ABSTRACT
The homogeneous nucleation of bismuth supersaturated vapor is studied in a laminar flow quartz tube nucleation chamber. The concentration, size, and morphology of outcoming aerosol particles are analyzed by a transmission electron microscope (TEM) and an automatic diffusion battery (ADB). The wall deposit morphology is studied by scanning electron microscopy. The rate of wall deposition is measured by the light absorption technique and direct weighting of the wall deposits. The confines of the nucleation region are determined in the "supersaturation cut-off" measurements inserting a metal grid into the nucleation zone and monitoring the outlet aerosol concentration response. Using the above experimental techniques, the nucleation rate, supersaturation, and nucleation temperature are measured. The surface tension of the critical nucleus and the radius of the surface of tension are determined from the measured nucleation parameters. To this aim an analytical formula for the nucleation rate is used, derived from author's previous papers based on the Gibbs formula for the work of formation of critical nucleus and the translation-rotation correction. A more accurate approach is also applied to determine the surface tension of critical drop from the experimentally measured bismuth mass flow, temperature profiles, ADB, and TEM data solving an inverse problem by numerical simulation. The simulation of the vapor to particles conversion is carried out in the framework of the explicit finite difference scheme accounting the nucleation, vapor to particles and vapor to wall deposition, and particle to wall deposition, coagulation. The nucleation rate is determined from simulations to be in the range of 10(9)-10(11) cm(-3) s(-1) for the supersaturation of Bi(2) dimers being 10(17)-10(7) and the nucleation temperature 330-570 K, respectively. The surface tension σ(S) of the bismuth critical nucleus is found to be in the range of 455-487 mN/m for the radius of the surface of tension from 0.36 to 0.48 nm. The function σ(S) changes weakly with the radius of critical nucleus. The value of σ(S) is from 14% to 24% higher than the surface tension of a flat surface.
ABSTRACT
The purpose of this study was to determine the extent of inappropriate admissions and days of stay in acute beds of patients who were admitted to hospital after attending the emergency department for urgent medical attention in Italy. The medical records of all adult patients (aged 16 years and over) on one randomly preselected day during the period January-December 2001 were reviewed. The retrospective application was made using the Appropriateness Evaluation Protocol list of criteria. Overall, 28.4 and 75.7% of hospital admissions and days of stay, respectively, were judged to be inappropriate. Results of the multiple logistic regression analysis indicated that inappropriate admission was significantly more likely in patients who lived closer to hospital, in younger patients, in patients from lower socio-economic classes, and in patients who did not receive diagnostic procedures in the emergency department. The proportion of patients whose admission was considered inappropriate was significantly lower in medical specialties wards. The number of inappropriate hospitalisation days was significantly higher in younger patients, in those admitted inappropriately, and in patients sampled close to discharge (during the final-third of his/her stay). The number of inappropriate hospitalisation days was significantly lower in patients admitted to surgical and traumatology/orthopaedics and medical specialties wards. Our findings indicate the need for specific interventions to reduce the prevalence of inappropriate hospital use and to modify physicians' attitudes and behaviours.
