空间飞行对稻田鱼腥藻遗传特性的影响

通过对具有高固氮酶活性的稻田鱼腥藻返地克隆株（ＡｏＳＲ１６）的回复再搭载及其返地样品的单克隆实验，发现空间飞行环境能导致该藻株再次出现性状分离现象，即部分单克隆株仍保持高固氮酶活性（如ＡｏＳＲ１６－１７），而另一部分单克隆株则回复到原始出发株（ＡｎａｂａｅｎａｏｒｙｚａＨＢ２３）的固氮酶活性水平。对ＡｏＳＲ１６－１７进行近两年的地面保持培养发现，这种高固氮酶活性的性状是可以遗传的。进一步通过ＲＡＰＤ分析方法，运用１２０个１０核苷酸随机引物对ＡｏＳＲ１６－１７和原始出发株的基因组ＤＮＡ进行多态性研究，结果发

淤泥湖退化水生植被恢复及其在湖泊资源天然生态库中作用的研究

对淤泥湖水生植被的天然恢复过程、群落组成、结构、功能与动态等进行了定位研究（１９９２～１９９５）．该湖水生植物共有２０科２９属４１种．４种生活型的植物种类在该湖均有分布，以沉水草本（１５种）和挺水草本（１３种）为多．８个分布区类型中世界广布成分１６种和东亚成分１０种．群落结构包括层次结构和层片结构．该彻共有８个群落类型；群落现存量３２０８．８ｇ·ｍ－２，全湖植被资源贮量为１６３６５．２ｔ．

ADSORBABILITY AND SEDIMENTATION EFFECT OF SUBMERGED MACROPHYTES ON SUSPENDED SOLIDS

To select better plant species for adsorption and deposition of suspended solids in water, effectively, eight species of submerged macrophytes, which are popular in the middle or downstream area of Yangtze River, were studied. The effects of their adsorbability and sedimentation on suspended solids were monitored in the microcosm systems with natural lake's sediment and water. Within one week's regular disturbance, according to their adsorbability of the macrophytes on suspended solids, the macrophytes were divided into two groups. Elodea nuttallii, Potamogeton crispus, Hydrilla verticillata, Myriophyllum spicatum, Potamogeton malaianus and Najas graminea were the macrophytes with stronger adsorbability. Vallisneria natans and Ceratoplyllum demersum were the macrophytes with weaker adsorbability. The average adsorbabilities of the two groups were 28.0 and 14.5 mg g(-1) FW-1, respectively. According to the sedimentation rate, the macrophytes were divided into three groups. P. crispus and H. verticillata were in the highest group. V.natans was in higher group. E nuttallii, M. spicatum, N. graminea, C demersum and P. malaianus were in the lowest group. The average sedimentation rates of the three groups were 3.42, 2.11 and 0.69 mg l(-1) d(-1). respectively. Therefore, P. crispus and H. verticillata were excellent species. C demersum was a poor species to improve transparency of water body.

Effects of polyaluminum chloride and copper sulfate on phosphorus and UV254 under different anoxic levels

Experimental sediments and water from shallow, eutrophic Dianchi Lakes were treated in a controlled laboratory microcosm using different chemicals under different anoxic levels. This study revealed that the polyaluminum chloride (PAC) was able to inhibit the phosphorus release and decrease the UV254 value at any anoxic level. When the DO concentrations were between 0.76-0.95 mg(.) L-1, the UV(254)value, total phosphorus (TP), and total dissolved phosphorus (TDP) in the water column were decreased by 71.93%, 87.12% and 64.24% respectively. The UV254, TP, and TDP were also decreased by 72.94%, 70.87% and 50.76% respectively at the levels of 4.56-5.32mg(.)L(-1) of DO concentrations. The treatment effects of TP and TDP in the water column using copper sulfate however were not as efficient as the PAC treatment. The UV254 value was increased with the addition of copper sulfate at every anoxic level tested but the chlorophyll-a (Chl-a) content was decreased rapidly and efficiently by copper sulfate more than the treatment by PAC. When the DO concentrations were 0.76-0.86mg(.)L(-1) and 4.75-5.14mg(.)L(-1), the Chl-a concentrations were decreased by 84.87% and 75.07% respectively through copper sulfate treatment. With additions of PAC and copper sulfate, the phosphorus fractions in sediments were shifted forward to the favorable shapes that have little ability of release. The TP concentrations in sediments were increased after treatment via PAC and copper sulfate. Under anoxic conditions, most of the BD-P (Fe-P) to NaOH-P (Al-P) was converted using the recommended PAC dose in BD-P rich sediment. Similar to the PAC, the copper sulfate also could flocculate the exchange phosphorus from sediment to overlying water. Overall though, the effects of copper sulfate treatment were not better than that of the PAC.

Records of enchytraeidae (Clitellata) from the People's Republic of China

Eleven species of terrestrial and aquatic Enchytraeidae are reported from southeastern China. Fridericia multisegmentata and Enchytraeus athecatus are new to science, while most of the others are recorded from the country for the first time.

White light emission from ultraviolet laser diode

A phosphor-conversion white light using an InGaN laser diode that emits 405 nm near-ultraviolet (n-UV) light and phosphors that emit in the red/green/blue region when excited by the n-UV light was fabricated. The relationship of the luminous flux and the luminous efficacy of the white light with injection current were discussed. Based on the evaluation method for luminous efficacy of light sources established by the Commission International de I'Eclairage (CIE) and the phosphor used in this experiment, a theoretical analysis of the experiment results and the maximum luminous efficacy of this white light fabrication method were also presented.

Growth and characterization of InN on sapphire substrate by RF-MBE

Indium nitride (InN) films were grown on sapphire substrates by radio-frequency plasma-excited molecular beam epitaxy (RF-MBE). Atomic force microscopy (AFM), reflection high-energy electron diffraction (RHEED), double-crystal X-ray diffraction (DCXRD) and photoluminescence (PL) spectroscopy were used to characterize the InN films. The results show that the InN films have good crystallinity, with full-width at half-maximum (FWHM) of InN (0 0 0 2) DCXRD peak being 14 arcmin. At room temperature, a strong PL peak at 0.79eV was observed. At 1.9eV or so, no peak was observed. In addition, it is found that the InN films grown with low-temperature (LT) InN buffer layer are of better quality than those without LT-InN buffer layer. (c) 2004 Elsevier B.V. All rights reserved.

Pressure behavior of Te isoelectronic centers in S-rich ZnS1-xTex alloy

The photoluminescence from ZnS1-xTex alloy with 0 < x < 0.3 was investigated under hydrostatic pressure up to 7 GPa. Two peaks were observed in the alloys with x < 0.01, which are related to excitons bound to isolated Te isoelectronic impurities (Te-1 centers) and Te pairs (Te-2 centers), respectively. Only the Te-2 related emissions were observed in the alloys with 0.01 < x < 0.03. The emissions in the alloys with 0.03 < x < 0.3 are attributed to the excitons bound to the Te-n (n greater than or equal to 3) cluster centers. The pressure coefficient of the Te-1 related peak is 89(4) meV/GPa, about 40% larger than that of the band gap of ZnS. On the other hand, the pressure coefficient of the Te-2 related emissions is only 52(4) meV/GPa, about 15% smaller than that of the ZnS band gap. A simple Koster-Slater model has been used to explain the different pressure behavior of the Te-1 and Te-2 centers. The pressure coefficient of the Te-3 centers is 62(2) meV/GPa. Then the pressure coefficients of the Te-n centers decrease rapidly with further increasing Te composition.

Photoelectrochemical behavior of a novel composite In0.15Ga0.85As/GaAs vertical bar GaAs/Al0.3Ga0.7As multiple quantum well electrode

A novel composite InxGa1-xAs/GaAs/GaAs/AlxGa1-xAs multiple quantum well material with different well widths was studied as a new kind of photoelectrode in a photoelectrochemical cell. The photocurrent spectrum and photocurrent-electrode potential curve were measured in ferrocene nonaqueous solution. Pronounced quantization effects and strong exciton absorption were observed in the photocurrent spectrum. The effects of surface states and interfacial states on the photocurrent-electrode potential curve are discussed. (C) 2000 Elsevier Science S.A. All rights reserved.

New insight into the origin of twin and grain boundary in InP

X-ray reflectivity curves show bi-crystal (twin) characteristics. Defect segregations at the twin boundary can be seen, whereas stress is relaxed at the edge of the boundary. Relaxation of the stress resulted in the formation of twins and other defects. As a result of the formation of such defects, a defect-free and stress-free zone or low defect density and small stress zone is created around the defects. Stress, chemical stoichiometry deviation and non-homogeneous distribution of impurities are the key factors that cause twins in LEC InP crystal growth. (C) 1999 Elsevier Science Ltd. All rights reserved.

Pressure behavior of deep centers in ZnSxTe1-x alloys

We have measured photoluminescence of ZnSxTe1-x alloys (x > 0.7) at 300 K and under hydrostatic pressure up to 7 GPa. The spectra contain only a broad emission band under excitation of the 406.7 nm line. Its pressure coefficients are 47, 62 and 45 meV/GPa for x = 0.98, 0.92 and 0.79 samples, which are about 26%, 7% and 38% smaller than that of the band gap in the corresponding alloys. The Stokes shifts between emission and absorption of the bands were calculated by fitting the pressure dependence of the emission intensity, being 0.29, 0.48 and 0.13 eV for the three samples, respectively. The small pressure coefficient and large Stokes shift indicate that the emission band observed in our samples may correspond to the Te isoelectronic center in the ZnSxTe1-x alloy.

HFC134a/HCFC141b混合气体水合物相平衡特性

国家自然科学基金