Search results for "Asteroid"
showing 10 items of 53 documents
Symbolic dynamics in a binary asteroid system
2020
We highlight the existence of a topological horseshoe arising from a a--priori stable model of the binary asteroid dynamics. The inspection is numerical and uses correctly aligned windows, as described in a recent paper by A. Gierzkiewicz and P. Zgliczy\'nski, combined with a recent analysis of an associated secular problem.
Persistence of Asteroids After a Close Encounter
1999
We present here a first approximation to the planar circular restricted 2 + 2 problem. In this four body problem, we consider that the two secondaries do not affect the primaries but they do influence each other. It can be seen as a model for near collision orbits of two asteroids if the primaries are the Sun and Jupiter ([3], [5]). In particular, we analyze the values of the Jacobi constant of the two asteroids before and after the close approach.
Pars Plana Vitrectomy for Visually Disturbing Vitreous Floaters in Pseudophacic Eyes
2011
Background The aim of this study was to evaluate the role of vitrectomy in patients with visually disturbing vitreous opacities. Patients and methods A retrospective analysis of the patient characteristics and the outcome of all pseudophacic eyes, which consecutively received in the decade 1996 to 2005 20 G pars plana vitrectomy for visually disturbing floaters, was carried out at the Mainz University Eye Clinic. Results Forty-one eyes of 32 patients (63 % university graduates, median age: 64 years) were included in the study. The mean axial length of the globe was 25.3 mm (range: 22.8 to 28.9 mm). Additional pathologies having influence on the vitreous condition were history of laser or cr…
Model‐based meta‐analysis of the time to first acute urinary retention or benign prostatic hyperplasia‐related surgery in patients with moderate or s…
2021
Aims Combination therapy of 5α‐reductase inhibitor and α‐blocker is a guideline‐endorsed therapeutic approach for patients with moderate‐to‐severe lower urinary tract symptoms or benign prostatic hyperplasia (LUTS/BPH) who are at risk of disease progression. We aimed to disentangle the contribution of clinical and demographic baseline characteristics affecting the risk of acute urinary retention or BPH‐related surgery (AUR/S) from the effect of treatment with drugs showing symptomatic and disease‐modifying properties. Methods A time‐to‐event model was developed using pooled data from patients (n = 10 238) enrolled into six clinical studies receiving placebo, tamsulosin, dutasteride or tamsu…
A new genus and species of asteraceae-inhabiting aphid (hemiptera: aphididae) from Costa Rica and Mexico
2013
P. 323-331 Ucrimyzus villalobosi Mier Durante & Pérez Hidalgo gen. n., sp. n. (Hemiptera: Aphididae: Macrosiphini) are described from apterous and alate viviparous females collected on species of genera Bidens, Schkuhria, Senecio and Stevia (Asteraceae: Asteroideae) in Costa Rica and Mexico. Principal components analysis (PCA) was done to verify that the studied aphids belong to a single species regardless of their geographical origin or host plant. Molecular analyses were carried out on the sequences of a fragment of the mitochondrial gene encoding for cytochrome c oxidase subunit 1 (COI) and of a fragment of the nuclear gene encoding elongation factor 1α (EF1α). The taxonomic discussion t…
Improved Method for Orbital Elements Differential Correction.
1990
As was pointed out by IAU in 1976, an important problem in fundamental astronomy is the improvement of the vernal equinox and equator positions. To this aim, it is necessary to know the accurate values of minor planets orbital elements. The classical methods of orbital elements differential corrections are based on linking the observations at different epochs considering equal derivatives respect to the initial and osculating elements. In this paper we present an improved method in which the least squares matrix coefficients is calculated from the integration of the Lagrange planetary equations and its derivatives.
A Middle Cambrian edrioasteroid from the Murero biota (NE Spain) with Australian affinities
2007
Abstract A Middle Cambrian edrioasteroid belonging to the genus Cambraster is described from the Middle Cambrian Murero biota (Cadenas Ibericas, NE Spain). Up to now, this genus was known only from Australia and France. This represents the first record of the class Edrioasteroidea in the Cambrian of Spain. Moreover, preliminary results on the diversity and biostratigraphic position of Cincta, Eocrinoidea and Edrioasteroidea from this area are reported.
The large TNO 2002 TC302
2020
VizieR online Data Catalogue associated with article published in journal Astronomy & Astrophysics with title 'The large Trans-Neptunian object 2002 TC302 from combined stellar occultation photometry and astrometry data.' (bibcode: 2020A&A...639A.134O)
Seeing Double:ASASSN-18bt Exhibits a Two-Component Rise in the Early-Time K2 Light Curve
2018
On 2018 Feb. 4.41, the All-Sky Automated Survey for SuperNovae (ASAS-SN) discovered ASASSN-18bt in the K2 Campaign 16 field. With a redshift of z=0.01098 and a peak apparent magnitude of B_{max}=14.31, ASASSN-18bt is the nearest and brightest SNe Ia yet observed by the Kepler spacecraft. Here we present the discovery of ASASSN-18bt, the K2 light curve, and pre-discovery data from ASAS-SN and the Asteroid Terrestrial-impact Last Alert System (ATLAS). The K2 early-time light curve has an unprecedented 30-minute cadence and photometric precision for an SN~Ia light curve, and it unambiguously shows a ~4 day nearly linear phase followed by a steeper rise. Thus, ASASSN-18bt joins a growing list o…
Analysis of the orbit of the Centaur asteroid 2009 HW77
2011
We present the time evolution of orbital elements of the Centaur asteroid 2009 HW77, discovered by KC and IE, forwards and backwards in time over a 10-Myr period. The dynamical behaviour is analysed using three software packages: the OrbFit, the swift and the Mercury integrators. Changes in the orbital elements of 2009 HW77 clones are calculated using the classification of Horner et al. It is shown that close approaches to the giant planets significantly change the asteroid orbit. Our computations made with the swift software and with the Mercury software give similar results. The half-life is about 5 Myr in both the forward and backward integrations. Moreover, our computations suggest that…