中国鲤科鱼类染色体组型的研究——Ⅸ.鳊亚科9种鱼和鲴亚科1种鱼的染色体组型

<正> 我们曾报道过分布于湖北省的鳊、鲴亚科鱼类的核型。本文继续报道采自四川和广东省的鳊、鲴亚科另10种鱼的核型考察结果。材料和方法四川半(歺又鱼)由于采集困难,仅分析了一尾雄鱼。其余9种鱼均分析了3—5尾,包括雌雄两种性别(表1)。染色体标本的制备采用体外短期培养肾细胞制片法(采自四川的鱼),或肾细胞直接制片法(采自广东的鱼)。根据我们实验室以前的工作,两种方法的核型分析结果基本上一致。每种鱼计数60—170个细胞确定其2n数。染色体分组按Levan氏的标准,核型分析方法和臂数计算均同以前的报道。核型图

How polluted is the Yangtze River? Water quality downstream from the Three Gorges Dam

The concentrations of major anions and cations, nitrogen and phosphorus, dissolved and particulate trace elements, and organic pollutants were determined for the middle and lower reaches of the Yangtze River (Changjiang) from below the Three Gorges Dam (TGD) to the mouth at Shanghai in November 2006. The concentration of dissolved inorganic phosphate (DIP) was constant at a low level of 6-8 mu gP/L, but the concentration of nitrate (NO3-) approximately doubled downstream and was closely correlated with K+. This translated to a daily load of well over 1000 It of dissolved inorganic nitrogen (DIN) at Datong. The average concentrations of dissolved Pb (0.078 +/- 0.023 mu g/L), Cd (0.024 +/- 0.009 mu g/L), Cr(0.57 +/- 0.09 mu g/L), Cu (1.9 +/- 0.7 mu g/L), and Ni (0.50 +/- 0.49 mu g/L) were comparable with those in other major world rivers, while As (3.3 +/- 1.3 mu g/L) and Zn (1.5 +/- 0.6 mu g/L) were higher by factors of 5.5 and 2.5, respectively. The trace element contents of suspended particles of As (31 +/- 28 mu g/g), Pb (83 +/- 34 mu g/g), and Ni (52 +/- 16 mu g/g) were close to maximum concentrations recommended for rivers by the European Community (EC). The average concentrations of Cd (2.6 +/- 1.6 mu g/g), Cr (185 +/- 102 mu g/g), Cu (115 +/- 106 mu g/g), and Zn (500 +/- 300 mu g/g) exceeded the EC standards by a factor of two, and Hg (4.4 +/- 4.7 mu g/g) by a factor of 4 to 5. Locally occurring peak concentrations exceed these values up to fourfold, among them the notorious elements As, Hg, and Tl. All dissolved and particulate trace element concentrations were higher than estimates made twenty years ago [Zhang, J., Geochemistry of trace metals from Chinese river/estuary systems: an overview. Estuar Coast Shelf Sci 1995; 41: 631-658.]. The enormous loads of anthropogenic pollutants disposed to the river were diluted by the large water discharge of the Yangtze even during the lowest flow resulting in the relatively low concentration levels of trace elements and organic pollutants observed. We estimated loads of e.g. As, Pb and Ni to the East China Sea to be about 4600 kg As d(-1), 3000 kg Pb d(-1), and 2000 kg Ni d(-1). About 6000 t d(-1) of dissolved organic carbon (DOC) was delivered into the sea at the time of our cruise. We tested for 236 organic pollutants, and only the most infamous were found to be barely above detection limits. We estimated that the load of chlorinated compounds, aromatic hydrocarbons, phenols, and PAHs were between 500 and 3500 kg d(-1). We also detected eight herbicides entering the estuary with loads of 5-350 kg d(-1). The pollutant load, even when at low concentrations, are considerable and pose an increasing threat to the health of the East China Sea ecosystem. (c) 2008 Elsevier B.V. All rights reserved.

Identification of a gene, ccr-1 (sll1242), required for chill-light tolerance and growth at 15 degrees C in Synechocystis sp PCC 6803

Synechocystis sp. PCC 6803 exposed to chill (5 degrees C)-light (100 mu mol photons m(-2) s(-1)) stress loses its ability to reinitiate growth. From a random insertion mutant library of Synechocystis sp. PCC 6803, a sll1242 mutant showing increased sensitivity to chill plus light was isolated. Mutant reconstruction and complementation with the wild-type gene confirmed the role of sll1242 in maintaining chill-light tolerance. At 15 degrees C, the autotrophic and mixotrophic growth of the mutant were both inhibited, paralleled by decreased photosynthetic activity. The expression of sll1242 was upregulated in Synechocystis sp. PCC 6803 after transfer from 30 to 15 degrees C at a photosynthetic photon flux density of 30 mu mol photons m(-2) S-1. sll1242, named ccr (cyanobacterial cold resistance gene)- 1, may be required for cold acclimation of cyanobacteria in light.

In situ studies on the distribution patterns and dynamics of microcystins in a biomanipulation fish - bighead carp (Aristichthys nobilis)

The distribution and dynamics of microcystins in various organs of the phytoplanktivorous bighead carp were studied monthly in Lake Taihu, which is dominated by toxic cyanobacteria. There was a good agreement between LC-MS and HPLC-UV determinations. Average recoveries of spiked fish samples were 63% for MC-RR and 71% for MC-LR. The highest MC contents in intestine, liver, kidney and spleen were 85.67, 2.83, 1.70 and 1.57 mu g g(-1) DW, respectively. MCs were much higher in mid-gut walls (1.22 mu g g(-1) DW) than in hind- and fore-gut walls (0.31 and 0.18 mu g g(-1) DW, respectively), suggesting the importance of mid-gut wall as major site for MC absorption. A cysteine conjugate of MC-LR was detected frequently in kidney. Among the muscle samples analyzed, 25% were above the provisional tolerable daily intake level by WHO. Bighead is strongly resistant to microcystins and can be used as biomanipulation fish to counteract cyanotoxin contamination in eutrophic waters. (c) 2006 Elsevier Ltd. All rights reserved.

Effects of solar ultraviolet radiation on photosynthesis of the marine red tide alga Heterosigma akashiwo (Raphidophyceae)

In order to assess the short- and long-term impacts of UV radiation (LTVR, 280-400 nm) on the red tide alga, Heterosigma akashiwo, we exposed the cells to three different solar radiation treatments (PAB: 280-700 rim, PA: 320-700 nm, R 400-700 nm) under both solar and artificial radiation. A significant decrease in the effective quantum yield () during high irradiance periods (i.e., local noon) was observed, but the cells partially recovered during the evening hours. Exposure to high irradiances for 15, 30, and 60 min under a solar simulator followed by the recovery (8 h) under dark, 9 and 100 mu mol photons m(-2) s(-1) of PAR, highlighted the importance of the irradiance level during the recovery period. Regardless the radiation treatments, the highest recovery (both in rate and total Y) was found at a PAR irradiance of 9 mu mol photons m(-2) s(-1), while the lowest was observed at 100 mu mol photons m(-2) s(-1). In all experiments, PAR was responsible for most of the observed inhibition; nevertheless, the cells exposed only to PAR had the highest recovery in any condition, as compared to the other radiation treatments. In long-term experiments (10 days) using semi-continuous cultures, there was a significant increase of UV-absorbing compounds (UVabc) per cell from 1.2 to > 4 x 10(-6) mu g UVabc cell(-1) during the first 3-5 days of exposure to solar radiation. The highest concentration of UVabc was found in samples exposed in the PAB as compared to PA and P treatments. Growth rates (mu) mimic the behavior of UV-absorbing compounds, and during the first 5 days mu increased from < 0.2 to ca. 0.8, and stayed relatively constant at this value during the rest of the experiment. The inhibition of the Y decreased with increasing acclimation of cells. All our data indicates that H. akashiwo is a sensitive species, but was able acclimate relatively fast (3-5 days) synthesizing UV-absorbing compounds and thus reducing any impact either on photosystem 11 or on growth. (c) 2006 Published by Elsevier B.V.

The change of gaseous carbon fluxes following the switch of dominant producers from macrophytes to algae in a shallow subtropical lake of China

Successions of lake ecosystems from clear-water, macrophyte-rich conditions into turbid states with abundant phytoplankton have taken place in many shallow lakes in China. However, little is know about the change of carbon fluxes in lakes during such processes. We conducted a case study in Lake Biandantang to investigate the change of carbon fluxes during such a regime shift. Dissolved aquatic carbon and gaseous carbon (methane (CH4) and carbon dioxide (CO2)) across air-water interface in three sites with different vegetation covers and compositions were studied and compared. CH4 emissions from three sites were 0.62 +/- 0.36, 0.70 +/- 0.36, and 1.31 +/- 0.57 mg m(-2) h(-1), respectively. Correlation analysis showed that macrophytes, rather than phytoplankton, directly positively affected CH4 emission. CO2 fluxes of three sites in Lake Biandantang were significantly different, and the average values were 77.8 +/- 20.4, 52.2 +/- 14.1 and 3.6 +/- 26.8 mg m(-2) h(-1), respectively. There were an evident trend that the larger macrophyte biomass, the lower CO2 emissions. Correlation analysis showed that in different sites, dominant plant controlled CO2 flux across air-water interface. In a year cycle, the percents of gaseous carbon release from lake accounting for net primary production were significantly different (from 39.3% to 2.8%), indicating that with the decline of macrophytes and regime shift, the lake will be a larger carbon source to the atmosphere. (c) 2006 Elsevier Ltd. All rights reserved.

The functional divergence of two glgP homologues in Synechocystis sp PCC 6803

Glycogen phosphorylase (GlgP, EC 2.4.1.1) catalyzes the cleavage of glycogen into glucose-1-phosphate (Glc-1-P), the first step in glycogen catabolism. Two glgP homologues are found in the genome of Synechocystis sp. PCC 6803, a unicellular cyanobacterium: sll1356 and slr1367. We report on the different functions of these glgP homologues. sll1356, rather than slr1367, is essential for growth at high temperatures. On the other hand, when CO2-fixation and the supply of glucose are both limited, slr1367 is the key factor in glycogen metabolism. In cells growing autotrophically, sll1356 plays a more important role in glycogen digestion than slr1367. This functional divergence is also supported by a phylogenetic analysis of glgP homologues in cyanobacteria.

Fixation of the type species of the genus Sinilabeo and description of a new species from the upper Yangtze river basin, China (Pisces : Cyprinidae)

The type species of the cyprinid genus Sinilabeo was misidentified as Varicorhinus tungting, and the species under the generic name belong to Bangana and Linichthys. In order to make Sinilabeo available, its type species is fixed under Article 70.3.2 of the 1999 edition of the International Code of Zoological Nomenclature as S. hummeli, a new species herein described from the upper Yangtze River basin in Chongqing City and Sichuan Province, South China. A re-definition is provided for Sinilabeo. It resembles Qianlabeo in having an upper lip only present in the side of the upper jaw and uncovered by the rostral fold, but missing in the median part of the upper jaw that, instead, bears a thin, flexible, and cornified sheath, covered by the rostral fold, a character that can separate both from all other existing genera of Asian labeonins. However, Sinilabeo is distinguished from Qianlabeo in the presence of a rostral fold disconnected from the lower lip; a broadly interrupted postlabial groove only restricted to the side of the lower jaw; an upper lip, which is only present in the side of the upper separated from it by a groove; 9-10 branched dorsal-fin rays; two pairs of tiny maxillary barbels.

1 x 4 Ge-on-SOI PIN Photodetector Array for Parallel Optical Interconnects

High-quality Ge film was epitaxially grown on silicon on insulator using the ultrahigh vacuum chemical vapor deposition. In this paper, we demonstrated that the efficient 1 4 germanium-on-silicon p-i-n photodetector arrays with 1.0 mu m Ge film had a responsivity as high as 0.65 A/W at 1.31 mu m and 0.32 A/W at 1.55 mu m, respectively. The dark current density was about 0.75 mA/cm(2) at 0 V and 13.9 mA/cm(2) at 1.0 V reverse bias. The detectors with a diameter of 25 mu m were measured at 1550 nm incident light under 0 V bias, and the result showed that the 3-dB bandwidth is 2.48 GHz. At a reverse bias of 3 V, the bandwidth is about 13.3 GHz. The four devices showed a good consistency.

Electronic structures of GaAs/AlxGa1-xAs quantum double

In the framework of effective mass envelope function theory, the electronic structures of GaAs/AlxGa1-xAs quantum double rings(QDRs) are studied. Our model can be used to calculate the electronic structures of quantum wells, wires, dots, and the single ring. In calculations, the effects due to the different effective masses of electrons and holes in GaAs and AlxGa1-xAs and the valence band mixing are considered. The energy levels of electrons and holes are calculated for different shapes of QDRs. The calculated results are useful in designing and fabricating the interrelated photoelectric devices. The single electron states presented here are useful for the study of the electron correlations and the effects of magnetic fields in QDRs.

Influence of AlN interfacial layer on electrical properties of high-Al-content Al0.45Ga0.55N/GaN HEMT structure

Unintentionally doped high-Al-content Al0.45Ga0.55N/GaN high electron mobility transistor (HEMT) structures with and without AlN interfacial layer were grown by metal-organic chemical vapor deposition (MOCVD) on two-inch sapphire substrates. The effects of AlN interfacial layer on the electrical properties were investigated. At 300 K, high two-dimensional electron gas (2DEG) density of 1.66 x 10(11) cm(-2) and high electron mobility of 1346 cm(2) V-1 s(-1) were obtained for the high Al content HEMT structure with a 1 nm AlN interfacial layer, consistent with the low average sheet resistance of 287 Omega/sq. The comparison of HEMT wafers with and without AlN interfacial layer shows that high Al content AlGaN/AlN/GaN heterostructures are potential in improving the electrical properties of HEMT structures and the device performances. (c) 2006 Elsevier B.V. All rights reserved.

Porous ZnAl2O4 spinel nanorods doped with Eu3+: synthesis and photoluminescence

Eu3+-doped zinc aluminate (ZnAl2O4) nanorods with a spinel structure were successfully synthesized via an annealing transformation of layered precursors obtained by a homogeneous coprecipitation method combined with surfactant assembly. These spinel nanorods, which consist of much finer nanofibres together with large quantities of irregular mesopores and which possess a large surface area of 93.2 m(2) g(-1) and a relatively narrow pore size distribution in the range of 6 - 20 nm, are an ideal optical host for Eu3+ luminescent centres. In this nanostructure, rather disordered surroundings induce the typical electric-dipole emission (D-5(0) --> F-7(2)) of Eu3+ to predominate and broaden.

Liquid-phase-epitaxy-grown InAsxSb1-x/GaAs for room-temperature 8-12 mu m infrared detectors

High-quality InAsxSb1-x (0 < x <= 0.3) films are grown on GaAs substrates by liquid phase epitaxy and electrical and optical properties of the films are investigated, revealing that the films exhibit Hall mobilities higher than 2x10(4) cm(2) V-1 s(-1) and cutoff wavelengths longer than 10 mu m at room temperature (RT). Photoconductors are fabricated from the films, and notable photoresponses beyond 8 mu m are observed at RT. In particular, for an InAs0.3Sb0.7 film, a photoresponse of up to 13 mu m with a maximum responsivity of 0.26 V/W is obtained at RT. Hence, the InAsxSb1-x films demonstrate attractive properties suitable for room-temperature, long-wavelength infrared detectors. (c) 2006 American Institute of Physics.

A 1.5 mu m n-type InGaAsP/InGaAsP modulation-doped multiple quantum well DFB laser by MOCVD

1.5 mu m n-type InGaAsP/InGaAsP modulation-doped multiple quantum well (MD-MQW) DFB lasers have been fabricated successfully by low pressure metal organic chemical vapour deposition (LP-MOCVD) technology. The experimental results indicate that n-type MD-MQWs can effectively reduce the threshold Current compared with conventional multiple quantum well DFB lasers. Theoretical analysis indicates that such an effect is due to the much smaller absorption loss and lower Auger recombination, compared with that in an undoped MQW structure. Moreover, the introduction of n-type dopant of suitable levels of concentration in the barrier layers enhances the dynamic characteristics of DFB lasers, due to a coupling between the adjacent quantum well layers and tunnelling-assisted injection, which can reduce the relatively long capture time and increase the effective differential gain 1/X dG/dn .

The effect of AlN growth time on the electrical properties of Al0.38Ga0.62N/AlN/GaN HEMT structures

Al0.38Ga0.62N/AIN/GaN HEMT structures have been grown by metal-organic chemical vapor deposition (MOCVD) on 2-inch sapphire substrates. Samples with AIN growth time of 0s (without AIN interlayer), 12, 15, 18 and 24s are characterized and compared. The electrical properties of two-dimensional electron gas (2DEG) are improved by introducing AIN interlayers. The AIN growth time in the range of 12-18s, corresponding to the AIN thickness of 1-1.5 nm, is appropriate for the design of Al0.38Ga0.62N/AIN/GaN HEMT structures. The lowest sheet resistance of 277 Omega sq(-1) and highest room temperature 2DEG mobility of 1460 cm(2)V(-1) s(-1) are obtained on structure with AIN growth time of 12s. The structure with AIN growth time of 15s exhibits the highest 2DEG concentration of 1.59 x 10(13) cm(-2) and the smallest RMS surface roughness of 0.2 nm. (c) 2006 Elsevier B.V. All rights reserved.