Synthesis and Characterization of Tetravalent Cation Substituted Mn-Zn Ferrite Suitable for High Frequency Applications

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Thermodynamic stability of fluid-fluid phase separation in binary athermal mixtures: The role of nonadditivity

We study the thermodynamic stability of fluid-fluid phase separation in binary nonadditive mixtures of hard-spheres for moderate size ratios. We are interested in elucidating the role played by small amounts of nonadditivity in determining the stability of fluid-fluid phase separation with respect to the fluid-solid phase transition. The demixing curves are built in the framework of the modified-hypernetted chain and of the Rogers-Young integral equation theories through the calculation of the Gibbs free energy. We also evaluate fluid-fluid phase equilibria within a first-order thermodynamic perturbation theory applied to an effective one-component potential obtained by integrating out the degrees of freedom of the small spheres. A qualitative agreement emerges between the two different approaches. We also address the determination of the freezing line by applying the first-order thermodynamic perturbation theory to the effective interaction between large spheres. Our results suggest that for intermediate size ratios a modest amount of nonadditivity, smaller than earlier thought, can be sufficient to drive the fluid-fluid critical point into the thermodinamically stable region of the phase diagram. These findings could be significant for rare-gas mixtures in extreme pressure and temperature conditions, where nonadditivity is expected to be rather small.Comment: 17 pages, 7 figures, to appear in J. Phys. Chem.

Autogoverno e autonomia. Baschi e siciliani a confronto

L'articolo si occupa delle origini del concetto di autonomia rintracciando nella giurisprudenza medievale le caratteristiche distinzioni con l'autogoverno

Visual and auditory temporal integration in healthy younger and older adults

As people age, they tend to integrate successive visual stimuli over longer intervals than younger adults. It may be expected that temporal integration is affected similarly in other modalities, possibly due to general, age-related cognitive slowing of the brain. However, the previous literature does not provide convincing evidence that this is the case in audition. One hypothesis is that the primacy of time in audition attenuates the degree to which temporal integration in that modality extends over time as a function of age. We sought to settle this issue by comparing visual and auditory temporal integration in younger and older adults directly, achieved by minimizing task differences between modalities. Participants were presented with a visual or an auditory rapid serial presentation task, at 40-100 ms/item. In both tasks, two subsequent targets were to be identified. Critically, these could be perceptually integrated and reported by the participants as such, providing a direct measure of temporal integration. In both tasks, older participants integrated more than younger adults, especially when stimuli were presented across longer time intervals. This difference was more pronounced in vision and only marginally significant in audition. We conclude that temporal integration increases with age in both modalities, but that this change might be slightly less pronounced in audition

The activation of non-linear optical response in Ag@ZnO nanocolloids under an external highly intense electric field

An extensive theoretical and experimental study of the non-linear optical properties of bare and silver-decorated zinc oxide (ZnO and Ag@ZnO) nanostructures, prepared by laser-generated plasmas in water and in water/polyvinyl alcohol (PVA) solutions, is reported. The z-scan technique was used to monitor the activation of the non-linear optical mechanisms, focusing an intense laser radiation through the nanocolloids under study. A classical formalism was adopted to explain the z-scan data of these anisotropic materials and to describe the influence of radiation torque and forces on the optically activated nanostructures. This modelling approach includes effects of nanoparticles rearrangements, also taking into account plasmonic effects. An interesting coupling between the nature of the optical limiting response and the nanostructures reorganization under the high-power laser excitation, used during the z-scan measurements, was found and, for the first time to our knowledge, was explained using a classical theoretical approach

Sustainable local development and environmental governance: a strategic planning experience

The emphasis on learning and adaptation among different actors at various political administrative levels and on various geographic scales has become a precondition for the emergence of sustainable development. It is possible to find the essential form of collaborative management by using a Strategic Plan, designed to determine a local model of sustainable competitiveness in economic, social and environmental terms. The adoption of a Strategic Plan stimulates a process of shared knowledge, through which it is possible to generate a new environmental governance (EG) that is truly representative of a local system. This paper presents, as a case study representative of the Italian context, the Strategic Plan of the Nebrodi area (SP), and assesses the structure of a new form of public and private environmental governance focused on sustainable concern. Finally, the SP could be considered a guideline for managing the local territorial and environmental system from a long-term perspective

The FCC-BCC-Fluid triple point for model pair interactions with variable softness

It is demonstrated that the coordinates of the fcc-bcc-fluid triple point of various model systems are located in a relatively narrow region, when expressed in terms of the two proper variables, characterizing the softness and strength of the interaction force at the mean interparticle separation. This can be regarded as a consequence of the "corresponding states principle" for strongly interacting particle systems we have put forward recently [S. A. Khrapak, M. Chaudhuri, and G. E. Morfill, J. Chem. Phys. {\bf 134}, 241101 (2011)]. The related possibilities to predict the existence and approximate location of the fcc-bcc-fluid triple point for a wide range of pair interactions with variable softness are illustrated. Relation of the obtained results to experimental studies of complex (dusty) plasmas are briefly discussed.Comment: 5 pages, 2 figures, 1 tabl

Brownian motion of graphene.

Brownian motion is a manifestation of the fluctuation-dissipation theorem of statistical mechanics. It regulates systems in physics, biology, chemistry, and finance. We use graphene as prototype material to unravel the consequences of the fluctuation-dissipation theorem in two dimensions, by studying the Brownian motion of optically trapped graphene flakes. These orient orthogonal to the light polarization, due to the optical constants anisotropy. We explain the flake dynamics in the optical trap and measure force and torque constants from the correlation functions of the tracking signals, as well as comparing experiments with a full electromagnetic theory of optical trapping. The understanding of optical trapping of two-dimensional nanostructures gained through our Brownian motion analysis paves the way to light-controlled manipulation and all-optical sorting of biological membranes and anisotropic macromolecules

Fast UPLC/PDA determination of squalene in Sicilian P.D.O. pistachio from Bronte: optimization of oil extraction method and analytical characterization

A fast reversed-phase UPLC method was developed for squalene determination in Sicilian pistachio samples that entry in the European register of the products with P.D.O. In the present study the SPE procedure was optimized for the squalene extraction prior to the UPLC/PDA analysis. The precision of the full analytical procedure was satisfactory and the mean recoveries were 92.8 + 0.3 % and 96.6 + 0.1 % for 25 and 50 mg L-1 level of addition, respectively. Selected chromatographic conditions allowed a very fast squalene determination; in fact it was well separated in ~ 0.54 min with good resolution. Squalene was detected in all the pistachio samples analyzed and the levels ranged from 55.45 to 226.34 mg . kg-1. Comparing our results with those of other studies it emerges that squalene contents in P.D.O. Sicilian pistachio samples, generally, were higher than those measured for other samples of different geographic origins