Ab initio hartree-fock investigation of beryllium slabs

An analysis of the electronic structure in beryllium slabs with an ab initio LCAO HF method is presented. Band structure, electronic density and density of states were determined for thin films of 1 to 4 atomic layers of Be. A comparison of the electronic structure in films of different thickness with the situation found for bulk Be and Be clusters shows strong modifications in the surface region and a progressive reconstruction of the bulk bonds.     

Su un gruppo di casi relativi ad onde magneto-idrodinamiche non omogenee

Sunto Riferendosi ad un fluido perfetto, incompressibile e di conducibilità elettrica infinita, soggetto ad un campo magnetico stazionario opportunamente assegnato, si introducono le equazioni della magneto-idrodinamica espresse in generiche coordinate curvilinee ortogonali. Si ricercano poi delle opportune ipotesi sotto le quali per tali equazioni è possibile il calcolo completo del campo magneto-idrodinamico, che risulta propagarsi per onde non omogenee nella direzione del detto campo magnetico stazionario assegnato. Sono poi trattati casi particolari in coordinate cartesiane e in coordinate cilindriche.     

Sulla formula risolutiva di un particolare problema della magneto-idrodinamica

ANNALI DELL'UNIVERSITA' DI FERRARA - Si presenta sotto una forma adatta all’interpretazione fisica la formula risolutiva di un problema trattato in un lavoro precedente e riguardante...     

Synthesis of 3-substituted-2,3,4,5-tetrahydro-1H-naphth[1,2-d]-imidazole-2,4,5-triones and 1-Substituted-2,3,4,9-tetrahydro-1H-naphth[2,3-d]imidazole-2,4,9-triones

Tricyclic compounds with an imidazolinone ring fused to 1,2- and 1,4-naphtoquinones were synthesized by a reaction of 4-amino-1,2-naphthoquinone and 2-amino-1,4-naphthoquinone with electrophilic symmetric and non symmetric diazenes.     

On the Quasistatic Limit of Dynamic Evolutions for a Peeling Test in Dimension One

The aim of this paper is to study the quasistatic limit of a one-dimensional model of dynamic debonding. We start from a dynamic problem that strongly couples the wave equation in a time-dependent domain with Griffith’s criterion for the evolution of the domain. Passing to the limit as inertia tends to zero, we find that the limit evolution satisfies a stability condition; however, the activation rule in Griffith’s (quasistatic) criterion does not hold in general, thus the limit evolution is not rate-independent.     

Development of an Accurate Mass Retention Time Database for Untargeted Metabolomic Analysis and Its Application to Plasma and Urine Pediatric Samples

Liquid-chromatography coupled to high resolution mass spectrometry (LC-HRMS) is currently the method of choice for untargeted metabolomic analysis. The availability of established protocols to achieve a high confidence identification of metabolites is crucial. The aim of this work is to describe the workflow that we have applied to build an Accurate Mass Retention Time (AMRT) database using a commercial metabolite library of standards. LC-HRMS analysis was carried out using a Vanquish Horizon UHPLC system coupled to a Q-Exactive Plus Hybrid Quadrupole-Orbitrap Mass Spectrometer (Thermo Fisher Scientific, Milan, Italy). The fragmentation spectra, obtained with 12 collision energies, were acquired for each metabolite, in both polarities, through flow injection analysis. Several chromatographic conditions were tested to obtain a protocol that yielded stable retention times. The adopted chromatographic protocol included a gradient separation using a reversed phase (Waters Acquity BEH C18) and a HILIC (Waters Acquity BEH Amide) column. An AMRT database of 518 compounds was obtained and tested on real plasma and urine samples analyzed in data-dependent acquisition mode. Our AMRT library allowed a level 1 identification, according to the Metabolomics Standards Initiative, of 132 and 124 metabolites in human pediatric plasma and urine samples, respectively. This library represents a starting point for future metabolomic studies in pediatric settings.     

Comprehensive Characterization of Chain End Groups of Vinylidene Fluoride Based Polymers

Summary: In this work an investigation of the chain end groups produced in the free radical copolymerization of vinilydene fluoride (VDF) and hexafluoropropylene (HFP) is performed. Type and amount of chain end groups are evaluated by a meticulous analytical characterization of VDF/HFP copolymer. At first pulsed gradient spin-echo nuclear magnetic resonance (spin-echo NMR) is used to identify all the chain end groups also at very low concentration (equal to 0.1 mmol · Kg⁻¹). The instrument sensitivity is increased of an order of magnitude in comparison with the traditional NMR. Moreover potentiometric titration and ion chromatography (IC) are also used to study the chain end groups and, as a consequence, the nature and the amount of the acidity showed by the polymer chains. In details two intensity of acidity are detected by potentiometric titration, namely strong and weak. The strong acidity is associated to the presence of residual surfactant and can be removed washing the polymer, while the weak acidity is due to free molecules of fluoride acid (HF). The standard ion chromatography facility is properly modified to quantify the fluoride in the polymer matrix without any pre extraction in water. Thanks to this the HF concentration in the polymer is evaluated with high accuracy. A detailed kinetic scheme for the VDF/HFP polymerization is also proposed taking into account all the findings obtained studying the chain end groups.     

Who's talking first? Consensus or lack thereof in coevolving opinion formation models

We investigate different opinion formation models on adaptive network topologies. Depending on the dynamical process, rewiring can either (i) lead to the elimination of interactions between agents in different states, and accelerate the convergence to a consensus state or break the network in noninteracting groups or (ii), counterintuitively, favor the existence of diverse interacting groups for exponentially long times. The mean-field analysis allows us to elucidate the mechanisms at play. Strikingly, allowing the interacting agents to bear more than one opinion at the same time drastically changes the model's behavior and leads to fast consensus.