Oxidative-gravimetric porosimetry of macroporous silicon

A simple nondestructive method to find the internal surface area, porosity, pore diameter, and pore density in macroporous silicon with through channels is suggested and tested. The porosity p is determined from the mass loss upon anodizing, and the surface area per unit volume, S _v , from the mass of SiO₂ formed on the pore surface upon thermal oxidation. The relations are given for calculation of the average pore diameter d and pore density N from the obtained S _v and p. Dependences of the specific surface area and porosity on the resistivity of initial n-Si in the range ρ = 3–25 Θ cm have been studied for samples with ordered and self-organized “lattices” of macropores. The obtained values are within the limits p = 27–50%, S _v = 2800–6000 cm²/cm³, d = 1.9–6.5 μm, and N = 1.4?10 × 10⁶ cm^?2, in agreement with the data fumished by microscopy.     

Using Literal and Grammatical Statistics for Authorship Attribution

Markov chains are used as a formal mathematical model for sequences of elements of a text. This model is applied for authorship attribution of texts. As elements of a text, we consider sequences of letters or sequences of grammatical classes of words. It turns out that the frequencies of occurrences of letter pairs and pairs of grammatical classes in a Russian text are rather stable characteristics of an author and, apparently, they could be used in disputed authorship attribution. A comparison of results for various modifications of the method using both letters and grammatical classes is given. Experimental research involves 385 texts of 82 writers. In the Appendix, the research of D.V. Khmelev is described, where data compression algorithms are applied to authorship attribution.     

Structure of a biocatalyst fibre containing modified β-galactosidase

Conclusions A connection between the composition of the spinning solution intended for preparation of a biocatalyst fibre, the conditions of fibre spinning, and the porosity characteristics of the fibre structure has been established.The possibility of purposefully regulating the catalytic properties of a biocatalyst fibre by varying the fibre structure has been demonstrated.Translated from Khimicheskie Volokna, No. 1, pp. 21–23, January–February, 1989.     

Formation of Porous Silicon by Nanopowder Sintering

Semiconductors - The technique of the electrochemical and photoelectrochemical etching of single-crystal silicon wafers commonly used to fabricate macroporous silicon layers is inefficient and...