CIE relative to long-term baseline variability, we have constructed a 4.52 million year (myr) long, high-resolution (~ 3 kyr) bulk sediment carbon isotope record spanning the lower Eocene to upper Paleocene (C25r-C24n) from a pelagic sediment section recovered at ODP Site 1262 in the southeast Atlantic. This section, which was orbitally-tuned utilizing high-resolution core log physical property and geochemical records, is the most stratigraphically complete upper Paleocene to lower Eocene sequence recovered to date. Time-series analysis of the carbon isotope record along with a high-resolution Fe intensity record obtained by XRF core scanner reveal cyclicity with variance concentrated primarily in the precession (21 kyr) and eccentricity bands (100 and 400-kyr) throughout the upper Paleocene-lower Eocene. In general, minima in δ 13C correspond with peaks in Fe (i.e., carbonate dissolution), both of which appear to be in phase with maxima in eccentricity. This covariance is consistent with excess oceanic uptake of isotopically depleted carbon resulting in lower carbonate saturation during periods of high eccentricity. This relationship includes all late Paleocene and early Eocene CIE confirming pacing by orbital forcing. The lone exception is the PETM, which appears to be out of phase with the 400-kyr cycle, though possibly in phase with the 100-kyr cycle, reinforcing the notion that a mechanism other than orbital forcing and/or an additional source of carbon is required to account for the occurrence and unusual scale of this event.

Testing the ``Wildfire Hypothesis:'' Terrestrial Organic Carbon Burning as the Cause of the Paleocene-Eocene Boundary Carbon Isotope Excursion

NASA Astrophysics Data System (ADS)

Moore, E. A.; Kurtz, A. C.

2005-12-01

The 3‰ negative carbon isotope excursion (CIE) at the Paleocene-Eocene boundary has generally been attributed to dissociation of seafloor methane hydrates. We are testing the alternative hypothesis that the carbon cycle perturbation resulted from wildfires affecting the extensive peatlands and coal swamps formed in the Paleocene. Accounting for the CIE with terrestrial organic carbon rather than methane requires a significantly larger net release of fossil carbon to the ocean-atmosphere, which may be more consistent with the extreme global warming and ocean acidification characteristic of the Paleocene-Eocene Thermal Maximum (PETM). While other researchers have noted evidence of fires at the Paleocene-Eocene boundary in individual locations, the research presented here is designed to test the "wildfire hypothesis" for the Paleocene-Eocene boundary by examining marine sediments for evidence of a global increase in wildfire activity. Such fires would produce massive amounts of soot, widely distributed by wind and well preserved in marine sediments as refractory black carbon. We expect that global wildfires occurring at the Paleocene-Eocene boundary would produce a peak in black carbon abundance at the PETM horizon. We are using the method of Gelinas et al. (2001) to produce high-resolution concentration profiles of black carbon across the Paleocene-Eocene boundary using seafloor sediments from ODP cores, beginning with the Bass River core from ODP leg 174AX and site 1209 from ODP leg 198. This method involves the chemical and thermal extraction of non-refractory carbon followed by combustion of the residual black carbon and measurement as CO2. Measurement of the δ 13C of the black carbon will put additional constraints on the source of the organic material combusted, and will allow us to determine if this organic material was formed prior to or during the CIE.

First Clarkforkian Equivalent Land Mammal Age in the Latest Paleocene Basal Sparnacian Facies of Europe: Fauna, Flora, Paleoenvironment and (Bio)stratigraphy

PubMed Central

Smith, Thierry; Quesnel, Florence; De Plöeg, Gaël; De Franceschi, Dario; Métais, Grégoire; De Bast, Eric; Solé, Floréal; Folie, Annelise; Boura, Anaïs; Claude, Julien; Dupuis, Christian; Gagnaison, Cyril; Iakovleva, Alina; Martin, Jeremy; Maubert, François; Prieur, Judicaël; Roche, Emile; Storme, Jean-Yves; Thomas, Romain; Tong, Haiyan; Yans, Johan; Buffetaut, Eric

2014-01-01

The Paleocene-Eocene Thermal Maximum (PETM) is correlated with the first occurrences of earliest modern mammals in the Northern Hemisphere. The latest Paleocene Clarkforkian North American Land Mammal Age, that has yielded rodents and carnivorans, is the only exception to this rule. However, until now no pre-PETM localities have yielded modern mammals in Europe or Asia. We report the first Clarkforkian equivalent Land Mammal Age in the latest Paleocene deposits of the basal Sparnacian facies at Rivecourt, in the north-central part of the Paris Basin. The new terrestrial vertebrate and macroflora assemblages are analyzed through a multidisciplinary study including sedimentologic, stratigraphic, isotopic, and palynological aspects in order to reconstruct the paleoenvironment and to evaluate biochronologic and paleogeographic implications. The mammals are moderately diverse and not abundant, contrary to turtles and champsosaurs. The macroflora is exceptional in preservation and diversity with numerous angiosperms represented by flowers, fruits, seeds and wood preserved as lignite material, revealing an abundance of Arecaceae, Betulaceae, Icacinaceae, Menispermaceae, Vitaceae and probably Cornaceae. Results indicate a Late Paleocene age based on carbon isotope data, palynology and vertebrate occurrences such as the choristoderan Champsosaurus, the arctocyonid Arctocyon, and the plesiadapid Plesiadapis tricuspidens. However, several mammal species compare better with the earliest Eocene. Among these, the particular louisinid Teilhardimys musculus, also recorded from the latest Paleocene of the Spanish Pyrenees, suggests a younger age than the typical MP6 reference level. Nevertheless, the most important aspect of the Rivecourt fauna is the presence of dental remains of a rodent and a “miacid” carnivoran, attesting to the presence of two modern mammalian orders in the latest Paleocene of Europe. Interestingly, these two groups are also the only modern groups recorded from the latest Paleocene of North America, making Rivecourt the first direct equivalent to the Clarkforkian Land Mammal Age outside of North America. PMID:24489703

Cenozoic climate change and diversification on the continental shelf and slope: evolution of gastropod diversity in the family Solariellidae (Trochoidea).

PubMed

Williams, S T; Smith, L M; Herbert, D G; Marshall, B A; Warén, A; Kiel, S; Dyal, P; Linse, K; Vilvens, C; Kano, Y

2013-04-01

Recent expeditions have revealed high levels of biodiversity in the tropical deep-sea, yet little is known about the age or origin of this biodiversity, and large-scale molecular studies are still few in number. In this study, we had access to the largest number of solariellid gastropods ever collected for molecular studies, including many rare and unusual taxa. We used a Bayesian chronogram of these deep-sea gastropods (1) to test the hypothesis that deep-water communities arose onshore, (2) to determine whether Antarctica acted as a source of diversity for deep-water communities elsewhere and (3) to determine how factors like global climate change have affected evolution on the continental slope. We show that although fossil data suggest that solariellid gastropods likely arose in a shallow, tropical environment, interpretation of the molecular data is equivocal with respect to the origin of the group. On the other hand, the molecular data clearly show that Antarctic species sampled represent a recent invasion, rather than a relictual ancestral lineage. We also show that an abrupt period of global warming during the Palaeocene Eocene Thermal Maximum (PETM) leaves no molecular record of change in diversification rate in solariellids and that the group radiated before the PETM. Conversely, there is a substantial, although not significant increase in the rate of diversification of a major clade approximately 33.7 Mya, coinciding with a period of global cooling at the Eocene-Oligocene transition. Increased nutrients made available by contemporaneous changes to erosion, ocean circulation, tectonic events and upwelling may explain increased diversification, suggesting that food availability may have been a factor limiting exploitation of deep-sea habitats. Tectonic events that shaped diversification in reef-associated taxa and deep-water squat lobsters in central Indo-West Pacific were also probably important in the evolution of solariellids during the Oligo-Miocene.

Cenozoic climate change and diversification on the continental shelf and slope: evolution of gastropod diversity in the family Solariellidae (Trochoidea)

PubMed Central

Williams, S T; Smith, L M; Herbert, D G; Marshall, B A; Warén, A; Kiel, S; Dyal, P; Linse, K; Vilvens, C; Kano, Y

2013-01-01

Recent expeditions have revealed high levels of biodiversity in the tropical deep-sea, yet little is known about the age or origin of this biodiversity, and large-scale molecular studies are still few in number. In this study, we had access to the largest number of solariellid gastropods ever collected for molecular studies, including many rare and unusual taxa. We used a Bayesian chronogram of these deep-sea gastropods (1) to test the hypothesis that deep-water communities arose onshore, (2) to determine whether Antarctica acted as a source of diversity for deep-water communities elsewhere and (3) to determine how factors like global climate change have affected evolution on the continental slope. We show that although fossil data suggest that solariellid gastropods likely arose in a shallow, tropical environment, interpretation of the molecular data is equivocal with respect to the origin of the group. On the other hand, the molecular data clearly show that Antarctic species sampled represent a recent invasion, rather than a relictual ancestral lineage. We also show that an abrupt period of global warming during the Palaeocene Eocene Thermal Maximum (PETM) leaves no molecular record of change in diversification rate in solariellids and that the group radiated before the PETM. Conversely, there is a substantial, although not significant increase in the rate of diversification of a major clade approximately 33.7 Mya, coinciding with a period of global cooling at the Eocene–Oligocene transition. Increased nutrients made available by contemporaneous changes to erosion, ocean circulation, tectonic events and upwelling may explain increased diversification, suggesting that food availability may have been a factor limiting exploitation of deep-sea habitats. Tectonic events that shaped diversification in reef-associated taxa and deep-water squat lobsters in central Indo-West Pacific were also probably important in the evolution of solariellids during the Oligo-Miocene. PMID:23610633

Can Cooler Heads Prevail?

NASA Astrophysics Data System (ADS)

Rice, A. R.

2015-12-01

The significant correlation between dropping temperatures throughout the Pliocene and the concomitant explosive expansion of the Hominid brain has led a number of workers to postulate climate change drove human evolution. Our brain (that of Homo sapiens), comprises 1-2 percent of our body weight but consumes 20 -25 percent of the body's caloric intake. We are "hotheads". Brains are extremely sensitive to overheating but we are endowed with unparalleled thermal regulation, much of it given over to protecting the Central Nervous System (CNS). Will there be reversed trends with global warming? The human brain has been shrinking since the end of the Ice Ages, losing about 150cc over the past 10,000 years. Polar bear skulls have been downsizing as well. Almost all mass extinctions or evolutionary upheavals are attributed to global warming: e.g. the Permian/Triassic (P/T) event, i.e., "The Great Dying", 250 million years ago (~90% of all life forms wiped out); the Paleocene/ Eocene Thermal Maximum (PETM) 55 million years ago. They may be analogs for what might await us. Large creatures, whose body size inhibits cooling, melted away during the PETM. Horses, initially the size of dogs then, reduced to the size of cats. An unanticipated hazard for humans that may attend extreme global warming is dumbing down or needing to retreat to the Poles as did those creatures that survived the P/T event (some references: http://johnhawks.net/research/hawks-2011-brain-size-selection-holocene; Kandel, E. et al Principles of Neural Science 4th ed. New York (US): McGraw-Hill, 2000; Selective Brain Cooling in Early Hominids:phylogenetic and evolutionary implications, Reeser, H., reeser@flmnh.ufl.edu; How the body controls brain temperature; the temperature shielding effect of cerebral blood flow, Mingming Z. et al. J Appl Physiol. 2006 November; 101(5): 1481-1488; news.nationalgeographic.com/ news/2014/03/140327-climate-change-shrinks-salamanders-global-warming-science/; Heat illness and heat stroke, www.ozemedicine.com/wiki/doku.php?id=heat illness 7/3/2010)

First Clarkforkian equivalent Land Mammal Age in the latest Paleocene basal Sparnacian facies of Europe: fauna, flora, paleoenvironment and (bio)stratigraphy.

PubMed

Smith, Thierry; Quesnel, Florence; De Plöeg, Gaël; De Franceschi, Dario; Métais, Grégoire; De Bast, Eric; Solé, Floréal; Folie, Annelise; Boura, Anaïs; Claude, Julien; Dupuis, Christian; Gagnaison, Cyril; Iakovleva, Alina; Martin, Jeremy; Maubert, François; Prieur, Judicaël; Roche, Emile; Storme, Jean-Yves; Thomas, Romain; Tong, Haiyan; Yans, Johan; Buffetaut, Eric

2014-01-01

The Paleocene-Eocene Thermal Maximum (PETM) is correlated with the first occurrences of earliest modern mammals in the Northern Hemisphere. The latest Paleocene Clarkforkian North American Land Mammal Age, that has yielded rodents and carnivorans, is the only exception to this rule. However, until now no pre-PETM localities have yielded modern mammals in Europe or Asia. We report the first Clarkforkian equivalent Land Mammal Age in the latest Paleocene deposits of the basal Sparnacian facies at Rivecourt, in the north-central part of the Paris Basin. The new terrestrial vertebrate and macroflora assemblages are analyzed through a multidisciplinary study including sedimentologic, stratigraphic, isotopic, and palynological aspects in order to reconstruct the paleoenvironment and to evaluate biochronologic and paleogeographic implications. The mammals are moderately diverse and not abundant, contrary to turtles and champsosaurs. The macroflora is exceptional in preservation and diversity with numerous angiosperms represented by flowers, fruits, seeds and wood preserved as lignite material, revealing an abundance of Arecaceae, Betulaceae, Icacinaceae, Menispermaceae, Vitaceae and probably Cornaceae. Results indicate a Late Paleocene age based on carbon isotope data, palynology and vertebrate occurrences such as the choristoderan Champsosaurus, the arctocyonid Arctocyon, and the plesiadapid Plesiadapis tricuspidens. However, several mammal species compare better with the earliest Eocene. Among these, the particular louisinid Teilhardimys musculus, also recorded from the latest Paleocene of the Spanish Pyrenees, suggests a younger age than the typical MP6 reference level. Nevertheless, the most important aspect of the Rivecourt fauna is the presence of dental remains of a rodent and a "miacid" carnivoran, attesting to the presence of two modern mammalian orders in the latest Paleocene of Europe. Interestingly, these two groups are also the only modern groups recorded from the latest Paleocene of North America, making Rivecourt the first direct equivalent to the Clarkforkian Land Mammal Age outside of North America.

Insights into the paleoclimate of the PETM from an ensemble of EMIC simulations

NASA Astrophysics Data System (ADS)

Keery, John; Holden, Philip; Edwards, Neil; Monteiro, Fanny; Ridgwell, Andy

2016-04-01

The Eocene epoch, and in particular, the Paleocene-Eocene Thermal Maximum (PETM) of 55.8 Ma, exhibit several features of particular interest for probing our understanding of the Earth system and carbon cycle. CO2 levels have not yet been definitively established, but were known to have varied considerably, peaking at up to several times modern values. Temperatures were several degrees higher than in the modern era, and there were periods of relatively rapid warming, with substantial variability in carbon cycle processes. The Eocene is therefore highly relevant for our understanding of the climate of the 21st Century. Earth system models of intermediate complexity (EMICs), with less detailed simulation of the dynamics of the atmosphere and oceans than general circulation models (GCMs), are sufficiently fast to allow climate modelling over long periods of geological time in comparatively short periods of computer run-time. This speed advantage of EMICs over GCMs permits an "ensemble" of model simulations to be run, allowing statistical analysis of results to be carried out, and allowing the uncertainties in model predictions to be estimated. Here we apply the EMICs PLASIM-GENIE, and GENIE-1, with an Eocene paleogeography which incorporates the major continental configurations and ocean connections, including a shallow strait linking the Arctic to the Tethys, but with neither the Tasman Gateway nor the Drake Passage yet open. Our two model strategy benefits from the detailed simulation of ocean biogeochemistry in GENIE-1, and the 3D spectral atmospheric dynamics in PLASIM-GENIE, which also provides boundary conditions for the GENIE-1 simulations. Using a 50-member ensemble of 1000-year quasi-equilibrium simulations with PLASIM-GENIE, we investigate the relative contributions of orbital and CO2 variability on climate and equator-pole temperature gradients. Results from PLASIM-GENIE are used to configure a harmonised ensemble of GENIE-1 simulations, which will be compared with newly obtained geochemical data on ocean oxygenation through the Eocene from the UK NERC RESPIRE project.

Anoxia and high primary production in the Paleogene central Arctic Ocean: First detailed records from Lomonosov Ridge

NASA Astrophysics Data System (ADS)

Stein, Ruediger; Boucsein, Bettina; Meyer, Hanno

2006-09-01

Except for a few discontinuous fragments of the Late Cretaceous/Early Cenozoic climate history and depositional environment, the paleoenvironmental evolution of the pre-Neogene central Arctic Ocean was virtually unknown prior to the IODP Expedition 302 (Arctic Ocean Coring Expedition-ACEX) drilling campaign on Lomonosov Ridge in 2004. Here we present detailed organic carbon (OC) records from the entire ca. 200 m thick Paleogene OC-rich section of the ACEX drill sites. These records indicate euxinic "Black Sea-type" conditions favorable for the preservation of labile aquatic (marine algae-type) OC occur throughout the upper part of the early Eocene and the middle Eocene, explained by salinity stratification due to freshwater discharge. The superimposed short-term ("Milankovitch-type") variability in amount and composition of OC is related to changes in primary production and terrigenous input. Prominent early Eocene events of algae-type OC preservation coincide with global δ13C events such as the PETM and Elmo events. The Elmo δ13C Event has been identified in the Arctic Ocean for the first time.

The Impact of the Latest Danian Event on Planktic Foraminiferal Faunas at ODP Site 1210 (Shatsky Rise, Pacific Ocean).

PubMed

Jehle, Sofie; Bornemann, André; Deprez, Arne; Speijer, Robert P

2015-01-01

The marine ecosystem has been severely disturbed by several transient paleoenvironmental events (<200 kyr duration) during the early Paleogene, of which the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma) was the most prominent. Over the last decade a number of similar events of Paleocene and Eocene age have been discovered. However, relatively little attention has been paid to pre-PETM events, such as the "Latest Danian Event" ("LDE", ~62.18 Ma), specifically from an open ocean perspective. Here we present new foraminiferal isotope (δ13C, δ18O) and faunal data from Ocean Drilling Program (ODP) Site 1210 at Shatsky Rise (Pacific Ocean) in order to reconstruct the prevailing paleoceanographic conditions. The studied five-meter-thick succession covers ~900 kyr and includes the 200-kyr-lasting LDE. All groups surface dwelling, subsurface dwelling and benthic foraminifera show a negative δ13C excursion of >0.6‰, similar in magnitude to the one previously reported from neighboring Site 1209 for benthic foraminifera. δ18O-inferred warming by 1.6 to 2.8°C (0.4-0.7‰ δ18O measured on benthic and planktic foraminiferal tests) of the entire water column accompanies the negative δ13C excursion. A well stratified upper ocean directly before and during the LDE is proposed based on the stable isotope gradients between surface and subsurface dwellers. The gradient is less well developed, but still enhanced after the event. Isotope data are supplemented by comprehensive planktic foraminiferal faunal analyses revealing a dominance of Morozovella species together with Parasubbotina species. Subsurface-dwelling Parasubbotina shows high abundances during the LDE tracing changes in the strength of the isotope gradients and, thus, may indicate optimal living conditions within a well stratified surface ocean for this taxon. In addition, distinct faunal changes are reported like the disappearance of Praemurica species right at the base of the LDE and the continuous replacement of M. praeangulata with M. angulata across the LDE.

Controls on fluvial metamorphosis during global warming at the Paleocene-Eocene boundary (56 Ma) in Spain: extreme droughts, extreme floods or both?

NASA Astrophysics Data System (ADS)

Castelltort, Sebastien; Chen, Chen; Guerit, Laure; Foreman, Brady; Paola, Chris; Adatte, Thierry

2017-04-01

How does global warming change the frequency and intensity of extreme weather events? The response to this question is partly preserved in the geological record. 56 Ma ago, global temperatures increased during the Paleocene-Eocene Thermal Maximum (PETM), leading to a major biotic turnover, but how this event affected the nature of extreme events remains unknown. On several continents, fluvial systems with sinuous channels within fine-grained floodplains suddenly transformed at the P-E boundary into apparently coarser-grained braid plains with frequent lateral migrations, washing their muddy floodplains to the seas. This landscape transformation has been related to aridification and intensification of precipitation allowing transport of coarser material as a result of P-E global warming, with important implications for predicting the consequences of current global change. Here we test this hypothesis by quantifying the magnitude of grain size change and flow depth at a representative P-E locality in Northern Spain. We find that the size of pebbles in transport and flow depth remained similar to, or even smaller than, pre-PETM conditions. This suggests that, if more seasonal and extreme precipitation occurred, they are not necessarily borne out in the predicted deeper flow depths and coarser grain sizes, but rather trigger a shift to multiple active channels. However, an alternative or complementary explanation may rest in pollen data found in coeval marine records and which document a dramatic vegetation shift from permanent conifer forests prior to the crisis into periodic vegetation in brief periods of rain during the hyperthermal episode. Such change induced by long periods of intense droughts, could have enhanced erodibility of channel banks by decreasing root-controlled cohesion of fine-grained floodplains and interfluves, promoting their lateral mobility and the observed fluvial metamorphosis. Thus, although water is regarded as the main agent sculpting fluvial landscapes, the absence of it during extreme droughts rather than its presence during extreme precipitation events, may be a dominant control on fluvial metamorphosis and landscape evolution.

Salinity of the Early and Middle Eocene Arctic Ocean From Oxygen Isotope Analysis of Fish Bone Carbonate

NASA Astrophysics Data System (ADS)

Waddell, L. M.; Moore, T. C.

2006-12-01

Plate tectonic reconstructions indicate that the Arctic was largely isolated from the world ocean during the early and middle Eocene, with exchange limited to shallow, and possibly intermittent, connections to the North Atlantic and Tethys (via the Turgay Strait). Relative isolation, combined with an intensification of the hydrologic cycle under an Eocene greenhouse climate, is suspected to have led to the development of a low- salinity surface water layer in the Arctic that could have affected deep and intermediate convection in the North Atlantic. Sediment cores recently recovered from the Lomonosov Ridge by the IODP 302 Arctic Coring Expedition (ACEX) allow for the first assessment of the salinity of the Arctic Ocean during the early and middle Eocene. Stable isotope analysis performed on the structural carbonate of fish bone apatite from ~30 samples between the ages of ~55 and ~44 myr yielded δ18O values between -6.84‰ and -2.96‰ VPDB, with a mean value of -4.89‰. From the δ18O values we calculate that the Arctic Ocean was probably brackish during most of the early and middle Eocene, with an average salinity of 19 to 24‰. Negative excursions in the δ18O record (<-6‰) indicate three events during which the salinity of the Arctic surface waters was severely lowered: the Paleocene Eocene Thermal Maximum (PETM), the Azolla event at ~49 Ma, and a third previously unidentified event at ~46 Ma. During the PETM, low salinities developed under conditions of increased regional precipitation and runoff associated with extreme high latitude warmth and possible tectonic uplift in the North Atlantic. During the other two low-salinity events, sea level was lowered by ~20-30 m, implying a possible severing of Arctic connections to the world ocean. The most positive δ18O value (-2.96‰) occurs at ~45 Ma, the age of the youngest dropstone discovered in the ACEX sediments, and may therefore correspond to a climatic cooling rather than a high salinity event.

The Impact of the Latest Danian Event on Planktic Foraminiferal Faunas at ODP Site 1210 (Shatsky Rise, Pacific Ocean)

PubMed Central

Jehle, Sofie; Bornemann, André; Deprez, Arne; Speijer, Robert P.

2015-01-01

The marine ecosystem has been severely disturbed by several transient paleoenvironmental events (<200 kyr duration) during the early Paleogene, of which the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma) was the most prominent. Over the last decade a number of similar events of Paleocene and Eocene age have been discovered. However, relatively little attention has been paid to pre-PETM events, such as the “Latest Danian Event” ("LDE", ~62.18 Ma), specifically from an open ocean perspective. Here we present new foraminiferal isotope (δ13C, δ18O) and faunal data from Ocean Drilling Program (ODP) Site 1210 at Shatsky Rise (Pacific Ocean) in order to reconstruct the prevailing paleoceanographic conditions. The studied five-meter-thick succession covers ~900 kyr and includes the 200-kyr-lasting LDE. All groups surface dwelling, subsurface dwelling and benthic foraminifera show a negative δ13C excursion of >0.6‰, similar in magnitude to the one previously reported from neighboring Site 1209 for benthic foraminifera. δ18O-inferred warming by 1.6 to 2.8°C (0.4–0.7‰ δ18O measured on benthic and planktic foraminiferal tests) of the entire water column accompanies the negative δ13C excursion. A well stratified upper ocean directly before and during the LDE is proposed based on the stable isotope gradients between surface and subsurface dwellers. The gradient is less well developed, but still enhanced after the event. Isotope data are supplemented by comprehensive planktic foraminiferal faunal analyses revealing a dominance of Morozovella species together with Parasubbotina species. Subsurface-dwelling Parasubbotina shows high abundances during the LDE tracing changes in the strength of the isotope gradients and, thus, may indicate optimal living conditions within a well stratified surface ocean for this taxon. In addition, distinct faunal changes are reported like the disappearance of Praemurica species right at the base of the LDE and the continuous replacement of M. praeangulata with M. angulata across the LDE. PMID:26606656

Hydrothermal vent complexes offshore Northeast Greenland: A potential role in driving the PETM

NASA Astrophysics Data System (ADS)

Reynolds, P.; Planke, S.; Millett, J. M.; Jerram, D. A.; Trulsvik, M.; Schofield, N.; Myklebust, R.

2017-06-01

Continental rifting is often associated with voluminous magmatism and perturbations in the Earth's climate. In this study, we use 2D seismic data from the northeast Greenland margin to document two Paleogene-aged sill complexes ≥ 18 000 and ≥ 10 000 km2 in size. Intrusion of the sills resulted in the contact metamorphism of carbon-rich shales, producing thermogenic methane which was released via 52 newly discovered hydrothermal vent complexes, some of which reach up to 11 km in diameter. Mass balance calculations indicate that the volume of methane produced by these intrusive complexes is comparable to that required to have caused the negative δ13 C isotope excursion associated with the PETM. Combined with data from the conjugate Norwegian margin, our study provides evidence for margin-scale, volcanically-induced greenhouse gas release during the late Paleocene/early Eocene. Given the abundance of similar-aged sill complexes in Upper Paleozoic-Mesozoic and Cretaceous-Tertiary basins elsewhere along the northeast Atlantic continental margin, our findings support a major role for volcanism in driving global climate change.

Astronomical calibration of the geological timescale: closing the middle Eocene gap

NASA Astrophysics Data System (ADS)

Westerhold, T.; Röhl, U.; Frederichs, T.; Bohaty, S. M.; Zachos, J. C.

2015-09-01

To explore cause and consequences of past climate change, very accurate age models such as those provided by the astronomical timescale (ATS) are needed. Beyond 40 million years the accuracy of the ATS critically depends on the correctness of orbital models and radioisotopic dating techniques. Discrepancies in the age dating of sedimentary successions and the lack of suitable records spanning the middle Eocene have prevented development of a continuous astronomically calibrated geological timescale for the entire Cenozoic Era. We now solve this problem by constructing an independent astrochronological stratigraphy based on Earth's stable 405 kyr eccentricity cycle between 41 and 48 million years ago (Ma) with new data from deep-sea sedimentary sequences in the South Atlantic Ocean. This new link completes the Paleogene astronomical timescale and confirms the intercalibration of radioisotopic and astronomical dating methods back through the Paleocene-Eocene Thermal Maximum (PETM, 55.930 Ma) and the Cretaceous-Paleogene boundary (66.022 Ma). Coupling of the Paleogene 405 kyr cyclostratigraphic frameworks across the middle Eocene further paves the way for extending the ATS into the Mesozoic.

New Data On The Distribution Of Calcareous Nannofossils During And After The Paleocene/Eocene Transition

NASA Astrophysics Data System (ADS)

Raffi, I.

2004-12-01

Major changes occur among calcareous nannofossil assemblages at the transition from Paleocene to Eocene. In most known P/E boundary sections with complete sediment records, the changes are associated to the brief, intensive interval of global warming, the Paleocene-Eocene Thermal Maximum (PETM), and a concomitant huge perturbation of the global carbon budget, the Carbon Isotope Excursion (CIE). Changes in nannofossil assemblages include: (A) occurrence of Rhomboaster spp. - D. araneus correlative with the CIE; (B) decrease in diversification of Fasciculithus spp. at the CIE onset; (C) occurrence of Zygrhablithus bijugatus and Fasciculithus spp./ Z. bijugatus abundance cross-over within the upper part of the CIE-PETM interval; and (D) extiction of the Paleocene genus Fasciculithus just above the CIE, an event that is closely followed by the further evolution of Rhomboaster - Tribrachiatus plexus. The genus Tribrachiatus subsequently radiates over the next ˜1 million years, a time interval showing further steps in the evolutionary history of calcareous nannofossils (speciations among discoasters and sphenoliths) during the Eocene. Quantitative analyses of selected calcareous nannofossils in deep-sea sections recovered from the Atlantic (DSDP Site 550, ODP Site 929, and ODP Sites 1262 and 1263 of Leg 208) and paleo-equatorial Pacific (ODP Sites 1215, 1220, 1221 of Leg 199) provide new informations about calcareous nannofossils across the Paleocene/Eocene transition interval. The distinctive Rhomboaster spp. - D. araneus association (RD) was previously considered to have a marked provincialism, restricted to the Atlantic Ocean and partially extending to the Tethys seaway and westernmost Indian Ocean. Detailed study of Leg 199 sections (from equatorial Pacific) and preliminary analyses at the P/E boundary of ODP Site 929 (from Ceara Rise in western equatorial Atlantic) and ODP Sites 1262 and 1263 (from Walvis Ridge in southern Atlantic) indicate some difference in the RD distribution. The sudden appearance and short co-existence of R. calcitrapa gr. and D. araneus, and the lowermost occurrence of R. cuspis at the onset of CIE clearly can be extended to the equatorial regions of the Atlantic as well as the Pacific Ocean. The genus Fasciculithus undergoes a substantial decrease in diversification at the onset of CIE, and perish completely shortly afterwards. This significant turnover appears to represent a global event observed in all the known P/E boundary sections from different oceans and paleo-latitudes. The abundance cross-over between Fasciculithus spp. and Z. bijugatus has been observed to occur within the the CIE-PETM interval in several deep-sea sections. In the central paleo-equatorial Pacific Ocean, however, Z. bijugatus specimens were not present at all, whereas a marked increase in abundance of R. cuspis was observed in conjunction with the final decline of Fasciculithus spp. Data from the western paleo-equatorial Atlantic Ocean (Site 929) shows only few Z. bijugatus, implying that this particular early Eocene turnover is absent in these equatorial regions. Thoracosphaera spp. shows a short abundance peak immediately above the carbonate barren interval at the P/E boundary, during the CIE, at paleo-equatorial Pacific Site 1220, which probably reflects a stressed surface water environment.

21 CFR 176.300 - Slimicides.

Code of Federal Regulations, 2013 CFR

2013-04-01

...) cyclohexanone 1,2-Bis(monobromoacetoxy) ethane [CA Reg. No. 3785-34-0] At a maximum level of 0.10 pound per ton... Methylenebisbutanethiolsulfonate Methylenebisthiocyanate 2-Nitrobutyl bromoacetate [CA Reg. No. 32815-96-6] At a maximum level of 0...)phosphonium sulfate (CAS Reg. No. 55566-30-8) Maximum use level of 84 mg/kg in the pulp slurry. The additive...

21 CFR 176.300 - Slimicides.

Code of Federal Regulations, 2012 CFR

2012-04-01

...) cyclohexanone 1,2-Bis(monobromoacetoxy) ethane [CA Reg. No. 3785-34-0] At a maximum level of 0.10 pound per ton... Methylenebisbutanethiolsulfonate Methylenebisthiocyanate 2-Nitrobutyl bromoacetate [CA Reg. No. 32815-96-6] At a maximum level of 0...)phosphonium sulfate (CAS Reg. No. 55566-30-8) Maximum use level of 84 mg/kg in the pulp slurry. The additive...

Measurement of cytoplasmic Ca2+ concentration in Saccharomyces cerevisiae induced by air cold plasma

NASA Astrophysics Data System (ADS)

Xiaoyu, DONG

2018-03-01

In this study, a novel approach to measure the absolute cytoplasmic Ca2+ concentration ([Ca2+]cyt) using the Ca2+ indicator fluo-3 AM was established. The parameters associated with the probe fluo-3 AM were optimized to accurately determine fluorescence intensity from the Ca2+-bound probe. Using three optimized parameters (final concentration of 6 mM probe, incubation time of 135 min, loading probe before plasma treatment), the maximum fluorescence intensity (F max = 527.8 a.u.) and the minimum fluorescence intensity (F min = 63.8 a.u.) were obtained in a saturated Ca2+ solution or a solution of lacking Ca2+. Correspondingly, the maximum [Ca2+]cyt induced by cold plasma was 1232.5 nM. Therefore, the Ca2+ indicator fluo-3 AM was successfully applied to measure the absolute [Ca2+]cyt in Saccharomyces cerevisiae stimulated by cold plasma at atmospheric air pressure.

Quantification of Biogenic Magnetite by Synchrotron X-ray Microscopy During the PETM

NASA Astrophysics Data System (ADS)

Wang, H.; Wang, J.; Kent, D. V.; Chen-Wiegart, Y. C. K.

2014-12-01

Exceptionally large biogenic magnetite crystals, including spearhead-like and spindle-like ones up to 4 microns, have been reported in clay-rich sediments recording the ~56 Ma Paleocene-Eocene thermal maximum (PETM) and carbon isotope excursion (CIE) in a borehole at Ancora, NJ and along with magnetotactic bacteria (MTB) chains, were suggested [Schumann et al. 2008 PNAS; Kopp et al. 2009 Paleoceanography] to account for the distinctive single domain (SD) rock magnetic properties of these sediments [Lanci et al. 2002 JGR]. However, because uncalibrated magnetic extraction techniques were used to provide material for TEM imaging of the biogenic magnetite, it is difficult to quantitatively analyze their concentration in the bulk clay. In this study, we use a synchrotron transmission X-ray microscope to image bulk CIE clay. We first take mosaic images of sub-millimeter-sized bulk clay samples, in which we can identify many of the various types of giant biogenic magnetite crystals, as well as several other types of iron minerals, such as pyrite framboids, siderite, and detrital magnetite. However, limited by the instrument resolution (~50 nm), we are not able to identify MTB chains let alone isolated magnetic nanoparticles that may be abundant the clay. To quantitatively estimate the concentration of the giant biogenic magnetite, we re-deposited the bulk clay sample in an alcohol solution on a silicon nitride membrane for 2D X-ray scans. After scanning a total area of 0.55 mm2 with average clay thickness of 4 μm, we identified ~40 spearheads, ~5 spindles and a few elongated rods and estimated their total magnetization as SD particles to be less than about 10% of the mass normalized clay for the scanned area. This result suggests that the giant biogenic magnetite is not a major source of the SD signal for the clay and is in good agreement with rock magnetic analyses using high-resolution first-order reversal curves and thermal fluctuation tomography on bulk CIE clay showing that most of the magnetite occurs as isolated, near-equant SD particles [Wang et al. 2013 PNAS]. This would also exclude a significant contribution from MTB chains and points to a non-biogenic origin, such as a comet impact plume condensate, for the magnetic nanoparticles [Kent et al. 2003 EPSL] in the very rapidly deposited CIE clays [Wright & Schaller 2014 PNAS].

21 CFR 176.300 - Slimicides.

Code of Federal Regulations, 2014 CFR

2014-04-01

...(monobromoacetoxy) ethane [CA Reg. No. 3785-34-0] At a maximum level of 0.10 pound per ton of dry weight fiber. Bis... Methylenebisthiocyanate 2-Nitrobutyl bromoacetate [CA Reg. No. 32815-96-6] At a maximum level of 0.15 pound per ton of dry.... No. 55566-30-8) Maximum use level of 84 mg/kg in the pulp slurry. The additive may also be added to...

Breakup magmatism on the Vøring Margin, mid-Norway: New insight from interpretation of high-quality 2D and 3D seismic reflection data

NASA Astrophysics Data System (ADS)

Abdelmalak, M. M.; Planke, S.; Millett, J.; Jerram, D. A.; Maharjan, D.; Zastrozhnov, D.; Schmid, D. W.; Faleide, J. I.; Svensen, H.; Myklebust, R.

2017-12-01

The Vøring Margin offshore mid-Norway is a classic volcanic rifted margin, characterized by voluminous Paleogene igneous rocks present on both sides of the continent-ocean boundary. The margin displays (1) thickened transitional crust with a well-defined lower crustal high-velocity body and prominent deep crustal reflections, the so-called T-Reflection, (2) seaward dipping reflector (SDR) wedges and a prominent northeast-trending escarpment on the Vøring Marginal High, and (3) extensive sill complexes in the adjacent Cretaceous Vøring Basin. During the last decade, new 2D and 3D industry seismic data along with improved processing techniques, such as broadband processing and noise reduction processing sequences, have made it possible to image and map the breakup igneous complex in much greater detail than previously possible. Our interpretation includes a combination of (1) seismic horizon picking, (2) integrated seismic-gravity-magnetic (SGM) interpretation, (3) seismic volcanostratigraphy, and (4) igneous seismic geomorphology. The results are integrated with published wide-angle seismic data, re-analyzed borehole data including new geochronology, and new geodynamic modeling of the effects of magmatism on the thermal history and subsidence of the margin. The extensive sill complexes and associated hydrothermal vent complexes in the Vøring Basin have a Paleocene-Eocene boundary age based on high-precision U/Pb dating combined with seismic mapping constraints. On the marginal high, our results show a highly variable crustal structure, with a pre-breakup configuration consisting of large-scale structural highs and sedimentary basins. These structures were in-filled and covered by basalt flows and volcanogenic sediments during the early stages of continental breakup in the earliest Eocene. Subsequently, rift basins developed along the continent-ocean boundary and where infilled by up to ca. 6 km thick basalt sequences, currently imaged as SDRs fed by a dike swarm imaged on seismic data. The addition of magma within the crust had a prominent effect on the thermal history and hydrocarbon maturation of the sedimentary basin, causing uplift, delayed subsidence, and possibly contributing to the triggering of global warming during the Paleocene-Eocene Thermal Maximum (PETM).

Velocity of sarcomere shortening in rat cardiac muscle: relationship to force, sarcomere length, calcium and time.

PubMed

Daniels, M; Noble, M I; ter Keurs, H E; Wohlfart, B

1984-10-01

The relation between force and velocity was determined in sixteen trabeculae of rat right ventricle as a function of time during a twitch, of sarcomere length and of external Ca2+ concentration, [Ca2+]o. The trabeculae were studied in modified Krebs-Henseleit solution at 25 degrees C. Force was measured with a semiconductor strain gauge. Sarcomere length was measured with a laser diffraction system. A servomotor system was used in which control could be switched between sarcomere length, muscle length and force. Force-velocity relations were derived from load clamps and from contractions in which sarcomere length was initially held constant followed by a quick release and slower release of the sarcomeres at controlled velocity. Force-velocity relations were fitted by Hill's equation (Hill, 1938), (Po-P) b = (P+a) V, where P = force, V = velocity, Po = isometric force in mN/mm2 and a and b are constants. For [Ca2+]o = 2.5 mM, with both interventions the values (mean +/- S.D.) were: b = 1.00 +/- 0.45 micron/s; a = 9.52 +/- 5.60 mN/mm2; Vo measured = 13.6 +/- 3.0 micron/s; Vo calculated = 13.4 +/- 3.4 micron/s; Po measured = 96.5 +/- 25.0 mN/mm2; Po calculated = 119.3 +/- 34.5 mN/mm2. Vo rose with [Ca2+]o to a maximum at [Ca2+]o = 1.2 mM when Po was about 50% of maximum, while Po rose with [Ca2+]o to a maximum at above 2.5 mM. Vo rose with time during the twitch to a maximum at 25 ms following onset of contraction; Po was then about 50% of the maximum that was obtained at 120 ms. Vo increased with sarcomere length from zero at a sarcomere length of 1.6 micron to a maximum at 1.85 micron. Between 1.85 micron and 2.3 micron, Vo was constant. At 1.85 micron, Po was about 60% of maximum Po. These results are compatible with the hypothesis that Vo is more sensitive than Po to the amount of Ca2+ bound to the contractile proteins, and that Vo reaches a maximal value with an amount of Ca2+ bound to the contractile proteins at which Po has obtained only about 50% of its maximal value.

Citric acid production from partly deproteinized whey under non-sterile culture conditions using immobilized cells of lactose-positive and cold-adapted Yarrowia lipolytica B9.

PubMed

Arslan, Nazli Pinar; Aydogan, Mehmet Nuri; Taskin, Mesut

2016-08-10

The present study was performed to produce citric acid (CA) from partly deproteinized cheese whey (DPCW) under non-sterile culture conditions using immobilized cells of the cold-adapted and lactose-positive yeast Yarrowia lipolytica B9. DPCW was prepared using the temperature treatment of 90°C for 15min. Sodium alginate was used as entrapping agent for cell immobilization. Optimum conditions for the maximum CA production (33.3g/L) in non-sterile DPCW medium were the temperature of 20°C, pH 5.5, additional lactose concentration of 20g/L, sodium alginate concentration of 2%, number of 150 beads/100mL and incubation time of 120h. Similarly, maximum citric acid/isocitric acid (CA/ICA) ratio (6.79) could be reached under these optimal conditions. Additional nitrogen and phosphorus sources decreased CA concentration and CA/ICA ratio. Immobilized cells were reused in three continuous reaction cycles without any loss in the maximum CA concentration. The unique combination of low pH and temperature values as well as cell immobilization procedure could prevent undesired microbial contaminants during CA production. This is the first work on CA production by cold-adapted microorganisms under non-sterile culture conditions. Besides, CA production using a lactose-positive strain of the yeast Y. lipolytica was investigated for the first time in the present study. Copyright © 2016 Elsevier B.V. All rights reserved.

Influence of periodically changing oxidizing and reducing environment on sulfur capture under PFBC conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yrjas, P.; Hupa, M.

1997-12-31

In the literature it has been reported that sulfur capture with limestone (CaCO{sub 3}) under atmospheric fluidized bed combustion conditions reaches a maximum at about 850 C. Previously, the maximum has been attributed to the sintering of the sorbent particles which decreases the reactive surface area. Lately, also another explanation has been reported. In this case the sulfur capture decrease at higher temperatures was concluded to be due to fluctuating oxidizing/reducing conditions in the atmospheric combustor. In this paper the influence of alternating oxidizing/reducing conditions on SO{sub 2} capture at atmospheric and elevated pressure (15 bar) is reported. In themore » pressurized case, the CO{sub 2} partial pressure was kept high enough to prevent CaCO{sub 3} from calcining and therefore the CaSO{sub 4} would not form CaO but CaCO{sub 3} from calcining and therefore the CaSO{sub 4} would not form CaO but CaCO{sub 3} under reducing conditions. The experiments were done with a pressurized TGA by periodically changing the gas environment between oxidizing (O{sub 2}, SO{sub 2}, CO{sub 2} and N{sub 2}) and slightly reducing (CO, SO{sub 2}, CO{sub 2} and N{sub 2}) gas mixtures at different temperatures. The results showed that under normal pressure and slightly reducing conditions CaO formation from CaSO{sub 4} increased with temperature as expected. However, no significant amounts of CaCO{sub 3} were formed from CaSO{sub 4} at elevated pressure. It was also concluded that since the formation of CaO from CaSO{sub 4} was relatively slow it could not explain the sharp sulfur capture maximum at about 850 C. Therefore, it was assumed that the strongly reducing zones, where CaS thermodynamically is the stable compound, may play a more important role than the slightly reducing zones, concerning the sulfur capture in fluidized bed combustors.« less

Should conventional angiography be the gold standard for carotid stenosis?

PubMed

Zhang, Wayne W; Harris, Linda M; Dryjski, Maciej L

2006-12-01

To compare conventional angiography (CA) and rotational angiography (RA) to assess the degree of angiographically-measured stenosis versus cross-sectional area (CSA) stenosis in an in vitro carotid model. Various grades of stenosis were created by adhering different amounts of silicone rubber sealant onto the inner wall of clear, radiolucent tubes. Following 2- and 3-projection CA and 20-projection RA, the tubes were transected at the actual maximum stenosis. The cross-sectional areas were digitally photographed, and CSA stenosis was calculated using ImageJ planimeter software. The differences among CA, RA, and CSA stenosis measurements were compared statistically. There was no significant difference between RA and CSA stenosis measurements (p=0.46). Conventional angiography with 2 or 3 projections between 0 degrees and 90 degrees underestimated the severity of disease in 19 (63%) of 30 samples. The maximum stenosis percentage was significantly lower in CA versus RA (p<0.0001 in 2-projection, p<0.0003 in 3-projection) and in CA versus CSA stenosis (p<0.0004 in 2-projection, p<0.001 in 3-projection). The maximum stenosis percentages measured by RA were less than CSA stenosis in 5 (71.4%) of 7 tubes (p=NS) containing 50% to 69% stenoses. Eight tubes had mountain-shaped lesions, which was significantly overestimated by RA (11.5%+/-9.7%, p<0.012). CA with 2 or 3 projections significantly underestimates the maximum stenosis in an in vitro model. RA may overestimate disease in patients with mountain-shaped plaques and may underestimate disease if the stenosis is <70%. Our data suggest that CA should not be the gold standard for the qualification of carotid endarterectomy in asymptomatic patients, nor for vascular laboratory quality assurance analysis.

Reconstruction of calmodulin single-molecule FRET states, dye interactions, and CaMKII peptide binding by MultiNest and classic maximum entropy

NASA Astrophysics Data System (ADS)

DeVore, Matthew S.; Gull, Stephen F.; Johnson, Carey K.

2013-08-01

We analyzed single molecule FRET burst measurements using Bayesian nested sampling. The MultiNest algorithm produces accurate FRET efficiency distributions from single-molecule data. FRET efficiency distributions recovered by MultiNest and classic maximum entropy are compared for simulated data and for calmodulin labeled at residues 44 and 117. MultiNest compares favorably with maximum entropy analysis for simulated data, judged by the Bayesian evidence. FRET efficiency distributions recovered for calmodulin labeled with two different FRET dye pairs depended on the dye pair and changed upon Ca2+ binding. We also looked at the FRET efficiency distributions of calmodulin bound to the calcium/calmodulin dependent protein kinase II (CaMKII) binding domain. For both dye pairs, the FRET efficiency distribution collapsed to a single peak in the case of calmodulin bound to the CaMKII peptide. These measurements strongly suggest that consideration of dye-protein interactions is crucial in forming an accurate picture of protein conformations from FRET data.

Reconstruction of Calmodulin Single-Molecule FRET States, Dye-Interactions, and CaMKII Peptide Binding by MultiNest and Classic Maximum Entropy

PubMed Central

DeVore, Matthew S.; Gull, Stephen F.; Johnson, Carey K.

2013-01-01

We analyze single molecule FRET burst measurements using Bayesian nested sampling. The MultiNest algorithm produces accurate FRET efficiency distributions from single-molecule data. FRET efficiency distributions recovered by MultiNest and classic maximum entropy are compared for simulated data and for calmodulin labeled at residues 44 and 117. MultiNest compares favorably with maximum entropy analysis for simulated data, judged by the Bayesian evidence. FRET efficiency distributions recovered for calmodulin labeled with two different FRET dye pairs depended on the dye pair and changed upon Ca2+ binding. We also looked at the FRET efficiency distributions of calmodulin bound to the calcium/calmodulin dependent protein kinase II (CaMKII) binding domain. For both dye pairs, the FRET efficiency distribution collapsed to a single peak in the case of calmodulin bound to the CaMKII peptide. These measurements strongly suggest that consideration of dye-protein interactions is crucial in forming an accurate picture of protein conformations from FRET data. PMID:24223465

Reconstruction of Calmodulin Single-Molecule FRET States, Dye-Interactions, and CaMKII Peptide Binding by MultiNest and Classic Maximum Entropy.

PubMed

Devore, Matthew S; Gull, Stephen F; Johnson, Carey K

2013-08-30

We analyze single molecule FRET burst measurements using Bayesian nested sampling. The MultiNest algorithm produces accurate FRET efficiency distributions from single-molecule data. FRET efficiency distributions recovered by MultiNest and classic maximum entropy are compared for simulated data and for calmodulin labeled at residues 44 and 117. MultiNest compares favorably with maximum entropy analysis for simulated data, judged by the Bayesian evidence. FRET efficiency distributions recovered for calmodulin labeled with two different FRET dye pairs depended on the dye pair and changed upon Ca 2+ binding. We also looked at the FRET efficiency distributions of calmodulin bound to the calcium/calmodulin dependent protein kinase II (CaMKII) binding domain. For both dye pairs, the FRET efficiency distribution collapsed to a single peak in the case of calmodulin bound to the CaMKII peptide. These measurements strongly suggest that consideration of dye-protein interactions is crucial in forming an accurate picture of protein conformations from FRET data.

Identification of the Paleocene-Eocene boundary in coastal strata in the Otway Basin, Victoria, Australia

NASA Astrophysics Data System (ADS)

Frieling, Joost; Huurdeman, Emiel P.; Rem, Charlotte C. M.; Donders, Timme H.; Pross, Jörg; Bohaty, Steven M.; Holdgate, Guy R.; Gallagher, Stephen J.; McGowran, Brian; Bijl, Peter K.

2018-02-01

Detailed, stratigraphically well-constrained environmental reconstructions are available for Paleocene and Eocene strata at a range of sites in the southwest Pacific Ocean (New Zealand and East Tasman Plateau; ETP) and Integrated Ocean Discovery Program (IODP) Site U1356 in the south of the Australo-Antarctic Gulf (AAG). These reconstructions have revealed a large discrepancy between temperature proxy data and climate models in this region, suggesting a crucial error in model, proxy data or both. To resolve the origin of this discrepancy, detailed reconstructions are needed from both sides of the Tasmanian Gateway. Paleocene-Eocene sedimentary archives from the west of the Tasmanian Gateway have unfortunately remained scarce (only IODP Site U1356), and no well-dated successions are available for the northern sector of the AAG. Here we present new stratigraphic data for upper Paleocene and lower Eocene strata from the Otway Basin, southeast Australia, on the (north)west side of the Tasmanian Gateway. We analyzed sediments recovered from exploration drilling (Latrobe-1 drill core) and outcrop sampling (Point Margaret) and performed high-resolution carbon isotope geochemistry of bulk organic matter and dinoflagellate cyst (dinocyst) and pollen biostratigraphy on sediments from the regional lithostratigraphic units, including the Pebble Point Formation, Pember Mudstone and Dilwyn Formation. Pollen and dinocyst assemblages are assigned to previously established Australian pollen and dinocyst zonations and tied to available zonations for the SW Pacific. Based on our dinocyst stratigraphy and previously published planktic foraminifer biostratigraphy, the Pebble Point Formation at Point Margaret is dated to the latest Paleocene. The globally synchronous negative carbon isotope excursion that marks the Paleocene-Eocene boundary is identified within the top part of the Pember Mudstone in the Latrobe-1 borehole and at Point Margaret. However, the high abundances of the dinocyst Apectodinium prior to this negative carbon isotope excursion prohibit a direct correlation of this regional bio-event with the quasi-global Apectodinium acme at the Paleocene-Eocene Thermal Maximum (PETM; 56 Ma). Therefore, the first occurrence of the pollen species Spinizonocolpites prominatus and the dinocyst species Florentinia reichartii are here designated as regional markers for the PETM. In the Latrobe-1 drill core, dinocyst biostratigraphy further indicates that the early Eocene ( ˜ 56-51 Ma) sediments are truncated by a ˜ 10 Myr long hiatus overlain by middle Eocene ( ˜ 40 Ma) strata. These sedimentary archives from southeast Australia may prove key in resolving the model-data discrepancy in this region, and the new stratigraphic data presented here allow for detailed comparisons between paleoclimate records on both sides of the Tasmanian Gateway.

CaFe2O4 as a self-sufficient solar energy converter

NASA Astrophysics Data System (ADS)

Tablero, C.

2017-10-01

An ideal solar energy to electricity or fuel converter should work without the use of any external bias potential. An analysis of self-sufficiency when CaFe2O4 is used to absorb the sunlight is carried out based on the CaFe2O4 absorption coefficient. We started to obtain this coefficient theoretically within the experimental bandgap range in order to fix the interval of possible values of photocurrents, maximum absorption efficiencies, and photovoltages and thus that of self-sufficiency considering only the radiative processes. Also for single-gap CaFe2O4, we evaluate an alternative for increasing the photocurrent and maximum absorption efficiency based on inserting an intermediate band using high doping or alloying.

A physiological basis for variation in the contractile properties of isolated rat heart.

PubMed Central

Lin, L E; McClellan, G; Weisberg, A; Winegrad, S

1991-01-01

1. The maximum Ca(2+)-activated force, maximum velocity of unloaded shortening and both Ca(2+)- and actin-activated ATPase activities of myosin have been measured in detergent-skinned preparations of isolated bundles of rat right ventricle after exposure of the intact tissue to different conditions of superfusion, mechanical activity and temperature. 2. Maximum Ca(2+)-activated force per unit cross-sectional area decreases with increasing cross-sectional area, and, in the absence of electrical stimulation, with the duration of superfusion. Maximum velocity of unloaded shortening is not influenced by these differences. 3. Actin-activated ATPase activity of myosin decreases as cross-sectional area increases and duration of superfusion increases, but the extent of the decrease in enzymatic activity is less than that of developed force. Ca(2+)-activated ATPase activity is independent of these differences. 4. Actin-activated ATPase activity in cryostatic sections of quickly frozen tissue is not uniform across the transverse section. In thin bundles, it is highest in the centre and lowest at the edge of the section, which correspond, respectively, to the centre and the surface of the tissue bundle. Exposure of the tissue section to 1 microM-cyclic AMP increases the actin-activated ATPase activity of myosin with the largest increase in activity occurring at or near the surface of the bundle. 5. Ca(2+)-activated ATPase activity of myosin is uniform across the transverse section and is not changed by cyclic AMP. 6. Electrical stimulation, elevated Ca2+ concentration in the superfusion medium, or isoprenaline partially or completely reverse the decline in maximum Ca(2+)-activated force produced by prolonged superfusion of the bundle before its skinning. 7. These observations are similar in many ways to those made on frog skeletal muscles by Elzinga, Howarth, Rull, Wilson & Woledge (1989a). An explanation based on the existence of a physiological mechanism for regulating the properties of force generators is proposed. Regulation of the attachment of the cross-bridge to an actin filament may be the basis for the regulatory mechanism. Images Fig. 4 Fig. 7 PMID:1667804

Geochemistry and depositional environments of Paleocene-Eocene phosphorites: Metlaoui Group, Tunisia

NASA Astrophysics Data System (ADS)

Garnit, Hechmi; Bouhlel, Salah; Jarvis, Ian

2017-10-01

The Late Paleocene-Early Eocene phosphorites of the Metlaoui Group in Tunisia are a world-class phosphate resource. We review the characteristics of phosphorites deposited in three areas: the Northern Basins; Eastern Basins; and Gafsa-Metlaoui Basin. Comprehensive new bulk rock elemental data are presented, together with complementary mineralogical and mineral chemical results. Carbonate fluorapatite (francolite) constitutes the dominant mineral phase in the deposits. Phosphorite samples are enriched in Cd, Sr, U, rare-earth elements and Y, together with environmentally diagnostic trace elements that provide detrital (Cr, Zr), productivity (Cu, Ni, Zn) and redox (Mo, V) proxies. Suboxic bottom-water conditions predominated, with suboxic to anoxic porewaters accompanying francolite precipitation. Phosphorite deposition occurred under increasingly arid climate conditions, accompanying global Paleocene-Eocene warming. The Northern Basins show the strongest Tethys Ocean influence, with surface seawater rare-earth element signatures consistently developed in the phosphorites. Bed-scale compositional variation indicates relatively unstable environmental conditions and episodes of sediment redeposition, with varying detrital supply and a relatively wet local climate. Glauconitic facies in the Northern Basins and the more isolated evaporite-associated phosphorites in the dryer Eastern Basins display the greatest diagenetic influences. The phosphorite - organic-rich marl - diatom-bearing porcelanite facies association in the Gafsa-Metlaoui Basin represents the classic coastal upwelling trinity. Modified Tethyan waters occurred within the Basin during phosphorite deposition, with decreasing marine productivity from NW to SE evidenced by systematically falling enrichment factors for Cu, Ni, Cd and Zn in the phosphorites. Productivity declined in concert with increasing basin isolation during the deposition of the commercial phosphorite beds in the latest Paleocene to earliest Eocene. This isolation trend was temporarily reversed during an episode of maximum flooding associated with the earliest Eocene Paleocene-Eocene Thermal Maximum (PETM).

Variations in Compressive Strength of Geopolymer due to the CaO Added Fly Ash

NASA Astrophysics Data System (ADS)

Zhao, Yuqing; Koumoto, Tatsuya; Kondo, Fumiyoshi

Recently, geopolymer has been a noteworthy material which can be used as a replacement for portland cement. The mechanical characteristics and consistency of the geopolymer are strongly affected by its chemical components of fly ash. The variations in compressive strength of geopolymer due to the CaO added fly ash were investigated in this paper. The compressive strengths of geopolymer were increased with an increase in the curing period, and the characteristics changed from the one of plastic soil material to brittle material such as concrete, regardless of CaO content. Also, the results of compressive strength and modulus of deformation showed their maximum value in the case of 8-10% CaO content. From this result, the maximum characteristics of the strengths were assumed to be exerted in case which the water draining process of geopolymer was balanced with the water absorbing process of additional CaO.

Hydrogen and electricity production in a light-assisted microbial photoelectrochemical cell with CaFe2O4 photocathode

NASA Astrophysics Data System (ADS)

Chen, Qing-Yun; Zhang, Kai; Liu, Jian-Shan; Wang, Yun-Hai

2017-04-01

A microbial photoelectrochemical cell (MPEC) was designed with a p-type CaFe2O4 semiconductor as the photoelectrode for simultaneous hydrogen and electricity production under light illumination. The CaFe2O4 photoelectrode was synthesized by the sol-gel method and well characterized by x-ray diffraction, field emission scanning electron microscope, and UV-Vis-NIR spectrophotometer. The linear sweep voltammogram of the CaFe2O4 photoelectrode presented the cathodic photocurrent output. For the MPEC, with an external resistance of 2000 Ω, the maximum power density of 143 mW was obtained. Furthermore, with an external resistance of 100 Ω, the maximum hydrogen production rate of 6.7 μL·cm-2 could be achieved. The MPEC with CaFe2O4 photocathode was compared to MPEC with other photocathodes as well as photocatalytic water splitting technology.

Melting phase relations in the MgSiO3-CaSiO3 system at 24 GPa

NASA Astrophysics Data System (ADS)

Nomura, Ryuichi; Zhou, Youmo; Irifune, Tetsuo

2017-12-01

The Earth's lower mantle is composed of bridgmanite, ferropericlase, and CaSiO3-rich perovskite. The melting phase relations between each component are key to understanding the melting of the Earth's lower mantle and the crystallization of the deep magma ocean. In this study, melting phase relations in the MgSiO3-CaSiO3 system were investigated at 24 GPa using a multi-anvil apparatus. The eutectic composition is (Mg,Ca)SiO3 with 81-86 mol% MgSiO3. The solidus temperature is 2600-2620 K. The solubility of CaSiO3 component into bridgmanite increases with temperature, reaching a maximum of 3-6 mol% at the solidus, and then decreases with temperature. The same trend was observed for the solubility of MgSiO3 component into CaSiO3-rich perovskite, with a maximum of 14-16 mol% at the solidus. The asymmetric regular solutions between bridgmanite and CaSiO3-rich perovskite and between MgSiO3 and CaSiO3 liquid components well reproduce the melting phase relations constrained experimentally. [Figure not available: see fulltext.

Dual-wavelength and efficient continuous-wave operation of a Yb:CaGd0.1Y0.9AlO4 laser

NASA Astrophysics Data System (ADS)

Di, J. Q.; Sai, Q. L.; Sun, X. H.; Xu, X. D.; Kong, L. C.; Xie, G. Q.; Liu, Y. L.; Teng, F.; Zhu, L.

2018-05-01

The spectra and laser properties of single crystalline Yb:CaGd0.1Y0.9AlO4 were investigated for the first time. The peak absorption cross-sections of 4.01 cm2 and 1.39  ×  10‑20 cm2 with full width at half maximum of 17 and 32 nm, and the maximum emission cross-sections of 2.11 and 1.53  ×  10‑20 cm2 were obtained for π and σ polarizations, respectively. The fluorescence decay time was 638 µs. The maximum continuous-wave laser achieved was 1.60 W with a slope efficiency of 23.4% for an a-cut Yb:CaGd0.1Y0.9AlO4 crystal. Dual-wavelength lasers at 1041.7 and 1044.9 nm were also demonstrated. The results show that Yb:CaGd0.1Y0.9AlO4 crystal is a promising ultra-short and dual-wavelength laser medium.

Paleogene blackshales in the central Arctic Ocean and paleoenvironment: Anoxia vs. high primary production vs. terrigenous input

NASA Astrophysics Data System (ADS)

Stein, R.; Weller, P.; Boucsein, B.

2006-12-01

During IODP Expedition 302 (Arctic Ocean Coring Experiment ACEX), the first scientific drilling campaign in the permantly ice-covered central Arctic Ocean on Lomonosov Ridge, a 430 m thick sequence of upper Cretaceaous to Quaternary sediments has been drilled. Here we present detailed organic carbon (OC) records from the entire ca. 200 m thick, upper Paleocene to middle Eocene blackshale-type section of the ACEX drill sites, characterized by OC contents of about 1 to 6%. Based on a multi-proxy organic geochemical approach (hydrogen indices, C/N and C/S ratios, stable carbon isotopes, biomarkers, and maceral composition), organic-carbon sources and paleoenvironmental conditions were reconstructed. The late Paleocene interval is characterized by oxic conditions and a predominance of reworked terrigenous OC. In contrast, euxinic "Black Sea-type" conditions favorable for the preservation of labile aquatic (marine algae-type) OC occur throughout the upper part of the early Eocene and the middle Eocene, explained by salinity stratification due to freshwater discharge. The superimposed short-term ("Milankovitch-type") variability in amount and composition of OC is related to changes in primary production and terrigenous input. Prominent early Eocene events of algae-type OC preservation coincide with global 13C events such as the Paleocene- Eocece Thermal Maximum (PETM) and Elmo events. During Eocene times of anoxia, OC accumulation rates were 5-20 times higher than modern ones. Whereas very low organic carbon accumulation rates of about 0.005 gC cm-2 ky-1 are typical for the modern (Holocene) central Arctic Ocean on Lomonosov Ridge, values of up to 0.1-0.15 gC cm-2 ky-1 were calculated for the Eocene ACEX section. Because major part of the OC deposited during Eocene times is of aquatic (marine) origin and the OC deposited during Holocene times is almost entirely of terrigenous origin, the difference between the modern and Eocene situation becomes even more drastic when comparing the values for aquatic (marine) OC accumulation. During the Eocene, primary productivity in the central Arctic Ocean may may have reached values of 50-75 gC m-2 y-1, i.e., values 5-10 times higher than modern ones.

Shear conditions in clavulanic acid production by Streptomyces clavuligerus in stirred tank and airlift bioreactors.

PubMed

Cerri, M O; Badino, A C

2012-08-01

In biochemical processes involving filamentous microorganisms, the high shear rate may damage suspended cells leading to viability loss and cell disruption. In this work, the influence of the shear conditions in clavulanic acid (CA) production by Streptomyces clavuligerus was evaluated in a 4-dm(3) conventional stirred tank (STB) and in 6-dm(3) concentric-tube airlift (ALB) bioreactors. Batch cultivations were performed in a STB at 600 and 800 rpm and 0.5 vvm (cultivations B1 and B2) and in ALB at 3.0 and 4.1 vvm (cultivations A1 and A2) to define two initial oxygen transfer conditions in both bioreactors. The average shear rate ([Formula: see text]) of the cultivations was estimated using correlations of recent literature based on experimental data of rheological properties of the broth (consistency index, K, and flow index, n) and operating conditions, impeller speed (N) for STB and superficial gas velocity in the riser (UGR) for ALB. In the same oxygen transfer condition, the [Formula: see text] values for ALB were higher than those obtained in STB. The maximum [Formula: see text] presented a strong correlation with a maximum consistency index (K (max)) of the broth. Close values of maximum CA production were obtained in cultivations A1 and A2 (454 and 442 mg L(-1)) with similar maximum [Formula: see text] values of 4,247 and 4,225 s(-1). In cultivations B1 and B2, the maximum CA production of 269 and 402 mg L(-1) were reached with a maximum [Formula: see text] of 904 and 1,786 s(-1). The results show that high values of average shear rate increase the CA production regardless of the oxygen transfer condition and bioreactor model.

Hydrogen peroxide modulates Ca2+-activation of single permeabilized fibres from fast- and slow-twitch skeletal muscles of rats.

PubMed

Plant, D R; Lynch, G S; Williams, D A

2000-01-01

We examined the effects of redox modulation on single membrane-permeabilized fibre segments from the fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus muscles of adult rats to determine whether the contractile apparatus was the redox target responsible for the increased contractility of muscles exposed to low concentrations of H2O2. The effects of H2O2 on maximum Ca2+-activated force were dose-dependent with 30 min exposure to 5 mM H2O2 causing a progressive decrease by 22+/-3 and 13+/-2% in soleus and EDL permeabilized muscle fibres, respectively. Lower concentrations of exogenous H2O2 (100 microM and 1 mM) had no effect on maximum Ca2+-activated force. Subsequent exposure to the reductant dithiothreitol (DTT, 10 mM, 10 min) fully reversed the H2O2-induced depression of force in EDL, but not in soleus muscle fibres. Incubation with DTT alone for 10 min did not alter Ca2+-activated force in either soleus or EDL muscle fibres. The sensitivity of the contractile filaments to Ca2+ (pCa50) was not altered by exposure to any concentration of exogenous H2O2. However, all concentrations of H2O2 diminished the Hill coefficient in permeabilized fibres from the EDL muscle, indicating that the cooperativity of Ca2+ binding to troponin is altered. H2O2 (5 mM) did not affect rigor force, which indicates that the number of crossbridges participating in contraction was not reduced. In conclusion, H2O2 may reduce the maximum Ca2+ activated force production in skinned muscle fibres by decreasing the force per crossbridge.

[Composition and potential contribution of iron, calcium and zinc of bread and pasta made with wheat and amaranth flours].

PubMed

Dyner, Luis; Drago, Silvina R; Piñeiro, Adriana; Sánchez, Hugo; González, Rolando; Villaamil, Edda; Valencia, Mirta E

2007-03-01

Amaranth, a traditional american crop that is nowadays given renewed importance, has good food potential value. The minerals contributed by the grain are quantitatively important. However, as the flour is obtained by total grinding of the grain, this process leads to the presence of anti-nutritional components, such as fitates, and therefore, the evaluation of the actual availability of the minerals of nutritional interest becomes necessary. The process of bread fermentation, plus the addition of fitases and enhancers of mineral availability such as citric and ascorbic acid, might improve mineral bioavailability. The objective of this work was to assess protein, ash, lipids and total dietary fiber content and evaluate the concentration and dialyzability of Fe, Zn and Ca (as mineral bioavailability indicator) in bread and pasta 100% wheat, and bread and pasta obtained by replacing 20% wheat flour (WF) with whole amaranth flour (WAF). Ascorbic acid (AA), citric acid (CA) and fitase were used as mineral bioavailability enhancers. The potential contribution of each mineral (PC) was calculated as each mineral concentration times its dialyzability. In 80:20 bread an increase of total dietary fiber and minerals, compared to 100% wheat products was observed. A maximum FePC in 80:20 bread was obtained with CA and fitase (0.55mg%). In pasta, the maximum effect was observed with CA (0.07 mg%). The CaPC was maximum in 80:20 pasta with CA (16.72 mg%). The greatest ZnPC was found in 80:20 bread with CA and fitase (0.40 mg%). The introduction of the WAF in fermented baked products with addition of CA and fitase allows to obtain nutritional advantages.

Optical and near-infrared study of the Ca-rich transient iPTF15eqv in the early phase

NASA Astrophysics Data System (ADS)

Kawahara, Naoki; Yamanaka, Masayuki; Kawabata, Koji; Nakaoka, Tatsuya; Kawabata, Miho; Maeda, Keiichi; Takaki, Katsutoshi; Akitaya, Hiroshi; Itoh, Ryosuke; Moritani, Yuki; Uemura, Makoto; Yoshida, Michitoshi

2018-01-01

Supernovae (SNe) exhibiting strong calcium features in their spectra are called Ca-rich transients. Frequently their early-phase spectra also exhibit helium absorption lines. They are mostly discovered in elliptical galaxies or at a remote location far from the host galaxy center. Well-observed samples are still too limited to clarify the explosion and progenitor properties. We present optical and near-infrared observations of a Ca-rich transient iPTF15eqv in the spiral galaxy NGC 3430. The data are obtained using 1.5-m Kanata telescope since Sep 28, 2015. While the discovery was at a post-maximum-phase, we infer the maximum date to be 30 days before the discovery date, by comparing its light curve and spectroscopic evolution to those of well-observed samples. The spectra exhibit absorption lines of He I and prominent emission lines of Ca II IR and [Ca II] from +31 to 69 d after the maximum date. We find that iPTF15eqv is more luminous than other Ca-rich transients by 1.5 to 2 mag on +31 d, and we estimate that the peak absolute magnitude in the R band is approximately -18 to -16.5 mag. The decline rate of the light curve between 30 and 60 d is similar to those of SNe Ib/c. The line velocity of the helium is similar to those of Ca-rich transients but also to SNe Ib. The ejecta properties inferred from our observations indicate that iPTF15eqv has a larger nickel mass than typical Ca-rich transients. While these properties show similarity to SNe Ib, we show that most of these properties are indeed shared by other Ca-rich transients. The properties of iPTF15eqv may thus still be regarded to be within the diversities among the Ca-rich transients.

Thermodynamic and themoeconomic optimization of isothermal endoreversible chemical engine models

NASA Astrophysics Data System (ADS)

Ocampo-García, A.; Barranco-Jiménez, M. A.; Angulo-Brown, F.

2017-12-01

A branch of finite-time thermodynamics (FTT) is the thermoeconomical analysis of simplified power plant models. The most studied models are those of the Curzon-Ahlborn (CA) and Novikov-Chambadal types. In the decade of 90's of the past century, the FTT analysis of thermal engines was extended to chemical engines. In the present paper we made a thermoeconomical analysis of heat engines and chemical engines of the CA and Novikov types. This study is carried out for isothermal endoreversible chemical engine models with a linear mass transfer law and under three different modes of thermodynamic performance (maximum power, maximum ecological function and maximum efficient power).

Premaximum observations of the type Ia SN 1990N

NASA Technical Reports Server (NTRS)

Leibundgut, Bruno; Kirshner, Robert P.; Filippenko, Alexei V.; Shields, Joseph C.; Foltz, Craig B.; Phillips, Mark M.; Sonneborn, George

1991-01-01

Spectroscopic and photometric observations of SN 1990N were obtained at ultraviolet and optical wavelengths, beginning 14 days before maximum light. The early observations reveal important differences from spectra of SN Ia's around maximum light. Photometry and spectroscopy obtained after maximum show that SN 1990N is a typical SN Ia and that most of the observed differences are due to the early epoch of the observations. The most significant characteristics are (1) the high velocities of Ca and Si up to 22,000 km/s; (2) the presence of Co and Fe 2 weeks before maximum; and (3) the more rapid increase in the UV flux compared to the optical. The most popular models for white dwarf deflagration that have provided the standard interpretation for SN Ia's at maximum light do not reproduce the high velocities of Ca II and Si II lines observed in SN 1990N.

Dramatically enhanced non-Ohmic properties and maximum stored energy density in ceramic-metal nanocomposites: CaCu3Ti4O12/Au nanoparticles

PubMed Central

2013-01-01

Non-Ohmic and dielectric properties of a novel CaCu3Ti4O12/Au nanocomposite were investigated. Introduction of 2.5 vol.% Au nanoparticles in CaCu3Ti4O12 ceramics significantly reduced the loss tangent while its dielectric permittivity remained unchanged. The non-Ohmic properties of CaCu3Ti4O12/Au (2.5 vol.%) were dramatically improved. A nonlinear coefficient of ≈ 17.7 and breakdown electric field strength of 1.25 × 104 V/m were observed. The maximum stored energy density was found to be 25.8 kJ/m3, which is higher than that of pure CaCu3Ti4O12 by a factor of 8. Au addition at higher concentrations resulted in degradation of dielectric and non-Ohmic properties, which is described well by percolation theory. PMID:24257060

Drivers of Intra-Summer Seasonality and Daily Variability of Coastal Low Cloudiness in California Subregions

NASA Astrophysics Data System (ADS)

Schwartz, R. E.; Iacobellis, S.; Gershunov, A.; Williams, P.; Cayan, D. R.

2014-12-01

Summertime low cloud intrusion into the terrestrial west coast of North America impacts human, ecological, and logistical systems. Over a broad region of the West Coast, summer (May - September) coastal low cloudiness (CLC) varies coherently on interannual to interdecadal timescales and has been found to be organized by North Pacific sea surface temperature. Broad-scale studies of low stratiform cloudiness over ocean basins also find that the season of maximum low stratus corresponds to the season of maximum lower tropospheric stability (LTS) or estimated inversion strength. We utilize a 18-summer record of CLC derived from NASA/NOAA Geostationary Operational Environmental Satellite (GOES) at 4km resolution over California (CA) to make a more nuanced spatial and temporal examination of intra-summer variability in CLC and its drivers. We find that uniform spatial coherency over CA is not apparent for intra-summer variability in CLC. On monthly to daily timescales, at least two distinct subregions of coastal California (CA) can be identified, where relationships between meteorology and stratus variability appear to change throughout summer in each subregion. While north of Point Conception and offshore the timing of maximum CLC is closely coincident with maximum LTS, in the Southern CA Bight and northern Baja region, maximum CLC occurs up to about a month before maximum LTS. It appears that summertime CLC in this southern region is not as strongly related as in the northern region to LTS. In particular, although the relationship is strong in May and June, starting in July the daily relationship between LTS and CLC in the south begins to deteriorate. Preliminary results indicate a moderate association between decreased CLC in the south and increased precipitable water content above 850 hPa on daily time scales beginning in July. Relationships between daily CLC variability and meteorological variables including winds, inland temperatures, relative humidity, and geopotential heights within and above the marine boundary layer are investigated and dissected by month, CA subregion, and cloud height. The rich spatial detail of the satellite derived CLC record is utilized to examine the propagation in time and space of CLC on synoptic scales within and among subregions.

Time scale controversy: Accurate orbital calibration of the early Paleogene

NASA Astrophysics Data System (ADS)

Roehl, U.; Westerhold, T.; Laskar, J.

2012-12-01

Timing is crucial to understanding the causes and consequences of events in Earth history. The calibration of geological time relies heavily on the accuracy of radioisotopic and astronomical dating. Uncertainties in the computations of Earth's orbital parameters and in radioisotopic dating have hampered the construction of a reliable astronomically calibrated time scale beyond 40 Ma. Attempts to construct a robust astronomically tuned time scale for the early Paleogene by integrating radioisotopic and astronomical dating are only partially consistent. Here, using the new La2010 and La2011 orbital solutions, we present the first accurate astronomically calibrated time scale for the early Paleogene (47-65 Ma) uniquely based on astronomical tuning and thus independent of the radioisotopic determination of the Fish Canyon standard. Comparison with geological data confirms the stability of the new La2011 solution back to 54 Ma. Subsequent anchoring of floating chronologies to the La2011 solution using the very long eccentricity nodes provides an absolute age of 55.530 ± 0.05 Ma for the onset of the Paleocene/Eocene Thermal Maximum (PETM), 54.850 ± 0.05 Ma for the early Eocene ash -17, and 65.250 ± 0.06 Ma for the K/Pg boundary. The new astrochronology presented here indicates that the intercalibration and synchronization of U/Pb and 40Ar/39Ar radioisotopic geochronology is much more challenging than previously thought.

Time scale controversy: Accurate orbital calibration of the early Paleogene

NASA Astrophysics Data System (ADS)

Westerhold, Thomas; RöHl, Ursula; Laskar, Jacques

2012-06-01

Timing is crucial to understanding the causes and consequences of events in Earth history. The calibration of geological time relies heavily on the accuracy of radioisotopic and astronomical dating. Uncertainties in the computations of Earth's orbital parameters and in radioisotopic dating have hampered the construction of a reliable astronomically calibrated time scale beyond 40 Ma. Attempts to construct a robust astronomically tuned time scale for the early Paleogene by integrating radioisotopic and astronomical dating are only partially consistent. Here, using the new La2010 and La2011 orbital solutions, we present the first accurate astronomically calibrated time scale for the early Paleogene (47-65 Ma) uniquely based on astronomical tuning and thus independent of the radioisotopic determination of the Fish Canyon standard. Comparison with geological data confirms the stability of the new La2011 solution back to ˜54 Ma. Subsequent anchoring of floating chronologies to the La2011 solution using the very long eccentricity nodes provides an absolute age of 55.530 ± 0.05 Ma for the onset of the Paleocene/Eocene Thermal Maximum (PETM), 54.850 ± 0.05 Ma for the early Eocene ash -17, and 65.250 ± 0.06 Ma for the K/Pg boundary. The new astrochronology presented here indicates that the intercalibration and synchronization of U/Pb and 40Ar/39Ar radioisotopic geochronology is much more challenging than previously thought.

Effect of partial meniscectomy at the medial posterior horn on tibiofemoral contact mechanics and meniscal hoop strains in human knees.

PubMed

Seitz, Andreas Martin; Lubomierski, Anja; Friemert, Benedikt; Ignatius, Anita; Dürselen, Lutz

2012-06-01

We examined the influence of partial meniscectomy of 10 mm width on 10 human cadaveric knee joints, as it is performed during the treatment of radial tears in the posterior horn of the medial meniscus, on maximum contact pressure, contact area (CA), and meniscal hoop strain in the lateral and medial knee compartments. In case of 0° and 30° flexion angle, 20% and 50% partial meniscectomy did not influence maximum contact pressure and area. Only in case of 60° knee flexion, 50% partial resection increased medial maximum contact pressure and decreased the medial CA statistically significant. However, 100% partial resection increased maximum contact pressure and decreased CA significantly in the meniscectomized medial knee compartment in all tested knee positions. No significant differences were noted for meniscal hoop strain. From a biomechanical point of view, our in vitro study suggests that the medial joint compartment is not in danger of accelerated cartilage degeneration up to a resection limit of 20% meniscal depth and 10 mm width. Contact mechanics are likely to be more sensitive to partial meniscectomy at higher flexion angles, which has to be further investigated. Copyright © 2011 Orthopaedic Research Society.

Highly efficient continuous-wave laser operation of LD-pumped Nd,Gd:CaF2 and Nd,Y:CaF2 crystals

NASA Astrophysics Data System (ADS)

Pang, Siyuan; Ma, Fengkai; Yu, Hao; Qian, Xiaobo; Jiang, Dapeng; Wu, Yongjing; Zhang, Feng; Liu, Jie; Xu, Jiayue; Su, Liangbi

2018-05-01

Spectroscopic properties of Nd:CaF2 crystals are investigated. The photoluminescence intensity in the near infrared region is drastically enhanced by co-doping Gd3+ ions and Y3+ in Nd:CaF2 crystals. Preliminary laser experiments are carried out with 0.3%Nd,5%Gd:CaF2 and 0.3%Nd,5%Y:CaF2 crystals under laser diode pumping; true continuous wave laser operation is achieved with slope efficiencies of 42% and 39%, respectively, and the maximum output power reaches 1.188 W.

Evidence for rapid climate change in the Mesozoic-Palaeogene greenhouse world.

PubMed

Jenkyns, Hugh C

2003-09-15

The best-documented example of rapid climate change that characterized the so-called 'greenhouse world' took place at the time of the Palaeocene-Eocene boundary: introduction of isotopically light carbon into the ocean-atmosphere system, accompanied by global warming of 5-8 degrees C across a range of latitudes, took place over a few thousand years. Dissociation, release and oxidation of gas hydrates from continental-margin sites and the consequent rapid global warming from the input of greenhouses gases are generally credited with causing the abrupt negative excursions in carbon- and oxygen-isotope ratios. The isotopic anomalies, as recorded in foraminifera, propagated downwards from the shallowest levels of the ocean, implying that considerable quantities of methane survived upward transit through the water column to oxidize in the atmosphere. In the Mesozoic Era, a number of similar events have been recognized, of which those at the Triassic-Jurassic boundary, in the early Toarcian (Jurassic) and in the early Aptian (Cretaceous) currently carry the best documentation for dramatic rises in temperature. In these three examples, and in other less well-documented cases, the lack of a definitive time-scale for the intervals in question hinders calculation of the rate of environmental change. However, comparison with the Palaeocene-Eocene thermal maximum (PETM) suggests that these older examples could have been similarly rapid. In both the early Toarcian and early Aptian cases, the negative carbon-isotope excursion precedes global excess carbon burial across a range of marine environments, a phenomenon that defines these intervals as oceanic anoxic events (OAEs). Osmium-isotope ratios ((187)Os/(188)Os) for both the early Toarcian OAE and the PETM show an excursion to more radiogenic values, demonstrating an increase in weathering and erosion of continental crust consonant with elevated temperatures. The more highly buffered strontium-isotope system ((87)Sr/(86)Sr) also shows relatively more radiogenic signatures during the early Toarcian OAE, but the early Aptian and Cenomanian-Turonian OAEs show the reverse effect, implying that increased rates of sea-floor spreading and hydrothermal activity dominated over continental weathering in governing sea-water chemistry. The Cretaceous climatic optimum (late Cenomanian to mid Turonian) also shows evidence for abrupt cooling episodes characterized by episodic invasion of boreal faunas into temperate and subtropical regions and changes in terrestrial vegetation; drawdown of CO(2) related to massive marine carbon burial (OAE) may be implicated here. The absence of a pronounced negative carbon-isotope excursion preceding the Cenomanian-Turonian OAE indicates that methane release is not necessarily connected to global deposition of marine organic carbon, but relative thermal maxima are common to all OAEs. 'Cold snaps' have also been identified from the Mesozoic record but their duration, causes and effects are poorly documented.

Mammalian faunal response to the Early Eocene Climatic Optimum (~53.5-48.5 mya) and a new terrestrial record of the associated carbon isotope excursion from Raven Ridge in the Uinta Basin, Colorado-Utah

NASA Astrophysics Data System (ADS)

Dutchak, A. R.

2010-12-01

Raven Ridge straddles the Colorado-Utah border on the northeastern edge of the Uinta Basin and consists of intertonguing units of the fluvial Colton and lacustrine Green River Formations. Fossil vertebrate localities along the ridge have produced a diverse mammalian fauna comprising 64 genera in 34 families. Included are the index taxa Smilodectes, Omomys, Heptodon, and Lambdotherium which suggest an age range of mid-Wasatchian (Wa5, ~53.5mya) through mid Bridgerian (Br2, ~48.5mya) for the Raven Ridge fauna. Others have shown that this time interval coincides with the onset, peak, and decline of the Early Eocene Climatic Optimum (EECO), an extended interval of globally warm temperatures following the Paleocene-Eocene Thermal Maximum (PETM) that is coincident with a large negative carbon excursion. The Raven Ridge fauna provides an excellent opportunity to investigate the effects of a lengthy interval of global warmth on mammalian diversity and ecosystem structure. To study changes in the mammalian fauna that occurred during the EECO, it was necessary to constrain the onset, peak, and decline of the EECO at Raven Ridge through chemostratigraphic correlation with established marine isotope curves. This was accomplished by analysis of approximately 300 sediment samples for Total Organic Carbon (TOC) content. TOC has been used successfully in the Bighorn Basin to identify the stratigraphic occurrence of the Carbon Isotope Excursion (CIE) associated with the PETM, which has roughly the same amplitude as the negative excursion associated with the EECO. The Raven Ridge TOC data show a large negative carbon excursion that starts during the Wa6 biochron, peaks during the Wa7 biochron, and is followed by a positive excursion near the Wa-Br boundary. This terrestrial δ13C pattern is consistent with results seen in established marine isotope curves across the EECO interval. The minimum δ13C value of the negative excursion is -29.67‰, which is comparable to the Bighorn CIE values, and the maximum δ13C value of the positive excursion is -20.51‰. The Raven Ridge mammalian fauna shows a gradual increase in generic diversity from Wa5, when the fauna was dominated by terrestrially-adapted ischyromyid rodents and the condylarth Hyopsodus, through the Wa6 and Wa7 biochrons when arboreal primates including microsyopids, omomyids, and adapids, increased in diversity and relative abundance. These results are consistent with diversity trends seen in meta-analyses of North American mammalian diversity during the EECO. The diversity increase at Raven Ridge is mirrored by a change in ranked familial abundance from a skewed distribution during Wa5 to more even distributions during Wa6-Br1 time, an interval which is shown by previous studies in Wyoming to coincide with a significant increase in floral diversity. One interpretation of these patterns is that there was a floral shift associated with the EECO in central North America, with the relatively open habitats of the mid-Wasatchian being replaced by more densely forested canopy systems, with increased niche space allowing for diversification and increased abundance of arboreal taxa, during the late Wasatchian and early Bridgerian.

Synthesis and thermoelectric property of Ca and In-doped n-type Bi85Sb15 alloy

NASA Astrophysics Data System (ADS)

Kadel, Kamal; Li, Wenzhi; Joshi, Giri; Ren, Zhifeng

2014-03-01

In the present work we investigated the thermo-electric properties of undoped Bi85Sb15 and different Ca-doped Bi85Sb15Cax (x =0.5, 2, and 5) and In-doped Bi85Sb15Inx(x =0.5, 2) alloys synthesized via arc-melting first and followed by ball milling and hot pressing. Effect of different Ca and In doping levels on transport properties of Bi85Sb15 alloys has been investigated. It is found that thermal conductivity decreases with increasing Ca and decreasing In. Electrical transport measurements show that power factor increases with doping level of Ca up to Bi85Sb15Ca2 and then decreases yielding the maximum power factor of 3.8 × 10-3 Wm-1K-2 and zT of 0.39 at room temperature for Bi85Sb15Ca2. For indium doping, power factor decreases with doping level from 0.5 to 2, yielding the maximum zT value of 0.37 at room temperature for Bi85Sb15In0.5. In this work, calcium doping in Bi85Sb15 alloy is found to yield better thermoelectric property than indium doping.

An investigation into Ca-DNA conformation as a function of relative humidity

NASA Astrophysics Data System (ADS)

Smith, Megan Schwenker

Raman spectroscopy experiments on CaDNA free-standing, highly-ordered wet-spun films containing various concentrations of CaCl2 show that CaDNA does not adopt the A conformation and reveals a maximum of DNA in the B conformation at 80% relative humidity. Swelling experiments on these same films give information as to the intermolecular spacing between molecules. Finally, a proof of principle measurement of the activation enthalpy of guanosine is also given.

Development of a histologically validated segmentation protocol for the hippocampal body.

PubMed

Steve, Trevor A; Yasuda, Clarissa L; Coras, Roland; Lail, Mohjevan; Blumcke, Ingmar; Livy, Daniel J; Malykhin, Nikolai; Gross, Donald W

2017-08-15

Recent findings have demonstrated that hippocampal subfields can be selectively affected in different disease states, which has led to efforts to segment the human hippocampus with in vivo magnetic resonance imaging (MRI). However, no studies have examined the histological accuracy of subfield segmentation protocols. The presence of MRI-visible anatomical landmarks with known correspondence to histology represents a fundamental prerequisite for in vivo hippocampal subfield segmentation. In the present study, we aimed to: 1) develop a novel method for hippocampal body segmentation, based on two MRI-visible anatomical landmarks (stratum lacunosum moleculare [SLM] & dentate gyrus [DG]), and assess its accuracy in comparison to the gold standard direct histological measurements; 2) quantify the accuracy of two published segmentation strategies in comparison to the histological gold standard; and 3) apply the novel method to ex vivo MRI and correlate the results with histology. Ultra-high resolution ex vivo MRI was performed on six whole cadaveric hippocampal specimens, which were then divided into 22 blocks and histologically processed. The hippocampal bodies were segmented into subfields based on histological criteria and subfield boundaries and areas were directly measured. A novel method was developed using mean percentage of the total SLM distance to define subfield boundaries. Boundary distances and subfield areas on histology were then determined using the novel method and compared to the gold standard histological measurements. The novel method was then used to determine ex vivo MRI measures of subfield boundaries and areas, which were compared to histological measurements. For direct histological measurements, the mean percentages of total SLM distance were: Subiculum/CA1 = 9.7%, CA1/CA2 = 78.4%, CA2/CA3 = 97.5%. When applied to histology, the novel method provided accurate measures for CA1/CA2 (ICC = 0.93) and CA2/CA3 (ICC = 0.97) boundaries, but not for the Subiculum/CA1 (ICC = -0.04) boundary. Accuracy was poorer using previous techniques for CA1/CA2 (maximum ICC = 0.85) and CA2/CA3 (maximum ICC = 0.88), with the previously reported techniques also performing poorly in defining the Subiculum/CA1 boundary (maximum ICC = 0.00). Ex vivo MRI measurements using the novel method were linearly related to direct measurements of SLM length (r 2 = 0.58), CA1/CA2 boundary (r 2 = 0.39) and CA2/CA3 boundary (r 2 = 0.47), but not for Subiculum/CA1 boundary (r 2 = 0.01). Subfield areas measured with the novel method on histology and ex vivo MRI were linearly related to gold standard histological measures for CA1, CA2, and CA3/CA4/DG. In this initial proof of concept study, we used ex vivo MRI and histology of cadaveric hippocampi to develop a novel segmentation protocol for the hippocampal body. The novel method utilized two anatomical landmarks, SLM & DG, and provided accurate measurements of CA1, CA2, and CA3/CA4/DG subfields in comparison to the gold standard histological measurements. The relationships demonstrated between histology and ex vivo MRI supports the potential feasibility of applying this method to in vivo MRI studies. Copyright © 2017. Published by Elsevier Inc.

Growth and Deposition of Inorganic Nutrient Elements in Developing Leaves of Zea mays L. 1

PubMed Central

Meiri, Avraham; Silk, Wendy Kuhn; Läuchli, André

1992-01-01

Spatial distributions of growth and of the concentration of some inorganic nutrient elements were analyzed in developing leaves of maize (Zea mays L.). Growth was analyzed by pinprick experiments with numerical analysis to characterize fields of velocity and relative elemental elongation rate. Inductively coupled plasma and atomic emission spectroscopy were used to measure nutrients extracted from segments of leaf tissue collected by position. Leaves 7 and 8, both elongating 3 millimeters per hour had maximum relative elemental growth rates of 0.06 to 0.08 millimeters per hour with maximum rates 20 to 50 millimeters from the node and cessation of growth by 90 millimeters from the node. Spatial distribution of dry weight density revealed that the rate of biomass deposition was maximum in the most rapidly expanding region and continued beyond the elongation zone. The nutrient elements K, Cl, Ca, Mg, and P showed different distribution patterns of ion density (on a dry weight basis). K and Cl had minimal density in the leaf tips; K density was maximum in the growing region, whereas Cl density was maximum at the region of growth cessation. Ca, Mg, and P had relatively high densities at the base of the elongation zone near the node and also in the tip regions. Near the node, P and Mg densities were higher in the young, growing leaves, whereas Ca density near the node was higher in older leaves that had completed elongation. Deposition rates of all nutrients were greatest in the region of maximum elongation rate. PMID:16669027

Facile solution-precipitation assisted synthesis and luminescence property of greenish-yellow emitting Ca{sub 6}Ba(PO{sub 4}){sub 4}O:Eu{sup 2+} phosphor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ji, Haipeng; Huang, Zhaohui, E-mail: huang118@cugb.edu.cn; Xia, Zhiguo, E-mail: xiazg@ustb.edu.cn

2016-03-15

Highlights: • Ca{sub 6}Ba(PO{sub 4}){sub 4}O:Eu{sup 2+} phosphor was prepared by the solution-precipitation assisted route. • The phosphors have satisfactory smooth grain surface and particle size. • It shows greenish-yellow color emission (maximum at 540 nm) upon blue light excitation. • Eu{sup 2+} is coordinated with isolated oxygen atoms and those from PO{sub 4} polyhedra. - Abstract: Greenish-yellow emitting microcrystalline Ca{sub 6}Ba(PO{sub 4}){sub 4}O:Eu{sup 2+} phosphor was successfully prepared by a solution-precipitation assisted high temperature reaction method. Phase structure, morphology and/or luminescence properties of the precursor and the as-prepared phosphors were characterized. The phase-pure Ca{sub 6}Ba(PO{sub 4}){sub 4}O:Eu{sup 2+} phosphorsmore » were obtained with smooth grain surface and particle size of 2–8 μm. Ca{sub 6}Ba(PO{sub 4}){sub 4}O:Eu{sup 2+} exhibits bright greenish-yellow color emission with its maximum at 540 nm upon UV-blue light excitation. The maximum position of the broad emission band is independent on the calcination temperature. The emission intensity increases with increasing calcination temperature due to improved crystallinity. Besides, the presence of two Eu{sup 2+} emission centers in the Ca{sub 6}Ba(PO{sub 4}){sub 4}O crystal lattice was confirmed and the coordination effects are considered concerning the roles of isolated O atoms and those from the PO{sub 4} tetrahedra.« less

Intracellular calcium and the mechanism of anodal supernormal excitability in langendorff perfused rabbit ventricles.

PubMed

Joung, Boyoung; Park, Hyung-Wook; Maruyama, Mitsunori; Tang, Liang; Song, Juan; Han, Seongwook; Piccirillo, Gianfranco; Weiss, James N; Lin, Shien-Fong; Chen, Peng-Sheng

2011-01-01

Anodal stimulation hyperpolarizes the cell membrane and increases the intracellular Ca(2+) (Ca(i)) transient. This study tested the hypothesis that the maximum slope of the Ca(i) decline (-(dCa(i)/dt)(max)) corresponds to the timing of anodal dip on the strength-interval curve and the initiation of repetitive responses and ventricular fibrillation (VF) after a premature stimulus (S(2)). We simultaneously mapped the membrane potential (V(m)) and Ca(i) in 23 rabbit ventricles. A dip in the anodal strength-interval curve was observed. During the anodal dip, ventricles were captured by anodal break excitation directly under the S(2) electrode. The Ca(i) following anodal stimuli is larger than that following cathodal stimuli. The S(1)-S(2) intervals of the anodal dip (203±10 ms) coincided with the -(dCa(i)/dt)(max) (199±10 ms, P=NS). BAPTA-AM (n=3), inhibition of the electrogenic Na(+)-Ca(2+) exchanger current (I(NCX)) by low extracellular Na(+) (n=3), and combined ryanodine and thapsigargin infusion (n=2) eliminated the anodal supernormality. Strong S(2) during the relative refractory period (n=5) induced 29 repetitive responses and 10 VF episodes. The interval between S(2) and the first non-driven beat was coincidental with the time of -(dCa(i)/dt)(max). Larger Ca(i) transient and I(NCX) activation induced by anodal stimulation produces anodal supernormality. The time of maximum I(NCX) activation is coincidental to the induction of non-driven beats from the Ca(i) sinkhole after a strong premature stimulation. All rights are reserved to the Japanese Circulation Society.

Interobserver Agreement on First-Stage Conversation Analytic Transcription

ERIC Educational Resources Information Center

Roberts, Felicia; Robinson, Jeffrey D.

2004-01-01

This investigation assesses interobserver agreement on conversation analytic (CA) transcription. Four professional CA transcribers spent a maximum of 3 hours transcribing 2.5 minutes of a previously unknown, naturally occurring, mundane telephone call. Researchers unitized transcripts into words, sounds, silences, inbreaths, outbreaths, and laugh…

Efficient continuous-wave, broadly tunable and passive Q-switching lasers based on a Tm3+:CaF2 crystal

NASA Astrophysics Data System (ADS)

Liu, Jingjing; Zhang, Cheng; Zu, Yuqian; Fan, Xiuwei; Liu, Jie; Guo, Xinsheng; Qian, Xiaobo; Su, Liangbi

2018-04-01

Laser operations in the continuous-wave as well as in the pulsed regime of a 4 at.% Tm3+:CaF2 crystal are reported. For the continuous-wave operation, a maximum average output power of 1.15 W was achieved, and the corresponding slope efficiency was more than 64%. A continuous tuning range of about 160 nm from 1877-2036 nm was achieved using a birefringent filter. Using Argentum nanorods as a saturable absorber, the significant pulsed operation of a passively Q-switched Tm3+:CaF2 laser was observed at 1935.4 nm for the first time, to the best of our knowledge. A maximum output power of 385 mW with 41.4 µJ pulse energy was obtained under an absorbed pump power of 2.04 W. The present results indicate that the Tm3+:CaF2 lasers could be promising laser sources to operate in the eye-safe spectral region.

Irreversibilities and efficiency at maximum power of heat engines: the illustrative case of a thermoelectric generator.

PubMed

Apertet, Y; Ouerdane, H; Goupil, C; Lecoeur, Ph

2012-03-01

Energy conversion efficiency at maximum output power, which embodies the essential characteristics of heat engines, is the main focus of the present work. The so-called Curzon and Ahlborn efficiency η(CA) is commonly believed to be an absolute reference for real heat engines; however, a different but general expression for the case of stochastic heat engines, η(SS), was recently found and then extended to low-dissipation engines. The discrepancy between η(CA) and η(SS) is here analyzed considering different irreversibility sources of heat engines, of both internal and external types. To this end, we choose a thermoelectric generator operating in the strong-coupling regime as a physical system to qualitatively and quantitatively study the impact of the nature of irreversibility on the efficiency at maximum output power. In the limit of pure external dissipation, we obtain η(CA), while η(SS) corresponds to the case of pure internal dissipation. A continuous transition between from one extreme to the other, which may be operated by tuning the different sources of irreversibility, also is evidenced.

Magnetoresistance measurements in Ferro -- Antiferromagnetic bilayers based on the Ca-doped lanthanum manganite system

NASA Astrophysics Data System (ADS)

Gomez, M. E.; Marin, L.; Ramirez, G.; Prieto, P.

2011-03-01

We studied the isothermal magnetic field dependence of the resistance behavior in ferromagnetic--antiferromagnetic interface based on the Ca-doped lanthanum manganite system at temperatures below Neel temperature of the antiferromagnetic layer. We studied the influence of the thickness of the AF-layer, tAF , and F-layer, tF , on the ZFC and FC magnetoresistance (MR) in La 2/3 Ca 1/3 Mn O3 (tF) / La 1/3 Ca 2(3 Mn O3 (tAF) bilayers. HFC was 400 Oe and the applied magnetic field, H. We systematically varied the tF and tAF thickness, maintaining constant the total bilayer thickness (d = tF +tAF) . We found that MR has hysteretic behavior as observed in [ La 2/3 Ca 1/3 Mn O3 (tF) / La 1/3 Ca 2(3 Mn O3 (tAF) ]N superlattices, but; MR increases with the increasing field from H=0 to a maximum and then decreases continuously. This behavior also appears for negative fields in both ZFC and FC loops. The position and magnitude of the maximum is not symmetric with respect to the axis H=0. Work supported by CENM-COLCIENCIAS contract RC-0043-(2005).

Quantitative Analysis of Ca, Mg, and K in the Roots of Angelica pubescens f. biserrata by Laser-Induced Breakdown Spectroscopy Combined with Artificial Neural Networks

NASA Astrophysics Data System (ADS)

Wang, J.; Shi, M.; Zheng, P.; Xue, Sh.; Peng, R.

2018-03-01

Laser-induced breakdown spectroscopy has been applied for the quantitative analysis of Ca, Mg, and K in the roots of Angelica pubescens Maxim. f. biserrata Shan et Yuan used in traditional Chinese medicine. Ca II 317.993 nm, Mg I 517.268 nm, and K I 769.896 nm spectral lines have been chosen to set up calibration models for the analysis using the external standard and artificial neural network methods. The linear correlation coefficients of the predicted concentrations versus the standard concentrations of six samples determined by the artificial neural network method are 0.9896, 0.9945, and 0.9911 for Ca, Mg, and K, respectively, which are better than for the external standard method. The artificial neural network method also gives better performance comparing with the external standard method for the average and maximum relative errors, average relative standard deviations, and most maximum relative standard deviations of the predicted concentrations of Ca, Mg, and K in the six samples. Finally, it is proved that the artificial neural network method gives better performance compared to the external standard method for the quantitative analysis of Ca, Mg, and K in the roots of Angelica pubescens.

X-Ray Microanalysis of Human Cementum

NASA Astrophysics Data System (ADS)

Alvarez-Pérez, Marco Antonio; Alvarez-Fregoso, Octavio; Ortiz-López, Jaime; Arzate, Higinio

2005-08-01

An energy dispersive x-ray microanalysis study was performed throughout the total length of cementum on five impacted human teeth. Mineral content of calcium, phosphorous, and magnesium were determined with an electron probe from the cemento-enamel junction to the root apex on the external surface of the cementum. The concentration profiles for calcium, phosphorous, and magnesium were compared by using Ca/P and Mg/Ca atomic percent ratio. Our findings demonstrated that the Ca/P ratio at the cemento-enamel junction showed the highest values (1.8 2.2). However, the area corresponding to the acellular extrinsic fiber cementum (AEFC) usually located on the coronal one-third of the root surface showed a Ca/P media value of 1.65. Nevertheless, on the area representing the fulcrum of the root there is an abrupt change in the Ca/P ratio, which decreases to 1.3. Our results revealed that Mg2+ distribution throughout the length of human cementum reached its maximum Mg/Ca ratio value of 1.3 1.4 at.% around the fulcrum of the root and an average value of 0.03%. A remarkable finding was that the Mg/Ca ratio pattern distribution showed that in the region where the Ca/P ratio showed a decreasing tendency, the Mg/Ca ratio reached its maximum value, showing a negative correlation. In conclusion, this study has established that clear compositional differences exist between AEFC and cellular mixed stratified cementum varieties and adds new knowledge about Mg2+ distribution and suggests its provocative role regulating human cementum metabolism.

Enhancing ethanol production from cellulosic sugars using Scheffersomyces (Pichia) stipitis

USDA-ARS?s Scientific Manuscript database

Studies were performed on the effect of CaCO3 and CaCl2 supplementation to fermentation medium for ethanol production from xylose, glucose, or their mixtures using Scheffersomyces (Pichia) stipitis. Both of these chemicals were found to improve maximum ethanol concentration and ethanol productivity....

Phase Composition and Hardening of Castable Al - Ca - Ni - Sc Alloys Containing 0.3% Sc

NASA Astrophysics Data System (ADS)

Belov, N. A.; Naumova, E. A.; Bazlova, T. A.; Doroshenko, V. V.

2017-05-01

The phase composition of aluminum alloys of the Al - Ca - Ni - Sc system containing 0.3 wt.% Sc is studied. It is shown that the aluminum solid solution may be in equilibrium not only with binary phases (Al4Ca, Al3Sc and Al3Ni) but also with a ternary Al9NiCa compound. The temperature of attainment of maximum hardening due to precipitation of nanoparticles of phase Al3Sc is determined for all the alloys studied. Principal possibility of creation of castable alloys based on an (Al) + Al4Ca + Al9NiCa eutectic, the hardening heat treatment of which does not require quenching, is substantiated.

Use of response surface methodology to evaluate the effect of metal ions (Ca2+, Ni2+, Mn2+, Cu2+) on production of antifungal compounds by Paenibacillus polymyxa.

PubMed

Raza, Waseem; Hongsheng, Wu; Qirong, Shen

2010-03-01

The effects of four metal ions (Ca(2+), Ni(2+), Mn(2+) and Cu(2+)) were evaluated on growth and production of antifungal compounds by Paenibacillus polymyxa SQR-21 and a quadratic predictive model was developed using response surface methodology (RSM). The results revealed, Mn(2+) and Ni(2+) showed most positive synergistic interactive affect on production of antifungal compounds followed by the positive interactive synergistic affect of Cu(2+) and Ni(2+) and then Mn(2+) and Cu(2+). While the interactive effect of Ca(2+) with all other three metals inhibited the production of antifungal compounds. The Mn(2+) (P=0.0384), Ni(2+) (P=0.0004) and Cu(2+) (P=0.0117) significantly affected the production of antifungal compounds while the effect of Ca(2+) (P=0.1851) was less significant. The maximum growth (OD(600)=1.55) was obtained at 500 (0), 125 (0), 100 (-2) and 37.5 (0) microM levels and the maximum size of inhibition zone (31 mm) was measured at 400 (-1), 150 (1), 400 (1) and 25 microM (-1) levels of Ca(2+), Mn(2+), Ni(2+) and Cu(2+), respectively. The RSM model provided an easy and effective way to determine the interactive effect of metal ions on production of antifungal compounds by P. polymyxa SQR-21 so that optimum media recipes can be developed to produce maximum amounts of antifungal compounds under laboratory and commercial fermentation conditions. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

Electrochemical double layers at the interface between glassy electrolytes and platinum: Differentiating between the anode and the cathode capacitance

NASA Astrophysics Data System (ADS)

Kruempelmann, J.; Mariappan, C. R.; Schober, C.; Roling, B.

2010-12-01

We have measured potential-dependent interfacial capacitances of two Na-Ca-phosphosilicate glasses and of an AgI-doped silver borate glass between ion-blocking Pt electrodes. An asymmetric electrode configuration with highly dissimilar electrode areas on both faces of the glass samples allowed us to determine the capacitance at the small-area electrode. Using equivalent circuit fitting we extract potential-dependent double-layer capacitances. The potential-dependent anodic capacitance exhibits a weak maximum and drops strongly at higher potentials. The cathodic capacitance exhibits a more pronounced maximum, this maximum being responsible for the maximum in the total capacitance observed in measurements in a symmetrical electrode configuration. The capacitance maxima of the Na-Ca phosphosilicate glasses show up at higher electrode potentials than the maxima of the AgI-doped silver borate glass. Remarkably, for both types of glasses, the potential of the cathodic capacitance maximum is closely related to the activation energy of the bulk ion transport. We compare our results to recent theoretical predictions by Shklovskii and co-workers.

Properties of Semi-dry Flue Gas Desulfurization Ash and Used for Phosphorus Removal

NASA Astrophysics Data System (ADS)

Yu, Y. P.; Fang, Y.; Chai, S. Y.; Zhuang, Z. Z.

2018-05-01

The composition of Semi-dry Flue Gas Desulfurization ash was as follows: CaSO3 · 0.5H2O and Ca(OH)2. Most of the particle size was about 8 µm particles were irregular and small, while the other part was rough and globular. CaSO3 strongly oxidized at about 466°C and Ca(OH)2 decomposed at ∼ 662°C. The maximum amount of phosphorus removal in Semi-dry Flue Gas Desulfurization ash was 79.898 mg/g.

Diode pumped tunable lasers based on Tm:CaF2 and Tm:Ho:CaF2 ceramics

NASA Astrophysics Data System (ADS)

Šulc, Jan; Němec, Michal; Jelinková, Helena; Doroshenko, Maxim E.; Fedorov, Pavel P.; Osiko, Vyacheslav V.

2014-02-01

The Tm:CaF2 (4% of TmF3) and Tm:Ho:CaF2 (2% of TmF3, 0.3% of HoF3) ceramics, prepared using hot pressing, and hot formation technique had been used as an active medium of diode pumped mid-infrared tunable laser. A fibre (core diameter 400 μm, NA = 0.22) coupled laser diode (LIMO, HLU30F400-790) was used to longitudinal pumping. The laser diode was operating in the pulsed regime (6 ms pulse length, 10 Hz repetition rate). The duty-cycle 6% ensures a low thermal load even under the maximum diode pumping power amplitude 25W (ceramics samples were only air-cooled). The laser diode emission wavelength was 786 nm. The 80mm long semi-hemispherical laser resonator consisted of a flat pumping mirror (HR @ 1.85 - 2.15 μm, HT @ 0.78 μm) and a curved (r = 150mm) output coupler with a reflectivity of ˜ 98% @ 1.85 - 2.0 μm for Tm:CaF2 laser or ˜ 99.5% @ 2.0 - 2.15 μm for Ho:Tm:CaF2. Tuning of the laser was accomplished by using a birefringent filter (single 1.5mm thick quartz plate) placed inside the optical resonator at the Brewster angle. Both samples offered broad and smooth tuning possibilities in mid-IR spectral range and the lasers were continuously tunable over ˜ 100 nm. The obtained Tm:CaF2 tunability ranged from 1892 to 1992nm (the maximum output energy 1.8mJ was reached at 1952nm for absorbed pumping energy 78 mJ). In case of Tm:Ho:CaF2 laser tunability from 2016 to 2111nm was reached (the maximum output energy 1.5mJ was reached at 2083nm for absorbed pumping energy 53 mJ). Both these material are good candidates for a future investigation of high energy, ultra-short, laser pulse generation.

SU-E-T-578: On Definition of Minimum and Maximum Dose for Target Volume

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gong, Y; Yu, J; Xiao, Y

Purpose: This study aims to investigate the impact of different minimum and maximum dose definitions in radiotherapy treatment plan quality evaluation criteria by using tumor control probability (TCP) models. Methods: Dosimetric criteria used in RTOG 1308 protocol are used in the investigation. RTOG 1308 is a phase III randomized trial comparing overall survival after photon versus proton chemoradiotherapy for inoperable stage II-IIIB NSCLC. The prescription dose for planning target volume (PTV) is 70Gy. Maximum dose (Dmax) should not exceed 84Gy and minimum dose (Dmin) should not go below 59.5Gy in order for the plan to be “per protocol” (satisfactory).A mathematicalmore » model that simulates the characteristics of PTV dose volume histogram (DVH) curve with normalized volume is built. The Dmax and Dmin are noted as percentage volumes Dη% and D(100-δ)%, with η and d ranging from 0 to 3.5. The model includes three straight line sections and goes through four points: D95%= 70Gy, Dη%= 84Gy, D(100-δ)%= 59.5 Gy, and D100%= 0Gy. For each set of η and δ, the TCP value is calculated using the inhomogeneously irradiated tumor logistic model with D50= 74.5Gy and γ50=3.52. Results: TCP varies within 0.9% with η; and δ values between 0 and 1. With η and η varies between 0 and 2, TCP change was up to 2.4%. With η and δ variations from 0 to 3.5, maximum of 8.3% TCP difference is seen. Conclusion: When defined maximum and minimum volume varied more than 2%, significant TCP variations were seen. It is recommended less than 2% volume used in definition of Dmax or Dmin for target dosimetric evaluation criteria. This project was supported by NIH grants U10CA180868, U10CA180822, U24CA180803, U24CA12014 and PA CURE Grant.« less

Terrestrial Palynology of Paleocene and Eocene Sediments Above the Chicxulub Impact Crater

NASA Astrophysics Data System (ADS)

Smith, V.; Warny, S.; Bralower, T. J.; Jones, H.; Lowery, C. M.; Smit, J.; Vajda, V.; Vellekoop, J.; 364 Scientists, E.

2017-12-01

International Ocean Discovery Program (IODP) Expedition 364, with support from the International Continental Scientific Drilling Program, cored through Paleocene and Eocene sediments and into the impact structure of the Chicxulub impact crater. Three palynological studies of the post-impact section are currently underway. The two other studies are investigating the dinoflagellate palynology and terrestrial palynology of the K/Pg boundary section, while this study focuses on the early Eocene terrestrial palynology of the IODP 364 core, which has yielded a diverse and well preserved pollen assemblage. A few samples from the Early Paleocene have also been examined but organic microfossil preservation is quite poor. Samples from this core are the oldest palynological record from the Yucatan peninsula. Sample preparation and detailed abundance counts of sixty samples throughout the post-impact section are in progress, with a particular focus on the Paleocene-Eocene Thermal Maximum (PETM) and the Early Eocene Climatic Optimum (EECO). Terrestrial palynomorph assemblages will be used to reconstruct paleoclimatological conditions throughout this time period. Floral response to hyperthermal events in the IODP 364 core will be compared with records from other Gulf of Mexico and Caribbean sections. In addition to the biological and paleoclimatological implications of this research, age control from foraminiferal and nannofossil biostratigraphy, paleomagnetism, and radiometric dating will provide a chronological framework for the terrestrial pollen biostratigraphy, with applications to hydrocarbon exploration in the Wilcox Formation and age equivalent sections in the Gulf of Mexico.

Effect of Sarcoplasmic Reticulum (SR) Calcium Content on SR Calcium Release Elicited by Small Voltage-Clamp Depolarizations in Frog Cut Skeletal Muscle Fibers Equilibrated with 20 mM EGTA

PubMed Central

Pape, Paul C.; Carrier, Nicole

1998-01-01

Cut muscle fibers from Rana temporaria (sarcomere length, 3.5–3.9 μm; 14–16°C) were mounted in a double Vaseline-gap chamber and equilibrated with an external solution that contained tetraethyl ammonium– gluconate and an internal solution that contained Cs as the principal cation, 20 mM EGTA, and 0 Ca. Fibers were stimulated with a voltage-clamp pulse protocol that consisted of pulses to −70, −65, −60, −45, and −20 mV, each separated by 400-ms periods at −90 mV. The change in total Ca that entered into the myoplasm (Δ[CaT]) and the Ca content of the SR ([CaSR]) were estimated with the EGTA/phenol red method (Pape, P.C., D.-S. Jong, and W.K. Chandler. 1995. J. Gen. Physiol. 106:259–336). Fibers were stimulated with the pulse protocol, usually every 5 min, so that the resting value of [CaSR] decreased from its initial value of 1,700–2,300 μM to values near or below 100 μM after 18–30 stimulations. Three main findings for the voltage pulses to −70, −65, and −60 mV are: (a) the depletion-corrected rate of Ca release (release permeability) showed little change when [CaSR] decreased from its highest level (>1,700 μM) to ∼1,000 μM; (b) as [CaSR] decreased below 1,000 μM, the release permeability increased to a maximum level when [CaSR] was near 300 μM that was on average about sevenfold larger than the values observed for [CaSR] > 1,000 μM; and (c) as [CaSR] decreased from ∼300 μM to <100 μM, the release permeability decreased, reaching half its maximum value when [CaSR] was ∼110 μM on average. It was concluded that finding b was likely due to a decrease in Ca inactivation, while finding c was likely due to a decrease in Ca-induced Ca release. PMID:9689025

L-type calcium channels refine the neural population code of sound level

PubMed Central

Grimsley, Calum Alex; Green, David Brian

2016-01-01

The coding of sound level by ensembles of neurons improves the accuracy with which listeners identify how loud a sound is. In the auditory system, the rate at which neurons fire in response to changes in sound level is shaped by local networks. Voltage-gated conductances alter local output by regulating neuronal firing, but their role in modulating responses to sound level is unclear. We tested the effects of L-type calcium channels (CaL: CaV1.1–1.4) on sound-level coding in the central nucleus of the inferior colliculus (ICC) in the auditory midbrain. We characterized the contribution of CaL to the total calcium current in brain slices and then examined its effects on rate-level functions (RLFs) in vivo using single-unit recordings in awake mice. CaL is a high-threshold current and comprises ∼50% of the total calcium current in ICC neurons. In vivo, CaL activates at sound levels that evoke high firing rates. In RLFs that increase monotonically with sound level, CaL boosts spike rates at high sound levels and increases the maximum firing rate achieved. In different populations of RLFs that change nonmonotonically with sound level, CaL either suppresses or enhances firing at sound levels that evoke maximum firing. CaL multiplies the gain of monotonic RLFs with dynamic range and divides the gain of nonmonotonic RLFs with the width of the RLF. These results suggest that a single broad class of calcium channels activates enhancing and suppressing local circuits to regulate the sensitivity of neuronal populations to sound level. PMID:27605536

Impaired systemic oxygen extraction in treated exercise pulmonary hypertension: a new engine in an old car?

PubMed

Faria-Urbina, Mariana; Oliveira, Rudolf K F; Segrera, Sergio A; Lawler, Laurie; Waxman, Aaron B; Systrom, David M

2018-01-01

Ambrisentan in 22 patients with pulmonary hypertension diagnosed during exercise (ePH) improved pulmonary hemodynamics; however, there was only a trend toward increased maximum oxygen uptake (VO 2 max) secondary to decreased maximum exercise systemic oxygen extraction (Ca-vO 2 ). We speculate that improved pulmonary hemodynamics at maximum exercise "unmasked" a pre-existing skeletal muscle abnormality.

Adsorption and Desorption Characteristics of Cd2+ and Pb2+ by Micro and Nano-sized Biogenic CaCO3

PubMed Central

Liu, Renlu; Guan, Yong; Chen, Liang; Lian, Bin

2018-01-01

The purpose of this study was to elucidate the characteristics and mechanisms of adsorption and desorption for heavy metals by micro and nano-sized biogenic CaCO3 induced by Bacillus subtilis, and the pH effect on adsorption was investigated. The results showed that the adsorption characteristics of Cd2+ and Pb2+ are well described by the Langmuir adsorption isothermal equation, and the maximum adsorption amounts for Cd2+ and Pb2+ were 94.340 and 416.667 mg/g, respectively. The maximum removal efficiencies were 97% for Cd2+, 100% for Pb2+, and the desorption rate was smaller than 3%. Further experiments revealed that the biogenic CaCO3 could maintain its high adsorption capability for heavy metals within wide pH ranges (3–8). The FTIR and XRD results showed that, after the biogenic CaCO3 adsorbed Cd2+ or Pb2+, it did not produce a new phase, which indicated that biogenic CaCO3 and heavy metal ions were governed by a physical adsorption process, and the high adsorptive capacity of biogenic CaCO3 for Cd2+ and Pb2+ were mainly attributed to its large total specific surface area. The findings could improve the state of knowledge about biogenic CaCO3 formation in the environment and its potential roles in the biogeochemical cycles of heavy metals. PMID:29434577

Effect of contact angle and contact angle hysteresis on the floatability of spheres at the air-water interface.

PubMed

Feng, Dong-Xia; Nguyen, Anh V

2017-10-01

The floatability of solid particles on the water surface governs many natural phenomena and industrial processes including film flotation and froth flotation separation of coal and valuable minerals. For many years, the contact angle (CA) has been postulated as the key factor in determining the particle floatability. Indeed, the maximum force (tenacity) supporting the flotation of fine spheres was conjectured to occur when the apical angle of the contact circle is equal to the contact angle. In this paper, the model predictions are reviewed and compared with experimental results. It is shown that CA can be affected by many physical and chemical factors such as surface roughness and chemical heterogeneity and can have a range of values known as the CA hysteresis. This multiple-valued CA invalidates the available theories on the floatability of spheres. Even the intuitive replacement of CA by the advancing (maximum) CA in the classical theories can be wrong. A few new examples are also reviewed and analyzed to demonstrate the significance of CA variation in controlling the particle floatability. They include the pinning of the contact line at the sharp edge, known as the Gibbs inequality condition, and the nearby interaction among floating particles, known as lateral inter-particle interaction. It is concluded that our quantitative understanding of the floatability of real particles being irregular and heterogeneous both morphologically and chemically is still far from being satisfactory. Copyright © 2017 Elsevier B.V. All rights reserved.

Elastic and inelastic light scattering from single bacterial spores in an optical trap allows the monitoring of spore germination dynamics

PubMed Central

Peng, Lixin; Chen, De; Setlow, Peter; Li, Yong-qing

2009-01-01

Raman scattering spectroscopy and elastic light scattering intensity (ESLI) were used to simultaneously measure levels of Ca-dipicolinic acid (CaDPA) and changes in spore morphology and refractive index during germination of individual B. subtilis spores with and without the two redundant enzymes (CLEs), CwlJ and SleB, that degrade spores’ peptidoglycan cortex. Conclusions from these measurements include: 1) CaDPA release from individual wild-type germinating spores was biphasic; in a first heterogeneous slow phase, Tlag, CaDPA levels decreased ∼15% and in the second phase ending at Trelease, remaining CaDPA was released rapidly; 2) in L-alanine germination of wild-type spores and spores lacking SleB: a) the ESLI rose ∼2-fold shortly before Tlag at T1; b) following Tlag, the ESLI again rose ∼2-fold at T2 when CaDPA levels had decreased ∼50%; and c) the ESLI reached its maximum value at ∼Trelease and then decreased; 3) in CaDPA germination of wild-type spores: a) Tlag increased and the first increase in ESLI occurred well before Tlag, consistent with different pathways for CaDPA and L-alanine germination; b) at Trelease the ESLI again reached its maximum value; 4) in L-alanine germination of spores lacking both CLEs and unable to degrade their cortex, the time ΔTrelease (Trelease–Tlag) for excretion of ≥75% of CaDPA was ∼15-fold higher than that for wild-type or sleB spores; and 5) spores lacking only CwlJ exhibited a similar, but not identical ESLI pattern during L-alanine germination to that seen with cwlJ sleB spores, and the high value for ΔTrelease. PMID:19374431

Improved model of the retardance in citric acid coated ferrofluids using stepwise regression

NASA Astrophysics Data System (ADS)

Lin, J. F.; Qiu, X. R.

2017-06-01

Citric acid (CA) coated Fe3O4 ferrofluids (FFs) have been conducted for biomedical application. The magneto-optical retardance of CA coated FFs was measured by a Stokes polarimeter. Optimization and multiple regression of retardance in FFs were executed by Taguchi method and Microsoft Excel previously, and the F value of regression model was large enough. However, the model executed by Excel was not systematic. Instead we adopted the stepwise regression to model the retardance of CA coated FFs. From the results of stepwise regression by MATLAB, the developed model had highly predictable ability owing to F of 2.55897e+7 and correlation coefficient of one. The average absolute error of predicted retardances to measured retardances was just 0.0044%. Using the genetic algorithm (GA) in MATLAB, the optimized parametric combination was determined as [4.709 0.12 39.998 70.006] corresponding to the pH of suspension, molar ratio of CA to Fe3O4, CA volume, and coating temperature. The maximum retardance was found as 31.712°, close to that obtained by evolutionary solver in Excel and a relative error of -0.013%. Above all, the stepwise regression method was successfully used to model the retardance of CA coated FFs, and the maximum global retardance was determined by the use of GA.

The Influence of Layer Thickness-Ratio on Magnetoresistance in La2/3Ca1/3MnO3/La1/3Ca2/3MnO3 Exchange Biased System

NASA Astrophysics Data System (ADS)

Gomez, Maria Elena; Milena Diez, Sandra; Cuartas, Lina Maria; Marin, Lorena; Prieto, Pedro

2012-02-01

Isothermal magnetic field dependence of the resistance in La2/3Ca1/3MnO3 (F-LCMO)/ La1/3Ca2/3MnO3(AF-LCMO) bilayer and AF-LCMO/F-LCMO/AF-LCMO trilayer at temperatures below N'eel temperature of the antiferromagnetic layer were carried out to study the thickness layers influence on magneto transport properties. We grew multilayers using a high oxygen pressure sputtering technique. We systematically varied the thickness of the F-LCMO layer, tF, maintaining constant the thickness of the AF-LCMO layer, tAF. We studied the influence of the thickness ratio tF/tAF on the ZFC and FC magnetoresistance (MR) loops. HFC was varied from 100 Oe to 400 Oe. We found that MR has hysteretic behavior as observed in [La2/3Ca1/3MnO3/La1/3Ca2/3MnO3]N superlattices, where MR increases with the increasing field from H=0 to a maximum and then it decreases continuously. The position and magnitude of the maximum is not symmetric with respect to the axis H=0 for both FC and ZFC loops. We found that magnetoresistance behavior of the bilayer and trilayer is thickness-ratio dependent for both ZFC and FC loops.

High quantum yield of the Egyptian blue family of infrared phosphors (MCuSi4O10, M = Ca, Sr, Ba)

NASA Astrophysics Data System (ADS)

Berdahl, Paul; Boocock, Simon K.; Chan, George C.-Y.; Chen, Sharon S.; Levinson, Ronnen M.; Zalich, Michael A.

2018-05-01

The alkaline earth copper tetra-silicates, blue pigments, are interesting infrared phosphors. The Ca, Sr, and Ba variants fluoresce in the near-infrared (NIR) at 909, 914, and 948 nm, respectively, with spectral widths on the order of 120 nm. The highest quantum yield ϕ reported thus far is ca. 10%. We use temperature measurements in sunlight to determine this parameter. The yield depends on the pigment loading (mass per unit area) ω with values approaching 100% as ω → 0 for the Ca and Sr variants. Although maximum quantum yield occurs near ω = 0, maximum fluorescence occurs near ω = 70 g m-2, at which ϕ = 0.7. The better samples show fluorescence decay times in the range of 130 to 160 μs. The absorbing impurity CuO is often present. Good phosphor performance requires long fluorescence decay times and very low levels of parasitic absorption. The strong fluorescence enhances prospects for energy applications such as cooling of sunlit surfaces (to reduce air conditioning requirements) and luminescent solar concentrators.

Fast microwave-assisted catalytic co-pyrolysis of corn stover and scum for bio-oil production with CaO and HZSM-5 as the catalyst.

PubMed

Liu, Shiyu; Xie, Qinglong; Zhang, Bo; Cheng, Yanling; Liu, Yuhuan; Chen, Paul; Ruan, Roger

2016-03-01

This study investigated fast microwave-assisted catalytic co-pyrolysis of corn stover and scum for bio-oil production with CaO and HZSM-5 as the catalyst. Effects of reaction temperature, CaO/HZSM-5 ratio, and corn stover/scum ratio on co-pyrolysis product fractional yields and selectivity were investigated. Results showed that co-pyrolysis temperature was selected as 550°C, which provides the maximum bio-oil and aromatic yields. Mixed CaO and HZSM-5 catalyst with the weight ratio of 1:4 increased the aromatic yield to 35.77 wt.% of feedstock, which was 17% higher than that with HZSM-5 alone. Scum as the hydrogen donor, had a significant synergistic effect with corn stover to promote the production of bio-oil and aromatic hydrocarbons when the H/C(eff) value exceeded 1. The maximum yield of aromatic hydrocarbons (29.3 wt.%) were obtained when the optimal corn stover to scum ratio was 1:2. Copyright © 2016 Elsevier Ltd. All rights reserved.

SHRIMP U-Pb detrital zircon dating to check subdivisions in metamorphic complexes: a case of study in the Nevado-Filábride complex (Betic Cordillera, Spain)

NASA Astrophysics Data System (ADS)

Santamaría-López, Ángel; Sanz de Galdeano, Carlos

2018-04-01

U-Pb dating on inherited detrital zircons has been applied to obtain the probable maximum age of deposition of the detrital protolith of the Nevado-Filábride complex (Betic Cordillera, Spain). Five of eight samples correspond to the lower part of the lithologic sequence of this complex, where radiometric dating of metasediments has not been presented till the present. The youngest age populations in the majority of samples are Carboniferous. The estimation of the maximum age of deposition in the lower and upper units is 349.1 ± 1.6 and 334.6 ± 2.9 Ma, respectively. In addition, samples show common age populations at ca. 490-630 and ca. 910-1010 Ma. Observations agree with the Carboniferous to early Permian U-Pb ages previously obtained in orthogneisses levels which are situated in the upper part of the complex. Combination of the minimum age of deposition deducible from the orthogneisses studies and the maximum ages of deposition obtained from the detrital zircons of this work, allow establishing the deposition of de studied lithological succession comprised between ca. 282 and 349 Ma or a shorter period.

Enhancement of force generated by individual myosin heads in skinned rabbit psoas muscle fibers at low ionic strength.

PubMed

Sugi, Haruo; Abe, Takahiro; Kobayashi, Takakazu; Chaen, Shigeru; Ohnuki, Yoshiki; Saeki, Yasutake; Sugiura, Seiryo

2013-01-01

Although evidence has been presented that, at low ionic strength, myosin heads in relaxed skeletal muscle fibers form linkages with actin filaments, the effect of low ionic strength on contraction characteristics of Ca(2+)-activated muscle fibers has not yet been studied in detail. To give information about the mechanism of muscle contraction, we have examined the effect of low ionic strength on the mechanical properties and the contraction characteristics of skinned rabbit psoas muscle fibers in both relaxed and maximally Ca(2+)-activated states. By progressively decreasing KCl concentration from 125 mM to 0 mM (corresponding to a decrease in ionic strength μ from 170 mM to 50 mM), relaxed fibers showed changes in mechanical response to sinusoidal length changes and ramp stretches, which are consistent with the idea of actin-myosin linkage formation at low ionic strength. In maximally Ca(2+)-activated fibers, on the other hand, the maximum isometric force increased about twofold by reducing KCl concentration from 125 to 0 mM. Unexpectedly, determination of the force-velocity curves indicated that, the maximum unloaded shortening velocity Vmax, remained unchanged at low ionic strength. This finding indicates that the actin-myosin linkages, which has been detected in relaxed fibers at low ionic strength, are broken quickly on Ca(2+) activation, so that the linkages in relaxed fibers no longer provide any internal resistance against fiber shortening. The force-velocity curves, obtained at various levels of steady Ca(2+)-activated isometric force, were found to be identical if they are normalized with respect to the maximum isometric force. The MgATPase activity of muscle fibers during isometric force generation was found not to change appreciably at low ionic strength despite the two-fold increase in Ca(2+)-activated isometric force. These results can be explained in terms of enhancement of force generated by individual myosin heads, but not by any changes in kinetic properties of cyclic actin-myosin interaction.

Late quaternary sediments, minerals, and inferred geochemical history of Didwana Lake, Thar Desert, India

USGS Publications Warehouse

Wasson, R.J.; Smith, G.I.; Agrawal, D.P.

1984-01-01

Variations in clastic sediment texture, mineralogy of both evaporites formed at the surface and precipitates formed below the lake floor, and the relative chemical activities of the major dissolved components of the chemical precipitates, have allowed reconstruction of the history of salinity and water-level changes in Didwana Lake, Thar Desert, India. Hypersaline conditions prevailed at about the Last Glacial Maximum, with little evidence of clastic sediments entering the lake. Between ca. 13,000 and 6000 B.P. the lake level fluctuated widely, the lake alternately hypersaline and fresh, and clastic sediments were delivered to the lake at a low rate. Deep-water conditions occurred ca. 6000 B.P. and clastic influx increased abruptly. The water level dropped towards 4000 B.P. when the lake dried briefly. Since 4000 B.P. the lake has been ephemeral with a lowered rate of sedimentation and mildly saline conditions rather like those of today. This sequence of changes documented in the lake parallels changes in vegetation recorded in published pollen diagrams from both the Thar and the Arabian Sea. Correlation of the various lines of evidence suggests that the climate of the Last Glacial Maximum at Didwana was dry and windy with a weak monsson circulation. The monsson was re-established between ca. 13,000 and a little before 6000 B.P., and, when winter rainfall increased ca. 6000 B.P., the lake filled to its maximum depth. ?? 1984.

Segmentized Clear Channel Assessment for IEEE 802.15.4 Networks.

PubMed

Son, Kyou Jung; Hong, Sung Hyeuck; Moon, Seong-Pil; Chang, Tae Gyu; Cho, Hanjin

2016-06-03

This paper proposed segmentized clear channel assessment (CCA) which increases the performance of IEEE 802.15.4 networks by improving carrier sense multiple access with collision avoidance (CSMA/CA). Improving CSMA/CA is important because the low-power consumption feature and throughput performance of IEEE 802.15.4 are greatly affected by CSMA/CA behavior. To improve the performance of CSMA/CA, this paper focused on increasing the chance to transmit a packet by assessing precise channel status. The previous method used in CCA, which is employed by CSMA/CA, assesses the channel by measuring the energy level of the channel. However, this method shows limited channel assessing behavior, which comes from simple threshold dependent channel busy evaluation. The proposed method solves this limited channel decision problem by dividing CCA into two groups. Two groups of CCA compare their energy levels to get precise channel status. To evaluate the performance of the segmentized CCA method, a Markov chain model has been developed. The validation of analytic results is confirmed by comparing them with simulation results. Additionally, simulation results show the proposed method is improving a maximum 8.76% of throughput and decreasing a maximum 3.9% of the average number of CCAs per packet transmission than the IEEE 802.15.4 CCA method.

Segmentized Clear Channel Assessment for IEEE 802.15.4 Networks

PubMed Central

Son, Kyou Jung; Hong, Sung Hyeuck; Moon, Seong-Pil; Chang, Tae Gyu; Cho, Hanjin

2016-01-01

This paper proposed segmentized clear channel assessment (CCA) which increases the performance of IEEE 802.15.4 networks by improving carrier sense multiple access with collision avoidance (CSMA/CA). Improving CSMA/CA is important because the low-power consumption feature and throughput performance of IEEE 802.15.4 are greatly affected by CSMA/CA behavior. To improve the performance of CSMA/CA, this paper focused on increasing the chance to transmit a packet by assessing precise channel status. The previous method used in CCA, which is employed by CSMA/CA, assesses the channel by measuring the energy level of the channel. However, this method shows limited channel assessing behavior, which comes from simple threshold dependent channel busy evaluation. The proposed method solves this limited channel decision problem by dividing CCA into two groups. Two groups of CCA compare their energy levels to get precise channel status. To evaluate the performance of the segmentized CCA method, a Markov chain model has been developed. The validation of analytic results is confirmed by comparing them with simulation results. Additionally, simulation results show the proposed method is improving a maximum 8.76% of throughput and decreasing a maximum 3.9% of the average number of CCAs per packet transmission than the IEEE 802.15.4 CCA method. PMID:27271626

Formation of fatty acids in photochemical conversions of saturated hydrocarbons

NASA Technical Reports Server (NTRS)

Telegina, T. A.; Pavlovskaya, T. Y.; Ladyzhenskaya, A. I.

1977-01-01

Abiogenic synthesis of fatty acids was studied in photochemical conversions of saturated hydrocarbons. It was shown that, in a hydrocarbon water CaCO3 suspension, the action of 254 nm UV rays caused the formation of fatty acids with a maximum number of carbon atoms in the chain not exceeding that in the initial hydrocarbon. Synthesis of acetic, propionic, butyric, valeric, caproic, enanthic and caprylic (in the case of octane) acids occurs in heptane water CaCO3 and octane water CaCO3 systems.

Acute effects of constant torque and constant angle stretching on the muscle and tendon tissue properties.

PubMed

Konrad, Andreas; Budini, Francesco; Tilp, Markus

2017-08-01

Static stretching induces acute structural changes of the muscle-tendon unit (MTU) that are related to the intensity or duration of stretching. It has been reported that stretching with a constant torque (CT) leads to greater joint range of motion changes than stretching with a constant angle (CA). Whether or not this difference is due to different structural changes of the MTUs of the lower leg and ankle plantar flexors is not known. Therefore, the purpose of this study was to compare the acute effects of single CA and CT stretching on various muscle and tendon mechanical properties. Seventeen young, healthy volunteers were tested on two separate days using either CT or CA stretching (4 × 30 s each). Before and after stretching, dorsiflexion range of motion (RoM), passive resistive torque (PRT), and maximum voluntary contraction (MVC) were measured with a dynamometer. Ultrasonography of the medial gastrocnemius (GM) muscle-tendon junction (MTJ) displacement allowed us to determine the length changes in the tendon and muscle, respectively, and hence to calculate their stiffness. Maximum dorsiflexion increased while PRT, muscle-tendon stiffness, and muscle stiffness decreased following both CA and CT stretching. There was a greater increase in RoM following CT stretching compared to CA stretching. Moreover, the decline in PRT was greater during CT stretching compared to CA stretching. As expected, several functional adaptations (RoM, PRT) were different between CT and CA stretching due to the higher intensity of CT stretching. However, no structural differences in the adaptations to the stretching modalities could be detected. We suggest that the different functional adaptations between CA and CT stretching are the consequence of different adaptations in the perception of stretch and pain.

Insulin-like growth factor-1 enhances rat skeletal muscle charge movement and L-type Ca2+ channel gene expression

PubMed Central

Wang, Zhong-Min; Laura Messi, María; Renganathan, Muthukrishnan; Delbono, Osvaldo

1999-01-01

We investigated whether insulin-like growth factor-1 (IGF-1), an endogenous potent activator of skeletal muscle proliferation and differentiation, enhances L-type Ca2+ channel gene expression resulting in increased functional voltage sensors in single skeletal muscle cells. Charge movement and inward Ca2+ current were recorded in primary cultured rat myoballs using the whole-cell configuration of the patch-clamp technique. Ca2+ current and maximum charge movement (Qmax) were potentiated in cells treated with IGF-1 without significant changes in their voltage dependence. Peak Ca2+ current in control and IGF-1-treated cells was -7·8 ± 0·44 and -10·5 ± 0·37 pA pF−1, respectively (P < 0·01), whilst Qmax was 12·9 ± 0·4 and 22·0 ± 0·3 nC μF−1, respectively (P < 0·01). The number of L-type Ca2+ channels was found to increase in the same preparation. The maximum binding capacity (Bmax) of the high-affinity radioligand [3H]PN200-110 in control and IGF-1-treated cells was 1·21 ± 0·25 and 3·15 ± 0·5 pmol (mg protein)−1, respectively (P < 0·01). No significant change in the dissociation constant for [3H]PN200-110 was found. Antisense RNA amplification showed a significant increase in the level of mRNA encoding the L-type Ca2+ channel α1-subunit in IGF-1-treated cells. This study demonstrates that IGF-1 regulates charge movement and the level of L-type Ca2+ channel α1-subunits through activation of gene expression in skeletal muscle cells. PMID:10087334

Removal of chromium (VI) ions from aqueous solutions using amine-impregnated TiO2 nanoparticles modified cellulose acetate membranes.

PubMed

Gebru, Kibrom Alebel; Das, Chandan

2018-01-01

In this work, TiO 2 nanoparticles (NPs) were modified using tetraethylenepentamine (TEPA), ethylenediamine (EDA), and hexamethylenetetramine (HMTA) amines using impregnation process. The prepared amine modified TiO 2 samples were explored as an additive to fabricate ultrafiltration membranes with enhanced capacity towards the removal of chromium ions from aqueous solution. Modified membranes were prepared from cellulose acetate (CA) polymer blended with polyethylene glycol (PEG) additive, and amine modified TiO 2 by using phase inversion technique. Fourier transform infrared spectroscopy (FTIR), zeta potential (ζ), thermo gravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), water contact angle (WCA), and atomic absorption spectrophotometer (AAS) studies were done to characterize the membranes in terms of chemical structure, electric charge, thermal stability, morphology, hydrophilicity, and removal performance. The pure water permeability and Cr (VI) ion removal efficiency of the unmodified (i.e. CA/U-Ti) and the amine modified (CA/Ti-HMTA, CA/Ti-EDA, and CA/Ti-TEPA) membranes were dependent on pH and metal ion concentration. Incorporation of amine modified TiO 2 composite to the CA polymer was found to improve the fouling and removal characteristics of the membranes during the chromium ultrafiltration process. The maximum removal efficiency result of Cr (VI) ions at pH of 3.5 using CA/Ti-TEPA membrane was 99.8%. The washing/regeneration cycle results in this study described as an essential part for prospect industrial applications of the prepared membranes. The maximum Cr (VI) removal results by using CA/Ti-TEPA membrane for four washing/regeneration cycles are 99.6%, 99.5%, 98.6% and, 96.6%, respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

L-type calcium channels refine the neural population code of sound level.

PubMed

Grimsley, Calum Alex; Green, David Brian; Sivaramakrishnan, Shobhana

2016-12-01

The coding of sound level by ensembles of neurons improves the accuracy with which listeners identify how loud a sound is. In the auditory system, the rate at which neurons fire in response to changes in sound level is shaped by local networks. Voltage-gated conductances alter local output by regulating neuronal firing, but their role in modulating responses to sound level is unclear. We tested the effects of L-type calcium channels (Ca L : Ca V 1.1-1.4) on sound-level coding in the central nucleus of the inferior colliculus (ICC) in the auditory midbrain. We characterized the contribution of Ca L to the total calcium current in brain slices and then examined its effects on rate-level functions (RLFs) in vivo using single-unit recordings in awake mice. Ca L is a high-threshold current and comprises ∼50% of the total calcium current in ICC neurons. In vivo, Ca L activates at sound levels that evoke high firing rates. In RLFs that increase monotonically with sound level, Ca L boosts spike rates at high sound levels and increases the maximum firing rate achieved. In different populations of RLFs that change nonmonotonically with sound level, Ca L either suppresses or enhances firing at sound levels that evoke maximum firing. Ca L multiplies the gain of monotonic RLFs with dynamic range and divides the gain of nonmonotonic RLFs with the width of the RLF. These results suggest that a single broad class of calcium channels activates enhancing and suppressing local circuits to regulate the sensitivity of neuronal populations to sound level. Copyright © 2016 the American Physiological Society.

Screening of agro-industrial wastes for citric acid bioproduction by Aspergillus niger NRRL 2001 through solid state fermentation.

PubMed

Dhillon, Gurpreet S; Brar, Satinder K; Kaur, Surinder; Verma, Mausam

2013-05-01

The citric acid (CA) industry is currently struggling to develop a sustainable and economical process owing to high substrate and energy costs. Increasing interest in the replacement of costly synthetic substrates by renewable waste biomass has fostered research on agro-industrial wastes and screening of raw materials for economical CA production. The food-processing industry generates substantial quantities of waste biomass that could be used as a valuable low-cost fermentation substrate. The present study evaluated the potential of different agro-industrial wastes, namely apple pomace (AP), brewer's spent grain, citrus waste and sphagnum peat moss, as substrates for solid state CA production using Aspergillus niger NRRL 2001. Among the four substrates, AP resulted in highest CA production of 61.06 ± 1.9 g kg(-1) dry substrate (DS) after a 72 h incubation period. Based on the screening studies, AP was selected for optimisation studies through response surface methodology (RSM). Maximum CA production of 312.32 g kg(-1) DS was achieved at 75% (v/w) moisture and 3% (v/w) methanol after a 144 h incubation period. The validation of RSM-optimised parameters in plastic trays resulted in maximum CA production of 364.4 ± 4.50 g kg(-1) DS after a 120 h incubation period. The study demonstrated the potential of AP as a cheap substrate for higher CA production. This study contributes to knowledge about the future application of carbon rich agro-industrial wastes for their value addition to CA. It also offers economic and environmental benefits over traditional ways used to dispose off agro-industrial wastes. © 2012 Society of Chemical Industry.

Hydration kinetics of CA{sub 2} and CA-Investigations performed on a synthetic calcium aluminate cement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klaus, S.R., E-mail: klaus@geol.uni-erlangen.de; Neubauer, J., E-mail: juergen.neubauer@gzn.uni-erlangen.de; Goetz-Neunhoeffer, F., E-mail: friedlinde.goetz@gzn.uni-erlangen.de

2013-01-15

Much is already known about the hydration of monocalcium aluminate (CA) in calcium aluminate cements (CACs). CA{sub 2} is known to be weakly hydraulic. Therefore, the hydration kinetics of CA{sub 2} were not of as great interest as those of the hydration of CAC. We were able to show that the hydration of CA{sub 2} begins as soon as the hydration rate of CA has reached its maximum and the first precipitation of C{sub 2}AH{sub 8} has started. The hydration of different CA/CA{sub 2} ratios was analyzed by the G-factor quantification. The individual contributions of the phases CA and CA{submore » 2} to the heat flow were calculated based on the amounts dissolved by applying thermodynamic data. The heat flow as calculated from XRD data was then compared with the measured heat flow. It obtained a good consistency between the two. The very pronounced influence of CA{sub 2} during hydration of CAC can be clearly demonstrated.« less

Sucrose uptake by pinocytosis in Amoeba proteus and the influence of external calcium

PubMed Central

1979-01-01

The relationship between Ca++ and pinocytosis was investigated in Amoeba proteus. Pinocytosis was induced with 0.01% alcian blue, a large molecular weight dye which binds irreversibly to the cell surface. The time-course and intensity of pinocytosis was monitored by following the uptake of [3H]SUCROSE. When the cells are exposed to 0.01% alcian blue, there is an immediate uptake of sucrose. The cells take up integral of 10% of their initial volume during the time-course of pinocytosis. The duration of pinocytosis in the amoeba is integral of 50 min, with maximum sucrose uptake occurring 15 min after the induction of pinocytosis. The pinocytotic uptake of sucrose is reversibly blocked at 3 degrees C and a decrease in pH increases the uptake of sucrose by pinocytosis. The process of pinocytosis is also dependent upon the concentration of the inducer in the external medium. The association between Ca++ and pinocytosis in A. proteus was investigated initially by determining the effect of the external Ca++ concentration on sucrose uptake induced by alcian blue. In Ca++-free medium, no sucrose uptake is observed in the presence of 0.01% alcian blue. As the Ca++ concentration is increased, up to a maximum of 0.1 mM, pinocytotic sucrose uptake is also increased. Increases in the external Ca++ concentration above 0.1 mM brings about a decrease in sucrose uptake. Further investigations into the association between Ca++ and pinocytosis demonstrated that the inducer of pinocytosis displaces surface calcium in the amoeba. It is suggested that Ca++ is involved in two separate stages in the process of pinocytosis; an initial displacement of surface calcium by the inducer which may increase the permeability of the membrane to solutes and a subsequent Ca++ influx bringing about localized increases in cytoplasmic Ca++ ion activity. PMID:512629

Diastolic scattered light fluctuation, resting force and twitch force in mammalian cardiac muscle

PubMed Central

Lakatta, E. G.; Lappé, D. L.

1981-01-01

1. When coherent light was passed through isolated isometric cardiac muscles during the diastolic or resting period, intensity fluctuations were observed in the scattered field. The frequency of these intensity fluctuations (f½) varied with many experimental interventions known to enhance Ca2+ flux into the cell. 2. In rat muscles stimulated at low frequencies (0.1 ± 2.0 min-1) stepwise increases (0.4-10 mm) of [Ca2+] in the bathing fluid ([Ca2+]e), or addition of ouabain (10-6-6 × 10-4 m) to the perfusate caused stepwise increases in f½. These were paralleled by increments in resting force (RF) such that the changes in f½ and RF were highly correlated. Substitution of K+ for Na+ in the perfusate resulted in parallel transients in RF and f½. 3. In contrast to the rat, most cat muscles stimulated at low frequencies in the steady state exhibited neither diastolic intensity fluctuations nor Ca2+-dependent changes in RF in [Ca2+]e of 10 mm or less; when [Ca2+]e was increased to 12-32 mm, however, steady-state Ca2+-dependent f½ and RF were observed. In a given [Ca2+]e reduction of [Na+]e increased f½. In the transient state following cessation of regular stimulation at more rapid rates (12-96 min-1) intensity fluctuations were present in all [Ca2+]e and decayed with time (seconds to minutes); the f½ and time course of the decay of the fluctuations were determined by the rate of prior stimulation and [Ca2+]e. 4. Maximum potentiation of twitch force in response to the above inotropic interventions was associated with an optimal level of f½ which was similar in both species; when higher levels of f½ were produced by more intense inotropic intervention, twitch force declined. Over the range of inotropic intervention up to and including that at which maximum twitch potentiation occurred, the increase in diastolic f½ predicted the extent of twitch potentiation with a high degree of accuracy (r > 0.97) both in the transient and steady states. 5. In contrast to the other inotropic interventions studied, catecholamines were unique in that neither f½ nor RF increased over a full range of concentrations that resulted in maximum potentiation of the twitch. 6. It is concluded from these observations that f½ reflects diastolic Ca2+-dependent myofilament interaction; the increase in the extent of this interaction by inotropic interventions that do not alter the affinity of the myofilaments for Ca2+ probably reflects an increase in diastolic myoplasmic [Ca2+], an optimal level of which is associated with maximal potentiation of twitch force; the difference in f½ in rat and cat muscles under a given set of in vitro conditions may be related to the marked species difference in the effectiveness of excitation—contraction coupling. PMID:7310715

Late Quaternary loess in northeastern Colorado: Part I - Age and paleoclimatic significance

USGS Publications Warehouse

Muhs, D.R.; Aleinikoff, J.N.; Stafford, Thomas W.; Kihl, R.; Been, J.; Mahan, S.A.; Cowherd, S.

1999-01-01

Loess in eastern Colorado covers an estimated 14000 km2, and is the westernmost part of the North American midcontinent loess province. Stratigraphic studies indicate there were two periods of loess deposition in eastern Colorado during late Quaternary time. The first period spanned ca. 20 000 to 12 000 14C yr B.P. (ca. 20-14 ka) and correlates reasonably well with the culmination and retreat of Pinedale glaciers in the Colorado Front Range during the last glacial maximum. The second period of loess deposition occurred between ca. 11 000 and 9000 14C yr B.P. This interval may be Holocene or may correlate with a hypothesized Younger Dryas glacial advance in the Colorado Front Range. Sedimentologic, mineralogic, and geochemical data indicate that as many as three sources could have supplied loess in eastern Colorado. These sources include glaciogenic silt (derived from the Colorado Front Range) and two bedrock sources, volcaniclastic silt from the White River Group, and clays from the Pierre Shale. The sediment sources imply a generally westerly paleowind during the last glacial maximum. New carbon isotope data, combined with published faunal data, indicate that the loess was probably deposited on a cool steppe, implying a last glacial maximum July temperature depression, relative to the present, of at least 5-6??C. Overall, loess deposition in eastern Colorado occurred mostly toward the end of the last glacial maximum, under cooler and drier conditions, with generally westerly winds from more than one source.

Luminescence and Site Occupancy of Eu2+ in Ba2 Ca(BO3)2

NASA Astrophysics Data System (ADS)

Li, Pan-Lai; Wang, Zhi-Jun; Yang, Zhi-Ping; Guo, Qing-Lin

2011-01-01

A green phosphor Ba2Ca(BO3)2:Eu2+ was synthesized by a high temperature solid-state reaction method under a reductive atmosphere. The luminescence and site occupancy of Eu2+ in Ba2Ca(BO3)2 are investigated. Ba2Ca(BO3)2:Eu2+ shows one green band (537 nm) under 400 nm near ultraviolet excitation which is suitable for UV LED. Ca2+ and Ba2+ ions in Ba2Ca(BO3)2 are replaced by Eu2+ ions, the Ba2Ca(BO3)2:Eu2+ shows a dissymmetrical emission band. The influence of Eu2+ doping concentrations on the emission intensity of Ba2Ca(BO3)2:Eu2+ is studied. It is found that the emission intensity is influenced by the Eu2+ concentration and reaches the maximum value at 2% Eu2+. According to the Dexter theory, the concentration quenching mechanisms of Eu2+ in Ba2Ca(BO3)2 are the d-dinteraction.

Optimizing the Dopant and Carrier Concentration of Ca5Al2Sb6 for High Thermoelectric Efficiency

PubMed Central

Yan, Yuli; Zhang, Guangbiao; Wang, Chao; Peng, Chengxiao; Zhang, Peihong; Wang, Yuanxu; Ren, Wei

2016-01-01

The effects of doping on the transport properties of Ca5Al2Sb6 are investigated using first-principles electronic structure methods and Boltzmann transport theory. The calculated results show that a maximum ZT value of 1.45 is achieved with an optimum carrier concentration at 1000 K. However, experimental studies have shown that the maximum ZT value is no more than 1 at 1000 K. By comparing the calculated Seebeck coefficient with experimental values, we find that the low dopant solubility in this material is not conductive to achieve the optimum carrier concentration, leading a smaller experimental value of the maximum ZT. Interestingly, the calculated dopant formation energies suggest that optimum carrier concentrations can be achieved when the dopants and Sb atoms have similar electronic configurations. Therefore, it might be possible to achieve a maximum ZT value of 1.45 at 1000 K with suitable dopants. These results provide a valuable theoretical guidance for the synthesis of high-performance bulk thermoelectric materials through dopants optimization. PMID:27406178

Evidence of nontermination of collective rotation near the maximum angular momentum in Rb75

NASA Astrophysics Data System (ADS)

Davies, P. J.; Afanasjev, A. V.; Wadsworth, R.; Andreoiu, C.; Austin, R. A. E.; Carpenter, M. P.; Dashdorj, D.; Finlay, P.; Freeman, S. J.; Garrett, P. E.; Görgen, A.; Greene, J.; Grinyer, G. F.; Hyland, B.; Jenkins, D. G.; Johnston-Theasby, F. L.; Joshi, P.; Macchiavelli, A. O.; Moore, F.; Mukherjee, G.; Phillips, A. A.; Reviol, W.; Sarantites, D.; Schumaker, M. A.; Seweryniak, D.; Smith, M. B.; Svensson, C. E.; Valiente-Dobon, J. J.; Ward, D.

2010-12-01

Two of the four known rotational bands in Rb75 were studied via the Ca40(Ca40,αp)Rb75 reaction at a beam energy of 165 MeV. Transitions were observed up to the maximum spin Imax of the assigned configuration in one case and one-transition short of Imax in the other. Lifetimes were determined using the residual Doppler shift attenuation method. The deduced transition quadrupole moments show a small decrease with increasing spin, but remain large at the highest spins. The results obtained are in good agreement with cranked Nilsson-Strutinsky calculations, which indicate that these rotational bands do not terminate, but remain collective at Imax.

Minireview: The Intimate Link Between Calcium Sensing Receptor Trafficking and Signaling: Implications for Disorders of Calcium Homeostasis

PubMed Central

2012-01-01

The calcium-sensing receptor (CaSR) regulates organismal Ca2+ homeostasis. Dysregulation of CaSR expression or mutations in the CASR gene cause disorders of Ca2+ homeostasis and contribute to the progression or severity of cancers and cardiovascular disease. This brief review highlights recent findings that define the CaSR life cycle, which controls the cellular abundance of CaSR and CaSR signaling. A novel mechanism, termed agonist-driven insertional signaling (ADIS), contributes to the unique hallmarks of CaSR signaling, including the high degree of cooperativity and the lack of functional desensitization. Agonist-mediated activation of plasma membrane-localized CaSR increases the rate of insertion of CaSR at the plasma membrane without altering the constitutive endocytosis rate, thereby acutely increasing the maximum signaling response. Prolonged CaSR signaling requires a large intracellular ADIS-mobilizable pool of CaSR, which is maintained by signaling-mediated increases in biosynthesis. This model provides a rational framework for characterizing the defects caused by CaSR mutations and the altered functional expression of wild-type CaSR in disease states. Mechanistic dissection of ADIS of CaSR should lead to optimized pharmacological approaches to normalize CaSR signaling in disorders of Ca2+ homeostasis. PMID:22745192

Magnetic and structural transitions in La1-xAxCoO3 ( A=Ca , Sr, and Ba)

NASA Astrophysics Data System (ADS)

Kriener, M.; Braden, M.; Kierspel, H.; Senff, D.; Zabara, O.; Zobel, C.; Lorenz, T.

2009-06-01

We report thermal-expansion, lattice-constant, and specific-heat data of the series La1-xAxCoO3 for 0≤x≤0.30 with A=Ca , Sr, and Ba. For the undoped compound LaCoO3 , the thermal-expansion coefficient α(T) exhibits a pronounced maximum around T=50K caused by a temperature-driven spin-state transition from a low-spin state of the Co3+ ions at low temperatures toward a higher spin state at higher temperatures. The partial substitution of the La3+ ions by divalent Ca2+ , Sr2+ , or Ba2+ ions causes drastic changes in the macroscopic properties of LaCoO3 . The large maximum in α(T) is suppressed and completely vanishes for x≳0.125 . For A=Ca three different anomalies develop in α(T) with further increasing x , which are visible in specific-heat data as well. Together with temperature-dependent x-ray data, we identify several phase transitions as a function of the doping concentration x and temperature. From these data we propose an extended phase diagram for La1-xCaxCoO3 .

Comparison of eastern tropical Pacific TEX86 and Globigerinoides ruber Mg/Ca derived sea surface temperatures: Insights from the Holocene and Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Hertzberg, Jennifer E.; Schmidt, Matthew W.; Bianchi, Thomas S.; Smith, Richard W.; Shields, Michael R.; Marcantonio, Franco

2016-01-01

The use of the TEX86 temperature proxy has thus far come to differing results as to whether TEX86 temperatures are representative of surface or subsurface conditions. In addition, although TEX86 temperatures might reflect sea surface temperatures based on core-top (Holocene) values, this relationship might not hold further back in time. Here, we investigate the TEX86 temperature proxy by comparing TEX86 temperatures to Mg/Ca temperatures of multiple species of planktonic foraminifera for two sites in the eastern tropical Pacific (on the Cocos and Carnegie Ridges) across the Holocene and Last Glacial Maximum. Core-top and Holocene TEX86H temperatures at both study regions agree well, within error, with the Mg/Ca temperatures of Globigerinoides ruber, a surface dwelling planktonic foraminifera. However, during the Last Glacial Maximum, TEX86H temperatures are more representative of upper thermocline temperatures, and are offset from G. ruber Mg/Ca temperatures by 5.8 °C and 2.9 °C on the Cocos Ridge and Carnegie Ridge, respectively. This offset between proxies cannot be reconciled by using different TEX86 temperature calibrations, and instead, we suggest that the offset is due to a deeper export depth of GDGTs at the LGM. We also compare the degree of glacial cooling at both sites based on both temperature proxies, and find that TEX86H temperatures greatly overestimate glacial cooling, especially on the Cocos Ridge. This study has important implications for applying the TEX86 paleothermometer in the eastern tropical Pacific.

Coefficient of performance and its bounds with the figure of merit for a general refrigerator

NASA Astrophysics Data System (ADS)

Long, Rui; Liu, Wei

2015-02-01

A general refrigerator model with non-isothermal processes is studied. The coefficient of performance (COP) and its bounds at maximum χ figure of merit are obtained and analyzed. This model accounts for different heat capacities during the heat transfer processes. So, different kinds of refrigerator cycles can be considered. Under the constant heat capacity condition, the upper bound of the COP is the Curzon-Ahlborn (CA) coefficient of performance and is independent of the time durations of the heat exchanging processes. With the maximum χ criterion, in the refrigerator cycles, such as the reversed Brayton refrigerator cycle, the reversed Otto refrigerator cycle and the reversed Atkinson refrigerator cycle, where the heat capacity in the heat absorbing process is not less than that in the heat releasing process, their COPs are bounded by the CA coefficient of performance; otherwise, such as for the reversed Diesel refrigerator cycle, its COP can exceed the CA coefficient of performance. Furthermore, the general refined upper and lower bounds have been proposed.

Sequential high gravity ethanol fermentation and anaerobic digestion of steam explosion and organosolv pretreated corn stover.

PubMed

Katsimpouras, Constantinos; Zacharopoulou, Maria; Matsakas, Leonidas; Rova, Ulrika; Christakopoulos, Paul; Topakas, Evangelos

2017-11-01

The present work investigates the suitability of pretreated corn stover (CS) to serve as feedstock for high gravity (HG) ethanol production at solids-content of 24wt%. Steam explosion, with and without the addition of H 2 SO 4 , and organosolv pretreated CS samples underwent a liquefaction/saccharification step followed by simultaneous saccharification and fermentation (SSF). Maximum ethanol concentration of ca. 76g/L (78.3% ethanol yield) was obtained from steam exploded CS (SECS) with 0.2% H 2 SO 4 . Organosolv pretreated CS (OCS) also resulted in high ethanol concentration of ca. 65g/L (62.3% ethanol yield). Moreover, methane production through anaerobic digestion (AD) was conducted from fermentation residues and resulted in maximum methane yields of ca. 120 and 69mL/g volatile solids (VS) for SECS and OCS samples, respectively. The results indicated that the implementation of a liquefaction/saccharification step before SSF employing a liquefaction reactor seemed to handle HG conditions adequately. Copyright © 2017 Elsevier Ltd. All rights reserved.

Preparation of core-shell structured CaCO3 microspheres as rapid and recyclable adsorbent for anionic dyes

NASA Astrophysics Data System (ADS)

Zhao, Mengen; Chen, Zhenhua; Lv, Xinyan; Zhou, Kang; Zhang, Jie; Tian, Xiaohan; Ren, Xiuli; Mei, Xifan

2017-09-01

Core-shell structured CaCO3 microspheres (MSs) were prepared by a facile, one-pot method at room temperature. The adsorbent dosage and adsorption time of the obtained CaCO3 MSs were investigated. The results suggest that these CaCO3 MSs can rapidly and efficiently remove 99-100% of anionic dyes within the first 2 min. The obtained CaCO3 MSs have a high Brunauer-Emmett-Teller surface area (211.77 m2 g-1). In addition, the maximum adsorption capacity of the obtained CaCO3 MSs towards Congo red was 99.6 mg g-1. We also found that the core-shell structured CaCO3 MSs have a high recycling capability for removing dyes from water. Our results demonstrate that the prepared core-shell structured CaCO3 MSs can be used as an ideal, rapid, efficient and recyclable adsorbent to remove dyes from aqueous solution.

Characterization and evaluation of antibacterial activity of plant mediated calcium oxide (CaO) nanoparticles by employing Mentha pipertia extract

NASA Astrophysics Data System (ADS)

Ijaz, Umber; Bhatti, Ijaz Ahmed; Mirza, Saima; Ashar, Ambreen

2017-10-01

The antibacterial activity of green synthesized calcium oxide nanoparticles was investigated using leaf extract of Mentha piperita in this study. The synthesized nanomaterial was subjected to characterization using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and energy dispersive x-ray spectroscopy (EDX). The SEM images showed agglomeration of disc shaped nanoparticles, and FTIR and EDX spectroscopy indicated intensive peaks for calcium ions and oxygen. Subsequently, the potential of nanoscale CaO was also evaluated for antimicrobial index against E. coli using the well diffusion method. A maximum zone of inhibition up to 42 mm was observed when 100 µg ml-1 material was loaded with inoculum size 50 µl of E. coli in sunlight exposure of 5 h. The experimental conditions were optimized using a central composite design using a response surface methodology. The maximum antimicrobial index of the CaO nanoparticle was 6 mm as a result of the optimized response. Furthermore, the minimum inhibitory concentration of the CaO nanoparticle showed 25 µg ml-1, an effective initial concentration for E.coli removal. The results revealed that the CaO nanocomposite synthesized via a green route was a promising candidate for the removal of E. coli present in drinking water, which is an important fecal indicator.

CaSO4:DY,Mn: A new and highly sensitive thermoluminescence phosphor for versatile dosimetry

NASA Astrophysics Data System (ADS)

Bahl, Shaila; Lochab, S. P.; Kumar, Pratik

2016-02-01

With the advent of newer techniques for dose reduction coupled with the development of more sensitive detectors, the radiation doses in radiological medical investigation are decreasing. Nevertheless, keeping the tenet in mind that all radiation doses could entail risk, there is a need to develop more sensitive dosimeters capable of measuring low doses. This paper gives the account of the development of a new and sensitive phosphor CaSO4:Dy,Mn and its characterization. The standard production procedure based on the recrystallization method was used to prepare CaSO4:Dy,Mn. The Thermoluminescence (TL) studies were carried out by exposing it with gamma radiation (Cs-137) from 10 μGy to 100 Gy. The theoretical studies to determine the number of peaks and kinetic parameters related to the TL glow peaks in CaSO4:Dy,Mn was performed using the Computerized Glow Curve Deconvolution (CGCD) method. Experiments were performed to determine optimum concentration of the dopants Dysprosium (Dy) and Mangnese (Mn) in the host CaSO4 so that maximum sensitivity of the phosphor may be achieved. The optimum dopant concentration turned out to be 0.1 mol%. As there were two dopants Dy and Mn their relative ratio were varied in steps of 0.025 keeping the concentration of total dopant (Dy and Mn) 0.1 mol% always. The maximum TL intensity was seen in the CaSO4:Dy(0.025),Mn(0.075) combination. The TL sensitivity of this phosphor was found to be about 2 and 1.8 times higher than that of popular phosphor CaSO4:Dy and LiF:Mg,Cu,P (TLD-700H) respectively. This new phosphor CaSO4:Dy,Mn showed fading of 11% which is similar to that of the standard phosphor CaSO4:Dy. The paper concludes that the new, highly sensitive TL phosphor CaSO4:Dy,Mn has shown higher sensitivity and hence the potential to replace commonly used CaSO4:Dy.

Photoluminescence of A- and B-site Eu{sup 3+}-substituted (Sr{sub x}Ba{sub 1−x}){sub 2}CaW{sub y}Mo{sub 1−y}O{sub 6} phosphors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sletnes, M.; Lindgren, M.; Valmalette, J.C.

The photoluminescence of two series of A- and B-site Eu{sup 3+} substituted (Sr{sub x}Ba{sub 1−x}){sub 2}CaW{sub y}Mo{sub 1−y}O{sub 6} double perovskite phosphor materials, (Sr{sub x}Ba{sub 1−x}){sub 1.96}Eu{sub 0.02}K{sub 0.02}CaW{sub y}Mo{sub 1−y}O{sub 6} and (Sr{sub x}Ba{sub 1−x}){sub 2}Ca{sub 0.96}Eu{sub 0.02}Li{sub 0.02}W{sub y}Mo{sub 1−y}O{sub 6} (x and y=0, 0.25, 0.50, 0.75, and 1), were studied systematically as a function of stoichiometry and crystal structure. The Eu{sup 3+} lattice sites controlled by co-doping with either K or Li were confirmed by Raman spectroscopy. The variation in integrated emission intensity and emission colour over the experimental matrix was examined using statistical tools, and themore » observed trends were rationalized based on the physical and electronic structure of the phosphors. Phosphors with Eu on B-site with maximum Sr content had remarkably higher emission intensities than all other materials, but the emission was more orange than red due to domination of the {sup 5}D{sub 0}–{sup 7}F{sub 1} (595 nm) transition of Eu{sup 3+}. The relative intensities of the {sup 5}D{sub 0}–{sup 7}F{sub 2} (615 nm) and {sup 5}D{sub 0}–{sup 7}F{sub 1} transitions of Eu{sup 3+}, and thus the red-shift of the emission, decreased linearly with increasing Sr content in the A-site Eu-substituted phosphors, and reached a maximum for Sr{sub 1.96}Eu{sub 0.02}K{sub 0.02}CaW{sub 0.25}Mo{sub 0.75}O{sub 6}. A maximum external quantum efficiency of 17% was obtained for the phosphor Sr{sub 2}Ca{sub 0.7}Eu{sub 0.15}Li{sub 0.15}W{sub 0.5}Mo{sub 0.5}O{sub 6} with Eu on B-site. - Highlights: • Systematic study of the photoluminescence of Eu{sup 3+}-doped (Sr{sub x}Ba{sub 1−x}){sub 2}CaW{sub y}Mo{sub 1−y}O{sub 6}. • The Eu{sup 3+} lattice sites were confirmed by Raman spectroscopy. • A large parameter space was investigated using statistical tools. • A maximum external QE of 17% was obtained for Sr{sub 2}Ca{sub 0.7}Eu{sub 0.15}Li{sub 0.15}W{sub 0.5}Mo{sub 0.5}O{sub 6}.« less

Studies on the synthesis of isotopes of superheavy element Lv (Z = 116)

NASA Astrophysics Data System (ADS)

Santhosh, K. P.; Safoora, V.

2017-11-01

The probable projectile-target combinations for the synthesis of superheavy nucleus 296Lv found in the cold valley of 296Lv have been identified by studying the interaction barrier of the colliding nuclei, probability of compound nucleus formation, P_{CN}, and survival probability W_{sur}. At energies near and above the Coulomb barrier, the capture, fusion and evaporation residue (ER) cross sections for the probable combinations for the hot and cold fusion reactions are systematically investigated. By considering intensities of the projectile beams, availabilities of the targets and half lives of the colliding nuclei, the combination 48Ca+248Cm is found to be the most probable projectile-target pair for the synthesis of 296Lv. The calculated maximum value of 2n, 3n, 4n and 5n channel cross section for the reaction 48Ca+248Cm are 0.599 pb, 5.957 pb, 4.805 pb, and 0.065 pb, respectively. Moreover, the production cross sections for the synthesis of isotopes 291-295,298Lv using 48Ca projectile on 243-247,250Cm targets are calculated. Among these reactions, the reactions 48Ca+247Cm → 295Lv and 48Ca+250Cm → 298Lv have maximum production cross section in 3n (10.697 pb) and 4n (12.006 pb) channel, respectively. Our studies on the SHE Lv using the combinations 48Ca+245Cm → 293Lv and 48Ca+248Cm → 296Lv are compared with available experimental data and with other theoretical studies. Our studies are in agreement with experimental data and we hope that these studies will be a guide for the future experiments to synthesize the isotopes of Lv.

Spring molybdenum enrichment in scallop shells: a potential tracer of diatom productivity in coastal temperate environments (Brittany, NW France)?

NASA Astrophysics Data System (ADS)

Barats, A.; Amouroux, D.; Pécheyran, C.; Chauvaud, L.; Thébault, J.; Donard, O. F. X.

2009-08-01

Skeletal molybdenum/calcium ([Mo]/[Ca])shell ratios were recently examined in bivalves. These ratios were determined by quantitative LA-ICP-MS analyses every third daily striae (i.e. a temporal resolution of 3 days) in 36 flat valves of the Great Scallop shells Pecten maximus (2-year old; 3 shells/year) collected in temperate coastal environments of Western Europe (42 to 49° N). Variations of ([Mo]/[Ca])shell ratio were significant and reproducible for scallops from a same population, from different years (1998-2004) and from different coastal temperate locations. ([Mo]/[Ca])shell exhibits typical profiles characterized by a background content, below the method detection limit (<0.003 μmol/mol) for most of the shell growth period, which is punctuated by a significant transient enrichment (0.031-2.1 μmol/mol) mainly occurring from May to June. The Bay of Brest (France) was especially investigated because of long term observations on scallop communities, environmental variables, and high resolution analyses of dissolved Mo in bottom seawater in 2000. In 2000, dissolved Mo exhibited significant increasing concentration just preceding a maximum of ([Mo]/[Ca])shell ratio. The environmental conditions preceding ([Mo]/[Ca])shell maximum events, both in 2000 and over the 7-year survey indicates a direct influence of the scallop environmental conditions at the sediment water interface subsequent to the intense and periodic spring bloom event. Spring maxima of ([Mo]/[Ca])shell ratio were found to be specifically related to the dynamic of spring diatom blooms and to the extent of the subsequent silicate depletion. ([Mo]/[Ca])shell records reveal thus unexpected biogeochemical routes of Mo, potentially related to coastal spring productivity.

Optimization of pH, temperature and CaCl2 concentrations for Ricotta cheese production from Buffalo cheese whey using Response Surface Methodology.

PubMed

Rashid, Abdul Ahid; Huma, Nuzhat; Zahoor, Tahir; Asgher, Muhammad

2017-02-01

The recovery of milk constituents from cheese whey is affected by various processing conditions followed during production of Ricotta cheese. The objective of the present investigation was to optimize the temperature (60-90 °C), pH (3-7) and CaCl2 concentration (2·0-6·0 mm) for maximum yield/recovery of milk constituents. The research work was carried out in two phases. In 1st phase, the influence of these processing conditions was evaluated through 20 experiments formulated by central composite design (CCD) keeping the yield as response factor. The results obtained from these experiments were used to optimize processing conditions for maximum yield using response surface methodology (RSM). The three best combinations of processing conditions (90 °C, pH 7, CaCl2 6 mm), (100 °C, pH 5, CaCl2 4 mm) and (75 °C, pH 8·4, CaCl2 4 mm) were exploited in the next phase for Ricotta cheese production from a mixture of Buffalo cheese whey and skim milk (9 : 1) to determine the influence of optimized conditions on the cheese composition. Ricotta cheeses were analyzed for various physicochemical (moisture, fat, protein, lactose, total solids, pH and acidity indicated) parameters during storage of 60 d at 4 ± 2 °C after every 15 d interval. Ricotta cheese prepared at 90 °C, pH 7 and CaCl2 6 mm exhibited the highest cheese yield, proteins and total solids, while high fat content was recorded for cheese processed at 100 °C, pH 5 and 4 mm CaCl2 concentration. A significant storage-related increase in acidity and NPN was recorded for all cheese samples.

Changes in North Atlantic deep-sea temperature during climatic fluctuations of the last 25,000 years based on ostracode Mg/Ca ratios

USGS Publications Warehouse

Dwyer, Gary S.; Cronin, Thomas M.; Baker, Paul A.; Rodriguez-Lazaro, Julio

2000-01-01

We reconstructed three time series of last glacial-to-present deep-sea temperature from deep and intermediate water sediment cores from the western North Atlantic using Mg/Ca ratios of benthic ostracode shells. Although the Mg/Ca data show considerable variability (“scatter”) that is common to single-shell chemical analyses, comparisons between cores, between core top shells and modern bottom water temperatures (BWT), and comparison to other paleo-BWT proxies, among other factors, suggest that multiple-shell average Mg/Ca ratios provide reliable estimates of BWT history at these sites. The BWT records show not only glacial-to-interglacial variations but also indicate BWT changes during the deglacial and within the Holocene interglacial stage. At the deeper sites (4500- and 3400-m water depth), BWT decreased during the last glacial maximum (LGM), the late Holocene, and possibly during the Younger Dryas. Maximum deep-sea warming occurred during the latest deglacial and early Holocene, when BWT exceeded modern values by as much as 2.5°C. This warming was apparently most intense around 3000 m, the depth of the modern-day core of North Atlantic deep water (NADW). The BWT variations at the deeper water sites are consistent with changes in thermohaline circulation: warmer BWT signifies enhanced NADW influence relative to Antarctic bottom water (AABW). Thus maximum NADW production and associated heat flux likely occurred during the early Holocene and decreased abruptly around 6500 years B.P., a finding that is largely consistent with paleonutrient studies in the deep North Atlantic. BWT changes in intermediate waters (1000-m water depth) of the subtropical gyre roughly parallel the deep BWT variations including dramatic mid-Holocene cooling of around 4°C. Joint consideration of the Mg/Ca-based BWT estimates and benthic oxygen isotopes suggests that the cooling was accompanied by a decrease in salinity at this site. Subsequently, intermediate waters warmed to modern values that match those of the early Holocene maximum of ∼7°C. Intermediate water BWT changes must also be driven by changes in ocean circulation. These results thus provide independent evidence that supports the hypothesis that deep-ocean circulation is closely linked to climate change over a range of timescales regardless of the mean climate state. More generally, the results further demonstrate the potential of benthic Mg/Ca ratios as a tool for reconstructing past ocean and climate conditions.

Traffic jam dynamics in stochastic cellular automata

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagel, K.; Schreckenberg, M.

1995-09-01

Simple models for particles hopping on a grid (cellular automata) are used to simulate (single lane) traffic flow. Despite their simplicity, these models are astonishingly realistic in reproducing start-stop-waves and realistic fundamental diagrams. One can use these models to investigate traffic phenomena near maximum flow. A so-called phase transition at average maximum flow is visible in the life-times of jams. The resulting dynamic picture is consistent with recent fluid-dynamical results by Kuehne/Kerner/Konhaeuser, and with Treiterer`s hysteresis description. This places CA models between car-following models and fluid-dynamical models for traffic flow. CA models are tested in projects in Los Alamos (USA)more » and in NRW (Germany) for large scale microsimulations of network traffic.« less

Enhancement of Force Generated by Individual Myosin Heads in Skinned Rabbit Psoas Muscle Fibers at Low Ionic Strength

PubMed Central

Sugi, Haruo; Abe, Takahiro; Kobayashi, Takakazu; Chaen, Shigeru; Ohnuki, Yoshiki; Saeki, Yasutake; Sugiura, Seiryo

2013-01-01

Although evidence has been presented that, at low ionic strength, myosin heads in relaxed skeletal muscle fibers form linkages with actin filaments, the effect of low ionic strength on contraction characteristics of Ca2+-activated muscle fibers has not yet been studied in detail. To give information about the mechanism of muscle contraction, we have examined the effect of low ionic strength on the mechanical properties and the contraction characteristics of skinned rabbit psoas muscle fibers in both relaxed and maximally Ca2+-activated states. By progressively decreasing KCl concentration from 125 mM to 0 mM (corresponding to a decrease in ionic strength μ from 170 mM to 50 mM), relaxed fibers showed changes in mechanical response to sinusoidal length changes and ramp stretches, which are consistent with the idea of actin-myosin linkage formation at low ionic strength. In maximally Ca2+-activated fibers, on the other hand, the maximum isometric force increased about twofold by reducing KCl concentration from 125 to 0 mM. Unexpectedly, determination of the force-velocity curves indicated that, the maximum unloaded shortening velocity Vmax, remained unchanged at low ionic strength. This finding indicates that the actin-myosin linkages, which has been detected in relaxed fibers at low ionic strength, are broken quickly on Ca2+ activation, so that the linkages in relaxed fibers no longer provide any internal resistance against fiber shortening. The force-velocity curves, obtained at various levels of steady Ca2+-activated isometric force, were found to be identical if they are normalized with respect to the maximum isometric force. The MgATPase activity of muscle fibers during isometric force generation was found not to change appreciably at low ionic strength despite the two-fold increase in Ca2+-activated isometric force. These results can be explained in terms of enhancement of force generated by individual myosin heads, but not by any changes in kinetic properties of cyclic actin-myosin interaction. PMID:23691080

Groundwater-quality data in the Santa Cruz, San Gabriel, and Peninsular Ranges Hard Rock Aquifers study unit, 2011-2012: results from the California GAMA program

USGS Publications Warehouse

Davis, Tracy A.; Shelton, Jennifer L.

2014-01-01

Results for constituents with nonregulatory benchmarks set for aesthetic concerns showed that iron concentrations greater than the CDPH secondary maximum contaminant level (SMCL-CA) of 300 μg/L were detected in samples from 19 grid wells. Manganese concentrations greater than the SMCL-CA of 50 μg/L were detected in 27 grid wells. Chloride was detected at a concentration greater than the SMCL-CA upper benchmark of 500 mg/L in one grid well. TDS concentrations in three grid wells were greater than the SMCL-CA upper benchmark of 1,000 mg/L.

Environmental forcing of terrestrial carbon isotope excursion amplification across five Eocene hyperthermals

NASA Astrophysics Data System (ADS)

Bowen, G. J.; Abels, H.

2015-12-01

Abrupt changes in the isotope composition of exogenic carbon pools accompany many major episodes of global change in the geologic record. The global expression of this change in substrates that reflect multiple carbon pools provides important evidence that many events reflect persistent, global redistribution of carbon between reduced and oxidized stocks. As the diversity of records documenting any event grows, however, discrepancies in the expression of carbon isotope change among substrates are almost always revealed. These differences in magnitude, pace, and pattern of change can complicate interpretations of global carbon redistribution, but under ideal circumstances can also provide additional information on changes in specific environmental and biogeochemical systems that accompanied the global events. Here we evaluate possible environmental influences on new terrestrial records of the negative carbon isotope excursions (CIEs) associated with multiple hyperthermals of the Early Eocene, which show a common pattern of amplified carbon isotope change in terrestrial paleosol carbonate records relative to that recorded in marine substrates. Scaling relationships between climate and carbon-cycle proxies suggest that that the climatic (temperature) impact of each event scaled proportionally with the magnitude of its marine CIE, likely implying that all events involved release of reduced carbon with a similar isotopic composition. Amplification of the terrestrial CIEs, however, does not scale with event magnitude, being proportionally less for the first, largest event (the PETM). We conduct a sensitivity test of a coupled plant-soil carbon isotope model to identify conditions that could account for the observed CIE scaling. At least two possibilities consistent with independent lines of evidence emerge: first, varying effects of pCO2 change on photosynthetic carbon isotope discrimination under changing background pCO2, and second, contrasting changes in regional hydroclimate during the PETM and subsequent hyperthermals. These mechanisms have very different implications for the reconstruction of environmental conditions, and resolving the correct interpretation will require new, complimentary records of plant and soil conditions associated with the Early Eocene hyperthermals.

Groundwater-quality data in the North San Francisco Bay Shallow Aquifer study unit, 2012: results from the California GAMA Program

USGS Publications Warehouse

Bennett, George L.; Fram, Miranda S.

2014-01-01

Results for constituents with non-regulatory benchmarks set for aesthetic concerns from the grid wells showed that iron concentrations greater than the CDPH secondary maximum contaminant level (SMCL-CA) of 300 μg/L were detected in 13 grid wells. Chloride was detected at a concentration greater than the SMCL-CA recommended benchmark of 250 mg/L in two grid wells. Sulfate concentrations greater than the SMCL-CA recommended benchmark of 250 mg/L were measured in two grid wells, and the concentration in one of these wells was also greater than the SMCL-CA upper benchmark of 500 mg/L. TDS concentrations greater than the SMCL-CA recommended benchmark of 500 mg/L were measured in 15 grid wells, and concentrations in 4 of these wells were also greater than the SMCL-CA upper benchmark of 1,000 mg/L.

The Effect of Ca Content on the Microstructure, Hardness and Tensile Properties of AZ81 Mg Cast Alloy

NASA Astrophysics Data System (ADS)

Allameh, S. H.; Emamy, M.

2017-05-01

The effects of various Ca contents (0.1-4 wt.%) on the microstructure and tensile properties of AZ81 magnesium alloy were investigated with the contribution of an analytical method. Ca addition (up to 1.0 wt.%) refined the alloy microstructure but further addition of Ca resulted in a coarse structure and introduced large dendrites within the grains. The changes in the microstructures revealed that Al4Ca, Al2Ca, τ-Mg32(A1,Zn)49 and ɛ-MgZn intermetallics are formed in the alloy as a result of Ca addition and Al consumption. The assessment of tensile properties of AZ81-1.0 wt.%Ca alloy showed the optimum values of yield strength and ultimate tensile strength, while AZ81-0.7 wt.%Ca alloy showed maximum elongation. The reduction in tensile properties of the cast alloy by the addition of more Ca was attributed to grain coarsening and evolution of a network of intermetallic compounds. FF study of tensile fractured surfaces indicated that Ca addition encourages brittle mode of fracture propagating through precipitated intermetallics in the structure.

Manganese in the shell of the bivalve Mytilus edulis: Seawater Mn or physiological control?

NASA Astrophysics Data System (ADS)

Freitas, Pedro S.; Clarke, Leon J.; Kennedy, Hilary; Richardson, Christopher A.

2016-12-01

Manganese in the shell calcite of marine bivalves has been suggested to reflect ambient seawater Mn concentrations, thus providing a high-resolution archive of past seawater Mn concentrations. However, a quantitative relationship between seawater Mn and shell Mn/Ca ratios, as well as clear understanding of which process(es) control(s) shell Mn/Ca, are still lacking. Blue mussels, Mytilus edulis, were grown in a one-year duration field experiment in the Menai Strait, U.K., to study the relationship between seawater particulate and dissolved Mn2+ concentrations and shell calcite Mn/Ca ratios. Shell Mn/Ca showed a well-defined intra-annual double-peak, with maximum values during early spring and early summer and low values during autumn and winter. Seawater particulate Mn peaked during winter and autumn, with a series of smaller peaks during spring and summer, whereas dissolved Mn2+ exhibited a marked single maximum during late-spring to early-summer, being low during the remainder of the year. Consequently, neither seawater particulate Mn nor dissolved Mn2+ concentrations explain the intra-annual variation of shell Mn/Ca ratios. A physiological control on shell Mn/Ca ratios is evident from the strong similarity and timing of the double-peaked intra-annual variations of Mn/Ca and shell growth rate (SGR), the latter corresponding to periods of increased metabolic activity (as indicated by respiration rate). It is thus likely that in M. edulis SGR influences shell Mn/Ca by altering the concentration or activity of Mn2+ within the extra-pallial fluid (EPF), by changing the flux of Mn into or the proportion of protein bound Mn within the EPF. By linking shell Mn/Ca ratios to the endogenous and environmental factors that determine growth and metabolic activity, this study helps to explain the lack of a consistent relationship between shell Mn/Ca in marine bivalve shell calcite and seawater particulate and dissolved Mn2+ concentrations. The use of Mn content from M. edulis shell calcite as a proxy for the dissolved and/or particulate Mn concentrations, and thus the biogeochemical processes that control them, remains elusive.

Structure of the skeletal muscle calcium release channel activated with Ca2+ and AMP-PCP.

PubMed Central

Serysheva, I I; Schatz, M; van Heel, M; Chiu, W; Hamilton, S L

1999-01-01

The functional state of the skeletal muscle Ca2+ release channel is modulated by a number of endogenous molecules during excitation-contraction. Using electron cryomicroscopy and angular reconstitution techniques, we determined the three-dimensional (3D) structure of the skeletal muscle Ca2+ release channel activated by a nonhydrolyzable analog of ATP in the presence of Ca2+. These ligands together produce almost maximum activation of the channel and drive the channel population toward a predominately open state. The resulting 30-A 3D reconstruction reveals long-range conformational changes in the cytoplasmic region that might affect the interaction of the Ca2+ release channel with the t-tubule voltage sensor. In addition, a central opening and mass movements, detected in the transmembrane domain of both the Ca(2+)- and the Ca2+/nucleotide-activated channels, suggest a mechanism for channel opening similar to opening-closing of the iris in a camera diaphragm. PMID:10512814

Seasonal growth and translocation of some major and trace elements in two Mediterranean grasses (Stipa tenacissima Loefl. ex L. and Lygeum spartum Loefl. ex L.)

NASA Astrophysics Data System (ADS)

Nedjimi, Bouzid

2018-05-01

The rangelands of Stipa tenacissima and Lygeum spartum (Poaceae) constitute one of the main typical ecosystems in the Iberian Peninsula and North Africa. This study examines the seasonal changes in aboveground biomass accumulation and translocation of some major (Ca and K) and trace elements (Br, Cr, Cu, Fe, Mn, Sr and Zn) from topsoil to shoots of these perennial grasses. Species, season and their interaction significantly affected the dry biomass (DW) and chemical composition of both species and their surrounding soil. The maximum DW was found in spring due to high physiological activity and was correlated positively with rainfall. A significant relationship between seasons and chemical elements was found. For both species the maximum concentrations of Ca, Cu and Zn were found in spring season. However L. spartum had the highest concentrations of K, Cr, Br, and Sr in autumn season, indicating exceptional ability of these species to accumulate large contents of these elements during the active growth periods. By way of contrast, in the topsoil the highest concentrations of almost all chemical elements were found in summer and autumn. Principal component analyses (PCA) showed that growth of L. spartum was highly associated with K, Ca, Zn, Br and Sr, whereas topsoil was correlated with Cu, Cr, Fe and Mn concentrations. Translocation factor (TFx) of chemical elements was not identical across the two species, demonstrating inter-specific variability to uptake chemical elements. The maximum values of TFx were recorded for K, Ca and Sr especially for L. spartum. To cope with arid conditions, S. tenacissima and L. spartum sprout quickly by increasing their rate of growth and nutrient uptake as soon as soil water is available after the rain.

Covariance Manipulation for Conjunction Assessment

NASA Technical Reports Server (NTRS)

Hejduk, M. D.

2016-01-01

Use of probability of collision (Pc) has brought sophistication to CA. Made possible by JSpOC precision catalogue because provides covariance. Has essentially replaced miss distance as basic CA parameter. Embrace of Pc has elevated methods to 'manipulate' covariance to enable/improve CA calculations. Two such methods to be examined here; compensation for absent or unreliable covariances through 'Maximum Pc' calculation constructs, projection (not propagation) of epoch covariances forward in time to try to enable better risk assessments. Two questions to be answered about each; situations to which such approaches are properly applicable, amount of utility that such methods offer.

A dynamic model of saliva secretion

PubMed Central

Palk, Laurence; Sneyd, James; Shuttleworth, Trevor J.; Yule, David I.; Crampin, Edmund J.

2010-01-01

We construct a mathematical model of the parotid acinar cell with the aim of investigating how the distribution of K+ and Cl− channels affects saliva production. Secretion of fluid is initiated by Ca2+ signals acting the Ca2+ dependent K+ and Cl− channels. The opening of these channels facilitates the movement of Cl− ions into the lumen which water follows by osmosis. We use recent results into both the release of Ca2+ from internal stores via the inositol (1,4,5)-trisphosphate receptor (IP3R) and IP3 dynamics to create a physiologically realistic Ca2+ model which is able to recreate important experimentally observed behaviours seen in parotid acinar cells. We formulate an equivalent electrical circuit diagram for the movement of ions responsible for water flow which enables us to calculate and include distinct apical and basal membrane potentials to the model. We show that maximum saliva production occurs when a small amount of K+ conductance is located at the apical membrane, with the majority in the basal membrane. The maximum fluid output is found to coincide with a minimum in the apical membrane potential. The traditional model whereby all Cl− channels are located in the apical membrane is shown to be the most efficient Cl− channel distribution. PMID:20600135

Effect of Ca addition on the damping capacity of Mg-Al-Zn casting alloys

NASA Astrophysics Data System (ADS)

Jun, Joong-Hwan; Moon, Jung-Hyun

2015-07-01

The influences of Ca addition on the microstructures and damping capacities of AZ91-(0˜2)%Ca casting alloys were investigated, on the basis of the results of X-ray diffractometry, optical microscopy, scanning electron microscopy and vibration tests in a single cantilever mode. The amount of intermetallic compounds decreased with increasing Ca content up to 0.5%, above which it increased; the average cell size showed the opposite tendency. All alloys exhibited similar damping levels in the strain-amplitude independent region. Considering the very low solubility of Ca in the matrix, and that most of the Ca elements are consumed by the formation of the Al2Ca phase and incorporation into the Mg17Al12 phase, this would be ascribed to the almost identical concentrations of Ca solutes distributed in the matrix. In the strain-amplitude dependent region, however, the AZ91-0.5%Ca alloy possessed the maximum damping capacity. From the viewpoint of microstructural evolution with Ca addition, the number density of compound particles is considered to be the principal factor affecting the damping behavior in the strain-amplitude dependent region.

Toxicity and removal efficiency of pharmaceutical metabolite clofibric acid by Typha spp.--potential use for phytoremediation?

PubMed

Dordio, Ana V; Duarte, Cátia; Barreiros, Margarida; Carvalho, A J Palace; Pinto, A P; da Costa, Cristina Teixeira

2009-02-01

A study was conducted to assess Typha spp.'s ability to withstand and remove, from water, a metabolite of blood lipid regulator drugs, clofibric acid (CA). At a concentration of 20 microg L(-1), Typha had removed >50% of CA within the first 48h, reaching a maximum of 80% by the end of the assay. Experimental conditions assured that photodegradation, adsorption to vessel walls and microbial degradation did not contribute to the removal. Exposure to higher CA concentrations did not affect Typha's photosynthetic pigments but the overall increase in enzyme activity (ascorbate and guaiacol peroxidases, catalase, superoxide dismutase) indicates that both roots and leaves were affected by the xenobiotic. Eventually, Typha seemed able to cope with the CA's induced oxidative damage suggesting its ability for phytoremediation of CA contaminated waters.

Production of tannase by the immobilized cells of Bacillus licheniformis KBR6 in Ca-alginate beads.

PubMed

Mohapatra, P K D; Mondal, K C; Pati, B R

2007-06-01

The present study was aimed at finding the optimal conditions for immobilization of Bacillus licheniformis KBR6 cells in calcium-alginate (Ca-alginate) beads and determining the operational stability during the production of tannin-acyl-hydrolase (tannase) under semicontinous cultivation. The active cells of B. licheniformis KBR6 were immobilized in Ca-alginate and used for the production of tannase. The influence of alginate concentration (5, 10, 20 and 30 g l(-1)) and initial cell loading on enzyme production were studied. The production of tannase increased significantly with increasing alginate concentration and reached a maximum enzyme yield of 0.56 +/- 0.03 U ml(-1) at 20 g l(-1). This was about 1.70-fold higher than that obtained by free cells. The immobilized cells produced tannase consistently over 13 repeated cycles and reached a maximum level at the third cycle. Scanning electron microscope study indicated that the cells in Ca-alginate beads remain in normal shape. The Ca-alginate entrapment is a promising immobilization method of B. licheniformis KBR6 for repeated tannase production. Tannase production by immobilized cells is superior to that of free cells because it leads to higher volumetric activities within the same period of fermentation. This is the first report of tannase production from immobilized bacterial cells. The bacterium under study can produce higher amounts of tannase with respect to other fungal strains within a short cultivation period.

Estimation of the solar Lyman alpha flux from ground based measurements of the Ca II K line

NASA Technical Reports Server (NTRS)

Rottman, G. J.; Livingston, W. C.; White, O. R.

1990-01-01

Measurements of the solar Lyman alpha and Ca II K from October 1981 to April 1989 show a strong correlation (r = 0.95) that allows estimation of the Lyman alpha flux at 1 AU from 1975 to December 1989. The estimated Lyman alpha strength of 3.9 x 10 to the 11th + or - 0.15 x 10 to the 11th photons/s sq cm on December 7, 1989 is at the same maximum levels seen in Cycle 21. Relative to other UV surrogates (sunspot number, 10.7 cm radio flux, and He I 10830 line strength), Lyman alpha estimates computed from the K line track the SME measurements well from solar maximum, through solar minimum, and into Cycle 22.

Efficiency of a thermodynamic motor at maximum power

NASA Astrophysics Data System (ADS)

Moreau, M.; Gaveau, B.; Schulman, L. S.

2012-02-01

Several recent theories address the efficiency of a macroscopic thermodynamic motor at maximum power and question the so-called Curzon-Ahlborn (CA) efficiency. Considering the entropy exchanges and productions in an n-sources motor, we study the maximization of its power and show that the controversies are partly due to some imprecision in the maximization variables. When power is maximized with respect to the system temperatures, these temperatures are proportional to the square root of the corresponding source temperatures, which leads to the CA formula for a bithermal motor. On the other hand, when power is maximized with respect to the transition durations, the Carnot efficiency of a bithermal motor admits the CA efficiency as a lower bound, which is attained if the duration of the adiabatic transitions can be neglected. Additionally, we compute the energetic efficiency, or “sustainable efficiency,” which can be defined for n sources, and we show that it has no other universal upper bound than 1, but that in certain situations, which are favorable for power production, it does not exceed ½.

Efficiency of a thermodynamic motor at maximum power.

PubMed

Moreau, M; Gaveau, B; Schulman, L S

2012-02-01

Several recent theories address the efficiency of a macroscopic thermodynamic motor at maximum power and question the so-called Curzon-Ahlborn (CA) efficiency. Considering the entropy exchanges and productions in an n-sources motor, we study the maximization of its power and show that the controversies are partly due to some imprecision in the maximization variables. When power is maximized with respect to the system temperatures, these temperatures are proportional to the square root of the corresponding source temperatures, which leads to the CA formula for a bithermal motor. On the other hand, when power is maximized with respect to the transition durations, the Carnot efficiency of a bithermal motor admits the CA efficiency as a lower bound, which is attained if the duration of the adiabatic transitions can be neglected. Additionally, we compute the energetic efficiency, or "sustainable efficiency," which can be defined for n sources, and we show that it has no other universal upper bound than 1, but that in certain situations, which are favorable for power production, it does not exceed ½. © 2012 American Physical Society

Differential effects of peroxynitrite on contractile protein properties in fast- and slow-twitch skeletal muscle fibers of rat.

PubMed

Dutka, T L; Mollica, J P; Lamb, G D

2011-03-01

Oxidative modification of contractile proteins is thought to be a key factor in muscle weakness observed in many pathophysiological conditions. In particular, peroxynitrite (ONOO(-)), a potent short-lived oxidant, is a likely candidate responsible for this contractile dysfunction. In this study ONOO(-) or 3-morpholinosydnonimine (Sin-1, a ONOO(-) donor) was applied to rat skinned muscle fibers to characterize the effects on contractile properties. Both ONOO(-) and Sin-1 exposure markedly reduced maximum force in slow-twitch fibers but had much less effect in fast-twitch fibers. The rate of isometric force development was also reduced without change in the number of active cross bridges. Sin-1 exposure caused a disproportionately large decrease in Ca(2+) sensitivity, evidently due to coproduction of superoxide, as it was prevented by Tempol, a superoxide dismutase mimetic. The decline in maximum force with Sin-1 and ONOO(-) treatments could be partially reversed by DTT, provided it was applied before the fiber was activated. Reversal by DTT indicates that the decrease in maximum force was due at least in part to oxidation of cysteine residues. Ascorbate caused similar reversal, further suggesting that the cysteine residues had undergone S-nitrosylation. The reduction in Ca(2+) sensitivity, however, was not reversed by either DTT or ascorbate. Western blot analysis showed cross-linking of myosin heavy chain (MHC) I, appearing as larger protein complexes after ONOO(-) exposure. The findings suggest that ONOO(-) initially decreases maximum force primarily by oxidation of cysteine residues on the myosin heads, and that the accompanying decrease in Ca(2+) sensitivity is likely due to other, less reversible actions of hydroxyl or related radicals.

Role of Retinal Nerve Fiber Layer Thickness and Optic Disk Measurement by OCT on Early Diagnosis of Glaucoma.

PubMed

Hua, Zanmei; Fang, Qiuyun; Sha, Xiangyin; Yang, Ruiming; Hong, Zuopeng

2015-03-01

Glaucoma is an eye disease that can lead to irreversible optic nerve damage and cause blindness. Optical coherence tomography (OCT) allows an early diagnosis of glaucoma by the measurements of the retinal nerve fiber and optic disc parameters. A retrospective study was designed to analyze the effects of the measurement of the retinal nerve fiber layer (RNFL) thickness and the optic disc tomography by spectral-domain OCT on the early diagnosis of suspected glaucoma and primary open angle glaucoma (POAG). This was a clinical case-control study. The RNFL thickness around the optic disc and optic disk tomographic parameters of the control (n = 51, 98 eyes), suspected glaucoma (n = 81, 146 eyes), and POAG groups (n = 55, 106 eyes) were measured by OCT. The parameters included superior, inferior, nasal and temporal mean RNFL thickness, disc area (DA), cup area (CA), rim area (RA), disc volume (DV), cup volume (CV), rim volume (RV), cup/disc area ratio (CA/DA), rim/disc area ratio (RA/DA), cup/disc volume ratio (CV/DV) and rim/disc volume ratio (RV/DV). Superior, nasal, and mean RNFL parameters, DA, CA,RA, DV, CV, CA/DA, RA/DA, CV/DV and RV/DV significantly differed among three groups by single-factorial ANOVA. Inferior and temporal RNFL thickness significantly differed between the control and POAG groups. No significant difference was observed in RV among three groups. In the POAG group, the maximum area under the ROC curve (AROC) of mean RNFL thickness was 0.845. The maximum AROC of optic disk parameters was RA/DA (0.998), followed by CA/DA (0.997). The AROC of CA, RA, CV, and DV were all > 0.900. OCT may serve as a useful diagnostic modality in distinguishing suspected glaucoma from POAG.

Effects of Food on the Pharmacokinetics of Omega-3-Carboxylic Acids in Healthy Japanese Male Subjects: A Phase I, Randomized, Open-label, Three-period, Crossover Trial.

PubMed

Shimada, Hitoshi; Nilsson, Catarina; Noda, Yoshinori; Kim, Hyosung; Lundström, Torbjörn; Yajima, Toshitaka

2017-09-01

Omega-3-carboxylic acids (OM3-CA) contain omega-3 free fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), as carboxylic acids. Food intake is known to affect the bioavailability of ethyl ester fatty acid formulations. We conducted a phase I study to investigate the effects of the timing of OM3-CA administration relative to food intake on the pharmacokinetics of EPA and DHA. In this randomized, open-label, three-period crossover study, Japanese healthy male subjects were administered 4×1 g OM3-CA capsules with continued fasting, before a meal, or after a meal. All subjects fasted for ≥10 h prior to drug/meal administration. The primary objective was to examine the effect of meal timing on the pharmacokinetics of EPA and DHA after OM3-CA administration. The secondary objectives were to examine the safety and tolerability of OM3-CA. A total of 42 Japanese subjects was enrolled in the study. The baseline-adjusted maximum concentration and area under the concentration-time curve from 0 to 72 h for EPA, DHA, and EPA +DHA were lower in the fasting and before meal conditions than in the after meal condition. The maximum total EPA, total DHA, and total EPA+DHA concentrations were reached later when administered in fasting conditions than in fed conditions, indicating slower absorption in fasting conditions. Diarrhea was reported by five, six, and no subjects in the fasting, before meal, and after meal conditions, respectively. The timing of OM3-CA administration relative to food intake influences the systemic bioavailability of EPA and DHA in healthy Japanese male subjects. NCT02372344.

Regulation of insulin secretion from islets of Langerhans rendered permeable by electric discharge

PubMed Central

Yaseen, M. Adel; Pedley, Kevin C.; Howell, Simon L.

1982-01-01

1. High-voltage electric discharge has been used to increase the permeability of B-cells of isolated islets of Langerhans to facilitate studies of the effects of normally impermeable substances on insulin secretion. 2. The application of an intense electric field increased the [14C]sucrose space of the islets from 37.8±3.1% to 86.2±5.2% of their total volume as assessed by 3H2O content. The cells remained permeable for at least 40min. 3. Ultrastructural studies showed no deleterious changes in the structure of the B-cells after discharge. 4. Insulin secretion from normal islets was unaffected by increasing the medium [Ca2+] from 10nm to 10μm. In the islets that had been rendered permeable by discharge, insulin secretion was significantly increased under these conditions, without any alteration in the release of lactate dehydrogenase, a cytoplasmic marker enzyme. 5. Studies of the dynamics of insulin release during perifusion showed that the response to increased (10μm) Ca2+ concentration was rapid and sustained over a period of at least 13min. 6. Secretion responses to Ca2+ in perifusion established that maximum release in permeabilized islets occurs at approx. 1μm-Ca2+ and half-maximum release occurs at approx. 0.6μm-Ca2+. 7. The study of the effect of agents that interfere with the microtubular microfilamentous system in B-cells using a perifusion system revealed that cytochalasin B caused a considerable increase, whereas vinblastine sulphate caused a significant inhibition, in insulin release in response to 1μm-Ca2+. 8. This technique should facilitate the study of the role of normally impermeable ions and metabolic intermediates in the regulation of insulin secretion. ImagesPLATE 1 PMID:6751326

Synthesis and luminescent properties of spindle-like CaWO{sub 4}:Sm{sup 3+} phosphors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Yue; Department of Physics, Dalian Maritime University, Dalian, Liaoning 116026; Liu, Yu

2012-01-15

Graphical abstract: In this paper, spindle-like CaWO{sub 4}:Sm{sup 3+} phosphors were prepared via a polyvinylpyrrolidone (PVP)-assisted sonochemical process. Dependence of emission intensity on Sm{sup 3+} ions concentration in the CaWO{sub 4}:Sm{sup 3+} phosphor were also calculated via a nonlinear fitting by using the formula y = ax/(1 + bx{sup c}). Highlights: Black-Right-Pointing-Pointer The samples were prepared via a PVP assisted sonochemical process. Black-Right-Pointing-Pointer The color coordinates for 1 mol% Sm{sup 3+} doped CaWO{sub 4} phosphor were calculated. Black-Right-Pointing-Pointer The D-D interaction is responsible for concentration quenching between Sm{sup 3+} ions. Black-Right-Pointing-Pointer The critical energy transfer distances (R{sub c}) were obtained.more » -- Abstract: Spindle-like CaWO{sub 4}:Sm{sup 3+} phosphors were prepared via a Polyvinylpyrrolidone (PVP)-assisted sonochemical process, and characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and photoluminescence spectroscopy (PL). The XRD results suggested that the prepared samples are single-phase. The FE-SEM images indicated that the prepared CaWO{sub 4}:Sm{sup 3+} phosphors are composed of many spindles with maximum average diameter of 150 nm and maximum average length of 500 nm. Under 404 nm excitation, the characteristic emissions corresponding to {sup 4}G{sub 5/2} {yields} {sup 6}H{sub J} (J = 5/2, 7/2, 9/2 and 11/2) transitions of Sm{sup 3+} in CaWO{sub 4} phosphors were observed. The color coordinates for 1 mol% Sm{sup 3+} doped CaWO{sub 4} phosphor were calculated to be (0.595, 0.404). The fluorescent concentration quenching of Sm{sup 3+} doped spindle-like phosphors was studied based on the Van Uitert's model, and it was found that the electric dipole-dipole (D-D) interaction is the dominant energy transfer mechanism between Sm{sup 3+} ions in the CaWO{sub 4}:Sm{sup 3+} phosphors. The critical energy transfer distance was estimated.« less

Development and characterisation of novel heterogeneous palm oil mill boiler ash-based catalysts for biodiesel production.

PubMed

Ho, Wilson Wei Sheng; Ng, Hoon Kiat; Gan, Suyin

2012-12-01

Novel heterogeneous catalysts from calcium oxide (CaO)/calcined calcium carbonate (CaCO(3)) loaded onto different palm oil mill boiler ashes were synthesised and used in the transesterification of crude palm oil (CPO) with methanol to yield biodiesel. Catalyst preparation parameters including the type of ash support, the weight percentage of CaO and calcined CaCO(3) loadings, as well as the calcination temperature of CaCO(3) were optimised. The catalyst prepared by loading of 15 wt% calcined CaCO(3) at a fixed temperature of 800°C on fly ash exhibited a maximum oil conversion of 94.48%. Thermogravimetric analysis (TGA) revealed that the CaCO(3) was transformed into CaO at 770°C and interacted well with the ash support, whereas rich CaO, Al(2)O(3) and SiO(2) were identified in the composition using X-ray diffraction (XRD). The fine morphology size (<5 μm) and high surface area (1.719 m(2)/g) of the fly ash-based catalyst rendered it the highest catalytic activity. Copyright © 2012 Elsevier Ltd. All rights reserved.

Morphological Properties of Slender Ca II H Fibrils Observed by Sunrise II

NASA Astrophysics Data System (ADS)

Gafeira, R.; Lagg, A.; Solanki, S. K.; Jafarzadeh, S.; van Noort, M.; Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta, J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco Suárez, D.; Riethmüller, T. L.; Schmidt, W.

2017-03-01

We use seeing-free high spatial resolution Ca II H data obtained by the Sunrise observatory to determine properties of slender fibrils in the lower solar chromosphere. In this work we use intensity images taken with the SuFI instrument in the Ca II H line during the second scientific flight of the Sunrise observatory to identify and track elongated bright structures. After identification, we analyze theses structures to extract their morphological properties. We identify 598 slender Ca II H fibrils (SCFs) with an average width of around 180 km, length between 500 and 4000 km, average lifetime of ≈400 s, and average curvature of 0.002 arcsec-1. The maximum lifetime of the SCFs within our time series of 57 minutes is ≈2000 s. We discuss similarities and differences of the SCFs with other small-scale, chromospheric structures such as spicules of type I and II, or Ca II K fibrils.

Calcium phosphate coatings modified with zinc- or copper- incorporation on Ti-40Nb alloy

NASA Astrophysics Data System (ADS)

Komarova, E. G.; Sedelnikova, M. B.; Sharkeev, Yu P.; Kazakbaeva, A. A.; Glukhov, I. A.; Khimich, M. A.

2017-05-01

The influence of the microarc oxidation parameters and electrolyte composition on the structure, properties and composition of CaP coatings modified with Zn- or Cu- incorporation on the Ti-40mas.%Nb (Ti-40Nb) alloy was investigated. The linear growth of thickness, roughness, and size of structural elements with process voltage increasing has been revealed. It was shown that the CaP coatings have the low contact angles with liquids and, consequently, high free surface energy. This indicates a high hydrophilicity of the coatings. X-ray diffraction analysis showed that the coatings have X-ray amorphous structure. The increase of the process voltage leads to the formation of such crystalline phases as CaHPO4 and β-Ca2P2O7 in the coatings. The maximum Ca/P atomic ratio was equal to 0.4, and Zn or Cu contents was equal to 0.3 or 0.2 at.%, respectively.

Atmospheric pCO2 reconstructed across five early Eocene global warming events

NASA Astrophysics Data System (ADS)

Cui, Ying; Schubert, Brian A.

2017-11-01

Multiple short-lived global warming events, known as hyperthermals, occurred during the early Eocene (56-52 Ma). Five of these events - the Paleocene-Eocene Thermal Maximum (PETM or ETM1), H1 (or ETM2), H2, I1, and I2 - are marked by a carbon isotope excursion (CIE) within both marine and terrestrial sediments. The magnitude of CIE, which is a function of the amount and isotopic composition of carbon added to the ocean-atmosphere system, varies significantly between marine versus terrestrial substrates. Here we use the increase in carbon isotope fractionation by C3 land plants in response to increased pCO2 to reconcile this difference and reconstruct a range of background pCO2 and peak pCO2 for each CIE, provided two potential carbon sources: methane hydrate destabilization and permafrost-thawing/organic matter oxidation. Although the uncertainty on each pCO2 estimate using this approach is low (e.g., median uncertainty = + 23% / - 18%), this work highlights the potential for significant systematic bias in the pCO2 estimate resulting from sampling resolution, substrate type, diagenesis, and environmental change. Careful consideration of each of these factors is required especially when applying this approach to a single marine-terrestrial CIE pair. Given these limitations, we provide an upper estimate for background early Eocene pCO2 of 463 +248/-131 ppmv (methane hydrate scenario) to 806 +127/-104 ppmv (permafrost-thawing/organic matter oxidation scenario). These results, which represent the first pCO2 proxy estimates directly tied to the Eocene hyperthermals, demonstrate that early Eocene warmth was supported by background pCO2 less than ∼3.5× preindustrial levels and that pCO2 > 1000 ppmv may have occurred only briefly, during hyperthermal events.

Are there pre-Quaternary geological analogues for a future greenhouse warming?

USGS Publications Warehouse

Haywood, A.M.; Ridgwell, A.; Lunt, D.J.; Hill, D.J.; Pound, M.J.; Dowsett, H.J.; Dolan, A.M.; Francis, J.E.; Williams, M.

2011-01-01

Given the inherent uncertainties in predicting how climate and environments will respond to anthropogenic emissions of greenhouse gases, it would be beneficial to society if science could identify geological analogues to the human race's current grand climate experiment. This has been a focus of the geological and palaeoclimate communities over the last 30 years, with many scientific papers claiming that intervals in Earth history can be used as an analogue for future climate change. Using a coupled ocean-atmosphere modelling approach, we test this assertion for the most probable pre-Quaternary candidates of the last 100 million years: the Mid- and Late Cretaceous, the Palaeocene-Eocene Thermal Maximum (PETM), the Early Eocene, as well as warm intervals within the Miocene and Pliocene epochs. These intervals fail as true direct analogues since they either represent equilibrium climate states to a long-term CO2 forcing-whereas anthropogenic emissions of greenhouse gases provide a progressive (transient) forcing on climate-or the sensitivity of the climate system itself to CO2 was different. While no close geological analogue exists, past warm intervals in Earth history provide a unique opportunity to investigate processes that operated during warm (high CO2) climate states. Palaeoclimate and environmental reconstruction/modelling are facilitating the assessment and calculation of the response of global temperatures to increasing CO2 concentrations in the longer term (multiple centuries); this is now referred to as the Earth System Sensitivity, which is critical in identifying CO2 thresholds in the atmosphere that must not be crossed to avoid dangerous levels of climate change in the long term. Palaeoclimatology also provides a unique and independent way to evaluate the qualities of climate and Earth system models used to predict future climate. ?? 2011 The Royal Society.

Climate sensitivity to Arctic seaway restriction during the early Paleogene

NASA Astrophysics Data System (ADS)

Roberts, Christopher D.; LeGrande, Allegra N.; Tripati, Aradhna K.

2009-09-01

The opening and closing of ocean gateways affects the global distribution of heat, salt, and moisture, potentially driving climatic change on regional to global scales. Between 65 and 45 million years ago (Ma), during the early Paleogene, exchange between the Arctic and global oceans occurred through two narrow and shallow seaways, the Greenland-Norway seaway and the Turgai Strait. Sediments from the Arctic Ocean suggest that, during this interval, the surface ocean was warm, brackish, and episodically enabled the freshwater fern Azolla to bloom. The precise mechanisms responsible for the development of these conditions in the Paleogene Arctic remain uncertain. Here we show results from an isotope-enabled, atmosphere-ocean general circulation model, which indicate that Northern Hemisphere climate would have been very sensitive to the degree of oceanic exchange through the Arctic seaways. We also present modelled estimates of seawater and calcite δ18O for the Paleogene. By restricting these seaways, we simulate freshening of the surface Arctic Ocean to ~ 6 psu and warming of sea-surface temperatures by 2 °C in the North Atlantic and 5-10 °C in the Labrador Sea. Our results may help explain the occurrence of low-salinity tolerant taxa in the Arctic Ocean during the Eocene and provide a mechanism for enhanced warmth in the north western Atlantic. We propose that the formation of a volcanic land-bridge between Greenland and Europe could have caused increased ocean convection and warming of intermediate waters in the Atlantic. If true, this result is consistent with the theory that bathymetry changes may have caused thermal destabilisation of methane clathrates and supports a tectonic trigger hypothesis for the Paleocene Eocene Thermal Maximum (PETM).

Are there pre-Quaternary geological analogues for a future greenhouse warming?

PubMed

Haywood, Alan M; Ridgwell, Andy; Lunt, Daniel J; Hill, Daniel J; Pound, Matthew J; Dowsett, Harry J; Dolan, Aisling M; Francis, Jane E; Williams, Mark

2011-03-13

Given the inherent uncertainties in predicting how climate and environments will respond to anthropogenic emissions of greenhouse gases, it would be beneficial to society if science could identify geological analogues to the human race's current grand climate experiment. This has been a focus of the geological and palaeoclimate communities over the last 30 years, with many scientific papers claiming that intervals in Earth history can be used as an analogue for future climate change. Using a coupled ocean-atmosphere modelling approach, we test this assertion for the most probable pre-Quaternary candidates of the last 100 million years: the Mid- and Late Cretaceous, the Palaeocene-Eocene Thermal Maximum (PETM), the Early Eocene, as well as warm intervals within the Miocene and Pliocene epochs. These intervals fail as true direct analogues since they either represent equilibrium climate states to a long-term CO(2) forcing--whereas anthropogenic emissions of greenhouse gases provide a progressive (transient) forcing on climate--or the sensitivity of the climate system itself to CO(2) was different. While no close geological analogue exists, past warm intervals in Earth history provide a unique opportunity to investigate processes that operated during warm (high CO(2)) climate states. Palaeoclimate and environmental reconstruction/modelling are facilitating the assessment and calculation of the response of global temperatures to increasing CO(2) concentrations in the longer term (multiple centuries); this is now referred to as the Earth System Sensitivity, which is critical in identifying CO(2) thresholds in the atmosphere that must not be crossed to avoid dangerous levels of climate change in the long term. Palaeoclimatology also provides a unique and independent way to evaluate the qualities of climate and Earth system models used to predict future climate.

The lacustrine record of the Dan-C2 hyperthermal event of the Boltysh Impact Crater, Ukraine

NASA Astrophysics Data System (ADS)

Ebinghaus, Alena; Jolley, David W.

2015-04-01

Vegetation response to rapid climate change in the geological record is a fundamental element in our understanding of ancient environments; however, the relationships between climate change, plant ecosystems and geological processes are still not fully understood. The filling of the K/Pg Boltysh meteorite crater, Ukraine, comprise a complete terrestrial sedimentological, palynological and δ13C record of the negative carbon isotope excursion of the early Danian hyperthermal episode. The meteorite impact formed a crater of c. 24 km in diameter at c. 65.2 Ma, which was filled with more than 500 m of organic- and fossil-rich claystones, siltstones and marls, interbedded with sandstones and less frequently gravelly sandstones. The sedimentary succession indicates a deep lake setting that was characterised by fluvial input of reworked basement material via a marginal delta system. Palynological investigations indicate a post-impact early- to mid-successional flora followed by a barren zone which coincides with the age of the Chicxulub impact and therefore argues for a series of impact events at the K/Pg boundary. This barren zone was succeeded by a fern spike marking an initial plant re-colonization. The following palynoflora suggests moisture availability oscillations (MAOs) reflecting 41 k.y. obliquity cycles, which can be correlated with lithological fluctuations during lake evolution. The aim is to conduct a detailed, complete facies analysis, and to correlate lake evolutionary aspects with climatic oscillations and vegetation change within the catchment area. This study will be compared with records of similar hyperthermal events, such as the Paleocene-Eocene Thermal Maximum (PETM) in the Western Interior in North America. This integrated approach will help to better understand the controlling factors of global warming events, and their effects on ancient sedimentary environments and ecosystems.

Features of Saccharomyces cerevisiae as a culture starter for the production of the distilled sugar cane beverage, cachaça in Brazil.

PubMed

Campos, C R; Silva, C F; Dias, D R; Basso, L C; Amorim, H V; Schwan, R F

2010-06-01

To evaluate the dominance and persistence of strains of Saccharomyces cerevisiae during the process of sugar cane fermentation for the production of cachaça and to analyse the microbial compounds produced in each fermentative process. Three S. cerevisiae strains were evaluated during seven consecutive 24-h fermentation batches using recycled inocula. The UFLA CA 116 strain had the largest population of viable organisms, and the maximum population was achieved in the fourth batch after 96 h of fermentation. The UFLA CA 1162 and UFLA CA 1183 strains grew more slowly, and the maximum population was reached in the seventh batch. Molecular characterization of isolated yeast cells using PFGE (pulse field gel electrophoresis) revealed that more than 86% of the isolates corresponded to the initially inoculated yeast strain. The concentration of aldehydes, esters, methanol, alcohol and volatile acids in the final-aged beverages were within the legal limits. Cachaça produced by select yeast strains exhibits analytical differences. UFLA CA 1162 and UFLA CA 116 S. cerevisiae isolates can be considered the ideal strains for the artisanal production of cachaça in Brazil. The use of select yeast strains can improve the quality and productivity of cachaça production. Our findings are important for the appropriate monitoring of yeast during sugar cane fermentation. In addition, we demonstrate that UFLA CA 116 and UFLA CA 1162, the ideal yeast strains for cachaça production, are maintained at a high population density. The persistence of these yeast strains in the fermentation of sugar cane juice promotes environmental conditions that prevent or decrease bacterial contamination. Thus, the use of select yeast strains for the production of cachaça is a viable economic alternative to standardize the production of this beverage.

Evidence of superconductivity on the border of quasi-2D ferromagnetism in Ca2RuO4 at high pressure.

PubMed

Alireza, Patricia Lebre; Nakamura, Fumihiko; Goh, Swee Kuan; Maeno, Yoshiteru; Nakatsuji, Satoru; Ko, Yuen Ting Chris; Sutherland, Michael; Julian, Stephen; Lonzarich, Gilbert George

2010-02-10

The layered perovskite Ca(2)RuO(4) is a spin-one Mott insulator at ambient pressure and exhibits metallic ferromagnetism at least up to ∼ 80 kbar with a maximum Curie temperature of 28 K. Above ∼ 90 and up to 140 kbar, the highest pressure reached, the resistivity and ac susceptibility show pronounced downturns below ∼ 0.4 K in applied magnetic fields of up to ∼ 10 mT. This indicates that our specimens of Ca(2)RuO(4) are weakly superconducting on the border of a quasi-2D ferromagnetic state.

Mechanical properties of high-temperature superconducting wires. Ph.D. Thesis - Illinois Inst. of Tech.

NASA Technical Reports Server (NTRS)

Goretta, K. C.; Cluff, J. A.; Joo, J.; Lanagan, M. T.; Singh, J. P.; Vasanthamohan, N.; Xin, Y.; Wong, K. W.

1995-01-01

Bending strength, fracture toughness, and elastic modulus data were acquired for YBa2Cu3O(x), Bi2Sr2CaCu2O(x) (Bi,Pb)2Sr2Ca2Cu3O(x), and Tl2Ba2Ca2Cu3O(x) bars. These data and thermal expansion coefficients strongly suggest that the maximum possible tensile strain without fracture of bulk tapes or wires is approximately equals 0.2%. In Ag-clad conductors, residual stresses will be of limited benefit, but fractures produced by larger strains can be accommodated by shunting current through the Ag.

Immobilized carbonic anhydrase on mesoporous cruciate flower-like metal organic framework for promoting CO2 sequestration.

PubMed

Ren, Sizhu; Feng, Yuxiao; Wen, Huan; Li, Conghai; Sun, Baoting; Cui, Jiandong; Jia, Shiru

2018-05-25

CO 2 capture by immobilized carbonic anhydrase (CA) has become an alternative and environmental friendly approach in CO 2 sequestration technology. However, the immobilized CA usually exhibits low CO 2 sequestration efficiency due to no gas adsorption function for the conventional CA supports. Metal organic frameworks (MOFs) are an excellent material for gas adsorption and enzyme immobilization. Herein, a combined immobilization system of CA and ZIF-8 with cruciate flower-like morphology for CO 2 adsorption was prepared for the first time by adsorbing CA onto ZIF-8. The immobilization efficiency was greater than 95%, and the maximum activity recovery reached 75%, indicating the highly efficient immobilization process. The resultant CA@ZIF-8 composites exhibited outstanding thermostability, the tolerance against denaturants, and reusability compared with free CA. Furthermore, we demonstrated for the first time that the shape of ZIF-8 could be controlled by adjusting concentrations of Zn 2+ ions at the high concentration of 2-methylimidazole (1 M). More importantly, we also demonstrated the applicability of the CA@ZIF-8 composites to the sequestration of CO 2 in carbonate minerals. The yields of the CaCO 3 obtained by using CA@ZIF-8 composites were 22-folds compared to free CA. Thus, this CA@ZIF-8 composite can be successfully used as a robust biocatalyst for sequestration of CO 2 . Copyright © 2018 Elsevier B.V. All rights reserved.

Tubular localization of silent calcium channels in crustacean skeletal muscle fibers.

PubMed

Monterrubio, J; Ortiz, G; Orkand, P M; Zuazaga, C

2002-01-01

Ca2+-induced Ca2+ release (CICR) in the superficial abdominal flexor muscle of the crustacean Atya lanipes appears to be mediated by a local control mechanism similar to that of vertebrate cardiac muscle, but with an unusually high gain. Thus, Ca2+ influx increases sufficiently the local concentration of Ca2+ in the immediate vicinity of the sarcoplasmic reticulum Ca2+ release channels to trigger the highly amplified release of Ca2+ required for contraction, but is too low to generate a macroscopic inward current (i.e., the Ca2+ channels are silent). To determine the localization of the silent Ca2+ Channels, the mechanical, electrophysiological and ultrastructural properties of the muscle were examined before and after formamide treatment, a procedure that produces the disruption of transverse tubules of striated muscle. We found that tubular disruption decreased tension generation by about 90%; reduced inward current (measured as Vmax, the maximum rate of rise of Sr2+ action potentials) by about 80%; and decreased membrane capacitance by about 77%. The results suggest that ca. 80% of the silent Ca2+ channels are located in the tubular system. Thus, these studies provide further evidence to support the local control mechanism of CICR in crustacean skeletal muscle.

Europium concentration effect on characteristics and luminescent properties of hydroxyapatite nanocrystalline powders

NASA Astrophysics Data System (ADS)

Nikolaev, Anton; Kolesnikov, Ilya; Frank-Kamenetskaya, Olga; Kuz'mina, Maria

2017-12-01

Series of Eu-apatites were synthesized by precipitation from aqueous solutions with the Eu/Ca atomic ratio from 0.5% to 5% at T = 90 °C. Resulting precipitates were studied using different experimental techniques including X-ray powder diffraction, infrared and raman spectroscopy, scanning elecrton microscopy, EDX and photoluminescent spectroscopy. Eu-doped Ca-deficit nanosized non-stoichiometric hydroxyapatite with high water content has been obtained throughout the experiment. Europium content in the synthesized apatites reaches 0.24 apfu (Eu/Ca = 2.5%). Relations between Eu content is the solution and precipitate have been established. It was shown that Eu-monacite starts to precipitate as secondary phase at Eu/Ca ratio in starting solution 1% or higher. Maximum luminescence is observed in apatite with ∼2% Eu/Ca ratio (which equals to ∼0.2 apfu and corresponds to 3% Eu/Ca ratio in the starting solution). As an important and brand-new result, apatite with 2% Eu/Ca ratio can be considered as the most appropriate material for the producing biolabels for luminescent research in medicine and biology.

Salinity bias on the foraminifera Mg/Ca thermometry: Correction procedure and implications for past ocean hydrographic reconstructions

NASA Astrophysics Data System (ADS)

Mathien-Blard, Elise; Bassinot, Franck

2009-12-01

Mg/Ca in foraminiferal calcite has recently been extensively used to estimate past oceanic temperatures. Here we show, however, that the Mg/Ca temperature relationship of the planktonic species Globigerinoides ruber is significantly affected by seawater salinity, with a +1 psu change in salinity resulting in a +1.6°C bias in Mg/Ca temperature calculations. If not accounted for, such a bias could lead, for instance, to systematic overestimations of Mg/Ca temperatures during glacial periods, when global ocean salinity had significantly increased compared to today. We present here a correction procedure to derive unbiased sea surface temperatures (SST) and δ18Osw from G. ruber TMg/Ca and δ18Of measurements. This correction procedure was applied to a sedimentary record to reconstruct hydrographic changes since the Last Glacial Maximum (LGM) in the Western Pacific Warm Pool. While uncorrected TMg/Ca data indicate a 3°C warming of the Western Pacific Warm Pool since the LGM, the salinity-corrected SST result in a stronger warming of 4°C.

2.4 μm diode-pumped Dy2+:CaF2 laser

NASA Astrophysics Data System (ADS)

Švejkar, Richard; Papashvili, Alexander G.; Šulc, Jan; Němec, Michal; Jelínková, Helena; Doroshenko, Maxim E.; Batygov, Sergei H.; Osiko, Vyacheslav V.

2018-01-01

In this work, a cryogenic cooled, longitudinal diode-pumped Dy2+ :CaF2 laser was investigated for the first time. The temperature dependence of the spectroscopy and the laser properties of Dy2+ :CaF2 are presented. The tested Dy2+ :CaF2 crystal was a longitudinal pump in a near-IR region (926 nm) by laser diode radiation. The maximal mean output power and slope efficiency at 78 K during the pulse regime of the laser were 57.5 mW and 7%, respectively. Furthermore, the CW regime was successfully tested and a maximum output power of 0.37 W was obtained for the absorbed pumping power 5.7 W. The emission laser wavelength was 2367 nm.

Calcium-ion transport by intact Ehrlich ascites-tumour cells. Role of respiratory substrates, Pi and temperature.

PubMed

Charlton, R R; Wenner, C E

1978-03-15

1. The interaction of intact Ehrlich ascites-tumour cells with Ca2+ at 37 degrees C consists of Ca2+ uptake followed by efflux from the cells. Under optimum conditions, two or three cycles of uptake and efflux are observed in the first 15 min after Ca2+ addition. 2. The respiratory substrates malate, succinate and ascorbate plus p-phenylenediamine support Ca2+ uptake. Ca2+ uptake at 37 degrees C is sensitive to the respiratory inhibitors rotenone and antimycin A when appropriate substrates are present. Ca2+ uptake and retention are inhibited by the uncoupler S-13. 3. Increasing extracellular Pi (12 to 30 mM) stimulates uncoupler-sensitive Ca2+ uptake, which reaches a maximum extent of 15 nmol/mg of protein when supported by succinate respiration. Ca2+ efflux is partially inhibited at 30 mM-Pi. 4. Optimum Ca2+ uptake occurs in the presence of succinate and Pi, suggesting that availability of substrate and Pi are rate-limiting. K. Ca2+ uptake occurs at 4 degrees C and is sensitive to uncouplers and oligomycin. Ca2+ efflux at this temperature is minimal. These data are consistent with a model in which passive diffusion of Ca2+ through the plasma membrane is followed by active uptake by the mitochondria. Ca2+ uptake is supported by substrates entering respiration at all three energy-coupling sites. Ca2+ efflux appears to be an active process with a high temperature coefficient.

Two fast-type fibers in claw closer and abdominal deep muscles of the Australian freshwater crustacean, Cherax destructor, differ in Ca2+ sensitivity and troponin-I isoforms.

PubMed

Koenders, Annette; Lamey, Tina M; Medler, Scott; West, Jan M; Mykles, Donald L

2004-07-01

One type of fast fiber and two types of slow (slow-twitch, S1 and slow-tonic, S2) fibers are found in decapod crustacean skeletal muscles that differ in contractile properties and myofibrillar protein isoform compositions. In this study the structural characteristics, protein isoform compositions, and Ca2+-activation properties of fast fibers in the claw closer (F1) and abdominal deep flexor (F2) muscles of Cherax destructor were analyzed. For comparison, myofibrillar protein isoform compositions of slow (long-sarcomere) fibers from claw and abdomen were also determined; our results indicate that the slow fibers in the claw closer were the slow-twitch (S1) type and those in the abdominal superficial flexor were primarily slow-tonic (S2) type. F1 fibers had shorter resting sarcomere lengths (2.93 microm in unstretched fibers and 3.06 microm in stretched fibers) and smaller fiber diameter (256 microm) than F2 fibers (sarcomere lengths 3.48 microm in unstretched and 3.46 microm in stretched; 747 microm diameter). Moreover, F1 fibers showed a narrower range in sarcomere lengths than F2 fibers (2.81 to 3.28 microm vs. 2.47 to 4.05 micro m in unstretched fibers). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting showed that the fast fibers from claw and abdomen differed in troponin-I composition; F1 fibers expressed two isoforms of troponin-I (TnI1 and TnI2) in approximately equal amounts, whereas F2 fibers expressed primarily TnI3 and lower levels of TnI1. F1 fibers were more sensitive to Ca2+, as shown by higher pCa values at threshold activation (pCa(10)=6.50+/-0.07) and at 50% maximum force (pCa(50)=6.43+/-0.07) than F2 fibers (pCa(10)=6.12+/-0.04 and pCa(50)=5.88+/-0.03, respectively). F1 fibers also had a greater degree of co-operativity in Ca2+ activation, as shown by a higher maximum slope of the force-pCa curve (n(Ca)=12.98+/-2.27 vs. 4.34+/-0.64). These data indicate that there is a greater fast fiber-type diversity in crustacean muscles than was previously supposed. Moreover, the differences in activation properties suggest that the TnI isoform composition influences the Ca2+ sensitivity of the contractile mechanism. Copyright 2004 Wiley-Liss, Inc.

Determination of Fusion Barrier Distributions from Quasielastic Scattering Cross Sections towards Superheavy Nuclei Synthesis

NASA Astrophysics Data System (ADS)

Tanaka, Taiki; Narikiyo, Yoshihiro; Morita, Kosuke; Fujita, Kunihiro; Kaji, Daiya; Morimoto, Kouji; Yamaki, Sayaka; Wakabayashi, Yasuo; Tanaka, Kengo; Takeyama, Mirei; Yoneda, Akira; Haba, Hiromitsu; Komori, Yukiko; Yanou, Shinya; Jean-Paul Gall, Benoît; Asfari, Zouhair; Faure, Hugo; Hasebe, Hiroo; Huang, Minghui; Kanaya, Jumpei; Murakami, Masashi; Yoshida, Atsushi; Yamaguchi, Takayuki; Tokanai, Fuyuki; Yoshida, Tomomi; Yamamoto, Shoya; Yamano, Yuki; Watanabe, Kenyu; Ishizawa, Satoshi; Asai, Masato; Aono, Ryuji; Goto, Shin-ichi; Katori, Kenji; Hagino, Kouichi

2018-01-01

In order to study the nucleus-nucleus interactions for syntheses of superheavy nuclei, we measured excitation functions for the quasielastic scattering of 48Ca+208Pb, 50Ti+208Pb, and 48Ca+248Cm using the gas-filled-type recoil ion separator GARIS. The quasielastic scattering events were clearly separated from deep-inelastic events by using GARIS and its focal plan detectors, except for high-incident-energy points. The quasielastic barrier distributions were successfully extracted for these systems, and compared with coupled-channels calculations. The results of the calculations indicate that vibrational and rotational excitations of the colliding nuclei, as well as neutron transfers before contact, strongly affect the structure of the barrier distribution. For the reactions of 48Ca+208Pb and 50Ti+208Pb, a local maximum of the barrier distribution occurred at the same energy as the peak of the 2n evaporation cross section of the system. On the other hand, for the hot fusion reaction of 48Ca+248Cm, the 4n evaporation cross section of the system peaks at energies well above the maximum of the barrier distribution. This may be attributed to the deformation of the target nucleus. We argue that these findings can be utilized to locate the optimal energy for future searches for undiscovered superheavy nuclei.

The impact of extracerebral organ failure on outcome of patients after cardiac arrest: an observational study from the ICON database.

PubMed

Nobile, Leda; Taccone, Fabio S; Szakmany, Tamas; Sakr, Yasser; Jakob, Stephan M; Pellis, Tommaso; Antonelli, Massimo; Leone, Marc; Wittebole, Xavier; Pickkers, Peter; Vincent, Jean-Louis

2016-11-14

We used data from a large international database to assess the incidence and impact of extracerebral organ dysfunction on prognosis of patients admitted after cardiac arrest (CA). This was a sub-analysis of the Intensive Care Over Nations (ICON) database, which contains data from all adult patients admitted to one of 730 participating intensive care units (ICUs) in 84 countries from 8-18 May 2012, except admissions for routine postoperative surveillance. For this analysis, patients admitted after CA (defined as those with "post-anoxic coma" or "cardiac arrest" as the reason for ICU admission) were included. Data were collected daily in the ICU for a maximum of 28 days; patients were followed up for outcome data until death, hospital discharge, or a maximum of 60 days in-hospital. Favorable neurological outcome was defined as alive at hospital discharge with a last available neurological Sequential Organ Failure Assessment (SOFA) subscore of 0-2. Among the 469 patients admitted after CA, 250 (53 %) had had out-of-hospital CA; 210 (45 %) patients died in the ICU and 357 (76 %) had an unfavorable neurological outcome. Non-survivors had a higher incidence of renal (43 vs. 16 %), cardiovascular (56 vs. 45 %), and respiratory (62 vs. 48 %) failure on admission and during the ICU stay than survivors (all p < 0.05). Similar results were found for patients with unfavorable vs. favorable neurological outcomes. In multivariable analysis, independent predictors of ICU mortality were renal failure on admission, high admission Simplified Acute Physiology Score (SAPS) II, high maximum serum lactate levels within the first 24 h after ICU admission, and development of sepsis. Independent predictors of unfavorable neurological outcome were mechanical ventilation on admission, high admission SAPS II score, and neurological dysfunction on admission. In this multicenter cohort, extracerebral organ dysfunction was common in CA patients. Renal failure on admission was the only extracerebral organ dysfunction independently associated with higher ICU mortality.

Positive Allosteric Modulation of the Calcium-sensing Receptor by Physiological Concentrations of Glucose*

PubMed Central

Medina, Johan; Nakagawa, Yuko; Nagasawa, Masahiro; Fernandez, Anny; Sakaguchi, Kazushige; Kitaguchi, Tetsuya; Kojima, Itaru

2016-01-01

The calcium-sensing receptor (CaSR) is activated by various cations, cationic compounds, and amino acids. In the present study we investigated the effect of glucose on CaSR in HEK293 cells stably expressing human CaSR (HEK-CaSR cells). When glucose concentration in the buffer was raised from 3 to 25 mm, a rapid elevation of cytoplasmic Ca2+ concentration ([Ca2+]c) was observed. This elevation was immediate and transient and was followed by a sustained decrease in [Ca2+]c. The effect of glucose was detected at a concentration of 4 mm and reached its maximum at 5 mm. 3-O-Methylglucose, a non-metabolizable analogue of glucose, reproduced the effect of glucose. Sucrose also induced an elevation of [Ca2+]c in HEK-CaSR cells. Similarly, sucralose was nearly as effective as glucose in inducing elevation of [Ca2+]c. Glucose was not able to increase [Ca2+]c in the absence of extracellular Ca2+. The effect of glucose on [Ca2+]c was inhibited by NPS-2143, an allosteric inhibitor of CaSR. In addition, NPS-2143 also inhibited the [Ca2+]c responses to sucralose and sucrose. Glucose as well as sucralose decreased cytoplasmic cAMP concentration in HEK-CaSR cells. The reduction of cAMP induced by glucose was blocked by pertussis toxin. Likewise, sucralose reduced [cAMP]c. Finally, glucose increased [Ca2+]c in PT-r parathyroid cells and in Madin-Darby canine kidney cells, both of which express endogenous CaSR. These results indicate that glucose acts as a positive allosteric modulator of CaSR. PMID:27613866

Calcium Chloride in Neonatal Parenteral Nutrition Solutions with and without Added Cysteine: Compatibility Studies Using Laser and Micro-Flow Imaging Methodology.

PubMed

Huston, Robert K; Christensen, J Mark; Alshahrani, Sultan M; Mohamed, Sumeia M; Clark, Sara M; Nason, Jeffrey A; Wu, Ying Xing

2015-01-01

Previous studies of compatibility of calcium chloride (CaCl2) and phosphates have not included particle counts in the range specified by the United States Pharmacopeia. Micro-flow imaging techniques have been shown to be comparable to light obscuration when determining particle count and size in pharmaceutical solutions. The purpose of this study was to do compatibility testing for parenteral nutrition (PN) solutions containing CaCl2 using dynamic light scattering and micro-flow imaging techniques. Solutions containing TrophAmine (Braun Medical Inc, Irvine, CA), CaCl2, and sodium phosphate (NaPhos) were compounded with and without cysteine. All solutions contained standard additives to neonatal PN solutions including dextrose, trace metals, and electrolytes. Control solutions contained no calcium or phosphate. Solutions were analyzed for particle size and particle count. Means of Z-average particle size and particle counts of controls were determined. Study solutions were compared to controls and United States Pharmacopeia (USP) Chapter 788 guidelines. The maximum amount of Phos that was compatible in solutions that contained at least 10 mmol/L of Ca in 2.5% amino acids (AA) was determined. Compatibility of these solutions was verified by performing analyses of 5 repeats of these solutions. Microscopic analyses of the repeats were also performed. Amounts of CaCl2 and NaPhos that were compatible in solutions containing 1.5%, 2%, 2.5%, and 3% AA were determined. The maximum amount of NaPhos that could be added to TrophAmine solutions of > = 2.5% AA containing at least 10 mmol/L of CaCl2 was 7.5 mmol/L. Adding 50 mg/dL of cysteine increased the amount of NaPhos that could be added to solutions containing 10 mmol/L of CaCl2 to 10 mmol/L. Calcium chloride can be added to neonatal PN solutions containing NaPhos in concentrations that can potentially provide an intravenous intake of adequate amounts of calcium and phosphorus.

Functional effects of uridine triphosphate on human skinned skeletal muscle fibers.

PubMed

Vianna-Jorge, R; Oliveira, C F; Mounier, Y; Suarez-Kurtz, G

1998-02-01

Chemically skinned human skeletal muscle fibers were used to study the effects of uridine triphosphate (UTP) on the tension-pCa relationship and on Ca2+ uptake and release by the sarcoplasmic reticulum (SR). Total replacement (2.5 mM) of adenosine triphosphate (ATP) with UTP (i) displaced the tension-pCa relationship to the left along the abcissae and increased maximum Ca(2+)-activated tension, both effects being larger in slow- than in fast-type fibers; (ii) markedly reduced Ca2+ uptake by the SR (evaluated by the caffeine-evoked tension) in both fiber types; (iii) had no effect on the rate of depletion of caffeine-sensitive Ca2+ stores during soaking in relaxing solutions; (iv) induced tension in slow- but not in fast-type fibers. The effects on the SR functional properties are consistent with the notion that UTP is a poor substitute for ATP as a substrate for the Ca ATPase pump and as an agonist of the ryanodine-sensitive Ca(2+)-release channel. The UTP-induced tension in human slow-type fibers is attributed to effect(s) of the nucleotide on the tension-pCa relationship of the contractile machinery. The present data reveal important differences between the effects of UTP on human versus rat muscle fibers.

Proton and neutron density distributions at supranormal density in low- and medium-energy heavy-ion collisions

NASA Astrophysics Data System (ADS)

Stone, J. R.; Danielewicz, P.; Iwata, Y.

2017-07-01

Background: The distribution of protons and neutrons in the matter created in heavy-ion collisions is one of the main points of interest for the collision physics, especially at supranormal densities. These distributions are the basis for predictions of the density dependence of the symmetry energy and the density range that can be achieved in a given colliding system. We report results of the first systematic simulation of proton and neutron density distributions in central heavy-ion collisions within the beam energy range of Ebeam≤800 MeV /nucl . The symmetric 40Ca+40Ca , 48Ca+48Ca , 100Sn+100Sn , and 120Sn+120Sn and asymmetric 40Ca+48Ca and 100Sn+120Sn systems were chosen for the simulations. Purpose: We simulate development of proton and neutron densities and asymmetries as a function of initial state, beam energy, and system size in the selected collisions in order to guide further experiments pursuing the density dependence of the symmetry energy. Methods: The Boltzmann-Uhlenbeck-Uehling (pBUU) transport model with four empirical models for the density dependence of the symmetry energy was employed. Results of simulations using pure Vlasov dynamics were added for completeness. In addition, the time-dependent Hartree-Fock (TDHF) model, with the SV-bas Skyrme interaction, was used to model the heavy-ion collisions at Ebeam≤40 MeV /nucl . Maximum proton and neutron densities ρpmax and ρnmax, reached in the course of a collision, were determined from the time evolution of ρp and ρn. Results: The highest total densities predicted at Ebeam=800 MeV /nucl . were of the order of ˜2.5 ρ0 (ρ0=0.16 fm-3 ) for both Sn and Ca systems. They were found to be only weakly dependent on the initial conditions, beam energy, system size, and a model of the symmetry energy. The proton-neutron asymmetry δ =(ρnmax-ρpmax) /(ρnmax+ρpmax) at maximum density does depend, though, on these parameters. The highest value of δ found in all systems and at all investigated beam energies was ˜0.17 . Conclusions: We find that the initial state, beam energy, system size, and a symmetry energy model affect very little the maximum proton and neutron densities, but have a subtle impact on the proton-neutron asymmetry. Most importantly, the variations in the proton-neutron asymmetry at maximum densities are related at most at 50% level to the details in the symmetry energy at supranormal density. The reminder is due to the details in the symmetry energy at subnormal densities and proton and neutron distributions in the initial state. This result brings to the forefront the need for a proper initialization of the nuclei in the simulation, but also brings up the question of microscopy, such as shell effects, that affect initial proton and neutron densities, but cannot be consistently incorporated into semiclassical transport models.

The relationship between the electronic structure and thermoelectric properties of Zintl compounds M2Zn5As4 (M = K, Rb).

PubMed

Yang, Gui; Yang, Jueming; Yan, Yuli; Wang, Yuanxu

2014-03-28

The electronic structure and the thermoelectric properties of M2Zn5As4 (M = K, Rb) are studied by the first principles and the semiclassical BoltzTraP theory. It is determined that they are semiconductors with an indirect band gap of about 1 eV, which is much larger than that of Ca5Al2Sb6 (0.50 eV). The calculated electronic localization function indicates that they are typical Zintl bonding compounds. The combination of heavy and light bands near the valence band maximum may improve their thermoelectric performance. Rb2Zn5As4 exhibits relatively large Seebeck coefficients, high electrical conductivities, and the large "maximum" thermoelectric figures of merit (ZeT). Compared with Ca5Al2Sb6, the highest ZeT of Rb2Zn5As4 appears at relatively low carrier concentration. For Rb2Zn4As5, the p-type doping may achieve a higher thermoelectric performance than n-type doping. The thermoelectric properties of Rb2Zn5As4 are possibly superior to those of Ca5Al2Sb6.

Statistical evaluation of nutritional components impacting phycocyanin production Synechocystis SP.

PubMed Central

Deshmukh, Devendra V.; Puranik, Pravin R.

2012-01-01

Alkaliphilic cyanobacterial cultures were isolated from Lonar lake (MS, India). Among the set of cultures, Synechocystis sp, was studied for phycocyanin production. A maximum yield was obtained in BG-11 medium at optimized conditions (pH 10 and 16 h light). In order to increase the phycocyanin yield media optimization based on the eight media components a Plackett-Burman design of the 12 experimental trials was used. As per the analysis CaCl2, 2H2O and Na2CO3 have been found to be the most influencing media components at 95% significance. Further the optimum concentrations of these components were estimated following a Box Wilson Central Composite Design (CCD) with four star points and five replicates at the center points for each of two factors was adopted for optimization of these two media components. The results indicated that there was an interlinked influence of CaCl2, 2H2O and Na2CO3 on 98% significance. The maximum yield of phycocyanin (12% of dry wt) could be obtained at 0.058 g/l and 0.115 g/l of CaCl2, 2H2O and Na2CO3, respectively. PMID:24031838

Magnetic-field-dependent dielectric constant in La2/3Ca1/3MnO3

NASA Astrophysics Data System (ADS)

Rivas, J.; Mira, J.; Rivas-Murias, B.; Fondado, A.; Dec, J.; Kleemann, W.; Señarís-Rodríguez, M. A.

2006-06-01

We report a rather high dependence of the dielectric permittivity on the magnetic field in La2/3Ca1/3MnO3. The variation is maximum at around 270K, little above the Curie temperature TC, and it reaches a 35% under only 0.5T. We attribute this phenomenon to the space-charge or interfacial polarization produced between the insulator and the metallic regions segregated intrinsically in the material above TC.

Plasma-Filled Rod-Pinch Diode Research on Gamble II

DTIC Science & Technology

2007-06-01

by the dashed red line in Fig. 3. CaF2 thermoluminescent dosimeters ( TLDs ) located on the front surface of the rolled edge measure the dose. The...half-maximum line-spread function] and high dose [23 rad(CaF2) at 1 m] with 1-2 MeV electron energies are unique capabilities that the PFRP offers...for radiographic imaging in this electron -energy range. The source distribution has a narrow central peak that can enhance the spatial resolution

Quantifying uncertainty in coral Sr/Ca-based SST estimates from Orbicella faveolata: A basis for multi-colony SST reconstructions

NASA Astrophysics Data System (ADS)

Richey, J. N.; Flannery, J. A.; Toth, L. T.; Kuffner, I. B.; Poore, R. Z.

2017-12-01

The Sr/Ca in massive corals can be used as a proxy for sea surface temperature (SST) in shallow tropical to sub-tropical regions; however, the relationship between Sr/Ca and SST varies throughout the ocean, between different species of coral, and often between different colonies of the same species. We aimed to quantify the uncertainty associated with the Sr/Ca-SST proxy due to sample handling (e.g., micro-drilling or analytical error), vital effects (e.g., among-colony differences in coral growth), and local-scale variability in microhabitat. We examine the intra- and inter-colony reproducibility of Sr/Ca records extracted from five modern Orbicella faveolata colonies growing in the Dry Tortugas, Florida, USA. The average intra-colony absolute difference (AD) in Sr/Ca of the five colonies during an overlapping interval (1997-2008) was 0.055 ± 0.044 mmol mol-1 (0.96 ºC) and the average inter-colony Sr/Ca AD was 0.039 ± 0.01 mmol mol-1 (0.51 ºC). All available Sr/Ca-SST data pairs from 1997-2008 were combined and regressed against the HadISST1 gridded SST data set (24 ºN and 82 ºW) to produce a calibration equation that could be applied to O. faveolata specimens from throughout the Gulf of Mexico/Caribbean/Atlantic region after accounting for the potential uncertainties in Sr/Ca-derived SSTs. We quantified a combined error term for O. faveolata using the root-sum-square (RMS) of the analytical, intra-, and inter-colony uncertainties and suggest that an overall uncertainty of 0.046 mmol mol-1 (0.81 ºC, 1σ), should be used to interpret Sr/Ca records from O. faveolata specimens of unknown age or origin to reconstruct SST. We also explored how uncertainty is affected by the number of corals used in a reconstruction by iteratively calculating the RMS error for composite coral time-series using two, three, four, and five overlapping coral colonies. Our results indicate that maximum RMS error at the 95% confidence interval on mean annual SST estimates is 1.4 ºC when a composite record is made from only two overlapping coral Sr/Ca records. The uncertainty decreases as additional coral Sr/Ca data are added, with a maximum RMS error of 0.5 ºC on mean annual SST for a five-colony composite. To reduce uncertainty to under 1 ºC, it is best to use Sr/Ca from three or more coral colonies from the same geographic location and time period.

Cementum structure in Beluga whale teeth

DOE PAGES

Stock, S. R.; Finney, L. A.; Telser, A.; ...

2016-11-09

We report that a large fraction of the volume of Beluga whale (Delphinapterus leucas) teeth consists of cementum, a mineralized tissue which grows throughout the life of the animal and to which the periodontal ligaments attach. Annular growth bands or growth layer groups (GLGs) form within Beluga cementum, and this study investigates GLG structure using X-ray fluorescence mapping and X-ray diffraction mapping with microbeams of synchrotron radiation. The Ca and Zn fluorescent intensities and carbonated hydroxyapatite (cAp) diffracted intensities rise and fall together and match the light-dark bands visible in transmitted light micrographs. Within the bands of maximum Ca andmore » Zn intensity, the ratio of Zn to Ca is slightly higher than in the minima bands. Further, the GLG cAp, Ca and Zn modulation is preserved throughout the cementum for durations >25 year.« less

ROS-mediated decline in maximum Ca2+-activated force in rat skeletal muscle fibers following in vitro and in vivo stimulation.

PubMed

Dutka, Travis L; Verburg, Esther; Larkins, Noni; Hortemo, Kristin H; Lunde, Per K; Sejersted, Ole M; Lamb, Graham D

2012-01-01

We hypothesised that normal skeletal muscle stimulated intensely either in vitro or in situ would exhibit reactive oxygen species (ROS)-mediated contractile apparatus changes common to many pathophysiological conditions. Isolated soleus (SOL) and extensor digitorum longus (EDL) muscles of the rat were bubbled with 95% O(2) and stimulated in vitro at 31°C to give isometric tetani (50 Hz for 0.5 s every 2 s) until maximum force declined to ≤30%. Skinned superficial slow-twitch fibers from the SOL muscles displayed a large reduction (∼41%) in maximum Ca(2+)-activated specific force (F(max)), with Ca(2+)-sensitivity unchanged. Fibers from EDL muscles were less affected. The decrease in F(max) in SOL fibers was evidently due to oxidation effects on cysteine residues because it was reversed if the reducing agent DTT was applied prior to activating the fiber. The GSH:GSSG ratio was ∼3-fold lower in the cytoplasm of superficial fibers from stimulated muscle compared to control, confirming increased oxidant levels. The presence of Tempol and L-NAME during in vitro stimulation prevented reduction in F(max). Skinned fibers from SOL muscles stimulated in vivo at 37°C with intact blood supply also displayed reduction in F(max), though to a much smaller extent (∼12%). Thus, fibers from muscles stimulated even with putatively adequate O(2) supply display a reversible oxidation-induced decrease in F(max) without change in Ca(2+)-sensitivity, consistent with action of peroxynitrite (or possibly superoxide) on cysteine residues of the contractile apparatus. Significantly, the changes closely resemble the contractile deficits observed in a range of pathophysiological conditions. These findings highlight how readily muscle experiences ROS-related deficits, and also point to potential difficulties when defining muscle performance and fatigue.

ROS-Mediated Decline in Maximum Ca2+-Activated Force in Rat Skeletal Muscle Fibers following In Vitro and In Vivo Stimulation

PubMed Central

Dutka, Travis L.; Verburg, Esther; Larkins, Noni; Hortemo, Kristin H.; Lunde, Per K.; Sejersted, Ole M.; Lamb, Graham D.

2012-01-01

We hypothesised that normal skeletal muscle stimulated intensely either in vitro or in situ would exhibit reactive oxygen species (ROS)-mediated contractile apparatus changes common to many pathophysiological conditions. Isolated soleus (SOL) and extensor digitorum longus (EDL) muscles of the rat were bubbled with 95% O2 and stimulated in vitro at 31°C to give isometric tetani (50 Hz for 0.5 s every 2 s) until maximum force declined to ≤30%. Skinned superficial slow-twitch fibers from the SOL muscles displayed a large reduction (∼41%) in maximum Ca2+-activated specific force (Fmax), with Ca2+-sensitivity unchanged. Fibers from EDL muscles were less affected. The decrease in Fmax in SOL fibers was evidently due to oxidation effects on cysteine residues because it was reversed if the reducing agent DTT was applied prior to activating the fiber. The GSH∶GSSG ratio was ∼3-fold lower in the cytoplasm of superficial fibers from stimulated muscle compared to control, confirming increased oxidant levels. The presence of Tempol and L-NAME during in vitro stimulation prevented reduction in Fmax. Skinned fibers from SOL muscles stimulated in vivo at 37°C with intact blood supply also displayed reduction in Fmax, though to a much smaller extent (∼12%). Thus, fibers from muscles stimulated even with putatively adequate O2 supply display a reversible oxidation-induced decrease in Fmax without change in Ca2+-sensitivity, consistent with action of peroxynitrite (or possibly superoxide) on cysteine residues of the contractile apparatus. Significantly, the changes closely resemble the contractile deficits observed in a range of pathophysiological conditions. These findings highlight how readily muscle experiences ROS-related deficits, and also point to potential difficulties when defining muscle performance and fatigue. PMID:22629297

One-dimensional non-LTE time-dependent radiative transfer of an He-detonation model and the connection to faint and fast-decaying supernovae

NASA Astrophysics Data System (ADS)

Dessart, Luc; Hillier, D. John

2015-02-01

We present non-LTE (non-Local-Thermodynamic-Equilibrium) time-dependent radiative transfer simulations for ejecta produced by the detonation of a helium shell at the surface of a low-mass carbon/oxygen white dwarf (WD). This mechanism is one possible origin for supernovae (SNe) with faint and fast-decaying light curves, such as .Ia SNe and Ca-rich transients. Our initial ejecta conditions at 1 d are given by the 0.18 B explosion model COp45HEp2 of Waldman et al. The 0.2 M⊙ ejecta initially contains 0.11 M⊙ of He, 0.03 M⊙ of Ca, and 0.03 M⊙ of Ti. We obtain an ˜ 5 d rise to a bolometric maximum of 3.59 × 1041 erg s-1, primarily powered by 48V decay. Multi-band light curves show distinct morphologies, with a rise to maximum magnitude (-14.3 to -16.7 mag) that varies between 3 to 9 d from the U to the K bands. Near-IR light curves show no secondary maximum. Because of the presence of both He I and Si II lines at early times we obtain a hybrid Type Ia/Ib classification. During the photospheric phase line blanketing is caused primarily by Ti II. At nebular times, the spectra show strong Ca II lines in the optical (but no [O I] 6300-6364 Å emission), and Ti II in the near-IR. Overall, these results match qualitatively the very disparate properties of .Ia SNe and Ca-rich transients. Although the strong Ti II blanketing and red colours that we predict are rarely observed, they are seen, for example, in OGLE-2013- SN-079. Furthermore, we obtain a faster light-curve evolution than, for example, PTF10iuv, indicating an ejecta mass >0.2 M⊙. An alternate scenario may be the merger of two WDs, one or both composed of He.

Echinacoside induces rat pulmonary artery vasorelaxation by opening the NO-cGMP-PKG-BKCa channels and reducing intracellular Ca2+ levels

PubMed Central

Gai, Xiang-yun; Wei, Yu-hai; Zhang, Wei; Wuren, Ta-na; Wang, Ya-ping; Li, Zhan-qiang; Liu, Shou; Ma, Lan; Lu, Dian-xiang; Zhou, Yi; Ge, Ri-li

2015-01-01

Aim: Sustained pulmonary vasoconstriction as experienced at high altitude can lead to pulmonary hypertension (PH). The main purpose of this study is to investigate the vasorelaxant effect of echinacoside (ECH), a phenylethanoid glycoside from the Tibetan herb Lagotis brevituba Maxim and Cistanche tubulosa, on the pulmonary artery and its potential mechanism. Methods: Pulmonary arterial rings obtained from male Wistar rats were suspended in organ chambers filled with Krebs-Henseleit solution, and isometric tension was measured using a force transducer. Intracellular Ca2+ levels were measured in cultured rat pulmonary arterial smooth muscle cells (PASMCs) using Fluo 4-AM. Results: ECH (30–300 μmol/L) relaxed rat pulmonary arteries precontracted by noradrenaline (NE) in a concentration-dependent manner, and this effect could be observed in both intact endothelium and endothelium-denuded rings, but with a significantly lower maximum response and a higher EC50 in endothelium-denuded rings. This effect was significantly blocked by L-NAME, TEA, and BaCl2. However, IMT, 4-AP, and Gli did not inhibit ECH-induced relaxation. Under extracellular Ca2+-free conditions, the maximum contraction was reduced to 24.54%±2.97% and 10.60%±2.07% in rings treated with 100 and 300 μmol/L of ECH, respectively. Under extracellular calcium influx conditions, the maximum contraction was reduced to 112.42%±7.30%, 100.29%±8.66%, and 74.74%±4.95% in rings treated with 30, 100, and 300 μmol/L of ECH, respectively. After cells were loaded with Fluo 4-AM, the mean fluorescence intensity was lower in cells treated with ECH (100 μmol/L) than with NE. Conclusion: ECH suppresses NE-induced contraction of rat pulmonary artery via reducing intracellular Ca2+ levels, and induces its relaxation through the NO-cGMP pathway and opening of K+ channels (BKCa and KIR). PMID:25864652

Multiple caloric effects in (Ba0.865Ca0.135Zr0.1089Ti0.8811Fe0.01)O3 ferroelectric ceramic

NASA Astrophysics Data System (ADS)

Patel, Satyanarayan; Chauhan, Aditya; Vaish, Rahul

2015-07-01

Multiple caloric effects have been investigated for Fe-doped bulk (Ba0.865Ca0.135Zr0.1089Ti0.8811Fe0.01)O3 (BCZTO-Fe) ferroelectric ceramic. Indirect predictions were made using Maxwell's relations in conjunction with data from experimental observations. It was revealed that bulk BCZTO-Fe has huge untapped potential for solid-state refrigeration. A peak electrocaloric effect of 0.45 K (347 K) was predicted for 0-3 kV.mm-1 electric field, significantly higher than other BCZTO based materials. A maximum elastocaloric cooling of 1.4 K (298 K) was achieved for applied stress of 0-200 MPa. Finally, an unforeseen component of electric field driven caloric effect has been reported as inverse piezocaloric effect, with a maximum temperature change of 0.28 K (298 K).

A diode-pumped Tm:CaYAlO4 laser at 1851 nm

NASA Astrophysics Data System (ADS)

Lan, Jinglong; Guan, Xiaofeng; Xu, Bin; Moncorgé, Richard; Xu, Huiying; Cai, Zhiping

2017-07-01

Laser emission at ~1850 nm is of great interest for neural stimulation applications. In this letter, we report on the diode-pumped continuous-wave (CW) and Q-switched (QS) laser operation of Tm:CaYAlO4 at 1851 nm, for the first time to our knowledge. In the CW regime, a maximum output power up to 0.62 W is obtained with a laser slope efficiency of about 18.0%. Using a Cr:ZnSe saturable absorber, QS laser operation is achieved with a maximum average output power of 0.25 W, the narrowest pulse width of 107 ns and the highest repetition rate of 5.85 kHz. The corresponding pulse peak power and pulse energy are about 388 W and 42.8 µJ, respectively. In this Q-switched mode, wavelength tuning is also realized over about 3 nm by slightly tilting the saturable absorber.

Preliminary Results of the Analysis

NASA Technical Reports Server (NTRS)

Pap, Judit

1995-01-01

The preliminary results of the photometry of CaII K spectroheliograms taken at the NationalSolar Observatory at Sacramento peak are presented in this paper. We have digitizedspectroheliograms for 1980 (maximum of SC21), 1985 (minimum of SC21), 1987 (beginning of theascending phase of SC22), 1988 and 1989 (ascending phase and maximum of SC22), and 1992(declining phase of SC22). We have analyzed images for 1992 and separated the plages, the magneticnetwork, internetwork elements and the chromospheric background using histogram method. Wehave derived the intensity and area of these features as well as the full disk intensity (Spatial KIndex). The Spatial K Index has been compared to the spectral Ca K index derived from the lineprofiles and total solar and UV irradiance measured by the UARS and NOAA9 satellites. Thecontribution of plages, the magnetic network and internetwork element to the changes observed intotal solar and UV irradiances are also estimated.

Coral Ba/Ca and Mn/Ca ratios as proxies of precipitation and terrestrial input at the eastern offshore area of Hainan Island

NASA Astrophysics Data System (ADS)

Jiang, Qiaowen; Cao, Zhimin; Wang, Daoru; Li, Yuanchao; Wu, Zhongjie; Ni, Jianyu

2017-12-01

Geochemical ratios in coral reef skeletons could be used as proxies to reconstruct past climatological and environmental records in data-poor regions. Using a 103-year data set (1902 to 2005), the annual variations in Ba/Ca and Mn/Ca ratios of Porites lutea skeletons at an eastern offshore area of Hainan Island (19°12´28.4´´N, 110°37´38.8´´E) were analyzed using inductively coupled plasma-optic emission spectrometry (ICP-OES). The analysis results showed that Ba/Ca ratios varied from a minimum of 3.120 μmol mol-1 in 1903 to a maximum of 10.064 μmol mol-1 in 1944, with an average of 5.256 μmol mol-1. Mn/Ca ratios varied from 0.206 to 5.708 μmol mol-1 with an annual average of 1.234 μmol mol-1, with peak values in 2001, 1964 and 1932, that correlated with strong rainfall events caused by typhoons. Variation in Ba/Ca and Mn/Ca ratios were compared with available river discharge and precipitation records, providing insight into past climatological events. Human activities and their indirect effects could impact the strength of the relationship between Ba/Ca and Mn/Ca ratios and observed precipitation and terrestrial input in the future.

Enhanced adsorption of U(VI) and 241Am(III) from wastewater using Ca/Al layered double hydroxide@carbon nanotube composites.

PubMed

Chen, Haijun; Chen, Zhe; Zhao, Guixia; Zhang, Zhibin; Xu, Chao; Liu, Yunhai; Chen, Jing; Zhuang, Li; Haya, Tasawar; Wang, Xiangke

2018-04-05

Ca/Al layered double hydroxide decorated carbon nanotube (Ca/Al-LDH@CNTs) composites were fabricated by co-precipitation method and hydrothermal aged treatment. The prepared Ca/Al-LDH@CNTs was characterized by SEM, TEM, EDS, XRD, FT-IR, UV-vis and XPS techniques, and applied to remove U(VI) from aqueous solutions under various environmental conditions (i.e., pH, ionic strength, temperature and contact time). The results indicated that the adsorption of U(VI) on Ca/Al-LDH@CNTs was four times higher than that of U(VI) on bare CNTs. The kinetic investigations reflected the chemisorption of U(VI) on Ca/Al-LDH@CNTs through oxygen-containing functional groups. The adsorption isotherms demonstrated that the adsorption of U(VI) was well fitted by Langmuir model and the maximum adsorption capacity of U(VI) on Ca/Al-LDH@CNTs was calculated to be 382.9 mg g -1 at 289.15 K. The thermodynamic parameters calculated from temperature-dependent isotherms suggested that U(VI) adsorption on Ca/Al-LDH@CNTs were endothermic and spontaneous process. Furthermore, Ca/Al-LDH@CNTs could remove ∼91% of 241 Am(III) at pH = 8.0, which confirmed Ca/Al-LDH@CNTs as a promising material for multiply low level radionuclides' pollution remediation. Copyright © 2017 Elsevier B.V. All rights reserved.

The Advantages of Collimator Optimization for Intensity Modulated Radiation Therapy

NASA Astrophysics Data System (ADS)

Doozan, Brian

The goal of this study was to improve dosimetry for pelvic, lung, head and neck, and other cancers sites with aspherical planning target volumes (PTV) using a new algorithm for collimator optimization for intensity modulated radiation therapy (IMRT) that minimizes the x-jaw gap (CAX) and the area of the jaws (CAA) for each treatment field. A retroactive study on the effects of collimator optimization of 20 patients was performed by comparing metric results for new collimator optimization techniques in Eclipse version 11.0. Keeping all other parameters equal, multiple plans are created using four collimator techniques: CA 0, all fields have collimators set to 0°, CAE, using the Eclipse collimator optimization, CAA, minimizing the area of the jaws around the PTV, and CAX, minimizing the x-jaw gap. The minimum area and the minimum x-jaw angles are found by evaluating each field beam's eye view of the PTV with ImageJ and finding the desired parameters with a custom script. The evaluation of the plans included the monitor units (MU), the maximum dose of the plan, the maximum dose to organs at risk (OAR), the conformity index (CI) and the number of fields that are calculated to split. Compared to the CA0 plans, the monitor units decreased on average by 6% for the CAX method with a p-value of 0.01 from an ANOVA test. The average maximum dose remained within 1.1% difference between all four methods with the lowest given by CAX. The maximum dose to the most at risk organ was best spared by the CAA method, which decreased by 0.62% compared to the CA0. Minimizing the x-jaws significantly reduced the number of split fields from 61 to 37. In every metric tested the CAX optimization produced comparable or superior results compared to the other three techniques. For aspherical PTVs, CAX on average reduced the number of split fields, lowered the maximum dose, minimized the dose to the surrounding OAR, and decreased the monitor units. This is achieved while maintaining the same control of the PTV.

Ca2+-induced delayed afterdepolarizations are triggered by dyadic subspace Ca2+ affirming that increasing SERCA reduces aftercontractions

PubMed Central

Noble, Penelope J.; Noble, Denis

2011-01-01

Ca2+-induced delayed afterdepolarizations (DADs) are depolarizations that occur after full repolarization. They have been observed across multiple species and cell types. Experimental results have indicated that the main cause of DADs is Ca2+ overload. The main hypothesis as to their initiation has been Ca2+ overflow from the overloaded sarcoplasmic reticulum (SR). Our results using 37 previously published mathematical models provide evidence that Ca2+-induced DADs are initiated by the same mechanism as Ca2+-induced Ca2+ release, i.e., the modulation of the opening of ryanodine receptors (RyR) by Ca2+ in the dyadic subspace; an SR overflow mechanism was not necessary for the induction of DADs in any of the models. The SR Ca2+ level is better viewed as a modulator of the appearance of DADs and the magnitude of Ca2+ release. The threshold for the total Ca2+ level within the cell (not only the SR) at which Ca2+ oscillations arise in the models is close to their baseline level (∼1- to 3-fold). It is most sensitive to changes in the maximum sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) pump rate (directly proportional), the opening probability of RyRs, and the Ca2+ diffusion rate from the dyadic subspace into the cytosol (both indirectly proportional), indicating that the appearance of DADs is multifactorial. This shift in emphasis away from SR overload as the trigger for DADs toward a multifactorial analysis could explain why SERCA overexpression has been shown to suppress DADs (while increasing contractility) and why DADs appear during heart failure (at low SR Ca2+ levels). PMID:21666112

Ultrasonic-assisted production of biodiesel from transesterification of palm oil over ostrich eggshell-derived CaO catalysts.

PubMed

Chen, Guanyi; Shan, Rui; Shi, Jiafu; Yan, Beibei

2014-11-01

In this study, waste ostrich eggshell-derived calcium oxide (denoted as CaO(OE)) particles were synthesized and explored as cost-effective catalysts for the ultrasonic-assisted transesterification of palm oil. The physicochemical properties of the resultant catalysts were characterized by XRD, N2 adsorption, XRF and Hammett indicator, while the catalytic activity was evaluated through transesterification of palm oil with methanol under ultrasonic conditions. More specifically, the CaO(OE) showed comparable catalytic activity to the one derived from commercial calcium carbonate (denoted as CaO(Lab)). Moreover, under ultrasonic conditions, the catalytic activity of CaO(OE) could be enhanced significantly. The maximum yield of fatty acid methyl esters could reach 92.7% under the optimal condition of reaction time of 60 min with ultrasonic power of 60% (120 W), methanol-to-oil ratio of 9:1, and catalyst loading of 8 wt.%. The results indicated that the CaO(OE) catalysts showed good catalytic performance and reusability, and may potentially reduce the cost of biodiesel production. Copyright © 2014 Elsevier Ltd. All rights reserved.

Dual-wavelength Nd:CaLnAlO4 lasers at 1.365 and 1.390 μm

NASA Astrophysics Data System (ADS)

Loiko, Pavel; Maria Serres, Josep; Mateos, Xavier; Xu, Xiaodong; Xu, Jun; Griebner, Uwe; Petrov, Valentin; Aguiló, Magdalena; Díaz, Francesc; Major, Arkady

2018-02-01

Tetragonal calcium rare-earth aluminates, CaLnAlO4, are attractive laser host crystals. The emission of Nd3+ ions at 1.3- 1.4 μm due to the 4F3/2 -> 4I13/2 transition is of interest for medicine, fiber optics, and light conversion. We report on compact Nd:CaLnAlO4 lasers using a plane-plane cavity. With an a-cut 0.8 at.% Nd:CaYAlO4 crystal diode-pumped at 802 nm, a maximum continuous-wave output power of 365 mW was achieved at 1.365 & 1.390 μm corresponding to the σ-polarization. The 4F3/2 -> 4I13/2 laser performance of the Nd:CaLnAlO4 crystals was compared to that from a monoclinic Nd:KGd(WO4)2. At the 4F3/2-> 4I11/2 transition (1.08 μm), a Nd:CaYAlO4 micro-laser generated multi-watt output (>4 W) with a slope efficiency of 39%.

The effects of catalysts on the conversion of organic matter and bio-fuel production in the microwave pyrolysis of sludge at different temperatures.

PubMed

Ma, Rui; Huang, Xiaofei; Zhou, Yang; Fang, Lin; Sun, Shichang; Zhang, Peixin; Zhang, Xianghua; Zhao, Xuxin

2017-08-01

Adding catalyst could improve the yields and qualities of bio-gas and bio-oil, and realize the oriented production. Results showed that the catalytic gas-production capacities of CaO were higher than those of Fe 2 O 3 , and the bio-gas yield at 800°C reached a maximum of 35.1%. Because the polar cracking active sites of CaO reduced the activation energy of the pyrolysis reaction and resulted in high catalytic cracking efficiencies. In addition, the quality of bio-oil produced by CaO was superior to that by Fe 2 O 3 , although the bio-oil yield of CaO was relatively weak. The light bio-fuel oriented catalytic pyrolysis could be realized when adding different catalysts. At 800°C, CaO was 45% higher than Fe 2 O 3 in aspect of H 2 production while Fe 2 O 3 was 103% higher than CaO in aspect of CH 4 production. Therefore, CaO was more suitable for H 2 production and Fe 2 O 3 was more suitable for CH 4 production. Copyright © 2017 Elsevier Ltd. All rights reserved.

Biosorption of clofibric acid and carbamazepine in aqueous solution by agricultural waste rice straw.

PubMed

Liu, Zhanguang; Zhou, Xuefei; Chen, Xiaohua; Dai, Chaomeng; Zhang, Juan; Zhang, Yalei

2013-12-01

Due to their widespread use, clofibric acid (CA) and carbamazepine (CBZ) have been frequently detected simultaneously at relatively high concentrations in aquatic environments. In this study, agricultural waste rice straw was employed as a potentially low-cost, effective and easy-to-operate biosorbent (RSB) to remove CA and CBZ. The adsorption of both pharmaceuticals followed pseudo second-order kinetics, and intraparticle diffusion was an important rate-limiting step. The adsorption isotherms of both drugs were fit well with Freundlich model. The adsorption of CA onto RSB was exothermic and was more likely to be dominated by physical processes, while the adsorption of CBZ was endothermic. Solution pH was determined to be the most important factor for CA adsorption, such that the adsorption capacity of CA onto RSB increased with the decline of solution pH. In the lower range of solution pH below 3.1, the CA removal efficiency was enhanced with the increase of biosorbent dosage. The CBZ removal efficiency was enhanced with the increase of RSB dosage without pH control. The maximum adsorption capacities were 126.3 mg/g for CA and 40.0 mg/g for CBZ.

Cellular automata rule characterization and classification using texture descriptors

NASA Astrophysics Data System (ADS)

Machicao, Jeaneth; Ribas, Lucas C.; Scabini, Leonardo F. S.; Bruno, Odermir M.

2018-05-01

The cellular automata (CA) spatio-temporal patterns have attracted the attention from many researchers since it can provide emergent behavior resulting from the dynamics of each individual cell. In this manuscript, we propose an approach of texture image analysis to characterize and classify CA rules. The proposed method converts the CA spatio-temporal patterns into a gray-scale image. The gray-scale is obtained by creating a binary number based on the 8-connected neighborhood of each dot of the CA spatio-temporal pattern. We demonstrate that this technique enhances the CA rule characterization and allow to use different texture image analysis algorithms. Thus, various texture descriptors were evaluated in a supervised training approach aiming to characterize the CA's global evolution. Our results show the efficiency of the proposed method for the classification of the elementary CA (ECAs), reaching a maximum of 99.57% of accuracy rate according to the Li-Packard scheme (6 classes) and 94.36% for the classification of the 88 rules scheme. Moreover, within the image analysis context, we found a better performance of the method by means of a transformation of the binary states to a gray-scale.

Exposure to As(III) and As(V) changes the Ca²⁺-activation properties of the two major fibre types from the chelae of the freshwater crustacean Cherax destructor.

PubMed

Williams, Gemma; Snow, Elizabeth T; West, Jan M

2014-10-01

Arsenic is a known carcinogen found in the soil in gold mining regions at concentrations thousands of times greater than gold. Mining releases arsenic into the environment and surrounding water bodies. The main chemical forms of arsenic found in the environment are inorganic arsenite (As(III)) and arsenate (As(V)). Yabbies (Cherax destructor) accumulate arsenic at levels comparable to those in the sediment of their environment but the effect on their physiological function is not known. The effects of arsenic exposure (10 ppm sodium arsenite, AsNaO2 - 5.7 ppm As(III)) and 10 ppm arsenic acid, Na2HAsO4·7H2O - 2.6 ppm As(V)) for 40 days on the contractile function of the two major fibre types from the chelae were determined. After exposure, individual fibres were isolated from the chela, "skinned" (membrane removed) and attached to the force recording apparatus. Contraction was induced in solutions containing increasing [Ca(2+)] until a maximum Ca(2+)-activation was obtained. Submaximal force responses were plotted as a percentage of the maximum Ca(2+)-activated force. As(V) exposure resulted in lower levels of calcium required for activation than As(III) indicating an increased sensitivity to Ca(2+) after long term exposure to arsenate compared to arsenite. Myosin heavy chain and tropomyosin content in individual fibres was also decreased as a result of arsenic exposure. Single fibres exposed to As(V) produced significantly more force than muscle fibres from control animals. Long-term exposure of yabbies to arsenic alters the contractile function of the two major fibre types in the chelae. Copyright © 2014 Elsevier B.V. All rights reserved.

Sulphation of CaO-Based Sorbent Modified in CO2 Looping Cycles

NASA Astrophysics Data System (ADS)

Manovic, Vasilije; Anthony, Edward J.; Loncarevic, Davor

CaO-based looping cycles for CO2 capture at high temperatures are based on cyclical carbonation of CaO and regeneration of CaCO3. The main limitation of natural sorbents is the loss of carrying capacity with increasing numbers of reaction cycles, resulting in spent sorbent ballast. Use of spent sorbent from CO2 looping cycles for SO2 capture is a possible solution investigated in this study. Three limestones were investigated: Kelly Rock (Canada), La Blanca (Spain) and Katowice (Poland). Carbonation/calcination cycles were performed in a tube furnace with original limestones and samples thermally pretreated for different times (i.e., sintered). The spent sorbent samples were sulphated in a thermogravimetric analyzer. Changes in the resulting pore structure were then investigated using mercury porosimetry. Final conversions of both spent and pretreated sorbents after longer sulphation times were comparable or higher than those observed for the original sorbents. Maximum sulphation levels strongly depend on sorbent porosity and pore surface area. The shrinkage of sorbent particles during calcination/cycling resulted in a loss of sorbent porosity (≤48%), which corresponds to maximum sulphation levels ˜55% for spent Kelly Rock and Katowice. However, this is ˜10% higher than for the original samples. By contrast, La Blanca limestone had more pronounced particle shrinkage during pretreatment and cycling, leading to lower porosity, <35%, resulting in sulphation conversion of spent samples <30%, significantly lower than for the original sample (45%). These results showed that spent sorbent samples from CO2 looping cycles can be used as sorbents for SO2 retention if significant porosity loss does not occur during CO2 reaction cycles. For spent Kelly Rock and Katowice samples final conversions are determined by the total pore volume available for the bulky CaSO4 product.

Factors affecting ultraviolet-A photon emission from β-irradiated human keratinocyte cells.

PubMed

Le, M; Mothersill, C E; Seymour, C B; Ahmad, S B; Armstrong, A; Rainbow, A J; McNeill, F E

2015-08-21

The luminescence intensity of 340±5 nm photons emitted from HaCaT (human keratinocyte) cells was investigated using a single-photon-counting system during cellular exposure to (90)Y β-particles. Multiple factors were assessed to determine their influence upon the quantity and pattern of photon emission from β-irradiated cells. Exposure of 1 x 10(4) cells/5 mL to 703 μCi resulted in maximum UVA photoemission at 44.8 x 10(3)±2.5 x 10(3) counts per second (cps) from live HaCaT cells (background: 1-5 cps); a 16-fold increase above cell-free controls. Significant biophoton emission was achieved only upon stimulation and was also dependent upon presence of cells. UVA luminescence was measured for (90)Y activities 14 to 703 μCi where a positive relationship between photoemission and (90)Y activity was observed. Irradiation of live HaCaT cells plated at various densities produced a distinct pattern of emission whereby luminescence increased up to a maximum at 1 x 10(4) cells/5 mL and thereafter decreased. However, this result was not observed in the dead cell population. Both live and dead HaCaT cells were irradiated and were found to demonstrate different rates of photon emission at low β activities (⩽400 μCi). Dead cells exhibited greater photon emission rates than live cells which may be attributable to metabolic processes taking place to modulate the photoemissive effect. The results indicate that photon emission from HaCaT cells is perturbed by external stimulation, is dependent upon the activity of radiation delivered, the density of irradiated cells, and cell viability. It is postulated that biophoton emission may be modulated by a biological or metabolic process.

Palaeozoic gas charging in the Ahnet-Timimoun basin, Algeria

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cawley, S.J.; Wilson, N.P.; Primmer, T.

1995-08-01

The Ahnet-Timimoun Basin, Southern Algeria, contains significant gas reserves expelled from originally oil prone Silurian and Frasnian shales. The gas is reservoired in Devonian and Carboniferous clastics in inversion anticlines formed, primarily, during the Hercynian orogeny. Integration of organic and inorganic geochemical techniques, such as AFTA, ZFTA, fluid inclusion analysis, vitrinite and chitinizoan reflectance, is entirely consistent with gas generation 300 +/- 30MY, immediately prior to or synchronous with the Hercynian orogeny. Data from gas fields has shown the remobilisation of gas during post Hercynian tectonics. A {open_quotes}two-event{close_quotes} heating/cooling history is proposed: (1) Maximum burial and palaeotemperature at ca. 300more » +/- 30MY prior to or synchronous with Hercynian uplift and cooling. (2) Cooling from a secondary peak (lower than maximum) palaeotemperature at ca. 30-60My following Creataceous burial. Calibrated thermal modelling indicates that Palaeozoic source rocks were heated above 200{degrees}C in the Late Carboniferous. Such high temperatures are consistent with the widespread occurrence of pyrophyllite in Silurian shales. Two end-member thermal models can account for the observed maturities. The first is a constant high Pre-Hercynian heat flow which rapidly decreases during Hercynian uplift to remain at Present day values of 50-75mW/m{sup 2}. Gas expulsion in this case commences much earlier than trap formation. The second is {open_quotes}normal{close_quotes} heat flow of ca. 50mW/m{sup 2} until ca. 310My with a rapid increase at ca. 290My followed by an equally rapid drop to constant present day values - in this model, petroleum generation and expulsion is late in relation to structuring.« less

Changes in the response of mitochondrial calcium transport to exogenous phosphate during development in flight muscle of the sheep blowfly Lucilla cuprina.

PubMed Central

Smith, R L; Bygrave, F L

1978-01-01

1. Ca2+ transport by mitochondria isolated from flight muscle of the sheep blowfly Lucilla cuprina does not occur in the absence of added P1. Maximum rates of transport are attained when about 2.5 mM-phosphate is present. 2. As mitochondria develop, high but not low phosphate concentrations begin to inhibit Ca2+ transport markedly; those isolated from 2-day-old flies for example, are inhibited by about 75% by 20 mM-phosphate. Maximum rates of transport, i.e. those measured in the presence of 2.5 mM-phosphate, begin to decline only when the fly is about 3 days old. 3. Mitochondrial phosphate transport activity does not change during development of the blowfly, but the endogenous concentration of the anion does. At emergence it is about 6nmol/mg of protein, increases to about 17 nmol/mg of protein at 2-3h and then rapidly declines to reach less than 5 nmol/mg of protein after 2 days of adult life. 4. Studies on the effect of phosphate on oxidation of alpha-glycerophosphate in the absence and presence of ADP reveal a lack of inhibition by high phosphate concentrations indicating that the anion does not influence Ca2+ transport by preventing the generation of the proton electrochemical gradient across the inner membrane. 5. It is concluded that the molecular assembly in the inner membrane of Lucilla mitochondria responsible for transporting Ca2+ is fully developed at emergence and remains so for at least 2-3 days of adult life. The possibility exists that Ca2+-transport activity in these mitochondria is controlled at least in part by P1. PMID:629784

First-Principles Study of Chemical Mixtures of CaCl2 and MgCl2 Hydrates for Optimized Seasonal Heat Storage

PubMed Central

2017-01-01

Chloride-based salt hydrates form a promising class of thermochemical materials (TCMs), having high storage capacity and fast kinetics. In the charging cycles of these hydrates however hydrolysis might appear along with dehydration. The HCl produced during the hydrolysis degrades and corrodes the storage system. Our GGA-DFT results show that the enthalpy charge during proton formation (an important step in hydrolysis) is much higher for CaCl2·2H2O (33.75 kcal/mol) than for MgCl2·2H2O (19.55 kcal/mol). This is a strong indicator that hydrolysis can be minimized by appropriate chemical mixing of CaCl2 and Mg Cl2 hydrates, which is also confirmed by recent experimental studies. GGA-DFT calculations were performed to obtain and analyze the optimized structures, charge distributions, bonding indicators and harmonic frequencies of various chemical mixtures hydrates and compared them to their elementary salts hydrates. We have further assessed the equilibrium products concentration of dehydration/hydrolysis of the chemical mixtures under a wide range of operating conditions. We observed that chemical mixing leads to an increase of the onset hydrolysis temperature with a maximum value of 79 K, thus increasing the resistance against hydrolysis with respect to the elementary salt hydrates. We also found that the chemical mixing of CaCl2 and MgCl2 hydrates widens the operating dehydration temperature range by a maximum value of 182 K (CaMg2Cl6·2H2O) and lowers the binding enthalpy with respect to the physical mixture by ≈65 kcal/mol for TCM based heat storage systems. PMID:28983386

Infrasound-induced hemodynamics, ultrastructure, and molecular changes in the rat myocardium.

PubMed

Pei, Zhaohui; Sang, Hanfei; Li, Ruiman; Xiao, Pingxi; He, Jiangui; Zhuang, Zhiqiang; Zhu, Miaozhang; Chen, Jingzao; Ma, Hong

2007-04-01

Recent interest in adverse effects of infrasound on organisms arises from health concerns. We assessed the association between infrasound exposure of 5 Hz at 130 dB and changes of cardiac ultrastructure and function in rats. Thirty-two Sprague-Dawley rats were randomized into control, 1, 7, and 14 days groups for 2 h of infrasound once daily according to planned schedules. Changes of cardiac ultrastructure, hemodynamics indices, intracellular Ca(2+) concentrations ([Ca(2+)](i)), and sarcoplasmic reticulum Ca(2+)-ATPase 2 (SERCA2) were detected. Heart rates in 1 day group were significantly increased compared with control group and no significant changes in other groups. Left ventricular systolic pressures were significantly increased with time. Left ventricular diastolic end pressure and maximum rising rates of left ventricular pressure (+dl/dt) were significantly increased in 7 and 14 days groups and not changed in 1 day group, compared with control group. Maximum dropping rates of left ventricular pressure (-dl/dt) were significantly decreased in 7 and 14 days groups and not changed in 1 day group, compared with control group. In heart cells, there were several swelled mitochondria in 1 day group, more swelled mitochondria in 7 days group, platelet aggregation in the intercellular substance in 14 days group. [Ca(2+)](i) were significantly increased with time. There was a significant increase in SERCA2 in 1 day group, while a significant decrease in 7 and 14 days groups, compared with control group. Infrasound of 5 Hz at 130 dB can damage cardiac ultrastructure and function. Changes of [Ca(2+)](i) and SERCA2 play an important role in the secondary cardiac damage. (c) 2007 Wiley Periodicals, Inc.

Deformation processed Al/Ca nano-filamentary composite conductors for HVDC applications

NASA Astrophysics Data System (ADS)

Czahor, C. F.; Anderson, I. E.; Riedemann, T. M.; Russell, A. M.

2017-07-01

Efficient long-distance power transmission is necessary as the world continues to implement renewable energy sources, often sited in remote areas. Light, strong, high-conductivity materials are desirable for this application to reduce both construction and operational costs. In this study an Al/Ca (11.5% vol.) composite with nano-filamentary reinforcement was produced by powder metallurgy then extruded, swaged, and wire drawn to a maximum true strain of 12.7. The tensile strength increased exponentially as the filament size was reduced to the sub-micron level. In an effort to improve the conductor’s ability to operate at elevated temperatures, the deformation-processed wires were heat-treated at 260°C to transform the Ca-reinforcing filaments to Al2Ca. Such a transformation raised the tensile strength by as much as 28%, and caused little change in ductility, while the electrical conductivity was reduced by only 1% to 3%. Al/Al2Ca composites are compared to existing conductor materials to show how implementation could affect installation and performance.

Muscle RANK is a key regulator of Ca2+ storage, SERCA activity, and function of fast-twitch skeletal muscles.

PubMed

Dufresne, Sébastien S; Dumont, Nicolas A; Boulanger-Piette, Antoine; Fajardo, Val A; Gamu, Daniel; Kake-Guena, Sandrine-Aurélie; David, Rares Ovidiu; Bouchard, Patrice; Lavergne, Éliane; Penninger, Josef M; Pape, Paul C; Tupling, A Russell; Frenette, Jérôme

2016-04-15

Receptor-activator of nuclear factor-κB (RANK), its ligand RANKL, and the soluble decoy receptor osteoprotegerin are the key regulators of osteoclast differentiation and bone remodeling. Here we show that RANK is also expressed in fully differentiated myotubes and skeletal muscle. Muscle RANK deletion has inotropic effects in denervated, but not in sham, extensor digitorum longus (EDL) muscles preventing the loss of maximum specific force while promoting muscle atrophy, fatigability, and increased proportion of fast-twitch fibers. In denervated EDL muscles, RANK deletion markedly increased stromal interaction molecule 1 content, a Ca(2+)sensor, and altered activity of the sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) modulating Ca(2+)storage. Muscle RANK deletion had no significant effects on the sham or denervated slow-twitch soleus muscles. These data identify a novel role for RANK as a key regulator of Ca(2+)storage and SERCA activity, ultimately affecting denervated skeletal muscle function. Copyright © 2016 the American Physiological Society.

Muscle RANK is a key regulator of Ca2+ storage, SERCA activity, and function of fast-twitch skeletal muscles

PubMed Central

Dufresne, Sébastien S.; Dumont, Nicolas A.; Boulanger-Piette, Antoine; Fajardo, Val A.; Gamu, Daniel; Kake-Guena, Sandrine-Aurélie; David, Rares Ovidiu; Bouchard, Patrice; Lavergne, Éliane; Penninger, Josef M.; Pape, Paul C.; Tupling, A. Russell

2016-01-01

Receptor-activator of nuclear factor-κB (RANK), its ligand RANKL, and the soluble decoy receptor osteoprotegerin are the key regulators of osteoclast differentiation and bone remodeling. Here we show that RANK is also expressed in fully differentiated myotubes and skeletal muscle. Muscle RANK deletion has inotropic effects in denervated, but not in sham, extensor digitorum longus (EDL) muscles preventing the loss of maximum specific force while promoting muscle atrophy, fatigability, and increased proportion of fast-twitch fibers. In denervated EDL muscles, RANK deletion markedly increased stromal interaction molecule 1 content, a Ca2+ sensor, and altered activity of the sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) modulating Ca2+ storage. Muscle RANK deletion had no significant effects on the sham or denervated slow-twitch soleus muscles. These data identify a novel role for RANK as a key regulator of Ca2+ storage and SERCA activity, ultimately affecting denervated skeletal muscle function. PMID:26825123

Variations in iron and calcium abundances during solar flares

NASA Astrophysics Data System (ADS)

Antonucci, E.; Martin, R.

1995-07-01

Evidence for variations in iron and calcium abundances during the impulsive phase of solar flares has been obtained by analyzing the Ca XIX and Fe XXV spectra, detected with the Bent Crystal Spectrometer of the Solar Maximum Mission. The plasma thermal conditions have been investigated by considering different temperature indicators: namely, the temperatures TCa and TFe, derived from the intensity ratios of the dielectronic recombination satellites to the resonance line, and the temperature TCaFe, calculated from the ratio of the resonance lines of Ca XIX and Fe XXV, which is also depending on the Fe/Ca abundance ratio. The observed values of TCa and TFe can be ascribed to the specific characteristics of the plasma therma distribution, the corresponding values of TCaFe can be explained by allowing also for variations in the Fe/Ca abundance ratio relative to the photospheric ratio by a factor within 0.2 and 2.4. According to the observed abundance variations, the events analyzed can be divided in Ca-rich and Fe-rich flares.

Intracellular Ca2+ transients in mouse soleus muscle after hindlimb unloading and reloading

NASA Technical Reports Server (NTRS)

Ingalls, C. P.; Warren, G. L.; Armstrong, R. B.; Hamilton, S. L. (Principal Investigator)

1999-01-01

The objective of this study was to determine whether altered intracellular Ca(2+) handling contributes to the specific force loss in the soleus muscle after unloading and/or subsequent reloading of mouse hindlimbs. Three groups of female ICR mice were studied: 1) unloaded mice (n = 11) that were hindlimb suspended for 14 days, 2) reloaded mice (n = 10) that were returned to their cages for 1 day after 14 days of hindlimb suspension, and 3) control mice (n = 10) that had normal cage activity. Maximum isometric tetanic force (P(o)) was determined in the soleus muscle from the left hindlimb, and resting free cytosolic Ca(2+) concentration ([Ca(2+)](i)), tetanic [Ca(2+)](i), and 4-chloro-m-cresol-induced [Ca(2+)](i) were measured in the contralateral soleus muscle by confocal laser scanning microscopy. Unloading and reloading increased resting [Ca(2+)](i) above control by 36% and 24%, respectively. Although unloading reduced P(o) and specific force by 58% and 24%, respectively, compared with control mice, there was no difference in tetanic [Ca(2+)](i). P(o), specific force, and tetanic [Ca(2+)](i) were reduced by 58%, 23%, and 23%, respectively, in the reloaded animals compared with control mice; however, tetanic [Ca(2+)](i) was not different between unloaded and reloaded mice. These data indicate that although hindlimb suspension results in disturbed intracellular Ca(2+) homeostasis, changes in tetanic [Ca(2+)](i) do not contribute to force deficits. Compared with unloading, 24 h of physiological reloading in the mouse do not result in further changes in maximal strength or tetanic [Ca(2+)](i).

Quantifying Ca2+ release and inactivation of Ca2+ release in fast- and slow-twitch muscles.

PubMed

Barclay, C J

2012-12-01

The aims of this study were to quantify the Ca(2+) release underlying twitch contractions of mammalian fast- and slow-twitch muscle and to comprehensively describe the transient inactivation of Ca(2+) release following a stimulus. Experiments were performed using bundles of fibres from mouse extensor digitorum longus (EDL) and soleus muscles. Ca(2+) release was quantified from the amount of ATP used to remove Ca(2+) from the myoplasm following stimulation. ATP turnover by crossbridges was blocked pharmacologically (N-benzyl-p-toluenesulphonamide for EDL, blebbistatin for soleus) and muscle heat production was used as an index of Ca(2+) pump ATP turnover. At 20°C, Ca(2+) release in response to a single stimulus was 34 and 84 μmol (kg muscle)(-1) for soleus and EDL, respectively, and increased with temperature (30°C: soleus, 61 μmol kg(-1); EDL, 168 μmol kg(-1)). Delivery of another stimulus within 100 ms of the first produced a smaller Ca(2+) release. The maximum magnitude of the decrease in Ca(2+) release was greater in EDL than soleus. Ca(2+) release recovered with an exponential time course which was faster in EDL (mean time constant at 20°C, 32.1 ms) than soleus (65.6 ms) and faster at 30°C than at 20°C. The amounts of Ca(2+) released and crossbridge cycles performed are consistent with a scheme in which Ca(2+) binding to troponin-C allowed an average of ∼1.7 crossbridge cycles in the two muscles.

Quantifying Ca2+ release and inactivation of Ca2+ release in fast- and slow-twitch muscles

PubMed Central

Barclay, C J

2012-01-01

The aims of this study were to quantify the Ca2+ release underlying twitch contractions of mammalian fast- and slow-twitch muscle and to comprehensively describe the transient inactivation of Ca2+ release following a stimulus. Experiments were performed using bundles of fibres from mouse extensor digitorum longus (EDL) and soleus muscles. Ca2+ release was quantified from the amount of ATP used to remove Ca2+ from the myoplasm following stimulation. ATP turnover by crossbridges was blocked pharmacologically (N-benzyl-p-toluenesulphonamide for EDL, blebbistatin for soleus) and muscle heat production was used as an index of Ca2+ pump ATP turnover. At 20°C, Ca2+ release in response to a single stimulus was 34 and 84 μmol (kg muscle)−1 for soleus and EDL, respectively, and increased with temperature (30°C: soleus, 61 μmol kg−1; EDL, 168 μmol kg−1). Delivery of another stimulus within 100 ms of the first produced a smaller Ca2+ release. The maximum magnitude of the decrease in Ca2+ release was greater in EDL than soleus. Ca2+ release recovered with an exponential time course which was faster in EDL (mean time constant at 20°C, 32.1 ms) than soleus (65.6 ms) and faster at 30°C than at 20°C. The amounts of Ca2+ released and crossbridge cycles performed are consistent with a scheme in which Ca2+ binding to troponin-C allowed an average of ∼1.7 crossbridge cycles in the two muscles. PMID:23027818

Matching of sarcoplasmic reticulum and contractile properties in rat fast- and slow-twitch muscle fibres.

PubMed

Trinh, Huong H; Lamb, Graham D

2006-07-01

1. The twitch characteristics (fast-twitch or slow-twitch) of skeletal muscle fibres are determined not only by the contractile apparatus properties of the fibre, but also by the time-course of Ca2+ release and re-uptake by the sarcoplasmic reticulum (SR). The present study examined, in individual fibres from non-transforming muscle of the rat, whether particular SR properties are matched to the contractile apparatus properties of the fibre, in particular in the case of fibres with fast-twitch contractile apparatus located in a slow-twitch muscle, namely the soleus. 2. Force was recorded in single, mechanically skinned fibres from extensor digitorum longus (EDL), gastrocnemius, peroneus longus and soleus muscles. Using repeated cycles in which the SR was emptied of all releasable Ca2+ and then reloaded, it was possible to determine the relative amount of Ca2+ present in the SR endogenously, the maximum SR capacity and the rate of Ca2+ loading. The sensitivity of the contractile apparatus to Ca2+ and Sr2+ was used to classify the fibres as fast-twitch (FT), slow-twitch (ST) or mixed (< 3% of the fibres examined) and thereby identify the likely troponin C and myosin heavy chain types present. 3. There was no significant difference in SR properties between the groups of FT fibres obtained from the four different muscles, including soleus. Despite some overlap in the SR properties of individual fibres between the FT and ST groups, the properties of the FT fibres in all four muscles studied were significantly different from those of the ST and mixed fibres. 4. In general, in FT fibres the SR had a larger capacity and the endogenous Ca2+ content was a relatively lower percentage of maximum compared with ST fibres. Importantly, in terms of their SR properties, FT fibres from soleus muscle more closely resembled FT fibres from other muscles than they did ST fibres from soleus muscle.

Phosphorus recovery from biogas fermentation liquid by Ca-Mg loaded biochar.

PubMed

Fang, Ci; Zhang, Tao; Li, Ping; Jiang, Rongfeng; Wu, Shubiao; Nie, Haiyu; Wang, Yingcai

2015-03-01

Shortage in phosphorus (P) resources and P wastewater pollution is considered as a serious problem worldwide. The application of modified biochar for P recovery from wastewater and reuse of recovered P as agricultural fertilizer is a preferred process. This work aims to develop a calcium and magnesium loaded biochar (Ca-Mg/biochar) application for P recovery from biogas fermentation liquid. The physico-chemical characterization, adsorption efficiency, adsorption selectivity, and postsorption availability of Ca-Mg/biochar were investigated. The synthesized Ca-Mg/biochar was rich in organic functional groups and in CaO and MgO nanoparticles. With the increase in synthesis temperature, the yield decreased, C content increased, H content decreased, N content remained the same basically, and BET surface area increased. The P adsorption of Ca-Mg/biochar could be accelerated by nano-CaO and nano-MgO particles and reached equilibrium after 360min. The process was endothermic, spontaneous, and showed an increase in the disorder of the solid-liquid interface. Moreover, it could be fitted by the Freundlich model. The maximum P adsorption amounts were 294.22, 315.33, and 326.63mg/g. The P adsorption selectivity of Ca-Mg/biochar could not be significantly influenced by the typical pH level of biogas fermentation liquid. The nano-CaO and nano-MgO particles of Ca-Mg/biochar could reduce the negative interaction effects of coexisting ions. The P releasing amounts of postsorption Ca-Mg/biochar were in the order of Ca-Mg/B600>Ca-Mg/B450>Ca-Mg/B300. Results revealed that postsorption Ca-Mg/biochar can continually release P and is more suitable for an acid environment. Copyright © 2014. Published by Elsevier B.V.

An oxidized metabolite of linoleic acid increases intracellular calcium in rat adrenal glomerulosa cells.

PubMed

Payet, Marcel D; Goodfriend, Theodore L; Bilodeau, Lyne; Mackendale, Cherilu; Chouinard, Lucie; Gallo-Payet, Nicole

2006-12-01

EKODE, an epoxy-keto derivative of linoleic acid, was previously shown to stimulate aldosterone secretion in rat adrenal glomerulosa cells. In the present study, we investigated the effect of exogenous EKODE on cytosolic [Ca(2+)] increase and aimed to elucidate the mechanism involved in this process. Through the use of the fluorescent Ca(2+)-sensitive dye Fluo-4, EKODE was shown to rapidly increase intracellular [Ca(2+)] ([Ca(2+)](i)) along a bell-shaped dose-response relationship with a maximum peak at 5 microM. Experiments performed in the presence or absence of Ca(2+) revealed that this increase in [Ca(2+)](i) originated exclusively from intracellular pools. EKODE-induced [Ca(2+)](i) increase was blunted by prior application of angiotensin II, Xestospongin C, and cyclopiazonic acid, indicating that inositol trisphosphate (InsP(3))-sensitive Ca(2+) stores can be mobilized by EKODE despite the absence of InsP(3) production. Accordingly, EKODE response was not sensitive to the phospholipase C inhibitor U-73122. EKODE mobilized a Ca(2+) store included in the thapsigargin (TG)-sensitive stores, although the interaction between EKODE and TG appears complex, since EKODE added at the plateau response of TG induced a rapid drop in [Ca(2+)](i). 9-oxo-octadecadienoic acid, another oxidized derivative of linoleic acid, also increases [Ca(2+)](i), with a dose-response curve similar to EKODE. However, arachidonic and linoleic acids at 10 microM failed to increase [Ca(2+)](i) but did reduce the amplitude of the response to EKODE. It is concluded that EKODE mobilizes Ca(2+) from an InsP(3)-sensitive store and that this [Ca(2+)](i) increase is responsible for aldosterone secretion by glomerulosa cells. Similar bell-shaped dose-response curves for aldosterone and [Ca(2+)](i) increases reinforce this hypothesis.

Late-glacial and Holocene records of fire and vegetation from Cradle Mountain National Park, Tasmania, Australia

NASA Astrophysics Data System (ADS)

Stahle, Laura N.; Chin, Hahjung; Haberle, Simon; Whitlock, Cathy

2017-12-01

Fire activity was reconstructed at five sites and vegetation history at three sites in northwest Tasmania, Australia in order to examine the climate and human drivers of environmental change in the region. Watershed-scale reconstructions of fire were compared to regional vegetation history. Fire activity was very low until ca. 12,000 cal yr BP. An early-Holocene fire maximum, ca. 11,800-9800 cal yr BP, occurred during the warmest interval of the Holocene as recorded by regional paleoclimate proxy records. This period of elevated burning was also coincident with an increase in arboreal sclerophyll plant taxa. A maximum in rainforest taxa occurred at ca. 8500-5800 cal yr BP concurrent with sharply diminished biomass burning compared with the early Holocene. The increase in rainforest taxa is attributed to elevated effective moisture during this period. Conditions were drier and variable in the late Holocene as compared with earlier periods. A rise in fire activity at ca. 4800-3200 cal yr BP was accompanied by an increase in sclerophyll taxa and decline of rainforest and subalpine taxa. Elevated palynological richness during the late Holocene co-occurred with high levels of charcoal suggesting that fires promoted high floristic diversity. At Cradle Mountain, there is no clear evidence that fire regimes or vegetation were extensively modified by humans prior to European settlement. Climate was the primary driver of fire activity over millennial timescales as explained by the close relationship between charcoal and climate proxy data.

Thirty Thousand Years of Vegetation Changes in the Alabama Hills, Owens Valley, California

NASA Astrophysics Data System (ADS)

Koehler, Peter A.; Anderson, R. Scott

1995-03-01

Twenty packrat ( Neotoma) middens recovered from three sites (1265-1535 m) in the Alabama Hills, Inyo County, California, provide a ca. 31,450-yr record of vegetation change. Located ca. 7 km east of the Sierra Nevada, the middens document that Utah juniper ( Juniperus osteosperma), Joshua tree ( Yucca brevifolia), and bitterbush ( Purshia tridentata) occupied the site between 31,450 and 19,070 yr B.P. Joshua tree and bitterbush departed by ca. 17,760 yr B.P., with cliffrose ( Purshia mexicana) and joint-fir ( Ephedra viridis) appearing. By 13,350 yr B.P., blackbush ( Coleogyne ramosissima) and cholla ( Opuntia echinocarpa) entered the record. Between 9540 and 7990 yr B.P., Utah juniper and other species now extralocal to the sites departed and modern components such as wolfberry ( Lycium andersonii) and rubber rabbitbrush ( Chrysothamnus teretifolius) appeared. The middle Holocene records little variation in plant macrofossil composition; however, pollen analysis reflects an increase in aquatic pollen types which might suggest more-open conditions. The transition to the modern vegetation associations at the sites occurred after ca. 2800 yr B.P. The record from the Alabama Hills correlates well with that of other regional vegetation data but documents conditions of increasing aridity earlier than many other packrat midden sites. A shift in understory vegetation between 19,070 and 17,760 yr B.P. may reflect a transition from glacial maximum to post-maximum conditions in the eastern Sierra Nevada.

Heat of combustion of tantalum-tungsten oxide thermite composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cervantes, Octavio G.; Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616; Kuntz, Joshua D.

2010-12-15

The heat of combustion of two distinctly synthesized stoichiometric tantalum-tungsten oxide energetic composites was investigated by bomb calorimetry. One composite was synthesized using a sol-gel (SG) derived method in which micrometric-scale tantalum is immobilized in a tungsten oxide three-dimensional nanostructured network structure. The second energetic composite was made from the mixing of micrometric-scale tantalum and commercially available (CA) nanometric tungsten oxide powders. The energetic composites were consolidated using the spark plasma sintering (SPS) technique under a 300 MPa pressure and at temperatures of 25, 400, and 500 C. For samples consolidated at 25 C, the density of the CA compositemore » is 61.65 {+-} 1.07% in comparison to 56.41 {+-} 1.19% for the SG derived composite. In contrast, the resulting densities of the SG composite are higher than the CA composite for samples consolidated at 400 and 500 C. The theoretical maximum density for the SG composite consolidated to 400 and 500 C are 81.30 {+-} 0.58% and 84.42 {+-} 0.62%, respectively. The theoretical maximum density of the CA composite consolidated to 400 and 500 C are 74.54 {+-} 0.80% and 77.90 {+-} 0.79%, respectively. X-ray diffraction analyses showed an increase of pre-reaction of the constituents with an increase in the consolidation temperature. The increase in pre-reaction results in lower stored energy content for samples consolidated to 400 and 500 C in comparison to samples consolidated at 25 C. (author)« less

Bingham fluid behavior of plagioclase-bearing basaltic magma: Approach from laboratory viscosity measurements

NASA Astrophysics Data System (ADS)

Ishibashi, H.; Sato, H.

2010-12-01

Datasets of one atmosphere high temperature rotational viscometry of the Fuji 1707 basalt (Ishibashi, 2009) were analyzed based on the Bingham fluid model, and both yield stress and Bingham viscosity were determined. Reproducibility of the dataset by the Bingham fluid model was slightly better than that by the power law fluid modes adopted in our previous study although both the fluid models well represent the dataset in practical perspective. The relation between Bingham viscosity and crystallinity was compared with the Krieger-Dougherty equation, and both the maximum packing fraction of crystals and intrinsic viscosity for Bingham viscosity were determined ca. 0.45 and ca. 5.25, respectively, revealing that the maximum packing fraction decreased and intrinsic viscosity increased concomitantly with the increase in shape-anisotropy of crystals. However, the obtained value of the product of the maximum packing fraction and intrinsic viscosity (= ca. 2.36) was similar to that of uniform, isotropic-shaped particles (= 2.5), indicating that the effect of crystal shape-anisotropy on Bingham viscosity might be predicted only by change of the maximum packing fraction. Finite yield stress was detected for crystallinity larger than 0.133; it increased with crystallinity which suggests that critical crystallinity for onset of yield stress is at least lower than 0.133. The upper limit value of the critical crystallinity resembles the value calculated numerically for randomly oriented uniform particles by Saar et al. (2001) (0.10-0.15 for width/length ratio of 0.1-0.2, which is similar to the ratios in the basalt) whereas crystals in the basalt were moderately parallel arranged and their sizes vary significantly. That fact might be explained as follows; effects of parallel arrangement and size variation of crystals on the critical crystallinity are offset by the effect of variation in crystal shape-anisotropy, which suggests that shape-anisotropy distribution of crystals must be a critical factor for the onset of yield stress. Keywords: magma, viscosity, Bingham fluid, yield stress, plagioclase

Inorganic fouling mitigation by salinity cycling in batch reverse osmosis.

PubMed

Warsinger, David M; Tow, Emily W; Maswadeh, Laith A; Connors, Grace B; Swaminathan, Jaichander; Lienhard V, John H

2018-06-15

Enhanced fouling resistance has been observed in recent variants of reverse osmosis (RO) desalination which use time-varying batch or semi-batch processes, such as closed-circuit RO (CCRO) and pulse flow RO (PFRO). However, the mechanisms of batch processes' fouling resistance are not well-understood, and models have not been developed for prediction of their fouling performance. Here, a framework for predicting reverse osmosis fouling is developed by comparing the fluid residence time in batch and continuous (conventional) reverse osmosis systems to the nucleation induction times for crystallization of sparingly soluble salts. This study considers the inorganic foulants calcium sulfate (gypsum), calcium carbonate (calcite), and silica, and the work predicts maximum recovery ratios for the treatment of typical water sources using batch reverse osmosis (BRO) and continuous reverse osmosis. The prediction method is validated through comparisons to the measured time delay for CaSO 4 membrane scaling in a bench-scale, recirculating reverse osmosis unit. The maximum recovery ratio for each salt solution (CaCO 3 , CaSO 4 ) is individually predicted as a function of inlet salinity, as shown in contour plots. Next, the maximum recovery ratios of batch and conventional RO are compared across several water sources, including seawater, brackish groundwater, and RO brine. Batch RO's shorter residence times, associated with cycling from low to high salinity during each batch, enable significantly higher recovery ratios and higher salinity than in continuous RO for all cases examined. Finally, representative brackish RO brine samples were analyzed to determine the maximum possible recovery with batch RO. Overall, the induction time modeling methodology provided here can be used to allow batch RO to operate at high salinity and high recovery, while controlling scaling. The results show that, in addition to its known energy efficiency improvement, batch RO has superior inorganic fouling resistance relative to conventional RO. Copyright © 2018 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gerthoffer, W.T.; Murphey, K.A.; Khoyi, M.A.

Previous studies have shown that muscarinic activation of airway smooth muscle in low Ca++ solutions increases myosin phosphorylation without increasing tension. Blocking Ca++ influx reduced phosphorylation, but not to basal levels. It was proposed that release of intracellular Ca++ contributed to dissociation of phosphorylation and contraction. To test this hypothesis the effects of ryanodine were studied under similar conditions. Ryanodine (10(-7) to 10(-5) M) antagonized caffeine-induced contraction of canine tracheal smooth muscle. Ryanodine also reduced carbachol-induced contractions and carbachol-induced myosin phosphorylation. The effect of ryanodine on potassium and serotonin-induced contractions was also investigated to test for a nonspecific inhibitory effect.more » In contrast to the effect on carbachol responses, ryanodine (10(-5) M) potentiated the contractile response to low concentrations of serotonin and potassium, but had no effect on the maximum response to either stimulant. Carbachol (10(-6) M) and ryanodine (10(-5) M) both significantly decreased /sup 45/Ca++ content of tracheal muscle. The effect of ryanodine and carbachol together on /sup 45/Ca++ content was not greater than either drug alone suggesting that ryanodine reduces the caffeine and carbachol responses by depleting releaseable Ca++ stores. Ryanodine significantly reduced Ca++-induced contraction and myosin phosphorylation in carbachol-stimulated muscle, suggesting that some of the Ca++ responsible for elevated phosphorylation is released from the sarcoplasmic reticulum.« less

The glacial/deglacial history of sedimentation in Bear Lake, Utah and Idaho

USGS Publications Warehouse

Rosenbaum, J.G.; Heil, C.W.

2009-01-01

Bear Lake, in northeastern Utah and southern Idaho, lies in a large valley formed by an active half-graben. Bear River, the largest river in the Great Basin, enters Bear Lake Valley ???15 km north of the lake. Two 4-m-long cores provide a lake sediment record extending back ???26 cal k.y. The penetrated section can be divided into a lower unit composed of quartz-rich clastic sediments and an upper unit composed largely of endogenic carbonate. Data from modern fluvial sediments provide the basis for interpreting changes in provenance of detrital material in the lake cores. Sediments from small streams draining elevated topography on the east and west sides of the lake are characterized by abundant dolomite, high magnetic susceptibility (MS) related to eolian magnetite, and low values of hard isothermal remanent magnetization (HIRM, indicative of hematite content). In contrast, sediments from the headwaters of the Bear River in the Uinta Mountains lack carbonate and have high HIRM and low MS. Sediments from lower reaches of the Bear River contain calcite but little dolomite and have low values of MS and HIRM. These contrasts in catchment properties allow interpretation of the following sequence from variations in properties of the lake sediment: (1) ca. 26 cal ka-onset of glaciation; (2) ca. 26-20 cal ka-quasicyclical, millennial-scale variations in the concentrations of hematite-rich glacial fl our derived from the Uinta Mountains, and dolomite- and magnetite-rich material derived from the local Bear Lake catchment (reflecting variations in glacial extent); (3) ca. 20-19 cal ka-maximum content of glacial fl our; (4) ca. 19-17 cal ka-constant content of Bear River sediment but declining content of glacial fl our from the Uinta Mountains; (5) ca. 17-15.5 cal ka-decline in Bear River sediment and increase in content of sediment from the local catchment; and (6) ca. 15.5-14.5 cal ka-increase in content of endogenic calcite at the expense of detrital material. The onset of glaciation indicated in the Bear Lake record postdates the initial rise of Lake Bonneville and roughly corresponds to the Stansbury shoreline. The lake record indicates that maximum glaciation occurred as Lake Bonneville reached its maximum extent ca. 20 cal ka and that deglaciation was under way while Lake Bonneville remained at its peak. The transition from siliciclastic to carbonate sedimentation probably indicates increasingly evaporative conditions and may coincide with the climatically driven fall of Lake Bonneville from the Provo shoreline. Although lake levels fluctuated during the Younger Dryas, the Bear Lake record for this period is more consistent with drier conditions, rather than cooler, moister conditions interpreted from many studies from western North America. Copyright ?? 2009 The Geological Society of America.

Control of calcium release and the effect of ryanodine in skinned muscle fibres of the toad.

PubMed Central

Lamb, G D; Stephenson, D G

1990-01-01

1. Skinned muscle fibres from the toad were used to investigate the roles of T-system membrane potential and Ca2+ in controlling the calcium release channels of the sarcoplasmic reticulum (SR). 2. Replacement of K+ in the bathing solution with Na+ produced a large contraction which could last for 30 s or more under certain circumstances. This prolonged contraction could be quickly and completely terminated by repolarizing the fibre in the K+ solution and then immediately re-initiated by returning to the Na+ solution. These data indicate that the membrane potential tightly controlled the substantial and prolonged release of calcium. 3. T-system depolarization in the presence of 10 mM-free EGTA (pCa greater than 9) markedly depleted the SR of Ca2+. This implies that depolarization of the T-system can still trigger substantial release of Ca2+ from the SR even when the myoplasmic [Ca2+] is very low and very heavily buffered by EGTA. 4. When the SR was heavily loaded with Ca2+, substitution of a weakly buffered high [Ca2+] solution (pCa 5.4, 50 microM-EGTA) could produce a small to moderate, transient contraction taking between 3 and 12 s to reach a peak and lasting 30 s or more. 5. This contraction may be produced at least partly by 'calcium-induced calcium release' as ruthenium red (2 microM) completely blocked the responses. Moreover, repeated substitutions produced successively smaller responses in parallel with the 'run-down' of the depolarization-induced contractions. 6. Depolarization could always produce an additional large and fast response at any stage during a 'Ca2(+)-induced' response. 7. In the presence of 25 microM-ryanodine, the rapid contraction produced by T-system depolarization was prolonged and could not be stopped by repolarization. During and after this contraction no depolarizing stimulus could induce a further contraction, even though in some fibres addition of 30 mM-caffeine produced a maximum response which indicated that there was still a substantial amount of calcium in the SR. 8. At pCa 6.4, 25 microM-ryanodine could itself induce a substantial slow contracture in a normally polarized fibre within 30-60 s, after which little or no response could be induced by T-system depolarization. At higher concentrations (25 microM) ryanodine produced a near-maximum contraction in only a few seconds.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:2167367

Detrital and volcanic zircon U-Pb ages from southern Mendoza (Argentina): An insight on the source regions in the northern part of the Neuquén Basin

NASA Astrophysics Data System (ADS)

Naipauer, Maximiliano; Tapia, Felipe; Mescua, José; Farías, Marcelo; Pimentel, Marcio M.; Ramos, Victor A.

2015-12-01

The infill of the Neuquén Basin recorded the Meso-Cenozoic geological and tectonic evolution of the southern Central Andes being an excellent site to investigate how the pattern of detrital zircon ages varies trough time. In this work we analyze the U-Pb (LA-MC-ICP-MS) zircon ages from sedimentary and volcanic rocks related to synrift and retroarc stages of the northern part of the Neuquén Basin. These data define the crystallization age of the synrift volcanism at 223 ± 2 Ma (Cerro Negro Andesite) and the maximum depositional age of the original synrift sediments at ca. 204 Ma (El Freno Formation). Two different pulses of rifting could be recognized according to the absolute ages, the oldest developed during the Norian and the younger during the Rhaetian-Sinemurian. The source regions of the El Freno Formation show that the Choiyoi magmatic province was the main source rock of sediment supply. An important amount of detrital zircons with Triassic ages was identified and interpreted as a source area related to the synrift magmatism. The maximum depositional age calculated for the Tordillo Formation in the Atuel-La Valenciana depocenter is at ca. 149 Ma; as well as in other places of the Neuquén Basin, the U-Pb ages calculated in the Late Jurassic Tordillo Formation do not agree with the absolute age of the Kimmeridgian-Tithonian boundary (ca. 152 Ma). The main source region of sediment in the Tordillo Formation was the Andean magmatic arc. Basement regions were also present with age peaks at the Carboniferous, Neoproterozoic, and Mesoproterozoic; these regions were probably located to the east in the San Rafael Block. The pattern of zircon ages summarized for the Late Jurassic Tordillo and Lagunillas formations were interpreted as a record of the magmatic activity during the Triassic and Jurassic in the southern Central Andes. A waning of the magmatism is inferred to have happened during the Triassic. The evident lack of ages observed around ca. 200 Ma suggests cessation of the synrift magmatism. The later increase in magmatic activity during the Early Jurassic is attributed to the onset of Andean subduction, with maximum peaks at ca. 191 and 179 Ma. The trough at ca. 165 Ma and the later increase in the Late Jurassic could be explained by changes in the relative convergence rate in the Andean subduction regime, or by the shift to a more mafic composition of the magmatism with minor zircon fertility.

Spring molybdenum enrichment in scallop shells: a potential tracer of diatom productivity in temperate coastal environments (Brittany, NW France)

NASA Astrophysics Data System (ADS)

Barats, A.; Amouroux, D.; Pécheyran, C.; Chauvaud, L.; Thébault, J.; Donard, O. F. X.

2010-01-01

Skeletal molybdenum/calcium ([Mo]/[Ca])shell ratios were examined in shells of the Great Scallop Pecten maximus collected in temperate coastal environments of Western Europe (42 to 49° N). These ratios were determined by quantitative LA-ICP-MS analyses of daily striae taken every third day (i.e. a temporal resolution of 3 days) in 36 flat valves (2-years old; 3 shells/year). Variations of ([Mo]/[Ca])shell ratios were significant and reproducible for scallops from the same population, from different years (1998-2004) and temperate coastal locations (NW France). The [Mo]/[Ca])shell ratios exhibit typical profiles characterized by a background content, below the detection limit for this method (<0.003 μmol/mol) for most of the shell growth period, which is punctuated by a significant transient enrichment (0.031-2.1 μmol/mol) mainly occurring from May to June. The Bay of Brest (France) was investigated in particular because of its long term observations on scallop communities, environmental variables, and high resolution analyses of dissolved Mo in bottom seawater in 2000. In 2000, dissolved Mo exhibited a significant increase in concentration just preceding the maximum ([Mo]/[Ca])shell ratio. Both the intense monitoring survey in 2000 and over the 7-year period indicates that the ([Mo]/[Ca])shell maximum is directly influenced by spring changes of environmental conditions at the sediment water interface (SWI), occurring subsequent to the intense and periodic spring bloom. Spring maxima of ([Mo]/[Ca])shell ratios are closely correlated to the extent of silicic acid and nitrate depletion in seawater between winter and late spring (r2=0.878 and 0.780, p<0.05, n=6) that reflects diatom uptake and productivity in the Bay of Brest. The Mo inputs in bottom waters and subsequent shell enrichment are thus suggested to be directly or indirectly influenced by such biogenic material input at the SWI. The [Mo]/[Ca])shell records thus reveal unexpected biogeochemical cycles of Mo influenced by coastal spring productivity, faithfully recorded in scallop shells.

Beat-to-Beat Variation in Periodicity of Local Calcium Releases Contributes to Intrinsic Variations of Spontaneous Cycle Length in Isolated Single Sinoatrial Node Cells

PubMed Central

Monfredi, Oliver; Maltseva, Larissa A.; Spurgeon, Harold A.; Boyett, Mark R.; Lakatta, Edward G.; Maltsev, Victor A.

2013-01-01

Spontaneous, submembrane local Ca2+ releases (LCRs) generated by the sarcoplasmic reticulum in sinoatrial nodal cells, the cells of the primary cardiac pacemaker, activate inward Na+/Ca2+-exchange current to accelerate the diastolic depolarization rate, and therefore to impact on cycle length. Since LCRs are generated by Ca2+ release channel (i.e. ryanodine receptor) openings, they exhibit a degree of stochastic behavior, manifested as notable cycle-to-cycle variations in the time of their occurrence. Aim The present study tested whether variation in LCR periodicity contributes to intrinsic (beat-to-beat) cycle length variability in single sinoatrial nodal cells. Methods We imaged single rabbit sinoatrial nodal cells using a 2D-camera to capture LCRs over the entire cell, and, in selected cells, simultaneously measured action potentials by perforated patch clamp. Results LCRs begin to occur on the descending part of the action potential-induced whole-cell Ca2+ transient, at about the time of the maximum diastolic potential. Shortly after the maximum diastolic potential (mean 54±7.7 ms, n = 14), the ensemble of waxing LCR activity converts the decay of the global Ca2+ transient into a rise, resulting in a late, whole-cell diastolic Ca2+ elevation, accompanied by a notable acceleration in diastolic depolarization rate. On average, cells (n = 9) generate 13.2±3.7 LCRs per cycle (mean±SEM), varying in size (7.1±4.2 µm) and duration (44.2±27.1 ms), with both size and duration being greater for later-occurring LCRs. While the timing of each LCR occurrence also varies, the LCR period (i.e. the time from the preceding Ca2+ transient peak to an LCR’s subsequent occurrence) averaged for all LCRs in a given cycle closely predicts the time of occurrence of the next action potential, i.e. the cycle length. Conclusion Intrinsic cycle length variability in single sinoatrial nodal cells is linked to beat-to-beat variations in the average period of individual LCRs each cycle. PMID:23826247

Biogenic Calcium Carbonate with Hierarchical Organic-Inorganic Composite Structure Enhancing the Removal of Pb(II) from Wastewater.

PubMed

Zhou, Xueli; Liu, Weizhen; Zhang, Jian; Wu, Can; Ou, Xinwen; Tian, Chen; Lin, Zhang; Dang, Zhi

2017-10-18

Calcium carbonate from geological sources (geo-CaCO 3 , e.g., calcite, aragonite) is used extensively in removing heavy metals from wastewater through replacement reaction. However, geo-CaCO 3 has an intrinsically compact crystalline structure that results in low efficiency in pollutant removal and thus its use may produce enormous sludge. In this work, biogenic calcium carbonate (bio-CaCO 3 ) derived from oyster shells was used to remove Pb(II) from wastewater and found to significantly outperform geo-CaCO 3 (calcite). The thermodynamics study revealed that the maximum adsorption capacity of bio-CaCO 3 for Pb(II) was three times that of geo-CaCO 3 , reaching up to 1667 mg/g. The kinetics study disclosed that the dissolution kinetics and the rate of intraparticle diffusion of bio-CaCO 3 were faster than those of geo-CaCO 3 . Extensive mechanism research through X-ray powder diffraction (XRD), scanning electron microscopy (SEM), N 2 adsorption/desorption test and mercury intrusion porosimetry showed that the hierarchical porous organic-inorganic hybrid structure of bio-CaCO 3 expedited the dissolution of CaCO 3 to provide abundant CO 3 2- active sites and facilitated the permeation and diffusion of Pb(II) into the bulk solid phases. In addition, Fourier transform infrared spectroscopy (FTIR) study, X-ray photoelectron spectroscopy (XPS) analysis, and the examination of Pb(II) removal ability of bio-CaCO 3 after calcination indicated that the organic functional groups of bio-CaCO 3 also facilitated the immobilization of Pb(II) into CaCO 3 particles, although the major contribution was from the hierarchical porous structure of bio-CaCO 3 .

The Institute of Medicine, the Food and Drug Administration, and the calcium conundrum.

PubMed

Neupane, Shristi; Knohl, Stephen J

2014-08-01

In the present article we aim to bring forward the apparent disconnect between two US government-sponsored entities - the Institute of Medicine (IOM) and the Food and Drug Administration (FDA) - regarding the safe upper limit of Ca intake. In light of the 2011 US Congress-appointed IOM report indicating an upper limit of elemental Ca intake of 2000-2500 mg/d in adults (based on age group), it is perplexing that the FDA has not yet required a change on the labelling of over-the-counter Ca-containing antacids, some of which indicate an upper limit of elemental Ca intake of 2800-3000 mg/d. Even more concerning is that Ca intake is rarely from supplementation in isolation. National Health and Nutrition Examination Survey (NHANES) data from 2003-2006 indicate that mean dietary Ca intakes for males ranged from 871 to 1266 mg/d and for females from 748 to 968 mg/d depending on the age group. The estimated total Ca (diet + supplements) intake exceeded the upper limit in 5 % of the population older than 50 years. Furthermore, NHANES data from 1999-2000 indicate that when Ca is taken as part of an antacid preparation, patients often fail to report this as Ca intake. Thus, individuals taking the maximum allowable dose of supplemental Ca as antacids are at high risk for complications associated with excess Ca intake. Our hope is that by describing Ca homeostasis and highlighting the risks and dangers of Ca overload, the FDA will align its recommendation with the IOM and solve the current Ca conundrum in the USA for the sake of patient safety.

Superiority of biphasic over monophasic defibrillation shocks is attributable to less intracellular calcium transient heterogeneity.

PubMed

Hwang, Gyo-Seung; Tang, Liang; Joung, Boyoung; Morita, Norishige; Hayashi, Hideki; Karagueuzian, Hrayr S; Weiss, James N; Lin, Shien-Fong; Chen, Peng-Sheng

2008-09-02

The purpose of this study was to test the hypothesis that superiority of biphasic waveform (BW) over monophasic waveform (MW) defibrillation shocks is attributable to less intracellular calcium (Ca(i)) transient heterogeneity. The mechanism by which BW shocks have a higher defibrillation efficacy than MW shocks remains unclear. We simultaneously mapped epicardial membrane potential (Vm) and Ca(i) during 6-ms MW and 3-ms/3-ms BW shocks in 19 Langendorff-perfused rabbit ventricles. After shock, the percentage of depolarized area was plotted over time. The maximum (peak) post-shock values (VmP and Ca(i)P, respectively) were used to measure heterogeneity. Higher VmP and Ca(i)P imply less heterogeneity. The defibrillation thresholds for BW and MW shocks were 288 +/- 99 V and 399 +/- 155 V, respectively (p = 0.0005). Successful BW shocks had higher VmP (88 +/- 9%) and Ca(i)P (70 +/- 13%) than unsuccessful MW shocks (VmP 76 +/- 10%, p < 0.001; Ca(i)P 57 +/- 8%, p < 0.001) of the same shock strength. In contrast, for unsuccessful BW and MW shocks of the same shock strengths, the VmP and Ca(i)P were not significantly different. The MW shocks more frequently created regions of low Ca(i) surrounded by regions of high Ca(i) (post-shock Ca(i) sinkholes). The defibrillation threshold for MW and BW shocks became similar after disabling the sarcoplasmic reticulum (SR) with thapsigargin and ryanodine. The greater efficacy of BW shocks is directly related to their less heterogeneous effects on shock-induced SR Ca release and Ca(i) transients. Less heterogeneous Ca(i) transients reduces the probability of Ca(i) sinkhole formation, thereby preventing the post-shock reinitiation of ventricular fibrillation.

Intestinal absorption of calcium from calcium ascorbate in rats.

PubMed

Tsugawa, N; Yamabe, T; Takeuchi, A; Kamao, M; Nakagawa, K; Nishijima, K; Okano, T

1999-01-01

The intestinal absorption of calcium (Ca) from Ca ascorbate (Ca-AsA) was investigated in normal rats. Each animal was perorally administered either 5mg (low dose) or 10mg (high dose) of Ca in 1ml of distilled water as Ca-AsA, Ca carbonate (CaCO3), or Ca chloride (CaCl2), which were intrinsically labeled with 45Ca using 45CaCl2. The amount of radioactivity in plasma was measured periodically up to 34h after dosing, and pharmacokinetic parameters were calculated from the radioactivity in plasma. The time taken to reach the maximum 45Ca level (Tmax) did not differ among the three groups. The area under the plasma 45Ca level/time curve (AUCinfinity) value for the Ca-AsA group was significantly higher than those for the CaCO3 and the CaCl2 groups. The radioactivity at Tmax (Cmax) for the Ca-AsA group was significantly higher than those for the CaCO3 and the CaCl2 groups for the low dose, and comparable with or significantly higher than those for the CaCl2 and CaCO3 groups for the high dose. Similar results were observed for whole-body 45Ca retention. Radioactivity in the femur 34h after dosing was the highest in the Ca-AsA group and the lowest in the CaCO3 group. The rank order of solubility in water, the first fluid (pH 1.2, JP-1) of JPXIII disintegration medium, acetate buffer solution (pH 4.0), triethanolamine-malate buffer solution (pH 7.0) and ammonium chloride buffer solution (pH 10.0) at 37 degrees C was CaCl2 > Ca-AsA > CaCO3. In contrast, the rank order of the solubility in the second fluid (pH 6.8, JP-2) of JPXIII disintegration medium at 37 degrees C was Ca-AsA > CaCl2 > CaCO3. These results indicate that the absorbability of Ca from Ca-AsA is almost comparable with, or higher than, that from CaCl2 and significantly higher than that from CaCO3 because of its high degree of solubility in the intestine. Therefore, Ca-AsA would be useful as a Ca supplement with relatively high absorption from intestine.

Fouling Resistant CA/PVA/TiO2 Imprinted Membranes for Selective Recognition and Separation Salicylic Acid from Waste Water

PubMed Central

Yu, Xiaopeng; Mi, Xueyang; He, Zhihui; Meng, Minjia; Li, Hongji; Yan, Yongsheng

2017-01-01

Highly selective cellulose acetate (CA)/poly (vinyl alcohol) (PVA)/titanium dioxide (TiO2) imprinted membranes were synthesized by phase inversion and dip coating technique. The CA blend imprinted membrane was synthesized by phase inversion technique with CA as membrane matrix, polyethyleneimine (PEI) as the functional polymer, and the salicylic acid (SA) as the template molecule. The CA/PVA/TiO2 imprinted membranes were synthesized by dip coating of CA blend imprinted membrane in PVA and different concentration (0.05, 0.1, 0.2, 0.4 wt %) of TiO2 nanoparticles aqueous solution. The SEM analysis showed that the surface morphology of membrane was strongly influenced by the concentration of TiO2 nanoparticles. Compared with CA/PVA-TiO2(0.05, 0.1, 0.2%)-MIM, the CA/PVA-TiO2(0.4%)-MIM possessed higher membrane flux, kinetic equilibrium adsorption amount, binding capacity and better selectivity for SA. It was found that the pseudo-second-order kinetic model was studied to describe the kinetic of CA/PVA-TiO2(0.2%)-MIM judging by multiple regression analysis. Adsorption isotherm analysis indicated that the maximum adsorption capacity for SA were 24.43 mg g−1. Moreover, the selectivity coefficients of CA/PVA-TiO2 (0.2%)-MIM for SA relative to p-hydroxybenzoic acid (p-HB) and methyl salicylate (MS) were 3.87 and 3.55, respectively. PMID:28184369

Response of ryanodine receptor channels to Ca2+ steps produced by rapid solution exchange.

PubMed Central

Laver, D R; Curtis, B A

1996-01-01

We used a flow method for Ca2+ activation of sheep cardiac and rabbit skeletal ryanodine receptor (RyR) channels in lipid bilayers, which activated RyRs in < 20 ms and maintained a steady [Ca2+] for 5 s. [Ca2+] was rapidly altered by flowing Ca(2+)-buffered solutions containing 100 or 200 microM Ca2+ from a perfusion tube inserted in the cis, myoplasmic chamber above the bilayer. During steps from 0.1 to 100 microM, [Ca2+] reached 0.3 microM (activation threshold) and 10 microM (maximum Po) in times consistent with predictions of a solution exchange model. Immediately following rapid RyR activation, Po was 0.67 (cardiac) and 0.45 (skeletal) at a holding voltage of +40 mV (cis/trans). Po then declined (at constant [Ca2+]) in 70% of channels (n = 25) with time constants ranging from .5 to 15 s. The mechanism for Po decline, whether it be adaptation or inactivation, was not determined in this study. cis, 2 mM Mg2+ reduced the initial Po for skeletal RyRs to 0.21 and marginally slowed the declining phase. During very rapid falls in [Ca2+] from mM (inhibited) to sub-microM (sub-activating) levels, skeletal RyR did not open. We conclude the RyR gates responsible for Ca(2+)-dependent activation and inhibition of skeletal RyRs can gate independently. Images FIGURE 1 FIGURE 8 PMID:8842211

AmeriFlux CA-Let Alberta - Mixed Grass Prairie

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flanagan, Lawrence B.

This is the AmeriFlux version of the carbon flux data for the site CA-Let Alberta - Mixed Grass Prairie. Site Description - Latitude 49.43° N; Longitude 112.56° W, altitude 951 meters,Mixed Grass Prairie that includes the following major species: Agropyron spp. (Wheat Grasses), Tragopogon dubius (Goat’s Beard), Vicia americana (Wild Vetch), Koleria cristata (June Grass), Eurotia lanata (Winter Fat), Stipa comata (Spear Grass), Achillea millefolium (Yarrow); Artemisia frigida (Pasture Sage); Carex spp. (Sedges), Bouteloua gracilis (Blue Grama Grass). Maximum canopy height varies from year to year

The relationship between Q gamma and Ca release from the sarcoplasmic reticulum in skeletal muscle

PubMed Central

1991-01-01

Asymmetric membrane currents and fluxes of Ca2+ release were determined in skeletal muscle fibers voltage clamped in a Vaseline-gap chamber. The conditioning pulse protocol 1 for suppressing Ca2+ release and the "hump" component of charge movement current (I gamma), described in the first paper of this series, was applied at different test pulse voltages. The amplitude of the current suppressed during the ON transient reached a maximum at slightly suprathreshold test voltages (- 50 to -40 mV) and decayed at higher voltages. The component of charge movement current suppressed by 20 microM tetracaine also went through a maximum at low pulse voltages. This anomalous voltage dependence is thus a property of I gamma, defined by either the conditioning protocol or the tetracaine effect. A negative (inward-going) phase was often observed in the asymmetric current during the ON of depolarizing pulses. This inward phase was shown to be an intramembranous charge movement based on (a) its presence in the records of total membrane current, (b) its voltage dependence, with a maximum at slightly suprathreshold voltages, (c) its association with a "hump" in the asymmetric current, (d) its inhibition by interventions that reduce the "hump", (e) equality of ON and OFF areas in the records of asymmetric current presenting this inward phase, and (f) its kinetic relationship with the time derivative of Ca release flux. The nonmonotonic voltage dependence of the amplitude of the hump and the possibility of an inward phase of intramembranous charge movement are used as the main criteria in the quantitative testing of a specific model. According to this model, released Ca2+ binds to negatively charged sites on the myoplasmic face of the voltage sensor and increases the local transmembrane potential, thus driving additional charge movement (the hump). This model successfully predicts the anomalous voltage dependence and all the kinetic properties of I gamma described in the previous papers. It also accounts for the inward phase in total asymmetric current and in the current suppressed by protocol 1. According to this model, I gamma accompanies activating transitions at the same set of voltage sensors as I beta. Therefore it should open additional release channels, which in turn should cause more I gamma, providing a positive feedback mechanism in the regulation of calcium release. PMID:1650812

Contractile properties and sarcoplasmic reticulum calcium content in type I and type II skeletal muscle fibres in active aged humans

PubMed Central

Lamboley, C R; Wyckelsma, V L; Dutka, T L; McKenna, M J; Murphy, R M; Lamb, G D

2015-01-01

This study examined the contractile properties and sarcoplasmic reticulum (SR) Ca2+ content in mechanically skinned vastus lateralis muscle fibres of Old (70 ± 4 years) and Young (22 ± 3 years) humans to investigate whether changes in muscle fibre properties contribute to muscle weakness in old age. In type II fibres of Old subjects, specific force was reduced by ∼17% and Ca2+ sensitivity was also reduced (pCa50 decreased ∼0.05 pCa units) relative to that in Young. S-Glutathionylation of fast troponin I (TnIf) markedly increased Ca2+ sensitivity in type II fibres, but the increase was significantly smaller in Old versus Young (+0.136 and +0.164 pCa unit increases, respectively). Endogenous and maximal SR Ca2+ content were significantly smaller in both type I and type II fibres in Old subjects. In fibres of Young, the SR could be nearly fully depleted of Ca2+ by a combined caffeine and low Mg2+ stimulus, whereas in fibres of Old the amount of non-releasable Ca2+ was significantly increased (by > 12% of endogenous Ca2+ content). Western blotting showed an increased proportion of type I fibres in Old subjects, and increased amounts of calsequestrin-2 and calsequestrin-like protein. The findings suggest that muscle weakness in old age is probably attributable in part to (i) an increased proportion of type I fibres, (ii) a reduction in both maximum specific force and Ca2+ sensitivity in type II fibres, and also a decreased ability of S-glutathionylation of TnIf to counter the fatiguing effects of metabolites on Ca2+ sensitivity, and (iii) a reduction in the amount of releasable SR Ca2+ in both fibre types. Key points Muscle weakness in old age is due in large part to an overall loss of skeletal muscle tissue, but it remains uncertain how much also stems from alterations in the properties of the individual muscle fibres. This study examined the contractile properties and amount of stored intracellular calcium in single muscle fibres of Old (70 ± 4 years) and Young (22 ± 3 years) adults. The maximum level of force production (per unit cross-sectional area) in fast twitch fibres in Old subjects was lower than in Young subjects, and the fibres were also less sensitive to activation by calcium. The amount of calcium stored inside muscle fibres and available to trigger contraction was also lower in both fast- and slow-twitch muscle fibres in the Old subjects. These findings indicate that muscle weakness in old age stems in part from an impaired capacity for force production in the individual muscle fibres. PMID:25809942

Contractile properties and sarcoplasmic reticulum calcium content in type I and type II skeletal muscle fibres in active aged humans.

PubMed

Lamboley, C R; Wyckelsma, V L; Dutka, T L; McKenna, M J; Murphy, R M; Lamb, G D

2015-06-01

Muscle weakness in old age is due in large part to an overall loss of skeletal muscle tissue, but it remains uncertain how much also stems from alterations in the properties of the individual muscle fibres. This study examined the contractile properties and amount of stored intracellular calcium in single muscle fibres of Old (70 ± 4 years) and Young (22 ± 3 years) adults. The maximum level of force production (per unit cross-sectional area) in fast twitch fibres in Old subjects was lower than in Young subjects, and the fibres were also less sensitive to activation by calcium. The amount of calcium stored inside muscle fibres and available to trigger contraction was also lower in both fast- and slow-twitch muscle fibres in the Old subjects. These findings indicate that muscle weakness in old age stems in part from an impaired capacity for force production in the individual muscle fibres. This study examined the contractile properties and sarcoplasmic reticulum (SR) Ca(2+) content in mechanically skinned vastus lateralis muscle fibres of Old (70 ± 4 years) and Young (22 ± 3 years) humans to investigate whether changes in muscle fibre properties contribute to muscle weakness in old age. In type II fibres of Old subjects, specific force was reduced by ∼17% and Ca(2+) sensitivity was also reduced (pCa50 decreased ∼0.05 pCa units) relative to that in Young. S-Glutathionylation of fast troponin I (TnIf ) markedly increased Ca(2+) sensitivity in type II fibres, but the increase was significantly smaller in Old versus Young (+0.136 and +0.164 pCa unit increases, respectively). Endogenous and maximal SR Ca(2+) content were significantly smaller in both type I and type II fibres in Old subjects. In fibres of Young, the SR could be nearly fully depleted of Ca(2+) by a combined caffeine and low Mg(2+) stimulus, whereas in fibres of Old the amount of non-releasable Ca(2+) was significantly increased (by > 12% of endogenous Ca(2+) content). Western blotting showed an increased proportion of type I fibres in Old subjects, and increased amounts of calsequestrin-2 and calsequestrin-like protein. The findings suggest that muscle weakness in old age is probably attributable in part to (i) an increased proportion of type I fibres, (ii) a reduction in both maximum specific force and Ca(2+) sensitivity in type II fibres, and also a decreased ability of S-glutathionylation of TnIf to counter the fatiguing effects of metabolites on Ca(2+) sensitivity, and (iii) a reduction in the amount of releasable SR Ca(2+) in both fibre types. © 2015 The Authors. The Journal of Physiology © 2015 The Physiological Society.

Different signaling pathway between sphingosine-1-phosphate and lysophosphatidic acid in Xenopus oocytes: functional coupling of the sphingosine-1-phosphate receptor to PLC-xbeta in Xenopus oocytes.

PubMed

Noh, S J; Kim, M J; Shim, S; Han, J K

1998-08-01

In Xenopus oocytes, both sphingosine-1-phosphate (S1P) and lysophosphatidic acid (LPA) activate Ca2+-dependent oscillatory Cl- currents by acting through membrane-bound receptors. External application of 50 microM S1P elicited a long-lasting oscillatory current that continued over 30 min from the beginning of oscillation, with 300 nA (n = 11) as a usual maximum peak of current, whereas 1-microM LPA treatment showed only transiently oscillating but more vigorous current responses, with 2,800 nA (n = 18) as a maximum peak amplitude. Both phospholipid-induced Ca2+-dependent Cl- currents were observed in the absence of extracellular Ca2+, were blocked by intracellular injection of the Ca2+ chelator, EGTA, and could not be elicited by treatment with thapsigargin, an inhibitor of endoplasmic reticulum (ER) Ca2+ ATPase. Intracellular Ca2+ release appeared to be from inositol 1,4,5-trisphosphate (IP3)-sensitive Ca2+ store, because Cl- currents were blocked by heparin injection. Pretreatment with the aminosteroid, U-73122, an inhibitor of G protein-mediated phospholipase C (PLC) activation, to oocytes inhibited the current responses evoked both by S1P and LPA. However, when they were injected with 10 ng of antisense oligonucleotide (AS-ODN) against Xenopus phospholipase C (PLC-xbeta), oocytes could not respond to S1P application, whereas they responded normally to LPA, indicating that the S1P signaling pathway goes through PLC-xbeta, whereas LPA signaling goes through another unknown PLC. To determine the types of G proteins involved, we introduced AS-ODNs against four types of G-protein alpha subunits that were identified in Xenopus laevis; G(q)alpha, G11alpha, G0alpha, and G(i1)alpha. Among AS-ODNs against the G alphas tested, AS-G(q)alpha and AS-G(i1)alpha to S1P and AS-G(q)alpha and AS-G11alpha to LPA specifically reduced current responses, respectively, to about 20-30% of controls. These results demonstrate that LPA and S1P, although they have similar structural features, release intracellular Ca2+ from the IP3-sensitive pool, use different components in their signal transduction pathways in Xenopus oocytes.

Evidence for Multiple Late Quaternary Glaciations in the Southernmost Cordillera Blanca, Peru

NASA Astrophysics Data System (ADS)

Smith, J. A.; Rodbell, D. T.; Ramage, J. M.

2007-12-01

Surface-exposure dating with in-situ-produced cosmogenic isotopes has provided the basis for a growing framework of glacial chronologies in the tropical Andes. In the Peruvian Andes, long chronologies (>400 ka) with relatively small local last glacial maximum (LLGM) advances have been reported for the central Cordillera Blanca (ca. 9°30'S) and Junin Plain (11°00'S), whereas preliminary data suggest a shorter record (<40 ka) in the intervening Cordillera Huayhuash (10°15'S). These seemingly contradictory findings raise several questions: Was the LLGM a relatively minor event in the Peruvian Andes, far exceeded by bigger, older advances? Which combination of geographic and geomorphic factors increases the likelihood that evidence of older advances will be preserved? With these questions in mind, we sought a site with both high peaks and a high-altitude plateau. The glaciated Nevado Jeulla Rajo massif (10°00'S, 77°16'W, peaks ca. 5600 masl) marks the southern end of the Cordillera Blanca and the Callejon de Huaylas valley in the central Peruvian Andes. The Conococha Plain (ca. 4050 masl) borders the western side of the massif. Large lateral moraines extend onto the Conococha Plain from the west-facing valleys and multiple moraine loops lie upvalley, closer to active ice margins. Surface-exposure dating (10Be) indicates that the largest lateral moraines from Jeullesh Valley are compound features deposited during the LLGM (ca. 30 ka) and a late-glacial readvance (ca. 16 ka). The LLGM/late-glacial moraines cross-cut an older pair of lateral moraines (ca. 70 ka) that may provide evidence for a smaller advance during marine isotope stage 4. Although the LLGM/late-glacial moraines are impressively large (ca. 150 m high), they do not represent the maximum ice extent in the region. Fluvial outwash deposits beyond the termini of the moraines on the Conococha Plain are underlain by lodgement till that is up to 20 m thick and extends ca. 6 km across the width of the Plain to the Rió Santa. The wide distribution of the till suggests that at least one older glaciation was far more extensive than any of the late Quaternary advances that we have dated by 10Be. The combination of high peaks, a high-altitude plateau, and an active fault may be ideal for enhancing preservation of older moraines and till deposits.

Sulfur capture under periodically changing oxidizing and reducing conditions in PFBC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zevenhoven, R.; Yrjas, P.; Hupa, M.

1999-07-01

During in situ sulfur capture with a calcium-based sorbent in fluidized bed combustion (FBC), a temperature optimum is found, at atmospheric pressure, at {approximately}850 C. The repeated decomposition of sulfated limestone during stages where the gas atmosphere surrounding the sorbent particle is not oxidizing but reducing has been identified to explain this maximum. Under pressurized (PFBC) conditions, an additional aspect is the direct conversion of calcium carbonate (CaCO{sub 3}) without the intermediate calcium oxide (CaO) due to the partial pressure of carbon dioxide (CO{sub 2}). In this work it was evaluated how stable calcium sulfate (CaSO{sub 4}) is in amore » gas atmosphere that periodically changes from oxidizing to reducing and vice versa. Atmospheric as well as elevated pressures are considered. CaO or CaCO{sub 3}, and/or calcium sulfide (CaS) are formed during the reducing stage. Using a pressurized thermogravimetric reactor (PTGR) a limestone was periodically sulfated under oxidizing conditions and decomposed under reducing conditions with carbon monoxide (CO), or with CO + H{sub 2} (hydrogen). Experiments at 1 bar and 15 bar were carried out, at temperatures from 850 C to 950 C, at C O and CO + H{sub 2} concentrations up to 4%-vol. The experimental data were modeled using simple first order (parallel) reaction schemes that allowed for sorbent structure changes. This gave rate parameters for the sulfation and the decomposition reactions, and identified the decomposition products. It was found that 1 bar, CO + H{sub 2} gives a higher reduction of CaSO{sub 4} than CO, at the same total concentration. The rate of decomposition increases faster with temperature than the sulfation, explaining the sulfation efficiency maximum mentioned above. At 15 bar, a different picture is seen. The reductive decomposition rate as well as the sulfation rate are slower, with CO as well as CO with small amounts of H{sub 2} as the reducing species. There is a significant effect of the water which is present in the gas at higher concentrations than H{sub 2}. Thermodynamics indicate that this leads to the decomposition of CaS, releasing H{sub 2}S.« less

Calcium and stretch activation modulate power generation in Drosophila flight muscle.

PubMed

Wang, Qian; Zhao, Cuiping; Swank, Douglas M

2011-11-02

Many animals regulate power generation for locomotion by varying the number of muscle fibers used for movement. However, insects with asynchronous flight muscles may regulate the power required for flight by varying the calcium concentration ([Ca(2+)]). In vivo myoplasmic calcium levels in Drosophila flight muscle have been found to vary twofold during flight and to correlate with aerodynamic power generation and wing beat frequency. This mechanism can only be possible if [Ca(2+)] also modulates the flight muscle power output and muscle kinetics to match the aerodynamic requirements. We found that the in vitro power produced by skinned Drosophila asynchronous flight muscle fibers increased with increasing [Ca(2+)]. Positive muscle power generation started at pCa = 5.8 and reached its maximum at pCa = 5.25. A twofold variation in [Ca(2+)] over the steepest portion of this curve resulted in a two- to threefold variation in power generation and a 1.2-fold variation in speed, matching the aerodynamic requirements. To determine the mechanism behind the variation in power, we analyzed the tension response to muscle fiber-lengthening steps at varying levels of [Ca(2+)]. Both calcium-activated and stretch-activated tensions increased with increasing [Ca(2+)]. However, calcium tension saturated at slightly lower [Ca(2+)] than stretch-activated tension, such that as [Ca(2+)] increased from pCa = 5.7 to pCa = 5.4 (the range likely used during flight), stretch- and calcium-activated tension contributed 80% and 20%, respectively, to the total tension increase. This suggests that the response of stretch activation to [Ca(2+)] is the main mechanism by which power is varied during flight. Copyright © 2011 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Possible metastable rhombohedral states of the bcc transition metals

NASA Astrophysics Data System (ADS)

Mehl, Michael; Finkenstadt, Daniel

2007-03-01

The energy E(c/a) for a bcc element stretched along its [001] axis (the Bain path) has a minimum at c/a = 1, a maximum at c/a = √2, and an elastically unstable local minimum at c/a > √2. A rhombohedral strain is an alternative method of connecting the bcc and fcc structures. The primitive lattice keeps R3m symmetry, with the angle α changing from 109.4^o (bcc), to 90^o (simple cubic), to 60^o (fcc). We studied this path for the non-magnetic bcc transition metals (V, Nb, Mo, Ta, and W) using both a full-potential LAPW and PAW VASP. Except for Ta, the energy E(α) has a local maximum at α=60^o, with local minima near 55^o and 70^o, the later having lower energy. We studied the elastic stability of the 70^o minimum structure. Only W is elastically stable in this structure, with the smallest eigenvalue of the elastic tensor at 4 GPa, while the other three elements are unstable. We discuss the possibility that Tungsten is actually metastable in this structure. We also consider the possible epitaxial growth of this structure. M. J. Mehl, A. Aguayo, L. L. Boyer, and R. De Coss, Phys. Rev. B 70, 014105 (2004).

Nearly metastable rhombohedral phases of bcc metals

NASA Astrophysics Data System (ADS)

Mehl, Michael J.; Finkenstadt, Daniel

2008-02-01

The energy E(c/a) for a bcc element stretched along its [001] axis (the Bain path) has a minimum at c/a=1 , a maximum at c/a=2 , and an elastically unstable local minimum at c/a>2 . An alternative path connecting the bcc and fcc structures is the rhombohedral lattice. The primitive lattice has R3¯m symmetry, with the angle α changing from 109.4° (bcc), to 90° (simple cubic), to 60 ° (fcc). We study this path for the non-magnetic bcc transition metals (V, Nb, Mo, Ta, and W) using both all-electron linearized augmented plane wave and projector augmented wave VASP codes. Except for Ta, the energy E(α) has a local maximum at α=60° , with local minima near 55° and 70° , the latter having lower energy, suggesting the possibility of a metastable rhombohedral state for these materials. We first examine the elastic stability of the 70° minimum structure, and determine that only W is elastically stable in this structure, with the smallest eigenvalue of the elastic tensor at 4GPa . We then consider the possibility that tungsten is actually metastable in this structure by looking at its vibrational and third-order elastic stability.

Interaction with Phosphoinositides Confers Adaptation onto the TRPV1 Pain Receptor

PubMed Central

Yao, Jing; Qin, Feng

2009-01-01

Adaptation is a common feature of many sensory systems. But its occurrence to pain sensation has remained elusive. Here we address the problem at the receptor level and show that the capsaicin ion channel TRPV1, which mediates nociception at the peripheral nerve terminals, possesses properties essential to the adaptation of sensory responses. Ca2+ influx following the channel opening caused a profound shift (∼14-fold) of the agonist sensitivity, but did not alter the maximum attainable current. The shift was adequate to render the channel irresponsive to normally saturating concentrations, leaving the notion that the channel became no longer functional after desensitization. By simultaneous patch-clamp recording and total internal reflection fluorescence (TIRF) imaging, it was shown that the depletion of phosphatidylinositol 4,5-bisphosphate (PIP2) induced by Ca2+ influx had a rapid time course synchronous to the desensitization of the current. The extent of the depletion was comparable to that by rapamycin-induced activation of a PIP2 5-phosphatase, which also caused a significant reduction of the agonist sensitivity without affecting the maximum response. These results support a prominent contribution of PIP2 depletion to the desensitization of TRPV1 and suggest the adaptation as a possible physiological function for the Ca2+ influx through the channel. PMID:19243225

Correspondence analysis to evaluate the transmission of Staphylococcus aureus strains in two New York State maximum-security prisons.

PubMed

Befus, M; Mukherjee, D V; Herzig, C T A; Lowy, F D; Larson, E

2017-07-01

Prisons/jails are thought to amplify the transmission of Staphylococcus aureus (SA) particularly methicillin-resistant SA infection and colonisation. Two independently pooled cross-sectional samples of detainees being admitted or discharged from two New York State maximum-security prisons were used to explore this concept. Private interviews of participants were conducted, during which the anterior nares and oropharynx were sampled and assessed for SA colonisation. Log-binomial regression and correspondence analysis (CA) were used to evaluate the prevalence of colonisation at entry as compared with discharge. Approximately 51% of admitted (N = 404) and 41% of discharged (N = 439) female detainees were colonised with SA. Among males, 59% of those admitted (N = 427) and 49% of those discharged (N = 393) were colonised. Females had a statistically significant higher prevalence (1·26: P = 0·003) whereas males showed no significant difference (1·06; P = 0·003) in SA prevalence between entry and discharge. CA demonstrated that some strains, such as spa types t571 and t002, might have an affinity for certain mucosal sites. Contrary to our hypothesis, the prison setting did not amplify SA transmission, and CA proved to be a useful tool in describing the population structure of strains according to time and/or mucosal site.

Phosphorylation of CaMKII in the rat dorsal raphe nucleus plays an important role in sleep-wake regulation.

PubMed

Cui, Su-Ying; Li, Sheng-Jie; Cui, Xiang-Yu; Zhang, Xue-Qiong; Yu, Bin; Sheng, Zhao-Fu; Huang, Yuan-Li; Cao, Qing; Xu, Ya-Ping; Lin, Zhi-Ge; Yang, Guang; Song, Jin-Zhi; Ding, Hui; Wang, Zi-Jun; Zhang, Yong-He

2016-02-01

The Ca(2+) modulation in the dorsal raphe nucleus (DRN) plays an important role in sleep-wake regulation. Calmodulin-dependent kinase II (CaMKII) is an important signal-transducing molecule that is activated by Ca(2+) . This study investigated the effects of intracellular Ca(2+) /CaMKII signaling in the DRN on sleep-wake states in rats. Maximum and minimum CaMKII phosphorylation was detected at Zeitgeber time 21 (ZT 21; wakefulness state) and ZT 3 (sleep state), respectively, across the light-dark rhythm in the DRN in rats. Six-hour sleep deprivation significantly reduced CaMKII phosphorylation in the DRN. Microinjection of the CAMKII activation inhibitor KN-93 (5 or 10 nmol) into the DRN suppressed wakefulness and enhanced rapid-eye-movement sleep (REMS) and non-REM sleep (NREMS). Application of a high dose of KN-93 (10 nmol) increased slow-wave sleep (SWS) time, SWS bouts, the mean duration of SWS, the percentage of SWS relative to total sleep, and delta power density during NREMS. Microinjection of CaCl2 (50 nmol) in the DRN increased CaMKII phosphorylation and decreased NREMS, SWS, and REMS. KN-93 abolished the inhibitory effects of CaCl2 on NREMS, SWS, and REMS. These data indicate a novel wake-promoting and sleep-suppressing role for the Ca(2+) /CaMKII signaling pathway in DRN neurons. We propose that the intracellular Ca(2+) /CaMKII signaling in the dorsal raphe nucleus (DRN) plays wake-promoting and sleep-suppressing role in rats. Intra-DRN application of KN-93 (CaMKII activation inhibitor) suppressed wakefulness and enhanced rapid-eye-movement sleep (REMS) and non-REMS (NREMS). Intra-DRN application of CaCl2 attenuated REMS and NREMS. We think these findings should provide a novel cellular and molecular mechanism of sleep-wake regulation. © 2015 International Society for Neurochemistry.

Predominant cause of prolonged low-frequency force depression changes during recovery after in situ fatiguing stimulation of rat fast-twitch muscle.

PubMed

Watanabe, Daiki; Wada, Masanobu

2016-11-01

To investigate time-dependent changes in sarcoplasmic reticulum (SR) Ca 2+ release and myofibrillar (my-) Ca 2+ sensitivity during recovery from prolonged low-frequency force depression (PLFFD), rat gastrocnemius muscles were electrically stimulated in situ. After 0 h (R0), 0.5 h (R0.5), 2 h (R2), 6 h (R6), or 12 h of recovery, the superficial gastrocnemius muscles were excised and used for biochemical and skinned fiber analyses. At R0, R0.5, R2, and R6, the ratio of force at 1 Hz to that at 50 Hz was decreased in the skinned fibers. The ratio of depolarization-induced force to the maximum Ca 2+ -activated force (depol/Ca 2+ force ratio) was utilized as an indicator of SR Ca 2+ release. At R0, both the depol/Ca 2+ force ratio and my-Ca 2+ sensitivity were decreased. At R0.5 and R2, my-Ca 2+ sensitivity was recovered, while the depol/Ca 2+ force ratio remained depressed. At R6, my-Ca 2+ sensitivity was decreased again, whereas the depol/Ca 2+ force ratio was nearly restored. Western blot analyses demonstrated that decreased my-Ca 2+ sensitivity at R6 and reduced depol/Ca 2+ force ratio at R0, R0.5, and R2 were accompanied by depressions in S-glutathionylated troponin I and increases in dephosphorylated ryanodine receptor 1, respectively. These results indicate that, in the early stage of recovery, reduced SR Ca 2+ release plays a primary role in the etiology of PLFFD, whereas decreased my-Ca 2+ sensitivity is involved in the late stage, and suggest that S-glutathionylation of troponin I and dephosphorylation of ryanodine receptor 1 contribute, at least partly, to fatiguing contraction-induced alterations in my-Ca 2+ sensitivity and SR Ca 2+ release, respectively. Copyright © 2016 the American Physiological Society.

Earth and Planetary Science Letters

NASA Technical Reports Server (NTRS)

Nishiizumi, K.; Klein, J.; Middleton, R.; Masarik, J.; Reedy, R. C.; Arnold, J. R.; Fink, D.

1997-01-01

Systematic measurements of the concentrations of cosmogen Ca-41 (half-life = 1.04 x 10(exp 5) yr) in the Apollo 15 long core 15001-15006 were performed by accelerator mass spectroscopy. Earlier measurements of cosmogenic Be-10, C-14, Al-26, Cl-36, and Mn-53 in the same core have provided confirmation and improvement of theoretical models for predicting production profiles of nuclides by cosmic ray induced spallation in the Moon and large meteorites. Unlike these nuclides, Ca-40 in the lunar surface is produced mainly by thermal neutron capture reactions on Ca-40. The maximum production of Ca-41, about 1 dpm/g Ca, was observed at a depth in the Moon of about 150 g/sq cm. For depths below about 300 g/sq cm, Ca-41 production falls off exponentially with an e-folding length of 175 g/sq cm. Neutron production in the Moon was modeled with the Los Alamos High Energy Transport Code System, and yields of nuclei produced by low-energy thermal and epithermal neutrons were calculated with the Monte Carlo N-Particle code. The new theoretical calculations using these codes are in good agreement with our measured Ca-41 concentrations as well as with Co-60 and direct neutron fluence measurements in the Moon.

Response of wheat seedlings to ni stress: effects of supplemental calcium.

PubMed

Ouzounidou, G; Moustakas, M; Symeonidis, L; Karataglis, S

2006-04-01

The effect of excess Ni (1 mM Ni) on wheat plants as well as the role of Ca (1 mM Ni+5000 microM Ca) for amelioration of toxicity and recovery of growth and photosynthesis in Ni-stressed wheat was evaluated. Growth, nutrient status (Ca, Mg, Fe, K, Na), and photosynthesis showed a distinct decrease strictly related to the period of treatment. Calcium ameliorated to a certain extent toxic symptoms of Ni, due to antagonistic action between Ni and Ca ions. Since chlorophyll content and variable fluorescence (Fv) decreased significantly, but Fo did not particularly change, the decrease of t1/2 with increasing duration of Ni exposure indicates negative changes on the acceptor side of PSII, which also may result from diminution of Calvin cycle. The maximum quantum yield for energy trapping was also suppressed. Plant transfer to Hoagland solution+5000 microM Ca caused recovery to plant morphology and physiology. Even in control plants, during recovery period an increased Ca concentration in plant tissues with concomitant increased rates of growth and morphology was observed. Ni concentration in plants exposed to 1 mM Ni+5000 microM Ca was lower than in plants exposed to 1 mM Ni. In all treatments a certain increase of plant nutrients was observed during recovery.

A compact circumstellar shell as the source of high-velocity features in SN 2011fe

NASA Astrophysics Data System (ADS)

Mulligan, Brian W.; Wheeler, J. Craig

2018-05-01

High-velocity features (HVFs), especially of Ca II, are frequently seen in Type Ia supernova observed prior to B-band maximum (Bmax). These HVFs evolve in velocity from more than 25 000 km s-1, in the days after first light, to about 18 000 km s-1 near Bmax. To recreate the evolution of the Ca II near-infrared triplet (CaNIR) HVFs in SN 2011fe, we consider the interaction between a model Type Ia supernova and compact circumstellar shells with masses between 0.003 and 0.012 M⊙. We fit the observed CaNIR feature using synthetic spectra generated from the models using SYN++. The CaNIR feature is better explained by the supernova model interacting with a shell than the model without a shell, with a shell of mass 0.005 M⊙ tending to be better fitting than the other shells. The evolution of the optical depth of CaNIR suggests that the ionization state of calcium within the ejecta and shell is not constant. We discuss the method used to measure the observed velocity of CaNIR and other features and conclude that HVFs or other components can be falsely identified. We briefly discuss the possible origin of the shells and the implications for the progenitor system of the supernova.

High-Field Quench Behavior and Protection of $$Bi_2 Sr_2 Ca Cu_2 O_x$$ Coils: Minimum and Maximum Quench Detection Voltages

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Tengming; Ye, Liyang; Turrioni, Daniele

Small insert coils have been built using a multifilamentary Bi2Sr2CaCu2Ox round wire, and characterized in background fields to explore the quench behaviors and limits of Bi2Sr2CaCu2Ox superconducting magnets, with an emphasis on assessing the impact of slow normal zone propagation on quench detection. Using heaters of various lengths to initiate a small normal zone, a coil was quenched safely more than 70 times without degradation, with the maximum coil temperature reaching 280 K. Coils withstood a resistive voltage of tens of mV for seconds without quenching, showing the high stability of these coils and suggesting that the quench detection voltagemore » shall be greater than 50 mV to not to falsely trigger protection. The hot spot temperature for the resistive voltage of the normal zone to reach 100 mV increases from ~40 K to ~80 K with increasing the operating wire current density Jo from 89 A/mm2 to 354 A/mm2 whereas for the voltage to reach 1 V, it increases from ~60 K to ~140 K, showing the increasing negative impact of slow normal zone propagation on quench detection with increasing Jo and the need to limit the quench detection voltage to < 1 V. These measurements, coupled with an analytical quench model, were used to access the impact of the maximum allowable voltage and temperature upon quench detection on the quench protection, assuming to limit the hot spot temperature to <300 K.« less

Calcium phosphates recovery from digester supernatant by fast precipitation and recrystallization

NASA Astrophysics Data System (ADS)

Vasenko, Liubov; Qu, Haiyan

2018-01-01

Conditional solubility of dicalcium phosphate dihydrate (DCPD) and hydroxyapatite (HAp) in digester supernatant was determined as a function of pH and was compared to its conditional solubility in distilled water. Conditional solubility of both substances in digester supernatant at pH >5-6 was higher than their conditional solubility in pure water due to the presence of impurities, and this influence is more significant for HAp. Amorphous CaP was precipitated through a fast precipitation process from digester supernatant with initial total phosphate concentration 0.008 mol/L and 0.015 mol/L and Ca/P ratios 2 and 5. The amorphous CaP can be subsequently recrystallized into crystalline CaP. Obtained amorphous products have Ca/P ratio > 1, which allow performing the recrystallization process without further Ca dosing into the system. Batch recrystallization of the amorphous products resulted in crystallization of HAp, DCPD or their mixture depending on the conditions of the process. Maximum achieved P-recovery was 69.5%. The increase of phosphate concentration and the addition of seeding decreased the yield of the process but promoted crystallization of DCPD. The increase of Ca/P ratio had a positive effect on the total P-recovery. Compared with the direct batch crystallization of CaP from digester supernatant, the two-step process with fast precipitation and recrystallization significantly improved the color of the obtained products.

[Change in concentration of cytosolic Ca2+ caused by extracellular ATP and ecto-ATP-ase activity in thymocytes and transformed MT-4 cells].

PubMed

Hrebinyk, S M; Artemenko, O Iu; Hryniuk, I I; Perepelitsyna, O M; Matyshevs'ka, O P

2009-01-01

The comparative study of extracellular ATP (ATP0) effect on free cytosolic calcium concentration ([Ca2+]i) in normal (isolated rat thymocytes) and transformed (leukosis MT-4 line) T-cells was carried out. Addition of 1 mM ATP to Ca-free incubation medium of both types of cells, loaded with indo-1, had no effect on [Ca2+]i level. Upon subsequent addition of 1 mM CaCl2 to the incubation medium the rapid and significant increase of [Ca2+]i in MT-4 cells was registered. This effect was maintained within 10 min and was not inhibited by phospholipase C inhibitor 0.2 mM neomycin, that was induced by cation entry into the cells from the extracellular medium. Both types of cells were shown to demonstrate ecto-ATPase activity in the presence of 1 mM MgCl2 or CaC12 in the incubation medium. Estimation of kinetic parameters has indicated that the maximum rate of extracellular ATP hydrolysis by MT-4 cells is higher and Mg2+ and Ca2+ activation constants are lower as compared to respective parameters of ATP hydrolysis by thymocytes. The possible functional significance of the increased level of ecto-ATPase activity in malignantly transformed cells is discussed.

U-Pb and Lu-Hf zircon geochronology of the Cañadón Asfalto Basin, Chubut, Argentina: Implications for the magmatic evolution in central Patagonia

NASA Astrophysics Data System (ADS)

Hauser, N.; Cabaleri, N. G.; Gallego, O. F.; Monferran, M. D.; Silva Nieto, D.; Armella, C.; Matteini, M.; Aparicio González, P. A.; Pimentel, M. M.; Volkheimer, W.; Reimold, W. U.

2017-10-01

The Cañadón Asfalto basin, central Chubut, Argentina, comprises a volcano-sedimentary sequence related to the opening of the Atlantic Ocean during Mesozoic times. The Lonco Trapial, Cañadón Asfalto and Cañadón Calcáreo formations are the main units related to the evolution of this basin. The Las Chacritas and Puesto Almada members are distinguished in the Cañadón Asfalto Formation. LA-HR-ICP-MS U-Pb and Lu-Hf data on zircon were obtained on these units. The Lonco Trapial Formation gave a weighted average age of 172.3 ± 1.8 Ma. A pyroclastic level from the Las Chacritas Member gave a weighted average age of 168.2 ± 2.2 Ma. Two U-Pb concordant ages of 160.3 ± 1.7 Ma on a laminated tuffite and 158.3 ± 1.3 Ma on a pyroclastic level were obtained for the Puesto Almada Member. Two maximum depositional ages constrain the sedimentary provenance areas for the basin: 1) A sample from the Sierra de la Manea range, where a controversial unit related either to the Cañadón Asfalto or to the Cañadón Calcáreo formation occurs, gave an age of 176.6 ± 1.0 Ma. Two younger zircon crystals indicate that this unit may be related to the Cañadón Calcáreo Formation. 2) A sandstone with cross-stratification from the Puesto Almada Member gave a maximum depositional age of 173.6 ± 6.4 Ma. In terms of U-Pb and Lu-Hf isotopes, two magmatic events are identified in central Patagonia: the Mamil Choique magmatic event characterized by negative εHf values around -5.0 and representing recycling during Permian times of Mesoproterozoic crust (TDM of ∼1.5 Ga), and the Cañadón Asfalto magmatic event with negative (-8.2) to positive (+4) εHf values and Meso- to Neoproterozoic TDM between 1.5 and 0.8 Ga. The younger event is characterized by three main cycles: C1 related to the Lonco Trapial magmatism, C2 to the Las Chacritas volcanism, and C3 to the Puesto Almada volcanism. These cycles are related with Marifil, Chon Aike and El Quemado formations volcanics events of Patagonia and the Neuquén Basin during the Mesozoic.

Effects of elevated physiological temperatures on sarcoplasmic reticulum function in mechanically skinned muscle fibers of the rat.

PubMed

van der Poel, C; Stephenson, D G

2007-07-01

Properties of the sarcoplasmic reticulum (SR) with respect to Ca(2+) loading and release were measured in mechanically skinned fiber preparations from isolated extensor digitorum longus (EDL) muscles of the rat that were either kept at room temperature (23 degrees C) or exposed to temperatures in the upper physiological range for mammalian skeletal muscle (30 min at 40 or 43 degrees C). The ability of the SR to accumulate Ca(2+) was significantly reduced by a factor of 1.9-2.1 after the temperature treatments due to a marked increase in SR Ca(2+) leak, which persisted for at least 3 h after treatment. Results with blockers of Ca(2+) release channels (ruthenium red) and SR Ca(2+) pumps [2,5-di(tert-butyl)-1,4-hydroquinone] indicate that the increased Ca(2+) leak was not through the SR Ca(2+) release channel or the SR Ca(2+) pump, although it is possible that the leak pathway was via oligomerized Ca(2+) pump molecules. No significant change in the maximum SR Ca(2+)-ATPase activity was observed after the temperature treatment, although there was a tendency for a decrease in the SR Ca(2+)-ATPase. The observed changes in SR properties were fully prevented by the superoxide (O(2)(*-)) scavenger Tiron (20 mM), indicating that the production of O(2)(*-) at elevated temperatures is responsible for the increase in SR Ca(2+) leak. Results show that physiologically relevant elevated temperatures 1) induce lasting changes in SR properties with respect to Ca(2+) handling that contribute to a marked increase in the SR Ca(2+) leak and, consequently, to the reduction in the average coupling ratio between Ca(2+) transport and SR Ca(2+)-ATPase and muscle performance, and 2) that these changes are mediated by temperature-induced O(2)(*-) production.

Underlying mechanism of the contractile dysfunction in atrophied ventricular myocytes from a murine model of hypothyroidism.

PubMed

Montalvo, Dolores; Pérez-Treviño, Perla; Madrazo-Aguirre, Katheryne; González-Mondellini, Fabio A; Miranda-Roblero, Hipólito O; Ramonfaur-Gracia, Diego; Jacobo-Antonio, Mariana; Mayorga-Luna, Maritza; Gómez-Víquez, Norma L; García, Noemí; Altamirano, Julio

2018-06-01

Hypothyroidism (Hypo) is a risk factor for cardiovascular diseases, including heart failure. Hypo rapidly induces Ca 2+ mishandling and contractile dysfunction (CD), as well as atrophy and ventricular myocytes (VM) remodeling. Hypo decreases SERCA-to-phospholamban ratio (SERCA/PLB), and thereby contributes to CD. Nevertheless, detailed spatial and temporal Ca 2+ cycling characterization in VM is missing, and contribution of other structural and functional changes to the mechanism underlying Ca 2+ mishandling and CD, as transverse tubules (T-T) remodeling, mitochondrial density (D mit ) and energy availability, is unclear. Therefore, in a rat model of Hypo, we aimed to characterize systolic and diastolic Ca 2+ signaling, T-T remodeling, D mit , citrate synthase (CS) activity and high-energy phosphate metabolites (ATP and phosphocreatine). We confirmed a decrease in SERCA/PLB (59%), which slowed SERCA activity (48%), reduced SR Ca 2+ (19%) and blunted Ca 2+ transient amplitude (41%). Moreover, assessing the rate of SR Ca 2+ release (dRel/dt), we found that early and maximum dRel/dt decreased, and this correlated with staggered Ca 2+ transients. However, dRel/dt persisted during Ca 2+ transient relaxation due to abundant late Ca 2+ sparks. Isoproterenol significantly up-regulated systolic Ca 2+ cycling. T-T were unchanged, hence, cannot explain staggered Ca 2+ transients and altered dRel/dt. Therefore, we suggest that these might be caused by RyR2 clusters desynchronization, due to diminished Ca 2+ -dependent sensitivity of RyR2, which also caused a decrease in diastolic SR Ca 2+ leak. Furthermore, D mit was unchanged and CS activity slightly decreased (14%), however, the ratio phosphocreatine/ATP did not change, therefore, energy deficiency cannot account for Ca 2+ and contractility dysregulation. We conclude that decreased SR Ca 2+ , due to slower SERCA, disrupts systolic RyR2 synchronization, and this underlies CD. Copyright © 2018 Elsevier Ltd. All rights reserved.

Superresolution Modeling of Calcium Release in the Heart

PubMed Central

Walker, Mark A.; Williams, George S.B.; Kohl, Tobias; Lehnart, Stephan E.; Jafri, M. Saleet; Greenstein, Joseph L.; Lederer, W.J.; Winslow, Raimond L.

2014-01-01

Stable calcium-induced calcium release (CICR) is critical for maintaining normal cellular contraction during cardiac excitation-contraction coupling. The fundamental element of CICR in the heart is the calcium (Ca2+) spark, which arises from a cluster of ryanodine receptors (RyR). Opening of these RyR clusters is triggered to produce a local, regenerative release of Ca2+ from the sarcoplasmic reticulum (SR). The Ca2+ leak out of the SR is an important process for cellular Ca2+ management, and it is critically influenced by spark fidelity, i.e., the probability that a spontaneous RyR opening triggers a Ca2+ spark. Here, we present a detailed, three-dimensional model of a cardiac Ca2+ release unit that incorporates diffusion, intracellular buffering systems, and stochastically gated ion channels. The model exhibits realistic Ca2+ sparks and robust Ca2+ spark termination across a wide range of geometries and conditions. Furthermore, the model captures the details of Ca2+ spark and nonspark-based SR Ca2+ leak, and it produces normal excitation-contraction coupling gain. We show that SR luminal Ca2+-dependent regulation of the RyR is not critical for spark termination, but it can explain the exponential rise in the SR Ca2+ leak-load relationship demonstrated in previous experimental work. Perturbations to subspace dimensions, which have been observed in experimental models of disease, strongly alter Ca2+ spark dynamics. In addition, we find that the structure of RyR clusters also influences Ca2+ release properties due to variations in inter-RyR coupling via local subspace Ca2+ concentration ([Ca2+]ss). These results are illustrated for RyR clusters based on super-resolution stimulated emission depletion microscopy. Finally, we present a believed-novel approach by which the spark fidelity of a RyR cluster can be predicted from structural information of the cluster using the maximum eigenvalue of its adjacency matrix. These results provide critical insights into CICR dynamics in heart, under normal and pathological conditions. PMID:25517166

Differential effects of arginine, glutamate and phosphoarginine on Ca(2+)-activation properties of muscle fibres from crayfish and rat.

PubMed

Jame, David W; West, Jan M; Dooley, Philip C; Stephenson, D George

2004-01-01

The effects of two amino acids, arginine which has a positively charged side-chain and glutamate which has a negatively charged side-chain on the Ca2+-activation properties of the contractile apparatus were examined in four structurally and functionally different types of skeletal muscle; long- and short-sarcomere fibres from the claw muscle of the yabby (a freshwater decapod crustacean), and fast- and slow-twitch fibres from limb muscles of the rat. Single skinned fibres were activated in carefully balanced solutions of different pCa (-log10[Ca2+]) that either contained the test solute ("test") or not ("control"). The effect of phosphoarginine, a phosphagen that bears a nett negative charge, was also compared to the effects of arginine. Results show that (i) arginine (33-36 mmol l(-1)) significantly shifted the force-pCa curve by 0.08-0.13 pCa units in the direction of increased sensitivity to Ca2+-activated contraction in all fibre types; (ii) phosphoarginine (9-10 mmol l(-1)) induced a significant shift of the force-pCa curve by 0.18-0.24 pCa units in the direction of increased sensitivity to Ca2+ in mammalian fast- and slow-twitch fibres, but had no significant effects on the force-pCa relation in either long- or short-sarcomere crustacean fibres; (iii) glutamate (36-40 mmol l(-1)), like arginine affected the force-pCa relation of all fibre types investigated, but in the opposite direction, causing a significant decrease in the sensitivity to Ca2+-activated contraction by 0.08-0.19 pCa units; (iv) arginine, phosphoarginine and glutamate had little or no effect on the maximum Ca2+-activated force of crustacean and mammalian fibres. The results suggest that the opposing effects of glutamate and arginine are not related to simply their charge structure, but must involve complex interactions between these molecules, Ca2+ and the regulatory and other myofibrillar proteins.

Mechanisms underlying the neurokinin A-induced contraction of the pregnant rat myometrium

PubMed Central

Shintani, Yoshinobu; Nishimura, Junji; Niiro, Naohisa; Hirano, Katsuya; Nakano, Hitoo; Kanaide, Hideo

2000-01-01

Using fura-PE3 fluorimetry and α-toxin permeabilization, the characteristics of the contractile responses to neurokinin A (NKA) were determined in the pregnant rat myometrium. NKA induced contractions in rat myometrium in a concentration-dependent manner. There were no significant differences in the maximum contractions and EC50 values between the pregnant and non-pregnant myometrium, however, the contraction of only the former was greatly enhanced in the presence of phosphoramidon (PPAD), an endopeptidase inhibitor. In the pregnant myometrium, NKA induced sustained increases in [Ca2+]i and tension in normal physiological saline solution, while only small transient increases in [Ca2+]i and tension were observed in Ca2+-free solution. Both diltiazem (10 μM) and SK-F 96365 (10 μM) significantly inhibited the NKA-induced elevations of [Ca2+]i and tension. The effects were additive when these drugs were used together. NKA induced a significant leftward shift of the [Ca2+]i-tension curve obtained by changing the external Ca2+ (0–2.5 mM) during depolarization with high K+ solution. This Ca2+-sensitizing effect by NKA was also observed in the α-toxin permeabilized myometrium. These results indicated that in the pregnant rat myometrium: (1) the responsiveness to NKA increased, although it was masked by the increase in the endopeptidase activity; (2) NKA induced contractions of the myometrium by increasing both [Ca2+]i and the myofilament Ca2+ sensitivity and (3) The NKA-induced [Ca2+]i elevation was partly due to the intracellular Ca2+ release and mainly due to the Ca2+ influx, which was thought to be through both voltage dependent calcium channels and non-specification channels. PMID:10882403

Determinants of relaxation rate in rabbit skinned skeletal muscle fibres

PubMed Central

Luo, Ye; Davis, Jonathan P; Smillie, Lawrence B; Rall, Jack A

2002-01-01

The influence of Ca2+-activated force, the rate of dissociation of Ca2+ from troponin C (TnC) and decreased crossbridge detachment rate on the time course of relaxation induced by flash photolysis of diazo-2 in rabbit skinned psoas fibres was investigated at 15 °C. The rate of relaxation increased as the diazo-2 chelating capacity (i.e. free [diazo-2]/free [Ca2+]) increased. At a constant diazo-2 chelating capacity, the rate of relaxation was independent of the pre-photolysis Ca2+-activated force in the range 0.3-0.8 of maximum isometric force. A TnC mutant that exhibited increased Ca2+ sensitivity caused by a decreased Ca2+ dissociation rate in solution (M82Q TnC) also increased the Ca2+ sensitivity of steady-state force and decreased the rate of relaxation in fibres by approximately twofold. In contrast, a TnC mutant with decreased Ca2+ sensitivity caused by an increased Ca2+ dissociation rate in solution (NHdel TnC) decreased the Ca2+ sensitivity of steady-state force but did not accelerate relaxation. Decreasing the rate of crossbridge kinetics by reducing intracellular inorganic phosphate concentration ([Pi]) slowed relaxation by approximately twofold and led to two phases of relaxation, a slow linear phase followed by a fast exponential phase. In fibres, M82Q TnC further slowed relaxation in low [Pi] conditions by approximately twofold, whereas NHdel TnC had no significant effect on relaxation. These results are consistent with the interpretation that the Ca2+-dissociation rate and crossbridge detachment rate are similar in fast-twitch skeletal muscle, such that decreasing either rate slows relaxation, but accelerating Ca2+ dissociation has little effect on relaxation. PMID:12482894

Acute effect of constant torque and angle stretching on range of motion, muscle passive properties, and stretch discomfort perception.

PubMed

Cabido, Christian E T; Bergamini, Juliana C; Andrade, André G P; Lima, Fernando V; Menzel, Hans J; Chagas, Mauro H

2014-04-01

The aim of the present study was to compare the acute effects of constant torque (CT) and constant angle (CA) stretching exercises on the maximum range of motion (ROMmax), passive stiffness (PS), and ROM corresponding to the first sensation of tightness in the posterior thigh (FSTROM). Twenty-three sedentary men (age, 19-33 years) went through 1 familiarization session and afterward proceeded randomly to both CA and CT treatment stretching conditions, on separate days. An isokinetic dynamometer was used to analyze hamstring muscles during passive knee extension. The subjects performed 4 stretches of 30 seconds each with a 15-second interval between them. In the CA stretching, the subject reached a certain ROM (95% of ROMmax), and the angle was kept constant. However, in the CT stretching exercise, the volunteer reached a certain resistance torque (corresponding to 95% of ROMmax) and it was kept constant. The results showed an increase in ROMmax for both CA and CT (p < 0.001), but the increase was greater for CT than for CA (CA vs. CT in poststretching, p = 0.002). Although the PS decreased for both CA and CT (p < 0.001), the decrease was greater for CT than for CA (CA vs. CT in poststretching, p = 0.002). The FSTROM increased for both CA and CT, but the increase for CT was greater than that for CA (CA vs. CT in poststretching, p = 0.003). The greater increase in ROMmax for the CT stretch may be explained by greater changes in the biomechanical properties of the muscle-tendon unit and stretch tolerance, as indicated by the results of PS and FSTROM.

Preparation and evaluation of Mn3GaN1-x thin films with controlled N compositions

NASA Astrophysics Data System (ADS)

Ishino, Sunao; So, Jongmin; Goto, Hirotaka; Hajiri, Tetsuya; Asano, Hidefumi

2018-05-01

Thin films of antiperovskite Mn3GaN1-x were grown on MgO (001) substrates by reactive magnetron sputtering, and their structural, magnetic, and magneto-optical properties were systematically investigated. It was found that the combination of the deposition rate and the N2 gas partial pressure could produce epitaxial films with a wide range of N composition (N-deficiency) and resulting c/a values (0.93 - 1.0). While the films with c/a = 0.992 - 1.0 were antiferromagnetic, the films with c/a = 0.93 - 0.989 showed perpendicular magnetic anisotropy (PMA) with the maximum PMA energy up to 1.5×106 erg/cm3. Systematic dependences of the energy spectra of the polar Kerr signals on the c/a ratio were observed, and the Kerr ellipticity was as large as 2.4 deg. at 1.9 eV for perpendicularly magnetized ferromagnetic thin films with c/a = 0.975. These results highlight that the tetragonal distortion plays an important role in magnetic and magneto-optical properties of Mn3GaN1-x thin films.

Flexible and porous cellulose aerogels/zeolitic imidazolate framework (ZIF-8) hybrids for adsorption removal of Cr(IV) from water

NASA Astrophysics Data System (ADS)

Bo, Shaoguo; Ren, Wenjing; Lei, Chao; Xie, Yuanbo; Cai, Yurong; Wang, Shunli; Gao, Junkuo; Ni, Qingqing; Yao, Juming

2018-06-01

The low cost of adsorption treatment of heavy metal ions in water has been extensively studied. In this paper, we have demonstrated a facile method of combining two emerging materials cellulose aerogels (CA) and metal-organic frameworks (MOFs) into one highly functional aerogel to adsorption removal of heavy metal ions from water, by entrapping MOF particles into a flexible and porous CA. The resultant hybrid cellulose aerogels had a highly porous structure with zeolitic imidazolate framework-8 (ZIF-8) loadings can reach 30 wt%. The hybrid cellulose aerogels (named as ZIF-8@CA) show good adsorption capacity for Cr(Ⅵ). The adsorption process of ZIF-8@CA is better described by pseudo-second-order kinetic model and Langmuir isotherm, with maximum monolayer adsorption capacity of 41.8 mg g-1 for Cr(Ⅵ), whose adsorption capacity has greatly improved when compared with a single CA or ZIF-8. Thus, such a flexible and durable hybrid cellulose aerogel is a very prospective material for metal ions cleanup and industrial wastewater purification.

Thermoresponsive Cellulose Acetate-Poly(N-isopropylacrylamide) Core-Shell Fibers for Controlled Capture and Release of Moisture.

PubMed

Thakur, Neha; Sargur Ranganath, Anupama; Sopiha, Kostiantyn; Baji, Avinash

2017-08-30

In this study, we used core-shell electrospinning to fabricate cellulose acetate-poly(N-isopropylacrylamide) (CA-PNIPAM) fibrous membranes and demonstrated the ability of these fibers to capture water from a high humid atmosphere and release it when thermally stimulated. The wettability of the fibers was controlled by using thermoresponsive PNIPAM as the shell layer. Scanning electron and fluorescence microscopes are used to investigate the microstructure of the fibers and confirm the presence of the core and shell phases within the fibers. The moisture capturing and releasing ability of these core-shell CA-PNIPAM fibers was compared with those of the neat CA and neat PNIPAM fibers at room temperature as well as at an elevated temperature. At room temperature, the CA-PNIPAM core-shell fibers are shown to have the maximum moisture uptake capacity among the three samples. The external temperature variations which trigger the moisture response behavior of these CA-PNIPAM fibers fall within the range of typical day and night cycles of deserts, demonstrating the potential use of these fibers for water harvesting applications.

High pressure luminescence spectra of CaMoO4:Ln3+ (Ln = Pr, Tb)

NASA Astrophysics Data System (ADS)

Mahlik, S.; Behrendt, M.; Grinberg, M.; Cavalli, E.; Bettinelli, M.

2013-03-01

Photoluminescence spectra and luminescence kinetics of pure CaMoO4 and CaMoO4 doped with Ln3+ (Ln = Pr or Tb) are presented. The spectra were obtained at high hydrostatic pressure up to 240 kbar applied in a diamond anvil cell. At ambient pressure undoped and doped samples exhibit a broad band emission extending between 380 and 700 nm with a maximum at 520 nm attributed to the {{MoO}}_{4}^{2-} luminescence. CaMoO4 doped with Pr3+ or Tb3+ additionally yields narrow emission lines related to f-f transitions. The undoped CaMoO4 crystal was characterized by a strong MoO{}_{4}^{2-} emission up to 240 kbar. In the cases of CaMoO4:Pr3+ and CaMoO4:Tb3+, high hydrostatic pressure caused quenching of Pr3+ and Tb3+ emission, and this effect was accompanied by a strong shortening of the luminescence lifetime. In doped samples, CaMoO4:Pr3+ and CaMoO4:Tb3+, quenching of the emission band attributed to {{MoO}}_{4}^{2-} was also observed, and at pressure above 130 kbar this luminescence was totally quenched. The effects mentioned above were related to the influence of the praseodymium (terbium) trapped exciton PTE (ITE—impurity trapped exciton) on the efficiency of the Pr3+ (Tb3+) and {{MoO}}_{4}^{2-} emissions.

33 CFR 162.205 - Suisun Bay, San Joaquin River, Sacramento River, and connecting waters, CA.

Code of Federal Regulations, 2010 CFR

2010-07-01

.... When going with the current, in slack water, or against a current of two knots or less, the maximum... knots. When going with the current, in slack water, or against a current of two knots or less, the...

Fission Barrier of ^254No at High Spin

NASA Astrophysics Data System (ADS)

Henning, G.; Khoo, T. L.; Seweryniak, D.; Back, B. B.; Bertone, P. F.; Carpenter, M. P.; Greene, J. P.; Gürdal, G.; Hoffman, C. R.; Janssens, R. V. F.; Kay, B. P.; Kondev, F. G.; Lauritsen, T.; Lister, C. J.; McCutchan, E. A.; Nair, C.; Rogers, A. M.; Zhu, S.; Chiara, C. J.; Hauschild, K.; Lopez-Martens, A.; Heinz, A.; Piot, J.; Chowdhury, P.; Lakshmi, S.

2010-11-01

Superheavy nuclei provide opportunities to study nuclear structure at the limits in charge, spin and excitation energy. These nuclei exist only because shell effects create a fission barrier Bf. Hence, it is important to determine Bf and its spin dependence. For ^254No, the maximum spin and energy were found [1] to be Imax= 22 and E* = 8 MeV in the reaction ^208Pb(^48Ca,2n) at a beam energy of 219 MeV. At 223 MeV, the maximum spin increases to 32. In contrast, the spin in ^220Th, produced [2] in the ^176Yb(^48 Ca,4n) reaction at 206 and 219 MeV, saturates at 20. A measurement of the entry distribution of ^254No at 223 MeV has been performed to determine Bf(I) and results will be reported.[4pt] [1] P. Reiter et al., Phys. Rev. Lett. 84, 3542 (2000).[0pt] [2] A. Heinz et al., Nucl. Phys. A682, 458c (2001)

Glacial History of Southernmost South America and Implications for Movement of the Westerlies and Antarctic Frontal Zone

NASA Astrophysics Data System (ADS)

Kaplan, M. R.; Fogwill, C. J.; Hulton, N. R.; Sugden, D. E.; Peter, K. W.

2004-12-01

The ~1 Myr glacial geologic record in southern South American is one of the few available terrestrial paleoclimate proxies at orbital and suborbital time scales in the middle latitudes of the Southern Hemisphere. Presently, southernmost Patagonia lies about 3\\deg north of the Antarctic frontal zone and within the middle latitude westerlies and the climate is controlled by the surrounding maritime conditions. Thus, the long-term glacial record provides insight into the history of climatic boundaries over the middle and high latitude southern ocean, including the upwind SE Pacific Ocean, tectonic-glacial evolution of the Andes, and global climate. To date, cosmogenic nuclide and 14C dating have focused on glacial fluctuations between 51 and 53\\deg S (Torres del Paine to northern Tierra del Fuego) during the last glacial cycle, including the late glacial period. At least 4 advances occurred between ca. 25 and 17 ka, with the maximum expansion of ice ca. 25-24 ka. Major deglaciation commenced after ca. 17.5 ka, which was interrupted by a major glacial-climate event ca. 14-12 ka. Modelling experiments suggest that the ice mass needed to form the glacial maximum moraines required about a 6\\deg cooling and a slight drying relative to the present. Such a fundamental temperature reduction, despite high summer isolation, strongly suggests northward movement of the westerlies and the polar front on millennial timescales. The Patagonian record also indicates that on orbital timescales equatorward movement of climate boundaries and glacial growth was in phase with major Northern Hemisphere ice volume change, despite high local summer insolation. At suborbital timescales, the picture is more complex. While major facets of the last glacial maximum appear to be in phase between the hemispheres, at least some late glacial events may be in step with Antarctic climate change. Present and future research will further constrain the timing of glacial events over the last 1 Myr and the relation with mountain valley evolution and Southern Hemisphere climate change.

Reconstruction of the glacial maximum recorded in the central Cantabrian Mountains (N Iberia)

NASA Astrophysics Data System (ADS)

Rodríguez-Rodríguez, Laura; Jiménez-Sánchez, Montserrat; José Domínguez-Cuesta, María

2014-05-01

The Cantabrian Mountains is a coastal range up to 2648 m altitude trending parallel to northern Iberian Peninsula edge at a maximum distance of 100 km inland (~43oN 5oW). Glacial sediments and landforms are generally well-preserved at altitudes higher than 1600 m, evidencing the occurrence of former glaciations. Previous research supports a regional glacial maximum prior to ca 38 cal ka BP and an advanced state of deglaciation by the time of the global Last Glacial Maximum (Jiménez-Sánchez et al., 2013). A geomorphological database has been produced in ArcGIS (1:25,000 scale) for an area about 800 km2 that partially covers the Redes Natural Reservation and Picos de Europa Regional Park. A reconstruction of the ice extent and flow pattern of the former glaciers is presented for this area, showing that an ice field was developed on the study area during the local glacial maximum. The maximum length of the ice tongues that drained this icefield was remarkably asymmetric between both slopes, recording 1 to 6 km-long in the northern slope and up to 19 km-long in southern one. The altitude difference between the glacier fronts of both mountain slopes was ca 100 m. This asymmetric character of the ice tongues is related to geologic and topo-climatic factors. Jiménez-Sánchez, M., Rodríguez-Rodríguez, L., García-Ruiz, J.M., Domínguez-Cuesta, M.J., Farias, P., Valero-Garcés, B., Moreno, A., Rico, M., Valcárcel, M., 2013. A review of glacial geomorphology and chronology in northern Spain: timing and regional variability during the last glacial cycle. Geomorphology 196, 50-64. Research funded by the CANDELA project (MINECO-CGL2012-31938). L. Rodríguez-Rodríguez is a PhD student with a grant from the Spanish national FPU Program (MECD).

75 FR 20565 - Marine Mammals; File No. 14636

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-20

..., Santa Cruz, CA, has applied in due form for a permit to conduct research on northern elephant seals... on northern elephant seals in California, including population growth and status, reproductive... metabolism, and sensory capacities. Northern elephant seals, totaling a maximum of 3,930 animals per year...

Hyper- and hypobaric processing of Tl-Ba-Ca-Cu-O superconductors

NASA Astrophysics Data System (ADS)

Goretta, K. C.; Routbort, J. L.; Shi, Donglu; Chen, J. G.; Hash, M. C.

1989-11-01

Tl-based superconductors of initial composition Tl:Ca:Ba:Cu equal to 2:2:2:3 and 1:3:1:3 were heated in oxygen at pressures of 10(sup 4) to 6 (times) 10(sup 5) Pa. The 2:2:2:3 composition formed primarily the 2-layer superconductor with zero resistance from 77 to 104 K. The 1:3:1:3 composition formed nearly phase pure 3-layer superconductor with a maximum zero resistance temperature of 120 K. Application of hyperbaric pressure influenced phase purities and transition temperatures slightly; phase purities decreased significantly with application of hypobaric pressures.

Kodak EDR2 film for patient skin dose assessment in cardiac catheterization procedures.

PubMed

Morrell, R E; Rogers, A T

2006-07-01

Patient skin doses were measured using Kodak EDR2 film for 20 coronary angiography (CA) and 32 percutaneous transluminal coronary angioplasty (PTCA) procedures. For CA, all skin doses were well below 1 Gy. However, 23% of PTCA patients received skin doses of 1 Gy or more. Dose-area product (DAP) was also recorded and was found to be an inadequate indicator of maximum skin dose. Practical compliance with ICRP recommendations requires a robust method for skin dosimetry that is more accurate than DAP and is applicable over a wider dose range than EDR2 film.

Determination of the calcium elemental abundance for 43 flares from SMM-XRP solar X-ray spectra

NASA Astrophysics Data System (ADS)

Lemen, J. R.; Sylwester, J.; Bentley, R. D.

The helium and lithium-like X-ray transitions of Ca XVIII-XIX have been used to make an absolute measurement of the coronal calcium elemental abundance relative to hydrogen (ACa) in solar flares. Cooling phase spectra of 43 flares obtained in channel 1 of the Bent Crystal Spectrometer on the Solar Maximum Mission have been analyzed. The abundance is determined from the intensity ratio of the Ca XIX resonance line (1S0 - 1P1) and nearby continuum. Attempts to correlate the ACa measurements with other observable features are discussed.

Calcium requirements of the modern broiler chicken as influenced by dietary protein and age.

PubMed

Driver, J P; Pesti, G M; Bakalli, R I; Edwards, H M

2005-10-01

Two experiments were conducted to examine the calcium requirements of broiler chickens fed corn-soybean meal diets. Experiment 1 used a 6 x 2 x 2 factorial arrangement and was conducted with broilers in floor pens during the grower phase (19 to 42 d). Diets were mixed with 6 levels of dietary Ca (0.325, 0.4, 0.475, 0.55, 0.625, and 0.9%) and 17 or 23% CP and fed to males and females separately. Experiment 2 was a 6 x 2 factorial design conducted using Petersime battery brooders during the starter phase (0 to 16 d). The same 6 levels of dietary Ca used in experiment 1 were fed separately to each sex, but only at the 23% level of CP. The diets used in both experiments were formulated to contain 0.45% nonphytin phosphorus. In experiment 1, grower chickens did not demonstrate significant body weight gain (BWG) or feed conversion ratio (FCR) response (g of feed per g of gain) to the different levels of Ca at either level of protein. The percentage tibia ash did not respond to increasing Ca levels beyond 0.625% Ca at either protein level. In experiment 2, BWG increased linearly up to 0.55 and 0.625% dietary Ca for males and females, respectively. Feed conversion ratio decreased linearly with increasing dietary Ca up to 0.625% Ca, and tibia ash was highest at 0.9% Ca for both sexes. These results suggest that the current NRC Ca requirements for the broiler starter (1.0%) are sufficient for maximum bone ash, but that Ca requirements for grower birds (0.9%) may be excessive for optimum BWG, FCR, and tibia ash.

The effects of vitamin D, K and calcium co-supplementation on carotid intima-media thickness and metabolic status in overweight type 2 diabetic patients with CHD.

PubMed

Asemi, Zatollah; Raygan, Fariba; Bahmani, Fereshteh; Rezavandi, Zohreh; Talari, Hamid Reza; Rafiee, Motahereh; Poladchang, Somayyeh; Darooghegi Mofrad, Manijeh; Taheri, Sara; Mohammadi, Ali Akbar; Esmaillzadeh, Ahmad

2016-07-01

This study was conducted to examine the effects of vitamin D, K and Ca co-supplementation on carotid intima-media thickness (CIMT) and metabolic status in overweight diabetic patients with CHD. This randomised, double-blind, placebo-controlled trial was conducted among sixty-six diabetic patients with CHD. Participants were randomly allocated into two groups to take either 5µg vitamin D, 90 µg vitamin K plus 500 mg Ca supplements (n 33) or placebo (n 33) twice a day for 12 weeks. Fasting blood samples were obtained at the beginning of the study and after the 12-week intervention period to determine related markers. Vitamin D, K and Ca co-supplementation resulted in a significant reduction in maximum levels of left CIMT (-0·04 (sd 0·22) v. +0·04 (sd 0·09) mm, P=0·02). Changes in serum vitamin D (+6·5 (sd 7·8) v. +0·4 (sd 2·2) ng/ml, P<0·001), Ca (+0·6 (sd 0·3) v. +0·1 (sd 0·1) mg/dl, P<0·001) and insulin concentrations (-0·9 (sd 3·1) v. +2·6 (sd 7·2) µIU/ml, P=0·01), homoeostasis model for assessment of estimated insulin resistance (-0·4 (sd 1·2) v. +0·7 (sd 2·3), P=0·01), β-cell function (-2·1 (sd 9·0) v. +8·9 (sd 23·7), P=0·01) and quantitative insulin sensitivity check index (+0·007 (sd 0·01) v. -0·006 (sd 0·02), P=0·01) in supplemented patients were significantly different from those in patients in the placebo group. Supplementation resulted in significant changes in HDL-cholesterol (+2·7 (sd 7·0) v. -2·5 (sd 5·7) mg/dl, P=0·002), high-sensitivity C-reactive protein (-1320·1 (sd 3758·3) v. +464·0 (sd 3053·3) ng/ml, P=0·03) and plasma malondialdehyde concentrations (-0·4 (sd 0·5) v. -1·0 (sd 1·1) µmol/l, P=0·007) compared with placebo. Overall, vitamin D, K and Ca co-supplementation for 12 weeks among diabetic patients with CHD had beneficial effects on maximum levels of left CIMT and metabolic status. The effect of vitamin D, K and Ca co-supplementation on maximum levels of left CIMT could be a chance finding.

Paleoclimatology Supports Physics: Our Energy Choices Will Have Large and Long-Lasting Consequences for Climate and Ecosystems

NASA Astrophysics Data System (ADS)

Harland, B.; Bradley, R. S.; Schlosser, P.; Rignot, E. J.; Dickens, G. R.; Boslough, M.; Alley, R. B.

2016-12-01

Interpretations of the paleoclimatic record show with increasing clarity and confidence that CO2 has been the most important of the many controls on Earth's climate history, providing a slow stabilizer but fast destabilizer through both forcing and feedbacks. From the Faint Young Sun through Snowball Earth, the warmth of the Cretaceous, the PETM, ice-age cycling, and many events between, our best understanding shows that CO2 has been an essential player. Many climate reconstructions are based on the biological record; we know what CO2 did to the climate in part from the ways that living things responded. If our climate models have a shortcoming, the full climate response to CO2 is larger than simulated for shorter times. Surprisingly large response may prove to be especially important for ice sheets and sea level.

Late Pleistocene to Holocene lake levels of Lake Warner, Oregon (USA) and their effect on archaeological site distribution patterns

NASA Astrophysics Data System (ADS)

Wriston, T.; Smith, G. M.

2017-12-01

Few chronological controls are available for the rise and fall of small pluvial lake systems in the Northwestern Great Basin. Within Warner Basin this control was necessary for interpretation of known archaeological sites and for predicting where evidence of its earliest inhabitants might be expected. We trenched along relic beach ridges of Lake Warner, surveyed a stratified sample of the area for archaeological sites, and excavated some sites and a nearby rockshelter. These efforts produced new ages that we used to construct a lake level curve for Lake Warner. We found that the lake filled the valley floor between ca. 30,000 cal yr BP and ca. 10,300 cal yr BP. In nearby basins, several oscillations are evident before ca. 21,100 cal yr BP, but a steep rise to the LGM maximum occurred between 21,000 and 20,000 cal yr BP. Lake Warner likely mirrored these changes, dropped to the valley floor ca. 18,340 cal yr BP, and then rose to its maximum highstand when its waters briefly reached 1454 m asl. After this highstand the lake receded to moderately high levels. Following ca. 14,385 cal yr BP, the lake oscillated between moderate to moderately-high levels through the Bolling-Allerod interstadials and into the Younger Dryas stadial. The basin's first occupants arrived along its shore around this time, while the lake still filled the valley floor. These earliest people carried either Western Stemmed or Clovis projectile points, both of which are found along the lake margin. The lake receded into the valley floor ca. 10,300 cal yr BP and dune development began, ringing wetlands and small lakes that persisted in the footprint of the once large lake. By the time Mazama tephra fell 7,600 cal yr BP it blanketed pre-existing dunes and marsh peats. Our Lake Warner lake level curve facilitates interdisciplinary testing and refinement of it and similar curves throughout the region while helping us understand the history of lake and the people who lived along its shores.

Citric acid modified kenaf core fibres for removal of methylene blue from aqueous solution.

PubMed

Sajab, Mohd Shaiful; Chia, Chin Hua; Zakaria, Sarani; Jani, Saad Mohd; Ayob, Mohd Khan; Chee, Kah Leong; Khiew, Poi Sim; Chiu, Wee Siong

2011-08-01

Chemically modified kenaf core fibres were prepared via esterification in the presence of citric acid (CA). The adsorption kinetics and isotherm studies were carried out under different conditions to examine the adsorption efficiency of CA-treated kenaf core fibres towards methylene blue (MB). The adsorption capacity of the kenaf core fibres increased significantly after the citric acid treatment. The values of the correlation coefficients indicated that the Langmuir isotherm fitted the experimental data better than the Freundlich isotherm. The maximum adsorption capacity of the CA-treated kenaf core fibres was found to be 131.6mg/g at 60°C. Kinetic models, pseudo-first-order, pseudo-second-order and intraparticle diffusion, were employed to describe the adsorption mechanism. The kinetic data were found to fit pseudo-second-order model equation as compared to pseudo-first-order model. The adsorption of MB onto the CA-treated kenaf core fibres was spontaneous and endothermic. Copyright © 2011 Elsevier Ltd. All rights reserved.

Fabrication and thermoelectric properties of Ca-Co-O ceramics with negative Seebeck coefficient

NASA Astrophysics Data System (ADS)

Gong, Chunlin; Shi, Zongmo; Zhang, Yi; Chen, Yongsheng; Hu, Jiaxin; Gou, Jianjun; Qin, Mengjie; Gao, Feng

2018-06-01

Ca-Co-O ceramics is typically p-type thermoelectric materials and possesses positive Seebeck coefficient. In this work, n-type Ca-Co-O ceramics with negative Seebeck coefficients were fabricated by sintering and annealing in a reducing atmosphere. The microstructures and thermoelectric properties of the ceramics were investigated. The results show that the carrier concentration and the carrier mobility dramatically increase after the samples were annealed in the reducing atmosphere. The electrical resistivity increases from 0.0663 mΩ·cm to 0.2974 mΩ·cm, while the negative Seebeck coefficients varies from -24.9 μV/K to -56.3 μV/K as the temperature increases from 323 K to 823 K, and the maximum power factor (PF, 1.536 mW/m·K2) is obtained at 623 K. The samples have n-type thermoelectric properties with large PF values and ZT value (ZT = 0.39, 823 K). The unusual results will pave a new way for studying Ca-Co-O thermoelectric ceramics.

The mechanical properties of fluoride salts at elevated temperatures. [candidate thermal energy storage materials for solar dynamic systems

NASA Technical Reports Server (NTRS)

Raj, S. V.; Whittenberger, J. D.

1989-01-01

The deformation behavior of CaF2 and LiF single crystals compressed in the 111 and the 100 line directions, respectively, are compared with the mechanical properties of polycrystalline LiF-22 (mol pct) CaF2 eutectic mixture in the temperature range 300 to 1275 K for strain rates varying between 7 x 10 to the -7th and 0.2/s. The true stress-strain curves for the single crystals were found to exhibit three stages in an intermediate range of temperatures and strain rates, whereas those for the eutectic showed negative work-hardening rates after a maximum stress. The true stress-strain rate data for CaF2 and LiF-22 CaF2 could be represented by a power-law relation with the strain rate sensitivities lying between 0.05 and 0.2 for both materials. A similar relation was found to be unsatisfactory in the case of LiF.

An N-methyl-D-aspartate receptor-independent excitatory action of partial reduction of extracellular [Mg2+] in CA1-region of rat hippocampal slices.

PubMed

Hamon, B; Stanton, P K; Heinemann, U

1987-03-31

Partial reduction of [Mg2+]o from 2 to 1 mM markedly enhanced neuronal responses evoked by Schaffer collateral-commissural fiber stimulation in the CA1-region of rat hippocampal slices. The amplitude of extracellular population potentials recorded in the CA1-pyramidal cell layer and maximum dV/dt of extracellular population EPSP's recorded in the CA1-pyramidal apical dendritic layer were both increased. However, unlike findings from slices where Mg2+ was completely removed from the bathing medium, there was no spontaneous or evoked epileptiform activity, and the N-methyl-D-aspartate (NMDA) receptor antagonist 2-amino-5-phosphonovalerate (2-APV) did not antagonize the enhancement of evoked responses. These results indicate that, in addition to the participation of NMDA receptors in the epileptiform activity observed when Mg2+ is completely removed from the bathing medium, there is also an NMDA receptor-independent excitatory action of partial reduction of [Mg2+]o in hippocampal slices.

The Arrival of Homo sapiens into the Southern Cone at 14,000 Years Ago.

PubMed

Politis, Gustavo G; Gutiérrez, María A; Rafuse, Daniel J; Blasi, Adriana

The Arroyo Seco 2 site contains a rich archaeological record, exceptional for South America, to explain the expansion of Homo sapiens into the Americas and their interaction with extinct Pleistocene mammals. The following paper provides a detailed overview of material remains found in the earliest cultural episodes at this multi-component site, dated between ca. 12,170 14C yrs B.P. (ca. 14,064 cal yrs B.P.) and 11,180 14C yrs B.P. (ca. 13,068 cal yrs B.P.). Evidence of early occupations includes the presence of lithic tools, a concentration of Pleistocene species remains, human-induced fractured animal bones, and a selection of skeletal parts of extinct fauna. The occurrence of hunter-gatherers in the Southern Cone at ca. 14,000 cal yrs B.P. is added to the growing list of American sites that indicate a human occupation earlier than the Clovis dispersal episode, but posterior to the onset of the deglaciation of the Last Glacial Maximum (LGM) in the North America.

Biotransformation of caffeoyl quinic acids from green coffee extracts by Lactobacillus johnsonii NCC 533.

PubMed

Bel-Rhlid, Rachid; Thapa, Dinesh; Kraehenbuehl, Karin; Hansen, Carl Erik; Fischer, Lutz

2013-01-01

The potential of Lactobacillus johnsonii NCC 533 to metabolize chlorogenic acids from green coffee extract was investigated. Two enzymes, an esterase and a hydroxycinnamate decarboxylase (HCD), were involved in this biotransformation. The complete hydrolysis of 5-caffeoylquinic acid (5-CQA) into caffeic acid (CA) by L. johnsonii esterase occurred during the first 16 h of reaction time. No dihydrocaffeic acid was identified in the reaction mixture. The decarboxylation of CA into 4-vinylcatechol (4-VC) started only when the maximum concentration of CA was reached (10 μmol/ml). CA was completely transformed into 4-VC after 48 h of incubation. No 4-vinylphenol or other derivatives could be identified in the reaction media. In this study we demonstrate the capability of L. johnsonii to transform chlorogenic acids from green coffee extract into 4-VC in two steps one pot reaction. Thus, the enzymatic potential of certain lactobacilli might be explored to generate flavor compounds from plant polyphenols.

Localized nuclear and perinuclear Ca(2+) signals in intact mouse skeletal muscle fibers.

PubMed

Georgiev, Tihomir; Svirin, Mikhail; Jaimovich, Enrique; Fink, Rainer H A

2015-01-01

Nuclear Ca(2+) is important for the regulation of several nuclear processes such as gene expression. Localized Ca(2+) signals (LCSs) in skeletal muscle fibers of mice have been mainly studied as Ca(2+) release events from the sarcoplasmic reticulum. Their location with regard to cell nuclei has not been investigated. Our study is based on the hypothesis that LCSs associated with nuclei are present in skeletal muscle fibers of adult mice. Therefore, we carried out experiments addressing this question and we found novel Ca(2+) signals associated with nuclei of skeletal muscle fibers (with possibly attached satellite cells). We measured localized nuclear and perinuclear Ca(2+) signals (NLCSs and PLCSs) alongside cytosolic localized Ca(2+) signals (CLCSs) during a hypertonic treatment. We also observed NLCSs under isotonic conditions. The NLCSs and PLCSs are Ca(2+) signals in the range of micrometer [FWHM (full width at half maximum): 2.75 ± 0.27 μm (NLCSs) and 2.55 ± 0.17 μm (PLCSs), S.E.M.]. Additionally, global nuclear Ca(2+) signals (NGCSs) were observed. To investigate which type of Ca(2+) channels contribute to the Ca(2+) signals associated with nuclei in skeletal muscle fibers, we performed measurements with the RyR blocker dantrolene, the DHPR blocker nifedipine or the IP3R blocker Xestospongin C. We observed Ca(2+) signals associated with nuclei in the presence of each blocker. Nifedipine and dantrolene had an inhibitory effect on the fraction of fibers with PLCSs. The situation for the fraction of fibers with NLCSs is more complex indicating that RyR is less important for the generation of NLCSs compared to the generation of PLCSs. The fraction of fibers with NLCSs and PLCSs is not reduced in the presence of Xestospongin C. The localized perinuclear and intranuclear Ca(2+) signals may be a powerful tool for the cell to regulate adaptive processes as gene expression. The intranuclear Ca(2+) signals may be particularly interesting in this respect.

Heat capacities of synthetic hedenbergite, ferrobustamite and CaFeSi2O6 glass

USGS Publications Warehouse

Haselton, H.T.; Robie, R.A.; Hemingway, B.S.

1987-01-01

Heat capacities have been measured for synthetic hedenbergite (9-647 K), ferrobustamite (5-746 K) and CaFeSi2O6 glass (6-380 K) by low-temperature adiabatic and differential scanning calorimetry. The heat capacity of each of these structural forms of CaFeSiO6 exhibits anomalous behavior at low temperatures. The X-peak in the hedenbergite heat-capacity curve at 34.5 K is due to antiferromagnetic ordering of the Fe2+ ions. Ferrobustamite has a bump in its heat-capacity curve at temperatures less than 20 K, which could be due to weak cooperative magnetic ordering or to a Schottky anomaly. Surprisingly, a broad peak with a maximum at 68 K is present in the heat-capacity curve of the glass. If this maximum, which occurs at a higher temperature than in hedenbergite is caused by magnetic ordering, it could indicate that the range of distortions of the iron sites in the glass is quite small and that coupling between iron atoms is stronger in the glass than in the edge-shared octahedral chains of hedenbergite. The standard entropy change, So298.15 - So0, is 174.2 ?? 0.3, 180.5 ?? 0.3 and 185.7 ?? 0.4 J/mol??K for hedenbergite, ferrobustamite and CaFeSi2O6 glass, respectively. Ferrobustamite is partially disordered in Ca-Fe distribution at high temperatures, but the dependence of the configuratonal entropy on temperature cannot be evaluated due to a lack of information. At high temperatures (298-1600 K), the heat capacity of hedenbergite may be represented by the equation Cop(J/mol??K) = 3l0.46 + 0.01257T-2039.93T -1 2 - 1.84604?? l06T-2 and the heat capacity of ferrobustamite may be represented by Cop(J/mol??K) = 403.83-0.04444T+ 1.597?? 10-5T2-3757.3T -1 2. ?? 1987.

Interannual physiological and growth responses of glacial Juniperus to changes in atmospheric [CO2] since the Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Gerhart, L. M.; Harris, J. M.; Ward, J. K.

2011-12-01

During the Last Glacial Maximum, atmospheric [CO2] was as low as 180 ppm and has currently risen to a modern value of 393 ppm as a result of fossil fuel combustion and deforestation. In order to understand how changing [CO2] influenced trees over the last 50,000 years, we analyzed carbon isotope ratios and width of individual tree rings from glacial Juniperus specimens preserved in the Rancho La Brea tar pits in southern California (aged 14-49 kyr BP). Modern trees were also analyzed to compare effects of changing precipitation, temperature and atmospheric [CO2] on physiology and growth. To assess physiological responses, we calculated ci/ca (intercellular [CO2]/atmospheric [CO2]) for each annual ring of each tree. This ratio incorporates numerous aspects of plant physiology, including stomatal conductance and photosynthetic capacity. In addition, we measured ring widths for each sample, and standardized these measurements into indices in order to compare across individuals. Mean ci/ca values remained constant throughout 50,000 years despite major environmental changes, indicating a long-term physiological set point for ci/ca in this group. Constant ci/ca ratios would be maintained through offsetting changes in stomatal conductance and photosynthetic capacity. Glacial Juniperus never experienced ci values below 90 ppm, suggesting a survival compensation point for Juniperus. In addition, glacial trees showed significantly reduced interannual variation in ci/ca, even though interannual climatic variability was as high during the LGM in this region as it is today. A lack of variability in ci/ca of glacial trees suggests that tree physiology was dominated by low [CO2], which shows low interannual variation. Modern trees showed high interannual variation in ci/ca, since water availability dominates current physiological responses and varies greatly from year to year. Interestingly, interannual variation in ring width index did not show significant differences between glacial and modern trees, suggesting these trees were adapted to maintain growth under low [CO2]. These adaptations may constrain the ability of modern trees to fully utilize increases in atmospheric [CO2]. These results have significant implications for our understanding of the adaptations of trees to changing [CO2] and indicate that the environmental factors that most strongly influence plant physiology may have changed over geologic time scales.

Understanding cold bias: Variable response of skeletal Sr/Ca to seawater pCO2 in acclimated massive Porites corals

PubMed Central

Cole, Catherine; Finch, Adrian; Hintz, Christopher; Hintz, Kenneth; Allison, Nicola

2016-01-01

Coral skeletal Sr/Ca is a palaeothermometer commonly used to produce high resolution seasonal sea surface temperature (SST) records and to investigate the amplitude and frequency of ENSO and interdecadal climate events. The proxy relationship is typically calibrated by matching seasonal SST and skeletal Sr/Ca maxima and minima in modern corals. Applying these calibrations to fossil corals assumes that the temperature sensitivity of skeletal Sr/Ca is conserved, despite substantial changes in seawater carbonate chemistry between the modern and glacial ocean. We present Sr/Ca analyses of 3 genotypes of massive Porites spp. corals (the genus most commonly used for palaeoclimate reconstruction), cultured under seawater pCO2 reflecting modern, future (year 2100) and last glacial maximum (LGM) conditions. Skeletal Sr/Ca is indistinguishable between duplicate colonies of the same genotype cultured under the same conditions, but varies significantly in response to seawater pCO2 in two genotypes of Porites lutea, whilst Porites murrayensis is unaffected. Within P. lutea, the response is not systematic: skeletal Sr/Ca increases significantly (by 2–4%) at high seawater pCO2 relative to modern in both genotypes, and also increases significantly (by 4%) at low seawater pCO2 in one genotype. This magnitude of variation equates to errors in reconstructed SST of up to −5 °C. PMID:27241795

Zn2+, not Ca2+, is the most effective cation for activation of dolichol kinase of mammalian brain.

PubMed

Sakakihara, Y; Volpe, J J

1985-12-15

The cation specificity of dolichol kinase of mammalian brain and the potential involvement of a Ca2+-calmodulin system in regulation of this enzyme have been studied. Among 10 divalent cations examined, Zn2+ was found to be most effective for the activation of dolichol kinase of rat and calf brain and cultured C-6 glial cells. The activations with Ca2+, Co2+, and Mg2+ were 53%, 32%, and 18% of the full activation with Zn2+, respectively. No combinations of the cations could activate the enzyme as much as Zn2+ alone. A role for a Ca2+-calmodulin system in the regulation of brain dolichol kinase was not supported by our data. First, the concentration of free Ca2+ required for the maximum activation of dolichol kinase was two to three orders of magnitude greater than the concentration required by typical calmodulin-dependent enzymes. Second, neither the depletion of calmodulin from the microsomal fraction nor the addition of exogenous calmodulin caused an alteration in the activation of dolichol kinase by Ca2+ (or Zn2+). Third, antagonists of calmodulin failed to suppress the activation of the enzyme by Ca2+ (or Zn2+). The data raise the possibility that Zn2+ is involved in the regulation of dolichol kinase in brain.

Effect of lattice strain on structural and magnetic properties of Ca substituted barium hexaferrite

NASA Astrophysics Data System (ADS)

Kumar, Sunil; Supriya, Sweety; Pandey, Rabichandra; Pradhan, Lagen Kumar; Singh, Rakesh Kumar; Kar, Manoranjan

2018-07-01

The calcium (Ca2+) substituted M-type barium hexaferrite (Ba1-xCaxFe12O19) for Ca2+ (x = 0.00, 0.025, 0.050, 0.075, 0.100, 0.150, and 0.200) have been synthesized by the citrate sol-gel method. The X-ray diffraction (XRD) patterns with Rietveld refinement reveal the formation of hexagonal crystal structure with P63/mmc space group. The lattice parameters a = b and c decrease, whereas lattice strain found to increase with the increase in Ca concentration in the samples. The analysis of Raman spectra well supports the XRD patterns analysis. The average particle size is obtained from the FE-SEM (Field Emission Scanning Electron Microscopy) micrographs and these are similar to that of crystallite size obtained from the XRD pattern analysis. The saturation magnetization and magnetocrystalline anisotropy have been obtained by employing the "Law of Approach (LA) to Saturation magnetization" technique at room temperature. The saturation magnetization and magnetocrystalline anisotropy constant are maximum for 5% Ca substitution in barium hexaferrite. It could be due to lattice strain mediated magnetism. However, these magnetic properties decrease for more than the 5% Ca substitution in barium hexaferrite. It could be due to decrease of magnetic exchange interaction (Fe-O-Fe) in the sample. A correlation between magnetic interaction and lattice strain has been observed in Ca2+ substituted M-type barium hexaferrite.

Understanding cold bias: Variable response of skeletal Sr/Ca to seawater pCO2 in acclimated massive Porites corals.

PubMed

Cole, Catherine; Finch, Adrian; Hintz, Christopher; Hintz, Kenneth; Allison, Nicola

2016-05-31

Coral skeletal Sr/Ca is a palaeothermometer commonly used to produce high resolution seasonal sea surface temperature (SST) records and to investigate the amplitude and frequency of ENSO and interdecadal climate events. The proxy relationship is typically calibrated by matching seasonal SST and skeletal Sr/Ca maxima and minima in modern corals. Applying these calibrations to fossil corals assumes that the temperature sensitivity of skeletal Sr/Ca is conserved, despite substantial changes in seawater carbonate chemistry between the modern and glacial ocean. We present Sr/Ca analyses of 3 genotypes of massive Porites spp. corals (the genus most commonly used for palaeoclimate reconstruction), cultured under seawater pCO2 reflecting modern, future (year 2100) and last glacial maximum (LGM) conditions. Skeletal Sr/Ca is indistinguishable between duplicate colonies of the same genotype cultured under the same conditions, but varies significantly in response to seawater pCO2 in two genotypes of Porites lutea, whilst Porites murrayensis is unaffected. Within P. lutea, the response is not systematic: skeletal Sr/Ca increases significantly (by 2-4%) at high seawater pCO2 relative to modern in both genotypes, and also increases significantly (by 4%) at low seawater pCO2 in one genotype. This magnitude of variation equates to errors in reconstructed SST of up to -5 °C.

An impurity intermediate band due to Pb doping induced promising thermoelectric performance of Ca5In2Sb6.

PubMed

Feng, Zhenzhen; Wang, Yuanxu; Yan, Yuli; Zhang, Guangbiao; Yang, Jueming; Zhang, Jihua; Wang, Chao

2015-06-21

Band engineering is one of the effective approaches for designing ideal thermoelectric materials. Introducing an intermediate band in the band gap of semiconducting thermoelectric compounds may largely increase the carrier concentration and improve the electrical conductivity of these compounds. We test this hypothesis by Pb doping in Zintl Ca5In2Sb6. In the current work, we have systematically investigated the electronic structure and thermoelectric performances of substitutional doping with Pb on In sites at a doping level of 5% (0.2 e per cell) for Ca5In2Sb6 by using density functional theory combined with semi-classical Boltzmann theory. It is found that in contrast to Zn doping, Pb doping introduces a partially filled intermediate band in the band gap of Ca5In2Sb6, which originates from the Pb s states by weakly hybridizing with the Sb p states. Such an intermediate band dramatically increases the electrical conductivity of Ca5In2Sb6 and has little detrimental effect on its Seebeck coefficient, which may increase its thermoelectric figure of merit, ZT. Interestingly, a maximum ZT value of 2.46 may be achieved at 900 K for crystalline Pb-doped Ca5In2Sb6 when the carrier concentration is optimized. Therefore, Pb-doped Ca5In2Sb6 may be a promising thermoelectric material.

Two Ca current components of the receptor current in the electroreceptors of the marine catfish Plotosus.

PubMed

Sugawara, Y

1989-02-01

In the isolated sensory epithelium of the Plotosus electroreceptor, the receptor current has been dissected into inward Ca current, ICa, and superimposed outward transient of Ca-gated K current, IK(Ca). In control saline (170 mM/liter Na), with IK(Ca) abolished by K blockers, ICa declined in two successive exponential phases with voltage-dependent time constants. Double-pulse experiments revealed that the test ICa was partially depressed by prepulses, maximally near voltage levels for the control ICa maximum, which suggests current-dependent inactivation. In low Na saline (80 mM/liter), ICa declined in a single phase with time constants similar to those of the slower phase in control saline. The test ICa was then unaffected by prepulses. The implied presence of two Ca current components, the fast and slow ICa's, were further examined. In control saline, the PSP externally recorded from the afferent nerve showed a fast peak and a slow tonic phase. The double-pulse experiments revealed that IK(Ca) and the peak PSP were similarly depressed, i.e., secondarily to inactivation of the peak current. The steady inward current, however, was unaffected by prolonged prepulses that were stepped to 0 mV, the in situ DC level. Therefore, the fast ICa seems to initiate IK(Ca) and phasic release of transmitter, which serves for phasic receptor responses. The slow ICa may provide persistent active current, which has been shown to maintain tonic receptor operation.

Modulatory effects of Cassia fistula fruits against free radicals and genotoxicity of mutagens.

PubMed

Kaur, Sandeep; Kumar, Manish; Kaur, Paramjeet; Kaur, Varinder; Kaur, Satwinderjeet

2016-12-01

Cassia fistula L. (Fabaceae) fruits are highly recommended in folklore medicine for curing various ailments. In the current study, methanol (CaFM), hexane (CaFH), chloroform (CaFCl), ethyl acetate (CaFE), butanol (CaFB) and aqueous (CaFA) fractions of C. fistula fruits were investigated for their potential to inhibit the genotoxicity of mutagens and free radicals. The antimutagenicity of fractions was evaluated against the reactive carcinogenic ester generating mutagen, 2-aminofluorene (2-AF) and frame-shift mutation inducing mutagen, 4-nitro-o-phenylenediamine (NPD) in Ames Salmonella typhimurium TA98 tester strain. Among the fractions, CaFE showed strongest protective effect against the mutagenicity of both S9-dependent and direct-acting mutagen with an inhibitory percentage of 81% and 64% at the concentration of 1 × 10 3 and 2.5 × 10 3 respectively. All the fractions were analyzed for free radical scavenging activity using DPPH, nitric oxide, lipid peroxidation and superoxide anion assays. CaFE fraction showed maximum antioxidant activity in comparison to other fractions with an IC 50 of 97.01, 172.36, 144 and 264.79 μg/ml respectively. High performance liquid chromatography showed the presence of catechin, epicatechin and umbelliferone in appreciable amount which may account for its efficacy in combating free radicals and also showed protective effect against the mutagenicity of S9-dependent mutagen, 2-AF. Copyright © 2016 Elsevier Ltd. All rights reserved.

Growth Temperature Dependence of Morphology of GaN Single Crystals in the Na-Li-Ca Flux Method

NASA Astrophysics Data System (ADS)

Wu, Xi; Hao, Hangfei; Li, Zhenrong; Fan, Shiji; Xu, Zhuo

2018-02-01

In this paper, the effect of growth temperature on the morphology and transparency of the GaN crystals obtained by the Li-Ca-added Na Flux method was studied. Addition of Li-Ca was attempted to control the growth habit and further improve transparency of GaN crystals. The samples with wurtzite structure of GaN were confirmed by the x-ray powder diffraction analysis. GaN single crystal with maximum size of about 6 mm was grown at 750°C. As the growth temperature was increased from 700°C to 850°C, the morphology of the crystals changed from pyramid to prism, and their surfaces became smooth. It was found that high growth temperature was beneficial to obtain a transparent crystal, but the evaporation of sodium would suppress its further growth. The E 2 (high) mode in the Raman spectra was at 568 cm-1, and the full-width at half-maximum values of this peak for the crystals obtained at 700°C, 750°C, 800°C, and 850°C were 7.5 cm-1, 10.3 cm-1, 4.4 cm-1, and 4.0 cm-1, respectively. It indicates that all the crystals are stress free and the transparent crystal grown at high temperature has high structural quality or low impurity concentrations.

ECOLOGICAL ENDPOINT MODELING: EFFECTS OF SEDIMENT ON FISH POPULATIONS

EPA Science Inventory

Sediment is one of the main stressors of concern for TMDLs (Total Maximum Daily Loads) for streams, and often it is a concern because of its impact on biological endpoints. The National Research Council (NRC) has recommended that the EPA promote the development of models that ca...

Small Ca2+ releases enable hour-long high-frequency contractions in midshipman swimbladder muscle.

PubMed

Nelson, Frank E; Hollingworth, Stephen; Marx, James O; Baylor, Stephen M; Rome, Lawrence C

2018-01-02

Type I males of the Pacific midshipman fish ( Porichthys notatus ) vibrate their swimbladder to generate mating calls, or "hums," that attract females to their nests. In contrast to the intermittent calls produced by male Atlantic toadfish ( Opsanus tau ), which occur with a duty cycle (calling time divided by total time) of only 3-8%, midshipman can call continuously for up to an hour. With 100% duty cycles and frequencies of 50-100 Hz (15°C), the superfast muscle fibers that surround the midshipman swimbladder may contract and relax as many as 360,000 times in 1 h. The energy for this activity is supported by a large volume of densely packed mitochondria that are found in the peripheral and central regions of the fiber. The remaining fiber cross section contains contractile filaments and a well-developed network of sarcoplasmic reticulum (SR) and triadic junctions. Here, to understand quantitatively how Ca 2+ is managed by midshipman fibers during calling, we measure (a) the Ca 2+ pumping-versus-pCa and force-versus-pCa relations in skinned fiber bundles and (b) changes in myoplasmic free [Ca 2+ ] (Δ[Ca 2+ ]) during stimulated activity of individual fibers microinjected with the Ca 2+ indicators Mag-fluo-4 and Fluo-4. As in toadfish, the force-pCa relation in midshipman is strongly right-shifted relative to the Ca 2+ pumping-pCa relation, and contractile activity is controlled in a synchronous, not asynchronous, fashion during electrical stimulation. SR Ca 2+ release per action potential is, however, approximately eightfold smaller in midshipman than in toadfish. Midshipman fibers have a larger time-averaged free [Ca 2+ ] during activity than toadfish fibers, which permits faster Ca 2+ pumping because the Ca 2+ pumps work closer to their maximum rate. Even with midshipman's sustained release and pumping of Ca 2+ , however, the Ca 2+ energy cost of calling (per kilogram wet weight) is less than twofold more in midshipman than in toadfish. © 2018 Nelson et al.

The Ca-looping process for CO2 capture and energy storage: role of nanoparticle technology

NASA Astrophysics Data System (ADS)

Valverde, Jose Manuel

2018-02-01

The calcium looping (CaL) process, based on the cyclic carbonation/calcination of CaO, has come into scene in the last years with a high potential to be used in large-scale technologies aimed at mitigating global warming. In the CaL process for CO2 capture, the CO2-loaded flue gas is used to fluidize a bed of CaO particles at temperatures around 650 °C. The carbonated particles are then circulated into a calciner reactor wherein the CaO solids are regenerated at temperatures near 950 °C under high CO2 concentration. Calcination at such harsh conditions causes a marked sintering and loss of reactivity of the regenerated CaO. This main drawback could be however compensated from the very low cost of natural CaO precursors such as limestone or dolomite. Another emerging application of the CaL process is thermochemical energy storage (TCES) in concentrated solar power (CSP) plants. Importantly, carbonation/calcination conditions to maximize the global CaL-CSP plant efficiency could differ radically from those used for CO2 capture. Thus, carbonation could be carried out at high temperatures under high CO2 partial pressure for maximum efficiency, whereas the solids could be calcined at relatively low temperatures in the absence of CO2 to promote calcination. Our work highlights the critical role of carbonation/calcination conditions on the performance of CaO derived from natural precursors. While conditions in the CaL process for CO2 capture lead to a severe CaO deactivation with the number of cycles, the same material may exhibit a high and stable conversion at optimum CaL-CSP conditions. Moreover, the type of CaL conditions influences critically the reaction kinetics, which plays a main role on the optimization of relevant operation parameters such as the residence time in the reactors. This paper is devoted to a brief review on the latest research activity in our group concerning these issues as well as the possible role of nanoparticle technology to enhance the activity of Ca-based materials at CaL conditions for CO2 capture and energy storage.

A New Multi-Basin Calibration for Estimating Paleo-Temperature Using Mg/Ca from Tests of Neogloboquadrina dutertrei

NASA Astrophysics Data System (ADS)

Collins, M. S.; Hertzberg, J. E.; Mekik, F.; Schmidt, M. W.

2017-12-01

Based on the thermodynamics of solid-solution substitution of Mg for Ca in biogenic calcite, magnesium to calcium ratios in planktonic foraminifera have been proposed as a means by which variations in habitat water temperatures can be reconstructed. Doing this accurately has been a problem, however, as we demonstrate that various calibration equations provide disparate temperature estimates from the same Mg/Ca dataset. We examined both new and published data to derive a globally applicable temperature-Mg/Ca relationship and from this relationship to accurately predict habitat depth for Neogloboquadrina dutertrei - a deep chlorophyll maximum dweller. N. dutertrei samples collected from Atlantic core tops were analyzed for trace element compositions at Texas A&M University, and the measured Mg/Ca ratios were used to predict habitat temperatures using multiple pre-existing calibration equations. When combining Atlantic and previously published Pacific Mg/Ca datasets for N. dutertrei, a notable dissolution effect was evident. To overcome this issue, we used the G. menardii Fragmentation Index (MFI) to account for dissolution and generated a multi-basin temperature equation using multiple linear regression to predict habitat temperature. However, the correlations between Mg/Ca and temperature, as well as the calculated MFI percent dissolved, suggest that N. dutertrei Mg/Ca ratios are affected equally by both variables. While correcting for dissolution makes habitat depth estimation more accurate, the lack of a definitively strong correlation between Mg/Ca and temperature is likely an effect of variable habitat depth for this species because most calibration equations have assumed a uniform habitat depth for this taxon.

Alpha-ketoglutarate decreases serum levels of C-terminal cross-linking telopeptide of type I collagen (CTX) in postmenopausal women with osteopenia: six-month study.

PubMed

Filip, Rafał S; Pierzynowski, Stefan G; Lindegard, Birger; Wernerman, Jan; Haratym-Maj, Agnieszka; Podgurniak, Małgorzata

2007-03-01

Several studies have shown that alpha-ketoglutaric acid (AKG) increases serum levels of proline and has beneficial effects on skeletal development. We studied the effect of alpha-ketoglutaric (AKG) acid calcium salt (6 g AKG and 1.68 Ca/day) or calcium alone (1.68 Ca/day) on serum C-terminal cross-linked telopeptide of type I collagen (CTX) and osteocalcin (OC), as well as on lumbar spine bone mineral density (BMD) in a randomized, parallel group, double-blind, 6-month study conducted on 76 postmenopausal women with osteopenia. The maximum decrease of the mean CTX level in the AKG-Ca group was observed after 24 weeks (37.0%, p = 0.006). The differences in CTX between study groups were statistically significant after 12 and 24 weeks. The OC serum level was not affected by treatments. The BMD of the AKG-Ca group increased by 1.6% from baseline; however, the difference between treatment groups was estimated as 0.9% (non-significant). This study suggests the potential usefulness of AKG-Ca in osteopenic postmenopausal women. AKG-Ca induced beneficial changes in serum CTX, which was consistent with preserving the bone mass in the lumbar spine; however, the long-term effect needs to be further investigated.

Alkali-activated complex binders from class C fly ash and Ca-containing admixtures.

PubMed

Guo, Xiaolu; Shi, Huisheng; Chen, Liming; Dick, Warren A

2010-01-15

Processes that maximize utilization of industrial solid wastes are greatly needed. Sodium hydroxide and sodium silicate solution were used to create alkali-activated complex binders (AACBs) from class C fly ash (CFA) and other Ca-containing admixtures including Portland cement (PC), flue gas desulfurization gypsum (FGDG), and water treatment residual (WTR). Specimens made only from CFA (CFA100), or the same fly ash mixed with 40 wt% PC (CFA60-PC40), with 10 wt% FGDG (CFA90-FGDG10), or with 10 wt% WTR (CFA90-WTR10) had better mechanical performance compared to binders using other mix ratios. The maximum compressive strength of specimens reached 80.0 MPa. Geopolymeric gel, sodium polysilicate zeolite, and hydrated products coexist when AACB reactions occur. Ca from CFA, PC, and WTR precipitated as Ca(OH)(2), bonded in geopolymers to obtain charge balance, or reacted with dissolved silicate and aluminate species to form calcium silicate hydrate (C-S-H) gel. However, Ca from FGDG probably reacted with dissolved silicate and aluminate species to form ettringite. Utilization of CFA and Ca-containing admixtures in AACB is feasible. These binders may be widely utilized in various applications such as in building materials and for solidification/stabilization of other wastes, thus making the wastes more environmentally benign.

Induction of defence gene expression by oligogalacturonic acid requires increases in both cytosolic calcium and hydrogen peroxide in Arabidopsis thaliana.

PubMed

Hu, Xiang Yang; Neill, Steven J; Cai, Wei Ming; Tang, Zhang Cheng

2004-06-01

Responses to oligogalacturonic acid (OGA) were determined in transgenic Arabidopsis thaliana seedlings expressing the calcium reporter protein aequorin. OGA stimulated a rapid, substantial and transient increase in the concentration of cytosolic calcium ([Ca2+]cyt) that peaked after ca. 15 s. This increase was dose-dependent, saturating at ca. 50 ug Gal equiv/ml of OGA. OGA also stimulated a rapid generation of H2O2. A small, rapid increase in H2O2 content was followed by a much larger oxidative burst, with H2O2 content peaking after ca. 60 min and declining thereafter. Induction of the oxidative burst by OGA was also dose-dependent, with a maximum response again being achieved at ca. 50 ug Gal equiv/mL. Inhibitors of calcium fluxes inhibited both increases in [Ca2+]cyt and [H2O2], whereas inhibitors of NADPH oxidase blocked only the oxidative burst. OGA increased strongly the expression of the defence-related genes CHS, GST, PAL and PR-1. This induction was suppressed by inhibitors of calcium flux or NADPH oxidase, indicating that increases in both cytosolic calcium and H2O2 are required for OGA-induced gene expression.

Magnetic properties of LCMO deposited films

NASA Astrophysics Data System (ADS)

Park, Seung-Iel; Jeong, Kwang Ho; Cho, Young Suk; Kim, Chul Sung

2002-04-01

La-Ca-Mn-O films were deposited with various thickness (500, 1000 and 1500°C) by RF-magnetron sputtering at 700°C and by the spin coating of sol-gel method at 400°C on LaAlO 3(1 0 0) and Si(1 0 0) single-crystal substrates. The crystal structure and chemical composition of the film grown by RF sputtering method were orthorhombic and La 0.89Ca 0.11MnO 3, respectively, while the film prepared by sol-gel spin coating was cubic with La 0.7Ca 0.3MnO 3. The temperature dependence of the resistance for the film grown by RF sputtering method with the thickness of 1000°C shows that a semiconductor-metal transition occurs at 242 K. The relative maximum magnetoresistance is about 273% at 226 K.

Luminescence investigation and thermal stability of blue-greenish emission generated from Ca3MgSi2O8: Eu2+ phosphor

NASA Astrophysics Data System (ADS)

Stefańska, D.; Dereń, P. J.

2018-06-01

Europium-doped silicate Ca3MgSi2O8 has been successfully obtained using solid-state reaction at 1400 °C in a vacuum atmosphere. The photoluminescence study of Eu2+ in investigated host showed broad emission band with a maximum at 480 nm attributed to the allowed 5d → 4f electron transition of Eu2+ located in two different crystallographic sites. The excitation, emission spectra as well as the luminescence decays were analyzed. Thermal quenching process begins at 240 K, however, the emission stability of investigated compound is quite good, and emission intensity reached to 70% of its initial value at 100 °C. The QE of Ca3MgSi2O8: 0.5% Eu2+ excited at 365 nm equal to 47%.

caCORE: a common infrastructure for cancer informatics.

PubMed

Covitz, Peter A; Hartel, Frank; Schaefer, Carl; De Coronado, Sherri; Fragoso, Gilberto; Sahni, Himanso; Gustafson, Scott; Buetow, Kenneth H

2003-12-12

Sites with substantive bioinformatics operations are challenged to build data processing and delivery infrastructure that provides reliable access and enables data integration. Locally generated data must be processed and stored such that relationships to external data sources can be presented. Consistency and comparability across data sets requires annotation with controlled vocabularies and, further, metadata standards for data representation. Programmatic access to the processed data should be supported to ensure the maximum possible value is extracted. Confronted with these challenges at the National Cancer Institute Center for Bioinformatics, we decided to develop a robust infrastructure for data management and integration that supports advanced biomedical applications. We have developed an interconnected set of software and services called caCORE. Enterprise Vocabulary Services (EVS) provide controlled vocabulary, dictionary and thesaurus services. The Cancer Data Standards Repository (caDSR) provides a metadata registry for common data elements. Cancer Bioinformatics Infrastructure Objects (caBIO) implements an object-oriented model of the biomedical domain and provides Java, Simple Object Access Protocol and HTTP-XML application programming interfaces. caCORE has been used to develop scientific applications that bring together data from distinct genomic and clinical science sources. caCORE downloads and web interfaces can be accessed from links on the caCORE web site (http://ncicb.nci.nih.gov/core). caBIO software is distributed under an open source license that permits unrestricted academic and commercial use. Vocabulary and metadata content in the EVS and caDSR, respectively, is similarly unrestricted, and is available through web applications and FTP downloads. http://ncicb.nci.nih.gov/core/publications contains links to the caBIO 1.0 class diagram and the caCORE 1.0 Technical Guide, which provide detailed information on the present caCORE architecture, data sources and APIs. Updated information appears on a regular basis on the caCORE web site (http://ncicb.nci.nih.gov/core).

Mitochondrial and myoplasmic [Ca2+] in single fibres from mouse limb muscles during repeated tetanic contractions

PubMed Central

Bruton, Joseph; Tavi, Pasi; Aydin, Jan; Westerblad, Håkan; Lännergren, Jan

2003-01-01

Previous studies on single fast-twitch fibres from mouse toe muscles have shown marked fatigue-induced changes in the free myoplasmic [Ca2+] ([Ca2+]i), while mitochondrial [Ca2+] remained unchanged. We have now investigated whether muscle fibres from the legs of mice respond in a similar way. Intact, single fibres were dissected from the soleus and extensor digitorum longus (EDL) muscles of adult mice. To measure [Ca2+]i, indo-1 was injected into the isolated fibres. Mitochondrial [Ca2+] was measured using Rhod-2 and confocal laser microscopy. Fatigue was induced by up to 1000 tetanic contractions (70 Hz) given at 2 s intervals. In soleus fibres, there was no significant decrease in tetanic [Ca2+]i at the end of the fatiguing stimulation, whereas tetanic force was significantly reduced by about 30 %. In 10 out of 14 soleus fibres loaded with Rhod-2 and subjected to fatigue, mitochondrial [Ca2+] increased to a maximum after about 50 tetani; this increase was fully reversed within 20 min after the end of stimulation. The force-frequency curve of the non-responding soleus fibres was shifted to higher frequencies compared to that of the responding fibres. In addition, eight out of nine Rhod-2-loaded EDL fibres showed similar changes in mitochondrial [Ca2+] during and after a period of fatiguing stimulation. The stimulation-induced increase in mitochondrial [Ca2+] was reduced when mitochondria were depolarised by application of carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone, whereas it was increased by application of an inhibitor of the mitochondrial Na+/Ca2+ exchange (CGP-37157). In conclusion, isolated slow-twitch muscle fibres show only modest changes in tetanic force and [Ca2+]i during repeated contractions. The increase in mitochondrial Ca2+ does not appear to be essential for activation of mitochondrial ATP production, nor does it cause muscle damage. PMID:12815178

Assessment of major ions and trace elements in groundwater supplied to the Monterrey metropolitan area, Nuevo León, Mexico.

PubMed

Mora, Abrahan; Mahlknecht, Jürgen; Rosales-Lagarde, Laura; Hernández-Antonio, Arturo

2017-08-01

The Monterrey metropolitan area (MMA) is the third greatest urban area and the second largest economic city of Mexico. More than four million people living in this megacity use groundwater for drinking, industrial and household purposes. Thus, major ion and trace element content were assessed in order to investigate the main hydrochemical properties of groundwater and determine if groundwater of the area poses a threat to the MMA population. Hierarchical cluster analysis using all the groundwater chemical data showed five groups of water. The first two groups were classified as recharge waters (Ca-HCO 3 ) coming from the foothills of mountain belts. The third group was also of Ca-HCO 3 water type flowing through lutites and limestones. Transition zone waters of group four (Ca-HCO 3 -SO 4 ) flow through the valley of Monterrey, whereas discharge waters of group 5 (Ca-SO 4 ) were found toward the north and northeast of the MMA. Principal component analysis performed in groundwater data indicates four principal components (PCs). PC1 included major ions Si, Co, Se, and Zn, suggesting that these are derived by rock weathering. Other trace elements such as As, Mo, Mn, and U are coupled in PC2 because they show redox-sensitive properties. PC3 indicates that Pb and Cu could be the less mobile elements in groundwater. Although groundwater supplied to MMA showed a high-quality, high mineralized waters of group 5 have NO 3 - concentrations higher than the maximum value proposed by international guidelines and SO 4 2- , NO 3 - , and total dissolved solid concentrations higher than the maximum levels allowed by the Mexican normative.

Physiological outperformance at the morphologically-transformed edge of the cyanobacteriosponge Terpios hoshinota (Suberitidae: Hadromerida) when confronting opponent corals.

PubMed

Wang, Jih-Terng; Hsu, Chia-Min; Kuo, Chao-Yang; Meng, Pei-Jie; Kao, Shuh-Ji; Chen, Chaolun Allen

2015-01-01

Terpios hoshinota, an encrusting cyanosponge, is known as a strong substrate competitor of reef-building corals that kills encountered coral by overgrowth. Terpios outbreaks cause significant declines in living coral cover in Indo-Pacific coral reefs, with the damage usually lasting for decades. Recent studies show that there are morphological transformations at a sponge's growth front when confronting corals. Whether these morphological transformations at coral contacts are involved with physiological outperformance (e.g., higher metabolic activity or nutritional status) over other portions of Terpios remains equivocal. In this study, we compared the indicators of photosynthetic capability and nitrogen status of a sponge-cyanobacteria association at proximal, middle, and distal portions of opponent corals. Terpios tissues in contact with corals displayed significant increases in photosynthetic oxygen production (ca. 61%), the δ13C value (ca. 4%), free proteinogenic amino acid content (ca. 85%), and Gln/Glu ratio (ca. 115%) compared to middle and distal parts of the sponge. In contrast, the maximum quantum yield (Fv/Fm), which is the indicator usually used to represent the integrity of photosystem II, of cyanobacteria photosynthesis was low (0.256~0.319) and showed an inverse trend of higher values in the distal portion of the sponge that might be due to high and variable levels of cyanobacterial phycocyanin. The inconsistent results between photosynthetic oxygen production and Fv/Fm values indicated that maximum quantum yields might not be a suitable indicator to represent the photosynthetic function of the Terpios-cyanobacteria association. Our data conclusively suggest that Terpios hoshinota competes with opponent corals not only by the morphological transformation of the sponge-cyanobacteria association but also by physiological outperformance in accumulating resources for the battle.

Relationships between free-living protozoa, cultivable Legionella spp., and water quality characteristics in three drinking water supplies in the Caribbean.

PubMed

Valster, Rinske M; Wullings, Bart A; van den Berg, Riemsdijk; van der Kooij, Dick

2011-10-01

The study whose results are presented here aimed at identifying free-living protozoa (FLP) and conditions favoring the growth of these organisms and cultivable Legionella spp. in drinking water supplies in a tropical region. Treated and distributed water (±30°C) of the water supplies of three Caribbean islands were sampled and investigated with molecular techniques, based on the 18S rRNA gene. The protozoan host Hartmannella vermiformis and cultivable Legionella pneumophila were observed in all three supplies. Operational taxonomic units (OTUs) with the highest similarity to the potential or candidate hosts Acanthamoeba spp., Echinamoeba exundans, E. thermarum, and an Neoparamoeba sp. were detected as well. In total, 59 OTUs of FLP were identified. The estimated protozoan richness did not differ significantly between the three supplies. In supply CA-1, the concentration of H. vermiformis correlated with the concentration of Legionella spp. and clones related to Amoebozoa predominated (82%) in the protozoan community. These observations, the low turbidity (<0.2 nephelometric turbidity units [NTU]), and the varying ATP concentrations (1 to 12 ng liter(-1)) suggest that biofilms promoted protozoan growth in this supply. Ciliophora represented 25% of the protozoan OTUs in supply CA-2 with elevated ATP concentrations (maximum, 55 ng liter(-1)) correlating with turbidity (maximum, 62 NTU) caused by corroding iron pipes. Cercozoan types represented 70% of the protozoan clones in supply CA-3 with ATP concentrations of <1 ng liter(-1) and turbidity of <0.5 NTU in most samples of distributed water. The absence of H. vermiformis in most samples from supply CA-3 suggests that growth of this protozoan is limited at ATP concentrations of <1 ng liter(-1).

Relationships between Free-Living Protozoa, Cultivable Legionella spp., and Water Quality Characteristics in Three Drinking Water Supplies in the Caribbean▿†

PubMed Central

Valster, Rinske M.; Wullings, Bart A.; van den Berg, Riemsdijk; van der Kooij, Dick

2011-01-01

The study whose results are presented here aimed at identifying free-living protozoa (FLP) and conditions favoring the growth of these organisms and cultivable Legionella spp. in drinking water supplies in a tropical region. Treated and distributed water (±30°C) of the water supplies of three Caribbean islands were sampled and investigated with molecular techniques, based on the 18S rRNA gene. The protozoan host Hartmannella vermiformis and cultivable Legionella pneumophila were observed in all three supplies. Operational taxonomic units (OTUs) with the highest similarity to the potential or candidate hosts Acanthamoeba spp., Echinamoeba exundans, E. thermarum, and an Neoparamoeba sp. were detected as well. In total, 59 OTUs of FLP were identified. The estimated protozoan richness did not differ significantly between the three supplies. In supply CA-1, the concentration of H. vermiformis correlated with the concentration of Legionella spp. and clones related to Amoebozoa predominated (82%) in the protozoan community. These observations, the low turbidity (<0.2 nephelometric turbidity units [NTU]), and the varying ATP concentrations (1 to 12 ng liter−1) suggest that biofilms promoted protozoan growth in this supply. Ciliophora represented 25% of the protozoan OTUs in supply CA-2 with elevated ATP concentrations (maximum, 55 ng liter−1) correlating with turbidity (maximum, 62 NTU) caused by corroding iron pipes. Cercozoan types represented 70% of the protozoan clones in supply CA-3 with ATP concentrations of <1 ng liter−1 and turbidity of <0.5 NTU in most samples of distributed water. The absence of H. vermiformis in most samples from supply CA-3 suggests that growth of this protozoan is limited at ATP concentrations of <1 ng liter−1. PMID:21873489

Silent calcium channels in skeletal muscle fibers of the crustacean Atya lanipes.

PubMed

Monterrubio, J; Lizardi, L; Zuazaga, C

2000-01-01

The superficial (tonic) abdominal flexor muscles of Atya lanipes do not generate Ca(2+) action potentials when depolarized and have no detectable inward Ca(2+) current. These fibers, however, are strictly dependent on Ca(2+) influx for contraction, suggesting that they depend on Ca(2+)-induced Ca(2+) release for contractile activation. The nature of the communication between Ca(2+) channels in the sarcolemmal/tubular membrane and Ca(2+) release channels in the sarcoplasmic reticulum in this crustacean muscle was investigated. The effects of dihydropyridines on tension generation and the passive electrical response were examined in current-clamped fibers: Bay K 8644 enhanced tension about 100% but did not alter the passive electrical response; nifedipine inhibited tension by about 70%. Sr(2+) and Ba(2+) action potentials could be elicited in Ca(2+)-free solutions. The spikes generated by these divalent cations were abolished by nifedipine. As the Sr(2+) or Ba(2+) concentrations were increased, the amplitudes of the action potentials and their maximum rate of rise, V(max), increased and tended towards saturation. Three-microelectrode voltage-clamp experiments showed that even at high (138 mm) extracellular Ca(2+) concentration the channels were silent, i.e., no inward Ca(2+) current was detected. In Ca(2+)-free solutions, inward currents carried by 138 mm Sr(2+) or Ba(2+) were observed. The currents activated at voltages above -40 mV and peaked at about 0 mV. This voltage-activation profile and the sensitivity of the channels to dihydropyridines indicate that they resemble L-type Ca(2+) channels. Peak inward current density values were low, ca. -33 microA/cm(2) for Sr(2+) and -14 microA/cm(2) for Ba(2+), suggesting that Ca(2+) channels are present at a very low density. It is concluded that Ca(2+)-induced Ca(2+) release in this crustacean muscle operates with an unusually high gain: Ca(2+) influx through the silent Ca(2+) channels is too low to generate a macroscopic inward current, but increases sufficiently the local concentration of Ca(2+) in the immediate vicinity of the sarcoplasmic reticulum Ca(2+) release channels to trigger the highly amplified release of Ca(2+) required for tension generation.

Effects of Ca2+ on oxidative phosphorylation in mitochondria from the thermogenic organ of marlin.

PubMed

O'Brien, J; Block, B A

1996-12-01

Mitochondria from the muscle-derived thermogenic (heater) organ and oxidative red muscle of the blue marlin (Makaira nigricans) were studied in order to evaluate aspects of the mechanism of thermogenesis in heater tissue. We investigated whether short-term Ca(2+)-induced uncoupling of mitochondria contributes to the thermogenic cycle of the heater organ by enhancing the respiration rate. Specific electrodes were used to obtain simultaneous measurements of oxygen consumption and Ca2+ fluxes on isolated mitochondria, and the effects of various concentrations of Ca2+ on respiration rates and the ADP phosphorylated/atomic oxygen consumed (P/O) ratio were examined. Addition of Ca2+ in excess of 10 mumol l-1 to respiring heater organ or red muscle mitochondria partially inhibited state 3 respiration and reduced the P/O ratio, indicating that the mitochondria were partially uncoupled. These effects were blocked by 2 mumol l-1 Ruthenium Red. In heater organ mitochondria, state 3 respiration rate and the P/O ratio were not significantly reduced by 1 mumol l-1 free Ca2+, a concentration likely to be near the maximum achieved in a stimulated cell. This indicates that transient increases in cytosolic Ca2+ concentration may not significantly reduce the P/O ratio of heater organ mitochondria. The activity of 2-oxoglutarate dehydrogenase in heater organ mitochondria was stimulated by approximately 15% by Ca2+ concentrations between 0.2 and 1 mumol l-1. These results suggest that heater organ mitochondria are able to maintain a normal P/O ratio and should maintain ATP output during transient increases in Ca2+ concentration, supporting a model in which an ATP-consuming process drives thermogenesis. Activation of mitochondrial dehydrogenases by low levels of Ca2+ may also enhance respiration and contribute to thermogenesis.

TNFα enhances force generation in airway smooth muscle

PubMed Central

Han, Young-Soo; Delmotte, Philippe

2017-01-01

Airway inflammation is a hallmark of asthma, triggering airway smooth muscle (ASM) hyperreactivity and airway remodeling. TNFα increases both agonist-induced cytosolic Ca2+ concentration ([Ca2+]cyt) and force in ASM. The effects of TNFα on ASM force may also be due to an increase in Ca2+ sensitivity, cytoskeletal remodeling, and/or changes in contractile protein content. We hypothesized that 24 h of exposure to TNFα increases ASM force by changing actin and myosin heavy chain (MyHC) content and/or polymerization. Porcine ASM strips were permeabilized with 10% Triton X-100, and force was measured in response to increasing concentrations of Ca2+ (pCa 9.0 to 4.0) in control and TNFα-treated groups. Relative phosphorylation of the regulatory myosin light chain (p-MLC) and total actin, MLC, and MyHC concentrations were quantified at pCa 9.0, 6.1, and 4.0. Actin polymerization was quantified by the ratio of filamentous to globular actin at pCa 9.0 and 4.0. For determination of total cross-bridge formation, isometric ATP hydrolysis rate at pCa 4.0 was measured using an enzyme-coupled NADH-linked fluorometric technique. Exposure to TNFα significantly increased force across the range of Ca2+ activation but did not affect the intrinsic Ca2+ sensitivity of force generation. The TNFα-induced increase in ASM force was associated with an increase in total actin, MLC, and MyHC content, as well as an increase in actin polymerization and an increase in maximum isometric ATP hydrolysis rate. The results of this study support our hypothesis that TNFα increases force generation in ASM by increasing the number of contractile units (actin-myosin content) contributing to force generation. PMID:28385814

3D seismic imaging of voluminous earliest Eocene buried lava fields and coastal escarpments off mid-Norway

NASA Astrophysics Data System (ADS)

Planke, Sverre; Millett, John M.; Maharjan, Dwarika; Jerram, Dougal A.; Mansour Abdelmalak, Mohamed

2017-04-01

Continental breakup between Greenland and NW Europe in the Paleogene was associated with massive basaltic volcanism, forming kilometer-thick sequences of flood basalts along the conjugate rifted margins. This event was temporarily associated with a warm world, the early Eocene greenhouse, and the short-lived Paleocene-Eocene Thermal Maximum (PETM). A 2500 km2 large industry-standard 3D seismic cube has recently been acquired on the Vøring Marginal High offshore mid-Norway to image sub-basalt sedimentary rocks. This cube also provides a unique opportunity for imaging top- and intra-basalt structures. Detailed seismic geomorphological interpretation of the Top basalt horizon reveal new insight into the late-stage development of the lava flow fields and the kilometer high coastal Vøring Escarpment. Subaerial lava flows with compressional ridges and inflated lava lobes cover the marginal high, with comparable structure and size to modern subaerial lava fields. Pitted surfaces, likely formed by lava emplaced in a wet environment, are present in the western part of the study area near the continent-ocean boundary. The prominent Vøring Escarpment formed when eastward-flowing lava reached the coastline. The escarpment morphology is influenced by pre-existing structural highs, and locally these highs are by-passed by the lava flows which are clearly deflected around them. Volcanogenic debris flows are well-imaged on the escarpment horizon along with large-scale slump blocks. Similar features exist in active volcanic environments, e.g. on the south coast of Hawaii. Numerous post-volcanic extensional faults and incised channels cut both into the marginal high and the escarpment, and show that the area was geologically active after the volcanism ceased. In conclusion, igneous seismic geomorphology and seismic volcanostratigraphy are two very powerful methods to understand the volcanic deposits and development of rifted margins, and the association of major volcanic events and global warming.

Early testosterone replacement attenuates intracellular calcium dyshomeostasis in the heart of testosterone-deprived male rats.

PubMed

Weerateerangkul, Punate; Shinlapawittayatorn, Krekwit; Palee, Siripong; Apaijai, Nattayaporn; Chattipakorn, Siriporn C; Chattipakorn, Nipon

2017-11-01

Testosterone deficiency in elderly men increases the risk of cardiovascular disease. In bilateral orchiectomized (ORX) animals, impaired cardiac Ca 2+ regulation was observed, and this impairment could be improved by testosterone replacement, indicating the important role of testosterone in cardiac Ca 2+ regulation. However, the temporal changes of Ca 2+ dyshomeostasis in testosterone-deprived conditions are unclear. Moreover, the effects of early vs. late testosterone replacement are unknown. We hypothesized that the longer the deprivation of testosterone, the greater the impairment of cardiac Ca 2+ homeostasis, and that early testosterone replacement can effectively reduce this adverse effect. Male Wistar rats were randomly divided into twelve groups, four sets of three. The first set were ORX for 2, 4 and 8 weeks, the second set were sham-operated groups of the same periods, the third set were ORX for 8 weeks coupled with a subcutaneous injection of vehicle (control), testosterone during weeks 1-8 (early replacement) or testosterone during weeks 5-8 (late replacement), and finally the 12-week sham-operated, ORX and ORX treated with testosterone groups. Cardiac Ca 2+ transients (n=4-5/group), L-type calcium current (I Ca-L ) (n=4/group), Ca 2+ regulatory proteins (n=6/group) and cardiac function (n=5/group) were determined. In the ORX rats, impaired cardiac Ca 2+ transients and reduced I Ca-L were observed initially 4 weeks after ORX as shown by decreased Ca 2+ transient amplitude, rising rate and maximum and average decay rates. No alteration of Ca 2+ regulatory proteins such as the L-type Ca 2+ channels, ryanodine receptor type 2, Na + -Ca 2+ exchangers and SERCA2a were observed. Early testosterone replacement markedly improved cardiac Ca 2+ transients, whereas late testosterone replacement did not. The cardiac contractility was also improved after early testosterone replacement. Impaired cardiac Ca 2+ homeostasis is time-dependent after testosterone deprivation. Early testosterone replacement improves cardiac Ca 2+ transient regulation and contractility, suggesting the necessity of early intervention in conditions of testosterone-deprivation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Mechanism of calmodulin recognition of the binding domain of isoform 1b of the plasma membrane Ca2+-ATPase: kinetic pathway and effects of methionine oxidation

PubMed Central

Slaughter, Brian D.; Bieber Urbauer, Ramona J.; Urbauer, Jeffrey L.; Johnson, Carey K.

2008-01-01

Calmodulin (CaM) binds to a domain near the C-terminus of the plasma-membrane Ca2+-ATPase (PMCA), causing the release of this domain and relief of its autoinhibitory function. We investigated the kinetics of dissociation and binding of Ca2+-CaM with a 28-residue peptide (C28W(1b)) corresponding to the CaM binding domain of isoform 1b of PMCA. CaM was labeled with a fluorescent probe on either the N-terminal domain at residue 34 or on the C-terminal domain at residue 110. Formation of complexes of CaM with C28W(1b) results in a decrease in the fluorescence yield of the fluorophore, allowing the kinetics of dissociation or binding to be detected. Using a maximum entropy method, we determined the minimum number and magnitudes of rate constants required to fit the data. Comparison of the fluorescence changes for CaM labeled on the C-terminal or N-terminal domain suggests sequential and ordered binding of the C-terminal and N-terminal domains of CaM with C28W(1b). For dissociation of C28W(1b) from CaM labeled on the N-terminal domain, we observed three time constants, indicating the presence of two intermediate states in the dissociation pathway. However, for CaM labeled on the C-terminal domain, we observed only two time constants, suggesting that the fluorescence label on the C-terminal domain was not sensitive to one of the kinetic steps. The results were modeled by a kinetic mechanism where an initial complex forms upon binding of the C-terminal domain of CaM to C28W(1b), followed by binding of the N-terminal domain, and then formation of a tight binding complex. Oxidation of methionine residues in CaM resulted in significant perturbations to the binding kinetics. The rate of formation of a tight binding complex was reduced, consistent with the lower effectiveness of oxidized CaM in activating the Ca2+ pump. PMID:17343368

Magnetic mesoporous Fe/carbon aerogel structures with enhanced arsenic removal efficiency.

PubMed

Lin, Yi-Feng; Chen, Jia-Ling

2014-04-15

Wastewater treatment has drawn significant research attention due to its associated environmental issues. Adsorption is a promising method for treating wastewater. The development of an adsorbent with a high surface area is important. Therefore, we successfully developed mesoporous Fe/carbon aerogel (CA) structures with high specific surface areas of 48 7m(2)/g via the carbonization of composite Fe3O4/phenol-formaldehyde resin structures, which were prepared using a hydrothermal process with the addition of phenol. The mesoporous Fe/CA structures were further used for the adsorption of arsenic ions with a maximum arsenic-ion uptake of calculated 216.9 mg/g, which is higher than that observed for other arsenic adsorbents. Ferromagnetic behavior was observed for the as-prepared mesoporous Fe/CA structures with an excellent response to applied external magnetic fields. As a result, the adsorbent Fe/CA structures can be easily separated from the solution using an external magnetic field. This study develops the mesoporous Fe/CA structures with high specific surface areas and an excellent response to an applied external magnetic field to provide a feasible approach for wastewater treatment including the removal of arsenic ions. Copyright © 2014 Elsevier Inc. All rights reserved.

Ionic conductivity of cold-pressed ceramics from grinding of R0.95M0.05F2.95 solid electrolytes ( R = La, Nd; M = Ca, Sr, Ba) synthesized by reaction in melt

NASA Astrophysics Data System (ADS)

Sorokin, N. I.; Ivanovskaya, N. A.; Sobolev, B. P.

2014-03-01

Cold-pressed ceramics of fluorine-conducting solid electrolytes La1 - y M y F3 - y ( M = Ca, Sr, Ba) and Nd1 - y Ca y F3 - y with y = 0.95 have been synthesized in a melt of RF3 ( R = La, Nd) and MF2 components in a fluorinating atmosphere and ground in a ball mill. The as-prepared ceramics require annealing, during which their porosity decreases and the conductivity is stably increased (by a factor of 250 for the R 1 - y M y F3 - y composition at 293 K). The Nd0.95Ca0.05F2.95 and Nd0.95Ca0.05F2.95 compositions have a maximum ionic conductivity σ(293 K) ˜ 5 × 10-6 Sm/cm. This value is larger (by a factor of about 10) than σ (293 K) for the R 1 - y M y F3 - y ceramics of tysonite phases prepared by mechanochemical synthesis with the cold pressing of reaction products.

Pepsin-solubilised collagen (PSC) from Red Sea cucumber (Stichopus japonicus) regulates cell cycle and the fibronectin synthesis in HaCaT cell migration.

PubMed

Park, Soo-Yeong; Lim, Hee Kyoung; Lee, Seogjae; Hwang, Hyeong Cheol; Cho, Somi K; Cho, Moonjae

2012-05-01

Pepsin-solubilised collagen (PSC) from Red Sea cucumber (Stichopus japonicus) was studied with respect to its wound-healing effects on a human keratinocyte (HaCaT) cell line. Disaggregated collagen fibres were treated with 0.1M NaOH for 24h and digested with pepsin for 72h to reach maximum yield of 26.6%. The results of an in vitro wound-healing test showed that migration of HaCaT cells was 1.5-fold faster on PSC-coated plates than on untreated plates. The migration rate of sea cucumber PSC was similar to that of rat PSC, but five times higher than that of bovine gelatin. HaCaT cells grown on PSC-coated plates revealed increased fibronectin synthesis (6-fold and 3-fold compared to gelatin and rat PSC, respectively). Additionally, sea cucumber PSCs induced HaCaT cell proliferation by decreasing the G1 phase by 5% and maintaining a larger population (8%) of cells in mitosis. Collagen from Red Sea cucumber might be useful as an alternative to mammalian collagen in the nutraceutical and pharmaceutical industries. Copyright © 2011 Elsevier Ltd. All rights reserved.

Wettability Patterning for Enhanced Dropwise Condensation

NASA Astrophysics Data System (ADS)

Ghosh, Aritra; Ganguly, Ranjan; Megaridis, Constantine

2014-11-01

Dropwise condensation (DwC), in order to be sustainable, requires removal of the condensate droplets. This removal is frequently facilitated by gravity. The rate of DwC heat transfer depends strongly on the maximum departing droplet diameter. Based on wettability patterning, we present a facile technique designed to control the maximum droplet size in DwC within vapor/air atmospheres, and demonstrate how this approach can be used to enhance the corresponding heat transfer rate. We examine various hydrophilic-superhydrophilic patterns, which, respectively sustain DwC and filmwise (FwC) condensation on the substrate. The fabrication method does notemploy any hydrophobizing agent. By juxtaposing parallel lines of hydrophilic (CA ~ 78°) and superhydrophilic (CA ~ 0°) regions on the condensing surface, we create alternating domains of DwC and FwC. The average droplet size on the DwC domain is reduced by ~ 60% compared to the theoretical maximum, which corresponds to the line width. We compare heat transfer rate between unpatternend DwC surfaces and patterned DwC surfaces. Even after sacrificing 40% of condensing area, we achieve up to 20% improvement in condensate collection rate using an interdigitated superhydrophilic pattern, inspired by the vein network of plant leaves. The bioinspired interdigitated pattern is found to outperform the straight hydrophilic-superhydrophilic pattern, particularly under higher vapor loadings in an air/vapor ambient atmosphere. NSF STTR Grant 1331817 via NBD Nano.

Milk-deteriorating exoenzymes from Pseudomonas fluorescens 041 isolated from refrigerated raw milk.

PubMed

Martins, Maurilio L; Pinto, Uelinton M; Riedel, Katharina; Vanetti, Maria C D

2015-03-01

The practice of refrigerating raw milk at the farm has provided a selective advantage for psychrotrophic bacteria that produce heat-stable proteases and lipases causing severe quality problems to the dairy industry. In this work, a protease (AprX) and a lipase (LipM) produced by Pseudomonas fluorescens 041, a highly proteolytic and lipolytic strain isolated from raw milk obtained from a Brazilian farm, have been purified and characterized. Both enzymes were purified as recombinant proteins from Escherichia coli . The AprX metalloprotease exhibited activity in a broad temperature range, including refrigeration, with a maximum activity at 37 °C. It was active in a pH range of 4.0 to 9.0. This protease had maximum activity with the substrates casein and gelatin in the presence of Ca (+2) . The LipM lipase had a maximum activity at 25 °C and a broad pH optimum ranging from 7.0 to 10. It exhibited the highest activity, in the presence of Ca (+2) , on substrates with long-chain fatty acid residues. These results confirm the spoilage potential of strain 041 in milk due to, at least in part, these two enzymes. The work highlights the importance of studies of this kind with strains isolated in Brazil, which has a recent history on the implementation of the cold chain at the dairy farm.

Impaired Ca2+ handling in penile arteries from prediabetic Zucker rats: involvement of Rho kinase.

PubMed

Villalba, Nuria; Contreras, Cristina; Hernández, Medardo; García-Sacristán, Albino; Prieto, Dolores

2011-06-01

Diabetes is associated with an increased vascular tone usually involved in the pathogenesis of diabetic cardiovascular complications such as hypertension, stroke, coronary artery disease, or erectile dysfunction (ED). Enhanced contractility of penile erectile tissue has been associated with augmented activity of the RhoA/Rho kinase (RhoK) pathway in models of diabetes-associated ED. The present study assessed whether abnormal vasoconstriction in penile arteries from prediabetic obese Zucker rats (OZRs) is due to changes in the intracellular Ca(2+) concentration ([Ca(2+)](i)) and/or in myofilament Ca(2+) sensitivity. Penile arteries from OZRs and lean Zucker rats (LZRs) were mounted on microvascular myographs for simultaneous measurements of [Ca(2+)](i) and tension. The relationships between [Ca(2+)](i) and contraction for the α(1)-adrenergic vasoconstrictor phenylephrine (PE) were left shifted and steeper in OZRs compared with LZRs, although the magnitude of the contraction was similar in both groups. In contrast, the vasoconstriction induced by the thromboxane A(2) receptor agonist U-46619 was augmented in arteries from OZRs, and this increase was associated with an increase in both the sensitivity and maximum responses to Ca(2+). The RhoK inhibitor Y-27632 (10 μM) reduced the vasoconstriction induced by PE to a greater extent in OZRs than in LZRs, without altering Ca(2+). Y-27632 inhibited with a greater potency the contraction elicited by high KCl in arteries from OZRs compared with LZRs without changing [Ca(2+)](i). RhoK-II expression was augmented in arteries from OZRs. These results suggest receptor-specific changes in the Ca(2+) handling of penile arteries under conditions of metabolic syndrome. Whereas augmented vasoconstriction upon activation of the thromboxane A(2) receptor is coupled to enhanced Ca(2+) entry, a RhoK-mediated enhancement of myofilament Ca(2+) sensitivity is coupled with the α(1)-adrenergic vasoconstriction in penile arteries from OZRs.

Ca2+ cycling between sarcoplasmic reticulum and mitochondria in rabbit cardiac myocytes.

PubMed Central

Bassani, J W; Bassani, R A; Bers, D M

1993-01-01

1. Shortening and intracellular Ca2+ (Ca2+i) transients were measured in isolated rabbit ventricular myocytes during paired contractures induced by rapid application of 10 mM caffeine. 2. Caffeine-induced contractures relax despite maintained presence of caffeine. In control solution, a second phasic caffeine contracture failed to appear, unless the sarcoplasmic reticulum (SR) was refilled by a series of electrically stimulated twitches during the interval between caffeine exposures. 3. The relaxation of caffeine-induced contractures in 0 Na(+)-0 Ca2+ solution has previously been shown to rely on mitochondrial Ca2+ uptake and sarcolemmal Ca2(+)-ATPase. Thus, a second caffeine contracture (T2) while still in 0 Na(+)-0 Ca2+ was greatly reduced compared to the first one (T1). However, the amplitude of T2 increased exponentially with the time interval, attaining a maximum of approximately 50% of T1 for an interval of 180-300 s, with a time constant (tau) of 41.2 s. Similar results were found for Ca2+i transients (tau = 45 s). 4. Inhibition of the mitochondrial Ca2+ uptake by the oxidative phosphorylation uncoupler, FCCP during T1 dramatically depressed T2. On the other hand, inhibition of the sarcolemmal Ca2(+)-ATPase (by increasing extracellular Ca2+ concentration, [Ca2+]o) resulted in increase of T2. Spermine inclusion during T1 also increased T2, possibly by an increase of mitochondrial Ca2+ uptake. 5. We conclude that Ca2+ taken up by mitochondria during the decline of T1 moves back to the SR after caffeine is removed, with a tau approximately 40 s. 6. Partial intracellular Na+ depletion by prolonged (3 min) perfusion with 0 Na(+)-0 Ca2+ solution before T1 (a) accelerated relaxation and [Ca2+]i decline during T1, and (b) slowed, but did not abolish, the recovery of T2 as the interval was increased. This effect was particularly pronounced when choline was used instead of Li+ as the Na+ substitute. 7. We further conclude that the mitochondrial Na(+)-Ca2+ antiporter influences the rate of net Ca2+ uptake by mitochondria and is also important in Ca2+ efflux from mitochondria during rest. PMID:8387590

Ca2+ cycling between sarcoplasmic reticulum and mitochondria in rabbit cardiac myocytes.

PubMed

Bassani, J W; Bassani, R A; Bers, D M

1993-01-01

1. Shortening and intracellular Ca2+ (Ca2+i) transients were measured in isolated rabbit ventricular myocytes during paired contractures induced by rapid application of 10 mM caffeine. 2. Caffeine-induced contractures relax despite maintained presence of caffeine. In control solution, a second phasic caffeine contracture failed to appear, unless the sarcoplasmic reticulum (SR) was refilled by a series of electrically stimulated twitches during the interval between caffeine exposures. 3. The relaxation of caffeine-induced contractures in 0 Na(+)-0 Ca2+ solution has previously been shown to rely on mitochondrial Ca2+ uptake and sarcolemmal Ca2(+)-ATPase. Thus, a second caffeine contracture (T2) while still in 0 Na(+)-0 Ca2+ was greatly reduced compared to the first one (T1). However, the amplitude of T2 increased exponentially with the time interval, attaining a maximum of approximately 50% of T1 for an interval of 180-300 s, with a time constant (tau) of 41.2 s. Similar results were found for Ca2+i transients (tau = 45 s). 4. Inhibition of the mitochondrial Ca2+ uptake by the oxidative phosphorylation uncoupler, FCCP during T1 dramatically depressed T2. On the other hand, inhibition of the sarcolemmal Ca2(+)-ATPase (by increasing extracellular Ca2+ concentration, [Ca2+]o) resulted in increase of T2. Spermine inclusion during T1 also increased T2, possibly by an increase of mitochondrial Ca2+ uptake. 5. We conclude that Ca2+ taken up by mitochondria during the decline of T1 moves back to the SR after caffeine is removed, with a tau approximately 40 s. 6. Partial intracellular Na+ depletion by prolonged (3 min) perfusion with 0 Na(+)-0 Ca2+ solution before T1 (a) accelerated relaxation and [Ca2+]i decline during T1, and (b) slowed, but did not abolish, the recovery of T2 as the interval was increased. This effect was particularly pronounced when choline was used instead of Li+ as the Na+ substitute. 7. We further conclude that the mitochondrial Na(+)-Ca2+ antiporter influences the rate of net Ca2+ uptake by mitochondria and is also important in Ca2+ efflux from mitochondria during rest.

SN 1991bg - A type Ia supernova with a difference

NASA Technical Reports Server (NTRS)

Leibundgut, Bruno; Kirshner, Robert P.; Phillips, Mark M.; Wells, Lisa A.; Suntzeff, N. B.; Hamuy, Mario; Schommer, R. A.; Walker, A. R.; Gonzalez, L.; Ugarte, P.

1993-01-01

While SN 1991bg is an unusual type Ia SN in such a feature as the brief duration of the photospheric phase, which ended only two weeks after maximum, it shares with other Ia SNs strong Si II and Ca II lines near maximum light. In addition, the light and color curve slopes are almost identical with the templates at late times. The spectral evolution of SN 1991bg is also unique but not unrecognizable; nevertheless, the peculiarities associated with this event complicate the fundamental question as to whether the Ia SNs make good standard candles.

Diode pumped Yb:CN laser at 1082 nm and intracavity doubling to the green spectral range

NASA Astrophysics Data System (ADS)

Liu, B.; Li, Y. L.; Jiang, H. L.

2011-08-01

A diode pumped Yb:CaNb2O6 (Yb:CN) laser at 1082 nm with a maximum output of 1.35 W at 13.3 W pump power has been demonstrated. The slope efficiency was 12.4%. Moreover, intracavity second-harmonic generation (SHG) has also been achieved with a maximum green power of 374 mW by using a LiB3O5 (LBO) nonlinear crystal. To the best of our knowledge, this is the first report on continuous wave (CW) green generation by intracavity frequency doubling Yb:CN laser.

Credit PSR. This view shows the southeast and northeast facades ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Credit PSR. This view shows the southeast and northeast facades of building as seen when looking west (264°). The open double doors reveal the curing room, which was kept at ambient temperatures. A maximum of 10,000 pounds (4,545 Kg) of class 1.1 propellants were permitted in this room, along with a maximum of 4 people. A separate room at the west end of the building housed temperature control equipment. Note the lightning rods on roof corners - Jet Propulsion Laboratory Edwards Facility, Solid Propellant Conditioning Building, Edwards Air Force Base, Boron, Kern County, CA

VizieR Online Data Catalog: X-Shooter spectroscopy of YSOs in Lupus (Frasca+, 2017)

NASA Astrophysics Data System (ADS)

Frasca, A.; Biazzo, K.; Alcala, J. M.; Manara, C. F.; Stelzer, B.; Covino, E.; Antoniucci, S.

2017-03-01

Membership, atmospheric parameters (Teff, logg, and [Fe/H]), radial velocity (RV), projected rotational velocity (vsini) and veiling at five wavelengths are listed for 102 Lupus YSO candidates in Table 1. Mass and age are also reported in Table 1 for the members, with the exception of subluminous sources. Table 2 reports the full width at 10% maximum of the Hα line and the fluxes in the Hα, Hβ, CaII-IRT, CaII-K, and NaI,D1,2 lines. Table 3 reports the fluxes for Paγ, Paβ, and Brγ measured in the NIR X-Shooter spectra. (3 data files).

Differences in biofilm formation of produce and poultry Salmonella enterica isolates and their persistence on spinach plants

USDA-ARS?s Scientific Manuscript database

Repeat irrigation of spinach plants with water containing Salmonella was used to determine Salmonella persistence on spinach leaves. Spinach plants were irrigated four times (biweekly) with water containing ca. 2.1 log CFU Salmonella per 100 ml water (the maximum generic E. coli MPN recommended by...

Influence of soil solution cation composition on boron adsorption by soils

USDA-ARS?s Scientific Manuscript database

Boron (B) adsorption on five arid-zone soil samples from California was investigated as a function of solution pH (4-10) and cation composition (Na, Ca, or Mg). Boron adsorption increased with increasing solution pH, reached an adsorption maximum near pH 9, and decreased with further increases with...

Co-regulation of photosynthetic capacity by nitrogen, phosphorus and magnesium in a subtropical Karst forest in China.

PubMed

Wang, Jing; Wen, Xuefa; Zhang, Xinyu; Li, Shenggong; Zhang, Da-Yong

2018-05-09

Leaf photosynthetic capacity is mainly constrained by nitrogen (N) and phosphorus (P). Little attention has been given to the photosynthetic capacity of mature forests with high calcium (Ca) and magnesium (Mg) in the Karst critical zone. We measured light-saturated net photosynthesis (A sat ), photosynthetic capacity (maximum carboxylation rate [V cmax ], and maximum electron transport rate [J max ]) as well as leaf nutrient contents (N, P, Ca, Mg, potassium [K], and sodium [Na]), leaf mass per area (LMA), and leaf thickness (LT) in 63 dominant plants in a mature subtropical forest in the Karst critical zone in southwestern China. Compared with global data, plants showed higher A sat for a given level of P. V cmax and J max were mainly co-regulated by N, P, Mg, and LT. The ratios of V cmax to N or P, and J max to N or P were significantly positively related to Mg. We speculate that the photosynthetic capacity of Karst plants can be modified by Mg because Mg can enhance photosynthetic N and P use efficiency.

Characterization of Chlorhexidine-Loaded Calcium-Hydroxide Microparticles as a Potential Dental Pulp-Capping Material.

PubMed

Priyadarshini, Balasankar M; Selvan, Subramanian T; Narayanan, Karthikeyan; Fawzy, Amr S

2017-06-22

This study explores the delivery of novel calcium hydroxide [Ca(OH)₂] microparticles loaded with chlorhexidine (CHX) for potential dental therapeutic and preventive applications. Herein, we introduce a new approach for drug-delivery to deep dentin-surfaces in the form of drug-loaded microparticles. Unloaded Ca(OH)₂ [Ca(OH)₂/Blank] and CHX-loaded/Ca(OH)₂ microparticles were fabricated by aqueous chemical-precipitation technique. The synthesized-microparticles were characterized in vitro for determination of surface-morphology, crystalline-features and thermal-properties examined by energy-dispersive X-ray scanning and transmission electron-microscopy (EDX-SEM/TEM), Fourier-transform infrared-spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential scanning-calorimetry (DSC). Time-related pH changes, initial antibacterial/biofilm-abilities and cytotoxicity of CHX-loaded/Ca(OH)₂ microparticles were evaluated. Microparticles were delivered to dentin-surfaces with subsequent SEM examination of treated dentin-substrates. The in vitro and ex vivo CHX-release profiles were characterized. Ca(OH)₂/Blank were hexagonal-shaped with highest z -average diameter whereas CHX-inclusion evidenced micro-metric spheres with distinguishable surface "rounded deposits" and a negative-shift in diameter. CHX:Ca(OH)₂/50 mg exhibited maximum encapsulation-efficiency with good antibacterial and cytocompatible properties. SEM examination revealed an intact layer of microparticles on exposed dentin-surfaces with retention of spherical shape and smooth texture. Microparticles loaded on dentin-surfaces showed prolonged release of CHX indicating substantial retention on dentin-substrates. This study validated the inherent-applicability of this novel drug-delivery approach to dentin-surfaces using micro-metric CHX-loaded/Ca(OH)₂ microparticles.

The Temperature and Structure Dependence of Surface Tension of CaO-SiO2-Na2O-CaF2 Mold Fluxes

NASA Astrophysics Data System (ADS)

Gao, Qiang; Min, Yi; Jiang, Maofa

2018-06-01

The surface tension of mold flux is one of the most important properties and varies with the temperature from the top to the bottom of the mold, which influences the adhesion and lubrication between the liquid mold flux and the solidified shell, further influencing the quality of the continuous billet. In the present paper, the effect of temperature on the surface tension of CaO-SiO2-Na2O-CaF2 mold-flux melts with different CaO/SiO2 mass ratios was investigated using the maximum-pull method. Furthermore, the microstructure of mold fluxes was analyzed using FT-IR and Raman spectra to discuss the change mechanism of surface tension. The results indicated that the temperature dependence of surface tension was different with different CaO/SiO2 mass ratios, and agreed with the modification of melt structure. When the CaO/SiO2 mass ratio was 0.67 and 0.85, the change of surface tension with temperature was relatively stable, and the influence of temperature on the structure was small. When the CaO/SiO2 mass ratio was 1.03 and 1.16, with an increase of temperature, the surface tension decreased linearly and the changing amplitude was large; the degree of polymerization of melts and average radii of silicon-oxygen anions also decreased, which intensified the molecular thermal motion and weakened the intermolecular interaction, resulting in a decrease of surface tension of melts.

Effects of prenatal low-dose beta radiation from tritiated water on learning and memory in rats and their possible mechanisms.

PubMed

Gao, W M; Wang, B; Zhou, X Y

1999-09-01

Pregnant adult Wistar rats were randomly divided into four groups. Three of these groups were irradiated with beta rays by a single intraperitoneal injection of tritiated water ((3)H(2)O) administered on the 13th day of gestation. The doses absorbed by their offspring were estimated to be 4.6, 9.2 and 27.3 cGy. The influence of radiation on the postnatal learning ability and memory behavior and on brain development of the offspring was investigated. The number of pyramidal cells (in areas CA1, CA2, CA3 and CA4) and neurons in the hippocampus of the offspring was also measured. In addition, the Ca(++) conductance of hippocampal pyramidal cells cultured in vitro was observed. The results showed that an exposure to 4.6 cGy could prolong avoidance response time significantly and decrease the number of hippocampal pyramidal cells in the CA1 area compared to controls. An exposure to 9.2 cGy significantly decreased the establishment of conditioned reflexes and the number of hippocampal pyramidal cells in the CA3 area. This exposure also induced the degeneration and malformation of hippocampal neurons cultured in vitro, in addition to decreasing the number of hippocampal neurons observed on each culture day. A dose of 27.3 cGy significantly decreased brain and body weights and the maximum electric conductance of Ca(++) in hippocampal pyramidal neurons. In general, dose-dependent effects were observed for most of the parameters assessed in the present study. Possible mechanisms are discussed.

The Temperature and Structure Dependence of Surface Tension of CaO-SiO2-Na2O-CaF2 Mold Fluxes

NASA Astrophysics Data System (ADS)

Gao, Qiang; Min, Yi; Jiang, Maofa

2018-02-01

The surface tension of mold flux is one of the most important properties and varies with the temperature from the top to the bottom of the mold, which influences the adhesion and lubrication between the liquid mold flux and the solidified shell, further influencing the quality of the continuous billet. In the present paper, the effect of temperature on the surface tension of CaO-SiO2-Na2O-CaF2 mold-flux melts with different CaO/SiO2 mass ratios was investigated using the maximum-pull method. Furthermore, the microstructure of mold fluxes was analyzed using FT-IR and Raman spectra to discuss the change mechanism of surface tension. The results indicated that the temperature dependence of surface tension was different with different CaO/SiO2 mass ratios, and agreed with the modification of melt structure. When the CaO/SiO2 mass ratio was 0.67 and 0.85, the change of surface tension with temperature was relatively stable, and the influence of temperature on the structure was small. When the CaO/SiO2 mass ratio was 1.03 and 1.16, with an increase of temperature, the surface tension decreased linearly and the changing amplitude was large; the degree of polymerization of melts and average radii of silicon-oxygen anions also decreased, which intensified the molecular thermal motion and weakened the intermolecular interaction, resulting in a decrease of surface tension of melts.

Experimental observation of charge-shift bond in fluorite CaF2.

PubMed

Stachowicz, Marcin; Malinska, Maura; Parafiniuk, Jan; Woźniak, Krzysztof

2017-08-01

On the basis of a multipole refinement of single-crystal X-ray diffraction data collected using an Ag source at 90 K to a resolution of 1.63 Å -1 , a quantitative experimental charge density distribution has been obtained for fluorite (CaF 2 ). The atoms-in-molecules integrated experimental charges for Ca 2+ and F - ions are +1.40 e and -0.70 e, respectively. The derived electron-density distribution, maximum electron-density paths, interaction lines and bond critical points along Ca 2+ ...F - and F - ...F - contacts revealed the character of these interactions. The Ca 2+ ...F - interaction is clearly a closed shell and ionic in character. However, the F - ...F - interaction has properties associated with the recently recognized type of interaction referred to as `charge-shift' bonding. This conclusion is supported by the topology of the electron localization function and analysis of the quantum theory of atoms in molecules and crystals topological parameters. The Ca 2+ ...F - bonded radii - measured as distances from the centre of the ion to the critical point - are 1.21 Å for the Ca 2+ cation and 1.15 Å for the F - anion. These values are in a good agreement with the corresponding Shannon ionic radii. The F - ...F - bond path and bond critical point is also found in the CaF 2 crystal structure. According to the quantum theory of atoms in molecules and crystals, this interaction is attractive in character. This is additionally supported by the topology of non-covalent interactions based on the reduced density gradient.

Effect of calcium oxide (CaO) and sawdust on adhesion and cohesion characteristics of sewage sludge under agitated and non-agitated drying conditions.

PubMed

Deng, Wen-Yi; Yuan, Min-Hao; Mei, Jing; Liu, Ya-Jun; Su, Ya-Xin

2017-03-01

Stickiness phenomenon is widely observed in sewage sludge drying practices. This paper is aimed at demonstrating and comparing the sticky properties of sewage sludge through non-agitated and agitated drying tests specially designed for sewage sludge. Special attentions were paid to the effects of additives, i.e. CaO, fine sawdust (FSD) and coarse sawdust (CSD), on the adhesive and cohesive characteristics of sewage sludge. The results indicated that the sticky properties of the sludge were markedly different under the different testing methods, and was also greatly influenced by CaO or sawdust addition. For instance, in the non-agitated drying tests, CaO can significantly enhance the maximum adhesive and cohesive stresses of the sludge, whereas in the agitated drying tests, the torque of agitation, which strongly correlated with the cohesive stress of the sludge, was lowered by CaO addition. During agitated drying process, sludge lump with CaO addition started to break up at higher moisture content than that of original sludge. On the other hand, sawdust also affected the sticky properties of sludge in a way that was totally different with CaO. After sawdust addition (at 5-10%WS (wet sludge basis)), the cohesive stress of the sludge was markedly increased due to strengthening of mechanical interlocking inside the sludge, whereas the adhesiveness of the sludge was lowered by sawdust addition. The influencing mechanisms of CaO and sawdust under the different testing methods were detailedly discussed in the paper. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of synthesis methods on the Ca{sub 3}Co{sub 4}O{sub 9} thermoelectric ceramic performances

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sotelo, A.; Rasekh, Sh.; Torres, M.A.

2015-01-15

Three different synthesis methods producing nanometric grain sizes, coprecipitation with ammonium carbonate, oxalic acid, and by attrition milling have been studied to produce Ca{sub 3}Co{sub 4}O{sub 9} ceramics and compared with the classical solid state route. These three processes have produced high reactive precursors and all the organic material and CaCO{sub 3}·have been decomposed in a single thermal treatment. Coprecipitation leads to pure Ca{sub 3}Co{sub 4}O{sub 9} phase, while attrition milling and classical solid state produce small amounts of Ca{sub 3}Co{sub 2}O{sub 6} secondary phase. Power factor values are similar for all three samples, being slightly lower for the onesmore » produced by attrition milling. These values are much higher than the obtained in samples prepared by the classical solid state method, used as reference. The maximum power factor values determined at 800 °C (∼0.43 mW/K{sup 2} m) are slightly higher than the best reported values obtained in textured ones which also show much higher density values. - Graphical abstract: Impressive raise of PF in Ca{sub 3}Co{sub 4}O{sub 9} thermoelectric materials obtained from nanometric grains. - Highlights: • Ca{sub 3}Co{sub 4}O{sub 9} has been produced by four different methods. • Precursors particle sizes influences on the final performances. • Coprecipitation methods produce single Ca{sub 3}Co{sub 4}O{sub 9} phase. • Power factor reaches values comparable to high density textured materials.« less

59Ni Production Rates in Mesosiderites Measured with Accelerator Mass Spectrometry

NASA Astrophysics Data System (ADS)

Fink, D.; Tuniz, C.; Herzog, G. F.; Albrecht, A.; Fifield, L. K.; Allan, G. L.; Paul, M.

1993-07-01

The cosmogenic radionuclide ^59Ni (t(sub)1/2 = 76 ky) has great potential as a monitor of thermal neutrons in metal-rich extraterrestrial materials. In deep samples from larger meteoroids (which can support a big neutron flux) containing >1% or so of nickel, thermal neutron capture on ^58Ni (sigma(sub)th = 4.6 b) is the dominant production mechanism. Near the surface of mm-size bodies production occurs via primary proton, fast neutron, and alpha reaction channels on Fe, Co, and Ni. We have applied AMS to the measurement of ^59Ni activities (see ref [1] for details) in four samples from the metal phase of the mesosiderites Estherville (fall, 1879) and Budulan, a find. The activities range from 1.5 to 3.5 dpm/g-Ni. Related work is described in refs. [2,3]. To discuss neutron fluxes in Budulan, we must correct the measured ^59Ni activities for terrestrial age. By using measured ^41Ca activities (13-19 dpm/kg-Fe [4]) and a maximum production rate, P(sub)Fe(^41Ca), in stony irons of 21 dpm/kg-Fe [5] we deduce a maximum terrestrial age of 35 ky. After correction for this terrestrial age and normalization to L-chondritic composition [6], the production rates of ^59Ni, P(sub)Fe(^59Ni), range from 5-13 dpm/g-Ni; these values are 2-3 times greater than those reported in [7] for large irons and ~10 times those for chondrites. References [4,8] present ^41Ca data in the silicate and metal phases from the same Estherville and Budulan samples. If thermal neutron production were solely responsible for P(sub)Fe(^59Ni) and P(sub)Sil(^41Ca) (the latter corrected for spallation of oxidized iron in pyroxene), then the thermal neutron fluxes, phi, inferred from each nuclide in a sample should be the same. We deduce ratios of phi(^59Ni)/phi(^41Ca) that range from 0.75 to 1.65. Differences in epithermal yields can account for only a minor fraction of this variation as the ratio of the total resonant neutron absorption integrals for ^40Ca and ^58Ni is within 10% of the ratio of the thermal neutron cross-sections alone. A twofold change in Budulan's terrestrial age alters the flux ratio by 10% at most. Like ^41Ca [9,10], P(sub)Fe(^59Ni) can be used to estimate shielding depths and lower limits on the pre-atmospheric radius. Calculations by [11] give a maximum value for P(sub)Fe(^59Ni) of 22 atoms/min/g-Ni at the center of an L-chondrite with a radius of 300 g/cm^2. The ^10Be and ^26Al activities in Estherville [5] and respective semi-empirical production rate formulas [12] set a maximum meteoroid radius of 300 g/cm^2. Our measured value for ^59Ni implies a lower radius limit of 150 g/cm^2 and shielding depths of 60-150 g/cm^2. Similarly for Budulan, we suggest a radius of 200 < R < 400 g/cm^2 and shielding depths from 40-200 g/cm^2. We infer that the above samples originated at relatively large depths (except for perhaps Budulan-2428) in meteoroids with preatmospheric radii > 30 cm, assuming a mesosiderite density of 5.5 g/cm^3. Interestingly, those samples (Budulan-2357 and Estherville-3311) having ^41Ca production rates that indicate a higher degree of shielding, have flux ratios equal to or less than 1; the other two samples have ^41Ca contents typical of near-surface exposure and have ratios phi(^59Ni)/phi(^41Ca) larger than unity. This correlation indicates that P(sub)59 from fast neutron reactions on ^60,61Ni enhances ^59Ni production at near surface regions. References: [1] Paul M. et al. (1993) Nucl. Inst. Meth., submitted. [2] Kutschera W. et al. (1992) Nucl. Inst. Meth., in press. [3] Klein J. et al.(1993) Meteoritics (this issue). [4] Albrecht A. et al. (1992) LPS XXIII, 5-6. [5] Vogt S. et al. (1991) Meteoritics, 26, 403. [6] Fink D. et al.(1992) LPS XXIII, 355-356. [7] Honda et al. (1967) Handb. Physik. 46(2), 613-632. [8] Fink D. et al. (1991) EPSL, 107, 115-128. [9] Fink D. et al. (1990) Nucl. Inst. Meth., B47, 79-96. [10] Klein J. et al. (1991) Meteoritics, 26, 358. [11] Spergel M. et al.(1986) Proc. LPS 16th; J. Geophys. Res., 91, D483-D494. [12] Graf et al. (1992) GCA, 54, 2521-2534.

Association of Carbonic Anhydrase Activity with Carboxysomes Isolated from the Cyanobacterium Synechococcus PCC7942 1

PubMed Central

Price, G. Dean; Coleman, John R.; Badger, Murray R.

1992-01-01

The development of a simple method for the isolation of purified carboxysomes from the cyanobacterium Synechococcus PCC7942 has made it possible to identify a specific and inducible, intracellular carbonic anhydrase (CA) activity that is strongly associated with carboxysomes. This was shown, in part, through enzyme recovery experiments that indicated that a clear majority of a CA activity that is sensitive to the CA inhibitor ethoxyzolamide (I50 = 4 μm) copurifies with a majority of the cell's ribulose-1,5-bisphosphate carboxylase/oxygenase activity in a highly purified pelletable fraction. Electron microscopy of this pelletable fraction revealed the presence of carboxysomes that were physically intact. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of carboxysome proteins showed that the large and small subunits of ribulose-1,5-bisphosphate carbosylase/oxygenase were clearly prominent and that several other minor proteins could be distinguished. The specific location of this carboxysomal CA activity is further reinforced by the finding that a previously isolated high CO2-requiring mutant, Type II/No. 68 (G.D. Price, M.R. Badger [1989] Plant Physiol 91: 514-525), displayed a 30-fold reduction in carboxysome-associated CA activity when tested under optimal conditions. Carboxysomal CA has the unusual property of being inactivated by dithiothreitol. The enzyme also requires 20 mm Mg2+ (as MgSO4) for near maximum activity; other divalent cations, such as Ca2+ and Mn2+, also stimulate carboxysomal CA activity, but to a lesser extent than Mg2+. Results are discussed in relation to the role of carboxysomes in the CO2-concentrating mechanism in cyanobacteria and the role that carboxysomal CA activity appears to play in this process. Images Figure 1 Figure 7 PMID:16653059

Calcium ion involvement in growth inhibition of mechanically stressed soybean (Glycine max) seedlings

NASA Technical Reports Server (NTRS)

Jones, R. S.; Mitchell, C. A.

1989-01-01

A 40-50% reduction in soybean [Glycine max (L.) Merr. cv. Century 84] hypocotyl elongation occurred 24 h after application of mechanical stress. Exogenous Ca2+ at 10 mM inhibited growth by 28% if applied with the Ca2+ ionophore A23187 to the zone of maximum hypocotyl elongation. La3+ was even more inhibitory than Ca2+, especially above 5 mM. Treatment with ethyleneglycol-bis-(beta-aminoethylether)-N, N, N', N'-tetraacetic acid (EGTA) alone had no effect on growth of non-stressed seedlings at the concentrations used but negated stress-induced growth reduction by 36% at 4 mM when compared to non-treated, stressed controls. Treatment with EDTA was ineffective in negating stress-induced growth inhibition. Calmodulin antagonists calmidazolium, chlorpromazine, and 48/80 also negated stress-induced growth reduction by 23, 50, and 35%, respectively.

Fluidized bed combustion residue as an alternative liming material and Ca source. [Prunus persica

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edwards, J.H.; Horton, B.D.; White, A.W. Jr.

1985-01-01

Fluidized bed combustion residue (FBCR), a by-product of fossil fuel fired boilers, was evaluated as a liming material and a source of calcium for peaches (Prunus persica (L.) Batsch). Incubation studies involving a medium textured soil indicated that FBCR (calcite (FBCRC) or dolomitic (FBCRD) sources) was as effective a liming amendment as the respective agricultural limestone. Maximum soil pH occurred after 26 days incubation with FBCRC, but soil pH increased continuously throughout 137 days incubation with dolomitic limestone. Ammonium acetate extractable Ca was not affected by calcitic source, but Mg concentration increased with rates with the two dolomitic sources, andmore » was highest in the FBCRD source after 137 days incubation. In greenhouse studies with Elberta peach seedlings, FBCRC was more effective in neutralizing soil acidity and increasing extractable soil Ca than calcitic limestone.« less

Antibacterial, antifungal, antispasmodic and Ca++ antagonist effects of Caesalpinia bonducella.

PubMed

Khan, Hidayat-Ullah; Ali, Irshad; Khan, Arif-Ullah; Naz, Rubina; Gilani, Anwarul Hassan

2011-02-01

Caesalpinia bonducella F. (Leguminosae) has been used as a folk medicine for a variety of ailments. The crude extract of C. bonducella and its fractions were studied for antibacterial, antifungal, antispasmodic and Ca++ antagonistic properties. The strongest antibacterial effect was displayed by the n-butanol (72%) and ethyl acetate (80%) fractions, followed by the crude extract (46% and 42%), against Escherichia coli and Bacillus subtilis, respectively. The plant extract and its fractions showed mild to excellent activity in antifungal bioassays, with maximum antifungal activity against Candida glaberata (80%) and Aspergillus flavus (70%) by the n-butanol and chloroform fractions, followed by the crude extract (70% and 65%). Caesalpinia bonducella extract caused concentration-dependent inhibition of spontaneous and high K+ (80 mM)-induced contractions of isolated rabbit jejunum preparations, similar to that caused by Verapamil. These results indicate that C. bonducella exhibits antibacterial, antifungal, spasmolytic and Ca++ channel blocking actions.

Reverse Micelle Mediated synthesis of Calcium Phosphate Nanocarriers for Controlled Release of Bovine Serum Albumin (BSA)

PubMed Central

Dasgupta, Sudip; Bandyopadhyay, Amit; Bose, Susmita

2010-01-01

Calcium phosphate (CaP) nanoparticle with calcium to phosphorus (Ca:P) molar ratio of 1.5:1 were synthesized using reverse micro emulsion. Ca(NO3)2.4H2O and H3PO4 were used as aqueous phase, cyclohexane as organic phase, and poly(oxyethylene)12 nonylphenol ether (NP-12) as surfactant. Depending on calcination temperature between 600 and 800 °C, CaP nanoparticle showed different phases calcium deficient hydroxyapatite (CDHA) and β-tricalcium phosphate (β-TCP), particle size between 48 and 69 nm, the BET specific average surface area between 73 m2/g and 57 m2/g. Bovine serum albumin (BSA) was used as a model protein to study loading and release behavior. Adsorptive property of BSA was investigated with the change in BET surface area of these nanoparticle and the pH of the suspension. At pH 7.5, maximum amount of BSA was adsorbed onto CaP nanoparticle. The release kinetics of BSA showed a gradual time dependent increase at pH 4.0 and 6.0 buffer solutions. However, the amount of released protein was significantly smaller at pH 7.2. BSA release rate also varied depending on the presence of different phases of CaPs in the system, β-TCP or CDHA. These results suggest that BSA protein release rate can be controlled by changing particle size, surface area and phase composition of CaP nanocarriers. PMID:19435617

Synthesis of highly efficient CaO-based, self-stabilizing CO2 sorbents via structure-reforming of steel slag.

PubMed

Tian, Sicong; Jiang, Jianguo; Yan, Feng; Li, Kaimin; Chen, Xuejing

2015-06-16

Capturing anthropogenic CO2 in a cost-effective and highly efficient manner is one of the most challenging issues faced by scientists today. Herein, we report a novel structure-reforming approach to convert steel slag, a cheap, abundant, and nontoxic calcium-rich industrial waste, as the only feedstock into superior CaO-based, self-stabilizing CO2 sorbents. The CO2 capture capacity of all the steel slag-derived sorbents was improved more than 10-fold compared to the raw slag, with the maximum uptake of CO2 achieving at 0.50 gCO2 gsorbent(-1). Additionally, the initial steel slag-derived sorbent could retain 0.25 gCO2 gsorbent(-1), that is, a decay rate of only 12% over 30 carbonation-calcination cycles, the excellent self-stabilizing property allowed it to significantly outperform conventional CaO, and match with most of the existing synthetic CaO-based sorbents. A synergistic effect that facilitated CO2 capture by CaO-based sorbents was clearly recognized when Mg and Al, the most common elements in steel slag, coexisted with CaO in the forms of MgO and Al2O3, respectively. During the calcium looping process, MgO served as a well spacer to increase the porosity of sorbents together with Al2O3 serving as a durable stabilizer to coresist the sintering of CaCO3 grains at high temperatures.

Effect of Substituted Ca on the Thermoelectric and Optoelectronic Properties of NaRh2O4 Under Pressure

NASA Astrophysics Data System (ADS)

Rahnamaye Aliabad, H. A.; Hosseini, N.

2018-03-01

In this paper, we have used the first principle calculations for investigation of the structural, optoelectronic and thermoelectric properties of NaRh2O4 compound and substituted with Ca onto the Na sites under pressure. The results show that there are two direct band gaps for the NaRh2O4 compound and three indirect band gaps for the CaRh2O4 compound at the top of the Fermi level. The size of the band gaps increases almost linearly with the increase of the pressure up to 37 GPa. The calculated density of states for the CaRh2O4 compound show that the Ca-3 p state plays a key role for enhancement of the thermoelectric figure of merit ( ZT). We found that the static dielectric function value decreases along the x, y and z directions for the CaRh2O4 compound with the increase of the pressure while it is constant along the x and y directions for the NaRh2O4 compound. The birefringence properties with metallic nature are achieved from the optical spectra. The thermoelectric results show that the maximum peak of the ZT shifts towards the higher value of temperature for the NaRh2O4 compound. The Ca substitution onto the Na sites in the NaRh2O4 compound enhances the ZT value of 0.79 at 250 K.

Composition and Elution Behavior of Various Elements from Printed Circuit Boards, Cathode-ray Tube Glass, and Liquid-crystal Displays in Waste Consumer Electronics.

PubMed

Inaba, Kazuho; Murata, Tomoyoshi; Yamamura, Shigeki; Nagano, Masaaki; Iwasaki, Kazuhiro; Nakajima, Daisuke; Takigami, Hidetaka

2018-01-01

The contents and elution behavior of metals in consumer electronics parts were determined so as to understand their maximum environmental risk. Elements contained most in printed-circuit boards were Cu, Si, Br, Ca, Al, Sn, Pb, Sb, Ba, Fe, Ni, Ti, and Zn; in cathode-ray tube glass were Si, Pb, Ba, Sr, Zn, Zr, Ca, and Sb; in arsenic contained liquid-crystal displays were Si, Ca, Sr, Ba, As, and Fe; and in antimony contained liquid-crystal displays were Si, Ba, Ca, Sb, Sr, Fe, and Sn. The elements eluted most from printed-circuit boards were Zn, Pb, and Cu; from cathode-ray tube glass were Pb, Zn, B, Ba, and Si; and from liquid-crystal displays were B and Si, and the toxic As and Sb. The amount eluted was greatest at acidic pH. It was revealed that officially recommended 6-h-shaking with a pure water test was insufficient to understand the real environmental risk of waste electronics.

Simultaneous separation and purification of chlorogenic acid, epicatechin, hyperoside and phlorizin from thinned young Qinguan apples by successive use of polyethylene and polyamide resins.

PubMed

Sun, Lijun; Liu, Dongjie; Sun, Jiaojiao; Yang, Xingbin; Fu, Minghai; Guo, Yurong

2017-09-01

The method for separating and purifying chlorogenic acid (CA), epicatechin (EC), hyperoside (HY) and phlorizin (PH) simutaneously from young Qinguan apples by successive use of X-5 and polyamide resins has been developed in this study. The order of adsorption capacities of X-5 for the four phenolics was PH>HY>EC>CA, and the adsorption equilibriums of the four phenolics onto X-5 resin conformed to Langmuir isotherms preferentially. The adsorption kinetics of EC and CA onto X-5 conformed to the pseudo-first-order model, while that of HY and PH accorded with the pseudo-second-order model. Interestingly, the values of equilibrium adsorption capacities (Q e ) calculated in the preferential kinetics models were closer to that of theoretical maximum adsorption capacities (Q 0 ) calculated by Langmuir isotherms. Through dynamic adsorption and desorption using X-5 and polyamide resins with ethanol solution as strippant, CA, EC, HY and PH were obtained with purities of 96.21%, 95.34%, 95.36% and 97.36%, respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

The Arrival of Homo sapiens into the Southern Cone at 14,000 Years Ago

PubMed Central

Politis, Gustavo G.; Gutiérrez, María A.; Blasi, Adriana

2016-01-01

The Arroyo Seco 2 site contains a rich archaeological record, exceptional for South America, to explain the expansion of Homo sapiens into the Americas and their interaction with extinct Pleistocene mammals. The following paper provides a detailed overview of material remains found in the earliest cultural episodes at this multi-component site, dated between ca. 12,170 14C yrs B.P. (ca. 14,064 cal yrs B.P.) and 11,180 14C yrs B.P. (ca. 13,068 cal yrs B.P.). Evidence of early occupations includes the presence of lithic tools, a concentration of Pleistocene species remains, human-induced fractured animal bones, and a selection of skeletal parts of extinct fauna. The occurrence of hunter-gatherers in the Southern Cone at ca. 14,000 cal yrs B.P. is added to the growing list of American sites that indicate a human occupation earlier than the Clovis dispersal episode, but posterior to the onset of the deglaciation of the Last Glacial Maximum (LGM) in the North America. PMID:27683248

Calcium and zinc differentially affect the structure of lipid membranes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kučerka, Norbert; Dushanov, Ermuhammad; Kholmurodov, Kholmirzo T.

Interactions of calcium (Ca 2+) and zinc (Zn 2+) cations with biomimetic membranes made of dipalmitoylphosphatidylcholine (DPPC) were studied by small angle neutron diffraction (SAND). Experiments show that the structure of these lipid bilayers is differentially affected by the two divalent cations. Initially, both Ca 2+ and Zn 2+ cause DPPC bilayers to thicken, while further increases in Ca 2+ concentration result in the bilayer thinning, eventually reverting to having the same thickness as pure DPPC. The binding of Zn 2+, on the other hand, causes the bilayers to swell to a maximum thickness, and the addition of more Znmore » 2+ does not result in a further thickening of the membrane. Agreement between our results obtained using oriented planar membranes and those from vesicular samples implies that the effect of cations on bilayer thickness is the result of electrostatic interactions, rather than geometrical constraints due to bilayer curvature. This notion is further reinforced by MD simulations. Lastly, the radial distribution functions reveal a strong interaction between Ca 2+ and the phosphate oxygens, while Zn 2+ shows a much weaker binding specificity.« less

Facile green synthesis of silver nanodendrite/cellulose acetate thin film electrodes for flexible supercapacitors.

PubMed

Devarayan, Kesavan; Park, Jiyoung; Kim, Hak-Yong; Kim, Byoung-Suhk

2017-05-01

In this study, we present a highly efficient and economical solution called as 'in situ hydrogenation' for preparation of highly conductive thin film electrode based on silver nanodendrites. The silver nanodendrite (AgND)/cellulose acetate (CA) thin film electrodes exhibited sheet resistance ranging from 0.32ohm/sq to 122.1ohm/sq which could be controlled by changing the concentration of both silver and polymer. In addition, these electrodes exhibited outstanding toughness during the bending test. Further, these thin film electrodes have great potential for scale-up with an average weight of 3mg/cm 2 and can be also combined with active nanomaterials such as multiwalled carbon nanotubes (MWCNTs) to fabricate AgND/CA/MWCNTs thin film for high-performance flexible supercapacitor electrode. The AgND/CA/MWCNTs electrodes exhibited a maximum specific capacitance of 237F/g at a current density of 0.3A/g. After 1000 cycles, the AgND/MWCNT/CA exhibited a decrease of 16.0% of specific capacitance. Copyright © 2017 Elsevier Ltd. All rights reserved.

Calcium and zinc differentially affect the structure of lipid membranes

DOE PAGES

Kučerka, Norbert; Dushanov, Ermuhammad; Kholmurodov, Kholmirzo T.; ...

2017-03-09

Interactions of calcium (Ca 2+) and zinc (Zn 2+) cations with biomimetic membranes made of dipalmitoylphosphatidylcholine (DPPC) were studied by small angle neutron diffraction (SAND). Experiments show that the structure of these lipid bilayers is differentially affected by the two divalent cations. Initially, both Ca 2+ and Zn 2+ cause DPPC bilayers to thicken, while further increases in Ca 2+ concentration result in the bilayer thinning, eventually reverting to having the same thickness as pure DPPC. The binding of Zn 2+, on the other hand, causes the bilayers to swell to a maximum thickness, and the addition of more Znmore » 2+ does not result in a further thickening of the membrane. Agreement between our results obtained using oriented planar membranes and those from vesicular samples implies that the effect of cations on bilayer thickness is the result of electrostatic interactions, rather than geometrical constraints due to bilayer curvature. This notion is further reinforced by MD simulations. Lastly, the radial distribution functions reveal a strong interaction between Ca 2+ and the phosphate oxygens, while Zn 2+ shows a much weaker binding specificity.« less

Synthesis of nanoparticles and its effect on properties of elastomeric nanocomposites

NASA Astrophysics Data System (ADS)

Shimpi, N. G.; Mishra, S.

2010-08-01

Calcium carbonate (CaCO3) nanoparticles (9, 15, and 21 nm) were synthesized by solution spray of CaCl2 and NH4HCO3 with sodium lauryl sulfate (SLS) as a stabilizing agent, and their effect was studied on polybutadiene rubber (PBR) with variations in wt% loading (4, 8, and 12%). The results of PBR nanocomposites were compared with commercial CaCO3 (40 μm) and fly ash (75 μm) filled PBR microcomposites. Properties such as tensile strength, young modulus, elongation at break, glass transition temperature, decomposition temperature, and abrasion resistances were determined. Profound effect in properties was observed, because nanometric size of CaCO3 particles synthesized using solution spray technique. Maximum improvement in mechanical and flame retarding properties was observed at 8 wt% of filler loading. This increment in properties was more pronounced in 9-nm size CaCO3. The results were not appreciable above 8 wt% of nanofillers because of agglomeration of nanoparticles. In addition, an attempt was made to consider modeling Young's modulus of PBR-nano CaCO3 which was predicted by modified Halpin-Tsai equation. It was observed that the predication by the Guth equation and modified Halpin-Tsai equation agreed very well with experimental, whereas the Halpin-Tsai equation can only applied to predict the modulus of rubber nanocomposites in the range of low addition of nanofiller, which agrees the Nielsen equation.

Synthesis and luminescence properties of blue-emitting phosphor Ca12 Al14 O32 F2 :Eu2+ for white light-emitting diode.

PubMed

Chen, Wanping; Zhang, Xinzhu; Wang, Liping

2017-09-01

A blue-emitting phosphor Ca 12 Al 14 O 32 F 2 :Eu 2+ was synthesized using a high-temperature solid-state reaction under a reductive atmosphere. The X-ray diffraction measurements indicate that a pure phase Ca 12 Al 14 O 32 F 2 :Eu 2+ can be obtained for low doping concentration of Eu 2+ . The phosphor has a strong absorption in the range 270-420 nm with a maximum at ~340 nm and blue emission in the range 400-500 nm with chromatic coordination of (0.152, 0.045). The optimal doping concentration is ~0.24. In addition, the luminescence properties of the as-synthesized phosphor were evaluated by comparison with those of Ca 12 Al 14 O 32 Cl 2 :Eu 2+ and the commercially available phosphor BaMgAl 10 O 17 :Eu 2+ . The emission intensity of Ca 12 Al 14 O 32 F 2 :Eu 2+ was ~72% that of BaMgAl 10 O 17 :Eu 2+ under excitation at λ = 375 nm. The results indicate that Ca 12 Al 14 O 32 F 2 :Eu 2+ has potential application as a near-UV-convertible blue phosphor for white light-emitting diodes. Copyright © 2017 John Wiley & Sons, Ltd.

Gamma spectrometry and chemical characterization of ceramic seeds with samarium-153 and holmium-166 for brachytherapy proposal.

PubMed

Valente, Eduardo S; Campos, Tarcísio P R

2010-12-01

Ceramic seeds were synthesized by the sol-gel technique with Si:Sm:Ca and Si:Ho:Ca. One set of seeds was irradiated in the TRIGA type nuclear reactor IPR-R1 and submitted to instrumental neutron activation analysis (INAA), K(0) method, to determine mass percentage concentration of natural samarium and holmium in the seed as well as to determine all existing radionuclides and their activities. Attention was paid to discrimination of Si-31, Ca-40, Ca-45, Ca-47, Ca-49, Sm-145, Sm-155, Sm-153 and Ho-166. A second sample was submitted to atomic emission spectrometry (ICP-AES) also to determine samarium and holmium concentrations in weight. A third sample was submitted to X-ray fluorescence spectrometry to qualitatively determine chemical composition. The measured activity was due to Sm-153 and Ho-166 with a well-characterized gamma spectrum. The X-ray fluorescence spectrum demonstrated that there is no discrepancy in seed composition. The maximum ranges in the water of beta particles from Sm-153 and Ho-166 decay were evaluated, as well as the dose rate and total dose delivered within the volume delimited by the range of the beta particles. The results are relevant for investigation of the viability of producing Sm-153 and Ho-166 radioactive seeds for use in brachytherapy. Copyright 2010 Elsevier Ltd. All rights reserved.

Inhibitory action of linoleamide and oleamide toward sarco/endoplasmic reticulum Ca2+-ATPase.

PubMed

Yamamoto, Sachiko; Takehara, Munenori; Ushimaru, Makoto

2017-01-01

SERCA maintains intracellular Ca 2+ homeostasis by sequestering cytosolic Ca 2+ into SR/ER stores. Two primary fatty acid amides (PFAAs), oleamide (18:1 9-cis ) and linoleamide (18:2 9,12-cis ), induce an increase in intracellular Ca 2+ levels, which might be caused by their inhibition of SERCA. Three major SERCA isoforms, rSERCA1a, hSERCA2b, and hSERCA3a, were individually overexpressed in COS-1 cells, and the inhibitory action of PFAAs on Ca 2+ -ATPase activity of SERCA was examined. The Ca 2+ -ATPase activity of each SERCA was inhibited in a concentration-dependent manner strongly by linoleamide (IC 50 15-53μM) and partially by oleamide (IC 50 8.3-34μM). Inhibition by other PFAAs, such as stearamide (18:0) and elaidamide (18:1 9-trans ), was hardly or slightly observed. With increasing dose, linoleamide decreased the apparent affinity for Ca 2+ and the apparent maximum velocity of Ca 2+ -ATPase activity of all SERCAs tested. Oleamide also lowered these values for hSERCA3a. Meanwhile, oleamide uniquely reduced the apparent Ca 2+ affinity of rSERCA1a and hSERCA2b: the reduction was considerably attenuated above certain concentrations of oleamide. The dissociation constants for SERCA interaction varied from 6 to 45μM in linoleamide and from 1.6 to 55μM in oleamide depending on the isoform. Linoleamide and oleamide inhibit SERCA activity in the micromolar concentration range, and in a different manner. Both amides mainly suppress SERCA activity by lowering the Ca 2+ affinity of the enzyme. Our findings imply a novel role of these PFAAs as modulators of intracellular Ca 2+ homeostasis via regulation of SERCA activity. Copyright © 2016 Elsevier B.V. All rights reserved.

ß-Adrenergic Stimulation Increases RyR2 Activity via Intracellular Ca2+ and Mg2+ Regulation

PubMed Central

Li, Jiao; Imtiaz, Mohammad S.; Beard, Nicole A.; Dulhunty, Angela F.; Thorne, Rick; vanHelden, Dirk F.; Laver, Derek R.

2013-01-01

Here we investigate how ß-adrenergic stimulation of the heart alters regulation of ryanodine receptors (RyRs) by intracellular Ca2+ and Mg2+ and the role of these changes in SR Ca2+ release. RyRs were isolated from rat hearts, perfused in a Langendorff apparatus for 5 min and subject to 1 min perfusion with 1 µM isoproterenol or without (control) and snap frozen in liquid N2 to capture their phosphorylation state. Western Blots show that RyR2 phosphorylation was increased by isoproterenol, confirming that RyR2 were subject to normal ß-adrenergic signaling. Under basal conditions, S2808 and S2814 had phosphorylation levels of 69% and 15%, respectively. These levels were increased to 83% and 60%, respectively, after 60 s of ß-adrenergic stimulation consistent with other reports that ß-adrenergic stimulation of the heart can phosphorylate RyRs at specific residues including S2808 and S2814 causing an increase in RyR activity. At cytoplasmic [Ca2+] <1 µM, ß-adrenergic stimulation increased luminal Ca2+ activation of single RyR channels, decreased luminal Mg2+ inhibition and decreased inhibition of RyRs by mM cytoplasmic Mg2+. At cytoplasmic [Ca2+] >1 µM, ß-adrenergic stimulation only decreased cytoplasmic Mg2+ and Ca2+ inhibition of RyRs. The Ka and maximum levels of cytoplasmic Ca2+ activation site were not affected by ß-adrenergic stimulation. Our RyR2 gating model was fitted to the single channel data. It predicted that in diastole, ß-adrenergic stimulation is mediated by 1) increasing the activating potency of Ca2+ binding to the luminal Ca2+ site and decreasing its affinity for luminal Mg2+ and 2) decreasing affinity of the low-affinity Ca2+/Mg2+ cytoplasmic inhibition site. However in systole, ß-adrenergic stimulation is mediated mainly by the latter. PMID:23533585

CaMKII effects on inotropic but not lusitropic force frequency responses require phospholamban

PubMed Central

Wu, Yiming; Luczak, Elizabeth D; Lee, Eun-Jeong; Hidalgo, Carlos; Yang, Jinying; Gao, Zhan; Li, Jingdong; Wehrens, Xander; Granzier, Henk; Anderson, Mark E

2014-01-01

Increasing heart rate enhances cardiac contractility (force frequency relationship, FFR) and accelerates cardiac relaxation (frequency-dependent acceleration of relaxation, FDAR). The positive FFR together with FDAR promotes rapid filling and ejection of blood from the left ventricle (LV) at higher heart rates. Recent studies indicate that the multifunctional Ca2+/calmodulin-dependent protein kinase II (CaMKII) is involved in regulating FFR and FDAR. We used isolated perfused mouse hearts to study the mechanisms of FFR and FDAR in different genetic models, including transgenic myocardial CaMKII inhibition (AC3-I) and phosphalamban knockout (PLN−/−). When the rate was increased from 360 beats/min to 630 beats/min in wild type mouse hearts, the LV developed pressure (LVDP) and the maximum rate of increase in pressure (dP/dt max) increased by 37.6 ± 4.7% and 77.0 ± 8.1%, respectively. However, hearts from AC3-I littermates showed no increase of LVDP and a relatively modest (20.4 ± 3.9 %) increase in dP/dt max. PLN−/− hearts had a negative FFR, and myocardial AC3-I expression did not change the FFR in PLN−/− mice. PLN−/− mouse hearts did not exhibit FDAR, while PLN−/−mice with myocardial AC3-I expression showed further frequency dependent reductions in cardiac relaxation, suggesting CaMKII targets in addition to PLN were critical to myocardial relaxation. We incubated a constitutively active form of CaMKII with chemically-skinned myocardium and found that several myofilament proteins were phosphorylated by CaMKII. However, CaMKII did not affect myofilament calcium sensitivity. Our study shows that CaMKII plays an important role in modulating FFR and FDAR in murine hearts and suggest that PLN is a critical target for CaMKII effects on FFR, while CaMKII effects on FDAR partially require PLN-alternative targets. PMID:22796260

Evaluating Non-potable Water Usage for Oil and Gas Purposes in the Permian Basin Using Reactive Transport Modeling

NASA Astrophysics Data System (ADS)

Marsac, K.; Navarre-Sitchler, A.

2017-12-01

Oil and gas company water usage is currently an area of concern in the water stressed western United States. 87% of recent wells in the Permian Basin are located in areas of high or extreme water stress. Using recycled produced water or groundwater that does not meet the USDW drinking water standards for oil and gas purposes could assist in relieving both water stress and tension between oil and gas companies and the public. However, non-USDW drinking water (TDS over 10,000 ppm) has the potential to react with formation water causing mineral precipitation, reducing the permeability of the producing formation. To evaluate the potential of non-potable water usage in the Permian Basin, available groundwater chemistry data was compiled into a database. Data was collected from the NETL-run NATCARB database, the USGS Produced Water and NWIS Databases, and the Texas Water Development Board. The created database went through a system of quality assurance and control for pH, TDS, depth and charge balance. Data was used to generate a set of waters representative of Permian Basin groundwater based on TDS, Ca/Mg ratio and Cl/SO4 ratio. Low, medium and high values of these three characteristics; representing the 25th, 50th and 75th percentile respectively; were used to create a matrix of 27 waters. Low TDS is 64,660 ppm, medium TDS is 98,486 ppm, and high TDS is 157,317 ppm. Ca/Mg ratios range from 1.98 to 7.26, and Cl/SO4 ratios range from 32.96 to 62.34. Results from mixing and titration models between these 27 waters and average Permian Basin water using Geochemist's Workbench show a maximum total precipitation of 1.815 cm3 in 1 L of water. In term of porosity, this represents a maximum porosity decrease due to mineral precipitation of 0.18%. This maximum precipitation scenario resulted from mixing average water with high TDS, high Ca/Mg ratio and low Cl/SO4 ratio water. We further investigate the impact of mineral precipitation on porosity and permeability using reactive transport modeling. A cylindrical, homogeneous PFLOTRAN reactive-transport model simulates the injection of high-TDS, high Ca/Mg, low Cl/SO4 water into the pay formation and the possible effects of precipitation over the lifetime of a well.

First satellite tracks of the Endangered black-capped petrel

USGS Publications Warehouse

Jodice, Patrick G.R.; Ronconi, Robert A.; Rupp, Ernst; Wallace, George E.; Satgé, Yvan

2015-01-01

The black-capped petrel Pterodroma hasitata is an endangered seabird with fewer than 2000 breeding pairs restricted to a few breeding sites in Haiti and the Dominican Republic. To date, use areas at sea have been determined entirely from vessel-based surveys and opportunistic sightings and, as such, spatial and temporal gaps in our understanding of the species’ marine range are likely. To enhance our understanding of marine use areas, we deployed satellite tags on 3 black-capped petrels breeding on Hispaniola, representing the first tracking study for this species and one of the first published tracking studies for any breeding seabird in the Caribbean. During chick rearing, petrels primarily used marine habitats in the southern Caribbean Sea (ca. 18.0° to 11.5°N, 70.0° to 75.5°W) between the breeding site and the coasts of Venezuela and Colombia. Maximum distance from the breeding sites ranged from ca. 500 to 1500 km during the chick-rearing period. During the post-breeding period, each bird dispersed north and used waters west of the Gulf Stream offshore of the mid- and southern Atlantic coasts of the USA as well as Gulf Stream waters and deeper pelagic waters east of the Gulf Stream. Maximum distance from the breeding sites ranged from ca. 2000 to 2200 km among birds during the nonbreeding period. Petrels used waters located within 14 different exclusive economic zones, suggesting that international collaboration will benefit the development of management strategies for this species.

Soil development on a Pleistocene terrace sequence, Boise Valley, Idaho

USGS Publications Warehouse

Othberg, K.L.; McDaniel, P.A.; Fosberg, M.A.

1997-01-01

Study of a sequence of terraces in the western Snake River Plain of Idaho reveals a record of at least seven terraces, the ages of which span the Pleistocene. In the Boise Valley, the youngest terraces are less than -14,500 yr and the oldest terraces are -1.7 Ma. Within this sequence, several relationships exist between soil morphology and terrace chronology. On terraces older than -14,500 yr, argillic horizon development generally increases with terrace age with maximum development occurring in soils of the oldest terraces. CaCO3- and SiO2-cemented duripans are found in soils on terraces that are late middle Pleistocene and older. By virtue of their physical and chemical properties, duripans are very resistant to erosion, and therefore provide stable records of CaCO3 and SiO2 accumulation throughout multiple cycles of loess deposition onto the terrace treads, pedogenesis, and partial erosion. Mean duripan thickness increases with age to a maximum of 0.66 m on the oldest terraces. Our results suggest that a geomorphic surface age of approximately 130,000 yr is required to form the initial plugged horizon that is characteristic of a duripan. CaCO3 and SiO2 accumulation is most rapid in duripans occupying geomorphic surfaces with ages ranging from 130,000 to 300,000 yr. After this, apparent accumulation rates decrease and little additional accumulation of these cementing agents occurs with time.

Effects of acidification on metal accumulation by aquatic plants and invertebrates. 1. Constructed wetlands

DOE Office of Scientific and Technical Information (OSTI.GOV)

Albers, P.H.; Camardese, M.B.

1993-06-01

Compared were concentrations of Al,Cd,Ca,Cu,Fe,Hg,Pb,Mg,Mn,Ni,P, and Zn in water, plants and aquatic insects of three acidified (pH [approximately] 5.0) and three nonacidified (pH [approximately] 6.5) constructed wetlands. Concentrations of Zn in water and bur-reed (Sparganium americanum) were higher in acidified wetlands than in nonacidified wetlands. Floating nonrooted plants contained mean concentrations of Fe, Mg, and Mn that were higher than recommended maximum levels for poultry feed. The mean concentrations of all metals in insects were below recommended maximum levels for poultry feed and below levels that cause toxic effects in wild birds. Smaller than expected increases of metal concentrations inmore » the water of acidified wetlands were probably due to limited mobilization of metals from the sediments and insignificant changes in sedimentation of aqueous metals. Calcium was lower in acidified than in nonacidified wetland water, but the Ca content of insects and bur-reed was not lower. Low concentrations of Ca in aquatic insects from both groups of wetlands indicated that calcium-rich crustaceans and mollusks are probably important to female waterfowl and their young during the spring, when invertebrates make up the majority of the diet. Although toxic effects from metal ingestion seem to be unlikely consequences of wetland acidification, the adverse effect of low pH on the occurrence of crustaceans and mollusks could threatened egg production and development of young.« less

Monitoring Potential Transport of Radioactive Contaminants in Shallow Ephemeral Channels: FY2017

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mizell, Steve A.; Campbell, Scott A.; McCurdy, Greg

The Desert Research Institute (DRI) is conducting a field assessment of the potential for contaminated soil to be transported from the Smoky Site Contamination Area (CA) as a result of storm runoff. This activity supports U.S. Department of Energy (DOE) Environmental Management Nevada Program (EM-NV) efforts to establish post-closure monitoring plans for the Smoky Site Soils Corrective Action Unit (CAU) 550. The work is intended to confirm the likely mechanism of transport and determine the meteorological conditions that might cause the movement of contaminated soils, as well as determine the particle size fraction that is most closely associated with transportedmore » radionuclide-contaminated soils. These data will facilitate the design of the appropriate post-closure monitoring program. In 2011, DRI installed a meteorological monitoring station on the west side of the Smoky Site CA and a hydrologic (runoff) monitoring station within the CA, near the east side. Air temperature, wind speed, wind direction, relative humidity, precipitation, solar radiation, barometric pressure, soil temperature, and soil water content are collected at the meteorological station. The maximum, minimum, and average or total values (as appropriate) for each of these parameters are recorded for each 10-minute interval. The maximum, minimum, and average water depth in the flume installed at the hydrology station are also recorded for every 10-minute interval. This report presents data collected from these stations during fiscal year (FY) 2017.« less

Can a fermentation gas mainly produced by rumen Isotrichidae ciliates be a potential source of biohydrogen and a fuel for a chemical fuel cell?

PubMed

Piela, Piotr; Michałowski, Tadeusz; Miltko, Renata; Szewczyk, Krzysztof; Sikora, Radosław; Grzesiuk, Elzbieta; Sikora, Anna

2010-07-01

Bacteria, fungi and protozoa inhabiting the rumen, the largest chamber of the ruminants' stomach, release large quantities of hydrogen during the fermentation of carbohydrates. The hydrogen is used by coexisting methanogens to produce methane in energy-yielding processes. This work shows, for the first time, a fundamental possibility of using a hydrogen-rich fermentation gas produced by selected rumen ciliates to feed a low-temperature hydrogen fuel cell. A biohydrogen fuel cell (BHFC) was constructed consisting of (i) a bioreactor, in which a hydrogen-rich gas was produced from glucose by rumen ciliates, mainly of the Isotrichidae family, deprived of intra- and extracellular bacteria, methanogens, and fungi, and (ii) a chemical fuel cell of the polymer-electrolyte type (PEFC). The fuel cell was used as a tester of the technical applicability of the fermentation gas produced by the rumen ciliates for power generation. The average estimated hydrogen yield was ca. 1.15 mol H2 per mol of fermented glucose. The BHFC performance was equal to the performance of the PEFC running on pure hydrogen. No fuel cell poisoning effects were detected. A maximum power density of 1.66 kW/m2 (PEFC geometric area) was obtained at room temperature. The maximum volumetric power density was 128 W/m3 but the coulombic efficiency was only ca. 3.8%. The configuration of the bioreactor limited the continuous operation time of this BHFC to ca. 14 hours.