Fish consumption by harbor seals (Phoca vitulina) in the San Juan Islands, Washington

The harbor seal (Phoca vitulina) is a large-bodied and abundant predator in the Salish Sea ecosystem, and its population has recovered since the 1970s after passage of the Marine Mammal Protection Act and the cessation of bounties. Little is known about how this large predator population may affect the recovery of fish stocks in the Salish Sea, where candidate marine protected areas are being proposed. We used a bioenergetics model to calculate baseline consumption rates in the San Juan Islands, Washington. Salmonids (Oncorhynchus spp.) and herring (Clupeidae) were the 2 most energetically important prey groups for biomass consumed by harbor seals. Estimated consumption of salmonids was 783 (±380 standard deviation [SD]) metric tons (t) in the breeding season and 675 (±388 SD t in the nonbreeding season. Estimated consumption of herring was 646 (±303 SD) t in the breeding season and 2151 (±706 SD) t in the nonbreeding season. Rockfish, a depressed fish stock currently in need of population recovery, composed one of the minor prey groups consumed by harbor seals (84 [±26 SD] t in the nonbreeding season). The variables of seal body mass and proportion of prey in seal diet explained >80% of the total variation in model outputs. Prey groups, such as rockfish, that are targeted for recovery may still be affected by even low levels of predation. This study highlights the importance of salmonids and herring for the seal population and provides a framework for refining consumption estimates and their confidence intervals with future data.

高放氧活性的PSII颗粒及胆酸抽提对其活性的影响

用Triton X--100增溶菠菜叶绿体，分离到高放氧活性的PSII颗粒。对增溶过程中的缓冲液pH Triton与叶绿素比例、Na~+ 浓度等因素进行分析，结果表明各因素相互间作用不大;pH的最佳范围为6.7～7.1。制备的PS-II颗粒放氧活性达210μmoles/mgchl.hr、DCIP→MV的光还原活性约为54μmoles O_2/mgchl.hr. P700与叶绿素比例为1/1900。放氧活性相当稳定，在0℃水浴保存的活性半衰期为80小时左右。该PSII颗粒的多肽分子量主要分布在68、56、46、34、28.5、25、20和17KD区域，其中25KD多肽占总蛋白质含量的40%经上。上述PSII颗粒经胆酸钠或Tris处理后，放氧活性和DPC→DCIP的希尔反应活性都有不同程度的下降，同时有一些蛋白质被抽提。胆酸钠抽提到的组分是65、58和15KD多肽;Tris则对34KD多肽的抽提作用最为显著。本文初步讨论了这些多肽与PSII氧化侧的关系。文中缩写：Tris-三羟甲基氨基甲烷;EDTA-乙二胺四乙酸;Tricine-一三（羟甲基）甲基甘氨酸;HEPES--N-2-羟乙基呱嗪-N-2-乙磺酸;DTT-二硫苏糖醇，DMBQ：2，5-二甲基对苯醌;DCIP-一二氯酚靛酚;ASC-抗环血酸;DPC-NN二苯氨基脲;MV-甲基紫精;SDS-十二烷基磺酸钠;Chl-叶绿素;LHCP-捕光色素蛋白复合体;PS-光系统;RuBP-二磷酸核酮糖;CF-叶绿体偶联因子;DCMU-二氯苯基二甲脲;Cyt-细胞色素。

重离子束治癌当中剂量监测探测器标定和校准装置

本实用新型涉及一种重离子束治癌当中剂量监测探测器标定和校准的装置。其结构特征是在束流轴线上依次放置准直器、剂量监测探测器、迷你型脊形过滤器、水箱和标准电离室，标准电离室置于水箱中。通过标准电离室在水介质中不同深度处吸收剂量的测量得到照射束流微小展宽Ｂｒａｇｇ峰（ｍｉｎｉ－ＳＯＢＰ）在水中的深度位置。在该深度位置处，利用标准电离室对剂量监测探测器进行了标定和校准，得到剂量监测探测器对具有高斯型分布微小展宽Ｂｒａｇｇ峰治癌束流测量的标定和校准因子。由该标定和校准因子，可以方便地控制肿瘤靶区内物理吸收剂量均匀或生物有效剂量均匀三维适形照射治疗的整个过程，满足实际临床治疗当中不同临床病例治疗的需要，提高了治疗装置的治疗效率。

An empirical study on income and efficiency of pond fish and nursery fish production in some selected areas of Pabna, Bangladesh

The study was designed to determine the costs, returns and relative profitability of pond fish and nursery fish production. In order to attain this objective, a total of 70 producers: 35 producing pond fish and 35 producing nursery fish were selected on the basis of purposive random sampling technique from 6 villages under two Upazilas (Sujanagar and Santhia) of Pabna district. It was estimated that per hectare per year gross cost of pond fish production was Tk 65,918 while gross return and net return were Tk 91,707 and Tk 25,789 respectively. Per hectare per year gross cost of nursery fish production was Tk 87,489 while gross return and net return were Tk 1,39,272 and Tk 51,783 respectively. The findings revealed that nursery fish production was more profitable than pond fish production. Cobb-Douglas production function was applied to realize the specific effect of the factors on pond fish and nursery fish production. It was observed that most of the included variables had significant impact on pond fish and nursery fish production. Out of five variables included in the function, all the variables had positive impact on return from pond fish production but stock value of pond, material cost and pond area had positive impact on return from nursery fish production.