Association Between VDR FokI Polymorphism and Intervertebral Disk Degeneration

AbstractIntervertebral disk degeneration (IDD) is strongly associated with genetic predisposition and environmental susceptibility. Several studies been conducted to investigate the potential association between IDD and FokI polymorphism located in the gene encoding the vitamin D receptor (VDR), and inconsistent conclusions had been reached among different ethnic populations. In order to assess the association between the FokI polymorphism and the risk of IDD, we performed a comprehensive and systematic meta-analysis. Candidate articles were retrieved from PubMed, EMBASE, China National Knowledge Infrastructure (CNKI), and China Biology Medical (CBM) with strict inclusion criteria in January 2015. Among the 54 articles that were retrieved, only eight studies met the inclusion criteria. The pooled data analysis based on allele contrast, homozygote, heterozygote, dominant, and recessive models revealed no significant correlation between the FokI polymorphism and the risk of IDD. However, when stratified by ethnicity, significant associations were detected for Hispanics based on allele contrast (OR=1.395, 95% CI=1.059–1.836, P=0.018), homozygote (OR=1.849, 95% CI=1.001–3.416, P=0.049), heterozygote (OR=1.254, 95% CI=1.049–1.498, P=0.013), and dominant (OR=1.742, 95% CI=1.174–2.583, P=0.006) models, and for Asians using the dominant model (OR=1.293, 95% CI=1.025–1.632, P=0.030), whereas there is no significant association detected for Caucasians. In conclusion, FokI polymorphism is not generally associated with IDD, but there is increased risk for IDD in Hispanics and Asians carrying FokI allele T

Electronic, optical and transport properties of van der Waals Transition-metal Dichalcogenides Heterostructures: A First-principle Study

Two-dimensional (2D) transition-metal dichalcogenide (TMD) MX$_2$ (M = Mo, W; X= S, Se, Te) possess unique properties and novel applications. In this work, we perform first-principles calculations on the van der Waals (vdW) stacked MX$_2$ heterostructures to investigate their electronic, optical and transport properties systematically. We perform the so-called Anderson's rule to classify the heterostructures by providing the scheme of the construction of energy band diagrams for the heterostructure consisting of two semiconductor materials. For most of the MX$_2$ heterostructures, the conduction band maximum (CBM) and valence band minimum (VBM) reside in two separate semiconductors, forming type II band structure, thus the electron-holes pairs are spatially separated. We also find strong interlayer coupling at $\Gamma$ point after forming MX$_2$ heterostructures, even leading to the indirect band gap. While the band structure near $K$ point remain as the independent monolayer. The carrier mobilities of MX$_2$ heterostructures depend on three decisive factors, elastic modulus, effective mass and deformation potential constant, which are discussed and contrasted with those of monolayer MX$_2$, respectively.Comment: 7 figure

The role of hydrogen coverage and location in 1,3-butadiene hydrogenation over Pt/SiO2

Hydrogenation of 1,3-butadiene over supported Pt particles has long been known as a structure sensitive reaction, yet the nature of this phenomenon has not been well understood. We have previously addressed the reaction pathway for 1,3-butadiene hydrogenation over similar to 22 nm Pt particles. In this study, the behaviors of SiO2 supported similar to 2.9 nm Pt particles towards 1,3-butadiene hydrogenation have been investigated with the aim of providing a fundamental explanation for the structure sensitivity of this reaction. Interestingly, it was found that the product distribution for the present catalyst towards 1,3-butadiene hydrogenation was sensitive to temperature. However, the evolution of 1,3-butadiene hydrogenation over the catalyst with temperature was not captured by in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The detected carbonaceous species on the Pt surface are more likely to be spectators rather than reaction intermediates for the formation of butenes and n-butane. To understand the behaviors of the catalyst, density functional theory (DFT) calculations were employed to explore the pathways for the formation of the products with low activation barriers. The results show that the coverage and the location of the hydrogen atom are the two key factors for the interpretation of the behavior of Pt particles towards 1,3-butadiene hydrogenation

Pt/TS-1 catalysts: Effect of the platinum loading method on the dehydrogenation of n-butane

A series of catalysts in which platinum was supported on the crystalline pure titanium silicalite (TS-1) were prepared using two different loading methods, namely, an ethylene glycol (EG) reduction method and the conventional incipient wetness impregnation (IM) technique. Various characterization techniques were used to study the effect of the loading method on the physicochemical and morphological properties of the prepared catalysts. Also the effect of the platinum-loading method on the dehydrogenation of n-butane was investigated in a fixed-bed reactor. The results show that the EG method favors the formation of a more-concentrated Pt dispersion, which results in much better catalytic activities for the selective formation of butenes and butadiene (> 97 %). This phenomenon is interpreted by carrying out density functional theory (DFT) calculations with focus on the relationship between the coverage of n-butane on Pt surface and the activation barrier for the first C-H bond cleavage