677 research outputs found
Pricing in Social Networks with Negative Externalities
We study the problems of pricing an indivisible product to consumers who are
embedded in a given social network. The goal is to maximize the revenue of the
seller. We assume impatient consumers who buy the product as soon as the seller
posts a price not greater than their values of the product. The product's value
for a consumer is determined by two factors: a fixed consumer-specified
intrinsic value and a variable externality that is exerted from the consumer's
neighbors in a linear way. We study the scenario of negative externalities,
which captures many interesting situations, but is much less understood in
comparison with its positive externality counterpart. We assume complete
information about the network, consumers' intrinsic values, and the negative
externalities. The maximum revenue is in general achieved by iterative pricing,
which offers impatient consumers a sequence of prices over time.
We prove that it is NP-hard to find an optimal iterative pricing, even for
unweighted tree networks with uniform intrinsic values. Complementary to the
hardness result, we design a 2-approximation algorithm for finding iterative
pricing in general weighted networks with (possibly) nonuniform intrinsic
values. We show that, as an approximation to optimal iterative pricing, single
pricing can work rather well for many interesting cases, but theoretically it
can behave arbitrarily bad
SHORT COMMUNICATION: Complementary tumor induction in neural grafts exposed to N-ethyl-N-nitrosourea and an activated myc gene
Using a combination of transplacental carcinogen exposure and retrovirus-mediated oncogene transfer into fetal brain transplants, we have studied complementary transformation by N-ethyl-N-nitrosourea (NEU) and the v-myc oncogene in the nervous system. Previous experiments had demonstrated that both agents will not induce tumors independently whereas simultaneous expression of v-H-ras and v-gag/myc exerted a powerful transforming potential in neural grafts. In order to identify other genetic alterations that co-operate with an activated myc gene, the neurotropic carcinogen NEU was used to generate mutations of cellular genes. On embryonic day 14 (ED14), pregnant donor animals (F344 rats) received a single i.v. dose of NEU (50 mg/kg). Twenty-four hours later (ED15), the fetal brains were removed, triturated and incubated with a retroviral vector carrying the v-gag/myc oncogene. Subsequently, these primary cell suspensions were transplanted stereotactically into the caudate-putamen of syngenic adult recipients. After latency periods of 3-6 months, 5 of 10 recipients harboring ED15 fetal brain transplants developed malignant, poorly differentiated neuroectodermal tumors in the grafts. No tumor development was observed in seven recipients harboring ED16 neural grafts. Cell lines were established from three tumors and the 110 kd gag/myc fusion protein encoded by the retroviral construct was identified in the tumors by Western blotting. Several candidate genes for mutational activation by NEU including the H-ras, K-ras and neu oncogenes were analyzed for specific point mutations by polymerase chain reaction (PCR) and direct DNA sequencing of the PCR products. However, no mutations were found in any of these genes. These findings lend further support to the multistep hypothesis of neoplastic transformation in the brain. The tumors induced in this model provide an interesting tool for the identification of genes that co-operate with an activated myc gene in neurocarcinogenesi
Risk of new onset diabetes mellitus in patients with asthma or COPD taking inhaled corticosteroids
SummaryBackgroundA recent case-controlled study reported an increased risk of diabetes mellitus in patients treated with inhaled corticosteroids for asthma or COPD, versus age-matched controls.ObjectiveThe purpose of the current study was to evaluate whether there was an increased risk of new onset diabetes mellitus or hyperglycaemia among patients with asthma or COPD treated with inhaled corticosteroids.MethodsA retrospective analysis evaluated all double-blind, placebo-controlled, trials in patients â„4 years of age involving budesonide or budesonide/formoterol in asthma (26 trials; budesonide: n = 9067; placebo: n = 5926), and in COPD (8 trials; budesonide: n = 4616; non-ICS: n = 3643). A secondary dataset evaluated all double-blind, controlled trials in asthma involving the use of inhaled corticosteroids (60 trials; budesonide: n = 33,496; fluticasone: n = 2773).ResultsIn the primary asthma dataset, the occurrence of diabetes mellitus/hyperglycaemia adverse events (AEs) was 0.13% for budesonide and 0.13% for placebo (HR 0.98 [95% CI: 0.38â2.50], p = 0.96) and serious adverse events (SAEs) was 0% for budesonide and 0.05% for placebo. In the secondary dataset, the occurrence of diabetes/hyperglycaemia as AE and SAE was 0.19% and 0.03%, respectively. In the COPD dataset, the occurrence of diabetes mellitus/hyperglycaemia AEs was 1.3% for budesonide and 1.2% for non-ICS (HR 0.99 [95% CI: 0.67â1.46], p = 0.96) and SAEs was 0.1% for budesonide and 0.03% for non-ICS.Conclusion and clinical relevanceTreatment with inhaled corticosteroids in patients with asthma or COPD was not associated with increased risk of new onset diabetes mellitus or hyperglycaemia
Comorbidity burden in axial spondyloarthritis: a cluster analysis
Objectives To examine how comorbidities cluster in axial spondyloarthritis (axSpA) and whether these clusters are associated with quality of life, global health and other outcome measures. Methods We conducted a cross-sectional study of consecutive patients meeting ASAS criteria for axSpA in Liverpool, UK. Outcome measures included quality of life (EQ5D), global health and disease activity (BASDAI). We used hierarchical cluster analysis to group patients according to 38 pre-specified comorbidities. In multivariable linear models, the associations between distinct comorbidity clusters and each outcome measure were compared, using axSpA patients with no comorbidities as the reference group. Analyses were adjusted for age, gender, symptom duration, BMI, deprivation, NSAID-use and smoking. Results We studied 419 patients (69% male, mean age 46 years). 255 patients (61%) had at least one comorbidity, among whom the median number was 1 (range 1â6). Common comorbidities were hypertension (19%) and depression (16%). Of 15 clusters identified, the most prevalent clusters were hypertension-coronary heart disease and depression-anxiety. Compared with patients with no comorbidities, the fibromyalgia-irritable bowel syndrome cluster was associated with adverse patient-reported outcome measures; these patients reported 1.5-unit poorer global health (95%CI 0.01, 2.9), reduced quality of life (0.25-unit lower EQ5D; 95%CI â0.37, â0.12) and 1.8-unit higher BASDAI (95% CI 0.4, 3.3). Similar effect estimates were found for patients in the depression-anxiety cluster. Conclusion Comorbidity is common among axSpA patients. The two most common comorbidities were hypertension and depression. Patients in the depression-anxiety and fibromyalgia-IBS clusters reported poorer health and increased axSpA severity
Museu Militar de Bragança: fundação, pråticas museológicas
O objecto de estudo decidido para este trabalho centra-se na reflexĂŁo sobre o Museu Militar de Bragança hoje, e as suas potencialidades enquanto gerador de desenvolvimento social. Para fazer esta reflexĂŁo consideramos pertinente a pesquisa histĂłrica do museu, desde a sua fundação, atendendo Ă função e os objectivos propostos inicialmente pela instituição, bem como aos procedimentos museolĂłgicos actualmente observados. O museu militar de Bragança surge no primeiro quartel do sĂ©culo XX como um espaço de salvaguarda das memĂłrias dos feitos bĂ©licos das forças militares sedeadas em Bragança. ApĂłs a erradicação da Ășltima unidade militar de Bragança, em 1958, o museu Ă© temporariamente encerrado e trasladado o acervo para o Museu Militar de Lisboa. JĂĄ na dĂ©cada de 80 do sĂ©culo XX o museu volta a ser instalado no local de origem, a torre de menagem do castelo, e impĂ”e-se como espaço \ memĂłria das vivĂȘncias militares da cidade. No entanto, cremos que, para que o Museu Militar potencie as suas ferramentas enquanto gerador de desenvolvimento social, seria desejĂĄvel consumar alguns procedimentos museolĂłgicos, actualmente jĂĄ impostos na Lei Quadro dos museus. Neste sentido, na segunda parte do presente trabalho propomo-nos estabelecer um plano geral de prĂĄticas museolĂłgicas adaptado ao caso concreto do Museu Militar de Bragança. O presente trabalho aspira assim: a caracterizar sucintamente o conceito actual de Museu; a descrever o edifĂcio onde estĂĄ instalado o Museu Militar de Bragança, que constitui parte integrante da sua valĂȘncia enquanto gerador de desenvolvimento local; a pesquisar o processo de fundação do museu, os seus objectivos e funçÔes enquanto parte integrante de um maior complexo militar como era o quartel. (...
Universal features in the growth dynamics of complex organizations
We analyze the fluctuations in the gross domestic product (GDP) of 152
countries for the period 1950--1992. We find that (i) the distribution of
annual growth rates for countries of a given GDP decays with ``fatter'' tails
than for a Gaussian, and (ii) the width of the distribution scales as a power
law of GDP with a scaling exponent . Both findings are in
surprising agreement with results on firm growth. These results are consistent
with the hypothesis that the evolution of organizations with complex structure
is governed by similar growth mechanisms.Comment: 4 pages, 7 ps figures, using Latex2e with epsf rotate and multicol
style files. Submitted to PR
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The confidence cult(ure)
In this paper we explore how confidence has become a technology of self that invites girls and women to work on themselves. The discussion demonstrates the extensiveness of what we call the âcult(ure) of confidenceâ across different areas of social life, and examines the continuities in the way that exponents of the confidence cult(ure) name, diagnose and propose solutions to archetypal feminist questions about labour, value and the body. Our analysis focuses on two broad areas of social life in which the notion of confidence has taken hold powerfully in the last few years: popular discussions about gender and work, and consumer body culture. Examining the incitements to self-confidence in these realms, we show how an emergent technology of confidence, systematically re-signifies feminist accounts, by turning away from structural inequalities and collectivist critiques of male domination into heightened modes of self-work and self-regulation, and by repudiating the injuries inflicted by the structures of inequality. We conclude by situating the âconfidence cult(ure)â in relation to wider debates about feminism, postfeminism and neoliberalism
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