激光诱发活塞的热负荷

活塞的热疲劳性能对柴油发动机的全寿命至关重要。由于能量有限和可控性差等缺点，现有实验系统均不能满意地进行活塞热负荷模拟实验。为此，提出并建立了一套激光诱发活塞热负荷的实验系统。该系统通过对激光束的空间整形，使之投射到活塞表面后诱发的温度场分布满足特定要求。基于PROFIBUS-DP现场总线技术实现了系统集成和实验过程的全反馈控制。针对活塞的典型热负荷条件，即高周热疲劳和热冲击分别进行实验，以模拟正常工作循环和“启动一停车”等热负荷或转速突变工况。通过设置加热一冷却周期或上限下限温度，可以获得相应的热负荷模拟实验效果。研究结果表明，采用经光束整形的激光进行活塞热负荷模拟实验具有周期短、可控性好等优点。 

变粘度柱状地幔上涌流对称轴上的温度、速度和粘度分布

本文对地幔粘度随温度和压力变化的牛顿流体,求得了控制上涌流动的流体力学方程组在对称轴处的渐近解。从而得到了对称轴上温度、上涌速度和粘度随深度的变化。计算结果对二组有代表性的地幔流变参数给出。结果表明,对称轴上的温度分布几乎与流变参数无关,而上涌速度则强烈依赖流变参数。

Superluminal optical solitons in a four-level tripod atomic system

With one weak probe field and two strong pumping fields, superluminal optical solitons are formed in a lifetime-broadened four-level tripod atomic medium. With proper parameters, both dark and bright solitons can occur in the highly resonant medium. The corresponding group velocity of the solitons can be superluminal. Meanwhile, the conditions for superluminal solitons occurrence are given.

兴山龙门河地区的植物群落与物种多样性研究

龙门河地区地处湖北省的西部，神农架的南坡，处于中亚热带向北亚热带过渡的地带。对其植物与植物群落的研究得到如下结果： 龙门河地区共有维管植物160科724属1737种，其中种了植物140科692属共1686种。其植物区系有显著的温带性，温带分布属共380属，占总属数的54.9%，这可能和该地区的地理位置，海拔及人为活动的影响有关，该地区的植物区系还具有古老性，特有属丰富特点，且有较多的珍稀濒危植物分布。 龙门河地区的植被共划分三个自然植被型共16个群系。在高海拔地区保存有较原始的落叶阔叶林，低海拔地区多为人为破坏后的次生类型。这些植被类型随环境条件的变化呈现较有规律的分布，依照其垂直分布的情况，可以将该地区植被划为三个带，即常绿阔叶林带低于海拔900(-1300)m;常绿落叶阔叶混交林位于海拔900(-1300)-600m之间;落叶阔叶林带在海拔1600(-1300)-2200m之间，无针叶林带在龙门河地区分布。应用TWINSPAN和DCA程序对各调查样地进行数量分类和排序结果说明，植物群落的分布与环境因子明显相关，但排序轴不能用海拔等单个的因子来解释。对各群落乔木层的Gleason丰富度指数，Shannon-Wiener指数及Pielou均匀度指数对比后发现，各种指数在不同的群落之间及不同海拔高度上没有明显的规律，这可能是由于人类活动混淆了群落成分及结构的结果。 锐齿槲栎林是神农架地区一种重要的落叶阔叶林，其分布广泛，保存较好。通过对锐齿槲栎种群大小结构的研究发现，中等大小的锐齿槲栎个体数量较多，幼苗与幼树的数量在不同样地间变化很大，其大小结构分布图中多有一定程度的缺失。锐齿槲栎种群多呈现聚集分布，不同的尺度下其聚集程序不同。在大多数尺度下，幼苗幼树的聚集程度比相同尺度下成体的聚集程序高。幼苗更新是锐齿槲栎更新的一种主要形式，其幼苗的出现与林窗的形成有密切的关系。在锐齿槲栎幼苗成长为幼树的过程中，同于种内与种间竞争的影响。导致了许多幼树的死亡。正是由于林窗形成等干扰因素的影响才使锐齿槲栎幼树得以进入群落上层。

一种较浅水域环境及生物样品采集的采样装置

本发明涉及环境科学或环境工程及水生生物实验研究用采样设备，特别是一种较浅水域环境及生物样品采集的采样装置。具体为包括撑架19固定架10、采样器2、风扇3、绳索8及插销7，撑架19两侧设有浮子5，带有采样器2的固定架10固接于撑架19的上方；在浮子5上安装有驱动其移动的风扇3，风扇3通过插销7与浮子5上的蓄电池9电连接；撑架19 的一侧固接有固定杆11，绳索8为两根，分别与采样器2及插销7相连接。本发明适用范围较广，其结构组成简单，操作便捷，可以应用于河道、海滩、池塘等较浅水域沉积物、水样及水体生物样品等的样品采集。而且本发明不需要大型动力设施及繁杂的日常维护，因此操作方便快捷，应用功能较强。

Lignans with Anti-HIV Activity from Schisandra propinqua var. sinensis

Fourteen new lignans, tiegusanins A-N (1-14), together with 13 known compounds were isolated from the aerial parts of Schisandra propinqua var. sinensis. The structures and absolute configurations of 1-13 were established using a combination of spectrosco

丙泊酚对大鼠海马CA1 区兴奋性突触传递的影响

　目的　观察500μmol/ L 丙泊酚对大鼠海马CA1 区电刺激诱发的兴奋性突触后电流 ( EPSC) 的影响,分析丙泊酚的可能作用机制。方法　断头法分离Wistar 大鼠(13～19 d) 海马半脑, 用切片机切出400μm 厚度的海马脑片,全细胞膜片钳技术记录CA1 区锥体神经元EPSC。实验分 两组:脂肪乳剂组( n = 6) 和丙泊酚组( n = 10) 。先以50μmol/ L 印防己毒素预孵脑片30 min 后,记录 基础EPSC 10 min ,然后加入450μl 脂肪乳剂或丙泊酚(相当于500 μmol/ L ) , 继续记录EPSC 40 min ;继而以配对刺激代替单刺激,观察EPSC2/ EPSC1 比率的变化;改变膜钳制电压( - 80～ + 60 mV) ,观察电流2电压( I2V) 曲线的变化。结果　脂肪乳剂对EPSC 无影响,500μmol/ L 丙泊酚降低 大鼠海马CA1 区EPSC 值,25～30 min 左右达最大抑制效果,EPSC 幅值下降至基础值的6715 % ,明 显低于脂肪乳剂组( P < 0105) ;而且500μmol/ L 丙泊酚明显降低EPSC2/ EPSC1 比率,也使I2V 曲线 左移,降低反转电位至- 35 mV 左右。结论　500μmol/ L 丙泊酚对大鼠海马CA1 区兴奋性突触传 递产生抑制作用,这可能与其增强突触前膜、突触后膜GABAA 受体活性有关。

Diet and feeding behavior of Rhinopithecus bieti at Xiaochangdu, Tibet: Adaptations to a marginal environment

The diet and feeding ecology of a wild subpopulation of black-and-white snub-nosed monkeys (Rhinopithecus bieti) were studied at Xiaochangdu in Honglaxueshan Nature Reserve, Tibet. This region is climatologically harsher than any other inhabited by non-human primates. Black-and-white snub-nosed monkeys fed on 48 parts of 25 plant species, at least three species of lichens and seven species of invertebrates. The number of food items exploited varied markedly among seasons, with dietary diversity being greatest in spring and summer. In winter, black-and-white snub-nosed monkeys had to subsist on fallback foods such as dried grass and bark. Ubiquitous lichens formed a major dietary constituent throughout the year, contributing about 75% of feeding records. Even though lichens act as a staple, our findings signify that the monkeys at Xiaochangdu prefer feeding on foliage, which is higher in protein content than the former. We provide evidence that black-and-white snub-nosed monkeys are able to cope with an array of food items other than lichens and hence can be regarded as feeding generalists. We discuss the results with reference to previous studies on other subpopulations living in habitats that are floristically more diverse and offer more plant food items than the marginal habitat at Xiaochangdu.

Bioaccumulation of polychlorinated dibenzo-p-dioxins and dibenzofurans in the foodweb of Ya-Er Lake area, China

Bioaccumulation of PCDD/F in the foodweb was investigated in the Ya-Er Lake area, which was heavily polluted by PCDD/F. The high concentrations of PCDD/F in sediment can be transferred and bioaccumulated by aquatic organisms and humans through various pathways. Benthonic invertebrate animals and aquatic plants with a lot of fibers in the root can accumulate PCDD/F from sediment and water. Snail (Bellamya aeruginosa), shrimp (Macrobranchium sp.) and freshwater mussel (Acuticosta chinensis (Lea)) took up PCDD/F from the water and maintained the emission patterns, whereas fish tended to selectively accumulate 2,3,7,8-substituted isomers. The tissues of fish-eating bird and duck (Anas platyrhynchos) were very highly contaminated by PCDD/F due to ingestion of fish and other aquatic organisms from sediment. The residual concentration in breast milk depended on the original concentration of PCDD/F in the food. A resident in Ya-Er Lake area showed a daily intake of PCDD/ F of about 9.14 pg TEQ/kg body weight/day. This is higher than the tolerable daily intake (TDI) for PCDD/F (1 pg TEQ/kg body weight/day), which was recommended by the World Health Organization (WHO). (C) 2001 Elsevier Science Ltd. All rights reserved.

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.

A Selective-Area Metal Bonding InGaAsP-Si Laser

A 1.55-mu m hybrid InGaAsP-Si laser was fabricated by the selective-area metal bonding method. Two Si blocking stripes, each with an excess-metals accommodated space, were used to separate the optical coupling area and the metal bonding areas. In such a structure, the air gap between the InGaAsP structure and Si waveguide has been reduced to be negligible. The laser operates with a threshold current density of 1.7 kA/cm(2) and a slope efficiency of 0.05 W/A under pulsed-wave operation. Room-temperature continuous lasing with a maximum output power of 0.45 mW is realized.

5kW后弯管波力发电装置的研究

在造波水槽内对后弯管浮体模型进行了波能转换性能的试验研究。通过对比试验，选定了最佳浮体模型——前方后圆浮室后伸型后弯管浮体。波能转换效率达ηA＝ 73.3% 。给出了该浮体模型的性能曲线及其无因次特性。测定了该模型最大锚泊力Fmax随浮体参数的变化规律。设计制造了5kW 后弯管波力发电浮体。该机组采用0.8m 直径的对称翼透平和无刷爪极发电机，输出直流电。采用单点锚泊系统，在珠江口桂山岛西南面海域进行海上试验。实测数据表明，海上试验瞬时功率大于5kW，超过机组设计额定值。