The effect of ultrasound on reactive crystallization is studied by measuring the induction time when nucleation is predominantly heterogeneous. Barium sulphate is used as the working substance precipitated by mixing aqueous BaCl2 and Na2SO4 solutions with relatively low concentrations compared to experiments for homogeneous nucleation. It is observed that at a given supersaturation level, the induction time significantly decreases with increasing ultrasonic energy input. The mechanism of the ultrasonic effect on heterogeneous nucleation is analyzed. The effect of ultrasound is to increase the diffusion coefficient (DAB) while reducing the contact angle (θ) and geometric factor (f). This gives rise to an increase in the heterogeneous nucleation rate and shorter induction time. The ultrasonic effect on critical supersaturation ratio (Scrit) is also investigated to determine the mechanism of ultrasonic effect on f and θ. Both the force from the cavitational bubble implosion and the nucleation process occurring at bubble/solution/foreign solid interface are proposed as the predominant reasons why contact angle (θ) decreases with the increase of energy input.

Introduction:Vitiligo is an acquired depigmentary condition caused by inactivation or destruction of melanocytes in epidermis and hair follicle. Worldwide incidence of 1% has been reported; similar to various dermatological clinics in India. Widespread prejudice, ignorance, taboos, lack of scientific appraisal, and confusion of vitiligo with leprosy makes it an immense psychological stress.Aim:To know the clinical profile of vitiligo patient with associated cofactors.Materials and Methods:Total 1,010 patients of vitiligo attended in outpatient department at Shree Krishna Hospital (SKH) and Matar camp, Gujarat over 1 year period from August 2011 to July 2012 were included in this study. Detail history and clinical examination of patients were done.Results:Out of 1,010 patients 57.3% were females and 42.7 % were males. Most cases developed vitiligo by 2nd decade of life. Progressive course was found in 60.9 % of patients. Vitiligo vulgaris (57.8%) was most common morphological type. Most common site of onset (41.5%) and involvement (75.7%) was lower limb. Family history was present in 20.4%.Conclusions:Vitiligo constitutes important dermatological disease especially in India. The data suggest that local epidemiological behavior of vitiligo need not be the same across different regions. Vitiligo differs substantially in various clinical aspects.

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