General properties of X-Ray Riches and X-Ray Flashes in comparison with Gamma-Ray Bursts

The X-Ray Flashes (XRFs) and X-Ray Riches (XRRs) are two subclasses of Gamma-Ray Bursts (GRBs), which have respectively no detection in the gamma-ray energy and very faint gamma to X-ray fluence. To investigate their nature we compiled a sample of 54 events observed by BeppoSAX and HETE-2, available in literature and from the web. To classify XRRs/XRFs for those two experiments, we adopted the same spectral hardness ratio. We studied their prompt emission in the X and γ range and their spectral parameters and compared them with those of GRBs. We find XRRs/XRFs are characterized by a significantly smaller value of Epeak while the spectral slopes α and β are quite similar. We analysed also the optical and X-ray afterglow fluxes and their ratio and compared them with that obtained for GRBs. We find that the distribution of X-ray flux of XRR/XRF afterglow is consistent with that of GRBs, which is incompatible with the off-axis model. For example, in the inhomogeneous jet model it implies that the observer anglefor an XRR/XRF is at most 2◦. It is also not explained by the high Redshift scenario

Measurement and control of a mechanical oscillator at its thermal decoherence rate

In real-time quantum feedback protocols, the record of a continuous measurement is used to stabilize a desired quantum state. Recent years have seen highly successful applications in a variety of well-isolated micro-systems, including microwave photons and superconducting qubits. By contrast, the ability to stabilize the quantum state of a tangibly massive object, such as a nanomechanical oscillator, remains a difficult challenge: The main obstacle is environmental decoherence, which places stringent requirements on the timescale in which the state must be measured. Here we describe a position sensor that is capable of resolving the zero-point motion of a solid-state, nanomechanical oscillator in the timescale of its thermal decoherence, a critical requirement for preparing its ground state using feedback. The sensor is based on cavity optomechanical coupling, and realizes a measurement of the oscillator's displacement with an imprecision 40 dB below that at the standard quantum limit, while maintaining an imprecision-back-action product within a factor of 5 of the Heisenberg uncertainty limit. Using the measurement as an error signal and radiation pressure as an actuator, we demonstrate active feedback cooling (cold-damping) of the 4.3 MHz oscillator from a cryogenic bath temperature of 4.4 K to an effective value of 1.1$\pm$0.1 mK, corresponding to a mean phonon number of 5.3$\pm$0.6 (i.e., a ground state probability of 16%). Our results set a new benchmark for the performance of a linear position sensor, and signal the emergence of engineered mechanical oscillators as practical subjects for measurement-based quantum control.Comment: 24 pages, 10 figures; typos corrected in main text and figure

The Turbulent Story of X-ray Bursts: Effects of Shear Mixing on Accreting Neutron Stars

During accretion, a neutron star (NS) is spun up as angular momentum is transported through its liquid surface layers. We study the resulting differentially rotating profile, focusing on the impact this has for type I X-ray bursts. The viscous heating is found to be negligible, but turbulent mixing can be activated. Mixing has the greatest impact when the buoyancy at the compositional discontinuity between accreted matter and ashes is overcome. This occurs preferentially at high accretion rates or low spin frequencies and may depend on the ash composition from the previous burst. We then find two new regimes of burning. The first is ignition in a layer containing a mixture of heavier elements with recurrence times as short as ~5-30 minutes, similar to short recurrence time bursts. When mixing is sufficiently strong, a second regime is found where accreted helium mixes deep enough to burn stably, quenching X-ray bursts altogether. The carbon-rich material produced by stable helium burning would be important for triggering and fueling superbursts.Comment: 3 pages, 3 figures. To appear in the proceedings of "Forty Years of Pulsars: Millisecond Pulsars, Magnetars and More" held in Montreal, Canada, August 12-17, 200

Microcephaly and macrocephaly. A study on anthropometric and clinical data from 308 subjects

Head circumference is the auxological parameter that most correlates with developmental anomalies in childhood. Head circumference (HC) two standard deviations (SD) below or above the mean defines microcephaly and macrocephaly, respectively. The aim of this retrospective study was to explore anthropometric parameters and clinical characteristics among subjects with abnormalities in HC who had been referred for developmental assessment. One hundred and sixty four subjects with microcephaly and 144 subjects with macrocephaly were enrolled from birth to 18 months of age. Head circumference at birth and the association with variables related to maternal health status, gestational age, growth pattern, brain imaging and clinical characteristics were analyzed. In some cases, an etiological diagnosis was made. In the two considered conditions, we found different anthropometric and clinical associations, some of which were statistically significant, with implications for ongoing neurodevelopmental surveillance

Swift and Fermi observations of X-ray flares: the case of Late Internal Shock

Simultaneous Swift and Fermi observations of gamma-ray bursts (GRBs) offer a unique broadband view of their afterglow emission, spanning more than ten decades in energy. We present the sample of X-ray flares observed by both Swift and Fermi during the first three years of Fermi operations. While bright in the X-ray band, X-ray flares are often undetected at lower (optical), and higher (MeV to GeV) energies. We show that this disfavors synchrotron self-Compton processes as origin of the observed X-ray emission. We compare the broadband properties of X-ray flares with the standard late internal shock model, and find that, in this scenario, X-ray flares can be produced by a late-time relativistic (Gamma>50) outflow at radii R~10^13-10^14 cm. This conclusion holds only if the variability timescale is significantly shorter than the observed flare duration, and implies that X-ray flares can directly probe the activity of the GRB central engine.Comment: 13 pages, 4 figures, accepted for publication in Ap

Recognizable neonatal clinical features of aplasia cutis congenita

Background: Aplasia cutis congenita (ACC), classified in nine groups, is likely to be underreported, since milder isolated lesions in wellbeing newborns could often be undetected, and solitary lesions in the context of polymalformative syndromes could not always be reported. Regardless of form and cause, therapeutic options have in common the aim to restore the deficient mechanical and immunological cutaneous protection and to limit the risk of fluid leakage or rupture of the exposed organs. We aimed to review our institutional prevalence, comorbidities, treatment and outcome of newborns with ACC. Methods: We conducted a retrospective study including all newborns affected by ACC and admitted at the University Mother-Child Department from October 2010 to October 2019. Anthropometric and clinical characteristics of ACC1 versus a non-isolated ACC group were analyzed. Results: We encountered 37 newborns, 16 with ACC1 versus 21 with non-isolated ACC. The incidence rate of 0.1% in ACC1 was higher than expected, while 19% of cases showed intrafamilial autosomal dominant transmission. Higher birth weight centile, though lower than reference population, being adequate for gestational age, normal Apgar score and euglycemia characterizing ACC1 resulted associated to a rapid tissue regeneration. Non-isolated ACC, in relation to concomitant congenital anomalies and higher prematurity rate, showed more surgical and medical complications along with the risk of neonatal death. Specifically, newborns with ACC4 were characterized by the frequent necessity of abdominal wall defect repair, responsible for the occurrence of an abdominal compartment syndrome. Conclusion: Prompt carefully assessment of the newborn with ACC in order to exclude concomitant other congenital malformations, provides clues to the underlying pathophysiology, and to the short-term prognosis. Family should be oriented toward identification of other family members affected by similar pathology, while obstetric history should exclude initial multiple pregnancy with death of a co-twin, placental anomalies and drug assumption. Molecular-genetic diagnosis and genetic counseling are integrative in individualized disease approach

The Non-Relativistic Evolution of GRBs 980703 and 970508: Beaming-Independent Calorimetry

We use the Sedov-Taylor self-similar solution to model the radio emission from the gamma-ray bursts (GRBs) 980703 and 970508, when the blastwave has decelerated to non-relativistic velocities. This approach allows us to infer the energy independent of jet collimation. We find that for GRB 980703 the kinetic energy at the time of the transition to non-relativistic evolution, t_NR ~ 40 d, is E_ST ~ (1-6)e51 erg. For GRB 970508 we find E_ST ~ 3e51 erg at t_NR ~ 100 d, nearly an order of magnitude higher than the energy derived in Frail, Waxman and Kulkarni (2000). This is due primarily to revised cosmological parameters and partly to the maximum likelihood fit we use here. Taking into account radiative losses prior to t_NR, the inferred energies agree well with those derived from the early, relativistic evolution of the afterglow. Thus, the analysis presented here provides a robust, geometry-independent confirmation that the energy scale of cosmological GRBs is about 5e51 erg, and additionally shows that the central engine in these two bursts did not produce a significant amount of energy in mildly relativistic ejecta at late time. Furthermore, a comparison to the prompt energy release reveals a wide dispersion in the gamma-ray efficiency, strengthening our growing understanding that E_gamma is a not a reliable proxy for the total energy.Comment: Submitted to ApJ; 13 pages, 6 figures, 1 table; high-resolution figures can be found at: http://www.astro.caltech.edu/~ejb/NR

TRAVAGGHIARI A JURNATA. INVESTIGATING DAY LABOR INSIDE SICILIAN TOMATOES ¿PLASTIC FACTORIES¿

La tesi rappresenta un tentativo di indagare il lavoro a giornata e le sue dimensioni, attraverso un'analisi di un mercato del lavoro agricolo destagionalizzato nel sud Italia. Essa si sforza di capire quali sono le convenzioni, i concetti di giustizia e le giustificazioni fornite dagli attori locali a sostegno del sistema del lavoro a giornata. L'analisi \ue8 basata su un lavoro di campo della durata di circa sei mesi realizzato nella cosiddetta Fascia Costiera Trasformata (Ragusa, Sicilia), un distretto agricolo caratterizzato dalla produzione di ortaggi freschi che rappresenta uno delle pi\uf9 gradi estensioni serricole italiane. Da circa quarant'anni la forza lavoro nella zona \ue8 costituita in gran parte da lavoratrici e lavoratori stranieri, provenienti per lo pi\uf9 dalla Tunisia (a partire dagli anni '60) e dalla Romania (a partire dagli anni 2000). Durante il lavoro di campo, l'autrice ha realizzato due mesi di osservazione partecipante (coperta e scoperta) all'interno di varie aziende agricole e di magazzini di confezionamento, due settimane di \u201cshadowing\u201d seguendo un commerciante in diversi mercati ortofrutticoli locali, e circa 100 tra interviste semi-strutturate e colloqui informali con braccianti, datori di lavoro e testimoni privilegiati (sindacalisti, membri delle istituzioni locali, volontari, etc.). La tesi cerca di spiegare che significa lavorare a giornata attraverso un'analisi empirica delle dimensioni e delle forme assunte da questo tipo di lavoro. Considera, dunque, l'indisponibilit\ue0 del tempo di vita e di lavoro vissuta dai braccianti; la sofferenza e il dolore causati da uno sforzo fisico incostante sul corpo dei lavoratori, cos\uec come lo stress mentale che che esso genera; l'insicurezza materiale vissuta dagli operai remunerati con salari bassi e incostanti; l'incertezza sul futuro che costringe i braccianti a \uabcampare alla giornata\ubb. Essa esplora, inoltre, il continuum formale-informale e le diverse configurazioni di semi-formalit\ue0 a cui il sistema del lavoro a giornata da origine. Secondariamente, la tesi si cimenta nel proposito di riflettere proprio sugli spazi, che costituisco il setting che \u201cospita\u201d e allo stesso tempo plasma il lavoro a giornata, proponendo quattro immagini idealtipiche dei luoghi di lavoro. Infine, il contributo considera come il genere, l'etinicit\ue0 e la classe dei lavoratori influenzano e sono influenzati dal lavoro a giornata, il quale produce diverse \u201cmatrici di dominazione\u201d e di \u201cagency\u201d. La conclusione appare come un invito a prendere in considerazione i costi sociali della filiera del cibo fresco, per quanto riguarda la produzione sociale di valore, l'impatto sui territori locali e sulla forza lavoro.The thesis attempts to investigate day labor and its dimensions, through the analysis of a deseasonalized agricultural labor market in the South of Italy. It tries to understand which are the conventions, the concepts of justice and justifications provided by the local actors to support day labor system. The findings are based on a six months fieldwork in the so called Fascia Costiera Trasformata (Ragusa, Sicily), an agricultural district characterized by the production of fresh crops that represents one of the biggest greenhouses areas in Italy. Since the last forty years, the workforce in the district has been mainly constituted by foreign (male and female) workers, mostly coming from Tunisia (since the 1960s) and Romania (since the 2000s). During her fieldwork, the author realized two months of (covered and uncovered) participant observation inside greenhouses and packinghouses companies, two week of \u201cshadowing\u201d following a broker inside local fruit and vegetable markets, and around 100 among semi-structured interviews and informal colloquies with farmworkers, employers and privileged testimonies (trade unionists, members of local institutions, volunteers, etc.). The thesis tries to explain what it means to work by the day through an empirical analysis of the dimensions and the forms assumed by day labor. Thus, it takes into consideration laborers' unavailability of their work and life time; the pain and suffering produced by an uneven physical endeavor on workers' bodies, as well as the mental stress that it generates; the material insecurity undergone by laborers remunerated through low and uneven salaries; the future uncertainties that bind workers to a daily model of existence. It also explores the continuum formal-informal and the several configurations of partial-formality that day labor system produces. Secondly, the thesis engages in the purpose of reflecting on the very spaces constituting the settings that \u201chost\u201d and at the same time shape day labor, proposing four ideal-typical \u201cimages\u201d of the workplaces. Finally, the contribution considers how workers' gender, ethnicity and class shape and are re-shaped by day labor system, that produces several \u201cmatrices of domination\u201d and \u201cagency\u201d. The conclusion appears as an invitation to take into consideration the social costs of eating fresh food, for what concerns social production of value, impact on local territories and on the workforce

A 450-day light curve of the radio afterglow of GRB 970508: Fireball calorimetry

We report on the results of an extensive monitoring campaign of the radio afterglow of GRB 970508, lasting 450 days after the burst. The spectral and temporal radio behavior indicate that the fireball has undergone a transition to sub-relativistic expansion at t~100 days. This allows us to perform "calorimetry" of the explosion. The derived total energy, ~5\times 10^{50} erg, is well below the ~5\times 10^{51} erg inferred under the assumption of spherical symmetry from gamma-ray and early afterglow observations. A natural consequence of this result, which can also account for deviations at t<100 days from the spherical relativistic fireball model predictions, is that the fireball was initially a wide-angle jet of opening angle ~30 degrees. Our analysis also allows to determine the energy fractions carried by electrons and magnetic field, and the density of ambient medium surrounding the fireball. We find that during the sub-relativistic expansion electrons and magnetic field are close to equipartition, and that the density of the ambient medium is ~1/cm^3. The inferred density rules out the possibility that the fireball expands into a strongly non-uniform medium, as would be expected, e.g., in the case of a massive star progenitor.Comment: 33 pages, including 7 figures, submitted to Ap