989 resultados para 3C 273


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Following an account of factors influencing the biological productivity of reservoirs in India, details are given of energy transformation through primary production. An ecosystem approach to the management of reservoir fisheries is discussed, considering also socio-economic factors to be taken into account.

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C、N、P是生物地球化学循环中的重要元素,其可利用性和各元素之间的平衡关系将生态系统的物质循环有机统一为一个整体。化学计量生态学为研究这几种基本元素间的平衡提供了一个有力的理论框架。许多研究表明,过度放牧会改变生态系统的结构和功能,而放牧如何影响植物的C:N:P化学计量关系的却少见报道。本研究以内蒙古锡林河流域沿水分梯度分布的草甸、草甸草原、典型草原和沙地四种植被类型中的灰脉苔草(Carex appendiculata)、贝加尔针茅(Stipa baicalensis)、羊草(Leymus chinensis)、大针茅(Stipa grandis)、小叶锦鸡儿(Caragana microphylla)、冷蒿(Artemisia frigid)、克氏针茅(S. krylovii)和榆树(Ulmus Pumila)疏林沙地8个草地群落为研究对象,对长期禁牧样地和自由放牧样地中273种植物,其中禁牧与放牧样地中的共有植物种为144个,测定了植物叶片C: N: P化学计量特征以及植株高度、丛幅面积、茎、叶和株(丛)生物量、茎叶比等功能性状,系统地研究了放牧对植物C:N:P化学计量特征和资源分配的影响。取得了如下主要研究结果和结论: 1. 放牧降低了植物叶片的C:N比,但增加了N:P比和C:P比。C:N:P 化学计量比的变化主要受叶片N和P含量变化的影响; 2. 植物C:N:P化学计量特征对放牧的响应同时受水分条件的制约。沿水分梯度分布的不同植被类型中,植物叶片C:N:P化学计量特征对放牧的响应不同。草甸群落中,植物叶片C含量显著降低,N和P含量显著增加;在草甸草原群落中,植物叶片C、P含量减少,N含量显著增加;而在典型草原群落中,植物叶片C、N和P含量均显著降低; 3. 在物种水平上,C、N、P含量对放牧的响应分为:显著增加、显著降低和没有显著变化三种类型。放牧影响下,植物叶片N含量和N:P比在显著升高的物种多于显著降低的,而叶片C含量、C:N和C:P显著降低的物种占的比例很小,表明植物对放牧适应策略与物种本身的生物学特性有着密切的关系。 4. 过度放牧使植物的植株高度、丛幅大小、株丛数、茎叶比和单株生物量均显著降低,即植物整体呈现小型化现象,进而导致群落初级生产力、茎和叶生物量下降。轻度放牧对物种的资源分配没有显著影响,单株(丛)生物量和群落茎、叶及总生物量均呈增加趋势,这与过度放牧的影响正好相反。 5. 过度放牧显著改变了物种的资源分配策略,使生物量向叶的分配比例增加,向茎的分配比例减少。资源优先向同化器官分配可能是草地植物对长期放牧干扰的一种重要适应对策。

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Except for the preliminary studies at Torry Research Station in Scotland, no results have been reported on the succession of the bacterial flora during the storage of fish in chilled water. The present work was undertaken to elucidate the dynamics of bacterial population changes in chilled fresh water under comparable conditions of storage in melting ice (+1° to +3°C.) which has been earlier studied by de Silva in 1960.

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In recent years, the ecological degradation, loss of technological sustenance and other multidimensional consequences caused by shrimp farming have made the experts and authorities bound to rethink about the development of the industry. The present study describes the water and sediment quality, and culture and management techniques in five selected shrimp farms at Paikgacha, Khulna throughout a production cycle from March to September 1997. The water quality parameters were found to be more or less suitable throughout the cycle. The concentration of the limiting major nutrients such as nitrogen and phosphorus and minor nutrients such as calcium and magnesium were satisfactorily high, concentrations of the organic matter content were also high. Remarkable negative correlation of shrimp production with secchi depth was observed among the farms. Production per cycle ranged between 273 kg/ha and as low as 63 kg/ha.

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In Tachypleus gigas (Muller) the fecundity varied from 1242 to 6565 with a mean of 3758±1962. Maximum fecundity was recorded in T. gigas ranging in carapace length between 161 and 170 mm. The ova diameter was between the range of 1.54 and 2.09 mm with a mean modal value of 1.81 mm. The mean number of ova per mm carapace length, per g body mass and per g ovary mass were 22±12.8, 7±2.0 and 27±3.3 respectively. Linear relationships were obtained between fecundity, carapace length, body mass and ovary mass of T. gigas.

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Background. The present study was undertaken to determine the role of preformed and induced anti-non-Gal antibodies in the rejection of hDAF pig-to-baboon kidney xenotransplants after anti-Gal antibody neutralization therapy. Methods. Seven baboons receiv

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从烙铁头蛇(Trimeresurus mucrosquamatus)的毒腺中提取mRNA,利用RT-PCR进行体外扩增,获得凝集素样蛋白基因,克隆至PMD18-T载体中,筛选出4种凝集素样蛋白基因(命名为TML-1、TML-2、TML-3和TML-4)。由基因序列推导出的氨基酸序列表明:TML-1,2,3,4序列中均有CRD结构。序列同源性比较和Cys位点分析推测:TML-1和TML-2可能分别是类似于flavocetin-A的蛇毒凝集素样蛋白的#alpha#亚基和#beta#亚基;TML-3可能类似于GPIb-bp的蛇毒凝集素样蛋白的#alpha#亚基,TML-4则可能是类似于IX/X-bp的蛇毒凝集素样蛋白的β亚基。

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Rhus chinensis, a species used in folk medicine by Chinese native people, the anti-HIV-1 activities of the petroleum ether, ethyl acetate, butanol and aqueous extract of Rhus chinensis, named as RC-1, RC-2, RC-3 and RC-4, respectively, was evaluated. The

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Anabas testudineus was cultured at different stocking density for the period of five months from May to September. Three stocking densities such as 50,000 (Treatment-1, T1), 56,250 (Treatment-2, T2) and 62,250/ha (Treatment-3, T3) were tested with three replications. After five months rearing, the mean weights of koi were 46.74±2.59, 40.44±2.98 and 37.27±3.01 in T-1, 2 and 3, respectively. The calculated production of native koi in T1 T2 and T3 were 1,916±314, 1,774.31 ±260 and 1,431 ±297 kg/ha, respectively which were significantly different (p<0.05) from each other.

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用光镜、扫描电镜及透射电镜首次研究了熊猴精子的结构。在光镜及电镜下,熊猴精子头的形状、顶体大小、核的结构等,与猕猴属其他种类相似。精子总长(79.49±0.11μm)及各部分的长度与藏酋猴相近,而与猕猴属其他种类存在明显差异(P<0.01)。本文的结果表明,熊猴可能在种系进化过程中与藏酋猴关系最近,而与猕猴属中其他种分离较早。

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This study was conducted to determine biological characteristics and population dynamics parameters of threadfin bream (Nemipterus japonicus) in Persian Gulf (Bushehr Province), during November 2006 and October 2007. The minimum and maximum specimens were 75-273 mm FL and their weight was 7.6 - 351.9 g. Based on the exponential relationship between fork length and weight, slope (b) for individuals, males and females was 2.987321, 2.992546 and 3.007314, respectively. The emptiness value (V) was 45.6% and it shows that N. japonicus is a moderate feeder. The results of Fp indicates that crustacean with 78.2% are main foods, mollusca (27.7%), fishes (20.7%), polychaeta (19.2%) and Foraminifera (11.7%) were identified as minor foods and phytoplanktons (9.9%), nematoda(8.0%), echinodermata (2.3%) and sea weeds (0.3%) were random foods. The reproduction studies showed the spawning season extended within 2 peaks, from April- May and September and main spawning occurs in spring season.The mean absolute and relative fecundities were 472388±42633 and 3817±293 (X±SE), respectively. The maximum, minimum and mean of oocyte diameter were 0.448, 0.022 and 0.221mm (SE=0.071), respectively.The fork length at 50% maturity estimated to be 20.25 cm for females. The growth coefficient (K) , length infinity (L∞ ) and ɸ' was estimated 0.42/yr , 34.17 cm and 2.69, respectively. The coefficient of total mortality, fishing mortality, natural mortality and E was 1.37, 0.43, 0.94 and 0.31, respectively.