The Initial Mass-Final Mass Relation of low- and intermediate-mass stars: constraints to the Asymptotic Giant Branch phase

The Initial-Final Mass Relation for low- and intermediate-mass stars links the mass of a white dwarf with the progenitor mass. It is a fundamental tool in both stellar evolution analysis (Asymptotic Giant Branch and white dwarf phases) and galaxy models (chemical evolution and luminosity contribution). In this thesis we investigate the main dependencies of the relation, so that the second dredge-up, the third dredge-up, the mass loss and the metallicity, comparing four theoretical models with a set of uniform semi-empirical data.ope

Precise Measurements of Self-absorbed Rising Reverse Shock Emission from Gamma-ray Burst 221009A

The deaths of massive stars are sometimes accompanied by the launch of highly relativistic and collimated jets. If the jet is pointed towards Earth, we observe a "prompt" gamma-ray burst due to internal shocks or magnetic reconnection events within the jet, followed by a long-lived broadband synchrotron afterglow as the jet interacts with the circum-burst material. While there is solid observational evidence that emission from multiple shocks contributes to the afterglow signature, detailed studies of the reverse shock, which travels back into the explosion ejecta, are hampered by a lack of early-time observations, particularly in the radio band. We present rapid follow-up radio observations of the exceptionally bright gamma-ray burst GRB 221009A which reveal an optically thick rising component from the reverse shock in unprecedented detail both temporally and in frequency space. From this, we are able to constrain the size, Lorentz factor, and internal energy of the outflow while providing accurate predictions for the location of the peak frequency of the reverse shock in the first few hours after the burst.Comment: 11 figures, 4 table

Determinants, causal connections and outcomes of corporate technology licensing : a systematic review and research agenda

Exchanges in markets for technology (MfT) have grown rapidly in recent years. MfT involve transactions for the use, diffusion and creation of technology. In this article we conduct a systematic review of the emerging market for technology literature and examine one of its most important aspects, corporate technology licensing. Using thematic analysis, we systematically review 78 papers published in 29 journals over 30 years covering the academic disciplines of technology/knowledge management, strategic management, entrepreneurship, innovation management and industrial economics. Based on this analysis, we present an organizing framework for the most prominent determinants, causal connections and outcomes of technology licensing research to date, and identify a research agenda highlighting important avenues for future research in this domai

Analysis of the IFI+Iqueye observations of the Crab pulsar taken around the epoch of the major November 2017 glitch

After a catastrophic supernova explosion, the core of a star collapses inwards until the contraction is halted and a new equilibrium configuration is reached. One of the possible stable remnants is the neutron star, where gravity is balanced by nuclear forces and the degenerate pressure provided by neutrons. A peculiar type of neutron star is the pulsar: a highly magnetised, fast rotating compact object which embodies an ideal astrophysical laboratory to study Physics under extreme conditions. The pulsar emission is characterised by a repeating signal, which usually has a well defined shape and occurs with an accuracy that could compete with that of the atomic clocks. Since this pulsing signal is due to the passage of the beamed emission from the poles of the star across the line of sight of the observer, the rotational period of the neutron star coincides with the time interval between two pulses, which correspond the same pole. Therefore, the analysis of the time of arrival of the pulses is a fundamental tool to constrain the timing behaviour, the rotational evolution and the physical properties of the pulsar. Indeed, albeit the signal coming from a pulsar is remarkably stable, sometimes the neutron star undergoes an unpredictable and sudden spin up event, called glitch, which is usually followed by an exponential decay of the rotational frequency ν towards the pre-glitch values. In this work we analyzed the time behaviour of the Crab pulsar (PSR B0531+21), which is the young neutron star at the centre of the Crab Nebula, with rotational frequency ν ∼ 30 Hz. Until 2017, the Crab pulsar was known to produce glitches with a spin frequency increase of 10 −9 ≤ ∆ν/ν ≤ 10 −7 ; however, around MJD 58064 (8 November 2017), the Crab experienced what is now confirmed to be its largest glitch ever detected: the magnitude of the step increase was ∆ν/ν = 0.516×10 −6 in the radio band. We parsed the observations of the Crab pulsar made with the very fast optical photon counter Iqueye, mounted at the 122 cm Galileo Telescope in Asiago through a dedicated optical fiber interface (IFI). The observations were carried out on 2017 October 4 and 7, November 17 and 18, December 30. The timing accuracy and the amount of data available allowed us to pinpoint the major November 2017 glitch in the optical domain and to compare it with the results provided by the Jodrell Bank radio ephemeris. Furthermore, we searched for evidence of changes in the geometry of the emission regions and/or in the magnetosphere of the pulsar possibly induced by the glitch

The Initial Mass-Final Mass Relation of low- and intermediate-mass stars: constraints to the Asymptotic Giant Branch phase

The Initial-Final Mass Relation for low- and intermediate-mass stars links the mass of a white dwarf with the progenitor mass. It is a fundamental tool in both stellar evolution analysis (Asymptotic Giant Branch and white dwarf phases) and galaxy models (chemical evolution and luminosity contribution). In this thesis we investigate the main dependencies of the relation, so that the second dredge-up, the third dredge-up, the mass loss and the metallicity, comparing four theoretical models with a set of uniform semi-empirical data

Impaired Mitochondrial Function and Marrow Failure in Patients Carrying a Variant of the <i>SRSF4</i> Gene

Serine/arginine-rich splicing factors (SRSFs) are a family of proteins involved in RNA metabolism, including pre-mRNA constitutive and alternative splicing. The role of SRSF proteins in regulating mitochondrial activity has already been shown for SRSF6, but SRSF4 altered expression has never been reported as a cause of bone marrow failure. An 8-year-old patient admitted to the hematology unit because of leukopenia, lymphopenia, and neutropenia showed a missense variant of unknown significance of the SRSF4 gene (p.R235W) found via whole genome sequencing analysis and inherited from the mother who suffered from mild leuko-neutropenia. Both patients showed lower SRSF4 protein expression and altered mitochondrial function and energetic metabolism in primary lymphocytes and Epstein–Barr-virus (EBV)-immortalized lymphoblasts compared to healthy donor (HD) cells, which appeared associated with low mTOR phosphorylation and an imbalance in the proteins regulating mitochondrial biogenesis (i.e., CLUH) and dynamics (i.e., DRP1 and OPA1). Transfection with the wtSRSF4 gene restored mitochondrial function. In conclusion, this study shows that the described variant of the SRSF4 gene is pathogenetic and causes reduced SRSF4 protein expression, which leads to mitochondrial dysfunction. Since mitochondrial function is crucial for hematopoietic stem cell maintenance and some genetic bone marrow failure syndromes display mitochondrial defects, the SRSF4 mutation could have substantially contributed to the clinical phenotype of our patient

Precise measurements of self-absorbed rising reverse shock emission from gamma-ray burst 221009A

The deaths of massive stars are sometimes accompanied by the launch of highly relativistic and collimated jets. If the jet is pointed towards Earth, we observe a ‘prompt’ gamma-ray burst due to internal shocks or magnetic reconnection events within the jet, followed by a long-lived broadband synchrotron afterglow as the jet interacts with the circumburst material. While there is solid observational evidence that emission from multiple shocks contributes to the afterglow signature, detailed studies of the reverse shock, which travels back into the explosion ejecta, are hampered by a lack of early-time observations, particularly in the radio band. We present rapid follow-up radio observations of the exceptionally bright gamma-ray burst GRB 221009A that reveal in detail, both temporally and in frequency space, an optically thick rising component from the reverse shock. From this, we are able to constrain the size, Lorentz factor and internal energy of the outflow while providing accurate predictions for the location of the peak frequency of the reverse shock in the first few hours after the burst. These observations challenge standard gamma-ray burst models describing reverse shock emission

Bursts from Space: MeerKAT – the first citizen science project dedicated to commensal radio transients

International audienceThe newest generation of radio telescopes is able to survey large areas with high sensitivity and cadence, producing data volumes that require new methods to better understand the transient sky. Here, we describe the results from the first citizen science project dedicated to commensal radio transients, using data from the MeerKAT telescope with weekly cadence. Bursts from Space: MeerKAT was launched late in 2021 and received ∼89 000 classifications from over 1000 volunteers in 3 months. Our volunteers discovered 142 new variable sources which, along with the known transients in our fields, allowed us to estimate that at least 2.1 per cent of radio sources are varying at 1.28 GHz at the sampled cadence and sensitivity, in line with previous work. We provide the full catalogue of these sources, the largest of candidate radio variables to date. Transient sources found with archival counterparts include a pulsar (B1845-01) and an OH maser star (OH 30.1–0.7), in addition to the recovery of known stellar flares and X-ray binary jets in our observations. Data from the MeerLICHT optical telescope, along with estimates of long time-scale variability induced by scintillation, imply that the majority of the new variables are active galactic nuclei. This tells us that citizen scientists can discover phenomena varying on time-scales from weeks to several years. The success both in terms of volunteer engagement and scientific merit warrants the continued development of the project, while we use the classifications from volunteers to develop machine learning techniques for finding transients