首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Recognizing the pervasive importance of materials science and engineering (MSE) to practically every facet of man’s life, this lecture takes a broad view of the origin and technical trends and achievements in MSE, briefly reviewing its history and relationship to society over many millennia, to the present day, with specific examples. Major emphasis, however, is placed on modern MSE as related to current national issues, using as illustrations of the latter natural resources, industry and the economy, research and development, education, and technology transfer. The discussion of these areas leads to consideration of the role of the Federal Government and the importance of and need for a coherent national policy to deal with critical issues, many of which are listed herein. Some important steps by the Government fostering high level coordination as well as cooperation among government, industry, and academe are cited. Having thus illustrated the pervasive and vital impact of MSE on society, and its current esteemed recognition and position of influence, the lecture concludes that in this period of global change — social, economic, and technological — there is a challenge to MSE to respond beneficially to societal needs more than ever before. The opportunity and mechanisms now exist. Greater participation in the public and political arenas, with mutual education, is indicated. NATHAN E. PROMISEL received his Bachelor of Science and Master of Science Degree at the Massachusetts Institute of Technology, did his doctorate work at Yale University, and received an Honorary Doctor of Engineering Degree at Michigan Technological University. He became Assistant Lab Director at International Silver Company, leaving in 1940, and Chief Materials Scientist and Engineer (aeronautics and weapons) and Materials Research Coordinator for the Department of the Navy, leaving in 1966. He is presently an International Consultant. Dr. Promisel has been a long-time member of the National Materials Advisory Board of the National Academies of Science and Engineering, and from 1966 to 1974 was its Executive Director. He was also a Member of the Office of Technology Assessment (Congress) Materials Advisory Committee, as well as Chairman or Member of numerous other Government and public technical groups. These included being Chairman of the U.S. Group for the Science Exchange Program with the U.S.S.R., for materials and electrometallurgy, and serving as Chairman of the NATO Aerospace Research Group (Materials and Structures). Dr. Promisel is a member of the National Academy of Engineering; Past President, Fellow, and Honorary Member, American Society for Metals; Past President and Founding Member of the Federation of Materials Societies; Honorary Member of AIME, ASTM, and SAE (Materials Division); Fellow of British Institute of Metals and SAMPE. He has presented distinguished lectures to The Electrochemical Society and ASTM. Dr. Promisel has received numerous awards and is the holder of two patents. He has written 65 technical papers and has been the author, contributor, or editor of eight books.  相似文献   

2.
3.
The lipid and protein composition of the perivitelline fluid of the eggs of Pomacea canaliculata was investigated. Two lipoproteins (PV 1 and PV 2) and one lipoprotein fraction (PV 3) were detected for the first time in gastropods. They represent 57.0, 7.5, and 35.5% of the egg total proteins, respectively. PV 1 is a glyco-carotene-protein complex with characteristics of a very high-density lipoprotein (VHDL). It has 0.33% lipids, mainly free sterols and phospholipids. The particle has a MW of 300 Kd and is composed of three subunits of 35, 32, and 28 Kd, respectively. PV 2 particle is a VHDL of 400 Kd and 3.75% lipids. The major lipid classes are free sterols and phospholipids and also have significant quantities of energy-providing triacylglycerides and free fatty acids. It is composed of two apoproteins of 67 and 31 Kd. PV 3 density corresponds to a high-density lipoprotein (HDL). It was fractionated into two subfractions "h" and "p". Fraction "h" contains 5.16% lipids, mainly free sterols, phospholipids, and free fatty acids, and two particles of 100 and 64 Kd. Dissociating electrophoresis showed two subunits of 34 and 29 Kd. Fraction "p" is composed of a single particle of 26 Kd that contains 9.5% lipids, which represents 30% of the total egg lipids. It has high levels of a carotenoid pigment. Besides it contains free fatty acids, hydrocarbons, sterified sterols, and triacylglycerides. These three fractions are probably the major supply of lipids and amino acids for the developing embryo.  相似文献   

4.
摘要:采用光学显微镜、扫描电镜、透射电镜、弯曲共振试验机和万能材料试验机等分析了复合添加质量分数0.8%Ni元素和0.1%Nb元素的Fe-Cr-Mo合金组织和析出相的大小、形态,研究了Ni和Nb元素的添加对Fe-Cr-Mo合金力学性能和阻尼性能的影响。结果表明,Ni和Nb元素的加入不但使合金晶粒显著细化,而且有效抑制了富Cr析出物的析出,使析出物明显细化且分布弥散。晶粒和析出物的细化同时提高了合金的强度和塑韧性,尤其是显著地提高了材料的塑性。1000和1100℃退火后,Ni和Nb元素的加入将提高减振合金的矫顽力,降低磁致伸缩系数,使减振合金的阻尼性能降低。900℃退火后,Ni和Nb元素的添加虽然提高了合金的矫顽力,但由于Mo元素的回溶使磁致伸缩系数增大,阻尼性能获得提高。  相似文献   

5.
Records of five inbred lines at the Livestock and Range Research Laboratory were used to evaluate effects of inbreeding and heterozygosity on preweaning traits. Members of each line were descendants of a single founder Hereford bull. A total of 8,065 records of birth weight and 7,380 records of preweaning daily gain and weaning weight were analyzed by derivative-free REML using a model that included fixed effects of sex, combination of year and month of birth and parity of dam, with covariates for direct and maternal genetic fractions of inheritance from the genetic groups, inbreeding, and heterozygosity fractions. Heterozygosity fractions were computed for crosses between lines. The random model effects were direct and maternal genetic and uncorrelated maternal permanent environmental and temporary environmental. Direct inbreeding and heterozygosity fractions averaged .098 and .343, and maternal inbreeding and heterozygosity fractions averaged .075 and .294. Regression coefficients of traits on direct and maternal inbreeding fractions were -5.8 +/- 1.1 and -4.7 +/- 1.3 for birth weight, -.189 +/- .031 and -.252 +/- .039 for preweaning daily gain, and -44.5 +/- 6.6 and -56.1 +/- 8.4 kg for weaning weight. Estimates for direct heritability, maternal heritability, and direct-maternal genetic correlations were .37, .12, and -.01 for birth weight; .16, .25, and -.27 for daily gain; and .17, .26, and -.21 for weaning weight. Results suggest that heterosis represents recovery of accumulated inbreeding depression. Results also indicate that selection can overcome inbreeding depression and antagonism exists between direct and maternal genetic effects for preweaning traits.  相似文献   

6.
唐钢高速线材厂控冷工艺及装置的技术分析   总被引:3,自引:0,他引:3  
介绍了唐钢高速线材厂设备引进情况与生产工艺流程,对该厂的水冷区的组成、布置、工作方式、导管结构特点及安装固定特点等结构技术特性,水冷工艺温度及特性曲线与温度控制进行了分析介绍,阐述了夹送辊的工作特点和工作方式,对吐丝机的机构特点、平衡、冷却及铁皮清除方式进行了分析介绍,此外还对风冷运输线的组成、布置、运行方式等技术结构特性进行了阐述。  相似文献   

7.
BACKGROUND: The first conventional x-rays of the paranasal sinuses were received in 1897, just two years after the detection of x-rays. During the following decades several modifications and extensions of conventional radiologic techniques were developed, but routine imaging procedures of the head and neck were mainly restricted to pictures of the paranasal sinuses and the temporal bone. In the fifties, tomography was developed, which gave us a more detailed insight of the anatomy and pathology of the paranasal sinuses and temporal bone. During the last two decades the development of new techniques, i.e. computed tomography (CT) and magnetic resonance imaging (MRI), has significantly increased the importance of modern imaging for the diagnostic evaluation of head and neck diseases. These diagnostic tools enable us to visualize anatomical structures and pathological entities with an accuracy never been expected beforehand. The pace of the improvement of these diagnostic tools, however, requires that both radiologist and otorhinolaryngologist keep up with the adequate indications of CT and MRI in the different areas of the head and neck. A close relationship and cooperation between radiologist and ENT surgeon is therefore indispensible for a fruitful and cost-effective use of modern imaging. Otherwise the patient is exposed to modern medical technology without an equivalent benefit. The purpose of the present paper is mainly to give an update and state of the art of modern imaging techniques in otorhinolaryngology, head and neck surgery. Different areas i.e. paranasal sinuses, temporal bone, salivary glands, oral cavity and oropharynx as well as the neck are discussed in terms of adequate indications for modern imaging in the diagnostic evaluation of different lesions.  相似文献   

8.
为推进绿色矿山建设、转变矿业发展方式,基于博弈论和系统动力学构建地方政府和矿山企业的博弈模型,并引入动态惩罚机制和动态激励机制,对博弈双方进行稳定性、均衡点分析以及模型仿真.研究结果表明:在静态机制下,地方政府和矿山企业的行为呈周期性变化,不能达到稳定均衡状态;当地方政府采用动态惩罚机制和动态激励机制时,演化博弈过程呈...  相似文献   

9.
Opiates and opioids have complex effects on the hypothalamic-pituitary-adrenal axis, and they stimulate the sympathetic nervous system. This study was designed to clarify the role of brain beta-endorphin in the mechanism by which stress increases plasma concentrations of adrenocorticotropin (ACTH), epinephrine (E), and norepinephrine (NE). Intracerebroventricular (i.c.v.) administration of beta-endorphin to rats significantly increased plasma ACTH levels at doses of 0.09, 0.3, and 1.5 nmol, and plasma E and NE levels at doses of 0.3 and 1.5 nmol. The rise of plasma ACTH, E, and NE levels by 0.3 nmol beta-endorphin was inhibited by intravenous (i.v.) administration of 2 mg/kg b.wt. naloxone. I.v. administration of anti-rat corticotropin-releasing hormone (CRH) rabbit serum completely blocked the beta-endorphin-induced ACTH secretion without affecting the secretion of E and NE. I.c.v. administration of anti-beta-endorphin rabbit gamma-globulin attenuated a 30-min restraint stress-induced rise of plasma ACTH levels without significant influence on the rise of E and NE levels, whereas i.v. administration of naloxone attenuated the restraint stress-induced rise of plasma ACTH, E and NE levels. These results suggest that i.c.v. administration of beta-endorphin stimulates the secretion of ACTH, E, and NE through opiate receptor, and that brain CRH mediates the beta-endorphin-induced secretion of ACTH. The results also suggest that brain beta-endorphin is, at least in part, involved in the restraint stress-induced stimulation of the hypothalamic-pituitary-adrenal axis, and that some opioids other than beta-endorphin are involved in the stimulatory mechanism of the autonomic nervous system and the adrenal medulla in the rat.  相似文献   

10.
The importance and value of manometry are presented with examples of patients in labour. It is important to distinguish between the pressures and the forces working on the fetus, especially as far as the causes of fetal bradycardia are concerned. Graphs of magnetic lag are shown in order to demonstrate that the tension on the fetus and sometimes on the placenta and the cord precedes and lasts longer than the increase in hydrostatic pressure which accompanies a contraction. The paper includes the following subjects: Introduction and general observations. The patient and the monitoring device and the tolerance to external and internal manometry by the patient. The concepts of pressure and force. The distrubution of pressures and forces in obstetrics. The measure of forces by their conversion into pressure in a manometric system. The interpretation of the results of the measure of pressure and force in obstetrics.  相似文献   

11.
1. Pharmacokinetic properties of difloxacin have been studied in pig and chicken after intravenous and oral administration. 2. The serum concentrations of difloxacin in pig and chicken after intravenous administration were best described by a two-compartment open model, giving distribution half-lives of 0.50 and 0.66 h and elimination half-lives of 7.92 and 4.10 h for pig and chicken respectively. The steady-state distribution volumes were 1.70 and 3.06 l/kg for pig and chicken respectively. 3. After oral administration of 5 mg/kg to pig and chicken, the serum concentrations reached maximal levels of 3.61 and 0.96 microg/ml respectively at 1.25 and 1.40 h. The elimination half-lives were 11.8 and 7.35 h for pig and chicken respectively. 4. The bioavailabilities of difloxacin were calculated as 93.7 (pig) and 86.9% (chicken).  相似文献   

12.
Ultrastructural changes in the visceral epithelium and proximal tubules of rats were studied by scanning and transmission electron microscopy during the onset and progression of puromycin aminonucleoside nephrosis (PAN)-induced proteinuria. These changes were compared with those that occur during a similar degree of proteinuria induced by intraperitoneal injections of albumin. With the onset of proteinuria and oliguria, PAN rats exhibit loss of podocyte pedicels and podocyte major processes, an increase in pinocytotic activity, and an accumulation of cytoplasmic vacuoles and granules of variable size, shape, and electron density. Loss of podocyte pedicels involves a gradual decrease in pedicel height beginning at the pedicel tip and progressing down the pedicel arm, formation of nublike protrusions and interpedicel microbridges (35 to 45 nm. in width and 40 to 60 nm. in length) along the pedicel's base, the merging of microbridges to form more extensive regions of interpedicel contact, and a gradual broadening and retraction of pedicels. In response to hyperalbuminemia-induced proteinuria, kidney podocytes exhibit reactions during PAN, however, the podocyte pedicels, slit pores, and major processes of rats with hyperalbuminemia-induced proteinuria remain discrete. The loss of pedicels and major processes during PAN, therefore, apparently results from the effects of puromycin aminonucleoside per se rather than from the proteinuria associated with this disease. The proximal tubules of rats with hyperalbuminemia-induced proteinurea exhibit the same characteristic changes as PAN rat proximal tubules (i.e., loss of brush border, dilated lumina, abnormally thin walls, and accumulation of periodic acid-Schiff positive electron-dense luminal casts and cytoplasmic protein absorption droplets). The significance of these ultrastructural findings during PAN and hyperalbuminemia-induced proteinurea are discussed in terms of the etiology of PAN.  相似文献   

13.
我国钛及钛合金板材标准化现状   总被引:2,自引:0,他引:2  
主要回顾了我国钛及钛合金板材标准化历程,重点介绍了本世纪钛板材国标体系的重要变化及完善情况,并与国外先进标准进行了对比,提出了进一步完善和发展我国钛板材标准体系的发展思路、改进意见和建议。  相似文献   

14.
15.
Pharmacokinetics of cationized goat colchicine-specific polyclonal immunoglobulin G (IgG) and antigen binding fragment (Fab) (cIgG and cFab, respectively) were studied in male adult Sprague-Dawley rats and compared with those of the native proteins (nIgG and nFab). All proteins were radioiodinated by the Iodogen method, and kinetics were investigated following trichloroacetic acid (TCA) precipitation or immunoprecipitation. Deiodination and catabolism were more pronounced with the cationized than the native proteins, especially for cFab. Both cIgG and cFab in plasma decreased more rapidly than nIgG and nFab. The elimination half-lives were 52.9 and 81.8 h for cIgG and nIgG, respectively. In addition, there was a 74-fold increase in the volume of distribution and a 114-fold increase in the systemic clearance of cIgG compared with nIgG. For cFab, the volume of distribution and systemic clearance were increased 6.4- and 3.5-fold, respectively. Organ uptake of cIgG and cFab was markedly increased compared with that of nIgG and nFab, especially in kidney, liver, spleen, and lung. Renal clearance of cIgG and cFab was also increased 30- and 10-fold compared with that of nIgG and nFab, respectively. The present data suggest that cationization of colchicine-specific IgG and Fab fragments increased the organ distribution and greatly altered their pharmacokinetics. Nevertheless, the smaller molecular size of Fab versus IgG did not enhance the distribution and clearance of cFab. These data pave the way for evaluating the biological efficacy of these more tissue-organ-interactive antibodies.  相似文献   

16.
A review of the current state of the world and Russian markets of arsenic and its compounds is presented, and prospects of the domestic market are shown. The dynamics of the world production of As and its prices for recent years is considered. The need for arsenic and its compounds in the midterm and long-term prospects is evaluated, and developmental tendencies of the markets are analyzed. The review of producers of this metal and As compounds is given. Special attention is paid to the market of special purity arsenic as the initial component for the developing gallium arsenide market; to clarify this question, a short analysis of the modern state of the market of GaAs and GaAs-based devices is given. Modern methods of deep purification of arsenic as well as the situation with arsenic emissions at domestic enterprises for roasting and smelting of nonferrous metal feedstock are considered. The problem of destruction of reserves of lewisite, yperite, and their mixtures in Russia is discussed. Proposals on the use of forming reaction masses as a nonconventional arsenic source are analyzed.  相似文献   

17.
Summary The results of an extensive and systematic study of surface phenomena on the interface between liquid metals and various refractory compounds are presented and generalized. Values of surface energy and angle of contact are determined for liquid metals and alloys.The classification of binary metallic systems according to the isotherms of free surface energy is scientifically justified. The interface activity of shrinkage in liquid metal-solid systems and the kinetics of infiltration of porous materials with liquid metals are investigated.The effect of the degree of wetting, amount of the liquid phase, initial porosity, and temperature on densification kinetics during sintering was studied in several systems.New methods of soldering ceramics to ceramics and to metals are described. Alloys and processes are proposed for soldering optical quartz to metals and for high temperature soldered joints between metals and ceramics. The use of adhesion-active binders for diamond tools and a method of metallization of diamond particles have been developed. The possibility of preparation of sintered sealing materials from porous iron with a low-melting filler is indicated.Abridged paper to the annual meeting of the Section of Physicotechnical Problems of Materials Science, Academy of Sciences, UkrSSR, February 19, 1964.  相似文献   

18.
OBJECTIVES: To compare the distributions of the genotypes and alleles of the M235T polymorphism of the angiotensinogen gene for hypertensive patients and normotensive controls. DESIGN: A study of association of genetic polymorphisms. SETTING: An outpatient clinic run by a university department handling referrals from primary care. PATIENTS: Two hundred and four subjects, 103 normal controls and 101 patients with newly diagnosed or documented hypertension. METHOD: Genomic DNA was extracted from peripheral blood leucocytes, amplified by polymerase chain reaction and digested with the restriction enzyme Tth 111 I. Methionine (M) and threonine (T) alleles were identified after electrophoresis. MAIN OUTCOME MEASURES: Prevalences of angiotensinogen genotypes and alleles for hypertensive patients and controls. Results: MM, TM and TT genotypes occurred in 3, 24 and 73% of controls and 1, 22 and 77% of hypertensive patients, respectively. The prevalences of the M and T alleles were 0.15 and 0.85 among controls and 0.12 and 0.88 among hypertensive patients. The prevalences of the angiotensinogen genotypes and alleles for controls and hypertensive patients did not differ significantly. CONCLUSIONS: Our findings differed from previous reports and suggested that this polymorphism is not associated with hypertension in this population.  相似文献   

19.
20.
The International Classification of Functioning, Disability and Health (ICF) represents a new way for rehabilitation psychologists and other health care providers to classify health and functioning. The ICF classifies functioning and disability through the constructs of Body Functions and Structures and Activities and Participation and addresses contextual influences through Environmental and Personal Factors. The ICF and its companion classification, the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, provide a complementary, broad, and meaningful picture of the health of an individual or of entire populations. Research and clinical implementation efforts suggest that the ICF is a useful and meaningful public health tool. The development of the ICF and its universe and scope of application are reviewed. Critical concepts are defined, the structure of the ICF is illustrated, and clinical-research utility are featured in light of the ethical considerations for responsible use by rehabilitation psychologists. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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