Reciprocity, Social Ties, and Competition in Markets for Experience Goods

Reciprocal customers may disproportionately improve the performance of markets for experience goods. Reciprocal customers reward (punish) firms for providing good (bad) quality by upholding (terminating) the customer relation. This may induce firms to provide good quality which, in turn, may induce a positive externality for nonreciprocal customers who would, in the absence of reciprocal types, face market breakdown. This efficiency-enhancing effect of reciprocity is boosted when there are social ties between consumers and competition between firms. The existence of social ties or competition alone does not improve market performance.social networks; reputation; reciprocity; experience goods; customer loyalty

Continuous phase-space representations for finite-dimensional quantum states and their tomography

Continuous phase spaces have become a powerful tool for describing, analyzing, and tomographically reconstructing quantum states in quantum optics and beyond. A plethora of these phase-space techniques are known, however a thorough understanding of their relations was still lacking for finite-dimensional quantum states. We present a unified approach to continuous phase-space representations which highlights their relations and tomography. The infinite-dimensional case from quantum optics is then recovered in the large-spin limit.Comment: 15 pages, 9 figures, v4: extended tomography analysis, added references and figure

Epidemiology of Traveler's Diarrhea

Among travelers from developed countries who visit developing countries, >60% may experience traveler' diarrhea, accounting for 40,000 travelers daily or >15 million travelers annually. Traveler' diarrhea is often accompanied by other symptoms, most often abdominal cramps. Although the spontaneous cure occurs after a mean of 4 days, a few patients have symptoms for weeks, and it is increasingly noted that some patients may later develop irritable bowel syndrome. Traveler' diarrhea is life threatening only exceptionally, but it frequently it leads to incapacitation. Both host factors (e.g., age, behavior, nationality, and genetic factors) and environmental factors (primarily the selected destination and hotel) play an important role in risk for traveler' diarrhe

3. Travel medicine—prevention based on epidemiological data

In travel medicine efforts should be concentrated on preventive measures that are necessary, and travellers should be spared the side effects, costs and stress of superfluous measures. Excess mortality abroad is mainly due to traffic and swimming accidents, indicating the need for appropriate control strategies. The morbidity in travellers to developing countries is high, and is primarily due to traveller's diarrhoea. As prophylaxis is ineffective or unrealistic, and as travellers often need fast relief, it is recommended to include loperamide and an antimicrobial agent in the travel kit. Recent studies have shown that the incidence rate per month of Plasmodium falciparum malaria in Africa may reach . The most frequently occurring immunizable diseases are hepatitis A () and hepatitis B (). For many tourists and some expatriates pre-travel advice (hygiene, measures against mosquito bites, etc.) as well as chemoprophylaxis and immunization can be limited to these infections, but those travelling or staying outside large centres need additional measure

Worldwide Efficacy of Bismuth Subsalicylate in the Treatment of Travelers' Diarrhea

So far four randomized studies, three of them double-blind and placebo-controlled, have investigated the role of bismuth subsalicylate (BSS) in the treatment of travelers' diarrhea. When compared with placebo BSS significantly reduced the number of unformed stools and increased the proportion of patients free of symptoms at the end of the trial. In the two studies that compared BSS with loperamide, the latter agent brought significantly faster relief. Diarrhea accompanied by dysenteric symptoms was influenced most favorably by administration of systemic antimicrobial agents. In all four studies only minor adverse effects were noted with BSSor the other active agents. One may include loperamide and a systemic antimicrobial agent in one's travel kit; however, loperamide should not be used for dysentery, and the antimicrobial agent should not be used in uncomplicated cases. As an alternative, although it is less effective, BSS has the unique advantage of being safe enough to use for all patients with travelers' diarrhe

Epidemiologic Studies of Travelers' Diarrhea, Severe Gastrointestinal Infections, and Cholera

A retrospective survey, which is based on interviews conducted between 1975 and 1984 with 20,000 European tourists returning from 15 destinations m various climatic zones, demonstrates that travelers' diarrhea is the most frequent health problem encountered by travelers in the tropics. The incidence varied from 4% to 51%, depending on the destination. High-risk groups were persons younger than 30 years, adventurous travelers, and travelers with preexisting gastrointestinal illnesses. Illness acquired at various geographic regions showed only minor differences in chronology and symptomatology. The clinical course of travelers' diarrhea was usually short and mild. Additionally: by longitudinal and retrospective analyses, the incidence and prognosis of gastrointestinal infections of greater severity that were acquired after a short stay in a developing country, such as giardiasis, amebiasis, typhoid fever, and cholera, were evaluated; typhoid fever and cholera, in particular, were found to be quite rar