‘Habent et urbes suum terminum’. Rovina e decadenza in alcuni luoghi dell’umanesimo Italiano*

The article focuses on the role the image of decadence and ruin played inItalian Quattrocento Humanism. The depiction of the ruins of ancient Rome, afrequent topic in humanistic poetry and a well-known approach to the themeinvestigated, constitutes the paper’s starting point. Beside the contemplationof ruins experienced in many ‘Roman’ poems, though, the fall of   Constantinople in 1453 provided humanists with a sense of impending doomon the whole ‘western’ world: the contemporary ruin of the Greek world wasseen, as some writings show, as an ‘apocalyptic’ event, which would eventually affect the whole of Christianity. It is argued, then, that in the humanistic depiction of ruins as an ongoing historical process, textual and thematic allusions to the Apocalypse act as a distinguishing feature

Growing massive black holes through super-critical accretion of stellar-mass seeds

The rapid assembly of the massive black holes that power the luminous quasars observed at $z \sim 6-7$ remains a puzzle. Various direct collapse models have been proposed to head-start black hole growth from initial seeds with masses $\sim 10^5\,\rm M_\odot$, which can then reach a billion solar mass while accreting at the Eddington limit. Here we propose an alternative scenario based on radiatively inefficient super-critical accretion of stellar-mass holes embedded in the gaseous circum-nuclear discs (CNDs) expected to exist in the cores of high redshift galaxies. Our sub-pc resolution hydrodynamical simulations show that stellar-mass holes orbiting within the central 100 pc of the CND bind to very high density gas clumps that arise from the fragmentation of the surrounding gas. Owing to the large reservoir of dense cold gas available, a stellar-mass black hole allowed to grow at super-Eddington rates according to the "slim disc" solution can increase its mass by 3 orders of magnitudes within a few million years. These findings are supported by simulations run with two different hydro codes, RAMSES based on the Adaptive Mesh Refinement technique and GIZMO based on a new Lagrangian Godunov-type method, and with similar, but not identical, sub-grid recipes for star formation, supernova feedback, black hole accretion and feedback. The low radiative efficiency of super-critical accretion flows are instrumental to the rapid mass growth of our black holes, as they imply modest radiative heating of the surrounding nuclear environment.Comment: 12 pages, 8 figures, 2 tables. Accepted for publication in MNRA

Hyperbolic metamaterials by directed self-assembly of block copolymers

Hyperbolic materials are high uniaxial anisotropic materials that display hyperbolic dispersion with distinctive properties, including negative refraction index, control over light propagation and enhanced Purcell factor. Naturally-occurring hyperbolic materials exhibit these properties only in reduced wavelength ranges, thus limiting their implementation into integrated optical devices. In order to tune the hyperbolic dispersion over broader bandwidths, artificial structures capable to guarantee a greater flexibility, i.e. hyperbolic metamaterials (HMMs), are required. So far, the realization of HMMs that work in the visible and near-infrared wavelength regions has been limited to the out-of-plane configuration due to technological costraints in the fabrication of periodic structures at sub-wavelength dimensions. Here we propose a novel concept of HMMs working in the in-plane configuration, based on the use of block copolymers (BCPs) capable to self-assemble into highly ordered polimeric masks with nanometric feature sizes and periodicity, serving as templates for the subsequent fabrication of hybrid metal-dielectric HMMs. This new class of HMMs can be exploited for metrological applications such as the enhancement of single photon source's (SPS) emission properties

Implementation of an asymmetric network equilibrium problem with detailed representation of unsignalized and signalized urban intersections

This paper discusses the implementation of an asymmetric network equilibrium model with detailed representation of unsignalized and signalized urban intersections. A software has been developed to solve the deterministic user equilibrium (DUE) problem which takes into account real urban intersections in their detailed configurations. During the first phase this software was tested on a “toy” network and then on the real network of Villafranca (a town near Verona Italy). The comparison between the equilibrium flow patterns resulting from the model and some traffic counts on the Villafranca network confirms that the model is good

Critical issues of double-metal layer coating on FBG for applications at high temperatures

Use of fiber Bragg gratings (FBGs) to monitor high temperature (HT) applications is of great interest to the research community. Standard commercial FBGs can operate up to 600 ∘ C. For applications beyond that value, specific processing of the FBGs must be adopted to allow the grating not to deteriorate. The most common technique used to process FBGs for HT applications is the regeneration procedure (RP), which typically extends their use up to 1000 ∘ C. RP involves a long-term annealing of the FBGs, to be done at a temperature ranging from 550 to 950 ∘ C. As at that temperature, the original coating of the FBGs would burn out, they shall stay uncoated, and their brittleness is a serious concern to deal with. Depositing a metal coating on the FBGs prior to process them for RP offers an effective solution to provide them with the necessary mechanical strengthening. In this paper, a procedure to provide the FBG with a bimetallic coating made by copper and nickel electrodeposition (ED) is proposed, discussing issues related to the coating morphology, adherence to the fiber, and effects on the grating spectral response. To define the processing parameters of the proposed procedure, production tests were performed on dummy samples which were used for destructive SEM-EDS analysis. As a critical step, the proposed procedure was shown to necessitate a heat treatment after the nickel ED, to remove the absorbed hydrogen. The spectral response of the FBG samples was monitored along the various steps of the proposed procedure and, as a final proof test for adherence stability of the bimetallic coating, along a heating/cooling cycle from room temperature to 1010 ∘ C. The results suggest that, given the emergence of Kirkendall voids at the copper-nickel interface, occurring at the highest temperatures (700-1010 ∘ C), the bimetallic layer could be employed as FBG coating up to 700 ∘ C

Lean maturity assessment in eto scenario

The obligatory path towards a lean manufacturing organization requires assessment and monitoring. However, a lean assessment framework is not yet available for the engineer to order (ETO) scenario. This work explored ten lean ETO maturity principles—identified from the literature—that take insight from three formally defined sets (Toyota Way, lean construction, and lean product development principles). A practical assessment model was proposed based on the evaluation of ten lean ETO objective criteria (four with mathematical formulation) and was validated on a real industrial case. A problem‐solving tool, including a new lean tool, called the Problem Focus Matrix (PFM), was also presented; this tool was aimed toward development of an integrated framework that would include the organization mission, management, and continuous improvement

Microstructural and mechanical properties of a novel cobalt and titanium free maraging steel for laser powder bed fusion

Maraging steels are widely used in Additive Manufacturing due to their good processability and outstanding combination of strength and toughness. 18Ni300 is one of the most employed maraging steels. However, it contains cobalt, which has recently been strictly regulated due to its environmental and health hazards, having been classified as carcinogenic. Moreover, this steel contains Ti, showing a high affinity for oxygen, leading to high oxide fractions in powder and final parts. In the current work an ultrahigh strength Co and Ti free maraging steel for AM was processed and characterized. The results were then compared to 18Ni300. The novel alloy, processed with Powder Bed Fusion - Laser Beam (PBF-LB) shows hardness, yield strength, and tensile strength of 525 HV1, 1475 MPa, and 1588 MPa, respectively, after solution annealing and aging treatments