977 resultados para radical scavenger hydroxyl radical, 1,2 selenazoles, COX, LOX


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A variety of N-acetyl-o-aryl-1,2-didehydroethylamines were synthesized by direct reduction-acetylation of beta-aryl-nitroolefins and assayed as HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs) for the first time. Compound 7a exhibited a TI v

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The purpose of the meeting was to: discuss and reach consensus on the implications of the FAO Marine Protected Area(MPA) guidelines; provide further input for BOBLME brochure and policies; agree on actions on the BOBLME MPA review; produce concept proposals for MPA pilot sites and to formalise the establishment of the BOBLME MPA working group.

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Por acuerdo del Seminario Latinoamericano sobre Estudios Oceanográficos realizado en la Universidad de Concepción, Chile, 20-25 noviembre de 1961, se recomendó la realización en Argentina de un Seminario sobre Biogeografía de Organismos Marinos, indicándose al Museo Argentino de Ciencias Naturales Bernardino Rivadavia como sede del mismo. Luego de varias conversaciones en Buenos Aires (Argentina), entre autoridades del Centro de Cooperación Científica para América Latina, del CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas), del Servicio de Hidrografía Naval, del mencionado Museo y del Instituto de Biología Marina de Mar del Plata, se acordó realizar los seminarios en éste último instituto del 1 al 6 octubre de 1962. Del 1 al 2 de octubre, se realizó el Seminario sobre Ciencias Básicas como prerrequisito para la Enseñanza de la Oceanografía, pero los documentos no fueron incluídos en este Boletín. Del 3 al 6 de octubre, tuvo lugar el Seminario sobre Biogeografía de Organismos Marinos, con la participación de investigadores de: Brasil, Colombia, Costa Rica, Chile, Mexico, Perú, Uruguay, Venezuela y de Argentina, y se incluyeron los siguientes trabajos publicados: Joly, A. - Extensao da flora marinha no sul do Brasil- nota preliminar; Etcheverry Daza, H. - Distribución geográfica de las algas del Pacífico; Diaz-Piferrer, M. - Biogeografía de las algas marinas tropicales de la costa Atlántica de America, Resumen,; Kuhneman, O. - Importancia de la vegetación en biogeografía marina; Boschi, E.E. - Los peneidos de Brasil, Uruguay y Argentina; Bernasconi, I. - Distribución geográfica de los equinoideos y asteroideos de la extremidad austral de Sudamérica; Szidat, L. - La parasitología como ciencia auxiliar para la biogeografía de organismos marinos; López, R.B. - Problemas de la distribución geográfica de los peces marinos sudamericanos; Ximénez, I. - Estudio preliminar de la distribución geográfica actual de los pinípedos en América Latina; Balech, E. - La división zonal en biología marina y su nomenclatura; Stuardo, J. - Distribución de los moluscos marinos litorales en Latinoamérica; Boltovskoy, E. - Provincias zoogeográficas de América del Sur y su sector Antártico según los foraminíferos bentónicos; Rioja, E. - Caracteres de la biogeografía marina de México y de Centro América; Balech, E. - Caracteres biogeográficos de la región de Argentina y Uruguay; Vannucci, M. - Zoogeografía marinha do Brasil.

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利用14C标记1,2,7,8-四氯代二苯并二噁英(1,2,7,8Tetrachloro[U—14C]dibenzodioxin,14C1,2,7,8TCDD)初步研究了其在鲤体内的分布和代谢规律。14C1,2,7,8-TCDD溶解于丙酮/植物油中,腹腔暴露。暴露1、2、4、8、12d后取样,肝脏、胆汁、腹腔脂肪等消化制样后用液闪仪测量放射性活度。肝脏和胆汁内的放射性活度同步变化,都是第8d达到峰值后下降。腹腔脂肪内1—2d放射性明显高于随后取样的样品。肝和腹腔脂肪的分布量之比呈现“S”型变化趋势。暴露4d

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This paper presents a critical comparison of static and switching performance of commercially available 1.2 kV SiC BJTs, MOSFETs and JFETs with 1.2 kV Si IGBTs. The experiments conducted are mainly focussed on investigating the temperature dependence of device performance. As an emerging commercial device, special emphasis is placed on SiC BJTs. The experimental data indicate that the SiC BJTs have relatively smaller conduction, off-state and turn-off switching losses, in comparison to the other devices. Furthermore, SiC BJTs have demonstrated much higher static current gain values in comparison to their silicon counterparts, thereby minimising driver losses. Based on the results, the suitability of SiC devices for high power density applications has been discussed. © 2013 IEEE.

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Nostoc sphaeroides Kutzing was cultivated in paddlewheel-driven raceway ponds and the growth kinetics of 1-2 mm and 3-4 mm colonies of N. sphaeroides was studied. The biomass productivities in 2.5 m(2) raceway ponds inoculated with 1-2 mm and 3-4 mm colonies were 5.2 and 0.25 g dry wt m(-2) stop d(-1), respectively. Furthermore, differently sized colonies showed different relative water content, total soluble carbohydrates, chlorophyll a content and density of filaments. This is the first report on mass culture of N. sphaeroides under outdoor conditions.

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The genome segments 1, 2, and 3 of the grass carp reovirus (GCRV), a tentative species assigned to genus Aquareouirus, family Reouiridae, were sequenced. The respective segments 1, 2, and 3 were 3949, 3877, and 3702 nucleotides long. Conserved moths 5' (GUUAUUU) and 3' (UUCAUC) were found at the ends of each segment. Each segment contains a single ORF and the negative strand does not permit identification of consistent ORFs. Sequence analysis revealed that VP2 is the viral polymerase, while VPI might represent the viral guanyly/methyl transferase (involved in the capping process of RNA transcripts) and VP3 the NTPase/helicase (involved in the transcription and capping of viral RNAs), The highest amino acid identities (26-41%) were found with orthoreovirus proteins. Further genomic characterization should provide insight about the genetic relationships between GCRV, aquareoviruses, and orthoreoviruses, It should also permit to precise the taxonomic status of these different viruses. (C) 2000 Academic Press.

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Using the transfer matrix renormalization group (TMRG) method, we study the connection between the first derivative of the thermal average of driving-term Hamiltonian (DTADH) and the trace of quantum critical behaviors at finite temperatures. Connecting with the exact diagonalization method, we give the phase diagrams and analyze the properties of each phase for both the ferromagnetic and anti-ferromagnetic frustrated J(3) anisotropy diamond chain models. The finite-temperature scaling behaviors near the critical regions are also investigated. Further, we show the critical behaviors driven by external magnetic field, analyze the formation of the 1/3 magnetic plateau and the influence of different interactions on those critical points for both the ferrimagnetic and anti-ferromagnetic distorted diamond chains.

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By means of the second derivative of the ground-state and first-excited energy, the quantum phase transitions (QPTs) for the distorted diamond chain (DDC) with ferromagnetic and antiferromagnetic frustrated interactions and the trimerized case are investigated, respectively. Our results show the plentiful quantum phases owing to the spin interaction competitions in the model. Meanwhile, by using the transfer-matrix renormalization-group technique, we study the two-site thermal entanglement of the DDC model in the thermodynamic limit for a further understanding of the QPTs.

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The thermodynamic properties of the spin-1/2 diamond quantum Heisenberg chain model have been investigated by means of the transfer matrix renormalization group (TMRG) method. Considering different crystal structures, by changing the interactions among different spins and the external magnetic fields, we first investigate the magnetic susceptibility, magnetization, and specific heat of the distorted diamond chain as a model of ferrimagnetic spin systems. The susceptibility and the specific heat show different features for different ferromagnetic (F) and antiferromagnetic (AF) interactions and different magnetic fields. A 1/3 magnetization plateau is observed at low temperature in a magnetization curve. Then, we discuss the theoretical mechanism of the double-peak structure of the magnetic susceptibility and the three-peak structure of the specific heat of the compound Cu-3(CO3)(2)(OH)(2), on which an elegant measurement was performed by Kikuchi [Phys. Rev. Lett. 94, 227201 (2005)]. Our computed results are consistent with the main characteristics of the experimental data. Meanwhile, we find that the double-peak structure of susceptibility can be found in several different kinds of spin interactions in the diamond chain. Moreover, a three-peak behavior is observed in the TMRG results of magnetic susceptibility. In addition, we perform calculations relevant for some experiments and explain the characteristics of these materials. (c) 2007 American Institute of Physics.

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By integrating a three-barrier, two-well resonant tunneling structure with a 1.2-mu m-thick, slightly doped n-GaAs layer, a photoinduced voltage shift on the order of magnitude of 100 mV in resonant current peaks has been verified at an irradiance of low light power density. The 1.2-mu m-thick, slightly doped n-GaAs layer manifests itself of playing an important role in enhancing photoelectric sensitivity. (c) 2005 Elsevier B.V. All rights reserved.

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In this study, we analyzed the operational characteristics of a 1.2-MW rice husk gasification and power generation plant located in Changxing, Zhejiang province, China. The influences of gasification temperature, equivalence ratio (ER), feeding rate and rice husk water content on the gasification characteristics in a fluidized bed gasifier were investigated. The axial temperature profile in the dense phase of the gasifier showed that inadequate fluidization occurred inside the bed, and that the temperature was closely related to changes in ER and feeding rate. The bed temperature increased linearly with increasing ER when the feeding rate was kept constant, while a higher feeding rate corresponded to a lower bed temperature at fixed ER. The gas heating value decreased with increasing temperature, while the feeding rate had little effect. When the gasification temperature was 700-800C, the gas heating value ranged from 5450-6400kJ/Nm3. The water content of the rice husk had an obvious influence on the operation of the gasifier: increases in water content up to 15% resulted in increasing ER and gas yield, while water contents above 15% caused aberrant temperature fluctuations. The problems in this plant are discussed in the light of operational experience of MW-scale biomass gasification and power generation plants.

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本工作通过较系统地研究Ziegler-Natta型钼催化体系对丁二烯聚合的催化作用,发现一类活性很高的钼催化剂。此类催化剂以无毒,资源丰富的加氢汽油为溶剂,活性已接近工业化的Ni、Co、Ti等体系。同时,本工作又找到了大幅度调节聚合物分子量和链结构的方法,发现了具有活性聚合特点的钼催化体系,初步考察了钼体系催化丁二烯聚合的动力学行为;并利用红外光谱,~(13)C-NRM、X-射线衍射和热分析等方法研究了所得聚合物的链结构和聚集态结构,对聚合物的基本性能也进行了初步考察,发现所得聚合物的一些基本性能超过天然橡胶。此类高活性钼催化剂由MoCl_4OR和(i-Bu)_2AlOAr组成,R为C_(8-18)烷基,Ar为芳基。本催化体系在70 ℃下催化丁二烯聚合时,催化剂用量为Mo/J摩尔比等于4 * 10~(-5)时,转化率可达78%。本体系聚合物分子量可用烯丙基卤等调节,其中烯丙基碘的效果最好。在Mo/J = 8 * 10~(-5)时,烯丙基碘/Mo摩尔比为0.1时即可使聚合物分子量下降约50万;烯丙基碘/Mo摩尔比为10时,聚合物重均分子量即小于20万(不加烯丙基碘为270万)。本体系聚合物分子量分布很窄,聚合温度为30 - 70 ℃时,_W/_n为1.5-2.0;_W/_n与聚合温度呈直线关系,利用外推法估计和动力学考察,本体系在-18 ℃左右有可能引发活性聚合。本体系聚丁二烯含有85%以上1,2-链节,其1,2-链节含量也可以用某些极性添加剂来调节。利用烯丙基碘做调节剂,可制得1,2-链节含量高达98%的聚丁二烯。烯丙基碘还可以调节聚合物链节的立体构型和序列分布;随着烯丙基碘用量的增加,间同1,2-链节增多,全同和无规1,2-链节减少,序列分布的有规性增加,链结构趋于规整。根据动力学初步研究结果,本体系催化丁二烯聚合的速度对单体浓度呈一级关系,表现活化能为17.07千卡/摩卡,催化剂利用率为4%,链增长速度常数为: k_(p30℃) = 40 (升/摩尔·分,下同), k_(p40℃) = 97, k_(p50℃) = 267, k_(p60℃) = 508, k_(p70℃) = 12077。本体系聚合物在烯丙基碘/Mo摩尔比小于2时,无论静态或拉伸下均为无定型;烯丙基碘/Mo摩尔比大于2而小于8时,静态下为无定型,而拉伸时产生结晶,与天然橡胶类似;烯丙基碘/Mo摩尔比大于8时,静态下亦有一定程度的结果。