1,438 research outputs found

    Women's experience of male circumcision in Papua New Guinea: a grounded theory study

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    Background: Understanding how women experience and manage the myriad issues of male circumcision (MC) for themselves, their sexual partners and their sons is essential to understanding broader HIV and sexual health issues in Papua New Guinea (PNG). A great diversity of traditional and contemporary circumcision and foreskin cutting practices exist across the country. Medical MC is currently being investigated as a HIV prevention strategy. Studies have documented mixed responses by women to MC as a HIV prevention method in PNG. Methods: Between 2012 and 2014, a grounded theory study was conducted using a two-phase approach. Data from a large mixed methods multi-site MC study in 2010/2011 was analysed for themes to inform specific questions for women. Semi-structured interviews and focus group discussions, that incorporated visual methods such as storyboarding, were then conducted with 67 women at two of the initial study sites - a rural oil palm plantation and an urban university site. Data were inductively analysed to identify codes, categories and a grounded theory. Results: Women have extensive knowledge about MC and foreskin cutting practices, despite cultural norms that mean most women do not participate in decision-making about MC or other penile modifications. Women gain knowledge through personal (sometimes negative) experiences of their partners or children, through cultural traditions and/or through formal training or education. Women who have formal education or training, or who hold formal roles in their communities reported a greater power of choice about their own decision-making, including how MC affects them. Educated women reported more opportunities to influence their partner's decision about MC or other penile modifications, to choose a new partner or arrange MC for their male child/ren. Conclusions: Increased formal and informal education (such as HIV and sexual health training) results in increased status for women and access to a greater range of choices. The often culturally sanctioned low-status roles for women in PNG can be changed with training and/or formal education, which gives more power and thus more choices. If women have greater power of choice, they are less vulnerable to harmful, unintended consequences that may result from a policy of medical MC

    Simulation and analysis of solenoidal ion sources

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    We present a detailed analysis and simulation of solenoidal, magnetically confined electron bombardment ion sources, aimed at molecular beam detection. The aim is to achieve high efficiency for singly ionized species while minimizing multiple ionization. Electron space charge plays a major role and we apply combined ray tracing and finite element simulations to determine the properties of a realistic geometry. The factors controlling electron injection and ion extraction are discussed. The results from simulations are benchmarked against experimental measurements on a prototype source

    The atomic structure and chemistry of Fe-rich steps on antiphase boundaries in Ti-doped Bi<sub>0.9</sub>Nd<sub>0.15</sub>FeO3

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    Stepped antiphase boundaries are frequently observed in Ti-doped Bi&lt;sub&gt;0.85&lt;/sub&gt;Nd&lt;sub&gt;0.15&lt;/sub&gt;FeO&lt;sub&gt;3&lt;/sub&gt;, related to the novel planar antiphase boundaries reported recently. The atomic structure and chemistry of these steps are determined by a combination of high angle annular dark field and bright field scanning transmission electron microscopy imaging, together with electron energy loss spectroscopy. The core of these steps is found to consist of 4 edge-sharing FeO&lt;sub&gt;6&lt;/sub&gt; octahedra. The structure is confirmed by image simulations using a frozen phonon multislice approach. The steps are also found to be negatively charged and, like the planar boundaries studied previously, result in polarisation of the surrounding perovskite matrix

    Determining the Anisotropic Exchange Coupling of CrO_2 via First-Principles Density Functional Theory Calculations

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    We report a study of the anisotropic exchange interactions in bulk CrO_2 calculated from first principles within density functional theory. We determine the exchange coupling energies, using both the experimental lattice parameters and those obtained within DFT, within a modified Heisenberg model Hamiltonian in two ways. We employ a supercell method in which certain spins within a cell are rotated and the energy dependence is calculated and a spin-spiral method that modifies the periodic boundary conditions of the problem to allow for an overall rotation of the spins between unit cells. Using the results from each of these methods, we calculate the spin-wave stiffness constant D from the exchange energies using the magnon dispersion relation. We employ a Monte Carlo method to determine the DFT-predicted Curie temperature from these calculated energies and compare with accepted values. Finally, we offer an evaluation of the accuracy of the DFT-based methods and suggest implications of the competing ferro- and antiferromagnetic interactions.Comment: 10 pages, 13 figure

    Texture, twinning and metastable "tetragonal" phase in ultrathin films of HfO<sub>2</sub> on a Si substrate

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    Thin HfO&lt;sub&gt;2&lt;/sub&gt; films grown on the lightly oxidised surface of (100) Si wafers have been examined using dark-field transmission electron microscopy and selected area electron diffraction in plan view. The polycrystalline film has a grain size of the order of 100 nm and many of the grains show evidence of twinning on (110) and (001) planes. Diffraction studies showed that the film had a strong [110] out-of-plane texture, and that a tiny volume fraction of a metastable (possibly tetragonal) phase was retained. The reasons for the texture, twinning and the retention of the metastable phase are discussed

    Engineering magnetic domain-wall structure in permalloy nanowires

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    Using Lorentz transmission electron microscopy we investigate the behavior of domain walls pinned at non-topographic defects in Cr(3 nm)/Permalloy(10 nm)/Cr(5 nm) nanowires of width 500 nm. The pinning sites consist of linear defects where magnetic properties are modified by a Ga ion probe with diameter ~ 10 nm using a focused ion beam microscope. We study the detailed change of the modified region (which is on the scale of the focused ion spot) using electron energy loss spectroscopy and differential phase contrast imaging on an aberration (Cs) corrected scanning transmission electron microscope. The signal variation observed indicates that the region modified by the irradiation corresponds to ~ 40-50 nm despite the ion probe size of only 10 nm. Employing the Fresnel mode of Lorentz transmission electron microscopy, we show that it is possible to control the domain wall structure and its depinning strength not only via the irradiation dose but also the line orientation.Comment: Accepted for publication in Physical Review Applie

    Impact of randomly distributed dopants on Ω-gate junctionless silicon nanowire transistors

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    This paper presents experimental and simulation analysis of an Ω-shaped silicon junctionless nanowire field-effect transistor (JL-NWT) with gate lengths of 150 nm and diameter of the Si channel of 8 nm. Our experimental measurements reveal that the ON-currents up to 1.15 mA/μm for 1.0 V and 2.52 mA/μm for the 1.8-V gate overdrive with an OFF-current set at 100 nA/μm. Also, the experiment data reveal more than eight orders of magnitude ON-current to OFF-current ratios and an excellent subthreshold slope of 66 mV/dec recorded at room temperature. The obtained experimental current-voltage characteristics are used as a reference point to calibrate the simulations models used in this paper. Our simulation data show good agreement with the experimental results. All simulations are based on drift-diffusion formalism with activated density gradient quantum corrections. Once the simulations methodology is established, the simulations are calibrated to the experimental data. After this, we have performed statistical numerical experiments of a set of 500 different JL-NWTs. Each device has a unique random distribution of the discrete dopants within the silicon body. From those statistical simulations, we extracted important figures of merit, such as OFF-current and ON-current, subthreshold slope, and voltage threshold. The performed statistical analysis, on samples of those 500 JL-NWTs, shows that the mean ID-VGs characteristic is in excellent agreement with the experimental measurements. Moreover, the mean ID-VGs characteristic reproduces better the subthreshold slope data obtained from the experiment in comparison to the continuous model simulation. Finally, performance predictions for the JL transistor with shorter gate lengths and thinner oxide regions are carried out. Among the simulated JL transistors, the configuration with 25-nm gate length and 2-nm oxide thickness shows the most promising characteristics offering scalable designs

    Mid-infrared intersubband absorption from p-Ge quantum wells grown on Si substrates

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    Mid-infrared intersubband absorption from p-Ge quantum wells with Si0.5Ge0.5 barriers grown on a Si substrate is demonstrated from 6 to 9 μm wavelength at room temperature and can be tuned by adjusting the quantum well thickness. Fourier transform infra-red transmission and photoluminescence measurements demonstrate clear absorption peaks corresponding to intersubband transitions among confined hole states. The work indicates an approach that will allow quantum well intersubband photodetectors to be realized on Si substrates in the important atmospheric transmission window of 8–13 μm

    Mid-Infrared Intersubband Absorption from P-Ge Quantum Wells on Si

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    Mid-infrared intersubband absorption from p-Ge quantum wells with Si0.5Ge0.5 barriers grown on a Si substrate is demonstrated from 6 to 9 μm wavelength at room temperature and can be tuned by adjusting the quantum well thickness. Fourier transform infra-red spectroscopy measurements demonstrate clear absorption peaks corresponding to intersubband transitions among confined hole states. The work indicates an approach that will allow quantum well intersubband photodetectors to be realized on Si substrates in the important atmospheric transmission window of 8–13 μm
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