Activation of hydrogen storage materials in the Li–Mg–N–H system: Effect on storage properties

We investigate the thermodynamics, kinetics, and capacity of the hydrogen storage reaction: Li₂Mg(NH)₂ + 2H₂  Mg(NH₂)₂ + 2LiH. Starting with LiNH₂ and MgH₂, two distinct procedures have been previously proposed for activating samples to induce the reversible storage reaction. We clarify here the impact of these two activation procedures on the resulting capacity for the Li–Mg–N–H reaction. Additionally, we measure the temperature-dependent kinetic absorption data for this hydrogen storage system. Finally, our experiments confirm the previously reported formation enthalpy (ΔH), hydrogen capacity, and pressure–composition–isotherm (PCI) data, and suggest that this system represents a kinetically (but not thermodynamically) limited system for vehicular on-board storage applications.     

粒状氮化镓微晶的合成及其结构性能的研究

在950℃的氮化温度下,通过单氢氧化镓（GaO2H）粉末与流动的NH3反应35 min制备出粒状GaN微晶.通过X射线衍射（XRD）和扫描电镜（SEM）研究发现,GaN粉末是六角纤锌矿结构的粒状微晶,其晶格常数a和c分别为0.3191 nm和0.5192 nm.X射线光电子能谱（XPS）揭示试样中有Ga-N键形成,Ga与N两元素比为1∶1.     

基于事件触发的电力系统H∞优化控制

针对大规模集中用电导致电力系统负荷端激增从而影响电力系统稳定性的问题,提出一种基于事件触发的H_∞优化控制方式。本文采用扇区法对单机无穷大电力系统进行线性化处理,之后通过模糊逻辑建立电力系统的T-S模糊模型。通过事件触发理论和模糊逻辑利用并行分布补偿(parallel distribution compensation,PDC)的方法设计系统控制器。H∞优化控制相比于传统的控制方法提高了系统的稳定性及抗干扰能力,因此本文根据李雅普诺夫稳定性理论和H∞优化控制理论,基于线性矩阵不等式(linear Matrix Inequality,LMI),给出了保证单机无穷大电力系统闭环渐进稳定的充分条件,并采用MATLAB仿真软件对系统进行仿真,从而证明稳定条件的存在。     

Self-sufficient Cytochrome P450s and their potential applications in biotechnology

Cytochrome P450s(CYPs) are ubiquitously found in all kingdoms of life, playing important role in various biosynthetic pathways as well as degradative pathways; accordingly find applications in a vast variety of areas from organic synthesis and drug metabolite production to modification of biomaterials and bioremediation.Significantly, CYPs catalyze chemically challenging C—H and C—C activation reactions using a reactive high-valent iron-oxo intermediate generated upon dioxygen activation at their heme center,while the other oxygen atom is reduced to the level of water by electrons provided through a reductase partner protein.Self-sufficient CYPs, encoding their heme domain and reductase protein in a single polypeptide, facilitate increased catalytic efficiency and render a less complicated system to work with.The self-sufficient CYP enzyme from CYP102A family(CYP102A1, BM3) is among the earliest and most-investigated model enzymes for mechanistic and structural studies as well as for biotechnological applications.An increasing number of self-sufficient CYPs from the same CYP102 family and from other families have also been reported in last decade.In this review, we introduce chemistry and biology of CYPs, followed by an overview of the characteristics of self-sufficient CYPs and representative reactions.Enzyme engineering efforts leading to novel self-sufficient CYP variants that can catalyze synthetically useful natural and non-natural(nature-mimicking) reactions are highlighted.Lastly, the strategy and efforts that aim to circumvent the challenges for improved thermostability, regio-and enantioselectivity,and total turnover number; associated with practical use of self-sufficient CYPs are reviewed.     

Sequence,Chromatin and Evolution of Satellite DNA

Satellite DNA consists of abundant tandem repeats that play important roles in cellular processes, including chromosome segregation, genome organization and chromosome end protection. Most satellite DNA repeat units are either of nucleosomal length or 5–10 bp long and occupy centromeric, pericentromeric or telomeric regions. Due to high repetitiveness, satellite DNA sequences have largely been absent from genome assemblies. Although few conserved satellite-specific sequence motifs have been identified, DNA curvature, dyad symmetries and inverted repeats are features of various satellite DNAs in several organisms. Satellite DNA sequences are either embedded in highly compact gene-poor heterochromatin or specialized chromatin that is distinct from euchromatin. Nevertheless, some satellite DNAs are transcribed into non-coding RNAs that may play important roles in satellite DNA function. Intriguingly, satellite DNAs are among the most rapidly evolving genomic elements, such that a large fraction is species-specific in most organisms. Here we describe the different classes of satellite DNA sequences, their satellite-specific chromatin features, and how these features may contribute to satellite DNA biology and evolution. We also discuss how the evolution of functional satellite DNA classes may contribute to speciation in plants and animals.     

Bioenergetic Alterations of Metabolic Redox Coenzymes as NADH,FAD and FMN by Means of Fluorescence Lifetime Imaging Techniques

Metabolic FLIM (fluorescence lifetime imaging) is used to image bioenergetic status in cells and tissue. Whereas an attribution of the fluorescence lifetime of coenzymes as an indicator for cell metabolism is mainly accepted, it is debated whether this is valid for the redox state of cells. In this regard, an innovative algorithm using the lifetime characteristics of nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) and flavin adenine dinucleotide (FAD) to calculate the fluorescence lifetime induced redox ratio (FLIRR) has been reported so far. We extended the FLIRR approach and present new results, which includes FLIM data of the various enzymes, such as NAD(P)H, FAD, as well as flavin mononucleotide (FMN). Our algorithm uses a two-exponential fitting procedure for the NAD(P)H autofluorescence and a three-exponential fit of the flavin signal. By extending the FLIRR approach, we introduced FLIRR1 as protein-bound NAD(P)H related to protein-bound FAD, FLIRR2 as protein-bound NAD(P)H related to free (unbound) FAD and FLIRR3 as protein-bound NAD(P)H related to protein-bound FMN. We compared the significance of extended FLIRR to the metabolic index, defined as the ratio of protein-bound NAD(P)H to free NAD(P)H. The statistically significant difference for tumor and normal cells was found to be highest for FLIRR1.     

H2O(g)对富氧燃烧超细颗粒物生成特性影响

为实现富氧燃烧技术的广泛推广,对煤粉燃烧在富氧气氛下的颗粒物排放特性进行了研究。在1800 K管式炉内进行煤焦燃烧试验,研究了富氧气氛下H₂O(g)体积分数(0、5%、10%、20%、30%)对煤焦燃烧超细颗粒物的影响;采用荷电低压撞击器(ELPI+)获得超细颗粒物质量和数量浓度粒径分布并进行分析。结果表明,H₂O(g)对超细颗粒物质量浓度和数量浓度粒径分布无影响,但会导致超细颗粒物的峰值波动。超细颗粒物总数量由最小粒径超细颗粒物决定,5种水蒸气浓度下EL?PI+第1级撞击器收集到的超细颗粒物数量占比均超过65%。超细颗粒物总质量由最大粒径超细颗粒物决定,5个水蒸气浓度下ELPI+第7级撞击器收集到的超细颗粒物质量占比均超过94%。低H₂O(g)浓度会抑制超细颗粒物生成,H₂O(g)体积分数为5%时的抑制作用最显著;高H₂O(g)浓度会促进超细颗粒物生成。这是因为一方面H₂O(g)与煤焦发生气化反应,使煤焦颗粒周围产生还原性气氛,促进矿物质还原为单质,进一步促进矿物质蒸发;另一方面气化反应是吸热反应,会降低煤焦颗粒燃烧温度,同时H₂O(g)加入也导致烟气热容增加进一步降低,煤焦燃烧温度抑制煤中矿物质的蒸发,导致超细颗粒物生成减少,是2种作用相互竞争的结果。此外,H₂O(g)的加入使超细颗粒物平均粒径增大,0~5%H₂O(g)时超细颗粒物平均粒径增大最迅速。     

CO2/H2S对油气管材的腐蚀规律

本文综述了CO2、H2S对油气管材的腐蚀机理及影响因素,提出了开发经济型油管的设想.     

Structure and blood compatibility of tetrahedral amorphous hydrogenated carbon formed by a magnetic-field-filter plasma stream

Tetrahedral amorphous hydrogenated carbon (ta-C:H) films with various substrate bias voltages were prepared using a magnetic-field-filter plasma stream deposition system. The microstructural and optical properties were studied using ellipsometric spectra. The refractive index n of each sample was obtained by simulating their ellipsometric spectral using Tauc-Lorentz oscillator model, and then the relative sp³ C ratio of each sample was calculated using Bruggeman effective medium approximation. The sp³ C fraction of each sample was quantified by using electron energy-loss spectroscopy (EELS). The blood compatibility of the samples was evaluated by tests of platelet adhesion, kinetic clotting time and thrombin time. The quantity and morphology of the adherent platelets on the surface of these samples were investigated using scanning electron microscopy. Results show that the spectroscopic ellipsometry is a helpful method to evaluate the sp³ carbon fraction of the carbon films. The substrate bias voltage has an obvious effect on sp³ content and blood compatibility of ta-C:H films. The sample prepared with substrate bias voltage of − 20 V showed the best blood compatibility. A simple bio-physical hypothetical model was proposed to explain the experiment results.     

矿山磨光球用钢XK5159H的生产试制

XK5159H钢连铸连轧棒材用于制造矿山磨光球，对于钢的纯净度、低倍组织、探伤结果及DI值等均有严格的要求，很难控制。我们通过制定内控化学成分及合理的工艺路线，使生产试制一次成功。