339 research outputs found
Agaricus Blazei In The Diet Of Broiler Chickens On Immunity, Serum Parameters And Antioxidant Activity
The effect of adding Agaricus blazei to the diet of broilers on immunity, serum parameters, and antioxidant activity was evaluated. A total of 840 1-day-old chicks were used, distributed among five levels of a completely randomized design (0.0, 0.05, 0.10, 0.15, and 0.20% A. blazei), with six replications and 28 birds per experimental unit. The weights of the thymus, spleen and cloacal bursa were not influenced (P > 0.05). Leukocytes, macrophages and nitric oxide were unaffected (P > 0.05), but at each supplementation level compared with the control, differences appeared in the percentages of eosinophils and macrophages (P 0.05) at 42 days. Hypocholesterolemic effect was demonstrated (P 0.05). The antioxidant activity of mushroom showed a positive linear effect (P < 0.05) on DPPH capture on day zero of meat cooling. The inclusion of A. blazei in the diet of broilers provided an immunostimulatory activity and hypocholesterolemic effect. Residual compounds with antioxidant activity were present in the meat, which may promote tissue protection of the animal in vivo, making possible the use of A. blazei as a natural additive.3742235224
Magnetic Ordering, Orbital Ordering and Resonant X-ray Scattering in Perovskite Titanates
The effective Hamiltonian for perovskite titanates is derived by taking into
account the three-fold degeneracy of orbitals and the strong
electron-electron interactions. The magnetic and orbital ordered phases are
studied in the mean-field approximation applied to the effective Hamiltonian. A
large degeneracy of the orbital states in the ferromagnetic phase is found in
contrast to the case of the doubly degenerate orbitals. Lifting of this
orbital degeneracy due to lattice distortions and spin-orbit coupling is
examined. A general form for the scattering cross section of the resonant x-ray
scattering is derived and is applied to the recent experimental results in
YTiO. The spin wave dispersion relation in the orbital ordered YTiO is
also studied.Comment: 10 pages, 6 figure
Manganites at Quarter Filling: Role of Jahn-Teller Interactions
We have analyzed different correlation functions in a realistic spin-orbital
model for half-doped manganites. Using a finite-temperature diagonalization
technique the CE phase was found in the charge-ordered phase in the case of
small antiferromagnetic interactions between electrons. It is shown
that a key ingredient responsible for stabilization of the CE-type spin and
orbital-ordered state is the cooperative Jahn-Teller (JT) interaction between
next-nearest Mn neighbors mediated by the breathing mode distortion of
Mn octahedra and displacements of Mn ions. The topological phase
factor in the Mn-Mn hopping leading to gap formation in one-dimensional models
for the CE phase as well as the nearest neighbor JT coupling are not able to
produce the zigzag chains typical for the CE phase in our model.Comment: 16 pages with 16 figures, contains a more detailed parameter estimate
based on the structural data by Radaelli et al. (accepted for publication in
Phys. Rev. B
Ordering and Fluctuation of Orbital and Lattice Distortion in Perovskite Manganese Oxides
Roles of orbital and lattice degrees of freedom in strongly correlated
systems are investigated to understand electronic properties of perovskite Mn
oxides such as La_{1-x}Sr_{x}MnO_{3}. An extended double-exchange model
containing Coulomb interaction, doubly degenerate orbitals and Jahn-Teller
coupling is derived under full polarization of spins with two-dimensional
anisotropy. Quantum fluctuation effects of Coulomb interaction and orbital
degrees of freedom are investigated by using the quantum Monte Carlo method. In
undoped states, it is crucial to consider both the Coulomb interaction and the
Jahn-Teller coupling in reproducing characteristic hierarchy of energy scales
among charge, orbital-lattice and spin degrees of freedom in experiments. Our
numerical results quantitatively reproduce the charge gap amplitude as well as
the stabilization energy and the amplitude of the cooperative Jahn-Teller
distortion in undoped compounds. Upon doping of carriers, in the absence of the
Jahn-Teller distortion, critical enhancement of both charge compressibility and
orbital correlation length is found with decreasing doping concentration. These
are discussed as origins of strong incoherence in charge dynamics. With the
Jahn-Teller coupling in the doped region, collapse of the Jahn-Teller
distortion and instability to phase separation are obtained and favorably
compared with experiments. These provide a possible way to understand the
complicated properties of lightly doped manganites.Comment: 22 pages RevTeX including 25 PS figures, submitted to Phys.Rev.B,
replaced version; two figures are replaced by Fig.17 with minor changes in
the tex
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