Czechoslovak Academy of Sciences

About: Czechoslovak Academy of Sciences is a based out in . It is known for research contribution in the topics: Catalysis & Polymerization. The organization has 13227 authors who have published 17335 publications receiving 272882 citations.

Optical Properties and Electronic Structure of Amorphous Germanium

Abstract: The optical constants of amorphous Ge are determined for the photon energies from 0.08 to 1.6 eV. From 0.08 to 0.5 eV, the absorption is due to k-conserving transitions of holes between the valence bands as in p-type crystals; the spin-orbit splitting is found to be 0.20 and 0.21 eV in non-annealed, and annealed samples respectively. The effective masses of the holes in the three bands are 0.49 m (respectively 0.43 m); 0.04 m, and 0.08 m. An absorption band is observed below the main absorption edge (at 300 °K the maximum of this band is at 0.86 eV); the absorption in this band increases with increasing temperature. This band is considered to be due to excitons bound to neutral acceptors, and these are presumably the same ones that play a decisive role in the transport properties and which are considered to be associated with vacancies. The absorption edge has the form: ω2ϵ2∼(hω−Eg)2 (Eg = 0.88 eV at 300 °K). This suggests that the optical transitions conserve energy but not k vector, and that the densities of states near the band extrema have the same energy-dependence as in crystalline Ge. A simple theory describing this situation is proposed, and comparison of it with the experimental results leads to an estimate of the localization of the conduction-band wavefunctions.

Rectangular Confidence Regions for the Means of Multivariate Normal Distributions

Abstract: For rectangular confidence regions for the mean values of multivariate normal distributions the following conjecture of 0. J. Dunn [3], [4] is proved: Such a confidence region constructed for the case of independent coordinates is, at the same time, a conservative confidence region for any case of dependent coordinates. This result is based on an inequality for the probabilities of rectangles in normal distributions, which permits one to factor out the probability for any single coordinate.

Hydrophilic Gels for Biological Use

Abstract: PLASTICS to-day enjoy wide use in many fields, and it is natural that the possibility of their employment in permanent contact with living tissues has been seriously considered. A study of the literature shows that almost all known plastics have been proposed for this purpose at various times. The question of structural similarity with the tissue has not, however, been emphasized although physiologically unfavourable effects were observed in most cases of application of normal type plastics.

Intrinsic stacking faults in body-centred cubic crystals

Abstract: A study of the possibility of the existence of stacking faults in b.c.c. crystals on {110} and {112} planes has been performed, representing the lattice by a central force interaction between atoms. The same study was also carried out for {111} planes in f.c.c. crystals. The results for the f.c.c. lattice are in full agreement with the predictions based on a hard-sphere model. However, the results for the b.c.c. lattice are very different and suggest that no stable instrinsic stacking faults of the same type as in f.c.c. crystals can exist either on {110} or on {112} planes in b.c.c. crystals.