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The phenomenon of electrification is the accumulation of electric charge in a material. Polymers may become electrified when subjected to intense friction during their processing or under working conditions and the accumulated electric charge may change their adhesion and friction properties. In this work, a study of the influence of molecular weight and chain mobility on the electrification of linear low-density polyethylenes under continuous extrusion is presented. The use of different die materials, polymer processing additives, as well as slip and no slip flow conditions allowed the identification of two different mechanisms for electric charge generation in the melts; namely, the stripping of an electrical double layer acting in the absence of slip, and dynamic frictional electrification, or tribocharging acting under strong slip conditions. The magnitude of the electric charge was found to increase with polymer molecular weight and die length, and exhibited a local maximum as a function of the average velocity of the melt in both cases. The height of the maximum increased along with the molecular mobility. The experimental results were compared with the numerical solution of the equation of continuity for charge transport and it is shown that it does not describe the experimental results because it does not consider the additional mechanism of charge generation introduced by strong slip at the die wall. POLYM. ENG. SCI., 48:386-394, 2008. © 2007 Society of Plastics Engineers, INTRODUCTION The phenomenon of electrification is the accumulation of electric charge in a material. The electric charge on a polymeric surface is usually removed by the air with the help [...]

Results show that although mutation in the wide-domain repressor CreA gene leads to an elevated levels of xlnB mRNA, none of the CreA consensus target sites are localized in the xlnB gene. Data suggest that the catabolite repression of the xlnB encoded xylanase is exerted in an indirect manner.

Research was conducted to examine the molecular cloning and transcriptional regulation of the Aspergillus nidulans xlnD gene encoding the 85-kDA beta-xylosidase. The primary structure of the protein had considerable similarity to the primary structures of the Trichoderma reesei and Aspergillus niger beta-xylodases. Western blot analysis revealed elevated levels of production of the enzyme in overexpressing transformants showing that the cloned sequences existing in pXE1 encode the previously characterized 85-kDa beta-xylosidase.

Saccharomyces cerevisiae cells expressing Aspergillus nidulans xlnA and xlnB genes produce X(sub 22) and X(sub 24) xylanases that hydrolyze xylan. The cells expressing xlnA show greater xylanase activity than those expressing xlnB. Xylanase activity in recombinant S. cerevisiae is less than that in A. nidulans cells transformed with the xlnA and xlnB genes and their upstream amino acids. The genes are open reading frames containing introns. The xlnA encoded protein has 187 residues and a molecular weight of 20,247 while the xlnB encoded protein has 182 residues and a molecular weight of 20,088.

Heterologous hybridization facilitates the cloning of the Aspergillus terreus gla1 gene, which encodes a glucoamylase. Transcriptional analysis of the gene reveals the presence of a protein having a C-terminus starch-binding domain and N-terminal catalytic domain. Examination of the influence of carbon sources on gla1 regulation reveals that starch and maltose stimulate the expression of the gene, while glucose represses the expression.

A novel method to induce genetic metamorphosis in industrial wine dry yeast is based on the resistance of the yeast mold to the antibiotic cycloheximide. The altered strain produces wine in an identical fashion to the old strain. The recombinant wine yeast strain emits a fungal enzyme during the microvivification process, and therefore, an increase in the flavor of the wine can be detected.

A letter to the editor and a response from the authors of the article "Relation of body fat distribution to hyperinsulinemia in children and adolescents: the Bogalusa Heart Study" in the September 1987 issue are presented.