Natural convection heat transfer at reduced pressures

This paper experimentally studies the natural convection heat transfer characteristics on horizontal and vertical plates at pressures lower than atmospheric value. Eight different pressures ranging from 10Pa to 101.325kPa, and three heating loads were used in the experiments. It is found that natural convection heat transfer characteristics at reduced pressures are independent of the plate arrangements and present different behaviors in two pressure ranges, 10Pa < p < 1000Pa and p > 1000Pa. The experimental heat transfer results are correlated into a non-dimensional equation to help the thermal design of stratosphere aircrafts and airborne equipment.     

Aluminium fractionation using cation exchange: comparison of results obtained after fractionation in the field and in the laboratory

Dissolved aluminium was fractionated in the field and the laboratory using a cation-exchange method. Although absolute differences between results obtained from field and laboratory fractionations were generally small, relative differences, expressed as the ratio between labile aluminium determined after laboratory fractionation (Al_ll) and that obtained after field fractionation (Al_lf) could be large. The differences found were not statistically significant, although this may simply reflect the spread in the results. Al_ll/Al_lf had no apparent relationship with the temperature difference between the field and the lab. Although some significant correlations were found between Al_ll/Al_lf and H⁺, no significant correlations were found with the equivalent relative difference in {H⁺} between the lab and the field; nor was any significant correlation found with dissolved organic carbon.     

An active and selective heterogeneous catalytic system for Michael addition

Potassium fluoride doped natural zeolite was found to be an efficient and selective solid base catalyst for 1,4-Michael addition. The catalyst is easily prepared and the workup procedure simplified by simple filtration.All products were obtained in high yields as well as short reaction times.     

Synthesis of (+)-boronolide and (+)-deacetylboronolide using Pd-catalyzed carbonylation and lactonization

(+)-Boronolide and (+)-deacetylboronolide were synthesized using Pd-catalyzed CO insertion and lactonization as the key step. As to the ¹³C NMR data of (+)-deacetylboronolide, the assignment at C-6 position should be revised.     

Miscanthus stem fragment – Reinforced polypropylene composites: Development of an optimized preparation procedure at small scale and its validation for differentiating genotypes

The production of ligno-cellulosic biomass-based composites requires the development of new methodologies to evaluate the reinforcement potential of a given biomass, such as miscanthus studied in the work. Miscanthus stems from thirteen genotypes were broken into elongated fragments and mixed with polypropylene composites in an internal mixer. The aim is to find the best protocol able to discriminate miscanthus genotypes for their reinforcement capability. The following process parameters were optimized in order to maximize the reinforcement effect of the stem fragment filler: mixing parameters (mixing time, rotor speed and chamber temperature), temperature, fragment content, size and length distributions and coupling agent. The relationship between the process parameters and the mechanical properties of composites were analyzed to evaluate the influence of genotype on reinforcement performance, showing the robustness of the protocol in effectively discriminating genotypes according to their reinforcing capacity.     

Matrix Isolation Infrared Spectra of Methylacetate III. UV-Induced Z→E photorotamerisation of Methylacetate in Argon Matrices

Abstract

Broadband UV-irradiation of methylacetate isolated in argon matrices causes rather strong modifications to appear in the IR spectrum. Evidence was obtained for a photochemical interconversion of the stable Z-conformer into the less stable E-conformer followed by photolytic decomposition of the latter into stable products. Most of these products could be identified from their IR absorptions. The reverse E→Z interconversion is a thermal process with an activation energy of about 10 kJmole^?1. A normal coordinate analysis based on a transferable valence force field obtained from the literature allowed to assign approximate IR frequencies of E-methylacetate.     

Two-electron entanglement in elliptically deformed quantum dots

Entropic entanglement measures of a two-dimensional system of two Coulombically interacting particles confined in an anisotropic harmonic potential are discussed in dependence on the anisotropy and the interaction strength. The harmonic approximation appears exact in the strong interaction limit, allowing determination of the asymptotic expression for the linear entropy. Entanglement properties are dramatically influenced by the anisotropy of the confining potential in the strong-correlation regime.