2,758 research outputs found
Creation of solitons and vortices by Bragg reflection of Bose-Einstein condensates in an optical lattice
We study the dynamics of Bose-Einstein condensates in an optical lattice and
harmonic trap. The condensates are set in motion by displacing the trap and
initially follow simple semiclassical paths, shaped by the lowest energy band.
Above a critical displacement, the condensate undergoes Bragg reflection. For
high atom densities, the first Bragg reflection generates a train of solitons
and vortices, which destabilize the condensate and trigger explosive expansion.
At lower densities, soliton and vortex formation requires multiple Bragg
reflections, and damps the center-of-mass motion.Comment: 5 pages including 5 figures (for higher resolution figures please
email the authors
OA13.01. Mind-Body Medicine Skills training for self-care and emotional well-being in medical students
Mental health care for medical staff and affiliated healthcare workers during the COVID-19 pandemic
The COVID-19 pandemic is an unprecedented challenge for society. Supporting the mental health of medical staff and affiliated healthcare workers (staff) is a critical part of the public health response. This paper details the effects on staff and addresses some of the organisational, team and individual considerations for supporting staff (pragmatically) during this pandemic. Leaders at all levels of health care organisations will find this a valuable resource. </jats:p
Displaced but not replaced: the impact of e-learning on academic identities in higher education.
Challenges facing universities are leading many to implement institutional strategies to incorporate e-learning rather than leaving its adoption up to enthusiastic individuals. Although there is growing understanding about the impact of e-learning on the student experience, there is less understanding of academics’ perceptions of e-learning and its impact on their identities. This paper explores the changing nature of academic identities revealed through case study research into the implementation of e-learning at one UK university. By providing insight into the lived experiences of academics in a university in which technology is not only transforming access to knowledge but also influencing the balance of power between academic and student in knowledge production and use, it is suggested that academics may experience a jolt to their ‘trajectory of self’ when engaging with e-learning. The potential for e-learning to prompt loss of teacher presence and displacement as knowledge expert may appear to undermine the ontological security of their academic identity
Towards a first principles description of phonons in NiPt disordered alloys: the role of relaxation
Using a combination of density-functional perturbation theory and the
itinerant coherent potential approximation, we study the effects of atomic
relaxation on the inelastic incoherent neutron scattering cross sections of
disordered NiPt alloys. We build on previous work, where
empirical force constants were adjusted {\it ad hoc} to agree with experiment.
After first relaxing all structural parameters within the local-density
approximation for ordered NiPt compounds, density-functional perturbation
theory is then used to compute phonon spectra, densities of states, and the
force constants. The resulting nearest-neighbor force constants are first
compared to those of other ordered structures of different stoichiometry, and
then used to generate the inelastic scattering cross sections within the
itinerant coherent potential approximation. We find that structural relaxation
substantially affects the computed force constants and resulting inelastic
cross sections, and that the effect is much more pronounced in random alloys
than in ordered alloys.Comment: 8 pages, 3 eps figures, uses revtex
Self-consistent nonspherical isothermal halos embedding zero-thickness disks
Disk-halo decompositions of galaxy rotation curves are generally performed in
a parametric way. We construct self-consistent models of nonspherical
isothermal halos embedding a zero-thickness disk, by assuming that the halo
distribution function is a Maxwellian. The method developed here can be used to
study other physically-based choices for the halo distribution function and the
case of a disk accompanied by a bulge. In a preliminary investigation we note
the existence of a fine tuning between the scalelengths R_{\Omega} and h,
respectively characterizing the rise of the rotation curve and the luminosity
profile of the disk, which surprisingly applies to both high surface brightness
and low surface brightness galaxies. This empirical correlation identifies a
much stronger conspiracy than the one required by the smoothness and flatness
of the rotation curve (disk-halo conspiracy). The self-consistent models are
characterized by smooth and flat rotation curves for very different
disk-to-halo mass ratios, hence suggesting that conspiracy is not as dramatic
as often imagined. For a typical rotation curve, with asymptotically flat
rotation curve at V_{\infty} (the precise value of which can also be treated as
a free parameter), and a typical density profile of the disk, self-consistent
models are characterized by two dimensionless parameters, which correspond to
the dimensional scales (the disk mass-to-light ratio M/L and the halo central
density) of standard disk-halo decompositions. We show that if the rotation
curve is decomposed by means of our self-consistent models, the disk-halo
degeneracy is removed and typical rotation curves are fitted by models that are
below the maximum-disk prescription. Similar results are obtained from a study
of NGC 3198. Finally, we quantify the flattening of the spheroidal halo, which
is significant, especially on the scale of the visible disk.Comment: accepted for publication in A&
Is the Shroud of Turin in Relation to the Old Jerusalem Historical Earthquake?
Phillips and Hedges suggested, in the scientific magazine Nature (1989), that
neutron radiation could be liable of a wrong radiocarbon dating, while proton
radiation could be responsible of the Shroud body image formation. On the other
hand, no plausible physical reason has been proposed so far to explain the
radiation source origin, and its effects on the linen fibres. However, some
recent studies, carried out by the first author and his Team at the Laboratory
of Fracture Mechanics of the Politecnico di Torino, found that it is possible
to generate neutron emissions from very brittle rock specimens in compression
through piezonuclear fission reactions. Analogously, neutron flux increments,
in correspondence to seismic activity, should be a result of the same
reactions. A group of Russian scientists measured a neutron flux exceeding the
background level by three orders of magnitude in correspondence to rather
appreciable earthquakes (4th degree in Richter Scale). The authors consider the
possibility that neutron emissions by earthquakes could have induced the image
formation on Shroud linen fibres, trough thermal neutron capture by Nitrogen
nuclei, and provided a wrong radiocarbon dating due to an increment in
C(14,6)content. Let us consider that, although the calculated integral flux of
10^13 neutrons per square centimetre is 10 times greater than the cancer
therapy dose, nevertheless it is100 times smaller than the lethal dose.Comment: 13 pages, 1 figur
Recommended from our members
Information needs after stroke: What to include and how to structure it on a website. A qualitative study using focus groups and card sorting
Background: Use of the Internet to obtain health and other information is increasing. Previous studies have identified the specific information needs of people with stroke but not in relation to the Internet. People with aphasia (PwA) may face barriers in accessing the Internet: Navigating websites requires an ability to categorise information and this ability is often impaired in PwA. The website categorisation preferences of people with stroke and with aphasia have not yet been reported.
Aims: This study aimed: (a) to determine what information people who have had a stroke would like to see on a website about living with stroke; (b) to determine the most effective means of structuring information on the website so that it is accessible to people with stroke; and c) to identify any differences between people with and without aphasia in terms of preferences for structuring information on the website.
Methods & Procedures: Participants were recruited from a hospital's Stroke Database. Focus groups were used to elicit what information participants wanted on a website about living with stroke. The themes raised were depicted on 133 cards. To determine the most effective way of structuring information on the website, and whether there were any differences in preferences between PwA and PwoA, participants used a modified closed card-sorting technique to sort the cards under website categories.
Outcomes & Results: A total of 48 people were invited, and 12 (25%) agreed to take part. We ran three focus groups: one with PwA (n = 5) and two with people without aphasia (PwoA) (n = 3, n = 4). Participants wanted more information about stroke causes and effects (particularly emotional issues), roles of local agencies, and returning to previous activities (driving, going out). All participants completed the card-sorting exercise. Few cards (6%) were categorised identically by everyone. Cards relating to local agencies and groups were not consistently categorised together. Cards relating to emotions were segregated. The categorisation preferences for PwA were more fragmented than those for PwoA: 60% of PwA agreed on the categorisation of 51% of the cards, whereas 60% of PwoA agreed on the categorisation of 76% of the cards.
Conclusions: Information needs covered all stages of the stroke journey. The card sorting was accessible to everyone, and provided evidence of structuring preferences and of some of the categorisation difficulties faced by PwA. More research is needed on what an accessible website looks like for PwA
Exploring disorganized attachment style among Malay mothers in Malaysia: a study using the Attachment Style Interview
This article explores emerging themes involving disorganized attachment style among Malay Muslim mothers using the Attachment Style Interview (ASI). Analysis of the 18 mothers with disorganized attachment style (those with combined anxious and avoidant styles) utilized themes deemed important from the attachment research literature and selected based on a careful reading of the narrative cases. These include more extreme negative interpersonal experiences than found in other insecure attachment style descriptors, and included partner violence and related isolation/social exclusion. It also indicated more complex cognitive-affective disturbance including mixed or contradictory dependency patterns and both angry and fearful attitudes to others. We discuss the concept of disorganized attachment style in relation to abuse, social exclusion, and its implication for psychopathology, intervention, and treatment
Phonons in random alloys: the itinerant coherent-potential approximation
We present the itinerant coherent-potential approximation(ICPA), an analytic,
translationally invariant and tractable form of augmented-space-based,
multiple-scattering theory in a single-site approximation for harmonic phonons
in realistic random binary alloys with mass and force-constant disorder.
We provide expressions for quantities needed for comparison with experimental
structure factors such as partial and average spectral functions and derive the
sum rules associated with them. Numerical results are presented for Ni_{55}
Pd_{45} and Ni_{50} Pt_{50} alloys which serve as test cases, the former for
weak force-constant disorder and the latter for strong. We present results on
dispersion curves and disorder-induced widths. Direct comparisons with the
single-site coherent potential approximation(CPA) and experiment are made which
provide insight into the physics of force-constant changes in random alloys.
The CPA accounts well for the weak force-constant disorder case but fails for
strong force-constant disorder where the ICPA succeeds.Comment: 19 pages, 12 eps figures, uses RevTex
- …