试析上市公司盈余管理的利弊及其规范

从信息不对称和会计学的角度揭示了上市公司盈余管理的必然性。在此基础上，分析了上市公司适度盈余管理的积极作用和过度盈余管理的弊端，并有针对性地提出了规范上市公司盈余管理行为的建议。     

“校本”理论举要——兼谈我国引进“校本”理论过程中的几个问题

起源于西方社会的三种“校本”理论形式———校本课程论、校本培训论以及校本管理论 ,已成为世界性的教育热点。解读这三种理论并剖析我国教育界试行或认识“校本”理论过程中的问题 ,将有助于人们进一步理解“校本”理念,将有利于“校本”理论与实践的中国化     

Synthesis and metabolism of vertebrate-type steroids by tissues of insects: a critical evaluation

This review covers the synthesis and the metabolism of vertebrate-type steroids (progesterone, testosterone, estradiol, corticosteroids) by insect tissues and discusses the significance of the reactions for insect physiology. Biosynthesis of vertebrate-type steroids from cholesterol hitherto has been demonstrated in only two insect species, i.e. the water beetle Acilius sulcatus (Coleoptera) and the tobacco hornworm Manduca sexta (Lepidoptera). In Acilius, steroid synthesis is associated with exosecretion (chemical defense). Nothing, however, is known about a physiological role of the C21 steroid conjugate present in ovaries and eggs of Manduca. No synthesis of vertebrate-type steroids was observed in any other insect investigated to date. Most metabolic conversions of steroids by insects concerned oxidoreduction of oxygen groups (hydroxysteroid dehydrogenase activity) and (polar and apolar) conjugate formation. All important enzymatic steps involved in synthesis and catabolism, as known from studies with tissues of vertebrates, were not, or hardly observed. The conclusion is drawn that typical vertebrate-type (C21, C19 and C18) steroids probably do not act as physiologically active substances in insects.     

Fuzzy数级数的收敛性

给出了Fuzzy数级数收敛的几个重要性质.     

Peptide selection by MHC class I molecules.

Synthetic peptides have been used to sensitize target cells and thereby screen for epitopes recognized by T cells. Most epitopes of cytotoxic T lymphocytes can be mimicked by synthetic peptides of 12-15 amino acids. Although in specific cases, truncations of peptides improves sensitization of target cells, no optimum length for binding to major histocompatibility complex (MHC) class I molecules has been defined. We have now analysed synthetic peptide captured by empty MHC class I molecules of the mutant cell line RMA-S. We found that class I molecules preferentially bound short peptides (nine amino acids) and selectively bound these peptides even when they were a minor component in a mixture of longer peptides. These results may help to explain the difference in size restriction of T-cell epitopes between experiments with synthetic peptides and those with naturally processed peptides.     

ART技术在儿童恒牙防龋中的临床应用

目的 评价ART技术(非创伤性充填)在儿童恒牙防龋中的临床效果极其可行性,探索适合我市儿童和农村开展防治龋病的方法.方法 采用日本松风FX-Ⅱ型玻璃离子材料完成128颗磨牙的窝沟充填和窝沟封闭,观察ART充填体封闭窝沟的保存情况.结果 对128颗恒磨牙进行ART充填封闭窝沟,1年半后复查,成功率达84.4%.结论 由于玻璃离子与牙釉质发生化学粘合,并向牙釉质释放氟,在很多可能发生龋坏的深窝沟点隙内保留,从而阻止龋病的发展.ART技术设备简单,操作方便,患儿易于接受,适合我市儿童和农村大规模推广应用.     

单体尺度及配比对共聚物电子结构及光吸收性质的影响

在紧束缚近似下，建立了二嵌段共聚物－（A)x-(B)y-的物理模型，研究了组成共聚物的均聚物单体对体系的电子结构及光学吸收性质等的影响，发现均聚物的尺度及配比对共聚物的电子结构及光吸收谱具有显著的调制作用，从而达到使共聚物发现不同颜色光的目的。     

Shingle-back lizards crush snail shells using temporal summation (tetanus) to increase the force of the adductor muscles

Summary During the crushing of hard objects, the adductor muscles ofTrachydosaurus are activated in an unfused tetanus with the tetanic pulses of the several motor units occurring in synchrony.     

麦芽根中5′-磷酸二酯酶的制备及性质

从麦芽根中提取5′－磷酸二酯酶，酶活可达474U／mL。将所得酶液用于水解酵母核糖核酸，得到5′－CMP、UMP、GMP、AMP4种单核苷酸。最佳反应条件为：底物RNA浓度为0.01g/mL，每毫升底物的酶用量为30U，酶解温度70℃，pH7.0，时间2h,5′－核苷酸转化率达80％。