Properties and Atmospheric Implication of Methylamine–Sulfuric Acid–Water Clusters

The presence of amines can increase aerosol formation rates. Most studies have been devoted to dimethylamine as the representative of amine; however, there have been a few works devoted to methylamine. In this study, theoretical calculations are performed on CH₃NH₂(H₂SO₄)_<i>m</i>(H₂O)_<i>n</i> (<i>m</i> = 0–3, <i>n</i> = 0–3) clusters. In addition to the structures and energetics, we focused on determining the following characteristics: (1) the growth mechanism, (2) the hydrate distributions and the influences of humidity and temperature, (3) Rayleigh scattering properties. We explored the cluster growth mechanism from a thermodynamics aspect by calculating the Gibbs free energy of adding a water or sulfuric acid molecule step by step at three atmospherically relevant temperatures. The relative ease of the reaction at each step is discussed. From the analysis of hydrate distributions, we find that CH₃NH₂(H₂SO₄)­(H₂O)₂, CH₃NH₂(H₂SO₄)₂, and CH₃NH₂(H₂SO₄)₃ are most likely to exist in the atmosphere. The general trend of hydration in all cases is more extensive with the growing relative humidity (RH), whereas the distributions do not significantly change with the temperature. Analysis of the Rayleigh scattering properties showed that both H₂SO₄ and H₂O molecules could increase the Rayleigh scattering intensities and isotropic mean polarizabilities, with greater influence by the sulfuric acid molecules. This work sheds light on the mechanism for further research on new particle formation (NPF) containing methylamine in the atmosphere

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Background<p>The toll-like receptor 2 (TLR2)-mediated immune response is critical for host defense against Mycobacterium tuberculosis. There is evidence that TLR10, a TLR2 signaling modulator, may be involved in progression of tuberculosis (TB).</p>Methods<p>Using a self-validating case–control design, we tested for an association between seven TLR10 polymorphisms and susceptibility to TB in three independent series with two distinct populations. Single-nucleotide polymorphism (SNP) genotypes were determined by the SNPscan^TM method. Three genetic models (additive, dominant, and recessive) as well as multiple-SNP score analyses were used to evaluate the risk of TB associated with the TLR10 SNPs.</p>Results<p>By comparing TB patients with healthy controls, we observed two SNPs (rs11466617 and rs4129009) that were associated with decreased risk of TB in the Tibetan population, but did not in the Chinese Han population. Further analysis demonstrated that the rs11466617 Chengdu cohort genotype served as a protective factor against the progression of latent TB infection (LTBI) to active TB under the recessive model. None of the SNPs were significantly different in comparisons of TB-uninfected people with LTBI individuals. Additionally, when the underlying four TB-associated loci were considered together in a multiple-SNP score analysis, we observed an allele dose-dependent decrease in TB risk in Tibetans.</p>Conclusion<p>Variants of TLR10 may show an ethnic specificity on susceptibility to TB in Tibetan individuals. rs11466617 affected the susceptibility to progress from LTBI to active TB disease, but was not associated with the establishment of LTBI after M. tuberculosis exposure. More studies are needed to verify this genetic epidemiological result and unravel the role of TLR10 SNPs in the pathogenesis of TB.</p

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Background<p>The toll-like receptor 2 (TLR2)-mediated immune response is critical for host defense against Mycobacterium tuberculosis. There is evidence that TLR10, a TLR2 signaling modulator, may be involved in progression of tuberculosis (TB).</p>Methods<p>Using a self-validating case–control design, we tested for an association between seven TLR10 polymorphisms and susceptibility to TB in three independent series with two distinct populations. Single-nucleotide polymorphism (SNP) genotypes were determined by the SNPscan^TM method. Three genetic models (additive, dominant, and recessive) as well as multiple-SNP score analyses were used to evaluate the risk of TB associated with the TLR10 SNPs.</p>Results<p>By comparing TB patients with healthy controls, we observed two SNPs (rs11466617 and rs4129009) that were associated with decreased risk of TB in the Tibetan population, but did not in the Chinese Han population. Further analysis demonstrated that the rs11466617 Chengdu cohort genotype served as a protective factor against the progression of latent TB infection (LTBI) to active TB under the recessive model. None of the SNPs were significantly different in comparisons of TB-uninfected people with LTBI individuals. Additionally, when the underlying four TB-associated loci were considered together in a multiple-SNP score analysis, we observed an allele dose-dependent decrease in TB risk in Tibetans.</p>Conclusion<p>Variants of TLR10 may show an ethnic specificity on susceptibility to TB in Tibetan individuals. rs11466617 affected the susceptibility to progress from LTBI to active TB disease, but was not associated with the establishment of LTBI after M. tuberculosis exposure. More studies are needed to verify this genetic epidemiological result and unravel the role of TLR10 SNPs in the pathogenesis of TB.</p

Accurate Determination of Silver Isotopic Composition in Silicate Rocks with Low Silver Abundance

Owing to the extremely low abundance of silver in the Earth’s crust and mantle, it remains a major challenge to eliminate matrix impurities to obtain accurate silver isotopic compositions in silicate rocks. To determine precise and accurate silver isotopic data in silicates, we have modified the traditional pretreatment procedures, assessed isobaric interference and matrix effects, and analyzed silver isotopic compositions in silicates. By modification of the silicate digestion and ion-exchange procedures, efficient elution of silver was achieved. The doping experimental results indicated that the matrix effect induced by Ti and Cr could be satisfactorily corrected using the internal standard Pd isotope pair of 108Pd–106Pd. The modified chemical chromatographic method effectively separates Ni from Ag in silicate samples, thereby minimizing the significant isobaric interference from Ni cations. As a result, the shifts in the δ109Ag value caused by cations can be corrected to less than 0.02‰. There are considerable shifts down to −0.82‰ in δ109Ag from the accepted δ109Ag value when soluble metasilicate is present in the solution, which might explain the discrepancies in measured δ109Ag values for silicate materials. To accurately analyze silver isotopic compositions, especially of silicates with extremely low silver abundance, a silver standard doping method with an optimum doping proportion (sample-to-standard material ratio of 2:8) has been shown to produce an acceptable measurement uncertainty from 0.04 to 0.06‰ (2SD). The high-precision δ109Ag value determined in this study for ultramafic rocks from Balmuccia and the basalt reference material, BHVO-2, of −0.044 ± 0.062‰ is consistent with that of −0.16 ± 0.07‰ reported by previous studies. Our study paves the way for the more extensive use of silver isotopes in studies of terrestrial/extraterrestrial rocks, something that will be of help in constraining the sources of precious metals in polymetallic ore deposits as well as core formation and volatile-element depletion in the early solar system