RESUMO
High-pressure oxygen is an integral part of fuel cell systems, many NASA in situ resource utilization concepts, and life support systems for extravehicular activity. Due to the limited information available for system designs over wide ranges of temperature and pressure, volumetric methods are applied to measure adsorption isotherms of O(2) and N(2) on NaX and NaY zeolites covering temperatures from 105 to 448 K and pressures up to 150 bar. Experimental data measured using two apparatuses with distinctly different designs show good agreement for overlapping temperatures. Excess adsorption isotherms are modeled using a traditional isotherm model for absolute adsorption with a correction for the gas capacity of the adsorption space. Comparing two models with temperature-dependent coefficients, a virial isotherm model provides a better description than a Toth isotherm model, even with the same number of parameters. With more virial coefficients, such as a cubic form in loading and quadratic form in reciprocal temperature, the virial model can describe all data accurately over wide ranges of temperature and pressure.
RESUMO
BACKGROUND: Cooling demyelinated nerves can reduce conduction block, potentially improving symptoms of MS. The therapeutic effects of cooling in patients with MS have not been convincingly demonstrated because prior studies were limited by uncontrolled designs, unblinded evaluations, reliance on subjective outcome measures, and small sample sizes. OBJECTIVE: To determine the effects of a single acute dose of cooling therapy using objective measures of neurologic function in a controlled, double-blinded setting, and to determine whether effects are sustained during daily cooling garment use. METHODS: Patients (n = 84) with definite MS, mild to moderate disability (Expanded Disability Status Scale score < 6.0), and self-reported heat sensitivity were randomized into a multicenter, sham-treatment controlled, double-blind crossover study. Patients had the MS Functional Composite (MSFC) and measures of visual acuity/contrast sensitivity assessed before and after high-dose or low-dose cooling for 1 hour with a liquid cooling garment. One week later, patients had identical assessments before and after the alternate treatment. Patients were then re-randomized to use the cooling garment 1 hour each day for a month or to have observation only. They completed self-rated assessments of fatigue, strength, and cognition during this time, and underwent another acute cooling session at the end of the period. After 1 week of rest, they had identical assessments during the alternate treatment. RESULTS: Body temperature declined during both high-dose and low-dose cooling, but high-dose produced a greater reduction (p < 0.0001). High-dose cooling produced a small improvement in the MSFC (0.076 +/- 0.66, p = 0.007), whereas low-dose cooling produced only a trend toward improvement (0.053 +/- 0.031, p = 0.09), but the difference between conditions was not significant. Timed gait testing and visual acuity/contrast sensitivity improved in both conditions as well. When patients underwent acute cooling following a month of daily cooling, treatment effects were similar. Patients reported less fatigue during the month of daily cooling, concurrently on the Rochester Fatigue Diary and retrospectively on the Modified Fatigue Impact Scale. CONCLUSIONS: Cooling therapy was associated with objectively measurable but modest improvements in motor and visual function as well as persistent subjective benefits.
