Structural, morphological, and magnetic characteristics of Cu-implanted nonpolar GaN films

Diluted magnetic nonpolar GaN:Cu films have been fabricated by implanting Cu ions into unintentionally doped nonpolar a-plane(1 1 (2) over bar 0) GaN films and a subsequent thermal annealing process. The structural, morphological and magnetic characteristics of the samples have been investigated by means of high-resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM), and superconducting quantum interference device (SQUID). The sample shows a clear ferromagnetism behavior at room temperature. It is significantly shown that with a Cu concentration as low as 0.75% the sample exhibits a saturation magnetization about 0.65 mu(B)/Cu atom. Moreover, the possible origin of the ferromagnetism for the sample was also discussed briefly. (C) 2009 Elsevier B. V. All rights reserved.

A logic for default reasoning

The need to make default assumptions is frequently encountered in reasoning about incompletely specified worlds. Inferences sanctioned by default are best viewed as beliefs which may well be modified or rejected by subsequent observations. It is this property which leads to the non-monotonicity of any logic of defaults. In this paper we propose a logic for default reasoning. We then specialize our treatment to a very large class of commonly occuring defaults. For this class we develop a complete proof theory and show how to interface it with a top down resolution theorem prover. Finally, we provide criteria under which the revision of derived beliefs must be effected.

Grimm1．107颗粒物分析仪和rp2000气溶胶采样仪在北京城区的测试对比

IEECAS SKLLQG

呼中自然保护区多年冻土活动层厚度的影响因子分析

以大兴安岭呼中国家级自然保护区为对象,调查了该区多年冻土的活动层厚度,并利用多重对比分析和相关分析方法,对多年冻土活动层的影响因子进行了分析。结果表明,多年冻土活动层厚度与多个环境因子之间存在着复杂的关系。土壤含水量、地形条件和不同群落对于活动层厚度具有重要影响,而活动层厚度也会反作用于这些影响因子。其中,土壤表层含水量与活动层厚度呈极显著负相关(P<0.001)。地形坡度和活动层厚度呈显著正相关(P=0.006)。几乎每个样带的海拔与活动层厚度都有显著的相关性,但在整个研究区域内海拔与活动层厚度不存在相关性。这说明活动层厚度的变异仅在本研究的样带尺度上具有规律性,而这种规律性在稍大尺度上会消失。对于不同的群落活动层厚度的多重对比分析表明,群落的差异对活动层厚度也有明显的影响,其中狭叶杜香-泥炭藓群落更有利于多年冻土的保存。

粘液繁殖体及其生态功能

对粘液繁殖体的概念、粘液性质、粘液繁殖体的研究现状及粘液繁殖体研究中存在的问题进行了论述。分布在干旱区的十字花科、爵床科、菊科等植物具有粘液繁殖体。有关粘液繁殖体的研究集中在具有粘液繁殖体植物的识别、粘液形态结构及成分、粘液溶出机制及过程、粘液繁殖体的生态功能等几个方面。尽管已有研究表明,粘液繁殖体具有促进种子远距离传播、促进繁殖体的萌发及苗的发育、使种子免受摩擦损害和动物捕食等生态功能,但目前人们对粘液繁殖体的生态意义尚不十分清楚,从多物种比较研究中阐明粘液繁殖体生态意义的研究尚很少见。继续识别具有粘液繁殖体的植物,改善现有的研究手段,加强粘液繁殖体对植被恢复价值的研究是目前粘液繁殖体研究面临的挑战。

基于氢键识别的分子设计

利用ＡＭ１方法研究了３，４二羰基苯乙胺与一系列双氨基化合物的分子识别作用。结果表明，双氢键的形成有利于体系能量的降低，并且具有亲疏水环境相一致的分子对有更稳定的能量状态。基于上述讨论，提出了微观环境匹配的识别分子设计原则。

牙鲆免疫系统和抗病力的研究

本文主要以一龄牙鲆为研究对象，研究了牙鲆免疫系统的组成，以初步探讨牙鲆的抗病机制，并为牙鲆生理状况的诊断建立快捷的方法；研究了牙鲆主要消化酶的活性，为牙鲆的营养强化进行基础性的研究；研究了含有大麻哈鱼生长激素基因的重组酵母菌对牙鲆的生长和非特异性免疫能力的影响；同时对牙鲆热激蛋白hsp70的cDNA进行了合成和扩增。本论文共包括四个部分，由十个实验组成，每个实验的研究内容介绍如下：实验1 利用姬姆萨染色技术观察了牙鲆血细胞的显微结构。结果表明，牙鲆的血细胞由红细胞和白细胞组成，两类细胞的显微结构具有明显的差异；红细胞有细胞核，在血细胞的组成中占较高比例；不同种类的白细胞其结构不同，实验中发现了血栓细胞、淋巴细胞、单核细胞；但是只凭借光学显微形态的差异难以对白细胞进行更确切的分类。实验2 利用透射电镜技术对牙鲆外周血细胞的超显微结构进行了观察。牙鲆的血细胞可以分为红细胞和白细胞；白细胞包括淋巴细胞、血栓细胞、单核细胞、粒细胞；粒细胞包含两种类型；实验中还发现了类似巨噬细胞的一类细胞，但未发现浆细胞的存在。实验3 利用区带毛细管电泳技术对牙鲆血清蛋白的组成进行了分析。实验条件下，牙鲆的血清蛋白主要包含三种类型，即P2.59, P1.60, P0.77。三种蛋白的分子量和稳定性各不相同，初步判断这三种蛋白主要为白蛋白、α球蛋白和β球蛋白。实验4和实验5 对溶菌酶和抗蛋白酶物质在假雄牙鲆体内的分布以及不同在组织和器官中的比活性进行了研究。溶菌酶广泛分布于牙鲆的体表粘液、鳃、血清、消化组织和脾、肾等组织中；抗蛋白酶物质广泛分布于体表粘液、鳃、血清、肌肉中。在不同的组织和器官中，这种酶的比活性不完全相同。体表粘液、血清、肝脏、前肠、肾、鳃中溶菌酶的比活性较高；胃、中肠、后肠、脾中溶菌酶的比活性较低；胆汁中溶菌酶的比活性最低。血清和体表粘液中抗蛋白酶物质的比活性较高，鳃和肌肉中抗蛋白酶物质的比活性较低。由实验结果可知，鳃和消化道在牙鲆抵抗病原微生物侵袭的过程中发挥着重要的作用。实验6 对碱性磷酸酶在牙鲆体内不同消化器官中的分布进行了研究。碱性磷酸酶在牙鲆的胃、肝脏、肠中广泛分布。在前肠和中肠部位酶的比活性较其它部位的高。胃中碱性磷酸酶的比活性随季节的不同没有显著变化，而肠和肝脏中酶的比活性随季节的不同具有较显著的变化。实验 7 对牙鲆体内消化酶的比活性进行了研究。在牙鲆的胃、前肠、中肠、后肠中可以检测出蛋白酶、脂肪酶、酶、纤维素酶的活性。胃中的蛋白酶主要为酸性蛋白酶，肠中的蛋白酶主要为碱性蛋白酶。肠中蛋白酶的比活性由前肠向后肠递减，前肠与中肠酶的比活性没有显著差异；牙鲆肠中脂肪酶的比活性较胃中的高，在肠的不同部位脂肪酶的比活性无显著差异；牙鲆前肠中酶的比活性最高，胃中的次之，中肠、后肠中淀粉酶的比活性较低；牙鲆的胃及肠道不同部位处的纤维素酶的比活性没有显著差异。随着牙鲆的生长，蛋白酶、脂肪酶、纤维素酶的比活性增强，酶的比活性减弱；其中胃和中肠内纤维素酶的比活性增强得较显著。实验8和实验9 研究了重组酵母菌对牙鲆的生长、血清中某些激素的含量、血清蛋白的含量，以及血清中溶菌酶和抗蛋白酶物质的比活性等生理指标的影响。通过投喂重组酵母菌，可以提高牙鲆血清中生长激素的含量，影响牙鲆血清中甲状腺激素和三碘甲状腺原氨酸的含量，促进牙鲆的生长，同时能够增加牙血清蛋白的含量，增强牙鲆血清中溶菌酶和抗蛋白酶物质的比活性。牙鲆体内生长激素含量的增加以及酵母菌细胞壁中的多糖成分都能够增强牙鲆的非特异性免疫能力。实验 10 对牙鲆肝脏中热激蛋白hsp70的cDNA序列进行了合成和PCR扩增。在实验条件下能够合成750bp左右的核酸序列，为进一步利用热激蛋白hsp70作为生理指标来诊断牙鲆的生理状态，以及研究热激蛋白在牙鲆抵抗外界胁迫中所发挥的作用提供了基础。

A Simulative Study on Effects of Climate Warming on Nutrient Contents and In Vitro Digestibility of Herbage Grown in Qinghai-Xizang Plateau

The increasing trend of air temperature along with the climate warming has been accepted gradual-ly by scientists and by the general public. Qinghai-Xizang Plateau, a unique geographic unit due to high-altitude climate, is one of the most susceptible regions to climate warming. Its ecosystem is very fragile and sensi-tive to climate change. In order to get a better understanding of the impacts of climate warming on the nutrient contents of herbage grown in Qinghai-Xizang Plateau, a simulative study was implemented at Daban Moutain by using temperature differences resulted from sites selected at different altitudes and nutrient contents and in vitro digestibility were determined for assessing the quality of the grown herbage. There were significant downtrends in crude protein (CP), ether extract (EE) and nitrogen free extract (NFE) contents of herbage along with the increase of temperature. It had a positive correlation between temperature and content of acid detergent fibre (ADF), acid detergent lignin (ADL) in herbage. In vitro digestibility of herbage decreased along with the in-crease of temperature. The results of this study indicated that climate warming significantly influence nutrient contents and in vitro digestibility of herbage grown in Qinghai-Xizang Plateau. It is suggested that the future climate warming especially the gradual rise of the night temperature could cause negative effect on herbage quality grown in Qinghai-Xizang Plateau by decreasing CP, EE, and NFE contents and increasing some indi-gestible ingredients such as crude fibre (CF), neutral detergent fibre (NDF), ADF, and ADL. This, conse-quently, decreases the ruminant assimilation ability.

Molecular systematics and biogeography of Crawfurdia, Metagentiana and Tripterospermum (Gentianaceae) based on nuclear ribosomal and plastid DNA sequences

Background and Aims The systematic position of the genus Metagentiana and its phylogenetic relationships with Crawfurdia, Gentiana and Tripterospermum have not been explicitly addressed. These four genera belong to one of two subtribes (Gentianinae) of Gentianeae. The aim of this paper is to examine the systematic position of Crawfurdia, Metagentiana and Tripterospermum and to clarify their phylogenetic affinities more clearly using ITS and trnL intron sequences.Methods Nucleotide sequences from the internal transcribed spacers (ITS) of nuclear ribosomal DNA and the plastid DNA trnL (UAA) intron were analysed phylogenetically. Ten of fourteen Metagentiana species were sampled, together with 40 species of other genera in the subtribe Gentianinae.Key Results The data support several previously published conclusions relating to the separation of Metagentiana from Gentiana and its closer relationships to Crawfurdia and Tripterospermum based on studies of gross morphology, floral anatomy, chromosomes, palynology, embryology and previous molecular data. The molecular clock hypothesis for the tested sequences in subtribe Gentianinae was not supported by the data (P < 0.05), so the clock-independent non-parametric rate smoothing method was used to estimate divergence time. This indicates that the separation of Crawfurdia, Metagentiana and Tripterospermum from Gentiana occurred about 11.4-21.4 Mya (million years ago), and the current species of these three genera diverged at times ranging from 0.4 to 6.2 Mya.Conclusions The molecular analyses revealed that Crawfurdia, Metagentiana and Tripterospermum do not merit status as three separate genera, because sampled species of Crawfurdia and Tripterospermum are embedded within Metagentiana. The speciation and rapid radiation of these three genera is likely to have occurred in western China as a result of upthrust of the Himalayas during the late Miocene and the Pleistocene.

储层注聚合物后测井评价研究

Since physical properties and resistivity of mixed formation fluid change after polymer and water flood reservoir, transformational electric properties of water and polymer flooded zones challenges log interpretation. Conventional log interpretation methods to water flooded reservoirs cannot be employed to water and polymer flooded zones. According to difficulties in water and polymer flooded zones interpretation, we analyzed the variation of electric properties of mixed formation fluid, reservoir parameters and log correspondences, then got further understanding of the applicability of Archie Equations. As the results, we provided reservoir parameter evaluation model in water and polymer flooded zones in this paper. This research shows that micro pore structure, physical parameters and electric correspondence of reservoirs change after being flooded by water and polymer. The resistivity variation of mixed formation fluid depends mainly on affixation conductivity of polymer and salinity of formation water, which is the key to log interpretation and evaluation. Therefore, we summerized the laws of log correspondence in different polymer injection ways, developed electric discrimination model for water and polymer flooded zones, as well as charts to identify flooding conditions with resistivity and sonic logs. Further rock-electric tests and conductive mechanism analysis indicate that the resistivity increasing coefficient(I) and water saturation(Sw) are still in concordance with classical Archie Equations, which can be utilized in quantitative evaluation on water and polymer flooded reservoirs. This sets of methods greatly improved accuracy in water and polymer flooded zone evaluation.