Sr Fraction Research Articles

Evaporation-free tandem-column separation for Sr from geological samples with high Rb/Sr ratios

A novel tandem column method was devised for effective purification of Sr from geological samples characterized by relatively high Rb/Sr ratios, employing a strategic sequence of columns of AG50-X12 cation resin, Chelex-100 chelating resin and AG50-X8 cation resin. The process initiates with the AG50-X12 column to remove most of the matrix elements, followed by the Chelex-100 column to remove the residual Rb under alkaline conditions despite its inability to adsorb alkali metals such as Na, K, and Rb. The Sr fraction was eluted directly into the Chelex-100 column from the AG50-X12 column by a NH3-NH4Cl solution. The final purification through the AG50-X8 column to eliminate residual NH4Cl ensures the effective removal of matrix elements (such as K, Na, Li, Ti, Al, Fe, Mg, Mn and Ca) and Rb. The Chelex-100 resin acts comparatively to a similar Sr-specific resin for Rb and Sr. This method proved its efficacy and precision by aligning the Sr isotopic ratios from a range of reference materials, (JR-1, JR-2, JB-2, BCR-2, BHVO-2, W-2, GSP-2, CRPG Mica-Mg, CRPG Mica-Fe and NIST SRM 987) with their published values, demonstrating its reliability for Sr isotope analysis in complex geological matrices.

A-Site Cation Disorder in SrxBa1-xNb2O6 (x = 0.25, 0.33, 0.50, 0.61) Studied by High-Resolution Resonant X-ray Powder Diffraction.

The dielectric and ferroelectric properties of SrxBa1-xNb2O6 (SBN, 0.2 < x < 0.8) are known to be affected by the Sr fraction and can be further controlled by various quenching schemes. Changes in A-site cation configuration are believed to be linked to these changes in properties. In this work, we study the A-site cation disorder in SBN by the use of high-resolution resonant X-ray powder diffraction. The experimental results show that the larger Ba2+ is found exclusively on the larger A2 site, while Sr2+ is found on both the A1 and A2 sites, with an increasing amount on A2 with an increasing Sr fraction. At elevated temperatures, a small migration of Sr2+ from A1 to A2 is observed for SBN50 and SBN61. Linking this change in occupancies to changes in the average cation size on the A1 and A2 sites allows for rationalization of the property changes observed for quenched samples. Furthermore, SBN25 is shown to deviate from the tetragonal P4bm structure and is found to be orthorhombic with a Cmm2 structure.

Overcoming significant challenges in extracting off-stoichiometric thermodynamics using the compound energy formalism through complementary use of experimental and first principles data: A case study of Ba1-xSrxFeO3-δ

The compound energy formulism (CEF) is a powerful framework to describe the thermodynamics of metal oxides as a function of off-stoichiometry, temperature, and composition. The thermodynamic properties are crucial materials design attributes in metal oxide-based oxygen-exchange chemical processes. Despite the richness of information an accurate CEF model provides, a method to determine a unique and accurate fit for oxygen-exchange materials remains elusive. This contribution details a method for fitting the CEF model that overcomes the current fitting challenges through three innovations: 1) the combination of density functional theory calculations with experimental data decorrelates excess terms and delineates the enthalpic/entropic contributions to the Gibbs free energy; 2) a systematic determination of the important CEF model terms, removing thermodynamic predetermining human intervention; 3) a self-consistent solution of the starting oxygen off-stoichiometry (δ0) of thermogravimetric measurements. Thus, our method enables the reliable extraction of off-stoichiometric metal oxide thermodynamic properties and facilitates rapid materials compositional screening, and reliable process design of systems dependent on off-stoichiometric redox-active metal oxides. We apply this method to a BaxSr1-xFeO3-δ test case. We find by systematically examining the performance of the CEF model fit with and without each innovation that all three innovations are necessary for an accurate fit. We determined that reduction enthalpy is higher and more sensitive to off stoichiometry when the Sr fraction is large (139.5 and 185.3 kJ/mol O2 for SrFeO3 at δ = 0 and δ = 0.5, respectively vs. nearly constant 83 kJ/mol O2 for BaFeO3). However, the reduction entropy is mostly insensitive to Sr fraction, but highly dependent on δ suggesting larger contributions in the non-configurational entropy parameters.

Rapid characterisation of Mars' mantle reservoirs by in situ laser ablation 87Sr/86Sr analysis of shocked feldspar (maskelynite)

The 87Sr/86Sr isotopic properties of martian meteorites, measured by isolation and purification of Rb and Sr fractions, have long been used to partially characterise Mars' mantle. However, this method is time-consuming, destructive, and subject to incorporation of terrestrial contamination due to precipitation of phases in fractures and/or grain boundaries prior to meteorite collection. In this study, we test the effectiveness of in situ acquisition of 87Sr/86Sr by laser ablation in maskelynite - a typically low Rb/Sr (<0.1) feldspar-composition glass formed during high-P shock metamorphism – as a method of rapid characterisation of Mars' mantle Sr isotope ratios. Element concentration maps and the results of unwashed and gently surface-leached bulk rock analyses indicate that terrestrial Sr has infiltrated the studied meteorites and affected bulk rock trace element budgets. However, maskelynite trace element concentrations are largely unaffected and their martian igneous Rb/Sr is preserved. In situ87Sr/86Sr analyses of maskelynite, checked against a newly developed Sr feldspar reference material (KAN, presented here and available on demand), accurately and precisely distinguish different shergottite mantle reservoirs. The measurements reproduce published data, have uncertainties on the 4th to 5th decimal place, and yield statistically indistinguishable results in analytical sessions separated by long periods of time. The data from 11 enriched shergottites reveal there to be subtle Sr isotope variation within the enriched shergottite mantle reservoir, or that there was crustal assimilation of radiogenic components into the shergottites, or that the shergottite liquids were extracted over a time period during which the mantle reservoir 87Sr/86Sr evolved. The limited published age range of the enriched shergottites, coupled with the absence of a correlation between in situ87Sr/86Sr and REE, Sr or Pb concentration in maskelynite, suggests that the isotope range is best explained by small variations in the enriched mantle reservoir. Given the presence of maskelynite (or plagioclase) in many meteorites, the in situ method will be useful when there are only very small volumes of material available and/or where terrestrial contamination is suspected.

Addressing the origin of highly catalytic activity of A-site Sr-doped perovskite cathodes for intermediate-temperature solid oxide fuel cells

Highly active cathode materials are crucial to accelerating the commercialization of intermediate-temperature solid oxide fuel cells (IT-SOFCs). Herein, Sr-doped Pr0.94Ba1-xSrxCo2O5+δ (PBSxCO) perovskite oxides are evaluated by experimental and theoretical studies. The phase transformation from tetragonal layered double perovskite to cubic simple perovskite can be identified with increasing the Sr fraction. Benefiting from enhanced electrical conductivity and oxygen surface rate, the PBSxCO catalysts deliver excellent electrochemical performance, as evidenced by symmetrical and completed cells test. Among all compositions, the Pr0.94Ba0.7Sr0.3Co2O5+δ (PBS0.3CO) cathode has the lowest polarization resistance (Rp) of 0.031 Ω cm2 at 700 °C. The PBS0.3CO cathode-based fuel cell produces a peak power density of 1077 mW cm−2, along with a steady operating for 130 h at 700 °C. From the density functional theoretical (DFT) calculations, it is discovered that stronger Co 3d-O 2p hybridization is recognized in the Sr substituting model compared with undoped one. Furthermore, the decreased free energy for oxygen adsorption may facilitate the oxygen reduction reaction (ORR) kinetics. These findings highlight the origin of optimal ORR activity induced by A-site alkaline earth doping in the perovskite catalysts, endowing the rational design of oxide catalysts.

An integrated approach to uncover anti-tumor active materials of Curcumae Rhizoma-Sparganii Rhizoma based on spectrum-effect relationship, molecular docking, and ADME evaluation

Ethnopharmacological relevanceCurcumae Rhizoma-Sparganii Rhizoma (CR-SR), an ancient and classical herbal couple, has been extensively used for tumor treatment in clinic of traditional Chinese medicines (TCMs). Aim of the studyThe study aimed to uncover the anti-tumor active materials of CR-SR water decoction (CR:SR = 1:1) via an integrated approach of spectrum-effect relationship, molecular docking, and ADME evaluation. Materials and methodsThe anti-tumor activities toward A549, HepG2, Hela, BGC-823, and MCF-7 cells of the different polar elution fractions (DPEFs) of CR, SR, and CR-SR were determined by Cell Counting Kit-8 (CCK-8) assay. Likewise, the DPEFs’ combinations of CR and SR were also tested. The chemical fingerprints of these fractions were profiled by HPLC. Meanwhile, HPLC-ESI-Q-TOF-MS/MS was applied for the identification of chemical components. The main effect-related compounds were screened out by spectrum-effect relationship and molecular docking method. The oral bioavailability and druggability of these active components were subsequently evaluated. Finally, five monomeric compounds were validated experimentally using HepG2 cells. ResultsThe 80% ethanol elution fraction of CR, SR, and CR-SR showed strong anti-tumor effects toward five cells. Also, the combinations with the 80% ethanol elution fraction of CR and SR showed stronger tumor inhibition effects among the DPEFs’ combinations of CR and SR. By spectrum-effect relationship, HPLC-MS, and molecular docking analysis, 24 main effect-related compounds seemed to have potential anti-tumor effects. ADME evaluation showed rutin performed low oral bioavailability and druggability. Therefore, we suppose that 23 compounds (including 4 unknown compounds) are the primary anti-tumor active components of CR-SR water decoction. Among them, zederone, curcumol, chlorogenic acid, calycosin, and curcumenol were validated successfully with good tumor inhibition effects. ConclusionsIn summary, this study demonstrated that the multi-components of CR-SR contribute to its anti-tumor effects. It established a rapid and useful strategy to explore the active material basis of traditional Chinese herbal couples with a multi-technology integrated approach in practice, including chromatography, mass spectrometry, machine algorithm models, online databases, and in vitro cell experiments.

Determination of 87Rb/86Sr and 87Sr/86Sr ratios and Rb–Sr contents on the same filament loading for geological samples by isotope dilution thermal ionization mass spectrometry

Isotope dilution thermal ionization mass spectrometry (ID-TIMS) is considered the “gold standard” for obtaining precise 87Rb/86Sr and 87Sr/86Sr isotope ratios and accurate elemental concentrations of Rb–Sr. However, the classical ID-TIMS technique is laborious and time-consuming because the purified Rb and Sr fractions must be individually loaded onto different independent filaments due to severe 87Rb isobaric interference on 87Sr. To overcome this issue, we developed a new method whereby Rb and Sr were sequentially measured by TIMS on the same filament, without venting, to obtain both ratios of 87Rb/86Sr and 87Sr/86Sr and concentrations of Rb and Sr. Results obtained from six silicate powders of certified reference materials are in good agreement with recommended values within ±0.002% for the 87Sr/86Sr ratio, ±2% for the 87Rb/86Sr ratio and the Rb and Sr elemental contents. The only exception is JG-1a, with slightly higher 87Rb/86Sr and slightly lower 87Sr/86Sr. This new method improved the analytical efficiency and sample throughput without compromising the analytical accuracy and precision. The filament consumption is reduced by 50% compared with conventional methods and therefore significantly reduces operation costs.

Accumulation of Potentially Toxic Elements in Mosses Collected in the Republic of Moldova.

For the second time, the moss biomonitoring technique was applied to evaluate the deposition of potentially toxic elements in the Republic of Moldova. The study was performed in the framework of the International Cooperative Program on Effects of Air Pollution on Natural Vegetation and Crops. Moss Hypnum cupressiforme Hedw. samples were collected in May 2020 from 41 sampling sites distributed over the entire territory of the country. The mass fractions of 35 elements (Na, Mg, Al, Cl, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Br, Se, Rb, Sr, Sb, Cs, Ba, Cd, La, Ce, Sm, Eu, Tb, Hf, Ta, Th, Pb, and U) were determined using neutron activation analysis and atomic absorption spectrometry. Comparing with 2015/2016 moss survey data, significant differences in the mass fractions of Cr, As, Se, Br, Sr, Sb, Cd, Pb, and Cu were found. Main air pollution sources (natural processes, transport, industry, agriculture, mining) were identified and characterized using factor and correlation analyses. GIS maps were built to point out the zones with the highest element mass fractions and to relate this to the known sources of contamination. Contamination factor, geo-accumulation index, pollution load index, and potential ecological risk index were calculated to assess the air pollution levels in the country. According to the calculated values, Moldova can be characterized as unpolluted to moderately polluted, with low potential ecological risk related to the degree of atmospheric deposition of potentially toxic elements. The cities of Chisinau and Balti were determined to experience particular environmental stress and are considered moderately polluted.

Authentication of PDO paprika powder (Pimentón de la Vera) by multivariate analysis of the elemental fingerprint determined by ED-XRF. A feasibility study

Products with a Protected Denomination of Origin (PDO) are vulnerable to misdescription of their true geographical origin. In this work a method has been developed that allows the authentication of La Vera paprika powder (Pimentón de la Vera), a PDO product from the central-west Spanish region, Extremadura. The mass fractions of Br, Ca, Cr, Cl, Cu, Fe, K, Mn, Ni, P, Rb, S, Sr and Zn determined by energy dispersive X-ray fluorescence (ED-XRF) are used for classification purposes by multivariate analysis using Soft Independent Modelling of Class Analogy (SIMCA) (PCA-Class) and Partial Least Square-Discriminant Analysis (PLS-DA). Sixty-seven paprika samples purchased in supermarkets around Europe and on-line via the official web-site of Pimentón de La Vera, were used to build up the models for prediction purposes. The PCA-class model of La Vera paprika powder had a sensitivity of 82%, a specificity of 100% and an accuracy of 91%, whereas the PLS-DA model had a sensitivity of 100%, a specificity of 91% and an accuracy of 96%.

Separation method for Pu, Am and Sr in large air filter sample sets

A sequential separation method for Pu, Am, and Sr was applied for unusually large sample sets of air filters. The sample sets were combined weekly air filters covering sampling time from three months to five years, while in original method, the analyzed air filters had sampling time of only 1-3 days, containing significantly less organic and inorganic matrix and natural radionuclides. The separation method is based on ashing and wet-ashing, followed by column separations with extraction chromatography and anion exchange. Reference materials IAEA-447, IAEA-384, and NIST-SRM-4353A were analyzed with the modified separation method. IAEA-384 was representing best the composition and radionuclide level in the air filter samples.•Compared to the original method, sample ashing took considerably longer time (one day vs. several days).•High concentration of natural radionuclides in the large air filter sample sets interfered first the determination of 241Am and 90Sr, until an anion exchange step was adopted for removal of 210Bi and 210Po from Am and Sr fractions.•After modification, the method is suitable for separating artificial radionuclides 238,239,240Pu, 241Am, and 90Sr from large sample sets of air filters.

A simple two-stage column chromatographic separation scheme for strontium, lead, neodymium and hafnium isotope analyses in geological samples by thermal ionization mass spectrometry or multi-collector inductively coupled plasma mass spectrometry.

Here, a two-stage column separation scheme is developed for the concomitant isolation of Sr, Pb, Nd, and Hf from geological samples. The first column, which consists of three resin layers (AG50W-X8 ion exchange resin + Ln specific resin + Sr specific resin), separates the high field strength element + rare earth element, Sr and Pb from the matrices. Subsequently, Nd and Hf are further separated from the high field strength element + rare earth element fraction on the second column using 1mL of Ln specific resin. The two-stage column process can be completed within about seven and a half hours for a batch of samples (20-30). The separated Sr fraction was ready for isotope ratio measurements by thermal ionization mass spectrometry. The Pb, Nd, and Hf fractions were converted to nitrate prior to isotopic analyses by multi-collector inductively coupled plasma mass spectrometry. The feasibility of this new procedure is confirmed by the analyses of four international rock standards (BCR-2, AGV-2, BHVO-2, and JB-3), which yielded isotope ratios that were in good agreement with other published data.

Intra- and Intertree Variability of the 87Sr/86Sr Ratio in Apple Orchards and Its Correlation with the Soil 87Sr/86Sr Ratio.

The 87Sr/86Sr ratio of horticultural products mostly derives from that of the bioavailable Sr fraction of the soil where they grow and, therefore, varies according to the local geolithological features. This study investigated the intra- and intertree variability of the 87Sr/86Sr ratio in two apple orchards in South Tyrol and its relation with the soil 87Sr/86Sr ratio. In both orchards, a moderate homogeneity of the 87Sr/86Sr ratio was observed among subsamples of the same tree part (shoot axes, leaves, apple peels, and pulps). Moreover, the 87Sr/86Sr ratio homogeneity among tree parts was high intratree and low intertree. The variability of the 87Sr/86Sr ratio within the tree and within the orchard is explained in light of the 87Sr/86Sr ratios of the soil. This 87Sr/86Sr variability within orchards does not preclude its use as a geographical tracer; however, this aspect should be evaluated to correctly design a sampling campaign or to generalize the results.

87Sr/86Sr compositional linkage between geological and biological materials: A case study from the Toyota granite region of Japan

The strontium isotope value (87Sr/86Sr) is often used to identify the origins of agricultural products and the movements of ancient people. Maps delineating the distribution of 87Sr/86Sr values can therefore be of great use. Previous 87Sr/86Sr distribution maps of stream sediments covering small areas of Japan largely reflect the 87Sr/86Sr values of underlying bedrock. It remains unclear, however, whether the 87Sr/86Sr values of stream sediments may also reflect the 87Sr/86Sr values of the nearby vegetation and fauna. We sought to resolve this question by investigating the relationship between 87Sr/86Sr values in biological samples and in geological samples from the sites from which the biological samples grew. The geological samples consisted of soil samples from 2 paddy fields and 13 bed sediment samples (grain size <180 μm) from streams surrounding the paddy fields. All were collected from regions underlain by Inagawa granite bedrock, i.e., granite geology, around Toyota, Aichi Prefecture, Japan. The biological samples consisted of 4 rice plants and 1 wild boar bone, all collected in or near the same paddy fields.In the geological samples, the 87Sr/86Sr values of water-extracted Sr (water-soluble Sr) and ammonium-acetate-extracted Sr (exchangeable Sr) fractions in paddy soils were almost the same as each other (0.7098–0.7100) and slightly lower than the 87Sr/86Sr values of bulk Sr fractions (0.7099–0.7106). The 87Sr/86Sr values of biological samples (0.7098–0.7100) were also similar to those of the water-soluble Sr and exchangeable Sr fractions in paddy soils, though they varied among the parts of plants analyzed. This indicates that exchangeable Sr is absorbed by plants from soils through nutrients and water, and ingested by herbivorous animals from soils through plants and water. The 87Sr/86Sr values of bulk Sr in paddy soils ranged somewhat widely, while those from stream sediments collected around paddy fields were less variable (0.7099–0.7100). The difference in 87Sr/86Sr values between the paddy soils and stream sediments, samples similarly derived from Inagawa granite bedrock, may be related to the variable degree of weathering, and ultimately to the mineral composition, of the samples. This difference, however, was smaller than the range of 87Sr/86Sr values observed in the watershed geology. We therefore propose that in a silicate-dominated geology of the type typical of Japan, an 87Sr/86Sr spatial distribution map (using both exchangeable Sr and bulk Sr fractions in stream sediments) can provide useful guidance for identifying the geographic origins of food or for serving other related purposes.

The strontium isotope distribution in water and sh within major South African catchments

Strontium has 4 naturally-occurring isotopes ( 84 Sr, 86 Sr, 87 Sr, 88 Sr) all of which are stable (Faure, 1986). Thee correlation between the 87 Sr/ 86 Sr isotope ratio of lake water and fish finn spine tissue was investigated in 23 lakes within 4 major South African catchments. Data showed that fish within a specific lake all have the same Sr isotope ratio in their n spine tissue regardless of species, age, sex and condition. The origin of the dissolved Sr fraction in lake water can be either from the natural weathering of upstream geological units or from an upstream anthropogenic source. The Sr isotopic ratios of the water samples were, however, constant over a multi-year period suggesting that the main source may be the more consistent geological environment. The Sr isotope ratio of river and lake water generally increases along the course of the rivers within the tertiary catchments of the areas investigated. In large rivers like the Vaal, where pollution also plays a role, the pattern is much more complicated. In the Olifants River catchment, Lake Middelburg, Lake Witbank and Lake Doornpoort have a similar Sr isotope ratio, which is distinct from Lake Bronkhorstspruit. Lake Loskop which is downstream from these lakes has a Sr isotope ratio between these two extremes, indicating mixing of water from upstream sources. Similarly Lake Arabie (Flag Boshielo), which is even further downstream, shows a Sr isotope composition between the composition of Lake Loskop and the lakes in the Elands River. Keywords : strontium isotope, 87 Sr/ 86 Sr, lake water, fish finn spine, water chemistry, Lake Loskop

Strategic Composition and Enrichment of the Mitochondrial Ca2+ Uniporter at Mitochondria-SR Associations Creates Hotspots for Mitochondrial Ca2+ Uptake in the Cardiac Muscle

The bioenergetic fueling of cardiac muscle activity is tuned by Ca2+ signals propagated from SR to the mitochondrial matrix (excitation-bioenergetics coupling). Effective activation of the low-affinity mitochondrial Ca2+ uniporter (mtCU) is promoted by high [Ca2+] nanodomains where SR is tethered to mitochondria. Cardiac mitochondria have very large inner membrane (IMM) surface with extensive cristae folding but their mtCU current density is reportedly extremely low. We hypothesized that efficient excitation-bioenergetics coupling would require biased mtCU activity towards mitochondria-SR associations by mtCU being there more abundant and/or more efficient. To this end, we first analyzed the submitochondrial distribution of mtCU's pore protein, MCU in rat and mouse heart. Immunofluorescence (IF) in cells showed significant non-mitochondrial crossreactions; hence, we performed IF on mitochondria isolated from cardiac muscle (mtIF). mtIF showed 50% of punctate MCU positive structures colocalized with type-2 ryanodine receptor, suggesting a location bias to mitochondria-SR associations. Further, in submitochondrial membrane fractions MCU and the SR marker calsequestrin were both enriched with the inner-outer membrane contact points. Mitochondrial membranes in the SR fraction (MMSR) harbored as high concentrations of MCU as the crude mitochondria and much higher levels of the essential MCU regulator EMRE. Gel-filtration analysis showed size profiles of non-denaturing detergent-solubilized MCU- vs. EMRE-containing complexes largely overlapping in the SR fraction, while revealed MCU containing complexes without EMRE in the crude mitochondria. Finally, Ca2+ flux assays revealed more efficient mtCU-mediated Ca2+ uptake by the MMSR than the crude mitochondria. Our data thus suggest a distribution bias in the mtCU channel components over the cardiac IMM, turning mitochondria-SR interfaces to Ca2+ uptake ‘hotspots’ harboring all-EMRE-supported MCU while leaving other IMM areas less responsive to Ca2+ owing to EMRE-less mtCUs.

Static and Dynamic Optical Properties of La1–xSrxFeO3−δ: The Effects of A-Site and Oxygen Stoichiometry

Perovskite oxides are a promising material class for photovoltaic and photocatalytic applications due to their visible band gaps, nanosecond recombination lifetimes, and great chemical diversity. However, there is limited understanding of the link between composition and static and dynamic optical properties, despite the critical role these properties play in the design of light-harvesting devices. To clarify these relationships, we systemically studied the optoelectronic properties in La1–xSrxFeO3−δ epitaxial films, uncovering the effects of A-site cation substitution and oxygen stoichiometry. Variable-angle spectroscopic ellipsometry was used to measure static optical properties, revealing a linear increase in absorption coefficient at 1.25 eV and a red-shifting of the optical absorption edge with increasing Sr fraction. The absorption spectra can be similarly tuned through the introduction of oxygen vacancies, indicating the critical role that nominal Fe valence plays in optical absorption. Dynamic opt...

Oxygen Evolution Reaction on La1–xSrxCoO3 Perovskites: A Combined Experimental and Theoretical Study of Their Structural, Electronic, and Electrochemical Properties

The bulk electronic structure, surface composition, conductivity, and electrochemical activity toward the oxygen evolution reaction for the La1–xSrxCoO3 perovskite series (with x = 0, 0.2, 0.4, 0.6, 0.8, 1) are investigated experimentally and theoretically. It is found that Sr substitutions have the effect of straightening the octahedral cage, aligning atoms along the Co–O–Co axis, and increasing the average oxidation state of the Co cations. As a consequence, both the ex situ electronic conductivity as well as the activity toward the oxygen evolution reaction are considerably improved. According to density-functional theory calculations, the alignment of the Co–O–Co bonds and the oxidation of the Co cations enhance the overlap between the occupied O 2p valence bands and the unoccupied Co 3d conduction bands, rationalizing the improvement of the conductivity as a function of the Sr fraction. Additionally, a study of the surface properties as a function of the Sr fraction, carried out by X-ray photoelectro...

Direct High-Precision Measurements of the (87)Sr/(86)Sr Isotope Ratio in Natural Water without Chemical Separation Using Thermal Ionization Mass Spectrometry Equipped with 10(12) Ω Resistors.

Thermal ionization mass spectrometry (TIMS) allows excellent precision for determining Sr isotope ratios in natural water samples. Traditionally, a chemical separation procedure using cation exchange resin has been employed to obtain a high purity Sr fraction from natural water, which makes sample preparation time-consuming. In this study, we present a rapid and precise method for the direct determination of the Sr isotope ratio of natural water using TIMS equipped with amplifiers with two 10(12) Ω resistors. To eliminate the (87)Rb isobaric interference, Re ribbons are used as filaments, providing a significant advantage over W ribbons in the inhibition of Rb(+) emission, based on systematically examining a series of NIST SRM987 standard doping with various amounts of Rb using Re and W ribbons. To validate the applicability of our method, twenty-two natural water samples, including different water types (rain, snow, river, lake and drinking water), that show a large range in Sr content variations (2.54-922.8 ppb), were collected and analyzed from North and South China. Analytical results show good precision (0.003-0.005%, 2 RSE) and the method was further validated by comparative analysis of the same water with and without chemical separation. The method is simple and rapid, eliminates sample preparation time, and prevents potential contamination during complicated sample-preparation procedures. Therefore, a high sample throughput inherent to the TIMS can be fully utilized.

Phosphorylation‐dependent Association of PDE3A1 with SERCA2 and its Regulation of SERCA2 Activity in Human Myocardium

PDE3 regulates cAMP‐mediated signaling in the heart. Studies in mice showed that PDE3A is associated with SERCA2, PLB and AKAP18 in a signaling complex in the SR that regulates inotropic responses. Immunohistochemical studies demonstrate that PDE3A is co‐localized in Z‐bands of human cardiomyocytes with desmin, SERCA2, PLB and AKAP18. In SR fractions, cAMP or rPKAc increased PLB phosphorylation and SERCA2 activity; this was potentiated specifically by PDE3 inhibition. During S6 chromatography of solubilized SR membranes, PDE3 activity was recovered in high‐ and low‐molecular‐weight (HMW, LMW) peaks. HMW peaks contained PDE3A1 and PDE3A2, while LMW contained PDE3A1, PDE3A2 and PDE3A3; PDE3A1 was the principal PKA‐phosphorylated isoform. Phosphorylation by rPKAc increased cAMP‐hydrolytic activity, shifted PDE3A from LMW to HMW peaks and increased the co‐IP of PDE3A with SERCA2 and AKAP18. Phosphorylation of rPDE3A by rPKAc increased co‐IP of rSERCA2 and rAKAP18. S292/S293, a site unique to PDE3A1, was identified by alanine substitutions as the principal site regulating this interaction. Phosphorylation of PDE3A1 at this site thus promotes its incorporation into SERCA2/AKAP18 signalosomes, where it regulates contractility by modulating phosphorylation‐dependent protein‐protein interactions, PLB phosphorylation and SERCA2 activity. Agents capable of blocking this interaction and increasing myocardial contractility may constitute a novel therapeutic approach for heart failure.

Scarce metals in conventional passenger vehicles and end-of-life vehicle shredder output.

Concurrent with the demand for cleaner, lighter, and more efficient vehicles, many scarce metals (SMs) are used in passenger vehicles because of their unique physical and chemical properties. To explore the recycling potential of these metals, it is important to understand their distribution in the vehicles as well as their fate at the vehicles' end-of-life. However, this information remains very scattered and sparse. In this paper, we present a study investigating the distribution of 31 SMs in selected electrical and electronic (EE) components of conventional passenger vehicles and in the end-of-life vehicle shredder fractions from a shredder plant in Switzerland. The results of the chemical analyses show that the mass fractions of Co, Sn, Sr, Ta, Y, and Zr were dominant with >20,000 g/t in the selected EE components and Ag, Ga, Mo, Sb, Sn, Sr, and Zr with >50 g/t in the analyzed shredder fractions. The largest masses of 17 SMs were found in the shredder light fraction, which is incinerated in municipal waste treatment plants mainly in Switzerland; thus, these SMs are currently not recovered. The SM mass fractions in both the EE components and the shredder fractions were projected to their total masses in 100 hypothetical midrange passenger vehicles. The resulting mass balance showed a mismatch of >50% for 23 metals, which indicates other important SM sources such as alloys.