Acoustic, thermal and flow processes in a water filled nanoporous glasses by time-resolved optical spectroscopy

We present heterodyne detected transient grating measurements on water filled Vycor 7930 in the range of temperature 20 - 90 degrees C. This experimental investigation enables to measure the acoustic propagation, the average density variation due the liquid flow and the thermal diffusion in this water filled nano-porous material. The data have been analyzed with the model of Pecker and Deresiewicz which is an extension of Biot model to account for the thermal effects. In the whole temperature range the data are qualitatively described by this hydrodynamic model that enables a meaningful insight of the different dynamic phenomena. The data analysis proves that the signal in the intermediate and long time-scale can be mainly addressed to the water dynamics inside the pores. We proved the existence of a peculiar interplay between the mass and the heat transport that produces a flow and back-flow process inside the nano-pores. During this process the solid and liquid dynamics have opposite phase as predicted by the Biot theory for the slow diffusive wave. Nevertheless, our experimental results confirm that transport of elastic energy (i.e. acoustic propagation), heat (i.e. thermal diffusion) and mass (i.e. liquid flow) in a liquid filled porous glass can be described according to hydrodynamic laws in spite of nanometric dimension of the pores. The data fitting, based on the hydrodynamic model, enables the extraction of several parameters of the water-Vycor system, even if some discrepancies appear when they are compared with values reported in the literature.Comment: 32 pages, 11 figure

Fast Analysis of Stop-Band FSS Integrated with Phased Array Antennas

This paper presents a method for the efficient analysis of multilayer frequency selective surfaces (FSSs) integrated with phased array of open-ended waveguides. The method is based on the assumption that all the periodic surfaces are arranged on the same spatial lattice (of arbitrary shape). The whole structure is represented as an equivalent multi-mode transmission line network, where each interface is characterized by an equivalent Generalized Scattering Matrix (GSM), computed through a fullwave analysis. To reduce the computational effort of the analysis a fast adaptive interpolation algorithm for the scattering matrix entries is included

Fast, multi-band photon detectors based on quantum well devices for beam-monitoring in new generation light sources

In order to monitor the photon-beam position for both diagnostics and calibration purposes, we have investigated the possibility to use InGaAs/InAlAs Quantum Well (QW) devices as position-sensitive photon detectors for Free-Electron Laser (FEL) or Synchrotron Radiation (SR). Owing to their direct, low-energy band gap and high electron mobility, such QW devices may be used also at Room Temperature (RT) as fast multi-band sensors for photons ranging from visible light to hard X-rays. Moreover, internal charge-amplification mechanism can be applied for very low signal levels, while the high carrier mobility allows the design of very fast photon detectors with sub-nanosecond response times. Segmented QW sensors have been preliminary tested with 100-fs-wide 400 nm laser pulses and X-ray SR. The reported results indicate that these devices respond with 100 ps rise-times to such ultra-fast laser pulses. Besides, linear scan on the back-pixelated device has shown that these detectors are sensitive to the position of each ultrashort beam bunch

Three-Dimensional Shapes of Spinning Helium Nanodroplets

A significant fraction of superfluid helium nanodroplets produced in a free-jet expansion have been observed to gain high angular momentum resulting in large centrifugal deformation. We measured single-shot diffraction patterns of individual rotating helium nanodroplets up to large scattering angles using intense extreme ultraviolet light pulses from the FERMI free-electron laser. Distinct asymmetric features in the wide-angle diffraction patterns enable the unique and systematic identification of the three-dimensional droplet shapes. The analysis of a large dataset allows us to follow the evolution from axisymmetric oblate to triaxial prolate and two-lobed droplets. We find that the shapes of spinning superfluid helium droplets exhibit the same stages as classical rotating droplets while the previously reported metastable, oblate shapes of quantum droplets are not observed. Our three-dimensional analysis represents a valuable landmark for clarifying the interrelation between morphology and superfluidity on the nanometer scale

The “Treasure of Como” and the Production of Solidi During the Late Roman Empire

The Como Treasure, discovered in 2018 during archaeological excavations in the Roman town of Novum Comum, consists of 1,000 solidi  and a few other gold artifacts – three rings, a small piece of an ingot and incomplete and unfinished gold jewelry. It is the most  important hoard of Roman gold coins discovered in Central/Western Europe in recent decades. The examination of the solidi allowed  for the study of the traces of workmanship and the reconstruction of the operative chain used in Late Antiquity mints. The gold was  melted under oxidizing conditions, purified by cupellation and cementation and then assayed. In order to obtain the blanks, foils were  made, cut in round plates with iron shears. Then the edges and the weight were adjusted al pezzo with iron files. As some of the  impurities visible to the naked eye show on some coins, iron filings from files accidentally got into the filings or gold waste used for  melting. Coins were obtained by minting using dies engraved according to a well determined sequence: after a subdivision of the die’s  surface with compasses, the figures and finally the inscriptions were engraved. The production process was concluded by checking the weight of the coins. In times of intensive production mints could shorten their production times by recoining old coins. In this case, the purity of the gold was checked by taking a sample from the center of the coins before their recoinage. These different stages required  specialized staff and ateliers with different features placed in a building that guaranteed high levels of security and that was well connected to the road network to allow supplies. These characteristics seem to be found in a building unearthed in old excavations in  Milan and already interpreted as a bath. On the basis of the information currently available, however, the possibility of it being the  mint of the comitatus cannot be ruled out

Free electron laser-driven ultrafast rearrangement of the electronic structure in Ti

High-energy density extreme ultraviolet radiation delivered by the FERMI seeded free-electron laser has been used to create an exotic nonequilibrium state of matter in a titanium sample characterized by a highly excited electron subsystem at temperatures in excess of 10 eV and a cold solid-density ion lattice. The obtained transient state has been investigated through ultrafast absorption spectroscopy across the Ti M2,3-edge revealing a drastic rearrangement of the sample electronic structure around the Fermi level occurring on a time scale of about 100 fs

NGS applications to understand invertebrate biodiversity of Antarctica and mechanisms of gene expression involved in climatic changes

Human activities, such as greenhouse emissions and pollution, are leading to global warming, environmental changes and biodiversity reduction. Pristine environments such as those of Antarctica are not immune to these phenomena, as is noticeable from the temperature shifts and ice-melting registered within the continent in recent decades. To date, many scientists focused on how marine species react to these changes but no molecular data are currently available for continental terrestrial invertebrates and in particular for Collembola (=springtails). Therefore, part of my PhD project was to study the transcriptomic response of the endemic Antarctic springtail Cryptopygus terranovus following a mid-term exposure of 20 days at 18°C. Expression data were compared with wild specimens sampled in native environment. Although individual plasticity in transcript modulation was recorded, several pathways appear to be differentially modulated: protein catabolism, fatty acid metabolism and a sexual response characterized by spermatid development were induced, while lipid catabolism was downregulated in treated samples. Moreover, the temperature experienced by these micro-invertebrates is a pivotal parameter to understand these animals' ecology and physiology. However, at present, detailed knowledge of microhabitat physical conditions in Antarctica is limited and biased towards sub-Antarctic and maritime Antarctic regions. To better understand these temperature conditions, it was analysed a year-round temperature data in ponds and soils in an area of the Victoria Land coast, comparing these measurements with air temperatures from the closest automatic weather station. Important difference in temperature dynamics between the air, soil and pond datasets was registered. Ponds were the warmest sites overall, mostly differing with the air temperatures due to their greater thermal capacity, which also influenced their patterns of freeze-thaw cycles and mean daily thermal excursion. Furthermore, to better understand the biodiversity of Collembola two new mitochondrial genomes of Antarctic springtails were sequenced and analysed. They were employed to revise the entire systematic of the class, its nucleotide composition and genome arrangement by comparing them to all the available sequences deposited in Genbank. In the phylogenetic analysis, with minor exceptions, it was confirmed the monophyly of Poduromorpha and Symphypleona sensu stricto (the latter recovered as the most basal group in the springtail phylogenetic tree), whereas monophyly of Neelipleona and Entomobryomorpha was only supported when some critical taxa in these two lineages were excluded. The genome arrangement review allowed to identify four new gene orders (one from the newly sequenced Tullbergia mixta), for a total of 16 models. Finally, nucleotide composition analyses confirmed the low AT bias in Collembola mitochondrial DNA respect to other Hexapoda, and that third codon position is inclined to mutation accumulation, especially in 4-fold amino-amino acids. To ease the process of mitochondrial genome analyses, it was created a web resource named EZmito, a free web server useful to analyse mitochondrial genomes. It is composed of five main tools: (i) EZsplit, useful to download and format sequences directly from the NCBI database; (ii) EZpipe, a pipeline designed to format mitochondrial sequences before the phylogenetic analysis; (iii) EZskew, which helps users to calculate nucleotide biases; (iv) EZcodon, a fast tool which calculates the Relative Synonym Codon Usage of different mtDNA species and (v) EZmix, which recognizes areas of inter molecular similarity indicative of the assembly of chimeric mitochondrial genomes. Interestingly, to date, the most used tool within the hub is EZcodon, followed by EZsplit and EZpipe

L’esprit « national » des villes communales des États Pontificaux à la fin du Moyen Âge. Le cas de Bologne

L’émergence d’une culture civique collective, d’une identité culturelle unitaire qui nait autour de la configuration politique urbaine, a été plusieurs fois mise en évidence dans le contexte des villes communales italiennes. À cette émergence, l’historiographie a souvent associé un processus de formation culturelle qui se rapproche de celui de la création d’un sentiment identitaire national : la coniuratio, moment créateur du principe associatif, qui a été définie comme le « mythe fondateur »..