731 research outputs found
Long-Term Valuation of Oral Mavacoxib in Osteoarthrosic Dogs Using Force Platform Analysis
The aim of this study was to assess the efficacy of mavacoxib, a cox-2 inhibitor, to improve the peak vertical force (PVF) and vertical impulse (VI) of lame client-owned dogs with severe coxofemoral osteoarthrosis (OA) by using a force platform. A group of ten canarian presa dogs with lameness and pain for a severe osteoarthrosis due to hip dysplasia were used for this study. Five additional sound dogs of the same breed were used as control groups. A single force platform used to register vertical forces was mounted in a 7 m runway. Mean (± SD) values for speed of dogs were 1.6±0.5 m/s. Data corresponding with 5 valid trials were recorded at walk at day 0, 7, 60 and 180 after starting treatment procedure. The dosing regimen consisted of a loading oral dose of 2 mg⁄ kg to be repeated after 14 days, thereafter the dosing interval was 1 month. OA dogs showed a significant improvement of PVF after two months of about 7% bm in the force exerted by diseased limbs and a significant VI improvement after two months of about 1.6% bm in the VI exerted by diseased limbs. This study clearly showed that dogs treated with mavacoxib increased PVF over time, as soon as seven days after medical therapy, demonstrating a high potential for clinical use in the treatment of lameness associated with OA of hip joint
Photoemission Spectroscopy from Inhomogeneous Models of Cuprates
We investigate the electronic dynamics in the underdoped cuprates focusing on
the effects of one-dimensional charge stripes. We address recent experimental
Angular-Resolved Photoemission Spectra results on
(LaNdSr)CuO. We find that various inhomogeneous
models can account for the distribution of quasiparticle weights close to
momentum and symmetry related points. The observed flat
dispersion region around the same point can only be addressed by
certain classes of those inhomogeneous models which locally break spin
symmetry. Homogeneous models including hopping elements up to second neighbors
cannot reproduce the experimental quasiparticle weight, since most of it is
centered around .Comment: 5 pages, color figure
Primary structure and electrophysiological characterization of two almost identical isoforms of toxin from Isometrus vittatus (family: Buthidae) scorpion venom.
Two almost identical proteins with 70 amino acid residues each, closely packed by four disufide bridges, and molecular masses of 7899.5 and 7884.7 were isolated and sequenced from the venom of the scorpion Isometrus vittatus from Pakistan. They differ by an acidic amino acid residue (glutamic or aspartic) at the same position 55 of the peptide chain, however, they exhibit the same length, the same charge and are undistinguishable when separated by C(18) reverse phase HPLC. The mixture of the two proteins called IsomTx1 depolarizes the cockroach isolated axon; artificial repolarization is followed by sustained repetitive activity, artificial hyperpolarization facilitates bursting activity observed as an answer to rapid depolarization to -60 mV. The depolarization is antagonized by TTX. In voltage-clamp experiments IsomTx1 increases axonal sodium permeability which has a particular importance between resting and threshold potentials and moderately slows down the fast inactivation. These characteristics closely resemble those of other anti-insect scorpion toxins classified as contractive toxins from Androctonus and Buthotus venoms
Microalgae biomass interaction in byopolymer gelled systems
Microalgae are an enormous biological resource, representing one of the most promising sources for the
development of new food products and applications. Pea protein/k-carrageenan/starch gels, interesting
vegetarian alternatives to dairy desserts, served as model systems to study the addition of microalgal
biomass, its effect, and subsequent rheological behaviour. Spirulina and Haematococcus gels presented
a markedly different rheological behaviour compared to the control mixed biopolymer gelled system.
The present goal is to clarify how these microalgae affect the gelation and interact with each biopolymer
present in the complex mixed gel system. Hence, the aim of the present work is to study the effect of
Spirulina and Haematococcus microalgal biomass addition on the rheological behaviour of pea protein, k-
carrageenan and starch simple gels, as well as in pea protein/k-carrageenan and pea protein/starch
systems. The gelation process was monitored in-situ through dynamic oscillatory measurements
(temperature, time and frequency sweep tests) for a 24 h maturation period, and rheological results were
supported with uorescence optical microscopy observations. The addition of Spirulina and Haematococcus
to biopolymer gelled systems induced signi cant changes in the gels’ rheological behaviour and
microstructure. In general, it was observed that the gelling mechanism is ruled by the biopolymers, while
microalgae seem to be embedded in the gel network acting as active particle llers. The addition of
Haematococcus resulted in more structured gels in comparison to the control and Spirulina systems. In
the case of k-carrageenan gels, both microalgae induced a large increase in the rheological parameters,
which should be related to the high ionic content of microalgal biomass. Spirulina addition on starch
systems promoted a decrease in the gels’ rheological parameters. This should be related to the starch
gelatinization process, probably by competing for water binding zones during the granules’ hydration
proces
Stability of homogeneous magnetic phases in a generalized t-J model
We study the stability of homogeneous magnetic phases in a generalized t-J
model including a same-sublattice hopping t' and nearest-neighbor repulsion V
by means of the slave fermion-Schwinger boson representation of spin operators.
At mean-field order we find, in agreement with other authors, that the
inclusion of further-neighbor hopping and Coulomb repulsion makes the
compressibility positive, thereby stabilizing at this level the spiral and Neel
orders against phase separation. However, the consideration of Gaussian
fluctuation of order parameters around these mean-field solutions produces
unstable modes in the dynamical matrix for all relevant parameter values,
leaving only reduced stability regions for the Neel phase. We have computed the
one-loop corrections to the energy in these regions, and have also briefly
considered the effects of the correlated hopping term that is obtained in the
reduction from the Hubbard to the t-J model.Comment: 5 pages, 5 figures, Revte
Charge and spin inhomogeneous phases in the Ferromagnetic Kondo Lattice Model
We study numerically the one-dimensional ferromagnetic Kondo lattice. This
model is widely used to describe nickel and manganese perovskites. Due to the
competition between double and super-exchange, we find a region where the
formation of magnetic polarons induces a charge-ordered state. This ordering is
present even in the absence of any inter-site Coulomb repulsion. There is an
insulating gap associated to the charge structure formation. We also study the
insulator-metal transition induced by a magnetic field which removes
simultaneously both charge and spin ordering.Comment: 7 pages, 11 figure
Efficiency of free energy calculations of spin lattices by spectral quantum algorithms
Quantum algorithms are well-suited to calculate estimates of the energy
spectra for spin lattice systems. These algorithms are based on the efficient
calculation of the discrete Fourier components of the density of states. The
efficiency of these algorithms in calculating the free energy per spin of
general spin lattices to bounded error is examined. We find that the number of
Fourier components required to bound the error in the free energy due to the
broadening of the density of states scales polynomially with the number of
spins in the lattice. However, the precision with which the Fourier components
must be calculated is found to be an exponential function of the system size.Comment: 9 pages, 4 figures; corrected typographical and minor mathematical
error
Doping dependence of the resonance peak and incommensuration in high- superconductors
The doping and frequency evolutions of the incommensurate spin response and
the resonance mode are studied based on the scenario of the Fermi surface
topology. We use the slave-boson mean-field approach to the
model and including the antiferromagnetic fluctuation correction in the
random-phase approximation. We find that the equality between the
incommensurability and the hole concentration is reproduced at low frequencies
in the underdoped regime. This equality observed in experiments was explained
{\it only} based on the stripe model before. We also obtain the downward
dispersion for the spin response and predict its doping dependence for further
experimental testing, as well as a proportionality between the low-energy
incommensurability and the resonance energy. Our results suggest a common
origin for the incommensuration and the resonance peak based on the Fermi
surface topology and the d-wave symmetry.Comment: 5 pages, 4 PS figure
Magnetic Phases of Electron-Doped Manganites
We study the anisotropic magnetic structures exhibited by electron-doped
manganites using a model which incorporates the double-exchange between orbital
ly degenerate electrons and the super-exchange between
electrons with realistic values of the Hund's coupling(), the
super-exchange coupling(), and the bandwidth(). We look at the
relative stabilities of the G, C and A type antiferromagnetic ph ases. In
particular we find that the G-phase is stable for low electron doping as seen
in experiments. We find good agreement with the experimentally observed
magnetic phase diagrams of electron-doped manganites
() such as NdSrMnO, PrSrMnO,
and SmCaMnO. We can also explain the experimentally
observed orbital structures of the C a nd A phases.
We also extend our calculation for electron-doped bilayer manganites of the
form RAMnO and predict that the C-phase will be
absent in t hese systems due to their reduced dimensionality.Comment: 7 .ps files included. To appear in Phys. Rev. B (Feb 2001
Primordial perturbations in a non singular bouncing universe model
We construct a simple non singular cosmological model in which the currently
observed expansion phase was preceded by a contraction. This is achieved, in
the framework of pure general relativity, by means of a radiation fluid and a
free scalar field having negative energy. We calculate the power spectrum of
the scalar perturbations that are produced in such a bouncing model and find
that, under the assumption of initial vacuum state for the quantum field
associated with the hydrodynamical perturbation, this leads to a spectral index
n=-1. The matching conditions applying to this bouncing model are derived and
shown to be different from those in the case of a sharp transition. We find
that if our bounce transition can be smoothly connected to a slowly contracting
phase, then the resulting power spectrum will be scale invariant.Comment: 11 pages, RevTeX 4, 8 figures, submitted to Phys. Rev.
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