110 research outputs found

    The Old Babylonian loan contract "Aegyptus 10.1" (= Boson 1936 n° 300)

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    The short article offers an updated transliteration, along with a commentary and a photograph, of an Old Babylonian tablet (known as "Aegyptus 10.1") belonging to the cuneiform collection of the library of the UniversitĂ  Cattolica del Sacro Cuore in Milan

    Evidence of radius inflation in stars approaching the slow-rotator sequence

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    Average stellar radii in open clusters can be estimated from rotation periods and projected rotational velocities under the assumption of random orientation of the spin axis. Such estimates are independent of distance, interstellar absorption, and models, but their validity can be limited by missing data (truncation) or data that only represent upper/lower limits (censoring). We present a new statistical analysis method to estimate average stellar radii in the presence of censoring and truncation. We use theoretical distribution functions of the projected stellar radius Rsin⁥iR \sin i to define a likelihood function in the presence of censoring and truncation. Average stellar radii in magnitude bins are then obtained by a maximum likelihood parametric estimation procedure. This method is capable of recovering the average stellar radius within a few percent with as few as ≈\approx 10 measurements. Here it is applied for the first time to the dataset available for the Pleiades. We find an agreement better than ≈\approx 10 percent between the observed RR vs MKM_K relationship and current standard stellar models for 1.2 ≄M/M⊙≄\ge M/M_{\odot} \ge 0.85 with no evident bias. Evidence of a systematic deviation at 2σ2\sigma level are found for stars with 0.8 ≄M/M⊙≄\ge M/M_{\odot} \ge 0.6 approaching the slow-rotator sequence. Fast-rotators (PP < 2 d) agree with standard models within 15 percent with no systematic deviations in the whole 1.2 ≄M/M⊙≄\ge M/M_{\odot} \ge 0.5 range. The evidence found of a possible radius inflation just below the lower mass limit of the slow-rotator sequence indicates a possible connection with the transition from the fast to the slow-rotator sequence.Comment: Accepted by Astronomy and Astrophysics, 11 pages, 6 figure

    Evidence of New Magnetic Transitions in Late-Type Dwarfs from Gaia DR2

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    The second Gaia data release contains the identification of 147 535 low-mass (≀1.4M⊙\le 1.4 M_{\odot}) rotational modulation variable candidates on (or close to) the main sequence, together with their rotation period and modulation amplitude. The richness, the period and amplitude range, and the photometric precision of this sample make it possible to unveil, for the first time, signatures of different surface inhomogeneity regimes in the amplitude-period density diagram. The modulation amplitude distribution shows a clear bimodality, with an evident gap at periods P≀2P \le 2 d. The low amplitude branch, in turn, shows a period bimodality with a main clustering at periods P≈P \approx 5 - 10 d and a secondary clustering of ultra-fast rotators at P≀0.5P \le 0.5 d. The amplitude-period multimodality is correlated with the position in the period-absolute magnitude (or period-color) diagram, with the low- and high-amplitude stars occupying different preferential locations. Here we argue that such a multimodality represents a further evidence of the existence of different regimes of surface inhomogeneities in young and middle-age low-mass stars and we lay out possible scenarios for their evolution, which manifestly include rapid transitions from one regime to another. In particular, the data indicate that stars spinning up close to break-up velocity undergo a very rapid change in their surface inhomogeneities configuration, which is revealed here for the first time. The multimodality can be exploited to identify field stars of age ∌\sim 100 -- 600 Myr belonging to the slow-rotator low-amplitude sequence, for which age can be estimated from the rotation period via gyrochronology relationships.Comment: 15 pages, 6 figures, Accepted by Ap

    Effects of a subadiabatic layer on convection and dynamos in spherical wedge simulations

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    We consider the effect of a subadiabatic layer at the base of the convection zone on convection itself and the associated large-scale dynamos in spherical wedge geometry. We use a heat conduction prescription based on the Kramers opacity law which allows the depth of the convection zone to dynamically adapt to changes in the physical characteristics such as rotation rate and magnetic fields. We find that the convective heat transport is strongly concentrated toward the equatorial and polar regions in the cases without a substantial radiative layer below the convection zone. The presence of a stable layer below the convection zone significantly reduces the anisotropy of radial enthalpy transport. Furthermore, the dynamo solutions are sensitive to subtle changes in the convection zone structure. We find that the kinetic helicity changes sign in the deeper parts of the convection zone at high latitudes in all runs. This region expands progressively toward the equator in runs with a thicker stably stratified layer.Comment: 32 pages, 18 figures, accepted to GAFD Special issue on 'Recent Developments in Natural Dynamos

    Motor and cognitive skills implicated in the Motor Observation Questionnaire for Teachers (MOQ-T): A multidisciplinary approach

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    This study was designed to determine the relationship between an observational measure of motor skills for teachers (i.e., MOQ-T), age, and some objectively assessed cognitive and motor indices. Two further goals were to examine which motor and cognitive factors predicted MOQ-T scores and to explore whether pupils with very low motor skills identified through MOQ-T also exhibited lower scores on objectively assessed motor and visuo-spatial tasks. A sample of 156 pupils aged 8.4 years–11.3 years and attending Italian primary school completed a battery of tests assessing writing speed, visuo-spatial abstract reasoning, fluency, and static balance abilities objectively assessed by measuring postural sway. Small to medium associations were found be- tween MOQ-T scores and age, motor, and cognitive parameters, respectively. Moreover, approximately 26% of the variance in MOQ-T was predicted by sway area in the eyes-open condition, visuo-spatial fluency, and writing speed. Finally, pupils at risk of developmental co- ordination disorder exhibited poorer writing speed, and motor and higher-order visuo-spatial deficits. In conclusion, the synergistic use of objective measures of motor and cognitive func- tioning and observational screening questionnaires such as MOQ-T should be encouraged at school to identify pupils at risk of developmental coordination disorder

    DNA Metabarcoding and Isolation by Baiting Complement Each Other in Revealing Phytophthora Diversity in Anthropized and Natural Ecosystems

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    Isolation techniques supplemented by sequencing of DNA from axenic cultures have provided a robust methodology for the study of Phytophthora communities in agricultural and natural ecosystems. Recently, metabarcoding approaches have emerged as new paradigms for the detection of Phytophthora species in environmental samples. In this study, Illumina DNA metabarcoding and a conventional leaf baiting isolation technique were compared to unravel the variability of Phytophthora communities in different environments. Overall, 39 rhizosphere soil samples from a natural, a semi-natural and a horticultural small-scale ecosystem, respectively, were processed by both baiting and metabarcoding. Using both detection techniques, 28 out of 39 samples tested positive for Phytophthora. Overall, 1,406,613 Phytophthora internal transcribed spacer 1 (ITS1) sequences and 155 Phytophthora isolates were obtained, which grouped into 21 taxa, five retrieved exclusively by baiting (P. bilorbang; P. cryptogea; P. gonapodyides; P. parvispora and P. pseudocryptogea), 12 exclusively by metabarcoding (P. asparagi; P. occultans; P. psycrophila; P. syringae; P. aleatoria/P. cactorum; P. castanetorum/P. quercina; P. iranica-like; P. unknown sp. 1; P. unknown sp. 2; P. unknown sp. 3; P. unknown sp. 4; P. unknown sp. 5) and four with both techniques (P. citrophthora, P. multivora, P. nicotianae and P. plurivora). Both techniques complemented each other in describing the variability of Phytophthora communities from natural and managed ecosystems and revealing the presence of rare or undescribed Phytophthora taxa

    Association between EEG Paroxysmal Abnormalities and Levels of Plasma Amino Acids and Urinary Organic Acids in Children with Autism Spectrum Disorder

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    Abnormalities in the plasma amino acid and/or urinary organic acid profile have been reported in autism spectrum disorder (ASD). An imbalance between excitatory and inhibitory neuronal activity has been proposed as a mechanism to explain dysfunctional brain networks in ASD, as also suggested by the increased risk of epilepsy in this disorder. This study explored the possible association between presence of EEG paroxysmal abnormalities and the metabolic profile of plasma amino acids and urinary organic acids in children with ASD. In a sample of 55 children with ASD (81.8% male, mean age 53.67 months), EEGs were recorded, and 24 plasma amino acids and 56 urinary organic acids analyzed. EEG epileptiform discharges were found in 36 (65%) children. A LASSO regression, adjusted by age and sex, was applied to evaluate the association of plasma amino acids and urinary organic acids profiles with the presence of EEG epileptiform discharges. Plasma levels of threonine (THR) (coefficient = −0.02, p = 0.04) and urinary concentration of 3-Hydroxy-3-Methylglutaric acid (HMGA) (coefficient = 0.04, p = 0.02) were found to be associated with the presence of epileptiform discharges. These results suggest that altered redox mechanisms might be linked to epileptiform brain activity in ASD
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