bluuebunny/crossref_metadata_2025 huggingface dataset:
Steady-state and transient photoconductivity in c-axis GaN nanowires grown by nitrogen-plasma-assisted molecular beam epitaxy
Authors: Sanford N. A. , Blanchard P. T. , Bertness K. A. , Mansfield L. , Schlager J. B. , Sanders A. W. , Roshko A. , Burton B. B. , George S. M.
Published: February 2010

Analysis of steady-state and transient photoconductivity measurements at room temperature performed on c-axis oriented GaN nanowires yielded estimates of free carrier concentration, drift mobility, surface band bending, and surface capture coefficient for electrons. Samples grown (unintentionally n-type) by nitrogen-plasma-assisted molecular beam epitaxy primarily from two separate growth runs were examined. The results revealed carrier concentration in the range of (3–6)×1016 cm−3 for one growth run, roughly 5×1014–1×1015 cm−3 for the second, and drift mobility in the range of 500–700 cm2/(V s) for both. Nanowires were dispersed onto insulating substrates and contacted forming single-wire, two-terminal structures with typical electrode gaps of ≈3–5 μm. When biased at 1 V bias and illuminated at 360 nm (3.6 mW/cm2) the thinner (≈100 nm diameter) nanowires with the higher background doping showed an abrupt increase in photocurrent from 5 pA (noise level) to 0.1–1 μA. Under the same conditions, thicker (151–320 nm) nanowires showed roughly ten times more photocurrent, with dark currents ranging from 2 nA to 1 μA. With the light blocked, the dark current was restored in a few minutes for the thinner samples and an hour or more for the thicker ones. The samples with lower carrier concentration showed similar trends. Excitation in the 360–550 nm range produced substantially weaker photocurrent with comparable decay rates. Nanowire photoconductivity arises from a reduction in the depletion layer via photogenerated holes drifting to the surface and compensating ionized surface acceptors. Simulations yielded (dark) surface band bending in the vicinity of 0.2–0.3 V and capture coefficient in the range of 10−23–10−19 cm2. Atomic layer deposition (ALD) was used to conformally deposit ≈10 nm of Al2O3 on several devices. Photoconductivity, persistent photoconductivity, and subgap photoconductivity of the coated nanowires were increased in all cases. TaN ALD coatings showed a reduced effect compared to the Al2O3 coated samples.
Note: Probing quadratic magneto-optical Kerr effects with a dual-beam system
Authors: Trudel Simon , Wolf Georg , Schultheiß Helmut , Hamrle Jaroslav , Hillebrands Burkard , Kubota Takahide , Ando Yasuo
Published: February 2010

In this Note, we present a dual-beam magneto-optical Kerr effect (MOKE) magnetometer for the study of quadratic MOKE in magnetic thin films. The two beams simultaneously probe the sample, located in the middle of a quadrupole magnet, at two angles of incidence (0° and 45°). This combination of two systems allows one to automatically and routinely perform measurements that are sensitive to the combined longitudinal and quadratic MOKE signals (45°), or the quadratic effect alone (0°). Orientation-dependent and automated quantitative analyses of the quadratic effect’s amplitude are also implemented. We present representative measurements on Heusler compound thin films to illustrate the newly combined capabilities of this instrument.
Interpretation of admittance, capacitance-voltage, and current-voltage signatures in Cu(In,Ga)Se2 thin film solar cells
Authors: Eisenbarth Tobias , Unold Thomas , Caballero Raquel , Kaufmann Christian A. , Schock Hans-Werner
Published: February 2010

A series of Cu(In,Ga)Se2 (CIGS) thin film solar cells with differently prepared heterojunctions has been investigated by admittance spectroscopy, capacitance-voltage (CV) profiling, and temperature dependent current-voltage (IVT) measurements. The devices with different CdS buffer layer thicknesses, with an In2S3 buffer or with a Schottky barrier junction, all show the characteristic admittance step at shallow energies between 40 and 160 meV, which has often been referred to as the N1 defect. No correlation between the buffer layer thickness and the capacitance step is found. IVT measurements show that the dielectric relaxation frequency of charge carriers in the CdS layers is smaller than the N1-resonance frequency at low temperatures where the N1 step in admittance is observed. These results strongly contradict the common assignment of the N1 response to a donor defect at or close to the heterointerface. In contrast, an explanation for the N1 response is proposed, which relates the admittance step to a non-Ohmic back-contact acting as a second junction in the device. The model, which is substantiated with numerical device simulations, allows a unified explanation of characteristic admittance, CV, and IVT features commonly observed in CIGS solar cells.
Electrode activation in cesium-free negative ion sources
Authors: Dudnikov Vadim , Johnson Rolland P.
Published: February 2010

Features of emission electrode activation leading to enhancement of negative ion emission in cesium-free discharges are discussed. In some ion sources with cesium-free discharges, the emission of negative ions has been increased significantly by emission electrode activation using strong heating of the negative biased electrode by discharge plasma. A simple explanation of this enhancement is that it is due to an accumulation on the emission surface of the plasma electrode of impurities with low ionization potential that decreases in surface work function and increases the secondary emission of negative ions similar to “Cesiation.” The negative biasing of emission surface is important for accumulation and trapping the impurities on the emission surface. To effectively control the activation process it is important to directly detect the evolution of the work function and the impurity concentration during electrode activation with enhancement of negative ion emission.
Fabrication of an optimized hexapole magnet for a 14.5 GHz electron cyclotron resonance ion source
Authors: Oh Byung-Hoon , Seo Chang Seog , In Sang-Ryul , Kim Tae-Seong
Published: February 2010

A hexapole magnet for a 14.5 GHz electron cyclotron resonance (ECR) ion source, where the maximum radial field on the wall of the plasma chamber is higher than 1.1 T, has been designed and fabricated. The size of the outer diameter and the number of the sector of the hexapole are optimized for a 14.5 GHz ECR ion source with the help of a three-dimensional field calculation code. Moreover, to make a strong and long-life magnet against the demagnetic field on the hexapole multilayered structure in radial and axial directions is considered in the design. The distributions of the demagnetic fields are estimated by the calculation of the radial field in a hexapole magnet and the axial field from the solenoid coils. Proper grades of magnetic materials depending on the strength of the demagnetic field are applied for the different layers. The magnetic fields of the measured and calculated ones have been compared.
The influence of shape and potential barrier on confinement energy levels in quantum dots
Authors: Lepadatu Ana-Maria , Stavarache Ionel , Ciurea Magdalena Lidia , Iancu Vladimir
Published: February 2010

The influence of the shape of silicon quantum dots embedded in an amorphous silica matrix on the quantum confinement energy levels, as well as that of the Si/SiO2 potential barrier, are studied. The energy levels are computed using both the infinite and finite rectangular quantum well models for spherical quantum dots and the infinite rectangular quantum well for prolate spheroidal quantum dots. The results are compared with each other and also with the experimental activation energies obtained from the temperature dependence of the dark current. These activation energies are identified with the differences between the quantum confinement energies, subject to the selection rules. The finite rectangular quantum well model takes into account the experimental value of the finite potential barrier and the matrix-to-dot electron mass ratio. The energy levels are smaller than those for the infinite rectangular quantum well case; they decrease when the potential barrier decreases and the mass ratio increases. Different aspects of the models are discussed. All the errors are less than about 4%. The spheroidal shape lifts the degeneracy on the magnetic quantum number. The energy levels can decrease or increase with eccentricity as a consequence of the different quantum confinement effects along the major and minor axes. The supplementary information on the magnetic quantum number is beneficial for optical applications.
Charge migration in Pb(Zr,Ti)O3 ceramics and its relation to ageing, hardening, and softening
Authors: Morozov M. I. , Damjanovic D.
Published: February 2010

The dielectric response of hard (Fe-doped) and soft (Nb-doped) rhombohedral Pb(Zr0.58Ti0.42)1−xMexO3 (Me=Fe or Nb) ceramics was studied at subswitching conditions over a wide range of temperatures (50–450 °C) and frequencies (10 mHz to 10 kHz). The results show qualitative differences in the behavior of the acceptor- and donor-doped samples. Hard materials exhibit a steep increase in the complex permittivity with decreasing frequency. The onset of the dispersion is thermally activated with activation energies of about 0.6–0.8 eV and is attributed here to oxygen vacancy hopping. The activation energy for ac conductivity observed in soft materials is estimated to be about 1.7 eV, corresponding to half of the energy gap of Pb(Zr,Ti)O3 and is thus consistent with electronic conduction. The relevance of ionic hopping conductivity in hard materials to ferroelectric aging/deaging and hardening is analyzed. Strong ionic conductivity in hard samples and its absence in soft samples agree well with the dipolar mechanism of aging in hard materials and the absence of significant aging in soft materials.
ELISA: A cryocooled 10 GHz oscillator with 10−15 frequency stability
Authors: Grop S. , Bourgeois P. Y. , Bazin N. , Kersalé Y. , Rubiola E. , Langham C. , Oxborrow M. , Clapton D. , Walker S. , De Vicente J. , Giordano V.
Published: February 2010

This article reports the design, the breadboarding, and the validation of an ultrastable cryogenic sapphire oscillator operated in an autonomous cryocooler. The objective of this project was to demonstrate the feasibility of a frequency stability of 3×10−15 between 1 and 1000 s for the European Space Agency deep space stations. This represents the lowest fractional frequency instability ever achieved with cryocoolers. The preliminary results presented in this paper validate the design we adopted for the sapphire resonator, the cold source, and the oscillator loop.
Killing–Yano forms of a class of spherically symmetric space-times: A unified generation of higher forms
Authors: Açık Ö. , Ertem Ü. , Önder M. , Verçin A.
Published: February 2010

Killing–Yano (KY) 2- and 3-forms of a class of spherically symmetric space-times that includes the well-known Minkowski, Schwarzschild, Reissner–Nordstrøm, Robertson–Walker, and six different forms of de Sitter space-times as special cases are derived in a unified and exhaustive manner. It is directly proved that while the Schwarzschild and Reissner–Nordstrøm space-times do not accept any KY 3-form and they accept only one 2-form, the Robertson–Walker space-time admits four KY 2-forms and only one KY 3-form. Maximal number of KY forms is obtained for Minkowski and all known forms of de Sitter space-times. Complete lists comprising explicit expressions of KY forms are given.
Atom lithography with metastable helium
Authors: Allred Claire S. , Reeves Jason , Corder Christopher , Metcalf Harold
Published: February 2010

A bright metastable helium (He∗) beam is collimated sequentially with the bichromatic force and three optical molasses velocity compression stages. Each He∗ atom in the beam has 20 eV of internal energy that can destroy a molecular resist assembled on a gold coated silicon wafer. Patterns in the resist are imprinted onto the gold layer with a standard selective etch. Patterning of the wafer with the He∗ was demonstrated with two methods. First, a mesh was used to protect parts of the wafer making an array of grid lines. Second, a standing wave of λ=1083 nm light was used to channel and focus the He∗ atoms into lines separated by λ/2. The patterns were measured with an atomic force microscope establishing an edge resolution of 80 nm. Our results are reliable and repeatable.
Size dependent domain configuration and electric field driven evolution in ultrathin ferroelectric films: A phase field investigation
Authors: Zhang Yihui , Li Jiangyu , Fang Daining
Published: February 2010

Size dependent domain configuration and its evolution under an external electric field are investigated for ultrathin ferroelectric films using an unconventional phase field method. The simulation reveals a series of domain configurations at different thicknesses, including zigzag patterns with eight variants or four variants coexisting, a vortex pattern with four variants coexisting, and a stripe pattern with two variants coexisting. When the film thickness falls below a critical value of 2.8 nm, the polarization vanishes, indicating the suppression of ferroelectricity. The evolution of domain configuration under an alternating electric field is also investigated, and the reduction in remnant polarization and coercive field with respect to decreasing thickness is observed.
Generalized phase-space tomography for intense beams
Authors: Stratakis D. , Kishek R. A. , Bernal S. , Fiorito R. B. , Haber I. , Reiser M. , O’Shea P. G. , Tian K. , Thangaraj J. C. T.
Published: February 2010

Tomographic phase-space mapping in an intense particle beam is reviewed. The diagnostic is extended to beams with space-charge by assuming linear forces and is implemented using either solenoidal or quadrupole focusing lattices. The technique is benchmarked against self-consistent simulation and against a direct experimental sampling of phase-space using a pinhole scan. It is demonstrated that tomography can work for time-resolved phase-space mapping and slice emittance measurement. The technique is applied to a series of proof-of-principle tests conducted at the University of Maryland.
Beam collimation and transport of quasineutral laser-accelerated protons by a solenoid field
Authors: Harres K. , Alber I. , Tauschwitz A. , Bagnoud V. , Daido H. , Günther M. , Nürnberg F. , Otten A. , Schollmeier M. , Schütrumpf J. , Tampo M. , Roth M.
Published: February 2010

This article reports about controlling laser-accelerated proton beams with respect to beam divergence and energy. The particles are captured by a pulsed high field solenoid with a magnetic field strength of 8.6 T directly behind a flat target foil that is irradiated by a high intensity laser pulse. Proton beams with energies around 2.3 MeV and particle numbers of 1012 could be collimated and transported over a distance of more than 300 mm. In contrast to the protons the comoving electrons are strongly deflected by the solenoid field. They propagate at a submillimeter gyroradius around the solenoid’s axis which could be experimentally verified. The originated high flux electron beam produces a high space charge resulting in a stronger focusing of the proton beam than expected by tracking results. Leadoff particle-in-cell simulations show qualitatively that this effect is caused by space charge attraction due to the comoving electrons. The collimation and transport of laser-accelerated protons is the first step to provide these unique beams for further applications such as postacceleration by conventional accelerator structures.
Miniature shock tube for laser driven shocks
Authors: Busquet Michel , Barroso Patrice , Melse Thierry , Bauduin Daniel
Published: February 2010

We describe in this paper the design of a miniature shock tube (smaller than 1 cm3) that can be placed in a vacuum vessel and allows transverse optical probing and longitudinal backside extreme ultraviolet emission spectroscopy in the 100–500Å range. Typical application is the study of laser launched radiative shocks, in the framework of what is called “laboratory astrophysics.”
Tubular alumina formed by anodization in the meniscal region
Authors: Lazarouk S. K. , Sasinovich D. A. , Borisenko V. E. , Muravski A. , Chigrinov V. , Kwok H. S.
Published: February 2010

A method to fabricate tubular nanoporous alumina layers by anodization of aluminum at current densities up to 1400 mA/cm2 and anodization rates up to 70 μm/min has been developed. It implies anodization in the meniscal region of the sample dipping into an electrolyte. The formed porous alumina has been found to be selforganized nanotube cells when the anodization current excides 100 mA/cm2. The formation of nanotubes is supposed to be controlled by the increased volume expansion factor (more than 2) at high forming current densities. The meniscal anodization allows fabrication of porous alumina nanotubes with desired tilt angles in the range of 0°–16°.
Analytical theory of finite-size effects in mechanical desorption of a polymer chain
Authors: Skvortsov A. M. , Klushin L. I. , Fleer G. J. , Leermakers F. A. M.
Published: February 2010

We discuss a unique system that allows exact analytical investigation of first- and second-order transitions with finite-size effects: mechanical desorption of an ideal lattice polymer chain grafted with one end to a solid substrate with a pulling force applied to the other end. We exploit the analogy with a continuum model and use accurate mapping between the parameters in continuum and lattice descriptions, which leads to a fully analytical partition function as a function of chain length, temperature (or adsorption strength), and pulling force. The adsorption-desorption phase diagram, which gives the critical force as a function of temperature, is nonmonotonic and gives rise to re-entrance. We analyze the chain length dependence of several chain properties (bound fraction, chain extension, and heat capacity) for different cross sections of the phase diagram. Close to the transition a single parameter (the product of the chain length N and the deviation from the transition point) describes all thermodynamic properties. We discuss finite-size effects at the second-order transition (adsorption without force) and at the first-order transition (mechanical desorption). The first-order transition has some unusual features: The heat capacity in the transition region increases anomalously with temperature as a power law, metastable states are completely absent, and instead of a bimodal distribution there is a flat region that becomes more pronounced with increasing chain length. The reason for this anomaly is the absence of an excess surface energy for the boundary between adsorbed and stretched coexisting phases (this boundary is one segment only): The two states strongly fluctuate in the transition point. The relation between mechanical desorption and mechanical unzipping of DNA is discussed.
Effect of self-affine fractal characteristics of surfaces on wetting
Authors: Sarkar S. , Patra S. , Gayathri N. , Banerjee S.
Published: February 2010

In this letter, we show experimentally that the wetting property of a solid surface crucially depends on the surface morphological parameters such as; (1) root mean square (rms) roughness σ, (2) in-plane roughness correlation length ξ, and (3) roughness exponent α of the self-affine surface. We have shown that the contact angle monotonically decreases with the increase in the rms local surface slope ρ (∝σ/ξα). We have shown that the same solid surface can be made hydrophobic or hydrophilic by merely tuning these self-affine surface morphological parameters.
Optimization towards high density quantum dots for intermediate band solar cells grown by molecular beam epitaxy
Authors: Zhou D. , Sharma G. , Thomassen S. F. , Reenaas T. W. , Fimland B. O.
Published: February 2010

We report high density quantum dots (QDs) formation with optimized growth temperature and V/III ratio. At lower growth temperature, QD density is increased, due to smaller surface migration length of In adatoms. With higher V/III, the QD density is higher but it results in large clusters formation and decreases the QD uniformity. The QD solar cell was fabricated and examined. An extended spectral response in contrast to the GaAs reference cell was presented but the external quantum efficiency at energies higher than GaAs band gap is reduced, resulting from the degradation for the emitter above the strained QD layers.
Genetic algorithm optimization of laser pulses for molecular quantum state excitation
Authors: Sharma Sitansh , Singh Harjinder , Balint-Kurti Gabriel G.
Published: February 2010

Conventionally optimal control theory has been used in the theoretical design of laser pulses through the direct variation in the electric field of the laser pulse as a function of time. This often leads to designed laser pulses which contain a broad and seemingly arbitrary frequency structure that varies in time in a manner which may be difficult to realize experimentally. In contrast, the experimental design of laser pulses has used a genetic algorithm (GA) approach, varying only those laser parameters actually available to the experimentalist. We investigate in this paper the possibility of using GA optimization methods in the theoretical design of laser pulses to bring about quantum state transitions in molecules. This allows us to select only a small limited number of parameters to vary and to choose these parameters so that they correspond to those available to the experimentalist. In the paper we apply our methods to the vibrational-rotational excitation of the HF molecule. We choose a small limited number of frequencies and vary only the associated electric field amplitudes and pulse envelopes. We show that laser pulses designed in this way can lead to very high transition probabilities.
Lateral organization of complex lipid mixtures from multiscale modeling
Authors: Tumaneng Paul W. , Pandit Sagar A. , Zhao Guijun , Scott H. L.
Published: February 2010

The organizational properties of complex lipid mixtures can give rise to functionally important structures in cell membranes. In model membranes, ternary lipid-cholesterol (CHOL) mixtures are often used as representative systems to investigate the formation and stabilization of localized structural domains (“rafts”). In this work, we describe a self-consistent mean-field model that builds on molecular dynamics simulations to incorporate multiple lipid components and to investigate the lateral organization of such mixtures. The model predictions reveal regions of bimodal order on ternary plots that are in good agreement with experiment. Specifically, we have applied the model to ternary mixtures composed of dioleoylphosphatidylcholine:18:0 sphingomyelin:CHOL. This work provides insight into the specific intermolecular interactions that drive the formation of localized domains in these mixtures. The model makes use of molecular dynamics simulations to extract interaction parameters and to provide chain configuration order parameter libraries.
A numerical study of mobility in thin films of fullerene derivatives
Authors: MacKenzie Roderick C. I. , Frost Jarvist M. , Nelson Jenny
Published: February 2010

The effect of functional group size on the electron mobility in films of fullerene derivatives is investigated numerically. A series of four C60 derivatives are formed by attaching saturated hydrocarbon chains to the C60 cage via a methano bridge. For each of the derivatives investigated, molecular dynamics is used to generate a realistic material morphology. Quantum chemical methods are then used to calculate intermolecular charge transfer rates. Finally, Monte Carlo methods are used to simulate time-of-flight experiments and thus calculate the electron mobility. It is found that as the length of the aliphatic side chain increases, the configurational disorder increases and thus the mobility decreases.
Interplay between micelle formation and waterlike phase transitions
Authors: Heinzelmann G. , Figueiredo W. , Girardi M.
Published: February 2010

A lattice model for amphiphilic aggregation in the presence of a structured waterlike solvent is studied through Monte Carlo simulations. We investigate the interplay between the micelle formation and the solvent phase transition in two different regions of temperature-density phase diagram of pure water. A second order phase transition between the gaseous (G) and high density liquid (HDL) phases that occurs at very high temperatures, and a first order phase transition between the low density liquid (LDL) and (HDL) phases that takes place at lower temperatures. In both cases, we find the aggregate size distribution curve and the critical micellar concentration as a function of the solvent density across the transitions. We show that micelle formation drives the LDL-HDL first order phase transition to lower solvent densities, while the transition G-HDL is driven to higher densities, which can be explained by the markedly different degrees of micellization in both cases. The diffusion coefficient of surfactants was also calculated in the LDL and HDL phases, changing abruptly its behavior due to the restructuring of waterlike solvent when we cross the first order LDL-HDL phase transition. To understand such behavior, we calculate the solvent density and the number of hydrogen bonds per water molecule close to micelles. The curves of the interfacial solvent density and the number of hydrogen bonds per water molecule in the first hydration signal a local phase change of the interfacial water, clarifying the diffusion mechanism of free surfactants in the solvent.
Ab initio characterization of the Ca–HCl van der Waals complex
Authors: Koput Jacek , Makarewicz Jan
Published: February 2010

The equilibrium structure and three-dimensional potential energy surface of the Ca–HCl van der Waals complex in its ground electronic state have been determined from accurate ab initio calculations using the coupled-cluster method, CCSD(T), in conjunction with basis sets of quadruple- and quintuple-zeta quality. The core-electron correlation, high-order valence-electron correlation, and scalar relativistic effects were investigated. The Ca–HCl complex was confirmed to be linear at equilibrium, with the vibrationless dissociation energy (into Ca and HCl) De of 287 cm−1. The vibration-rotation energy levels of various Ca–HCl isotopomers were predicted using the variational method. The predicted spectroscopic constants can be useful in a further analysis of high-resolution vibration-rotation spectra of the Ca–HCl complex.
Intimate partner violence and other partner-related factors: correlates of sexually transmissible infections and risky sexual behaviours among young adult African American women
Authors: Seth Puja , Raiford Jerris L. , Robinson LaShun S. , Wingood Gina M. , DiClemente Ralph J.
Published: February 2010

Background: Intimate partner violence and other partner-related factors have been associated with acquiring sexually transmissible infections (STIs) and engaging in risky sexual behaviour. The present study examined partner-related risk factors for STIs and risky sexual behaviours among an urban sample of African American women. Methods: African American women, between 18 and 29 years (n = 848), participated in the study at baseline. Participants completed a 40-min Audio Computer Assisted Survey Interview assessing sociodemographics, partner-related factors and HIV/STI-associated sexual risk behaviours. Subsequently, participants provided two vaginal swab specimens for STIs. Results: The findings indicated that risky sexual behaviours and STIs were prevalent in this sample: 35.6% reported a risky sexual partner, 65.4% reported inconsistent condom use and 17% tested positive for a laboratory-confirmed STI. Women reporting a history of intimate partner violence were more likely to report risky sexual partners (adjusted odds ratio (AOR) = 2.00; 95% confidence interval (CI) = 1.5–2.8), inconsistent condom use (AOR = 1.60; 95% CI = 1.1–2.3) and test positive for an STI (AOR = 1.46; 95% CI = 0.99–2.1). Women reporting high partner-related barriers to condom use were more likely to report risky sexual partners (AOR = 1.69; 95% CI = 1.2–2.3), inconsistent condom use (AOR = 2.13; 95% CI = 1.5–3.0) and test positive for an STI (AOR = 1.98; 95% CI = 1.3–3.0). Finally, women with older partners were more likely to report risky sexual partners (AOR = 1.53; 95% CI = 1.1–2.1) and test positive for an STI (AOR = 1.46; 95% CI = 1.0–2.2). Conclusions: This study examines partner-related risk factors for STIs and risky sexual behaviours among African American women. These findings underscore the need for combined intimate partner violence and HIV/STI prevention programs for this disproportionately affected high-risk group.
Problems with condoms may be reduced for men taking ample time to apply them
Authors: Crosby Richard A. , Graham Cynthia A. , Yarber William L. , Sanders Stephanie A.
Published: February 2010

Background: One potentially important antecedent of experiencing problems with condom use during penile-vaginal sex is the amount of time that men (and perhaps women) allow for condom application. To examine whether men reporting that ample time was available to apply a male condom (the last time a condom was used for penile-vaginal sex) were also less likely to report problems with condom use such as breakage, slippage and erection difficulties during that sexual event. Methods: A convenience sample of men (n = 440) was recruited via advertisements in newspapers (two urban and one small town) and a blog on the website of a condom sales company. Men completed a questionnaire posted on the website of The Kinsey Institute for Research in Sex, Gender, and Reproduction. Inclusion criteria were that participants were: at least 18 years old; used condoms for penile-vaginal intercourse in the past 3 months; and able to read English. Results: In controlled, event-specific analyses, men reporting that they did not have sufficient time for condom application were ~three times more likely to report breakage and ~2.4 times more likely to report slippage. In addition, men who reported that they lacked time for condom application were ~2.4 times more likely to experience any of nine sexual problems, 3.4 times more likely to report difficulty with erection, 2.1 times more likely to report reduced sexual pleasure, 2.2 times more likely to report reduced sexual pleasure of their female partner and 2.6 times more likely to report that the condom irritated their partner’s vagina. Conclusions: This is the first study using an event-specific analysis to examine the effect of not having enough time for condom application on condom breakage, slippage and several outcomes related to sexual pleasure. Sexually transmissible infections and pregnancy prevention messages should include recommendations to men to take their time applying condoms.
Pilot of non-invasive (oral fluid) testing for HIV within a community setting
Authors: Birrell Frances , Staunton Shaun , Debattista Joseph , Roudenko Nicole , Rutkin William , Davis Craig
Published: February 2010

Background: The present study sought to determine the level of undiagnosed HIV infection within a community setting of men who have sex with men (MSM) and identify any associated sexual risk behaviours. Methods: A total of 427 MSM were recruited in sex-on-premises venues (SOPV) and gay bars within the inner city of Brisbane. An additional 37 MSM were recruited in a smaller, regional centre (Toowoomba). Oral fluid testing for HIV antibodies was undertaken using the Orasure collection system and assay. Each participant was invited to complete a brief behaviour questionnaire and submit an oral fluid specimen. Confirmed serology results were linked to reported sexual behaviours, testing patterns and HIV status. Results: Of the 464 men surveyed, 33 identified as HIV-positive, and all of these were reactive by the Orasure assay. A further eight people who identified as negative or unknown serostatus, had confirmed Orasure reactive results, resulting in 1.9% of the ‘non-HIV positive’ MSM sample unaware of their positive HIV status. Therefore, 19.5% of the total confirmed HIV-positive individuals were not aware of their true serostatus. Conclusions: A significant minority of HIV-positive MSM are currently unaware of their positive serostatus. However, an analysis of their risk behaviour does not seem to indicate any significant difference to those who are HIV-negative. Interestingly, 86% of those who were unaware they were HIV-positive identified that they had been tested in the previous 6 months and all of them claimed to have been tested in the previous 2 years.
A retrospective case note review of sex worker attendees at sexual health clinics in the western suburbs of Sydney
Authors: Kakar Sheena Rajesh , Biggs Karen , Chung Charles , Sawleshwarkar Shailendra , Mindel Adrian , Lagios Katerina , Hillman Richard J.
Published: February 2010

Background: Sex workers (SWs) are globally recognised to be at high risk for the acquisition and transmission of sexually transmissible infections (STIs). There is a paucity of published data concerning SWs from the western suburbs of Sydney, with the last published study conducted in 1988. Therefore, we conducted a study to determine the demographics, sexual practices and health care needs of SWs attending Sexual Health Clinics (SHCs) in the region. Methods: Self-identified SWs presenting to SHCs in western Sydney between April 2007 and March 2008 were identified using clinic databases. A case note review was then undertaken. Results: One hundred and eighty-five female SWs were included in the analysis. Ninety-eight (54.5%) were born overseas (predominantly China) and 82 (45.6%) were born in Australia. One hundred and seventeen (68%) were English speaking backgrounds (ESB), while 55 (32%) were from non-English speaking backgrounds (NESB). Seventy-two (38.9%) were symptomatic on attendance, with vaginal discharge the most common symptom. Chlamydia was the most commonly reported STI in the previous 12 months with 28 cases (15.1%). SWs from NESB were significantly more likely to be older, symptomatic, have a hepatitis B diagnosis in the previous year and work more shifts per week, compared with SWs from ESB. SWs born overseas were more likely to be symptomatic than Australian born SWs who, in turn, were more likely to have a hepatitis C diagnosis in the previous year. Conclusion: SWs from NESB would potentially benefit from evidenced-based, culturally and linguistically appropriate interventions and targeted health promotion.
Triple-class HIV antiretroviral therapy failure in an Australian primary care setting
Authors: Bloch Mark , Farris Maria , Tilden Dominic , Gowers Andrew , Cunningham Nicola
Published: February 2010

Objective: To determine the prevalence, characteristics and virological outcomes of triple-class antiretroviral drug failure (TCF) and triple-class virological failure (TCVF) in HIV-infected patients attending an Australian high caseload primary care clinic. Methods: Cross-sectional observational study using a retrospective review of electronic medical records from 1007 patients with HIV attending Holdsworth House Medical Practice in Darlinghurst, Australia, between 2007 and 2008. TCF was defined as failure (virological, immunological, clinical, intolerance or other) of at least one drug in each of the three major classes of highly active antiretroviral therapy. Results: A total of 51 patients (5.1%) with TCF were identified. Of these patients, 31.4% had experienced virological failure of each of the three main drug classes. Eighty-eight percent of patients with TCF and 75% of patients with TCVF had achieved virological suppression (HIV RNA <400 copies mL–1). Total mean (s.d.) duration on antiretroviral therapy (ART) was 12.2 (3.3) years, with patients receiving an average of 18 antiretroviral drugs during this period. Reasons for treatment change included intolerance (88% of patients), virological failure (84%), immunological failure (24%) and poor adherence (20%). Conclusions: The prevalence of TCF and TCVF in patients with long-term HIV infection and extensive antiretroviral experience is low in primary care sites. Despite experiencing failure to the three main classes of ART, successful virological outcomes are still achievable in the majority of such patients.
Providing high quality information about human papillomavirus for women after treatment for high-grade cervical dysplasia
Authors: Dyson Suzanne , Pitts Marian , Lyons Anthony , Mullins Robyn
Published: February 2010

Background: The present study aimed to inform the production of a resource for women who have had a high-grade cervical abnormality and are scheduled to undergo testing for human papillomavirus (HPV) at their 12-month follow-up. Methods: Two rounds of semi-structured, qualitative interviews were held with women who were attending a gynaecological oncology clinic at a major teaching hospital for women in Melbourne, Australia, 6 months after treatment for cervical intraepithelial neoplasia (CIN) to receive a follow-up Pap test and colposcopy. In an initial round of interviews, we gauged the reactions of 16 women to an existing information brochure containing general information about HPV. Based on the findings from the interviews, a second brochure aimed specifically for women scheduled to undergo HPV testing as part of their post treatment follow-up was drafted. Feedback was then gathered from a further 12 women. Results: While all participants had received some information and counselling about HPV and HPV testing as part of their treatment, many still experienced high levels of stress and anxiety about cancer and the sexually transmissible nature of HPV. Many also still had unanswered questions about HPV, their treatment regime and future prognosis. Conclusion: For a brochure to provide an effective adjunct to counselling, it is essential that it is carefully developed and pilot tested to ensure that it is easily understood and meets the information needs of the target audience. Such materials need to provide both medical and psychosocial information about HPV and be presented in accessible, easy to understand language.
Misclassification bias: diversity in conceptualisations about having 'had sex'
Authors: Sanders Stephanie A. , Hill Brandon J. , Yarber William L. , Graham Cynthia A. , Crosby Richard A. , Milhausen Robin R.
Published: February 2010

Background: Understanding the signification of the word ‘sex’ has implications for both medical research and clinical practice. Little is known about how people of varying ages define sex and how situational qualifiers influence definitions across age groups. To our knowledge, this is the first study of a representative sample to assess attitudes about which sexual behaviours constitute having ‘had sex’ and to examine possible mediating factors (gender, age, giving/receiving stimulation, male ejaculation, female orgasm, condom use or brevity). Methods: A telephone survey of English-speaking residents of Indiana (USA) using random-digit-dialling produced a final sample of 204 men and 282 women (n = 486) ranging in age from 18 to 96 years. Questions assessed the respondents’ attitudes on manual-genital (MG), oral-genital (OG), penile-vaginal intercourse (PVI) and penile-anal intercourse (PAI) behaviours. Results: There was no universal consensus on which behaviours constituted having ‘had sex’. More than 90% responded ‘yes’ to PVI but one in five responded ‘no’ to PAI, three in 10 responded ‘no’ to OG and about half endorsed MG. Fewer endorsed PVI with no male ejaculation (89.1%) compared with PVI without a qualifier (94.8%, P < 0.001). MG was endorsed more often when received (48.1%) than given (44.9%, P < 0.001). Among men, the oldest and youngest age groups were significantly less likely to believe certain behaviours constituted having ‘had sex’. Conclusions: These findings highlight the need to use behaviour-specific terminology in sexual history taking, sex research, sexual health promotion and sex education. Researchers, educators and medical practitioners should exercise caution and not assume that their own definitions of having ‘had sex’ are shared by their research participants or patients.
A case-control study of men with non-gonococcal urethritis at Auckland Sexual Health Service: rates of detection of Mycoplasma genitalium
Authors: Hilton Jackie , Azariah Sunita , Reid Murray
Published: February 2010

Background: Previous studies have identified Mycoplasma genitalium as a cause of urethritis in men. As there is no New Zealand data, a case-control study was conducted to determine whether this organism is a significant cause of urethritis in men presenting to Auckland Sexual Health Service. Methods: Enrolment for the study commenced in March 2006 and finished in February 2008. Inclusion criteria for cases of non-gonococcal urethritis were onset of urethritis symptoms within one month confirmed by urethral Gram staining showing ≥10 polymorphonuclear leucocytes per high-powered field. Controls were men presenting during the same time period for asymptomatic sexual health screening. All participants were tested for Neisseria gonorrhoeae, M. genitalium, and Chlamydia trachomatis. Information regarding symptoms, sexual behaviour and treatment was collected using a standard questionnaire. Results: We recruited 209 cases and 199 controls with a participation rate of 96%. The prevalence of C. trachomatis and M. genitalium in non-gonococcal urethritis cases was 33.5% and 10% respectively. Co-infection with these organisms was uncommon (1.9%). C. trachomatis and M. genitalium were diagnosed in 4% and 2% of controls, respectively, and both infections were detected significantly less often than in the cases (P < 0.0001, P < 0.005). Cases were more likely to report inconsistent condom use, multiple sexual contacts and not having sexual intercourse in the last week (P = 0.03, P = 0.02, P = 0.03). A past history of non-gonococcal urethritis was a significant predictor of current symptoms (P < 0.0001). Conclusions: This is the first study to investigate M. genitalium infection in New Zealand men. Our results confirm that M. genitalium is a cause of non-gonococcal urethritis in men presenting to our service.
Is screening asymptomatic men who have sex with men for urethral gonorrhoea worthwhile?
Authors: Ryder Nathan , Lockart Ian G. , Bourne Chris
Published: February 2010

We determined the prevalence of symptomatic and asymptomatic urethral gonorrhoea among men who have sex with men (MSM) at our Australian sexual health clinic. Asymptomatic MSM are screened using the Roche Amplicor® PCR, whereas culture is used for symptomatic MSM. We analysed data from all MSM tested for urethral gonorrhoea from March 2006 to July 2008. Among the 4453 asymptomatic MSM, there were two (0.04%) diagnoses of urethral gonorrhoea, compared with 38 (3.13%) among 1213 symptomatic MSM. Despite a high prevalence of symptomatic infection, asymptomatic urethral gonococcal infection was extremely uncommon among MSM seen in our sexual health clinic.
Ron Germain: Towards a grand unified theory
Authors: Maxmen Amy
Published: February 2010

As data floods in, Germain works overtime to decipher which immunological information matters and how it can be applied to saving lives.
Measurement of the temperature and the resistivity of an impulse arc in variable-pressure CO2
Authors: A Robledo-Martinez  , H Sobral  , A Ruiz-Meza
Published: February 2010

In the text (in the last sentences of sections 4 and 5) we incorrectly quoted a yield of 1.16 × 1013molecules J -1for CO production. The correct figure is 2.7 × 1018molecules J -1. This shows that CO2experienced dissociation, and a corresponding CO formation, at a rate that is comparable to that found by other researchers (e.g. [18]).

Reference

[18] Levine J S, Gregory G L, Harvey G A, Howell W E, Borucki W J and Orville R E1982Geophys. Res. Lett.9893–6
Temporal evolution and spatial distribution of dust creation events in Tore Supra and in ASDEX Upgrade studied by CCD image analysis
Authors: Hong Suk-Ho , Grisolia Christian , Rohde Volker , Monier-Garbet Pascale
Published: February 2010

Images of wide-angle visible standard CCD cameras contain information on dust creation events (DCEs) that occur during plasma operations. Analysing the straight line-like dust traces in the shallow volume of scrape-off layer along the vacuum vessel, caused by plasma–dust interaction, the database on the DCEs is built. The database provides short/long term temporal evolution and spatial distribution of origins of DCEs in fusion devices. We have studied the DCEs of CIMES (2006) and DITS (2007) Tore Supra (TS) campaigns, and the DCEs of the 2007 ASDEX Upgrade (AUG) campaign. The results from the TS CIMES campaign show different patterns of DCEs meaning different plasma–wall interaction depending on power coupling. The TS DITS campaign indicates that dusts may be an operational limit if a fixed plasma operation scenario is used repeatedly. Different behaviours of DCEs between the carbon limiter machine and the full tungsten divertor machine are found, which is important for next generation fusion machines like ITER.
Assessment of compatibility of ICRF antenna operation with full W wall in ASDEX Upgrade
Authors: Bobkov Vl.V. , Braun F. , Dux R. , Herrmann A. , Giannone L. , Kallenbach A. , Krivska A. , Müller H.W. , Neu R. , Noterdaeme J.-M. , Pütterich T. , Rohde V. , Schweinzer J. , Sips A. , Zammuto I.
Published: February 2010

The compatibility of ICRF (ion cyclotron range of frequencies) antenna operation with high-Z plasma facing components is assessed in ASDEX Upgrade (AUG) with its tungsten (W) first wall.

The mechanism of ICRF-related W sputtering was studied by various diagnostics including the local spectroscopic measurements of W sputtering yield Y
W on antenna limiters. Modification of one antenna with triangular shields, which cover the locations where long magnetic field lines pass only one out of two (0π)-phased antenna straps, did not influence the locally measured Y
W values markedly. In the experiments with antennas powered individually, poloidal profiles of Y
W on limiters of powered antennas show high Y
W close to the equatorial plane and at the very edge of the antenna top. The Y
W-profile on an unpowered antenna limiter peaks at the location projecting to the top of the powered antenna.

An interpretation of the Y
W measurements is presented, assuming a direct link between the W sputtering and the sheath driving RF voltages deduced from parallel electric near-field (E
||) calculations and this suggests a strong E
|| at the antenna limiters. However, uncertainties are too large to describe the Y
W poloidal profiles.

In order to reduce ICRF-related rise in W concentration C
W, an operational approach and an approach based on calculations of parallel electric fields with new antenna designs are considered. In the operation, a noticeable reduction in Y
W and C
W in the plasma during ICRF operation with W wall can be achieved by (a) increasing plasma–antenna clearance; (b) strong gas puffing; (c) decreasing the intrinsic light impurity content (mainly oxygen and carbon in AUG). In calculations, which take into account a realistic antenna geometry, the high E
|| fields at the antenna limiters are reduced in several ways: (a) by extending the antenna box and the surrounding structures parallel to the magnetic field; (b) by increasing the average strap–box distance, e.g. by increasing the number of toroidally distributed straps; (c) by a better balance of (0π)-phased contributions to RF image currents.