995 resultados para 159-959A


Relevância:

10.00% 10.00%

Publicador:

Resumo:

This paper present a study on sex ratio and reveals segregation or aggregation of males and females in accordance with environmental conditions, the differential behaviour of sexes, and due to fishing.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

密度制约是否为自然森林维持物种共存的普遍性机制,生态学家对此一直就有争议。目前密度制约的普遍性研究主要集中于热带森林,而针对亚热带森林的研究还比较少见。本文以浙江古田山24 公顷亚热带常绿阔叶林固定监测样地第一次调查数据为基础,主要采用点格局分析的双变量函数g(r),研究了密度制约是否作用于样地内大部分木本植物,目的在于探讨密度制约在亚热带常绿阔叶林内物种多样性维持中的作用。 检验密度制约效应的常用方法是: 假定在种内竞争、种内个体之间的病虫害传播等条件下,种群的聚集程度是否随年龄的增加而下降。但是生境的异质性也可能导致种群聚集程度的下降。所以在密度制约的普遍性检验之前,首先分析了生境异质性是否影响树木的分布,然后分析种群分布格局,探讨除了生境异质性以外其它影响种群分布的驱动因子,同时为分析密度制约的发生做解释。结果发现生境异质性影响古田山树木的分布。用完全随机零模型不排除异质性,被检验的64个物种几乎在0-30m所有的尺度上都表现聚集。用异质性泊松分布零模型排除异质性,59个被检验物种中58个表现聚集。排不排除异质性,同种聚集都在整个样地中占主要地位,而且随着远离目标个体同种个体的密度逐渐下降,植株主要聚集在同种邻体的周围。结合下面的关联性分析,更新植株主要集中在成年个体周围,说明除了生境异质性效应促进树木聚集分布以外,以繁殖体为中心的局部扩散是大部分物种同种聚集的主要原因。 环境异质性影响树木分布,干扰密度制约的检验。然而,排除生境异质性的影响,也不能肯定密度制约是否是群落物种多样性普遍性的维持机制。用随机标签零模型案例-对照设计,小径级生长阶段的树木格局作为案例,成年树作为对照代表生境异质性的作用,通过小径级树木格局与成年树格局相比,排除生境异质性的干扰,64个被检验物种中50种(78.1%)表现了密度制约稀疏效应。结果表明密度制约稀疏机制调节了样地大部分物种,是古田山亚热带森林群落物种多样性维持的重要机制。同时,密度制约稀疏效应主要发生在局部尺度上,与同种短距离聚集结果一致。另外,密度制约稀疏效应更易于影响丰富种(24公顷样地内个体数>1000)的种群结构。 Janzen-Connell假说的距离制约模型认为繁殖体制约后代更新成功,导致成年树个体间距增大,并得到众多的野外观察证明。然而,在大尺度的森林样地研究中,没有发现这个效应广泛存在。本研究采用独立性零模型分析了不同生活史阶段在空间上的关联性,特别是成年树和幼树、小树的关联性,反过来推演是否成年树对后代的距离制约驱动了种群分布的空间动态。综合分析古田山64个物种的不同径级阶段的空间关联性,同时参照Condit 等(1992,1994)的研究结果:成年树对后代的距离制约效应在小于5m的尺度上发生强烈。有20个物种(31.3%)的更新体聚集密度最高点在离成年树≥5m的距离上,加上21个物种的更新体与成年树的关联性成相互排斥和随机分布,64个被检验的物种中有41(64.1%)个物种表现了Janzen-Connell 假说的繁殖体对后代的距离制约效应。同时,54(84.4%)个物种的小树成为新的成年树,出现在成年体周围小于5m的距离内的比例最高。结果表明这个效应提高成年树的间距是有限的,然而,它仍然调节了样地内大部分物种的分布格局,促进了物种共存。 同种密度制约调节建成树木(胸径≥1cm)的空间结构得到很好的研究。然而最近的研究表明:病菌不仅在同种个体之间传播,同时也在近缘物种之间传播。因此,只包括同种个体的密度制约模型可能大大低估了密度制约效应的作用。本研究分析了古田山24 公顷内159 个物种。运用平均谱系多样性指数(APd) 和最近分类谱系多样性指数(NTPd)检验随着目标个体径级的增加系统发育结构变化的趋势。研究发现,在15、20、30m 的尺度上,APd 指数都随着生长阶段的增加而显著提高,在10、15、20、30m 的尺度上,NTPd 随着生长阶段的增加而显著提高;在5m 的尺度上,谱系多样性与生长阶段不存在显著关联性,这些结果表明谱系多样性制约与取样尺度相关。在DBH >30 cm 生长阶段, APd 下降,NTPd 上升,说明谱系多样性制约加大老树之间的谱系距离,但是由于类似的生境偏好,又倾向于聚集在类似的生境。 本研究的结果表明同种和近缘种的密度制约是亚热带常绿阔叶林生物多样性群落水平上重要的维持机制,为Janzen-Connell 假说提供了支持;同时,生境异质性和局部扩散能在维持森林物种多样性中发挥重要作用。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Even though smoke curing is a very elegant method of preserving fish, the resultant products have only a very restricted shelf-life, unless stored under refrigerated conditions. The main source of spoilage is the early setting in of a vigorous growth of moulds. This problem is of a serious nature even in temperate climatic conditions. In full and universal recognition of the gravity of the problem, the FAO conference on herring technology held in September 1950 at Bergen in Norway has recommended the problem of "means of prevention of mould growth in smoked products" for future research study. This note records an interesting observation made at this Laboratory on the inhibitory action of sodium chloride on the development of mould in smoked fishery products.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Culture of Magur, Clarias batrachus on an experimental basis was carried out for a total of 159 days in 6 earthen ponds each of 0.02 ha in area, singly in 2 ponds and in combination with Rohu, Labeo rohita in 4 ponds. Three different artificial feeds were used. Growth of Magur varied from 89 to 110 and survival form 93 to 100%. Out of the 3 feeds used, feed formulation 2 yielded better results. Length-weight relationship parameters were found as log W=0.4979067+1.878346 log L; -1.1116438+2.3511497 log L; and -1.238157+2.433125 log L indicating growth to be not isometric. Relative condition factor (K u) was close to or higher than 1.0 only in fishes higher than 200 mm of total length; K. values which were less than 1.0 up to January, reached values greater than 1.0 by March-April. Condition appears to be influenced by spawning rather than feeding.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

An experiment was conducted for a period of 110 days to study the effect of different rice brans on the growth of Thai silver barb (Puntius gonionotus, Bleeker) in rainfed seasonal ponds (30 m² each). Each of the ponds was stocked with 150 fish with the mean initial body weight of 2.03 ± 0.03 g. There were three treatments namely R1, R2 and R3 each having four replicates. Three types of rice bran namely coarse, auto (fine) and red were applied to the treatments R1, R2 and R3 respectively. Fish received different types of rice bran at a rate of 5% of body weight daily. The water quality parameters were found within the productive range. The results showed that treatment R1 produced significantly (p<0.05) highest growth and treatment R2 produced the lowest growth. The survival rates varied between 77 and 84% with treatment R3 producing the highest survival. However, the overall best production (1530 kg/ha) and economic return for the culture period was obtained in treatment R1 receiving coarse rice bran. The results of the present study demonstrated that the coarse rice bran resulted in better growth and production of P. gonionotus.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The fecundity and sex- ratio of Borbodes gonionotus were studied. The fecundity of 99 gravid females varied from 18001 (total length 197 mm and body weight 72 g) to 42034 (total length 187 mm and body weight 159 g). The mean fecundity was 24959.23 ± 6961.48 (for mean total length 210.50 ± 17.26 mm, mean body weight 118.16 ± 37.34g, mean ovary length 70.21 ± 27.30 mm, mean ovary weight 13.66 ± 7.12 g and mean ovary breadth 15.4 ± 2.79 mm). The relationship between fecundity (F) and other parameters such as total length, total body weight, ovary length, ovary weight and ovary breadth were studied. The fish was highly fecund and the number of eggs produced was more or less directly proportional to other different lengths.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Growth, mortality and stock parameters of Johnieops sina (Cuvier) based on the data collected from 1989 to 1994 from Sassoon Dock and New Ferry Wharf landing centres of Greater Bombay has been discussed here. The von Bertallanffy's growth parameters for this species were estimated as follows, L∞= 266 mm, K=0.91 per year and W∞=193 g. This species grows to 159 and 223 mm at the end of first and second year of its life. The mortality parameters estimated were Z=6.17, M=2. 03 and F=4.14. The E and U were calculated as 0.62 and 0.63 respectively. Length cohort and Thompson Bell analyses show that there is no decline in the catches at the present level of fishing. But even by doubling the efforts the catches can go up by only 9.4 % indicating that the fishing efforts is not economical and proportional to the increase in yield.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Collections of phytoplankton were made by Mr. Durairatnamat various stations between latitude 5°S and 25°S and longitude 78° E and 101° E (Fig. 1) from December 1962 to January 1963 during a cruise of the research vessel "Umitaka Maru" belonging to the Tokyo University of Fisheries. This vessel was engaged in work in connection with the International Indian Ocean Expedition (I.I.O.E.). The collections made from these stations (T.G.) were examined at the Fisheries Research Station, Colombo, for the various diatoms present and the findings are reported in this paper.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

我国牡丹资源丰富、药用历史悠久,但长期以来,资源与药效关系不清严重阻碍着丹皮的产业化发展。建立一套综合评价体系,比较不同牡丹资源间的差异,科学评价、准确定位各地不同品种的利用价值,对稳定我国丹皮质量、可持续、集约化发展丹皮产业具有重要的意义。 本实验以我国丰富的药用牡丹资源为材料,从观赏和药用价值两方面首先探讨综合评价牡丹资源的体系。在观赏价值考察中重点比较了花型、花色、花期等性状;药用价值则从根的产量、重金属含量以及七种主要药效成分含量三方面来比较;重金属含量以原子分光光度法检测,药效成分则以高效液相色谱和质谱进行分离鉴定和定性、定量检测。利用建立的综合评价体系对野生种、各地药用品种进行了评价,对丹皮生产相关环节的问题进行了讨论,并初步探讨了药效成分的遗传规律。结果如下: 1、引种的野生牡丹药用价值不比栽培品种高,建议作为育种材料。 2、不同品种间药效成分含量存在显著差异,综合比较‘JSF’、‘CKL’、‘凤丹’适于药用栽培,‘赵粉’、‘朱砂垒’、‘首案红’等品种适宜观赏栽培,‘太平红’、‘JPH’等可花药兼用。 3、不同的土壤、气候环境对丹皮药效成分含量有明显的影响,丹皮中重金属含量主要与土壤环境关系密切。 4、根的粗细程度与药效成分含量关系不大,建议市场药材分级时充分考虑。 5、丹皮的药效成分含量与株龄、采收期、储藏时期关系密切;建议采收、应用根据各地的品种、气候条件及市场情况而定,在保证较高药效成分含量的前提下,尽量缩短生产、流通周期。 6、催花、嫁接对一些牡丹品种的药用价值影响不大,可合理开发利用。 7、药效成分的遗传有一定的规律,86%的子代丹皮酚含量高于父母本或亲本之一;丹皮酚原苷和没食子酰羟基芍药苷含量受父本影响较大,而芍药苷、苯甲酰芍药苷、丹皮酚新苷、没食子酰丹皮酚苷含量受母本影响较大。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The present paper gives a comparative account of the hydrological conditions and phytoplankton within the Continental Shelf and beyond the Continental Shelf. 54 water samples were taken for hydrological analysis and 18 surface tows for plankton.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

以人浓缩白细胞来源的CD14+单核细胞为前体,建立体外快速培养树突状细胞(dendritic cell,DC)的方法.采用密度梯度离心和MACS磁珠分选系统,收集高纯度的CD14+单核细胞;以rGM-CSF、rIL-4联合分化2天诱导不成熟DC,再将分化后的细胞以rTNF-α、IL-1β、IL-6、PGE2共同活化2天得到成熟DC.流式细胞仪检测结果表明,分化2天的不成熟DC具有吞噬能力,且表型HLA-DR、CD40、CD80表达在80%以上,CD83、CD86基本小表达,成熟后的DC能够激活T细胞增殖,HLA-DR表达增高,CD83、CD86表达占85%.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

下载PDF阅读器甲状旁腺激素(Parathyroid Hormone,PTH)是治疗骨质疏松症的药物之一.将人工合成全长人PTH(hPTH(1-84))的核苷酸序列插入pThioHis A载体中,然后转化大肠杆菌(Escherichia coli.),在IPTG的诱导下,成功实现了rhPTH(1-84)的原核表达.通过发酵条件的优化,初步确定1:40接种.LB+30% M9盐溶液的发酵培养基,37℃培养至OD600nm=0.8时,加入终浓度为0.6 mmol/L的IPTG,诱导8 h的较优发酵程序.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The complex, fragmented and diverse aspects of a sustainable development perspective are translated into an eight-point framework that defines a problem boundary larger than that traditionally adopted by civil engineers. This leads to practical questions intended to inform engineers who ask 'am I being sustainable?' during project implementation. The value of the questions is tested against a case history of a wastewater treatment project. This demonstrates the relevance of the questions to successive project delivery phases of defining the problem, choosing a solution and implementing that solution through design, construction and operation. The case history highlights that answers to several of the additional questions raised by considering this wider problem space are currently buried within government and clients' policies, regulations and standard practice; these answers may not be accessible to the professional engineer.