首页 | 官方网站   微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 468 毫秒
1.
2.
对水镁石、水菱镁石和斜方云石资源及其加工和应用进行了评述。包括上述资源的发展历史、化学组成和物性参数、资源储量和矿石品位、生产加工以及在不同领域(如镁质阻燃剂、中和剂、重金属离子脱除剂、镁肥、饲料添加剂等)的应用,并对它们的发展前景进行了展望。  相似文献   

3.
The development of new methods for preparing polyfunctional organometallics has made a broad range of such reagents available for various transition metal-catalyzed cross-couplings. An overview of the most general preparation methods will be presented. Applications to practical cross-coupling procedures will be covered, emphasizing the functional group compatibility and the reaction scope.  相似文献   

4.
Poor air hygiene as a result of bioaerosol contamination has caused diverse forms of adverse health effects and diseases. In addition, global biosecurity is threatened by purposeful use of biowarfare agents and the vulnerability of people to the infectious agents. Accordingly, developments in high-volume biosampling, including aerosol-to-hydrosol techniques with low cut-off size, real-time bioaerosol detection, adequate biological quantification, and exposure control, as well as the investigation of the link between disease outcome and bioaerosol exposure, are current areas of bioaerosol research. Although milestone progress has been achieved both in bioaerosol sampling and analysis techniques since late 1800s, compared to atmospheric chemistry the bioaerosol field is still understudied. This is partially because of the lack of both bioaerosol scientists and multidisciplinary collaboration. It is becoming necessary to develop a pool of scientists with different expertise, e.g., bioaerosol scientists, environmental engineers, biomedical engineers, epidemiologists, microbiologists, chemists, physicists, as well as researchers in other engineering fields, in mitigating bioaerosol-related adverse health effects, eliminating diseases, and preventing and controlling epidemic outbreaks. This work is conducted to broadly review current state-of-the-art sciences and technologies in the bioaerosol field. In tackling the challenges ahead, the review also provides perspectives for bioaerosol research needs, and further reminds bioaerosol scientists of those existing technologies in other fields that can be leveraged. In view of the past, forward-looking hypotheses and revolutional perspectives are needed to be formed in order to allow the bioaerosol research have major impacts in the academic community in this new millennium.  相似文献   

5.
6.
The rapidly growing chemistry of the cations, radicals, and anions based on the group 14 elements heavier than carbon (Si, Ge, Sn, and Pb) is one of the most important organometallic fields. Recent developments in this research area moved such species from the class of short-lived reactive intermediates to the class of easily accessible, isolable, and fully characterizable compounds. In this Account, we deal with the major accomplishments in the field of the stable representatives of "heavy" cations, radicals, and anions.  相似文献   

7.
8.
9.
In this Account, we recount on our studies of 1'-hydroxy-2'-acetonaphthone (HAN, a proton transfer prototype molecule) in gas, solutions, and nanocavities. The internal H-bond photoreaction in HAN leads to a keto type structure, and following its formation, an internal twisting motion gives birth to keto rotamers. Theory, temperature, and solvent effects on its photodynamics show the involvement of efficient radiationless processes in both keto structures. When HAN is caged in a cyclodextrin nanocavity, the spectroscopy, photodynamics, and issues of twisting motion are strongly affected and could be tuned: a behavior relevant to those of many chemical and biological systems.  相似文献   

10.
Metals, ligands, and cancer   总被引:12,自引:0,他引:12  
  相似文献   

11.
Summary Cholesterol is a universal constituent of all animal cells and therefore occurs in all foods of animal origin. Cholesterol is the mother substance of bile acid and of sex hormones and has other important physiological roles. Cholesterol is synthesized in the body from acetate obtainable from ingested carbohydrate, fat. or protein, of animal or vegetable origin. The fate of cholesterol in the body has not been definitely established. The cause of atherosclerosis is unknown. Atherosclerosis occurs in young as well as old individuals. Atherosclerosis is the number-one killer today. Diagnosis of atherosclerosis in the healthy individual is not possible. Treatment of atherosclerosis is empirical. Reduction of blood cholesterol levels by dietary means is difficult under conditions consonant with good nutrition. A well-balanced intake of all available foods on a modified total caloric basis appears to be the practical approach to the problem of fat, cholesterol, and atherosclerosis. Presented at the 47th Annual, Meeting, American Oil Chemists’ Society, Houston, Tex., April 23–25, 1956.  相似文献   

12.
Kritchevsky  David  Story  Jon A. 《Lipids》1978,13(5):366-369
Epidemiological data suggest that populations subsisting on high fiber diets are free of a number of the diseases of Western civilization, among them coronary heart disease. Studies in animals and man show that each type of fiber exerts it own specific influence. Thus, in man bran has no effect on serum lipids, but pectin lowers cholesterol levels. In animals fed atherogenic diets, alfalfa and pectin exert some measure of protection, but cellulose does not. To fully understand the mode of action of dietary fiber, it is necessary to ascertain the mechanism(s) of action of each chemical component of that fiber.  相似文献   

13.
14.
Plant protein isolates (wheat gluten, soy, and pea protein) were treated in a thermoplastic extrusion process, yielding protein based bioplastic material. The application of glycerol as plasticizer in amounts of 50–67% of total mass and high temperatures above 140°C led to smooth and homogeneous extrudates. Viscosity measurements of the protein melt under extrusion conditions confirmed the thermoplastic behavior, obeying the power law with power law indices of 0.31‐0.4. Chemical changes in the material were qualitatively shown by amino acid analysis and fluorescence measurement. High moisture sensitivity and low mechanical stability of the extrudates, as determined by solubility, water vapor permeability, sorption isotherms, and tensile strength, can be partially ascribed to the high glycerol content. The application of pure protein bioplastics for technical purposes, e.g., as packing material, is discussed on basis of the presented data considering stability, appearance, and long time storage. POLYM. ENG. SCI., 55:1912–1919, 2015. © 2014 Society of Plastics Engineers  相似文献   

15.
A pH-responsive hydrogel consists of polypeptides only is a promising biomaterial with the advantages of good biocompatibility and non-toxicity. This work reports the synthesis of poly-L-ornithine(poc) (polyLOpoc) serving as the precursor for hydrogels of poly-L-ornithine (polyOrn) and poly(L-arginine-r-L-ornithine) (poly(Arg-r-Orn)). Their controllable degree of crosslinking, good mechanical properties, good biocompatibility, and pH-responsibility are detailedly investigated. The swelling ratio of polyOrn hydrogel in acidic aqueous solution is 5.7 times higher than that in a basic environment. In the deprotection of phenoxycarbonyl group, polyLOpoc releases amino pendant groups, which attack the remaining poc-protected amino groups to fulfill self-crosslinking without any crosslinking agent. In addition, the pH-responsive behavior of hydrogels is visualized by aggregation-induced emission phenomena with polyOrn and poly(Arg-r-Orn) containing tetrakis(4-aminophenyl)ethene moisture.  相似文献   

16.
In this study, we prepared polystyrene (PS) resin nanocomposites with antistatic properties by melt‐blending PS with nanoscale zinc oxide (ZnO). The effects of nanoscale ZnO on the electrical and physical characteristics of the PS nanocomposites were investigated. Two kinds of nanoscale powders, spherical zinc oxide (s‐ZnO) and zinc oxide whisker (w‐ZnO), were selected. The coupling agents vinyltriethoxysilane (VTES) and phenyltriethoxysilane (PTES) were used to improve the compatibility between the nanopowders and PS resin. The addition of s‐ZnO and w‐ZnO improved the antistatic characteristics of the materials. The surface resistivities of the s‐ZnO and w‐ZnO nanocomposites were significantly reduced by modification with VTES and PTES. The addition of ZnO nanopowder increased the flexural modulus and reduced the flexural strength. The silane coupling agents improved the flexural properties of the nanocomposites. The glass‐transition temperatures and thermal degradation temperatures of the ZnO/PS nanocomposites increased with ZnO content. Treatment with silane increased the glass‐transition temperatures and thermal degradation temperatures of the composites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2266–2273, 2005  相似文献   

17.
18.
Basic theory and principles of degumming, refining, bleaching, and deodorization are reviewed. Composition of crude oils, hydration of ions and molecules, neutralization of organic acid, and separation and modification of products by centrifugation, adsorption, and vacuum steam distillation are briefly summarized. Reactions of vegetable oils include hydration, neutralization, and oxidation.  相似文献   

19.
This paper was delivered on Wednesday 12 September 1979 as the Opening Address of the Society's 19th Biennial Symposium held at Ranmoor House, Sheffield University.  相似文献   

20.
Weanling rats were fed on diets of rice/beans (RB) with or without mineral (M) supplement; vitamin A (A); M + A (MA); or milk (L), containing from 3 to 14% protein. As determined by various measures, the best results were observed in the group fed the RB diet, supplemented with L. This group was followed by those receiving the MA and M diets. Protein utilization in the RB diet, as well as minimum protein requirement for maintaining body weight, depend on the supplementary nutrients. The mechanism of this effect may be related to the appetite of the animals and to the voluntary intake, which is influenced and regulated by the diet composition.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司    京ICP备09084417号-23

京公网安备 11010802026262号