A Free Boundary Problem Modelling the Electrolysis of Aluminium

The goal of this note is to show existence and uniqueness for a stationary one-phase Stefan problem with source at the free boundary modelling the electrolysis of aluminium.     

怀孕期头发中一些元素含量的变化趋势

用同步辐射激发X射线荧光分析,对11个产妇怀孕期间头发内一些元素含量的变化趋势进行了测量,在各自对比的基础上,得到了一些结果。     

Method for detecting superconducting stripes in high-temperature superconductors based on nonlinear resistivity measurements

We theoretically study the effect that stripelike superconducting inclusions would have on the nonlinear resistivity in single crystals. Even if the stripe orientation varies throughout the sample between two orthogonal directions due to twinning, we predict that there should be a universal dependence of the nonlinear resistivity on the angle between the applied current and the crystal axes. This prediction can be used to test the existence of superconducting stripes at and above the superconducting transition temperature in cuprate superconductors.     

Effect of stoichiometry and pH on the structure and properties of Chitosan/Chondroitin sulfate complexes

This work reports the formation of chitosan (CHT)/chondroitin sulfate (CS) polyelectrolyte complexes and evaluates the changes in their complexation-stoichiometries, crystallinity, and mechanical properties at different pHs used for both complex preparation and swelling. Through high-performance liquid chromatography, the changes in CHT/CS complex stoichiometry due to CS release from CHT/CS complexes, which occurred mainly during swelling at pH ??6, were determined. In addition, strong evidences of self-assembling on CHT/CS complex network as swelled at pH?12 buffer were observed by WAXS patterns. Such a new rearrangement of the network increases the CHT/CS complexes rigidity as well as their elastic moduli, E, as observed through compressive tests. The results found in this work provide new information to allow the tailoring of the biofunctionalities of the CHT/CS complex for the development of physiological pH-compatible materials.     

Investigation of the bioenergy potential of microalgae Scenedesmus acuminatus by physicochemical characterization and kinetic analysis of pyrolysis

In this work, the bioenergy potential of green microalgae Scenedesmus acuminatus was evaluated through the psychochemical characteristics and kinetic study of pyrolysis, where the results indicate a good candidate for application in the thermochemical process due to its low moisture and ash content and high calorific value. Its thermal behavior under a heating rate of 10 °C min^?1 and inert atmosphere shows that decomposition occurs in two stages. Stage I (125–309 °C) involves the pyrolysis of carbohydrates and protein and stage II (309–501 °C) the pyrolysis of lipids. The Starink isoconversional method showed a better application for simulation curves, compared with methods of FWO and KAS. The average values of activated energy were 107.1 and 132.6 kJ mol^?1 for stages I and II, respectively, which indicates that pyrolysis occurs more easily in stage I than in stage II. The conversion rate curves show that the calculated kinetic parameters are satisfactory for the evaluation of the thermochemical systems.

     

Formation of Symmetric Structures in the Dynamics of Repelling Particles

We consider Hamiltonian systems corresponding to the motions of a system of N repelling particles evolving in space under the action deriving from a very long range potential energy; the asymptotic behavior of the system is analysed for the cases U=− ln r and . Only special “asymptotic?shapes” are reached, which may present quite interesting symmetries and correspond to the critical points of a gradient system. The relationships between the original Hamiltonian and the asymptotic gradient system are discussed. Accepted: May 25, 1999     

Efficient synthesis and dehydration reaction of trichloromethylated 2‐(3‐phenyl‐5‐hydroxy‐4,5‐dihydro‐1H‐pyrazol‐1‐yl)‐4‐aryl‐5‐alkylthiazoles

A convenient method for the synthesis of a novel series of 11, specifically substituted, noncondensed 5,5‐bicycles 2‐[3‐phenyl‐5‐hydroxy‐5‐trichloromethyl‐4,5‐dihydro‐1H‐pyrazol‐1‐yl]‐4‐aryl‐5‐alkylthiazoles ( 3a–k ; 65–94% yield) from the reactions of 3‐phenyl‐5‐hydroxy‐5‐trichloromethyl‐4,5‐dihydro‐1H‐1‐pyrazolethiocarboxyamide ( 1 ) with substituted 2‐bromo‐4′‐acetophenones ( 2a–f ) and 2‐bromo‐4′‐propiophenones ( 2g–k ) is reported. Dehydration of compounds 3a–k with a mixture of concentrated sulfuric acid/chloroform furnished the corresponding 2‐[3‐phenyl‐5‐trichloromethyl‐1H‐pyrazol‐1‐yl]‐4‐aryl‐5‐alkylthiazoles ( 4a–k ) in good yields (61–93%). © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:132–137, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10113     

Superabsorbent hydrogel nanocomposites based on starch-g-poly(sodium acrylate) matrix filled with cellulose nanowhiskers

Superabsorbents hydrogel nanocomposites based on starch-g-poly(sodium acrylate) and cellulose nanowhiskers (CNWs) were synthesized. A set of experiments was performed to evaluate the influence of some factors such as NaAc/starch mass ratio, crosslinker, and nanowhiskers amount in the swelling capacity and swelling kinetics. Increasing the NaAc/starch mass ratio up to 7 leads to an increase in the water uptake at a maximum value, however, higher ratios decreased that value due to the increase of crosslinking points. Similarly, the incorporation of CNWs up to 10 wt% provided an improvement in the swelling due to the hydrophilic groups from cellobiose units. Further, the incorporation of CNWs diminishes the water uptake. Besides, the CNWs improved the mechanical properties. SEM images showed that CNWs increase the average porous size of composites. The composites presented good responsive behavior in relation to pH and salt presence allowing those materials suitable for many potential applications.