正交实验设计方法在B to B电子商务体系质量改进中的应用

电子商务在全球快速地发展，中国企业面临着由B to C方式向B to B方式的转变，本文采用正交实验设计的方法来解决已建成电子商务体系的质量，以满足新的需求。     

葡萄球菌肠毒素B抗肿瘤作用的实验研究

探讨了葡萄球菌肠毒素B(SEB)对动物移植性肿瘤的抑制作用。以小鼠移植性肿瘤肝癌(Heps)、L2网织细胞瘤和肉瘤180(S180)为模型,环磷酰胺为阳性对照组,生理盐水为阴性对照组,观察不同剂量(5、10和20ng·Kg-1·d-1)SEB的抗肿瘤作用。不同剂量的SEB对小鼠肝癌(Heps)有明显抑制作用,抑瘤率分别为44.6%、46.7%和51.8%(P值均<0.05),对小鼠L2网织细胞瘤也有一定的抑制作用,抑瘤率分别为17.4%、44.7%(P<0.05)和44.1%(P<0.05)。SEB对小鼠S180的抑制作用不显著。结论是葡萄球菌肠毒素B(SEB)具有抗肿瘤效应,可作为一种有前途的抗肿瘤制剂进行研究。     

Market microstructure in a global B2B network

On‐line marketplaces raise several interesting issues, among them the relevance of location when content is digitized, and the assessment of a supplier's capabilities when buyers worldwide only have electronic contact with sellers. In global B2B on‐line marketplaces, market microstructures, i.e. which firms compete for the same customers, are thus likely to be influenced by how customers value location and firm capabilities in their decisions to do business with different suppliers on‐line. We suggest that both these sets of attributes will continue to matter on‐line—firms possessing similar capabilities, as well as firms that are similar in location by country, time zones or clusters, will compete for business from the same customers. We model the similarity in competitive positions between pairs of firms based on the overlap in their customer networks, using data on actual interactions between supplier and customer banks on an electronic trading system. Using QAP network regression techniques on the 100 largest banks in this industry, we find that similarity in capabilities influences who competes with whom, and that location still matters in a global B2B exchange. Interestingly, location influences who a firm's competitors are, but not where its customers are from. Copyright © 2001 John Wiley & Sons, Ltd.     

Are the Best Small Companies the Best Investments?

Previous research finds that large companies previously judged to be excellent growth companies have subsequently been poor investments. We examine small companies selected by Business Week on the basis of multiple criteria used in annual articles featuring highly rated growth companies. We study the investment performance over the three years before eleven annual Business Week publications and the three years after publication. We find positive excess returns in the pre‐publication period, but negative excess returns in the post‐publication period. This reversal in investment performance appears to be due to a mean‐reversion tendency in operating performance, in which the earnings and the past rates of return on capital of such companies subsequently decrease significantly.     

GLAMOUR VERSUS VALUE: TRADING BEHAVIOR OF INSTITUTIONS AND INDIVIDUAL INVESTORS

We design a new metric to measure the net buying and selling by institutions and individual investors and find that from 1980 to 2004 institutional investors were net buyers of growth stocks and net sellers of value stocks, implying that individual investors were net buyers of value stocks and net sellers of glamour stocks. The institutional preference for glamour and value stocks seems to be related to sell‐side analysts' recommendations and recent favorable stock price performances, especially during the post‐1994 period. Finally, the institutional buying of growth stocks and sale of value stocks was not based on superior information.     

ALL THINGS CONSIDERED,TAXES DRIVE THE JANUARY EFFECT

The multitude of explanations for the January effect leaves the reader confused about its primary cause(s): is it tax‐loss selling, window dressing, information, bid‐ask bounce, or a combination of these causes? The confusion arises, in part, because evidence has generally been presented in support of a particular hypothesis though the same evidence may be consistent with another hypothesis. Furthermore, prior work does not adequately control for the bid‐ask bounce. In this article we try to disentangle different explanations of the January effect and identify its primary cause. We find that tax‐related selling is the most important cause, overshadowing other explanations.     

The Effects of Screening and Monitoring on Credit Rationing of SMEs

In this paper, we seek to empirically assess which determinants of the capability and incentives of banks to screen and monitor firms are significant in explaining credit rationing to Italian SMEs. After testing for the presence of non‐random selection bias and the potential endogeneity of some determinants of interest, the probit model results we obtain suggest that the average banking size and the multiple banking relationship phenomenon are statistically significant factors affecting credit rationing, presumably through their impact on the aforementioned banks' capability and incentives. Other potential determinants of banks' incentives to monitor and screen, such as local banking competition and firm' capacity to collateralize, are never significant. However, when we split the sample according to the level of competition in credit markets, we find that the estimated marginal effects of all significant determinants of interest are larger in absolute value than those obtained when using the whole sample.     

On the Statistical Significance of Event Effects on Unsystematic Volatility

We develop a method for determining the significance of the effect of a certain event (stock split, corporate restructuring, change in regulation, etc.) on unsystematic volatility of asset returns. Simulations show that the suggested tests reject the true null hypothesis of no effect on volatility at appropriate levels, whereas the rejection rates of a false null hypothesis increase with the magnitude of the effect. An application of the method to corporate spin‐offs reveals statistically significant and long‐lasting estimated increases in unsystematic volatility of parent companies' returns.     

Capital structure around the world: The roles of firm- and country-specific determinants

We analyze the importance of firm-specific and country-specific factors in the leverage choice of firms from 42 countries around the world. Our analysis yields two new results. First, we find that firm-specific determinants of leverage differ across countries, while prior studies implicitly assume equal impact of these determinants. Second, although we concur with the conventional direct impact of country-specific factors on the capital structure of firms, we show that there is an indirect impact because country-specific factors also influence the roles of firm-specific determinants of leverage.