Andreev reflections on Y1-xCaxBa2Cu3O7-delta evidence for an unusual proximity effect

We have measured Andreev reflections between an Au tip and Y_{1-x}Ca_{x}Ba_{2}Cu_{3}O_{7 - \delta} thin films in the in-plane orientation. The conductance spectra are best fitted with a pair potential having the "d_{x^{2}-y^{2}+is" symmetry. We find that the amplitude of the "is" component is enhanced as the contact transparency is increased. This is an indication for an unusual proximity effect that modifies the pair potential in the superconductor near the surface with the normal metal.Comment: 4 pages, 4 figure

What Statistics Canada Survey Data Sources are Available to Study Neurodevelopmental Conditions and Disabilities in Children and Youth?

Researchers with an interest in examining and better understanding the social context of children suffering from neurodevelopmental disabilities can benefit by using data from a wide variety of Statistics Canada surveys as well as the information contained in administrative health databases. Selective use of a particular survey and database can be informative particularly when demographics, samples, and content align with the goals and outcomes of the researcher’s questions of interest. Disabilities are not merely conditions in isolation. They are a key part of a social context involving impairment, function, and social facilitators or barriers, such as work, school and extracurricular activities. Socioeconomic factors, single parenthood, income, and education also play a role in how families cope with children’s disabilities. Statistics indicate that five per cent of Canadian children aged five to 14 years have a disability, and 74 per cent of these are identified as having a neurodevelopmental condition and disability. A number of factors must be taken into account when choosing a source of survey data, including definitions of neurodevelopmental conditions, the target group covered by the survey, which special populations are included or excluded, along with a comparison group, and the survey’s design. Surveys fall into categories such as general health, disability-specific, and children and youth. They provide an excellent opportunity to look at the socioeconomic factors associated with the health of individuals, as well as how these conditions and disabilities affect families. However rich the information gleaned from survey data, it is not enough, especially given the data gaps that exist around the health and well-being of children and older youths. This is where administrative and other data can be used to complement existing data sources. Administrative data offer specific information about neurological conditions that won’t be collected in general population surveys, given the nature of such surveys. While researchers can glean information from survey data such as functional health and disability, social inclusion or exclusion, and the role of social determinants in the lives of these children and their families, administrative data can identify rare neurodevelopmental conditions and disabilities not captured in general surveys. Analyzing information from all these sources can lead to a more nuanced understanding of the economic and social impacts, and functional limitations in daily living, that patients and their families experience with certain neurodevelopmental conditions and disabilities. Statistics Canada surveys offer a plethora of information for researchers interested in neurodevelopmental disabilities and social determinants of health. As these surveys are national in their scope, they provide a wealth of information for statistical analysis from people across Canada. This information can be used to inform researchers, policy makers, and families of people who live with neurodevelopmental conditions and disabilities. For example, sophisticated microsimulation modelling techniques have been conducted to project the health and economic impacts from such disabilities 20 years into the future. Such projections will be vital for policy-makers tasked with designing services and programs to assist these people. Much work remains to be done, however. Statistics Canada has already begun working on the potential for using administrative data to conceptualize childhood disability, as well as using data that has been anonymized in national administrative databases to study the health of Canada’s children. These are excellent bases from which to build future research

Participation in Physical Activity for Children with Neurodevelopmental Disorders

The purpose of this study was to compare rates of participation for children (4–9 years of age) with neurodevelopmental disorders (NDDs) with and without externalizing behavior problems (EBPs) with children without disability and to examine mediators of the relation between disability and physical activity participation. Data for this study were drawn from Cycle 7 (2006-07) of the Canadian National Longitudinal Survey of Children and Youth (NLSCY). The frequency of children's participation in organized sports or physical activities varied depending on the child's health condition with children with NDDs and both NDDs and EBPs participating least in organized sports or physical activities followed by children with EBPs only. In contrast, there were no statistically significant differences by health group for children's participation in unorganized sports or physical activities. These differences remained even after controlling for the effects of other child and family sociodemographic characteristics, except for children with EBPs only. These findings highlight the importance of considering children's primary and other existing health conditions as well as family sociodemographic characteristics in order to better understand the factors that influence participation in organized physical activities for children with disabilities

Reply to Comment on "Completely positive quantum dissipation"

This is the reply to a Comment by R. F. O'Connell (Phys. Rev. Lett. 87 (2001) 028901) on a paper written by the author (B. Vacchini, ``Completely positive quantum dissipation'', Phys.Rev.Lett. 84 (2000) 1374, arXiv:quant-ph/0002094).Comment: 2 pages, revtex, no figure

Symmetry and Temperature dependence of the Order parameter in MgB2 from point contact measurements

We have performed differential conductance versus voltage measurements of Au/MgB2 point contacts. We find that the dominant component in the conductance is due to Andreev reflection. The results are fitted to the theoretical model of BTK for an s-wave symmetry from which we extract the value of the order parameter (Delta) and its temperature dependence. From our results we also obtain a lower experimental bound on the Fermi velocity in MgB2.Comment: 7 pages (Including figure captions) and 4 figure

Local and macroscopic tunneling spectroscopy of Y(1-x)CaxBa2Cu3O(7-d) films: evidence for a doping dependent is or idxy component in the order parameter

Tunneling spectroscopy of epitaxial (110) Y1-xCaxBa2Cu3O7-d films reveals a doping dependent transition from pure d(x2-y2) to d(x2-y2)+is or d(x2-y2)+idxy order parameter. The subdominant (is or idxy) component manifests itself in a splitting of the zero bias conductance peak and the appearance of subgap structures. The splitting is seen in the overdoped samples, increases systematically with doping, and is found to be an inherent property of the overdoped films. It was observed in both local tunnel junctions, using scanning tunneling microscopy (STM), and in macroscopic planar junctions, for films prepared by either RF sputtering or laser ablation. The STM measurements exhibit fairly uniform splitting size in [110] oriented areas on the order of 10 nm2 but vary from area to area, indicating some doping inhomogeneity. U and V-shaped gaps were also observed, with good correspondence to the local faceting, a manifestation of the dominant d-wave order parameter

Scanning tunneling spectroscopy of a-axis YBa_2Cu_3O_7-\delta films:k-selectivity and the shape of the superconductor

Tunneling spectroscopy of epitaxial (100) oriented \chem{YBa_2Cu_3O_{7-\delta}} films was performed using an STM at 4.2 K. On atomically smooth areas, tunneling spectra revealing clear U-shaped gaps with relatively low zero bias conductance were measured. These spectra can be well fitted to the tunneling theory into a d-wave superconductor only when introducing a strong dependence of the tunneling probability on the wave-vector \emph{\textbf{k}}. Possible origins for this \emph{\textbf{k}}-selectivity in STM measurements will be discussed. On other areas, V-shaped gaps as well as zero bias conductance peaks are observed, indicating relaxation of \emph{\textbf{k}}-selectivity and the effect of nanofaceting, respectively.Comment: 7 epl pages, 4 embeded figure