High Se Research Articles

Time-Resolved Examination of Fungal Selenium Redox Transformations.

Selenium (Se) is both a micronutrient required for most life and an element of environmental concern due to its toxicity at high concentrations, and both bioavailability and toxicity are largely influenced by the Se oxidation state. Environmentally relevant fungi have been shown to aerobically reduce Se(IV) and Se(VI), the generally more toxic and bioavailable Se forms. The goal of this study was to shed light on fungal Se(IV) reduction pathways and biotransformation products over time and fungal growth stages. Two Ascomycete fungi were grown with moderate (0.1 mM) and high (0.5 mM) Se(IV) concentrations in batch culture over 1 month. Fungal growth was measured throughout the experiments, and aqueous and biomass-associated Se was quantified and speciated using analytical geochemistry, transmission electron microscopy (TEM), and synchrotron-based X-ray absorption spectroscopy (XAS) approaches. The results show that Se transformation products were largely Se(0) nanoparticles, with a smaller proportion of volatile, methylated Se compounds and Se-containing amino acids. Interestingly, the relative proportions of these products were consistent throughout all fungal growth stages, and the products appeared stable over time even as growth and Se(IV) concentration declined. This time-series experiment showing different biotransformation products throughout the different growth phases suggests that multiple mechanisms are responsible for Se detoxification, but some of these mechanisms might be independent of Se presence and serve other cellular functions. Knowing and predicting fungal Se transformation products has important implications for environmental and biological health as well as for biotechnology applications such as bioremediation, nanobiosensors, and chemotherapeutic agents.

Effect of Foliar Application of Sodium Selenate on Mineral Relationships in Brassicaceae Crops

The relationships of selenium (Se) with other elements in plants is important for producing functional food with high Se contents and a predicted quality. To unveil the peculiarities of the element interactions, eight botanical varieties of Brassica oleracea L. were grown in similar conditions with or without foliar application of sodium selenate. High varietal differences, elicited by the Se supply, were recorded with regard to the accumulation of the elements examined, except for Mg, P and Si. Cabbage florets (broccoli and cauliflower) were characterized by both the lowest total mineral content and number of elements showing content changes under the Se supply (7–8 out of 25), whereas in Savoy cabbage, the highest number of minerals displayed content changes (13–14 from 25). The Se treatment did not significantly interfere with the high correlation coefficients recorded between Sr–Ca, Co–Ni and Zn–Mg (0.824–0.952). The selenium biofortification value varied from 12 to 138 depending on the species and was inversely correlated with the Si accumulation in the control plants (r = −0.872, p < 0.001). A significant decrease in the correlation coefficients occurred due to the Se supply regarding Zn with P and Co, Ca with Co and Li, Li and V, and Na and Sn, while the V–Pb relationship was significantly enhanced. Among the 25 elements studied, Cr demonstrated the highest number of significant correlation coefficient changes (with K, Na, P, Si, Zn, Cu, Co, I, As, Pb, and V). The results of this research prove the variability of the element interactions under foliar Se treatments in Brassica oleracea plants and reveal, for the first time, an inverse correlation between the Se biofortification level and Si content in untreated plants.

Interaction between dietary selenium and methylmercury on growth performance, deposition and health parameters in rainbow trout fed selenium-rich tuna-based diets or selenium-poor plant-based diets

This study evaluated the effect of dietary mercury (Hg) and selenium (Se) sources and levels on growth performance, Hg and Se accumulation, pro-inflammatory cytokine levels and global health parameters in rainbow trout juveniles. A 6-month feeding trial was carried out with a control plant-based diet (containing analyzed Se and Hg levels: 0.3 and 0 mg/kg diet, respectively) or a control tuna-based diet (containing analyzed Se and Hg levels: 7.5 and 0.3 mg/kg diet, respectively) supplemented with 0 or 1.5 mg Se/kg diet supplied either as sodium selenite (Se(IV)) or selenomethionine (SeMet) combined with 0, 1.6 or 2 mg Hg/kg diet supplied as methylmercury (MeHg). Fish sampling was carried out at 2 times: after a short (21 days) and a long term dietary exposure (168 days). In the short term, a temporarily reduced growth was noticed in fish fed MeHg-supplemented plant-based diet in absence of dietary Se supplementation. MeHg supplementation increased pro-inflammatory cytokine TNF-α and IL-1β levels in plant and tuna-based diets. MeHg supplementation also affected short-term fish global health parameters with an increase of glucose and albumin levels in tuna-based diets. The addition of SeMet in MeHg-supplemented tuna-based diets protected against the increase of TNF-α level in the long term whereas the addition of Se(IV) in MeHg-supplemented tuna-based diets decreased whole-body Hg level and retention in the short term. In the long term, a reduced growth, a higher feed conversion ratio and a lower protein efficiency ratio were recorded in fish fed Se(IV)-supplemented tuna-based diets in absence of MeHg supplementation. The addition of Se(IV) or SeMet in tuna-based diets increased plasma IL-6 level. The addition of MeHg in plant and tuna-based diets increased Se accumulation and retention. This work underlines that different forms of Se supplementation, in two dietary background context (low basal Se level in plant-based diets and high basal Se level in tuna-based diets), have specific effects on metabolism and biological consequences of dietary MeHg. Dietary inorganic Se (but not organic Se) affected MeHg metabolism by reducing Hg accumulation in fish. However, dietary organic Se displayed better ability to afford protection against MeHg pro-inflammatory effects.

The Controlling Factors of Soil Selenium Content in a Selenium-Deficient Area in Southwest China

Selenium (Se) is a beneficial microelement for humans, and its varying abundances and shortages have attracted widespread concern. The accumulation process of soil Se is quite complicated, being controlled by multiple factors. However, the influence mechanism of soil properties, climate, and topographic conditions on Se distribution is still unclear in Se-deficient areas. For this study, we collected 2804 samples from cropland soil to assess the levels of Se and the factors that influence those levels in Se-deficient areas of southwestern China. The Se content in this area (0.17 mg/kg) was less than the mean value of China as a whole (0.29 mg/kg). Moran’s I index and a random forest (RF) model showed that higher Se levels were mostly observed in the southern and northern sections of the area we studied. The RF model had excellent performance in predicting soil Se content, with an accuracy of 64%. The use of Shapley additive explanations indicated that soil organic matter (SOM) and mean annual precipitation (MAP) were the critical factors determining Se distribution. The areas with high SOM and MAP showed high Se levels. The information obtained from this work can provide guidance for agricultural planning in Se-deficient areas.

Distribution of Se in Floating Coals with Densimetric Fractions in China

Scholars at home and abroad have studied the concentrations of Se in coal and the relationship between Se and sulfur assignment. However, little attention has been paid to the study of Se in floating coal, especially the distribution pattern of Se in floating coal of densimetric fractions and the influencing factors. A total of 138 coal samples were collected from 14 provinces and cities in China to test the Se and sulfur concentrations in coal, and we carried out the comparison of Se with forms of sulfur with 81 of them. A total of 10 coal samples were selected for float-and-sink analyses to investigate the distribution pattern of Se in floating coal. The results showed that the average Se concentration of Chinese coal was 2.26 μg/g, which is identical with the results of previous research studies, which found an average Se concentration of 2~3 μg/g. Selenium was not uniformly distributed in floating coals of densimetric fractions but it had some regularity. The main controlling factor was the sulfur content in the coal. The Se concentrations of the high-sulfur coal showed a “linear growth” distribution with an increasing density, the Se concentrations of the floating coal in each densimetric fraction increased slowly and the Se concentrations of the floating coal of a densimetric fraction > 2.00 g/cm3 increased sharply. The other controlling factor was the ash yield of the coal. The Se concentrations of the low–medium-sulfur floating coal showed a “parabolic-like” distribution, i.e., low Se concentrations at both ends and high Se concentrations at the middle densimetric fraction. With the increase in the ash content of the coal from 18.23% to 51.92%, the densimetric fraction with the highest Se concentration gradually progressed from 1.40 g/cm3 to 1.50 g/cm3, 1.60 g/cm3 and 1.80 g/cm3 in order. The correlation between the selenium of the raw coal from different regions and the total sulfur, pyrite sulfur and organic sulfur was not significant. However, there existed a significant correlation between Se, total sulfur, pyrite sulfur and organic sulfur in floating coals from the same mining area and depositional environment, among which pyrite sulfur was the most correlated with Se, followed by total sulfur and organic sulfur.

Selenium Uptake from Livestock Pasture Extremely Enriched in Selenium, Molybdenum and Uranium: A Field and X-ray Absorption Study

The agricultural soils of West Limerick, Ireland, contain very localised, extremely high natural Se concentrations that reach levels that are very toxic to grazing livestock. The Carboniferous shales that formed in anoxic deep-water marine environments are the source of the selenium, which, along with the other redox-sensitive elements of molybdenum, uranium, arsenic and vanadium, were mobilised and reprecipitated in post-glacial anoxic marshes. The result has been a history of selenosis and molybdenosis in livestock in this important dairy province. Soils collected at 10–20 cm from five different agricultural sites were analysed, and all yielded concentrations greatly in excess of the safe Se limits of 3–10 mg kg−1; the highest value recorded was 1265.8 mg kg−1 Se. The highest recorded value for Mo in these soils was 1627.5 mg kg−1, and for U, 658.8 mg kg−1. There was a positive correlation between Se, Mo U and organic matter in the soils. Analysis of non-accumulator pasture grasses (Lolium perenne (perennial ryegrass), Festuca arundinacea (tall fescue), Dactylis glomerata (cocksfoot) and Phleum pretense (timothy grass)) revealed the shoot/leaf to contain up to 78.05 mg kg−1 Se while Trifolium repens (white clover) leaves contained 296.15 mg kg−1 Se. An in situ growing experiment using the Se accumulator species Brassica oleracea revealed 971.2 mg kg−1 Se in the leaves of premier kale, which also contained 1000.4 mg kg−1 Mo. Translocation factors (TFs) were generally higher for Mo than Se across all plant species. Combined X-ray absorption near edge spectroscopy (XANES) with micro-X-ray fluorescence (μ-XRF) showed the Se was present in the soil predominantly as the reduced immobile phase, elemental Se (Se0), but also as bioavailable organoselenium species, mainly selenomethionine (SeMet). SeMet was also the main species identified within both the Se non-accumulator and Se accumulator plants. The Se soil–plant system in West Limerick is dominated by SeMet, and uptake into the cattle pasture results in selenosis in the grazing dairy herds. The hyperaccumulating Brassica oleracea species could be used to extract both the Se and Mo to reduce the toxicity of the blighted fields.

Identification of the spatial patterns and controlling factors of Se in soil and rice in Guangxi through hot spot analysis.

Selenium (Se) is essential to human health, anti-cancer, possessing antioxidant, and antiviral properties. In this study, the spatial patterns of rice Se and their varying relationship with soil Se on a regional scale were studied using hot spot analysis for the agricultural soils in Guangxi. According to the hot and cold spot maps, rice Se correlates positively with soil Se in Guangxi agricultural soils. High rice Se accompanies high soil Se in the central part of Guangxi (e.g., Liuzhou, Laibin), and low rice Se is in line with low soil Se in the western part (e.g., Baise). However, the hot spot analysis maps indicate that southwestern Guangxi exhibits a special characteristic of low rice Se with high soil Se (e.g., Chongzuo). This special pattern is strongly associated with the high concentrations of Fe2O3 (ferromanganese nodules) in the carbonate rock area. The hot spot analysis proves useful in revealing the spatial patterns of rice Se in Guangxi and identifying the hidden patterns.

Study on the relationship between selenium and cadmium in diseased human lungs

Cadmium (Cd) is a toxic environmental metal that interacts with selenium (Se) and contributes to many lung diseases. Humans have widespread exposures to Cd through diet and cigarette smoking, and studies in rodent models show that Se can protect against Cd toxicities. We sought to identify whether an antagonistic relationship existed between Se and Cd burdens and determine whether this relationship may associate with metabolic variation within human lungs. We performed metabolomics of 31 human lungs, including 25 with end-stage lung disease due to idiopathic pulmonary fibrosis, cystic fibrosis, chronic obstructive lung disease (COPD)/emphysema and other causes, and 6 non-diseased lungs. Results showed pathway associations with Cd including amino acid, lipid and energy-related pathways. Metabolic pathways varying with Se had considerable overlap with these pathways. Hierarchical cluster analysis (HCA) of individuals according to metabolites associated with Cd showed partial separation of disease types, with COPD/emphysema in the cluster with highest Cd, and non-diseased lungs in the cluster with the lowest Cd. When compared to HCA of metabolites associated with Se, the results showed that the cluster containing COPD/emphysema had the lowest Se, and the non-diseased lungs had the highest Se. A greater number of pathway associations occurred for Cd to Se ratio than either Cd or Se alone, indicating that metabolic patterns were more dependent on Cd to Se ratio than on either alone. Network analysis of interactions of Cd and Se showed network centrality was associated with pathways linked to polyunsaturated fatty acids involved in inflammatory signaling. Overall, the data show that metabolic pathway responses in human lung vary with Cd and Se in a pattern suggesting that Se is antagonistic to Cd toxicity in humans.

Methodological approaches to optimize multiplex oral fluid SARS-CoV-2 IgG assay performance and correlation with serologic and neutralizing antibody responses

BackgroundOral fluid (hereafter, saliva) is a non-invasive and attractive alternative to blood for SARS-CoV-2 IgG testing; however, the heterogeneity of saliva as a matrix poses challenges for immunoassay performance. ObjectivesTo optimize performance of a magnetic microparticle-based multiplex immunoassay (MIA) for SARS-CoV-2 IgG measurement in saliva, with consideration of: i) threshold setting and validation across different MIA bead batches; ii) sample qualification based on salivary total IgG concentration; iii) calibration to U.S. SARS-CoV-2 serological standard binding antibody units (BAU); and iv) correlations with blood-based SARS-CoV-2 serological and neutralizing antibody (nAb) assays. MethodsThe salivary SARS-CoV-2 IgG MIA included 2 nucleocapsid (N), 3 receptor-binding domain (RBD), and 2 spike protein (S) antigens. Gingival crevicular fluid (GCF) swab saliva samples were collected before December 2019 (n = 555) and after molecular test-confirmed SARS-CoV-2 infection from 113 individuals (providing up to 5 repeated-measures; n = 398) and used to optimize and validate MIA performance (total n = 953). Combinations of IgG responses to N, RBD and S and total salivary IgG concentration (μg/mL) as a qualifier of nonreactive samples were optimized and validated, calibrated to the U.S. SARS-CoV-2 serological standard, and correlated with blood-based SARS-CoV-2 IgG ELISA and nAb assays. ResultsThe sum of signal to cutoff (S/Co) to all seven MIA SARS-CoV-2 antigens and disqualification of nonreactive saliva samples with ≤15 μg/mL total IgG led to correct classification of 62/62 positives (sensitivity [Se] = 100.0%; 95% confidence interval [CI] = 94.8%, 100.0%) and 108/109 negatives (specificity [Sp] = 99.1%; 95% CI = 97.3%, 100.0%) at 8-million beads coupling scale and 80/81 positives (Se = 98.8%; 95% CI = 93.3%, 100.0%] and 127/127 negatives (Sp = 100%; 95% CI = 97.1%, 100.0%) at 20-million beads coupling scale. Salivary SARS-CoV-2 IgG crossed the MIA cutoff of 0.1 BAU/mL on average 9 days post-COVID-19 symptom onset and peaked around day 30. Among n = 30 matched saliva and plasma samples, salivary SARS-CoV-2 MIA IgG levels correlated with corresponding-antigen plasma ELISA IgG (N: ρ = 0.76, RBD: ρ = 0.83, S: ρ = 0.82; all p < 0.001). Correlations of plasma SARS-CoV-2 nAb assay area under the curve (AUC) with salivary MIA IgG (N: ρ = 0.68, RBD: ρ = 0.78, S: ρ = 0.79; all p < 0.001) and with plasma ELISA IgG (N: ρ = 0.76, RBD: ρ = 0.79, S: ρ = 0.76; p < 0.001) were similar. ConclusionsA salivary SARS-CoV-2 IgG MIA produced consistently high Se (> 98.8%) and Sp (> 99.1%) across two bead coupling scales and correlations with nAb responses that were similar to blood-based SARS-CoV-2 IgG ELISA data. This non-invasive salivary SARS-CoV-2 IgG MIA could increase engagement of vulnerable populations and improve broad understanding of humoral immunity (kinetics and gaps) within the evolving context of booster vaccination, viral variants and waning immunity.

Selenium and mercury concentrations, Se:Hg molar ratios and their effect on the antioxidant system in wild mammals

The aim of this study was to a) evaluate the concentration of Se and Hg and their relationship in the tissues of 4 species of wild mammals, including Se:Hg molar ratios, and b) evaluate the effect of the analysed elements and their mutual proportions expressed as Se:Hg molar ratio, on the antioxidant system in the tissues of the tested animals. The study was performed on 31 animals belonging to four species: wild boar, red fox, roe deer, brown hare. Determination of Hg in liver, kidney and muscle of animals was performed using an AMA 254 mercury analyser. Total Se concentrations were determined using the spectrofluorometric method.In omnivores demonstrated higher Se concentrations in all analysed organs compared to the herbivores. The highest concentration of Hg was found in the kidneys of the tested animals, and the lowest in the muscles. High and moderate correlation between Se and Hg was observed in the liver of omnivorous, while in herbivores this correlation was weak. In all analysed samples, the Se:Hg molar ratios were above 1 (min: liver 5.9, max: kidney 110). Generally, the highest Se:Hg ratio values were found in kidney and the lowest in liver of tested animals. No significant correlation was found between GPx, GST and SOD activity and Se or Hg concentration in analysed organs. But it was observed that Se:Hg molar was negatively correlated with CAT activity in the most samples.The obtained results may suggest that omnivorous animals demonstrate greater Hg sequestration in the liver than herbivores, which has been proposed as one of the mechanisms of Se antagonistic action towards Hg. The ratio between Se and Hg, rather than the concentration of these elements in organs, affected the antioxidant status in the animal organism, specifically the CAT activity.

Key Factors in Early Diagnosis of Myopia Progression within Ocular Biometric Parameters by Scheimpflug Technology

The aim of this study was to evaluate the relationship between myopia and ocular biometric variables using the Pentacam AXL® single rotation Scheimpflug camera. This prospective, cross-sectional, single-center study was performed in fifty Caucasian patients aged between 18 and 30 years (24.84 ± 3.04 years). The measured variables included maximum and minimum keratometry (K1 and K2, respectively), anterior chamber depth (ACD), corneal horizontal diameter or white to white (WTW), central corneal thickness (CCT), corneal asphericity (Q), and axial length (AXL). The tomographic and biometric measurements were considered optimal when the quality factor was greater than 95% according to the manufacturer's software instructions. The AXL presented a significant correlation with the spherical equivalent without cycloplegia (SE without CP), age at onset of myopia (r = -0.365, p = 0.012), mean keratometry (Km) (r = -0.339, p = 0.016), ACD (r = 0.304, p = 0.032), and WTW (r = 0.406, p = 0.005). The eyes with AXL higher than 25 mm had earlier onset; higher SE without CP, AXL, and Q; and a flatter Km. AXL is the biometric variable with the greatest influence on the final refractive state in the adult myopic eye. Ophthalmologists and optometric management must consider these biometric differences in order to identify the most appropriate correction techniques in each case. The use of the Pentacam AXL in ocular biometric measurement is effective, reproducible, and non-invasive.

Chalcolithic copper production and use in the western end of the Iberian Peninsula: The testimony of Castro de Chibanes (Portugal)

Recent archaeological excavations identified a prehistoric occupation at Castro de Chibanes (Setúbal Peninsula, Portugal) displaying ceramic crucibles and metal artefacts in stratigraphic levels assigned to 2500–1900 cal BC. Apart from basic tools such as flat axes and awls, the collection includes ceramic crucibles, with emphasis to an uncommon example with a pouring lip and four feet. The studied set was completed with metal prills and artefacts from neighbouring Chalcolithic settlements of Rotura and Pedrão. The studied collection was characterised by chemical and microstructural techniques (p-EDXRF, micro-PIXE, optical microscopy and SEM-EDS). Overall, the results point to a local production of copper with variable arsenic contents, agreeing with the composition of artefacts (Cu with 0.14 to 4.4 wt% As), whose post-casting manufacture included hammering and annealing (recrystallized grains and annealing twins), although with incipient conditions that prevented a full compositional homogenisation. These results were compared with the Chalcolithic metallurgy of southwestern Iberian Peninsula, allowing to integrate the Setúbal Peninsula region into a wider context of metal production and use during the 3rd millennium BC. Finally, a supposed Bell Beaker “tanged dagger” was found to be composed by a leaded bronze alloy with a worked microstructure exhibiting Cu-Fe sulphides with high Se contents. The contradiction between analytical features and ancient chronology led to a revision of the typology and chronology of this bronze, showing the importance of the integration of analytical and archaeological research.

Stabilization and functionalization of selenium nanoparticles mediated by green tea and Pu-Erh tea polysaccharides

To explore a novel strategy for the combination of selenium (Se) and tea polysaccharides, monodispersed spherical nanoparticles of red amorphous elemental Se (SeNPs) of 70 nm and 35 nm in diameter with high Se content of 84 % and 86 % and significant proliferative inhibition on human carcinoma cells but low toxicity to human normal cells were prepared from the reaction between ascorbic acid and selenite using green tea and Pu-Erh tea crude polysaccharides (GTCPs and PTCPs) as templets, respectively. In particular, PTCPs showed stronger stabilizing effects compared to GTCPs according to the smaller size, and higher electrostatic stability of those SeNPs modified by PTCPs, though GTCPs exhibited more advantages in enhancing the anti-proliferative activity of SeNPs. Furthermore, tea crude polysaccharides were found a better stabilizer and functional decorator of SeNPs compared to the purified polysaccharides. This study confirmed the excellent potential of tea polysaccharides in the stabilization and functionalization of SeNPs.

Characteristics of Soil Selenium Enrichment And Its Effects on the Aboveground Parts Of Abelmoschus Manihot (L.) Medic

Pot experiments were carried out to study characteristics of soil selenium (Se) enrichment and its influence on Chinese medicinal plant Abelmoschus manihot, and selenium contents in aboveground parts of A. manihot under conditions of natural Se-rich, low soils and exogenous Se addition were analyzed. Results indicated that contents of total Se and various Se fractions of natural Se-rich soil were significantly higher than that of Se-low soil (P &lt; 0.05), and Se content in aboveground parts of A. manihot grown in natural Serich soil was significantly higher than that in natural Se-low soil (P &lt; 0.05). The Se content in aboveground parts of A. manihot increased with the increase of soil total Se content, soil pH and contents of various Se fractions, showing significant tolerance to high Se. Moreover, it was initially found that A. manihot could effectively absorb soil Se even in relatively low Se soil conditions (soil Se content of 0.11~0.12 mg/kg) and thus reaching the standard of Se-rich crops. Bangladesh J. Bot. 51(4): 961-970, 2022 (December) Special

Se(IV)/Se(VI) adsorption mechanisms on natural and on Ca-modified zeolite for Mediterranean soils amended with the modified zeolite: prospects for agronomic applications

In the present study, the ability of a modified CaCl2 zeolite (Ca-Z) to both increase Se(IV) availability and restrict Se(VI) mobility in soils is examined. As it was resulted from batch experiments and verified by X-ray absorption fine structure (XAFS) and X-ray fluorescence (XRF) spectroscopies, higher amounts of both Se species adsorbed on Ca-Z compared to natural zeolite (Z-N) forming outer-sphere complexes while the oxidation state did not alter during agitation of samples. Thereafter, Ca-Z was incorporated in six Greek soils, divided into acid and alkaline, at a 20% (w/w) rate and a series of equilibrium batch experiments were performed with soils alone and soils-Ca-Z mixtures to investigate sorption and desorption processes and mechanisms. The acid soils, either treated with Ca-Z or not, adsorbed higher amounts of Se(IV) than alkaline ones, whereas soils alone did not adsorb Se(VI) but impressively high adsorption of Se(VI) occurred in the Ca-Z-treated soils. Desorption of Se(IV) was higher from the Ca-Z-treated soils and especially from the acid soils. Higher distribution coefficients of desorption than the distribution coefficients of sorption were observed, clearly pointing to a hysteresis mechanism. The experimental data fitted with Langmuir and Freundlich isotherms. In the presence of Ca-Z, the Langmuir qm values increased indicating higher Se(IV) retention while Langmuir bL values decreased suggesting lower bonding strength and higher Se(IV) mobility. Overall, treating the soils with Ca-Z increased Se(IV) adsorption and mobility whereas it provided sites for Se(VI) adsorption that did not exist in the studied soils.

Trace Element Composition of Molybdenite: Deposit Type Discrimination and Limitations

Molybdenite is a common sulfide hosting many trace elements. Trace elements in molybdenite from individual deposits have been widely used to constrain the source and conditions of ore-forming fluids. However, the relationship between the trace element composition of molybdenite and deposit types has not been well investigated from a large dataset. Here, simple statistics and partial least squares–discriminant analysis (PLS-DA) were used to determine whether different types of deposits can be distinguished by trace elements in molybdenite and what factors control the variations in trace element composition based on published laser ablation ICP–MS data. Molybdenite from porphyry deposits is separated from that from quartz veins, greisen Sn–W, granite vein Mo, and granodiorite Mo deposits. The former is characterized by relatively high Re, Cu, Ag, Se, Pb, Bi, and Te contents, whereas the latter has higher Ni, Co, Sn, Sb and W contents. Molybdenite from the quartz vein Au ± W deposits (Au-dominated), and porphyry Cu–Au–Mo (moderate Au) are separated from other deposits without gold due to positive correlations with Au, Sb, Te, Pb, and Bi for the former. Assemblages of Au–Sb–Te–Pb–Bi in molybdenite are thus useful to discriminate as to whether deposits contain gold and the degree of gold mineralization. Higher oxygen fugacity is responsible for the relative enrichment of W in molybdenite from greisen Sn–W deposits, whereas lower oxygen fugacity results in the relative enrichment of Re in molybdenite from porphyry Cu ± Mo ± Au and Mo ± Cu ± Au deposits. There are some limitations to using molybdenite as an indicator mineral because of the complex occurrences of elements in molybdenite, large compositional variations within a specific deposit type, and an imbalanced dataset. To develop molybdenite as an indicator mineral tool, further work should be carried out to overcome these limitations. This study provides an attempt to classify deposit types using molybdenite trace elements and has important implications for ore genesis research and mineral exploration.

Construction of unique conductive networks in carbon nanotubes/polymer composites via poly(ε-caprolactone) inducing partial aggregation of carbon nanotubes for microwave shielding enhancement

• Unique conductive networks of individual CNTs and CNT clusters are constructed. • Poly(ε-caprolactone) inducing partial aggregation of CNTs creates CNT clusters. • The unique conductive networks show high conductivity and microwave SE. • Balance amounts for CNTs and PCL exist for the unique conductive networks. • Polymer pairs are important to form the unique conductive networks. Herein, a unique conductive network, which includes individual carbon nanotubes (CNT) and some CNT clusters (CNT/CNT-cluster) formed via poly(ε-caprolactone) (PCL) inducing partial aggregation of CNTs, is constructed in CNTs filled CPCs. Three different kinds of polymers, which are isotactic polypropylene (PP), polystyrene (PS) and polylactic acid (PLA), are used to evaluate the effect of polymer matrix on the unique conductive network. A comparative study on the electrical conductivity and microwave shielding properties are also carried in these composites. The effect of CNTs and PCL loadings on the formation of CNT-clusters in the samples is also discussed in this study. Due to PCL inducing partial aggregation of CNTs and the good distribution of residue CNTs in PLA, the excellent CNT/CNT-cluster conductive network is formed in the CNT/PCL/PLA composites. Comparing with the traditional conductive network, the CNT/CNT-cluster conductive network exhibits high efficiency for improving electrical conductivity and microwave shielding property.

A phosphonium ionic liquid conjugated magnetic graphitic carbon nitride nanocomposite: an effective sample pretreatment tool for selenium separation and determination.

We established an innovative and easy-to-use methodology for selenium (Se) extraction and determination from real water samples utilizing a magnetic nanocomposite adsorbent (MNC-SPE) aided by an inductively coupled plasma mass spectrometry (ICP-MS) approach. The MNC-SPE adsorbent was fabricated by hybridizing Fe3O4 nanoparticles on the surface of carbon nitride nanosheets (GCN NSs) that were coated with 1-hexyl-3-methylimidazolium hexafluorophosphate ionic liquid (P-IL). A variety of techniques were used to thoroughly analyze the structural and chemical characteristics of MNC-SPE, and appear to have a great number of diverse active surface functional units (imidazole ring and -NH3+). In order to optimize the key factors affecting the Se extraction, parameters including the adsorbent dosage, contact time, eluent type, eluent volume, eluent time, and reusability of adsorbent were extensively studied. The proposed approach was validated under the optimal reaction conditions, and it showed good linearity between 0.15 and 100 pg μL-1 with a significant R2 value (R2 = 0.9994) toward Se metal. Besides, the Se limit of detection (LOD) and limit of quantification (LOQ) are 0.063 pg μL-1 and 0.147 pg μL-1, respectively. Further, by utilizing tap and river water samples, the applicability of the validated method was tested; the approach showed high Se recovery values in the range of 87.6-115.5% for the spiked real-world samples and the interday and intraday precision (RSD%) values of the approach were 4.8% (n = 6). The MNC-SPE can be regenerated and reused for four consecutive extraction-desorption cycles by employing 0.5 M NaOH eluent.

Trace Elements in Blood of Sea Ducks from Dutch Harbor and Izembek Lagoon, Alaska

Abstract In 2001, we collected whole blood from sea ducks—Steller's eider Polysticta stelleri, harlequin duck Histrionicus histrionicus, black scoter Melanitta nigra, and long-tailed duck Clangula hyemalis—wintering at Dutch Harbor, Alaska, and from Steller's eiders molting at Izembek Lagoon on the Alaska Peninsula. Analysis of blood samples was done for 19 trace elements, of which 17 were detected in one or more samples. In Steller's eiders, mean concentrations of six trace elements (As, B, Fe, Hg, Se, and Mo) were greater at Dutch Harbor and mean concentrations of four trace elements (Cr, Cu, Mg, and Zn) were greater at Izembek Lagoon. Among sea ducks at Dutch Harbor, mean concentrations of five trace elements (Cu, Hg, Se, Zn, and V) differed by species: Steller's eiders had greater concentrations of Cu, Zn, and V in their blood; black scoters had the highest concentration of Se; and harlequin ducks had the highest Hg level, with a mean concentration slightly above a threshold effect level. One Steller's eider and one harlequin duck from Dutch Harbor had blood Pb levels above background concentrations. We have no observations to indicate that concentrations of these trace elements were associated with adverse effects.

Genetically predicted selenium concentrations and thyroid function: A two-sample Mendelian randomization study.

The impact of selenium (Se) on human thyroid function remains unclear, with inconsistent results from recent epidemiological studies. Moreover, the observed associations are prone to bias due to potential confounding and reverse causation. Mendelian randomization (MR) analysis facilitates the large minimization of biases produced by environmental and lifestyle influences, providing unconfounded estimates of causal effects using instrumental variables. We aim to examine the association between Se concentrations and human thyroid function using a two-sample MR analysis. Genetic instruments for Se concentrations, including toenail and blood (TAB) and blood Se concentrations, were identified from a genome-wide association study (GWAS) of blood Se (n = 5477) and toenail Se levels (n = 4162). GWAS summary statistics on thyroid phenotypes were downloaded from the ThyroidOmics consortium, including thyroid-stimulating hormone (TSH) (n = 54,288), free thyroxin (FT4) (n = 49,269), hypo (n = 53,423), and hyperthyroidism (n = 51,823). The MR study was conducted using the inverse-variance weighted (IVW) method, supplemented with the weighted median and the mode-based method. Genetically determined TAB Se was negatively associated with FT4 (β = -.067; 95% confidence interval [CI] = -0.106, -0.028; p = 0.001) using the IVW analyses, as well in the additional analyses using the weighted median and weighted-mode methods. No evidence in heterogeneity, pleiotropyor outlier single-nucleotide polymorphisms was detected (all p > 0.05). Suggestive casual association between increased genetically determined TAB Se concentrations and decreased hypothyroidism risk was found by the IVW method (odds ratio [OR] = 0.847; 95% CI = 0.728, 0.985; p = 0.031). The causal effect of TAB Se on FT4 was observed in women (β = -.076; 95% CI = -0.129, -0.024; p = 0.004). However, the influence of genetically determined higher Se concentrations on TSH levels and hyperthyroidism revealed insignificance in the primary and sensitivity analyses. The present MR study indicated that high Se concentration enable the decreasing of FT4 levels, and the effects of Se concentrations on FT4 remain sex-specific.