Thermal migration of alloying agents in aluminium

NASA Astrophysics Data System (ADS)

Cooil, S. P.; Mørtsell, E. A.; Mazzola, F.; Jorge, M.; Wenner, S.; Edmonds, M. T.; Thomsen, L.; Klemm, H. W.; Peschel, G.; Fuhrich, A.; Prieto, M.; Schmidt, Th; Miwa, J. A.; Holmestad, R.; Wells, J. W.

2016-11-01

The in situ thermal migration of alloying agents in an Al-Mg-Si-Li alloy is studied using surface sensitive photo-electron and electron diffraction/imaging techniques. Starting with the preparation of an almost oxide free surface (oxide thickness = 0.1 nm), the relative abundance of alloying agents (Mg, Li and Si) at the surface are recorded at various stages of thermal annealing, from room temperature to melting (which is observed at 550 ◦C). Prior to annealing, the surface abundances are below the detection limit ≪1%, in agreement with their bulk concentrations of 0.423% Si, 0.322% Mg and 0.101% Li (atomic %). At elevated temperatures, all three alloying agents appear at drastically increased concentrations (13.3% Si, 19.7% Mg and 45.3% Li), but decrease again with further elevation of the annealing temperature or after melting. The temperature at which the migration occurs is species dependent, with Li migration occurring at significantly higher temperatures than Si and Mg. The mechanism of migration also appears to be species dependent with Li migration occurring all over the surface but Mg migration being restricted to grain boundaries.

Low work function silicon collector for thermionic converters

NASA Technical Reports Server (NTRS)

Chang, K. H.; Shimada, K.

1976-01-01

To improve the efficiency of present thermionic converters, single crystal silicon was investigated as a low work function collector material. The experiments were conducted in a test vehicle which resembled an actual thermionic converter. Work function as low as 1.0eV was obtained with an n-type silicon. The stabilities of the activated surfaces at elevated temperatures were tested by raising the collector temperature up to 829 K. By increasing the Cs arrival rate, it was possible to restore the originally activated low work function of the surface at elevated surface temperatures. These results, plotted in the form of Rasor-Warner curve, show a behavior similar to that of metal electrode except that the minimum work function was much lower with silicon than with metals.

Interpretation of Ground Temperature Anomalies in Hydrothermal Discharge Areas

NASA Astrophysics Data System (ADS)

Price, Adam N.; Lindsey, Cary R.; Fairley, Jerry P.

2017-12-01

Researchers have long noted the potential for shallow hydrothermal fluids to perturb near-surface temperatures. Several investigators have made qualitative or semiquantitative use of elevated surface temperatures; for example, in snowfall calorimetry, or for tracing subsurface flow paths. However, a quantitative framework connecting surface temperature observations with conditions in the subsurface is currently lacking. Here, we model an area of shallow subsurface flow at Burgdorf Hot Springs, a rustic commercial resort in the Payette National Forest, north of McCall, ID, USA. We calibrate the model using shallow (0.2 m depth) ground temperature measurements and overburden thickness estimates from seismic refraction studies. The calibrated model predicts negligible loss of heat energy from the laterally migrating fluids at the Burgdorf site, in spite of the fact that thermal anomalies are observed in the unconsolidated near-surface alluvium. Although elevated near-surface ground temperatures are commonly assumed to result from locally high heat flux, this conflicts with the small apparent heat loss during lateral flow inferred at the Burgdorf site. We hypothesize an alternative explanation for near-surface temperature anomalies that is only weakly dependent on heat flux, and more strongly controlled by the Biot number, a dimensionless parameter that compares the rate at which convection carries heat away from the land surface to the rate at which it is supplied by conduction to the interface.

FDTD analysis of body-core temperature elevation in children and adults for whole-body exposure.

PubMed

Hirata, Akimasa; Asano, Takayuki; Fujiwara, Osamu

2008-09-21

The temperature elevations in anatomically based human phantoms of an adult and a 3-year-old child were calculated for radio-frequency whole-body exposure. Thermoregulation in children, however, has not yet been clarified. In the present study, we developed a computational thermal model of a child that is reasonable for simulating body-core temperature elevation. Comparison of measured and simulated temperatures revealed thermoregulation in children to be similar to that of adults. Based on this finding, we calculated the body-core temperature elevation in a 3-year-old child and an adult for plane-wave exposure at the basic restriction in the international guidelines. The body-core temperature elevation in the 3-year-old child phantom was 0.03 degrees C at a whole-body-averaged specific absorption rate of 0.08 W kg(-1), which was 35% smaller than in the adult female. This difference is attributed to the child's higher body surface area-to-mass ratio.

Evaluation of Temperature Elevation During Root Canal Treatment with Dual Wavelength Laser: 2780 nm Er,Cr:YSGG and 940 nm Diode.

PubMed

Al-Karadaghi, Tamara Sardar; Gutknecht, Norbert; Jawad, Hussein A; Vanweersch, Leon; Franzen, Rene

2015-09-01

The purpose of this study was to evaluate the effects of dual wavelength (2780 nm Er,Cr:YSGG and 940 nm diode) laser with radial firing tip (RFT) on the external root surface and sub-surfaces, in terms of temperature changes during laser-assisted root canal treatment. A significant factor that may limit the use of lasers in endodontics is the possible thermal injury to tooth supporting structures. A total of 50 sound single-rooted extracted teeth were divided randomly into two groups (n = 25). Group A, irradiated with Er,Cr:YSGG laser at 1.06 W, 50 Hz, and 50 μs was a control group, and group B was irradiated with dual wavelength of Er,Cr:YSGG laser with the same settings as group A and a diode laser of 0.51 W at 4 ms and 10 ms pulse duration. K-type thermocouples were used to record temperature changes at the cervical, middle, and apical root thirds, on root surfaces and sub-surfaces, arising from delivery of laser energy through RFT. Temperature elevation in group B was significantly higher in the middle and apical thirds of the prepared samples than in group A (p < 0.0001). Group B presented a mean temperature elevation of 5.07°C on the apical surface region corresponding to a 1.48 mm dentin thickness, whereas a mean temperature increase of 7.72°C was recorded corresponding to dentin thickness of 0.95 mm. Within the studied parameters, the dual wavelength laser did not result in adverse thermal changes on the external root surface in vitro.

49 CFR 173.247 - Bulk packaging for certain elevated temperature materials.

Code of Federal Regulations, 2012 CFR

2012-10-01

... constructed of carbon steel which is in elevated temperature material service is excepted from § 178.345-7(d... constructed such that the stress in the packaging does not exceed one fourth (0.25) of the ultimate strength... kettle tires; CG height is measured perpendicular from the road surface). (2) High stability kettles. (i...

Environmental effects on the tensile strength of chemically vapor deposited silicon carbide fibers

NASA Technical Reports Server (NTRS)

Bhatt, R. T.; Kraitchman, M. D.

1985-01-01

The room temperature and elevated temperature tensile strengths of commercially available chemically vapor-deposited (CVD) silicon carbide fibers were measured after 15 min heat treatment to 1600 C in various environments. These environments included oxygen, air, argon and nitrogen at one atmosphere and vacuum at 10/9 atmosphere. Two types of fibers were examined which differed in the SiC content of their carbon-rich coatings. Threshold temperature for fiber strength degradation was observed to be dependent on the as-received fiber-flaw structure, on the environment and on the coating. Fractographic analyses and flexural strength measurements indicate that tensile strength losses were caused by surface degradation. Oxidation of the surface coating is suggested as one possible degradation mechanism. The SiC fibers containing the higher percentage of SiC near the surface of the carbon-rich coating show better strength retention and higher elevated temperature strength.

Daily air temperature interpolated at high spatial resolution over a large mountainous region

USGS Publications Warehouse

Dodson, R.; Marks, D.

1997-01-01

Two methods are investigated for interpolating daily minimum and maximum air temperatures (Tmin and Tmax) at a 1 km spatial resolution over a large mountainous region (830 000 km2) in the U.S. Pacific Northwest. The methods were selected because of their ability to (1) account for the effect of elevation on temperature and (2) efficiently handle large volumes of data. The first method, the neutral stability algorithm (NSA), used the hydrostatic and potential temperature equations to convert measured temperatures and elevations to sea-level potential temperatures. The potential temperatures were spatially interpolated using an inverse-squared-distance algorithm and then mapped to the elevation surface of a digital elevation model (DEM). The second method, linear lapse rate adjustment (LLRA), involved the same basic procedure as the NSA, but used a constant linear lapse rate instead of the potential temperature equation. Cross-validation analyses were performed using the NSA and LLRA methods to interpolate Tmin and Tmax each day for the 1990 water year, and the methods were evaluated based on mean annual interpolation error (IE). The NSA method showed considerable bias for sites associated with vertical extrapolation. A correction based on climate station/grid cell elevation differences was developed and found to successfully remove the bias. The LLRA method was tested using 3 lapse rates, none of which produced a serious extrapolation bias. The bias-adjusted NSA and the 3 LLRA methods produced almost identical levels of accuracy (mean absolute errors between 1.2 and 1.3??C), and produced very similar temperature surfaces based on image difference statistics. In terms of accuracy, speed, and ease of implementation, LLRA was chosen as the best of the methods tested.

GPS-derived estimates of surface mass balance and ocean-induced basal melt for Pine Island Glacier ice shelf, Antarctica

NASA Astrophysics Data System (ADS)

Shean, David E.; Christianson, Knut; Larson, Kristine M.; Ligtenberg, Stefan R. M.; Joughin, Ian R.; Smith, Ben E.; Stevens, C. Max; Bushuk, Mitchell; Holland, David M.

2017-11-01

In the last 2 decades, Pine Island Glacier (PIG) experienced marked speedup, thinning, and grounding-line retreat, likely due to marine ice-sheet instability and ice-shelf basal melt. To better understand these processes, we combined 2008-2010 and 2012-2014 GPS records with dynamic firn model output to constrain local surface and basal mass balance for PIG. We used GPS interferometric reflectometry to precisely measure absolute surface elevation (zsurf) and Lagrangian surface elevation change (Dzsurf/ Dt). Observed surface elevation relative to a firn layer tracer for the initial surface (zsurf - zsurf0') is consistent with model estimates of surface mass balance (SMB, primarily snow accumulation). A relatively abrupt ˜ 0.2-0.3 m surface elevation decrease, likely due to surface melt and increased compaction rates, is observed during a period of warm atmospheric temperatures from December 2012 to January 2013. Observed Dzsurf/ Dt trends (-1 to -4 m yr-1) for the PIG shelf sites are all highly linear. Corresponding basal melt rate estimates range from ˜ 10 to 40 m yr-1, in good agreement with those derived from ice-bottom acoustic ranging, phase-sensitive ice-penetrating radar, and high-resolution stereo digital elevation model (DEM) records. The GPS and DEM records document higher melt rates within and near features associated with longitudinal extension (i.e., transverse surface depressions, rifts). Basal melt rates for the 2012-2014 period show limited temporal variability despite large changes in ocean temperature recorded by moorings in Pine Island Bay. Our results demonstrate the value of long-term GPS records for ice-shelf mass balance studies, with implications for the sensitivity of ice-ocean interaction at PIG.

Temperature Inversions and Nighttime Convection in the Martian Tropics

NASA Astrophysics Data System (ADS)

Hinson, D. P.; Spiga, A.; Lewis, S.; Tellmann, S.; Paetzold, M.; Asmar, S. W.; Häusler, B.

2013-12-01

We are using radio occultation measurements from Mars Express, Mars Reconnaissance Orbiter, and Mars Global Surveyor to characterize the diurnal cycle in the lowest scale height above the surface. We focus on northern spring and summer, using observations from 4 Martian years at local times of 4-5 and 15-17 h. We supplement the observations with results obtained from large-eddy simulations and through data assimilation by the UK spectral version of the LMD Mars Global Circulation Model. We previously investigated the depth of the daytime convective boundary layer (CBL) and its variations with surface elevation and surface properties. We are now examining unusual aspects of the temperature structure observed at night. Most important, predawn profiles in the Tharsis region contain an unexpected layer of neutral static stability at pressures of 200-300 Pa with a depth of 4-5 km. The mixed layer is bounded above by a midlevel temperature inversion and below by another strong inversion adjacent to the surface. The sharp temperature minimum at the base of the midlevel inversion suggests the presence of a thin water ice cloud layer, with the further implication that radiative cooling at cloud level can induce convective activity at lower altitudes. Conversely, nighttime profiles in Amazonis show no sign of a midlevel inversion or a detached mixed layer. These regional variations in the nighttime temperature structure appear to arise in part from large-scale variations in topography, which have several notable effects. First, the CBL is much deeper in the Tharsis region than in Amazonis, owing to a roughly 6-km difference in surface elevation. Second, large-eddy simulations show that daytime convection is not only deeper above Tharsis but also considerably more intense than it is in Amazonis. Finally, the daytime surface temperatures are comparable in the two regions, so that Tharsis acts as an elevated heat source throughout the CBL. These topographic effects are expected to enhance the vertical mixing of water vapor above elevated terrain, which might lead to the formation and regional confinement of nighttime clouds.

Stabilizing Nanocrystalline Oxide Nanofibers at Elevated Temperatures by Coating Nanoscale Surface Amorphous Films.

PubMed

Yao, Lei; Pan, Wei; Luo, Jian; Zhao, Xiaohui; Cheng, Jing; Nishijima, Hiroki

2018-01-10

Nanocrystalline materials often exhibit extraordinary mechanical and physical properties but their applications at elevated temperatures are impaired by the rapid grain growth. Moreover, the grain growth in nanocrystalline oxide nanofibers at high temperatures can occur at hundreds of degrees lower than that would occur in corresponding bulk nanocrystalline materials, which would eventually break the fibers. Herein, by characterizing a model system of scandia-stabilized zirconia using hot-stage in situ scanning transmission electron microscopy, we discover that the enhanced grain growth in nanofibers is initiated at the surface. Subsequently, we demonstrate that coating the fibers with nanometer-thick amorphous alumina layer can enhance their temperature stability by nearly 400 °C via suppressing the surface-initiated grain growth. Such a strategy can be effectively applied to other oxide nanofibers, such as samarium-doped ceria, yttrium-stabilized zirconia, and lanthanum molybdate. The nanocoatings also increase the flexibility of the oxide nanofibers and stabilize the high-temperature phases that have 10 times higher ionic conductivity. This study provides new insights into the surface-initiated grain growth in nanocrystalline oxide nanofibers and develops a facile yet innovative strategy to improve the high-temperature stability of nanofibers for a broad range of applications.

Method for producing electricity from a fuel cell having solid-oxide ionic electrolyte

DOEpatents

Mason, David M.

1984-01-01

Stabilized quadrivalent cation oxide electrolytes are employed in fuel cells at elevated temperatures with a carbon and/or hydrogen containing fuel anode and an oxygen cathode. The fuel cell is operated at elevated temperatures with conductive metallic coatings as electrodes and desirably having the electrolyte surface blackened. Of particular interest as the quadrivalent oxide is zirconia.

Chemical states of surface oxygen during CO oxidation on Pt(1 1 0) surface revealed by ambient pressure XPS

DOE PAGES

Yu, Youngseok; Koh, Yoobin Esther; Lim, Hojoon; ...

2017-10-20

Here, the study of CO oxidation on Pt(110) surface is revisited using ambient pressure x-ray photoemission spectroscopy. When the surface temperature reaches the activation temperature for CO oxidation under elevated pressure conditions, both the α-phase of PtO 2 oxide and chemisorbed oxygen are formed simultaneously on the surface. Due to the exothermic nature of CO oxidation, the temperature of the Pt surface increases as CO oxidation takes place. As the CO/O 2 ratio increases, the production of CO 2 increases continuously and the surface temperature also increases. Interestingly, within the diffusion limited regions, the amount of surface oxide changes littlemore » while the chemisorbed oxygen is reduced.« less

Chemical states of surface oxygen during CO oxidation on Pt(1 1 0) surface revealed by ambient pressure XPS

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

Yu, Youngseok; Koh, Yoobin Esther; Lim, Hojoon

Here, the study of CO oxidation on Pt(110) surface is revisited using ambient pressure x-ray photoemission spectroscopy. When the surface temperature reaches the activation temperature for CO oxidation under elevated pressure conditions, both the α-phase of PtO 2 oxide and chemisorbed oxygen are formed simultaneously on the surface. Due to the exothermic nature of CO oxidation, the temperature of the Pt surface increases as CO oxidation takes place. As the CO/O 2 ratio increases, the production of CO 2 increases continuously and the surface temperature also increases. Interestingly, within the diffusion limited regions, the amount of surface oxide changes littlemore » while the chemisorbed oxygen is reduced.« less

METHOD FOR TREATING GRAPHITE PRODUCT

DOEpatents

Gurinsky, D.H.

1961-08-01

A method is described for treating a carbon body with a carbonyl consisting of nickel, iron, and mixtures thereof. The carbonyl is decomposed in a non-oxidizing atmosphere into a mixture of the metal and carbon monoxide on the surface of a carbon body heated to above the decomposition point of the carbonyl. The temperature is increased of the carbon body to an elevated temperature above the point at which a liquid eutectic mixture of the metal and carbon of the carbon body is formed at the surface and below that at which substantial carburization occurs. The elevated temperature is maintained whereby the liquid mixture flows over the surface of the carbon body. The carbon body is cooled below the decomposition temperature of the carbonyl of the metal and to a temperature suitable for forming the carbonyl of the metal. The carbon body is then contacted with carbon monoxide at the carbonyl-forming temperature, whereby carbonyl of the metal is formed in and on the carbon body. The carbonyl is removed from the carbon body by gasifying the carbonyl. (AEC)

Low earth orbit durability evaluation of Haynes 188 solar receiver material

NASA Technical Reports Server (NTRS)

De Groh, Kim K.; Rutledge, Sharon K.; Burke, Christopher A.; Dever, Therese M.; Olle, Raymond M.; Terlep, Judith A.

1992-01-01

The effects of elevated-temperature vacuum and elevated-temperature atomic oxygen exposure on the mass, surface chemistry, surface morphology, and optical properties of Haynes 188, a possible heat receiver material for space-based solar dynamic power systems, have been studied. Pristine and surface modified Haynes 188 were exposed to vacuum less than or equal to 10 exp -6 torr at 820 C for 5215.5 h, and to atomic oxygen in an air plasma asher at 34 and 827 C for fluences up to 5.6 x 10 exp 21 atoms/sq cm. Results obtained indicate that vacuum heat treatment caused surface morphology and chemistry changes with corresponding optical property changes. Atomic oxygen exposure caused optical property changes which diminished with time. Mass changes are considered to be negligible for both exposures.

Enhanced Climatic Warming Over the Tibetan Plateau Due to Doubling CO2: A Model Study

NASA Technical Reports Server (NTRS)

Chen, Baode; Chao, Winston C.; Liu, Xiaodong; Lau, William K. M. (Technical Monitor)

2001-01-01

A number of studies have presented the evidences that surface climate change associated with global warming at high elevation sites shows more pronounced warming than at low elevations, i.e. an elevation dependency of climatic warming pointed out that snow-albedo feedback may be responsible for the excessive warming in the Swiss Alps. From an ensemble of climate change experiments of increasing greenhouse gases and aerosols using an air-sea coupled climate model, Eyre and Raw (1999) found a marked elevation dependency of the simulated surface screen temperature increase over the Rocky Mountains. Using almost all available instrumental records, Liu and Chen (2000) showed that the main portion of the Tibetan Plateau (TP) has experienced significant ground temperature warming since the middlebrows, especially in winter, and that there is a tendency for the warming trend to increase with elevation in the TP as well as its surrounding areas. In this paper, we will investigate the mechanism of elevation dependency of climatic warming in the TP by using a high-resolution regional climate model.

Constraints on Late Tertiary Elevation of the Colorado Plateau From Carbonate Clumped- Isotope Thermometry

NASA Astrophysics Data System (ADS)

Huntington, K. W.; Wernicke, B. P.; Eiler, J. M.

2009-05-01

Topography is a first-order expression of the buoyancy of the lithosphere, and the timing and pattern of elevation change can place fundamental constraints on mantle flow and continental dynamics. We investigate the timing of Colorado Plateau uplift using clumped-isotope thermometry to independently constrain both the temperature and isotopic composition of ancient surface waters based on the 13C-18O bond enrichment in carbonates. Analyses of ancient lake sediments from the plateau interior and adjacent lowlands are compared to signals recorded by modern sediments collected over 3 km of elevation in the region. Comparison of modern and ancient samples deposited near sea level provides an opportunity to quantify the influence of climate on changes in temperature, and therefore more accurately assess the contribution from changes in elevation. Both modern and ancient (Miocene-Pliocene) carbonates record near-surface spring/summer lake water temperatures that vary strongly with elevation. Modern and ancient lake carbonate temperature lapse rates of -4.2±0.7°C/km and -4.1±0.6°C/km, respectively, suggest that little if any post-16 Ma change in elevation of the southern plateau is required to explain the data. Agreement of δ18O data for modern and ancient surface waters supports this interpretation. The zero-elevation intercept of the ancient trend is 7.7±2.0°C warmer than the modern trend, indicating significant cooling due to climate change since Late Miocene time. The temperature data are permissive of up to 450 m of uplift or 250 m of subsidence of the plateau interior since 6 Ma, but do not support km-scale changes. Combined with previous constraints, the data suggest that most uplift of the south-central plateau occurred during Late Cretaceous/earliest Tertiary time, favoring uplift mechanisms such as crustal thickening by channel flow, hydration of the mantle lithosphere due to volatile flux from the Laramide flat slab, or dynamic topography associated with slab foundering. The data do not support explanations that ascribe most uplift to ca. 40-0 Ma disposal of the Farallon or North American mantle lithosphere.

Novel development of the micro-tensile test at elevated temperature using a test structure with integrated micro-heater

NASA Astrophysics Data System (ADS)

Ang, W. C.; Kropelnicki, P.; Soe, Oak; Ling, J. H. L.; Randles, A. B.; Hum, A. J. W.; Tsai, J. M. L.; Tay, A. A. O.; Leong, K. C.; Tan, C. S.

2012-08-01

This paper describes the novel development of a micro-tensile testing method that allows testing at elevated temperatures. Instead of using a furnace, a titanium/platinum thin film micro-heater was fabricated on a conventional dog-bone-shaped test structure to heat up its gauge section locally. An infrared (IR) camera with 5 µm resolution was employed to verify the temperature uniformity across the gauge section of the test structure. With this micro-heater-integrated test structure, micro-tensile tests can be performed at elevated temperatures using any conventional tensile testing system without any major modification to the system. In this study, the tensile test of the single crystal silicon (SCS) thin film with (1 0 0) surface orientation and <1 1 0> tensile direction was performed at room temperature and elevated temperatures, up to 300 °C. Experimental results for Young's modulus as a function of temperature are presented. A micro-sized SCS film showed a low dependence of mechanical properties on temperature up to 300 °C.

Transformation twinning of Ni-Mn-Ga characterized with temperature-controlled atomic force microscopy.

PubMed

Reinhold, Matthew; Watson, Chad; Knowlton, William B; Müllner, Peter

2010-06-01

The magnetomechanical properties of ferromagnetic shape memory alloy Ni-Mn-Ga single crystals depend strongly on the twin microstructure, which can be modified through thermomagnetomechanical training. Atomic force microscopy (AFM) and magnetic force microscopy (MFM) were used to characterize the evolution of twin microstructures during thermomechanical training of a Ni-Mn-Ga single crystal. Experiments were performed in the martensite phase at 25 degrees C and in the austenite phase at 55 degrees C. Two distinct twinning surface reliefs were observed at room temperature. At elevated temperature (55 degrees C), the surface relief of one twinning mode disappeared while the other relief remained unchanged. When cooled back to 25 degrees C, the twin surface relief recovered. The relief persisting at elevated temperature specifies the positions of twin boundaries that were present when the sample was polished prior to surface characterization. AFM and MFM following thermomechanical treatment provide a nondestructive method to identify the crystallographic orientation of each twin and of each twin boundary plane. Temperature dependent AFM and MFM experiments reveal the twinning history thereby establishing the technique as a unique predictive tool for revealing the path of the martensitic and reverse transformations of magnetic shape memory alloys.

Transformation twinning of Ni–Mn–Ga characterized with temperature-controlled atomic force microscopy

PubMed Central

Reinhold, Matthew; Watson, Chad; Knowlton, William B.; Müllner, Peter

2010-01-01

The magnetomechanical properties of ferromagnetic shape memory alloy Ni–Mn–Ga single crystals depend strongly on the twin microstructure, which can be modified through thermomagnetomechanical training. Atomic force microscopy (AFM) and magnetic force microscopy (MFM) were used to characterize the evolution of twin microstructures during thermomechanical training of a Ni–Mn–Ga single crystal. Experiments were performed in the martensite phase at 25 °C and in the austenite phase at 55 °C. Two distinct twinning surface reliefs were observed at room temperature. At elevated temperature (55 °C), the surface relief of one twinning mode disappeared while the other relief remained unchanged. When cooled back to 25 °C, the twin surface relief recovered. The relief persisting at elevated temperature specifies the positions of twin boundaries that were present when the sample was polished prior to surface characterization. AFM and MFM following thermomechanical treatment provide a nondestructive method to identify the crystallographic orientation of each twin and of each twin boundary plane. Temperature dependent AFM and MFM experiments reveal the twinning history thereby establishing the technique as a unique predictive tool for revealing the path of the martensitic and reverse transformations of magnetic shape memory alloys. PMID:20589105

Thermal effect of climate change on groundwater-fed ecosystems

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

Burns, Erick R.; Zhu, Yonghui; Zhan, Hongbin

Groundwater temperature changes will lag surface temperature changes from a changing climate. Steady state solutions of the heat-transport equations are used to identify key processes that control the long-term thermal response of springs and other groundwater discharge to climate change, in particular changes in (1) groundwater recharge rate and temperature and (2) land-surface temperature transmitted through the vadose zone. Transient solutions are developed to estimate the time required for new thermal signals to arrive at ecosystems. The solution is applied to the volcanic Medicine Lake highlands, California, USA, and associated springs complexes that host groundwater-dependent ecosystems. In this system, uppermore » basin groundwater temperatures are strongly affected only by recharge conditions. However, as the vadose zone thins away from the highlands, changes in the average annual land-surface temperature also influence groundwater temperatures. Transient response to temperature change depends on both the conductive time scale and the rate at which recharge delivers heat. Most of the thermal response of groundwater at high elevations will occur within 20 years of a shift in recharge temperatures, but the large lower elevation springs will respond more slowly, with about half of the conductive response occurring within the first 20 years and about half of the advective response to higher recharge temperatures occurring in approximately 60 years.« less

Thermal effect of climate change on groundwater-fed ecosystems

DOE PAGES

Burns, Erick R.; Zhu, Yonghui; Zhan, Hongbin; ...

2017-04-24

Groundwater temperature changes will lag surface temperature changes from a changing climate. Steady state solutions of the heat-transport equations are used to identify key processes that control the long-term thermal response of springs and other groundwater discharge to climate change, in particular changes in (1) groundwater recharge rate and temperature and (2) land-surface temperature transmitted through the vadose zone. Transient solutions are developed to estimate the time required for new thermal signals to arrive at ecosystems. The solution is applied to the volcanic Medicine Lake highlands, California, USA, and associated springs complexes that host groundwater-dependent ecosystems. In this system, uppermore » basin groundwater temperatures are strongly affected only by recharge conditions. However, as the vadose zone thins away from the highlands, changes in the average annual land-surface temperature also influence groundwater temperatures. Transient response to temperature change depends on both the conductive time scale and the rate at which recharge delivers heat. Most of the thermal response of groundwater at high elevations will occur within 20 years of a shift in recharge temperatures, but the large lower elevation springs will respond more slowly, with about half of the conductive response occurring within the first 20 years and about half of the advective response to higher recharge temperatures occurring in approximately 60 years.« less

Thermal effect of climate change on groundwater-fed ecosystems

NASA Astrophysics Data System (ADS)

Burns, Erick R.; Zhu, Yonghui; Zhan, Hongbin; Manga, Michael; Williams, Colin F.; Ingebritsen, Steven E.; Dunham, Jason B.

2017-04-01

Groundwater temperature changes will lag surface temperature changes from a changing climate. Steady state solutions of the heat-transport equations are used to identify key processes that control the long-term thermal response of springs and other groundwater discharge to climate change, in particular changes in (1) groundwater recharge rate and temperature and (2) land-surface temperature transmitted through the vadose zone. Transient solutions are developed to estimate the time required for new thermal signals to arrive at ecosystems. The solution is applied to the volcanic Medicine Lake highlands, California, USA, and associated springs complexes that host groundwater-dependent ecosystems. In this system, upper basin groundwater temperatures are strongly affected only by recharge conditions. However, as the vadose zone thins away from the highlands, changes in the average annual land-surface temperature also influence groundwater temperatures. Transient response to temperature change depends on both the conductive time scale and the rate at which recharge delivers heat. Most of the thermal response of groundwater at high elevations will occur within 20 years of a shift in recharge temperatures, but the large lower elevation springs will respond more slowly, with about half of the conductive response occurring within the first 20 years and about half of the advective response to higher recharge temperatures occurring in approximately 60 years.

Thermal effect of climate change on groundwater-fed ecosystems

USGS Publications Warehouse

Burns, Erick; Zhu, Yonghui; Zhan, Hongbin; Manga, Michael; Williams, Colin F.; Ingebritsen, Steven E.; Dunham, Jason B.

2017-01-01

Groundwater temperature changes will lag surface temperature changes from a changing climate. Steady state solutions of the heat-transport equations are used to identify key processes that control the long-term thermal response of springs and other groundwater discharge to climate change, in particular changes in (1) groundwater recharge rate and temperature and (2) land-surface temperature transmitted through the vadose zone. Transient solutions are developed to estimate the time required for new thermal signals to arrive at ecosystems. The solution is applied to the volcanic Medicine Lake highlands, California, USA, and associated springs complexes that host groundwater-dependent ecosystems. In this system, upper basin groundwater temperatures are strongly affected only by recharge conditions. However, as the vadose zone thins away from the highlands, changes in the average annual land-surface temperature also influence groundwater temperatures. Transient response to temperature change depends on both the conductive time scale and the rate at which recharge delivers heat. Most of the thermal response of groundwater at high elevations will occur within 20 years of a shift in recharge temperatures, but the large lower elevation springs will respond more slowly, with about half of the conductive response occurring within the first 20 years and about half of the advective response to higher recharge temperatures occurring in approximately 60 years.

Atmospheric Structure and Diurnal Variations at Low Altitudes in the Martian Tropics

NASA Astrophysics Data System (ADS)

Hinson, David P.; Spiga, A.; Lewis, S.; Tellmann, S.; Pätzold, M.; Asmar, S.; Häusler, B.

2013-10-01

We are using radio occultation measurements from Mars Express, Mars Reconnaissance Orbiter, and Mars Global Surveyor to characterize the diurnal cycle in the lowest scale height above the surface. We focus on northern spring and summer, using observations from 4 Martian years at local times of 4-5 and 15-17 h. We supplement the observations with results obtained from large-eddy simulations and through data assimilation by the UK spectral version of the LMD Mars Global Circulation Model. We previously investigated the depth of the daytime convective boundary layer (CBL) and its variations with surface elevation and surface properties. We are now examining unusual aspects of the temperature structure observed at night. Most important, predawn profiles in the Tharsis region contain an unexpected layer of neutral static stability at pressures of 200-300 Pa with a depth of 4-5 km. The mixed layer is bounded above by a midlevel temperature inversion and below by another strong inversion adjacent to the surface. The narrow temperature minimum at the base of the midlevel inversion suggests the presence of a water ice cloud layer, with the further implication that radiative cooling at cloud level can induce convective activity at lower altitudes. Conversely, nighttime profiles in Amazonis show no sign of a midlevel inversion or a detached mixed layer. These regional variations in the nighttime temperature structure appear to arise in part from large-scale variations in topography, which have several notable effects. First, the CBL is much deeper in the Tharsis region than in Amazonis, owing to a roughly 6-km difference in surface elevation. Second, large-eddy simulations show that daytime convection is not only deeper above Tharsis but also considerably more intense than it is in Amazonis. Finally, the daytime surface temperatures are comparable in the two regions, so that Tharsis acts as an elevated heat source throughout the CBL. These topographic effects are expected to enhance the vertical mixing of water vapor above elevated terrain, which might lead to the formation and regional confinement of nighttime clouds.

Mass Balance Changes and Ice Dynamics of Greenland and Antarctic Ice Sheets from Laser Altimetry

NASA Astrophysics Data System (ADS)

Babonis, G. S.; Csatho, B.; Schenk, T.

2016-06-01

During the past few decades the Greenland and Antarctic ice sheets have lost ice at accelerating rates, caused by increasing surface temperature. The melting of the two big ice sheets has a big impact on global sea level rise. If the ice sheets would melt down entirely, the sea level would rise more than 60 m. Even a much smaller rise would cause dramatic damage along coastal regions. In this paper we report about a major upgrade of surface elevation changes derived from laser altimetry data, acquired by NASA's Ice, Cloud and land Elevation Satellite mission (ICESat) and airborne laser campaigns, such as Airborne Topographic Mapper (ATM) and Land, Vegetation and Ice Sensor (LVIS). For detecting changes in ice sheet elevations we have developed the Surface Elevation Reconstruction And Change detection (SERAC) method. It computes elevation changes of small surface patches by keeping the surface shape constant and considering the absolute values as surface elevations. We report about important upgrades of earlier results, for example the inclusion of local ice caps and the temporal extension from 1993 to 2014 for the Greenland Ice Sheet and for a comprehensive reconstruction of ice thickness and mass changes for the Antarctic Ice Sheets.

Estimation of surface temperature variations due to changes in sky and solar flux with elevation

NASA Technical Reports Server (NTRS)

Hummer-Miller, S.

1981-01-01

The magnitude of elevation effects due to changes in solar and sky fluxes, on interpretation of single thermal images and composite products such as temperature difference and thermal inertia, are examined. Simple expressions are derived for the diurnal behavior of the two parameters, by fitting field observations in one tropic (Hawaii) and two semi-arid climates (Wyoming and Colorado) (Hummer-Miller, 1981). It is shown that flux variations with elevation can cause changes in the mean diurnal temperature gradient from -4 to -14 degrees C/km, evaluated at 2000 m. Changes in the temperature-difference gradient of 1 to 2 degrees C/km are also produced which is equivalent to an effective thermal-inertia gradient of 100 W s(exp 1/2)/sq m-K-km. An example is presented showing an elevation effect of 12 degrees C on the day and night thermal scenes of a test site in Arizona.

Temperature evaluation of dental implant surface irradiated with high-power diode laser.

PubMed

Rios, F G; Viana, E R; Ribeiro, G M; González, J C; Abelenda, A; Peruzzo, D C

2016-09-01

The prevalence of peri-implantitis and the absence of a standard approach for decontamination of the dental implant surface have led to searches for effective therapies. Since the source of diode lasers is portable, has reduced cost, and does not cause damage to the titanium surface of the implant, high-power diode lasers have been used for this purpose. The effect of laser irradiation on the implants is the elevation of the temperature surface. If this elevation exceeds 47 °C, the bone tissue is irreversibly damaged, so for a safety therapy, the laser parameters should be controlled. In this study, a diode laser of GaAsAl was used to irradiate titanium dental implants, for powers 1.32 to 2.64 W (real) or 2.00 to 4.00 W (nominal), in continuous/pulsed mode DC/AC, with exposure time of 5/10 s, with/without air flow for cooling. The elevation of the temperature was monitored in real time in two positions: cervical and apical. The best results for decontamination using a 968-nm diode laser were obtained for a power of 1.65 and 1.98 W (real) for 10 s, in DC or AC mode, with an air flow of 2.5 l/min. In our perspective in this article, we determine a suggested approach for decontamination of the dental implant surface using a 968-nm diode laser.

An Investigation of a Photographic Technique of Measuring High Surface Temperatures

NASA Technical Reports Server (NTRS)

Siviter, James H., Jr.; Strass, H. Kurt

1960-01-01

A photographic method of temperature determination has been developed to measure elevated temperatures of surfaces. The technique presented herein minimizes calibration procedures and permits wide variation in emulsion developing techniques. The present work indicates that the lower limit of applicability is approximately 1,400 F when conventional cameras, emulsions, and moderate exposures are used. The upper limit is determined by the calibration technique and the accuracy required.

Integrated Emissivity And Temperature Measurement

DOEpatents

Poulsen, Peter

2005-11-08

A multi-channel spectrometer and a light source are used to measure both the emitted and the reflected light from a surface which is at an elevated temperature relative to its environment. In a first method, the temperature of the surface and emissivity in each wavelength is calculated from a knowledge of the spectrum and the measurement of the incident and reflected light. In the second method, the reflected light is measured from a reference surface having a known reflectivity and the same geometry as the surface of interest and the emitted and the reflected light are measured for the surface of interest. These measurements permit the computation of the emissivity in each channel of the spectrometer and the temperature of the surface of interest.

Lubricant-infused micro/nano-structured surfaces with tunable dynamic omniphobicity at high temperatures

DOE PAGES

Daniel, Daniel; Mankin, Max N.; Belisle, Rebecca A.; ...

2013-06-10

Omniphobic surfaces that can repel fluids at temperatures higher than 100 °C are rare. Most state-of- the-art liquid-repellent materials are based on the lotus effect, where a thin air layer is maintained throughout micro/nanotextures leading to high mobility of liquids. However, such behavior eventually fails at elevated temperatures when the surface tension of test liquids decreases significantly. Here, we demonstrate a class of lubricant-infused structured surfaces that can maintain a robust omniphobic state even for low-surface-tension liquids at temperatures up to at least 200 °C. We also demonstrate how liquid mobility on such surfaces can be tuned by a factormore » of 1000.« less

Reduced deuterium retention in simultaneously damaged and annealed tungsten

NASA Astrophysics Data System (ADS)

Simmonds, M. J.; Wang, Y. Q.; Barton, J. L.; Baldwin, M. J.; Yu, J. H.; Doerner, R. P.; Tynan, G. R.

2017-10-01

Deuterium (D) retention in polycrystalline tungsten (W) with copper (Cu) ion damage concurrently produced at elevated surface temperature is investigated. An in situ heated stage held W samples at a controlled temperature up to 1243 K, which were subjected to displacement damage produced by 3.4 MeV Cu ions. D retention is subsequently explored by exposure of the W samples held at 383 K to a D2 plasma ion fluence of 1024 D+/m2. Nuclear reaction analysis (NRA), utilizing the D(3He,p)4He nuclear reaction, is used to probe the D concentration in the near surface up to 6 μm. Thermal desorption spectroscopy (TDS) is used to measure outgassed HD and D2 molecules to determine the bulk D concentration. Both NRA and TDS measure a significant reduction in D retention for samples damaged at elevated temperature. TDS quantitatively shows that the lowest energy trap remains largely unaffected while higher energy traps, induced by Cu ions, are annealed and approach intrinsic concentrations as the temperature during ion damage approaches 1243 K. Analysis of TDS data yields an activation energy of (0.10 ± 0.02) eV for recovery of ion-damage induced traps at elevated temperature.

Dominant factors controlling glacial and interglacial variations in the treeline elevation in tropical Africa

PubMed Central

Wu, Haibin; Guiot, Joël; Brewer, Simon; Guo, Zhengtang; Peng, Changhui

2007-01-01

The knowledge of tropical palaeoclimates is crucial for understanding global climate change, because it is a test bench for general circulation models that are ultimately used to predict future global warming. A longstanding issue concerning the last glacial maximum in the tropics is the discrepancy between the decrease in sea-surface temperatures reconstructed from marine proxies and the high-elevation decrease in land temperatures estimated from indicators of treeline elevation. In this study, an improved inverse vegetation modeling approach is used to quantitatively reconstruct palaeoclimate and to estimate the effects of different factors (temperature, precipitation, and atmospheric CO2 concentration) on changes in treeline elevation based on a set of pollen data covering an altitudinal range from 100 to 3,140 m above sea level in Africa. We show that lowering of the African treeline during the last glacial maximum was primarily triggered by regional drying, especially at upper elevations, and was amplified by decreases in atmospheric CO2 concentration and perhaps temperature. This contrasts with scenarios for the Holocene and future climates, in which the increase in treeline elevation will be dominated by temperature. Our results suggest that previous temperature changes inferred from tropical treeline shifts may have been overestimated for low-CO2 glacial periods, because the limiting factors that control changes in treeline elevation differ between glacial and interglacial periods. PMID:17535920

Dominant factors controlling glacial and interglacial variations in the treeline elevation in tropical Africa.

PubMed

Wu, Haibin; Guiot, Joël; Brewer, Simon; Guo, Zhengtang; Peng, Changhui

2007-06-05

The knowledge of tropical palaeoclimates is crucial for understanding global climate change, because it is a test bench for general circulation models that are ultimately used to predict future global warming. A longstanding issue concerning the last glacial maximum in the tropics is the discrepancy between the decrease in sea-surface temperatures reconstructed from marine proxies and the high-elevation decrease in land temperatures estimated from indicators of treeline elevation. In this study, an improved inverse vegetation modeling approach is used to quantitatively reconstruct palaeoclimate and to estimate the effects of different factors (temperature, precipitation, and atmospheric CO(2) concentration) on changes in treeline elevation based on a set of pollen data covering an altitudinal range from 100 to 3,140 m above sea level in Africa. We show that lowering of the African treeline during the last glacial maximum was primarily triggered by regional drying, especially at upper elevations, and was amplified by decreases in atmospheric CO(2) concentration and perhaps temperature. This contrasts with scenarios for the Holocene and future climates, in which the increase in treeline elevation will be dominated by temperature. Our results suggest that previous temperature changes inferred from tropical treeline shifts may have been overestimated for low-CO(2) glacial periods, because the limiting factors that control changes in treeline elevation differ between glacial and interglacial periods.

Modification of Surface Density of a Porous Medium

NASA Technical Reports Server (NTRS)

Stackpoole, Margaret M. (Inventor); Espinoza, Christian (Inventor)

2016-01-01

A method for increasing density of a region of a porous, phenolic bonded ("PPB") body adjacent to a selected surface to increase failure tensile strength of the adjacent region and/or to decrease surface recession at elevated temperatures. When the surface-densified PPB body is brought together with a substrate, having a higher failure tensile strength, to form a composite body with a PPB body/substrate interface, the location of tensile failure is moved to a location spaced apart from the interface, the failure tensile strength of the PPB body is increased, and surface recession of the material at elevated temperature is reduced. The method deposits and allows diffusion of a phenolic substance on the selected surface. The PPB body and the substrate may be heated and brought together to form the composite body. The phenolic substance is allowed to diffuse into the PPB body, to volatilize and to cure, to provide a processed body with an increased surface density.

Global patterns in lake ecosystem responses to warming based on the temperature dependence of metabolism.

PubMed

Kraemer, Benjamin M; Chandra, Sudeep; Dell, Anthony I; Dix, Margaret; Kuusisto, Esko; Livingstone, David M; Schladow, S Geoffrey; Silow, Eugene; Sitoki, Lewis M; Tamatamah, Rashid; McIntyre, Peter B

2017-05-01

Climate warming is expected to have large effects on ecosystems in part due to the temperature dependence of metabolism. The responses of metabolic rates to climate warming may be greatest in the tropics and at low elevations because mean temperatures are warmer there and metabolic rates respond exponentially to temperature (with exponents >1). However, if warming rates are sufficiently fast in higher latitude/elevation lakes, metabolic rate responses to warming may still be greater there even though metabolic rates respond exponentially to temperature. Thus, a wide range of global patterns in the magnitude of metabolic rate responses to warming could emerge depending on global patterns of temperature and warming rates. Here we use the Boltzmann-Arrhenius equation, published estimates of activation energy, and time series of temperature from 271 lakes to estimate long-term (1970-2010) changes in 64 metabolic processes in lakes. The estimated responses of metabolic processes to warming were usually greatest in tropical/low-elevation lakes even though surface temperatures in higher latitude/elevation lakes are warming faster. However, when the thermal sensitivity of a metabolic process is especially weak, higher latitude/elevation lakes had larger responses to warming in parallel with warming rates. Our results show that the sensitivity of a given response to temperature (as described by its activation energy) provides a simple heuristic for predicting whether tropical/low-elevation lakes will have larger or smaller metabolic responses to warming than higher latitude/elevation lakes. Overall, we conclude that the direct metabolic consequences of lake warming are likely to be felt most strongly at low latitudes and low elevations where metabolism-linked ecosystem services may be most affected. © 2016 John Wiley & Sons Ltd.

Monte Carlo simulations of skin exposure to electromagnetic field from 10 GHz to 1 THz

NASA Astrophysics Data System (ADS)

Sasaki, Kensuke; Mizuno, Maya; Wake, Kanako; Watanabe, Soichi

2017-09-01

In this study, we present an assessment of human-body exposure to an electromagnetic field at frequencies ranging from 10 GHz to 1 THz. The energy absorption and temperature elevation were assessed by solving boundary value problems of the one-dimensional Maxwell equations and a bioheat equation for a multilayer plane model. Dielectric properties were measured in~vitro at frequencies of up to 1 THz at body temperature. A Monte Carlo simulation was conducted to assess variations of the transmittance into a skin surface and temperature elevation inside a body by considering the variation of the tissue thickness due to individual differences among human bodies. Furthermore, the impact of the dielectric properties of adipose tissue on temperature elevation, for which large discrepancies between our present measurement results and those in past works were observed, was also examined. We found that the dielectric properties of adipose tissue do not impact on temperature elevation at frequencies over 30 GHz. The potential risk of skin burn was discussed on the basis of the temperature elevation in millimeter-wave and terahertz-wave exposure. Furthermore, the consistency of the basic restrictions in the international guidelines set by ICNIRP was discussed.

Systems and Methods for Integrated Emissivity and Temperature Measurement of a Surface

DOEpatents

Poulsen, Peter

2005-11-08

A multi-channel spectrometer and a light source are used to measure both the emitted and the reflected light from a surface which is at an elevated temperature relative to its environment. In a first method, the temperature of the surface and emissivity in each wavelength is calculated from a knowledge of the spectrum and the measurement of the incident and reflected light. In the second method, the reflected light is measured from a reference surface having a known reflectivity and the same geometry as the surface of interest and the emitted and the reflected light are measured for the surface of interest. These measurements permit the computation of the emissivity in each channel of the spectrometer and the temperature of the surface of interest.

Undercoat prevents blistering of silver plating at elevated temperatures

NASA Technical Reports Server (NTRS)

Kuster, C. A.

1967-01-01

Gold undercoat prevents blistering in the silver plating of Inconel 718 seals from steam at high temperatures. The undercoat is diffused into the surface of the parent metal by baking prior to silver plating.

High Resolution Photogrammetric Digital Elevation Models Across Calving Fronts and Meltwater Channels in Greenland

NASA Astrophysics Data System (ADS)

Le Bel, D. A.; Brown, S.; Zappa, C. J.; Bell, R. E.; Frearson, N.; Tinto, K. J.

2014-12-01

Photogrammetric digital elevation models (DEMs) are a powerful approach for understanding elevation change and dynamics along the margins of the large ice sheets. The IcePod system, mounted on a New York Air National Guard LC-130, can measure high-resolution surface elevations with a Riegl VQ580 scanning laser altimeter and Imperx Bobcat IGV-B6620 color visible-wavelength camera (6600x4400 resolution); the surface temperature with a Sofradir IRE-640L infrared camera (spectral response 7.7-9.5 μm, 640x512 resolution); and the structure of snow and ice with two radar systems. We show the use of IcePod imagery to develop DEMs across calving fronts and meltwater channels in Greenland. Multiple over-flights of the Kangerlussaq Airport ramp have provided a test of the technique at a location with accurate, independently-determined elevation. Here the photogrammetric DEM of the airport, constrained by ground control measurements, is compared with the Lidar results. In July 2014 the IcePod ice-ocean imaging system surveyed the calving fronts of five outlet glaciers north of Jakobshavn Isbrae. We used Agisoft PhotoScan to develop a DEM of each calving front using imagery captured by the IcePod systems. Adjacent to the ice sheet, meltwater plumes foster mixing in the fjord, moving warm ocean water into contact with the front of the ice sheet where it can undercut the ice front and trigger calving. The five glaciers provide an opportunity to examine the calving front structure in relation to ocean temperature, fjord circulation, and spatial scale of the meltwater plumes. The combination of the accurate DEM of the calving front and the thermal imagery used to constrain the temperature and dynamics of the adjacent plume provides new insights into the ice-ocean interactions. Ice sheet margins provide insights into the connections between the surface meltwater and the fate of the water at the ice sheet base. Surface meltwater channels are visualized here for the first time using the combination of Lidar, photogrammetry DEMs and infrared imagery. These techniques leverage electromagnetic surface properties that allow us to identify the presence of water, measure the slope and elevation of the channel, as well as the two-dimensional temperature variability of the water/ice/snow in multiple melt channels within a drainage system.

Hydrological response and thermal effect of karst springs linked to aquifer geometry and recharge processes

NASA Astrophysics Data System (ADS)

Luo, Mingming; Chen, Zhihua; Zhou, Hong; Zhang, Liang; Han, Zhaofeng

2018-03-01

To be better understand the hydrological and thermal behavior of karst systems in South China, seasonal variations in flow, hydrochemistry and stable isotope ratios of five karst springs were used to delineate flow paths and recharge processes, and to interpret their thermal response. Isotopic data suggest that mean recharge elevations are 200-820 m above spring outlets. Springs that originate from high elevations have lower NO3 - concentrations than those originating from lower areas that have more agricultural activity. Measured Sr2+ concentrations reflect the strontium contents of the host carbonate aquifer and help delineate the spring catchment's saturated zone. Seasonal variations of NO3 - and Sr2+ concentrations are inversely correlated, because the former correlates with event water and the latter with baseflow. The mean annual water temperatures of springs were only slightly lower than the local mean annual surface temperature at the outlet elevations. These mean spring temperatures suggest a vertical gradient of 6 °C/vertical km, which resembles the adiabatic lapse rate of the Earth's stable atmosphere. Seasonal temperature variations in the springs are in phase with surface air temperatures, except for Heilongquan (HLQ) spring. Event-scale variations of thermal response are dramatically controlled by the circulation depth of karst systems, which determines the effectiveness of heat exchange. HLQ spring undergoes the deepest circulation depth of 820 m, and its thermal responses are determined by the thermally effective regulation processes at higher elevations and the mixing processes associated with thermally ineffective responses at lower elevations.

Application of Sol-Gel Method as a Protective Layer on a Specular Reflective Surface for Secondary Reflector in a Solar Receiver

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

Afrin, Samia; Dagdelen, John; Ma, Zhiwen

Highly-specular reflective surfaces that can withstand elevated-temperatures are desirable for many applications including reflective heat shielding in solar receivers and secondary reflectors, which can be used between primary concentrators and heat collectors. A high-efficiency, high-temperature solar receiver design based on arrays of cavities needs a highly-specular reflective surface on its front section to help sunlight penetrate into the absorber tubes for effective flux spreading. Since this application is for high-temperature solar receivers, this surface needs to be durable and to maintain its optical properties through the usable life. Degradation mechanisms associated with elevated temperatures and thermal cycling, which include cracking,more » delamination, corrosion/oxidation, and environmental effects, could cause the optical properties of surfaces to degrade rapidly in these conditions. Protected mirror surfaces for these applications have been tested by depositing a thin layer of SiO2 on top of electrodeposited silver by means of the sol-gel method. To obtain an effective thin film structure, this sol-gel procedure has been investigated extensively by varying process parameters that affect film porosity and thickness. Endurance tests have been performed in a furnace at 150 degrees C for thousands of hours. This paper presents the sol-gel process for intermediate-temperature specular reflective coatings and provides the long-term reliability test results of sol-gel protected silver-coated surfaces.« less

The Importance of Biologically Relevant Microclimates in Habitat Suitability Assessments

PubMed Central

Varner, Johanna; Dearing, M. Denise

2014-01-01

Predicting habitat suitability under climate change is vital to conserving biodiversity. However, current species distribution models rely on coarse scale climate data, whereas fine scale microclimate data may be necessary to assess habitat suitability and generate predictive models. Here, we evaluate disparities between temperature data at the coarse scale from weather stations versus fine-scale data measured in microhabitats required for a climate-sensitive mammal, the American pika (Ochotona princeps). We collected two years of temperature data in occupied talus habitats predicted to be suitable (high elevation) and unsuitable (low elevation) by the bioclimatic envelope approach. At low elevations, talus surface and interstitial microclimates drastically differed from ambient temperatures measured on-site and at a nearby weather station. Interstitial talus temperatures were frequently decoupled from high ambient temperatures, resulting in instantaneous disparities of over 30°C between these two measurements. Microhabitat temperatures were also highly heterogeneous, such that temperature measurements within the same patch of talus were not more correlated than measurements at distant patches. An experimental manipulation revealed that vegetation cover may cool the talus surface by up to 10°C during the summer, which may contribute to this spatial heterogeneity. Finally, low elevation microclimates were milder and less variable than typical alpine habitat, suggesting that, counter to species distribution model predictions, these seemingly unsuitable habitats may actually be better refugia for this species under climate change. These results highlight the importance of fine-scale microhabitat data in habitat assessments and underscore the notion that some critical refugia may be counterintuitive. PMID:25115894

The importance of biologically relevant microclimates in habitat suitability assessments.

PubMed

Varner, Johanna; Dearing, M Denise

2014-01-01

Predicting habitat suitability under climate change is vital to conserving biodiversity. However, current species distribution models rely on coarse scale climate data, whereas fine scale microclimate data may be necessary to assess habitat suitability and generate predictive models. Here, we evaluate disparities between temperature data at the coarse scale from weather stations versus fine-scale data measured in microhabitats required for a climate-sensitive mammal, the American pika (Ochotona princeps). We collected two years of temperature data in occupied talus habitats predicted to be suitable (high elevation) and unsuitable (low elevation) by the bioclimatic envelope approach. At low elevations, talus surface and interstitial microclimates drastically differed from ambient temperatures measured on-site and at a nearby weather station. Interstitial talus temperatures were frequently decoupled from high ambient temperatures, resulting in instantaneous disparities of over 30 °C between these two measurements. Microhabitat temperatures were also highly heterogeneous, such that temperature measurements within the same patch of talus were not more correlated than measurements at distant patches. An experimental manipulation revealed that vegetation cover may cool the talus surface by up to 10 °C during the summer, which may contribute to this spatial heterogeneity. Finally, low elevation microclimates were milder and less variable than typical alpine habitat, suggesting that, counter to species distribution model predictions, these seemingly unsuitable habitats may actually be better refugia for this species under climate change. These results highlight the importance of fine-scale microhabitat data in habitat assessments and underscore the notion that some critical refugia may be counterintuitive.

Experimental and FDTD study of silicon surface morphology induced by femtosecond laser irradiation at a high substrate temperature.

PubMed

Deng, Guoliang; Feng, Guoying; Zhou, Shouhuan

2017-04-03

Substrate temperature is an important parameter for controlling the properties of femtosecond laser induced surface structures besides traditional ways. The morphology on silicon surface at different temperatures are studied experimentally. Compared to those formed at 300 K, smoother ripples, micro-grooves and nano/micro-holes are formed at 700 K. A two temperature model and FDTD method are used to discuss the temperature dependence of surface structures. The results show that the increased light absorption at elevated temperature leads to the reduction of surface roughness. The type-g feature in the FDTD-η map at 700 K, which corresponds to the energy deposition modulation parallel to the laser polarization with a periodicity bigger than the wavelength, is the origin of the formation of grooves. This work can benefit both surface structures based applications and the study of femtosecond laser-matter interactions.

Comparison of elevation and remote sensing derived products as auxiliary data for climate surface interpolation

USGS Publications Warehouse

Alvarez, Otto; Guo, Qinghua; Klinger, Robert C.; Li, Wenkai; Doherty, Paul

2013-01-01

Climate models may be limited in their inferential use if they cannot be locally validated or do not account for spatial uncertainty. Much of the focus has gone into determining which interpolation method is best suited for creating gridded climate surfaces, which often a covariate such as elevation (Digital Elevation Model, DEM) is used to improve the interpolation accuracy. One key area where little research has addressed is in determining which covariate best improves the accuracy in the interpolation. In this study, a comprehensive evaluation was carried out in determining which covariates were most suitable for interpolating climatic variables (e.g. precipitation, mean temperature, minimum temperature, and maximum temperature). We compiled data for each climate variable from 1950 to 1999 from approximately 500 weather stations across the Western United States (32° to 49° latitude and −124.7° to −112.9° longitude). In addition, we examined the uncertainty of the interpolated climate surface. Specifically, Thin Plate Spline (TPS) was used as the interpolation method since it is one of the most popular interpolation techniques to generate climate surfaces. We considered several covariates, including DEM, slope, distance to coast (Euclidean distance), aspect, solar potential, radar, and two Normalized Difference Vegetation Index (NDVI) products derived from Advanced Very High Resolution Radiometer (AVHRR) and Moderate Resolution Imaging Spectroradiometer (MODIS). A tenfold cross-validation was applied to determine the uncertainty of the interpolation based on each covariate. In general, the leading covariate for precipitation was radar, while DEM was the leading covariate for maximum, mean, and minimum temperatures. A comparison to other products such as PRISM and WorldClim showed strong agreement across large geographic areas but climate surfaces generated in this study (ClimSurf) had greater variability at high elevation regions, such as in the Sierra Nevada Mountains.

Experimental Techniques Verified for Determining Yield and Flow Surfaces

NASA Technical Reports Server (NTRS)

Lerch, Brad A.; Ellis, Rod; Lissenden, Cliff J.

1998-01-01

Structural components in aircraft engines are subjected to multiaxial loads when in service. For such components, life prediction methodologies are dependent on the accuracy of the constitutive models that determine the elastic and inelastic portions of a loading cycle. A threshold surface (such as a yield surface) is customarily used to differentiate between reversible and irreversible flow. For elastoplastic materials, a yield surface can be used to delimit the elastic region in a given stress space. The concept of a yield surface is central to the mathematical formulation of a classical plasticity theory, but at elevated temperatures, material response can be highly time dependent. Thus, viscoplastic theories have been developed to account for this time dependency. Since the key to many of these theories is experimental validation, the objective of this work (refs. 1 and 2) at the NASA Lewis Research Center was to verify that current laboratory techniques and equipment are sufficient to determine flow surfaces at elevated temperatures. By probing many times in the axial-torsional stress space, we could define the yield and flow surfaces. A small offset definition of yield (10 me) was used to delineate the boundary between reversible and irreversible behavior so that the material state remained essentially unchanged and multiple probes could be done on the same specimen. The strain was measured with an off-the-shelf multiaxial extensometer that could measure the axial and torsional strains over a wide range of temperatures. The accuracy and resolution of this extensometer was verified by comparing its data with strain gauge data at room temperature. The extensometer was found to have sufficient resolution for these experiments. In addition, the amount of crosstalk (i.e., the accumulation of apparent strain in one direction when strain in the other direction is applied) was found to be negligible. Tubular specimens were induction heated to determine the flow surfaces at elevated temperatures. The heating system induced a large amount of noise in the data. By reducing thermal fluctuations and using appropriate data averaging schemes, we could render the noise inconsequential. Thus, accurate and reproducible flow surfaces (see the figure) could be obtained.

Electronic and chemical structure of the H 2O/GaN(0001) interface under ambient conditions

DOE PAGES

Zhang, Xueqiang; Ptasinska, Sylwia

2016-04-25

We employed ambient pressure X-ray photoelectron spectroscopy to investigate the electronic and chemical properties of the H 2O/GaN(0001) interface under elevated pressures and/or temperatures. A pristine GaN(0001) surface exhibited upward band bending, which was partially flattened when exposed to H 2O at room temperature. However, the GaN surface work function was slightly reduced due to the adsorption of molecular H 2O and its dissociation products. At elevated temperatures, a negative charge generated on the surface by a vigorous H 2O/GaN interfacial chemistry induced an increase in both the surface work function and upward band bending. We tracked the dissociative adsorptionmore » of H 2O onto the GaN(0001) surface by recording the core-level photoemission spectra and obtained the electronic and chemical properties at the H 2O/GaN interface under operando conditions. In conclusion, our results suggest a strong correlation between the electronic and chemical properties of the material surface, and we expect that their evolutions lead to significantly different properties at the electrolyte/ electrode interface in a photoelectrochemical solar cell.« less

Design of an experimental apparatus for measurement of the surface tension of metastable fluids

NASA Astrophysics Data System (ADS)

Vinš, V.; Hrubý, J.; Hykl, J.; Blaha, J.; Šmíd, B.

2013-04-01

A unique experimental apparatus for measurement of the surface tension of aqueous mixtures has been designed, manufactured, and tested in our laboratory. The novelty of the setup is that it allows measurement of surface tension by two different methods: a modified capillary elevation method in a long vertical capillary tube and a method inspired by the approach of Hacker (National Advisory Committee for Aeronautics, Technical Note 2510, 1-20, 1951), i.e. in a short horizontal capillary tube. Functionality of all main components of the apparatus, e.g., glass chamber with the capillary tube, temperature control unit consisting of two thermostatic baths with special valves for rapid temperature jumps, helium distribution setup allowing pressure variation above the liquid meniscus inside the capillary tube, has been successfully tested. Preliminary results for the surface tension of the stable and metastable supercooled water measured by the capillary elevation method at atmospheric pressure are provided. The surface tension of water measured at temperatures between +26 °C and -11 °C is in good agreement with the extrapolated IAPWS correlation (IAPWS Release on Surface Tension of Ordinary Water Substance, September 1994); however it disagrees with data by Hacker.

A global database of lake surface temperatures collected by in situ and satellite methods from 1985–2009

PubMed Central

Sharma, Sapna; Gray, Derek K; Read, Jordan S; O’Reilly, Catherine M; Schneider, Philipp; Qudrat, Anam; Gries, Corinna; Stefanoff, Samantha; Hampton, Stephanie E; Hook, Simon; Lenters, John D; Livingstone, David M; McIntyre, Peter B; Adrian, Rita; Allan, Mathew G; Anneville, Orlane; Arvola, Lauri; Austin, Jay; Bailey, John; Baron, Jill S; Brookes, Justin; Chen, Yuwei; Daly, Robert; Dokulil, Martin; Dong, Bo; Ewing, Kye; de Eyto, Elvira; Hamilton, David; Havens, Karl; Haydon, Shane; Hetzenauer, Harald; Heneberry, Jocelyne; Hetherington, Amy L; Higgins, Scott N; Hixson, Eric; Izmest’eva, Lyubov R; Jones, Benjamin M; Kangur, Külli; Kasprzak, Peter; Köster, Olivier; Kraemer, Benjamin M; Kumagai, Michio; Kuusisto, Esko; Leshkevich, George; May, Linda; MacIntyre, Sally; Müller-Navarra, Dörthe; Naumenko, Mikhail; Noges, Peeter; Noges, Tiina; Niederhauser, Pius; North, Ryan P; Paterson, Andrew M; Plisnier, Pierre-Denis; Rigosi, Anna; Rimmer, Alon; Rogora, Michela; Rudstam, Lars; Rusak, James A; Salmaso, Nico; Samal, Nihar R; Schindler, Daniel E; Schladow, Geoffrey; Schmidt, Silke R; Schultz, Tracey; Silow, Eugene A; Straile, Dietmar; Teubner, Katrin; Verburg, Piet; Voutilainen, Ari; Watkinson, Andrew; Weyhenmeyer, Gesa A; Williamson, Craig E; Woo, Kara H

2015-01-01

Global environmental change has influenced lake surface temperatures, a key driver of ecosystem structure and function. Recent studies have suggested significant warming of water temperatures in individual lakes across many different regions around the world. However, the spatial and temporal coherence associated with the magnitude of these trends remains unclear. Thus, a global data set of water temperature is required to understand and synthesize global, long-term trends in surface water temperatures of inland bodies of water. We assembled a database of summer lake surface temperatures for 291 lakes collected in situ and/or by satellites for the period 1985–2009. In addition, corresponding climatic drivers (air temperatures, solar radiation, and cloud cover) and geomorphometric characteristics (latitude, longitude, elevation, lake surface area, maximum depth, mean depth, and volume) that influence lake surface temperatures were compiled for each lake. This unique dataset offers an invaluable baseline perspective on global-scale lake thermal conditions as environmental change continues. PMID:25977814

A global database of lake surface temperatures collected by in situ and satellite methods from 1985-2009.

PubMed

Sharma, Sapna; Gray, Derek K; Read, Jordan S; O'Reilly, Catherine M; Schneider, Philipp; Qudrat, Anam; Gries, Corinna; Stefanoff, Samantha; Hampton, Stephanie E; Hook, Simon; Lenters, John D; Livingstone, David M; McIntyre, Peter B; Adrian, Rita; Allan, Mathew G; Anneville, Orlane; Arvola, Lauri; Austin, Jay; Bailey, John; Baron, Jill S; Brookes, Justin; Chen, Yuwei; Daly, Robert; Dokulil, Martin; Dong, Bo; Ewing, Kye; de Eyto, Elvira; Hamilton, David; Havens, Karl; Haydon, Shane; Hetzenauer, Harald; Heneberry, Jocelyne; Hetherington, Amy L; Higgins, Scott N; Hixson, Eric; Izmest'eva, Lyubov R; Jones, Benjamin M; Kangur, Külli; Kasprzak, Peter; Köster, Olivier; Kraemer, Benjamin M; Kumagai, Michio; Kuusisto, Esko; Leshkevich, George; May, Linda; MacIntyre, Sally; Müller-Navarra, Dörthe; Naumenko, Mikhail; Noges, Peeter; Noges, Tiina; Niederhauser, Pius; North, Ryan P; Paterson, Andrew M; Plisnier, Pierre-Denis; Rigosi, Anna; Rimmer, Alon; Rogora, Michela; Rudstam, Lars; Rusak, James A; Salmaso, Nico; Samal, Nihar R; Schindler, Daniel E; Schladow, Geoffrey; Schmidt, Silke R; Schultz, Tracey; Silow, Eugene A; Straile, Dietmar; Teubner, Katrin; Verburg, Piet; Voutilainen, Ari; Watkinson, Andrew; Weyhenmeyer, Gesa A; Williamson, Craig E; Woo, Kara H

2015-01-01

Global environmental change has influenced lake surface temperatures, a key driver of ecosystem structure and function. Recent studies have suggested significant warming of water temperatures in individual lakes across many different regions around the world. However, the spatial and temporal coherence associated with the magnitude of these trends remains unclear. Thus, a global data set of water temperature is required to understand and synthesize global, long-term trends in surface water temperatures of inland bodies of water. We assembled a database of summer lake surface temperatures for 291 lakes collected in situ and/or by satellites for the period 1985-2009. In addition, corresponding climatic drivers (air temperatures, solar radiation, and cloud cover) and geomorphometric characteristics (latitude, longitude, elevation, lake surface area, maximum depth, mean depth, and volume) that influence lake surface temperatures were compiled for each lake. This unique dataset offers an invaluable baseline perspective on global-scale lake thermal conditions as environmental change continues.

A global database of lake surface temperatures collected by in situ and satellite methods from 1985–2009

USGS Publications Warehouse

Sharma, Sapna; Gray, Derek; Read, Jordan S.; O'Reilly, Catherine; Schneider, Philipp; Qudrat, Anam; Gries, Corinna; Stefanoff, Samantha; Hampton, Stephanie; Hook, Simon; Lenters, John; Livingstone, David M.; McIntyre, Peter B.; Adrian, Rita; Allan, Mathew; Anneville, Orlane; Arvola, Lauri; Austin, Jay; Bailey, John E.; Baron, Jill S.; Brookes, Justin D; Chen, Yuwei; Daly, Robert; Ewing, Kye; de Eyto, Elvira; Dokulil, Martin; Hamilton, David B.; Havens, Karl; Haydon, Shane; Hetzenaeur, Harald; Heneberry, Jocelyn; Hetherington, Amy; Higgins, Scott; Hixson, Eric; Izmest'eva, Lyubov; Jones, Benjamin M.; Kangur, Kulli; Kasprzak, Peter; Kraemer, Benjamin; Kumagai, Michio; Kuusisto, Esko; Leshkevich, George; May, Linda; MacIntyre, Sally; Dörthe Müller-Navarra,; Naumenko, Mikhail; Noges, Peeter; Noges, Tiina; Pius Niederhauser,; North, Ryan P.; Andrew Paterson,; Plisnier, Pierre-Denis; Rigosi, Anna; Rimmer, Alon; Rogora, Michela; Rudstam, Lars G.; Rusak, James A.; Salmaso, Nico; Samal, Nihar R.; Daniel E. Schindler,; Geoffrey Schladow,; Schmidt, Silke R.; Tracey Schultz,; Silow, Eugene A.; Straile, Dietmar; Teubner, Katrin; Verburg, Piet; Voutilainen, Ari; Watkinson, Andrew; Weyhenmeyer, Gesa A.; Craig E. Williamson,; Kara H. Woo,

2015-01-01

Global environmental change has influenced lake surface temperatures, a key driver of ecosystem structure and function. Recent studies have suggested significant warming of water temperatures in individual lakes across many different regions around the world. However, the spatial and temporal coherence associated with the magnitude of these trends remains unclear. Thus, a global data set of water temperature is required to understand and synthesize global, long-term trends in surface water temperatures of inland bodies of water. We assembled a database of summer lake surface temperatures for 291 lakes collected in situ and/or by satellites for the period 1985–2009. In addition, corresponding climatic drivers (air temperatures, solar radiation, and cloud cover) and geomorphometric characteristics (latitude, longitude, elevation, lake surface area, maximum depth, mean depth, and volume) that influence lake surface temperatures were compiled for each lake. This unique dataset offers an invaluable baseline perspective on global-scale lake thermal conditions as environmental change continues.

Gas diffusion electrode setup for catalyst testing in concentrated phosphoric acid at elevated temperatures

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

Wiberg, Gustav K. H., E-mail: gustav.wiberg@gmail.com, E-mail: m.arenz@chem.ku.dk; Fleige, Michael; Arenz, Matthias, E-mail: gustav.wiberg@gmail.com, E-mail: m.arenz@chem.ku.dk

2015-02-15

We present a detailed description of the construction and testing of an electrochemical cell setup allowing the investigation of a gas diffusion electrode containing carbon supported high surface area catalysts. The setup is designed for measurements in concentrated phosphoric acid at elevated temperature, i.e., very close to the actual conditions in high temperature proton exchange membrane fuel cells (HT-PEMFCs). The cell consists of a stainless steel flow field and a PEEK plastic cell body comprising the electrochemical cell, which exhibits a three electrode configuration. The cell body and flow field are braced using a KF-25 vacuum flange clamp, which allowsmore » an easy assembly of the setup. As demonstrated, the setup can be used to investigate temperature dependent electrochemical processes on high surface area type electrocatalysts, but it also enables quick screening tests of HT-PEMFC catalysts under realistic conditions.« less

Gas diffusion electrode setup for catalyst testing in concentrated phosphoric acid at elevated temperatures

NASA Astrophysics Data System (ADS)

Wiberg, Gustav K. H.; Fleige, Michael; Arenz, Matthias

2015-02-01

We present a detailed description of the construction and testing of an electrochemical cell setup allowing the investigation of a gas diffusion electrode containing carbon supported high surface area catalysts. The setup is designed for measurements in concentrated phosphoric acid at elevated temperature, i.e., very close to the actual conditions in high temperature proton exchange membrane fuel cells (HT-PEMFCs). The cell consists of a stainless steel flow field and a PEEK plastic cell body comprising the electrochemical cell, which exhibits a three electrode configuration. The cell body and flow field are braced using a KF-25 vacuum flange clamp, which allows an easy assembly of the setup. As demonstrated, the setup can be used to investigate temperature dependent electrochemical processes on high surface area type electrocatalysts, but it also enables quick screening tests of HT-PEMFC catalysts under realistic conditions.

Few apparent short-term effects of elevated soil temperature and increased frequency of summer precipitation on the abundance and taxonomic diversity of desert soil micro- and meso-fauna

USGS Publications Warehouse

Darby, B.J.; Neher, D.A.; Housman, D.C.; Belnap, J.

2011-01-01

Frequent hydration and drying of soils in arid systems can accelerate desert carbon and nitrogen mobilization due to respiration, microbial death, and release of intracellular solutes. Because desert microinvertebrates can mediate nutrient cycling, and the autotrophic components of crusts are known to be sensitive to rapid desiccation due to elevated temperatures after wetting events, we studied whether altered soil temperature and frequency of summer precipitation can also affect the composition of food web consumer functional groups. We conducted a two-year field study with experimentally-elevated temperature and frequency of summer precipitation in the Colorado Plateau desert, measuring the change in abundance of nematodes, protozoans, and microarthropods. We hypothesized that microfauna would be more adversely affected by the combination of elevated temperature and frequency of summer precipitation than either effect alone, as found previously for phototrophic crust biota. Microfauna experienced normal seasonal fluctuations in abundance, but the effect of elevated temperature and frequency of summer precipitation was statistically non-significant for most microfaunal groups, except amoebae. The seasonal increase in abundance of amoebae was reduced with combined elevated temperature and increased frequency of summer precipitation compared to either treatment alone, but comparable with control (untreated) plots. Based on our findings, we suggest that desert soil microfauna are relatively more tolerant to increases in ambient temperature and frequency of summer precipitation than the autotrophic components of biological soil crust at the surface.

Impact of climate change environmental conditions on the resilience of different formulations of the biocontrol agent Candida sake CPA-1 on grapes.

PubMed

Carbó, A; Torres, R; Teixidó, N; Usall, J; Medina, A; Magan, N

2018-07-01

Biocontrol agents have become components of integrated crop protection systems for controlling economically important fungal pathogens. Candida sake CPA-1 is a biocontrol agent of fungal pathogens of fruits, both pre- and post-harvest. While the efficacy of different formulations have been examined previously, few studies have considered the resilience of different formulations under changing climatic conditions of elevated temperature, drought stress and increased atmospheric CO 2 . This study examined the effect of (a) temperature × RH × elevated CO 2 (400 vs 1000 ppm) on the temporal establishment and viability of two dry and one liquid C. sake CPA-1 formulations on grape berry surfaces; (b) temperature stress (25 vs 35°C); and (c) elevated CO 2 levels. Results indicated that temperature, RH and CO 2 concentration influenced the establishment and viability of the formulations but there was no significant difference between formulations. For the combined three-component factors, increased temperature (35°C) and lower RH (40%) reduced the viable populations on grapes. The interaction with elevated CO 2 improved the establishment of viable populations of the formulations tested. Viable populations greater than Log 4 CFUs per g were recovered from the grape surfaces suggesting that these had conserved resilience for control of Botrytis rot in grapes. The interaction between environmental factors that are expected to occur in response to climate change (CC) will have a significant impact on food security and availability. Little information exists on how elevated temperature, drought stress and increased CO 2 will have on the efficacy of biocontrol agents. The impact of these factors on the viability of different formulations of the biocontrol yeast Candida sake on the surface of grapes berries was evaluated for the first time. Such knowledge is critical for projecting the efficacy of biocontrol under climate change conditions and to identify formulations that have the necessary resilience to perform under CC conditions. © 2018 The Society for Applied Microbiology.

Improved Mechanical Properties of Various Fabric-Reinforced Geocomposite at Elevated Temperature

NASA Astrophysics Data System (ADS)

Samal, Sneha; Phan Thanh, Nhan; Petríková, Iva; Marvalová, Bohadana

2015-07-01

This article signifies the improved performance of the various types of fabric reinforcement of geopolymer as a function of physical, thermal, mechanical, and heat-resistant properties at elevated temperatures. Geopolymer mixed with designed Si:Al ratios of 15.6 were synthesized using three different types of fabric reinforcement such as carbon, E-glass, and basalt fibers. Heat testing was conducted on 3-mm-thick panels with 15 × 90 mm surface exposure region. The strength of carbon-based geocomposite increased toward a higher temperature. The basalt-reinforced geocomposite strength decreased due to the catastrophic failure in matrix region. The poor bridging effect and dissolution of fabric was observed in the E-glass-reinforced geocomposite. At an elevated temperature, fiber bridging was observed in carbon fabric-reinforced geopolymer matrix. Among all the fabrics, carbon proved to be suitable candidate for the high-temperature applications in thermal barrier coatings and fire-resistant panels.

Verification of Experimental Techniques for Flow Surface Determination

NASA Technical Reports Server (NTRS)

Lissenden, Cliff J.; Lerch, Bradley A.; Ellis, John R.; Robinson, David N.

1996-01-01

The concept of a yield surface is central to the mathematical formulation of a classical plasticity theory. However, at elevated temperatures, material response can be highly time-dependent, which is beyond the realm of classical plasticity. Viscoplastic theories have been developed for just such conditions. In viscoplastic theories, the flow law is given in terms of inelastic strain rate rather than the inelastic strain increment used in time-independent plasticity. Thus, surfaces of constant inelastic strain rate or flow surfaces are to viscoplastic theories what yield surfaces are to classical plasticity. The purpose of the work reported herein was to validate experimental procedures for determining flow surfaces at elevated temperatures. Since experimental procedures for determining yield surfaces in axial/torsional stress space are well established, they were employed -- except inelastic strain rates were used rather than total inelastic strains. In yield-surface determinations, the use of small-offset definitions of yield minimizes the change of material state and allows multiple loadings to be applied to a single specimen. The key to the experiments reported here was precise, decoupled measurement of axial and torsional strain. With this requirement in mind, the performance of a high-temperature multi-axial extensometer was evaluated by comparing its results with strain gauge results at room temperature. Both the extensometer and strain gauges gave nearly identical yield surfaces (both initial and subsequent) for type 316 stainless steel (316 SS). The extensometer also successfully determined flow surfaces for 316 SS at 650 C. Furthermore, to judge the applicability of the technique for composite materials, yield surfaces were determined for unidirectional tungsten/Kanthal (Fe-Cr-Al).

Range-Wide Latitudinal and Elevational Temperature Gradients for the World's Terrestrial Birds: Implications under Global Climate Change

PubMed Central

La Sorte, Frank A.; Butchart, Stuart H. M.; Jetz, Walter; Böhning-Gaese, Katrin

2014-01-01

Species' geographical distributions are tracking latitudinal and elevational surface temperature gradients under global climate change. To evaluate the opportunities to track these gradients across space, we provide a first baseline assessment of the steepness of these gradients for the world's terrestrial birds. Within the breeding ranges of 9,014 bird species, we characterized the spatial gradients in temperature along latitude and elevation for all and a subset of bird species, respectively. We summarized these temperature gradients globally for threatened and non-threatened species and determined how their steepness varied based on species' geography (range size, shape, and orientation) and projected changes in temperature under climate change. Elevational temperature gradients were steepest for species in Africa, western North and South America, and central Asia and shallowest in Australasia, insular IndoMalaya, and the Neotropical lowlands. Latitudinal temperature gradients were steepest for extratropical species, especially in the Northern Hemisphere. Threatened species had shallower elevational gradients whereas latitudinal gradients differed little between threatened and non-threatened species. The strength of elevational gradients was positively correlated with projected changes in temperature. For latitudinal gradients, this relationship only held for extratropical species. The strength of latitudinal gradients was better predicted by species' geography, but primarily for extratropical species. Our findings suggest threatened species are associated with shallower elevational temperature gradients, whereas steep latitudinal gradients are most prevalent outside the tropics where fewer bird species occur year-round. Future modeling and mitigation efforts would benefit from the development of finer grain distributional data to ascertain how these gradients are structured within species' ranges, how and why these gradients vary among species, and the capacity of species to utilize these gradients under climate change. PMID:24852009

The rising greenhouse effect: experiments and observations in and around the Alps

NASA Astrophysics Data System (ADS)

Philipona, R.

2010-09-01

The rapid temperature increase of more than 1°C in central Europe over the last three decades is larger than expected from anthropogenic greenhouse warming. Surface radiation flux measurements in and around the Alps in fact confirm that not only thermal longwave radiation but also solar shortwave radiation increased since the 1980s. Surface energy budget analyses reveal the rising surface temperature to be well correlated with the radiative forcing, and also show an increase of the kinetic energy fluxes explaining the rise of atmospheric water vapor. Solar radiation mainly increased due to a strong decline of anthropogenic aerosols since mid of the 1980s. While anthropogenic aerosols were mainly accumulated in the boundary layer, this reduction let solar radiation to recover (solar brightening after several decades of solar dimming) mainly at low altitudes around the Alps. At high elevations in the Alps, solar forcing is much smaller and the respective temperature rise is also found to be smaller than in the lowlands. The fact that temperature increases less in the Alps than at low elevations is unexpected in the concept of greenhouse warming, but the radiation budget analyses clearly shows that in the plains solar forcing due to declining aerosols additionally increased surface temperature, whereas in the Alps temperature increased primarily due to greenhouse warming that is particularly manifested by a strong water vapor feedback.

Air and ground temperatures along elevation and continentality gradients in Southern Norway

NASA Astrophysics Data System (ADS)

Farbrot, Herman; Hipp, Tobias; Etzelmüller, Bernd; Humlum, Ole; Isaksen, Ketil; Strand Ødegârd, Rune

2010-05-01

The modern southern boundary for Scandinavian permafrost is located in the mountains of Southern Norway. Permafrost and seasonal frost are considered key components of the cryosphere, and the climate-permafrost relation has acquired added importance with the increasing awareness and concern of rising air temperatures. The three-year research project CRYOLINK ("Permafrost and seasonal frost in southern Norway") aims at improving knowledge on past and present ground temperatures, seasonal frost, and distribution of mountain permafrost in Southern Norway by addressing the fundamental problem of heat transfer between the atmosphere and the ground surface. Hence, several shallow boreholes have been drilled, and a monitoring program to measure air and ground temperatures was started August 2008. The borehole areas (Juvvass, Jetta and Tron) are situated along a west-east transect and, hence, a continentality gradient, and each area provides boreholes at different elevations. Here we present the first year of air and ground temperatures from these sites and discuss the influence of air temperature and ground surface charcteristics (snow conditions, sediments/bedrock, vegetation) on ground temperatures.

A 400-year ice core melt layer record of summertime warming in the Alaska Range

NASA Astrophysics Data System (ADS)

Winski, D.; Osterberg, E. C.; Kreutz, K. J.; Wake, C. P.; Ferris, D. G.; Campbell, S. W.; Baum, M.; Raudzens Bailey, A.; Birkel, S. D.; Introne, D.; Handley, M.

2017-12-01

Warming in high-elevation regions has socially relevant impacts on glacier mass balance, water resources, and sensitive alpine ecosystems, yet very few high-elevation temperature records exist from the middle or high latitudes. While many terrestrial paleoclimate records provide critical temperature records from low elevations over recent centuries, melt layers preserved in alpine glaciers present an opportunity to develop calibrated, annually-resolved temperature records from high elevations. We present a 400-year temperature record based on the melt-layer stratigraphy in two ice cores collected from Mt. Hunter in the Central Alaska Range. The ice core record shows a 60-fold increase in melt frequency and water equivalent melt thickness between the pre-industrial period (before 1850) and present day. We calibrate the melt record to summer temperatures based on local and regional weather station analyses, and find that the increase in melt production represents a summer warming of at least 2° C, exceeding rates of temperature increase at most low elevation sites in Alaska. The Mt. Hunter melt layer record is significantly (p<0.05) correlated with surface temperatures in the central tropical Pacific through a Rossby-wave like pattern that induces high temperatures over Alaska. Our results show that rapid alpine warming has taken place in the Alaska Range for at least a century, and that conditions in the tropical oceans contribute to this warming.

Glacier albedo change and its relationship to surface temperature change from MODIS data: Queen Elizabeth Islands, Arctic Canada, 2001-2015

NASA Astrophysics Data System (ADS)

Mortimer, C.; Sharp, M. J.

2016-12-01

Glacier and ice cap surface albedo change over the Canadian High Arctic is assessed using measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors for the period 2001-2015. Mean summer black-sky broadband surface albedo (MCD43A3 v05) over all glaciated surfaces in the Queen Elizabeth Islands south of 80°N decreased at a rate of 0.0038 ± 0.0037 yr-1 over that period. The bulk of this albedo decrease occurred from 2008 to 2012 when mean summer albedo was anomalously low. Albedo declines were greatest in the west of the QEI and at lower elevations on the ice caps. The period 2005-2012 included some of the warmest summers in the region since at least the 1950s. Between 2001 and 2015, mean summer glacier surface temperatures for the QEI (south of 80°N), derived from MODIS data (MOD11A2 v05), increased at a rate of 0.034 ± 0.037 °C yr-1. Net shortwave energy is modulated by changes in the surface albedo and is the largest source of summer melt energy in the QEI. During 2001-2015, the summer albedo record was negatively correlated with the mean summer glacier surface temperature record across 91% of the region; clusters of positive correlations between surface temperature and albedo were observed at high elevations in eastern Ellesmere Island.

West Flank Coso, CA FORGE 3D temperature model

DOE Data Explorer

Doug Blankenship

2016-03-01

x,y,z data of the 3D temperature model for the West Flank Coso FORGE site. Model grid spacing is 250m. The temperature model for the Coso geothermal field used over 100 geothermal production sized wells and intermediate-depth temperature holes. At the near surface of this model, two boundary temperatures were assumed: (1) areas with surface manifestations, including fumaroles along the northeast striking normal faults and northwest striking dextral faults with the hydrothermal field, a temperature of ~104˚C was applied to datum at +1066 meters above sea level elevation, and (2) a near-surface temperature at about 10 meters depth, of 20˚C was applied below the diurnal and annual conductive temperature perturbations. These assumptions were based on heat flow studies conducted at the CVF and for the Mojave Desert. On the edges of the hydrothermal system, a 73˚C/km (4˚F/100’) temperature gradient contour was established using conductive gradient data from shallow and intermediate-depth temperature holes. This contour was continued to all elevation datums between the 20˚C surface and -1520 meters below mean sea level. Because the West Flank is outside of the geothermal field footprint, during Phase 1, the three wells inside the FORGE site were incorporated into the preexisting temperature model. To ensure a complete model was built based on all the available data sets, measured bottom-hole temperature gradients in certain wells were downward extrapolated to the next deepest elevation datum (or a maximum of about 25% of the well depth where conductive gradients are evident in the lower portions of the wells). After assuring that the margins of the geothermal field were going to be adequately modelled, the data was contoured using the Kriging method algorithm. Although the extrapolated temperatures and boundary conditions are not rigorous, the calculated temperatures are anticipated to be within ~6˚C (20˚F), or one contour interval, of the observed data within the Coso geothermal field. Based on a lack of temperature data west of 74-2TCH, the edges of this model still seem to have an effect on West Flank modeled temperatures.

Optical and electronic properties of sub-surface conducting layers in diamond created by MeV B-implantation at elevated temperatures

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

Willems van Beveren, L. H., E-mail: laurensw@unimelb.edu.au; Bowers, H.; Ganesan, K.

2016-06-14

Boron implantation with in-situ dynamic annealing is used to produce highly conductive sub-surface layers in type IIa (100) diamond plates for the search of a superconducting phase transition. Here, we demonstrate that high-fluence MeV ion-implantation, at elevated temperatures avoids graphitization and can be used to achieve doping densities of 6 at. %. In order to quantify the diamond crystal damage associated with implantation Raman spectroscopy was performed, demonstrating high temperature annealing recovers the lattice. Additionally, low-temperature electronic transport measurements show evidence of charge carrier densities close to the metal-insulator-transition. After electronic characterization, secondary ion mass spectrometry was performed to mapmore » out the ion profile of the implanted plates. The analysis shows close agreement with the simulated ion-profile assuming scaling factors that take into account an average change in diamond density due to device fabrication. Finally, the data show that boron diffusion is negligible during the high temperature annealing process.« less

Analysis of The Surface Radiative Budget Using ATLAS Data for San Juan, Puerto Rico

NASA Technical Reports Server (NTRS)

Luvall, Jeffrey C.; Rickman, D. L.; Gonzalez, J.; Comarazamy, Daniel; Picon, Ana

2007-01-01

The additional beating of the air over the city is the result of the replacement of naturally vegetated surfaces with those composed of asphalt, concrete, rooftops and other man-made materials. The temperatures of these artificial surfaces can be 20 to 40 C higher than vegetated surfaces. This produces a dome of elevated air temperatures 5 to 8 C greater over the city, compared to the air temperatures over adjacent rural areas. Urban landscapes are a complex mixture of vegetated and nonvegetated surfaces. It is difficult to take enough temperature measurements over a large city area to characterize the complexity of urban radiant surface temperature variability. The NASA Airborne Thermal and Land Applications Sensor (ATLAS) operates in the visual and IR bands was used in February 2004 to collect data from San Juan, Puerto Rico with the main objective of investigating the Urban Heat Island (UHI) in tropical cities.

Reduced deuterium retention in simultaneously damaged and annealed tungsten

DOE PAGES

Simmonds, M. J.; Wang, Y. Q.; Barton, J. L.; ...

2017-06-24

Deuterium (D) retention in polycrystalline tungsten (W) with copper (Cu) ion damage concurrently produced at elevated surface temperature is investigated in this paper. An in situ heated stage held W samples at a controlled temperature up to 1243 K, which were subjected to displacement damage produced by 3.4 MeV Cu ions. D retention is subsequently explored by exposure of the W samples held at 383 K to a D 2 plasma ion fluence of 10 24 D +/m 2. Nuclear reaction analysis (NRA), utilizing the D( 3He,p) 4He nuclear reaction, is used to probe the D concentration in the nearmore » surface up to 6 μm. Thermal desorption spectroscopy (TDS) is used to measure outgassed HD and D 2 molecules to determine the bulk D concentration. Both NRA and TDS measure a significant reduction in D retention for samples damaged at elevated temperature. TDS quantitatively shows that the lowest energy trap remains largely unaffected while higher energy traps, induced by Cu ions, are annealed and approach intrinsic concentrations as the temperature during ion damage approaches 1243 K. Finally, analysis of TDS data yields an activation energy of (0.10 ± 0.02) eV for recovery of ion-damage induced traps at elevated temperature.« less

Effect of elevated temperature on the tensile strength of Napier/glass-epoxy hybrid reinforced composites

NASA Astrophysics Data System (ADS)

Ridzuan, M. J. M.; Majid, M. S. Abdul; Afendi, M.; Firdaus, A. Z. Ahmad; Azduwin, K.

2017-11-01

The effects of elevated temperature on the tensile strength of Napier/glass-epoxy hybrid reinforced composites and its morphology of fractured surfaces are discussed. Napier/glass-epoxy hybrid reinforced composites were fabricated by using vacuum infusion method by arranging Napier fibres in between sheets of woven glass fibres. Napier and glass fibres were laminated with estimated volume ratios were 24 and 6 vol. %, respectively. The epoxy resin was used as matrix estimated to 70 vol. %. Specimens were tested to failure under tension at a cross-head speed of 1 mm/min using Universal Testing Machine (Instron) with a load cell 100 kN at four different temperatures of RT, 40°C, 60°C and 80°C. The morphology of fractured surface of hybrid composites was investigated by field emission scanning electron microscopy. The result shows reduction in tensile strength at elevated temperatures. The increase in the temperature activates the process of diffusion, and generates critical stresses which cause the damage at first-ply or at the centre of the hybrid plate, as a result lower the tensile strength. The observation of FESEM images indicates that the fracture mode is of evolution of localized damage, from fibre/matrix debonding, matric cracking, delamination and fibre breakage.

Reduced deuterium retention in simultaneously damaged and annealed tungsten

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

Simmonds, M. J.; Wang, Y. Q.; Barton, J. L.

Deuterium (D) retention in polycrystalline tungsten (W) with copper (Cu) ion damage concurrently produced at elevated surface temperature is investigated in this paper. An in situ heated stage held W samples at a controlled temperature up to 1243 K, which were subjected to displacement damage produced by 3.4 MeV Cu ions. D retention is subsequently explored by exposure of the W samples held at 383 K to a D 2 plasma ion fluence of 10 24 D +/m 2. Nuclear reaction analysis (NRA), utilizing the D( 3He,p) 4He nuclear reaction, is used to probe the D concentration in the nearmore » surface up to 6 μm. Thermal desorption spectroscopy (TDS) is used to measure outgassed HD and D 2 molecules to determine the bulk D concentration. Both NRA and TDS measure a significant reduction in D retention for samples damaged at elevated temperature. TDS quantitatively shows that the lowest energy trap remains largely unaffected while higher energy traps, induced by Cu ions, are annealed and approach intrinsic concentrations as the temperature during ion damage approaches 1243 K. Finally, analysis of TDS data yields an activation energy of (0.10 ± 0.02) eV for recovery of ion-damage induced traps at elevated temperature.« less

Air and Ground Surface Temperature Relations in a Mountainous Basin, Wolf Creek, Yukon Territory

NASA Astrophysics Data System (ADS)

Roadhouse, Emily A.

The links between climate and permafrost are well known, but the precise nature of the relationship between air and ground temperatures remains poorly understood, particularly in complex mountain environments. Although previous studies indicate that elevation and potential incoming solar radiation (PISR) are the two leading factors contributing to the existence of permafrost at a given location, additional factors may also contribute significantly to the existence of mountain permafrost, including vegetation cover, snow accumulation and the degree to which individual mountain landscapes are prone to air temperature inversions. Current mountain permafrost models consider only elevation and aspect, and have not been able to deal with inversion effects in a systematic fashion. This thesis explores the relationship between air and ground surface temperatures and the presence of surface-based inversions at 27 sites within the Wolf Creek basin and surrounding area between 2001 and 2006, as a first step in developing an improved permafrost distribution TTOP model. The TTOP model describes the relationship between the mean annual air temperature and the temperature at the top of permafrost in terms of the surface and thermal offsets (Smith and Riseborough, 2002). Key components of this model are n-factors which relate air and ground climate by establishing the ratio between air and surface freezing (winter) and thawing (summer) degree-days, thus summarizing the surface energy balance on a seasonal basis. Here we examine (1) surface offsets and (2) freezing and thawing n-factor variability at a number of sites through altitudinal treeline in the southern Yukon. Thawing n-factors (nt) measured at individual sites remained relatively constant from one year to the next and may be related to land cover. During the winter, the insulating effect of a thick snow cover results in higher surface temperatures, while thin snow cover results in low surface temperatures more closely related to the winter air temperatures. The application of n-factor modeling techniques within the permafrost region, and the verification of these techniques for a range of natural surfaces, is essential to the determination of the thermal and physical response to potential climate warming in permafrost regions. The presence of temperature inversions presents a unique challenge to permafrost probability mapping in mountainous terrain. While elsewhere the existence of permafrost can be linearly related to elevation, the presence of frequent inversions challenges this assumption, affecting permafrost distribution in ways that the current modeling techniques cannot accurately predict. At sites across the Yukon, inversion-prone sites were predominantly situated in U-shaped valleys, although open slopes, mid-slope ridges and plains were also identified. Within the Wolf Creek basin and surrounding area, inversion episodes have a measurable effect on local air temperatures, occurring during the fall and winter seasons along the Mount Sima trail, and year-round in the palsa valley. Within the discontinuous permafrost zone, where average surface temperatures are often close to zero, even a relatively small change in temperature in the context of future climate change could have a widespread impact on permafrost distribution.

Low-latitude high elevation of the leading edge of southern Eurasia throughout the Cenozoic

NASA Astrophysics Data System (ADS)

Ingalls, M.; Rowley, D. B.; Colman, A. S.; Olack, G.; Currie, B.; Li, S.

2016-12-01

The elevation history of the Tibetan Plateau promises insight into the mechanisms and dynamics that develop and sustain high topography over tens of millions of years. We present the first continuous Cenozoic elevation history from two proximal sedimentary basins on the southern Tibetan Plateau, as well as preliminary paleoaltimetry results from the south-central and central Plateau (Sangsang and Lunpola). The oxygen stable isotope and Δ47 clumped isotope compositions of non-marine carbonates allow us to constrain the carbonate formation temperatures and reconstruct the paleo-precipitation record of the Eocene to Pliocene Oiyug Basin and Paleocene to Eocene Penbo Basin. We exploit the systematic decrease of surface temperature and meteoric water δ18O with elevation. Minimally altered and unaltered pedogenic carbonates from the Oiyug Basin yield Δ47, CDES values of 0.625 to 0.755, that correspond with temperatures of 1-30 °C using a (Zaarur et al., 2013) Δ47 thermometer for low temperature carbonates. Similarly, the Penbo Basin yields Δ47, CDES values of 0.700-0.730, corresponding with temperatures of 6-12°C. Our paleoelevation estimates for the well-studied Oiyug basin ( 6100-4200 meters) support previous evidence (Spicer et al., 2003; Currie et al., 2005; Polissar et al., 2009; Currie et al., 2016) that high elevations were attained in southern Tibet by at least 30 Ma. Our paleoelevation estimates for the Penbo Basin (4100±550 meters) extends the altitude record of the southern Plateau to pre-India-Asia collision. Preliminary results from Sangsang, further west along the Indus-Yarlung Suture, and Lunpola, on the central Plateau, allow us to develop a spatially and temporally more complex paleo-altitude map and land surface evolution of the Tibetan Plateau since the onset of continent-continent collision.

Variability of AVHRR-Derived Clear-Sky Surface Temperature over the Greenland Ice Sheet.

NASA Astrophysics Data System (ADS)

Stroeve, Julienne; Steffen, Konrad

1998-01-01

The Advanced Very High Resolution Radiometer is used to derive surface temperatures for one satellite pass under clear skies over the Greenland ice sheet from 1989 through 1993. The results of these temperatures are presented as monthly means, and their spatial and temporal variability are discussed. Accuracy of the dry snow surface temperatures is estimated to be better than 1 K during summer. This error is expected to increase during polar night due to problems in cloud identification. Results indicate the surface temperature of the Greenland ice sheet is strongly dominated by topography, with minimum surface temperatures associated with the high elevation regions. In the summer, maximum surface temperatures occur during July along the western coast and southern tip of the ice sheet. Minimum temperatures are found at the summit during summer and move farther north during polar night. Large interannual variability in surface temperatures occurs during winter associated with katabatic storm events. Summer temperatures show little variation, although 1992 stands out as being colder than the other years. The reason for the lower temperatures during 1992 is believed to be a result of the 1991 eruption of Mount Pinatubo.

Simulation of hydrodynamics, temperature, and dissolved oxygen in Beaver Lake, Arkansas, 1994-1995

USGS Publications Warehouse

Haggard, Brian; Green, W. Reed

2002-01-01

The tailwaters of Beaver Lake and other White River reservoirs support a cold-water trout fishery of significant economic yield in northwestern Arkansas. The Arkansas Game and Fish Commission has requested an increase in existing minimum flows through the Beaver Lake dam to increase the amount of fishable waters downstream. Information is needed to assess the impact of additional minimum flows on temperature and dissolved-oxygen qualities of reservoir water above the dam and the release water. A two-dimensional, laterally averaged hydrodynamic, thermal and dissolved-oxygen model was developed and calibrated for Beaver Lake, Arkansas. The model simulates surface-water elevation, currents, heat transport and dissolved-oxygen dynamics. The model was developed to assess the impacts of proposed increases in minimum flows from 1.76 cubic meters per second (the existing minimum flow) to 3.85 cubic meters per second (the additional minimum flow). Simulations included assessing (1) the impact of additional minimum flows on tailwater temperature and dissolved-oxygen quality and (2) increasing initial water-surface elevation 0.5 meter and assessing the impact of additional minimum flow on tailwater temperatures and dissolved-oxygen concentrations. The additional minimum flow simulation (without increasing initial pool elevation) appeared to increase the water temperature (<0.9 degrees Celsius) and decrease dissolved oxygen concentration (<2.2 milligrams per liter) in the outflow discharge. Conversely, the additional minimum flow plus initial increase in pool elevation (0.5 meter) simulation appeared to decrease outflow water temperature (0.5 degrees Celsius) and increase dissolved oxygen concentration (<1.2 milligrams per liter) through time. However, results from both minimum flow scenarios for both water temperature and dissolved oxygen concentration were within the boundaries or similar to the error between measured and simulated water column profile values.

Protection of 310l Stainless Steel from Wear at Elevated Temperatures using Conicraly Thermal Spray Coatings with and without Sic Addition

NASA Astrophysics Data System (ADS)

Zhang, Yan; Zhang, Tao; Li, Kaiyang; Li, Dongyang

2017-10-01

Due to its high oxidation resistance, 310L stainless steel is often used for thermal facilities working at high-temperatures. However, the steel may fail prematurely at elevated temperatures when encounter surface mechanical attacks such as wear. Thermal spray coatings have been demonstrated to be effective in protecting the steel from wear at elevated temperatures. In this study, we investigated the effectiveness of high velocity oxy-fuel(HVOF) spraying CoNiCrAlY/SiC coatings in resisting wear of 310L stainless steel at elevated temperature using a pin-on-disc wear tester. In order to further improve the performance of the coating, 5%SiC was added to the coating. It was demonstrated that the CoNiCrAlY/SiC coating after heat treatment markedly suppressed wear. However, the added SiC particles did not show benefits to the wear resistance of the coating. Microstructures of CoNiCrAlY coatings with and without the SiC addition were characterized in order to understand the mechanism responsible for the observed phenomena.

Accelerated warming at high elevations: a review of the current evidence and proposals for future research (Invited)

NASA Astrophysics Data System (ADS)

Pepin, N. C.

2013-12-01

Arctic amplification, whereby enhanced warming is evident at high latitudes, is well accepted amongst the scientific community. Increased warming at high elevations is more controversial and is often given the more vague term 'elevational dependency'. The way in which different approaches (mountain surface data, radiosondes, satellite data and models) often yield different results is discussed, along with the differences between these approaches. Analyses of surface data differ in the stations chosen for comparison, the time period, elevational range, and methods of trend identification. An analysis of global datasets using over a thousand stations (GHCN, CRU) and defining change by the most common method of calculating the linear gradient of a best fit line (linear regression) shows no simple relationship between warming rate and elevation. There are however feedback mechanisms in the mountain environment (e.g. cryospheric change, water vapor and treelines) which, although they may enhance warming at certain elevations, are fairly poorly understood. Warming rates are also shown to be influenced by factors in the mountain environment other than elevation, including topography (aspect, slope, topographic exposure) as well as mean annual temperature, but the relative influences of such controls have yet to be disentangled from those that show a more simple elevationally-dependent signal. Mountain summits and exposed ridge sites are shown to show least variability in warming rates, rising up above a sea of noise. Radiosondes and satellite data are further removed from changes on the ground (surface temperatures) and studies using such data tend to be rather divorced from the mountain environment and need calibration/comparison with surface datasets. Reanalyses such as NCEP/NCAR and ERA, although having good spatial coverage, tend to suffer from the same problems. Following a discussion of differences between all these approaches, a plan to develop an integrated global approach to this issue will be discussed.

Shear wave EMAT thickness measurements of low carbon steel at 450 °C without cooling

NASA Astrophysics Data System (ADS)

Lunn, Natasha; Potter, Mark; Dixon, Steve

2017-02-01

Performing high temperature online inspection without plant shutdown is highly desirable, yet, development of portable or permanently installed high temperature ultrasonic sensors, without the need for sample surface preparation, remains a key challenge. Low carbon steel pipelines operating at elevated temperatures often develop a magnetostrictive oxide coating (magnetite), which improves electromagnetic acoustic transducer (EMAT) efficiency below the Curie temperature of magnetite (575 °C), via a magnetostrictive mechanism. Coupling the inherent non-contacting nature of EMATs with the enhanced efficiency from a magnetite coating, we are able to continuously operate an uncoded EMAT at elevated temperatures without permanent installation or surface preparation. In this work, a high temperature shear wave EMAT utilizing a high field, high Curie point, permanent magnet has been developed to generate ultrasonic bulk thickness measurements on magnetite coated steel at temperatures of up to 450 °C, without cooling. Relatively high signal-to-noise ratios, in the region of 30 dB for single shot data, have been measured at 450 °C using this technique. The EMAT design and results from high temperature trials, including the performance with change in temperature, sample thickness and EMAT-sample lift-off, are presented here.

Storage Capacity and Water Quality of Lake Ngardok, Babeldaob Island, Republic of Palau, 1996-98

USGS Publications Warehouse

Yeung, Chiu Wang; Wong, Michael F.

1999-01-01

A bathymetric survey conducted during March and April, 1996, determined the total storage capacity Lake Ngardok to be between 90 and 168 acre-feet. Elevation-surface area and elevation-capacity curves summarizing the current relations among elevation, surface area, and storage capacity were created from the bathymetric map. Rainfall and lake-elevation data collected from April 1996 to March 1998 indicated that lake levels correlated to rainfall values with lake elevation rising rapidly in response to heavy rainfall and then returning to normal levels within a few days. Mean lake elevation for the 22 month period of data was 59.5 feet which gives a mean storage capacity of 107 acre-feet and a mean surface area of 24.1 acre. A floating mat of reeds, which covered 58 percent of the lake surface area at the time of the bathymetric survey, makes true storage capacity difficult to estimate. Water-quality sampling during April 1996 and November 1997 indicated that no U.S. Environmental Protection Agency primary drinking-water standards were violated for analyzed organic and inorganic compounds and radionuclides. With suitable biological treatment, the lake water could be used for drinking-water purposes. Temperature and dissolved oxygen measurements indicated that Lake Ngardok is stratified. Given that air temperature on Palau exhibits little seasonal variation, it is likely that this pattern of stratification is persistent. As a result, complete mixing of the lake is probably rare. Near anaerobic conditions exist at the lake bottom. Low dissolved oxygen (3.2 milligrams per liter) measured at the outflow indicated that water flowing past the outflow was from the deep oxygen-depleted depths of the lake.

Properties of Free-Machining Aluminum Alloys at Elevated Temperatures

NASA Astrophysics Data System (ADS)

Faltus, Jiří; Karlík, Miroslav; Haušild, Petr

In areas close to the cutting tool the workpieces being dry machined could be heated up to 350°C and they may be impact loaded. Therefore it is of interest to study mechanical properties of corresponding materials at elevated temperatures. Free-machining alloys of Al-Cu and Al-Mg-Si systems containing Pb, Bi and Sn additions (AA2011, AA2111B, AA6262, and AA6023) were subjected to Charpy U notch impact test at the temperatures ranging from 20 to 350°C. The tested alloys show a sharp drop in notch impact strength KU at different temperatures. This drop of KU is caused by liquid metal embrittlement due to the melting of low-melting point dispersed phases which is documented by differential scanning calorimetry. Fracture surfaces of the specimens were observed using a scanning electron microscope. At room temperature, the fractures of all studied alloys exhibited similar ductile dimple fracture micromorphology, at elevated temperatures, numerous secondary intergranular cracks were observed.

Rhenium/Oxygen Interactions at Elevated Temperatures

NASA Technical Reports Server (NTRS)

Jacobson, Nathan; Myers, Dwight; Zhu, Dong-Ming; Humphrey, Donald

2000-01-01

The oxidation of pure rhenium is examined from 600-1400 C in oxygen/argon mixtures. Linear weight loss kinetics are observed. Gas pressures, flow rates, and temperatures are methodically varied to determine the rate controlling steps. The reaction at 600 and 800 C appears to be controlled by a chemical reaction step at the surface; whereas the higher temperature reactions appear to be controlled by gas phase diffusion of oxygen to the rhenium surface. Attack of the rhenium appears to be along grain boundaries and crystallographic planes.

Interactive effects of climate change and eutrophication on the dinoflagellate-bearing benthic foraminifer Marginopora vertebralis

NASA Astrophysics Data System (ADS)

Uthicke, S.; Vogel, N.; Doyle, J.; Schmidt, C.; Humphrey, C.

2012-06-01

Elevated sea surface temperatures caused by global climate change and increased nutrient concentrations resulting from land runoff both are stressors for calcifying coral reef organisms. Here, we test the hypothesis that increased temperature leads to bleaching in dinoflagellate-bearing foraminifera similar to corals and that increased nutrients through runoff can exaggerate stress on the holobiont. In an experiment manipulating temperatures alone, we have shown that mortality of Marginopora vertebralis increased with temperatures. Most individuals died after 7 days at 34°C, ~5°C above current summer maxima. Survival at 37 days was >98% at 28°C. After 7 days of exposure to 31 or 32°C, photosynthesis of the endosymbionts was compromised, as indicated by several photophysiological parameters (effective quantum yield and apparent photosynthetic rate). In a flow-though experiment manipulating both temperature (three levels, 26, 29 and 31°C) and nitrate concentrations (3 levels, ~0.5, 1.0 and 1.4 μmol l-1 NO3 -), elevated temperature had a significant negative effect on most parameters measured. At 31°C, most photopigments (measured by UPLC) in the foraminifera were significantly reduced. The only pigment that increased was the photoprotective diatoxanthin. Several other parameters measured (maximum and effective quantum yield, O2 production in light, organic carbon contents) also significantly decreased with temperature. Optode-based respirometry demonstrated that the presence of symbionts at elevated temperatures represents a net carbon loss for the host. Growth rates of M. vertebralis and mortality at the end of the experiment were significantly affected by both temperature increase and nitrate addition. We conclude that these foraminifera bleach in a similar fashion to corals and that global sea surface temperature change and nitrate increases are stressors for these protists. Furthermore, this provides support for the hypothesis that management of local stressors elevates resilience of coral reefs to global stressors.

Forcing Mechanisms for the Variations of Near-surface Temperature Lapse Rates along the Himalayas, Tibetan Plateau (HTP) and Their Surroundings

NASA Astrophysics Data System (ADS)

Kattel, D. B.; Yao, T.; Ullah, K.; Islam, G. M. T.

2016-12-01

This study investigates the monthly characteristics of near-surface temperature lapse rates (TLRs) (i.e., governed by surface energy balance) based on the 176 stations 30-year (1980 to 2010) dataset covering a wide range of topography, climatic regime and relief (4801 m) in the HTP and its surroundings. Empirical analysis based on techniques in thermodynamics and hydrostatic system were used to obtain the results. Steepest TLRs in summer is due to strong dry convection and shallowest in winter is due to inversion effect is the general pattern of TLR that reported in previous studies in other mountainous region. Result of this study reports a contrast variation of TLRs from general patterns, and suggest distinct forcing mechanisms in an annual cycle. Shallower lapse rate occurs in summer throughout the regions is due to strong heat exchange process within the boundary layer, corresponding to the warm and moist atmospheric conditions. There is a systematic differences of TLRs in winter between the northern and southern slopes the Himalayas. Steeper TLRs in winter on the northern slopes is due to intense cooling at higher elevations, corresponding to the continental dry and cold air surges, and considerable snow-temperature feedback. The differences in elevation and topography, as well as the distinct variation of turbulent heating and cooling, explain the contrast TLRs (shallower) values in winter on the southern slopes. Distinct diurnal variations of TLRs and its magnitudes between alpine, dry, humid and coastal regions is due to the variations of adiabatic mixing during the daytime in the boundary layer i.e., associated with the variations in net radiations, elevation, surface roughness and sea surface temperature. The findings of this study is useful to determine the temperature range for accurately modelling in various field such as hydrology, glaciology, ecology, forestry, agriculture, as well as inevitable for climate downscaling in complex mountainous terrain.

Modeled Seasonal Variations of Firn Density Induced by Steady State Surface Air Temperature Cycle

NASA Technical Reports Server (NTRS)

Jun, Li; Zwally, H. Jay; Koblinsky, Chester J. (Technical Monitor)

2001-01-01

Seasonal variations of firn density in ice-sheet firn layers have been attributed to variations in deposition processes or other processes within the upper firn. A recent high-resolution (mm scale) density profile, measured along a 181 m core from Antarctica, showed small-scale density variations with a clear seasonal cycle that apparently was not-related to seasonal variations in deposition or known near-surface processes (Gerland and others 1999). A recent model of surface elevation changes (Zwally and Li, submitted) produced a seasonal variation in firn densification, and explained the seasonal surface elevation changes observed by satellite radar altimeters. In this study, we apply our 1-D time-dependent numerical model of firn densification that includes a temperature-dependent formulation of firn densification based on laboratory measurements of grain growth. The model is driven by a steady-state seasonal surface temperature and a constant accumulation rate appropriate for the measured Antarctic ice core. The modeled seasonal variations in firn density show that the layers of snow deposited during spring to mid-summer with the highest temperature history compress to the highest density, and the layers deposited during later summer to autumn with the lowest temperature history compress to the lowest density. The initial amplitude of the seasonal difference of about 0.13 reduces to about 0.09 in five years and asymptotically to 0.92 at depth, which is consistent with the core measurements.

Sensitivity of potential evapotranspiration and simulated flow to varying meteorological inputs, Salt Creek watershed, DuPage County, Illinois

USGS Publications Warehouse

Whitbeck, David E.

2006-01-01

The Lamoreux Potential Evapotranspiration (LXPET) Program computes potential evapotranspiration (PET) using inputs from four different meteorological sources: temperature, dewpoint, wind speed, and solar radiation. PET and the same four meteorological inputs are used with precipitation data in the Hydrological Simulation Program-Fortran (HSPF) to simulate streamflow in the Salt Creek watershed, DuPage County, Illinois. Streamflows from HSPF are routed with the Full Equations (FEQ) model to determine water-surface elevations. Consequently, variations in meteorological inputs have potential to propagate through many calculations. Sensitivity of PET to variation was simulated by increasing the meteorological input values by 20, 40, and 60 percent and evaluating the change in the calculated PET. Increases in temperatures produced the greatest percent changes, followed by increases in solar radiation, dewpoint, and then wind speed. Additional sensitivity of PET was considered for shifts in input temperatures and dewpoints by absolute differences of ?10, ?20, and ?30 degrees Fahrenheit (degF). Again, changes in input temperatures produced the greatest differences in PET. Sensitivity of streamflow simulated by HSPF was evaluated for 20-percent increases in meteorological inputs. These simulations showed that increases in temperature produced the greatest change in flow. Finally, peak water-surface elevations for nine storm events were compared among unmodified meteorological inputs and inputs with values predicted 6, 24, and 48 hours preceding the simulated peak. Results of this study can be applied to determine how errors specific to a hydrologic system will affect computations of system streamflow and water-surface elevations.

Atmospheric Models For Over-Ocean Propagation Loss

DTIC Science & Technology

2015-08-24

Radiosonde balloons are launched daily at selected loca- tions, and measure temperature, dew point temperature, and air pressure as they ascend. Radiosondes...different times of year and locations. The result was used to estimate high-reliability SHF/EHF air -to-surface radio link performance in a maritime...environment. I. INTRODUCTION Air -to-surface radio links differ from typical satellite com- munications links in that the path elevation angles are lower

A 400-Year Ice Core Melt Layer Record of Summertime Warming in the Alaska Range

NASA Astrophysics Data System (ADS)

Winski, Dominic; Osterberg, Erich; Kreutz, Karl; Wake, Cameron; Ferris, David; Campbell, Seth; Baum, Mark; Bailey, Adriana; Birkel, Sean; Introne, Douglas; Handley, Mike

2018-04-01

Warming in high-elevation regions has societally important impacts on glacier mass balance, water resources, and sensitive alpine ecosystems, yet very few high-elevation temperature records exist from the middle or high latitudes. While a variety of paleoproxy records provide critical temperature records from low elevations over recent centuries, melt layers preserved in alpine glaciers present an opportunity to develop calibrated, annually resolved temperature records from high elevations. Here we present a 400-year temperature proxy record based on the melt layer stratigraphy of two ice cores collected from Mt. Hunter in Denali National Park in the central Alaska Range. The ice core record shows a sixtyfold increase in water equivalent total annual melt between the preindustrial period (before 1850 Common Era) and present day. We calibrate the melt record to summer temperatures based on weather station data from the ice core drill site and find that the increase in melt production represents a summer warming rate of at least 1.92 ± 0.31°C per century during the last 100 years, exceeding rates of temperature increase at most low-elevation sites in Alaska. The Mt. Hunter melt layer record is significantly (p < 0.05) correlated with surface temperatures in the central tropical Pacific through a Rossby wave-like pattern that enhances high temperatures over Alaska. Our results show that rapid alpine warming has taken place in the Alaska Range for at least a century and that conditions in the tropical oceans contribute to this warming.

Comparison of Surface Mountain Climate With Equivalent Free Air Parameters Extracted From NCEP/NCAR Reanalysis: Kilimanjaro, Tanzania.

NASA Astrophysics Data System (ADS)

Pepin, N. C.; Hardy, D.; Duane, W.; Losleben, M.

2007-12-01

It is difficult to predict future climate changes in areas of complex relief, since mountains generate their own climates distinct from the free atmosphere. Thus trends in climate at the mountain surface are different from those in the free air. We compare surface climate (temperature and vapour pressure) measured at seven elevations on the south-western slope of Kilimanjaro, the tallest free standing mountain in Africa, with equivalent observations in the free atmosphere from NCEP/NCAR reanalysis data for September 2004 to January 2006. Correlations between daily surface and free air temperature anomalies are greatest at low elevations below 2500 metres, meaning that synoptic (inter-diurnal) variability is the major control here. However, temperatures and moisture on the higher slopes above the treeline (3000 m) are decoupled from the free atmosphere, showing intense heating/cooling by day/night and import of moisture from lower elevations during the day. The lower forested slopes thus act as a moisture source, with large vapour pressure excesses reported in comparison with the free atmosphere (>5 hPa) which move upslope during daylight and subside downslope at night. Strong seasonal contrasts are shown in the vigour of the montane thermal circulation, but interactions with free air circulation (as represented by flow indices developed from reanalysis wind components) are complex. Upper air flow strength and direction (at 500 mb) have limited influence on surface heating and upslope moisture advection, which are dominated by the diurnal cycle rather than inter-diurnal synoptic controls. Thus local changes in surface characteristics (e.g. deforestation) could have a direct influence on the mountain climate of Kilimanjaro, making the upper slopes somewhat divorced from larger scale advective changes associated with global warming.

Effect of molecular desorption on the electronic properties of self-assembled polarizable molecular monolayers.

PubMed

Wang, Gunuk; Jeong, Hyunhak; Ku, Jamin; Na, Seok-In; Kang, Hungu; Ito, Eisuke; Jang, Yun Hee; Noh, Jaegeun; Lee, Takhee

2014-04-01

We investigated the interfacial electronic properties of self-assembled monolayers (SAM)-modified Au metal surface at elevated temperatures. We observed that the work functions of the Au metal surfaces modified with SAMs changed differently under elevated-temperature conditions based on the type of SAMs categorized by three different features based on chemical anchoring group, molecular backbone structure, and the direction of the dipole moment. The temperature-dependent work function of the SAM-modified Au metal could be explained in terms of the molecular binding energy and the thermal stability of the SAMs, which were investigated with thermal desorption spectroscopic measurements and were explained with molecular modeling. Our study will aid in understanding the electronic properties at the interface between SAMs and metals in organic electronic devices if an annealing treatment is applied. Copyright © 2013 Elsevier Inc. All rights reserved.

Effects of service environments on aluminum-brazed titanium (ABTi)

NASA Technical Reports Server (NTRS)

Cotton, W. L.

1978-01-01

Aluminum brazed titanium (ABTi) structures were evaluated during prolonged exposure to extreme environments: elevated temperature exposure to airline service fluids, hydraulic fluid, and seawater, followed by laboratory corrosion tests. Solid-face and perforated face honeycomb sandwich panel specimens, stressed panel assemblies, and faying surface brazed joints were tested. The corrosion resistance of ABTi is satisfactory for commercial airline service. Unprotected ABTi proved inherently resistant to attack by all of the extreme service aircraft environments except: seawater at 700 K (800 F) and above, dripping phosphate ester hydraulic fluid at 505 K (450 F), and a marine environment at ambient temperature. The natural oxides and deposits present on titanium surfaces in airline service provide protection against hot salt corrosion pitting. Coatings are required to protect titanium dripping phosphate ester fluid at elevated temperatures and to protect exposed acoustic honeycomb parts against corrosion in a marine environment.

Developmental Effects of Ocean Acidification Conditions and Elevated Temperature on Homarus Americanus Larvae

NASA Astrophysics Data System (ADS)

Mcveigh, H.; Waller, J. D.

2016-02-01

The Gulf of Maine is experiencing a rapid warming in sea surface temperature and a marked decrease in pH. This study aimed to quantify the impact of elevated temperature and acidification on the larval development of the iconic American lobster (Homarus americanus). Experimental conditions were reflective of current and IPCC predicted levels of temperature and pCO2 to be reached by the end of the century. Larvae were measured for growth (carapace length), development time, and survivorship over the larval duration. Treatments of elevated temperatures experienced decreased development time across the larval stages of H. americanus. Consequently mortality increased at a significantly higher rate under elevated temperature. An increase in larval mortality may decrease recruitment to the commercial fishery, thus impacting the most valuable single species in the state of Maine. Furthermore, experimental pCO2 treatments yielded a significantly decreased development time between larval stages II and III, yet did not have a significant impact on carapace length or mortality. This study indicates that warmer temperatures may have a greater influence than decreased pH on larval development and survival. Determining how this species may respond to changing climactic conditions will better inform the sustainability efforts of such a critical marine fishery.

A Wetness Index Using Terrain-Corrected Surface Temperature and Normalized Difference Vegetation Index Derived from Standard MODIS Products: An Evaluation of Its Use in a Humid Forest-Dominated Region of Eastern Canada

PubMed Central

Hassan, Quazi K.; Bourque, Charles P.-A.; Meng, Fan-Rui; Cox, Roger M.

2007-01-01

In this paper we develop a method to estimate land-surface water content in a mostly forest-dominated (humid) and topographically-varied region of eastern Canada. The approach is centered on a temperature-vegetation wetness index (TVWI) that uses standard 8-day MODIS-based image composites of land surface temperature (TS) and surface reflectance as primary input. In an attempt to improve estimates of TVWI in high elevation areas, terrain-induced variations in TS are removed by applying grid, digital elevation model-based calculations of vertical atmospheric pressure to calculations of surface potential temperature (θS). Here, θS corrects TS to the temperature value to what it would be at mean sea level (i.e., ∼101.3 kPa) in a neutral atmosphere. The vegetation component of the TVWI uses 8-day composites of surface reflectance in the calculation of normalized difference vegetation index (NDVI) values. TVWI and corresponding wet and dry edges are based on an interpretation of scatterplots generated by plotting θS as a function of NDVI. A comparison of spatially-averaged field measurements of volumetric soil water content (VSWC) and TVWI for the 2003-2005 period revealed that variation with time to both was similar in magnitudes. Growing season, point mean measurements of VSWC and TVWI were 31.0% and 28.8% for 2003, 28.6% and 29.4% for 2004, and 40.0% and 38.4% for 2005, respectively. An evaluation of the long-term spatial distribution of land-surface wetness generated with the new θS-NDVI function and a process-based model of soil water content showed a strong relationship (i.e., r2 = 95.7%). PMID:28903212

A Paleoclimate Modeling Perspective on the Challenges to Quantifying Paleoelevation

NASA Astrophysics Data System (ADS)

Poulsen, C. J.; Aron, P.; Feng, R.; Fiorella, R.; Shen, H.; Skinner, C. B.

2016-12-01

Surface elevation is a fundamental characteristic of the land surface. Gradients in elevation associated with mountain ranges are a first order control on local and regional climate; weathering, erosion and nutrient transport; and the evolution and biodiversity of organisms. In addition, surface elevations are a proxy for the geodynamic processes that created them. Efforts to quantify paleoelevation have relied on reconstructions of mineralogical and fossil proxies that preserve environmental signals such as surface temperature, moist enthalpy, or surface water isotopic composition that have been observed to systematically vary with elevation. The challenge to estimating paleoelevation from proxies arises because the modern-day elevation dependence of these environmental parameters is not constant and has differed in the past in response to changes in both surface elevation and other climatic forcings, including greenhouse gas and orbital variations. For example, downward mixing of vapor that is isotopically enriched through troposphere warming under greenhouse forcing reduces the isotopic lapse rate. Without considering these factors, paleoelevation estimates for orogenic systems can be in error by hundreds of meters or more. Isotope-enabled climate models provide a tool for separating the climate response to these forcings into elevation and non-elevation components and for identifying the processes that alter the elevation dependence of environmental parameters. Our past and ongoing work has focused on the simulated climate response to surface uplift of the South American Andes, the North American Cordillera, and the Tibetan-Himalyan system during the Cenozoic, and its implication for interpreting proxy records from these regions. This work demonstrates that the climate response to uplift, and the implications for interpreting proxy records, varies tremendously by region. In this presentation, we synthesize climate responses to uplift across orogens, present new results examining the affect of orbital variations on elevation-dependent environmental parameters, and discuss the implications of our work for quantifying paleoelevations.

Temperature-dependent rate models of vascular cambium cell mortality

Treesearch

Matthew B. Dickinson; Edward A. Johnson

2004-01-01

We use two rate-process models to describe cell mortality at elevated temperatures as a means of understanding vascular cambium cell death during surface fires. In the models, cell death is caused by irreversible damage to cellular molecules that occurs at rates that increase exponentially with temperature. The models differ in whether cells show cumulative effects of...

Iron-based alloy and nitridation treatment for PEM fuel cell bipolar plates

DOEpatents

Brady, Michael P [Oak Ridge, TN; Yang, Bing [Oak Ridge, TN; Maziasz, Philip J [Oak Ridge, TN

2010-11-09

A corrosion resistant electrically conductive component that can be used as a bipolar plate in a PEM fuel cell application is composed of an alloy substrate which has 10-30 wt. % Cr, 0.5 to 7 wt. % V, and base metal being Fe, and a continuous surface layer of chromium nitride and vanadium nitride essentially free of base metal. A oxide layer of chromium vanadium oxide can be disposed between the alloy substrate and the continuous surface nitride layer. A method to prepare the corrosion resistant electrically conductive component involves a two-step nitridization sequence by exposing the alloy to a oxygen containing gas at an elevated temperature, and subsequently exposing the alloy to an oxygen free nitrogen containing gas at an elevated temperature to yield a component where a continuous chromium nitride layer free of iron has formed at the surface.

Interpretation of Ground Temperature Anomalies in Hydrothermal Discharge Areas

NASA Astrophysics Data System (ADS)

Price, A. N.; Lindsey, C.; Fairley, J. P., Jr.

2017-12-01

Researchers have long noted the potential for shallow hydrothermal fluids to perturb near-surface temperatures. Several investigators have made qualitative or semi-quantitative use of elevated surface temperatures; for example, in snowfall calorimetry, or for tracing subsurface flow paths. However, little effort has been expended to develop a quantitative framework connecting surface temperature observations with conditions in the subsurface. Here, we examine an area of shallow subsurface flow at Burgdorf Hot Springs, in the Payette National Forest, north of McCall, Idaho USA. We present a simple analytical model that uses easily-measured surface data to infer the temperatures of laterally-migrating shallow hydrothermal fluids. The model is calibrated using shallow ground temperature measurements and overburden thickness estimates from seismic refraction studies. The model predicts conditions in the shallow subsurface, and suggests that the Biot number may place a more important control on the expression of near-surface thermal perturbations than previously thought. In addition, our model may have application in inferring difficult-to-measure parameters, such as shallow subsurface discharge from hydrothermal springs.

Method and apparatus for measuring surface contour on parts with elevated temperatures

DOEpatents

Horvath, Mark S.; Nance, Roy A.; Cohen, George H.; Fodor, George

1991-01-01

The invention is directed to a method and apparatus for measuring the surface contour of a test piece, such as the bow of a radioactive fuel rod, which is completely immersed in water. The invention utilizes ultrasonic technology and is capable of measuring surface contours of test pieces which are at a higher temperature than the surrounding water. The presence of a test piece at a higher temperature adversely affects the distance measurements by causing thermal variations in the water near the surface of the test piece. The contour measurements depend upon a constant temperature of the water in the path of the ultrasonic wave to provide a constant acoustical velocity (the measurement is made by the time of flight measurement for an ultrasonic wave). Therefore, any variations of water temperature near the surface will introduce errors degrading the measurement. The present invention overcomes these problems by assuring that the supply of water through which the ultrasonic waves travel is at a predetermined and constant temperature.

Microstructure and elevated-temperature erosion-oxidation behaviour of aluminized 9Cr-1Mo Steel

NASA Astrophysics Data System (ADS)

Huttunen-Saarivirta, E.; Honkanen, M.; Tsipas, S. A.; Omar, H.; Tsipas, D.

2012-10-01

Degradation of materials by a combination of erosive wear and atmospheric oxidation at elevated temperatures constitutes a problem in some power generation processes, such as fluidized-bed combustion. In this work, 9Cr-1Mo steel, a common tube material in combustion chambers, is coated by a pack cementation method from an Al-containing pack in order to improve the resistance to erosion-oxidation at elevated temperatures. The resulting coating is studied in terms of microstructure and microhardness and tested for its resistance against impacts by sand particles in air at temperatures of 550-700 °C under several conditions, with thickness changes and appearance of the exposed surfaces being studied. The coating was found to contain several phases and layers, the outermost of which was essentially Al-rich and contained e.g., small AlN precipitates. The microhardness values for such coating ranged from 950 to 1100 HV20g. The coating provided the substrate with increased protection particularly against normal particle impacts, as manifested by smaller thickness losses for coated specimens as compared to uncoated counterparts. However, much of the coating was lost under all test conditions, despite the fact that particle debris formed a homogeneous layer on the surface. These results are described and discussed in this paper.

Temperature of ground water at Philadelphia, Pennsylvania, 1979- 1981

USGS Publications Warehouse

Paulachok, Gary N.

1986-01-01

Anthropogenic heat production has undoubtedly caused increased ground-water temperatures in many parts of Philadelphia, Pennsylvania, as shown by temperatures of 98 samples and logs of 40 wells measured during 1979-81. Most sample temperatures were higher than 12.6 degrees Celsius (the local mean annual air temperature), and many logs depict cooling trends with depth (anomalous gradients). Heating of surface and shallow-subsurface materials has likely caused the elevated temperatures and anomalous gradients. Solar radiation on widespread concrete and asphalt surfaces, fossil-fuel combustion, and radiant losses from buried pipelines containing steam and process chemicals are believed to be the chief sources of heat. Some heat from these and other sources is transferred to deeper zones, mainly by conduction. Temperatures in densely urbanized areas are commonly highest directly beneath the land surface and decrease progressively with depth. Temperatures in sparsely urbanized areas generally follow the natural geothermal gradient and increase downward at about that same rate.

Cu self-sputtering MD simulations for 0.1-5 keV ions at elevated temperatures

NASA Astrophysics Data System (ADS)

Metspalu, Tarvo; Jansson, Ville; Zadin, Vahur; Avchaciov, Konstantin; Nordlund, Kai; Aabloo, Alvo; Djurabekova, Flyura

2018-01-01

Self-sputtering of copper under high electric fields is considered to contribute to plasma buildup during a vacuum breakdown event frequently observed near metal surfaces, even in ultra high vacuum condition in different electric devices. In this study, by means of molecular dynamics simulations, we analyze the effect of surface temperature and morphology on the yield of self-sputtering of copper with ion energies of 0.1-5 keV. We analyze all three low-index surfaces of Cu, {1 0 0}, {1 1 0} and {1 1 1}, held at different temperatures, 300 K, 500 K and 1200 K. The surface roughness relief is studied by either varying the angle of incidence on flat surfaces, or by using arbitrary roughened surfaces, which result in a more natural distribution of surface relief variations. Our simulations provide detailed characterization of copper self-sputtering with respect to different material temperatures, crystallographic orientations, surface roughness, energies, and angles of ion incidence.

Planetary quarantine program

NASA Technical Reports Server (NTRS)

1971-01-01

A quantitative means was developed to investigate the sensitivity of current spacecraft sterilization plans to variations in D-values. A quantitative expression was derived to represent the distribution of D-values among a population of naturally occurring organisms. An investigation was made of (1) the inactivation of both Bacillus subtilis var. niger spores and Cape Kennedy soil spores by gamma-radiation at room temperature in a nitrogen environment, and (2) the thermoradiation resistance of Cape Kennedy soil spores at elevated temperatures below 125 C. The relation between standard survival experiments with bacterial spores in soils and results obtained on spacecraft surfaces is discussed. Sporocidal properties of aqueous formaldehyde can be increased by elevating the temperature.

Development of a Hydrodynamic and Transport model of Bellingham Bay in Support of Nearshore Habitat Restoration

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

Wang, Taiping; Yang, Zhaoqing; Khangaonkar, Tarang

2010-04-22

In this study, a hydrodynamic model based on the unstructured-grid finite volume coastal ocean model (FVCOM) was developed for Bellingham Bay, Washington. The model simulates water surface elevation, velocity, temperature, and salinity in a three-dimensional domain that covers the entire Bellingham Bay and adjacent water bodies, including Lummi Bay, Samish Bay, Padilla Bay, and Rosario Strait. The model was developed using Pacific Northwest National Laboratory’s high-resolution Puget Sound and Northwest Straits circulation and transport model. A sub-model grid for Bellingham Bay and adjacent coastal waters was extracted from the Puget Sound model and refined in Bellingham Bay using bathymetric lightmore » detection and ranging (LIDAR) and river channel cross-section data. The model uses tides, river inflows, and meteorological inputs to predict water surface elevations, currents, salinity, and temperature. A tidal open boundary condition was specified using standard National Oceanic and Atmospheric Administration (NOAA) predictions. Temperature and salinity open boundary conditions were specified based on observed data. Meteorological forcing (wind, solar radiation, and net surface heat flux) was obtained from NOAA real observations and National Center for Environmental Prediction North American Regional Analysis outputs. The model was run in parallel with 48 cores using a time step of 2.5 seconds. It took 18 hours of cpu time to complete 26 days of simulation. The model was calibrated with oceanographic field data for the period of 6/1/2009 to 6/26/2009. These data were collected specifically for the purpose of model development and calibration. They include time series of water-surface elevation, currents, temperature, and salinity as well as temperature and salinity profiles during instrument deployment and retrieval. Comparisons between model predictions and field observations show an overall reasonable agreement in both temporal and spatial scales. Comparisons of root mean square error values for surface elevation, velocity, temperature, and salinity time series are 0.11 m, 0.10 m/s, 1.28oC, and 1.91 ppt, respectively. The model was able to reproduce the salinity and temperature stratifications inside Bellingham Bay. Wetting and drying processes in tidal flats in Bellingham Bay, Samish Bay, and Padilla Bay were also successfully simulated. Both model results and observed data indicated that water surface elevations inside Bellingham Bay are highly correlated to tides. Circulation inside the bay is weak and complex and is affected by various forcing mechanisms, including tides, winds, freshwater inflows, and other local forcing factors. The Bellingham Bay model solution was successfully linked to the NOAA oil spill trajectory simulation model “General NOAA Operational Modeling Environment (GNOME).” Overall, the Bellingham Bay model has been calibrated reasonably well and can be used to provide detailed hydrodynamic information in the bay and adjacent water bodies. While there is room for further improvement with more available data, the calibrated hydrodynamic model provides useful hydrodynamic information in Bellingham Bay and can be used to support sediment transport and water quality modeling as well as assist in the design of nearshore restoration scenarios.« less

Warming and increased precipitation frequency on the Colorado Plateau: Implications for biological soil crusts and soil processes

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

Zelikova TJ; Hosman DC; Grote EE

2011-03-21

Frequent hydration and drying of soils in arid systems can accelerate desert carbon and nitrogen mobilization due to respiration, microbial death, and release of intracellular solutes. Because desert microinvertebrates can mediate nutrient cycling, and the autotrophic components of crusts are known to be sensitive to rapid desiccation due to elevated temperatures after wetting events, we studied whether altered soil temperature and frequency of summer precipitation can also affect the composition of food web consumer functional groups. We conducted a two-year field study with experimentally-elevated temperature and frequency of summer precipitation in the Colorado Plateau desert, measuring the change in abundancemore » of nematodes, protozoans, and microarthropods. We hypothesized that microfauna would be more adversely affected by the combination of elevated temperature and frequency of summer precipitation than either effect alone, as found previously for phototrophic crust biota. Microfauna experienced normal seasonal fluctuations in abundance, but the effect of elevated temperature and frequency of summer precipitation was statistically non-significant for most microfaunal groups, except amoebae. The seasonal increase in abundance of amoebae was reduced with combined elevated temperature and increased frequency of summer precipitation compared to either treatment alone, but comparable with control (untreated) plots. Based on our findings, we suggest that desert soil microfauna are relatively more tolerant to increases in ambient temperature and frequency of summer precipitation than the autotrophic components of biological soil crust at the surface.« less

Analysis of Abrasive Blasting of DOP-26 Iridium Alloy

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

Ohriner, Evan Keith; Zhang, Wei; Ulrich, George B

2012-01-01

The effects of abrasive blasting on the surface geometry and microstructure of DOP-26 iridium alloy (Ir-0.3% W-0.006% Th 0.005% Al) have been investigated. Abrasive blasting has been used to control emissivity of components operating at elevated temperature. The effects of abrasive blasting conditions on surface morphology were investigated both experimentally and by numerical modeling. The simplified model, based on finite element analysis of a single angular particle impacting on Ir alloy disk, calculates the surface deformation and residual strain distribution. The experimental results and modeling results both indicate that the surface geometry is not sensitive to the abrasive blast processmore » conditions of nozzle pressure and standoff distance considered in this study. On the other hand, the modeling results suggest that the angularity of the abrasive particle has an important role in determining surface geometry, which in turn, affects the emissivity. Abrasive blasting causes localized surface strains and localized recrystallization, but it does not affect grain size following extended exposure at elevated temperature. The dependence of emissivity of the DOP-26 alloy on mean surface slope follows a similar trend to that reported for pure iridium.« less

Nanocrystals feel the heat

NASA Astrophysics Data System (ADS)

Liang, Liangliang; Liu, Xiaogang

2018-03-01

Phosphors often suffer luminescence quenching at elevated temperatures. Now, thermal quenching can be combated with surface phonon-assisted energy transfer, enabling the luminescence of ultrasmall upconversion nanophosphors to be dramatically enhanced.

Coating for hot sliding seals

NASA Technical Reports Server (NTRS)

Stock, J.

1979-01-01

Heat resistant paint is effective surface coating for sliding seals that must operate at elevated temperatures. Economical paint is easy to apply, offers minimal friction, and improves reliability of seals.

Influence of Working Temperature on The Formation of Electrospun Polymer Nanofibers

NASA Astrophysics Data System (ADS)

Yang, Guang-Zhi; Li, Hai-Peng; Yang, Jun-He; Wan, Jia; Yu, Deng-Guang

2017-01-01

Temperature is an important parameter during electrospinning, and virtually, all solution electrospinning processes are conducted at ambient temperature. Nanofiber diameters presumably decrease with the elevation of working fluid temperature. The present study investigated the influence of temperature variations on the formation of polymeric nanofibers during single-fluid electrospinning. The surface tension and viscosity of the fluid decreased with increasing working temperature, which led to the formation of high-quality nanofibers. However, the increase in temperature accelerated the evaporation of the solvent and thus terminated the drawing processes prematurely. A balance can be found between the positive and negative influences of temperature elevation. With polyacrylonitrile (PAN, with N, N-dimethylacetamide as the solvent) and polyvinylpyrrolidone (PVP, with ethanol as the solvent) as the polymeric models, relationships between the working temperature ( T, K) and nanofiber diameter ( D, nm) were established, with D = 12598.6 - 72.9 T + 0.11 T 2 ( R = 0.9988) for PAN fibers and D = 107003.4 - 682.4 T + 1.1 T 2 ( R = 0.9997) for PVP nanofibers. Given the fact that numerous polymers are sensitive to temperature and numerous functional ingredients exhibit temperature-dependent solubility, the present work serves as a valuable reference for creating novel functional nanoproducts by using the elevated temperature electrospinning process.

Mixture and method for simulating soiling and weathering of surfaces

DOEpatents

Sleiman, Mohamad; Kirchstetter, Thomas; Destaillats, Hugo; Levinson, Ronnen; Berdahl, Paul; Akbari, Hashem

2018-01-02

This disclosure provides systems, methods, and apparatus related to simulated soiling and weathering of materials. In one aspect, a soiling mixture may include an aqueous suspension of various amounts of salt, soot, dust, and humic acid. In another aspect, a method may include weathering a sample of material in a first exposure of the sample to ultraviolet light, water vapor, and elevated temperatures, depositing a soiling mixture on the sample, and weathering the sample in a second exposure of the sample to ultraviolet light, water vapor, and elevated temperatures.

Computation of temperature elevation in rabbit eye irradiated by 2.45-GHz microwaves with different field configurations.

PubMed

Hirata, Akimasa; Watanabe, Soichi; Taki, Masao; Fujiwara, Osamu; Kojima, Masami; Sasaki, Kazuyuki

2008-02-01

This study calculated the temperature elevation in the rabbit eye caused by 2.45-GHz near-field exposure systems. First, we calculated specific absorption rate distributions in the eye for different antennas and then compared them with those observed in previous studies. Next, we re-examined the temperature elevation in the rabbit eye due to a horizontally-polarized dipole antenna with a C-shaped director, which was used in a previous study. For our computational results, we found that decisive factors of the SAR distribution in the rabbit eye were the polarization of the electromagnetic wave and antenna aperture. Next, we quantified the eye average specific absorption rate as 67 W kg(-1) for the dipole antenna with an input power density at the eye surface of 150 mW cm(-2), which was specified in the previous work as the minimum cataractogenic power density. The effect of administrating anesthesia on the temperature elevation was 30% or so in the above case. Additionally, the position where maximum temperature in the lens appears is discussed due to different 2.45-GHz microwave systems. That position was found to appear around the posterior of the lens regardless of the exposure condition, which indicates that the original temperature distribution in the eye was the dominant factor.

Influence of Annealing on the Depth Microstructure of the Shot Peened Duplex Stainless Steel at Elevated Temperature

NASA Astrophysics Data System (ADS)

Feng, Qiang; She, Jia; Xiang, Yong; Wu, Xianyun; Wang, Chengxi; Jiang, Chuanhai

The depth profiles of residual stresses and lattice parameters in the surface layers of shot peened duplex stainless steel at elevated temperature were investigated utilizing X-ray diffraction analysis. At each deformation depth, residual stress distributions in both ferrite and austenite were studied by X-ray diffraction stress analysis which is performed on the basis of the sin2ψ method and the lattice parameters were explored by Rietveld method. The results reveal that difference changes of depth residual compressive stress profiles between ferrite and austenite under the same annealing condition are resulted from the diverse coefficient of thermal expansion, dislocation density, etc. for different phases in duplex stainless steel. The relaxations of depth residual stresses in austenite are more obvious than those in ferrite. The lattice parameters decrease in the surface layer with the extending of annealing time, however, they increase along the depth after annealing for 16min. The change of the depth lattice parameters can be ascribed to both thermal expansion and the relaxation of residual stress. The different changes of microstructure at elevated temperature between ferrite and austenite are discussed.

Comparison of two vertical condensation obturation techniques: Touch 'n Heat modified and System B.

PubMed

Silver, G K; Love, R M; Purton, D G

1999-08-01

The aims of this study were firstly to compare the area of canal occupied by gutta-percha, sealer or voids using the System B heating device with that obtained by a modified vertical condensation technique using the Touch 'n Heat: and secondly to compare the temperature changes at the root canal wall and external root surface during obturation with the above techniques. Forty-five resin blocks, each with a standardized, simulated, prepared main root canal and five lateral canals, were assigned to three equal experimental groups. The canals were obturated using either the System B technique at two different temperature settings, or vertical condensation with a Touch 'n Heat instrument as the heat source. A heat transfer model was used to simultaneously record internal and external root surface temperature elevations during obturation by the three techniques. Data were analysed using unpaired Student's t-test and Mann-Whitney U-test. Both obturation techniques produced root fillings consisting of over 90% gutta-percha at most levels, although the percentages of sealer and voids 2-3 mm from the working length following System B obturation were higher than those found following modified vertical condensation. Modified vertical condensation resulted in more gutta-percha in lateral canals. Obturation was accomplished more quickly using the System B, and temperature elevations produced during obturation with the System B were significantly less (P < 0.001) than with vertical condensation. An elevation of external root surface temperature by more than 10 degrees C occurred during vertical condensation. The results suggest that the System B may produce an acceptable obturation and that the use of a Touch 'n Heat source during vertical condensation may result in damage to the periodontium.

Seasonal Changes in Titan's Surface Temperatures

NASA Technical Reports Server (NTRS)

Jennins, Donald E.; Cottini, V.; Nixon, C. A.; Flasar, F. M.; Kunde, V. G.; Samuelson, R. E.; Romani, P. N.; Hesman, B. E.; Carlson, R. C.; Gorius, N. J. P.;

High-Temperature Modal Survey of a Hot-Structure Control Surface

NASA Technical Reports Server (NTRS)

Spivey, Natalie D.

2011-01-01

Ground vibration tests are routinely conducted for supporting flutter analysis for subsonic and supersonic vehicles; however, for hypersonic vehicles, thermoelastic vibration testing techniques are neither well established nor routinely performed. New high-temperature material systems, fabrication technologies and high-temperature sensors expand the opportunities to develop advanced techniques for performing ground vibration tests at elevated temperatures. When high-temperature materials, which increase in stiffness when heated, are incorporated into a hot-structure that contains metallic components that decrease in stiffness when heated, the interaction between those materials can affect the hypersonic flutter analysis. A high-temperature modal survey will expand the research database for hypersonics and improve the understanding of this dual-material interaction. This report discusses the vibration testing of the carbon-silicon carbide Ruddervator Subcomponent Test Article, which is a truncated version of a full-scale hot-structure control surface. Two series of room-temperature modal test configurations were performed in order to define the modal characteristics of the test article during the elevated-temperature modal survey: one with the test article suspended from a bungee cord (free-free) and the second with it mounted on the strongback (fixed boundary). Testing was performed in the NASA Dryden Flight Research Center Flight Loads Laboratory Large Nitrogen Test Chamber.

Temperature dependence of interfacial structures and acidity of clay edge surfaces

NASA Astrophysics Data System (ADS)

Liu, Xiandong; Lu, Xiancai; Cheng, Jun; Sprik, Michiel; Wang, Rucheng

2015-07-01

In the pursuit of a microscopic understanding of the effects of temperature on the surface reactivity of clay minerals, we conducted first principles molecular dynamics (FPMD) simulations to study the interfacial structures and acidity of clay edge surfaces at elevated temperatures. The common edge surfaces ((0 1 0) and (1 1 0) types) of phyllosilicates were investigated at 348 K and 423 K, and the results were compared with those previously derived at ambient conditions. We found that the stable surface sites are the same as at ambient conditions, including tbnd Al(OH2)2 (6-fold Al), tbnd Al(OH2) (5-fold Al) and tbnd Si(OH) on the (0 1 0) facet, and tbnd Al(OH2), tbnd Al(OH)Sitbnd and tbnd Si(OH) on the (1 1 0) surface. The FPMD-based vertical energy gap technique was applied to compute the acidity constants of edge sites and the resulting pKa values show a decreasing trend with temperature. The results demonstrate that although changes in the point of zero charge of the entire material are insignificant up to 348 K, the decrease in surface pKa can be 3 pKa units, while it can be as large as 6 pKa units up to 423 K. The derived interface structures and pKa values can be used in future experimental and modeling research, e.g., in interpreting experiments and predicting the surface complexation of metal cations and organics. This study therefore provides a physical basis for investigating the interfacial processes of clay minerals in environments that experience elevated P-T conditions, such as sedimentary basins and geological nuclear waste repositories.

Illustrating harvest effects on site microclimate in a high-elevation forest stand.

Treesearch

W.B. Fowler; T.D. Anderson

1987-01-01

Three-dimensional contour surfaces were drawn for physiologically active radiation (PAR) and air and soil temperatures from measurements taken at a high-elevation site (1450 m) near the crest of the Cascade Range in central Washington. Measurements in a clearcut were compared with measurements from an adjacent uncut stand. Data for 31 days in July and August 1985...

ELECTRODEPOSITION OF NICKEL ON URANIUM

DOEpatents

Gray, A.G.

1958-08-26

A method is described for preparing uranium objects prior to nickel electroplating. The process consiats in treating the surface of the uranium with molten ferric chloride hexahydrate, at a slightiy elevated temperature. This treatment etches the metal surface providing a structure suitable for the application of adherent electrodeposits and at the same time plates the surface with a thin protective film of iron.

Effects of the thermal discharge from an offshore power plant on plankton and macrobenthic communities in subtropical China.

PubMed

Lin, Jie; Zou, Xinqing; Huang, Faming

2018-06-01

The ecological impact of thermal discharge has become an important issue in the field of marine and environmental protection. We focused on the effects of thermal discharge on seawater temperature and biological communities based on data from before (2006) and after (2013-2014) the construction of a power plant. The thermal discharge induced stratification, which resulted in changes in the vertical hydrodynamic conditions. Stratification combined with elevated temperatures significantly affected the phytoplankton abundance and community structure. Elevated seawater temperatures decreased the chlorophyll-a concentrations by 34% and 63%, at the surface and bottom, respectively. The elevated seawater temperature at the bottom might not be high enough to significantly affect the macrobenthos, but significantly affected the phytoplankton and zooplankton communities. Because these communities serve as food for the macrobenthic community, their changes resulted in growth of the macrobenthos. Furthermore, this effect induced macrobenthic community succession, resulting in decreased species diversity and increased dominance. Copyright © 2018 Elsevier Ltd. All rights reserved.

Aging and failure mode of electrochemical double layer capacitors during accelerated constant load tests

NASA Astrophysics Data System (ADS)

Kötz, R.; Ruch, P. W.; Cericola, D.

Electrochemical double layer capacitors of the BCAP0350 type (Maxwell Technologies) were tested under constant load conditions at different voltages and temperatures. The aging of the capacitors was monitored during the test in terms of capacitance, internal resistance and leakage current. Aging was significantly accelerated by elevated temperature or increased voltage. Only for extreme conditions at voltages of 3.5 V or temperatures above 70 °C the capacitors failed due to internal pressure build-up. No other failure events such as open circuit or short circuit were detected. Impedance measurements after the tests showed increased high frequency resistance, an increased distributed resistance and most likely an increase in contact resistance between electrode and current collector together with a loss of capacitance. Capacitors aged at elevated voltages (3.3 V) exhibited a tilting of the low frequency component, which implies an increase in the heterogeneity of the electrode surface. This feature was not observed upon aging at elevated temperatures (70 °C).

Thermal behavior of cylindrical buckling restrained braces at elevated temperatures.

PubMed

Talebi, Elnaz; Tahir, Mahmood Md; Zahmatkesh, Farshad; Yasreen, Airil; Mirza, Jahangir

2014-01-01

The primary focus of this investigation was to analyze sequentially coupled nonlinear thermal stress, using a three-dimensional model. It was meant to shed light on the behavior of Buckling Restraint Brace (BRB) elements with circular cross section, at elevated temperature. Such bracing systems were comprised of a cylindrical steel core encased in a strong concrete-filled steel hollow casing. A debonding agent was rubbed on the core's surface to avoid shear stress transition to the restraining system. The numerical model was verified by the analytical solutions developed by the other researchers. Performance of BRB system under seismic loading at ambient temperature has been well documented. However, its performance in case of fire has yet to be explored. This study showed that the failure of brace may be attributed to material strength reduction and high compressive forces, both due to temperature rise. Furthermore, limiting temperatures in the linear behavior of steel casing and concrete in BRB element for both numerical and analytical simulations were about 196°C and 225°C, respectively. Finally it is concluded that the performance of BRB at elevated temperatures was the same as that seen at room temperature; that is, the steel core yields prior to the restraining system.

Some effects of topography, soil moisture, and sea-surface temperature on continental precipitation as computed with the GISS coarse mesh climate model

NASA Technical Reports Server (NTRS)

Spar, J.; Cohen, C.

1981-01-01

The effects of terrain elevation, soil moisture, and zonal variations in sea/surface temperature on the mean daily precipitation rates over Australia, Africa, and South America in January were evaluated. It is suggested that evaporation of soil moisture may either increase or decrease the model generated precipitation, depending on the surface albedo. It was found that a flat, dry continent model best simulates the January rainfall over Australia and South America, while over Africa the simulation is improved by the inclusion of surface physics, specifically soil moisture and albedo variations.

Effects of Loading Frequency on Fatigue Behavior, Residual Stress, and Microstructure of Deep-Rolled Stainless Steel AISI 304 at Elevated Temperatures

NASA Astrophysics Data System (ADS)

Nikitin, I.; Juijerm, P.

2018-02-01

The effects of loading frequency on the fatigue behavior of non-deep-rolled (NDR) and deep-rolled (DR) austenitic stainless steel AISI 304 were systematically clarified at elevated temperatures, especially at temperatures exhibiting the dynamic strain aging (DSA) phenomena. Tension-compression fatigue tests were performed isothermally at temperatures of 573 K and 773 K (300 °C and 500 °C) with different loading frequencies of 5, 0.5, 0.05, and 0.005 Hz. For the DR condition, the residual stresses and work-hardening states will be presented. It was found that DSA would be detected at appropriate temperatures and deformation rates. The cyclic deformation curves and the fatigue lives of the investigated austenitic stainless steel AISI 304 are considerably affected by the DSA, especially on the DR condition having high dislocation densities at the surface and in near-surface regions. In the temperature range of the DSA, residual stresses and work-hardening states of the DR condition seem to be stabilized. The microstructural alterations were investigated by transmission electron microscopy (TEM). At an appropriate temperature with low loading frequency, the plastic deformation mechanism shifted from a wavy slip manner to a planar slip manner in the DSA regimes, whereas the dislocation movements were obstructed.

Temperature dependence of Fe/++/ crystal field spectra - Implications to mineralogical mapping of planetary surfaces

NASA Technical Reports Server (NTRS)

Sung, C.-M.; Singer, R. B.; Parkin, K. M.; Burns, R. G.; Osborne, M.

1977-01-01

Results are reported of Fe(++) crystal field spectral measurements for olivines and pyroxenes up to 400 C. The results are correlated with crystal structure data at elevated temperatures, and the validity of remote-sensed identifications of minerals on hot surfaces of the moon and Mercury is assessed. Two techniques were used to obtain spectra of minerals at elevated temperatures using a spectrophotometer. One employed a diamond cell assembly or a specially designed sample holder to measure polarized absorption spectra of heated single crystals. For the other technique, a sample holder was designed to attach to a diffuse reflectance accessory to produce reflectance spectra of heated powdered samples. Polarized absorption spectra of forsterite at 20-400 C are shown in a graph. Other graphs show the temperature dependence of Fe(++) crystal field bands in olivines, the diffuse reflectance spectra of olivine at 40-400 C, the polarization absorption spectra of orthopyroxene at 30-400 C, the diffuse reflectance spectra of pigeonite at 40-400 C, and unpolarized absorption spectra of lunar pyroxene from Apollo 15 rock 15058.

Spatial Relationships Between Snow Contaminant Content, Grain Size, and Surface Temperature in Multi-spectral Remote Sensing Data of Mt. Rainier, WA

NASA Astrophysics Data System (ADS)

Kay, J. E.; Hansen, G.; Gillespie, A.; Pettit, E.

2002-12-01

Relating cryosphere change to climate change requires estimation of radiative fluxes on snow-covered surfaces. The distribution of, and relationship between, snow-pack properties that affect radiative balance can be estimated with high-resolution remote-sensing data. MODIS/ASTER airborne simulator (MASTER) data were collected at Mt. Rainier to reveal spatial patterns of, and correlations between, snow contaminant content, grain size, and temperature. The visible and near-infrared (VNIR: 11 bands, 0.4-1.0 μm) and the short-wave infrared (SWIR: 14 bands, 1.6-2.4 μm) data are processed to bi-directional reflectance (BDR) and albedo, by removing atmospheric effects and by normalizing to Solar irradiance and incidence angle. VNIR BDR and albedo are used as a proxy for snow contaminant content. Physical and optical grain size are estimated by comparing SWIR BDR and albedo to modeled and measured spectra, and ground-truth measurements. The thermal infrared data (TIR: 10 bands, 8-13 μm) are processed to temperature by removing emissivity and atmospheric effects. In combination, the VNIR, SWIR, and TIR data reveal a distinct pattern of contaminants, grain size, and temperature related to a recent snowfall and the end-of-the-summer melting season. At lower elevations, the surface accumulation of dirty lag deposits resulted in snow with very low visible albedo (20-30 %), large physical and optical grain radii (500-1500 μm, 200 μm), and temperatures near the melting point. At higher elevations, the recent snowfall left snow with low contaminant content, and a higher visible albedo (60-90 %). However, a region near the summit with smaller physical and optical grain radii (400 μm, 100 μm), and temperatures below the melting point, is distinguished from a middle elevation region with grain sizes and temperatures similar to the lower region. Contaminants reduce VNIR albedo and significantly enhance absorption of incoming solar radiation. The spatial correlation between temperature and grain size supports the idea that rapid, destructive metamorphism occurs when snow temperatures are at the melting point.

Soil temperature investigations using satellite acquired thermal-infrared data in semi-arid regions. Thesis. Final Report; [Utah

NASA Technical Reports Server (NTRS)

Day, R. L.; Petersen, G. W.

1983-01-01

Thermal-infrared data from the Heat Capacity Mapping Mission satellite were used to map the spatial distribution of diurnal surface temperatures and to estimate mean annual soil temperatures (MAST) and annual surface temperature amplitudes (AMP) in semi-arid east central Utah. Diurnal data with minimal snow and cloud cover were selected for five dates throughout a yearly period and geometrically co-registered. Rubber-sheet stretching was aided by the WARP program which allowed preview of image transformations. Daytime maximum and nighttime minimum temperatures were averaged to generation average daily temperature (ADT) data set for each of the five dates. Five ADT values for each pixel were used to fit a sine curve describing the theoretical annual surface temperature response as defined by a solution of a one-dimensinal heat flow equation. Linearization of the equation produced estimates of MAST and AMP plus associated confidence statistics. MAST values were grouped into classes and displayed on a color video screen. Diurnal surface temperatures and MAST were primarily correlated with elevation.

Strengthening silicon carbide by quenching

NASA Technical Reports Server (NTRS)

Gruver, R. M.; Platts, D. R.; Kirchner, H. P.

1974-01-01

Quenching was used to form compressive surface layers in hot-pressed silicon carbide. The presence of the compressive stresses was verified by slotted rod tests. The slotted rod tip deflection was retained at temperatures to at least 1380 C, showing that the stresses are not relieved immediately at elevated temperatures. The flexural strength and impact resistance of specimens quenched from moderate temperatures (2000 C) were increased. Frequently, specimens quenched from higher temperatures were weakened by thermal shock damage.

Ultraviolet Light-Assisted Copper Oxide Nanowires Hydrogen Gas Sensor

NASA Astrophysics Data System (ADS)

Sihar, Nabihah; Tiong, Teck Yaw; Dee, Chang Fu; Ooi, Poh Choon; Hamzah, Azrul Azlan; Mohamed, Mohd Ambri; Majlis, Burhanuddin Yeop

2018-05-01

We fabricated copper oxide nanowires (CuO NWs) ultraviolet (UV) light-assisted hydrogen gas sensor. The fabricated sensor shows promising sensor response behavior towards 100 ppm of H2 at room temperature and elevated temperature at 100 °C when exposed to UV light (3.0 mW/cm2). One hundred-cycle device stability test has been performed, and it is found that for sample elevated at 100 °C, the UV-activated sample achieved stability in the first cycle as compared to the sample without UV irradiation which needed about 10 cycles to achieve stability at the initial stage, whereas the sample tested at room temperature was able to stabilize with the aid of UV irradiation. This indicates that with the aid of UV light, after some "warming up" time, it is possible for the conventional CuO NW sensor which normally work at elevated temperature to function at room temperature because UV source is speculated to play a dominant role to increase the interaction of the surface of CuO NWs and hydrogen gas molecules absorbed after the light exposure.

Ultraviolet Light-Assisted Copper Oxide Nanowires Hydrogen Gas Sensor.

PubMed

Sihar, Nabihah; Tiong, Teck Yaw; Dee, Chang Fu; Ooi, Poh Choon; Hamzah, Azrul Azlan; Mohamed, Mohd Ambri; Majlis, Burhanuddin Yeop

2018-05-15

We fabricated copper oxide nanowires (CuO NWs) ultraviolet (UV) light-assisted hydrogen gas sensor. The fabricated sensor shows promising sensor response behavior towards 100 ppm of H 2 at room temperature and elevated temperature at 100 °C when exposed to UV light (3.0 mW/cm 2 ). One hundred-cycle device stability test has been performed, and it is found that for sample elevated at 100 °C, the UV-activated sample achieved stability in the first cycle as compared to the sample without UV irradiation which needed about 10 cycles to achieve stability at the initial stage, whereas the sample tested at room temperature was able to stabilize with the aid of UV irradiation. This indicates that with the aid of UV light, after some "warming up" time, it is possible for the conventional CuO NW sensor which normally work at elevated temperature to function at room temperature because UV source is speculated to play a dominant role to increase the interaction of the surface of CuO NWs and hydrogen gas molecules absorbed after the light exposure.

Tectonic and climatic significance of a late Eocene low-relief, high-level geomorphic surface, Colorado

NASA Technical Reports Server (NTRS)

Gregory, Kathryn M.; Chase, Clement G

1994-01-01

New paleobotanical data suggest that in the late Eocene the erosion surface which capped the Front Range, Colorado was 2.2-2.3 km in elevation, which is similar to the 2.5-km present elevation of surface remnants. This estimated elevation casts doubt on the conventional belief that the low-relief geomorphic surface was formed by lateral planation of streams to a base level not much higher than sea level and that the present deeply incised canyons must represent Neogene uplift of Colorado. Description of the surface, calculations of sediment volume, and isostatic balance and fluvial landsculpting models demonstrate that while the high elevation of the erosion surface was due to tectonic forces, its smoothness was mostly a result of climatic factors. A sediment balance calculated for the Front Range suggests that from 2 to 4 km of material were eroded by the late Eocene, consistent with fission track ages. This amount of erosion would remove a significant portionof the 7 km of Laramide upper crustal thickening. Isostatic modeling implies that the 2.2-3.3 km elevation was most likely created by lower crustal thickening during the Laramide. A numerical model of fluvial erosion and deposition suggests a way that a late Eocene surface could have formed at this high elevation without incision. A humid climate with a preponderance of small storm events will diffusively smooth topography and is a possible mechanism for formation oflow-relief, high-level surfaces. Paleoclimate models suggest a lack of large strom events in the late Eocene because of cool sea surface temperatures in the equatorial region. Return to a drier but stormier climate post-Eocene could have caused the incision of the surface by young canyons. By this interpretation, regional erosion surfaces may represent regional climatic rather than tectonic conditions.

A global model simulation for 3-D radiative transfer impact on surface hydrology over the Sierra Nevada and Rocky Mountains

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

Lee, W. -L.; Gu, Y.; Liou, K. N.

2015-05-19

We investigate 3-D mountain effects on solar flux distributions and their impact on surface hydrology over the western United States, specifically the Rocky Mountains and the Sierra Nevada, using the global CCSM4 (Community Climate System Model version 4; Community Atmosphere Model/Community Land Model – CAM4/CLM4) with a 0.23° × 0.31° resolution for simulations over 6 years. In a 3-D radiative transfer parameterization, we have updated surface topography data from a resolution of 1 km to 90 m to improve parameterization accuracy. In addition, we have also modified the upward-flux deviation (3-D–PP (plane-parallel)) adjustment to ensure that the energy balance atmore » the surface is conserved in global climate simulations based on 3-D radiation parameterization. We show that deviations in the net surface fluxes are not only affected by 3-D mountains but also influenced by feedbacks of cloud and snow in association with the long-term simulations. Deviations in sensible heat and surface temperature generally follow the patterns of net surface solar flux. The monthly snow water equivalent (SWE) deviations show an increase in lower elevations due to reduced snowmelt, leading to a reduction in cumulative runoff. Over higher-elevation areas, negative SWE deviations are found because of increased solar radiation available at the surface. Simulated precipitation increases for lower elevations, while it decreases for higher elevations, with a minimum in April. Liquid runoff significantly decreases at higher elevations after April due to reduced SWE and precipitation.« less

Surface Superstructure of Carbon Nanotubes on Highly Oriented Pyrolytic Graphite Annealed at Elevated Temperatures

NASA Astrophysics Data System (ADS)

An, Bai; Fukuyama, Seiji; Yokogawa, Kiyoshi; Yoshimura, Masamichi

1998-06-01

Carbon nanotubes deposited on highly oriented pyrolytic graphite (HOPG) are annealed in ultra high vacuum. The effect of annealing temperature on the surface morphology of the carbon nanotubes on HOPG is examined by scanning tunneling microscopy. The ring-like surface superstructure of (\\sqrt {3}× \\sqrt {3})R30° of graphite is found on the carbon nanotubes annealed above 1593 K. The tips of the carbon nanotubes are destroyed and the stacking misarrangement between the upper and the lower walls of the tube join with HOPG resulting in the superstructure.

Elevated-Temperature Tests Under Static and Aerodynamic Conditions on Honeycomb-Core Sandwich Panels

NASA Technical Reports Server (NTRS)

Groen, Joseph M.; Johnson, Aldie E., Jr.

1959-01-01

Stainless-steel honeycomb-core sandwich panels which differed primarily in skin thicknesses were tested at elevated temperatures under static and aerodynamic conditions. The results of these tests were evaluated to determine the insulating effectiveness and structural integrity of the panels. The static radiant-heating tests were performed in front of a quartz-tube radiant heater at panel skin temperatures up to 1,5000 F. The aerodynamic tests were made in a Mach 1.4 heated blowdown wind tunnel. The tunnel temperature was augmented by additional heat supplied by a radiant heater which raised the panel surface temperature above 8000 F during air flow. Static radiant-heating tests of 2 minutes duration showed that all the panels protected the load-carrying structure about equally well. Thin-skin panels showed an advantage for this short-time test over thick-skin panels from a standpoint of weight against insulation. Permanent inelastic strains in the form of local buckles over each cell of the honeycomb core caused an increase in surface roughness. During the aero- dynamic tests all of the panels survived with little or no damage, and panel flutter did not occur.

An anisotropic thermomechanical damage model for concrete at transient elevated temperatures.

PubMed

Baker, Graham; de Borst, René

2005-11-15

The behaviour of concrete at elevated temperatures is important for an assessment of integrity (strength and durability) of structures exposed to a high-temperature environment, in applications such as fire exposure, smelting plants and nuclear installations. In modelling terms, a coupled thermomechanical analysis represents a generalization of the computational mechanics of fracture and damage. Here, we develop a fully coupled anisotropic thermomechanical damage model for concrete under high stress and transient temperature, with emphasis on the adherence of the model to the laws of thermodynamics. Specific analytical results are given, deduced from thermodynamics, of a novel interpretation on specific heat, evolution of entropy and the identification of the complete anisotropic, thermomechanical damage surface. The model is also shown to be stable in a computational sense, and to satisfy the laws of thermodynamics.

Structural, morphological and optical properties of pulsed laser deposited ZnSe/ZnSeO3 thin films

NASA Astrophysics Data System (ADS)

Hassan, Syed Ali; Bashir, Shazia; Zehra, Khushboo; Salman Ahmed, Qazi

2018-04-01

The effect of varying laser pulses on structural, morphological and optical behavior of Pulsed Laser Deposited (PLD) ZnSe/ZnSeO3 thin films has been investigated. The films were grown by employing Excimer laser (100 mJ, 248 nm, 18 ns, 30 Hz) at various number of laser pulses i.e. 3000, 4000, 5000 and 6000 with elevated substrate temperature of 300 °C. One film was grown at Room Temperature (RT) by employing 3000 number of laser pulses. In order to investigate the structural analysis of deposited films, XRD analysis was performed. It was observed that the room temperature is not favorable for the growth of crystalline film. However, elevated substrate temperature to 300°C, two phases with preferred orientation of ZnSeO3 (2 1 2) and ZnSe (3 3 1) were identified. AFM and SEM analysis were performed to explore the surface morphology of grown films. Morphological analysis also confirmed the non-uniform film growth at room temperature. At elevated substrate temperature (300 °C), the growth of dendritic rods and cubical crystalline structures are observed for lower number of laser pulses i.e. 3000 and 4000 respectively. With increased number of pulses i.e. 5000 and 6000, the films surface morphology becomes smooth which is confirmed by measurement of surface RMS roughness. Number of grains, skewness, kurtosis and other parameters have been evaluated by statistical analysis. In order to investigate the thickness, and optical properties of deposited films, ellipsometery and UV–Vis spectroscopy techniques were employed. The estimated band gap energy is 2.67 eV for the film grown at RT, whereas band gap values varies from 2.80 eV to 3.01 eV for the films grown at 300 °C with increasing number of laser pulses.

Near-surface temperature lapse rates in a mountainous catchment in the Chilean Andes

NASA Astrophysics Data System (ADS)

Ayala; Schauwecker, S.; Pellicciotti, F.; McPhee, J. P.

2011-12-01

In mountainous areas, and in the Chilean Andes in particular, the irregular and sparse distribution of recording stations resolves insufficiently the variability of climatic factors such as precipitation, temperature and relative humidity. Assumptions about air temperature variability in space and time have a strong effect on the performance of hydrologic models that represent snow processes such as accumulation and ablation. These processes have large diurnal variations, and assumptions that average over longer time periods (days, weeks or months) may reduce the predictive capacity of these models under different climatic conditions from those for which they were calibrated. They also introduce large uncertainties when such models are used to predict processes with strong subdiurnal variability such as snowmelt dynamics. In many applications and modeling exercises, temperature is assumed to decrease linearly with elevation, using the free-air moist adiabatic lapse rate (MALR: 0.0065°C/m). Little evidence is provided for this assumption, however, and recent studies have shown that use of lapse rates that are uniform in space and constant in time is not appropriate. To explore the validity of this approach, near-surface (2 m) lapse rates were calculated and analyzed at different temporal resolution, based on a new data set of spatially distributed temperature sensors setup in a high elevation catchment of the dry Andes of Central Chile (approx. 33°S). Five minutes temperature data were collected between January 2011 and April 2011 in the Ojos de Agua catchment, using two Automatic Weather Stations (AWSs) and 13 T-loggers (Hobo H8 Pro Temp with external data logger), ranging in altitude from 2230 to 3590 m.s.l.. The entire catchment was snow free during our experiment. We use this unique data set to understand the main controls over temperature variability in time and space, and test whether lapse rates can be used to describe the spatial variations of air temperature in a high elevation catchment. Our main result is that the assumption of a MALR is appropriate to describe the average variability of temperature over the entire measurement period (and possibly for daily scales), but that hourly near-surface lapse rates vary considerably and can deviate strongly from the MALR. This diurnal variability in lapse rates is associated with changes in wind direction and variations in wind velocity. Shallow lapse rates, in particular, occur during the morning, in correspondence to low wind speeds and change in wind direction from katabatic wind to valley wind and are associated with a weaker correlation between air temperature and elevation, while steeper lapse rates (meaning by this that temperature decreases more with elevation) closer to the MALR are typical of the afternoon hours from 13.00 on (and correspond to high wind speed), and are representative of a more linear dependency between air temperature and elevation. The steepest LRs, however, occur in the evening at 20.00-21.00, when wind velocity drops again and wind direction changes from valley wind to katabatic wind. It is clear that the wind regime is the main controls on LRs variability, and it is important to validate these findings with data sets from a second season.

DOE Award No. FG02-93ER14331 Final Technical Report

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

Bartynski, Robert

We have studyed new aspects of the relationships between nanoscale surface features and heterogeneous catalysis or electrocatalysis. We concentrate on atomically rough and morphologically unstable surfaces of catalytic metal single crystals (Re, Ru, Ir) that undergo nanoscale faceting when interacting with strongly adsorbed species (e.g. O, N, C) at elevated temperatures.

Methane Cycling in a Warming Wetland

NASA Astrophysics Data System (ADS)

Noyce, G. L.; Megonigal, P.; Rich, R.; Kirwan, M. L.; Herbert, E. R.

2017-12-01

Coastal wetlands are global hotspots of carbon (C) storage, but the future of these systems is uncertain. In June 2016, we initiated an in-situ, active, whole-ecosystem warming experiment in the Smithsonian's Global Change Research Wetland to quantify how warming and elevated CO2 affect the stability of coastal wetland soil C pools and contemporary rates of C sequestration. Transects are located in two plant communities, dominated by C3 sedges or C4 grasses. The experiment has a gradient design with air and soil warming treatments ranging from ambient to +5.1 °C and heated plots consistently maintain their target temperature year-round. In April 2017, an elevated CO2 treatment was crossed with temperature in the C3community. Ongoing measurements include soil elevation, C fluxes, porewater chemistry and redox potential, and above- and below-ground growth and biomass. In both years, warming increased methane (CH4) emissions (measured at 3-4 week intervals) from spring through fall at the C3 site, but had little effect on emissions from the C4 site. Winter (Dec-Mar) emissions showed no treatment effect. Stable isotope analysis of dissolved CH4 and DIC also indicated that warming had differing effects on CH4 pathways in the two vegetation communities. To better understand temperature effects on rates of CH4 production and oxidation, 1 m soil cores were collected from control areas of the marsh in summer 2017 and incubated at temperatures ranging from 4 °C to 35 °C. Warming increased CH4 production and oxidation rates in surface samples and oxidation rates in the rooting zone samples from both sites, but temperature responses in deep (1 m) soil samples were minimal. In the surface and rooting zone samples, production rates were also consistently higher in C3 soils compared to C4 soils, but, contrary to our expectations, the temperature response was stronger in the C4 soils. However, oxidation in C3 rooting zone samples did have a strong temperature response. The ratio of CO2:CH4 decreased with increasing temperature in surface samples from both sites, indicating that anaerobic respiration in surface soil may become increasingly methanogenic with warming. In contrast, the rooting zone and deep soil samples showed the opposite trend, again suggesting that the soil profile will not respond consistently to warming.

Design and analysis of aerospace structures at elevated temperatures. [aircraft, missiles, and space platforms

NASA Technical Reports Server (NTRS)

Chang, C. I.

1989-01-01

An account is given of approaches that have emerged as useful in the incorporation of thermal loading considerations into advanced composite materials-based aerospace structural design practices. Sources of structural heating encompass not only propulsion system heat and aerodynamic surface heating at supersonic speeds, but the growing possibility of intense thermal fluxes from directed-energy weapons. The composite materials in question range from intrinsically nonheat-resistant polymer matrix systems to metal-matrix composites, and increasingly to such ceramic-matrix composites as carbon/carbon, which are explicitly intended for elevated temperature operation.

Nanoionics and Nanocatalysts: Conformal Mesoporous Surface Scaffold for Cathode of Solid Oxide Fuel Cells

PubMed Central

Chen, Yun; Gerdes, Kirk; Song, Xueyan

2016-01-01

Nanoionics has become increasingly important in devices and systems related to energy conversion and storage. Nevertheless, nanoionics and nanostructured electrodes development has been challenging for solid oxide fuel cells (SOFCs) owing to many reasons including poor stability of the nanocrystals during fabrication of SOFCs at elevated temperatures. In this study, a conformal mesoporous ZrO2 nanoionic network was formed on the surface of La1−xSrxMnO3/yttria-stabilized zirconia (LSM/YSZ) cathode backbone using Atomic Layer Deposition (ALD) and thermal treatment. The surface layer nanoionic network possesses open mesopores for gas penetration, and features a high density of grain boundaries for enhanced ion-transport. The mesoporous nanoionic network is remarkably stable and retains the same morphology after electrochemical operation at high temperatures of 650–800 °C for 400 hours. The stable mesoporous ZrO2 nanoionic network is further utilized to anchor catalytic Pt nanocrystals and create a nanocomposite that is stable at elevated temperatures. The power density of the ALD modified and inherently functional commercial cells exhibited enhancement by a factor of 1.5–1.7 operated at 0.8 V at 750 °C. PMID:27605121

Making Activated Carbon for Storing Gas

NASA Technical Reports Server (NTRS)

Wojtowicz, Marek A.; Serio, Michael A.; Suuberg, Eric M.

2005-01-01

Solid disks of microporous activated carbon, produced by a method that enables optimization of pore structure, have been investigated as means of storing gas (especially hydrogen for use as a fuel) at relatively low pressure through adsorption on pore surfaces. For hydrogen and other gases of practical interest, a narrow distribution of pore sizes <2 nm is preferable. The present method is a variant of a previously patented method of cyclic chemisorption and desorption in which a piece of carbon is alternately (1) heated to the lower of two elevated temperatures in air or other oxidizing gas, causing the formation of stable carbon/oxygen surface complexes; then (2) heated to the higher of the two elevated temperatures in flowing helium or other inert gas, causing the desorption of the surface complexes in the form of carbon monoxide. In the present method, pore structure is optimized partly by heating to a temperature of 1,100 C during carbonization. Another aspect of the method exploits the finding that for each gas-storage pressure, gas-storage capacity can be maximized by burning off a specific proportion (typically between 10 and 20 weight percent) of the carbon during the cyclic chemisorption/desorption process.

Bombardment-induced segregation and redistribution

NASA Astrophysics Data System (ADS)

Lam, N. Q.; Wiedersich, H.

During ion bombardment, a number of processes can alter the compositional distribution and microstructure in near-surface regions of alloys. The relative importance of each process depends principally on the target composition, temperature, and ion characteristics. In addition to displacement mixing leading to a randomization of atomic locations, and preferential loss of alloying elements by sputtering, which are dominant at relatively low temperatures, several thermally-activated processes, including radiation-enhanced diffusion, radiation-induced segregation and Gibbsian adsorption, also play important roles. At elevated temperatures, nonequilibrium point defects induced by ion impacts become mobile and tend to anneal out by recombination and diffusion to extended sinks, such as dislocations, grain boundaries and free surfaces. The high defect concentrations, far exceeding the thermodynamic equilibrium values, can enhance diffusion-controlled processes, while persistent defect fluxes, originating from the spatial non-uniformity in defect production and annihilation, give rise to local redistribution of alloy constituents because of radiation-induced segregation. Moreover, when the alloy is maintained at high temperature, Gibbsian adsorption, driven by the reduction in free energy of the system, occurs even without irradiation; it involves a compositional perturbation in a few atom layers near the alloy surface. The combination of these processes leads to the complex development of a compositionally-modified layer in the subsurface region. Considerable progress has been made recently in identifying and understanding the relative contributions from the individual processes under various irradiation conditions. In the present paper, selected examples of these different phenomena and their synergistic effects on the evolution of the near-surface compositions of alloys during sputtering and ion implantation at elevated temperatures are discussed.

Role of RuO2(100) in surface oxidation and CO oxidation catalysis on Ru(0001).

PubMed

Flege, Jan Ingo; Lachnitt, Jan; Mazur, Daniel; Sutter, Peter; Falta, Jens

2016-01-07

We have studied the oxidation of the Ru(0001) surface by in situ microscopy during exposure to NO2, an efficient source of atomic oxygen, at elevated temperatures. In a previous investigation [Flege et al., Phys. Rev. B: Condens. Matter Mater. Phys., 2008, 78, 165407], at O coverages exceeding 1 monolayer, using the combination of intensity-voltage (I(V)) low-energy electron microscopy (LEEM) and multiple scattering calculations for the (00) beam in the very-low-energy range (E≤ 50 eV) we identified three surface components during the initial Ru oxidation: a (1 × 1)-O chemisorption phase, the RuO2(110) oxide phase, and a surface oxide structure characterized by a trilayer O-Ru-O stacking. Here, we use dark-field LEEM imaging and micro-illumination low-energy electron diffraction in the range of 100 to 400 eV to show that this trilayer phase is actually a RuO2(100)-(1 × 1) phase with possibly mixed O and Ru surface terminations. This identification rationalizes the thermodynamic stability of this phase at elevated temperatures and is consistent with the observation of catalytic activity of the phase in CO oxidation.

Improvement in Fatigue Performance of Aluminium Alloy Welded Joints by Laser Shock Peening in a Dynamic Strain Aging Temperature Regime.

PubMed

Su, Chun; Zhou, Jianzhong; Meng, Xiankai; Huang, Shu

2016-09-26

As a new treatment process after welding, the process parameters of laser shock peening (LSP) in dynamic strain aging (DSA) temperature regimes can be precisely controlled, and the process is a non-contact one. The effects of LSP at elevated temperatures on the distribution of the surface residual stress of AA6061-T6 welded joints were investigated by using X-ray diffraction technology with the sin² ϕ method and Abaqus software. The fatigue life of the welded joints was estimated by performing tensile fatigue tests. The microstructural evolution in surface and fatigue fractures of the welded joints was presented by means of surface integrity and fracture surface testing. In the DSA temperature regime of AA6061-T6 welded joints, the residual compressive stress was distributed more stably than that of LSP at room temperature. The thermal corrosion resistance and fatigue properties of the welded joints were also improved. The experimental results and numerical analysis were in mutual agreement.

Improvement in Fatigue Performance of Aluminium Alloy Welded Joints by Laser Shock Peening in a Dynamic Strain Aging Temperature Regime

PubMed Central

Su, Chun; Zhou, Jianzhong; Meng, Xiankai; Huang, Shu

2016-01-01

As a new treatment process after welding, the process parameters of laser shock peening (LSP) in dynamic strain aging (DSA) temperature regimes can be precisely controlled, and the process is a non-contact one. The effects of LSP at elevated temperatures on the distribution of the surface residual stress of AA6061-T6 welded joints were investigated by using X-ray diffraction technology with the sin2ϕ method and Abaqus software. The fatigue life of the welded joints was estimated by performing tensile fatigue tests. The microstructural evolution in surface and fatigue fractures of the welded joints was presented by means of surface integrity and fracture surface testing. In the DSA temperature regime of AA6061-T6 welded joints, the residual compressive stress was distributed more stably than that of LSP at room temperature. The thermal corrosion resistance and fatigue properties of the welded joints were also improved. The experimental results and numerical analysis were in mutual agreement. PMID:28773920

MANTLE CONVECTION, PLATE TECTONICS, AND VOLCANISM ON HOT EXO-EARTHS

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

Van Summeren, Joost; Conrad, Clinton P.; Gaidos, Eric, E-mail: summeren@hawaii.edu

Recently discovered exoplanets on close-in orbits should have surface temperatures of hundreds to thousands of Kelvin. They are likely tidally locked and synchronously rotating around their parent stars and, if an atmosphere is absent, have surface temperature contrasts of many hundreds to thousands of Kelvin between permanent day and night sides. We investigated the effect of elevated surface temperature and strong surface temperature contrasts for Earth-mass planets on the (1) pattern of mantle convection, (2) tectonic regime, and (3) rate and distribution of partial melting, using numerical simulations of mantle convection with a composite viscous/pseudo-plastic rheology. Our simulations indicate thatmore » if a close-in rocky exoplanet lacks an atmosphere to redistribute heat, a {approx}>400 K surface temperature contrast can maintain an asymmetric degree 1 pattern of mantle convection in which the surface of the planet moves preferentially toward subduction zones on the cold night side. The planetary surface features a hemispheric dichotomy, with plate-like tectonics on the night side and a continuously evolving mobile lid on the day side with diffuse surface deformation and vigorous volcanism. If volcanic outgassing establishes an atmosphere and redistributes heat, plate tectonics is globally replaced by diffuse surface deformation and volcanism accelerates and becomes distributed more uniformly across the planetary surface.« less

Inversion structure and winter ozone distribution in the Uintah Basin, Utah, U.S.A.

NASA Astrophysics Data System (ADS)

Lyman, Seth; Tran, Trang

2015-12-01

The Uintah Basin in Utah, U.S.A. experiences high concentrations of ozone during some winters due to strong, multi-day temperature inversions that facilitate the buildup of pollution from local sources, including the oil and gas industry. Together, elevation of monitoring sites and proximity to oil and gas wells explain as much as 90% of spatial variability in surface ozone concentrations during inversion episodes (i.e., R2 = 0.90). Inversion conditions start earlier and last longer at lower elevations, at least in part because lower elevations are more insulated from winds aloft that degrade inversion conditions and dilute produced ozone. Surface air transport under inversions is dominated by light, diurnal upslope-downslope flow that limits net transport distances. Thus, different areas of the Basin are relatively isolated from each other, allowing spatial factors like elevation and proximity to sources to strongly influence ozone concentrations at individual sites.

Sensors for ceramic components in advanced propulsion systems

NASA Technical Reports Server (NTRS)

Koller, A. C.; Bennethum, W. H.; Burkholder, S. D.; Brackett, R. R.; Harris, J. P.

1995-01-01

This report includes: (1) a survey of the current methods for the measurement of surface temperature of ceramic materials suitable for use as hot section flowpath components in aircraft gas turbine engines; (2) analysis and selection of three sensing techniques with potential to extend surface temperature measurement capability beyond current limits; and (3) design, manufacture, and evaluation of the three selected techniques which include the following: platinum rhodium thin film thermocouple on alumina and mullite substrates; doped silicon carbide thin film thermocouple on silicon carbide, silicon nitride, and aluminum nitride substrates; and long and short wavelength radiation pyrometry on the substrates listed above plus yttria stabilized zirconia. Measurement of surface emittance of these materials at elevated temperature was included as part of this effort.

75 FR 54822 - Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition To List the Jemez...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-09

... be surface active (feeding and mating). Moreover, elevated temperatures lead to increases in oxygen... disease and parasites. Effects from temperature increases are discussed in greater detail under Factor E... distribution and occurrence as well as its oxygen consumption rates and growth rates (Wyman and Hawksley...

A Warmer Atmosphere on Mars Near the Noachian-Hesperian Boundary: Evidence from Basal Melting of the South Polar Ice Cap (Dorsa Argentea Formation)

NASA Astrophysics Data System (ADS)

Fastook, J. L.; Head, J. W.; Marchant, D. R.; Forget, F.; Madeleine, J.-B.

2011-03-01

Dorsa Argentea Formation (Noachian-Hesperian) eskers are evidence for basal melting. Ice-flow models show that the mean annual south polar temperature must be raised to -50° to -75°C, providing an independent estimate of elevated lower latitude surface temperature.

Temperature sensitivity of soil organic carbon mineralization along an elevation gradient in the Wuyi Mountains, China.

PubMed

Wang, Guobing; Zhou, Yan; Xu, Xia; Ruan, Honghua; Wang, Jiashe

2013-01-01

Soil organic carbon (SOC) actively participates in the global carbon (C) cycle. Despite much research, however, our understanding of the temperature sensitivity of soil organic carbon (SOC) mineralization is still very limited. To investigate the responses of SOC mineralization to temperature, we sampled surface soils (0-10 cm) from evergreen broad-leaf forest (EBF), coniferous forest (CF), sub-alpine dwarf forest (SDF), and alpine meadow (AM) along an elevational gradient in the Wuyi Mountains, China. The soil samples were incubated at 5, 15, 25, and 35°C with constant soil moisture for 360 days. The temperature sensitivity of SOC mineralization (Q(10)) was calculated by comparing the time needed to mineralize the same amount of C at any two adjacent incubation temperatures. Results showed that the rates of SOC mineralization and the cumulative SOC mineralized during the entire incubation significantly increased with increasing incubation temperatures across the four sites. With the increasing extent of SOC being mineralized (increasing incubation time), the Q(10) values increased. Moreover, we found that both the elevational gradient and incubation temperature intervals significantly impacted Q(10) values. Q(10) values of the labile and recalcitrant organic C linearly increased with elevation. For the 5-15, 15-25, and 25-35°C intervals, surprisingly, the overall Q(10) values for the labile C did not decrease as the recalcitrant C did. Generally, our results suggest that subtropical forest soils may release more carbon than expected in a warmer climate.

Temperature changes induced by 809-nm GaAlAs laser at the implant-bone interface during simulated surface decontamination.

PubMed

Kreisler, Matthias; Al Haj, Haitham; D'Hoedt, Bernd

2003-02-01

The aim of the study was to investigate temperature changes at the implant-bone interface during simulated implant surface decontamination with a 809-nm gallium-aluminium-arsenid (GaAlAs) semiconductor laser. Stepped cylinder implants with a diameter of 3.8 mm and a length of 11 mm with two different surfaces (sand-blasted and acid etched, and hydroxyapatite-coated) were inserted into bone blocks cut from freshly resected pig femurs. Access holes of 0.5 mm were drilled into the bone, to allow K-type thermocouples to contact periimplant bone in different parts of the cavity. An artificial periimplant bone defect provided access for laser irradiation in the coronal third. A 600-micrometer optic fiber was used at a distance of 0.5 mm from the implant surface. Power output varied between 0.5 and 2.5 W in the continuous wave mode. The bone block was placed into a 37 degrees C water bath in order to simulate in vivo thermal conductivity and diffusitivity of heat. Temperature elevations during irradiation were registered for a period of 120 s. In mean, the critical threshold of 47 degrees C was exceeded after 9.0 s at 2.5 W, 12.5 s at 2.0 W, 18.0 s at 1.5 W and 30.5 s at 1.0 W. Surface characteristics did not have a significant effect on temperature elevations. In an energy-dependent manner, implant surface decontamination with an 809-nm GaAlAs laser must be limited in time to allow the implant and bone to cool down. Clinical guidelines are presented to avoid tissue damage.

Temperature Dependent Effects of Elevated CO2 on Shell Composition and Mechanical Properties of Hydroides elegans: Insights from a Multiple Stressor Experiment

PubMed Central

Chan, Vera B. S.; Thiyagarajan, Vengatesen; Lu, Xing Wen; Zhang, Tong; Shih, Kaimin

2013-01-01

The majority of marine benthic invertebrates protect themselves from predators by producing calcareous tubes or shells that have remarkable mechanical strength. An elevation of CO2 or a decrease in pH in the environment can reduce intracellular pH at the site of calcification and thus interfere with animal’s ability to accrete CaCO3. In nature, decreased pH in combination with stressors associated with climate change may result in the animal producing severely damaged and mechanically weak tubes. This study investigated how the interaction of environmental drivers affects production of calcareous tubes by the serpulid tubeworm, Hydroides elegans. In a factorial manipulative experiment, we analyzed the effects of pH (8.1 and 7.8), salinity (34 and 27‰), and temperature (23°C and 29°C) on the biomineral composition, ultrastructure and mechanical properties of the tubes. At an elevated temperature of 29°C, the tube calcite/aragonite ratio and Mg/Ca ratio were both increased, the Sr/Ca ratio was decreased, and the amorphous CaCO3 content was reduced. Notably, at elevated temperature with decreased pH and reduced salinity, the constructed tubes had a more compact ultrastructure with enhanced hardness and elasticity compared to decreased pH at ambient temperature. Thus, elevated temperature rescued the decreased pH-induced tube impairments. This indicates that tubeworms are likely to thrive in early subtropical summer climate. In the context of climate change, tubeworms could be resilient to the projected near-future decreased pH or salinity as long as surface seawater temperature rise at least by 4°C. PMID:24265732

Stream Temperature Estimation From Thermal Infrared Images

NASA Astrophysics Data System (ADS)

Handcock, R. N.; Kay, J. E.; Gillespie, A.; Naveh, N.; Cherkauer, K. A.; Burges, S. J.; Booth, D. B.

2001-12-01

Stream temperature is an important water quality indicator in the Pacific Northwest where endangered fish populations are sensitive to elevated water temperature. Cold water refugia are essential for the survival of threatened salmon when events such as the removal of riparian vegetation result in elevated stream temperatures. Regional assessment of stream temperatures is limited by sparse sampling of temperatures in both space and time. If critical watersheds are to be properly managed it is necessary to have spatially extensive temperature measurements of known accuracy. Remotely sensed thermal infrared (TIR) imagery can be used to derive spatially distributed estimates of the skin temperature (top 100 nm) of streams. TIR imagery has long been used to estimate skin temperatures of the ocean, where split-window techniques have been used to compensate for atmospheric affects. Streams are a more complex environment because 1) most are unresolved in typical TIR images, and 2) the near-bank environment of stream corridors may consist of tall trees or hot rocks and soils that irradiate the stream surface. As well as compensating for atmospheric effects, key problems to solve in estimating stream temperatures include both subpixel unmixing and multiple scattering. Additionally, fine resolution characteristics of the stream surface such as evaporative cooling due to wind, and water surface roughness, will effect measurements of radiant skin temperatures with TIR devices. We apply these corrections across the Green River and Yakima River watersheds in Washington State to assess the accuracy of remotely sensed stream surface temperature estimates made using fine resolution TIR imagery from a ground-based sensor (FLIR), medium resolution data from the airborne MASTER sensor, and coarse-resolution data from the Terra-ASTER satellite. We use linear spectral mixture analysis to isolate the fraction of land-leaving radiance originating from unresolved streams. To compensate the data for atmospheric effects we combine radiosonde profiles with a physically based radiative transfer model (MODTRAN) and an in-scene relative correction adapted from the ISAC algorithm. Laboratory values for water emissivities are used as a baseline estimate of stream emissivities. Emitted radiance reflected by trees in the stream near-bank environment is estimated from the height and canopy temperature, using a radiosity model.

Long-term climate patterns in Alaskan surface temperature and precipitation and their biological consequences

USGS Publications Warehouse

Simpson, James J.; Hufford, Gary L.; Fleming, Michael D.; Berg, Jared S.; Ashton, J.B.

2002-01-01

Mean monthly climate maps of Alaskan surface temperature and precipitation produced by the parameter-elevation regression on independent slopes model (PRISM) were analyzed. Alaska is divided into interior and coastal zones with consistent but different climatic variability separated by a transition region; it has maximum interannual variability but low long-term mean variability. Pacific decadal oscillation (PDO)- and El Nino Southern Oscillation (ENSO)-type events influence Alaska surface temperatures weakly (1-2/spl deg/C) statewide. PDO has a stronger influence than ENSO on precipitation but its influence is largely localized to coastal central Alaska. The strongest influence of Arctic oscillation (AO) occurs in northern and interior Alaskan precipitation. Four major ecosystems are defined. A major eco-transition zone occurs between the interior boreal forest and the coastal rainforest. Variability in insolation, surface temperature, precipitation, continentality, and seasonal changes in storm track direction explain the mapped ecosystems. Lack of westward expansion of the interior boreal forest into the western shrub tundra is influenced by the coastal marine boundary layer (enhanced cloud cover, reduced insolation, cooler surface and soil temperatures).

Design principles for contamination abatement in scientific satellites.

NASA Technical Reports Server (NTRS)

Naumann, R. J.

1972-01-01

It is shown that deposition of contamination films on satellite optics can be controlled by the following means: isolating critical optical surfaces from the rest of the spacecraft; avoiding or minimizing the use of nonmetallic material, particularly near or in line of sight of optical surfaces; avoiding materials with high vapor pressures; subjecting materials to vacuum baking prior to use, to drive off the volatile outgassing products; keeping the critical surfaces at temperatures above the ambient; avoiding elevated operational temperatures for nonmetallic materials; paying special attention to optics exposed to intense UV-, X-ray, or particular radiation; avoiding water-vapor sources; and directing RCS plumes away from critical surfaces. Methods of controlling particulate contaminants are also proposed.

High-Temperature Modal Survey of a Hot-Structure Control Surface

NASA Technical Reports Server (NTRS)

Spivey, Natalie Dawn

2010-01-01

Ground vibration tests or modal surveys are routinely conducted for supporting flutter analysis for subsonic and supersonic vehicles; however, for hypersonic vehicle applications, thermoelastic vibration testing techniques are not well established and are not routinely performed for supporting hypersonic flutter analysis. New high-temperature material systems, fabrication technologies and high-temperature sensors expand the opportunities to develop advanced techniques for performing ground vibration tests at elevated temperatures. High-temperature materials have the unique property of increasing in stiffness when heated. When these materials are incorporated into a hot-structure, which includes metallic components that decrease in stiffness with increasing temperature, the interaction between the two materials systems needs to be understood because that interaction could ultimately affect the hypersonic flutter analysis. Performing a high-temperature modal survey will expand the research database for hypersonics and will help build upon the understanding of the dual material interaction. This paper will discuss the vibration testing of the Carbon-Silicon Carbide Ruddervator Subcomponent Test Article which is a truncated version of the full-scale X-37 hot-structure control surface. In order to define the modal characteristics of the test article during the elevated-temperature modal survey, two series of room-temperature modal test configurations had to be performed. The room-temperature test series included one with the test article suspended from a bungee cord (free-free) and the second with it mounted on the strongback (fixed boundary condition) in NASA Dryden's Flight Loads Lab large nitrogen test chamber.

Determination of Interannual to Decadal Changes in Ice Sheet Mass Balance from Satellite Altimetry

NASA Technical Reports Server (NTRS)

Zwally, H. Jay; Busalacchi, Antonioa J. (Technical Monitor)

2001-01-01

A major uncertainty in predicting sea level rise is the sensitivity of ice sheet mass balance to climate change, as well as the uncertainty in present mass balance. Since the annual water exchange is about 8 mm of global sea level equivalent, the +/- 25% uncertainty in current mass balance corresponds to +/- 2 mm/yr in sea level change. Furthermore, estimates of the sensitivity of the mass balance to temperature change range from perhaps as much as - 10% to + 10% per K. Although the overall ice mass balance and seasonal and inter-annual variations can be derived from time-series of ice surface elevations from satellite altimetry, satellite radar altimeters have been limited in spatial coverage and elevation accuracy. Nevertheless, new data analysis shows mixed patterns of ice elevation increases and decreases that are significant in terms of regional-scale mass balances. In addition, observed seasonal and interannual variations in elevation demonstrate the potential for relating the variability in mass balance to changes in precipitation, temperature, and melting. From 2001, NASA's ICESat laser altimeter mission will provide significantly better elevation accuracy and spatial coverage to 86 deg latitude and to the margins of the ice sheets. During 3 to 5 years of ICESat-1 operation, an estimate of the overall ice sheet mass balance and sea level contribution will be obtained. The importance of continued ice monitoring after the first ICESat is illustrated by the variability in the area of Greenland surface melt observed over 17-years and its correlation with temperature. In addition, measurement of ice sheet changes, along with measurements of sea level change by a series of ocean altimeters, should enable direct detection of ice level and global sea level correlations.

Improving representation of canopy temperatures for modeling subcanopy incoming longwave radiation to the snow surface

NASA Astrophysics Data System (ADS)

Webster, Clare; Rutter, Nick; Jonas, Tobias

2017-09-01

A comprehensive analysis of canopy surface temperatures was conducted around a small and large gap at a forested alpine site in the Swiss Alps during the 2015 and 2016 snowmelt seasons (March-April). Canopy surface temperatures within the small gap were within 2-3°C of measured reference air temperature. Vertical and horizontal variations in canopy surface temperatures were greatest around the large gap, varying up to 18°C above measured reference air temperature during clear-sky days. Nighttime canopy surface temperatures around the study site were up to 3°C cooler than reference air temperature. These measurements were used to develop a simple parameterization for correcting reference air temperature for elevated canopy surface temperatures during (1) nighttime conditions (subcanopy shortwave radiation is 0 W m-2) and (2) periods of increased subcanopy shortwave radiation >400 W m-2 representing penetration of shortwave radiation through the canopy. Subcanopy shortwave and longwave radiation collected at a single point in the subcanopy over a 24 h clear-sky period was used to calculate a nighttime bulk offset of 3°C for scenario 1 and develop a multiple linear regression model for scenario 2 using reference air temperature and subcanopy shortwave radiation to predict canopy surface temperature with a root-mean-square error (RMSE) of 0.7°C. Outside of these two scenarios, reference air temperature was used to predict subcanopy incoming longwave radiation. Modeling at 20 radiometer locations throughout two snowmelt seasons using these parameterizations reduced the mean bias and RMSE to below 10 W m s-2 at all locations.

Thermal regimes and snowpack relations of periglacial talus slopes, Sierra Nevada, California, USA.

Treesearch

Constance I Millar; Robert D. Westfall; Diane L. Delany

2014-01-01

Thermal regimes of eight periglacial talus slopes, at contrasting elevations, aspects, and substrates, in the Sierra Nevada, California, had complex microclimatic patterns partially decoupled from external conditions. Over three years, warm seasons showed mean talus matrix temperatures and daily variances lower than surfaces and cooler than free-air; talus surface and...

Thermal Behavior of Cylindrical Buckling Restrained Braces at Elevated Temperatures

PubMed Central

Talebi, Elnaz; Tahir, Mahmood Md.; Yasreen, Airil

2014-01-01

The primary focus of this investigation was to analyze sequentially coupled nonlinear thermal stress, using a three-dimensional model. It was meant to shed light on the behavior of Buckling Restraint Brace (BRB) elements with circular cross section, at elevated temperature. Such bracing systems were comprised of a cylindrical steel core encased in a strong concrete-filled steel hollow casing. A debonding agent was rubbed on the core's surface to avoid shear stress transition to the restraining system. The numerical model was verified by the analytical solutions developed by the other researchers. Performance of BRB system under seismic loading at ambient temperature has been well documented. However, its performance in case of fire has yet to be explored. This study showed that the failure of brace may be attributed to material strength reduction and high compressive forces, both due to temperature rise. Furthermore, limiting temperatures in the linear behavior of steel casing and concrete in BRB element for both numerical and analytical simulations were about 196°C and 225°C, respectively. Finally it is concluded that the performance of BRB at elevated temperatures was the same as that seen at room temperature; that is, the steel core yields prior to the restraining system. PMID:24526915

Thermally Driven Electronic Topological Transition in FeTi

NASA Astrophysics Data System (ADS)

Yang, F. C.; Muñoz, J. A.; Hellman, O.; Mauger, L.; Lucas, M. S.; Tracy, S. J.; Stone, M. B.; Abernathy, D. L.; Xiao, Yuming; Fultz, B.

2016-08-01

Ab initio molecular dynamics, supported by inelastic neutron scattering and nuclear resonant inelastic x-ray scattering, showed an anomalous thermal softening of the M5- phonon mode in B 2 -ordered FeTi that could not be explained by phonon-phonon interactions or electron-phonon interactions calculated at low temperatures. A computational investigation showed that the Fermi surface undergoes a novel thermally driven electronic topological transition, in which new features of the Fermi surface arise at elevated temperatures. The thermally induced electronic topological transition causes an increased electronic screening for the atom displacements in the M5- phonon mode and an adiabatic electron-phonon interaction with an unusual temperature dependence.

Thermal Inactivation of Aerosolized Bacillus subtilis var. niger Spores

PubMed Central

Mullican, Charles L.; Buchanan, Lee M.; Hoffman, Robert K.

1971-01-01

A hot-air sterilizer capable of exposing airborne microorganisms to elevated temperatures with an almost instantaneous heating time was developed and evaluated. With this apparatus, aerosolized Bacillus subtilis var. niger spores were killed in about 0.02 sec when exposed to temperatures above 260 C. This is about 500 times faster than killing times reported by others. Extrapolation and comparison of data on the time and temperature required to klll B. subtilis var. niger spores on surfaces show that approximately the same killing time is required as is necessary for spores in air, if corrections are made for the heating time of the surface. PMID:5002138

Assimilation and High Resolution Forecasts of Surface and Near Surface Conditions for the 2010 Vancouver Winter Olympic and Paralympic Games

NASA Astrophysics Data System (ADS)

Bernier, Natacha B.; Bélair, Stéphane; Bilodeau, Bernard; Tong, Linying

2014-01-01

A dynamical model was experimentally implemented to provide high resolution forecasts at points of interests in the 2010 Vancouver Olympics and Paralympics Region. In a first experiment, GEM-Surf, the near surface and land surface modeling system, is driven by operational atmospheric forecasts and used to refine the surface forecasts according to local surface conditions such as elevation and vegetation type. In this simple form, temperature and snow depth forecasts are improved mainly as a result of the better representation of real elevation. In a second experiment, screen level observations and operational atmospheric forecasts are blended to drive a continuous cycle of near surface and land surface hindcasts. Hindcasts of the previous day conditions are then regarded as today's optimized initial conditions. Hence, in this experiment, given observations are available, observation driven hindcasts continuously ensure that daily forecasts are issued from improved initial conditions. GEM-Surf forecasts obtained from improved short-range hindcasts produced using these better conditions result in improved snow depth forecasts. In a third experiment, assimilation of snow depth data is applied to further optimize GEM-Surf's initial conditions, in addition to the use of blended observations and forecasts for forcing. Results show that snow depth and summer temperature forecasts are further improved by the addition of snow depth data assimilation.

Modeling of the heat transfer performance of plate-type dispersion nuclear fuel elements

NASA Astrophysics Data System (ADS)

Ding, Shurong; Huo, Yongzhong; Yan, XiaoQing

2009-08-01

Considering the mutual actions between fuel particles and the metal matrix, the three-dimensional finite element models are developed to simulate the heat transfer behaviors of dispersion nuclear fuel plates. The research results indicate that the temperatures of the fuel plate might rise more distinctly with considering the particle swelling and the degraded surface heat transfer coefficients with increasing burnup; the local heating phenomenon within the particles appears when their thermal conductivities are too low. With rise of the surface heat transfer coefficients, the temperatures within the fuel plate decrease; the temperatures of the fuel plate are sensitive to the variations of the heat transfer coefficients whose values are lower, but their effects are weakened and slight when the heat transfer coefficients increase and reach a certain extent. Increasing the heat generation rate leads to elevating the internal temperatures. The temperatures and the maximum temperature differences within the plate increase along with the particle volume fractions. The surface thermal flux goes up along with particle volume fractions and heat generation rates, but the effects of surface heat transfer coefficients are not evident.

Electronic properties and surface reactivity of SrO-terminated SrTiO3 and SrO-terminated iron-doped SrTiO3

PubMed Central

Staykov, Aleksandar; Tellez, Helena; Druce, John; Wu, Ji; Ishihara, Tatsumi; Kilner, John

2018-01-01

Abstract Surface reactivity and near-surface electronic properties of SrO-terminated SrTiO3 and iron doped SrTiO3 were studied with first principle methods. We have investigated the density of states (DOS) of bulk SrTiO3 and compared it to DOS of iron-doped SrTiO3 with different oxidation states of iron corresponding to varying oxygen vacancy content within the bulk material. The obtained bulk DOS was compared to near-surface DOS, i.e. surface states, for both SrO-terminated surface of SrTiO3 and iron-doped SrTiO3. Electron density plots and electron density distribution through the entire slab models were investigated in order to understand the origin of surface electrons that can participate in oxygen reduction reaction. Furthermore, we have compared oxygen reduction reactions at elevated temperatures for SrO surfaces with and without oxygen vacancies. Our calculations demonstrate that the conduction band, which is formed mainly by the d-states of Ti, and Fe-induced states within the band gap of SrTiO3, are accessible only on TiO2 terminated SrTiO3 surface while the SrO-terminated surface introduces a tunneling barrier for the electrons populating the conductance band. First principle molecular dynamics demonstrated that at elevated temperatures the surface oxygen vacancies are essential for the oxygen reduction reaction. PMID:29535797

Effect of LID (Registered) processing on the microstructure and mechanical properties of Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo titanium foil-gauge materials

NASA Technical Reports Server (NTRS)

Balckburn, Linda B.

1987-01-01

A study was undertaken to determine the mechanical properties and microstructures resulting from Liquid Interface Diffusion (LID -Registered) processing of foil-gauge specimens of Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo coated with varying amounts of LID material. In addition, the effects of various elevated temperature exposures on the concentration profiles of the LID alloying elements were investigated, using specimens with a narrow strip of LID material applied to the surface. Room and elevated temperature tensile properties were determined for both coated and uncoated specimens. Optical microscopy was used to examine alloy microstructures, and scanning electron microscopy to examine fracture surface morphologies. The chemical concentration profiles of the strip-coated specimens were determined with an electron microprobe.

Hemodialysis Catheter Heat Transfer for Biofilm Prevention and Treatment.

PubMed

Richardson, Ian P; Sturtevant, Rachael; Heung, Michael; Solomon, Michael J; Younger, John G; VanEpps, J Scott

2016-01-01

Central line-associated bloodstream infections (CLABSIs) are not easily treated, and many catheters (e.g., hemodialysis catheters) are not easily replaced. Biofilms (the source of infection) on catheter surfaces are notoriously difficult to eradicate. We have recently demonstrated that modest elevations of temperature lead to increased staphylococcal susceptibility to vancomycin and significantly soften the biofilm matrix. In this study, using a combination of microbiological, computational, and experimental studies, we demonstrate the efficacy, feasibility, and safety of using heat as an adjuvant treatment for infected hemodialysis catheters. Specifically, we show that treating with heat in the presence of antibiotics led to additive killing of Staphylococcus epidermidis with similar trends seen for Staphylococcus aureus and Klebsiella pneumoniae. The magnitude of temperature elevation required is relatively modest (45-50°C) and similar to that used as an adjuvant to traditional cancer therapy. Using a custom-designed benchtop model of a hemodialysis catheter, positioned with tip in the human vena cava as well as computational fluid dynamic simulations, we demonstrate that these temperature elevations are likely achievable in situ with minimal increased in overall blood temperature.

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

Hasegawa, Tomo; Shahed, Syed Mohammad Fakruddin; Sainoo, Yasuyuki

We formed an epitaxial film of CeO{sub 2}(111) by sublimating Ce atoms on Ru(0001) surface kept at elevated temperature in an oxygen ambient. X-ray photoemission spectroscopy measurement revealed a decrease of Ce{sup 4+}/Ce{sup 3+} ratio in a small temperature window of the growth temperature between 1070 and 1096 K, which corresponds to the reduction of the CeO{sub 2}(111). Scanning tunneling microscope image showed that a film with a wide terrace and a sharp step edge was obtained when the film was grown at the temperatures close to the reduction temperature, and the terrace width observed on the sample grown atmore » 1060 K was more than twice of that grown at 1040 K. On the surface grown above the reduction temperature, the surface with a wide terrace and a sharp step was confirmed, but small dots were also seen in the terrace part, which are considerably Ce atoms adsorbed at the oxygen vacancies on the reduced surface. This experiment demonstrated that it is required to use the substrate temperature close to the reduction temperature to obtain CeO{sub 2}(111) with wide terrace width and sharp step edges.« less

Modeling of microclimatic characteristics of highland area

NASA Astrophysics Data System (ADS)

Sitdikova, Iuliia; Rusin, Igor

2013-04-01

Microclimatic characteristics of highlands may vary considerably over distances of a few meters depending on slope and aspect. There is a problem of estimation of components of surface energy balance based on observation of single stations for description of microclimate highlands. The aim of this paper is to develop a method that would restore microclimatic characteristics of terrain, based on observations of the single station, by physical extrapolation. The input parameters to obtain the microclimatic characteristics are as follows: air temperature, relative humidity, and wind speed on two vertical levels, air pressure, surface temperature, direct and diffused solar radiation and surface albedo. The recent version of the Meteorological Radiation Model (MRM) has been used to calculate a solar radiation over the area and to estimate an influence of cloudiness amounts. The height, slope and aspect were accounted at each point with using a digital elevation model. Have been supposed that air temperature and specific humidity vary with altitude only. Net radiation was calculated at all points of the area. Supposed that the difference between the surface temperature and the air temperature is a linear function of net radiation. The empirical coefficient, which depends on wind speed with adjustment of given area. Latent and sensible fluxes are calculated by using the modified Bowen ratio, which varies on the area. Method was tested on field research in Krasnodar region (RF). The meteorological observations were made every three hour on actinometric and gradient sites. The editional gradient site with different orientation of the slope was organized from 400 meters of the main site. Topographic survey of area was made 1x1,3 km in size for a digital elevation model constructing. At all points of the area of radiation and heat balance were calculated. The results of researches are the maps of surface temperature, net radiation, latent and sensible fluxes. The calculations showed that the average value of components of heat balance by area differ significantly from the data observed on meteorological station.

Consequences arising from elevated surface temperatures on human blood.

PubMed

Hamilton, Kathrin F; Schmidt, Verena I; Mager, Ilona; Schmitz-Rode, Thomas; Steinseifer, Ulrich

2010-09-01

Heat in blood pumps is generated by losses of the electrical motor and bearings. In the presented study the influence of tempered surfaces on bulk blood and adhesions on these surfaces was examined. Titanium alloy housing dummies were immersed in 25 mL heparinized human blood. The dummies were constantly tempered at specific temperatures (37-45 °C) over 15 min. Blood samples were withdrawn for blood parameter analysis and the determination of the plasmatic coagulation cascade. The quantities of adhesion on surfaces were determined by drained weight. Blood parameters do not alter significantly up to surface temperatures of 45 °C. In comparison to the control specimen, a drop in the platelet count can be observed, but is not significantly temperature dependent. The mean mass of adhesions at 41 °C increased up to 66% compared to 37 °C. Thus, heat generated in electrical motors and contact bearings may influence the amount of adhesions on surfaces. © 2010, Copyright the Authors. Artificial Organs © 2010, International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Marine Microbial Gene Abundance and Community Composition in Response to Ocean Acidification and Elevated Temperature in Two Contrasting Coastal Marine Sediments.

PubMed

Currie, Ashleigh R; Tait, Karen; Parry, Helen; de Francisco-Mora, Beatriz; Hicks, Natalie; Osborn, A Mark; Widdicombe, Steve; Stahl, Henrik

2017-01-01

Marine ecosystems are exposed to a range of human-induced climate stressors, in particular changing carbonate chemistry and elevated sea surface temperatures as a consequence of climate change. More research effort is needed to reduce uncertainties about the effects of global-scale warming and acidification for benthic microbial communities, which drive sedimentary biogeochemical cycles. In this research, mesocosm experiments were set up using muddy and sandy coastal sediments to investigate the independent and interactive effects of elevated carbon dioxide concentrations (750 ppm CO 2 ) and elevated temperature (ambient +4°C) on the abundance of taxonomic and functional microbial genes. Specific quantitative PCR primers were used to target archaeal, bacterial, and cyanobacterial/chloroplast 16S rRNA in both sediment types. Nitrogen cycling genes archaeal and bacterial ammonia monooxygenase ( amoA ) and bacterial nitrite reductase ( nirS ) were specifically targeted to identify changes in microbial gene abundance and potential impacts on nitrogen cycling. In muddy sediment, microbial gene abundance, including amoA and nirS genes, increased under elevated temperature and reduced under elevated CO 2 after 28 days, accompanied by shifts in community composition. In contrast, the combined stressor treatment showed a non-additive effect with lower microbial gene abundance throughout the experiment. The response of microbial communities in the sandy sediment was less pronounced, with the most noticeable response seen in the archaeal gene abundances in response to environmental stressors over time. 16S rRNA genes ( amoA and nirS ) were lower in abundance in the combined stressor treatments in sandy sediments. Our results indicated that marine benthic microorganisms, especially in muddy sediments, are susceptible to changes in ocean carbonate chemistry and seawater temperature, which ultimately may have an impact upon key benthic biogeochemical cycles.

Surface compositional variations of Mo-47Re alloy as a function of temperature

NASA Technical Reports Server (NTRS)

Hoekje, S. J.; Outlaw, R. A.; Sankaran, S. N.

1993-01-01

Molybdenum-rhenium alloys are candidate materials for the National Aero-Space Plane (NASP) as well as for other applications in generic hypersonics. These materials are expected to be subjected to high-temperature (above 1200 C) casual hydrogen (below 50 torr), which could potentially degrade the material strength. Since the uptake of hydrogen may be controlled by the contaminant surface barriers, a study of Mo-47Re was conducted to examine the variations in surface composition as a function of temperature from 25 C to 1000 C. Pure molybdenum and rhenium were also examined and the results compared with those for the alloy. The analytical techniques employed were Auger electron spectroscopy, electron energy loss spectroscopy, ion scattering spectroscopy, and x ray photoelectron spectroscopy. The native surface was rich in metallic oxides that disappeared at elevated temperatures. As the temperature increased, the carbon and oxygen disappeared by 800 C and the surface was subsequently populated by the segregation of silicon, presumably from the grain boundaries. The alloy readily chemisorbed oxygen, which disappeared with heating. The disappearance temperature progressively increased for successive dosings. When the alloy was exposed to 800 torr of hydrogen at 900 C for 1 hour, no hydrogen interaction was observed.

Tribological behavior of CrN-coated Cr-Mo-V steels used as die materials

NASA Astrophysics Data System (ADS)

Çelik, Gülşah Aktaş; Polat, Şeyda; Atapek, Ş. Hakan

2017-12-01

DIN 1.2343 and 1.2367 steels are commonly used as die materials in aluminum extrusion, and single/duplex/multi-coatings enhance their surface properties. The design of an appropriate substrate/coating system is important for improving the tribological performance of these steels under service conditions because the load-carrying capacity of the system can be increased by decreasing the plastic deformation of the substrate. In this study, the tribological behavior of CrN-coated Cr-Mo-V steels (DIN 1.2343, 1.2367, and 1.2999 grades) was investigated using different setups and tribological pairs at room and elevated temperatures. The aim of this study was to reveal the wear resistance of a suggested system (1.2999/CrN) not yet studied and to understand both the wear and the failure characteristics of coated systems. The results showed that (i) among the steels studied, the DIN 1.2999 grade steel exhibited the lowest friction coefficient because it had the highest load-carrying capacity as a result of secondary hardening at elevated temperatures; (ii) at room temperature, both abrasive tracks and adhesive layers were observed on the worn surfaces; and (iii) a combination of chemical reactions and progressive oxidation caused aluminum adhesion on the worn surface, and the detachment of droplets and microcracking were the characteristic damage mechanisms at high temperatures.

In situ soft XAS study on nickel-based layered cathode material at elevated temperatures: A novel approach to study thermal stability

DOE PAGES

Yoon, Won -Sub; Yang, Xiao -Qing; Haas, Otto; ...

2014-10-29

Tracking thermally induced reactions has always been challenging for electrode materials of electrochemical battery systems. Traditionally, a variety of calorimetric techniques and in situ XRD at elevated temperatures has been used to evaluate the thermal stability of electrode materials. These techniques are capable of providing variations in heat capacity, mass and average bulk composition of materials only. Herein, we report investigation of thermal characteristics of Li 0.33Ni 0.8Co 0.15Al 0.05O 2 by using in situ soft XAS measurements in combination with XRD. Fluorescence yield and partial electron yield measurements are used simultaneously to obtain element selective surface and bulk information.more » Fluorescence yield measurements reveal no energy change of the absorption peak and thus no valence state change in the bulk. However, electron yield measurements indicate that NiO-type rock salt structure is formed at the surface at temperatures above 200°C while no evidence for a surface reaction near Co sites in investigated temperature range is found. These results clearly show that in situ soft XAS can give a unique understanding of the role of each element in the structural transformation under thermal abuse offering a useful guidance in developing new battery system with improved safety performance.« less

Optical Fier Based System for Multiple Thermophysical Properties for Glove Box, Hot Cell and In-Pile Application

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

Ban, Heng

Thermal diffusivity of materials is of interest in nuclear applications at temperatures in excess of 2000°C. Commercial laser flash apparatus (LFA) that heats samples with a furnace typically do not reach these elevated temperatures nor are they easily adapted to a glove-box or hot cell environment. In this research, we performed work on an experimental technique using single laser surface heating, i.e. heating the disk sample only at its front surface with the continuous wave (CW) laser, to allow measurement of thermal diffusivity at very high temperatures within a small chamber. Thermal diffusivity is measured using a separate pulsed lasermore » on the front side and IR detector on the rear side. The new way of heating provides easy operation in comparison to other heating methods. The measurement of sample reference temperature is needed for the measured thermal diffusivity. A theoretical model was developed to describe transient heat transfer across the sample due to the laser pulse, starting from the steady state temperature of the sample heated by the CW laser. The experimental setup was established with a 500W CW laser and maximum 50 Joule pulse laser irradiated at the front surface of the sample. The induced temperature rise at the rear surface, along with the steady-state temperature at the front surface, was recorded for the determination of thermal diffusivity and the sample temperature. Three samples were tested in vacuum over a wide temperature range of 500°C to 2100°C, including graphite, Inconel 600 and tungsten. The latter two samples were coated with sprayed graphite on their front surfaces in order to achieve surface absorption/emission needs, i.e. high absorptivity of the front surface against relatively low emissivity of the rear surface. Thermal diffusivity of graphite determined by our system are within a 5% difference of the commercial LFA data at temperatures below 1300°C and agree well with its trend at higher temperatures. Good agreement would also exist for Inconel 600 and tungsten. Despite large uncertainty of measuringthe sample temperature, the uncertainties of thermal diffusivity are less than 6% for all samples at elevated temperatures. The results indicate that single laser surface heating could be convenient and practical for the application of the LFA measurements without extra uncertainty, as temperature dependence of thermal diffusivity is usually negligible in the sample. Moreover, it is concluded that unequal surface treatment, i.e., high absorption on the front side and low emission on the rear side, greatly improves the measurement in serval aspects: less power requirement of the CW laser, less uncertainty of measured thermal diffusivity, and more uniform temperature distribution in the sample. The result of this research can be used as a general guideline for the design of this type of measurement system for nuclear applications. It can also be used directly to design and build a system similar to the one implemented in this project.« less

Sputtering graphite coating to improve the elevated-temperature cycling ability of the LiMn2O4 electrode.

PubMed

Wang, Jiexi; Zhang, Qiaobao; Li, Xinhai; Wang, Zhixing; Guo, Huajun; Xu, Daguo; Zhang, Kaili

2014-08-14

To improve the cycle performance of LiMn2O4 at elevated temperature, a graphite layer is introduced to directly cover the surface of a commercial LiMn2O4-based electrode via room-temperature DC magnetron sputtering. The as-modified cathodes display improved capacity retention as compared to the bare LiMn2O4 cathode (BLMO) at 55 °C. When sputtering graphite for 30 min, the sample shows the best cycling performance at 55 °C, maintaining 96.2% capacity retention after 200 cycles. Reasons with respect to the graphite layer for improving the elevated-temperature performance of LiMn2O4 are systematically investigated via the methods of cyclic voltammetry, electrochemical impedance spectroscopy, X-ray photoelectron spectrometry, scanning and transmission electron microscopy, X-ray diffraction and inductively coupled plasma-atomic emission spectrometry. The results demonstrate that the graphite coated LiMn2O4 cathode has much less increased electrode polarization and electrochemical impedance than BLMO during the elevated-temperature cycling process. Furthermore, the graphite layer is able to alleviate the severe dissolution of manganese ions into the electrolyte and mitigate the morphological and structural degradation of LiMn2O4 during cycling. A model for the electrochemical kinetics process is also suggested for explaining the roles of the graphite layer in suppressing the Mn dissolution.

Greenland ice sheet surface temperature, melt and mass loss: 2000-06

USGS Publications Warehouse

Hall, D.K.; Williams, R.S.; Luthcke, S.B.; DiGirolamo, N.E.

2008-01-01

A daily time series of 'clear-sky' surface temperature has been compiled of the Greenland ice sheet (GIS) using 1 km resolution moderate-resolution imaging spectroradiometer (MODIS) land-surface temperature (LST) maps from 2000 to 2006. We also used mass-concentration data from the Gravity Recovery and Climate Experiment (GRACE) to study mass change in relationship to surface melt from 2003 to 2006. The mean LST of the GIS increased during the study period by ???0.27??Ca-1. The increase was especially notable in the northern half of the ice sheet during the winter months. Melt-season length and timing were also studied in each of the six major drainage basins. Rapid (<15 days) and sustained mass loss below 2000 m elevation was triggered in 2004 and 2005 as recorded by GRACE when surface melt begins. Initiation of large-scale surface melt was followed rapidly by mass loss. This indicates that surface meltwater is flowing rapidly to the base of the ice sheet, causing acceleration of outlet glaciers, thus highlighting the metastability of parts of the GIS and the vulnerability of the ice sheet to air-temperature increases. If air temperatures continue to rise over Greenland, increased surface melt will play a large role in ice-sheet mass loss.

Elevated surface temperature depresses survival of banner-tailed kangaroo rats: will climate change cook a desert icon?

PubMed

Moses, Martin R; Frey, Jennifer K; Roemer, Gary W

2012-01-01

Modest increases in global temperature have been implicated in causing population extirpations and range shifts in taxa inhabiting colder environs and in ectotherms whose thermoregulation is more closely tied to environmental conditions. Many arid-adapted endotherms already experience conditions at their physiological limits, so it is conceivable that they could be similarly affected by warming temperatures. We explored how climatic variables might influence the apparent survival of the banner-tailed kangaroo rat (Dipodomys spectabilis), a rodent endemic to the Chihuahuan Desert of North America and renowned for its behavioral and physiological adaptations to arid environments. Relative variable weight, strength of variable relationships, and other criteria indicated that summer, diurnal land surface temperature (SD_LST) was the primary environmental driver of apparent survival in these arid-adapted rodents. Higher temperatures had a negative effect on apparent survival, which ranged from 0.15 (SE = 0.04) for subadults to 0.50 (SE = 0.07) for adults. Elevated SD_LST may negatively influence survival through multiple pathways, including increased water loss and energy expenditure that could lead to chronic stress and/or hyperthermia that could cause direct mortality. Land surface temperatures are predicted to increase by as much 6.5°C by 2099, reducing apparent survival of adults to ~0.15 in some regions of the species' range, possibly causing a shift in their distribution. The relationship between SD_LST and survival suggests a mechanism whereby physiological tolerances are exceeded resulting in a reduction to individual fitness that may ultimately cause a shift in the species' range over time.

Fabrication of titanium thermal protection system panels by the NOR-Ti-bond process

NASA Technical Reports Server (NTRS)

Wells, R. R.

1971-01-01

A method for fabricating titanium thermal protection system panels is described. The method has the potential for producing wide faying surface bonds to minimize temperature gradients and thermal stresses resulting during service at elevated temperatures. Results of nondestructive tests of the panels are presented. Concepts for improving the panel quality and for improved economy in production are discussed.

Proof of concept for the simplified breakdown of cellulose by combining Pseudomonas putida strains with surface displayed thermophilic endocellulase, exocellulase and β-glucosidase.

PubMed

Tozakidis, Iasson E P; Brossette, Tatjana; Lenz, Florian; Maas, Ruth M; Jose, Joachim

2016-06-10

The production and employment of cellulases still represents an economic bottleneck in the conversion of lignocellulosic biomass to biofuels and other biocommodities. This process could be simplified by displaying the necessary enzymes on a microbial cell surface. Such an approach, however, requires an appropriate host organism which on the one hand can withstand the rough environment coming along with lignocellulose hydrolysis, and on the other hand does not consume the generated glucose so that it remains available for subsequent fermentation steps. The robust soil bacterium Pseudomonas putida showed a strongly reduced uptake of glucose above a temperature of 50 °C, while remaining structurally intact hence recyclable, which makes it suitable for cellulose hydrolysis at elevated temperatures. Consequently, three complementary, thermophilic cellulases from Ruminiclostridium thermocellum were displayed on the surface of the bacterium. All three enzymes retained their activity on the cell surface. A mixture of three strains displaying each one of these enzymes was able to synergistically hydrolyze filter paper at 55 °C, producing 20 μg glucose per mL cell suspension in 24 h. We could establish Pseudomonas putida as host for the surface display of cellulases, and provided proof-of-concept for a fast and simple cellulose breakdown process at elevated temperatures. This study opens up new perspectives for the application of P. putida in the production of biofuels and other biotechnological products.

Modelling study of sea breezes in a complex coastal environment

NASA Astrophysics Data System (ADS)

Cai, X.-M.; Steyn, D. G.

This study investigates a mesoscale modelling of sea breezes blowing from a narrow strait into the lower Fraser valley (LFV), British Columbia, Canada, during the period of 17-20 July, 1985. Without a nudging scheme in the inner grid, the CSU-RAMS model produces satisfactory wind and temperature fields during the daytime. In comparison with observation, the agreement indices for surface wind and temperature during daytime reach about 0.6 and 0.95, respectively, while the agreement indices drop to 0.4 at night. In the vertical, profiles of modelled wind and temperature generally agree with tethersonde data collected on 17 and 19 July. The study demonstrates that in late afternoon, the model does not capture the advection of an elevated warm layer which originated from land surfaces outside of the inner grid. Mixed layer depth (MLD) is calculated from model output of turbulent kinetic energy field. Comparison of MLD results with observation shows that the method generates a reliable MLD during the daytime, and that accurate estimates of MLD near the coast require the correct simulation of wind conditions over the sea. The study has shown that for a complex coast environment like the LFV, a reliable modelling study depends not only on local surface fluxes but also on elevated layers transported from remote land surfaces. This dependence is especially important when local forcings are weak, for example, during late afternoon and at night.

Investigation of Water Dissociation and Surface Hydroxyl Stability on Pure and Ni-Modified CoOOH by Ambient Pressure Photoelectron Spectroscopy

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

Chen, Zhu; Kronawitter, Coleman X.; Waluyo, Iradwikanari

Water adsorption and reaction on pure and Ni-modified CoOOH nanowires were investigated using ambient pressure photoemission spectroscopy (APPES). The unique capabilities of APPES enable us to observe water dissociation and monitor formation of surface species on pure and Ni-modified CoOOH under elevated pressures and temperatures for the first time. Over a large range of pressures (UHV to 1 Torr), water dissociates readily on the pure and Ni-modified CoOOH surfaces at 27 °C. With an increase in H 2O pressure, a greater degree of surface hydroxylation was observed for all samples. At 1 Torr H 2O, ratios of different oxygen speciesmore » indicate a transformation of CoOOH to CoO xH y in pure and Ni-modified CoOOH. In temperature dependent studies, desorption of weakly bound water and surface dehydroxylation were observed with increasing temperature. In conclusion, larger percentages of surface hydroxyl groups at higher temperatures were observed on Ni-modified CoOOH compared to pure CoOOH, which indicates an increased stability of surface hydroxyl groups on these Ni-modified surfaces.« less

Investigation of Water Dissociation and Surface Hydroxyl Stability on Pure and Ni-Modified CoOOH by Ambient Pressure Photoelectron Spectroscopy

DOE PAGES

Chen, Zhu; Kronawitter, Coleman X.; Waluyo, Iradwikanari; ...

2017-09-07

Water adsorption and reaction on pure and Ni-modified CoOOH nanowires were investigated using ambient pressure photoemission spectroscopy (APPES). The unique capabilities of APPES enable us to observe water dissociation and monitor formation of surface species on pure and Ni-modified CoOOH under elevated pressures and temperatures for the first time. Over a large range of pressures (UHV to 1 Torr), water dissociates readily on the pure and Ni-modified CoOOH surfaces at 27 °C. With an increase in H 2O pressure, a greater degree of surface hydroxylation was observed for all samples. At 1 Torr H 2O, ratios of different oxygen speciesmore » indicate a transformation of CoOOH to CoO xH y in pure and Ni-modified CoOOH. In temperature dependent studies, desorption of weakly bound water and surface dehydroxylation were observed with increasing temperature. In conclusion, larger percentages of surface hydroxyl groups at higher temperatures were observed on Ni-modified CoOOH compared to pure CoOOH, which indicates an increased stability of surface hydroxyl groups on these Ni-modified surfaces.« less

The Impact of Elevated Temperatures on Continental Carbon Cycling in the Paleogene

NASA Astrophysics Data System (ADS)

Pancost, R. D.; Handley, L.; Taylor, K. W.; Collinson, M. E.; Weijers, J.; Talbot, H. M.; Hollis, C. J.; Grogan, D. S.; Whiteside, J. H.

2010-12-01

Recent climate and biogeochemical modelling suggests that methane flux from wetlands and soils was greater during past greenhouse climates, due to a combination of higher continental temperatures, an enhanced hydrological cycle, and elevated primary production. Here, we examine continental environments in the Paleogene using a range of biomarker proxies (complemented by palaeobotanical approaches), including air temperatures derived from the distribution of soil bacterial glycerol dialkyl glycerol tetraethers (the MBT/CBT proxy), as well as evidence from wetland and lacustrine settings for enhanced methane cycling. Previously published and new MBT/CBT records parallel sea surface temperature records, suggesting elevated continental temperatures during the Eocene even at mid- to high latitudes (New Zealand, 20-28°C; the Arctic, 17°C; across the Sierra Nevada, 15-25°C; and SE England, 20-30°C). Such temperatures are broadly consistent with paleobotanical records and would have directly led to increased methane production via the metabolic impact of temperature on rates of methanogenesis. To test this, we have determined the distributions and carbon isotopic compositions of archaeal ether lipids and bacterial hopanoids in thermally immature Eocene lignites. In particular, the Cobham lignite, deposited in SE England and spanning the PETM, is characterised by markedly higher concentrations of both methanogen and methanotroph biomarkers compared to modern and Holocene temperate peats. Elevated temperatures, by fostering either stratification and/or decreased oxygen solubility, could have also led to enhanced methane production in Paleogene lakes. Both the Messel Shale (Germany) and Green River Formation, specifically the Parachute Creek oil shale horizons (Utah and Wyoming), are characterised by strongly reducing conditions (including euxinic conditions in the latter), as well as abundant methanogen and methanotroph biomarkers. Such results confirm model predictions of elevated Eocene methane levels relative to the Holocene (x10), but suggest that even these could be underestimates as they do not take into account lacustrine production and are generally characterised by lower high latitude temperatures than proxies suggest.

Untangling the contribution of aspect, drainage position and elevation to the spatial variability of fine surface fuels in south east Australian forests

NASA Astrophysics Data System (ADS)

Sheridan, Gary; nyman, petter; Duff, Tom; Baillie, Craig; Bovill, William; Lane, Patrick; Tolhurst, Kevin

2015-04-01

The prediction of fuel moisture content is important for estimating the rate of spread of wildfires, the ignition probability of firebrands, and for the efficient scheduling of prescribed fire. The moisture content of fine surface fuels varies spatially at large scales (10's to 100's km) due to variation in meteorological variables (eg. temperature, relative humidity, precipitation). At smaller scales (100's of metres) in steep topography spatial variability is attributed to topographic influences that include differences in radiation due to aspect and slope, differences in precipitation, temperature and relative humidity due to elevation, and differences in soil moisture due to hillslope drainage position. Variable forest structure and canopy shading adds further to the spatial variability in surface fuel moisture. In this study we aim to combine daily 5km resolution gridded weather data with 20m resolution DEM and vegetation structure data to predict the spatial variability of fine surface fuels in steep topography. Microclimate stations were established in south east Australia to monitor surface fine fuel moisture continuously (every 15 minutes) using newly developed instrumented litter packs, in addition to temperature and relative humidity measurements inside the litter pack, and measurement of precipitation and energy inputs above and below the forest canopy. Microclimate stations were established across a gradient of aspect (5 stations), drainage position (7 stations), elevation (15 stations), and canopy cover conditions (6 stations). The data from this extensive network of microclimate stations across a broad spectrum of topographic conditions is being analysed to enable the downscaling of gridded weather data to spatial scales that are relevant to the connectivity of wildfire fuels and to the scheduling and outcome of prescribed fires. The initial results from the first year of this study are presented here.

Liquid oxygen liquid acquisition device bubble point tests with high pressure lox at elevated temperatures

NASA Astrophysics Data System (ADS)

Jurns, J. M.; Hartwig, J. W.

2012-04-01

When transferring propellant in space, it is most efficient to transfer single phase liquid from a propellant tank to an engine. In earth's gravity field or under acceleration, propellant transfer is fairly simple. However, in low gravity, withdrawing single-phase fluid becomes a challenge. A variety of propellant management devices (PMDs) are used to ensure single-phase flow. One type of PMD, a liquid acquisition device (LAD) takes advantage of capillary flow and surface tension to acquire liquid. The present work reports on testing with liquid oxygen (LOX) at elevated pressures (and thus temperatures) (maximum pressure 1724 kPa and maximum temperature 122 K) as part of NASA's continuing cryogenic LAD development program. These tests evaluate LAD performance for LOX stored in higher pressure vessels that may be used in propellant systems using pressure fed engines. Test data shows a significant drop in LAD bubble point values at higher liquid temperatures, consistent with lower liquid surface tension at those temperatures. Test data also indicates that there are no first order effects of helium solubility in LOX on LAD bubble point prediction. Test results here extend the range of data for LOX fluid conditions, and provide insight into factors affecting predicting LAD bubble point pressures.

Liquid Oxygen Liquid Acquisition Device Bubble Point Tests with High Pressure LOX at Elevated Temperatures

NASA Technical Reports Server (NTRS)

Jurns, John M.; Hartwig, Jason W.

2011-01-01

When transferring propellant in space, it is most efficient to transfer single phase liquid from a propellant tank to an engine. In earth s gravity field or under acceleration, propellant transfer is fairly simple. However, in low gravity, withdrawing single-phase fluid becomes a challenge. A variety of propellant management devices (PMD) are used to ensure single-phase flow. One type of PMD, a liquid acquisition device (LAD) takes advantage of capillary flow and surface tension to acquire liquid. The present work reports on testing with liquid oxygen (LOX) at elevated pressures (and thus temperatures) (maximum pressure 1724 kPa and maximum temperature 122K) as part of NASA s continuing cryogenic LAD development program. These tests evaluate LAD performance for LOX stored in higher pressure vessels that may be used in propellant systems using pressure fed engines. Test data shows a significant drop in LAD bubble point values at higher liquid temperatures, consistent with lower liquid surface tension at those temperatures. Test data also indicates that there are no first order effects of helium solubility in LOX on LAD bubble point prediction. Test results here extend the range of data for LOX fluid conditions, and provide insight into factors affecting predicting LAD bubble point pressures.

High tolerance to temperature and salinity change should enable scleractinian coral Platygyra acuta from marginal environments to persist under future climate change.

PubMed

Chui, Apple Pui Yi; Ang, Put

2017-01-01

With projected changes in the marine environment under global climate change, the effects of single stressors on corals have been relatively well studied. However, more focus should be placed on the interactive effects of multiple stressors if their impacts upon corals are to be assessed more realistically. Elevation of sea surface temperature is projected under global climate change, and future increases in precipitation extremes related to the monsoon are also expected. Thus, the lowering of salinity could become a more common phenomenon and its impact on corals could be significant as extreme precipitation usually occurs during the coral spawning season. Here, we investigated the interactive effects of temperature [24, 27 (ambient), 30, 32°C] and salinity [33 psu (ambient), 30, 26, 22, 18, 14 psu] on larval settlement, post-settlement survival and early growth of the dominant coral Platygyra acuta from Hong Kong, a marginal environment for coral growth. The results indicate that elevated temperatures (+3°C and +5°C above ambient) did not have any significant effects on larval settlement success and post-settlement survival for up to 56 days of prolonged exposure. Such thermal tolerance was markedly higher than that reported in the literature for other coral species. Moreover, there was a positive effect of these elevated temperatures in reducing the negative effects of lowered salinity (26 psu) on settlement success. The enhanced settlement success brought about by elevated temperatures, together with the high post-settlement survival recorded up to 44 and 8 days of exposure under +3°C and +5°C ambient respectively, resulted in the overall positive effects of elevated temperatures on recruitment success. These results suggest that projected elevation in temperature over the next century should not pose any major problem for the recruitment success of P. acuta. The combined effects of higher temperatures and lowered salinity (26 psu) could even be beneficial. Therefore, corals that are currently present in marginal environments like Hong Kong, as exemplified by the dominant P. acuta, are likely to persist in a warmer and intermittently less saline, future ocean.

High tolerance to temperature and salinity change should enable scleractinian coral Platygyra acuta from marginal environments to persist under future climate change

PubMed Central

Chui, Apple Pui Yi; Ang, Put

2017-01-01

With projected changes in the marine environment under global climate change, the effects of single stressors on corals have been relatively well studied. However, more focus should be placed on the interactive effects of multiple stressors if their impacts upon corals are to be assessed more realistically. Elevation of sea surface temperature is projected under global climate change, and future increases in precipitation extremes related to the monsoon are also expected. Thus, the lowering of salinity could become a more common phenomenon and its impact on corals could be significant as extreme precipitation usually occurs during the coral spawning season. Here, we investigated the interactive effects of temperature [24, 27 (ambient), 30, 32°C] and salinity [33 psu (ambient), 30, 26, 22, 18, 14 psu] on larval settlement, post-settlement survival and early growth of the dominant coral Platygyra acuta from Hong Kong, a marginal environment for coral growth. The results indicate that elevated temperatures (+3°C and +5°C above ambient) did not have any significant effects on larval settlement success and post-settlement survival for up to 56 days of prolonged exposure. Such thermal tolerance was markedly higher than that reported in the literature for other coral species. Moreover, there was a positive effect of these elevated temperatures in reducing the negative effects of lowered salinity (26 psu) on settlement success. The enhanced settlement success brought about by elevated temperatures, together with the high post-settlement survival recorded up to 44 and 8 days of exposure under +3°C and +5°C ambient respectively, resulted in the overall positive effects of elevated temperatures on recruitment success. These results suggest that projected elevation in temperature over the next century should not pose any major problem for the recruitment success of P. acuta. The combined effects of higher temperatures and lowered salinity (26 psu) could even be beneficial. Therefore, corals that are currently present in marginal environments like Hong Kong, as exemplified by the dominant P. acuta, are likely to persist in a warmer and intermittently less saline, future ocean. PMID:28622371

Novel Phenylethynyl Imide Silanes as Coupling Agents for Titanium Alloy

NASA Technical Reports Server (NTRS)

Park, C.; Lowther, S. E.; Smith, J. G., Jr.; Conell, J. W.; Hergenrother, P. M.; SaintClair, T. L.

2004-01-01

The durability of titanium (Ti) alloys bonded with high temperature adhesives such as polyimides has failed to attain the level of performance required for many applications. The problem to a large part is attributed to the instability of the surface treatment on the Ti substrate. Although Ti alloy adhesive specimens with surface treatments such as chromic acid anodization, Pasa-Jell, Turco, etc. have provided high initial mechanical properties, these properties have decreased as a function of aging at ambient temperature and faster, when aged at elevated temperatures or in a hot-wet environment. As part of the High Speed Civil Transport program where Ti honeycomb sandwich structure must perform for 60,000 hours at 177 C, work was directed to the development of environmentally safe, durable Ti alloy surface treatments.

Nanostructuring of Palladium with Low-Temperature Helium Plasma

PubMed Central

Fiflis, P.; Christenson, M.P.; Connolly, N.; Ruzic, D.N.

2015-01-01

Impingement of high fluxes of helium ions upon metals at elevated temperatures has given rise to the growth of nanostructured layers on the surface of several metals, such as tungsten and molybdenum. These nanostructured layers grow from the bulk material and have greatly increased surface area over that of a not nanostructured surface. They are also superior to deposited nanostructures due to a lack of worries over adhesion and differences in material properties. Several palladium samples of varying thickness were biased and exposed to a helium helicon plasma. The nanostructures were characterized as a function of the thickness of the palladium layer and of temperature. Bubbles of ~100 nm in diameter appear to be integral to the nanostructuring process. Nanostructured palladium is also shown to have better catalytic activity than not nanostructured palladium. PMID:28347109

Nanostructuring of Palladium with Low-Temperature Helium Plasma.

PubMed

Fiflis, P; Christenson, M P; Connolly, N; Ruzic, D N

2015-11-25

Impingement of high fluxes of helium ions upon metals at elevated temperatures has given rise to the growth of nanostructured layers on the surface of several metals, such as tungsten and molybdenum. These nanostructured layers grow from the bulk material and have greatly increased surface area over that of a not nanostructured surface. They are also superior to deposited nanostructures due to a lack of worries over adhesion and differences in material properties. Several palladium samples of varying thickness were biased and exposed to a helium helicon plasma. The nanostructures were characterized as a function of the thickness of the palladium layer and of temperature. Bubbles of ~100 nm in diameter appear to be integral to the nanostructuring process. Nanostructured palladium is also shown to have better catalytic activity than not nanostructured palladium.

High Temperatures Health Monitoring of the Condensed Water Height in Steam Pipe Systems

NASA Technical Reports Server (NTRS)

Lih, Shyh-Shiuh; Bar-Cohen, Yoseph; Lee, Hyeong Jae; Badescu, Mircea; Bao, Xiaoqi; Sherrit, Stewart; Takano, Nobuyuki; Ostlund, Patrick; Blosiu, Julian

2013-01-01

Ultrasonic probes were designed, fabricated and tested for high temperature health monitoring system. The goal of this work was to develop the health monitoring system that can determine the height level of the condensed water through the pipe wall at high temperature up to 250 deg while accounting for the effects of surface perturbation. Among different ultrasonic probe designs, 2.25 MHz probes with air backed configuration provide satisfactory results in terms of sensitivity, receiving reflections from the target through the pipe wall. A series of tests were performed using the air-backed probes under irregular conditions, such as surface perturbation and surface disturbance at elevated temperature, to qualify the developed ultrasonic system. The results demonstrate that the fabricated air-backed probes combined with advanced signal processing techniques offer the capability of health monitoring of steam pipe under various operating conditions.

Consolidated ethanol production from Jerusalem artichoke tubers at elevated temperature by Saccharomyces cerevisiae engineered with inulinase expression through cell surface display.

PubMed

Khatun, M Mahfuza; Liu, Chen-Guang; Zhao, Xin-Qing; Yuan, Wen-Jie; Bai, Feng-Wu

2017-02-01

Ethanol fermentation from Jerusalem artichoke tubers was performed at elevated temperatures by the consolidated bioprocessing strategy using Saccharomyces cerevisiae MK01 expressing inulinase through cell surface display. No significant difference was observed in yeast growth when temperature was controlled at 38 and 40 °C, respectively, but inulinase activity with yeast cells was substantially enhanced at 40 °C. As a result, enzymatic hydrolysis of inulin was facilitated and ethanol production was improved with 89.3 g/L ethanol produced within 72 h from 198.2 g/L total inulin sugars consumed. Similar results were also observed in ethanol production from Jerusalem artichoke tubers with 85.2 g/L ethanol produced within 72 h from 185.7 g/L total sugars consumed. On the other hand, capital investment on cooling facilities and energy consumption for running the facilities would be saved, since regular cooling water instead of chill water could be used to cool down the fermentation system.

Activated carbon derived from waste coffee grounds for stable methane storage.

PubMed

Kemp, K Christian; Baek, Seung Bin; Lee, Wang-Geun; Meyyappan, M; Kim, Kwang S

2015-09-25

An activated carbon material derived from waste coffee grounds is shown to be an effective and stable medium for methane storage. The sample activated at 900 °C displays a surface area of 1040.3 m(2) g(-1) and a micropore volume of 0.574 cm(3) g(-1) and exhibits a stable CH4 adsorption capacity of ∼4.2 mmol g(-1) at 3.0 MPa and a temperature range of 298 ± 10 K. The same material exhibits an impressive hydrogen storage capacity of 1.75 wt% as well at 77 K and 100 kPa. Here, we also propose a mechanism for the formation of activated carbon from spent coffee grounds. At low temperatures, the material has two distinct types with low and high surface areas; however, activation at elevated temperatures drives off the low surface area carbon, leaving behind the porous high surface area activated carbon.

Activated carbon derived from waste coffee grounds for stable methane storage

NASA Astrophysics Data System (ADS)

Kemp, K. Christian; Baek, Seung Bin; Lee, Wang-Geun; Meyyappan, M.; Kim, Kwang S.

2015-09-01

An activated carbon material derived from waste coffee grounds is shown to be an effective and stable medium for methane storage. The sample activated at 900 °C displays a surface area of 1040.3 m2 g-1 and a micropore volume of 0.574 cm3 g-1 and exhibits a stable CH4 adsorption capacity of ˜4.2 mmol g-1 at 3.0 MPa and a temperature range of 298 ± 10 K. The same material exhibits an impressive hydrogen storage capacity of 1.75 wt% as well at 77 K and 100 kPa. Here, we also propose a mechanism for the formation of activated carbon from spent coffee grounds. At low temperatures, the material has two distinct types with low and high surface areas; however, activation at elevated temperatures drives off the low surface area carbon, leaving behind the porous high surface area activated carbon.

Thermal Pollution Mathematical Model. Volume 6; Verification of Three-Dimensional Free-Surface Model at Anclote Anchorage; [environment impact of thermal discharges from power plants

NASA Technical Reports Server (NTRS)

Lee, S. S.; Sengupta, S.; Tuann, S. Y.; Lee, C. R.

1980-01-01

The free-surface model presented is for tidal estuaries and coastal regions where ambient tidal forces play an important role in the dispersal of heated water. The model is time dependent, three dimensional, and can handle irregular bottom topography. The vertical stretching coordinate is adopted for better treatment of kinematic condition at the water surface. The results include surface elevation, velocity, and temperature. The model was verified at the Anclote Anchorage site of Florida Power Company. Two data bases at four tidal stages for winter and summer conditions were used to verify the model. Differences between measured and predicted temperatures are on an average of less than 1 C.

The Use of ATLAS Data to Quantify Surface Radiative Budgets in Four US Cities

NASA Technical Reports Server (NTRS)

Luvall, Jeffrey; Gonzalez, Jorge; Rickman, Douglas; Quattrochi, Dale; Schiller, Steve; Comarazamy, Daniel; Estes, Maury

2011-01-01

The additional heating of the air over the city is the result of the replacement of naturally vegetated surfaces with those composed of asphalt, concrete, rooftops and other manmade materials. The temperatures of these artificial surfaces can be 20 to 40 C higher than vegetated surfaces. This produces a dome of elevated air temperatures 5 to 8 C greater over the city, compared to the air temperatures over adjacent rural areas. This effect is called the "urban heat island". Urban landscapes are a complex mixture of vegetated and non-vegetated surfaces. It is difficult to take enough temperature measurements over a large city area to. The use of remotely sensed data from airborne scanners is ideal to characterize the complexity of urban albedo and radiant surface temperatures. The National Aeronautics and Space Administration (NASA) Airborne Thermal and Land Applications Sensor (ATLAS) operates in the visual and IR bands was used to collect data from Salt Lake City, UT, Sacramento, CA, Baton Rouge, LA. And San Juan, Puerto Rico with the main objective of investigating the Urban Heat Island (UHI). In this presentation we will examine the techniques of analyzing remotely sensed data for measuring the effect of various urban surfaces on their contribution to the urban heat island effect.

Recent Changes in the Greenland Ice Sheet as Seen from Space

NASA Technical Reports Server (NTRS)

Hall, Dorothy K.

2011-01-01

Many changes in the Greenland Ice Sheet have been reported in the recent scientific literature and have been attributed to various responses of the ice sheet due to regional (and global) warming. Because melting of the ice sheet would contribute approximately 7 m to sea-level rise, the lives and habitat of hundreds of millions of people worldwide would be directly and indirectly affected if continued ice-sheet melting occurs. As mean-annual global temperatures have increased, there has been an increasing focus on studying the Greenland Ice Sheet using available satellite data, and numerous expeditions have been undertaken. Regional "clear-sky" surface temperature increases since the early 1980s in the Arctic, measured using Advanced Very High Resolution Radiometer (AVHRR) infrared data, range from 0.57+/-0.02 C to 0.72+/-0.10 C per decade. Arctic warming has important implications for ice-sheet mass balance because much of the periphery of the Greenland Ice Sheet is already near O C during the melt season, and is thus vulnerable to more extensive melting if temperatures continue to increase. An increase in melting of the ice sheet would accelerate sea-level rise, an issue of increasing concern to billions of people worldwide. The surface temperature of the ice sheet has been studied in even greater detail using Moderate-Resolution Imaging Spectroradiometer (MODIS) data in the six individual drainage basins as well as for the ice sheet as a whole. Surface temperature trends in the decade of the 2000s have not been strong, according to the MODIS measurements. In addition to surface-temperature increases over the last few decades as measured by AVHRR, other changes have been observed such as accelerated movement of many of Greenland's outlet glaciers and sudden draining of supraglacial lakes. Decreasing mass of the ice sheet since (at least) 2002 has been measured using Gravity Recovery and Climate Experiment (GRACE) data, along with an build-up of ice at the higher elevations and a decrease of ice at the lower elevations as measured using airborne Lidar and Ice, Cloud and Land Elevation Satellite (ICESat) data. The seminar will address the above issues using a variety of NASA satellite data and ground observations.

Identifying anthropogenic anomalies in air, surface and groundwater temperatures in Germany.

PubMed

Benz, Susanne A; Bayer, Peter; Blum, Philipp

2017-04-15

Human activity directly influences ambient air, surface and groundwater temperatures. The most prominent phenomenon is the urban heat island effect, which has been investigated particularly in large and densely populated cities. This study explores the anthropogenic impact on the thermal regime not only in selected urban areas, but on a countrywide scale for mean annual temperature datasets in Germany in three different compartments: measured surface air temperature, measured groundwater temperature, and satellite-derived land surface temperature. Taking nighttime lights as an indicator of rural areas, the anthropogenic heat intensity is introduced. It is applicable to each data set and provides the difference between measured local temperature and median rural background temperature. This concept is analogous to the well-established urban heat island intensity, but applicable to each measurement point or pixel of a large, even global, study area. For all three analyzed temperature datasets, anthropogenic heat intensity grows with increasing nighttime lights and declines with increasing vegetation, whereas population density has only minor effects. While surface anthropogenic heat intensity cannot be linked to specific land cover types in the studied resolution (1km×1km) and classification system, both air and groundwater show increased heat intensities for artificial surfaces. Overall, groundwater temperature appears most vulnerable to human activity, albeit the different compartments are partially influenced through unrelated processes; unlike land surface temperature and surface air temperature, groundwater temperatures are elevated in cultivated areas as well. At the surface of Germany, the highest anthropogenic heat intensity with 4.5K is found at an open-pit lignite mine near Jülich, followed by three large cities (Munich, Düsseldorf and Nuremberg) with annual mean anthropogenic heat intensities >4K. Overall, surface anthropogenic heat intensities >0K and therefore urban heat islands are observed in communities down to a population of 5000. Copyright © 2017 Elsevier B.V. All rights reserved.

Sliding friction and wear behavior of high entropy alloys at room and elevated temperatures

NASA Astrophysics Data System (ADS)

Kadhim, Dheyaa

Structure-tribological property relations have been studied for five high entropy alloys (HEAs). Microhardness, room and elevated (100°C and 300°C) temperature sliding friction coefficients and wear rates were determined for five HEAs: Co0.5 Cr Cu0.5 Fe Ni1.5 Al Ti0.4; Co Cr Fe Ni Al0.25 Ti0.75; Ti V Nb Cr Al; Al0.3CoCrFeNi; and Al0.3CuCrFeNi2. Wear surfaces were characterized with scanning electron microscopy and micro-Raman spectroscopy to determine the wear mechanisms and tribochemical phases, respectively. It was determined that the two HEAs Co0.5 Cr Cu0.5 Fe Ni1.5 Al Ti0.4 and Ti V Nb Cr Al exhibit an excellent balance of high hardness, low friction coefficients and wear rates compared to 440C stainless steel, a currently used bearing steel. This was attributed to their more ductile body centered cubic (BCC) solid solution phase along with the formation of tribochemical Cr oxide and Nb oxide phases, respectively, in the wear surfaces. This study provides guidelines for fabricating novel, low-friction, and wear-resistant HEAs for potential use at room and elevated temperatures, which will help reduce energy and material losses in friction and wear applications.

Austrian glaciers in historical documents of the last 400 years: implications for historical hydrology

NASA Astrophysics Data System (ADS)

Fischer, Andrea; Seiser, Bernd

2014-05-01

First documentations of Austrian glaciers date from as early as 1601. Early documentations were triggered by glacier advances that created glacier-dammed lakes that caused floods whenever the dam collapsed . Since then, Austrian glaciers have been documented in drawings, descriptions and later on in maps and photography. These data are stored in historical archives but today only partly exploited for historical glaciology. They are of special interest for historical hydrology in glacier-covered basins, as the extent of the snow, firn and ice cover and its elevation affect the hydrological response of the basin to precipitation events in several ways: - Firn cover: the more area is covered by firn, the higher is the capacity for retention or even refreezing of liquid precipitation and melt water. - Ice cover: the area covered by glaciers can be affected by melt and contributes to a peak discharge on summer afternoons. - Surface elevation and temperatures: in case of precipitation events, the lower surface temperatures and higher surface elevation of the glaciers compared to ice-free ground have some impact on the capacity to store precipitation. - Glacier floods: for the LIA maximum around 1850, a number of advancing glaciers dammed lakes which emptied during floods. These parameters show different variability with time: glacier area varies only by about 60% to 70% between the LIA maximum and today. The variability of the maximum meltwater peak changes much more than the area. Even during the LIA maximum, several years were extremely warm, so that more than twice the size of today's glacier area was subject to glacier melt. The minimum elevations of large glaciers were several hundred meters lower than today, so that in terms of today's summer mean temperatures, the melt water production from ice ablation would have been much higher than today. A comparison of historical glacier images and description with today's makes it clear that the extent of the snow cover and thus the albedo of the glacier surface has been highly variable. This has significant impact on the meltwater production. These historical glacier data complement the first available runoff data from the early 20th century taken close to the glacier tongues.

Surface elevation change on ice caps in the Qaanaaq region, northwestern Greenland

NASA Astrophysics Data System (ADS)

Saito, Jun; Sugiyama, Shin; Tsutaki, Shun; Sawagaki, Takanobu

2016-09-01

A large number of glaciers and ice caps (GICs) are distributed along the Greenland coast, physically separated from the ice sheet. The total area of these GICs accounts for 5% of Greenland's ice cover. Melt water input from the GICs to the ocean substantially contributed to sea-level rise over the last century. Here, we report surface elevation changes of six ice caps near Qaanaaq (77°28‧N, 69°13‧W) in northwestern Greenland based on photogrammetric analysis of stereo pair satellite images. We processed the images with a digital map plotting instrument to generate digital elevation models (DEMs) in 2006 and 2010 with a grid resolution of 500 m. Generated DEMs were compared to measure surface elevation changes between 2006 and 2010. Over the study area of the six ice caps, covering 1215 km2, the mean rate of elevation change was -1.1 ± 0.1 m a-1. This rate is significantly greater than that previously reported for the 2003-2008 period (-0.6 ± 0.1 m a-1) for GICs all of northwestern Greenland. This increased mass loss is consistent with the rise in summer temperatures in this region at a rate of 0.12 °C a-1 for the 1997-2013 period.

Thermally Driven Electronic Topological Transition in FeTi

DOE PAGES

Yang, F. C.; Muñoz, J. A.; Hellman, O.; ...

2016-08-08

In this paper, ab initio molecular dynamics, supported by inelastic neutron scattering and nuclear resonant inelastic x-ray scattering, showed an anomalous thermal softening of the M 5 - phonon mode in B2-ordered FeTi that could not be explained by phonon-phonon interactions or electron-phonon interactions calculated at low temperatures. A computational investigation showed that the Fermi surface undergoes a novel thermally driven electronic topological transition, in which new features of the Fermi surface arise at elevated temperatures. Finally, the thermally induced electronic topological transition causes an increased electronic screening for the atom displacements in the M 5 - phonon mode andmore » an adiabatic electron-phonon interaction with an unusual temperature dependence.« less

Monitoring the Thermal Regime at Hot Creek and Vicinity, Long Valley Caldera, Eastern California

NASA Astrophysics Data System (ADS)

Clor, L. E.; Hurwitz, S.; Howle, J.

2015-12-01

Hot Creek Gorge contains the most obvious surface expression of the hydrothermal system in Long Valley Caldera, California, discharging 200-300 L/s of thermal water according to USGS measurements made since 1988. Formerly, Hot Creek was a popular public swimming area, but it was closed in 2006 due to unpredictable temperature fluctuations and sporadic geysering of thermal water within the creek (Farrar et al. USGS Fact Sheet2007-3045). The USGS has monitored the thermal regime in the area since the mid-1980s, including a long-term series of studies 0.6 km away at well CH-10b. Temperature measurements in the ~100 m deep well, which have been performed on an intermittent basis since it was drilled in 1983, reveal a complex temperature profile. Temperatures increase with depth to a maximum at about 45 meters below the ground surface, and then decrease steadily to the bottom of the well. The depth of the temperature maximum in the well (~45 m) corresponds to an elevation of ~2,120 m, roughly equivalent to the elevation of Hot Creek, and appears to sample the same hydrothermal flow system that supplies thermal features at the surface in the gorge. Starting in the early 1990s, the maximum temperature in CH-10b rose from 93.4°C to its peak in 2007 at 101.0°C. A cooling trend was observed beginning in 2009 and continues to present (99.3°C in June 2015). As the input into CH-10b is at the elevation of the creek, it exhibits the potential for response to thermal events at Hot Creek, and could provide a useful tool for monitoring future hazards. On short timescales, CH-10b also responds to large global earthquakes, greater than ~M7. These responses are captured with continuously logged high-frequency data (5s), and are usually characterized by a co-seismic water level drop of up to ten centimeters. Water levels tend to recover to pre-earthquake levels within a few hours to days.

Temperature suitability for malaria climbing the Ethiopian Highlands

NASA Astrophysics Data System (ADS)

Lyon, Bradfield; Dinku, Tufa; Raman, Anita; Thomson, Madeleine C.

2017-06-01

While the effect of climate change on the prevalence of malaria in the highlands of Eastern Africa has been the topic of protracted debate, temperature is widely accepted as a fundamentally important environmental factor constraining its transmission. Air temperatures below approximately 18 °C and 15 °C, respectively, prohibit the development of the Plasmodium falciparum and P. vivax parasites responsible for the majority of malaria cases in Ethiopia. Low temperatures also impede the development rates of the Anopheles mosquito vectors. While locations of sufficiently high elevation have temperatures below these transmission thresholds, a fundamental question is how such temperature ‘threshold elevations’ are changing with time. A lack of high quality, high spatial resolution climate data has previously prohibited a rigorous investigation. Using a newly developed national temperature dataset for Ethiopia that combines numerous in-situ surface observations with downscaled reanalysis data, we here identify statistically significant increases in elevation for both the 18 °C and 15 °C thresholds in highland areas between 1981-2014. Substantial interannual and spatial variations in threshold elevations are identified, the former associated with the El Niño Southern-Oscillation and the latter with the complex climate of the region. The estimated population in locations with an upward trend in the 15 °C threshold elevation is approximately 6.5 million people (2.2 million for 18 °C). While not a direct prediction of the additional population made vulnerable to malaria through a shift to higher temperature, our results underscore a newly acquired ability to investigate climate variability and trends at fine spatial scales across Ethiopia, including changes in a fundamental constraint on malaria transmission in the Ethiopian Highlands.

Mosquito control pesticides and sea surface temperatures have differential effects on the survival and oxidative stress response of coral larvae.

PubMed

Ross, Cliff; Olsen, Kevin; Henry, Michael; Pierce, Richard

2015-04-01

The declining health of coral reefs is intensifying worldwide at an alarming rate due to the combined effects of land-based sources of pollution and climate change. Despite the persistent use of mosquito control pesticides in populated coastal areas, studies examining the survival and physiological impacts of early life-history stages of non-targeted marine organisms are limited. In order to better understand the combined effects of mosquito pesticides and rising sea surface temperatures, we exposed larvae from the coral Porites astreoides to selected concentrations of two major mosquito pesticide ingredients, naled and permethrin, and seawater elevated +3.5 °C. Following 18-20 h of exposure, larvae exposed to naled concentrations of 2.96 µg L(-1) or greater had significantly reduced survivorship compared to controls. These effects were not detected in the presence of permethrin or elevated temperature. Furthermore, larval settlement, post-settlement survival and zooxanthellae density were not impacted by any treatment. To evaluate the sub-lethal stress response of larvae, several oxidative stress endpoints were utilized. Biomarker responses to pesticide exposure were variable and contingent upon pesticide type as well as the specific biomarker being employed. In some cases, such as with protein carbonylation and catalase gene expression, the effects of naled exposure and temperature were interactive. In other cases pesticide exposure failed to induce any sub-lethal stress response. Overall, these results demonstrate that P. astreoides larvae have a moderate degree of resistance against short-term exposure to ecologically relevant concentrations of pesticides even in the presence of elevated temperature. In addition, this work highlights the importance of considering the complexity and differential responses encountered when examining the impacts of combined stressors that occur on varying spatial scales.

Analyzing the Effects of Climate Change on Sea Surface Temperature in Monitoring Coral Reef Health in the Florida Keys Using Sea Surface Temperature Data

NASA Technical Reports Server (NTRS)

Jones, Jason; Burbank, Renane; Billiot, Amanda; Schultz, Logan

2011-01-01

This presentation discusses use of 4 kilometer satellite-based sea surface temperature (SST) data to monitor and assess coral reef areas of the Florida Keys. There are growing concerns about the impacts of climate change on coral reef systems throughout the world. Satellite remote sensing technology is being used for monitoring coral reef areas with the goal of understanding the climatic and oceanic changes that can lead to coral bleaching events. Elevated SST is a well-documented cause of coral bleaching events. Some coral monitoring studies have used 50 km data from the Advanced Very High Resolution Radiometer (AVHRR) to study the relationships of sea surface temperature anomalies to bleaching events. In partnership with NOAA's Office of National Marine Sanctuaries and the University of South Florida's Institute for Marine Remote Sensing, this project utilized higher resolution SST data from the Terra's Moderate Resolution Imaging Spectroradiometer (MODIS) and AVHRR. SST data for 2000-2010 was employed to compute sea surface temperature anomalies within the study area. The 4 km SST anomaly products enabled visualization of SST levels for known coral bleaching events from 2000-2010.

Paleoclimate and paleoelevation in the western US Cordillera, 80 Ma to Present

NASA Astrophysics Data System (ADS)

Snell, K. E.; Thompson, J. M.; Foreman, B. Z.; Wernicke, B. P.; Chamberlain, C. P.; Eiler, J. M.; Koch, P. L.

2011-12-01

Disentangling local to regional paleoclimatic signals from paleoelevation changes in the terrestrial sedimentary record is challenging, and can be done with confidence only by compiling spatially and temporally distributed datasets (preferably drawing on diverse proxies). Spatial coverage is particularly important for paleoelevation reconstruction because climate at low elevation sites must be known to identify higher paleoelevation sites and to quantify their altitude. The abundance of previous paleoclimatic and paleoelevation studies from the western United States can provide some of the necessary temporal and spatial framework for discriminating signals of climate change from elevation changes. Here, we present a compilation of previously published and new paleotemperature data from the western United States from the Late Cretaceous - Present derived from leaf physiognomy MAT estimates and carbonate clumped-isotope temperature estimates. After coarsely binning the data into high paleoelevation (>2 km) and lower paleoelevation (<2 km) sites (according to original interpretations made by the authors of previous studies), we compare the general temporal patterns of temperature change from western North America with those implied by the marine stable isotope record. Within this framework, we begin to evaluate sites of uncertain paleoelevation that cannot be compared with contemporaneous, adjacent low elevation sites. In this compilation, both low and high elevation land temperatures are warmer than today during the Late Cretaceous, reach an apex during the early-middle Eocene and then cool to the Present (sharply from the late Miocene to Pleistocene). The observed pattern matches reasonably well with the coarse temporal pattern of climate change based on the marine oxygen isotope record. Paleobotanical data reflect mean annual temperature (MAT), whereas the clumped isotope data from paleosol and lacustrine carbonates appear to be biased toward summer temperatures. Throughout the Late Mesozoic and Cenozoic, both MAT and summer paleotemperature estimates are higher than modern MAT and summer temperature, but the relatively consistent difference between these records implies a seasonal range in temperature that was similar to modern. Summer temperatures from low paleoelevation sites during the Late Cretaceous to the Early Eocene are relatively warm (30 - 40 degrees C), though these values may include a few degrees of radiant solar heating of the surface. Interestingly, Early Eocene-aged carbonate samples from southwest Montana are cooler on average than other carbonate samples of roughly the same age, but are similar in temperature to samples thought to be at high elevation during the Late Cretaceous. Thus, these samples may reflect high elevation summer temperatures, rather than low elevation temperatures, demonstrating the utility of this combined spatial and temporal approach to evaluating terrestrial paleoenvironmental records.

An Imminent Revolution in Modeling Interactions of Ice Sheets With Climate

NASA Astrophysics Data System (ADS)

Hughes, T.

2008-12-01

Modeling continental ice sheets was inaugurated by meteorologists William Budd and Uwe Radok, with mathematician Richard Jenssen, in 1971. Their model calculated the thermal and mechanical regime using measured surface accumulation rates, temperatures, and elevations, and bed topography. This top-down approach delivered a basal thermal regime of temperatures or melting rates for an assumed basal geothermal heat flux. When Philippe Huybrechts and others incorporated time, largely unknownpast surface conditions had a major effect on present basal thermal conditions. This approach produced ice-sheet models with only a slow response to external forcing, whereas the glacial geological record and climate records from ice and ocean cores show that ice sheets can have rapid changes in size and shape independent of external forcing. These top-down models were wholly inadequate for reconstructing former ice sheets at the LGM for CLIMAP in 1981. Ice-sheet areas,elevations, and volumes provided the albedo, surface topography, and sea-surface area as input to climate models. A bottom-up model based on dated glacial geology was developed to provide the areal extent and basal thermal regime of ice sheets at the LGM. Basal thermal conditions determined ice-bed coupling and therefore the elevation of ice sheets. High convex ice surfaces for slow sheet flow lower about 20 percent when a frozen bed becomes thawed. As further basal melting drowns bedrock bumps that "pin" basal ice, the ice surface becomes concave in fast stream flow that ends as low floating ice shelves at marine ice margins. A revolution in modeling interactions between glaciation, climate, and sea level is driven by new Greenland and Antarctic data from Earth-orbiting satellites, airborne and surface traverses, and deep drilling. We anticipate continuous data acquisition of surface albedo, accumulation/ablation rates, elevations, velocities, and temperatures over a whole ice sheet, mapping basal thermal conditions by radar, seismic, and magnetic profiling, and direct measurement of basal conditions by deep drilling and coring into the ice and the bed. These data allow calculating the geothermal heat flux and mapping flow of basal meltwater from geothermal sources to sinks at the termini of ice streams, which discharge up to 90 percent of the ice. James Fastook has a preliminary solution of the full momentum equation needed to model ice streams. Douglas MacAyeal has pioneered modeling catastrophic ice-shelf disintegration that releases "armadas" of icebergs into the world ocean, to extract heat from ocean surface water and thereby reduce the critical ocean-to-atmosphere heat exchange that drives global climate. Ice sheets are the only component of Earth's climate machine that can destroy itself-- swiftly--and thereby radically and rapidly alter global climate and sea level.

Pyrrole Hydrogenation over Rh(111) and Pt(111) Single-Crystal Surfaces and Hydrogenation Promotion Mediated by 1-Methylpyrrole: A Kinetic and Sum-Frequency Generation Vibrational Spectroscopy Study

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

Kliewer, Christopher J.; Bieri, Marco; Somorjai, Gabor A.

Sum-frequency generation (SFG) surface vibrational spectroscopy and kinetic measurements using gas chromatography have been used to study the adsorption and hydrogenation of pyrrole over both Pt(111) and Rh(111) single-crystal surfaces at Torr pressures (3 Torr pyrrole, 30 Torr H{sub 2}) to form pyrrolidine and the minor product butylamine. Over Pt(111) at 298 K it was found that pyrrole adsorbs in an upright geometry cleaving the N-H bond to bind through the nitrogen evidenced by SFG data. Over Rh(111) at 298 K pyrrole adsorbs in a tilted geometry relative to the surface through the p-aromatic system. A pyrroline surface reaction intermediate,more » which was not detected in the gas phase, was seen by SFG during the hydrogenation over both surfaces. Significant enhancement of the reaction rate was achieved over both metal surfaces by adsorbing 1-methylpyrrole before reaction. SFG vibrational spectroscopic results indicate that reaction promotion is achieved by weakening the bonding between the N-containing products and the metal surface because of lateral interactions on the surface between 1-methylpyrrole and the reaction species, reducing the desorption energy of the products. It was found that the ring-opening product butylamine was a reaction poison over both surfaces, but this effect can be minimized by treating the catalyst surfaces with 1-methylpyrrole before reaction. The reaction rate was not enhanced with elevated temperatures, and SFG suggests desorption of pyrrole at elevated temperatures.« less

Quantifying the impact of human activity on temperatures in Germany

NASA Astrophysics Data System (ADS)

Benz, Susanne A.; Bayer, Peter; Blum, Philipp

2017-04-01

Human activity directly influences ambient air, surface and groundwater temperatures. Alterations of surface cover and land use influence the ambient thermal regime causing spatial temperature anomalies, most commonly heat islands. These local temperature anomalies are primarily described within the bounds of large and densely populated urban settlements, where they form so-called urban heat islands (UHI). This study explores the anthropogenic impact not only for selected cities, but for the thermal regime on a countrywide scale, by analyzing mean annual temperature datasets in Germany in three different compartments: measured surface air temperature (SAT), measured groundwater temperature (GWT), and satellite-derived land surface temperature (LST). As a universal parameter to quantify anthropogenic heat anomalies, the anthropogenic heat intensity (AHI) is introduced. It is closely related to the urban heat island intensity, but determined for each pixel (for satellite-derived LST) or measurement point (for SAT and GWT) of a large, even global, dataset individually, regardless of land use and location. Hence, it provides the unique opportunity to a) compare the anthropogenic impact on temperatures in air, surface and subsurface, b) to find main instances of anthropogenic temperature anomalies within the study area, in this case Germany, and c) to study the impact of smaller settlements or industrial sites on temperatures. For all three analyzed temperature datasets, anthropogenic heat intensity grows with increasing nighttime lights and declines with increasing vegetation, whereas population density has only minor effects. While surface anthropogenic heat intensity cannot be linked to specific land cover types in the studied resolution (1 km × 1 km) and classification system, both air and groundwater show increased heat intensities for artificial surfaces. Overall, groundwater temperature appears most vulnerable to human activity; unlike land surface temperature and surface air temperature, groundwater temperatures are elevated in cultivated areas as well. At the surface of Germany, the highest anthropogenic heat intensity with 4.5 K is found at an open-pit lignite mine near Jülich, followed by three large cities (Munich, Düsseldorf and Nuremberg) with annual mean anthropogenic heat intensities > 4 K. Overall, surface anthropogenic heat intensities > 0 K and therefore urban heat islands are observed in communities down to a population of 5,000.

SEM/XPS analysis of fractured adhesively bonded graphite fibre-reinforced polyimide composites

NASA Technical Reports Server (NTRS)

Devilbiss, T. A.; Messick, D. L.; Wightman, J. P.; Progar, D. J.

1985-01-01

The surfaces of the graphite fiber-reinforced polyimide composites presently pretreated prior to bonding with polyimide adhesive contained variable amounts of a fluoropolymer, as determined by X-ray photoelectron spectroscopy. Lap shear strengths were determined for unaged samples and for those aged over 500- and 1000-hour periods at 177 and 232 C. Unaged sample lap strengths, which were the highest obtained, exhibited no variation with surface pretreatment, but a significant decrease is noted with increasing aging temperature. These thermally aged samples, however, had increased surface fluorine concentration, while a minimal concentration was found in unaged samples. SEM demonstrated a progressive shift from cohesive to adhesive failure for elevated temperature-aged composites.

Forging Oxide-Dispersion-Strengthened Superalloys

NASA Technical Reports Server (NTRS)

Harf, F. H.; Glasgow, T. K.; Moracz, D. J.; Austin, C. M.

1986-01-01

Cladding of mild steel prevents surface cracking when alloy contacts die. Continual need for improvements in properties of alloys capable of withstanding elevated temperatures. Accomplished by using oxide-dispersion-strengthed superalloys such as Inconel Alloy MA 6000. Elevated tensile properties of forged alloy equal those of hot-rolled MA 6000 bar. Stress-rupture properties somewhat lower than those of bar stock but, at 1,100 degrees C, exceed those of strongest commercial single crystal, directionally solidified and conventionally cast superalloys.

Recent surface temperature trends in the interior of East Antarctica from borehole firn temperature measurements and geophysical inverse methods

USGS Publications Warehouse

Muto, A.; Scambos, T.A.; Steffen, K.; Slater, A.G.; Clow, G.D.

2011-01-01

We use measured firn temperatures down to depths of 80 to 90 m at four locations in the interior of Dronning Maud Land, East Antarctica to derive surface temperature histories spanning the past few decades using two different inverse methods. We find that the mean surface temperatures near the ice divide (the highest-elevation ridge of East Antarctic Ice Sheet) have increased approximately 1 to 1.5 K within the past ???50 years, although the onset and rate of this warming vary by site. Histories at two locations, NUS07-5 (78.65S, 35.64E) and NUS07-7 (82.07S, 54.89E), suggest that the majority of this warming took place in the past one or two decades. Slight cooling to no change was indicated at one location, NUS08-5 (82.63S, 17.87E), off the divide near the Recovery Lakes region. In the most recent decade, inversion results indicate both cooler and warmer periods at different sites due to high interannual variability and relatively high resolution of the inverted surface temperature histories. The overall results of our analysis fit a pattern of recent climate trends emerging from several sources of the Antarctic temperature reconstructions: there is a contrast in surface temperature trends possibly related to altitude in this part of East Antarctica. Copyright 2011 by the American Geophysical Union.

Diffusion mechanisms in chemical vapor-deposited iridium coated on chemical vapor-deposited rhenium

NASA Technical Reports Server (NTRS)

Hamilton, J. C.; Yang, N. Y. C.; Clift, W. M.; Boehme, D. R.; Mccarty, K. F.; Franklin, J. E.

1992-01-01

Radiation-cooled rocket thruster chambers have been developed which use CVD Re coated with CVD Ir on the interior surface that is exposed to hot combustion gases. The Ir serves as an oxidation barrier which protects the structural integrity-maintaining Re at elevated temperatures. The diffusion kinetics of CVD materials at elevated temperatures is presently studied with a view to the prediction and extension of these thrusters' performance limits. Line scans for Ir and Re were fit on the basis of a diffusion model, in order to extract relevant diffusion constants; the fastest diffusion process is grain-boundary diffusion, where Re diffuses down grain boundaries in the Ir overlayer.

Using ATM laser altimetry to constrain surface mass balance estimates and supraglacial hydrology of the Greenland Ice Sheet

NASA Astrophysics Data System (ADS)

Studinger, M.; Medley, B.; Manizade, S.; Linkswiler, M. A.

2016-12-01

Repeat airborne laser altimetry measurements can provide large-scale field observations to better quantify spatial and temporal variability of surface processes contributing to seasonal elevation change and therefore surface mass balance. As part of NASA's Operation IceBridge the Airborne Topographic Mapper (ATM) laser altimeter measured the surface elevation of the Greenland Ice Sheet during spring (March - May) and fall (September - October) of 2015. Comparison of the two surveys reveals a general trend of thinning for outlet glaciers and for the ice sheet in a manner related to elevation and latitude. In contrast, some thickening is observed on the west (but not on the east) side of the ice divide above 2200 m elevation in the southern half, below latitude 69°N.The observed magnitude and spatial patterns of the summer melt signal can be utilized as input into ice sheet models and for validating reanalysis of regional climate models such as RACMO and MAR. We use seasonal anomalies in MERRA-2 climate fields (temperature, precipitation) to understand the observed spatial signal in seasonal change. Aside from surface elevation change, runoff from meltwater pooling in supraglacial lakes and meltwater channels accounts for at least half of the total mass loss. The ability of the ATM laser altimeters to image glacial hydrological features in 3-D and determine the depth of supraglacial lakes could be used for process studies and for quantifying melt processes over large scales. The 1-meter footprint diameter of ATM laser on the surface, together with a high shot density, allows for the production of large-scale, high-resolution, geodetic quality DEMs (50 x 50 cm) suitable for fine-scale glacial hydrology research and as input to hydrological models quantifying runoff.

Thermal regimes of Rocky Mountain lakes warm with climate change

PubMed Central

Roberts, James J.

2017-01-01

Anthropogenic climate change is causing a wide range of stresses in aquatic ecosystems, primarily through warming thermal conditions. Lakes, in response to these changes, are experiencing increases in both summer temperatures and ice-free days. We used continuous records of lake surface temperature and air temperature to create statistical models of daily mean lake surface temperature to assess thermal changes in mountain lakes. These models were combined with downscaled climate projections to predict future thermal conditions for 27 high-elevation lakes in the southern Rocky Mountains. The models predict a 0.25°C·decade-1 increase in mean annual lake surface temperature through the 2080s, which is greater than warming rates of streams in this region. Most striking is that on average, ice-free days are predicted to increase by 5.9 days ·decade-1, and summer mean lake surface temperature is predicted to increase by 0.47°C·decade-1. Both could profoundly alter the length of the growing season and potentially change the structure and function of mountain lake ecosystems. These results highlight the changes expected of mountain lakes and stress the importance of incorporating climate-related adaptive strategies in the development of resource management plans. PMID:28683083

Thermal regimes of Rocky Mountain lakes warm with climate change

USGS Publications Warehouse

Roberts, James J.; Fausch, Kurt D.; Schmidt, Travis S.; Walters, David M.

2017-01-01

Anthropogenic climate change is causing a wide range of stresses in aquatic ecosystems, primarily through warming thermal conditions. Lakes, in response to these changes, are experiencing increases in both summer temperatures and ice-free days. We used continuous records of lake surface temperature and air temperature to create statistical models of daily mean lake surface temperature to assess thermal changes in mountain lakes. These models were combined with downscaled climate projections to predict future thermal conditions for 27 high-elevation lakes in the southern Rocky Mountains. The models predict a 0.25°C·decade-1increase in mean annual lake surface temperature through the 2080s, which is greater than warming rates of streams in this region. Most striking is that on average, ice-free days are predicted to increase by 5.9 days ·decade-1, and summer mean lake surface temperature is predicted to increase by 0.47°C·decade-1. Both could profoundly alter the length of the growing season and potentially change the structure and function of mountain lake ecosystems. These results highlight the changes expected of mountain lakes and stress the importance of incorporating climate-related adaptive strategies in the development of resource management plans.

Thermal regimes of Rocky Mountain lakes warm with climate change.

PubMed

Roberts, James J; Fausch, Kurt D; Schmidt, Travis S; Walters, David M

2017-01-01

Anthropogenic climate change is causing a wide range of stresses in aquatic ecosystems, primarily through warming thermal conditions. Lakes, in response to these changes, are experiencing increases in both summer temperatures and ice-free days. We used continuous records of lake surface temperature and air temperature to create statistical models of daily mean lake surface temperature to assess thermal changes in mountain lakes. These models were combined with downscaled climate projections to predict future thermal conditions for 27 high-elevation lakes in the southern Rocky Mountains. The models predict a 0.25°C·decade-1 increase in mean annual lake surface temperature through the 2080s, which is greater than warming rates of streams in this region. Most striking is that on average, ice-free days are predicted to increase by 5.9 days ·decade-1, and summer mean lake surface temperature is predicted to increase by 0.47°C·decade-1. Both could profoundly alter the length of the growing season and potentially change the structure and function of mountain lake ecosystems. These results highlight the changes expected of mountain lakes and stress the importance of incorporating climate-related adaptive strategies in the development of resource management plans.

2014 and 2015 anomalies in temperature and the epipelagic fish community in the eastern Gulf of Alaska and implications for juvenile fish.

NASA Astrophysics Data System (ADS)

Rhea-Fournier, W.

2016-02-01

Summer eastern Gulf of Alaska fisheries oceanography surveys of the epipelagic in 2014 and 2015 indicated elevated near surface temperatures, changes in the fish community, and variability in prey quality. The Alaska Fisheries Science Center deployed CTDs to observe temperature profiles, surface trawls to collect fish, and plankton nets to collect zooplankton from 2010 to 2015 along the coast and offshore of Baranof and Chichagof Island . Average near surface temperature for 2014 and 2015 were significantly higher than previous years with an increase of over 3.5 degrees relative to 2012. Young of the year groundfish that occupy the epipelagic in the summer prior to pelagic and demersal migration experienced changes in relative abundance that included a decrease in pollock, Pacific cod, and arrowtooth flounder and an increase in sablefish. The warmer temperatures allowed Elasmobranchs from tropical regions to migrate north including blue sharks and Thresher sharks which represented a northern range extension. Other anomalous fish catches in the nearshore in 2014 and 2015 included multiple ocean sunfish, Mola mola, and the abundance of Pacific pomfret, a piscivorous species usually found in offshore waters. Zooplankton collections analyzed for caloric content and lipid allocation indicated interannual variability with an increase of condition in 2014 and a significant decrease in 2015. While the elevated temperatures of 2014 and 2015 may have provided suitable habitat and range extensions for lower latitude and offshore species, the combination of accelerated metabolism due to higher thermal experience, depleted energetic input from prey, and increase in predators has the potential to decrease survival of juvenile fish in the epipelagic.

Catalytic combustion of hydrogen-air mixtures in stagnation flows

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

Ikeda, H.; Libby, P.A.; Williams, F.A.

1993-04-01

The interaction between heterogeneous and homogeneous reactions arising when a mixture of hydrogen and air impinges on a platinum plate at elevated temperature is studied. A reasonably complete description of the kinetic mechanism for homogeneous reactions is employed along with a simplified model for heterogeneous reactions. Four regimes are identified depending on the temperature of the plate, on the rate of strain imposed on the flow adjacent to the plate and on the composition and temperature of the reactant stream: (1) surface reaction alone; (2) surface reaction inhibiting homogeneous reaction; (3) homogeneous reaction inhibiting surface reaction; and (4) homogeneous reactionmore » alone. These regimes are related to those found earlier for other chemical systems and form the basis of future experimental investigation of the chemical system considered in the present study.« less

Lunar Polar Cold Traps: Spatial Distribution and Temperatures

NASA Astrophysics Data System (ADS)

Paige, David A.; Siegler, M.; Lawrence, D. J.

2006-09-01

We have developed a ray-tracing and radiosity model that can accurately calculate lunar surface and subsurface temperatures for arbitrary topography. Using available digital elevation models for the lunar north and south polar regions derived from Clementine laser altimeter and image data, as well as ground-based radar data, we have calculated lunar surface and subsurface temperatures at 2 km resolution that include full effects of indirect solar and infrared radiation due to topography. We compare our thermal model results with maps of epithermal neutron flux measured by Lunar Prospector. When we use the ray tracing and thermal model to account for the effects of temperature and topography on the neutron measurements, our results show that the majority of the moon's polar cold traps are not filled with water ice.

Time lag between the tropopause height and the levels of 7Be concentration in near surface air

NASA Astrophysics Data System (ADS)

Ioannidou, A.; Vasileiadis, A.; Melas, D.

2012-04-01

The concentration of 7Be at near surface air has been determined over 2009, a year of a deep solar minimum, in the region of Thessaloniki, Greece at 40°62' N, 22°95'E. In geomagnetic latitudes over 40° N, the elevation of the tropopause during the warm summer months and the vertical exchange of air masses within the troposphere cause greater mixture of the air masses resulting in higher concentration levels for 7Be in surface air. The positive correlation between the monthly activity concentration of 7Be and the tropopause height (0.94, p < 0.0001), and also between 7Be concentration and the temperature T (°C) (R = 0.97, p < 0.001), confirm that the increased rate of vertical transport within the troposphere, especially during warmer summer months, has as a result the descent to surface of air masses enriched in 7Be. However, the 7Be concentration levels in near surface air are not expected to respond immediately to the change of elevation of the tropopause. It was found that there's a time lag of ~ 3 days between the change in the daily surface concentrations of 7Be the change in the elevation of the tropopause.

An extended laser flash technique for thermal diffusivity measurement of high-temperature materials

NASA Technical Reports Server (NTRS)

Shen, F.; Khodadadi, J. M.

1993-01-01

Knowledge of thermal diffusivity data for high-temperature materials (solids and liquids) is very important in analyzing a number of processes, among them solidification, crystal growth, and welding. However, reliable thermal diffusivity versus temperature data, particularly those for high-temperature liquids, are still far from complete. The main measurement difficulties are due to the presence of convection and the requirement for a container. Fortunately, the availability of levitation techniques has made it possible to solve the containment problem. Based on the feasibility of the levitation technology, a new laser flash technique which is applicable to both levitated liquid and solid samples is being developed. At this point, the analysis for solid samples is near completion and highlights of the technique are presented here. The levitated solid sample which is assumed to be a sphere is subjected to a very short burst of high power radiant energy. The temperature of the irradiated surface area is elevated and a transient heat transfer process takes place within the sample. This containerless process is a two-dimensional unsteady heat conduction problem. Due to the nonlinearity of the radiative plus convective boundary condition, an analytic solution cannot be obtained. Two options are available at this point. Firstly, the radiation boundary condition can be linearized, which then accommodates a closed-form analytic solution. Comparison of the analytic curves for the temperature rise at different points to the experimentally-measured values will then provide the thermal diffusivity values. Secondly, one may set up an inverse conduction problem whereby experimentally obtained surface temperature history is used as the boundary conditions. The thermal diffusivity can then be elevated by minimizing the difference between the real heat flux boundary condition (radiation plus convection) and the measurements. Status of an experimental study directed at measuring the thermal diffusivity of high-temperature solid samples of pure Nickel and Inconel 718 superalloys are presented. Preliminary measurements showing surface temperature histories are discussed.

Effect of increased temperature, CO2, and iron on nitrate uptake and primary productivity in the coastal Ross Sea

NASA Astrophysics Data System (ADS)

Bronk, D. A.; Spackeen, J.; Sipler, R. E.; Bertrand, E. M.; Roberts, Q. N.; Xu, K.; Baer, S. E.; McQuaid, J.; Zhu, Z.; Walworth, N. G.; Hutchins, D. A.; Allen, A. E.

2016-02-01

Western Antarctic Seas are rapidly changing as a result of elevated concentrations of CO2 and rising sea surface temperatures. It is critical to determine how the structure and function of microbial communities will be impacted by these changes in the future because the Southern Ocean has seasonally high rates of primary production, is an important sink for anthropogenic CO2, and supports a diverse assemblage of higher trophic level organisms. During the Austral summer of 2013 and 2015, a collaborative research group conducted a series of experiments to understand how the individual and combined effects of temperature, CO2, and iron impact Ross Sea microorganisms. Our project used a variety of approaches, including batch experiments, semi-continuous experiments, and continuous-culturing over extended time intervals, to determine how future changes may shift Ross Sea microbial communities and how nutrient cycling and carbon biogeochemistry may subsequently be altered. Chemical and biological parameters were measured throughout the experiments to assess changes in community composition and nutrient cycling, including uptake rate measurements of nitrate and bicarbonate by different size fractions of microorganisms. Relative to the control, nitrate uptake rates significantly increased when temperature and iron were elevated indicating that temperature and iron are important physical drivers that influence nutrient cycling. Elevations in temperature and iron independently and synergistically produced higher rates than elevated CO2. Our nutrient uptake results also suggest that the physiology of large microorganisms will be more impacted by climate change variables than small microorganisms.

Mathematical Modelling of Arctic Polygonal Tundra with Ecosys: 1. Microtopography Determines How Active Layer Depths Respond to Changes in Temperature and Precipitation

NASA Astrophysics Data System (ADS)

Grant, R. F.; Mekonnen, Z. A.; Riley, W. J.; Wainwright, H. M.; Graham, D.; Torn, M. S.

2017-12-01

Microtopographic variation that develops among features (troughs, rims, and centers) within polygonal landforms of coastal arctic tundra strongly affects movement of surface water and snow and thereby affects soil water contents (θ) and active layer depth (ALD). Spatial variation in ALD among these features may exceed interannual variation in ALD caused by changes in climate and so needs to be represented in projections of changes in arctic ALD. In this study, increases in near-surface θ with decreasing surface elevation among polygon features at the Barrow Experimental Observatory (BEO) were modeled from topographic effects on redistribution of surface water and snow and from lateral water exchange with a subsurface water table during a model run from 1981 to 2015. These increases in θ caused increases in thermal conductivity that in turn caused increases in soil heat fluxes and hence in ALD of up to 15 cm with lower versus higher surface elevation which were consistent with increases measured at BEO. The modeled effects of θ caused interannual variation in maximum ALD that compared well with measurements from 1985 to 2015 at the Barrow Circumpolar Active Layer Monitoring (CALM) site (R2 = 0.61, RMSE = 0.03 m). For higher polygon features, interannual variation in ALD was more closely associated with annual precipitation than mean annual temperature, indicating that soil wetting from increases in precipitation may hasten permafrost degradation beyond that caused by soil warming from increases in air temperature. This degradation may be more rapid if increases in precipitation cause sustained wetting in higher features.

Temporal and spatial variabilities in the surface moisture content of a fine-grained beach

NASA Astrophysics Data System (ADS)

Namikas, S. L.; Edwards, B. L.; Bitton, M. C. A.; Booth, J. L.; Zhu, Y.

2010-01-01

This study examined spatial and temporal variations in the surface moisture content of a fine-grained beach at Padre Island, Texas, USA. Surface moisture measurements were collected on a 27 × 24 m grid that extended from the dune toe to the upper foreshore. The grid was surveyed at 2 to 4 h intervals for two tidal cycles, generating 17 maps of the spatial distribution of surface moisture. Simultaneous measurements of air temperature and humidity, wind speed and direction, tidal elevation, and water table elevation were used to interpret observed changes in surface moisture. It was found that the spatial distribution of surface moisture was broadly characterized by a cross-shore gradient of high to low content moving landward from the swash zone. The distribution of surface moisture was conceptualized in terms of three zones: saturated (> 25%), intermediate or transitional (5-25%), and dry (< 5%). The position of the saturated zone corresponded to the uppermost swash zone and therefore shifted in accordance with tidal elevation. Moisture contents in the intermediate and dry zones were primarily related to variation in water table depth (which was in turn controlled by tidal elevation) and to a lesser extent by evaporation. Signals associated with atmospheric processes such as evaporation were muted by the minimal degree of variation in atmospheric parameters experienced during most of the study period, but were apparent for the last few hours. The observed spatial and temporal variations in moisture content correspond reasonably well with observations of key controlling processes, but more work is needed to fully characterize this process suite.

Processes regulating watershed chemical export during snowmelt, fraser experimental forest, Colorado

USGS Publications Warehouse

Stottlemyer, R.

2001-01-01

In the Central Rocky Mountains, snowfall dominates precipitation. Airborne contaminants retained in the snowpack can affect high elevation surface water chemistry during snowmelt. At the Fraser Experimental Forest (FEF), located west of the Continental Divide in Central Colorado, snowmelt dominates the annual hydrograph, and accounts for >95% of annual stream water discharge. During the winters of 1989-1993, we measured precipitation inputs, snowpack water equivalent (SWE) and ion content, and stream water chemistry every 7-10 days along a 3150-3500 m elevation gradient in the subalpine and alpine Lexen Creek watershed. The study objectives were to (1) quantify the distribution of SWE and snowpack chemical content with elevation and aspect, (2) quantify snowmelt rates, temperature of soil, snowpack, and air with elevation and aspect, and (3) use change in upstream-downstream water chemistry during snowmelt to better define alpine and subalpine flowpaths. The SWE increased with elevation (P - 3??C) temperatures throughout winter which resulted in significant snowpack ion loss. By snowpack PWE in mid May, the snowpack had lost almost half the cumulative precipitation H+, NH4+, and SO42- inputs and a third of the NO3- input. Windborne soil particulate inputs late in winter increased snowpack base cation content. Variation in subalpine SWE and snowpack ion content with elevation and aspect, and wind redistribution of snowfall in the alpine resulted in large year-to-year differences in the timing and magnitude of SWE, PWE, and snowpack ion content. The alpine stream water ion concentrations changed little during snowmelt indicating meltwater passed quickly through surface porous soils and was well mixed before entering the stream. Conversely, subalpine stream water chemistry was diluted during snowmelt suggesting much melt water moved to the stream as shallow subsurface lateral flow. Published by Elsevier Science B.V.

Adult exposure to ocean acidification is maladaptive for larvae of the Sydney rock oyster Saccostrea glomerata in the presence of multiple stressors.

PubMed

Parker, Laura M; O'Connor, Wayne A; Byrne, Maria; Coleman, Ross A; Virtue, Patti; Dove, Michael; Gibbs, Mitchell; Spohr, Lorraine; Scanes, Elliot; Ross, Pauline M

2017-02-01

Parental effects passed from adults to their offspring have been identified as a source of rapid acclimation that may allow marine populations to persist as our surface oceans continue to decrease in pH. Little is known, however, whether parental effects are beneficial for offspring in the presence of multiple stressors. We exposed adults of the oyster Saccostrea glomerata to elevated CO 2 and examined the impacts of elevated CO 2 (control = 392; 856 µatm) combined with elevated temperature (control = 24; 28°C), reduced salinity (control = 35; 25) and reduced food concentration (control = full; half diet) on their larvae. Adult exposure to elevated CO 2 had a positive impact on larvae reared at elevated CO 2 as a sole stressor, which were 8% larger and developed faster at elevated CO 2 compared with larvae from adults exposed to ambient CO 2 These larvae, however, had significantly reduced survival in all multistressor treatments. This was particularly evident for larvae reared at elevated CO 2 combined with elevated temperature or reduced food concentration, with no larvae surviving in some treatment combinations. Larvae from CO 2 -exposed adults had a higher standard metabolic rate. Our results provide evidence that parental exposure to ocean acidification may be maladaptive when larvae experience multiple stressors. © 2017 The Author(s).

Adult exposure to ocean acidification is maladaptive for larvae of the Sydney rock oyster Saccostrea glomerata in the presence of multiple stressors

PubMed Central

O'Connor, Wayne A.; Byrne, Maria; Virtue, Patti; Dove, Michael; Gibbs, Mitchell; Spohr, Lorraine; Scanes, Elliot; Ross, Pauline M.

2017-01-01

Parental effects passed from adults to their offspring have been identified as a source of rapid acclimation that may allow marine populations to persist as our surface oceans continue to decrease in pH. Little is known, however, whether parental effects are beneficial for offspring in the presence of multiple stressors. We exposed adults of the oyster Saccostrea glomerata to elevated CO2 and examined the impacts of elevated CO2 (control = 392; 856 µatm) combined with elevated temperature (control = 24; 28°C), reduced salinity (control = 35; 25) and reduced food concentration (control = full; half diet) on their larvae. Adult exposure to elevated CO2 had a positive impact on larvae reared at elevated CO2 as a sole stressor, which were 8% larger and developed faster at elevated CO2 compared with larvae from adults exposed to ambient CO2. These larvae, however, had significantly reduced survival in all multistressor treatments. This was particularly evident for larvae reared at elevated CO2 combined with elevated temperature or reduced food concentration, with no larvae surviving in some treatment combinations. Larvae from CO2-exposed adults had a higher standard metabolic rate. Our results provide evidence that parental exposure to ocean acidification may be maladaptive when larvae experience multiple stressors. PMID:28202683

Manufacture of silicon-based devices having disordered sulfur-doped surface layers

DOEpatents

Carey, III; Edward, James [Newton, MA; Mazur, Eric [Concord, MA

2008-04-08

The present invention provides methods of fabricating a radiation-absorbing semiconductor wafer by irradiating at least one surface location of a silicon substrate, e.g., an n-doped crystalline silicon, by a plurality of temporally short laser pulses, e.g., femtosecond pulses, while exposing that location to a substance, e.g., SF.sub.6, having an electron-donating constituent so as to generate a substantially disordered surface layer (i.e., a microstructured layer) that incorporates a concentration of that electron-donating constituent, e.g., sulfur. The substrate is also annealed at an elevated temperature and for a duration selected to enhance the charge carrier density in the surface layer. For example, the substrate can be annealed at a temperature in a range of about 700 K to about 900 K.

Surface degradation of polymer insulators under accelerated climatic aging in weather-ometer

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

Xu, G.; McGrath, P.B.; Burns, C.W.

1996-12-31

Climatic aging experiments were conducted on two types of outdoor polymer insulators by using a programmable weather-ometer. The housing materials for the insulators were silicone rubber (SR) and ethylene propylene diene monomer (EPDM). The accelerated aging stresses were comprised of ultraviolet radiation, elevated temperature, temperature cycling, thermal shock and high humidity. Their effects on the insulator surface conditions and electrical performance wee examined through visual inspection and SEM studies, contact angle measurements, thermogravimetric analysis (TGA), energy dispersive spectroscopy (EDS) analysis, and 50% impulse flashover voltage tests. The results showed a significant damage on the insulator surface caused by some ofmore » the imposed aging stresses. The EDS analysis suggested a photooxidation process that happened on the insulator surface during the aging period.« less

Thermal testing results of an electroformed nickel secondary (M2) mirror

NASA Astrophysics Data System (ADS)

Smith, David R.; Gale, David M.; Cabrera Cuevas, Lizeth; Lucero Álvarez, Maribel; Castro Santos, David; Olmos Tapia, Arak

2016-07-01

To support higher-frequency operation, the Large Millimeter Telescope/Gran Telescopio Milimetrico (or LMT/GTM) is replacing its existing monolithic aluminum secondary mirror (M2). The new mirror is a segmented design based on the same electroformed nickel reflector panel technology that is already in use for the primary reflector segments. While the new M2 is lighter and has better surface accuracy than the original mirror, the electroformed panels are more sensitive to high temperatures. During the design phase, concerns were raised over the level of temperature increase that could occur at M2 during daytime observations. Although the panel surface is designed to scatter visible light, the LMT primary mirror is large enough to cause substantial solar heating, even at significant angular separation from the Sun. To address these concerns, the project conducted a series of field tests, within the constraint of having minimum impact on night time observations. The supplier sent two coupon samples of a reflector panel prepared identically to their proposed M2 surface. Temperature sensors were mounted on the samples and they were temporarily secured to the existing M2 mirror at different distances from the center. The goal was to obtain direct monitoring of the surface temperature under site thermal conditions and the concentration effects from the primary reflector. With the sensors installed, the telescope was then commanded to track the Sun with an elevation offset. Initially, elevation offsets from as far as 40 degrees to as close as 6 degrees were tested. The 6 degree separation test quickly passed the target maximum temperature and the telescope was returned to a safer separation. Based on these initial results, a second set of tests was performed using elevation separations from 30 degrees to 8 degrees. To account for the variability of site conditions, the temperature data were analyzed using multiple metrics. These metrics included maximum temperature, final time average temperature, and an curve fit for heating/ cooling. The results indicate that a solar separation angle of 20 degrees should be suitable for full performance operation of the LMT/GTM. This separation not only is sufficient to avoid high temperatures at the mirror, but also provides time to respond to any emergency conditions that could occur (e.g., switching to a generator after a power failure) for observations that are ahead of the motion of the Sun. Additionally, even approaches of 10 to 15 degrees of angular separation on the sky may be achievable for longer wavelength observations, though these would likely be limited to positions that are behind the position of the Sun along its motion.

Interactive effects of elevated temperature and CO2 levels on energy metabolism and biomineralization of marine bivalves Crassostrea virginica and Mercenaria mercenaria.

PubMed

Ivanina, Anna V; Dickinson, Gary H; Matoo, Omera B; Bagwe, Rita; Dickinson, Ashley; Beniash, Elia; Sokolova, Inna M

2013-09-01

The continuing increase of carbon dioxide (CO2) levels in the atmosphere leads to increases in global temperatures and partial pressure of CO2 (PCO2) in surface waters, causing ocean acidification. These changes are especially pronounced in shallow coastal and estuarine waters and are expected to significantly affect marine calcifiers including bivalves that are ecosystem engineers in estuarine and coastal communities. To elucidate potential effects of higher temperatures and PCO2 on physiology and biomineralization of marine bivalves, we exposed two bivalve species, the eastern oysters Crassostrea virginica and the hard clams Mercenaria mercenaria to different combinations of PCO2 (~400 and 800μatm) and temperatures (22 and 27°C) for 15weeks. Survival, bioenergetic traits (tissue levels of lipids, glycogen, glucose and high energy phosphates) and biomineralization parameters (mechanical properties of the shells and activity of carbonic anhydrase, CA) were determined in clams and oysters under different temperature and PCO2 regimes. Our analysis showed major inter-species differences in shell mechanical traits and bioenergetics parameters. Elevated temperature led to the depletion of tissue energy reserves indicating energy deficiency in both species and resulted in higher mortality in oysters. Interestingly, while elevated PCO2 had a small effect on the physiology and metabolism of both species, it improved survival in oysters. At the same time, a combination of high temperature and elevated PCO2 lead to a significant decrease in shell hardness in both species, suggesting major changes in their biomineralization processes. Overall, these studies show that global climate change and ocean acidification might have complex interactive effects on physiology, metabolism and biomineralization in coastal and estuarine marine bivalves. Copyright © 2013 Elsevier Inc. All rights reserved.

Physiological acclimation to elevated temperature in a reef-building coral from an upwelling environment

NASA Astrophysics Data System (ADS)

Mayfield, A. B.; Fan, T.-Y.; Chen, C.-S.

2013-12-01

Recent work has found that pocilloporid corals from regions characterized by unstable temperatures, such as those exposed to periodic upwelling, display a remarkable degree of phenotypic plasticity. In order to understand whether important reef builders from these upwelling reefs remain physiologically uncompromised at temperatures they will experience in the coming decades as a result of global climate change, a long-term elevated temperature experiment was conducted with Pocillopora damicornis specimens collected from Houbihu, a small embayment within Nanwan Bay, southern Taiwan that is characterized by 8-9 °C temperature changes during upwelling events. Upon nine months of exposure to nearly 30 °C, all colony (mortality and surface area), polyp ( Symbiodinium density and chlorophyll a content), tissue (total thickness), and molecular (gene expression and molecular composition)-level parameters were documented at similar levels between experimental corals and controls incubated at 26.5 °C, suggesting that this species can readily acclimate to elevated temperatures that cause significant degrees of stress, or even bleaching and mortality, in conspecifics of other regions of the Indo-Pacific. However, the gastrodermal tissue layer was relatively thicker in corals of the high temperature treatment sampled after nine months, possibly as an adaptive response to shade Symbiodinium from the higher photosynthetically active radiation levels that they were experiencing at that sampling time. Such shading may have prevented high light and high temperature-induced photoinhibition, and consequent bleaching, in these samples.

Monitoring eruptive activity at Mount St. Helens with TIR image data

USGS Publications Warehouse

Vaughan, R.G.; Hook, S.J.; Ramsey, M.S.; Realmuto, V.J.; Schneider, D.J.

2005-01-01

Thermal infrared (TIR) data from the MASTER airborne imaging spectrometer were acquired over Mount St. Helens in Sept and Oct, 2004, before and after the onset of recent eruptive activity. Pre-eruption data showed no measurable increase in surface temperatures before the first phreatic eruption on Oct 1. MASTER data acquired during the initial eruptive episode on Oct 14 showed maximum temperatures of ???330??C and TIR data acquired concurrently from a Forward Looking Infrared (FLIR) camera showed maximum temperatures ???675??C, in narrow (???1-m) fractures of molten rock on a new resurgent dome. MASTER and FLIR thermal flux calculations indicated a radiative cooling rate of ???714 J/m2/S over the new dome, corresponding to a radiant power of ???24 MW. MASTER data indicated the new dome was dacitic in composition, and digital elevation data derived from LIDAR acquired concurrently with MASTER showed that the dome growth correlated with the areas of elevated temperatures. Low SO2 concentrations in the plume combined with sub-optimal viewing conditions prohibited quantitative measurement of plume SO2. The results demonstrate that airborne TIR data can provide information on the temperature of both the surface and plume and the composition of new lava during eruptive episodes. Given sufficient resources, the airborne instrumentation could be deployed rapidly to a newly-awakening volcano and provide a means for remote volcano monitoring. Copyright 2005 by the American Geophysical Union.

Trend Assessment of Spatio-Temporal Change of Tehran Heat Island Using Satellite Images

NASA Astrophysics Data System (ADS)

Saradjian, M. R.; Sherafati, Sh.

2015-12-01

Numerous investigations on Urban Heat Island (UHI) show that land cover change is the main factor of increasing Land Surface Temperature (LST) in urban areas, especially conversion of vegetation and bare soil to concrete, asphalt and other man-made structures. On the other hand, other human activities like those which cause to burning fossil fuels, that increase the amount of carbon dioxide, may raise temperature in global scale in comparison with small scales (urban areas). In this study, multiple satellite images with different spatial and temporal resolutions have been used to determine Land Surface Temperature (LST) variability in Tehran metropolitan area. High temporal resolution of AVHRR images have been used as the main data source when investigating temperature variability in the urban area. The analysis shows that UHI appears more significant at afternoon and night hours. But the urban class temperature is almost equal to its surrounding vegetation and bare soil classes at around noon. It also reveals that there is no specific difference in UHI intense during the days throughout the year. However, it can be concluded that in the process of city expansion in years, UHI has been grown both spatially and in magnitude. In order to locate land-cover types and relate them to LST, Thematic Mapper (TM) images have been exploited. The influence of elevation on the LST has also been studied, using digital elevation model derived from SRTM database.

Shock Response of Commercial Purity Polycrystalline Magnesium Under Uniaxial Strain at Elevated Temperatures

NASA Astrophysics Data System (ADS)

Wang, Tianxue; Zuanetti, Bryan; Prakash, Vikas

2017-12-01

In the present paper, results of plate impact experiments designed to investigate the onset of incipient plasticity in commercial purity polycrystalline magnesium (99.9%) under weak uniaxial strain compression and elevated temperatures up to melt are presented. The dynamic stress at yield and post yield of magnesium, as inferred from the measured normal component of the particle velocity histories at the free (rear) surface of the target plate, are observed to decrease progressively with increasing test temperatures in the range from 23 to 500 °C. At (higher) test temperatures in the range 500-610 °C, the rate of decrease of dynamic stress with temperature at yield and post-yield in the sample is observed to weaken. At still higher test temperatures (617 and 630 °C), a dramatic increase in dynamic yield as well as flow stress is observed indicating a change in dominant mechanism of plastic deformation as the sample approaches the melt point of magnesium at strain rates of 105/s. In addition to these measurements at the wavefront, the plateau region of the free surface particle velocity profiles indicates that the longitudinal (plastic) impedance of the magnesium samples decreases continuously as the sample temperatures are increased from room to 610 °C, and then reverses trend (indicating increasing material longitudinal impedance/strength) as the sample temperatures are increased to 617 and 630 °C. Electron back scattered diffraction analysis of the as-received and annealed pre-test magnesium samples reveal grain coarsening as well as grain re-orientation to a different texture during the heating process of the samples.

Investigation of structural and magnetic properties of rapidly-solidified iron-silicon alloys at ambient and elevated temperatures

DOE PAGES

Jayaraman, T. V.; Meka, V. M.; Jiang, X.; ...

2018-01-09

Here we investigated the ambient temperature structural properties (thickness, width, microstructure, and lattice parameter), and the ambient and high temperature (up to 900 K) direct current (DC) magnetic properties—saturation magnetization (M S) and intrinsic coercivity (H CI)—of rapidly-solidified (melt-spun) Fe-x wt.% Si (x = 3, 5, & 8) alloys. The wheel surface speeds selected for the study were 30 m/s and 40 m/s. The ribbons produced at the lower wheel surface speed (30 m/s) were continuous having relatively uniform edges compared to the ribbons produced at the higher wheel surface speed. The thickness and the width of the melt-spun ribbonsmore » ranged between ~15 and 60 μm and 500–800 μm, respectively. The x-ray diffraction spectra of the melt-spun ribbons indicated the presence of disordered α-phase, irrespective of the composition, and the wheel surface speed. The lattice parameter decreased gradually as a function of increasing silicon content from ~0.2862 nm (Fe-3 wt.% Si) to ~0.2847 nm (Fe-8 wt.% Si). The wheel surface speed showed an insignificant effect on M S while increased silicon content resulted in a decreasing trend in M S. Elevated temperature evaluation of the magnetization (M-T curves at ~7.96 kA/m) in the case of Fe-3 & 5 wt.% Si alloy ribbons was distinctly different from that of the Fe-8 wt.% Si alloy ribbons. The curves of the as-prepared Fe-3 wt.% Si and Fe-5 wt.% Si alloy ribbons were irreversible while that of Fe-8 wt.% Si was reversible. The M S for any of the combinations of wheel surface speed and composition decreased monotonically with the increase in temperature (from 300 to 900 K). While H CI increased with the increase in temperature for all the wheel surface speed and composition combination, its nature of increase is distinct for Fe-8 wt.% Si alloy ribbons compared to Fe-3 & 5 wt.% Si alloys ribbons. Finally, it appears that rapidly-solidified Fe-3 wt.% Si and Fe-5 wt.% Si alloys ribbons are primarily comprised of the α phase (disordered phase) while the Fe-8 wt.% Si alloy ribbons are comprised primarily of disordered phase along with minor constituents of an ordered phase.« less

Investigation of structural and magnetic properties of rapidly-solidified iron-silicon alloys at ambient and elevated temperatures

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

Jayaraman, T. V.; Meka, V. M.; Jiang, X.

Here we investigated the ambient temperature structural properties (thickness, width, microstructure, and lattice parameter), and the ambient and high temperature (up to 900 K) direct current (DC) magnetic properties—saturation magnetization (M S) and intrinsic coercivity (H CI)—of rapidly-solidified (melt-spun) Fe-x wt.% Si (x = 3, 5, & 8) alloys. The wheel surface speeds selected for the study were 30 m/s and 40 m/s. The ribbons produced at the lower wheel surface speed (30 m/s) were continuous having relatively uniform edges compared to the ribbons produced at the higher wheel surface speed. The thickness and the width of the melt-spun ribbonsmore » ranged between ~15 and 60 μm and 500–800 μm, respectively. The x-ray diffraction spectra of the melt-spun ribbons indicated the presence of disordered α-phase, irrespective of the composition, and the wheel surface speed. The lattice parameter decreased gradually as a function of increasing silicon content from ~0.2862 nm (Fe-3 wt.% Si) to ~0.2847 nm (Fe-8 wt.% Si). The wheel surface speed showed an insignificant effect on M S while increased silicon content resulted in a decreasing trend in M S. Elevated temperature evaluation of the magnetization (M-T curves at ~7.96 kA/m) in the case of Fe-3 & 5 wt.% Si alloy ribbons was distinctly different from that of the Fe-8 wt.% Si alloy ribbons. The curves of the as-prepared Fe-3 wt.% Si and Fe-5 wt.% Si alloy ribbons were irreversible while that of Fe-8 wt.% Si was reversible. The M S for any of the combinations of wheel surface speed and composition decreased monotonically with the increase in temperature (from 300 to 900 K). While H CI increased with the increase in temperature for all the wheel surface speed and composition combination, its nature of increase is distinct for Fe-8 wt.% Si alloy ribbons compared to Fe-3 & 5 wt.% Si alloys ribbons. Finally, it appears that rapidly-solidified Fe-3 wt.% Si and Fe-5 wt.% Si alloys ribbons are primarily comprised of the α phase (disordered phase) while the Fe-8 wt.% Si alloy ribbons are comprised primarily of disordered phase along with minor constituents of an ordered phase.« less

Triton's surface-atmosphere energy balance

USGS Publications Warehouse

Stansberry, J.A.; Yelle, R.V.; Lunine, J.I.; McEwen, A.S.

1992-01-01

We explore the energetics of Triton's surface-atmosphere system using a model that includes the turbulent transfer of sensible heat as well as insolation, reradiation, and latent heat transport. The model relies on a 1?? by 1?? resolution hemispheric bolometric albedo map of Triton for determining the atmospheric temperature, the N2 frost emissivity, and the temperatures of unfrosted portions of the surface consistent with a frost temperature of ???38 K. For a physically plausible range of heat transfer coefficients, we find that the atmospheric temperature roughly 1 km above the surface is approximately 1 to 3 K hotter than the surface. Atmospheric temperatures of 48 K suggested by early analysis of radio occultation data cannot be obtained for plausible values of the heat transfer coefficients. Our calculations indicate that Triton's N2 frosts must have an emissivity well below unity in order to have a temperature of ???38 K, consistent with previous results. We also find that convection over small hot spots does not significantly cool them off, so they may be able to act as continous sources of buoyancy for convective plumes, but have not explored whether the convection is vigorous enough to entrain particulate matter thereby forming a dust devil. Our elevated atmospheric temperatures make geyser driven plumes with initial upward velocities ???10 m s-1 stagnate in the lower atmosphere. These "wimpy" plumes provide a possible explanation for Triton's "wind streaks.". ?? 1992.

Electromagnetic Characterization of Carbon Nanotube Films Subject to an Oxidative Treatment at Elevated Temperature (Preprint)

DTIC Science & Technology

2010-07-01

response to the tip causes a redistribution of charge on the tip in order to maintain the equipotential surface of the sphere, and also results in a shift...can be obtained. In some instances these treatments lead to uncapping of nanotubes. Geng et al. [25] have shown that the surfaces of SWNT bundles...20] discovered a new and catalyst-free method for the growth of CNTs: surface decomposition of silicon carbide (SiC). This thermal decomposition

Regional scale estimates of baseflow and factors influencing baseflow in the Upper Colorado River Basin

USGS Publications Warehouse

Rumsey, Christine; Miller, Matthew P.; Susong, David D.; Tillman, Fred D.; Anning, David W.

2015-01-01

Results suggest that approximately half of the streamflow in the UCRB is baseflow derived from groundwater discharge to streams. Higher baseflow yields typically occur in upper elevation areas of the UCRB. PCA identified precipitation, snow, sand content of soils, elevation, land surface slope, percent grasslands, and percent natural barren lands as being positively correlated with baseflow yield; whereas temperature, potential evapotranspiration, silt and clay content of soils, percent agriculture, and percent shrublands were negatively correlated with baseflow yield.

Fossil Chironomidae (Insecta: Diptera) as Paleothermometers in the African Tropics

NASA Astrophysics Data System (ADS)

Eggermont, H.; Heiri, O.; Russell, J.; Vuille, M.; Audenaert, L.; Klaassen, G.; Verschuren, D.

2008-12-01

Reconstruction of Africa's temperature history from natural climate archives such as lake sediments is essential to amend the current scarcity of information on natural tropical climate and ecosystem variability. Chironomids are well-established paleothermometers in north-temperate/boreal regions, but their potential in tropical lakes has never before been assessed. We surveyed sub-fossil chironomid assemblages in surface sediments from 65 lakes and permanent pools in southwestern Uganda and central/southern Kenya, spanning elevations between 489 and 4575 m asl. Using various subsets of lakes and corresponding Surface-Water Temperatures (SWTemp) and Mean Annual Air Temperatures (MATemp), we developed a series of inference models for quantitative paleotemperature reconstruction. Models using both low-, mid- and high-elevation sites suffer to some extent from the small number of samples between 2500 and 3500 m asl, and from the presence of ecologically distinct but morphologically indistinguishable taxa. Models confined to mountain sites produce poorer error statistics, but are less prone to the biogeographical and taxonomic complexities associated with long climatic gradients. Overall, error statistics compare favourably with those of inference models developed for temperate regions, indicating that fossil assemblages of African Chironomidae can be valuable indicators of past temperature change. We subsequently used these models to evaluate whether high-elevation lakes in the Rwenzori Mountains (>3000 m asl) have been impacted by climate warming in recent centuries by comparing temperatures inferred from chironomid assemblages in modern sediments with those derived from chironomid assemblages in sediments deposited within or briefly after the Little Ice Age (1270-1850 AD). Depending on the model used, between 44 and 63% of the 16 lakes studied indicate significantly warmer temperatures in recent times (corresponding with an average MATemp rise of 0.88 ° C, and average SWTemp rise of 1.33 ° C), while all but one of the other lakes show temperature changes that are statistically insignificant. We conclude that chironomid communities in Rwenzori lakes adequately record past temperature changes, with potential for evaluating the impacts of past air temperature variation on the long-term dynamics of the Rwenzori glaciers.

THE MELTING MECHANISM OF DNA TETHERED TO A SURFACE

PubMed Central

QAMHIEH, KHAWLA; WONG, KA-YIU; LYNCH, GILLIAN C.; PETTITT, B. MONTGOMERY

2009-01-01

The details of melting of DNA immobilized on a chip or nanoparticle determines the sensitivity and operating characteristics of many analytical and synthetic biotechnological devices. Yet, little is known about the differences in how the DNA melting occurs between a homogeneous solution and that on a chip. We used molecular dynamics simulations to explore possible pathways for DNA melting on a chip. Simulation conditions were chosen to ensure that melting occurred in a submicrosecond timescale. The temperature was set to 400 K and the NaCl concentration was set to 0.1 M. We found less symmetry than in the solution case where for oligomeric double-stranded nucleic acids both ends melted with roughly equal probability. On a prepared silica surface we found melting is dominated by fraying from the end away from the surface. Strand separation was hindered by nonspecific surface adsorption at this temperature. At elevated temperatures the melted DNA was attracted to even uncharged organically coated surfaces demonstrating surface fouling. While hybridization is not the simple reverse of melting, this simulation has implications for the kinetics of hybridization. PMID:19802357

An analysis of surface air temperature trends and variability along the Andes

NASA Astrophysics Data System (ADS)

Franquist, Eric S.

Climate change is difficult to study in mountainous regions such as the Andes since steep changes in elevation cannot always be resolved by climate models. However, it is important to examine temperature trends in this region as rises in surface air temperature are leading to the melting of tropical glaciers. Local communities rely on the glacier-fed streamflow to get their water for drinking, irrigation, and livestock. Moreover, communities also rely on the tourism of hikers who come to the region to view the glaciers. As the temperatures increase, these glaciers are no longer in equilibrium with their current climate and are receding rapidly and decreasing the streamflow. This thesis examines surface air temperature from 858 weather stations across Ecuador, Peru, and Chile in order to analyze changes in trends and variability. Three time periods were studied: 1961--1990, 1971--2000, and 1981--2010. The greatest warming occurred during the period of 1971--2000 with 92% of the stations experiencing positive trends with a mean of 0.24°C/decade. There was a clear shift toward cooler temperatures at all latitudes and below elevations of 500 m during the most recent time period studied (1981--2010). Station temperatures were more strongly correlated with the El Nino Southern Oscillation (ENSO), than the Pacific Decadal Oscillation (PDO), and the Southern Annular Mode (SAM). A principal component analysis confirmed ENSO as the main contributor of variability with the most influence in the lower latitudes. There were clear multidecadal changes in correlation strength for the PDO. The PDO contributed the most to the increases in station temperature trends during the 1961--1990 period, consistent with the PDO shift to the positive phase in the middle of this period. There were many strong positive trends at individual stations during the 1971--2000 period; however, these trends could not fully be attributed to ENSO, PDO, or SAM, indicating anthropogenic effects of greenhouse gas emissions as the most likely cause.

The Benefits of Using Dense Temperature Sensor Networks to Monitor Urban Warming

NASA Astrophysics Data System (ADS)

Twine, T. E.; Snyder, P. K.; Kucharik, C. J.; Schatz, J.

2015-12-01

Urban heat islands (UHIs) occur when urban and suburban areas experience temperatures that are elevated relative to their rural surroundings because of differences in the fraction of gray and green infrastructure. Studies have shown that communities most at risk for impacts from climate-related disasters (i.e., lower median incomes, higher poverty, lower education, and minorities) tend to live in the hottest areas of cities. Development of adequate climate adaptation tools for cities relies on knowledge of how temperature varies across space and time. Traditionally, a city's urban heat island has been quantified using near-surface air temperature measurements from a few sites. This methodology assumes (1) that the UHI can be characterized by the difference in air temperature from a small number of points, and (2) that these few points represent the urban and rural signatures of the region. This methodology ignores the rich information that could be gained from measurements across the urban to rural transect. This transect could traverse elevations, water bodies, vegetation fraction, and other land surface properties. Two temperature sensor networks were designed and implemented in the Minneapolis-Saint Paul, MN and Madison, WI metropolitan areas beginning in 2011 and 2012, respectively. Both networks use the same model sensor and record temperature every 15 minutes from ~150 sensors. Data from each network has produced new knowledge of how temperature varies diurnally and seasonally across the cities and how the UHI magnitude is influenced by weather phenomena (e.g., wind, snow cover, heat waves) and land surface characteristics such as proximity to inland lakes. However, the two metropolitan areas differ in size, population, structure, and orientation to water bodies. In addition, the sensor networks were established in very different manners. We describe these differences and present lessons learned from the design and ongoing efforts of these two dense networks located in the Midwest USA.

Replication of surface features from a master model to an amorphous metallic article

DOEpatents

Johnson, William L.; Bakke, Eric; Peker, Atakan

1999-01-01

The surface features of an article are replicated by preparing a master model having a preselected surface feature thereon which is to be replicated, and replicating the preselected surface feature of the master model. The replication is accomplished by providing a piece of a bulk-solidifying amorphous metallic alloy, contacting the piece of the bulk-solidifying amorphous metallic alloy to the surface of the master model at an elevated replication temperature to transfer a negative copy of the preselected surface feature of the master model to the piece, and separating the piece having the negative copy of the preselected surface feature from the master model.

Livelihoods Poised Between Cold and Dry: Modeling Land Surface Phenologies and Phenometric Lapse Rates in Central Asian Highland Pastures

NASA Astrophysics Data System (ADS)

Henebry, G. M.; Tomaszewska, M. A.; Krehbiel, C. P.; Kelgenbaeva, K.

2016-12-01

To explore the vulnerability of high-elevation communities in the Kyrgyz Republic and in Uzbekistan to changing climatic, sociodemographic, and socioeconomic conditions, we assembled image time series to characterize the condition of pastures near villages at high elevation (>2000 masl) and in remote pastures at higher elevations. Here we describe the application of the convex quadratic (CxQ) model of land surface phenology to highland pasturelands for selected oblasts in the Kyrgyz Republic and in eastern Uzbekistan. We used 16 years (2000-2015) of Landsat normalized difference vegetation index (NDVI) data with MODIS land surface temperature data processed into accumulated growing degree-days. The peak height of the NDVI and the thermal time to peak are two key phenological metrics derived analytically from the fitted parameter coefficients of the CxQ model for each pixel time series. Both exhibited sensitivity to elevation, which we describe in terms of phenometric lapse rates (PLRs). Interannual variation in PLRs was expressed differently for the peak NDVI and the thermal time to peak. Peak NDVI increased with elevation up to a point but also exhibited more spatial variation in dry years than in wetter years. Thermal time to peak exhibited strong, highly significant negative linear relationships to elevation with steeper slopes in drier years. Both types of PLRs were modulated by aspect. These relationships and the associated CxQ models by elevation and aspect can provide expectations against which to detect changes in pasture status as a result of management or weather.

Room temperature CO and H2 sensing with carbon nanoparticles.

PubMed

Kim, Daegyu; Pikhitsa, Peter V; Yang, Hongjoo; Choi, Mansoo

2011-12-02

We report on a shell-shaped carbon nanoparticle (SCNP)-based gas sensor that reversibly detects reducing gas molecules such as CO and H(2) at room temperature both in air and inert atmosphere. Crystalline SCNPs were synthesized by laser-assisted reactions in pure acetylene gas flow, chemically treated to obtain well-dispersed SCNPs and then patterned on a substrate by the ion-induced focusing method. Our chemically functionalized SCNP-based gas sensor works for low concentrations of CO and H(2) at room temperature even without Pd or Pt catalysts commonly used for splitting H(2) molecules into reactive H atoms, while metal oxide gas sensors and bare carbon-nanotube-based gas sensors for sensing CO and H(2) molecules can operate only at elevated temperatures. A pristine SCNP-based gas sensor was also examined to prove the role of functional groups formed on the surface of functionalized SCNPs. A pristine SCNP gas sensor showed no response to reducing gases at room temperature but a significant response at elevated temperature, indicating a different sensing mechanism from a chemically functionalized SCNP sensor.

Genetically tunable M13 phage films utilizing evaporating droplets.

PubMed

Alberts, Erik; Warner, Chris; Barnes, Eftihia; Pilkiewicz, Kevin; Perkins, Edward; Poda, Aimee

2018-01-01

This effort utilizes a genetically tunable system of bacteriophage to evaluate the effect of charge, temperature and particle concentration on biomaterial synthesis utilizing the coffee ring (CR) effect. There was a 1.6-3 fold suppression of the CR at higher temperatures while maintaining self-assembled structures of thin films. This suppression was observed in phage with charged and uncharged surface chemistry, which formed ordered and disordered assemblies respectively, indicating CR suppression is not dependent on short-range ordering or surface chemistry. Analysis of the drying process suggests weakened capillary flow at elevated temperatures caused CR suppression and could be further enhanced for controlled assembly for advanced biomaterials. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Climate change and the impact of extreme temperatures on aviation

NASA Astrophysics Data System (ADS)

Coffel, E.; Horton, R.

2014-12-01

Weather is the most significant factor affecting aircraft operations, accounting for 70-80% of passenger delays and costing airlines hundreds of millions of dollars per year in lost revenue. Temperature and airport elevation significantly influence the maximum allowable takeoff weight of an aircraft by changing the surface air density and thus the lift produced at a given speed. For a given runway length, airport elevation, and aircraft type there is a temperature threshold above which the airplane cannot take off at its maximum weight and thus must be weight restricted. The number of summer days necessitating weight restriction has increased since 1980 along with the observed increase in surface temperature. Climate change is projected to increase mean temperatures at all airports and significantly increase the frequency and severity of extreme heat events at some. These changes will negatively affect aircraft performance, leading to increased weight restrictions especially at airports with short runways and little room to expand. For a Boeing 737-800 aircraft, we find that the number of weight restriction days between May and September will increase by 50-100% at four major airports in the United States by 2050-2070 under the RCP8.5 high emissions scenario. These performance reductions may have a significant economic effect on the airline industry, leading to lower profits and higher passenger fares. Increased weight restrictions have previously been identified as potential impacts of climate change, but this study is the first to quantify the effect of higher temperatures on commercial aviation.

Theoretical evidence for unexpected O-rich phases at corners of MgO surfaces

NASA Astrophysics Data System (ADS)

Bhattacharya, Saswata; Berger, Daniel; Reuter, Karsten; Ghiringhelli, Luca M.; Levchenko, Sergey V.

2017-12-01

Realistic oxide materials are often semiconductors, in particular at elevated temperatures, and their surfaces contain undercoordinated atoms at structural defects such as steps and corners. Using hybrid density-functional theory and ab initio atomistic thermodynamics, we investigate the interplay of bond-making, bond-breaking, and charge-carrier trapping at the corner defects at the (100) surface of a p -doped MgO in thermodynamic equilibrium with an O2 atmosphere. We show that by manipulating the coordination of surface atoms, one can drastically change and even reverse the order of stability of reduced versus oxidized surface sites.

Alumina Volatility in Water Vapor at Elevated Temperatures: Application to Combustion Environments

NASA Technical Reports Server (NTRS)

Opila, Elizabeth J.; Myers, Dwight L.

2003-01-01

The volatility of alumina in high temperature water vapor was determined by measuring weight loss of sapphire coupons at temperatures between 1250 and 1500 C, water vapor partial pressures between 0.15 and 0.68 atm in oxygen, at one atmosphere total pressure, and a gas velocity of 4.4 centimeters per second. The variation of the volatility with water vapor partial pressure was consistent with Al(OH)3(g) formation. The enthalpy of reaction to form Al(OH)3(g) from alumina and water vapor was found to be 210 plus or minus 20 kJ/mol. Surface rearrangement of ground sapphire surfaces increased with water vapor partial pressure, temperature and volatility rate. Recession rates of alumina due to volatility were determined as a function of water vapor partial pressure and temperature to evaluate limits for use of alumina in long term applications in combustion environments.

Gas-phase measurements of combustion interaction with materials for radiation-cooled chambers

NASA Technical Reports Server (NTRS)

Barlow, R. S.; Lucht, R. P.; Jassowski, D. M.; Rosenberg, S. D.

1991-01-01

Foil samples of Ir and Pt are exposed to combustion products in a controlled premixed environment at atmospheric pressure. Electrical heating of the foil samples is used to control the surface temperature and to elevate it above the radiative equilibrium temperature within the test apparatus. Profiles of temperature and OH concentration in the boundary layer adjacent to the specimen surface are measured by laser-induced fluorescence. Measured OH concentrations are significantly higher than equilibrium concentrations calculated for the known mixture ratio and the measured temperature profiles. This result indicates that superequilibrium concentrations of H-atoms and O-atoms are also present in the boundary layer, due to partial equilibrium of the rapid binary reactions of the H2/O2 chemical kinetic system. These experiments are conducted as part of a research program to investigate fundamental aspects of the interaction of combustion gases with advanced high-temperature materials for radiation-cooled thrusters.

Snowmelt in a High Latitude Mountain Catchment: Effect of Vegetation Cover and Elevation

NASA Astrophysics Data System (ADS)

Pomeroy, J. W.; Essery, R. L.; Ellis, C. R.; Hedstrom, N. R.; Janowicz, R.; Granger, R. J.

2004-12-01

The energetics and mass balance of snowpacks in the premelt and melt period were compared from three elevation bands in a high latitude mountain catchment, Wolf Creek Research Basin, Yukon. Elevation is strongly correlated with vegetation cover and in this case the three elevation bands (low, middle, high) correspond to mature spruce forest, dense shrub tundra and sparse tundra (alpine). Measurements of radiation, ground heat flux, snow depth, snowfall, air temperature, wind speed were made on a half-hourly basis at the three elevations for a 10 year period. Sondes provided vertical gradients of air temperature, humidity, wind speed and air pressure. Snow depth and density surveys were conducted monthly. Comparisons of wind speed, air temperature and humidity at three elevations show that the expected elevational gradients in the free atmosphere were slightly enhanced just above the surface canopies, but that the climate at the snow surface was further influenced by complex canopy effects. Premelt snow accumulation was strongly affected by intercepted snow in the forest and blowing snow sublimation in the sparse tundra but not by the small elevational gradients in snowfall. As a result the maximum premelt SWE was found in the mid-elevation shrub tundra and was roughly double that of the sparse tundra or forest. Minimum variability of SWE was observed in the forest and shrub tundra (CV=0.25) while in the sparse tundra variability doubled (CV=0.5). Snowmelt was influenced by differences in premelt accumulation as well as differences in the net energy fluxes to snow. Elevation had a strong effect on the initiation of melt with the forest melt starting on average 16 days before the shrub tundra and 19 days before the sparse tundra. Mean melt rates showed a maximum in middle elevations and increased from 860 kJ/day in the forest to 1460 kJ/day in the sparse tundra and 2730 kJ/day in the shrub tundra. The forest canopy reduced melt while the shrub canopy enhanced it relative to the sparsely vegetated tundra. Duration of melt was similar in the forest and shrub tundra at 20 days while the sparse tundra was shorter at 13 days; the differences due to differing snow accumulation and melt rates. The greatest variability in the timing and rate of melt was found in the shrub tundra, where the effect of the shrub canopy over snow depends on snow depth and insolation and is reduced in years with high snow accumulation or extensive cloudy periods in spring. The results show that it is necessary to consider the combination of elevation and vegetation effects on snow microclimate and melt processes in high latitude mountain catchments, but that weather patterns induce substantial variability on the effect these factors.

Hot Air Balloon Experiments to Measure the Break-up of the Nocturnal Drainage Flow in Complex Terrain.

NASA Astrophysics Data System (ADS)

Berman, N. S.; Fernando, H. J. S.; Colomer, J.; Levy, M.; Zieren, L.

1997-11-01

In order to extend our understanding of the thermally driven atmospheric winds and their influence on pollutant transport, a hot air balloon experiment was conducted over a four day period in June, 1997 near Nogales, Arizona. The focus was on the early morning break-up of the stable down-slope and down-valley flow and the establishment of a convective boundary layer near the surface in the absence of synoptic winds. Temperature, elevation, position and particulate matter concentration were measured aloft and temperature gradient and wind velocity were measured at ground level. The wind velocity within the stable layer was generally less than 1.5 m/s. Just above the stable layer (about 300 meters above the valley) the wind shifted leading to an erosion of the stable layer from above. Surface heating after sunrise created a convective layer which rose from the ground until the stable layer was destroyed. Examples of temperature fluctuation measurements at various elevations during the establishment of the convective flow will be presented. Implications of results for turbulence parameterizations needed for numerical models of wind fields in complex terrain will be discussed.

Environmental Flow for Sungai Johor Estuary

NASA Astrophysics Data System (ADS)

Adilah, A. Kadir; Zulkifli, Yusop; Zainura, Z. Noor; Bakhiah, Baharim N.

2018-03-01

Sungai Johor estuary is a vital water body in the south of Johor and greatly affects the water quality in the Johor Straits. In the development of the hydrodynamic and water quality models for Sungai Johor estuary, the Environmental Fluid Dynamics Code (EFDC) model was selected. In this application, the EFDC hydrodynamic model was configured to simulate time varying surface elevation, velocity, salinity, and water temperature. The EFDC water quality model was configured to simulate dissolved oxygen (DO), dissolved organic carbon (DOC), chemical oxygen demand (COD), ammoniacal nitrogen (NH3-N), nitrate nitrogen (NO3-N), phosphate (PO4), and Chlorophyll a. The hydrodynamic and water quality model calibration was performed utilizing a set of site specific data acquired in January 2008. The simulated water temperature, salinity and DO showed good and fairly good agreement with observations. The calculated correlation coefficients between computed and observed temperature and salinity were lower compared with the water level. Sensitivity analysis was performed on hydrodynamic and water quality models input parameters to quantify their impact on modeling results such as water surface elevation, salinity and dissolved oxygen concentration. It is anticipated and recommended that the development of this model be continued to synthesize additional field data into the modeling process.

Newly Designed Apparatus for Measuring the Angular Dependent Surface Emittance in a Wide Wavelength Range and at Elevated Temperatures up to 1400°C

NASA Astrophysics Data System (ADS)

Rydzek, M.; Stark, T.; Arduini-Schuster, M.; Manara, J.

2012-11-01

An optimized apparatus for measuring the angular dependent surface emittance up to elevated temperatures has been designed. This emittance measurement apparatus (EMMA) is coupled to a Bruker Vertex 70v FTIR-spectrometer, so that a wavelength range from about 2 μm up to 25 μm is accessible. The central part of the new apparatus is a double walled, stainless steel vessel which can be evacuated or filled with various gases or with air. Inside the vessel a cylindrical tube furnace is pivot-mounted on a system of discs, for automatically rotating up to an angle of 180°. This allows both, the measurement at different detection angles (0° to 85°) and a consecutive measurement of sample and black-body reference without ventilating and opening the pot. The aim of this work is to present the newly designed emittance measurement apparatus which enables the determination of the angular dependent spectral emittance of opaque samples at temperatures up to 1400 °C. Next to the setup of the apparatus, the measurement results of various materials are presented at different detection angles.

Residential Exposure to Nighttime Retained Heat in the El Paso, Texas, USA Desert Metroplex

NASA Astrophysics Data System (ADS)

Amaya, M. A.; Mohammed, M.; Pingitore, N. E.; Aldouri, R. K.; Benedict, B. A.

2013-12-01

The urban heat island is a well recognized and extensively studied phenomenon that has accelerating importance resulting from two trends associated with world-wide population growth: increasing urbanization and global warming. Urbanization, particularly when unplanned and haphazard, changes such thermal parameters as albedo, surface roughness, and heat capacities of surface materials. Rapid urbanization in the contiguous El Paso, Texas, USA - Ciudad Juarez, Chihuahua, Mexico bi-national metroplex has produced an urban heat island that is warmer than the surrounding Chihuahuan desert (temperature: 35-40 C summer; high elevation: 600-1675 m; rainfall: less than 250 mm annual). Despite the extensive literature on the urban heat island, little is known about urban nighttime land surface temperatures. We employed infrared satellite imaging to establish the variation of nighttime neighborhood surface temperatures across the city of El Paso, as well as all of El Paso County. The underlying purpose of our continuing investigation is to evaluate the geography of morbidity risk: are different neighborhoods at different risk of high nighttime temperatures. Those risks can include heat stress, and irritability and sleep deprivation, with possible resultant violence. Heat exposure at night is significant because residents are at home and 90% of El Pasoans do not have 'refrigerated' air conditioning, but instead have evaporative coolers, which are less expensive to own and operate, but are less effective since they raise the humidity of the partially cooled air. Our geographically weighted regression model showed that both day and nighttime land surface temperatures correlated with the normalized difference vegetation index, population density, and albedo. The association with the index and albedo was stronger during the daytime and with population density during the nighttime. Vegetation (negative) and population density (positive) were the dominant temperature drivers, with albedo and elevation as secondary drivers. Using archived satellite imagery we determined that over the last two decades there has been an increase in both day and nighttime temperatures. With no expected change in urban growth and global warming, local residents will be at increasing risk in the future, as will residents in other urban centers in the desert southwest of the US. We currently are evaluating exposure risk in different population sectors. Do the aged or the poor reside in higher risk neighborhoods? Are there simple measures that can be taken to ameliorate nighttime temperatures?

Effects of experimental warming and elevated CO2 on surface methane and CO­2 fluxes from a boreal black spruce peatland

NASA Astrophysics Data System (ADS)

Gill, A. L.; Finzi, A.; Hsieh, I. F.; Giasson, M. A.

2016-12-01

High latitude peatlands represent a major terrestrial carbon store sensitive to climate change, as well as a globally significant methane source. While elevated atmospheric carbon dioxide concentrations and warming temperatures may increase peat respiration and C losses to the atmosphere, reductions in peatland water tables associated with increased growing season evapotranspiration may alter the nature of trace gas emission and increase peat C losses as CO2 relative to methane (CH4). As CH4 is a greenhouse gas with twenty times the warming potential of CO2, it is critical to understand how surface fluxes of CO2 and CH4 will be influenced by factors associated with global climate change. We used automated soil respiration chambers to assess the influence of elevated atmospheric CO2 and whole ecosystem warming on peatland CH4 and CO2 fluxes at the SPRUCE (Spruce and Peatland Responses Under Climatic and Environmental Change) Experiment in northern Minnesota. Here we report soil iCO2 and iCH4 flux responses to the first year of belowground warming and the first season of whole ecosystem warming and elevated CO2 treatments. We find that peat methane fluxes are more sensitive to warming treatments than peat CO2 fluxes, particularly in hollow peat microforms. Surface CO2:CH4 flux ratios decreased across warming treatments, suggesting that the temperature sensitivity of methane production overshadows the effect of peat drying and surface aeration in the short term. δ13C of the emitted methane was more depleted in the early and late growing season, indicating a transition from hydrogenotrophic to acetoclastic methanogenesis during periods of high photosynthetic input. The measurement record demonstrates that belowground warming has measureable impacts on the nature of peat greenhouse gas emission within one year of treatment.

Strengthening of oxidation resistant materials for gas turbine applications

NASA Technical Reports Server (NTRS)

Platts, D. R.; Kirchner, H. P.; Gruver, R. M.

1972-01-01

Compressive surface layers were formed on hot-pressed silicon carbide and nitride. The objective of these treatments was to improve the impact resistance of these materials at 1590 K (2400 F). Quenching was used to form compressive surface layers on silicon carbide. The presence of the compressive stresses was demonstrated by slotted rod tests. Compressive stresses were retained at elevated temperatures. Improvements in impact resistance at 1590 K (2400 F) and flexural strength at room temperature were achieved using cylindrical rods 3.3 mm (0.13 in.) in diameter. Carburizing treatments were used to form the surface layers on silicon nitride. In a few cases using rectangular bars improvements in impact resistance at 1590 K (2400 F) were observed.

The effect of surface oxide layer on the rate of hydrogen emission from aluminum and its alloys in a high vacuum

NASA Technical Reports Server (NTRS)

Makarova, V. I.; Zyabrev, A. A.

1979-01-01

The influence of surface oxide layers on the kinetics of hydrogen emission at the high vacuum of 10 to the minus 8th power torr was investigated at temperatures from 20 to 450 C using samples of pure AB00 aluminum and the cast alloy AMg. Cast and deformed samples of AMts alloy were used to study the effect of oxide film thickness on the rate of hydrogen emission. Thermodynamic calculations of the reactions of the generation and dissociation of aluminum oxide show that degasification at elevated temperatures (up to 600 C) and high vacuum will not reduce the thickness of artificially-generated surface oxide layers on aluminum and its alloys.

The role of oxidation in the fretting wear process

NASA Technical Reports Server (NTRS)

Bill, R. C.

1980-01-01

Fretting experiments were conducted on titanium, a series of Ni-Cr-Al alloys and on some high temperature turbine alloys at room temperature and at elevated temperatures in air and in various inert environments. It was found that, depending on temperature and environment, the fretting behavior of the materials examined could be classified according to four general types of behavior. Briefly, these types of behavior were: (1) the complete absence of oxidation, as in inert environments, generally leading to low rates of fretting wear but high fretting friction; (2) gradual attrition of surface oxide with each fretting stroke, found in these experiments to operate in concert with other dominating mechanisms; (3) rapid oxidation at surface fatigue damage sites, resulting in undermining and rapid disintegration of the load bearing surface; and (4) the formation of coherent, protective oxide film, resulting in low rates of fretting wear. An analytical model predicting conditions favorable to the fourth type of behavior was outlined.

Thermal decomposition of fullerene nanowhiskers protected by amorphous carbon mask

NASA Astrophysics Data System (ADS)

Guo, Hongxuan; Wang, Chengxiang; Miyazawa, Kun'Ichi; Wang, Hongxin; Masuda, Hideki; Fujita, Daisuke

2016-12-01

Fullerene nanostructures are well known for their unique morphology, physical and mechanical properties. The thermal stability of fullerene nanostructures, such as their sublimation at high temperature is also very important for studying their structures and applications. In this work, We observed fullerene nanowhiskers (FNWs) in situ with scanning helium ion microscopy (HIM) at elevated temperatures. The FNWs exhibited different stabilities with different thermal histories during the observation. The pristine FNWs were decomposed at the temperatures higher than 300 °C in a vacuum environment. Other FNWs were protected from decomposition with an amorphous carbon (aC) film deposited on the surface. Based on high spacial resolution, aC film with periodic structure was deposited by helium ion beam induced deposition (IBID) on the surface of FNWs. Annealed at the high temperature, the fullerene molecules were selectively sublimated from the FNWs. The periodic structure was formed on the surface of FNWs and observed by HIM. Monte Carlo simulation and Raman characterization proved that the morphology of the FNWs was changed by helium IBID at high temperature. This work provides a new method of fabricating artificial structure on the surface of FNWs with periodic aC film as a mask.

Modeling hydrodynamics, water quality, and benthic processes to predict ecological effects in Narragansett Bay

EPA Science Inventory

The environmental fluid dynamics code (EFDC) was used to study the three dimensional (3D) circulation, water quality, and ecology in Narragansett Bay, RI. Predictions of the Bay hydrodynamics included the behavior of the water surface elevation, currents, salinity, and temperatur...

Do Titan's Mountains Betray the Late Acquisition of its Current Atmosphere

NASA Technical Reports Server (NTRS)

Moore, Jeffrey Morgan; Nimmo, F.

2011-01-01

Titan may have acquired its massive atmosphere relatively recently in solar system history [1,2,3,4]. Prior to that time, Titan would have been nearly airless, with its volatiles frozen or sequestered. Present-day Titan experiences only small (approximately 4 K) pole-to-equator variations, owing to efficient heat transport via the thick atmosphere [5]; these temperature variations would have been much larger (approximately 20 K) in the absence of an atmosphere. If Titan's ice shell is conductive, the change in surface temperature associated with the development of an atmosphere would have led to changes in shell thickness. In particular, the poles would move down (inducing compression) while the equator would move up. Figure 1 shows the predicted change in surface elevation as a result of the change in surface temperature, using the numerical conductive shell thickness model of [6

Tracking the Polar Front south of New Zealand using penguin dive data

NASA Astrophysics Data System (ADS)

Sokolov, Serguei; Rintoul, Stephen R.; Wienecke, Barbara

2006-04-01

Nearly 36,000 vertical temperature profiles collected by 15 king penguins are used to map oceanographic fronts south of New Zealand. There is good correspondence between Antarctic Circumpolar Current (ACC) front locations derived from temperatures sampled in the upper 150 m along the penguin tracks and front positions inferred using maps of sea surface height (SSH). Mesoscale features detected in the SSH maps from this eddy-rich region are also reproduced in the individual temperature sections based on dive data. The foraging strategy of Macquarie Island king penguins appears to be influenced strongly by oceanographic structure: almost all the penguin dives are confined to the region close to and between the northern and southern branches of the Polar Front. Surface chlorophyll distributions also reflect the influence of the ACC fronts, with the northern branch of the Polar Front marking a boundary between low surface chlorophyll to the north and elevated values to the south.

Examination of elevation dependency in observed and projected temperature change in the Upper Indus Basin and Western Himalaya

NASA Astrophysics Data System (ADS)

Fowler, H. J.; Forsythe, N. D.; Blenkinsop, S.; Archer, D.; Hardy, A.; Janes, T.; Jones, R. G.; Holderness, T.

2013-12-01

We present results of two distinct, complementary analyses to assess evidence of elevation dependency in temperature change in the UIB (Karakoram, Eastern Hindu Kush) and wider WH. The first analysis component examines historical remotely-sensed land surface temperature (LST) from the second and third generation of the Advanced Very High Resolution Radiometer (AVHRR/2, AVHRR/3) instrument flown on NOAA satellite platforms since the mid-1980s through present day. The high spatial resolution (<4km) from AVHRR instrument enables precise consideration of the relationship between estimated LST and surface topography. The LST data product was developed as part of initiative to produce continuous time-series for key remotely sensed spatial products (LST, snow covered area, cloud cover, NDVI) extending as far back into the historical record as feasible. Context for the AVHRR LST data product is provided by results of bias assessment and validation procedures against both available local observations, both manned and automatic weather stations. Local observations provide meaningful validation and bias assessment of the vertical gradients found in the AVHRR LST as the elevation range from the lowest manned meteorological station (at 1460m asl) to the highest automatic weather station (4733m asl) covers much of the key range yielding runoff from seasonal snowmelt. Furthermore the common available record period of these stations (1995 to 2007) enables assessment not only of the AVHRR LST but also performance comparisons with the more recent MODIS LST data product. A range of spatial aggregations (from minor tributary catchments to primary basin headwaters) is performed to assess regional homogeneity and identify potential latitudinal or longitudinal gradients in elevation dependency. The second analysis component investigates elevation dependency, including its uncertainty, in projected temperature change trajectories in the downscaling of a seventeen member Global Climate Model (GCM) perturbed physics ensemble (PPE) of transient (130-year) simulations using a moderate resolution (25km) regional climate model (RCM). The GCM ensemble is the17-member QUMP (Quantifying Uncertainty in Model Projections) ensemble and the downscaling is done using HadRM3P, part of the PRECIS regional climate modelling system. Both the RCM and GCMs are models developed the UK Met Office Hadley Centre and are based on the HadCM3 GCM. Use of the multi-member PPE enables quantification of uncertainty in projected temperature change while the spatial resolution of RCM improves insight into the role of elevation in projected rates of change. Furthermore comparison with the results of the remote sensing analysis component - considered to provide an 'observed climatology' - permits evaluation of individual ensemble members with regards to biases in spatial gradients in temperature as well timing and magnitude of annual cycles.

Effects of temperature and surface contamination on D retention in ultrathin Li films on TZM

DOE PAGES

Capece, A. M.; Roszell, J. P.; Skinner, C. H.; ...

2014-10-29

Here in this work, we investigate deuterium retention at the Mo-Li interface by studying thin Li films three monolayers thick on a TZM Mo alloy. Li films at temperatures between 315 and 460 K were exposed to a deuterium ion beam and D retention was measured using temperature programmed desorption. In the absence of oxygen, D is retained as LiD, and the relative amount of retained D decreases with increasing substrate temperature. In three-monolayer thick lithium oxide films, the amount of D retained was 2.5 times higher than the amount retained as LiD in the metallic Li film. However, oxygenmore » reduces the thermal stability of D in the film, causing D 2O and D 2 to be released from the surface at temperatures 150-200 K below the LiD decomposition temperature. These results highlight the importance of maintaining a metallic Li layer for high D retention in Li films on TZM at elevated temperatures.« less

Effects of temperature and surface contamination on D retention in ultrathin Li films on TZM

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

Capece, A. M.; Roszell, J. P.; Skinner, C. H.

Here in this work, we investigate deuterium retention at the Mo-Li interface by studying thin Li films three monolayers thick on a TZM Mo alloy. Li films at temperatures between 315 and 460 K were exposed to a deuterium ion beam and D retention was measured using temperature programmed desorption. In the absence of oxygen, D is retained as LiD, and the relative amount of retained D decreases with increasing substrate temperature. In three-monolayer thick lithium oxide films, the amount of D retained was 2.5 times higher than the amount retained as LiD in the metallic Li film. However, oxygenmore » reduces the thermal stability of D in the film, causing D 2O and D 2 to be released from the surface at temperatures 150-200 K below the LiD decomposition temperature. These results highlight the importance of maintaining a metallic Li layer for high D retention in Li films on TZM at elevated temperatures.« less

Identification and management of microbial contaminations in a surface drinking water source.

PubMed

Aström, J; Pettersson, T J R; Stenström, T A

2007-01-01

Microbial contamination of surface waters constitutes a health risk for drinking water consumers which may be lowered by closing the raw water intake. We have evaluated microbial discharge events reported in the river Göta älv, which is used for raw water supply to the city of Göteborg. Elevated levels of faecal indicator bacteria were observed during periods of closed raw water intake. High bacteria levels were, however, also occasionally detected during periods of open intake, probably as a result of microbial discharge far upstream in the river which may be difficult to predict and manage by closing the intake. Accumulated upstream precipitations, resulting in surface runoff and wastewater contaminations in the catchment, correlated positively with the levels of total coliforms, E. coli, intestinal enterococci and sulfite-reducing clostridia. Levels of faecal indicator organisms were negatively correlated to the water temperature due to enhanced survival at lower temperatures. Wastewater discharges from a municipality located just upstream of the water intake resulted in elevated E. coli concentrations downstream at the raw water intake for Göteborg. To improve the prediction of microbial contaminations within the river Göta älv, monitoring data on turbidity and upstream precipitation are of particular importance.

Stability of peatland carbon to rising temperatures

DOE PAGES

Wilson, R. M.; Hopple, A. M.; Tfaily, M. M.; ...

2016-12-13

Peatlands contain one-third of soil carbon (C), mostly buried in deep, saturated anoxic zones (catotelm). The response of catotelm C to climate forcing is uncertain, because prior experiments have focused on surface warming. Here, we show that deep peat heating of a 2 m-thick peat column results in an exponential increase in CH 4 emissions. But, this response is due solely to surface processes and not degradation of catotelm peat. Incubations show that only the top 20–30 cm of peat from experimental plots have higher CH 4 production rates at elevated temperatures. Radiocarbon analyses demonstrate that CH 4 and COmore » 2 are produced primarily from decomposition of surface-derived modern photosynthate, not catotelm C. Furthermore, there are no differences in microbial abundances, dissolved organic matter concentrations or degradative enzyme activities among treatments. Our results suggest that although surface peat will respond to increasing temperature, the large reservoir of catotelm C is stable under current anoxic conditions.« less

Stability of peatland carbon to rising temperatures

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

Wilson, R. M.; Hopple, A. M.; Tfaily, M. M.

Peatlands contain one-third of soil carbon (C), mostly buried in deep, saturated anoxic zones (catotelm). The response of catotelm C to climate forcing is uncertain, because prior experiments have focused on surface warming. Here, we show that deep peat heating of a 2 m-thick peat column results in an exponential increase in CH 4 emissions. But, this response is due solely to surface processes and not degradation of catotelm peat. Incubations show that only the top 20–30 cm of peat from experimental plots have higher CH 4 production rates at elevated temperatures. Radiocarbon analyses demonstrate that CH 4 and COmore » 2 are produced primarily from decomposition of surface-derived modern photosynthate, not catotelm C. Furthermore, there are no differences in microbial abundances, dissolved organic matter concentrations or degradative enzyme activities among treatments. Our results suggest that although surface peat will respond to increasing temperature, the large reservoir of catotelm C is stable under current anoxic conditions.« less

Current Analogues of Future Climate Indicate the Likely Response of a Sensitive Montane Tropical Avifauna to a Warming World

PubMed Central

Anderson, Alexander S.; Storlie, Collin J.; Shoo, Luke P.; Pearson, Richard G.; Williams, Stephen E.

2013-01-01

Among birds, tropical montane species are likely to be among the most vulnerable to climate change, yet little is known about how climate drives their distributions, nor how to predict their likely responses to temperature increases. Correlative models of species’ environmental niches have been widely used to predict changes in distribution, but direct tests of the relationship between key variables, such as temperature, and species’ actual distributions are few. In the absence of historical data with which to compare observations and detect shifts, space-for-time substitutions, where warmer locations are used as analogues of future conditions, offer an opportunity to test for species’ responses to climate. We collected density data for rainforest birds across elevational gradients in northern and southern subregions within the Australian Wet Tropics (AWT). Using environmental optima calculated from elevational density profiles, we detected a significant elevational difference between the two regions in ten of 26 species. More species showed a positive (19 spp.) than negative (7 spp.) displacement, with a median difference of ∼80.6 m across the species analysed that is concordant with that expected due to latitudinal temperature differences (∼75.5 m). Models of temperature gradients derived from broad-scale climate surfaces showed comparable performance to those based on in-situ measurements, suggesting the former is sufficient for modeling impacts. These findings not only confirm temperature as an important factor driving elevational distributions of these species, but also suggest species will shift upslope to track their preferred environmental conditions. Our approach uses optima calculated from elevational density profiles, offering a data-efficient alternative to distribution limits for gauging climate constraints, and is sensitive enough to detect distribution shifts in this avifauna in response to temperature changes of as little as 0.4 degrees. We foresee important applications in the urgent task of detecting and monitoring impacts of climate change on montane tropical biodiversity. PMID:23936005

Current analogues of future climate indicate the likely response of a sensitive montane tropical avifauna to a warming world.

PubMed

Anderson, Alexander S; Storlie, Collin J; Shoo, Luke P; Pearson, Richard G; Williams, Stephen E

2013-01-01

Among birds, tropical montane species are likely to be among the most vulnerable to climate change, yet little is known about how climate drives their distributions, nor how to predict their likely responses to temperature increases. Correlative models of species' environmental niches have been widely used to predict changes in distribution, but direct tests of the relationship between key variables, such as temperature, and species' actual distributions are few. In the absence of historical data with which to compare observations and detect shifts, space-for-time substitutions, where warmer locations are used as analogues of future conditions, offer an opportunity to test for species' responses to climate. We collected density data for rainforest birds across elevational gradients in northern and southern subregions within the Australian Wet Tropics (AWT). Using environmental optima calculated from elevational density profiles, we detected a significant elevational difference between the two regions in ten of 26 species. More species showed a positive (19 spp.) than negative (7 spp.) displacement, with a median difference of ∼80.6 m across the species analysed that is concordant with that expected due to latitudinal temperature differences (∼75.5 m). Models of temperature gradients derived from broad-scale climate surfaces showed comparable performance to those based on in-situ measurements, suggesting the former is sufficient for modeling impacts. These findings not only confirm temperature as an important factor driving elevational distributions of these species, but also suggest species will shift upslope to track their preferred environmental conditions. Our approach uses optima calculated from elevational density profiles, offering a data-efficient alternative to distribution limits for gauging climate constraints, and is sensitive enough to detect distribution shifts in this avifauna in response to temperature changes of as little as 0.4 degrees. We foresee important applications in the urgent task of detecting and monitoring impacts of climate change on montane tropical biodiversity.

Theoretical kinetics of O + C 2H 4

DOE PAGES

Li, Xiaohu; Jasper, Ahren W.; Zádor, Judit; ...

2016-06-01

The reaction of atomic oxygen with ethylene is a fundamental oxidation step in combustion and is prototypical of reactions in which oxygen adds to double bonds. For 3O+C 2H 4 and for this class of reactions generally, decomposition of the initial adduct via spin-allowed reaction channels on the triplet surface competes with intersystem crossing (ISC) and a set of spin-forbidden reaction channels on the ground-state singlet surface. The two surfaces share some bimolecular products but feature different intermediates, pathways, and transition states. In addition, the overall product branching is therefore a sensitive function of the ISC rate. The 3O+C 2Hmore » 4 reaction has been extensively studied, but previous experimental work has not provided detailed branching information at elevated temperatures, while previous theoretical studies have employed empirical treatments of ISC. Here we predict the kinetics of 3O+C 2H 4 using an ab initio transition state theory based master equation (AITSTME) approach that includes an a priori description of ISC. Specifically, the ISC rate is calculated using Landau–Zener statistical theory, consideration of the four lowest-energy electronic states, and a direct classical trajectory study of the product branching immediately after ISC. The present theoretical results are largely in good agreement with existing low-temperature experimental kinetics and molecular beam studies. Good agreement is also found with past theoretical work, with the notable exception of the predicted product branching at elevated temperatures. Above ~1000 K, we predict CH 2CHO+H and CH 2+CH 2O as the major products, which differs from the room temperature preference for CH 3+HCO (which is assumed to remain at higher temperatures in some models) and from the prediction of a previous detailed master equation study.« less

Global mountain topography and the fate of montane species under climate change

NASA Astrophysics Data System (ADS)

Elsen, Paul R.; Tingley, Morgan W.

2015-08-01

Increasing evidence indicates that species throughout the world are responding to climate change by shifting their geographic distributions. Although shifts can be directionally heterogeneous, they often follow warming temperatures polewards and upslope. Montane species are of particular concern in this regard, as they are expected to face reduced available area of occupancy and increased risk of extinction with upslope movements. However, this expectation hinges on the assumption that surface area decreases monotonically as species move up mountainsides. We analysed the elevational availability of surface area for a global data set containing 182 of the world's mountain ranges. Sixty-eight per cent of these mountain ranges had topographies in which area did not decrease monotonically with elevation. Rather, mountain range topographies exhibited four distinct area-elevation patterns: decreasing (32% of ranges), increasing (6%), a mid-elevation peak in area (39%), and a mid-elevation trough in area (23%). These findings suggest that many species, particularly those of foothills and lower montane zones, may encounter increases in available area as a result of shifting upslope. A deeper understanding of underlying mountain topography can inform conservation priorities by revealing where shifting species stand to undergo area increases, decreases and bottlenecks as they respond to climate change.

Method for welding beryllium

DOEpatents

Dixon, Raymond D.; Smith, Frank M.; O'Leary, Richard F.

1997-01-01

A method is provided for joining beryllium pieces which comprises: depositing aluminum alloy on at least one beryllium surface; contacting that beryllium surface with at least one other beryllium surface; and welding the aluminum alloy coated beryllium surfaces together. The aluminum alloy may be deposited on the beryllium using gas metal arc welding. The aluminum alloy coated beryllium surfaces may be subjected to elevated temperatures and pressures to reduce porosity before welding the pieces together. The aluminum alloy coated beryllium surfaces may be machined into a desired welding joint configuration before welding. The beryllium may be an alloy of beryllium or a beryllium compound. The aluminum alloy may comprise aluminum and silicon.

Method for welding beryllium

DOEpatents

Dixon, R.D.; Smith, F.M.; O`Leary, R.F.

1997-04-01

A method is provided for joining beryllium pieces which comprises: depositing aluminum alloy on at least one beryllium surface; contacting that beryllium surface with at least one other beryllium surface; and welding the aluminum alloy coated beryllium surfaces together. The aluminum alloy may be deposited on the beryllium using gas metal arc welding. The aluminum alloy coated beryllium surfaces may be subjected to elevated temperatures and pressures to reduce porosity before welding the pieces together. The aluminum alloy coated beryllium surfaces may be machined into a desired welding joint configuration before welding. The beryllium may be an alloy of beryllium or a beryllium compound. The aluminum alloy may comprise aluminum and silicon. 9 figs.

Predicting Individual Tree and Shrub Species Distributions with Empirically Derived Microclimate Surfaces in a Complex Mountain Ecosystem in Northern Idaho, USA

NASA Astrophysics Data System (ADS)

Holden, Z.; Cushman, S.; Evans, J.; Littell, J. S.

2009-12-01

The resolution of current climate interpolation models limits our ability to adequately account for temperature variability in complex mountainous terrain. We empirically derive 30 meter resolution models of June-October day and nighttime temperature and April nighttime Vapor Pressure Deficit (VPD) using hourly data from 53 Hobo dataloggers stratified by topographic setting in mixed conifer forests near Bonners Ferry, ID. 66%, of the variability in average June-October daytime temperature is explained by 3 variables (elevation, relative slope position and topographic roughness) derived from 30 meter digital elevation models. 69% of the variability in nighttime temperatures among stations is explained by elevation, relative slope position and topographic dissection (450 meter window). 54% of variability in April nighttime VPD is explained by elevation, soil wetness and the NDVIc derived from Landsat. We extract temperature and VPD predictions at 411 intensified Forest Inventory and Analysis plots (FIA). We use these variables with soil wetness and solar radiation indices derived from a 30 meter DEM to predict the presence and absence of 10 common forest tree species and 25 shrub species. Classification accuracies range from 87% for Pinus ponderosa , to > 97% for most other tree species. Shrub model accuracies are also high with greater than 90% accuracy for the majority of species. Species distribution models based on the physical variables that drive species occurrence, rather than their topographic surrogates, will eventually allow us to predict potential future distributions of these species with warming climate at fine spatial scales.

Recent increase in maximum temperature at the tropical treeline of North America

NASA Astrophysics Data System (ADS)

Biondi, F.

2009-12-01

There are only a handful of weather stations above 3000 m in the entire American Cordillera, from Alaska to Tierra del Fuego. I present a surface instrumental record of high elevation (treeline) ecoclimatic variables for the tropics of North America. Besides its high elevation (3760 m) and tropical (19.5°N) features, this site is also located in the North American Monsoon System, making the data relevant to a broad suite of environmental issues. Automated half-hour data collected on Nevado de Colima, Mexico, from 2001 to 2009 show an increase in maximum temperature during the dry winter season, while incoming solar radiation remained stationary. Since minimum temperature did not increase as much, the daily range of air temperature has expanded over time. At this elevation, with average daily barometric pressure of 655 ± 1.4 hPa, maximum temperatures reflect the annual and daily energy cycle because of the dominant role of ground heating caused by incoming shortwave radiation. In fact, spring is the warmest season in this area, as it is followed by pronounced cooling during the summer monsoon because of increased cloudiness. The observed warming is associated with reduced wind speed, especially around solar noon, and is therefore most likely driven by reduced atmospheric flow, suggesting that the energy and water balance of high elevation tropical ecosystems are changing in unexpected ways. Further measurements and regional modeling experiments are therefore needed, given the staggering consequences this could have for any resource managers and policy makers concerned with trans-boundary (Mexico-US) terrestrial, coastal, and oceanic issues.

The effects of cooling systems on CO2-lased human enamel.

PubMed

Lian, H J; Lan, W H; Lin, C P

1996-12-01

The thermal effects on dentin during CO2 laser irradiation on human enamel were investigated. To simulate the clinical practice, two cooling methods (air and water spray) were applied immediately after laser exposure, whereas one group without cooling was served as control. Three hundred and sixty uniform tooth blocks were obtained from freshly extracted human third molars. Temperature change measurements were made via electrical thermocouple implanted within the tooth block 2 mm away from the enamel surface. Experimental treatments consisted of lasing without cooling, lasing with 0.5-ml/sec water cooling, and lasing with 15-psi air cooling. Our results indicated that (1) both air- and water-cooling groups could reduce temperature elevation significantly; (2) the larger power energy resulted in the higher temperature elevation. In conclusion, for CO2 laser irradiation on human enamel both water- and air-cooling methods may be effective on prevention of thermal damage of pulp.

Destabilization of emulsions by natural minerals.

PubMed

Yuan, Songhu; Tong, Man; Wu, Gaoming

2011-09-15

This study developed a novel method to destabilize emulsions and recycle oils, particularly for emulsified wastewater treatment. Natural minerals were used as demulsifying agents, two kinds of emulsions collected from medical and steel industry were treated. The addition of natural minerals, including artificial zeolite, natural zeolite, diatomite, bentonite and natural soil, could effectively destabilize both emulsions at pH 1 and 60 °C. Over 90% of chemical oxygen demand (COD) can be removed after treatment. Medical emulsion can be even destabilized by artificial zeolite at ambient temperature. The mechanism for emulsion destabilization by minerals was suggested as the decreased electrostatic repulsion at low pH, the enhanced gathering of oil microdroplets at elevated temperature, and the further decreased surface potential by the addition of minerals. Both flocculation and coalescence were enhanced by the addition of minerals at low pH and elevated temperature. Copyright © 2011 Elsevier B.V. All rights reserved.

Estimation of tropical forest canopy temperatures, thermal response numbers, and evapotranspiration using an aircraft-based thermal sensor

NASA Technical Reports Server (NTRS)

Luvall, Jeffrey C.; Lieberman, Diana; Lieberman, Milton; Hartshorn, Gary S.; Peralta, Rodolfo

1990-01-01

Thermal infrared Multispectral Scanner (TIMS) data were collected at a resolution of 5 to 10 m from a tropical rain forest over an elevation gradient from 35 to 2700 m in the Braulio Carrillo National Park in Costa Rica. Flight lines were repeated with a 15 to 30 minute time difference for measurement of forest canopy thermal response over time. Concurrent radiosonde measurements of atmospheric profiles of air temperature and moisture provided inputs to LOWTRAN6 for atmospheric radiance corrections of the TIMS data. Techniques for using calibrated aircraft-based thermal scanner data to examine tropical forest canopy thermal properties are described. Forest canopy temperature changes over time assessed between repeated, duplicated flight lines were combined with estimates of surface radiative energy measurements from towers above the forest canopy to determine temperature spatial variability, calculate Thermal Response Numbers (TRN), and estimate evapotranspiration along the elevation gradient from selected one hectare forest inventory plots.

An inverse method for estimation of the acoustic intensity in the focused ultrasound field

NASA Astrophysics Data System (ADS)

Yu, Ying; Shen, Guofeng; Chen, Yazhu

2017-03-01

Recently, a new method which based on infrared (IR) imaging was introduced. Authors (A. Shaw, et al and M. R. Myers, et al) have established the relationship between absorber surface temperature and incident intensity during the absorber was irradiated by the transducer. Theoretically, the shorter irradiating time makes estimation more in line with the actual results. But due to the influence of noise and performance constrains of the IR camera, it is hard to identify the difference in temperature with short heating time. An inverse technique is developed to reconstruct the incident intensity distribution using the surface temperature with shorter irradiating time. The algorithm is validated using surface temperature data generated numerically from three-layer model which was developed to calculate the acoustic field in the absorber, the absorbed acoustic energy during the irradiation, and the consequent temperature elevation. To assess the effect of noisy data on the reconstructed intensity profile, in the simulations, the different noise levels with zero mean were superposed on the exact data. Simulation results demonstrate that the inversion technique can provide fairly reliable intensity estimation with satisfactory accuracy.

Methods for developing time-series climate surfaces to drive topographically distributed energy- and water-balance models

USGS Publications Warehouse

Susong, D.; Marks, D.; Garen, D.

1999-01-01

Topographically distributed energy- and water-balance models can accurately simulate both the development and melting of a seasonal snowcover in the mountain basins. To do this they require time-series climate surfaces of air temperature, humidity, wind speed, precipitation, and solar and thermal radiation. If data are available, these parameters can be adequately estimated at time steps of one to three hours. Unfortunately, climate monitoring in mountain basins is very limited, and the full range of elevations and exposures that affect climate conditions, snow deposition, and melt is seldom sampled. Detailed time-series climate surfaces have been successfully developed using limited data and relatively simple methods. We present a synopsis of the tools and methods used to combine limited data with simple corrections for the topographic controls to generate high temporal resolution time-series images of these climate parameters. Methods used include simulations, elevational gradients, and detrended kriging. The generated climate surfaces are evaluated at points and spatially to determine if they are reasonable approximations of actual conditions. Recommendations are made for the addition of critical parameters and measurement sites into routine monitoring systems in mountain basins.Topographically distributed energy- and water-balance models can accurately simulate both the development and melting of a seasonal snowcover in the mountain basins. To do this they require time-series climate surfaces of air temperature, humidity, wind speed, precipitation, and solar and thermal radiation. If data are available, these parameters can be adequately estimated at time steps of one to three hours. Unfortunately, climate monitoring in mountain basins is very limited, and the full range of elevations and exposures that affect climate conditions, snow deposition, and melt is seldom sampled. Detailed time-series climate surfaces have been successfully developed using limited data and relatively simple methods. We present a synopsis of the tools and methods used to combine limited data with simple corrections for the topographic controls to generate high temporal resolution time-series images of these climate parameters. Methods used include simulations, elevational gradients, and detrended kriging. The generated climate surfaces are evaluated at points and spatially to determine if they are reasonable approximations of actual conditions. Recommendations are made for the addition of critical parameters and measurement sites into routine monitoring systems in mountain basins.

Thermoelastic Stress Analysis: An NDE Tool for the Residual Stress Assessment of Metallic Alloys

NASA Technical Reports Server (NTRS)

Gyekenyesi, Andrew L.; Baaklini, George Y.

2000-01-01

During manufacturing, certain propulsion components that will be used in a cyclic fatigue environment are fabricated to contain compressive residual stresses on their surfaces because these stresses inhibit the nucleation of cracks. Overloads and elevated temperature excursions cause the induced residual stresses to dissipate while the component is still in service, lowering its resistance to crack initiation. Research at the NASA Glenn Research Center at Lewis Field has focused on employing the Thermoelastic Stress Analysis technique (TSA, also recognized as SPATE: Stress Pattern Analysis by Thermal Emission) as a tool for monitoring the residual stress state of propulsion components. TSA is based on the fact that materials experience small temperature changes when they are compressed or expanded. When a structure is cyclically loaded (i.e., cyclically compressed and expanded), the resulting surface-temperature profile correlates to the stress state of the structure s surface. The surface-temperature variations resulting from a cyclic load are measured with an infrared camera. Traditionally, the temperature amplitude of a TSA signal has been theoretically defined to be linearly dependent on the cyclic stress amplitude. As a result, the temperature amplitude resulting from an applied cyclic stress was assumed to be independent of the cyclic mean stress.

High-temperature electronics applications in space exploration

NASA Astrophysics Data System (ADS)

Jurgens, R. F.

1982-05-01

One of the most exciting applications of high-temperature electronics is related to the exploration of the planet Venus. On this planet the atmospheric temperatures range from about 170 K at elevations of 100 km to a searing 730 K near the surface. Mechanisms for exploring the atmosphere might include balloons, airplanes, surface landers, and surface-launched probes. Balloons, for example, could fly in the region from 20 (320 C at 22 bars) to 60 km (-20 C at 0.2 bar). Suitable balloon fabrics presently exclude excursions to lower altitudes; however, adequate electronic systems could survive to 325 C. Small airplanes would require more sophisticated electronics for guidance and control. Long life surface landers would most likely be developed first, as these could be used to measure long-term variations in weather. Ranging transponders would be important for ephemeris development, measurement of spin state, and studies of general relativity. Surface temperatures of 460 C and pressures of 90 bars present a challenge to the developers of such instruments. Other space applications for high-temperature electronics include transponders for the surface of Mercury, near solar drag-free orbiters, and deep atmospheric penetrators for Jupiter and Saturn. Each of these has its own particular problems with respect to instrumentation adequate to meet the desired scientific goals. This paper is primarily concerned with defining possible mission applications, the required electronic systems, and the approaches that are currently being studied for their development.

High-temperature electronics applications in space exploration

NASA Technical Reports Server (NTRS)

Jurgens, R. F.

1982-01-01

One of the most exciting applications of high-temperature electronics is related to the exploration of the planet Venus. On this planet the atmospheric temperatures range from about 170 K at elevations of 100 km to a searing 730 K near the surface. Mechanisms for exploring the atmosphere might include balloons, airplanes, surface landers, and surface-launched probes. Balloons, for example, could fly in the region from 20 (320 C at 22 bars) to 60 km (-20 C at 0.2 bar). Suitable balloon fabrics presently exclude excursions to lower altitudes; however, adequate electronic systems could survive to 325 C. Small airplanes would require more sophisticated electronics for guidance and control. Long life surface landers would most likely be developed first, as these could be used to measure long-term variations in weather. Ranging transponders would be important for ephemeris development, measurement of spin state, and studies of general relativity. Surface temperatures of 460 C and pressures of 90 bars present a challenge to the developers of such instruments. Other space applications for high-temperature electronics include transponders for the surface of Mercury, near solar drag-free orbiters, and deep atmospheric penetrators for Jupiter and Saturn. Each of these has its own particular problems with respect to instrumentation adequate to meet the desired scientific goals. This paper is primarily concerned with defining possible mission applications, the required electronic systems, and the approaches that are currently being studied for their development.

Mathematical Modelling of Arctic Polygonal Tundra with Ecosys : 1. Microtopography Determines How Active Layer Depths Respond to Changes in Temperature and Precipitation

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

Grant, R. F.; Mekonnen, Z. A.; Riley, W. J.

Microtopographic variation that develops among features (troughs, rims, and centers) within polygonal landforms of coastal arctic tundra strongly affects movement of surface water and snow and thereby affects soil water contents (θ) and active layer depth (ALD). Spatial variation in ALD among these features may exceed interannual variation in ALD caused by changes in climate and so needs to be represented in projections of changes in arctic ALD. For this study, increases in near-surface θ with decreasing surface elevation among polygon features at the Barrow Experimental Observatory (BEO) were modeled from topographic effects on redistribution of surface water and snowmore » and from lateral water exchange with a subsurface water table during a model run from 1981 to 2015. These increases in θ caused increases in thermal conductivity that in turn caused increases in soil heat fluxes and hence in ALD of up to 15 cm with lower versus higher surface elevation which were consistent with increases measured at BEO. The modeled effects of θ caused interannual variation in maximum ALD that compared well with measurements from 1985 to 2015 at the Barrow Circumpolar Active Layer Monitoring (CALM) site (R 2 = 0.61, RMSE = 0.03 m). For higher polygon features, interannual variation in ALD was more closely associated with annual precipitation than mean annual temperature, indicating that soil wetting from increases in precipitation may hasten permafrost degradation beyond that caused by soil warming from increases in air temperature. This degradation may be more rapid if increases in precipitation cause sustained wetting in higher features.« less

Mathematical Modelling of Arctic Polygonal Tundra with Ecosys : 1. Microtopography Determines How Active Layer Depths Respond to Changes in Temperature and Precipitation

DOE PAGES

Grant, R. F.; Mekonnen, Z. A.; Riley, W. J.; ...

2017-11-17

Microtopographic variation that develops among features (troughs, rims, and centers) within polygonal landforms of coastal arctic tundra strongly affects movement of surface water and snow and thereby affects soil water contents (θ) and active layer depth (ALD). Spatial variation in ALD among these features may exceed interannual variation in ALD caused by changes in climate and so needs to be represented in projections of changes in arctic ALD. For this study, increases in near-surface θ with decreasing surface elevation among polygon features at the Barrow Experimental Observatory (BEO) were modeled from topographic effects on redistribution of surface water and snowmore » and from lateral water exchange with a subsurface water table during a model run from 1981 to 2015. These increases in θ caused increases in thermal conductivity that in turn caused increases in soil heat fluxes and hence in ALD of up to 15 cm with lower versus higher surface elevation which were consistent with increases measured at BEO. The modeled effects of θ caused interannual variation in maximum ALD that compared well with measurements from 1985 to 2015 at the Barrow Circumpolar Active Layer Monitoring (CALM) site (R 2 = 0.61, RMSE = 0.03 m). For higher polygon features, interannual variation in ALD was more closely associated with annual precipitation than mean annual temperature, indicating that soil wetting from increases in precipitation may hasten permafrost degradation beyond that caused by soil warming from increases in air temperature. This degradation may be more rapid if increases in precipitation cause sustained wetting in higher features.« less

Is the boundary layer of an ionic liquid equally lubricating at higher temperature?

PubMed

Hjalmarsson, Nicklas; Atkin, Rob; Rutland, Mark W

2016-04-07

Atomic force microscopy has been used to study the effect of temperature on normal forces and friction for the room temperature ionic liquid (IL) ethylammonium nitrate (EAN), confined between mica and a silica colloid probe at 25 °C, 50 °C, and 80 °C. Force curves revealed a strong fluid dynamic influence at room temperature, which was greatly reduced at elevated temperatures due to the reduced liquid viscosity. A fluid dynamic analysis reveals that bulk viscosity is manifested at large separation but that EAN displays a nonzero slip, indicating a region of different viscosity near the surface. At high temperatures, the reduction in fluid dynamic force reveals step-like force curves, similar to those found at room temperature using much lower scan rates. The ionic liquid boundary layer remains adsorbed to the solid surface even at high temperature, which provides a mechanism for lubrication when fluid dynamic lubrication is strongly reduced. The friction data reveals a decrease in absolute friction force with increasing temperature, which is associated with increased thermal motion and reduced viscosity of the near surface layers but, consistent with the normal force data, boundary layer lubrication was unaffected. The implications for ILs as lubricants are discussed in terms of the behaviour of this well characterised system.

Ice-atmosphere interactions in the Canadian High Arctic: Implications for the thermo-mechanical evolution of terrestrial ice masses

NASA Astrophysics Data System (ADS)

Wohlleben, Trudy M. H.

Canadian High Arctic terrestrial ice masses and the polar atmosphere evolve codependently, and interactions between the two systems can lead to feedbacks, positive and negative. The two primary positive cryosphere-atmosphere feedbacks are: (1) The snow/ice-albedo feedback (where area changes in snow and/or ice cause changes in surface albedo and surface air temperatures, leading to further area changes in snow/ice); and (2) The elevation - mass balance feedback (where thickness changes in terrestrial ice masses cause changes to atmospheric circulation and precipitation patterns, leading to further ice thickness changes). In this thesis, numerical experiments are performed to: (1) quantify the magnitudes of the two feedbacks for chosen Canadian High Arctic terrestrial ice masses; and (2) to examine the direct and indirect consequences of surface air temperature changes upon englacial temperatures with implications for ice flow, mass flux divergence, and topographic evolution. Model results show that: (a) for John Evans Glacier, Ellesmere Island, the magnitude of the terrestrial snow/ice-albedo feedback can locally exceed that of sea ice on less than decadal timescales, with implications for glacier response times to climate perturbations; (b) although historical air temperature changes might be the direct cause of measured englacial temperature anomalies in various glacier and ice cap accumulation zones, they can also be the indirect cause of their enhanced diffusive loss; (c) while the direct result of past air temperature changes has been to cool the interior of John Evans Glacier, and its bed, the indirect result has been to create and maintain warm (pressure melting point) basal temperatures in the ablation zone; and (d) for Devon Ice Cap, observed mass gains in the northwest sector of the ice cap would be smaller without orographic precipitation and the mass balance---elevation feedback, supporting the hypothesis that this feedback is playing a role in the evolution of the ice cap.

Effects of elevated CO2 and temperature on forest floor litter decomposition and chemistry

EPA Science Inventory

Forest floor can be a major component of the carbon held in forested soils. In mature forests it represents the balance between additions and decomposition under current climate conditions. Because of its position at the soil surface, this reservoir of C is highly susceptible...

UV ATTENUATION NEAR CORAL REEFS IN THE FLORIDA KEYS: LIGHT ABSORPTION BY CDOM AND PARTICLES

EPA Science Inventory

We have investigated the roles of chromophoric dissolved organic matter (CDOM) and suspended particles in the attenuation of UV radiation in the middle and lower regions of the Florida Keys. Extended exposure to UV radiation, along with elevated sea surface temperatures, impairs...

Positron-induced Auger-electron study of the Ge(100) surface: Positron thermal desorption and surface condition

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

Soininen, E.; Schwab, A.; Lynn, K.G.

1991-05-01

Positron-annihilation-induced Auger-electron spectroscopy (PAES) was used to study the effects of oxygen, residual gases, and temperature on a Ge(100) surface. Three low-energy Auger peaks were detected at 50, 90, and 100--150 eV, attributed to {ital M}{sub 2,3}{ital M4}{ital M4}, {ital M}{sub 2,3}{ital M4}{ital V}, and {ital M}{sub 1}{ital M4}{ital M4} Auger transitions, respectively. An estimated (4{plus minus}1)% of the surface-trapped positrons annihilate with Ge 3{ital p}--level electrons. The sensitivity of PAES to the surface condition is demonstrated. The PAES yield from a Ge(100) surface is reduced at elevated temperatures, in accord with an activation process earlier found in several positroniummore » (Ps) -fraction experiments. A desorption model adopted from these studies does not describe accurately the PAES results at higher temperatures ({gt}500 {degree}C), where the PAES intensity levels off to 5% of the room-temperature value. Possible sources for the discrepancy are discussed and models for positron trapping to deep surface traps are introduced. On the Ge(100) surface, an upper limit for Ps emission near the melting point is 97%. The error in calibration parameters due to the earlier assumption of 100% Ps emission seems to introduce only small errors into the Ps-fraction measurements.« less

Ozone reaction with interior building materials: Influence of diurnal ozone variation, temperature and humidity

NASA Astrophysics Data System (ADS)

Rim, Donghyun; Gall, Elliott T.; Maddalena, Randy L.; Nazaroff, William W.

2016-01-01

Elevated tropospheric ozone concentrations are associated with increased morbidity and mortality. Indoor ozone chemistry affects human exposure to ozone and reaction products that also may adversely affect health and comfort. Reactive uptake of ozone has been characterized for many building materials; however, scant information is available on how diurnal variation of ambient ozone influences ozone reaction with indoor surfaces. The primary objective of this study is to investigate ozone-surface reactions in response to a diurnally varying ozone exposure for three common building materials: ceiling tile, painted drywall, and carpet tile. A secondary objective is to examine the effects of air temperature and humidity. A third goal is to explore how conditioning of materials in an occupied office building might influence subsequent ozone-surface reactions. Experiments were performed at bench-scale with inlet ozone concentrations varied to simulate daytime (ozone elevated) and nighttime (ozone-free in these experiments) periods. To simulate office conditions, experiments were conducted at two temperatures (22 °C and 28 °C) and three relative humidity values (25%, 50%, 75%). Effects of indoor surface exposures were examined by placing material samples in an occupied office and repeating bench-scale characterization after exposure periods of 1 and 2 months. Deposition velocities were observed to be highest during the initial hour of ozone exposure with slow decrease in the subsequent hours of simulated daytime conditions. Daily-average ozone reaction probabilities for fresh materials are in the respective ranges of (1.7-2.7) × 10-5, (2.8-4.7) × 10-5, and (3.0-4.5) × 10-5 for ceiling tile, painted drywall, and carpet tile. The reaction probability decreases by 7%-47% across the three test materials after two 8-h periods of ozone exposure. Measurements with the samples from an occupied office reveal that deposition velocity can decrease or increase with time. Influence of temperature and humidity on ozone-surface reactivity was not strong.

Photoluminescence Probing of Complex H2O Adsorption on InGaN/GaN Nanowires.

PubMed

Maier, Konrad; Helwig, Andreas; Müller, Gerhard; Hille, Pascal; Teubert, Jörg; Eickhoff, Martin

2017-02-08

We demonstrate that the complex adsorption behavior of H 2 O on InGaN/GaN nanowire arrays is directly revealed by their ambient-dependent photoluminescence properties. Under low-humidity, ambient-temperature, and low-excitation-light conditions, H 2 O adsorbates cause a quenching of the photoluminescence. In contrast, for high humidity levels, elevated temperature, and high excitation intensity, H 2 O adsorbates act as efficient photoluminescence enhancers. We show that this behavior, which can only be detected due to the low operation temperature of the InGaN/GaN nanowires, can be explained on the basis of single H 2 O adsorbates forming surface recombination centers and multiple H 2 O adsorbates forming surface passivation layers. Reversible creation of such passivation layers is induced by the photoelectrochemical splitting of adsorbed water molecules and by the interaction of reactive H 3 O + and OH - ions with photoactivated InGaN surfaces. Due to electronic coupling of adsorbing molecules with photoactivated surfaces, InGaN/GaN nanowires act as sensitive nanooptical probes for the analysis of photoelectrochemical surface processes.

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

Ritchie, IAltenberger, RKNalla, YSano LWagner, RO

The effect of surface treatment on the stress/life fatigue behavior of a titanium Ti-6Al-4V turbine fan blade alloy is investigated in the regime of 102 to 106 cycles to failure under fully reversed stress-controlled isothermal push-pull loading between 25? and 550?C at a frequency of 5 Hz. Specifically, the fatigue behavior was examined in specimens in the deep-rolled and laser-shock peened surface conditions, and compared to results on samples in the untreated (machined and stress annealed) condition. Although the fatigue resistance of the Ti-6Al-4V alloy declined with increasing test temperature regardless of surface condition, deep-rolling and laser-shock peening surface treatmentsmore » were found to extend the fatigue lives by factors of more than 30 and 5-10, respectively, in the high-cycle and low-cycle fatigue regimes at temperatures as high as 550?C. At these temperatures, compressive residual stresses are essentially relaxed; however, it is the presence of near-surface work hardened layers, with a nanocystalline structure in the case of deep-rolling and dense dislocation tangles in the case of laser-shock peening, which remain fairly stable even after cycling at 450?-550?C, that provide the basis for the beneficial role of mechanical surface treatments on the fatigue strength of Ti-6Al-4V at elevated temperatures.« less

PAES study of the positron thermal desorption from a Ge(100) surface

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

Soininen, E.; Schwab, A.; Lynn, K.G.

1991-02-01

Positron induced Auger electron spectroscopy (PAES) from a clean Ge(100) surface was studied as a function of temperature. Three low-energy Auger peaks were detected at 50 eV, 90 eV and 100--150 eV, attributed to M{sub 2,3}M{sub 4}M{sub 4}, M{sub 2,3}M{sub 4}V and M{sub 1}M{sub 4}M{sub 4} Auger transitions, respectively. An estimated 4({plus minus}1)% of the surface trapped positrons annihilate with Ge 3p level electrons. The PAES yield from a Ge(100) surface is reduced at elevated temperatures, in accordance with an activation process found earlier in several Ps fraction experiments. A desorption model adopted from these studies does not accurately describemore » the PAES intensity at higher temperatures ({gt}500 {degree}C), which levels off at 5% of the room temperature value. Possible sources for the discrepancy are discussed. On a Ge(100) surface, an upper limit for the Ps emission near the melting point is 97%. The error in calibration parameters due to the earlier assumption of 100% Ps emission from Ge surfaces seems to induce only small errors to the Ps fraction measurements.« less

America's Urban Forests: Keeping Our Cities Cool

NASA Technical Reports Server (NTRS)

Luvall, Jeffrey C.; Quattrochi, Dale A.

1997-01-01

The additional heating of the air over the city is the result of the replacement of naturally vegetated surfaces with those composed of asphalt, concrete, rooftops and other man-made materials. The temperatures of these artificial surfaces can be 20 to 40 C higher than vegetated surfaces. Materials such as asphalt store much of the sun's energy and remains hot long after sunset. This produces a dome of elevated air temperatures 5 to 8 C greater over the city, compared to the air temperatures over adjacent rural areas. This effect is called the "urban heat island". Tree canopies can reduce the urban heat island effect by dissipating the solar energy received by transpiring water from leaf surfaces which cools the air by taking "heat" from the air to evaporate the water and by shading surfaces like asphalt, roofs, and concrete parking lots which prevents initial heating and storage of heat. It is difficult to take enough temperature measurements over a large city area to characterize the surface temperature variability and quantify the temperature reduction effects of tree canopies. However, the use of remotely sensed thermal data from airborne scanners are ideal for the task. In a study funded by NASA, a series of flights over Huntsville AL were performed in September 1994 and over Atlanta in May 1997. In this article we will examine the techniques of analyzing remotely sensed data for measuring the effect of tree canopies in reducing the urban heat island effect.

Lower responsiveness of canopy evapotranspiration rate than of leaf stomatal conductance to open-air CO2 elevation in rice.

PubMed

Shimono, Hiroyuki; Nakamura, Hirofumi; Hasegawa, Toshihiro; Okada, Masumi

2013-08-01

An elevated atmospheric CO2 concentration ([CO2 ]) can reduce stomatal conductance of leaves for most plant species, including rice (Oryza sativa L.). However, few studies have quantified seasonal changes in the effects of elevated [CO2 ] on canopy evapotranspiration, which integrates the response of stomatal conductance of individual leaves with other responses, such as leaf area expansion, changes in leaf surface temperature, and changes in developmental stages, in field conditions. We conducted a field experiment to measure seasonal changes in stomatal conductance of the uppermost leaves and in the evapotranspiration, transpiration, and evaporation rates using a lysimeter method. The study was conducted for flooded rice under open-air CO2 elevation. Stomatal conductance decreased by 27% under elevated [CO2 ], averaged throughout the growing season, and evapotranspiration decreased by an average of 5% during the same period. The decrease in daily evapotranspiration caused by elevated [CO2 ] was more significantly correlated with air temperature and leaf area index (LAI) rather than with other parameters of solar radiation, days after transplanting, vapor-pressure deficit and FAO reference evapotranspiration. This indicates that higher air temperatures, within the range from 16 to 27 °C, and a larger LAI, within the range from 0 to 4 m(2)  m(-2) , can increase the magnitude of the decrease in evapotranspiration rate caused by elevated [CO2 ]. The crop coefficient (i.e. the evapotranspiration rate divided by the FAO reference evapotranspiration rate) was 1.24 at ambient [CO2 ] and 1.17 at elevated [CO2 ]. This study provides the first direct measurement of the effects of elevated [CO2 ] on rice canopy evapotranspiration under open-air conditions using the lysimeter method, and the results will improve future predictions of water use in rice fields. © 2013 John Wiley & Sons Ltd.

Occurrence and Detectability of Thermal Anomalies on Europa

NASA Astrophysics Data System (ADS)

Hayne, Paul O.; Christensen, Philip R.; Spencer, John R.; Abramov, Oleg; Howett, Carly; Mellon, Michael; Nimmo, Francis; Piqueux, Sylvain; Rathbun, Julie A.

2017-10-01

Endogenic activity is likely on Europa, given its young surface age of and ongoing tidal heating by Jupiter. Temperature is a fundamental signature of activity, as witnessed on Enceladus, where plumes emanate from vents with strongly elevated temperatures. Recent observations suggest the presence of similar water plumes at Europa. Even if plumes are uncommon, resurfacing may produce elevated surface temperatures, perhaps due to near-surface liquid water. Detecting endogenic activity on Europa is one of the primary mission objectives of NASA’s planned Europa Clipper flyby mission.Here, we use a probabilistic model to assess the likelihood of detectable thermal anomalies on the surface of Europa. The Europa Thermal Emission Imaging System (E-THEMIS) investigation is designed to characterize Europa’s thermal behavior and identify any thermal anomalies due to recent or ongoing activity. We define “detectability” on the basis of expected E-THEMIS measurements, which include multi-spectral infrared emission, both day and night.Thermal anomalies on Europa may take a variety of forms, depending on the resurfacing style, frequency, and duration of events: 1) subsurface melting due to hot spots, 2) shear heating on faults, and 3) eruptions of liquid water or warm ice on the surface. We use numerical and analytical models to estimate temperatures for these features. Once activity ceases, lifetimes of thermal anomalies are estimated to be 100 - 1000 yr. On average, Europa’s 10 - 100 Myr surface age implies a resurfacing rate of ~3 - 30 km2/yr. The typical size of resurfacing features determines their frequency of occurrence. For example, if ~100 km2 chaos features dominate recent resurfacing, we expect one event every few years to decades. Smaller features, such as double-ridges, may be active much more frequently. We model each feature type as a statistically independent event, with probabilities weighted by their observed coverage of Europa’s surface. Our results show that if Europa is resurfaced continuously by the processes considered, there is a >99% chance that E-THEMIS will detect a thermal anomaly due to endogenic activity. Therefore, if no anomalies are detected, these models can be ruled out, or revised.

Temperature and Water Depth Monitoring Within Chum Salmon Spawning Habitat Below Bonneville Dam -- Annual Report -- October 2007-September 2008

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

Arntzen, Evan V.

2009-07-14

The overall goal of the project described in this report is to provide a sound scientific basis for operation of the Federal Columbia River Power System (FCRPS) in ways that will effectively protect and enhance chum salmon populations----a species listed in March 1999 as threatened under the Endangered Species Act of 1973 (ESA). The study objective during fiscal year 2008 was to provide real-time data on Ives Island area water temperature and water surface elevations from the onset of chum salmon spawning through the end of chum salmon emergence. Sampling locations included areas where riverbed temperatures were elevated, potentially influencingmore » alevin development and emergence timing. In these locations, hydrosystem operation caused large, frequent changes in river discharge that affected salmon habitat by dewatering redds and altering egg pocket temperatures. The 2008 objective was accomplished using temperature and water-level sensors deployed inside piezo¬meters. Sensors were integrated with a radio telemetry system such that real-time data could be downloaded remotely and posted hourly on the Internet.« less

Temperature and heat in informal settlements in Nairobi

PubMed Central

Misiani, Herbert; Okoth, Jerrim; Jordan, Asha; Gohlke, Julia; Ouma, Gilbert; Arrighi, Julie; Zaitchik, Ben F.; Jjemba, Eddie; Verjee, Safia; Waugh, Darryn W.

2017-01-01

Nairobi, Kenya exhibits a wide variety of micro-climates and heterogeneous surfaces. Paved roads and high-rise buildings interspersed with low vegetation typify the central business district, while large neighborhoods of informal settlements or “slums” are characterized by dense, tin housing, little vegetation, and limited access to public utilities and services. To investigate how heat varies within Nairobi, we deployed a high density observation network in 2015/2016 to examine summertime temperature and humidity. We show how temperature, humidity and heat index differ in several informal settlements, including in Kibera, the largest slum neighborhood in Africa, and find that temperature and a thermal comfort index known colloquially as the heat index regularly exceed measurements at the Dagoretti observation station by several degrees Celsius. These temperatures are within the range of temperatures previously associated with mortality increases of several percent in youth and elderly populations in informal settlements. We relate these changes to surface properties such as satellite-derived albedo, vegetation indices, and elevation. PMID:29107977

Temperature and heat in informal settlements in Nairobi.

PubMed

Scott, Anna A; Misiani, Herbert; Okoth, Jerrim; Jordan, Asha; Gohlke, Julia; Ouma, Gilbert; Arrighi, Julie; Zaitchik, Ben F; Jjemba, Eddie; Verjee, Safia; Waugh, Darryn W

2017-01-01

Nairobi, Kenya exhibits a wide variety of micro-climates and heterogeneous surfaces. Paved roads and high-rise buildings interspersed with low vegetation typify the central business district, while large neighborhoods of informal settlements or "slums" are characterized by dense, tin housing, little vegetation, and limited access to public utilities and services. To investigate how heat varies within Nairobi, we deployed a high density observation network in 2015/2016 to examine summertime temperature and humidity. We show how temperature, humidity and heat index differ in several informal settlements, including in Kibera, the largest slum neighborhood in Africa, and find that temperature and a thermal comfort index known colloquially as the heat index regularly exceed measurements at the Dagoretti observation station by several degrees Celsius. These temperatures are within the range of temperatures previously associated with mortality increases of several percent in youth and elderly populations in informal settlements. We relate these changes to surface properties such as satellite-derived albedo, vegetation indices, and elevation.

Refraction of microwave signals by water vapor

NASA Technical Reports Server (NTRS)

Goldfinger, A. D.

1980-01-01

Tropospheric water vapor causes a refractive path length effect which is typically 5-10% of the 'dry' tropospheric effect and as large as several meters at elevation angles below 5 deg. The vertical water vapor profile is quite variable, and measurements of intensive atmospheric parameters such as temperature and humidity limited to the surface do not adequately predict the refractive effect. It is suggested that a water vapor refraction model that is a function of the amount of precipitable water alone can be successful at low elevation angles. From an extensive study of numerical ray tracings through radiosonde balloon data, such a model has been constructed. The model predicts the effect at all latitudes and elevation angles between 2 and 10 deg to an accuracy of better than 4% (11 cm at 3 deg elevation angle).

Snow cover distribution over elevation zones in a mountainous catchment

NASA Astrophysics Data System (ADS)

Panagoulia, D.; Panagopoulos, Y.

2009-04-01

A good understanding of the elevetional distribution of snow cover is necessary to predict the timing and volume of runoff. In a complex mountainous terrain the snow cover distribution within a watershed is highly variable in time and space and is dependent on elevation, slope, aspect, vegetation type, surface roughness, radiation load, and energy exchange at the snow-air interface. Decreases in snowpack due to climate change could disrupt the downstream urban and agricultural water supplies, while increases could lead to seasonal flooding. Solar and longwave radiation are dominant energy inputs driving the ablation process. Turbulent energy exchange at the snow cover surface is important during the snow season. The evaporation of blowing and drifting snow is strongly dependent upon wind speed. Much of the spatial heterogeneity of snow cover is the result of snow redistribution by wind. Elevation is important in determining temperature and precipitation gradients along hillslopes, while the temperature gradients determine where precipitation falls as rain and snow and contribute to variable melt rates within the hillslope. Under these premises, the snow accumulation and ablation (SAA) model of the US National Weather Service (US NWS) was applied to implement the snow cover extent over elevation zones of a mountainous catchment (the Mesochora catchment in Western-Central Greece), taking also into account the indirectly included processes of sublimation, interception, and snow redistribution. The catchment hydrology is controlled by snowfall and snowmelt and the simulated discharge was computed from the soil moisture accounting (SMA) model of the US NWS and compared to the measured discharge. The elevationally distributed snow cover extent presented different patterns with different time of maximization, extinction and return during the year, producing different timing of discharge that is a crucial factor for the control and management of water resources systems.

In-situ GPS records of surface mass balance, firn compaction rates, and ice-shelf basal melt rates for Pine Island Glacier, Antarctica

NASA Astrophysics Data System (ADS)

Shean, D. E.; Christianson, K.; Larson, K. M.; Ligtenberg, S.; Joughin, I. R.; Smith, B.; Stevens, C.

2016-12-01

In recent decades, Pine Island Glacier (PIG) has experienced marked retreat, speedup and thinning due to ice-shelf basal melt, internal ice-stream instability and feedbacks between these processes. In an effort to constrain recent ice-stream dynamics and evaluate potential causes of retreat, we analyzed 2008-2010 and 2012-2014 GPS records for PIG. We computed time series of horizontal velocity, strain rate, multipath-based antenna height, surface elevation, and Lagrangian elevation change (Dh/Dt). These data provide validation for complementary high-resolution WorldView stereo digital elevation model (DEM) records, with sampled DEM vertical error of 0.7 m. The GPS antenna height time series document a relative surface elevation increase of 0.7-1.0 m/yr, which is consistent with estimated surface mass balance (SMB) of 0.7-0.9 m.w.e./yr from RACMO2.3 and firn compaction rates from the IMAU-FDM dynamic firn model. An abrupt 0.2-0.3 m surface elevation decrease due to surface melt and/or greater near-surface firn compaction is observed during a period of warm atmospheric temperatures from December 2012 to January 2013. Observed surface Dh/Dt for all PIG shelf sites is highly linear with trends of -1 to -4 m/yr and <0.4 m residuals. Similar Dh/Dt estimates with reduced variability are obtained after removing expected downward GPS pole base velocity from observed GPS antenna Dh/Dt. Estimated Dh/Dt basal melt rates are 10 to 40 m/yr for the outer PIG shelf and 4 m/yr for the South shelf. These melt rates are similar to those derived from ice-bottom acoustic ranging, phase-sensitive ice-penetrating radar, and high-resolution stereo DEM records. The GPS/DEM records document higher melt rates within and near transverse surface depressions and rifts associated with longitudinal extension. Basal melt rates for the 2012-2014 period show limited temporal variability, despite significant change in ocean heat content. This suggests that sub-shelf melt rates are less sensitive to ocean heat content than previously reported, at least for these locations and time periods.

Thermally stable single-atom platinum-on-ceria catalysts via atom trapping

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

Jones, John; Xiong, Haifeng; DelaRiva, Andrew

2016-07-08

Catalysts based on single atoms of scarce precious metals can lead to more efficient use through enhanced reactivity and selectivity. However, single atoms on catalyst supports can be mobile and aggregate into nanoparticles when heated at elevated temperatures. High temperatures are detrimental to catalyst performance unless these mobile atoms can be trapped. We used ceria powders having similar surface areas but different exposed surface facets. When mixed with a platinum/ aluminum oxide catalyst and aged in air at 800°C, the platinum transferred to the ceria and was trapped. Polyhedral ceria and nanorods were more effective than ceria cubes at anchoringmore » the platinum. Performing synthesis at high temperatures ensures that only the most stable binding sites are occupied, yielding a sinter-resistant, atomically dispersed catalyst.« less

Experience of the JPL Exploratory Data Analysis Team at validating HIRS2/MSU cloud parameters

NASA Technical Reports Server (NTRS)

Kahn, Ralph; Haskins, Robert D.; Granger-Gallegos, Stephanie; Pursch, Andrew; Delgenio, Anthony

1992-01-01

Validation of the HIRS2/MSU cloud parameters began with the cloud/climate feedback problem. The derived effective cloud amount is less sensitive to surface temperature for higher clouds. This occurs because as the cloud elevation increases, the difference between surface temperature and cloud temperature increases, so only a small change in cloud amount is needed to effect a large change in radiance at the detector. By validating the cloud parameters it is meant 'developing a quantitative sense for the physical meaning of the measured parameters', by: (1) identifying the assumptions involved in deriving parameters from the measured radiances, (2) testing the input data and derived parameters for statistical error, sensitivity, and internal consistency, and (3) comparing with similar parameters obtained from other sources using other techniques.

Monitoring Eruptive Activity at Mount St. Helens with TIR Image Data

NASA Technical Reports Server (NTRS)

Vaughan, R. G.; Hook, S. J.; Ramsey, M. S.; Realmuto, V. J.; Schneider, D. J.

2005-01-01

Thermal infrared (TIR) data from the MASTER airborne imaging spectrometer were acquired over Mount St. Helens in Sept and Oct, 2004, before and after the onset of recent eruptive activity. Pre-eruption data showed no measurable increase in surface temperatures before the first phreatic eruption on Oct 1. MASTER data acquired during the initial eruptive episode on Oct 14 showed maximum temperatures of similar to approximately 330 C and TIR data acquired concurrently from a Forward Looking Infrared (FLIR) camera showed maximum temperatures similar to approximately 675 C, in narrow (approximately 1-m) fractures of molten rock on a new resurgent dome. MASTER and FLIR thermal flux calculations indicated a radiative cooling rate of approximately 714 J/m(exp 2)/s over the new dome, corresponding to a radiant power of approximately 24 MW. MASTER data indicated the new dome was dacitic in composition, and digital elevation data derived from LIDAR acquired concurrently with MASTER showed that the dome growth correlated with the areas of elevated temperatures. Low SO2 concentrations in the plume combined with sub-optimal viewing conditions prohibited quantitative measurement of plume SO2. The results demonstrate that airborne TIR data can provide information on the temperature of both the surface and plume and the composition of new lava during eruptive episodes. Given sufficient resources, the airborne instrumentation could be deployed rapidly to a newly-awakening volcano and provide a means for remote volcano monitoring.

Sensors for ceramic components in advanced propulsion systems: Summary of literature survey and concept analysis, task 3 report

NASA Technical Reports Server (NTRS)

Bennethum, W. H.; Sherwood, L. T.

1988-01-01

The results of a literature survey and concept analysis related to sensing techniques for measuring of surface temperature, strain, and heat flux for (non-specific) ceramic materials exposed to elevated temperatures (to 2200 K) are summarized. Concepts capable of functioning in a gas turbine hot section environment are favored but others are reviewed also. Recommendation are made for sensor development in each of the three areas.

Potential for Small Unmanned Aircraft Systems applications for identifying groundwater-surface water exchange in a meandering river reach

USGS Publications Warehouse

Pai, H.; Malenda, H.; Briggs, Martin A.; Singha, K.; González-Pinzón, R.; Gooseff, M.; Tyler, S.W.; ,

2017-01-01

The exchange of groundwater and surface water (GW-SW), including dissolved constituents and energy, represents a critical yet challenging characterization problem for hydrogeologists and stream ecologists. Here, we describe the use of a suite of high spatial-resolution remote-sensing techniques, collected using a small unmanned aircraft system (sUAS), to provide novel and complementary data to analyze GW-SW exchange. sUAS provided centimeter-scale resolution topography and water surface elevations, which are often drivers of exchange along the river corridor. Additionally, sUAS-based vegetation imagery, vegetation-top elevation, and normalized difference vegetation index (NDVI) mapping indicated GW-SW exchange patterns that are difficult to characterize from the land surface and may not be resolved from coarser satellite-based imagery. We combined these data with estimates of sediment hydraulic conductivity to provide a direct estimate of GW “shortcutting” through meander necks, which was corroborated by temperature data at the riverbed interface.

Potential for Small Unmanned Aircraft Systems Applications for Identifying Groundwater-Surface Water Exchange in a Meandering River Reach

NASA Astrophysics Data System (ADS)

Pai, H.; Malenda, H. F.; Briggs, M. A.; Singha, K.; González-Pinzón, R.; Gooseff, M. N.; Tyler, S. W.

2017-12-01

The exchange of groundwater and surface water (GW-SW), including dissolved constituents and energy, represents a critical yet challenging characterization problem for hydrogeologists and stream ecologists. Here we describe the use of a suite of high spatial resolution remote sensing techniques, collected using a small unmanned aircraft system (sUAS), to provide novel and complementary data to analyze GW-SW exchange. sUAS provided centimeter-scale resolution topography and water surface elevations, which are often drivers of exchange along the river corridor. Additionally, sUAS-based vegetation imagery, vegetation-top elevation, and normalized difference vegetation index mapping indicated GW-SW exchange patterns that are difficult to characterize from the land surface and may not be resolved from coarser satellite-based imagery. We combined these data with estimates of sediment hydraulic conductivity to provide a direct estimate of GW "shortcutting" through meander necks, which was corroborated by temperature data at the riverbed interface.

Surface temperature patterns in complex terrain: Daily variations and long-term change in the central Sierra Nevada, California

USGS Publications Warehouse

Lundquist, J.D.; Cayan, D.R.

2007-01-01

A realistic description of how temperatures vary with elevation is crucial for ecosystem studies and for models of basin-scale snowmelt and spring streamflow. This paper explores surface temperature variability using temperature data from an array of 37 sensors, called the Yosemite network, which traverses both slopes of the Sierra Nevada in the vicinity of Yosemite National Park, California. These data indicate that a simple lapse rate is often a poor description of the spatial temperature structure. Rather, the spatial pattern of temperature over the Yosemite network varies considerably with synoptic conditions. Empirical orthogonal functions (EOFs) were used to identify the dominant spatial temperature patterns and how they vary in time. Temporal variations of these surface temperature patterns were correlated with large-scale weather conditions, as described by National Centers for Environmental Prediction-National Center for Atmospheric Research Reanalysis data. Regression equations were used to downscale larger-scale weather parameters, such as Reanalysis winds and pressure, to the surface temperature structure over the Yosemite network. These relationships demonstrate that strong westerly winds are associated with relatively warmer temperatures on the east slope and cooler temperatures on the west slope of the Sierra, and weaker westerly winds are associated with the opposite pattern. Reanalysis data from 1948 to 2005 indicate weakening westerlies over this time period, a trend leading to relatively cooler temperatures on the east slope over decadal timescale's. This trend also appears in long-term observations and demonstrates the need to consider topographic effects when examining long-term changes in mountain regions. Copyright 2007 by the American Geophysical Union.

Mountain Permafrost in the Yukon Territory, Canada: Mapping and Modelling

NASA Astrophysics Data System (ADS)

Lewkowicz, A. G.; Bonnaventure, P.; Schultz, E.; Etzelmuller, B.

2006-12-01

The distribution and characteristics of mountain permafrost in North America are poorly known compared to lowland permafrost, and predictions of climatic change impacts are therefore subject to a higher degree of uncertainty. Recent DC resistivity soundings in association with borehole temperature information in the Yukon Territory, show the wide range of permafrost conditions that can exist at sites separated by short distances. To provide baseline information for future modelling, efforts are underway to produce a detailed map of permafrost probability in the mountains of the southern half of the Yukon Territory (60-65°N), an area greater than 200 x 103km2. The methodology is based on the Basal Temperature of Snow (BTS) technique, first developed in the European Alps. Ground surface temperatures measured at the base of snow > 80 cm thick in late winter are an indicator of permafrost presence or absence. We have used this method successfully in three study areas of about 200 km2: first, Wolf Creek basin near Whitehorse (Lewkowicz and Ednie, 2004) and now the western side of the Ruby Range adjacent to Kluane Lake, and the Haines Summit area in northwestern British Columbia. In each area, (1) we installed miniature temperature loggers at the ground surface and in the air to check on the timing of the BTS measurements; (2) we measured BTS values in the elevation zone across which permafrost was expected to become widespread; (3) we modelled the BTS spatial field using elevation (from a 30 m DEM) and potential incoming solar radiation (PISR) as the independent variables; and (4) we used logistic regression to compare the modelled BTS values with pit observations made in late-summer of the presence or absence of frozen ground. Both elevation and PISR were significant in the Wolf Creek and Ruby Range sites which have relatively continental climates and fall within the Upper Yukon-Stikine Basin climatic region (Wahl et al., 1987). For the Haines Summit area, however, PISR was not significant, likely reflecting the much more maritime climate of this area and the frequent fogs that are present. More than 50 new air and ground temperature monitoring stations were installed in spring 2006 as the first step to extend the modelling to the remaining mountainous parts of the Yukon Territory. We selected sites within the four climatic regions encompassing discontinuous permafrost that we had not previously sampled: the Faro area (Central Yukon Basin region, extensive discontinuous zone), Johnson's Crossing (Pelly-Cassiar Mountains region, sporadic discontinuous zone), Sa Dena Hes mine (Liard Basin region, extensive discontinuous zone) and the Keno area (Ogilvie-Mackenzie Mountains region, extensive discontinuous zone). Each of the stations is equipped to measure air temperature, ground surface temperature, ground temperature at a depth of 1 m (to evaluate the thermal offset), and snow depth (interpreted from I-button miniature loggers installed on a stake). These measurements will not only be used for permafrost modelling but will generate a unique data-set of air and ground surface temperatures which will be employed to investigate the frequency of air temperature inversions, their relation to topography and their effect on permafrost. The first complete monthly results (July 2006) demonstrate the expected wide variability in air and ground surface temperatures at both regional and local scales that makes modelling mountain permafrost so challenging.

Wood properties of Scots pines (Pinus sylvestris) grown at elevated temperature and carbon dioxide concentration.

PubMed

Kilpeläinen, Antti; Peltola, Heli; Ryyppö, Aija; Sauvala, Kari; Laitinen, Kaisa; Kellomäki, Seppo

2003-09-01

Impacts of elevated temperature and carbon dioxide concentration ([CO2]) on wood properties of 15-year-old Scots pines (Pinus sylvestris L.) grown under conditions of low nitrogen supply were investigated in open-top chambers. The treatments consisted of (i) ambient temperature and ambient [CO2] (AT+AC), (ii) ambient temperature and elevated [CO2] (AT+EC), (iii) elevated temperature and ambient [CO2] (ET+AC) and (iv) elevated temperature and elevated [CO2] (ET+EC). Wood properties analyzed for the years 1992-1994 included ring width, early- and latewood width and their proportions, intra-ring wood density (minimum, maximum and mean, as well as early- and latewood densities), mean fiber length and chemical composition of the wood (cellulose, hemicellulose, lignin and acetone extractive concentration). Absolute radial growth over the 3-year period was 54% greater in AT+EC trees and 30 and 25% greater in ET+AC and ET+EC trees, respectively, than in AT+AC trees. Neither elevated temperature nor elevated [CO2] had a statistically significant effect on ring width, early- and latewood widths or their proportions. Both latewood density and maximum intra-ring density were increased by elevated [CO2], whereas fiber length was increased by elevated temperature. Hemicellulose concentration decreased and lignin concentration increased significantly in response to elevated temperature. There were no statistically significant interaction effects of elevated temperature and elevated [CO2] on the wood properties, except on earlywood density.

Kinetics of radiation-induced precipitation at the alloy surface

NASA Astrophysics Data System (ADS)

Lam, N. Q.; Nguyen, T.; Leaf, G. K.; Yip, S.

1988-05-01

Radiation-induced precipitation of a new phase at the surface of an alloy during irradiation at elevated temperatures was studied with the aid of a kinetic model of segregation. The preferential coupling of solute atoms with the defect fluxes gives rise to a strong solute enrichment at the surface, which, if surpassing the solute solubility limit, leads to the formation of a precipitate layer. The moving precipitate/matrix interface was accommodated by means of a mathematical scheme that transforms spatial coordinates into a reference frame in which the boundaries are immobile. Sample calculations were performed for precipitation of the γ'-Ni 3Si layer on Ni-Si alloys undergoing electron irradiation. The dependences of the precipitation kinetics on the defect-production rate, irradiation temperature, internal defect sink concentration and alloy composition were investigated systematically.

Options to Improve Rain Snow Parameterization in Surface Based Models

NASA Astrophysics Data System (ADS)

Feiccabrino, J. M.

2017-12-01

Precipitation phase determination is of upmost importance in a number of surface based hydrological, ecological, and safety models. However, precipitation phase at Earth's surface is a result of cloud and atmospheric properties not measured by surface weather stations. Nonetheless, they can be inferred from the available surface datum. This study uses 681,620 weather observations with air temperatures between -3 and 5°C and identified precipitation occurring at the time of the observation to determine simple, yet accurate, thresholds for precipitation phase determination schemes (PPDS). This dataset represents 38% and 42% of precipitation observations over a 16 year period for 85 Swedish, and 84 Norwegian weather stations. The misclassified precipitation (error) from PPDS using AT, dew-point temperature (DT) and wet-bulb temperature (WB) thresholds were compared using a single threshold PPDS. The Norwegian observations between -3 and 5°C resulted in 11.64%, 11.21%, and 8.42% error for DT (-0.2°C), AT (1.2°C), and WB (0.3°C) thresholds respectively. Individual station thresholds had a range of -0.7 to 1.2°C, -1.2 to 0.9°C, and -0.1 to 2.5°C for WB, DP, and AT respectively. To address threshold variance while decreasing error, weather stations were grouped into nine landscape categories; windward (WW) ocean, WW coast, WW fjord, WW hill, WW mountain, leeward (LW) mountain, LW hill, LW rolling hills, and LW coast. Landscape classification was based on location relative to the Scandinavian Mountains, and the % water or range of elevation within 15KM. Within landscapes, stations share similar land atmosphere exchanges which differ from other landscapes. These differences change optimal thresholds for PPDS between landscapes. Also tested were threshold temperature affects based on assumed atmospheric differences for the following observation groups; 1.) occurring before and after an air mass boundary, 2.) with different water temperatures and/or NAO phases, 3.) with snow cover, 4.) coupled with higher elevation stations and 5.) with different cloud heights. For example, in Norway, as the unsaturated layer depth beneath clouds increased, AT thresholds warmed. Cloud height adjusted AT thresholds reduced error by 5% before threshold adjustments for landscapes.

Long-Term Stability of Residual Stress Improvement by Water Jet Peening Considering Working Processes.

PubMed

Hashimoto, Tadafumi; Osawa, Yusuke; Itoh, Shinsuke; Mochizuki, Masahito; Nishimoto, Kazutoshi

2013-06-01

To prevent primary water stress corrosion cracking (PWSCC), water jet peening (WJP) has been used on the welds of Ni-based alloys in pressurized water reactors (PWRs). Before WJP, the welds are machined and buffed in order to conduct a penetrant test (PT) to verify the weld qualities to access, and microstructure evolution takes place in the target area due to the severe plastic deformation. The compressive residual stresses induced by WJP might be unstable under elevated temperatures because of the high dislocation density in the compressive stress layer. Therefore, the stability of the compressive residual stresses caused by WJP was investigated during long-term operation by considering the microstructure evolution due to the working processes. The following conclusions were made: The compressive residual stresses were slightly relaxed in the surface layers of the thermally aged specimens. There were no differences in the magnitude of the relaxation based on temperature or time. The compressive residual stresses induced by WJP were confirmed to remain stable under elevated temperatures. The stress relaxation at the surface followed the Johnson-Mehl equation, which states that stress relaxation can occur due to the recovery of severe plastic strain, since the estimated activation energy agrees very well with the self-diffusion energy for Ni. By utilizing the additivity rule, it was indicated that stress relaxation due to recovery is completed during the startup process. It was proposed that the long-term stability of WJP under elevated temperatures must be assessed based on compressive stresses with respect to the yield stress. Thermal elastic-plastic creep analysis was performed to predict the effect of creep strain. After 100 yr of simulated continuous operation at 80% capacity, there was little change in the WJP compressive stresses under an actual operating temperature of 623 K. Therefore, the long-term stability of WJP during actual operation was analytically predicted.

In Situ Neutron Diffraction of Rare-Earth Phosphate Proton Conductors Sr/Ca-doped LaPO4 at Elevated Temperatures

NASA Astrophysics Data System (ADS)

Al-Wahish, Amal; Al-Binni, Usama; Bridges, C. A.; Huq, A.; Bi, Z.; Paranthaman, M. P.; Tang, S.; Kaiser, H.; Mandrus, D.

Acceptor-doped lanthanum orthophosphates are potential candidate electrolytes for proton ceramic fuel cells. We combined neutron powder diffraction (NPD) at elevated temperatures up to 800° C , X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) to investigate the crystal structure, defect structure, thermal stability and surface topography. NPD shows an average bond length distortion in the hydrated samples. We employed Quasi-Elastic Neutron Scattering (QENS) and electrochemical impedance spectroscopy (EIS) to study the proton dynamics of the rare-earth phosphate proton conductors 4.2% Sr/Ca-doped LaPO4. We determined the bulk diffusion and the self-diffusion coefficients. Our results show that QENS and EIS are probing fundamentally different proton diffusion processes. Supported by the U.S. Department of Energy.

Recent Basal Melting of a Mid-Latitude Glacier on Mars

NASA Astrophysics Data System (ADS)

Butcher, Frances E. G.; Balme, M. R.; Gallagher, C.; Arnold, N. S.; Conway, S. J.; Hagermann, A.; Lewis, S. R.

2017-12-01

Evidence for past basal melting of young (late Amazonian-aged), debris-covered glaciers in Mars' mid-latitudes is extremely rare. Thus, it is widely thought that these viscous flow features (VFFs) have been perennially frozen to their beds. We identify an instance of recent, localized wet-based mid-latitude glaciation, evidenced by a candidate esker emerging from a VFF in a tectonic rift in Tempe Terra. Eskers are sedimentary ridges deposited in ice-walled meltwater conduits and are indicative of glacial melting. We compare the candidate esker to terrestrial analogues, present a geomorphic map of landforms in the rift, and develop a landsystem model to explain their formation. We propose that the candidate esker formed during a transient phase of wet-based glaciation. We then consider the similarity between the geologic setting of the new candidate esker and that of the only other candidate esker to be identified in association with an existing mid-latitude VFF; both are within tectonic graben/rifts proximal to volcanic provinces. Finally, we calculate potential basal temperatures for a range of VFF thicknesses, driving stresses, mean annual surface temperatures, and geothermal heat fluxes, which unlike previous studies, include the possible role of internal strain heating. Strain heating can form an important additional heat source, especially in flow convergence zones, or where ice is warmer due to elevated surface temperatures or geothermal heat flux. Elevated geothermal heat flux within rifts, perhaps combined with locally-elevated strain heating, may have permitted wet-based glaciation during the late Amazonian, when cold climates precluded more extensive wet-based glaciation on Mars.

Effect of thermal annealing on the redistribution of alkali metals in Cu(In,Ga)Se2 solar cells on glass substrate

NASA Astrophysics Data System (ADS)

Kamikawa, Yukiko; Nishinaga, Jiro; Ishizuka, Shogo; Tayagaki, Takeshi; Guthrey, Harvey; Shibata, Hajime; Matsubara, Koji; Niki, Shigeru

2018-03-01

The precise control of alkali-metal concentrations in Cu(In,Ga)Se2 (CIGS) solar cells via post deposition treatment (PDT) has recently attracted attention. When PDT is performed at an elevated temperature, an accompanying annealing effect is expected. Here, we investigate how thermal annealing affects the redistribution of alkali metals in CIGS solar cells on glass substrates and the properties of the solar cells. In addition, we investigate the origin of non-homogeneous alkali-metal depth profiles that are typical of CIGS grown using a three-stage process. In particular, we use secondary-ion mass spectrometry measurements of the ion concentration as a function of distance from the CIGS surface to investigate the impact of thermal annealing on the distribution of alkali metals (Na, Ka, and Rb) and constituent elements (Ga and In) in the CIGS absorbers. We find that the depth profiles of the alkali metals strongly reflect the density of sites that tend to accommodate alkali metals, i.e., vacancies. Annealing at elevated temperature caused a redistribution of the alkali metals. The thermal-diffusion kinetics of alkali metals depends strongly on the species involved. We introduced low flux potassium fluoride (KF) to study a side effect of KF-PDT, i.e., Na removal from CIGS, separately from its predominant effects such as surface modification. When sufficient amounts of Na are supplied from the soda lime glass via annealing at an elevated temperature, the negative effect was not apparent. Conversely, when the Na supply was not sufficient, it caused a deterioration of the photovoltaic properties.

Ocean, Land and Meteorology Studies Using Space-Based Lidar Measurements

NASA Technical Reports Server (NTRS)

Hu,Yongxiang

2009-01-01

CALIPSO's main mission objective is studying the climate impact of clouds and aerosols in the atmosphere. CALIPSO also collects information about other components of the Earth's ecosystem, such as oceans and land. This paper introduces the physics concepts and presents preliminary results for the valueadded CALIPSO Earth system science products. These include ocean surface wind speeds, column atmospheric optical depths, ocean subsurface backscatter, land surface elevations, atmospheric temperature profiles, and A-train data fusion products.

Improving impact resistance of ceramic materials by energy absorbing surface layers

NASA Technical Reports Server (NTRS)

Kirchner, H. P.; Seretsky, J.

1974-01-01

Energy absorbing surface layers were used to improve the impact resistance of silicon nitride and silicon carbide ceramics. Low elastic modulus materials were used. In some cases, the low elastic modulus was achieved using materials that form localized microcracks as a result of thermal expansion anisotropy, thermal expansion differences between phases, or phase transformations. In other cases, semi-vitreous or vitreous materials were used. Substantial improvements in impact resistance were observed at room and elevated temperatures.

Trends in 1970-2010 southern California surface maximum temperatures: extremes and heat waves

NASA Astrophysics Data System (ADS)

Ghebreegziabher, Amanuel T.

Daily maximum temperatures from 1970-2010 were obtained from the National Climatic Data Center (NCDC) for 28 South Coast Air Basin (SoCAB) Cooperative Network (COOP) sites. Analyses were carried out on the entire data set, as well as on the 1970-1974 and 2006-2010 sub-periods, including construction of spatial distributions and time-series trends of both summer-average and annual-maximum values and of the frequency of two and four consecutive "daytime" heat wave events. Spatial patterns of average and extreme values showed three areas consistent with climatological SoCAB flow patterns: cold coastal, warm inland low-elevation, and cool further-inland mountain top. Difference (2006-2010 minus 1970-1974) distributions of both average and extreme-value trends were consistent with the shorter period (1970-2005) study of previous study, as they showed the expected inland regional warming and a "reverse-reaction" cooling in low elevation coastal and inland areas open to increasing sea breeze flows. Annual-extreme trends generally showed cooling at sites below 600 m and warming at higher elevations. As the warming trends of the extremes were larger than those of the averages, regional warming thus impacts extremes more than averages. Spatial distributions of hot-day frequencies showed expected maximum at inland low-elevation sites. Regional warming again thus induced increases at both elevated-coastal areas, but low-elevation areas showed reverse-reaction decreases.

Implicit Coupling Approach for Simulation of Charring Carbon Ablators

NASA Technical Reports Server (NTRS)

Chen, Yih-Kanq; Gokcen, Tahir

2013-01-01

This study demonstrates that coupling of a material thermal response code and a flow solver with nonequilibrium gas/surface interaction for simulation of charring carbon ablators can be performed using an implicit approach. The material thermal response code used in this study is the three-dimensional version of Fully Implicit Ablation and Thermal response program, which predicts charring material thermal response and shape change on hypersonic space vehicles. The flow code solves the reacting Navier-Stokes equations using Data Parallel Line Relaxation method. Coupling between the material response and flow codes is performed by solving the surface mass balance in flow solver and the surface energy balance in material response code. Thus, the material surface recession is predicted in flow code, and the surface temperature and pyrolysis gas injection rate are computed in material response code. It is demonstrated that the time-lagged explicit approach is sufficient for simulations at low surface heating conditions, in which the surface ablation rate is not a strong function of the surface temperature. At elevated surface heating conditions, the implicit approach has to be taken, because the carbon ablation rate becomes a stiff function of the surface temperature, and thus the explicit approach appears to be inappropriate resulting in severe numerical oscillations of predicted surface temperature. Implicit coupling for simulation of arc-jet models is performed, and the predictions are compared with measured data. Implicit coupling for trajectory based simulation of Stardust fore-body heat shield is also conducted. The predicted stagnation point total recession is compared with that predicted using the chemical equilibrium surface assumption

Temperature-dependent quantum efficiency degradation of K-Cs-Sb bialkali antimonide photocathodes grown by a triple-element codeposition method

DOE PAGES

Ding, Zihao; Karkare, Siddharth; Feng, Jun; ...

2017-11-09

K-Cs-Sb bialkali antimonide photocathodes grown by a triple-element codeposition method have been found to have excellent quantum efficiency (QE) and outstanding near-atomic surface smoothness and have been employed in the VHF gun in the Advanced Photoinjector Experiment (APEX), however, their robustness in terms of their lifetime at elevated photocathode temperature has not yet been investigated. In this paper, the relationship between the lifetime of the K-Cs-Sb photocathode and the photocathode temperature has been investigated. The origin of the significant QE degradation at photocathode temperatures over 70 °C has been identified as the loss of cesium atoms from the K-Cs-Sb photocathode,more » based on the in situ x-ray analysis on the photocathode film during the decay process. The findings from this work will not only further the understanding of the behavior of K-Cs-Sb photocathodes at elevated temperature and help develop more temperature-robust cathodes, but also will become an important guide to the design and operation of the future high-field rf guns employing the use of such photocathodes.« less

Temperature-dependent quantum efficiency degradation of K-Cs-Sb bialkali antimonide photocathodes grown by a triple-element codeposition method

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

Ding, Zihao; Karkare, Siddharth; Feng, Jun

K-Cs-Sb bialkali antimonide photocathodes grown by a triple-element codeposition method have been found to have excellent quantum efficiency (QE) and outstanding near-atomic surface smoothness and have been employed in the VHF gun in the Advanced Photoinjector Experiment (APEX), however, their robustness in terms of their lifetime at elevated photocathode temperature has not yet been investigated. In this paper, the relationship between the lifetime of the K-Cs-Sb photocathode and the photocathode temperature has been investigated. The origin of the significant QE degradation at photocathode temperatures over 70 °C has been identified as the loss of cesium atoms from the K-Cs-Sb photocathode,more » based on the in situ x-ray analysis on the photocathode film during the decay process. The findings from this work will not only further the understanding of the behavior of K-Cs-Sb photocathodes at elevated temperature and help develop more temperature-robust cathodes, but also will become an important guide to the design and operation of the future high-field rf guns employing the use of such photocathodes.« less

Analysis of Screen Channel LAD Bubble Point Tests in Liquid Oxygen at Elevated Temperature

NASA Technical Reports Server (NTRS)

Hartwig, Jason; McQuillen, John

2011-01-01

The purpose of this paper is to examine the key parameters that affect the bubble point pressure for screen channel Liquid Acquisition Devices in cryogenic liquid oxygen at elevated pressures and temperatures. An in depth analysis of the effect of varying temperature, pressure, and pressurization gas on bubble point is presented. Testing of a 200 x 1400 and 325 x 2300 Dutch Twill screen sample was conducted in the Cryogenics Components Lab 7 facility at the NASA Glenn Research Center in Cleveland, Ohio. Test conditions ranged from 92 to 130K and 0.138 - 1.79 MPa. Bubble point is shown to be a strong function of temperature with a secondary dependence on pressure. The pressure dependence is believed to be a function of the amount of evaporation and condensation occurring at the screen. Good agreement exists between data and theory for normally saturated liquid but the model generally under predicts the bubble point in subcooled liquid. Better correlation with the data is obtained by using the liquid temperature at the screen to determine surface tension of the fluid, as opposed to the bulk liquid temperature.

Temperature variation of pitch in a pitch pot

NASA Astrophysics Data System (ADS)

Droste, Stefan; Klinger, Charles

2007-05-01

Opticians have for years kept polishing pitch in electrified containers called "pitch pots" that keeps it in at an elevated temperature. The temperature is adjusted to achieve the desired pitch viscosity. When pitch is desired, the optician will remove the cover, reach into the pot and scoop out a glob of pitch with his hand. However, without thinking, most opticians will "fold over" or "push aside" the top layer of pitch to select pitch from deeper in the pot. This paper documents the change in temperature as the distance from the top surface increases. It also shows the effect of insulating the top cover.

Characterizing near-surface firn from the scattered signal component of glacier surface reflections detected in airborne radio-echo sounding measurements

NASA Astrophysics Data System (ADS)

Rutishauser, A.; Grima, C.; Sharp, M. J.; Blankenship, D. D.; Young, D. A.; Cawkwell, F.; Dowdeswell, J. A.

2016-12-01

With recent summer warming, surface melt on Canadian Arctic ice caps has intensified and extended to higher elevations in ice cap accumulation areas. Consequently, more meltwater percolates into the near-surface firn, and refreezes as ice layers where firn temperatures are below freezing. This process can increase firn densification rates, causing a lowering of the glacier surface height even in the absence of mass changes. Thus, knowledge of spatio-temporal variations in the near-surface firn stratigraphy is important for interpreting altimetrically-derived estimates of ice cap mass balance. We investigate the use of the scattering signal component of glacier surface reflections in airborne radio-echo sounding (RES) measurements to characterize the near-surface firn stratigraphy. The scattering signal distribution over Devon Ice Cap is compared to firn stratigraphy derived from ground-based radar data. We identify three distinct firn facies zones at different elevation ranges. The scattered signal component changes significantly between the different firn facies zones: low scattering correlates to laterally homogeneous firn containing thin, flat and continuous ice layers at elevations above 1800 m and below 1200 m, where firn consists mainly of ice. Higher scattering values are found from 1200-1800 m where the firn contains discrete, undulating ice layers. No correlation was found between the scattering component and surface roughness. Modelled scattering values for the measured roughness were significantly less than the observed values, and did not reproduce their observed spatial distribution. This indicates that the scattering component is determined mainly by the structure of near-surface firn. Our results suggest that the scattering component of surface reflections from airborne RES measurements has potential for characterizing heterogeneity in the spatial structure of firn that is affected by melting and refreezing processes.

The effect of elevated temperatures on the life history and insecticide resistance phenotype of the major malaria vector Anopheles arabiensis (Diptera: Culicidae).

PubMed

Oliver, Shüné V; Brooke, Basil D

2017-02-14

Temperature plays a crucial role in the life history of insects. Recent climate change research has highlighted the importance of elevated temperature on malaria vector distribution. This study aims to examine the role of elevated temperatures on epidemiologically important life-history traits in the major malaria vector, Anopheles arabiensis. Specifically, the differential effects of temperature on insecticide-resistant and susceptible strains were examined. Two laboratory strains of A. arabiensis, the insecticide-susceptible SENN and the insecticide-resistant SENN DDT strains, were used to examine the effect of elevated temperatures on larval development and adult longevity. The effects of various elevated temperatures on insecticide resistance phenotypes were also examined and the biochemical basis of the changes in insecticide resistance phenotype was assessed. SENN and SENN DDT larvae developed at similar rates at elevated temperatures. SENN DDT adult survivorship did not vary between control and elevated temperatures, while the longevity of SENN adults at constantly elevated temperatures was significantly reduced. SENN DDT adults lived significantly longer than SENN at constantly elevated temperatures. Elevated rearing temperatures, as well as a short-term exposure to 37 and 39 °C as adults, augmented pyrethroid resistance in adult SENN DDT, and increased pyrethroid tolerance in SENN. Detoxification enzyme activity was not implicated in this phenotypic effect. Quercertin-induced synergism of inducible heat shock proteins negated this temperature-mediated augmentation of pyrethroid resistance. Insecticide-resistant A. arabiensis live longer than their susceptible counterparts at elevated temperatures. Exposure to heat shock augments pyrethroid resistance in both resistant and susceptible strains. This response is potentially mediated by inducible heat shock proteins.

Ice core age dating and paleothermometer calibration based on isotope and temperature profiles from deep boreholes at Vostok Station (East Antarctica)

NASA Astrophysics Data System (ADS)

Salamatin, Andrey N.; Lipenkov, Vladimir Y.; Barkov, Nartsiss I.; Jouzel, Jean; Petit, Jean Robert; Raynaud, Dominique

1998-04-01

An interpretation of the deuterium profile measured along the Vostok (East Antarctica) ice core down to 2755 m has been attempted on the basis of the borehole temperature analysis. An inverse problem is solved to infer a local "geophysical metronome," the orbital signal in the surface temperature oscillations expressed as a sum of harmonics of Milankovich periods. By correlating the smoothed isotopic temperature record to the metronome, a chronostratigraphy of the Vostok ice core is derived with an accuracy of ±3.0-4.5 kyr. The developed timescale predicts an age of 241 kyr at a depth of 2760 m. The ratio δD/δTi between deuterium content and cloud temperature fluctuations (at the top of the inversion layer) is examined by fitting simulated and measured borehole temperature profiles. The conventional estimate of the deuterium-temperature slope corresponding to the present-day spatial ratio (9 per mil/°C) is confirmed in general. However, the mismatch between modeled and measured borehole temperatures decreases noticeably if we allow surface temperature, responsible for the thermal state of the ice sheet, to undergo more intensive precession oscillations than those of the inversion temperature traced by isotope record. With this assumption, we obtain the long-term temporal deuterium-temperature slope to be 5.8-6.5 per mil/°C which implies that the glacial-interglacial temperature increase over central Antarctica was about 15°C in the surface temperature and 10°C in the inversion temperature. Past variations of the accumulation rate and the corresponding changes in the ice-sheet surface elevation are simultaneously simulated.

Fatigue life assessment of 316L stainless steel and DIN-1.4914 martensitic steel before and after TEXTOR exposure

NASA Astrophysics Data System (ADS)

Shakib, J. I.; Ullmaier, H.; Little, E. A.; Schmitz, W.; Faulkner, R. G.; Chung, T. E.

1992-09-01

The effects of plasma exposure in the TEXTOR tokomak on elevated temperature fatigue lifetime and failure micromechanisms of 316L austenitic stainless steel and DIN 1.4914 martensitic steel (NET reference heats) have been evaluated. Fatigue tests were carried out in vacuum in the temperature range 150°-450°C and compared with data from reference specimens.Plasma-induced surface modifications lead to significant deterioration in fatigue life of 316L steel, whereas the lifetime of 1.4914 steel is unaffected. Fatigue in the 1.4914 steel is surface-initiated only at high stresses. At low stress amplitudes internal fatigue initiation at inclusions was observed.

Near-surface air temperature lapse rate in a humid mountainous terrain on the southern slopes of the eastern Himalayas

NASA Astrophysics Data System (ADS)

Kattel, Dambaru Ballab; Yao, Tandong; Panday, Prajjwal Kumar

2018-05-01

Based on climatic data from 18 stations on the southern slopes of the eastern Himalayas in Bhutan for the period from 1996 to 2009, this paper investigates monthly characteristics of the near-surface air temperature lapse rate (TLR). The station elevations used in this study range from 300 to 2760 m a. s. l. TLRs were evaluated using a linear regression model. The monthly values of maximum TLRs were always smaller than those of the minimum TLRs, which is in contrast to results from the surrounding mountainous regions. In this study, annual patterns of TLRs were somewhat consistent, particularly in the summer; during the other seasons, patterns contrasted to results from the southeastern Tibetan Plateau (China) and were almost comparable to results from Nepal. The shallowest observed values for TLRs in summer are due to intense latent heating at the higher elevation, associated with water vapor condensation from moist convection and evapotranspiration, and decreasing sensible heating at lower elevation, due to heavier rainfall, cloud, and forest cover. When compared to summer, the steeper TLRs in the non-monsoon season are due to sensible heating at the lower elevations, corresponding to dry and clear weather seasons, as well as increasing cooling at higher elevations, particularly in winter due to snow and cloud cover. Owing to lower albedo and higher aerodynamic roughness of forested areas, the TLRs were considerably reduced in daytime because of the dissipation of sensible heat to the atmospheric boundary layer. The distinct variation in diurnal TLR range is due to the diurnal variation in net radiation associated with reduced turbulent heating in the day and increased turbulent heating in the night, in addition to the effect of moisture and cloud cover. The shallower values of TLRs in this study when compared with the surrounding mountainous regions are due to high humidity, as well as the differing elevations and local climates.

Methods for providing ceramic matrix composite components with increased thermal capacity

NASA Technical Reports Server (NTRS)

Steibel, James Dale (Inventor); Utah, David Alan (Inventor)

2001-01-01

A method for enhancing the cooling capability of a turbine component made from a ceramic matrix composite. The method improves the thermal performance of the component by producing a surface having increased cooling capacity, thereby allowing the component to operate at a higher temperature. The method tailors the available surface area on the cooling surface of the composite component by depositing a particulate layer of coarse grained ceramic powders of preselected size onto the surface of the ceramic matrix composite component. The size of the particulate is selectively tailored to match the desired surface finish or surface roughness of the article. The article may be designed to have different surface finishes for different locations, so that the application of different sized powders can provide different cooling capabilities at different locations, if desired. The compositions of the particulates are chemically compatible with the ceramic material comprising the outer surface or portion of the ceramic matrix composite. The particulates are applied using a slurry and incorporated into the article by heating to an elevated temperature without melting the matrix, the particulates or the fiber reinforcement.

Preliminary demonstration using localized skin temperature elevation as observed with thermal imaging as an indicator of fat-specific absorption during focused-field radiofrequency therapy.

PubMed

Key, Douglas J

2014-07-01

This study incorporates concurrent thermal camera imaging as a means of both safely extending the length of each treatment session within skin surface temperature tolerances and to demonstrate not only the homogeneous nature of skin surface temperature heating but the distribution of that heating pattern as a reflection of localization of subcutaneous fat distribution. Five subjects were selected because of a desire to reduce abdomen and flank fullness. Full treatment field thermal camera imaging was captured at 15 minute intervals, specifically at 15, 30, and 45 minutes into active treatment with the purpose of monitoring skin temperature and avoiding any patterns of skin temperature excess. Peak areas of heating corresponded anatomically to the patients' areas of greatest fat excess ie, visible "pinchable" fat. Preliminary observation of high-resolution thermal camera imaging used concurrently with focused field RF therapy show peak skin heating patterns overlying the areas of greatest fat excess.

A Limited Comparison of the Thermal Durability of Polyimide Candidate Matrix Polymers with PMR-15

NASA Technical Reports Server (NTRS)

Bowles, Kenneth J.; Papadopoulos, Demetrios S.; Scheiman, Daniel A.; Inghram, Linda L.; McCorkle, Linda S.; Klans, Ojars V.

2003-01-01

Studies were conducted with six different candidate high-temperature neat matrix resin specimens of varied geometric shapes to investigate the mechanisms involved in the thermal degradation of polyimides like PMR-15. The metrics for assessing the quality of these candidates were chosen to be glass transition temperature (T(sub g)), thermo-oxidative stability, dynamic mechanical properties, microstructural changes, and dimensional stability. The processing and mechanical properties were not investigated in the study reported herein. The dimensional changes and surface layer growth were measured and recorded. The data were in agreement with earlier published data. An initial weight increase reaction was observed to be dominating at the lower temperatures. However, at the more elevated temperatures, the weight loss reactions were prevalent and probably masked the weight gain reaction. These data confirmed the findings of the existence of an initial weight gain reaction previously reported. Surface- and core-dependent weight losses were shown to control the polymer degradation at the higher temperatures.

Synthesis of illite-smectite from smectite at earth surface temperatures and high pH

USGS Publications Warehouse

Eberl, D.D.; Velde, Bruce; McCormick, T.C.

1993-01-01

It is well known that illite-smectite can form from smectite at elevated temperatures in natural and experimental systems. However, the conversion of smectite to illite-smectite is also found in some natural systems that have never been heated. The present experiments show that illite layers can form from smectite by chemical reaction at 35° and 60°C at high solution pH. The rate of this reaction is accelerated by wetting and drying.

Relative sliding durability of two candidate high temperature oxide fiber seal materials

NASA Technical Reports Server (NTRS)

Dellacorte, Christopher; Steinetz, Bruce M.

1991-01-01

A test program to determine the relative sliding durability of two candidate ceramic fibers for high temperature sliding seal applications is described. Pin on disk tests were used to evaluate potential seal materials. Friction during the tests and fiber wear, indicated by the extent of fibers broken in a test bundle or yarn, was measured at the end of a test. In general, friction and wear increase with test temperature. This may be due to a reduction in fiber strength, a change in the surface chemistry at the fiber/counterface interface due to oxidation, adsorption and/or desorption of surface species and, to a lesser extent, an increase in counterface surface roughness due to oxidation at elevated temperatures. The relative fiber durability correlates with tensile strength indicating that tensile data, which is more readily available than sliding durability data, may be useful in predicting fiber wear behavior under various conditions. A simple model developed using dimensional analysis shows that the fiber durability is related to a dimensionless parameter which represents the ratio of the fiber strength to the fiber stresses imposed by sliding.

A surface acoustic wave ICP sensor with good temperature stability.

PubMed

Zhang, Bing; Hu, Hong; Ye, Aipeng; Zhang, Peng

2017-07-20

Intracranial pressure (ICP) monitoring is very important for assessing and monitoring hydrocephalus, head trauma and hypertension patients, which could lead to elevated ICP or even devastating neurological damage. The mortality rate due to these diseases could be reduced through ICP monitoring, because precautions can be taken against the brain damage. This paper presents a surface acoustic wave (SAW) pressure sensor to realize ICP monitoring, which is capable of wireless and passive transmission with antenna attached. In order to improve the temperature stability of the sensor, two methods were adopted. First, the ST cut quartz was chosen as the sensor substrate due to its good temperature stability. Then, a differential temperature compensation method was proposed to reduce the effects of temperature. Two resonators were designed based on coupling of mode (COM) theory and the prototype was fabricated and verified using a system established for testing pressure and temperature. The experiment result shows that the sensor has a linearity of 2.63% and hysteresis of 1.77%. The temperature stability of the sensor has been greatly improved by using the differential compensation method, which validates the effectiveness of the proposed method.

Microstructure Evolution and Mechanical Response of Nanolaminate Composites Irradiated with Helium at Elevated Temperatures

DOE PAGES

Li, Nan; Demkowicz, Michael J.; Mara, Nathan A.

2017-09-12

In this paper, we summarize recent work on helium (He) interaction with various heterophase boundaries under high temperature irradiation. We categorize the ion-affected material beneath the He-implanted surface into three regions of depth, based on the He/vacancy ratio. The differing defect structures in these three regions lead to the distinct temperature sensitivity of He-induced microstructure evolution. The effect of He bubbles or voids on material mechanical performance is explored. Finally, overall design guidelines for developing materials where He-induced damage can be mitigated in materials are discussed.

Thermo-Mechanical Characterization of Silicon Carbide-Silicon Carbide Composites at Elevated Temperatures Using a Unique Combustion Facility

DTIC Science & Technology

2009-09-10

Calibration Tool(s) Surface Temperature ~1250oC Furnace, R-type TC & IR Gas Temperature < 1800oC R-type TC Gas Velocity ~ Mach 0.5 XS -4 High Speed...Camera Equivalence Ratio ~ 0.9 HVOFTM Flow Controller Gas Composition H 2 O, O 2 ,CO 2 , CO, NOx Testo XL 350 Gas Analyzer Mechanical Loading Fatigue...unavailability, however, gas velocity was measured using the X-StreamTM XS -4 High Speed Camera. The range of our interest was the velocity in the upstream of a

A review of recent measurements of optical and thermal properties of α-mercuric iodide

NASA Astrophysics Data System (ADS)

Burger, A.; Morgan, S. H.; Silberman, E.; Nason, D.; Cheng, A. Y.

1992-11-01

The band gap energy of α-mercuric iodide was measured recently at elevated temperatures using optical absorption and reflection methods. In addition, reflection spectral measurements indicate that the temperature dependence of the exciton peak can provide a means of measuring, in a nondisturbing and remote manner, the local surface temperature of an α-mercuric iodide crystal during its growth from the vapor. Recent measurements of the thermal diffusivity and thermal expansion tensors have confirmed the anisotropy of this material and have implications for growth morphology and the generation of lattice defects.

Evaluation of High Temperature Knitted Spring Tubes for Structural Seal Applications

NASA Technical Reports Server (NTRS)

Taylor, Shawn C.; DeMange, Jeffrey J.; Dunlap, Patrick H., Jr.; Steinetz, Bruce M.

2004-01-01

Control surface seals are crucial to current and future space vehicles, as they are used to seal the gaps surrounding body flaps, elevons, and other actuated exterior surfaces. During reentry, leakage of high temperature gases through these gaps could damage underlying lower temperature structures such as rudder drive motors and mechanical actuators, resulting in impaired vehicle control. To be effective, control surface seals must shield lower temperature structures from heat transfer by maintaining sufficient resiliency to remain in contact with opposing sealing surfaces through multiple compression cycles. The current seal exhibits significant loss of resiliency after a few compression cycles at elevated temperatures (i.e., 1900 F) and therefore would be inadequate for advanced space vehicles. This seal utilizes a knitted Inconel X-750 spring tube as its primary resilient element. As part of a larger effort to enhance seal resiliency, researchers at the NASA Glenn Research Center performed high temperature compression testing (up to 2000 F) on candidate spring tube designs employing material substitutions and modified geometries. These tests demonstrated significant improvements in spring tube resiliency (5.5x better at 1750 F) through direct substitution of heat treated Rene 41 alloy in the baseline knit design. The impact of geometry modification was minor within the range of parameters tested, however trends did suggest that moderate resiliency improvements could be obtained by optimizing the current spring tube geometry.

49 CFR 172.325 - Elevated temperature materials.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 2 2013-10-01 2013-10-01 false Elevated temperature materials. 172.325 Section... REQUIREMENTS, AND SECURITY PLANS Marking § 172.325 Elevated temperature materials. (a) Except as provided in paragraph (b) of this section, a bulk packaging containing an elevated temperature material must be marked...

49 CFR 172.325 - Elevated temperature materials.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 2 2012-10-01 2012-10-01 false Elevated temperature materials. 172.325 Section... REQUIREMENTS, AND SECURITY PLANS Marking § 172.325 Elevated temperature materials. (a) Except as provided in paragraph (b) of this section, a bulk packaging containing an elevated temperature material must be marked...

On the averaging area for incident power density for human exposure limits at frequencies over 6 GHz

NASA Astrophysics Data System (ADS)

Hashimoto, Yota; Hirata, Akimasa; Morimoto, Ryota; Aonuma, Shinta; Laakso, Ilkka; Jokela, Kari; Foster, Kenneth R.

2017-04-01

Incident power density is used as the dosimetric quantity to specify the restrictions on human exposure to electromagnetic fields at frequencies above 3 or 10 GHz in order to prevent excessive temperature elevation at the body surface. However, international standards and guidelines have different definitions for the size of the area over which the power density should be averaged. This study reports computational evaluation of the relationship between the size of the area over which incident power density is averaged and the local peak temperature elevation in a multi-layer model simulating a human body. Three wave sources are considered in the frequency range from 3 to 300 GHz: an ideal beam, a half-wave dipole antenna, and an antenna array. 1D analysis shows that averaging area of 20 mm  ×  20 mm is a good measure to correlate with the local peak temperature elevation when the field distribution is nearly uniform in that area. The averaging area is different from recommendations in the current international standards/guidelines, and not dependent on the frequency. For a non-uniform field distribution, such as a beam with small diameter, the incident power density should be compensated by multiplying a factor that can be derived from the ratio of the effective beam area to the averaging area. The findings in the present study suggest that the relationship obtained using the 1D approximation is applicable for deriving the relationship between the incident power density and the local temperature elevation.

FirefOx Design Reference fO2 Sensor for Hot, Deep Atmospheres

NASA Astrophysics Data System (ADS)

Izenberg, N.; Papadakis, S.; Deglau, D.; Francomacaro, A. S.

2016-12-01

Understanding the composition of the lowest portion of Venus' atmosphere is critical to knowing the stable mineralogy of the rocks there. Oxygen gas is a critical trace component, with fugacity, or partial pressure, estimated in the range of 10-19 to 10-22 from early probe measurements down to 22km altitude (Pioneer Venus, Venera), chemical equilibrium measurements, and other modeling. "FirefOx" is a simple oxygen fugacity sensor with the express purpose of determining the partial pressure of oxygen in the lowest scale heights of the Venus atmosphere, and especially the lowest hundreds of meters; the surface atmosphere interface, where the atmosphere and surface move to thermodynamic equilibrium. Knowledge of the fO2 at the surface atmosphere interface is crucial to determining the stable mineralogy of surface materials (e.g. magnetite vs. hematite) and gas chemistry in the near-surface atmosphere FirefOx is a Metal/Metal Oxide oxygen fugacity sensor intended to be mounted on the outside of a Venus descent probe, with electronics housed inside a thermally controlled environment. The sole sensor capability is the precise, accurate detection of the partial pressure of oxygen gas (fO2) in the near-surface environment of Venus, at up to 95-bar pressure (predominantly CO2. Surface temperatures at mean planetary elevation are near 735 K, thus a required operational temperature range of 710-740 K covers a range of near-surface elevations. FirefOx system requirements are low ( 100-200 grams, mass, milliwatt power, several kilobytes total science data). A design reference sensor, composed of custom, Yittria-ZrO ceramic electrolyte, with an encapsulated Pd/PdO standard and patterned Pt electrodes has demonstrated scientifically useful signal-to-noise millivolt level potential at temperatures as low as 620 K, relatable to fO2 by a Nernst equation E = RT/4F ln(PO2/PrefO2) where E = open circuit potential across the sensor electrolyte, R = universal gas constant, T = temperature, F = Faraday constant, PrefO2 = reference oxygen pressure, and PO2 = unknown oxygen pressure of the outside environment. The FirefOx sensor shows promise for direct fO2 measurement on potential upcoming Venus in situ and other deep atmosphere probes.

Influence of surface oxygenated groups on the formation of active Cu species and the catalytic activity of Cu/AC catalyst for the synthesis of dimethyl carbonate

NASA Astrophysics Data System (ADS)

Zhang, Guoqiang; Li, Zhong; Zheng, Huayan; Hao, Zhiqiang; Wang, Xia; Wang, Jiajun

2016-12-01

Activated carbon (AC) supported Cu catalysts are employed to study the influence of surface oxygenated groups on the formation of active Cu species and the catalytic activity of Cu/AC catalyst for oxidative carbonylation of methanol to dimethyl carbonate (DMC). The AC supports are thermal treated under different temperatures in order to adjust the levels of surface oxygenated groups. The AC supports are characterized by BET, TPD-MS and XRD, and the Cu/AC catalysts are characterized by BET, XRD, TEM, XPS, AAS, CH3OH-TPD and N2O chemisorption. The results show that as the treatment temperature is below 800 °C, the BET surface area of the corresponding AC supports are nearly unchanged and close to that of the original AC (1529.6 m2/g). But as the thermal treatment temperature is elevated from 1000 to 1600 °C, the BET surface area of AC supports gradually decreases from 1407.6 to 972.2 m2/g. After loading of Cu, the BET surface area of copper catalysts is in the range of 834.4 to 1545.3 m2/g, which is slightly less than that of the respective supports. When AC is thermal treated at 400 and 600 °C, the unstable carboxylic acid and anhydrides groups are selectively removed, which has weakened the mobility and agglomeration of Cu species during the calcination process, and thus improve the Cu species dispersion over AC support. But as the treatment temperature is elevated from 600 °C to 1200 °C, the Cu species dispersion begins to decline suggesting further removal of stable surface oxygenated groups is unfavorable for Cu species dispersion. Moreover, higher thermal treatment temperature (above 1200 °C) promotes the graphitization degree of AC and leds to the decrease of Cu loading on AC support. Meanwhile, the removal of surface oxygenated groups by thermal treatment is conducive to the formation of more π-sites, and thus promote the reduction of Cu2+ to Cu+ and Cu0 as active centers. The specific surface area of (Cu+ + Cu0) is improved by thermal treatment of AC, however, the space time yield of DMC on unit specific surface area of (Cu+ + Cu0) is in the range of 23.1-49.1 mg h-1 m-2, which is much less than that (77.6 mg h-1 m-2) of the original catalyst. The possible reason is that the removal of surface oxygenated groups results in AC support transforms from hydrophilicity to hydrophobicity, which is detrimental for the adsorption of CH3OH resulting in the decreased local concentration of CH3OH on active Cu species.

The Role of Vegetation Response to Elevated CO2 in Modifying Land-Atmosphere Feedback Across the Central United States Agro-Ecosystem

NASA Astrophysics Data System (ADS)

Drewry, D.; Kumar, P.; Sivapalan, M.; Long, S.; Liang, X.

2009-05-01

Recent local-scale observational studies have demonstrated significant modifications to the partitioning of incident energy by two key mid-west agricultural species, soy and corn, as ambient atmospheric CO2 concentrations are experimentally augmented to projected future levels. The uptake of CO2 by soy, which utilizes the C3 photosynthetic pathway, has likewise been observed to significantly increase under elevated growth CO2 concentrations. Changes to the sensible and latent heat exchanges between the land surface and the atmospheric boundary layer (ABL) across large portions of the mid-western US has the potential to affect ABL growth and composition, and consequently feed-back to the near-surface environment (air temperature and vapor content) experienced by the vegetation. Here we present a simulation analysis that examines the changes in land-atmosphere feedbacks associated with projected increases in ambient CO2 concentrations over extended soy/corn agricultural areas characteristic of the US mid-west. The model canopies are partitioned into several layers, allowing for resolution of the shortwave and longwave radiation regimes that drive photosynthesis, stomatal conductance and leaf energy balance in each layer, along with the canopy microclimate. The canopy component of the model is coupled to a multi-layer soil-root model that computes soil moisture and heat transport and root water uptake. Model skill in capturing the sub-diurnal variability in canopy-atmosphere exchange is evaluated through multi-year records of canopy-top eddy covariance CO2, water vapor and heat fluxes collected at the Bondville (Illinois) FluxNet site. An evaluation of the ability of the model to simulate observed changes in energy balance components (canopy temperature, net radiation and soil heat flux) under elevated CO2 concentrations projected for 2050 (550 ppm) is made using observations collected at the SoyFACE Free Air Carbon Enrichment (FACE) experimental facilities located in central Illinois, by incorporating observed acclimations in leaf biochemsitry and canopy structure. The simulation control volume is then extended by coupling the canopy models to a simple model of daytime mixed-layer (ML) growth and composition, ie. air temperature and vapor content. Through this coupled canopy-ABL model we quantify the impact of elevated CO2 and vegetation acclimation on ML growth, temperature and vapor content and the consequent feedbacks to the land surface by way of the near-surface environment experienced by the vegetation. Particular focus is placed on the role of short-term drought, and possible changes in land cover composition between soy, a C3 crop, and corn, a more water-use efficient C4 crop, on modulating the strength of these CO2-induced feedbacks.

Development of a Trajectory Model for the Analysis of Stratospheric Water Vapor

NASA Astrophysics Data System (ADS)

Koby, Timothy Robert

To study stratospheric water vapor, a new trajectory model was created. The model is built from first principles specific to stratospheric motion and can run on any gridded dataset, making it more versatile than current solutions. The design of a new model was motivated by measurements of elevated stratospheric water vapor, which in situ isotopic measurements have determined to be tropospheric in origin. A moist stratosphere has substantial feedbacks in the climate system including radiative, chemical, and biological effects. Additionally, elevated stratospheric water vapor is theorized as an important coupling in the historical transition to the Eocene, 56 million years ago, as well as emergence from the Eocene 40 million years ago. This transition mirrors modern climate change, both in surface temperature and carbon dioxide increase. However, the historical transition became much more extreme and settled to a state of warm temperatures from the equator to the poles with little variation in between. The lack of latitudinal gradient in temperature is associated with a moist stratosphere, which provides additional motivation for thoroughly understanding the effects of adding water vapor to the stratosphere in a climatological context. The time evolution of water vapor enhancements from convective injection is analyzed by initializing trajectories over satellite-measured water vapor enhancements. The model runs show water vapor concentrations that remain elevated over the background concentrations for several days and often over a week, which is of the timescale that warrants concern over increased halogen catalyzed ozone loss and the subsequent risk to public health. By analyzing stratospheric winds during the summer months over North America using normalized angular momentum, a pattern of frequent stratospheric anticyclonic activity over North America emerges as a unique feature of the region. This provides a mechanism for the modeled persistent elevated water vapor and validates observations. In a climate like today's with increasing surface radiative forcing, the magnitude and frequency of convective injection may increase, with dramatic consequences on the climate system and human health.

Size-Dependent Melting Behavior of Colloidal In, Sn, and Bi Nanocrystals

PubMed Central

Liu, Minglu; Wang, Robert Y.

2015-01-01

Colloidal nanocrystals are a technologically important class of nanostructures whose phase change properties have been largely unexplored. Here we report on the melting behavior of In, Sn, and Bi nanocrystals dispersed in a polymer matrix. This polymer matrix prevents the nanocrystals from coalescing with one another and enables previously unaccessed observations on the melting behavior of colloidal nanocrystals. We measure the melting temperature, melting enthalpy, and melting entropy of colloidal nanocrystals with diameters of approximately 10 to 20 nm. All of these properties decrease as nanocrystal size decreases, although the depression rate for melting temperature is comparatively slower than that of melting enthalpy and melting entropy. We also observe an elevated melting temperature during the initial melt-freeze cycle that we attribute to surface stabilization from the organic ligands on the nanocrystal surface. Broad endothermic melting valleys and very large supercoolings in our calorimetry data suggest that colloidal nanocrystals exhibit a significant amount of surface pre-melting and low heterogeneous nucleation probabilities during freezing. PMID:26573146

Theoretical study of cathode surfaces and high-temperature superconductors

NASA Technical Reports Server (NTRS)

Mueller, Wolfgang

1995-01-01

Calculations are presented for the work functions of BaO on W, Os, Pt, and alloys of Re-W, Os-W, and Ir-W that are in excellent agreement with experiment. The observed emission enhancement for alloy relative to tungsten dispenser cathodes is attributed to properties of the substrate crystal structure and explained by the smaller depolarization of the surface dipole on hexagonal as compared to cubic substrates. For Ba and BaO on W(100), the geometry of the adsorbates has been determined by a comparison of inverse photoemission spectra with calculated densities of unoccupied states based on the fully relativistic embedded cluster approach. Results are also discussed for models of scandate cathodes and the electronic structure of oxygen on W(100) at room and elevated temperatures. A detailed comparison is made for the surface electronic structure of the high-temperature superconductor YBa2Cu3O7 as obtained with non-, quasi-, and fully relativistic cluster calculations.

Energy flux parametrization as an opportunity to get Urban Heat Island insights: The case of Athens, Greece (Thermopolis 2009 Campaign).

PubMed

Loupa, G; Rapsomanikis, S; Trepekli, A; Kourtidis, K

2016-01-15

Energy flux parameterization was effected for the city of Athens, Greece, by utilizing two approaches, the Local-Scale Urban Meteorological Parameterization Scheme (LUMPS) and the Bulk Approach (BA). In situ acquired data are used to validate the algorithms of these schemes and derive coefficients applicable to the study area. Model results from these corrected algorithms are compared with literature results for coefficients applicable to other cities and their varying construction materials. Asphalt and concrete surfaces, canyons and anthropogenic heat releases were found to be the key characteristics of the city center that sustain the elevated surface and air temperatures, under hot, sunny and dry weather, during the Mediterranean summer. A relationship between storage heat flux plus anthropogenic energy flux and temperatures (surface and lower atmosphere) is presented, that results in understanding of the interplay between temperatures, anthropogenic energy releases and the city characteristics under the Urban Heat Island conditions.

Ignition and combustion of bulk metals at normal, elevated and reduced gravity

NASA Technical Reports Server (NTRS)

Branch, Melvyn C.; Daily, John W.; Abbud-Madrid, Angel

1995-01-01

Knowledge of the oxidation, ignition, and combustion of bulk metals is important for fire safety in the production, management, and utilization of liquid and gaseous oxygen for ground based and space applications. This proposal outlines studies in continuation of research initiated earlier under NASA support to investigate the ignition and combustion characteristics of bulk metals under varying gravity conditions. Metal ignition and combustion have not been studied previously under these conditions and the results are important not only for improved fire safety but also to increase knowledge of basic ignition and combustion mechanisms. The studies completed to date have led to the development of a clean and reproducible ignition source and diagnostic techniques for combustion measurements and have provided normal, elevated, and reduced gravity combustion data on a variety of different pure metals. The research conducted under this grant will use the apparatus and techniques developed earlier to continue the elevated and low gravity experiments, and to develop the overall modeling of the ignition and combustion process. Metal specimens are to be ignited using a xenon short-arc lamp and measurements are to be made of the ignition energy, surface temperature history, burning rates, spectroscopy of surface and gas products, and surface morphology and chemistry. Elevated gravity will be provided by the University of Colorado Geotechnical Centrifuge and microgravity will be obtained in NASA's DC-9 Reduced Gravity aircraft.

Rapid regional surface uplift of the northern Altiplano plateau revealed by multiproxy paleoclimate reconstruction

NASA Astrophysics Data System (ADS)

Kar, Nandini; Garzione, Carmala N.; Jaramillo, Carlos; Shanahan, Timothy; Carlotto, Victor; Pullen, Alex; Moreno, Federico; Anderson, Veronica; Moreno, Enrique; Eiler, John

2016-08-01

The central Altiplano is inferred to have experienced ∼ 2.5 ± 1km surface uplift between ∼10 and 6 Ma, while the southern Altiplano experienced a similar magnitude of surface uplift that began earlier, between ∼16 and 9 Ma. To properly constrain the along strike timing of the Altiplano plateau surface uplift, it is necessary to know how and when the northernmost part of the Altiplano plateau evolved. We reconstruct the paleoclimate and infer the corresponding paleoelevation from the Miocene-Pliocene deposits of the Descanso-Yauri basin (14-15°S) in the northernmost part of the Altiplano plateau using 4 different proxies, including carbonate clumped isotope composition (i.e., Δ47 values), carbonate δ18Oc, leaf wax δDwax and pollen assemblages from paleosol, lacustrine and palustrine carbonates and organic-rich sediments. The isotopic signatures reflect past climate conditions of mean annual air temperature (Δ47) and meteoric water isotope values (δ18Oc, δDwax). Our results show that the northernmost plateau remained at low elevation (0.9 ± 0.8 to 2.1 ± 0.9km) until late Miocene time (∼9 Ma) characterized by ∼15 °C warmer than modern temperature (mean annual air temperature of 23 ± 4 °C, 2σ), low elevation vegetation and precipitation signature with reconstructed □ δ18Omw (VSMOW) of - 8.3 ± 2.0 ‰ (2 σ) from carbonate (δ18Oc) and - 8.6 ± 1.8 ‰ (2 σ) from leaf wax (δDwax). Modern elevations of 4 km were not reached until 5.4 ± 1.0Ma, as indicated by a negative shift in δDwax (VSMOW) from - 143.4 ± 12.8 ‰ (2 σ) to - 209.2 ± 21.1 ‰ (2 σ) between 9.1 ± 0.7 and 5.4 ± 1.0Ma. The timing of surface uplift of the northernmost Altiplano is consistent with the evidence for late Miocene surface uplift of the central Altiplano (16-19°S) between 10 and 6 Ma, and indicates that regional scale uplift in the northern-central plateau significantly postdates the onset of surface uplift in the southern Altiplano (19-22°S) between ∼16 and 9 Ma. These results are consistent with piecemeal removal of the lower dense lithosphere, combined with possible lower/middle crustal flow from south to north in the plateau acting as the main mechanisms for the formation of the Altiplano plateau.

A spectroscopic experimental and computer-assisted empirical model for the production and energetics of excited oxygen molecules formed by atom recombination on shuttle tile surfaces

NASA Technical Reports Server (NTRS)

Owan, D. A.

1981-01-01

A visible emission spectroscopic method was developed. The amounts of excited singlet and triplet oxygen molecules produced by recombination on the Space Shuttle Orbiter thermal protective tiles at elevated temperatures are determined. Rate constants and energetics of the extremely exothermic reaction are evaluated in terms of a chemical and mathematical model. Implications for potential contribution to Shuttle surface reentry heating fluxes are outlined.

Process of forming catalytic surfaces for wet oxidation reactions

NASA Technical Reports Server (NTRS)

Jagow, R. B. (Inventor)

1977-01-01

A wet oxidation process was developed for oxidizing waste materials, comprising dissolved ruthenium salt in a reactant feed stream containing the waste materials. The feed stream is introduced into a reactor, and the reactor contents are then raised to an elevated temperature to effect deposition of a catalytic surface of ruthenium black on the interior walls of the reactor. The feed stream is then maintained in the reactor for a period of time sufficient to effect at least partial oxidation of the waste materials.

Dynamic measurements of the spreading of liquid metals in controlled atmospheres with in situ surface preparation and analysis

NASA Astrophysics Data System (ADS)

Peebles, D. E.; Peebles, H. C.; Ohlhausen, J. A.; Hurst, M. J.

1996-02-01

A specially designed ultrahigh vacuum in situ surface analysis and wetting system has been constructed to study the spreading of liquid metal solders on carefully prepared and well-characterized solid substrates. The system consists of a standard ultrahigh vacuum surface analysis chamber linked to a reaction chamber for wetting or other experiments at pressures up to atmospheric. A sophisticated video system allows real-time monitoring of the spreading of the liquid metal through both side and top views. An infrared imaging system allows accurate remote temperature measurements. Sample surfaces are prepared and spreading experiments performed without intermediate exposure of the surfaces to the contaminating atmospheres. Solder spreading is performed under 50 Torr of highly purified helium gas to allow for adequate thermal coupling between the solder and the substrate. Initial studies have been completed for the spreading of pure tin solder on copper substrates in the absence of any fluxing agent. Three types of copper substrate surfaces were investigated in these experiments: the sputter-cleaned, air-exposed, and the as-received surface. Surface chemical analysis by x-ray photoelectron spectroscopy showed the air-exposed surface to consist of about 3 nm of Cu2O, while the as-received surface consisted of about 8 nm of Cu2O. The sputter-cleaned surface contained less than one monolayer (0.3 nm) of Cu2O. Spreading experiments utilizing a linear temperature ramp show that pure tin solder spreads readily on oxidized copper surfaces at elevated temperatures. The initiation temperature for rapid tin spreading on the as-received copper surface was 325 °C. Decreasing the thickness of the oxide on the surface lowered the observed temperature for the initiation of spreading and increased the rate of spreading. On the sputter-cleaned copper surface, rapid solder spreading was observed immediately upon melting of the solder.

Seasonal variations of the backscattering coefficient measured by radar altimeters over the Antarctic Ice Sheet

NASA Astrophysics Data System (ADS)

Ibrahime Adodo, Fifi; Remy, Frédérique; Picard, Ghislain

2018-05-01

Spaceborne radar altimeters are a valuable tool for observing the Antarctic Ice Sheet. The radar wave interaction with the snow provides information on both the surface and the subsurface of the snowpack due to its dependence on the snow properties. However, the penetration of the radar wave within the snowpack also induces a negative bias on the estimated surface elevation. Empirical corrections of this space- and time-varying bias are usually based on the backscattering coefficient variability. We investigate the spatial and seasonal variations of the backscattering coefficient at the S (3.2 GHz ˜ 9.4 cm), Ku (13.6 GHz ˜ 2.3 cm) and Ka (37 GHz ˜ 0.8 cm) bands. We identified that the backscattering coefficient at Ku band reaches a maximum in winter in part of the continent (Region 1) and in the summer in the remaining (Region 2), while the evolution at other frequencies is relatively uniform over the whole continent. To explain this contrasting behavior between frequencies and between regions, we studied the sensitivity of the backscattering coefficient at three frequencies to several parameters (surface snow density, snow temperature and snow grain size) using an electromagnetic model. The results show that the seasonal cycle of the backscattering coefficient at Ka frequency is dominated by the volume echo and is mainly driven by snow temperature evolution everywhere. In contrast, at S band, the cycle is dominated by the surface echo. At Ku band, the seasonal cycle is dominated by the volume echo in Region 1 and by the surface echo in Region 2. This investigation provides new information on the seasonal dynamics of the Antarctic Ice Sheet surface and provides new clues to build more accurate corrections of the radar altimeter surface elevation signal in the future.

Microrefuges and the occurrence of thermal specialists: implications for wildlife persistence amidst changing temperatures

USGS Publications Warehouse

Hall, L. Embere; Chalfoun, Anna D.; Beever, Erik; Loosen, Anne E.

2016-01-01

BackgroundContemporary climate change is affecting nearly all biomes, causing shifts in animal distributions, phenology, and persistence. Favorable microclimates may buffer organisms against rapid changes in climate, thereby allowing time for populations to adapt. The degree to which microclimates facilitate the local persistence of climate-sensitive species, however, is largely an open question. We addressed the importance of microrefuges in mammalian thermal specialists, using the American pika (Ochotona princeps) as a model organism. Pikas are sensitive to ambient temperatures, and are active year-round in the alpine where conditions are highly variable. We tested four hypotheses about the relationship between microrefuges and pika occurrence: 1) Local-habitat Hypothesis (local-habitat conditions are paramount, regardless of microrefuge); 2) Surface-temperature Hypothesis (surrounding temperatures, unmoderated by microrefuge, best predict occurrence); 3) Interstitial-temperature Hypothesis (temperatures within microrefuges best predict occurrence), and 4) Microrefuge Hypothesis (the degree to which microrefuges moderate the surrounding temperature facilitates occurrence, regardless of other habitat characteristics). We examined pika occurrence at 146 sites across an elevational gradient. We quantified pika presence, physiographic habitat characteristics and forage availability at each site, and deployed paired temperature loggers at a subset of sites to measure surface and subterranean temperatures.ResultsWe found strong support for the Microrefuge Hypothesis. Pikas were more likely to occur at sites where the subsurface environment substantially moderated surface temperatures, especially during the warm season. Microrefugium was the strongest predictor of pika occurrence, independent of other critical habitat characteristics, such as forage availability.ConclusionsBy modulating surface temperatures, microrefuges may strongly influence where temperature-limited animals persist in rapidly warming environments. As climate change continues to manifest, efforts to understand the changing dynamics of animal-habitat relationships will be enhanced by considering the quality of microrefuges.

Laser-assisted micro sheet forming

NASA Astrophysics Data System (ADS)

Holtkamp, Jens; Gillner, Arnold

2008-01-01

The fast growing market for micro technical products requires parts with increasing complexity. While sheet metal forming enables low cost mass production with short cycle times, it is limited by the maximum degree of deformation and the quality of the cut edge. The technology of warm forming partially eliminates these deficiencies. This operation takes place at elevated temperatures before structural transformation is initiated. It combines characteristic advantages of traditional cold and hot forming processes. Lasers as heat sources provide a high, selective and controllable energy input. The general difficulty of a uniform temperature distribution during the heating process can be reached by using an Axicon which generates an annulus on the sheet metal surface. The temperature of the workpiece, measured by a pyrometer, is tuned by a PI-Controller. A tool incorporating a multistage operation die is used for the manufacturing of up to three parts at the same time. The tool is integrated into a hydraulical press. A gearwheel made of the magnesium alloy AZ31 is chosen as metal demonstrator. The quality of these punched parts could be significantly improved at elevated temperatures

The Use of ATLAS Data to Quantify Surface Radiative Budget Alteration Through Urbanization for San Juan, Puerto Rico.

NASA Technical Reports Server (NTRS)

Luvall, Jeffrey C.; Rickman, Douglas L.; Gonzalez, Jorge; Schiller, Steve

2006-01-01

The additional heating of the air over the city is the result of the replacement of naturally vegetated surfaces with those composed of asphalt, concrete, rooftops and other manmade materials. The temperatures of these artificial surfaces can be 20 to 40 0 C higher than vegetated surfaces. Materials such as asphalt store much of the sun s energy and remains hot long after sunset. This produces a dome of elevated air temperatures 5 to 8 C greater over the city, compared to the air temperatures over adjacent rural areas. This effect is called the "urban heat island". Urban landscapes are a complex mixture of vegetated and nonvegetated surfaces. It is difficult to take enough temperature measurements over a large city area to characterize the complexity of urban radiant surface temperature variability. However, the use of remotely sensed thermal data from airborne scanners are ideal for the task. The NASA Airborne Thermal and Land Applications Sensor (ATLAS) operates in the visual and IR bands was used in February 2004 to collect data from San Juan, Puerto Rico with the main objective of investigating the Urban Heat Island (UHI) in tropical cities. In this presentation we will examine the techniques of analyzing remotely sensed data for measuring the effect of various urban surfaces on their contribution to the urban heat island effect. Results from data collected from other US cities of Sacramento, Salt Lake City and Baton Rouge will be used to compare the "urban fabric" among the cities.

Cyclic tests of P-bulb end-seal designs for a shuttle-type wing-elevon cove membrane seal

NASA Technical Reports Server (NTRS)

Hunt, L. R.

1979-01-01

Four P-bulb end seal designs were tested at room temperature in a cyclic seal test apparatus. Test results show that all the P-bulb end seals have the durability required for a 100 mission life (neglecting possible elevated-temperature effects) and three of the four P-bulbs provide an adequate seal against a 7.0-kPa air pressure differential. Antifriction material attached to the P-bulb rub surface reduced friction slightly but could degrade the sealing effectiveness. A flat rub surface molded into the P-bulb discouraged wrinkling and rolling and thereby reduced leakage. However, the P-bulbs lacked resilience, as indicated by increased leakage when P-bulb compression was reduced. The best P-bulb design tested included an antifriction interface bonded to a flat surface molded into the P-bulb.

Response of surface CH4 and CO2 fluxes to whole ecosystem warming and elevated CO2 in a boreal black spruce peatland, northern Minnesota

NASA Astrophysics Data System (ADS)

Hsieh, I. F.; Gill, A. L.; Finzi, A.

2017-12-01

Potential increase in peatland C losses by environmental change has been presented by impacting the balance of CO2 and CH4 sequestration and release. While temperature warming may accelerate the temperature-sensitive processes and release CO2 and CH4 from peat C stores, factors associated with warming and that associated with elevated CO2 concentration may alter the intrinsic characteristics of CO2 and CH4 emission from peatland. By leveraging Spruce and Peatland Responses Under Changing Environments (SPRUCE) experiment, we measured peat surface CO2 and CH4 fluxes and their i13C signatures across a gradient of warming temperatures in a boreal black spruce peat bog in 2015 and 2016 growing seasons. Elevated CO2 (eCO2) treatment was added to the warming experiment in June, 2016. Our results show both CH4 and CO2 flux increased with warming temperature in the two-year measurement period. Total emission for both gases were higher in 2016 with whole ecosystem warming than that in 2015 with deep peat heat warming. The 2016 increase in CO2 emission was significantly larger in the hummock microtopographic position compared to hollows. The opposite was true for CH4 fluxes, where the increase was strongest in the hollows. In fact, CH4 flux from hummocks declined in 2016 compared to 2015, suggesting lower overall rates of CH4 production and/or greater rates of methanotrophy. The increase (less depleted) in i13C -CH4 signatures suggest acetoclastic methanogensis increased its contribution to total CH4 production across the growing season and in response to experimental warming, while hydrogenotrophic methanogenesis dominated total CH4 production. On the contrary, results of i13C-CO2 show no significant change in the contribution of different sources to total CO2 emission through time or across warming temperature. On the other hand, i13C-CO2 signatures under CO2 fumigation in 2016 was significantly depleted since the eCO2 initiation, indicating a rapid increase in plant productivity and the subsequent belowground transfer of photosynthate. Our results emphasize the susceptibleness of northern peat bog to changes in the environment by illustrating measureable influences of whole ecosystem warming and elevated CO2 on greenhouse gases emission.

Neogene paleoelevation of intermontane basins in a narrow, compressional mountain range, southern Central Andes of Argentina

NASA Astrophysics Data System (ADS)

Hoke, Gregory D.; Giambiagi, Laura B.; Garzione, Carmala N.; Mahoney, J. Brian; Strecker, Manfred R.

2014-11-01

The topographic growth of mountain ranges at convergent margins results from the complex interaction between the motion of lithospheric plates, crustal shortening, rock uplift and exhumation. Constraints on the timing and magnitude of elevation change gleaned from isotopic archives preserved in sedimentary sequences provide insight into how these processes interact over different timescales to create topography and potentially decipher the impact of topography on atmospheric circulation and superposed exhumation. This study uses stable isotope data from pedogenic carbonates collected from seven different stratigraphic sections spanning different tectonic and topographic positions in the range today, to examine the middle to late Miocene history of elevation change in the central Andes thrust belt, which is located immediately to the south of the Altiplano-Puna Plateau, the world's second largest orogenic plateau. Paleoelevations are calculated using previously published local isotope-elevation gradients observed in modern rainfall and carbonate-formation temperatures determined from clumped isotope studies in modern soils. Calculated Neogene basin paleoelevations are between 1 km and 1.9 km for basins that today are located between 1500 and 3400 m elevation. Considering the modern elevation and δ18O values of precipitation at the sampling sites, three of the intermontane basins experienced surface uplift between the end of deposition during the late Miocene and present. The timing of elevation change cannot be linked to any documented episodes of large-magnitude crustal shortening. Paradoxically, the maximum inferred surface uplift in the core of the range is greatest where the crust is thinnest. The spatial pattern of surface uplift is best explained by eastward migration of a crustal root via ductile deformation in the lower crust and is not related to flat-slab subduction.

Ectotherm thermal stress and specialization across altitude and latitude.

PubMed

Buckley, Lauren B; Miller, Ethan F; Kingsolver, Joel G

2013-10-01

Gradients of air temperature, radiation, and other climatic factors change systematically but differently with altitude and latitude. We explore how these factors combine to produce altitudinal and latitudinal patterns of body temperature, thermal stress, and seasonal overlap that differ markedly from patterns based solely on air temperature. We use biophysical models to estimate body temperature as a function of an organism's phenotype and environmental conditions (air and surface temperatures and radiation). Using grasshoppers as a case study, we compare mean body temperatures and the incidence of thermal extremes along altitudinal gradients both under past and current climates. Organisms at high elevation can experience frequent thermal stress despite generally cooler air temperatures due to high levels of solar radiation. Incidences of thermal stress have increased more rapidly than have increases in mean conditions due to recent climate change. Increases in air temperature have coincided with shifts in cloudiness and solar radiation, which can exacerbate shifts in body temperature. We compare altitudinal thermal gradients and their seasonality between tropical and temperate mountains to ask whether mountain passes pose a greater physiological barrier in the tropics (Janzen's hypothesis). We find that considering body temperature rather than air temperature generally increases the amount of overlap in thermal conditions along gradients in elevation and thus decreases the physiological barrier posed by tropical mountains. Our analysis highlights the limitations of predicting thermal stress based solely on air temperatures, and the importance of considering how phenotypes influence body temperatures.

Development of a CE-QUAL-W2 temperature model for Crystal Springs Lake, Portland, Oregon

USGS Publications Warehouse

Buccola, Norman L.; Stonewall, Adam J.

2016-05-19

Model simulations (scenarios) were run with lower water surface elevations in Crystal Springs Lake and increased shading to the lake to assess the relative effect the lake and pond characteristics have on water temperature. The Golf Pond was unaltered in all scenarios. The models estimated that lower lake elevations would result in cooler water downstream of the Golf Pond and shorter residence times in the lake. Increased shading to the lake would also provide substantial cooling. Most management scenarios resulted in a decrease in 7-day average of daily maximum values by about 2.0– 4.7 °F (1.1 –2.6 °C) for outflow from Crystal Springs Lake during the period of interest. Outflows from the Golf Pond showed a net temperature reduction of 0.5–2.7 °F (0.3–1.5 °C) compared to measured values in 2014 because of solar heating and downstream warming in the Golf Pond resulting from mixing with inflow from Reed Lake.

Brassinosteroid signaling-dependent root responses to prolonged elevated ambient temperature.

PubMed

Martins, Sara; Montiel-Jorda, Alvaro; Cayrel, Anne; Huguet, Stéphanie; Roux, Christine Paysant-Le; Ljung, Karin; Vert, Grégory

2017-08-21

Due to their sessile nature, plants have to cope with and adjust to their fluctuating environment. Temperature elevation stimulates the growth of Arabidopsis aerial parts. This process is mediated by increased biosynthesis of the growth-promoting hormone auxin. How plant roots respond to elevated ambient temperature is however still elusive. Here we present strong evidence that temperature elevation impinges on brassinosteroid hormone signaling to alter root growth. We show that elevated temperature leads to increased root elongation, independently of auxin or factors known to drive temperature-mediated shoot growth. We further demonstrate that brassinosteroid signaling regulates root responses to elevated ambient temperature. Increased growth temperature specifically impacts on the level of the brassinosteroid receptor BRI1 to downregulate brassinosteroid signaling and mediate root elongation. Our results establish that BRI1 integrates temperature and brassinosteroid signaling to regulate root growth upon long-term changes in environmental conditions associated with global warming.Moderate heat stimulates the growth of Arabidopsis shoots in an auxin-dependent manner. Here, Martins et al. show that elevated ambient temperature modifies root growth by reducing the BRI1 brassinosteroid-receptor protein level and downregulating brassinosteroid signaling.

Degradation analysis of a Ni-based layered positive-electrode active material cycled at elevated temperatures studied by scanning transmission electron microscopy and electron energy-loss spectroscopy

NASA Astrophysics Data System (ADS)

Kojima, Y.; Muto, S.; Tatsumi, K.; Kondo, H.; Oka, H.; Horibuchi, K.; Ukyo, Y.

We investigate the local structural changes in a positive electrode of a lithium ion secondary battery (LiNi 0.8Co 0.15Al 0.05O 2 (NCA) as the active material) associated with charge-discharge cycling at elevated temperatures by scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS). STEM-EELS spectral imaging reveals the evolution of a NiO-like phase localized near the surface and grain boundary regions after many cycles. The amounts of capacity fading and resistance increase are discussed based on the results of the semiquantitative estimation of NiO-like and other product phases. We also identify the chemical state of lithium in the NiO-like phase substituting for Ni.

Magnetically aligned nanodomains: application in high-performance ion conductive membranes.

PubMed

Hasani-Sadrabadi, Mohammad Mahdi; Majedi, Fatemeh Sadat; Coullerez, Géraldine; Dashtimoghadam, Erfan; VanDersarl, Jules John; Bertsch, Arnaud; Moaddel, Homayoun; Jacob, Karl I; Renaud, Philippe

2014-05-28

Polyelectrolyte-coated magnetic nanoparticles were prepared by decorating the surface of superparamagnetic iron oxide nanoparticles (SPIONs) with crosslinked chitosan oligopolysaccharide (CS). These positively charged particles (CS-SPIONs) were then added to a negatively charged polymer (Nafion), and cast into membranes under an applied magnetic field. TEM and SAXS measurements confirmed this process created aligned, cylindrical nanodomains in the membranes. This was also indirectly confirmed by proton conductivity values. The strong electrostatic interaction between chitosan and Nafion prevented oxygen permeability and water evaporation at elevated temperatures through the proton conductive channels. The resultant proton exchange membranes showed lower conduction dependency to relative humidity, which is highly desirable for hydrogen fuel cells. The fuel cell performance tests were performed on the designed polyelectrolyte membrane by hydrogen-oxygen single cells at elevated temperature (120 °C) and low relative humidity.

Climatological and statistical characteristics of the Haines Index for North America

Treesearch

Julie A. Winkler; Brian E. Potter; Dwight F. Wilhelm; Ryan P. Shadbolt; Krerk Piromsopa; Xindi Bian

2007-01-01

The Haines Index is an operational tool for evaluating the potential contribution of dry, unstable air to the development of large or erratic plume-dominated wildfires. The index has three variants related to surface elevation, and is calculated from temperature and humidity measurements at atmospheric pressure levels. To effectively use the Haines Index, fire...

Effects of elevated CO2 and temperature on phytoplankton community biomass, species composition and photosynthesis during an experimentally induced autumn bloom in the western English Channel

NASA Astrophysics Data System (ADS)

Keys, Matthew; Tilstone, Gavin; Findlay, Helen S.; Widdicombe, Claire E.; Lawson, Tracy

2018-05-01

The combined effects of elevated pCO2 and temperature were investigated during an experimentally induced autumn phytoplankton bloom in vitro sampled from the western English Channel (WEC). A full factorial 36-day microcosm experiment was conducted under year 2100 predicted temperature (+4.5 °C) and pCO2 levels (800 µatm). Over the experimental period total phytoplankton biomass was significantly influenced by elevated pCO2. At the end of the experiment, biomass increased 6.5-fold under elevated pCO2 and 4.6-fold under elevated temperature relative to the ambient control. By contrast, the combined influence of elevated pCO2 and temperature had little effect on biomass relative to the control. Throughout the experiment in all treatments and in the control, the phytoplankton community structure shifted from dinoflagellates to nanophytoplankton . At the end of the experiment, under elevated pCO2 nanophytoplankton contributed 90 % of community biomass and was dominated by Phaeocystis spp. Under elevated temperature, nanophytoplankton comprised 85 % of the community biomass and was dominated by smaller nanoflagellates. In the control, larger nanoflagellates dominated whilst the smallest nanophytoplankton contribution was observed under combined elevated pCO2 and temperature ( ˜ 40 %). Under elevated pCO2, temperature and in the control there was a significant decrease in dinoflagellate biomass. Under the combined effects of elevated pCO2 and temperature, dinoflagellate biomass increased and was dominated by the harmful algal bloom (HAB) species, Prorocentrum cordatum. At the end of the experiment, chlorophyll a (Chl a) normalised maximum photosynthetic rates (PBm) increased > 6-fold under elevated pCO2 and > 3-fold under elevated temperature while no effect on PBm was observed when pCO2 and temperature were elevated simultaneously. The results suggest that future increases in temperature and pCO2 simultaneously do not appear to influence coastal phytoplankton productivity but significantly influence community composition during autumn in the WEC.

Development of advanced material composites for use as internal insulation for LH2 tanks (gas layer concept)

NASA Technical Reports Server (NTRS)

Gille, J. P.

1972-01-01

A program is described that was conducted to develop an internal insulation system for potential application to the liquid hydrogen tanks of a reusable booster, where the tanks would be subjected to repeated high temperatures. The design of the internal insulation is based on a unique gas layer concept, in which capillary or surface tension effects are used to maintain a stable gas layer, within a cellular core structure, between the tank wall and the contained liquid hydrogen. Specific objectives were to select materials for insulation systems that would be compatible with wall temperatures of 350 F and 650 F during reentry into the earth's atmosphere, and to fabricate and test insulation systems under conditions simulating the operating environment. A materials test program was conducted to evaluate the properties of candidate materials at elevated temperatures and at the temperature of liquid hydrogen, and to determine the compatibility of the materials with a hydrogen atmosphere at the appropriate elevated temperature. The materials that were finally selected included Kapton polyimide films, silicone adhesives, fiber glass batting, and in the case of the 350 F system, Teflon film.

Investigation of structural and magnetic properties of rapidly-solidified iron-silicon alloys at ambient and elevated temperatures

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

Jayaraman, T. V.; Meka, V. M.; Jiang, X.

In this work, we investigated the ambient temperature structural properties (~300 K) and the ambient and high temperature (up to 900 K) direct current (DC) magnetic properties of melt-spun Fe-x wt.% Si (x = 3, 5, & 8) alloys. The wheel surface speeds selected for the study were 30 m/s and 40 m/s. The thickness, width, lattice parameter, saturation magnetization (MS), and intrinsic coercivity (HCI) of the melt spun ribbons are presented and compared with data in the literature. The ribbons produced at the lower wheel surface speed (30 m/s) were continuous having relatively uniform edges compared to the ribbonsmore » produced at the higher wheel surface speed. The thickness and the width of the melt-spun ribbons ranged between ~15-60 μm and 500-800 μm, respectively. The x-ray diffraction spectra of the melt-spun ribbons indicated the presence of disordered α-phase, irrespective of the composition, and the wheel-surface speed. The lattice parameter decreased gradually as a function of increasing silicon content from ~0.2862 nm (Fe-3 wt.% Si) to ~0.2847 nm (Fe-8 wt.% Si). Wheel surface speed was not shown to have a significant effect on the magnetization, but primarily impacted the ribbon structure. A decreasing trend in the saturation magnetization was observed as a function of increased silicon content. The intrinsic coercivity of the melt-spun alloys ranged between ~50 to 200 A/m. Elevated temperature evaluation of the magnetization in the case of Fe-3 & 5 wt.% Si alloy ribbons was distinctly different from the Fe-8 wt.% Si alloy ribbons. The curves of the as-prepared Fe-3 wt.% Si and Fe-5 wt.% Si alloy ribbons were irreversible while that of Fe-8 wt.% Si was reversible. The MS for any of the combinations of wheel surface speed and composition decreased monotonically with the increase in temperature (from 300 – 900 K). The percentage decrease in MS from 300 K to 900 K for the Fe-3 wt.% Si and Fe-5 wt.% Si alloys was ~19-22 %, while the percentage decrease in the same temperature range for Fe-8 wt.% Si alloy was ~26-30 %. It appears that Fe-3 wt.% Si and Fe-5 wt.% Si alloys ribbons are primarily comprised of the α phase (disordered phase) with any minor constituents being beyond the detection limits of the studies performed, while the Fe-8 wt.% Si alloy ribbons are comprised of disordered and regions of short-range ordering.« less

Temperature changes across CO2-lased dentin during multiple exposures

NASA Astrophysics Data System (ADS)

Zakariasen, Kenneth L.; Barron, Joseph R.; Boran, Thomas L.

1990-06-01

The literature increasingly indicates that lasers will have a multitude of applications for dental hard tissue procedures, e.g. preventive therapy, caries removal, laser etching and endodontic therapy. However, it is critical that such laser therapies avoid the production of heat levels which will be damaging to the surrounding vital tissues, such as the dental pulp and periodontal tissues. Our preliminary research on temperature changes across C02 lased dentin indicated that for single preventive therapeutic exposures (1.2 W., 0. 1 sec., 1.0 mm focal spot) the mean temperature rise across 350 j.tm of dentin was 0.57 0C while across 1000 .tm of dentin the mean rise was only 0.18 °C. Further research utilizing multiple preventive therapeutic exposures (1.2 W., 0. 1 sec., 1.0 mm focal spot, 3 x 1.0 sec. intervals) showed mean temperature elevations of 1.56 0C across 350 m of dentin and 0.66 O across 1000 xm of dentin. While these temperature elevations, which would be associated with preventive therapy, are very low and would be biologically acceptable, it must be noted that exposures of higher intensities are required to fuse enamel and porcelain, or remove decay. This current research investigates temperature elevations which occuT during C02 lasing utilizing the following exposure parameters: 8.0 W., 1.0 mm focal spot, 0.1 sec. exposures, 2 or 4 exposures per site pulsed 1.0 sec. apart. Three dentin thicknesses were utilized, i.e. 1000 jim, 1500 p.tm and 2000 .tm. Four sections of each thickness were utilized with four exposure sites per specimen (2 with 2 exposures, 2 with 4 exposures). All dentin sections were prepared from non-carious third molars using a hard tissue microtome. A thermistor was placed on the dentin surface opposite each lased site and temperature changes were recorded for approximately 50 sec. following lasing. Mean temperature elevations ranged from a high of 3.07 C for the 1000 xm section utilizing four exposures to a low of 0.37 0C for the 2000 m section utilizing two exposures. Analysis of Variance (p < .0001) and Duncan's Multiple Range Test (p =.05) indicated significant differences existed among the mean temperature elevations observed. While significant differences in temperature elevation can be observed both by numbers of exposures and by dentin thickness, it would appear that, under the conditions of this study, the temperature changes across CO2 lased dentin are all relatively low. It should be reiterated that the lasing parameters used in this study are far in excess of those necessary for preventive applications and are, in fact, in the range of exposures which will fuse enamel and dental porcelain, or remove dental caries. The modest temperature elevations observed, combined with the relatively severe exposure parameters utilized on thin sections of dentin, demonstrate the effective protective barrier which dentin provides for the dental pulp relative to heat damage from C02 lasing.

Magnetite solubility and phase stability in alkaline media at elevated temperatures

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

Ziemniak, S.E.; Jones, M.E.; Combs, K.E.S.

Magnetite, Fe{sub 3}O{sub 4}, is the dominant oxide constituent of the indigenous corrosion layers that form on iron base alloys in high purity, high temperature water. The apparent simultaneous stability of two distinct oxidation states of iron in this metal oxide is responsible for its unique solubility behavior. The present work was undertaken to extend the experimental and theoretical bases for estimating solubilities of an iron corrosion product (Fe{sub 3}O{sub 4}/Fe(OH){sub 2}) over a broader temperature range and in the presence of complexing, pH-controlling reagents. These results indicate that a surface layer of ferrous hydroxide controls magnetite solubility behavior atmore » low temperatures in much the same manner as a surface layer of nickel(II) hydroxide was previously reported to control the low temperature solubility behavior of NiO. The importance of Fe(III) ion complexes implies not only that most previously-derived thermodynamic properties of the Fe(OH){sub 3}{sup {minus}} ion are incorrect, but that magnetite phase stability probably shifts to favor a sodium ferric hydroxyphosphate compound in alkaline sodium phosphate solutions at elevated temperatures. The test methodology involved pumping alkaline solutions of known composition through a bed of Fe{sub 3}O{sub 4} granules and analyzing the emerging solution for Fe. Two pH-controlling reagents were tested: sodium phosphate and ammonia. Equilibria for the following reactions were described in thermodynamic terms: (a) Fe(OH){sub 2}/Fe{sub 3}O{sub 4} dissolution and transformation, (b) Fe(II) and Fe(III) ion hydroxocomplex formation (hydrolysis), (c) Fe(II) ion amminocomplex formation, and (d) Fe(II) and Fe(III) ion phosphatocomplex formation. 36 refs.« less

Simulation of hydrodynamics, temperature, and dissolved oxygen in Table Rock Lake, Missouri, 1996-1997

USGS Publications Warehouse

Green, W. Reed; Galloway, Joel M.; Richards, Joseph M.; Wesolowski, Edwin A.

2003-01-01

Outflow from Table Rock Lake and other White River reservoirs support a cold-water trout fishery of substantial economic yield in south-central Missouri and north-central Arkansas. The Missouri Department of Conservation has requested an increase in existing minimum flows through the Table Rock Lake Dam from the U.S. Army Corps of Engineers to increase the quality of fishable waters downstream in Lake Taneycomo. Information is needed to assess the effect of increased minimum flows on temperature and dissolved- oxygen concentrations of reservoir water and the outflow. A two-dimensional, laterally averaged, hydrodynamic, temperature, and dissolved-oxygen model, CE-QUAL-W2, was developed and calibrated for Table Rock Lake, located in Missouri, north of the Arkansas-Missouri State line. The model simulates water-surface elevation, heat transport, and dissolved-oxygen dynamics. The model was developed to assess the effects of proposed increases in minimum flow from about 4.4 cubic meters per second (the existing minimum flow) to 11.3 cubic meters per second (the increased minimum flow). Simulations included assessing the effect of (1) increased minimum flows and (2) increased minimum flows with increased water-surface elevations in Table Rock Lake, on outflow temperatures and dissolved-oxygen concentrations. In both minimum flow scenarios, water temperature appeared to stay the same or increase slightly (less than 0.37 ?C) and dissolved oxygen appeared to decrease slightly (less than 0.78 mg/L) in the outflow during the thermal stratification season. However, differences between the minimum flow scenarios for water temperature and dissolved- oxygen concentration and the calibrated model were similar to the differences between measured and simulated water-column profile values.

Influence of elevated carbon dioxide and temperature on belowground carbon allocation and enzyme activities in tropical flooded soil planted with rice.

PubMed

Bhattacharyya, P; Roy, K S; Neogi, S; Manna, M C; Adhya, T K; Rao, K S; Nayak, A K

2013-10-01

Changes in the soil labile carbon fractions and soil biochemical properties to elevated carbon dioxide (CO2) and temperature reflect the changes in the functional capacity of soil ecosystems. The belowground root system and root-derived carbon products are the key factors for the rhizospheric carbon dynamics under elevated CO2 condition. However, the relationship between interactive effects of elevated CO2 and temperature on belowground soil carbon accrual is not very clear. To address this issue, a field experiment was laid out to study the changes of carbon allocation in tropical rice soil (Aeric Endoaquept) under elevated CO2 and elevated CO2 + elevated temperature conditions in open top chambers (OTCs). There were significant increase of root biomass by 39 and 44 % under elevated CO2 and elevated CO2 + temperature compared to ambient condition, respectively. A significant increase (55 %) of total organic carbon in the root exudates under elevated CO2 + temperature was noticed. Carbon dioxide enrichment associated with elevated temperature significantly increased soil labile carbon, microbial biomass carbon, and activities of carbon-transforming enzyme like β-glucosidase. Highly significant correlations were noticed among the different soil enzymes and soil labile carbon fractions.

Role of Absolute Humidity in the Inactivation of Influenza Viruses on Stainless Steel Surfaces at Elevated Temperatures ▿

PubMed Central

McDevitt, James; Rudnick, Stephen; First, Melvin; Spengler, John

2010-01-01

Influenza virus has been found to persist in the environment for hours to days, allowing for secondary transmission of influenza via inanimate objects known as fomites. We evaluated the efficacy of heat and moisture for the decontamination of surfaces for the purpose of preventing of the spread of influenza. Aqueous suspensions of influenza A virus were deposited onto stainless steel coupons, allowed to dry under ambient conditions, and exposed to temperatures of 55°C, 60°C, or 65°C and relative humidity (RH) of 25%, 50%, or 75% for up to 1 h. Quantitative virus assays were performed on the solution used to wash the viruses from these coupons, and results were compared with the solution used to wash coupons treated similarly but left under ambient conditions. Inactivation of influenza virus on surfaces increased with increasing temperature, RH, and exposure time. Reductions of greater than 5 logs of influenza virus on surfaces were achieved at temperatures of 60 and 65°C, exposure times of 30 and 60 min, and RH of 50 and 75%. Our data also suggest that absolute humidity is a better predictor of surface inactivation than RH and allows the prediction of survival using two parameters rather than three. Modest amounts of heat and adequate moisture can provide effective disinfection of surfaces while not harming surfaces, electrical systems, or mechanical components, leaving no harmful residues behind after treatment and requiring a relatively short amount of time. PMID:20435770

Diamond structure recovery during ion irradiation at elevated temperatures

NASA Astrophysics Data System (ADS)

Deslandes, Alec; Guenette, Mathew C.; Belay, Kidane; Elliman, Robert G.; Karatchevtseva, Inna; Thomsen, Lars; Riley, Daniel P.; Lumpkin, Gregory R.

2015-12-01

CVD diamond is irradiated by 5 MeV carbon ions, with each sample held at a different temperature (300-873 K) during irradiations. The defect structures resulting from the irradiations are evident as vacancy, interstitial and amorphous carbon signals in Raman spectra. The observed variation of the full width at half maximum (FWHM) and peak position of the diamond peak suggests that disorder in the diamond lattice is reduced for high temperature irradiations. The dumbbell interstitial signal is reduced for irradiations at 873 K, which suggests this defect is unstable at these temperatures and that interstitials have migrated to crystal surfaces. Near edge X-ray absorption fine structure (NEXAFS) spectroscopy results indicate that damage to the diamond structure at the surface has occurred for room temperature irradiations, however, this structure is at least partially recovered for irradiations performed at 473 K and above. The results suggest that, in a high temperature irradiation environment such as a nuclear fusion device, in situ annealing of radiation-created defects can maintain the diamond structure and prolong the lifetime of diamond components.

Surface Tension and Viscosity of SCN and SCN-acetone Alloys at Melting Points and Higher Temperatures Using Surface Light Scattering Spectrometer

NASA Technical Reports Server (NTRS)

Tin, Padetha; deGroh, Henry C., III.

2003-01-01

Succinonitrile has been and is being used extensively in NASA's Microgravity Materials Science and Fluid Physics programs and as well as in several ground-based and microgravity studies including the Isothermal Dendritic Growth Experiment (IDGE). Succinonitrile (SCN) is useful as a model for the study of metal solidification, although it is an organic material, it has a BCC crystal structure and solidifies dendriticly like a metal. It is also transparent and has a low melting point (58.08 C). Previous measurements of succinonitrile (SCN) and alloys of succinonitrile and acetone surface tensions are extremely limited. Using the Surface Light Scattering technique we have determined non invasively, the surface tension and viscosity of SCN and SCN-Acetone Alloys at different temperatures. This relatively new and unique technique has several advantages over the classical methods such as, it is non invasive, has good accuracy and measures the surface tension and viscosity simultaneously. The accuracy of interfacial energy values obtained from this technique is better than 2% and viscosity about 10 %. Succinonitrile and succinonitrile-acetone alloys are well-established model materials with several essential physical properties accurately known - except the liquid/vapor surface tension at different elevated temperatures. We will be presenting the experimentally determined liquid/vapor surface energy and liquid viscosity of succinonitrile and succinonitrile-acetone alloys in the temperature range from their melting point to around 100 C using this non-invasive technique. We will also discuss about the measurement technique and new developments of the Surface Light Scattering Spectrometer.

Fabrication of highly dense SiN4 ceramics without additives by high pressure sintering

NASA Technical Reports Server (NTRS)

Takatori, K.; Shimade, M.; Koizumi, M.

1984-01-01

Silicon nitride (Si3N4) is one of candidate materials for the engineering ceramics which is used at high temperatures. The mechanical strengths of hot pressed or sintered Si2N4 ceramics containing some amount of additives, however, are deteriorated at elevated temperatures. To improve the high temperature strength of Si3N4 ceramics, an attempt to consolidate Si3N4 without additives was made by high pressure sintering technique. Scanning electron micrographs of fracture surfaces of the sintered bodies showed the bodies had finely grained and fully self-bonded sintered bodies were 310N sq m at room temperature and 174N/sq m at 1200 C.

Microplastics have a more profound impact than elevated temperatures on the predatory performance, digestion and energy metabolism of an Amazonian cichlid.

PubMed

Wen, Bin; Zhang, Nan; Jin, Shi-Rong; Chen, Zai-Zhong; Gao, Jian-Zhong; Liu, Ying; Liu, Han-Peng; Xu, Zhe

2018-02-01

Knowledge on the impacts of microplastics (MPs) pollution on freshwater environments and biota remains limited. Meanwhile, freshwater ecosystems have been threatened by elevated temperatures caused by climate change. To date, no information exists on how MPs-especially under elevated temperature conditions-affect predatory performance, digestive processes and metabolic pathways in freshwater organisms. Here, we examined MPs, elevated temperature and their combined effects on juveniles (0+ group) of an Amazonian cichlid, the discus fish (Symphysodon aequifasciatus). For 30 days, fish were exposed to ambient or elevated temperatures (i.e., 28 or 31 °C) in the absence or presence of MPs (i.e., 0 or 200 μg/L). The following metrics were quantified: MPs accumulation; predatory performance; and biomarkers involved in neurotransmission, digestion and energy production. The results showed that survival rate and body length were not affected by MPs, elevated temperatures or their combination. Elevated temperatures resulted in an increase in MP concentrations in fish bodies. Exposure to MPs decreased the post-exposure predatory performance (PEPP) at ambient temperatures but not at elevated temperatures. Elevated temperatures, however, had no effect on the PEPP but antagonistically interacted with MPs, leading to similar predatory performances under present and future conditions. Acetylcholinesterase (AChE) activity was only affected by MPs and decreased in the presence of MPs, indicating adverse effects in nervous and neuromuscular function and, thus, potentially in predatory performance. Trypsin activity was only influenced by MPs and decreased during exposure to MPs. Elevated temperatures or MPs alone increased the amylase activity but interacted antagonistically. Lipase activity was not influenced by either of the two stressors. In contrast, alkaline phosphatase (ALP) activity was affected by MPs or elevated temperatures alone and decreased with both stressors. Such results indicate deficits in the digestive capabilities of early-stage S. aequifasciatus under elevated temperature conditions and especially during exposure to MPs. Electron transport system (ETS) activity was not influenced by either of the two stressors. Both elevated temperatures and MPs alone increased LDH activity; however, the interaction between the two stressors cancelled activity but was still higher than activity in present conditions. Citrate synthase (CS) activity decreased with elevated temperature but increased during exposure to MPs. Cytochrome c oxidase (COX) activity was only influenced by MPs and increased in the presence of MPs. Thus, S. aequifasciatus juveniles exposed to elevated temperatures and MPs not only relied on anaerobic glycolysis for energy production but also depended on aerobic metabolism in the presence of MPs. Overall, these findings suggested that MPs showed a greater impact than elevated temperatures on the predatory performance, digestion and energy production of S. aequifasciatus. Nevertheless, juvenile survival and growth were minimally impacted, and thus, S. aequifasciatus could cope with near-future temperature increases and MP exposure. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of thermal annealing on the redistribution of alkali metals in Cu(In,Ga)Se 2 solar cells on glass substrate

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

Kamikawa, Yukiko; Nishinaga, Jiro; Ishizuka, Shogo

The precise control of alkali-metal concentrations in Cu(In,Ga)Se 2 (CIGS) solar cells via post deposition treatment (PDT) has recently attracted attention. When PDT is performed at an elevated temperature, an accompanying annealing effect is expected. Here, we investigate how thermal annealing affects the redistribution of alkali metals in CIGS solar cells on glass substrates and the properties of the solar cells. In addition, we investigate the origin of non-homogeneous alkali-metal depth profiles that are typical of CIGS grown using a three-stage process. In particular, we use secondary-ion mass spectrometry measurements of the ion concentration as a function of distance frommore » the CIGS surface to investigate the impact of thermal annealing on the distribution of alkali metals (Na, Ka, and Rb) and constituent elements (Ga and In) in the CIGS absorbers. We find that the depth profiles of the alkali metals strongly reflect the density of sites that tend to accommodate alkali metals, i.e., vacancies. Annealing at elevated temperature caused a redistribution of the alkali metals. The thermal-diffusion kinetics of alkali metals depends strongly on the species involved. We introduced low flux potassium fluoride (KF) to study a side effect of KF-PDT, i.e., Na removal from CIGS, separately from its predominant effects such as surface modification. When sufficient amounts of Na are supplied from the soda lime glass via annealing at an elevated temperature, the negative effect was not apparent. Conversely, when the Na supply was not sufficient, it caused a deterioration of the photovoltaic properties.« less

Effect of thermal annealing on the redistribution of alkali metals in Cu(In,Ga)Se 2 solar cells on glass substrate

DOE PAGES

Kamikawa, Yukiko; Nishinaga, Jiro; Ishizuka, Shogo; ...

2018-03-07

The precise control of alkali-metal concentrations in Cu(In,Ga)Se 2 (CIGS) solar cells via post deposition treatment (PDT) has recently attracted attention. When PDT is performed at an elevated temperature, an accompanying annealing effect is expected. Here, we investigate how thermal annealing affects the redistribution of alkali metals in CIGS solar cells on glass substrates and the properties of the solar cells. In addition, we investigate the origin of non-homogeneous alkali-metal depth profiles that are typical of CIGS grown using a three-stage process. In particular, we use secondary-ion mass spectrometry measurements of the ion concentration as a function of distance frommore » the CIGS surface to investigate the impact of thermal annealing on the distribution of alkali metals (Na, Ka, and Rb) and constituent elements (Ga and In) in the CIGS absorbers. We find that the depth profiles of the alkali metals strongly reflect the density of sites that tend to accommodate alkali metals, i.e., vacancies. Annealing at elevated temperature caused a redistribution of the alkali metals. The thermal-diffusion kinetics of alkali metals depends strongly on the species involved. We introduced low flux potassium fluoride (KF) to study a side effect of KF-PDT, i.e., Na removal from CIGS, separately from its predominant effects such as surface modification. When sufficient amounts of Na are supplied from the soda lime glass via annealing at an elevated temperature, the negative effect was not apparent. Conversely, when the Na supply was not sufficient, it caused a deterioration of the photovoltaic properties.« less

Room temperature deposition of gold onto the diffuse and sharp diffraction spot Si(111)-( 3 × 3) R30° Au surfaces

NASA Astrophysics Data System (ADS)

Plass, Richard; Marks, Laurence D.

1996-06-01

Room temperature gold depositions onto Si(111)-( 3 × 3) R30° Au surfaces with diffuse and sharp diffraction spots [Surf. Sci. 242 (1991) 73] (diffuse and sharp 3 × 3 Au hereafter) under UHV conditions has been monitored using transmission electron diffraction (TED). Both systems display an increase in surface structure diffraction spot intensities up to the completion of 1.0 monolayer (ML) after which the surface beams display an exponential decrease in intensity with coverage. The exponential decay rate decreases after roughly 1.33 ML. These results can be attributed to gold initially diffusing to and filling 3 × 3 Au gold trimer sites in vacancy type surface domain walls [Surf. Sci. 342 (1995) 233], then filling one of three possible sites on the 3 × 3 Au structure with essentially no surface diffusion, disrupting nearby gold trimers. Gold deposition onto the diffuse type structure caused the formation and expansion of satellite arcs around the strongest 3 × 3 beams similar to those seen by others [Surf. Sci. 242 (1991) 73; Jpn. J. Appl. Phys. 16 (1977) 891; J. Vac. Sci. Technol. A 10 (1992) 3486] at elevated temperatures while the sharp structure displayed only a modest shoulder formation near the strongest 3 × 3 beams.

Method for the preparation of high surface area high permeability carbons

DOEpatents

Lagasse, Robert R.; Schroeder, John L.

1999-05-11

A method for preparing carbon materials having high surface area and high macropore volume to provide high permeability. These carbon materials are prepared by dissolving a carbonizable polymer precursor, in a solvent. The solution is cooled to form a gel. The solvent is extracted from the gel by employing a non-solvent for the polymer. The non-solvent is removed by critical point drying in CO.sub.2 at an elevated pressure and temperature or evaporation in a vacuum oven. The dried product is heated in an inert atmosphere in a first heating step to a first temperature and maintained there for a time sufficient to substantially cross-link the polymer material. The cross-linked polymer material is then carbonized in an inert atmosphere.

Illumination Conditions at the Asteroid 4 Vesta: Implications for the Presence of Water Ice

NASA Technical Reports Server (NTRS)

Stubbs, Timothy J.; Wang, Yongli

2011-01-01

The mean illumination conditions and surface temperatures over one orbital period are calculated for the Asteroid 4 Vesta using a coarse digital elevation model produced from Hubble Space Telescope images. Even with the anticipated effects of finer-scale topography taken into account, it is unlikely that any significant permanently shadowed regions currently exist on Vesta due to its large axial tilt (approx. = 27deg). However, under present day conditions, it is predicted that about half of Vesta's surface has an average temperature of less than 145 K, which, based on previous thermal modeling of main belt asteroids, suggests that water ice could survive in the top few meters of the vestal regolith on billion-year timescales.

Effects of wintertime atmospheric river landfalls on surface air temperatures in the Western US: Analyses and model evaluation

NASA Astrophysics Data System (ADS)

Kim, J.; Guan, B.; Waliser, D. E.; Ferraro, R.

2016-12-01

Landfalling atmospheric rivers (ARs) affect the wintertime surface air temperatures as shown in earlier studies. The AR-related surface air temperatures can exert significant influence on the hydrology in the US Pacific coast region especially through rainfall-snowfall partitioning and the snowpack in high elevation watersheds as they are directly related with the freezing-level altitudes. These effects of temperature perturbations can in turn affect hydrologic events of various time scales such as flash flooding by the combined effects of rainfall and snowmelt, and the warm season runoff from melting snowpack, especially in conjunction with the AR effects on winter precipitation and rain-on-snow events in WUS. Thus, understanding the effects of AR landfalls on the surface temperatures and examining the capability of climate models in simulating these effects are an important practical concern for WUS. This study aims to understand the effects of AR landfalls on the characteristics of surface air temperatures in WUS, especially seasonal means and PDFs and to evaluate the fidelity of model data produced in the NASA downscaling experiment for the 10 winters from Nov. 1999 to Mar. 2010 using an AR-landfall chronology based on the vertically-integrated water vapor flux calculated from the MERRA2 reanalysis. Model skill is measured using metrics including regional means, a skill score based on correlations and mean-square errors, the similarity between two PDF shapes, and Taylor diagrams. Results show that the AR landfalls are related with higher surface air temperatures in WUS, especially in inland regions. The AR landfalls also reduce the range of surface air temperature PDF, largely by reducing the events in the lower temperature range. The shift in the surface air temperature PDF is consistent with the positive anomalies in the winter-mean temperature. Model data from the NASA downscaling experiment reproduce the AR effects on the temperature PDF, at least qualitatively; however, the skill in representing the spatial variations in the temperature anomalies is low. The skill of these model data also varies according to regions and the configuration of simulations. It was also found that the variations in model skill in simulating the spatial variability according to the model resolution is not systematic.

Field-calibrated model of melt, refreezing, and runoff for polar ice caps: Application to Devon Ice Cap

NASA Astrophysics Data System (ADS)

Morris, Richard M.; Mair, Douglas W. F.; Nienow, Peter W.; Bell, Christina; Burgess, David O.; Wright, Andrew P.

2014-09-01

Understanding the controls on the amount of surface meltwater that refreezes, rather than becoming runoff, over polar ice masses is necessary for modeling their surface mass balance and ultimately for predicting their future contributions to global sea level change. We present a modified version of a physically based model that includes an energy balance routine and explicit calculation of near-surface meltwater refreezing capacity, to simulate the evolution of near-surface density and temperature profiles across Devon Ice Cap in Arctic Canada. Uniquely, our model is initiated and calibrated using high spatial resolution measurements of snow and firn densities across almost the entire elevation range of the ice cap for the summer of 2004 and subsequently validated with the same type of measurements obtained during the very different meteorological conditions of summer 2006. The model captures the spatial variability across the transect in bulk snowpack properties although it slightly underestimates the flow of meltwater into the firn of previous years. The percentage of meltwater that becomes runoff is similar in both years; however, the spatial pattern of this melt-runoff relationship is different in the 2 years. The model is found to be insensitive to variation in the depth of impermeable layers within the firn but is very sensitive to variation in air temperature, since the refreezing capacity of firn decreases with increasing temperature. We highlight that the sensitivity of the ice cap's surface mass balance to air temperature is itself dependent on air temperature.

One-third of reef-building corals face elevated extinction risk from climate change and local impacts.

PubMed

Carpenter, Kent E; Abrar, Muhammad; Aeby, Greta; Aronson, Richard B; Banks, Stuart; Bruckner, Andrew; Chiriboga, Angel; Cortés, Jorge; Delbeek, J Charles; Devantier, Lyndon; Edgar, Graham J; Edwards, Alasdair J; Fenner, Douglas; Guzmán, Héctor M; Hoeksema, Bert W; Hodgson, Gregor; Johan, Ofri; Licuanan, Wilfredo Y; Livingstone, Suzanne R; Lovell, Edward R; Moore, Jennifer A; Obura, David O; Ochavillo, Domingo; Polidoro, Beth A; Precht, William F; Quibilan, Miledel C; Reboton, Clarissa; Richards, Zoe T; Rogers, Alex D; Sanciangco, Jonnell; Sheppard, Anne; Sheppard, Charles; Smith, Jennifer; Stuart, Simon; Turak, Emre; Veron, John E N; Wallace, Carden; Weil, Ernesto; Wood, Elizabeth

2008-07-25

The conservation status of 845 zooxanthellate reef-building coral species was assessed by using International Union for Conservation of Nature Red List Criteria. Of the 704 species that could be assigned conservation status, 32.8% are in categories with elevated risk of extinction. Declines in abundance are associated with bleaching and diseases driven by elevated sea surface temperatures, with extinction risk further exacerbated by local-scale anthropogenic disturbances. The proportion of corals threatened with extinction has increased dramatically in recent decades and exceeds that of most terrestrial groups. The Caribbean has the largest proportion of corals in high extinction risk categories, whereas the Coral Triangle (western Pacific) has the highest proportion of species in all categories of elevated extinction risk. Our results emphasize the widespread plight of coral reefs and the urgent need to enact conservation measures.

Warming and pCO2 effects on Florida stone crab larvae

NASA Astrophysics Data System (ADS)

Gravinese, Philip M.; Enochs, Ian C.; Manzello, Derek P.; van Woesik, Robert

2018-05-01

Greenhouse gas emissions are increasing ocean temperatures and the partial pressure of CO2 (pCO2), resulting in more acidic waters. It is presently unknown how elevated temperature and pCO2 will influence the early life history stages of the majority of marine coastal species. We investigated the combined effect of elevated temperature (30 °C control and 32 °C treatment) and elevated pCO2 (450 μatm control and 1100 μatm treatment) on the (i) growth, (ii) survival, (iii) condition, and (iv) morphology of larvae of the commercially important Florida stone crab, Menippe mercenaria. At elevated temperature, larvae exhibited a significantly shorter molt stage, and elevated pCO2 caused stage-V larvae to delay metamorphosis to post-larvae. On average, elevated pCO2 resulted in a 37% decrease in survivorship relative to the control; however the effect of elevated temperature reduced larval survivorship by 71%. Exposure to both elevated temperature and pCO2 reduced larval survivorship by 80% relative to the control. Despite this, no significant differences were detected in the condition or morphology of stone crab larvae when subjected to elevated temperature and pCO2 treatments. Although elevated pCO2 could result in a reduction in larval supply, future increases in seawater temperatures are even more likely to threaten the future sustainability of the stone-crab fishery.

Elevated [CO2] does not ameliorate the negative effects of elevated temperature on drought-induced mortality in Eucalyptus radiata seedlings.

PubMed

Duan, Honglang; Duursma, Remko A; Huang, Guomin; Smith, Renee A; Choat, Brendan; O'Grady, Anthony P; Tissue, David T

2014-07-01

It has been reported that elevated temperature accelerates the time-to-mortality in plants exposed to prolonged drought, while elevated [CO(2)] acts as a mitigating factor because it can reduce stomatal conductance and thereby reduce water loss. We examined the interactive effects of elevated [CO(2)] and temperature on the inter-dependent carbon and hydraulic characteristics associated with drought-induced mortality in Eucalyptus radiata seedlings grown in two [CO(2)] (400 and 640 μL L(-1)) and two temperature (ambient and ambient +4 °C) treatments. Seedlings were exposed to two controlled drying and rewatering cycles, and then water was withheld until plants died. The extent of xylem cavitation was assessed as loss of stem hydraulic conductivity. Elevated temperature triggered more rapid mortality than ambient temperature through hydraulic failure, and was associated with larger water use, increased drought sensitivities of gas exchange traits and earlier occurrence of xylem cavitation. Elevated [CO(2)] had a negligible effect on seedling response to drought, and did not ameliorate the negative effects of elevated temperature on drought. Our findings suggest that elevated temperature and consequent higher vapour pressure deficit, but not elevated [CO(2)], may be the primary contributors to drought-induced seedling mortality under future climates. © 2013 John Wiley & Sons Ltd.

Use of a Multiwavelength Pyrometer in Several Elevated Temperature Aerospace Applications

NASA Technical Reports Server (NTRS)

Ng, Daniel; Fralick, Gustave

2001-01-01

A multiwavelength pyrometer was developed for applications unique to aerospace environments. It was shown to be a useful and versatile technique for measuring temperature, even when the emissivity is unknown. It has also been used to measure the surface temperatures of ceramic zircomia thermal barrier coatings and alumina. The close agreement between pyrometer and thin film thermocouple temperatures provided an independent check. Other applications of the multiwavelength pyrometer are simultaneous surface and bulk temperature measurements of a transparent material, and combustion gas temperature measurement using a special probe interfaced to the multiwavelength pyrometer via an optical fiber. The multiwavelength pyrometer determined temperature by transforming the radiation spectrum in a broad wavelength region to produce a straight line (in a certain spectral region), whose intercept in the vertical axis gives the temperature. Implicit in a two-color pyrometer is the assumption of wavelength independent emissivity. Though the two data points of a two-color pyrometer similarly processed would result immediately in a similar straight line to give the unknown temperature, the two-color pyrometer lacks the greater data redundancy of the multiwavelength pyrometer, which enables it to do so with improved accuracy. It also confirms that emissivity is indeed wavelength independent, as evidenced by a multitude of the data lying on a simple straight line. The multiwavelength pyrometer was also used to study the optical transmission properties of a nanostructured material from which a quadratic exponential functional frequency dependence of its spectral transmission was determined. Finally, by operating the multiwavelength pyrometer in a very wide field of view mode, the surface temperature distribution of a large hot surface was obtained through measurement of just a single radiation spectrum.

Oxidation of high-temperature alloys (superalloys) at elevated temperatures in air: I

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

Hussain, N.; Shahid, K.A.; Rahman, S.

1994-04-01

Four commercial alloys - Hastelloy C-4, alloy 1.4306S (SS 304L), Incoloy 800H, and Incoloy 825 - were studied for their oxidation behavior at elevated temperatures. Specimens were exposed to air from 600 to 1200[degree]C for 1 to 400 hr. Reaction kinetics of oxidation were determined, and the morphology of the surface-oxide scales was investigated. Hastelloy C-4 showed better resistance to oxidation for exposure temperatures up to 1000[degree]C in comparison with the other three alloys. In this temperature range, it follows a cubic rate law of oxidation due to formation of uniform, protective, and adherent oxide scales. The latter three alloysmore » obeyed the parabolic rate law at 1000[degree]C and 1200[degree]C, but for lower temperatures a mixed behavior was shown. The oxide layer developed on the alloy 1.4306S was always in the form of stratified nodules/warts. For longer exposures the nodules joined each other to form continuous but discrete layers. Incoloy 800H and Incoloy 825 behaved in an almost identical manner, their reaction kinetics being governed by the parabolic rate law throughout the temperature range. Oxide spalling was observed at all temperatures. In contrast to Incoloy 800H the Incoloy 825 was totally oxidized for longer exposures at 1200[degree]C. 16 refs., 12 figs., 1 tab.« less

FDTD analysis of human body-core temperature elevation due to RF far-field energy prescribed in the ICNIRP guidelines.

PubMed

Hirata, Akimasa; Asano, Takayuki; Fujiwara, Osamu

2007-08-21

This study investigated the relationship between the specific absorption rate and temperature elevation in an anatomically-based model named NORMAN for exposure to radio-frequency far fields in the ICNIRP guidelines (1998 Health Phys. 74 494-522). The finite-difference time-domain method is used for analyzing the electromagnetic absorption and temperature elevation in NORMAN. In order to consider the variability of human thermoregulation, parameters for sweating are derived and incorporated into a conventional sweating formula. First, we investigated the effect of blood temperature variation modeling on body-core temperature. The computational results show that the modeling of blood temperature variation was the dominant factor influencing the body-core temperature. This is because the temperature in the inner tissues is elevated via the circulation of blood whose temperature was elevated due to EM absorption. Even at different frequencies, the body-core temperature elevation at an identical whole-body average specific absorption rate (SAR) was almost the same, suggesting the effectiveness of the whole-body average SAR as a measure in the ICNIRP guidelines. Next, we discussed the effect of sweating on the temperature elevation and thermal time constant of blood. The variability of temperature elevation caused by the sweating rate was found to be 30%. The blood temperature elevation at the basic restriction in the ICNIRP guidelines of 0.4 W kg(-1) is 0.25 degrees C even for a low sweating rate. The thermal time constant of blood temperature elevation was 23 min and 52 min for a man with a lower and a higher sweating rate, respectively, which is longer than the average time of the SAR in the ICNIRP guidelines. Thus, the whole-body average SAR required for blood temperature elevation of 1 degrees C was 4.5 W kg(-1) in the model of a human with the lower sweating coefficients for 60 min exposure. From a comparison of this value with the basic restriction in the ICNIRP guidelines of 0.4 W kg(-1), the safety factor was 11.

Temperature and Water Depth Monitoring Within Chum Salmon Spawning Habitat Below Bonneville Dam : Annual Report October 2007-September 2008

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

Arntzen, E.V.

2009-07-14

The overall goal of the project described in this report is to provide a sound scientific basis for operation of the Federal Columbia River Power System (FCRPS) in ways that will effectively protect and enhance chum salmon populations - a species listed in March 1999 as threatened under the Endangered Species Act of 1973 (ESA). The study objective during fiscal year 2008 was to provide real-time data on Ives Island area water temperature and water surface elevations from the onset of chum salmon spawning through the end of chum salmon emergence. Sampling locations included areas where riverbed temperatures were elevated,more » potentially influencing alevin development and emergence timing. In these locations, hydrosystem operation caused large, frequent changes in river discharge that affected salmon habitat by dewatering redds and altering egg pocket temperatures. The 2008 objective was accomplished using temperature and water-level sensors deployed inside piezometers. Sensors were integrated with a radio telemetry system such that real-time data could be downloaded remotely and posted hourly on the Internet. During our overall monitoring period (October 2007 through June 2008), mean temperature in chum spawning areas was nearly 2 C warmer within the riverbed than in the overlying river. During chum salmon spawning (mid-November 2007 through December2007), mean riverbed temperature in the Ives Island area was 14.5 C, more than 5 C higher than in the river, where mean temperature was 9.4 C. During the incubation period (January 2008 through mid-May 2008), riverbed temperature was approximately 3 C greater than in the overlying river (10.5 C and 7.2 C, respectively). Chum salmon preferentially select spawning locations where riverbed temperatures are elevated; consequently the incubation time of alevin is shortened before they emerge in the spring.« less

Analysis of Viking infrared thermal mapping data of Mars. The effects of non-ideal surfaces on the derived thermal properties of Mars

NASA Technical Reports Server (NTRS)

Muhleman, D. O.; Jakosky, B. M.

1979-01-01

The thermal interia of the surface of Mars varies spatially by a factor of eight. This is attributable to changes in the average particle size of the fine material, the surface elevation, the atmospheric opacity due to dust, and the fraction of the surface covered by rocks and fine material. The effects of these non-ideal properties on the surface temperatures and derived thermal inertias are modeled, along with the the effects of slopes, CO2 condensed onto the surface, and layering of fine material upon solid rock. The non-ideal models are capable of producing thermal behavior similar to that observed by the Viking Infrared Thermal Mapper, including a morning delay in the post-dawn temperature rise and an enhanced cooling in the afternoon relative to any ideal, homogeneous model. The enhanced afternoon cooling observed at the Viking-1 landing site is reproduced by the non-ideal models while that atop Arsia Mons volcano is not, but may be attributed to the observing geometry.

Estimates of Ice Sheet Mass Balance from Satellite Altimetry: Past and Future

NASA Technical Reports Server (NTRS)

Zwally, H. Jay; Zukor, Dorothy J. (Technical Monitor)

2001-01-01

A major uncertainty in predicting sea level rise is the sensitivity of ice sheet mass balance to climate change, as well as the uncertainty in present mass balance. Since the annual water exchange is about 8 mm of global sea level equivalent, the 20% uncertainty in current mass balance corresponds to 1.6 mm/yr in sea level change. Furthermore, estimates of the sensitivity of the mass balance to temperature change range from perhaps as much as - 10% to + 10% per K. A principal purpose of obtaining ice sheet elevation changes from satellite altimetry has been estimation of the current ice sheet mass balance. Limited information on ice sheet elevation change and their implications about mass balance have been reported by several investigators from radar altimetry (Seasat, Geosat, ERS-1&2). Analysis of ERS-1&2 data over Greenland for 7 years from 1992 to 1999 shows mixed patterns of ice elevation increases and decreases that are significant in terms of regional-scale mass balances. Observed seasonal and interannual variations in ice surface elevation are larger than previously expected because of seasonal and interannUal variations in precipitation, melting, and firn compaction. In the accumulation zone, the variations in firn compaction are modeled as a function of temperature leaving variations in precipitation and the mass balance trend. Significant interannual variations in elevation in some locations, in particular the difference in trends from 1992 to 1995 compared to 1995 to 1999, can be explained by changes in precipitation over Greenland. Over the 7 years, trends in elevation are mostly positive at higher elevations and negative at lower elevations. In addition, trends for the winter seasons (from a trend analysis through the average winter elevations) are more positive than the corresponding trends for the summer. At lower elevations, the 7-year trends in some locations are strongly negative for summer and near zero or slightly positive for winter. These observations also demonstrate the potential for relating the variability in mass balance to changes in precipitation, temperature, and melting. Beginning in January 2002, NASA's ICESat laser altimeter mission will provide significantly better elevation accuracy and spatial coverage to 86E latitude and to the margins of the ice sheets.

Oxidative stress in deep scattering layers: Heat shock response and antioxidant enzymes activities of myctophid fishes thriving in oxygen minimum zones

NASA Astrophysics Data System (ADS)

Lopes, Ana Rita; Trübenbach, Katja; Teixeira, Tatiana; Lopes, Vanessa M.; Pires, Vanessa; Baptista, Miguel; Repolho, Tiago; Calado, Ricardo; Diniz, Mário; Rosa, Rui

2013-12-01

Diel vertical migrators, such as myctophid fishes, are known to encounter oxygen minimum zones (OMZ) during daytime in the Eastern Pacific Ocean and, therefore, have to cope with temperature and oxidative stress that arise while ascending to warmer, normoxic surface waters at night-time. The aim of this study was to investigate the antioxidant defense strategies and heat shock response (HSR) in two myctophid species, namely Triphoturus mexicanus and Benthosema panamense, at shallow and warm surface waters (21 kPa, 20-25 °C) and at hypoxic, cold (≤1 kPa, 10 °C) mesopelagic depths. More specifically, we quantified (i) heat shock protein concentrations (HSP70/HSC70) (ii) antioxidant enzyme activities [including superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST)], and (iii) lipid peroxidation [malondialdehyde (MDA) levels]. HSP70/HSC70 levels increased in both myctophid species at warmer, well-oxygenated surface waters probably to prevent cellular damage (oxidative stress) due to increased oxygen demand under elevated temperatures and reactive oxygen species (ROS) formation. On the other hand, CAT and GST activities were augmented under hypoxic conditions, probably as preparatory response to a burst of oxyradicals during the reoxygenation phase (while ascending). SOD activity decreased under hypoxia in B. panamense, but was kept unchanged in T. mexicanus. MDA levels in B. panamense did not change between the surface and deep-sea conditions, whereas T. mexicanus showed elevated MDA and HSP70/HSC70 concentrations at warmer surface waters. This indicated that T. mexicanus seems to be not so well tuned to temperature and oxidative stress associated to diel vertical migrations. The understanding of such physiological strategies that are linked to oxygen deprivation and reoxygenation phases may provide valuable information about how different species might respond to the impacts of environmental stressors (e.g. expanding mesopelagic hypoxia) coupled with global climate change.

Satellite observations of surface temperature during the March 2015 total solar eclipse.

PubMed

Good, Elizabeth

2016-09-28

The behaviour of remotely sensed land surface temperatures (LSTs) from the spinning-enhanced visible and infrared imager (SEVIRI) during the total solar eclipse of 20 March 2015 is analysed over Europe. LST is found to drop by up to several degrees Celcius during the eclipse, with the minimum LST occurring just after the eclipse mid-point (median=+1.5 min). The drop in LST is typically larger than the drop in near-surface air temperatures reported elsewhere, and correlates with solar obscuration (r=-0.47; larger obscuration = larger LST drop), eclipse duration (r=-0.62; longer duration = larger LST drop) and time (r=+0.37; earlier eclipse = larger LST drop). Locally, the LST drop is also correlated with vegetation (up to r=+0.6), with smaller LST drops occurring over more vegetated surfaces. The LSTs at locations near the coast and at higher elevation are also less affected by the eclipse. This study covers the largest area and uses the most observations of eclipse-induced surface temperature drops to date, and is the first full characterization of satellite LST during an eclipse (known to the author). The methods described could be applied to Geostationary Operational Environmental Satellite (GOES) LST data over North America during the August 2017 total solar eclipse.This article is part of the themed issue 'Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse'. © 2016 The Author(s).

Satellite observations of surface temperature during the March 2015 total solar eclipse

PubMed Central

2016-01-01

The behaviour of remotely sensed land surface temperatures (LSTs) from the spinning-enhanced visible and infrared imager (SEVIRI) during the total solar eclipse of 20 March 2015 is analysed over Europe. LST is found to drop by up to several degrees Celcius during the eclipse, with the minimum LST occurring just after the eclipse mid-point (median=+1.5 min). The drop in LST is typically larger than the drop in near-surface air temperatures reported elsewhere, and correlates with solar obscuration (r=−0.47; larger obscuration = larger LST drop), eclipse duration (r=−0.62; longer duration = larger LST drop) and time (r=+0.37; earlier eclipse = larger LST drop). Locally, the LST drop is also correlated with vegetation (up to r=+0.6), with smaller LST drops occurring over more vegetated surfaces. The LSTs at locations near the coast and at higher elevation are also less affected by the eclipse. This study covers the largest area and uses the most observations of eclipse-induced surface temperature drops to date, and is the first full characterization of satellite LST during an eclipse (known to the author). The methods described could be applied to Geostationary Operational Environmental Satellite (GOES) LST data over North America during the August 2017 total solar eclipse. This article is part of the themed issue ‘Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse’. PMID:27550764

An Experimental Real-Time Ocean Nowcast/Forecast System for Intra America Seas

NASA Astrophysics Data System (ADS)

Ko, D. S.; Preller, R. H.; Martin, P. J.

2003-04-01

An experimental real-time Ocean Nowcast/Forecast System has been developed for the Intra America Seas (IASNFS). The area of coverage includes the Caribbean Sea, the Gulf of Mexico and the Straits of Florida. The system produces nowcast and up to 72 hours forecast the sea level variation, 3D ocean current, temperature and salinity fields. IASNFS consists an 1/24 degree (~5 km), 41-level sigma-z data-assimilating ocean model based on NCOM. For daily nowcast/forecast the model is restarted from previous nowcast. Once model is restarted it continuously assimilates the synthetic temperature/salinity profiles generated by a data analysis model called MODAS to produce nowcast. Real-time data come from satellite altimeter (GFO, TOPEX/Poseidon, ERS-2) sea surface height anomaly and AVHRR sea surface temperature. Three hourly surface heat fluxes, including solar radiation, wind stresses and sea level air pressure from NOGAPS/FNMOC are applied for surface forcing. Forecasts are produced with available NOGAPS forecasts. Once the nowcast/forecast are produced they are distributed through the Internet via the updated web pages. The open boundary conditions including sea surface elevation, transport, temperature, salinity and currents are provided by the NRL 1/8 degree Global NCOM which is operated daily. An one way coupling scheme is used to ingest those boundary conditions into the IAS model. There are 41 rivers with monthly discharges included in the IASNFS.

Scots pine responses to elevated temperature and carbon dioxide concentration: growth and wood properties.

PubMed

Kilpeläinen, Antti; Peltola, Heli; Ryyppö, Aija; Kellomäki, Seppo

2005-01-01

Growth and wood properties of 20-year-old Scots pine (Pinus sylvestris L.) trees were studied for 6 years in 16 closed chambers providing a factorial combination of two temperature regimes (ambient and elevated) and two carbon dioxide concentrations ([CO2]) (ambient and twice ambient). The elevation of temperature corresponded to the predicted effect at the site of a doubling in atmospheric [CO2]. Annual height and radial growth and wood properties were analyzed during 1997-2002. Physical wood properties analyzed included early- and latewood widths and their proportions, intra-ring wood densities, early- and latewood density and mean fiber length. Chemical wood properties analyzed included concentrations of acetone-soluble extractives, lignin, cellulose and hemicellulose. There were no significant treatment effects on height growth during the 6-year study. Elevated [CO2] increased ring width by 66 and 47% at ambient and elevated temperatures, respectively. At ambient [CO2], elevated temperature increased ring width by 19%. Increased ring width in response to elevated [CO2] resulted from increases in both early- and latewood width; however, there was no effect of the treatments on early- and latewood proportions. Mean wood density, earlywood density and fiber length increased in response to elevated temperature. The chemical composition of wood was affected by elevated [CO2], which reduced the cellulose concentration, and by elevated temperature, which reduced the concentration of acetone-soluble extractives. Thus, over the 6-year period, radial growth was significantly increased by elevated [CO2], and some wood properties were significantly affected by elevated temperature or elevated [CO2], or both, indicating that climate change may affect the material properties of wood.

Conduit for high temperature transfer of molten semiconductor crystalline material

NASA Technical Reports Server (NTRS)

Fiegl, George (Inventor); Torbet, Walter (Inventor)

1983-01-01

A conduit for high temperature transfer of molten semiconductor crystalline material consists of a composite structure incorporating a quartz transfer tube as the innermost member, with an outer thermally insulating layer designed to serve the dual purposes of minimizing heat losses from the quartz tube and maintaining mechanical strength and rigidity of the conduit at the elevated temperatures encountered. The composite structure ensures that the molten semiconductor material only comes in contact with a material (quartz) with which it is compatible, while the outer layer structure reinforces the quartz tube, which becomes somewhat soft at molten semiconductor temperatures. To further aid in preventing cooling of the molten semiconductor, a distributed, electric resistance heater is in contact with the surface of the quartz tube over most of its length. The quartz tube has short end portions which extend through the surface of the semiconductor melt and which are lef bare of the thermal insulation. The heater is designed to provide an increased heat input per unit area in the region adjacent these end portions.

Fracture resistance of a TiB2 particle/SiC matrix composite at elevated temperature

NASA Technical Reports Server (NTRS)

Jenkins, Michael G.; Salem, Jonathan A.; Seshadri, Srinivasa G.

1988-01-01

The fracture resistance of a comercial TiB2 particle/SiC matrix composite was evaluated at temperatures ranging from 20 to 1400 C. A laser interferometric strain gauge (LISG) was used to continuously monitor the crack mouth opening displacement (CMOD) of the chevron-notched and straight-notched, three-point bend specimens used. Crack growth resistance curves (R-curves) were determined from the load versus displacement curves and displacement calibrations. Fracture toughness, work-of-fracture, and R-curve levels were found to decrease with increasing temperature. Microstructure, fracture surface, and oxidation coat were examined to explain the fracture behavior.

Fracture resistance of a TiB2 particle/SiC matrix composite at elevated temperature

NASA Technical Reports Server (NTRS)

Jenkins, Michael G.; Salem, Jonathan A.; Seshadri, Srinivasa G.

1989-01-01

The fracture resistance of a commercial TiB2 particle/SiC matrix composite was evaluated at temperatures ranging from 20 to 1400 C. A laser interferometric strain gauge (LiSG) was used to continuously monitor the crack mouth opening displacement (CMOD) of the chevron-notched and straight-notched, three-point bend specimens used. Crack growth resistance curves (R-curves) were determined from the load versus displacement curves and displacement calibrations. Fracture toughness, work-of-fracture, and R-curve levels were found to decrease with increasing temperature. Microstructure, fracture surface, and oxidation coat were examined to explain the fracture behavior.

Characterizing the Siple Coast Ice Stream System using Satellite Images, Improved Topography, and Integrated Aerogeophysical Measurements

NASA Technical Reports Server (NTRS)

Scambos, Ted

2003-01-01

A technique for improving elevation maps of the polar ice sheets has been developed using AVHRR images. The technique is based on 'photoclinometry' or 'shape from shading', a technique used in the past for mapping planetary surfaces where little elevation information was available. The fundamental idea behind photoclinometry is using the brightness of imaged areas to infer their surface slope in the sun-illuminated direction. Our version of the method relies on a calibration of the images based on an existing lower-resolution digital elevation model (DEM), and then using the images to improve the input DEM resolution to the scale of the image data. Most current DEMs covering the ice sheets are based on Radar altimetry data, and have an inherent resolution of 10 to 25 km at best - although the grid scale of the DEM is often finer. These DEMs are highly accurate (to less than 1 meter); but they report the mean elevation of a broad area, thus erasing smaller features of glaciological interest. AVHRR image data, when accurately geolocated and calibrated, provides surface slope measurements (based on the pixel brightness under known lighting conditions) every approximately 1.1 km. The limitations of the technique are noisiness in the image data, small variations in the albedo of the snow surface, and the integration technique used to create an elevation field from the image-derived slopes. Our study applied the technique to several ice sheet areas having some elevation data; Greenland, the Amery Ice Shelf, the Institute Ice Stream, and the Siple Coast. For the latter, the input data set was laser-altimetry data collected under NSF's SOAR Facility (Support Office for Aerogeophysical Research) over the onset area of the Siple Coast. Over the course of the grant, the technique was greatly improved and modified, significantly improving accuracy and reducing noise from the images. Several publications resulted from the work, and a follow-on proposal to NASA has been submitted to apply the same method to MODIS data using ICESat and other elevation input information. This follow-on grant will explore two applications that are facilitated by the improved surface morphology characterizations of the ice sheets: accumulation and temperature variations near small undulations in the ice.

Near Infrared Multispectral Mapping of Venus Supports the Hypothesis that Tessera Plateau Material was Formed in the Presence of Surface Water

NASA Astrophysics Data System (ADS)

Mueller, N. T.; Tsang, C.; Nunes, D. C.; Helbert, J.; Dyar, M. D.; Smrekar, S. E.

2017-12-01

The VIRTIS instrument on Venus Express observed surface thermal emission from the surface. Studies of 1020nm data showed that tessera plateaus, intensely tectonically deformed highlands that predate most other terrains, have significantly lower thermal emission than other highlands. Lower thermal emission could be due either to lower surface emissivity, supporting the hypothesis that tessera are analogous to continental crust on Earth, or to a bias of Magellan altimetry, which does not fully resolve the topographic relief of tessera terrain. To eliminate this ambiguity, we additionally investigate the spectral windows at 1100 and 1180nm. Data are reduced to surface emissivity using an atmospheric radiative transfer model to account for atmospheric scattering and absorption/emission. Magellan altimetry was used to model atmospheric column height and surface temperature. The model uses a binary (collision-induced) absorption coefficient for each window. It fits absolute radiance and gradient with surface elevation reasonably well, although there are indications that the assumed adiabatic temperature lapse rate is not appropriate globally. The 1100nm band has a relatively low signal-to-noise ratio at the latitudes of the tessera plateaus, but Alpha Regio is visible in both the 1020 and the 1180nm band. The difference in emissivity between Alpha and the adjacent corona Eve, which has a similar elevation as Alpha, is 3.6% at 1020nm, but only 2% at 1180nm. The altimetry bias equivalent to the 1020nm deviation is 230 m, while the equivalent is only 70m at 1180nm. An altimetry bias therefore cannot fully explain the observations, and there must be a real difference in emissivity. The observations are consistent with the hypothesis that Alpha Regio has a more felsic composition. The emissivity spectra of granites at Venus temperatures are lower than those of basalt at 1020nm, but the difference decreases or vanishes towards the 1180nm window. The most plausible explanation for continent-sized felsic plateaus would be a formation analogous to Earth's continents, i.e. differentiation of basaltic crust in the presence of water.

The combined effects of temperature and CO2 lead to altered gene expression in Acropora aspera

NASA Astrophysics Data System (ADS)

Ogawa, D.; Bobeszko, T.; Ainsworth, T.; Leggat, W.

2013-12-01

This study explored the interactive effects of near-term CO2 increases (40-90 ppm above current ambient) during a simulated bleaching event (34 °C for 5 d) of Acropora aspera by linking physiology to expression patterns of genes involved in carbon metabolism. Symbiodinium photosynthetic efficiency ( F v / F m ) was significantly depressed by the bleaching event, while elevated pressure of CO2 (pCO2) slightly mitigated the effects of increased temperature on F v / F m during the final 4 d of the recovery period, however, did not affect the loss of symbionts. Elevated pCO2 alone had no effect on F v / F m or symbiont density. Expression of targeted Symbiodinium genes involved in carbon metabolism and heat stress response was not significantly altered by either increased temperature and/or CO2. Of the selected host genes, two carbonic anhydrase isoforms (coCA2 and coCA3) exhibited the largest changes, most notably in crossed bleaching and elevated pCO2 treatments. CA2 was significantly down-regulated on day 14 in all treatments, with the greatest decrease in the crossed treatment (relative expression compared to control = 0.16; p < 0.05); CA3 showed a similar trend, with expression levels 0.20-fold of controls on day 14 ( p < 0.05) in the elevated temperature/pCO2 treatment. The synergistic effects of ocean acidification and bleaching were evident during this study and demonstrate that increased pCO2 in surface waters will impact corals much sooner than many studies utilising end-of-century pCO2 concentrations would indicate.

Gas exchange, growth, and defense responses of invasive Alliaria petiolata (Brassicaceae) and native Geum vernum (Rosaceae) to elevated atmospheric CO2 and warm spring temperatures.

PubMed

Anderson, Laurel J; Cipollini, Don

2013-08-01

Global increases in atmospheric CO2 and temperature may interact in complex ways to influence plant physiology and growth, particularly for species that grow in cool, early spring conditions in temperate forests. Plant species may also vary in their responses to environmental changes; fast-growing invasives may be more responsive to rising CO2 than natives and may increase production of allelopathic compounds under these conditions, altering species' competitive interactions. We examined growth and physiological responses of Alliaria petiolata, an allelopathic, invasive herb, and Geum vernum, a co-occurring native herb, to ambient and elevated spring temperatures and atmospheric CO2 conditions in a factorial growth chamber experiment. At 5 wk, leaves were larger at high temperature, and shoot biomass increased under elevated CO2 only at high temperature in both species. As temperatures gradually warmed to simulate seasonal progression, G. vernum became responsive to CO2 at both temperatures, whereas A. petiolata continued to respond to elevated CO2 only at high temperature. Elevated CO2 increased thickness and decreased nitrogen concentrations in leaves of both species. Alliaria petiolata showed photosynthetic downregulation at elevated CO2, whereas G. vernum photosynthesis increased at elevated temperature. Flavonoid and cyanide concentrations decreased significantly in A. petiolata leaves in the elevated CO2 and temperature treatment. Total glucosinolate concentrations and trypsin inhibitor activities did not vary among treatments. Future elevated spring temperatures and CO2 will interact to stimulate growth for A. petiolata and G. vernum, but there may be reduced allelochemical effects in A. petiolata.

Linkages between Snow Cover Seasonality, Terrain, and Land Surface Phenology in the Highland Pastures of Kyrgyzstan

NASA Astrophysics Data System (ADS)

Henebry, Geoffrey; Tomaszewska, Monika; Kelgenbaeva, Kamilya

2017-04-01

In the highlands of Kyrgyzstan, vertical transhumance is the foundation of montane agropastoralism. Terrain attributes, such as elevation, slope, and aspect, affect snow cover seasonality, which is a key influence on the timing of plant growth and forage availability. Our study areas include the highland pastures in Central Tien Shan mountains, specifically in the rayons of Naryn and At-Bashy in Naryn oblast, and Alay and Chong-Alay rayons in Osh oblast. To explore the linkages between snow cover seasonality and land surface phenology as modulated by terrain and variations in thermal time, we use 16 years (2001-2016) of Landsat surface reflectance data at 30 m resolution with MODIS land surface temperature and snow cover products at 1 km and 500 m resolution, respectively, and two digital elevation models, SRTM and ASTER GDEM. We model snow cover seasonality using frost degree-days and land surface phenology using growing degree-days as quadratic functions of thermal time: a convex quadratic (CxQ) model for land surface phenology and a concave quadratic (CvQ) model for snow cover seasonality. From the fitted parameter coefficients, we calculated phenometrics, including "peak height" and "thermal time to peak" for the CxQ models and "trough depth" and "thermal time to trough" for the CvQ models. We explore how these phenometrics change as a function of elevation and slope-aspect interactions and due to interannual variability. Further, we examine how snow cover duration and timing affects the subsequent peak height and thermal time to peak in wetter, drier, and normal years.

Surface-Wind Anomalies in North-Atlantic and North Pacific from SSM/I Observations: Influence on Temperature of Adjoining Land Regions

NASA Technical Reports Server (NTRS)

Otterman, Joseph; Atlas, R.; Ingraham, J.; Ardizzone, J.; Starr, D.; Terry, J.

1998-01-01

Surface winds over the oceans are derived from Special Sensor Microwave Imager (SSM/I) measurements, assigning direction by Variational Analysis Method (VAM). Validations by comparison with other measurements indicate highly-satisfactory data quality. Providing global coverage from 1988, the dataset is a convenient source for surface-wind climatology. In this study, the interannual variability of zonal winds is analyzed concentrating on the westerlies in North Atlantic and North Pacific, above 30 N. Interannual differences in the westerlies exceeding 10 m sec (exp -1) are observed over large regions, often accompanied by changes of the same magnitude in the easterlies below 30 N. We concentrate on February/March, since elevated temperatures, by advancing snow-melt, can produce early spring. The extremely strong westerlies in 1997 observed in these months over North Atlantic (and also North Pacific) apparently contributed to large surface-temperature anomalies in western Europe, on the order of +3 C above the climatic monthly average for England and France. At these latitudes strong positive anomalies extended in a ring around the globe. We formulated an Index of South westerlies for the North Atlantic, which can serve as an indicator for day-by-day advection effects into Europe. In comparing 1997 and 1998 with the previous years, we establish significant correlations with the temperature anomalies (one to five days later, depending on the region, and on the season). This variability of the ocean-surface winds and of the temperature anomalies on land may be related to the El Nino/La Nina oscillations. Such large temperature fluctuations over large areas, whatever the cause, can be regarded as noise in attempts to assess long-term trends in global temperature.

Unusual two-dimensional behavior of iron-based superconductors with low anisotropy

NASA Astrophysics Data System (ADS)

Kalenyuk, A. A.; Pagliero, A.; Borodianskyi, E. A.; Aswartham, S.; Wurmehl, S.; Büchner, B.; Chareev, D. A.; Kordyuk, A. A.; Krasnov, V. M.

2017-10-01

We study angular-dependent magnetoresistance in iron-based superconductors Ba1 -xNaxFe2As2 and FeTe1 -xSex . Both superconductors have relatively small anisotropies γ ˜2 and exhibit a three-dimensional (3D) behavior at low temperatures. However, we observe that they start to exhibit a profound two-dimensional behavior at elevated temperatures and in applied magnetic field parallel to the surface. We conclude that the unexpected two-dimensional (2D) behavior of the studied low-anisotropic superconductors is not related to layeredness of the materials, but is caused by appearance of surface superconductivity when magnetic field exceeds the upper critical field Hc 2(T ) for destruction of bulk superconductivity. We argue that the corresponding 3D-2D bulk-to-surface dimensional transition can be used for accurate determination of the upper critical field.

An assessment of The Effects of Elevation and Aspect on Deposition of Airborne Pollution and Water Quality in an Alpine Critical Zone: San Juan Mountains, Colorado, USA

NASA Astrophysics Data System (ADS)

Price, A.; Giardino, J. R.; Marcantonio, F.

2015-12-01

The alpine critical zone is affected by various inputs, storages, pathways, and outputs. Unfortunately, many of these processes distribute the pollutants beyond the immediate area and into the surrounding biological and anthropogenic communities. Years of mining and improper disposal of the tailings and acid-mine drainage have degraded the quality of surface water within the San Juan Mountains. However, mining may not be the only factor significantly affecting the surface water quality in this high-elevation environment. As a high elevation system, this area is a fragile ecosystem with inputs ranging from local mining to atmospheric transport and deposition. Studies from around the world have shown atmospheric transport and deposition affect high-elevation systems. Thus, a significant question arises: does elevation or aspect affect the volume and rate of atmospheric deposition of pollutants? We assume atmospheric deposition occurs on the slopes in addition to in streams, lakes, and ponds. Deposition on slopes can be transported to nearby surface waters and increase the impact of the atmospheric pollutants along with residence time. Atmospheric deposition data were collected for aluminum, iron, manganese, nitrate, phosphate, and sulfate. Water chemistry data were collected for the same constituents as the atmospheric deposition with the addition of temperature, dissolved oxygen, pH, and specific conductance. Deposition samples were collected on a five-day sampling regime during two summers. Water quality samples were collected in-stream adjacent to the deposition-ample collectors. Collection sites were located on opposite sides of Red Mountain at five equal elevations providing two different aspects. The north side is drained by Red Mountain Creek and the south side is drained by Mineral Creek. Differences in atmospheric deposition and water quality at different elevations and aspects suggest there is a relationship between aspect and elevation on atmospheric pollution deposition. It is suggested that degradation of water quality in the San Juan Mountains is affected by atmospheric deposition along with the damage sustained from local mining activities. These results facilitate a better understanding of this high-elevation critical-zone system.

Analysis and modelling of surface Urban Heat Island in 20 Canadian cities under climate and land-cover change.

PubMed

Gaur, Abhishek; Eichenbaum, Markus Kalev; Simonovic, Slobodan P

2018-01-15

Surface Urban Heat Island (SUHI) is an urban climate phenomenon that is expected to respond to future climate and land-use land-cover change. It is important to further our understanding of physical mechanisms that govern SUHI phenomenon to enhance our ability to model future SUHI characteristics under changing geophysical conditions. In this study, SUHI phenomenon is quantified and modelled at 20 cities distributed across Canada. By analyzing MODerate Resolution Imaging Spectroradiometer (MODIS) sensed surface temperature at the cities over 2002-2012, it is found that 16 out of 20 selected cities have experienced a positive SUHI phenomenon while 4 cities located in the prairies region and high elevation locations have experienced a negative SUHI phenomenon in the past. A statistically significant relationship between observed SUHI magnitude and city elevation is also recorded over the observational period. A Physical Scaling downscaling model is then validated and used to downscale future surface temperature projections from 3 GCMs and 2 extreme Representative Concentration Pathways in the urban and rural areas of the cities. Future changes in SUHI magnitudes between historical (2006-2015) and future timelines: 2030s (2026-2035), 2050s (2046-2055), and 2090s (2091-2100) are estimated. Analysis of future projected changes indicate that 15 (13) out of 20 cities can be expected to experience increases in SUHI magnitudes in future under RCP 2.6 (RCP 8.5). A statistically significant relationship between projected future SUHI change and current size of the cities is also obtained. The study highlights the role of city properties (i.e. its size, elevation, and surrounding land-cover) towards shaping their current and future SUHI characteristics. The results from this analysis will help decision-makers to manage Canadian cities more efficiently under rapidly changing geophysical and demographical conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Micro-mechanisms of Surface Defects Induced on Aluminum Alloys during Plastic Deformation at Elevated Temperatures

NASA Astrophysics Data System (ADS)

Gali, Olufisayo A.

Near-surface deformed layers developed on aluminum alloys significantly influence the corrosion and tribological behavior as well as reduce the surface quality of the rolled aluminum. The evolution of the near-surface microstructures induced on magnesium containing aluminum alloys during thermomechanical processing has been investigated with the aim generating an understanding of the influence of individual forming parameters on its evolution and examine the microstructure of the roll coating induced on the mating steel roll through material transfer during rolling. The micro-mechanisms related to the various features of near-surface microstructure developed during tribological conditions of the simulated hot rolling process were identified. Thermomechanical processing experiments were performed with the aid of hot rolling (operating temperature: 550 to 460 °C, 4, 10 and 20 rolling pass schedules) and hot forming (operating temperature: 350 to 545 °C, strain rate: 4 x 10-2 s-1) tribo-simulators. The surface, near-surface features and material transfer induced during the elevated temperature plastic deformation were examined and characterized employing optical interferometry, SEM/EDS, FIB and TEM. Near-surface features characterized on the rolled aluminum alloys included; cracks, fractured intermetallic particles, aluminum nano-particles, oxide decorated grain boundaries, rolled-in oxides, shingles and blisters. These features were related to various individual rolling parameters which included, the work roll roughness, which induced the formation of shingles, rolling marks and were responsible for the redistribution of surface oxide and the enhancements of the depth of the near-surface damage. The enhanced stresses and strains experienced during rolling were related to the formation and propagation of cracks, the nanocrystalline structure of the near-surface layers and aluminum nano-particles. The mechanism of the evolution of the near-surface microstructure were determined to include grain boundary sliding which induced the cracks at the surface and subsurface of the alloy, magnesium diffusion to free surfaces, crack propagation from shear stresses and the shear strains inducing the nanocrystalline grain structure, the formation of shingles by the shear deformation of micro-wedges induced by the work roll grooves, and the deformation of this oxide covered micro-wedges inducing the rolled-in oxides. Magnesium diffusion to free surfaces was identified as inducing crack healing due to the formation of MgO within cracks and was responsible for the oxide decorated grain boundaries. An examination of the roll coating revealed a complex layered microstructure that was induced through tribo-chemical and mechanical entrapment mechanisms. The microstructure of the roll coating suggested that the work roll material and the rolled aluminum alloy were essential in determining its composition and structure. Subsequent hot forming processes revealed the rich oxide-layer of the near-surface microstructure was beneficial for reducing the coefficient of friction during tribological contact with the steel die. Damage to the microstructure include cracks induced from grain boundary sliding of near-surface grains and the formation of oxide fibres within cracks of the near-surface deformed layers.

Evaporation/SST Sensitivity Over the Tropical Oceans During ENSO Events as Estimated from the da Silva, Young, Levitus Surface Marine Data Set

NASA Technical Reports Server (NTRS)

Robertson, F. R.; Fitzjarrald, D. E.; Sohn, B.-J.; Arnold, James E. (Technical Monitor)

2001-01-01

The da Silva, Young and Levitus Surface Marine Atlas, based on observations from the Comprehensive Ocean Atmosphere Data Set (COADS) Release 1, has been used to investigate the relationship between evaporation and sea-surface temperature (SST) over the global oceans. For the period 1950 to 1987 SST, surface latent heat flux, and other related variables have been filtered to minimize data uncertainties and to focus upon interannual variations associated with warm (El Nino) and cold (La Nina) ENSO events. Compositing procedures have enabled identification of systematic variations in latent heat fluxes accompanying these events and the relationship to spatial anomalies in ocean surface wind speed and humidity. The evaporation response associated with ENSO sea surface temperature (SST) variability is systematic in nature and composed of offsetting contributions from the surface wind and humidity variations. During warm events exceeding 1.0 S.D. delta SST, increases in the surface humidity deficit, delta(qs-qa), between the surface and 2m height dominate regions of positive SST anomalies and lead to increases in evaporation of almost 2 Wm (exp -2) at deltaSST = 0.23 K. Despite the increases in specific humidity, relative humidity decreases slightly in regions of elevated SSTs. For the most part, variations in wind speed are consistent with previous investigations. Weakening of the equatorial easterlies (and generation of westerlies) between 160 degrees E and 140 degrees W dominates during the early phases of warm events. Elevated wind speeds in adjacent subtropical regions and in the eastern equatorial Pacific subsequently develop too. The net contribution of these winds, which reflect adjustments in Hadley and Walker circulation components is toward reduced evaporation. Results for cold periods are approximately similar, but opposite in sign to warm events, though evidence of different temporal evolution is noted.

The coupled effects of environmental composition, temperature and contact size-scale on the tribology of molybdenum disulfide

NASA Astrophysics Data System (ADS)

Khare, Harmandeep S.

Liquid lubricants are precluded in an exceedingly large number of consumer as well as extreme applications as a means to reduce friction and wear at the sliding interface of two bodies. The extraterrestrial environment is one such example of an extreme environment which has motivated the development of advanced solid lubricant materials. Mechanical systems for space require fabrication, assembly, transportation and testing on earth before launch and deployment. Solid lubricants for space are expected to not only operate efficiently in the hard vacuum of space but also withstand interactions with moisture or oxygen during the terrestrial storage, transportation and assembly prior to deployment and launch. Molybdenum disulfide (MoS2) is considered the gold standard in solid lubricants for space due to its excellent tribological properties in ultra-high vacuum. However in the presence of environmental species such as water and oxygen or at elevated temperatures, the lubricity and endurance of MoS2 is severely limited. Past studies have offered several hypotheses for the breakdown of lubrication of MoS2 under the influence of water and oxygen, although exact mechanisms remain unknown. Furthermore, it is unclear if temperature acts as a driver solely for oxidation or for thermally activated slip and thermally activated desorption as well. The answers to these questions are of fundamental importance to improving the reliability of existing MoS2-based solid lubricants for space, as well as for guiding the design of advanced lamellar solid lubricant coatings. This dissertation aims to elucidate: (1) the role of water on MoS2 oxidation, (2) the role of water on MoS2 friction, (3) the role of oxygen on MoS2 friction, (4) the contribution of thermal activation to ambient-temperature friction, and (5) effects of length-scale. The results of this study showed that water does not cause oxidation of MoS2. Water increases ambient-temperature friction of MoS2 directly through a combination of both surface adsorption and diffusion into the coating subsurface. Thermally activated desiccation effectively dries the bulk of the coating, yielding low values of friction coefficient even at ambient humidity and temperature. Friction of MoS2 decreases with increasing temperature between 25°C and 100°C in the presence of environmental water and increases in the presence of oxygen alone. At temperatures greater than 100°C, friction generally increases with temperature only in the presence of environmental oxygen; at these elevated temperatures, friction decreases with increasing humidity. The transition from room-temperature increase to elevated-temperature decrease in friction with increasing humidity is found to be a strong function of the contact history as well as coating microstructure. Lastly, the contribution of nanoscale tribofilms to macroscale friction was studied through nanotribometry. Friction measured on the worn MoS2 coating with a nano-scale AFM probe showed direct and quantifiable evidence of sliding-induced surface modification of MoS2; friction measured on the perfectly ordered single crystal MoS2 was nearly an order of magnitude lower than friction on worn MoS2. Although friction coefficients measured with a nanoscale probe showed high surface sensitivity, micron-sized AFM probes gave friction coefficients similar to those obtained in the macroscale, suggesting the formation of surface films in-situ during sliding with the colloidal probe. A reduction in friction is observed after annealing for both the nanoscale and microscale probes, suggesting a strong overriding effect of the desiccated bulk over surface adsorption in driving the friction response at these length-scales.

Nitriding of super alloys for enhancing physical properties

DOEpatents

Purohit, A.

1984-06-25

The invention teaches the improvement of certain super alloys by exposing the alloy to an atmosphere of elemental nitrogen at elevated temperatures in excess of 750/sup 0/C but less than 1150/sup 0/C for an extended duration, viz., by nitriding the surface of the alloy, to establish barrier nitrides of the order of 25 to 100 micrometers thickness. These barrier

Nonlinear, interacting responses to climate limit grassland production under global change.

PubMed

Zhu, Kai; Chiariello, Nona R; Tobeck, Todd; Fukami, Tadashi; Field, Christopher B

2016-09-20

Global changes in climate, atmospheric composition, and pollutants are altering ecosystems and the goods and services they provide. Among approaches for predicting ecosystem responses, long-term observations and manipulative experiments can be powerful approaches for resolving single-factor and interactive effects of global changes on key metrics such as net primary production (NPP). Here we combine both approaches, developing multidimensional response surfaces for NPP based on the longest-running, best-replicated, most-multifactor global-change experiment at the ecosystem scale-a 17-y study of California grassland exposed to full-factorial warming, added precipitation, elevated CO2, and nitrogen deposition. Single-factor and interactive effects were not time-dependent, enabling us to analyze each year as a separate realization of the experiment and extract NPP as a continuous function of global-change factors. We found a ridge-shaped response surface in which NPP is humped (unimodal) in response to temperature and precipitation when CO2 and nitrogen are ambient, with peak NPP rising under elevated CO2 or nitrogen but also shifting to lower temperatures. Our results suggest that future climate change will push this ecosystem away from conditions that maximize NPP, but with large year-to-year variability.

Precursor-Surface Reactions in Plasma Deposition of Silicon Thin Films

NASA Astrophysics Data System (ADS)

Bakos, Tamas

2005-03-01

Device-quality hydrogenated amorphous silicon (a-Si:H) thin films are usually grown by plasma deposition under conditions where the SiH3 radical is the dominant deposition precursor. In this presentation, we report results of first-principles density functional theory calculations on the interactions of the SiH3 radical with the crystalline Si(100)-(2x1):H surface in conjunction with molecular-dynamics simulations of a-Si:H thin film growth by SiH3 radicals, which elucidate the pathways and energetics of surface reactions that govern important film properties. In particular, we show that an SiH3 radical can insert into strained surface Si-Si dimer bonds, abstract surface H through an Eley-Rideal mechanism, and passivate surface dangling bonds; these reactions follow exothermic and barrierless pathways that lead to a temperature-independent growth rate in agreement with experimental measurements. We also identify a thermally activated surface H abstraction process, in which the SiH3 radical diffuses through overcoordinated surface Si atoms until it encounters a favorable site for H abstraction; the diffusion and H-abstraction steps have commensurate activation barriers. This mechanism explains partly the reduction of the film H content at elevated substrate temperatures.

Life at extreme elevations on Atacama volcanoes: the closest thing to Mars on Earth?

PubMed

Schmidt, S K; Gendron, E M S; Vincent, K; Solon, A J; Sommers, P; Schubert, Z R; Vimercati, L; Porazinska, D L; Darcy, J L; Sowell, P

2018-03-20

Here we describe recent breakthroughs in our understanding of microbial life in dry volcanic tephra ("soil") that covers much of the surface area of the highest elevation volcanoes on Earth. Dry tephra above 6000 m.a.s.l. is perhaps the best Earth analog for the surface of Mars because these "soils" are acidic, extremely oligotrophic, exposed to a thin atmosphere, high UV fluxes, and extreme temperature fluctuations across the freezing point. The simple microbial communities found in these extreme sites have among the lowest alpha diversity of any known earthly ecosystem and contain bacteria and eukaryotes that are uniquely adapted to these extreme conditions. The most abundant eukaryotic organism across the highest elevation sites is a Naganishia species that is metabolically versatile, can withstand high levels of UV radiation and can grow at sub-zero temperatures, and during extreme diurnal freeze-thaw cycles (e.g. - 10 to + 30 °C). The most abundant bacterial phylotype at the highest dry sites sampled (6330 m.a.s.l. on Volcán Llullaillaco) belongs to the enigmatic B12-WMSP1 clade which is related to the Ktedonobacter/Thermosporothrix clade that includes versatile organisms with the largest known bacterial genomes. Close relatives of B12-WMSP1 are also found in fumarolic soils on Volcán Socompa and in oligotrophic, fumarolic caves on Mt. Erebus in Antarctica. In contrast to the extremely low diversity of dry tephra, fumaroles found at over 6000 m.a.s.l. on Volcán Socompa support very diverse microbial communities with alpha diversity levels rivalling those of low elevation temperate soils. Overall, the high-elevation biome of the Atacama region provides perhaps the best "natural experiment" in which to study microbial life in both its most extreme setting (dry tephra) and in one of its least extreme settings (fumarolic soils).

Effects of elevated temperature and CO2 concentration on photosynthesis of the alpine plants in Zoige Plateau, China

NASA Astrophysics Data System (ADS)

Zijuan, Zhou; Peixi, Su; Rui, Shi; Tingting, Xie

2017-04-01

Increasing temperature and carbon dioxide concentration are the important aspects of global climate change. Alpine ecosystem response to global change was more sensitive and rapid than other ecosystems. Increases in temperature and atmospheric CO2concentrations have strong impacts on plant physiology. Photosynthesis is the basis for plant growth and the decisive factor for the level of productivity, and also is a very sensitive physiological process to climate change. In this study, we examined the interactive effects of elevated temperature and atmospheric CO2 concentration on the light response of photosynthesis in two alpine plants Elymus nutans and Potentilla anserine, which were widely distributed in alpine meadow in the Zoige Plateau, China. We set up as follows: the control (Ta 20˚ C, CO2 380μmolṡmol-1), elevated temperature (Ta 25˚ C, CO2 380 μmolṡmol-1), elevated CO2 concentration (Ta 20˚ C, CO2 700μmolṡmol-1), elevated temperature and CO2 concentration (Ta 25˚ C, CO2 700μmolṡmol-1). The results showed that compared to P. anserine, E. nutans had a higher maximum net photosynthetic rate (Pnmax), light saturation point (LSP) and apparent quantum yield (AQY) in the control. Elevated temperature increased the Pnmaxand LSP values in P. anserine, while Pnmaxand LSP were decreased in E. nutans. Elevated CO2 increased the Pnmaxand LSP values in E. nutans and P. anserine, while the light compensation point (LCP) decreased; Elevated both temperature and CO2, the Pnmaxand LSP were all increased for E. nutans and P. anserine, but did not significantly affect AQY. We concluded that although elevated temperature had a photoinhibition for E. nutans, the interaction of short-term elevated CO2 concentration and temperature can improve the photosynthetic capacity of alpine plants. Key Words: elevated temperature; CO2 concentration; light response; alpine plants

Coupling between diffusion and orientation of pentacene molecules on an organic surface.

PubMed

Rotter, Paul; Lechner, Barbara A J; Morherr, Antonia; Chisnall, David M; Ward, David J; Jardine, Andrew P; Ellis, John; Allison, William; Eckhardt, Bruno; Witte, Gregor

2016-04-01

The realization of efficient organic electronic devices requires the controlled preparation of molecular thin films and heterostructures. As top-down structuring methods such as lithography cannot be applied to van der Waals bound materials, surface diffusion becomes a structure-determining factor that requires microscopic understanding. Scanning probe techniques provide atomic resolution, but are limited to observations of slow movements, and therefore constrained to low temperatures. In contrast, the helium-3 spin-echo (HeSE) technique achieves spatial and time resolution on the nm and ps scale, respectively, thus enabling measurements at elevated temperatures. Here we use HeSE to unveil the intricate motion of pentacene admolecules diffusing on a chemisorbed monolayer of pentacene on Cu(110) that serves as a stable, well-ordered organic model surface. We find that pentacene moves along rails parallel and perpendicular to the surface molecules. The experimental data are explained by admolecule rotation that enables a switching between diffusion directions, which extends our molecular level understanding of diffusion in complex organic systems.

Substrate temperature dependence of ZnTe epilayers grown on GaAs(0 0 1) by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Zhao, Jie; Zeng, Yiping; Liu, Chao; Li, Yanbo

2010-04-01

ZnTe thin films have been grown on GaAs(0 0 1) substrates at different temperatures with constant Zn and Te beam equivalent pressures (BEPs) by molecular beam epitaxy (MBE). In situ reflection high-energy electron diffraction (RHEED) observation indicates that two-dimensional (2D) growth mode can be established after around one-minute three-dimensional (3D) nucleation by increasing the substrate temperature to 340 °C. We found that Zn desorption from the ZnTe surface is much greater than that of Te at higher temperatures, and estimated the Zn sticking coefficient by the evolution of growth rate. The Zn sticking coefficient decreases from 0.93 to 0.58 as the temperature is elevated from 320 to 400 °C. The ZnTe epilayer grown at 360 °C displays the narrowest full-width at half-maximum (FWHM) of 660 arcsec from (0 0 4) reflection in double-crystal X-ray rocking curve (DCXRC) measurements. The surface morphology of ZnTe epilayers is strongly dependent on the substrate temperature, and the root-mean-square (RMS) roughness diminishes drastically with the increase in temperature.

Needle metabolome, freezing tolerance and gas exchange in Norway spruce seedlings exposed to elevated temperature and ozone concentration.

PubMed

Riikonen, Johanna; Kontunen-Soppela, Sari; Ossipov, Vladimir; Tervahauta, Arja; Tuomainen, Marjo; Oksanen, Elina; Vapaavuori, Elina; Heinonen, Jaakko; Kivimäenpää, Minna

2012-09-01

Northern forests are currently experiencing increasing mean temperatures, especially during autumn and spring. Consequently, alterations in carbon sequestration, leaf biochemical quality and freezing tolerance (FT) are likely to occur. The interactive effects of elevated temperature and ozone (O(3)), the most harmful phytotoxic air pollutant, on Norway spruce (Picea abies (L.) Karst.) seedlings were studied by analysing phenology, metabolite concentrations in the needles, FT and gas exchange. Sampling was performed in September and May. The seedlings were exposed to a year-round elevated temperature (+1.3 °C), and to 1.4× ambient O(3) concentration during the growing season in the field. Elevated temperature increased the concentrations of amino acids, organic acids of the citric acid cycle and some carbohydrates, and reduced the concentrations of phenolic compounds, some organic acids of the shikimic acid pathway, sucrose, cyclitols and steroids, depending on the timing of the sampling. Although growth onset occurred earlier at elevated temperature, the temperature of 50% lethality (LT(50)) was similar in the treatments. Photosynthesis and the ratio of photosynthesis to dark respiration were reduced by elevated temperature. Elevated concentrations of O(3) reduced the total concentration of soluble sugars, and tended to reduce LT(50) of the needles in September. These results show that alterations in needle chemical quality can be expected at elevated temperatures, but the seedlings' sensitivity to autumn and spring frosts is not altered. Elevated O(3) has the potential to disturb cold hardening of Norway spruce seedlings in autumn, and to alter the water balance of the seedling through changes in stomatal conductance (g(s)), while elevated temperature is likely to reduce g(s) and consequently reduce the O(3)-flux inside the leaves.

Holocene thinning of the Greenland ice sheet.

PubMed

Vinther, B M; Buchardt, S L; Clausen, H B; Dahl-Jensen, D; Johnsen, S J; Fisher, D A; Koerner, R M; Raynaud, D; Lipenkov, V; Andersen, K K; Blunier, T; Rasmussen, S O; Steffensen, J P; Svensson, A M

2009-09-17

On entering an era of global warming, the stability of the Greenland ice sheet (GIS) is an important concern, especially in the light of new evidence of rapidly changing flow and melt conditions at the GIS margins. Studying the response of the GIS to past climatic change may help to advance our understanding of GIS dynamics. The previous interpretation of evidence from stable isotopes (delta(18)O) in water from GIS ice cores was that Holocene climate variability on the GIS differed spatially and that a consistent Holocene climate optimum-the unusually warm period from about 9,000 to 6,000 years ago found in many northern-latitude palaeoclimate records-did not exist. Here we extract both the Greenland Holocene temperature history and the evolution of GIS surface elevation at four GIS locations. We achieve this by comparing delta(18)O from GIS ice cores with delta(18)O from ice cores from small marginal icecaps. Contrary to the earlier interpretation of delta(18)O evidence from ice cores, our new temperature history reveals a pronounced Holocene climatic optimum in Greenland coinciding with maximum thinning near the GIS margins. Our delta(18)O-based results are corroborated by the air content of ice cores, a proxy for surface elevation. State-of-the-art ice sheet models are generally found to be underestimating the extent and changes in GIS elevation and area; our findings may help to improve the ability of models to reproduce the GIS response to Holocene climate.

Elevated seawater temperature, not pCO2, negatively affects post-spawning adult mussels (Mytilus edulis) under food limitation.

PubMed

Clements, Jeff C; Hicks, Carla; Tremblay, Réjan; Comeau, Luc A

2018-01-01

Pre-spawning blue mussels ( Mytilus edulis ) appear sensitive to elevated temperature and robust to elevated p CO 2 ; however, the effects of these stressors soon after investing energy into spawning remain unknown. Furthermore, while studies suggest that elevated p CO 2 affects the byssal attachment strength of Mytilus trossulus from southern latitudes, p CO 2 and temperature impacts on the byssus strength of other species at higher latitudes remain undocumented. In a 90 day laboratory experiment, we exposed post-spawning adult blue mussels ( M. edulis ) from Atlantic Canada to three p CO 2 levels ( p CO 2 ~625, 1295 and 2440 μatm) at two different temperatures (16°C and 22°C) and assessed energetic reserves on Day 90, byssal attachment strength on Days 30 and 60, and condition index and mortality on Days 30, 60 and 90. Results indicated that glycogen content was negatively affected under elevated temperature, but protein, lipid, and overall energy content were unaffected. Reduced glycogen content under elevated temperature was associated with reduced condition index, reduced byssal thread attachment strength, and increased mortality; elevated p CO 2 had no effects. Overall, these results suggest that the glycogen reserves of post-spawning adult M. edulis are sensitive to elevated temperature, and can result in reduced health and byssal attachment strength, leading to increased mortality. These results are similar to those reported for pre-spawning mussels and suggest that post-spawning blue mussels are tolerant to elevated p CO 2 and sensitive to elevated temperature. In contrast to previous studies, however, elevated pCO 2 did not affect byssus strength, suggesting that negative effects of elevated p CO 2 on byssus strength are not universal.

To Demonstrate an Integrated Solution for Plasma-Material Interfaces Compatible with an Optimized Core Plasma

NASA Astrophysics Data System (ADS)

Goldston, Robert; Brooks, Jeffrey; Hubbard, Amanda; Leonard, Anthony; Lipschultz, Bruce; Maingi, Rajesh; Ulrickson, Michael; Whyte, Dennis

2009-11-01

The plasma facing components in a Demo reactor will face much more extreme boundary plasma conditions and operating requirements than any present or planned experiment. These include 1) Power density a factor of four or more greater than in ITER, 2) Continuous operation resulting in annual energy and particle throughput 100-200 times larger than ITER, 3) Elevated surface operating temperature for efficient electricity production, 4) Tritium fuel cycle control for safety and breeding requirements, and 5) Steady state plasma confinement and control. Consistent with ReNeW Thrust 12, design options are being explored for a new moderate-scale facility to assess core-edge interaction issues and solutions. Key desired features include high power density, sufficient pulse length and duty cycle, elevated wall temperature, steady-state control of an optimized core plasma, and flexibility in changing boundary components as well as access for comprehensive measurements.

Ultrahigh Oxidation Resistance and High Electrical Conductivity in Copper-Silver Powder.

PubMed

Li, Jiaxiang; Li, Yunping; Wang, Zhongchang; Bian, Huakang; Hou, Yuhang; Wang, Fenglin; Xu, Guofu; Liu, Bin; Liu, Yong

2016-12-22

The electrical conductivity of pure Cu powder is typically deteriorated at elevated temperatures due to the oxidation by forming non-conducting oxides on surface, while enhancing oxidation resistance via alloying is often accompanied by a drastic decline of electrical conductivity. Obtaining Cu powder with both a high electrical conductivity and a high oxidation resistance represents one of the key challenges in developing next-generation electrical transferring powder. Here, we fabricate a Cu-Ag powder with a continuous Ag network along grain boundaries of Cu particles and demonstrate that this new structure can inhibit the preferential oxidation in grain boundaries at elevated temperatures. As a result, the Cu-Ag powder displays considerably high electrical conductivity and high oxidation resistance up to approximately 300 °C, which are markedly higher than that of pure Cu powder. This study paves a new pathway for developing novel Cu powders with much enhanced electrical conductivity and oxidation resistance in service.

A Bacterial Pathogen Displaying Temperature-Enhanced Virulence of the Microalga Emiliania huxleyi

PubMed Central

Mayers, Teaghan J.; Bramucci, Anna R.; Yakimovich, Kurt M.; Case, Rebecca J.

2016-01-01

Emiliania huxleyi is a globally abundant microalga that plays a significant role in biogeochemical cycles. Over the next century, sea surface temperatures are predicted to increase drastically, which will likely have significant effects on the survival and ecology of E. huxleyi. In a warming ocean, this microalga may become increasingly vulnerable to pathogens, particularly those with temperature-dependent virulence. Ruegeria is a genus of Rhodobacteraceae whose population size tracks that of E. huxleyi throughout the alga’s bloom–bust lifecycle. A representative of this genus, Ruegeria sp. R11, is known to cause bleaching disease in a red macroalga at elevated temperatures. To investigate if the pathogenicity of R11 extends to microalgae, it was co-cultured with several cell types of E. huxleyi near the alga’s optimum (18°C), and at an elevated temperature (25°C) known to induce virulence in R11. The algal populations were monitored using flow cytometry and pulse-amplitude modulated fluorometry. Cultures of algae without bacteria remained healthy at 18°C, but lower cell counts in control cultures at 25°C indicated some stress at the elevated temperature. Both the C (coccolith-bearing) and S (scale-bearing swarming) cell types of E. huxleyi experienced a rapid decline resulting in apparent death when co-cultured with R11 at 25°C, but had no effect on N (naked) cell type at either temperature. R11 had no initial negative impact on C and S type E. huxleyi population size or health at 18°C, but caused death in older co-cultures. This differential effect of R11 on its host at 18 and 25°C suggest it is a temperature-enhanced opportunistic pathogen of E. huxleyi. We also detected caspase-like activity in dying C type cells co-cultured with R11, which suggests that programmed cell death plays a role in the death of E. huxleyi triggered by R11 – a mechanism induced by viruses (EhVs) and implicated in E. huxleyi bloom collapse. Given that E. huxleyi has recently been shown to have acquired resistance against EhVs at elevated temperature, bacterial pathogens with temperature-dependent virulence, such as R11, may become much more important in the ecology of E. huxleyi in a warming climate. PMID:27379036

A Bacterial Pathogen Displaying Temperature-Enhanced Virulence of the Microalga Emiliania huxleyi.

PubMed

Mayers, Teaghan J; Bramucci, Anna R; Yakimovich, Kurt M; Case, Rebecca J

2016-01-01

Emiliania huxleyi is a globally abundant microalga that plays a significant role in biogeochemical cycles. Over the next century, sea surface temperatures are predicted to increase drastically, which will likely have significant effects on the survival and ecology of E. huxleyi. In a warming ocean, this microalga may become increasingly vulnerable to pathogens, particularly those with temperature-dependent virulence. Ruegeria is a genus of Rhodobacteraceae whose population size tracks that of E. huxleyi throughout the alga's bloom-bust lifecycle. A representative of this genus, Ruegeria sp. R11, is known to cause bleaching disease in a red macroalga at elevated temperatures. To investigate if the pathogenicity of R11 extends to microalgae, it was co-cultured with several cell types of E. huxleyi near the alga's optimum (18°C), and at an elevated temperature (25°C) known to induce virulence in R11. The algal populations were monitored using flow cytometry and pulse-amplitude modulated fluorometry. Cultures of algae without bacteria remained healthy at 18°C, but lower cell counts in control cultures at 25°C indicated some stress at the elevated temperature. Both the C (coccolith-bearing) and S (scale-bearing swarming) cell types of E. huxleyi experienced a rapid decline resulting in apparent death when co-cultured with R11 at 25°C, but had no effect on N (naked) cell type at either temperature. R11 had no initial negative impact on C and S type E. huxleyi population size or health at 18°C, but caused death in older co-cultures. This differential effect of R11 on its host at 18 and 25°C suggest it is a temperature-enhanced opportunistic pathogen of E. huxleyi. We also detected caspase-like activity in dying C type cells co-cultured with R11, which suggests that programmed cell death plays a role in the death of E. huxleyi triggered by R11 - a mechanism induced by viruses (EhVs) and implicated in E. huxleyi bloom collapse. Given that E. huxleyi has recently been shown to have acquired resistance against EhVs at elevated temperature, bacterial pathogens with temperature-dependent virulence, such as R11, may become much more important in the ecology of E. huxleyi in a warming climate.

Using Selective Drainage Methods to Extract Continuous Surface Flow from 1-Meter Lidar-Derived Digital Elevation Data

USGS Publications Warehouse

Poppenga, Sandra K.; Worstell, Bruce B.; Stoker, Jason M.; Greenlee, Susan K.

2010-01-01

Digital elevation data commonly are used to extract surface flow features. One source for high-resolution elevation data is light detection and ranging (lidar). Lidar can capture a vast amount of topographic detail because of its fine-scale ability to digitally capture the surface of the earth. Because elevation is a key factor in extracting surface flow features, high-resolution lidar-derived digital elevation models (DEMs) provide the detail needed to consistently integrate hydrography with elevation, land cover, structures, and other geospatial features. The U.S. Geological Survey has developed selective drainage methods to extract continuous surface flow from high-resolution lidar-derived digital elevation data. The lidar-derived continuous surface flow network contains valuable information for water resource management involving flood hazard mapping, flood inundation, and coastal erosion. DEMs used in hydrologic applications typically are processed to remove depressions by filling them. High-resolution DEMs derived from lidar can capture much more detail of the land surface than courser elevation data. Therefore, high-resolution DEMs contain more depressions because of obstructions such as roads, railroads, and other elevated structures. The filling of these depressions can significantly affect the DEM-derived surface flow routing and terrain characteristics in an adverse way. In this report, selective draining methods that modify the elevation surface to drain a depression through an obstruction are presented. If such obstructions are not removed from the elevation data, the filling of depressions to create continuous surface flow can cause the flow to spill over an obstruction in the wrong location. Using this modified elevation surface improves the quality of derived surface flow and retains more of the true surface characteristics by correcting large filled depressions. A reliable flow surface is necessary for deriving a consistently connected drainage network, which is important in understanding surface water movement and developing applications for surface water runoff, flood inundation, and erosion. Improved methods are needed to extract continuous surface flow features from high-resolution elevation data based on lidar.

Daily temperature records from a mesonet in the foothills of the Canadian Rocky Mountains, 2005-2010

NASA Astrophysics Data System (ADS)

Wood, Wendy H.; Marshall, Shawn J.; Whitehead, Terri L.; Fargey, Shannon E.

2018-03-01

Near-surface air temperatures were monitored from 2005 to 2010 in a mesoscale network of 230 sites in the foothills of the Rocky Mountains in southwestern Alberta, Canada. The monitoring network covers a range of elevations from 890 to 2880 m above sea level and an area of about 18 000 km2, sampling a variety of topographic settings and surface environments with an average spatial density of one station per 78 km2. This paper presents the multiyear temperature dataset from this study, with minimum, maximum, and mean daily temperature data available at https://doi.org/10.1594/PANGAEA.880611. In this paper, we describe the quality control and processing methods used to clean and filter the data and assess its accuracy. Overall data coverage for the study period is 91 %. We introduce a weather-system-dependent gap-filling technique to estimate the missing 9 % of data. Monthly and seasonal distributions of minimum, maximum, and mean daily temperature lapse rates are shown for the region.

A Two-Dimensional Liquid Structure Explains the Elevated Melting Temperatures of Gallium Nanoclusters.

PubMed

Steenbergen, Krista G; Gaston, Nicola

2016-01-13

Melting in finite-sized materials differs in two ways from the solid-liquid phase transition in bulk systems. First, there is an inherent scaling of the melting temperature below that of the bulk, known as melting point depression. Second, at small sizes changes in melting temperature become nonmonotonic and show a size-dependence that is sensitive to the structure of the particle. Melting temperatures that exceed those of the bulk material have been shown to occur for a very limited range of nanoclusters, including gallium, but have still never been ascribed a convincing physical explanation. Here, we analyze the structure of the liquid phase in gallium clusters based on molecular dynamics simulations that reproduce the greater-than-bulk melting behavior observed in experiments. We observe persistent nonspherical shape distortion indicating a stabilization of the surface, which invalidates the paradigm of melting point depression. This shape distortion suggests that the surface acts as a constraint on the liquid state that lowers its entropy relative to that of the bulk liquid and thus raises the melting temperature.

Antarctic Firn Compaction Rates from Repeat-Track Airborne Radar Data: I. Methods

NASA Technical Reports Server (NTRS)

Medley, B.; Ligtenberg, S. R. M.; Joughin, I.; Van Den Broeke, M. R.; Gogineni, S.; Nowicki, S.

2015-01-01

While measurements of ice-sheet surface elevation change are increasingly used to assess mass change, the processes that control the elevation fluctuations not related to ice-flow dynamics (e.g. firn compaction and accumulation) remain difficult to measure. Here we use radar data from the Thwaites Glacier (West Antarctica) catchment to measure the rate of thickness change between horizons of constant age over different time intervals: 2009-10, 2010-11 and 2009-11. The average compaction rate to approximately 25m depth is 0.33ma(exp -1), with largest compaction rates near the surface. Our measurements indicate that the accumulation rate controls much of the spatio-temporal variations in the compaction rate while the role of temperature is unclear due to a lack of measurements. Based on a semi-empirical, steady-state densification model, we find that surveying older firn horizons minimizes the potential bias resulting from the variable depth of the constant age horizon. Our results suggest that the spatiotemporal variations in the firn compaction rate are an important consideration when converting surface elevation change to ice mass change. Compaction rates varied by up to 0.12ma(exp -1) over distances less than 6km and were on average greater than 20% larger during the 2010-11 interval than during 2009-10.

Differential in surface elevation change across mangrove forests in the intertidal zone

NASA Astrophysics Data System (ADS)

Fu, Haifeng; Wang, Wenqing; Ma, Wei; Wang, Mao

2018-07-01

A better understanding of surface elevation changes in different mangrove forests would improve our predictions of sea-level rise impacts, not only upon mangrove species distributions in the intertidal zone, but also on the functioning of these wetlands. Here, a two-year (2015-2017) dataset derived from 18 RSET-MH (rod surface elevation table-marker horizon) stations at Dongzhaigang Bay, Hainan, China, was analyzed to investigate how surface elevation changes differed across mangrove species zones. The current SET data indicated a rather high rate (9.6 mm y-1, on average) of surface elevation gain that was mostly consistent with that (8.1 mm y-1, on average) inferred from either the 137Cs or 210Pb dating of sediment cores. In addition, these surface elevation changes were sensitive to elevation in the intertidal zone and differed significantly between the two study sites (Sanjiang and Houpai). Mangrove species inhabiting the lower intertidal zone tended to experience greater surface elevation change at Sanjiang, which agrees with the general view that sedimentation and elevation gains are driven by elevation in the intertidal zone (i.e., greater when positioned lower in the intertidal profile). However, at Houpai, both surface elevation change and surface accretion showed the opposite trend (i.e., greater when positioned higher in the intertidal profile). This study's results indicate that the pattern of surface elevation changes across the intertidal profile maybe inconsistent due to intricate biophysical controls. Therefore, instead of using a constant rate, models should presume a topography that evolves at differing rates of surface elevation change in different species zones across the intertidal profile when predicting the impacts of sea-level rise on mangrove distributions.

Tolerance to Elevated Temperature and Ocean Acidification of the Larvae of the Solitary Corals Fungia fungites (Linnaues, 1758) and Lithophyllon repanda (Dana, 1846).

PubMed

Baria, Maria Vanessa B; Kurihara, Haruko; Harii, Saki

2015-10-01

Increase in atmospheric CO₂is the main driver of global climate change and is projected to elevate sea surface temperature by at least 2°C and to decrease oceanic pH by 0.3 to 0.4 units by the end of the century. These factors seriously threaten coral reef ecosystems worldwide. In Okinawa, solitary corals are an important feature of the coral community structure. While previous studies on the effects of ocean warming (OW), ocean acidification (OA) and its combination on larval survival focused on colonial coral species, the present study assessed the effect of high temperature on larvae from solitary corals. In this study, we examined the influence of OW (control = 28°C; control +3 = 31°C; control + 6 = 34°C) and OA (control, pCO₂= 400 to 500 μatm; medium, pCO₂= 1000 to 1300 μatm; high, pCO₂= 1700 to 2200 μatm) on the larval survival of two solitary corals, Fungia fungites and Lithophyllon repanda for eight days. Results showed that F. fungites was neither affected by OW, OA, nor its combination. Similarly, survival of L. repanda was not affected by OA however it was significantly affected by temperature. Temperature tolerance varies between species; L. repanda (+3°C above ambient) has lower tolerance than F. fungites (+6°C above ambient). This observation suggests that fungiid larvae had higher tolerance to elevated temperature stress relative to other scleractinian corals. With the projected increase in OW and OA in the future, fungiidsmay retain good potential to widely disperse and successfully recruit to natal and other neighbouring reefs.

The influence of glacier ice temperature on the long-term evolution of longitudinal valley profiles: Can a landscape escape from the "glacial buzzsaw"?

NASA Astrophysics Data System (ADS)

Dühnforth, M.; Anderson, R. S.; Colgan, W.

2012-04-01

The long-term pattern of glacial erosion in alpine valleys leads to characteristic longitudinal valley profiles. While landscape evolution models commonly take glacier sliding velocity to be the dominant control on erosion, the influence of spatial and temporal variations in glacier ice temperature on the efficiency of erosion over long timescales (>1 Ma) remains largely unexplored. Yet, the thermal field of a glacier can strongly influence the pattern of sliding. Temperate glaciers, with basal temperatures at the pressure melting point (PMP), slide whenever and wherever the glacial hydrology produces high water pressures. In contrast, in polythermal glaciers, erosion efficiency is strongly linked to basal ice temperature; when and where basal ice temperatures are below the PMP sliding, and hence erosion, are limited. We present results from numerical models in which we explore the influence of variations in glacier ice temperature on long-term glacial erosion processes in alpine valleys. These simulations are motivated by the persistent appeal of geomorphologists to polar glacial conditions to explain sites of unusually low glacial erosion rates. We employ a transient 1D (flowline) ice flow model that numerically solves the continuity equation for ice, and includes a depth-averaged approximation for longitudinal coupling stress. We prescribe separate winter and summer surface mass balance profiles: a capped elevation-dependent snowfall pattern in winter, and we capture both daily and seasonal oscillations in ablation using a positive degree day algorithm in summer. The steady-state ice temperature within the glacier is calculated using the conventional 2D (cross-sectional) heat equation (i.e. diffusion, advection and production terms) at a prescribed interval. The ice temperature model uses the surface temperature at the end of each melt season as the surface boundary condition, and a prescribed geothermal gradient as the basal boundary condition. Basal sliding is limited to sites where the basal ice is at the PMP. Glacial erosion rate is parameterized as a function of sliding velocity, which in turn depends upon a flotation fraction that is parameterized to account for annual variations in the glacial hydrologic system. We explore the long-term glacial erosion pattern when the landscape is subjected to different rock uplift rates, and to climates ranging from continental to maritime. Of specific interest to us are conditions that favor polythermal glaciers in which the basal ice at high elevations becomes cold. In such cases, rock uplift can outpace limited glacial erosion, allowing high peaks to escape from the "glacial buzzsaw" while basal ice at lower elevations remains at the PMP, allowing sliding and erosion. These simulations also allow a more formal assessment of the conditions under which cold basal ice can be invoked to explain low glacial erosion rates, and the conditions under which variations in rock erodibility may instead be invoked as the major control on erosion.

Ullmann-type coupling of brominated tetrathienoanthracene on copper and silver

NASA Astrophysics Data System (ADS)

Gutzler, Rico; Cardenas, Luis; Lipton-Duffin, Josh; El Garah, Mohamed; Dinca, Laurentiu E.; Szakacs, Csaba E.; Fu, Chaoying; Gallagher, Mark; Vondráček, Martin; Rybachuk, Maksym; Perepichka, Dmitrii F.; Rosei, Federico

2014-02-01

We report the synthesis of extended two-dimensional organic networks on Cu(111), Ag(111), Cu(110), and Ag(110) from thiophene-based molecules. A combination of scanning tunnelling microscopy and X-ray photoemission spectroscopy yields insight into the reaction pathways from single molecules towards the formation of two-dimensional organometallic and polymeric structures via Ullmann reaction dehalogenation and C-C coupling. The thermal stability of the molecular networks is probed by annealing at elevated temperatures of up to 500 °C. On Cu(111) only organometallic structures are formed, while on Ag(111) both organometallic and covalent polymeric networks were found to coexist. The ratio between organometallic and covalent bonds could be controlled by means of the annealing temperature. The thiophene moieties start degrading at 200 °C on the copper surface, whereas on silver the degradation process becomes significant only at 400 °C. Our work reveals how the interplay of a specific surface type and temperature steers the formation of organometallic and polymeric networks and describes how these factors influence the structural integrity of two-dimensional organic networks.We report the synthesis of extended two-dimensional organic networks on Cu(111), Ag(111), Cu(110), and Ag(110) from thiophene-based molecules. A combination of scanning tunnelling microscopy and X-ray photoemission spectroscopy yields insight into the reaction pathways from single molecules towards the formation of two-dimensional organometallic and polymeric structures via Ullmann reaction dehalogenation and C-C coupling. The thermal stability of the molecular networks is probed by annealing at elevated temperatures of up to 500 °C. On Cu(111) only organometallic structures are formed, while on Ag(111) both organometallic and covalent polymeric networks were found to coexist. The ratio between organometallic and covalent bonds could be controlled by means of the annealing temperature. The thiophene moieties start degrading at 200 °C on the copper surface, whereas on silver the degradation process becomes significant only at 400 °C. Our work reveals how the interplay of a specific surface type and temperature steers the formation of organometallic and polymeric networks and describes how these factors influence the structural integrity of two-dimensional organic networks. Electronic supplementary information (ESI) available: Additional STM data and DFT results. See DOI: 10.1039/c3nr05710k

Wetter subtropics in a warmer world: Contrasting past and future hydrological cycles

NASA Astrophysics Data System (ADS)

Burls, Natalie J.; Fedorov, Alexey V.

2017-12-01

During the warm Miocene and Pliocene Epochs, vast subtropical regions had enough precipitation to support rich vegetation and fauna. Only with global cooling and the onset of glacial cycles some 3 Mya, toward the end of the Pliocene, did the broad patterns of arid and semiarid subtropical regions become fully developed. However, current projections of future global warming caused by CO2 rise generally suggest the intensification of dry conditions over these subtropical regions, rather than the return to a wetter state. What makes future projections different from these past warm climates? Here, we investigate this question by comparing a typical quadrupling-of-CO2 experiment with a simulation driven by sea-surface temperatures closely resembling available reconstructions for the early Pliocene. Based on these two experiments and a suite of other perturbed climate simulations, we argue that this puzzle is explained by weaker atmospheric circulation in response to the different ocean surface temperature patterns of the Pliocene, specifically reduced meridional and zonal temperature gradients. Thus, our results highlight that accurately predicting the response of the hydrological cycle to global warming requires predicting not only how global mean temperature responds to elevated CO2 forcing (climate sensitivity) but also accurately quantifying how meridional sea-surface temperature patterns will change (structural climate sensitivity).

Improving Simulations of Precipitation Phase and Snowpack at a Site Subject to Cold Air Intrusions: Snoqualmie Pass, WA

NASA Astrophysics Data System (ADS)

Wayand, N. E.; Stimberis, J.; Zagrodnik, J.; Mass, C.; Lundquist, J. D.

2016-12-01

Low-level cold air from eastern Washington state often flows westward through mountain passes in the Washington Cascades, creating localized inversions and locally reducing climatological temperatures. The persistence of this inversion during a frontal passage can result in complex patterns of snow and rain that are difficult to predict. Yet, these predictions are critical to support highway avalanche control, ski resort operations, and modeling of headwater snowpack storage. In this study we used observations of precipitation phase from a disdrometer and snow depth sensors across Snoqualmie Pass, WA, to evaluate surface-air-temperature-based and mesoscale-model-based predictions of precipitation phase during the anomalously warm 2014-2015 winter. The skill of surface-based methods was greatly improved by using air temperature from a nearby higher-elevation station, which was less impacted by low-level inversions. Alternatively, we found a hybrid method that combines surface-based predictions with output from the Weather Research and Forecasting mesoscale model to have improved skill over both parent models. These results suggest that prediction of precipitation phase in mountain passes can be improved by incorporating observations or models from above the surface layer.

Comparing Wavelengths

NASA Image and Video Library

2015-12-12

This side-by-side rendering of the Sun at the same time in two different wavelengths of extreme ultraviolet light helps to visualize the differing features visible in each wavelength (Dec. 10-11, 2015). Most prominently, we can see much finer strands of plasma looping above the surface in the 171 Angstrom wavelength (gold) than in the 304 Angstrom wavelength (red), which captures cooler plasma closer to the Sun's surface. SDO observes the Sun in 10 different wavelengths with each one capturing somewhat different features at various temperatures and elevations above the Sun. http://photojournal.jpl.nasa.gov/catalog/PIA20214

Tensile testing apparatus

NASA Technical Reports Server (NTRS)

Blackburn, L. B.; Ellingsworth, J. R. (Inventor)

1985-01-01

An improved mechanical extensometer is described for use with a constant load creep test machine. The dead weight of the extensometer is counterbalanced by two pairs of weights connected through a pulley system and to rod extension and leading into the furnace where the test sample is undergoing elevated temperature (above 500 F.) tensile testing. Novel gripper surfaces, conical tip and flat surface are provided in each sampling engaging platens to reduce the grip pressure normally required for attachment of the extensometer to the specimen and reduce initial specimen bending normally associated with foil-gage metal testing.

Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components. [examined with a scanning electron microscope

NASA Technical Reports Server (NTRS)

Campbell, J. E.

1974-01-01

The uses of scanning electron microscopy in assessing changes that occur in spores exposed to wet and dry heat cycles at elevated temperatures were examined. Several species of Bacillus and other nonspore-forming species of organisms were used for the experiment. Surface morphology of viable and nonviable organisms was clearly detectable by this method, making it a potentially useful technique for investigating microbial inactivation on space vehicle surfaces and components. Micrographs of the spores and bacterial cells are provided.

Simulating potential structural and operational changes for Detroit Dam on the North Santiam River, Oregon, for downstream temperature management

USGS Publications Warehouse

Buccola, Norman L.; Rounds, Stewart A.; Sullivan, Annett B.; Risley, John C.

2012-01-01

Detroit Dam was constructed in 1953 on the North Santiam River in western Oregon and resulted in the formation of Detroit Lake. With a full-pool storage volume of 455,100 acre-feet and a dam height of 463 feet, Detroit Lake is one of the largest and most important reservoirs in the Willamette River basin in terms of power generation, recreation, and water storage and releases. The U.S. Army Corps of Engineers operates Detroit Dam as part of a system of 13 reservoirs in the Willamette Project to meet multiple goals, which include flood-damage protection, power generation, downstream navigation, recreation, and irrigation. A distinct cycle in water temperature occurs in Detroit Lake as spring and summer heating through solar radiation creates a warm layer of water near the surface and isolates cold water below. Controlling the temperature of releases from Detroit Dam, therefore, is highly dependent on the location, characteristics, and usage of the dam's outlet structures. Prior to operational changes in 2007, Detroit Dam had a well-documented effect on downstream water temperature that was problematic for endangered salmonid fish species, releasing water that was too cold in midsummer and too warm in autumn. This unnatural seasonal temperature pattern caused problems in the timing of fish migration, spawning, and emergence. In this study, an existing calibrated 2-dimensional hydrodynamic water-quality model [CE-QUAL-W2] of Detroit Lake was used to determine how changes in dam operation or changes to the structural release points of Detroit Dam might affect downstream water temperatures under a range of historical hydrologic and meteorological conditions. The results from a subset of the Detroit Lake model scenarios then were used as forcing conditions for downstream CE-QUAL-W2 models of Big Cliff Reservoir (the small reregulating reservoir just downstream of Detroit Dam) and the North Santiam and Santiam Rivers. Many combinations of environmental, operational, and structural options were explored with the model scenarios. Multiple downstream temperature targets were used along with three sets of environmental forcing conditions representing cool/wet, normal, and hot/dry conditions. Five structural options at Detroit Dam were modeled, including the use of existing outlets, one hypothetical variable-elevation outlet such as a sliding gate, a hypothetical combination of a floating outlet and a fixed-elevation outlet, and a hypothetical combination of a floating outlet and a sliding gate. Finally, 14 sets of operational guidelines for Detroit Dam were explored to gain an understanding of the effects of imposing different downstream minimum streamflows, imposing minimum outflow rules to specific outlets, and managing the level of the lake with different timelines through the year. Selected subsets of these combinations of operational and structural scenarios were run through the downstream models of Big Cliff Reservoir and the North Santiam and Santiam Rivers to explore how hypothetical changes at Detroit Dam might provide improved temperatures for endangered salmonids downstream of the Detroit-Big Cliff Dam complex. Conclusions that can be drawn from these model scenarios include: *The water-temperature targets set by the U.S. Army Corps of Engineers for releases from Detroit Dam can be met through a combination of new dam outlets or a delayed drawdown of the lake in autumn. *Spring and summer dam operations greatly affect the available release temperatures and operational flexibility later in the autumn. Releasing warm water during midsummer tends to keep more cool water available for release in autumn. *The ability to meet downstream temperature targets during spring depends on the characteristics of the available outlets. Under existing conditions, although warm water sometimes is present at the lake surface in spring and early summer, such water may not be available for release if the lake level is either well below or well above the spillway crest. *Managing lake releases to meet downstream temperature targets depends on having outlet structures that can access both (warm) lake surface water and (cold) deeper lake water throughout the year. The existing outlets at Detroit Dam do not allow near-surface waters to be released during times when the lake surface level is below the spillway (spring and autumn). *Using the existing outlets at Detroit Dam, lake level management is important to the water temperature of releases because it controls the availability and depth of water at the spillway. When lake level is lowered below the spillway crest in late summer, the loss of access to warm water at the lake surface can result in abrupt changes to release temperatures. *Because the power-generation intakes (penstocks) are 166 feet below the full-pool lake level, imposing minimum power production requirements at Detroit Dam limits the amount of warm surface water that can be expelled from the lake in midsummer, thereby postponing and amplifying warm outflows from Detroit Lake into the autumn spawning season. *Likewise, imposing minimum power production requirements at Detroit Dam in autumn can limit the amount of cool hypolimnetic water that is released from the lake, thereby limiting cool outflows from Detroit Lake during the autumn spawning season. *Model simulations indicate that a delayed drawdown of Detroit Lake in autumn would result in better control over release temperatures in the immediate downstream vicinity of Big Cliff Dam, but the reduced outflows necessary to retain more water in the lake in late summer are more susceptible to rapid heating downstream. *Compared to the existing outlets at Detroit Dam, floating or sliding-gate outlet structures can provide greater control over release temperatures because they provide better access to warm water at the lake surface and cooler water at depth. These conclusions can be grouped into several common themes. First, optimal and flexible management and achievement of downstream temperature goals requires that releases of warm water near the surface of the lake and cold water below the thermocline are both possible with the available dam outlets during spring, summer, and autumn. This constraint can be met to some extent with existing outlets, but only if access to the spillway is extended into autumn by keeping the lake level higher than called for by the current rule curve (the typical target water-surface elevation throughout the year). If new outlets are considered, a variable-elevation outlet such as a sliding gate structure, or a floating outlet in combination with a fixed-elevation outlet at sufficient depth to access cold water, is likely to work well in terms of accessing a range of water temperatures and achieving downstream temperature targets. Furthermore, model results indicate that it is important to release warm water from near the lake surface during midsummer. If not released downstream, the warm water will build up at the top of the lake as a result of solar energy inputs and the thermocline will deepen, potentially causing warm water to reach the depth of deeper fixed-elevation outlets in autumn, particularly when the lake level is drawn down to make room for flood storage. Delaying the drawdown in autumn can help to keep the thermocline above such outlets and preserve access to cold water. Although it is important to generate hydropower at Detroit Dam, minimum power-production requirements limit the ability of dam operators to meet downstream temperature targets with existing outlet structures. The location of the power penstocks below the thermocline in spring and most of summer causes the release of more cool water during summer than is optimal. Reducing the power-production constraint allows the temperature target to be met more frequently, but at the cost of less power generation. Finally, running the Detroit Dam, Big Cliff Dam, and North Santiam and Santiam River models in series allows dam operators to evaluate how different operational strategies or combinations of new dam outlets might affect downstream temperatures for many miles of critical endangered salmonid habitat. Temperatures can change quickly in these downstream reaches as the river exchanges heat with its surroundings, and heating or cooling of 6 degrees Celsius is not unusual in the 40–50 miles downstream of Big Cliff Dam. The results published in this report supersede preliminary results published in U.S. Geological Survey Open-File Report 2011-1268 (Buccola and Rounds, 2011). Those preliminary results are still valid, but the results in this report are more current and comprehensive.

Nitrogen assimilation and transpiration: key processes conditioning responsiveness of wheat to elevated [CO2] and temperature.

PubMed

Jauregui, Iván; Aroca, Ricardo; Garnica, María; Zamarreño, Ángel M; García-Mina, José M; Serret, Maria D; Parry, Martin; Irigoyen, Juan J; Aranjuelo, Iker

2015-11-01

Although climate scenarios have predicted an increase in [CO(2)] and temperature conditions, to date few experiments have focused on the interaction of [CO(2)] and temperature effects in wheat development. Recent evidence suggests that photosynthetic acclimation is linked to the photorespiration and N assimilation inhibition of plants exposed to elevated CO(2). The main goal of this study was to analyze the effect of interacting [CO(2)] and temperature on leaf photorespiration, C/N metabolism and N transport in wheat plants exposed to elevated [CO(2)] and temperature conditions. For this purpose, wheat plants were exposed to elevated [CO(2)] (400 vs 700 µmol mol(-1)) and temperature (ambient vs ambient + 4°C) in CO(2) gradient greenhouses during the entire life cycle. Although at the agronomic level, elevated temperature had no effect on plant biomass, physiological analyses revealed that combined elevated [CO(2)] and temperature negatively affected photosynthetic performance. The limited energy levels resulting from the reduced respiratory and photorespiration rates of such plants were apparently inadequate to sustain nitrate reductase activity. Inhibited N assimilation was associated with a strong reduction in amino acid content, conditioned leaf soluble protein content and constrained leaf N status. Therefore, the plant response to elevated [CO(2)] and elevated temperature resulted in photosynthetic acclimation. The reduction in transpiration rates induced limitations in nutrient transport in leaves of plants exposed to elevated [CO(2)] and temperature, led to mineral depletion and therefore contributed to the inhibition of photosynthetic activity. © 2015 Scandinavian Plant Physiology Society.

Temperature changes across porcelain during multiple exposure CO2 lasing

NASA Astrophysics Data System (ADS)

Barron, Joseph R.; Zakariasen, Kenneth L.; Peacocke, Larry

1990-06-01

Research indicates that laser energy may provide a useful method for glazing and fusing porcelain for intraoral prosthetic purposes. However, it is not known whether such lasing will result in the production of heat levels that may be damaging to adjacent vital tissues such as the dental pulp and periodontal tissues. This research is designed to measure the magnitude of temperature rise across porcelain observed during multiple exposure C02 lasing. Fifteen porcelain examples of 1000 jim (5), 1500 pm (5) and 2000 tm (5) x each received five C02 laser exposures on the same exposure site at 1.0 sec. intervals at 8.0 watts (0.2 sec. per exposure with a 1 mm focal spot). A YSI 144201 thermilinear precision thermistor was placed on the porcelain surface opposite each laser exposure site. Temperature rise above ambient was recorded by an HP3421A data acquisition unit and HP9816 technical microcomputer. Recording continued for sufficient time to allow temperatures to return to ambient. The mean temperature elevations ranged from a low of 2.97 0C (2000 pm) to a high of 7.77 °C (1000 μm). ANOVA and Duncan's Multiple Range Test indicated significant differences in temperature rise by porcelain thickness. It would appear from the results of this research that temperature elevations adjacent to lased porcelain may be sufficiently controllable that safe intraoral porcelain lasing will be possible.

Elevated temperature altered photosynthetic products in wheat seedlings and organic compounds and biological activity in rhizopshere soil under cadmium stress.

PubMed

Jia, Xia; Zhao, YongHua; Wang, WenKe; He, Yunhua

2015-09-23

The objective of this study was to investigate the effects of slightly elevated atmospheric temperature in the spring on photosynthetic products in wheat seedlings and on organic compounds and biological activity in rhizosphere soil under cadmium (Cd) stress. Elevated temperature was associated with increased soluble sugars, reducing sugars, starch, and total sugars, and with decreased amino acids in wheat seedlings under Cd stress. Elevated temperature improved total soluble sugars, free amino acids, soluble phenolic acids, and organic acids in rhizosphere soil under Cd stress. The activity of amylase, phenol oxidase, invertase, β-glucosidase, and l-asparaginase in rhizosphere soil was significantly improved by elevated temperature under Cd stress; while cellulase, neutral phosphatase, and urease activity significantly decreased. Elevated temperature significantly improved bacteria, fungi, actinomycetes, and total microorganisms abundance and fluorescein diacetate activity under Cd stress. In conclusion, slightly elevated atmospheric temperature in the spring improved the carbohydrate levels in wheat seedlings and organic compounds and biological activity in rhizosphere soil under Cd stress in the short term. In addition, elevated atmospheric temperature in the spring stimulated available Cd by affecting pH, DOC, phenolic acids, and organic acids in rhizosphere soil, which resulted in the improvement of the Cd uptake by wheat seedlings.

Elevated temperature altered photosynthetic products in wheat seedlings and organic compounds and biological activity in rhizopshere soil under cadmium stress

PubMed Central

Jia, Xia; Zhao, YongHua; Wang, WenKe; He, Yunhua

2015-01-01

The objective of this study was to investigate the effects of slightly elevated atmospheric temperature in the spring on photosynthetic products in wheat seedlings and on organic compounds and biological activity in rhizosphere soil under cadmium (Cd) stress. Elevated temperature was associated with increased soluble sugars, reducing sugars, starch, and total sugars, and with decreased amino acids in wheat seedlings under Cd stress. Elevated temperature improved total soluble sugars, free amino acids, soluble phenolic acids, and organic acids in rhizosphere soil under Cd stress. The activity of amylase, phenol oxidase, invertase, β-glucosidase, and l-asparaginase in rhizosphere soil was significantly improved by elevated temperature under Cd stress; while cellulase, neutral phosphatase, and urease activity significantly decreased. Elevated temperature significantly improved bacteria, fungi, actinomycetes, and total microorganisms abundance and fluorescein diacetate activity under Cd stress. In conclusion, slightly elevated atmospheric temperature in the spring improved the carbohydrate levels in wheat seedlings and organic compounds and biological activity in rhizosphere soil under Cd stress in the short term. In addition, elevated atmospheric temperature in the spring stimulated available Cd by affecting pH, DOC, phenolic acids, and organic acids in rhizosphere soil, which resulted in the improvement of the Cd uptake by wheat seedlings. PMID:26395070

Elevated temperature altered photosynthetic products in wheat seedlings and organic compounds and biological activity in rhizopshere soil under cadmium stress

NASA Astrophysics Data System (ADS)

Jia, Xia; Zhao, Yonghua; Wang, Wenke; He, Yunhua

2015-09-01

The objective of this study was to investigate the effects of slightly elevated atmospheric temperature in the spring on photosynthetic products in wheat seedlings and on organic compounds and biological activity in rhizosphere soil under cadmium (Cd) stress. Elevated temperature was associated with increased soluble sugars, reducing sugars, starch, and total sugars, and with decreased amino acids in wheat seedlings under Cd stress. Elevated temperature improved total soluble sugars, free amino acids, soluble phenolic acids, and organic acids in rhizosphere soil under Cd stress. The activity of amylase, phenol oxidase, invertase, β-glucosidase, and L-asparaginase in rhizosphere soil was significantly improved by elevated temperature under Cd stress; while cellulase, neutral phosphatase, and urease activity significantly decreased. Elevated temperature significantly improved bacteria, fungi, actinomycetes, and total microorganisms abundance and fluorescein diacetate activity under Cd stress. In conclusion, slightly elevated atmospheric temperature in the spring improved the carbohydrate levels in wheat seedlings and organic compounds and biological activity in rhizosphere soil under Cd stress in the short term. In addition, elevated atmospheric temperature in the spring stimulated available Cd by affecting pH, DOC, phenolic acids, and organic acids in rhizosphere soil, which resulted in the improvement of the Cd uptake by wheat seedlings.

Nanostructure templating using low temperature atomic layer deposition

DOEpatents

Grubbs, Robert K [Albuquerque, NM; Bogart, Gregory R [Corrales, NM; Rogers, John A [Champaign, IL

2011-12-20

Methods are described for making nanostructures that are mechanically, chemically and thermally stable at desired elevated temperatures, from nanostructure templates having a stability temperature that is less than the desired elevated temperature. The methods comprise depositing by atomic layer deposition (ALD) structural layers that are stable at the desired elevated temperatures, onto a template employing a graded temperature deposition scheme. At least one structural layer is deposited at an initial temperature that is less than or equal to the stability temperature of the template, and subsequent depositions made at incrementally increased deposition temperatures until the desired elevated temperature stability is achieved. Nanostructure templates include three dimensional (3D) polymeric templates having features on the order of 100 nm fabricated by proximity field nanopatterning (PnP) methods.

Dislocation nucleation facilitated by atomic segregation

NASA Astrophysics Data System (ADS)

Zou, Lianfeng; Yang, Chaoming; Lei, Yinkai; Zakharov, Dmitri; Wiezorek, Jörg M. K.; Su, Dong; Yin, Qiyue; Li, Jonathan; Liu, Zhenyu; Stach, Eric A.; Yang, Judith C.; Qi, Liang; Wang, Guofeng; Zhou, Guangwen

2018-01-01

Surface segregation--the enrichment of one element at the surface, relative to the bulk--is ubiquitous to multi-component materials. Using the example of a Cu-Au solid solution, we demonstrate that compositional variations induced by surface segregation are accompanied by misfit strain and the formation of dislocations in the subsurface region via a surface diffusion and trapping process. The resulting chemically ordered surface regions acts as an effective barrier that inhibits subsequent dislocation annihilation at free surfaces. Using dynamic, atomic-scale resolution electron microscopy observations and theory modelling, we show that the dislocations are highly active, and we delineate the specific atomic-scale mechanisms associated with their nucleation, glide, climb, and annihilation at elevated temperatures. These observations provide mechanistic detail of how dislocations nucleate and migrate at heterointerfaces in dissimilar-material systems.

Verification and transfer of thermal pollution model. Volume 4: User's manual for three-dimensional rigid-lid model

NASA Technical Reports Server (NTRS)

Lee, S. S.; Nwadike, E. V.; Sinha, S. E.

1982-01-01

The theory of a three dimensional (3-D) mathematical thermal discharge model and a related one dimensional (1-D) model are described. Model verification at two sites, a separate user's manual for each model are included. The 3-D model has two forms: free surface and rigid lid. The former allows a free air/water interface and is suited for significant surface wave heights compared to mean water depth, estuaries and coastal regions. The latter is suited for small surface wave heights compared to depth because surface elevation was removed as a parameter. These models allow computation of time dependent velocity and temperature fields for given initial conditions and time-varying boundary conditions. The free surface model also provides surface height variations with time.

Biodegradable and Multifunctional Polymer Micro-Tubes for Targeting Photothermal Therapy

PubMed Central

Wang, Xin; Yu, Guoping; Han, Xiyu; Zhang, Hua; Ren, Jing; Wu, Xia; Qu, Yanfeng

2014-01-01

We describe an innovative form of polymer micro-tubes with diverse functions including biodegradation, magnetic manipulation, and photothermal effect that employs and activates photothermal therapy to target cancer cells. The micro-tube comprised soybean protein isolate, poly-l-glutamic acid, magnetite nanoparticles, plus gold nanoparticles. Through electrostatic force, these components, with opposite charges, formed pairs of layers in the pores of the template, various bilayers of soybean protein isolate and poly-l-glutamic acid served as the biodegradable building wall to each micro-tube. The layers of magnetite nanoparticle functionalized micro-tubes enabled the micro-tube manipulate to target the cancer cells by using an external magnetic field. The photo-thermal effect of the layer of gold nanoparticles on the outer surface of the micro-tubes, when under irradiation and when brought about by the near infrared radiation, elevated each sample’s temperature. In addition, and when under the exposure of the near infrared radiation, the elevated temperature of the suspension of the micro-tubes, likewise with a concentration of 0.2 mg/mL, and similarly with a power of 2 W and as well maintained for 10 min, elevated the temperature of the suspension beyond 42 °C. Such temperatures induced apoptosis of target cancer cells through the effect of photothermal therapy. The findings assert that structured micro-tubes have a promising application as a photothermal agent. From this assertion, the implications are that this multifunctional agent will significantly improve the methodology for cancer diagnosis and therapy. PMID:24992593

Impacts of beaver dams on hydrologic and temperature regimes in a mountain stream

NASA Astrophysics Data System (ADS)

Majerova, M.; Neilson, B. T.; Schmadel, N. M.; Wheaton, J. M.; Snow, C. J.

2015-08-01

Beaver dams affect hydrologic processes, channel complexity, and stream temperature in part by inundating riparian areas, influencing groundwater-surface water interactions, and changing fluvial processes within stream systems. We explored the impacts of beaver dams on hydrologic and temperature regimes at different spatial and temporal scales within a mountain stream in northern Utah over a 3-year period spanning pre- and post-beaver colonization. Using continuous stream discharge, stream temperature, synoptic tracer experiments, and groundwater elevation measurements, we documented pre-beaver conditions in the first year of the study. In the second year, we captured the initial effects of three beaver dams, while the third year included the effects of ten dams. After beaver colonization, reach-scale (~ 750 m in length) discharge observations showed a shift from slightly losing to gaining. However, at the smaller sub-reach scale (ranging from 56 to 185 m in length), the discharge gains and losses increased in variability due to more complex flow pathways with beaver dams forcing overland flow, increasing surface and subsurface storage, and increasing groundwater elevations. At the reach scale, temperatures were found to increase by 0.38 °C (3.8 %), which in part is explained by a 230 % increase in mean reach residence time. At the smallest, beaver dam scale (including upstream ponded area, beaver dam structure, and immediate downstream section), there were notable increases in the thermal heterogeneity where warmer and cooler niches were created. Through the quantification of hydrologic and thermal changes at different spatial and temporal scales, we document increased variability during post-beaver colonization and highlight the need to understand the impacts of beaver dams on stream ecosystems and their potential role in stream restoration.

Carbohydrate metabolism in the subtending leaf cross-acclimates to waterlogging and elevated temperature stress and influences boll biomass in cotton (Gossypium hirsutum).

PubMed

Wang, Haimiao; Chen, Yinglong; Hu, Wei; Wang, Shanshan; Snider, John L; Zhou, Zhiguo

2017-11-01

Short-term waterlogging and chronic elevated temperature occur concomitantly in the cotton (Gossypium hirsutum) growing season. While previous research about co-occurring waterlogging and elevated temperature has focused primarily on cotton fiber, no studies have investigated carbohydrate metabolism of the subtending leaf (a major source leaf for boll development) cross-acclimation to aforementioned stressors. To address this, plants were exposed to ambient (31.6/26.5°C) and elevated (34.1/29.0°C) temperatures during the whole flowering and boll formation stage, and waterlogging (0, 3, 6 days) beginning on the day of anthesis. Both waterlogging and high temperature limited boll biomass (reduced by 1.19-32.14%), but effects of different durations of waterlogging coupled with elevated temperature on carbohydrate metabolism in the subtending leaf were quite different. The 6-day waterlogging combined with elevated temperature had the most negative impact on net photosynthetic rate (Pn) and carbohydrate metabolism of any treatment, leading to upregulated GhSusA and GhSusC expression and enhanced sucrose synthase (SuSy, EC 2.4.1.13) activity for sucrose degradation. A prior exposure to waterlogging for 3 days improved subtending leaf performance under elevated temperature. Pn, sucrose concentrations, Rubisco (EC 4.1.1.39) activity, and cytosolic fructose-1,6-bisphosphatase (cy-FBPase, EC 3.1.3.11) activity in the subtending leaf significantly increased, while SuSy activity decreased under 3 days waterlogging and elevated temperature combined relative to elevated temperature alone. Thus, we concluded that previous exposure to a brief (3 days) waterlogging stress improved sucrose composition and accumulation cross-acclimation to high temperature later in development not only by promoting leaf photosynthesis but also inhibiting sucrose degradation. © 2017 Scandinavian Plant Physiology Society.

Ecological effects of feral biofuel crops in constructed oak ...

EPA Pesticide Factsheets

The effects of elevated temperatures and drought on constructed oak savannahs were studied to determine the interactive effects of potentially invasive feral biofuel species and climate change on native grassland communities. A total of 12 sunlit mesocosm were used. Each mesocosm held three tubs. One had six native plant species; one had five native species with the annual crop Sorghum bicolor and one had five native species along with the weedy perennial Sorghum halepense. The experimental treatments were ambient (control), elevated temperature, drought, or a combination of elevated temperature and drought. Total aboveground biomass of the community was greatest in the control and drought treatments, lowest with elevated temperature + drought, and intermediate in high temperature treatments (P<0.0001). Sorghum species produced significantly less biomass than the native grass species (P< 0.05). S. bicolor seed biomass was greatest under elevated temperature and lowest in the elevated temperature + drought treatment (P=0.0002). Neither of the Sorghum species significantly affected active soil bacterial biomass. Active bacterial biomass was lowest in the drought and elevated temperature and drought treatments (P<0.05). Active soil fungal biomass was highest in the tubs containing S. bicolor. Percent total carbon in the soil increased between 2010 and 2011 (P=0.0054); it was lowest in the elevated temperature and drought mesocosms (P<0.05). Longer term studi

Changes in frozen ground and vegetation on northern slopes of the Bayan Har Mountains on northeastern Qinghai-Tibetan Plateau, Southwest China

NASA Astrophysics Data System (ADS)

Jin, X.

2017-12-01

The Bayan Har Mountains (BHM) on northeastern Qinghai-Tibetan Plateau, Southwest China, is representative of elevational permafrost. Permafrost in the BHM is mostly warm (<-1°C) and mosaicked with seasonally frozen ground and taliks in discontinuous permafrost zones. Warming climate has led, is leading, and will lead to marked and profound permafrost changes. Consequently, permafrost changes significantly affect hydrology, ecology and engineered infrastructures in the source area of Yellow River. Due to the limited monitoring data, however, the permafrost in the BHM is poorly understood. Based on temperature measurements from boreholes established since 2010 and other historical archives, and field investigations since 2011, this study aims at analyzing spatiotemporal changes of permafrost and their associations with vegetation characteristics. Preliminary results show that: (1) It is evident that permafrost temperatures decrease with rising elevations. Mean annual ground temperature is generally above 0°C at elevations below 4,350 m a. s. l.; Above 4,520 m a. s. l. , permafrost temperature is lower than -0.5°C; (2) From 2011 to 2016, permafrost temperatures increased by 0.02-0.11°C at elevations below 4,400 m a. s. l. , but they decreased by 0.04°C above 4,520 m a. s. l.; (3) About 64 species of vegetation were found around the boreholes. Mesoxerophytes are the dominant species at elevations below 4,400 m a. s. l. in the areas of seasonally frozen ground, and; the cyperaceae dominate above 4,520 m a. s. l. in the permafrost zones. With rising elevations, aboveground biomass increases, but the species richness declines, maybe due to the variations in hydrothermal combinations and grazing. Under a warming and wetting climate, permafrost degradation, as evidenced by the reduction in areal extent of permafrost and thickening active layer, may result in declining or depletion of near-surface soil moisture due to the lowering permafrost and supra-permafrost water tables, and in shifting of alpine vegetation from meadows to steppes, and even in converting of alpine steppes to deserts in some areas due to the diminishing of water availability. Further study will focus on the quantitative relationships between frozen ground and alpine vegetation, and the symbiosis of the permafrost and alpine wetlands.

Elevated temperature and CO(2) concentration effects on xylem anatomy of Scots pine.

PubMed

Kilpeläinen, Antti; Gerendiain, Ane Zubizarreta; Luostarinen, Katri; Peltola, Heli; Kellomäki, Seppo

2007-09-01

We studied the effects of elevated temperature and carbon dioxide concentration ([CO(2)]) alone and together on wood anatomy of 20-year-old Scots pine (Pinus sylvestris L.) trees. The study was conducted in 16 closed chambers, providing a factorial combination of two temperature regimes and two CO(2) concentrations (ambient and elevated), with four trees in each treatment. The climate scenario included a doubling of [CO(2)] and a corresponding increase of 2-6 degrees C in temperature at the site depending on the season. Anatomical characteristics analyzed were annual earlywood, latewood and ring widths, intra-ring wood densities (earlywood, latewood and mean wood density), tracheid width, length, wall thickness, lumen diameter, wall thickness:lumen diameter ratio and mass per unit length (coarseness), and numbers of rays, resin canals and tracheids per xylem cross-sectional area. Elevated [CO(2)] increased ring width in four of six treatment years; earlywood width increased in the first two years and latewood width in the third year. Tracheid walls in both the earlywood and latewood tended to become thicker over the 6-year treatment period when temperature or [CO(2)] was elevated alone, whereas in the combined treatment they tended to become thinner relative to the tracheids of trees grown under ambient conditions. Latewood tracheid lumen diameters were larger in all the treatments relative to ambient conditions over the 6-year period, whereas lumen diameters in earlywood increased only in response to elevated [CO(2)] and were 3-6% smaller in the treatments with elevated temperature than in ambient conditions. Tracheid width, length and coarseness were greater in trees grown in elevated than in ambient temperature. The number of resin canals per mm(2) decreased in the elevated [CO(2)] treatment and increased in the elevated temperature treatments relative to ambient conditions. The treatments decreased the number of rays and tracheids per mm(2) of cross-sectional area, the greatest decrease occurring in the elevated [CO(2)] treatment. It seemed that xylem anatomy was affected more by elevated temperature than by elevated [CO(2)] and that the effects of temperature were confined to the earlywood.

Combined Effect of Textured Patterns and Graphene Flake Additives on Tribological Behavior under Boundary Lubrication

PubMed Central

Cai, Zhen-bing; Zhao, Lei; Zhang, Xu; Yue, Wen; Zhu, Min-hao

2016-01-01

A ball-on-plate wear test was employed to investigate the effectiveness of graphene (GP) nanoparticles dispersed in a synthetic-oil-based lubricant in reducing wear. The effect by area ratio of elliptically shaped dimple textures and elevated temperatures were also explored. Pure PAO4 based oil and a mixture of this oil with 0.01 wt% GP were compared as lubricants. At pit area ratio of 5%, GP-base oil effectively reduced friction and wear, especially at 60 and 100°C. Under pure PAO4 oil lubrication, the untextured surfaces gained low friction coefficients (COFs) and wear rates under 60 and 100°C. With increasing laser—texture area ratio, the COF and wear rate decreased at 25 and 150°C but increased at 60 and 100°C. Under the GP-based oil lubrication, the textured surface with 5% area ratio achieved the lowest COF among those of the area ratios tested at all test temperatures. Meanwhile, the textured surface with 20% area ratio obtained the highest COF among those of the area ratios. With the joint action of GP and texture, the textured surface with 10% area ratio exhibited the best anti-wear performance among all of the textured surfaces at all test temperatures. PMID:27054762

Warm waters, bleached corals

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

Roberts, L.

1990-10-12

Two researchers, Tom Goreau of the Discovery Laboratory in Jamaica and Raymond Hayes of Howard University, claim that they have evidence that nearly clinches the temperature connection to the bleached corals in the Caribbean and that the coral bleaching is an indication of Greenhouse warming. The incidents of scattered bleaching of corals, which have been reported for decades, are increasing in both intensity and frequency. The researchers based their theory on increased temperature of the seas measured by satellites. However, some other scientists feel that the satellites measure the temperature of only the top few millimeters of the water andmore » that since corals lie on reefs perhaps 60 to 100 feet below the ocean surface, the elevated temperatures are not significant.« less

On the Regulation of the Pacific Warm Pool Temperature

NASA Technical Reports Server (NTRS)

Chou, Ming-Dah; Chou, Sue-Hsien; Chan, Pui-King; Lau, William K. M. (Technical Monitor)

2002-01-01

In the tropical western Pacific, regions of the highest sea surface temperature (SST) and the largest cloud cover are found to have the largest surface heating, primarily due to the weak evaporative cooling associated with weak winds. This situation is in variance with the suggestions that the temperature in the Pacific warm pool is regulated either by the reduced solar heating due to an enhanced cloudiness or by the enhanced evaporative cooling due to an elevated SST. It is clear that an enhanced surface heating in an enhanced convection region is not sustainable and must be interrupted by variations in large-scale atmospheric circulation. As the deep convective regions shift away from regions of high SST due primarily to seasonal variation and secondarily to interannual variation of the large-scale atmospheric and oceanic circulation, both trade wind and evaporative cooling in the high SST region increase, leading to a reduction in SST. We conclude that the evaporative cooling associated with the seasonal and interannual variations of trade winds in the primary factor that prevent the warm pool SST from increasing to a value much higher than what is observed.

Development of structural ceramics having large crack-healing ability and fracture toughness

NASA Astrophysics Data System (ADS)

Takahashi, Koji; Yokouchi, Masahiro; Lee, Sang-Kee; Ando, Kotoji

2004-02-01

Al2O3 reinforced by SiC whiskers (Al2O3/SiC-W) was hot pressed to investigate the crack-healing behavior. Semi-elliptical surface cracks of 50 to 450μm in surface length were introduced using a Vickers indenter. The specimens containing pre-cracks were crack-healed at temperatures between 1000°C and 1300°C for 1h in air, and their strengths were measured by three-point bending tests at room temperature and elevated temperatures between 400°C and 1300°C. The results show that Al2O3/SiC-W possesses considerable crack-healing ability. The surface cracks with length of 2c=100μm could be healed by crack-healing at 1200°C or 1300°C for 1h in air. The maximum crack size that can be healed for Al2O3/SiC-W is 2c=200μm. Fracture toughness of the material was also determined. As expected, the SiC whiskers made their Al2O3 tougher.

Development and Testing of High Surface Area Iridium Anodes for Molten Oxide Electrolysis

NASA Technical Reports Server (NTRS)

Shchetkovskiy, Anatoliy; McKechnie, Timothy; Sadoway, Donald R.; Paramore, James; Melendez, Orlando; Curreri, Peter A.

2010-01-01

Processing of lunar regolith into oxygen for habitat and propulsion is needed to support future space missions. Direct electrochemical reduction of molten regolith is an attractive method of processing, because no additional chemical reagents are needed. The electrochemical processing of molten oxides requires high surface area, inert anodes. Such electrodes need to be structurally robust at elevated temperatures (1400-1600?C), be resistant to thermal shock, have good electrical conductivity, be resistant to attack by molten oxide (silicate), be electrochemically stable and support high current density. Iridium with its high melting point, good oxidation resistance, superior high temperature strength and ductility is the most promising candidate for anodes in high temperature electrochemical processes. Several innovative concepts for manufacturing such anodes by electrodeposition of iridium from molten salt electrolyte (EL-Form? process) were evaluated. Iridium electrodeposition to form of complex shape components and coating was investigated. Iridium coated graphite, porous iridium structure and solid iridium anodes were fabricated. Testing of electroformed iridium anodes shows no visible degradation. The result of development, manufacturing and testing of high surface, inert iridium anodes will be presented.

Development and Testing of High Surface Area Iridium Anodes for Molten Oxide Electrolysis

NASA Technical Reports Server (NTRS)

Shchetkovskiy, Anatoliy; McKechnie, Timothy; Sadoway, Donald R.; Paramore, James; Melendez, Orlando; Curreri, Peter A.

2010-01-01

Processing of lunar regolith into oxygen for habitat and propulsion is needed to support future space missions. Direct electrochemical reduction of molten regolith is an attractive method of processing, because no additional chemical reagents are needed. The electrochemical processing of molten oxides requires high surface area, inert anodes. Such electrodes need to be structurally robust at elevated temperatures (1400-1600 C), be resistant to thermal shock, have good electrical conductivity, be resistant to attack by molten oxide (silicate), be electrochemically stable and support high current density. Iridium with its high melting point, good oxidation resistance, superior high temperature strength and ductility is the most promising candidate for anodes in high temperature electrochemical processes. Several innovative concepts for manufacturing such anodes by electrodeposition of iridium from molten salt electrolyte (EL-Form process) were evaluated. Iridium electrodeposition to form of complex shape components and coating was investigated. Iridium coated graphite, porous iridium structure and solid iridium anodes were fabricated. Testing of electroformed iridium anodes shows no visible degradation. The result of development, manufacturing and testing of high surface, inert iridium anodes will be presented.

Is Obsidian Hydration Dating Affected by Relative Humidity?

USGS Publications Warehouse

Friedman, I.; Trembour, F.W.; Smith, G.I.; Smith, F.L.

1994-01-01

Experiments carried out under temperatures and relative humidities that approximate ambient conditions show that the rate of hydration of obsidian is a function of the relative humidity, as well as of previously established variables of temperature and obsidian chemical composition. Measurements of the relative humidity of soil at 25 sites and at depths of between 0.01 and 2 m below ground show that in most soil environments, at depths below about 0.25 m, the relative humidity is constant at 100%. We have found that the thickness of the hydrated layer developed on obsidian outcrops exposed to the sun and to relative humidities of 30-90% is similar to that formed on other portions of the outcrop that were shielded from the sun and exposed to a relative humidity of approximately 100%. Surface samples of obsidian exposed to solar heating should hydrate more rapidly than samples buried in the ground. However, the effect of the lower mean relative humidity experiences by surface samples tends to compensate for the elevated temperature, which may explain why obsidian hydration ages of surface samples usually approximate those derived from buried samples.

Thermal dependence of sprint performance in the lizard Psammodromus algirus along a 2200-meter elevational gradient: Cold-habitat lizards do not perform better at low temperatures.

PubMed

Zamora-Camacho, Francisco Javier; Rubiño-Hispán, María Virtudes; Reguera, Senda; Moreno-Rueda, Gregorio

2015-08-01

Sprint speed has a capital relevance in most animals' fitness, mainly for fleeing from predators. Sprint performance is maximal within a certain range of body temperatures in ectotherms, whose thermal upkeep relies on exogenous thermal sources. Ectotherms can respond to diverse thermal environments either by shifting their thermal preferences or maintaining them through different adaptive mechanisms. Here, we tested whether maximum sprint speed of a lizard that shows conservative thermal ecology along a 2200-meter elevational gradient differs with body temperature in lizards from different elevations. Lizards ran faster at optimum than at suboptimum body temperature. Notably, high-elevation lizards were not faster than mid- and low-elevation lizards at suboptimum body temperature, despite their low-quality thermal environment. This result suggests that both preferred body temperature and thermal dependence of speed performance are co-adapted along the elevational gradient. High-elevation lizards display a number of thermoregulatory strategies that allow them to achieve high optimum body temperatures in a low thermal-quality habitat and thus maximize speed performance. As for reproductive condition, we did not find any effect of it on sprint speed, or any significant interaction with elevation or body temperature. However, strikingly, gravid females were significantly slower than males and non-gravid females at suboptimum temperature, but performed similarly well at optimal temperature. Copyright © 2015 Elsevier Ltd. All rights reserved.

Friction behavior for clay minerals during dehydration process: implication for unstable friction at shallow portion along subducting plate

NASA Astrophysics Data System (ADS)

Kubo, T.; Katayama, I.

2016-12-01

Along plate boundary subduction thrusts, the transformation of smectite to illite within fault gouge at temperatures around 100 - 200 °C is one of the key mineralogical changes thought to control the updip limit of seismicity (Hyndman et al., 1997). Since hydration state of clay minerals is possible to vary from moment to moment in nature, it is important to investigate the effect of dehydration and hydrate state on frictional properties with progression of a removal of water is rare. In this study, we focus on the effect of dehydration of water on the frictional properties of clay minerals by temperature-rising test. For the friction experiments, starting materials we used are Ca-montmorillonite, which were placed on the simulated fault surface and two side blocks were placed together to produce a double-direct shear configuration. The sample assembly was heated by an external furnace up to 400 °C that is monitored by thermocouples located in the central part of sample assembly. After steady-state friction at room temperature we started to elevate the temperature around the specimen at a constant heating rate of 1, 3, and 10 °C/min. Ca-montmorillonite gouge showed unique friction behavior development as elevated temperature, which is divided into three stages; (1) friction coefficient decreased at relative low temperature, (2) friction coefficient increased at middle temperature, and (3) stick-slip behavior occurred at high temperature. Stick-slip behavior as elevated temperature implies to have a potential of velocity weakening behavior. Observed stick-slip behavior occurs at a temperature of 320 °C, which is extremely higher from a temperature range of occurring dehydration for Ca-montmorillonite (100 - 200 °C). However, at low heating rate the temperature that stick-slip behavior occurs shifted to lower temperature. Our preliminary results suggest that the observed systematical shift suggest that these frictional behavior is likely to be controlled by dehydration reaction kinetics. Dehydration of clay minerals change friction behavior, and play a key role for the occurrence of earthquakes along subducting plate.

Monolith electroplating process

DOEpatents

Agarrwal, Rajev R.

2001-01-01

An electroplating process for preparing a monolith metal layer over a polycrystalline base metal and the plated monolith product. A monolith layer has a variable thickness of one crystal. The process is typically carried in molten salts electrolytes, such as the halide salts under an inert atmosphere at an elevated temperature, and over deposition time periods and film thickness sufficient to sinter and recrystallize completely the nucleating metal particles into one single crystal or crystals having very large grains. In the process, a close-packed film of submicron particle (20) is formed on a suitable substrate at an elevated temperature. The temperature has the significance of annealing particles as they are formed, and substrates on which the particles can populate are desirable. As the packed bed thickens, the submicron particles develop necks (21) and as they merge into each other shrinkage (22) occurs. Then as micropores also close (23) by surface tension, metal density is reached and the film consists of unstable metal grain (24) that at high enough temperature recrystallize (25) and recrystallized grains grow into an annealed single crystal over the electroplating time span. While cadmium was used in the experimental work, other soft metals may be used.

Electromagnetic Acoustic Transducers for Robotic Nondestructive Inspection in Harsh Environments.

PubMed

Choi, Sungho; Cho, Hwanjeong; Lindsey, Matthew S; Lissenden, Cliff J

2018-01-11

Elevated temperature, gamma radiation, and geometric constraints inside dry storage casks for spent nuclear fuel represent a harsh environment for nondestructive inspection of the cask and require that the inspection be conducted with a robotic system. Electromagnetic acoustic transducers (EMATs) using non-contact ultrasonic transduction based on the Lorentz force to excite/receive ultrasonic waves are suited for use in the robotic inspection. Periodic permanent magnet EMATs that actuate/receive shear horizontal guided waves are developed for application to robotic nondestructive inspection of stress corrosion cracks in the heat affected zone of welds in stainless steel dry storage canisters. The EMAT's components are carefully selected in consideration of the inspection environment, and tested under elevated temperature and gamma radiation doses up to 177 °C and 5920 krad, respectively, to evaluate the performance of the EMATs under realistic environmental conditions. The effect of gamma radiation is minimal, but the EMAT's performance is affected by temperatures above 121 °C due to the low Curie temperature of the magnets. Different magnets are needed to operate at 177 °C. The EMAT's capability to detect notches is also evaluated from B-scan measurements on 304 stainless steel welded plate containing surface-breaking notches.

Simulation and observations of annual density banding in skeletons of Montastraea (Cnidaria: Scleractinia) growing under thermal stress associated with ocean warming

USGS Publications Warehouse

Worum, F.P.; Carricart-Ganivet, J. P.; Benson, L.; Golicher, D.

2007-01-01

We present a model of annual density banding in skeletons of Montastraea coral species growing under thermal stress associated with an ocean-warming scenario. The model predicts that at sea-surface temperatures (SSTs) <29??C, high-density bands (HDBs) are formed during the warmest months of the year. As temperature rises and oscillates around the optimal calcification temperature, an annual doublet in the HDB (dHDB) occurs that consists of two narrow HDBs. The presence of such dHDBs in skeletons of Montastraea species is a clear indication of thermal stress. When all monthly SSTs exceed the optimal calcification temperature, HDBs form during the coldest, not the warmest, months of the year. In addition, a decline in mean-annual calcification rate also occurs during this period of elevated SST. A comparison of our model results with annual density patterns observed in skeletons of M. faveolata and M. franksi, collected from several localities in the Mexican Caribbean, indicates that elevated SSTs are already resulting in the presence of dHDBs as a first sign of thermal stress, which occurs even without coral bleaching. ?? 2007, by the American Society of Limnology and Oceanography, Inc.

Tensile test of pressureless-sintered silicon nitride at elevated temperature

NASA Technical Reports Server (NTRS)

Matsusue, K.; Fujisawa, Y.; Takahara, K.

1985-01-01

Uniaxial tensile strength tests of pressureless sintered silicon nitride were carried out in air at temperatures ranging from room temperature up to 1600 C. Silicon nitrides containing Y2O3, Al2O3, Al2O3-MgO, or MgO-CeO2 additives were tested. The results show that the composition of the additive used influences the strength characteristics of the silicon nitride. The tensile strength rapidly decreased at temperatures above 1000 C for the materials containing MgO as the additive and above 1000 C for the material with Y2O3. When the temperature increased to as high as 1300 C, the strength decreased to about 10 percent of the room temperature strength in each case. Observations of the fracture origin and of the crack propagation on the fracture surfaces are discussed.

Surface elevation dynamics in a regenerating mangrove forest at Homebush Bay, Australia

USGS Publications Warehouse

Rogers, K.; Saintilan, N.; Cahoon, D.

2005-01-01

Following the dieback of an interior portion of a mangrove forest at Homebush Bay, Australia, surface elevation tables and feldspar marker horizons were installed in the impacted, intermediate and control forest to measure vertical accretion, elevation change, and shallow subsidence. The objectives of the study were to determine current vertical accretion and elevation change rates as a guide to understanding mangrove dieback, ascertain the factors controlling surface elevation change, and investigate the sustainability of the mangrove forest under estimated sea-level rise conditions. The study demonstrates that the influences on surface dynamics are more complex than soil accretion and soil autocompaction alone. During strong vegetative regrowth in the impacted forest, surface elevation increase exceeded vertical accretion apparently as a result of belowground biomass production. In addition, surface elevation in all forest zones was correlated with total monthly rainfall during a severe El Ni?o event, highlighting the importance of rainfall to groundwater recharge and surface elevation. Surface elevation increase for all zones exceeded the 85-year sea level trend for Sydney Harbour. Since mean sea-level also decreased during the El Ni?o event, the decrease in surface elevation did not translate to an increase in inundation frequency or influence the sustainability of the mangrove forest. These findings indicate that subsurface soil processes such as organic matter accumulation and groundwater flux can significantly influence mangrove surface elevation, and contribute to the long-term sustainability of mangrove systems under a scenario of rising sea levels.

U-Zr alloy: XPS and TEM study of surface passivation

NASA Astrophysics Data System (ADS)

Paukov, M.; Tkach, I.; Huber, F.; Gouder, T.; Cieslar, M.; Drozdenko, D.; Minarik, P.; Havela, L.

2018-05-01

Surface reactivity of Uranium metal is an important factor limiting its practical applications. Bcc alloys of U with various transition metals are much less reactive than pure Uranium. So as to specify the mechanism of surface protection, we have been studying the U-20 at.% Zr alloy by photoelectron spectroscopy and transmission electron microscopy. The surface was studied in as-obtained state, in various stages of surface cleaning, and during an isochronal annealing cycle. The analysis based on U-4f, Zr-3p, and O-1 s spectra shows that a Zr-rich phase segregates at the surface at temperatures exceeding 550 K, which provides a self-assembled coating. The comparison of oxygen exposure of the stoichiometric and coated surfaces shows that the coating is efficiently preventing the oxidation of uranium even at elevated temperatures. The coating can be associated with the UZr2+x phase. TEM study indicated that the coating is about 20 nm thick. For the clean state, the U-4f core-level lines of the bcc alloy are practically identical to those of α-U, revealing similar delocalization of the 5f electronic states.