Very weak electron-phonon coupling and strong strain coupling in manganites

The coupling of the manganite stripe phase to the lattice and to strain has been investigated via transmission electron microscopy studies of polycrystalline and thin film manganites. In polycrystalline \PCMOfiftwo a lockin to $q/a^*=0.5$ in a sample with $x>0.5$ has been observed for the first time. Such a lockin has been predicted as a key part of the Landau CDW theory of the stripe phase. Thus it is possible to constrain the size of the electron-phonon coupling in the CDW Landau theory to between 0.04% and 0.05% of the electron-electron coupling term. In the thin film samples, films of the same thickness grown on two different substrates exhibited different wavevectors. The different strains present in the films on the two substrates can be related to the wavevector observed via Landau theory. It is demonstrated that the the elastic term which favours an incommensurate modulation has a similar size to the coupling between the strain and the wavevector, meaning that the coupling of strain to the superlattice is unexpectedly strong.Comment: 6 pages, 7 figure

The therapeutic alliance in psychotherapy for adolescent depression: Differences between treatment types and change over time

Although the alliance is usually considered a generic factor common to all therapies, there are theoretical reasons to suspect that it may develop differently in different types of therapies. Yet, in youth psychotherapy, little is known about this issue to date. This study investigated whether the mean strength of the alliance, as well as its trajectory over time, differed between three equally effective psychological treatments for adolescent depression. Data were drawn from the IMPACT study, a randomized controlled trial comparing cognitive-behavioral therapy (CBT) and short-term psychoanalytic psychotherapy (STPP) versus a brief psychosocial intervention (BPI) in the treatment of adolescent depression. Adolescents’ (N = 338) and therapists’ (n = 159) ratings of the alliance were collected using the Working Alliance Inventory short form at 6, 12, and 36 weeks after randomization. Data were analyzed using multilevel linear models. Results showed that adolescents’ and therapists’ mean alliance ratings differed between treatment types, being highest in CBT and lowest in the STPP at all time points. Mean therapists’ alliance ratings increased slightly over time in all arms, while mean adolescents’ ratings were stable over time in CBT and BPI but slightly increased in the STPP group. These findings suggest that the mean strength of the alliance differs between treatment type, and future research is required to pinpoint what factors contribute to these differences and their relationship with treatment outcomes

The alliance–outcome association in the treatment of adolescent depression

A growing body of research has consistently demonstrated a relationship between alliance and treatment outcomes in youth psychotherapy. However, past research often suffered methodological issues that prevented detailed investigation of temporal relationships between alliance and symptomatology. The current study explored the directions of effect between alliance and outcome by examining the associations between early alliance and subsequent outcome while controlling for patients’ baseline severity and prior symptom change. It also examined potential moderators of this association. Data were drawn from the IMPACT study, a randomized controlled trial comparing cognitive-behavioural therapy (CBT) and short-term psychoanalytic psychotherapy (STPP) versus a brief psychosocial intervention (BPI) in the treatment of adolescent depression. Adolescents (N=224) and therapist (n=139) rated the alliance 6 weeks after randomization. Depression severity and overall psychopathology were assessed at baseline, 6, 12, 36, 52 and 86 weeks after randomization. Patients’ age, gender, baseline depression severity, conduct disorder symptoms and treatment type were examined as potential moderators of the alliance-outcome association. Data were analysed using multilevel models. Findings suggested that higher early alliance ratings were associated with subsequent symptom reduction, even after controlling for prior symptom change and baseline severity. There was evidence that the strength of this association was strongest in CBT patients, weaker in STPP, and statistically indistinguishable from zero in BPI. These findings suggest that early therapeutic alliance with adolescents may influence subsequent outcome independent of prior symptom change and initial severity but that the effect of the alliance on outcome might vary across treatment types

The factor structure of the Working Alliance Inventory Short-form in youth psychotherapy: an empirical investigation

Objective: The Working Alliance Inventory short form (WAI-S) is one of the most commonly used alliance measures with adolescents. Yet, its factor structure has received minimal attention in the youth alliance literature. This study investigated the factor structure of the WAI-S in psychotherapy for adolescent depression and explored its measurement invariance across time, therapeutic approaches and patients’ and therapists’ perspectives. The existence of method effects associated with the negatively worded items of the scale was also assessed. Method: The setting of this study is the IMPACT trial, a randomised controlled trial assessing the effects of three therapeutic interventions in the treatment of adolescent depression. The WAI-S was completed at 6, 12 and 36 weeks after randomisation by 338 adolescents and 159 therapists. Data were analysed using confirmatory factor analysis. Results: The hypothesised Bond-Task-Goal alliance structure was not supported and a general, one-factor model was found to be more psychometrically valid. The existence of a method effect and measurement invariance across time and treatment arms were also found. Conclusions: While the distinction between the specific alliance dimensions is conceptually and clinically interesting, at an empirical level the alliance features of the WAI-S in youth psychotherapy remain strongly intercorrelated

The structure of intercalated water in superconducting Na0.35_{0.35}CoO2⋅_{2}\cdot1.37D2_{2}O: Implications for the superconducting phase diagram

We have used electron and neutron powder diffraction to elucidate the structural properties of superconducting \NaD. Our measurements show that our superconducting sample exhbits a number of supercells ranging from ${1/3}a^{*}$ to ${1/15}a^{*}$, but the most predominant one, observed also in the neutron data, is a double hexagonal cell with dimensions \dhx. Rietveld analysis reveals that \deut\space is inserted between CoO$_{2}$ sheets as to form a layered network of NaO$_{6}$ triangular prisms. Our model removes the need to invoke a 5K superconducting point compound and suggests that a solid solution of Na is possible within a constant amount of water $y$.Comment: 4 pages, 3 figure

Strain control of superlattice implies weak charge-lattice coupling in La0.5_{0.5}Ca0.5_{0.5}MnO3_3

We have recently argued that manganites do not possess stripes of charge order, implying that the electron-lattice coupling is weak [Phys Rev Lett \textbf{94} (2005) 097202]. Here we independently argue the same conclusion based on transmission electron microscopy measurements of a nanopatterned epitaxial film of La$_{0.5}$Ca$_{0.5}$MnO$_3$. In strain relaxed regions, the superlattice period is modified by 2-3% with respect to the parent lattice, suggesting that the two are not strongly tied.Comment: 4 pages, 4 figures It is now explained why the work provides evidence to support weak-coupling, and rule out charge orde

Wave functions in the neighborhood of a toroidal surface; hard vs. soft constraint

The curvature potential arising from confining a particle initially in three-dimensional space onto a curved surface is normally derived in the hard constraint $q \to 0$ limit, with $q$ the degree of freedom normal to the surface. In this work the hard constraint is relaxed, and eigenvalues and wave functions are numerically determined for a particle confined to a thin layer in the neighborhood of a toroidal surface. The hard constraint and finite layer (or soft constraint) quantities are comparable, but both differ markedly from those of the corresponding two dimensional system, indicating that the curvature potential continues to influence the dynamics when the particle is confined to a finite layer. This effect is potentially of consequence to the modelling of curved nanostructures.Comment: 4 pages, no fig