59 resultados para Petrarca, Francesco, 1304-1374.


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The crystallization and unusual crystalline morphologies of compatible mixtures of tetrahydrofuran-methyl methacrylate diblock copolymer with tetrahydrofuran homopolymer were studied. It is shown that the PTHF [poly(tetrahydrofuran)] block of the copolymer cocrystalizes with the PTHF homopolymer in the PTHF microphase of the blend. However, the degree of crystallinity of the PTHF block is always lower than that of the PTHF homopolymer in the PTHF microphase. The crystallizability of the PTHF microphase increases appreciably with increasing PTHF microphase size and PTHF homopolymer weight fraction in the microphase. The morphology study of the blends shows that the crystalline morphology is strongly dependent on blend composition, copolymer composition and PTHF block length, as well as crystallization temperature. When alternating PTHF and PMMA [poly(methyl methacrylate)] lamellae are formed, the macroscopic crystalline morphology could be only observed when the thickness of the PTHF lamellae is large enough (similar to 20 nm). In the blend where PMMA spherical or cylindrical microphases are formed, the crystalline morphology changes dramatically with the change in the PTHF microdomain size and PMMA interdomain distance. Many unusual crystalline morphologies have been observed. A study of the solution-crystallized morphology of the blends at different temperatures shows that the morphology is also strongly dependent on the isothermal crystallization temperature, suggesting that the PMMA microdomains may have different effects on the morphology formation when the blend is crystallized at different rates.

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The conformation analysis and study on structure-taste relation-ships of 4 taste compounds have been performed, the results reveal that the sweetnees will decrease with the increase of the specific dihedral angle O-1-C-2-C-3-C-4, and the mechanism was intepreted.

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味觉化合物的构象与活性的关系许禄,姚喻元(中国科学院长春应用化学研究所应用谱学开放实验室,长春,130022)关键词味觉化合物,分子力学,构象分析分子结构和味觉的相关性是一个非常活跃的研究领域,许多人从不同的侧面进行这方面的研究,并总结出一定的规律[...

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热带西太平洋环流是副热带环流与热带环流关键分量,毗邻西太平洋暖池,对暖池的形成与变化有重要的作用。然而,目前为止,热带西太平洋环流还有许多问题,包括动力结构还不清楚。因此,论文针对热带西太平洋环流的研究不仅在太平洋环流动力学上有理论意义,而且对气候变化的研究和预测也具有理论和实用价值。 太平洋北赤道流分叉是大洋,特别是太平洋西部边界流海域的一个非常突出的环流现象,它是大洋中副热带大流环和热带流环的发源地,很大程度上决定着海盆尺度的大洋环流结构,在大洋环流动力学上具有非常重要的意义和地位;同时它决定着大洋西边界区质量、热量的经向输送,进而对气候变化产生重要影响,是气候系统中不可忽视的重要分量。因此,北赤道流分叉的研究,不仅具有在海洋动力学上科学意义,而且对气候变化和预测也有实践意义。 从30年代至今,关于北赤道流分叉的研究有两种,一是根据实际观测水文数据,二是由数值模拟结果得出结论。用观测数据做出的结果,相对比较接近实际,但资料的分辨率较差,会引起估算结果的偏差;数值模拟结果有较高的时空分辨率,但由于模式本身的某些缺点会导致结果偏离实际。目前为止,诸多有关北赤道流分叉的结果,如分叉纬度变化的结论很不一致。所以,如何找到一种高时空分辨率的数据或提出一个比较符合物理实际并得到实测数据验证的数值模式是研究北赤道流分叉的关键。 本文用1992年10月到2004年12月高时空分辨率的卫星高度计数据,通过计算迹线的方法,确定了北赤道流分叉的纬度。结果表明,年平均分叉纬度约在13.4°N. 关于北赤道流分叉的季节变化,6月份发生在最南端(12.9°N),12月份发生在最北端(14.1°N)。12年的平均结果显示,7月份的分叉纬度比6月份和8月份明显偏大,这是局地风应力旋度导致的结果。本文同时研究了北赤道流分叉的年际变化,结果表明在厄尔尼诺年,北赤道流分叉纬度北移,在拉尼娜年,分叉纬度南移。 在热带西太平洋地区,特别是西边界流区和印度尼西亚贯通流邻近海域,岛屿众多,地形非常复杂,历史水文数据和测流数据又极少,所以几乎无法用分析观测数据的方法求得这一海域海洋环流,特别是次表层环流结构的深刻了解。因此,本文利用一个既适用于开阔大洋又适宜于地形变化剧烈海域的混合坐标海洋模式HYCOM,模拟了热带西太平洋环流,特别是西边界流及其相关海流,如,新几内亚沿岸潜流、棉兰老潜流、赤道潜流和印度尼西亚贯通流的气候态及其月、季变化。模式结果再现了该海域主要流系及其季节变化,模拟得到的海面高度场与卫星高度计数据基本一致;模拟所得的诸多关键断面上的海流、温度和盐度结构与实地观测数据(Johnson et al., 2002)有良好的一致性,说明本文的HYCOM模拟结果是比较可信、可靠的,可以用来做西太平洋环流分析用。本文得到结果如下: (1)赤道潜流究竟起源于何处,是赤道环流动力学上一个重要问题。鉴于实测数据缺乏和赤道潜流起源邻近海域地形复杂,相关研究很少,仅有的几项研究结果认为赤道潜流起源于135-137°E。本文一系列经向跨赤道断面的纬向流速模拟结果表明,赤道潜流最西源于129-130°E之间;另外,事实上,从200米层水平环流的模拟结果来看,赤道潜流有4个源头,各季有所不同:(i) 新几内亚沿岸潜流在135°E附近汇入赤道潜流;与Tsuchiya et al.(1989)结论相同;(ii) 来自棉兰老海流,这与Lu and McCreary(1995),Gu and Philander(1997)结论相同;(iii) 南海水经民都洛海峡、苏禄海和苏拉威西海西部由哈马黑拉岛以北进入赤道潜流,特别是,在春、夏、秋季;(iv) 印度洋海水经班达海和马鲁古海沿苏拉威西东岸北上沿哈马黑拉岛以东汇入赤道潜流(特别是春季)。所以,赤道潜流就水源来说,它有来自南海、印度洋和棉兰老以东的海水,就其起源来说,还是应该算从129-130°E开始的。 (2)棉兰老潜流发现于80年代末,尽管棉兰老潜流的起源对这一海域环流动力学非常重要,但由于资料缺乏,其起源的研究甚少。本文的模拟结果表明棉兰老潜流似乎有一部分水来自棉兰老海流,这主要在300-500米层。但更重要的是,从马鲁古海西边界(苏拉威西岛以东)向北的一支流更是棉兰老潜流的重要水源,说明棉兰老潜流的水源有相当部分是来自南半球,在600,700米层,特别是800,900和1000米层,棉兰老海流流速急剧减小至几乎看不到,而棉兰老潜流非常突出,其水源主要来自南半球苏拉威西岛东部向北的流动。至于棉兰老潜流的去处,500,600米层的模拟结果显示,棉兰老潜流在12-13°N附近,一大部分向东流去,一小部分向南加入棉兰老海流。在700米层以下,棉兰老潜流则在12°N向东流去,这与Hu and Cui(1989, 1991)和Wang and Hu(1998)的结果一致。 (3)关于印度尼西亚贯通流。HYCOM模拟的印度尼西亚贯通流年平均状况指出:250米以浅,印度尼西亚贯通流由西太平洋主要经由望加锡海峡进入东印度洋;300米以深,印度尼西亚贯通流反向,由东印度洋经由弗罗勒斯海、班达海和马鲁古海的西部边界进入太平洋。由200米层环流可以看出,从民都洛海峡南下的南海水是进入望加锡海峡构成印度尼西亚贯通流的主要的来源,另一小部分来自棉兰老海流。 (4)关于黑潮南海分支。在本文的模拟结果中,一年四季都有明显的黑潮分支由吕宋北端向西北进入南海后,沿大约21°N附近向西南流动,宽约100-200公里,深达300-400米,最大流速一般可达20厘米/秒,最大在冬季,可达40厘米/秒,流量约为6.5Sv,冬季强,5、9月份偏弱。证明了仇德忠、杨天鸿、郭忠信(1984)和郭忠信、杨天鸿、仇德忠(1985)关于南海黑潮分支存在的论述,并在一定程度上定量的解释了其季节变化规律。

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冲绳海槽是一个目前正在扩张的弧后盆地,海槽具有特殊的地形、地球物理特征,广泛发育的断裂构造和频繁的岩浆活动,因此多年来一直是中外学者关注的地区之一。特别是近年来在冲绳海槽断裂带附近发现了计多热液活动区,促使人们从新的角度去重新认识冲绳海槽。冲绳海槽的热液沉物中富含Zn、Pb、Cu、Fe、Au、Ag、Hg等多种有用的金属元素,其潜在的巨大经济价值以及对热液活动研究的理论意义也使得冲绳海槽现代海底热液活动的研究成为众人瞩目的焦点。本论文运用显徽镜、X-射线衍射分析、扫描电镜分析、仪器中子活化分析、同位素质谱分析等先进的技术手段和方法,对冲绳海槽现代海底热液沉积物矿物组成、形貌特征、结构构造、矿物生成顺序、成矿作用阶段、元素的赋存状态、元素地球化学特征、以及重要元素的同位素组成等进行了系统的分析与研究,探讨了冲绳海槽现代海底热液活动的规律及其成矿作用机制,工作中获得一些新的发现和较前人工作更加深入的认识。(1)根据主要矿物的不同,将本区的热液沉积物分为硫化物矿石、以重晶石为主的硫酸盐矿石和以硬石膏为主的硫酸盐矿石等三类。硫化物矿石主要由闪锌矿、方铅矿、黄铁矿和黄铜矿和黄铜矿组成,明显地分为疏松粗粒和致密细粒两部分,代表着两个成矿作用阶段;在以重晶石为主的硫酸盐矿石中重晶石和非晶质SiO_2成为主要矿物,亦明显地分为粗粒和细粒两部分;在以硬石膏为主的硫酸盐矿石中,无色透明的自形板状硬石膏占了85%左右,其次为黑色细粒的硫化物。(2)利用电子探针和仪器中子活化分析法对部分金属元素的赋存状态进行了研究。结果表明,Zn、Pb、Cu、Fe的主要载体矿物和富集矿物为相应的硫化物。在各类矿石的粗颗粒矿物中,闪锌矿中Au的含量最高,其它矿物Au的含量相对较低;Au在细粒的矿物集合体中含量明显高于粗粒矿物。在分析过程中,首次在以重晶石为主的硫酸盐矿石中发现了颗粒状的单质Ag矿物,它是Ag的主要存在形式。除了单质Ag矿物外,Ag还有另外两种富集成矿形式,一是存在于银矿物(如:硫砷银矿)之中,另一种是以类质同象或分散态存在于各种硫化物和硫酸盐矿物中。Hg的主要载体矿物为方铅矿,而富集矿物为辰砂。(3)在硫化物矿石中,Zn的含量较高,在30%以上,Pb、Fe次之,其含量均大于5%;硫酸盐矿石中Ba、Ca为主要组分,金属元素的含量普遍较低,多数含量在3%以下。在各类矿石中Au、Ag、Hg相对明显富集,Au含量可达9.8ppm,Ag为6500ppm,Hg为77ppm。(4)地球化学研究结果表明,不同的元素其来源不尽相同,Au、Hg、Zn、Cu、Fe主要来自火成岩,Pb则主要来源于火山岩和沉积物,其中沉积物的影响可能更大。Ag可能来自地球深部的物质。(5)对不同类型矿石及单矿物的硫同位素研究表明,无论是硫化物集合体还是单矿物闪锌矿,δ~(34)S值变化范围都不大,均在5.2-7.2‰之间,表现出一致的来源与演化过程,而与其它热液活动区相比δ~(34)S明显偏高。重晶石、硬石膏的δ~(34)S值与其它地区相差不大,其变化范围在23-23‰之间。以上结果说明在热液流体成矿的不同阶段,硫的来源不同。在早期阶段,硫可能主要来自海水与周围的岩石,此后因流体受岩将活动的影响,硫主要来自岩浆和地球深部物质,在热液流体成矿的后期阶段的硫化物沉淀过程中,海水又对硫的来源起到巨大的影响。

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Ochotona curzoniae and Microtus oeconomus are the native mammals living on the Qinghai-TibetanPlateau of China. The molecular mechanisms of their acclimatization to the Plateau-hypoxia remain unclear. Expressions of hepatic hypoxia-inducible factor (HIF)-1 alpha, insulin-like growth factor-I (IGF-I)/IGF binding protein (BP)-1(IGFBP-1; including genes), and key metabolic enzymatic genes [lactate dehydrogenase (LDH)-A/isocitrate dehydrogenase (ICD)] are compared in Qinghai-Tibetan- Plateau mammals andsea- level mice after injection of CoCl2 (20, 40, or 60 mg/ kg) and normobaric hypoxia (16.0% O-2, 10.8% O-2, and 8.0% O-2) for 6 h, tested by histochemistry, Western blot analysis, ELISA, and RT-PCR. Major results are CoCl2 markedly increased 1) HIF-1 alpha only in mice, 2) hepatic and circulatory IGF-I in M. oeconomus, 3) hepatic IGFBP-1 in mice and O. curzoniae, and 4) LDH-A but reduced ICD mRNA in mice (CoCl2 20 mg/kg) but were unchanged in the Tibetan mammals. Normobaric hypoxia markedly 1) increased HIF-1 alpha and LDH-A mRNA in mice and M. oeconomus (8.0% O-2) not in O. curzoniae, and 2) reduced ICD mRNA in mice and M. oeconomus (8.0% O-2) not in O. curzoniae. Results suggest that 1) HIF-1 alpha responsiveness to hypoxia is distinct in lowland mice and plateau mammals, reflecting a diverse tolerance of the three species to hypoxia; 2) CoCl2 induces diversities in HIF-1, IGF-I/IGFBP-1 protein or genes in mice, M. oeconomus, and O. curzoniae. In contrast, HIF-1 mediates IGFBP-1 transcription only in mice and in M. oeconomus (subjected to severe hypoxia); 3) differences in IGF-I/IGFBP-1 expressions induced by CoCl2 reflect significant diversities in hormone regulation and cell protection from damage; and 4) activation of anaerobic glycolysis and reduction of Krebs cycle represents strategies of lowland-animals vs. the stable metabolic homeostasis of plateau- acclimatized mammals.

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To reveal the potential contribution of grassland ecosystems to climate change, we examined the energy exchange over an alpine Kobresia meadow on the northeastern Qinghai-Tibetan Plateau. The annual pattern of energy exchange showed a clear distinction between periods of frozen soil with the daily mean soil temperature at 5 cm (T-s5 ≤ 0 ° C) and non-frozen soil (T-s5 > 0 ° C). More than 80% of net radiation was converted to sensible heat (H) during the frozen soil period, but H varied considerably with the change in vegetation during the non-frozen soil period. Three different sub-periods were further distinguished for the later period: (1) the pre-growth period with Bowen ratio (β) > 1 was characterized by a high β of 3.0 in average and the rapid increase of net radiation associated with the increases of H, latent heat (LE) and soil heat; (2) during the Growth period when β ≤ 1, the LE was high but H fluxes was low with β changing between 0.3 and 0.4; (3) the post-growth period with average β of 3.6 when H increased again and reached a second maximum around early October. The seasonal pattern suggests that the phenology of the vegetation and the soil water content were the major factors affecting the energy partitioning in the alpine meadow ecosystem. © 2005 Elsevier B.V. All rights reserved.

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This dissertation starts from the point that the prestack time migration can been considered as an approximation of the prestack depth migration, giving a wave equation based prestack time migration approach. The new approach includes: analytically getting the travel time and amplitude based on the one way wave equation and the stationary-phase theory, using ‘spread’ imaging method and imaging following the prestack depth migration, updating the velocity model with respect to the flats of the events in CRP gathers. Based on this approach, we present a scheme that can image land seismic data without field static correction. We may determine the correct near surface velocities and stack velocities by picking up the residual correction of the events in the CRP gathers. We may get the rational migration section based on the updated velocities and correct the migration section from a floating datum plane to a universal datum plane. We may adaptively determine the migration aperture according to the dips of the imaging structures. This not only speed up the processing, but may suppress the migration noise produce by the extra aperture. We adopt the deconvolution imaging condition of wave equation migration. It may partially compensate the geometric divergence. In this scheme, we use the table-driven technique which may enhance the computational efficiency. If the subsurface is much more complicated, it may be impossible to distinguish the DTS curve. To solve this problem, we proposed a technique to determine the appropriate range of the DTS curve. We synthesize DTS panel in this range using different velocities and depths, and stack the amplitude around the zero time. Determine the correct velocity and location of the considered grid point by comparing the values.

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Glutenite reservoir is one of the most important reservoir types in china. Because of its particularity of rock structure and pore structure, it is usually difficult in development, especially for its serious heterogeneity. On the basis of seismic, well logs, core data and production performance, the lower Wuerhe group can be divided into one second-order sequences, two third-order sequences and twenty two subsequences, corresponding to the five stages and twenty two minlayers. In addition, the fault systems are interpreted and the control action of fault systems to reservoir development is also described. The lower Wuerhe formation of 8th district belongs to fluvial-dominated fan delta sedimentation, according to the analysis of well logs, logging data and core data. It can be subdivided into two kinds of subfacies and nine kinds of microfacies. The fan delta plain subfacies mainly consist of braided channel, unconcentrated flow, mud flow and sieve deposit microfacies. The fan delta front subfacies include subaqueous distributary channel, subaqueous interdistributary channel, debris flow, subaqueous barrier and grain flow microfacies. Combined with the regional geological characteristics, the porosity model of lower Wuerhe formation is performed using core data. A permeability model based on the flow zone index is also formed according to the pore throat characteristics and flow property. Finally, the heterogeneity is analyzed. The result shows that the lower Wuerhe formation has a feature of middle-high heterogeneity, and it is controlled by material sources and sedimentary facies belt.

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攀西地区龙帚山和二滩玄武岩形成于较低程度地幔部分熔融条件(<7%),部分熔融过程中Ir,Ru和Rh表现其相容性而Pt和Pd为不相容元素.这些样品多含较高的铂族元素(PGE),其Pd/Ir和Cu/Pd比值远高于原始地幔值.部分熔融过程中有少量硫化物(约0.007%)残留于地幔源区,岩浆上升过程中则有部分岩浆达到硫饱和而分离出富集PGE的硫化物(约0.020%~0.033%).Os,Ir和Pt在结晶分异过程中形成铂族金属合金进入铬铁矿或硫化物,导致Pt和Pd的解耦及Ir含量出现很大变化.玄武质岩浆中熔离出的硫化物可能为邻近喷发通道的镁铁-超镁铁质岩体形成Cu-Ni-PGE矿床(化)提供重要的物质来源.

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四川力马河镍矿是峨眉山大火成岩省一个重要的岩浆硫化物矿床。本文通过对其主要岩、矿石类型Re、0s及其同位素组成的分析,综合探讨了成矿岩体原始岩浆性质、矿石硫化物成因、成矿机制及Re-Os同位素等时线年龄。结果表明,力马河镍不同类型岩矿石样品初始0s同位素组成是不均一的,富硫化物的网脉状矿石 及其选纯硫化物Os同位素组成初始值差异较小,其等时线年龄为265士35 Ma,与岩体错石SHRIMP年龄263士3Ma基本相当}硫化物含量较低的岩、矿石样品间初始Os同位素组成差异较大,其表观等时线年龄大于成矿年龄。分析认为。岩矿样品初始Os同位素组成的不均一是由含较高放射成因187Os丰度的硫化物熔体和含较低放射成因187Os丰度的硅酸盐熔体不同比例混合造成的。混合模型分析表明,硫化物含量超过3O% 的矿石样品初始187 Os/188Os基本接近,硫化物含量低于3O %的岩矿石样品初始 187Os/188Os随硫化物含量上的不同,差异很大,为岩浆硫化物矿床Re-Os等时线年龄出现多组年龄解的现象提供了一种可能的解释。成矿岩体中含放射成因187Os丰度最低的岩石样品 (t一260Ma)在5左右、Cu/Pd比值在7000左右,表明是基本没有受到地壳混染及硫化物熔离影响的原始岩浆结晶分异产物,估计原始岩浆Os含量在1×10 左右,为苦橄质岩浆。矿石硫化物Re/Os比值显著高于任何赋矿橄榄岩,7o,(£一260Ma)高达110左右,综合分析揭示了力马河镍矿硫化物为二次熔离成因,模式分析认为,矿石硫化物是由原始岩浆经历R一2000左右的硫化物熔离后,其亏损岩浆再经R一200左右的硫化物熔离形成,与二次熔离相对应,成矿岩浆也经历了两次混染作用,分别为上、下地壳7%左右的混染。