1,280 research outputs found

    Large-Scale Structure Shocks at Low and High Redshifts

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    Cosmological simulations show that, at the present time, a substantial fraction of the gas in the intergalactic medium (IGM) has been shock-heated to T>10^5 K. Here we develop an analytic model to describe the fraction of shocked, moderately overdense gas in the IGM. The model is an extension of the Press & Schechter (1974) description for the mass function of halos: we assume that large-scale structure shocks occur at a fixed overdensity during nonlinear collapse. This in turn allows us to compute the fraction of gas at a given redshift that has been shock-heated to a specified temperature. We show that, if strong shocks occur at turnaround, our model provides a reasonable description of the temperature distribution seen in cosmological simulations at z~0, although it does overestimate the importance of weak shocks. We then apply our model to shocks at high redshifts. We show that, before reionization, the thermal energy of the IGM is dominated by large-scale structure shocks (rather than virialized objects). These shocks can have a variety of effects, including stripping ~10% of the gas from dark matter minihalos, accelerating cosmic rays, and creating a diffuse radiation background from inverse Compton and cooling radiation. This radiation background develops before the first stars form and could have measurable effects on molecular hydrogen formation and the spin temperature of the 21 cm transition of neutral hydrogen. Finally, we show that shock-heating will also be directly detectable by redshifted 21 cm measurements of the neutral IGM in the young universe.Comment: 12 pages, 8 figures, submitted to Ap

    Structure and tanning properties of dialdehyde carboxymethyl cellulose: Effect of degree of substitution

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    Content: Developing novel tanning agents from renewable biomass is regarded as an effective strategy for sustainable leather industry. In this study, a series of dialdehyde carboxymethyl cellulose (DCMC) were prepared by periodate oxidation of carboxymethyl cellulose (CMC) with varying degrees of substitution (DS: 0.7, 0.9 and 1.2). The structural properties of DCMC were characterized. Size Exclusive Chromatography measurements showed that CMC underwent severe degradation during periodate oxidation, resulting in the decline of weight-average molecular weight from 250,000 g/mol to around 13,000 g/mol. FT-IR analysis illustrated that aldehyde group was successfully introduced into DCMC. The aldehyde group content of DCMC decreased from 8.38 mmol/g to 2.95 mmol/g as the DS rose from 0.7 to 1.2. Interestingly, formaldehyde was found to be produced in DCMC, and its content was 159.4, 151.7 and 38.4 mg/L, respectively when the DS of CMC was 0.7, 0.9 and 1.2, respectively. Further analysis by HPLC found that fructose was formed during oxidative degradation, and was subsequently oxidized to generate formaldehyde. This was in accordance with the fact that higher DS resulted in lower formaldehyde content in DCMC. The whole reaction mechanism is still under investigation at the moment. Tanning trials showed that the shrinkage temperature and thickening rate of DCMC tanned leather decreased as the DS increased. This should be due to the difference in aldehyde content of DCMC. Leather tanned by DCMC-0.7 (DS of CMC was 0.7) had the highest shrinkage temperature of 81°C and thickening rate of 76%. It was noteworthy that the formaldehyde content in DCMC tanned leather was only 0.11-0.40 mg/kg even though DCMC contained a small amount of formaldehyde. In general, we hope the work on dialdehyde tanning agent derived from CMC could provide some essential data for the development of sustainable tanning material and process. Take-Away: 1. Higher degree of substitution (DS) of CMC resulted in lower aldehyde group content of DCMC. 2. The formaldehyde content of DCMC was negatively correlated with DS. 3. The tanning performance of DCMC with lower DS was better

    Stability and Hopf Bifurcation Analysis of a Vector-Borne Disease with Time Delay

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    A delay-differential modelling of vector-borne is investigated. Its dynamics are studied in terms of local analysis and Hopf bifurcation theory, and its linear stability and Hopf bifurcation are demonstrated by studying the characteristic equation. The stability and direction of Hopf bifurcation are determined by applying the normal form theory and the center manifold argument

    The Effects of Force on the Structure Deformation of Wing for Flapping-wing

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    This paper investigated the effects of aerodynamic force and inertial force on the structure deformation of wing. The aerodynamic force was tested from the wind tunnel experiment. The study indicated the quantity of aerodynamic force and inertial force is equal. The maximum deformation was produced by aerodynamic force or resultant force when wing is located on horizontal situation. The study of wing structure deformation provide guide for design and optimization of wing for flapping-wing.Keywords: Flapping-wing; aerodynamic force; inertial force; structure deformatio

    Apocynin Improves Insulin Resistance through Suppressing Inflammation in High-Fat Diet-Induced Obese Mice

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    We investigated the effects of apocynin on high-fat diet- (HFD-) induced insulin resistance in C57BL/6 mice. After 12 weeks of HFD, the mice that exhibited insulin resistance then received 5 weeks of apocynin (2.4 g/L, in water). Following apocynin treatment, fasting glucose, insulin, and glucose tolerance test showed significant improvement in insulin sensitivity in HFD-fed mice. We demonstrated that serum levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and leptin were remarkably reduced with apocynin treatment. We also found that mRNA expression of TNF-α, IL-6, and monocyte chemoattractant protein-1 (MCP-1) in the liver and mRNA expression of TNF-α, IL-6, MCP-1, and leptin in adipose tissue were suppressed by apocynin. Furthermore, the activity of transcription factor NF-κB in the liver was significantly suppressed with apocynin treatment. These results suggest that apocynin may reduce inflammatory factors in the blood, liver, and adipose tissue, resulting in amelioration of insulin resistance in HFD-fed mice

    The effect of personalized intervention on the cognitive function of elderly inpatients

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    目的  对住院老年患者进行早期认知功能护理干预,评价其效果。方法  2013年1月—2015年1月入院老年科病房的120名患者,运用MMSE量表对其认知功能进行评价,观察干预效果。结果  MMSE总分及MMSE量表中时间定向、短期记忆及插画条目干预后有改善(P<0.05),地点定向、语言记忆、注意力、物品命名、语言复述、阅读能力、语言能力及语言表达条目改善不明显(P>0.05)。 结论  个性化的认知干预能够延缓和改善患者认知功能障碍,提高老年患者的生活质量。Objectives: To assess the effect of the early cognitive function nursing intervention on the cognitive function of elderly inpatients. Methods: A total of 120 elderly inpatients in geriatrics ward were rolled from January 2013 to January 2015, and we evaluate the cognitive function of them and gave personalized intervention to them by MMSE scale. Results: The total score of MMSE was increased (P<0.05); The entries of time orientation, short-term memory and illustration were improved significantly after three-month intervention (P<0.05); The entries of place orientation, language, memory, attention, article name, repeat language, reading skills, language skills and language were not improved significantly. Conclusions:  Personalized cognitive intervention could improve the cognitive dysfunction and the quality of life of elderly patients

    Light Harvesting Mechanism of Photosystem II in Photosynthesis:

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    As one of the most important chemical reactions on the earth, the photosynthetic reaction has gained much attention. For example, foliage and algae possess superior abilities to harvest luminous energy from sunlight in photosynthetic reactions by capturing lights with the light-harvesting complex (LHC) and transferring the energy from LHC to the reaction center (RC) in Photosystem II (PSII), to realize the continuous and efficient transformation from luminous energy to chemistry energy. In this article, the progresses in the studies on the crystal structure of PSII, the energy and electron transfer mechanism, and artificial simulation on photo-induced electron transfer are reviewed. Additionally, the initiating mechanism of hydrogen-abstraction photoinitiators, and the inspiration of the principles and mechanisms of photo-induced electron transfer in macromolecular photoinitiators were also discussed. It is believed that properly choosing covalent chains of appropriate types and length as the bridge between electron donor and electron acceptor is crucial for improving the initiating efficiency of photoinitiators. Keywords: photosynthesis; photosystem; light harvesting; photoinitiator; electron transfe

    Identification of quality markers of Xiaojin Pills using a combination of high-performance liquid chromatographtandem mass spectrometry and multivariate analysis

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    Purpose: To establish an appropriate quality control method for Xiaojin pills using high-performance liquid chromatograph-tandem mass spectrometry combined with multivariate analysis.Methods: High-performance liquid chromatograph-tandem mass spectrometry was established to detect and quantify 13 chemical components of Xiaojin Pills. In order to evaluate the quality difference between diverse specimens of Xiaojin Pills, several multivariate statistical techniques were applied to analyze the dissimilarity between different batches of samples, including principal composition analysis method and clustering methodology.Results: Five chemical components were identified as primary quality markers, which can be used to accurately distinguish various samples and command the quality of Xiaojin Pills.Conclusion: The results afford a professionally scientific basis for the quality monitoring of Xiaojin Pills and also furnishes reasonable ideas and suggestions for the quality control of other traditional drugs.Keywords: Xiaojin Pills, HPLC-MS/MS, Quality control, Chemometrics, Quality marker

    Src-family protein tyrosine kinases: a promising target for treating chronic pain

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    Abstract Despite growing knowledge of the mechanisms of chronic pain, it remains a major challenge facing clinical practice. Src-family protein tyrosine kinases (SFKs), a group of non-receptor protein tyrosine kinases, have been implicated in neuronal development and synaptic plasticity. SFKs are critically central to various transmembrane receptors e.g. G-protein coupled receptor (GPCR), EphB receptor (EphBR), increased intracellular calcium, epidermal growth factor (EGF) and other growth factors that regulate the phosphorylation of N-methyl-D-aspartic acid receptor (NMDAR) 2B subunit, thus contributing to the development of chronic pain. SFKs have also been regarded as an important point of convergence of intracellular signaling components that regulate microglia functions and the immune response. Additionally, intrathecal administration of SFKs inhibitors significantly alleviates mechanical allodynia in different chronic pain models. Thus, here we reviewed the current evidence of the role of SFKs in the development of chronic pain caused by complete Freund's adjuvant (CFA) injection, peripheral nerve injury (PNI), streptozotocin (STZ) injection and bone metastasis. Moreover, the role of SFKs on the development of morphine tolerance has also been discussed. Management of SFKs therefore emerged as a potential therapeutic target for the treatment of chronic pain in terms of safety and efficacy. Key words Chronic pain; Src-family protein tyrosine kinases; N-methyl-D-aspartic acid receptor; Microglia
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