2,804 research outputs found
Exponential Temperature Dependence of Penetration Depth in Single Crystal MgB_2
The temperature dependence of the London penetration depth,lambda(T), was
measured in both single crystal and polycrystalline MgB_2 samples by a
high-resolution, radio frequency technique. A clear exponential temperature
dependence of lambda(T) was observed at low temperature, indicating s-wave
pairing. A BCS fit to the lowest temperature data gives an in-plane energy gap
Delta of 2.6\pm0.2 meV (2\Delta/T_c=1.5\pm0.1), which is significantly smaller
than the standard BCS weak coupling value of 3.5. We find that the data are
best described by a two-gap model.Comment: Minor corrections added, as per published articl
Sickness certification system in the United Kingdom: qualitative study of views of general practitioners in Scotland
Objectives: To explore how general practitioners operate the sickness certification system, their views on the system, and suggestions for change.
Design: Qualitative focus group study consisting of 11 focus groups with 67 participants.
Setting: General practitioners in practices in Glasgow, Tayside, and Highland regions, Scotland.
Sample: Purposive sample of general practitioners, with further theoretical sampling of key informant general practitioners to examine emerging themes.
Results: General practitioners believed that the sickness certification system failed to address complex, chronic, or doubtful cases. They seemed to develop various operational strategies for its implementation. There appeared to be important deliberate misuse of the system by general practitioners, possibly related to conflicts about roles and incongruities in the system. The doctor-patient relationship was perceived to conflict with the current role of general practitioners in sickness certification. When making decisions about certification, the general practitioners considered a wide variety of factors. They experienced contradictory demands from other system stakeholders and felt blamed for failing to make impossible reconciliations. They clearly identified the difficulties of operating the system when there was no continuity of patient care. Many wished either to relinquish their gatekeeper role or to continue only with major changes.
Conclusions: Policy makers need to recognise and accommodate the range and complexity of factors that influence the behaviour of general practitioners operating as gatekeepers to the sickness certification system, before making changes. Such changes are otherwise unlikely to result in improvement. Models other than the primary care gatekeeper model should be considered
Destruction of chain-superconductivity in YBa_2Cu_4O_8 in a weak magnetic field
We report measurements of the temperature dependent components of the
magnetic penetration depth {\lambda}(T) in single crystal samples of
YBa_2Cu_4O_8 using a radio frequency tunnel diode oscillator technique. We
observe a downturn in {\lambda}(T) at low temperatures for currents flowing
along the b and c axes but not along the a axis. The downturn in {\lambda}_b is
suppressed by a small dc field of ~0.25 T. This and the zero field anisotropy
of {\lambda}(T) likely result from proximity induced superconducting on the CuO
chains, however we also discuss the possibility that a significant part of the
anisotropy might originate from the CuO2 planes.Comment: 5 page
Are Social Welfare Policies âPro-Lifeâ? An Individual-Level Analysis of Low-Income Women
This paper tests the hypothesis that low-income womenâs likelihood of choosing abortion will decrease as their access to and participation in social welfare programs increases. Though an affirmative finding could challenge the coherence of a morally and fiscally conservative Republican coalition and thus improve prospects for the safety netâs political future, findings from a sample of low-SES, urban mothers do not support this hypothesis. Welfare program participation and state welfare generosity are positively associated with the likelihood of choosing abortion. The existence and magnitude of this relationship, however, is mediated by the rules of state welfare bureaucracies and also varies by womenâs race and marital status. Limitations on abortion access appear to reduce abortions, while the nongovernmental safety net does not affect abortion decisions.
Effect of Hole Doping on the Electronic Structure of Tl2201
We discuss doping dependencies of the electronic structure and Fermi surface
of the monolayer TlCuBaCuO (Tl2201). The TlO bands
are found to be particularly sensitive to doping in that these bands rapidly
move to higher energies as holes are added into the system. Such doping effects
beyond the rigid band picture should be taken into account in analyzing and
modeling the electronic spectra of the cuprates.Comment: 2 pages, Submitted to Physica C / Proceedings of the M2S-HTSC-VIII
Conferenc
Alluvial Fan Development at Franklin Bluffs, Alaska
This paper is concerned with the developmental history of alluvial fans forming in a tundra climate. The study was made at Franklin Bluffs, Alaska (69° 48\u27 - 70° 00\u27 N, 148° 40\u27 W), during the summer of 1961. The area is an ideal place in which to study the developmental history of alluvial fans in that so many stages are present in a relatively small area.
A theoretical sequence of fan development was set up, illustrated by examples from the Franklin Bluffs, which show how certain characteristics of an alluvial fan, forming in a tundra climate, change as the sequence advances. The sequence was designated A, B, C, D, and E, where A is the youngest, near talus cone stage, and E is the oldest, near graded stage.
Certain characteristics were found to constitute a continuum of changes in the sequence. The two most continuously changing factors are the difference in slope, between that of the drainage area and that of the fan, and the relative size of each fan -vs- drainage area. Also, in the progress of the sequence, the intensity of mass wasting decreases. Related to the type and intensity of mass-wasting and the amount and size distribution of surficial rock material and the amount and type of vegetation. The climax of the sequence is characterized by the approach to a well vegetated graded stage on which a permanent channel forms if sufficiently continuous discharge is present
Linear magnetoresistance in a quasi-free two dimensional electron gas in an ultra-high mobility GaAs quantum well
We report a magnetotransport study of an ultra-high mobility
(\,cm\,V\,s) -type GaAs
quantum well up to 33 T. A strong linear magnetoresistance (LMR) of the order
of 10 % is observed in a wide temperature range between 0.3 K and 60 K. The
simplicity of our material system with a single sub-band occupation and free
electron dispersion rules out most complicated mechanisms that could give rise
to the observed LMR. At low temperature, quantum oscillations are superimposed
onto the LMR. Both, the featureless LMR at high and the quantum
oscillations at low follow the empirical resistance rule which states that
the longitudinal conductance is directly related to the derivative of the
transversal (Hall) conductance multiplied by the magnetic field and a constant
factor that remains unchanged over the entire temperature range. Only
at low temperatures, small deviations from this resistance rule are observed
beyond that likely originate from a different transport mechanism for
the composite fermions
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