噬菌蛭弧菌的分离及初步鉴定

采用双层平板法,以滤膜过滤的方法来收集噬菌蛭弧菌,以嗜水气单胞菌(Aeromonas hudrophila)、荧光假单胞菌(Pseudomonas fluorescent)和绿脓杆菌(Pseudomonas aeruginosa)为宿主菌,进行噬菌蛭弧菌的分离研究;并在此基础上,通过接触酶检测和寄生性确认对噬菌蛭弧菌(Bdellovibrio bacteriovorus)进行了初步的鉴定。结果表明未使用滤膜过滤,采用自来水琼脂双层平板法分离噬菌蛭弧菌的效果较好;并经过接触酶和寄生性检测初步鉴定此BD-SP

武汉月湖水生植被重建的实践与启示

通过生物操纵、浮水植物和植物浮岛原位净化、岸边人工湿地净化和科学种植等措施,2—3年内,在长江中游地区、面积为0.66km2、水质为劣Ⅴ类的重富营养湖泊武汉月湖重建了以菹草和伊乐藻为优势种的沉水植物先锋群落,2005年春季的沉水植物盖度达到45%,提高了透明度。利用水位低、透明度相对高的冬季种植伊乐藻、菹草等适合冬春季生长的沉水植物是建立沉水植物先锋群落的一个有效途径。重污染水体过低的透明度是重建沉水植被的主要限制因子,在低水位或较高透明度时期,水生植物可以耐受相对较高的污染负荷,并且在有条件降低水位时,

厚颌鲂的年龄结构及生长特性

以鳞片作为鉴定年龄的材料,对龙溪河厚颌鲂(Megalobrama pellegrini)种群开展年龄结构与生长特性的研究。结果表明,厚颌鲂鳞片年轮结构呈疏密切割型,年轮特征显著,可用于年龄鉴定,3~4月是年轮形成高峰时间。种群由0~7龄共8个龄组组成,以低龄个体为主,1~3龄个体占83.14%,体长分布主要集中在130~250 mm间(77.71%)。体质量分布主要集中在50~250 g(64.33%)。群体总性比为♀∶♂=1∶1.03,符合1∶1理论比值。体长和鳞径呈直线关系,体长和体质量呈幂函数关系且

模拟微重力对泥鳅体外受精和胚胎发育的影响(英文)

theprojectofknowledgeinnovationprogramofCAS (GrantNO .KSCX2 SW 3 2 2 ) ;andtheprojectofChinesemannedspaceflight

浮桥河水库浮游植物的多样性及其演变

1997年4月至1998年1月对浮桥河水库浮游植物状况进行了调查,结果表明:该水库常见浮游植物约189种,隶属于8门92属,其中硅藻门25属64种,绿藻门39属79种,蓝藻门17属30种,甲藻门、隐藻门、裸藻门、黄藻门及金藻门种类较少。其个体密度年平均为44.9×104ind/L;生物量年平均为6.439mg/L,其中蓝藻占33.37%,硅藻和绿藻分别占20.68%和20.16%,甲藻占16.31%。浮游植物现存量的季节变化表现为从春季开始平稳上升,至秋季达到最大值。蓝藻、硅藻、绿藻等主要种类的季节变化按

氯氰菊酯对大型溞的毒性研究

研究了农药氯氰菊酯对大型氵蚤的毒性效应 ,结果显示 :氯氰菊酯对大型氵蚤有明显的毒性作用 ,其 2 4h-LC50 为 4.81 mg/L,实验毒性为中级 .同时也研究了国际标准毒物重铬酸钾对大型氵蚤的毒性为 2 4h-LC50 为 0 .3 8mg/L,表明该大型氵蚤对毒物较为敏感 .最后讨论了实验条件对大型氵蚤2 4h-LC50 的影响

Diurnal changes of behavior and respiration of Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis) in captivity

A preliminary study was carried out to investigate diurnal changes of behavior of three, one adult mate, one adult female, and one juvenile female, Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis) in captivity. The respiration and behavior of the porpoises were recorded for 222 hr across 42 days. Behavioral data were recorded for eight general categories: aerial display and fast swimming, begging for fish, playing, nonsexual socializing, sexual behavior, resting, rubbing, and miscellaneous (i.e., other behaviors not included in the above categories). Each behavioral category was scored using one-zero sampling with 10-min intervals. The adult male showed shorter mean respiratory intervals at night (19:00-7:00 h), whereas the mean respiratory intervals of the females were shorter during the day (7:00-19:00 h). Begging for fish of all individuals, playing of the juvenile female, nonsexual socializing, and miscellaneous behavior of the adult female and resting of the male were observed more easily in the day, and aerial display and fast swimming of the adults and resting of the females were observed more easily at night. No significant diurnal difference was found, however, in the remaining categories of each individual. Each of the three porpoises therefore showed a distinct diurnal pattern, but none was obviously more active in the daytime than during the nighttime. Results suggest that daytime-only feeding schedules may be insufficient to meet the energetic needs of marine mammals that show a 24-hr activity cycle, and that nighttime feeding may be a worthwhile addition to husbandry routines.

First-principles study of UC2 and U2C3

The electronic structure and mechanical properties Of UC2 and U2C3 have been systematically investigated using first-principles calculations by the projector-augmented-wave (PAW) method. Furthermore, in order to describe precisely the strong on-site Coulomb repulsion among the localized U 5f electrons, we adopt the generalized gradient approximation +U formalisms for the exchange-correlation term. We show that our calculated structural parameters and electronic properties for UC2 and U2C3 are in good agreement with the experimental data by choosing an appropriate Hubbard U = 3 eV. As for the chemical bonding nature, the contour plot of charge density and total density of states suggest that UC2 and U2C3 are metallic mainly contributed by the 5f electrons, mixed with significant covalent component resulted from the strong C-C bonds. The present results also illustrate that the metal-carbon (U-C) bonding and the carbon-carbon covalent bonding in U2C3 are somewhat weaker than those in UC2, leading to the weaker thermodynamic stability at high temperature as observed by experiments.

Characterization of stress induced in SOS and Si/gamma-Al2O3/Si heteroepitaxial thin films by Raman spectroscopy

Raman spectroscopy technique has been performed to investigate the stress induced in as-grown silicon-on-sapphire (SOS), solid-phase-epitaxy (SPE) re-grown SOS, and Si/gamma-Al2O3/Si double-heteroepitaxial thin films. It was demonstrated that the residual stress in SOS film, arising from mismatch and difference of thermal expansion coefficient between silicon and sapphire, was reduced efficiently by SPE process, and that the stress in Si/gamma-Al2O3/Si thin film is much smaller than that of as-grown SOS and SPE upgraded SOS films. The stress decrease for double heteroepitaxial film Si/gamma-Al2O3/Si mainly arises from the smaller lattice mismatching of 2.4% between silicon top layer and the gamma-Al2O3/Si epitaxiial composite substrate, comparing with the large lattice mismatch of 13% for SOS films. It indicated that gamma-Al2O3/Si as a silicon-based epitaxial substrate benefits for reducing the residual stress for further growth of silicon layer, compared with on bulk sapphire substrate. (c) 2005 Elsevier B.V. All rights reserved.

The correlation between preferred orientation and performance of ITO thin films

The tin-doped indium oxide (ITO) thin films were prepared by reactive thermal evaporation on the glass substrates. The effects of substrate temperatures (T-s) on the grain preferred orientation, the electrical and optical properties of ITO films were studied. X-ray diffraction (XRD) patterns indicated that the preferred orientation of film changes from (222) to (400) as T, > 200 degrees C. It can be explained by that the low-index crystallographic planes are easier to be formed when the adatoms have high surface mobility. The Hall measurements indicated that both the concentration and mobility of carrier increase with increasing T,,,. The grain orientation of film does not influence the transmissivity and the carrier concentration, but enhances the carrier mobility. The transmissivity of ITO films is over 90% in the visible wavelength region (except that of the film deposited at 125 degrees C). A minimum resistivity of 5 X 10-4 Omega cm is achieved for the (400) preferred orientation film. Thus, the highest figure of merit of 3.5 x 10(-2) square/Omega is obtained for the film with (400) preferred orientation. The correlation between the preferred orientation and electrical and optical properties are discussed.

Structural characterization of cubic GaN grown on GaAs(001) substrates

Structural characteristics of cubic GaN epilayers grown on GaAs(001) were studied using X-ray double-crystal diffraction technique. The structure factors of cubic GaN(002) and (004) components are approximately identical. However, the integrated intensities of the rocking curve for cubic (002) components are over five times as those of (004) components. The discrepancy has been interpreted in detail considering other factors. In the conventional double crystal rocking curve, the peak broadening includes such information caused by the orientation distribution (mosaicity) and the distribution of lattice spacing. These two kinds of distributions can be distinguished by the triple-axis diffraction in which an analyser crystal is placed in front of the detector. Moreover, the peak broadening was analysed by reciprocal lattice construction and Eward sphere. By using triple-axis diffraction of cubic (002) and (113) components, domain size and dislocation density were estimated. The fully relaxed lattice parameter of cubic GaN was determined to be about 0.451 +/- 0.001nm.

Competition between band gap and yellow luminescence in undoped GaN grown by MOVPE on sapphire substrate

Undoped GaN epilayer on c-face (0 0 0 1) sapphire substrate has been grown by metalorganic vapor-phase epitaxy (MOVPE) in a horizontal-type low-pressure two-channel reactor. Photoluminescence (PL) as a function of temperature and excitation intensity have been systematically studied, and the competition between near band gap ultraviolet (UV) and defect-related yellow luminescence (YL) has been extensively investigated, It is revealed that the ratio of the UV-to-YL peak intensities depends strongly on the excitation intensity and the measurement temperature. The obtained results have been analyzed in comparison with the theoretical predications based on a bimolecular model. (C) 2001 Elsevier Science B.V. All rights reserved.