共查询到20条相似文献，搜索用时 593 毫秒
1.
Hessenbruch A 《Endeavour》2002,26(4):137-141
The identity of x-rays was initially mysterious, their connotations including morbidity and the otherworldly. Gradually they became routine, finding a place in the high-energy end of the electromagnetic spectrum. Radiologists established a niche in hospitals, contributing to the industrialization of healthcare. Control of x-ray tube output was improved while an infrastructure enforcing radiation protection accompanied the continued growth of the field. X-ray diffraction proved a powerful tool with which to examine substances at the atomic scale. Since 1950, x-ray researchers have taken advantage of synchrotrons’ copious production of continuous x-ray spectra, and the marriage of x-rays with electronics has led to a cornucopia of cheap and highly efficient analytical tools. 相似文献
2.
化学和元极学都研究物质及物质的变化规律，有很多相通相合的地方。用元极学的三元观战来看待化学，以此建立化学相应的观点来拓展化学研究的对象。提出化学要突破“有”的实体的研究范围，扩展到无比广阔的“无”的研究领域。 相似文献
3.
化学品特别是高风险化学品污染所造成的环境与健康问题已经成为影响我国公众健康的危险因素,以及人民对美好生活追求的重要阻碍。如何在确保化学品为人类社会带来福祉的同时,最大限度地降低其对环境与人群健康的危害,是化学领域特别是环境化学领域亟待解决的问题。文章系统总结了全氟化合物等化学品的风险识别、风险防范、替代品研发及评估等最新研究进展;探讨了如何通过绿色化学手段,结合高风险化学品全生命周期的风险管控,实现从根源上降低环境风险;并论述了高风险化学品全生命周期的研究进展、发展方向和实施策略。 相似文献
4.
糖尿病是一种常见的复杂性疾病,发病原因既有遗传因素又有环境因素,属于多遗传基因。目前人类根据对糖尿病患者体内某些物质的变化进行了研究,发现了诸如下丘脑神经肽、c肽联合胰岛素、肿瘤坏死因子、瘦素等物质。在糖尿病患者体内这些物质的含量有的提高,而有的却发生了相应的下降．主要是对这几种物质进行介绍,以使人们能更加准确地了解糖尿病的发病机制,从而研制出能更加行之有效的治疗方法。 相似文献
5.
《Research Policy》2023,52(8):104827
Are laboratory safety practices a tax on scientific productivity? We examine this question by exploiting the substantial increase in safety regulations at the University of California following the shocking death of a research assistant in 2008. Difference-in-differences analyses show that relative to “dry labs” that use theoretical and computational methods, the publication rates of “wet labs” that conduct experiments using chemical and biological substances did not change significantly after the shock. At the same time, we find that wet labs that used dangerous compounds more frequently before the shock reduced their reliance on flammable materials and unfamiliar hazardous compounds afterward, even though their overall research agenda does not appear to be affected. Our findings suggest that laboratory safety may shape the production of science, but they do not support the claim that safety practices impose a significant tax on research productivity. 相似文献
6.
化学通过化学键的剪裁和重组,以及超越分子层次的非共价作用和组装,创造和构建了一个全新的物质世界,为其它学科的创新研究和快速发展提供了不竭的知识基础和物质保障。纵观化学科学近年来的发展,化学正在不断走向＂精准＂化。本文结合国内外化学学科发展的现状,从合成化学,单分子单原子操纵和自组装三个方面对化学走向精准化的趋势进行了评述。首先,从官能团化学键种类转化控制的区域选择性到反应产物空间构型控制的立体选择性,两个方面论述了合成化学在反应选择性控制上走向精准化;其次探讨了利用单分子和单原子的操纵来实现分子和原子层次上对化学反应进行精确控制的策略;第三,则对利用自组装这一新一代的方法来实现分子层次以上有序结构的精准构建进行了讨论和展望。 相似文献
7.
Per-ke Albertsson Ph.D. 《Endeavour》1977,1(2):69-74
The separation of simple organic substances by distribution between two immiscible phases is a traditional technique in preparative and analytical chemistry. Latterly, the method has been extended to cover the increasingly important field of polymers—especially those of biological importance—and the micro constituents of cells. By appropriate choice of phases the method can be made highly selective, and it is particularly valuable for the treatment of labile substances that may be irreversibly damaged by conventional methods. 相似文献
8.
Sutirtha Chakraborty Anindya Dasgupta Harendra Nath Das Om Prakash Singh Asok Kumar Mandal Nikhiles Mandal 《Indian journal of clinical biochemistry : IJCB》2009,24(2):194-197
Oxidative stress has been found to play important role in several neuropsychiatric diseases including Obsessive Compulsive
Disorder. A longitudinal case control study was conducted to evaluate the oxidative stress in 30 newly diagnosed obsessive
compulsive disorder patients and same number of control patients. Serum thiobarbituric acid reacting substances, plasma ascorbate
were assessed to evaluate oxidative stress and Yale Brown obsessive compulsive scale for disease severity before and after
treatment with Fluoxetine at the average dosage of 40 mg/day. Improvement in Yale Brown obsessive compulsive scale score by
about 43% after 12 weeks treatment was associated with significantly decreased thiobarbituric acid reacting substances and
increased plasma ascorbate values (p < 0.05). The newly diagnosed obsessive compulsive disorder patients had higher serum
thiobarbituric acid reacting substances as well as a lower plasma ascorbate levels than the control population. Thus, the
present study suggested a significant role of oxidative stress in obsessive compulsive disorder and showed that a successful
treatment with Fluoxetine not only improves the clinical scenario but also reduces the oxidative stress that may further improve
the prognosis of the disease. 相似文献
9.
Noel G. Coley 《Endeavour》1998,22(4):143-147
Poison has long been a common murder weapon, but in early nineteenth-century Britain toxic substances were readily available and little attention was paid to toxicology. In 1820 the use of poisonous substances in food manufacture was exposed and it was also realized that medical jurisprudence, including toxicology, was already well advanced in some European countries. Better training in these subjects for British doctors was begun, led by three prominent physicians, Robert Christison, Alfred Taylor and Thomas Stevenson. The professions of analytical chemist and Public Analyst were enhanced and the importance of chemical evidence in poison trials was established. 相似文献
10.
介绍化学品从传统的物质管理到产品管理的体系现状,从物质使用环节入手,减少有害化学物质的倒逼化学品环境管理模式,以至实现有毒有害化学物质的全过程管控。发达国家通过实施政策法规和环境标签非强制手段,提供化学物质管控的技术、建立替代评估模型,在引导公众自愿前提下倡导企业在更广泛的产品和化学物质领域开展信息收集和公开制度。借鉴国外产品中化学品管理的丰富经验,在法律规定下由少到多分别列明管控的物质清单和产品清单,以替代评估为技术支持,引导公众自愿推进管理,为我国化学品管理决策提供有力支持。 相似文献
11.
Leo H. Baekeland 《Journal of The Franklin Institute》1910,169(1):55-60
Bakelite is a liquid compound of phenol and formaldehyde which on solidification resembles amber in appearance and when used in combination with wood, paper, asbestos, graphite and other substances produces a solid non-resistant, non-inflammable insulating material which promises to have many applications in various industries. 相似文献
12.
It is very difficult, if not impossible, to remove the last traces of hypo from photographic papers by any known procedure of washing. The sulfur in the residual hypo ultimately, and especially under abnormal conditions of temperature and humidity, combines with the silver image to form yellowish brown silver sulfide. This phenomenon is known as sulfiding or “fading” of the image. The various factors which affect the rate of fading of images and the washing out of hypo from films and papers are outlined.Chemical methods of hypo elimination have been proposed from time to time but the majority of these have not been satisfactory because they tend to leave substances such as thionates in the photographic material, which are equally as difficult to wash out as hypo and which also tend to sulfide or fade the silver image. A new hypo eliminator is recommended consisting of two volatile chemicals, hydrogen peroxide and ammonia. This eliminator oxidizes the hypo to sodium sulfate, which is inert and soluble in water, while any excess eliminator evaporates on drying.Two formulas and treatments are proposed: (1) Complete elimination of hypo for use by the professional, advanced amateur, and photofinisher who demand the highest standard of photographic quality in their prints.(2) Almost complete elimination of hypo (less than o.oi milligram per square inch).Since the conditions to which prints will be subjected are rarely known in advance, use of the “complete elimination treatment” is advised in all cases. 相似文献
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14.
Until recently the search for substances having desired biological properties depended largely on systematic screening of very large numbers of compounds, as in the development of the sulphonamide drugs. Today, the alliance of computer graphics with theoretical chemistry is beginning to make it possible to predict the kind of molecule which will produce a particular effect. 相似文献
15.
Morphine, which is obtained from poppies, has pharmacological properties which make it both a powerful pain-relieving drug and a narcotic feared for the dependency which it induces in those who use it. Study of the mode of action of morphine has revealed related endogenous substances in the brain. These brain opiates have remarkable properties, which researchers are just beginning to discover. 相似文献
16.
It is well established that male moths are attracted to the females by physiologically highly active substances (pheromones) secreted by the latter. Research has revealed the chemical nature of many of these pheromones and much attention has been directed to putting them to practical use, with other methods, for the field control of pests. 相似文献
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思维是人们认识过程的高级阶段,它是一种对物质及其变化等客观事物的概括的、间接的反映过程,是反映客观事物的一般特性和规律性的联系和关系。培养学生的化学思维能力是化学教学中的一个现实问题。 相似文献
19.
应用绿色化学思维对有机化学实验室管理进行了初步的研究,通过增强绿色化实验管理意识、选择实验教学内容和方法、合理处理＂三废＂等方法,有效促进有机化学实验绿色化管理的改革。 相似文献
20.
D.H. Rouvray 《Endeavour》1977,1(1):23-31
Computer techniques are indispensable for storing and retrieving information on the seven million different chemical substances now known, and will become increasingly important as their number and complexity grow. A necessary prerequisite is the unambiguous representation of molecular structure in terms of symbols suitable for computer usage. This article reviews the development of chemical symbolism from its inception in the ancient civilizations to its use in modern notational systems. 相似文献