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1.
近年来新西兰政府大力调整其科技政策,在建设知识社会的蓝图下,建构了科技投资的基本框架,凸显了知识、经济、环境、社会四大目标,另外通过对投资决策、运行和监督的改革,使政府科技投资的机制更为科学有效,本文还给出了新西兰政府近年来科技投资的分配比例状况,阐明了其投资的重点领域。  相似文献   

2.
We outline a framework for analyzing episodes from the history of science in which the application of mathematics plays a constitutive role in the conceptual development of empirical sciences. Our starting point is the inferential conception of the application of mathematics, recently advanced by Bueno and Colyvan (2011). We identify and discuss some systematic problems of this approach. We propose refinements of the inferential conception based on theoretical considerations and on the basis of a historical case study. We demonstrate the usefulness of the refined, dynamical inferential conception using the well-researched example of the genesis of general relativity. Specifically, we look at the collaboration of the physicist Einstein and the mathematician Grossmann in the years 1912–1913, which resulted in the jointly published “Outline of a Generalized Theory of Relativity and a Theory of Gravitation,” a precursor theory of the final theory of general relativity. In this episode, independently developed mathematical theories, the theory of differential invariants and the absolute differential calculus, were applied in the process of finding a relativistic theory of gravitation. The dynamical inferential conception not only provides a natural framework to describe and analyze this episode, but it also generates new questions and insights. We comment on the mathematical tradition on which Grossmann drew, and on his own contributions to mathematical theorizing. The dynamical inferential conception allows us to identify both the role of heuristics and of mathematical resources as well as the systematic role of problems and mistakes in the reconstruction of episodes of conceptual innovation and theory change.  相似文献   

3.
采用羟甲基化技术对碱木质素进行活化,对比了羟甲基化前后未质素改性酚醛树脂胶的粘结强度、残留甲醛、贮存稳定性和热稳定性等性能,为木质素的高值应用探讨新的途径.试验结果表明在木质素对笨酚的替代率低于30%务件下,以分离提纯后的木质素可直接应用于酚醛树脂胶粘剂的改性;而当替代率大于50%后,木质素的羟甲基化展示对木质素改性酚醛树脂的胶结强度、热稳定性具有良好的促进作用.但木质素的羟甲基化作用同时也导致木质素改性酚醛树脂中残留甲醛含量增加,进而导致制备的胶粘荆的贮存稳定性降低,可以通过改变合成过程中甲醛和碱的用量来达到降低酚醛树脂中残留甲醛含量.  相似文献   

4.
Summary Four new hexapeptide analogues of C-terminal Substance P fragment with increased solubility in aqueous solutions are described. The peptides contain histidine in positions 6, 8, 9 and 10, respectively. The effect of the structural changes on the hypotensive activity and antigenic properties of analogues was compared. It was found that substitution of amino acid residues in various positions in the C-terminal hexapeptide of Substance P resulted in different effects on the hypotensive and antigenic properties, respectively. Only the [His6] SP6-11 analogue had an unchanged antigenic structure when compared with the C-terminal region of Substance P, but it showed an almost total loss of hypotensive activity. The [His9] SP6-11 analogue retained 50% of the hypotensive activity of the C-terminal hexapeptide but showed a markedly reduced expression of the antigenic epitope localized in this region of Substance P.  相似文献   

5.
运行的超声电机会产生温升,过高的温升对超声电机的机械特性及使用寿命都有较大影响。本文首先通过实验证明压电陶瓷元件发热和摩擦层摩擦发热是超声电机温升的主要热源;然后,分别以压电陶瓷元件发热和摩擦层摩擦发热为热源,建立其相应的温度场热分布模型。并用有限元软件分别对压电陶瓷元件发热场和接触摩擦发热场进行仿真计算。计算结果表明,压电陶瓷片发热源部分,热量最大处为压电陶瓷片粘贴面的内圈;接触摩擦发热中,摩擦产生的热量集中在接触表面。  相似文献   

6.
简要概述了日本的科学基金情况,重点分析了日本学术振兴会(JSPS)及其管理的科学基金。日本学术振兴会(JSPS)相当于日本的国家科学基金会,其负责管理的科学研究费补助金是日本政府出资的科学研究基金中资助金额最大、资助范围最广、资助项目数量最多的竞争性科学基金。其对基础研究的资助政策、方向遴选、评审程序、经费分配、管理机制等对其它国家的基础研究政府资助机构具有借鉴和示范意义。介绍了科学研究费补助金资助的研究类型和申请程序,分析了近10年科学研究费补助金的预算及年增长率、近12年科学研究费补助金的项目资助率情况、近5年科学研究费补助金的领域分配与资助情况、2005年科学研究费补助金资助情况等。对科学研究费补助金的基金项目资助战略予以全面分析,对我国相关部门的管理工作有重要参考价值和借鉴意义。  相似文献   

7.
Asbestos-induced cell damage is initiated by a reaction at the plasma membrane. The effect of chrysotile (which is more hemolytic and releases more silicic acid than other types of asbestos) on permeability changes of liposomes has been investigated. The destabilizing effect rises when the amount of chrysotile is increased. Silicon dioxide is one major constituent which could be a hemolytic agent, and a cause of damage. It also caused an increase of permeability of liposomes.  相似文献   

8.
巷道布置对围岩稳定性影响的数值模拟   总被引:1,自引:0,他引:1  
采用理论分析不同应力场下巷道轴线与最大水平主应力方向夹角的最佳角度,利用数值模拟不同夹角情况下,巷道围岩应力分布、正前方应力分布及变形特征。得出:1)最大水平主应力σH〉最小水平主应力σh〉垂直主应力σr时,最佳角度为0°;σt〉σH〉σh时,最佳角度为90°;σH〉σa〉σA时,最佳夹角为α0.2)巷道开挖后,水平应力在两帮出现应力降低区,在顸、底板出现应力集中区;垂直应力在两帮出现应力集中区,在顶、底板出现应力降低区;随角度变化,应力变化区均有明显变化,正前方断面的最大主应力变化明显。3)巷道达到最佳角度时,围岩变形相对较小,最大主应力围绕在巷道周边,呈环状或类环状分布;其它角度时,围岩变形相对较大,最大主应力逐渐向顶、底板的四角或两帮发展。  相似文献   

9.
The present study identified aloe-emodin (AE, a hydroxyanthraquinone from Aloe vera and other plants) as a new anti-angiogenic compound with inhibitory effects in an in vivo angiogenesis assay and evaluates its effects on specific key steps of the angiogenic process. AE inhibits endothelial cell proliferation, but this effect is not cell specific, since AE also inhibits tumor cell proliferation. Cell migration and invasion are not remarkably affected by AE. On the other hand, AE has different effects on endothelial and tumor cell gelatinases. Two main targets of the pharmacological action of AE as an anti-angiogenic compound seem to be urokinase secretion and tubule formation of endothelial cells. Finally, AE produces a remarkable photocytotoxic effect on tumor cells. Taken together, our data indicate that AE can behave both as an anti-tumor and an anti-angiogenic compound and suggest that AE could be a candidate drug for photodynamic therapy. Received 7 September 2006; received after revision 17 October 2006; accepted 31 October 2006  相似文献   

10.
介绍了一种基于超高频RFID的物联网前端感知系统的设计和实现,以及主要模块的功能,然后分别从硬件结构,工作流程和软件设计三个方面进行了详细阐述.本系统的工作频率在860~960 MHz可调节,能支持EPC Gen2和ISO/IEC 18000-6B/6C标准.它的射频前端是以射频芯片AS3992为核心,使用内部集成的功放,外加一系列外围电路实现.其优点是体积小、重量轻、集成度高和功耗低.实验结果表明,该系统的读写距离能达到2.5m,能够满足实际应用的需要.  相似文献   

11.
Summary When the specific activities of the catechin oxidases (catechin as the substrate) which were released from the roots of the seedlings of alfalfa, tomato, wheat, lettuce and corn were compared, it was found that the oxidizing activity was absent from the root exudate of corn seedlings. A 6.3 kDa protein was purified from the root exudate of corn seedlings and in the presence of this protein, the oxidation of catechin was inhibited. This inhibitor is responsible for the inability of the root exudate of corn seedlings to oxidize catechin.  相似文献   

12.
目的研究建立稳定的昆明小鼠皮肤局部缺血模型。方法取40只雌性昆明小鼠,随机分为A/B两组,每组20只。分别在小鼠背部建立深达皮下筋膜层的u型皮瓣。A组为3.3×1.5cm皮瓣组.B组为2.5×1.5CITI皮瓣组。皮瓣游离缘垫以医用橡胶,缝合切口,造成皮肤缺血模型,术后观察皮瓣发绀水肿及坏死情况,并用散斑全景实时血流成像仪(MoorFLH)检测皮瓣血流。结果肉眼观察,3.3×1.5cm皮瓣组在术后第2天,50%小鼠皮瓣末端坏死,坏死面积达皮瓣面积的(37.20±4.83)%。术后第3天100%小鼠皮瓣末端坏死。并随时间的延长,坏死面积逐渐扩大。2.5×1.5皮瓣组在术后第1天皮瓣出现发绀,水肿,发绀水肿面积占(77.46±4.51)%,术后第3,第5天发绀水肿区面积逐渐减小,至术后第7天,发绀、水肿完全消退。散斑全景实时血流成像仪(MoorFLPI)检测皮肤血流显示,术后第1天皮瓣显著性缺血(P〈0.05),术后第7天血流基本恢复到术前水平。结论成功建立了昆明小鼠皮肤局部缺血模型,为进一步研究组织微血管再生的机理和策略提供简单而稳定的动物模型。  相似文献   

13.
目的研究RNA干扰对肝门部胆管癌细胞株QRC939抑癌基因甲基化的影响,初步探谤其在胆管癌治疗中的价值。方法构建靶向hDNMT1的发夹式siRNA表达载体;运用脂质体介导法将其转染人胆管癌细胞QBC939;RT-PCR法检测不同时间点hDNMT1、CDH1、p15的表达水平;MSP方法检测转染前后抑癌基因CDH1、p15的甲基纯状态;MTT检测各组细胞的增殖能力。结果1)hDNMT1的基因沉默恢复了抑癌基因CDH1、p15的表达水平;2)CDH1、p15的表达沉默是由启动子高甲基亿导致的;3)转染靶向hDNMT1的发夹式siRNA表达载体能有效地抑制QBC939的增殖能力。结论靶向hDNMT1的发夹式siRNA表达载体能有效、持续、稳定发挥对hDNMT1的基因沉默作用,恢复抑癌基因CDH1、p15的表达水平,从而抑制QBC939肿瘤细胞增殖。  相似文献   

14.
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16.
烯二炔类抗肿瘤抗生素的生物合成研究进展   总被引:3,自引:0,他引:3  
烯二炔类抗生素以其独特的化学结构和强烈的抗肿瘤活性成为化学、生物和医药领域重点关注的对象。本文简要介绍了近年来关于烯二炔化合物的生物合成研究进展,以及运用组合生物合成的原理创造新型烯二炔结构类似物的前景。烯二炔类抗生素为我们研究复杂天然产物的生物合成提供了一个很好的模型,其基因和生化水平机制的阐明将进一步丰富组合生物合成的内容和手段,最终有利于发现和发展新型的抗肿瘤药物。  相似文献   

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18.
Transgenic cultigens may become feral as we know of some non-transgenic cultigens. The article explains two basic ways how cultigens become feral: through hybridization with a closely related wild plant and through revert to the wild-type. A long list of examples of cultigens becoming feral in Central Europe is presented. The process of becoming feral is compared to the naturalization of non-native species (Exotic Species Model). Ecological long-term effects of both cultigens becoming feral and non-native species being naturalized are discussed with special regard to the predictability of such events. The ecological aspects discussed in the article are as significant for transgenic cultigens as for non-transgenic cultigens.  相似文献   

19.
Studies of regulatory mechanisms of sleep-wake rhythms have benefited greatly from mathematical modeling. There are two major frameworks of modeling: one integrates homeostatic and circadian regulations and the other consists of multiple interacting oscillators. In this article, model constructions based on these respective frameworks and their characteristics are reviewed. The two-process model and the multioscillator model are explained in detail. An appropriate mathematical abstraction is also shown to provide a viewpoint unifying the model structures, which might seem to be distinct. Recently acquired knowledge of neural regulatory mechanisms of sleep-wake rhythm has prompted modeling at the neural network level. Such a detailed model is also reviewed, and could be used to explore a possible neural mechanism underlying a pathological state of sleep-wake rhythm.  相似文献   

20.
Two pteridine-containing bromophysostigmine alkaloids, urochordamine A and B, which were isolated from ascidians as larval metamorphosis promoters, were converted to more polar compounds, urochordamine A and B, respectively, when left standing in protic solvents. These four compounds promoted larval metamorphosis of the ascidianHalocynthia roretzi in the order A>A>B>B, and induced metamorphosis of the pediveliger larvae of the musselMytilus edulis galloprovincialis.  相似文献   

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