Initial development of microdamage under impact loading

In this paper, the initial development of microdamage in material subjected to impulsive loading was investigated experimentally and analytically with controllable short-load duration. Based on a general solution to the statistical evolution of a one-dimensional system of ideal microcracks, a prerequisite to experimental investigation of nucleation of microcracks was derived. By counting the number of microcracks, the distribution of nucleation of microcracks was studied. The law of the nucleation rate of microcracks can be expressed as a separable function of stress and cracksize. It is roughly linear dependence on loading stress. The normalized number density of microcracks is in agreement with that of a second-phase particle.

慢性吗啡给予、戒断及再给药过程中大鼠海马感觉门控的动态变化

药物成瘾被认为是药物长期作用于脑而产生的一种慢性复吸性脑疾病,长期反复的药物(如吗啡)滥用会导致一系列严重后果,如药物依赖、药物耐受、强迫性药物寻求等.本实验利用条件化位置偏好(conditioned place preference,CPP)模型来检测大鼠对吗啡依赖和心理渴求等过程;采用双声刺激听觉诱发电位来研究大鼠在慢性吗啡给予、戒断以及再给药过程中海马感觉门控(N40)的动态变化.吗啡组大鼠注射吗啡(10mg/kg,i.p.)12d,经历第一次戒断12d,再次注射吗啡(2.5mg/kg,i.p.)1d,之后经历第二次戒断2d;对照组大鼠注射同体积生理盐水,其余实验条件与吗啡组相同.CPP实验表明,这种药物给予方法促使大鼠对吗啡产生药物依赖和心理渴求.双声刺激诱发电位实验表明,吗啡组大鼠在吗啡给予期间海马感觉门控受到损伤;第一次戒断期的第1～2天海马感觉门控能力减弱,第3天增强,第4～12天逐渐恢复到正常水平;再次给予吗啡后海马感觉门控能力与对照组相比显著降低,并且随后2d的戒断期内海马感觉门控能力也一直保持较低水平,表明再次给药使大鼠海马感觉门控对吗啡更加敏感化.结果提示,长期反复的吗啡给予及再给药干扰了海马的感觉门控能力,吗啡成瘾对大脑可能产生长期影响.

利用夏季自然发情的云南黄牛进行奶牛胚胎移植效果研究

利用夏季自然发情的云南黄牛为受体,开展了奶牛体内冷冻胚胎移植.留用的114头受体牛中,本地黄牛59头,年龄在3～10岁,均为经产牛,最终移植27头,西杂牛56头(其中2岁以下的青年牛26头),移植29头(青年牛11头),两个品种受体利用率分别为45.8%和51.8%;移植后妊娠率分别为59.3%和55.2%;解冻的63枚胚胎移植给了56头受体牛,A级胚胎单独移植和B、C级胚胎搭配移植最终妊娠结果分别是58.5%(24/41)和53.3%(8/15);发情后第6 d和第7 d移植妊娠率分别为56%和58.1%.结果表明,1～10岁的西杂牛和3～10岁体型较大的本地黄牛均可作为受体移植奶牛胚胎;利用自然发情的云南黄牛做受体移植效果较为理想,是一种经济、方便、适合云南广大农村推广的技术途径;A级胚胎单独移植和B、C级搭配移植可获得较为理想的妊娠结果;处于发情后第6 d和第7 d的云南黄牛都可以作为桑囊期奶牛胚胎的移植受体.

滇金丝猴栖息地植物多样性研究

采用路线调查与标准地调查相结合的方法,结合历史资料,对滇金丝猴栖息地的野生植物资源进行了实地野外调查研究,分析了植物多样性及其受威胁状况.结果表明:(1)栖息地具有丰富的植物物种多样性,有维管束植物217科789属3533种(含亚种、变种),其中,国家重点保护野生植物有117种;(2)该区植物区系成分具有复杂性、多样性,明显偏重于温带性质、且植物区系起源古老,有中国特有分布属90个,其中,古特有属59个;(3)该区具有丰富的植被类型,包括4个植被型组,10个植被型,47个群系,具有较高的保护和科研价值.同时针对栖息地植物多样性受威胁状况,提出了植被恢复、生态移民及社区共管是保护植物多样性的有效措施.

TEMPERATURE EFFECT ON POROUS SILICON LUMINESCENCE

A theoretical surface-state model of porous-silicon luminescence is proposed. The temperature effect on the PhotoLuminescence (PL) spectrum for pillar and spherical structures is considered, and it is found that the effect is dependent on the doping concentration, the excitation strength, and the shape and dimensions of the Si microstructure. The doping concentration has an effect on the PL intensity at high temperatures and the excitation strength has an effect on the PL intensity at low temperaturs. The variations of the PL intensity with temperature are different for the pillar and spherical structures. At low temperatures the PL intensity increases in the pillar structure, while in the spherical structure the PL intensity decreases as the temperature increases, at high temperatures the PL intensities have a maximum for both models. The temperature, at which the PL intensity reaches its maximum, depends on the doping concentration. The PL spectrum has a broader peak structure in the spherical structure than in the pillar structure. The theoretical results are in agreement with experimental results.

STUDIES OF THE PROMISING MATERIAL COSI2 ON GAAS SUBSTRATES

The thermal stability of CoSi2 thin films on GaAs substrates has been studied using a variety of techniques. The CoSi2 thin films were formed by depositing Co(500 angstrom) and Si(1800 angstrom) layers on GaAs substrates by electron-beam evaporation followed by annealing processes, where the Si inter-layer was used as a diffusion/reaction barrier at the interface. The resistivity of CoSi2 thin films formed is about 30 muOMEGA cm. The Schottky barrier height of CoSi2/n-GaAs is 0.76 eV and the ideality factor is 1.14 after annealing at 750-degrees-C for 30 min. The CoSi2/GaAs interface is determined to be thermally stable and the thin film morphologically uniform on GaAs after 900-degrees-C/30 s anneal. The CoSi2 thin films fulfill the requirements in GaAs self-aligned gate technology.

落叶松人工林养分循环与养分利用效率研究

通过对抚顺市温道林场20、53和69年生长白落叶松（Larix olgensis）人工林生物量和营养元素的积累与分配、养分利用效率和养分再吸收效率、养分生物循环的研究，探讨了长白落叶松生长发育不同阶段的养分生态学特征；对东北林业大学帽儿山实验林场17年生兴安落叶松（Larix gmelinii）人工林进行5年的施肥（NH4NO3，15 g•m-2•a-1），研究了施肥对人工林养分生物循环的影响。结果表明： （1）20、53和69年生单株落叶松生物量分别为33.14 kg•tree-1、311.42 kg•tree-1和408.46 kg•tree-1，随林龄的增长而增加。各器官生物量的分配格局为：树干>根>树枝>树皮>针叶。树干生物量的分配比例为50.16%~69.20%，随林龄的增长比例增大，而其他器官生物量的分配比例则逐渐减小。20、53和69年生单株落叶松净生产力分别为3.04 kg•tree-1•a-1、9.68 kg•tree-1•a-1和10.21 kg•tree-1•a-1，随林龄的增长而增大。针叶和树干的净生产力最大，分别占整株林木净生产力的40.07%~47.93%和27.32%~40.97%，并且随林龄的增长而增大。树枝、树皮和根的净生产力则表现出随林龄的增长呈抛物线状。 （2）20、53和69年生单株落叶松N、P、K、Ca、Mg等5种营养元素的总贮量分别为308.14 g•tree-1、2021.01 g•tree-1和2485.24 g•tree-1，随林龄的增长而增加。5种营养元素的贮量大小为：Ca>N>K>Mg>P。树干养分贮量的分配比例为19.74%~34.23%，随林龄的增长呈抛物线状。针叶、树枝和树皮的养分贮量占整株林木养分贮量的比例为35.16%~45.59%，建议在采伐木材时实施去皮、打枝等措施，留下针叶、树枝和树皮在林地中，让其自然分解以使营养元素重新归还利用，对于维持林地的养分平衡和长期生产力具有积极作用。 （3）20、53和69年生单株落叶松年吸收养分量分别为35.31 g•tree-1•a-1、97.83 g•tree-1•a-1和100.08 g•tree-1•a-1，随林龄的增长而增加。5种营养元素的年吸收量大小为：Ca>N>K>Mg>P。落叶松的养分利用效率随林龄的增长而增大，但生长到一定年龄阶段后，其养分利用效率逐渐趋于稳定。落叶松的最佳采伐年龄应为养分利用效率保持稳定时的年龄，此时采伐单位干材所带走的林地养分量较少。不同营养元素的利用效率不同，P的利用效率最高，Mg、K次之，N、Ca最低。不同器官的养分利用效率不同，树干的养分利用效率最高，其次是根、树枝、树皮，针叶最低。随着林龄的增长，树干和根的养分利用效率增大，而树枝和树皮的养分利用效率减小。 （4）落叶松叶片的N再吸收效率为50.76%~55.11%，随林龄的增长表现出增大的趋势；P和K再吸收效率分别为64.38%~68.85%和87.85%~90.62%，随林龄的增长表现出减小的趋势。从养分利用效率和养分再吸收效率综合判断，本研究区落叶松生长可能受土壤N、P、K供应的限制，3种营养元素的限制作用大小为：K>P>N。 （5）落叶松人工林养分的年吸收量、年存留量和年归还量分别为51.94~78.35 kg•hm-2•a-1、17.77~29.43 kg•hm-2•a-1和34.18~48.92 kg•hm-2•a-1，均随林龄的增长而减少，这与林分密度逐渐减小有关。5种营养元素的年吸收量和年存留量大小均为：Ca>N>K>Mg>P，年归还量大小为：Ca>N>Mg>K>P。落叶松人工林的养分循环速率为0.624~0.658，随林龄的增长而增大。5种营养元素的循环速率以Mg、N最快，Ca、P次之，K最慢。K的循环速率较低，可能与研究区土壤K含量较低而表现出的K再吸收效率较高有关。 （6）施肥导致落叶松叶片N再吸收效率显著降低，而凋落叶片的N浓度显著增加，从而使凋落叶片的C/N比由80.29降低到60.29。施肥林地凋落叶片C/N比的降低使其分解速率加快，有利于其养分归还土壤，从而加快了系统的养分循环速率，提高了系统的养分利用率。因此，在人工林经营中，施肥不仅能提高林地生产力，而且对于维持林地养分循环具有积极作用。

不同土地利用和施肥方式对土壤酶活性及相关肥力因子的影响

以中国科学院海伦农业生态实验站长期定位试验为平台,研究了不同土地利用和施肥方式对土壤酶活性和相关肥力因子的影响,结果表明,种植苜蓿和土地休闲两种方式与裸地相比脲酶、转化酶、磷酸酶、过氧化氢酶活性、土壤全碳、全氮含量和碱解氮、速效磷、速效钾含量均显著增加。其中,脲酶活性增加了24.5%和25.0%,转化酶活性增加了18.4%和18.9%,磷酸酶活性增加了54.6%和50.4%,过氧化氢酶活性增加了8.52%和59.3%,土壤全碳、全氮含量分别增加了13.8%、13.0%和36.8%、33.7%,但苜蓿和休闲两种方式间无显著差异。不同施肥方式间相比,土壤酶活性、土壤全碳、全氮及土壤有效养分含量相差显著,其高低顺序为:NPKOM(氮、磷、钾肥+有机肥)>NPKST(氮、磷、钾肥+秸秆)>NPK(氮、磷、钾肥)>CK(无肥)处理;施肥特别是施有机肥,显著提高了土壤酶活性,使土壤全碳、全氮、有效养分含量显著增加。这表明黑土经自然恢复和人工恢复及施肥后土壤肥力提高,土壤质量得到改善。

Profiling of Complex Microbial Populations by Denaturing Gradient Gel Electrophoresis Analysis of Polymerase Chain Reaction-Amplified Genes Coding for 16S rRNA

We describe a new molecular approach to analyzing the genetic diversity of complex microbial populations. This technique is based on the separation of polymerase chain reaction-amplified fragments of genes coding for 16S rRNA, all the same length, by denaturing gradient gel electrophoresis (DGGE). DGGE analysis of different microbial communities demonstrated the presence of up to 10 distinguishable bands in the separation pattern, which were most likely derived from as many different species constituting these populations, and thereby generated a DGGE profile of the populations. We showed that it is possible to identify constituents which represent only 1% of the total population. With an oligonucleotide probe specific for the V3 region of 16S rRNA of sulfate-reducing bacteria, particular DNA fragments from some of the microbial populations could be identified by hybridization analysis. Analysis of the genomic DNA from a bacterial biofilm grown under aerobic conditions suggests that sulfate-reducing bacteria, despite their anaerobicity, were present in this environment. The results we obtained demonstrate that this technique will contribute to our understanding of the genetic diversity of uncharacterized microbial populations.

沈阳西郊污灌区农田铜锌铅污染特征分析

为评价污水灌溉区农田土壤重金属污染状况,采用单因子指数和综合多因子指数法,对沈阳西郊污灌区农田土壤重金属铜锌铅的污染特征进行了研究。结果表明,于洪区宁官、高明、胡孤家和四台子四个样点土壤均受到三种重金属污染,其中宁官点0～10 cm土层铜、锌、铅含量分别达到69.74 mg.kg-1、275.09 mg.kg-1和81.83mg.kg-1,分别是当地土壤背景值的2.82、4.59和3.60倍。各样点土壤有效态铜、锌、铅含量也远高于未受污染地区的平均含量,土壤铜、锌、铅有效态含量占全量的比例分别为4.65%～15.46%、1.36%～3.84%和5.46%～18.86%。说明沈阳西郊污灌区农田土壤重金属污染较严重,必须通过工程、生物及化学措施进行长期的污染治理。

Determination of diphenhydramine by capillary electrophoresis with tris(2,2 '-bipyridyl)ruthenium(II) electrochemiluminescence detection

Tris(2,2'-bipyridyl)ruthenium(II) electrochemiluminescence detection in a capillary electrophoresis separation system was used for the determination of diphenhydramine. In this study, platinum disk electrode (300 mum in diameter) was used as a working electrode and the influence of applied potential and buffer conditions were investigated. Under optimal conditions: 1.2 V applied potential, pH 8.50, 15 kV separation voltage and 10 mmol l(-1) running buffer, the calibration curve of diphenhydramine was linear over the range of 4 x 10(-8) to 1 x 10(-5) Mol l(-1). This technique gave satisfactory precision, and relative standard deviations of migration times and chemiluminescence peak intensities were less than 1 and 6%, respectively. The technique was applied to animal studies for determination of diphenhydramine extracted from rabbit plasma and urine samples, and the extraction efficiency were between 92 and 98.5%.

Preparation of poly(4-vinylpyridine)/silica hybrids supported cyclopentadienyltitanium trichloride (CpTiCl3) catalyst and styrene polymerization

Poly(4 - vinylpyridine)/silica( PVP/SiO2) organic - inorganic nanoscale hybrid was prepared using sol - gel method, in which PVP was used as an organic component and TEOS as a SiO2 precusor, This hybrid was used as CpTiCl3 support. The XPS and IR measurements showed that two kinds of catalytic active site were formed through analyzing the interaction mode between support and CpTiCl3. The results of styrene polymerization showed that syndiotactic was the highest at 50 degreesC. The catalytic activity was 1.09 x 10(6) g PS/ (mol Ti . h) at 70 degreesC when n(Al)/n(Ti) = 1500. GPC results showed a bimodal molecular weight distribution.

Studies on the electrical conductivity of carbon black filled polymers

The conductivity mechanism for a carbon black (CB) filled high-density polyethylene (HDPE) compound was investigated in this work. From the experimental results obtained, it can be seen that the relation between electrical current density (J) and applied voltage across the sample (V) coincides with Simmons's equation (i.e., the electrical resistivity of the compound decreases with the applied voltage, especially at the critical voltage). The minimum electrical resistivity occurs near the glass transition temperature (T-g) of HDPE (198 K). It can be concluded that electron tunneling is an important mechanism and a dominant transport process in the HDPE/CB composite. A new model of carbon black dispersion in the matrix was established, and the resistivity was calculated by using percolation and quantum mechanical theories. (C) 1996 John Wiley & Sons, Inc.