Gas gun ramp loading of Kel-F 81 targets using a ceramic graded areal density flyer system

Kel-F 81 (PCTFE/Polychlorotrifluoroethylene) polymer targets were subjected to ramp loadings generated by a ceramic flyer accelerated into the targets by a gas gun in the plate impact configuration. This approach used a ceramic graded areal density flyer in conjunction with a ceramic buffer plate to induce a ramp loading in the target. The flyer was comprised of a rapid prototyped alumina ceramic. The loading was observed with embedded electromagnetic particle velocity gauges (PV gauges) with the results compared with ANSYS Autodyn™ hydrocode simulations. Experimental results show that ramp loadings of varying duration and magnitude were induced into the target. These loadings can be described as shockless compressions leading to shocked states within the material. In addition, numerical simulations provided further insight into the loading approach – with good agreement found with experimental data, opening the potential to design more complex loading systems in future

The bactericidal effect of shock waves

There are a variety of theories relating to the origins of life on our home planet, some of which discuss the possibility that life may have been spread via inter-planetary bodies. There have been a number of investigations into the ability of life to withstand the likely conditions generated by asteroid impact (both contained in the impactor and buried beneath the planet surface). Previously published data regarding the ability of bacteria to survive such applied shockwaves has produced conflicting conclusions. The work presented here used an established and published technique in combination with a single stage gas gun, to shock and subsequently recover Escherichia coli populations suspended in a phosphate buffered saline solution. Peak pressure across the sample region was calculated via numerical modelling. Survival data against peak sample pressure for recovered samples is presented alongside control tests. SEM micrographs of shocked samples are presented alongside control sets to highlight key differences between cells in each case

Trends in and predictors of carbapenem consumption across North American hospitals: Results from a multicenter survey by the MAD-ID research network

This Special Issue is dedicated to the late Dr. Charles (Charlie) D. Hufford, former Professor of Pharmacognosy and Associate Dean for Research and Graduate Studies at University of Mississippi [...]

Uncertainty analysis of data collected using embedded magnetic particle velocity gauges

The uncertainties in particle velocity and position-time data collected using embedded magnetic gauges are presented. Data were also collected on the resistance change of gauge elements under shock loading and the effect of the element width, as opposed to length, on the observed rise times, as two factors that can affect the data quality and uncertainty analysis. A new method of fitting to the shock tracker data is also proposed. The data were collected using gas gun experiments on Comp-B and PCTFE targets. For a well characterized setup, the uncertainty in the particle velocity data can be reduced to such a level that noise and other ‘random’ variations in the data can be more significant. This highlights the importance of reducing these factors and collecting high quality data but also investigating additional sources of error, such as the resistance change of the elements under shock loading, in order to determine the true uncertainty

An affine continuum mechanical model for cross-linked F-actin networks with compliant linker proteins

Cross-linked actin networks are important building blocks of the cytoskeleton. In order to gain deeper insight into the interpretation of experimental data on actin networks, adequate models are required. In this paper we introduce an affine constitutive network model for cross-linked F-actin networks based on nonlinear continuum mechanics, and specialize it in order to reproduce the experimental behavior of in vitro reconstituted model networks. The model is based on the elastic properties of single filaments embedded in an isotropic matrix such that the overall properties of the composite are described by a free-energy function. In particular, we are able to obtain the experimentally determined shear and normal stress responses of cross-linked actin networks typically observed in rheometer tests. In the present study an extensive analysis is performed by applying the proposed model network to a simple shear deformation. The single filament model is then extended by incorporating the compliance of cross-linker proteins and further extended by including viscoelasticity. All that is needed for the finite element implementation is the constitutive model for the filaments, the linkers and the matrix, and the associated elasticity tensor in either the Lagrangian or Eulerian formulation. The model facilitates parameter studies of experimental setups such as micropipette aspiration experiments and we present such studies to illustrate the efficacy of this modeling approach

The characteristics of cognitive neuroscience tests in a schizophrenia cognition clinical trial: Psychometric properties and correlations with standard measures.

In comparison to batteries of standard neuropsychological tests, cognitive neuroscience tests may offer a more specific assessment of discrete neurobiological processes that may be aberrant in schizophrenia. However, more information regarding psychometric properties and correlations with standard neuropsychological tests and functional measures is warranted to establish their validity as treatment outcome measures. The N-back and AX-Continuous Performance Task (AX-CPT) are two promising cognitive neuroscience tests designed to measure specific components of working memory and contextual processing respectively. In the current study, we report the psychometric properties of multiple outcome measures from these two tests as well as their correlations with standard neuropsychological measures and functional capacity measures. The results suggest that while the AX-CPT and N-back display favorable psychometric properties, they do not exhibit greater sensitivity or specificity with functional measures than standard neurocognitive tests

Clinical Outcomes in Patients with Heterogeneous Vancomycin-Intermediate Staphylococcus aureus Bloodstream Infection

The prevalence of heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) infections varies in the literature, a problem complicated by the lack of routine screening procedures; however, limited data suggest that hVISA has been associated with persistent bloodstream infections (BSI) and vancomycin failure, yet these studies have been confounded by design issues. We conducted this study to compare the characteristics of patients with BSI caused by hVISA with those with vancomycin-susceptible Staphylococcus aureus (VSSA) treated with vancomycin. This retrospective, multicenter matched (1:1) cohort study compared the clinical characteristics and outcomes of hVISA and VSSA. Patients with hVISA methicillin-resistant Staphylococcus aureus (MRSA) BSI from 2004 to 2012 were matched to VSSA-MRSA BSI patients. The primary outcome was failure of vancomycin treatment, defined as a composite of persistent bacteremia (≥7 days), persistent signs and symptoms, change of MRSA antibiotic, recurrent BSI, or MRSA-related mortality. We identified 122 matched cases. The overall vancomycin failure rate was 57% (82% hVISA versus 33% VSSA; P \u3c 0.001). The individual components of failure in hVISA versus VSSA were persistent bacteremia, 59% versus 21% (P \u3c 0.001); change in MRSA therapy, 54% versus 25% (P = 0.001); MRSA-related mortality, 21% versus 10% (P = 0.081); and recurrence of BSI, 26% versus 2% (P \u3c 0.001). Using logistic regression analysis and adjusting for covariates, hVISA (adjusted odds ratio [aOR], 11.1; 95% confidence interval [CI], 4.3 to 28.7) and intensive care unit (ICU) admission (aOR, 4.5; 95% CI, 1.8 to 11.6) were still independently associated with vancomycin failure. Relative to VSSA BSI, patients with hVISA were more likely to experience failure of vancomycin treatment, including persistent bacteremia and recurrence. Our results indicate that hVISA was responsible for considerable morbidity

Multicenter Study of High-Dose Daptomycin for Treatment of Enterococcal Infections

Enterococci are among the leading pathogens isolated in hospital-acquired infections. Current antimicrobial options for vancomycin-resistant enterococci (VRE) are limited. Prior data suggests that daptomycin \u3e 6mg/kg/day may be used to treat enterococcal infections. We retrospectively evaluated the effectiveness and safety of high-dose daptomycin (HD-daptomycin) therapy (\u3e 6 mg/kg) in a multicenter cohort of adult patients with enterococcal infections to describe the characteristics and outcomes. Two-hundred and forty-five patients were evaluated. Enterococcus faecium was identified in 175 (71%), followed by 49 (20%) Enterococcus faecalis and 21 (9%) Enterococcus spp., overall 204 (83%) were VRE. Enterococcal infections included bacteremia (173, 71%), intra-abdominal (35, 14%) and bone/joint (25, 10%). The median dose and duration of HD-daptomycin was 8.2 mg/kg/day (IQR 7.7-9.7) and 10 days (IQR 6-15), respectively. Overall clinical success rate was 89% (193/218) and microbiological eradication was observed in 93% (177/191) of patients. The median time to clearance of blood cultures on HD-daptomycin was 3 days (IQR 2-5). Thirty-day all cause mortality rate was 27% and 5 (2%) patients developed daptomycin nonsusceptible enterococcal strains while on HD-daptomycin. Seven patients (3%) had creatine phosphokinase (CPK) elevation, yet no HD-daptomycin regimen was discontinued due to an elevated CPK and all patients were asymptomatic. Overall, there was a high frequency of clinical success and microbiological eradication in patients treated with HD-daptomycin for enterococcal infections, even in patients with complicated and difficult to treat infections. No adverse event-related discontinuation of HD-daptomycin was noted. HD-daptomycin may be an option for the treatment of enterococcal infections

Utility of Nontraditional Risk Markers in Atherosclerotic Cardiovascular Disease Risk Assessment

AbstractBackgroundThe improvement in discrimination gained by adding nontraditional cardiovascular risk markers cited in the 2013 American College of Cardiology/American Heart Association cholesterol guidelines to the atherosclerotic cardiovascular disease (ASCVD) risk estimator (pooled cohort equation [PCE]) is untested.ObjectivesThis study assessed the predictive accuracy and improvement in reclassification gained by the addition of the coronary artery calcium (CAC) score, the ankle–brachial index (ABI), high-sensitivity C-reactive protein (hsCRP) levels, and family history (FH) of ASCVD to the PCE in participants of MESA (Multi-Ethnic Study of Atherosclerosis).MethodsThe PCE was calibrated (cPCE) and used for this analysis. The Cox proportional hazards survival model, Harrell’s C statistics, and net reclassification improvement analyses were used. ASCVD was defined as myocardial infarction, coronary heart disease–related death, or fatal or nonfatal stroke.ResultsOf 6,814 MESA participants not prescribed statins at baseline, 5,185 had complete data and were included in this analysis. Their mean age was 61 years; 53.1% were women, 9.8% had diabetes, and 13.6% were current smokers. After 10 years of follow-up, 320 (6.2%) ASCVD events occurred. CAC score, ABI, and FH were independent predictors of ASCVD events in the multivariable Cox models. CAC score modestly improved the Harrell’s C statistic (0.74 vs. 0.76; p = 0.04); ABI, hsCRP levels, and FH produced no improvement in Harrell’s C statistic when added to the cPCE.ConclusionsCAC score, ABI, and FH were independent predictors of ASCVD events. CAC score modestly improved the discriminative ability of the cPCE compared with other nontraditional risk markers