Numerical Analysis of LEC Growth of GaAs with an Axial Magnetic Field

A set of numerical analyses for momentum and heat transfer For a 3 in. (0.075 m) diameter Liquid Encapsulant Czochralski (LEC) growth of single-crystal GaAs with or without all axial magnetic field was carried Out using the finite-element method. The analyses assume a pseudosteady axisymmetric state with laminar floats. Convective and conductive heat transfers. radiative heat transfer between diffuse surfaces and the Navier-Stokes equations for both melt and encapsulant and electric current stream function equations Cor melt and crystal Lire considered together and solved simultaneously. The effect of the thickness of encapsulant. the imposed magnetic field strength as well as the rotation rate of crystal and crucible on the flow and heat transfer were investigated. (C) 2002 Published by Elsevier Science Ltd.

Constant volume combustion of aluminum and cornstarch dust in microgravity

The subject of the present work is to report an experimental comparative study of the effect of dispersion-induced turbulence on dust combustion in constant volume vessel, carried out both in normal gravity and in microgravity environment. Dispersion system with small scale of turbulence, creating uniform homogeneous mixture, was used in experiments. To improve reproducibility of the explosion data an ignitor of small energy, with local soft ignition was developed. Both factors contributed to acquisition of more reproducible experimental data. In experiments under microgravity conditions a dust suspension during combustion remains constant. This makes possible to study dust explosion under stationary dust suspension without influence of turbulence.

室温铁磁性半导体Mn_xGa_(1-x)Sb

采用离子注入、离子沉积及后期退火方法制备了稀磁半导体单晶Mn_xGa_(1-x)Sb，在室温下（300 K）获得了单晶的磁滞回线。用X射线衍射方法分析了铁磁性半导体单晶Mn_xGa_(1-x)Sb的结构，用电化学C-V法分析了单晶的载流子浓度分布。由X射线衍射得知，Mn_xGa_(1-x)Sb中Mn含量逐渐由近表面处的x = 0.09下降到晶片内部的x = 0。电化学C-V测得单晶的空穴浓度高达1 * 10~(21)cm~(-3)，表明Mn_xGa_(1-x)Sb单晶中大部分Mn原子占据Ga位，起受主作用。

Phase-sensitive atom localization in a loop Lambda-system

The behaviour of the Lambda-system has been studied theoretically in the context of atom localization. In addition to the probe field and the standing wave driving field, a microwave field is introduced to couple the two lower states, and as a result our Lambda-system forms a closed loop. Therefore phase-sensitive atom localization is expected. Indeed by appropriate choice of the relative phase between three fields, an improvement by a factor of 2 has been found in the detection probability of atoms within the sub-wavelength domain of the standing wave. The effect of other parameters is also investigated.

Time domain synthesis of electro-optical birefringent system for optical waveform generation

In this paper is described a novel technique for producing an electro-optical intensity synthesizer which can generate different periodic time domain waveforms through only sine or cosine wave applied-voltages. The synthesizer presented here consists of a series of stages between two polarizers, with each stage consisting of an electro-optic element and a compensator. Every electro-optical element has the same applied-voltage function but different azimuth angles and ratios between the longitudinal and transverse lengths. The main principle is the synthesis of an electro-optic effect and a polarization interference effect in the time domain. This technique is based on an expanded Fourier positive-direction searching algorithm, which can not only simplify the calculation process but also produces many choices of structural parameters for different waveforms generation. A three-stage synthesis of an electro-optical birefringent system for continuous square waveform is undertaken to prove the principle.

中国碎米蕨类及其相关类群的系统学研究

通过形态学、解剖学、孢粉学、植物地理学及分子系统学等方面的研究，探讨了中国碎米蕨类及其相关类群的系统关系，并对它们的分类进行了修订。 1.解剖学 对碎米蕨类及相关类群36个种的叶表皮特征进行了研究，结果发现该性状对于划分大的类群具有一定的系统学意义。大多数中国蕨科成员如粉背蕨属、旱蕨属和黑心蕨属等连同裸子蕨科中的泽泻蕨属和金毛裸蕨属在叶表皮性状上比较一致。它们之间的亲缘关系较近，是碎米蕨类成员。金粉蕨属、粉叶蕨属、翠蕨属和铁线蕨属与上述类群不同，其上表皮细胞或上下表皮细胞均明显加长，但气孔器仍同碎米蕨类植物一样，为无规则型、极细胞型或腋下细胞型。在所研究的类群中，只有凤尾蕨属和Anopteris的气孔器为聚合型。 2.孢粉学 在光镜和扫描电镜下对中国蕨科、裸子蕨科和凤尾蕨科等83种 (含变种) 植物的孢子进行了观察。根据孢子的颜色、结构和表面纹饰等可将其分成3种类型：大多数中国蕨科成员如粉背蕨属等和裸子蕨科中的泽泻蕨属和金毛裸蕨属的孢子同属第一种类型，颜色较深，表面纹饰由周壁形成。珠蕨属和凤丫蕨属的孢子属第二种类型，颜色较淡，周壁薄，由外壁和周壁共同形成表面纹饰。金粉蕨属、凤尾蕨属、翠蕨属和粉叶蕨属的孢子为第三种类型，颜色较浅，由外壁形成表面纹饰的基本轮廓，具明显的赤道翼。从孢粉学的角度来看，中国蕨科和裸子蕨科都是不自然的。中国蕨属和薄鳞蕨属的孢子形态同粉背蕨属相似，应并入后者。另外，同属新旧世界的种类其孢子纹饰往往有明显的区别, 可能代表了不同的类群。 3.分子系统学 测定了碎米蕨类及相关类群34种植物的rbcL 和trnL-F序列，并结合GenBank上下载的相关资料进行分析。结果发现中国蕨科和裸子蕨科都不是自然类群。在系统树上，Cheilanthes、隐囊蕨属、粉背蕨属、旱蕨属、黑心蕨属等同裸子蕨科中的泽泻蕨属和金毛裸蕨属等聚在一起，构成碎米蕨群。珠蕨属、凤丫蕨属和Llavea则形成另一分支，不是碎米蕨类成员。金粉蕨属在分支图上与南亚的Actiniopteris形成姐妹群，并与凤尾蕨属、粉叶蕨属和翠蕨属等关系近缘，放入凤尾蕨类应更为合适。 系统分析的结果表明，旧世界分布的类群与美洲的同属植物大都关系疏远，如黑心蕨属、金毛裸蕨属和Cheilanthes等。另外，亚洲分布的中国蕨属、粉背蕨属、碎米蕨属、薄鳞蕨属、隐囊蕨属和拟旱蕨属Mildella的成员聚在一起，它们之间的系统关系因为形成了多歧分支而没有得到很好的解决。但是，薄鳞蕨属、中国蕨属和大理碎米蕨等同粉背蕨属的成员聚在一起，并入后者应更为合理。另外，宜昌旱蕨与碎米蕨属的成员关系近缘，支持将前者转入碎米蕨属。 4.植物地理学 碎米蕨类植物的间断分布非常明显。泽泻蕨和戟叶黑心蕨等在形态特征上与美洲的同属种类有明显的区别，可能代表了不同的类群。大多数亚洲碎米蕨类成员如粉背蕨属、中国蕨属和薄鳞蕨属等以中国西南部的横断山区或喜马拉雅为分布中心，可能与喜马拉雅山的隆起有关。 5.分类处理 综合各方面的研究成果，作者认为国产碎米蕨类包括6个属3个群：黑心蕨属、旱蕨属、粉背蕨属、碎米蕨属、拟泽泻蕨属和拟金毛裸蕨属。《中国植物志》中记载的隐囊蕨属、毛旱蕨和旱蕨类成员因其系统学位置不清，暂时作为独立的群处理。 在野外考察和大量标本（包括模式）考证的基础上，对国产碎米蕨类及其相关类群 (特别是粉背蕨属) 进行了修订, 澄清了一些种的分类问题。发现1新种，对1新变种进行了拉丁文描述，使其名称有效。提出新组合5个，另有6种7变种被首次归并。

植物对重金属砷和镉胁迫适应的分子机理初探

随着现代工业的发展，重金属污染日趋严重。重金属污染引发的环境和健康问题在许多国家都有报道，我国的重金属污染状况也不容乐观。土壤和水体中的重金属污染可以通过食物链进入人体，对人类健康造成很大的危害，如诱发癌症 和畸胎等。 植物修复是一种利用植物对重金属或有机污染物的超富集能力清除或减低污染的环境生物技术。植物修复的生物学机制的研究为这项技术走向实用化奠定了基础。植物修复近期的进展可能来自于可更有效地富集重金属的植物品种的选择、土壤条件的改善等;但长远看来，植物修复技术的巨大进步将取决于新的可更好地抵抗重金属或降解有机毒物的基因的鉴定和克隆，并通过转基因技术创造一批新的植物品种，如可迅速大量富集重金属的高生物量的用作环境净化的植物，以及可排拒重金属吸收的粮食、蔬菜和水果等作物。 本研究针对砷污染的植物修复机制，以超富集砷的凤尾蕨属植物——蜈蚣草为试材取得了如下进展： 1． 以从砷污染地区采集的蜈蚣草（Pteris vittataL．）为植物材料，利用抑制消减杂交(SSH)分离了经砷诱导处理与其对照间表达有差异的cDNA片段，以期得到与砷富集密切相关的基因。其中筛选到的一个cDNA片段与ABC transporter (ATP-binding cassette transporter)有较高的同源性。通过RACE方法对该基因进行了克隆，并进行了初步的结构和功能分析。结果表明所获得的PvABCTl (Accession No. AY496966)为一全长cDNA，长度为2165 bp，其中开读框架为1791 bp，编码597个氨基酸。该基因所编码的蛋白中含有2个ABC transporter特性结构域，1个ATP-binding cassette和2个ATP/GTP结合位点(P-loop)，没有明显的跨膜区。 2． 对蜈蚣草在砷胁迫下PvABCT1基因的表达模式进行了研究。转录水平分析表明PvABCT1的表达受砷的诱导。进一步通过PvABCTl-GFP融合基因在洋葱细胞中的表达进行亚细胞定位，结果显示该基因可能定位于细胞质中。 3． 为了研究所克隆的PvABCT1基因的功能，本研究构建了PvABCT1的酵母表达载体，把该基因转入因ACR3基因缺失而对砷敏感的酵母突变株。酵母功能互补实验表明PvABCT1不仅不能与ACR3基因功能互补，反而使酵母对砷的敏感性增加，同时酵母细胞中的砷含量较未转化的酵母细胞增加。即在转入PvABCT1后，酵母细胞吸收了更多的砷。这暗示该基因与蜈蚣草中砷的高吸收有关。 针对食品重金属污染问题，本研究探讨了减低蔬菜对重金属吸收的方法及其 作用机理，取得了如下进展： 1．研究了钙离子和镧离子对镉离子胁迫下生菜种子萌发和植株生长的影响，结果表明在种子萌发时外施4 mM CaCI2或0.04 mg/L La(N03)3均可提高生菜对重金属镉的抗性。 2．通过检测0.5 mM CdCl2胁迫下生菜植株中的镉含量以及外施钙离子或镧离子后相应的镉含量，发现4 mM CaCl2可以增加镉胁迫下生菜植株中镉的积累;而0.04 mg/L La(N03)3可以降低镉胁迫下生菜植株中镉的积累。 3．对生菜中植物络合素合酶基因进行了克隆，通过RT-PCR分析以及植物络合素( phytochelatins，PCs)的检测，探讨了外施钙离子或镧离子对镉胁迫下生菜植株中植物络合素合酶基因在转录水平的表达量、植物络合素含量以及镉的积累三者之间的关系。结果表明：4 mM CaCl2可以提高镉胁迫下生菜植株中植物络合素合酶基因在转录水平的表达以及植物络合素的含量，增加镉的积累;而0.04 mg/L La(N03)3虽然同样可以提高植物络合素合酶基因在转录水平的表达以及植物络合素的含量，却能降低镉胁迫下生菜植株中镉的积累。这暗示外施钙离子可以促进用于重金属污染环境修复的植物对重金属的吸收，而外施镧离子可以用于降低叶菜类蔬菜中重金属镉的积累。

无指盘臭蛙免疫调节肽、其基因和变异体及其在制药中的应用

本发明涉及无指盘臭蛙免疫调节肽、基因和变异体及其在制药中的应用，属生物医学技术领域。无指盘臭蛙免疫调节肽是一种环状多肽，分子量1791.12道尔顿，等电点 9.84，无指盘臭蛙免疫调节肽的全序列为：Thr Ser Arg Cys Tyr Ile Gly Tyr Arg Arg Lys Val Val Cys Ser(TSRCYIGYRRKVVCS)，其第4位的半胱氨酸和第14位的半胱氨酸形成分子内二硫键。编码的基因由307个核苷酸组成，其中编码成熟部分的为第 141-186位核苷酸。无指盘臭蛙免疫调节肽原始序列中第4个氨基酸发生替代所产生的变异体，人工合成的无指盘臭蛙免疫调节肽及其变异体具有强烈的免疫调节活性和肿瘤抑制活性，作为制备免疫调节、肿瘤治疗和化疗药物的应用。本发明还具有序列简单、合成方便等优点。

High rate of chimeric gene origination by retroposition in plant genomes

Retroposition is widely found to play essential roles in origination of new mammalian and other animal genes. However, the scarcity of retrogenes in plants has led to the assumption that plant genomes rarely evolve new gene duplicates by retroposition, de

异硫氰酸苯酯衍生化法测定微透析样品中氨基酸的方法

本发明涉及一种异硫氰酸苯酯衍生化法测定脑内透析样品中氨基酸的方法，属生物医学领域。该方法由样品的采集(即脑内微透析)、样品的衍生和干燥以及HPLC分离等组成。实验前一周，在动物特定部位埋植透析导管。待恢复后，安装透析探针，并以一定流速灌流人工脑脊液，间隔一定时间收集一次透析样品。然后，在样品中加入一定量的内标试剂，经冷冻干燥、异硫氰酸苯酯衍生、再干燥、稀释等步骤处理后，样品经反相HPLC洗脱，紫外检测。本发明具有简便快速、衍生产物稳定、分析时间短、化学选择性和分析灵敏度高(可达1pmol)、一、二级氨基酸均可检测的分析方法，由此可实现微透析与反相高压液色谱紫外检测技术结合对脑内痕量活性物质的动态监测。

铈对微囊藻的生长效应及被富集的动力学研究

研究了稀土元素Ce4+对铜绿微囊藻生长效应及其被铜绿微囊藻富集的动力学过程。结果表明:当Ce4+的添加浓度小于0.2mg/L时,对铜绿微囊藻的生长有促进作用,当Ce4+的添加浓度大于0.2mg/L时铜绿微囊藻的生长受到抑制。Ce4+在铜绿微囊藻中富集的动力学过程可用二级吸附动力学模型表征。

Effect of water temperature on the growth performance and digestive enzyme activities of Chinese longsnout catfish (Leiocassis longirostris Gunther)

The present study was carried out to investigate the influence of water temperature on the growth performance and digestive enzyme (pepsin, trypsin and lipase) activities of Chinese longsnout catfish. Triplicate groups of Chinese longsnout catfish (35.6 +/- 0.48 g, mean +/- SE) were reared at different water temperatures (20, 24, 28 and 32 degrees C). The feeding rate (FR), specific growth rate (SGR) and feed efficiency ratio (FER) were significantly affected by water temperatures and regression relationships between water temperature and FI, SGR as well as FER were expressed as FR=-0.016T2+0.91T-10.88 (n=12, R2=0.8752), SGR=-0.026T2+1.39T-17.29 (n=12, R2=0.7599) and FER=-0.013T2+0.70T-8.43 (n=12, R2=0.7272). Based on these, the optimum temperatures for FR, SGR and FER were 27.66, 26.69 and 26.44 degrees C respectively. The specific activities of digestive enzymes at 24 or 28 degrees C were significantly higher than that at 20 or 32 degrees C. In addition, there was a significant linear regression between FR or SGR and specific activities of pepsin and lipase, which indicated that pepsin and lipase played important roles in regulating growth through nutrient digestion in Chinese longsnout catfish.

Bioaccumulative characteristics of hexabromocyclododecanes in freshwater species from an electronic waste recycling area in China

Hexabromocyclododecanes (HBCDs) are now emerging ubiquitous contaminants due to their wide usage, persistence and toxicities. To investigate the bioaccumulative characteristics of HBCDs, sediments, Winkle (Littorina littorea), crucian carp (Carassius carassius) and loach (Misgurnus anguillicaudatus) were collected from two streams near an E-waste dismantling site in China. and HBCD exposure test was then conducted on Chinese rare minnow. The concentration of HBCDs was 14 ng g(-1) dry weight in sediments, 186. 377 and 1791 ng g(-1) lipid weight in winkle, crucian carp and loach, respectively. gamma-HBCD was found to be the dominant diastereoisomer in the sediments (63% of total HBCDs). However, alpha-HBCD was selectively accumulated in the biotic samples and contributed to 77%, 63% and 63% of total HBCDs in winkle, crucian carp and loach, respectively. Moreover, an enrichment of (-)-enantiomers of alpha- and gamma-HBCD were found in the winkle. The reverse results were observed in the crucian carp and loach. Similar observations of diastereoisomeric and enantiomeric composition were obtained in Chinese rare minnow with those found in the crucian carp and loach. These results indicate that the freshwater species from the streams are contaminated by HBCDs. alpha-HBCD can be selectively accumulated in organisms and the accumulative characteristics are enantioselective among species. (C) 2009 Elsevier Ltd. All rights reserved.