Cosmological Radio Emission induced by WIMP Dark Matter

We present a detailed analysis of the radio synchrotron emission induced by WIMP dark matter annihilations and decays in extragalactic halos. We compute intensity, angular correlation, and source counts and discuss the impact on the expected signals of dark matter clustering, as well as of other astrophysical uncertainties as magnetic fields and spatial diffusion. Bounds on dark matter microscopic properties are then derived, and, depending on the specific set of assumptions, they are competitive with constraints from other indirect dark matter searches. At GHz frequencies, dark matter sources can become a significant fraction of the total number of sources with brightness below the microJansky level. We show that, at this level of fluxes (which are within the reach of the next-generation radio surveys), properties of the faint edge of differential source counts, as well as angular correlation data, can become an important probe for WIMPs.Comment: 19 pages, 26 figures. v2: comments and references added, to appear in JCA

Microwave integrated circuits for space applications

Monolithic microwave integrated circuits (MMIC), which incorporate all the elements of a microwave circuit on a single semiconductor substrate, offer the potential for drastic reductions in circuit weight and volume and increased reliability, all of which make many new concepts in electronic circuitry for space applications feasible, including phased array antennas. NASA has undertaken an extensive program aimed at development of MMICs for space applications. The first such circuits targeted for development were an extension of work in hybrid (discrete component) technology in support of the Advanced Communication Technology Satellite (ACTS). It focused on power amplifiers, receivers, and switches at ACTS frequencies. More recent work, however, focused on frequencies appropriate for other NASA programs and emphasizes advanced materials in an effort to enhance efficiency, power handling capability, and frequency of operation or noise figure to meet the requirements of space systems

Galactic synchrotron emission from WIMPs at radio frequencies

Dark matter annihilations in the Galactic halo inject relativistic electrons and positrons which in turn generate a synchrotron radiation when interacting with the galactic magnetic field. We calculate the synchrotron flux for various dark matter annihilation channels, masses, and astrophysical assumptions in the low-frequency range and compare our results with radio surveys from 22 MHz to 1420 MHz. We find that current observations are able to constrain particle dark matter with "thermal" annihilation cross-sections, i.e. (\sigma v) = 3 x 10^-26 cm^3/s, and masses M_DM < 10 GeV. We discuss the dependence of these bounds on the astrophysical assumptions, namely galactic dark matter distribution, cosmic rays propagation parameters, and structure of the galactic magnetic field. Prospects for detection in future radio surveys are outlined.Comment: 25 pages, 9 figures. Published JCAP versio

A dark matter interpretation for the ARCADE excess?

The ARCADE 2 Collaboration has recently measured an isotropic radio emission which is significantly brighter than the expected contributions from known extra-galactic sources. The simplest explanation of such excess involves a "new" population of unresolved sources which become the most numerous at very low (observationally unreached) brightness. We investigate this scenario in terms of synchrotron radiation induced by WIMP annihilations or decays in extragalactic halos. Intriguingly, for light-mass WIMPs with thermal annihilation cross-section, and fairly conservative clustering assumptions, the level of expected radio emission matches the ARCADE observations.Comment: 5 pages, 3 figures. v2: one benchmark model added, comments and references expanded, to appear in PR

Self-care symptom-management strategies amongst women living with HIV /AI DS in an urban area in KwaZulu-Natal

People living with HIV and AIDS experience a number of symptoms such as fatigue, nausea and vomiting, fever and anxiety during the various stages of the illness. This has a negative effect on their quality of life. Women are the most commonly infected group and are at greater risk of acquiring HIV than men. In addition to their vulnerability, women have other responsibilities in society and expectations from society to fulfil. Women’s health-seeking and health practice behaviours are often hindered by a number of factors, including family responsibilities, poverty and fear. This paper presents the findings of a qualitative study aimed at exploring the self-care symptom management strategies used by women living with HIV and AIDS in an urban area in KwaZulu- Natal in 2006. Eleven participants were selected through a purposive sampling method until saturation was reached. Individuals were assessed in depth, using the symptom-management strategy interview. Qualitative content analysis was used to examine the transcribed interviews, using a deductive approach based on the categories of self-care symptom-management strategies. Various physical and psychological symptoms and a number of self-care symptom-management strategies were reported by the participants and these included taking medication and seeking help. The study makes recommendations on how to improve women’s ability to employ a self-care strategy in managing their HIV- and AIDS-related symptoms.Web of Scienc

Sources and types of information on self-care symptom management strategies for HIV and AIDS

Human Immunodeficiency Virus (HIV) has been known to exist for more than three decades now and there are still new infections being documented, with the recent statistics showing that, in the year 2012, there were about 2.3 (1.9–2.7) million new infections worldwide(UNAIDS [Joint United Nations Programme on HIV/AIDS] 2013:4). Prevention programmes such as the LoveLife HIV prevention programme in South Africa that targets the youth have been established and are running effectively. Prevention programmes are involved in a number of initiatives, including voluntary counselling and testing, treatment for sexually transmitted diseases, condom promotion campaigns, abstinence, prevention of mother-to-child transmission (PMTCT) programmes and many more (Global HIV Prevention Working Group 2004:1). It has been documented, however, that the coverage of prevention programmes is low, as only a fraction of people who are at risk of being infected are able to access proven programmes for prevention (Global HIV Prevention Working Group 2004:1). People who are living with HIV have been documented as experiencing a number of related symptoms, such as anxiety and depression as well as other physical symptoms, and they use different strategies in order to manage these symptoms (Marie Modeste & Majeke 2010). Those living with HIV need information on how to manage these symptoms and maintain their health (O’Grady 2008:261; Tsai, Hsiung & Holzemer 2002:301).Department of HE and Training approved lis

Mentoring Entrepreneurial Networks : mapping conceptions of participants in technological-based business incubators in Brazil

La agenda de la investigación reciente sobre emprendedores incluye el análisis de las estructuras cognitivas de los empresarios de éxito, revelándose como una herramienta importante a la hora de examinar una trayectoria emprendedora. Mediante técnicas de mapas cognitivos, este estudio explora los conceptos de una trayectoria de éxito y la red en sí misma como un todo, para el desarrollo de esta carrera. Fueron estudiados 53 empresarios en siete viveros tecnológicos de la ciudad de Recife, Pernambuco, Brasil. El objetivo específico de este estudio era situar los significados comunes de los emprendedores del vivero teniendo en cuenta las redes de apoyo informal. Este tipo de redes ofrecen apoyo a la carrera empresarial, y el presente estudio examina tanto las características como el modelo conceptual que subyace bajo éstas. La recolección de datos fue realizada por medio de entrevistas a través de la técnica de evocación libre. Los significados comunes indican la existencia de categorías de pensamiento inherentes que fomentan el contexto de la red en el entorno del vivero, especialmente en las redes-mentor. Los resultados refuerzan la interpretación de un modelo mentor informal que emerge de las evocaciones predominantes respecto a una carrera de éxito y de la red en sí misma como promotora de su desarrollo.The recent entrepreneurship research agenda includes the analysis of cognitive structures of successful entrepreneurs, revealing an important tool for the examination of an entrepreneurial career. Using techniques of cognitive maps, this study explores the concepts of a successful career and the network itself, as a whole, for career development. Fifty-three entrepreneurs were studied, in seven technological incubators in the city of Recife, Pernambuco, Brazil. Specifically, this study aimed to map the shared meanings of the incubated entrepreneurs regarding informal support networks. Such networks support the entrepreneurial career and the present study explores the characteristics and the conceptual model that underlies the networks. The data collection was achieved through interviews through a free evocation technique. The shared meanings indicate the existence of inherent thought categories that support network context in the incubator environment, mainly the mentoring networks. The results endorse the interpretation of an informal mentoring model emerging from the dominant evocations concerning a successful career and of the network itself as promoter of career development