581 research outputs found
NMR study of a bimesogenic liquid crystal with two nematic phases
Recent interest in bimesogenic liquid crystals showing two nematic phases has led us to investigate the nematic mean-field interactions in these nematic phases by using rigid solutes as probes. The nematic potential that is modelled by two independent Maier-Saupe terms is successful in fitting the observed dipolar couplings (order parameters) of para-, meta- and ortho-dichlorobenzene solutes in both the nematic phases of 39 wt% of 4-n-pentyl-4′-cyanobiphenyl (5CB) in α,ω-bis(4-4′-cyanobiphenyl)nonane (CB_C9_CB) to better than the 5% level. The derived liquid-crystal potential parameters G₁ and G₂ for each solute in the N and Ntb phases will be discussed. The most interesting observation is that G1 (associated with size and shape interactions) is almost constant in the Ntb phase, whereas G₂ (associated with longer-range electrostatic interactions) has large variation, even changing sign
Spin-transfer switching and low-field precession in exchange-biased spin valve nano-pillars
Using a three-dimensional focused-ion beam lithography process we have
fabricated nanopillar devices which show spin transfer torque switching at zero
external magnetic fields. Under a small in-plane external bias field, a
field-dependent peak in the differential resistance versus current is observed
similar to that reported in asymmetrical nanopillar devices. This is
interpreted as evidence for the low-field excitation of spin waves which in our
case is attributed to a spin-scattering asymmetry enhanced by the IrMn exchange
bias layer coupled to a relatively thin CoFe fixed layer.Comment: 11 pages, 4 figures. To appear in APL, April 200
Critical Current Oscillations in Strong Ferromagnetic Pi-Junctions
We report magnetic and electrical measurements of Nb Josephson junctions with
strongly ferromagnetic barriers of Co, Ni and Ni80Fe20 (Py). All these
materials show multiple oscillations of critical current with barrier thickness
implying repeated 0-pi phase-transitions in the superconducting order
parameter. We show in particular that the Co barrier devices can be accurately
modelled using existing clean limit theories and so that, despite the high
exchange energy (309 meV), the large IcRN value in the pi-state means Co
barriers are ideally suited to the practical development of superconducting
pi-shift devices.Comment: 4 pages 3 figures 1 table. Revised version as accepted for
publication. To appear in Physical Review Letter
An audit of the quality of inpatient care for adults with learning disability in the UK
OBJECTIVES: To audit patient hospital records to evaluate the performance of acute general and mental health services in delivering inpatient care to people with learning disability and explore the influence of organisational factors on the quality of care they deliver. SETTING: Nine acute general hospital Trusts and six mental health services. PARTICIPANTS: Adults with learning disability who received inpatient hospital care between May 2013 and April 2014. PRIMARY AND SECONDARY OUTCOME MEASURES: Data on seven key indicators of high-quality care were collected from 176 patients. These covered physical health/monitoring, communication and meeting needs, capacity and decision-making, discharge planning and carer involvement. The impact of services having an electronic system for flagging patients with learning disability and employing a learning disability liaison nurse was assessed. RESULTS: Indicators of physical healthcare (body mass index, swallowing assessment, epilepsy risk assessment) were poorly recorded in acute general and mental health inpatient settings. Overall, only 34 (19.3%) patients received any assessment of swallowing and 12 of the 57 with epilepsy (21.1%) had an epilepsy risk assessment. For most quality indicators, there was a non-statistically significant trend for improved performance in services with a learning disability liaison nurse. The presence of an electronic flagging system showed less evidence of benefit. CONCLUSIONS: Inpatient care for people with learning disability needs to be improved. The work gives tentative support to the role of a learning disability liaison nurse in acute general and mental health services, but further work is needed to confirm these benefits and to trial other interventions that might improve the quality and safety of care for this high-need group
Supercurrent diode effect in thin film Nb tracks
We demonstrate nonreciprocal critical current in 65 nm thick polycrystalline
and epitaxial Nb thin films patterned into tracks. The nonreciprocal behavior
gives a supercurrent diode effect, where the current passed in one direction is
a supercurrent and the other direction is a normal state (resistive) current.
We study the variation of the diode effect with temperature and magnetic field,
and find an unexpected dependence with the width of the Nb tracks from 2-10
m. For both polycrystalline and epitaxial samples, we find that tracks of
width 4 m provides the largest supercurrent diode efficiency of up to
, with the effect reducing or disappearing in the widest tracks of
10 m. It is anticipated that the supercurrent diode will become a
ubiquitous component of the superconducting computer.Comment: 15 pages, 4 figure
Growth and Characterization of -Mn Structured CoZn Thin Films
Thin films of polycrystalline -Mn structure CoZn have been grown on
thermally oxidized Si substrates by co-sputtering from elemental targets
followed by annealing. A range of films grown with variable Co deposition power
and fixed Zn deposition power were produced, so as to vary the proportions of
the two elements reaching the substrate, which were annealed post-growth.
Whilst all films exhibited a (211) -Mn structure CoZn texture in X-ray
diffraction, transmission electron microscopy showed that the composition with
the highest integrated intensity for that Bragg peak contained large vacancies
and was covered by a thick ZnO cap owing to being Co-deficient overall. CoZn
films deposited at ratios tuned to give the optimal volume fraction of
-Mn were continuous, with crystallites up to 200~nm in size, with a much
thinner ZnO cap layer. Magnetic measurements show that such optimal CoZn films
have a Curie temperature ~K and saturation magnetization
of 120~emu/cm, properties close to those reported for bulk crystals. The
-Mn structure is chiral (P432/P432 space group) and is known
to give rise to a Dzyaloshinkii-Moriya interaction (DMI) that stabilizes
room-temperature skyrmions in the bulk. Our thin films are thus a potential
materials platform, compatible with planar processing technology, for magnetic
skyrmions arising from a bulk DMI.Comment: v2 corrects minor typographical error
Modification of perpendicular magnetic anisotropy and domain wall velocity in Pt/Co/Pt by voltage-induced strain
The perpendicular magnetic anisotropy Keff, magnetization reversal, and field-driven domain wall velocity in the creep regime are modified in Pt/Co(0.85–1.0 nm)/Pt thin films by strain applied via piezoelectric transducers. Keff, measured by the extraordinary Hall effect, is reduced by 10 kJ/m3 by tensile strain out-of-plane ez5931024, independently of the film thickness, indicating a dominant volume contribution to the magnetostriction. The same strain reduces the coercive field by 2–4 Oe, and increases the domain wall velocity measured by wide-field Kerr microscopy by 30-100%, with larger changes observed for thicker Co layers. We consider how strain-induced changes in the perpendicular magnetic anisotropy can modify the coercive field and domain wall velocity
Legislative strengthening meets party support in international assistance: a closer relationship?
Recent reports recommend that international efforts to help strengthen legislatures in emerging democracies should work more closely with support for building stronger political parties and competitive party systems. This article locates the recommendations within international assistance more generally and reviews the arguments. It explores problems that must be addressed if the recommendations are to be implemented effectively. The article argues that an alternative, issue-based approach to strengthening legislatures and closer links with civil society could gain more traction. However, that is directed more centrally at promoting good governance for the purpose of furthering development than at democratisation goals sought by party aid and legislative strengtheners in the democracy assistance industry
0-pi oscillations in nanostructured Nb/Fe/Nb Josephson junctions
The physics of the phase shift in ferromagnetic Josephson junctions may
enable a range of applications for spin-electronic devices and quantum
computing. We investigate transitions from ``0'' to ``'' states in
Nb/Fe/Nb Josephson junctions by varying the Fe barrier thickness from 0.5 nm to
5.5 nm. From magnetic measurements we estimate for Fe a magnetic dead layer of
about 1.1 nm. By fitting the characteristic voltage oscillations with existing
theoretical models we extrapolate an exchange energy of 256 meV, a Fermi
velocity of m/s and an electron mean free path of 6.2 nm, in
agreement with other reported values. From the temperature dependence of the
product we show that its decay rate exhibits a nonmonotonic
oscillatory behavior with the Fe barrier thickness.Comment: 7 pages, 5 figures, accepted for publication in Eur. Phys. J.
The Normal State Resistivity of Grain Boundaries in YBa2Cu3O7-delta
Using an optimized bridge geometry we have been able to make accurate
measurements of the properties of YBa2Cu3O7-delta grain boundaries above Tc.
The results show a strong dependence of the change of resistance with
temperature on grain boundary angle. Analysis of our results in the context of
band-bending allows us to estimate the height of the potential barrier present
at the grain boundary interface.Comment: 11 pages, 3 figure
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