884 resultados para Lek Paradox
Resumo:
Using pooled data from the 2008-2011 National Health Interview Survey and employing multinomial and binomial logistic regression methods, this research examines disparities in rates of obesity and incidence of diabetes between individual Hispanic subgroups in comparison to non-Hispanic whites and blacks. Immigration status(including nativity, duration in the United States, and citizenship status) is hypothesized to play a central role in rates and obesity and incidence of diabetes. Unlike Cuban-Americans, Mexican-Americans, Puerto Ricans, and other Hispanics were more likely to be overweight as well as obese when compared to non-Hispanic whites. Mexican-Americans had the only significance in prevalence of type 2 diabetes in comparison to non-Hispanic whites. Both of these health outcomes are strongly associated with the various immigration variables.
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It is possible for a pair of dichotomous, categorical variables to have an overall positive association (say) in a stratified population, and at the same time be negatively associated in every stratum. This (essentially) is Simpson's paradox. A graphical device, the risk diagram, provides insight into Simpson's paradox and related concepts.
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A 59-year-old woman was examined because of weight gain, increasing fatigue and secondary amenorrhoea, which occurred after a complicated delivery at age 18. The finding of an increased TSH concentration was initially considered as primary hypothyroidism and substitution therapy was commenced. Because of the concomitant secondary amenorrhoea the patient was referred for additional endocrinological investigations.
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The St. Petersburg Paradox was first presented by Nicholas Bernoulli in 1713. It is related to a gambling game whose mathematical expected payoff is infinite, but no reasonable person would pay more than $25 to play it. In the history, a number of ideas in different areas have been developed to solve this paradox, and this report will mainly focus on mathematical perspective of this paradox. Different ideas and papers will be reviewed, including both classical ones of 18th and 19th century and some latest developments. Each model will be evaluated by simulation using Mathematica.
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The late Paleozoic Cutler Formation, where exposed near the modern-day town of Gateway, Colorado, has traditionally been interpreted as the product of alluvial fan deposition within the easternmost portion of the Paradox Basin. The Paradox Basin formed between the western margin of the Uncompahgre Uplift segment of the Ancestral Rocky Mountains and the western paleoshoreline of the North American portion of Pangea. The Paradox Basin region is commonly thought to have experienced semi-arid to arid conditions and warm temperatures during the Pennsylvanian and Permian. Evidence described in this paper support prior interpretations regarding paleoclimate conditions and the inferred depositional environment for the Cutler Formation near Gateway, Colorado. Plant fossils collected from the late Paleozoic Cutler Formation in The Palisade Wilderness Study Area (managed by the U.S. Department of the Interior, Bureau of Land Management) of western Colorado include Calamites, Walchia, Pecopteris, and many calamitean fragments. The flora collected is interpreted to have lived in an arid or semi-arid environment that included wet areas of limited areal extent located near the apex of an alluvial fan system. Palynological analysis of samples collected revealed the presence of the common Pennsylvanian palynomorphs Thymospora pseudothiessenii and Lophotriletes microsaetosus. These fossils suggest that warm and at least seasonally and locally wet conditions existed in the area during the time that the plants were growing. All evidence of late Paleozoic plant life collected during this study was found along the western margin of the Uncompahgre Uplift segment of the Ancestral Rocky Mountains. During the late Paleozoic, sediment was eroded from the Uncompahgre Uplift and deposited in the adjacent Paradox Basin. The preservation of plant fossils in the most proximal parts of the Paradox Basin is remarkable due to the fact that much of the proximal Cutler Formation consists of conglomerates and sandstones deposited as debris flow and by fluvial systems. The plants must have grown in a protected setting, possibly an abandoned channel on the alluvial fan, and been rapidly buried in the subsiding Paradox Basin. It is likely that there was abundant vegetation in and adjacent to low-lying wet areas at the time the Cutler Formation was deposited.
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Six full-term newborn infants are described who suffered from severe adult respiratory distress syndrome (ARDS). The triggering event was intrauterine/perinatal asphyxia in five, and group B streptococcal (GBS) septicemia in three. All had severe respiratory distress/failure and were ventilated mechanically with high concentrations of inspired oxygen and positive end-expiratory pressure. Radiography of the chest showed dense bilateral consolidation with air bronchograms and reduced lung volume. Persistent pulmonary hypertension (PPH) was documented in all cases. The coincidence of ARDS and PPH rendered respiratory management extremely difficult. For this reason high-frequency ventilation was instituted in all patients in order to improve CO2 elimination and induce respiratory alkalosis. Acute complications of respiratory therapy were encountered in five patients (pneumothorax, pulmonary interstitial emphysema, pneumopericardium). Three infants died (irreversible septic shock, progressive severe hypoxemia, and sudden cardiac arrest) after 17, 80, and 175 h of life. Histologic examination of the lungs was possible in all fatal cases and revealed typical changes of acute to subacute stages of ARDS. Three infants survived, the mean time of mechanical respiratory support being 703 h. Two patients were still dependent on oxygen after 1 month of life, and all survivors had increased interstitial markings and increased lung volumes on their chest roentgenograms at this time.
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In many animals, males congregate in leks that females visit for the sole purpose of mating. We observed male and female behavior on 3 different-sized leks of the bower-building cichlid fish Nyassachromis cf. microcephalus to test predictions of 3 prominent lek models: the "hotshot," "hot spot," and "female preference" models. In this system, we were able to refine these predictions by distinguishing between indirect mate choice, by which females restrict their set of potential mates in the absence of individual male assessment, and direct mate choice, by which females assess males and their territories through dyadic behavioral interactions. On no lek were males holding central territories favored by indirect or direct mate choice, contrary to the prediction of the hotshot model that leks form because inferior males establish territories surrounding hotshot males preferred by females. Average female encounter rate of males increased with lek size, a pattern typically interpreted as evidence that leks form through female preference for lekking males, rather than because males congregate in hot spots of high female density. Female propensity to engage in premating behavior once courted did not increase with lek size, suggesting female preference for males on larger leks operated through indirect choice rather than direct choice based on individual assessment. The frequency of male-male competitive interactions increased with lek size, whereas their foraging rate decreased, implying a cost to males maintaining territories on larger leks. Together these data most strongly support the female preference model, where females may benefit through indirect mate choice for males able to meet the competitive cost of occupying larger leks.
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Seit der richtungweisenden wie einflußreichen Arbeit von Downs (1957) wird in der empirischen Wahlforschung das „Paradox der Wahlbeteiligung“ kontrovers diskutiert. Kritiker des ökonomischen Ansatzes führen gerade dieses Paradox an, um die Grenzen von Rational-Choice-Theorien aufzuzeigen (z.B. Green und Shapiro 1994). Ausgangspunkt dieser Debatte ist zunächst der Versuch von Downs, die Beteiligung von Individuen an politischen Wahlen mit der Theorie rationaler Entscheidung zu erklären: Demnach beteiligen sich Wahlberechtigte an Wahlen, wenn aus ihrer Sicht der erwartete Nutzen der Wahlbeteiligung (etwa persönliche Vorteile nach dem Wahlsieg der präferierten Partei) die anfallenden Kosten der Wahlbeteiligung (etwa zeitlicher Aufwand für Beschaffung, Auswertung und Analyse von Informationen über das Politikangebot) übersteigt. Wahlberechtigte diskontieren den zu maximierenden Nutzen aus ihrer Wahlbeteiligung mit der Wahrscheinlichkeit, daß ihre eigene Stimme der präferierten Partei zum Wahlsieg verhilft. Allerdings tendiert diese Wahrscheinlichkeit, den Wahlausgang alleine zu entscheiden, mit der anwachsenden Größe des Elektorats gegen Null. Da aber aus Sicht des einzelnen Wählers die eigene Stimme so gut wie keinen entscheidenden Einfluß auf den Wahlausgang hat, aber mit Sicherheit Informations-, Opportunitäts- und Teilnahmekosten anfallen, die dann immer größer als die mit der Erfolgswahrscheinlichkeit gewichteten Nutzeneinkommen sind, ist es höchst unwahrscheinlich, daß sich ein instrumentell rationaler Akteur an politischen Wahlen beteiligt (Downs 1957: 244–245). Jedoch sind in modernen Demokratien die Beteiligungen an politischen Wahlen mitunter beträchtlich, und diese empirische Beobachtung widerspricht der ökonomischen Theorie des Wählens von Downs (1957)1. Es stellt sich also die Frage, warum sich Wahlberechtigte an politischen Wahlen beteiligen und warum die Wahlbeteiligungen zumeist recht hoch sind (vgl. Palfrey und Rosenthal 1993).
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BACKGROUND Transmitted HIV-1 drug-resistance mutations(TDR) are transmitted from treatment-failing or treatment-naïve patients. Although prevalence of drug-resistance in treatment-failing patients has declined in developed countries, TDR prevalence has not. Mechanisms causing this paradox are poorly explored. METHODS We included recently-infected, treatment-naïve patients with genotypic-resistance-tests performed ≤1year post-infection and <2013. Potential risk factors for TDR were analyzed using logistic regression. Association of TDR prevalences with population viral load(PVL) from treatment-patients during 1997-2011 was estimated with Poisson regression for all TDR and individually for most frequent resistance-mutations against each drug class(M184V/L90M/K103N). RESULTS We included 2421 recently-infected, treatment-naïve patients and 5399 treatment-failing patients. TDR prevalence fluctuated considerably over time. Two opposing developments could explain these fluctuations: generally continuous increases in TDR(Odds Ratio[OR]=1.13,p=0.010), punctuated by sharp decreases when new drug-classes were introduced. Overall, TDR prevalence increased with decreasing PVL(Rate Ratio[RR]=0.91/1000Log10-PVL,p=0.033). Additionally, we observed that the transmitted high-fitness-cost mutation M184V was positively associated with PVL of treatment-failing patients carrying M184V(RR=1.50/100Log10-PVL,p<0.001). Such association was absent and negative for K103N(RR-K103N=1.00/100Log10-PVL,p=0.99) and L90M(RR-L90M=0.75/100Log10-PVL,p=0.022), respectively. CONCLUSIONS Transmission of antiretroviral drug-resistance is temporarily reduced by the introduction of new drug classes and driven by treatment-failing and treatment-naïve patients. These findings suggest a continuous need for new drugs, early detection/treatment of HIV-1-infection.