Low-pressure multipass Raman spectrometer.

Nonintrusive, quantitative measurements of thermodynamic properties of flows associated with propulsion systems are pivotal to advance their design and optimization. Laser-based diagnostics are ideal to provide quantitative results without influencing the flow; however, the environments in which such flows exist are often not conducive for such techniques. Namely, they often lack the optical accessibility required to facilitate the delivery of incident laser radiation and the subsequent collection of induced signals. A particularly challenging, yet crucial, task is to measure thermodynamic properties of plumes issuing from thrusters operating within a vacuum chamber. Large chambers used to simulate the vacuum of space generally lack optical ports that can facilitate complex laser-based measurements. Additionally, the near-vacuum environments within such chambers coupled with the ability of thrusters to efficiently expand the gas flowing through their nozzles lead to plumes with prohibitively low number densities (pressures below 1 Torr). Thus, there is a need to develop a diagnostic system that can offer high throughput without the use of free-space optical ports. Moreover, facilities where propulsion systems are tested typically lack vibrationally isolated space for diagnostic equipment and accurate climate control. As a result, such a high-throughput system must also be compact, versatile, and robust. To this end, the present work describes a fiber-coupled, multipass cell, spontaneous Raman scattering spectroscopy system. This system is intended to provide accurate temperature measurements within low-pressure environments via H2 rotational Raman thermometry. Proof-of-principle measurements are successfully performed at pressures as low as 67 Pa (500 mTorr). Techniques to maintain the signal-to-noise ratio at lower pressures, and the trade-offs associated with them, are discussed and evaluated. Finally, the ability of this system to facilitate additional quantitative measurements is also discussed.

Moderate and Severe Blood Pressure Elevation Associated with Stroke in the Mexican Hispanic Population.

BACKGROUND: Stroke is the fourth leading cause of death in US. Amongst other factors such as age, sex, race, genetics, obesity, diabetes etc., hypertension continues to be the leading contributing factor towards stroke. Studies regarding stroke in Hispanics are sparse and inconclusive. OBJECTIVES: The objective of the present study is to investigate the potential association between blood pressure elevation and risk of ischemic stroke among the Mexican Hispanic population. METHODS: A retrospective data analysis was carried out for a planned case-control study with case-control ratios of 1:2. Mexican Hispanic cases were from the ElPasoStroke database with diagnosed hypertension that had sustained an ischemic stroke (n = 505) and Mexican Hispanics diagnosed with hypertension who were stroke-free as controls from the 2005-2010 NHANES databases (n = 1010). In this analysis, we included subjects who had data on systolic, diastolic or mean arterial blood pressures for cases (327) and controls (772). In cases, blood pressure was determined by the initial admission measurement, and in controls, the first measured blood pressure was used. The unadjusted and adjusted effects of continuous measurements of systolic, diastolic and mean arterial blood pressure on stroke were determined using logistic regression analyses. Subjects were further classified into groups based on prehypertension and hypertension ranges, as established by the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC7). Unadjusted and adjusted logistic regression models were also used to determine the effect of categorized blood pressures. RESULTS: Our data indicate that per unit increase in systolic, diastolic or mean arterial blood pressure elevates the odds of stroke among the Mexican Hispanic population. Adjusted analysis of categorized blood pressures showed that mild or moderate/severe high blood pressure significantly associated with odds of stroke. Maintaining and controlling blood pressure at more stringent and lower levels, specifically lowering mean arterial pressure may effectively reduce the odds of ischemic stroke among the Mexican Hispanic population. CONCLUSION: Elevation of blood pressure increases the odds of stroke among the Mexican Hispanic population. Our results provide new strategies to manage the stroke prevention and health disparity issues among the Mexican Hispanic population.

Metabolic syndrome associated with ischemic stroke among the Mexican Hispanic population in the El Paso/US-Mexico border region.

The Hispanic population carries a disproportionate burden of stroke compared with the non-Hispanic White population. Most studies have been conducted on Caribbean Hispanics, indicating a need to better understand the characteristics of stroke and its prevalence among the Hispanic populations of Mexican descent. In this report, data were collected in the El Paso/US-Mexico border region, where 82% of the population is Mexican Hispanic, through a retrospective study of ischemic stroke from 2005-2010. Odds ratios (ORs), 95% confidence intervals, logistic regression, and multivariate analysis of the ORs adjusted for other variables, were used to analyze the effects of various risk factors on ischemic stroke. The metabolic syndrome and its components, specifically hypertension, diabetes, and dyslipidemia appeared to be strongly associated with ischemic stroke in the Mexican Hispanic population. Mexican Hispanic ischemic stroke patients were nearly 7 times more likely to have this syndrome, compared with Mexican Hispanic controls from the National Health and Nutrition Examination Survey. Likewise, the patients were nearly 40 times more likely to have hypertension and 11 times more likely to have diabetes. Efforts to prevent ischemic stroke and limit its impact in the Mexican Hispanic population should focus on controlling hypertension and diabetes.

Embryologic Association of Tornwaldt's Cyst with Cerebral Artery Abnormalities and Infarction: A Case Report.

Background and Purpose. Tornwaldt's cysts are rare nasopharyngeal lesions that develop from remnants of the embryonic notochord. Summary of Case. We reported a twelve-year-old female stroke patient with Tornwaldt's cysts, whose father also suffered a stroke at age fifty two with the presence of an abdominal aortic aneurysm, suggesting a genetic influence in this case. Conclusions. This paper suggests an etiologic connection between Tornwaldt's cysts and cerebral vasculature abnormalities by way of notochordal dysfunction during development, likely the result of perturbation of notochord-derived molecular cues during development or biogenesis.