Advancements in latent space network modelling

The ubiquity of relational data has motivated an extensive literature on network analysis, and over the last two decades the latent space approach has become a popular network modelling framework. In this approach, the nodes of a network are represented in a low-dimensional latent space and the probability of interactions occurring are modelled as a function of the associated latent coordinates. This thesis focuses on computational and modelling aspects of the latent space approach, and we present two main contributions. First, we consider estimation of temporally evolving latent space networks in which interactions among a fixed population are observed through time. The latent coordinates of each node evolve other time and this presents a natural setting for the application of sequential monte carlo (SMC) methods. This facilitates online inference which allows estimation for dynamic networks in which the number of observations in time is large. Since the performance of SMC methods degrades as the dimension of the latent state space increases, we explore the high-dimensional SMC literature to allow estimation of networks with a larger number of nodes. Second, we develop a latent space model for network data in which the interactions occur between sets of the population and, as a motivating example, we consider a coauthorship network in which it is typical for more than two authors to contribute to an article. This type of data can be represented as a hypergraph, and we extend the latent space framework to this setting. Modelling the nodes in a latent space provides a convenient visualisation of the data and allows properties to be imposed on the hypergraph relationships. We develop a parsimonious model with a computationally convenient likelihood. Furthermore, we theoretically consider the properties of the degree distribution of our model and further explore its properties via simulation

An examination of social workers\u27 knowledge of Family Preservation Services in child welfare

The purpose of the study was to determine how knowledgeable the San Bernardino County Department of Children\u27s Services (DCS) social workers were about Family Preservation Services has been to determine if that intervention works to alleviate out-of-home placements

Behavioral sleep problems and their potential impact on developing executive function in children

Bedtime resistance and night waking are common sleep problems throughout childhood, especially in the early years. These sleep problems may lead to difficulties in neurobehavioral functioning, but most research into childhood sleep problems has not emphasized the importance of the developmental context in which disruptions in neurobehavioral and daytime functioning occur. We review the development of sleep as well as executive functioning (EF) in childhood and suggest that EF may be particularly vulnerable to the effects of these common childhood sleep problems because of its prolonged course of maturation. Behavioral problems associated with common sleep problems suggest poor self-regulation in the context of sleep loss, and developing EF skills play important roles in self-regulation. A research agenda that considers a developmental approach to sleep and sleep problems in the context of childhood EF performance is outlined to promote future research in this area

Sleep Restriction in Children and Executive Function Performance

Experimental sleep restriction yields data that shows how sleep loss causes declining daytime function in cognition and behaviour, yet few experimental studies have been conducted with preschool children between the ages of 3 and 5 years of age. During the preschool period children achieve important milestones in cognitive development while a significant minority also experience behavioural sleep problems regularly. There is no empirically-based consensus on the impact of reduced sleep in preschool children. To address this gap, parents of preschool children were recruited in a participatory design study to provide input in designing an accessible home-based experimental sleep study with conditions of sleep restriction and sleep fragmentation. Child participants in the experimental study wore actigraphs for 10 days to record their sleep during 7 days of baseline measurement, followed by 3 days of experimental measurement. Children were randomly assigned to a control condition, a 40-minute or 20-minute sleep restriction condition, or to a sleep fragmentation condition where they were kept awake for 20 minutes after first falling asleep. Daytime cognitive outcomes were assessed after the third experimental night using an assessment battery of developmentally-appropriate executive function measures of working memory, response inhibition, and delay of gratification. Contrary to expectation, less sleep relative to baseline was not associated with measured executive function performance decrements among children without pre-existing sleep problems. Experimentally imposing greater sleep restriction before assessment may be necessary to measure changes in executive functioning measures for this age group

Juxta-membrane S-acylation of plant receptor-like kinases is likely fortuitous and does not necessarily impact upon function

This work was funded by UK Biotechnology and Biological Sciences Research Council Grants BB/M024911/1 and BB/M010996/1 to P.A.H.S-acylation is a common post-translational modification of membrane protein cysteine residues with many regulatory roles. S-acylation adjacent to transmembrane domains has been described in the literature as affecting diverse protein properties including turnover, trafficking and microdomain partitioning. However, all of these data are derived from mammalian and yeast systems. Here we examine the role of S-acylation adjacent to the transmembrane domain of the plant pathogen perceiving receptor-like kinase FLS2. Surprisingly, S-acylation of FLS2 adjacent to the transmembrane domain is not required for either FLS2 trafficking or signalling function. Expanding this analysis to the wider plant receptor-like kinase family we find that S-acylation adjacent to receptor-like kinase domains is common, affecting ~25% of Arabidopsis receptor-like kinases, but poorly conserved between orthologues through evolution. This suggests that S-acylation of receptor-like kinases at this site is likely the result of chance mutation leading to cysteine occurrence. As transmembrane domains followed by cysteine residues are common motifs for S-acylation to occur, and many S-acyl transferases appear to have lax substrate specificity, we propose that many receptor-like kinases are fortuitously S-acylated once chance mutation has introduced a cysteine at this site. Interestingly some receptor-like kinases show conservation of S-acylation sites between orthologues suggesting that S-acylation has come to play a role and has been positively selected for during evolution. The most notable example of this is in the ERECTA-like family where S-acylation of ERECTA adjacent to the transmembrane domain occurs in all ERECTA orthologues but not in the parental ERECTA-like clade. This suggests that ERECTA S-acylation occurred when ERECTA emerged during the evolution of angiosperms and may have contributed to the neo-functionalisation of ERECTA from ERECTA-like proteins.Publisher PDFPeer reviewe