Nucleation of superconductivity in finite metallic multilayers: Effect of the symmetry

The influence of the finite dimensions of superconducting metallic multilayers on H-T phase diagram is studied. It is established that the geometrical symmetry of the samples determines crucially the dependencies. For samples where the symmetry plane is in the middle of the superconducting layer the values are, for temperatures close to T _c , larger than the values of the samples for which the symmetry plane lies in the middle of the normal layer. The results are analysed on the basis of the Ginzburg-Landau approach and are explained by considering the different symmetry of the wave function describing the system. The experimental results are in good agreement with the elaborated model, which takes into account the actual symmetry of the samples.Received: 23 July 2004, Published online: 5 November 2004PACS: 74.78.Fk Multilayers, superlattices, heterostructures - 74.20.De Phenomenological theories (two-fluid, Ginzburg-Landau, etc.) - 74.45. + c Proximity effects; Andreev effect; SN and SNS junctions     

Transport properties of nanoperforated Nb thin films

Porous silicon, obtained by electrochemical etching, has been used as a substrate for the growth of nanoperforated Nb thin films. The films, deposited by UHV magnetron sputtering, inherited from the Si substrates their structure, made of holes of 10 nm diameter and of 20 and 40 nm spacing, which provide an artificial pinning lattice. Commensurability effects between the Abrikosov vortex lattice and the artificial array of holes were investigated by transport measurements.     

Transport in Quantum Multi-barrier Systems as Random Walks on a Lattice

Journal of Statistical Physics - Coulomb and log-gases are exchangeable singular Boltzmann–Gibbs measures appearing in mathematical physics at many places, in particular in random matrix...     

Terahertz probe of individual subwavelength objects in a water environment

Terahertz (THz) spectroscopy and imaging have been heralded for some time as potentially revolutionary techniques for biomedical applications. Label‐free detection of molecules and recognition of molecular events are often mentioned as the most exciting possibilities. A crucial practical goal, however, is the ability to perform such measurements on tiny amounts of biological fluids or even on individual organic structures. Living cells, for instance, have diameters at most of some tens of micrometers, i.e. at least λ/10 even for few‐THz radiation. Furthermore, all analyses relevant for a biological perspective must be performed in a water environment, which presents a strong absorption across the whole THz spectral range, severely limiting the penetration of the electromagnetic field. Here, it is shown how both issues can be overcome with a lab‐on‐a‐chip approach based on a microfluidic platform coupled to a plasmonic antenna. Using a quantum cascade laser as THz illumination source, liquid volumes down to the picoliter range are probed, and direct operation on individual 10‐µm diameter microparticles flowing in water is shown. The present demonstration opens the way to the development of THz biosensing of individual living cells and small probe volumes.     

Neurophysiological and functional MRI evidence of reorganization of cortical motor areas in cerebral arteriovenous malformation

Functional magnetic resonance imaging (fMRI) research has shown that brain arteriovenous malformations (AVMs) lead to reorganization of cortical motor areas. Since it is known that blood oxygenation level-dependent signal in fMRI may be influenced by the hemodynamic perturbation associated with the presence of the AVM, in the present study, a combined exploration with fMRI and transcranial magnetic stimulation was performed in a patient with a right rolandic AVM in order to explore the relationship between neuronal and hemodynamic activity. The combined protocol of investigation adopted in this study was able to provide significant information regarding neuronal activity of the different cortical areas that partake to post-lesional reorganization.     

A Note on the Metastability of the Ising Model: The Alternate Updating Case

We study the metastable behavior of the two-dimensional Ising model in the case of an alternate updating rule: parallel updating of spins on the even (odd) sublattice are permitted at even (odd) times. We show that although the dynamics is different from the Glauber serial case the typical exit path from the metastable phase remains the same.     

The importance of radiochemistry for the characterization of NORM and of environments contaminated by NORM

Naturally occuring radioactive materials (NORM) are present in the environment and they can be concentrated by technical activities, particularly those involving natural resources. This article describes radioanalytical problems arising in the accurate determination of natural radionuclides in NORM and in the environment contaminated by NORM. The solution of these problems is of particular importance since the results can be used to estimate the dose to workers and to the population. A special emphasis is given to the reliability of the radiochemical methods and procedures applied for the detection and measurement of alpha or beta emitters by radiometric or non-radiometric techniques.     

(2-Pyridyl)phenyl methanol: a new reagent for metal-free reduction of nitro aromatic compounds

As previously reported for 1-(2-pyridyl)-2-propen-1-ol, (2-pyridyl)phenyl methanol is able to react as hydrogen donor towards nitro aromatic and heteroaromatic compounds. Operating in the presence of methyl acrylate as an aza-Michael acceptor, a domino process involving reduction and conjugate addition steps allows the one pot formation of β-amino esters. The crucial role of the pyridine nucleus in making this purely thermal reactivity of carbinols possible has been shown.