35 research outputs found
Core pinning by intragranular nanoprecipitates in polycrystalline MgCNi_3
The nanostructure and magnetic properties of polycrystalline MgCNi_3 were
studied by x-ray diffraction, electron microscopy, and vibrating sample
magnetometry. While the bulk flux-pinning force curve F_p(H) indicates the
expected grain-boundary pinning mechanism just below T_c = 7.2 K, a systematic
change to pinning by a nanometer-scale distribution of core pinning sites is
indicated by a shift of F_p(H) with decreasing temperature. The lack of scaling
of F_p(H) suggests the presence of 10 to 20% of nonsuperconducting regions
inside the grains, which are smaller than the diameter of fluxon cores 2xi at
high temperature and become effective with decreasing temperature when xi(T)
approaches the nanostructural scale. Transmission electron microscopy revealed
cubic and graphite nanoprecipitates with 2 to 5 nm size, consistent with the
above hypothesis since xi(0) = 6 nm. High critical current densities, more than
10^6 A/cm^2 at 1 T and 4.2 K, were obtained for grain colonies separated by
carbon. Dirty-limit behavior seen in previous studies may be tied to electron
scattering by the precipitates, indicating the possibility that strong core
pinning might be combined with a technologically useful upper critical field if
versions of MgCNi_3 with higher T_c can be found.Comment: 5 pages, 6 figures, submitted to PR
The Determinants of young Adult Social well-being and Health (DASH) study: diversity, psychosocial determinants and health.
Purpose: The Determinants of young Adult Social well-being and Health longitudinal study draws on life-course models to understand ethnic differences in health. A key hypothesis relates to the role of psychosocial factors in nurturing the health and well-being of ethnic minorities growing up in the UK. We report the effects of culturally patterned exposures in childhood. Methods: In 2002/2003, 6643 11â13 year olds in London, ~80 % ethnic minorities, participated in the baseline survey. In 2005/2006, 4782 were followed-up. In 2012â2014, 665 took part in a pilot follow-up aged 21â23 years, including 42 qualitative interviews. Measures of socioeconomic and psychosocial factors and health were collected. Results: Ethnic minority adolescents reported better mental health than White British, despite more adversity (e.g. economic disadvantage, racism). It is unclear what explains this resilience but findings support a role for cultural factors. Racism was an adverse influence on mental health, while family care and connectedness, religious involvement and ethnic diversity of friendships were protective. While mental health resilience was a feature throughout adolescence, a less positive picture emerged for cardio-respiratory health. Both, mental health and cultural factors played a role. These patterns largely endured in early 20s with family support reducing stressful transitions to adulthood. Education levels, however, signal potential for socio-economic parity across ethnic groups
The Flux-Line Lattice in Superconductors
Magnetic flux can penetrate a type-II superconductor in form of Abrikosov
vortices. These tend to arrange in a triangular flux-line lattice (FLL) which
is more or less perturbed by material inhomogeneities that pin the flux lines,
and in high- supercon- ductors (HTSC's) also by thermal fluctuations. Many
properties of the FLL are well described by the phenomenological
Ginzburg-Landau theory or by the electromagnetic London theory, which treats
the vortex core as a singularity. In Nb alloys and HTSC's the FLL is very soft
mainly because of the large magnetic penetration depth: The shear modulus of
the FLL is thus small and the tilt modulus is dispersive and becomes very small
for short distortion wavelength. This softness of the FLL is enhanced further
by the pronounced anisotropy and layered structure of HTSC's, which strongly
increases the penetration depth for currents along the c-axis of these uniaxial
crystals and may even cause a decoupling of two-dimensional vortex lattices in
the Cu-O layers. Thermal fluctuations and softening may melt the FLL and cause
thermally activated depinning of the flux lines or of the 2D pancake vortices
in the layers. Various phase transitions are predicted for the FLL in layered
HTSC's. The linear and nonlinear magnetic response of HTSC's gives rise to
interesting effects which strongly depend on the geometry of the experiment.Comment: Review paper for Rep.Prog.Phys., 124 narrow pages. The 30 figures do
not exist as postscript file
Evolutionary Processes, Moral Luck, and the Ethical Responsibilities of the Manager
The article of record as published may be located at http://dx.doi.org/10.1007/s10551-009-0071-7The responsibilities of the manager have
been examined through several lenses in the business
ethics literature: Kantian (Bowie, 1999), contractarian
(Donaldson and Dunfee, 1999), consequentialist (Friedman,
1970), and virtue ethics (Solomon,1992), to name
just four. This paper explores what the ethical responsibilities
of the manager would look like if viewed through
an evolutionary lens. Discussion is focused on the impact
of evolutionary thinking on the process of moral reasoning,
rather than on the sources or the substance of
morality. The conclusion is reached that the evolutionary
lens supports the view that moral luck plays an important
role in how we assign ethical responsibilities
Innovations, Stakeholders & Entrepreneurship
effectuation, entrepreneurship, innovation, stakeholder,