中华鲟(Acipenser sinensis)及相关种类的mtDNA控制区串联重复序列及其进化意义

采用 PCR技术和 DNA测序技术 ,发现了我国一级珍稀保护动物中华鲟 ( Acipensersinensis)线粒体 DNA( mt DNA)的控制区 ( D- loop)存在数目不等的串联重复序列 ,该重复序列造成了中华鲟广泛的异质性现象 .从分子水平进行了不同类型重复序列变化规律的研究 ,同时还初探了重复序列在我国其它几种鲟鱼类的存在情况 ,发现在白鲟 ( Psephurus gladius)、达氏鲟 ( A.dabryanus)和史氏鲟 ( A.schrenckii)均存在类似的重复序列结构 .序

人工湿地生态系统的除藻研究

国家杰出青年科学基金(3992 50 0 7); 欧盟国际合作项目(ERBIC 1 8CT 960 0 59)

利用EIA生物测试法快速定量筛选环境样品中的二噁污染物

将采集的环境样品分作 3份 ,1份用于高分辨色质联用多离子检测测定二的毒性当量浓度 TEQ,另 2份分别用 7-乙氧基 -异吩唑酮 -脱乙基酶 ( EROD)活力诱导法和酶免疫法 ( Enzyme Immuno Assay,EIA)进行生物测试 .结果表明 EIA和EROD这 2种生物试验方法均具有较好的准确性和很宽的线性范围 .比较 Micro- EROD分析结果与化学分析结果以及 EIA分析结果与化学分析结果 ,发现 Micro- EROD生物试验所测得的 TEQ值均高于化学分析法的 TEQ值

氯化高汞对大型溞的慢性毒性

在换水静置条件下(25℃),氯化高汞(以Hg~(++)计)对大型溞的48小时LC_(50)值及其可信限为13.5(±2.1)微克/升。试验个体饲以斜生栅藻单个培养,在汞含量为1—21微克/升浓度下,产仔总数经方差分析表明组间差异显著(F>F_(0.05))。各浓度组(X)与产仔总数(Y)的关系为:Y=-51.823X+4320.960(r=-0.904,p<0.01)。净增殖率(R_0)随浓度升高而逐渐下降。存活和生长用方差分析及D值检验表明对照组与各浓度组之间(差异数分别小于各自的D值20.89和0.1

Effect of dietary cyanobacteria on growth and accumulation of microcystins in Nile tilapia (Oreochromis niloticus)

A 12-week growth trial was conducted in a flow-through system to investigate the chronic toxic effect of dietary intake of cyanobacteria on growth, feed utilization and microcystins accumulation in Nile tilapia (Oreochromis niloticus L.) (initial body weight: 5.6 g). Six isonitrogenous and isocaloric diets were formulated to include different contents of cyanobacteria with the dietary microcystins increasing from 0 to 5460.06 ng/g diet. The results showed that dietary intake of cyanobacteria could increase the growth of tilapia while there are no impacts on feed conversion efficiency or mortality. Feeding rate was higher for the diets containing highest cyanobacteria. Microcystins were mostly accumulated in fish liver. The relationship between microcystins contents in muscle, liver, spleen and dietary intake could be described by quadratic equations. Microcystins content in the muscle of Nile tilapia in present study exceeded the upper limit of the tolerable daily intake (TDI) of microcystins suggested by the WHO (0.04 mu g/kg body weight/d). It is suggested that Nile tilapia fed on toxic cyanobacteria is not suitable for human food. (c) 2006 Elsevier B.V. All rights reserved.

Study of GaN thin films grown on vicinal SiC (0001) substrates by molecular beam epitaxy

A detailed study of the characteristics of undoped GaN films, grown on either vicinal or nominal flat SiC (0001) substrates by molecular beam epitaxy, has been carried out using photoluminescence and Raman scattering techniques. The I I K photoluminescence spectra of the GaN film grown on the vicinal SiC (0001) substrate show a strong and sharp near-bandgap peak (full width at half maximum (FWHM) similar to 16 meV). This feature contrasts with that of the GaN film grown on the nominal flat SiC (0001) substrate where the I I K photoluminescence spectra exhibit the near-bandgap peak (FWHM similar to 25 meV) and the intensity is approximately seven times weaker than that of the vicinal film sample. The redshift of the near-bandgap peak associated with excitons bound to shallow donors is related to the stress caused by both the lattice mismatch and the thermal expansion coefficient difference between GaN and SiC substrates. The measured thermal activation energy of the shallow donor of 33.4 meV is determined by using an Arrhenius plot of the near-bandgap luminescence versus I IT from the slope of the graph at high temperature. The temperature dependence of the FWHM of the near-bandgap luminescence has also been studied. The Raman scattering measurements from the vicinal film reveal that the E-2 phonon peak is strengthened and the A(1)(LO) phonon peak is shifted towards the low-frequency side with enhanced intensity, in comparison to that from the nominal flat film, suggesting a reduction in the density of defects and a lower free carrier concentration in the vicinal GaN film.

Photoluminescence properties of a GaN0.015As0.985/GaAs single quantum well under short pulse excitation

Under short pulse laser excitation, we have observed an extra high-energy photoluminescence (PL) emission from GaNAs/GaAs single quantum wells (QWs). It dominates the PL spectra under high excitation and/or at high temperature. By measuring the PL dependence on both temperature and excitation power and by analyzing the time-resolved PL results, we have attributed the PL peak to the recombination of delocalized excitons in QWs. Furthermore, a competition process between localized and delocalized excitons is observed in the temperature-dependent PL spectra under the short pulse excitation. This competition is believed to be responsible for the temperature-induced S-shaped PL shift often observed in the disordered alloy semiconductor system under continuous-wave excitation. (C) 2001 American Institute of Physics.

Self-assembled quantum dots, wires and quantum-dot lasers

Molecular beam epitaxy-grown self-assembled In(Ga)As/GaAs and InAs/InAlAs/InP quantum dots (QDs) and quantum wires (QWRs) have been studied. By adjusting growth conditions, surprising alignment. preferential elongation, and pronounced sequential coalescence of dots and wires under specific condition are realized. The lateral ordering of QDs and the vertical anti-correlation of QWRs are theoretically discussed. Room-temperature (RT) continuous-wave (CW) lasing at the wavelength of 960 nm with output power of 3.6 W from both uncoated facets is achieved fi-om vertical coupled InAs/GaAs QDs ensemble. The RT threshold current density is 218 A/cm(2). A RT CW output power of 0.6 W/facet ensures at least 3570 h lasing (only drops 0.83 dB). (C) 2001 Elsevier Science B.V, All rights reserved.

Self-assembled InAs/GaAs quantum dots and quantum dot laser

Systematic study of molecular beam epitaxy-grown self-assembled In(Ga)As/GaAs, In-AlAs/AlGaAs/GaAs, and InAs/InAlAs/InP quantum dots (QDs) is demonstrated. By adjusting growth conditions, surprising alignment, preferential elongation, and pronounced sequential coalescence of dots under the specific condition are realized. Room-temperature (RT) continuous-wave (CW) lasing at the wavelength of 960 nm with output power of 1 W is achieved from vertical coupled InAs/GaAs QDs ensemble. The RT threshold current density is 218 A/cm(2). An RT CW output power of 0.53 W ensures at least 3 000 h lasing (only drops 0.83 db). This is one of the best results ever reported.

Study on methane hydration process in a semi-continuous stirred tank reactor

The methane hydration process is investigated in a semi-continuous stirred tank reactor. Liquid temperatures and reaction rates without stirrer are compared with those occurring with stirrer, while at the same time better stirring conditions of the methane hydration process are given by the experiments. Some basic data of fluid mechanics, for example, stirring Reynolds number, Froucle number and stirrer power, are calculated during the methane hydration process, which can be applied to evaluate stirrer capacity and provide some basic data for a scaled up reactor. Based on experiment and calculations in this work, some conclusions are drawn. First, the stirrer has great influence on the methane hydration process. Batch stirring is helpful to improve the mass transfer and heat transfer performances of the methane hydration process. Second, induction time can be shortened effectively by use of the stirrer. Third, in this paper, the appropriate stirring velocity and stirring time were 320 rpm and 30 min, respectively, at 5.0 MPa, for which the storage capacity and reaction time were 159.1 V/V and 370 min, respectively. Under the condition of the on-flow state, the initial stirring Reynolds number of the fluid and the stirring power were 12,150 and 0.54 W, respectively. Fourth, some suggestions, for example, the use of another type of stirrer or some baffles, are proposed to accelerate the methane hydration process. Comparing with literature data, higher storage capacity and hydration rate are achieved in this work. Moreover, some fluid mechanics parameters are calculated, which can provide some references to engineering application.

两种端乙炔基芳醚砜单体的核磁研究双端乙炔基芳醚砜溶液聚合反应和催化剂的研究非等温DSC法测双[4－（4－乙炔基苯氧基）苯基]砜（酮）的本体聚合反应动力学

本工作对下面两种端乙炔基芳醚砜单体的核磁共振谱进行了研究。通过加入位移试剂Eu（fod）_3引起共振吸收峰化学位移值的变化趋热及同核去偶，'H选择质子去偶的方法分别对其'H谱和~(13)C谱（COM）做了归属。在确认对化合物＜I＞'H谱和~(13)C谱（COM）归属的基础上，演绎出三种苯环上取代基团的'H和~(13)C化学位移取代参数。这些基团的取代参数目前在文献中尚未见报导，用这些参数来计算化的＜II＞的'H和~(13)C谱（COM）化学位移值时，与观测值有较好的吻合。本工作对双[4－（4－乙炔基苯氧基）苯基]砜的溶液聚合反就（DMSO）作溶剂、PdCl_2·2DMSO作催化剂）进行了研究。采用高压液体色谱和旋转薄层色谱分离反应的各种中间产物，通过中间产物的红外和'HNMR谱变化，演绎聚合反应的历程，还在'H核磁谱仪样品管内做了短时间反应，跟踪记录反应信息。聚合产物自始至终可分为溶于二氯甲烷和不溶于二氯甲烷两部分。在整个反应过程中，可溶性产物逐渐转变成不溶性产物，色谱分析表明可溶性产物是由未反应的单体、线型及环状低聚物、聚合度在9－10的齐聚物和少量聚合度更高的组分构成的。从称重测量不溶性产物所占比重和可溶性产物的高压液体色谱诸吸收峰峰高的变化，推算出聚合反应过程中单体、主要中间产物的变化趋势。可溶性产物的红外光谱中2920、1665－25、960－930、890，760－730 cm~(-1)吸收峰和'HNMR谱中的5.3, 3.5ppm吸收表明产物具有共轭多烯结构。'HNMR谱在芳核质子区出现7.7ppm吸收峰表明反应初期已有环化现象，这点与本体聚合反应是不同的。不溶性产物除聚合度或交联度高以外，与可溶性产物在结构上也有差异，其芳化程度高很多。从不同反应时间中间产物的红外和'HNMR谱（可溶部分）变化，显示了溶液聚合反应历程十分复杂，同时存在着几种反应。主反应是氯化钯络合物引发的配位络合聚合反应，钯络合物与单体的端乙炔基络合生成活性中心，三键在顺式位打开，生成共轭多烯增长链。链增长过程中伴随着热引起的多烯链顺－反异构化，部分反式多烯分子内环化，继而脱质于芳化生成三取代苯形式的环交联，芳化过程中可发生链的局部断裂。最终产物是共轭多烯链间通过芳环，炔烯桥交联成的体型聚合物。多烯和端乙炔基之间，多烯－多烯之间可发生Diels-Alder反应，因此溶液聚合产物再经短时间热处理，芳化程度增高，玻璃化温度大幅度提高。另外还研究了反应的溶剂效应和增加因含量对反应产率的影响，发现用氯仿和二氯甲烷作溶剂有利于共轭多烯链的顺－反异构化，固含量在2.25－11.25％范围，聚合产率变化不大。本文还对适用于双端炔基聚合反应的催化剂作了广泛的试探，首先考察了若干钯络合物，发现除PdCl_2·2DMSO外，PdCl_2·2MeCN、PdCl_2·2PhCN络合物也可作为双端炔基芳醚砜溶液聚合的催化剂。钴、镍的膦络合物[Co(PPh_3)_2]Cl_2、[Ni(PPh_3)_2]Cl_2可使双端炔基芳醚砜环化生成环状低聚物。极性溶剂四氢呋，二氧六环。氯仿和三氯甲烷可以用作Ziegler-Natta催化剂聚合双端炔基芳醚砜的溶剂。用AlEt_3-Ti(OBu)_4催化得到的聚合物以顺式多烯为主，玻璃化浊度高于250℃，热形变稳定性好。Al/Ti比在6－8时催化活性较高。用稀土体系的Ziegler-Natta催化剂AlEt_3-NdCl_3·2THF、AlEt_3－（CF_3COO）_3Nd也可得到类似的催化效果。制备了以双氰为配位基的高分子－钯络合物，在催化双端炔基单体聚合时具有与类似的低分子钯络合物PdCl_2·2MeCN相近的效果。改变高分子催化剂的N／Pd比未出现明显的活性高峰。这部分工作还有待深入，予期在进一步深入研究之后，该高分子催化剂可用于制备双端乙炔基芒醚砜增强复合材料的连续化浸渍工序，让单体的氯仿溶液流经高分子－钯络合物填充的柱子形成齐聚物后，再浸渍涂层，可缩短成型的热固化时间，具有较大的经济意义。用非等温DSC法测定了双[4-(4-乙炔基苯氧（基)苯基]砜和双[4-(4-乙炔基苯氧基)苯基]酮的本体热聚合及有PdCl_2·2DMSO存在下的催化聚合的反劝力学参数，并与文献报导的（3－乙炔基苯氧基）苯模型物和双[4－（3－乙炔基苯氧基）苯基]砜的本体热聚合反应动力学参数进行比较。经电子计算机最小二乘曲线拟合程序汞得的结果表明表现反就活化能Eap，指数前因子A均与DSC的升温速率和转化率无关。讨论了模型物端乙炔基的位置和链上砜基，羰基的存在对聚合反应的影响，还通过对DSC升温过程中试样的红外光谱跟踪，解释了DSC峰表征的化学反应。

CMOS超高频整流器

提出了一个适用于无源UHF RFID标签芯片的全CMOS整流器.整流器包括射频-直流转换电路、偏置电路、直流-直流转换电路和振荡器电路.整流器的工作频率范围是860～960 MHz.基于0.18μm,1p6m的标准数字CMOS工艺,设计并实现了无源UHF RFID标签芯片的整流器.该设计采用开关电容电路技术动态地消除了CMOS管开启电压的问题,在标准数字CMOS工艺下实现了高效率的超高频整流器.整流器的面积为180μm×140μm.当输入900MHz,-16dBm的射频信号时,整流器的输出电压为1.2V,启动时间为980μs.