Stronger instruments and refined covariate balance in an observational study of the effectiveness of prompt admission to intensive care units

Instrumental variable methods, subject to appropriate identification assumptions, enable consistent estimation of causal effects in the presence of unobserved confounding. Near–far matching has been proposed as one analytic method to improve inference by strengthening the effect of the instrument on the exposure and balancing observable characteristics between groups of subjects with low and high values of the instrument. However, in settings with hierarchical data (e.g. patients nested within hospitals), or where several covariate interactions must be balanced, conventional near–far matching algorithms may fail to achieve the requisite covariate balance. We develop a new matching algorithm, that combines near–far matching with refined covariate balance, to balance large numbers of nominal covariates while also strengthening the instrumental variable. This extension of near–far matching is motivated by a case-study that aims to identify the causal effect of prompt admission to an intensive care unit on 7-day and 28-day mortality

Directionality as a Sequence Effect in Programmed Learning of a Verbal Concept

Thirty years ago Sidney Pressey (1926) published an article describing an apparatus for presenting multiple choice questions which gave the student immediate feedback regarding the correctness of his response to the questions. Although this device was intended to be a testing machine rather than a teaching machine , it is often generously designated the status of being the first teaching machine. Pressey\u27s machine had little impact upon the educational world and for a generation teaching machines were all but forgotten. In the 1950\u27s B.F. Skinner began the modern movement to automate education. Psychologists, but as noted by Bugeleki (1964, p. 208) not necessarily as psychologists have been largely responsible for the recent excitement about teaching machines

Potential utilisation of assessment centre methodology to enhance student placement outcomes, experiences and employability

Background: Placements are of particular importance due to the richness of learning associated with placement experiences and the wider links they represent to industry and the community. Students often refer to placements as the most significant, productive and memorable component of their training. Importantly, placements also provide the opportunity for students to become work ready, i.e., integrate their knowledge into a new set of employable skills and personal qualities. There is now increased emphasis on employability by employers and universities alike; in fact, it now represents a critical performance measure for Australian universities. Despite these key points, there appears to be inconsistencies in approaches to maximising work placements across and within Universities. Assessment centre methodology may represent a useful approach to standardise and optimise work placements for all stakeholders. Assessment centre methodology has been used successfully for selection purposes in industry for the past 50 years. However, their use as a developmental tool is less prominent. Furthermore, their application in the higher education setting, particularly in the context of placements and student development appears under researched.Overview of issue: Only one published study was found that reported the use of a developmental assessment centre with a post-graduate sample. That study took place over 10 years ago when the concept of employability was still gaining recognition and work placements were less common. The current paper reviews this unique concept in the context of the existing literature and the current needs of Universities, employers and students.Discussion: It is argued that the reconsideration of assessment centre methodology for development represents an innovative approach to consistently maximising work placement outcomes, experiences and employability.Conclusions: Given the importance and increased use of placements, the application of assessment centre methodology within the placement curriculum warrants further research. This methodology represents a standardised approach for implementation within a range of placement programs to enhance student development, placement outcomes and employability.<br /

Evaluation methodology for work integrated learning - placements : a discussion paper

Background: This paper will address the evaluation of WIL (placements) in order to provide a strategy to improve performance in universities\u27 WIL as benchmarked in the AUSSE, GDS and placement unit feedback.Overview of issue: Although WIL placements are important and valuable for student engagement, learning, graduate employability and industry partnerships, there are few empirical studies or reviews that inform evaluation methodology for them. The assessment of placement outcomes and the student experience is typically more complex than evaluation of a standard university unit because of the wide variation that occurs with placements. Students are likely to be working in different organisations, and working on different projects within their various disciplines. Adding to this complexity, the organisation supervisor is an additional stakeholder critical to the placement experience, and who ultimately makes the judgment of student performance. Although an organisation supervisor may complete an individual feedback form for their students, generally this information is not strategically aligned within a broader university evaluation process. Initial examination of available literature revealed that the multi-dimensional perspective (organisational supervisor, placement co-ordinator and student) is not usually incorporated into evaluation of placements to inform continuous improvement for example. There are gaps in the evaluation process which could be addressed through more&nbsp; comprehensive evaluation that could be utilised across Faculties and Institutions. In 2010, we will conduct an inter-faculty project to develop and trial an evaluation methodology for WIL placements. It will incorporate a triangulated approach including student, organisation and university supervisor feedback. Preliminary results gained from this project will be discussed.Argument: An evaluation methodology that is inclusive of a triangulated approach, would provide university stakeholders with comprehensive feedback that could be used to strategically inform continuous improvement efforts in Institutions in the areas of WIL placements.Implications: The importance of triangulated data gathering leading to a comprehensive evaluation and subsequent improvement strategies will be concluded. Suggested evaluation process and potential tools will be presented.<br /

A Bayesian model selection approach to mediation analysis.

Genetic studies often seek to establish a causal chain of events originating from genetic variation through to molecular and clinical phenotypes. When multiple phenotypes share a common genetic association, one phenotype may act as an intermediate for the genetic effects on the other. Alternatively, the phenotypes may be causally unrelated but share genetic loci. Mediation analysis represents a class of causal inference approaches used to determine which of these scenarios is most plausible. We have developed a general approach to mediation analysis based on Bayesian model selection and have implemented it in an R package, bmediatR. Bayesian model selection provides a flexible framework that can be tailored to different analyses. Our approach can incorporate prior information about the likelihood of models and the strength of causal effects. It can also accommodate multiple genetic variants or multi-state haplotypes. Our approach reports posterior probabilities that can be useful in interpreting uncertainty among competing models. We compared bmediatR with other popular methods, including the Sobel test, Mendelian randomization, and Bayesian network analysis using simulated data. We found that bmediatR performed as well or better than these alternatives in most scenarios. We applied bmediatR to proteome data from Diversity Outbred (DO) mice, a multi-parent population, and demonstrate the power of mediation with multi-state haplotypes. We also applied bmediatR to data from human cell lines to identify transcripts that are mediated through or are expressed independently from local chromatin accessibility. We demonstrate that Bayesian model selection provides a powerful and versatile approach to identify causal relationships in genetic studies using model organism or human data

Mapping the complete glycoproteome of virion-derived HIV-1 gp120 provides insights into broadly neutralizing antibody binding

The surface envelope glycoprotein (SU) of Human immunodeficiency virus type 1 (HIV-1), gp120SU plays an essential role in virus binding to target CD4+ T-cells and is a major vaccine target. Gp120 has remarkably high levels of N-linked glycosylation and there is considerable evidence that this “glycan shield” can help protect the virus from antibody-mediated neutralization. In recent years, however, it has become clear that gp120 glycosylation can also be included in the targets of recognition by some of the most potent broadly neutralizing antibodies. Knowing the site-specific glycosylation of gp120 can facilitate the rational design of glycopeptide antigens for HIV vaccine development. While most prior studies have focused on glycan analysis of recombinant forms of gp120, here we report the first systematic glycosylation site analysis of gp120 derived from virions produced by infected T lymphoid cells and show that a single site is exclusively substituted with complex glycans. These results should help guide the design of vaccine immunogens

Tracing a Disk Wind in NGC 3516

X-ray spectra of AGN often contain signatures indicative of absorption in multiple layers of gas whose ionization-state and covering fraction may vary with time. It has been unclear to date how much of the observed X-ray spectral and timing behavior in AGN can be attributed to variations in absorption, versus variations in the strengths of emission or reflection components. Diagnostics of the inner regions of AGN cannot be reliably performed until the origin of observed effects is understood. We investigate the role of the X-ray absorbers in the Seyfert 1 galaxy NGC 3516. Time-averaged and flux-selected spectroscopy is used to examine the behavior of NGC 3516 observed in Chandra HETG and XMM data from Oct 2006. New H-like and He-like emission and absorption features discovered in the Fe K regime reveal a previously unknown zone of circumnuclear gas in NGC 3516 with log xi ~ 4.3 and column density 1E23 cm^-2. A lower-ionization layer with log xi ~2 and of similar column density is confirmed from previous observations, this layer has a covering fraction around 50%, and changes in covering provide a simple explanation of a deep dip in the light curve that we interpret as an eclipse of the continuum due to passage of a cloud across the sight line within half a day. These inner zones of absorbing gas are detected to have outflow velocities in the range 1000-2000 km/s, this, and constraints on radial location are consistent with an origin as part of a disk wind in NGC 3516.Comment: 10 pages, 8 figures, accepted by A&A Feb 26 2008 Version 2: Figs 1 & 2 were corrected for a problem with ACIS section of the data. Little impact on text of the pape

Factors Associated with the Diversification of the Gut Microbial Communities within Chimpanzees from Gombe National Park.

The gastrointestinal tract harbors large and diverse populations of bacteria that vary among individuals and within individuals over time. Numerous internal and external factors can influence the contents of these microbial communities, including diet, geography, physiology, and the extent of contact among hosts. To investigate the contributions of such factors to the variation and changes in gut microbial communities, we analyzed the distal gut microbiota of individual chimpanzees from two communities in Gombe National Park, Tanzania. These samples, which were derived from 35 chimpanzees, many of whom have been monitored for multiple years, provide an unusually comprehensive longitudinal depth for individuals of known genetic relationships. Although the composition of the great-ape microbiota has been shown to codiversify with host species, indicating that host genetics and phylogeny have played a major role in its differentiation over evolutionary timescales, the geneaological relationships of individual chimpanzees did not coincide with the similarity in their gut microbial communities. However, the inhabitants from adjacent chimpanzee communities could be distinguished based on the contents of their gut microbiota. Despite the broad similarity of community members, as would be expected from shared diet or interactions, long-term immigrants to a community often harbored the most distinctive gut microbiota, suggesting that individuals retain hallmarks of their previous gut microbial communities for extended periods. This pattern was reinforced in several chimpanzees sampled over long temporal scales, in which the major constituents of the gut microbiota were maintained for nearly a decade