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

Transmission Range Evaluations for Connected Vehicles at Highway-Rail Grade Crossings

This study evaluates the transmission range requirements of Connected Vehicles (CVs) at Highway-Rail Grade Crossings (HRGCs) in terms of safety improvement. The safety improvement of HRGCs is evaluated by using a reliability-based risk analysis that calculates risk of collision for CVs and non-CVs. Trains are assumed to have onboard units that transmit train location and speed information to CVs via vehicle to vehicle communications. The stopping distance and time to collision of a vehicle are the demand functions in reliability-based risk analysis. The demand functions consist of probability density functions of a vehicle’s initial speed, perception-reaction time, initial deceleration rate, final speed, and final deceleration rate. Train arrival time depending on the train speed and transmission range is the supply threshold for calculating the CV’s risk of collision at passive HRGCs. The transmission range’s projected highway distance is the supply threshold for CVs at active HRGCs. After deriving probability density functions of demand functions from the published data, Monte Carlo simulations generate the probabilities or risks that a CV would fail to stop within the transmission range or train arrival time. With the provision of a 600 m transmission range, the risk of collision for the CV is lower than that for the non-CV with a 300 m sight distance to the train at the passive HRGC. The CV’s risk of collision is lower than the non-CV’s with a 300 m transmission range at active HRGCs. The CV application at HRGCs can improve safety by reducing CVs’ risk of collision. A 600 m transmission range is desirable at passive HRGCs. A 300 m transmission is sufficient for CVs at active HRGCs. Overall, a 600 m transmission range is feasible to improve the safety at passive and active HRGCs

Visual performance with two frequent replacement toric hydrogel contact lens designs

Many studies in the past have compared toric hydrogel lens designs with regard to vision, stability, and patient satisfaction. While each of these variables is important in the success of contact lens fitting, few studies in the literature have explored the relationship between lens design and visual performance, specifically as it relates to functional daily activities. This study was developed to identify whether or not a correlation exists between lens design and visual performance by comparing the prism ballasted Soflens 66 toric lens to the double slab-off Acuvue toric hydrogel lens. Eight subjects were fit with each lens to wear for one week, after which visual performance was assessed with the following tests: logMAR visual acuity, speed and accuracy of stereopsis, dynamic visual acuity, and accommodative facility. The subjects were also required to complete a questionnaire at the end of the week regarding the performance of each lens. It was found that due to the small sample size, there was no statistically significant difference between the two lenses with regard to many of the visual performance measurements. One question from the questionnaire pertaining to frequency of blur when shifting focus from near to far was determined to be statistically significant, showing the Acuvue toric lens design to be preferred by the subjects involved in the study. Without regard to statistical significance, it did appear that a relationship exists between lens design and visual performance, as subjects wearing the prism ballasted lens performed better than when wearing the double slab-off lens in many categories. To further validate these findings, future studies with larger sample sizes are therefore warranted

A comparison of treatment outcomes for individuals with substance use disorder alone and individuals with probable dual diagnosis

The co-occurrence of substance use and mental health problems, often referred to as dual diagnosis (DD), is increasingly recognised as commonplace within substance abuse treatment programs. Two-hundred and thirty-four individuals from 9 Australian Salvation Army drug and alcohol rehabilitation programs completed a 3-month post-discharge telephone follow-up. Using a cut-off score from the Psychiatric Subscale of the Addiction Severity Index (5th ed.), 66.7% were classified as likely to have DD and 33.3% as substance use disorder only (SUD). Both groups reported comparable and decreased substance use levels at follow-up, yet DD individuals perceived less improvement in substance use problems. Comparable improvements were reported in the areas of: symptom distress and recovery from symptoms. This was despite greater scope for improvement in individuals with DD. Duration of treatment and access to post treatment services were also assessed. Understanding factors effecting treatment outcomes is imperative for the implementation of effective, evidence based treatment programs

The Incidence of Central Serous Chorioretinopathy after Photorefractive Keratectomy and Laser In Situ Keratomileusis

Purpose. To assess the incidence of central serous chorioretinopathy (CSCR) following laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK). Methods. A chart review was performed to identify all patients with CSCR and a previous history of LASIK or PRK. Results. Over the 6-year study period, 1 of 4,876 eyes which had LASIK or PRK at the Moran Eye Center was diagnosed with CSCR. One other patient was referred from an outside center, developed CSCR symptoms one month after PRK. Both patients were managed conservatively with a final visual acuity of 20/20 or better. All other patients presented 4 or more years after refractive surgery. Conclusions. We report the first 2 CSCR cases developing within one month after PRK. The low incidence argues against a causal association. Topical corticosteroids or anxiety may elevate cortisol levels presenting therapeutic challenges for the management of CSCR after PRK or LASIK

Effectiveness of Impairment-Specific Exercises to Improve Balance and Reduce Fall Risk in Community-Dwelling Older Adults

Ph.D., Rehabilitation Sciences -- Drexel University, 201