Kinetics of Crystallization of Binary Melts of Eutectic-Forming Substances

The crystal nucleation and growth rates in eutectic-forming melts are experimentally determined using a universal technique for finding the kinetic parameters of processes involving phase transformations. It is shown that, with an increase in the concentration of the impurity component, the crystal nucleation and growth rates gradually decrease and reach a minimum at a eutectic point. It is confirmed that inter- and extrapolation equations known in the theory of crystallization of one-component melts can be used to obtain reliable values of the kinetic parameters in the crystallization of binary melts at large supercoolings.     

Early soot formation stages in low-pressure diffusional counterflow hydrocarbon flames

Early soot formation stages were investigated in low-pressure counterflow hydrocarbon flames. A mechanism is proposed for the formation of aggregates and discrete spherical soot particles. It is proposed that the formation of the physical surface is preceded by the emergence of a skeleton structure consisting of carbon molecule chains as a result of their polarizing and dipole interaction with the charged soot nuclei.Kiev. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 3, pp. 97–100, May–June, 1993.     

Calculations of thermal ignition time of hydrogen–air mixtures taking into account quantum corrections

The effect of quantum corrections to the rate constants of chemical reactions on the time of thermal ignition of hydrogen-containing mixtures is studied. It is shown that, at high pressures (30–100) atm and temperatures in the range of (700–900) K, accounting for the quantum corrections to the initiation reaction H₂ + O₂ → 2OH brings the data on the calculated ignition delay times of the hydrogen-containing mixture into agreement with the previously published results of measurements.     

Formic Acid Production Via Methane Peroxide Oxidation Over Oxalic Acid Activated Fe-MFI Catalysts

Topics in Catalysis - The process of synthesis of formic acid via partial peroxide oxidation of methane over Fe-MFI zeolites, as well as the influence of the catalyst activation by oxalic acid on...     

Surface‐enhanced fluorescence of in situ synthesized polysilanesilver nanoparticles

To produce surface plasmons, silver nanoparticles are synthesized in situ in a pseudo‐template system based on polyhydrosilanes. Adsorption on the silver nanoparticle surface produces a thin layer of polymer with properties different from those of bulk polysilane. The metal‐adsorbed polymer layer serves as a spacer between the polysilane fluorophore and the plasmonic nanoparticle. This prevents quenching of the polysilane emission and leads to a strong surface‐enhanced fluorescence through coupling of surface plasmons having a resonance frequency that matches the emission frequency of the polymeric emitter. Copyright © 2012 Society of Chemical Industry     

Environmentally friendly,energy-saving technology for encapsulation of granules in thin waterproof polymer shells

For enhancing environmental safety, aqueous emulsions of polymer solutions are suggested as encapsulants for the combined process of prilling of melt drops in an encapsulant solution followed by separation of the encapsulant solvent from the granules by utilizing the residual heat of the phase transition.     

Carbon nanotube air-bubble interactions studied by atomic force microscopy

Interaction forces between a multi-walled carbon nanotube (MWCNT) and an air-bubble in pure deionized water and methyl isobutyl carbinol (MIBC) solutions were measured by atomic force microscopy (AFM). The MWCNT terminated probe was brought into contact with the bubble at controlled applied forces. The repulsive steps followed by attractive jumps recorded in the approach force curves correspond to changes in the MWCNT diameter along its length, an observation confirmed by transmission electron microscopy (TEM) data. By processing the retraction part of the force curves obtained in pure water it is possible to estimate the end diameter of the carbon nanotube with nanometer resolution using a capillary force model.     

Utilization pattern of fuelwood plants by the Halam community of Tripura,Northeast India

The present study was undertaken to identify the fuelwood plant species and their utilization pattern by the Halam community of Tripura. The main objective of this study was to assess the species preference as fuelwood, the total value index, and the fuelwood value index (FVI) of 22 species. The majority of the households use the plant resources for domestic purpose. Although the community’s mostly preferred fuelwood species were Tectona grandis L.f, Shorea robusta C. F. Gaertn, and Gmelina arborea Roxb, a total of 22 species were reported from the study site. Trewia nudiflora L., Albizia procera Benth., Dysoxylum procerum Hierm., and Cassia siamea Lam. were also reported as fuelwood species with good wood quality (FVI). Thus awareness on the use of these species as fuelwood can be increased in the community to reduce stress on the preferred species and the surrounding forest.     

Effect of Fe doping on structure,magnetic and electrical properties La0.7Ca0.3Mn0.5Fe0.5O3 manganite

The crystal and magnetic structures of La_0.7Ca_0.3Mn_0.5Fe_0.5O₃ compound have been studied by neutron powder diffraction in the temperature range of 10–300 К. The magnetization and electrical resistivity measurements have been also performed in the temperature range of 5–300?K in magnetic fields up to 1?T. These experimental results indicate a formation of a complex magnetic state in which the long-range antiferromagnetic G-type phase coexists with the short-range ferromagnetic clusters. The electrical conductivity of La_0.7Ca_0.3Mn_0.5Fe_0.5O₃ demonstrates an anomalous temperature behavior suggesting a switching between different states. The origin of the unconventional magnetic state, the mechanisms of the electrical conductivity, and correlation between magnetic and transport properties in this manganite have been discussed.     

Comments on the self-focusing of short light pulses

A simple analysis of the self-focusing of a short pulse shows that the distance at which the focal region first appears exceeds the minimum focusing distance Zfby an amount dependent upon the initial pulsewidth. This focal region subsequently expands as it moves down the medium, the limiting width being the width of the portion of the pulse above the critical power.