Spin dynamics of the ferromagnetic superconductor UGe2_{2}

Inelastic neutron scattering was used to study the low energy magnetic excitations of the ferromagnetic superconductor UGe$_{2}$. The ferromagnetic fluctuations are of Ising nature with a non-conserved magnetization and have an intermediate behavior between localized and itinerant magnetism.Comment: European Conference on Neutron Scattering, Montpellier 2003 (to appear in Physica B

Motor-driven Dynamics of Cytoskeletal FIlaments in Motility Assays

We model analytically the dynamics of a cytoskeletal filament in a motility assay. The filament is described as rigid rod free to slide in two dimensions. The motor proteins consist of polymeric tails tethered to the plane and modeled as linear springs and motor heads that bind to the filament. As in related models of rigid and soft two-state motors, the binding/unbinding dynamics of the motor heads and the dependence of the transition rates on the load exerted by the motor tails play a crucial role in controlling the filament's dynamics. Our work shows that the filament effectively behaves as a self-propelled rod at long times, but with non-Markovian noise sources arising from the coupling to the motor binding/unbinding dynamics. The effective propulsion force of the filament and the active renormalization of the various friction and diffusion constants are calculated in terms of microscopic motor and filament parameters. These quantities could be probed by optical force microscopy.Comment: 13 pages, 8 figures, 1 Tabl

Theoretical Study on Coexistence of Ferromagnetism and Superconductivity

On the basis of a two-dimensional t-t' Hubbard model in ferromagnetic and paramagnetic states, the triplet superconducting mechanism is investigated by the third-order perturbation theory with respect to the on-site Coulomb interaction U. In general, the superconducting state is more stable in the paramagnetic state than in the ferromagnetic state. As a special case, the dominant ferromagnetic superconductivity is obtained by the electron-electron correlation between the electronlike majority and holelike minority bands. Furthermore, it is pointed out that in some cases the two bands play an essential role for the coexistence of superconductivity and ferromagnetism.Comment: 5 pages, 10 figure

Pathogenicity, antibiogram and biochemical characteristics of Luminescent Vibrio harveyi, associated with 'Black Shell Disease' of Penaeus monodon

Bacterial isolation was made from shrimps Penaeus monodon showing characteristic external symptoms of 'black shell disease' from shrimp farms located in southeast coast of India. The isolates were screened on TeBS agar plates and 0/129 for the selective isolation of Vibrio sp. Based on the morphological, biochemical and physiological characteristics, the isolate (RJM5) was characterized as luminescent Vibrio harveyi." Antibiogram of V. Imrueyi indicated that it was highly sensitive to chloramphenicol. ciprofloxacin, nalidixic acid and streptomycin. The pathogenicity studies confirmed that the isolate (V.harveyi) was moderately virulent

Pressure-temperature phase diagram of ferromagnetic superconductors

The symmetry approach to the description of the (P,T) phase diagram of ferromagnet superconductors with triplet pairing is developed. Taking into account the recent experimental observations made on UCoGe it is considered the case of a crystal with orthorhombic structure and strong spin-orbital coupling. It is shown that formation of ferromagnet superconducting state from a superconducting state is inevitably accompanied by the first order type transition.Comment: 4 pages, 1 figur

Force Dependence of the Michaelis Constant in a Two-State Ratchet Model for Molecular Motors

We present a quantitative analysis of recent data on the kinetics of ATP hydrolysis, which has presented a puzzle regarding the load dependence of the Michaelis constant. Within the framework of coarse grained two-state ratchet models, our analysis not only explains the puzzling data, but provides a modified Michaelis law, which could be useful as a guide for future experiments.Comment: 4 pages, 3 eps figures, accepted for publication on Physical Review Letter

Lameness in UK dairy cows: a review of the current status

Lameness in dairy cattle has been reported as a concern for welfare and economic reasons for over 20 years. This concern has been expressed from across the industry and has prompted the launch of a number of initiatives to address the problem. This article reviews the current status of lameness in dairy cows in the UK, outlines the current understanding of the condition and its impacts on welfare and productivity, and highlights areas where evidence is still lacking

Pressure dependence of the magnetization in the ferromagnetic superconductor UGe_2

The recent discovery that superconductivity occurs in several clean itinerant ferromagnets close to low temperature magnetic instabilities naturally invites an interpretation based on a proximity to quantum criticality. Here we report measurements of the pressure dependence of the low temperature magnetisation in one of these materials, UGe_2. Our results show that both of the magnetic transitions observed in this material as a function of pressure are first order transitions and do not therefore correspond to quantum critical points. Further we find that the known pressure dependence of the superconducting transition is not reflected in the pressure dependence of the static susceptibility. This demonstrates that the spectrum of excitations giving superconductivity is not that normally associated with a proximity to quantum criticality in weak itinerant ferromagnets. In contrast our data suggest that instead the pairing spectrum might be related to a sharp spike in the electronic density of states that also drives one of the magnetic transitions.Comment: to appear in Phys. Rev. Let

A Microscopic Mechanism for Muscle's Motion

The SIRM (Stochastic Inclined Rods Model) proposed by H. Matsuura and M. Nakano can explain the muscle's motion perfectly, but the intermolecular potential between myosin head and G-actin is too simple and only repulsive potential is considered. In this paper we study the SIRM with different complex potential and discuss the effect of the spring on the system. The calculation results show that the spring, the effective radius of the G-actin and the intermolecular potential play key roles in the motion. The sliding speed is about $4.7\times10^{-6}m/s$ calculated from the model which well agrees with the experimental data.Comment: 9 pages, 6 figure