试析当前美国实力地位的变化

当前,美国深陷伊拉克战争泥潭,有人提出美实力地位正发生由盛转衰的变化.通过分析可知美国硬实力仍举世无双,软实力在世界各地仍具有重要影响,而美国创新机制和自我修复能力为美提供巨大的力量来源.在未来较长时间内美国仍将保持一超独霸地位.另一方面,世界各国对美国更加缺乏信任,伊拉克战争大大销蚀美实力等,都构成了美国实力的局限.鉴此,美国不得不加强国际合作,承担相应国际责任,外交政策最终向现实主义回归.     

Stable model categories are categories of modules

A stable model category is a setting for homotopy theory where the suspension functor is invertible. The prototypical examples are the category of spectra in the sense of stable homotopy theory and the category of unbounded chain complexes of modules over a ring. In this paper we develop methods for deciding when two stable model categories represent ‘the same homotopy theory’. We show that stable model categories with a single compact generator are equivalent to modules over a ring spectrum. More generally stable model categories with a set of generators are characterized as modules over a ‘ring spectrum with several objects’, i.e., as spectrum valued diagram categories. We also prove a Morita theorem which shows how equivalences between module categories over ring spectra can be realized by smashing with a pair of bimodules. Finally, we characterize stable model categories which represent the derived category of a ring. This is a slight generalization of Rickard's work on derived equivalent rings. We also include a proof of the model category equivalence of modules over the Eilenberg-Mac Lane spectrum HR and (unbounded) chain complexes of R-modules for a ring R.     

On essential extensions of reduced rings and domains

A ring is said to be a left essential extension of a reduced ring (domain) if it contains a left ideal which is a reduced ring (domain) and intersects nontrivially every nonzero twosided ideal of the ring. We prove that every ring which is a left essential extension of a reduced ring is a subdirect sum of rings which are essential extensions of domains, but the converse implication does not hold. We give some applications of this result and discuss several related questions.Received: 6 January 2003     

Mapping properties of wave and scattering operators for two-body Schrödinger operators

The modified wave and scattering operators are shown to be bounded between weighted L ²-spaces for two-body Schrödinger operators with long range potentials.     

美国初中级教育中对自然科学教师的培养及职业标准

对自然科学教师的培养及职业标准的研究是当代世界各国教育改革的焦点之一。本文试就美国对初中级教育中对自然科学教师的职业准备及其培养标准加以介绍和描述,特别是对美国七十年代以来对自然科学教育由重视到不重视再到重视的具体过程分析,以此为我国自然科学教师的培养提供借鉴作用。     

Peptides-XXXXVI: Studies in the synthesis of an analogue of hen egg white lysozyme

The previously synthesised (1–37), (38–75), (76–93), (94–104), (105–117) and (118–129) fragments of the analogue were combined making extensive use of the DCCI/HONSu method. The final coupling involved the (1–75) and (76–129) sub-fragments. Aggregation of the latter fragment caused problems in purification by routine gel filtration methods employing Enzacryl K2 or Sephadex LH60. The fully protected (1–129) product was partially purified by washing, then deprotectcd and purified by gel filtration and ion exchange chromatography. Satisfactory removal of the acetamidomethyl group used for cysteine protection could not be achieved.     

The Study of Anti-tumor Activity of Trichosanthin by Cyclic Voltammogram

IthasbeenreportedthatTrichosanthi11(TCS),isolatedfromrkiI-ilolt)ii,hasanti-tumorI-4andanti-vira1activities5-'.Someanti-tun1orremedies,whicharedesignedfromTCS,arebeingtestedanddeveloped'-.'.StudyingthebioIogicalphenomenonbyelectrochemicalmethodsisanewhotresearchspotemerginginrecentyears".Manyresultsshowedthatnotonlytheenzymesystemsuchassuccinatedehydrogenasedisplayedthediode-likebehaviorduringtheelectrontransferprocess",butalsothehigh1yorganizedorganeIle,forexample,mitochondria,andevenintac…     

The structure of cyclopentene oxide determined by gas phase electron diffraction

The r_g structure of cyclopentene oxide has been determined by the simultaneous least squares analysis of electron diffraction and microwave spectroscopic data. The investigation has reaffirmed previous studies indicating that the molecule prefers a boat conformation. The methylene and epoxide flap angles obtained are 152.3±2.1° and 104.7±1.0° respectively. Other structural parameters determined are: r_g (C-H avg.) = 1.120±0.004 Å; r_g (C-C avg.) = 1.538±0.002 Å; r_g (C-O) = 1.443±0.003 Å, and r_g (C-C) = 1.482±0.004 Å for the carbon-carbon bond in the three membered epoxide ring. These results compare favorably with the reported structures of ethylene oxide and cyclohexene oxide. A tentative rationalization of the unusual boat conformation is also offered.     

双头基两亲分子研究进展

本文介绍了双头基两亲分子的结构特征与性质, 概述了由双头基两亲分子在气液界面形成的单分子膜以及在体相中形成的囊泡的特征, 并介绍了这类两亲分子在催化、生物矿化、药物缓释、膜破解以及纳米材料等方面的应用研究。对其研究前景进行了展望。     

Interesting interferences in a direct serum creatinine reaction

A spectrophotometric study on a direct picric acid reaction for creatinine in severely jaundiced serums is described. A problem appears to be caused by the oxidation of bilirubin which minimizes rising absorbance when using continuous measurement. Simple examples of interferences with the kinetic mode are shown along with the hitherto unreported interference of the drug, Cephalothin, which also undergoes a picric acid reaction. A procedure in which a delta absorbance is obtained after decolorization of the Jaffé complex by acidification is shown as one available means for obviating the bilirubin effect. However, the theory that Jaffé-reactive interferences do not decolorize with the same acid treatment is not totally applicable when the drug, Cephalothin, is present.