用动态规划方法探讨油松人工林最适密度

本文采用Richards函数的修正式拟合林分直径生长,并考虑间伐引起的林分直径非生长性增长,将林分平均直径和每公顷株数作为状态变量,将林分价值作为指标函数,建立了离散确定性动态规划模型,求出了油松(Pinus tabulaeformis)人工林各地位级不同年龄、不同初始状态的林分最适经营密度。     

THE IN VITRO PROTECTION OF PENICILLIN FROM INACTIVATION BY PENICILLINASE

(1) A combination of penicillin and immune plasma protein has been obtained which possesses bacteriostatic activity. (2) The presence of the penicillinase immune plasma protein in this mixture protects penicillin in vitro from destruction by penicillinase.     

银与光所产生的协同效应的微生物灭活现象观察

研究发现在使用紫外线(UV-A,395nm)进行照射时,银溶液对微生物的灭活作用得到增强,特别是对真核微生物的灭活作用得到显著增强。为解明这种银与光所产生的协同效应的微生物灭活机理,使用电子自旋共振仪(Electron Spin Resonance,ESR)对溶液进行检测,并采用扫描电子显微镜(SEM)以及测定线粒体酶活性等方法,推测出了其作用机理,即在光照下氧化银(Ag2O)被激活并与水分子发生反应产生羟基自由基(.OH)。羟基自由基破坏真核微生物的细胞壁,失活其细胞内线粒体酶活性,从而引起真核微生物细胞死灭。     

氨气敏电极法测定土壤全氮

用氨气敏电极测定土壤全氮,方法简单、快速、准确,操作安全,无需蒸馏和滴定。按照本文拟定的方法:首先在消解的溶液中加入10M 的 NaOH,使溶液近中性,以免测定时因待测液中加大量浓 NaOH 而引起液温剧烈变化。我们所制备的电极内充液可以减小电极薄膜内外两边溶液的渗透压差别。因此,所述方法测定土壤全氮要比一般氨气敏电极法更为准确。用所述氨气敏电极法和常用的开氏蒸馏法对17个含氮范围很广的土样测定所得的结果完全一致。因而所述方法适宜于批量土样全氮的测定。     

INACTIVATION OF THE IRRITANT TOXICANTS OF POISON IVY AND RELATED COMPOUNDS BY TYROSINASE

The action of mushroom tyrosinase on the oxidation of the irritant principles of poison ivy and on related toxic compounds has been demonstrated by measuring oxygen consumption, color change, decrease in phenolic groups and reduction in dermatitis-producing properties of these compounds on human and guinea-pig skin. The action of tyrosinase on poison ivy toxicants occurs both in vitro and on the human skin.