1,784 research outputs found
Development of new technologies and methods for next-generation gamma-ray telescopes
No full textL’Astrofisica delle Alte Energie (AAE) è fondamentale per la comprensione di fenomeni stellari estremi ed eventi su scala cosmologica. Il campo della AAE è nato nel 1962, quando l’esperimento di Rossi e Giacconi portò alla scoperta delle prime sorgenti di raggi X extraterrestri. Nel corso degli ultimi settant’anni, sono stati fatti incredibili progressi relativamente alle tecnologie, tecniche e strumenti a disposizione per studiare il cielo X e gamma. Tuttavia, importanti questioni risultano ancora aperte, soprattutto nel regime dei raggi X duri e gamma molli, es: quale sia l’origine della linea di annichilazione e+/e- dal centro galattico, qual è la natura del motore centrale delle esplosioni dei lampi gamma (gamma-ray bursts, GRB) e molti altri.
La strumentazione attuale non dispone di sufficienti capacità di localizzazione, risoluzione spaziale, sensibilità, per affrontare questi problemi, né ha capacità di effettuare misure polarimetriche. Lo scopo di questa tesi è quindi di esplorare ed avanzare le tecnologie ed i metodi che ci permetteranno di superare queste limitazioni e, allo stesso tempo, di prepararci a sfruttare in modo ottimale le prossime missioni di AE.
Descriveremo nello specifico i recenti progressi che abbiamo ottenuto nell’aumentare il livello tecnologico delle lenti di Laue per usi astrofisici. Le lenti di Laue sono ottiche per raggi X/gamma innovative, vasato sulla legge della diffrazione di Bragg, che possono permetterci di costruire strumenti focalizzanti per AE capaci di operare oltre il limite di ∼70 keV (ottenuto dalla missione NuSTAR attraverso l’impiego di ottiche ad incidenza radente multi-layer) ed arrivare fino a∼ 700 keV. L’implementazione di ottiche focalizzanti per raggi gamma molli porterà ad un significativo aumento nella sensibilità dei nostri strumenti, fino a 3 ordini di magnitudine in più rispetto a strumenti a vista diretta.
Descriveremo il design del concetto di missione spaziale ASTENA, sottomesso alla call ESA “Voyage 2050” e basato su questo tipo di ottiche. ASTENA porterà due strumenti: il Wide Field Monitor (WFM), un rivelatore a campo ampio con capacità di imaging e spettrometria, ed il Narrow Field Telescope (NFT), un telescopio per raggi gamma molli bassato su una lente di Laue. I nostri sforzi si sono concentrati sull’ottimizzare e caratterizzare questi due strumenti. In questo lavoro, nello specifico, ci siamo concentrati sullo stimare le capacità polarimetriche di NFT e WFM, in modo da comprendere come questi strumenti potranno giocare un ruolo nel campo della polarimetria delle alte energie.
Infine, siccome progressi tecnologici devono sempre essere accompagnati da progressi metodologici, abbiamo affrontato una questione di vecchia data nel campo dei lampi gamma: trovare un metodo consistente ed affidabile per simulare curve di luce (LC) dei GRB. LC simulate sono utilizzate per ottimizzare future missioni spaziali e caratterizzare le attuali osservazioni; tuttavia, la simulazione di curve di luce è una sfida complessa, in quanto gli attuali modelli fisici basati sul paradigma degli shock interni non sono capaci di riprodurre la grande diversità morfologica delle LC osservate. D’altro canto, costruire template di LC a partire da altri strumenti/missioni richiede di disaccoppiare in maniera opportuna il segnale reale dal rumore. In questo lavoro, abbiamo investigato un nuovo approccio di simulazione basato su un modello stocastico combinato a moderni algoritmi di machine learning.
Obiettivo di questa tesi è stato lo sviluppo di tecnologie innovative per progredire la strumentazione per astrofisica delle alte energie da differenti punti di vista interconnessi. Allo stesso tempo, abbiamo iniziato ad esplorare nuove tecniche basate sull’intelligenza artificiale, che necessariamente giocheranno un ruolo fondamentale nello studio delle future missioni per AE e nel campo dei lampi gamma.High Energy Astrophysics (HEA) studies are fundamental to understanding extreme stellar and
cosmological scale phenomena. The field of HEA was born in 1962, with Rossi and Giacconi’s rocket experiment leading to the discovery of the first extraterrestrial X-ray sources. Over the last seventy years, vast improvements have been made in technologies, techniques, and instruments to study the X and gamma-ray sky. However, outstanding questions are still open, in particular in the hard X-/soft gamma-ray regime: for example, the origin of the e+/e− annihilation line coming from the galactic centre, the nature of the engine that powers gamma ray bursts’ (GRBs) explosions, the geometry and explosion mechanisms of supernova emission, and many more.
The currently available instrumentation lacks sufficient localisation capabilities, spatial and energetic resolution, sensitivity, and the ability to perform polarimetric measurements. Such limitations have thus hindered further advancements in the HEA field. In this context, this thesis aims to explore and advance the technologies and methods that will allow us to overcome such limits and prepare us for an optimal exploitation of upcoming HE missions.
We will focus specifically on the recent progress we made in advancing the technological readiness of Laue lenses for astrophysics applications. Laue lenses are innovative hard X/soft gamma-ray optics based on Bragg’s diffraction law, allowing HE focusing instruments to operate beyond the current limit of ∼70 keV, based on multi-layer grazing incident mirrors (as in the NuSTAR mission), to ∼700 keV. The implementation of soft gamma-ray focusing optics will result in a significant increase in sensitivity, up to three orders of magnitude higher than direct view instruments.
We will describe the design of a new space mission concept based on this type of optics: the Advanced Surveyor for Transient Events and Nuclear Astrophysics (ASTENA), proposed to ESA for the call "Voyage 2050". ASTENA will include two instruments: the Wide Field Monitor (WFM), a wide field detector with both imaging and spectrometric capabilities, and the Narrow Field Telescope (NFT), a soft gamma-ray telescope based on a Laue lens. We concentrated our efforts on optimising the design of those two instruments and characterising their properties to meet several scientific requirements. In this work, we specifically focused on estimating the polarimetric capabilities of both NFT and WFM to understand how those instruments can play a new competitive role in high-energy polarimetry.
Finally, technological advancements should always be accompanied by new methodological advancements. We focused on a long-standing challenge in the GRB field: finding a robust and reliable way to simulate light curves (LCs) of GRB events. GRBs are among the most fascinating sources observed in the high-energy sky, and mock GRB LCs can be used to exploit future HE missions optimally and characterise current GRB observations. However, simulating their light curves remains challenging since physical models based on the internal shock paradigm fail to reproduce the diversity of the observed LCs’ morphologies. On the other hand, by constructing LC templates from other instruments/missions, one faces the challenge of properly decoupling the real signal from the noise. This work investigates a new approach to simulate GRB LCs based on stochastic models combined with modern machine learning techniques.
This thesis work aims to develop innovative technologies to advance our instrumentation for high-energy astrophysics from different, interconnected points of view. At the same time, we start exploring new artificial intelligence-based techniques, which inevitably will play a key role in the analysis of upcoming HE missions, particularly in the ever-expanding field of GRBs
Preliminary investigations on the use of preceramic polymers to produce metal matrix composites, via powder metallurgy techniques
No full textCeramic-reinforced metal matrix composites were produced by means of preceramic polymers, as precursors for the ceramic phase, and powders of metal alloy as matrix.
The use of preceramic polymers as precursors for a reinforcing ceramic phase in metallic components represents a well known technique to produce 3D interpenetrating composites.
However, it was poorly investigated so far. Only few results were published in literature, concerning the use of polycarbosilane in Ti or Fe-Cr alloys. In the present work the use of a polysiloxanes, as precursor for a SiOC reinforcing and/or reacting phase, dispersed within a metal matrix is reported. Commercial metal alloys’ powders are investigated
Poéticas experimentales en el espacio público Ánima Lisa: Lima, Perú
No full textARQUITECTO(S) DISEÑADOR(ES): Colectivo Ánima Lisa: Santiago y Rodrigo Vera, Luis Aberto Castillo, Daniel Sánchez, Fabio Rodríguez.
CIUDAD / MUNICIPIO: Lim
La necropoli delle Ripaie
No full textStudio delle fasi protostoriche della necropoli delle Ripaie di Volterra (fine età del Bronzo, età del Ferro, periodo Orientalizzante
Il milanese Francesco Ellio traduttore del 'Persiles' di Cervantes (1626)
No full textThe essay presents a research around the figure of the Milanese poet Francesco Ellio,
who lived in Milan in the early seventeenth century and is so far known for being the
author of idylls. In this paper Ellio, whose dense network of contacts and relationships in the
Lombard city is gathered, is studied because he is the author of the first Italian translation of
Cervantes’ Perciles, the last masterpiece of the Hispanic genius, published in 1617. The translation
was edited in Venice for the printer Fontana in 1626, placing itself among the last traces
of Ellio’s life, and will remain the only one in Italian until the nineteenth century
An advanced pulse-avalanche stochastic model of long gamma-ray burst light curves
No full textContext. A unified explanation of the variety of long-duration gamma-ray burst (GRB) light curves (LCs) is essential for identifying the dissipation mechanism and possibly the nature of their central engines. In the past, a model was proposed to describe GRB LCs as the outcome of a stochastic pulse avalanche process, possibly originating from a turbulent regime, and it was tested by comparing average temporal properties of simulated and real LCs. Recently, we revived this model and optimised its parameters using a genetic algorithm (GA), a machine-learning-based approach. Our findings suggested that GRB inner engines may operate near a critical regime.
Aims. Here we present an advanced version of the model, which allows us to constrain the peak flux distribution of individual pulses, and evaluate its performance on a new dataset of GRBs observed by the Fermi Gamma-ray Burst Monitor (GBM).
Methods. After introducing new model parameters and a further comparison metric, that is the observed signal-to-noise (S/N) distribution, we test the new model on three complementary datasets: CGRO/BATSE, Swift/BAT, and Fermi/GBM. As in our previous work, the model parameters are optimised using a GA.
Results. The updated sets of parameters achieve a further reduction in loss compared to both the original model and our earlier optimisation. The different values of the parameters across the datasets are shown to originate from the different energy passbands, effective areas, trigger algorithms, and, ultimately, different GRB populations of the three experiments.
Conclusions. Our results further underpin the stochastic and avalanche character of the dissipation process behind long GRB prompt emission, with an emphasis on the near-critical behaviour, and establish this new model as a reliable tool for generating realistic GRB LCs as they would be seen with future experiments
Nuovi dati dalla necropoli delle Ripaie: i materiali sporadici
No full textL'articolo presenta lo studio di un lotto significativo di materiali sporadici databili tra la prima età del Ferro e il periodo Orientalizzante recuperati negli anni 1969-70 nell'area della necropoli delle Ripaie di Volterra
Sonoma twaini Ferro 2016, new species
No full text13. Sonoma twaini new species Fig. 13, 17; Map 39. Description. Holotype, male. Measurements: head 0.25 long, 0.31 wide; pronotum 0.30 long, 0.34 wide; elytra 0.59 long, 0.28 wide; antennomeres 1–11 total 0.57; total length 1.92. Body brown, maxillary palpi and legs paler. Body with moderate length setae (approximately 1/2 or less width of eye). Head. Eyes prominent, maximum length in dorsal view 0.47x length of first antennal segment, with approximately 30 facets. Antennomere 2 approximately 0.90x width of 1; 3 smallest. Thorax. Elytra with indistinct sutural foveae; 2 foveae lateral to sutural fovea; central row of 3 foveae in basal 1/3. Winged. Metatibia unmodified. Abdomen. Tergite IV with transverse patch of microtrichia narrowly interrupted at midline. Basal lateral foveae on ventrites V–VII. Basal pubescence present on all visible ventrites. Aedeagus. Elongate. Left paramere: equal in length to endophallus; subequal in width from base to apex; with 4–5 stout apical setae and 3 ventral subapical setae. Endophallus: widest at basal 1/5; with two ventral processes arising 2/3 from base projecting perpendicular to aedeagus; apex bent 90° to the left. Right paramere: 2/3 length left paramere; subequal in width from base to apex; with 4–5 stout apical setae and 3 ventral subapical setae. Type Material. Holotype, male: * T. R. Haig Whiskeytown Shasta Co. Cal. III.9.1973 (1♂). Deposited in CSCA. Paratypes (n=4). UNITED STATES: CALIFORNIA: Shasta Co.: * T. R.Haig Whiskeytown Shasta Co.Cal. III.9.1973 (CSCA) (2♂). * T. R.Haig Whiskeytown Shasta Co.Cal. I.31.1973 (CSCA) (1♂). Trinity Co.: * CALIF:Trinity Co. Junction City III-12-1981 T. R.Haig coll. (FMNH) (1♂). Geographical Distribution. Sonoma twaini is only known from two locations, one each in Shasta and Trinity counties, California. Comments. Sonoma twaini was collected in January and March, collection method is unknown. Aedeagal characters of S. twaini are superficially similar to S. wintuorum, S. stewarti, and S. colberti all of which share a similar gestalt comprised of narrow, elongate parameres and an elongate endophallus with elaborate apical hooks or processes. The flowing combination of characters will separate S. twaini from the others: endophallus with two ventral processes arising 2/3 from base projecting perpendicular to aedeagus [absent in S. wintuorum, S. stewarti, and S. colberti]; without elongate thin posteriorly directed process arising 2/3 from base of endophallus [present in S. wintuorum and S. stewarti]; endophallus with single apical process [two in S. wintuorum, three in S. colberti]. Etymology. Sonoma twaini is named for the character Mark Twain, developed by Samuel Langhorne Clemens, an author, lecturer, philosopher, humanitarian, champion of science, and humorist. Clemens lived in California for awhile, but traveled nowhere near where this species occurs—the author forgives the oversight.Published as part of Ferro, Michael L., 2016, Fourteen new species of Sonoma Casey (Coleoptera: Staphylinidae: Pselaphinae) with a key to species from western North America, pp. 1-57 in Insecta Mundi 2016 (472) on page 17, DOI: 10.5281/zenodo.517050
Interval between Removal of a 4.7 mg Deslorelin Implant after a 3-, 6-, and 9-Month Treatment and Restoration of Testicular Function in Tomcats
No full textDeslorelin implants have been used to produce a reversible sterilization in several species. In cats, the prolonged duration (12-15 months in tomcats and 18-22 months in queen) is often too much for cat breeders who request early implant removal. The interval between implant removal and resumption of reproductive function in cats has never been investigated. Eighteen tomcats received a 4.7 mg deslorelin implant placed in the periumbilical area and surgically removed during all seasons of the year after 3, 6, or 9 months (n = 6, 6, and 6 cats, respectively). Following implant removal, all cats received a clinical exam every two weeks, including testicular ultrasonographic measurement, observation of penile spikes, and blood collection for serum testosterone assay. Restoration of serum testosterone secretion occurred after 23 ± 6, 23 ± 6, and 22 ± 7 days in the 3-, 6-, and 9-month groups, respectively. Restoration of testicular function was confirmed by histology in 13/15 cats undergoing orchiectomy at the end of the study while the owners of the remaining two cats opted to maintain their animals intact. Removal of a 4.7 mg deslorelin implant after 3, 6, or 9 months is followed by resumption of serum testosterone secretion after about 3 weeks independent of age or season
Appetite Stimulant and Anti-Emetic Effect of Mirtazapine Transdermal Ointment in Cats Affected by Lymphoma Following Chemotherapy Administration: A Multi-Centre Retrospective Study
No full textIn humans, mirtazapine can prevent chemotherapy-induced nausea and vomiting (CINV) and improve cancer patients’ quality of life (QoL). This drug is being increasingly used as an appetite stimulant in cats. The hypothesis of this retrospective study was that mirtazapine could reduce the incidence of CINV and weight loss in feline patients affected by lymphoma. The objectives were to report the use of mirtazapine transdermal ointment and assess the incidence of gastrointestinal (GI) toxicity and weight loss in cats diagnosed with lymphoma and receiving chemotherapy. Transdermal mirtazapine was topically administered to the inner surface of the pinna (2 mg/cat/daily) for 14 days following chemotherapy administration. Data recorded from 20 patients were collected. Different grades of GI toxicity were shown in 8/20 (40%) patients. Body weight (BW), body condition score (BCS), and muscle condition score (MCS) improved in 12/20 (60%), 6/20 (30%), and 2/20 (10%) cats, respectively. Mirtazapine-induced adverse events (AEs) occurred in 4/20 (20%) cats and did not require mirtazapine discontinuation. Substantial weight loss was not encountered, suggesting that patients had an adequate food intake after chemotherapy administration. Transdermal mirtazapine ointment was considered safe and well tolerated
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