Synthesis of zinc oxide porous structures by anodization with water as an electrolyte

We report a simple, reliable and one-step method of synthesizing ZnO porous structures at room temperature by anodization of zinc (Zn) sheet with water as an electrolyte and graphite as a counter electrode. We observed that the de-ionized (DI) water used in the experiment is slightly acidic (pH=5.8), which is due to the dissolution of carbon dioxide from the atmosphere forming carbonic acid. Porous ZnO is characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and photoluminescence (PL) studies. The current-transient measurement is carried out using a Gamry Instruments Reference 3000 and the thickness of the deposited films is measured using a Dektak surface profilometer. The PL, Raman and X-ray photoelectron spectroscopy are used to confirm the presence of ZnO phase. We have demonstrated that the hybrid structures of ZnO and poly (3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) exhibit good rectifying characteristics. The evaluated barrier height and the ideality factor are 0.45 eV and 3.6, respectively.

Synthon identification in co-crystals and polymorphs with IR spectroscopy. Primary amides as a case study

IR spectroscopy has been widely employed to distinguish between different crystal forms such as polymorphs, clathrates, hydrates and co-crystals. IR has been used to monitor co-crystal formation and single synthon detection. In this work, we have developed a strategy to identify multiple supramolecular synthons in polymorphs and co-crystals with this technique. The identification of multiple synthons in co-crystals with IR is difficult for several reasons. In this paper, a four step method involving well assigned IR spectral markers that correspond to bonds in a synthon is used. IR spectra of three forms of the co-crystal system, 4-hydroxybenzoic acid: 4,4'-bipyridine (2 : 1), show clear differences that may be attributed to differences in the synthon combinations existing in the forms (synthon polymorphism). These differences were picked out from the three IR spectra and the bands analysed and assigned to synthons. Our method first identifies IR marker bands corresponding to (covalent) bonds in known/model crystals and then the markers are mapped in known co-crystals having single synthons. Thereafter, the IR markers are queried in known co-crystals with multiple synthons. Finally they are queried in unknown co-crystals with multiple synthons. In the last part of the study, the N-H stretching absorptions of primary amides that crystallize with the amide dimers linked in a ladder like chain show two specific absorptions which are used as marker absorptions and all variations of this band structure have been used to provide details on the environment around the dimer. The extended dimer can accordingly be easily distinguished from the isolated dimer.

Transition Between Detonation and Deflagration in a Tube with a Cavity

In this paper, the transition of a detonation from deflagration was investigated numerically while a detonation wave propagates in a tube with a sudden change in cross section, referred to as the expansion cavity. The dispersion-controlled scheme was adopted to solve Euler equations of axis-symmetric flows implemented with detailed chemical reaction kinetics of hydrogen-oxygen (or hydrogen-air) mixture. The fractional step method was applied to treat the stiff problems of chemical reaction flow. It is observed that phenomena of detonation quenching and reigniting appear when the planar detonation front diffracts at the vertex of the expansion cavity entrance. Numerical results show that detonation front in mixture of higher sensitivity keeps its substantial coupled structure when it propagates into the expansion cavity. However, the leading shock wave decouples with the combustion zone if mixture of lower sensitivity was set as the initial gas.

Molecular Techniques for Dicistrovirus Detection without RNA Extraction or Purification

Dicistroviridae is a new family of small, nonenveloped, and +ssRNA viruses pathogenic to both beneficial arthropods and insect pests as well. Triatoma virus (TrV), a dicistrovirus, is a pathogen of Triatoma infestans (Hemiptera: Reduviidae), one of the main vectors of Chagas disease. In this work, we report a single-step method to identify TrV, a dicistrovirus, isolated from fecal samples of triatomines. The identification method proved to be quite sensitive, even without the extraction and purification of RNA virus.

Advances towards behaviour-based indoor robotic exploration

215 p.

较高阶非线性抽运-探测过程中的空间效应

在飞秒抽运一探测光谱技术中，空间分辨的探测光信号反映了在不同空间位置的材料的非线性效应。当抽运光强度增大时，探测光信号中会出现明显的高阶特别是五阶非线性效应。利用劈裂算子方法直接解决了一维非线性传播方程的问题。在数值模拟中，研究了在不同抽运强度和位置下的抽运一探测过程中的五阶非线性效应。在足够高的抽运场下，探测信号出现清晰的振荡，显示了三阶和五阶非线性效应之间的干涉。当空间位置离抽运场中心足够远时，五阶比三阶非线性效应的衰减快得多，对其物理机制和趋势进行了定性的讨论。

The Voting Rights Act, Shelby County, and Redistricting: Improving Estimates of Racially Polarized Voting in a Multiple-Election Context

The Supreme Court’s decision in Shelby County has severely limited the power of the Voting Rights Act. I argue that Congressional attempts to pass a new coverage formula are unlikely to gain the necessary Republican support. Instead, I propose a new strategy that takes a “carrot and stick” approach. As the stick, I suggest amending Section 3 to eliminate the need to prove that discrimination was intentional. For the carrot, I envision a competitive grant program similar to the highly successful Race to the Top education grants. I argue that this plan could pass the currently divided Congress.

Without Congressional action, Section 2 is more important than ever before. A successful Section 2 suit requires evidence that voting in the jurisdiction is racially polarized. Accurately and objectively assessing the level of polarization has been and continues to be a challenge for experts. Existing ecological inference methods require estimating polarization levels in individual elections. This is a problem because the Courts want to see a history of polarization across elections.

I propose a new 2-step method to estimate racially polarized voting in a multi-election context. The procedure builds upon the Rosen, Jiang, King, and Tanner (2001) multinomial-Dirichlet model. After obtaining election-specific estimates, I suggest regressing those results on election-specific variables, namely candidate quality, incumbency, and ethnicity of the minority candidate of choice. This allows researchers to estimate the baseline level of support for candidates of choice and test whether the ethnicity of the candidates affected how voters cast their ballots.

Diretrizes para a gestão de emergência em situações de acidentes químicos: estudo em uma universidade pública do Estado do Rio de Janeiro.

Instituições de Ensino Superior (IES) que realizam atividades de ensino e pesquisa em Química, em geral são potenciais áreas de risco de acidentes, uma vez que utilizam substâncias químicas perigosas em seus processos de ensino e pesquisa. Esta pesquisa se justifica em face da existência de substâncias de natureza química e biológica as quais possuem riscos à saúde e ao meio ambiente e de alguns acidentes já ocorridos em diversas IES no Brasil e exterior. O objetivo da pesquisa foi elaborar diretrizes para a gestão de emergências em acidentes químicos que possam ser aplicadas nos laboratórios de um Instituto de Química de uma Universidade Pública do Estado do Rio de Janeiro. Trata-se de um estudo exploratório e descritivo, aplicado a um caso estudado, de uma emergência. Realizou-se de revisão em literatura especializada, visitas aos laboratórios, registros fotográficos e entrevistas dirigidas a funcionários, técnicos e professores do IQ. A metodologia de avaliação de vulnerabilidade baseou-se no método dos cinco passos da Federal Emergency Management Agency. O estudo de caso mostrou que o Instituto de Química não possui uma Gestão de Emergências Químicas, com ausência de brigada de incêndio e o não cumprimento de normas técnicas e regulamentares. Apesar disso, existem laboratórios que possuem um perfil satisfatório quanto à segurança e saúde. O estudo mostrou também que a metodologia de Análise de Vulnerabilidade é uma boa ferramenta para elaboração de diretrizes voltadas para um Plano de Emergência, quando conduzida por equipe especializada.

An efficient frequency-domain algorithm for wave scattering problems with application to jet noise

This paper presents a pseudo-time-step method to calculate a (vector) Green function for the adjoint linearised Euler equations as a scattering problem in the frequency domain, for use as a jet-noise propagation prediction tool. A method of selecting the acoustics-related solution in a truncated spatial domain while suppressing any possible shear-layer-type instability is presented. Numerical tests for 3-D axisymmetrical parallel mean flows against semi-analytical reference solutions indicate that the new iterative algorithm is capable of producing accurate solutions with modest computational requirements.

体外分步诱导猕猴胚胎干细胞为肝细胞

采用分阶段诱导方法模拟肝细胞体内发育,建立体外诱导猕猴胚胎干细胞(rhesus monkey embryonic stem cells,rESCs)分化为成熟肝细胞的体系,对研究以ES细胞为基础的临床替代治疗人类晚期肝脏疾病具有重要的意义.将rESCs团块在含有10%FBS的DMEM培养基中悬浮培养11d,形成含有早期内胚层细胞的拟胚体(embryonic bodies,EB)并开始表达早期肝细胞的部分基因或蛋白,将11日龄EB接种至包被有ECM的组织培养皿,分阶段加入aFGF、BMP-4及OSM.经aFGF和BMP-4诱导7～10d后,分化细胞形态变为具有双核的多角形细胞,表达早期和中期肝细胞特异性的蛋白(AFP、ALB及CK18)和基因(AFP、ALB、APOH,G-6-P及TAT),并具有储存糖原的功能.撤除aFGF和BMP-4,添加OSM继续诱导7～10 d,分化的细胞表达成熟肝细胞所特有基因CYP1B1和ADH1C,并具有摄取靛青绿的能力.

Hepatocyte growth factor enhances the generation of high-purity oligodendrocytes from human embryonic stem cells

Generation of homogeneous oligodendrocytes as donor cells is essential for human embryonic stem cell (hESC)-based cell therapy for demylinating diseases. Herein we present a novel method for efficiently obtaining mature oligodendrocytes from hESCs with high purity (79.7 +/- 6.9%), using hepatocyte growth factor (HGF) and G5 supplement(containing insulin, transferrin, selenite, biotin, hydrocortisone, basic fibroblast growth factor and epidermal growth factor) in a four-step method. We induced hESCs into neural progenitors (NP) with HGF (5 ng/ml) and G5 (1 x) supplemented medium in an adherent differentiation system. The purified NPs were amplified in suspension as neurospheres for 1 month, and terminal oligodendrocyte differentiation was then induced by G5 supplement withdrawal and HGF treatment (20 ng/ml). The cells generated displayed typical morphologies of mature oligodendrocytes and expressed oligodendrocyte markers O4 and myelin basic protein (MBP). Our result revealed that HGF significantly enhanced the proliferation of hESC-derived NPs and promoted the differentiation as well as the maturation of oligodendrocytes from NPs. Further studies suggest that HGF/c-Met signaling pathway might play an important role in oligodendrocyte differentiation in our system. Our studies provide a means for generating the clinically relevant cell type and a platform for deciphering the molecular mechanisms that control oligodendrocyte differentiation. (C) 2009 International Society of Differentiation. Published by Elsevier Ltd. All rights reserved.

Numerically stable Monte Carlo-burnup-thermal hydraulic coupling schemes

This paper presents stochastic implicit coupling method intended for use in Monte-Carlo (MC) based reactor analysis systems that include burnup and thermal hydraulic (TH) feedbacks. Both feedbacks are essential for accurate modeling of advanced reactor designs and analyses of associated fuel cycles. In particular, we investigate the effect of different burnup-TH coupling schemes on the numerical stability and accuracy of coupled MC calculations. First, we present the beginning of time step method which is the most commonly used. The accuracy of this method depends on the time step length and it is only conditionally stable. This work demonstrates that even for relatively short time steps, this method can be numerically unstable. Namely, the spatial distribution of neutronic and thermal hydraulic parameters, such as nuclide densities and temperatures, exhibit oscillatory behavior. To address the numerical stability issue, new implicit stochastic methods are proposed. The methods solve the depletion and TH problems simultaneously and use under-relaxation to speed up convergence. These methods are numerically stable and accurate even for relatively large time steps and require less computation time than the existing methods. © 2013 Elsevier Ltd. All rights reserved.

Organic/inorganic hybrid solar cells based on SnS/SnO nanocrystals and MDMO-PPV

SnS/SnO heterojunction structured nanocrystals with zigzag rod-like connected morphology were prepared by using a simple two-step method. Bulk heterojunction solar cells were fabricated using the SnS/SnO nanocrystals blended with poly(2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene) (MDMO-PPV) as the active layer. Compared with solar cells using SnS nanoparticles hybridized with MDMO-PPV as the active layer, the SnS/SnO devices showed better performance, with a power conversion efficiency higher by about one order in magnitude.

Growth of GaAs on Si by using a thin Si film as buffer layer

We report a novel technique for growing high-quality GaAs on Si substrate. The process involves deposition of a thin amorphous Si film prior to the conventional two-step growth. The GaAs layers grown on Si by this technique using metalorganic chemical vapor deposition exhibit a better surface morphology and higher crystallinity as compared to the samples gown by conventional two-step method. The full width at half maximum (FWHM) of the x-ray (004) rocking curve for 2.2 mu m thick GaAs/Si epilayer grown by using this new method is 160arcsec. The FWHM of the photoluminescence spectrum main peak for this sample is 2.1 meV. These are among the best results reported so far. In addition, the mechanism of this new growth method was studied using high-resolution transmission electron microscopy.

PHOTOLUMINESCENCE SPECTRUM STUDY OF THE GAAS/SI EPILAYER GROWN BY USING A THIN AMORPHOUS SI FILM AS BUFFER LAYER

Recently, we reported successful growth of high-quality GaAs/Si epilayers by using a very thin amorphous Si film as buffer layer. In this paper, the impurity properties of this kind of GaAs/Si epilayers have been studied by using PL spectrum, SIMS and Hall measurement. Compared to a typical PL spectrum of the GaAs/Si epilayers grown by conventional two-step method, a new peak was observed in our PL spectrum at the energy of 1.462 eV, which is assigned to the band-to-silicon acceptor recombination. The SIMS analysis indicates that the silicon concentration in this kind of GaAs/Si epilayers is about 10(18) cm(-3). But its carrier concentration (about 4 x 10(17) cm(-3)) is lower than the silicon concentration. The lower carrier concentration in this kind of GaAs/Si epilayer can be interpreted both as the result of higher compensation and as the result of the formation of the donor-defect complex. We also found that the high-quality and low-Si-concentration GaAs/Si epilayers can be regrown by using this kind of GaAs/Si epilayer as substrate. The FWHM of the X-ray (004) rocking curve from this regrowth GaAs epilayer is 118 '', it is much less than that of the first growth GaAs epilayer (160 '') and other reports for the GaAs/Si epilayer grown by using conventional two-step method (similar to 200 '').