'From Zionism to Communism': Emilio Sereni and the Consiglio di Gestione in postwar Italy

This essay demonstrates that it is impossible to appreciate the actions of the Italian communist Emilio Sereni without considering his Zionist background. Anyone who is interested in understanding the complexities of communism in the past century and to avoid simplistic conclusions about this ideology will benefit from the study. The problem at stake is that researchers often approach communism in a monolithic manner, which does not adequately explain the multiform manifestations (practical and theoretical) of that phenomenon. This ought to change and to this extent this essay hopes to contribute to that recent strand of historical research that challenges simplistic views on communism. More specifically, by analysing the Management Councils that Sereni created in postwar Italy, we can see that many of their features in fact derived from, or found their deepest origins in, his previous experience as a committed socialist Zionist. The study, then, also relates Sereni to and looks at the broader experiences of early twentieth-century Zionism and Italian communism in the early postwar years

Stress relaxation in epithelial monolayers is controlled by the actomyosin cortex

Epithelial monolayers are one-cell thick tissue sheets that separate internal and external environments. As part of their function, they have to withstand extrinsic mechanical stresses applied at high strain rates. However, little is known about how monolayers respond to mechanical deformations. Here, by subjecting suspended epithelial monolayers to stretch, we find that they dissipate stresses on a minute time-scale in a process that involves an increase in monolayer length, pointing to active remodelling of cell architecture during relaxation. Strikingly, monolayers consisting of tens of thousands of cells relax stress with similar dynamics to single rounded cells and both respond similarly to perturbations of actomyosin. By contrast, cell-cell junctional complexes and intermediate filaments do not relax tissue stress, but form stable connections between cells, allowing monolayers to behave rheologically as single cells. Taken together our data show that actomyosin dynamics governs the rheological properties of epithelial monolayers, dissipating applied stresses, and enabling changes in monolayer length.Peer ReviewedPostprint (published version

Exclusion of Stellar Companions to Exoplanet Host Stars

Given the frequency of stellar multiplicity in the solar neighborhood, it is important to study the impacts this can have on exoplanet properties and orbital dynamics. There have been numerous imaging survey projects established to detect possible low-mass stellar companions to exoplanet host stars. Here we provide the results from a systematic speckle imaging survey of known exoplanet host stars. In total, 71 stars were observed at 692~nm and 880~nm bands using the Differential Speckle Survey Instrument (DSSI) at the Gemini-North Observatory. Our results show that all but 2 of the stars included in this sample have no evidence of stellar companions with luminosities down to the detection and projected separation limits of our instrumentation. The mass-luminosity relationship is used to estimate the maximum mass a stellar companion can have without being detected. These results are used to discuss the potential for further radial velocity follow-up and interpretation of companion signals.Comment: 11 pages, 4 figures, 3 tables, accepted for publication in A

Mapping out the time-evolution of exoplanet processes

There are many competing theories and models describing the formation, migration and evolution of exoplanet systems. As both the precision with which we can characterize exoplanets and their host stars, and the number of systems for which we can make such a characterization increase, we begin to see pathways forward for validating these theories. In this white paper we identify predicted, observable correlations that are accessible in the near future, particularly trends in exoplanet populations, radii, orbits and atmospheres with host star age. By compiling a statistically significant sample of well-characterized exoplanets with precisely measured ages, we should be able to begin identifying the dominant processes governing the time-evolution of exoplanet systems.Comment: Astro2020 white pape

Fractional viscoelastic models for power-law materials.

Soft materials often exhibit a distinctive power-law viscoelastic response arising from broad distribution of time-scales present in their complex internal structure. A promising tool to accurately describe the rheological behaviour of soft materials is fractional calculus. However, its use in the scientific community remains limited due to the unusual notation and non-trivial properties of fractional operators. This review aims to provide a clear and accessible description of fractional viscoelastic models for a broad audience and to demonstrate the ability of these models to deliver a unified approach for the characterisation of power-law materials. The use of a consistent framework for the analysis of rheological data would help classify the empirical behaviours of soft and biological materials, and better understand their response

TOI-1055 b: Neptunian planet characterised with HARPS, TESS, and CHEOPS

CONTEXT: TOI-1055 is a Sun-like star known to host a transiting Neptune-sized planet on a 17.5-day orbit (TOI-1055 b). Radial velocity (RV) analyses carried out by two independent groups using nearly the same set of HARPS spectra have provided measurements of planetary masses that differ by ∼2σ. AIMS: Our aim in this work is to solve the inconsistency in the published planetary masses by significantly extending the set of HARPS RV measurements and employing a new analysis tool that is able to account and correct for stellar activity. Our further aim was to improve the precision on measurements of the planetary radius by observing two transits of the planet with the CHEOPS space telescope. METHODS: We fit a skew normal function to each cross correlation function extracted from the HARPS spectra to obtain RV measurements and hyperparameters to be used for the detrending. We evaluated the correlation changes of the hyperparameters along the RV time series using the breakpoint technique. We performed a joint photometric and RV analysis using a Markov chain Monte Carlo scheme to simultaneously detrend the light curves and the RV time series. RESULTS: We firmly detected the Keplerian signal of TOI-1055 b, deriving a planetary mass of Mb = 20.4−2.5+2.6 M⊕ (∼12%). This value is in agreement with one of the two estimates in the literature, but it is significantly more precise. Thanks to the TESS transit light curves combined with exquisite CHEOPS photometry, we also derived a planetary radius of Rb = 3.490−0.064+0.070 R⊕ (∼1.9%). Our mass and radius measurements imply a mean density of ρb = 2.65−0.35+0.37 g cm−3 (∼14%). We further inferred the planetary structure and found that TOI-1055 b is very likely to host a substantial gas envelope with a mass of 0.41−0.20+0.34 M⊕ and a thickness of 1.05−0.29+0.30 R⊕. CONCLUSIONS: Our RV extraction combined with the breakpoint technique has played a key role in the optimal removal of stellar activity from the HARPS time series, enabling us to solve the tension in the planetary mass values published so far for TOI-1055 b

Fractional viscoelastic models for power-law materials

Soft materials often exhibit a distinctive power-law viscoelastic response arising from broad distribution of time-scales present in their complex internal structure. A promising tool to accurately describe the rheological behaviour of soft materials is fractional calculus. However, its use in the scientific community remains limited due to the unusual notation and non-trivial properties of fractional operators. This review aims to provide a clear and accessible description of fractional viscoelastic models for a broad audience and to demonstrate the ability of these models to deliver a unified approach for the characterisation of power-law materials. The use of a consistent framework for the analysis of rheological data would help classify the empirical behaviours of soft and biological materials, and better understand their response