Marginal Proportional Hazards Models for Clustered Interval-Censored Data with Time-Dependent Covariates

The Botswana Combination Prevention Project was a cluster-randomized HIV prevention trial whose follow-up period coincided with Botswana’s national adoption of a universal test-and-treat strategy for HIV management. Of interest is whether, and to what extent, this change in policy (i) modified the observed preventative effects of the study intervention and (ii) was associated with a reduction in the population-level incidence of HIV in Botswana. To address these questions, we propose a stratified proportional hazards model for clustered interval-censored data with time-dependent covariates and develop a composite expectation maximization algorithm that facilitates estimation of model parameters without placing parametric assumptions on either the baseline hazard functions or the within-cluster dependence structure. We show that the resulting estimators for the regression parameters are consistent and asymptotically normal. We also propose and provide theoretical justification for the use of the profile composite likelihood function to construct a robust sandwich estimator for the variance. We characterize the finite-sample performance and robustness of these estimators through extensive simulation studies. Finally, we conclude by applying this stratified proportional hazards model to a re-analysis of the Botswana Combination Prevention Project, with the national adoption of a universal test-and-treat strategy now modeled as a time-dependent covariate

Multidimensional optimal droop control for DC microgrids in military applications

Reliability is a key consideration when microgrid technology is implemented in military applications. Droop control provides a simple option without requiring communication between microgrid components, increasing the control system reliability. However, traditional droop control does not allow the microgrid to utilize much of the power available from a solar resource. This paper applies an optimal multidimensional droop control strategy for a solar resource connected in a microgrid at a military patrol base. Simulation and hardware-in-the-loop experiments of a sample microgrid show that much more power from the solar resource can be utilized, while maintaining the system’s bus voltage around a nominal value, and still avoiding the need for communication between the various components

Neuroimaging of Prayer: Questions of Validity

Studies investigating the brain in relation to religious experiences via neuroimaging tools have increased considerably. Most assume without verification that religious experience (e.g., prayer) while inside an imaging machine is the same as in normal settings. Addressing the validity of this assumption, we utilized a mock fMRI to compare self-reported typical prayer experience and 3 experimental conditions (silent room, initial fMRI, and acclimated fMRI). Forty-two individuals participated. In multiple aspects the “typical” and silent room conditions were indistinguishable; however, typical and fMRI conditions differed significantly. In sum, it was not clear what previous studies measured. These findings highlight the need for imaging research exploring religious experiences to include thorough debriefing protocols to disambiguate interpretations and facilitate meta-analytic efforts

Construction of a Database for Socio-Demographic, Medico-Legal, Anatomic, and Genomic Research into Suicide

poster abstractSuicide is a potentially preventable tragedy. Over 180 cases of suicide a year occur in Marion County. We have created a database that permits integration of socio-demographic data, medico-legal information, anatomic images, and genomic results. We have collected over 50 cases to date. We will show results of analyses looking at method of suicide, toxicology results, and genomic biomarker correlates. It is hoped that this resource would permit the study of risk factors and the creation of predictive algorithms that may better identify people at risk, and lead to early intervention and prevention efforts

Proposed host galaxies of repeating fast radio burst sources detected by CHIME/FRB

We present a search for host galaxy associations for the third set of repeating fast radio burst (FRB) sources discovered by the CHIME/FRB Collaboration. Using the ~1 arcmin CHIME/FRB baseband localizations and probabilistic methods. We identify potential host galaxies of two FRBs, 20200223B and 20190110C at redshifts of 0.06024(2) and 0.12244(6), respectively. We also discuss the properties of a third marginal candidate host galaxy association for FRB 20191106C with a host redshift of 0.10775(1). The three putative host galaxies are all relatively massive, fall on the standard mass-metallicity relationship for nearby galaxies, and show evidence of ongoing star formation. They also all show signatures of being in a transitional regime, falling in the "green valley" which is between the bulk of star-forming and quiescent galaxies. The plausible host galaxies identified by our analysis are consistent with the overall population of repeating and non-repeating FRB hosts while increasing the fraction of massive and bright galaxies. Coupled with these previous host associations, we identify a possible excess of FRB repeaters whose host galaxies have M_u - M_r colors redder than the bulk of star-forming galaxies. Additional precise localizations are required to confirm this trend.Comment: 11 pages, submitted to AAS journal

Ancient Latin American objects in the archive: selections from the George and Louise Patten collection of Salem Hyde cultural artifacts at the University of Tennessee at Chattanooga

https://scholar.utc.edu/exhibition-records/1004/thumbnail.jp

Multiwavelength Constraints on the Origin of a Nearby Repeating Fast Radio Burst Source in a Globular Cluster

Since fast radio bursts (FRBs) were discovered, their precise origins have remained a mystery. Multiwavelength observations of nearby FRB sources provide one of the best ways to make rapid progress in our understanding of the enigmatic FRB phenomenon. We present results from a sensitive, broadband multiwavelength X-ray and radio observational campaign of FRB 20200120E, the closest known extragalactic repeating FRB source. At a distance of 3.63 Mpc, FRB 20200120E resides in an exceptional location, within a ~10 Gyr-old globular cluster in the M81 galactic system. We place deep limits on both the persistent X-ray luminosity and prompt X-ray emission at the time of radio bursts from FRB 20200120E, which we use to constrain possible progenitors for the source. We compare our results to various classes of X-ray sources and transients. In particular, we find that FRB 20200120E is unlikely to be associated with: ultraluminous X-ray bursts (ULXBs), similar to those observed from objects of unknown origin in other extragalactic globular clusters; giant flares, like those observed from Galactic and extragalactic magnetars; or most intermediate flares and very bright short X-ray bursts, similar to those seen from magnetars in the Milky Way. We show that FRB 20200120E is also unlikely to be powered by a persistent or transient ultraluminous X-ray (ULX) source or a young, extragalactic pulsar embedded in a Crab-like nebula. We also provide new constraints on the compatibility of FRB 20200120E with accretion-based FRB models involving X-ray binaries and models that require a synchrotron maser process from relativistic shocks to generate FRB emission. These results highlight the power that multiwavelength observations of nearby FRBs can provide for discriminating between potential FRB progenitor models.Comment: 58 pages, 10 figures, 7 tables, submitte

CHIME/FRB Discovery of 25 Repeating Fast Radio Burst Sources

We present the discovery of 25 new repeating fast radio burst (FRB) sources found among CHIME/FRB events detected between 2019 September 30 and 2021 May 1. The sources were found using a new clustering algorithm that looks for multiple events co-located on the sky having similar dispersion measures (DMs). The new repeaters have DMs ranging from $\sim$220 pc cm$^{-3}$ to $\sim$1700 pc cm$^{-3}$, and include sources having exhibited as few as two bursts to as many as twelve. We report a statistically significant difference in both the DM and extragalactic DM (eDM) distributions between repeating and apparently nonrepeating sources, with repeaters having lower mean DM and eDM, and we discuss the implications. We find no clear bimodality between the repetition rates of repeaters and upper limits on repetition from apparently nonrepeating sources after correcting for sensitivity and exposure effects, although some active repeating sources stand out as anomalous. We measure the repeater fraction and find that it tends to an equilibrium of $2.6_{-2.6}^{+2.9}$% over our exposure thus far. We also report on 14 more sources which are promising repeating FRB candidates and which merit follow-up observations for confirmation.Comment: Submitted to ApJ. Comments are welcome and follow-up observations are encouraged

Drug Release Kinetics from Poly(ethylene glycol) Hydrogels for Wound Dressings

Prolonged field care (PFC) for treatment of battlefield and trauma injuries requires the advancement of wound management techniques in order to prevent loss of life or limb prior to hospitalization in austere combat locations where medical evacuation is delayed. The goal of this project is to design a hydrogel wound dressing capable of providing sustained release of antibiotics, analgesics, and hemostatic agents over a three-day period. Poly(ethylene glycol) (PEG) hydrogels were fabricated through crosslinking using redox initiators – ammonium persulfate (APS) and tetramethylethylene diamine (TEMED). Hydrogels were characterized through the mass swelling ratio (qm) to determine the mesh size (ξ) and thus qualitatively predict the release kinetics of the therapeutic drugs. Hydrogels with incorporated therapeutic drug were placed in known volumes of deionized water, from which aliquots were taken at set time intervals. A UV Visible Spectrophotometer determined the aliquots’ absorbance which determined the cumulative release kinetics. Ultimately, three-day sustained release of the therapeutic drugs from the PEG hydrogel was achieved through retarding the diffusion of the therapeutic drugs by incorporating acrylic acid