Time-Varying Beta Estimators in the Mexican Emerging Market

This paper compares the performance of three different time-varying betas that have never previously been compared: the rolling OLS estimator, a nonparametric estimator and an estimator based on GARCH models. The study is conducted using returns from the Mexican stock market grouped into six portfolios for the period 2003-2009. The comparison, based on asset pricing perspective and mean-variance space returns, concludes that GARCH based beta estimators outperform the others when the comparison is in terms of time series while the nonparametric estimator is more appropriate in the cross-sectional context.time-varying beta, nonparametric estimator, GARCH based beta estimator

Anatomical variants and coronary anomalies detected by dual-source coronary computed tomography angiography in North-eastern Thailand

Purpose: Congenital coronary anomalies are uncommon, with an incidence ranging from 0.17% in autopsy cases to 1.2% in angiographically evaluated cases. The recent development of dual-source coronary computed tomography angiography (coronary CTA) allows accurate and noninvasive depiction of coronary artery anomalies. Material and methods: A retrospective study included a total of 924 patients who underwent coronary CTA because of known or suspected coronary artery disease. In each study, coronary artery anomalies (CAs) were investigated. Results: A total of 924 patients (mean age 51.2 ±12.8 years), who underwent dual-source coronary CTA, were studied. The overall prevalence of CAs in our study was 3.7%, with the following distribution: four single coronary artery, 14 anomalous origin from opposite sinus of Valsalva, three absent left main, four high take-off coronary artery, three anomalous left coronary artery from pulmonary artery, and eight coronary artery fistulas. Conclusions: The present study supports the use of coronary CTA as a reliable noninvasive tool for defining anomalous coronary arteries in an appropriate clinical setting and provides detailed three-dimensional anatomic information that may be difficult to obtain with invasive coronary angiography

USSR Space Life Sciences Digest, issue 16

This is the sixteenth issue of NASA's USSR Life Sciences Digest. It contains abstracts of 57 papers published in Russian language periodicals or presented at conferences and of 2 new Soviet monographs. Selected abstracts are illustrated with figures and tables from the original. An additional feature is the review of a book concerned with metabolic response to the stress of space flight. The abstracts included in this issue are relevant to 33 areas of space biology and medicine. These areas are: adaptation, biological rhythms, bionics, biospherics, body fluids, botany, cardiovascular and respiratory systems, developmental biology, endocrinology, enzymology, exobiology, gastrointestinal system, genetics, gravitational biology, habitability and environmental effects, hematology, human performance, immunology, life support systems, man-machine systems, mathematical modeling, metabolism, microbiology, musculoskeletal system, neurophysiology, nutrition, operational medicine, perception, personnel selection, psychology, radiobiology, reproductive biology, and space biology

Drugs for preventing red blood cell dehydration in people with sickle cell disease.

BACKGROUND: Sickle cell disease is an inherited disorder of hemoglobin, resulting in abnormal red blood cells. These are rigid and may block blood vessels leading to acute painful crises and other complications. Recent research has focused on therapies to rehydrate the sickled cells by reducing the loss of water and ions from them. Little is known about the effectiveness and safety of such drugs. This is an updated version of a previously published review. OBJECTIVES: To assess the relative risks and benefits of drugs to rehydrate sickled red blood cells. SEARCH METHODS: We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group\u27s Haemoglobinopathies Trials Register. We also searched online trials registries for any ongoing trials (01 July 2018).Last search of the Group\u27s Haemoglobinopathies Trials Register: 08 October 2018. SELECTION CRITERIA: Randomized or quasi-randomized controlled trials of drugs to rehydrate sickled red blood cells compared to placebo or an alternative treatment. DATA COLLECTION AND ANALYSIS: Both authors independently selected studies for inclusion, assessed study quality and extracted data. MAIN RESULTS: Of the 51 studies identified, three met the inclusion criteria, including 524 people with sickle cell disease aged between 12 and 65 years of age. One study tested the effectiveness of zinc sulphate as compared to placebo and the remaining two assessed senicapoc versus placebo. No deaths were seen in any of the studies (low-quality evidence). The zinc sulphate study showed a significant reduction in painful crises (in a total of 145 participants) over one and a half years, mean difference -2.83 (95% confidence interval -3.51 to -2.15) (moderate-quality evidence). However, analysis was restricted due to limited statistical data. Changes to red blood cell parameters and blood counts were inconsistent (very low-quality evidence). No serious adverse events were noted in the study. The Phase II dose-finding study of senicapoc (a Gardos channel blocker) compared to placebo showed that the high dose senicapoc showed significant improvement in change in hemoglobin level, the number and proportion of dense red blood cells, red blood cell count and indices and hematocrit value (very low-quality evidence). The results with low-dose senicapoc were similar to the high-dose senicapoc group but of lesser magnitude. There was no difference in the frequency of painful crises between the three groups (low-quality evidence). A subsequent Phase III study of senicapoc was terminated early since there was no difference observed between the treatment and control groups in the primary end point of painful crises. AUTHORS\u27 CONCLUSIONS: While the results of zinc for reducing sickle-related crises are encouraging, larger and longer-term multicenter studies are needed to evaluate the effectiveness of this therapy for people with sickle cell disease.While the Phase II and the prematurely terminated phase III studies of senicapoc showed that the drug improved red blood cell survival (depending on dose), this did not lead to fewer painful crises.Given this is no longer an active area of research, this review will no longer be regularly updated