Semiclassical Theory of Elastic Perturbation

Transition probabilities formulation to explain perturbation effects in elastic differential scattering cross section measurement

Extrasolar planet taxonomy: a new statistical approach

In this paper we present the guidelines for an extrasolar planet taxonomy. The discovery of an increasing number of extrasolar planets showing a vast variety of planetary parameters, like Keplerian orbital elements and environmental parameters, like stellar masses, spectral types, metallicity etc., prompts the development of a planetary taxonomy. In this work via principal component analysis followed by hierarchical clustering analysis, we report the definition of five robust groups of planets. We also discuss the physical relevance of such analysis, which may provide a valid basis for disentangling the role of the several physical parameters involved in the processes of planet formation and subsequent evolution. For instance, we were able to divide the hot Jupiters into two main groups on the basis of their stellar masses and metallicities. Moreover, for some groups, we find strong correlations between metallicity, semi-major axis and eccentricity. The implications of these findings are discussed.Comment: accepted for publication on Ap

I. Collisional evolution and reddening of asteroid surfaces: The problem of conflicting timescales and the role of size-dependent effects

Space weathering is the generic term used for processes that modify the optical properties of surfaces of atmosphereless rocky bodies under exposure to the space environment. The general agreement about the relevance of the effects of space weathering on the spectral properties of S-complex asteroids fails when some basic quantitative estimates are attempted. In particular, there is severe disagreement regarding the typical timescales for significant spectral reddening to occur, ranging from 1 Myr to 1 Gyr. Generally speaking, the spectral reddening of an individual object can be considered as the sum of three terms, one (which is relevant for statistical analyses) depending on the exposure of the object to space weathering during its lifetime, a second one due to the original surface composition, and a third one (a "noise" term) due to the combination of poorly constrained effects (e.g., structure and texture of the surface). The surface of an asteroid is usually covered by regolith, and its presence and properties presumably play a critical role in the weathering processes. In this paper we discuss the role played by collisional evolution in affecting the spectral properties of asteroids and refreshing the surfaces due to the formation of ejecta, and the necessity of a simultaneous modeling of collisions and weathering processes. We introduce a new idea, based on the possibility of a sort of saturation of the refreshing process whenever a massive reaccumulation of the impact ejecta takes place. In this case, a dependence of the overall reddening on the asteroid size should naturally come out. We show that this conclusion is indeed supported by available main belt asteroid spectroscopic data.Comment: Accepted by MNRA

Equivalent static methods for seismic design of straight integral abutment bridges

Integral abutment bridges (IABs) are becoming the solution of choice in the low to mid-length ranges because of their low cost compared with traditional solutions and their good performance under seismic actions. The main drawback of these bridges is the need to consider soil-structure interaction to assess their performance, a problem that is more pronounced for actions implying horizontal deck movements, such as temperature or the specific focus of this paper, that is, seismic action. In IAB design, simplified models are often used, where soil-structure interaction is modeled by means of beams on non-linear Winkler springs for the evaluation of seismic behavior. This paper, starting from an existing non-linear dynamic model (NLDM) that describes IABs longitudinal seismic response, derives two equivalent static models: one non-linear and the other linear, for displacement- or force-based design respectively. A parametric study is carried out to assess the static models performance in terms of the main design internal actions versus the NLDM. Finally, the assessed model errors are discussed in the context of partial factors safety format

The stellar content of the infalling molecular clump G286.21+0.17

The early evolution during massive star cluster formation is still uncertain. Observing embedded clusters at their earliest stages of formation can provide insight into the spatial and temporal distribution of the stars and thus probe different star cluster formation models. We present near-infrared imaging of an 8'*13'(5.4pc*8.7pc) region around the massive infalling clump G286.21+0.17(also known as BYF73). The stellar content across the field is determined and photometry is derived in order to { obtain} stellar parameters for the cluster members. We find evidence for some sub-structure (on scales less than a pc diameter) within the region with apparently at least three different sub-clusters associated with the molecular clump based on differences in extinction and disk fractions. At the center of the clump we identify a deeply embedded sub-cluster. Near-infrared excess is detected for 39-44% in the two sub-clusters associated with molecular material and 27% for the exposed cluster. Using the disk excess as a proxy for age this suggests the clusters are very young. The current total stellar mass is estimated to be at least 200 Msun. The molecular core hosts a rich population of pre-main sequence stars. There is evidence for multiple events of star formation both in terms of the spatial distribution within the star forming region and possibly from the disk frequency.Comment: Submitted to A

Heating of near-Earth objects and meteoroids due to close approaches to the Sun

It is known that near-Earth objects (NEOs) during their orbital evolution may often undergo close approaches to the Sun. Indeed it is estimated that up to ~70% of them end their orbital evolution colliding with the Sun. Starting from the present orbital properties, it is possible to compute the most likely past evolution for every NEO, and to trace its distance from the Sun. We find that a large fraction of the population may have experienced in the past frequent close approaches, and thus, as a consequence, a considerable Sun-driven heating, not trivially correlated to the present orbits. The detailed dynamical behaviour, the rotational and the thermal properties of NEOs determine the exact amount of the resulting heating due to the Sun. In the present paper we discuss the general features of the process, providing estimates of the surface temperature reached by NEOs during their evolution. Moreover, we investigate the effects of this process on meteor-size bodies, analyzing possible differences with the NEO population. We also discuss some possible effects of the heating which can be observed through remote sensing by ground-based surveys or space missions.Comment: 8 pages, 5 figures, accepted by MNRA

The Cratering History of Asteroid (2867) Steins

The cratering history of main belt asteroid (2867) Steins has been investigated using OSIRIS imagery acquired during the Rosetta flyby that took place on the 5th of September 2008. For this purpose, we applied current models describing the formation and evolution of main belt asteroids, that provide the rate and velocity distributions of impactors. These models coupled with appropriate crater scaling laws, allow the cratering history to be estimated. Hence, we derive Steins' cratering retention age, namely the time lapsed since its formation or global surface reset. We also investigate the influence of various factors -like bulk structure and crater erasing- on the estimated age, which spans from a few hundred Myrs to more than 1Gyr, depending on the adopted scaling law and asteroid physical parameters. Moreover, a marked lack of craters smaller than about 0.6km has been found and interpreted as a result of a peculiar evolution of Steins cratering record, possibly related either to the formation of the 2.1km wide impact crater near the south pole or to YORP reshaping.Comment: Accepted by Planetary and Space Scienc

Clonidine for post-traumatic stress disorder: a systematic review of the current evidence

Background: Clonidine is a centrally acting anti-adrenergic agent that may have applications in post-traumatic stress disorder (PTSD), particularly for sleep.Objective: In this systematic review, we aimed to summarize the effect of clonidine on sleep quality and duration, nightmares, and PTSD symptom severity in adults with PTSD.Method: PubMed (Medline), Embase, PsycINFO, CINAHL, and clinicaltrials.gov were searched up to April 2023. Studies on clonidine use in adult PTSD patients reporting data on the effect on sleep, nightmares, and PTSD symptoms were included. A narrative summary and a meta-analysis of the study findings are presented.Results: Ten reports, accounting for N = 569 patients with PTSD (145 on clonidine and 436 controls), were included in the final selection. There were four case reports, four observational studies, one non-blind clinical trial, and one crossover randomized controlled trial (RCT). Median clonidine dose was 0.15 mg/day (range: 0.1-0.5 mg/day). Median follow-up time was 31 days (range: 3 days to 19 months). The quality of the evidence was rated from very low to low. There was marked between-study heterogeneity and low power in the individual studies, but many reported improved sleep quality, nightmare reduction, and improvement of PTSD symptoms for patients treated with clonidine. Meta-analysis was only possible for two studies reporting the effect of clonidine on nightmares, and showed no difference from the comparator (i.e. prazosin or terazosin) (odds ratio: 1.16; 95% confidence interval: 0.66 to 2.05), potentially pointing towards non-inferiority between these medications.Conclusions: Future research, such as well-powered RCTs, is needed to identify the efficacy in the lower dose range and the most suitable treatment group, and to obtain good evidence on the effects of clonidine in the treatment of sleep disorders related to PTSD.Post-traumatic stress disorder (PTSD) is associated with hyperarousal and sleep disorders, reflecting adrenergic nervous system involvement.The use of anti-adrenergic drugs to target the sympathetic activation in PTSD is rational. However, previous reports on prazosin, a peripherally acting agent, yielded weak evidence.Clonidine, a central adrenergic antagonist, shows promise in improving sleep, nightmares, and PTSD symptoms, but further research is needed because the quality of the current evidence is low.Antecedentes: La clonidina es un agente antiadren & eacute;rgico de acci & oacute;n central que podr & iacute;a tener aplicaciones en el trastorno de estr & eacute;s postraum & aacute;tico (TEPT), particularmente para el sue & ntilde;o.Objetivo: En esta revisi & oacute;n sistem & aacute;tica el objetivo fue resumir el efecto de la clonidina sobre la calidad y duraci & oacute;n del sue & ntilde;o, las pesadillas y la gravedad de los s & iacute;ntomas de TEPT en adultos con TEPT.M & eacute;todo: Se realizaron b & uacute;squedas en PubMed (Medline), Embase, PsycINFO, CINAHL y Clinicaltrials.gov hasta abril de 2023. Se incluyeron estudios sobre el uso de clonidina en pacientes adultos con TEPT informando datos sobre el efecto en el sue & ntilde;o, pesadillas y s & iacute;ntomas de TEPT. Se presenta un resumen narrativo y un metan & aacute;lisis de los hallazgos del estudio.Resultados: En la selecci & oacute;n final se incluyeron diez comunicaciones, que representaban N = 569 pacientes con TEPT (145 con clonidina y 436 controles). Hubo 4 informes de casos, 4 estudios observacionales, 1 ensayo cl & iacute;nico no ciego y 1 ensayo cl & iacute;nico aleatorizado (ECA) cruzado. La dosis mediana de clonidina fue de 0,15 mg/d & iacute;a (rango: 0,1-0,5 mg/d & iacute;a). La mediana del tiempo de seguimiento fue de 31 d & iacute;as (entre 3 d & iacute;as y 19 meses). La calidad de la evidencia se calific & oacute; de muy baja a baja. Hubo una marcada heterogeneidad entre los estudios y un poder estad & iacute;stico bajo en los estudios individuales, pero muchos informaron una mejor calidad del sue & ntilde;o, una reducci & oacute;n de las pesadillas y una mejor & iacute;a de los s & iacute;ntomas de TEPT en los pacientes tratados con clonidina. El metan & aacute;lisis solo fue posible para dos estudios que informaron el efecto de la clonidina sobre las pesadillas y no mostr & oacute; diferencias con el comparador (es decir, prazosina o terazosina) (OR: 1,16; IC del 95 %: 0,66; 2,05), potencialmente apuntando hacia una no inferioridad entre estos medicamentos.Conclusiones: Se necesitan investigaciones futuras, como ECA de suficiente poder, para identificar la eficacia en el rango de dosis m & aacute;s bajo, el grupo de tratamiento m & aacute;s adecuado y obtener buena evidencia de los efectos de la clonidina para el tratamiento de los trastornos del sue & ntilde;o relacionados con el TEPT

Mass Segregation in NGC 2298: limits on the presence of an Intermediate Mass Black Hole

[abridged] Theoretical investigations have suggested the presence of Intermediate Mass Black Holes (IMBHs, with masses in the 100-10000 Msun range) in the cores of some Globular Clusters (GCs). In this paper we present the first application of a new technique to determine the presence or absence of a central IMBH in globular clusters that have reached energy equipartition via two-body relaxation. The method is based on the measurement of the radial profile for the average mass of stars in the system, using the fact that a quenching of mass segregation is expected when an IMBH is present. Here we measure the radial profile of mass segregation using main-sequence stars for the globular cluster NGC 2298 from resolved source photometry based on HST-ACS data. The observations are compared to expectations from direct N-body simulations of the dynamics of star clusters with and without an IMBH. The mass segregation profile for NGC 2298 is quantitatively matched to that inferred from simulations without a central massive object over all the radial range probed by the observations, that is from the center to about two half-mass radii. Profiles from simulations containing an IMBH more massive than ~ 300-500 Msun (depending on the assumed total mass of NGC 2298) are instead inconsistent with the data at about 3 sigma confidence, irrespective of the IMF and binary fraction chosen for these runs. While providing a null result in the quest of detecting a central black hole in globular clusters, the data-model comparison carried out here demonstrates the feasibility of the method which can also be applied to other globular clusters with resolved photometry in their cores.Comment: 21 pages, 3 figures, ApJ accepte