Preparation of ultra‐low‐density microcellular materials

Microcellular polymeric materials can be obtained by the polymerization of a high‐internal‐phase emulsion. These materials are good candidates as targets toward inertial confinement fusion. This application requires severe specifications, including a very low density and a small cell size. In this study, we examined the influence of parameters such as emulsification conditions, surfactant nature, and the presence of a porogen on the obtainment of those requirements. It was possible to obtain microcellular polymeric foams with apparent densities as low as 0.0126 g/cm³. However, it was difficult to obtain very low material density and still maintain a small average pore size. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2053–2063, 2005     

Viscoelastic response of solid rocket motor components for service life assessment

A methodology for determining the response of rocket motor materials and bondlines to thermal loadings by measuring their dynamic mechanical properties is reported. The critical temperatures at which debonding and/or propellant cracking occur and the number of thermal cycles required to induce failure were evaluated. These results were compared with those from instrumented rocket motors subjected to similar thermal loadings. A model, developed for fibre reinforced composites, was applied to the propellant-inhibitor bimaterial obtained from a rocket motor. The internal energy dissipation due to a lack of perfect adhesion at the propellant–inhibitor interface, tan δ_adh, was used to give an indication of the failure mode of the bondline (i.e., adhesive failure at the interface or cohesive failure in the propellant) and the bond adhesion parameter, C, was related to the bond strength measured by rectangular bond-in-tension tests. This revised version was published online in November 2006 with corrections to the Cover Date.     

Has risk associated with smoking increased? Results from the Copenhagen Center for Prospective Population Studies

BACKGROUND: Two recent much cited publications have raised the concern that risk associated with cigarette smoking has so far been underestimated. In this study we wish to determine whether excess all-cause mortality associated with smoking has increased during the last 20-30 years in a study population representative of the general Danish population and whether any such changes relate to changes in smoking behaviour. METHODS: Pooled data from three prospective population studies conducted in Copenhagen with detailed information on smoking habits. A total of 31,194 subjects, 17,669 males and 13,525 females, initially examined between 1964 and 1992 with examinations repeated at intervals from 1-10 years, were followed until 1995 for all-cause mortality. Relative mortality risk in smokers versus never-smokers was calculated within periods of five calendar years and compared throughout the study period. RESULTS: Male smokers' exposure did not change during the study period whereas female smokers' exposure to tobacco increased in terms of age at smoking onset, quantity smoked and depth of inhalation. During follow-up 5744 males and 2900 females died. In males, death rate ratios (comparing continuous smokers with never-smokers) did not change in the study period. In females, ratios increased from 1964-1978 to 1979-1994 by a factor of 1.3 (95% confidence interval 1.0-1.8). CONCLUSIONS: In agreement with the observed changes in smoking habits, excess mortality in male smokers did not increase whereas excess mortality in female smokers increased slightly.     

A SURVEY OF ARYLAMINE N-ACETYLTRANSFERASE ACTIVITY IN COMMON FRUITS AND VEGETABLES

The N-acetyltransferase activity was determined in 58 common fruits and vegetables. The assay was based on acetylation of 2-aminofluorene or p-amino-benzoic acid, followed by high pressure liquid chromatographic analysis of products and remaining nonacetylated substrate. The highest specific activities were observed in Balsam pear which contained 17.37 ± 1.45 N-acetyl aminofluorene nmole/min/mg protein and 46.27 ± 6.87 N-acetyl p-aminobenzoic acid nmole/min/mg protein. N-acetyltransferase activities within the remaining 57 foodstuffs analyzed ranged from none detected to 3.39 ± 0.72 N-acetyl aminofluorene nmole/min/mg protein and none detected to 32.45 ± 6.55 N-acetyl p-aminobenzoic acid nmole/min/mg protein. This is the first demonstration of acetyl CoA: arylamine N-acetyltransferase activity in common foodstuffs.     

Current concepts in dentin bonding: focusing on dentinal adhesion factors

With greater need for treating root surface lesions, dentinal adhesives are more in demand. For successful treatment, all factors--dentin, tooth, patient and materials--must be considered.     

Characterization of the bioactive form and molecular determinants of recognition of cyclic enkephalin peptides at the delta-opioid receptor

An extensive and systematic search strategy to determine the conformational profile of 12 cyclic disulfide-bridged opioid peptides with varying affinities at the delta receptor has been carried out to identify the structure that is recognized by the delta receptor for each analogue. The methods and procedures used here for the conformational search have already been validated for [D-Pen2,D-Pen5] enkephalin (DPDPE), one member of this family. Use of these methods led to a low-energy solution conformation of DPDPE in excellent agreement with all the geometric properties deduced from its solution nmr spectra. Each of the analogue was subjected to the same procedure, involving a combination of molecular dynamics simulations at high and low temperature. The study was repeated in two environmental conditions, an apolar environment, simulated by using a distance-dependent dielectric constant, and a polar environment by embedding the peptides in a high constant dielectric (epsilon = 80). An automated comparison of the different conformers based on their backbone rms and average distance between the key aromatic moieties was followed by graphic analysis using maximum structural overlap. The cross-comparison of the conformations for each analogue revealed a unique conformer that may be recognized by the delta receptor for each high-affinity analogue that permitted maintaining the critical elements required for recognition in a simple spatial orientation, while maximizing similarity in other regions.     

Smart cars, smart highways

Advanced electronics is being used to unclog the transportation network and allow private vehicles, trucks, buses and trains to move further faster. already a range of technologies and ideas have been explored, deployed, and tested as part of the Intelligent Vehicle Highway System programs in the United States and Japan, and in the Road Transport Informatics program in Europe. The authors describe how these latest electronics for automobiles and roadways herald far fewer traffic jams, greater safety, and perhaps even a decline in pollution     

Catch me if you can: are catechol- and indoleamine genes pleiotropic QTLs for common mental disorders?

The aim of this study was to determine the effect of a short-term ethinyl estradiol/levonorgestrel medication on blood flow in the uterine arteries in postmenopausal women in a prospective placebo-controlled double-blind study. Twenty-one healthy postmenopausal woman at least 2 years after menopause received 60 micrograms ethinyl estradiol (EE) for 14 days followed by 40 micrograms EE plus 125 micrograms levonorgestrel (LNG) for 12 days (total treatment period 26 days). Sonographically, uterine volume, endometrial thickness, and blood flow in the uterine arteries [as reflected by pulsatility (PI) and resistance indices (RI)] were measured. Uterine size increased from 44 to 80 mL (day 14, p < 0.001) and 87 mL (day 26, p = NS). Endometrium grew from 3 to 8 mm (day 14, p < 0.001) and 11 mm (day 26, p = NS). Uterine arterial PI fell from 2.76 to 1.37 (day 14, p < 0.001) and 1.34 (day 26, p = NS), whereas RI fell from 0.9 to 0.68 (day 14 and day 26, p < 0.001). In conclusion, short-term treatment with LNG does not antagonize the vascular effect of EE on the uterine arteries as reflected by PI and RI. This result might have clinical significance in the selection of the progestin used in hormonal replacement therapy.