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Some properties of gas mixtures, composed predominately of helium and lesser amounts of CO2 and isobutane, were measured in a prototype drift chamber. The studies are motivated by the desire to reduce the multiple scattering inside the drift chamber at future high-luminosity, low-energy facilities such as 4 factories, T/charm factories, and B factories. The low atomic number of helium greatly reduces the multiple scattering contribution to the momentum resolution compared to an argon-based gas mixture. The position resolution, pulse height, efficiency, and breakdown characteristics were measured for various gas mixtures. A mixture of 83% He, 10% CO2, and 7% isobutane gives comparable results to that of an argon-based gas commonly used in drift chambers.

Background Motor neuron degeneration and malnutrition alter body composition in amyotrophic lateral sclerosis (ALS). Resulting loss of weight, fat mass (FM) and fat-free mass (FFM) shorten survival. Nutritional management relies on body weight or body mass index (BMI); neither reliably indicates malnutrition nor differentiates body compartments. Objectives 1) Develop an equation to compute FM and FFM using clinical data, validated against dual energy x-ray absorptiometry (DXA); and 2) Examine the effect of computed FM and FFM on course and survival. Design We studied 364 ALS patients from three cohorts: in Cohort #1 using logistic regression on clinical and demographic data to create an equation (test cohort). In Cohort #2 we validated computed FM and FFM using this equation against DXA (validation cohort). In Cohort #3, we examined the effect of computed body composition on course and survival. Results In Cohort #1 (n = 29) the model incorporated sex, age, BMI and bulbar-onset to create an equation to estimate body fat (% body fat = 1.73—(19.80*gender [1 if male or 0 if female]) + (0.25*weight [kg] + (0.95*BMI)—(5.20*1 if bulbar-onset or *0 if limb-onset). In Cohort #2 (n = 104), body composition using this equation, compared to other published equations, showed the least variance from DXA-values. In Cohort #3 (n = 314), loss of body composition over 6-months was greater in males. Adjusted survival was predicted by low baseline FM (HR 1.39, 95% confidence interval [CI] 1.07, 1.80), and loss of FM (HR 1.87, 95% CI 1.30, 2.69) and FFM (HR 1.73, 95% CI 1.20, 2.49) over 6 months. Conclusion Our equation broadens the traditional nutritional evaluation in clinics and reliably estimates body composition. Measuring body composition could target FM as a focus for nutritional management to ensure adequate energy intake and complement measures, such as the ALS functional rating scale-revised score and forced vital capacity, currently used.