Algebraic decay of velocity fluctuations in a confined fluid

Computer simulations of a colloidal particle suspended in a fluid confined by rigid walls show that, at long times, the velocity correlation function decays with a negative algebraic tail. The exponent depends on the confining geometry, rather than the spatial dimensionality. We can account for the tail by using a simple mode-coupling theory which exploits the fact that the sound wave generated by a moving particle becomes diffusive.

Quantum decay of metastable states in small magnetic particles

We present an imaginary-time path-integral study of the problem of quantum decay of a metastable state of a uniaxial magnetic particle placed in the magnetic field at an arbitrary angle. Our findings agree with earlier results of Zaslavskii obtained by mapping the spin Hamiltonian onto a particle Hamiltonian. In the limit of low barrier, weak dependence of the decay rate on the angle is found, except for the field which is almost normal to the anisotropy axis, where the rate is sharply peaked, and for the field approaching the parallel orientation, where the rate rapidly goes to zero. This distinct angular dependence, together with the dependence of the rate on the field strength, provides an independent test for macroscopic spin tunneling.

La Obra de Cayetano Garviso: 1807- post. 1871: cirujano vasco-navarro liberal en América

L'autor d'aquest llibre dona a conèixer alguns aspectes de l'exercici de la medicina en la dècada de 1840 a la zona del Río de la Plata, a partir de la figura del metge basc-navarrés Cayetano Garviso, cirurgià que emigrà a Argentina durant la Primera Guerra Carlista. Ara bé, tot i que aquest personatge es va moure per bona part de Sudamèrica, el treball es centra en la part de la seva biografia i el seu exercici professional desenvolupada a Espanya, Montevideo i Buenos Aires.