1,236 research outputs found
The MiMeS Project: Magnetism in Massive Stars
The Magnetism in Massive Stars (MiMeS) Project is a consensus collaboration
among the foremost international researchers of the physics of hot, massive
stars, with the basic aim of understanding the origin, evolution and impact of
magnetic fields in these objects. The cornerstone of the project is the MiMeS
Large Program at the Canada-France-Hawaii Telescope, which represents a
dedication of 640 hours of telescope time from 2008-2012. The MiMeS Large
Program will exploit the unique capabilities of the ESPaDOnS spectropolarimeter
to obtain critical missing information about the poorly-studied magnetic
properties of these important stars, to confront current models and to guide
theory.Comment: 6 pages, 3 figures, proceedings of IAUS 259: Cosmic Magnetic Field
âBecoming a Familyâ: Developmental Processes Represented in Blended Family Discourse
We adopted a process-focus in order to gain a deeper understanding of how (step) blended family members experiencing different developmental pathways discursively represented their processes of becoming a family. Using a qualitative/interpretive method, we analyzed 980 pages of interview transcripts with stepparents and stepchildren. We studied the first four years of family development, using the five developmental pathways developed by Baxter, Braithwaite, and Nicholson (1999). Three salient issues identified in the family experiences were boundary management, solidarity, and adaptation. While the negotiation of these issues varied across the five trajectories, there were commonalities across family experiences that helped determine whether families had a successful experience of becoming a family. Implications for blended family researchers and practitioners are also discussed
Electric Pulse Induced Resistive Switching, Electronic Phase Separation, and Possible Superconductivity in a Mott insulator
Metal-insulator transitions (MIT) belong to a class of fascinating physical
phenomena, which includes superconductivity, and colossal magnetoresistance
(CMR), that are associated with drastic modifications of electrical resistance.
In transition metal compounds, MIT are often related to the presence of strong
electronic correlations that drive the system into a Mott insulator state. In
these systems the MIT is usually tuned by electron doping or by applying an
external pressure. However, it was noted recently that a Mott insulator should
also be sensitive to other external perturbations such as an electric field. We
report here the first experimental evidence of a non-volatile
electric-pulse-induced insulator-to-metal transition and possible
superconductivity in the Mott insulator GaTa4Se8. Our Scanning Tunneling
Microscopy experiments show that this unconventional response of the system to
short electric pulses arises from a nanometer scale Electronic Phase Separation
(EPS) generated in the bulk material.Comment: Highlight in Advanced Functional Materials 18, 1-4 (2008) doi :
10.1002/adfm.20080055
Statistics of Magnetic Fields for OB Stars
Based on an analysis of the catalog of magnetic fields, we have investigated
the statistical properties of the mean magnetic fields for OB stars. We show
that the mean effective magnetic field of a star can be used as a
statistically significant characteristic of its magnetic field. No correlation
has been found between the mean magnetic field strength and
projected rotational velocity of OB stars, which is consistent with the
hypothesis about a fossil origin of the magnetic field. We have constructed the
magnetic field distribution function for B stars, , that has a
power-law dependence on with an exponent of . We have
found a sharp decrease in the function F for {\cal B}\lem 400 G
that may be related to rapid dissipation of weak stellar surface magnetic
fields.Comment: 22 pages, 7 figures, accepted Astronomy Letters, 2010, vol.36, No.5,
pp.370-379, contact E-mail: [email protected]
How do Fermi liquids get heavy and die?
We discuss non-Fermi liquid and quantum critical behavior in heavy fermion
materials, focussing on the mechanism by which the electron mass appears to
diverge at the quantum critical point. We ask whether the basic mechanism for
the transformation involves electron diffraction off a quantum critical spin
density wave, or whether a break-down in the composite nature of the heavy
electron takes place at the quantum critical point. We show that the Hall
constant changes continously in the first scenario, but may ``jump''
discontinuously at a quantum critical point where the composite character of
the electron quasiparticles changes.Comment: Revised version with many new references added. To appear as a
topical review in Journal of Physics: Condensed Matter Physics. Two column
version http://www.physics.rutgers.edu/~coleman/online/questions.ps.g
CareTrack Australia: assessing the appropriateness of adult healthcare: protocol for a retrospective medical record review
Introduction: In recent years in keeping with international best practice, clinical guidelines for common conditions have been developed, endorsed and disseminated by peak national and professional bodies. Yet evidence suggests that there remain considerable gaps between the care that is regarded as appropriate by such guidelines and the care received by patients. With an ageing population and increasing treatment options and expectations, healthcare is likely to become unaffordable unless more appropriate care is provided. This paper describes a study protocol that seeks to determine the percentage of healthcare encounters in which patients receive appropriate care for 22 common clinical conditions and the reasons why variations exist from the perspectives of both patients and providers. Methods/design: A random stratified sample of at least 1000 eligible participants will be recruited from a representative cross section of the adult Australian population. Participants' medical records from the years 2009 and 2010 will be audited to assess the appropriateness of the care received for 22 common clinical conditions by determining the percentage of healthcare encounters at which the care provided was concordant with a set of 522 indicators of care, developed for these conditions by a panel of 43 disease experts. The knowledge, attitudes and beliefs of participants and healthcare providers will be examined through interviews and questionnaires to understand the factors influencing variations in care.Tamara D Hunt, Shanthi A Ramanathan, Natalie A Hannaford, Peter D Hibbert, Jeffrey Braithwaite, Enrico Coiera, Richard O Day, Johanna I Westbrook, William B Runcima
The Lorentz force in atmospheres of CP stars: Aurigae
Several dynamical processes may induce considerable electric currents in the
atmospheres of magnetic chemically peculiar (CP) stars. The Lorentz force,
which results from the interaction between the magnetic field and the induced
currents, modifies the atmospheric structure and induces characteristic
rotational variability of the hydrogen Balmer lines. To study this phenomena we
have initiated a systematic spectroscopic survey of the Balmer lines variation
in magnetic CP stars. In this paper we continue presentation of results of the
program focusing on the high-resolution spectral observations of A0p star \aur
(HD 40312). We have detected a significant variability of the H,
H, and H spectral lines during full rotation cycle of the star.
This variability is interpreted in the framework of the model atmosphere
analysis, which accounts for the Lorentz force effects. Both the inward and
outward directed Lorentz forces are considered under the assumption of the
axisymmetric dipole or dipole+quadrupole magnetic field configurations. We
demonstrate that only the model with the outward directed Lorentz force in the
dipole+quadrupole configuration is able to reproduce the observed hydrogen line
variation. These results present new strong evidences for the presence of
non-zero global electric currents in the atmosphere of an early-type magnetic
star.Comment: 10 figure
Turning Points in the Evolution of Isolated Neutron Stars' Magnetic Fields
During the life of isolated neutron stars (NSs) their magnetic field passes
through a variety of evolutionary phases. Depending on its strength and
structure and on the physical state of the NS (e.g. cooling, rotation), the
field looks qualitatively and quantitatively different after each of these
phases. Three of them, the phase of MHD instabilities immediately after NS's
birth, the phase of fallback which may take place hours to months after NS's
birth, and the phase when strong temperature gradients may drive thermoelectric
instabilities, are concentrated in a period lasting from the end of the
proto--NS phase until 100, perhaps 1000 years, when the NS has become almost
isothermal. The further evolution of the magnetic field proceeds in general
inconspicuous since the star is in isolation. However, as soon as the product
of Larmor frequency and electron relaxation time, the so-called magnetization
parameter, locally and/or temporally considerably exceeds unity, phases, also
unstable ones, of dramatic changes of the field structure and magnitude can
appear. An overview is given about that field evolution phases, the outcome of
which makes a qualitative decision regarding the further evolution of the
magnetic field and its host NS.Comment: References updated, typos correcte
Low-energy magnetic response of the noncentrosymmetric heavy-fermion superconductor CePt3Si studied via inelastic neutron scattering
The low-energy magnetic excitations of the noncentrosymmetric heavy-fermion
superconductor CePt3Si have been measured with inelastic neutron scattering on
a single crystal. Kondo-type spin fluctuations with an anisotropic wave vector
dependence are observed in the paramagnetic state. These fluctuations do not
survive in the antiferromagnetically ordered state below TN=2.2 K but are
replaced by damped spin waves, whose dispersion is much stronger along the
c-axis than in other directions. No change is observed in the excitation
spectrum or the magnetic order as the system enters the superconducting state
below Tc=0.7 K.Comment: Revised version: 8 pages, 7 figure
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