ABA triblock copolymers: from controlled synthesis to controlled function

The ABA amphiphilic block copolymers, poly(hydroxyethyl methacrylate-hlock-methylphenylsilane-block-hydroxyethyl methacrylate) (PHEMA-PMPS-PHEMA) and poly[oligo(ethylene glycol) methyl ether methacrylate-block-methylphenylsilane-block-oligo(ethylene glycol). methyl ether methacrylate] (POEGMA-PMPS-POEGMA) were successfully synthesised via atom transfer radical polymerisation (ATRP). Macroinitiators suitable for the ATRP of oligo(ethylene glycol) methyl ether methacrylate and 2-hydroxyethyl methacrylate were synthesised from the condensation reaction of alpha,omega-dihalopolymethylphenylsilane and 2'-hydroxyethyl 2-bromo-2-methylpropanoate. The copolymers were characterised using H-1 NMR and C-13 NMR spectroscopy and molecular weight characteristics were determined using size exclusion chromatography and H-1 NMR. The aggregation behaviour of some of the copolymers in water was studied using transmission and scanning electron microscopy and dynamic light scattering. These revealed the prevalent aggregate species to be micelles. Larger aggregates of 300-1000 nm diameter were also observed. The UV induced degradation of the aggregates was studied by UV-Vis spectroscopy. The thermal behaviour of selected copolymers was studied by differential scanning calorimetry and microphase separation of the two components was demonstrated

The Effects of Thermonuclear Reaction-Rate Variations on 26Al Production in Massive Stars: a Sensitivity Study

We investigate the effects of thermonuclear reaction rate variations on 26Al production in massive stars. The dominant production sites in such events were recently investigated by using stellar model calculations: explosive neon-carbon burning, convective shell carbon burning, and convective core hydrogen burning. Post-processing nucleosynthesis calculations are performed for each of these sites by adopting temperature-density-time profiles from recent stellar evolution models. For each profile, we individually multiplied the rates of all relevant reactions by factors of 10, 2, 0.5 and 0.1, and analyzed the resulting abundance changes of 26Al. Our simulations are based on a next-generation nuclear physics library, called STARLIB, which contains a recent evaluation of Monte Carlo reaction rates. Particular attention is paid to quantifying the rate uncertainties of those reactions that most sensitively influence 26Al production. For stellar modelers our results indicate to what degree predictions of 26Al nucleosynthesis depend on currently uncertain nuclear physics input, while for nuclear experimentalists our results represent a guide for future measurements. We tabulate the results of our reaction rate sensitivity study for each of the three distinct massive star sites referred to above. It is found that several current reaction rate uncertainties influence the production of 26Al. Particularly important reactions are 26Al(n,p)26Mg, 25Mg(alpha,n)28Si, 24Mg(n,gamma)25Mg and 23Na(alpha,p)26Mg. These reactions should be prime targets for future measurements. Overall, we estimate that the nuclear physics uncertainty of the 26Al yield predicted by the massive star models explored here amounts to about a factor of 3.Comment: 44 pages, 16 figure

Charged-Particle Thermonuclear Reaction Rates: III. Nuclear Physics Input

The nuclear physics input used to compute the Monte Carlo reaction rates and probability density functions that are tabulated in the second paper of this series (Paper II) is presented. Specifically, we publish the input files to the Monte Carlo reaction rate code RatesMC, which is based on the formalism presented in the first paper of this series (Paper I). This data base contains overwhelmingly experimental nuclear physics information. The survey of literature for this review was concluded in November 2009.Comment: 132 page

Effect of diet composition and weight loss on resting energy expenditure in the POUNDS LOST study

Weight loss reduces energy expenditure, but it is unclear whether dietary macronutrient composition affects this reduction. We hypothesized that energy expenditure might be modulated by macronutrient composition of the diet. The POUNDS LOST study, a prospective, randomized controlled trial in 811 overweight/obese people who were randomized in a 2×2 design to diets containing 20en% or 40en% fat and 15en% or 25en% (diets with 65%, 55%, 45% and 35% carbohydrate) provided the data to test this hypothesis. Resting energy expenditure (REE) was measured at baseline, 6 and 24 months using a ventilated hood. REE declined at 6 months by 99.5±8.0 kcal/d in men and 55.2±10.6 kcal/d in women during the first 6 months. This decline was related to the weight loss, and there was no difference between the diets. REE had returned to baseline by 24 months, but body weight was still 60% below baseline. Measured REE at 6 months was significantly lower than the predicted (−18.2±6.7 kcal/d) and was the result of significant reductions from baseline in the low fat diets (65% or 55% carbohydrate), but not in the high fat diet groups. By 24 months the difference had reversed with measured REE being slightly but significantly higher than predicted (21.8±10.1 kcal/d). In conclusion, we found that REE fell significantly after weight loss but was not related to diet composition. Adaptive thermogenesis was evident at 6 months, but not at 24 months

Modular proteins from the Drosophila sallimus (sls) gene and their expression in muscles with different extensibility

The passive elasticity of the sarcomere in striated muscle is determined by large modular proteins, such as titin in vertebrates. In insects, the function of titin is divided between two shorter proteins, projectin and sallimus (Sls), which are the products of different genes. The Drosophila sallimus (sls) gene codes for a protein of 2 MDa. The N-terminal half of the protein is largely made up of immunoglobulin domains and unique sequence; the C-terminal half has two stretches of sequence similar to the elastic PEVK region of titin, and at the end of the molecule there is a region of tandem Ig and fibronectin domains. We have investigated splicing pathways of the sls gene and identified isoforms expressed in different muscle types, and at different stages of Drosophila development. The 5’ half of sls codes for zormin and kettin; both proteins contain Ig domains and can be expressed as separate isoforms, or as larger proteins linked to sequence downstream. There are multiple splicing pathways between the kettin region of sls and sequence coding for the two PEVK regions. All the resulting protein isoforms have sequence derived from the 3’ end of the sls gene. Splicing of exons varies at different stages of development. Kettin RNA is predominant in the embryo, and longer transcripts are expressed in larva, pupa and adult. Sls isoforms in the indirect flight muscle (IFM) are zormin, kettin and Sls(700), in which sequence derived from the end of the gene is spliced to kettin RNA. Zormin is in both M-line and Z-disc. Kettin and Sls(700) extend from the Z-disc to the ends of the thick filaments, though, Sls(700) is only in the myofibril core. These shorter isoforms would contribute to the high stiffness of IFM. Other muscles in the thorax and legs have longer Sls isoforms with varying amounts of PEVK sequence; all span the I-band to the ends of the thick filaments. In muscles with longer Ibands, the proportion of PEVK sequence would determine the extensibility of the sarcomere. Alternative Sls isoforms could regulate the stiffness of the many fibre types in Droso phila muscles