Approximate decoding for network coded inter-dependent data

In this paper, we consider decoding of loss tolerant data encoded by network coding and transmitted over error-prone networks. Intermediate network nodes typically perform the random linear network coding in a Galois field and a Gaussian elimination is used for decoding process in the terminal nodes. In such settings, conventional decoding approaches can unfortunately not reconstruct any encoded data unless they receive at least as many coded packets as the original number of packets. In this paper, we rather propose to exploit the incomplete data at a receiver without major modifications to the conventional decoding architecture. We study the problem of approximate decoding for inter-dependent sources where the difference between source vectors is characterized by a unimodal distribution. We propose a mode-based algorithm for approximate decoding, where the mode of the source data distribution is used to reconstruct source data. We further improve the mode-based approximate decoding algorithm by using additional short information that is referred to as position similarity information (PSI). We analytically study the impact of PSI size on the approximate decoding performance and show that the optimal size of PSI can be determined based on performance requirements of applications. The proposed approach has been tested in an illustrative example of data collection in sensor networks. The simulation results confirm the benefits of approximate decoding for inter-dependent sources and further show that 93.3% of decoding errors are eliminated when the approximate decoding uses appropriate PSI

Impact of school policies on non-communicable disease risk factors - a systematic review.

BACKGROUND: Globally, non-communicable diseases (NCDs) are identified as one of the leading causes of mortality. NCDs have several modifiable risk factors including unhealthy diet, physical inactivity, tobacco use and alcohol abuse. Schools provide ideal settings for health promotion, but the effectiveness of school policies in the reduction of risk factors for NCD is not clear. This study reviewed the literature on the impact of school policies on major NCD risk factors. METHODS: A systematic review was conducted to identify, collate and synthesize evidence on the effectiveness of school policies on reduction of NCD risk factors. A search strategy was developed to identify the relevant studies on effectiveness of NCD policies in schools for children between the age of 6 to 18 years in Ovid Medline, EMBASE, and Web of Science. Data extraction was conducted using pre-piloted forms. Studies included in the review were assessed for methodological quality using the Effective Public Health Practice Project (EPHPP) quality assessment tool. A narrative synthesis according to the types of outcomes was conducted to present the evidence on the effectiveness of school policies. RESULTS: Overall, 27 out of 2633 identified studies were included in the review. School policies were comparatively more effective in reducing unhealthy diet, tobacco use, physical inactivity and inflammatory biomarkers as opposed to anthropometric measures, overweight/obesity, and alcohol use. In total, for 103 outcomes independently evaluated within these studies, 48 outcomes (46%) had significant desirable changes when exposed to the school policies. Based on the quality assessment, 18 studies were categorized as weak, six as moderate and three as having strong methodological quality. CONCLUSION: Mixed findings were observed concerning effectiveness of school policies in reducing NCD risk factors. The findings demonstrate that schools can be a good setting for initiating positive changes in reducing NCD risk factors, but more research is required with long-term follow up to study the sustainability of such changes

Child obesity cut-offs as derived from parental perceptions: cross-sectional questionnaire.

BACKGROUND: Overweight children are at an increased risk of premature mortality and disease in adulthood. Parental perceptions and clinical definitions of child obesity differ, which may lessen the effectiveness of interventions to address obesity in the home setting. The extent to which parental and objective weight status cut-offs diverge has not been documented. AIM: To compare parental perceived and objectively derived assessment of underweight, healthy weight, and overweight in English children, and to identify sociodemographic characteristics that predict parental under- or overestimation of a child's weight status. DESIGN AND SETTING: Cross-sectional questionnaire completed by parents linked with objective measurement of height and weight by school nurses, in English children from five regions aged 4-5 and 10-11 years old. METHOD: Parental derived cut-offs for under- and overweight were derived from a multinomial model of parental classification of their own child's weight status against school nurse measured body mass index (BMI) centile. RESULTS: Measured BMI centile was matched with parent classification of weight status in 2976 children. Parents become more likely to classify their children as underweight when they are at the 0.8th centile or below, and overweight at the 99.7th centile or above. Parents were more likely to underestimate a child's weight if the child was black or South Asian, male, more deprived, or the child was older. These values differ greatly from the BMI centile cut-offs for underweight (2nd centile) and overweight (85th). CONCLUSION: Clinical and parental classifications of obesity are divergent at extremes of the weight spectrum

Scoping the impact of the national child measurement programme feedback on the child obesity pathway: study protocol.

BACKGROUND: The National Child Measurement Programme was established to measure the height and weight of children at primary school in England and provides parents with feedback about their child's weight status. In this study we will evaluate the impact of the National Child Measurement Programme feedback on parental risk perceptions of overweight, lifestyle behaviour and health service use. METHODS: The study will be a prospective cohort study of parents of children enrolled in the National Child Measurement Programme and key service providers from 5 primary care trusts (administrative bodies responsible for providing primary and secondary care services). We will conduct baseline questionnaires, followed by provision of weight feedback and 3 follow up questionnaires over the course of a year. Questionnaires will measure change in parental risk perception of overweight, health behaviours and health service use. Qualitative interviews will be used to identify barriers and facilitators to change. This study will produce preliminary data on National Health Service costs associated with weight feedback and determine which feedback approach (letter and letter plus telephone) is more effective. DISCUSSION: This study will provide the first large scale evaluation of the National Child Measurement Programme feedback. Findings from this evaluation will inform future planning of the National Child Measurement Programme.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

School policies, built environment and practices for non-communicable disease (NCD) prevention and control in schools of Delhi, India.

OBJECTIVE: To assess school policies, built environment and practices for prevention and control of non-communicable diseases in schools of Delhi, India. METHODS: School built environments and policies were assessed using a structured observation checklist in 10 private and 9 government schools which were randomly selected from all 184 co-educational schools with primary to senior secondary level education in Delhi, India. A self-administered questionnaire was also completed by teachers from each school (n = 19) to capture information specific to school policies. Surveys were also conducted with parent of students in class II (aged 6-7 years; n = 574) and student in class XI (aged 15-16 years, n = 755) to understand school practices. RESULTS: The majority of government (88.9%; n = 8) and private (80%; n = 8) schools reported having comprehensive school health policy. In terms of specific health behaviours, policies related to diet and nutrition in government schools were mostly restricted to primary levels with provision of the mid-day meal programme. All schools had two physical education periods per week of about 45-50 minutes. Most schools were compliant with tobacco-free school guidelines (n = 15 out of 19) and had alcohol control policies (n = 13 out of 19). Parent and student reports of practices indicated that school policies were not consistently implemented. CONCLUSION: Most schools in Delhi have policies that address health behaviours in students, but there was considerable variation in the types and number of policies and school environments. Government schools are more likely to have policies in place than private schools. Further work is needed to evaluate how these policies are implemented and to assess their impact on health outcomes