378 research outputs found
Orthorhombicity mixing of s- and d- gap components in without involving the chains
Momentum decoupling develops when forward scattering dominates the pairing
interaction and implies tendency for decorrelation between the physical
behavior in the various regions of the Fermi surface. In this regime it is
possible to obtain anisotropic s- or d-wave superconductivity even with
isotropic pairing scattering. We show that in the momentum decoupling regime
the distortion of the planes is enough to explain the experimental
reports for s- mixing in the dominantly d-wave gap of . In the
case of spin fluctuations mediated pairing instead, a large part of the
condensate must be located in the chains in order to understand the
experiments.Comment: LATEX file and 3 Postscript figure
Annealing-Dependent Magnetic Depth Profile in Ga[1-x]Mn[x]As
We have studied the depth-dependent magnetic and structural properties of
as-grown and optimally annealed Ga[1-x]Mn[x]As films using polarized neutron
reflectometry. In addition to increasing total magnetization, the annealing
process was observed to produce a significantly more homogeneous distribution
of the magnetization. This difference in the films is attributed to the
redistribution of Mn at interstitial sites during the annealing process. Also,
we have seen evidence of significant magnetization depletion at the surface of
both as-grown and annealed films.Comment: 5 pages, 3 figure
Magnetic and chemical nonuniformity in Ga[1-x]Mn[x]As films as probed by polarized neutron and x-ray reflectometry
We have used complementary neutron and x-ray reflectivity techniques to
examine the depth profiles of a series of as-grown and annealed Ga[1-x]Mn[x]As
thin films. A magnetization gradient is observed for two as-grown films and
originates from a nonuniformity of Mn at interstitial sites, and not from local
variations in Mn at Ga sites. Furthermore, we see that the depth-dependent
magnetization can vary drastically among as-grown Ga[1-x]Mn[x]As films despite
being deposited under seemingly similar conditions. These results imply that
the depth profile of interstitial Mn is dependent not only on annealing, but is
also extremely sensitive to initial growth conditions. We observe that
annealing improves the magnetization by producing a surface layer that is rich
in Mn and O, indicating that the interstitial Mn migrates to the surface.
Finally, we expand upon our previous neutron reflectivity study of
Ga[1-x]Mn[x]As, by showing how the depth profile of the chemical composition at
the surface and through the film thickness is directly responsible for the
complex magnetization profiles observed in both as-grown and annealed films.Comment: Now Published in Physical Review
Phenomenological description of the microwave surface impedance and complex conductivity of high- single crystals
Measurements of the microwave surface impedance and
of the complex conductivity of high-quality, high- single
crystals of YBCO, BSCCO, TBCCO, and TBCO are analyzed. Experimental data of
and are compared with calculations based on a modified
two-fluid model which includes temperature-dependent quasiparticle scattering
and a unique temperature variation of the density of superconducting carriers.
We elucidate agreement as well as disagreement of our analysis with the salient
features of the experimental data. Existing microscopic models are reviewed
which are based on unconventional symmetry types of the order parameter and on
novel mechanisms of quasiparticle relaxation.Comment: 15 pages, 17 figures, 1 tabl
Dissociation of accumulated genetic risk and disease severity in patients with schizophrenia
Genotype–phenotype correlations of common monogenic diseases revealed that the degree of deviation of mutant genes from wild-type structure and function often predicts disease onset and severity. In complex disorders such as schizophrenia, the overall genetic risk is still often >50% but genotype–phenotype relationships are unclear. Recent genome-wide association studies (GWAS) replicated a risk for several single-nucleotide polymorphisms (SNPs) regarding the endpoint diagnosis of schizophrenia. The biological relevance of these SNPs, however, for phenotypes or severity of schizophrenia has remained obscure. We hypothesized that the GWAS ‘top-10' should as single markers, but even more so upon their accumulation, display associations with lead features of schizophrenia, namely positive and negative symptoms, cognitive deficits and neurological signs (including catatonia), and/or with age of onset of the disease prodrome as developmental readout and predictor of disease severity. For testing this hypothesis, we took an approach complementary to GWAS, and performed a phenotype-based genetic association study (PGAS). We utilized the to our knowledge worldwide largest phenotypical database of schizophrenic patients (n>1000), the GRAS (Göttingen Research Association for Schizophrenia) Data Collection. We found that the ‘top-10' GWAS-identified risk SNPs neither as single markers nor when explored in the sense of a cumulative genetic risk, have any predictive value for disease onset or severity in the schizophrenic patients, as demonstrated across all core symptoms. We conclude that GWAS does not extract disease genes of general significance in schizophrenia, but may yield, on a hypothesis-free basis, candidate genes relevant for defining disease subgroups
Clinical supervision for clinical psychology students in Uganda: an initial qualitative exploration
Background
Burn out in clinical psychologists working in low income countries has been reported. Clinical supervisory structures do not yet exist in Uganda. A way to decrease levels of burn out and increase quality of care for people with mental illness is through clinical supervision. The aim of this study was to explore the initial experiences of supervision for clinical psychology students in Uganda to ascertain whether or not clinical supervision is culturally appropriate, and what aspects of supervision had been helpful and unhelpful.
Methods
A qualitative design with thematic analysis was utilized. A focus group was held with 12 second year clinical psychology students to ask their experiences of receiving supervision.
Results
Data analysis created five themes. Firstly, the negative emotions that resulted from the training processed were discussed, and how supervision helped and did not help the students to manage these. Secondly, the students voiced that supervision helped them to learn through observational experiences, co-therapist roles and parallel processes within the supervisory relationship. Thirdly, supervision had taught the clinical psychology students their role as a clinical psychology student, how to act within the Ugandan mental health system and skills to conduct therapy. Fourthly, suggestions for the future of supervision were given, with the students requesting for it to start earlier in the training, for supervisors who can meet with the students on a regular basis to be selected and for the training the students receive at university to match the skills required on their placements, with a request for more practical techniques rather than theory. The final theme related to left over miscellaneous data, such as the students agreeing with each other.
Conclusions
The students stated that supervision was helpful overall, implying that clinical supervision is culturally appropriate for clinical psychology students in Uganda. Suggestions for future supervision were given. In order to decrease high levels of staff burn out in the mental health systems in Uganda, supervisory structures with an emphasis on self care need to be established
Additive genetic variation in schizophrenia risk is shared by populations of African and European descent
Previous studies have emphasized ethnically heterogeneous human leukocyte antigen (HLA) classical allele associations to rheumatoid arthritis (RA) risk. We fine-mapped RA risk alleles within the major histocompatibility complex (MHC) in 2782 seropositive RA cases and 4315 controls of Asian descent. We applied imputation to determine genotypes for eight class I and II HLA genes to Asian populations for the first time using a newly constructed pan-Asian reference panel. First, we empirically measured high imputation accuracy in Asian samples. Then we observed the most significant association in HLA-DRβ1 at amino acid position 13, located outside the classical shared epitope (Pomnibus = 6.9 × 10(-135)). The individual residues at position 13 have relative effects that are consistent with published effects in European populations (His > Phe > Arg > Tyr ≅ Gly > Ser)--but the observed effects in Asians are generally smaller. Applying stepwise conditional analysis, we identified additional independent associations at positions 57 (conditional Pomnibus = 2.2 × 10(-33)) and 74 (conditional Pomnibus = 1.1 × 10(-8)). Outside of HLA-DRβ1, we observed independent effects for amino acid polymorphisms within HLA-B (Asp9, conditional P = 3.8 × 10(-6)) and HLA-DPβ1 (Phe9, conditional P = 3.0 × 10(-5)) concordant with European populations. Our trans-ethnic HLA fine-mapping study reveals that (i) a common set of amino acid residues confer shared effects in European and Asian populations and (ii) these same effects can explain ethnically heterogeneous classical allelic associations (e.g. HLA-DRB1*09:01) due to allele frequency differences between populations. Our study illustrates the value of high-resolution imputation for fine-mapping causal variants in the MHC
Evidence-based activism: Patients' organisations, users' and activist's groups in knowledge
This article proposes the notion of ‘evidence-based activism’ to capture patients’ and health activists’ groups’ focus on knowledge production and knowledge mobilisation in the governance of health issues. It introduces empirical data and analysis on groups active in four countries (France, Ireland, Portugal and the United Kingdom), and in four condition-areas (rare diseases, Alzheimer’s disease, ADHD – Attention Deficit Hyperactivity Disorder and childbirth). It shows how these groups engage with, and articulate a variety of credentialed knowledge and ‘experiential knowledge’ with a view to explore concerned people’s situations, to make themselves part and parcel of the networks of expertise on their conditions in their national contexts, and to elaborate evidence on the issues they deem important to address both at an individual and at a collective level. This article argues that in contrast to health movements which contest institutions from the outside, patients’ and activists’ groups which embrace ‘evidence-based activism’ work ‘from within’ to imagine new epistemic and political appraisal of their causes and conditions. ‘Evidence-based activism’ entails a collective inquiry associating patients/activists and specialists/professionals in the conjoint fabrics of scientific statements and political claims. From a conceptual standpoint, ‘evidence-based activism’ sheds light on the ongoing co-production of matters of fact and matters of concern in contemporary technological democracies
Phosphorescent Platinum(II) and Palladium(II) Complexes with Azatetrabenzoporphyrins—New Red Laser Diode-Compatible Indicators for Optical Oxygen Sensing
Clinical supervision for clinical psychology students in Uganda: an initial qualitative exploration
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