A planar quasi-optical SIS receiver for array applications

A planar, quasi-optical SIS receiver operating at 230 GHz is described. The receiver consists of a 2 x 5 array of half wave dipole antennas with ten niobium-aluminum oxide-niobium SIS junctions on a quartz dielectric-filled parabola. The 1.4 GHz intermediate frequency is coupled from the mixer via coplanar strip transmission lines and 4:1 balun transformers. The receiver is operated at 4.2 K in a liquid helium immersion cryostat. We report accurate measurements of the performance of single receiver elements. A mixer noise temperature of 89 K DSB, receiver noise temperature of 156 K DSB, and conversion loss of 3 dB into a matched load have been obtained

Reassessment of vertebrate ichnotaxa from the Upper Carboniferous ‘Fern Ledges’, Lancaster Formation, Saint John, New Brunswick, Canada

Vertebrate ichnotaxa described by George Frederic Matthew in 1910 from the Upper Carboniferous (Lower Pennsylvanian) ‘Fern Ledges’ of Saint John, New Brunswick, were dismissed as dubious trackways by previous authors. Thus, three new ichnospecies Matthew described appeared in the 1975 Treatise on Invertebrate Paleontology as “unrecognized or unrecognizable” and were mostly forgotten by vertebrate ichnologists. These traces include Hylopus (?) variabilis, Nanopus (?) vetustus and Bipezia bilobata. One ichnospecies, Hylopus (?) variabilis, here is retained as a valid tetrapod footprint ichnotaxon and reassigned to the ichnogenus Limnopus as a new combination, together with other poorly preserved specimens Matthew labeled, but never described. Nanopus (?) vetustus and Bipezia bilobata named by Matthew in the same paper, have been reexamined and remain as nomina dubia.

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

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

Patterns of HIV prevalence among injecting drug users in the cross-border area of Lang Son Province, Vietnam, and Ning Ming County, Guangxi Province, China

BACKGROUND: To assess patterns of injecting drug use and HIV prevalence among injecting drug users (IDUs) in an international border area along a major heroin trans-shipment route. METHODS: Cross-sectional surveys of IDUs in 5 sites in Lang Son Province, Vietnam (n = 348) and 3 sites in Ning Ming County, Guangxi Province, China (n = 308). Respondents were recruited through peer referral ("snowball") methods in both countries, and also from officially recorded lists of IDUs in Vietnam. A risk behavior questionnaire was administered and HIV counseling and testing conducted. RESULTS: Participants in both countries were largely male, in their 20s, and unmarried. A majority of subjects in both countries were members of ethnic minority groups. There were strong geographic gradients for length of drug injecting and for HIV seroprevalence. Both mean years injecting and HIV seroprevalence declined from the Vietnamese site farthest from the border to the Chinese site farthest from the border. 10.6% of participants in China and 24.5% of participants in Vietnam reported crossing the international border in the 6 months prior to interview. Crossing the border by IDUs was associated with (1) distance from the border, (2) being a member of an ethnic minority group, and (3) being HIV seropositive among Chinese participants. CONCLUSION: Reducing the international spread of HIV among IDUs will require programs at the global, regional, national, and "local cross border" levels. At the local cross border level, the programs should be coordinated on both sides of the border and on a sufficient scale that IDUs will be able to readily obtain clean injection equipment on the other side of the border as well as in their country of residence

A systems-level analysis of total-body PET data reveals complex skeletal metabolism networks in vivo

Bone is now regarded to be a key regulator of a number of metabolic processes, in addition to the regulation of mineral metabolism. However, our understanding of complex bone metabolic interactions at a systems level remains rudimentary. in vitro molecular biology and bioinformatics approaches have frequently been used to understand the mechanistic changes underlying disease at the cell level, however, these approaches lack the capability to interrogate dynamic multi-bone metabolic interactions in vivo. Here we present a novel and integrative approach to understand complex bone metabolic interactions in vivo using total-body positron emission tomography (PET) network analysis of murine 18F-FDG scans, as a biomarker of glucose metabolism in bones. In this report we show that different bones within the skeleton have a unique glucose metabolism and form a complex metabolic network, which could not be identified using single tissue simplistic PET standard uptake values analysis. The application of our approach could reveal new physiological and pathological tissue interactions beyond skeletal metabolism, due to PET radiotracers diversity and the advent of clinical total-body PET systems

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