Stoner-Wohlfart model applied to bicrystal magnetoresistance hysteresis

We calculate numerically the magnetization direction as function of magnetic field in the Stoner-Wohlfart theory and are able to reproduce the shape of the low-field magnetoresistance hysteresis observed in manganite grain boundary junctions. Moreover, we show that it is necessary to include biaxial magnetocrystalline anisotropy to fully describe the grain boundary magnetoresistance in La$_{0.7}$Sr$_{0.3}$MnO$_3$/SrTiO$_3$ bicrystal tunnel junctions.Comment: 5 pages, 4 figure

Infrared spectroscopic variability of Cygnus X-3 in outburst and quiescence

We present four epochs of high-resolution infrared spectroscopy of the peculiar X-ray binary Cygnus X-3. The observations cover quiescent, small flaring and outburst states of the system as defined by radio and X-ray monitoring. The underlying infrared spectrum of the source, as observed during radio and X-ray quiescence and small flaring states, is one of broad, weak HeII and NV emission. Spectral variability in this state is dominated by modulation at the 4.8 hr orbital period of the system. H-band spectra confirm the significant hydrogen depletion of the mass donor. The closest spectral match to the quiescent infrared spectrum of Cyg X-3 is an early-type WN Wolf-Rayet star. In outburst, the infrared spectrum is dramatically different, with the appearance of very strong twin-peaked HeI emission displaying both day-to-day variability and V(iolet)/R(ed) variations with orbital phase. The most likely explanation appears to be an enhanced stellar wind from the companion. Thus X-ray and radio outbursts in this system are likely to originate in mass-transfer, and not disc, instabilities, and the lengthening of the orbital period will not be smooth but will be accelerated during these outbursts. Furthermore, the appearance of these lines is suggestive of an asymmetric emitting region. We propose that the wind in Cyg X-3 is significantly flattened in the plane of the binary orbit. This may explain the observed twin-peaked HeI features as well as reconciling a massive Wolf-Rayet secondary with the relatively small optical depth to X-rays, if the disc wind is inclined at some angle to the line of sight.Comment: 13 pages, 7 figures. Accepted for publication in MNRA

The Housing and Support Needs of Older People with Visual Impairment

Visual impairment is one of the most prevalent anddisabling conditions among older people, and yet verylittle research has been conducted that could inform thedevelopment of appropriate public services. In order toaddress this deficiency, Thomas Pocklington Trust fundedresearch to examine the housing and support needs of 400visually impaired people aged over 55.The study found that:? There is little professional recognition, or offers of help andadvice for the anxiety, depression, and sense of profoundloss that people experience with late onset of visualimpairment.? Both blind and partially sighted people need timely andholistic assessment, rehabilitation, affordable equipment andregular review.? People with sight loss do not wish to leave their homes.Home is the epicentre of a mental map that assistsorientation and continuity following sight loss.? Social isolation and lack of human contact are majorproblems for people with sight loss.? People with sight loss have poor knowledge of supportgroups, community services and/or specialist housingoptions for older people with visual impairment. Visual impairment is one of the most prevalent anddisabling conditions among older people, and yet verylittle research has been conducted that could inform thedevelopment of appropriate public services. In order toaddress this deficiency, Thomas Pocklington Trust fundedresearch to examine the housing and support needs of 400visually impaired people aged over 55.The study found that:? There is little professional recognition, or offers of help andadvice for the anxiety, depression, and sense of profoundloss that people experience with late onset of visualimpairment.? Both blind and partially sighted people need timely andholistic assessment, rehabilitation, affordable equipment andregular review.? People with sight loss do not wish to leave their homes.Home is the epicentre of a mental map that assistsorientation and continuity following sight loss.? Social isolation and lack of human contact are majorproblems for people with sight loss.? People with sight loss have poor knowledge of supportgroups, community services and/or specialist housingoptions for older people with visual impairment

The importance of quadrupole sources in prediction of transonic tip speed propeller noise

A theoretical analysis is presented for the harmonic noise of high speed, open rotors. Far field acoustic radiation equations based on the Ffowcs-Williams/Hawkings theory are derived for a static rotor with thin blades and zero lift. Near the plane of rotation, the dominant sources are the volume displacement and the rho U(2) quadrupole, where u is the disturbance velocity component in the direction blade motion. These sources are compared in both the time domain and the frequency domain using two dimensional airfoil theories valid in the subsonic, transonic, and supersonic speed ranges. For nonlifting parabolic arc blades, the two sources are equally important at speeds between the section critical Mach number and a Mach number of one. However, for moderately subsonic or fully supersonic flow over thin blade sections, the quadrupole term is negligible. It is concluded for thin blades that significant quadrupole noise radiation is strictly a transonic phenomenon and that it can be suppressed with blade sweep. Noise calculations are presented for two rotors, one simulating a helicopter main rotor and the other a model propeller. For the latter, agreement with test data was substantially improved by including the quadrupole source term

Meeting the needs of older peoplewith visual impairment: social care orsocial exclusion?

This paper is based on the research study ?Housing and supportneeds of older people with visual impairment ? experiences andchallenges? (Hanson et al, 2002).1The full findings of this study are reported in another occasionalpaper produced by Thomas Pocklington Trust.2 It is, however, usefulto state that this study found evidence that sight loss in later life hassignificant emotional consequences, often unacknowledged byprofessionals. It also showed how older people with visionimpairment often have their own coping strategies, but are less ablethan sighted peers to carry out certain daily tasks.The study suggested that professionals should offer sensitive andtimely support, in a more collaborative manner, and that serviceshave to be monitored and evaluated to avoid wide-ranging needsremaining unmet. In respect of the home environment, researchindicated that adequate and accessible domestic space in which todo housework safely, low vision equipment and the provision ofovernight accommodation for guests and carers was required.Most participants in the study wished to stay in their homes andneighbourhoods. When asked about possible alternative options,participants emphasised the importance of location and sufficientspace. If they were considering supported housing, they requiredfull information about how it addressed their particular needs.This paper focuses on whether older people with visual impairmentare vulnerable to social exclusion if their social care needs are unmet. In particular, this paper argues that:? Greater professional collaboration is required to improve eyeclinic and community support services.? Relevant staff should aim to provide timely and holisticassessments of need.? Older people with vision impairment have significant needs asregards home care support, access to information, psychologicalstress and social isolation.? Initiatives such as peer support groups and resource centres offeropportunities to tackle social exclusion arising from unmetneeds. This paper is based on the research study ?Housing and supportneeds of older people with visual impairment ? experiences andchallenges? (Hanson et al, 2002).1The full findings of this study are reported in another occasionalpaper produced by Thomas Pocklington Trust.2 It is, however, usefulto state that this study found evidence that sight loss in later life hassignificant emotional consequences, often unacknowledged byprofessionals. It also showed how older people with visionimpairment often have their own coping strategies, but are less ablethan sighted peers to carry out certain daily tasks.The study suggested that professionals should offer sensitive andtimely support, in a more collaborative manner, and that serviceshave to be monitored and evaluated to avoid wide-ranging needsremaining unmet. In respect of the home environment, researchindicated that adequate and accessible domestic space in which todo housework safely, low vision equipment and the provision ofovernight accommodation for guests and carers was required.Most participants in the study wished to stay in their homes andneighbourhoods. When asked about possible alternative options,participants emphasised the importance of location and sufficientspace. If they were considering supported housing, they requiredfull information about how it addressed their particular needs.This paper focuses on whether older people with visual impairmentare vulnerable to social exclusion if their social care needs are unmet. In particular, this paper argues that:? Greater professional collaboration is required to improve eyeclinic and community support services.? Relevant staff should aim to provide timely and holisticassessments of need.? Older people with vision impairment have significant needs asregards home care support, access to information, psychologicalstress and social isolation.? Initiatives such as peer support groups and resource centres offeropportunities to tackle social exclusion arising from unmetneeds

Malmquist Bias and the Distance to the Virgo Cluster

This paper investigates the impact of Malmquist bias on the distance to the Virgo cluster determined by the H_0 Key Project using M100, and consequently on the derived value of H_0. Malmquist bias is a volume-induced statistical effect which causes the most probable distance to be different from the raw distance measured. Consideration of the bias in the distance to the Virgo cluster raises this distance and lowers the calculated value of H_0. Monte Carlo simulations of the cluster have been run for several possible distributions of spirals within the cluster and of clusters in the local universe. Simulations consistent with known information regarding the cluster and the errors of measurement result in a bias of about 6.5%-8.5%. This corresponds to an unbiased distance of 17.2-17.4 Mpc and a value of H_0 in the range 80-82 km/s/Mpc. The problem of determining the bias to Virgo illustrates several key points regarding Malmquist bias. Essentially all conventional astronomical distance measurements are subject to this bias. In addition, the bias accumulates when an attempt is made to construct "distance ladders" from measurements which are individually biased. As will be shown in the case of Virgo, the magnitude and direction of the bias are sensitive to the spatial distribution of the parent poputation from which the observed object is drawn - a distribution which is often poorly known. This leads to uncertainty in the magnitude of the bias, and adds to the importance of minimizing the number of steps in "distance ladders".Comment: 19 pages, 3 figures, Latex, To appear in Ap

Diagnostics Of Disks Around Hot Stars

We discuss three different observational diagnostics related to disks around hot stars: absorption line determinations of rotational velocities of Be stars; polarization diagnostics of circumstellar disks; and X-ray line diagnostics of one specific magnetized hot star, theta(1) Ori C. Some common themes that emerge from these studies include (a) the benefits of having a specific physical model as a framework for interpreting diagnostic data; (b) the importance of combining several different types of observational diagnostics of the same objects; and (c) that while there is often the need to reinterpret traditional diagnostics in light of new theoretical advances, there are many new and powerful diagnostics that are, or will soon be, available for the study of disks around hot stars

Canonical Formalism for a 2n-Dimensional Model with Topological Mass Generation

The four-dimensional model with topological mass generation that was found by Dvali, Jackiw and Pi has recently been generalized to any even number of dimensions (2n-dimensions) in a nontrivial manner in which a Stueckelberg-type mass term is introduced [S. Deguchi and S. Hayakawa, Phys. Rev. D 77, 045003 (2008), arXiv:0711.1446]. The present paper deals with a self-contained model, called here a modified hybrid model, proposed in this 2n-dimensional generalization and considers the canonical formalism for this model. For the sake of convenience, the canonical formalism itself is studied for a model equivalent to the modified hybrid model by following the recipe for treating constrained Hamiltonian systems. This formalism is applied to the canonical quantization of the equivalent model in order to clarify observable and unobservable particles in the model. The equivalent model (with a gauge-fixing term) is converted to the modified hybrid model (with a corresponding gauge-fixing term) in a Becchi-Rouet-Stora-Tyutin (BRST)-invariant manner. Thereby it is shown that the Chern-Pontryagin density behaves as an observable massive particle (or field). The topological mass generation is thus verified at the quantum-theoretical level.Comment: 29 pages, no figures, minor corrections, published versio

Unified aeroacoustics analysis for high speed turboprop aerodynamics and noise. Volume 3: Application of theory for blade loading, wakes, noise, and wing shielding

Results of the program for the generation of a computer prediction code for noise of advanced single rotation, turboprops (prop-fans) such as the SR3 model are presented. The code is based on a linearized theory developed at Hamilton Standard in which aerodynamics and acoustics are treated as a unified process. Both steady and unsteady blade loading are treated. Capabilities include prediction of steady airload distributions and associated aerodynamic performance, unsteady blade pressure response to gust interaction or blade vibration, noise fields associated with thickness and steady and unsteady loading, and wake velocity fields associated with steady loading. The code was developed on the Hamilton Standard IBM computer and has now been installed on the Cray XMP at NASA-Lewis. The work had its genesis in the frequency domain acoustic theory developed at Hamilton Standard in the late 1970s. It was found that the method used for near field noise predictions could be adapted as a lifting surface theory for aerodynamic work via the pressure potential technique that was used for both wings and ducted turbomachinery. In the first realization of the theory for propellers, the blade loading was represented in a quasi-vortex lattice form. This was upgraded to true lifting surface loading. Originally, it was believed that a purely linear approach for both aerodynamics and noise would be adequate. However, two sources of nonlinearity in the steady aerodynamics became apparent and were found to be a significant factor at takeoff conditions. The first is related to the fact that the steady axial induced velocity may be of the same order of magnitude as the flight speed and the second is the formation of leading edge vortices which increases lift and redistribute loading. Discovery and properties of prop-fan leading edge vortices were reported in two papers. The Unified AeroAcoustic Program (UAAP) capabilites are demonstrated and the theory verified by comparison with the predictions with data from tests at NASA-Lewis. Steady aerodyanmic performance, unsteady blade loading, wakes, noise, and wing and boundary layer shielding are examined