Supernova-driven outflows and chemical evolution of dwarf spheroidal galaxies

We present a general phenomenological model for the metallicity distribution (MD) in terms of [Fe/H] for dwarf spheroidal galaxies (dSphs). These galaxies appear to have stopped accreting gas from the intergalactic medium and are fossilized systems with their stars undergoing slow internal evolution. For a wide variety of infall histories of unprocessed baryonic matter to feed star formation, most of the observed MDs can be well described by our model. The key requirement is that the fraction of the gas mass lost by supernova-driven outflows is close to unity. This model also predicts a relationship between the total stellar mass and the mean metallicity for dSphs in accord with properties of their dark matter halos. The model further predicts as a natural consequence that the abundance ratios [E/Fe] for elements such as O, Mg, and Si decrease for stellar populations at the higher end of the [Fe/H] range in a dSph. We show that for infall rates far below the net rate of gas loss to star formation and outflows, the MD in our model is very sharply peaked at one [Fe/H] value, similar to what is observed in most globular clusters. This suggests that globular clusters may be end members of the same family as dSphs.Comment: 8 pages, 3 figures, to be published in the Proceedings of the National Academy of Science

IS A BEEF DEFICIENCY PAYMENT PARETO-SUPERIOR IN SOUTH KOREA?

South Korea uses a quota and a tariff on beef imports to keep farm prices high. Part of the quota rents are used to support indirect benefits to producers. The welfare costs of these policies are analyzed. Following a suggestion of Hayami, a deficiency payment financed by tariff revenues from increased imports is considered as an alternative to the quota. As Anderson (1983) found for Japan, a deficiency payment is Pareto-superior only if indirect benefits from the quota revenue are ignored.International Relations/Trade,

Impacts of Competitive Position on Export Propensity and Intensity: An Empirical Study of Manufacturing Firms in China

We examine the impacts of competitive industry position on firms’ export propensity and intensity in China. Drawing on the resource-based view and the structure-conduct-performance paradigm of firm behavior, we investigate whether firms with competitive industry position through cost leadership or differentiation strategy have different export behaviors. We use a longitudinal data of 213,662 manufacturing firms in China from 1998 to 2005 to show that firms that have developed competitive advantages in the domestic market are more likely to export and have higher levels of export intensity. Indigenous and foreign manufacturing firms exhibit different patterns of export behaviors. Foreign firms with differentiation advantages focus on local market expansion instead of seeking opportunity in export markets.

State Ownership and Firm Innovation in China: An Integrated View of Institutional and Efficiency Logics

Using two longitudinal panel datasets of Chinese manufacturing firms, we assess whether state ownership benefits or impedes firms’ innovation. We show that state ownership in an emerging economy enables a firm to obtain crucial R&D resources but makes the firm less efficient in using those resources to generate innovation, and we find that a minority state ownership is an optimal structure for innovation development in this context. Moreover, the inefficiency of state ownership in transforming R&D input into innovation output decreases when industrial competition is high, as well as for start-up firms. Our findings integrate the efficiency logic (agency theory), which views state ownership as detrimental to innovation, and institutional logic, which notes that governments in emerging economies have critical influences on regulatory policies and control over scarce resources. We discuss the implications of these findings for research on state ownership and firm innovation in emerging economies

The benefits of selecting phenotype-specific variants for applications of mixed models in genomics

Applications of linear mixed models (LMMs) to problems in genomics include phenotype prediction, correction for confounding in genome-wide association studies, estimation of narrow sense heritability, and testing sets of variants (e.g., rare variants) for association. In each of these applications, the LMM uses a genetic similarity matrix, which encodes the pairwise similarity between every two individuals in a cohort. Although ideally these similarities would be estimated using strictly variants relevant to the given phenotype, the identity of such variants is typically unknown. Consequently, relevant variants are excluded and irrelevant variants are included, both having deleterious effects. For each application of the LMM, we review known effects and describe new effects showing how variable selection can be used to mitigate them.National Institute on Aging (Brain eQTL Study (dbGaP phs000249.v1.p1)

The effect of cotton-based collection methods on eosinophil cationic protein (ECP) concentrations detected in saliva

Teck Yee Wong, David Koh, Andrew Wee, Vivian Ng, Yong Tat Koh, Zhenjie Sum, Gerald KohDepartment of Community, Occupational and Family Medicine, Yong Loo Lin School of Medicine, National University of Singapore, SingaporeBackground: Salivary eosinophil cationic protein (ECP) level has the potential to be an assessment tool for asthma. Its measurement is not well-established and needs standardization. We studied how passive drool (PD) and two commercial devices, Salivette® (cotton-based device) and Sorbette® (cellulose–cotton-based-device), may affect ECP levels during collection among healthy subjects.Methods: Study I (n = 10) involved direct sampling of healthy adult subjects with Salivette® and Sorbette®. Study II (n = 33) involved ‘indirect’ sampling of previously collected PD by both devices.Results: In study I, ECP levels were detected in all PD samples but only in three with Sorbette® and none with Salivette® (collection order: PD, Sorbette® and Salivette®). We changed the order of collection (Salivette®, Sorbette®, PD) and the results were similar (ECP levels detected in all PD samples, three with Sorbette® and only one with Salivette®). In study II, ECP levels in saliva collected by PD was 12.8 μg/L (median) and using Sorbette® and Salivette® were < 2.0 μg/L and 3.4 μg/L respectively (p < 0.01). ECP levels in PD correlated with Sorbette® (rs = 0.79, p < 0.01) and Salivette® (rs = 0.62, p 0.01).Conclusion: Compared to PD, saliva collected using cotton or cellulose-based collection devices resulted in lower measurable ECP levels.Keywords: salivary ECP, collection method

Colorectal cancer screening: Barriers to the faecal occult blood test (FOBT) and colonoscopy in Singapore

Introduction: This study aims to identify the barriers to adopting faecal occult blood test (FOBT) and colonoscopy as colorectal cancer (CRC) screening methods among the eligible target population of Singapore. Materials and methods: This study was previously part of a randomised controlled trial reported elsewhere. Data was collected from Singapore residents aged 50 and above, via a household sample survey. The study recruited subjects who were aware of CRC screening methods, and interviewed them about the barriers to screening that they faced. Collected results on barriers to each screening method were analysed separately. Results: Out of the 343 subjects, 85 (24.8%) recruited knew about FOBT and/or colonoscopy. Most of the respondents (48.9%) cited not having symptoms as the reason for not using the FOBT. This is followed by inconvenience (31.1%), not having any family history of colon cancer (28.9%), lack of time (28.9%) and lack of reminders/recommendation (28.9%). Of the respondents who indicated not choosing colonoscopy as a screening method, more than one-half (54.8%) identified not having any symptoms as the main barrier for them, followed by not having any family history (38.7%) and having a healthy/low-risk lifestyle (29.0%). There was no difference between the reported barriers to each of the screening methods and the respondents\u27 dwelling types. Conclusions: Lack of knowledge, particularly the misconceptions of not having symptoms and being healthy, were identified as the main barriers to FOBT and colonoscopy as screening methods. Interventions to increase the uptake of CRC screening in this population should be tailored to address this misconception