共查询到20条相似文献，搜索用时 798 毫秒
1.
《中国科学院院刊(英文版)》2008,22(3):186-187
China is believed to be a country especially endowed with the fossils and materials related to early human evolution, next only to the African continent in terms of fecundity and systematism. These materials, including physical and cultural remains of huminids, their associated fauna and flora as well as prehistoric sites, are essential for probing the human origin and evolution. Yet, experts say that the studies of these fossils and artefacts are far from being adequate and perfect in China because they have been plagued by many weak points. 相似文献
2.
口腔局部用药SrCl2与NaF的电化学研究 总被引：3，自引：0，他引：3
利用电化学的原理以及牙体生物电测量的结果,计算并分析SrCl_2和NaF这两种口腔临床牙体病常用的药物,结果显示,Sr~(2+)由于带正电荷,很难透入活体牙而达到治疗目的,作为口腔内局部用药是值得商榷的;F~-则相反,能够透入牙体而达到治疗的目的,作为口腔内局部用药是可行的,但使用方法有待进一步改进. 相似文献
3.
为保存因外伤所致的伴有部分冠折的离体脱位牙,在对患儿体外根管充填治疗后,用螺纹钉加光因化复合树脂修复其缺损的牙冠,同时用ＰＨ为１．０的枸椽酸处理牙根表面,对１８例２１只患牙进行了即刻再植,结果表明,以往常被扫弃的伴有冠折的完全性脱位牙,在经过适当的治疗处理后可以再植成功。 相似文献
4.
Ramsden E 《Isis; an international review devoted to the history of science and its cultural influences》2011,102(4):659-688
In a series of experiments at the National Institute of Mental Health, the animal ecologist John B. Calhoun offered rats everything they needed, except space. The resulting population explosion was followed by a series of "social pathologies"--violence, sexual deviance, and withdrawal. This essay examines the influence of Calhoun's experiments among psychologists and sociologists concerned with the effects of the built environment on health and behavior. Some saw evidence of the danger of the crowd in Calhoun's "rat cities" and fastened on a method of analysis that could be transferred to the study of urban man. Others, however, cautioned against drawing analogies between rodents and humans. The ensuing dispute saw social scientists involved in a careful negotiation over the structure and meaning of Calhoun's experimental systems and, with it, over the significance of the crowd in the laboratory, institution, and city. 相似文献
5.
Pettit M 《Isis; an international review devoted to the history of science and its cultural influences》2006,97(4):659-677
This essay presents a historical epistemology of the nineteenth-century controversy concerning a scientific hoax, the Cardiff giant. My focus is on the shifting meanings given to the giant, which were based on epistemologies derived from scientific authority, religious belief, and market relations. In 1869 a farmer in Cardiff, New York, claimed to have discovered the fossilized remains of a prehistoric, perhaps biblical, giant on his property. While some scientists stressed the need to cooperate with commercial showmen, enthusiasm for the giant incited the ire of others, who sought to debunk it and the culture that sustained it. Drawing on local newspaper reports, memoirs, nineteenth-century exposés, and publicity materials associated with the giant's display, I link the episode to the history of popular and scientific observation. The giant was a particularly troubling spectacle because as an object of inquiry it blurred the modern boundaries separating nature, society, and religion. 相似文献
6.
In prehistoric times carbon wasknown in the form of soot andcharcoal. Ever since AntoineLavoisier in 1792 and Smithson Te-net in 1797 demonstrated that dia-mond and graphite are allotropicforms of carbon[1], people have beeninterested in converting the relativelyabundant carbon materials into muchrarer diamond. It is found that dia-mond burnt in oxygen yields exactlythe same amount of carbon dioxideas that produced by burning the sameweight of carbon, proving diamondconsists of pure carbon.S… 相似文献
7.
De Bont R 《Isis; an international review devoted to the history of science and its cultural influences》2003,94(4):604-630
Although he died in obscurity, the Belgian museum conservator Aimé Rutot (1847-1933) was one of the most famous European archaeologists between 1900 and 1920. The focus of his scientific interest was stone flints, which he claimed to be the oldest known human tools, so-called eoliths. Skeptics maintained that the flints showed no marks of human workmanship, but Rutot nevertheless managed to spread his "Eolithic theory" in an important part of the scientific community. This essay demonstrates how material objects--series of stone flints and sets of statues that purported to reconstruct prehistoric "races"--were given scientific meaning by Rutot. Rutot diffused his ideas by disseminating his stones and statues, thus enlarging his networks of influence. For a time he managed to be at the material center of a trade network as well as at the intellectual center of archaeological debate. The essay shows how Rutot achieved this status and how he eventually fell from favor among serious scientists. 相似文献
8.
Roel C. G. M. Lauwerier 《Endeavour》1986,10(4)
Of the animal artifacts encountered by archaeologists, bones and teeth are the ones most commonly found. Systematic study of these — particularly of their distribution and the different species involved —can throw much light on the diet and eating habits of people in the past. 相似文献
9.
《中国科学院院刊(英文版)》2008,22(2):69-69
Many small seed-eating rodents bury their food in an erratic manner called scatter-hoarding because they are unable to defend one large hoard. This process has a complicated influence on seed dispersal, as shown in the work by ZHANG Zhibin at the CAS Institute of Zoology and his co-workers. 相似文献
10.
《中国科学院院刊(英文版)》2009,23(1):22-23
Acomplete fossil skeleton of spotted hyena unearthed on 26 July, 2008 in nearlyperfect preservation, exhilarates CAS paleontologists, as the discovery in north China might offer new clues about the interactions between prehistoric faunas of Africa and Eurasia, and meanwhile afford a clue to the big extinction of large amount of species occurring about 11,000 years ago. 相似文献
11.
Dhananjay Andure Kiran Pote Vishal Khatri Nitin Amdare Ramchandra Padalkar Maryada Venkata Rami Reddy 《Indian journal of clinical biochemistry : IJCB》2016,31(4):423-430
Lymphatic filariasis is a mosquito borne parasitic infection and can severely affect the normal working ability of an individual. Currently there is no vaccine available to prevent this infection and the development of a potential vaccine could effectively support the on-going mass drug administration program by World Health Organization (WHO). Filarial parasites have complex mechanisms to modulate the host immune responses against them. The glutathione-S-transferases (GST) are the important enzymes effectively involved to counteract the oxidative free radicals produced by the host. In the present study, we have shown that the mastomys which are fully permissible rodents for Brugia malayi when immunized with Wuchereria bancrofti recombinant GST (rWbGST) could induce 65.5 % in situ cytotoxicity against B. malayi infective (L3) larvae. There was a balanced Th1/Th2 immune response in the vaccinated animals, characterized by higher levels of WbGST-specific IgG1 and IgG2a antibodies and pronounced IFN-γ, IL-10 and IL-4 cytokines production by the spleen cells. 相似文献
12.
13.
14.
Nora Nikolac 《Biochemia medica : ?asopis Hrvatskoga dru?tva medicinskih biokemi?ara / HDMB》2014,24(1):57-67
In the clinical laboratory setting, interferences can be a significant source of laboratory errors with potential to cause serious harm for the patient. After hemolysis, lipemia is the most frequent endogenous interference that can influence results of various laboratory methods by several mechanisms. The most common preanalytical cause of lipemic samples is inadequate time of blood sampling after the meal or parenteral administration of synthetic lipid emulsions. Although the best way of detecting the degree of lipemia is measuring lipemic index on analytical platforms, laboratory experts should be aware of its problems, like false positive results and lack of standardization between manufacturers. Unlike for other interferences, lipemia can be removed and measurement can be done in a clear sample. However, a protocol for removing lipids from the sample has to be chosen carefully, since it is dependent on the analytes that have to be determined. Investigation of lipemia interference is an obligation of manufacturers of laboratory reagents; however, several literature findings report lack of verification of the declared data. Moreover, the acceptance criteria currently used by the most manufacturers are not based on biological variation and need to be revised. Written procedures for detection of lipemia, removing lipemia interference and reporting results from lipemic samples should be available to laboratory staff in order to standardize the procedure, reduce errors and increase patient safety. 相似文献
15.
我国地热资源相当丰富,应用潜力巨大,因此,大力发展地热能能够缓解能源供应紧张局面,很大程度上解决因大量使用化石能源所造成严重的空气污染问题。在我国,应根据资源分布特点制定地热发展规划,在资源品质较好的地区发展地热发电,在有条件的地区发展各种地热直接利用技术,采用综合梯级利用提高资源利用效率。今后开发利用地热能,政府应加大对地热能利用的政策支持,鼓励企业加大资金投入;同时开发商应做好规划和布局,优选技术路线,使得地热能的利用由无序变有序,朝着更加科学合理的方向发展。 相似文献
16.
金缕梅科(广义)的叶结构及分类 总被引：2，自引：0，他引：2
金缕梅科(广义)Hamamelidaceae包括29属，约140种。 此科的化石出现得较早，是双子叶植物中的一个比较古老的科。 本文的目的是系统研究此科透明叶的各种性状特征，并检验它们是否具有分类学意义。 本文研究了金缕梅科29属、60余种的叶的各种性状在科内的分布及演化趋势，并根据这方面的证据对此科的分类提出一些修正意见，系统描述部分介绍了金缕梅科各属叶的形态特征。 相似文献
17.
斜齿圆柱齿轮机构正确啮合的条件之一是两齿轮互相啮合轮齿的倾斜方向一致。在实际工作中，经常会遇到更换一件或两件齿轮情况，需要对其进行测绘。在测绘时，应准确确定斜齿圆柱齿轮的分度圆柱螺旋角，应尽量减小测绘误差，保证斜齿圆柱齿轮的传动质量和强度不发生太大的变化。为此，在现场总结以下几种便捷的测绘方法，仅供参考。 相似文献
18.
对前牙牙冠严重缺损者采用一次性药物根管充填,制作桩核,即时备牙,取模,制作金属烤瓷冠,从而明显减少了患者就诊天数及时间。通过５０７颗粒临床观察,总有效率达９２．７０％,与常规根充后作桩核制作烤瓷冠的２５４颗牙作对比,无统计学差别。分析探讨了烤瓷冠的临床操作要点。 相似文献
19.
Strong, Weak, and Latent Ties and the Impact of New Media 总被引：2，自引：0，他引：2
Caroline Haythornthwaite 《The Information Society》2002,18(5):385-401
This article argues that consideration of the strength of ties between communicators can help reconcile disparate results on the impact of new media on social relations. It is argued from the research literature and studies by the author that where ties are strong, communicators can influence each other to adapt and expand their use of media to support the exchanges important to their tie, but where ties are weak, communicators are dependent on common, organizationally established means of communication and protocols established by others. Due to this differential use of media, a new medium that adds means and opportunities for previously unconnected others to communicate will have positive effects on weak ties and weak-tie networks, in particular by laying an infrastructure of latent ties (ones that exist technically but have not yet been activated), and providing an opportunity for weak ties to develop and strengthen. A new medium may also have positive effects on strongly tied pairs where it adds another means of communicating and supports the communication needs and tasks of the pair. However, where a new medium replaces a former, common means of communication, the dependence of weak ties on a common medium makes weak-tie networks highly susceptible to dissolution. In contrast, strong-tie networks, with their connections via multiple relations and multiple media, can be expected to be more robust under conditions of change. 相似文献
20.
We here present and characterize a programmable nanoliter scale droplet-on-demand device that can be used separately or readily integrated into low cost single layer rapid prototyping microfluidic systems for a wide range of user applications. The passive microfluidic device allows external (off-the-shelf) electronically controlled pinch valves to program the delivery of nanoliter scale aqueous droplets from up to 9 different inputs to a central outlet channel. The inputs can be either continuous aqueous fluid streams or microliter scale aqueous plugs embedded in a carrier fluid, in which case the number of effective input solutions that can be employed in an experiment is no longer strongly constrained (100 s–1000 s). Both nanoliter droplet sequencing output and nanoliter-scale droplet mixing are reported with this device. Optimization of the geometry and pressure relationships in the device was achieved in several hardware iterations with the support of open source microfluidic simulation software and equivalent circuit models. The requisite modular control of pressure relationships within the device is accomplished using hydrodynamic barriers and matched resistance channels with three different channel heights, custom parallel reversible microfluidic I/O connections, low dead-volume pinch valves, and a simply adjustable array of external screw valves. Programmable sequences of droplet mixes or chains of droplets can be achieved with the device at low Hz frequencies, limited by device elasticity, and could be further enhanced by valve integration. The chip has already found use in the characterization of droplet bunching during export and the synthesis of a DNA library. 相似文献