Polarisation measurements with a CdTe pixel array detector for Laue hard X-ray focusing telescopes

Polarimetry is an area of high energy astrophysics which is still relatively unexplored, even though it is recognized that this type of measurement could drastically increase our knowledge of the physics and geometry of high energy sources. For this reason, in the context of the design of a Gamma-Ray Imager based on new hard-X and soft gamma ray focusing optics for the next ESA Cosmic Vision call for proposals (Cosmic Vision 2015-2025), it is important that this capability should be implemented in the principal on-board instrumentation. For the particular case of wide band-pass Laue optics we propose a focal plane based on a thick pixelated CdTe detector operating with high efficiency between 60-600 keV. The high segmentation of this type of detector (1-2 mm pixel size) and the good energy resolution (a few keV FWHM at 500 keV) will allow high sensitivity polarisation measurements (a few % for a 10 mCrab source in 106s) to be performed. We have evaluated the modulation Q factors and minimum detectable polarisation through the use of Monte Carlo simulations (based on the GEANT 4 toolkit) for on and off-axis sources with power law emission spectra using the point spread function of a Laue lens in a feasible configuration.Comment: 10 pages, 6 pages. Accepted for publication in Experimental Astronom

A focal plane detector design for a wide-band Laue-lens telescope

The energy range above 60 keV is important for the study of many open problems in high energy astrophysics such as the role of Inverse Compton with respect to synchrotron or thermal processes in GRBs, non thermal mechanisms in SNR, the study of the high energy cut-offs in AGN spectra, and the detection of nuclear and annihilation lines. Recently the development of high energy Laue lenses with broad energy bandpasses from 60 to 600 keV have been proposed for a Hard X ray focusing Telescope (HAXTEL) in order to study the X-ray continuum of celestial sources. The required focal plane detector should have high detection efficiency over the entire operative range, a spatial resolution of about 1 mm, an energy resolution of a few keV at 500 keV and a sensitivity to linear polarization. We describe a possible configuration of the focal plane detector based on several CdTe/CZT pixelated layers stacked together to achieve the required detection efficiency at high energy. Each layer can operate both as a separate position sensitive detector and polarimeter or work with other layers to increase the overall photopeak efficiency. Each layer has a hexagonal shape in order to minimize the detector surface required to cover the lens field of view. The pixels would have the same geometry so as to provide the best coupling with the lens point spread function and to increase the symmetry for polarimetric studies.Comment: 10 pages, 9 figure

Oropharyngeal HPV infection: prevalence and sampling methods among HIV-infected men in South Africa.

Worldwide, 96,000 cases of oropharyngeal cancer (OPC) occurred in 2012. Human papillomavirus (HPV) is a risk factor for OPC. Data on oropharyngeal HPV infection are limited. There is no consensus on the best sampling method for detecting the infection. We describe the prevalence of oropharyngeal HPV infection among HIV-infected men and compare the performance of oral rinses and swabs in detecting oropharyngeal HPV infection. Paired oral rinses and swabs for 181 men were tested for HPV DNA using the Roche Linear Array. Performance was determined by the number of infections detected and the percentage of samples with adequate DNA extraction. Agreement between sampling methods was assessed by the kappa statistic. Prevalence of oropharyngeal HPV infection with rinse samples was 1.8% (three infections) and 0.6% (one infection) with swabs (p = 0.06). Adequate cellular DNA extraction was more likely with rinse (93.4%) than swab samples (89.0%, p = 0.05). There was moderate agreement between the methods (kappa = 0.49). The prevalence of oropharyngeal HPV DNA infection among this predominantly heterosexual sample of men living with HIV was low and consistent with the infrequent oral sex practices. Oral rinse performed better than oral swab in detecting oropharyngeal HPV DNA infection and might contribute to screening for OPCs

Development status of a Laue lens project for gamma-ray astronomy

We report the status of the HAXTEL project, devoted to perform a design study and the development of a Laue lens prototype. After a summary of the major results of the design study, the approach adopted to develop a Demonstration Model of a Laue lens is discussed, the set up described, and some results presented.Comment: 11 pages, 11 figures, 2007 SPIE Conference on Optics for EUV, X-Ray, and Gamma-Ray Astronomy II

Incidence, Persistence, Clearance, and Correlates of Genital Human Papillomavirus Infection and Anogenital Warts in a Cohort of Men Living With Human Immunodeficiency Virus in South Africa.

OBJECTIVE: To estimate the incidence; persistence and correlates of human papillomavirus (HPV) infection and anogenital warts (AGW) among men living with human immunodeficiency virus (MLHIV). METHODS: Overall, 304 MLHIV 18 years or older were enrolled and attended follow-up visits at 6, 12, and 18 months. Clinicians examined for AGW, collected blood, and penile swabs for HPV testing (Roche Linear Array) at each visit. Time to AGW incidence or clearance was estimated by Kaplan-Meier method. Factors associated with persistent HPV infection and AGW clearance were evaluated with generalized estimating equations and Cox regression, respectively. RESULTS: Mean age of participants was 38 years (standard deviation, 8 years); 25% reported more than 1 sexual partner in the past 3 months. Most (65%) participants were on antiretroviral treatment (ART) with a median CD4 count of 445 cells/?L (interquartile range, 328-567). Prevalence of HPV infection and AGW at enrolment were 79% (224 of 283) and 12% (36 of 304), respectively. Two hundred fifty-nine men were followed up for a median (interquartile range) 1.4 years (0.5-1.7 years). Incidence of any-genital HPV infection was 2.9 (95% confidence interval, 1.5-5.5) per 100 person-years. Persistence of any-genital HPV infection was 35% (68 of 192) and was higher among MLHIV with low CD4 count (adjusted odds ratio, 3.54; 95% confidence interval, 2.07-6.05). Incidence of AGW was 1.4 per 100 person-years. Men living with human immunodeficiency virus with high CD4 count were more likely to clear AGW than those with low CD4 count (adjusted hazard ratio, 3.69; 95% confidence interval, 1.44-9.47). No associations were observed between persistent genital HPV infection, AGW clearance with enrolment ART status or duration. CONCLUSIONS: Human immunodeficiency virus-positive men have a high burden of genital HPV infection and AGW. The ART and HPV vaccine could reduce this burden

Exploring the Hard X-/soft gamma-ray Continuum Spectra with Laue Lenses

The history of X-ray astronomy has shown that any advancement in our knowledge of the X-ray sky is strictly related to an increase in instrument sensitivity. At energies above 60 keV, there are interesting prospects for greatly improving the limiting sensitivity of the current generation of direct viewing telescopes (with or without coded masks), offered by the use of Laue lenses. We will discuss below the development status of a Hard X-Ray focusing Telescope (HAXTEL) based on Laue lenses with a broad bandpass (from 60 to 600 keV) for the study of the X-ray continuum of celestial sources. We show two examplesof multi-lens configurations with expected sensitivity orders of magnitude better ($\sim 1 \times 10^{-8}$ photons cm$^{-2}$ s$^{-1}$ keV$^{-1}$ at 200 keV) than that achieved so far. With this unprecedented sensitivity, very exciting astrophysical prospects are opened.Comment: 4 pages, 10 figures, to be published in the Proc. of the 39th ESLAB Symosium, 19-21 April 200

Prevalence of anogenital HPV infection, related disease and risk factors among HIV-infected men in inner-city Johannesburg, South Africa: baseline findings from a cohort study.

BACKGROUND: Persistent high-risk human papillomavirus (HR-HPV) infection is associated with the development of anogenital cancers, particularly in men living with HIV (MLWH). We describe the prevalence of anogenital HPV infection, abnormal anal cytology and anogenital warts (AGWs) in MLWH in Johannesburg, and explore whether HPV infection and receipt of antiretroviral treatment is associated with detection of abnormal anal cytology and AGWs. METHODS: We enrolled a cohort of 304 sexually-active MLWH ≥18 years, who completed a questionnaire and physical examination. Genital swabs were collected from all men and intra-anal swabs from 250 (82%). Swabs were tested for HPV DNA and genotypes, and anal smears graded using the Bethesda classification. Factors associated with anogenital disease were assessed by logistic regression models. RESULTS: Two thirds were receiving antiretroviral treatment, for a median 33 months (IQR = 15-58) and 54% were HIV-virologically suppressed. Only 5% reported ever having sex with men. Among 283 genital swabs with valid results, 79% had any HPV, 52% had HR-HPV and 27% had >1 HR-HPV infection. By comparison, 39% of the 227 valid intra-anal swabs had detectable HPV, 25% had any HR-HPV and 7% >1 HR infection. While most anal smears were normal (51%), 20% had ASCUS and 29% were LSIL. No cases had HSIL or cancer. Infection with >1 HR type (adjusted OR [aOR] = 2.39; 95%CI = 1.02-5.58) and alpha-9 types (aOR = 3.98; 95%CI = 1.42-11.16) were associated with having abnormal cytology. Prevalence of AGWs was 12%. Infection with any LR type (aOR = 41.28; 95%CI = 13.57-125.62), >1 LR type (aOR = 4.14; 95%CI = 1.60-10.69), being <6 months on antiretroviral treatment (aOR = 6.90; 95%CI = 1.63-29.20) and having a CD4+ count <200 cells/μL (aOR = 5.48; 95%CI: 1.60-18.78) were associated with having AGWs. CONCLUSIONS: In this population, anogenital HR-HPV infection and associated low-grade disease is common, but severe anal dysplasia was not detected. Findings reinforce the need for HPV vaccination in men for preventing both AGWs and HR-HPV infection. Given the absence of anal HSILs, however, the findings do not support the use of anal screening programmes in this population