Zero-Dimensional Superconducting Fluctuations and Fluctuating Diamagnetism in Lead Nanoparticles

High resolution SQUID magnetization measurements in lead nanoparticles are used to study the fluctuating diamagnetism in zero-dimensional condition, namely for particle size d lesser than the coherence length. The diamagnetic magnetization Mdia (H, T= const) as a function of the field H at constant temperature is reported in the critical region and compared with the behaviour in the temperature range where the first-order fluctuation correction is expected to hold. The magnetization curves are analysed in the framework of exact fluctuation theories based on the Ginzburg-Landau functional for the coherence length much greater than d. The role of the upturn field Hup where Mdia reverses the field dependence is discussed and its relevance for the study of the fluctuating diamagnetism, particularly in the critical region where the first-order fluctuation correction breaks down, is pointed out. The size and temperature dependence of Hup is theoretically derived and compared to the experimental data. The relevance and the magnetization curves for non-evanescent field and of the upturn field for the study of the fluctuating diamagnetism above the superconducting transition temperature is emphasized

NEGATIVE SYNERGISM BETWENN THE COMBINATION OF STEROID AND LOW MOLECULAR WEIGHT HEPARIN (LMWH) ON BONE METABOLISM, IN PATIENTS TREATED FOR LYMPHOMA

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Potentialities and limits of magnetoelasticity applications for noise detection and attenuation

Starting from the basic phenomena of direct and inverse magnetostriction, the status of art of actual application and material development are critically reviewed. Important developments in noise detection and control are pointed out and several innovations are also reported. On the other hand, the crucial improvements to be performed in material performance, devices techniques and modeling are clearly discussed. In particular the first characterization of a new device, based on a novel composite material made of magnetic particles dispersed in an elastic matrix, able of self-attenuation of vibrations also at the resonance frequency, is reported and discussed. Since some problems in vibration control are related to the induction of a spontaneous acoustic mode in the core of the device used for the oscillations detection and/or attenuation, this new system appears to be very interesting for the researchers community involved in noise control and monitoring

State of the art and development trends of novel nanostructured elastomagnetic composites

The coupling between elastic and magnetic properties of composite materials made of magnetic particles uniformly dispersed into an elastic matrix was revised. The influence of particles content and size was considered. A unified simple model of the direct and inverse elastomagnetic effect was furnished explaining the experimental results in different experimental conditions. Some applications of elastomagnetic materials in both sensors and actuators are reported and their potentiality is discussed. The correlation between strain and electric conduction in this kind of materials is also presented and the first experimental results on this topic are reported

Modello della fluttuazione e stati pre-quantici

Gli oscillatori di Bernoulli sono entità di tipo classico sottomesse ad un forzamento che proviene dal vuoto quantistico. Eliminato il rumore quantico dall’equazione del moto, questa assume la forma di un teorema generalizzato di Kapitza per il “grado di libertà classico”. Le densità classiche risolventi si sommano con semplici funzioni di distribuzione all’ appropriata densità quantistica. Se nella transizione allo stato quantico l’effetto tunnel è trascurabile, e il campo di velocità che si arresta alla frontiera classica è dominante, la dinamica dell’oscillatore risulta particolarmente semplice (caso pre-quantico). Gli esempi a ciò più aderenti sono costituiti dagli oscillatori per i quali l’interazione col vuoto è meno forte, per cui gli autovalori dell’energia meccanica restano determinati dalla condizione di invarianza adiabatica classica (regola di Bohr-Sommerfeld)

Improved model for thermal treatment of metallic ribbons by continuous laser source: Application to amorphous metals

The thermal model describing the c.w.-annealing of ribbon-shaped materials irradiated by a moving laser beam has been revised and imrpoved. New experimental results on the initial permeability of annealed metallic glasses are presented. © 1983 Società Italiana di Fisica

Stress Sensitivity Coefficient In Polycrystalline and Amorphous Ferromagnetic Materials Below Room-temperature

The piezomagnetic coupling coefficient (the >) is quantitatively investigated below room temperature and a comparison is made among polycrystalline samples and amorphous ones. The technique used is an original one. It experimentally consists in the measurement of the amplitude of magnetoelastic waves, their resonance frequency and differential susceptibility; theoretically, it consists in coupling Newton's law of force with the piezomagnetic state equations. The results clearly show different responses of polycrystalline samples with respect to the amorphous ones; in particular the nonmonotonic behaviour of the > for metallic glasses is interesting for establishing their actual magnetic states at low temperature

Un modello di evoluzione verso l’equilibrio termodinamico reinterpretato

Alla luce di recenti risultati nel campo della fisica semiclassica dei trasferimenti di energia riconsideriamo un modello standard di evoluzione verso l’equilibrio termodinamico, fondato sulle equazioni di velocità e sulla legge dell’azione di massa, nella sua forma più semplice. Un singolo oscillatore meccanico, di tipo classico, è sottomesso all’azione di un ambiente termodinamico. Le collisioni di tipo esotermico risultano a priori dominanti, ma lo stato energetico dell’oscillatore è sostenuto dall’interazione con il vuoto quantistico. Attraverso un modello di fluttuazione, calcoliamo l’emissività dell’oscillatore in funzione della sua energia meccanica e verifichiamo che il modello riproduce l’evoluzione verso l’equilibrio incorporando le fluttuazioni