Experimental prediction of performance by superconducting cables

Broken superconductor method of short sample testing makes possible the prediction of the performance of well cooled, stabilized, superconducting cable coils. It yields a field-versus-current curve for a short sample of cable. Plots are given for the superconductor and copper currents at various magnetic field strengths

Stranded superconducting cable of improved design

High-current cable developed in liquid helium cooled magnets uses aluminum wire interspersed with the superconductor strands. The aluminum maintains higher electrical conductivity, is light in weight, and has low thermal capacity

Promoting and maintaining health of people with sight loss: A scoping study

This study was undertaken in response to a request by the Thomas Pocklington Trust to identify and explore the following issues: • The needs and concerns regarding immediate risks to health and safety related to sight loss; • Additional risks arising from sight loss for those who are also managing a long term disease; • The difficulties in maintaining and promoting health; • Whether or not health promotion activities and policies sufficiently address perceived needs. Findings pertaining to these objectives have been generated from data collected in Leeds, UK, a city where innovative programming for sight loss has either been planned or is being incorporated into health planning and a review of the literature. Findings related to the last two issues indicate that gaps exist in service provision for maintaining health and emphasise the need for more explicitly targeted health promotion initiatives that could address current weaknesses. - A review of the literature; - Focus group discussions with a range of people who had experienced sight loss; - Interviews with professional practitioners engaged in service provision to this population; - An expert hearing with four professional practitioners, one of whom had sight loss, and two service users with sight loss. Most participants were from the West Yorkshire region and the services described in the study are largely located in Leeds. Evidence from the literature review suggests that people with visual impairment have increased risk of accidents within the home and that ensuing consequences include injuries incurred and decreased confidence. Rates of depression among people who are blind or partially sighted are far higher than in the wider population and the likelihood of depression increases with age, although psycho-social interventions and technological assistance can be successfully implemented to improve quality of life. Sight loss together with other long term health conditions exacerbates the impact of other health conditions and has particularly severe impact on the wellbeing of older people insofar as it may affect their mobility, which in turn increases their risk of falls and depression. The nature and level of support available to people is variable but it is clear that access both to the right information at the right time and to appropriate services is a critical issue. Focus group discussions, interviews and the expert hearing corroborated and extended the themes noted in the literature and discuss the differential impact of different risks to health and the difficulties of coping with these at different times in a person’s life. A simple typology was defined using two dimensions of experience (‘stage of life’ and ‘early/late onset of sight loss’) as a means of organizing findings and providing a means of making further distinctions in interpreting the data. Potentially, this scheme can allow health promotion initiatives to be targeted more effectively to stages at which people with sight loss are more likely to encounter specific difficulties in managing and maintaining their health. There was a clear consensus throughout the study that interventions to meet the needs of people with sight loss must be tailored to meet the specific needs of individuals: people with sight loss are not a homogeneous group and the way in which each person experiences the challenges of sight loss and of managing their health will inevitably vary from person to person. Recommendations generated by this study include: • The scope for more pro-active services and need for closer collaboration between service providers; • The need for provision and promotion of targeted information; • The need for greater awareness of the needs of people with visual impairments among generic service providers; and • Further research that explores the usefulness of the typology with a larger sample more representative of population demographics such as BME communities that are more likely to slip through the cracks of service provision

A simple derivation of the electromagnetic field of an arbitrarily moving charge

The expression for the electromagnetic field of a charge moving along an arbitrary trajectory is obtained in a direct, elegant, and Lorentz invariant manner without resorting to more complicated procedures such as differentiation of the Lienard-Wiechert potentials. The derivation uses arguments based on Lorentz invariance and a physically transparent expression originally due to J.J.Thomson for the field of a charge that experiences an impulsive acceleration.Comment: The following article has been accepted by the American Journal of Physics. After it is published, it will be found at http://scitation.aip.org/ajp; 12 pages, 1 figur

Foster carers influence brood pathogen resistance in ants.

Social organisms face a high risk of epidemics, and respond to this threat by combining efficient individual and collective defences against pathogens. An intriguing and little studied feature of social animals is that individual pathogen resistance may depend not only on genetic or maternal factors, but also on the social environment during development. Here, we used a cross-fostering experiment to investigate whether the pathogen resistance of individual ant workers was shaped by their own colony of origin or by the colony of origin of their carers. The origin of care-giving workers significantly influenced the ability of newly eclosed cross-fostered Formica selysi workers to resist the fungal entomopathogen Beauveria bassiana. In particular, carers that were more resistant to the fungal entomopathogen reared more resistant workers. This effect occurred in the absence of post-infection social interactions, such as trophallaxis and allogrooming. The colony of origin of eggs significantly influenced the survival of the resulting individuals in both control and pathogen treatments. There was no significant effect of the social organization (i.e. whether colonies contain a single or multiple queens) of the colony of origin of either carers or eggs. Our experiment reveals that social interactions during development play a central role in moulding the resistance of emerging workers

Resonator-Aided Single-Atom Detection on a Microfabricated Chip

We use an optical cavity to detect single atoms magnetically trapped on an atom chip. We implement the detection using both fluorescence into the cavity and reduction in cavity transmission due to the presence of atoms. In fluorescence, we register 2.0(2) photon counts per atom, which allows us to detect single atoms with 75% efficiency in 250 microseconds. In absorption, we measure transmission attenuation of 3.3(3)% per atom, which allows us to count small numbers of atoms with a resolution of about 1 atom.Comment: 4.1 pages, 5 figures, and submitted to Physical Review Letter

A survey for redshifted molecular and atomic absorption lines - II. Associated HI, OH and millimetre lines in the z >~ 3 Parkes quarter-Jansky flat-spectrum sample

We present the results of a z>2.9 survey for HI 21-cm and molecular absorption in the hosts of radio quasars using the GMRT and the Tidbinbilla 70-m telescope. Previously published searches, which are overwhelmingly at redshifts of z<1, exhibit a 42% detection rate (31 out of 73 sources), and the inclusion of our survey yields a 17% detection rate (2 out of 12 sources) at z>2.5. We therefore believe that our high redshift selection is responsible for our exclusive non-detections, and find that at ultra-violet luminosities of >10e23 W/Hz, 21-cm absorption has never been detected. We also find this to not only apply to our targets, but also those at low redshift exhibiting similar luminosities, giving zero detections out of a total of 16 sources over z=0.24 to 3.8. This is in contrast to the < 10e23 W/Hz sources where there is a near 50% detection rate of 21-cm absorption. The mix of 21-cm detections and non-detections is currently attributed to orientation effects, where according to unified schemes of active galactic nuclei, 21-cm absorption is more likely to occur in sources designated as radio galaxies (type-2 objects, where the nucleus is viewed through dense obscuring circumnuclear gas) than in quasars(type-1 objects, where we have a direct view to the nucleus). However, due to the exclusively high ultra-violet luminosities of our targets it is not clear whether orientation effects alone can wholly account for the distribution, although there exists the possibility that the large luminosities are indicative of a changing demographic of galaxy types. We also find that below luminosities of ~10e23 W/Hz, both type-1 and type-2 objects have a 50% likelihood of exhibiting 21-cm absorption.Comment: 21 pages, accepted by MNRA

Importance of an Astrophysical Perspective for Textbook Relativity

The importance of a teaching a clear definition of the ``observer'' in special relativity is highlighted using a simple astrophysical example from the exciting current research area of ``Gamma-Ray Burst'' astrophysics. The example shows that a source moving relativistically toward a single observer at rest exhibits a time ``contraction'' rather than a ``dilation'' because the light travel time between the source and observer decreases with time. Astrophysical applications of special relativity complement idealized examples with real applications and very effectively exemplify the role of a finite light travel time.Comment: 5 pages TeX, European Journal of Physics, in pres

Improved qubit bifurcation readout in the straddling regime of circuit QED

We study bifurcation measurement of a multi-level superconducting qubit using a nonlinear resonator biased in the straddling regime, where the resonator frequency sits between two qubit transition frequencies. We find that high-fidelity bifurcation measurements are possible because of the enhanced qubit-state-dependent pull of the resonator frequency, the behavior of qubit-induced nonlinearities and the reduced Purcell decay rate of the qubit that can be realized in this regime. Numerical simulations find up to a threefold improvement in qubit readout fidelity when operating in, rather than outside of, the straddling regime. High-fidelity measurements can be obtained at much smaller qubit-resonator couplings than current typical experimental realizations, reducing spectral crowding and potentially simplifying the implementation of multi-qubit devices.Comment: 9 pages, 6 figure