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1.
Alpha-synuclein (α-Syn) localizes at presynaptic terminal and modulates synaptic functions. Increasing evidence demonstrate that α-Syn oligomers, forming at the early of aggregation, are cytotoxic and is thus related to brain neurodegenerative diseases. Herein, we find that vitamin D (VD) can reduce neurocytotoxicity. The reduced neurocytotoxicity might be attributed to the less amount of large-sized α-Syn oligomers inhibited by VD, measured by electrochemical collision at single particle level, which are not observable with traditionally ensembled method. Single-cell amperometry (SCA) results show that VD can recover the amount of neurotransmitter release during exocytosis induced by α-Syn oligomers, further verifying the neuroprotection of VD. Our study reveals the neuroprotective role of VD through inhibiting α-Syn aggregation, which is envisioned to be of great importance in treatment and prevention of the neurodegenerative diseases.  相似文献   
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3.
Dr Martin Seah, NPL, was the initiator, founder, and first chairman of the Surface Analysis Working Group (SAWG) at the Consultative Committee for Amount of Substance, Metrology in Chemistry and Biology (CCQM) at the Bureau International des Poids et Mesures (BIPM), the international organization established by the Metre Convention. This tribute letter summarizes his achievements during his chairmanship and his long-running impact on the successful work of the group after his retirement.  相似文献   
4.
Time-of-flight secondary ion mass spectrometry (TOF-SIMS), when used for the analysis of complex material samples, typically provides data that are complicated and challenging to understand. Therefore, additional data analysis techniques, such as multivariate analysis, are often required to facilitate the interpretation of TOF-SIMS data. In this study, a new method based on the information entropy (Shannon entropy) is proposed as an indicator of the outline characteristics of an unknown sample, such as changes in the material within the sample and mixing conditions. The Shannon entropy values are calculated using the relative intensity of every secondary ion normalized to the total ion count and reflect the diversity of secondary ions in the spectrum. Mixed samples containing two organic electroluminescence materials of different ratios, multilayers of Irganox 1010, and other organic materials were employed to evaluate the utility of Shannon entropy in the analysis of TOF-SIMS data. The findings demonstrate that the Shannon entropy of a spectrum indicates differences in materials and changes in the conditions of a material in a sample without the need for peak identification or the knowledge of specific peaks corresponding to the materials in the sample.  相似文献   
5.
Metal–organic chemical vapor deposition (MOCVD) is one of the best growth methods for GaN-based materials as well-known. GaN-based materials with very quality are grown the MOCVD, so we used this growth technique to grow InAlN/GaN and AlN/GaN heterostructures in this study. The structural and surface properties of ultrathin barrier AlN/GaN and InAlN/GaN heterostructures are studied by X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements. Screw, edge, and total dislocation densities for the grown samples have been calculated by using XRD results. The lowest dislocation density is found to be 1.69 × 108 cm−2 for Sample B with a lattice-matched In0.17Al0.83N barrier. The crystal quality of the studied samples is determined using (002) symmetric and (102) asymmetric diffractions of the GaN material. In terms of the surface roughness, although reference sample has a lower value as 0.27 nm of root mean square values (RMS), Sample A with 4-nm AlN barrier layer exhibits the highest rough surface as 1.52 nm of RMS. The structural quality of the studied samples is significantly affected by the barrier layer thickness. The obtained structural properties of the samples are very important for potential applications like high-electron mobility transistors (HEMTs).  相似文献   
6.
The detection of cancer biomarkers is of great significance for the early screening of cancer. Detecting the content of sarcosine in blood or urine has been considered to provide a basis for the diagnosis of prostate cancer. However, it still lacks simple, high-precision and wide-ranging sarcosine detection methods. In this work, a Ti3C2TX/Pt–Pd nanocomposite with high stability and excellent electrochemical performance has been synthesized by a facile one-step alcohol reduction and then used on a glassy carbon electrode (GCE) with sarcosine oxidase (SOx) to form a sarcosine biosensor (GCE/Ti3C2TX/Pt–Pd/SOx). The prominent electrocatalytic activity and biocompatibility of Ti3C2TX/Pt–Pd enable the SOx to be highly active and sensitive to sarcosine. Under the optimized conditions, the prepared biosensor has a wide linear detection range to sarcosine from 1 to 1000 µM with a low limit of detection of 0.16 µM (S/N = 3) and a sensitivity of 84.1 µA/mM cm2. Besides, the reliable response in serum samples shows its potential in the early diagnosis of prostate cancer. More importantly, the successful construction and application of the amperometric biosensor based on Ti3C2TX/Pt–Pd will provide a meaningful reference for detecting other cancer biomarkers.  相似文献   
7.
We report on the investigation of electropreconcentration phenomena in micro-/nanofluidic devices integrating 100 μm long nanochannels using 2D COMSOL simulations based on the coupled Poisson–Nernst–Planck and Navier–Stokes system of equations. Our numerical model is used to demonstrate the influence of key governing parameters such as electrolyte concentration, surface charge density, and applied axial electric field on ion concentration polarization (ICP) dynamics in our system. Under sufficiently extreme surface-charge-governed transport conditions, ICP propagation is shown to enable various transient and stationary stacking and counter-flow gradient focusing mechanisms of anionic analytes. We resolve these spatiotemporal dynamics of analytes and electrolyte ICP over disparate time and length scales, and confirm previous findings that the greatest enhancement is observed when a system is tuned for analyte focusing at the charge, excluding microchannel, nanochannel electrical double layer (EDL) interface. Moreover, we demonstrate that such tuning can readily be achieved by including additional nanochannels oriented parallel to the electric field between two microchannels, effectively increasing the overall perm-selectivity and leading to enhanced focusing at the EDL interfaces. This approach shows promise in providing added control over the extent of ICP in electrokinetic systems, particularly under circumstances in which relatively weak ICP effects are observed using only a single channel.  相似文献   
8.
We determine the proton affinity (PA) and gas-phase basicity (GB) of amino acid α-alanine at a chemically accurate level by performing explicitly-correlated CCSD(T)-F12b/aug-cc-pVDZ geometry optimizations and normal mode vibrational frequency calculations as well as CCSD(T)-F12b/aug-cc-pVTZ energy computations at the possible neutral and protonated geometries. Temperature effects at 298.15 K considering translational, rotational, and vibrational enthalpy and entropy corrections are obtained via standard statistical mechanics utilizing the molecular geometries and the harmonic vibrational energy levels. Both the amino nitrogen (N) and the carbonyl oxygen (O) atoms are proven to be potential protonation sites and a systematic conformational search reveals 3 N- and 9 O-protonated conformers in the 0.00–7.88 and 25.43–30.43 kcal/mol energy ranges at 0 K, respectively. The final computed PA and GB values at (0)298.15 K in case of N-protonation are (214.47)216.80 and 207.07 kcal/mol, respectively, whereas the corresponding values for O-protonation are (189.04)190.63 and 182.31 kcal/mol. The results of the benchmark high-level coupled-cluster computations are utilized to assess the accuracy of several lower-level cost-effective methods such as MP2 and density functional theory with various functionals (SOGGA11-X, M06-2X, PBE0, B3LYP, M06, TPSS).  相似文献   
9.
ZSM-5分子筛具有极其均匀的孔道结构、 良好的形状选择性和催化活性及耐水热稳定性, 是一种高效、 绿色的固体催化剂, 被广泛应用于石油催化裂化、 精细化工和环境保护等领域. 但其单一的微孔结构大大降低了客体分子的流通扩散性, 导致由大分子参与的芳烃烷基化反应受到极大限制. 本文采用NaOH/四丙基氢氧化铵(TPAOH)混合碱处理微孔ZSM-5, 制备了具备高结晶度、 高比表面积的等级孔微孔-介孔ZSM-5中空分子筛材料, 该材料在保持微孔孔道良好水热稳定性和大量活性中心的同时, 还通过介孔的引入进一步促进反应物及产物的扩散, 使间三甲苯苄基化反应的转化率提高了3.8倍. 通过在等级孔微孔-介孔ZSM-5中空材料上负载Fe, 开发出了具有双功能的等级孔微孔-介孔Fe2O3/ZSM-5中空催化剂, 该催化剂在苯的苄基化反应中表现出优异的催化性能, 当Fe负载量(质量分数)为6.67%, 反应温度为75 ℃, 反应时间为15 min时, 转化率高达98.3%, 选择性为81.6%, 最终收率达到80.2%.  相似文献   
10.
通过光还原沉积法, 利用氧空位诱导作用, 在Ni掺杂的缺陷态TiO2纳米管阵列(TNT-Ni)上得到金属 Pd含量不同的Pd-TNT-Ni催化剂. 采用场发射扫描电子显微镜(SEM)、 X射线光电子能谱(XPS)、 紫外-可见 漫反射(UV-Vis DRS)、 表面光电压(SPV)、 光致发光光谱(PL)和电化学测试等表征手段, 探究了Pd与Ni掺杂的缺陷态TiO2纳米管阵列之间的强相互作用对其光吸收特性和载流子分离及传输效率的影响, 阐明了强相互 作用对材料光催化活性的调控机理, 提出了Pd增强Pd-TNT-Ni光催化性能的作用机理. 结果表明, 通过光还 原法制备的Pd纳米颗粒尺寸为10~20 nm的Pd120-TNT-Ni样品的光响应值为4.22 mA/cm2, 是未负载Pd样品光 响应值(1.14 mA/cm2)的3.7倍, 其具有最佳的平均产氢速率(5.16 mmol·g?1·h?1), 是TNT样品平均产氢速率 (0.45 mmol·g?1·h?1)的12倍, 表明Pd与缺陷态TiO2纳米管阵列之间的强相互作用驱动了载流子的分离及传输, 且Pd作为电子捕获势阱及反应活性位点, 显著提高了材料的光催化性能.  相似文献   
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