1,377 research outputs found

    Distribution dynamics: a spatial perspective

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    It is quite common in cross-sectional convergence analyses that data exhibit spatial dependence. Within the literature adopting the distribution dynamics approach, authors typically opt for spatial prefiltering. We follow an alternative route and propose a procedure based on an estimate of the mean function of a conditional density for which we develop a two-stage non-parametric estimator that allows for spatial dependence estimated via a spline estimator of the spatial correlation function. The finite sample performance of this estimator is assessed via Monte Carlo simulations. We apply the procedure that incorporates the proposed spatial non-parametric estimator to data on per capita personal income in US states and metropolitan statistical areas

    In vitro propagation of isoëtes sabatina (Isoetaceae): A key conservation challenge for a critically endangered quillwort

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    Isoëtes sabatina is an aquatic quillwort endemic to Italy. It is one of the rarest quillworts in Europe, and is critically endangered due to restricted range and to the continuous decline of both population and habitat quality. This study aims to develop an optimized protocol to reproduce and grow I. sabatina sporelings. Mature and immature megaspores were mixed with mature microspores to evaluate the influence of the developmental stage on germination and sporeling development. Two substrates, distilled water and water-agar medium, were tested for germination and sporeling emergence, and three substrates, sand, lake sediment and water-agar, were tested for transplants. A high percentage of megaspore germination (a total of 79.1%) was obtained in both substrates, higher for mature than immature spores. A total of 351 sporelings were produced in distilled water and water-agar cultures, with similar percentages (64.5% and 69.6%, respectively). The development stage of the megaspores affected both germination and sporeling development. Sporeling emergence showed significantly higher percentages in mature megaspores than immature ones (69.6% vs. 11.6%, respectively), with 85% of germinated spores developing sporelings. Only transplants over water-agar medium were successful. This protocol could be useful for the propagation of sporelings as the key step towards the planning of in situ actions to save this Mediterranean quillwort from extinction

    Atomic and Molecular Data for Optical Stellar Spectroscopy

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    High-precision spectroscopy of large stellar samples plays a crucial role for several topical issues in astrophysics. Examples include studying the chemical structure and evolution of the Milky Way galaxy, tracing the origin of chemical elements, and characterizing planetary host stars. Data are accumulating from instruments that obtain high-quality spectra of stars in the ultraviolet, optical and infrared wavelength regions on a routine basis. These instruments are located at ground-based 2- to 10-m class telescopes around the world, in addition to the spectrographs with unique capabilities available at the Hubble Space Telescope. The interpretation of these spectra requires high-quality transition data for numerous species, in particular neutral and singly ionized atoms, and di- or triatomic molecules. We rely heavily on the continuous efforts of laboratory astrophysics groups that produce and improve the relevant experimental and theoretical atomic and molecular data. The compilation of the best available data is facilitated by databases and electronic infrastructures such as the NIST Atomic Spectra Database, the VALD database, or the Virtual Atomic and Molecular Data Centre (VAMDC). We illustrate the current status of atomic data for optical stellar spectra with the example of the Gaia-ESO Public Spectroscopic Survey. Data sources for 35 chemical elements were reviewed in an effort to construct a line list for a homogeneous abundance analysis of up to 100000 stars.Comment: Published 30 April 2015 in Physica Script

    Stabilization of earthen plasters: Exchange of knowledge and experiences between Italy and Morocco

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    The preservation of earthen architectural heritage and earthen contemporary architecture asks for the experimentation and the development of proper materials and intervention techniques in order to prevent decays which may compromise the conservation of earthen heritage over time. This research program, thanks to a bilateral cooperation between the CNRST-UCA and CNR-ICVBC, aims to design and test earth-based plasters stabilized with traditional products (gypsum or lime), in order to acquire information necessary to develop more durable earthen mixtures to be applied both on existing and new buildings. The experimental campaign intends to assess the capacity of these stabilized plasters to guarantee an appropriate protection of earthen walls. The plasters have been tested at first in laboratory, then they have been applied on an earthen building in the outskirts of Marrakesh. The performances of the on site plasters are still under study and will not be presented in this paper

    Isoëtes sabatina (Isoëtaceae, Lycopodiopsida): Taxonomic distinctness and preliminary ecological insights

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    Isoëtes sabatina is the rarest aquatic quillwort in Europe. Although recently found (2013) in Lake Bracciano (central Italy), the species is just one step away from extinction with an estimated population not exceeding 400 individuals and a spatial range of a few hundred square metres. Lake Bracciano is a deep, oligo-mesotrophic Mediterranean volcanic lake that has been subjected to human activities. From January to October 2017, the lake experienced a dramatic water level decrease (up to −1.50 m), which significantly affected the littoral zone and the habitat of I. sabatina. To improve the chances of survival of I. sabatina, the first eco-taxonomic investigation on this species was carried out to describe its genetic distinctness, physical and chemical requirements and companion species. The phylogenetic position of I. sabatina was investigated by applying standard DNA barcoding methods. Simultaneously, during summer 2019, the physical and chemical features of water and sediments of the I. sabatina population and five small Alpine lakes colonized by Isoëtes echinospora – a supposed close relative – were characterized. These data were then compared with the available data on the trophic requirements of the target obligate aquatic Isoëtes, together with Isoëtes lacustris and Isoëtes malinverniana. The present survey confirmed the taxonomic and ecological distinctness of I. sabatina – providing the first evidence of genetic differentiation from I. echinospora. Isoëtes sabatina grows in waters with temperature, conductivity and total alkalinity up to 30°C, 561 Î¼S cm−1 and 3.45 meq L−1, respectively. The edaphic requirements of I. sabatina confirm its outstanding conservation value, and this study offers a basic understanding of how to prevent its extinction. Now, all possible actions must be taken immediately to save this species

    Cool gas and dust in M33: Results from the Herschel M33 extended survey (HERM33ES)

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    We present an analysis of the first space-based far-IR-submm observations of M 33, which measure the emission from the cool dust and resolve the giant molecular cloud complexes. With roughly half-solar abundances, M33 is a first step towards young low-metallicity galaxies where the submm may be able to provide an alternative to CO mapping to measure their H2_2 content. In this Letter, we measure the dust emission cross-section σ\sigma using SPIRE and recent CO and \HI\ observations; a variation in σ\sigma is present from a near-solar neighborhood cross-section to about half-solar with the maximum being south of the nucleus. Calculating the total H column density from the measured dust temperature and cross-section, and then subtracting the \HI\ column, yields a morphology similar to that observed in CO. The H2_2/\HI\ mass ratio decreases from about unity to well below 10% and is about 15% averaged over the optical disk. The single most important observation to reduce the potentially large systematic errors is to complete the CO mapping of M 33.Comment: 5 pages, 5 figures Accepted for publication in Astronomy and Astrophysic

    Monthly fluctuations in 25-hydroxy-vitamin D levels in day and rotating night shift hospital workers

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    Purpose Epidemiological studies have suggested that indoor hospital employees, either day or night shift workers, are at high risk of metabolic and cardiovascular diseases. Interestingly, previous reports have also described a higher prevalence of vitamin D (25OHD) deficiency among these workers. However, few studies have determined the monthly variations in 25OHD levels in indoor hospital employees. Methods To address this lack of knowledge, in 2018, during the periodic health surveillance checks at the Service of Occupational Medicine, we measured 25OHD levels in a group of indoor hospital workers (88 rotating night shift workers vs 200 day workers). Each participant received a single annual health surveillance check. Results The mean levels of 25OHD were consistently below the lower limit of the normal range in both groups throughout the year. Only in the summer, day workers but not rotating night shift workers (mean 25.9 +/- 11.3 ng/ml vs 23.1 +/- 9.1 ng/ml; p = 0.042) showed levels significantly higher than those in the other seasons. This difference remained statistically significant even after correction for study covariates [beta = - 1.649 (CI - 0.283/- 3.482), p = 0.039]. A cosinor analysis confirmed that the difference in the 25OHD levels between groups was present later in the year. Conclusions We found that relatively young healthy hospital workers, especially those with rotating night shifts, in the absence of significant metabolic risk factors, have a high risk of 25OHD deficiency/insufficiency. Because 25OHD deficiency may lead to a progression to more severe conditions such as osteoporosis or bone fractures, our results should be verified in larger cohorts including different ancestries
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