Secondary organic aerosol (SOA) affects the earth's radiation balance and global climate. High-elevation areas are sensitive to global climate change. However, at present, SOA origins and seasonal ...variations are understudied in remote high-elevation areas. In this study, particulate samples were collected from July 2012 to July 2013 at the remote Nam Co (NC) site, Central Tibetan Plateau and analyzed for SOA tracers from biogenic (isoprene, monoterpenes and beta -caryophyllene) and anthropogenic (aromatics) precursors. Among these compounds, isoprene SOA (SOAI) tracers represented the majority (26.6 plus or minus 44.2 ng m-3), followed by monoterpene SOA (SOAM) tracers (0.97 plus or minus 0.57 ng m-3), aromatic SOA (SOAA) tracer (2,3-dihydroxy-4-oxopentanoic acid, DHOPA, 0.25 plus or minus 0.18 ng m-3) and beta -caryophyllene SOA tracer ( beta -caryophyllenic acid, 0.09 plus or minus 0.10 ng m-3). SOAI tracers exhibited high concentrations in the summer and low levels in the winter. The similar temperature dependence of SOAI tracers and isoprene emission suggested that the seasonal variation of SOAI tracers at the NC site was mainly influenced by the isoprene emission. The ratio of high-NOx to low-NOx products of SOAI (2-methylglyceric acid to 2-methyltetrols) was highest in the winter and lowest in the summer, due to the influence of temperature and relative humidity. The seasonal variation of SOAM tracers was impacted by monoterpenes emission and gas-particle partitioning. During the summer to the fall, temperature effect on partitioning was the dominant process influencing SOAM tracers' variation; while the temperature effect on emission was the dominant process influencing SOAM tracers' variation during the winter to the spring. SOAM tracer levels did not elevate with increased temperature in the summer, probably resulting from the counteraction of temperature effects on emission and partitioning. The concentrations of DHOPA were 1-2 orders of magnitude lower than those reported in the urban regions of the world. Due to the transport of air pollutants from the adjacent Bangladesh and northeastern India, DHOPA presented relatively higher levels in the summer. In the winter when air masses mainly came from northwestern India, mass fractions of DHOPA in total tracers increased, although its concentrations declined. The SOA-tracer method was applied to estimate secondary organic carbon (SOC) from these four precursors. The annual average of SOC was 0.22 plus or minus 0.29 mu gC m-3, with the biogenic SOC (sum of isoprene, monoterpenes and beta -caryophyllene) accounting for 75 %. In the summer, isoprene was the major precursor with its SOC contributions of 81 %. In the winter when the emission of biogenic precursors largely dropped, the contributions of aromatic SOC increased. Our study implies that anthropogenic pollutants emitted in the Indian subcontinent could be transported to the TP and have an impact on SOC over the remote NC.
Intestinal IgA, which is regulated by gut microbiota, has a crucial role in maintenance of intestinal homeostasis and in protecting the intestines from inflammation. However, the means by which ...microbiota promotes intestinal IgA responses remain unclear. Emerging evidence suggests that the host can sense gut bacterial metabolites in addition to pathogen-associated molecular patterns and that recognition of these small molecules influences host immune response in the intestines and beyond. We reported here that microbiota metabolite short-chain fatty acid acetate promoted intestinal IgA responses, which was mediated by "metabolite-sensing" GPR43. GPR43
mice demonstrated lower levels of intestinal IgA and IgA
gut bacteria compared with those in wild type (WT) mice. Feeding WT but not GPR43
mice acetate but not butyrate promoted intestinal IgA response independent of T cells. Acetate promoted B-cell IgA class switching and IgA production in vitro in the presence of WT but not GPR43
dendritic cells (DCs). Mechanistically, acetate-induced DC expression of Aldh1a2, which converts Vitamin A into its metabolite retinoic acid (RA). Moreover, blockade of RA signaling inhibited the acetate induction of B-cell IgA production. Our studies thus identified a new pathway by which microbiota promotes intestinal IgA response through its metabolites.
It is still common for terminally ill patients to suffer from pain, and the development of palliative care faces many obstacles. The value of death to human society is ignored, and the intrinsic ...relationship between the meaning of life and the value of death has not been fully explored. This article discusses the current status of palliative care in China, how clinicians reflect and respond, the change of the whole society's concept of palliative care, and suggestions for action, and tries to provide a medical humanistic perspective for walking out of the dilemma of palliative care.
The intestinal lumen harbors nearly 100 trillion commensal bacteria that exert crucial function for health. An elaborate balance between immune responses and tolerance to intestinal microbiota is ...required to maintain intestinal homeostasis. This process depends on diverse regulatory mechanisms, including both innate and adaptive immunity. Dysregulation of the homeostasis between intestinal immune systems and microbiota has been shown to be associated with the development of inflammatory bowel diseases (IBD) in genetically susceptible populations. In this review, we discuss the recent progress reported in studies of distinct types of regulatory immune cells in the gut, including intestinal intraepithelial lymphocytes, Foxp3(+) regulatory T cells, regulatory B cells, alternatively activated macrophages, dendritic cells, and innate lymphoid cells, and how dysfunction of this immune regulatory system contributes to intestinal diseases such as IBD. Moreover, we discuss the manipulation of these regulatory immune cells as a potential therapeutic method for management of intestinal inflammatory disorders.
Austenite stability is essentially important in improving the cryogenic toughness of cryogenic Ni steels and guiding the development of Ni-saving cryogenic steels. The austenite stability in the ...cryogenic Ni steels is influenced by many microstructure features, making it a complicated issue which is lack of a systematic discussion. In this article, the microstructural effects on the thermal and mechanical stability of austenite in the cryogenic Ni steels are reviewed and discussed. The thermal stability of austenite (TSA) will be enhanced by the enrichment of austenite-stabilizing elements in the austenite which decreases the martensite-start (
M
s
) temperature. The grain refinement enhances the TSA by synergistically increasing the nonchemical driving force for the martensite transformation and the concentrations of austenite-stabilizing elements in the austenite. The excessive increase in the volume fraction of austenite weakens the TSA by decreasing the concentrations of austenite-stabilizing elements in the austenite. The film austenite is usually thermally more stable than the block austenite owing to its higher concentrations of austenite-stabilizing elements. The mechanical stability of austenite (MSA) is also influenced by the concentrations of austenite-stabilizing elements which affect the
M
s
temperature. The reports on the effect of grain size of austenite on the MSA are inconsistent. Both negligible and important effects of the grain size of austenite on the MSA are analyzed. The grain orientation of austenite affects the MSA via changing the Schmid factor and the additional driving force for the martensite transformation. The orientation which yields a larger value of Schmid factor would exhibit a lower MSA. The MSA is affected by the matrix or the neighboring phase due to the stress and strain partitioning among austenite and other constituent phases. The dislocation multiplication could weaken the MSA by assisting the nucleation and growth of martensite embryo and enhance the MSA by hindering the motion of embryo/austenite interfaces when dislocation density is sufficiently large. Austenite with a combination of a high TSA and a moderate or high MSA is considered to be effective strategies to enhance cryogenic toughness of the cryogenic Ni steels.
Bacillus coagulans is a probiotic bacterium that produces spores. Due to its excellent stability, it has been widely used in medicine, food and chemical industry. Recent studies have shown that B. ...coagulans has therapeutic effects on intestinal diseases, such as acute diarrhoea, irritable bowel syndrome, antibiotic-related diarrhoea, constipation and colitis via modulation of the microbiota composition, host immunity and metabolism. Additionally, toxicological experiments and a large number of clinical observations have showed that B. coagulans is safe and has no effect of mutagenicity, teratogenicity or genotoxicity. This review summarises the latest advances associated with B. coagulans, from its biological features, probable action mechanisms, toxicity, and medical applications.
Biodegradable metals have attracted considerable attentions in recent years. Besides the early launched biodegradable Mg and Fe metals, Zn, an essential element with osteogenic potential of human ...body, is regarded and studied as a new kind of potential biodegradable metal quite recently. Unfortunately, pure Zn is soft, brittle and has low mechanical strength in the practice, which needs further improvement in order to meet the clinical requirements. On the other hand, the widely used industrial Zn-based alloys usually contain biotoxic elements (for instance, ZA series contain toxic Al elements up to 40 wt.%), which subsequently bring up biosafety concerns. In the present work, novel Zn-1X binary alloys, with the addition of nutrition elements Mg, Ca and Sr were designed (cast, rolled and extruded Zn-1Mg, Zn-1Ca and Zn-1Sr). Their microstructure and mechanical property, degradation and in vitro and in vivo biocompatibility were studied systematically. The results demonstrated that the Zn-1X (Mg, Ca and Sr) alloys have profoundly modified the mechanical properties and biocompatibility of pure Zn. Zn-1X (Mg, Ca and Sr) alloys showed great potential for use in a new generation of biodegradable implants, opening up a new avenue in the area of biodegradable metals.
Telomerase, the enzyme that synthesizes telomeric DNA, is not expressed in most human somatic cells but is activated with in vitro immortalization and during tumorigenesis, and repressed by cell ...differentiation. Of the two components of the core enzyme, the catalytic protein hTERT is limiting for activity. To investigate mechanisms of hTERT gene regulation, we have cloned genomic sequences encompassing the complete hTERT transcription unit. The hTERT gene consists of 16 exons and 15 introns spanning ∼35 kb. Transient transfections of immortal human cells with potential regulatory 5′ sequences linked to a reporter, combined with deletion analysis of these sequences, indicated that elements responsible for promoter activity are contained within a region extending from 330 bp upstream of the ATG to the second exon of the gene. Assays in different cell types have shown that the hTERT promoter is inactive in normal and in transformed pre-immortal cells, but, like telomerase, it is activated with cell immortalization. Sequence analysis revealed that the hTERT promoter is GC-rich, lacks TATA and CAAT boxes but contains binding sites for several transcription factors that may be involved in its regulation. The abundance of these sites suggests the possibility that hTERT expression may be subject to multiple levels of control and be regulated by different factors in different cellular contexts.
Composite micro plates with periodic microstructure at very small length scale have been a focus of intensive research. When length scale of the microstructure descends below millimetre level, size ...effects may emerge. To account for microstructure effect on the elastic wave band gap of microscopic composite plates, we propose a numerical framework based on the modified couple stress theory of elasto-dynamics associated with a non-classical 3-node triangular (T3) Mindlin plate finite element. Since couple stress elasto-dynamics incorporates dependence on the material scale length, the proposed approach is sensitive to size effects with microscopic problems while remaining compatible with macroscopic problems. In terms of the finite element implementation, we implemented a T3 plate finite element with 9 nodal degrees of freedom under the Mindlin kinematics assumptions. The approach presents enhanced flexibility to discretize complex microstructures owing to the triangular element topology, and offers sensitivity to account for size effects of microscopic problems. Therefore, it represents a good option for the design of band gap periodic composite micro plates. Validation of the framework is performed through comparison with both analytical and numerical models.
•First numerical work on bandgap analysis using couple-stress Mindlin plate element.•First bandgap analysis using triangular plate element and high-order continuum.•Extended Bazelay element to Mindlin assumptions within high-order continuum theory.
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