GMS和亚洲棉种内传统杂种间杂种优势的比较研究     

向平 Kajjidoni  ST 等 《国外作物育种》2001,20(2):67-67

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Polymer brushes   总被引：1，自引：0，他引：1  

Milner ST 《Science (New York, N.Y.)》1991,251(4996):905-914

Polymers attached by one end to an interface at relatively high coverage stretch away from the interface to avoid overlapping, forming a polymer "brush." This simple picture may serve as the basis for models in diverse interfacial systems in polymer science, such as polymeric surfactants, stabilized suspensions of colloidal particles, and structures formed by block copolymers. The structure and dynamics of polymer brushes have been the subject of considerable theoretical and experimental activity in recent years. An account is given of recent advances in theoretical understanding of stretched polymers at interfaces, and the diverse experimental probes of systems modeled by brushes are briefly reviewed.  相似文献   

New mechanisms for chemistry at surfaces     

Ceyer ST 《Science (New York, N.Y.)》1990,249(4965):133-139

It is becoming increasingly apparent that chemistry at surfaces, whether it be heterogeneous catalysis, semiconductors etching, or chemical vapor deposition, is controlled by much more than the nature and structure of the surface. Recent experiments that principally make use of molecular beam techniques have revealed that the energy at which an incident molecule collides with a surface can be the key factor in determining its reactivity with or on the surface. In addition, the collision energy of an incident particle has proven essential to the finding of new mechanisms for reaction or desorption of molecules at surfaces, collision-induced activation and collision-induced desorption. These phenomena are often responsible for the different surface chemistry observed under conditions of high reactant pressure, such as those present during a heterogeneous catalytic reaction, and of low pressure of reactants (< 10(-4) torr), such as those present in an ultrahigh vacuum surface science experiment. This knowledge of the microscopic origins of the effect of pressure on the chemistry at surfaces has allowed the development of a scheme to bypass the high-pressure requirement. Reactions that are normally observed only at high reactant pressures, and which are the ones most often of practical importance, can now be carried out in low-pressure, ultrahigh vacuum environments.  相似文献   

绵羊肠毒血症 诊治     

周恒 《四川畜牧兽医》2018,(4)

正1病原导致绵羊肠毒血症的病原为D型产气荚膜梭菌,又称D型魏氏梭菌或绵羊中毒杆菌,一般的消毒药可杀死本菌繁殖体,但芽孢抵抗力较强,需95℃2.5 h方可杀死。2流行特点2.1多发于绵羊发病羊多数为膘情中上的绵羊,两岁以内的幼龄羊发病较为多见。D型产气荚膜梭菌能产生有很强抵抗力的芽孢。芽孢随饲料和饮水进入健康羊体内,当遇阴雨连绵、气温多变的季节,羊采食多汁嫩草或  相似文献   

铜仁市青(木奈)引种栽培试验     

周恒  龙香菊 《中国南方果树》2009,38(4)

从果实经济性状、生长结果习性、物候期等方面观察记载了青(木奈)在铜仁市的引种表现.结果表明,青(木奈)能适应引进地的生态条件,表现良好.在主要栽培技术上作了探索,使结果初期的产量达到了较高水平.  相似文献   

Stability of copigmented anthocyanins and ascorbic acid in a grape juice model system     

Brenes CH  Del Pozo-Insfran D  Talcott ST 《Journal of agricultural and food chemistry》2005,53(1):49-56

The stability of red grape anthocyanins (Vitis vinifera) was evaluated in a model juice system during normal (25 degrees C) and accelerated storage (35 degrees C) in the presence of ascorbic acid. Rosemary polyphenolic cofactors (0, 0.2, and 0.4% v/v) were evaluated as anthocyanin stabilizing agents. Cofactor addition resulted in concentration-dependent hyperchromic (up to 178%) and bathochromic (up to 23 nm) shifts, indicating a more intense red coloration of the models. Anthocyanin and ascorbic acid degradation followed first-order kinetics during storage. Results showed that copigmented treatments underwent a lower conversion of L-ascorbic acid into dehydroascorbic acid during storage when compared to the control, favorably impacting the vitamin retention of these models. Copigmentation did not affect anthocyanin degradation in the absence of ascorbic acid but in its presence aided to retain a higher anthocyanin content than the control. This study indicated that the addition of anthocyanin cofactors could be used to reduce the pigment and vitamin degradation while masking detrimental color changes in anthocyanin containing products.  相似文献   

好望角芦荟的组织培养与快速繁殖   总被引：3，自引：0，他引：3  

罗静  周恒  袁德奎 《安徽农业科学》2005,33(7):1213-1213,1231

以好望角芦荟的茎段、叶片、根段为外植体,进行了组织培养与快速繁殖研究。结果表明:外植体以茎段为宜;最佳芽诱导和增殖培养基均为MS+蔗糖3.5%+琼脂0.7%+6-BA2mg/L+IBA0.1mg/L;生根壮苗培养基是MS+蔗糖2%+0.55%琼脂+IBA1.5mg/L+KT0.2mg/L。移栽基质以腐质土为好,成活率可达92%,且组培苗长势健壮。  相似文献   

提高羔羊成活率的综合措施     

周恒 《贵州畜牧兽医》2010,34(4):35-36

贵州省毕节地区牧垦场位于海拔高度2000m以上的高寒山区，多年来，羔羊的成活率仅为50％～75％。为了解羔羊死亡的原因，笔者于2009-2010年4月对该场母羊群的500只羔羊进行调查，并采取了相应的预防措施。  相似文献   

What is your neurologic diagnosis? Osteochondroma of the dorsal process of T4     

Marioni K  Hathcock JT  Simpson ST 《Journal of the American Veterinary Medical Association》2001,219(7):917-920

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Gastrointestinal parasites in ostriches (Struthio camelus)     

Sotiraki ST  Georgiades G  Antoniadou-Sotiriadou K  Himonas CA 《The Veterinary record》2001,149(3):84-86

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