Bayesian comparison of latent variable models: Conditional vs marginal likelihoods

Typical Bayesian methods for models with latent variables (or random effects) involve directly sampling the latent variables along with the model parameters. In high-level software code for model definitions (using, e.g., BUGS, JAGS, Stan), the likelihood is therefore specified as conditional on the latent variables. This can lead researchers to perform model comparisons via conditional likelihoods, where the latent variables are considered model parameters. In other settings, however, typical model comparisons involve marginal likelihoods where the latent variables are integrated out. This distinction is often overlooked despite the fact that it can have a large impact on the comparisons of interest. In this paper, we clarify and illustrate these issues, focusing on the comparison of conditional and marginal Deviance Information Criteria (DICs) and Watanabe-Akaike Information Criteria (WAICs) in psychometric modeling. The conditional/marginal distinction corresponds to whether the model should be predictive for the clusters that are in the data or for new clusters (where "clusters" typically correspond to higher-level units like people or schools). Correspondingly, we show that marginal WAIC corresponds to leave-one-cluster out (LOcO) cross-validation, whereas conditional WAIC corresponds to leave-one-unit out (LOuO). These results lead to recommendations on the general application of the criteria to models with latent variables.Comment: Manuscript in press at Psychometrika; 31 pages, 8 figure

Long-term impacts of parental migration on Chinese children’s psychosocial well-being: mitigating and exacerbating factors

PURPOSE: Prolonged separation from migrant parents raises concerns for the well-being of 60 million left behind children (LBC) in rural China. This study aimed to investigate the impact of current and previous parental migration on child psychosocial well-being, with a focus on emotional and behavioral outcomes, while considering factors in family care and support. METHODS: Children were recruited from schools in migrant-sending rural areas in Zhejiang and Guizhou provinces by random stratified sampling. A self-administered questionnaire measured children’s psychosocial well-being, demographics, household characteristics, and social support. Multiple linear regression models examined the effects of parental migration and other factors on psychosocial difficulties. RESULTS: Data from 1930 current, 907 previous, and 701 never LBC were included (mean age 12.4, SD 2.1). Adjusted models showed both previous and current parental migration was associated with significantly higher overall psychosocial difficulties, involving aspects of emotion, conduct, peer relationships, hyperactivity, and pro-social behaviors. Parental divorce and lack of available support demonstrated a strong association with greater total difficulties. While children in Guizhou had much worse psychosocial outcomes than those in Zhejiang, adjusted subgroup analysis showed similar magnitude of between-province disparities regardless of parental migration status. However, having divorced parents and lack of support were greater psychosocial risk factors for current and previous-LBC than for never LBC. CONCLUSIONS: Parental migration has an independent, long-lasting adverse effect on children. Psychosocial well-being of LBC depends more on the relationship bonds between nuclear family members and the availability of support, rather than socioeconomic status

Algae Derived Biofuel

One of the most promising fuel alternatives is algae biodiesel. Algae reproduce quickly, produce oils more efficiently than crop plants, and require relatively few nutrients for growth. These nutrients can potentially be derived from inexpensive waste sources such as flue gas and wastewater, providing a mutual benefit of helping to mitigate carbon dioxide waste. Algae can also be grown on land unsuitable for agricultural purposes, eliminating competition with food sources. This project focused on cultivating select algae species under various environmental conditions to optimize oil yield. Membrane studies were also conducted to transfer carbon di-oxide more efficiently. An LCA study was also conducted to investigate the energy intensive steps in algae cultivation

Inter-individual variation in nucleotide excision repair in young adults: effects of age, adiposity, micronutrient supplementation and genotype

Nucleotide excision repair (NER) is responsible for repairing bulky helix-distorting DNA lesions and is essential for the maintenance of genomic integrity. Severe hereditary impairment of NER leads to cancers such as those in xeroderma pigmentosum, and more moderate reductions in NER capacity have been associated with an increased cancer risk. Diet is a proven modifier of cancer risk but few studies have investigated the potential relationships between diet and NER. In the present study, the plasmid-based host cell reactivation assay was used to measure the NER capacity in peripheral blood mononuclear cells from fifty-seven volunteers aged 18–30 years before and after 6 weeks of supplementation with micronutrients (selenium and vitamins A, C and E). As a control, nine individuals remained unsupplemented over the same period. Volunteers were genotyped for the following polymorphisms in NER genes: ERCC5 Asp1104His (rs17655); XPC Lys939Gln (rs2228001); ERCC2 Lys751Gnl (rs13181); XPC PAT (an 83 bp poly A/T insertion–deletion polymorphism in the XPC gene). NER capacity varied 11-fold between individuals and was inversely associated with age and endogenous DNA strand breaks. For the first time, we observed an inverse association between adiposity and NER. No single polymorphism was associated with the NER capacity, although significant gene–gene interactions were observed between XPC Lys939Gln and ERCC5 Asp1104His and XPC Lys939Gln and ERCC2 Lys751Gnl. While there was no detectable effect of micronutrient supplementation on NER capacity, there was evidence that the effect of fruit intake on the NER capacity may be modulated by the ERCC2 Lys751Gnl single nucleotide polymorphism

Expression profiling indicating low selenium-sensitive microRNA levels linked to cell cycle and cell stress response pathways in the CaCo-2 cell line

Se is an essential micronutrient for human health, and fluctuations in Se levels and the potential cellular dysfunction associated with it may increase the risk for disease. Although Se has been shown to influence several biological pathways important in health, little is known about the effect of Se on the expression of microRNA (miRNA) molecules regulating these pathways. To explore the potential role of Se-sensitive miRNA in regulating pathways linked with colon cancer, we profiled the expression of 800 miRNA in the CaCo-2 human adenocarcinoma cell line in response to a low-Se (72 h at <40 nm) environment using nCounter direct quantification. These data were then examined using a range of in silico databases to identify experimentally validated miRNA-mRNA interactions and the biological pathways involved. We identified ten Se-sensitive miRNA (hsa-miR-93-5p, hsa-miR-106a-5p, hsa-miR-205-5p, hsa-miR-200c-3p, hsa-miR-99b-5p, hsa-miR-302d-3p, hsa-miR-373-3p, hsa-miR-483-3p, hsa-miR-512-5p and hsa-miR-4454), which regulate 3588 mRNA in key pathways such as the cell cycle, the cellular response to stress, and the canonical Wnt/β-catenin, p53 and ERK/MAPK signalling pathways. Our data show that the effects of low Se on biological pathways may, in part, be due to these ten Se-sensitive miRNA. Dysregulation of the cell cycle and of the stress response pathways due to low Se may influence key genes involved in carcinogenesis

A parent focused child obesity prevention intervention improves some mother obesity risk behaviors : the Melbourne infant program

BackgroundThe diets, physical activity and sedentary behavior levels of both children and adults in Australia are suboptimal. The family environment, as the first ecological niche of children, exerts an important influence on the onset of children\u27s habits. Parent modeling is one part of this environment and a logical focus for child obesity prevention initiatives. The focus on parent\u27s own behaviors provides a potential opportunity to decrease obesity risk behaviors in parents as well.ObjectiveTo assess the effect of a parent-focused early childhood obesity prevention intervention on first-time mothers\u27 diets, physical activity and TV viewing time.MethodsThe Melbourne InFANT Program is a cluster-randomized controlled trial which involved 542 mothers over their newborn\u27s first 18 months of life. The intervention focused on parenting skills and strategies, including parental modeling, and aimed to promote development of healthy child and parent behaviors from birth, including healthy diet, increased physical activity and reduced TV viewing time. Data regarding mothers\u27 diet (food frequency questionnaire), physical activity and TV viewing times (self-reported questionnaire) were collected using validated tools at both baseline and post-intervention. Four dietary patterns were derived at baseline using principal components analyses including frequencies of 55 food groups. Analysis of covariance was used to measure the impact of the intervention.ResultsThe scores of both the &quot;High-energy snack and processed foods&quot; and the &quot;High-fat foods&quot; dietary patterns decreased more in the intervention group: -0.22 ([MINUS SIGN]0.42;-0.02) and [MINUS SIGN]0.25 ([MINUS SIGN]0.50;-0.01), respectively. No other significant intervention vs. control effects were observed regarding total physical activity, TV viewing time, and the two other dietary patterns, i.e. &quot;Fruits and vegetables&quot; and &quot;Cereals and sweet foods&quot;.ConclusionsThese findings suggest that supporting first-time mothers to promote healthy lifestyle behaviors in their infants impacts maternal dietary intakes positively. Further research needs to assess ways in which we might further enhance those lifestyle behaviors not impacted by the InFANT intervention

Co-design and content validity of the movement measurement in the early years (MoveMEY) tool for assessing movement behaviour of pre-school aged children

Abstract Background Movement behaviours (physical activity, sedentary behaviour, and sleep) are important for pre-school children’s health and development. Currently, no tools with appropriate content validity exist that concurrently capture these movement behaviours in young children. The aim of this study was to co-design and assess the content validity of a novel tool to concurrently measure movement behaviours in pre-school aged children (aged 3–4 years). Methods We followed four distinct steps to develop and assess the content validity of Movement Measurement in the Early Years (MoveMEY): (1) We conducted an extensive literature search, to identify pre-existing proxy measurement tools (questionnaires and diaries) to inform the design of a novel tool, which aimed to effectively capture movement behaviour guidelines of pre-school aged children. (2) We facilitated focus group discussions with parents and carers of pre-school aged children (n = 11) and (3) a qualitative survey with free text responses was completed by topic relevant researchers (n = 6), to co-design the measurement tool. (4) We assessed the content validity of the developed tool, MoveMEY, through interviews with parents of pre-school aged children (n = 12) following piloting of the tool. Results We developed an initial version of MoveMEY based on the format of an existing questionnaire and by mapping the content of questions to the guidelines. Co-design of MoveMEY resulted in changes to the format (e.g. short questionnaire to a seven-day diary) and content (e.g. inclusion of ‘general information’ questions on illness, disabilities and sleep disturbances; question on screen time before bed). Content validity assessment demonstrated that the items of MoveMEY were relevant and comprehensive for the assessment of children’s movement behaviours. MoveMEY was felt to be comprehensible, however, parental suggestions were implemented to finalise and improve MoveMEY (e.g. adding examples to questions aiming to detect moderate to vigorous physical activity). Conclusion MoveMEY is the first co-designed measurement tool that has relevance for assessing the movement behaviour guidelines of pre-school aged children. Parent/carer and topic relevant researcher involvement throughout the development process resulted in a seven-day daily reported activity diary that is comprehensive of children’s movement behaviours and comprehensible to parents and carers

Mediators of improved child diet quality following a health promotion intervention: the Melbourne InFANT program

BACKGROUND: Young children’s diets are currently suboptimal. Given that mothers have a critical influence on children’ diets, they are typically a target of interventions to improve early childhood nutrition. Understanding the maternal factors which mediate an intervention’s effect on young children’s diets is important, but has not been well investigated. This research aimed to test whether maternal feeding knowledge, maternal feeding practices, maternal self-efficacy, and maternal dietary intakes acted as mediators of the effect of an intervention to improve child diet quality. METHODS: The Melbourne Infant Feeding Activity and Nutrition Trial (InFANT) Program was a cluster-randomized controlled trial, conducted from 2008–2010. This novel, low-dose, health promotion intervention was delivered quarterly over 15 months and involved educational activities, promotion of peer discussion, a DVD and written materials. Post-intervention, when children were approximately 18 months of age, child diets were assessed using multiple 24-hour recalls and a purpose-developed index of diet quality, the Obesity Protective Dietary Index. Maternal mediators were assessed using a combination of previously validated and purpose-deigned tools. Mediation analysis was conducted using the test of joint significance and difference of coefficients methods. RESULTS: Across 62 parents’ groups in Melbourne, Australia, 542 parents were recruited. Post- intervention, higher maternal feeding knowledge and lower use of foods as rewards was found to mediate the direct intervention effect on child diet quality. While other aspects of maternal feeding practices, self-efficacy and dietary intakes did not act as mediators, they were associated with child diet quality. CONCLUSIONS: Mediation analysis of this novel health promotion intervention showed the importance of maternal feeding knowledge and use of foods as rewards in impacting child diet quality. The other maternal factors assessed were appropriate targets but further research on how to impact these in an intervention is important. This evidence of intervention efficacy and mediation provides important insights for planning future interventions. TRIAL REGISTRATION: Current Controlled Trials ISRCTN81847050, registered 23 November 2007. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12966-014-0137-5) contains supplementary material, which is available to authorized users

A Solidarity Machine? Hong Kong Labour NGOs in Guangdong

Although the literature on labour NGOs (LNGOs) in China has significantly expanded, few scholars have attempted to subject the work of these organizations to a Marxist perspective. This article draws on a recently developed Marxian theoretical framework on social movements to analyse the pioneering work of Hong Kong LNGOs and their partners in the province of Guangdong, China. Over the past 15 years, the Hong Kong groups, as they are known collectively, have been ideally placed to develop specific interventions in response to migrant workers’ pursuance of wage claims and improved working conditions during a time of increased rights awareness and widespread labour shortages. While consistently careful to remain the right side of China’s restrictive laws on freedom of association and demonstrations, the Hong Kong LNGOs were able to contribute to a narrative of class-based collective solidarity that has yielded significant gains for workers