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Picollo F.,National Institute of Nuclear Physics, Italy | Picollo F.,University of Turin | Picollo F.,National Interuniversity Consortium for the Physical science of Matter | Rubanov S.,University of Melbourne | And 19 more authors.
Acta Materialia | Year: 2016

We report on the structural modifications induced by a λ = 532 nm ns-pulsed high-power laser on sub-superficial graphitic layers in single-crystal diamond realized by means of MeV ion implantation. A systematic characterization of the structures obtained under different laser irradiation conditions (power density, number of pulses) and subsequent thermal annealing was performed by different electron microscopy techniques. The main feature observed after laser irradiation is the thickening of the pre-existing graphitic layer. Cross-sectional SEM imaging was performed to directly measure the thickness of the modified layers, and subsequent selective etching of the buried layers was employed to both assess their graphitic nature and enhance the SEM imaging contrast. In particular, it was found that for optimal irradiation parameters the laser processing induces a six-fold increase the thickness of sub-superficial graphitic layers without inducing mechanical failures in the surrounding crystal. TEM microscopy and EELS spectroscopy allowed a detailed analysis of the internal structure of the laser-irradiated layers, highlighting the presence of different nano-graphitic and amorphous layers. The obtained results demonstrate the effectiveness and versatility of high-power laser irradiation for an accurate tuning of the geometrical and structural features of graphitic structures embedded in single-crystal diamond, and open new opportunities in diamond fabrication. © 2015 Acta Materialia Inc.

D'Angelo E.,University of Pavia | D'Angelo E.,Connectivity | Solinas S.,Connectivity | Garrido J.,University of Pavia | And 10 more authors.
Functional Neurology | Year: 2013

Realistic modeling is a new advanced methodology for investigating brain functions. Realistic modeling is based on a detailed biophysical description of neurons and synapses, which can be integrated into microcircuits. The latter can, in turn, be further integrated to form large-scale brain networks and eventually to reconstruct complex brain systems. Here we provide a review of the realistic simulation strategy and use the cerebellar network as an example. This network has been carefully investigated at molecular and cellular level and has been the object of intense theoretical investigation. The cerebellum is thought to lie at the core of the forward controller operations of the brain and to implement timing and sensory prediction functions. The cerebellum is well described and provides a challenging field in which one of the most advanced realistic microcircuit models has been generated. We illustrate how these models can be elaborated and embedded into robotic control systems to gain insight into how the cellular properties of cerebellar neurons emerge in integrated behaviors. Realistic network modeling opens up new perspectives for the investigation of brain pathologies and for the neurorobotic field. © CIC Edizioni Internazionali.

Mura F.,Ludwig Maximilians University of Munich | Bhattacharjee S.M.,Institute of Physics, Bhubaneswar | Maji J.,Chennai Mathematical Institute | Masetto M.,University of Padua | And 4 more authors.
Journal of Low Temperature Physics | Year: 2016

In the quantum Efimov effect, identical bosons form infinitely many bound trimer states at the bound dimer dissociation threshold, with their energy spectrum obeying a universal geometrical scaling law. Inspired by the formal correspondence between the possible trajectories of a quantum particle and the possible conformations of a polymer chain, the existence of a triple-stranded DNA bound state when a double-stranded DNA is not stable was recently predicted by modelling three directed polymer chains in low-dimensional lattices, both fractal ((Formula presented.)) and euclidean ((Formula presented.)). A finite melting temperature for double-stranded DNA requires in (Formula presented.) the introduction of a weighting factor penalizing the formation of denaturation bubbles, that is non-base paired portions of DNA. The details of how bubble weighting is defined for a three-chain system were shown to crucially affect the presence of Efimov-like behaviour on a fractal lattice. Here we assess the same dependence on the euclidean (Formula presented.) lattice, by setting up the transfer matrix method for three infinitely long chains confined in a finite size geometry. This allows us to discriminate unambiguously between the absence of Efimov-like behaviour and its presence in a very narrow temperature range, in close correspondence with what was already found on the fractal lattice. When present, however, no evidence is found for triple-stranded bound states other than the ground state at the two-chain melting temperature. © 2016 Springer Science+Business Media New York

Ahmadipanah S.,University of Tabriz | Kheradmand R.,University of Tabriz | Prati F.,University of Insubria | Prati F.,National Interuniversity Consortium for the Physical science of Matter
IEEE Photonics Technology Letters | Year: 2014

Cavity solitons in a driven vertical-cavity surface-emitting laser (VCSEL) above threshold can amplify the modulation of the injected field over a bandwidth larger than 100 GHz by exploiting the combined low frequency amplification of a bistable optical system with the enhanced relaxation oscillation frequency of an injection-locked laser. © 2014 IEEE.

Giacco F.,The Second University of Naples | Lippiello E.,The Second University of Naples | Lippiello E.,National Interuniversity Consortium for the Physical science of Matter | Ciamarra M.P.,University of Naples Federico II
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2012

The suppression of friction between sliding objects, modulated or enhanced by mechanical vibrations, is well established. However, the precise conditions of occurrence of these phenomena are not well understood. Here we address these questions focusing on a simple spring-block model, which is relevant to investigate friction both at the atomistic as well as the macroscopic scale. This allows us to investigate the influence on friction of the properties of the external drive, of the geometry of the surfaces over which the block moves, and of the confining force. Via numerical simulations and a theoretical study of the equations of motion, we identify the conditions under which friction is suppressed and/or recovered, and we evidence the critical role played by surface modulations and by the properties of the confining force. © 2012 American Physical Society.

Ami D.,University of Milan Bicocca | Ami D.,National Interuniversity Consortium for the Physical science of Matter | Di Segni M.,Laboratory of Medical Genetics | Forcella M.,University of Milan Bicocca | And 6 more authors.
European Journal of Histochemistry | Year: 2014

The so called chromosome preparation is a procedure consisting of three strictly connected stages that enables to obtain chromosomes of quality suitable for cytogenetic analysis. Interestingly, experimental evidence strongly suggested that chromosome spreading and swelling (key processes that allow their counting and detailed structural analysis) are induced in the last fixative-evaporation stage by the interaction, mediated by acetic acid, between water from the environmental humidity, and the cytoplasmic matrix and the chro-matin. However, since a considerable variation in the quality of chromosome preparations is observed, strongly depending on the environmental conditions in which the procedure takes place, a better comprehension of the mechanisms underlying chromosome preparation is required. To this aim, here we analysed intact lymphocytes before and at each stage of the chromosome preparation protocol by Fourier transform infrared (FTIR) spec-troscopy, a technique widely used for the study not only of isolated biomolecules, but also of complex biological systems, such as whole cells. Interestingly, we found that the chromosome preparation protocol induces significant structural changes of cell proteins and DNA, in particular due to the interaction with acetic acid. Moreover, noteworthy, through the monitoring of changes in the water combination band between 2300 and 1800 cm-1, we provided evidence at molecular level of the crucial role of the bound water to the cytoplasmic matrix and to the chromatin in determining the chromosome spreading and swelling. Our FTIR results, therefore, underline the need to perform the last fixative-evaporation stage in standardized and optimized temperature and relative humidity conditions, thus providing chromosomes of high quality for the cytogenet-ic analysis that would lead in this way to more reliable results. © D. Ami et al., 2014.

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