643 research outputs found

    The Adelaide VHF radar: Capabilities and future plans

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    The VHF radar at Buckland Park, South Australia commenced operation in January, 1984. The radar is located adjacent to the 2-MHz ionospheric radar. The routine method for measuring horizontal wind velocity is the space antenna technique (SA) while the Doppler technique is used to measure vertical velocities. It is possible to swing the transmitting beam in the east-west plane, allowing Doppler measurements of the EW wind component

    The Internet and HIV study: design and methods

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    BACKGROUND: The Internet provides a new meeting ground, especially for gay men, that did not exist in the early 1990s. Several studies have found increased levels of high risk sexual behaviour and sexually transmissible infections (STI) among gay men who seek sex on the Internet, although the underlying processes are not fully understood. Research funded by the UK Medical Research Council (2002–2004) provided the opportunity to consider whether the Internet represents a new sexual risk environment for gay and bisexual men living in London. METHODS: The objectives of the Internet and HIV study are to: (i) measure the extent to which gay men living in London seek sexual partners on the Internet; (ii) compare the characteristics of London gay men who do and do not seek sex on the Internet; (iii) examine whether sex with Internet-partners is less safe than with other sexual partners; (iv) compare use of the Internet with other venues where men meet sexual partners; (v) establish whether gay men use the Internet to actively seek partners for unprotected anal intercourse; (vi) determine the potential for using the Internet for HIV prevention. These objectives have been explored using quantitative and qualitative research methods in four samples of London gay men recruited and interviewed both online and offline. The four samples were: (i) gay men recruited through Internet chat rooms and profiles; (ii) HIV positive gay men attending an NHS hospital outpatients clinic; (iii) gay men seeking an HIV test in an NHS HIV testing or sexual health clinic; (iv) gay men recruited in the community. RESULTS: Quantitative data were collected by means of confidential, anonymous self-administered questionnaires (n>4000) completed on-line by the Internet sample. Qualitative data were collected by means of one-to-one interviews (n = 128) conducted either face-to-face or on-line. CONCLUSION: The strength of the Internet and HIV study is its methodological plurality, drawing on both qualitative and quantitative research among online and offline samples, as well as taking advantage of recent advances in web survey design. The study's findings will help us better understand the role of the Internet in relation to gay men's sexual practic

    The Collapse of Atomically-Cooled Primordial Haloes. I. High Lyman-Werner Backgrounds

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    Pristine, atomically-cooled haloes are leading contenders for the sites of primordial quasar formation because atomic cooling triggers rapid baryon collapse that can create 104^4 - 105^5 M_{\odot} black hole seeds. However, until now no numerical simulations with a wide range of halo spins and assembly histories have followed the collapse for the times required to form a black hole. We have now performed cosmological simulations of baryon collapse in atomically-cooled haloes for times that are sufficient for supermassive stars to form and die as direct-collapse black holes (DCBHs). Our simulations reveal that fragmentation of the accretion disk at the center of the halo after \sim 500 kyr is nearly ubiquitous and in most cases leads to the formation of binary or multiple supermassive stellar systems. They also confirm that rapid baryon collapse proceeds for the times required for these stars to form DCBHs. Our discovery raises the exciting possibility of detecting gravitational waves from DCBH mergers with LISA and tidal disruption events in the near infrared with the James Webb Space Telescope and ground-based telescopes in the coming decade.Comment: 13 pages, 10 figures, submitted to MNRA

    "It pains me because as a woman you have to breastfeed your baby": decision-making about infant feeding among African women living with HIV in the UK

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    OBJECTIVES: UK guidance advises HIV-positive women to abstain from breast feeding. Although this eliminates the risk of postnatal vertical transmission of HIV, the impact of replacement feeding on mothers is often overlooked. This qualitative study examines, for the first time in the UK, decision-making about infant feeding among African women living with HIV. METHODS: Between 2010 and 2011, we conducted semistructured interviews with 23 HIV-positive African women who were pregnant or had recently given birth. We recruited participants from three HIV antenatal clinics in London. RESULTS: Women highlighted the cultural importance of breast feeding in African communities and the social pressure to breast feed, also describing fears that replacement feeding would signify their HIV status. Participants had significant concerns about physical and psychological effects of replacement feeding on their child and felt their identity as good mothers was compromised by not breast feeding. However, almost all chose to refrain from breast feeding, driven by the desire to minimise vertical transmission risk. Participants' resilience was strengthened by financial assistance with replacement feeding, examples of healthy formula-fed children and support from partners, family, peers and professionals. CONCLUSIONS: The decision to avoid breast feeding came at considerable emotional cost to participants. Professionals should be aware of the difficulties encountered by HIV-positive women in refraining from breast feeding, especially those from migrant African communities where breast feeding is culturally normative. Appropriate financial and emotional support increases women's capacity to adhere to their infant-feeding decisions and may reduce the emotional impact

    Loss to Follow-Up After Pregnancy Among Sub-Saharan Africa-Born Women Living With Human Immunodeficiency Virus in England, Wales and Northern Ireland: Results From a Large National Cohort.

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    BACKGROUND: Little is known about retention in human immunodeficiency virus (HIV) care in HIV-positive women after pregnancy in the United Kingdom. We explored the association between loss to follow-up (LTFU) in the year after pregnancy, maternal place of birth and duration of UK residence, in HIV-positive women in England, Wales, and Northern Ireland. METHODS: We analyzed combined data from 2 national data sets: the National Study of HIV in Pregnancy and Childhood; and the Survey of Prevalent HIV Infections Diagnosed, including pregnancies in 2000 to 2009 in women with diagnosed HIV. Logistic regression models were fitted with robust standard errors to estimate adjusted odds ratios (AOR). RESULTS: Overall, 902 of 7211 (12.5%) women did not access HIV care in the year after pregnancy. Factors associated with LTFU included younger age, last CD4 in pregnancy of 350 cells/μL or greater and detectable HIV viral load at the end of pregnancy (all P < 0.001). On multivariable analysis, LTFU was more likely in sub-Saharan Africa-born (SSA-born) women than white UK-born women (AOR, 2.17; 95% confidence interval, 1.50-3.14; P < 0.001). The SSA-born women who had migrated to the UK during pregnancy were 3 times more likely than white UK-born women to be lost to follow-up (AOR, 3.19; 95% confidence interval, 1.94-3.23; P < 0.001). CONCLUSIONS: One in 8 HIV-positive women in England, Wales, and Northern Ireland did not return for HIV care in the year after pregnancy, with SSA-born women, especially those who migrated to the United Kingdom during pregnancy, at increased risk. Although emigration is a possible explanatory factor, disengagement from care may also play a role

    Fostering Motivation toward Chemistry through Augmented Reality Educational Escape Activities. A Self-Determination Theory Approach

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    There is little doubt that motivation influences the extent to which individuals engage with online learning experiences. With the increasing role of digital technologies within chemistry higher education, this study illustrates how an augmented reality (AR)-supported educational escape activity (EEA), based on topics of inorganic stereochemistry, can be employed within an online environment. The design aspects of our activity were guided by principles of Self-Determination Theory (SDT)─an intrinsic-extrinsic theory of motivation. We sought to actively support the fundamental needs of competency, autonomy, and relatedness. Our control group was provided with a copy of our EEA that utilized two-dimensional drawings. Reported measures of competency were seen as a positive predictor of intrinsic motivation. However, in this study, this was not observed to be a positive predictor of academic performance. The introduction of AR, over and above the EEA, did not result in any significant differences in reported intrinsic motivation or post-test scores on our stereochemistry test instrument. Collected qualitative data suggest that participants found the activity to be useful and engaging. Through students’ discussions, we have provided evidence of how design aspects of the EEA support the psychological needs satisfaction outlined by SDT. The design of our EEA provides one approach to implementing this style of learning activity, in a way that supports virtual presence and is scalable to large student cohorts

    Augmented reality and worked examples: Targeting organic chemistry competence

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    Instructional guidance, provided using worked examples, helps the inexperienced learner cope with complex information, that may be difficult to process in limited capacity working memory. For students of chemistry, such complex information can pertain to the visualisation of structural changes in molecules throughout chemical reactions. This can be alleviated through the affordances of augmented reality (AR) technology. 3D structures are important as they have a crucial impact on the chemical and physical properties of molecules. Within a framework of Cognitive Load Theory, this study illustrates how AR-supported worked examples may enhance learning of electrophilic aromatic substitution. The participant cohort were FHEQ level 5 undergraduate students studying a module of organic chemistry. In addition, the achievement motivation of learner's was also explored, and how this may be impacted by the provision of AR technology and worked examples. The control group was provided with a copy of our worked examples that contained 2D reaction mechanism drawings. Data was collected using a combination of quantitative instruments and qualitative surveys/interviews. For this cohort of students, significant intragroup improvements, and greater normalised change values, in conceptual understanding were observed in the AR group. This was not observed in the control group. No significant intergroup differences in reported cognitive load or achievement motivation of students were found. This was unaffected when introducing prior relevant chemistry experience as a covariate. Student feedback and subsequent thematic analysis show not only the positive impacts on student engagement, but also how students convey their understanding of electrophilic aromatic substitution principles

    Exploring the effect of augmented reality on cognitive load, attitude, spatial ability, and stereochemical perception

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    Augmented reality (AR) has the capacity to afford a virtual experience that obviates the reliance on using two-dimensional representations of 3D molecules for teaching stereochemistry to undergraduate students. Using a combination of quantitative instruments and qualitative surveys/interviews, this study explored the relationships between students’ attitudes, perceived cognitive load, spatial ability, and academic performance when engaging in an asynchronous online stereochemistry activity. Our activity was designed using elements of game-based learning, and integrated AR technologies. The control group was provided with a copy of our activity that used two-dimensional drawings, whereas the AR group completed an activity using the AR technologies. For this cohort of students, results indicated significant improvement in academic performance in both the control and AR groups. The introduction of AR technologies did not result in the AR group outperforming the control group. Participants from both groups displayed significant improvements in spatial ability throughout the research period. Further, a moderate correlation (rs = 0.416) between students’ spatial ability and academic performance was found. No significant intergroup differences in the perceived cognitive loads of students were observed. A significant difference was observed on one item of the Intellectual Accessibility subscale of the ASCI (V2), Complicated–Simple. We found no correlation for student attitude or cognitive load with academic performance. The findings of this study provide insights for future AR-related studies to explore the role of spatial ability, student attitude, and cognitive load in learning performance
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