Introduction to the Symposium: Causal Inference and Public Health

Assessing the extent to which public health research findings can be causally interpreted continues to be a critical endeavor. In this symposium, we invited several researchers to review issues related to causal inference in social epidemiology and environmental science and to discuss the importance of external validity in public health. Together, this set of articles provides an integral overview of the strengths and limitations of applying causal inference frameworks and related approaches to a variety of public health problems, for both internal and external validity

Utah geothermal commercialization planning. Semi-annual progress report, January 1, 1979--June 30, 1979

The effects of the Utah geothermal planning project were concentrated on the Utah geothermal legislation, the Roosevelt Hot Springs time phased project plan and the Salt Lake County area development plan. Preliminary findings indicate a potential for heat pump utilization, based on market interest and the existence of suitable groundwater conditions. (MHR

“This Place Is Going to Burn”: Measuring Prison Climate in Three Facilities

Despite the common adage that prison facilities often carry a unique mark of the “warden’s world,” few studies have compared characteristics among individual facilities over time. This study utilizes two waves of prison surveys (N = 525) that produce markers of perceived prison climate at the facility level; contributions fill three voids in correctional literature: facility-level comparison of prison climate; interactions of institutional characteristics; and predictors of change over time. Research is conducted within three facilities in one U.S. Midwest state, utilizing social climate instruments (primarily EssenCES) established internationally. Three main findings result: First, facilities-as-place share commonalities but also exert distinguishable and independent effects on perceived livability. Second, the study confirms several metrics that exert influence on livability, including staff support, inmate support, and inmate threat. Third, statistical models capture climate change over time and identify significant predictors, including measures of support, threat, and “assurance” (sense of belonging and purpose). Four regression models consistently capture meaningful change during a particularly volatile state-wide environment, with each facility responding somewhat differently. The authors suggest that measures of prison climate over time may indicate a conceptual tensile strength, or potential breaking point, in institutional stability

Critical exponents in Ising spin glasses

We determine accurate values of ordering temperatures and critical exponents for Ising Spin Glass transitions in dimension 4, using a combination of finite size scaling and non-equilibrium scaling techniques. We find that the exponents $\eta$ and $z$ vary with the form of the interaction distribution, indicating non-universality at Ising spin glass transitions. These results confirm conclusions drawn from numerical data for dimension 3.Comment: 6 pages, RevTeX (or Latex, etc), 10 figures, Submitted to PR

Finding the complement of the invariant manifolds transverse to a given foliation for a 3D flow

A method is presented to establish regions of phase space for 3D vector fields through which pass no co-oriented invariant 2D submanifolds transverse to a given oriented 1D foliation. Refinements are given for the cases of volume-preserving or Cartan-Arnol’d Hamiltonian flows and for boundaryless submanifolds

A luciferase-based approach for measuring HBGA blockade antibody titers against human norovirus

Background: Noroviruses are the most common cause of viral gastroenteritis worldwide, yet there is a deficit in the understanding of protective immunity. Surrogate neutralization assays have been widely used that measure the ability of antibodies to block virus-like particle (VLP) binding to histo-blood group antigens (HBGAs). However, screening large sample sets against multiple antigens using the traditional HBGA blocking assay requires significant investment in terms of time, equipment, and technical expertise, largely associated with the generation of purified VLPs. Methods: To address these issues, a luciferase immunoprecipitation system (LIPS) assay was modified to measure the norovirus-specific HBGA blockade activity of antibodies. The assay (designated LIPS-Blockade) was validated using a panel of well-characterized homotypic and heterotypic hyperimmune sera as well as strain-specific HBGA blocking monoclonal antibodies. Results: The LIPS-Blockade assay was comparable in specificity to a standard HBGA blocking protocol performed with VLPs. Using time-ordered patient sera, the luciferase-based approach was also able to detect changes in HBGA blocking titers following viral challenge and natural infection with norovirus. Conclusion: In this study we developed a rapid, robust, and scalable surrogate neutralization assay for noroviruses that circumvented the need for purified VLPs. This LIPS-Blockade assay should streamline the process of large-scale immunological studies, ultimately aiding in the characterization of protective immunity to human noroviruses

Using Hierarchical Centering to Facilitate a Reversible Jump MCMC Algorithm for Random Effects Models

The first author was supported by a studentship jointly funded by the University of St Andrews and EPSRC, through the National Centre for Statistical Ecology (EPSRC grant EP/C522702/1), with subsequent funding from EPSRC/NERC grant EP/I000917/1.Hierarchical centering has been described as a reparameterization method applicable to random effects models. It has been shown to improve mixing of models in the context of Markov chain Monte Carlo (MCMC) methods. A hierarchical centering approach is proposed for reversible jump MCMC (RJMCMC) chains which builds upon the hierarchical centering methods for MCMC chains and uses them to reparameterize models in an RJMCMC algorithm. Although these methods may be applicable to models with other error distributions, the case is described for a log-linear Poisson model where the expected value λλ includes fixed effect covariates and a random effect for which normality is assumed with a zero-mean and unknown standard deviation. For the proposed RJMCMC algorithm including hierarchical centering, the models are reparameterized by modelling the mean of the random effect coefficients as a function of the intercept of the λλ model and one or more of the available fixed effect covariates depending on the model. The method is appropriate when fixed-effect covariates are constant within random effect groups. This has an effect on the dynamics of the RJMCMC algorithm and improves model mixing. The methods are applied to a case study of point transects of indigo buntings where, without hierarchical centering, the RJMCMC algorithm had poor mixing and the estimated posterior distribution depended on the starting model. With hierarchical centering on the other hand, the chain moved freely over model and parameter space. These results are confirmed with a simulation study. Hence, the proposed methods should be considered as a regular strategy for implementing models with random effects in RJMCMC algorithms; they facilitate convergence of these algorithms and help avoid false inference on model parameters.PostprintPeer reviewe

A Quantitative Model of Energy Release and Heating by Time-dependent, Localized Reconnection in a Flare with a Thermal Loop-top X-ray Source

We present a quantitative model of the magnetic energy stored and then released through magnetic reconnection for a flare on 26 Feb 2004. This flare, well observed by RHESSI and TRACE, shows evidence of non-thermal electrons only for a brief, early phase. Throughout the main period of energy release there is a super-hot (T>30 MK) plasma emitting thermal bremsstrahlung atop the flare loops. Our model describes the heating and compression of such a source by localized, transient magnetic reconnection. It is a three-dimensional generalization of the Petschek model whereby Alfven-speed retraction following reconnection drives supersonic inflows parallel to the field lines, which form shocks heating, compressing, and confining a loop-top plasma plug. The confining inflows provide longer life than a freely-expanding or conductively-cooling plasma of similar size and temperature. Superposition of successive transient episodes of localized reconnection across a current sheet produces an apparently persistent, localized source of high-temperature emission. The temperature of the source decreases smoothly on a time scale consistent with observations, far longer than the cooling time of a single plug. Built from a disordered collection of small plugs, the source need not have the coherent jet-like structure predicted by steady-state reconnection models. This new model predicts temperatures and emission measure consistent with the observations of 26 Feb 2004. Furthermore, the total energy released by the flare is found to be roughly consistent with that predicted by the model. Only a small fraction of the energy released appears in the super-hot source at any one time, but roughly a quarter of the flare energy is thermalized by the reconnection shocks over the course of the flare. All energy is presumed to ultimately appear in the lower-temperature T<20 MK, post-flare loops