c-axis Raman Scattering in MgB2: Observation of a Dirty-Limit Gap in the pi-bands

Raman scattering spectra from the ac-face of thick MgB2 single crystals were measured in zz, xz and xx polarisations. In zz and xz polarisations a threshold at around 29 cm^{-1} forms in the below Tc continuum but no pair-breaking peak is seen, in contrast to the sharp pair-breaking peak at around 100 cm^{-1} seen in xx polarisation. The zz and xz spectra are consistent with Raman scattering from a dirty superconductor while the sharp peak in the xx spectra argues for a clean system. Analysis of the spectra resolves this contradiction, placing the larger and smaller gap magnitudes in the sigma and pi bands, and indicating that relatively strong impurity scattering is restricted to the pi bands.Comment: Revised manuscript accepted for publication in Physical Review Letter

Carbon-substitution effect on the electronic properties of MgB2_2 single crystals

The electronic properties of the carbon substituted MgB$_2$ single crystals are reported. The carbon substitution drops T$_c$ below 2 K. In-plane resistivity shows a remarkable increase in residual resistivity by C-substitution, while the change of in-plane/out-of-plane Hall coefficients is rather small. Raman scattering spectra indicate that the E$_{2g}$-phonon frequency radically hardens with increasing the carbon-content, suggesting the weakening of electron-phonon coupling. Another striking C-effect is the increases of the second critical fields in both in-plane and out-of-plane directions, accompanied by a reduction in the anisotropy ratio. The possible changes in the electronic state and the origin of T$_c$-suppression by C-substitution are discussed.Comment: 6 pages, 8 figure

Vortex core shrinkage in a two gap superconductor: application to MgB2

As a model for the vortex core in MgB2 we study a two band model with a clean sigma band and a dirty pi band. We present calculations of the vortex core size in both bands as a function of temperature and show that there exists a Kramer-Pesch effect in both bands even though only one of the bands is in the clean limit. We present calculations for different pi band diffusivities and coherence lengths.Comment: Submitted to M2S-HTSC-VIII conference proceeding

Perceptual Pluralism

Perceptual systems respond to proximal stimuli by forming mental representations of distal stimuli. A central goal for the philosophy of perception is to characterize the representations delivered by perceptual systems. It may be that all perceptual representations are in some way proprietarily perceptual and differ from the representational format of thought (Dretske 1981; Carey 2009; Burge 2010; Block ms.). Or it may instead be that perception and cognition always trade in the same code (Prinz 2002; Pylyshyn 2003). This paper rejects both approaches in favor of perceptual pluralism, the thesis that perception delivers a multiplicity of representational formats, some proprietary and some shared with cognition. The argument for perceptual pluralism marshals a wide array of empirical evidence in favor of iconic (i.e., image-like, analog) representations in perception as well as discursive (i.e., language-like, digital) perceptual object representations

Origin of superconductivity transition broadening in MgB2

We report resistivity and magnetization of single crystal MgB2, focusing on the broadening of superconducting (SC) transition in magnetic fields. In-plane and out-of-plane resistivity indicate that the broadening of superconducting transition is independent of Lorentz force and that it is merely dependent on the magnetic field direction. In magnetization, diamagnetic signal begins to appear at almost the same temperature as the onset temperature of resistivity transition. These results suggest that the broadening is attributed not to the surface superconductivity but to the superconducting fluctuation or the vortex-liquid picture, owing to the short coherence length and the high transition temperature of MgB2.Comment: 8pages, 6 figures, to be published in Physica

Flux flow resistivity in the two-gap superconductivity

We investigate the flux flow state in a two-gap superconductor in which two s-wave gaps with different amplitudes exist on two separate Fermi surfaces. The flux flow resistivity is obtained on the basis of the Bardeen-Stephen relation and the result agrees well with the anomalous field dependence of the flow resistivity recently observed in the two-gap superconductor MgB2. Some typical properties of the vortex in this system are also discussed.Comment: 5 pages, 1 figure. Some typos are corrected. Some comments are added. To be published in J. Phys. Soc. Jp

Pathological gambling subtypes: A comparison of treatment-seeking and non-treatment-seeking samples from Brazil and Canada

Background: Pathological gambling (PG) is a heterogeneous disorder. The identification and characterization of PG subtypes could lead to tailored treatment approaches, which may, in turn, improve treatment outcomes. Objective: To investigate PG subtypes based on personality traits across two different cultural and clinical settings. Consistent with the Pathways Model, we hypothesized the presence of three subtypes (behaviorally conditioned — BC, emotionally vulnerable — EV, and antisocial impulsivist — AI). Methods: 140 PG adults from São Paulo, Brazil (SP sample) and 352 adults with PG (n = 214) or sub-clinical PG (n = 138) from Toronto, Canada (TO sample) completed the Temperament and Character Inventory (TCI). Latent-class analysis was used to investigate subtypes. Results: A 2-class solution was the best model for the pooled SP and TO samples. Class 1 presented a normative personality profile and was composed exclusively of participants from Toronto (BC subtype). Class 2 was characterized by high novelty seeking, high harm avoidance, and low self-directedness, and included participants from both SP and TO (EV subtype). When sub-clinical PGs were excluded from the analysis, a single-class solution better characterized the SP and TO samples. Conclusions: Our results suggest that PG severity, rather than community or clinical settings, may have an effect on PG subtypes. The generalizability of the results is limited by the demographic and clinical features of the selected samples. Future neurobiological studies may contribute to the categorization of subjects into PG subtypes based on different underlying biological pathways

Highly Efficient F, Cu Doped TiO2 Anti-bacterial Visible Light Active Photocatalytic Coatings to Combat Hospital-Acquired Infections

Bacterial infections are a major threat to the health of patients in healthcare facilities including hospitals. One of the major causes of patient morbidity is infection with Staphylococcus aureus. One of the the most dominant nosocomial bacteria, Methicillin Resistant Staphylococcus aureus (MRSA) have been reported to survive on hospital surfaces (e.g. privacy window glasses) for up to 5 months. None of the current anti-bacterial technology is efficient in eliminating Staphylococcus aureus. A novel transparent, immobilised and superhydrophilic coating of titanium dioxide, co-doped with fluorine and copper has been prepared on float glass substrates. Antibacterial activity has demonstrated (by using Staphylococcus aureus), resulting from a combination of visible light activated (VLA) photocatalysis and copper ion toxicity. Co-doping with copper and fluorine has been shown to improve the performance of the coating, relative to a purely fluorine-doped VLA photocatalyst. Reductions in bacterial population of log10 = 4.2 under visible light irradiation and log10 = 1.8 in darkness have been achieved, compared with log10 = 1.8 under visible light irradiation and no activity, for a purely fluorine-doped titania. Generation of reactive oxygen species from the photocatalytic coatings is the major factor that significantly reduces the bacterial growth on the glass surfaces

Cognitive change in cognitive-behavioural therapy

BACKGROUND: Although cognitive-behavioural therapy (CBT) is a well-established treatment for adult depression, its efficacy and efficiency may be enhanced by better understanding its mechanism(s) of action. According to the theoretical model of CBT, symptom improvement occurs via reductions in maladaptive cognition. However, previous research has not established clear evidence for this cognitive mediation model. METHODS: The present study investigated the cognitive mediation model of CBT in the context of a randomized controlled trial of CBT v. antidepressant medication (ADM) for adult depression. Participants with major depressive disorder were randomized to receive 16 weeks of CBT (n = 54) or ADM (n = 50). Depression symptoms and three candidate cognitive mediators (dysfunctional attitudes, cognitive distortions and negative automatic thoughts) were assessed at week 0 (pre-treatment), week 4, week 8 and week 16 (post-treatment). Longitudinal associations between cognition and depression symptoms, and mediation of treatment outcome, were evaluated in structural equation models. RESULTS: Both CBT and ADM produced significant reductions in maladaptive cognition and depression symptoms. Cognitive content and depression symptoms were moderately correlated within measurement waves, but cross-lagged associations between the variables and indirect (i.e. mediated) treatment effects were non-significant. CONCLUSIONS: The results provide support for concurrent relationships between cognitive and symptom change, but not the longitudinal relationships hypothesized by the cognitive mediation model. Results may be indicative of an incongruence between the timing of measurement and the dynamics of cognitive and symptom change