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1.
Mosquitoes feeding on insect larvae 总被引：1，自引：0，他引：1
Caged Aedes aegypti and Culex tarsalis are attracted to insect larvae, engorge on their body fluids, and produce viable eggs. Attractiveness of the larvae is related to their size, shape, and color but not to their movement. The possibility that wild mosquitoes substitute insect hemolymph for vertebrate blood is discussed. 相似文献
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贫困农村社区不同类型农户信息需求特性分析 总被引：3，自引：0，他引：3
在贫困农村社区中,不同类型农户因其生产生活活动的不同,决定了他们对信息需求的差异,自给自足型农户主要关注对新品种等最基本的农业信息,种植（养殖）专业型农户更关注市场价格信息和其他农业相关信息,而兼业型农户的信息需求更倾向于非农就业机会。在获取信息的渠道上,自给自足型农户更多地依赖传统的人际交流途径,而另两类农户在利用人际交流的基础上,趋于更多地利用大众传媒途径。信息在社区内呈现出从信息拥有量高的农户向信息量低的农户传播的梯度趋势,对信息占有的多寡,决定了不同农户在社区内地位的强弱,并影响其在进一步获得信息过程中的优劣。 相似文献
3.
Ribosomal RNA (rRNA) sequences were used to establish the phylogenetic affiliations of symbioses in which prokaryotes appear to confer sulfur-based chemoautotrophy on their invertebrate hosts. Two submarine hydrothermal vent animals, the vestimentiferan tube worm Riftia pachyptila and the clam Calyptogena magnifica, and a tidal-flat bivalve, Solemya velum, were inspected. 5S rRNA's were extracted from symbiont-bearing tissues, separated into unique forms, and their nucleotide sequences determined and related to other 5S rRNA's in a phylogenetic tree analysis. The prokaryotic symbionts are related to one another and affiliated with the same narrow phylogenetic grouping as Escherichia coli and Pseudomonas aeruginosa. The sequence comparisons suggest that Riftia is more closely related to the bivalves than their current taxonomic status would suggest. 相似文献
4.
Mueller UG 《Science (New York, N.Y.)》1991,254(5030):442-444
In eusocial Hymenoptera, the haplodiploid system of sex determination creates relatedness asymmetries such that workers are more closely related on average to their sisters than to their brothers. For such societies, kin-selection theory and sex-ratio theory predict that workers maximize their inclusive fitness by biasing the investment sex ratio toward females. To test the prediction of sex-ratio biasing, relatedness asymmetries were experimentally manipulated in colonies of the primitively eusocial bee Augochlorella striata (Halictidae: Hymenoptera) by removing or not removing foundress queens. Queenright colonies (relatedness asymmetry present) produced a more female-biased sex ratio than did queenless colonies (relatedness asymmetry absent). Worker reproduction and unmated replacement queens can be discounted as alternative explanations. Workers therefore facultatively adjusted their colony's sex ratio and, in the presence of a relatedness asymmetry, biased the investment sex ratio toward their more closely related sisters and away from their more distantly related brothers. 相似文献
5.
作物种质资源亦称遗传资源或基因资源,它蕴藏于作物各类品种、品系、类型、野生种和近缘野生植物中,是改良农作物的基因来源,是农作物新品种选育和相关学科研究的重要物质基础和可靠保证。而指纹图谱是鉴别品种、品系的有力工具。鉴于此介绍了山西省作物种质资源的丰富度、当前国际、国内及山西省作物种质资源的研究现状,分析了存在的问题及原因,并从指纹图谱方面对山西省作物种质资源的研究提出了相应的对策。 相似文献
6.
主要研究了芬斯勒度量的射影Ricci曲率.首先,在一个完备的芬斯勒流形上,证明了关于芬斯勒度量的射影Ricci曲率的一个比较定理.其次,刻画了两个共形相关的芬斯勒度量的射影Ricci曲率的关系.在此基础上,证明了两个位似相关的芬斯勒度量的射影Ricci曲率是相等的. 相似文献
7.
溶藻弧菌是一种海洋和海洋生物中普遍存在的致病菌,能够感染人类和多种水产品.细菌粘附在介质表面,分泌胞外基质将自身包裹其中从而形成生物膜,具有极高的抗药性和免疫逃逸能力,人类许多细菌感染均与生物膜有关.就溶藻弧菌生物膜进行综述,为相关研究提供理论参考. 相似文献
8.
随着基因组学的发展,利用大量的序列信息鉴定和克隆抗旱相关基因以改良作物的生产性能具有重要意义。作物抗旱性属数量遗传,其数量性状位点的鉴定是分子标记辅助选择改良作物抗旱性的基础。笔者就作物抗旱基因鉴定及相关功能基因组学的最新进展作系统的介绍,并探讨了今后作物抗旱性研究发展方向。 相似文献
9.
利用SPSS、UCINET软件,对中国知网（CNKI）中已发表的科技查新系统领域的文献进行聚类、社会网络分析,以探讨当前国内科技查新系统的研究现状,总结归纳与其相关研究主题及相互关系,以期为科技查新系统的研究提供借鉴。 相似文献
10.
Ehleringer JR Schulze ED Ziegler H Lange OL Farquhar GD Cowar IR 《Science (New York, N.Y.)》1985,227(4693):1479-1481
Most mistletoes parasitize higher plants by tapping the xylem (a conduction tissue) of their hosts. Field observations of diurnal gas exchange parameters and carbon isotope ratios in xylem-tapping mistletoes from three continents support the hypotheses that water use efficiency and carbon isotope composition are related and that mistletoes which are parasitic for water are also nutrient parasites, differing in their water use efficiency relative to that of their hosts on the basis of host nitrogen supply in the transpiration stream. 相似文献
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Projecting subunits of an average diameter of 80 A are found on the cristae of mitochondria prepared from the muscle of Ascaris lumbricoides. A spectroscopic examination of the cytochrome content of these mitochondria shows no detectable cytochrome c(1), a, or a(3) and does reveal cytochromes of types c and b. Subunits in the same size range are found in cytochrome c deficient mitochondria of the emergent bee, while the frequency of their occurrence along the cristae is decreased relative to the adult bee. Apparently, the cytochrome content of the respiratory chain is not related to the size of the subunits, but may be related to the frequency of occurrence of the subunits. 相似文献
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14.
不同产区烤烟主流烟气中11种成分含量的差异及相关性 总被引：1，自引：0，他引：1
为烤烟新品种选育、适宜种植区域规划和卷烟降焦减害新产品的研发提供参考,以全国6个不同产烟区的57个单料烟样品为材料,在ISO抽吸模式下,研究同一等级模块卷烟烟气中11种烟气成分(4种常规化学成分,7种有害成分)的含量差异及其相关性。结果表明:1)在同一等级配方模块卷烟中,同省份烤烟主流烟气中11种成分含量的差异较小,而不同省份则差异较大。2)在卷烟主流烟气的11种成分中,水分含量除与巴豆醛含量达极显著正相关(相关系数0.540,P0.01)、与苯酚含量达极显著负相关(相关系数-0.370,P0.01)外,与其他指标的相关性较小;而总粒相物、烟碱和焦油含量与其他指标的相关性较大。3)卷烟危害性指数与烟气中氨含量的相关性最大,相关系数为0.890;与烟气中总粒相物、焦油、CO、HCN、NNK、苯并[a]芘、苯酚含量呈中度相关,相关系数为0.508~0.752;与烟气中烟碱含量的相关性最弱,相关系数为0.441。 相似文献
15.
随着人们对海洋生物资源研究的日益关注,藻类生物资源的挖掘也越来越受到重视,近年来其在农业领域的应用和价值也日益凸显。目前,人们对藻类资源在农业中的应用研究主要集中在对藻类生物肥料和生物刺激剂的探索,即为农作物寻找新的肥料来源,但对其作用机制的研究还缺乏总结。为此,本文综述了国内外相关研究进展,重点介绍了藻类资源在农业种植业中的利用,阐述了藻类细胞及其产物在农业工程中的应用与发展,包括藻类作为生物肥料和生物刺激剂、藻类资源在农业环境修复以及农作物产品保鲜等方面的应用。此外,本文还总结了藻类资源在农业应用中的主要机理：①藻类的固碳、固氮以及解磷作用,可提高土壤营养物质含量,调节土壤微生物活力,促进植物生长;②藻类分泌的胞外聚合物有助于改善土壤荒漠化及盐碱化,降低农药污染风险和提高土壤肥料利用效率;③藻类细胞的生物吸附性有助于重金属污染土壤的修复;④海藻多糖的抑菌、抗病毒和保鲜功能等。总而言之,藻类资源在农业种植业中具有广阔的应用前景和巨大的开发价值。未来的研究应着眼于藻类细胞活性物质的促生长机理和藻类资源的田间规模评价,重视分子生物学技术的应用,挖掘更多样化的藻类应用潜力,为藻类生物质的开发和农业可持续发展提供理论依据。 相似文献
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花卉生长的好坏以及花期的应时与否不仅与花卉自身习性、栽培措施有关,而且还与许多外界环境条件有很大关系。通过对花卉生长环境的调控,可以有效提高花卉的品质及应时能力,使花卉生产更好地迎合人们的需求。笔者就光照、温度、植物生长调节剂、肥料等几个方面阐述了环境因素对花卉生长和花期的影响。 相似文献
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Analysis of neighboring aromatic groups in four biphenyl peptides or peptide analogs and 34 proteins reveals a specific aromatic-aromatic interaction. Aromatic pairs (less than 7 A between phenyl ring centroids) were analyzed for the frequency of pair type, their interaction geometry (separation and dihedral angle), their nonbonded interaction energy, the secondary structural locations of interacting residues, their environment, and their conservation in related molecules. The results indicate that on average about 60 percent of aromatic side chains in proteins are involved in aromatic pairs, 80 percent of which form networks of three or more interacting aromatic side chains. Phenyl ring centroids are separated by a preferential distance of between 4.5 and 7 A, and dihedral angles approaching 90 degrees are most common. Nonbonded potential energy calculations indicate that a typical aromatic-aromatic interaction has energy of between -1 and -2 kilocalories per mole. The free energy contribution of the interaction depends on the environment of the aromatic pair. Buried or partially buried pairs constitute 80 percent of the surveyed sample and contribute a free energy of between -0.6 and -1.3 kilocalories per mole to the stability of the protein's structure at physiologic temperature. Of the proteins surveyed, 80 percent of these energetically favorable interactions stabilize tertiary structure, and 20 percent stabilize quaternary structure. Conservation of the interaction in related molecules is particularly striking. 相似文献
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本文应用同工酶凝胶电泳分离技术,比较分析了南瓜属3个栽培种9个品种的亲缘关系。结果表明中国南瓜是栽培南瓜种的主干,既与美洲南瓜接近,又与黑籽南瓜接近,而后两者亲缘关系则相距甚远。 相似文献
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生态文明意识是社会意识形态的形式之一,是人们关于保护大自然和维护生态安全的进步思想观念。游客作为旅游活动的主体,其行为与意识都与旅游地生态保护息息相关。以大理洱海流域为个案,调查国内旅游者生态意识的基本情况。利用EXCEL进行数据录入,利用平均数、平均方差等定量法进行分析。主要结论为:洱海流域国内游客生态意识普遍较高,生态意识与旅游行为吻合度较高,而生态意识的高低受多种因素影响。基于上述调研结论,提出有助于洱海流域旅游者生态意识形成的相关建议。 相似文献
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介绍了植物染色体原位杂交技术的产生、发展过程,以及该技术与其它生物学技术相结合而形成的一些新技术,如:细菌人工染色体荧光原位杂交、DNA纤维荧光原位杂交、基因组原位杂交、原位PCR技术等。综述了这些技术在甘蔗研究中的应用情况。 相似文献