A Viscoelastic Constitutive Model with Nonlinear Evolutionary Internal Variables

Based on the internal variable theory, a viscoelastic constitutive model of a highly deformable continuous medium is proposed. A set of second rank tensorial internal state variables corresponding to Biot's strain is introduced, and a nonlinear evolution

亚热带森林外生菌根真菌的生态学研究

菌根是一种植物营养根与土壤真菌形成的共生体，在自然界中分布广泛。外生菌根真菌是菌根真菌的重要类群，其宿主植物约占陆地植物总数的3%左右。由于外生菌根真菌的宿主植物常常是一些生态系统的优势种和建群种，并且这些真菌还参与了许多森林生态系统的有机和无机元素循环、物种的竞争和共存、生物多样性的维持、生态系统的演替等过程，因而对外生菌根真菌的研究有助于对这些生态系统维持和演替机制的深入理解。本文通过外生菌根真菌的种类鉴定和多样性，外生菌根真菌种群的遗传结构，外生菌根真菌群落的结构、空间格局及植物-菌根真菌空间关系，外生菌根真菌接种对植物生长和竞争的影响等四个方面的研究，使我们对这一地区的外生菌根真菌的种类组成、空间分布和传播规律、年度变化、以及对植物群落组成和多样性的影响等方面，有一个初步了解。 外生菌根真菌的鉴定和种类组成是进行菌根真菌研究的前提之一。在第一章中，主要通过子实体形态分类和分子方法，对大型真菌的种类进行了鉴定。在对东灵山和都江堰森林的调查中分别发现的大型真菌106种和98种，菌根真菌比例分别为44.3%和69.4%，木生真菌比例分别为16%和10.2%。按Fellner的评价标准，两个森林群落均属于健康的生态系统。我们应用ITS-RFLP和ITS序列比较的方法对地上子实体、地下菌根及分离培养的菌种进行了种类鉴定和分析。结果表明，ITS-RFLP可以用来进行外生菌根真菌的种类鉴定，而序列分析能够提供更为可靠的信息。二者的结合，可以使我们建立菌根真菌分子数据库成为可能。 种群遗传结构的研究包括种群中个体的空间分布和亲缘关系等方面，有助于加深我们对种群的生殖和传播方式，菌根真菌与风、雨、动物等生态因子的关系等方面的理解。第二章主要以两个外生菌根真菌种群为例，对种群遗传结构中空间距离与遗传相似性的关系、种群结构的年度变化等方面进行了探讨。正红菇（Russula vinosa）种群具有较高的遗传多样性，每个子实体来自不同的克隆。空间距离-遗传相似性关系和空间格局分析的结果均表明，这一正红菇的种群结构可能是由短距离孢子传播产生的，而不可能是无性生长或长距离孢子传播形成的。在对隐花青鹅膏菌（Amanita manginiana）连续两年的种群结构进行了研究中，种群的每一个子实体也均来自不同的克隆。遗传相似性分析、AMOVA、遗传相似性-空间距离关系的结果均显示，这两年的种群在遗传相似性和种群结构上均具有显著差异。对此的一个合理的解释就是，这一外生菌根真菌种群来说，其个体由有性孢子发育为子实体的时间可能超过一年，因而2001和2002年的个体并非同一种群的连续世代。 外生菌根真菌群落可以定义为在一定地理范围和时间尺度内不同外生菌根真菌种群的组合。对外生菌根真菌群落的研究有助于揭示森林生态系统中菌根真菌与植物、菌根真菌与环境因子、以及菌根真菌之间的相互关系。在第三章中，我们应用点格局的分析方法和二元逻辑回归分析对外生菌根真菌的主要类群，即鹅膏菌科，牛肝菌科和红菇科，的空间格局及其与周围（5×5米样方）树种组成的关系进行研究。结果表明，某些树种与特定类群菌根真菌的子实体出现有负相关，而三个类群的外生菌根真菌在克隆生长上的差异并不是子实体空间分布的决定因素。而在较小尺度上（450平方米样方）研究也表明，三个主要外生菌根真菌类群的空间分布为聚集半径不等的集群分布，并且其空间分布不依赖于木本植物的分布。外生菌根真菌主要类群在空间分布上具有相互抑制的特点，而抑制能力的大小可能与菌根真菌地下菌丝体的分布范围及连续性有关。 外生菌根真菌的盆栽接种实验通常用来验证菌根真菌-宿主植物的相互关系，不但有理论意义，也是大田实验和大规模生产应用的基础。第四章中进行了两个实验，对外生菌根真菌多样性与宿主植物生长的关系以及菌根真菌与植物之间竞争平衡的关系进行了初步研究。在外生菌根真菌多样性对马尾松生长影响实验中，菌根真菌接种并未显著促进马尾松幼苗的生长和生物量积累，不同的菌种与地上、地下生物量的积累存在不同（正或负）的相关关系。外生菌根真菌的多样性水平与马尾松幼苗的针叶数量存在显著的正相关，并且随接种时间的延长相关关系更为显著。外生菌根真菌多样性水平还与马尾松幼苗地下生物量的累积呈显著的正相关关系。在外生菌根真菌对三种植物的竞争平衡和共存的影响实验中，外生菌根真菌接种没有显著促进马尾松幼苗的生长，但对漆树和枹栎幼苗的生长有显著影响。外生菌根真菌接种能够在两个外生菌根真菌宿主植物竞争中降低枹栎对马尾松的优势，在马尾松和漆树的竞争中降低马尾松的优势，并促使枹栎与漆树（一个外生菌根真菌宿主和一个非宿主植物）的竞争处于不稳定状态。 本文首次通过生态学的角度对外生菌根真菌的物种多样性、种群结构、群落中的空间格局、以及外生菌根真菌与植物生长的关系进行了较为全面的研究。在大型真菌的多样性方面，菌根和木生真菌比例的引入可以完善森林生态系统的健康评价体系，而分子数据库的建立使对大型真菌尤其是外生菌根真菌多样性的长期监测成为可能;在种群遗传结构方面，本文验证了红菇属和鹅膏菌属克隆较小的特点，以及红菇属菌根真菌以短距离孢子传播为主的繁殖特性，并首次从生活史特点的角度解释菌根真菌的种群结构的年度差异;在菌根真菌群落的空间格局方面，本文首次应用二元逻辑回归和点格局分析的方法研究外生菌根真菌的空间分布及菌根真菌－植物关系，并发现三个类群的外生菌根真菌在子实体分布上具有相互排斥的特点;在控制实验中，本文首次研究了菌根真菌接种的多样性水平对宿主植物的影响，首次研究了外生菌根真菌接种对三个物种之间竞争与共存的影响。虽然这些研究在很多方面都仅得到初步的结果，但我们希望这些探索可以为今后对外生菌根真菌的生态学研究提供有益的启示。

玉米 rbcL 基因与兰藻 rbcS 基因定向融合及它们在宿主大肠杆菌中的表达

二磷酸核酮糖羧化酶/氧化酶(简称Rubisco, EC, 4.1.1.39)是绿色植物光合作用中参与固定CO2的关键酶。在高等植物，该酶是由8个分子量为55KD的大亚基(LSU)和8个分子量为14KD的小亚基(SSU)构成的16聚体。每个大亚基有四个活性中心，具有双向催化功能，其编码基因位于叶绿体基因组大单拷贝区;小亚基功能还不清楚，它由核基因组编码且有几个拷贝;未成熟小亚基N端有一段transit peptide，靠它的定向跨越叶绿体膜。迄今为止，取自几种植物材料的这二种亚基的氨基酸顺序和编码基因的核苷酸顺序分析业已完成。为该酶的遗传操作奠定了必要的基础。 由于Rubisco与人类利用太阳能和提高作物产量直接相关，所以成为通过生物技术进行改造的重大项目。 巢状假囊细菌(Anacyslis nidulans) R2是一种不含限制性内切酶的单细胞原核生物，能营光合作用，其Rubisco大亚基的氨基酸顺序与玉米的LSU同源性高达80%，但是第四个活性部位(Leu 456位)与玉米不同(Sys, 459位)，由此导致其对CO2的亲合力降低。另一方面，其rbcL与rbcS仅相隔93个bp，且同属一个操纵子。这意味着有可能用同源DNA片段等位交换的办法来改造其rbcL基因。 根据现有的资料，设计出玉米rbcL与兰藻rbcS定向重组于pUC119的兰图：先从pANP1155中切出0.7kb含蓝藻rbcS的PstI-HindIII片段，克隆进pUC119的lacZ启动子下游得pTAS28，采用Reverse primer作引物进行核苷酸顺序分析，确认蓝藻rbcS基因座落在pTAS28正链上。随后从pZmc460中切出包含玉米rbcL基因1.7kb的BglII-HincII片段，将它插入pTAS28的HincⅡ-BamHⅠ双酶切位点，得到pTMN3;为了比较，在另一个质粒pTMN7于1.7kb片段之前加进0.1kb的PstI-HaeIII蓝藻DNA。根据玉米rbcL基因核苷酸顺序（1218-1251）合成一个Oligonucleotide probe，对这三个质粒的总RNA抽提物进行Northern Blot，得到明显的杂交斑点;接着用菌体总蛋白冻干品进行了Western分析，并以新鲜的玉米和烟草叶片为对照，得到阳性结果。显然这二种基因重组之后仍能在宿主E. coli中正常表达。 真正的挑战应是下一步用上述二种质粒转化兰藻A. nidulans R2，考查其能否整合进基因组并表现出较低的氧化酶活性。

The brave new era of human genetic testing

The commercialization of 'big science' is in full swing, leading to situations in which the ethical principles of academia are beginning to be compromised. This is exemplified by the profitable business of genetic ancestry testing. The goals of this sort

眼镜蛇毒神经生长因子对成年猫坐骨神经损伤后的作用

目的　探讨从眼镜蛇毒分离纯化出的神经生长因子(nerve grow th facto r, N GF) 对成年猫坐骨神经 损伤后的影响。方法　制成成年猫坐骨神经损伤模型, 损伤局部注射蛇毒N GF 2 Lgö(kg·d) , 分别治疗10 d 和30 d, 并与对照组(损伤坐骨神经, 不给药物) 比较。结果　术后10 d, 对照组术侧远端神经纤维数量比治疗组明显减少 (P < 0. 01) , 治疗组术侧足底刺激出现早, 肢体活动恢复快。术后30 d, 治疗组术侧远端神经纤维大量再生, 再生神 经纤维数量已明显超过对照组和术后10 d 组水平(P < 0. 01) , 但结构紊乱, 轴突和郎氏结消失。术侧肢体在连续注 射N GF 16 d 左右出现足底刺激反应消失, 肢体瘫痪等改变。结论　眼镜蛇毒N GF 在神经损伤早期应用能减轻神 经纤维发生的溃变, 促进受损神经的再生与功能恢复; 而损伤局部长时间注射蛇毒N GF 则会导致神经纤维增生过 度, 丧失传导功能。

Food composition and dietary overlap of macroinvertebrates in a shallow eutrophic lake in China: spatial and temporal variations

The present study was conducted in Lake Donghu, a suburban eutrophic lake arising from the middle reaches of the Yangtze River, China. Food composition of 32 taxa of zoobenthos was analyzed from 1251 gut samples. Macroinvertebrate primary consumers ingested mainly detritus, sand grains and diatoms. The predators primarily preyed on rotifers, crustaceans, oligochaetes and chironomid larvae. The dietary overlap was relatively high among collector taxa but low among other macroinvertebrates. Food composition and dietary overlap of macroinvertebrates changed considerably, both spatially and temporally. Food web structure differed between inshore and offshore regions of Lake Donghu. The inshore web was relatively complex and dynamic whereas the offshore web was simple and stable. Taxon-specific changes of diet seem to have little effect on the benthic food web structure in offshore waters of a eutrophic lake.

Temperature dependence of the formation of nano-scale indium clusters in InAlGaN alloys on Si(111) substrates

The temperature dependence of the formation of nano-scale indium clusters in InAlGaN quaternary alloys, which are grown by metalorganic chemical vapour deposition on GaN/Si(111) epilayers, is investigated. Firm evidence is provided to support the existence of phase separation, or nano-scale In-rich clusters, by the combined results of high-resolution transmission electron microscopy (HRTEM), high-resolution x-ray diffraction (HRXRD) and micro-Raman spectra. The results of HRXRD and Raman spectra indicate that the degree of phase separation is strong and the number of In clusters in the InAlGaN layers on silicon substrate is higher at lower growth temperatures than that at higher growth temperatures, which limits the In and Al incorporated into the InAlGaN quaternary alloys. The detailed mechanism of luminescence in this system is studied by low temperature photoluminescence (LT-PL). We conclude that the ultraviolet (UV) emission observed in the quaternary InAlGaN alloys arises from the matrix of a random alloy, and the second emission peak in the blue-green region results from the nano-scale indium clusters.

GaInNAs/GaAs multiple-quantum well resonant-cavity-enhanced photodetectors at 1.3 mu m

A GaInNAs/GaAs multiple quantum well (MQW) resonant-cavity enhanced photodetector (RCF-PD) operated at a wavelength of 1.3 mum with the full width at half maximum of 4nm has been demonstrated. The GaInNAs RCE - PD was grown by molecular beam epitaxy using a homemade ion-removed dc plasma cell as a nitrogen source. GaInNAs/GaAs MQW shows a strong exciton peak at room temperature, which is very beneficial for applications in long-wavelength absorption devices. For a 100 mum diameter RCE-PD, the dark current is 20 and 32 pA at biases of 0 and 6 V, respectively, and the breakdown voltage is - 18 V. The measured 3 dB bandwidth is 308 MHz, which is limited by the resistance of p-type distributed Bragg reflector mirror. The tunable wavelength in a range of 18 nm with the angle of incident light was observed.

Fast Discrimination of Commerical Corn Varieties Based on Near Infrared Spectra

The existing methods for the discrimination of varieties of commodity corn seed are unable to process batch data and speed up identification, and very time consuming and costly. The present paper developed a new approach to the fast discrimination of varieties of commodity corn by means of near infrared spectral data. Firstly, the experiment obtained spectral data of 37 varieties of commodity corn seed with the Fourier transform near infrared spectrometer in the wavenurnber range from 4 000 to 12 000 cm (1). Secondly, the original data were pretreated using statistics method of normalization in order to eliminate noise and improve the efficiency of models. Thirdly, a new way based on sample standard deviation was used to select the characteristic spectral regions, and it can search very different wavenumbers among all wavenumbers and reduce the amount of data in part. Fourthly, principal component analysis (PCA) was used to compress spectral data into several variables, and the cumulate reliabilities of the first ten components were more than 99.98%. Finally, according to the first ten components, recognition models were established based on BPR. For every 25 samples in each variety, 15 samples were randomly selected as the training set. The remaining 10 samples of the same variety were used as the first testing set, and all the 900 samples of the other varieties were used as the second testing set. Calculation results showed that the average correctness recognition rate of the 37 varieties of corn seed was 94.3%. Testing results indicate that the discrimination method had higher precision than the discrimination of various kinds of commodity corn seed. In short, it is feasible to discriminate various varieties of commodity corn seed based on near infrared spectroscopy and BPR.

Broadband external cavity tunable quantum dot lasers with low injection current density

Broadband grating-coupled external cavity laser, based on InAs/GaAs quantum dots, is achieved. The device has a wavelength tuning range from 1141.6 nm to 1251.7 nm under a low continuous-wave injection current density (458 A/cm(2)). The tunable bandwidth covers consecutively the light emissions from both the ground state and the 1st excited state of quantum dots. The effects of cavity length and antireflection facet coating on device performance are studied. It is shown that antireflection facet coating expands the tuning bandwidth up to similar to 150 nm, accompanied by an evident increase in threshold current density, which is attributed to the reduced interaction between the light field and the quantum dots in the active region of the device.

神二2号机组保温状况的测试、分析及改进建议

介绍了神二2号机组保温状况，进行了热力测试，找出了机组在保温方面存在的问题，分析了保温不良对机组的影响，并提出了改进建议