Manifestation of vortex depinning transition in nonlinear current-voltage characteristics of polycrystalline superconductor Y_{1-x}Pr_{x}Ba_2Cu_3O_7

We present our recent results on the temperature dependence of current-voltage characteristics for polycrystalline Y_{1-x}Pr_{x}Ba_2Cu_3O_7 superconductors with x = 0.0, 0.1 and 0.3. The experimental results are found to be reasonably well fitted for all samples by a power like law. According to the theoretical interpretation of the obtained results, nonlinear deviation of our current-voltage characteristics curves from Ohmic behavior below Tc is attributed to the manifestation of dissipation processes related to the current induced depinning of Abrikosov vortices.Comment: Accepted for publication in PL

Subtransmission overhead lines mechanical monitoring for fast detection of damaging events

Different harmful events affecting high voltage overhead lines (OHLs) cause changes in the mechanical tension (tensile strength) of conductors. A mechanical monitoring of OHLs, therefore, can provide useful additional information (compared with the information provided by the widely used SCADA systems) about the power system state. The tension measurements combined with a few environmental measurements (air temperature, wind speed) can be used for an automatic (fast) detection of different events and for their approximate location along an OHL, reducing the impact of these events. Referring to 132-150 kV sub-transmission OHLs, this paper proposes some original algorithms, based on the mechanical monitoring of OHLs, for the automatic detection of the following events: conductor breaking, fall of trees on the conductors, ice/snow sleeve accretion on the conductors, strands breaking and galloping. The proposed algorithms require a limited number of sensors placed along the OHLs for measurements of the conductor tension and weather-related quantities

Covalent functionalization enables good dispersion and anisotropic orientation of multi-walled carbon nanotubes in a poly(l-lactic acid) electrospun nanofibrous matrix boosting neuronal differentiation

A biocompatible porous scaffold obtained via electrospinning a nanocomposite solution of poly(l-lactic acid) and 4-methoxyphenyl functionalized multi-walled carbon nanotubes is presented here for the first time for the enhancement of neurite outgrowth. Optimization of blend preparation and deposition parameters paves the way to the obtainment of defect-free random networks of nanofibers with homogeneous diameters in the hundreds of nanometers length scale. The tailored covalent functionalization of nanotube surfaces allows a homogeneous dispersion of the nanofillers within the polymer matrix, diminishing their natural tendency to aggregate and form bundles. This results in a remarkable effect on the crystallization temperature, as evidenced through differential scanning calorimetry. Furthermore, transmission electron microscopy shows carbon nanotubes anisotropically aligned along the fiber axes, a feature believed to enhance neurite adhesion and growth. Indeed, microscopy images show neurites extension along the direction of nanofibers, highlighting the extreme relevance of scaffold morphology in engineering complex tissue environments. Furthermore, a remarkable effect on increasing the neurite outgrowth results when using the fibrous scaffold containing dispersed carbon nanotubes in comparison with an analogous one made of only polymer, providing further evidence of the key role played by carbon nanostructures in inducing neuronal differentiation

Determinants of surgeon choice in cases of suspected implant rupture following mastectomy or aesthetic breast surgery: Clinical implications

Implant ruptures may be diagnosed by physical examination, ultrasound (US), and magnetic resonance imaging (MRI). The absence of standard guidelines to approach to implant ruptures may cause unnecessary surgical revisions in the absence of radiological confirmation of prosthetic damages.The purpose of this study was to analyze the diagnostic procedures applied to patients with suspected prosthetic rupture and surgeon choices to perform a revision or to plan a clinical and radiological follow-up.We conducted a retrospective study on 62 women submitted to revision surgery due to radiological diagnosis of suspected implant rupture, following mastectomy or aesthetic reconstruction, and admitted to a Plastic Surgery Department between 2008 and 2018.Seventy-three implants, believed to be ruptured, were explanted. One-third of these were intact and unnecessarily explanted. US associated with MRI evaluation resulted in the most helpful diagnostical method.A standardized clinical and radiological approach is essential to manage breast implant ruptures successfully. An innovative protocol is proposed in order to: ensure the appropriate management of implant ruptures and prevent unnecessary surgical revisions; reduce the risk of claims for medical malpractice in cases of unsatisfactory final aesthetic results or worse than before

Pinning of spiral fluxons by giant screw dislocations in YBa_2Cu_3O_7 single crystals: Josephson analog of the fishtail effect

By using a highly sensitive homemade AC magnetic susceptibility technique, the magnetic flux penetration has been measured in YBa_2Cu_3O_7 single crystals with giant screw dislocations (having the structure of the Archimedean spirals) exhibiting a=3 spiral turnings, the pitch b=18.7 microns and the step height c=1.2nm (the last parameter is responsible for creation of extended weak-link structure around the giant defects). The magnetic field applied parallel to the surface enters winding around the weak-link regions of the screw in the form of the so-called spiral Josephson fluxons characterized by the temperature dependent pitch b_f(T). For a given temperature, a stabilization of the fluxon structure occurs when b_f(T) matches b (meaning an optimal pinning by the screw dislocations) and manifests itself as a pronounced low-field peak in the dependence of the susceptibility on magnetic field (applied normally to the surface) in the form resembling the high-field (Abrikosov) fishtail effect.Comment: see also http://www.jetpletters.ac.ru/ps/1886/article_28701.shtm

Interfacial Morphology Addresses Performance of Perovskite Solar Cells Based on Composite Hole Transporting Materials of Functionalized Reduced Graphene Oxide and P3HT

The development of novel hole transporting materials (HTMs) for perovskite solar cells (PSCs) that can enhance device's reproducibility is a largely pursued goal, even to the detriment of a very high efficiency, since it paves the way to an effective industrialization of this technology. In this work, we study the covalent functionalization of reduced graphene oxide (RGO) flakes with different organic functional groups with the aim of increasing the stability and homogeneity of their dispersion within a poly(3-hexylthiophene) (P3HT) HTM. The selected functional groups are indeed those recalling the two characteristic moieties present in P3HT, i.e., the thienyl and alkyl residues. After preparation and characterization of a number of functionalized RGO@P3HT blends, we test the two containing the highest percentage of dispersed RGO as HTMs in PSCs and compare their performance with that of pristine P3HT and of the standard Spiro-OMeTAD HTM. Results reveal the big influence of the morphology adopted by the single RGO flakes contained in the composite HTM in driving the final device performance and allow to distinguish one of these blends as a promising material for the fabrication of highly reproducible PSCs

Diffuse-light absorption spectroscopy and chemometrics for discrimination and quantification of extra virgin olive oil adulterants

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Pathway to an excitonic coherence

This paper discusses the combined effects of optical excitation power, interface roughness, lattice temperature, and applied magnetic fields on the spin-coherence of excitonic states in GaAs/AlGaAs multiple quantum wells. For low optical powers, at lattice temperatures between 4 K and 50 K, the scattering with acoustic phonons and short-range interactions appear as the main decoherence mechanisms. Statistical fluctuations of the band-gap however become also relevant in this regime and we were able to deconvolute them from the decoherence contributions. The circularly polarized magneto-photoluminescence unveils a non-monotonic tuning of the coherence for one of the spin components at low magnetic fields. This effect has been ascribed to the competition between short-range interactions and spin-flip scattering, modulated by the momentum relaxation time