Synthesis, characterization and 11C radiolabeling of aminophenyl benzothiazoles:structural effects on the alkylation of amino group

Several aminophenyl benzothiazoles were prepared with a view to using them as amyloid binding agents for imaging β-amyloid in Alzheimer's disease. These precursors were radiolabeled with 11C-positron-emitting radioisotope using an automated synthesizer and selected radiolabeled compounds were further purified by HPLC. Our results demonstrate that changes in structure have a major influence on the radioactive yield and the ease with which the radiolabel can be introduced. Aminophenyl benzothiazoles with an attached isopropyl group resisted dialkylation perhaps due to steric hindrance caused by this group. Straight chain attachment of methyl, ethyl, butyl, and crotyl groups in the structure decreased the radiochemical yield. Notably, the o-aminophenyl benzothiazole derivatives were difficult to alkylate despite stringent experimental conditions. This reactivity difference is attributed to the hydrogen bonding characteristics of the o-amino group with the nitrogen atom of the thiazole ring

The declining representativeness of the British party system, and why it matters

In a recent article, Michael Laver has explained ‘Why Vote-Seeking Parties May Make Voters Miserable’. His model shows that, while ideological convergence may boost congruence between governments and the median voter, it can reduce congruence between the party system and the electorate as a whole. Specifically, convergence can increase the mean distance between voters and their nearest party. In this article we show that this captures the reality of today’s British party system. Policy scale placements in British Election Studies from 1987 to 2010 confirm that the pronounced convergence during the past decade has left the Conservatives and Labour closer together than would be optimal in terms of minimising the policy distance between the average voter and the nearest major party. We go on to demonstrate that this comes at a cost. Respondents who perceive themselves as further away from one of the major parties in the system tend to score lower on satisfaction with democracy. In short, vote-seeking parties have left the British party system less representative of the ideological diversity in the electorate, and thus made at least some British voters miserable

HIV risk behaviors among female IDUs in developing and transitional countries

Abstract Background A number of studies suggest females may be more likely to engage in injection and sex risk behavior than males. Most data on gender differences come from industrialized countries, so data are needed in developing countries to determine how well gender differences generalize to these understudied regions. Methods Between 1999 and 2003, 2512 male and 672 female current injection drug users (IDUs) were surveyed in ten sites in developing countries around the world (Nairobi, Beijing, Hanoi, Kharkiv, Minsk, St. Petersburg, Bogotá, Gran Rosario, Rio, and Santos). The survey included a variety of questions about demographics, injecting practices and sexual behavior. Results Females were more likely to engage in risk behaviors in the context of a sexual relationship with a primary partner while males were more likely to engage in risk behaviors in the context of close friendships and casual sexual relationships. After controlling for injection frequency, and years injecting, these gender differences were fairly consistent across sites. Conclusion Gender differences in risk depend on the relational contexts in which risk behaviors occur. The fact that female and male risk behavior often occurs in different relational contexts suggests that different kinds of prevention interventions which are sensitive to these contexts may be necessary.</p

Generalized Huygens principle with pulsed-beam wavelets

Huygens' principle has a well-known problem with back-propagation due to the spherical nature of the secondary wavelets. We solve this by analytically continuing the surface of integration. If the surface is a sphere of radius $R$, this is done by complexifying $R$ to $R+ia$. The resulting complex sphere is shown to be a real bundle of disks with radius $a$ tangent to the sphere. Huygens' "secondary source points" are thus replaced by disks, and his spherical wavelets by well-focused pulsed beams propagating outward. This solves the back-propagation problem. The extended Huygens principle is a completeness relation for pulsed beams, giving a representation of a general radiation field as a superposition of such beams. Furthermore, it naturally yields a very efficient way to compute radiation fields because all pulsed beams missing a given observer can be ignored. Increasing $a$ sharpens the focus of the pulsed beams, which in turn raises the compression of the representation.Comment: 49 pages, 14 figure

Knowledge and innovation: The strings between global and local dimensions of sustainable growth

The modern growth literature pays much attention to innovation and knowledge as drivers of endogenous developments in a competitive open economic system. This paper reviews concisely the literature in this field and addresses in particular micro- and macro-economic interactions at local or regional levels, based on clustering and networking principles, in which sustainability conditions also play a core role. The paper then develops a so-called knowledge circuit model comprising the relevant stakeholders, which aims to offer a novel framework for applied policy research at the meso-economic level