17,672 research outputs found
Orbital magnetization in periodic insulators
Working in the Wannier representation, we derive an expression for the
orbital magnetization of a periodic insulator. The magnetization is shown to be
comprised of two contributions, an obvious one associated with the internal
circulation of bulk-like Wannier functions in the interior, and an unexpected
one arising from net currents carried by Wannier functions near the surface.
Each contribution can be expressed as a bulk property in terms of Bloch
functions in a gauge-invariant way. Our expression is verified by comparing
numerical tight-binding calculations for finite and periodic samples.Comment: submitted to PRL; signs corrected in Eqs. (11), (12), (19), and (20
Deformation of Silica Aerogel During Fluid Adsorption
Aerogels are very compliant materials - even small stresses can lead to large
deformations. In this paper we present measurements of the linear deformation
of high porosity aerogels during adsorption of low surface tension fluids,
performed using a Linear Variable Differential Transformer (LVDT). We show that
the degree of deformation of the aerogel during capillary condensation scales
with the surface tension, and extract the bulk modulus of the gel from the
data. Furthermore we suggest limits on safe temperatures for filling and
emptying low density aerogels with helium.Comment: 8 pages, 5 figures, submitted to PR
Detoxification in rehabilitation in England: effective continuity of care or unhappy bedfellows?
There is evidence that residential detoxification alone does not provide satisfactory treatment outcomes and that outcomes are significantly enhanced when clients completing residential detoxification attend rehabilitation services (Gossop, Marsden, Stewart, & Rolfe, 1999; Ghodse, Reynolds, Baldacchino, et al., 2002). One way of increasing the likelihood of this continuity of treatment is by providing detoxification and rehabilitation within the same treatment facility to prevent drop-out, while the client awaits a rehabilitation bed or in the transition process. However, there is little research evidence available on the facilities that offer both medical detoxification and residential rehabilitation. The current study compares self-reported treatment provision in 87 residential rehabilitation services in England, 34 of whom (39.1%) reported that they offered detoxification services within their treatment programmes. Although there were no differences in self-reported treatment philosophies, residential rehabilitation services that offered detoxification were typically of shorter duration overall, had significantly more beds and reported offering more group work than residential rehabilitation services that did not offer detoxification. Outcomes were also different, with twice as many clients discharged on disciplinary grounds from residential rehabilitation services without detoxification facilities. The paper questions the UK classification of residential drug treatment services as either detoxification or rehabilitation and suggests the need for greater research focus on the aims, processes and outcomes of this group of treatment providers
Experiences of parenting and clinical intervention for mothers affected by personality disorder: a pilot qualitative study combining parent and clinician perspectives
Background: Evidence-based parenting programmes are recommended for the treatment of child mental health difficulties. Families with complex psychosocial needs show poorer retention and outcomes when participating in standard parenting programmes. The Helping Families Programme (HFP) is a 16-week community-based parenting intervention designed to meet the needs of these families, including families with parental personality disorder. This study aimed to explore the help seeking and participatory experiences of parents with a diagnosis of personality disorder. It further aimed to examine the acceptability of referral and intervention processes for the HFP from the perspectives of (i) clinicians referring into the programme; and (ii) referred parents.
Method: Semi-structured interviews were conducted with parents recruited to receive HFP (n = 5) as part of a research case series and the referring NHS child and adolescent mental health service (CAMHS) clinicians (n = 5). Transcripts were analysed using Interpretive Phenomenological Analysis.
Results: Four themes were identified for parents: (i) the experience of parenthood, (ii) being a parent affected by personality disorder, (iii) experience of the intervention, and (iv) qualities of helping. Three themes emerged for clinicians: (i) challenges of addressing parental need, (ii) experience of engaging parents with personality disorders and (iii) limited involvement during HFP. Comparison of parent and clinician themes led to the identification of two key interlinked themes: (i) concerns prior to receiving the intervention, and (ii) the challenges of working together without a mutual understanding.
Conclusions: This pilot study identifies potentially significant challenges of working with parents affected by personality disorder and engaging them in HFP and other similar interventions. Results have important wider clinical implications by highlighting potential barriers to engagement and participation and providing insights on how these barriers might be overcome. Findings have been used to inform the referral and intervention processes of a pilot RCT and further intervention development
The quenching of compressible edge states around antidots
We provide a systematic quantitative description of the edge state structure
around a quantum antidot in the integer quantum Hall regime. The calculations
for spinless electrons within the Hartree approximation reveal that the widely
used Chklovskii et al. electrostatic description greatly overestimates the
widths of the compressible strips; the difference between these approaches
diminishes as the size of the antidot increases. By including spin effects
within density functional theory in the local spin-density approximation, we
demonstrate that the exchange interaction can suppress the formation of
compressible strips and lead to a spatial separation between the spin-up and
spin-down states. As the magnetic field increases, the outermost compressible
strip, related to spin-down states starts to form. However, in striking
contrast to quantum wires, the innermost compressible strip (due to spin-up
states) never develops for antidots.Comment: submitted to Phys. Rev. Let
Universality of residence-time distributions in non-adiabatic stochastic resonance
We present mathematically rigorous expressions for the residence-time and
first-passage-time distributions of a periodically forced Brownian particle in
a bistable potential. For a broad range of forcing frequencies and amplitudes,
the distributions are close to periodically modulated exponential ones.
Remarkably, the periodic modulations are governed by universal functions,
depending on a single parameter related to the forcing period. The behaviour of
the distributions and their moments is analysed, in particular in the low- and
high-frequency limits.Comment: 8 pages, 1 figure New version includes distinction between
first-passage-time and residence-time distribution
Inelastic nucleon contributions in nuclear response functions
We estimate the contribution of inelastic nucleon excitations to the
inclusive cross section in the CEBAF kinematic range.
Calculations are based upon parameterizations of the nucleon structure
functions measured at SLAC. Nuclear binding effects are included in a
vector-scalar field theory, and are assumed have a minimal effect on the
nucleon excitation spectrum. We find that for q\lsim 1 GeV the elastic and
inelastic nucleon contributions to the nuclear response functions are
comparable, and can be separated, but with roughly a factor of two uncertainty
in the latter from the extrapolation from data. In contrast, for q\rsim 2 GeV
this uncertainty is greatly reduced but the elastic nucleon contribution is
heavily dominated by the inelastic nucleon background.Comment: 20 pages, 7 figures available from the authors at Department of
Physics and Astronomy, University of Rochester, Rochester NY 1462
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