56 resultados para Giorgione, 1477-1511.


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Pheromones are chemical cues released and sensed by individuals of the same species, which are of major importance in regulating reproductive and social behaviors of mammals. Generally, they are detected by the vomeronasal system (VNS). Here, we first investigated and compared an essential genetic component of vomeronasal chemoreception, that is, TRPC2 gene, of four marine mammals varying the degree of aquatic specialization and related terrestrial species in order to provide insights into the evolution of pheromonal olfaction in the mammalian transition from land to water. Our results based on sequence characterizations and evolutionary analyses, for the first time, show the evidence for the ancestral impairment of vomeronasal pheromone signal transduction pathway in fully aquatic cetaceans, supporting a reduced or absent dependence on olfaction as a result of the complete adaptation to the marine habitat, whereas the amphibious California sea lion was found to have a putatively functional TRPC2 gene, which is still under strong selective pressures, reflecting the reliance of terrestrial environment on chemical recognition among the semiadapted marine mammals. Interestingly, our study found that, unlike that of the California sea lion, TRPC2 genes of the harbor seal and the river otter, both of which are also semiaquatic, are pseudogenes. Our data suggest that other unknown selective pressures or sensory modalities might have promoted the independent absence of a functional VNS in these two species. In this respect, the evolution of pheromonal olfaction in marine mammals appears to be more complex and confusing than has been previously thought. Our study makes a useful contribution to the current understanding of the evolution of pheromone perception of mammals in response to selective pressures from an aquatic environment.

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利用各种色谱(硅胶和凝胶)方法,从藤三七[Boussingaultia gracilis Miers var.pseudobaselloides Bailey]的70%(体积分数)的乙醇提取物中分离得到2个黄烷醇类化合物(1,2)和4个黄酮类化合物(3~6).采用UV,IR,MS 和1D,2D NMR方法,分别鉴定出如下化合物: 7-羟基-5-甲氧基-8-甲基-6-甲酰基-3,4-黄烷二醇,命名为藤三七醇A(1);4,7-二羟基-5-甲氧基-8-甲基-6-甲酰基黄烷(2);7-O-methylunonal(3);5,7-二羟基-6,8-二甲基-2-苯基-4H-1-苯并吡喃-4-酮(4);Desmosflavone(5)和Demethoxymatteucinol(6).其中化合物1是一个新的黄烷二醇化合物,化合物2~6为首次从该植物中分离得到.抗HIV-1活性筛选结果表明: 化合物1,2,5,6对HIV-1诱导合胞体的形成具有一定的抑制作用,其半数有效浓度(EC50)分别为45.09,48.73,55.47 和 82.75 μmol/L,治疗指数(TI)分别为1.41,1.20,7.15 和》8.51.

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Boussingaultia gracilis Miers var. pseudobaselloides Bailey (Basellaccae) is a folk medicine used as an analgesic and supplements, only a few research was reported on the chemical constituents of this plant. This paper presented its chemical and anti-HIV

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采用细胞成份的选择性抽提方法,结合常规电镜和DGD(Diethylene Glycol Distearate)包埋一去包电镜技术制备典型涡鞭毛虫前环或的细胞核骨架,结果表明其核内存在一个蛋白性质的纤维网状结构,并且通过核纤层与中等纤维发生联系形成一个贯穿核质的骨架体重,即使在未经任何提提处理的情况下,前环藻细胞的染色体之间仍然存在骨架结构,根据典型涡革命毛虫的特点及细胞核骨架的定义,可以肯定其中包含了核骨架部分,这一实验结果排除了核骨架是因抽提处理造成结构象的可能性,另外,在制备核骨架时,于选择性抽提液CSK液中加入1%巯基乙醇抑制二硫键的形成,结果同样观察到核内有一个致密的纤维网络结构,并且与选择性抽提制备的核骨架相似,这也说明核骨架结构并不是由于蛋白质分子间二硫键的交联而赞成的结构假象,以上结果都证明该核骨架是一个真实存在的结构。

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Ca~(++)离子能极大地激活五步蛇蛇毒PLA_2的酶活力,Na离子只能在一定程度上激活,作者推测在测定PLA_2酶活力的底物溶液中可以不加Na~+离子。

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饲养在滇池水中的椭圆背角无齿蚌氨基酸含量只有饲养在松华坝水库水中蚌的氨基酸含量一半,质量分数分别是680 57mg/hg和1477 14mg/hg。检测表明椭圆背角无齿蚌对砷、铅、锌、铜、铁元素有一定的富集能力,说明由于滇池污染,椭圆背角无齿蚌在滇池中虽然可以生存,但这一物种资源的利用价值受到严重影响。

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Iron deficiency can induce cyanobacteria to synthesize siderophore receptor proteins on the outer membrane to enhance the uptake of iron. In this study, an outer membrane of high purity was prepared from Anabaena sp. PCC 7120 based on aqueous polymer two-phase partitioning and discontinuous sucrose density ultra-centrifugation, and the induction of outer membrane proteins by iron deficiency was investigated using 2-D gel electrophoresis. At least. five outer membrane proteins were newly synthesized or significantly up-regulated in cells transferred to iron-deficient conditions, which were all identified to be siderophore receptor proteins according to MALDI-TOF-MS analyses. Bacterial luciferase reporter genes luxAB were employed to monitor the transcription of the encoding genes. The genes were induced by iron deficiency at the transcriptional level in different responsive modes. Luciferase activity expressed from an iron-regulated promoter may be used as a bioreporter for utilizable iron in natural water samples. (C) 2009 National Natural Science Foundation of China and Chinese Academy of Sciences. Published by Elsevier Limited and Science in China Press. All rights reserved.

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A new method to measure reciprocal four-port structures, using a 16-term error model, is presented. The measurement is based on 5 two-port calibration standards connected to two of the ports, while the network analyzer is connected to the two remaining ports. Least-squares-fit data reduction techniques are used to lower error sensitivity. The effect of connectors is deembedded using closed-form equations. (C) 2007 Wiley Periodicals, Inc.

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生物质快速热解制油技术能以连续的工艺和工厂化的生产方式将木屑等生物质转化为易储存、易运输、能量密度高的生物油,是目前受到较多关注的一种转换技术。生物油既可以在锅炉中直接燃烧使用,也可用于热解气化制备合成气,再进一步合成为高品质的液体燃料。 为更好地处理生物油燃烧与热解过程中出现的问题,并为燃烧与热解反应装置的设计及优化提供必要数据,本文首先对由木屑在自热式生物质热解液化装置中热解得到的生物油进行了各种理化特性的分析,之后利用热重、热重-红外联用、管式炉等对生物油的热解与燃烧特性进行了实验研究。 生物油在氮气与氧气气氛下、不同升温速率的热重分析试验表明:生物油的热解分为两个阶段,第一阶段为生物油中低沸点有机物的挥发以及各组分间反应生成各类产物的过程,第二阶段为各种重组分的裂解过程。而生物油的燃烧则分为三个阶段,即前期的挥发与裂解和最后焦炭的燃烧过程。升温速率的升高使得氮气气氛中生物油样品的初始失重温度、失重峰值温度及对应的最大失重速率均有所增大,且在较高升温速率(20℃/min)下,较少含炭残余物形成。随升温速率升高,生物油着火温度提高,最终失重率无显著变化。采用热重-红外联用技术,对生物油热解过程中所释放气体进行了实时监测,在线分析结果表明,反应初始阶段主要析出物为自由水、低沸点的酸类、醇类、醛类、酮类等,随后主要释放物为水、CO2等,主要来自重组分的裂解。最后根据热重数据对热解与燃烧各段反应进行了动力学拟合。动力学分析结果表明:氮气气氛中生物油的热解过程可用两个一级反应来描述,对应其热解过程中的两个不同阶段,而生物油的燃烧过程可用三个一级反应来表示。 生物油的管式炉热解实验表明:随热解温度的升高,生物油产气率不断提高,在1100℃时达到最大值398ml/g。生物油热解气体产物中主要包含H2、CO、CO2及烃类如CH4、C2H4、C2H6等,产气热值在16.9~19.1MJ/Nm3间。在900℃下,生物油各种产物气体、残炭、焦油的比例约为30:6:64,残炭含量低于同温度下木粉热解结果,而焦油含量较高。

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利用双离子束外延技术制备了CeO_2/Si薄膜,椭圆偏振仪测得薄膜厚度为100nm,折射系数约为2.455。实验中发现未经退火处理的CeO_2室温光致发光(PL)谱存在着“紫移”现象,其移动距离约为65nm。利用XRD和XPS对薄膜结构及价态进行分析后表明,PL谱的移动与氧化物中Ce离子价态有关。当Ce离子价态发生Ce~(4+)→Ce~(3+)变化时,其PL谱峰位要从蓝光区向紫光区移动,出现发光峰“紫峰”现象。

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种子雨是森林植物种群更新的主要方式之一,是森林生态系统自我繁衍和恢复的主要手段。为了解长白山阔叶红松林种子雨的组成及其时空变化,参照BCI 50ha 样地技术规范,在长白山阔叶红松林25ha长期监测样地内设置了150个种子收集器,从2006年5月15日到2007年11月8日,每15天收集掉落于收集器中的果实、种子及其相关附属物等。所收到的样品分别鉴定其种类并分为成熟种实、未成熟种实、花絮、果实或种子碎片及其附属物4类,记录各类别的数量,然后分别烘干称重。 研究期间,共收集到11科12属22种木本植物的种子及其它生殖器官残体,包括成熟种实16种,未成熟种实17种,花序12种,翅2种,果实或种子碎片及其附属物10种。累计收集到种实136664粒,其中成熟种实32358粒,占所有种实总数的23.80%。种实数最多的树种是紫椴(Tilia amurensis),其次为水曲柳(Fraxinus mandshuica),两个树种种实数占总数的89.54%。种实总重量为3320.93g,其中成熟种实总重量为1242.85g,占37.4%。成熟种实中水曲柳和紫椴的重量最大,其次是色木槭(Acer mono),假色槭(A. pseudo-sieboldianum)、糠椴(T. mandshuric)和红松(Pinus koraiensis)。 种子雨数量年际变化明显,2006年种子雨密度为1370.25粒/m2,2007年为249.47粒/m2,差异极显著(P<0.001)。但不同年份种子雨的季节动态趋势一致,均有两个明显的大高峰期和一个小高峰期。不同物种种子雨扩散的时间格局大致可以分为“单峰”和“双峰”两种类型,在时间上体现了不同物种的更新策略。 150个收集器均收到了成熟种实,各收集器中的种实数呈偏态分布,种实数在150-250之间的收集器数量最多,共68个,种实数小于50的收集器有5个,种实数大于250的收集器共37个。样地内成熟种实数量及其空间分布差异明显,收集器中种实数在1000个以上的有3个,最多达1511个,聚集分布于样地的西北角;收集器中种实数最少的只有22个种实。种实重量的空间分布与种实数分布一样存在较明显的空间差异,只是差异性相对偏弱一些,且与种实数量的空间分布不一致。