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

转生长激素基因促进鲤鱼胸腺的发育

采用显微注射方法,获得转“全鱼”生长激素(GH)基因鲤鱼(转基因鱼),并对其胸腺发育进行观察。1龄F_1转基因鱼胸腺显著增大、重量增加。单侧胸腺最大重量达295mg,最小为190mg,平均为218.6mg;而对照鱼胸腺最大重量仅为81mg,最小只有20mg,平均为42.5mg。转基因鱼与对照鱼胸腺绝对重量之比为5.14:1,胸腺重量指数之比为2.97:1。显微观察表明,转基因鱼胸腺高度发达,外区明显增厚,胸腺细胞高度密集;而对照鱼胸腺出现退化,外区较薄,淋巴细胞分布较为稀疏,可见明显的脂肪细胞团。电子显微

不同基因型水稻幼苗摄取东湖水磷形态的动力学研究

研究比较了汕优63和金优77两种不同基因型水稻在幼苗期于武昌东湖水中生长时体内磷含量及其变化速率。结果表明,金优77较汕优63能更有效地利用天然水中的磷。将湖水中的磷划分为总磷(TP)、总溶解反应磷(TSP)、总反应磷(TRP)、溶解性反应磷(SRP)4种不同的磷形态,研究比较了两种不同基因型水稻幼苗期对天然水体中各磷形态的摄取动力学行为,结果表明金优77较汕优63能更快速而有效地利用各磷形态。

人工诱导异源四倍体、新四倍体及异源三倍体白鲫的细胞遗传学研究

作者比较了第一代异源四倍体鱼、异源三倍体鱼、新四倍体鱼与亲本白鲫、红鲫及其杂交一代的染色体组型。三种亲本的二倍体染色体数均为100，但其组型分组各有差异，白鲫染色体组型公式：12m＋36sm＋32st十20t,NF＝148，在亚中着丝点组中有一对特大的标记染色体；红鲫染色体组型：20m＋34sm＋26st＋20t,NF＝154；白鲫×红鲫杂种染色体组型：16m＋35sm＋29st＋20t,NF＝151，有一条与白鲫相似的特大标记染色体，证实其组型由白鲫和红鲫各提供一套染色体组组成。异源三倍体的染色体数为1

丝藻目的一新属——骈丝藻属

<正> 1976年6月至8月,中国科学院青藏高原综合科学考察队藏北分队对冈底斯山,念青唐古拉山以北,昆仑山以南的广大藏北地区进行了多学科的综合考察。我所陈宜瑜同志参加了这次考察,对该地区各种水体的水生生物进行了广泛地采集,在采得的标本中,藻类是十分丰富的。我们在鉴定该区振泉湖藻类标本时,发现一特殊类型的藻类。通过对液浸标本和固定染色标本的研究,确定它是绿藻门丝藻目的一新属。

Isolation and characterization of polymorphic microsatellites in a sex-reversal fish, rice field eel (Monopterus albus)

The rice field eel (Monopterus albus) is a fish of economic importance in China and some Asian countries. From a (GT)(n)-enriched genomic library, 30 microsatellites were developed by employing the fast isolation by AFLP of sequences containing repeats (FIASCO) protocol. Thirteen loci exhibited polymorphism with two to 13 alleles (mean 7.9 alleles/locus) in a test population and observed heterozygosity ranged from 0.3125 to 0.9688 (mean 0.7140). These loci should provide sufficient level of genetic variation to study the fine-scale population structure and reproductive ecology of the species.

Transgene for growth hormone in common carp (Cyprinus carpio L.) promotes thymus development

The transgenic carp were produced by micro-injection of CAgcGHc into the fertilized eggs. Observation of the thymus development between the transgenics and non-transgenic controls was carried out. The thymus of one-year-old transgenics F1 showed a great increase in both size and weight. The unilateral thymus of the transgenics weighed from 190 to 295 mg with average 218.6 mg, whereas the unilateral thymus of the controls weighed 20-81 mg with average 42.5 mg; i.e. the thymus weight in the transgenics was 5.14 fold over that in the controls. The index of thymus/body weight in the transgenics was 2.97 fold over the controls. Light microscopy observation indicated that the thymus of the transgenics; well developed with the thickened outer region and compactly arranged thymocytes, while the thymus in the controls were degenerating with the thinned outer region, scattered thymocytes and groups of fatty cells. Further analysis with the electron microscopy revealed that pro-liferous cells in the transgenics; were mainly small lymphocytes and no pathological changes were found. The results confirmed that the "All-fish" GH-transgene promotes thymus development and thymocyte proliferation, and retards thymus degeneration. The study has laid a foundation for further analysis of the immunobiological function in GH-transgenic carp.

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.

Silica-based 64-channel arrayed waveguide gratings with double functions

Silica-based 64-channel arrayed waveguide gratings (AWGs) with double functions and 0.4 nm (50 GHz) channel spacing have been designed and fabricated. On the same component, Gauss and flat-top output response spectra are obtained simultaneously. The test results show that when the insertion loss ranges from 3.5 dB to 6 dB,the crosstalk is better than -34 dB, the 1 dB bandwidth is 0.12 nm, the 3 dB bandwidth is 0,218 nm, and the polarization-dependent loss (PDL) is less than 0.5 dB for Gauss response. When the insertion loss ranges,from 5.8 dB to 7.8 dB, the crosstalk is better than -30 dB, the 1 dB bandwidth is 0.24 nm, the 3 dB bandwidth is 0.33 nm, and the PDL is less than 0.2 dB for flat-top response.

Growth and characterization of AlGaN/AlN/GaN HEMT structures with a compositionally step-graded AlGaN barrier layer

A new AlGaN/AlN/GaN high electron mobility transistor (HEMT) structure using a compositionally step-graded AlGaN barrier layer is grown on sapphire by metalorganic chemical vapour deposition (MOCVD). The structure demonstrates significant enhancement of two-dimensional electron gas (2DEG) mobility and smooth surface morphology compared with the conventional HEMT structure with high Al composition AlGaN barrier. The high 2DEG mobility of 1806 cm(2)/Vs at room temperature and low rms surface roughness of 0.220 nm for a scan area of 5 mu m x 5 mu m are attributed to the improvement of interfacial and crystal quality by employing the step-graded barrier to accommodate the large lattice mismatch stress. The 2DEG sheet density is independent of the measurement temperature, showing the excellent 2DEG confinement of the step-graded structure. A low average sheet resistance of 314.5 Omega/square, with a good resistance uniformity of 0.68%, is also obtained across the 50 mm epilayer wafer. HEMT devices are successfully fabricated using this material structure, which exhibits a maximum extrinsic transconductance of 218 mS/mm and a maximum drain current density of 800 mA/mm.

Annealing and activation of silicon implanted in semi-insulating InP substrates

We have investigated the annealing and activation of silicon implanted in both as-grown Fe-doped semi-insulating (SI) InP substrate and undoped SI InP substrate obtained by annealing high purity conductive InP wafer (wafer-annealed). Si implantations were performed at an energy of 500 keV and a dose of 1 X 10(15) cm(-2). Following the implantations, rapid thermal annealing (RTA) cycles were carried out for 30 s at different temperatures. The results of Raman measurements show that for 700degreesC/30s RTA, the two Si-implanted SI InP substrates have acquired a high degree of lattice recovery and electrical activation. However, further Hall measurements indicate that the carrier concentration of the wafer-annealed SI InP substrate is about three times higher than that of the as-grown Fe-doped SI InP substrate. The difference can be ascribed to the low Fe concentration of the wafer-annealed SI InP substrate.These experimental data imply that the use of the wafer-annealed SI InP substrate can be conducive to the improvement of InP-based device performances. (C) 2003 Elsevier Ltd. All rights reserved.

Electronic properties of sulfur passivated undoped-n(+) type GaAs surface studied by photoreflectance

Photoreflectance (PR) has been used to study surface electronic properties (electric field, Fermi level pinning, and density of surface states) of undoped-n(+) (UN+) GaAs treated in the solution of ammonium sulfide in isopropanol. Complex Fourier transformation (CFT) of PR spectra from passivated surface shows that the sulfur overlay on GaAs surface makes no contribution to Franz-Keldysh oscillations (FKOs). The barrier height measured by PR is derived from surface states directly, rather than the total barrier height, which includes the potentials derived from Ga-S and As-S dipole layers. Comparing with native oxidated surface, the passivation leads to 80 meV movement of surface Fermi level towards the conduction band minimum, and reduction by more than one order in density of surface states. (C) 2003 Elsevier Science B.V. All rights reserved.

Atomic hydrogen induced step bunching and fabrication of quantum wire arrays on GaAs (311)A substrate by molecular beam epitaxy

Atomic hydrogen assisted molecular beam epitaxy (MBE) is a novel type of epitaxial growth of nanostructures. The GaAs (311)A surface naturally forms one-dimensional step arrays by step bunching along the direction of (-233) and the space period is around 40nm. The step arrays extend over several mum without displacement. The InGaAs quantum wire arrays are grown on the step arrays as the basis. Our results may prompt further development of more uniform quantum wire and quantum dot arrays.

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.

The effect of substrate orientation on the morphology of InAs nanostructures on (001) and (11n)A/B(n=1-5) InP substrates

Strained InAs nanostructures have been grown by solid-source molecular beam epitaxy in In0.52Al0.48As matrix on different InP substrate surfaces ((0 0 1) and (1 1 n)A/B (n = 1 - 5)). The morphology of the nanostructures was characterized using atomic force microscopy (AFM). The AFM results reveal interesting differences in the size, shape, and alignment of the nanostructures between different oriented surfaces. It was found that some faceted nanostructures tend to form on A-type surfaces, the shape and the alignment of these nanostructures show clear dependence on the substrate orientation. Samples grown on (0 0 1) and B-type surfaces showed preferentially dense round dots. Dots formed on (1 1 3)B, (1 1 3)B and (1 1 5)B surfaces have a higher dot density and size homogeneity, which shows a potential for the production of high-quality and customized self-assembled quantum dots for photonics applications. (C) 2000 Elsevier Science B.V. All rights reserved.