Gap bootstrap methods for massive data sets with an application to transportation engineering

In this paper we describe two bootstrap methods for massive data sets. Naive applications of common resampling methodology are often impractical for massive data sets due to computational burden and due to complex patterns of inhomogeneity. In contrast, the proposed methods exploit certain structural properties of a large class of massive data sets to break up the original problem into a set of simpler subproblems, solve each subproblem separately where the data exhibit approximate uniformity and where computational complexity can be reduced to a manageable level, and then combine the results through certain analytical considerations. The validity of the proposed methods is proved and their finite sample properties are studied through a moderately large simulation study. The methodology is illustrated with a real data example from Transportation Engineering, which motivated the development of the proposed methods.Comment: Published in at http://dx.doi.org/10.1214/12-AOAS587 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Size effect in the ionization energy of PAH clusters

We report the first experimental measurement of the near-threshold photo-ionization spectra of polycyclic aromatic hydrocarbon clusters made of pyrene C16H10 and coronene C24H12, obtained using imaging photoelectron photoion coincidence spectrometry with a VUV synchrotron beamline. The experimental results of the ionization energy are confronted to calculated ones obtained from simulations using dedicated electronic structure treatment for large ionized molecular clusters. Experiment and theory consistently find a decrease of the ionization energy with cluster size. The inclusion of temperature effects in the simulations leads to a lowering of this energy and to a quantitative agreement with the experiment. In the case of pyrene, both theory and experiment show a discontinuity in the IE trend for the hexamer

Predictors of Stunting, Wasting and Underweight among Tanzanian Children Born to HIV-Infected Women.

Children born to human immunodeficiency virus (HIV)-infected women are susceptible to undernutrition, but modifiable risk factors and the time course of the development of undernutrition have not been well characterized. The objective of this study was to identify maternal, socioeconomic and child characteristics that are associated with stunting, wasting and underweight among Tanzanian children born to HIV-infected mothers, followed from 6 weeks of age for 24 months. Maternal and socioeconomic characteristics were recorded during pregnancy, data pertaining to the infant's birth were collected immediately after delivery, morbidity histories and anthropometric measurements were performed monthly. Multivariate Cox proportional hazards methods were used to assess the association between potential predictors and the time to first episode of stunting, wasting and underweight. A total of 2387 infants (54.0% male) were enrolled and followed for a median duration of 21.2 months. The respective prevalence of prematurity (<37 weeks) and low birth weight (<2500 g) was 15.2% and 7.0%; 11.3% of infants were HIV-positive at 6 weeks. Median time to first episode of stunting, wasting and underweight was 8.7, 7.2 and 7.0 months, respectively. Low maternal education, few household possessions, low infant birth weight, child HIV infection and male sex were all independent predictors of stunting, wasting and underweight. In addition, preterm infants were more likely to become wasted and underweight, whereas those with a low Apgar score at birth were more likely to become stunted. Interventions to improve maternal education and nutritional status, reduce mother-to-child transmission of HIV, and increase birth weight may lower the risk of undernutrition among children born to HIV-infected women

Suppression of mitochondrial respiration through recruitment of p160 myb binding protein to PGC-1α : modulation by p38 MAPK

The transcriptional coactivator PPAR gamma coactivator 1 α (PGC-1α) is a key regulator of metabolic processes such as mitochondrial biogenesis and respiration in muscle and gluconeogenesis in liver. Reduced levels of PGC-1α in humans have been associated with type II diabetes. PGC-1α contains a negative regulatory domain that attenuates its transcriptional activity. This negative regulation is removed by phosphorylation of PGC-1α by p38 MAPK, an important kinase downstream of cytokine signaling in muscle and β-adrenergic signaling in brown fat. We describe here the identification of p160 myb binding protein (p160MBP) as a repressor of PGC-1α. The binding and repression of PGC-1α by p160MBP is disrupted by p38 MAPK phosphorylation of PGC-1α. Adenoviral expression of p160MBP in myoblasts strongly reduces PGC-1α's ability to stimulate mitochondrial respiration and the expression of the genes of the electron transport system. This repression does not require removal of PGC-1α from chromatin, suggesting that p160MBP is or recruits a direct transcriptional suppressor. Overall, these data indicate that p160MBP is a powerful negative regulator of PGC-1α function and provide a molecular mechanism for the activation of PGC-1α by p38 MAPK. The discovery of p160MBP as a PGC-1α regulator has important implications for the understanding of energy balance and diabetes

Obesity epidemic has emerged among Nigerians

Background: Data from the WHO shows that the prevalence of overweight and obesity increased by ~20% between 2002 and 2010 in Nigeria. We conducted this study to examine the correlates of this fast growing epidemic. Methods: We conducted a cross-sectional study among a random sample of 1058 adults, who were visitors and staff of a government worksite in Abuja, an urban city in Nigeria. The study participants had varying socio-economic status and a wide range of occupations, including skilled labor and professionals. Log-binomial regression models were used to estimate the multivariable-adjusted associations of potential determinants with the prevalence of overweight and obesity. Result The mean age and body-mass index of the study population were 42 years ± (9.3) and 27 kg/m2 ± (4.8). The overall prevalence of overweight or obesity (body-mass index ≥ 25 kg/m2) was 64% (74% of the women and 57% of the men). For women compared to men, the prevalence ratio (PR) and (95% confidence interval, CI) was 1.24 (95% CI 1.08, 1.43, p = 0.004), for overweight, and 2.54 (95% CI 2.08, 3.10, p = <0.0001), for obesity. Individuals aged 40 – 49 years were more likely to be overweight or obese. The PR for overweight and obesity was 1.45 (95% CI 1.07, 1.97), p for age trend = 0.002 and 8.07(95% CI 3.01, 21.66, p for age trend = <0.0001) for those aged 40 – 49 years, compared with those aged <30 years. Compared with the individuals in the lower socio-economic status, the PR for obesity among those in the middle and high socio-economic statuses, were 1.39 (95% CI 1.13, 1.72) and 1.24 (95% CI 0.97, 1.59) respectively, p for trend = 0.003. Conclusion: About two-thirds of urban, professional, high socio-economic status Nigerian adults are either overweight or obese. The prevalence of overweight and obesity among this population of adult Nigerians, is as high as it is in the United Kingdom. Female gender and older age were independent predictors of overweight and obesity; while middle or high socio-economic status were independently associated with obesity

H+ transport is an integral function of the mitochondrial ADP/ATP carrier.

The mitochondrial ADP/ATP carrier (AAC) is a major transport protein of the inner mitochondrial membrane. It exchanges mitochondrial ATP for cytosolic ADP and controls cellular production of ATP. In addition, it has been proposed that AAC mediates mitochondrial uncoupling, but it has proven difficult to demonstrate this function or to elucidate its mechanisms. Here we record AAC currents directly from inner mitochondrial membranes from various mouse tissues and identify two distinct transport modes: ADP/ATP exchange and H+ transport. The AAC-mediated H+ current requires free fatty acids and resembles the H+ leak via the thermogenic uncoupling protein 1 found in brown fat. The ADP/ATP exchange via AAC negatively regulates the H+ leak, but does not completely inhibit it. This suggests that the H+ leak and mitochondrial uncoupling could be dynamically controlled by cellular ATP demand and the rate of ADP/ATP exchange. By mediating two distinct transport modes, ADP/ATP exchange and H+ leak, AAC connects coupled (ATP production) and uncoupled (thermogenesis) energy conversion in mitochondria

Vitamin A and zinc supplementation among pregnant women to prevent placental malaria: a randomized, double-blind, placebo-controlled trial in Tanzania

BACKGROUND: Malaria causes nearly 200 million clinical cases and approximately half a million deaths each year, primarily in sub-Saharan Africa.1 The risk of malaria increases during pregnancy,2 a period during which its prevention is especially important. Not only do pregnant women experience greater severity of illness compared with nonpregnant women,2 but studies have shown strong associations between prenatal malaria and maternal anemia,2 fetal loss, low birthweight, and infant mortality.2 Improving preventive measures that specifically target malaria in pregnancy is a global health priority.3 METHODS: Study design and participants. This randomized, doubleblind, placebo-controlled trial was implemented at 8 antenatal care clinics in the urban Temeke and Ilala districts of Dar es Salaam, Tanzania. The trial was registered RESULTS: A total of 2,500 screened participants were enrolled in the trial. The trial profile is shown in Figure 1. It was not possible to collect placentas from 875 participants for the following reasons: miscarriages (fetal loss before 28 weeks of gestation) (N = 234), delivery outside of Dar es Salaam or at a non-study hospital (N = 577), or withdrawal from the study (N = 34). Of the remaining 1,589 women, 1,404 placental samples were obtained (88%); histology results were available for 1,361 participants. PCR results were available for 1,158 participants, and 1,404 participants had either histology or PCR results available. CONCLUSION: This study is the first to examine the impact of vitamin A and zinc supplementation starting in early pregnancy on placental malaria. We observed that supplementation with 25 mg zinc per day from the first trimester until delivery was associated with a 36% (95% CI = 9–56%) reduced risk of histopathology-positive placental infection, but not PCRpositive infection. Vitamin A supplementation had no impact on placental malaria, but was associated with an increased risk for severe anemia

Vitamins and Perinatal Outcomes Among HIV-Negative Women in Tanzania.

Prematurity and low birth weight are associated with high perinatal and infant mortality, especially in developing countries. Maternal micronutrient deficiencies may contribute to these adverse outcomes. In a double-blind trial in Dar es Salaam, Tanzania, we randomly assigned 8468 pregnant women (gestational age of fetus, 12 to 27 weeks) who were negative for human immunodeficiency virus infection to receive daily multivitamins (including multiples of the recommended dietary allowance) or placebo. All the women received prenatal supplemental iron and folic acid. The primary outcomes were low birth weight (<2500 g), prematurity, and fetal death. The incidence of low birth weight was 7.8% among the infants in the multivitamin group and 9.4% among those in the placebo group (relative risk, 0.82; 95% confidence interval [CI], 0.70 to 0.95; P=0.01). The mean difference in birth weight between the groups was modest (67 g, P<0.001). The rates of prematurity were 16.9% in the multivitamin group and 16.7% in the placebo group (relative risk, 1.01; 95% CI, 0.91 to 1.11; P=0.87), and the rates of fetal death were 4.3% and 5.0%, respectively (relative risk, 0.87; 95% CI, 0.72 to 1.05; P=0.15). Supplementation reduced both the risk of a birth size that was small for gestational age (<10th percentile; 10.7% in the multivitamin group vs. 13.6% in the placebo group; relative risk, 0.77; 95% CI, 0.68 to 0.87; P<0.001) and the risk of maternal anemia (hemoglobin level, <11 g per deciliter; relative risk, 0.88; 95% CI, 0.80 to 0.97; P=0.01), although the difference in the mean hemoglobin levels between the groups was small (0.2 g per deciliter, P<0.001). Multivitamin supplementation reduced the incidence of low birth weight and small-for-gestational-age births but had no significant effects on prematurity or fetal death. Multivitamins should be considered for all pregnant women in developing countries. (ClinicalTrials.gov number, NCT00197548 [ClinicalTrials.gov].)

Plasma 25-hydroxyvitamin D and risk of breast cancer in the Nurses' Health Study II

Introduction Experimental evidence indicates vitamin D may play an important role in breast cancer etiology but epidemiologic evidence to date is inconsistent. Vitamin D comes from dietary intake and sun exposure and plasma levels of 25-hydroxyvitamin D (25(OH)D) are considered the best measure of vitamin D status. Methods We conducted a prospective nested case-control study within the Nurses\u27 Health Study II (NHSII). Plasma samples collected in 1996 to 1999 were assayed for 25(OH)D in 613 cases, diagnosed after blood collection and before 1 June 2007, and in 1,218 matched controls. Multivariate relative risks (RR) and 95% confidence intervals (CI) were calculated by conditional logistic regression, adjusting for several breast cancer risk factors. Results No significant association was observed between plasma 25(OH)D levels and breast cancer risk (top vs. bottom quartile multivariate RR = 1.20, 95% CI (0.88 to 1.63), P-value, test for trend = 0.32). Results were similar when season-specific quartile cut points were used. Results did not change when restricted to women who were premenopausal at blood collection or premenopausal at diagnosis. Results were similar between estrogen receptor (ER)+/progesterone receptor (PR)+ and ER-/PR- tumors (P-value, test for heterogeneity = 0.51). The association did not vary by age at blood collection or season of blood collection, but did vary when stratified by body mass index (P-value, test for heterogeneity = 0.01). Conclusions Circulating 25(OH)D levels were not significantly associated with breast cancer risk in this predominantly premenopausal population