991 resultados para 675
Resumo:
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.
Resumo:
Gulf of Mexico, white shrimp, Litopenaeus setiferus, catch statistics have been collected by NOAA’s National Marine Fisheries Service for over 50 years. Recent occurrences such as natural and manmade disasters have raised awareness for the need to publish these types of data. Here we report shrimp data collected from 1984 to 2011. These 28 years of catch history are the time series used in the most recent Gulf of Mexico white shrimp stock assessment. Fishing effort for this stock has fluctuated over the period reported, ranging from 54,675 to 162,952 days fished. Catch averaged 55.7 million pounds per year, increasing significantly over the times series. In addition, catch rates have been increasing in recent years, with CPUE levels ranging from 315 lb/day fished in 2002, to 1,175 lb/ day fished in 2008. The high CPUE’s we have measured is one indication that the stock was not in decline during this time period. Consequently, we believe the decline in effort levels is due purely to economic factors. Current stock assessments are now using these baseline data to provide managers with further insights into the Gulf L. setiferus stocks.
Resumo:
The dusky rockfish (Sebastes ciliatus) of the North Pacific Ocean has been considered a single variable species with light and dark forms distributed in deep and shallow water, respectively. These forms have been subjected to two distinct fisheries separately managed by federal and state agencies: the light deep form is captured in the offshore trawl fishery; the dark shallow form, in the nearshore jig fishery. The forms have been commonly recognized as the light dusky and dark dusky rockfishes. From morphological evidence correlated with color differences in some 400 specimens, we recognize two species corresponding with these color forms. Sebastes ciliatus (Tilesius) is the dark shallow-water species found in depths of 5−160 m in the western Aleutian Islands and eastern Bering Sea to British Columbia. The name Sebastes variabilis (Pallas) is resurrected from the synonymy of S. ciliatus to apply to the deeper water species known from depths of 12−675 m and ranging from Hokkaido, Japan, through the Aleutian Islands and eastern Bering Sea, to Oregon. Sebastes ciliatus is uniformly dark blue to black, gradually lightening on the ventrum, with a jet black peritoneum, a smaller symphyseal knob, and fewer lateral-line pores compared to S. variabilis. Sebastes variabilis is more variable in body color, ranging from light yellow to a more usual tan or greenish brown to a nearly uniform dark dorsum, but it invariably has a distinct red to white ventrum. Synonymies, diagnoses, descriptions, and geographic distributions are provided for each species.
Resumo:
OsPRP1是水稻中特有的,编码一类富含脯氨酸蛋白(proline-rich protein, PRP)的基因家族,该家族有4个成员。在GenBank中,仅找到了一个结构相对接近的玉米PRP蛋白,但是对它的研究仅限于序列上的某些描述,而且在序列上,仍然与这4个OsPRP1蛋白有明显的差别。OsPRP1蛋白明显有别于前人(1999)所描述的4类PRP蛋白。它们是植物中一类新的小分子量的PRP蛋白,仅有一个保守结构域而属于DUF1210蛋白超家族的成员。 四个OsPRP1基因在基因组中紧密串联排列,而且编码区高度保守,基因结构也高度一致,证明它们来源于同一个祖先基因,是通过基因复制的方式产生的。PAML分析也证明它们在进化时间上的相互距离并不远。而在进化过程中由于执行生理功能上的某种重要性,在编码区表现出很的保守性,因而很难在RNA水平和蛋白水平上研究四个OsPRP1基因的表达差异。但是它们在表达调节区(如启动子区)显示出明显的差异。在克隆启动子的基础上,用GUS报告基因的策略,没有检测到它们在拟南芥中的表达活性,说明它们具有一定的种属特异性。而在水稻中,这四个基因的表达显示出了明显的时序和空间差异,既表现出在组织器官及其发育阶段上的特异性和变化,又在一定程度上表现出交叉,出现了功能上的分化和重叠。根据启动子区上的顺式元件,检测了这些基因对6种植物生长调节物质和3种非生物胁迫因子的应答反应,证明它们的表达调节也表现出显著的差异和分化。因此,四个基因的进化出现了功能退化、亚功能化和产生新功能等多种命运,比理论模型预期的要复杂得多,可能在执行生理功能和对环境反应上具有各自的生物学意义。 植物细胞壁是多种碳水化合物和蛋白质相互交织在一起的亲水性网络。在保护和支撑原生质、细胞通信、细胞分化、细胞对生物的和非生物胁迫的抗性等方面发挥着重要作用。目前已知的大多数植物PRP蛋白被描述成细胞壁结构性蛋白。OsPRP1基因家族编码的蛋白质都有一个N-端信号肽,暗示它们可能是一类分泌蛋白。我们用OsPRP1.1::GFP融合蛋白进行了亚细胞定位,证明了OsPRP1蛋白的确也是细胞壁相关蛋白。用原核表达体系表达了GST-融合蛋白,制备抗体,通过免疫印迹证明这些蛋白不溶于温和的提取缓冲溶液中,但可以被高盐和强碱溶液溶解,且分子量增加了三倍。证明在体内可能出现修饰、与细胞壁其它组分相交联的现象。 在这四个基因中,只有OsPRP1.2能够在水稻根中特异表达。根的原位杂交实验证明,OsPRP1在分化成熟程度低的细胞中大量表达,而在分化成熟程度高的细胞中几乎不表达。GUS染色的结果同样发现,基因在维管柱特别是中柱鞘附近的薄壁细胞的表达比别的细胞要强得多,而且在根的生长方向上表现出与发育相关的表达特征。说明OsPRP1基因可能参与了这些细胞的分化、发育过程。而基因表达的组织器官特异性的差异和对不同刺激因素的不同反应意味着它们可能参与了多种生理过程。为此构建了一个RNAi的表达载体,转化水稻,Southern杂交实验得到9个单位点插入的T2代独立株系,其中有6个株系与野生型对照相比,主根的早期伸长受到显著抑制,主根的一级侧根地数量减少,根尖分生区的细胞在轴向上的伸长受到了抑制。结合表达定位和原位杂交的结果,我们对它们在植物生长发育中的功能进行了深入探讨。
Resumo:
In deriving the flamelet model for nonpremixed combustion certain terms, but not the unsteady term, are assumed to be negligible. This results in a relation between all reacting scalars and the mixture fraction as independent variable. An ideal test of the flamelet assumption can be based on direct numerical simulation (DNS) data, if all reacting scalars are conditioned on mixture fraction and conditional moments are evaluated. The fundamental assumption of the flamelet model are unwillingly justified. The unsteady and steady formulations of the same equations are compared and found that unsteadiness is important in an unsteady simulation.
Resumo:
The field emission properties of nanostructured carbon films deposited by cathodic vacuum arc in a He atmosphere have been studied by measuring the emission currents and the emission site density. The films have an onset field of ∼ 3 V/μm. The emission site density is viewed on a phosphor anode and it increases rapidly with applied field. It is assumed that the emission occurs from surface regions with a range of field enhancement factors but with a constant work function. The field enhancement factor is found to have an exponential distribution.
Resumo:
查对中国南部赤腹松鼠标本(40l号)的基础上,发现分布于云南东北部昭通地区的赤腹松鼠与赤腹松 鼠其他亚种有明显的区别。毛色特征:背部棕黄色,背中央区域稍带黑色;腹部至前胸栗红色;喉、颏部棕灰色; 尾毛背腹无明显差异,尾毛末端棕黄、次末端黑,尾末端具棕黄色(稍黄白)区域;前后足背棕褐色,稍带黑色。 进一步对头骨可量性状数据进行分析(差异系数),结果表明:分布于该地区的赤腹松鼠分别与赤腹松鼠其他13个 亚种两两之间至少有一项差异系数大于1.28,系一新亚种c蹴f眦i珏r猫e唧如me谢z,啪t撕g啪s泌s妇p.nov.。