3,267 research outputs found
Anomalous Anisotropic Magnetoresistance in Heavy-Fermion PrFe4P12
We have investigated the anisotropy of the magnetoresistance in the Pr-based
HF compound PrFe4P12. The large anisotropy of effective mass and its strong
field dependence have been confirmed by resistivity measurements. Particularly
for H||[111], where the effective mass is most strongly enhanced, the non-Fermi
liquid behavior has been observed. Also, we have found the angular dependence
of the magnetoresistance sharply enhanced at H||[111], which is evidently
correlated with both the non-Fermi liquid behavior and the high-field ordered
state (B-phase).Comment: 3 pages, 3 figures. J. Phys. Soc. Jpn. Vol.77, No.8, in pres
Drastic change in transport of entropy with quadrupolar ordering in PrFeP
The antiferroquadrupolar ordering of PrFeP is explored by
probing thermal and thermoelectric transport. The lattice thermal conductivity
drastically increases with the ordering, as a consequence of a large drop in
carrier concentration and a strong electron-phonon coupling. The low level of
carrier density in the ordered state is confirmed by the anomalously large
values of the Seebeck and Nernst coefficients. The results are reminiscent of
URuSi and suggest that both belong to the same class of aborted
metal-insulator transitions. The magnitude of the Nernst coefficient, larger
than in any other metal, indicates a new route for Ettingshaussen cooling at
Kelvin temperatures.Comment: final published versio
Water immersion increases the concentration of the immunoreactive N-terminal fragment of pro-atrial natriuretic factor in human plasma
Atrial natriuretic factor (ANF) N-terminal (ANF 1–98) and C-terminal (ANF 99–126) fragments were determined by radioimmunoassay in human plasma. Mean basal plasma ANF N-terminal concentrations in 9 healthy subjects were 461 ± 58 fmol/ml,significantly (p<0.0001) higher than ANF C-terminal concentrations ( 4.8 ± 0.5 fmol/ml). Central volume stimulation by one hour head-out water immersion (WI) induced a significant (p<0.01) increase of the C-terminal peptide levels to 11.6 ± 2.3 fmol/ml,paralleled by a significant (p<0.001) increase of the N-terminal fragment levels to 749 ± 96 fmol/ml. Increases of plasma concentrations of both fragments upon WI correlated significantly (r=0.71;p<0.05). These data suggest cosecretion of the N-terminal fragment with the C-terminal fragment of pro ANF 1–126 following a physiological stimulus of ANF release in man
D-branes in T-fold conformal field theory
We investigate boundary dynamics of orbifold conformal field theory involving
T-duality twists. Such models typically appear in contexts of non-geometric
string compactifications that are called monodrofolds or T-folds in recent
literature. We use the framework of boundary conformal field theory to analyse
the models from a microscopic world-sheet perspective. In these backgrounds
there are two kinds of D-branes that are analogous to bulk and fractional
branes in standard orbifold models. The bulk D-branes in T-folds allow
intuitive geometrical interpretations and are consistent with the classical
analysis based on the doubled torus formalism. The fractional branes, on the
other hand, are `non-geometric' at any point in the moduli space and their
geometric counterparts seem to be missing in the doubled torus analysis. We
compute cylinder amplitudes between the bulk and fractional branes, and find
that the lightest modes of the open string spectra show intriguing non-linear
dependence on the moduli (location of the brane or value of the Wilson line),
suggesting that the physics of T-folds, when D-branes are involved, could
deviate from geometric backgrounds even at low energies. We also extend our
analysis to the models with SU(2) WZW fibre at arbitrary levels.Comment: 38 pages, no figure, ams packages. Essentially the published versio
Social Workers in International Relief and Development: A Natural Fit
This study sought to examine the compatibility between social work competencies with humanitarian assistance job skills requirements in the market. A systematic analysis of international job descriptions (N=500) was conducted with a focus on the skills required of potential employees. The main themes identified and operationalized into discrete skills and/or behaviors were: technical expertise, intra- and extra-organizational competencies, personal abilities, sector specialization, education, and language requirements. To aid educators in curriculum building, the identified skills were cross-referenced with the Council on Social Work Education’s Education Policy and Accreditation Standards practice behaviors to determine how they translate into standardized competencies. The study offers important implications for social work education and discusses several venues for social work employment in international relief and development careers. [AUTHOR ABSTRACT
Exotic Heavy Fermion State in the Filled Skutterudite PrFeP Uncovered by the de Haas-van Alphen Effect
We report the de Haas-van Alphen (dHvA) experiment on the filled skutterudite
PrFeP exhibiting apparent Kondo-like behaviors in the transport and
thermal properties. We have found enormously enhanced cyclotron effective mass
in the high field phase (HFP), which
indicates that PrFeP is the first Pr-compound in which really heavy
mass has been unambiguously confirmed. Also in the low field non-magnetic
ordered phase (LOP), we observed the dHvA branch with that is quite heavy taking into account its small Fermi surface volume
(0.15% of the Brillouin zone size). The insensitivity of mass in LOP against
the magnetic field suggests that the quadrupolar interaction plays a main role
both in the mass renormalization and the LOP formation.Comment: 5 pages, 5 figures, Phys. Rev. B (01 October 2002) in pres
Magnetic anisotropy, first-order-like metamagnetic transitions and large negative magnetoresistance in the single crystal of GdPdSi
Electrical resistivity (), magnetoresistance (MR), magnetization,
thermopower and Hall effect measurements on the single crystal
GdPdSi, crystallizing in an AlB-derived hexagonal structure are
reported. The well-defined minimum in at a temperature above N\'eel
temperature (T= 21 K) and large negative MR below 3T, reported
earlier for the polycrystals, are reproducible even in single crystals. Such
features are generally uncharacteristic of Gd alloys. In addition, we also
found interesting features in other data, e.g., two-step first-order-like
metamagnetic transitions for the magnetic field along [0001] direction. The
alloy exhibits anisotropy in all these properties, though Gd is a S-state ion.Comment: RevTeX, 5 pages, 6 encapsulated postscript figures; scheduled to be
published in Phy. Rev. B (01 November 1999, B1
Domain walls in (Ga,Mn)As diluted magnetic semiconductor
We report experimental and theoretical studies of magnetic domain walls in an
in-plane magnetized (Ga,Mn)As dilute moment ferromagnetic semiconductor. Our
high-resolution electron holography technique provides direct images of domain
wall magnetization profiles. The experiments are interpreted based on
microscopic calculations of the micromagnetic parameters and
Landau-Lifshitz-Gilbert simulations. We find that the competition of uniaxial
and biaxial magnetocrystalline anisotropies in the film is directly reflected
in orientation dependent wall widths, ranging from approximately 40 nm to 120
nm. The domain walls are of the N\'eel type and evolve from near-
walls at low-temperatures to large angle [10]-oriented walls and small
angle [110]-oriented walls at higher temperatures.Comment: 5 pages, 4 figure
Observation of Fermi-surface-dependent nodeless superconducting gaps in Ba0.6K0.4Fe2As2
The recent discovery of superconductivity in iron-arsenic compounds below a
transition temperature (Tc) as high as 55K ended the monopoly of copper oxides
(cuprates) in the family of high-Tc superconductors. A critical issue in
understanding this new superconductor, as in the case of cuprates, is the
nature, in particular the symmetry and orbital dependence, of the
superconducting gap. There are conflicting experimental results, mostly from
indirect measurements of the low energy excitation gap, ranging from one gap to
two gaps, from line nodes to nodeless gap function in momentum space. Here we
report a direct observation of the superconducting gap, including its momentum,
temperature, and Fermi surface (FS) dependence in Ba0.6K0.4Fe2As2 (Tc = 37 K)
using angle-resolved photoelectron spectroscopy. We find two superconducting
gaps with different values: a large gap (~ 12 meV) on the two small hole-like
and electron-like FS sheets, and a small gap (~ 6 meV) on the large hole-like
FS. Both gaps, closing simultaneously at the bulk Tc, are nodeless and nearly
isotropic around their respective FS sheets. The isotropic pairing interactions
are strongly orbital dependent, as the ratio 2Delta/kBTc switches from weak to
strong coupling on different bands. The same and surprisingly large
superconducting gap due to strong pairing on the two small FS, which are
connected by the (pi, 0) spin-density-wave vector in the parent compound,
strongly suggests that the pairing mechanism originates from the inter-band
interactions between these two nested FS sheets.Comment: 4 figure
Unusual behaviors in the transport properties of REFeP (RE: La, Ce, Pr, and Nd)
We have investigated the resistivity (), thermoelectric power (TEP) and
Hall coefficient () on high quality single crystals of
REFeP. TEP in CeFeP is extremely large (
0.5mV/K at 290K) with a peak of 0.75mV/K at around 65K. The Hall
mobility also shows a peak at 65K, suggesting carriers with heavy masses
developed at lower temperatures related with the f-hybridized band. Both Pr-
and Nd- systems exhibit an apparent increase of with decreasing
temperature far above their magnetic transition temperatures. In the same
temperature ranges, TEP exhibits unusually large absolute values of -50V/K
for PrFeP and -15V/K for NdFeP, respectively.
For PrFeP, such anomalous transport properties suggest an unusual
ground state, possibly related with the Quadrupolar Kondo effect.Comment: 5 pages, 8 figure
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