Cut-off Characterisation of Energy Spectra of Bright Fermi Sources: Current instrument limits and future possibilities

In this paper some of the brightest GeV sources observed by the Fermi-LAT were analysed, focusing on their spectral cut-off region. The sources chosen for this investigation were the brightest blazar flares of 3C~454.3 and 3C~279 and the Vela pulsar with a reanalysis with the latest Fermi-LAT software. For the study of the spectral cut-off we first explored the Vela pulsar spectrum, whose statistics in the time interval of the 3FGL catalog allowed strong constraints to be obtained on the parameters. We subsequently performed a new analysis of the flaring blazar SEDs. For these sources we obtained constraints on the cut-off parameters under the assumption that their underlying spectral distribution is described by a power-law with a stretched exponential cut-off. We then highlighted the significant potential improvements on such constraints by observations with next generation ground based Cherenkov telescopes, represented in our study by the Cherenkov Telescope Array (CTA). Adopting currently available simulations for this future observatory, we demonstrate the considerable improvement in cut-off constraints achievable by observations with this new instrument when compared with that achievable by satellite observations.Comment: total number of pages 24, including 6 pages of references. Accepted by Astroparticle Physic

On wind-wave interaction phenomena at low Reynolds numbers

After decades of research efforts, wind-wave interaction mechanisms have been recognized as extremely elusive. The reason is the complex nature of the problem, which combines complex coupling mechanisms between turbulent wind and water waves with the presence of multiple governing parameters, such as the friction Reynolds number of the wind, the water depth and the wind fetch. As shown unequivocally here, the use of suitable flow settings allows us to reduce the complex problem of wind-wave interaction to its essential features, mainly as a function of the sole friction Reynolds number of the wind. The resulting numerical solution allows us to study the interactions between water and air layers with their own fluid properties, and to unveil very interesting features, such as an oblique wave pattern travelling upstream and a wave-induced Stokes sublayer. The latter is responsible for a drag reduction mechanism in the turbulent wind. Despite the simulated flow conditions being far from the intense events occurring at the ocean-atmosphere interface, the basic flow phenomena unveiled here may explain some experimental evidence in wind-wave problems. Among other things, the wave-induced Stokes sublayer may shed light on the large scatter of the drag coefficient data in field measurements where swell waves of arbitrary directions are often present. Hence the present results and the developed approach pave the way for the understanding and modelling of the surface fluxes at the ocean-atmosphere interface, which are of overwhelming importance for climate science

Lo Slovo na voznesenie di Kirill Turovskij: esegesi, celebrazione, parenesi

Il presente saggio si pone come obiettivo la verifica dell’ipotesi sulla specificità dell’omiletica di Kirill Turovskij nel confronto con i sermoni comuni di epoca kieviana (XI-XIII sec.) attraverso l’analisi dello Slovo na voznesenie (Omelia per l’ascensione). Recenti studi sullo Slovo na verbnoe voskresen’e (Omelia per la domenica delle palme) e sullo Slovo o rasslablennom (Omelia sul paralitico) mi hanno permesso di scorgere un nesso fra tale specificità e la finalità esegetica di queste omelie, al cui interno prevalgono procedimenti esegetici. L’analisi delle funzioni delle citazioni bibliche nello Slovo na voznesenie, condotta in questa sede, mostra però la finalità in primo luogo celebrativa del discorso, realizzata di preferenza da procedimenti di drammatizzazione. Questo dato mi ha allora indotto a riconsiderare l’ipotesi di partenza, individuando le ragioni della specificità dell’omiletica di Kirill Turovskij nell’imitatio ricreativa dei testi della tradizione patristica nelle loro varietà funzionali: la varietà esegetica, esemplificata dai commentari ai libri biblici, e quella celebrativa, esemplificata dalle omelie festive. In questo modo l’omiletica di Kirill Turovskij fonda nella predicazione slava orientale dei primi secoli la distinzione (già bizantina e occidentale) fra omelie esegetiche e omelie festive.The present article aims at verifying an hypothesis about the significance of Kirill Turovskij’s homiletics within medieval East Slavic preaching of Kievan period (11th-13th centuries), doing so through the analysis of his Slovo na voznensenie (Homily for ascension). In recent studies of his Slovo na verbnoe voskresen’e (Homily for Palm Sunday) and Slovo o rasslablennom (Homily about the sick man), I explained their difference from Kievan common sermons by the chiefly exegetical aim the author pursued (and the prevalence of exegetical devices within the texts). The analysis of how biblical quotations function in the Slovo na vosnesenie shows that this homily differs from the others in that it has a chiefly celebratory purpose, fulfilled through dramatizing devices. This insight leads me to reassess the previous hypothesis, tracing the innovation of Kirill Turovskij’s homiletics back to his cultured approach to Patristic tradition. The author plainly perceived and accepted Patristic writings as theoretical models, and was able to re-create their functional varieties – the exegetical variety, exemplified by Patristic homilies in the Bible, and the celebratory one, exemplified by Patristic festal homilies – thus establishing within his homiletics, as well as medieval East Slavic preaching, the Byzantine division between exegetical and festal homilies and the Western one between homily and sermon

Sulle varietà dell’omiletica di Kirill Turovskij: lo Slovo po Pascě

About the Varieties of Kirill Turovskij’s Homiletics: the Slovo po Pascě On the basis of recent studies aimed at investigating Kirill Turovskij’s preaching, an hypothesis regarding the specificity of his homiletics emerged. If compared with the corpus of instructional sermons dating back to the Kievan period (11th-13th centuries), Kirill Turovskij’s homilies stand out for the particular liturgical function that biblical quotations serve within them. In the Slovo na verbnoe voskresenie (Homily for Palm Sunday) and the Slovo o rasslablennom (Homily about the sick man), this function advances primarily an exegetical aim, fulfilled through exegetical devices, while in the Slovo na voznesenie (Homily for Ascension) this very function serves primarily a celebratory aim, fulfilled through dramatizing devices. Recalling patristic models, the homilies seemingly follow – within Turovskij’s homiletics, as well as medieval East Slavic preaching – the Byzantine division between exegetical and festal homilies and the Western one between homily and sermon. The analysis of the Slovo po Pascě (Homily for Low Sunday [Sunday after Easter]) offered in the present article confirms the previous hypothesis. The homily, founded on a chain of biblical, hymnographic, patristic and Byzantine references clearly pointing to its liturgical, patristic and Byzantine sources, closely recovered here, functionally reproduces patristic festal homilies, thus demonstrating the variety of Turovskij’s homiletics

Sl.eccl. мудрость. Studi per un lexicon plurilingue dei termini religiosi e filosofico-teologici

Церк.-слав. ‘мудрость’. Предварительные исследования в области многоязычно- го лексикона религиозной и философско-богословской лексики Цель статьи – определение семантики церк.-слав. ‘мудрость’, её отражения в средневековых восточнославянских и допетровских источниках (XII-XVIII вв.). Упо- требление слова было проверено в историческом разделе Национального кор- пуса русского языка, а контексты его употребления были извлечены из того же источника. Обработка материалов направлена на установление набора значений слова и его возможной семантической вариативности. В рамках проекта много- язычного лексикона религиозной и философско-богословской лексики, получен- ные результаты свидетельствуют о полезности прямого исследования источников наряду с изучением семантики слов, зафиксированной в словарях, или даже вме- сто последнего.Church Slavonic мудрость. Studies for a Multilingual Lexicon of Religious and Philosophical- Theological Words The article aims at defining the semantics of Church Slavonic мудрость as it emerges from medieval and pre-modern Eastern Slavic sources dating from the 12th to 18th century. Occurrences were verified in the historical sub-section of the Russian National Corpus. Elaboration of the collected data is directed at delineating the range of meanings of the term and evaluating its possible semantic variations (also according to the typology and chronology of the sources). For the multilingual lexicon of religious and philosophical-theological words, the results of the inquiry are so disparate as to favor a return to the individual sources over meanings derived from dictionaries

Максим Грек на Западе. Κ реконструкции его пребывания в Италии

В статье предлагается исследование двух узловых моментов раннего этапа биографии Максима Грека: период между его приездом во Флоренцию и отъездом в Мирандолу и его последние годы в Италии. Цель работы – восстановление его жизненного пути на Западе. Используются славянские источники, авторитетные биографии и достижения новейших исследований.The article aims at contributing to the restoration of Maximus the Greek’s journey in the West by investigating two turnings points in the earlier period of his biography: the interval between his arrival in Florence and his departure to Mirandola, and the last years he spent in Italy. Investigation is grounded in direct Slavic sources, authoritative biographies and the results of the most recent studies

VHE observations of the gamma-ray binary system LS 5039 with H.E.S.S

LS 5039 is a gamma-ray binary system observed in a broad energy range, from radio to TeV energies. The binary system exhibits both flux and spectral modulation as a function of its orbital period. The X-ray and very-high-energy (VHE, E > 100 GeV) gamma-ray fluxes display a maximum/minimum at inferior/superior conjunction, with spectra becoming respectively harder/softer, a behaviour that is completely reversed in the high-energy domain (HE, 0.1 < E < 100 GeV). The HE spectrum cuts off at a few GeV, with a new hard component emerging at E > 10 GeV that is compatible with the low-energy tail of the TeV emission. The low 10 - 100 GeV flux, however, makes the HE and VHE components difficult to reconcile with a scenario including emission from only a single particle population. We report on new observations of LS 5039 conducted with the High Energy Stereoscopic System (H.E.S.S.) telescopes from 2006 to 2015. This new data set enables for an unprecedentedly-deep phase-folded coverage of the source at TeV energies, as well as an extension of the VHE spectral range down to ~120 GeV, which makes LS 5039 the first gamma-ray binary system in which a spectral overlap between satellite and ground-based gamma-ray observatories is obtained.Comment: Proceeding for ICRC 201

Influence of skin-layer microstructure in ultrafast laser surface treatment

In this work, the morphology of AISI 316L stainless steel surfaces, textured with ultrafast laser machining, was studied by scanning probe microscopy. In particular, correlations between the morphology and the polycrystalline microstructure of the material were searched. Topographic maps of the treated surfaces revealed a transition from small-sized to larger size and rather irregular features, driven by increase in laser fluence and depending on process parameters. In addition, a metrological analysis of the material grains demonstrated a shape and size similarity with laser-induced features attained for certain process parameters, suggesting that surface texture turns influenced by the microstructure of the skin-layer

Reconnection in a slow Coronal Mass Ejection

This paper aims at studying reconnection occurring in the aftermath of the 28 May 2004, CME, first imaged by the LASCO (Large Angle and Spectrometric Coronagraph) C2 at 11:06 UT. The CME was observed in White Light and UV radiation: images acquired by the LASCO C2 and C3 coronagraphs and spectra acquired by UVCS (Ultraviolet Coronagraph Spectrometer) allowed us to identify the level at which field lines, stretched outwards by the CME ejection, reconnect below the CME bubble. As the CME propagates outwards, reconnection occurs at increasingly higher levels. The process goes on at a low pace for several hours: here we give the profile of the reconnection rate vs. heliocentric distance over a time interval of &asymp;14 h after the CME onset, extending estimates of the reconnection rate to larger distances than previously inferred by other authors. The reconnection rate appears to decrease with time/altitude. We also calculate upper and lower limits to the density in the diffusion region between 4 and 7 <I>R</I>_&#x2299; and conclude by comparing estimates of the classical and anomalous resistivity in the diffusion region with the value inferred from the data. The latter turns out to be &ge;5 order of magnitudes larger than predicted by classical or anomalous theories, pointing to the need of identifying the process responsible for the observed value

Study of the wettability behavior of stainless steel surfaces after ultrafast laser texturing

The interest in superhydrophobic surfaces has grown exponentially over recent decades. Since the lotus leaf dual hierarchical structure was discovered, researchers have investigated the foundations of this behavior and many methods have been developed to obtain superhydrophobic surfaces. In this paper the possibility to use ultrafast laser treatments to obtain hydrophobic and superhydrophobic stainless surfaces was investigated on a AISI 316L stainless steel, ranging the total energy doses provided to the surfaces from 178 to 1143 J/cm2. As SEM-FEG images reveals, different surface microstructures can be obtained at the increasing values of energy dose. Independently on the specific values of laser treatment, all the obtained samples showed hydrophobic values of static contact angle. However, only particular surface microstructures allowed obtaining a self-cleaning surface characterized by low values of both contact angle hysteresis and roll-off angle. The obtained results led to define the effect of the laser parameters on the morphological, chemical and wetting surface properties allowing one to design new textures with the desired wetting properties, from “lotus effect” surfaces to “rose petal effect” surfaces