Vortices in quantum droplets: Analogies between boson and fermion systems

The main theme of this review is the many-body physics of vortices in quantum droplets of bosons or fermions, in the limit of small particle numbers. Systems of interest include cold atoms in traps as well as electrons confined in quantum dots. When set to rotate, these in principle very different quantum systems show remarkable analogies. The topics reviewed include the structure of the finite rotating many-body state, universality of vortex formation and localization of vortices in both bosonic and fermionic systems, and the emergence of particle-vortex composites in the quantum Hall regime. An overview of the computational many-body techniques sets focus on the configuration interaction and density-functional methods. Studies of quantum droplets with one or several particle components, where vortices as well as coreless vortices may occur, are reviewed, and theoretical as well as experimental challenges are discussed.Comment: Review article, 53 pages, 53 figure

Blocking phenomena in granular magnetic alloys through magnetization, Hall effect, and magnetoresistance experiments

Magnetization and magnetotransport were measured in CoxAg1-x granular composites as a function of temperature and applied magnetic field. A transition from blocked to superparamagnetic behavior with increasing temperatures can be observed in magnetization, giant magnetoresistance and the extraordinary Hall effect measurements. However, the blocking temperature determined from magnetotransport measurements is systematically lower than the one estimated from magnetic measurements. This is due to the selective magnetic scattering, which is enhanced for smaller particles, while the magnetization probes the whole particle size distribution. (C) 2003 American Institute of Physics.82576376

Synthesis and characterization of novel scaffold for bone tissue engineering based on Whartons´s jelly

A composite is a material made of more than one component, and the bond between the components is on a scale larger than the atomic scale. The objective of the present study was to synthesize and perform the structural characterization and biological evaluation of a new biocomposite (BCO) based on a novel combination of an organic and an inorganic phase, for bone tissue engineering applications. The organic phase consisted of Wharton´s Jelly (WJ), which was obtained from embryonic tissue following a protocol developed by our laboratory. The inorganic phase consisted of bioceramic particles (BC), produced by sintering hydroxyapatite (HA) with β- tricalcium phosphate (β-TCP), and bioactive glass particles (BG). Each phase of the BCO was fully characterized by SEM, EDS, XRD and FTIR. Biocompatibility was evaluated in vivo in the tibiae of Wistar rats (n=40). Histological evaluation was performed at 0, 1, 7, 14, 30 and 60 days. XRD showed the phases corresponding to HA and β-TCP, whereas diffractogram of BG showed it to have an amorphous structure. EDS showed mainly Si and Na, Ca, P in BG, and Ca and P in HA and β-TCP. FTIR identified bonds between the organic and inorganic phases. From a mechanical viewpoint, the composite showed high flexural strength of 40.3±0.8MPa. The synthesized BCO exhibited adequate biocompatibility as shown by formation of lamellar type bone linked by BG and BC particles. The biomaterial presented here showed excellent mechanical and biocompatibility properties for its potential clinical use.Fil: Martinez, Cristian. Universidad de Buenos Aires. Facultad de Ingenieria. Instituto de Ingeniería Biomédica; Argentina. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Anatomía Patológica; Argentina. Universidad Nacional de Cuyo. Facultad de Odontologia; ArgentinaFil: Fernández, Carlos. Universidad de Buenos Aires. Facultad de Ingenieria. Instituto de Ingeniería Biomédica; ArgentinaFil: Prado, Miguel Oscar. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ozols, Andres. Universidad de Buenos Aires. Facultad de Ingenieria. Instituto de Ingeniería Biomédica; ArgentinaFil: Olmedo, Daniel Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Anatomía Patológica; Argentin

Quantum Size Effect transition in percolating nanocomposite films

We report on unique electronic properties in Fe-SiO2 nanocomposite thin films in the vicinity of the percolation threshold. The electronic transport is dominated by quantum corrections to the metallic conduction of the Infinite Cluster (IC). At low temperature, mesoscopic effects revealed on the conductivity, Hall effect experiments and low frequency electrical noise (random telegraph noise and 1/f noise) strongly support the existence of a temperature-induced Quantum Size Effect (QSE) transition in the metallic conduction path. Below a critical temperature related to the geometrical constriction sizes of the IC, the electronic conductivity is mainly governed by active tunnel conductance across barriers in the metallic network. The high 1/f noise level and the random telegraph noise are consistently explained by random potential modulation of the barriers transmittance due to local Coulomb charges. Our results provide evidence that a lowering of the temperature is somehow equivalent to a decrease of the metal fraction in the vicinity of the percolation limit.Comment: 21 pages, 8 figure