The strange case of Dr. Petit and Mr. Dulong

The Dulong-Petit limiting law for the specific heats of solids, one of the first general results in thermodynamics, has provided Mendeleev with a powerful tool for devising the periodic table and gave an important support to Boltzmann's statistical mechanics. Even its failure at low temperature, accounted for by Einstein, paved the way to the the quantum mechanical theory of solids. These impressive consequences are even more surprising if we bear in mind that, when this law was announced, thermal phenomena were still explained using Lavoisier's concept of caloric and Dalton's atomic theory was in its infancy. Recently, however, bitter criticisms charging Dulong and Petit of `data fabrication' and fraud, have been raised. This work is an attempt to restore a more balanced view of the work performed by these two great scientists and to give them back the place they deserve in the framework of the development of modern science.Comment: Submitted to "Quaderni di Storia della Fisica", SIF (Italian Physical Society) publishe

EDACs and test integration strategies for NAND flash memories

Mission-critical applications usually presents several critical issues: the required level of dependability of the whole mission always implies to address different and contrasting dimensions and to evaluate the tradeoffs among them. A mass-memory device is always needed in all mission-critical applications: NAND flash-memories could be used for this goal. Error Detection And Correction (EDAC) techniques are needed to improve dependability of flash-memory devices. However also testing strategies need to be explored in order to provide highly dependable systems. Integrating these two main aspects results in providing a fault-tolerant mass-memory device, but no systematic approach has so far been proposed to consider them as a whole. As a consequence a novel strategy integrating a particular code-based design environment with newly selected testing strategies is presented in this pape

Stretched--exponential relaxation in arrays of coupled rotators

We consider the non--equilibrium dynamics of a chain of classical rotators coupled at its edges to an external reservoir at zero temperature. We find that the energy is released in a strongly discontinuous fashion, with sudden jumps alternated with long stretches during which dissipation is extremely weak. The jumps mark the disappearance of strongly localized structures, akin to the rotobreather solutions of the Hamiltonian model, which act as insulating boundaries of a hot central core. As a result of this complex kinetics, the ensemble--averaged energy follows a stretched exponential law until a residual pseudo--stationary state is attained, where the hot core has reduced to a single localized object. We give a statistical description of the relaxation pathway and connect it to the properties of return periods of rare events in correlated time series. This approach sheds some light into the microscopic mechanism underlying the slow dynamics of the system. Finally, we show that the stretched exponential law remains unaltered in the presence of isotopic disorder.Comment: 13 Figure

Biopolymer gels with "physical" cross-links: gelation kinetics, aging, heterogeneous dynamics, and macroscopic mechanical properties

Alginate is a natural biopolymer that forms, in the presence of divalent cations, ionic-bound gels typifying a large class of biological gels stabilized by non-covalent cross-links, and displaying a consistent restructuring kinetics. We investigate the kinetics of formation and aging of alginate gels by slow permeation of a curing CaCl2 agent by means of photon correlation imaging, a novel optical technique that allows obtaining the microscopic dynamics of the sample, while retaining at the same time the spatial resolution of imaging techniques. Specifically, the gelling kinetics displays a peculiar non-diffusive behavior, and the subsequent restructuring of the gel structure shares several features in common with the aging of colloidal gels, in particular for what concerns the occurrence of heterogeneous dynamics effects. A comparative analysis of the gel macroscopic mechanical properties at different aging stages further highlights distinctive effects arising from the non-permanent nature of the bonds

Spatially: Resolved heterogeneous dynamics in a strong colloidal gel

We re-examine the classical problem of irreversible colloid aggregation, showing that the application of Digital Fourier Imaging (DFI), a class of optical correlation methods that combine the power of light scattering and imaging, allows one to pick out novel useful evidence concerning the restructuring processes taking place in a strong colloidal gel. In particular, the spatially-resolved displacement fields provided by DFI strongly suggest that the temporally-intermittent local rearrangements taking place in the course of gel ageing are characterized by very long-ranged spatial correlations

Analisi sperimentale su collegamenti tradizionali e rinforzati nelle capriate lignee

I giunti cosiddetti “di carpenteria” sono senza dubbio tra i più comuni utilizzati per il collegamento di elementi lignei nelle capriate storiche, presentandosi in differenti configurazioni che, comunque, si rifanno quasi sempre al tradizionale giunto a dente semplice. Sebbene tale tipo di nodo si presenti con una grande variabilità di geometria (angolo di intaglio, profondità di intaglio, lunghezza del tacco nell’elemento che presenta l’intaglio), il principio di funzionamento è sempre basato sulla trasmissione di forze per contatto diretto e sull’attrito all’interfaccia tra i due elementi collegati: si osserva che tale ultimo contributo è quasi sempre trascurato nella progettazione in situazione normale, ma diviene essenziale per una corretta valutazione del comportamento sismico della struttura. Eventuali elementi metallici e connettori presenti nel nodo non sono deputati alla trasmissione degli sforzi, almeno in situazioni di normale utilizzo, ma risultano di fondamentale importanza nel mantenere la funzionalità del nodo anche in presenza di sollecitazioni che possano indurre sconnessioni, come nel caso sismico. Il cosiddetto “rinforzo” di tali tipologie di nodi può essere realizzato con metodologie e modalità anche assai differenti tra loro, ma la scelta adottata ne condizionerà inevitabilmente il comportamento meccanico non solo in termini di resistenza ma anche di rigidezza e duttilità, aspetti questi ben più importanti ai fini del comportamento sismico. Si nota, ad esempio, che la classica schematizzazione a cerniera non è più sufficiente a descrivere in maniera adeguata il comportamento globale della struttura in cui tale nodo è inserito, e può portare a valutazioni completamente errate sulle sue reali capacità portanti, in modo particolare in presenza di azioni eccezionali. Esistono, in questo campo, un numero limitato di studi finalizzati alla caratterizzazione dei giunti di carpenteria rinforzati, da riguardarsi come giunti a comportamento semirigido. Da alcuni anni, presso l’Università di Trento e, recentemente, in collaborazione con l’Università del Minho, Guimarães (Portogallo), è attiva una linea di ricerca che si occupa di indagare in maniera approfondita il comportamento dei nodi di carpenteria nelle strutture lignee esistenti. Sono di seguito illustrati alcuni recenti risultati sperimentali su alcune tipologie di collegamento tradizionale rinforzato, illustrando un possibile approccio per l’utilizzo di questi dati al fine di una modellazione sismica di capriate storiche con giunti tradizionali. La ricerca sperimentale e numerica sui nodi di carpenteria rinforzati, è attualmente inserita nel progetto nazione RELUIS finanziato dal Dipartimento della Protezione Civile (REte nazionale Laboratori Universitari di Ingegneria Sismica, linea 1/3a).RELUIS (Rete Laboratori Universitari Ingegneria Sismica)Fundação para a Ciência e a Tecniologia (FCT

Electrodeposition from molybdate aqueous solutions: a preliminary study

The electrochemistry of molybdenum (Mo) and its oxides is very important for several applications in electrocatalysis,batteries,sensors and in particular for CIGS-based solar cells,where metal Mo is used as back contact.Properties and the fabrication method of Mo films are of fundamental importance,because they could induce significant changes in solar cell performances.The most important issues in the electrochemical behaviour of Mo are the nature and stability of its surface oxides,which are strongly dependent on deposition bath pH.Ivanova et al. (2006) reported that it is possible to accomplish the cathodic reduction of molybdate ions to metallic Mo from electrolytes containing HF.The addition of this acid selectively prevents the polymerization of MoO42- anions,therefore its concentration plays a fundamental role.A hard drawback connected to deposition in acid media is the strong hydrogen evolution,since H+ reduction is the reaction thermodynamically favoured,therefore it is necessary to apply a very high current density for appreciably depositing Mo.In this work,we report some preliminary results dealing with the electrodeposition process from molybdate aqueous solutions to grow thin films on different substrates and nanowires inside the channels of polycarbonate membranes;electrolyte pH was varied in order to evidence its role on the nature of the deposits,which were characterized by EDS,SEM,RAMAN and XRD analyses

Optical extinction, refractive index, and multiple scattering for suspensions of interacting colloidal particles

We provide a general microscopic theory of the scattering cross-section and of the refractive index for a system of interacting colloidal particles, exact at second order in the molecular polarizabilities. In particular: a) we show that the structural features of the suspension are encoded into the forward scattered field by multiple scattering effects, whose contribution is essential for the so-called "optical theorem" to hold in the presence of interactions; b) we investigate the role of radiation reaction on light extinction; c) we discuss our results in the framework of effective medium theories, presenting a general result for the effective refractive index valid, whatever the structural properties of the suspension, in the limit of particles much larger than the wavelength; d) by discussing strongly-interacting suspensions, we unravel subtle anomalous dispersion effects for the suspension refractive index.Comment: Submitted to Journal of Chemical Physics 37 pages, 4 figure

The staging of gastritis with the olga system in the italian setting. histological features and gastric cancer risk

BACKGROUND: Recently OLGA (Operative Link on Gastritis Assessment) classification has been proposed to identify high-risk forms of gastritis that can evolve in gastric cancer (stages III and IV). Helicobacter pylori infection and age older than 40 have been considered as independent risk factor for high-risk OLGA stages

Nanostructured electrochemical devices for sensing, energy conversion and storage

Nanostructured materials are attracting growing interest for improving performance of devices and systems of large technological interest. In this work, the principal results about the use of nanostructured materials in the field of electrochemical energy storage, electrochemical water splitting, and electrochemical sensing are presented. Nanostructures were fabricated with two different techniques. One of these was the electrodeposition of the desired material inside the channels of a porous support acting as template. The other one was based on displacement reaction induced by galvanic contact between metals with different electrochemical nobility. In the present work, a commercial polycarbonate membrane was used as template. In the field of the electrochemical energy storage, the attention was focused on lead-acid battery, and it has been found that nanostructured morphology enhances the active mass utilization up to about 80%, with consequent increase of specific energy and cycling rates to unattainable values for the commercial battery. Nanostructured Ni-IrO2 composite electrodes showed valuable catalytic activity for water oxidation. By comparison with other Ni-based electrocatalyst, this electrode appears as the most promising anode for electrochemical water splitting in alkaline cells. Also in the field of sensing, the nanostructured materials fabricated by displacement reaction showed performance of high interest. Some new results about the use of copper nanowires for H2O22 sensing will be showed, evidencing better performance in comparison with copper thin film. In this work, we will show that nanostructured electrodes are very promising candidate to form different electrochemical setups that operate more efficiently comparing to device with flat electrode materials