9,630 research outputs found
Coulomb Driven New Bound States at the Integer Quantum Hall States in GaAs/Al(0.3)Ga(0.7)As Single Heterojunctions
Coulomb driven, magneto-optically induced electron and hole bound states from
a series of heavily doped GaAs/Al(0.3)Ga(0.7)As single heterojunctions (SHJ)
are revealed in high magnetic fields. At low magnetic fields (nu > 2), the
photoluminescence spectra display Shubnikov de-Haas type oscillations
associated with the empty second subband transition. In the regime of the
Landau filling factor nu < 1 and 1 < nu <2, we found strong bound states due to
Mott type localizations. Since a SHJ has an open valence band structure, these
bound states are a unique property of the dynamic movement of the valence holes
in strong magnetic fields
Frame-like Geometry of Double Field Theory
We relate two formulations of the recently constructed double field theory to
a frame-like geometrical formalism developed by Siegel. A self-contained
presentation of this formalism is given, including a discussion of the
constraints and its solutions, and of the resulting Riemann tensor, Ricci
tensor and curvature scalar. This curvature scalar can be used to define an
action, and it is shown that this action is equivalent to that of double field
theory.Comment: 35 pages, v2: minor corrections, to appear in J. Phys.
Interventions to Promote More Effective Balance-Recovery Reactions in Industrial Settings: New Perspectives on Footwear and Handrails
âChange-in-supportâ balance-recovery reactions that involve rapid stepping or reaching movements play a critical role in preventing falls. Recent geriatrics studies have led to new interventions to improve ability to execute these reactions effectively. Some of these interventions have the potential to reduce fall risk for younger persons working in industrial settings. In this paper, we review research pertaining to two such interventions: 1) balance-enhancing footwear insoles designed to improve stepping reactions, and 2) proximity-triggered handrail cueing systems designed to improve reach-to-grasp reactions. The insole has a raised ridge around the perimeter that is intended to improve balance control by providing increased stimulation of sensory receptors on the footsole in situations where loss of balance may be imminent. The cueing system uses flashing lights and/or verbal prompts to attract attention to the handrail and ensure that the brain registers its location, thereby facilitating more rapid and accurate grasping of the rail if and when sudden loss of balance occurs. Results to date support the efficacy of both interventions in geriatric populations. There is also some evidence that these interventions may improve balance control in younger persons; however, further research is needed to confirm their efficacy in preventing falls in industrial settings
Online self-compassion training to improve the wellbeing of youth with chronic medical conditions: protocol for a randomised control trial
Background
Chronic medical conditions (CMCs) affect up to 35% of children and adolescents. Youth with chronic medical conditions are at an increased risk of psychological distress and reduced health-related quality of life, and report rates of mental illness up to double that of their physically healthy peers. Accessible, evidence-based interventions for young people with chronic illness are urgently required to improve their mental health and daily functioning. Self-compassion involves taking a mindful, accepting approach to difficult experiences, being aware that one is not alone in oneâs suffering, and being kind and understanding with oneself during challenging times. Self-compassion shares strong associations with mental health outcomes among young people and preliminary work indicates that interventions that build self-compassion have the potential to substantially improve youth mental health. Self-compassion is also associated with better physical and mental health outcomes among individuals living with CMCs. While face-to-face self-compassion training is available, there are several barriers to access for youth with CMCs. Online self-compassion training potentially offers an accessible alternative for this high-risk group.
Methods
Self-Compassion Online (SCO) is a self-compassion program that has been tested with a non-clinical adult group. For the proposed trial, a reference group of youth (16â25âyears) with chronic illness reviewed the program and proposed adaptations to improve its suitability for youth with chronic illness. In alignment with the SPIRIT Checklist, this paper outlines the protocol for a CONSORT-compliant, single-blind randomised controlled trial to test the efficacy of the adapted program, relative to a waitlist control, for improving self-compassion, wellbeing, distress, emotion regulation, coping and quality of life among young Australians with CMCs. Mechanisms of action and feasibility of SCO will be analysed using quantitative data and participant interviews, respectively. Finally, cost-utility will be analysed using health-related quality of life data.
Discussion
The SCO program could provide a scalable solution for improving psychological outcomes and quality of life among youth with chronic illness. The proposed trial will be the first to determine its efficacy for improving these outcomes, relative to waitlist control.
Trial registration
The trial was registered on the Australian New Zealand Clinical Trials Registry on the 11th April 2019, ACTRN12619000572167
Extended BRST invariance in topological Yang Mills theory revisited
Extended BRST invariance (BRST plus anti-BRST invariances) provides in
principle a natural way of introducing the complete gauge fixing structure
associated to a gauge field theory in the minimum representation of the
algebra. However, as it happens in topological Yang Mills theory, not all gauge
fixings can be obtained from a symmetrical extended BRST algebra, where
antighosts belong to the same representation of the Lorentz group of the
corresponding ghosts. We show here that, at non interacting level, a simple
field redefinition makes it possible to start with an extended BRST algebra
with symmetric ghost antighost spectrum and arrive at the gauge fixing action
of topological Yang Mills theory.Comment: Interaction terms heve been included in all the calculations. Two
references added. Version to be published in Phys. Rev. D. 7 pages, Latex, no
figure
The Antiferromagnetic Band Structure of La2CuO4 Revisited
Using the Becke-3-LYP functional, we have performed band structure
calculations on the high temperature superconductor parent compound, La2CuO4.
Under the restricted spin formalism (rho(alpha) equal to rho(beta)), the
R-B3LYP band structure agrees well with the standard LDA band structure. It is
metallic with a single Cu x2-y2/O p(sigma) band crossing the Fermi level. Under
the unrestricted spin formalism (rho(alpha) not equal to rho(beta)), the UB3LYP
band structure has a spin polarized antiferromagnetic solution with a band gap
of 2.0 eV, agreeing well with experiment. This state is 1.0 eV (per formula
unit) lower than that calculated from the R-B3LYP. The apparent high energy of
the spin restricted state is attributed to an overestimate of on-site Coulomb
repulsion which is corrected in the unrestricted spin calculations. The
stabilization of the total energy with spin polarization arises primarily from
the stabilization of the x2-y2 band, such that the character of the eigenstates
at the top of the valence band in the antiferromagnetic state becomes a strong
mixture of Cu x2-y2/O p(sigma) and Cu z2/O' p(z). Since the Hohenberg-Kohn
theorem requires the spin restricted and spin unrestricted calculations give
exactly the same ground state energy and total density for the exact
functionals, this large disparity in energy reflects the inadequacy of current
functionals for describing the cuprates. This calls into question the use of
band structures based on current restricted spin density functionals (including
LDA) as a basis for single band theories of superconductivity in these
materials.Comment: 13 pages, 8 figures, to appear in Phys. Rev. B, for more information
see http://www.firstprinciples.co
Competition between normal and intruder states inside the "Island of Inversion"
The beta decay of the exotic 30Ne (N=20) is reported. For the first time, the
low-energy level structure of the N=19, 30Na (Tz = 4), is obtained from
beta-delayed gamma spectroscopy using fragment-beta-gamma-gamma coincidences.
The level structure clearly displays "inversion", i.e., intruder states with
mainly 2p2h configurations displacing the normal states to higher excitation
energies. The good agreement in excitation energies and the weak and
electromagnetic decay patterns with Monte Carlo Shell Model calculations with
the SDPF-M interaction in the sdpf valence space illustrates the small d3/2 -
f7/2 shell gap. The relative position of the "normal dominant" and "intruder
dominant" excited states provides valuable information to understand better the
N=20 shell gap.Comment: 4 pages, 5 figure
Origins and population genetics of sambar deer (Cervus unicolor) introduced to Australia and New Zealand
Context. Some populations of introduced species cause significant undesirable impacts but can also
act as reservoirs for genetic diversity. Sambar deer (Cervus unicolor) are âVulnerableâ in their native
range and invasive in Australia and New Zealand. Genetic data can be used to determine whether
these introduced populations might serve as genetic reservoirs for declining native populations and
to identify spatial units for management. Aims. We aimed to identify the provenance of sambar deer
in Australia and New Zealand, and to characterise their genetic diversity and population structure.
Methods. We used mitochondrial control region sequences and 18 nuclear microsatellite loci of 24
New Zealand and 63 Australian sambar deer collected across continuous habitat in each location.
We estimated genetic diversity and population differentiation by using pairwise FST, AMOVA, and
STRUCTURE analyses. We compared our data with 27 previously published native and invasive range
sequences to identify phylogenetic relationships. Key results. Sambar deer in Australia and New
Zealand are genetically more similar to those in the west of the native range (South and Central
Highlands of India, and Sri Lanka), than to those in the east (eastern India, and throughout Southeast
Asia). Nuclear genetic diversity was lower than in the native range; only one mitochondrial haplotype
was found in each introduced population. Australian and New Zealand sambar deer were genetically
distinct but there was no population structure within either population. Conclusions. The genetic
differences we identified between these two introduced populations at putatively neutral loci
indicate that there also may be underlying diversity at functional loci. The lack of population genetic
structure that we found within introduced populations suggests that individuals within these popula-
tions do not experience barriers to dispersal across the areas sampled. Implications. Although
genetic diversity is reduced in the introduced range compared with the native range, sambar deer
in Australia and New Zealand harbour unique genetic variants that could be used to strengthen
genetic diversity in populations under threat in the native range. The apparent high levels of gene
flow across the areas we sampled suggest that localised control is unlikely to be effective in Australia
and New Zealand
- âŠ