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The FT-IR spectra of a thin layer of pure 4-chloro-2′-hydroxy-4′-pentyloxyazobenzene (CHPAB) were studied as a function of temperature. A detailed analysis of the intensity variations was performed by a method based on principal component analysis (PCA). It was shown that the phase transition temperatures obtained by means of PCA and those determined by differential scanning calorimetry (DSC), the most widely used technique in the field, were nearly identical. The PCA results revealed that the transition from solid to a liquid crystalline (LC) phase (smectic A) is more drastic phase transition in terms of infrared absorption changes. The nematic to isotropic phase transition is much less infrared sensitive. Very much smaller absorption changes are associated with the transition between the smectic and nematic mesophases. The pattern of the intensity changes strictly is correlated with the orientation of the CHPAB molecules towards the surface windows due to the surface-induced homeotropic alignment of LC molecules. The important role of hydrogen bonding interaction on the observed transition is disclosed.

Total Dental Access (TDA) is the teledentistry project within the Department of Defense. This project enables referring dentists from the US Armed Forces to consult with specialists on the status of a patient. TDA focuses on three areas of dentistry: patient care, continuing education and dentist-laboratory communications. One of the goals of this project is to increase patient access to quality dental care. The other goal is to establish a cost effective telemedicine system. This paper describes the evolution of a teledentistry system, the main features of POTS-based, ISDN-based and Web-based systems used, advantages, disadvantages and cost-effectiveness of these systems. Data has been collected on the frequency of use, technical problems occurred, avoided patient or specialist travel and the total number of consults. A cost-effectiveness analysis has been conducted on the data collected. The results of this analysis will be presented.

The authors present the results of surgical treatment obtained in 288 children with tetralogy of Fallot. In 127 children palliative procedures (pulmonary-systemic anastomoses) were employed, whereas 161 patients were subjected to total surgical corrections of the defect, performed in cardiopulmonary bypass. In 127 (79%) belonging to the latter group the correction was a single stage procedure, and in 34 (21%), it followed pulmonary-systemic anastomoses. Perioperative mortality rate in children subjected to single stage procedures was 12%, being lightly lower than the rate observed in patients subjected to two stage procedures. The analysis of operative results corrected for age revealed a higher mortality rate in children operated when less then two years of age (17%) in comparison to older patients (11%).