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In spite of their ubiquitous applications, the characterization of glass fibers by means of all-optical techniques is still facing some limitations. Recently, X-ray absorption has been proposed as a method for visualizing the inner structure of both standard and microstructure optical fibers. Here, we exploit X-ray absorption as nondestructive technique for the characterization of optical glass fibers. Starting from absorption contrast X-ray computed micro-tomography measurements, we obtain information about the spatial profile of the fiber refractive index at optical frequencies. We confirm the validity of our approach by comparing its results with complementary characterization techniques, based on electron spectroscopy or multiphoton microscopy.

Metasurfaces have been extensively engineered to produce a wide range of optical phenomena, allowing unprecedented control over the propagation of light. However, they are generally designed as single-purpose devices without a modifiable post-fabrication optical response, which can be a limitation to real-world applications. In this work, we report a nanostructured planar fused silica metalens permeated with a nematic liquid crystal (NLC) and gold nanoparticle solution. The physical properties of embedded NLCs can be manipulated with the application of external stimuli, enabling reconfigurable optical metasurfaces. We report all-optical, dynamic control of the metalens optical response resulting from thermo-plasmonic induced changes of the NLC solution associated with the nematic-isotropic phase transition. A continuous and reversible tuning of the metalens focal length is experimentally demonstrated, with a variation of 80 um (0.16% of the 5 cm nominal focal length) along the optical axis. This is achieved without direct mechanical or electrical manipulation of the device. The reconfigurable properties are compared with corroborating numerical simulations of the focal length shift and exhibit close correspondence., Comment: Main text

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In this paper, we present a simple and robust numerical method able to predict, with high accuracy, the photo-thermal effects occurring for a gold nanoparticles arrangement under externally applied strain. The physical system is numerically implemented in the COMSOL Multiphysics simulation platform. The gold nanoparticles distributions are excited by linearly polarized light. By considering the system at rest and under the action of a mechanical stress, we analyze the extinction cross section, and we observe the production of heat at the nanoscale. The purpose of this work is to describe how sensitive the local temperature of the gold nanoparticles arrangement is to the formation of localized photo-thermal hot spots.

Pyrite, FeS2, nanoparticles were obtained through a one-pot solvothermal synthesis, without surfactants, carried out at room pressure and mild temperature (?180{\textdegree}C). A thorough characterization of the products was thus performed, including scanning-electron-microscope micromorphology, X-ray diffraction (XRD), diffuse reflectance spectroscopy, and X-ray absorption spectroscopy (both in the XANES and EXAFS regions).Monophasic pyrite products are obtained as aggregates having an approximate dimension of few hundreds of nm. The Scherrer analysis of the Bragg reflections suggests that these aggregates are clusters of smaller units, having a mean size of ~25 nm. The XRD measurements point to a small but significant increase of the Fe{\textendash}S bond distance (+1.7 \%) with respect to reference data. The optical behavior of the pyrite nanoparticles is indistinguishable from that of the bulk pyrite.These results point to the one-pot synthesis as an efficient and {\textquotedblleft}green{\textquotedblright} way of obtaining pyrite nanoparticles exhibiting the same technological properties as bulk pyrite. Indeed these nanoparticles can be considered as a product viable for numerous technological applications in the solar-energy conversion and storage fields.

In questo lavoro gli autori analizzano le problematiche della progettazione sismica dei telai controventati ad instabilità impeditata (Buckling-Restrained Braced Frame – BRBF), tipologia per la quale l’Eurocodice 8 non fornisce alcuna indicazione. Pertanto viene adottata una metodologia progettuale che ricalca il format procedurale che l’Eurocodice 8 prescrive per i telai controventati convenzionali (CBF). Nell’articolo, in particolare, dapprima si descrive il comportamento meccanico della diagonale ad instabilità impedita, successivamente viene illustrata la metodologia di progetto adottata per i BRBF, che viene quindi applicata ad alcuni casi di studio per valutarne l’affidabilità mediante l’analisi critica della risposta non-lineare delle soluzioni progettate. L’efficacia prestazionale dei BRBF progettati con tale metodologia viene infine saggiata mediante confronti con la risposta non-lineare dei controventi concentrici a X progettati secondo l’Eurocodice 8.

Background Helicobacter pylori infection causes chronic oxidative stress on gastric mucosa, thereby causing mucosal damage and increasing the risk of gastric adenocarcinoma. Nrf2 is an important transcription factor, regulating the antioxidant response in the cells. Nrf2 signaling is repressed by Keap1 at basal condition and induced by oxidative stress. The aim of our study was to analyze whether the H. pylori proteins interfered in the Nrf2/Keap1 pathway. Material and Methods Gene expression in AGS cells transiently and stably transfected was analyzed by real-time PCR. Immunoprecipitation and immunofluorescence assays were performed to investigate the ability of H. pylori proteins to interfere with the Nrf2 pathway. Results We demonstrated that the H. pylori HspB protein interferes with Nrf2/Keap1 pathway. When HspB was transiently transfected in AGS cells, a significant increase in Keap1 gene expression was induced. The same result was observed when AGS cells were HspB stably transfected. In this case, the increase in Keap1 was associated with reduced gene expression of Nrf2, and of the antioxidant enzymes superoxide dismutase, hemeoxygenase-1, and phase II detoxifying enzyme NAD(P)H:quinone oxidoreductase-1. Immunoprecipitation and immunofluorescence assays confirmed the ability of HspB protein to interfere with the Nrf2 pathway. Lastly, in HspB-transfected AGS cells, sustained activation of IL-8, COX2, MMP3, and MMP7 was demonstrated. Conclusion The results here reported suggest that inhibited nuclear translocation of Nrf2, associated with induced inflammation and increased production of MMPs, might represent a condition enhancing the risk of gastric adenocarcinoma.

Atti del seminario conclusivo del progetto di ricerca DPC-ReLUIS 2005-2008. Napoli, 4-5 dicembre 2008

La sostituzione dei ponti in ambiente urbano presenta spesso notevoli difficoltà, derivanti dall’esistenza di vincoli strutturali e non. Questi possono essere dettati dalla geometria o da esigenze architettoniche, ma anche dall’interazione della nuova opera con le opere ed i fabbricati circostanti, cosi come con i sottoservizi. Per questo motivo, la scelta progettuale finale risulta spesso un compromesso tra le varie esigenze che hanno condizionato lo sviluppo del progetto. In questa memoria viene presentato il progetto di un ponte in cemento armato a volta obliqua di spessore variabile di 27 metri di luce, attualmente in fase di completamento nel comune di Napoli. Malgrado le dimensioni contenute dell’opera, sia durante la fase di progettazione che durante quella di costruzione, sono emersi una serie di problemi che hanno dettato le scelte finali del progettista. In particolare, per quanto concerne la statica dell’opera, le analisi strutturali hanno rivelato un comportamento della volta obliqua non facilmente intuibile a priori. L’opera viene realizzata con diversi tipi di calcestruzzo per i vari elementi strutturali, tra cui anche il calcestruzzo autocompattante SCC che, malgrado la doppia inclinazione dell’estradosso dell’impalcato, ha mostrato, attraverso una accurata campagna di prove condotte in sito e in laboratorio, la possibilità di utilizzo anche per elementi particolarmente inclinati.

The equation of motion of linear dynamic systems with viscoelastic memory is usually expressed in a integrodifferential form, and its numerical solution is computationally heavy. In two recent papers, the writers suggested that the system memory be accounted for through the introduction of a number of additional internal variables. Following this approach, the motion of the system is governed by a set of first-order, linear differential equations, whose solution is quite easy. In this paper, the approach is extended to single-degree-offreedom systems subjected to random, nonstationary excitation. The equations governing the time variation of the second-order statistics are derived, and an effective step-by-step solution procedure is proposed. Numerical example shows the accuracy of the procedure for white and nonwhite excitations.