3,804 research outputs found

    Constraints from TcT_c and the isotope effect for MgB2_2

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    With the constraint that Tc=39T_c = 39 K, as observed for MgB2_2, we use the Eliashberg equations to compute possible allowed values of the isotope coefficient, β\beta. We find that while the observed value β=0.32\beta= 0.32 can be obtained in principle, it is difficult to reconcile a recently calculated spectral function with such a low observed value

    Ultrasonic studies of the magnetic phase transition in MnSi

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    Measurements of the sound velocities in a single crystal of MnSi were performed in the temperature range 4-150 K. Elastic constants, controlling propagation of longitudinal waves reveal significant softening at a temperature of about 29.6 K and small discontinuities at \sim28.8 K, which corresponds to the magnetic phase transition in MnSi. In contrast the shear elastic moduli do not show any softening at all, reacting only to the small volume deformation caused by the magneto-volume effect. The current ultrasonic study exposes an important fact that the magnetic phase transition in MnSi, occurring at 28.8 K, is just a minor feature of the global transformation marked by the rounded maxima or minima of heat capacity, thermal expansion coefficient, sound velocities and absorption, and the temperature derivative of resistivity.Comment: 4 pages, 4 figure

    The effect of steam distillation time on the yield and composition of the oil from Kunzea ambigua

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    Kunzea ambigua (Sm.) Druce (Myrtaceae), commonly known as ‘Tick Bush’ is a woody shrub, indigenous to Australia and New Zealand. It thrives in the granite soils of the north-east coast and Bass Strait islands of Tasmania. The therapeutic and antimicrobial properties of the essential oil have been documented [1,2]. The nature of the small, leathery leaves necessitates a long distillation time to achieve maximum oil yield. Oils were collected at set distillation times of 1, 3, 5, 10, 30, 60, 90, 120, 150, 180, and 240 mins. Yields and chemical compositions were determined by GC FID and identification of components was confirmed by Kovats Indices and mass spectra. Although the distillation of monoterpenes contributed to the most rapid phase of oil accumulation, which occurred at around 30 minutes, the narrow, lanceolate leaves of K. ambigua required in excess of 4 hours for complete extraction of the heavier components. The concentration of oxygenated monoterpenes, such as terpinen-4-ol and a-terpineol, had peak oil recovery at between 30 and 60 minutes. Recovery of 1,8-cineole maximized at 30 minutes, following a similar pattern to the monoterpenes. The cyclic ether component of this oxygenated monoterpene may well contribute to the different behavior under the conditions of steam distillation. In contrast, increasing amounts of the oxygenated sesquiterpenes, globulol and viridiflorol accumulated with time and it may be assumed that the complete extraction of essential oils from the vegetative material was not achieved. Both components are regarded as integral to the aroma, contributing a floral/citrus element to the bouquet of the typical Kunzea oil [3]. Oils containing higher ratios of these heavy components may be achieved by combining fractions collected onwards from one and a half hours into the steam distillation process. This enhanced the percentage of globulol from 17±3 in the unfractionated, total oil yield to 27±4 in the 46% of the oil collected in the later stages of the distillation. Likewise, the percentage of viridiflorol can be increased from 10±2 to 17±2%. Research is continuing into shortened distillation times using super-heated steam and into the antibacterial and antifungal properties of the oil of K. ambigua

    First order isotropic - smectic-A transition in liquid crystal-aerosil gels

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    The short-range order which remains when the isotropic to smectic-A transition is perturbed by a gel of silica nanoparticles (aerosils) has been studied using high-resolution synchrotron x-ray diffraction. The gels have been created \textit{in situ} in decylcyanobiphenyl (10CB), which has a strongly first-order isotropic to smectic-A transition. The effects are determined by detailed analysis of the temperature and gel density dependence of the smectic structure factor. In previous studies of the continuous nematic to smectic-A transition in a variety of thermotropic liquid crystals the aerosil gel appeared to pin, at random, the phase of the smectic density modulation. For the isotropic to smectic-A transition the same gel perturbation yields different results. The smectic correlation length decreases more slowly with increasing random field variance in good quantitative agreement with the effect of a random pinning field at a transition from a uniform phase directly to a phase with one-dimensional translational order. We thus compare the influence of random fields on a \textit{freezing} transition with and without an intervening orientationally ordered phase.Comment: 8 pages, 8 figure

    General massive one-loop off-shell three-point functions

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    In this work we compute the most general massive one-loop off-shell three-point vertex in D-dimensions, where the masses, external momenta, and exponents of propagators are arbitrary. This follows our previous paper in which we have calculated several new hypergeometric series representations for massless and massive (with equal masses) scalar one-loop three-point functions, in the negative dimensional approach.Comment: 16 pages, 2 figures, 4 table

    Progressive genetic aberrations detected by comparative genomic hybridization in squamous cell cervical cancer

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    Genetic changes orchestrated by human papillomaviruses are the most important known factors in carcinogenesis of the uterine cervix. However, it is clear that additional genetic events are necessary for tumour progression. We have used comparative genomic hybridization to document non-random chromosomal gains and losses within a subset of 37 cervical carcinomas matched for clinical stage Ib, but with different lymph node status. There were significantly more chromosomal changes in the primary tumours when the lymph nodes were positive for metastases. The most frequent copy number alterations were loss of 3p, 11q, 6q and 10q and gain of 3q. The smallest areas of loss and gain on chromosome 3 were 3p14–22 and 3q24–26. The study identifies progressive DNA copy number changes associated with early-stage invasive cervical cancers with and without lymph node metastases, a factor of potential prognostic and therapeutic value. © 2000 Cancer Research Campaign http://www.bjcancer.co

    Informing creation of the FEEDS Toolkit to support parent-delivered interventions for eating, drinking and swallowing difficulties in young children with neurodisability: intervention use by neurodevelopmental diagnosis and healthcare professional role

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    Background The FEEDS (Focus on Early Eating, Drinking and Swallowing) study focused on interventions used to improve feeding for children with neurodisability and eating, drinking and swallowing difficulties (EDSD), and the outcomes viewed as important by healthcare professionals (HPs) and parent carers. The FEEDS Toolkit was created subsequently as an intervention decision aid to be used collaboratively by parent carers and HPs. This study aimed to inform on current intervention practices and influence toolkit design by ascertaining whether specific intervention use varied by a child’s main diagnosis and by specific HP role.Methods FEEDS survey data were grouped by child’s main diagnosis and HP role. Main diagnoses included autism spectrum disorder (ASD) n=183; Down syndrome (DS) n=69; cerebral palsy (CP) n=30). HPs included were speech and language therapists (SLT) n=131; occupational therapists (OT) n=63; physiotherapists (PT) n=57; paediatricians n=50; dieticians n=40; nurses n=32 and health visitors n=14.Results Most interventions were used commonly across diagnoses. However, some interventions were used more commonly with specific conditions, for example, positioning (CP 85%, DS 70%, ASD 23%, strategies/programmes aimed at changing behaviour at mealtimes (ASD 52%, CP 8%, DS 11%); visual supports (ASD 58%, CP 0%, DS 21%). HPs reported using a broad range of interventions, SLTs (mean=13.9), dieticians (12.3), OTs (12.7) and paediatricians (11.1). There was overlap between intervention use and HP role, for example, positioning (100% PT, 97% SLT, 94% OT, 73% paediatricians and 69% nurses).Conclusions Interdisciplinary working is common when managing EDSD, with all HP types using multiple interventions. A child’s main diagnosis does not substantially influence intervention use, and the individual context of each child requires consideration in intervention selection. Study findings have supported development of the FEEDS Toolkit for use in feeding services

    Phase Changes in Internally Mixed Maleic Acid/Ammonium Sulfate Aerosols

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    A temperature controlled flow tube system equipped with Fourier transform infrared (FTIR) detection of particle phase and relative humidity was used to measure the deliquescence and efflorescence of ammonium sulfate, maleic acid, and internally mixed maleic acid/ammonium sulfate particles. Our results indicate that maleic acid aerosols begin to take up water starting at a low relative humidity, ∼20%, and continue the constant uptake of water until the final deliquescence relative humidity (DRH), 89%, is reached. Internally mixed particles containing maleic acid and ammonium sulfate were found to deliquesce at a lower relative humidity (RH) than either of the pure species. Efflorescence studies indicated that while pure maleic acid particles crystallize at ∼18% RH, pure ammonium sulfate and all mixed aerosols effloresce at or just below 30% RH. Taken together, our results suggest that the presence of water-soluble organics internally mixed with ammonium sulfate aerosol could increase the range of conditions under which the aerosol is a solution

    'Reclaiming the criminal' : the role and training of prison officers in England, 1877-1914

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    This article examines the role and training of prison officers in England, between 1877 and 1914. It is concerned with the changing penal philosophies and practices of this period and how these were implemented in local prisons, and the duties of the prison officer. More broadly, this article argues that the role of the prison officer and their training (from 1896) reflect wider ambiguities in prison policy and practice during this period
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