Adequate Sulfur Research Articles

Tandem Carbon Hollow Spheres with Tailored Inner Structure as Sulfur Immobilization for Superior Lithium–Sulfur Batteries

AbstractThe construction of lithium–sulfur battery cathode materials while simultaneously achieving high areal sulfur‐loading, adequate sulfur utilization, efficient polysulfides inhibition, rapid ion diffusion, etc. remains a major challenge. Herein, an internal regulatory strategy to fabricate the unique walnut‐like yolk–shell carbon flower@carbon nanospheres is presented (WSYCS) as sulfur hosts. The internal carbon flower, suitable cavity, and external carbon layer effectively disperse the insulate sulfur, accommodate volumetric expansion, and confine polysulfides, thus improving the performance of lithium–sulfur batteries. The finite element simulation method also deduces the enhanced Li+ diffusion and lithium–sulfur reaction kinetics. More importantly, WSYCS2 is grafted onto carbon fiber (CF) by electro‐spinning method to form a tandem WSYCS2@CF 3D film as a sulfur host for the free‐standing electrode. The corresponding battery exhibits an extremely high areal capacity of 15.5 mAh cm−2 with a sulfur loading of 13.4 mg cm−2. Particularly, the flexible lithium–sulfur pouch cell delivers a high capacity of 8.1 mAh cm−2 and excellent capacity retention of 65% over 800 cycles at a relatively high rate of 1C, corresponding to a calculated energy density of 539 Wh kg−1 and 591 Wh L−1. This work not only provides guidance for tailoring thick carbon/sulfur electrodes but also boosts the development of practical lithium–sulfur batteries.

Realizing high-capacity all-solid-state lithium-sulfur batteries using a low-density inorganic solid-state electrolyte

Lithium-sulfur all-solid-state batteries using inorganic solid-state electrolytes are considered promising electrochemical energy storage technologies. However, developing positive electrodes with high sulfur content, adequate sulfur utilization, and high mass loading is challenging. Here, to address these concerns, we propose using a liquid-phase-synthesized Li3PS4-2LiBH4 glass-ceramic solid electrolyte with a low density (1.491 g cm−3), small primary particle size (~500 nm) and bulk ionic conductivity of 6.0 mS cm−1 at 25 °C for fabricating lithium-sulfur all-solid-state batteries. When tested in a Swagelok cell configuration with a Li-In negative electrode and a 60 wt% S positive electrode applying an average stack pressure of ~55 MPa, the all-solid-state battery delivered a high discharge capacity of about 1144.6 mAh g−1 at 167.5 mA g−1 and 60 °C. We further demonstrate that the use of the low-density solid electrolyte increases the electrolyte volume ratio in the cathode, reduces inactive bulky sulfur, and improves the content uniformity of the sulfur-based positive electrode, thus providing sufficient ion conduction pathways for battery performance improvement.

Hepatic Betaine-Homocysteine Methyltransferase Activity in the Chicken Is Influenced by Dietary Intake of Sulfur Amino Acids, Choline and Betaine

There is much interest in the metabolism of homocysteine, because elevated plasma homocysteine [hyperhomocyst(e)inemia] is an independent risk factor for the development of cardiovascular disease. Four chick assays were conducted to determine the effects of varying dietary sulfur amino acids, choline and betaine on the activity of hepatic betaine-homocysteine methyltransferase (BHMT), an enzyme likely to be important in modulating plasma homocysteine. In Experiment 1, chicks were fed a purified crystalline amino acid diet containing adequate sulfur amino acids and choline. Excess dietary methionine, or the combination of excess cystine with choline or betaine, caused a small increase (P < 0.05) in BHMT activity. In Experiment 2, use of a methionine-deficient purified diet resulted in a threefold increase (P < 0.05) in BHMT activity, and addition of choline or betaine further increased (P < 0.05) BHMT activity. In Experiment 3, use of a methionine-deficient corn-peanut meal diet increased BHMT (P < 0.05) relative to that of chicks supplemented with adequate methionine, and addition of surfeit choline to the methionine-deficient basal diet caused a further increase (P < 0.05). In Experiment 4, addition of both surfeit choline and surfeit betaine to the methionine-deficient corn-peanut meal diet caused an increase (P < 0.05) in BHMT activity relative to that observed in chicks fed the methionine-deficient basal diet. These assays show that large increases in BHMT activity can be produced under methionine-deficient conditions, especially in the presence of excess choline or betaine.

Sustainable N2 photofixation promoted by Fe-doped MoSy/CuxS grown on copper mesh

Photocatalysts composed of novel nanoparticles grown on the surface of copper mesh are synthesized by electrodeposition under ambient condition. It is first applied in a liquid membrane reactor without any organic scavengers or precious metal co-catalysts for the photocatalytic reduction of N2 to NH3. The liquid membrane reaction greatly improves the problem of nitrogen insoluble to reinforce the contact between the reactants. The catalyst with copper mesh substrate possesses excellent recyclability and stability. The results show that Fe-doped MoSy/CuxS photocatalyst supported by copper mesh (FMC-cm) significantly improved the photoreduction performance. When Fe was doped in CuxS and MoSy simultaneously, the FMC3-cm sample had the best reaction activity, nearly 9.0 times higher than that of pristine CuxS. The characterization results reveal that the mixed crystallization of copper sulfide and molybdenum sulfide formed type-II heterostructure containing three redox pairs, Cu+/Cu2+, Mo4+/Mo6+ and Fe2+/Fe3+, and introduced adequate sulfur vacancies, which provided rich active sites for N2 adsorption and activation. The synergistic effect of heterostructure and redox cycles effectively promoted the transport and separation of photogenerated carriers and enhanced the redox ability of photocatalyst.

Isobutane dehydrogenation over high-performanced sulfide V-K/γ-Al2O3 catalyst: Modulation of vanadium species and intrinsic effect of potassium

Compared with industrial used Pt- and Cr-based catalyst in dehydrogenation (DH) of light alkanes, the sulfide V-K/γ-Al2O3 catalyst reported in this study shows lower cost and toxicity, and significant DH performance. The yield to isobutene reached as high as 52.9%, which is among the highest reported to date. We attribute such high isobutene yield to the precise modulation of polymerization degree for vanadium species via doping of potassium and indicating that the synergy between vanadium species and acid sites is critical to enhance the DH performance. Our previous work showed sulfidation promoted the increase of DH performance for vanadium-based catalyst, and we go further in this study to explore the correlation between increased range of DH performance and the added potassium. The different loaded potassium leads to variation in sulfidation degree, affecting the properties of vanadium species and acid properties consequently. The potassium was distributed uniformly on surface of the sulfide vanadium-based catalyst and was predominantly bonded with the vanadium species rather than with the γ-Al2O3 support. With increasing the potassium amount from 0 to 3 wt%, the acid amount kept decreasing, and some specific strong acid sites appeared once adequate sulfur was introduced in the V-K/γ-Al2O3 catalyst. The characterization and DFT results both revealed that the doped potassium contributes to regulating the vanadium species in the oligomeric state. The synergy between vanadium species and acid properties was regulated by the added potassium simultaneously, and thus the DH performance was enhanced. This study provides promising strategy for preparation of environment-friendly model industrial DH catalyst.

High temperature patterns at the onset of seed maturation determine seed yield and quality in oilseed rape (Brassica napus L.) in relation to sulphur nutrition

High temperatures during the crop reproductive stage impact seed yield and quality. The changing climate will require consideration of the effects of high temperature events that differ from their intensity, their duration and their frequency over the seed quality-building stages. The impact of these features deserve to be investigated at the light of induced thermo-sensitization which can lead to alleviate expected negative impacts. In our work, maturing seeds of the sulphur-demanding crop, oilseed rape, were exposed to several temperature sequences that varied in intensity, duration and frequency at the onset of seed maturation. Results-measured in seeds that were at the onset of maturation when the temperature stress occurred-indicated that (i) the longer the cumulated duration of the temperature stress, the more negatively impacted the quality criteria with decreased fatty acids (FAs) concentration, increased ω6:ω3 ratio, lower seed membrane integrity and increased seed dormancy and (ii) a mild stress event prior to heat peaks had an alleviating effect on the negative impact of the later heat peaks (priming effect) on seed nitrogen, desiccation tolerance and the phytohormones involved in thermoinhibition. Sulphur restriction was positive on FAs, protein concentration and negative on breaking dormancy. In addition, sulphur supply interfered with temperature modality, features such that positive impact of sulphur limitation on boosting oxidative response were cancelled with intense late heat peaks. This work provides insights to define thermopriming protocols in relation to the timing of quality building processes, their respective optimal temperature and adequate sulphur supply.

Regulation of senescence-associated protease genes by sulphur availability according to barley (Hordeum vulgare L.) phenological stage.

Proteases are responsible for protein degradation during leaf senescence, allowing nutrients to be redirected to sink tissues. In a previous work, we reported that sulphur deficiency produced a delay in the leaf senescence of barley (Hordeum vulgare L.) plants, at both vegetative and reproductive stages. In this work, we analyse the effect of sulphur deficiency on the expression of several genes coding for proteases of different catalytic groups, which have been strongly associated with leaf senescence. Four independent experiments were performed in order to impose low sulphur availability conditions: one of steady-state sulphur deficiency during the vegetative stage and three of sulphur starvation during vegetative and reproductive stages. Sulphur deficiency inhibited or reduced the senescence-associated induction of seven of the eight proteases analysed. Their induction, as well as senescence and phloem amino acid remobilization, could be achieved with senescence inducers such as methyl-jasmonate (a hormonal stimulus) and darkness, but with different rates of induction dependent on each gene. Sulphur deficiency also exerted an opposite effect on the expression of two cysteine-protease genes (HvSAG12 and HvLEGU) as well as on one serine-protease gene (HvSUBT) according to leaf age and plant phenological stages. All three genes were induced in green leaves but were repressed in senescent leaves of sulphur-deficient plants at the vegetative stage. At the reproductive stage, both cysteine-proteases were only repressed in senescent leaves, while the serine-protease was induced in green and senescent leaves by sulphur deficiency. Our results highlight the relevance of adequate sulphur nutrition in order to ensure leaf senescence onset and induction of protease genes, which will consequently impact on grain protein composition and quality. In addition, our results provide evidence that leaf age, plant developmental stage and the nature of the stress modulate the sulphur responses.

The Immunogenicity of a Proline-Substituted Altered Peptide Ligand toward the Cancer-Associated TEIPP Neoepitope Trh4 Is Unrelated to Complex Stability.

Human cancers frequently display defects in Ag processing and presentation allowing for immune evasion, and they therefore constitute a significant challenge for T cell-based immunotherapy. We have previously demonstrated that the antigenicity of tumor-associated Ags can be significantly enhanced through unconventional residue modifications as a novel tool for MHC class I (MHC-I)-based immunotherapy approaches. We have also previously identified a novel category of cancer neo-epitopes, that is, T cell epitopes associated with impaired peptide processing (TEIPP), that are selectively presented by MHC-I on cells lacking the peptide transporter TAP. In this study, we demonstrate that substitution of the nonanchoring position 3 into a proline residue of the first identified TEIPP peptide, the murine Trh4, results in significantly enhanced recognition by antitumor CTLs toward the wild-type epitope. Although higher immunogenicity has in most cases been associated with increased MHC/peptide complex stability, our results demonstrate that the overall stability of H-2Db in complex with the highly immunogenic altered peptide ligand Trh4-p3P is significantly reduced compared with wild-type H-2Db/Trh4. Comparison of the crystal structures of the H-2Db/Trh4-p3P and H-2Db/Trh4 complexes revealed that the conformation of the nonconventional methionine anchor residue p5M is altered, deleting its capacity to form adequate sulfur-π interactions with H-2Db residues, thus reducing the overall longevity of the complex. Collectively, our results indicate that vaccination with Thr4-p3P significantly enhances T cell recognition of targets presenting the wild-type TEIPP epitope and that higher immunogenicity is not necessarily directly related to MHC/peptide complex stability, opening for the possibility to design novel peptide vaccines with reduced MHC/peptide complex stability.

Reducing the acrylamide‐forming potential of wheat

AbstractAcrylamide is a Class 2a carcinogen that was discovered in a variety of popular foods, including baked cereal products, in 2002. The predominant route for its formation is from free asparagine and reducing sugars in the Maillard reaction, with free asparagine concentration being the main determinant of acrylamide‐forming potential in cereal products. The European Commission set “indicative” levels for acrylamide in food in 2011 and 2013, and is currently reviewing its options for further measures. Agronomic and genetic approaches to reducing the acrylamide‐forming potential of wheat include the evaluation of existing varieties for low asparagine accumulation in the grain, ensuring adequate sulfur fertilization in relation to nitrogen supply, developing an understanding of the genetic control of asparagine metabolism, and identifying quantitative trait loci or molecular markers for low asparagine accumulation in the grain. Asparagine concentration in grain is affected by environmental factors (E), genetic factors (G), and interactions between the two (G × E). This paper reviews the continuing efforts being made to reduce the acrylamide‐forming potential of wheat, and to increase awareness of the issue among wheat breeders, farmers, and the food industry.

Brassica napus L. cultivars show a broad variability in their morphology, physiology and metabolite levels in response to sulfur limitations and to pathogen attack

Under adequate sulfur supply, plants accumulate sulfate in the vacuoles and use sulfur-containing metabolites as storage compounds. Under sulfur-limiting conditions, these pools of stored sulfur-compounds are depleted in order to balance the nitrogen to sulfur ratio for protein synthesis. Stress conditions like sulfur limitation and/or pathogen attack induce changes in the sulfate pool and the levels of sulfur-containing metabolites, which often depend on the ecotypes or cultivars. We are interested in investigating the influence of the genetic background of canola (Brassica napus) cultivars in sulfur-limiting conditions on the resistance against Verticillium longisporum. Therefore, four commercially available B. napus cultivars were analyzed. These high-performing cultivars differ in some characteristics described in their cultivar pass, such as several agronomic traits, differences in the size of the root system, and resistance to certain pathogens, such as Phoma and Verticillium. The objectives of the study were to examine and explore the patterns of morphological, physiological and metabolic diversity in these B. napus cultivars at different sulfur concentrations and in the context of plant defense. Results indicate that the root systems are influenced differently by sulfur deficiency in the cultivars. Total root dry mass and length of root hairs differ not only among the cultivars but also vary in their reaction to sulfur limitation and pathogen attack. As a sensitive indicator of stress, several parameters of photosynthetic activity determined by PAM imaging showed a broad variability among the treatments. These results were supported by thermographic analysis. Levels of sulfur-containing metabolites also showed large variations. The data were interrelated to predict the specific behavior during sulfur limitation and/or pathogen attack. Advice for farming are discussed.

Major Sulphur Compounds in Plants and their Role in Human Nutrition and Health - An overview

Major sulphur compounds in plants include amino acids methionine and cysteine, vitamins thiamine and biotin and others of value from the viewpoint of human health, such as aliin (a precursor of alicin), glucisinolates (GSL), glutathione (GSH) and methylsulfonylmethane (MSM). Of these, methionine and thymine are essential nutrients and humans must obtain these from plant foods. Although cysteine is not an essential amino acid, its derivative - acetylcystein or N-acetylesystein - is used for the treatment of paracetamol toxicity , mucolytic (mucus dissolving) therapy, acute renal failure and psychiatric disorders. In recent years, the plant food that has received most attention is garlic, responsible for the production of alicin, which is credited for preventing cardiovascular disorders. Similarly , vegetables from the family Brassicae, such as, broccoli, cabbage and turnip rape have gained attention due to the presence of glucosinolates, which are reported to be useful in curing cancer. Glutathionate (GSH) pool is important in preventing diseases where increased oxidative stresses are implicated or where there is protein-energy malnutrition seen as a secondary manifestation, such as in AIDS, cancer, burns, chronic digestive diseases and alcoholism. Methylsulfonylmethane (MSM) is used for treating arthritis. Since plants obtain their sulphur from soil, adequate sulphur fertilization can play an important role in producing plant products with higher amounts of S-compounds, but there have been very few agronomic studies on this subject. The main objective of this review is to emphasize the need for such studies in India, especially in view of the fact that about 42% soils are deficient in sulphur.

Silicate melt inclusions in the Qiushuwan granitoids, northern Qinling belt, China: Implications for the formation of a porphyry Cu–Mo deposit as a reduced magmatic system

Melt inclusions (MIs) in quartz from granitoids in the northern Qinling belt were studied using microthermometry and laser Raman spectroscopy. The total homogenization of melt inclusions occurs in a mean range between 1050 and 1100°C. Laser Raman experiments reveal H2O, C2H6, C4H6 and CH4 as the dominant volatile compounds. Our results provide insights into the temperatures of magma crystallization and the dominantly reducing environment during the early magmatic stage. Based on ore mineralogy, and on the volatile species content in the MIs, we evidence firstly that the Qiushuwan porphyry Cu–Mo deposit in the Qinling–Dabie–Sulu orogenic belt was derived from a reduced magmatic system, emplaced at relatively deep domains more than 10km deep, and secondly, that the magmas that are responsible for the generation of Qiushuwan were either derived from an inherently reduced source, or reduced during ascent and emplacement. The mechanism might have involved the assimilation of sedimentary material with minimal crustal interaction. The parental magmas likely underwent reduction essentially by loss of all of their SO2 by degassing, as evidenced by the low S content in melt inclusions. These reduced materials provided adequate sulfur source for the formation of the porphyry Cu–Mo deposits with obvious zonation, which plays a key role in the mineralization; finally, we conclude that the reduced environment and the relatively deep domain of magma emplacement probably limited the extent of mineralization, generating only a relatively small Cu–Mo deposit in Qiushuwan, located within the northern Qinling accretionary belt.

Adequate S supply protects barley plants from adverse effects of salinity stress by increasing thiol contents

As the salt-affected areas are expected to increase substantially in subsequent years, the impact of salinity on plant growth and yield is likely to increase. One of the first consequences of plant exposure to high saline concentrations is the formation of reactive oxygen species (ROS). In order to allow adjustment of the cellular redox state, plant antioxidative system has to be activated. This system involves several enzymes and compounds, as the sulphur-containing metabolite glutathione (GSH). Therefore, our aim was to determine whether adequate sulphur nutrition might alleviate the adverse effects of salt stress on barley plants grown in the presence of different sulphate application rate and exposed to 100 mM NaCl, by studying differences in growth parameters, lipid peroxidation, sulphate and thiol accumulation and sulphur assimilation pathway. In salt-treated plants, an adequate sulphur supply allows adequate GSH synthesis (high-thiol concentration) thus avoiding the effects of ROS on photosynthetic functions (no effect on both chlorophyll and protein content), whereas in S-deficient plants, salt stress leads to excess ROS production that induces stress and plants showed reduction of photosynthetic efficiency (loss of chlorophyll and protein contents). As thiol levels are more abundant in S-sufficient plants than in those S-deficient, one might expect that S-sufficient plants are more able to remove the harmful effects of high salinity. The comparison of malondialdehyde levels between +S and −S salt-treated plants strongly supports this idea. In conclusion, we found that plant sulphur nutritional status plays a key role in the metabolic modifications necessary to cope with salt stress.

Overexpression of serine acetlytransferase produced large increases in O-acetylserine and free cysteine in developing seeds of a grain legume

There have been many attempts to increase concentrations of the nutritionally essential sulphur amino acids by modifying their biosynthetic pathway in leaves of transgenic plants. This report describes the first modification of cysteine biosyntheis in developing seeds; those of the grain legume, narrow leaf lupin (Lupinus angustifolius, L.). Expression in developing lupin embryos of a serine acetyltransferase (SAT) from Arabidopsis thaliana (AtSAT1 or AtSerat 2;1) was associated with increases of up to 5-fold in the concentrations of O-acetylserine (OAS), the immediate product of SAT, and up to 26-fold in free cysteine, resulting in some of the highest in vivo concentrations of these metabolites yet reported. Despite the dramatic changes in free cysteine in developing embryos of SAT overexpressers, concentrations of free methionine in developing embryos, and the total cysteine and methionine concentrations in mature seeds were not significantly altered. Pooled F2 seeds segregating for the SAT transgene and for a transgene encoding a methionine- and cysteine-rich sunflower seed storage protein also had increased OAS and free cysteine, but not free methionine, during development, and no increase in mature seed total sulphur amino acids compared with controls lacking SAT overexpression. The data support the view that the cysteine biosynthetic pathway is active in developing seeds, and indicate that SAT activity limits cysteine biosynthesis, but that cysteine supply is not limiting for methionine biosynthesis or for storage protein synthesis in maturing lupin embryos in conditions of adequate sulphur nutrition. OAS and free methionine, but not free cysteine, were implicated as signalling metabolites controlling expression of a gene for a cysteine-rich seed storage protein.

Sulphate sorption/desorption behavior vis-à-vis thermodynamic characteristics of some sulphur deficient soils of West Bengal

Sulphate sorption/desorption in four sulphur deficient soil series, namely, Aeric Haplaquept, Fluventic Ustochrept, Typic Fluvaquent and Typic Ustorthent of the Bengal basin was examined at 35°C. The sulphate sorption/desorption data were fitted to six adsorption isotherms, namely, Langmuir, Freundlich, Tempkin, Fitter and Sutton, Gunary and Initial Mass Sulphur (IMS) Adsorption equations were derived, in order to predict better adsorption/desorption processes and parameters. The derived data on these isotherms revealed higher sulphate sorption and also greater extent of hysteresis (indicating greater deficiency) in Aeric Haplaquept and Typic Ustorthent soils. The sorption/desorption capacity of these soils varied moderately with the variations in pH, iron and aluminum fractions, available phosphorus, exchangeable calcium plus magnesium, clay content and organic carbon content of the experimental soils. The data, thus obtained were employed to work out Gibb's free energy of sulphate sorption/desorption, the negative value of which essentially favored the sorption processes in these soils. Soils having greater irreversible sulphate sorption capacity (deficiency) require adequate sulphur (33–50 kg ha−1) in order to ensure optimum plant growth and yield.

A Cu–CeO[sub 2]-LDC Composite Anode for LSGM Electrolyte-Supported Solid Oxide Fuel Cells

A bilayer structure with a 250 μm thick La 0.8 Sr 0.2 Ga 0.83 Mg 0.17 O 3―δ (LSGM) electrolyte layer and a 150 μm porous La 0.4 Ce 0.6 O 2―δ (LDC) anode skeleton was fabricated by a copressing/cofiring method. Single cells based on the bilayer structure with a low loading of Cu (10 wt %)―CeO 2 (5 wt %) impregnated into the porous LDC as an anode and a screen-printed SrCo 0.8 Fe 0.2 O 3―δ layer as a cathode were evaluated with H 2 and CH 4 fuels from 650 to 800°C. The maximum power densities at 800°C were 880 and 275 mW cm ―2 with H 2 and CH 4 as fuels, respectively. The Cu―CeO 2 ―LDC composite anode was free of visible coking in dry CH 4 and had adequate sulfur tolerance with up to 200 ppm H 2 S in dry H 2 . The utilization of this fuel-flexible anode might simplify the processing of the LSGM-based cells while maintaining adequate cell performance.

Some physicochemical and antinutritional properties of raw flours and protein isolates from Mucuna pruriens (velvet bean) and Canavalia ensiformis (jack bean)

SummaryThe legumes Canavalia ensiformis and Mucuna pruriens are underexploited in tropical Mexico. Their seeds have good nutritional potential, but contain antinutritional factors. Physicochemical and antinutritional properties were determined for raw flours (RF) and protein isolates (PI) produced from these legumes. Protein content in the PI was 737 g kg–1 for C. ensiformis and 666 g kg–1 for M. pruriens. Protein isolation improved in vitro digestibility, while maintaining high lysine levels and adequate sulphur amino acids content. Antinutritional factors such as cyanogenic glucosides, cyanide precursors from hydrolysis, tannins and trypsin inhibitors were lower in the PIs than in the RFs. The reduction in canavanine levels, a structural analogue of arginine, in the C. ensiformis PI was noteworthy. These PIs thus have potential applications in the development of new food ingredients in tropical regions using processes that improve nutritional value.

Mass Transfer Kinetics in the Desulphurisation of Pig Iron with CaO and CaC&lt;sub&gt;2&lt;/sub&gt;

This paper discusses the effect of the main parameters that affect the desulphurization reaction efficiency. The study was conducted by evaluating different reaction sites within the metal, the slag and the reducing agents. It was possible to establish a mass transfer model that determines the amounts of the reducing agents needed to maintain adequate sulphur levels in the pig iron. Industrial trials showed the accuracy of our model.

Arsenic incorporation into authigenic pyrite, Bengal Basin sediment, Bangladesh

Sediment from two deep boreholes (∼400 m) approximately 90 km apart in southern Bangladesh was analyzed by X-ray absorption spectroscopy (XAS), total chemical analyses, chemical extractions, and electron probe microanalysis to establish the importance of authigenic pyrite as a sink for arsenic in the Bengal Basin. Authigenic framboidal and massive pyrite (median values 1500 and 3200 ppm As, respectively), is the principal arsenic residence in sediment from both boreholes. Although pyrite is dominant, ferric oxyhydroxides and secondary iron phases contain a large fraction of the sediment-bound arsenic between approximately 20 and 100 m, which is the depth range of wells containing the greatest amount of dissolved arsenic. The lack of pyrite in this interval is attributed to rapid sediment deposition and a low sulfur flux from riverine and atmospheric sources. The ability of deeper aquifers (>150 m) to produce ground water with low dissolved arsenic in southern Bangladesh reflects adequate sulfur supplies and sufficient time to redistribute the arsenic into pyrite during diagenesis.

Refined understanding of sulphur amino acid nutrition in hybrid striped bass,Morone chrysops♀×M. saxatilis♂

Previous studies have indicated that the level of total sulphur amino acids (TSAA) (methionine+cystine) is most limiting in practical diet formulations for hybrid striped bass (HSB), especially if animal feedstuffs are replaced with plant feedstuffs. Reduction in costly animal feedstuffs such as fish meal, while maintaining adequate dietary levels of TSAA, may enhance the cost effectiveness of production. Therefore, this study investigated three different aspects of sulphur amino acid nutrition of HSB including: (1) the efficacy of crystalline methionine hydroxy analogue (MHA) and liquid MHA (Alimet™) relative to l-methionine in meeting the requirement for TSAA; (2) the cystine-sparing value for methionine; and (3) the influence of various sulphur amino acid supplements on ammonia excretion. During three separate feeding trials (2, 6 and 10 weeks in duration), juvenile HSB were fed various diets including a basal diet deficient in TSAA (0.33% or 0.51% of diet), and experimental diets supplemented on an equal-sulphur basis with different levels of either l-methionine, Alimet™ or crystalline MHA. Diets containing TSAA at 1% of diet and different ratios of cystine to methionine (60:40, 55:45, 50:50 and 45:55) were also fed to re-evaluate the sparing effects of cystine on methionine. In trial 1, over the course of 10 weeks, Alimet™ was 73% as effective in promoting weight gain as l-methionine at the same concentration while MHA was 83% as effective. After 6 weeks in trial 2, fish fed Alimet™ at 1.25% of diet displayed similar growth performance as those fed TSAA at 1.0% of diet, while weight gain of fish fed Alimet™ at 1% was only 58% of that displayed by fish fed TSAA at 1.0%. No significant differences in weight gain, feed utilization or survival were observed among fish fed diets containing various ratios of cystine to methionine, although the diet with 60:40 cystine to methionine had the lowest numerical responses. Inclusion of MHA or Alimet™ did not affect TAN excretion of HSB. These findings will aid in refining diet formulations for HSB to ensure adequate sulphur amino acid nutrition.