Preparation of activated carbons from cherry stones by activation with potassium hydroxide

Using cherry stones, the preparation of activated carbon has been undertaken in the present study by chemical activation with potassium hydroxide. A series of KOH-activated products was prepared by varying the carbonisation temperature in the 400-900 °C range. Such products were characterised texturally by gas adsorption (N₂, −196 °C), mercury porosimetry, and helium and mercury density measurements. FT-IR spectroscopy was also applied. The carbons prepared as a rule are microporous and macroporous solids. The degree of development of surface area and porosity increases with increasing carbonisation temperature. For the carbon heated at 900 °C the specific surface area (BET) is 1624 m² g⁻¹, the micropore volume is 0.67 cm³ g⁻¹, the mesopore volume is 0.28 cm³ g⁻¹, and the macropore volume is 1.84 cm³ g⁻¹.     

Evaluation of fluid-filled fractures during acoustic measurements on tube waves

The problem of reflection, transmission, and conversion of the tube wave on a fracture intersecting a borehole is investigated. We consider the case where an acoustic sonde is placed inside a borehole and the fracture separates two different elastic half-spaces and is filled with a porous material. Bibliography: 5 titles. __________ Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 324, 2005, pp. 121–128.     

Magnetooptical investigation of the micromagnetic structure and magnetization processes in Co69Fe4Si12B15 amorphous microwires

Magnetooptical investigation of the micromagnetic structure of Co₆₉Fe₄Si₁₂B₁₅ amorphous microwires 10–50 μm in diameter is carried out. The existence of domains with transverse circumferential magnetization is experimentally demonstrated in the near-surface region of microwires. The dependence of the width of circular domains on the length and diameter of wires is obtained. It is shown that the near-surface micromagnetic structure of amorphous wires is changed under a stretch-induced stress. It is proved that the magnetization reversal of microwires in a longitudinal magnetic field occurs due to the rotation of local magnetization vectors in circular domains.     

Low-temperature reaction of magnesium with fluorobenzene

The low-temperature reaction of magnesium with fluorobenzene has been investigated. Joint condensation of magnesium and fluorobenzene vapours at low temperatures quantitatively gave phenylmagnesium fluoride in one stage.     

Two-spin-majority cellular automaton as a model of 2D cluster and interface growth

A new probabilistic cellular automaton model is introduced to simulate cluster and interface growth in two dimensions. The dynamics of this model is an extension to higher dimensions of the compact directed percolation studied by Essam. Numerical results indicate that the two-dimensional cluster coarsening and growth can be described only approximately by the conventional cluster size scaling due to a crossover in the growth mode. The spreading of the initially flat interface follows a purely diffusional,t ^1/2, law.     

Isotopic effects in H-atom abstraction from matrix molecules by methyl radicals in poly(methyl methacrylate). Determination of the scale of relative reagent motions

The H-abstraction by ?H₃ and ?D₃ radicals from PMMA molecules is investigated at 77 and 120 K. The film samples are prepared from the mixture of normal and deuterated PMMA. The reaction is of the first order with respect to radical concentration. Its rate is retarded in time as compared to the exponential law. An analysis of the molecular product ratio for the reaction allows the primary isotopic effect to be estimated. The initial reaction rate depends nonmonotonously on the proportion of the deuterated polymer in the matrix. Namely, there exists a range of isotopic compositions, with the reaction rate increasing with the portion of a deuteropolymer in the mixture. At 77 K the reaction rate of ?D₃ is lower than that of ?H₃ in PMMA of a mixed isotopic composition. This results from the proximity of ?D₃ with unreactive parental macromolecules, which reduces the local H concentrations around ?D₃ as compared to the mean concentration. At 120 K the radical decay rates do not differ. This fact cannot be explained by unfrozen mobilities of radicals at high temperatures or by their migration from parental macromolecules. The phenomenon is interpreted in terms of thermal fluctuations involving a great area around a radical and ensuring its migration within this area. The electron spin echo method is used to estimate the distance between a radical and its parental macromolecule, a ≥ 9.6 Å. This is the lower limit of the reaction accessibility.