Until now there exists no calculation of the phonon density of states of amorphous SiO, and related materials, which could interpret the experimentally detected splittings between longitudinal and transverse modes in their optical phonon spectra. This problem is solved by taking into account the influence of the vibrationally induced polarization on the motion of atoms. A simple model for the description of this polarization in non-crystalline SiO, is developed and used for the calculation of t h e density of states of LO and TO phonons in the framework of a coherent potential approximation for structurally disordered systems. This new method leads also to the determination of the I R response function and to simple analytical expressions for the microscopic parameters of the model, i.e. the bond angle at the oxygen atom and transverse dynamic effective charges. The values of these parameters are determined from I R transmission spectra of thin SiO, layers prepared with the help of different methods. The calculated density of states and I R response function are in good agreement with corresponding experimental results.

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We detect f o r the first t i m e TO and LO phonon modes of amorphous (a) Si02 films by angle-of-incidence dependent IR transmission. By comparison of Raman (R) and infrared (IR) spectra Galeener and Lucovsky explained several peaks observed in first o r d e r R spectra of a-Si02 /I/, GeOZ /2/, and BeF2 /3/ by the existence'of longitudinal optical (LO) vibrational modes. Although an accurate determination of the frequency and polarization of phonons in thinf films is very important for various electron-phonon interaction and transport processes, only a few applications of this original idea exist until now /4 to 6/. We represent in this paper an extension of this useful'approach and provide for the first time a direct experimental and theoretical confirmation of Galeener' s and Lucovsky' s prediction.with t r a n s v e r s e optical (TO) phonons. Therefore, TO modes lead t o peaks in the imaginary part E of the frequency dependent dielectric function E = el + i E in the IR region. However, in reflection and transmission spectra obtained from It is well known that electromagnetic waves interact in "infinite" crystals only

Objective To study changes in the peritoneal micro-circulation during continuous ambulatory peritoneal dialysis (CAPD) by studying change in the microcirculation of the fingernails of CAPD patients. Setting A university department. Design A cross-sectional study of 10 nondiabetic patients on CAPD. Intervention Hemorrheological tests of fingernail microcirculation using equipment built at our university. Main Outcome Measures Microcirculation was characterized by estimation of capillary density, red blood cell (RBC) column diameter, torque index, and RBC flow velocity semiquantitatively using videocapillaroscopy at the fingernail fold and plasma viscosimetry. Findings were correlated with treatment duration, peritoneal clearance, state of capillary morphology and hemodynamics, and lipid and fibrinogen levels. Results Treatment duration was significantly correlated (p ≤ 0.05) with low-density lipoprotein (LDL) (r = 0.776) and clearances of urea (r = -0.583), uric acid (r = -0.666), and potassium (r = -0.764). Changes in capillary morphology were correlated to clearances of urea (r = 0.643) and uric acid (r = 0.701). The fibrinogen concentration increases plasma viscosity (r = 0.799) and deteriorates the capillary state (r = -0.706). In addition, plasma viscosity correlates to cholesterol (r = 0.620, NS) and LDL (r = 0.781), but not to high-density lipoprotein and triglycerides. Conclusion CAPD treatment results in lipid abnormalities and high fibrinogen levels that may cause microvascular damage and poor perfusion. These interactions may explain the deterioration of peritoneal transport in some CAPD patients.