Effect of extrusion ratio on the microstructure, texture and mechanical properties of (Mg/AZ91)(m)-SiCp composite

Cast Mg/SiCp and AZ91/SiCp composites were successfully hot extruded vis-a-vis cast and unreinforced Mg and AZ91 alloy up to low (R=15:1) and high (R=54:1) extrusion ratios at 350 degrees C. Significant matrix grain refinement was noticed after extrusion due to dynamic recrystallization; the degree of refinement being relatively higher for the two composites. The AZ91 based materials (AZ91 and AZ91/SiCp) exhibited comparatively finer grain size both in cast condition and after extrusion due to strong pinning effect from alloying elements as well as Mg17Al12 intermetallic phase. Compositional analyses eliminated the possibility of any interfacial reaction between matrix (Mg/AZ91) and second phase reinforcement (SiCp) in case of the composites. Texture evolution shows the formation of < 10 (1) over bar0 >parallel to ED texture fibre for all the materials after extrusion irrespective of SiCp addition or alloying which is primarily due to the deformation of the matrix phase. Micro-hardness did not significantly increased on extrusion in comparison to the respective cast materials for both composites and unreinforced alloys. Dynamic mechanical analysis, however, confirmed that the damping properties were affected by the extrusion ratio and to a lesser extent, due to the presence of second phase at room temperature as well as at higher temperature (300 degrees C). (C) 2014 Elsevier B.V. All rights reserved.

Viscosity bound for anisotropic superfluids in higher derivative gravity

In the present paper, based on the principles of gauge/gravity duality we analytically compute the shear viscosity to entropy (eta/s) ratio corresponding to the super fluid phase in Einstein Gauss-Bonnet gravity. From our analysis we note that the ratio indeed receives a finite temperature correction below certain critical temperature (T < T-c). This proves the non universality of eta/s ratio in higher derivative theories of gravity. We also compute the upper bound for the Gauss-Bonnet coupling (lambda) corresponding to the symmetry broken phase and note that the upper bound on the coupling does not seem to change as long as we are close to the critical point of the phase diagram. However the corresponding lower bound of the eta/s ratio seems to get modified due to the finite temperature effects.

Technologies for Measuring Currents in Coastal Environments, Portland, Maine, October 26-28, 2005:workshop proceedings

The Alliance for Coastal Technologies (ACT) Workshop entitled "Technologies for Measuring Currents in Coastal Environments" was held in Portland, Maine, October 26-28, 2005, with sponsorship by the Gulf of Maine Ocean Observing System (GoMOOS), an ACT partner organization. The primary goals of the event were to summarize recent trends in nearshore research and management applications for current meter technologies, identify how current meters can assist coastal managers to fulfill their regulatory and management objectives, and to recommend actions to overcome barriers to use of the technologies. The workshop was attended by 25 participants representing state and federal environmental management agencies, manufacturers of current meter technologies, and researchers from academic institutions and private industry. Common themes that were discussed during the workshop included 1) advantages and limitations of existing current measuring equipment, 2) reliability and ease of use with each instrument type, 3) data decoding and interpretation procedures, and 4) mechanisms to facilitate better training and guidance to a broad user group. Seven key recommendations, which were ranked in order of importance during the last day of the workshop are listed below. 1. Forums should be developed to facilitate the exchange of information among users and industry: a) On-line forums that not only provide information on specific instruments and technologies, but also provide an avenue for the exchange of user experiences with various instruments (i.e. problems encountered, cautions, tips, advantages, etc). (see References for manufacturer websites with links to application and technical forums at end of report) b) Regional training/meetings for operational managers to exchange ideas on methods for measuring currents and evaluating data. c) Organize mini-meetings or tutorial sessions within larger conference venues. 2. A committee of major stakeholders should be convened to develop common standards (similar to the Institute of Electrical and Electronics Engineers (IEEE) committee) that enable users to switch sensors without losing software or display capabilities. (pdf contains 28 pages)

High voltage cathodes for Na-ion batteries: Na3V2O2x(PO4)2F3-2x system

254 p : il, graf. col.

Administração de cafeína durante a gestação altera parâmetros testiculares na prole de camundongos C57/BL6 na vida adulta

Metabólitos ativos da cafeína apresentam toxicidade, podendo causar efeitos deletérios em muitos órgãos no período fetal pelo consumo materno. O estudo objetivou avaliar o papel da administração de cafeína durante a gestação em vários parâmetros importantes para a função testicular em camundongos adultos C57BL/6. Fêmeas grávidas foram divididas em: grupo controle (C), que receberam injeções de sol. salina (0,9% NaCl) e grupo cafeína (CF), que receberam diariamente injeções subcutâneas de 20 mg / kg de cafeína. Filhotes tiveram livre acesso à ração padrão desde o desmame até três meses de idade, quando foram mortos. O grupo CF apresentou uma redução no consumo alimentar (C = 4,36 0,14; CF = 3,79 0,05/g, p<0,05) e ganho de massa corporal (C = 25,73 0,14; CF = 21,08 0,41/g, p=0,0001). Ainda este grupo, apresentou alterações estruturais nos testículos da prole, como redução no peso relativo (C = 0,078 0,003; CF = 0,063 0,002/g, p=0,002), diâmetro tubular (C = 455,4 2,7; CF = 393,5 3,1/m, p=0,0001), lume tubular (C = 310,6 2,5; CF = 254,8 2,9/m, p=0.0001) e altura do epitélio seminífero (C = 144,8 0,9; CF = 138,7 1,3/m, p=0,0005) observados pela técnica de morfometria. Testosterona sérica avaliada por quimioluminescência foi reduzida (C = 6,6 2,8; CF = 0,5 0,2/ng/ml, p=0.04). Western Blotting foi utilizado para análise de expressão protéica. Houve aumento do receptor de leptina (C = 0,81 0,04; CF = 1,28 0,15/g, p=0,01), do receptor para o hormônio leteinizante (C = 0,92 0,05; CF = 0,74 0,05/g, p=0,01),da aromatase (C = 0,32 0,03; CF = 0,48 0,05/g, p=0,03) e do regulador pró apoptose (C = 0,27 0,02; CF = 0,42 0,03/g, p=0,01) enquanto o receptor para hormônio folículo estimulante (FSHR) (C = 0,76 0,06; CF = 0,56 0,04/g, p=0,02), o receptor para proteína reguladora da esteroidogênese (C = 1,009 0,065; CF = 0,584 0,060/g, p=0,0007), a proteína do fator de crescimento vascular endotelial (C = 0,33 0,08; CF = 0,05 0,01/g, p=0,009), o receptor de androgênio (C = 0,97 0,11; CF = 0,59 0,07/g, p=0,02) e o antígeno nuclear de proliferação celular (C = 0,93 0,11; CF = 0,48 0,07/g, p=0,01) foram reduzidos. Este estudo sugere que o consumo de cafeína durante a gravidez parece ser nocivo à fertilidade de animais machos, caracterizando o fenômeno de programação, o que gera alterações funcionais e estruturais nos testículos da prole adulta.

Increasing Creel Interview Efficiency Through Early Survey Termination

Operational modifications based on recreational angler activity patterns can be successfully formulated to increase creel survey efficiency without a significant loss of information. This study was conducted to estimate the amount of Texas marine sport-boat angler interview and retained fish data (bay and Gulf) that would be missed both coastwide and within each bay system if surveys were terminated early when no angler interviews were conducted by a specified time. Using this method, <3 percent of the total interviews and retained fish would be missed coastwide by terminating surveys at 1400 hours on weekends and 1600 hours on weekdays throughout the survey year. This would result in the early termination of 14 percent of the weekend surveys and 23 percent of the weekday surveys, thus allowing an annual redirection of 440 work-hours and $6,063 in operating expenses.

中国东北样带草原段关键种——羊草茎、叶显微结构的生态可塑性及群落功能群组成和多样性研究

陆地样带是国际地圈——生物圈计划(IGBP)研究中最引入注目的创新之一。目前，国际上已经设立了15条陆地样带，研究内容涉及环境梯度分析、气候变化对植被初级生产力的影响及环境变化、土地利用等与植被变化的对应关系等。沿该陆地样带分布较广的关键种生理适应性等方面对影响其生理功能形态结构的研究较少，特别是茎、叶等组织功能研究较少。 中国东北样带(NECT)是全球陆地样带的重要组成部分，多年来已开展了大量深入系统的研究工作，已成为我国生态学、地学等学科的重要研究平台。本研究以中国东北样带中西段广泛分布的重要关键种——羊草（Leymus chinensis）为研究对象，分析了羊草茎、叶显微结构的生态可塑性及其与水分利用效率的关系，进而阐述了羊草适应不同生境条件，特别是适应水分变化的机制，为揭示羊草及其种群、群落乃至以羊草为优势种或建群种的草地生态系统在全球变化背景下的发展趋势提供理论依据。 基于2001年7～8月第3次中国东北样带考察资料，采用高精度Olympus显微镜及C同位素分析技术（δ13C判别值），结合在野外取样过程中测定的样地土壤含水量和海拔高度，以及近十年各样地年降水量和年均温度气象资料，分析了羊草茎、叶显微结构和水分利用变化与环境因子的关系，以及以羊草为建群种或共建种的无牧和放牧样地群落生物量、物种多样性和植物功能型组成变化与环境因子的关系。 结果表明：羊草叶片表面及内部主要显微结构特征参数各样地间有不同程度的差异，其中气孔密度与降水量呈线性正相关。代表气孔开张程度的气孔长度和宽度变化与土壤含水量呈线性相关。叶表面角质层厚度与海拔高度变化关系较大，并以上表面角质层厚度变化最为明显，主要受海拔高度升高引起的紫外线照射增强的影响。运动细胞带宽度占叶面积比虽然与各环境因子关系不很密切，但温度变化的影响较突出，这一显微结构调整与气孔变化构成干旱——高温调节机制。叶片表面毛茸的变化也是非常显著的，但与各环境因子关系密切程度均不大，可以肯定的是在土壤水分状况较好的生境下羊草叶片表面毛茸密度及长度明显增加，而一些干旱生境中常表现为毛茸较少、较短，个别样地基本没有发育较好的毛茸。总体上看，羊草叶片对干旱化的形态结构调整以气孔密度和开张程度的变化最大，是羊草叶片调节水分利用效率的重要适应性生态可塑性调整。 与叶片相比，羊草茎横切面结构特征的变化与各环境因子关系的显著性不是很强，但各样地间的差异是比较显著的，许多结构调整可能与土壤养分条件的变化有一定关系，如茎秆粗度变化、基本薄壁组织厚度和中央空腔（髓腔）直径的变化等，但本研究未能涉及这方面内容，有待于进一步研究。 羊草水分利用效率与降水量和土壤含水量呈显著的负相关关系，即随降水量和土壤含水量增大羊草水分利用效率明显降低，蒸腾耗水增大，这一生理变化与显微结构的调整关系密切，特别是气孔密度与气孔宽度在水分较差生境中明显减小，从而有利于适应干旱环境，减少耗水量。表现比较突出的是非地带性林西样地，其降水量处于10个样地的中等偏低水平，但其δ13C判别值较低，达-26.063‰，与降水量较大的长岭、双辽样地几乎相当，并比相邻的林东和克旗样地明显低，其气孔密度、开张程度及叶脉后生导管直径均较高（大），但其土壤水分状况是最好的样地之一，尽管取样时不幸遇到雨天，但从其群落类型——羊草杂类草草甸，并伴生许多中、湿生种类上看，其生境的湿润程度是毋庸置疑的。这一非地带性样地中羊草结构的变化从另一侧面反映了羊草显微结构调整对水分环境的适应。δ13C判别值是一个非常敏感的参数，在分析植物水分利用效率及其相关领域的研究中应深入利用。 群落植物功能群组成与环境因子及群落初级生产力关系研究结果表明，丛生禾草生长型功能群、旱生和中旱生植物水分生态类型功能群具有明显的地带性变化规律，并与群落生物量变化关系密切，变异性较低，占群落生物量比例较大，可考虑作为植物功能型组合对无牧样地植被变化进行评估和预测。在放牧影响下，C4植物光合类型功能群呈现明显的地带性变化，并在群落中所起的作用明显增强，亦可考虑作为评估和预测植被变化的植物功能型组合。无牧样地与放牧样地研究结果均表明，按Raunkiaer划分的地面芽、地下芽、地上芽和一年生植物生活型功能群，其地带性变化不明显，或变异率高，或占群落生物量比例小，不宜作植物功能群组合对植被变化进行评估和预测。

The genetic diversity of Acipenser stellatus populations in the Caspian Sea was studied using microsatellite technique

A total of 361 caudal fin samples were collected from adult A. stellatus specimens caught in the north Caspian Sea, including specimens from Kazakhstan (Ural River), Russia (Volga River), Azerbaijan (Kura River), specimens caught in the south Caspian Sea including specimens from Fishery Zone 1 (from Astara to Anzali), Fishery Zone 2 (from Anzali to Ramsar), Fishery Zone 3 (from Nowshahr to Babolsar), Fishery Zone 4 (from Miyankaleh to Gomishan) as well as from specimens caught in Turkmenistan (all specimens were collected during the sturgeon stock assessment survey). About 2 g of fin tissue was removed from each caudal fin sample, stored in 96% ethyl alcohol and transferred to the genetic laboratory of the International Sturgeon Research Institute. Genomic DNA was extracted using phenol-chloroform method. The quality and quantity of DNA was assessed using 1% Agarose gel electrophoresis and Polymerase Chain Reaction (PCR) was conducted on the target DNA using 15 paired microsatellite primer. PCR products were electrophoresed on polyacrylamide gels (6%) that were stained using silver nitrate. Electrophoretic patterns and DNA bands were analyzed with BioCapt software. Allele count and frequency, genetic diversity, expected heterozygosity and observed heterozygosity allele number, and the effective allele number, genetic similarity and genetic distance, FST and RST were calculated. The Hardy Wienberg Equilibrium based on X2 and Analysis of Molecular Variance (AMOVA) at 10% confidence level was calculated using the Gene Alex software. Dendrogram for genetic distances and identities were calculated using TFPGA program for any level of the hierarchy. It is evident from the results obtained that the 15 paired primers studied, polymorphism was observed in 10 pairs in 12 loci, while one locus did not produce DNA bands. Mean allele number was 13.6. Mean observed and expected heterozygosity was 0.86 and 0.642, respectively. It was also seen that specimens from all regions were not in Hardy Wienberg Equilibrium in most of the loci (P≤0.001). Highest Fst (0.063) was observed when comparing specimens from Fishery Zone 2 and Fishery Zone 4 (Nm=3.7) and lowest FST (0.028) was observed when comparing specimens from the Volga River and those from the Ural River (8.7). Significant differences (P<0.01) were observed between RST recorded in the specimens studied. Highest genetic distance (0.604) and lowest genetic resemblance (0.547) were observed between specimens from Fishery zones 2 and 4. Lowest genetic distance (0.311) and highest genetic resemblance (0.733) was observed between specimens from Turkmenistan and specimens from Fishery zone 1. Based on the genetic dendrogeram tree derived by applying UPGMA algorithm, A. stellatus specimens from Fishery zone 2 or in other words specimens from the Sepidrud River belong to one cluster which divides into two clusters, one of which includes specimens from Fishery zones 1, 3 and 4 and specimens from Turkmenistan while the other cluster includes specimens from Ural, Volga and Kura Rivers. It is thus evident that the main population of this species belongs to the Sepidrud River. Results obtained from the present study show that at least eight different populations of A. stellatus are found in the north and south Caspian Sea, four of which are known populations including the Ural River population, the Volga River population, the Kura River population and the Sepidrud River populations. The four other populations identified belonging to Fishery zones 1, 3, and 4 and to Turkmenistan are most probably late or early spawners of the spring run and autumn run of each of the major rivers mentioned. Specific markers were also identified for each of the populations identified. The Ural River population can be identified using primers Spl-68, 54b and Spl-104, 163 170, 173, the Volga River population can be identified using primers LS-54b and Spl-104, 170, 173 113a and similarly the population from the Kura River can be identified using primers LS-34, 54b and Spl-163, 173 and that from the Sepidrud River can be identified using primers LS-19, 34, 54b and Spl-105, 113b. This study gives evidence of the presence of different populations of this species and calls for serious measures to be taken to protect the genetic stocks of these populations. Considering that the population of A. stellatus in Fishery zone 2 is an independent population of the Sepidrud River in the Gilan Province, the catch of these fishes in the region needs to be controlled and regulated in order to restore the declining stocks of this species.

Effects of external magnetic field on the effective g factor of (Ga,Mn)As

With the help of time resolved magneto-optic Kerr rotation measurements, the optically induced spin precession in heavily doped diluted magnetic semiconductor Ga0.937Mn0.063 As was observed. It was found that the effective g factor increases with increasing magnetic field, which is attributed to the magnetic-field-induced increase of the density of the non-localized holes. Those free holes will couple with the localized magnetic ions by p-d interactions, leading to the formation of spontaneous magnetization in Ga0.937Mn0.063As, which in turn to the enhancement of the effective g factor.

Kinetic Model Study on Enzymatic Hydrolysis of Cellulose Using Artificial Neural Networks

Enzymatic hydrolysis of cellulose was highly complex because of the unclear enzymatic mechanism and many factors that affect the heterogeneous system. Therefore, it is difficult to build a theoretical model to study cellulose hydrolysis by cellulase. Artificial neural network (ANN) was used to simulate and predict this enzymatic reaction and compared with the response surface model (RSM). The independent variables were cellulase amount X-1, substrate concentration X-2, and reaction time X-3, and the response variables were reducing sugar concentration Y-1 and transformation rate of the raw material Y-2. The experimental results showed that ANN was much more suitable for studying the kinetics of the enzymatic hydrolysis than RSM. During the simulation process, relative errors produced by the ANN model were apparently smaller than that by RSM except one and the central experimental points. During the prediction process, values produced by the ANN model were much closer to the experimental values than that produced by RSM. These showed that ANN is a persuasive tool that can be used for studying the kinetics of cellulose hydrolysis catalyzed by cellulase.

Replacement of methane from quartz sand-bearing hydrate with carbon dioxide-in-water emulsion

The replacement of CH4 from its hydrate in quartz sand with 90:10, 70:30, and 50:50 (W-CO2:W-H2O) carbon dioxide-in-water (C/W) emulsions and liquid CO2 has been performed in a cell with size of empty set 36 x 200 mm. The above emulsions were formed in a new emulsifier, in which the temperature and pressure were 285.2 K and 30 MPa, respectively, and the emulsions were stable for 7-12 h. The results of replacing showed that 13.1-27.1%, 14.1-25.5%, and 14.6-24.3% of CH4 had been displaced from its hydrate with the above emulsions after 24-96 It of replacement, corresponding to about 1.5 times the CH4 replaced with high-pressure liquid CO2. The results also showed that the replacement rate of CH4 with the above emulsions and liquid CO2 decreased from 0.543, 0.587, 0.608, and 0.348 1/h to 0.083, 0.077, 0.069, and 0.063 1/h with the replacement time increased from 24 to 96 h. It has been indicated by this study that the use of CO2 emulsions is advantageous compared to the use of liquid CO2 in replacing CH4 from its hydrate.

外磁场对(Ga,Mn)As有效g因子的影响

利用时间分辨Kerr旋光技术测量低温下稀磁半导体Ga_(0.937)Mn_(0.063)As中光注入极化载流子的自旋进动信号,并观察到自旋极化载流子的有效g因子值随外磁场的增强而增大的反常现象.这归结于磁场导致局域化空穴转化为非局域化空穴,从而使自发磁化强度增强,有效g因子值增大.基于此物理图像,进一步给出了(Ga,Mn)As的有效g因子与外磁场的关系式.

Multi-armed poly(L-glutamic acid)-graft-oligoethylenimine copolymers as efficient nonviral gene delivery vectors

Background The application of polyethylenimine (PEI) in gene delivery has been severely limited by significant cytotoxicity that results from a nondegradable methylene backbone and high cationic charge density. It is therefore necessary to develop novel biodegradable PEI derivates for low-toxic, highly efficient gene delivery.Methods A series of novel cationic copolymers with various charge density were designed and synthesized by grafting different kinds of oligoethylenimine (OEI) onto a determinate multi-armed poly(L-glutamic acid) backbone. The molecular structures of multi-armed poly(L-glutamic acid)-graft-OEI (MP-g-OEI) copolymers were characterized using nuclear magnetic resonance, viscosimetry and gel permeation chromatography. Moreover, the MP-g-OEI/DNA complexes were measured by a gel retardation assay, dynamic light scattering and atomic force microscopy to determine DNA binding ability, particle size, zeta potential, complex formation and shape, respectively. MP-g-OEI copolymers were also evaluated in Chinese hamster ovary and human embryonic kidney-293 cells for their cytotoxicity and transfection efficiency.