Mechanical behaviour with temperatures of aluminum matrix composites with CNTs

Aluminum is a very useful structural metal employed in different industrial sectors, in particular it is used in large quantities in automotive, aeronautic and nautical industries. The main reasons of its wide use are: a very good oxidation resistance, excellent ductility, low melting temperature (660 °C) and low density (2.71 g/cm3). However, in order to reduce the emissions and fuel consumption is necessary to reduce the overall weight of vehicles by increasing mechanical properties of the structural material. The improvement of mechanical properties is normally achieved through use of reinforcement in materials, used like matrix, in order to improve some specific characteristics. In this work composites of carbon nanotubes (CNTs) dispersed in aluminum were made. The most difficulties in the preparation of this type of composite are represented by the low wettability between metallic matrix and fillers and the possibility of the oxidation of metal during melting with consequent decreasing of mechanical proprieties. The composite was obtained by three consecutive step: the first one is the functionalization of fillers surface to improve the fillers dispersion, the second one is the dispersion of fillers in the matrix by powder mixing and the third one is the melting and casting of the mix prepared. In particular, fillers used are multi walled carbon nanotubes (MWCNTs) with functionalized surface by treatment with a solfonitric solution. Melting and casting are carried out with the aid of an induction furnace with a controlled atmosphere system and centrifugal casting. Argon is the inert gas used to prevent the oxidation of aluminium during fusion. Young’s modulus was evaluated at different temperature and correlated with the different CNTs percentage. The dispersion rate of fillers and the microstructure of the sample were evaluated by FESEM micrograph

Electrokinetic Lattice Boltzmann solver coupled to Molecular Dynamics: application to polymer translocation

We develop a theoretical and computational approach to deal with systems that involve a disparate range of spatio-temporal scales, such as those comprised of colloidal particles or polymers moving in a fluidic molecular environment. Our approach is based on a multiscale modeling that combines the slow dynamics of the large particles with the fast dynamics of the solvent into a unique framework. The former is numerically solved via Molecular Dynamics and the latter via a multi-component Lattice Boltzmann. The two techniques are coupled together to allow for a seamless exchange of information between the descriptions. Being based on a kinetic multi-component description of the fluid species, the scheme is flexible in modeling charge flow within complex geometries and ranging from large to vanishing salt concentration. The details of the scheme are presented and the method is applied to the problem of translocation of a charged polymer through a nanopores. In the end, we discuss the advantages and complexities of the approach

The effect of being awardees for academic careers. ERC and FIRB recipients' outcomes compared to ordinary academics – performances and promotions

Some individual funding schemes aim at recognize excellence of early and/or mid-career researchers in order to allow them boost their potential. Some schemes are munificent endowments, assuring autonomy and security. This is the case of one of the European flagship schemes – the European Research Council (ERC). In Italy, a very similar scheme called FIRB has a similar rationale. Both schemes are supposed to make excellence “fly higher”. The paper checks whether such ERC and FIRB recipients are thereafter more productive in terms of quality and influence testing against a control group of Italian academics of similar age, rank and discipline who did not win such individual grants. Results show that ERC recipients ameliorate research performance more than FIRB recipients did, although differences with control group don’t show always a particular additional effect in research outputs when comparing with pre-awarding performances (difference-in-difference tests). On the other hand, we find a strong Matthew effect in promotions, being the credential of having recipient of an ERC or a FIRB per se the strongest predictor of promotion, other achievements being equal. Policy recommendations speculate whether an egalitarian non-stratified higher education system like the Italian one is ideal home for these schemes, and whether the Italian system can afford a national scheme overlapping international ones, considering long-lasting shortage of financial resources and the egalitarian structure of its system

The gender promotion gap in Italy

The topic of gender differences and career progression is high not only on the scholarly agenda, it is often discussed in the media as well – sometimes in quite controversial terms. We investigate this theme in Italy, a country that in recent years introduced a level of institutional autonomy in determining the career paths of academics. We provide analysis of census data about promotion to full professorship, looking at indicators of productivity, rank, age and prestige of an individual’s department of affiliation. Our analysis also takes into account institutional performative indicators, which affect promotion probabilities. Our study (Marini & Meschitti 2018) found that when promotion decisions lacked transparency a strong discrimination existed against women, despite their productivity matching that of their male counterparts. However, gender discrimination was almost absent when fully transparent procedures were adopted. The seminar will also look at whether this discrimination can be explained by similarities in professors’ communities (those in charge of bestowing promotions), considering specifically the combination of discipline and institution

Amplification of surface plasmon polaritons in the presence of nonlinearity and spectral signatures of threshold crossover

We describe effects of nonlinearity on propagation of surface plasmon polaritons (SPPs) at an interface between a metal and an amplifying medium of the externally pumped two-level atoms. Using Maxwell equations we derive the nonlinear dispersion law and demonstrate that, the nonlinear saturation of the linear gain leads to formation of stationary SPP modes with the intensities independent from the propagation distance. Transition to the regime of stationary propagation is similar to the threshold crossover in lasers and leads to narrowing of the SPP spectrum.Comment: http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-34-18-286

Ginzburg-Landau equation bound to the metal-dielectric interface and transverse nonlinear optics with amplified plasmon polaritons

Using a multiple-scale asymptotic approach, we have derived the complex cubic Ginzburg-Landau equation for amplified and nonlinearly saturated surface plasmon polaritons propagating and diffracting along a metal-dielectric interface. An important feature of our method is that it explicitly accounts for nonlinear terms in the boundary conditions, which are critical for a correct description of nonlinear surface waves. Using our model we have analyzed filamentation and discussed bright and dark spatially localized structures of plasmons.Comment: http://link.aps.org/doi/10.1103/PhysRevA.81.03385

From endorsement of ambivalent sexism to psychological IPV victimization: The role of attitudes supportive of IPV, legitimating myths of IPV, and acceptance of psychological aggression.

Research on intimate partner violence (IPV) has recognized psychological abuse as a precursor of physical and sexual violence in intimate relationships. However, risk factors in predicting women’s psychological abuse victimization in such a context are still unclear. The goal of the present work was to investigate the role of ambivalent sexism on psychological IPV victimization, by taking into account in the same study the effect of three additional social-psychological factors: women’s i) attitudes supportive of IPV, ii) endorsement of legitimating myths of IPV, and iii) acceptance of psychological aggression in intimate relationships. A total of 408 Italian young women (Mage = 23.87; SD = 2.39) involved in non-marital heterosexual romantic relationships completed measures aimed at assessing i) hostile and benevolent sexism, ii) attitudes supportive of IPV, iii) legitimating myths of IPV, iv) prevalence of psychological abuse experienced within the last 12 months, and performed a task developed ad hoc to measure v) acceptance of psychological aggression in intimate relationships. Results showed that the effect of ambivalent sexism on participants’ prevalence of psychological abuse was mediated by the endorsement of attitudes supportive of IPV and legitimating myths of IPV, as well as by acceptance of psychological aggression. Findings are discussed based on literature about ambivalent sexism, and attitudes and beliefs about IP

Which is the temperature of granular systems? A mean field model of free cooling inelastic mixtures

We consider a mean field model describing the free cooling process of a two component granular mixture, a generalization of so called Maxwell model. The cooling is viewed as an ordering process and the scaling behavior is attributed to the presence of an attractive fixed point at $v=0$ for the dynamics. By means of asymptotic analysis of the Boltzmann equation and of numerical simulations we get the following results: 1)we establish the existence of two different partial granular temperatures, one for each component, which violates the Zeroth Law of Thermodynamics; 2) we obtain the scaling form of the two distribution functions; 3) we prove the existence of a continuous spectrum of exponents characterizing the inverse-power law decay of the tails of the velocity, which generalizes the previously reported value 4 for the pure model; 4) we find that the exponents depend on the composition, masses and restitution coefficients of the mixture; 5) we also remark that the reported distributions represent a dynamical realization of those predicted by the Non Extensive Statistical Mechanics, in spite of the fact that ours stem from a purely dynamical approach.Comment: 23 pages, 9 figures. submitted for publicatio

Steady state properties of a mean field model of driven inelastic mixtures

We investigate a Maxwell model of inelastic granular mixture under the influence of a stochastic driving and obtain its steady state properties in the context of classical kinetic theory. The model is studied analytically by computing the moments up to the eighth order and approximating the distributions by means of a Sonine polynomial expansion method. The main findings concern the existence of two different granular temperatures, one for each species, and the characterization of the distribution functions, whose tails are in general more populated than those of an elastic system. These analytical results are tested against Monte Carlo numerical simulations of the model and are in general in good agreement. The simulations, however, reveal the presence of pronounced non-gaussian tails in the case of an infinite temperature bath, which are not well reproduced by the Sonine method.Comment: 23 pages, 10 figures, submitted for publicatio

Dark Matter searches using gravitational wave bar detectors: quark nuggets and newtorites

Many experiments have searched for supersymmetric WIMP dark matter, with null results. This may suggest to look for more exotic possibilities, for example compact ultra-dense quark nuggets, widely discussed in literature with several different names. Nuclearites are an example of candidate compact objects with atomic size cross section. After a short discussion on nuclearites, the result of a nuclearite search with the gravitational wave bar detectors Nautilus and Explorer is reported. The geometrical acceptance of the bar detectors is 19.5 $\rm m^2$ sr, that is smaller than that of other detectors used for similar searches. However, the detection mechanism is completely different and is more straightforward than in other detectors. The experimental limits we obtain are of interest because, for nuclearites of mass less than $10^{-5}$ g, we find a flux smaller than that one predicted considering nuclearites as dark matter candidates. Particles with gravitational only interactions (newtorites) are another example. In this case the sensitivity is quite poor and a short discussion is reported on possible improvements.Comment: published on Astroparticle Physics Sept 25th 2016 replaced fig 1