2,957 research outputs found
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 at future linear collider (NLC). We find that the virtual exchange
KK gravitons can modify the cross-section
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
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