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Objectives\ud \ud To compare prevalence and severity of diaper dermatitis (DD) in infants and toddlers (babies) across three countries (China, USA, and Germany), including diapered skin measures and caregiver practices.\ud \ud \ud \ud Methods\ud \ud A cross‐sectional study of 1791 babies (~600 from each country) was recruited at each clinical site. Based on regional toilet‐training habits, exclusively diaper‐wearing infants were recruited between ages 2‐8 months in China and 2‐18 months in the USA and Germany. DD was measured, as well as skin pH, transepidermal water loss (TEWL), and relative humidity (RH) in the diapered region. Caregiver habits were collected via a questionnaire and included information on hygienic practices.\ud \ud \ud \ud Results\ud \ud Diaper dermatitis was highest in the perianal area, followed by the intertriginous, genital, and buttock regions. In general, DD was significantly lower in babies in China, highest in Germany, and intermediate in the USA. This rank ordering of DD by geography was also observed in baby age 2‐8 months. The lower DD observed in China was associated with lower skin pH and TEWL on diapered skin and decreased RH in the diaper. Chinese caregivers had the highest rate of prophylactic topical product usage, the most robust cleaning of the diapered area, lack of cleansing after urine‐only diaper changes, and Chinese infants spent the least time in an overnight diaper.\ud \ud \ud \ud Conclusions\ud \ud These data suggest caregiver behaviors including prophylactic use of topical products, thorough cleaning after stooling and reduced time in an overnight diaper are associated with less DD, lower superficial skin pH, and enhanced skin barrier.

Lysholm twin screw expanders are being developed to recover work from the two phase flash expansion of organic fluids. The work described in this thesis was carried out to maximise the efficiency of such machines by improving the inlet port design. To this end the flow in the inlet port was investigated both analytically and experimentally.\ud \ud The theoretical analysis was carried out on the assumption of one-dimensional steady flow allowing for thermal non-equilibrium and relative motion between the phases with corrections to allow for boundary layer growth. The equations thereby developed were solved by means of a numerical procedure together with the calculus of variations to design the port as a circular cross section nozzle of optimum adiabatic efficiency. The resulting design was then modified to progressively transform its cross section from circular at the inlet to the characteristic irregular shape of a screw expander inlet port at the exit.\ud \ud The experimental work involved the construction of both the circular and modified cross section port designs and their testing in a closed loop containing Refrigerant 113 as the working fluid. The loop was well instrumented and the void fraction distribution in the port exit plane was measured with a fibre optic probe whose tip position was varied by a specially designed computer controlled traversing system.\ud \ud Predicted and measured values of void fraction differed on average by only 2.1% in the circular cross section design and 4.5% in the transformed design. The corresponding differences in pressure along the port length were well within 1.0%. The procedure developed for improved design therefore appears to be substantially validated.