NLO-QCD corrections to e+ e- --> hadrons in models of TeV-scale gravity

We present results on NLO-QCD corrections to the process e+ e- --> hadrons via photon-, Z- and graviton-exchange in the context of TeV-scale gravity models. The quantitative impact of these QCD corrections for searches of extra dimensions at a Linear Collider is briefly discussed.Comment: 10 pages, LaTeX, using axodraw.st

A Dyad Model of Calling Behaviour with Tie Strength Dynamics

This paper investigates the dynamic relation between callers' social ties and their wireless phone service consumption. We construct a large pair-level panel dataset with information on the number of each pair's common contacts, calling activities, prices, and each caller's characteristics over a one-year time period. We estimate a dynamic model that encapsulates the evolving relationship between each pair of consumers. We find the amount of communications between a pair of consumers increases with the strength of their tie, which is higher when these two consumers share more common contacts. Our results support the reciprocity rule in telephone calls, i.e. when individual A initiates more (less) phone calls to individual B in one month, their social tie will be strengthened (weakened) and individual B will make more (less) calls to individual A in the subsequent months. We demonstrate the implications of our results in evaluating the return of temporary price promotions and designing price plans. Our results underscore the importance of incorporating social network characteristics in the study of telecommunications markets

The Impacts of Shopbots on Online Consumer Search

Online price comparison agents (shopbots) allow consumers to instantaneously receive price and other information from many online retailers. Online consumer clickstream data from ComScore Inc. demonstrate that consumers are increasingly using shopbots to conduct search. This phenomenon raises such questions as "how do shopbots change consumers' search behavior?" and "do they reduce consumers' online search?" Conventional wisdom suggests that consumers are expected to search less because shopbots have displayed prices and other relative information from retailers on the search result page(s). Surprisingly, this study demonstrates the opposite result. That is, consumers are actually visiting more online retailer web sites after using shopbots. This finding suggests that after searching for an item through a shopbot and receiving the price information, consumers will continue to look for detailed information about the online retailers by visiting their web sites. The empirical finding is explained by an analytical model, which shows that on the one hand shopbots reduce the marginal benefit of searching additional online stores; on the other hand they reduce the cost of search. Therefore whether shopbots reduce consumer search depends on the cost of reducing per unit of risk, which is decided by a number of factors, such as marginal search costs, price dispersion and quality differentiation among stores, price and quality correlation, and consumers' relative preference for service quality. The model also gives sufficient and necessary conditions under which shopbots increase consumer surplus

Pricing of Complements and Network Effects

We discuss the case of a monopolist of a base good in the presence of a complementary good provided either by it or by another firm. We assess and calibrate the extent of the influence on the profits from the base good that is created by the existence of the complementary good. We establish an equivalence between a model of a base and a complementary good and a reduced-form model of the base good in which network effects are assumed in the consumers' utility functions as a surrogate for the presence of direct or indirect network effects, such as complementary goods produced by other firms. We also assess and calibrate the influence on profits of the intensity of network effects and quality improvements in both goods. We evaluate the incentive that a monopolist of the base good has to improve its quality rather than that of the complementary good under different market structures. Finally, based on our results, we discuss a possible explanation of the fact that Microsoft Office has a significantly higher price than Microsoft Windows although both products have comparable market shares

Quantifying the benefits of entry into local phone service

Local telecommunications competition was an important goal of the 1996 Telecommunications Act. We evaluate the consumer welfare effects of entry into residential local telephone service in New York State using household-level data from September 1999 to March 2003. We address the prevalence of nonlinear tariffs by developing a discrete/continuous demand model that allows for service bundling and unobservable provider quality. We find that the average subscriber to the entrants' services gains a monthly equivalent of $2.33, or 6.2% of her bill, in welfare from competition. These gains accrue primarily from firm differentiation and new plan introductions rather than from price effects

Quantifying the benefits of entry into local phone service

Local telecommunications competition was an important goal of the 1996 Telecommunications Act. We evaluate the consumer welfare effects of entry into residential local telephone service in New York State using household-level data from September 1999 to March 2003. We address the prevalence of nonlinear tariffs by developing a discrete/continuous demand model that allows for service bundling and unobservable provider quality. We find that the average subscriber to the entrants’ services gains a monthly equivalent of $2.33, or 6.2% of her bill, in welfare from competition. These gains accrue primarily from firm differentiation and new plan introductions rather than from price effects

Higgs production in association with top quark pair at e+e- colliders in theories of higher dimensional gravity

The models of large extra compact dimensions, as suggested by Arkani-Hamed, Dimopoulos and Dvali, predict exciting phenomenological consequences with gravitational interactions becoming strong at the TeV scale. Such theories can be tested at the existing and future colliders. In this paper, we study the contribution of virtual Kaluza-Klein excitations in the process $e^+e^- \to t \bar t H$ at future linear collider (NLC). We find that the virtual exchange KK gravitons can modify the cross-section $\sigma(e^+e^- \to t \bar t H)$ significantly from its Standard Model value and will allow the effective string scale to be probed up to 7.9 TeV.Comment: 10 pages, Latex, 4 postscript figure

Hepatocyte-specific activation of NF-κB does not aggravate chemical hepatocarcinogenesis in transgenic mice

The NF-κB signalling pathway plays important roles in liver organogenesis and cardnogenesis. Mouse embryos deficient in IKKβ die in mid-gestation, due to excessive apoptosis of hepatoblasts. Although activation of the NF-κB signalling pathway has been demonstrated in human hepatocellular carcinoma, the role of NF-κB is controversial. Here, we have generated transgenic mice in which a constitutively active form of IKKβ was expressed in a hepatocyte-specific manner. Using electrophoretic mobility shift assay, we documented increased NF-κB activities and up-regulated levels of NF-κB downstream target genes, Bcl-xL and STAT5, in the transgenic mouse livers. These results confirmed that the NF-κB pathway was activated in the livers of the transgenic mice. However, there was no significant difference in tumour formation between transgenic and wild-type mice up to an age of 50 weeks. When we treated the transgenic mice with the chemical carcinogen diethylnitrosamine (DEN), we observed no significant differences in the incidence and size of liver tumours formed in these mice with and without DEN treatment at 35 weeks of age, suggesting that the activated NF-κB pathway in the livers of the transgenic mice did not enhance hepatocarcinogenesis. Interestingly, some of the transient transgenic embryos (E12.5) had abnormal excessive accumulation of nucleated red blood cells in their developing livers. In summary, NF-κB activation in hepatocytes did not significantly affect chemical hepatocarcinogenesis. In addition, the TTR/IKKCA transgenic mice may serve as a useful model for studying the role of NF-κB activation in hepatocarcinogenesis as well as inflammatory and metabolic diseases. Copyright © 2008 Pathological Society of Great Britain and Ireland.postprin

Emergency Care Handover (ECHO study) across care boundaries : the need for joint decision making and consideration of psychosocial history

Background: Inadequate handover in emergency care is a threat to patient safety. Handover across care boundaries poses particular problems due to different professional, organisational and cultural backgrounds. While there have been many suggestions for standardisation of handover content, relatively little is known about the verbal behaviours that shape handover conversations. This paper explores both what is communicated (content) and how this is communicated (verbal behaviours) during different types of handover conversations across care boundaries in emergency care. Methods: Three types of interorganisational (ambulance service to emergency department (ED) in ‘resuscitation’ and ‘majors’ areas) and interdepartmental handover conversations (referrals to acute medicine) were audio recorded in three National Health Service EDs. Handover conversations were segmented into utterances. Frequency counts for content and language forms were derived for each type of handover using Discourse Analysis. Verbal behaviours were identified using Conversation Analysis. Results: 203 handover conversations were analysed. Handover conversations involving ambulance services were predominantly descriptive (60%–65% of utterances), unidirectional and focused on patient presentation (75%–80%). Referrals entailed more collaborative talk focused on the decision to admit and immediate care needs. Across all types of handover, only 1.5%–5% of handover conversation content related to the patient's social and psychological needs. Conclusions: Handover may entail both descriptive talk aimed at information transfer and collaborative talk aimed at joint decision-making. Standardisation of handover needs to accommodate collaborative aspects and should incorporate communication of information relevant to the patient's social and psychological needs to establish appropriate care arrangements at the earliest opportunity