Brief Overview of the Partial Oxidation of Methane to Synthesis Gas

A review of the main developments in the partial oxidation of methane to synthesis gas since the first paper in 1929 to the present day is given. The reaction is discussed from the view of the thermodynamics; the main catalysts studied for the reaction are summarised, and the reaction mechanism is discussed. The review is not comprehensive, but it is designed to provide a general background to the most important developments in the field.     

FDTD analysis of wave propagation in nonlinear absorbing and gainmedia

An explicit finite-difference time-domain (FDTD) scheme for wave propagation in certain kinds of nonlinear media such as saturable absorbers and gain layers in lasers is proposed here. This scheme is an extension of the auxiliary differential equation FDTD approach and incorporates rate equations that govern the time-domain dynamics of the atomic populations in the medium. For small signal intensities and slowly varying pulses, this method gives the same results as frequency-domain methods using the linear susceptibility function. Population dynamics for large signal intensities and the transient response for rapidly varying pulses in two-level (absorber) and four-level (gain) atomic media are calculated to demonstrate the advantages of this approach     

Far-field reflectometry for characterization of active antennas

Testing active antennas or polarimetric radar calibrators in the far field (plane wave excitation) is complicated by imperfect isolation between transmit and receive channels. We describe a far-field reflectometry setup which overcomes this problem. A large dynamic range is achieved by modulating the active element bias and using a quadrature receiver and lock-in detection scheme. A calibration method and a novel mixer phase-error correction scheme are described. The system is capable of full polarimetric characterization of active scatterers     

Characterization of circulating CD4+ CD8+ lymphocytes in healthy individuals prompted by identification of a blood donor with a markedly elevated level of CD4+ CD8+ lymphocytes

During flow cytometric analysis of lymphocytes from healthy donors, we identified a donor (donor A) with 22% CD4+ CD8+ cells (versus values of < 4% for 65 other controls). To determine if CD4+ CD8+ cells from donor A and other controls were similar, we first defined the phenotypic profile of control CD4+ CD8+ cells. Enriched CD4+ CD8+ cell populations for 10 controls were prepared by a two-step positive selection scheme with anti-CD4-coated magnetic beads and anti-CD8-coated culture flasks; the selected population averaged 69% CD4+ CD8+ cells and 31% CD4+ CD8- cells. For all 10 controls, two subsets of CD4+ CD8+ cells, CD4dim CD8bright and CD4bright CD8dim, were observed. Phenotypic profiles of these two CD4+ CD8+ subsets were defined by pairing anti-CD8 with other monoclonal antibodies, and the profiles were compared with each other and with those of CD4+ CD8-, CD4- CD8bright, and CD4- CD8dim cells. CD8bright and CD4bright CD8dim cells differed in their proportions of CD62-L+ cells and in their levels of CD11a and CD2 expression. Both CD4+ CD8+ subsets resembled CD4+ CD8- cells in CD45RA, CD45RO, and CD25 expression; the comparable CD- CD8+ cells in CD62-L expression; and CD4- CD8bright cells in CD11b, CD11b, CD16/56, and CD28 expression. CD38 expression in both CD4+ CD8+ subsets was decreased compared with those of other cell subsets. Whereas control CD4+ CD8+ cells averaged 33% CD4dim CD8bright, CD4+ CD8+ cells from donor A were > 90% CD4dim CD8bright. Donor A CD4dim CD8bright cells exhibited proportional decreases in CD25 and CD62-L expression and increases in CD11b and CD54 expression compared with those of control CD4dim CD8bright cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

Rap1 mediates sustained MAP kinase activation induced by nerve growth factor

Activation of mitogen-activated protein (MAP) kinase (also known as extracellular-signal-regulated kinase, or ERK) by growth factors can trigger either cell growth or differentiation. The intracellular signals that couple growth factors to MAP kinase may determine the different effects of growth factors: for example, transient activation of MAP kinase by epidermal growth factor stimulates proliferation of PC12 cells, whereas they differentiate in response to nerve growth factor, which acts partly by inducing a sustained activation of MAP kinase. Here we show that activation of MAP kinase by nerve growth factor involves two distinct pathways: the initial activation of MAP kinase requires the small G protein Ras, but its activation is sustained by the small G protein Rap1. Rap1 is activated by CRK adaptor proteins and the guanine-nucleotide-exchange factor C3G, and forms a stable complex with B-Raf, an activator of MAP kinase. Rap1 is required for at least two indices of neuronal differentiation by nerve growth factor: electrical excitability and the induction of neuron-specific genes. We propose that the activation of Rap1 by C3G represents a common mechanism to induce sustained activation of the MAP kinase cascade in cells that express B-Raf.     

俄罗斯莫斯科Tyufeleva Roshcha公园

Tyufeleva Roshcha公园于2018年夏季开始对外开放,是一个占地10 hm2的公共公园,位于欧洲最大的私人开发项目之一的“ZilArt”的核心地带。“ZilArt”是一个面积达90 hm2的功能混合型社区,其设计目的是重新缝合数十年来被Zil车厂割裂的城市肌理。     

Failure of elastic‐plastic core–shell microcapsules under compression

Characterization of the failure behavior of microcapsules is extremely important to control the release of their core actives by mechanical forces. The strain and stress of elastic‐plastic uninflated core–shell microcapsules at failure (rupture or bursting) has been determined using finite element modeling (FEM) and micromanipulation compression experiments. The ductile failure of polymeric microcapsules at high deformations is considered to occur when the maximum strain in the shell exceeds a critical strain, resulting in their rupture. FEM has been used to determine the maximum strains present in the capsule wall at different deformations for three types of shell material: elastic, elastic—perfectly plastic and elastic—perfectly plastic with strain hardening at large strains. The results obtained were used to determine the failure strain and stress of melamine‐formaldehyde microcapsules, with average population values of ～0.48 and ～350 MPa, respectively. Thus, the elastic‐plastic stress–strain relationship has been determined for the core–shell microcapsules tested. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

2009年度精选装备

在这次的年度推荐中,我们汇集了过去12个月里最让我们怦然心动的相机、镜头、摄影配件和图像处理软件。尽管过去的一年中全球经济还是不太景气,但值得庆幸的是,这并没有阻碍影像厂商为我们带来一流的摄影器材。如果说经济危机对摄影相关产品的市场有什么影响的话,总体上看也是利大于弊的:更严峻的经济形势迫使厂商不得不想方设法地施展出更多的创意,并且比以往更多地关注于用户的需求——对于我们     

Unified Approach to the Characterization of Coupled Composite Laminates: Benchmark Configurations and Special Cases

Benchmark stacking sequence configurations with up to 21 plies are presented for laminates with properties similar to conventional materials, and against which new forms of coupled laminate behavior can be assessed. The benchmark configurations include fully uncoupled extensionally isotropic laminates and fully isotropic laminates, together with a special class of uncoupled laminate, possessing matching elastic properties in both extension and bending; more commonly referred to as a quasi-homogeneous orthotropic laminate. The concept of an equivalent isotropic laminate is also introduced as a universally applicable datum, useful for characterization of ply number groupings for which no benchmark configurations exist. Most of the benchmark configurations are found to possess nonsymmetric stacking sequences, which also serves to demonstrate that stacking sequence symmetry is neither sufficient nor necessary for fully uncoupled laminate designs. Finally, dimensionless parameters are provided for each stacking sequence, from which the ABD matrix is shown to be readily derived.