Asymptotically MDS Array BP-XOR Codes

Belief propagation or message passing on binary erasure channels (BEC) is a low complexity decoding algorithm that allows the recovery of message symbols based on bipartite graph prunning process. Recently, array XOR codes have attracted attention for storage systems due to their burst error recovery performance and easy arithmetic based on Exclusive OR (XOR)-only logic operations. Array BP-XOR codes are a subclass of array XOR codes that can be decoded using BP under BEC. Requiring the capability of BP-decodability in addition to Maximum Distance Separability (MDS) constraint on the code construction process is observed to put an upper bound on the maximum achievable code block length, which leads to the code construction process to become a harder problem. In this study, we introduce asymptotically MDS array BP-XOR codes that are alternative to exact MDS array BP-XOR codes to pave the way for easier code constructions while keeping the decoding complexity low with an asymptotically vanishing coding overhead. We finally provide and analyze a simple code construction method that is based on discrete geometry to fulfill the requirements of the class of asymptotically MDS array BP-XOR codes.Comment: 8 pages, 4 figures, to be submitte

Means-Tested Income Support, Portfolio Choice and Decumulation in Retirement

We investigate the impact of means tested public income transfers on post-retirement decumulation and portfolio choice using theoretical simulations and panel data on Australian Age Pensioners. Means tested public pension payments in Australia have broad coverage and give insight into the incentive responsiveness of well-off, as well as poorer households. Via numerical solutions to a discrete time, finite horizon dynamic programming problem, we simulate the optimal consumption and portfolio allocation strategies for a retired household subject to assets and income tests. Relative to benchmark, means tested households should optimally decumulate faster early in retirement, and choose more risky portfolios. Panel data tests on inferred wealth for pensioner households show evidence of more rapid spending early in retirement. However they also show that better-off households continue to accumulate, even when facing a steeper implicit tax rate on wealth than applies to poorer households. Wealthier households also hold riskier portfolios. Results from tests for Lorenz dominance of the panel wealth distribution show no decrease in wealth inequality over the five years of the study.retirement wealth; life-cycle saving; public pension; portfolio choice

Differences In Chronic Pain Prevalence Between Men And Women At Mid-Life: A Systematic Review Protocol

BACKGROUND: Epidemiological literature has revealed differences in chronic pain (CP) prevalence in men and women. Women have been found to be more likely to develop CP compared to men at different points of the life-course, such as childhood and old age. Less is known about differences in prevalence by sex during mid-life. While CP is most prevalent later in life, biological and physical changes in mid-life may predispose to an earlier differentiation in CP distribution – for example due to the menopause. The aim of this study is to describe the prevalence of CP at midlife in men and women, and to identify how these differences relate to results pertaining to other periods in the life-course. METHODS: This systematic review follows PRISMA guidelines. An electronic search will identify appropriate studies in the following databases: MEDLINE, to be accessed through Web of Science; and EMBASE, AMED and PSYCHinfo to be accessed through OVID. Two reviewers will independently screen each title and abstract and subsequently each full text following the inclusion criteria outlined in this protocol. The reference lists of eligible papers will also be screened to identify any further eligible studies. Any inconsistencies between reviewer decisions will be resolved through discussion. Studies eligible for data extraction will report estimates of CP prevalence, of prevalence for each sex, and difference in prevalence between sexes. Two reviewers will conduct data extraction using a standardised data extraction form. Quality assessment will be conducted using a risk of bias assessment tool for prevalence studies. The findings will be reported in a narrative synthesis and will comment on expected heterogeneity, following the Social Research Council Methods Programme guidelines. A random effects meta-analysis will be conducted where the reviewers can justify combining results. DISCUSSION: This review will summarise the prevalence of CP in men and women at mid-life, based on existing evidence. It is expected that the results will identify gaps in knowledge and areas for further research

Objectively measured physical capability levels and mortality: systematic review and meta-analysis

Objective: To do a quantitative systematic review, including published and unpublished data, examining the associations between individual objective measures of physical capability (grip strength, walking speed, chair rising, and standing balance times) and mortality in community dwelling populations. Design: Systematic review and meta-analysis. Data sources: Relevant studies published by May 2009 identified through literature searches using Embase (from 1980) and Medline (from 1950) and manual searching of reference lists; unpublished results were obtained from study investigators. Study selection: Eligible observational studies were those done in community dwelling people of any age that examined the association of at least one of the specified measures of physical capability (grip strength, walking speed, chair rises, or standing balance) with mortality. Data synthesis: Effect estimates obtained were pooled by using random effects meta-analysis models with heterogeneity between studies investigated. Results: Although heterogeneity was detected, consistent evidence was found of associations between all four measures of physical capability and mortality; those people who performed less well in these tests were found to be at higher risk of all cause mortality. For example, the summary hazard ratio for mortality comparing the weakest with the strongest quarter of grip strength (14 studies, 53 476 participants) was 1.67 (95% confidence interval 1.45 to 1.93) after adjustment for age, sex, and body size (I2=84.0%, 95% confidence interval 74% to 90%; P from Q statistic <0.001). The summary hazard ratio for mortality comparing the slowest with the fastest quarter of walking speed (five studies, 14 692 participants) was 2.87 (2.22 to 3.72) (I2=25.2%, 0% to 70%; P=0.25) after similar adjustments. Whereas studies of the associations of walking speed, chair rising, and standing balance with mortality have only been done in older populations (average age over 70 years), the association of grip strength with mortality was also found in younger populations (five studies had an average age under 60 years). Conclusions: Objective measures of physical capability are predictors of all cause mortality in older community dwelling populations. Such measures may therefore provide useful tools for identifying older people at higher risk of death. With Contributions from Dr P.A. Bath, University of Sheffiel

Is birthweight associated with total and aggressive/lethal prostate cancer risks? A systematic review and meta-analysis

BACKGROUND: It has been hypothesised that intrauterine exposures are important for subsequent prostate cancer risk. Prior epidemiological studies have used birthweight as a proxy of cumulative intrauterine exposures to test this hypothesis, but results have been inconsistent partly because of limited statistical power. METHODS: We investigated birthweight in relation to prostate cancer in the Medical Research Council (MRC) National Survey of Health and Development (NSHD) using Cox proportional hazards models. We then conducted a meta-analysis of birthweight in relation to total and aggressive/lethal prostate cancer risks, combining results from the NSHD analysis with 13 additional studies on this relationship identified from a systematic search in four major scientific literature databases through January 2015. RESULTS: Random-effects models found that per kg increase in birthweight was positively associated with total (OR=1.02, 95% confidence interval (95% CI)=1.00, 1.05; I(2)=13%) and aggressive/lethal prostate cancer (OR=1.08, 95% CI=0.99, 1.19; I(2)=40%). Sensitivity analyses restricted to studies with birthweight extracted from medical records demonstrated stronger positive associations with total (OR=1.11, 95% CI=1.03, 1.19; I(2)=0%) and aggressive/lethal (OR=1.37, 95% CI=1.09, 1.74; I(2)=0%) prostate cancer. These studies heavily overlapped with those based in Nordic countries. CONCLUSIONS: This study provides evidence that heavier birthweight may be associated with modest increased risks of total and aggressive/lethal prostate cancer, which supports the hypothesis that intrauterine exposures may be related to subsequent prostate cancer risks

Pubertal maturation and affective symptoms in adolescence and adulthood: evidence from a prospective birth cohort

The higher prevalence of affective symptoms among women compared to men emerges in adolescence, and it has been associated with pubertal maturation. However, it remains unclear whether pubertal timing has long-term influences on affective symptoms. Using data from the British 1946 birth cohort, we investigated whether pubertal timing was associated with affective symptoms over the life course, distinguishing those with symptoms in adolescence only, symptoms in adulthood only, and symptoms in both adolescence and adulthood. In females, there was no evidence that early pubertal maturation was a risk factor for affective symptoms. However, those with particularly late menarche (≥15 years) showed a lower risk of adult-onset affective symptoms (OR = 0.54, 95% CI: 0.31, 0.95). This effect of late pubertal timing was not explained by a range of socio-behavioural factors. In contrast, in males, late pubertal timing was associated with increased risk of adolescent-onset affective symptoms that tracked into adulthood (OR = 2.10, 95% CI: 1.44, 3.06). This effect was partly explained by low pre-pubertal BMI. Sex-specific effects of pubertal timing on the long-term risk of affective symptoms might be due to different effects of gonadal hormonal on the CNS, as well as different social experiences during puberty

Decline in Search Speed and Verbal Memory Over 26 Years of Midlife in a British Birth Cohort

BACKGROUND: Cognitive capabilities change in later life, although their onset and rate of decline, and how they are shaped by lifetime socioeconomic position, childhood cognition and adult health status are all unclear. METHODS: From the Medical Research Council National Survey of Health and Development, we analysed 3,192 participants undergoing one or more cognitive assessments at ages 43, 53, 60-64 and 69. Linear mixed models described cognitive trajectories, adjusting for factors across the life course. RESULTS: For both search speed and verbal memory, better performance at age 43 (the intercept) was associated with higher paternal and own education, childhood cognition, and adult occupational class. For search speed, the trajectory was best described as a quadratic function (decline of 45.6 letters/5-years + 4.6 letters). Verbal memory showed a linear decline of 0.20 words/5-years between ages 43 and 60 and a steeper linear decline of 0.95 words/5-years between ages 60 and 69. Decline in verbal memory in the latter period was steeper in those with higher educational achievements at age 26 (additional 0.28 words/5-years for highest attainment). CONCLUSIONS: Decline in verbal memory and search speed across midlife is evident, though with different non-linear trajectories. By implication, pathways to cognitive impairment and dementia in older age may have their origins in this period

Infant weight gain and adolescent body mass index: comparison across two British cohorts born in 1946 and 2001

Objective To investigate how the relationship of infant weight gain with adolescent body mass index (BMI) differs for individuals born during compared to before the obesity epidemic era. Design Data from two British birth cohorts, the 1946 National Survey of Health and Development (NSHD, n = 4,199) and the 2001 Millennium Cohort Study (MCS, n = 9,417), were used to estimate and compare associations of infant weight gain between ages 0-3 years with adolescent outcomes. Main outcome measures BMI Z-scores and overweight/ obesity at ages 11 and 14 years. Results Infant weight gain, in Z-scores, was positively associated with adolescent BMI Z-scores in both cohorts. Non-linearity in the MCS meant that associations were only stronger than in the NSHD when infant weight gain was above -1 Z-score. Using decomposition analysis, between-cohort differences in association accounted for 20-30% of the differences (secular increases) in BMI Z-scores, although the underlying estimates were not precise with 95% confidence intervals (CI) crossing zero. Conversely, between-cohort differences in the distribution of infant weight gain accounted for approximately 9% of the differences (secular increases) in BMI Z-scores, and the underlying estimates were precise with 95% CI not crossing zero. Relative to normal weight gain (change of -0.67 to +0.67 Z-scores between ages 0-3 years), very rapid infant weight gain (> 1.34), but not rapid weight gain (+0.67 to +1.34), was associated with higher BMI Z-scores more strongly in the MCS (β = 0.790; 95% CI = 0.717, 0.862 at age 11 years) than the NSHD (0.573; 0.466, 0.681); p < 0.001 for between-cohort difference. The relationship of slow infant weight gain (< -0.67) with lower adolescent BMI was also stronger in the MCS. Very rapid or slow infant weight gain were not, however, more strongly associated with increased risk of adolescent overweight/ obesity or thinness, respectively, in the more recently born cohort. Conclusions Greater infant weight gain, at the middle/ upper-end of the distribution, was more strongly associated with higher adolescent BMI among individuals born during (compared to before) the obesity epidemic. Combined with a secular change toward greater infant weight gain, these results suggest that there are likely to be associated negative consequences for population-level health and wellbeing in the future, unless effective interventions are developed and implemented