Human papillomaviruses (HPV) infecting the genital tract are associated with warts and anogenital malignancies. Although HPV is a highly prevalent sexually transmitted disease (STD), the majority of research has focused on female cohorts due to gender specific sequelae. Our objective was to measure the epidemiological features and seroprevalences of HPV-6/11 and 16 in a predominantly male group of STD clinic patients. High-risk individuals (n=687), who attended the public STD clinic were administered a behavioural questionnaire and serum tested for antibodies against HPV-6/11 and HPV-16 capsids via capture enzyme-linked immunosorbent assay. Despite the male predominance in this study, women were significantly more likely to have antibodies against both HPV-6/11 and HPV-16. Condom use appeared to be partially protective against HPV-16 seropositivity only. In conclusion, despite exhibiting increased risk behaviour, men were less likely to be HPV seropositive. Additional studies utilizing male cohorts are warranted to further elucidate this phenomenon.
Multiple-quantum-well light-emitting diode (LED) structures of InGaN/GaN were grown by metalorganic chemical vapor deposition on Si(111) substrates via ZrB2(0001) buffer layers and a GaN template comprising composite AlxGa1-xN (where x lies in the range from 0 to 1) transition layers to minimize cracking due to thermal expansion mismatch between Si and GaN. Photoluminescence and electroluminescence results from the LED structures compared favorably with similar measurements obtained on identical LED structures grown on sapphire substrates. However, in spite of all the precautions taken, cracking was still present in the LED structures. Scanning electron microscopy and transmission electron microscopy in plan-view and cross-section geometries were conducted on the LED structures to examine the presence and the influence of various defects such as microvoids, micropipes, and threading dislocations on the mechanism of cracking. Our results suggest that the crack network propagates from microvoids on the surface of the LED structure. The formation of microvoids appears to originate from imperfections in the epitaxial ZrB2(0001) buffer layer.
The structural and optical properties of ten-stack InAs/GaAsSb quantum dots (QDs) with different spacer layer thicknesses (ds = 2, 5, 10, and 15 nm) are reported. X-ray diffraction analysis reveals that the strain relaxation of the GaAsSb spacers increases linearly from 0% to 67% with larger ds due to higher elastic stress between the spacer and GaAs matrix. In addition, the dislocation density in the spacers with ds = 10 nm is lowest as a result of reduced residual strain. The photoluminescence peak energy from the QDs does not change monotonically with increasing ds due to the competing effects of decreased compressive strain and weak electronic coupling of stacked QD layers. The QD structure with ds = 10 nm is demonstrated to have improved luminescence properties and higher carrier thermal stability.
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