56,320 research outputs found
Magnetotransport in polycrystalline LaSrMnO thin films of controlled granularity
Polycrystalline LaSrMnO (LSMO) thin films were
synthesized by pulsed laser ablation on single crystal (100) yttria-stabilized
zirconia (YSZ) substrates to investigate the mechanism of magneto-transport in
a granular manganite. Different degrees of granularity is achieved by using the
deposition temperature (T) of 700 and 800 C. Although no
significant change in magnetic order temperature (T) and saturation
magnetization is seen for these two types of films, the temperature and
magnetic field dependence of their resistivity ((T, H)) is strikingly
dissimilar. While the (T,H) of the 800 C film is comparable to that
of epitaxial samples, the lower growth temperature leads to a material which
undergoes insulator-to-metal transition at a temperature (T 170
K) much lower than T. At T T, the resistivity is characterized by
a minimum followed by ln \emph{T} divergence at still lower temperatures. The
high negative magnetoresistance ( 20) and ln \emph{T} dependence
below the minimum are explained on the basis of Kondo-type scattering from
blocked Mn-spins in the intergranular material. Further, a striking feature of
the T = 700 C film is its two orders of magnitude larger anisotropic
magnetoresistance (AMR) as compared to the AMR of epitaxial films. We attribute
it to unquenching of the orbital angular momentum of 3d electrons of Mn ions in
the intergranular region where crystal field is poorly defined.Comment: 26 pages, 7 figure
Reply on `comment on our paper `Single two-level ion in an anharmonic-oscillator trap: Time evolution of the Q function and population inversion ''
We show here that the model Hamiltonian used in our paper for ion vibrating
in a q-analog harmonic oscillator trap and interacting with a classical
single-mode light field is indeed obtained by replacing the usual bosonic
creation and annihilation operators of the harmonic trap model by their
q-deformed counterparts. The approximations made in our paper amount to using
for the ion-laser interaction in a q-analog harmonic oscillator trap, the
operator F_{q}=exp{-(|\epsilon|^2}/2)}exp{i\epsilon A^{\dagger}}exp{i\epsilon
A}, which is analogous to the corresponding operator for ion in a harmonic
oscillator trap that is . In our article we do not claim to have diagonalized the
operator, , for which the basis states
|g,m> and |e,m> are not analytic vectors.Comment: Revtex, 4pages. To be Published in Physical Review A59, NO.4(April
99
ANALYZING TECHNICAL AND ECONOMIC INTERRELATIONSHIPS IN HAWAII'S LONGLINE FISHERY
This paper provides an analysis of technical and economic interrelationships among species harvested in Hawaii's pelagic longline fishery. The results indicate that this multispecies fishery is characterized by a joint production process, meaning that the regulation of one species would affect the harvest of other species. It implies that a single species regulation may not be appropriate in managing the longline fishery. Estimates of own-price output supply elasticities suggest that fisher's decisions on the amounts of each species harvested are independent of own expected prices. However, as evidenced by the estimates of cross-price elasticities, there are a number of significant technical-economic interactions among species. Failing to reject the null hypothesis of input-output separability suggests that management of the entire fishery as a whole by partial area/seasonal closure or by a 'limited entry' system as in the past is justified instead of regulating a few key species.Resource /Energy Economics and Policy,
Decays of bottom mesons emitting tensor meson in final state using ISGW II model
In this paper, we investigate phenomenologically two-body weak decays of the
bottom mesons emitting pseudoscalar/vector meson and a tensor meson. Form
factors are obtained using the improved ISGW II model. Consequently, branching
ratios for the CKM-favored and CKM-suppressed decays are calculated.Comment: 32 pages, to be published in Phys. Rev.
Linear and Nonlinear Optical Properties of Graphene Quantum Dots: A Computational Study
Due to the advantage of tunability via size, shape, doping and relatively low
level of loss and high extent of spatial confinement, graphene quantum dots
(GQDs) are emerging as an effective way to control light by molecular
engineering. The collective excitation in GQDs shows both high energy plasmon
frequency along with frequencies in the terahertz (THz) region making these
systems powerful materials for photonic technologies. Here, we report a
systematic study of the linear and nonlinear optical properties of large
varieties of GQDs (400 systems) in size and topology utilizing the strengths of
both semiempirical and first-principles methods. Our detailed study shows how
the spectral shift and trends in the optical nonlinearity of GQDs depends on
their structure, size and shape. Among the circular, triangular, stripe, and
random shaped GQDs, we find that GQDs with inequivalent sublattice atoms always
possess lower HOMO-LUMO gap, broadband absorption and high nonlinear optical
coefficients. Also, we find that for majority of the GQDs with interesting
linear and nonlinear optical properties have zigzag edges, although reverse is
not always true. We strongly believe that our findings can act as guidelines to
design GQDs in optical parametric oscillators, higher harmonic generators and
optical modulators.Comment: 21 pages, 11 figures, 4 table
Electrochemical incineration of wastes
The novel technology of waste removal in space vehicles by electrochemical methods is presented to convert wastes into chemicals that can be eventually recycled. The important consideration for waste oxidation is to select a right kind of electrode (anode) material that should be stable under anodic conditions and also a poor electrocatalyst for oxygen and chlorine evolution. On the basis of long term electrolysis experiments on seven different electrodes and on the basis of total organic carbon reduced, two best electrodes were identified. The effect of redox ions on the electrolyte was studied. Though most of the experiments were done in mixtures of urine and waste, the experiments with redox couples involved 2.5 M sulfuric acid in order to avoid the precipitation of redox ions by urea. Two methods for long term electrolysis of waste were investigated: (1) the oxidation on Pt and lead dioxide electrodes using the galvanostatic methods; and (2) potentiostatic method on other electrodes. The advantage of the first method is the faster rate of oxidation. The chlorine evolution in the second method is ten times less then in the first. The accomplished research has shown that urine/feces mixtures can be oxidized to carbon dioxide and water, but current densities are low and must be improved. The perovskite and Ti4O7 coated with RuO2 are the best electrode materials found. Recent experiment with the redox agent improves the current density, however, sulphuric acid is required to keep the redox agent in solution to enhance oxidation effectively. It is desirable to reduce the use of acid and/or find substitutes
Driven diffusive systems with mutually interactive Langmuir kinetics
We investigate the simple one-dimensional driven model, the totally
asymmetric exclusion process, coupled to mutually interactive Langmuir
kinetics. This model is motivated by recent studies on clustering of motor
proteins on microtubules. In the proposed model, the attachment and detachment
rates of a particle are modified depending upon the occupancy of neighbouring
sites. We first obtain continuum mean-field equations and in certain limiting
cases obtain analytic solutions. We show how mutual interactions increase
(decrease) the effects of boundaries on the phase behavior of the model. We
perform Monte Carlo simulations and demonstrate that our analytical
approximations are in good agreement with the numerics over a wide range of
model parameters. We present phase diagrams over a selective range of
parameters.Comment: 9 pages, 8 Figure
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