Modification of Tefzel film through graft copolymerization

The graft copolymerization of styrene (st) and methacrylonitrile (MAN) onto Tefzel film in aqueous media by the preirradiation method has been studied. In order to follow the effect of preswelling of the backbone polymer, grafting was attempted onto preirradiated Tefzel film and monomer preswollen, preirradiated Tefzel film. Optimum conditions pertaining to maximum percentage of grafting of st and MAN have been evaluated. Grafting onto preswollen, preirradiated Tefzel film displayed better results. The effect of different alcohols of increasing chain length on the percentage of grafting of st and MAN was also studied. Graft copolymerization of st showed an increase, while grafting with MAN exhibited a decrease, in the percentage of grafting in the presence of alcohols as compared to that obtained in the aqueous medium. Characterization of the graft copolymers was made by IR and thermogravimetric studies. Tefzel‐graft‐polystyrene showed improved thermal stability while the MAN grafted onto preswollen, preirradiated Tefzel film produced graft copolymer with poor thermal stability. Copyright © 2004 Society of Chemical Industry     

Strong segregation gettering of transition metals by implantation-formed cavities and boron-silicide precipitates in silicon

We have mechanistically and quantitatively characterized the binding of transition-metal impurities in Si to cavities formed by He implantation and to B---Si precipitates resulting from B implantation. Both sinks are inferred to act by the segregation of metal atoms to pre-existing low-energy sites, namely surface chemisorption sites in the case of cavities and bulk solution sites in the case of the B---Si phase. These gettering processes exhibit large binding energies, and they are predicted to remain active for arbitrarily small initial impurity concentrations as a result of the segregation mechanisms. Both appear promising for gettering in Si devices.     

Nonlinear versus linear control in the robust stabilizability oflinear uncertain systems via fixed-order output feedback

This paper considers the problem of robustly stabilizing an uncertain system via fixed-order output feedback control. This problem is considered by defining a notion of robust stabilizability with a quadratic storage function. This notion is closely related to the notion of quadratic stabilizability. The main result of the paper shows that if an uncertain system is robustly stabilizable with a quadratic storage function via a nonlinear time-varying controller, then it will also be robustly stabilizable with a quadratic storage function via a linear time-invariant controller of the same order     

Post-tonsillectomy bacteraemia in children

It has been postulated that the bacteraemia rate following guillotine tonsillectomy is lower than that following dissection tonsillectomy due to intra-operative compression of tonsillar blood vessels by the guillotine. The aim of this study was to evaluate the incidence of bacteraemia following dissection and guillotine tonsillectomy. Sixty-four patients undergoing elective tonsillectomy for recurrent acute tonsillitis were randomly selected, 32 underwent dissection tonsillectomy and 32 guillotine tonsillectomy. Positive intra-operative blood cultures were obtained in 16 patients (25 per cent), nine (28.1 per cent) of the dissection group and seven (21.8 per cent) of the guillotine group. There was no significant difference between the two methods (Chi-squared test, p = 0.77).     

Faculty Mentoring: A Unique Approach to Training Graduate Students How to Teach

A summary of the motivations and observations of a recent faculty mentoring project designed to provide a graduate student with practical teaching experience is provided. The motivation for the project, the approach taken, and the results of the project are described from the perspective of the faculty mentor, the student trainee, and the student being taught in the class.     

Men and women in optometry. II. Attitudes toward career and family

BACKGROUND: Optometry has experienced a dramatic upward shift in the percentage of women entering the profession during the past 20 years. Our survey assessed the mechanisms for sustaining balance in professional and personal roles used by women optometrists and how these mechanisms may differ from those of their male colleagues. METHODS: A survey questionnaire was mailed to a large nationwide random sample of optometrists, composed of equal numbers of men and women. RESULTS: Data were analyzed from 353 men and 358 women; margin of error was +4%. Most of the respondents indicated they derived personal satisfaction from their career. A majority of both groups did not indicate that lack of time for their career was a source of frustration. However, significantly more women than men indicated some frustration in pursuing those activities that lead to career advancement. There were significant differences in response patterns of men and women about the effect of family, child care, and household work on their careers. CONCLUSIONS: Both men and women optometrists are satisfied with their careers and neither group feels compelled to choose between career and family. Optometrists do not fit into one pattern, but instead make individualized career choices on the basis of needs.     

Water,Energy and Environment Nexus: The California Experience

The paper addresses the local and inter-state connections between water, energy and the environment. Using California and the western USA as a case study, the paper highlights the difficulties of balancing the needs of diverse stakeholders and protecting valuable resources while providing reliable and safe supplies of both water and energy to agricultural, industrial and residential customers. The investigation of these complex relationships is necessary to inform local and national policy decisions regarding the management of water, energy and the environment.     

Effects of bis(2-ethylhexyl) phthalate on chromosomes of human leukocytes and human fetal lung cells

Blood from two male and two female donors was exposed at 37degrees for 4 hr to concentrations of 60.0, 6.0, 0.6, and 0.06 mug of a widely used plasticizer, bis (2-ethylhexyl) phthalate, per milliliter of blood. The bis(2-ethylhexyl) phthalate was solubilized with polysorbate 80. Appropriate polysorbate and nonpolysorbate controls also were established. Following the 4 hr of incubation, phytohemagglutinin was added and tissue cultures were established. In addition, human fetal lung cells were exposed in tissue culture to a medium containing 6.0 mug/ml of bis(2-ethylhexyl) phthalate in polysorbate 80 for 5 days. Similar controls also were established for these experiments. Analysis of chromosome preparations from all cultures obtained failed to show any increased evidence of isochromatid and chromatid breaks or gaps or abnormal forms at any studied concentration when compared to the control cultures. In addition, analysis of fetal lung cell preparations for aneuploidy failed to reveal any differences between cells from study and control cultures. This study involved a short-term exposure to bis(2-ethylhexyl) phthalate in various concentrations which did not cause damage in leukocytes or fetal lung cells.