We present a combined mineralogical, chemical, and Sr-Nd isotopic study of hydrothermal alteration effects in near-surface Pleistocene rhyolite sampled at two distinct localities from the Los Azufres ...geothermal field (LAGF), Mexico. The alteration mineralogy of the near-surface rocks is dominated by silica polymorph minerals (cristobalite, tridymite, opal, and quartz), and kaolinite, showing an intense silicification in most altered samples. In some samples, alteration minerals berlinite, alunite, opal, and wollastonite, are also present. Sulfur (80–28, 300 μg/g) and LOI (1.36–12.18%) contents were used to indicate the intensity of alteration for the LAGF rock samples. The changes were considered as significant when they exceeded the analytical errors. Two main types of chemical and isotopic effects were documented: (1) small loss of both SiO2 and alkalis represented by one pair of samples, which did not show significant changes in the most major elements, REEs, Nb and Ta negative anomalies, nor in the normalized multiple-element LILE/REE, LILE/HFSE, and REE/HFSE ratio parameters, but indicated significant increase in Al, Fe, Ba, Ga, and Pb; and (2) significant gain of SiO2 accompanied by loss of alkalis for the rest of the rock samples collected from a different site showed significant decrease of most major elements, all REE concentrations and normalized multiple-element ratio parameters as well as changes in numerous trace element concentrations. During this alteration, the size of the Nb and Ta negative anomalies became smaller as a result of the alteration of the second type. Both types of alteration showed significant changes in 87Sr/86Sr, but generally not in 143Nd/144Nd, probably related to the involvement of highly heterogeneous crust in terms of 87Sr/86Sr.
•The first extensive hydrothermal alteration study of near-surface rhyolite•Significant hydrothermal alteration changes of major and trace elements•Changes in multiple element LILE/REE, LILE/HFSE, and REE/HFSE ratio parameters•Opposite changes in 87Sr/86Sr
Breast milk is the recommended source of nutrients for infant growth, but its adequacy to meet infants' mineral and trace element needs is unknown.
We used breast-milk mineral and trace element ...concentrations of Guatemalan mothers at 3 lactation stages to estimate total daily intakes and to determine whether intakes were associated with early infant growth.
In this cross-sectional study, breast-milk samples were collected from Mam-Mayan mothers during transitional (5-17 d, n = 56), early (18-46 d, n = 75), and established (4-6 mo, n = 103) lactation; z scores for weight (WAZ), length (LAZ), and head circumference (HCAZ) were measured. Concentrations of 11 minerals (calcium, potassium, magnesium, sodium, copper, iron, manganese, rubidium, selenium, strontium, and zinc) were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS). WHO equations were used to calculate the estimated energy requirement, which was divided by the energy density of breast milk to estimate daily milk volume, and this number was multiplied by breast-milk mineral concentrations to estimate intakes. Principal component analyses identified clusters of minerals; principal components (PCs) were used in regression analyses for anthropometric outcomes.
Estimated breast-milk intakes during established lactation were insufficient to compensate for the lower milk sodium, copper, manganese, and zinc concentrations in male infants and the lower sodium, iron and manganese concentrations in female infants. Estimated intakes of calcium, magnesium, potassium, sodium, and selenium were below the Institute of Medicine Adequate Intake for both sexes at all 3 stages of lactation. In early lactation, multiple linear regressions showed that PC1 (calcium, magnesium, potassium, rubidium, and strontium intakes) was positively associated with WAZ, LAZ, and HCAZ. In established lactation, the same PC with sodium added was positively associated with all 3 anthropometric outcomes; a second PC (PC2: zinc, copper, and selenium intakes) was associated with WAZ and LAZ but not HCAZ.
Breast milk may be inadequate in selected minerals and trace elements where higher estimated intakes were associated with greater infant growth.
The essential metals for humans: a brief overview Zoroddu, Maria Antonietta; Aaseth, Jan; Crisponi, Guido ...
Journal of inorganic biochemistry,
June 2019, 2019-06-00, 20190601, Letnik:
195
Journal Article
Recenzirano
The human body needs about 20 essential elements in order to function properly and among them, for certain, 10 are metal elements, though for every metal we do need, there is another one in our body ...we could do without it. Until about 1950 poor attention was given to the so-called “inorganic elements” and while researches on “organic elements” (C, N, O and H) and organic compounds were given high priority, studies on essential inorganic elements were left aside.
Base on current knowledge it is ascertained today that metals such as Na, K, Mg, Ca, Fe, Mn, Co, Cu, Zn and Mo are essential elements for life and our body must have appropriate amounts of them.
Here a brief overview to highlight their importance and current knowledge about their essentiality.
The human body needs about 20 essential elements in order to function properly and among them, for certain, 10 are metal elements, such as Na, K, Mg, Ca, Fe, Mn, Co, Cu, Zn, Mo.
Here a brief overview to highlight their importance and current knowledge about their essentiality. Display omitted
•Essential elements for life•Essential metal ions for human body•Bulk and trace essential metal ions•Metals for life and hard and soft chemical character
Selenium, an essential trace element, has been investigated as a potential cancer prevention agent. However, several studies have indicated that selenium supplementation may be associated with an ...increased risk of type 2 diabetes (T2D), although an equivocal relation of this nature requires confirmation.
We examined the association between baseline plasma concentrations of selenium and the prevalence of T2D, as well as whether participant characteristics or intake of other antioxidant nutrients modified this relation.
We conducted cross-sectional analyses of 1727 participants from the Selenium Trial, a randomized clinical trial of selenium supplementation for colorectal adenoma chemoprevention that had data for baseline selenium plasma concentrations, T2D status, and dietary intake. Logistic regression modeling was used to evaluate the associations between plasma selenium concentrations and prevalent T2D, adjusting for confounding factors. Heterogeneity of effect by participant characteristics was evaluated utilizing likelihood-ratio tests.
Mean ± SD plasma selenium concentrations for those with T2D compared with those without T2D were 143.6 ± 28.9 and 138.7 ± 27.2 ng/mL, respectively. After adjustment for confounding, higher plasma selenium concentrations were associated with a higher prevalence of T2D, with ORs (95% CIs) of 1.25 (0.80, 1.95) and 1.77 (1.16, 2.71) for the second and third tertiles of plasma selenium, respectively, compared with the lowest tertile (P-trend = 0.007). No significant effect modification was observed for age, sex, body mass index, smoking, or ethnicity. Increased odds of T2D were seen among those who were in the highest tertile of plasma selenium and the highest category of intake of β-cryptoxanthin (P-trend = 0.03) and lycopene (P-trend = 0.008); however, interaction terms were not significant.
These findings show that higher plasma concentrations of selenium were significantly associated with prevalent T2D among participants in a selenium supplementation trial. Future work is needed to elucidate whether there are individual characteristics, such as blood concentrations of other antioxidants, which may influence this relation.
A persistent problem in the study of garnet geochemistry is that the consideration of major elements alone excludes a wealth of information preserved by trace elements, particularly the rare-earth ...elements (REEs). This is despite the fact that trace elements are generally less vulnerable to diffusive resetting, and are sensitive to a broader spectrum of geochemical interactions involving the entire mineral assemblage, including the growth and/or dissolution of accessory minerals. We outline a technique for the routine acquisition of high-resolution 2D trace element maps by LA-ICP-MS, and introduce an extension of the software package
XMapTools
for rapid processing of LA-ICP-MS data to visualise and interpret compositional zoning patterns. These methods form the basis for investigating the mechanisms controlling geochemical mobility in garnet, which are argued to be largely dependent on the interplay between element fractionation, mineral reactions and partitioning, and the length scales of intergranular transport. Samples from the Peaked Hill shear zone, Reynolds Range, central Australia, exhibit contrasting trace element distributions that can be linked to a detailed sequence of growth and dissolution events. Trace element mapping is thus employed to place garnet evolution in a specific paragenetic context and derive absolute age information by integration with existing U–Pb monazite and Sm–Nd garnet geochronology. Ultimately, the remarkable preservation of original growth zoning and its subtle modification by subsequent re-equilibration is used to ‘see through’ multiple superimposed events, thereby revealing a previously obscure petrological and temporal record of metamorphism, metasomatism, and deformation.
Frustrated Lewis pairs (FLPs) have been the subject of considerable study since the field's inception. While much of the research into FLPs has centered around small molecule activation for diverse ...stoichiometric and catalytic transformations, intramolecular FLPs also show promise as chelating ligands. The cooperative action of Lewis basic and acidic moieties enables intramolecular FLPs to stabilize low oxidation state centers and (consequently) reactive molecular fragments through a donor‐acceptor approach, making them an attractive ligand class in main group element chemistry. This review outlines the state of FLP chelation to date throughout the p‐block, encompassing primarily groups 13–16.
Frustrated Lewis pairs (FLPs) have been at the forefront of main group element‐mediated small molecule activation for over 15 years. The utility of intramolecular FLPs as chelating ligands for the stabilization of low oxidation state p‐block elements has been comparatively less explored. This review highlights recent progress in this emerging field and highlights spaces for further development.
•A system is proposed to obtain heterogeneous rocks with irregular inclusions.•Realistic inclusion geometry is obtained and controlled by combining the circular parameterization and Fourier ...transformation.•An unique overlapping detection algorithm based on level-set function is developed to allocate inclusions.•Hydraulic fracturing are captured by integrating cohesive pore pressure elements into traditional finite element model.•A systematic hybrid finite-discrete approach for investigating hydraulic fracturing of heterogeneous rocks is proposed and validated.
A systematic hybrid approach for modelling the hydraulic fracturing process of heterogeneous rocks with irregular inclusions is developed. This approach is based on a series of computational algorithms, including Fourier series transformation, level-set-based overlapping detection, and the finite-discrete element method. Three major steps are included: (1) circular parameterization and Fourier transformation are employed to reproduce realistic inclusion contours with arbitrary irregular shapes; (2) a novel overlapping detection method based on a level-set function is employed to allocate irregular inclusions effectively and efficiently; and (3) the finite-discrete element model is established by integrating cohesive elements with pore pressure nodes into the solid mesh to simulate the progressive hydraulic fracture and interface crack of heterogeneous rocks. To validate the proposed hybrid approach, modelling results by the established model are compared with numerical simulations in the literature. In addition, the influences of injection speed and interface strength on the mechanical and fracturing responses of heterogeneous rocks are discussed. The results demonstrate that the proposed hybrid approach is capable of simulating the hydraulic fracturing process of heterogeneous rocks.
This study investigates the partitioning of rare earth elements (REE) from La to Gd between molten metal and silicate to evaluate potential fractionation occurring during core-mantle differentiation. ...We report molten metal-silicate liquid partition coefficients from 24 multi-anvil experiments, extending the range of pressure, previously ranging from 1 to 8 GPa, up to 14 GPa. Experiments were performed at temperatures of between 2300 and 2560 K, and for oxygen fugacities ranging from the IW (Iron-Wüstite buffer) to IW–4. Metal-silicate partition coefficients for the studied REE vary with the oxygen fugacity and S concentration in the metallic phase of the system. These elements were all lithophile during the Earth's accretion. By compiling all existing data on molten metal-silicate liquid partitioning, REE partitioning between the mantle and core during the Earth's accretion can be determined for a wide range of P, T and fo2 conditions representing the early evolution of planetary bodies from planetesimals to planets. REE concentrations of the bulk silicate Earth (BSE) are calculated from accretion scenarios using varying proportions and compositions of chondritic building blocks. The models selected are those that reproduce the Earth's nucleosynthetic isotope signature and the Ni/Co, Th/U and Nb/Ta ratios of the BSE. The BSE refractory element enrichment factor determined from REE data is equal to 2.88 (relative to CI chondrites). This calculation takes into account the depletion in volatile elements in the Earth compared to chondrites. This new estimate is in good agreement with previous determinations based on analysis of the upper mantle rocks, which supports the idea of a chemically homogeneous mantle. We also confirm that the formation of the core, with or without segregation of a sulfide phase, does not fractionate Sm/Nd and cannot be responsible for the 142Nd excess measured in modern terrestrial samples relative to chondrites.
•DREE vary with the fo2 and S concentration in metal.•REE remain lithophile and unfractionated throughout Earth's accretion.•Core formation is not responsible for the Earth's 142Nd excess compared to chondrites.•BSE RLE enrichment factor determined from REE partitioning data is equal to 2.88.•This enrichment factor supports the idea of a chemically homogeneous mantle.
It has been widely accepted that 5-methylcytosine is the only form of DNA methylation in mammalian genomes. Here we identify N(6)-methyladenine as another form of DNA modification in mouse embryonic ...stem cells. Alkbh1 encodes a demethylase for N(6)-methyladenine. An increase of N(6)-methyladenine levels in Alkbh1-deficient cells leads to transcriptional silencing. N(6)-methyladenine deposition is inversely correlated with the evolutionary age of LINE-1 transposons; its deposition is strongly enriched at young (<1.5 million years old) but not old (>6 million years old) L1 elements. The deposition of N(6)-methyladenine correlates with epigenetic silencing of such LINE-1 transposons, together with their neighbouring enhancers and genes, thereby resisting the gene activation signals during embryonic stem cell differentiation. As young full-length LINE-1 transposons are strongly enriched on the X chromosome, genes located on the X chromosome are also silenced. Thus, N(6)-methyladenine developed a new role in epigenetic silencing in mammalian evolution distinct from its role in gene activation in other organisms. Our results demonstrate that N(6)-methyladenine constitutes a crucial component of the epigenetic regulation repertoire in mammalian genomes.
Transposable elements give rise to interspersed repeats, sequences that comprise most of our genomes. These mobile DNAs have been historically underappreciated - both because they have been presumed ...to be unimportant, and because their high copy number and variability pose unique technical challenges. Neither impediment now seems steadfast. Interest in the human mobilome has never been greater, and methods enabling its study are maturing at a fast pace. This Review describes the activity of transposable elements in human cancers, particularly long interspersed element-1 (LINE-1). LINE-1 sequences are self-propagating, protein-coding retrotransposons, and their activity results in somatically acquired insertions in cancer genomes. Altered expression of transposable elements and animation of genomic LINE-1 sequences appear to be hallmarks of cancer, and can be responsible for driving mutations in tumorigenesis.
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