6,919 research outputs found

    Quenched chirality in RbNiCl3_3

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    The critical behaviour of stacked-triangular antiferromagnets has been intensely studied since Kawamura predicted new universality classes for triangular and helical antiferromagnets. The new universality classes are linked to an additional discrete degree of freedom, chirality, which is not present on rectangular lattices, nor in ferromagnets. However, the theoretical as well as experimental situation is discussed controversially, and generic scaling without universality has been proposed as an alternative scenario. Here we present a careful investigation of the zero-field critical behaviour of RbNiCl3_3, a stacked-triangular Heisenberg antiferromagnet with very small Ising anisotropy. From linear birefringence experiments we determine the specific heat exponent α\alpha as well as the critical amplitude ratio A+/AA^+/A^-. Our high-resolution measurements point to a single second order phase transition with standard Heisenberg critical behaviour, contrary to all theoretical predictions. From a supplementary neutron diffraction study we can exclude a structural phase transition at TN_N. We discuss our results in the context of other available experimental results on RbNiCl3_3 and related compounds. We arrive at a simple intuitive explanation which may be relevant for other discrepancies observed in the critical behaviour of stacked-triangular antiferromagnets. In RbNiCl3_3 the ordering of the chirality is suppressed by strong spin fluctuations, yielding to a different phase diagram, as compared to e.g.\@ CsNiCl3_3, where the Ising anisotropy prevents these fluctuations

    Radiometric temperature analysis of the Hayabusa spacecraft re-entry

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    Hayabusa, an unmanned Japanese spacecraft, was launched to study and collect samples from the surface of the asteroid 25143 Itokawa. In June 2010, the Hayabusa spacecraft completed it’s seven year voyage. The spacecraft and the sample return capsule (SRC) re-entered the Earth’s atmosphere over the central Australian desert at speeds on the order of 12 km/s. This provided a rare opportunity to experimentally investigate the radiative heat transfer from the shock-compressed gases in front of the sample return capsule at true-flight conditions. This paper reports on the results of observations from a tracking camera situated on the ground about 100 km from where the capsule experienced peak heating during re-entry

    Acceptability of the female condom in different groups of women in South Africa - A multicentred study to inform the national female condom introductory strategy

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    Objectives. To assess the acceptability of the female condom to different groups of women and their partners in South Africa. Design. Descriptive, cross-sectional study. Setting. Multicentre study conducted in five sites. Subjects. The study recruited 678 women from five centres-to an acceptability trial of the female condom. Acceptability and successful use varied between the centres. Outcome measures. Factors affecting successful use and willingness and intention to use the method again. Results. In total, 209 women used the condom at least once. Discontinuation rates were high, with partner reluctance to try the method as the main reason given for discontinuation at all sites. Women who had previous experience with the male condom or who received a more intensive training session generally found the device easier to use. The main issues concerning women were over-lubrication (27%) and concern that the device was too large (28%). The majority of women said that they would be interested in using the method again (86%) and would recommend it to friends (95%). Conclusions. Overcoming partner opposition is an important issue to address when introducing the method. The study was used to address the national introductory strategy of the female condom, which began in 1998

    A novel MC4R mutation associated with childhood-onset obesity: A case report

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    The melanocortin-4-receptor gene (MC4R) is a key regulator of energy homeostasis, food intake and body weight. MC4R gene mutations are associated with early-onset severe obesity. Most patients are heterozygotes, with some reports of homozygotes and compound het-erozygotes. The authors report a case involving an eight-year-old girl with progressive weight gain from infancy, body mass index 44 kg/m: (\u3e97th percentile), hyperphagia, hvperinsulinemia and increased linear growth. There was no phenotvpe of morbid obesity in the parents or sibling. Coding regions and intron-exon boundaries of the genes encoding leptin, Ieptin receptor, pro-opiomelanocortin and MC4R were analyzed. Two heterozygous coding mutations in the MCR4 gene (S94N and C293R) were detected, of which the second has not been previously reported. The mutations were on opposite chromosomes, confirming compound heterozygosity. The molecular findings and clinical features associated with this novel MC4R mutation are described. The authors emphasize that rare mutations can be found in some patients with severe childhood-onset obesity

    Sub-micron, Metal Gate, High-к Dielectric, Implant-free, Enhancement-mode III-V MOSFETs

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    The performance of 300nm, 500nm and 1μm metal gate, implant free, enhancement mode III-V MOSFETs are reported. Devices are realised using a 10nm MBE grown Ga2O3/(GaxGd1-x)2O3 high-κ (κ=20) dielectric stack grown upon a δ-doped AlGaAs/InGaAs/AlGaAs/GaAs heterostructure. Enhancement mode operation is maintained across the three reported gate lengths with a reduction in threshold voltage from 0.26 V to 0.08 V as the gate dimension is reduced from 1 μm to 300 nm. An increase in transconductance is also observed with reduced gate dimension. Maximum drain current of 420 μA/μm and extrinsic transconductance of 400 µS/µm are obtained from these devices. Gate leakage current of less than 100pA and subthreshold slope of 90 mV/decade were obtained for all gate lengths. These are believed to be the highest performance submicron enhancement mode III-V MOSFETs reported to date

    Acceptability of the female condom in different groups Of women in South Africa-A Multicentred study to inform the national female condom introductory strategy

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    Objectives. To assess the acceptability of the female condom to different groups of women and their partners in South Africa.Design. Descriptive, cross-sectional study.Setting. Multicentre study conducted in five sites.Subjects. The study recruited 678 women from five centres to an acceptability trial of the female condom. Acceptability and successful use varied between the centres. Outcome measures. Factors affecting successful use and willingness and intention to use the method again.Results. In total, 209 women used the condom at least once. Discontinuation rates were high, with partner reluctance to try the method as the main reason given for discontinuation at all sites. Women who had previous experience with the male condom or who received a more intensive training session generally found the device easier to use. The main issues concerning women were over-lubrication (27%) and concern that the device was too large (28%). The majority of women said that they would be interested in using the method again (86%) and would recommend it to friends (95%).Conclusions. Overcoming partner opposition is an important issue to address when introducing the method. The study was used to address the national introductory strategy of the female condom, which began in 1998

    Disclosure of conventional and complementary medicine use to medical doctors and complementary medicine practitioners: A survey of rates and reasons amongst those with chronic conditions.

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    Chronic conditions are prolonged and complex, leading patients to seek multiple forms of care alongside conventional treatment, including complementary medicine (CM). These multiple forms of care are often used concomitantly, requiring patient-provider communication about treatments used in order to manage potential risks. In response, this study describes rates and reasons for disclosure/non-disclosure of conventional medicine use to CM practitioners, and CM use to medical doctors, by individuals with chronic conditions. A survey was conducted online in July and August 2017 amongst the Australian adult population. Participants with chronic conditions were asked about their disclosure-related communication with CM practitioners (massage therapist, chiropractor, acupuncturist, naturopath) and medical doctors. Patients consulting different professions reported varying disclosure rates and reasons. Full disclosure (disclosed ALL) to medical doctors was higher (62.7%-79.5%) than full disclosure to CM practitioners (41.2%-56.9%). The most strongly reported reason for disclosing to both MDs and CM practitioners was I wanted them to fully understand my health status, while for non-disclosure it was They did not ask me about my CM/medicine use. Reasons regarding concerns or expectations around the consultation or patient-provider relationship were also influential. The findings suggest that patient disclosure of treatment use in clinical consultation for chronic conditions may be improved through patient education about its importance, direct provider inquiry, and supportive patient-provider partnerships. Provision of optimal patient care for those with chronic conditions requires greater attention to patient-provider communication surrounding patients' wider care and treatment use
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