葛仙米光合活性对盐胁迫的反应

收集人工条件下培养的葛仙米球形群体，以不同浓度的NaCl溶液处理，当浓度超过0．2mol／L后，叶绿素a荧光的可变部分（Fv）与最大荧光（Fm）之比值（Fv／Fm）与NaCl浓度呈负相关，光合放氧速率也随着NaCl浓度升高而降低．这两者随氯化钠浓度升高而降低的趋势均呈现出两个阶段性：低NaCl浓度时的缓慢降低阶段和高NaCl浓度时的快速降低阶段．Fv／Fm比值的转折点在0．2mol／L，而光合放氧速率的在0．4mol／L，后者与海水的浓度接近．呼吸作用几乎不受NaCl的影响．光系统I（PSI）和光系统II

鸭儿湖地区多氯代二苯并二/呋喃(PCDD/F)的污染状况及其来源归宿的初步研究

对鸭儿湖地区的底泥和土壤样品中的多氯代二苯并二／呋喃（ＰＣＤＤ／Ｆ）的污染状况进行了研究．结果表明，鸭儿湖部分地区已被ＰＣＤＤ／Ｆ严重污染，该类污染物来源于附近某化工厂排放的化工废水，其中，ＰＣＤＤ／Ｆ主要以高氯取代的ＨｐＣＤＤｓ和ＯＣＤＤ为主，总结我们的已有实验结果，鸭儿湖１号氧化塘中高残留的ＰＣＤＤ／Ｆ如果控制不当将会转移扩散，可能造成对周围环境的进一步污染．

广东鲮鱼鱼苗的流行病及其预防试验

<正> 鲮鱼[Cirrhina molitorella(Cur.＆Val.)]是广东地区饲养的家鱼之一,群众有一套用“大草”养它的经验,但在饲育过程中,鱼苗往往发生一种流行病,导致大量死亡。患病的鱼苗,身体瘦弱,体色发黑,游动缓慢,常浮游在靠近池边的水面上,不久即翻身死亡。情况严重时全池鱼苗能全部死完。但过去并没有引起水产科学工作者的注意。为了提高角苗的成活率和鱼苗的体质,给培育鱼种和饲养成鱼打下更好的基础,对鲮角鱼苗病的研

Site-directed gene integration in transgenic zebrafish mediated by cre recombinase using a combination of mutant Lox sites

With current gene-transfer techniques in fish, insertion of DNA into the genome occurs randomly and in many instances at multiple sites. Associated position effects, copy number differences, and multiple gene interactions make gene expression experiments difficult to interpret and fish phenotype less predictable. To meet different fish engineering needs, we describe here a gene targeting model in zebrafish. At first, four target zebrafish lines, each harboring a single genomic lox71 target site, were generated by zebrafish transgenesis. The zygotes of transgenic zebrafish lines were coinjected with capped Cre mRNA and a knockin vector pZklox66RFP. Site-specific integration event happened from one target zebrafish line. In this line two integrant zebrafish were obtained from more than 80,000 targeted embryos (integrating efficiency about 10(-4) to 10(-5)) and confirmed to have a sole copy of the integrating DNA at the target genome site. Genomic polymerase chain reaction analysis and DNA sequencing verified the correct gene target events where lox71 and lox66 have accurately recombined into double mutant lox72 and wild-type loxP. Each integrant zebrafish chosen for analysis harbored the transgene rfp at the designated egfp concatenates. Although the Cre-mediated recombination is site specific, it is dependent on a randomly placed target site. That is, a genomic target cannot be preselected for integration based solely on its sequence. Conclusively, an rfp reporter gene was successfully inserted into the egfp target locus of zebrafish genome by Cre-lox-mediated recombination. This site-directed knockin system using the lox71/lox66 combination should be a promising gene-targeting platform serving various purposes in fish genetic engineering.

Acid volatile sulfide and simultaneously extracted metals in the sediment cores of the Pearl River Estuary, South China

The acid-volatile sulfide (AVS), simultaneously extracted metals (SEM), total metals, and chemical partitioning in the sediment cores of the Pearl River Estuary (PRE) were studied. The concentrations of total metals, AVS, and SEM in the sediment cores were generally low in the river outlet area, increased along the seaward direction, and decreased again at the seaward boundary of the estuary. The amounts of AVS were generally greater in deeper sediments than in surface sediments. SEM/AVS was > 1 in the surface sediments and in the river outlet cores. The ratio was < 1 in the sediments down the profiles, suggesting that AVS might play a major role in binding heavy metals in the deep sediments of the PRE. The SEM may contain different chemical forms of trace metals in the sediments, depending on the metal reaction with 1 M cold HCl in the AVS procedure compared with the results of the sequential chemical extraction. The SEM/AVS ratio prediction may overestimate trace metal availability even in the sediments with high AVS concentrations. (c) 2004 Elsevier Inc. All rights reserved.

Genetic structure of Chinese sucker population Myxocyprinus asiaticus in the Yangtze River based on mitochondrial DNA marker

The sequencing analysis of the mitochondrial DNA control region (mtCR DNA) was performed to assess the genetic divergence and population structure of the Chinese sucker Myxocyprinus asiaticus (Cypriniformes Catostomidae) using four sample lots from natural populations of the Yangtze River. The mtCR DNA sequences of approximately 920 base pairs were obtained. A total of 223 nucleotide positions were polymorphic, and these defined 39 haplotypes. Of the 39 haplotypes, 37 (90%) were not shared, and among the populations as a whole there was little sharing of haplotypes. The average haplotype diversity (0.958) and the average nucleotide diversity (0.052) indicated a higher level of genetic diversity of Chinese sucker through the river. Analysis of molecular variation (AMOVA) of data revealed significant partitioning of variance (P<0.001) among populations (60.29%), and within populations (39.71%). The topology according to the neighbor joining and maximum parsimony methods showed mosaic composition of the 39 haplotypes, suggesting that the populations wore not completely divergent. The pairwise F statistic values, however, indicated that the population structuring existed to some extent among the geographic populations. There was a positive relationship between the aquatic distance and the genetic distance (Fst) among the populations (P<0.05). Based on our data, it is suggested that genetic drift, gene flow, and stochastic events are the possible factors influencing the population structure and genetic variation.

Removal of dibutyl phthalate by a staged, vertical-flow constructed wetland

Two sets of small scale systems of staged, vertical-flow constructed wetlands (VFCW) were operated in a greenhouse to study the purification of dibutyl phthalate (DBP) in admeasured water. Each system consisted of two chambers in which water flowed downward in chamber I and then upward in chamber 2. The systems were intermittently fed with wastewater under a hydraulic load of 420 mm(.)d(-1). The measured influent concentrations of DBP in the experimental system were 9.84 mg(.)l(-1), while the other system was used as a control and received no DBP. Effluent concentrations of the treated system averaged 5.82 mug(.)l(-1) and were far below the Chinese DBP discharge standard of less than or equal to0.2 mg(.)l(-1). These results indicate the potential purification capacity of this new kind of constructed wetland in removing DBP from a polluted water body.

Growth hormone gene transfer in common carp

The first successful case of transgenic fish was achieved in 1984. It is in a model system that the integration and expression of recombinant human growth hormone (hGH) in host red common carp (Cyprinus carpio, red var.) have been thoroughly studied. Recently, the integration sites have been recovered and characterized. Compared with non-transgenic peers, hGH-transgenic fish are prior in dietary utilization and growth performance. In view of bio-safety and bio-ethics, an "all-fish" construct CAgcGH, grass carp growth hormone fused with common carp P-actin promoter, has been generated and transferred into Yellow River carp (C carpio, local strain in Yellow River) fertilized eggs. Under middle-scale trial, CAgcGH-transgenics show higher growth rate and food conversion efficiency than the controls, which is consistent to laboratory findings. To avoid the potential impact of transgenic fish on the environment, a sterile strain of transgenic triploid fish has been successfully produced. The "all-fish" transgenic common carp is also approved safe enough as daily food, according to a test based on the pathological principles of new medicines issued by the Ministry of Health of China. The "all-fish" transgenic common carp with growth enhancement is now ready for market, but looking for governmental authorization. (C) 2003 Editions scientifiques et medicales Elsevier SAS and Ifremer/IRD/Inra/Cemagref. All rights reserved.

Mode Characteristics for Square Resonators With a Metal Confinement Layer

Microsquare resonators laterally confined by SiO2/Au/air multilayer structure are investigated by light ray method with reflection phase-shift of the multiple layers and two-dimensional (2-D) finite-difference time-domain (FDTD) technique. The reflectivity and phase shift of the mode light ray on the sides of the square resonator with the semiconductor/SiO2/Au/air multilayer structure are calculated for TE and TM modes by transfer matrix method. Based on the reflection phase shift and the reflectivity, the mode wavelength and factor are calculated by the resonant condition and the mirror loss, which are in agreement well with that obtained by the FDTD simulation. We find that the mode factor increases greatly with the increase of the SiO2 layer thickness, especially as d < 0.3 mu m. For the square resonator with side length 2 mu m and refractive index 3.2, anticrossing mode couplings are found for confined TE modes at wavelength about 1.6 mu m at d = 0.11 mu m, and confined TM modes at d = 0.71 mu m, respectively.

Dispersion-compensating photonic crystal fibers with special characteristics

Based on the modified dual core structure, three kinds of special photonic crystal fibers are presented, which are extremely large negative dispersion, super-broad bond, and large area made field dispersion-compensating photonic crystal fibers (DCPCF). For extremely large negative dispersion DCPCF, the peak of negative dispersion reaches -5.9 x 10(4) ps/(mn km). Super-broad bond DCPCF has broadband large negative dispersion and the dispersion value varies linearly from -380 ps/(nm km) to -420 ps/(nm km) in the C band. The designed large area made field DCPCF has a peak dispersion of -1203 ps/(nm km) with the inner core mode area of 47 mu m(2) and outer core mode area of 835 mu m(2). Furthermore, for the large area mode field DCPCF, the experimental result is also obtained. (C) 2008 Wiley Periodicals, Inc.

Electronic structure of ZnO wurtzite quantum wires

The electronic structure and optical properties of ZnO wurtzite quantum wires with radius R >= 3 nm are studied in the framework of six-band effective-mass envelope function theory. The hole effective-mass parameters of ZnO wurtzite material are calculated by the empirical pseudopotential method. It is found that the electron states are either two-fold or four-fold degenerate. There is a dark exciton effect when the radius R of the ZnO quantum wires is in the range of [3,19.1] nm (dark range in our model). The dark ranges of other wurtzite semiconductor quantum wires are calculated for comparison. The dark range becomes smaller when the |Delta(so)| is larger, which also happens in the quantum-dot systems. The linear polarization factor of ZnO quantum wires is larger when the temperature is higher.

Growth of single crystalline ZnxCd1-xS nanocombs by metallo-organic chemical vapor deposition

Single crystalline ternary ZnxCd1-xS nanocombs, which have 'comb' shaped' teeth on one side, have been synthesized by a one-step metallo-organic chemical vapor deposition process at a low temperature of 420 degrees C. The asymmetric, growth behavior of the nanocombs is likely to be induced by the polarization of the c-ptane. Because of the uniform structure and perfect geometrical shape, the nanoteeth could be potentially useful as nanocantilever arrays for nanosensors and, nanotweezers. (c) 2006 Elsevier B.V. All rights reserved.

Fabrication of thermo-optic switch in silicon-on-insulator

Silicon-on-insulator technology has been used to fabricate 2 x 2 thermo-optic switches. The switch shows crosstalk of -23.4 dB and extinction ratio of 18.1 dB in the bar-state. The switching speed is less than 30 mus and the power consumption is about 420 mW The measured excess loss is 1.8 dB. These merits make the switch more attractive for applications in wavelength division multiplexing.

Raman scattering of nanocrystalline silicon embedded in SiO2

Raman scattering of nanocrystalline silicon embedded in SiO2 matrix is systematically investigated. It is found that the Raman spectra can be well fitted by 5 Lorentzian lines in the Raman shift range of 100-600 cm(-1). The two-phonon scattering is also observed in the range of 600-1100 cm(-1) The experimental results indicate that the silicon crystallites in the films consist of nanocrystalline phase and amorphous phase; both can contribute to the Raman scattering. Besides the red-shift of the first order optical phonon modes with the decreasing size of silicon nanocrystallites, we have also found an enhancement effect on the second order Raman scattering, and the size effect on their Raman shift.

Photoluminescence from surface-oxidized Ge nanoclusters

Photoluminescence from gas-evaporated Ge nanoclusters consisting of a crystalline core encased in an oxide shell are presented. An as-grown sample shows room temperature luminescence with separate peaks around 357 and 580 nm. Prolonged air exposure of the clusters reduces the Ge core dimensions, and the emission initially at 580 nm shifts to 420 nm; however, the violet luminescence at 357 nm displays no difference. These results indicate that there are two mechanisms involved with light emission from Ge nanoclusters, visible light emission associated with the quantum confinement effect, and violet light emission correlated to luminescent centers. (C) 1998 Elsevier Science B.V.