Variation In Se Concentration Research Articles

Hyperaccumulator Stanleya pinnata: In Situ Fitness in Relation to Tissue Selenium Concentration.

Earlier studies have shown that Stanleya pinnata benefits from selenium hyperaccumulation through ecological benefits and enhanced growth. However, no investigation has assayed the effects of Se hyperaccumulation on plant fitness in the field. This research aimed to analyze how variation in Se accumulation affects S. pinnata fitness, judged from physiological and biochemical performance parameters and herbivory while growing naturally on two seleniferous sites. Natural variation in Se concentration in vegetative and reproductive tissues was determined, and correlations were explored between Se levels with fitness parameters, herbivory damage, and plant defense compounds. Leaf Se concentration varied between 13- and 55-fold in the two populations, averaging 868 and 2482 mg kg−1 dry weight (DW). Furthermore, 83% and 31% of plants from the two populations showed Se hyperaccumulator levels in leaves (>1000 mg kg−1 DW). In seeds, the Se levels varied 3–4-fold and averaged 3372 and 2267 mg kg−1 DW, well above the hyperaccumulator threshold. Plant size and reproductive parameters were not correlated with Se concentration. There was significant herbivory pressure even on the highest-Se plants, likely from Se-resistant herbivores. We conclude that the variation in Se hyperaccumulation did not appear to enhance or compromise S. pinnata fitness in seleniferous habitats within the observed Se range.

Two-dimensional Janus material MoS2(1-x)Se2x (0 < x < 1) for photovoltaic applications: A machine learning and density functional study

Janus transition-metal dichalcogenides MoSSe has been attracted much attention due to its excellent electronic properties induced by mirror symmetry breaking. In this work, based on machine learning and density functional theory, the photoelectric conversion coefficient (PCE) along with the variation of Se concentration in MoS2(1-x)Se2x (0 < x < 1) are explored. Ten most important features are sorted out by calculating the Pearson correlation coefficient matrices to identify the linear relationship between any two features and their correlation. The coefficient of determination (R2), root mean square error (RMSE) and mean absolute relative error (MARE) are evaluated for the built machine learning models of random forest (RF) and multiple linear regression (MLR). For the prediction of the PCE, the RF algorithm using structural information and computational features obtained from DFT calculations is validated possessing high efficiency. In a wide range of doping concentrations (n = 32%–96%), we predict that the PCE of MoS2(1-x)Se2x has a high value larger than 18%. High optical absorption intensity in an order of 105 cm−1 is obtained in MoS0.89Se1.11, which has potential application in solar cell.

Selenium deficiency risk in central Kenya highlands: an assessment from the soil to the body.

Selenium (Se) deficiency is associated with increased risk of clinical disorders. Yet, it has not been considered as an important public health issue in Africa. The health burden of this 'hidden hunger' remains largely unknown. Using a case study of central Kenya highlands, a cross-sectional survey assesses Se status of agricultural soils, foods, hair, and actual average dietary Se intake of the local population and investigates the soil-food Se concentration and Se intake-individual Se status relationships. The survey examines eight locations characterized by different agricultural soil types and assesses average dietary Se intake among 159 children and 111 women based on 24-h dietary recall data. Soil Se concentration does not explain Se concentration in foods, which instead is associated with soil's pH, organic matter, and P and Fe content. Cereal grains, beans and potato/green banana form a large portion of the local diet while intake of animal-based foods is limited. This results in Se intake of 15 and 33µgp-1d-1 for children and women, respectively. On average, 87% of children and 97% of women have inadequate average daily dietary Se intake, and the hair Se concentration of 92% children and 94% women is below the reference values. Soil's characteristics contribute to variation in Se concentration in foods and consequently the dietary Se intake. A low diversified diet is a key contributing factor to inadequate dietary Se intake in the region. These findings call for the need to investigate potential intervention measure and the health burden of Se deficiency.

Electronic structure and thermoelectric properties of PbTe1−xSex from first-principles calculations

Electronic structures and thermoelectric transport properties of a series of PbTe1−xSex solid solutions have been investigated using density functional theory and Boltzmann transport equation with constant relaxation time approximation. The evolution of the band structure with the variation of Se concentration has been studied systematically. It has been found out that the Seebeck coefficients and power factors of p-type PbTe1−xSex solid solutions decrease continuously with increasing Se concentration, which is mainly due to the higher the Se concentration, the flatter the density of states near the edge of the valence band. The dependence of the thermoelectric transport coefficients on carrier concentration and temperature was discussed in detail. Our studies provide a guidance for future experiments to search high-efficiency p-type PbTe1−xSex solid solutions.

Selenium Accumulation, Speciation and Localization in Brazil Nuts (Bertholletia excelsa H.B.K.).

More than a billion people worldwide may be selenium (Se) deficient, and supplementation with Se-rich Brazil nuts may be a good strategy to prevent deficiency. Since different forms of Se have different nutritional value, and Se is toxic at elevated levels, careful seed characterization is important. Variation in Se concentration and correlations of this element with other nutrients were found in two batches of commercially available nuts. Selenium tissue localization and speciation were further determined. Mean Se levels were between 28 and 49 mg kg−1, with up to 8-fold seed-to-seed variation (n = 13) within batches. Brazil nut Se was mainly in organic form. While present throughout the seed, Se was most concentrated in a ring 1 to 2 mm below the surface. While healthy, Brazil nuts should be consumed in moderation. Consumption of one seed (5 g) from a high-Se area meets its recommended daily allowance; the recommended serving size of 30 g may exceed the allowable daily intake (400 μg) or even its toxicity threshold (1200 μg). Based on these findings, the recommended serving size may be re-evaluated, consumers should be warned not to exceed the serving size and the seed may be sold as part of mixed nuts, to avoid excess Se intake.

Cation Exchange Mediated Synthesis and Tuning of Bimodal Plasmon in Alloyed Ternary Cu3BiS3–xSex Nanorods

We report a robust methodology for synthesizing monodisperse alloyed Bi2S3–xSex nanorods (NRs) to tune optical properties with the variation of Se concentration. The intercalation of Cu(I) into the presynthetic Bi2S3–xSex NRs converted to ternary Cu3BiS3–xSex NRs via cation exchange process. The transformation was monitored through the formation of core/shell Bi2S3–xSex/Cu3BiS3–xSex nanorod heterostructures. Shape anisotropy results in near-infrared bimodal localized surface plasmon resonance (LSPR) in Cu3BiS3–xSex nanorod over a broad range from 600 to 3500 nm with increase of Se:S ratio. The LSPR sensitivity, defined as the change in the LSPR peak wavelength per unit change in the refractive index (RI) of the medium, was estimated to be 250–350 nm/RI unit, much higher than other copper chalcogenides like Cu2S/Cu2Se. A fast photodetector was fabricated by Cu3BiS3–xSex NRs with high photocurrent gain value (∼125) with Se alloying. The intrinsic Cu vacancies and the effective mass of charge carriers play i...

Natural variation of selenium in Brazil nuts and soils from the Amazon region

Brazil nut tree (Bertholletia excelsa) is native of the Amazon rainforest. Brazil nuts are consumed worldwide and are known as the richest food source of selenium (Se). Yet, the reasoning for such Se contents is not well stablished. We evaluated the variation in Se concentration of Brazil nuts from Brazilian Amazon basin, as well as soil properties, including total Se concentration, of the soils sampled directly underneath the trees crown, aiming to investigate which soil properties influence Se accumulation in the nuts. The median Se concentration in Brazil nuts varied from 2.07 mg kg−1 (in Mato Grosso state) to 68.15 mg kg−1 (in Amazonas state). Therefore, depending on its origin, a single Brazil nut could provide from 11% (in the Mato Grosso state) up to 288% (in the Amazonas state) of the daily Se requirement for an adult man (70 μg). The total Se concentration in the soil also varied considerably, ranging from <65.76 to 625.91 μg kg−1, with highest Se concentrations being observed in soil samples from the state of Amazonas. Se accumulation in Brazil nuts generally increased in soils with higher total Se content, but decreased under acidic conditions in the soil. This indicates that, besides total soil Se concentration, soil acidity plays a major role in Se uptake by Brazil nut trees, possibly due to the importance of this soil property to Se retention in the soil.

Band gap engineering in lead sulphur selenide (PbS1−x Se x ) thin films synthesized by chemical bath deposition method

Nanocrystalline PbS1−xSex (0 ≤ x ≤ 1) thin films have been deposited on silica glass substrate by the chemical bath deposition technique. The deposited PbS1−xSex thin films were smooth and mirror-like gray in color. The films were characterized by a variety of techniques and the effect of selenium (Se) concentration analyzed. The X-ray diffraction analyses revealed that all the PbS1−xSex thin films were polycrystalline and had the face centered cubic structure. Variation in Se concentration had a significant effect on the preferred orientation of the crystallites. The lattice constant and inter planer distance increased linearly with the gradual addition of Se in the PbS1−xSex thin films. Energy dispersive X-ray analysis confirmed that all the samples have stoichiometric composition. The surface morphology of the films has been examined using scanning electron microscopy. The optical absorption spectroscopy study revealed that the optical band gap of the PbS1−xSex thin films tuned from near-infrared to visible region (1.32–1.08 eV) by simple and cost effective route.

Natural variation of selenium concentration in diverse tea plant (Camellia sinensis) accessions at seedling stage

Selenium (Se) is a dietary essential trace element for humans and animals. Owing to Se being obtained from food or other source of supplementation, Se-enriched tea is a possible source of supplemental Se and thus has been drawing much attention. This study aimed to identify the variation of the Se concentrations among 14 elite Camellia sinensis cultivars against two-Se-levels supplementation at seedling stage. In the present study, the genetic diversity was assessed by 93 alleles revealed by 12 SSR primers in the C. sinensis accessions. Among the scored 93 alleles, 81 (87.10%) were polymorphic, and the average Nei's gene diversity (He) was 0.253 and average shannon information index (I) was 0.394, indicating a relatively high genetic variation. Significant variations were observed for the Se concentration among the accessions in both treatments (P<0.01), ranging from 0.300–0.445mgkg−1 and 0.357–0.537mgkg−1 in control (0) and Se-supplied (4mgkg−1) treatments respectively. The quality components content, tea polyphenols and amino acid, were sensitive to Se-supplement in a few of accessions, whereas soluble sugar and aqueous extract content appeared unchanged between the contrast treatments. In addition, the genetic variation among the tea plant cultivars was not well correlated with the Se concentration. Even then, the genetic variation in Se concentration across the 14 accessions indicated the possibility of utilizing tea plant accessions to develop optimized cultivars for Se-enriched tea. For the relative high Se concentration in the tea, tea plant is supposed to be a Se-enriched species. These results may enhance our understanding the genetic variation in tea plant.

Experimental Synthesis of the Stibnite-Antimonselite Solid Solution Series

Experiments on the Sb-S-Se system were conducted at 300°C, and a continuous stibnite-antimonselite binary solid solution was established. By substituting S for Se, the compositions of S-rich and Se-rich endmembers were confirmed as Sb2S3 and Sb2Se3, respectively. Based on Se/(S+Se) ratios of microprobe analyses, binary stibnite-antimonselite solid solutions are defined as stibnite, selenium stibnite, sulfur antimonselite, and antimonselite. Microhardness of the stibnite subseries (Sb = 60.11-72.58, S = 13.20-27.63, and Se = 0.00-27.23 wt%) and the antimonselite subseries (Sb = 49.29-59.25, Se = 28.89-51.94, S = 0.00-12.10 wt%) varies from 112.95 to 127.72 kg/mm2. The variation of Se concentration is continuous throughout the series, confirming a random substitution of Se for S. Crystallographic parameters obtained from the series vary as follows: a = 1.123375-1.163890 nm, b = 1.132502-1.179553 nm, c = 0.383914-0.398071 nm, D = 4.593-5.896 g.cm-3, and V = 0.488425-0.546500 nm3. As evident from the above data, the higher the Se concentration, the larger the crystallographic parameters. The Sb-S-Se binary solid solutions obey Vegard's law.

Plant availability of inorganic and organic selenium fertiliser as influenced by soil organic matter content and pH

The objective of the present study was to investigate the influence of soil organic matter content and pH on plant availability of both inorganic and organic selenium (Se) fertilisers. Further, the risk of Se leaching after application of inorganic Se fertiliser was evaluated. A new interpretation of an older field study at different sites in Southern Norway showed that organic C was correlated with grain Se concentration in wheat, barley and oats, explaining up to 60% of the variation in Se concentration. Pot experiments with a peat soil, a loam soil and a peat/loam soil mixture were conducted for the present study at a range of pH values between pH 5 and 7. Below pH 6, Se uptake from added Se fertiliser was higher in the soil types with high organic matter content than in the loam. The opposite occurred at a soil pH above 6, where Se uptake was higher in the loam than in the peat soil. A simple leaching experiment after one growing season confirmed the findings of the pot experiments that Se availability in the loam soil with a relatively low organic matter content increased with increasing pH, whereas it decreased in the peat soil. Neither Se yeast, nor pure Se methionine, used as organic Se fertiliser, resulted in any significant uptake of Se when added at concentrations similar to the inorganic Se applications.

Relationship between soybean seed selenium and harvested grain selenium

Field experiments were conducted on sandy loam soils in Prince Edward Island (PEI) with two cultivars of soybeans at two locations to determine the relationship between Se concentration in the seed sown and the Se concentration found in the harvested soybean crop. Seeds containing a range of Se from 0.78 to 38.5 mg kg−1 were used. These variable concentrations of seed Se were obtained in field experiments by varying the rates of seed and foliar applied Se. Grain Se concentration increased with increased Se concentration in the planted seed. A high proportion of the variation in Se concentration in the harvested soybean crop was explained by variation in the Se content of the planted seed (R2 = 0.98). The regression was calculated using averages of cultivars for both locations. From the regression equation it could be predicted that planting seed containing 24 mg Se kg−1 would produce a soybean crop containing 0.5 mg Se kg−1. When used at 200 kg soybean per tonne ration this would provide a Se concentration of 0.1 mg kg−1 assuming negligible contributions from other ingredients. Selenium concentration of 0.1 mg kg−1 in animal ration is considered adequate to protect livestock from Se deficiency diseases. Key words: Podzol soils, seed-applied Se, grain Se