CaSR-mediated interactions between calcium and magnesium homeostasis in mice.

PubMed

Quinn, Stephen J; Thomsen, Alex R B; Egbuna, Ogo; Pang, Jian; Baxi, Khanjan; Goltzman, David; Pollak, Martin; Brown, Edward M

2013-04-01

Calcium (Ca) and magnesium (Mg) homeostasis are interrelated and share common regulatory hormones, including parathyroid hormone (PTH) and vitamin D. However, the role of the calcium-sensing receptor (CaSR) in Mg homeostasis in vivo is not well understood. We sought to investigate the interactions between Mg and Ca homeostasis using genetic mouse models with targeted inactivation of PTH (PTH KO) or both PTH and the calcium-sensing receptor (CaSR) (double knockout, DKO). Serum Mg is lower in PTH KO and DKO mice than in WT mice on standard chow, whereas supplemental dietary Ca leads to equivalent Mg levels for all three genotypes. Mg loading increases serum Mg in all genotypes; however, the increase in serum Mg is most pronounced in the DKO mice. Serum Ca is increased with Mg loading in the PTH KO and DKO mice but not in the WT mice. Here, too, the hypercalcemia is much greater in the DKO mice. Serum and especially urinary phosphate are reduced during Mg loading, which is likely due to intestinal chelation of phosphate by Mg. Mg loading decreases serum PTH in WT mice and increases serum calcitonin in both WT and PTH KO mice but not DKO mice. Furthermore, Mg loading elevates serum 1,25-dihydroxyvitamin D in all genotypes, with greater effects in PTH KO and DKO mice, possibly due to reduced levels of serum phosphorus and FGF23. These hormonal responses to Mg loading and the CaSR's role in regulating renal function may help to explain changes in serum Mg and Ca found during Mg loading.

Multi-proxy Reconstructions of the Eastern Equatorial Pacific: Measuring Sr/Ca, Ba/Ca, and Li/Mg in Modern Corals Using ICP-OES

NASA Astrophysics Data System (ADS)

Cheung, A. H.; Cole, J. E.; Vetter, L.; Jimenez, G.; Thompson, D. M.; Tudhope, A. W.

2017-12-01

Sea surface temperature (SST) in the Eastern Equatorial Pacific (EEP) exhibits large variability on multiple timescales. These variations are often related to modes of climate variability that exert significant influence on global climate, such as the El Niño Southern Oscillation. However, the short length and sparsity of instrumental data in the EEP limits our ability to discern changes in this region. Geochemical signals in corals can help extend instrumental data further back in time. While δ18O and Sr/Ca are the most commonly analyzed geochemical tracers of SST in corals, they often have site-specific complications. Several alternatives (e.g., Li/Mg) have been proposed to overcome these challenges, but have yet to be applied to long climate records, in part due to the cost and time required to measure these elements. Here, we develop a new method that uses Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) to analyze Li/Mg, Sr/Ca, and Ba/Ca ratios in coral aragonite. We apply this method to two Porites spp. corals collected from the northern Galapagos archipelago (Wolf and Darwin Islands). We specifically assess the fidelity of Li/Mg and Sr/Ca to reconstruct SST, and Ba/Ca to reconstruct upwelling conditions. Our results confirm that both Li/Mg and Sr/Ca track SST. We show that despite analytical noise, downcore reconstructions of Li/Mg have the potential to provide additional information about SST that is not present in reconstructions generated from Sr/Ca alone. Skeletal Ba/Ca shows little relationship with upwelling, perhaps because of the distance of our sites from the center of upwelling in the southern Galapagos. These results demonstrate the potential for analyzing Sr, Li, Ba, Mg simultaneously in corals with a cost- and time- efficient method, which may be applied to coral paleoclimate sites worldwide.

Mg2+ activates the ryanodine receptor type 2 (RyR2) at intermediate Ca2+ concentrations.

PubMed

Chugun, Akihito; Sato, Osamu; Takeshima, Hiroshi; Ogawa, Yasuo

2007-01-01

To clarify whether activity of the ryanodine receptor type 2 (RyR2) is reduced in the sarcoplasmic reticulum (SR) of cardiac muscle, as is the case with the ryanodine receptor type 1 (RyR1), Ca(2+)-dependent [(3)H]ryanodine binding, a biochemical measure of Ca(2+)-induced Ca(2+) release (CICR), was determined using SR vesicle fractions isolated from rabbit and rat cardiac muscles. In the absence of an adenine nucleotide or caffeine, the rat SR showed a complicated Ca(2+) dependence, instead of the well-documented biphasic dependence of the rabbit SR. In the rat SR, [(3)H]ryanodine binding initially increased as [Ca(2+)] increased, with a plateau in the range of 10-100 microM Ca(2+), and thereafter further increased to an apparent peak around 1 mM Ca(2+), followed by a decrease. In the presence of these modulators, this complicated dependence prevailed, irrespective of the source. Addition of 0.3-1 mM Mg(2+) unexpectedly increased the binding two- to threefold and enhanced the affinity for [(3)H]ryanodine at 10-100 microM Ca(2+), resulting in the well-known biphasic dependence. In other words, the partial suppression of RyR2 is relieved by Mg(2+). Ca(2+) could be a substitute for Mg(2+). Mg(2+) also amplifies the responses of RyR2 to inhibitory and stimulatory modulators. This stimulating effect of Mg(2+) on RyR2 is entirely new, and is referred to as the third effect, in addition to the well-known dual inhibitory effects. This effect is critical to describe the role of RyR2 in excitation-contraction coupling of cardiac muscle, in view of the intracellular Mg(2+) concentration.

Mechanochemical synthesis of MgF2 - MF2 composite systems (M = Ca, Sr, Ba)

NASA Astrophysics Data System (ADS)

Scholz, G.; Breitfeld, S.; Krahl, T.; Düvel, A.; Heitjans, P.; Kemnitz, E.

2015-12-01

The capability of mechanochemical synthesis for the formation of MgF2-MF2 (M: Ca, Sr, Ba) composites, solid solutions or well-defined compounds was tested applying a fluorination of different fluorine-free metal sources with NH4F directly at milling. No evidence was found for a substitution of Mg2+ with Ca2+ (Sr2+, Ba2+) ions, or vice versa, in rutile or fluorite structure. However, an equimolar ratio of Mg2+ to the second cation allows the mechanochemical synthesis of tetrafluoromagnesates, MMgF4, which is more and more hampered the smaller the radius of the cation M2+ is. BaMgF4 is formed even phase pure from the acetates, SrMgF4 can only be observed in a mixture accompanied by the binary fluorides. In addition, 19F MAS NMR spectra along with calculations of 19F isotropic chemical shift values according to the superposition model point to the formation of a metastable phase of CaMgF4, which disappears at thermal treatment and decomposes into the binary fluorides CaF2 and MgF2.

Sr and Mg Isotopes of post-glacial limestones: implications for the chemical evolution of the Neoproterozoic Ocean after snowball earth

NASA Astrophysics Data System (ADS)

Liu, C.; Wang, Z.; Macdonald, F. A.

2013-12-01

The variation of ocean chemistry after the Marinoan (~635Ma) glaciation reflects the integrated effect of changes in continental weathering, carbonate precipitation and hydrothermal process in response to the extreme climatic event. To reconstruct the contemporary seawater chemistry, we analyzed Sr and Mg isotopes of the post-glacial carbonate overlying cap dolostones in the basal Ediacaran Ol Formation of the Tsagaan Olom Group in southwestern Mongolia. We employed an incremental leaching technique by dissolving carbonates sequentially with ammonium acetate and increasing concentrations of acetic acid to separate metals from various mineral phases in the carbonate (including surface adsorbed phases, calcite and dolomite). The leachates from each step and the dissolved bulk samples passed through chromatographic columns to extract pure Mg and Sr, which were then analyzed for their isotopic compositions by MC-ICP-MS (Neptune) at Yale University. Elemental ratios (Mg/Ca and Sr/(Mg+Ca)) in each leaching steps were measured as well. The following observations were noted from these experiments. First, the Mg/Ca ratio of the leachate decreased in the first few steps, reached a plateau in the middle steps and increased in the last few steps, implying a leaching sequence of surface-adsorbed phases, calcite and dolomite. Second, the Sr/(Mg+Ca) ratios remain almost constant except in the first two steps, suggesting similar Sr concentrations in different carbonates but elevated values in surface-adsorbed phases. Third, variations of both δ26MgDSM3 and 87Sr/86Sr values of the leachates with leaching steps exhibit similar trends to Mg/Ca, indicating enrichment of 26Mg and 87Sr in dolomite. Fourth, 87Sr/86Sr values of the leachates exhibit a wider plateau than δ26MgDSM3, denoting a binary mixing of dissolved calcite and dolomite in the last few steps. Finally, higher 87Sr/86Sr ratios and δ26MgDSM3 values were observed for bulk samples than their calcite components. The 87Sr/86Sr values of the plateau steps in each sample vary from 0.7075 to 0.7087, with the lowest values close to the proposed post-glacial seawater values. The δ26MgDSM3 of the plateau steps in samples preserving seawater 87Sr/86Sr values increase from -3.0‰ in the basal part to -2.7‰ in upper sections, which could be explained by the following possibilities: 1) seawater δ26MgDSM3 values increased by ~0.3‰ due to enhanced silicate weathering after deglaciation; 2) the increase was due to a temperature increase of ~20°C; 3) Mg isotopes of the samples in upper sections were less effected by the transformation of aragonite into calcite during diagenesis; or 4) a larger proportion of the carbonates in upper sections were originally precipitated as aragonite.

Effect of Mg2+ on the control of Ca2+ release in skeletal muscle fibres of the toad.

PubMed Central

Lamb, G D; Stephenson, D G

1991-01-01

1. The effect of myoplasmic Mg2+ on Ca2+ release was examined in mechanically skinned skeletal muscle fibres, in which the normal voltage-sensor control of Ca2+ release is preserved. The voltage sensors could be activated by depolarizing the transverse tubular (T-) system by lowering the [K+] in the bathing solution. 2. Fibres spontaneously contracted when the free [Mg2+] was decreased from 1 to 0.05 mM, with no depolarization or change of total ATP, [Ca2+] or pH (pCa 6.7, 50 microM-EGTA). After such a 'low-Mg2+ response' the sarcoplasmic reticulum (SR) was depleted of Ca2+ and neither depolarization nor caffeine (2 mM) could induce a response, unless the [Mg2+] was raised and the SR reloaded with Ca2+. Exposure to 0.05 mM-Mg2+ at low [Ca2+] (2 mM-free EGTA, pCa greater than 8.7) also induced Ca2+ release and depleted the SR. 3. The response to low [Mg2+] was unaffected by inactivation of the voltage sensors, but was completely blocked by 2 microM-Ruthenium Red indicating that it involved Ca2+ efflux through the normal Ca2+ release channels. 4. In the absence of ATP (and creatine phosphate), complete removal of Mg2+ (i.e. no added Mg2+ with 1 mM-EDTA) did not induce Ca2+ release. Depolarization in the absence of Mg2+ and ATP also did not induce Ca2+ release. 5. Depolarization in 10 mM-Mg2+ (pCa 6.7, 50 microM-EGTA, 8 mM-total ATP) did not produce any response. In the presence of 1 mM-EGTA to chelate most of the released Ca2+, depolarizations in 10 mM-Mg2+ did not noticeably deplete the SR of Ca2+, whereas a single depolarization in 1 mM-Mg2+ (and 1 mM-EGTA) resulted in marked depletion. Depolarization in the presence of D600 and 10 mM-Mg2+ produced use-dependent 'paralysis', indicating that depolarization in 10 mM-Mg2+ did indeed activate the voltage sensors. 6. Depolarization in the presence of 10 mM-Mg2+ and 25 microM-ryanodine neither interfered with the normal voltage control of Ca2+ release nor caused depletion of the Ca2+ in the SR even after returning to 1 mM-Mg2+ for 1 min, indicating that few if any of the release channels had been opened by the depolarization.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1708823

Development of biodegradable Zn-1X binary alloys with nutrient alloying elements Mg, Ca and Sr.

PubMed

Li, H F; Xie, X H; Zheng, Y F; Cong, Y; Zhou, F Y; Qiu, K J; Wang, X; Chen, S H; Huang, L; Tian, L; Qin, L

2015-05-29

Biodegradable metals have attracted considerable attentions in recent years. Besides the early launched biodegradable Mg and Fe metals, Zn, an essential element with osteogenic potential of human body, is regarded and studied as a new kind of potential biodegradable metal quite recently. Unfortunately, pure Zn is soft, brittle and has low mechanical strength in the practice, which needs further improvement in order to meet the clinical requirements. On the other hand, the widely used industrial Zn-based alloys usually contain biotoxic elements (for instance, ZA series contain toxic Al elements up to 40 wt.%), which subsequently bring up biosafety concerns. In the present work, novel Zn-1X binary alloys, with the addition of nutrition elements Mg, Ca and Sr were designed (cast, rolled and extruded Zn-1Mg, Zn-1Ca and Zn-1Sr). Their microstructure and mechanical property, degradation and in vitro and in vivo biocompatibility were studied systematically. The results demonstrated that the Zn-1X (Mg, Ca and Sr) alloys have profoundly modified the mechanical properties and biocompatibility of pure Zn. Zn-1X (Mg, Ca and Sr) alloys showed great potential for use in a new generation of biodegradable implants, opening up a new avenue in the area of biodegradable metals.

Development of biodegradable Zn-1X binary alloys with nutrient alloying elements Mg, Ca and Sr

PubMed Central

Li, H. F.; Xie, X. H.; Zheng, Y. F.; Cong, Y.; Zhou, F. Y.; Qiu, K. J.; Wang, X.; Chen, S. H.; Huang, L.; Tian, L.; Qin, L.

2015-01-01

Biodegradable metals have attracted considerable attentions in recent years. Besides the early launched biodegradable Mg and Fe metals, Zn, an essential element with osteogenic potential of human body, is regarded and studied as a new kind of potential biodegradable metal quite recently. Unfortunately, pure Zn is soft, brittle and has low mechanical strength in the practice, which needs further improvement in order to meet the clinical requirements. On the other hand, the widely used industrial Zn-based alloys usually contain biotoxic elements (for instance, ZA series contain toxic Al elements up to 40 wt.%), which subsequently bring up biosafety concerns. In the present work, novel Zn-1X binary alloys, with the addition of nutrition elements Mg, Ca and Sr were designed (cast, rolled and extruded Zn-1Mg, Zn-1Ca and Zn-1Sr). Their microstructure and mechanical property, degradation and in vitro and in vivo biocompatibility were studied systematically. The results demonstrated that the Zn-1X (Mg, Ca and Sr) alloys have profoundly modified the mechanical properties and biocompatibility of pure Zn. Zn-1X (Mg, Ca and Sr) alloys showed great potential for use in a new generation of biodegradable implants, opening up a new avenue in the area of biodegradable metals. PMID:26023878

Assessment of the Coral Temperature Proxies for Orbicella faveolata in the Southwestern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Vara, M. A.; DeLong, K. L.; Herrmann, A. D.; Ouellette, G., Jr.; Richey, J. N.

2017-12-01

Coral Sr/Ca is a robust proxy of sea surface temperature (SST); however, discrepancies in the Sr/Ca-SST relationship among colonies of the same species may reduce confidence in absolute temperature reconstructions. Furthermore, terrestrial carbonate weathering can provide local sources of Sr and/or Ca to coastal waters that may disrupt the temperature-based coral Sr/Ca signal. Thus other trace metal SST proxies have been suggested to circumvent these issues (Li/Ca, Li/Mg, and Sr-U). Coral Ba/Ca has been used as a proxy for runoff and coastal upwelling, and therefore may be used to identify intervals when these processes overprint the Sr/Ca-SST signal. This study tests multiple coral SST proxies using reproducibility assessments to determine the best performing SST proxy. We conduct these assessments with cores recovered in 1991 by the U.S. Geological Survey from five Orbicella faveolata colonies from three reefs offshore of Veracruz, Mexico (19.06°N, 96.93°W) in water depths varying from 3 to 12 m. Previous studies found micromilling the complex skeletal structure of O. faveolata challenging and that monthly resolution may not recover full seasonal cycles. We use a laser ablation inductively coupled plasma mass spectrometer to simultaneously sample this coral's structure at weekly intervals spanning 8 years for Li/Ca, Li/Mg, Sr-U, Sr/Ca, and Ba/Ca. Here we found coral Li/Ca means and seasonal variations are similar among colonies thus this proxy may capture absolute temperature and SST variability. Similar to previous research with Porites corals, Li/Ca in these O. faveolata corals decreases with increases in SST with similar slopes and intercepts. During the last 10 years of these corals' lives, coral Sr/Ca analysis reveals a mean shift among colonies suggesting an external source could have disrupted the Sr/Ca signal, possibly seasonal runoff and/or winter upwelling common to Veracruz waters. Coral Ba/Ca analyses reveals elevated values in winters that coincide with increases in coral Sr/Ca in the deeper colony suggesting upwelling is occurring at that location. However, the coral Ba/Ca does not coincide with increase coral Sr/Ca in the shallower coral indicating no direct influence from runoff. Coral Li/Mg and Sr-U do not show substantial seasonal variations as expected with a coral-SST proxy.

Modulation of Cardiac Ryanodine Receptor Channels by Alkaline Earth Cations

PubMed Central

Diaz-Sylvester, Paula L.; Porta, Maura; Copello, Julio A.

2011-01-01

Cardiac ryanodine receptor (RyR2) function is modulated by Ca2+ and Mg2+. To better characterize Ca2+ and Mg2+ binding sites involved in RyR2 regulation, the effects of cytosolic and luminal earth alkaline divalent cations (M2+: Mg2+, Ca2+, Sr2+, Ba2+) were studied on RyR2 from pig ventricle reconstituted in bilayers. RyR2 were activated by M2+ binding to high affinity activating sites at the cytosolic channel surface, specific for Ca2+ or Sr2+. This activation was interfered by Mg2+ and Ba2+ acting at low affinity M2+-unspecific binding sites. When testing the effects of luminal M2+ as current carriers, all M2+ increased maximal RyR2 open probability (compared to Cs+), suggesting the existence of low affinity activating M2+-unspecific sites at the luminal surface. Responses to M2+ vary from channel to channel (heterogeneity). However, with luminal Ba2+or Mg2+, RyR2 were less sensitive to cytosolic Ca2+ and caffeine-mediated activation, openings were shorter and voltage-dependence was more marked (compared to RyR2 with luminal Ca2+or Sr2+). Kinetics of RyR2 with mixtures of luminal Ba2+/Ca2+ and additive action of luminal plus cytosolic Ba2+ or Mg2+ suggest luminal M2+ differentially act on luminal sites rather than accessing cytosolic sites through the pore. This suggests the presence of additional luminal activating Ca2+/Sr2+-specific sites, which stabilize high Po mode (less voltage-dependent) and increase RyR2 sensitivity to cytosolic Ca2+ activation. In summary, RyR2 luminal and cytosolic surfaces have at least two sets of M2+ binding sites (specific for Ca2+ and unspecific for Ca2+/Mg2+) that dynamically modulate channel activity and gating status, depending on SR voltage. PMID:22039534

Role of magnesium oxide and strontium oxide as modifiers in silicate-based bioactive glasses: Effects on thermal behaviour, mechanical properties and in-vitro bioactivity.

PubMed

Bellucci, Devis; Sola, Antonella; Salvatori, Roberta; Anesi, Alexandre; Chiarini, Luigi; Cannillo, Valeria

2017-03-01

The composition of a CaO-rich silicate bioglass (BG_Ca-Mix, in mol%: 2.3 Na 2 O; 2.3 K 2 O; 45.6 CaO; 2.6 P 2 O 5 ; 47.2 SiO 2 ) was modified by replacing a fixed 10mol% of CaO with MgO or SrO or fifty-fifty MgO-SrO. The thermal behaviour of the modified glasses was accurately evaluated via differential thermal analysis (DTA), heating microscopy and direct sintering tests. The presence of MgO and/or SrO didn't interfere with the thermal stability of the parent glass, since all the new glasses remained completely amorphous after sintering (treatment performed at 753°C for the glass with MgO; at 750°C with SrO; at 759°C with MgO and SrO). The sintered samples achieved good mechanical properties, with a Young's modulus ranging between 57.9±6.7 for the MgO-SrO modified composition and 112.6±8.0GPa for the MgO-modified one. If immersed in a simulated body fluid (SBF), the modified glasses after sintering retained the strong apatite forming ability of the parent glass, in spite of the presence of MgO and/or SrO. Moreover, the sintered glasses, tested with MLO-Y4 osteocytes by means of a multi-parametrical approach, showed a good bioactivity in vitro, since neither the glasses nor their extracts caused any negative effect on cell viability or any inhibition on cell growth. The best results were achieved by the MgO-modified glasses, both BGMIX_Mg and BGMIX_MgSr, which were able to exert a strong stimulating effect on the cell growth, thus confirming the beneficial effect of MgO on the glass bioactivity. Copyright © 2016 Elsevier B.V. All rights reserved.

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

Ogawa, E.; Suzuki, S.; Tsuzuki, H.

Mice were subcutaneoulsy injected with Sr/sup 90/ or Sr/sup 85/, and effects of various drugs on their 3-day excretion and retention on the 4th day were investigated. Among chelating agents, NaCa citrate, NaMg citrate, NaSr citrate, Achromycin (or tetracycline), and aspartic MgK (alone or in combination with NH/sub 4/Cl) displayed Sr-eliminating effects. ATP increased only the excretion without diminishing the retention in bone. EDTA, DTPA, BADE, tricarballylate, Na citrate and NaPb citrate were not effective. Among salts, Mg salt, sulfite, and thiosulfate were effective in eliminating Sr. The last exerted a greater effect when given concurrently with Mg, Ca, ormore » Sr salt. Ca and Sr salt exerted no effect, and ammonium chloride promoted only urinary secretion, not extending to local or total excretion. Such salts as induce alkalosis conversely exerted inhibitory effects. Among hormones, glucocorticoids had Sreliminating effects. TSH was effective, and antithyroidal drugs conversely seemed to have excretion-diminishing effects. Among vitamins, cocarboxylase increased Sr excretion, but did not decrease the retention in bone. Also metabolic inhibitors were ineffective, and NaF conversely increased bone deposition of Sr. Among diuretics, SHdrugs, and weak chelating agents, there were no effective drugs. (JAIF)« less

Relationships between water, otolith, and scale chemistries of westslope cutthroat trout from the Coeur d'Alene River, Idaho: the potential application of hard-part chemistry to describe movements in freshwater

Treesearch

Brian K. Wells; Bruce E. Rieman; James L. Clayton; Donna L. Horan; Cynthia M. Jones

2003-01-01

We quantified Mg:Ca, Mn:Ca, Sr:Ca, and Ba:Ca molar ratios from an area representing the summer 2000 growth season on otoliths and scales from 1-year-old westslope cutthroat trout Oncorhyncus clarki lewisi collected from three streams in the Coeur d'Alene River, Idaho, system. We also quantified Mg:Ca, Sr:Ca, and Ba:Ca molar ratios in the water...

Intrareef variations in Li/Mg and Sr/Ca sea surface temperature proxies in the Caribbean reef-building coral Siderastrea siderea

NASA Astrophysics Data System (ADS)

Fowell, Sara E.; Sandford, Kate; Stewart, Joseph A.; Castillo, Karl D.; Ries, Justin B.; Foster, Gavin L.

2016-10-01

Caribbean sea surface temperatures (SSTs) have increased at a rate of 0.2°C per decade since 1971, a rate double that of the mean global change. Recent investigations of the coral Siderastrea siderea on the Belize Mesoamerican Barrier Reef System (MBRS) have demonstrated that warming over the last 30 years has had a detrimental impact on calcification. Instrumental temperature records in this region are sparse, making it necessary to reconstruct longer SST records indirectly through geochemical temperature proxies. Here we investigate the skeletal Sr/Ca and Li/Mg ratios of S. siderea from two distinct reef zones (forereef and backreef) of the MBRS. Our field calibrations of S. siderea show that Li/Mg and Sr/Ca ratios are well correlated with temperature, although both ratios are 3 times more sensitive to temperature change in the forereef than in the backreef. These differences suggest that a secondary parameter also influences these SST proxies, highlighting the importance for site- and species-specific SST calibrations. Application of these paleothermometers to downcore samples reveals highly uncertain reconstructed temperatures in backreef coral, but well-matched reconstructed temperatures in forereef coral, both between Sr/Ca-SSTs and Li/Mg-SSTs, and in comparison to the Hadley Centre Sea Ice and Sea Surface Temperature record. Reconstructions generated from a combined Sr/Ca and Li/Mg multiproxy calibration improve the precision of these SST reconstructions. This result confirms that there are circumstances in which both Li/Mg and Sr/Ca are reliable as stand-alone and combined proxies of sea surface temperature. However, the results also highlight that high-precision, site-specific calibrations remain critical for reconstructing accurate SSTs from coral-based elemental proxies.

Sr/Ca and Mg/Ca in Glycymeris glycymeris (Bivalvia) shells from the Iberian upwelling system: Ontogeny and environmental control

NASA Astrophysics Data System (ADS)

Freitas, Pedro; Richardson, Christopher; Chenery, Simon; Monteiro, Carlos; Butler, Paul; Reynolds, David; Scourse, James; Gaspar, Miguel

2017-04-01

Bivalve shells have a great potential as high-resolution geochemical proxy archives of marine environmental conditions. In addition, sclerochronology of long-lived bivalve species (e.g. Arctica islandica) provides a timeline of absolutely dated shell material for geochemical analysis that can extend into the past beyond the lifetime of single individuals through the use of replicated crossmatched centennial to millennial chronologies. However, the interpretation of such records remains extremely challenging and complex, with multiple environmental and biological processes affecting element incorporation in the shell (e.g. crystal fabrics, organic matrix, biomineralization mechanisms and physiological processes). As a result, the effective use of bivalve shell elemental/Ca ratios as palaeoenvironmental proxies has been limited, often to species-specific applications or applications restricted to particular environmental settings. The dog-cockle, Glycymeris glycymeris, is a relatively long-lived bivalve (up to 200 years) that occurs in coarse-grained subtidal sediments of coastal shelf seas of Europe and North West Africa. Glycymeris glycymeris shells provide a valuable, albeit not fully explored, archive to reconstruct past environmental variability in an area lacking sclerochronological studies due to the rarity of long-lived bivalves and lack of coral reefs. In this study, we evaluate the potential of Sr/Ca and Mg/Ca ratios in G. glycymeris shells as geochemical proxies of upwelling conditions in the Iberian Upwelling System, the northern section of the Canary Current Eastern Boundary Upwelling System. Sr/Ca and Mg/Ca generally co-varied significantly and a clear ontogenetic, non-environmental related change in Sr/Ca and Ba/Ca variability was observed. High Sr/Ca and Mg/Ca ratios in older shells (> 10 years old) were found to be associated with the occurrence of growth lines deposited during the winter reduction in shell growth. Nevertheless, Sr/Ca and Mg/Ca variation in older shells was synchronous with contemporary environmental conditions, i.e. upwelling intensity and salinity. The use of Sr or Mg in G. glycymeris shells as valid geochemical environmental proxies in the Iberian Upwelling System remains complex and requires further research to unravel environmental and physiological/biomineralization controls. This study was financed by the Portuguese Fundação para a Ciência e Tecnologia (FCT) GLYCY Project (contract PTDC/AAC-CLI/118003/2010) and a sabbatical grant to PSF (Ref: SFRH/BSAB/127786/2016), co-supported by POCH and the European Social Fund. Funding for consumable costs was provided by Bangor University.

Research on The Removal of Scale Ions from Circulating Cooling Wastewater by Chemical Coagulation Process

NASA Astrophysics Data System (ADS)

Du, Song; Jin, Wenbiao; Duan, Feng

2018-06-01

In this paper, the circulating cooling wastewater was treated by chemical coagulation process through adding NaOH/Na2CO3.The effect of NaOH and Na2CO3 dose on removal of scale ions, such as Ca2+, Mg2+, Ba2+, Sr2+, SiO2, was studied and the removal mechanism was discussed. The results showed that the increase of NaOH dose was beneficial to the removal of above-mentioned scale ions. When NaOH was only added, the removal efficiency of Ca2+, Mg2+, Ba2+, Sr2+, SiO2 was 86.3%, 91.6%, 86.5%, 58.1%, 84.2%, respectively. When 680 mg/L of NaOH and 300 mg/L of Na2CO3 were added, and the effluent pH was above 11.2, the removal efficiency of Ca2+, Mg2+ was 95.8% and 89.4%, respectively, and the concentration of Ca2+and Mg2+ was below 20 mg/L, which met the target of wastewater treatment. Finally the possible removal mechanism of Ca2+, Mg2+, Ba2+, Sr2+and SiO2 was discussed.

Tracing mineral weathering reactions in the critical zone using Mg, Ca, and Sr isotopes, Luquillo Mountains, Puerto Rico

NASA Astrophysics Data System (ADS)

Buss, H. L.; White, A. F.; Vivit, D.; Bullen, T. D.; Blum, A. E.; Dessert, C.; Gaillardet, J.

2008-12-01

Mineral weathering in the critical zone directly impacts the availability of many important soil nutrients. As part of the USGS Water Energy and Biogeochemical Budgets (WEBB) program and the Critical Zone Exploration Network, we are investigating mineral nutrient distributions and fluxes in depth profiles (to 16 m) at five sites in the Bisley 1 catchment in the Luquillo Mountains of Puerto Rico. The Bisley 1 catchment contains a thick regolith developed on marine bedded, andesitic, volcaniclastic bedrock. Pore waters were sampled as a function of depth from nested suction water samplers. Pore water chemistry was analyzed and compared to total chemistry of solid samples taken from augered cores. Mg, Ca and Sr isotope ratios were measured of the pore waters at the Institut de Physique du Globe de Paris (Mg) and at the USGS in Menlo Park, CA (Ca, Sr). The Mg isotope ratios increase with increasing depth from δ26Mg = -0.772 at the surface to - 0.267 at depth, relative to the DSM3 standard. Sr isotope ratios vary from 0.70922 to 0.71016 87Sr/86Sr, with no discernible depth trend. The regolith is highly weathered and is depleted in primary minerals (except quartz) with respect to bedrock. Volumetric strain, calculated with respect to quartz, indicates approximately 25% volume collapse occurred relative to the original volume of the bedrock. Plagioclase, chlorite, pyroxene, and amphibole weather at the bedrock-regolith interface. The regolith contains quartz, kaolinite, other clays, and iron and manganese oxides. Increasing solid and pore water Mg concentrations and δ26Mg with depth likely indicate a two step weathering process wherein high-Mg chlorite dissolves at the bedrock-regolith interface and forms Mg-containing secondary clays and oxides, which then dissolve within the regolith profile.

Control of renal calcium, phosphate, electrolyte, and water excretion by the calcium-sensing receptor.

PubMed

Tyler Miller, R

2013-06-01

Through regulation of excretion, the kidney shares responsibility for the metabolic balance of calcium (Ca(2+)) with several other tissues including the GI tract and bone. The balances of Ca(2+) and phosphate (PO4), magnesium (Mg(2+)), sodium (Na(+)), potassium (K(+)), chloride (Cl(-)), and water (H2O) are linked via regulatory systems with overlapping effects and are also controlled by systems specific to each of them. Cloning of the calcium-sensing receptor (CaSR) along with the recognition that mutations in the CaSR gene are responsible for two familial syndromes characterized by abnormalities in the regulation of PTH secretion and Ca(2+) metabolism (Familial Hypocalciuric Hypercalcemia, FHH, and Autosomal Dominant Hypocalcemia, ADH) made it clear that extracellular Ca(2+) (Ca(2+)o) participates in its own regulation via a specific, receptor-mediated mechanism. Demonstration that the CaSR is expressed in the kidney as well as the parathyroid glands combined with more complete characterizations of FHH and ADH established that the effects of elevated Ca(2+) on the kidney (wasting of Na(+), K(+), Cl(-), Ca(2+), Mg(2+) and H2O) are attributable to activation of the CaSR. The advent of positive and negative allosteric modulators of the CaSR along with mouse models with global or tissue-selective deletion of the CaSR in the kidney have allowed a better understanding of the functions of the CaSR in various nephron segments. The biology of the CaSR is more complicated than originally thought and difficult to define precisely owing to the limitations of reagents such as anti-CaSR antibodies and the difficulties inherent in separating direct effects of Ca(2+) on the kidney mediated by the CaSR from associated CaSR-induced changes in PTH. Nevertheless, renal CaSRs have nephron-specific effects that contribute to regulating Ca(2+) in the circulation and urine in a manner that assures a narrow range of Ca(2+)o in the blood and avoids excessively high concentrations of Ca(2+) in the urine. Published by Elsevier Ltd.

A theoretical study of the positive and dipositive ions of M(NH3)n and M(H2O)n for M = Mg, Ca, or Sr

NASA Technical Reports Server (NTRS)

Bauschlicher, Charles W., Jr.; Sodupe, Mariona; Partridge, Harry

1992-01-01

The structure and binding energies are determined for many of the M(H2O)n(+) and M(H2O)n(2+) species, for n = 1-3 and M = Mg, Ca, or Sr. The trends are explained in terms of metal sp or sd-sigma hybridization and core polarization. The M(NH3)n(+) systems, with M = Mg or Sr, are also studied. For the positive ions, the low-lying excited states are also studied and compared with experiment. The calculations suggest an alternative interpretation of the SrNH3(+) spectrum.

Anthrax and the geochemistry of soils in the contiguous United States

USGS Publications Warehouse

Griffin, Dale W.; Silvestri, Erin E.; Bowling, Charlena Y.; Boe, Timothy; Smith, David B.; Nichols, Tonya L.

2014-01-01

Soil geochemical data from sample sites in counties that reported occurrences of anthrax in wildlife and livestock since 2000 were evaluated against counties within the same states (MN, MT, ND, NV, OR, SD and TX) that did not report occurrences. These data identified the elements, calcium (Ca), manganese (Mn), phosphorus (P) and strontium (Sr), as having statistically significant differences in concentrations between county type (anthrax occurrence versus no occurrence). Tentative threshold values of the lowest concentrations of each of these elements (Ca = 0.43 wt %, Mn = 142 mg/kg, P = 180 mg/kg and Sr = 51 mg/kg) and average concentrations (Ca = 1.3 wt %, Mn = 463 mg/kg, P = 580 mg/kg and Sr = 170 mg/kg) were identified from anthrax-positive counties as prospective investigative tools in determining whether an outbreak had “potential” or was “likely” at any given geographic location in the contiguous United States.

Effect of paleoseawater composition on hydrothermal exchange in midocean ridges

NASA Astrophysics Data System (ADS)

Antonelli, Michael A.; Pester, Nicholas J.; Brown, Shaun T.; DePaolo, Donald J.

2017-11-01

Variations in the Mg, Ca, Sr, and SO4 concentrations of paleoseawater can affect the chemical exchange between seawater and oceanic basalt in hydrothermal systems at midocean ridges (MOR). We present a model for evaluating the nature and magnitude of these previously unappreciated effects, using available estimates of paleoseawater composition over Phanerozoic time as inputs and 87Sr/86Sr of ophiolite epidosites and epidote-quartz veins as constraints. The results suggest that modern hydrothermal fluids are not typical due to low Ca and Sr relative to Mg and SO4 in modern seawater. At other times during the last 500 million years, particularly during the Cretaceous and Ordovician, hydrothermal fluids had more seawater-derived Sr and Ca, a prediction that is supported by Sr isotope data. The predicted 87Sr/86Sr of vent fluids varies cyclically in concert with ocean chemistry, with some values much higher than the modern value of ˜0.7037. The seawater chemistry effects can be expressed in terms of the transfer efficiency of basaltic Ca and Sr to seawater in hydrothermal systems, which varies by a factor of ˜1.6 over the Phanerozoic, with minima when seawater Mg and SO4 are low. This effect provides a modest negative feedback on seawater composition and 87Sr/86Sr changes. For the mid-Cretaceous, the low 87Sr/86Sr of seawater requires either exceptionally large amounts of low-temperature exchange with oceanic crust or that the weathering flux of continentally derived Sr was especially small. The model also has implications for MOR hydrothermal systems in the Precambrian, when low-seawater SO4 could help explain low seawater 87Sr/86Sr.

Effect of paleoseawater composition on hydrothermal exchange in midocean ridges

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

Antonelli, Michael A.; Pester, Nicholas J.; Brown, Shaun T.

Variations in the Mg, Ca, Sr, and SO 4 concentrations of paleoseawater can affect the chemical exchange between seawater and oceanic basalt in hydrothermal systems at midocean ridges (MOR). Here, we present a model for evaluating the nature and magnitude of these previously unappreciated effects, using available estimates of paleoseawater composition over Phanerozoic time as inputs and 87Sr/ 86Sr of ophiolite epidosites and epidote-quartz veins as constraints. The results suggest that modern hydrothermal fluids are not typical due to low Ca and Sr relative to Mg and SO 4 in modern seawater. At other times during the last 500 millionmore » years, particularly during the Cretaceous and Ordovician, hydrothermal fluids had more seawater-derived Sr and Ca, a prediction that is supported by Sr isotope data. The predicted 87Sr/ 86Sr of vent fluids varies cyclically in concert with ocean chemistry, with some values much higher than the modern value of ~0.7037. The seawater chemistry effects can be expressed in terms of the transfer efficiency of basaltic Ca and Sr to seawater in hydrothermal systems, which varies by a factor of ~1.6 over the Phanerozoic, with minima when seawater Mg and SO 4 are low. This effect provides a modest negative feedback on seawater composition and 87Sr/ 86Sr changes. For the mid-Cretaceous, the low 87Sr/ 86Sr of seawater requires either exceptionally large amounts of low-temperature exchange with oceanic crust or that the weathering flux of continentally derived Sr was especially small. Lastly, the model also has implications for MOR hydrothermal systems in the Precambrian, when low-seawater SO 4 could help explain low seawater 87Sr/ 86Sr.« less

Effect of paleoseawater composition on hydrothermal exchange in midocean ridges

DOE PAGES

Antonelli, Michael A.; Pester, Nicholas J.; Brown, Shaun T.; ...

2017-11-06

Variations in the Mg, Ca, Sr, and SO 4 concentrations of paleoseawater can affect the chemical exchange between seawater and oceanic basalt in hydrothermal systems at midocean ridges (MOR). Here, we present a model for evaluating the nature and magnitude of these previously unappreciated effects, using available estimates of paleoseawater composition over Phanerozoic time as inputs and 87Sr/ 86Sr of ophiolite epidosites and epidote-quartz veins as constraints. The results suggest that modern hydrothermal fluids are not typical due to low Ca and Sr relative to Mg and SO 4 in modern seawater. At other times during the last 500 millionmore » years, particularly during the Cretaceous and Ordovician, hydrothermal fluids had more seawater-derived Sr and Ca, a prediction that is supported by Sr isotope data. The predicted 87Sr/ 86Sr of vent fluids varies cyclically in concert with ocean chemistry, with some values much higher than the modern value of ~0.7037. The seawater chemistry effects can be expressed in terms of the transfer efficiency of basaltic Ca and Sr to seawater in hydrothermal systems, which varies by a factor of ~1.6 over the Phanerozoic, with minima when seawater Mg and SO 4 are low. This effect provides a modest negative feedback on seawater composition and 87Sr/ 86Sr changes. For the mid-Cretaceous, the low 87Sr/ 86Sr of seawater requires either exceptionally large amounts of low-temperature exchange with oceanic crust or that the weathering flux of continentally derived Sr was especially small. Lastly, the model also has implications for MOR hydrothermal systems in the Precambrian, when low-seawater SO 4 could help explain low seawater 87Sr/ 86Sr.« less

[The functions of calcium-sensing receptor in regulating mineral metabolism.

PubMed

Kinoshita, Yuka

Calcium-sensing receptor(CaSR)which belongs to a G protein-coupled receptor family is one of the key elements in regulating calcium homeostasis. CaSR has been identified as a receptor to control parathyroid hormone(PTH)secretion in parathyroid glands according to serum calcium ion(Ca2+)levels. It has also been shown that CaSR controls reabsorption of water and several cations including Ca2+and magnesium ion(Mg2+)in renal tubular cells. This review summarizes the functions and roles of CaSR in mineral metabolism that are exerted in parathyroid glands, kidney, and intestine.

Determination of element/Ca ratios in foraminifera and corals using cold- and hot-plasma techniques in inductively coupled plasma sector field mass spectrometry

NASA Astrophysics Data System (ADS)

Lo, Li; Shen, Chuan-Chou; Lu, Chia-Jung; Chen, Yi-Chi; Chang, Ching-Chih; Wei, Kuo-Yen; Qu, Dingchuang; Gagan, Michael K.

2014-02-01

We have developed a rapid and precise procedure for measuring multiple elements in foraminifera and corals by inductively coupled plasma sector field mass spectrometry (ICP-SF-MS) with both cold- [800 W radio frequency (RF) power] and hot- (1200 W RF power) plasma techniques. Our quality control program includes careful subsampling protocols, contamination-free workbench spaces, and refined plastic-ware cleaning process. Element/Ca ratios are calculated directly from ion beam intensities of 24Mg, 27Al, 43Ca, 55Mn, 57Fe, 86Sr, and 138Ba, using a standard bracketing method. A routine measurement time is 3-5 min per dissolved sample. The matrix effects of nitric acid, and Ca and Sr levels, are carefully quantified and overcome. There is no significant difference between data determined by cold- and hot-plasma methods, but the techniques have different advantages. The cold-plasma technique offers a more stable plasma condition and better reproducibility for ppm-level elements. Long-term 2-sigma relative standard deviations (2-RSD) for repeat measurements of an in-house coral standard are 0.32% for Mg/Ca and 0.43% for Sr/Ca by cold-plasma ICP-SF-MS, and 0.69% for Mg/Ca and 0.51% for Sr/Ca by hot-plasma ICP-SF-MS. The higher sensitivity and enhanced measurement precision of the hot-plasma procedure yields 2-RSD precision for μmol/mol trace elements of 0.60% (Mg/Ca), 9.9% (Al/Ca), 0.68% (Mn/Ca), 2.7% (Fe/Ca), 0.50% (Sr/Ca), and 0.84% (Ba/Ca) for an in-house foraminiferal standard. Our refined ICP-SF-MS technique, which has the advantages of small sample size (2-4 μg carbonate consumed) and fast sample throughput (5-8 samples/hour), should open the way to the production of high precision and high resolution geochemical records for natural carbonate materials.

Differential response of corals to regional mass-warming events as evident from skeletal Sr/Ca and Mg/Ca ratios

NASA Astrophysics Data System (ADS)

Clarke, Harry; D'Olivo, Juan Pablo; Falter, James; Zinke, Jens; Lowe, Ryan; McCulloch, Malcolm

2017-05-01

During the summer of 2010/2011, a regional marine heat wave resulted in coral bleaching of variable severity along much of the western coastline of Australia. At Ningaloo Reef, a 300 km long fringing reef system and World Heritage site, highly contrasting coral bleaching was observed between two morphologically distinct nearshore reef communities located on either side of the Ningaloo Peninsula: Tantabiddi (˜20% bleaching) and Bundegi (˜90% bleaching). For this study, we collected coral cores (Porites sp.) from Tantabiddi and Bundegi reef sites to assess the response of the Sr/Ca temperature proxy and Mg/Ca ratios to the variable levels of thermal stress imposed at these two sites during the 2010/2011 warming event. We found that there was an anomalous increase in Sr/Ca and decrease in Mg/Ca ratios in the Bundegi record that was coincident with the timing of severe coral bleaching at the site, while no significant changes were observed in the Tantabiddi record. We show that the change in the relationship of Sr/Ca and Mg/Ca ratios with temperature at Bundegi during the 2010/2011 event reflects changes in related coral "vital" processes during periods of environmental stress. These changes were found to be consistent with a reduction in active transport of Ca2+ to the site of calcification leading to a reduction in calcification rates and reduced Rayleigh fractionation of incorporated trace elements.

Ca and Sr Isotope Sytematics in Mid-Ocean Ridge Hydrothermal Fluids

NASA Astrophysics Data System (ADS)

Pester, N. J.; Syverson, D. D.; Higgins, J. A.; Seyfried, W. E., Jr.

2016-12-01

We report a comprehensive suite of Ca isotopic data (δ44/40Ca) from mid-ocean ridge hydrothermal fluids, standardized relative to seawater. Samples were acquired from 7 different vent fields on the EPR, JdFR and MAR during expeditions between 1999 and 2014. All endmember hydrothermal fluids (within analytical uncertainty) reflect an entirely MORB-dominated signal (-1.0 to -1.2 ‰). This rather uniform signal, despite variable fluid chemistries and a mixture of mafic to ultramafic host lithologies, is somewhat surprising given the noteworthy Ca concentrations in both the hydrothermal fluids and precursor seawater. One explanation for this observation involves the change in anhydrite (CaSO4) saturation with increasing temperature, and the molal concentration ratio of [Mg]:[Ca]:[SO4] in modern seawater of 53:10:28. The near quantitative removal of seawater Mg to silicate alteration phases, favorable at all temperatures, is largely charge balanced by exchange for basaltic Ca, and this process alone can account for the majority of the rock dominated δ44/40Casw signal. That these values are equivalent to MORB, however, suggests a high proportion of this Mg-Ca exchange occurs after seawater Ca precipitates as anhydrite in lower temperature (recharge) regimes of the hydrothermal system, aided by the low [Ca]/[SO4]. 87/86Sr ratios of hydrothermal fluids exhibit a seawater signal of 20 to 30% and Sr is therefore not quantitatively removed during incipient anhydrite formation. Strontium mobility in hydrothermal systems is still poorly understood, but the offset between the Ca and Sr isotopic signatures is consistent with near-equilibrium partitioning of Sr into anhydrite observed in recent experiments. Such observations from modern MOR systems place important constraints on the role of hydrothermal fluxes in paleo-seawater evolution, such as feedbacks involving significant variability in [Mg]:[Ca]:[SO4] ratios of seawater suggested over much of the Phanerozoic.

Population ecology and shell chemistry of a phytal ostracode species (Loxoconcha matagordensis) in the Chesapeake Bay watershed

USGS Publications Warehouse

Vann, C.D.; Cronin, T. M.; Dwyer, Gary S.

2004-01-01

Population ecology and shell chemistry were studied in the phytal ostracode Loxoconcha matagordensis (Swain 1955) collected from Zostera marina seagrass beds in the Chesapeake Bay to provide seasonal constraints on shell secretion time for paleothermometry. Population density and age structure were defined by two main breeding cycles that occurred between 01 to 15 June and 02 to 16 August 2001. The time interval between breeding cycles was ???2 months and total juvenile standing crop increased almost three-fold between the first and second breeding cycles. Dark brown over-wintered adults comprised the majority of the population between March and April 2001, while newly secreted translucent adults were predominant between June and September. Seasonal shell Mg/Ca and Sr/Ca ratios were positively correlated with water temperature at both sites, with the strongest correlations occurring between June and September from newly secreted shells at Dameron Marsh. Old, dark brown shells contained 10% to 23% and 1% to 6% less Mg/Ca and Sr/Ca, respectively, than new shells. Because a fossil assemblage of L. matagordensis will contain ???30% old shells (dark-brown), these results suggest that fossil Mg/Ca ratios yield an integrated late spring to summer temperature signal. Shell Mg/Ca and Sr/Ca ratios of specimens of L. matagordensis collected from living Zostera were positively correlated, suggesting that temperature may influence both elemental ratios. Mg/Ca and Sr/Ca ratios of fossil shells of the related species Loxoconcha sp. A obtained from four sediment cores were also studied and exhibited a weaker correlation between the two elemental ratios. ?? 2004 Elsevier B.V. All rights reserved.

A case of gain-of-function mutation in calcium-sensing receptor: supplemental hydration is required for renal protection.

PubMed

Suzuki, M; Aso, T; Sato, T; Michimata, M; Kazama, I; Saiki, H; Hatano, R; Ejima, Y; Miyama, N; Sato, A; Matsubara, M

2005-06-01

The calcium-sensing receptor (CaSR) regulates the extracellular calcium level, mainly by controlling parathyroid hormon secretion and renal calcium reabsorption. In gain-of-function CaSR mutations, the genetic abnormalities increase CaSR activity leading to the development of such clinical manifestations as hypercalciuric hypocalcemia and hypoparathyroidism. We report a Japanese case of CaSR gain-of-function mutation and represent a therapeutic intervention based on the functional characteristics of CaSR in renal tubule. DNA sequence analysis revealed a heterozygous G to T mutation identified in a 12-year-old Japanese girl presenting with sporadic onset of hypercalciuric hypocalcemia and hypoparathyroidism. The mutation is located in the N-terminal extracellular domain of the CaSR gene, one of the most important parts for the three-dimensional construction of the receptor, resulting in the substitution of phenylalanine for cysteine at amino acid 131 (C131F) in exon 3. Based on the diagnosis of the gain-of-function mutation in the CaSR, oral hydrochlorothiazide administration and supplemental hydration were started in addition to calcium supplementation. The combination therapy of thiazide and supplemental hydration markedly reduced both renal calcium excretion and urinary calcium concentration from 0.4-0.7 to less than 0.1 mg/mg (urinary calcium/creatinine ratio) and from 10-15 to 3-5 mg/dl (urinary calcium concentration), respectively. This therapy stopped the progression of renal calcification during the follow-up period. Supplemental hydration should be considered essential for the following reasons: (1) calcium supplementation activates the CaSR in the kidney and suppresses renal urinary concentrating ability, (2) the thiazide has a diuretic effect, (3) as calcium supplementation increases renal calcium excretion, the supplemental hydration decreases urinary calcium concentration by increasing urinary volume, thereby diminishing the risk of intratubular crystallization of calcium ion.

An apparent "vital effect" of calcification rate on the Sr/Ca temperature proxy in the reef coral Montipora capitata

USGS Publications Warehouse

Kuffner, Ilsa; Jokiel, Paul L.; Rodgers, Kuulei; Andersson, Andreas; Mackenzie, Fred T.

2012-01-01

Measuring the strontium to calcium ratio in coral skeletons reveals information on seawater temperatures during skeletal deposition, but studies have shown additional variables may affect the ratio. Here we measured Sr/Ca in the reef coral, Montipora capitata, grown in six mesocosms continuously supplied with seawater from the adjacent reef flat. Three mesocosms were ambient controls, and three had seawater chemistry simulating "ocean acidification" (OA). We found that Sr/Ca was not affected by the OA treatment, and neither was coral calcification for these small colonies (larger colonies did show an OA effect). The lack of OA effects allowed us to test the hypothesis that coral growth rate can affect Sr/Ca using the natural range in calcification rates of the corals grown at the same temperature. We found that Sr/Ca was inversely related to calcification rate (Sr/Ca = 9.39 - 0.00404 mmol/mol * mg day-1 cm-2, R2 = 0.32). Using a previously published calibration curve for this species, a 22 mg day-1 colony-1 increase in calcification rate introduced a 1°C warmer temperature estimate, with the 27 corals reporting "temperatures" ranging from 24.9 to 28.9, with mean 26.6 ± 0.9°C SD. Our results lend support to hypotheses invoking kinetic processes and growth rate to explain vital effects on Sr/Ca. However, uncertainty in the slope of the regression of Sr/Ca on calcification and a low R-squared value lead us to conclude that Sr/Ca could still be a useful proxy in this species given sufficient replication or by including growth rate in the calibration.

Rapid ionic modifications during the aequorin-detected calcium transient in a skinned canine cardiac Purkinje cell

PubMed Central

1985-01-01

A microprocessor-controlled system of microinjections and microaspirations has been developed to change, within approximately 1 ms, the [free Ca2+] at the outer surface of the sarcoplasmic reticulum (SR) wrapped around individual myofibrils (0.3-0.4 micron radius) of a skinned canine cardiac Purkinje cell (2.5-4.5 micron overall radius) at different phases of a Ca2+ transient. Simultaneously monitoring tension and aequorin bioluminescence provided two methods for estimating the peak myoplasmic [free Ca2+] reached during the spontaneous cyclic Ca2+ release from the SR obtained in the continuous presence of a bulk solution [free Ca2+] sufficiently high to overload the SR. These methods gave results in excellent agreement for the spontaneous Ca2+ release under a variety of conditions of pH and [free Mg2+], and of enhancement of Ca2+ release by calmodulin. Disagreement was observed, however, when the Ca2+ transient was modified during its ascending phase. The experiments also permitted quantification of the aequorin binding within the myofibrils and determination of its operational apparent affinity constant for Ca2+ at various [free Mg2+] levels. An increase of [free Ca2+] at the outer surface of the SR during the ascending phase of the Ca2+ transient induced further release of Ca2+. In contrast, an increase of [free Ca2+] during the descending phase of the Ca2+ transient did not cause further Ca2+ release. Varying [free H+], [free Mg2+], or the [Na+]/[K+] ratio had no significant effect on the Ca2+ transient during which the modification was applied, but it altered the subsequent Ca2+ transient. Therefore, Ca2+ appears to be the major, if not the only, ion controlling Ca2+ release from the SR rapidly enough to alter a Ca2+ transient during its course. PMID:3981128

Superconductivity above 100 K in Bi(Pb)-Ca-Sr-Cu-O films made by thermal decomposition of metal carboxylates

NASA Astrophysics Data System (ADS)

Klee, M.; de Vries, J. W. C.; Brand, W.

1988-11-01

Superconducting layers in the Bi(Pb)-Ca-Sr-Cu-O system are prepared by thermal decomposition of metal carboxylates. The films are deposited on MgO single crystal and ceramic substrates using a spin-coating and dip-coating process. The Bi-Ca-Sr-Cu-O films consist mainly of the low- Tc phase ( c-axis=3.073 nm), whereas partial substitution of Bi by Pb favours the formation of the high- Tc phase ( c-axis=3.707 nm). Films deposited on MgO (100) are strong c-axis preferentially oriented grown. While the Bi-Ca-Sr-Cu-O films show a step in the resistance versus temperature curve ( Tcf⋍80 K) due to the presence of the low- Tc and the high- Tc phase, the Bi(Pb)-Ca-Sr-Cu-O films have an onset at 110 K and are superconducting at 104 K. The temperature dependence of the critical current indicates that in the Bi-Ca-Sr-Cu-O system weak links of superconductor-isolator-superconductor type are present, while in the Bi(Pb)-Ca-Sr-Cu-O samples the contact is formed by normal-metal barriers. Using magnetic fields up to 5 T, the anisotropy of the resistive transition of the high- Tc phase was studied. In Bi(Pb)-Ca-Sr-Cu-O films the anisotropy ratio is about 18, and the corresponding coherence lengths are ξ ab(0)⋍3.6 nm and ξ c(0)⋍0.2 nm. These values are nearly the same as in the low- Tc phase.

The structural, electronic, magnetic and optical properties of the half-metallic binary alloys ZCl3 (Z=Be, Mg, Ca, Sr): A first-principles study

NASA Astrophysics Data System (ADS)

Song, Jun-Tao; Zhang, Jian-Min

2018-06-01

The investigations of the electronic and magnetic properties show the binary Heusler alloys ZCl3 (Z = Be, Mg, Ca, Sr) are half-metallic (HM) ferromagnets with an integer magnetic moment (Mt) of 1 μB /f.u.. The alloy BeCl3 is thermodynamic meta-stable, while other alloys are thermodynamic stable according to their cohesive energies and formation energies. Moreover, wide HM regions for alloys ZCl3 (Z = Be, Mg, Ca, Sr) show their HM characters are robust when the lattices are expanded or compressed under uniform and tetragonal strains. Finally, some optical properties are analyzed in detail, such as the dielectric function, the absorption coefficient, the refractive index and the extinction coefficient.

Theoretical studies of the local structures and spin Hamiltonian parameters for Cu2+ in alkaline earth alumino borate glasses

NASA Astrophysics Data System (ADS)

Guo, Jia-Xing; Wu, Shao-Yi; Kuang, Min-Quan; Peng, Li; Wu, Li-Na

2018-01-01

The local structures and spin Hamiltonian parameters are theoretically studied for Cu2+ in alkaline earth alumino borate (XAB, X = Mg, Ca and Sr) glasses by using the perturbation calculations for tetragonally elongated octahedral 3d9 groups. The [CuO6]10- groups are subject to the large relative tetragonal elongation ratios of 15.4%, 13.4% and 13.0% for MgAB, CaAB and SrAB glasses, respectively, arising from the Jahn-Teller effect. The decreasing cubic field parameter Dq, orbital reduction factor k and relative elongation ratio with the increase of the radius of alkaline earth ion X from Mg to Ca or Sr are analyzed for the studied systems in a uniform way.

Unique antitumor property of the Mg-Ca-Sr alloys with addition of Zn

PubMed Central

Wu, Yuanhao; He, Guanping; Zhang, Yu; Liu, Yang; Li, Mei; Wang, Xiaolan; Li, Nan; Li, Kang; Zheng, Guan; Zheng, Yufeng; Yin, Qingshui

2016-01-01

In clinical practice, tumor recurrence and metastasis after orthopedic prosthesis implantation is an intensely troublesome matter. Therefore, to develop implant materials with antitumor property is extremely necessary and meaningful. Magnesium (Mg) alloys possess superb biocompatibility, mechanical property and biodegradability in orthopedic applications. However, whether they possess antitumor property had seldom been reported. In recent years, it showed that zinc (Zn) not only promote the osteogenic activity but also exhibit good antitumor property. In our present study, Zn was selected as an alloying element for the Mg-1Ca-0.5Sr alloy to develop a multifunctional material with antitumor property. We investigated the influence of the Mg-1Ca-0.5Sr-xZn (x = 0, 2, 4, 6 wt%) alloys extracts on the proliferation rate, cell apoptosis, migration and invasion of the U2OS cell line. Our results show that Zn containing Mg alloys extracts inhibit the cell proliferation by alteration the cell cycle and inducing cell apoptosis via the activation of the mitochondria pathway. The cell migration and invasion property were also suppressed by the activation of MAPK (mitogen-activated protein kinase) pathway. Our work suggests that the Mg-1Ca-0.5Sr-6Zn alloy is expected to be a promising orthopedic implant in osteosarcoma limb-salvage surgery for avoiding tumor recurrence and metastasis. PMID:26907515

Barnacles - recorders of environmental conditions with unique geochemical signatures

NASA Astrophysics Data System (ADS)

Vinzenz Ullmann, Clemens; Gale, Andy; Korte, Christoph; Frei, Robert; Huggett, Jenny; Wray, Dave

2017-04-01

Barnacles are calcite-forming arthropods that occur in a wide range of habitats in modern times and are found in sedimentary successions reaching back to the Paleozoic. Despite potential use of their mostly low-Mg calcite hard parts for palaeoenvironmental reconstructions, their geochemical composition has been little studied. Here, we present the first comprehensive overview of barnacle geochemistry, with C and O isotope, as well as Mg/Ca, Sr/Ca, Mn/Ca and Fe/Ca data for multiple samples of 42 species covering the orders Sessilia, Scalpelliformes, and Lepadiformes. XRD analyses confirm calcite as the only significant carbonate mineral of the studied barnacle shell material. Apart from one species, median Mg/Ca ratios fall below 50 mmol/mol, the approximate limit for low-Mg-calcite. In the order Sessilia, the scuta and terga are on average enriched in Mg by 36 % over the unmoveable plates. Amongst the calcite-forming marine animals, barnacles have very high Sr/Ca ratios of 2.6 to 5.9 mmol/mol, amongst the highest known for calcite secreting animals. Mn/Ca and Fe/Ca ratios are commonly low and compatible with other modern shell calcite, but can be strongly enriched to > 1 mmol/mol in proximal habitats, particularly close to areas strongly affected by human activity. Carbon and oxygen isotope data indicate formation of the calcite in or near isotopic equilibrium with ambient water conditions. Apart from species showing δ18O values below 0 ‰ V-PDB, a negative correlation of oxygen isotope ratios with Sr/Ca ratios is observed, which may be related to metabolic activity. Compositional patterns in barnacle shell material, particularly high Sr concentrations and Mg distribution in shell plates of the Sessilia, point to a great potential of barnacles for high fidelity reconstruction of past seawater chemistry and environmental conditions complementary to other archives.

Stable isotopes, Sr/Ca, and Mg/Ca in biogenic carbonates from Petaluma Marsh, northern California, USA

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

Ingram, B.L.; De Deckker, P.; Chivas, A.R.

2004-10-19

Stable isotope ({sup 18}O/{sup 16}O and {sup 13}C/{sup 12}C) and minor-element compositions (Sr/Ca and Mg/Ca ratios) of ostracodes and gastropods separated from marsh sediments from San Francisco Bay, Northern California, were used to reconstruct paleoenvironmental changes in Petaluma Marsh over the past 700 yr. The value of {delta}{sup 18}O in the marsh carbonates reflects changes in freshwater inflow, evaporation, and temperature. Mg/Ca and Sr/Ca in ostracode calcite reflect changes in both freshwater inflow and temperature, although primarily reflect temperature changes in the salinity range of about 10-35 {per_thousand}. Ostracode {delta}{sup 18}O values show a gradual increase by 5 {per_thousand} betweenmore » 500 yr BR and the present, probably reflecting rising sea level and increased evaporation in the marsh. Superimposed on this trend are higher frequency Mg/Ca and {delta}{sup 18}O variations (3-4 {per_thousand}), probably reflecting changes in freshwater inflow and evaporation. A period of low Mg/Ca occurred between about 100-300 cal yr BP, suggesting wetter and cooler conditions during the Little Ice Age. Higher Mg/Ca ratios occurred 600-700 cal yr BP, indicating drier and warmer conditions during the end of the Medieval Warm Period. Both ostracode and gastropod {delta}{sup 13}C values decrease up-core, reflecting decomposition of marsh vegetation, which changes from C{sub 4} ({delta}{sup 13}C {approx} -12{per_thousand}) to CAM ({delta}{sup 13}C = -26 {per_thousand})-type vegetation over time.« less

Stable isotopes, Sr/Ca, and Mg/Ca in biogenic carbonates from Petaluma Marsh, northern California, USA

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

Ingram, B.L.; Deckker, P. de; Chivas, A.R.

1998-10-01

Stable isotope ({sup 18}O/{sup 16}O and {sup 13}C/{sup 12}C) and minor-element compositions (Sr/Ca and Mg/Ca ratios) of ostracodes and gastropods separated from marsh sediments from San Francisco Bay, Northern California, were used to reconstruct paleoenvironmental changes in Petaluma March over the past 700 yr. The value of {delta}{sup 18}O in the marsh carbonates reflects changes in freshwater inflow, evaporation, and temperature. Mg/Ca and Sr/Ca in ostracode calcite reflect changes in both freshwater inflow and temperature, although primarily reflect temperature changes in the salinity range of about 10--35{per_thousand}. Ostracode {delta}{sup 18}O values show a gradual increase by 5{per_thousand} between 500 yrmore » BP and the present, probably reflecting rising sea level and increased evaporation in the marsh. Superimposed on this trend are higher frequency Mg/Ca and {delta}{sup 18}O variations (3--4{per_thousand}), probably reflecting changes in freshwater inflow and evaporation. A period of low Mg/Ca occurred between about 100--300 cal yr BP, suggesting wetter and cooler conditions during the Little Ice Age. Higher Mg/Ca ratios occurred 600--700 cal yr BP, indicating drier and warmer conditions during the end of the Medieval Warm Period. Both ostracode and gastropod {delta}{sup 13}C values decrease up-core, reflecting decomposition of marsh vegetation, which changes from C{sub 4} ({delta}{sup 13}C {approximately} {minus}12{per_thousand}) to CAM ({delta}{sup 13}C = {minus}26{per_thousand})-type vegetation over time.« less

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

Walser, M.; Robinson, B.H.B.

The ratio of excreted (Sr/sub u/) to filtered (Sr/sub o/) radiostrontium (Sr/sup 85/) was compared with the ratio of excreted (Ca/sub u/) to filtered (Ca/ sub o/) calcium in human subjects and dogs undergoing a variety of diuretic procedures. The relation Sr/sub u//Sr/sub o/ = (Ca/sub u/,/Ca/sub o//sup 0.7/ serves to predict Sr/sub u//Sr/sub o/ from Ca/su b u//Ca/sub o/with a standard error of estimate of 15% over a wide range of variation (30- to 200-fold) in the 2 quantities. The equation can be derived from the assumptions that the 2 ions are reabsorbed at rates proportional to the localmore » concentrations in the tubular fluid, and that the rate constant for Sr reabsorption is always 0.7 times that for Ca reabsorption. This relation was not affected by adrenocortical activity (in man), parathyroid activity, hypercalcemia, acid-base balance, Mg clearance, or diuretics (chlorothiazide or hydrochlorothiazide). Sulfate or ferrocyanide infusion was also without effect, presumably because the affinity of each of the 2 anions for Ca is similar to its affinity for Sr. Citrate, which binds Ca more strongly, diminishes renal discrimination between Ca and Sr. Although this relation has high predictive value (r* = 0.98), it does not establish that the reabsorption of Ca and Sr are first-order processes nor that the 2 ions share a common mechanism. (H.H.D.)« less

A two-year automated dripwater chemistry study in a remote cave in the tropical south Pacific: Using [Cl-] as a conservative tracer for seasalt contribution of major cations

NASA Astrophysics Data System (ADS)

Tremaine, Darrel M.; Sinclair, Daniel J.; Stoll, Heather M.; Lagerström, Maria; Carvajal, Carlos P.; Sherrell, Robert M.

2016-07-01

Stalagmite Mg/Ca and Sr/Ca ratios are commonly interpreted as proxies for past hydrologic conditions and are often used to supplement carbon and oxygen stable isotope records. While the processes that control these element ratios, including water-rock interaction, dripwater residence time, and upstream precipitation of calcite, are well understood in continental caves, there have been few investigations of dripwater Element/Ca (X/Ca) evolution in coastal marine caves where seasalt can have a strong influence on the incoming Mg/Ca ratio. We instrumented a marine cave on the remote South Pacific island of Niue to record daily cave microclimate, as well as weekly-integrated drip rates, dripwater oxygen and hydrogen isotopes, and dripwater chemistry over a period of twenty-two months. Using chloride as a conservative tracer for sea-spray, we calculate that seasalt input accounts for a large portion of dripwater Na, SO4, and Mg (89%, 93%, and 85% respectively) and a smaller portion of the Ca and Sr (19% and 17%). During the second year of this study a gradual decrease (by ∼18%) in dripwater chlorinity was observed, suggesting that an epikarst-hosted seasalt aerosol inventory was being diluted over time. Minor element to calcium ratios for B, K, Cl, SO4, Mg, Na, Sr, and Fe all strongly covary over the observation period, suggesting that although sea-spray plays a significant role in modulating incoming drip chemistry, prior calcite precipitation (PCP) dominates chemical evolution within the epikarst. During a prolonged drought episode, evaporative enrichments in dripwater δD and δ18O (+4‰ and 0.5‰, respectively) were observed to coincide with increased cation and anion concentrations, strong Ca removal via PCP, and increases in Sr/Ca and Mg/Ca ratios (28% and 34%, respectively), suggesting that concomitant enrichment in speleothem δ18O and X/Ca ratios may be interpreted as multi-proxy evidence for dry climate conditions. We use modern dripwater chemistry and empirical water-calcite distribution coefficients to predict a range of stalagmite X/Ca ratios. We then forward model a number of scenarios that could modulate stalagmite chemistry, including increased/decreased seasalt input and changing dripwater flow path through calcite, dolomite, and aragonite bedrock. One major implication from this study is that even if PCP and flow path lithology remain constant over time, changing seasalt input can drive stalagmite Mg/Ca and Sr/Ca ratios away from PCP-controlled covariation, and lead to strongly varying Sr/Mg ratios. Thus in order to interpret coastal cave stalagmite X/Ca records accurately, it is necessary to estimate seasalt input and analyze parent drip and bedrock chemistry to quantify the influence of each contributing process.

Influence of Sn-Mg co-substitution on the microstructural and magnetic characteristics of M-type SrCaLa hexagonal ferrites

NASA Astrophysics Data System (ADS)

Yang, Yujie; Wang, Fanhou; Huang, Duohui; Shao, Juxiang; Tang, Jin; Ur Rehman, Khalid Mehmood; Wu, Zhen

2018-04-01

Sn-Mg co-substituted M-type SrCaLa hexaferrites Sr0.5Ca0.2La0.3Fe12.0-2x(SnMg)xO19 (0.0 ≤ x ≤ 0.5) have been synthesized by ball milling and calcining. The results of X-ray diffraction show that a single magnetoplumbite phase is exhibited in all the samples and no impurity phase is observed in the structure. Lattice constants (c and a) increase with increasing Sn-Mg content (x) from 0.0 to 0.5. Platelet like structure exhibited by FE-SEM micrographs confirms the hexagonal structure of the synthesized samples. The saturation magnetization (Ms) first increases with increasing SnMg content (x) from 0.0 to 0.1, and then decreases when Sn-Mg content (x) ≥ 0.1. The remanent magnetization (Mr), Mr/Ms ratio, coercivity (Hc), magnetic anisotropy field (Ha) and first anisotropy constant (K1) decrease with increasing Sn-Mg content (x) from 0.0 to 0.5.

Application of computational thermodynamics in the study of magnsium alloys and bulk metallic glasses

NASA Astrophysics Data System (ADS)

Cao, Hongbo

In this thesis, the application of the computational thermodynamics has been explored on two subjects, the study of magnesium alloys (Chapter 1-5) and bulk metallic glasses (BMGs) (Chapter 6-9). For the former case, a strategy of experiments coupled with the CALPHAD approach was employed to establish a thermodynamic description of the quaternary system Mg-Al-Ca-Sr focusing on the Mg-rich phase equilibria. Multicomponent Mg-rich alloys based on the MgAl-Ca-Sr system are one of the most promising candidates for the high temperature applications in the transportation industry. The Mg-Al-Ca-Sr quaternary consists of four ternaries and six binaries. Thermodynamic descriptions of all constituent binaries are available in the literature. Thermodynamic descriptions of the two key ternaries, Mg-Al-Sr and Mg-Al-Ca, were obtained by an efficient and reliable methodology, combining computational thermodynamics with key experiments. The obtained thermodynamic descriptions were validated by performing extensive comparisons between the calculations and experimental information. Thermodynamic descriptions of the other two ternaries, MgCa-Sr and Al-Ca-Sr, were obtained by extrapolation. For the later case, a computational thermodynamic strategy was formulated to obtain a minor but optimum amount of additional element into a base alloy to improve its glass forming ability (GFA). This was done through thermodynamically calculating the maximum liquidus depressions caused by various alloying addition (or replacement) schemes. The success of this approach has been examined in two multicomponent systems, Zr-based Zr-Cu-Ni-Al-Ti and Cu-rich Cu-Zr-Ti-Y. For both cases, experimental results showed conclusively that the GFA increases more than 100% from the base alloy to the one with minor but optimal elemental addition. Furthermore, a thermodynamic computational approach was employed to identify the compositions of Zr-Ti-Ni-Cu-Al alloys exhibiting low-lying liquidus surfaces, which tend to favor the BMG formation. Guided by these calculations, several series of new Zr-based alloys with excellent GFA were synthesized. The approach using the thermodynamically calculated liquidus temperatures was proved to be robust in locating BMGs and can be considered as a universal method to predict novel BMGs not only of scientific interest but also potential technological applications.

Mg Isotope variations of Marinoan Cap Carbonates: implications for the chemical evolution of Neoproterozoic Ocean after snowball earth

NASA Astrophysics Data System (ADS)

Liu, C.; Macdonald, F. A.; Raub, T.; Wang, Z.; Evans, D. A.

2012-12-01

We report Mg isotope profiles of two cap-carbonates: Nuccaleena formation from south Australia (mostly dolostones) and Tsagaan Oloom Formation from southwest Mongolia (including dolostones, aragonite crystal fans, and lime-mudstones). These data provide additional constraints on the chemical evolution of Neoproterozoic Oceans after the Marinoan deglaciation. An incremental leaching technique using ammonium acetate and various concentrations of acetic acid and hydrochloric acid was applied to separate metals in various forms from cap-carbonates (including surface adsorbed phases, calcite, dolomite and clay minerals). The leachates were then passed through chromatographic columns to extract pure Mg and Sr, which were then analyzed for their isotopic compositions by MC-ICP-MS (Neptune) at Yale University. Elemental ratios (Mg/Ca and Sr/Ca) in each leaching steps were also measured. Our results show that small variations of δ26MgDSM3 with leaching steps were observed in most dolostone samples when secondary calcite is absent. In contrast, large Mg isotope variations (up to 1.5 per mil) were shown in the leaching steps of limestone and crystal fans. The primary δ26MgDSM3 value of each sample was chosen from the leachate that has the lowest 87Sr/86Sr ratios. The δ26MgDSM3 value of Nuccaleena dolostone increases from -2.2‰ at the basal part of the section to -1.7‰ in the middle, and then turns back to -2.0‰ on the top, with a positive correlation between 26Mg/24Mg and 87Sr/86Sr ratios, implying that the high δ26MgDSM3 values may be caused by alteration or inherit from continental-derived fluids. In contrast, small δ26MgDSM3 variations in Tsagaan Oloom dolostones were exhibited in different leaching steps or cross the section (~-1.7‰), with high 87Sr/86Sr ratios (~0.7090), resembling cap dolostones from middle part of Nuccaleena dolostone, implying that they are formed in a similar environment. However, the δ26MgDSM3 value of upper lime-mudstones and crystal fans from Tsagaan Oloom Formation oscillate between -3.4‰ to -1.9‰ with a negative correlation between δ26MgDSM3 and Ca/Mg, and without any correlation with 87Sr/86Sr ratios, indicating mixing of co-precipitated multiple carbonate phases with different mineralogy.

Thin films of the Bi2Sr2Ca2Cu3O(x) superconductor

NASA Technical Reports Server (NTRS)

Mei, YU; Luo, H. L.; Hu, Roger

1990-01-01

Using RF sputtering technique, thin films of near single phase Bi2Sr2Ca2Cu3O(x) were successfully prepared on SrTiO3(100), MgO(100), and LaAlO3(012) substrates. Zero resistance of these films occurred in the range of 90-105 K.

Effects of increased pCO2 and geographic origin on purple sea urchin (Strongylocentrotus purpuratus) calcite elemental composition

NASA Astrophysics Data System (ADS)

LaVigne, M.; Hill, T. M.; Sanford, E.; Gaylord, B.; Russell, A. D.; Lenz, E. A.; Hosfelt, J. D.; Young, M. K.

2012-12-01

Ocean acidification will likely have negative impacts on invertebrates producing skeletons composed of calcium carbonate. Skeletal solubility is partly controlled by the incorporation of "foreign" ions (such as Mg and Sr) into the crystal lattice of these skeletal structures, a process that is sensitive to a variety of biological and environmental factors. Here we explore the effects of life stage, oceanographic region of origin, and changes in the partial pressure of carbon dioxide in seawater (pCO2) on trace elemental composition in the purple sea urchin (Strongylocentrotus purpuratus). We show that, similar to other urchin taxa, adult purple sea urchins have the ability to precipitate skeleton composed of a range of biominerals spanning low to high magnesium calcites. Mg/Ca and Sr/Ca ratios were substantially lower in adult spines compared to adult tests. On the other hand, trace elemental composition was invariant among adults collected from four oceanographically distinct regions along the US west coast (Oregon, Northern California, Central California, and Southern California). Skeletons of newly settled juvenile urchins that originated from adults from the four regions exhibited intermediate Mg/Ca and Sr/Ca between adult spine and test endmembers, indicating that skeleton precipitated during early life stages is more soluble than adult spines and less soluble than adult tests. Mean skeletal Mg/Ca or Sr/Ca of juvenile skeleton did not vary with source region when larvae were reared under present-day, global-average seawater carbonate conditions (400 ppm; pH = 8.02 ± 0.03 1 SD; Ωcalcite = 3.3 ± 0.2 1 SD). However, when reared under elevated CO2 (900 ppm; pH = 7.72 ± 0.03; Ωcalcite = 1.8 ± 0.1), skeletal Sr/Ca in juveniles exhibited increased variance across the four regions. Although larvae from the northern populations (Oregon, Northern California, Central California) did not exhibit differences in Mg or Sr incorporation under elevated CO2 (Sr/Ca = 2.09 ± 0.06 mmol mol-1; Mg/Ca = 66.9 ± 4.1 mmol mol-1), juveniles of Southern California origin partitioned ∼ 8% more Sr into their skeletons when exposed to higher CO2 (Sr/Ca = 2.26 ± 0.05 vs. 2.10 ± 0.03 mmol mol-1 1 SD). Together these results suggest that the diversity of carbonate minerologies present across different skeletal structures and life stages in purple sea urchins does not translate into an equivalent plasticity of response associated with geographic variation or temporal shifts in seawater properties. Rather, composition of S. purpuratus skeleton precipitated during both early and adult life history stages appears relatively robust to spatial gradients and predicted changes in seawater carbonate chemistry for 2100. An exception to this trend may arise during early life stages, where certain populations of purple sea urchins may alter skeletal mineral precipitation rates and composition beyond a given CO2 threshold. The degree to which this latter geochemical plasticity might affect mineral stability and solubility in a future, altered ocean requires additional study.

STABILIZATION OF SPIDER CRAB NERVE MEMBRANES BY ALKALINE EARTHS, AS MANIFESTED IN RESTING POTENTIAL MEASUREMENTS

PubMed Central

Guttman, Rita

1940-01-01

1. The alkaline earths, Ba, Sr, Ca, and Mg, in isotonic solutions of their chlorides, have, in general, no effect upon the resting potential of non-medullated spider crab nerve. 2. Ba, Sr, and Ca can, however, prevent the depressing action of K upon the resting potential. The order of effectiveness of these ions in this regard is the following: Ba > Sr > Ca. 3. Ba, Sr, Ca, and Mg oppose the depressing action of veratrine sulfate upon the resting potential. The order of effectiveness is Ba > Sr > Ca > Mg. The relation between drop in potential caused by veratrine sulfate and the logarithm of the veratrine sulfate concentration is a linear one. 4. The action of various other organic ions and molecules which depress the resting potential: saponin, amyl urethane, chloral hydrate, and Na salicylate is neutralized by Ba. 5. Hypertonic sea water solutions do not affect the resting potential. Also, preliminary experiments indicate that the nerves do not shrink in hypertonic solutions although they swell in hypotonic sea water. 6. The alkaline earths depress excitability reversibly. The various organic agents which depress the resting potential also depress excitability, in most cases, reversibly, but the concentrations necessary to depress excitability are much smaller than those necessary to depress the resting potential. 7. The relation of these findings to theories put forward as possible explanations of resting potential phenomena is considered. PMID:19873160

Hydrothermal Preparation and Characterization of Ultralong Strontium-Substituted Hydroxyapatite Whiskers Using Acetamide as Homogeneous Precipitation Reagent

PubMed Central

Xu, Jianqiang; Yang, Yaoqi; Wan, Rong; Zhang, Weibin

2014-01-01

The ultralong strontium- (Sr-) substituted hydroxyapatite (SrHAp) whiskers were successfully prepared using acetamide as homogeneous precipitation reagent. The effect of the Sr substitution amount on the lattice constants and proliferation of human osteoblast cells (MG-63) was further investigated. The results showed that the SrHAp whiskers with diameter of 0.2–12 μm and ultralong length up to 200 μm were obtained and the Sr substitution level could be facilely tailored by regulating the initial molar ratio of Sr/(Sr + Ca) in raw materials. The Sr2+ replaced part of Ca2+ and the lattice constants increased apparently with the increase of the Sr substitution amount. Compared with the pure HAp whiskers, the Sr substitution apparently stimulated the proliferation of MG-63 at certain extracted concentrations. Our study suggested that the obtained SrHAp whiskers might be used as bioactive and mechanical reinforcement materials for hard tissue regeneration applications. PMID:24592192

Genesis of post-collisional calc-alkaline and alkaline granitoids in Qiman Tagh, East Kunlun, China

NASA Astrophysics Data System (ADS)

Yu, Miao; Feng, Chengyou; Zhao, Yiming; Li, Daxin

2015-12-01

The post-collisional magmatism of Qiman Tagh is characterized by the intrusion of voluminous intermediate to felsic granitoids, including syenogranite, monzogranite, granodiorite, tonalite and diorite. The granitoids can be divided into two magmatic suites: Calc-alkaline (CA) and alkaline (Alk), which were emplaced from ~ 236 Ma to ~ 204 Ma. The CA suite contains metaluminous granodiorites and monzogranites. Typical Qiman Tagh CA granodiorites show moderately fractionated REE patterns ((La/Yb)N = 4.35-25.11) with significant negative Eu anomalies (Eu/Eu* = 0.54-1.34), and the primitive mantle-normalized spidergrams show strong depletion of Nb and Sr. The Qiman Tagh CA monzogranites show similar fractionated REE patterns ((La/Yb)N = 2.70-13.5) with less prominent negative Eu anomalies, and the chondrite-normalized spidergrams show strongly depleted Ba, Nb and Sr. The Alk suite, including syenogranite, is highly potassic (K2O/Na2O = 1.09-3.56) and peraluminous (A/CNK = 0.91-1.06). Compared to typical Qiman Tagh CA granodiorites, the Qiman Tagh Alk granitoids can be distinguished by their higher Rb, Nb, Ga/Al, FeO*/MgO, Y/Sr and Rb/Sr, as well as their lower Mg#, MgO, CaO, Al2O3, Sr, Co, V, Eu/Eu*, Ba/Nb, La/Nb, Ba/La and Ce/Nb. The Qiman Tagh CA rocks were most likely to be derived from the partial melting of garnet-amphibolite-facies rocks in the lower crust, leaving behind anhydrous granulite-facies rocks with plagioclase and garnet in the residue. The Alk rocks may have formed by the continued partial melting of granulite-facies rocks at elevated temperatures (> 830 °C).

Water-Rock Interactions in the Peridotite Aquifer of the Oman-UAE Ophiolite: Strontium Isotopic Ratio and Geochemical Evolution of Groundwater

NASA Astrophysics Data System (ADS)

Bompard, Nicolas; Matter, Juerg; Teagle, Damon

2016-04-01

The peridotite aquifer in Wadi Tayin, Sultanate of Oman, is a perfect example of natural carbonation of ultramafic rocks. In situ mineral carbonation is considered the most safest and permanent option of CO2 Capture and Sequestration (CCS). However, the process itself is yet to be characterised and a better understanding of the mechanisms involved in natural mineral carbonation is needed before geo-engineering it. We used the 87Sr/86Sr system to follow the water-rock interactions along the groundwater flowpath in the peridotite aquifer and to determine the sources of divalent cations (Mg2+, Ca2+) required for mineral carbonation. The Sr-isotope data of groundwater show that the aquifer rocks are the main source for divalent cations (Mg2+, Ca2+ and Sr2+) and secondary carbonates are their main sink. The groundwater 87Sr/86Sr ratio evolves with its pH: from 87Sr/86Sr = 0.7087 (n=3) to 0.7082 (n=8) between pH 7 and 8, and from 0.7086 (n=6) at pH 9 to 0.07075 (n=9) at pH 11. This evolution seems to support a two-step model for the water-rock interactions in the peridotite aquifer. From pH 7 to 8, secondary Ca-carbonate precipitation buffers the pH rise resulting from peridotite serpentinisation. From pH 9 to 11, peridotite serpentinisation drives the pH to alkaline condition. The change from a Mg-rich to a Ca-rich groundwater at pH 9 seems to confirm the two-step model.

Thermal properties and surface reactivity in simulated body fluid of new strontium ion-containing phosphate glasses.

PubMed

Massera, J; Petit, L; Cardinal, T; Videau, J J; Hupa, M; Hupa, L

2013-06-01

In this paper, we investigate the effect of SrO substitution for CaO in 50P₂O₅-10Na₂-(40-x)CaO-xSrO glass system (x from 0 to 40) on the thermal and structural properties and also on the glass reactivity in simulated body fluid (SBF) in order to find new glass candidates for biomedical glass fibers. The addition of SrO at the expense of CaO seems to restrain the leaching of phosphate ions in the solution limiting the reduction of the solution pH. We observed the formation of an apatite layer at the surface of the glasses when in contact with SBF. SrO and MgO were found in the apatite layer of the strontium ion-containing glasses, the concentration of which increases with an increase of SrO content. We think that it is the presence of MgO and SrO in the layer which limits the leaching of phosphate in the solution and thus the glass dissolution in SBF.

Who's your momma? Recognizing maternal origin of juvenile steelhead using injections of strontium chloride to create transgenerational marks

USGS Publications Warehouse

Shippentower, Gene E.; Schreck, Carl B.; Heppell, Scott A.

2011-01-01

We sought to determine whether a strontium chloride injection could be used to create a transgenerational otolith mark in steelhead Oncorhynchus mykiss. Two strontium injection trials and a survey of strontium: calcium (Sr:Ca) ratios in juvenile steelhead from various steelhead hatcheries were conducted to test the feasibility of the technique. In both trials, progeny of fish injected with strontium had significantly higher Sr:Ca ratios in the primordial region of their otoliths, as measured by an electron wavelength dispersive microprobe. In trial 1, the 5,000-mg/L treatment level showed that 56.8% of the otoliths were correctly classified, 12.2% being misclassified as belonging to the 0-mg/L treatment. In trial 2, the 20,000-mg/L treatment level showed that 30.8% of the otoliths were correctly classified, 13.5% being misclassified as belonging to the 0-mg/L treatment. There were no differences in the fertilization rates of eggs or survival rates of fry between the treatment and control groups. The Sr:Ca ratios in otoliths collected from various hatchery populations of steelhead varied and were greater than those found in otoliths from control fish in both of our injection trials. This study suggests that the marking technique led to recognizable increases in Sr:Ca ratios in some otoliths collected from fry produced by injected females. Not all progeny showed such increases, however, suggesting that the method holds promise but requires further refinement to reduce variation. Overall, there was a correct classification of about 40% across all treatments and trials; the variation in Sr:Ca ratios found among experimental trials and hatcheries indicates that care must be taken if the technique is employed where fish from more than one hatchery could be involved.

High Resolution Glacial-interglacial Climatic Variations in the South China Sea during the Last 220,000 Years

NASA Astrophysics Data System (ADS)

Huang, K.; You, C.; Li, M.; Shieh, Y.

2002-12-01

The Asian monsoon plays an important role of both regional and global climatic variations. The South China Sea (SCS) located between Southeast Asia continent and Western Pacific Ocean is an ideal place for studying oceanographic responses and changes of monsoon system in the past. Planktonic foraminiferal shells separated from two deep sea cores, ODP Site 1144 and SCS 15B, located near the northeast continental slope and the central ocean basin respectively were used to reconstruct high-resolution climatic records during the last 220 kyrs. Average of 20 individual foraminiferal shells were hand picked and cleaned thoroughly for high precision trace element/calcium ratios (i.e., Mg/Ca, Sr/Ca, and Ba/Ca) determination using a Thermo-Fannigan Element II ICP-MS installed at NCKU. Isotopic compositions of oxygen, carbon, boron and strontium also were measured by stable isotope ratio or Triton TI thermal ionization mass spectrometer. Mg/Ca and Sr/Ca in foraminiferal shells are sensitive proxies for sea surface temperature, chemical weathering and hydrothermal activity on seafloor. The SCS foraminiferal shells Mg/Ca and Sr/Ca show negative correlation with interesting glacial-interglacial variations. The calculated Mg/Ca SSTs varied as large as 6-7 °C with the highest temperature occurred at oxygen stage 5. The Sr/Ca ratios change about 16 % (1.200-1.429 mmole/mole), possibly a result of periodic sea level changes which influencing terrigenous inputs or continental shelves weathering. On the other hand, the Ba/Ca display large variations (0.031-0.117 mmole/mole), possibly reflecting upwelling intensity or SCS bottom water chemistry. The boron isotopic compositions in planktonic foraminiferal shells are used to estimate pH in the surface ocean. Combining these proxies, high-resolution oceanic environmental records in the SCS were reconstructed for the last 220 kyrs. The results obtained from the SCS can be used to gain a better understanding of land-sea interaction in this region.

Evaluation of the Impacts of Marine Salts and Asian Dust on the Forested Yakushima Island Ecosystem, a World Natural Heritage Site in Japan.

PubMed

Nakano, Takanori; Yokoo, Yoriko; Okumura, Masao; Jean, Seo-Ryong; Satake, Kenichi

2012-11-01

To elucidate the influence of airborne materials on the ecosystem of Japan's Yakushima Island, we determined the elemental compositions and Sr and Nd isotope ratios in streamwater, soils, vegetation, and rocks. Streamwater had high Na and Cl contents, low Ca and HCO(3) contents, and Na/Cl and Mg/Cl ratios close to those of seawater, but it had low pH (5.4 to 7.1), a higher Ca/Cl ratio than seawater, and distinct (87)Sr/(86)Sr ratios that depended on the bedrock type. The proportions of rain-derived cations in streamwater, estimated by assuming that Cl was derived from sea salt aerosols, averaged 81 % for Na, 83 % for Mg, 36 % for K, 32 % for Ca, and 33 % for Sr. The Sr value was comparable to the 28 % estimated by comparing Sr isotope ratios between rain and granite bedrock. The soils are depleted in Ca, Na, P, and Sr compared with the parent materials. At Yotsuse in the northwestern side, plants and the soil pool have (87)Sr/(86)Sr ratios similar to that of rainwater with a high sea salt component. In contrast, the Sr and Nd isotope ratios of soil minerals in the A and B horizons approach those of silicate minerals in northern China's loess soils. The soil Ca and P depletion results largely from chemical weathering of plagioclase and of small amounts of apatite and calcite in granitic rocks. This suggests that Yakushima's ecosystem is affected by large amounts of acidic precipitation with a high sea salt component, which leaches Ca and its proxy (Sr) from bedrock into streams, and by Asian dust-derived apatite, which is an important source of P in base cation-depleted soils.

Fluorine Kα X-Ray Emission Spectra of MgF2, CaF2, SrF2 and BaF2

NASA Astrophysics Data System (ADS)

Sugiura, Chikara; Konishi, Wataru; Shoji, Shizuko; Kojima, Shinjiro

1990-11-01

The fluorine Kα emission spectra in fluorescence from a series of alkaline-earth fluorides MF2 (M=Mg, Ca, Sr and Ba) are measured with a high-resolution two-crystal vacuum spectrometer. An anomalously low intensity of the K1L1 satellite peak arising from 1s-1(2s2p)-1 initial states is observed for SrF2. The measured emission spectra are presented along with the UPS spectra of the F- 2p valence bands obtained by Poole et al. and the fluorine K absorption-edge spectra by Oizumi et al. By using these spectra, the first peak or shoulder in the fluorine K absorption-edge spectra is identified as being due to a core exciton which is formed below the bottom of the conduction band. The binding energy of the exciton is estimated to be 1.3(± 0.3), 1.1(± 0.2), 1.0(± 0.2) and 1.7(± 0.2) eV for MgF2, CaF2, SrF2 and BaF2, respectively.

Growth rate variation and potential paleoceanographic proxies in Primnoa pacifica: Insights from high-resolution trace element microanalysis

NASA Astrophysics Data System (ADS)

Aranha, Renita; Edinger, Evan; Layne, Graham; Piercey, Glenn

2014-01-01

Red tree coral, Primnoa pacifica, is one of the more common habitat-forming deep-sea gorgonian corals in the northeast Pacific Ocean, growing in colonies up to 2 m high and living for decades to hundreds of years. Growth characteristics of P. pacifica were studied in Dixon Entrance, northern British Columbia, and the Olympic Coast National Marine Sanctuary, Washington State, USA, based on samples collected in July 2008. To minimize the impact of scientific sampling on coral populations, only dead coral skeletons and dislodged live corals were collected. Ages and growth rates were measured using band counts, and checked against AMS-14C ages of gorgonin rings. Ba/Ca, Mg/Ca, Na/Ca and Sr/Ca ratios in the calcite cortex were measured using radial Secondary Ion Mass Spectrometer (SIMS) transects with a spot size of <20 μm and separation distance of 25 μm. Growth banding was consistent in width between the central mixed zone consisting of calcite and gorgonin and the dominantly calcite cortex. Average annual radial growth rate of the nine corals analysed ranged from 0.23 to 0.58 mm/yr, with an average growth rate of 0.32 mm/yr in Dixon Entrance and 0.36 m/yr in OCNMS. These growth rates are slightly higher than P. pacifica growth rates from the Gulf of Alaska, and more than four times the growth rates of sister species Primnoa resedaeformis in the northwest Atlantic. Primary productivity is likely a more important driver of geographic variation in Primnoa growth rates than temperature or current strength. Both Dixon Entrance and OCNMS are areas with high primary productivity and strong tidal currents. Lack of post-Atomic Bomb radiocarbon in all but one of the gorgonin samples, and long radiocarbon reservoir ages in the Northeast Pacific, made radiocarbon-based verification of coral ages and growth rates difficult due to wide errors in calibrated age estimates. Mg/Ca and Sr/Ca ratios were inversely correlated in two of the three corals analyzed, and showed evidence of interannual variation. Mg/Ca ratios ranged from 70 to 136 mmol mol-1, and Sr/Ca ratios from 2.041 to 3.14 mmol mol-1. Previously published relationships between gorgonian calcite Mg/Ca and seawater temperature yielded average temperatures matching ambient measurements, but the intra- and inter-annual variation in apparent temperature based on the Mg/Ca ratios was more than double the observed variation in modern seawater temperature ranges in the region. Annual variation in Mg/Ca and Sr/Ca could be related to seasonal changes in precipitation efficiency, which is likely a function of short-term fluctuations in coral growth rate, in turn related to variation in primary productivity. Seasonal and interannual variations in food availability, driven by primary productivity, may affect skeletal growth rate, hence Mg/Ca and Sr/Ca ratios. Primnoid coral skeletal microgeochemistry probably records temporal changes in both temperature and primary productivity.

The Electronic Structures and Optical Properties of Alkaline-Earth Metals Doped Anatase TiO2: A Comparative Study of Screened Hybrid Functional and Generalized Gradient Approximation

PubMed Central

Ma, Jin-Gang; Zhang, Cai-Rong; Gong, Ji-Jun; Wu, You-Zhi; Kou, Sheng-Zhong; Yang, Hua; Chen, Yu-Hong; Liu, Zi-Jiang; Chen, Hong-Shan

2015-01-01

Alkaline-earth metallic dopant can improve the performance of anatase TiO2 in photocatalysis and solar cells. Aiming to understand doping mechanisms, the dopant formation energies, electronic structures, and optical properties for Be, Mg, Ca, Sr, and Ba doped anatase TiO2 are investigated by using density functional theory calculations with the HSE06 and PBE functionals. By combining our results with those of previous studies, the HSE06 functional provides a better description of electronic structures. The calculated formation energies indicate that the substitution of a lattice Ti with an AEM atom is energetically favorable under O-rich growth conditions. The electronic structures suggest that, AEM dopants shift the valence bands (VBs) to higher energy, and the dopant-state energies for the cases of Ca, Sr, and Ba are quite higher than Fermi levels, while the Be and Mg dopants result into the spin polarized gap states near the top of VBs. The components of VBs and dopant-states support that the AEM dopants are active in inter-band transitions with lower energy excitations. As to optical properties, Ca/Sr/Ba are more effective than Be/Mg to enhance absorbance in visible region, but the Be/Mg are superior to Ca/Sr/Ba for the absorbance improvement in near-IR region. PMID:28793520

The Electronic Structures and Optical Properties of Alkaline-Earth Metals Doped Anatase TiO2: A Comparative Study of Screened Hybrid Functional and Generalized Gradient Approximation.

PubMed

Ma, Jin-Gang; Zhang, Cai-Rong; Gong, Ji-Jun; Wu, You-Zhi; Kou, Sheng-Zhong; Yang, Hua; Chen, Yu-Hong; Liu, Zi-Jiang; Chen, Hong-Shan

2015-08-24

Alkaline-earth metallic dopant can improve the performance of anatase TiO2 in photocatalysis and solar cells. Aiming to understand doping mechanisms, the dopant formation energies, electronic structures, and optical properties for Be, Mg, Ca, Sr, and Ba doped anatase TiO2 are investigated by using density functional theory calculations with the HSE06 and PBE functionals. By combining our results with those of previous studies, the HSE06 functional provides a better description of electronic structures. The calculated formation energies indicate that the substitution of a lattice Ti with an AEM atom is energetically favorable under O-rich growth conditions. The electronic structures suggest that, AEM dopants shift the valence bands (VBs) to higher energy, and the dopant-state energies for the cases of Ca, Sr, and Ba are quite higher than Fermi levels, while the Be and Mg dopants result into the spin polarized gap states near the top of VBs. The components of VBs and dopant-states support that the AEM dopants are active in inter-band transitions with lower energy excitations. As to optical properties, Ca/Sr/Ba are more effective than Be/Mg to enhance absorbance in visible region, but the Be/Mg are superior to Ca/Sr/Ba for the absorbance improvement in near-IR region.

[Effects of hypoxic acclimatization on myocardial sarcoplasmic reticulum ATPase and 45Ca2+ uptake in rats].

PubMed

Long, Chao-liang; Zhang, Yan-fang; Yin, Zhao-yun; Wang, Hai

2005-08-01

To study the effect of acute hypoxia and hypoxic acclimatization on myocardial function of rats. Eighteen male Wistar rats were randomly divided into three groups: normoxic control, acute hypoxia and intermittent hypoxic acclimatization group (n=6). After being exposed to hypoxia (8000 m) for 4 h before and after intermittent hypoxic acclimatization (3000 m and 5000 m, 14 d respectively, 4 h/d), the rats were decapitated and then myocardial sarcoplasmic reticulum (SR) were derived from cardiac muscles. Activities of Na+, K(+)-ATPase, Ca2+, Mg2(+)-ATPase in SR, phosphorylation of phospholamban (PLB) and the ability of 45Ca2+ uptake in SR were observed in all these three groups. 1) Hypoxia had no effects on the activity of Na+, K(+)-ATPase in rats myocardial SR of rats. 2) Compared with normoxic control rats, the activity of Ca2+, Mg2(+)-ATPase in myocardial SR of rats after acute hypoxia was reduced significantly (P<0.01). After intermittent hypoxic acclimatization, its activity increased significantly as compared with that of acute hypoxic rats (P<0.01). 3) The phosphorylation of PLB in acute hypoxic rats was reduced significantly compared with normoxic control rats. After intermittent hypoxic acclimatization, its phosphorylation was increased significantly compared with that of acute hypoxic rats. It suggests that hypoxic acclimatization could alleviate the inhibition of calcium pump. 4) The ability of 45Ca2+ uptake of SR in acute hypoxic rats was decreased significantly. After hypoxic acclimatization, its ability was strengthened significantly. These results suggest that the increased function of myocardial SR calcium pump, the strengthened phosphorylation of PLB to alleviate the inhibition of calcium pump and the increased function of Ca2+ transport in SR are the mechanisms of hypoxic acclimatization protecting cardiac functions from injury induced by severe hypoxia.

Luminescence Properties of Self-Activated Mm(VO4)2 (M = Mg, Ca, Sr, and Ba) Phosphors Synthesized by Solid-State Reaction Method.

PubMed

Min, Xin; Huang, Zhaohui; Fang, Minghao; Liu, Yan'gai; Tang, Chao; Wu, Xiaowen

2016-04-01

In this paper, M3(VO4)2 (M = Mg, Ca, Sr, and Ba) self-activated phosphors were prepared by a solid-state reaction method at 1,000 °C for 5 h. The phase formation and micrographs were analyzed by X-ray diffraction and scanning electron microscopy. The Ca3(VO4)2 phosphor does not show any emission peaks under excitation with ultraviolet (UV) light. However, the M3(VO4)2 (M = Mg, Sr, and Ba) samples are effectively excited by UV light chips ranging from 200 nm to 400 nm and exhibit broad emission bands due to the charge transfer from the oxygen 2p orbital to the vacant 3d orbital of the vanadium in the VO4. The color of these phosphors changes from yellow to light blue via blue-green with increasing ionic radius from Mg to Sr to Ba. The luminescence lifetimes and quantum yield decrease with the increasing unit cell volume and V-V distance, in the order of Mg3(VO4)2 to Sr3(VO4)2 to Ba3(VO4)2. The emission intensity decreases with the increase of temperatures, but presents no color shift. This confirms that these self-activated M3(VO4)2 phosphors can be suggested as candidates of the single-phase phosphors for light using UV light emitting diodes (LEDs).

Interactions between calcium and phosphorus in the regulation of the production of fibroblast growth factor 23 in vivo

PubMed Central

Quinn, Stephen J.; Thomsen, Alex R. B.; Pang, Jian L.; Kantham, Lakshmi; Bräuner-Osborne, Hans; Pollak, Martin; Goltzman, David

2013-01-01

Calcium and phosphorus homeostasis are highly interrelated and share common regulatory hormones, including FGF23. However, little is known about calcium's role in the regulation of FGF23. We sought to investigate the regulatory roles of calcium and phosphorus in FGF23 production using genetic mouse models with targeted inactivation of PTH (PTH KO) or both PTH and the calcium-sensing receptor (CaSR; PTH-CaSR DKO). In wild-type, PTH KO, and PTH-CaSR DKO mice, elevation of either serum calcium or phosphorus by intraperitoneal injection increased serum FGF23 levels. In PTH KO and PTH-CaSR DKO mice, however, increases in serum phosphorus by dietary manipulation were accompanied by severe hypocalcemia, which appeared to blunt stimulation of FGF23 release. Increases in dietary phosphorus in PTH-CaSR DKO mice markedly decreased serum 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] despite no change in FGF23, suggesting direct regulation of 1,25(OH)2D3 synthesis by serum phosphorus. Calcium-mediated increases in serum FGF23 required a threshold level of serum phosphorus of about 5 mg/dl. Analogously, phosphorus-elicited increases in FGF23 were markedly blunted if serum calcium was less than 8 mg/dl. The best correlation between calcium and phosphorus and serum FGF23 was found between FGF23 and the calcium × phosphorus product. Since calcium stimulated FGF23 production in the PTH-CaSR DKO mice, this effect cannot be mediated by the full-length CaSR. Thus the regulation of FGF23 by both calcium and phosphorus appears to be fundamentally important in coordinating the serum levels of both mineral ions and ensuring that the calcium × phosphorus product remains within a physiological range. PMID:23233539

Sr, Mg cosubstituted HA porous macro-granules: potentialities as resorbable bone filler with antiosteoporotic functions.

PubMed

Landi, Elena; Uggeri, Jacopo; Medri, Valentina; Guizzardi, Stefano

2013-09-01

Porous macro-granules of nanostructured apatite with Ca ions partially cosubstituted with Mg and Sr ions in different ratios (SrMgHAs), were synthesized at 37°C and compared with Mg and/or Sr free apatites (MgHAs and HA). Strontium improved the Mg substitution extent in the apatite and the chemical-physical and thermal stability of the resulting cosubstituted apatite. Porous macro-granules of 400-600 micron with selected composition were tested for the ionic release in synthetic body fluid and the data were related with the results of preliminary cell investigation in vitro. As compared to the corresponding Sr-free granulate, the SrMgHA could be exploited to prolong the beneficial Mg release during the bone regeneration process. In addition the contemporary in situ supply of Sr, an antiosteoporotic and anticarie ion, could influence the quality of new hard tissues. The ionic multirelease created a more favorable environment for human osteoblasts, demonstrated by a proliferative effect for each dose tested in the range 0.1-10 mg/mL. Copyright © 2013 Wiley Periodicals, Inc.

Dysregulated Zn2+ homeostasis impairs cardiac type-2 ryanodine receptor and mitsugumin 23 functions, leading to sarcoplasmic reticulum Ca2+ leakage.

PubMed

Reilly-O'Donnell, Benedict; Robertson, Gavin B; Karumbi, Angela; McIntyre, Connor; Bal, Wojciech; Nishi, Miyuki; Takeshima, Hiroshi; Stewart, Alan J; Pitt, Samantha J

2017-08-11

Aberrant Zn 2+ homeostasis is associated with dysregulated intracellular Ca 2+ release, resulting in chronic heart failure. In the failing heart a small population of cardiac ryanodine receptors (RyR2) displays sub-conductance-state gating leading to Ca 2+ leakage from sarcoplasmic reticulum (SR) stores, which impairs cardiac contractility. Previous evidence suggests contribution of RyR2-independent Ca 2+ leakage through an uncharacterized mechanism. We sought to examine the role of Zn 2+ in shaping intracellular Ca 2+ release in cardiac muscle. Cardiac SR vesicles prepared from sheep or mouse ventricular tissue were incorporated into phospholipid bilayers under voltage-clamp conditions, and the direct action of Zn 2+ on RyR2 channel function was examined. Under diastolic conditions, the addition of pathophysiological concentrations of Zn 2+ (≥2 nm) caused dysregulated RyR2-channel openings. Our data also revealed that RyR2 channels are not the only SR Ca 2+ -permeable channels regulated by Zn 2+ Elevating the cytosolic Zn 2+ concentration to 1 nm increased the activity of the transmembrane protein mitsugumin 23 (MG23). The current amplitude of the MG23 full-open state was consistent with that previously reported for RyR2 sub-conductance gating, suggesting that in heart failure in which Zn 2+ levels are elevated, RyR2 channels do not gate in a sub-conductance state, but rather MG23-gating becomes more apparent. We also show that in H9C2 cells exposed to ischemic conditions, intracellular Zn 2+ levels are elevated, coinciding with increased MG23 expression. In conclusion, these data suggest that dysregulated Zn 2+ homeostasis alters the function of both RyR2 and MG23 and that both ion channels play a key role in diastolic SR Ca 2+ leakage. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Structural diversity of alkaline-earth 2,5-thiophenedicarboxylates

NASA Astrophysics Data System (ADS)

Balendra; Ramanan, Arunachalam

2017-03-01

Exploration of the structural landscape of the system containing divalent alkaline-earth metal ion (Mg, Ca and Sr) with the rigid 2,5-thiophenedicarboxylic acid (TDC) under varying solvothermal condition (DMF, DMA and DEF) yielded five new crystals: [Mg(TDC) (DEF)2(H2O)1/2] (1), [Ca(TDC) (DMA)] (2), [Ca(TDC) (DMA) (H2O)] (3), [Sr(TDC) (DMA)] (4) and [Sr(TDC) (DMA) (H2O)] (5) and two known solids. Single crystal structures of all the solids are characteristic of extended coordination interaction between metal and carboxylate ions. While the smaller magnesium ion crystallized into a 2D coordination polymer, the larger calcium and strontium compounds resulted into the growth of 3D metal organic frameworks. All the solids show blue emission arising from intra ligand charge transfer.

Modulation of sarcoplasmic reticulum Ca(2+)-release channels by caffeine, Ca2+, and Mg2+ in skinned myocardial fibers of fetal and adult rats.

PubMed

Su, J Y; Chang, Y I

1993-05-01

Ryanodine causes depression of the caffeine-induced tension transient (ryanodine depression) in skinned muscle fibers, because it blocks the sarcoplasmic reticulum (SR) Ca(2+)-release channels [Su, J. Y. (1988) Pflügers Arch 411:132-136, 371-377; (1992) Pflügers Arch 421:1-6]. This study was performed to examine the sensitivity of SR Ca(2+)-release channels to ryanodine in fetal compared to adult myocardium and to investigate the influence of Ca2+, caffeine, and Mg2+ on ryanodine depression in skinned fibers. Ryanodine (0.3 nM-1 microM) caused a dose-dependent depression in skinned myocardial fibers of the rat, and the fetal fibers (IC50 approximately 74 nM) were 26-fold less sensitive than those of the adult (IC50 approximately 2.9 nM). The depression induced by 0.1 microM or 1 microM ryanodine was a function of [caffeine], or [Ca2+] (pCa < 6.0), which was potentiated by caffeine, and an inverse function of [Mg2+]. At pCa > 8.0 plus 25 mM caffeine, a 20% ryanodine depression was observed in both the fetal and adult fibers, indicating independence from Ca2+. Ryanodine depression in skinned fibers of the fetus was less affected than that seen in the adult by pCai, [caffeine]i, or 25 mM caffeine plus pCai or plus pMgi (IC50 approximately pCa 4.5 versus 5.1; caffeine 12.7 mM versus 2 mM; pCa 6.7 versus 7.3; and pMg 3.9 versus 3.3 respectively). The results show that the SR Ca(2+)-release channel in both fetal and adult myocardium is modulated by Ca2+, caffeine, and Mg2+.(ABSTRACT TRUNCATED AT 250 WORDS)

Nandrolone decanoate treatment affects sarcoplasmic reticulum Ca(2+) ATPase function in skinned rat slow- and fast-twitch fibres.

PubMed

Bouhlel, Aicha; Joumaa, Wissam H; Léoty, Claude

2003-09-01

The effects of anabolic-androgenic steroid administration on the function of the sarcoplasmic reticulum (SR) pump were investigated in chemically skinned fibres from the extensor digitorum longus (EDL) and soleus muscles of sedentary rats. Twenty male rats were divided into two groups, one group received an intramuscular injection of nandrolone decanoate (15 mg x kg(-1)) weekly for 8 weeks, the second received similar weekly doses of vehicle (sterile peanut oil). Compared with control muscles, nandrolone decanoate treatment reduced SR Ca(2+) loading in EDL and soleus fibres by 49% and 29%, respectively. In control and treated muscles, the rate of Ca(2+) leakage depended on the quantity of Ca(2+) loaded. Furthermore, for similar SR Ca(2+) contents, the Ca(2+) leakage rate was not significantly modified by nandrolone decanoate treatment. Nandrolone decanoate treatment thus affects Ca (2+) uptake by the SR in a fibre-type dependent manner.

Primary fragmentation pathways of gas phase [M(uracil-H)(uracil)]+ complexes (M=Zn, Cu, Ni, Co, Fe, Mn, Cd, Pd , Mg, Ca, Sr, Ba, and Pb): loss of uracil versus HNCO.

PubMed

Ali, Osama Y; Randell, Nicholas M; Fridgen, Travis D

2012-04-23

Complexes formed between metal dications, the conjugate base of uracil, and uracil are investigated by sustained off-resonance irradiation collision-induced dissociation (SORI-CID) in a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. Positive-ion electrospray spectra show that [M(Ura-H)(Ura)](+) (M=Zn, Cu, Ni, Co, Fe, Mn, Cd, Pd, Mg, Ca, Sr, Ba, or Pb) is the most abundant ion even at low concentrations of uracil. SORI-CID experiments show that the main primary decomposition pathway for all [M(Ura-H)(Ura)](+) , except where M=Ca, Sr, Ba, or Pb, is the loss of HNCO. Under the same SORI-CID conditions, when M is Ca, Sr, Ba, or Pb, [M(Ura-H)(Ura)](+) are shown to lose a molecule of uracil. Similar results were observed under infrared multiple-photon dissociation excitation conditions, except that [Ca(Ura-H)(Ura)](+) was found to lose HNCO as the primary fragmentation product. The binding energies between neutral uracil and [M(Ura-H)](+) (M=Zn, Cu, Ni, Fe, Cd, Pd ,Mg, Ca, Sr Ba, or Pb) are calculated by means of electronic-structure calculations. The differences in the uracil binding energies between complexes which lose uracil and those which lose HNCO are consistent with the experimentally observed differences in fragmentation pathways. A size dependence in the binding energies suggests that the interaction between uracil and [M(Ura-H)](+) is ion-dipole complexation and the experimental evidence presented supports this. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The elemental composition of purple sea urchin (Strongylocentrotus purpuratus) calcite and potential effects of pCO2 during early life stages

NASA Astrophysics Data System (ADS)

LaVigne, M.; Hill, T. M.; Sanford, E.; Gaylord, B.; Russell, A. D.; Lenz, E. A.; Hosfelt, J. D.; Young, M. K.

2013-06-01

Ocean acidification will likely have negative impacts on invertebrates producing skeletons composed of calcium carbonate. Skeletal solubility is partly controlled by the incorporation of "foreign" ions (e.g. magnesium) into the crystal lattice of these skeletal structures, a process that is sensitive to a variety of biological and environmental factors. Here we explore effects of life stage, oceanographic region of origin, and changes in the partial pressure of carbon dioxide in seawater (pCO2) on trace elemental composition in the purple sea urchin (Strongylocentrotus purpuratus). We show that, similar to other urchin taxa, adult purple sea urchins have the ability to precipitate skeleton composed of a range of biominerals spanning low- to high-Mg calcites. Mg / Ca and Sr / Ca ratios were substantially lower in adult spines compared to adult tests. On the other hand, trace elemental composition was invariant among adults collected from four oceanographically distinct regions spanning a range of carbonate chemistry conditions (Oregon, Northern California, Central California, and Southern California). Skeletons of newly settled juvenile urchins that originated from adults from the four regions exhibited intermediate Mg / Ca and Sr / Ca between adult spine and test endmembers, indicating that skeleton precipitated during early life stages is more soluble than adult spines and less soluble than adult tests. Mean skeletal Mg / Ca or Sr / Ca of juvenile skeleton did not vary with source region when larvae were reared under present-day, global-average seawater carbonate conditions (400 μatm; pHT = 8.02 ± 0.03 1 SD; Ωcalcite = 3.3 ± 0.2 1 SD). However, when reared under elevated pCO2 (900 μatm; pHT = 7.73 ± 0.03; Ωcalcite = 1.8 ± 0.1), skeletal Sr / Ca in juveniles exhibited increased variance across the four regions. Although larvae from the northern populations (Oregon, Northern California, Central California) did not exhibit differences in Mg or Sr incorporation under elevated pCO2 (Sr / Ca = 2.10 ± 0.06 mmol mol-1; Mg / Ca = 67.4 ± 3.9 mmol mol-1), juveniles of Southern California origin partitioned ~8% more Sr into their skeletons when exposed to higher pCO2 (Sr / Ca = 2.26 ± 0.08 vs. 2.09 ± 0.005 mmol mol-1 1 SD). Together these results suggest that the diversity of carbonate minerologies present across different skeletal structures and life stages in purple sea urchins does not translate into an equivalent geochemical plasticity of response associated with geographic variation or temporal shifts in seawater properties. Rather, composition of S. purpuratus skeleton precipitated during both early and adult life history stages appears relatively robust to spatial gradients and predicted future changes in carbonate chemistry. An exception to this trend may arise during early life stages, where certain populations of purple sea urchins may alter skeletal mineral precipitation rates and composition beyond a given pCO2 threshold. This potential for geochemical plasticity during early development in contrast to adult stage geochemical resilience adds to the growing body of evidence that ocean acidification can have differing effects across organismal life stages.

Mg/Ca, Sr/Ca, and stable isotopes in modern and Holocene Protothaca staminea shells from a northern California coastal upwelling region

USGS Publications Warehouse

Takesue, R.K.; VanGeen, A.

2004-01-01

This study explores the potential of intertidal Protothaca staminea shells as high-resolution geochemical archives of environmental change in a coastal upwelling region. Mg/Ca and Sr/Ca ratios were analyzed by excimer laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) at sub-weekly temporal resolution in shells growing ???1 mm per month. Growth patterns of a modern P. staminea shell from Humboldt Bay, California, collected in December 1999 made it possible to infer a lifespan from 1993 to 1998. Growth hiatuses in the shell may have excluded records of extreme events. Mg/Ca ratios appeared to be partly controlled by water temperature; the correlation coefficient between temperature and Mg/Ca was r = 0.71 in one of four growth increments. Significant year-to-year differences in the sensitivity of Mg/Ca to temperature in P. staminea could not be explained, however. Sr/Ca ratios appeared to be more closely related to shell growth rate. Oxygen isotopes, measured at 2-week temporal resolution in the same shell, did not show a clear relation to local temperature in summer, possibly because temperatures were higher and less variable at the King Salmon mudflat, where the shell was collected, than in the main channel of Humboldt Bay, where water properties were monitored. Negative shell ??13C values (<-0.5???) marked spring and summer coastal upwelling events. The Mg contents of P. staminea midden shells dated to ???3 ka and ???9 ka were significantly lower than in the modern shell. This may have resulted from degradation of a Mg-rich shell organic matrix and precluded quantitative interpretation of the older high-resolution records. Elevated ??13C values in the ???3 ka shell suggested that the individual grew in highly productive or stratified environment, such as a shallow coastal embayment or lagoon. Copyright ?? 2004 Elsevier Ltd.

Mg/Ca and Sr/Ca as novel geochemical proxies for understanding sediment transport processes within coral reefs

NASA Astrophysics Data System (ADS)

Gacutan, J.; Vila-Concejo, A.; Nothdurft, L. D.; Fellowes, T. E.; Cathey, H. E.; Opdyke, B. N.; Harris, D. L.; Hamylton, S.; Carvalho, R. C.; Byrne, M.; Webster, J. M.

2017-10-01

Sediment transport is a key driver of reef zonation and biodiversity, where an understanding of sediment dynamics gives insights into past reef processes and allows the prediction of geomorphic responses to changing environmental conditions. However, modal conditions within the back-reef seldom promote sediment transport, hence direct observation is inherently difficult. Large benthic foraminifera (LBF) have previously been employed as 'tracers' to infer sediment transport pathways on coral reefs, as their habitat is largely restricted to the algal flat and post-mortem, their calcium carbonate test is susceptible to sediment transport forces into the back-reef. Foraminiferal test abundance and post-depositional test alteration have been used as proxies for sediment transport, although the resolution of these measures becomes limited by low test abundance and the lack of variation within test alteration. Here we propose the novel use of elemental ratios as a proxy for sediment transport. Two species, Baculogypsina sphaerulata and Calcarina capricornia, were analysed using a taphonomic index within One Tree and Lady Musgrave reefs, Great Barrier Reef (Australia). Inductively coupled plasma-atomic emission spectrometry (ICP-AES) was used to determine Mg/Ca and Sr/Ca and these ratios were compared with taphonomic data. Decreases in test Mg/Ca accompany increases in Sr/Ca in specimens from algal-flat to lagoonal samples in both species, mirroring trends indicated by taphonomic values, therefore indicating a relationship with test alteration. To delineate mechanisms driving changes in elemental ratios, back-scattered electron (BSE) images, elemental mapping and in situ quantitative spot analyses by electron microprobe microanalysis (EPMA) using wavelength dispersive X-ray spectrometers (WDS) were performed on un-altered algal flat and heavily abraded tests for both species. EPMA analyses reveal heterogeneity in Mg/Ca between spines and the test wall, implying the loss of appendages results in a decrease in Mg/Ca. BSE imaging and WDS elemental mapping provided evidence for cementation, facilitated by microbial-boring as the primary cause of increasing Sr/Ca. These novel proxies hold advantages over taphonomic measures and further provide a rapid method to infer sediment transport pathways within back-reef environments.

Structural study of some divalent aluminoborate glasses using ultrasonic and positron annihilation techniques

NASA Astrophysics Data System (ADS)

Saddeek, Yasser B.; Mohamed, Hamdy F. M.; Azooz, Moenis A.

2004-07-01

Positron annihilation lifetime (PAL), ultrasonic techniques, and differential thermal analysis (DTA) were performed to study the structure of some aluminoborate glasses. The basic compositions of these glasses are 50 B2O3 + 10 Al2O3 + 40 RO (wt%), where RO is the divalent oxide (MgO, CaO, SrO, and CdO). The ultrasonic data show that the rigidity increases from MgO to CaO then decrease at SrO and again increases at CdO. The glass transition temperature (determined from DTA) decreases from MgO to SrO then increases at CdO. The trend of the thermal properties was attributed to thermal stability. The experimental data are correlated with the internal glass structure and its connectivity. The PAL data show that an inversely correlation between the relative fractional of the open hole volume and the density of the samples. Also, there is a good correlation between the ortho-positronium (o-Ps) lifetime (open hole volume size) and the bulk modulus of the samples (determined from ultrasonic technique). The open volume hole size distribution for the samples shows that the open volume holes expand in size for CaO, SrO, MgO, and CdO, respectively with their distribution function moving to higher volume size.

Rainfall Control of Karst Solution and the Inter/Intra Annual Hydrogeochemical Evolution of Cave Dripwater: A Long-term, Site-specific Study, Soreq Cave, Israel

NASA Astrophysics Data System (ADS)

Burstyn, Yuval; Bar-Matthews, Miryam; Ayalon, Avner; Matthews, Alan

2016-04-01

Speleothem laminae preserve climate information transferred to the cave via dripwater. High spatial resolution methods allow in situ measurement of geochemical and isotopic proxies at seasonal resolution. Existing hydrogeochemical calibration models suggest that high rainfall inhibits karst water chemical evolution, resulting in low δ 18O values, and low Mg/Ca and Sr/Ca ratios that are not necessarily correlated. Drought periods display opposite chemical behaviour owing to lower infiltration rates and increased Prior Calcite Precipitation (PCP). This study aims to provide a site-specific, high-resolution hydrogeochemical calibration for the Soreq Cave. We examine four sites that were continuously sampled since 1990. Four main rainfall conditions are characterized: very wet years, average, drought and very dry years. Two sites are fed by 'fast drips', which only become active after ˜ 250mm rainfall has accumulated since the beginning of the winter season. Two sites, located deeper in the cave, are fed by 'slow drips' that are active all year round. Drip rate measurements identify two main reservoirs - fissure and matrix - that mainly differ in residence time. The δ 18O of fissure water is closer to that of mean annual rainfall (˜ -6 ‰VSMOW), while matrix values are higher (˜ -3.5 ‰VSMOW). Two main Sr and Mg sources are identified - dolomitic bedrock (Mg/Ca ˜ 700 mM/M, Sr/Ca ˜ 0.4 mM/M) and soil leachate (Mg/Ca ˜ 300 mM/M, Sr/Ca ˜ 1.1 mM/M). Most cave dripwater evolves from ˜ 1:1 soil-bedrock solution. PCP effect on dripwater solution at each site is estimated by comparing the ln(Mg/Ca) vs ln(Sr/Ca) linear slope to the PCP slope calculated using cave specific D(Mg) and D(Sr). Soreq Cave PCP slope is similar to the global slope of 0.88± 0.13. The composition and chemical evolution of each reservoir and its contribution to water influx at each site is primarily governed by annual effective infiltration. Higher seasonal amplitude in δ 18O, Mg/Ca and Sr/Ca in all sites is positively correlated to increase in rainfall. For the deeper site, with rock cover of >40 m, the `classic' wet-dry model can be applied - more soil input and less PCP in the wetter years and vice-versa. Conversely, in the shallower sites, high PCP is observed in wetter years. Results from this study are compared with high-resolution δ 18O and trace element records of modern speleothems (age ˜ 20y). The speleothem from the deeper site shows a good match with the hydrogeochemical data, thus supporting the applicability of the model to palaeoclimate studies. However, the speleothem from the shallow site shows a strong winter bias, which may be due to complete secession of summer drip during dry years (micro-hiatuses), or during wetter years, considerable winter calcite precipitation resulting in minimal summer imprint on each seasonal lamina. We plan to analyse a fast growing modern sample from the shallow site to resolve this seasonal bias. Therefore, contemporaneous speleothem records from different sites can be utilized to estimate past changes in annual and decadal effective infiltration, allowing evaluation of water availability in the region during periods of rapid climate change. [1] Orland, I.J. et al. 2014. Chemical Geology, v. 363, p. 322-333.

The impact of biotic/abiotic interfaces in mineral nutrient cycling: A study of soils of the Santa Cruz chronosequence, California

USGS Publications Warehouse

White, A.F.; Schulz, M.S.; Vivit, D.V.; Bullen, T.D.; Fitzpatrick, J.

2012-01-01

Biotic/abiotic interactions between soil mineral nutrients and annual grassland vegetation are characterized for five soils in a marine terrace chronosequence near Santa Cruz, California. A Mediterranean climate, with wet winters and dry summers, controls the annual cycle of plant growth and litter decomposition, resulting in net above-ground productivities of 280-600gm -2yr -1. The biotic/abiotic (A/B) interface separates seasonally reversible nutrient gradients, reflecting biological cycling in the shallower soils, from downward chemical weathering gradients in the deeper soils. The A/B interface is pedologically defined by argillic clay horizons centered at soil depths of about one meter which intensify with soil age. Below these horizons, elevated solute Na/Ca, Mg/Ca and Sr/Ca ratios reflect plagioclase and smectite weathering along pore water flow paths. Above the A/B interface, lower cation ratios denote temporal variability due to seasonal plant nutrient uptake and litter leaching. Potassium and Ca exhibit no seasonal variability beneath the A/B interface, indicating closed nutrient cycling within the root zone, whereas Mg variability below the A/B interface denotes downward leakage resulting from higher inputs of marine aerosols and lower plant nutrient requirements.The fraction of a mineral nutrient annually cycled through the plants, compared to that lost from pore water discharge, is defined their respective fluxes F j,plants=q j,plants/(q j,plants+q j,discharge) with average values for K and Ca (F K,plants=0.99; F Ca,plants=0.93) much higher than for Mg and Na (F Mg,plants 0.64; F Na,plants=0.28). The discrimination against Rb and Sr by plants is described by fractionation factors (K Sr/Ca=0.86; K Rb/K=0.83) which are used in Rayleigh fractionation-mixing calculations to fit seasonal patterns in solute K and Ca cycling. K Rb/K and K24Mg/22Mg values (derived from isotope data in the literature) fall within fractionation envelopes bounded by inputs from rainfall and mineral weathering. K Sr/Ca and K44Ca/40Ca fractionation factors fall outside these envelopes indicating that Ca nutrient cycling is closed to these external inputs. Small net positive K and Ca fluxes (6-14molm -2yr -1), based on annual mass balances, indicate that the soils are accumulating mineral nutrients, probably as a result of long-term environmental disequilibrium. ?? 2011.

Empirical calibration of shell chemistry of Cyprideis torosa (Jones, 1850) (Crustacea: Ostracoda)

NASA Astrophysics Data System (ADS)

Marco-Barba, J.; Ito, E.; Carbonell, E.; Mesquita-Joanes, F.

2012-09-01

Cyprideis torosa is a species of ostracode that inhabits a wide range of aquatic habitats in which its low Alk/Ca requirement is met. Its fossil remains are widely used in palaeoecological studies of coastal environments and inland salt lakes. We collected C. torosa from 20 water bodies near Valencia, Spain. Temperature, chlorophyll a concentration, electrical conductivity, and the concentration of major ions and oxygen isotopes were measured at each site. Between 2 and 20 live individuals of C. torosa were collected per site, their instar stage and sex determined and their shell chemistry (Mg/Ca, Sr/Ca and carbon and oxygen isotope composition) analyzed. Three of these sites were sampled monthly for one year, and ostracode population structure and shell chemistry (20-40 shells) were analyzed. The water chemistry varied widely between sites. TDS (total dissolved solids) ranged from 0.5 to 71.8 g/L but chloride was always the dominant anion. There is a significant positive relationship between ostracode and water δ18O except at high TDS (>20 g/L) when shell δ18O values are lower than expected. No effect of either temperature or water Mg/Ca is observed on the Mg/Ca in the ostracode calcite in waters with Mg/Ca < 6 (molar ratio). Ostracode shell Sr/Ca is strongly and significantly related to water Sr/Ca. δ13C values in C. torosa shells are ˜2‰ lower than observed δ13CDIC. These results provide new and more accurate quantification tools to reconstruct past hydrochemistry from C. torosa shells.

The Calcium-Sensing Receptor in Health and Disease.

PubMed

Díaz-Soto, G; Rocher, A; García-Rodríguez, C; Núñez, L; Villalobos, C

2016-01-01

The extracellular calcium-sensing receptor (CaSR) is a unique G protein-coupled receptor (GPCR) activated by extracellular Ca 2+ and by other physiological cations including Mg 2+ , amino acids, and polyamines. CaSR is the most important master controller of the extracellular Ca 2+ homeostatic system being expressed at high levels in the parathyroid gland, kidney, gut and bone, where it regulates parathyroid hormone (PTH) secretion, vitamin D synthesis, and Ca 2+ absorption and resorption, respectively. Gain and loss of function mutations in the CaSR are responsible for severe disturbances in extracellular Ca 2+ metabolism. CaSR agonists (calcimimetics) and antagonists (calcilytics) are in use or under intense research for treatment of hyperparathyroidism secondary to kidney failure and hypocalcemia with hypercalciuria, respectively. Expression of the CaSR extends to other tissues and systems beyond the extracellular Ca 2+ homeostatic system including the cardiovascular system, the airways, and the nervous system where it may play physiological functions yet to be fully understood. As a consequence, CaSR has been recently involved in different pathologies including uncontrolled blood pressure, vascular calcification, asthma, and Alzheimer's disease. Finally, the CaSR has been shown to play a critical role in cancer either contributing to bone metastasis and/or acting as a tumor suppressor in some forms of cancer (parathyroid cancer, colon cancer, and neuroblastoma) and as oncogene in others (breast and prostate cancers). Here we review the role of CaSR in health and disease in calciotropic tissues and others beyond the extracellular calcium homeostatic system. Copyright © 2016 Elsevier Inc. All rights reserved.

Molecular dynamics of ion hydration in the presence of small carboxylated molecules and implications for calcification.

PubMed

Hamm, Laura M; Wallace, Adam F; Dove, Patricia M

2010-08-19

The aspartate-rich macromolecules found at nucleation sites of calcifying organisms are widely implicated in regulating biomineral formation. Anecdotal evidence suggests that their ability to influence the onset of nucleation and composition of calcified structures may arise from effects on ion hydration. This study investigates the interactions of acidic amino acids and dipeptides with hydrated cations using molecular dynamics. By monitoring the hydration states of Mg2+, Ca2+, and Sr2+ during their approach to negatively charged molecules, we show that carboxylate moieties of Asp promote dehydration of Ca2+ and Sr2+. A contact ion pair (CIP) is not required to disrupt cation hydration, and we demonstrate that reductions and rearrangements of first shell water can begin at ion-Asp separation distances as large as approximately 4.9 A for Ca2+ and approximately 5.1 A for Sr2+. CIP formation between Ca2+ and Sr2+ and carboxylate groups decreases the total first shell coordination number from an average of 8.0 and 8.4 in bulk water to 7.5 and 8.0, respectively. The energy barrier to physically replacing waters about Ca2+ with carboxylate oxygen atoms is small (approximately 2 kcal/mol) as compared to a somewhat larger barrier for Sr2+ (approximately 4 kcal/mol). This may be explained by differences in the strength of Coulombic interactions between the cations and the Asp, resulting in different paths of approach toward Asp for Ca2+ and Sr2+. In contrast, the primary solvation shell of Mg2+ remains largely unchanged during interactions with Asp until the abrupt physical replacement of water by carboxylate oxygen atoms, which comes at a high energetic cost. These insights support the claim that carboxylated biomolecules increase the growth rate of calcite by lowering the energy barrier to Ca2+ dehydration. The findings also suggest a physical basis for the idea that ion-specific behaviors of Ca2+ and Mg2+ in cellular systems arise from a critical balance between water binding in the ion hydration shells versus their interactions with ligands present in intracellular environments.

Matching watershed and otolith chemistry to establish natal origin of an endangered desert lake sucker

USGS Publications Warehouse

Strohm, Deanna D.; Budy, Phaedra; Crowl, Todd A.

2017-01-01

Stream habitat restoration and supplemental stocking of hatchery-reared fish have increasingly become key components of recovery plans for imperiled freshwater fish; however, determining when to discontinue stocking efforts, prioritizing restoration areas, and evaluating restoration success present a conservation challenge. In this study, we demonstrate that otolith microchemistry is an effective tool for establishing natal origin of the June Sucker Chasmistes liorus, an imperiled potamodromous fish. This approach allows us to determine whether a fish is of wild or hatchery origin in order to assess whether habitat restoration enhances recruitment and to further identify areas of critical habitat. Our specific objectives were to (1) quantify and characterize chemical variation among three main spawning tributaries; (2) understand the relationship between otolith microchemistry and tributary chemistry; and (3) develop and validate a classification model to identify stream origin using otolith microchemistry data. We quantified molar ratios of Sr:Ca, Ba:Ca, and Mg:Ca for water and otolith chemistry from three main tributaries to Utah Lake, Utah, during the summer of 2013. Water chemistry (loge transformed Sr:Ca, Ba:Ca, and Mg:Ca ratios) differed significantly across all three spawning tributaries. We determined that Ba:Ca and Sr:Ca ratios were the most important variables driving our classification models, and we observed a strong linear relationship between water and otolith values for Sr:Ca and Ba:Ca but not for Mg:Ca. Classification models derived from otolith element : Ca signatures accurately sorted individuals to their experimental tributary of origin (classification tree: 89% accuracy; random forest model: 91% accuracy) and determined wild versus hatchery origin with 100% accuracy. Overall, this study aids in evaluating the effectiveness of restoration, tracking progress toward recovery, and prioritizing future restoration plans for fishes of conservation concern. Our results have further application, such as identifying subpopulations that provide the greatest reproductive contribution to a metapopulation or finding the reproductive area and origin of invasive fishes.

Determination of (87)Sr/(86)Sr and δ(88/86)Sr ratios in plant materials using MC-ICP-MS.

PubMed

Liu, Hou-Chun; Chung, Chuan-Hsiung; You, Chen-Feng; Chiang, Yi-Hsuan

2016-01-01

A protocol for highly accurate and precise determination of Sr isotope ratios in plant materials, (87)Sr/(86)Sr and δ (88/86)Sr, by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) is presented in this study. An Eichrom Sr resin was used for matrix separation and an improved Zr empirical external normalization coupled with standard-sample bracketing method (Zr EEN-SSB) was applied to mass bias correction during Sr isotope MC-ICP-MS measurements. Potential influences of matrix elements, and polyatomic and isobaric interferences on the Sr isotopic determination were further evaluated using NIST SRM 987 Sr isotopic standard spiked with various amount of Ca, Mg, and Rb contents. Concentrations of Ca and Mg lower than 30 ng g(-1) or Rb < 2 ng g(-1) in 150 ng g(-1) Sr analyte were estimated to have only a minor effect on Sr isotope ratios determination. On the other hand, intensity differences between sample and standards (IntSample/IntStandards) represented a large δ (88/86)Sr deviation of <0.9 or >1.3, reflecting the significance of intensity bias attributed to different mass bias behavior. An apple leaf material, NIST SRM 1515, was adopted as the plant material for overall evaluation of sample digestion, matrix separation, and potential spectral interferences on the measurements of Sr isotope ratios. Our results suggest that the partially remaining organic compounds in the incomplete digestion would have a significant bias on the extraction chromatography procedure, resulting in sizable uncertainty in δ (88/86)Sr ratios. Thus, complete digestion of the organic-enriched materials is of great importance for efficiency assurance in matrix separation. Extraction chromatography works well for the total digested samples, where Ca, Mg, and Rb were efficiently removed. The obtained average (87)Sr/(86)Sr and δ (88/86)Sr values for the NIST SRM 1515 apple leaves are 0.71398 ± 0.00004 and 0.23 ± 0.03‰ (2SD, n = 10), respectively.

Quantifying the effect of diagenetic recrystallization on the Mg isotopic composition of marine carbonates

NASA Astrophysics Data System (ADS)

Chanda, Piyali; Fantle, Matthew S.

2017-05-01

The Mg and Sr isotopic compositions (δ26Mg and 87Sr/86Sr) of pore fluids and bulk carbonates from Ocean Drilling Project Site 1171 (South Tasman Rise; 2148.2 m water depth) are reported, in order to evaluate the potential of diagenesis to alter carbonate-based geochemical proxies in an open marine system. Given the trace amounts of Mg in marine carbonates relative to coexisting pore fluids, diagenesis can alter carbonate δ26Mg, a promising proxy for seawater δ26Mg that may help elucidate long-term changes in the global Mg cycle. Constraints on the effect of diagenetic recrystallization on carbonate δ26Mg are therefore critical for accurate proxy interpretations. This study provides context for assessing the fidelity of geochemical proxy-reconstructions using the primary components (i.e., foraminiferal tests and nannofossils) of bulk carbonate sediments. We find that pore fluid δ26Mg values (on the DSM3 scale) at Site 1171 increase systematically with depth (from -0.72‰ to -0.39‰ in the upper ∼260 m), while the δ26Mg of bulk carbonates decrease systematically with depth (from -2.23‰ to -5.00‰ in the upper ∼260 m). This variability is ascribed primarily to carbonate recrystallization, with a small proportion of the variability due to down-hole changes in nannofossil and foraminiferal species composition. The inferred effect of diagenesis on bulk carbonate δ26Mg correlates with down-core changes in Mg/Ca, Sr/Ca, Na/Ca, and 87Sr/86Sr. A depositional reactive-transport model is employed to validate the hypothesis that calcite recrystallization in this system can generate sizeable shifts in carbonate δ26Mg. Model fits to the data suggest a fractionation factor and a partition coefficient that are consistent with previous work, assuming calcite recrystallization rates of ⩽7%/Ma constrained by Sr geochemistry. In addition, either partial dissolution or a distinctly different previous diagenetic regime must be invoked in order to explain aspects of the elemental chemistry and 87Sr/86Sr of relatively deep sediments from Holes A and C. This study indicates that the dynamics of a given sedimentary system can significantly alter bulk carbonate geochemistry, and presents a framework for considering the potential impact of such alteration on picked archives such as foraminiferal tests and nannofossils. Ultimately, this study contributes to the development of δ26Mg as a proxy for seawater δ26Mg by quantifying the susceptibility of carbonate δ26Mg to diagenetic alteration, particularly in sediments in open marine systems. This study suggests that because of the sensitivity of carbonate δ26Mg to diagenetic recrystallization, it can, in certain systems, be used to quantify the impact of diagenesis on carbonate-based geochemical proxies.

Quasi-2D silicon structures based on ultrathin Me2Si (Me = Mg, Ca, Sr, Ba) films

NASA Astrophysics Data System (ADS)

Migas, D. B.; Bogorodz, V. O.; Filonov, A. B.; Borisenko, V. E.; Skorodumova, N. V.

2018-04-01

By means of ab initio calculations with hybrid functionals we show a possibility for quasi-2D silicon structures originated from semiconducting Mg2Si, Ca2Si, Sr2Si and Ba2Si silicides to exist. Such a 2D structure is similar to the one of transition metal chalcogenides where silicon atoms form a layer in between of metal atoms aligned in surface layers. These metal surface atoms act as pseudo passivation species stabilizing crystal structure and providing semiconducting properties. Considered 2D Mg2Si, Ca2Si, Sr2Si and Ba2Si have band gaps of 1.14 eV, 0.69 eV, 0.33 eV and 0.19 eV, respectively, while the former one is also characterized by a direct transition with appreciable oscillator strength. Electronic states of the surface atoms are found to suppress an influence of the quantum confinement on the band gaps. Additionally, we report Sr2Si bulk in the cubic structure to have a direct band gap of 0.85 eV as well as sizable oscillator strength of the first direct transition.

Structural transitions in hybrid improper ferroelectric C a3T i2O7 tuned by site-selective isovalent substitutions: A first-principles study

NASA Astrophysics Data System (ADS)

Li, C. F.; Zheng, S. H.; Wang, H. W.; Gong, J. J.; Li, X.; Zhang, Y.; Yang, K. L.; Lin, L.; Yan, Z. B.; Dong, Shuai; Liu, J.-M.

2018-05-01

C a3T i2O7 is an experimentally confirmed hybrid improper ferroelectric material, in which the electric polarization is induced by a combination of the coherent Ti O6 octahedral rotation and tilting. In this work, we investigate the tuning of ferroelectricity of C a3T i2O7 using isovalent substitutions on Ca sites. Due to the size mismatch, larger/smaller alkaline earths prefer A'/A sites, respectively, allowing the possibility for site-selective substitutions. Without extra carriers, such site-selected isovalent substitutions can significantly tune the Ti O6 octahedral rotation and tilting, and thus change the structure and polarization. Using the first-principles calculations, our study reveals that three substituted cases (Sr, Mg, and Sr+Mg) show divergent physical behaviors. In particular, (CaTiO3) 2SrO becomes nonpolar, which can reasonably explain the suppression of polarization upon Sr substitution observed in experiment. In contrast, the polarization in (MgTiO3) 2CaO is almost doubled upon substitutions, while the estimated coercivity for ferroelectric switching does not change. The (MgTiO3) 2SrO remains polar but its structural space group changes, with moderate increased polarization and possible different ferroelectric switching paths. Our study reveals the subtle ferroelectricity in the A3T i2O7 family and suggests one more practical route to tune hybrid improper ferroelectricity, in addition to the strain effect.

Structural basis for regulation of human calcium-sensing receptor by magnesium ions and an unexpected tryptophan derivative co-agonist.

PubMed

Zhang, Chen; Zhang, Tuo; Zou, Juan; Miller, Cassandra Lynn; Gorkhali, Rakshya; Yang, Jeong-Yeh; Schilmiller, Anthony; Wang, Shuo; Huang, Kenneth; Brown, Edward M; Moremen, Kelley W; Hu, Jian; Yang, Jenny J

2016-05-01

Ca(2+)-sensing receptors (CaSRs) modulate calcium and magnesium homeostasis and many (patho)physiological processes by responding to extracellular stimuli, including divalent cations and amino acids. We report the first crystal structure of the extracellular domain (ECD) of human CaSR bound with Mg(2+) and a tryptophan derivative ligand at 2.1 Å. The structure reveals key determinants for cooperative activation by metal ions and aromatic amino acids. The unexpected tryptophan derivative was bound in the hinge region between two globular ECD subdomains, and represents a novel high-affinity co-agonist of CaSR. The dissection of structure-function relations by mutagenesis, biochemical, and functional studies provides insights into the molecular basis of human diseases arising from CaSR mutations. The data also provide a novel paradigm for understanding the mechanism of CaSR-mediated signaling that is likely shared by the other family C GPCR [G protein (heterotrimeric guanine nucleotide-binding protein)-coupled receptor] members and can facilitate the development of novel CaSR-based therapeutics.

The effect of age and gender on 38 chemical element contents in human iliac crest investigated by instrumental neutron activation analysis.

PubMed

Zaichick, Sofia; Zaichick, Vladimir

2010-01-01

To understand the role of major, minor, and trace elements in the etiology of bone diseases including osteoporosis, it is necessary to determine the normal levels and age-related changes of bone chemical elements. The effect of age and gender on 38 chemical element contents in intact iliac crest of 84 apparently healthy 15-55 years old women (n=38) and men (n=46) was investigated by neutron activation analysis. Mean values (M+/-SEM) for mass fraction (on dry weight basis) of Ca, Cl, Co, Fe, K, Mg, Mn, Na, P, Rb, Sr, and Zn for both female and male taken together were Ca - 169+/-3g/kg, Cl - 1490+/-43 mg/kg, Co - 0.0073+/-0.0024 mg/kg, Fe - 177+/-24 mg/kg, K - 1820+/-79 mg/kg, Mg - 1840+/-48 mg/kg, Mn - 0.316+/-0.013 mg/kg, Na - 4970+/-87 mg/kg, P - 79.7+/-1.5 g/kg, Rb - 1.89+/-0.22 mg/kg, Sr - 312+/-15 mg/kg, and Zn - 65.9+/-3.4 mg/kg, respectively. The upper limit of mean contents of Cs, Eu, Hg, Sb, Sc, and Se were Cs < or = 0.09 mg/kg, Eu < or = 0.005 mg/kg, Hg < or = 0.005 mg/kg, Sb < or = 0.004 mg/kg, Sc < or = 0.001 mg/kg, and Se < or = 0.1mg/kg, respectively. In all bone samples the contents of Ag, As, Au, Ba, Br, Cd, Ce, Cr, Gd, Hf, La, Lu, Nd, Sm, Ta, Tb, Th, U, Yb, and Zr were under detection limits. The Ca, Mg, and P contents decrease with age, regardless of gender. Higher Ca, Mg, P, and Sr mass fractions as well as lower Fe content are typical of female iliac crest as compared to those in male bone. Copyright 2009 Elsevier GmbH. All rights reserved.

Functionalized inorganic membranes for gas separation

DOEpatents

Ku, Anthony Yu-Chung [Rexford, NY; Ruud, James Anthony [Delmar, NY; Molaison, Jennifer Lynn [Marietta, GA; Schick, Louis Andrew ,; Ramaswamy, Vidya [Niskayuna, NY

2008-07-08

A porous membrane for separation of carbon dioxide from a fluid stream at a temperature higher than about 200.degree. C. with selectivity higher than Knudsen diffusion selectivity. The porous membrane comprises a porous support layer comprising alumina, silica, zirconia or stabilized zirconia; a porous separation layer comprising alumina, silica, zirconia or stabilized zirconia, and a functional layer comprising a ceramic oxide contactable with the fluid stream to preferentially transport carbon dioxide. In particular, the functional layer may be MgO, CaO, SrO, BaO, La.sub.2O.sub.3, CeO.sub.2, ATiO.sub.3, AZrO.sub.3, AAl.sub.2O.sub.4, A.sup.1FeO.sub.3, A.sup.1MnO.sub.3, A.sup.1CoO.sub.3, A.sup.1NiO.sub.3, A.sup.2HfO.sub.3, A.sup.3CeO.sub.3, Li.sub.2ZrO.sub.3, Li.sub.2SiO.sub.3, Li.sub.2TiO.sub.3 or a mixture thereof; wherein A is Mg, Ca, Sr or Ba; A.sup.1 is La, Ca, Sr or Ba; A.sup.2 is Ca, Sr or Ba; and A.sup.3 is Sr or Ba.

Cenozoic seawater Sr/Ca evolution

NASA Astrophysics Data System (ADS)

Sosdian, Sindia M.; Lear, Caroline H.; Tao, Kai; Grossman, Ethan L.; O'Dea, Aaron; Rosenthal, Yair

2012-10-01

Records of seawater chemistry help constrain temporal variations in geochemical processes that impact the global carbon cycle and climate through Earth's history. Here we reconstruct Cenozoic seawater Sr/Ca (Sr/Casw) using fossil Conus and turritellid gastropod Sr/Ca. Combined with an oxygen isotope paleotemperature record from the same samples, the gastropod record suggests that Sr/Caswwas slightly higher in the Eocene (˜11.4 ± 3 mmol/mol) than today (˜8.54 mmol/mol) and remained relatively stable from the mid- to late Cenozoic. We compare our gastropod Cenozoic Sr/Casw record with a published turritellid gastropod Sr/Casw record and other published biogenic (benthic foraminifera, fossil fish teeth) and inorganic precipitate (calcite veins) Sr/Caswrecords. Once the uncertainties with our gastropod-derived Sr/Casw are taken into account the Sr/Casw record agrees reasonably well with biogenic Sr/Caswrecords. Assuming a seawater [Ca] history derived from marine evaporite inclusions, all biogenic-based Sr/Casw reconstructions imply decreasing seawater [Sr] through the Cenozoic, whereas the calcite vein Sr/Casw reconstruction implies increasing [Sr] through the Cenozoic. We apply a simple geochemical model to examine the implications of divergence among these seawater [Sr] reconstructions and suggest that the interpretation and uncertainties associated with the gastropod and calcite vein proxies need to be revisited. Used in conjunction with records of carbonate depositional fluxes, our favored seawater Sr/Ca scenarios point to a significant increase in the proportion of aragonite versus calcite deposition in shelf sediments from the Middle Miocene, coincident with the proliferation of coral reefs. We propose that this occurred at least 10 million years after the seawater Mg/Ca threshold was passed, and was instead aided by declining levels of atmospheric carbon dioxide.

Electrolytes comprising metal amide and metal chlorides for multivalent battery

DOEpatents

Liao, Chen; Zhang, Zhengcheng; Burrell, Anthony; Vaughey, John T.

2017-03-21

An electrolyte includes compounds of formula M.sup.1X.sub.n and M.sup.2Z.sub.m; and a solvent wherein M.sup.1 is Mg, Ca, Sr, Ba, Sc, Ti, Al, or Zn; M.sup.2 is Mg, Ca, Sr, Ba, Sc, Ti, Al, or Zn; X is a group forming a covalent bond with M.sup.1; Z is a halogen or pseudo-halogen; n is 1, 2, 3, 4, 5, or 6; and m is 1, 2, 3, 4, 5, or 6.

Hydration energies and structures of alkaline earth metal ions, M2+(H2O)n, n = 5-7, M = Mg, Ca, Sr, and Ba.

PubMed

Rodriguez-Cruz, S E; Jockusch, R A; Williams, E R

1999-09-29

The evaporation of water from hydrated alkaline earth metal ions, produced by electrospray ionization, was studied in a Fourier transform mass spectrometer. Zero-pressure-limit dissociation rate constants for loss of a single water molecule from the hydrated divalent metal ions, M(2+)(H(2)O)(n) (M = Mg, Ca, and Sr for n = 5-7, and M = Ba for n = 4-7), are measured as a function of temperature using blackbody infrared radiative dissociation. From these values, zero-pressure-limit Arrhenius parameters are obtained. By modeling the dissociation kinetics using a master equation formalism, threshold dissociation energies (E(o)) are determined. These reactions should have a negligible reverse activation barrier; therefore, E(o) values should be approximately equal to the binding energy or hydration enthalpy at 0 K. For the hepta- and hexahydrated ions at low temperature, binding energies follow the trend expected on the basis of ionic radii: Mg > Ca > Sr > Ba. For the hexahydrated ions at high temperature, binding energies follow the order Ca > Mg > Sr > Ba. The same order is observed for the pentahydrated ions. Collisional dissociation experiments on the tetrahydrated species result in relative dissociation rates that directly correlate with the size of the metals. These results indicate the presence of two isomers for hexahydrated magnesium ions: a low-temperature isomer in which the six water molecules are located in the first solvation shell, and a high-temperature isomer with the most likely structure corresponding to four water molecules in the inner shell and two water molecules in the second shell. These results also indicate that the pentahydrated magnesium ions have a structure with four water molecules in the first solvation shell and one in the outer shell. The dissociation kinetics for the hexa- and pentahydrated clusters of Ca(2+), Sr(2+), and Ba(2+) are consistent with structures in which all the water molecules are located in the first solvation shell.

Synthesis and coordination chemistry of TpC*MI complexes where M=Mg, Ca, Sr, Ba and Zn and TpC*=tris[3-(2-methoxy-1,1-dimethyl)pyrazolyl]hydroborate.

PubMed

Chisholm, Malcolm H; Gallucci, Judith C; Yaman, Gulsah

2009-01-14

Reactions involving MI2 where M=Mg, Ca, Sr, Ba or Zn and M'TpC* where M'=Na or Tl and TpC*=tris[3-methoxy-1,1-dimethyl)pyrazolyl]hydroborate in tetrahydrofuran are described leading to the isolation and characterization of the complexes TpC*MgI, , TpC*CaI, , TpC*SrI, , TpC*SrI(THF), , TpC*BaI, , TpC*BaI(pz*H), , where pz*H=3-(2-methoxyl-1,1-dimethyl)pyrazole, TpC*BaI.1/2toluene, and TpC*ZnI, . The compounds , , , , and have been characterized by single-crystal X-ray crystallography. Compounds and are isostructural and are salt-like containing kappa6-TpM+ cations and I- anions. In all other structures, the iodide is bound to the metal and TpC* is kappa6 bonded to the group 2 M(2+) ions. Reactions involving TpC*CaI, , and sodium or lithium alkoxides or amides failed to yield the amide or alkoxide calcium TpC* derivative, though related reactions involving TpC*ZnI, , and KOSiMe3 proceeded quantitatively to yield kappa3TpC*ZnOSiMe3, , which was also structurally characterized and shown to have the kappa3-TpC* bound ligand.

Correlated study of initial Sr-87/Sr-86 and Al-Mg isotopic systematics and petrologic properties in a suite of refractory inclusions from the Allende meteorite

NASA Technical Reports Server (NTRS)

Podosek, Frank A.; Zinner, Ernst K.; Lundberg, Laura L.; Brannon, Joyce C.; Macpherson, Glenn J.

1991-01-01

The abundance and the distribution of Al-26, and the initial Sr-87/Sr-86 ratios were determined in a suite of six coarse-grained Ca-Al-rich inclusions from the Allende meteorite, using, respectively, petrographic and chemical characterizations and ion-probe mass spectrometric analyses of the Al-Mg isotopic system, and thermal emission spectrometric analyses of the Rb-Sr system. Results establish a firm association between primitive Al-26/Al-27 and primitive Sr-87/Sr-86 found in each of these inclusions. None of the results required interpretation in terms of heterogeneously distributed Al-26.

Characterization of ryanodine receptor and Ca2+-ATPase isoforms in the thermogenic heater organ of blue marlin (Makaira nigricans).

PubMed

Morrissette, Jeffery M; Franck, Jens P G; Block, Barbara A

2003-03-01

A thermogenic organ is found beneath the brain of billfishes (Istiophoridae), swordfish (Xiphiidae) and the butterfly mackerel (Scombridae). The heater organ has been shown to warm the brain and eyes up to 14 degrees C above ambient water temperature. Heater cells are derived from extraocular muscle fibers and express a modified muscle phenotype with an extensive transverse-tubule (T-tubule) network and sarcoplasmic reticulum (SR) enriched in Ca(2+)-ATPase (SERCA) pumps and ryanodine receptors (RyRs). Heater cells have a high mitochondria content but have lost most of the contractile myofilaments. Thermogenesis has been hypothesized to be associated with release and reuptake of Ca(2+). In this study, Ca(2+) fluxes in heater SR vesicles derived from blue marlin (Makaira nigricans) were measured using fura-2 fluorescence. Upon the addition of MgATP, heater SR vesicles rapidly sequestered Ca(2+). Uptake of Ca(2+) was thapsigargin sensitive, and maximum loading ranged between 0.8 micro mol Ca(2+) mg(-1) protein and 1.0 micro mol Ca(2+) mg(-1) protein. Upon the addition of 10 mmol l(-1) caffeine or 350 micro mol l(-1) ryanodine, heater SR vesicles released only a small fraction of the loaded Ca(2+). However, ryanodine could elicit a much larger Ca(2+) release event when the activity of the SERCA pumps was reduced. RNase protection assays revealed that heater tissue expresses an RyR isoform that is also expressed in fish slow-twitch skeletal muscle but is distinct from the RyR expressed in fish fast-twitch skeletal muscle. The heater and slow-twitch muscle RyR isoform has unique physiological properties. In the presence of adenine nucleotides, this RyR remains open even though cytoplasmic Ca(2+) is elevated, a condition that normally closes RyRs. The fast Ca(2+) sequestration by the heater SR, coupled with a physiologically unique RyR, is hypothesized to promote Ca(2+) cycling, ATP turnover and heat generation. A branch of the oculomotor nerve innervates heater organs, and, in this paper, we demonstrate that heater cells contain large 'endplate-like' clusters of acetylcholine receptors that appear to provide a mechanism for nervous control of thermogenesis.

Microwave-assisted rapid synthesis and characterization of CaF₂ particles-filled cellulose nanocomposites in ionic liquid.

PubMed

Deng, Fu; Fu, Lian-Hua; Ma, Ming-Guo

2015-05-05

In this article, we try to compound cellulose/alkali earth metal fluorides (MF2, M=Ca, Mg, Sr, Ba) nanocomposites via microwave-assisted ionic liquid method, wherein cellulose/CaF2 and cellulose/MgF2 were successfully synthesized through this method while cellulose/SrF2 and cellulose/BaF2 could not be synthesized. We focused on the synthesis of cellulose/CaF2 and investigated the influences of the different time and different temperature for the synthesis of cellulose/CaF2 nanocomposites. The influence of different heating methods such as oil-bath heating method was also studied. Ionic liquid ([Bmim][BF4]) was used for dissolving microcrystalline cellulose and providing the source of fluoride ionic and the alkali earth metal nitrate (Ca(NO3)2, Mg(NO3)2, Sr(NO3)2, and Ba(NO3)2) was used as the reaction initiator. They were investigated by X-ray powder diffraction (XRD), Fourier transform infrared spectrometry (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TG), derivative thermogravimetric (DTG), and energy-dispersive X-ray spectra (EDS). The different heating modes have influence on the morphology and property. The different temperature and heating time also have a certain influence on the morphology and crystallinity of calcium fluoride. Copyright © 2014 Elsevier Ltd. All rights reserved.

Fast and accurate determination of K, Ca, and Mg in human serum by sector field ICP-MS.

PubMed

Yu, Lee L; Davis, W Clay; Nuevo Ordonez, Yoana; Long, Stephen E

2013-11-01

Electrolytes in serum are important biomarkers for skeletal and cellular health. The levels of electrolytes are monitored by measuring the Ca, Mg, K, and Na in blood serum. Many reference methods have been developed for the determination of Ca, Mg, and K in clinical measurements; however, isotope dilution thermal ionization mass spectrometry (ID-TIMS) has traditionally been the primary reference method serving as an anchor for traceability and accuracy to these secondary reference methods. The sample matrix must be separated before ID-TIMS measurements, which is a slow and tedious process that hindered the adoption of the technique in routine clinical measurements. We have developed a fast and accurate method for the determination of Ca, Mg, and K in serum by taking advantage of the higher mass resolution capability of the modern sector field inductively coupled plasma mass spectrometry (SF-ICP-MS). Each serum sample was spiked with a mixture containing enriched (44)Ca, (26)Mg, and (41)K, and the (42)Ca(+):(44)Ca(+), (24)Mg(+):(26)Mg(+), and (39)K(+):(41)K(+) ratios were measured. The Ca and Mg ratios were measured in medium resolution mode (m/Δm ≈ 4 500), and the K ratio in high resolution mode (m/Δm ≈ 10 000). Residual (40)Ar(1)H(+) interference was still observed but the deleterious effects of the interference were minimized by measuring the sample at K > 100 ng g(-1). The interferences of Sr(++) at the two Ca isotopes were less than 0.25 % of the analyte signal, and they were corrected with the (88)Sr(+) intensity by using the Sr(++):Sr(+) ratio. The sample preparation involved only simple dilutions, and the measurement using this sample preparation approach is known as dilution-and-shoot (DNS). The DNS approach was validated with samples prepared via the traditional acid digestion approach followed by ID-SF-ICP-MS measurement. DNS and digested samples of SRM 956c were measured with ID-SF-ICP-MS for quality assurance, and the results (mean ± expanded uncertainty in mg dL(-1) unit) for Ca (DNS = 10.14 ± 0.13, digested = 10.11 ± 0.10), Mg (DNS = 2.093 ± 0.008, digested = 2.098 ± 0.007), and K (DNS = 15.48 ± 0.11, digested = 15.50 ± 0.28) were in good agreement with the certified values (Ca = 10.17 ± 0.06, Mg = 2.084 ± 0.023, K = 15.55 ± 0.13). Major sources of uncertainty are sample measurement, spike calibration, and instrument factor including mass discrimination of the spectrometer and the detector deadtime.

Chemical compositions and precipitation timing of basement carbonate vein from fossil spreading ridge of South China Sea

NASA Astrophysics Data System (ADS)

Ding, W.; Chen, Y.

2016-12-01

Eighteen calcium carbonate veins within the igneous basement recovered close to the fossil spreading ridge of the South China Sea during the Integrated Ocean Drilling Program (IODP) Expedition 349 were investigated. These carbonates are of primarily either calcite or aragonite, or some mixed aragonite and calcite, with rarely ankerite. The chemical (Ca, Mg, Sr, Mn, Fe) contents and isotopic (87Sr/86Sr, δ18O, δ18C) compositions of the veins were determined to study the evolving chemistry of hydrothermal fluids and to constrain the timing of vein formation. The carbonate δ18O values range from -5.0 to -0.2 ‰ PDB, indicating these are typical low temperature basement carbonates. Chemical analyses show distinct Mg/Ca and Sr/Ca ratios for aragonite and calcite. 87Sr/86Sr ratios show negative correlations with both the depth and δ18O-calculated formation temperature, and are independent of mineralogy with both aragonite and calcite, indicating more geochemically evolved carbonated have precipitated from warmer fluids. The hightest 87Sr/86Sr ratios of vein samples at each drill site are believed to reflect the contemporaneous seawater compositions when carbonates precipitated. No unambiguous precipitation ages can be constrained by correlating 87Sr/86Sr ratios with the global seawater Sr isotope evolution. However, based on correlations of vein chemical composition with depth and formation temperature, as well as the Neogene post-spreading magmatism, we hypothesize 10 Ma is a particular time favoring the formation of carbonate veins in our study area.

Evolution of the carbon cycle and seawater temperature from the Triassic-Jurassic boundary to the Early Toarcian based on brachiopod geochemistry

NASA Astrophysics Data System (ADS)

Müller, Tamás; Tomašových, Adam

2017-04-01

The ecological crisis and extinction at the end of the Triassic coincides with several environmental perturbations such as global temperature rise, ocean acidification and carbon isotope anomalies, with a large observed negative carbon isotope excursion (CIE) in the Late Rhaetian as well. Followed by the ETE, the Early Jurassic was characterized by marked fluctuations of the global seawater temperature and carbon cycle. Carbon isotope records are showing positive and remarkable negative excursions. A particular example of these phenomena is connected to the Toarcian Oceanic Anoxic Event (TOAE). The δ13C record of the TOAE is showing a negative excursion of a high magnitude, suggesting the injection of large amount of light carbon into the ocean-atmosphere system, coinciding with rapid global warming and widespread anoxia. Beside the TOAE there are many other, smaller scale carbon isotope anomalies and environmental perturbations at the Sinemurian-Pliensbachian transition or at the Pliensbachian-Toarcian boundary. In our study, we provide new brachiopod δ13C, δ18O, and Mg/Ca data from the time interval starting in the Rhaetian till the end of the Early Toarcian. Considering the strong resistance of brachiopod shells against diagenesis, our aim is to reconstruct seawater temperature, seawater Mg/Ca, and carbon cycle evolution based on a reliable geochemical proxy database of the studied time interval. The samples have been collected from various localities across Europe achieving a good, at least ammonite subzone scale resolution for the Rhaetian stage and for the Lower Jurassic. The geochemical preservation of the shell material have been tested by several approaches. Thin-sections were made from the shells and analyzed by electron microprobe and ICP-OES to evaluate their preservation by assessing concentrations of Fe, Mn, Sr, and their ratios (Mn/Ca, Sr/Ca). Considering the various elemental composition data of fossil and recent brachiopods published by several authors, we established thresholds as Sr/Ca > 0,46 ( 400 ppm Sr) and Mn/Ca < 0,37 ( 200 ppm Mn) for samples with good preservation and Sr/Ca > 0,34 ( 300 ppm Sr) and Mn/Ca < 1 ( 460 ppm Mn) for moderate preservation. Samples not fitting to this criteria were excluded from the data sets used in our interpretations. We find that average values of Mg/Ca measured on different species collected in the same stratigraphic level show low variability, suggesting minor species-specific effects on this ratio. High-resolution transects through shells of some species detect cyclic fluctuations in Mg/Ca that coincide with growth lines, suggesting that this ratio captures changes in temperature seasonality.

Chemical weathering outputs from the flood plain of the Ganga

NASA Astrophysics Data System (ADS)

Bickle, Michael J.; Chapman, Hazel J.; Tipper, Edward; Galy, Albert; De La Rocha, Christina L.; Ahmad, Talat

2018-03-01

Transport of sediment across riverine flood plains contributes a significant but poorly constrained fraction of the total chemical weathering fluxes from rapidly eroding mountain belts which has important implications for chemical fluxes to the oceans and the impact of orogens on long term climate. We report water and bedload chemical analyses from the Ganges flood-plain, a major transit reservoir of sediment from the Himalayan orogen. Our data comprise six major southern tributaries to the Ganga, 31 additional analyses of major rivers from the Himalayan front in Nepal, 79 samples of the Ganga collected close to the mouth below the Farakka barrage every two weeks over three years and 67 water and 8 bedload samples from tributaries confined to the Ganga flood plain. The flood plain tributaries are characterised by a shallow δ18O - δD array, compared to the meteoric water line, with a low δDexcess from evaporative loss from the flood plain which is mirrored in the higher δDexcess of the mountain rivers in Nepal. The stable-isotope data confirms that the waters in the flood plain tributaries are dominantly derived from flood plain rainfall and not by redistribution of waters from the mountains. The flood plain tributaries are chemically distinct from the major Himalayan rivers. They can be divided into two groups. Tributaries from a small area around the Kosi river have 87Sr/86Sr ratios >0.75 and molar Na/Ca ratios as high as 6. Tributaries from the rest of the flood plain have 87Sr/86Sr ratios ≤0.74 and most have Na/Ca ratios <1. One sample of the Gomti river and seven small adjacent tributaries have elevated Na concentrations likely caused by dissolution of Na carbonate salts. The compositions of the carbonate and silicate components of the sediments were determined from sequential leaches of floodplain bedloads and these were used to partition the dissolved cation load between silicate and carbonate sources. The 87Sr/86Sr and Sr/Ca ratios of the carbonate inputs were derived from the acetic-acid leach compositions and silicate Na/Ca and 87Sr/86Sr ratios derived from silicate residues from leaching. Modelling based on the 87Sr/86Sr and Sr/Ca ratios of the carbonate inputs and 87Sr/86Sr ratios of the silicates indicates that the flood plain waters have lost up to 70% of their Ca (average ∼ 50%) to precipitation of secondary calcite which is abundant as a diagenetic cement in the flood plain sediments. 31% of the Sr, 8% of the Ca and 45% of the Mg are calculated to be derived from silicate minerals. Because of significant evaporative loss of water across the flood plain, and in the absence of hydrological data for flood plain tributaries, chemical weathering fluxes from the flood plain are best calculated by mass balance of the Na, K, Ca, Mg, Sr, SO4 and 87Sr/86Sr compositions of the inputs, comprising the flood plain tributaries, Himalayan rivers and southern rivers, with the chemical discharge in the Ganga at Farakka. The calculated fluxes from the flood plain for Na, K, Ca and Mg are within error of those estimated from changes in sediment chemistry across the flood plain (Lupker et al., 2012, Geochemica Cosmochimica Acta). Flood plain weathering supplies between 41 and 63% of the major cation and Sr fluxes and 58% of the alkalinity flux carried by the Ganga at Farakka which compares with 24% supplied by Himalayan rivers and 18% by the southern tributaries.

Uptake of alkaline earth metals in Alcyonarian spicules (Octocorallia)

NASA Astrophysics Data System (ADS)

Taubner, I.; Böhm, F.; Eisenhauer, A.; Garbe-Schönberg, D.; Erez, J.

2012-05-01

Alcyonarian corals (Octocorallia) living in shallow tropical seas produce spicules of high-Mg calcite with ˜13 mol% MgCO3. We cultured the tropical alcyonarian coral Rhythisma fulvum in experiments varying temperature (19-32 °C) and pH (8.15-8.44). Alkalinity depletion caused by spicule formation systematically varied in the temperature experiments increasing from 19 to 29 °C. Spicules were investigated for their elemental ratios (Mg/Ca, Sr/Ca) using ICP-OES, δ44/40Ca using TIMS, as well as δ18O and δ13C by IRMS. Mg/Ca increased with temperature from 146 to 164 mmol/mol, in good agreement with the range observed for marine inorganic calcite. Mg/Ca increased by 1.0 ± 0.4 mmol/mol/°C, similar to the sensitivity of Miliolid foraminifera. The pH experiments revealed a linear relationship between Mg/Ca and carbonate ion concentration of +0.03 ± 0.02 mmol/mol/μMol. Sr/Ca ranges from 2.5 to 2.9 mmol/mol being in good agreement with other high-Mg calcites. Temperature and pH experiments showed linear dependencies of Sr/Ca matching inorganic calcite trends and pointing to a decoupling of crystal precipitation rate and calcification rate. Ca isotopes range between 0.7‰ and 0.9‰ in good agreement with aragonitic scleractinian corals and calcitic coccoliths. Presumably Ca isotopes are fractionated by a biological mechanism that may be independent of the skeletal mineralogy. We observe no temperature trend, but a significant decrease of δ44/40Ca with increasing pH. This inverse correlation may characterise biologically controlled intracellular calcification. Oxygen isotope ratios are higher than expected for isotopic equilibrium with a temperature sensitivity of -0.15 ± 0.03‰/°C. Carbon isotope ratios are significantly lower than expected for equilibrium and positively correlated with temperature with a slope of 0.20 ± 0.04‰/°C. Many of our observations on trace element incorporation in R. fulvum may be explained by inorganic processes during crystal formation, which do not comply with the intracellular mode of calcification in Alcyonarian corals. The observed elemental and isotopic compositions, however, could be explained if the partitioning caused by biological mechanisms mimics the effects of inorganic processes.

Synthesis, spectroscopic characterization, thermal analysis and electrical conductivity studies of Mg(II), Ca(II), Sr(II) and Ba(II) vitamin B2 complexes

NASA Astrophysics Data System (ADS)

Refat, Moamen S.; Moussa, Mohamed A. A.; Mohamed, Soha F.

2011-05-01

Riboflavin (RF) complexes of Mg(II), Ca(II), Sr(II) and Ba(II) were successfully synthesized. Structures of metal complexes obtained were confirmed and characterized by elemental analysis, molar conductance, and infrared spectra. DC electrical conductivity measurements indicated that the alkaline earth metal (II) complexes of RF ligand are non-electrolytes. Elemental analysis of chelates suggest that the metal(II) ligand ratio is 1:2 with structure formula as [M(RF) 2( X) 2]· nH 2O. Infrared assignments clearly show that RF ligand coordinated as a bidentate feature through azomethine nitrogen of pyrazine ring and C dbnd O of pyrimidine-2,4-dione. Thermal analyses of Mg(II), Ca(II), Sr(II) and Ba(II) complexes were investigated using (TG/DSC) under atmospheric nitrogen between 30 and 800 °C. The surface morphology of the complexes was studied by SEM. The electrical conductivities of RF and its metal complexes were also measured with DC electrical conductivity in the temperature range from room to 483 K.

Middle Holocene daily light cycle reconstructed from the strontium/calcium ratios of a fossil giant clam shell

PubMed Central

Hori, Masako; Sano, Yuji; Ishida, Akizumi; Takahata, Naoto; Shirai, Kotaro; Watanabe, Tsuyoshi

2015-01-01

Insolation is an important component of meteorological data because solar energy is the primary and direct driver of weather and climate. Previous analyses of cultivated giant clam shells revealed diurnal variation in the Sr/Ca ratio, which might reflect the influence of the daily light cycle. We applied proxy method to sample from prehistoric era, a fossil giant clam shell collected at Ishigaki Island in southern Japan. The specimen was alive during the middle Holocene and thus exposed to the warmest climate after the last glacial period. This bivalve species is known to form a growth line each day, as confirmed by the analysis of the Sr enrichment bands using EPMA and facilitated age-model. We analyzed the Sr/Ca, Mg/Ca and Ba/Ca ratios along the growth axis, measuring a 2-μm spot size at 2-μm interval using NanoSIMS. The Sr/Ca ratios in the winter layers are characterized by a striking diurnal cycle consisting of narrow growth lines with high Sr/Ca ratios and broad growth bands with low Sr/Ca ratios. These variations, which are consistent with those of the cultivated clam shell, indicate the potential for the reconstruction of the variation in solar insolation during the middle Holocene at a multi-hourly resolution. PMID:25736488

Photoluminescence and cathodoluminescence properties of Eu{sup 3+} ions activated AMoO{sub 4} (A = Mg, Ca, Sr, Ba) phosphors

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

Du, Peng; Yu, Jae Su, E-mail: jsyu@khu.ac.kr

2015-10-15

Highlights: • Under 393 nm excitation, strong red emission located at 615 nm was observed in all the samples. • The Eu{sup 3+}-activated CaMoO{sub 4} phosphor exhibited the strongest PL properties. • The CIE chromaticity coordinate of Eu{sup 3+}-activated CaMoO{sub 4} phosphor was (0.647,0.352). • The color purity of Eu{sup 3+}-activated CaMoO{sub 4} phosphor was 92.8%. • Strong CL properties were observed in the Eu{sup 3+}-activated CaMoO{sub 4} phosphor. - Abstract: Eu{sup 3+}-activated AMoO{sub 4} (A = Mg, Ca, Sr, Ba) phosphors were synthesized by a solid-state reaction method. Photoluminescence and cathodoluminescence (CL) spectra as well as X-ray diffraction patternsmore » were measured to characterize the fabricated samples. Under 393 nm excitation, strong red emissions located at ∼615 nm corresponding to the {sup 5}D{sub 0} → {sup 7}F{sub 2} transition of Eu{sup 3+} ions were observed in all the samples. Compared with other Eu{sup 3+} ions activated AMoO{sub 4} (A = Mg, Sr, Ba) phosphors, Eu{sup 3+}-activated CaMoO{sub 4} phosphor exhibited the strongest red emission intensity with better Commission Internationale de L’Eclairage chromaticity coordinate and higher color purity. Furthermore, the CL results indicated that the Eu{sup 3+}-activated CaMoO{sub 4} phosphor had excellent luminescence properties.« less

Synthesis, spectroscopic and thermal studies of Mg(II), Ca(II), Sr(II) and Ba(II) diclofenac sodium complexes as anti-inflammatory drug and their protective effects on renal functions impairment and oxidative stress

NASA Astrophysics Data System (ADS)

El-Megharbel, Samy M.; Hamza, Reham Z.; Refat, Moamen S.

2015-01-01

The main task of our present study is the preparation of newly complexes of Mg(II), Ca(II), Sr(II) and Ba(II) with diclofenac which succeeded to great extent in alleviating the side effects of diclofenac alone and ameliorating the kidney function parameters and antioxidant capacities with respect to diclofenac treated group alone. The Mg(II), Ca(II), Sr(II) and Ba(II) with diclofenac have been synthesized and characterized using infrared, electronic and 1H NMR spectral, thermogravimetric and conductivity measurements. The diclofenac ligand has been found to act as bidentate chelating agent. Diclofenac complexes coordinate through the oxygen's of the carboxyl group. The molar ratio chelation is 1:2 (M2+-dic) with general formula [M(dic)2(H2O)2]ṡnH2O. Antibacterial screening of the alkaline earth metal complexes against Escherichia coli (Gram - ve), Bacillus subtilis (Gram + ve) and anti-fungal (Asperagillus oryzae, Asperagillus niger, Asperagillus flavus) were investigated. The kidney functions in male albino rats were ameliorated upon treatment with metal complexes of dic, which are represented by decreasing the levels of urea and uric acid to be located within normal values. The other looks bright spot in this article is the assessment of antioxidant defense system including SOD, CAT and MDA with the help of Sr2+, Mg2+ and Ca2+-dic complexes. The hormones related to kidney functions and stresses have been greatly ameliorated in groups treated with dic complexes in comparable with dic treated group.

Removal of metals from landfill leachate by sorption to activated carbon, bone meal and iron fines.

PubMed

Modin, Hanna; Persson, Kenneth M; Andersson, Anna; van Praagh, Martijn

2011-05-30

Sorption filters based on granular activated carbon, bone meal and iron fines were tested for their efficiency of removing metals from landfill leachate. Removal of Al, As, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Mo, Ni, Pb, Sr and Zn were studied in a laboratory scale setup. Activated carbon removed more than 90% of Co, Cr, Cu, Fe, Mn and Ni. Ca, Pb, Sr and Zn were removed but less efficiently. Bone meal removed over 80% of Cr, Fe, Hg, Mn and Sr and 20-80% of Al, Ca, Cu, Mo, Ni, Pb and Zn. Iron fines removed most metals (As, Ca, Co, Cr, Cu, Fe, Mg, Mn, Pb, Sr and Zn) to some extent but less efficiently. All materials released unwanted substances (metals, TOC or nutrients), highlighting the need to study the uptake and release of a large number of compounds, not only the target metals. To remove a wide range of metals using these materials two or more filter materials may need to be combined. Sorption mechanisms for all materials include ion exchange, sorption and precipitation. For iron fines oxidation of Fe(0) seems to be important for metal immobilisation. Copyright © 2011 Elsevier B.V. All rights reserved.

Luminescence characteristics of Dy3+ activated Na 2Sr 2Mg (BO 3)2F 2: Dy 3+ phosphor

NASA Astrophysics Data System (ADS)

Wani, Javaid A.; Dhoble, N. S.; Dhoble, S. J.

2012-11-01

In this paper, we have reported a new Na 2Sr 2Mg (BO 3)2F 2:Dy 3+ thermoluminescence (TL) phosphor prepared via the wet chemical method. Prepared phosphor was characterized by X-ray powder diffraction, photoluminescence (PL), TL and scanning electronmicroscopy techniques. The scanning electronmicroscopic image of Na 2Sr 2Mg (BO 3)2F 2:Dy 3+ phosphor confirms the micron size of particles. Under the PL study, the characteristic emission spectrum of Dy 3+ corresponding to 4F 9/2→6H 15/2 (481 nm) and 4F 9/2→6H 13/2 (576 nm) transitions was observed. The TL property of the as prepared phosphor was also found to be good. TL intensity of Na 2Sr2Mg(BO 3)F 2:Dy 3+ phosphors at 0.99 kGy exposure of γ-irradiations was compared with standard CaSO 4:Dy phosphor. It was seen that TL intensity of Na 2Sr 2Mg (BO 3)2F 2: Dy 3+ phosphors is 1.1 times less compared with the standard CaSO 4:Dy TL dosimeter phosphor. The kinetic parameters are also discussed in detail. The values of activation energy E (eV) and frequency factor S (s -1) were found to be 0.57 eV and 1.25×106 s-1, respectively.

Structures, phase transitions and microwave dielectric properties of the 6H perovskites Ba 3BSb 2O 9, B=Mg, Ca, Sr, Ba

NASA Astrophysics Data System (ADS)

Ling, Chris D.; Rowda, Budwy; Avdeev, Maxim; Pullar, Robert

2009-03-01

We present a complete temperature-composition phase diagram for Ba 3BSb 2O 9, B=Mg, Ca, Sr, Ba, along with their electrical behavior as a function of B. These compounds have long been recognized as 6H-type perovskites, but (with the exception of B=Mg) their exact structures and properties were unknown due to their low symmetries, temperature-dependent phase transitions, and difficulties in synthesizing pure samples. The full range of possible space group symmetries is observed, from ideal hexagonal P6 3/ mmc to monoclinic C2/ c to triclinic P1¯. Direct second-order transitions between these phases are plausible according to group theory, and no evidence was seen for any further intermediate phases. The phase diagram with respect to temperature and the effective ionic radius of B is remarkably symmetrical for B=Mg, Ca, and Sr. For B=Ba, a first-order phase transition to a locally distorted phase allows a metastable hexagonal phase to persist to lower temperatures than expected before decomposing around 600 K. Electrical measurements revealed that dielectric permittivity corrected for porosity does not change significantly as a function of B and is in a good agreement with the values predicted by the Clausius-Mossotti equation.

Indirect ultraviolet detection of alkaline earth metal ions using an imidazolium ionic liquid as an ultraviolet absorption reagent in ion chromatography.

PubMed

Liu, Yong-Qiang; Yu, Hong

2017-04-01

A convenient and versatile method was developed for the separation and detection of alkaline earth metal ions by ion chromatography with indirect UV detection. The chromatographic separation of Mg 2+ , Ca 2+ , and Sr 2+ was performed on a carboxylic acid base cation exchange column using imidazolium ionic liquid/acid as the mobile phase, in which the imidazolium ionic liquid acted as an UV-absorption reagent. The effects of imidazolium ionic liquids, detection wavelength, acids in the mobile phase, and column temperature on the retention of Mg 2+ , Ca 2+ , and Sr 2+ were investigated. The main factors influencing the separation and detection were the background UV absorption reagent and the concentration of hydrogen ion in ion chromatography with indirect UV detection. The successful separation and detection of Mg 2+ , Ca 2+ , and Sr 2+ within 14 min were achieved using the selected chromatographic conditions, and the detection limits (S/N = 3) were 0.06, 0.12, and 0.23 mg/L, respectively. A new separation and detection method of alkaline earth metal ions by ion chromatography with indirect UV detection was developed, and the application range of ionic liquids was expanded. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

CaI and SrI molecules for iodine determination by high-resolution continuum source graphite furnace molecular absorption spectrometry: Greener molecules for practical application.

PubMed

Zanatta, Melina Borges Teixeira; Nakadi, Flávio Venâncio; da Veiga, Márcia Andreia Mesquita Silva

2018-03-01

A new method to determine iodine in drug samples by high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS) has been developed. The method measures the molecular absorption of a diatomic molecule, CaI or SrI (less toxic molecule-forming reagents), at 638.904 or 677.692nm, respectively, and uses a mixture containing 5μg of Pd and 0.5μg of Mg as chemical modifier. The method employs pyrolysis temperatures of 1000 and 800°C and vaporization temperatures of 2300 and 2400°C for CaI and SrI, respectively. The optimized amounts of Ca and Sr as molecule-forming reagents are 100 and 150µg, respectively. On the basis of interference studies, even small chlorine concentrations reduce CaI and SrI absorbance significantly. The developed method was used to analyze different commercial drug samples, namely thyroid hormone pills with three different iodine amounts (15.88, 31.77, and 47.66µg) and one liquid drug with 1% m v -1 active iodine in their compositions. The results agreed with the values informed by the manufacturers (95% confidence level) regardless of whether CaI or SrI was determined. Therefore, the developed method is useful for iodine determination on the basis of CaI or SrI molecular absorption. Copyright © 2017 Elsevier B.V. All rights reserved.

Seasonal Trends and Inter-Individual Heterogeneity: A multi-species record of Mg, Sr, Ba, & Mn in Planktic Foraminifera from the Modern Cariaco Basin

NASA Astrophysics Data System (ADS)

Davis, C. V.; Thunell, R.; Astor, Y. M.

2017-12-01

The trace element to calcium ratios (TE/Ca) of planktic foraminifera shells are a valuable tool for paleoceanographic reconstructions, and represent a combination of environmental, ecological and biological signals. We present here a three-year record (2010-2013) of TE/Ca (Mg, Sr, Ba, Mn) from four species of foraminifera (Orbulina universa, Globigerina ruber, Globigerinella siphonifera, and Globorotalia menardii) collected by plankton tow in the modern Cariaco basin. Each tow is paired with in situ measurements of water column properties, allowing a direct comparison between shell geochemistry and calcification environment. A combination of Laser Ablation and solution ICP-MS analyses are used to document seasonality, primarily due to the alternating influence of wind-driven coastal upwelling and riverine inputs, in shell TE/Ca. Individual shell data further allows for the quantification of trace element heterogeneity among individual shells within single tows. All TE/Ca ratios vary temporally and show inter-individual variability within single tows. The spread in TE/Ca differs between element and species, with Mg/Ca ratios being the most variable. Despite this, Mg/Ca still tracks temperature changes in G. ruber, O. universa, and G. menardii, with G. ruber most closely reproducing sea surface temperature. Some species show chamber-to-chamber differences in trace element ratios, with G. ruber Mg/Ca and Ba/Ca decreasing in younger chambers (but not other elements) and Mg/Ca, Mn/Ca and Ba/Ca decreasing in younger chambers in G. siphonifera. We find the original Mn/Ca to be variable both temporally and between species, with G. menardii in some samples having extremely high ratios (100 μmol/mol). Assessing seasonal trends and environmental drivers of TE/Ca variability and quantifying the extent of inter-individual heterogeneity in these species will inform the use of their shells as geochemical proxies.

Hydration Energies and Structures of Alkaline Earth Metal Ions, M2+ (H2O)n, n = 5–7, M = Mg, Ca, Sr, and Ba

PubMed Central

Rodriguez-Cruz, Sandra E.; Jockusch, Rebecca A.

2005-01-01

The evaporation of water from hydrated alkaline earth metal ions, produced by electrospray ionization, was studied in a Fourier transform mass spectrometer. Zero-pressure-limit dissociation rate constants for loss of a single water molecule from the hydrated divalent metal ions, M2+(H2O)n (M = Mg, Ca, and Sr for n = 5–7, and M = Ba for n = 4–7), are measured as a function of temperature using blackbody infrared radiative dissociation. From these values, zero-pressure-limit Arrhenius parameters are obtained. By modeling the dissociation kinetics using a master equation formalism, threshold dissociation energies (Eo) are determined. These reactions should have a negligible reverse activation barrier; therefore, Eo values should be approximately equal to the binding energy or hydration enthalpy at 0 K. For the hepta- and hexahydrated ions at low temperature, binding energies follow the trend expected on the basis of ionic radii: Mg > Ca > Sr > Ba. For the hexahydrated ions at high temperature, binding energies follow the order Ca > Mg > Sr > Ba. The same order is observed for the pentahydrated ions. Collisional dissociation experiments on the tetrahydrated species result in relative dissociation rates that directly correlate with the size of the metals. These results indicate the presence of two isomers for hexahydrated magnesium ions: a low-temperature isomer in which the six water molecules are located in the first solvation shell, and a high-temperature isomer with the most likely structure corresponding to four water molecules in the inner shell and two water molecules in the second shell. These results also indicate that the pentahydrated magnesium ions have a structure with four water molecules in the first solvation shell and one in the outer shell. The dissociation kinetics for the hexa- and pentahydrated clusters of Ca2+, Sr2+, and Ba2+ are consistent with structures in which all the water molecules are located in the first solvation shell. PMID:16429612

Interstitial water studies on small core samples, Leg 15

USGS Publications Warehouse

Sayles, Fred L.; Manheim, Frank T.; Waterman, Lee S.

1973-01-01

Analyses of pore fluids from reducing environments demonstrate that reduction of SO4 is accompanied by large increases in alkalinity and strong depletion of Ca and Mg. The data are compatible with a model of replacement of Fe3+ in clay lattices by Mg from the interstitial solutions and the precipitation of pyrite. Depletions of Na in the interstitial solutions are related to Mg losses by a ratio of approximately 1:3. Pore fluids from oxidizing pelagic sediments exhibit little SO4 depletion. Losses of Mg are accompanied by the addition of Ca to the pore solutions on a nearly 1:1 basis. Strong Sr enrichment is also found in these solutions. The magnitude of the Sr increase suggests that considerable carbonate recrystallization has occurred. As part of an extensive interlaboratory and analytical calibration, the effect of squeezing sediment at different temperatures has been studied in depth. Samples of a variety of lithologies have been included. Enrichment of K by as much as 24 percent and depletion of Mg and Ca by up to 7 percent occurs during warming. However, no significant effect upon Cl and SO4 could be detected. The strongest effects are seen in the minor constituents studied. On warming, Sr, Si, and B are enriched as much as 19, 40, and 60 percent, respectively. The size of the observed concentration changes varies with the mineralogy of the sediment, but is significant in all types studied, particularly with regards to Mg and K.

Methods of reforming hydrocarbon fuels using hexaaluminate catalysts

DOEpatents

Gardner, Todd H [Morgantown, WV; Berry, David A [Morgantown, WV; Shekhawat, Dushyant [Morgantown, WV

2012-03-27

A metal substituted hexaaluminate catalyst for reforming hydrocarbon fuels to synthesis gas of the general formula AB.sub.yAl.sub.12-yO.sub.19-.delta., A being selected from alkali metals, alkaline earth metals and lanthanide metals or mixtures thereof. A dopant or surface modifier selected from a transitions metal, a spinel of an oxygen-ion conductor is incorporated. The dopant may be Ca, Cs, K, La, Sr, Ba, Li, Mg, Ce, Co, Fe, Ir, Rh, Ni, Ru, Cu, Pe, Os, Pd, Cr, Mn, W, Re, Sn, Gd, V, Ti, Ag, Au, and mixtures thereof. The oxygen-ion conductor may be a perovskite selected from M'RhO.sub.3, M'PtO.sub.3, M'PdO.sub.3, M'IrO.sub.3, M'RuO.sub.3 wherein M'=Mg, Sr, Ba, La, Ca; a spinel selected from MRh.sub.2O.sub.4, MPt.sub.2O.sub.4, MPd.sub.2O.sub.4, MIr.sub.2O.sub.4, MRu.sub.2O.sub.4 wherein M=Mg, Sr, Ba, La, Ca and mixtures thereof; a florite is selected from M''O.sub.2.

Structures and unimolecular chemistry of M(Pro2-H)(+) (M = Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu, Zn) by IRMPD spectroscopy, SORI-CID, and theoretical studies.

PubMed

Jami-Alahmadi, Yasaman; Fridgen, Travis D

2016-01-21

M(Pro2-H)(+) complexes were electrosprayed and isolated in an FTICR cell where their unimolecular chemistries and structures were explored using SORI-CID and IRMPD spectroscopy. These experiments were augmented by computational methods such as electronic structure, simulated annealing, and atoms in molecules (AIM) calculations. The unimolecular chemistries of the larger metal cation (Ca(2+), Sr(2+) and Ba(2+)) complexes predominantly involve loss of neutral proline whereas the complexes involving the smaller Mg(2+) and transition metal dications tend to lose small neutral molecules such as water and carbon dioxide. Interestingly, all complexes involving transition metal dications except for Cu(Pro2-H)(+) lose H2 upon collisional or IRMPD activation. IRMPD spectroscopy shows that the intact proline in the transition metal complexes and Cu(Pro2-H)(+) is predominantly canonical (charge solvated) while for the Ca(2+), Sr(2+), and Ba(2+) complexes, proline is in its zwitterionic form. The IRMPD spectra for both Mg(Pro2-H)(+) and Mn(Pro2-H)(+) are concluded to have contributions from both charge-solvated and canonical structures.

Effects of solvent and alkaline earth metals on the heat-induced precipitation process of sodium caseinate.

PubMed

Lopez, Francesco; Cuomo, Francesca; Nostro, Pierandrea Lo; Ceglie, Andrea

2013-01-01

The precipitation temperatures of sodium caseinate in H(2)O and D(2)O in the presence of Mg(2+), Ca(2+), Sr(2+) and Ba(2+) were investigated through fluorescence, turbidity and conductivity experiments. As for the ability of the divalent cations (1-17.5mM) to induce the precipitation process in H(2)O, the sequence Ba(2+) ≥ Ca(2+)>Mg(2+)>Sr(2+) was found. Remarkably, while at low salt concentrations (<10mM) precipitation temperatures (T(Ps)) were found to change significantly depending on the specific cation, at higher concentrations (>10mM) the differences among the different cations were greatly reduced. By fitting these results with a modified Jones-Dole equation, we confirmed that the less hydrated ions possess a greater capacity to induce precipitation. In D(2)O, the order of ion ability to induce caseinate precipitation was Ba(2+)>Ca(2+)>Sr(2+)>Mg(2+). The different hydrophobicity between D(2)O and H(2)O was shown to affect significantly the T(Ps) of caseinate in the presence of calcium, strontium and barium. Copyright © 2012 Elsevier Ltd. All rights reserved.

Phosphate base laser glasses

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

Izumitani, T.; Tsuru, M.

1980-12-16

A phosphate base laser glass comprising 55-70% P2O5, 1-15% Al2O3, 0-25% Li2O, 0-25% Na2O, 0-8% K2O, the total proportion of Li2O, Na2O, and K2O being 10-25%, 0-15% BaO, 0-15% ZnO, 0-15% CaO , 0-15%, sro, 0-15% MgO, the total proportion of BaO, ZnO, CaO, SrO, and MgO being 5-15%, 0-5% Y2O3, 0-5% La2O3, 0-5% GeO2, 0-5% CeO2, 0-3% Nb2O5, 0-3% MnO2, 0-2% Ta2O5, 0-1% Sb2O3, and 0.01-5% Nd2O3, all % being mole %. The phosphate base laser glass of this invention has a high induced emission cross section, a low non-linear refractive index coefficient, and excellent acid resistance and divitrificationmore » resistance. By replacing partially or wholely one or more of LiO2, Na2O, K2O, BaO, ZnO, CaO, SrO, MgO or Al2O3 by LiF, NaF, KF , BaF2ZnF2, CaF2, SrF2, MgF2 or AlF3, respectively, the above properties of the laser glass are further improved.« less

Theoretical Studies of the Spin Hamiltonian Parameters and Local Distortions for Cu2+ in Alkaline Earth Lead Zinc Phosphate Glasses

NASA Astrophysics Data System (ADS)

Wang, Bo-Kun; Wu, Shao-Yi; Yuan, Zi-Yi; Liu, Zi-Xuan; Jiang, Shi-Xin; Liu, Zheng; Yao, Zi-Jian; Teng, Bao-Hua; Wu, Ming-He

2016-08-01

The spin Hamiltonian parameters and local structures are theoretically studied for Cu2+-doped alkaline earth lead zinc phosphate (RPPZ, R=Mg, Ca, Sr, and Ba) glasses based on the high-order perturbation calculations for a tetragonally elongated octahedral 3d9 cluster. The relative elongation ratios are found to be ρ≈3.2%, 4.4%, 4.6%, and 3.3% for R=Mg, Ca, Sr, and Ba, respectively, because of the Jahn-Teller effect. The whole decreasing crystal-field strength Dq and orbital reduction factor k from Mg to Sr are ascribed to the weakening electrostatic coulombic interactions and the increasing probability of productivity of nonbridge oxygen (and hence increasing Cu2+-O2- electron cloud admixtures) under PbO addition, respectively, with increasing alkali earth ionic radius. The anomalies (the largest Dq and the next highest k among the systems) for R=Ba are attributed to the cross linkage of this large cation in the network. The overall increasing order (Mg≤Ba

Superconductivity in the Sn-Ba-Sr-Y-Cu-O system

NASA Technical Reports Server (NTRS)

Aleksandrov, K. S.; Khrustalev, B. P.; Krivomazov, S. N.; Petrov, M. I.; Vasilyev, A. D.; Zwegintsev, S. A.

1991-01-01

After the discovery of high-T(sub c) superconductivity in the La-Ba-Cu-O compound, several families of superconducting oxides were synthesized. Here, researchers report the results of the search for superconductivity in the compounds based on tin which has a lone electron pair like Bi, Tl, and Pb. The following compounds were synthesized: Sn1Ba1Sr1Cu3O(sub x), Sn1Ba1Ca1Cu3O(sub x), Sn1Ba1Mg1Cu3O(sub x), Sn1Sr1Ca1Cu3O(sub x), Sn1Sr1Mg1Cu3O(sub x), and Sn1Ca1Mg1Cu3O(sub x). The initial components were oxides and carbonates of the appropriate elements. A standard firing-grinding procedure was used. Final heating was carried out at 960 C during 12 hours. Then the samples were cooled inside the furnace. All the synthesis cycles were carried out in air atmosphere. Among the synthesized compounds only Sn1Ba1Sr1Cu3O(sub x) showed remarkable conductivity. Other compounds were practically dielectrics. Presence of a possible superconductivity in Sn1Ba1Sr1Cu3O(sub x) was defined by using the Meissner effect. At low temperature a deviation from paramagnetic behavior is observed. The hysteresis loops obtained at lower temperature undoubtly testify to the presence of a superconductive phase in the sample. However, the part of the superconductive phase in the Sn1Ba1Sr1Cu3O(sub x) ceramic turned out to be small, less than 2 percent, which agrees with the estimation from magnetic data. In order to increase the content of the superconductive phase, two-valent cations Ba and Sr were partially substituted by univalent (K) and three-valent ones (Y).

Ca and Mg isotope constraints on the origin of Earth's deepest δ13 C excursion

NASA Astrophysics Data System (ADS)

Husson, Jon M.; Higgins, John A.; Maloof, Adam C.; Schoene, Blair

2015-07-01

Understanding the extreme carbon isotope excursions found in carbonate rocks of the Ediacaran Period (635-541 Ma), where δ13 C of marine carbonates (δ13 Ccarb) reach their minimum (- 12 ‰) for Earth history, is one of the most vexing problems in Precambrian geology. Known colloquially as the 'Shuram' excursion, the event has been interpreted by many as a product of a profoundly different Ediacaran carbon cycle. More recently, diagenetic processes have been invoked, with the very negative δ13 C values of Ediacaran carbonates explained via meteoric alteration, late-stage burial diagenesis or growth of authigenic carbonates in the sediment column, thus challenging models which rely upon a dramatically changing redox state of the Ediacaran oceans. Here we present 257 δ 44 / 40 Ca and 131 δ26 Mg measurements, along with [Mg], [Mn] and [Sr] data, from carbonates of the Ediacaran-aged Wonoka Formation (Fm.) of South Australia to bring new isotope systems to bear on understanding the 'Shuram' excursion. Data from four measured sections spanning the basin reveal stratigraphically coherent trends, with variability of ∼1.5‰ in δ26 Mg and ∼1.2‰ in δ 44 / 40 Ca. This Ca isotope variability dwarfs the 0.2-0.3 ‰ change seen coeval with the Permian-Triassic mass extinction, the largest recorded in the rock record, and is on par with putative changes in the δ 44 / 40 Ca value of seawater seen over the Phanerozoic Eon. Changes in both isotopic systems are too large to explain with changes in the isotopic composition of Ca and Mg in global seawater given modern budgets and residence times, and thus must be products of alternative processes. Relationships between δ 44 / 40 Ca and [Sr] and δ26 Mg and [Mg] are consistent with mineralogical control (e.g., aragonite vs. calcite, limestone vs. dolostone) on calcium and magnesium isotope variability. The most pristine samples in the Wonoka dataset, preserving Sr concentrations (in the 1000s of ppm range) and δ 44 / 40 Ca values inherited from an originally aragonitic polymorph, have δ13 Ccarb of - 8 ‰ to - 7 ‰ , thereby providing strong geochemical evidence that extremely negative δ13 Ccarb values are primary products of the Ediacaran surface environment.

Chemical weathering of a marine terrace chronosequence, Santa Cruz, California. Part II: Solute profiles, gradients and the comparisons of contemporary and long-term weathering rates

USGS Publications Warehouse

White, A.F.; Schulz, M.S.; Stonestrom, David A.; Vivit, D.V.; Fitzpatrick, J.; Bullen, T.D.; Maher, K.; Blum, A.E.

2009-01-01

The spatial and temporal changes in hydrology and pore water elemental and 87Sr/86Sr compositions are used to determine contemporary weathering rates in a 65- to 226-kyr-old soil chronosequence formed from granitic sediments deposited on marine terraces along coastal California. Soil moisture, tension and saturation exhibit large seasonal variations in shallow soils in response to a Mediterranean climate. These climate effects are dampened in underlying argillic horizons that progressively developed in older soils, and reached steady-state conditions in unsaturated horizons extending to depths in excess of 15 m. Hydraulic fluxes (qh), based on Cl mass balances, vary from 0.06 to 0.22 m yr-1, resulting in fluid residence times in the terraces of 10-24 yrs. As expected for a coastal environment, the order of cation abundances in soil pore waters is comparable to sea water, i.e., Na > Mg > Ca > K > Sr, while the anion sequence Cl > NO3 > HCO3 > SO4 reflects modifying effects of nutrient cycling in the grassland vegetation. Net Cl-corrected solute Na, K and Si increase with depth, denoting inputs from feldspar weathering. Solute 87Sr/86Sr ratios exhibit progressive mixing of sea water-dominated precipitation with inputs from less radiogenic plagioclase. While net Sr and Ca concentrations are anomalously high in shallow soils due to biological cycling, they decline with depth to low and/or negative net concentrations. Ca/Mg, Sr/Mg and 87Sr/86Sr solute and exchange ratios are similar in all the terraces, denoting active exchange equilibration with selectivities close to unity for both detrital smectite and secondary kaolinite. Large differences in the magnitudes of the pore waters and exchange reservoirs result in short-term buffering of the solute Ca, Sr, and Mg. Such buffering over geologic time scales can not be sustained due to declining inputs from residual plagioclase and smectite, implying periodic resetting of the exchange reservoir such as by past vegetational changes and/or climate. Pore waters approach thermodynamic saturation with respect to albite at depth in the younger terraces, indicating that weathering rates ultimately become transport-limited and dependent on hydrologic flux. Contemporary rates Rsolute are estimated from linear Na and Si pore weathering gradients bsolute such that Rsolute = frac(qh, bsolute ?? Sv) where Sv is the volumetric surface area and ?? is the stoichiometric coefficient. Plagioclase weathering rates (0.38-2.8 ?? 10-15 mol m-2 s-1) are comparable to those based on 87Sr/86Sr mass balances and solid-state Na and Ca gradients using analogous gradient approximations. In addition, contemporary solute gradients, under transport-limited conditions, approximate long-term solid-state gradients when normalized against the mass of protolith plagioclase and its corresponding aqueous solubility. The multi-faceted weathering analysis presented in this paper is perhaps the most comprehensive yet applied to a single field study. Within uncertainties of the methods used, present day weathering rates, based on solute characterizations, are comparable to average long-term past rates as evidenced by soil profiles.

Strontium concentrations in corrosion products from residential drinking water distribution systems.

PubMed

Gerke, Tammie L; Little, Brenda J; Luxton, Todd P; Scheckel, Kirk G; Maynard, J Barry

2013-05-21

The United States Environmental Protection Agency (US EPA) will require some U.S. drinking water distribution systems (DWDS) to monitor nonradioactive strontium (Sr(2+)) in drinking water in 2013. Iron corrosion products from four DWDS were examined to assess the potential for Sr(2+) binding and release. Average Sr(2+) concentrations in the outermost layer of the corrosion products ranged from 3 to 54 mg kg(-1) and the Sr(2+) drinking water concentrations were all ≤0.3 mg L(-1). Micro-X-ray adsorption near edge structure spectroscopy and linear combination fitting determined that Sr(2+) was principally associated with CaCO3. Sr(2+) was also detected as a surface complex associated with α-FeOOH. Iron particulates deposited on a filter inside a home had an average Sr(2+) concentration of 40.3 mg kg(-1) and the associated drinking water at a tap was 210 μg L(-1). The data suggest that elevated Sr(2+) concentrations may be associated with iron corrosion products that, if disturbed, could increase Sr(2+) concentrations above the 0.3 μg L(-1) US EPA reporting threshold. Disassociation of very small particulates could result in drinking water Sr(2+) concentrations that exceed the US EPA health reference limit (4.20 mg kg(-1) body weight).

Sarcoplasmic reticulum Ca2+ uptake and leak properties, and SERCA isoform expression, in type I and type II fibres of human skeletal muscle.

PubMed

Lamboley, C R; Murphy, R M; McKenna, M J; Lamb, G D

2014-03-15

The Ca(2+) uptake properties of the sarcoplasmic reticulum (SR) were compared between type I and type II fibres of vastus lateralis muscle of young healthy adults. Individual mechanically skinned muscle fibres were exposed to solutions with the free [Ca(2+)] heavily buffered in the pCa range (-log10[Ca(2+)]) 7.3-6.0 for set times and the amount of net SR Ca(2+) accumulation determined from the force response elicited upon emptying the SR of all Ca(2+). Western blotting was used to determine fibre type and the sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) isoform present in every fibre examined. Type I fibres contained only SERCA2 and displayed half-maximal Ca(2+) uptake rate at ∼pCa 6.8, whereas type II fibres contained only SERCA1 and displayed half-maximal Ca(2+) uptake rate at ∼pCa 6.6. Maximal Ca(2+) uptake rate was ∼0.18 and ∼0.21 mmol Ca(2+) (l fibre)(-1) s(-1) in type I and type II fibres, respectively, in good accord with previously measured SR ATPase activity. Increasing free [Mg(2+)] from 1 to 3 mM had no significant effect on the net Ca(2+) uptake rate at pCa 6.0, indicating that there was little or no calcium-induced calcium release occurring through the Ca(2+) release channels during uptake in either fibre type. Ca(2+) leakage from the SR at pCa 8.5, which is thought to occur at least in part through the SERCA, was ∼2-fold lower in type II fibres than in type I fibres, and was little affected by the presence of ADP, in marked contrast to the larger SR Ca(2+) leak observed in rat muscle fibres under the same conditions. The higher affinity of Ca(2+) uptake in the type I human fibres can account for the higher relative level of SR Ca(2+) loading observed in type I compared to type II fibres, and the SR Ca(2+) leakage characteristics of the human fibres suggest that the SERCAs are regulated differently from those in rat and contribute comparatively less to resting metabolic rate.

Investigating the influence of Na+ and Sr2+ on the structure and solubility of SiO2-TiO2-CaO-Na2O/SrO bioactive glass.

PubMed

Li, Y; Placek, L M; Coughlan, A; Laffir, F R; Pradhan, D; Mellott, N P; Wren, A W

2015-02-01

This study was conducted to determine the influence that network modifiers, sodium (Na+) and strontium (Sr2+), have on the solubility of a SiO2-TiO2-CaO-Na2O/SrO bioactive glass. Glass characterization determined each composition had a similar structure, i.e. bridging to non-bridging oxygen ratio determined by X-ray photoelectron spectroscopy. Magic angle spinning nuclear magnetic resonance (MAS-NMR) confirmed structural similarities as each glass presented spectral shifts between -84 and -85 ppm. Differential thermal analysis and hardness testing revealed higher glass transition temperatures (Tg 591-760 °C) and hardness values (2.4-6.1 GPa) for the Sr2+ containing glasses. Additionally the Sr2+ (~250 mg/L) containing glasses displayed much lower ion release rates than the Na+ (~1,200 mg/L) containing glass analogues. With the reduction in ion release there was an associated reduction in solution pH. Cytotoxicity and cell adhesion studies were conducted using MC3T3 Osteoblasts. Each glass did not significantly reduce cell numbers and osteoblasts were found to adhere to each glass surface.

Characterization of the slow calcium channel binding sites for ( sup 3 H)SR 33557 in rat heart sarcolemmal membranes

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

Chatelain, P.; Beaufort, P.; Meysmans, L.

1991-01-01

SR 33557 represents a new class of compounds (indolizine sulfone) that inhibit L-type Ca2+ channels. ({sup 3}H)SR 33557 has been shown to bind with high affinity (Kd congruent to 0.36 nM, calculated from saturation isotherms and association/dissociation kinetics) to a single class of sites in a purified preparation of rat cardiac sarcolemmal membranes. The binding was found to be saturable and reversible. The maximal binding capacity was in approximately 1:1 stoichiometry with that of other Ca2+ channel antagonists. Various divalent cations (Mg2+, Mn2+, Ca2+, Ba2+, and Cd2+) were shown to inhibit specific ({sup 3}H)SR 33557 binding, with Cd2+ being themore » most potent. Among several receptor or channel ligands (including omega-conotoxin and Na+ and K+ channel modulators), only the L-type Ca2+ channel antagonists were found to displace ({sup 3}H)SR 33557. However, dihydropyridines, phenylalkylamines, benzothiazepines, and diphenylbutylpiperidines were found to inhibit ({sup 3}H)SR 33557 in a noncompetitive manner as demonstrated by displacement and saturation experiments in addition to dissociation kinetics. From these results, we suggest that SR 33557 binds with high affinity to a unique site on the L-type Ca2+ channel found in rat cardiac sarcolemmal membranes.« less

Population inversion calculations using near resonant charge exchange as a pumping mechanism

NASA Technical Reports Server (NTRS)

Chubb, D. L.; Rose, J. R.

1972-01-01

Near resonance charge exchange between ions of a large ionization potential gas such as helium or neon and vapors of metals such as zinc, cadmium, selenium, or tellurium has produced laser action in the metal ion gas. The possibility of obtaining population inversions in near resonant charge exchange systems (Xe-Ca, Xe-Mg, Xe-Sr, Xe-Ba, Ar-Mg, N-Ca) was investigated. The analysis is an initial value problem that utilizes rate equations for the densities of relevant levels of the laser gas (Ca, Ba, Mg, or Sr) and an electron energy equation. Electron excitation rates are calculated using the Bohr-Thomson approximation for the cross section. Approximations to experimental values of the electron ionization cross section and the ion-atom charge exchange cross section are used. Preliminary results have been obtained for the Ca-Xe system and show that it is possible to obtain gains greater than 10 to the 14th power/m with inversion times up to 8x10 to the minus 7th power second. A possible charge exchange laser system using a MPD arc plasma accelerator is also described.

Regulation of Ca2+ Sparks by Ca2+ and Mg2+ in Mammalian and Amphibian Muscle. An RyR Isoform-specific Role in Excitation–Contraction Coupling?

PubMed Central

Zhou, Jingsong; Launikonis, Bradley S.; Ríos, Eduardo; Brum, Gustavo

2004-01-01

Ca2+ and Mg2+ are important mediators and regulators of intracellular Ca2+ signaling in muscle. The effects of changes of cytosolic [Ca2+] or [Mg2+] on elementary Ca2+ release events were determined, as functions of concentration and time, in single fast-twitch permeabilized fibers of rat and frog. Ca2+ sparks were identified and their parameters measured in confocal images of fluo-4 fluorescence. Solutions with different [Ca2+] or [Mg2+] were rapidly exchanged while imaging. Faster and spatially homogeneous changes of [Ca2+] (reaching peaks >100 μM) were achieved by photolysing Ca NP-EGTA with laser flashes. In both species, incrementing cytosolic [Ca2+] caused a steady, nearly proportional increase in spark frequency, reversible upon [Ca2+] reduction. A greater change in spark frequency, usually transient, followed sudden increases in [Ca2+] after a lag of 100 ms or more. The nonlinearity, lag, and other features of this delayed effect suggest that it requires increase of [Ca2+] inside the SR. In the frog only, increases in cytosolic [Ca2+] often resulted, after a lag, in sparks that propagated transversally. An increase in [Mg2+] caused a fall of spark frequency, but with striking species differences. In the rat, but not the frog, sparks were observed at 4–40 mM [Mg2+]. Reducing [Mg2+] below 2 mM, which should enable the RyR channel's activation (CICR) site to bind Ca2+, caused progressive increase in spark frequency in the frog, but had no effect in the rat. Spark propagation and enhancement by sub-mM Mg2+ are hallmarks of CICR. Their absence in the rat suggests that CICR requires RyR3 para-junctional clusters, present only in the frog. The observed frequency of sparks corresponds to a channel open probability of 10−7 in the frog or 10−8 in the rat. Together with the failure of photorelease to induce activation directly, this indicates a basal inhibition of channels in situ. It is proposed that relief of this inhibition could be the mechanism by which increased SR load increases spark frequency. PMID:15452201

Inorganic profile of some Brazilian medicinal plants obtained from ethanolic extract and ''in natura'' samples

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

Ferreira, M.O.M.; de Sousa, P.T.; Salvador, V.L.R.

The Anadenathera macrocarpa, Schinus molle, Hymenaea courbaril, Cariniana legalis, Solidago microglossa and Stryphnodendron barbatiman, were collected ''in natura'' samples (leaves, flowers, barks and seeds) from different commercial suppliers. The pharmaco-active compounds in ethanolic extracts had been made by the Mato Grosso Federal University (UFMT). The energy-dispersive x-ray fluorescence (ED-XRF) spectrometry was used for the elemental analysis in different parts of the plants and respective ethanolic extracts. The Ca, Cl, Cu, Fe, K, Mg, Mn, Na, Ni, P, Rb, S, Sr and Zn concentrations were determined by the fundamental parameters method. Some specimens showed a similar inorganic profile for ''in natura''more » and ethanolic extract samples and some ones showed a distinct inorganic profile. For example, the Anadenathera macrocarpa showed a similar concentration in Mg, P, Cu, Zn and Rb elements in ''in natura'' and ethanolic extract samples; however very different concentration in Na, S, Cl, K , Ca, Mn, Fe and Sr was observed in distinctive samples. The Solidago microglossa showed the K, Ca, Cl, S, Mg, P and Fe elements as major constituents in both samples, suggesting that the extraction process did not affect in a considerable way the ''in natura'' inorganic composition. The elemental composition of the different parts of the plants (leaves, flowers, barks and seeds) has been also determined. For example, the Schinus molle specimen showed P, K, Cl and Ca elements as major constituents in the seeds, Mg, K and Sr in the barks and Mg, S, Cl and Mn in the leaves, demonstrating a differentiated elementary distribution. These inorganic profiles will contribute to evaluate the quality control of the Brazilian herbaceous trade and also will assist to identify which parts of the medicinal plants has greater therapeutic effect.« less

Magnesium stable isotope ecology using mammal tooth enamel

NASA Astrophysics Data System (ADS)

Martin, Jeremy E.; Vance, Derek; Balter, Vincent

2015-01-01

Geochemical inferences on ancient diet using bone and enamel apatite rely mainly on carbon isotope ratios (δ13C) and to a lesser extent on strontium/calcium (Sr/Ca) and barium/calcium (Ba/Ca) elemental ratios. Recent developments in nontraditional stable isotopes provide an unprecedented opportunity to use additional paleodietary proxies to disentangle complex diets such as omnivory. Of particular relevance for paleodietary reconstruction are metals present in large quantity in bone and enamel apatite, providing that biologically mediated fractionation processes are constrained. Calcium isotope ratios (δ44Ca) meet these criteria but exhibit complex ecological patterning. Stable magnesium isotope ratios (δ26Mg) also meet these criteria but a comprehensive understanding of its variability awaits new isotopic data. Here, 11 extant mammal species of known ecology from a single locality in equatorial Africa were sampled for tooth enamel and, together with vegetation and feces, analyzed for δ26Mg, δ13C, Sr/Ca, and Ba/Ca ratios. The results demonstrate that δ26Mg incorporated in tooth enamel becomes heavier from strict herbivores to omnivores/faunivores. Using data from experimentally raised sheep, we suggest that this 26Mg enrichment up the trophic chain is due to a 26Mg enrichment in muscle relative to bone. Notably, it is possible to distinguish omnivores from herbivores, using δ26Mg coupled to Ba/Ca ratios. The potential effects of metabolic and dietary changes on the enamel δ26Mg composition remain to be explored but, in the future, multiproxy approaches would permit a substantial refinement of dietary behaviors or enable accurate trophic reconstruction despite specimen-limited sampling, as is often the case for fossil assemblages.

Mechanism of chloride-dependent release of Ca2+ in the sarcoplasmic reticulum of rabbit skeletal muscle.

PubMed Central

Sukhareva, M; Morrissette, J; Coronado, R

1994-01-01

We investigated the effect of Cl- on the Ca2+ permeability of rabbit skeletal muscle junctional sarcoplasmic reticulum (SR) using 45Ca2+ fluxes and single channel recordings. In 45Ca2+ efflux experiments, the lumen of the SR was passively loaded with solutions of 150 mM univalent salt containing 5 mM 45Ca2+. Release of 45Ca2+ was measured by rapid filtration in the presence of extravesicular 0.4-0.8 microM free Ca2+ and 150 mM of the same univalent salt loaded into the SR lumen. The rate of release was 5-10 times higher when the univalent salt equilibrated across the SR-contained Cl- (Tris-Cl, choline-Cl, KCl) instead of an organic anion or other halides (gluconate-, methanesulfonate-, acetate-, HEPES-, Br-, I-). Cations (K+, Tris+) could be interchanged without a significant effect on the release rate. To determine whether Cl- stimulated ryanodine receptors, we measured the stimulation of release by ATP (5 mM total) and caffeine (20 mM total) and the inhibition by Mg2+ (0.8 mM estimated free) in Cl(-)-free and Cl(-)-containing solutions. The effects of ATP, caffeine, and Mg2+ were the largest in K-gluconate and Tris-gluconate, intermediate in KCl, and notably poor or absent in choline-Cl and Tris-Cl. Procaine (10 mM) inhibited the caffeine-stimulated release measured in K-gluconate, whereas the Cl- channel blocker clofibric acid (10 mM) but not procaine inhibited the caffeine-insensitive release measured in choline-Cl. Ruthenium red (20 microM) inhibited release in all solutions. In SR fused to planar bilayers we identified a nonselective Cl- channel (PCl: PTris: PCa = 1:0.5:0.3) blocked by ruthenium red and clofibric acid but not by procaine. These conductive and pharmacological properties suggested the channel was likely to mediate Cl(-)-dependent SR Ca2+ release. The absence of a contribution of ryanodine receptors to the Cl(-)-dependent release were indicated by the lack of an effect of Cl- on the open probability of this channel, a complete block by procaine, and a stimulation rather than inhibition by clofibric acid. A plug model of Cl(-)-dependent release, whereby Cl- removed the inhibition of the nonselective channel by large anions, was formulated under the assumption that nonselective channels and ryanodine receptor channels operated separately from each other in the terminal cisternae. The remarkably large contribution of Cl- to the SR Ca2+ permeability suggested that nonselective Cl- channels may control the Ca2+ permeability of the SR in the resting muscle cell. Images FIGURE 8 FIGURE 13 PMID:7948689

Synthesis of bimetallic trifluoroacetates through a crystallochemical investigation of their monometallic counterparts: the case of (A, A')(CF3COO)2·nH2O (A, A' = Mg, Ca, Sr, Ba, Mn).

PubMed

Dulani Dhanapala, B; Mannino, Natalie A; Mendoza, Laura M; Tauni Dissanayake, K; Martin, Philip D; Suescun, Leopoldo; Rabuffetti, Federico A

2017-01-31

Owing to their potential as single-source precursors for compositionally complex materials, there is growing interest in the rational design of multimetallic compounds containing fluorinated ligands. In this work, we show that chemical and structural principles for a materials-by-design approach to bimetallic trifluoroacetates can be established through a systematic investigation of the crystal-chemistry of their monometallic counterparts. A(CF 3 COO) 2 ·nH 2 O (A = Mg, Ca, Sr, Ba, Mn) monometallic trifluoroacetates were employed to demonstrate the feasibility of this approach. The crystal-chemistry of monometallic trifluoroacetates was mapped using variable-temperature single-crystal X-ray diffraction, powder X-ray diffraction, and thermal analysis. The evolution with temperature of the previously unknown crystal structure of Mg(CF 3 COO) 2 ·4H 2 O was found to be identical to that of Mn(CF 3 COO) 2 ·4H 2 O. More important, the flexibility of Mn x (CF 3 COO) 2x ·4H 2 O (x = 1, 3) to adopt two structures, one isostructural to Mg(CF 3 COO) 2 ·4H 2 O, the other isostructural to Ca 3 (CF 3 COO) 6 ·4H 2 O, enabled the synthesis of Mg-Mn and Ca-Mn bimetallic trifluoroacetates. Mg 0.45 Mn 0.55 (CF 3 COO) 2 ·4H 2 O was found to be isostructural to Mg(CF 3 COO) 2 ·4H 2 O and exhibited isolated metal-oxygen octahedra with Mg 2+ and Mn 2+ nearly equally distributed over the metal sites (Mg/Mn: 45/55). Ca 1.72 Mn 1.28 (CF 3 COO) 6 ·4H 2 O was isostructural to Ca 3 (CF 3 COO) 6 ·4H 2 O and displayed trimers of metal-oxygen corner-sharing octahedra; Ca 2+ and Mn 2+ were unequally distributed over the central (Ca/Mn: 96/4) and terminal (Ca/Mn: 38/62) octahedral sites.

Lattice thermal transport in group II-alloyed PbTe

NASA Astrophysics Data System (ADS)

Xia, Yi; Hodges, James M.; Kanatzidis, Mercouri G.; Chan, Maria K. Y.

2018-04-01

PbTe, one of the most promising thermoelectric materials, has recently demonstrated a thermoelectric figure of merit (ZT) of above 2.0 when alloyed with group II elements. The improvements are due mainly to significant reduction of lattice thermal conductivity (κl), which was in turn attributed to nanoparticle precipitates. However, a fundamental understanding of various phonon scattering mechanisms within the bulk alloy is still lacking. In this work, we apply the newly-developed density-functional-theory-based compressive sensing lattice dynamics approach to model lattice heat transport in PbTe, MTe, and Pb0.94M0.06Te (M = Mg, Ca, Sr, and Ba) and compare our results with experimental measurements, with focus on the strain effect and mass disorder scattering. We find that (1) CaTe, SrTe, and BaTe in the rock-salt structure exhibit much higher κl than PbTe, while MgTe in the same structure shows anomalously low κl; (2) lattice heat transport of PbTe is extremely sensitive to static strain induced by alloying atoms in solid solution form; (3) mass disorder scattering plays a major role in reducing κl for Mg/Ca/Sr-alloyed PbTe through strongly suppressing the lifetimes of intermediate- and high-frequency phonons, while for Ba-alloyed PbTe, precipitated nanoparticles are also important.

Growth rates, stable oxygen isotopes (δ18O), and strontium (Sr/Ca) composition in two species of Pacific sclerosponges (Acanthocheatetes wellsi and Astrosclera willeyana) with δ18O calibration and application to paleoceanography

NASA Astrophysics Data System (ADS)

Grottoli, AndréA. G.; Adkins, Jess F.; Panero, Wendy R.; Reaman, Daniel M.; Moots, Kate

2010-06-01

The isotopic and elemental composition of sclerosponge skeletons is used to reconstruct paleoceanographic records. Yet few studies have systematically examined the natural variability in sclerosponge skeletal δ18O, growth, and Sr/Ca, and how that may influence the interpretation of sclerosponge proxy records. Here, we analyzed short records in seven specimens of Acanthocheatetes wellsi (high-Mg calcite, 21 mol% Mg) from Palau, four A. wellsi (high-Mg calcite, 21 mol% Mg) from Saipan, and three Astrosclera willeyana (aragonite) sclerosponges from Saipan, as well as one long record in an A. wellsi specimen from Palau spanning 1945-2001.5. In Saipan, species-specific and mineralogical effects appear to have a negligible effect on sclerosponge δ18O, facilitating the direct comparison of δ18O records between species at a given location. At both sites, A. wellsi δ18O and growth rates were sensitive to environmental conditions, but Sr/Ca was not sensitive to the same conditions. High-resolution δ18O analyses confirmed this finding as both A. wellsi and A. willeyana deposited their skeleton in accordance with the trends in isotopic equilibrium with seawater, though with a 0.27‰ offset in the case of A. willeyana. In the high-Mg-calcite species A. wellsi, Mg may be interfering with Sr incorporation into the skeleton. On multidecadal timescales, A. wellsi sclerosponge δ18O in Palau tracked the Southern Oscillation Index variability post-1977, but not pre-1977, coincident with the switch in the Pacific Decadal Oscillation (PDO) at ˜1976. This suggests that water mass circulation in the region is influenced by El Niño— Southern Oscillation variability during positive PDO phases, but not during negative ones.

Growth Rates, Stable Oxygen Isotopes (18O), and Strontium (Sr/Ca) Composition in Two Species of Pacific Sclerosponges (Acanthocheatetes wellsi and Astrosclera willeyana) with 18O Calibration and Application to Paleoceanography

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

Grottoli, A.; Adkins, J; Panero, W

2010-01-01

The isotopic and elemental composition of sclerosponge skeletons is used to reconstruct paleoceanographic records. Yet few studies have systematically examined the natural variability in sclerosponge skeletal {delta}{sup 18}O, growth, and Sr/Ca, and how that may influence the interpretation of sclerosponge proxy records. Here, we analyzed short records in seven specimens of Acanthocheatetes wellsi (high-Mg calcite, 21 mol% Mg) from Palau, four A. wellsi (high-Mg calcite, 21 mol% Mg) from Saipan, and three Astrosclera willeyana (aragonite) sclerosponges from Saipan, as well as one long record in an A. wellsi specimen from Palau spanning 1945-2001.5. In Saipan, species-specific and mineralogical effects appearmore » to have a negligible effect on sclerosponge {delta}{sup 18}O, facilitating the direct comparison of {delta}{sup 18}O records between species at a given location. At both sites, A. wellsi {delta}{sup 18}O and growth rates were sensitive to environmental conditions, but Sr/Ca was not sensitive to the same conditions. High-resolution {delta}{sup 18}O analyses confirmed this finding as both A. wellsi and A. willeyana deposited their skeleton in accordance with the trends in isotopic equilibrium with seawater, though with a 0.27{per_thousand} offset in the case of A. willeyana. In the high-Mg-calcite species A. wellsi, Mg may be interfering with Sr incorporation into the skeleton. On multidecadal timescales, A. wellsi sclerosponge {delta}{sup 18}O in Palau tracked the Southern Oscillation Index variability post-1977, but not pre-1977, coincident with the switch in the Pacific Decadal Oscillation (PDO) at {approx}1976. This suggests that water mass circulation in the region is influenced by El Nino-Southern Oscillation variability during positive PDO phases, but not during negative ones.« less

Coordinate downregulation of CaM kinase II and phospholamban accompanies contractile phenotype transition in the hyperthyroid rabbit soleus.

PubMed

Jiang, M; Xu, A; Jones, D L; Narayanan, N

2004-09-01

This study investigated the effects of l-thyroxine-induced hyperthyroidism on Ca(2+)/calmodulin (CaM)-dependent protein kinase (CaM kinase II)-mediated sarcoplasmic reticulum (SR) protein phosphorylation, SR Ca(2+) pump (Ca(2+)-ATPase) activity, and contraction duration in slow-twitch soleus muscle of the rabbit. Phosphorylation of Ca(2+)-ATPase and phospholamban (PLN) by endogenous CaM kinase II was found to be significantly lower (30-50%) in soleus of the hyperthyroid compared with euthyroid rabbit. Western blotting analysis revealed higher levels of sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) 1 ( approximately 150%) Ca(2+) pump isoform, unaltered levels of SERCA2 Ca(2+) pump isoform, and lower levels of PLN ( approximately 50%) and delta-, beta-, and gamma-CaM kinase II (40 approximately 70%) in soleus of the hyperthyroid rabbit. SR vesicles from hyperthyroid rabbit soleus displayed approximately twofold higher ATP-energized Ca(2+) uptake and Ca(2+)-stimulated ATPase activities compared with that from euthyroid control. The V(max) of Ca(2+) uptake (in nmol Ca(2+).mg SR protein(-1).min(-1): euthyroid, 818 +/- 73; hyperthyroid, 1,649 +/- 90) but not the apparent affinity of the Ca(2+)-ATPase for Ca(2+) (euthyroid, 0.97 +/- 0.02 microM, hyperthyroid, 1.09 +/- 0.04 microM) differed significantly between the two groups. CaM kinase II-mediated stimulation of Ca(2+) uptake by soleus muscle SR was approximately 60% lower in the hyperthyroid compared with euthyroid. Isometric twitch force of soleus measured in situ was significantly greater ( approximately 36%), and the time to peak force and relaxation time were significantly lower ( approximately 30-40%), in the hyperthyroid. These results demonstrate that thyroid hormone-induced transition in contractile properties of the rabbit soleus is associated with coordinate downregulation of the expression and function of PLN and CaM kinase II and selective upregulation of the expression and function of SERCA1, but not SERCA2, isoform of the SR Ca(2+) pump.

Assessment of spatial variability of heavy metals in Metropolitan Zone of Toluca Valley, Mexico, using the biomonitoring technique in mosses and TXRF analysis.

PubMed

Zarazúa-Ortega, Graciela; Poblano-Bata, Josefina; Tejeda-Vega, Samuel; Ávila-Pérez, Pedro; Zepeda-Gómez, Carmen; Ortiz-Oliveros, Huemantzin; Macedo-Miranda, Guadalupe

2013-01-01

This study is aimed at assessing atmospheric deposition of heavy metals using the epiphytic moss genera Fabronia ciliaris collected from six urban sites in the Metropolitan Zone of the Toluca Valley in Mexico. The concentrations of K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Rb, Sr, and Pb were determined by total reflection X-ray fluorescence technique. Results show that the average metal concentration decrease in the following order: Fe (8207 mg/Kg) > Ca (7315 mg/Kg) > K (3842 mg/Kg) > Ti (387 mg/Kg) > Mn, Zn (191 mg/Kg) > Sr (71 mg/Kg) > Pb (59 mg/Kg) > Cu, V (32 mg/Kg) > Cr (24 mg/Kg) > Rb (13 mg/Kg) > Ni (10 mg/Kg). Enrichment factors show a high enrichment for Cr, Cu, Zn, and Pb which provides an evidence of anthropogenic impact in the industrial and urban areas, mainly due to the intense vehicular traffic and the fossil fuel combustion. Monitoring techniques in mosses have proved to be a powerful tool for determining the deposition of heavy metals coming from diverse point sources of pollution.

Magnesium- and strontium-co-substituted hydroxyapatite: the effects of doped-ions on the structure and chemico-physical properties.

PubMed

Aina, Valentina; Lusvardi, Gigliola; Annaz, Basil; Gibson, Iain R; Imrie, Flora E; Malavasi, Gianluca; Menabue, Ledi; Cerrato, Giuseppina; Martra, Gianmario

2012-12-01

The present study is aimed at investigating the contribution of two biologically important cations, Mg(2+) and Sr(2+), when substituted into the structure of hydroxyapatite (Ca(10)(PO(4))(6)(OH)(2),HA). The substituted samples were synthesized by an aqueous precipitation method that involved the addition of Mg(2+)- and Sr(2+)-containing precursors to partially replace Ca(2+) ions in the apatite structure. Eight substituted HA samples with different concentrations of single (only Mg(2+)) or combined (Mg(2+) and Sr(2+)) substitution of cations have been investigated and the results compared with those of pure HA. The obtained materials were characterized by X-ray powder diffraction, specific surface area and porosity measurements (N(2) adsorption at 77 K), FT-IR and Raman spectroscopies and scanning electron microscopy. The results indicate that the co-substitution gives rise to the formation of HA and β-TCP structure types, with a variation of their cell parameters and of the crystallinity degree of HA with varying levels of substitution. An evaluation of the amount of substituents allows us to design and prepare BCP composite materials with a desired HA/β-TCP ratio.

Characterization of Carbonate Crust from Deep-sea Methane Seeps on the Northern US Atlantic Margin.

NASA Astrophysics Data System (ADS)

Gabitov, R. I.; Borrelli, C.; Buettner, J.; Testa, M.; Garner, B.; Weremeichik, J.; Thomas, J. B.; Wahidi, M.; Thirumalai, R. V. K. G.; Kirkland, B. L.; Skarke, A. D.

2017-12-01

Authigenic carbonate minerals widely occur at the seafloor as carbonate crusts and are often directly linked to microbial activity, about which promotion of carbonate crystal growth and geochemistry are not entirely understood. To evaluate a potential metabolic contribution, studies were conducted on carbonate crust collected from a methane seep and on precipitation experiments which produced inorganic aragonite crystallized at high pressure. Among the samples collected during a NSF sponsored cruise to the North Atlantic Continental Margin of the United States (off of New England) in July-August 2016, we analyzed one carbonate crust sample (AD4835 BB-4522) collected at 39.805860; -69.592593 and at a depth of 1419.6 m. In this crust sample, two textural types of aragonite were identified: 1) groundmass consisting of fine grey crystals (<1 µm in size); 2) veins consisting of white acicular crystals (up to 100 µm in width). In addition, large equant quartz crystals (>100 µm, 24.9 wt%), feldspar (5.6 wt%), and dolomite (3.6 wt%), and trace amount of troilite were identified using XRD, SEM, and optical microscopy. The sample was cut into slabs parallel to crust growth assuming the crust grew in a downward direction. Concentrations of Na, Mg, Al, Si, S, K, Ca, Mn, Fe, Sr, Zr, Ba, and U were measured in the direction parallel to growth of the crust using LA-ICP-MS. Proportions of Si, Al, (Na+K), Mg, S, and Fe in the groundmass suggest the occurrence of sub-micron inclusions of alkali feldspar, and potentially pyroxene, Fe oxide, and Fe sulfide, which were impossible to avoid with the instrument's spatial resolution. The occurrence of micro non-carbonate inclusions causes high elemental concentrations compared to the values expected for aragonite crystallized from seawater. White aragonite acicular crystals were free of silicate and sulfide inclusions, and therefore, yielded lower concentrations of all measured elements except Sr compared to the groundmass. Analyzed Mg and Sr are consistent with published data for deep-sea corals. Also, Sr is similar to experimental data on inorganic aragonite. Mg/Ca, Sr/Ca, Ba/Ca, and U/Ca of the fluid from which acicular aragonite grew were calculated based on partition coefficients from inorganic aragonite precipitated at 100 bars.

The distribution of Sr and REE between diopside and silicate liquid. [Rare Earth Elements

NASA Technical Reports Server (NTRS)

Grutzeck, M.; Kridelbaugh, S.; Weill, D.

1974-01-01

Experimental determination of the distribution coefficients in diopside-liquid pairs for strontium and nine rare-earth elements in the system CaMgSi2O6-NaAlSi3O8-CaAl2Si2O8. In experiments in air at 1265 C it is found that most of the Sr(2+), Eu(2+), and RE(3+) ions substitute for Ca(2+) and, in addition, a coupled substitution of Al(3+) for Si(4+) occurs. All of the trace ions considered are found to be excluded from the diopside lattice relative to the liquid. In the case of the trivalent ions the exclusion is much more pronounced for La and Ce, which have ionic radii larger than that of Ca(2+) in 8-fold oxygen coordination. Divalent Sr and Eu with even larger radii are also strongly excluded.

The laser microprobe mass analyser for determining partitioning of minor and trace elements among intimately associated macerals: an example from the Swallow Wood coal bed, Yorkshire, UK

USGS Publications Warehouse

Lyons, P.C.; Morelli, J.J.; Hercules, D.M.; Lineman, D.; Thompson-Rizer, C. L.; Dulong, F.T.

1990-01-01

A study of the elemental composition of intimately associated coal macerals in the English Swallow Wood coal bed was conducted using a laser microprobe mass analyser, and indicated a similar trace and minor elemental chemistry in the vitrinite and cutinite and a different elemental signature in the fusinite. Three to six sites were analysed within each maceral during the study by laser micro mass spectrometry (LAMMS). Al, Ba, Ca, Cl, Cr, Dy, F, Fe, Ga, K, Li, Mg, Na, S, Si, Sr, Ti, V, and Y were detected by LAMMS in all three macerals but not necessarily at each site analysed. The signal intensities of major isotopic peaks were normalized to the signal intensity of the m z 85 peak (C7H) to determine the relative minor- and trace-element concentrations among the three dominant macerals. The vitrinite and the cutinite were depleted in Ba, Ca, Dy, Li, Mg, Sr, and Y relative to their concentrations observed in the fusinite. The cutinite was distinguished over vitrinite by less Ti, V, Cr and Ca, and K Ca $ ??1 (relative signal intensities). The fusinite, relative to the cutinite and vitrinite, was relatively depleted in Cr, Sc, Ti, and V. The fusinite, as compared with both the cutinite and vitrinite, was relatively enriched in Ba, Ca, Dy, Li, Mg, Sr, and Y, and also showed the most intense m z 64, 65, 66 signals (possibly S2+, HS2+, H2S2+, respectively). The LAMMS data indicate a common source for most elements and selective loss from the maceral precursors in the peat or entrapment of certain elements as mineral matter, most likely during the peat stage or during early diagenesis. The relatively high amounts of Ba, Ca, Dy, Li, Mg, Sr, and Y in the fusinite are consistent with micron and submicron mineral-matter inclusions such as carbonates and Ca-Al phosphates (probably crandallite group minerals). Mineralogical data on the whole coal, the LAMMS chemistry of the vitrinite and cutinite, and scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDAX) of the elements in the macerals are consistent with the presence of micron and submicron inclusions of clays such as kaolinite, illite, and Ca-rich or Ca-bearing minerals (e.g. calcite, Ca-Al phosphates, and illite) which are different in kind and proportions in the three macerals. The variance as measured by the F-statistic for all three macerals indicates generally a nonuniform distribution of minor and trace elements in all three macerals, thus supporting a mineral-matter (inorganic) origin of the elements analysed. Exceptions are Al, K, Fe, Ga, and Sr in the vitrinite and cutinite, which is consistent with organic complexing or a uniform distribution of micron or submicron mineral matter such as illite and phosphate(s). ?? 1990.

Effect of cryogenic temperature on spectroscopic and laser properties of Er,La:SrF2-CaF2 crystal

NASA Astrophysics Data System (ADS)

Švejkar, Richard; Šulc, Jan; Němec, Michal; Jelínková, Helena; Doroshenko, Maxim E.; Nakladov, Andrei N.; Osiko, Vjatcheslav V.

2016-03-01

The laser and spectroscopic properties of crystal Er,La:SrF2-CaF2 at temperature range 80 - 300 K, which is appropriate for generation of radiation around 2.7 um is presented. The sample of Er,La:SrF2-CaF2 (concentration Er(0.04), La(0.12):Ca(0.77)Sr(0.07)) had plan-parallel face-polished faces without anti-reflection coatings (thickness 8.2 mm). During spectroscopy and laser experiments the Er,La:SrF2-CaF2 was attached to temperature controlled copper holder and it was placed in vacuum chamber. The transmission and emission spectra of Er,La:SrF2-CaF2 together with the fluorescence decay time were measured in dependence on temperature. The excitation of Er,La:SrF2-CaF2 was carried out by a laser diode radiation (pulse duration 5 ms, repetition rate 20 Hz, pump wavelength 973 nm). Laser resonator was hemispherical, 140 mm in length with at pumping mirror (HR @ 2.7 µm) and spherical output coupler (r = 150 mm, R = 95 % @ 2.5 - 2.8 µm). Tunability of laser at 80 K in range 2690 - 2765 nm was obtained using MgF2 birefringent filter. With decreasing temperature of sample the fluorescence lifetime of manifold 4I11/2 (upper laser level) became shorter and intensity of up-conversion radiation was increasing. The highest slope efficiency with respect to absorbed power was 2.3 % at 80 K. The maximum output of peak amplitude power was 0.3 W at 80 K, i.e. 1.5 times higher than measured this value at 300 K. The wavelength generated by Er,La:SrF2-CaF2 laser (2.7 µm) is relatively close to absorption peak of water (3 µm) and so, one of the possible usage should be in medicine and spectroscopy.

Superconductivity in Bi-(Pb)-Sr-Ca-Cu-O films made by thermal decomposition of metal carboxylates: Preparation, characterisation and magnetisation

NASA Astrophysics Data System (ADS)

de Vries, J. W. C.; Klee, M.; Marbach, G.; Stotz, S.

1989-12-01

Superconducting films in the system Bi-(Pb)-Sr-Ca-Cu-O are made by thermal decomposition of metal carboxylates. The layers are deposited by dip-coating and spin-coating on ceramic and single-crystal MgO substrates. In lead-free samples a continuous path of the high-T c phase ( Bi2Sr2Ca2Cu33O10 + δ, Tc ≈ 110 K), leading to zero-resistance at 95 K, can be obtained after firing at 878°C for 3 h. From DC magnetisation measurements in an external field of 10 mT, it followed that the relative amount of the high- Tc phase ( Bi2Sr2Ca2Cu3O10 + δ) and the low-T c phase ( Bi2 ( Sr, Ca) 3Cu2O8 + δ, Tc ≈ 80 K) is about 14:86. Substitution of 20% of bismuth by lead yields, after firing at 850°C or 860°C, the high- Tc phase as the major phase, as can be deduced both from X-ray diffraction and DC magnetisation measurements. The resistance is zero at 104 K and the relative quantity of high-T c to low-T c phase is about 60:40 to 75:25.

In vitro/vivo drug release and anti-diabetic cardiomyopathy properties of curcumin/PBLG-PEG-PBLG nanoparticles.

PubMed

Tong, Fei; Chai, Rongkui; Jiang, Haiying; Dong, Bo

2018-01-01

The objective of this study was to survey the therapeutic function of curcumin-encapsulated poly(gamma-benzyl l-glutamate)-poly(ethylene glycol)-poly(gammabenzyl l-glutamate) (PBLG-PEG-PBLG) (P) on diabetic cardiomyopathy (DCM) via cross regulation effect of calcium-sensing receptor (CaSR) and endogenous cystathionine-γ-lyase (CSE)/hydrogen sulfide (H 2 S). Diabetic rats were preconditioned with 20 mg/kg curcumin or curcumin/P complex continuously for 8 weeks. The blood and myocardiums were collected, the level of serum H 2 S was observed, and the [Ca 2+ ] i content was measured in myocardial cells, and hematoxylin-eosin, CaSR, CSE, and calmodulin (CaM) expression were detected. Both curcumin and curcumin/P pretreatment alleviated pathological morphological damage of myocardium, increased H 2 S and [Ca 2+ ] i levels, and upregulated the expression of CaSR, CSE, and CaM as compared to DCM group, while curcumin/P remarkably augmented this effect. PBLG-PEG-PBLG could improve water-solubility and bioactivity of curcumin and curcumin/PBLG-PEG-PBLG significantly alleviated diabetic cardiomyopathy.

Binding of Dissolved Strontium by Micrococcus luteus

PubMed Central

Faison, Brendlyn D.; Cancel, Carmen A.; Lewis, Susan N.; Adler, Howard I.

1990-01-01

Resting cells of Micrococcus luteus have been shown to remove strontium (Sr) from dilute aqueous solutions of SrCl2 at pH 7. Loadings of 25 mg of Sr per g of cell dry weight were achieved by cells exposed to a solution containing 50 ppm (mg/liter) of Sr. Sr binding occurred in the absence of nutrients and did not require metabolic activity. Initial binding was quite rapid (<0.5 h), although a slow, spontaneous release of Sr was observed over time. Sr binding was inhibited in the presence of polyvalent cations but not monovalent cations. Ca and Sr were bound preferentially over all other cations tested. Sr-binding activity was localized on the cell envelope and was sensitive to various chemical and physical pretreatments. Bound Sr was displaced by divalent ions or by H+. Other monovalent ions were less effective. Bound Sr was also removed by various chelating agents. It was concluded that Sr binding by M. luteus is a reversible equilibrium process. Both ion exchange mediated by acidic cell surface components and intracellular uptake may be involved in this activity. PMID:16348370

A preliminary analysis of trace-elemental signatures in statoliths of different spawning cohorts for Dosidicus gigas off EEZ waters of Chile

NASA Astrophysics Data System (ADS)

Liu, Bilin; Chen, Xinjun; Fang, Zhou; Hu, Song; Song, Qian

2015-12-01

We applied solution-based ICP-MS method to quantify the trace-elemental signatures in statoliths of jumbo flying squid, Dosidius gigas, which were collected from the waters off northern and central Chile during the scientific surveys carried out by Chinese squid jigging vessels in 2007 and 2008. The age and spawning date of the squid were back-calculated based on daily increments in statoliths. Eight elemental ratios (Sr/Ca, Ba/Ca, Mg/Ca, Mn/Ca, Na/Ca, Fe/Ca, Cu/Ca and Zn/Ca) were analyzed. It was found that Sr is the second most abundant element next to Ca, followed by Na, Fe, Mg, Zn, Cu, Ba and Mn. There was no significant relationship between element/Ca and sea surface temperature (SST) and sea surface salinity (SSS), although weak negative or positive tendency was found. MANOVA analysis showed that multivariate elemental signatures did not differ among the cohorts spawned in spring, autumn and winter, and no significant difference was found between the northern and central sampling locations. Classification results showed that all individuals of each spawned cohorts were correctly classified. This study demonstrates that the elemental signatures in D. gigas statoliths are potentially a useful tool to improve our understanding of its population structure and habitat environment.

Sr-containing hydroxyapatite: morphologies of HA crystals and bioactivity on osteoblast cells.

PubMed

Aina, Valentina; Bergandi, Loredana; Lusvardi, Gigliola; Malavasi, Gianluca; Imrie, Flora E; Gibson, Iain R; Cerrato, Giuseppina; Ghigo, Dario

2013-04-01

A series of Sr-substituted hydroxyapatites (HA), of general formula Ca(10-x)Srx(PO4)6(OH)2, where x=2 and 4, were synthesized by solid state methods and characterized extensively. The reactivity of these materials in cell culture medium was evaluated, and the behavior towards MG-63 osteoblast cells (in terms of cytotoxicity and proliferation assays) was studied. Future in vivo studies will give further insights into the behavior of the materials. A paper by Lagergren et al. (1975), concerning Sr-substituted HA prepared by a solid state method, reports that the presence of Sr in the apatite composition strongly influences the apatite diffraction patterns. Zeglinsky et al. (2012) investigated Sr-substituted HA by ab initio methods and Rietveld analyses and reported changes in the HA unit cell volume and shape due to the Sr addition. To further clarify the role played by the addition of Sr on the physico-chemical properties of these materials we prepared Sr-substituted HA compositions by a solid state method, using different reagents, thermal treatments and a multi-technique approach. Our results indicated that the introduction of Sr at the levels considered here does influence the structure of HA. There is also evidence of a decrease in the crystallinity degree of the materials upon Sr addition. The introduction of increasing amounts of Sr into the HA composition causes a decrease in the specific surface area and an enrichment of Sr-apatite phase at the surface of the samples. Bioactivity tests show that the presence of Sr causes changes in particle size and/or morphology during soaking in MEM solution; on the contrary the morphology of pure HA does not change after 14 days of reaction. The presence of Sr, as Sr-substituted HA and SrCl2, in cultures of human MG-63 osteoblasts did not produce any cytotoxic effect. In fact, Sr-substituted HA increased the proliferation of osteoblast cells and enhanced cell differentiation: Sr in HA has a positive effect on MG-63 cells. In contrast, Sr ions alone, at the concentrations released by Sr-HA (1.21-3.24 ppm), influenced neither cell proliferation nor differentiation. Thus the positive effects of Sr in Sr-HA materials are probably due to the co-action of other ions such as Ca and P. Copyright © 2012 Elsevier B.V. All rights reserved.

Early cements versus pore-water chemical composition in the subsurface of the sabkha of Abu Dhabi

NASA Astrophysics Data System (ADS)

Paul, Andreas; Yuan, Peng; Court, Wesley M.; Lokier, Stephen W.; Dutton, Kirsten E.; Van der Land, Cees; Lessa Andrade, Luiza; Sherry, Angela; Head, Ian M.

2017-04-01

The coastal sabkha of Abu Dhabi is a complex depositional system in an extremely arid climate. This depositional system is marked by the formation of primary carbonate and microbial deposits, and by the development of secondary evaporite and cement phases. A number of earlier studies have assessed the formation of these secondary phases, yet no research has established a relationship between lateral and vertical variations in the chemical composition of pore water and the nature of, in particular, the precipitating pore-filling cements, re-crystallisation features and dissolution. This study aims to establish an understanding of the environmental and sedimentary factors that control early post-depositional changes to sediment composition as a result of sediment - pore water interactions. A particular focus is to characterise changes in the chemistry of the pore water throughout a tidal cycle, aiming at understanding how the influx of 'fresh' lagoonal sea water influences the chemistry of the pore water, and which elements are replenished on a daily basis. The initial data presented here is based upon the relationship between the petrographic analysis of sediment samples and lateral and vertical variations in the chemistry of in-situ sampled pore water. The pore water is characterised with respect to pH, salinity, alkalinity, dissolved organic carbon, and the concentrations of a variety of common metallic and non-metallic elements, including (but not limited to) Ca, Fe, Mg, P, S and Sr. Initial results show that concentrations of Mg, P, and V, and the ratios Mg/Ca and Sr/Ca are highest at the seaward sampling locations. Contrastingly, individual concentrations for Ca, Sr, Fe, Si, and Cu are highest at the most landward locality. In particular the higher concentrations for Ca and Sr might indicate diagenetic processes and are thus enriched as a result of e.g. aragonite dissolution. A striking pattern in Mg concentrations show the highest values for this element within a buried microbial mat. This might point to an enrichment process within this organo-sedimentary layer, that might ultimately contribute to bacterially controlled and/or mediated dolomite formation.

Membranes for separation of carbon dioxide

DOEpatents

Ku, Anthony Yu-Chung [Rexford, NY; Ruud, James Anthony [Delmar, NY; Ramaswamy, Vidya [Niskayuna, NY; Willson, Patrick Daniel [Latham, NY; Gao, Yan [Niskayuna, NY

2011-03-01

Methods for separating carbon dioxide from a fluid stream at a temperature higher than about 200.degree. C. with selectivity higher than Knudsen diffusion selectivity include contacting a porous membrane with the fluid stream to preferentially transport carbon dioxide. The porous membrane includes a porous support and a continuous porous separation layer disposed on a surface of the porous support and extending between the fluid stream and the porous support layer. The porous support comprises alumina, silica, zirconia, stabilized zirconia, stainless steel, titanium, nickel-based alloys, aluminum-based alloys, zirconium-based alloys or a combination thereof. Median pore size of the porous separation layer is less than about 10 nm, and the porous separation layer comprises titania, MgO, CaO, SrO, BaO, La.sub.2O.sub.3, CeO.sub.2, HfO.sub.2, Y.sub.2O.sub.3, VO.sub.z, NbO.sub.z, TaO.sub.z, ATiO.sub.3, AZrO.sub.3, AAl.sub.2O.sub.4, A.sup.1FeO.sub.3, A.sup.1MnO.sub.3, A.sup.1CoO.sub.3, A.sup.1NiO.sub.3, A.sup.2HfO.sub.3, A.sup.3 CeO.sub.3, Li.sub.2ZrO.sub.3, Li.sub.2SiO.sub.3, Li.sub.2TiO.sub.3, Li.sub.2HfO.sub.3, A.sup.4N.sup.1.sub.yO.sub.z, Y.sub.xN.sup.1.sub.yO.sub.z, La.sub.xN.sup.1.sub.yO.sub.z, HfN.sup.2.sub.yO.sub.z, or a combination thereof; wherein A is La, Mg, Ca, Sr or Ba; A.sup.1 is La, Ca, Sr or Ba; A.sup.2 is Ca, Sr or Ba; A.sup.3 is Sr or Ba; A.sup.4 is Mg, Ca, Sr, Ba, Ti or Zr; N.sup.1 is V, Nb, Ta, Cr, Mo, W, Mn, Si or Ge; N.sup.2 is V, Mo, W or Si; x is 1 or 2; y ranges from 1 to 3; and z ranges from 2 to 7.

Leucogranites in Lhozag, southern Tibet: Implications for the tectonic evolution of the eastern Himalaya

NASA Astrophysics Data System (ADS)

Huang, Chunmei; Zhao, Zhidan; Li, Guangming; Zhu, Di-Cheng; Liu, Dong; Shi, Qingshang

2017-12-01

Petrogenesis of the Himalayan leucogranite is strongly influenced by conditions which are associated with the tectonic evolution of Himalayan orogen. In this article, we present petrological, geochronological and geochemical results of the Lhozag leucogranites that crop out alongside the South Tibetan Detachment System (STDS) in the east of Himalaya. Zircon U-Pb dating revealed three episodes of leucogranitic magmatism in Lhozag at 17.8 ± 0.1 Ma, 15.1 ± 0.1 Ma, and 12.0 ± 0.1 Ma, respectively. The Lhozag leucogranites show relatively low εNd(t), low zircon εHf(t) and high initial 87Sr/86Sr ratios, which are similar to the High Himalayan Crystalline Series (HHCS), indicating that they were derived from the HHCS. The characteristics of relatively high Na2O and Rb contents, high Rb/Sr ratios and low CaO, MgO, TFe2O3, TiO2, and Sr contents indicate that both the ca. 18 Ma Lhozag tourmaline leucogranites and the ca. 15 Ma Lhozag two-mica granites were derived from fluid-absent muscovite-dehydration melting of metasediments. The opposite geochemistry characteristics of the ca. 12 Ma Khula Kangri two-mica granites imply that these granites are derived from fluid-present melting of metasediments. Four Khula Kangri two-mica granite samples with relatively lower TiO2, TFe2O3, MgO, and CaO contents, higher Rb concentrations and Rb/Sr ratios could be evolved from the Khula Kangri two-mica granites with relatively lower Rb/Sr ratios. The melting behaviors of the Lhozag leucogranites varied from fluid-absent melting to fluid-present melting, implying that there were P-T-XH2O variations in the deep crust. The tectonic evolution would give rise to variation of P-T-XH2O variation, and subsequent transformation of melting behavior. Our new results display the transformation of melting behavior of the Lhozag leucogranites, which implies the tectonic evolution from earlier N-S extension to later E-W extension in the eastern Himalaya at ca. 12 Ma.

Endogenous and maximal sarcoplasmic reticulum calcium content and calsequestrin expression in type I and type II human skeletal muscle fibres.

PubMed

Lamboley, C R; Murphy, R M; McKenna, M J; Lamb, G D

2013-12-01

The relationship between sarcoplasmic reticulum (SR) Ca(2+) content and calsequestrin (CSQ) isoforms was investigated in human skeletal muscle. A fibre-lysing assay was used to quantify the endogenous Ca(2+) content and maximal Ca(2+) capacity of the SR in skinned segments of type I and type II fibres from vastus lateralis muscles of young healthy adults. Western blotting of individual fibres showed the great majority contained either all fast or all slow isoforms of myosin heavy chain (MHC), troponins C and I, tropomyosin and SERCA, and that the strontium sensitivity of the force response was closely indicative of the troponin C isoform present. The endogenous SR Ca(2+) content was slightly lower in type I compared to type II fibres (0.76 ± 0.03 and 0.85 ± 0.02 mmol Ca(2+) per litre of fibre, respectively), with virtually all of this Ca(2+) evidently being in the SR, as it could be rapidly released with a caffeine-low [Mg(2+)] solution (only 0.08 ± 0.01 and <0.07 mmol l(-1), respectively, remaining). The maximal Ca(2+) content that could be reached with SR Ca(2+) loading was 1.45 ± 0.04 and 1.79 ± 0.03 mmol l(-1) in type I and type II fibres, respectively (P < 0.05). In non-lysed skinned fibres, where the SR remained functional, repeated cycles of caffeine-induced Ca(2+) release and subsequent Ca(2+) reloading similarly indicated that (i) maximal SR Ca(2+) content was lower in type I fibres than in type II fibres (P < 0.05), and (ii) the endogenous Ca(2+) content represented a greater percentage of maximal content in type I fibres compared to type II fibres (∼59% and 41%, respectively, P < 0.05). Type II fibres were found on average to contain ∼3-fold more CSQ1 and ∼5-fold less CSQ2 than type I fibres (P < 0.001). The findings are consistent with the SR Ca(2+) content characteristics in human type II fibres being primarily determined by the CSQ1 abundance, and in type I fibres by the combined amounts of both CSQ1 and CSQ2.

Endogenous and maximal sarcoplasmic reticulum calcium content and calsequestrin expression in type I and type II human skeletal muscle fibres

PubMed Central

Lamboley, C R; Murphy, R M; McKenna, M J; Lamb, G D

2013-01-01

The relationship between sarcoplasmic reticulum (SR) Ca2+ content and calsequestrin (CSQ) isoforms was investigated in human skeletal muscle. A fibre-lysing assay was used to quantify the endogenous Ca2+ content and maximal Ca2+ capacity of the SR in skinned segments of type I and type II fibres from vastus lateralis muscles of young healthy adults. Western blotting of individual fibres showed the great majority contained either all fast or all slow isoforms of myosin heavy chain (MHC), troponins C and I, tropomyosin and SERCA, and that the strontium sensitivity of the force response was closely indicative of the troponin C isoform present. The endogenous SR Ca2+ content was slightly lower in type I compared to type II fibres (0.76 ± 0.03 and 0.85 ± 0.02 mmol Ca2+ per litre of fibre, respectively), with virtually all of this Ca2+ evidently being in the SR, as it could be rapidly released with a caffeine-low [Mg2+] solution (only 0.08 ± 0.01 and <0.07 mmol l−1, respectively, remaining). The maximal Ca2+ content that could be reached with SR Ca2+ loading was 1.45 ± 0.04 and 1.79 ± 0.03 mmol l−1 in type I and type II fibres, respectively (P < 0.05). In non-lysed skinned fibres, where the SR remained functional, repeated cycles of caffeine-induced Ca2+ release and subsequent Ca2+ reloading similarly indicated that (i) maximal SR Ca2+ content was lower in type I fibres than in type II fibres (P < 0.05), and (ii) the endogenous Ca2+ content represented a greater percentage of maximal content in type I fibres compared to type II fibres (∼59% and 41%, respectively, P < 0.05). Type II fibres were found on average to contain ∼3–fold more CSQ1 and ∼5–fold less CSQ2 than type I fibres (P < 0.001). The findings are consistent with the SR Ca2+ content characteristics in human type II fibres being primarily determined by the CSQ1 abundance, and in type I fibres by the combined amounts of both CSQ1 and CSQ2. PMID:24127619

Seasonal Variability of Riverine Geochemistry (87Sr/86Sr, δ13CDIC, δ44/40Ca, and major ions) in Permafrost Watersheds on the North Slope of Alaska

NASA Astrophysics Data System (ADS)

Lehn, G. O.; Jacobson, A. D.; Douglas, T. A.; McClelland, J. W.; Khosh, M. S.; Barker, A. J.

2014-12-01

Global climate models predict amplified warming at high latitudes, where permafrost soils have historically acted as a carbon sink. As warming occurs, the seasonally thawed active layer will propagate downward into previously frozen mineral-rich soil, releasing carbon and introducing unique chemical weathering signatures into rivers. We use variations in the 87Sr/86Sr, δ13CDIC, δ44/40Ca, and major ion geochemistry of rivers to track seasonal active layer dynamics. We collected water from six streams on the North Slope of Alaska between May and October, 2009 and 2010. All rivers drain continuous permafrost but three drain tussock tundra-dominated watersheds and three drain steeper bedrock catchments with minor tundra coverage. In tundra streams, elevated 87Sr/86Sr ratios, low δ13CDIC values and major ions ([Na+]+[K+]/ [Ca+2]+[Mg+2]) in spring melt runoff suggest flushing of shallow soils with relatively low carbonate content. By July, 87Sr/86Sr ratios stabilize at relatively low values and δ13CDIC at relatively higher values, indicating the active layer thawed into deeper carbonate-rich soils. In bedrock streams, elevated 87Sr/86Sr ratios correlate with high discharge. By late fall, bedrock stream 87Sr/86Sr ratios decrease steadily, consistent with increased carbonate weathering. Nearly constant δ13CDIC values and high [SO4-2] for most of the melt season imply significant sulfuric acid-carbonate weathering in bedrock streams. δ13CDIC values suggest a shift to carbonic acid-carbonate weathering in late 2010, possibly due to limited oxygen for pyrite oxidation during freezing of the active layer. δ44/40Ca values in both tundra and bedrock streams increase during the seasons, suggesting increased uptake of 40Ca by plants. δ44/40Ca values of rivers are at least 0.1-0.2‰ higher than their watershed soils, rocks and sediments, suggesting significant plant uptake. Our findings show how seasonal changes in mineral weathering have potential for tracking active layer dynamics.

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

Beninson, D.; Ramos, E.; Touzet, R.

The results of measurements of {sup 90}Sr and natural Sr in the bones of children and the food products of the corresponding diets are presented and discussed. The data show that the levels of {sup 90}Sr/Ca in the total diet are very close to that of milk for children during the first year of life. Typical incorporations in very small children, during the last three years in Argentina, were of the order of several pC of {sup 90}Sr and about a mg of natural Sr per day. Results of measurements of {sup 90}Sr in bone samples of distinct age groups,more » for which detailed information on the dietetic history can be obtained, are presented. The typical levels were of the orders of one pC/g Ca. Natural strontium in the bone appears to increase slowly with age. The factors of discrimination were estimated for various age groups, using a simple model and data on the diet and bones. The evaluations of {sup 90}Sr and natural Sr agree adequately and suggest that babies discriminate less between the strontiums than older children and adults. (tr-auth)« less

Mechanisms to Explain the Elemental Composition of the Initial Aragonite Shell of Larval Oysters

NASA Astrophysics Data System (ADS)

Haley, Brian A.; Hales, Burke; Brunner, Elizabeth L.; Kovalchik, Kevin; Waldbusser, George G.

2018-04-01

Calcifying organisms face increasing stress from the changing carbonate chemistry of an acidifying ocean, particularly bivalve larvae that live in upwelling regions of the world, such as the coastal and estuarine waters of Oregon (USA). Arguably the first and most significant developmental hurdle faced by larval oysters is formation of their initial prodissoconch I (PDI) shell, upon which further ontological development depends. We measured the minor metal compositions (Sr/Ca, Mg/Ca) of this aragonitic PDI shell and of post-PDI larval Crassostrea gigas shell, as well as the water they were reared in, over ˜20 days for a May and an August cohort in 2011, during which time there was no period of carbonate under-saturation. After testing various methods, we successfully isolated the shell from organic tissue using a 5% active chlorine bleach solution. Elemental compositions (Sr, Mg, C, N) of the shells post-treatment showed that shell Sr/Ca ranged from 1.55 to 1.82 mmol/mol; Mg/Ca from 0.60 to 1.11 mmol/mol, similar to the few comparable published data for larval oyster aragonite compositions. We compare these data in light of possible biomineralization mechanisms: an amorphous calcium carbonate (ACC) path, an intercellular path, and a direct-from-seawater path to shell formation via biologically induced inorganic precipitation of aragonite. The last option provides a mechanistic explanation for: (1) the accelerated precipitation rates of biogenic calcification in the absence of a calcifying fluid; (2) consistently elevated precipitation rates at varying ambient-water saturation states; and (3) the high Ca-selectivity of the early larval calcification despite rapid precipitation rates.

Optical characteristics of sol-gel derived M3SiO5:Eu3+ (M = Sr, Ca and Mg) nanophosphors for display device technology

NASA Astrophysics Data System (ADS)

Singh, Devender; Sheoran, Suman; Bhagwan, Shri; Kadyan, Sonika

2016-12-01

A series of trivalent europium-doped M3SiO5 (M = Sr, Ca and Mg) phosphors were synthesized using sol-gel process at 950°C. Samples were further reheated at high temperature to study the effect of reheating on crystal structure and optical characteristics. X-ray diffraction measurement of these materials was carried out to know the crystal structure. Diffraction pattern showed monoclinic structure having space group Cm for Ca3SiO5 materials. However, tetragonal phase with space group P4/ncc was observed for Sr3SiO5 materials. Mg3SiO5 material show mixed diffraction peaks at 950 and 1,150°C. Transmission electron microscopic analysis was used to estimate the particle size of silicates. Photoluminescence emission spectra were recorded to check the luminescence properties of prepared materials. These phosphors exhibited a strong orange-red light under excitation at 395 nm. The prepared phosphors exhibited most intense peak in 610-620 nm region due to the 5D0→7F2 transition of europium (III) ion available in lattice. To overcome the deficiency of red silicates, M3SiO5 materials were explored and they might be integrated with ultraviolet LEDs to generate light which may be suitable for display applications.

Survey on composition and bioconcentration potential of 12 metallic elements in King Bolete (Boletus edulis) mushroom that emerged at 11 spatially distant sites.

PubMed

Falandysz, Jerzy; Frankowska, Aneta; Jarzynska, Grazyna; Dryzałowska, Anna; Kojta, Anna K; Zhang, Dan

2011-01-01

This paper provides data on baseline concentrations, interrelationships and bioconcentration potential of 12 metallic elements by King Bolete collected from 11 spatially distant sites across Poland. There are significant differences in concentrations of metals (Al, Ba, Ca, Cd, Cu, Fe, K, Mg, Mn, Na, Sr, Zn) and their bioconcentration potential in King Bolete Boletus edulis at 11 spatially distant sites surveyed across Poland. These have resulted from significant geographical differences in trace metal concentrations in a layer (0-10 cm) of organic and mineral soil underneath to fruiting bodies and possible local bioavailabilities of macro- (Ca, K, Mg, Na) and trace metals (Al, Ba, Cd, Cu, Fe, Mn, Sr, Zn) to King Bolete. The use of highly appreciated wild-grown edible King Bolete mushroom has established a baseline measure of regional minerals status, heavy metals pollution and assessment of intake rates for wild mushroom dish fanciers against which future changes can be compared. Data on Cd, Cu and Zn from this study and from literature search can be useful to set the maximum limit of these metals in King Bolete collected from uncontaminated (background) areas. In this report also reviewed are data on Al, Ba, Ca, Cd, Cu, Fe, K, Mg, Mn, Na, Sr and Zn accumulation in King Bolete.

Impact of salinity on element incorporation in two benthic foraminiferal species with contrasting magnesium contents

NASA Astrophysics Data System (ADS)

Geerken, Esmee; de Nooijer, Lennart Jan; van Dijk, Inge; Reichart, Gert-Jan

2018-04-01

Accurate reconstructions of seawater salinity could provide valuable constraints for studying past ocean circulation, the hydrological cycle and sea level change. Controlled growth experiments and field studies have shown the potential of foraminiferal Na / Ca as a direct salinity proxy. Incorporation of minor and trace elements in foraminiferal shell carbonate varies, however, greatly between species and hence extrapolating calibrations to other species needs validation by additional (culturing) studies. Salinity is also known to impact other foraminiferal carbonate-based proxies, such as Mg / Ca for temperature and Sr / Ca for sea water carbonate chemistry. Better constraints on the role of salinity on these proxies will therefore improve their reliability. Using a controlled growth experiment spanning a salinity range of 20 units and analysis of element composition on single chambers using laser ablation-Q-ICP-MS, we show here that Na / Ca correlates positively with salinity in two benthic foraminiferal species (Ammonia tepida and Amphistegina lessonii). The Na / Ca values differ between the two species, with an approximately 2-fold higher Na / Ca in A. lessonii than in A. tepida, coinciding with an offset in their Mg content ( ˜ 35 mmol mol-2 versus ˜ 2.5 mmol mol-1 for A. lessonii and A. tepida, respectively). Despite the offset in average Na / Ca values, the slopes of the Na / Ca-salinity regressions are similar between these two species (0.077 versus 0.064 mmol mol-1 change per salinity unit). In addition, Mg / Ca and Sr / Ca are positively correlated with salinity in cultured A. tepida but show no correlation with salinity for A. lessonii. Electron microprobe mapping of incorporated Na and Mg of the cultured specimens shows that within chamber walls of A. lessonii, Na / Ca and Mg / Ca occur in elevated bands in close proximity to the primary organic lining. Between species, Mg banding is relatively similar, even though Mg content is 10 times lower and that variation within the chamber wall is much less pronounced in A. tepida. In addition, Na banding is much less prominent in this species than it is in A. lessonii. Inter-species differences in element banding reported here are hypothesized to be caused by differences in biomineralization controls responsible for element uptake.

Highly oriented Bi-based thin films with zero resistance at 106 K

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

Kula, W.; Sobolewski, R.; Gorecka, J.

1991-03-01

This paper reports on fabrication and characterization of nearly single-phase superconducting Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} thin films. The films were dc magnetron sputtered from heavily Pb-doped (Pb/Bi molar ratios up to 1.25), sintered targets on unheated MgO, SrTiO{sub 3}, CaNdAlO{sub 4}, and SrLaAlO{sub 4} single crystals. For the films grown on the (100) oriented MgO substrate, less than 1 hour of annealing in air at 870{degrees} C was sufficient to obtain more than 90% of the 110-K-phase material, with highly c-axis oriented crystalline structure and zero resistivity at 106 K. The films fabricated on the other substrates alsomore » exhibited a narrow superconducting transition and were fully superconducting above 100 K, but they consisted of a mixed-phase material with a large percentage of the 80 K phase.« less

Influence of strontium on structure, sintering and biodegradation behaviour of CaO-MgO-SrO-SiO2-P2O5-CaF2 glasses

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

Goel, Ashutosh; Rajagopal, Raghu R.; Ferreira, Jose M.

The present study investigates the influence of SrO on structure, apatite forming ability, physico-chemical degradation and sintering behaviour of melt-quenched bioactive glasses with composition: mol.% (36.07 – x) CaO – x SrO - 19.24 MgO – 5.61 P2O5 – 38.49 SiO2 – 0.59 CaF2, where x varies between 0 – 10. The detailed structural analysis of glasses has been made by infra red spectroscopy (FTIR) and magic angle spinning-nuclear magnetic resonance spectroscopy (MAS-NMR). Silicon was predominantly present as Q2 (Si) species while phosphorus was found in orthophosphate type environment in all the investigated glasses. The apatite forming ability of glassesmore » was investigated by immersion of glass powders in simulated body fluid (SBF) for time durations varying between 1 h – 7 days. While increasing Sr2+/Ca2+ ratio in glasses did not affect the structure of glasses significantly, their apatite forming ability was decreased considerably. Further, physico-chemical degradation of glasses has been studied in accordance with ISO 10993-14 “Biological evaluation of medical devices – Part 14: Identification and quantification of degradation products from ceramics” in Tris HCl and citric acid buffer and the possible implications of ion release profile from glasses in different solutions has been discussed. The addition of strontium in glasses led to a 7-fold decrease in chemical degradation of glasses in Tris-HCl. The sintering of glass powders rendered glass-ceramics (GCs) with varying degree of crystallinity and good flexural strength (98-131 MPa) where the mechanical properties depend on the nature and amount of crystalline phases present in GCs.« less

Cardioprotective effect of Sida rhomboidea. Roxb extract against isoproterenol induced myocardial necrosis in rats.

PubMed

Thounaojam, Menaka C; Jadeja, Ravirajsinh N; Ansarullah; Karn, Sanjay S; Shah, Jigar D; Patel, Dipak K; Salunke, Sunita P; Padate, Geeta S; Devkar, Ranjitsinh V; Ramachandran, A V

2011-05-01

The present study investigates cardioprotective effect of Sida rhomboidea. Roxb (SR) extract on heart weight, plasma lipid profile, plasma marker enzymes, lipid peroxidation, endogenous enzymatic and non-enzymatic antioxidants and membrane bound ATPases against isoproterenol (IP) induced myocardial necrosis (MN) in rats. Rats treated with IP (85 mg/kg, s.c.) recorded significant (p<0.05) increment in heart weight, plasma lipid profile, plasma marker enzymes of cardiac damage, cardiac lipid peroxidation (LPO) and activity levels of Ca(+2) ATPase whereas there was significant (p<0.05) decrease in plasma HDL, cardiac endogenous enzymatic and non-enzymatic antioxidants, Na(+)-K(+) ATPase and Mg(+2) ATPase. Pre-treatment with SR extract (400 mg/kg per day, p.o.) for 30 consecutive days followed by IP injections on days 29th and 30th, showed significant (p<0.05) decrease in heart weight, plasma lipid profile, plasma marker enzymes of cardiac damage, cardiac lipid peroxidation, Ca(+2) ATPase and significant increase in plasma HDL, cardiac endogenous enzymatic and non-enzymatic antioxidants, Na(+)-K(+) ATPase and Mg(+2) ATPase compared to IP treated group. Hence, this study is the first scientific report on cardioprotective effect of SR against IP induced MN in rats. Copyright © 2010 Elsevier GmbH. All rights reserved.

Mechanisms of intragastric pH sensing.

PubMed

Goo, Tyralee; Akiba, Yasutada; Kaunitz, Jonathan D

2010-12-01

Luminal amino acids and lack of luminal acidity as a result of acid neutralization by intragastric foodstuffs are powerful signals for acid secretion. Although the hormonal and neural pathways underlying this regulatory mechanism are well understood, the nature of the gastric luminal pH sensor has been enigmatic. In clinical studies, high pH, tryptic peptides, and luminal divalent metals (Ca(2+) and Mg(2+)) increase gastrin release and acid production. The calcium-sensing receptor (CaSR), first described in the parathyroid gland but expressed on gastric G cells, is a logical candidate for the gastric acid sensor. Because CaSR ligands include amino acids and divalent metals, and because extracellular pH affects ligand binding in the pH range of the gastric content, its pH, metal, and nutrient-sensing functions are consistent with physiologic observations. The CaSR is thus an attractive candidate for the gastric luminal sensor that is part of the neuroendocrine negative regulatory loop for acid secretion.

Analysis and design of a calcium-based sulfur sorbent for applications in integrated gasification combined cycle energy systems

NASA Astrophysics Data System (ADS)

Hasler, David Johann Ludwig

The reactivity of various Ca-based sorbent materials in pelletized form with H2S or CO2 was investigated at high temperatures (750--880°C). An extensive study was conducted to compare the performance of sorbent pellets derived from plaster of Paris and limestone. Multicycle absorption and regeneration tests showed that plaster-based pellets out performed the limestone-based pellets primarily due to a higher surface area and mesoporosity. The effect of pore-modifiers on the reactivity of limestone with H 2S was investigated by incorporating additives such as cornstarch, graphite and polyvinylalcohol (PVA) in the sorbent. Multicycle sulfidation and regeneration tests of the modified sorbent showed that starch did not improve the reactivity of the limestone, graphite reduced the reactivity, while PVA improved it. The effect of the chemical additives MgO and SrO on the performance of CaO-based sorbent pellets was investigated. The effect of MgO was tested by starting with materials that contained MgCO3 in a natural form, such as dolomite. The effect of SrO was tested by starting with SrCO 3 either co-precipitated with CaCO3 or by wet-mixing SrCO 3 with limestone in slurry form. The MgO was found to improve the thermal stability of the CaO-based sorbent but lowered the overall absorption capacity of the material when reacted with CO2 or H2S, while SrO decreased the thermal stability of the sorbent when it was reacted with CO2; no absorption tests were run with H2S. A study of the performance of pelletized CaO-based cores coated with a refractory material such as alumina and limestone or alumina and kaolin was conducted. The reactivity of the core and shell pellets with H2S was determined. The strength and durability of the pellets were determined by using crushing strength analysis and abrasion resistance tests. Pellets coated with either alumina and limestone or alumina and kaolin proved to be strong and adequate for use in industrial reactors. A semi-empirical mathematical model was developed to represent the reaction of H2S with a sorbent pellet. The model was based on the well-known shrinking core model and it was applied successfully for the analysis of both pellet cores and core and shell pellets reacting with H2S.

Calcium and strontium isotope fractionation during precipitation from aqueous solutions as a function of temperature and reaction rate; II. Aragonite

NASA Astrophysics Data System (ADS)

AlKhatib, Mahmoud; Eisenhauer, Anton

2017-07-01

In order to study Strontium (Sr) partitioning and isotope fractionation of Sr and Calcium (Ca) in aragonite we performed precipitation experiments decoupling temperature and precipitation rates (R∗, μmol/m2 h) in the interval of about 2.3-4.5 μmol/m2 h. Aragonite is the only pure solid phase precipitated from a stirred solutions exposed to an atmosphere of NH3 and CO2 gases throughout the spontaneous decomposition of (NH4)2CO3. The order of reaction with respect to Ca ions is one and independent of temperature. However, the order of reaction with respect to the dissolved inorganic carbon (DIC) is temperature dependent and decreases from three via two to one as temperature increases from 12.5 and 25.0 to 37.5 °C, respectively. Strontium distribution coefficient (DSr) increases with decreasing temperature. However, R∗ responds differently depending on the initial Sr/Ca concentration and temperature: at 37.5 °C DSr increase as a function of increasing R∗ but decrease for 12.5 and 25 °C. Not seen at 12.5 and 37.5 °C but at 25 °C the DSr-R∗ gradient is also changing sign depending on the initial Sr/Ca ratio. Magnesium (Mg) adsorption coefficient between aragonite and aqueous solution (DMg) decreases with temperature but increases with R∗ in the range of 2.4-3.8 μmol/m2 h. Strontium isotope fractionation (Δ88/86Sraragonite-aq) follows the kinetic type of fractionation and become increasingly negative as a function of R∗ for all temperatures. In contrast Ca isotope fractionation (Δ44/40Caaragonite-aq) shows a different behavior than the Sr isotopes. At low temperatures (12.5 and 25 °C) Ca isotope fractionation (Δ44/40Caaragonite-aq) becomes positive as a function of R∗. In contrast, at 37.5 °C and as a function of increasing R∗ the Δ44/40Caaragonite-aq show a Sr type like behavior and becomes increasingly negative. Concerning both the discrepant behavior of DSr as a function of temperature as well as for the Ca isotope fractionation as a function of temperature we infer that the switch of sign in the trace element partitioning as well as in the direction of the Ca isotope fractionation is probably due to the switch of complexation from a Ca2+-NH3 complexation at and below 25 °C to an Ca2+-H2O aquacomplex at 37.5 °C. The DSr-Δ88/86Srcalcite-aq correlation for calcite is independent of temperature in contrast to aragonite. We interpreted the strong DSr-temperature dependency of aragonite, the smaller range of Sr isotope fractionation as well as the shallower Δ88/86Srcalcite-aq-R∗ gradients to be a consequence of the increased aragonite solubility and the "Mg blocking effect". In contrast to Sr the Ca isotope fractionation values in calcite and aragonite depend both on the complexation in solution and independent on polymorphism.

Modification of Ca isotope and trace metal composition of the major matrices involved in shell formation of Mytilus edulis

NASA Astrophysics Data System (ADS)

Heinemann, Agnes; Fietzke, Jan; Eisenhauer, Anton; Zumholz, Karsten

2008-01-01

In this study we present the first combined investigation into the composition of the major matrices involved in calcification processes (surrounding water, extrapallial fluid, aragonite, and calcite) of Mytilus edulis with respect to their calcium isotope (δ44/40Ca) and elemental compositions (Sr/Ca and Mg/Ca). Our aim was to examine the suitability of Mytilus edulis as a proxy archive and to contribute to the understanding of the process of biomineralization. Mytilus edulis specimens were live collected from the Schwentine Estuary, Kiel Fjord, and North Sea (Sylt). δ44/40Ca was determined by thermal ionization mass spectrometry (TIMS) accompanied by measurements of Mg/Ca and Sr/Ca using inductively coupled plasma-optical emission spectroscopy (ICP-OES). The elemental and isotopic compositions of the investigated matrices showed systematic offsets. The carbonates are strongly depleted in their magnesium and strontium concentrations and fractionated toward lighter calcium isotope compositions relative to the surrounding Schwentine Estuary water. The opposite is observed for the extrapallial fluid (EPF). Our findings extend the results of previous studies reporting a strong biological control and the interaction of different environmental conditions influencing biomineralization. Future studies should focus on the temporal development of the interrelation between the different matrices.

Diagenesis in tephra-rich sediments from the Lesser Antilles Volcanic Arc: Pore fluid constraints

NASA Astrophysics Data System (ADS)

Murray, Natalie A.; McManus, James; Palmer, Martin R.; Haley, Brian; Manners, Hayley

2018-05-01

We present sediment pore fluid and sediment solid phase results obtained during IODP Expedition 340 from seven sites located within the Grenada Basin of the southern Lesser Antilles Volcanic Arc region. These sites are generally characterized as being low in organic carbon content and rich in calcium carbonate and volcanogenic material. In addition to the typical reactions related to organic matter diagenesis, pore fluid chemistry indicates that the diagenetic reactions fall within two broad categories; (1) reactions related to chemical exchange with volcanogenic material and (2) reactions related to carbonate dissolution, precipitation, or recrystallization. For locations dominated by reaction with volcanogenic material, these sites exhibit increases in dissolved Ca with coeval decreases in Mg. We interpret this behavior as being driven by sediment-water exchange reactions from the alteration of volcanic material that is dispersed throughout the sediment package, which likely result in formation of Mg-rich secondary authigenic clays. In contrast to this behavior, sediment sequences that exhibit decreases in Ca, Mg, Mn, and Sr with depth suggest that carbonate precipitation is an active diagenetic process affecting solute distributions. The distributions of pore fluid 87Sr/86Sr reflect these competitive diagenetic reactions between volcanic material and carbonate, which are inferred by the major cation distributions. From one site where we have solid phase 87Sr/86Sr (site U1396), the carbonate fraction is found to be generally consistent with the contemporaneous seawater isotope values. However, the 87Sr/86Sr of the non-carbonate fraction ranges from 0.7074 to 0.7052, and these values likely represent a mixture of local arc volcanic sources and trans-Atlantic eolian sources. Even at this site where there is clear evidence for diagenesis of volcanogenic material, carbonate diagenesis appears to buffer pore fluid 87Sr/86Sr from the larger changes that might be expected given the high abundance of tephra in these sediments. Part of this carbonate buffering, at this site as well as throughout the region, derives from the fact that the Sr concentration in the non-carbonate fraction is generally low (<200 ppm), whereas the carbonate fraction has Sr concentrations approaching ∼1000 ppm.

Hydrochemical effects on the life cycle, shell size, thickness, and chemistry of ostracode Cyprideis torosa

NASA Astrophysics Data System (ADS)

Marco-Barba, J.; Ito, E.; Mezquita, F.; Carbonell, E.

2006-12-01

Cyprideis torosa is a species of ostracode that inhabits and reproduces in wide range of ionic concentrations as long as (carbonate alkalinity)/Ca ratio is low. It is found in inland springs, lakes, estuaries, wetlands and seawater evaporation ponds as long as its Alk/Ca requirement is met. We collected C. torosa from 20 sites near Valencia, Spain in early spring 2004. Main environmental variables were analyzed in situ or in the lab, including temperature and concentration of major ions and oxygen isotopes. Several (2-20) live individuals were sorted out, their growth instar, sex and size measured and their shell chemistry (Mg/Ca, Sr/Ca and oxygen isotopes) analyzed. Three of these 20 sites were sampled monthly for an entire year, and its population structure, juvenile and adult shell chemistry (between 20 and 40 shells) analyzed. The chemistry of the single-visit sites varied widely with TDS from 9 to 2200 meq/L. Generally, Cl was the most dominant anion, with an averaged value of 76% (16% - 94%). CO3 plus HCO3 varied between 0.4 and 64% and SO4 between 4 and 26%. Principal Components Analysis showed that all waters follow a similar solute evolution trend of increasing Cl and SO4 and decreasing carbonate alkalinity with increasing TDS. Water δ18O also increase with TDS suggesting evaporation is the dominant driver of solute evolution. Among the sites sampled monthly, U1 is a HCO3>Ca>Mg>SO4 spring with the TDS of 9 meq/L. Sites P5 and P7 are part of a coastal wetland system of Cl>Na>Mg~SO4>Ca>HCO3 composition with TDS of 1700meq/L and 270meq/L, respectively. Water temperature varies from 12 to 30°C in P5, 13 to 33°C in P7 and 16 to 30°C in U1. At all 3 sites, the highest temperature occurred in July. The longest animals have the highest shell Ca content, and size is related to water chemistry. Both males and females are smaller in high TDS waters, and in particular, in high SO4 waters. The shell-water oxygen isotope fractionation decreases drastically at higher TDS. Cation composition of the shells show a trend of decreasing values of Mg/Cashell/Mg/Cawater with TDS as might be expected since ostracodes form low-Mg calcite shells. This trend is also observed between Sr/Cashell/Sr/ Cawater and TDS albeit with a large scatter. The changes in the population structure suggest that in U1, moulting from A-1 to A occur throughout the year whereas in P5 and P7, this moulting process is restricted to spring and fall months. This is corroborated by oxygen isotope values and Mg/Ca and Sr/Ca of adult and juvenile shells from all 3 sites: observed changes in U1 shells parallel the changes in U1 water; for P5 and P7, no such parallel is observed probably because A-1 juveniles live longer and do not moult until favorable conditions occur, and all the adults collected over the course of the year had calcified during a narrower time window. This is in agreement with the trend observed in the whole dataset.

Fidelity of the Sr/Ca proxy in recording ocean temperature in the western Atlantic coral Siderastrea siderea

USGS Publications Warehouse

Kuffner, Ilsa B.; Roberts, Kelsey E.; Flannery, Jennifer A.; Morrison, Jennifer M.; Richey, Julie

2017-01-01

Massive corals provide a useful archive of environmental variability, but careful testing of geochemical proxies in corals is necessary to validate the relationship between each proxy and environmental parameter throughout the full range of conditions experienced by the recording organisms. Here we use samples from a coral-growth study to test the hypothesis that Sr/Ca in the coral Siderastrea siderea accurately records sea-surface temperature (SST) in the subtropics (Florida, USA) along 350 km of reef tract. We test calcification rate, measured via buoyant weight, and linear extension (LE) rate, estimated with Alizarin Red-S staining, as predictors of variance in the Sr/Ca records of 39 individual S. siderea corals grown at four outer-reef locations next to in-situ temperature loggers during two, year-long periods. We found that corals with calcification rates < 1.7 mg cm−2 d−1 or < 1.7 mm yr−1 LE returned spuriously high Sr/Ca values, leading to a cold-bias in Sr/Ca-based SST estimates. The threshold-type response curves suggest that extension rate can be used as a quality-control indicator during sample and drill-path selection when using long cores for SST paleoreconstruction. For our corals that passed this quality control step, the Sr/Ca-SST proxy performed well in estimating mean annual temperature across three sites spanning 350 km of the Florida reef tract. However, there was some evidence that extreme temperature stress in 2010 (cold snap) and 2011 (SST above coral-bleaching threshold) may have caused the corals not to record the temperature extremes. Known stress events could be avoided during modern calibrations of paleoproxies.

Testing the fidelity of the Sr/Ca proxy in recording ocean temperature in a western Atlantic coral

NASA Astrophysics Data System (ADS)

Kuffner, I. B.; Roberts, K.; Flannery, J. A.; Richey, J. N.; Morrison, J. M.

2017-12-01

Massive corals provide a useful archive of environmental variability, but careful testing of geochemical proxies in corals is necessary to validate the relationship between each proxy and environmental parameter throughout the full range of conditions experienced by the recording organisms. Here we use samples from a field-based coral-growth study to test the hypothesis that Sr/Ca in the coral Siderastrea siderea accurately records sea-surface temperature (SST) in the subtropics (Florida, USA) along 350 km of reef tract. We test calcification rate, measured via buoyant weight, and linear extension (LE) rate, estimated with Alizarin Red-S staining, as predictors of variance in the Sr/Ca records of 39 individual S. siderea corals grown at four outer-reef locations next to in-situ temperature loggers during two, year-long periods. We found that corals with calcification rates less than 1.7 mg cm-2 d-1 or LE rates less than 1.7 mm yr-1 returned spuriously high Sr/Ca values, leading to a cold bias in Sr/Ca-based SST estimates. The threshold-type response curves suggest that LE rate can be used as a quality-control indicator during sample and microdrill-path selection when using long cores for SST paleoreconstruction. For our corals that passed this quality control step, the Sr/Ca-SST proxy performed well in estimating mean annual SST across three sites spanning 350 km of the Florida reef tract. However, there was some evidence that extreme temperature stress in 2010 (cold snap) and 2011 (SST above coral-bleaching threshold) may have caused the corals not to record the temperature extremes. Known stress events could be avoided during modern calibrations of paleoproxies.

A comparative study on effects of heterotrophic microbial activity on the stability of bivalve and coral carbonate during early diagenesis.

NASA Astrophysics Data System (ADS)

Lange, Skadi M.; Krause, Stefan; Immenhauser, Adrian; Ritter, Ann-Christin; Gorb, Stanislav N.; Kleinteich, Thomas; Treude, Tina

2016-04-01

Following deposition and shallow burial, marine biogenic carbonates are exposed to an environment that is geochemically affected by a manifold of bacterial metabolic redox processes. To allow for comparison of potential microbe-mediated alteration effects on carbonates, we used aragonitic bivalve shell samples and porous aragonitic coral fragments for incubation experiments in oxic- and anoxic seawater media. The media contained marine sediment slurries or bacterial cultures to mimic the natural processes in vitro. The results for anoxic experimental media containing bivalve shell samples or coral fragments displayed considerable changes in carbonate-system parameters (pH, AT, CA, DIC) and divalent-cation ratios (Mg/Ca, Mg/Sr, Sr/Ca) over time. Furthermore, incubated bivalve shell samples were altered in morphology, elemental composition and isotopic signature. Coral-fragment bearing oxic incubations were run at two temperature regimes and divalent-cation ratios of the high-temperature bacterial medium displayed withdrawal of Ca2+ and Sr2+ from the medium, thus indicating microbe-induced secondary aragonite precipitation. Analyses of coral fragments include electron-microprobe mapping and X-ray microtomography to resolve elemental sample composition and pore-space alteration features, respectively. Up to this point our results indicate that heterotrophic bacterial activity has the potential to affect surficial or open pore space in carbonate archives by increasing rates of alteration relative to sterile environments.

New insight into the ternary complexes of uranyl carbonate in seawater.

PubMed

Beccia, M R; Matara-Aho, M; Reeves, B; Roques, J; Solari, P L; Monfort, M; Moulin, C; Den Auwer, C

2017-11-01

Uranium is naturally present in seawater at trace levels and may in some cases be present at higher concentrations, due to anthropogenic nuclear activities. Understanding uranium speciation in seawater is thus essential for predicting and controlling its behavior in this specific environmental compartment and consequently, its possible impact on living organisms. The carbonato calcic complex Ca 2 UO 2 (CO 3 ) 3 was previously identified as the main uranium species in natural seawater, together with CaUO 2 (CO 3 ) 3 2- . In this work, we further investigate the role of the alkaline earth cation in the structure of the ternary uranyl-carbonate complexes. For this purpose, artificial seawater, free of Mg 2+ and Ca 2+ , using Sr 2+ as a spectroscopic probe was prepared. Combining TRLIF and EXAFS spectroscopy, together with DFT and theoretical thermodynamic calculations, evidence for the presence of Sr alkaline earth counter ion in the complex structure can be asserted. Furthermore, data suggest that when Ca 2+ is replaced by Sr 2+ , SrUO 2 (CO 3 ) 3 2- is the main complex in solution and it occurs with the presence of at least one monodentate carbonate in the uranyl coordination sphere. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of Wood Aging on Wine Mineral Composition and 87Sr/86Sr Isotopic Ratio.

PubMed

Kaya, Ayse D; Bruno de Sousa, Raúl; Curvelo-Garcia, António S; Ricardo-da-Silva, Jorge M; Catarino, Sofia

2017-06-14

The evolution of mineral composition and wine strontium isotopic ratio 87 Sr/ 86 Sr (Sr IR) during wood aging were investigated. A red wine was aged in stainless steel tanks with French oak staves (Quercus sessiliflora Salisb.), with three industrial scale replicates. Sampling was carried out after 30, 60, and 90 days of aging, and the wines were evaluated in terms of general analysis, phenolic composition, total polysaccharides, multielement composition, and Sr IR. Li, Be, Mg, Al, Sc, Ti, V, Mn, Co, Ni, Cu, Zn, Ga, Ge, As, Rb, Sr, Y, Zr, Mo, Sb, Cs, Ba, Pr, Nd, Sm, Eu, Dy, Ho, Er, Yb, Lu, Tl, and Pb elements and 87 Sr/ 86 Sr were determined by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS) and Na, K, Ca, and Fe by flame atomic absorption spectrometry (FAAS). Two-way ANOVA was applied to assess wood aging and time effect on Sr IR and mineral composition. Wood aging resulted in significantly higher concentrations of Mg, V, Co, Ni, and Sr. At the end of the aging period, wine exhibited statistically identical Sr IR compared to control. Study suggests that wood aging does not affect 87 Sr/ 86 Sr, not precluding the use of this parameter for wine traceability purposes.

Experimentally determined biomediated Sr partition coefficient for dolomite: Significance and implication for natural dolomite

NASA Astrophysics Data System (ADS)

Sánchez-Román, Mónica; McKenzie, Judith A.; de Luca Rebello Wagener, Angela; Romanek, Christopher S.; Sánchez-Navas, Antonio; Vasconcelos, Crisógono

2011-02-01

Two strains of moderately halophilic bacteria were grown in aerobic culture experiments containing gel medium to determine the Sr partition coefficient between dolomite and the medium from which it precipitates at 15 to 45 °C. The results demonstrate that Sr incorporation in dolomite does occur not by the substitution of Ca, but rather by Mg. They also suggest that Sr partitioning between the culture medium and the minerals is better described by the Nernst equation ( DSrdol = Sr dol/Sr bmi), instead of the Henderson and Kracek equation ( DSrdol = (Sr/Ca) dol/(Sr/Ca) solution. The maximum value for DSrdol occurs at 15 °C in cultures with and without sulfate, while the minimum values occur at 35 °C, where the bacteria exhibit optimal growth. For experiments at 25, 35 and 45 °C, we observed that DSrdol values are greater in cultures with sulfate than in cultures without sulfate, whereas DSrdol values are smaller in cultures with sulfate than in cultures without sulfate at 15 °C. Together, our observations suggest that DSrdol is apparently related to microbial activity, temperature and sulfate concentration, regardless of the convention used to assess the DSrdol. These results have implications for the interpretation of depositional environments of ancient dolomite. The results of our culture experiments show that higher Sr concentrations in ancient dolomite could reflect microbial mediated primary precipitation. In contrast, previous interpretations concluded that high Sr concentrations in ancient dolomites are an indication of secondary replacement of aragonite, which incorporates high Sr concentrations in its crystal lattice, reflecting a diagenetic process.

Chemical modeling for precipitation from hypersaline hydrofracturing brines.

PubMed

Zermeno-Motante, Maria I; Nieto-Delgado, Cesar; Cannon, Fred S; Cash, Colin C; Wunz, Christopher C

2016-10-15

Hypersaline hydrofracturing brines host very high salt concentrations, as high as 120,000-330,000 mg/L total dissolved solids (TDS), corresponding to ionic strengths of 2.1-5.7 mol/kg. This is 4-10 times higher than for ocean water. At such high ionic strengths, the conventional equations for computing activity coefficients no longer apply; and the complex ion-interactive Pitzer model must be invoked. The authors herein have used the Pitzer-based PHREEQC computer program to compute the appropriate activity coefficients when forming such precipitates as BaSO4, CaSO4, MgSO4, SrSO4, CaCO3, SrCO3, and BaCO3 in hydrofracturing waters. The divalent cation activity coefficients (γM) were computed in the 0.1 to 0.2 range at 2.1 mol/kg ionic strength, then by 5.7 mol/kg ionic strength, they rose to 0.2 for Ba(2+), 0.6 for Sr(2+), 0.8 for Ca(2+), and 2.1 for Mg(2+). Concurrently, the [Formula: see text] was 0.02-0.03; and [Formula: see text] was 0.01-0.02. While employing these Pitzer-derived activity coefficients, the authors then used the PHREEQC model to characterize precipitation of several of these sulfates and carbonates from actual hydrofracturing waters. Modeled precipitation matched quite well with actual laboratory experiments and full-scale operations. Also, the authors found that SrSO4 effectively co-precipitated radium from hydrofracturing brines, as discerned when monitoring (228)Ra and other beta-emitting species via liquid scintillation; and also when monitoring gamma emissions from (226)Ra. Copyright © 2016 Elsevier Ltd. All rights reserved.

Interpreting environmental signals from the coralline sponge Astrosclera willeyana

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

Fallon, S J; McCulloch, M T; Guilderson, T P

2004-06-30

Coralline sponges (sclerosponges) have been proposed as a new source for paleo subsurface temperature reconstructions by utilizing methods developed for reef-building corals. However unlike corals, coralline sponges do not have density variations making age determination difficult. In this study we examined multiple elemental rations (B, Mg, Sr, Ba, U) in the coralline sponge Astrosclera willeyana. We also measured skeletal density profiles along the outer ''living'' edge of the sponges and this data indicates significant thickening of skeletal material over intervals of 2-3 mm or 2-3 years. This suggests that any skeletal recovered environmental record from Astrosclera willeyana is an integrationmore » of signals over a 2-3 year period. Sponge Sr/Ca seemed to hold the most promise as a recorder of water temperature and we compared Sr/Ca from 2 sponges in the Great Barrier Reef and one from Truk in Micronesia to their respective sea surface temperature record. The correlations were not that strong ({approx} r=-0.5) but they were significant. It appears that the signal smoothing due to thickening or perhaps even some biologic control on Sr skeletal partitioning limits the use of Sr/Ca as an indicator of water temperature in Astrosclera willeyana.« less

An easy access to nanocrystalline alkaline earth metal fluorides - just by shaking

NASA Astrophysics Data System (ADS)

Dreger, M.; Scholz, G.; Kemnitz, E.

2012-04-01

High energy ball milling as fast, direct and solvent free method allows an easy access to nanocrystalline alkaline earth metal fluorides MF2 (M: Mg, Ca, Sr, Ba). Comparable metal sources (acetates, carbonates, hydroxides, alkoxides) were used for the reaction with NH4F as fluorinating agent. Even very simple manual shaking experiments between NH4F and the corresponding hydroxides in the stoichiometric ratio (M:F = 1:2, M: Ca, Sr, Ba) give phase pure fluorides. Moreover, comparable classical thermal reactions in closed crucibles at higher temperatures provide phase pure crystalline fluorides in nearly all cases as well.

Effect of Mg(2+), Ca(2+), Sr(2+) and Ba(2+) metal ions on the antifungal activity of ZnO nanoparticles tested against Candida albicans.

PubMed

Haja Hameed, Abdulrahman Syedahamed; Karthikeyan, Chandrasekaran; Senthil Kumar, Venugopal; Kumaresan, Subramanian; Sasikumar, Seemaisamy

2015-01-01

The antifungal ability of pure and alkaline metal ion (Mg(2+), Ca(2+), Sr(2+) and Ba(2+)) doped ZnO nanoparticles (NPs) prepared by the co-precipitation method was tested against the pathogenic yeast, Candida albicans (C. albicans), and the results showed that the Mg-doped ZnO NPs possessed greater effect than the other alkaline metal ion doped ZnO NPs. The impact of the concentration of Mg doped ZnO sample on the growth of C. albicans was also studied. The Minimal Fungicidal Concentration (MFC) of the Mg doped ZnO NPs was found to be 2000 μg/ml for which the growth of C. albicans was completely inhibited. The ZnO:Mg sample (1.5mg/ml) with various concentrations of histidine reduced the fungicidal effect of the nanoparticles against C. albicans, which was deliberately explained by the role of ROS. The ZnO:Mg sample added with 5mM of histidine scavenged the ample amount of generated ROS effectively. The binding of the NPs with fungi was observed by their FESEM images and their electrostatic attraction is confirmed by the zeta potential measurement. Copyright © 2015. Published by Elsevier B.V.

Ab initio study of the structural phase transitions of the double perovskites Sr2MWO6 (M=Zn, Ca, Mg)

NASA Astrophysics Data System (ADS)

Petralanda, U.; Etxebarria, I.

2014-02-01

We study the interplay of structural distortions in double perovskites Sr2MWO6 (M = Zn, Ca, Mg) by means of first-principles calculations and group theoretical analysis. Structure relaxations of the cubic, tetragonal, and monoclinic phases show that the ground states of the three compounds are monoclinic, although the energy difference between the monoclinic and tetragonal structures is very small in the case of Sr2MgWO6. The symmetry analysis of the distortions involved in the experimental and calculated low-temperature structures shows that the amplitude of two primary distortions associated to rigid rotations of the MX6 and WO6 octahedra are dominant, although the amplitude of a third mode related to deformations of the MX6 groups can not be neglected. The energy maps of the space spanned by the three relevant modes are calculated, and the couplings among the modes are evaluated, showing that the role of a hard secondary mode (in the Landau sense) coupled trilinearly to the two primary instabilities is crucial to stabilize the monoclinic ground state. Results suggest that the key role of the trilinear coupling among three modes could be rather common. A phenomenological theory including the effects of the chemical pressure is also developed. We find that the evolution of the stiffness constants in terms of the atomic substitution follows an accurate linear dependence and that the influence of quantum saturation of the order parameters could stabilize the tetragonal phase of Sr2MgWO6.

Factors Affecting Transformation of Micrococcus lysodeikticus

PubMed Central

Kloos, Wesley E.

1969-01-01

Relatively high transfo mation frequencies were obtained with Micrococcus lysodeikticus cells, previou[ill]sly grown in defined broth, with a tris(hydroxymethyl)-aminomethane-glutamate b uffer containing Mg++, Ca++, Ba++, or Sr++. PMID:5788710

Dissociation Energies of the Alkaline Earth Monofluorides

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

BLUE, GARY D.; GREEN, JOHN W.; EHLERT, THOMAS C.

1963-08-24

New results and theoretical calculations are presented that indicate consistently high dissocintion energies for all the alkaline earth monofluorides. Experimental results were obtained by utilizing a mass spectrometer to analyze the vapors from a heated Ta Knudsen cell containing an alkaline earth fluoride salt with Al present as a reducing agent. Ionization efficiency curves were obtained and temperature dependence investigations were made to determine the molecular precursor of the ions observed. Values of the equilibrium constants at different temperatures were used together with the free-energy functions to calculate the third law heats of reaction at 298 deg K. Data aremore » tabulated for the heats of various reactions for Al--MF2 systems with M = Mg, Ca, Sr, and Ba, and dissociation energies of MF molecules by various methods for Be, Mg, Ca, Sr, and Ba. (C.H.)« less

INFRARED MULTIPLE-PHOTON PHOTODISSOCIATION OF GAS-PHASE GROUP II METAL-NITRATE ANIONS

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

Jos Oomens; Linda Myers; Ryan Dain

2008-06-01

Infrared spectra of gas-phase metal-nitrate anions M(NO3)3-, where M=Mg2+, Ca2+, Sr2+ and Ba2+, were recorded by infrared multiple photon dissociation (IRMPD) spectroscopy. Photodissociation of each of the precursors produces NO3- through the elimination of a neutral M(NO3)2 unit. An absorption pattern characteristic of metal nitrates is observed in the IRMPD spectra, including the symmetric and antisymmetric NO3 stretches. The latter is split into high and low frequency components as a result of perturbation of the nitrate symmetry by complexation to the metal ion, and the magnitude of the splitting decreases following the trend Mg2+ > Ca2+ > Sr2+ ? Ba2+.more » The experimental spectra are in good general agreement with those obtained from density functional theory calculations.« less

Trace metal (Mg/Ca and Sr/Ca) analyses of single coccoliths by Secondary Ion Mass Spectrometry

NASA Astrophysics Data System (ADS)

Prentice, Katy; Jones, Tom Dunkley; Lees, Jackie; Young, Jeremy; Bown, Paul; Langer, Gerald; Fearn, Sarah; EIMF

2014-12-01

Here we present the first multi-species comparison of modern and fossil coccolith trace metal data obtained from single liths. We present both trace metal analyses (Sr, Ca, Mg and Al) and distribution maps of individual Paleogene fossil coccoliths obtained by Secondary Ion Mass Spectrometry (SIMS). We use this data to determine the effects of variable coccolith preservation and diagenetic calcite overgrowths on the recorded concentrations of strontium and magnesium in coccolith calcite. The analysis of coccoliths from deep-ocean sediments spanning the Eocene/Oligocene transition demonstrates that primary coccolith calcite is resistant to the neomorphism that is common in planktonic foraminifera from similar depositional environments. Instead, where present, diagenetic calcite forms distinct overgrowths over primary coccolith calcite rather than replacing this calcite. Diagenetic overgrowths on coccoliths are easily distinguished in SIMS analyses on the basis of relatively higher Mg and lower Sr concentrations than co-occurring primary coccolith calcite. This interpretation is confirmed by the comparable SIMS analyses of modern cultured coccoliths of Coccolithus braarudii. Further, with diagenetic calcite overgrowth being the principle source of bias in coccolith-based geochemical records, we infer that lithologies with lower carbonate content, deposited below the palaeo-lysocline, are more likely to produce geochemical records dominated by primary coccolith calcite than carbonate-rich sediments where overgrowth is ubiquitous. The preservation of primary coccolith carbonate in low-carbonate lithologies thus provides a reliable geochemical archive where planktonic foraminifera are absent or have undergone neomorphism.

[Application of ICP-MS to Identify the Botanic Source of Characteristic Honey in South Yunnan].

PubMed

Wei, Yue; Chen, Fang; Wang, Yong; Chen, Lan-zhen; Zhang, Xue-wen; Wang, Yan-hui; Wu, Li-ming; Zhou, Qun

2016-01-01

By adopting inductively coupled plasma mass spectrometry (ICP-MS) combined with chemometric analysis technology, 23 kinds of minerals in four kinds of characteristic honey derived from Yunnan province were analyzed. The result showed that 21 kinds of mineral elements, namely Na, Mg, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Cd, Sb, Ba, Tl and Pb, have significant differences among different varieties of honey. The results of principal component analysis (PCA) showed that the cumulative variance contribution rate of the first four main components reached 77.74%, seven kinds of elements (Mg, Ca, Mn, Co, Sr, Cd, Ba) from the first main component contained most of the honey information. Through the stepwise discriminant analysis, seven kinds of elements (Mg, K, Ca, Cr, Mn, Sr, Pb) were filtered. out and used to establish the discriminant function model, and the correct classification rates of the proposed model reached 90% and 86.7%, respectively, which showed elements contents could be effectively indicators to discriminate the four kinds characteristic honey in southern Yunnan Province. In view of all the honey samples were harvested from apiaries located at south Yunnan Province where have similar climate, soil and other environment conditions, the differences of the mineral elements contents for the honey samples mainly due to their corresponding nectariferous plant. Therefore, it is feasible to identify honey botanical source through the differences of mineral elements.

Interaction of SR 33557 with skeletal muscle calcium channel blocker receptors in the baboon: characterization of its binding sites

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

Sol-Rolland, J.; Joseph, M.; Rinaldi-Carmona, M.

1991-05-01

A procedure for the isolation of primate skeletal microsomal membranes was initiated. Membranes exhibited specific enzymatic markers such as 5'-nucleotidase, Ca{sup 2}{sup +},Mg({sup 2}{sup +})-adenosine triphosphatase and an ATP-dependent calcium uptake. Baboon skeletal microsomes bound specifically with high-affinity potent Ca{sup 2}{sup +} channel blockers such as dihydropyridine, phenylalkylamine and benzothiazepine derivatives. Scatchard analysis of equilibrium binding assays with ({sup 3}H)(+)-PN 200-110, ({sup 3}H)(-)-desmethoxyverapamil (( {sup 3}H)(-)-D888) and ({sup 3}H)-d-cis-dilitiazem were consistent with a single class of binding sites for the three radioligands. The pharmacological profile of SR 33557, an original compound with calcium antagonist properties, was investigated using radioligand bindingmore » studies. SR 33557 totally inhibited the specific binding of the three main classes of Ca{sup 2}{sup +} channel effectors and interacted allosterically with them. In addition, SR 33557 bound with high affinity to a homogeneous population of binding sites in baboon skeletal muscle.« less

High resolution stable isotopes and elemental analysis on benthic foraminifera: a 4000 yr BP record from the ria de Muros (NW Spain)

NASA Astrophysics Data System (ADS)

Pena, L. D.; Francés, G.; Diz, P.; Nombela, M. A.; Alejo, I.

2003-04-01

Carbon and oxygen stable isotopes and ICP-OES elemental ratio concentrations (Mg/Ca, Sr/Ca, Ba/Ca) from core EUGC-3B (42 45.10'N; 9 02.23'W, at 38 m.b.s.l. and 410 cm length) were measured over monospecific benthic foraminiferal samples (Nonion fabum) ranging over the last 4500 yr BP. From the oldest analysed sample (289 cm) to the core top, stable isotopes signal shows that the whole record can be separated into 4 intervals lasting each of them about 1000 yr. The lowermost interval (4300-3000 yr BP) is characterized by relatively stable delta 18O values (mean 1.77 per mil). Delta 13C is relatively low except for a maximum around 3300 cal BP (-1.50 per mil). An abrupt decrease down to the minimum value in delta 13C (-4.41 per mil) is accomplished in approximately 200 yr. Mg/Ca and Ba/Ca match perfectly this event, both of them showing the respective maxima values. Sr/Ca has a very similar behaviour to that of delta 13C but with smoother fluctuations. We attribute high values of delta 13C, Sr/Ca and Ba/Ca to periods of enhanced coastal productivity, probably due to reinforced upwelling events in the region. According to Mg/Ca signal this reinforcement took place during a relatively warmer period. The most remarkable feature during the two next periods (3000-1900 yr BP and 1900-1000 yr BP) consists of a stepwise increase of delta 13C values punctuated by a sharp decrease at the end of each interval. All the remaining proxies exhibit a nearly constant trend over these intervals. Each period can be interpreted as a weak enhance of marine productivity that the system does not hold up and finally aborts. The most recent interval represents the establishment of current conditions in the coastal system. The most conspicuous event from this interval consists of an abrupt decrease of the delta 18O that lasted for 300 yr. This event could be correlated with the well recognized warm climatic event known as the Medieval Warm Period. However the Mg/Ca ratio does not show high values at this moment. Therefore a salinity decrease caused by enhanced run off can be also invoked to explain low delta 18O values. A hypothetical warmer and wetter period could support both interpretations. Acknowledgements to EU HOLSMEER Project (EVK2-CT-2000-00060) and Paleostudies Program. Contribution 269 of EX-1.

[Determination of 22 inorganic elements in different parts of Lantana camara by ICP-OES].

PubMed

Zhou, Wei-ming; Wang, Ru-yi; Chen, Liu-sheng; Huang, Chuan-bin

2014-10-01

To determine the contents of 22 inorganic elements in different parts of Lantana camara by inductively coupled plasma optical emission spectroscopy (ICP-OES). HNO3-H2O2 digested system was used to completely decompose the organic compounds effectually by microwave digestion. The 22 inorganic elements such as K, Ca, Mg, Fe, Al, Na, Zn, Mn and Cr were determined by ICP-OES under set up working conditions. The contents of K, Ca and Mg were the most in different parts of Lantana camara; The contents of K, Ca, Mg, Mn, Sr and Cu in the leaf were more those that in the root and branch; The contents of Fe, Na, Cr and Ni in the root were more than those in the leaf and branch; The contents of Mn, Zn, Sr and Cu in the branch were more than those in the root and the leaf; The contents of Pb and Cd were higher than the national standard and Cr had high content in different parts of Lantana camara. The determination method is quick, easy and accurate with high sensitivity, which can determine the contents of 22 inorganic elements accurately in different parts of Lantana camara.

Sea surface temperature variability in the Gulf of Mexico from 1734-2008 CE: A reconstruction using cross-dated Sr/Ca records from the coral Siderastrea siderea

NASA Astrophysics Data System (ADS)

DeLong, K. L.; Flannery, J. A.; Quinn, T. M.; Maupin, C. R.; Lin, K.; Shen, C.

2013-12-01

Sea surface temperature (SST) variability in the Gulf of Mexico impacts climate in Central and North America because the Gulf is a major source of moisture and is a source region for the Gulf Stream, which transports ocean heat northward. Here we use skeletal variations in coral Sr/Ca from three Siderastrea siderea coral colonies within the Dry Tortugas National Park in the southeastern Gulf of Mexico (24°42'N, 82°48'W) to develop 274 years of monthly-resolved SST variations. The cross-dated chronology, determined by counting annual density bands and correlating Sr/Ca variations, is verified by four replicated high precision 230Th dates (×1.7-37 years, 2σ). Calibration and verification of our replicated coral Sr/Ca-SST reconstruction with Dry Tortugas SST (r = 0.98 and 0.55 for monthly and 36-month smoothed, respectively; 1992-2008 CE) and Key West, Florida surface air temperature (1895-2008 CE) measurements reveals similar covariance (r = 0.96 and 0.56 for monthly and 36-month smoothed, respectively). The absolute coral SST reconstruction is consistent with SST recorded at the Dry Tortugas lighthouse from 1879-1907 CE indicating that this coral Sr/Ca-SST relationship is stable on centennial time scales. The Sr/Ca-SST reconstruction reveals ~2.0°C interannual variability, ~1.5°C decadal fluctuations, and a 0.7°C warming trend for the past 274 years. Secular variability in our reconstruction is similar to approximately decadally resolved planktic foraminifer Mg/Ca records from the northern Gulf of Mexico. The coral Sr/Ca-SST reconstruction reveals colder decades (~1.5°C) suggesting a reduction in moisture and ocean heat flux from the Gulf of Mexico. We find winter extremes are more variable than summer extremes (×2.2°C vs. ×1.6°C, 2σ) with a stronger warming trend (1°C) in the summers suggesting continued warming may increase coral bleaching.

Formation waters from Mississippian-Pennsylvanian reservoirs, Illinois basin, USA: Chemical and isotopic constraints on evolution and migration

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

Stueber, A.M.; Walter, L.M.; Huston, T.J.

1993-02-01

We have analyzed a suite of seventy-four formation-water samples from Mississippian and Pennsylvanian carbonate and siliciclastic strata in the Illinois basin for major, minor, and trace element concentrations and for strontium isotopic composition. A subset of these samples was also analyzed for boron isotopic composition. Data are used to interpret origin of salinity and chemical and Sr isotopic evolution of the brines and in comparison with a similar data set from an earlier study of basin formation waters from Silurian-Devonian reservoirs. Systematics of Cl-Br-Na show that present Mississippian-Pennsylvanian brine salinity can be explained by a combination of subaerial seawater evaporationmore » short of halite saturation and subsurface dissolution of halite from an evaporite zone in the middle Mississippian St. Louis Limestone, along with extensive dilution by mixing with meteoric waters. Additional diagenetic modifications in the subsurface interpreted from cation/Br ratios include K depletion through interaction with clay minerals, Ca enrichment, and Mg depletion by dolomitization, and Sr enrichment through CaCO[sub 3] recrystallization and dolomitization. Ste. Genevieve Limestone (middle Mississippian) formation waters show [sup 87]Sr/[sup 86]Sr ratios in the range 0.70782-0.70900, whereas waters from the siliciclastic reservoirs are in the rante 0.70900-0.71052. Inverse correlations between [sup 87]Sr/[sup 86]Sr and B,Li, and Mg concentrations suggest that the brines acquired radiogenic [sup 87]Sr through interaction with siliciclastic minerals. Completely unsystematic relations between [sup 87]Fr/[sup 86]Sr and 1/Sr are observed; Sr concentrations in Ste. Genevieve and Aux Vases (middle Mississippian) waters appear to be buffered by equilibrium with respect to SrSo[sub 4]. These formation waters are distinguished from Silurian-Devonian brines in the basin by elevated Cl/Br and Na/Br ratios and by unsystematic Sr isotope relationships.« less

40 CFR 799.6786 - TSCA water solubility: Generator column method.

Code of Federal Regulations, 2011 CFR

2011-07-01

..., concentrations expressed in milligrams per liter (mg/L) are approximately equal to 10−3 g/103 g or parts per... section. (E) Two 6-port high-pressure rotary switching valves in paragraph (c)(3)(ii) of this section. (F... Seawater1 Chemical Amount NaF 3 mg SrCl2.6H2O 20 mg H3BO3 30 mg KBr 100 mg KCl 700 mg CaCl2.2H2O 1.47 gram...

[Analysis of changes in minerals contents during cider fermentation process by inductively coupled plasma mass spectrometry].

PubMed

Ye, Meng-qi; Yue, Tian-li; Gao, Zhen-peng; Yuan, Ya-hong; Nie, Gang

2015-01-01

The changes in mineral elements during cider fermentation process were determined using ICP-MS. The results showed that the main minerals in the fermentation liquor included K, Na, Ca, Mg, Fe, Mn, Zn, Cu, Sr and B. The content of K was the highest in both the apple juice and the cider, being 1 853. 83 and 1 654. 38 mg . L-1 respectively. The content of minerals was in dynamic changes along with the fermentation process. As a whole, during 72-120 h and 144-216 h, most of the minerals contents underwent great fluctuation. Especially when fermented for 192 h, the content of most of the minerals reached peak value or valley value. The content of Fe and Zn achieved their peak value, while the content of K, Na, Ca, Mg, Mn and B achieved valley value. But during the following 24 h, the content of minerals underwent a sharp reversal. After fermentation, the content of K, Mg, Cu, Zn and B decreased significantly, while the content of Na, Ca, Mn, Fe and Sr did not change significantly. The correlational analysis was conducted to evaluate the correlation between the mineral elements, and the result showed that the correlation between Ca and Mn was the most significant, with the correlation index reaching 0. 924. The information of this study will supply sufficient data for the fermentation process control and quality improvement of cider.

Prevention of ventricular arrhythmia and calcium dysregulation in a catecholaminergic polymorphic ventricular tachycardia mouse model carrying calsequestrin-2 mutation.

PubMed

Alcalai, Ronny; Wakimoto, Hiroko; Arad, Michael; Planer, David; Konno, Tetsuo; Wang, Libin; Seidman, Jon G; Seidman, Christine E; Berul, Charles I

2011-03-01

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a familial arrhythmic syndrome caused by mutations in genes encoding the calcium-regulation proteins cardiac ryanodine receptor (RyR2) or calsequestrin-2 (CASQ2). Mechanistic studies indicate that CPVT is mediated by diastolic Ca(2+) overload and increased Ca(2+) leak through the RyR2 channel, implying that treatment targeting these defects might be efficacious in CPVT. CPVT mouse models that lack CASQ2 were treated with Ca(2+) -channel inhibitors, β-adrenergic inhibitors, or Mg(2+) . Treatment effects on ventricular arrhythmia, sarcoplasmic reticulum (SR) protein expression and Ca(2+) transients of isolated myocytes were assessed. Each study agent reduced the frequency of stress-induced ventricular arrhythmia in mutant mice. The Ca(2+) channel blocker verapamil was most efficacious and completely prevented arrhythmia in 85% of mice. Verapamil significantly increased the SR Ca(2+) content in mutant myocytes, diminished diastolic Ca(2+) overload, increased systolic Ca(2+) amplitude, and prevented Ca(2+) oscillations in stressed mutant myocytes. Ca(2+) channel inhibition by verapamil rectified abnormal calcium handling in CPVT myocytes and prevented ventricular arrhythmias. Verapamil-induced partial normalization of SR Ca(2+) content in mutant myocytes implicates CASQ2 as modulator of RyR2 activity, rather than or in addition to, Ca(2+) buffer protein. Agents such as verapamil that attenuate cardiomyocyte calcium overload are appropriate for assessing clinical efficacy in human CPVT. © 2010 Wiley Periodicals, Inc.

Prevention of Ventricular Arrhythmia and Calcium Dysregulation in a Catecholaminergic Polymorphic Ventricular Tachycardia Mouse Model Carrying Calsequestrin-2 Mutation

PubMed Central

Alcalai, Ronny; Wakimoto, Hiroko; Arad, Michael; Planer, David; Konno, Tetsuo; Wang, Libin; Seidman, Jon G.; Seidman, Christine E.; Berul, Charles I

2010-01-01

Background Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a familial arrhythmic syndrome caused by mutations in genes encoding the calcium-regulation proteins cardiac ryanodine receptor (RyR2) or calsequestrin-2 (CASQ2). Mechanistic studies indicate that CPVT is mediated by diastolic Ca2+ overload and increased Ca2+ leak through the RyR2 channel, implying that treatment targeting these defects might be efficacious in CPVT. Method and results CPVT mouse models that lack CASQ2 were treated with Ca2+-channel inhibitors, β-adrenergic inhibitors, or Mg2+. Treatment effects on ventricular arrhythmia, sarcoplasmic reticulum (SR) protein expression and Ca2+ transients of isolated myocytes were assessed. Each study agent reduced the frequency of stress-induced ventricular arrhythmia in mutant mice. The Ca2+ channel blocker verapamil was most efficacious and completely prevented arrhythmia in 85% of mice. Verapamil significantly increased the SR Ca2+ content in mutant myocytes, diminished diastolic Ca2+ overload, increased systolic Ca2+ amplitude, and prevented Ca2+ oscillations in stressed mutant myocytes. Conclusions Ca2+ channel inhibition by verapamil rectified abnormal calcium handling in CPVT myocytes and prevented ventricular arrhythmias. Verapamil-induced partial normalization of SR Ca2+ content in mutant myocytes implicates CASQ2 as modulator of RyR2 activity, rather than or in addition to, Ca2+ buffer protein. Agents such as verapamil that attenuate cardiomyocyte calcium overload are appropriate for assessing clinical efficacy in human CPVT. PMID:20807279

Materials and methods for the separation of oxygen from air

DOEpatents

MacKay, Richard; Schwartz, Michael; Sammells, Anthony F.

2003-07-15

Metal oxides particularly useful for the manufacture of catalytic membranes for gas-phase oxygen separation processes having the formula: O.sub.5+z where: x and x' are greater than 0; y and y' are greater than 0; x+x' is equal to 2; y+y' is less than or equal to 2; z is a number that makes the metal oxide charge neutral; A is an element selected from the lanthanide elements; A' is an element selected from Be, Mg, Ca, Sr, Ba and Ra; A" is an element selected from the f block lanthanides, Be, Mg, Ca, Sr, Ba and Ra; B is an element selected from the group consisting of Al, Ga, In or mixtures thereof and B" is Co or Mg, with the exception that when B" is Mg, A' and A" are not Mg. The metal oxides are useful for preparation of dense membranes which may be formed from dense thin films of the mixed metal oxide on a porous metal oxide element. The invention also provides methods and catalytic reactors for oxygen separation and oxygen enrichment of oxygen deficient gases which employ mixed conducting metal oxides of the above formula.

A novel mechanism of tandem activation of ryanodine receptors by cytosolic and SR luminal Ca2+ during excitation-contraction coupling in atrial myocytes.

PubMed

Maxwell, Joshua T; Blatter, Lothar A

2017-06-15

In atrial myocytes excitation-contraction coupling is strikingly different from ventricle because atrial myocytes lack a transverse tubule membrane system: Ca 2+ release starts in the cell periphery and propagates towards the cell centre by Ca 2+ -induced Ca 2+ release from the sarcoplasmic reticulum (SR) Ca 2+ store. The cytosolic Ca 2+ sensitivity of the ryanodine receptor (RyRs) Ca 2+ release channel is low and it is unclear how Ca 2+ release can be activated in the interior of atrial cells. Simultaneous confocal imaging of cytosolic and intra-SR calcium revealed a transient elevation of store Ca 2+ that we termed 'Ca 2+ sensitization signal'. We propose a novel paradigm of atrial ECC that is based on tandem activation of the RyRs by cytosolic and luminal Ca 2+ through a 'fire-diffuse-uptake-fire' (or FDUF) mechanism: Ca 2+ uptake by SR Ca 2+ pumps at the propagation front elevates Ca 2+ inside the SR locally, leading to luminal RyR sensitization and lowering of the cytosolic Ca 2+ activation threshold. In atrial myocytes Ca 2+ release during excitation-contraction coupling (ECC) is strikingly different from ventricular myocytes. In many species atrial myocytes lack a transverse tubule system, dividing the sarcoplasmic reticulum (SR) Ca 2+ store into the peripheral subsarcolemmnal junctional (j-SR) and the much more abundant central non-junctional (nj-SR) SR. Action potential (AP)-induced Ca 2+ entry activates Ca 2+ -induced Ca 2+ release (CICR) from j-SR ryanodine receptor (RyR) Ca 2+ release channels. Peripheral elevation of [Ca 2+ ] i initiates CICR from nj-SR and sustains propagation of CICR to the cell centre. Simultaneous confocal measurements of cytosolic ([Ca 2+ ] i ; with the fluorescent Ca 2+ indicator rhod-2) and intra-SR ([Ca 2+ ] SR ; fluo-5N) Ca 2+ in rabbit atrial myocytes revealed that Ca 2+ release from j-SR resulted in a cytosolic Ca 2+ transient of higher amplitude compared to release from nj-SR; however, the degree of depletion of j-SR [Ca 2+ ] SR was smaller than nj-SR [Ca 2+ ] SR . Similarly, Ca 2+ signals from individual release sites of the j-SR showed a larger cytosolic amplitude (Ca 2+ sparks) but smaller depletion (Ca 2+ blinks) than release from nj-SR. During AP-induced Ca 2+ release the rise of [Ca 2+ ] i detected at individual release sites of the nj-SR preceded the depletion of [Ca 2+ ] SR , and during this latency period a transient elevation of [Ca 2+ ] SR occurred. We propose that Ca 2+ release from nj-SR is activated by cytosolic and luminal Ca 2+ (tandem RyR activation) via a novel 'fire-diffuse-uptake-fire' (FDUF) mechanism. This novel paradigm of atrial ECC predicts that Ca 2+ uptake by sarco-endoplasmic reticulum Ca 2+ -ATPase (SERCA) at the propagation front elevates local [Ca 2+ ] SR , leading to luminal RyR sensitization and lowering of the activation threshold for cytosolic CICR. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

Next neighbors effect along the Ca-Sr-Ba-åkermanite join: Long-range vs. short-range structural features

NASA Astrophysics Data System (ADS)

Dondi, Michele; Ardit, Matteo; Cruciani, Giuseppe

2013-06-01

An original approach has been developed herein to explore the correlations between short- and long-range structural properties of solid solutions. X-ray diffraction (XRD) and electronic absorption spectroscopy (EAS) data were combined on a (Ca,Sr,Ba)2(Mg0.7Co0.3)Si2O7 join to determine average and local distances, respectively. Instead of varying the EAS-active ion concentration along the join, as has commonly been performed in previous studies, the constant replacement of Mg2+ by a minimal fraction of a similar size cation (Co2+) has been used to assess the effects of varying second-nearest neighbor cations (Ca, Sr, Ba) on the local distances of the first shell. A comparison between doped and un-doped series has shown that, although the overall symmetry of the Co-centered T1-site was retained, greater relaxation occurs at the CoO4 tetrahedra which become increasingly large and more distorted than the MgO4 tetrahedra. This is indicated by an increase in both the quadratic elongation (λT1) and the bond angle variance (σ2T1) distortion indices, as the whole structure expands due to an increase in size in the second-nearest neighbors. This behavior highlights the effect of the different electronic configurations of Co2+ (3d7) and Mg2+ (2p6) in spite of their very similar ionic size. Furthermore, although the overall symmetry of the Co-centered T1-site is retained, relatively limited (<10 deg) angular variations in O-Co2+-O occur along the solid solution series and large changes are found in molar absorption coefficients showing that EAS Co2+-bands are highly sensitive to change in the local structure.

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

PubMed Central

2012-01-01

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

Elevated levels of ferrimagnetic metals in foodchains supporting the Guam cluster of neurodegeneration: do metal nucleated crystal contaminants [corrected] evoke magnetic fields that initiate the progressive pathogenesis of neurodegeneration?

PubMed

Purdey, Mark

2004-01-01

Elevated levels of aluminium (Al), strontium (Sr), barium (Ba), iron (Fe), manganese (Mn) cations - combined with deficiencies of magnesium (Mg)/calcium (Ca) - have been observed in the foodchains that traditionally support the Chamorro populations affected by high incidence clusters of Alzheimer (AD), Parkinson-like (PD), motor neurone diseases and multiple sclerosis on the island of Guam. Soils drawn from the cluster region demonstrated an excessive fivefold increase in 'magnetic susceptibility' readings in relation to soils from disease free adjoining regions. A multifactorial aetiological hypothesis is proposed that pivots upon the combined exposure to high levels of natural/industrial sources of ferrimagnetic/ferroelectric compounds incorporating Al, Fe, Mn, Sr, Ba (e.g., via yam/seafood consumption or exposure to world war 2 (WW2) munitions) and to low levels of Mg/Ca in all S. Pacific locations where these clusters of neurodegenerative disease have simultaneously erupted. Once gut/blood brain barrier permeability is impaired, the increased uptake of Al, Fe, Sr, Ba, or Mn into the Mg/Ca depleted brain leads to rogue metal substitutions at the Mg/Ca vacated binding domains on various enzyme/proteoglycan groups, causing a broad ranging disruption in Mg/Ca dependent systems - such as the glutamine synthetase which prevents the accumulation of neurotoxic glutamate. The rogue metals chelate sulphate, disrupting sulphated-proteoglycan mediated inhibition of crystal proliferation, as well as its regulation of the Fibroblast growth factor receptor complex which disturbs the molecular conformation of those receptors and their regulation of transphosphorylation between intracellular kinase domains; ultimately collapsing proteoglycan mediated cell-cell signalling pathways which maintain the growth and structural integrity of the neuronal networks. The depression of Mg/Ca dependent systems in conjunction with the progressive ferrimagnetisation of the CNS due to an overload of rogue ferroelectric/ferrimagnetic metal contaminants, enables 'seeding' of metal-protein crystalline arrays that can proliferate in the proteoglycan depleted brain. The resulting magnetic field emissions initiate a free radical mediated progressive pathogenesis of neurodegeneration. The co-clustering of these various types of disease in select geographical pockets around the world suggests that all of these conditions share a common early life exposure to ferromagnetic metal nucleating agents in their multifactorial aetiology. Factors such as individual genetics, the species of metal involved, etc., dictate which specific class of disease will emerge as a delayed neurotoxic response to these environmental insults.

Evidence of Sr/Ca and Mg/Ca Temperature Invariance in Live Aragonitic Hoeglundina elegans Tests from the Little Bahama Bank

NASA Astrophysics Data System (ADS)

Blanks, J. K.; Hintz, C. J.; Chandler, G. T.; Shaw, T. J.; McCorkle, D. C.; Bernhard, J. M.

2007-12-01

Mg/Ca and Sr/Ca were analyzed from core-top individual Hoeglundina elegans aragonitic tests collected from three continental slope depths within the South Carolina and Little Bahama Bank continental slope environs (220 m to 1084 m). Our study utilized only individuals that labeled with the vital probe CellTracker Green - unlike bulk core-top material often stained with Rose Bengal, which has known inconsistencies in distinguishing live from dead foraminifera. DSr x 10 values were consistently 1.74 $ pm 0.23 across all sampling depths. The analytical error in DSr values (0.7%) determined by ICP-MS between repeated measurements on individual H. elegans tests across all depths was less than analytical error on repeated measurements from standards. Variation in DSr values was not directly explained by a linear temperature relationship (p=0.0003, R2=0.44) over the temperature range of 4.9-11.4°C with a sensitivity of 59.8 μmol/mol/1°C. The standard error by regressing DSr across temperature yields + 3.4°C, which is nearly 3x greater that reported in previous studies. Sr/Ca was more sensitive for calibrating temperature than Mg/Ca in H. elegans. Observed scatter in DSr was too great across individuals of the same size and of different sizes to resolve ontogenetic effects. However, higher DSr values were associated with smaller individuals and warmer/shallower sampling depths. The highest DSr values were observed at the intermediate sampling depth (~600 m). No significant ontogenetic relationship was found across DSr values in different sized individuals due to tighter overall constrained variance; however lower DSr values were observed from several smaller individuals. Several dead tests of H. elegans showed no significant differences in DSr values compared to live specimens cleaned by standard cleaning methods, unlike higher dead than live DMg values observed for the same individuals. There were no significant deviations in DSr across batches cleaned on separate days, unlike the observed sensitivity of DMg across batches. A subset of samples were reductively cleaned (hydrazine solution); and exhibited DMg values within analytical precision of those observed for non-reductively cleaned samples. Therefore, deviations in DMg values resulting from the removal of the reductive cleaning step did not explain analytical errors greater than published values for Mg/Ca or the high variance across same sized individuals. Variation in DMg values across the same cleaning methods and from dead individuals suggests the need for a careful look into how foraminiferal aragonite should be processed. These findings provide evidence that both Mg and Sr in benthic foraminiferal aragonite reflect factors in addition to temperature and pressure that may interfere with absolute temperature calibrations. Funded by NSF OCE 0351029, OCE 0437366, and OCE-0350794.

Regulation of axonal and dendritic growth by the extracellular calcium-sensing receptor (CaSR)

PubMed Central

Vizard, Thomas N.; O'Keeffe, Gerard W.; Gutierrez, Humberto; Kos, Claudine H.; Riccardi, Daniela; Davies, Alun M.

2009-01-01

The extracellular calcium-sensing receptor (CaSR) monitors the systemic extracellular free ionized calcium level ([Ca2+]o) in organs involved in systemic [Ca2+]o homeostasis. However, the CaSR is also expressed in the nervous system where its role is unknown. Here we find high levels of the CaSR in perinatal mouse sympathetic neurons when their axons are innervating and branching extensively in their targets. Manipulating CaSR function in these neurons by varying [Ca2+]o, using CaSR agonists and antagonists or expressing a dominant-negative CaSR markedly affects neurite growth in vitro Sympathetic neurons lacking the CaSR have smaller neurite arbors in vitro, and sympathetic innervation density is reduced in CaSR-deficient mice in vivo. Hippocampal pyramidal neurons, which also express the CaSR, have smaller dendrites when transfected with dominant-negative CaSR in postnatal organotypic cultures. Our findings reveal a crucial role for the CaSR in regulating the growth of neural processes in the peripheral and central nervous systems. PMID:18223649

Ramifications of codoping SrI2:Eu with isovalent and aliovalent impurities

NASA Astrophysics Data System (ADS)

Feng, Qingguo; Biswas, Koushik

2016-12-01

Eu2+ doped SrI2 is an important scintillator having applications in the field of radiation detection. Codoping techniques are often useful to improve the electronic response of such insulators. Using first-principles based approach, we report on the properties of SrI2:Eu and the influence of codoping with aliovalent (Na, Cs) and isovalent (Mg, Ca, Ba, and Sn) impurities. These codopants do not preferably bind with Eu and are expected to remain as isolated impurities in the SrI2 host. As isolated defects they display amphoteric behavior having, in most cases, significant ionization energies of the donor and acceptor levels. Furthermore, the acceptor states of Na, Cs, and Mg can bind with I-vacancy forming charge compensated donor-acceptor pairs. Such pairs may also bind additional holes or electrons similar to the isolated defects. Lack of deep-to-shallow behavior upon codoping and its ramifications will be discussed.

Magnesium inhibition of ryanodine-receptor calcium channels: evidence for two independent mechanisms.

PubMed

Laver, D R; Baynes, T M; Dulhunty, A F

1997-04-01

The gating of ryanodine receptor calcium release channels (RyRs) depends on myoplasmic Ca2+ and Mg2+ concentrations. RyRs from skeletal and cardiac muscle are activated by microm Ca2+ and inhibited by mm Ca2+ and Mg2+. 45Ca2+ release from skeletal SR vesicles suggests two mechanisms for Mg2+-inhibition (Meissner, Darling & Eveleth, 1986, Biochemistry 25:236-244). The present study investigates the nature of these mechanisms using measurements of single-channel activity from cardiac- and skeletal RyRs incorporated into planar lipid bilayers. Our measurements of Mg2+- and Ca2+-dependent gating kinetics confirm that there are two mechanisms for Mg2+ inhibition (Type I and II inhibition) in skeletal and cardiac RyRs. The mechanisms operate concurrently, are independent and are associated with different parts of the channel protein. Mg2+ reduces Po by competing with Ca2+ for the activation site (Type-I) or binding to more than one, and probably two low affinity inhibition sites which do not discriminate between Ca2+ and Mg2+ (Type-II). The relative contributions of the two inhibition mechanisms to the total Mg2+ effect depend on cytoplasmic [Ca2+] in such a way that Mg2+ inhibition has the properties of Types-I and II inhibition at low and high [Ca2+] respectively. Both mechanisms are equally important when [Ca2+] = 10 microm in cardiac RyRs or 1 microm in skeletal RyRs. We show that Type-I inhibition is not the sole mechanism responsible for Mg2+ inhibition, as is often assumed, and we discuss the physiological implications of this finding.

Optical materials characterization final technical report february 1, 1978-september 30, 1978. Technical note

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

Feldman, A.; Horowitz, D.; Waxter, R.M.

1979-02-01

Data obtained as part of the Optical Materials Characterization Program are summarized in this report. Room temperature values of refractive index as a function of wavelength are presented for the following materials: commercially grown KCl, reactive atmosphere processed (RAP) KCl, KCl nominally doped with 1.5% KI, hot forged CaF2, fusion cast CaF2, CaF2 doped with Er (0.001% to 3% Er), SrF2, chemical vapor deposited (CVD) ZnSe (2 specimens), and ZnS (CVD, 2 specimens). Data for the thermo-optic constant (dn/dT) and the linear thermal expansion coefficient are given for the following materials over the temperature range -180 degrees C to 200more » degrees C: Al2O3, BaF2, CaF2, CdF2, KBr, KCl, LiF, MgF2, NaCl, NaF, SrF2, ZnS (CVD), and ZnSe (CVD). The piezo-optic constants of the following materials are presented: As2S3 glass, CaF2, BaF2, Ge, KCl, fused SiO2, SrF2, a chalcogenide glass (Ge 33%, As 12%, Se 55%) and ZnSe (CVD).« less

Left ventricular wall stress and sarcoplasmic reticulum Ca(2+)-ATPase gene expression in renal hypertensive rats: dose-dependent effects of ACE inhibition and AT1-receptor blockade.

PubMed

Zierhut, W; Studer, R; Laurent, D; Kästner, S; Allegrini, P; Whitebread, S; Cumin, F; Baum, H P; de Gasparo, M; Drexler, H

1996-05-01

Cardiac hypertrophy is associated with altered Ca2+ handling and may predispose to the development of LV dysfunction and cardiac failure. At the cellular level, the re-expression of ANF represents a well-established marker of myocyte hypertrophy while the decreased expression of the sarcoplasmatic reticulum (SR) Ca(2+)-ATPase is thought o play a crucial role in the alterations of Ca2+ handling and LV function. We assessed the dose-dependent effect of chronic ACE inhibition or AT1 receptor blockade on cardiac function in relation to the cardiac expression of the SR Ca(2+)-ATPase and ANF. Renal hypertensive rats (2K-1C) were treated for 12 weeks with three different doses of the ACE inhibitor benazepril, the AT1-receptor antagonist valsartan (each drug 0.3, 3, and 10 mg/kg per day i.p.) or placebo. LV dimensions, hypertrophy and wall stress were determined in vivo by magnetic resonance imaging and the gene expressions of ANF and SR Ca(2+)-ATPase were quantified by Northern blot. Low doses of both drugs did not affect blood pressure, hypertrophy, systolic wall stress and the ANF and SR Ca(2+)-ATPase gene expression. High doses of each drug reduced systolic blood pressure, wall stress, and LV hypertrophy to a similar extent and to values comparable to normotensive, age-matched rats. In addition, high dose treatment reduced LV end-systolic and end-diastolic volume as compared to untreated 2K-1C animals and normalized the mRNA levels of both ANF and SR Ca(2+)-ATPase (as compared to normotensive animals). We conclude that in this model, high doses of ACE inhibition and AT1-receptor blockade are necessary to normalize systolic blood pressure, LV hypertrophy and systolic LV wall stress which, in turn, is associated with restoration of a normal cardiac phenotype with respect to SR Ca(2+)-ATPase and ANF and normalization of cardiac function.

Formation of the 110-K superconducting phase in Pb-doped Bi-Sr-Ca-Cu-O thin films

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

Kula, W.; Sobolewski, R.; Gorecka, J.

1991-09-15

Investigation of the 110-K Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub {ital x}} phase formation in superconducting thin films of Bi-based cuprates is reported. The films were dc magnetron sputtered from single Bi(Pb)-Sr-Ca-Cu-O targets of various stoichiometries, and subsequently annealed in air at high temperatures. The influence of the initial Pb content, annealing conditions, as well as the substrate material on the growth of the 110-K phase was investigated. We found that the films, fully superconducting above 100 K could be reproducibly fabricated on various dielectric substrates from Pb-rich targets by optimizing annealing conditions for each initial Pb/Bi ratio. Heavy Pb dopingmore » considerably accelerated formation of the 110-K phase, reducing the film annealing time to less than 1 h. Films containing, according to the x-ray measurement, more than 90% of the 110-K phase were obtained on MgO substrates, after sputtering from the Bi{sub 2}Pb{sub 2.5}Sr{sub 2}Ca{sub 2.15}Cu{sub 3.3}O{sub {ital x}} target and annealing in air for 1 h at 870 {degree}C. The films were {ital c}-axis oriented, with 4.5-K-wide superconducting transition, and zero resistivity at 106 K. Their critical current density was 2 {times} 10{sup 2} A/cm{sup 2} at 90 K, and above 10{sup 4} A/cm{sup 2} below 60 K. The growth of the 110-K phase on epitaxial substrates, such as CaNdAlO{sub 4} and SrTiO{sub 3}, was considerably deteriorated, and the presence of the 80- and 10-K phases was detected. Nevertheless, the best films deposited on these substrates were fully superconducting at 104 K and exhibited critical current densities above 2 {times} 10{sup 5} A/cm{sup 2} below 60 K{minus}one order of magnitude greater than the films deposited on MgO.« less

Properties of Ca2+ release induced by clofibric acid from the sarcoplasmic reticulum of mouse skeletal muscle fibres

PubMed Central

Ikemoto, Takaaki; Endo, Makoto

2001-01-01

To characterize the effect of clofibric acid (Clof) on the Ca2+ release mechanism in the sarcoplasmic reticulum (SR) of skeletal muscle, we analysed the properties of Clof-induced Ca2+ release under various conditions using chemically skinned skeletal muscle fibres of the mouse.Clof (>0.5 mM) released Ca2+ from the SR under Ca2+-free conditions buffered with 10 mM EGTA (pCa >8).Co-application of ryanodine and Clof at pCa >8 but not ryanodine alone reduced the Ca2+ uptake capacity of the SR. Thus, Ca2+ release induced by Clof at pCa >8 must be a result of the activation of the ryanodine receptor (RyR).At pCa >8, (i) Clof-induced Ca2+ release was inhibited by adenosine monophosphate (AMP), (ii) the inhibitory effect of Mg2+ on the Clof-induced Ca2+ release was saturated at about 1 mM, and (iii) Clof-induced Ca2+ release was not inhibited by procaine (10 mM). These results indicate that Clof may activate the RyR-Ca2+ release channels in a manner different from Ca2+-induced Ca2+ release (CICR).In addition to this unique mode of opening, Clof also enhanced the CICR mode of opening of RyR-Ca2+ release channels.Apart from CICR, a high concentration of Ca2+ might also enhance the unique mode of opening by Clof.These results suggest that some features of Ca2+ release activated by Clof are similar to those of physiological Ca2+ release (PCR) in living muscle cells and raise the possibility that Clof may be useful in elucidating the mechanism of PCR in skeletal muscle. PMID:11606311

Environmental control of U concentration and 234U/238U in speleothems at subannual resolution

NASA Astrophysics Data System (ADS)

Hu, C.; Henderson, G. M.

2003-12-01

Trace element and isotope variability in speleothems encodes a range of information about the past environment, although its interpretation is often problematic. U concentration and isotopes have frequently been analysed in speleothems in order to provide chronology, but their use as environmental proxies in their own right has not been comprehensively investigated. In this study, we have investigated the environmental controls of U in a stalagmite from the Central Yangtze Valley in China. This stalagmite grew rapidly throughout the Holocone and contains visible annual layers about 300microns thick. Analysis of a portion of the stalagmite corresponding to the 1970s by electron probe, LA-ICP-MS, and by physical subsampling indicate clear annual cycles in Sr/Ca, Mg/Ca, and Ba/Ca. The reasonably open cave structure and the correlation of Sr/Ca with Mg/Ca suggest that temperature exerts considerable control over these trace element variations. U/Ca also varies seasonally by up to 42 % and shows a clear anti-correlation with Mg/Ca (correlation coefficient -0.64). Based on the inverse relationship between U/Ca and temperature exhibited in other carbonates (e.g. corals) the speleothem U/Ca is suggested to be controlled primarily by temperature and may provide a paleo cave thermometer with less rainfall influence than Mg/Ca. Ongoing monitoring of the cave temperature and humidity will assess the robustness of this conclusion and the sensitivity of speleothem U/Ca to temperature. (234U/238U) in this stalagmite range from 1.733 to 1.872 during the Holocene. The U concentration is high enough (typically 0.48 ppm) and growth rate fast enough, that (234U/238U) can also be measured at a subannual resolution. The expected alpha-recoil control of excess 234U supply suggests that these measurements may provide a measure of the transit time of recharge waters to the stalagmite during the seasonal cycle. Such a proxy would enable deconvolution of temperature and recharge-rate control in trace element records from speleothems.

The excretion of biotrace elements using the multitracer technique in tumour-bearing mice.

PubMed

Wang, X; Tian, J; Yin, X M; Zhang, X; Wang, Q Z

2000-12-01

A radioactive multitracer solution obtained from the nuclear reaction of selenium with 25 MeV/nucleon 40Ar ions was used for investigation of trace element excretion into the faeces and urine of cancerous mice. The excretion rates of 22 elements (Na, K, Rb, Mg, Ca, Sr, Ga, As, Sc, V, Cr, Mn, Co, Fe, Y, Zr, Mo, Nb, Tc, Ru, Ag and In) were simultaneously measured under strictly identical experimental conditions, in order to clarify the excretion behavior of these elements in cancerous mice. The faecal and urinary excretion rates of Mg, Sr, Ga, As, Sc, V, Cr, Mn, Co, Fe, Y, Zr, Nb, Ru and Mo in cancerous mice, showed the in highest value at 0-8 hours. The accumulative excretion of Ca, Mo, Y and Zr was decreased and Na, Fe, Mn and Co increased in tumour-bearing mice, when compared to normal mice.

Theoretical study of the alkali and alkaline-earth monosulfides

NASA Technical Reports Server (NTRS)

Partridge, Harry; Langhoff, Stephen R.; Bauschlicher, Charles W., Jr.

1988-01-01

Ab initio calculations have been used to obtain accurate spectroscopic constants for the X2Pi and A2Sigma(+) states of the alkali sulfides and the X1Sigma(+), a3Pi, and A1Pi states of the alkaline-earth sulfides. In contrast to the alkali oxides, the alkali sulfides are found to have X2Pi ground states, due to the larger electrostatic interaction. Dissociation energies of 3.27 eV for BeS, 2.32 eV for MgS, 3.29 eV for CaS, and 3.41 eV for SrS have been obtained for the X1Sigma(+) states of the alkaline-earth sulfides, in good agreement with experimental results. Core correlation is shown to increase the Te values for the a3Pi and A1Pi states of MgS, CaS, and SrS.

Interstitial solutions and diagenesis in deeply buried marine sediments: results from the Deep Sea Drilling Project

USGS Publications Warehouse

Sayles, F.L.; Manheim, F.T.

1975-01-01

Through the Deep Sea Drilling Project samples of interstitial solutions of deeply buried marine sediments throughout the World Ocean have been obtained and analyzed. The studies have shown that in all but the most slowly deposited sediments pore fluids exhibit changes in composition upon burial. These changes can be grouped into a few consistent patterns that facilitate identification of the diagenetic reactions occurring in the sediments. Pelagic clays and slowly deposited (<1 cm/103yr) biogenic sediments are the only types that exhibit little evidence of reaction in the pore waters. In most biogenic sediments sea water undergoes considerable alteration. In sediments deposited at rates up to a few cm/103 yr the changes chiefly involve gains of Ca2+ and Sr2+ and losses of Mg2+ which balance the Ca2+ enrichment. The Ca-Mg substitution may often reach 30 mM/kg while Sr2+ may be enriched 15-fold over sea water. These changes reflect recrystallization of biogenic calcite and the substitution of Mg2+ for Ca2+ during this reaction. The Ca-Mg-carbonate formed is most likely a dolomitic phase. A related but more complex pattern is found in carbonate sediments deposited at somewhat greater rates. Ca2+ and Sr2+ enrichment is again characteristic, but Mg2+ losses exceed Ca2+ gains with the excess being balanced by SO4post staggered2- losses. The data indicate that the reactions are similar to those noted above, except that the Ca2+ released is not kept in solution but is precipitated by the HCO3post staggered- produced in SO4post staggered2- reduction. In both these types of pore waters Na+ is usually conservative, but K+ depletions are frequent. In several partly consolidated sediment sections approaching igneous basement contact, very marked interstitial calcium enrichment has been found (to 5.5 g/kg). These phenomena are marked by pronounced depletion in Na+, Si and CO2, and slight enhancement in Cl-. The changes are attributed to exchange of Na+ for Ca2+ in silicate minerals forming from submarine weathering of igneous rocks such as basalts. Water is also consumed in these reactions, accounting for minor increases in total interstitial salinity. Terrigenous, organic-rich sediments deposited rapidly along continental margins also exhibit significant evidences of alteration. Microbial reactions involving organic matter lead to complete removal of SO4post staggered2-, strong HCO3post staggered- enrichment, formation of NH4post staggered+, and methane synthesis from H2 and CO2 once SO4post staggered2- is eliminated. K+ and often Na+ (slightly) are depleted in the interstitial waters. Ca2+ depletion may occur owing to precipitation of CaCO3. In most cases interstitial Cl- remains relatively constant, but increases are noted over evaporitic strata, and decreases in interstitial Cl- are observed in some sediments adjacent to continents. ?? 1975.

Synthesis and characterization of Eu{sup 3+}-doped CaZrO{sub 3}-based perovskite-type phosphors. Part I: Determination of the Eu{sup 3+} occupied site using the ALCHEMI technique

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

Sakaida, Satoshi; Shimokawa, Yohei; Asaka, Toru

2015-07-15

Highlights: • Eu{sup 3+}-doped CaZrO{sub 3}-based compounds were synthesized by the solid state reaction. • PL emission intensity at 614 nm was changed by the second dopant cations. • The site substituted by Eu{sup 3+} cations was investigated by using XRD and ALCHEMI technique. • The dominant Eu{sup 3+} substitution site was found as the B site (Zr{sup 4+}) in the CaZrO{sub {sup 3}}. • The dominant Eu{sup 3+} substitution site could be strongly influenced by the co-dopants. - Abstract: Eu{sup 3+}-doped CaZrO{sub 3}, SrZrO{sub 3}, and Mg{sup 2+}- or Sr{sup 2+}-co-doped CaZrO{sub 3} were synthesized by conventional solid statemore » reaction and their photoluminescence (PL) properties were characterized. The Eu{sup 3+}-doped CaZrO{sub 3}-based compounds exhibited characteristic emissions of Eu{sup 3+} (f–f transition). The intensity of the main PL emission peak at 614 nm increased with Mg{sup 2+} co-doping, while it decreased with the amount of co-doped Sr{sup 2+}. The site substituted by Eu{sup 3+} cations in the CaZrO{sub 3}-based compounds was investigated by X-ray diffraction analysis and energy-dispersive X-ray analysis based on the electron channeling effects in transmission electron microscopy. The Eu{sup 3+} cations were determined to occupy mainly the B site (Zr{sup 4+}) in CaZrO{sub 3}. The dominant Eu{sup 3+} substitution site was also strongly influenced by the co-dopant, and the ionic radius of the co-dopant was identified as an important factor that determines the dominant Eu{sup 3+} substitution site.« less

The origin of Neoproterozoic Cap Carbonates: a view from Mg and Sr Isotopes

NASA Astrophysics Data System (ADS)

Liu, C.; Raub, T. D.; Evans, D. A.; Wang, Z.

2010-12-01

Neoproterozoic cap carbonates are suggested to document Earth’s transition from a ‘snowball earth’ to an ‘extreme greenhouse’ environment. Geochemistry of these rocks is essential for its paleo-environment reconstruction, and Mg and Sr isotopes can help to understand its origin and constrain geochemical evolution of the contemporary ocean. In this study, we studied Mg and Sr isotope composition of 18 cap dolostone samples from Nuccaleena formation carbonate and one from the the mixed siliciclastic transition at its base at Elatina Creek in Adelaide Geosyncline of South Australia. We established a step-leaching procedure using ammonium acetate, various concentrations of acetic acid, and HCl on four of these cap carbonate samples to untangle the isotopic signatures of its various constituent phases. 87Sr/86Sr values of the leachates in each sample decrease continuously as leaching process proceeds and sometimes rebound as silicates are dissolved. The lowest leachate 87Sr/86Sr values, down to 0.7084, are lower than the reported dolostone(~0.7096) but still higher than those of limestones overlying the dolostone in other basins(~0.7079), indicating an input of increasing level of weathering to the ocean over the course of cap-carbonate precipitation. In contrast, δ26MgDSM3 variation with progressing leaching steps exhibits a wave pattern (variation up to 0.4~0.5‰) during the leaching processes, due to different chemical affinity of Mg in various mineral phases. More importantly, Mg isotope composition of the portion that is associated with stratigraphically low, minimum Sr isotope composition is similar to those of contemporary corals (or inorganic aragonite precipitation), but up to ca. 0.6 per mil lower than stratigraphically-higher values, suggesting a warmer weather and/or more significant silicate weathering than contemporary Earth’s climate, and a transition from physical weathering to chemical weather during deglaciation.

Influences of Sr dose on the crystal structure parameters and Sr distributions of Sr-incorporated hydroxyapatite.

PubMed

Guo, D G; Hao, Y Z; Li, H Y; Fang, C Q; Sun, L J; Zhu, H; Wang, J; Huang, X F; Ni, P F; Xu, K W

2013-10-01

Stoichiometric strontium-incorporated hydroxyapatite (Sr-HA) with different Sr concentrations [Sr/(Sr+Ca)] were synthesized using a wet chemical approach and characterized by X-ray diffraction, Fourier-transformed infrared absorption, X-ray photoelectron spectroscopy, and Rietveld Structure Refinement. The crystal lattice parameter, Sr distribution, chemical state of Sr, and also the relationships between their variations and the Sr concentrations have been intensively studied. The results show that both the crystal lattice parameters and crystal plane space of Sr-HA remarkably increase with the Sr concentration increasing. Whether Sr preferably occupies the Ca(I) site or Ca(II) site after incorporated into apatite lattice depends on the Sr number incorporated into apatite. All the Sr ions completely occupy the Ca(II) sites when the Sr concentration is below 5%. With the exception of partial Sr ions occupying the Ca(II) sites, the other Sr ions start to occupy the Ca(I) sites when the Sr concentration doped in HA is beyond 10%. The ratio of Sr ions occupying the Ca(I) sites increases with the further raising Sr concentration up to 20%. The Sr ions inherit the chemical state and environment of the original Ca(I) or Ca(II) site after incorporated into apatite. Copyright © 2013 Wiley Periodicals, Inc.

Regional and interspecific variation in Sr, Ca, and Sr/Ca ratios in avian eggshells from the USA.

PubMed

Mora, Miguel A; Brattin, Bryan; Baxter, Catherine; Rivers, James W

2011-08-01

To examine regional variation in strontium (Sr), which at high concentrations may reduce eggshell quality, increase egg breakage and reproductive failure, we analyzed Sr, and calcium (Ca) concentrations and Sr/Ca ratios in eggshells from 20 avian species from California, Texas, Idaho, Kansas, and Michigan. In addition, we included data previously reported from Arizona to expand the regional comparisons and to better establish patterns of Sr, and Sr/Ca ratios in bird species across the United States. We found Sr concentrations varied significantly among regions, among species, and among foraging guilds; this variability is strongly influenced by the Sr/Ca ratios in surface water from locations close to the region where the eggshells were collected. Sr concentrations and Sr/Ca ratios were significantly higher in bird eggshells from the Volta wildlife region in the San Joaquin Valley, California and in various locales from Arizona. Sr concentrations and Sr/Ca ratios in bird eggshells from other locations in the USA were lower than those detected in these two regions. Among foraging guilds, invertivores had the highest Sr concentrations and Sr/Ca ratios and carnivores had the lowest. In general, the Sr/Ca ratio increased strongly with increasing Sr concentrations (R(2) = 0.99, P < 0.0001). There was a significant correlation (R(2) = 0.58, P < 0.0001) between Sr/Ca ratios in water and the average Sr/Ca ratios in eggshells suggesting that these values could be determined from Sr/Ca ratios in water. Eggshell thickness was poorly correlated with Sr (R(2) = 0.03) but had a significant and positive correlation with Ca and was more properly correlated by a quadratic equation (R(2) = 0.50, Thickness = 2.13 - 0.02Ca - 3.07 * 10(-5)Ca(2)). Our study provides further evidence that Sr accumulates significantly in the avian eggshell, in some regions at concentrations which could be of concern for potential negative effects on reproduction. We suggest that when assessing the effects of metals on avian reproduction in regions with high Sr deposits in rock and soil, Sr concentrations in the eggshell also should be measured to evaluate additional effects on thickness and reproduction.

The Density and Compressibility of BaCO3-SrCO3-CaCO3-K2CO3-Na2CO3-Li2CO3 Liquids: New Measurements and a Systematic Trend with Cation Field Strength

NASA Astrophysics Data System (ADS)

Hurt, S. M.; Lange, R. A.; Ai, Y.

2015-12-01

The volumetric properties of multi-component carbonate liquids are required to extend thermodynamic models that describe partial melting of the deep mantle (e.g. pMELTS; Ghiorso et al., 2003) to carbonate-bearing lithologies. Carbonate in the mantle is an important reservoir of carbon, which is released to the atmosphere as CO2 through volcanism, and thus contributes to the carbon cycle. Although MgCO3 is the most important carbonate component in the mantle, it is not possible to directly measure the 1-bar density and compressibility of MgCO3 liquid because, like other alkaline-earth carbonates, it decomposes at a temperature lower than its melting temperature. Despite this challenge, Liu and Lange (2003) and O'Leary et al. (2015) showed that the one bar molar volume, thermal expansion and compressibility of the CaCO3 liquid component could be obtained by measuring the density and sound speeds of stable liquids in the CaCO3-Li2CO3-Na2CO3-K2CO3 quaternary system at one bar. In this study, this same strategy is employed on SrCO3- and BaCO3-bearing alkali carbonate liquids. The density and sound speed of seven liquids in the SrCO3-Li2CO3-Na2CO3-K2CO3 quaternary and three liquids in the BaCO3-Li2CO3-Na2CO3-K2CO3 quaternary were measured from 739-1367K, with SrCO3 and BaCO3 concentrations ranging from 10-50 mol%. The density measurements were made using the double-bob Archimedean method and sound speeds were obtained with a frequency-sweep acoustic interferometer. The molar volume and sound speed measurements were used to calculate the isothermal compressibility of each liquid, and the results show the volumetric properties mix ideally with composition. The partial molar volume and compressibility of the SrCO3 and BaCO3 components are compared to those obtained for the CaCO3 component as a function of cation field strength. The results reveal a systematic trend that allows the partial molar volume and compressibility of the MgCO3 liquid component to be estimated.

Influence of Land Use, Discharge and Impervious Surfaces on the Geochemistry of the Anacostia River, Washington DC.

NASA Astrophysics Data System (ADS)

MacAvoy, S. E.; De Filippis, N.

2016-12-01

Challenges facing urban rivers include water stormwater runoff and changing water chemistry, not only from air and water pollution, but also from altered geology with the development of "urban karst" (concrete). The Anacostia River in Washington, D.C. has 75% of its watershed classified as urban or impervious, and is among the 10 most contaminated rivers in the USA. In addition to its relatively well-documented organic contamination problems, we hypothesize that concrete could be substantially altering its geochemistry. Here we report findings from 6 locations along the Anacostia River and its tributaries that indicate both seasonally elevated Na and Cl (becoming brackish, 2000-3000 mg/L Total Dissolved Solids, in a suburban creek), and elevated cations in low flow suburban tributaries. Concentrations of all major cations (Ca, Mg, K, Na) strongly, and positively, covaried (factor scores (FC) >0.88). However Ca/Sr ratios negatively covaried with major cations (FC -0.64). This suggests the weathering of low Sr minerals, such as those in concrete. In urbanized portions of the river, Ca/Sr was >200, which is a concrete weathering indicator in areas with silica mineral bedrock (Anacostia bedrock consists of Precambrian phyllits, sericite, chlorite, quartzite, slate and schist). Mean ± SE Sr was 0.13 ± 0.02 mg/L in the most urban area, but 0.37 ± 0.03 mg/L in the most suburban. This supports the hypothesis that the source of elevated cations in the urban areas is concrete weathering, not bedrock mineral weathering. Inorganic N was not correlated strongly with cations. Mean NO3- was highest at the most suburban site (1.8 ± 0.2 mg/L), but rose above 3 mg/L in some samples at all sites. Elevated NO3- did not appear to vary with season or discharge rate at time of sampling. NH4+ was generally lower than 1 mg/L but spiked to 3.4 mg/L at the most urban site. These data follow patterns expected for "urban stream syndrome". Suburban areas, with their relatively small streams, show greater winter salting effects than more urban areas down stream. Suburban areas also show higher NO3- (and occasionally higher NH4+) than urban areas except in winter. The geochemistry of highly urbanized systems may be significantly altered and understanding this effect will help in the development of plans for more effective watershed rehabilitation.

Versatile fluoride substrates for Fe-based superconducting thin films

NASA Astrophysics Data System (ADS)

Kurth, F.; Reich, E.; Hänisch, J.; Ichinose, A.; Tsukada, I.; Hühne, R.; Trommler, S.; Engelmann, J.; Schultz, L.; Holzapfel, B.; Iida, K.

2013-04-01

We demonstrate the growth of Co-doped BaFe2As2 (Ba-122) thin films on CaF2 (001), SrF2 (001), and BaF2 (001) single crystal substrates using pulsed laser deposition. All films are grown epitaxially despite of a large misfit of -10.6% for BaF2 substrate. For all films, a reaction layer is formed at the interface confirmed by X-ray diffraction and for the films grown on CaF2 and BaF2 additionally by transmission electron microscopy. The superconducting transition temperature of the film on CaF2 is around 27 K, whereas the corresponding values of the films on SrF2 and BaF2 are around 22 K and 21 K, respectively. The Ba-122 on CaF2 shows almost identical crystalline quality and superconducting properties as films on Fe-buffered MgO.

Induction of CaSR expression circumvents the molecular features of malignant CaSR null colon cancer cells.

PubMed

Singh, Navneet; Chakrabarty, Subhas

2013-11-15

We recently reported on the isolation and characterization of calcium sensing receptor (CaSR) null human colon cancer cells (Singh et al., Int J Cancer 2013; 132: 1996-2005). CaSR null cells possess a myriad of molecular features that are linked to a highly malignant and drug resistant phenotype of colon cancer. The CaSR null phenotype can be maintained in defined human embryonic stem cell culture medium. We now show that the CaSR null cells can be induced to differentiate in conventional culture medium, regained the expression of CaSR with a concurrent reversal of the cellular and molecular features associated with the null phenotype. These features include cellular morphology, expression of colon cancer stem cell markers, expression of survivin and thymidylate synthase and sensitivity to fluorouracil. Other features include the expression of epithelial mesenchymal transition linked molecules and transcription factors, oncogenic miRNAs and tumor suppressive molecule and miRNA. With the exception of cancer stem cell markers, the reversal of molecular features, upon the induction of CaSR expression, is directly linked to the expression and function of CaSR because blocking CaSR induction by shRNA circumvented such reversal. We further report that methylation and demethylation of the CaSR gene promoter underlie CaSR expression. Due to the malignant nature of the CaSR null cells, inclusion of the CaSR null phenotype in disease management may improve on the mortality of this disease. Because CaSR is a robust promoter of differentiation and mediates its action through diverse mechanisms and pathways, inactivation of CaSR may serve as a new paradigm in colon carcinogenesis. Copyright © 2013 UICC.

β-Adrenergic stimulation increases the intra-sarcoplasmic reticulum Ca2+ threshold for Ca2+ wave generation

PubMed Central

Domeier, Timothy L; Maxwell, Joshua T; Blatter, Lothar A

2012-01-01

β-Adrenergic signalling induces positive inotropic effects on the heart that associate with pro-arrhythmic spontaneous Ca2+ waves. A threshold level of sarcoplasmic reticulum (SR) Ca2+ ([Ca2+]SR) is necessary to trigger Ca2+ waves, and whether the increased incidence of Ca2+ waves during β-adrenergic stimulation is due to an alteration in this threshold remains controversial. Using the low-affinity Ca2+ indicator fluo-5N entrapped within the SR of rabbit ventricular myocytes, we addressed this controversy by directly monitoring [Ca2+]SR and Ca2+ waves during β-adrenergic stimulation. Electrical pacing in elevated extracellular Ca2+ ([Ca2+]o= 7 mm) was used to increase [Ca2+]SR to the threshold where Ca2+ waves were consistently observed. The β-adrenergic agonist isoproterenol (ISO; 1 μm) increased [Ca2+]SR well above the control threshold and consistently triggered Ca2+ waves. However, when [Ca2+]SR was subsequently lowered in the presence of ISO (by lowering [Ca2+]o to 1 mm and partially inhibiting sarcoplasmic/endoplasmic reticulum calcium ATPase with cyclopiazonic acid or thapsigargin), Ca2+ waves ceased to occur at a [Ca2+]SR that was higher than the control threshold. Furthermore, for a set [Ca2+]SR level the refractoriness of wave occurrence (Ca2+ wave latency) was prolonged during β-adrenergic stimulation, and was highly dependent on the extent that [Ca]SR exceeded the wave threshold. These data show that acute β-adrenergic stimulation increases the [Ca2+]SR threshold for Ca2+ waves, and therefore the primary cause of Ca2+ waves is the robust increase in [Ca2+]SR above this higher threshold level. Elevation of the [Ca2+]SR wave threshold and prolongation of wave latency represent potentially protective mechanisms against pro-arrhythmogenic Ca2+ release during β-adrenergic stimulation. PMID:22988136

Isotopically distinct reservoirs in the solar nebula: Isotope anomalies in Vigarano meteorite inclusions

NASA Technical Reports Server (NTRS)

Loss, R. D.; Lugmair, G. W.; Davis, A. M.; Macpherson, G. J.

1994-01-01

The isotopic compositions of Mg, Ca, Ti, Cr, Zn, Sr, Ba, Nd, and Sm were measured in four relatively unaltered refractory inclusions from the Vigarano carbonaceous chondrite meteorite. Three of the inclusions (USNM 1623-2, 1623-3, and 1623-8) show similar Mg, Ca, Ti, and Cr isotopic compositions to those found in most inclusions in the Allende carbonaceous chondrite. This indicates that these Vigarano inclusions sampled the same isotopic reservoirs as the majority of the Allende inclusions that isotope signatures in the latter were not significantly modified by the secondary alteration that permeates most Allende inclusions. In contrast, inclusion 1623-5 has large deficits in Mg-26, Ca-48, and Ti-50 and small but distinct Cr-54, Zn-66, Sr-84, Ba-135, Ba-137, and Sm-144 anomalies. The magnitudes of these unusual anomalies in the refractory elements are within analytical uncertainty of those found in the Allende 'FUN" inclusion C1, yet 1623-5 has a very different bulk chemical composition from C1. The fact that 1623-5 and C1 have identical isotopic anomalies yet have significantly distinct major and trace element contents provide convincing evidence for the presence of isotopically distinct reservoirs in the early solar system.

Phase Transformation and Creep of Mg-Al-Ca Based Die-Cast Alloys

NASA Astrophysics Data System (ADS)

Suzuki, Akane; Saddock, Nicholas D.; Jones, J. Wayne; Pollock, Tresa M.

The microstructure and microstructural stability of die-cast AC53 (Mg-5Al-3Ca) and AXJ530 (Mg-5Al-3Ca-0.15Sr) have been investigated in detail by transmission electron microscopy (TEM). Both alloys have an as-cast microstructure of α-Mg with (Mg, Al)2Ca (dihexagonal C36) eutectic at grain boundaries. During aging at 573 K, the C36 phase transforms to Al2Ca (cubic Cl5) phase. These two phases have a crystallographic orientation relationship of (0001)C36//{111}C15 and [2110]C36//[011]C15, and the transformation from C36 to C15 occurs by a shear-assisted process. Despite this change in the phase constitution, the network structure of the intermetallic compound(s) surrounding α-Mg grains is fairly stable, morphologically, even after prolonged exposure at elevated temperature. In the α-Mg matrix phase, precipitation of Al2Ca was observed after aging for 360 ks at 573 K. The precipitates are disc-shaped with a habit plane of {111}C15//(0001)α. AXJ530 shows higher creep resistance than AC53. The dislocation substructure that evolved during creep deformation was investigated in both alloys, and the basal and non-basal slip of a-dislocation and other slip modes of a+c- dislocations were observed. The relationship between creep properties and microstructure is discussed.

Multiple episodes of zeolite deposition in fractured silicic tuff

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

Carlos, B.A.; Chipera, S.J.; Snow, M.G.

Fractures in silicic tuffs above the water table at Yucca Mountain, Nevada, USA contain two morphologies of heulandite with different compositions. Tabular heulandite is zoned, with Sr-rich cores and Mg-rich rims. Later prismatic heulandite is nearly the same composition as the more magnesian rims. Heulandite and stellerite may occur between layers of calcite, and calcite occurs locally between generations of heulandite. Thermodynamic modeling, using estimated thermodynamic data and observed chemical compositions for heulandite and stellerite, shows that stellerite is the favored zeolite unless Ca concentrations are reduced or Mg and/or Sr concentrations are significantly elevated above current Yucca Mountain waters.

Development and Application of Sr/Ca-δ18O-Sea Surface Temperature calibrations for Last Glacial Maximum-Aged Isopora corals in the Great Barrier Reef

NASA Astrophysics Data System (ADS)

Brenner, L. D.; Linsley, B. K.; Potts, D. C.; Felis, T.; Mcgregor, H. V.; Gagan, M. K.; Inoue, M.; Tudhope, A. W.; Esat, T. M.; Thompson, W. G.; Tiwari, M.; Fallon, S.; Humblet, M.; Yokoyama, Y.; Webster, J.

2016-12-01

Isopora (Acroporidae) are sub-massive to massive corals found on most modern and fossil Indo-Pacific reefs. Despite their abundance, they are largely absent from the paleoceanographic literature but have the potential to provide proxy data where other commonly used corals, such as Porites, are sparse. The retrieval of Isopora fossils during International Ocean Discovery Program Leg 325 in the Great Barrier Reef (GBR) signaled the need to evaluate their possible paleoceanographic utility. We developed modern skeletal Sr/Ca- and δ18O-sea surface temperature (SST) calibrations for six modern Isopora colonies collected at Heron Island in the southern GBR. Pairing the coral Sr/Ca record with monthly SST data yielded Reduced Major Axis Sr/Ca- and δ18O-SST sensitivities of -0.054 mmol/mol/°C and -0.152 ‰/°C, respectively, falling within the range of published Porites values. We applied our Isopora-based regressions and previously published sensitivities from other species to a suite (n=37) of fossil samples collected from IODP 32. The calibrations produced a range of 3-7°C of warming, averaging 5°C, in the GBR from 22 ka to modern climate. This SST change is similar or slightly larger than other coral studies and larger than planktonic foraminifera Mg/Ca records. The planktonic Mg/Ca records from the Indonesian and Western Pacific Warm Pools indicate a warming of 3-3.5°C since 23ka (Linsley et al., 2010) while a fossil coral record from Tahiti indicates a warming of 3.2°C from 9.5ka to present (DeLong et al., 2010) and western Pacific coral records suggest a cooling of 5-6°C (Gagan et al., 2010; Guilderson et al., 1994: Beck et al., 1997), although these value might require rescaling (Gagan et al., 2012) resulting in slightly warmer temperature calculations. Our Isopora fossils from the GBR speak to the spatial heterogeneity of warming since the LGM and the continued need to develop more records for a more comprehensive understanding of the deglaciation.

Reduction of perifusate magnesium alters inotropic response of papillary muscle to ion channel modulators.

PubMed

Manju, L; Nair, R Renuka

2005-09-01

Magnesium has a significant role in the regulation of ion transport. Marginal deficiency of Mg can therefore affect myocardial excitability and contractility. This study was taken up with the objective of examining the inotropic response of the myocardium to variation in extracellular [Mg]o and identifying the ion channels and pumps mediating the inotropic changes. Electrically stimulated rat papillary muscle was used as the experimental model and mechanical changes were recorded using a physiograph. Channel specific antagonists were used to identify the channels mediating the functional changes. Diastolic Ca2+ levels were determined in isolated myocytes by the ratiometric method using the fluorescent indicator Fura2-AM. A negative association was observed between the level of [Mg]o and force of contraction, with a peak at 0.48 mM Mg. The force of contraction in Mg deficient medium (0.48 mM) was 158% of control (1.2 mM Mg) (p < 0.001). Inotropic response to the L-type channel antagonist (verapamil-1 microm) and NaK ATPase inhibitor (Ouabain-0.3 mM) was augmented in Mg deficiency (p < 0.005), indicating activation of the channel and the pump. The response to T-type channel inhibitor (NiCl2-40 microM) was attenuated in Mg deficiency (p < 0.05). The response to the sarcoplasmic reticular Ca pump inhibitor (caffeine-10 mM) and the SR Ca2+ release channel inhibitor (ryanodine-1 microM) were not significantly affected by Mg deficiency. Diastolic level of Ca2+ increased with a decrease in Mg (p < 0.05). The observations of the study lead to the conclusion that the positive inotropic response in Mg deficiency is mediated by an increase in basal Ca2+ combined with Ca-induced-Ca release consequent to Ca2+ influx through L-type Ca channel. Variation in sensitivity to Ca channel blockers and NaK ATPase inhibitor in Mg deficiency can have pharmacological implications.

Paraná-Etendeka basalts in Misiones, Argentina; characterization and petrogenetic inferences

NASA Astrophysics Data System (ADS)

Rämö, O. T.; Heikkilä, P. A.

2013-12-01

The Early Cretaceous (ca. 130 Ma) Paraná-Etendeka flood basalts constitute one of the major Phanerozoic LIP sequences with an original volume probably in excess of 2.3 Mkm3.The bulk of this volcanic system is preserved in South America (Brazil, Uruguay, Paraguay, Argentina), where it manifests the onset of South Atlantic opening at present 25 degrees Southern Latitude. The sequence is overwhelmingly basaltic (ca. 90%), but also includes contemporaneous silicic volcanic rocks. Known as the Serra Geral Suite (e.g., Bellieni et al., 1984), it fills the Paraná Basin with a northward deepening strata of lavas with a maximum thickness of ca. 1500 m. We have collected and examined basalt samples from the west-central part (western flank) of the Paraná Basin in Misiones State, northeastern Argentina (54-55 degrees Western Longitude), where the estimated thickness of the basalt succession decreases from ca. 700 m in the east to ca. 300 m in the west. The examined samples are massive, aphyric (or microphyric with plagioclase and altered olivine microphenocrysts), and geochemically relatively evolved (Mg number 50-35) basalts and basaltic andesites. Their MgO values are between 6 and 3.7 wt.% and Ni content is relatively low (65-20 ppm). Incompatible trace element values increase with increasing fractionation (decreasing Mg number), e.g., Zr from 135 to 290 ppm, Ce from 45 to 105 ppm, Nd from 20 to 50 ppm, Sm from 5 to 11 ppm, Ba from 280 to 600 ppm, and Y from 25 to 50 ppm. In terms of Ti, the samples fall into two groups (1.9-2.3 and ca. 3.8 wt.% TiO2). These values conform, respectively, to the high-Ti, high-Ti/Y Paranapanema and Pitanga magma types of Peate et al. (1992) that govern the northern half of the Paraná basalt succession. Initial Nd and Sr isotope compositions of the two groups are remarkably uniform. Our analyzed ten samples have an average initial (at 134.6 Ma) epsilon-Nd value of -4.2 × 0.3 (1 SD) and an average initial 87Sr/86Sr of 0.70570 × 0.00015 (1 SD). No change in the initial values is observed with fractionation. This probably renders crustal contamination by the surrounding Precambrian bedrock negligible within the observed fractionation window (Mg number 50-35). The initial Nd and Sr isotope compositions of the basalts from Misiones comply with the isotope composition of the EM1 mantle component. Non-modal equilibrium melting modeling utilizing the Zr/Nb and Ce/Y values implies, for an overall primitive mantle source, a change in the melting regime from garnet lherzolite (Pitanga) to spinel lherzolite (Paranapanema).

Drug pharmacokinetics and pharmacodynamics: PET and microdial studies of SR 46349B, a selective 5HT2 antagonist

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

Tan, P.; Dewey, S.L.; Gatley, S.J.

1994-05-01

The brain serotonin system is an important molecular target in drug development. SR 46349B is a propenone oxime ether derivative with a high affinity and selectivity for the serotonin 5HT2 receptor (Kd=1.2 nM). We have labeled SR 46349B with carbon-11 via N-methylation of a nor-precursor (supplied by Sanofi Recherche) with C-11 methyl iodide. Purification by HPLC gave [11C]SR 46349B in 98% radiochemical purity with a specific activity of 1.5 Ci/{mu}mol. Serial PET studies were carried out in a baboon for a 60 minute study period with a two hour time interval between studies. The first study was at baseline andmore » the second after pretreatment with altanserin (0.5 mg/kg iv, 30 min prior to [11C]SR 46349B). Carbon-11 peaked at ca. 20 minutes in the frontal, parietal, temporal and occipital cortices where it plateaued for the rest of the study. Cerebellum, thalamus and striatum peaked at ca. 10 minutes and cleared to 62%, 72% and 80% of peak by 60 min. At 60 minutes, the frontal cortex to cerebellum ratio was 1.5. Treatment with altanserin reduced the frontal cortex to cerebellum ratio to 1.0. HPLC of mouse brain homogenate after [11C]SR 46349B showed >94% of the C-11 was parent compound. Microdialysis in freely moving rats after injection of SR 46349B (n=6; 10 mg/kg, ip) showed an average peak increase in extracellular dopamine of 375% which is higher than the 150% effect of altanserin. Spontaneous movements were markedly reduced. The pharmacokinetics of [11C] SR 46349B in cortical areas is consistent with the long term effects of SR 46349B on 5HT2 receptors and the elevations in extracellular dopamine without increased locomotor activity are consistent with serotonin mediated disinhibition of striatal dopamine release via blockade of serotonin receptors.« less

Frequency distribution and correlation among mineral elements in Lycium andersonii from the northern Mojave Desert

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

Wallace, A.; Romney, E,M.; Alexander, G.V.

1980-01-01

Two hundred samples of leaves of Lycium andersonii A. Gray, each representing one plant and divided among six different locations, were assayed by emission spectrography. Information for 12 different elements is reported in terms of concentrations, frequency distribution, correlations, and some soil characteristics. The objective was to ascertain the nature of variability for mineral elements within a species. Composition varied significantly for all 12 elements among locations, all within about 20 km. At least part of the variation was due to soil characteristics. Samples from Rock Valley were highest in K, Na, and Li, which effect is associated with volcanicmore » outcrop. Samples from Mercury Valley were highest in P, Mg, Ba, and B. At least Mg is related to the soil composition. Correlation coefficients between element pairs were often very different for all 200 samples versus those obtained for individual locations. Some of the values for all 200 samples together proved to be artifacts. The highest correlation was for Ca x Sr (positive) and next was Ca x Mg (also positive). Most correlations were slightly or strongly positive (24 to 32). Only P x Ca, Ca x Na, Ca x B, and Sr x P seemed to be significantly negative of the 32 correlations examined. Frequency distribution patterns where common populations were grouped were often normally distributed. Li, as previously reported, and Na, Cu, Mn,and B and Ba at some locations were not normally distributed. Wide variations in the concentrations of individual elements in leaves of these species were encountered.« less

Anthropogenic metal enrichment of snow and soil in north-eastern European Russia.

PubMed

Walker, T R; Young, S D; Crittenden, P D; Zhang, H

2003-01-01

Trace metal composition of winter snowpack, snow-melt filter residues and top-soil samples were determined along three transects through industrial towns in the Usa basin, North-East Russia: Inta, Usinsk and Vorkuta. Snow was analysed for Ag, Al, As, Ba, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sr and Zn using ICP-MS (Ca and K by F-AAS for Vorkuta only), pH and acidity/alkalinity. Filter residues were analysed for: Al, Ba, Ca, Cd, Cu, K, Mg, Mn, Ni, Pb, Sr and Zn using F-AAS and GF-AAS; top-soil samples were analysed for Ba, Cu, Mg, Mn, Na, Ni, Pb, Sr, Zn using F-AAS. Results indicate elevated concentrations of elements associated with alkaline combustion ash around the coal mining towns of Vorkuta and Inta. There is little evidence of deposition around the gas and oil town of Usinsk. Atmospheric deposition in the vicinity of Vorkuta, and to a lesser extent Inta, added significantly to the soil contaminant loading as a result of ash fallout. Acid deposition was associated with pristine areas whereas alkaline combustion ash near to emission sources more than compensated for the acidity caused by SO2.

Calibrating multiple isotopic proxies in a modern aragonite speleothem from northeast India

NASA Astrophysics Data System (ADS)

Ronay, E.; Oster, J. L.; Sharp, W. D.; Marks, N.; Erhardt, A.; Breitenbach, S. F. M.

2017-12-01

Uranium, strontium, and calcium isotope ratios in calcite speleothems are used as proxies for water-soil-rock interactions and prior calcite precipitation, and thus provide information about effective rainfall amount variations, primarily in semi-arid or highly seasonal regions. However, less is known about how these proxies function in humid regions and in aragonite speleothems. In this study, we use meteorological data to calibrate (234U/238U)i and 87Sr/86Sr in a modern aragonite speleothem from northeast India, the rainiest place on Earth, to determine how these proxies reflect effective monsoon rainfall amount. MAW-0201 is an annually laminated aragonite stalagmite that grew from 1960-2013 in Mawmluh Cave, Meghalaya, India. Rainfall here is extremely seasonal due to the Indian Summer Monsoon (ISM), which brings several meters of rain to the region each summer, but with inter-annual variability in total rainfall. The δ18O in Mawmluh dripwater and speleothems reflects moisture source and transport, rather than rainfall amount. Variations in Mg, U, and Ba concentrations in MAW-0201 show seasonal and multi-annual variability. U and Mg are closely correlated, but multi-year periods show significant anti-correlation. The Mg and U distribution coefficients in calcite and aragonite indicate correlated periods are times of prior calcite precipitation (PCP) and anti-correlated periods are times of prior aragonite precipitation (PAP) in the epikarst. We use δ44/40Ca to test this hypothesis, as Ca isotopes fractionate differently during calcite and aragonite precipitation and speleothem δ44/40Ca will record unique PAP and PCP fingerprints. We propose such shifts from PCP to PAP reflect hydrologic variability and/or flow path changes, which provide a useful tool for understanding epikarst hydrology but may also be a complicating factor in speleothem-based paleoclimate interpretations. Preliminary (234U/238U)i (always <1) and 87Sr/86Sr spanning 1991-2009 each show significant variability outside of analytical error. (234U/238U)i displays a decadal trend, gradually increasing until 2000 and decreasing to the end of the record. Several years in the 87Sr/86Sr record have anomalously high values, which may reflect increased sea spray input and provide unique information on the wind component of the ISM.

Spatial and ontogenetic variability in the chemical composition of juvenile common sole ( Solea solea) otoliths

NASA Astrophysics Data System (ADS)

Tanner, S. E.; Vasconcelos, R. P.; Reis-Santos, P.; Cabral, H. N.; Thorrold, S. R.

2011-01-01

A description of variations in the chemical composition of fish otoliths at different spatial scales and life history stages is a prerequisite for their use as natural tags in fish population connectivity and migration studies. Otolith geochemistry of juvenile common sole ( Solea solea), a marine migrant species collected in six Portuguese estuaries was examined. Elemental ratios (Mg:Ca, Mn:Ca, Cu:Ca, Sr:Ca, Ba:Ca, Pb:Ca) were analysed in two zones of the right otolith (corresponding to late larval and juvenile stages) using laser ablation inductively coupled plasma mass spectrometry (ICP-MS). Stable carbon and oxygen isotopes (δ 13C and δ 18O) were determined in left otoliths using isotopic ratio monitoring mass spectrometry (irm-MS). Significant differences in otolith geochemical signatures were found among estuaries, among sites within estuaries and between otolith zones. Several elemental ratios (Mg:Ca, Mn:Ca, Cu:Ca and Sr:Ca) showed consistent patterns between otolith zones and were likely influenced by environmental factors and ontogenetic effects associated with physiological changes during metamorphosis. Assignment of individuals to their collection estuary based on the otolith geochemical signatures was more accurate at the site level (81%) than among estuaries (69%). Site temperature was not correlated with any of the elemental or isotope ratios, but salinity was significantly correlated with Ba:Ca, δ 13C and δ 18O. Observed spatial variations among estuaries and sites within estuaries indicate that geochemical signatures in otoliths are accurate natural tags of estuarine habitat in common sole. Nevertheless, the significant variations observed between otolith zones should be taken into account in the design of population connectivity studies.

The comparative kinetics of Ca, Sr, And Ra in a freshwater turtle, Trachemys scripta

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

Hinton, T.G.

1989-01-01

The accumulation of {sup 45}Ca, {sup 47}Ca, {sup 88}Sr, and {sup 226}Ra was studied in the yellow-bellied slider, a common freshwater turtle of the Southeastern US. The author was particularly interested in testing the hypothesis of competitive inhibition, a concept whereby decreasing the intake of a stable dietary element increases the absorption and retention of chemically similar radionuclides. He established four specific hypotheses and examined the processes of absorption and elimination as a function of stable dietary calcium (2 and 20 mg g{sup {minus}1}), season (summer, fall, winter and spring), and age and sex of the animals (hatchlings, juveniles, adultmore » males, adult females, and gravid females). Turtles were gavaged with radionuclides and the gamma-emitting isotopes were detected during serial whole-body counts performed on the live animals for up to 480 d. The analysis of the beta-emitting {sup 45}Ca was accomplished by chemical separation procedures. Data were fit to a two-component exponential retention model by nonlinear regression. The 10-fold reduction in dietary Ca did not affect the elimination rate constants, and increased the assimilation of Sr and Ra only within juveniles. For all animals the absorption of Ca was significantly greater than Sr, and likewise, Sr was greater than Ra. Mean absorptions were generally higher than values reported for other organisms. Unlike many other organisms, absorption rates did not decline at maturity. He suspects that high Ca demands in constructing and maintaining the massive shell, necessitated by the turtle's survival strategy, may contribute to the high absorption, as well as the lack of a decline at maturity. Elimination rate constants were greatest in the summer and declined to levels that were generally not distinguishable from zero in the spring, winter, and fall seasons.« less

Minor elements incorporation control by ionic radius and growth rate on a stalagmite from the Chauvet Cave (SE-France)

NASA Astrophysics Data System (ADS)

Bourdin, C.; Douville, E.; Genty, D.

2009-12-01

A multi-elemental study focusing on earth-alkalis (Mg, Ca, Sr and Ba), uranium and rare-earth elements (REE) in the calcite of a stalagmite from the Chauvet Cave (SE of France) has been achieved by ICP-MS. The Chau-stm6 stalagmite which grew from 33 to 11.5 ky had already been dated and the published d13C and d18O profile is used as a paleoclimatic benchmark. Ba and Sr profiles show an abrupt concentration increase at the beginning of the last deglaciation whereas U and Mg feature a decreasing trend. REY (REE+yttrium) concentrations decrease markedly during early deglaciation (between 15 and 14.5 ky). The transition corresponds to a change from a slow to a fast growth rate. These variations can be explained by the crystallographic control of ionic radii of the minor elements: incorporation of small ions compared to Ca such as U, Mg, heavy REE are favoured during slow growth period (i.e. glacial) whereas large ions such as Ba, Sr and light REE are preferentially precipitated during fast growth period (i.e. Bolling-Allerod). This crystallographic effect seems to be dominant here because the soil above the cave is sparse. And may not have played a major role on the opposite to the water-limestone interaction.

Air Plasma-Sprayed La2Zr2O7-SrZrO3 Composite Thermal Barrier Coating Subjected to CaO-MgO-Al2O3-SiO2 (CMAS)

NASA Astrophysics Data System (ADS)

Cai, Lili; Ma, Wen; Ma, Bole; Guo, Feng; Chen, Weidong; Dong, Hongying; Shuang, Yingchai

2017-08-01

La2Zr2O7-SrZrO3 composite thermal barrier coatings (TBCs) were prepared by air plasma spray (APS). The La2Zr2O7-SrZrO3 composite TBCs covered with calcium-magnesium-aluminum-silicate (CMAS) powder, as well as the powder mixture of CMAS and spray-dried La2Zr2O7-SrZrO3 composite powder, were heat-treated at 1250 °C in air for 1, 4, 8, and 12 h. The phase constituents and microstructures of the reaction products were characterized by x-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. Experimental results showed that the La2Zr2O7-SrZrO3 composite TBCs had higher CMAS resistance than 8YSZ coating. A dense new layer developed between CMAS and La2Zr2O7-SrZrO3 composite TBCs during interaction, and this new layer consisted mostly of apatite (Ca2La8(SiO4)6O2) and c-ZrO2. The newly developed layer effectively protected the La2Zr2O7-SrZrO3 composite TBCs from further CMAS attack.

Deep-sea ostracode shell chemistry (Mg:Ca ratios) and late Quaternary Arctic Ocean history

USGS Publications Warehouse

Cronin, T. M.; Dwyer, Gary S.; Baker, P.A.; Rodriguez-Lazaro, J.; Briggs, W.M.; ,

1996-01-01

The magnesium:calcium (Mg:Ca) and strontium:calcium (Sr:Ca) ratios were investigated in shells of the benthic ostracode genus Krithe obtained from 64 core-tops from water depths of 73 to 4411 m in the Arctic Ocean and Nordic seas to determine the potential of ostracode shell chemistry for palaeoceanographic study. Shells from the Polar Surface Water (−1 to −1.5°C) had Mg:Ca molar ratios of about 0.006–0.008; shells from Arctic Intermediate Water (+0.3 to +2.0°C) ranged from 0.09 to 0.013. Shells from the abyssal plain and ridges of the Nansen, Amundsen and Makarov basins and the Norwegian and Greenland seas had a wide scatter of Mg:Ca ratios ranging from 0.007 to 0.012 that may signify post-mortem chemical alteration of the shells from Arctic deep-sea environments below about 1000 m water depth. There is a positive correlation (r2 = 0.59) between Mg:Ca ratios and bottom-water temperature in Krithe shells from Arctic and Nordic seas from water depths <900 m. Late Quaternary Krithe Mg:Ca ratios were analysed downcore using material from the Gakkel Ridge (water depths 3047 and 3899 m), the Lomonosov Ridge (water depth 1051 m) and the Amundsen Basin (water depth 4226 m) to test the core-top Mg:Ca temperature calibration. Cores from the Gakkel and Lomonosov ridges display a decrease in Mg:Ca ratios during the interval spanning the last glacial/deglacial transition and the Holocene, perhaps related to a decrease in bottom water temperatures or other changes in benthic environments.

S-type granite from the Gongpoquan arc in the Beishan Orogenic Collage, southern Altaids: Implications for the tectonic transition

NASA Astrophysics Data System (ADS)

Wang, Xinyu; Yuan, Chao; Zhang, Yunying; Long, Xiaoping; Sun, Min; Wang, Lixing; Soldner, Jeremie; Lin, Zhengfan

2018-03-01

Voluminous Paleozoic intrusions occur in the Beishan Orogenic Collage (BOC) and their genesis and tectonic background are important to reconstruct the accretion-collision processes in the southernmost Altaids. Paleozoic is an important period for arc development in the BOC, where the Gongpoquan and Huaniushan arcs are located. There are two pulses of magmatism in the Huaniushan and Gongpoquan arcs, i.e., the ca. 470-423 Ma I-type and ca. 424-395 Ma S- and A-type granitoids. In this study, we focus on two peraluminous granitic plutons in the Gongpoquan arc, i.e., the Baitoushan muscovite granite and Haergen two-mica granite, aiming at unraveling their petrogenesis and tectonic background. Zircon LA-ICP-MS U-Pb dating yields emplacement ages of ca. 409-395 Ma and ca. 409 Ma for the Baitoushan and Haergen plutons, respectively. Both the granitic plutons are strongly peraluminous with A/CNK ratios of 1.10-1.20, indicative of S-type affinities. The rocks are characterized by high SiO2 and K2O contents with high CaO/Na2O ratios. Moreover, the rocks possess low MgO contents, Rb/Sr and Rb/Ba ratios, together with their relatively high initial 87Sr/86Sr ratios (0.7139-0.7152) and less radiogenic εNd(t) values (-3.15 to -5.17), implying a clay-poor and plagioclase-rich crustal source. Compared with earlier pulse of arc-related magmatism (ca. 470-423 Ma), the latter pulse of magmatism (ca. 424-395 Ma) consists mainly of "normal granite" characterized by higher SiO2 (>66%) and K2O contents, weaker fractionated REE patterns and lower δEu values, and gabbroic to dioritic intrusions are only sporadic. Moreover, the granitoids of the latter pulse show variable but more crust-like Sr-Nd isotopic compositions ((87Sr/86Sr)0 = 0.7038-0.7327; εNd(t) = -6.70 to +0.33) than the earlier ones ((87Sr/86Sr)0 = 0.7024-0.7080; εNd(t) = -2.56 to +8.86), indicating that the Early Devonian (ca. 424-395 Ma) experienced extensive crustal melting with minor involvement of mantle materials. Considering Early Devonian geological evidence, the transition from I- to S- and A-type magmatism probably reflects the Early Devonian amalgamation between the Gongpoquan and Huaniushan arcs, which caused not only regional unconformity and strong deformation-metamorphism, but also extensive melting of the accreted crustal materials in the BOC.

Reversal of subcellular remodelling by losartan in heart failure due to myocardial infarction

PubMed Central

Babick, Andrea; Chapman, Donald; Zieroth, Shelley; Elimban, Vijayan; Dhalla, Naranjan S

2012-01-01

This study tested the reversal of subcellular remodelling in heart failure due to myocardial infarction (MI) upon treatment with losartan, an angiotensin II receptor antagonist. Twelve weeks after inducing MI, rats were treated with or without losartan (20 mg/kg; daily) for 8 weeks and assessed for cardiac function, cardiac remodelling, subcellular alterations and plasma catecholamines. Cardiac hypertrophy and lung congestion in 20 weeks MI-induced heart failure were associated with increases in plasma catecholamine levels. Haemodynamic examination revealed depressed cardiac function, whereas echocardiographic analysis showed impaired cardiac performance and marked increases in left ventricle wall thickness and chamber dilatation at 20 weeks of inducing MI. These changes in cardiac function, cardiac remodelling and plasma dopamine levels in heart failure were partially or fully reversed by losartan. Sarcoplasmic reticular (SR) Ca2+-pump activity and protein expression, protein and gene expression for phospholamban, as well as myofibrillar (MF) Ca2+-stimulated ATPase activity and α-myosin heavy chain mRNA levels were depressed, whereas β-myosin heavy chain expression was increased in failing hearts; these alterations were partially reversed by losartan. Although SR Ca2+-release activity and mRNA levels for SR Ca2+-pump were decreased in failing heart, these changes were not reversed upon losartan treatment; no changes in mRNA levels for SR Ca2+-release channels were observed in untreated or treated heart failure. These results suggest that the partial improvement of cardiac performance in heart failure due to MI by losartan treatment is associated with partial reversal of cardiac remodelling as well as partial recovery of SR and MF functions. PMID:22947202

Double-perovskites A 2FeMoO 6- δ (A = Ca, Sr, Ba) as anodes for solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Zhang, Leilei; Zhou, Qingjun; He, Qiang; He, Tianmin

Double-perovskites A 2FeMoO 6- δ (A = Ca, Sr, Ba) have been investigated as potential anode materials for solid oxide fuel cells (SOFCs). At room temperature, A 2FeMoO 6- δ compounds crystallize in monoclinic, tetragonal, and cubic structures for A = Ca, Sr, and Ba, respectively. A weak peak observed at around 880 cm -1 in the Raman spectra can be attributed to traces of AMoO 4. XPS has confirmed the coexistence of Fe 2+-Mo 6+ and Fe 3+-Mo 5+ electronic configurations. Moreover, a systematic shift from Fe 2+/3+-Mo 6+/5+ to Fe 2+-Mo 6+ configuration is seen with increasing A-site cation size. A 2FeMoO 6- δ samples display distinct electrical properties in H 2, which can be attributed to different degrees of degeneracy of the Fe 2+-Mo 6+ and Fe 3+-Mo 5+ configurations. Ca 2FeMoO 6- δ is unstable in a nitrogen atmosphere, while Sr 2FeMoO 6- δ and Ba 2FeMoO 6- δ are stable up to 1200 °C. The thermal expansion coefficients of Sr 2FeMoO 6- δ and Ba 2FeMoO 6- δ are very close to that of La 0.9Sr 0.1Ga 0.8Mg 0.2O 3- δ (LSGM). The performances of cells with 300 μm thick LSGM electrolyte, double-perovskite SmBaCo 2O 5+ x cathodes, and A 2FeMoO 6- δ anodes follow the sequence Ca 2FeMoO 6- δ < Ba 2FeMoO 6- δ < Sr 2FeMoO 6- δ. The maximum power densities of a cell with an Sr 2FeMoO 6- δ anode reach 831 mW cm -2 in dry H 2 and 735 mW cm -2 in commercial city gas at 850 °C, respectively.

An assessment of the Ca weathering sources to surface waters on the Precambrian Shield in central Ontario.

PubMed

Watmough, Shaun

2018-06-01

There is increasing concern over the negative ecological impacts caused by falling calcium (Ca) concentrations in lakes, particularly in central Ontario, Canada. Forecasting regional changes in lake Ca concentrations relies on accurate estimates of mineral weathering rates that are not widely available. In this study, bulk atmospheric deposition, surface water and soil chemistry along with 87 Sr/ 86 Sr isotope measurements were used to provide regional insight into weathering controls on Ca concentrations in lakes. Regionally, Ca concentrations in 90% of 129 lakes sampled in central Ontario were <0.1 mmol L -1 and the Ca/Sr ratio in lakes increased and the K/Sr ratio decreased with increasing Sr concentration, which is indicative of greater Ca sources from calcite or apatite in the higher Ca lakes. Significant relationships between 87 Sr/ 86 Sr ratios and Ca/Sr rations in dilute acid (0.1 M HCl) soil extracts are also indicative of the presence of trace amounts of calcite or apatite in surficial soils. Within the low (<0.7 mmol L -1 ) Ca lakes, defined in this study that are considered most at risk from falling Ca concentrations, 87 Sr/ 86 Sr ratios fell within the range observed in weak acid soil extracts and were also significantly related to Ca/Na and K/Sr ratios in surface waters. There were large inconsistencies however, between Ca/Na ratios and Ca/Sr in surface waters and soil acid extracts that suggest differences in 87 Sr/ 86 Sr ratios in surface waters of the low Ca lakes do not simply reflect differences in Ca derived from non-silicate minerals in surficial soils and that that Ca sources from deeper soil or bedrock are also important contributors to surface water Ca in these low Ca lakes. Copyright © 2018 Elsevier B.V. All rights reserved.

The impact of biotic/abiotic interfaces in mineral nutrient cycling: A study of soils of the Santa Cruz chronosequence, California

USGS Publications Warehouse

White, Art F.; Schulz, Marjorie S.; Vivit, Davison V.; Bullen, Tomas D.; Fitzpatrick, John A.

2012-01-01

The fraction of a mineral nutrient annually cycled through the plants, compared to that lost from pore water discharge, is defined their respective fluxes Fj,plants = qj,plants/(qj,plants + qj,discharge) with average values for K and Ca (FK,plants = 0.99; FCa,plants = 0.93) much higher than for Mg and Na (FMg,plants 0.64; FNa,plants = 0.28). The discrimination against Rb and Sr by plants is described by fractionation factors (KSr/Ca = 0.86; KRb/K = 0.83) which are used in Rayleigh fractionation-mixing calculations to fit seasonal patterns in solute K and Ca cycling. KRb/K and K24Mg/22Mg values (derived from isotope data in the literature) fall within fractionation envelopes bounded by inputs from rainfall and mineral weathering. KSr/Ca and K44Ca/40Ca fractionation factors fall outside these envelopes indicating that Ca nutrient cycling is closed to these external inputs. Small net positive K and Ca fluxes (6–14 mol m-2 yr-1), based on annual mass balances, indicate that the soils are accumulating mineral nutrients, probably as a result of long-term environmental disequilibrium.

Structural, Optical and Impedance Spectroscopic Characterizations of Nanocrystalline A2Ti2Zr5O16 (A = Mg, Ca, Ba and Sr)

NASA Astrophysics Data System (ADS)

Sandeep, K.; Thomas, Jijimon K.; Solomon, Sam

2018-04-01

A nanocrystalline A2Ti2Zr5O16 (A = Mg, Ca, Ba and Sr) system has been synthesized by a modified combustion technique. The cation-deficient calzirtite (Ca2Ti2Zr5O16) is found to be a tetragonal structure with the space group I4(1)/acd. The average size of the particle from the transmission electron microscopy image is estimated to be 23.30 nm and 20.16 nm for Ca2Ti2Zr5O16 and Ba2Ti2Zr5O16, respectively. The optical bandgap calculated using a Tauc plot is between 3.01 eV and 3.46 eV. Raman and Fourier transform infrared spectroscopy (FTIR) studies were carried out to confirm the phase purity of the sample. The scanning electron microscopy (SEM) image of a Ca2Ti2Zr5O16 sample sintered at 1360°C for 3 h shows minimum porosity with 96% of the theoretical density. The frequency-dependent dielectric study shows that the dielectric constant is maximized at low frequencies and decreases as the frequency increases. The Cole-Cole plot reveals that the material exhibits conduction due to the contributions of grain, grain boundary and electrode effects. The photoluminescence spectra of the samples were recorded and the transitions causing emission have been identified.

Spectral identifiers from roasting process of Arabica and Robusta green beans using Laser-Induced Breakdown Spectroscopy (LIBS)

NASA Astrophysics Data System (ADS)

Wirani, Ayu Puspa; Nasution, Aulia; Suyanto, Hery

2016-11-01

Coffee (Coffea spp.) is one of the most widely consumed beverages in the world. World coffee consumption is around 70% comes from Arabica, 26% from Robusta , and the rest 4% from other varieties. Coffee beverages characteristics are related to chemical compositions of its roasted beans. Usually testing of coffee quality is subjectively tasted by an experienced coffee tester. An objective quantitative technique to analyze the chemical contents of coffee beans using LIBS will be reported in this paper. Optimum experimental conditions was using of 120 mJ of laser energy and delay time 1 μs. Elements contained in coffee beans are Ca, W, Sr, Mg, Na, H, K, O, Rb, and Be. The Calcium (Ca) is the main element in the coffee beans. Roasting process will cause the emission intensity of Ca decreased by 42.45%. In addition, discriminant analysis was used to distinguish the arabica and robusta variants, either in its green and roasted coffee beans. Observed identifier elements are Ca, W, Sr, and Mg. Overall chemical composition of roasted coffee beans are affected by many factors, such as the composition of the soil, the location, the weather in the neighborhood of its plantation, and the post-harvesting process of the green coffee beans (drying, storage, fermentation, and roasting methods used).

Elemental composition of normal primary tooth enamel analyzed with XRMA and SIMS.

PubMed

Sabel, Nina; Dietz, Wolfram; Lundgren, Ted; Nietzsche, Sandor; Odelius, Hans; Rythén, Marianne; Rizell, Sara; Robertson, Agneta; Norén, Jörgen G; Klingberg, Gunilla

2009-01-01

There is an interest to analyze the chemical composition of enamel in teeth from patients with different developmental disorders or syndromes and evaluate possible differences compared to normal composition. For this purpose, it is essential to have reference material. The aim of this study was to, by means of X-ray micro analyses (XRMA) and secondary ion mass spectrometry (SIMS), present concentration gradients for C, O, P and Ca and F, Na, Mg, Cl, K and Sr in normal enamel of primary teeth from healthy individuals. 36 exfoliated primary teeth from 36 healthy children were collected, sectioned, and analyzed in the enamel and dentin with X-ray micro analyses for the content of C, O, P and Ca and F, Na MgCl, K and Sr. This study has supplied reference data for C, O, P and Ca in enamel in primary teeth from healthy subjects. No statistically significant differences in the elemental composition were found between incisors and molars.The ratio Ca/P is in concordance with other studies. Some elements have shown statistically significant differences between different levels of measurement. These results may be used as reference values for research on the chemical composition of enamel and dentin in primary teeth from patients with different conditions and/or syndromes.

Thermodynamic screening of metal-substituted MOFs for carbon capture.

PubMed

Koh, Hyun Seung; Rana, Malay Kumar; Hwang, Jinhyung; Siegel, Donald J

2013-04-07

Metal-organic frameworks (MOFs) have emerged as promising materials for carbon capture applications due to their high CO2 capacities and tunable properties. Amongst the many possible MOFs, metal-substituted compounds based on M-DOBDC and M-HKUST-1 have demonstrated amongst the highest CO2 capacities at the low pressures typical of flue gasses. Here we explore the possibility for additional performance tuning of these compounds by computationally screening 36 metal-substituted variants (M = Be, Mg, Ca, Sr, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, W, Sn, and Pb) with respect to their CO2 adsorption enthalpy, ΔH(T=300K). Supercell calculations based on van der Waals density functional theory (vdW-DF) yield enthalpies in good agreement with experimental measurements, out-performing semi-empirical (DFT-D2) and conventional (LDA & GGA) functionals. Our screening identifies 13 compounds having ΔH values within the targeted thermodynamic window -40 ≤ ΔH ≤ -75 kJ mol(-1): 8 are based on M-DODBC (M = Mg, Ca, Sr, Sc, Ti, V, Mo, and W), and 5 on M-HKUST-1 (M = Be, Mg, Ca, Sr and Sc). Variations in the electronic structure and the geometry of the structural building unit are examined and used to rationalize trends in CO2 affinity. In particular, the partial charge on the coordinatively unsaturated metal sites is found to correlate with ΔH, suggesting that this property may be used as a simple performance descriptor. The ability to rapidly distinguish promising MOFs from those that are "thermodynamic dead-ends" will be helpful in guiding synthesis efforts towards promising compounds.

Calcium buffering properties of sarcoplasmic reticulum and calcium-induced Ca2+ release during the quasi-steady level of release in twitch fibers from frog skeletal muscle

PubMed Central

Fénelon, Karine; Lamboley, Cédric R.H.; Carrier, Nicole

2012-01-01

Experiments were performed to characterize the properties of the intrinsic Ca2+ buffers in the sarcoplasmic reticulum (SR) of cut fibers from frog twitch muscle. The concentrations of total and free calcium ions within the SR ([CaT]SR and [Ca2+]SR) were measured, respectively, with the EGTA/phenol red method and tetramethylmurexide (a low affinity Ca2+ indicator). Results indicate SR Ca2+ buffering was consistent with a single cooperative-binding component or a combination of a cooperative-binding component and a linear binding component accounting for 20% or less of the bound Ca2+. Under the assumption of a single cooperative-binding component, the most likely resting values of [Ca2+]SR and [CaT]SR are 0.67 and 17.1 mM, respectively, and the dissociation constant, Hill coefficient, and concentration of the Ca-binding sites are 0.78 mM, 3.0, and 44 mM, respectively. This information can be used to calculate a variable proportional to the Ca2+ permeability of the SR, namely d[CaT]SR/dt ÷ [Ca2+]SR (denoted release permeability), in experiments in which only [CaT]SR or [Ca2+]SR is measured. In response to a voltage-clamp step to −20 mV at 15°C, the release permeability reaches an early peak followed by a rapid decline to a quasi-steady level that lasts ∼50 ms, followed by a slower decline during which the release permeability decreases by at least threefold. During the quasi-steady level of release, the release amplitude is 3.3-fold greater than expected from voltage activation alone, a result consistent with the recruitment by Ca-induced Ca2+ release of 2.3 SR Ca2+ release channels neighboring each channel activated by its associated voltage sensor. Release permeability at −60 mV increases as [CaT]SR decreases from its resting physiological level to ∼0.1 of this level. This result argues against a release termination mechanism proposed in mammalian muscle fibers in which a luminal sensor of [Ca2+]SR inhibits release when [CaT]SR declines to a low level. PMID:23008434

Calcium buffering properties of sarcoplasmic reticulum and calcium-induced Ca(2+) release during the quasi-steady level of release in twitch fibers from frog skeletal muscle.

PubMed

Fénelon, Karine; Lamboley, Cédric R H; Carrier, Nicole; Pape, Paul C

2012-10-01

Experiments were performed to characterize the properties of the intrinsic Ca(2+) buffers in the sarcoplasmic reticulum (SR) of cut fibers from frog twitch muscle. The concentrations of total and free calcium ions within the SR ([Ca(T)](SR) and [Ca(2+)](SR)) were measured, respectively, with the EGTA/phenol red method and tetramethylmurexide (a low affinity Ca(2+) indicator). Results indicate SR Ca(2+) buffering was consistent with a single cooperative-binding component or a combination of a cooperative-binding component and a linear binding component accounting for 20% or less of the bound Ca(2+). Under the assumption of a single cooperative-binding component, the most likely resting values of [Ca(2+)](SR) and [Ca(T)](SR) are 0.67 and 17.1 mM, respectively, and the dissociation constant, Hill coefficient, and concentration of the Ca-binding sites are 0.78 mM, 3.0, and 44 mM, respectively. This information can be used to calculate a variable proportional to the Ca(2+) permeability of the SR, namely d[Ca(T)](SR)/dt ÷ [Ca(2+)](SR) (denoted release permeability), in experiments in which only [Ca(T)](SR) or [Ca(2+)](SR) is measured. In response to a voltage-clamp step to -20 mV at 15°C, the release permeability reaches an early peak followed by a rapid decline to a quasi-steady level that lasts ~50 ms, followed by a slower decline during which the release permeability decreases by at least threefold. During the quasi-steady level of release, the release amplitude is 3.3-fold greater than expected from voltage activation alone, a result consistent with the recruitment by Ca-induced Ca(2+) release of 2.3 SR Ca(2+) release channels neighboring each channel activated by its associated voltage sensor. Release permeability at -60 mV increases as [Ca(T)](SR) decreases from its resting physiological level to ~0.1 of this level. This result argues against a release termination mechanism proposed in mammalian muscle fibers in which a luminal sensor of [Ca(2+)](SR) inhibits release when [Ca(T)](SR) declines to a low level.

Compositional variations at ultra-structure length scales in coral skeleton

NASA Astrophysics Data System (ADS)

Meibom, Anders; Cuif, Jean-Pierre; Houlbreque, Fanny; Mostefaoui, Smail; Dauphin, Yannicke; Meibom, Karin L.; Dunbar, Robert

2008-03-01

Distributions of Mg and Sr in the skeletons of a deep-sea coral ( Caryophyllia ambrosia) and a shallow-water, reef-building coral ( Pavona clavus) have been obtained with a spatial resolution of 150 nm, using the NanoSIMS ion microprobe at the Muséum National d'Histoire Naturelle in Paris. These trace element analyses focus on the two primary ultra-structural components in the skeleton: centers of calcification (COC) and fibrous aragonite. In fibrous aragonite, the trace element variations are typically on the order of 10% or more, on length scales on the order of 1-10 μm. Sr/Ca and Mg/Ca variations are not correlated. However, Mg/Ca variations in Pavona are strongly correlated with the layered organization of the skeleton. These data allow for a direct comparison of trace element variations in zooxanthellate and non-zooxanthellate corals. In both corals, all trace elements show variations far beyond what can be attributed to variations in the marine environment. Furthermore, the observed trace element variations in the fibrous (bulk) part of the skeletons are not related to the activity of zooxanthellae, but result from other biological activity in the coral organism. To a large degree, this biological forcing is independent of the ambient marine environment, which is essentially constant on the growth timescales considered here. Finally, we discuss the possible detection of a new high-Mg calcium carbonate phase, which appears to be present in both deep-sea and reef-building corals and is neither aragonite nor calcite.

Experimental studies on cycling stable characteristics of inorganic phase change material CaCl2·6H2O-MgCl2·6H2O modified with SrCl2·6H2O and CMC

NASA Astrophysics Data System (ADS)

He, Meizhi; Yang, Luwei; Zhang, Zhentao

2018-01-01

By means of mass ratio method, binary eutectic hydrated salts inorganic phase change thermal energy storage system CaCl2·6H2O-20wt% MgCl2·6H2O was prepared, and through adding nucleating agent 1wt% SrCl2·6H2O and thickening agent 0.5wt% carboxy methyl cellulose (CMC), inoganic phase change material (PCM) modified was obtained. With recording cooling-melting curves simultaneously, this PCM was frozen and melted for 100 cycles under programmable temperature control. After per 10 cycles, the PCM was charaterized by differential scanning calorimeter (DSC), X-ray diffraction (XRD) and density meter, then analysing variation characteristics of phase change temperature, supercooling degree, superheat degree, latent heat, crystal structure and density with the increase of cycle index. The results showed that the average values of average phase change temperature for cooling and heating process were 25.70°C and 27.39°C respectively with small changes. The average values of average supercooling and superheat degree were 0.59°C and 0.49°C respectively, and the maximum value was 1.10°C. The average value and standard deviation of latent heat of fusion were 120.62 J/g and 1.90 J/g respectively. Non-molten white solid sediments resulted from phase separation were tachyhydrite (CaMg2Cl6·12H2O), which was characterized by XRD. Measuring density of the PCM after per 10 cycles, and the results suggested that the total mass of tachyhydrite was limited. In summary, such modified inoganic PCM CaCl2·6H2O-20wt% MgCl2·6H2O-1wt% SrCl2·6H2O-0.5wt% CMC could stay excellent circulation stability within 100 cycles, and providing reference value in practical use.

The series Bi2Sr2Ca(n-1) Cu(n)O(2n+4) (1 less than or equal to n less than or equal to 5): Phase stability and superconducting properties

NASA Technical Reports Server (NTRS)

Deguire, Mark R.; Bansal, Narottam P.; Farrell, David E.; Finan, Valerie; Kim, Cheol J.; Hills, Bethanie J.; Allen, Christopher J.

1989-01-01

Phase relations at 850 and 870 C, melting transitions in air, oxygen, and helium were studied for Bi(2.1)Sr(1.9) CuO6 and for the Bi2Sr2Ca(n-1) Cu(n)O(2n+4) for n = 1, 2, 3, 4, 5, and infinity (CaCuO2). Up to 870 C, the n = 2 composition resides in the compatibility tetrahedron bounded by Bi(2+x)(Sr,Ca)(3-y) Cu2O8, (Sr,Ca)14 Cu24O41, Ca2CuO3, and a Bi-Sr-Ca-O phase. The n is greater than or equal to 3 compositions reside in the compatibility tetrahedron Bi(2+x)(Sr,Ca)(3-y) Cu2O8 - (Sr,Ca)14 Cu24O41 - Ca2CuO3 - CuO up to 850 C. However, Bi(2+x)Sr(4-y) Cu3O10 forms for n is greater than or equal to 3 after extended heating at 870 C. Bi(2+x)Sr(2-y) CuO6 and Bi(2+x)(Sr,Ca)(3-y) Cu2O8 melt in air at 914 C and 895 C respectively. During melting, all of the compositions studied lose 1 to 2 percent by weight of oxygen from the reduction of copper. Bi(2+x)Sr(2-y) CuO6, Bi(2+n)(Sr,Ca)(3-y) Cu2O8, and Bi(2+x)(Sr,Ca)(4-y) Cu3O10 exhibit crystallographic alignment in a magnetic field, with the c-axes orienting parallel to the field.

First-principles study on interlayer state in alkali and alkaline earth metal atoms intercalated bilayer graphene

NASA Astrophysics Data System (ADS)

Kaneko, Tomoaki; Saito, Riichiro

2017-11-01

Energetics and electronic structures of alkali metal (Li, Na, K, Rb, and Cs) and alkaline earth metal (Be, Mg, Ca, Sr, and Ba) atoms intercalated bilayer graphene are systematically investigated using first-principles calculations based on density functional theory. Formation of alkali and alkaline earth metal atoms intercalated bilayer graphene is exothermic except for Be and Mg. The interlayer state between two graphene layers is occupied for K, Rb, Cs, Ca, Sr, and Ba. We find that the energetic position of the interlayer states between bilayer graphene monotonically shifts downward with increasing of interlayer distance. The interlayer distances of more than 4.5 Å and 4.0 Å, respectively, are necessary for the occupation of the interlayer state in bilayer graphene for alkali and alkaline earth metal atoms, which is almost independent of the intercalant metal species. We discuss the relevance to occurrence of superconductivity for the metal intercalated bilayer graphene in terms of the occupation of the interlayer state and the phonon frequency of metal ions.

Chemical data and statistical interpretations for rocks and ores from the Ranger uranium mine, Northern Territory, Australia

USGS Publications Warehouse

Nash, J. Thomas; Frishman, David

1983-01-01

Analytical results for 61 elements in 370 samples from the Ranger Mine area are reported. Most of the rocks come from drill core in the Ranger No. 1 and Ranger No. 3 deposits, but 20 samples are from unmineralized drill core more than 1 km from ore. Statistical tests show that the elements Mg, Fe, F, Be, Co, Li, Ni, Pb, Sc, Th, Ti, V, CI, As, Br, Au, Ce, Dy, La Sc, Eu, Tb, Yb, and Tb have positive association with uranium, and Si, Ca, Na, K, Sr, Ba, Ce, and Cs have negative association. For most lithologic subsets Mg, Fe, Li, Cr, Ni, Pb, V, Y, Sm, Sc, Eu, and Yb are significantly enriched in ore-bearing rocks, whereas Ca, Na, K, Sr, Ba, Mn, Ce, and Cs are significantly depleted. These results are consistent with petrographic observations on altered rocks. Lithogeochemistry can aid exploration, but for these rocks requires methods that are expensive and not amenable to routine use.

Hydrostatic pressure effects on the structural, elastic and thermodynamic properties of the complex transition metal hydrides A2OsH6 (A = Mg, Ca, Sr and Ba)

NASA Astrophysics Data System (ADS)

Souadia, Z.; Bouhemadou, A.; Boudrifa, O.; Bin-Omran, S.; Khenata, R.; Al-Douri, Y.

2017-10-01

We report a systematic first-principles density functional theory study on the pressure dependence of the structural parameters, elastic constants and related properties and thermodynamic properties of the complex transition metal hydrides Mg2OsH6, Ca2OsH6, Sr2OsH6 and Ba2OsH6. The calculated structural parameters are in excellent agreement with the existing data in the scientific literature. The single-crystal elastic constants and related properties were predicted using the stress-strain method. The elastic moduli of the polycrystalline aggregates were evaluated via the Voigt-Reuss-Hill approach. The dependences of the lattice parameter, bulk modulus, volume thermal expansion coefficient, isobaric and isochoric heat capacity and Debye temperature on the pressure and temperature, ranging from 0 to 15 GPa and from 0 to 1000 K, respectively, were investigated using the quasi-harmonic Debye model in combination with first-principles calculations.

Temperature dependence of pre-edge features in Ti K-edge XANES spectra for ATiO₃ (A = Ca and Sr), A₂TiO₄ (A = Mg and Fe), TiO₂ rutile and TiO₂ anatase.

PubMed

Hiratoko, Tatsuya; Yoshiasa, Akira; Nakatani, Tomotaka; Okube, Maki; Nakatsuka, Akihiko; Sugiyama, Kazumasa

2013-07-01

XANES (X-ray absorption near-edge structure) spectra of the Ti K-edges of ATiO3 (A = Ca and Sr), A2TiO4 (A = Mg and Fe), TiO2 rutile and TiO2 anatase were measured in the temperature range 20-900 K. Ti atoms for all samples were located in TiO6 octahedral sites. The absorption intensity invariant point (AIIP) was found to be between the pre-edge and post-edge. After the AIIP, amplitudes damped due to Debye-Waller factor effects with temperature. Amplitudes in the pre-edge region increased with temperature normally by thermal vibration. Use of the AIIP peak intensity as a standard point enables a quantitative comparison of the intensity of the pre-edge peaks in various titanium compounds over a wide temperature range.

Infrared Multiple-Photon Photodissociation of Gas-Phase Group II Metal-Nitrate Anions

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

C. M. Leavitt; Jos Oomens; R. P. Dain

2008-06-01

Infrared spectra of gas-phase metal-nitrate anions M(NO{sub 3}){sub 3}{sup -}, where M = Mg{sup 2+}, Ca{sup 2+}, Sr{sup 2+} and Ba{sup 2+}, were recorded by infrared multiple-photon dissociation (IRMPD) spectroscopy. Photodissociation of each of the precursors produces NO{sub 3}{sup -} through the elimination of a neutral M(NO{sub 3}){sub 2} unit. An absorption pattern characteristic of metal nitrates is observed in the IRMPD spectra, including the symmetric and antisymmetric NO{sub 3} stretches. The latter is split into high-and low-frequency components as a result of perturbation of the nitrate symmetry by complexation to the metal ion, and the magnitude of the splittingmore » decreases following the trend Mg{sup 2+} > Ca{sup 2+} > Sr{sup 2+} {approx_equal} Ba{sup 2+}. The experimental spectra are in good general agreement with those obtained from density functional theory (DFT) calculations.« less

Calcium-dependent phosphodiesterase 1C inhibits renin release from isolated juxtaglomerular cells

PubMed Central

Ortiz-Capisano, M. Cecilia; Liao, Tang-Dong; Ortiz, Pablo A.

2009-01-01

Renin release from the juxtaglomerular (JG) cell is stimulated by the second messenger cAMP and inhibited by calcium. We previously showed JG cells contain a calcium sensing receptor (CaSR), which, when stimulated, decreases cAMP formation and inhibits renin release. We hypothesize CaSR activation decreases cAMP and renin release, in part, by stimulating a calcium calmodulin-activated phosphodiesterase 1 (PDE1). We incubated our primary culture of JG cells with two selective PDE1 inhibitors [8-methoxymethil-IBMX (8-MM-IBMX; 20 μM) and vinpocetine (40 μM)] and the calmodulin inhibitor W-7 (10 μM) and measured cAMP and renin release. Stimulation of the JG cell CaSR with the calcimimetic cinacalcet (1 μM) resulted in decreased cAMP from a basal of 1.13 ± 0.14 to 0.69 ± 0.08 pM/mg protein (P < 0.001) and in renin release from 0.89 ± 0.16 to 0.38 ± 0.08 μg ANG I/ml·h−1·mg protein−1 (P < 0.001). However, the addition of 8-MM-IBMX with cinacalcet returned both cAMP (1.10 ± 0.19 pM/mg protein) and renin (0.57 ± 0.16 μg ANG I/ml·h−1·mg protein−1) to basal levels. Similar results were obtained with vinpocetine, and also with W-7. Combining 8-MM-IBMX and W-7 had no additive effect. To determine which PDE1 isoform is involved, we performed Western blot analysis for PDE1A, B, and C. Only Western blot analysis for PDE1C showed a characteristic band apparent at 80 kDa. Immunofluorescence showed cytoplasmic distribution of PDE1C and renin in the JG cells. In conclusion, PDE1C is expressed in isolated JG cells, and contributes to calcium's inhibitory modulation of renin release from JG cells. PMID:19741056

Raman-Spektren der Hexathiohypodiphosphate des NH4, Mg, Ca, Sr und Ba

NASA Astrophysics Data System (ADS)

Pätzmann, Ulrich; Brockner, Wolfgang

1987-06-01

The title compounds have been prepared and their Raman spectra recorded. The observed frequencies of (NH4)4P2S6 and Mg2P2S6 are assigned on the basis of P2S64- units with D3d symmetry. The Raman spectra of the Calcium, Strontium and Barium compounds indicate symmetry splitting, therefore the P2S64- frequencies are assigned with C2h symmetry. This assignment is supported by the correlation D3d → C2h. It is concluded that Sr2P2S6 and Ba2P2S6 crystallize in the monoclinic modification II.

Modulation of cytosolic and intra-sarcoplasmic reticulum calcium waves by calsequestrin in rat cardiac myocytes

PubMed Central

Kubalova, Zuzana; Györke, Inna; Terentyeva, Radmila; Viatchenko-Karpinski, Serge; Terentyev, Dmitry; Williams, Simon C; Györke, Sandor

2004-01-01

Waves of Ca2+-induced Ca2+ release occur in various cell types and are involved in the pathology of certain forms of cardiac arrhythmia. These arrhythmias include catecholaminergic polymorphic ventricular tachycardia (CPVT), certain cases of which are associated with mutations in the cardiac calsequestrin gene (CASQ2). To explore the mechanisms of Ca2+ wave generation and unravel the underlying causes of CPVT, we investigated the effects of adenoviral-mediated changes in CASQ2 protein levels on the properties of cytosolic and sarcoplasmic reticulum (SR) Ca2+ waves in permeabilized rat ventricular myocytes. The free [Ca2+] inside the sarcoplasmic reticulum ([Ca2+]SR) was monitored by fluo-5N entrapped into the SR, and cytosolic Ca2+ was imaged using fluo-3. Overexpression of CASQ2 resulted in significant increases in the amplitude of Ca2+ waves and interwave intervals, whereas reduced CASQ2 levels caused drastic reductions in the amplitude and period of Ca2+ waves. CASQ2 abundance had no impact on resting diastolic [Ca2+]SR or on the amplitude of the [Ca2+]SR depletion signal during the Ca2+ wave. However, the recovery dynamics of [Ca2+]SR following Ca2+ release were dramatically altered as the rate of [Ca2+]SR recovery increased ∼3-fold in CASQ2-overexpressing myocytes and decreased to 30% of control in CASQ2-underexpressing myocytes. There was a direct linear relationship between Ca2+ wave period and the half-time of basal [Ca2+]SR recovery following Ca2+ release. Loading the SR with the low affinity exogenous Ca2+ buffer citrate exerted effects quantitatively similar to those observed on overexpressing CASQ2. We conclude that free intra-SR [Ca2+] is a critical determinant of cardiac Ca2+ wave generation. Our data indicate that reduced intra-SR Ca2+ binding activity promotes the generation of Ca2+ waves by accelerating the dynamics of attaining a threshold free [Ca2+]SR required for Ca2+ wave initiation, potentially accounting for arrythmogenesis in CPVT linked to mutations in CASQ2. PMID:15486014

A reconstruction of sea surface temperature variability in the southeastern Gulf of Mexico from 1734 to 2008 C.E. using cross-dated Sr/Ca records from the coral Siderastrea siderea

NASA Astrophysics Data System (ADS)

DeLong, Kristine L.; Flannery, Jennifer A.; Poore, Richard Z.; Quinn, Terrence M.; Maupin, Christopher R.; Lin, Ke; Shen, Chuan-Chou

2014-05-01

This study uses skeletal variations in coral Sr/Ca from three Siderastrea siderea coral colonies within the Dry Tortugas National Park in the southeastern Gulf of Mexico (24°42'N, 82°48'W) to reconstruct monthly sea surface temperature (SST) variations from 1734 to 2008 Common Era (C.E.). Calibration and verification of the replicated coral Sr/Ca-SST reconstruction with local, regional, and historical temperature records reveals that this proxy-temperature relationship is stable back to 1879 C.E. The coral SST reconstruction contains robust interannual ( 2.0°C) and multidecadal variability ( 1.5°C) for the past 274 years, the latter of which does not covary with the Atlantic Multidecadal Oscillation. Winter SST extremes are more variable than summer SST extremes (±2.2°C versus ±1.6°C, 2σ) suggesting that Loop Current transport in the winter dominates variability on interannual and longer time scales. Summer SST maxima are increasing (+1.0°C for 274 years, σMC = ±0.5°C, 2σ), whereas winter SST minima contain no significant trend. Colder decades ( 1.5°C) during the Little Ice Age (LIA) do not coincide with decades of sunspot minima. The coral SST reconstruction contains similar variability to temperature reconstructions from the northern Gulf of Mexico (planktic foraminifer Mg/Ca) and the Caribbean Sea (coral Sr/Ca) suggesting areal reductions in the Western Hemisphere Warm Pool during the LIA. Mean summer coral SST extremes post-1985 C.E. (29.9°C) exceeds the long-term summer average (29.2°C for 1734-2008 C.E.), yet the warming trend after 1985 C.E. (0.04°C for 24 years, σMC = ±0.5, 2σ) is not significant, whereas Caribbean coral Sr/Ca studies contain a warming trend for this interval.

The major-ion composition of Cenozoic seawater: the past 36 million years from fluid inclusions in marine halite

USGS Publications Warehouse

Brennan, Sean T.; Lowenstein, Tim K.; Cendon, Dioni I.

2013-01-01

Fluid inclusions from ten Cenozoic (Eocene-Miocene) marine halites are used to quantify the major-ion composition (Mg2+, Ca2+, K+, Na+, SO42−, and Cl−) of seawater over the past 36 My. Criteria used to determine a seawater origin of the halites include: (1) stratigraphic, sedimentologic, and paleontologic observations; (2) Br− in halite; (3) δ34S of sulfate minerals; (4) 87Sr/86Sr of carbonates and sulfates; and (5) fluid inclusion brine compositions and evaporation paths, which must overlap from geographically separated basins of the same age to confirm a “global” seawater chemical signal. Changes in the major-ion chemistry of Cenozoic seawater record the end of a systematic, long term (>150 My) shift from the Ca2+-rich, Mg2+- and SO42−-poor seawater of the Mesozoic (“CaCl2 seas”) to the “MgSO4 seas” (with higher Mg2+ and SO42−>Ca2+) of the Cenozoic. The major ion composition of Cenozoic seawater is calculated for the Eocene-Oligocene (36-34 Ma), Serravallian-Tortonian (13.5-11.8 Ma) and the Messinian (6-5 Ma), assuming chlorinity (565 mmolal), salinity, and the K+ concentration (11 mmolal) are constant and the same as in modern seawater. Fluid inclusions from Cenozoic marine halites show that the concentrations of Mg2+and SO42− have increased in seawater over the past 36 My and the concentration of Ca2+ has decreased. Mg2+ concentrations increased from 36 mmolal in Eocene-Oligocene seawater (36-34 Ma) to 55 mmolal in modern seawater. The Mg2+/Ca2+ ratio of seawater has risen from ∼2.3 at the end of the Eocene, to 3.4 and 4.0, respectively, at 13.5 to 11.8 Ma and 6 to 5 Ma, and to 5 in modern seawater. Eocene-Oligocene seawater (36-34 Ma) has estimated ranges of SO42− = 14–23 mmolal and Ca2+ = 11–20 mmolal. If the (Ca2+)(SO42−) product is assumed to be the same as in modern seawater (∼300 mmolal2), Eocene-Oligocene seawater had Ca2+ ∼16 mmolal and SO42− ∼19 mmolal. The same estimates of Ca2+ and SO42− for Serravallian-Tortonian seawater (13.5-11.8 Ma) are SO42− = 19–27 mmolal and Ca2+ = 8–16 mmolal and SO42− ∼24 mmolal and Ca2+ ∼ 13 mmolal if the (Ca2+)(SO42−) product is equal to that in modern seawater. Messinian seawater has an estimated range of SO42− ∼21–29 mmolal and Ca2+ ∼7–15 mmolal with SO42− ∼26 mmolal and Ca2+ ∼12 mmolal assuming the (Ca2+)(SO42−) product is equal to that in modern seawater. Regardless of the estimation procedure, SO42− shows progressively increasing concentrations from 36 Ma to the present values, which are the highest of the Cenozoic.

Influence of several metal ions on the gelation activation energy of silicon tetraethoxide

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.

1988-01-01

The effects of nine metal cations (Li(+), Na(+), Mg(2+), Ca(2+), Sr(2+), Cu(2+), Al(3+), La(3+), and Y(3+) on silica gel formation has been investigated by studying the hydrolysis and polycondensation of silicon tetraethoxide (TEOS) in the presence of metal nitrates. The influence of water: TEOS mole ratio, metal ion concentration, and the reaction temperature has been investigated. The overall activation energy for gel formation has been determined from the temperature dependence of the time of gelation for each system. The activation energy for -Si-O-Si- network formation is found to be 54.5 kJ/mol. The gel formation time as well as the activation energy sharply increase in the presence of Cu(2+), Al(3+), La(3+) and Y(3+). In contrast, the presence of Li(+), Na(+), Mg(2+), Ca(2+), or, Sr(2+) lowers the gelation time, but has no appreciable effect on the activation energy. This difference may be attributed to the participation or nonparticipation of the metal ions in the formation of the three-dimensional polymeric network during the polycondensation step. The concentration of metal ion (Mg(2+), Ca(2+), Y(3+) or the water: TEOS mole ratio had no appreciable effect on the gelation activation energy. A simple test has been proposed to determine whether a metal ion would act as a network intermediate or modifier in silica and other glassy networks.

Effects of elevated physiological temperatures on sarcoplasmic reticulum function in mechanically skinned muscle fibers of the rat.

PubMed

van der Poel, C; Stephenson, D G

2007-07-01

Properties of the sarcoplasmic reticulum (SR) with respect to Ca(2+) loading and release were measured in mechanically skinned fiber preparations from isolated extensor digitorum longus (EDL) muscles of the rat that were either kept at room temperature (23 degrees C) or exposed to temperatures in the upper physiological range for mammalian skeletal muscle (30 min at 40 or 43 degrees C). The ability of the SR to accumulate Ca(2+) was significantly reduced by a factor of 1.9-2.1 after the temperature treatments due to a marked increase in SR Ca(2+) leak, which persisted for at least 3 h after treatment. Results with blockers of Ca(2+) release channels (ruthenium red) and SR Ca(2+) pumps [2,5-di(tert-butyl)-1,4-hydroquinone] indicate that the increased Ca(2+) leak was not through the SR Ca(2+) release channel or the SR Ca(2+) pump, although it is possible that the leak pathway was via oligomerized Ca(2+) pump molecules. No significant change in the maximum SR Ca(2+)-ATPase activity was observed after the temperature treatment, although there was a tendency for a decrease in the SR Ca(2+)-ATPase. The observed changes in SR properties were fully prevented by the superoxide (O(2)(*-)) scavenger Tiron (20 mM), indicating that the production of O(2)(*-) at elevated temperatures is responsible for the increase in SR Ca(2+) leak. Results show that physiologically relevant elevated temperatures 1) induce lasting changes in SR properties with respect to Ca(2+) handling that contribute to a marked increase in the SR Ca(2+) leak and, consequently, to the reduction in the average coupling ratio between Ca(2+) transport and SR Ca(2+)-ATPase and muscle performance, and 2) that these changes are mediated by temperature-induced O(2)(*-) production.

Effect of ADP on slow-twitch muscle fibres of the rat: implications for muscle fatigue.

PubMed

Macdonald, W A; Stephenson, D G

2006-05-15

Slow-twitch mechanically skinned fibres from rat soleus muscle were bathed in solutions mimicking the myoplasmic environment but containing different [ADP] (0.1 microm to 1.0 mm). The effect of ADP on sarcoplasmic reticulum (SR) Ca2+-content was determined from the magnitude of caffeine-induced force responses, while temporal changes in SR Ca2+-content allowed determination of the effective rates of the SR Ca2+-pump and of the SR Ca2+-leak. The SR Ca2+-pump rate, estimated at pCa (-log10[Ca2+]) 7.8, was reduced by 20% as the [ADP] was increased from 0.1 to 40 microm, with no further alteration when the [ADP] was increased to 1.0 mm. The SR Ca2+-leak rate constant was not altered by increasing [ADP] from 0.1 to 40 microm, but was increased by 26% when the [ADP] was elevated to 1.0 mm. This ADP-induced SR Ca2+-leak was insensitive to ruthenium red but was abolished by 2,5-di(tert-butyl)-1,4-hydroquinone (TBQ), indicating that the leak pathway is via the SR Ca2+-pump and not the SR Ca2+-release channel. The decrease in SR Ca2+-pump rate and SR Ca2+-leak rate when [ADP] was increased led to a 40% decrease in SR Ca2+-loading capacity. Elevation of [ADP] had only minor direct effects on the contractile apparatus of slow-twitch fibres. These results suggest that ADP has only limited depressing effects on the contractility of slow-twitch muscle fibres. This is in contrast to the marked effects of ADP on force responses in fast-twitch muscle fibres and may contribute to the fatigue-resistant nature of slow-twitch muscle fibres.

Screening tests in toxicity or drug effect studies with use of centrifichem general-purpose spectrophotometeric analyzer

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

Nagy, B.; Bercz, J.P.

CentrifiChem System 400 general-purpose spectrophotometric analyzer which can process simultaneously 30 samples and reads the reactions within milliseconds was used for toxicity studies. Organic and inorganic chemicals were screened for inhibitory action of the hydrolytic activity of sarcoplasmic reticulum (SR) Ca,Mg-ATPase and that of the sacrolemmal (SL) Na,K-ATPase, or mitochondrial ATPase (M). SR and SL were prepared from rabbit muscles, Na,K-ATPase from pig kidneys, M from pig hearts. Pseudosubstrates of paranitrophenyl phosphate and 2,4-dinitrophenyl phosphate, both proven high energy phosphate substitutes for ATPase coupled ion transfer were used. The reaction rates were followed spectrophotometrically at 405 nm measuring the accumulationmore » of yellow nitrophenolate ions. The reported calcium transfer coupling ratio to hydrolysis of 2:1 was ascertained with use of /sup 45/Ca in case of SR. Inhibition constants (pI) on SR, SL, and M for the pseudosubstrate hydrolysis will be given for over 20 chemicals tested. The applicability of the system to general toxicity testing and to general cardio-effective drug screening will be presented.« less

Sr/Ca ratios in cold-water corals - a 'low-resolution' temperature archive?

NASA Astrophysics Data System (ADS)

Rüggeberg, Andres; Riethdorf, Jan-Rainer; Raddatz, Jacek; López Correa, Matthias; Montagna, Paolo; Dullo, Wolf-Christian; Freiwald, André

2010-05-01

One of the basic data to understand global change and past global changes is the measurement and the reconstruction of temperature of marine water masses. E.g. seawater temperature controls the density of seawater and in combination with salinity is the major driving force for the oceans circulation system. Geochemical investigations on cold-water corals Lophelia pertusa and Desmophyllum cristagalli indicated the potential of these organisms as high-resolution archives of environmental parameters from intermediate and deeper water masses (Adkins and Boyle 1997). Some studies tried to use cold-water corals as a high-resolution archive of temperature and salinity (Smith et al. 2000, 2002; Blamart et al. 2005; Lutringer et al. 2005). However, the fractionation of stable isotopes (delta18O and delta13C) and element ratios (Sr/Ca, Mg/Ca, U/Ca) are strongly influenced by vital effects (Shirai et al. 2005; Cohen et al. 2006), and difficult to interpret. Nevertheless, ongoing studies indicate the potential of a predominant temperature dependent fractionation of distinct isotopes and elements (e.g. Li/Ca, Montagna et al. 2008; U/Ca, Mg/Ca, delta18O, Lòpez Correa et al. 2008; delta88/86Sr, Rüggeberg et al. 2008). Within the frame of DFG-Project TRISTAN and Paläo-TRISTAN (Du 129/37-2 and 37-3) we investigated live-collected specimens of cold-water coral L. pertusa from all along the European continental margin (Northern and mid Norwegian shelves, Skagerrak, Rockall and Porcupine Bank, Galicia Bank, Gulf of Cadiz, Mediterranean Sea). These coral samples grew in waters characterized by temperatures between 6°C and 14°C. Electron Microprobe investigations along the growth direction of individual coral polyps were applied to determine the relationship between the incorporation of distinct elements (Sr, Ca, Mg, S). Cohen et al. (2006) showed for L. pertusa from the Kosterfjord, Skagerrak, that ~25% of the coral's Sr/Ca ratio is related to temperature, while 75% are influenced by the calcification rate of the organism. However, the Sr/Ca-temperature relation of our L. pertusa specimens suggest, that mean values are more reliable for temperature reconstruction along a larger temperature range than local high-resolution investigations. Additionally, our results plot on same line of Sr/Ca-temperature relationship like tropical corals indicating a similar behaviour of element incorporation during calcification. References: Adkins JF, Boyle EA (1997) Changing atmospheric ∆14C and the record of deep water paleoventilation ages. Paleoceanography 12:337-344 Blamart D, Rollion-Bard C, Cuif J-P, Juillet-Leclerc A, Lutringer A, Weering Tv, Henriet J-P (2005) C and O isotopes in a deep-sea coral (Lophelia pertusa) related to skeletal microstructure. In: Freiwald A, Roberts JM (eds) Cold-water Corals and Ecosystems. Springer-Verlag, Berlin Heidelberg, p 1005-1020 Cohen AL, Gaetani GA, Lundälv T, Corliss BH, George RY (2006) Compositional variability in a cold-water scleractinian, Lophelia pertusa: New insights into vital effects. Geochemistry, Geophysics, Geosystems 7:Q12004, doi:12010.11029/12006GC001354 López Correa M, Montagna P, Rüggeberg A, McCulloch M, Taviani M, Freiwald A (2008) Trace elements and stable isotopes in recent North Atlantic Lophelia pertusa along a latitudal gradient and from fossil Mediterranean sites. ASLO 2008 Summer Meeting, St. John's, Newfoundland & Labrador, Canada, 08.06.-13.06.2008, p. 47 Lutringer A, Blamart D, Frank N, Labeyrie L (2005) Paleotemperatures from deep-sea corals: scale effects. In: Freiwald A, Roberts JM (eds) Cold-water Corals and Ecosystems. Springer-Verlag, Berlin, Heidelberg, p 1081-1096 Montagna P, López-Correa M, Rüggeberg A, McCulloch M, Rodolfo-Metalpa R, Dullo W-C, Ferrier-Pagès C, Freiwald A, Henderson G, Mazzoli C, Russo S, Silenzi S, Taviani M (2008) Coral Li/Ca in micro-structural domains as a temperature proxy. Goldschmidt Conference, Vancouver, British Columbia, Canada Rüggeberg A, Fietzke J, Liebetrau V, Eisenhauer A, Dullo W-C, Freiwald A (2008) Stable strontium isotopes (delta88/86Sr) in cold-water corals — A new proxy for reconstruction of intermediate ocean water temperatures. Earth and Planetary Science Letters 269:569-574 Shirai K, Kusakabe M, Nakai S, Ishii T, Watanabe T, Hiyagon H, Sano Y (2005) Deep-sea coral geochemistry: Implication for the vital effect. Chemical Geology 224:212-222 Smith JE, Schwarcz HP, Risk MJ (2002) Patterns of isotopic disequilibria in azooxanhtellate coral skeletons. Hydrobiologia 471:111-115 Smith JE, Schwarcz HP, Risk MJ, McConnaughey TA, Keller N (2000) Paleotemperatures from deep-sea corals: Overcoming 'vital effects'. Palaios 15:25-32

The cargo receptor p24A facilitates calcium sensing receptor maturation and stabilization in the early secretory pathway

PubMed Central

Stepanchick, Ann; Breitwieser, Gerda E.

2010-01-01

The calcium sensing receptor (CaSR) is a Family 3/C G protein-coupled receptor with slow and partial targeting to the plasma membrane in both native and heterologous cells. We identified cargo receptor family member p24A in yeast two-hybrid screens with the CaSR carboxyl terminus. Interactions were confirmed by immunoprecipitation of either p24A or CaSR in transiently transfected HEK293 cells. Only the immaturely glycosylated form of CaSR interacts with p24A. Dissociation likely occurs in the endoplasmic reticulum Golgi intermediate compartment (ERGIC) or cis-Golgi, since only the uncleaved form of a CaSR mutant sensitive to the trans-Golgi enzyme furin was coimmunoprecipitated with p24A. p24A and p24A(ΔGOLD) significantly increased total and plasma membrane CaSR protein but p24A(FF/AA) did not. The CaSR carboxyl terminus distal to T868 is required for differential sensitivity to p24A and its mutants. Interaction with p24A therefore increases CaSR stability in the ER and enhances plasma membrane targeting. Neither wt Sar1p or the T39N mutant increased CaSR maturation or abundance while the H79G mutant increased abundance but prevented maturation of CaSR. These results suggest that p24A is the limiting factor in CaSR trafficking in the early secretory pathway, and that cycling between the ER and ERGIC protects CaSR from degradation. PMID:20361938

Relationships between water and paddlefish Polyodon spathula dentary elemental and stable-isotopic signatures: potential application for reconstructing environmental history

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

Bock, Lindsey R.; Whitledge, Gregory W.; Pracheil, Brenda M.

The objectives of this study were to characterize relationships between water and paddlefish Polyodon spathula dentary Sr:Ca, δ 18O and stable hydrogen isotope ratio (δD) to determine the accuracy with which individual P. spathula could be assigned to their collection locations using dentary-edge Sr:Ca, δD and δ 18O. A laboratory experiment was also conducted to determine whether dentary Sr:Ca in age 0 year P. spathula would reflect shifts in water Sr:Ca to which fish were exposed. Significant linear relationships between water and dentary Sr:Ca, δD and δ 18O were observed, although the relationship between water and dentary δ 18O wasmore » weaker than those for Sr:Ca and δD. Classification success for individual fish to collection locations that differed in water Sr:Ca, δD and δ 18O ranged from 86 to 100% based on dentary-edge Sr:Ca, δD and δ18O. Dentary Sr:Ca increased significantly in laboratory-reared age 0 year P. spathula following 4 weeks of exposure to elevated water Sr:Ca; dentary Sr:Ca of fish held in water with elevated Sr:Ca was also significantly higher than that of control fish reared in ambient laboratory water. Results indicated that P. spathula dentaries reflect water signatures for commonly-applied natural chemical markers and strongly suggest that dentary microchemistry and stable-isotopic compositions will be applicable for reconstructing P. spathula environmental history in locations where sufficient spatial differences in water chemistry occur.« less

Relationships between water and paddlefish Polyodon spathula dentary elemental and stable-isotopic signatures: potential application for reconstructing environmental history

DOE PAGES

Bock, Lindsey R.; Whitledge, Gregory W.; Pracheil, Brenda M.; ...

2016-07-26

The objectives of this study were to characterize relationships between water and paddlefish Polyodon spathula dentary Sr:Ca, δ 18O and stable hydrogen isotope ratio (δD) to determine the accuracy with which individual P. spathula could be assigned to their collection locations using dentary-edge Sr:Ca, δD and δ 18O. A laboratory experiment was also conducted to determine whether dentary Sr:Ca in age 0 year P. spathula would reflect shifts in water Sr:Ca to which fish were exposed. Significant linear relationships between water and dentary Sr:Ca, δD and δ 18O were observed, although the relationship between water and dentary δ 18O wasmore » weaker than those for Sr:Ca and δD. Classification success for individual fish to collection locations that differed in water Sr:Ca, δD and δ 18O ranged from 86 to 100% based on dentary-edge Sr:Ca, δD and δ18O. Dentary Sr:Ca increased significantly in laboratory-reared age 0 year P. spathula following 4 weeks of exposure to elevated water Sr:Ca; dentary Sr:Ca of fish held in water with elevated Sr:Ca was also significantly higher than that of control fish reared in ambient laboratory water. Results indicated that P. spathula dentaries reflect water signatures for commonly-applied natural chemical markers and strongly suggest that dentary microchemistry and stable-isotopic compositions will be applicable for reconstructing P. spathula environmental history in locations where sufficient spatial differences in water chemistry occur.« less

SALT EFFECTS ON EGGS AND NAUPLII OF ARTEMIA SALINA L

PubMed Central

Boone, Eleanor; Baas-Becking, L. G. M.

1931-01-01

Eggs of Artemia salina L., the brine shrimp, are easily obtainable in large quantities. Ecdysis takes place in two stages: (a) extrusion of the inner membrane, and (b) ecdysis of the nauplius from that membrane. The conditions which allow for the former are much more varied than those for the latter. Nauplii form in only solutions of a few sodium salts; and, in Mg, Ca, and Sr salts, potassium is very toxic. The possible environment for the nauplii (1 M total molarity) has been ascertained for chlorides of Na, K, Mg, and Ca. The facts observed account for the peculiar distribution of the organism. PMID:19872620

Highly Resolved Mg/Ca Depth Profiles of Planktic Foraminifer test Walls Using Single shot Measurements of fs-LA-ICPMS

NASA Astrophysics Data System (ADS)

Jochum, K. P.; Schiebel, R.; Stoll, B.; Weis, U.; Haug, G. H.

2017-12-01

Foraminifers are sensitive archives of changes in climate and marine environment. It has been shown that the Mg/Ca signal is a suitable proxy of seawater temperature, because the incorporation of Mg depends on ambient water temperature. In contrast to most former studies, where this ratio is determined by solution-based bulk analysis of 20 - 30 specimens, we have investigated Mg/Ca in single specimens and single chambers at high resolution. A new fs-200 nm-LA-ICPMS technique was developed for the µm-sized layered calcite shells. To generate depth profiles with a resolution of about 50 nm/shot, we chose a low fluence of about 0.3 Jcm-2 and performed single shot measurements of the double charged 44Ca++ and the single charged 25Mg+ ions together. Precision (RSD) of the Mg/Ca data is about 5 %. Calibration was performed with the carbonate reference material MACS-3 from the USGS. Our results for different species from the Arabian Sea and Caribbean Sea demonstrate that Mg/Ca of different chambers vary and indicate that the foraminifer individuals built their chambers in different water depths and/or experienced seasonal changes in seawater temperature caused, for example, by upwelling (cold) versus stratified (warm) conditions. Typically, the Mg/Ca ratios of the final two chambers of the planktic foraminifer Globorotalia menardii from a sediment core of the Arabian Sea differ by about 5 mmol/mol from earlier chambers (2 mmol/mol) corresponding to seawater temperatures of 28 °C and 18 °C, respectively. In addition, mass fractions of other elements like Sr, Mn, Fe, Ba, and U have been determined with fs-LA-ICPMS using fast line scans, and thus provide further insights in the ecology of foraminifers.

Migration and rearing histories of chinook salmon (Oncorhynchus tshawytscha) determined by ion microprobe Sr isotope and Sr/Ca transects of otoliths

USGS Publications Warehouse

Bacon, C.R.; Weber, P.K.; Larsen, K.A.; Reisenbichler, R.; Fitzpatrick, J.A.; Wooden, J.L.

2004-01-01

Strontium isotope and Sr/Ca ratios measured in situ by ion microprobe along radial transects of otoliths of juvenile chinook salmon (Oncorhynchus tshawytscha) vary between watersheds with contrasting geology. Otoliths from ocean-type chinook from Skagit River estuary, Washington, had prehatch regions with 87Sr/86Sr ratios of ???0.709, suggesting a maternally inherited marine signature, extensive fresh water growth zones with 87Sr/86Sr ratios similar to those of the Skagit River at ???0.705, and marine-like 87Sr/86Sr ratios near their edges. Otoliths from stream-type chinook from central Idaho had prehatch 87Sr/86Sr ratios ???0.711, indicating that a maternal marine Sr isotopic signature is not preserved after the ???1000- to 1400-km migration from the Pacific Ocean. 87Sr/86Sr ratios in the outer portions of otoliths from these Idaho juveniles were similar to those of their respective streams (???0.708-0.722). For Skagit juveniles, fresh water growth was marked by small decreases in otolith Sr/Ca, with increases in Sr/Ca corresponding to increases in 87Sr/86Sr with migration into salt water. Otoliths of Idaho fish had Sr/Ca radial variation patterns that record seasonal fluctuation in ambient water Sr/Ca ratios. The ion microprobe's ability to measure both 87Sr/86Sr and Sr/Ca ratios of otoliths at high spatial resolution in situ provides a new tool for studies of fish rearing and migration. ?? 2004 NRC Canada.

Elemental signatures in otoliths of hatchery rainbow trout (Oncorhynchus mykiss): Distinctiveness and utility fo detecting origins and movement

USGS Publications Warehouse

Gibson-Reinemer, D. K.; Johnson, B.M.; Martinez, P.J.; Winkelman, D.L.; Koenig, A.E.; Woodhead, J.D.

2009-01-01

Otolith chemistry in freshwater has considerable potential to reveal patterns of origin and movement, which would benefit traditional fisheries management and provide a valuable tool to curb the spread of invasive and illicitly stocked species. We evaluated the relationship between otolith and water chemistry for five markers (Ba/Ca, Mn/Ca, Sr/ Ca, Zn/Ca, and 87Sr/86Sr) in rainbow trout (Oncorhynchus mykiss) using the existing hatchery system in Colorado and Wyoming, USA, to provide controlled, seminatural conditions. Otolith Ba/Ca, Sr/Ca, and 87Sr/86Sr reflected ambient levels, whereas Mn/Ca and Zn/Ca did not. Using only the markers correlated with water chemistry, we classified fish to their hatchery of origin with up to 96% accuracy when element and isotope data were used together. Large changes in 87Sr/Sr were evident in otolith transects, although subtler changes in Sr/Ca were also detectable. Our results suggest the relatively few otolith markers that reflect ambient chemistry can discriminate among locations and track movements well enough to provide valuable insight in a variety of applied contexts.

Allometric constraints on Sr/Ca and Ba/Ca partitioning in terrestrial mammalian trophic chains.

PubMed

Balter, Vincent

2004-03-01

In biological systems, strontium (Sr) and barium (Ba) are two non-essential elements, in comparison to calcium (Ca) which is essential. The Sr/Ca and Ba/Ca ratios tend to decrease in biochemical pathways which include Ca as an essential element, and these processes are termed biopurification of Ca. The quantitative pathway of the biopurification of Ca in relation to Sr and Ba between two biological reservoirs ( Rn and R(n -1)) is measured with an observed ratio (OR) expressed by the (Sr/Ca) Rn /(Sr/Ca)( Rn-1) and (Ba/Ca) Rn /(Ba/Ca)( Rn-1) ratios. For a mammalian organism, during the whole biopurification of Ca starting with the diet to the ultimate reservoir of Ca which is the bone, the mean values for ORSr and ORBa are 0.25 and 0.2, respectively. In this study, published Sr/Ca and Ba/Ca ratios are used for three sets of soils, plants, and bones of herbivorous and carnivorous mammals, each comprising a trophic chain, to illustrate the biopurification of Ca at the level of trophic chains. Calculated ORSr and ORBa of herbivore bones in relation to plants and of bones of carnivores in relation to bones of herbivores give ORSr=0.30+/-0.08 and ORBa=0.16+/-0.08, thus suggesting that trophic chains reflect the Sr/Ca and Ba/Ca fluxes that are prevalent at the level of a mammalian organism. The slopes of the three regression equations of log(Sr/Ca) vs. log(Ba/Ca) are similar, indicating that the process of biopurification of Ca with respect to Sr and Ba is due to biological processes and is independent of the geological settings. Modifications of the logarithmic expression of the Sr/Ca and Ba/Ca relationship allow a new formula of the biopurification process to be deduced, leading to the general equation ORBa=ORSr(1.79+/-0.33), where the allometric coefficient is the mean of the slopes of the three regression equations. Some recent examples are used to illustrate this new analysis of predator-prey relations between mammals. This opens up new possibilities for the utilization of Ba/Ca and Sr/Ca in addition to stable isotope ratios (delta13C and delta15N) for the determination of the relative contribution of different food sources to an animal's diet.

Activation by divalent cations of a Ca2+-activated K+ channel from skeletal muscle membrane.

PubMed

Oberhauser, A; Alvarez, O; Latorre, R

1988-07-01

Several divalent cations were studied as agonists of a Ca2+-activated K+ channel obtained from rat muscle membranes and incorporated into planar lipid bilayers. The effect of these agonists on single-channel currents was tested in the absence and in the presence of Ca2+. Among the divalent cations that activate the channel, Ca2+ is the most effective, followed by Cd2+, Sr2+, Mn2+, Fe2+, and Co2+. Mg2+, Ni2+, Ba2+, Cu2+, Zn2+, Hg2+, and Sn2+ are ineffective. The voltage dependence of channel activation is the same for all the divalent cations. The time-averaged probability of the open state is a sigmoidal function of the divalent cation concentration. The sigmoidal curves are described by a dissociation constant K and a Hill coefficient N. The values of these parameters, measured at 80 mV are: N = 2.1, K = 4 X 10(-7) mMN for Ca2+; N = 3.0, K = 0.02 mMN for Cd2+; N = 1.45, K = 0.63 mMN for Sr2+; N = 1.7, K = 0.94 mMN for Mn2+; N = 1.1, K = 3.0 mMN for Fe2+; and N = 1.1 K = 4.35 mMN for Co2+. In the presence of Ca2+, the divalent cations Cd2+, Co2+, Mn2+, Ni2+, and Mg2+ are able to increase the apparent affinity of the channel for Ca2+ and they increase the Hill coefficient in a concentration-dependent fashion. These divalent cations are only effective when added to the cytoplasmic side of the channel. We suggest that these divalent cations can bind to the channel, unmasking new Ca2+ sites.

The effect of drinking water quality on the health and longevity of people-A case study in Mayang, Hunan Province, China

NASA Astrophysics Data System (ADS)

Lu, J.; Yuan, F.

2017-08-01

Drinking water is an important source for trace elements intake into human body. Thus, the drinking water quality has a great impact on people’s health and longevity. This study aims to study the relationship between drinking water quality and human health and longevity. A longevity county Mayang in Hunan province, China was chosen as the study area. The drinking water and hair of local centenarians were collected and analyzed the chemical composition. The drinking water is weak alkaline and rich in the essential trace elements. The daily intakes of Ca, Cu, Fe, Se, Sr from drinking water for residents in Mayang were much higher than the national average daily intake from beverage and water. There was a positive correlation between Ni and Pb in drinking water and Ni and Pb in hair. There were significant correlations between Cu, K in drinking water and Ba, Ca, Mg, Sr in the hair at the 0.01 level. The concentrations of Mg, Sr, Se in drinking water showed extremely significant positive relation with two centenarian index 100/80% and 100/90% correlation. Essential trace elements in drinking water can be an important factor for local health and longevity.

The Ca2+-ATPase pump facilitates bidirectional proton transport across the sarco/endoplasmic reticulum.

PubMed

Espinoza-Fonseca, L Michel

2017-03-28

Ca 2+ transport across the sarco/endoplasmic reticulum (SR) plays an essential role in intracellular Ca 2+ homeostasis, signalling, cell differentiation and muscle contractility. During SR Ca 2+ uptake and release, proton fluxes are required to balance the charge deficit generated by the exchange of Ca 2+ and other ions across the SR. During Ca 2+ uptake by the SR Ca 2+ -ATPase (SERCA), two protons are countertransported from the SR lumen to the cytosol, thus partially compensating for the charge moved by Ca 2+ transport. Studies have shown that protons are also transported from the cytosol to the lumen during Ca 2+ release, but a transporter that facilitates proton transport into the SR lumen has not been described. In this article we propose that SERCA forms pores that facilitate bidirectional proton transport across the SR. We describe the location and structure of water-filled pores in SERCA that form cytosolic and luminal pathways for protons to cross the SR membrane. Based on this structural information, we suggest mechanistic models for proton translocation to the cytosol during active Ca 2+ transport, and into the SR lumen during SERCA inhibition by endogenous regulatory proteins. Finally, we discuss the physiological consequences of SERCA-mediated bidirectional proton transport across the SR membrane of muscle and non-muscle cells.

Electrical and magnetic properties of several ruthenates and superconductivity in magnesium boride and MgCNi(3)

NASA Astrophysics Data System (ADS)

He, Tao

2002-09-01

Perovskite-based ruthenates have been receiving considerable attention both because of their interesting and variable magnetic properties, and because of the discovery of exotic superconductivity in the layered ruthenate Sr 2RuO4. Another perovskite, SrRuO3, is the only known oxide ferromagnet with a 4d transition metal, and magnetism is easily suppressed by Ca doping. The suppression of ferromagnetic interactions in SrxCa1-xRuO3 has frequently been attributed to the orthorhombic structural distortion, either through the crossover to classical antiferromagnetic interactions, or, alternatively, to a nearly ferromagnetic metal. This study reports the comparison of the magnetic properties of Srx(Na0.5La0.5)1-xRuO 3 to SrxCa1-xRuO3, showing that there is a much faster suppression of ferromagnetic interactions in the former case. Neither orthorhombic distortion nor cation size disorder can explain the observed difference. Instead, the difference may be attributed to charge disorder on the A-site, which greatly affects the local environment of Ru atoms and leads to the faster suppression of the long-range ferromagnetic state. The magnetic ground state of perovskite structure CaRuO3 has been enigmatic for decades. This study also shows that paramagnetic CaRuO 3 can be made ferromagnetic by very small amounts of partial substitution of Ru by various transition metals. The results are consistent with the recent proposal that CaRuO3 is not a classical antiferromagnet, but rather is poised at a critical point between ferromagnetic and paramagnetic ground states. Ti, Fe, Mn and Ni doping result in ferromagnetic behavior. The second part of this thesis is on the superconductivity of MgB 2 and MgCNi3. Since the discovery of superconductivity in MgB2 in January 2001, detailed information on its properties has been rapidly accumulated. The reported properties, the very simple structure, and the commercial availability of this material make MgB2 a favorite candidate for large scale and electronic applications. In thin film fabrication, the reactivity of MgB2 with substrate materials or insulating or metallic layers in multi-layer circuits is an important factor. In this work the reactivity of MgB2 with powdered forms of common substrate and electronic materials is studied. Some oxides and nitrides prove to be potentially good substrates for making thin films, while others, including some commonly used substrates like Al2O3, SrTiO 3, and SiO2, have serious chemical compatibility problems. In the latter case, caution should be taken when fabricating thin films. This thesis also describes the discovery of superconductivity at 8 K in the perovskite structure compound MgCNi3. This material is the three-dimensional analogue of the LnNi2B2C family of superconductors, which have Tcs up to 16K. The itinerant electrons in both LnNi2B2C and MgCNi3 are based on partial filling of Ni d-states, which generally leads to ferromagnetism, as is the case in metallic Ni. The very high relative proportion of Ni in MgCNi3 is especially suggestive of the possible importance of magnetic interactions in the superconductivity, and, further, the lower Tc of the three-dimensional compound is contrary to conventional ideas.

ß-Adrenergic Stimulation Increases RyR2 Activity via Intracellular Ca2+ and Mg2+ Regulation

PubMed Central

Li, Jiao; Imtiaz, Mohammad S.; Beard, Nicole A.; Dulhunty, Angela F.; Thorne, Rick; vanHelden, Dirk F.; Laver, Derek R.

2013-01-01

Here we investigate how ß-adrenergic stimulation of the heart alters regulation of ryanodine receptors (RyRs) by intracellular Ca2+ and Mg2+ and the role of these changes in SR Ca2+ release. RyRs were isolated from rat hearts, perfused in a Langendorff apparatus for 5 min and subject to 1 min perfusion with 1 µM isoproterenol or without (control) and snap frozen in liquid N2 to capture their phosphorylation state. Western Blots show that RyR2 phosphorylation was increased by isoproterenol, confirming that RyR2 were subject to normal ß-adrenergic signaling. Under basal conditions, S2808 and S2814 had phosphorylation levels of 69% and 15%, respectively. These levels were increased to 83% and 60%, respectively, after 60 s of ß-adrenergic stimulation consistent with other reports that ß-adrenergic stimulation of the heart can phosphorylate RyRs at specific residues including S2808 and S2814 causing an increase in RyR activity. At cytoplasmic [Ca2+] <1 µM, ß-adrenergic stimulation increased luminal Ca2+ activation of single RyR channels, decreased luminal Mg2+ inhibition and decreased inhibition of RyRs by mM cytoplasmic Mg2+. At cytoplasmic [Ca2+] >1 µM, ß-adrenergic stimulation only decreased cytoplasmic Mg2+ and Ca2+ inhibition of RyRs. The Ka and maximum levels of cytoplasmic Ca2+ activation site were not affected by ß-adrenergic stimulation. Our RyR2 gating model was fitted to the single channel data. It predicted that in diastole, ß-adrenergic stimulation is mediated by 1) increasing the activating potency of Ca2+ binding to the luminal Ca2+ site and decreasing its affinity for luminal Mg2+ and 2) decreasing affinity of the low-affinity Ca2+/Mg2+ cytoplasmic inhibition site. However in systole, ß-adrenergic stimulation is mediated mainly by the latter. PMID:23533585

Strontium (Sr) separation from seawater using titanate adsorbents: Effects of seawater matrix ions on Sr sorption behavior

NASA Astrophysics Data System (ADS)

Ryu, Jungho; Hong, Hye-jin; Ryu, Taegong; Park, In-Su

2017-04-01

Strontium (Sr) which has many industrial applications such as ferrite magnet, ceramic, and fire works exists in seawater with the concentration of approximately 7 mg/L. In previous report estimating economic potential on recovery of various elements from seawater in terms of their commercial values and concentrations in seawater, Sr locates upper than approximate break-even line, which implies Sr recovery from seawater can be potentially profitable. Recently, Sr separation from seawater has received great attention in the environmental aspect after Fukushima Nuclear Power Plant (NPP) accident which released much amount of radioactive Sr and Cs. Accordingly, the efficient separation of radioactive elements released to seawater has become critical as an important technological need as well as their removal from radioactive wastes. So far, it has been introduced to separate Sr from aqueous media by various methods including solvent extraction, adsorption by solid materials, and ion exchange. Among them, the adsorption technique using solid adsorbents is of great interest for selectively separating Sr from seawater with respect to low concentration level of Sr. In this study, we synthesized titanate nanotube (TiNT) by simple hydrothermal reaction, characterized its physicochemical properties, and systematically evaluated Sr sorption behavior under various reaction conditions corresponding to seawater environment. The synthesized TiNT exhibited the fibril-type nanotube structure with high specific surface area of 260 m2/g. The adsorption of Sr on TiNT rapidly occurred following pseudo-second-order kinetic model, and was in good agreement with Langmuir isotherm model, indicating maximum adsorption capacity of 97 mg/g. Based on Sr uptake and Na release with stoichiometric balance, sorption mechanism of Sr on TiNT was found to be ion-exchange between Na in TiNT lattice and Sr in solution phase, which was also confirmed by XRD and Raman analysis. Among competitive ions, Ca significantly hindered Sr sorption on TiNT, whereas Na had little effect on Sr sorption despite the sorption mechanism of Na-exchange. The effect of Ca on Sr sorption was evaluated in detail by introducing distribution coefficient (Kd) that is critical factor to determine the selectivity, revealing slightly higher selectivity for Sr. The adsorption-desoption test of Sr in real seawater medium enabled to determine Kd and concentration factor (CF) for co-existing matrix ions in seawater, and these values were assessed in both aspects of removal and recovery of Sr from seawater. The TiNT could be easily regenerated by acid treatment and reused for repeated cycle, supporting its long term use for the practical application of removing and recovering Sr from seawater.

A novel method to develop an otolith microchemistry model to determine striped bass habitat use in the San Francisco Estuary

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

Phillis, C C; Ostrach, D J; Gras, M

2006-06-14

Otolith Sr/Ca has become a popular tool for hind casting habitat utilization and migration histories of euryhaline fish. It can readily identify habitat shifts of diadromous fish in most systems. Inferring movements of fish within estuarine habitat, however, requires a model of that accounts of the local water chemistry and the response of individual species to that water chemistry, which is poorly understood. Modeling is further complicated by the fact that high marine Sr and Ca concentrations results in a rapid, nonlinear increase in water Sr/Ca and {sup 87}Sr/{sup 86}Sr between fresh and marine waters. Here we demonstrate a novelmore » method for developing a salinity-otolith Sr/Ca model for the purpose of reconstructing striped bass (Morone saxatilis) habitat use in the San Francisco Bay estuary. We used correlated Sr/Ca and {sup 87}Sr/{sup 86}Sr ratios measurements from adult otoliths from striped bass that experienced a range of salinities to infer striped bass otolith Sr/Ca response to changes in salinity and water Sr/Ca ratio. Otolith {sup 87}Sr/{sup 86}Sr can be assumed to accurately record water {sup 87}Sr/{sup 86}Sr because there is no biological fractionation of Sr isotopes. Water {sup 87}Sr/{sup 86}Sr can in turn be used to estimate water salinity based on the mixing of fresh and marine water with known {sup 87}Sr/{sup 86}Sr ratios. The relationship between adjacent analyses on otoliths of Sr/Ca and {sup 87}Sr/{sup 86}Sr by LA-ICP-MS and MC-ICP-MS (r{sup 2} = 0.65, n = 66) is used to predict water salinity from a measured Sr/Ca ratio. The nature of this non-linear model lends itself well to identifying residence in the Delta and to a lesser extent Suisun Bay, but does not do well locating residence within the more saline bays west of Carquinez Strait. An increase in the number of analyses would improve model confidence, but ultimately the precision of the model is limited by the variability in the response of individual fish to water Sr/Ca.« less

Hot cracking during welding and casting

NASA Astrophysics Data System (ADS)

Cao, Guoping

Aluminum welds are susceptible to liquation cracking in the partially melted zone (PMZ). Using the multicomponent Scheil model, curves of temperature vs. fraction solid (T-fS) during solidification were calculated for the PMZ and weld metals (WMs). These curves were used to predict the crack susceptibility by checking if the harmful condition of WM fS > PMZ fS exists during PMZ solidification and reduce the susceptibility by minimizing this condition. This approach was tested against full-penetration welds of alloys 7075 and 2024 and it can be used to guide the selection or development of filler metals. Liquation cracking in the PMZ in welds of Al-Si cast alloys was also investigated. The crack susceptibility was evaluated by circular-patch test, and full-penetration welds made with filler metals 1100, 4043, 4047 and 5356. Liquation cracking was significant with filler metals 1100 and 5356 but slight with filler metals 4043 and 4047. In all welds, liquation cracks were completely backfilled, instead of open as in full-penetration welds of wrought alloys 2219 and 6061. The T-fS curves showed that alloy A357 has a much higher fraction liquid for backfilling before PMZ solidification was essentially over. Hot tearing in Mg-xAl-yCa alloys was studied by constrained rod casting (CRC) in a steel mold. The hot tearing susceptibility decreased significantly with increasing Ca content (y) but did not change much with the Al content (x). An instrumented CRC with a steel mold was developed to detect the onset of hot tearing. The secondary phases, eutectic content, solidification path, and freezing range were examined. Hot tearing in Mg-Al-Sr alloys was also studied by CRC in a steel mold. With Mg-(4,6,8)Al-1.5Sr alloys, the hot tearing susceptibility decreased significantly with increasing Al content. With Mg-(4,6,8)Al-3Sr alloys, the trend was similar but not as significant. At the same Al content, the hot tearing susceptibility decreased significantly with increasing Sr content. Instrumented CRC with a steel mold was also used to test hot tearing of Mg-Al-Sr alloys. Cracking occurred at a higher temperature in alloys most susceptible to cracking than in alloys least susceptible.

Alteration and mineralization of an oceanic forearc and the ophiolite-ocean crust analogy

USGS Publications Warehouse

Alt, J.C.; Teagle, D.A.H.; Brewer, T.; Shanks, Wayne C.; Halliday, A.

1998-01-01

Mineralogical, chemical, and isotopic (O, C, S, and Sr) analyses were performed on minerals and bulk rocks from a forearc basement section to understand alteration processes and compare with mid-ocean ridges (MOR) and ophiolites. Ocean Drilling Program Hole 786B in the Izu-Bonin forearc penetrates 103 m of sediment and 725 m into volcanic flows, breccias, and basal dikes. The rocks comprise boninites and andesites to rhyolites. Most of the section was affected by low-temperature (<100??C) seawater alteration, with temperatures increasing downward. The rocks are partly (5-25%) altered to smectite, Fe-oxyhydroxide, calcite, and phillipsite, and exhibit gains of K, Rb, and P, loss of Ca, variable changes in Si, Na, Mg, Fe, Sr, and Y, and elevated ??18O and 87Sr/86Sr. Higher temperatures (???150??C) in the basal dikes below 750 m led to more intense alteration and formation of chlorite-smectite, corrensite, albite, K-feldspar, and quartz (??chlorite). A 5 m thick hydrothermally altered and pyritized zone at 815 m in the basal dikes reacted with mixtures of seawater and hydrothermal fluids to Mg-chlorite, albite, and pyrite, and gained Mg and S and lost Si and Ca. Focused flow of hydrothermal fluids produced sericitization halos (Na-K sericite, quartz, pyrophyllite, K-feldspar, and pyrite) along quartz veins at temperatures of 200??-250??C. High 87Sr/86Sr ratios of chloritized (???0.7055) and sericitized (???0.7065) rocks indicate involvement of seawater via mixing with hydrothermal fluids. Low ??34S of sulfide (???2 to -5.5???) and sulfate (12.5???) are consistent with input of magmatic SO2 into hydrothermal fluids and disproportionation to sulfide and sulfate. Alteration processes were generally similar to those at MORs, but the arc section is more intensively altered, in part because of the presence of abundant glassy rocks and mafic phases. The increase in alteration grade below 750 m and the mineralization in the basal dikes are analogous to changes that occur near the base of the volcanic section in MOR and the Troodos ophiolite.

Understanding the Calcium Isotope and Trace Metal Composition of Elasmobranch Teeth: Implications for Recreating the δ44/40Ca of Seawater

NASA Astrophysics Data System (ADS)

Akhtar, A.; Higgins, J. A.

2017-12-01

Non-traditional stable isotopes in marine fossils have the potential to act as archives of paleo-seawater chemistry, biological evolution, and ancient ecosystems. In particular, bioapatite in elasmobranch enamel has been shown to be a robust proxy for environmental, geochemical and ecological reconstructions through Earth history due to its temporal range (from Devonian to present day) and resistance to diagenetic alteration. Moreover, frequent replacement rates of teeth in individuals, and high species level diversity and global distribution ensure a sample suite that encompasses a wide range of geographies and ecosystems. Here we present δ44/40Ca, δ87/86Sr and trace element (e.g. Sr/Ca, Mg/Ca) data from a suite of 300 teeth spanning the Cretaceous to present day and representing primary, secondary and tertiary piscivores. Modern teeth analyzed as part of this study have an average δ44/40Ca value of -2.07±0.48‰ (2s, n = 80) and Sr/Ca ratio of 2.30±0.24 mmol/mol (2s, n = 40), both offset from present day seawater (0 permil and 8.6 mmol/mol, respectively) due to a combination of inorganic (e.g. mineral precipitation) and biological (e.g. ionic regulation) effects. The total range in δ44/40Ca values in modern teeth is 1.19‰, the same order as that expected for variations in the δ44/40Ca value of ancient seawater. Using results from synthetic apatite synthesis experiments, mathematical modeling, and measurements of shark soft-tissue (e.g. blood and flesh), we explore sources of Ca isotope variability in shark teeth and evaluate their potential as archives of ancient seawater chemistry.

Sarcoplasmic reticulum Ca2+ permeation explored from the lumen side in mdx muscle fibers under voltage control

PubMed Central

Robin, Gaëlle; Berthier, Christine

2012-01-01

Under resting conditions, external Ca2+ is known to enter skeletal muscle cells, whereas Ca2+ stored in the sarcoplasmic reticulum (SR) leaks into the cytosol. The nature of the pathways involved in the sarcolemmal Ca2+ entry and in the SR Ca2+ leak is still a matter of debate, but several lines of evidence suggest that these Ca2+ fluxes are up-regulated in Duchenne muscular dystrophy. We investigated here SR calcium permeation at resting potential and in response to depolarization in voltage-controlled skeletal muscle fibers from control and mdx mice, the mouse model of Duchenne muscular dystrophy. Using the cytosolic Ca2+ dye Fura2, we first demonstrated that the rate of Ca2+ increase in response to cyclopiazonic acid (CPA)–induced inhibition of SR Ca2+-ATPases at resting potential was significantly higher in mdx fibers, which suggests an elevated SR Ca2+ leak. However, removal of external Ca2+ reduced the rate of CPA-induced Ca2+ increase in mdx and increased it in control fibers, which indicates an up-regulation of sarcolemmal Ca2+ influx in mdx fibers. Fibers were then loaded with the low-affinity Ca2+ dye Fluo5N-AM to measure intraluminal SR Ca2+ changes. Trains of action potentials, chloro-m-cresol, and depolarization pulses evoked transient Fluo5N fluorescence decreases, and recovery of voltage-induced Fluo5N fluorescence changes were inhibited by CPA, demonstrating that Fluo5N actually reports intraluminal SR Ca2+ changes. Voltage dependence and magnitude of depolarization-induced SR Ca2+ depletion were found to be unchanged in mdx fibers, but the rate of the recovery phase that followed depletion was found to be faster, indicating a higher SR Ca2+ reuptake activity in mdx fibers. Overall, CPA-induced SR Ca2+ leak at −80 mV was found to be significantly higher in mdx fibers and was potentiated by removal of external Ca2+ in control fibers. The elevated passive SR Ca2+ leak may contribute to alteration of Ca2+ homeostasis in mdx muscle. PMID:22371362

Sequestration of Sr(II) By Calcium Oxalate - a Batch Uptake Study And EXAFS Analysis of Model Compounds And Reaction Products

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

Singer, D.M.; Johnson, S.B.; Catalano, J.G.

Calcium oxalate monohydrate (CaC{sub 2}O{sub 4}{center_dot}H{sub 2}O -- abbreviated as CaOx) is produced by two-thirds of all plant families, comprising up to 80 wt.% of the plant tissue and found in many surface environments. It is unclear, however, how CaOx in plants and soils interacts with metal ions and possibly sequesters them. This study examines the speciation of Sr(II){sub aq} following its reaction with CaOx. Batch uptake experiments were conducted over the pH range 4--10, with initial Sr solution concentrations, [Sr]{sub aq}, ranging from 1 x 10{sup -4} to 1 x 10{sup -3} M and ionic strengths ranging of 0.001--0.1more » M, using NaCl as the background electrolyte. Experimental results indicate that Sr uptake is independent of pH and ionic strength over these ranges. After exposure of CaOx to Sr{sub aq} for two days, the solution Ca concentration, [Ca]{sup aq}, increased for all samples relative to the control CaOx suspension (with no Sr added). The amount of Sr{sub aq} removed from solution was nearly equal to the total [Ca]{sup aq} after exposure of CaOx to Sr. These results suggest that nearly 90% of the Sr is removed from solution to a solid phase as Ca is released into solution. We suggest that the other 10% is sequestered through surface adsorption on a solid phase, although we have no direct evidence for this. Extended X-ray absorption fine structure (EXAFS) spectroscopy was used to determine the molecular-level speciation of Sr in the reaction products. Deconvolutions of the Sr K-edge EXAFS spectra were performed to identify multi-electron excitation (MEE) features. MEE effects were found to give rise to low-frequency peaks in the Fourier transform before the first shell of oxygen atoms and do not affect EXAFS fitting results. Because of potential problems caused by asymmetric distributions of Sr-O distances when fitting Sr K-edge EXAFS data using the standard harmonic model, we also employed a cumulant expansion model and an asymmetric analytical model to account for anharmonic effects in the EXAFS data. For Sr-bearing phases with low to moderate first-shell (Sr-O pair correlation) anharmonicity, the cumulant expansion model is sufficient for EXAFS fitting; however, for higher degrees of anharmonicity, an analytical model is required. Based on batch uptake results and EXAFS analyses of reaction products, we conclude that Sr is dominantly sequestered by a solid phase at the CaOx surface, likely the result of a dissolution-reprecipitation mechanism, to form SrC{sub 2}O{sub 4} of mixed hydration state (i.e. SrO{sub x}{center_dot}nH{sub 2}O, where n = 0, 1, or 2). Surprisingly, no spectroscopic or XRD evidence was found for a (Sr,Ca)Ox solid solution or for a separate SrCO3 phase. In addition, we found no evidence for Sr(II) inner-sphere sorption complexes on CaOx surfaces based on lack of Sr-Ca second-neighbor pair correlations in the EXAFS spectra, although some type of Sr(II) surface complex (perhaps a type B Sr-oxalate ternary complex or an outer-sphere Sr(II) complex) or some as yet undetected Sr-bearing solid phases are needed to account for approximately 10% of Sr uptake by CaOx. The formation of a hydrated SrOx phase in environments under conditions similar to those of our experiments should retard Sr mobility and could be a significant factor in the biogeochemical cycling of Sr in soils and sediments or in plants and plant litter where CaOx is present.« less

Monthly Strontium/Calcium oscillations in symbiotic coral aragonite: Biological effects limiting the precision of the paleotemperature proxy

USGS Publications Warehouse

Meibom, A.; Stage, M.; Wooden, J.; Constantz, B.R.; Dunbar, R.B.; Owen, A.; Grumet, N.; Bacon, C.R.; Chamberlain, C.P.

2003-01-01

In thermodynamic equilibrium with sea water the Sr/Ca ratio of aragonite varies predictably with temperature and the Sr/Ca ratio in coral have thus become a frequently used proxy for past Sea Surface Temperature (SST). However, biological effects can offset the Sr/Ca ratio from its equilibrium value. We report high spatial resolution ion microprobe analyses of well defined skeletal elements in the reef-building coral Porites lutea that reveal distinct monthly oscillations in the Sr/Ca ratio, with an amplitude in excess of ten percent. The extreme Sr/Ca variations, which we propose result from metabolic changes synchronous with the lunar cycle, introduce variability in Sr/Ca measurements based on conventional sampling techniques well beyond the analytical precision. These variations can limit the accuracy of Sr/Ca paleothermometry by conventional sampling techniques to about 2??C. Our results may help explain the notorious difficulties involved in obtaining an accurate and consistent calibration of the Sr/Ca vs. SST relationship.

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

PubMed Central

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

2016-01-01

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

Cardiac microvascular endothelial cells express a functional Ca+ -sensing receptor.

PubMed

Berra Romani, Roberto; Raqeeb, Abdul; Laforenza, Umberto; Scaffino, Manuela Federica; Moccia, Francesco; Avelino-Cruz, Josè Everardo; Oldani, Amanda; Coltrini, Daniela; Milesi, Veronica; Taglietti, Vanni; Tanzi, Franco

2009-01-01

The mechanism whereby extracellular Ca(2+) exerts the endothelium-dependent control of vascular tone is still unclear. In this study, we assessed whether cardiac microvascular endothelial cells (CMEC) express a functional extracellular Ca(2+)-sensing receptor (CaSR) using a variety of techniques. CaSR mRNA was detected using RT-PCR, and CaSR protein was identified by immunocytochemical analysis. In order to assess the functionality of the receptor, CMEC were loaded with the Ca(2+)-sensitive fluorochrome, Fura-2/AM. A number of CaSR agonists, such as spermine, Gd(3+), La(3+) and neomycin, elicited a heterogeneous intracellular Ca(2+) signal, which was abolished by disruption of inositol 1,4,5-trisphosphate (InsP(3)) signaling and by depletion of intracellular stores with cyclopiazonic acid. The inhibition of the Na(+)/Ca(2+) exchanger upon substitution of extracellular Na(+) unmasked the Ca(2+) signal triggered by an increase in extracellular Ca(2+) levels. Finally, aromatic amino acids, which function as allosteric activators of CaSR, potentiated the Ca(2+) response to the CaSR agonist La(3+). These data provide evidence that CMEC express CaSR, which is able to respond to physiological agonists by mobilizing Ca(2+) from intracellular InsP(3)-sensitive stores. Copyright 2008 S. Karger AG, Basel.

Multianalytical determination of trace elements in atmospheric biomonitors by k0-INAA, ICP-MS and AAS

NASA Astrophysics Data System (ADS)

Freitas, M. C.; Pacheco, A. M. G.; Dionísio, I.; Sarmento, S.; Baptista, M. S.; Vasconcelos, M. T. S. D.; Cabral, J. P.

2006-08-01

Elemental contents of atmospheric biomonitors—epiphytic lichens and tree bark, exposed in continuous and discontinuous modes—have been assessed through k0-standardised instrumental neutron activation analysis ( k0-INAA) (two different institutions), inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrometry (AAS). Certified reference materials—ISE-921 (river clay), NIST-1547 (peach leaves), ICHTJ-INCT-TL-1 (tea leaves; TL-1 hereinafter) and IAEA-336 (lichen material), and nonparametric statistics—rank-order correlations (Spearman RS) and enhanced-sign tests (Wilcoxon T)—were used for analytical control and data comparison, respectively. In general, quality of procedures was deemed good, except for k0-INAA in determining Br, Cu and Na, all likely affected by high counting statistics, and/or contamination issues (the latter). Results for Cu, Ni, Pb and Sr (by both ICP-MS and AAS) revealed that, despite an outstanding correlation (asymptotic p=0.000), they could be viewed as statistically equal for Cu only: AAS tended to yield higher values for Pb and Ni, and lower ones for Sr. The comparison between ICP-MS and k0-INAA data from TUDelft, for Al, Ca, Cu, Mg, Mn, Na, Ti and V, showed an excellent correlation (as above) and random (relative) magnitude for Cu, Mg, Mn and Ti only: ICP-MS tended to yield higher values for Al, Na and V, and lower ones for Ca, whereas between k0-INAA data from TUDelft and ITN, for Br, Ca and Na, resulted in systematically higher [Br] and [Ca] variates from TUDelft, even if all corresponding data sets were found to correlate at stringent significance levels. In a few cases, though—Ca, Sr in lichens; Pb in bark—matrix effects did appear to interfere in the outcome of matched-pairs, signed-rank tests, since random hierarchy of variates could be asserted just when lichen and bark data sets were processed separately.

Effect of ADP on slow-twitch muscle fibres of the rat: implications for muscle fatigue

PubMed Central

Macdonald, W A; Stephenson, D G

2006-01-01

Slow-twitch mechanically skinned fibres from rat soleus muscle were bathed in solutions mimicking the myoplasmic environment but containing different [ADP] (0.1 μm to 1.0 mm). The effect of ADP on sarcoplasmic reticulum (SR) Ca2+-content was determined from the magnitude of caffeine-induced force responses, while temporal changes in SR Ca2+-content allowed determination of the effective rates of the SR Ca2+-pump and of the SR Ca2+-leak. The SR Ca2+-pump rate, estimated at pCa (−log10[Ca2+]) 7.8, was reduced by 20% as the [ADP] was increased from 0.1 to 40 μm, with no further alteration when the [ADP] was increased to 1.0 mm. The SR Ca2+-leak rate constant was not altered by increasing [ADP] from 0.1 to 40 μm, but was increased by 26% when the [ADP] was elevated to 1.0 mm. This ADP-induced SR Ca2+-leak was insensitive to ruthenium red but was abolished by 2,5-di(tert-butyl)-1,4-hydroquinone (TBQ), indicating that the leak pathway is via the SR Ca2+-pump and not the SR Ca2+-release channel. The decrease in SR Ca2+-pump rate and SR Ca2+-leak rate when [ADP] was increased led to a 40% decrease in SR Ca2+-loading capacity. Elevation of [ADP] had only minor direct effects on the contractile apparatus of slow-twitch fibres. These results suggest that ADP has only limited depressing effects on the contractility of slow-twitch muscle fibres. This is in contrast to the marked effects of ADP on force responses in fast-twitch muscle fibres and may contribute to the fatigue-resistant nature of slow-twitch muscle fibres. PMID:16556653

Regulation by divalent cations of /sup 3/H-baclofen binding to GABA/sub B/ sites in rat cerebellar membranes

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

Kato, K.; Goto, M.; Fukuda, H.

1983-02-21

When investigating the effects of divalent cations (Mg/sup 2 +/, Ca/sup 2 +/, Sr/sup 2 +/, Ba/sup 2 +/, Mn/sup 2 +/ and Ni/sup 2 +/) on /sup 3/H-baclofen binding to rat cerebellar synaptic membranes, we found that the specific binding of /sup 3/H-baclofen was not only dependent on divalent cations, but was increased dose-dependently in the presence of these cations. The effects were in the following order of potency: Mn/sup 2 +/ approx. = Ni/sup 2 +/ > Mg/sup 2 +/ > Ca/sup 2 +/ > Sr/sup 2 +/ > Ba/sup 2 +/. Scatchard analysis of the binding datamore » revealed a single component of the binding sites in the presence of 2.5 mM MgCl/sub 2/, 2.5 mM CaCl/sub 2/ or 0.3 mM MnCl/sub 2/ whereas two components appeared in the presence of 2.5 mM MnCl/sub 2/ or 1 mM NiCl/sub 2/. In the former, divalent cations altered the apparent affinity (K/sub d/) without affecting density of the binding sites (B/sub max/). In the latter, the high-affinity sites showed a higher affinity and lower density of the binding sites than did the single component of the former. As the maximal effects of four cations (Mg/sup 2 +/, Ca/sup 2 +/, Mn/sup 2 +/, and Ni/sup 2 +/) were not additive, there are probably common sites of action of these divalent cations. Among the ligands for GABA/sub B/ sites, the affinity for (-), (+) and (+/-)baclofen, GABA and ..beta..-phenyl GABA increased 2 - 6 fold in the presence of 2.5 mM MnCl/sub 2/, in comparison with that in HEPES-buffered Krebs solution (containing 2.5 mM CaCl/sub 2/ and 1.2 mM MgSO/sub 4/), whereas that for muscimol was decreased to one-fifth. Thus, the affinity of GABA/sub B/ sites for its ligands is probably regulated by divalent cations, through common sites of action.« less

Trace elements distribution in hawksbill turtle (Eretmochelys imbricata) and green turtle (Chelonia mydas) tissues on the northern coast of Bahia, Brazil.

PubMed

de Macêdo, Gustavo R; Tarantino, Taiana B; Barbosa, Isa S; Pires, Thaís T; Rostan, Gonzalo; Goldberg, Daphne W; Pinto, Luis Fernando B; Korn, Maria Graças A; Franke, Carlos Roberto

2015-05-15

Concentrations of elements (As, Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, Ni, Pb, Sb, Se, Sr, V, Zn) were determined in liver, kidneys and bones of Eretmochelys imbricata and Chelonia mydas specimens found stranded along the northern coast of Bahia, Brazil. Results showed that the concentrations of Cd, Cu, Ni and Zn in the liver and kidneys of juvenile C. mydas were the highest found in Brazil. We also observed a significant difference (p<0.05) on the bioaccumulation of trace elements between the two species: Al, Co, Mo, Na and Se in the liver; Al, Cr, Cu, K, Mo, Ni, Pb, Sr and V in the kidneys; and Al, Ba, Ca, Cd, Mn, Ni, Pb, Se, Sr and V in the bones. This study represents the first report on the distribution and concentration of trace elements in E. imbricata in the Brazilian coast. Copyright © 2015 Elsevier Ltd. All rights reserved.

Fidelity of the Sr/Ca proxy in recording ocean temperature in the western Atlantic coral Siderastrea siderea

NASA Astrophysics Data System (ADS)

Kuffner, Ilsa B.; Roberts, Kelsey E.; Flannery, Jennifer A.; Morrison, Jennifer M.; Richey, Julie N.

2017-01-01

Massive corals provide a useful archive of environmental variability, but careful testing of geochemical proxies in corals is necessary to validate the relationship between each proxy and environmental parameter throughout the full range of conditions experienced by the recording organisms. Here we use samples from a coral-growth study to test the hypothesis that Sr/Ca in the coral Siderastrea siderea accurately records sea-surface temperature (SST) in the subtropics (Florida, USA) along 350 km of reef tract. We test calcification rate, measured via buoyant weight, and linear extension (LE) rate, estimated with Alizarin Red-S staining, as predictors of variance in the Sr/Ca records of 39 individual S. siderea corals grown at four outer-reef locations next to in-situ temperature loggers during two, year-long periods. We found that corals with calcification rates < 1.7 mg cm-2 d-1 or < 1.7 mm yr-1 LE returned spuriously high Sr/Ca values, leading to a cold-bias in Sr/Ca-based SST estimates. The threshold-type response curves suggest that extension rate can be used as a quality-control indicator during sample and drill-path selection when using long cores for SST paleoreconstruction. For our corals that passed this quality control step, the Sr/Ca-SST proxy performed well in estimating mean annual temperature across three sites spanning 350 km of the Florida reef tract. However, there was some evidence that extreme temperature stress in 2010 (cold snap) and 2011 (SST above coral-bleaching threshold) may have caused the corals not to record the temperature extremes. Known stress events could be avoided during modern calibrations of paleoproxies.