Multi-chord fiber-coupled interferometer with a long coherence length laser

This paper describes a 561 nm laser heterodyne interferometer that provides time-resolved measurements of line-integrated plasma electron density within the range of 10^15-10^18 cm^(-2). Such plasmas are produced by railguns on the Plasma Liner Experiment (PLX), which aims to produce \mu s-, cm-, and Mbar-scale plasmas through the merging of thirty plasma jets in a spherically convergent geometry. A long coherence length, 320 mW laser allows for a strong, sub-fringe phase-shift signal without the need for closely-matched probe and reference path lengths. Thus only one reference path is required for all eight probe paths, and an individual probe chord can be altered without altering the reference or other probe path lengths. Fiber-optic decoupling of the probe chord optics on the vacuum chamber from the rest of the system allows the probe paths to be easily altered to focus on different spatial regions of the plasma. We demonstrate that sub-fringe resolution capability allows the interferometer to operate down to line-integrated densities of order 10^15 cm^(-2).Comment: submitted to Rev. Sci. Instrum. (2011

Ideal magnetohydrodynamic simulation of magnetic bubble expansion as a model for extragalactic radio lobes

Nonlinear ideal magnetohydrodynamic (MHD) simulations of the propagation and expansion of a magnetic "bubble" plasma into a lower density, weakly-magnetized background plasma are presented. These simulations mimic the geometry and parameters of the Plasma Bubble Expansion Experiment (PBEX) [A. G. Lynn, Y. Zhang, S. C. Hsu, H. Li, W. Liu, M. Gilmore, and C. Watts, Bull. Amer. Phys. Soc. {\bf 52}, 53 (2007)], which is studying magnetic bubble expansion as a model for extra-galactic radio lobes. The simulations predict several key features of the bubble evolution. First, the direction of bubble expansion depends on the ratio of the bubble toroidal to poloidal magnetic field, with a higher ratio leading to expansion predominantly in the direction of propagation and a lower ratio leading to expansion predominantly normal to the direction of propagation. Second, an MHD shock and a trailing slow-mode compressible MHD wavefront are formed ahead of the bubble as it propagates into the background plasma. Third, the bubble expansion and propagation develop asymmetries about its propagation axis due to reconnection facilitated by numerical resistivity and to inhomogeneous angular momentum transport mainly due to the background magnetic field. These results will help guide the initial experiments and diagnostic measurements on PBEX.Comment: 33 pages, 37 figures, submitted to Physics of Plasma

Enterococcal biofilm formation and virulence in an optimized murine model of foreign body-associated urinary tract infections

Catheter-associated urinary tract infections (CAUTIs) constitute the majority of nosocomial UTIs and pose significant clinical challenges. Enterococcal species are among the predominant causative agents of CAUTIs. However, very little is known about the pathophysiology of Enterococcus-mediated UTIs. We optimized a murine model of foreign body-associated UTI in order to mimic conditions of indwelling catheters in patients. In this model, the presence of a foreign body elicits major histological changes and induces the expression of several proinflammatory cytokines in the bladder. In addition, in contrast to naïve mice, infection of catheter-implanted mice with Enterococcus faecalis induced the specific expression of interleukin 1β (IL-1β) and macrophage inflammatory protein 1α (MIP-1α) in the bladder. These responses resulted in a favorable niche for the development of persistent E. faecalis infections in the murine bladders and kidneys. Furthermore, biofilm formation on the catheter implant in vivo correlated with persistent infections. However, the enterococcal autolytic factors GelE and Atn (also known as AtlA), which are important in biofilm formation in vitro, are dispensable in vivo. In contrast, the housekeeping sortase A (SrtA) is critical for biofilm formation and virulence in CAUTIs. Overall, this murine model represents a significant advance in the understanding of CAUTIs and underscores the importance of urinary catheterization during E. faecalis uropathogenesis. This model is also a valuable tool for the identification of virulence determinants that can serve as potential antimicrobial targets for the treatment of enterococcal infections

Molecular analysis of type 3 fimbrial genes from Escherichia coli, Klebsiella and Citrobacter species

Background: Catheter-associated urinary tract infection (CAUTI) is the most common nosocomial infection in the United States and is caused by a range of uropathogens. Biofilm formation by uropathogens that cause CAUTI is often mediated by cell surface structures such as fimbriae. In this study, we characterised the genes encoding type 3 fimbriae from CAUTI strains of Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Citrobacter koseri and Citrobacter freundii

Viability and Application of Mounting Personal PID VOC Sensors to Small Unmanned Aircraft Systems

Using a UAS-mounted sensor to allow for a rapid response to areas that may be difficult to reach or potentially dangerous to human health can increase the situational awareness of first responders of an aircraft crash site through the remote detection, identification, and quantification of airborne hazardous materials. The primary purpose of this research was to evaluate the remote sensing viability and application of integrating existing commercial-off-the-shelf (COTS) sensors with small unmanned aircraft system (UAS) technology to detect potentially hazardous airborne contaminants in emergency leak or spill response situations. By mounting the personal photoionization detector (PID) with volatile organic compound VOC sensor technology on UAS platforms, the needed information may be obtained at an optimum range and resolution without needlessly exposing a human to possible adverse conditions

The Leg-Tuck versus the Plank-Hold Relative to the Army Combat Fitness Test: Interactions with Body Composition, Strength and Sex.

In 2020 the U.S. Army replaced their older physical fitness test with the Army Combat Fitness Test (ACFT) to replicate modern battlefield demands. One component of the test, the leg-tuck (LTK) was found to disproportionately fail female soldiers. Following an independent review, the Army adopted the plank-hold (PLK), attempting to limit the influence of sex differences during the assessment. However, research regarding performance, relationships, and the influence of sex on the LTK versus the PLK is limited. PURPOSE: To determine relationships between the LTK, PLK, sex, body composition and abdominal and grip strength. METHODS: 49 physically active civilian college students (28 males, 21 females) were recruited as a surrogate population for Army personnel in this study. The following data were collected in one session: height; body mass (BM), body fat (BF%) and muscle mass percentage (MM%) measured via bioelectrical impedance analysis; combined grip strength (CGS) from both hands; the LTK; and the PLK. ACFT standards were utilized for the LTK and PLK for all participants and a 10-minute rest was provided between tests. Independent t-tests compared sexes in all variables (p\u3c.05). Partial correlations controlling for sex detailed relationships between the LTK and PLK and the other variables (p\u3c.05). Stepwise regression controlling for sex derived predictive relationships for the LTK and PLK. RESULTS: There were significant between-sex differences with males being taller, having greater BM, MM%, and performing better in CGS and the LTK. Females had greater BF%. There was no significant between-sex difference found in PLK performance. The LTK significantly correlated with PLK (r=.404), height (r=.546), BM (r=.343), BF% (r=-.639), MM% (r=.697) and CGS (r=.732). In addition to the relationship with the LTK, the PLK only correlated with BF% (r=-.295). Stepwise regression analysis showed LTK performance was predicted by sex (r2=.441), grip strength (r2=.595), and PLK performance (r2=.662). When controlling for sex, a significant predictive relationship was not produced for the PLK. CONCLUSION: Compared to the LTK, the PLK appeared to minimize the influence of sex and body composition on task performance in college-aged civilians. More research is needed on whether the PLK relates to Army job tasks

Multi-chord fiber-coupled interferometry of supersonic plasma jets and comparisons with synthetic data

A multi-chord fiber-coupled interferometer [Merritt et al., Rev. Sci. Instrum. 83, 033506 (2012)] is being used to make time-resolved density measurements of supersonic argon plasma jets on the Plasma Liner Experiment [Hsu et al., Bull. Amer. Phys. Soc. 56, 307 (2011)]. The long coherence length of the laser (>10 m) allows signal and reference path lengths to be mismatched by many meters without signal degradation, making for a greatly simplified optical layout. Measured interferometry phase shifts are consistent with a partially ionized plasma in which an initially positive phase shift becomes negative when the ionization fraction drops below a certain threshold. In this case, both free electrons and bound electrons in ions and neutral atoms contribute to the index of refraction. This paper illustrates how the interferometry data, aided by numerical modeling, are used to derive total jet density, jet propagation velocity (~15-50 km/s), jet length (~20-100 cm), and 3D expansion.Comment: 6 pages, 4 figures, invited paper at the 19th High Temperature Plasma Diagnostics Conference, Monterey, CA, May 6--10, 201