21,323 research outputs found
Thin Films of 3He -- Implications on the Identification of 3 He -A
Recently the identification of 3He-A with the axial state has been
questioned. It is suggested that the A-phase can actually be in the axiplanar
state. We point out in the present paper that experiments in a film geometry
may be useful to distinguish the above two possibilities. In particular a
second order phase transition between an axial and an axiplanar state would
occur as a function of thickness or temperature.Comment: 3 pages, no figures latex- revtex aps accepted by J. of Low
Temperature Physic
First-principles characterization of ferromagnetic Mn5Ge3 for spintronic applications
In the active search for potentially promising candidates for spintronic
applications, we focus on the intermetallic ferromagnetic Mn5Ge3 compound and
perform accurate first-principles FLAPW calculations within density functional
theory. Through a careful investigation of the bulk electronic and magnetic
structure, our results for the total magnetization, atomic magnetic moments,
metallic conducting character and hyperfine fields are found to be in good
agreement with experiments, and are elucidated in terms of a hybridization
mechanism and exchange interaction. In order to assess the potential of this
compound for spin-injection purposes, we calculate Fermi velocities and degree
of spin-polarization; our results predict a rather high spin-injection
efficiency in the diffusive regime along the hexagonal c-axis. Magneto-optical
properties, such as L_2,3 X-ray magnetic circular dichroism, are also reported
and await comparison with experimental data.Comment: 10 pages with 6 figures, to appear in Phys. Rev.
Fouling mechanisms in constant flux crossflow ultrafiltration
Four fouling models due to Hermia (complete pore blocking, intermediate pore blocking, cake filtration and standard pore blocking), have long been used to describe membrane filtration and fouling in constant transmembrane pressure (ΔP) operation of membranes. A few studies apply these models to constant flux dead-end filtration systems. However, these models have not been reported for constant flux crossflow filtration, despite the frequent use of this mode of membrane operation in practical applications. We report derivation of these models for constant flux crossflow filtration. Of the four models, complete pore blocking and standard pore blocking were deemed inapplicable due to contradicting assumptions and relevance, respectively. Constant flux crossflow fouling experiments of dilute latex bead suspensions and soybean oil emulsions were conducted on commercial poly (ether sulfone) flat sheet ultrafiltration membranes to explore the models’ abilities to describe such data. A model combining intermediate pore blocking and cake filtration appeared to give the best agreement with the experimental data. Below the threshold flux, both the intermediate pore blocking model and the combined model fit the data well. As permeate flux approached and passed the threshold flux, the combined model was required for accurate fits. Based on this observation, a physical interpretation of the threshold flux is proposed: the threshold flux is the flux below which cake buildup is negligible and above which cake filtration becomes the dominant fouling mechanism
Network Structure, Topology and Dynamics in Generalized Models of Synchronization
We explore the interplay of network structure, topology, and dynamic
interactions between nodes using the paradigm of distributed synchronization in
a network of coupled oscillators. As the network evolves to a global steady
state, interconnected oscillators synchronize in stages, revealing network's
underlying community structure. Traditional models of synchronization assume
that interactions between nodes are mediated by a conservative process, such as
diffusion. However, social and biological processes are often non-conservative.
We propose a new model of synchronization in a network of oscillators coupled
via non-conservative processes. We study dynamics of synchronization of a
synthetic and real-world networks and show that different synchronization
models reveal different structures within the same network
Half-metallicity and efficient spin injection in AlN/GaN:Cr (0001) heterostructure
First-principles investigations of the structural, electronic and magnetic
properties of Cr-doped AlN/GaN (0001) heterostructures reveal that Cr
segregates into the GaN region, that these interfaces retain their important
half-metallic character and thus yield efficient (100 %) spin polarized
injection from a ferromagnetic GaN:Cr electrode through an AlN tunnel barrier -
whose height and width can be controlled by adjusting the Al concentration in
the graded bandgap engineered Al(1-x)Ga(x)N (0001) layers.Comment: submitted for publicatio
Magnetically Mediated Transparent Conductors: InO doped with Mo
First-principles band structure investigations of the electronic, optical and
magnetic properties of Mo-doped InO reveal the vital role of magnetic
interactions in determining both the electrical conductivity and the
Burstein-Moss shift which governs optical absorption. We demonstrate the
advantages of the transition metal doping which results in smaller effective
mass, larger fundamental band gap and better overall optical transmission in
the visible -- as compared to commercial Sn-doped InO. Similar behavior
is expected upon doping with other transition metals opening up an avenue for
the family of efficient transparent conductors mediated by magnetic
interactions
Casorati Determinant Form of Dark Soliton Solutions of the Discrete Nonlinear Schr\"odinger Equation
It is shown that the -dark soliton solutions of the integrable discrete
nonlinear Schr\"odinger (IDNLS) equation are given in terms of the Casorati
determinant. The conditions for reduction, complex conjugacy and regularity for
the Casorati determinant solution are also given explicitly. The relationship
between the IDNLS and the relativistic Toda lattice is discussed.Comment: First version was uploaded in 23 Jun 2005. Published in Journal of
the Physical Society of Japan in May, 200
Role of Coulomb correlation on magnetic and transport properties of doped manganites: La0.5Sr0.5MnO3 and LaSr2Mn2O7
Results of LSDA and LSDA+U calculations of the electronic structure and
magnetic configurations of the 50% hole-doped pseudocubic perovskite
La0.5Sr0.5MnO3 and double layered LaSr2Mn2O7 are presented. We demonstrate that
the on-site Coulomb correlation (U) of Mn d electrons has a very different
influence on the (i) band formations, (ii) magnetic ground states, (iii)
interlayer exchange interactions, and (iv) anisotropy of the electrical
transport in these two manganites. A possible reason why the LSDA failures in
predicting observed magnetic and transport properties of the double layered
compound - in contrast to the doped perovskite manganite - is considered on the
basis of a p-d hybridization analysis.Comment: 11 pages, 3 figure
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