椭圆背角无齿蚌对水中重金属的积累作用及其氨基酸含量的变化

饲养在滇池水中的椭圆背角无齿蚌氨基酸含量只有饲养在松华坝水库水中蚌的氨基酸含量一半,质量分数分别是680 57mg/hg和1477 14mg/hg。检测表明椭圆背角无齿蚌对砷、铅、锌、铜、铁元素有一定的富集能力,说明由于滇池污染,椭圆背角无齿蚌在滇池中虽然可以生存,但这一物种资源的利用价值受到严重影响。

武汉东湖不同湖区底泥总磷含量及变化的研究

以武汉东湖为对象 ,研究了 1 998.0 3— 1 999.0 2期间不同营养水平湖区底泥中 (0—5cm ,5— 1 0cm)总磷的含量及季节动态。 6个站平均总磷含量为 1 .1 5mg/g ,同 80年代初相比 ,Ⅰ、Ⅱ站底泥中总磷含量分别增高 1 .42倍和 1 .0 3倍。受污水排放影响较重的 0站磷含量高达 2 .78mg/g,而受污水排放影响较小的Ⅳ、Ⅴ站仅分别为 0 .52mg/g和 0 .50mg/g。东湖底泥中磷年平均含量与湖水中磷年平均浓度相关系数极高 (r=0 .997,n =5

水体富营养化对大型底栖动物群落结构及多样性的影响

在武汉东湖营养水平不同的四个湖区 ,对大型底栖动物的群落结构和物种多样性进行周年研究。大型底栖动物的物种多样性与营养水平呈相反趋势 ,富营养化导致多样性明显降低。研究还表明 ,霍甫水丝蚓的密度与水体营养水平呈正相关系 ,在超富营养水体中其密度最高 ,年平均 350 2ind ./m2 ,最高可达 1 0 52 4ind ./m2 ,这与其能忍受由于富营养导致的低氧环境有关 ;而在中营养水体中平均密度仅 2 7ind ./m2 。首次讨论了中国长足摇蚊与水体营养水平的关系 ,研究结果显示 ,中国长足摇蚊应属

草鱼、团头鲂对标记水蕹菜消化吸收的初步研究

应用~(32)P作示踪原子标记水蕹菜,对其消化吸收率,草鱼平均为(5)天61.39％,团头鲂为(8)天62.30％。在比放射性强度为680×10~4贝可/升的标记液中,标记24小时水蕹菜对~(32)P的吸收率达99％。

Serum concentrations of gonadotropins and steroid hormones of Neophocaena phocaenoides asiaeorientalis in middle and lower regions of the Yangtze River

As a relatively isolated and unique freshwater population, the Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis) is the most endangered subpopulation of this species. The objective of this study was to improve our understanding of their reproductive endocrinology by measuring (radioimmunoassay) serum concentrations of FSH, LH, estradiol (E-2), progesterone (P-4) and testosterone (T-2) in free-ranging animals. Blood samples were collected from 66 Yangtze finless porpoises (41 males and 25 females) captured in the middle and lower reaches of the Yangtze River. Based on significant variation of serum T-2 concentrations in males with body length (BL) > 138 cm, we inferred that they were mature; in these animals, there were significant seasonal variations in serum T-2 concentrations, with the highest concentrations in March and April (502.0 +/- 319.8 ng/dL, mean +/- S.D.) and the lowest in December (79.4 +/- 83.2 ng/dL). Serum T-2 concentrations positively correlated with serum concentrations of LH and weakly correlated with serum concentrations of E-2, whereas there was a significant negative correlation between serum LH and FSH concentrations in males > 138 cm. The smallest apparently pregnant female porpoise had a BL of 130 cm. Serum P-4 concentrations ranged from 13.2 to 112.4 ng/mL (43.9 +/- 28.3 ng/mL) in pregnant females, and fluctuated under 1.0 ng/mL in non-pregnant females with BL > 130 cm. Serum LH concentrations were significantly higher in non-pregnant females > 130 cm versus those females < 130 cm. To our knowledge, this is the first study of endocrine-related maturity and seasonal breeding characteristics of the Yangtze finless porpoise. (c) 2006 Elsevier Inc. All rights reserved.

Effects of submerged macrophytes on kinetics of alkaline phosphatase in Lake Donghu - I. Unfiltered water and sediments

The impacts of submerged macrophytes on kinetics of alkaline phosphatase were studied in two 680 m(2) enclosures in a shallow Chinese freshwater lake (Donghu Lake) from April to October 1996, and two experimental pools (120 m(2)) built inland in 1998. The submerged macrophytes were Vallisneria sp, Potamogeton crispus. In the presence of macrophytes, the concentration of orthophosphate was significantly lower, coupled with the decreasing function of organic P hydrolysis, in terms of lower V-max and higher K-m values of aIkaline phosphatase in water, filtered and unfiltered (0.45 mu m); in the interstitial water, the V-max values of the enzyme in sediments were significantly lower, exhibited by a spatial and vertical profile. The results implied the key role of submerged macrophytes was the retention of P nutrients. (C) 2000 Elsevier Science Ltd. All rights reserved.

Studies on the biology of Chaoborus flavicans (Meigen) (Diptera : Chaoboridae) in a fish-free eutrophic pond, Japan

Population dynamics of Chaoborus flavicans larvae of various instars was studied from November 1986 to December 1987 in a eutrophic, fish-free pond, Japan. First and 2nd instar larvae were observed from late April to late October, indicating a reproductive period of about half a year. C. flavicans overwintered in the 4th instar larvae. In water column samples, total density of all instars was 680-23 680 m(-2), and pupal density 0-2 600 m(-2); larvae of the Ist, 2nd, and 3rd instars showed 5-6 density peaks in 1987, suggesting that 5-6 generations occur during a year (peaks of the 4th instar larvae were not clear, probably due to their longer development than those of younger instars). In sediment samples, no Ist and 2nd instar larvae were found, 3rd instar larvae were found occasionally but density of the 4th instar larvae was 280-18 600 m(-2), and pupal density varied between 0-502 m(-2). Fouth instar larvae accumulated in sediment in the cold season and in the water column in the warm season; high temperature and low oxygen concentration were the most important factors limiting the distribution of larvae in the sediment in summer in the NIES pond. The dry weight of total C. flavicans larvae was 0.08-4.2 g m(-2) in sediment samples and 24-599 mu g l(-1) (0.10-2.40 g m(-2)) in water column samples. Comparisons of maximum densities in the NIES pond in different years and in waters of different trophic status show that density is generally higher in eutrophic than in oligotrophic habitats.

InAs/GaSb superlattices for photodetection in short wavelength infrared range

The first report of a short wavelength infrared detector based on type II InAs/GaSb superlattices is presented. Very short period superlattices containing InAs (2ML)/GaSb (8ML) superlattices (SLs) were grown by molecular-beam epitaxy on GaSb substrates. The photoluminescence showed a cut-off wavelength at 2.1 mu m at 10 K and 2.6 mu m at 300 K. Room-temperature optical transmittance spectra shows obvious absorption in InAs (2ML)/GaSb (8ML) SL in the range of 450-680 meV, i.e. 1.8-2.7 mu m. The cut-off wavelength moved from 2.3 mu m to 2.6 mu m with temperature rising from 77 K to 300 K in photoresponse spectra. The blackbody response R-v exponentially decreased as a function of 1/T in two temperature sections (130-200 K and 230-300 K). The blackbody detectivity D-bb(center dot) was beyond 1 x 10(8) cmHz(1/2)/W at room temperature. (C) 2009 Elsevier B.V. All rights reserved.

High-quality GaN grown by gas-source MBE

High-quality GaN epilayers were consistently obtained using a home-made gas-sourer MBE system on sapphire substrates. Room-temperature electron mobility of the grown GaN film is 300 cm(2)/V s with a background electron concentration as low as 2 x 10(17) cm(-3) The full-width at half-maximum of the GaN (0 0 0 2) double-crystal X-ray rocking curve is 6 arcmin. At low temperature (3.5 K), the FWHM of the: near-band-edge photoluminescence emission line is 10 meV. Furthermore, using piezoelectric effect alone with the high-quality films, two-dimensional electron gas was formed in a GaN/AlN/GaN/sapphire structure. Its room-temperature and low-temperature (77 K) electron mobility is 680 cm(2)/V s and 1700 cm(2)/V s, and the corresponding sheet electron density is 3.2 x 10(13) and 2.6 x 10(13) cm(-2), respectively. (C) 2001 Published by Elsevier Science.

草甘膦的土壤酶效应研究

为了探讨当今世界使用量最大的除草剂——草甘膦的土壤环境效应,本文采用室内模拟方法,较为系统地研究了我国4类土壤:褐土、黄绵土、风沙土和红壤,共11个土样中4种主要酶类(脲酶、转化酶、磷酸酶以及脱氢酶)活性与草甘膦间的关系,计算并得到了能够表征土壤轻度污染的生态剂量值ED10。结果表明:非缓冲液法较好地反映了土壤酶的实际情况;草甘膦总体上激活土壤脲酶、转化酶和脱氢酶活性,最大增幅分别为190%、1372%和42%;抑制磷酸酶活性,最大幅度为35%;磷酸酶与草甘膦间为完全抑制作用机理;激活脱氢酶活性揭示出草甘膦导致了土壤中微生物活性增强,从侧面反映出草甘膦是一种毒性较低的农药。计算获得4类供试土壤褐土、黄绵土、风沙土和红壤ED10值分别为168.3、438.5、35.1和141.4mg·kg-1;在一定程度上用土壤酶活性比生物来表征土壤污染程度更敏感。土壤性质对草甘膦的毒性有重要影响。