90 research outputs found
Hierarchical black hole triples in young star clusters: Impact of Kozai-Lidov resonance on mergers
No full textMergers of compact-object binaries are one of the most powerful sources of gravitational waves (GWs) in the frequency range of second-generation ground-based GW detectors (advanced LIGO and Virgo). Dynamical simulations of young dense star clusters (SCs) indicate that ~27 per cent of all double compact-object binaries are members of hierarchical triple systems (HTs). In this paper, we consider 570 HTs composed of three compact objects (black holes or neutron stars) that formed dynamically in N-body simulations of young dense SCs. We simulate them for a Hubble time with a new code based on the Mikkola's algorithmic regularization scheme, including the 2.5 post-Newtonian term. We find that ~88 per cent of the simulated systems develop Kozai-Lidov (KL) oscillations. KL resonance triggers the merger of the inner binary in three systems (corresponding to 0.5 per cent of the simulated HTs), by increasing the eccentricity of the inner binary. Accounting for KL oscillations leads to an increase of the total expected merger rate by ≈50 per cent. All binaries that merge because of KL oscillations were formed by dynamical exchanges (i.e. none is a primordial binary) and have chirp mass >20 M⊙. This result might be crucial to interpret the formation channel of the first recently detected GW events
Cartagine come Troia e Priamo come Penteo: una Ilioupersis sul Citerone (Ovidio, Metamorfosi III e Marlowe, Dido Queen of Carthage II)
No full textLa ‘traduzione’ del II libro dell’Eneide nel II
atto di Dido Queen of Carthage di Christopher
Marlowe è stata spesso derubricata come un
ardito tour de force drammatico. Ma il lungo
monologo di Enea, per quanto negletto,
si rivela fondamentale per comprendere
l’architettura simbolica della tragedia di
Marlowe, poiché diviene una potentissima
‘realizzazione’ dei tropi amorosi che
incorniciano il libro IV dell’Eneide. Attraverso
la poesia ovidiana, le fiamme (reali e
metaforiche) di Elena che incendiano Troia
diventano un’acuta prolessi drammatica della
tragedia dell’amore distruttivo di Didone. Ma
la finissima rilettura marloviana dell’ornatus
del libro IV, nella Ilioupersis elisabettiana, si
spinge addirittura oltre. Anche le similitudini
‘tragiche’ che illustrano il furor di Didone
vengono infatti rilette e ‘drammatizzate’ da
Marlowe nel racconto della morte di Priamo
(un brano a sua volta fondamentale nella
dinamica tragica dell’Amleto shakespeariano).
E ancora attraverso Ovidio, nella sua riscrittura
metamorfica delle Baccanti: una tragedia
lontana da Troia, ma vicinissima a Didone.
Come spesso accade, tuttavia, questa rilettura
rinascimentale ci spinge ad affinare ancor più
la nostra comprensione della poesia latina e
delle dinamiche allusive che la innervano.Marlowe’s ‘translation’ of Book 2 of the
Aeneid (Aeneas’ lengthy «tale to Dido» in Act
2 of Dido Queen of Carthage) has often
been dismissed as a tour de force in the art of
dramatic soliloquy. This neglected speech however
plays a pivotal role in the symbolic architecture of
the play as Marlowe turns the whole tale of the
fall of Troy into a most powerful ‘literalisation’
of the love metaphors that frame Aeneid 4
(Virgil’s proper ‘tragedy of Dido’): thus, through
Ovid’s elegiac poetry, Helen’s (figurative and
literal) flames in Marlowe’s Troy are a proleptic
key to interpret Dido’s tragedy of destructive love.
However, Marlowe’s play with Virgil’s ornatus
in Aeneas’ monologue proves even more intricate
than that. There are in fact other literary echoes
in the furor imagery of Aeneid 4 that Marlowe
subtly manages to reactivate and dramatize in
his tale of the death of Priam (a passage that
seems to be very important for Hamlet too as he
instructs the players at Elsinore). The intertext
that serves to twist Virgil’s imagery, this time,
comes from a rather unexpected tragedy, one
very far from Troy, but very close to Dido,
read through the all-important parodic lens of
Ovid’s Metamorphoses. But, as is often the
case with Marlowe, this makes us reconsider our
interpretation of Virgil’s poetry as well and its
fundamental role in understanding Ovid’s poetry
Dynamics of stellar black holes in young star clusters with different metallicities - II. Black hole-black hole binaries
No full textIn this paper, we study the formation and dynamical evolution of black hole-black hole (BH-BH) binaries in young star clusters (YSCs), by means of N-body simulations. The simulations include metallicity-dependent recipes for stellar evolution and stellar winds, and have been run for three different metallicities (Z = 0.01, 0.1 and 1 Z⊙). Following recent theoretical models of wind mass-loss and core-collapse supernovae, we assume that the mass of the stellar remnants depends on the metallicity of the progenitor stars. We find that BH-BH binaries form efficiently because of dynamical exchanges: in our simulations, we find about 10 times more BH-BH binaries than double neutron star binaries. The simulated BH-BH binaries form earlier in metal-poor YSCs, which host more massive black holes (BHs) than in metal-rich YSCs. The simulated BH-BH binaries have very large chirp masses (up to 80 M⊙), because the BH mass is assumed to depend on metallicity, and because BHs can grow in mass due to the merger with stars. The simulated BH-BH binaries span a wide range of orbital periods (10-3-107 yr), and only a small fraction of them (0.3 per cent) is expected to merge within a Hubble time. We discuss the estimated merger rate from our simulations and the implications for Advanced VIRGO and LIGO
dMyc functions downstream of yorkie to promote the supercompetitive behavior of hippo pathway mutant Cells
No full textGenetic analyses in Drosophila epithelia have suggested that the phenomenon of "cell competition" could participate in organ homeostasis. It has been speculated that competition between different cell populations within a growing organ might play a role as either tumor promoter or tumor suppressor, depending on the cellular context. The evolutionarily conserved Hippo (Hpo) signaling pathway regulates organ size and prevents hyperplastic disease from flies to humans by restricting the activity of the transcriptional cofactor Yorkie (yki). Recent data indicate also that mutations in several Hpo pathway members provide cells with a competitive advantage by unknown mechanisms. Here we provide insight into the mechanism by which the Hpo pathway is linked to cell competition, by identifying dMyc as a target gene of the Hpo pathway, transcriptionally upregulated by the activity of Yki with different binding partners. We show that the cellautonomous upregulation of dMyc is required for the supercompetitive behavior of Yki-expressing cells and Hpo pathway mutant cells, whereas the relative levels of dMyc between Hpo pathway mutant cells and wild-type neighboring cells are critical for determining whether cell competition promotes a tumor-suppressing or tumor-inducing behavior. All together, these data provide a paradigmatic example of cooperation between tumor suppressor genes and oncogenes in tumorigenesis and suggest a dual role for cell competition during tumor progression depending on the output of the genetic interactions occurring between confronted cells. © 2010 Ziosi et al
Sustainable Artificial Intelligence through Continual Learning
No full textThe increasing attention on Artificial Intelligence (AI) regulamentation has led to the definition of a set of ethical principles grouped into the Sustainable AI framework. In this article, we identify Continual Learning, an active area of AI research, as a promising approach towards the design of systems compliant with the Sustainable AI principles. While Sustainable AI outlines general desiderata for ethical applications, Continual Learning provides means to put such desiderata into practice
«Diptycha ex ebore»: osservazioni per uno studio lessicale
No full textIl lavoro comprende uno studio linguistico dell’aggettivo greco DIPTYCHOS , in particolare per quanto riguarda il suo valore sostantivato di «tavoletta» (§ 2), deii corrispondenti latini (§ 3), prima dell’ingresso del prestito diptychum, specializzatosi nel IV secolo per indicare i dittici eburnei (§ 4). Vengono poi esaminate presenze e influsso dei dittici nella poesia di Claudiano (forse da identificare con il poeta rappresentato nel dittico detto “del poeta e della Musa”), al di là della presenza stessa del sostantivo diptychum (§ 5). Si seguοno infine in alcuni autori cristiani le evoluzioni del termine e le sue risemantizzazioni, che si accompagnano ad una evoluzione funzionale, ovvero in alcuni casi, ad un riuso rituale dei dittici nella liturgia cristiana (§ 6-7)
CONTESTED TERRITORY: VIOLENCE, ORGANISED CRIME AND TERRITORIAL PRACTICES IN CONTEMPORARY HONDURAS
No full textThe relationship between organised crime and territory is a complex one, and one which affects extensively security dynamics. Especially in countries plagued by violence and insecurity, like Honduras, territory is strategically important for criminal actors, that usually seek to obtain territorial control in certain areas and often compete over it with their rivals and authorities. Despite this, Honduras remains a highly understudied country in academic and policy discourses on the issue, especially due to the objectively dangerous nature of the criminal groups present in the country and the elevated levels of corruption and impunity that permeate it. As a result, the ways in which criminal groups shape the country’s territory, affecting local communities and security dynamics, remains an underexplored aspect in the literature. Especially, little is known about the way in which criminal groups’ presence, activities, and interactions shape space and territory across different scales in Honduras.
By drawing upon thirty semi-structured interviews with Honduran residents, ex-residents, and experts on criminal groups, activities, and dynamics in the country, and the analysis of official judicial documents, secondary literature, available public reports, and media outlets, this qualitative case study explores the ways in which criminal, state, and non-state actors shape the territory in Honduras in the context of a liberal market democracy. By focusing on different scales, respectively the local, regional, and national, and the interplay among these, this study aims at painting a picture of the bordering and territorial practices that different actors – especially criminal groups – have been carrying out in the country approximately in the last three decades. Adopting an interdisciplinary approach, this thesis consolidates and integrates the literature on organised crime, violence, the state-crime nexus, territory and territorial practices, and borders and bordering practices with original empirical research.
By focusing on gangs in urban areas of the country, drug trafficking organisations in rural ones, and state-crime relationships across the national territory, I argue that these actors have been able to actively produce and shape the country’s territory along micro, meso, and national lines, often establishing authority on it, and have contributed to shaping the Honduran territory as a deeply contested space. In doing so, I argue, these groups mirror – and, at the same time, are embedded into – the dynamics of capital accumulation and resource commodification entrenched in the country’s history of capitalist and neo-colonial exploitation and occupation throughout the centuries
L’Hpo pathway è coinvolto nel controllo della proliferazione e nel mantenimento della popolazione neuroepiteliale larvale
No full textLa recente scoperta di cellule tumorali di origine staminale ha esteso la complessità e la rilevanza delle dinamiche di sviluppo coinvolte nella tumorigenesi.
Nella larva di Drosophila i neuroni originano da cellule staminali chiamate neuroblasti, caratterizzati da una divisione di tipo asimmetrico, da cui avranno origine un nuovo neuroblasto e una cellula progenitrice di neuroni/glia (GMC). Nel lobo ottico del cervello larvale i neuroblasti che origineranno i neuroni della medulla e della lamina prendono origine da una popolazione composta di cellule neuroepiteliali, caratterizzate da una proliferazione di tipo simmetrico, a cui segue il passaggio a neuroblasto con divisione asimmetrica.
La deregolazione dei meccanismi di self-renewal e di proliferazione di questa popolazione cellulare potrebbe essere determinante nella comparsa di cellule staminali tumorali e un passaggio chiave potrebbe essere la perturbazione dei meccanismi molecolari che determinano il passaggio da divisione simmetrica a divisione asimmetrica.
I nostri dati mostrano che nel tessuto neuroepiteliale la cascata di segnalazione dell’Hippo pathway è del tutto simile a quella descritta nei tessuti epiteliali di origine imaginale, ed è coinvolta nel controllo della proliferazione e del mantenimento della popolazione neuroepiteliale. Riportiamo inoltre che l’oncoproteina dMyc è fortemente espressa nelle cellule di origine neuroepiteliale, suggerendone un ruolo nel controllo del destino cellulare del neuroepitelio, e che la sua regolazione è in parte determinata dall’attività dell’Hippo pathway.
Dati in letteratura riportano il possibile coinvolgimento della via di segnalazione di decapentaplegic (dpp) nella sopravvivenza di questa popolazione cellulare e in questo contesto proponiamo un modello in cui la via di segnalazione dell’Hippo pathway e di dpp coordinano il passaggio da cellula neuroepiteliale a neuroblasto
Representational bias in expression and annotation of emotions in audiovisual databases
No full textSaakyan W, Hakobyan O, Drimalla H. Representational bias in expression and annotation of emotions in audiovisual databases. In: Wicke P, Ziosi M, Cunha JM, Trotta A, eds. Proceedings of the 1st International Conference on AI for People: Towards Sustainable AI, CAIP 2021, 20-24 November 2021, Bologna, Italy. EAI; 2021
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