1,937 research outputs found

    A direct proof of Z-stability for AH algebras of bounded topological dimension

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    We prove that a unital simple approximately homogeneous (AH) C*-algebra with no dimension growth absorbs the Jiang-Su algebra tensorially without appealing to the classification theory of these algebras. Our main result continues to hold under the slightly weaker hypothesis of exponentially slow dimension growth.Comment: 15 pages, no figure

    Update on HIV in Western Europe

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    HIV infection in Western Europe is mainly concentrated among men who have sex with men, heterosexuals who acquired HIV from sub-Saharan African countries, and in people who inject drugs. The rate of newly diagnosed cases of HIV has remained roughly stable since 2004 whereas the number of people living with HIV has slowly increased due to new infections and the success of antiretroviral therapy in prolonging life. An ageing population is gradually emerging that will require additional care. There are large differences across countries in HIV testing rates, proportions of people who present to care with low CD4+ cell counts, accessibility to treatment and care, and rates of retention once in care. Improved collection of HIV surveillance data will benefit countries and help to understand their epidemic better. However, social inequalities experienced by people with HIV still remain in some regions and urgently need to be addressed

    The Infrared Imaging Spectrograph (IRIS) for TMT: the atmospheric dispersion corrector

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    We present a conceptual design for the atmospheric dispersion corrector (ADC) for TMT's Infrared Imaging Spectrograph (IRIS). The severe requirements of this ADC are reviewed, as are limitations to observing caused by uncorrectable atmospheric effects. The requirement of residual dispersion less than 1 milliarcsecond can be met with certain glass combinations. The design decisions are discussed and the performance of the design ADC is described. Alternative options and their performance tradeoffs are also presented.Comment: SPIE Astronomical Instrumentation 201

    A more representative chamber: representation and the House of Lords

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    Since 1997 there has been substantive reform of the House of Lords in an effort to make the chamber ‘more democratic and more representative’. Whilst the Labour government failed to press ahead with any of the proposed plans for further reform following the removal of the bulk of the hereditary peers in 1999, it remained committed to the notion that such reform must make the second chamber ‘more representative’. The coalition government's programme advocates a long-term aspiration for a House wholly or mainly elected on the basis of proportional representation, and a short-term approach based on additional appointments to ensure a balance of the parties. What is clear in all of these proposals for reform is a desire for the House of Lords to become more representative than it is at present. However, what is less clear is what is meant by ‘representative’ – who the House of Lords is supposed to represent, and what form representation will take. Moreover, in proposing to make the chamber more representative, either through appointment or election, little attention has been paid to how the current House of Lords provides representation. This article examines these questions in the context of Pitkin's classic conceptions of representation and peers' attitudes towards their own representative rol

    Hybridization and Back-Crossing in Giant Petrels (Macronectes giganteus and M. halli) at Bird Island, South Georgia, and a Summary of Hybridization in Seabirds

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    Hybridization in natural populations provides an opportunity to study the evolutionary processes that shape divergence and genetic isolation of species. The emergence of pre-mating barriers is often the precursor to complete reproductive isolation. However, in recently diverged species, pre-mating barriers may be incomplete, leading to hybridization between seemingly distinct taxa. Here we report results of a long-term study at Bird Island, South Georgia, of the extent of hybridization, mate fidelity, timing of breeding and breeding success in mixed and conspecific pairs of the sibling species, Macronectes halli (northern giant petrel) and M . giganteus (southern giant petrel). The proportion of mixed-species pairs varied annually from 0.4-2.4% (mean of 1.5%), and showed no linear trend with time. Mean laying date in mixed-species pairs tended to be later than in northern giant petrel, and always earlier than in southern giant petrel pairs, and their breeding success (15.6%) was lower than that of conspecific pairs. By comparison, mixed-species pairs at both Marion and Macquarie islands always failed before hatching. Histories of birds in mixed-species pairs at Bird Island were variable; some bred previously or subsequently with a conspecific partner, others subsequently with a different allospecific partner, and some mixed-species pairs remained together for multiple seasons. We also report the first verified back-crossing of a hybrid giant petrel with a female northern giant petrel. We discuss the potential causes and evolutionary consequences of hybridization and back-crossing in giant petrels and summarize the incidence of back-crossing in other seabird species

    Incubation Time of Acute Human Immunodeficiency Virus (HIV) Infection and Duration of Acute HIV Infection Are Independent Prognostic Factors of Progression to AIDS

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    The severity and the duration of acute human immunodeficiency virus (HIV) infection (AHI) are associated with a faster rate of progression to AIDS, but the prognostic value of the length of incubation time of AHI (IncAHI), defined as the time between HIV infection and AHI, on progression to AIDS has not been assessed. We explored this issue prospectively in 70 individuals with documented AHI and a known date of HIV infection. The median IncAHI was 21.5 days (range, 5-70 days), and the median duration of AHI was 15.5 days (range, 3-67 days). The adjusted relative hazard of progression to AIDS or to a CD4+ count 15.5 days, compared with those with shorter duration. Both IncAHI and duration of AHI were independent predictors of progression. This suggests that early pathogenic events before the onset of AHI influence the rate of HIV disease progressio

    Understanding early uptake of PrEP by female sex workers in Zimbabwe.

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    Female sex workers (FSW) are prioritised for increased access to pre-exposure prophylaxis (PrEP), although rates of uptake remain sub-optimal, particularly across Southern Africa. In the first two years of its availability in Zimbabwe, 37.1% of FSW in trial sites initiated PrEP and received at least one re-supply. We conducted a qualitative study on perceptions of PrEP among 19 early users selected from sites with varying rates of PrEP initiation. Narrative interviews examined the pathways taken by FSW from hearing about PrEP, through their decision to start taking it, and early experiences. FSW appreciated PrEP's introduction within familiar and trusted "friendly" services tailored for sex workers and valued positive encouragement from clinic staff and peers over negative influence from family members. They also found PrEP difficult to understand at first, and feared side effects and rare adverse complications described in information leaflets. While FSW identified individual strategies for remembering to take their medication, they also relied on structured peer adherence support, leading some FSW to actively promote the method to other FSW as "PrEP champions". Information on how early users experience a new prevention technology such as PrEP can inform design of interventions that leverage existing support structures and target key barriers

    A Pilot Survey for the H2_2O Southern Galactic Plane Survey (HOPS)

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    We describe observations with the Mopra radiotelescope designed to assess the feasibility of the H2_2O maser southern Galactic plane survey (HOPS). We mapped two one-square-degree regions along the Galactic plane using the new 12 mm receiver and the UNSW Mopra spectrometer (MOPS). We covered the entire spectrum between 19.5 and 27.5 GHz using this setup with the main aims of finding out which spectral lines can be detected with a quick mapping survey. We report on detected emission from H2_2O masers, NH3_3 inversion transitions (1,1), (2,2) and (3,3), HC3_3N (3-2), as well as several radio recombination lines.Comment: accepted by PAS
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