2003年美国总统绿色化学挑战奖

论述了一年一度的美国总统绿色化学挑战奖,对于绿色化学研究、推动化学化工等领域的安全与环保工作有启发和指导意义。2003年获奖的个人和公司已经揭晓,介绍了他们的绿色化学成就——固体氧化物催化剂合成的无废水工艺(更新合成路线奖)、微生物法生产1,3．丙二醇(改进溶剂和反应条件奖)、EcoWorx(tm)地毯片(设计更安全化学品奖)、温和的选择性脂肪酶催化聚合(绿色化学学术奖)、高效而环境友好的生物杀真菌剂Serenade(r)(小企业奖)等,指出与生物技术相结合是未来化学化工的重要方向。     

一种具有防欺骗和挑战应答时限的动态身份认证技术

文章简要回顾了身份认证技术的发展历程和目前应用的动态身份认证技术原理,介绍了一种具有防欺骗和挑战应答时限的动态认证技术,以及此技术在现有技术上的改进和发展。该技术安全、可靠、简便易行,可以拒绝第三方的重放攻击,有效地防止了第三方对口令的猜测和穷举攻击,广泛应用于电子政务、网上银行、网上营销等各领域。     

Effects of replacing inorganic salts of trace minerals with organic trace minerals in the diet of prepartum cows on quality of colostrum and immunity of newborn calves

Our objectives were to evaluate the impact of supplementary trace mineral (TM) form—inorganic salts (STM; Co, Cu, Mn, Zn sulfates, and Na selenite) or organic (OTM; Co, Cu, Mn, Zn proteinates, and selenized yeast)—in the prepartum diet on quantity and quality of colostrum, passive immunity, antioxidant biomarkers, cytokine responses to lipopolysaccharide (LPS), health, and growth of newborn calves. Pregnant heifers (n = 100) and cows (n = 173) were enrolled at 45 d before calving, blocked by parity and body condition score, and allocated randomly to STM (50 heifers; 86 cows) or OTM (50 heifers; 87 cows) supplementation. Cows in both treatments were fed the same diet, except for the source of supplementary TM. Within 2 h of calving, dams and calves were separated, colostrum was harvested, the yield was measured, and a sample was saved for posterior analyses of colostrum quality. A subgroup of calves (n = 68) had a blood sample collected before colostrum feeding. After colostrum feeding, all samples and data collection were limited to 163 calves (STM = 82; OTM = 81) fed 3 L of good quality (Brix% >22) maternal colostrum via nipple bottle minutes after harvesting. Concentration of IgG in colostrum and serum was determined 24 h after colostrum feeding using radial immunodiffusion. Concentration of TM in colostrum and serum were performed by inductively coupled plasma mass spectrometry. Activity of glutathione peroxidase, ferric reducing ability of plasma, and concentration of superoxide dismutase were evaluated in plasma by colorimetric assays. Ex vivo whole blood stimulation with LPS was performed on d 7 of life to evaluate cytokine responses in a subgroup of 66 calves. Health events were recorded from birth to weaning, and body weight was recorded at birth (all calves) and on d 30 and 60 (heifers only). Continuous variables were analyzed by ANOVA and binary responses were analyzed by logistic regression. Complete replacement of STM by OTM in prepartum diet resulted in greater concentration of Se (461 vs. 543 ± 7 μg/g; ± SEM) but did not alter the concentration or total mass of other TM and IgG in colostrum. Female calves of the OTM group had greater concentration of Se in serum at birth (0.23 vs. 0.37 ± 0.05 μg/mL), were lighter in weight at birth (40.9 vs. 38.8 ± 0.6 kg) and weaning (93.2 vs. 89.7 ± 1.6 kg) than those of the STM group. Maternal treatments did not affect passive immunity or antioxidant biomarkers. On d 7, basal concentrations (log₁₀ of concentration in pg/mL) of IFNγ (0.70 vs. 0.95 ± 0.083) and LPS-stimulated concentrations of CC chemokine ligand 2 (CCL2; 2.45 vs. 2.54 ± 0.026), CC chemokine ligand 3 (CCL3; 2.63 vs. 2.76 ± 0.038), IL-1α (2.32 vs. 2.49 ± 0.054), and IL-1β (3.62 vs. 3.86 ± 0.067) were greater in OTM than in STM. Supplementation with OTM in pregnant heifers, but not in pregnant cows, reduced the incidence of preweaning health problems in their calves (36.4 vs. 11.5%). Complete replacement of STM by OTM in the prepartum diet did not cause major changes in colostrum quality, passive immunity, and antioxidant capacity, but increased cytokine and chemokine responses to LPS on d 7 of life and benefited preweaning health of calves born to primiparous cows.     

发展高等职业教育之我见

发展高等职业教育，机遇与挑战并存，我们必须抓住机遇，迎接挑战。针对师资水平低、毕业生就业难，培养目标不到位及高职教育资金来源等问题，采取相应措施，如建立一支强大的教师队伍、与企业合作、更新观念、实行素质教育等，谋求高职教育大发展。     

关于我国风电产业发展的若干思考

风力发电作为一种绿色能源越来越受到世界各国的重视并得到了广泛的开发和利用。近年来,在国家大力发展清洁能源政策的扶持下,我国风电产业以超预期的速度迅猛发展,但与世界上风电发展水平较高的国家相比,我国风电发展相对滞后,产业基础比较薄弱,风电发展仍面临一些挑战。分析了我国风电产业发展过程中出现的主要问题并就如何促进我国风电产业健康发展提出了对策与建议。     

独立学院大学生就业问题探究

独立学院毕业生被社会认同需要一个过程,他们的就业工作已成为了独立学院面临的重大问题之一.通过分析独立学院大学生就业现状、存在的问题及就业困难因素,以做好独立学院学生就业工作为出发点,对独立学院大学生如何应对就业进行自我分析与思考.     

美国现代化进程中对传统价值观念的反叛和回归

起源于英国的清教主义（Puritanism）在北美殖民地得以实践和发展,并对美国产生了巨大影响。清教的天职思想（theidea of calling）、山巅之城（a city upon a hill）、因信称义（justification by gmcetllrough faith）等核心理念在美国人的工作观、成功观及个人主义取向上表现得淋漓尽致。随着美国现代化进程的推进,传统的清教价值观念在20世纪受到不同程度的挑战：20年代“迷惘的一代”,50、60年代“反叛的一代”以各种方式挑衅着美国传统的清教价值观念。但在貌似反叛的背后其实是一种对传统价值观念艰难的守卫与奋力的回归。这样的努力集中体现在70年代节制的生活方式及80、90年代“回归的一代”身上。不论美国现代化进程对美国传统价值观念有多大的冲击,都不会动摇其在美国历史发展中的重要地位,也不会消弭其在美国人心中的深远影响,因为美国传统价值观念是美国立国的基础,铸就了美国的民族特性,成就了美国的现代化。     

天地一体化网络发展趋势与挑战

随着技术的发展和应用需求的多样化,传统的“烟囱式冶发展的卫星网络存在的功能单一,相互孤立,运行依赖于地面等问题逐渐凸显,不能满足我国军事、经济和人民生活水平发展的迫切需求。天地一体化网络综合利用新型信息网络技术,充分发挥天基、地基等网络的优势,可以实现支撑国家重大战略行动,促进多元信息传输共享。天地一体化网络主要由天基网络、空基网络、海基网络、地面移动网络等组成。,结合地面网络化技术的发展,天地一体化网络应该具有向智慧化、协同化、标识化发展,和从“以主机为中心冶向“以信息为中心冶过渡的趋势。同时,提出天地一体化网络的发展也面临组网协议、安全保障、互联融合、在轨验证等诸多方面的挑战。     

我国城市机动化问题的认识与对策

小汽车快速增长既是我国大城市当前一个普遍现象，也是各界争议的热门话题，本文试图站在客观公正的立场上讨论小汽车增长的机制动因利弊得失，澄清机动化的概念可能的途径以及对城市发展的影响，阐明中国城市在快速城市化和机动化双重压力下，应该采取的正确对策。     

面对混凝土工业可持续发展的挑战

面对可持续发展的挑战，混凝土主要原材料需要调整生产与合理使用。减少或保持现有硅酸盐水泥熟料的产量，以减少向大气排放CO2；水泥总体产量可以通过大掺量工业废料来满足建设的需要，以减小对环境的压力；骨料生产和质量亟待很大的改善，以尽量减少混凝土的用水量；此外必须从可持续发展的高度，重视和考虑混凝土结构的耐久性。