Input-output relationship and economics of pangas monoculture and carp-pangas polyculture in two districts of Bangladesh

An attempt was made to study the input-output relationships and economics of pangas monoculture and carp-pangas polyculture in Bangladesh. By analyzing the data collected from 50 pangas farms and 55 carp-pangas farms, the study has investigated the production systems of two technologies and the effects of fingerling stocking and applications of feed and fertilizer on fisheries income. The data were collected from the fishermen of Trishal and Bhaluka of Mymensingh district, and Kahaloo and Adamdighee of Bogra district during 2001-02. For pangas monoculture, the stocking density was 31,561 per ha while it was 55,017 per ha in carp-pangas polyculture. Most of the farmers used urea, TSP and lime before stocking. Rice and wheat bran happened to be the most common feed ingredients for both types of culture in general. Other important ingredients used were mustard oil-cakes, rice polish, wheat flour, fish meal, bone meal, soybean meal and poultry litter. In terms of quantities, rice bran and wheat bran dominated the farmers list. Rice and wheat bran together constituted about 60% of all studied feeds. Feed cost constituted 59.13% of total costs for pangas monoculture and 67.44% for carp-pangas polyculture. Per ha productions of pangas and carp-pangas in a single culture cycle were 15,508 kg and 19,745 kg, respectively. Per ha gross profits were estimated to be Tk 310,311 and Tk 464,418 for pangas monoculture and carp-pangas polyculture, respectively. Net profit appeared to be Tk 264,216 per ha for pangas monoculture and Tk 416,509 per ha for carp-pangas polyculture. The BCRs calculated were 1.46 and 1.68 for monoculture and polyculture, respectively. The break-even costs per kg of fish were estimated at Tk 36.93 for pangas and Tk 30.93 for mixed species which was much lower than the prices the producers received. Break-even productions were estimated at 10,702 kg per ha for pangas monoculture and 11,784 kg per ha for carp-pangas polyculture. Fingerling and feed cost, and pond size significantly explained the variation of income from pangas monoculture. These factors have significantly influenced the income from the crop. Functional analysis shows that 1% increase in the feed cost might increase 0.51% of pangas income and 0.41% in carp-pangas income. No other inputs had shown this much of responses to increasing income from a fish.

GENETIC DIVERSITY IN THE CHINESE PANGOLIN (MANIS-PENTADACTYLA) - INFERRED FROM RESTRICTION ENZYME ANALYSIS OF MITOCHONDRIAL DNAS

Two different forms of Chinese pangolins can be recognized according to the color of their scales, i.e., brown and dusky. We analyzed mitochondrial DNA (mtDNA) purified from the livers of seven dusky and six brown Chinese pangolins from the same locality, using cleavage patterns from 19 restriction enzymes. From the 19 6-bp recognition enzymes used, 51-56 sites were observed. By combining the cleavage patterns for each enzyme, the 13 samples were classified into four restriction types: two in dusky and two in brown Chinese pangolins. The estimated number of nucleotide substitutions per site in dusky and brown types is 0.002, and that between dusky and brown types is 0.012. Divergence between brown and dusky forms began 0.6 Myr ago, provided the mean rate of sequence divergence is 0.02 per Myr in mtDNA. Our results suggest that there is considerable divergence in Chinese pangolins, and brown and dusky Chinese pangolins may be quite different forms or, at least, belong to different maternal groups.

DNA 拓扑异构酶Ⅱ的结构和作用原理

1976年美国国立卫生研究所的 Gellert 等从大肠杆菌中提取到解旋酶 (gyrase, 也叫细菌DNA 拓扑异构酶Ⅱ ,以下简称 TopoⅡ )以来, 对 TopoⅡ的作用机制一直存在争议. Tse (1980)报道, Topo Ⅱ能同时打断 DNA 的两条链,TopoⅡ的两个亚基键分别与断开的 DNA 的两个5'末端连接, 并互相错开4个碱基对，以便让另一股 DNA 双链通过。

A comparison of four sustainable manufacturing strategies

Effective use of materials is one possible component of a sustainable manufacturing strategy. There are many such strategies proposed in the literature and used in practice, with confusion over what they are, what the differences among them may be and how they can be used by practitioners in design and manufacture to improve the sustainability of their product and processes. This paper reviews the literature on sustainable manufacturing strategies that deliver improved material performance. Four primary strategies were found: waste minimisation; material efficiency; resource efficiency; and eco-efficiency. The literature was analysed to determine the key characteristics of these sustainable manufacturing strategies and 17 characteristics were found. The four strategies were then compared and contrasted against all the characteristics. While current literature often uses these strategy titles in a confusing, occasionally inter-changeable manner, this study attempts to create clear separation between them. Definition, scope and practicality of measurement are shown to be key characteristics that impact upon the ability of manufacturing companies to make effective use of the proposed strategy. It is observed that the most actionable strategies may not include all of the dimensions of interest to a manufacturer wishing to become more sustainable, creating a dilemma between ease of implementation and breadth of impact. © 2008 Taylor & Francis.

新疆伊犁地区夏季浮游动物群落结构特征

2006年6—7月在新疆伊犁地区对伊犁河干流、三大支流(特克斯河、巩乃斯河和喀什河)、恰甫其海水库、吉林台水库、间歇性水体和小水塘中的浮游动物进行了调查.共鉴定浮游动物134属217种,其中原生动物95属153种,占浮游动物物种数的71%;轮虫27属51种,占23%;枝角类7属8种,占4%;桡足类5属5种,占2%.伊犁河干流、小水塘和间歇性水体浮游动物种类数较多,分别达132、114和92种,吉林台水库种类数最少,仅7种.浮游动物密度和生物量均以恰甫其海水库最高,分别为11391ind.L-1和2.79m

Zn~(2+)胁迫对绿球藻生长、生理特性及细胞结构的影响

Zn2+对绿球藻胁迫的实验浓度为0.1、1、10、50、100、200、400mg/L,BG11培养基作对照。实验结果表明,在特定浓度条件下,Zn2+对绿球藻的生长、生理特性以及细胞结构具有显著影响。低浓度Zn2+(0.1—1mg/L)对绿球藻生长基本没有影响;浓度在10—50mg/L时,绿球藻能维持一定的生长速率;但当Zn2+浓度大于100mg/L时,绿球藻的生长受到显著抑制。绿球藻Chla+Chlb以及Chla含量均随培养基中Zn2+浓度的升高而逐渐减少。当Zn2+浓度低于10mg/L时,绿球藻的净光

Silver paint as a soldering agent for DyBaCuO single-domains welding

Silver paint has been tested as a soldering agent for DyBaCuO single-domain welding. Junctions have been manufactured on Dy-Ba-Cu-O single-domains cut either along planes parallel to the c-axis or along the ab-planes. Microstructural and superconducting characterisations of the samples have been performed. For both types of junctions, the microstructure in the joined area is very clean: no secondary phase or Ag particles segregation has been observed. Electrical and magnetic measurements for all configurations of interest are reported $\rho(T)$ curves, and Hall probe mapping). The narrow resistive superconducting transition reported for all configurations shows that the artificial junction does not affect significantly the measured superconducting properties of the material.

草鱼仔鱼耳石的自然标记和生长轮的清晰度

将野生和人工繁殖的草鱼仔鱼的耳石取出并置于显微镜下观察微结构特征。结果表明 :草鱼耳石一般有一个圆形或卵圆形的原基和中心核 ,但有 0 4 1%～ 4 6 7%的样本具有双原基或双中心核。343尾野生仔鱼中 ,6 71%的个体在矢耳石和微耳石上具有营养转换标记 ,而 187尾人工繁殖的仔鱼中 ,在矢耳石和微耳石上出现营养转换标记的比例分别是 6 4 17%和 5 0 80 % ;在营养转换标记处 ,矢耳石和微耳石的直径分别为 5 4 12±9 4 9μm和 4 0 4 8± 7 0 2 μm (n =5

Study of thermal effects in bulk RE-BCO superconductors submitted to a variable magnetic field

When bulk RE-BCO superconductors are used as permanent magnets in engineering applications, they are likely to experience transient variations of the applied magnetic field. The resulting vortex motion may cause a significant temperature increase. As a consequence the initial trapped flux is reduced. In the present work, we first focus on the cause of a temperature increase. The temperature distribution within a superconducting finite cylinder subjected to an alternating magnetic field is theoretically predicted. Results are compared to experimental data obtained by two temperature sensors attached to a bulk YBCO pellet. Second, we consider curative methods for reducing the effect of heat flux on the temperature increase. Hall-probe mappings on YBCO samples maintained out of the thermal equilibrium are performed for two different morphologies : a plain single domain and a single domain with a regularly spaced hole array. The drilled single-domain displays a trapped induction which is weakly affected by the local heating while displaying a high trapped field. © 2006 IOP Publishing Ltd.