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Matrella S.,University of Salerno | Vitiello C.,University of Salerno | Mella M.,University of Insubria | Vigliotta G.,University of Salerno | And 3 more authors.
Macromolecular Bioscience | Year: 2015

Intrinsic antimicrobial thermoplastic A(BC) n copolymers (n = 1, 2, 4), where A was poly(ethylene glycol) (PEG), BC was a random chain of methylmethacrylate (MMA), and alkyl-aminoethyl methacrylate (AAEMA), were synthesized and the antimicrobial activity and hemolyticity were evaluated on plaques obtained by casting as a function of the architecture, the N-substituent groups of the AAEMAs (methyl, ethyl, isopropyl, and tert-butyl groups) and the hydrophobic/charge density balance. Antimicrobial effectiveness and efficiency is controlled by the surface charge density and by the influence of N-alkyl groups on the surface morphology. Also interestingly, it is the absence of hemolitytic activity in all copolymers. In presence of Escherichia coli, the A(BC)2 copolymer with 40% of N-methyl groups is the most efficient, killing 91% of the bacteria already after 1.5 h. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mancusi D.,University of Salerno | Mancusi D.,CNR Institute of Neuroscience | Giubileo F.,University of Salerno | Giubileo F.,CNR Institute of Neuroscience | And 7 more authors.
Physica C: Superconductivity and its Applications | Year: 2014

The temperature dependent first and third harmonics of the AC magnetic susceptibility χ1,3(T) have been measured on Bi4O4S3. The χ1(T) magnetic response is due to the intergranular contribution with a transition temperature Tc ≈ 4.4 K. The dependencies of the χ3(T) on the AC field amplitude and frequency reveal a critical state with the presence of the flux creep and the flux flow regimes. In fact, the field dependencies of the effective activation energy and of the frequency dependent critical current density have been found to be described with power laws characteristic of the collective creep regime involving large flux bundles. © 2014 Elsevier B.V. All rights reserved.

Mancusi D.,University of Salerno | Mancusi D.,CNR Institute of Neuroscience | Polichetti M.,University of Salerno | Polichetti M.,Research Center for Nanomaterials and Nanotechnology | And 3 more authors.
Superconductor Science and Technology | Year: 2015

The temperature-dependent fundamental ac susceptibility of a granular superconductor in the absence of dc fields has been analyzed by developing a phenomenological model for effective magnetic fields, taking into account the influence of the magnetic interaction between the intergranular and the intragranular magnetizations due to demagnetizing effects. For this purpose a policrystal Fe-based superconductor FeSe0.5Te0.5 sample has been studied. By the frequency dependence of the peaks of the temperature-dependent imaginary part of the fundamental complex susceptibility, the dependence on temperature of the characteristic times both for intergranular and intragranular relaxations of magnetic flux are derived, and the corresponding relaxation processes due to combinations of the flux creep, the flux flow and the thermally activated flux flow regimes are identified on the basis of the effective magnetic fields both at the sample surface and at the grains' surfaces. Such characteristic times, through the Havriliak-Negami function, determine the temperature and the frequency dependences of the complex susceptibility. The comparison of the numerically obtained curves with the experimental ones confirms the relevance, for identifying the intergranular and intragranular contributions to the ac magnetic response and the corresponding flux dynamical regimes, of the interaction between the intergranular and intragranular magnetizations due to demagnetizing effects. © 2015 IOP Publishing Ltd.

Mancusi D.,University of Salerno | Mancusi D.,CNR Institute of Neuroscience | Di Giorgio C.,University of Salerno | Di Giorgio C.,Research Center for Nanomaterials and Nanotechnology | And 20 more authors.
Superconductor Science and Technology | Year: 2014

A magnetic study of superconductor/ferromagnet bilayers was performed by hysteresis loops and temperature-dependent magnetization measurements. The superconductor/ferromagnet bilayers consist of a Nb film deposited on a Py film with weak perpendicular magnetic anisotropy. By comparing the temperature-dependent magnetization data obtained on samples with different ferromagnetic layer thickness, a decrease of the magnetic pinning with increasing thickness of the ferromagnetic layer has been found. This is confirmed by the reduction of the Nb film critical current density at low fields extracted by using the magnetic irreversibility of the hysteresis loops. The reduction of the pinning can be related to the increase of the stripe width in the ferromagnetic layer observed by magnetic force microscopy (MFM) measurements. © 2014 IOP Publishing Ltd.

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