104 research outputs found
Tachoastrometry: astrometry with radial velocities
No full textContext. Spectra of composite systems (e.g., spectroscopic binaries) contain spatial information that can be retrieved by measuring the radial velocities (i.e., Doppler shifts) of the components in four observations with the slit rotated by 90 degrees in the sky.
Aims. We aim at developing a framework to describe the method and to test its capabilities in a real case.
Methods. By using basic concepts of slit spectroscopy we show that the geometry of composite systems can be reliably retrieved by measuring only radial velocity differences taken with different slit angles. The spatial resolution is determined by the precision with which differential radial velocities can be measured.
Results. We use the UVES spectrograph at the VLT to observe the known spectroscopic binary star HD 188088 (HIP 97944), which has a maximum expected separation of 23 milli-arcseconds. We measure an astrometric signal in radial velocity of 276 m s(-1), which corresponds to a separation between the two components at the time of the observations of 18 +/- 2 milli-arcseconds. The stars were aligned east-west. We describe a simple optical device to simultaneously record pairs of spectra rotated by 180 degrees, thus reducing systematic effects. We compute and provide the function expressing the shift of the centroid of a seeing-limited image in the presence of a narrow slit.
Conclusions. The proposed technique is simple to use and our test shows that it is amenable for deriving astrometry with milliarcsecond accuracy or better, beyond the diffraction limit of the telescope. The technique can be further improved by using simple devices to simultaneously record the spectra with 180 degrees angles. This device together with an optimized data analysis will further reduce the measurement errors. With tachoastrometry, radial velocities and astrometric positions can be measured simultaneously for many double line system binaries in an easy way. The method is not limited to binary stars, but can be applied to any astrophysical configuration in which spectral lines are generated by separate (non-rotational symmetric) regions
Water Rights in Archaic and Classical Greek Cities: Old and New Problems Revisited
No full textL’articolo affronta il tema, poco studiato, del regime delle acque nelle città del mondo greco. Dopo una prima parte in cui vengono trattati i problemi posti dalla terminologia tecnica ricorrente a proposito della gestione delle risorse idriche nelle fonti letterarie e soprattutto epigrafiche, l’attenzione si sposta sul piccolo corpus di leggi mirante a regolare il regime e l’uso delle acque presente nella sezione dei “nomoi georgikoi” delle Leggi di Platone con lo scopo di accertare se questo riflettesse la normali prassi in materia nell’amministrazione delle città greche o appartenesse alla dimensione “utopica” del progetto delle Leggi. Viene fatta una prima distinzione tra l’acqua potabile la cui gestione avveniva sotto il diretto controllo della polis e l’acqua per l’irrigazione il cui uso era in linea di principio aperto a tutti pur, di volta in volta, con limitazioni. Quanto ai diritti di proprietà, mentre in particolare i corsi d’acqua, e l’acqua che essi portavano, “appartenevano” alla città, i diritti sull’acqua di pertinenza dei singoli terreni (sorgenti, pozzi, acque di raccolta, ecc.) andavano di pari passo con i diritti di proprietà sui terreni stessi. Oggetto di specifica regolamentazione erano in particolare le servitù. Nell’ultima parte vengono analizzati i problemi giuridici posti dall’iscrizione di Eretria relativa alla bonifica, mediante canalizzazioni sotterranee, di un’area paludosa nel territorio della città (IG XII, 9, 191) e dai documenti epigrafici (contratti e horoi) relativi al cosiddetto “acquedotto di Acarne” ad Atene. Viene prospettata la possibilità che, come nel caso dei diritti minerari, si debba presupporre l’esistenza di una separazione, in rapporto al diritto a goderne, tra diritti di superficie e diritti sul sottosuolo
Weekly Variations of Well-Being and Interactions with Training and Match Intensities: A Descriptive Case Study in Youth Male Soccer Players
No full textNumerical Study and Geometrical Investigation of an Inclined Passive Wall Solar Chimney over the Ventilation Performance of an Attached Room
No full textThe present numerical work investigates by means of Constructal Design the influence of the geometry of an inclined passive wall solar chimney on the ventilation performance of an attached room. The main purpose is to maximize the mass flow rate of air in the chimney/attached room. The problem is subjected to two constraints: the chimney and room areas. Three degrees of freedom are investigated: the ratio between the exit and inferior bases widths of the chimney (W-e/W-g), the ratio between the width of the chimney inferior basis and the absorber wall height (W-g/H-a), and the ratio between the opening that connects chimney and room and the absorber wall height (H-i/H-a). It is considered unsteady, incompressible, free convective, turbulent flows in a two-dimensional domain. The finite volume method is used to solve the time-averaged equations of continuity, momentum and conservation of energy. For closure of turbulence, it is employed the k-e model. Results showed that the best geometric configuration led to a mass flow rate 5.7 times superior than the worst configuration, showing the importance of solar chimney desing in this problem. Moreover, a strong sensibility of the investigated ratios on the mass flow rate was noticed
Renormalized chemical kinetics and benchmark quantum mechanical rates: activation energies and tunnelling transitivities for the reactions of fluorine atoms with H2 and HD
No full textIn this paper, scaling and renormalization procedures are developed beyond
the Arrhenius equation and the Transition State Theory, regarding two key observables in reaction kinetics, the rate constant as a function of temperature (and its reciprocal, the generalised lifetime), and the apparent activation energy (and its reciprocal, the transitivity function). Coupled first-order equations-dependent on time and on temperature-are formulated in alternative coupling scheme they link experimental results to effective modelling, or vice versa molecular dynamics simulations to predictions. The passage from thermal to tunnelling regimes is uniformly treated and applied to converged quantum mechanical calculations of rate constants available for the prototypical three-atom reactions of fluorine atoms with both H2 and HD: these are exothermic processes dominated by moderate tunnel, needing formal extension to cover the low-temperature regime where aspects of universal behaviour are shown to emerge. The results that have been validated towards experimental information in the 10-350 K temperature range, document the complexity of commonly considered elementary chemical reactions: they are relevant for modelling atmospheric and astrophysical environments. Perspectives are indicated of advances towards other types of transitions and to a global generality of processes of interest in applied chemical kinetics in biophysics and in astrochemistry
Demetrius of Phalerum and Late Fourth-Century Athenian Society: Response to Delfim Leão
No full textIl contributo affronta una serie di questioni, di metodo e di contenuto, poste dalla figura di Demetrio Falereo e dal suo governo nella città di Atene tra il 317 e il 307 a.C., e in particolare la natura della tradizione antica riguardo a questo discusso personaggio, il ruolo "istituzionale" che egli rivestì nel decennio in cui ebbe una posizione di preminenza, il carattere del regime timocratico che stabilì nella città e, infine, il significato delle leggi che, nella sua veste di "nomothetes", egli introdusse in rapporto alle dinamiche della società ateniese emerse soprattutto a partire dal periodo "licurgheo". Si conclude che, nonostante la tradizione ostile al personaggio, la tesi da lui sostenuta di avere voluto "correggere" la democrazia non è poi così lontana dalla realtà.Abstract
In this response some questions concerning Demetrius of Phalerum’s ten-year rule at Athens (317-307 BC) are examined with regard to his institutional position, to the character of his regime and to the nature and scope of his legislation. Continuity with political and social issues already in the agenda of «Lycurgan» Athens and the «practical» nature of his reforms are underlined. It is concluded that Demetrius’ claim to have "corrected" Athenian democracy was not too far off the mark
Emended description of Mycobacterium abscessus, Mycobacterium abscessus subsp. abscessus and mycobacterium abscessus subsp. bolletii and designation of Mycobacterium abscessus subsp. massiliense comb. nov
No full textThe taxonomic position of members of the Mycobacterium abscessus complex has been the subject of intensive investigation and, in some aspects confusion, in recent years as a result of varying approaches to genetic data interpretation. Currently, the former species Mycobacterium massiliense and Mycobacterium bolletii are grouped together as Mycobacterium abscessus subsp. bolletii. They differ greatly, however, as the former M. bolletii has a functional erm(41) gene that confers inducible resistance to macrolides, the primary therapeutic antimicrobials for M. abscessus, while in the former M. massiliense the erm(41) gene is non-functional. Furthermore, previous whole genome studies of the M. abscessus group support the separation of M. bolletii and M. massiliense. To shed further light on the population structure of Mycobacterium abscessus, 43 strains and three genomes retrieved from GenBank were subjected to pairwise comparisons using three computational approaches: verage ucleotide dentity, enome to enome istance and single nucleotide polymorphism analysis. The three methods produced overlapping results, each demonstrating three clusters of strains corresponding to the same number of taxonomic entities. The distances were insufficient to warrant distinction at the species level, but met the criteria for differentiation at the subspecies level. Based on prior erm(41)-related phenotypic data and current genomic data, we conclude that the species M. abscessus encompasses, in adjunct to the presently recognized subspecies M. abscessus subsp. abscessus and M. abscessus subsp. bolletii, a third subspecies for which we suggest the name M. abscessus subsp. massiliense comb. nov. (type strain CCUG 48898T=CIP 108297T=DSM 45103T=KCTC 19086T)
IS1245 restriction fragment length polymorphism typing of Mycobacterium avium isolates: proposal for standardization
No full textMycobacterium avium has become a major human pathogen, primarily due to the emergence of the AIDS epidemic. Restriction fragment length polymorphism (RFLP) typing, using insertion sequence IS1245 as a probe, provides a powerful tool in the molecular epidemiology of M. avium-related infections and will facilitate
well-founded studies into the sources of M. avium infections in animal and environmental reservoirs. The
standardization of this technique allows computerization of IS1245 RFLP patterns for comparison on a local
level and the establishment of M. avium DNA fingerprint databases for interlaboratory comparison. Moreover,
by combining international DNA typing results of M. avium complex isolates from a broad spectrum of sources,
long-lasting questions on the epidemiology of this major agent of mycobacterial infections will be answered
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