438 research outputs found
Greybody Factors for Brane Scalar Fields in a Rotating Black-Hole Background
We study the evaporation of (4+n)-dimensional rotating black holes into
scalar degrees of freedom on the brane. We calculate the corresponding
absorption probabilities and cross-sections obtaining analytic solutions in the
low-energy regime, and compare the derived analytic expressions to numerical
results, with very good agreement. We then consider the high-energy regime,
construct an analytic high-energy solution to the scalar-field equation by
employing a new method, and calculate the absorption probability and
cross-section for this energy regime, finding again a very good agreement with
the exact numerical results. We also determine the high-energy asymptotic value
of the total cross-section, and compare it to the analytic results derived from
the application of the geometrical optics limit.Comment: Latex file, 30 pages, 5 figures, typos corrected, version published
in Phys. Rev.
Occupational therapy for people with psychotic conditions in community settings: a pilot randomized controlled trial
OBJECTIVES: To investigate the effectiveness of a long established intervention, occupational therapy for people with psychotic conditions, and to inform future research designs.
DESIGN: A pilot randomized controlled trial.
SETTING: Two community mental health teams in a UK city.
PARTICIPANTS: Forty-four adults with schizophrenia or other psychotic conditions, and functional problems.
INTERVENTIONS: Twelve months of individualized occupational therapy in community settings, as an adjunct to usual care and compared to treatment as usual. A two to one randomization ratio was used in favour of occupational therapy.
OUTCOME MEASURES: Social Functioning Scale, Scale for the Assessment of Negative Symptoms and employment.
RESULTS: Both groups' scores on Social Functioning Scale and Scale for the Assessment of Negative Symptoms showed significant improvement over 12 months. The Social Functioning Scale overall mean difference for occupational therapy was 2.33, P=0.020 and for treatment as usual was 6.17, P=0.023. The Scale for the Assessment of Negative Symptoms total mean difference for occupational therapy was -16.25, P<0.001 and for treatment as usual was -17.36, P= 0.011. There were no differences between the two groups on any of the outcome measures. After 12 months the occupational therapy group showed clinically significant improvements that were not apparent in the control group. These were in four subscales of the Social Functioning Scale: relationships, independence performance, independence competence and recreation. Out of 30 people receiving occupational therapy those with a clinical level of negative symptoms reduced from 18 (64%) to 13 (46%), P=0.055.
CONCLUSION: This pilot study suggested that individualized occupatio
Benznidazole biotransformation and multiple targets in <i>Trypanosoma</i> cruzi revealed by metabolomics
<b>Background</b><p></p>
The first line treatment for Chagas disease, a neglected tropical disease caused by the protozoan parasite Trypanosoma cruzi, involves administration of benznidazole (Bzn). Bzn is a 2-nitroimidazole pro-drug which requires nitroreduction to become active, although its mode of action is not fully understood. In the present work we used a non-targeted MS-based metabolomics approach to study the metabolic response of T. cruzi to Bzn.<p></p>
<b>Methodology/Principal findings</b><p></p>
Parasites treated with Bzn were minimally altered compared to untreated trypanosomes, although the redox active thiols trypanothione, homotrypanothione and cysteine were significantly diminished in abundance post-treatment. In addition, multiple Bzn-derived metabolites were detected after treatment. These metabolites included reduction products, fragments and covalent adducts of reduced Bzn linked to each of the major low molecular weight thiols: trypanothione, glutathione, γ-glutamylcysteine, glutathionylspermidine, cysteine and ovothiol A. Bzn products known to be generated in vitro by the unusual trypanosomal nitroreductase, TcNTRI, were found within the parasites, but low molecular weight adducts of glyoxal, a proposed toxic end-product of NTRI Bzn metabolism, were not detected.<p></p>
<b>Conclusions/significance</b><p></p>
Our data is indicative of a major role of the thiol binding capacity of Bzn reduction products in the mechanism of Bzn toxicity against T. cruzi
Hawking emission from quantum gravity black holes
We address the issue of modelling quantum gravity effects in the evaporation
of higher dimensional black holes in order to go beyond the usual
semi-classical approximation. After reviewing the existing six families of
quantum gravity corrected black hole geometries, we focus our work on
non-commutative geometry inspired black holes, which encode model independent
characteristics, are unaffected by the quantum back reaction and have an
analytical form compact enough for numerical simulations. We consider the
higher dimensional, spherically symmetric case and we proceed with a complete
analysis of the brane/bulk emission for scalar fields. The key feature which
makes the evaporation of non-commutative black holes so peculiar is the
possibility of having a maximum temperature. Contrary to what happens with
classical Schwarzschild black holes, the emission is dominated by low frequency
field modes on the brane. This is a distinctive and potentially testable
signature which might disclose further features about the nature of quantum
gravity.Comment: 36 pages, 18 figures, v2: updated reference list, minor corrections,
version matching that published on JHE
Braneworld stars and black holes
We look for spherically symmetric star or black hole solutions on a
Randall-Sundrum brane from the perspective of the bulk. We take a known bulk
solution, and analyse possible braneworld trajectories within it that
correspond, from the braneworld point of view, to solutions of the brane
Tolman-Oppenheimer-Volkoff equations. Our solutions are therefore embedded
consistently into a full bulk solution. We find the full set of static
gravitating matter sources on a brane in a range of bulk spacetimes, analyzing
which can correspond to physically sensible sources. Finally, we look at
time-dependent trajectories in a Schwarzschild--anti de Sitter spacetime as
possible descriptions of time-dependent braneworld black holes, highlighting
some of the general features one might expect, as well as some of the
difficulties involved in getting a full solution to the question.Comment: 39 pages, 15 figure
Structure-based design and synthesis of antiparasitic pyrrolopyrimidines targeting pteridine reductase 1
The treatment of Human African Trypanosomiasis remains a major unmet health need in sub-Saharan Africa. Approaches involving new molecular targets are important and pteridine reductase 1 (PTR1), an enzyme that reduces dihydrobiopterin in Trypanosoma spp. has been identified as a candidate target and it has been shown previously that substituted pyrrolo[2,3-d]pyrimidines are inhibitors of PTR1 from T. brucei (J. Med. Chem. 2010, 53, 221-229). In this study, 61 new pyrrolo[2,3-d]pyrimidines have been prepared, designed with input from new crystal structures of 23 of these compounds complexed with PTR1, and evaluated in screens for enzyme inhibitory activity against PTR1 and in vitro antitrypanosomal activity. 8 compounds were sufficiently active in both screens to take forward to in vivo evaluation. Thus although evidence for trypanocidal activity in a stage I disease model in mice was obtained, the compounds were too toxic to mice for further development
Collaborative research exploring mental health service user perspectives on acute inpatient occupational therapy
Introduction:User perspectives are important for understanding why people engage with occupational therapy during an admission for acute mental health issues, and can be used to inform service provision and development. Method: Twenty-two recent and current inpatients participated in six semi-structured individual interviews and three focus groups. Data from the two methods were initially subject to separate thematic analysis. Then a further stage of constant comparative analysis, of both data sets, generated the findings presented here. Findings: Three themes were identified: (1) ‘A tiny sort of world’ expressed experiences of being restricted; (2) ‘Relief’ indicated how occupational therapy offered relief from the ward and experiences of mental ill-health; and (3) ‘Something to do’ suggested specific purposes for engaging in occupation. These themes indicate how service users experience and value occupational therapy for different reasons at different times. The approach of occupational therapists to service users, valuing them as occupational beings, is a key aspect of their experience. Conclusion: The profession is challenged to design flexible opportunities for occupational engagement which simultaneously provide relief and distraction, address diverse occupational needs, and are feasible within the resource restrictions of acute mental health services
Analytical studies of Hawking radiation and quasinormal modes in rotating linear dilatonic black hole
The rotating linear dilatonic black hole is an asymptotically non-flat
solution to Einstein-Maxwell-Dilaton-Axion gravity theory due to the existence
of non-trivial matter fields. We have analytically studied the wave equation of
scalar field in this background and shown that the radial wave equation can be
solved in terms of hypergeometric function. By determining the ingoing and the
outgoing fluxes at the asymptotic infinity, we have found the analytical
expressions for reflection coefficient and greybody factor for certain scalar
modes. In the high frequency regime, we obtain the Hawking temperature by
comparing the blackbody spectrum with the radiation spectrum resulting from
reflection coefficient. It is shown that the Hawking temperature, which depends
only on the linear dilatonic background parameter, does not agree with the
temperature calculated from surface gravity. At last, the quasinormal modes of
scalar field perturbation are presented, which shows that the rotating linear
dilationic black hole is unstable for certain modes apart from the superradiant
modes.Comment: 7 pages, 2 figures Comments are welcom
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Occupational Therapy and Multidisciplinary Working on Acute Psychiatric Wards: The Tompkins Acute Ward Study
There is limited research into occupational therapy and interprofessional working on acute psychiatric wards. This study aimed to explore relations between occupational therapists and other members of the multidisciplinary team through structured interviews with 47 staff on 14 acute psychiatric wards.
The study found that occupational therapists provided assessments, group activities and individual therapeutic work, with the assessment and development of activities of daily living being central. Linking patients with community resources in preparation for discharge was also important. Severity of illness among patients and speed of discharge were barriers to effective input. Nurses and psychiatrists appreciated occupational therapy input but rarely the breadth of the role. Multidisciplinary relations were generally positive, although some ward teams were disinclined to include occupational therapists in communications and decision making. The occupational therapists appreciated their professional knowledge and opinion being respected and considered.
The study concluded that occupational therapists play an important if often misunderstood role on acute psychiatric wards, but that their involvement could be significantly increased through the employment of more experienced occupational therapists and the provision of interprofessional education. Further research is required to explore the facilities, resources and support required to maximise occupational therapy input and identify areas for increased interprofessional working
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