Time-dependent coupled oscillator model for charged particle motion in the presence of a time varyingmagnetic field

The dynamics of time-dependent coupled oscillator model for the charged particle motion subjected to a time-dependent external magnetic field is investigated. We used canonical transformation approach for the classical treatment of the system, whereas unitary transformation approach is used when managing the system in the framework of quantum mechanics. For both approaches, the original system is transformed to a much more simple system that is the sum of two independent harmonic oscillators which have time-dependent frequencies. We therefore easily identified the wave functions in the transformed system with the help of invariant operator of the system. The full wave functions in the original system is derived from the inverse unitary transformation of the wave functions associated to the transformed system.Comment: 16 page

Spin-transfer torque in magnetic multilayer nanopillars

We consider a quasi one-dimensional configuration consisting of two small pieces of ferromagnetic material separated by a metallic one and contacted by two metallic leads. A spin-polarized current is injected from one lead. Our goal is to investigate the correlation induced between the magnetizations of the two ferromagnets by spin-transfer torque. This torque results from the interaction between the magnetizations and the spin polarization of the current. We discuss the dynamics of a single ferromagnet, the extension to the case of two ferromagnets, and give some estimates for the parameters based on experiments.Comment: To appear in the Journal of Physics: Conference Series (Proceedings of the International Conference on Nanoscience and Technology, Basel, 2006

Putative spin liquid in the triangle-based iridate Ba3_3IrTi2_2O9_9

We report on thermodynamic, magnetization, and muon spin relaxation measurements of the strong spin-orbit coupled iridate Ba$_3$IrTi$_2$O$_9$, which constitutes a new frustration motif made up a mixture of edge- and corner-sharing triangles. In spite of strong antiferromagnetic exchange interaction of the order of 100~K, we find no hint for long-range magnetic order down to 23 mK. The magnetic specific heat data unveil the $T$-linear and -squared dependences at low temperatures below 1~K. At the respective temperatures, the zero-field muon spin relaxation features a persistent spin dynamics, indicative of unconventional low-energy excitations. A comparison to the $4d$ isostructural compound Ba$_3$RuTi$_2$O$_9$ suggests that a concerted interplay of compass-like magnetic interactions and frustrated geometry promotes a dynamically fluctuating state in a triangle-based iridate.Comment: Physical Review B accepte

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Impacts of different dietary lipid sources on growth performance, fatty acid composition and antioxidant enzyme activity of juvenile black sea bream, Acanthopagrus schlegeli

The aim of the present study was to evaluate the impacts of diets supplemented with different lipid sources on growth performance, body composition, fatty acid profile, and hepatic antioxidant enzyme activity of juvenile black sea bream, Acanthopagrus schlegeli (initial mean weight, 1.1±0.02g). Four isonitrogenous and isolipidic diets were formulated with either fish oil (FO), soybean oil (SO), linseed oil (LO) or a mixture of SO and LO (SO+LO). The results showed that survival, weight gain, feed efficiency and protein efficiency ratios of black sea bream were not affected by dietary lipid sources (p>0.05). Liver and muscle of fish fed the SO diet had high concentration of linoleic acid, while those of fish fed the LO diet were high in linolenic acid. Liver and muscle of fish fed the FO diet had significantly (p<0.05) higher levels of eicosapentaenoic acid and docosahexaenoic acid, compared to fishes fed the SO and LO diets. Superoxide dismutase and glutathione peroxidase enzymes activities in liver of black sea bream were not influenced by dietary lipid sources. Our findings suggest that SO and/or LO can be used as a substitute for FO in black sea bream diets without adverse effects on growth performance and antioxidant enzyme activity, when the essential fatty acid requirements are present in diets for black sea bream

Nonlinear couplings and tree amplitudes in gauge theories

Following a remark advanced by Feynman,we study the connection between the form of the nonlinear vertices involving gauge particles and the Abelian gauge invariance of physical tree amplitudes. We show that this requirement, together with some natural assumptions, fixes uniquely the structure of the Yang-Mills theory. However, the constraints imposed by the above property are not sufficient to single out the gauge theory of gravitation.Comment: 12 pages. Requires macros RevTeX, prepictex, pictex, postpictex. TeX source is 69373 byte

Testing the SUSY-QCD Yukawa coupling in a combined LHC/ILC analysis

In order to establish supersymmetry (SUSY) at future colliders, the identity of gauge couplings and the corresponding Yukawa couplings between gauginos, sfermions and fermions needs to be verified. Here a first phenomenological study for determining the Yukawa coupling of the SUSY-QCD sector is presented, using a method which combines information from LHC and ILC.Comment: 5pp, slightly expanded version of contributions to the Proc. of the Linear Collider Workshop (LCWS 06), Bangalore, India, 9-13 March 2006, and the Proc. of the 14th International Conference on Supersymmetry and the Unification of Fundamental Interactions (SUSY 06), Irvine, California, USA, 12-17 June 200