995 resultados para 242
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We propose a new learning method to infer a mid-level feature representation that combines the advantage of semantic attribute representations with the higher expressive power of non-semantic features. The idea lies in augmenting an existing attribute-based representation with additional dimensions for which an autoencoder model is coupled with a large-margin principle. This construction allows a smooth transition between the zero-shot regime with no training example, the unsupervised regime with training examples but without class labels, and the supervised regime with training examples and with class labels. The resulting optimization problem can be solved efficiently, because several of the necessity steps have closed-form solutions. Through extensive experiments we show that the augmented representation achieves better results in terms of object categorization accuracy than the semantic representation alone. © 2012 Springer-Verlag.
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白鲟是是世界上最大的淡水鱼之一,为我国独有,被誉为"长江中的活化石".目前白鲟群体已极度濒危,获取其新鲜材料非常困难,因此本文以保存于中科院水生所标本馆的福尔马林固定白鲟标本为研究材料,尝试从其肌肉、心脏、鳍条和肝脏组织提取白鲟基因组DNA,并检验相近种匙吻鲟和中华鲟微卫星引物对白鲟有无适用性.实验包括福尔马林固定白鲟标本从组织预处理到消化、抽提等步骤的整体优化过程;通过一系列对比试验分析在不同条件下提取到基因组DNA片段大小的差异,最终实现了福尔马林固定白鲟标本基因组DNA的稳定提取,并提出后续实验的延
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Concepts of function are central to design but statements about a device's functions can be interpreted in different ways. This raises problems for researchers trying to clarify the foundations of design theory and for those developing design support-tools that can represent and reason about function. By showing how functions relate systems to their sub-systems and super-systems, this article illustrates some limitations of existing function terminology and some problems with existing function statements. To address these issues, a system-relative function terminology is introduced. This is used to demonstrate that systems function not only with respect to their most local super-system, but also with respect to their more global super-systems. © 2012 Elsevier Ltd. All rights reserved.
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根据鲫鱼类PKR蛋白激酶基因(CaPKR-like)的全长cDNA序列,克隆CaPKR-likeZα结构域cDNA(Zα1、Zα2和Zα1Zα2),原核表达成功获得3种融合蛋白PZα1、PZα2和PZα1Zα2。凝胶阻滞实验结果显示:PZα1、PZα2、PZα1和PZα2混合表达蛋白不能与聚肌胞苷酸(PolyI∶C)结合,而表达完整的Zα结构域的PZα1Zα2与PolyI∶C有明显的结合现象。另外,3种表达多肽PZα1、PZα2和PZα1Zα2在体外分别都能聚合形成二聚体。与PZα1相比,PZα2和PZα
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从斜带石斑鱼垂体提取总RNA ,再取其 5 0ng合成SMARTcDNA。从所构建的垂体SMARTcDNA质粒文库中筛选到生长激素 /催乳素基因家族的 2个成员的全长cDNA片段 :生长激素 (GH )基因全长为 938bp ,编码 2 0 4个氨基酸 ;催乳素基因 (PRL)全长为 14 2 9bp ,编码 2 12个氨基酸。采用计算机软件Mega 2和CLUSTALW1 6 4b对 9种鱼的生长激素 /催乳素基因家族的 3个成员 (GH、PRL和生长催乳素SL)的氨基酸序列进行系统分析 ,构建NJ分支
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本文从“激素黄鳝”传言的由来、避孕药的本质、催肥机制、给药途径、外源激素在黄鳝养殖和研究中的应用、黄鳝养殖生产现状等方面进行了分析,认为“激素黄鳝”的说法是不正确的,在养殖生产中黄鳝服用激素类药物增肥既没有可能,也没有必要,在经济上也不合算。
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自 1998年大洪水后 ,为了保障人民生命财产的安全 ,水利部门正在规划一系列长江中下游防洪整治工程。根据工程规划方案 ,结合白豚和江豚种群目前的现状 ,综合分析了部分规划中的防洪工程对白豚和江豚的影响。主要包括两个方面 ,一是施工期间的影响 ,二是工程结束后对环境的改变而带来的影响。经分析认为 ,有些工程 ,如洲湾裁弯取直工程、鄱阳湖建闸控制工程将对白豚和江豚产生巨大不利影响 ,建议在近期内不考虑实施。另一些工程如在施工期间和完工后采取积极、有效的保护措施 ,从白豚和江豚保护的角度分析是可行的
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应用地高辛标记的对虾白斑杆状病毒 (whitespotsyndromebaculovirus,WSSV)核酸探针 ,与人工感染后不同时间采集的对虾组织样品进行原位杂交 ,以动态研究病毒从侵染至对虾发病死亡的过程。将典型感染WSSV的病虾组织投喂健康对虾 ,结果显示 :WSSV首先通过侵染消化道上皮进入虾体内增殖 ,此后随着细胞裂解、病毒粒子释放 ,游离的病毒粒子伴随血淋巴循环进而侵染其它靶组织 ,直至对虾发病死亡。
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以含水华的鱼塘水作为进水灌溉两套上行流 -下行流人工湿地系统 ,系统内种植芦苇等水生植物。灌溉一周后收集人工湿地进出水水样 ,用HPLC法检测其藻毒素含量 ,结合温度、电位、溶氧等理化指标和细菌、藻类数量的变化 ,分析人工湿地系统对藻毒素的去除效果及影响其效果的可能因素。结果表明 ,人工湿地系统对藻毒素有一定的去除作用 ,对藻毒素含量 0 .117g/L的进水 ,两套系统去除率分别为 6 8.5%和 34.6 % ,芦苇 -水葱组合的湿地系统去除效果优于茭白 -石菖蒲组合的湿地系统。在三种主要藻毒素RR、
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将鲤鱼(或泥鳅)精子在保存液内与人生长激素(hGH)重组质粒DNA保温,再与鲤(或泥鳅)卵受精。由此发育的鱼苗经DNA分子杂交和PCR检测证明,33.3%(或37.0%)的个体带hGH基因,其拷贝数在4—150/细胞之间。在一定条件下,精子可作为携带外源基因的载体,通过受精作用产生转基因鱼。
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用豌豆叶绿体陪伴蛋白(ch-cpn60)的杭体对衣藻和多种蓝藻细胞提取液作West-ernblot分析表明:真核的衣藻和原核的有异形胞丝状蓝藻的一种鱼腥藻中存在一种与豌豆ch-cpn60抗体有交叉反应的蛋白,其一个亚基的分子量与豌豆该蛋白的分子量相似,而另一亚基的分子量高于豌豆的β亚基分子量。绿藻和丝状蓝藻中这一蛋白在热处理后含量增加,而经-20℃冷处理12h后含量明显下降。在单细胞蓝藻中则检测不到这种蛋白。
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InGaAs quantum dots (QDs) and nanowires have been grown on GaAs by metal-organic chemical vapour deposition on GaAs (100) and (111)B substrates, respectively. InGaAs QD lasers were fabricated and characterised. Results show ground-state lasing at about 1150 nm in devices with lengths greater than 2.5 mm. We also observed a strong influence of nanowire density on nanowire height specific to nanowires with high indium composition. This dependency was attributed to the large difference of diffusion length on (111)B surfaces between In and Ga reaction species, with In being the more mobile species. Selective area epitaxy for applications in quantum-dot optoelectronic device integration is also discussed in this paper. ©2006 IEEE.
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对东湖异养细菌群落结构采用系统分类和微机聚类分析方法作了比较研究。169株由东湖Ⅰ、Ⅱ、Ⅲ站水体中分离的异养细菌分别隶属于30个细菌属。其中以芽孢杆菌属居于明显优势,其次是微球菌属。在不同水域或水层,细菌的分布表现有一定的差别,但各站间多样性指数值没有明显的差异。基于113项生物学特性检测结果,采用lBM PC/XT微机聚类分析后计算各站细菌的多样性指数发现:Ⅰ站明显高于Ⅱ、Ⅲ两站,43项检测系统所得结果与此表现了一致的趋势。这与东湖各站水环境的理化分析参数是比较吻合的。作者对以上结果作了讨论。
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A laboratory-based methodology to launch cylindrical sand slugs at high velocities is developed. The methodology generates well-characterised soil ejecta without the need for detonation of an explosive; this laboratory-based tool thereby allows for the experimental investigation of the soil-structure events. The experimental set-up comprises a launcher with a cylindrical cavity and a piston to push out the sand slug. The apparatus is used to launch both dry and water-saturated sand slugs. High speed photography is used to characterise the evolution of the sand slugs after launch. We find that the diameter of the slugs remains unchanged, and the sand particles possess only an axial component of velocity. However, the sand particles have a uniform spatial gradient of axial velocity and this results in lengthening of the slugs as they travel towards their target. Thus, the density of the sand slugs remains spatially homogenous but decreases with increasing time. The velocity gradient is typically higher in the dry sand slugs than that of the water-saturated slugs. The pressure exerted by the slugs on a rigid-stationary target is measured by impacting the slugs against a direct impact Kolsky bar. After an initial high transient pressure, the pressure reduces to a value of approximately ρv 2 where ρ is the density of the impacting sand slug and v is the particle velocity. This indicates that loading due to the sand is primarily inertial in nature. The momentum transmitted to the Kolsky bar was approximately equal to the incident momentum of the sand slugs, regardless of whether they are dry or water-saturated. © 2013 Elsevier Ltd. All rights reserved.
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<正> 1978年7月下旬至9月中旬,作者到华南地区13个水库进行湖沼学调查,共采集了浮游动物定性样品27个,定量样品38个。经初步鉴定,发现轮虫种类非常丰富,共有57种,其中包括新种1个,新亚种3个,新纪录3个。现描述于下。模式标本均存中国科学院水生生物研究所。