Genesis of the structure and the phase and elemental compositions of an aluminum oxide catalyst in the isomerization process of n-butylenes

An investigation of the changes in the characteristics of the porous structure, phase, and elemental compositions of catalyst samples for the isomerization of n-butylenes using a set of physicochemical methods has been conducted. In has been established that under hydrothermal conditions of the isomerization process, aluminum oxide recrystallization takes place, resulting in a decrease of its specific surface value and a displacement of the maximum of the distribution of pore diameters to the region of greater values. A porous structure transformation scheme has been suggested while operating the isomerization catalyst for n-butylenes. It has been supposed that the partial phase change of γ-Al2O3 into δ-Al 2O3 occurring under industrial conditions of the isomerization of n-butylenes is caused by an accumulation of metal compound admixtures supplied with the feed flow. © 2009 Pleiades Publishing, Ltd

Genome-Wide Crossover Distribution in Arabidopsis thaliana Meiosis Reveals Sex-Specific Patterns along Chromosomes

In most species, crossovers (COs) are essential for the accurate segregation of homologous chromosomes at the first meiotic division. Their number and location are tightly regulated. Here, we report a detailed, genome-wide characterization of the rate and localization of COs in Arabidopsis thaliana, in male and female meiosis. We observed dramatic differences between male and female meiosis which included: (i) genetic map length; 575 cM versus 332 cM respectively; (ii) CO distribution patterns: male CO rates were very high at both ends of each chromosome, whereas female CO rates were very low; (iii) correlations between CO rates and various chromosome features: female CO rates correlated strongly and negatively with GC content and gene density but positively with transposable elements (TEs) density, whereas male CO rates correlated positively with the CpG ratio. However, except for CpG, the correlations could be explained by the unequal repartition of these sequences along the Arabidopsis chromosome. For both male and female meiosis, the number of COs per chromosome correlates with chromosome size expressed either in base pairs or as synaptonemal complex length. Finally, we show that interference modulates the CO distribution both in male and female meiosis

Genesis of the structure and the phase and elemental compositions of an aluminum oxide catalyst in the isomerization process of n-butylenes

An investigation of the changes in the characteristics of the porous structure, phase, and elemental compositions of catalyst samples for the isomerization of n-butylenes using a set of physicochemical methods has been conducted. In has been established that under hydrothermal conditions of the isomerization process, aluminum oxide recrystallization takes place, resulting in a decrease of its specific surface value and a displacement of the maximum of the distribution of pore diameters to the region of greater values. A porous structure transformation scheme has been suggested while operating the isomerization catalyst for n-butylenes. It has been supposed that the partial phase change of γ-Al2O3 into δ-Al 2O3 occurring under industrial conditions of the isomerization of n-butylenes is caused by an accumulation of metal compound admixtures supplied with the feed flow. © 2009 Pleiades Publishing, Ltd

Genesis of the structure and the phase and elemental compositions of an aluminum oxide catalyst in the isomerization process of n-butylenes

An investigation of the changes in the characteristics of the porous structure, phase, and elemental compositions of catalyst samples for the isomerization of n-butylenes using a set of physicochemical methods has been conducted. In has been established that under hydrothermal conditions of the isomerization process, aluminum oxide recrystallization takes place, resulting in a decrease of its specific surface value and a displacement of the maximum of the distribution of pore diameters to the region of greater values. A porous structure transformation scheme has been suggested while operating the isomerization catalyst for n-butylenes. It has been supposed that the partial phase change of γ-Al2O3 into δ-Al 2O3 occurring under industrial conditions of the isomerization of n-butylenes is caused by an accumulation of metal compound admixtures supplied with the feed flow. © 2009 Pleiades Publishing, Ltd

Thinning of a vertical free draining aqueous film incorporating colloidal particles

The drainage under gravity of a vertical foam film formed on a wire frame has been investigated. Dual-wavelength optical interferometry was used so that unambiguous fringe order assignments could be made, enabling absolute film thicknesses to be calculated with confidence. Films were stabilized by nonionic polypropylene glycol surfactant. Halfmicrometer silica particles with varying degrees of hydrophobicity were added to the film-forming liquid to investigate their effect on film drainage rate and stability. Hydrophilic particles had little or no effect, while hydrophobic particles slowed the drainage of the film and caused a minor increase in film lifetime, from &sim;10 to &sim;30 s. In both the hydrophilic and hydrophobic cases the films ruptured when they reached a thickness of &sim;2 particle diameters. Particles of intermediate hydrophobicity had the most significant effect, increasing film lifetime by an order of magnitude over that for hydrophilic particles. The intermediate particles allowed films to thin down to a thickness less than the particle diameter, indicating that particles bridge across the entire film. This did not occur with more hydrophobic particles even though they were embedded in each of the two film surfaces. These results correlate well with previous literature on particle-laden foams. The film thickness and drainage measurements allow drainage mechanisms for the different particles to be identified, thus providing a mechanistic explanation for the observation by several previous authors that foams formed in the presence of particles, for example during mineral processing, have the greatest stability when the particles are of intermediate hydrophobicity.<br /