1,060 research outputs found
Cross-Border Investment, Conflict of Laws, and the Privatization of Securities Law
The rapid acceleration of transnational investing is occurring in an environment in which emerging markets, and foreign interest in these markets, are exploding. The issues involved with cross-border investment, conflict of laws and the privatization of securities law are examined
Aging Effect in Ceramic Superconductors
A three-dimensional lattice of the Josephson junctions with a finite
self-conductance is employed to model ceramic superconductors. Using Monte
Carlo simulations it is shown that the aging disappears in the strong screening
limit. In the weeak screening regime aging is present even at low temperatures.
For intermediate values of the self-inductance aging occurs at intermediate
temperatures interval but is suppressed entirely at high and low temperatures.
Our results are in good agreement with experiments.Comment: 5 pages, 5 eps figures, to appear in Physical Review Letter
Paramagnetic Meissner Effect in Multiply-Connected Superconductors
We have measured a paramagnetic Meissner effect in Nb-Al2O3-Nb Josephson
junction arrays using a scanning SQUID microscope. The arrays exhibit
diamagnetism for some cooling fields and paramagnetism for other cooling
fields. The measured mean magnetization is always less than 0.3 flux quantum
(in terms of flux per unit cell of the array) for the range of cooling fields
investigated. We demonstrate that a new model of magnetic screening, valid for
multiply-connected superconductors, reproduces all of the essential features of
paramagnetism that we observe and that no exotic mechanism, such as d-wave
superconductivity, is needed for paramagnetism.Comment: 4 pages, 3 figures, LaTe
Second harmonics and compensation effect in ceramic superconductors
A three-dimensional lattice of the Josephson junctions with a finite
self-conductance is employed to model the ceramic superconductors. The
nonlinear ac susceptibility and the compensation effect are studied by Monte
Carlo simulations in this model. The compensation effect is shown to be due to
the existence of the chiral glass phase. We demonstrate, in agreement with
experiments, that this effect may be present in the ceramic superconductors
which show the paramagnetic Meissner effect.Comment: 6 pages, latex, 4 figures, Phys. Rev. B (accepted
Design of Proportional-Resonant Control for Current Harmonic Compliance in Electric Railway Power Systems
This paper presents the process of designing proportional-resonant controller for a four-quadrant rectifier in electric railway traction system. In the context of ever-stricter power quality and electromagnetic compatibility standards in electric railway power systems, developers of electric locomotives need to adapt with new ways to comply. This paper develops on the process of designing a four-quadrant rectifier proportional-resonant control for mitigation of low frequency current harmonic distortion, a novel method in the field of railway EMC. The control parameters are determined through analytical modeling of the rectifier through transfer functions. For the purpose of studying the harmonic distortion mitigation effects, only the current control loop was modeled and designed. The modeling starts with simplification of the model via large-signal modeling of the power converter. The parameters of the circuit then were used to develop the transfer functions, and select the appropriate parameter values of the current loop plant. The control loop and parameters were evaluated on test locomotive to validate the control, with results confirming the improved impact on the electromagnetic compatibility and conformity to regulation
The origin of paramagnetic magnetization in field-cooled YBa2Cu3O7 films
Temperature dependences of the magnetic moment have been measured in
YBa_2Cu_3O_{7-\delta} thin films over a wide magnetic field range (5 <= H <=
10^4 Oe). In these films a paramagnetic signal known as the paramagnetic
Meissner effect has been observed. The experimental data in the films, which
have strong pinning and high critical current densities (J_c ~ 2 \times 10^6
A/cm^2 at 77 K), are quantitatively shown to be highly consistent with the
theoretical model proposed by Koshelev and Larkin [Phys. Rev. B 52, 13559
(1995)]. This finding indicates that the origin of the paramagnetic effect is
ultimately associated with nucleation and inhomogeneous spatial redistribution
of magnetic vortices in a sample which is cooled down in a magnetic field. It
is also shown that the distribution of vortices is extremely sensitive to the
interplay of film properties and the real experimental conditions of the
measurements.Comment: RevTex, 8 figure
Three-dimensional flux states as a model for the pseudogap phase of transition metal oxides
We propose that the pseudogap state observed in the transition metal oxides
can be explained by a three-dimensional flux state, which exhibits
spontaneously generated currents in its ground state due to electron-electron
correlations. We compare the energy of the flux state to other classes of mean
field states, and find that it is stabilized over a wide range of and
. The signature of the state will be peaks in the neutron diffraction
spectra, the location and intensity of which are presented. The dependence of
the pseudogap in the optical conductivity is calculated based on the parameters
in the model.Comment: submitted to Phys. Rev. B on January 8, 200
Antiferromagnetic vs ferromagnetic interactions and spin-glass-like behavior in ruthenates
We have made a series of gradient-corrected relativistic full-potential
density-functional calculation for Ca-substituted and hole-doped SrRuO in
para, ferro, and -, -, and -type antiferromagnetic states. Magnetic
phase-diagram data for SrCaRuO at 0 K are presented. Neutron
diffraction measurement combined with total energy calculations show that
spin-glass behavior with short-range antiferromagnetic interactions rules in
CaRuO. The substitution of Sr by Ca in SrRuO decreases the
ferromagnetic interaction and enhances the -type antiferromagnetic
interaction; the -AF state is found to stabilize around = 0.75
consistent with experimental observations. Inclusion of spin-orbit coupling is
found to be important in order to arrive at the correct magnetic ground state
in ruthenates.Comment: 5 pages, 3 figures. Solid state communications (in press
Non-Fermi liquid behavior of SrRuO_3 -- evidence from infrared conductivity
The reflectivity of the itinerant ferromagnet SrRuO_3 has been measured
between 50 and 25,000 cm-1 at temperatures ranging from 40 to 300 K, and used
to obtain conductivity, scattering rate, and effective mass as a function of
frequency and temperature. We find that at low temperatures the conductivity
falls unusually slowly as a function of frequency (proportional to
\omega^{-1/2}), and at high temperatures it even appears to increase as a
function of frequency in the far-infrared limit. The data suggest that the
charge dynamics of SrRuO_3 are substantially different from those of
Fermi-liquid metals.Comment: 4 pages, 3 postscript figure
Extending colonic mucosal microbiome analysis - Assessment of colonic lavage as a proxy for endoscopic colonic biopsies
This study was supported through GI Research funds and MRC Grant Ref: MR/M00533X/1 to GH.Peer reviewedPublisher PD
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