Results 1 - 10 of 19146
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[en] Regiomontanus made 29 measurements of the meridian zenith distance of the Sun in Nurnberg between 1472 and 1475, and Walther made 746 more in the same city between 1475 and 1504. In using the observations, they are first corrected for refraction and parallax. The observed values are then fitted to values calculated from the ephemeris of the Sun. After the fitting the standard deviation of the residuals is 95 arcsec for the observations made by Regiomontanus and 55 arcsec for those made by Walther. The residuals for all groups show strong correlation over considerable periods of time, and they may not be treated as statistically independent. The total variation in zenith distance between the summer and winter solstices was too small by the order of 80 arcsec. The error estimate takes at least partial account of the correlation of the residuals. The corresponding value of the Earth's spin acceleration is -51 +- 91 parts in 109 per century. Thus the observations do not give us a useful estimate of the acceleration. However, they do give us useful information about the actual accuracy of pre-telescopic observations and the performance of early instruments. (author)
[en] The validity of the short scale and the impossibility of the scale are again confirmed by comparison of the implications of the alternative estimates of the distance of the Virgo E cluster for the absolute magnitudes of the globular clusters, the RR Lyrae and the Mira-type variables
[fr]La validite de l'echelle courte, et l'impossibilite de l'echelle longue sont confirmees une fois de plus par la comparaison des implications des estimations alternatives de la distance de l'amas Virgo E, pour la magnitude absolue des amas globulaires, des RR Lyrae, et des variables de type Mira Ceti
[en] The B- and H-band versions of the Tully-Fisher relation between absolute magnitude and maximum rotation velocity (or 21 cm line width) of disk galaxies are calibrated by means of the relevant parameters of the Galaxy. This leads to a first crucial test of the extragalactic distance scales and corresponding values of the Hubble constant. The short scale (H0 approximately equal to 95 km x s-1 x Mpc-1) is closely confirmed; the long scale (H'0 approximately equal to 50) is rejected at highly significant levels
[fr]Les versions de la relation de Tully-Fisher (dans les bandes B et H) entre la magnitude absolue et la vitesse de rotation maximale (ou la largeur de la raie a 21 cm) etablies pour les galaxies en disque, sont calibrees a l'aide des parametres de la galaxie. Ceci conduit a un premier test crucial des echelles extragalactiques de distance, et des valeurs correspondantes de la constante de Hubble. L'echelle courte (H0 approximativement = a 95 km.s-1.Mpc-1) est confirmee avec precision et l'echelle longue (H'0 approximativement = a 50) est rejetee, a un niveau tres eleve de signification statistique
[en] We propose a scheme for perfect transfer of an unknown qubit state via the discrete-time quantum walk on a line or a circle. For this purpose, we introduce an additional coin operator which is applied at the end of the walk. This operator does not depend on the state to be transferred. We show that perfect state transfer over an arbitrary distance can be achieved only if the walk is driven by an identity or a flip coin operator. Other biased coin operators and the Hadamard coin allow perfect state transfer over finite distances only. Furthermore, we show that quantum walks ending with a perfect state transfer are periodic. (paper)
[en] We use deep wide-field photometry from the Large Binocular Camera to study the stellar and structural properties of the recently discovered Andromeda X and Andromeda XVII (And X and And XVII) dwarf galaxies. Using the mean apparent magnitude of the horizontal branch (HB), we derive distances of 621 ± 20 kpc to And X and 734 ± 23 kpc to And XVII, closer by >60 kpc than the previous estimates which were based on red giant branch (RGB) observations. Thus, our results warrant against the use of the RGB tip method for determining distances to systems with sparsely populated RGBs and show how crucial HB observations are in obtaining accurate distances in systems such as these. We find that And X is a relatively faint (MV = -7.36), highly elongated (ε = 0.48) system at a distance of 174 ± 62 kpc from Andromeda. And XVII is brighter (MV = -8.61) with an M31-centric distance of 73 kpc which makes it one of the closest satellites to Andromeda. Both galaxies are metal-poor: we derive <[Fe/H]> = -2.2 for And X, while And XVII shows <[Fe/H]>= -2.0, consistent with the relation of higher luminosity dwarfs being more metal-rich. Additionally, both galaxies show considerable intrinsic spreads in metallicity (0.2 and 0.3 dex for And X and And XVII, respectively), consistent with multiple stellar populations.
[en] An approach for solving the minimum zone circle based on the minimum circumscribed circle is presented in this note. Three candidate points of the minimum zone circle are selected according to the minimum circumscribed circle. Another candidate point can be determined based on the distance operator easily. It has been carried out to solve the minimum zone circle effectively. (technical design note)
[en] The traditional multi-step approach to the extragalactic distance scale can be by-passed by using the Galaxy as fundamental calibrator. The current best values of the basic scale factors of the Galaxy are tabulated. This new approach leads to several crucial tests of the long and short distance scales and corresponding values of the Hubble constant
[fr]L'etude traditionnelle, par etapes successives, des echelles extragalactiques de distance peut etre evitee en utilisant la Galaxie comme etalon fondamental. Les meilleures valeurs couramment admises pour les facteurs galactiques de calibration sont tabulees. Cette nouvelle facon d'aborder le probleme conduit a plusieurs tests cruciaux des echelles longue et courte de distance et des valeurs correspondantes de la constante de Hubble
[en] For the first time, we presented the tunable photonic crystals (PCs)-enhanced fluorescence by changing distance between fluorescent dyes and matched PCs. An assembly approach was employed to form the polyelectrolyte multilayer films on the PCs to adjust the distance between the fluorescent dyes and PCs. It was found the PCs-enhanced fluorescence behaviors exhibited the distance dependence. The layer number of polyelectrolytes between fluorescent dyes and PC films will have a considerable effect on the fluorescence properties of fluorescent dyes. The monolayer polyelectrolyte deposited on the PC surface can absorb more oppositely charged fluorophore molecules by an electrostatic interaction, resulting in an outstanding fluorescence enhancement compared to that on the PC film. With increasing the interlayers of polyelectrolytes between PCs and fluorophore molecules, the PC-enhanced fluorescence factors will decrease. Therefore, the distance between the fluorophores and matched PCs can be easily modulated to realize the tunable PC-enhanced fluorescence. The tunable PC-enhanced fluorescent material will have a promising application in the responsive fluorescence devices and sensors.