A preliminary numerical model of the Geminid meteoroid stream

A pilot numerical model of the Geminid meteoroid stream is presented. This model implies cometary origin of the stream. Ejection of relatively small amount of particles (90 000 test meteoroids with masses 0.02, 0.003 and 0.0003 g) from the asteroid (3200) Phaethon (the parent body) was simulated, and their evolution was followed till the present time. The particles close to the Earth orbit were considered as the ‘shower’. It was found that the width of the model shower is at least twice less comparatively the real shower. The maximum activity of the model shower is dislocated and occurs about one day late. The most probable reason for both discrepancies is the drastic transformation of the parent body orbit during rapid release of the volatiles in the process of the stream initial formation. The dispersion of the model stream was evaluated in terms of the Southworth–Hawkins D-criterion

Finding of the Low Molecular Weight Inhibitors of Resuscitation Promoting Factor Enzymatic and Resuscitation Activity

Background: Resuscitation promoting factors (RPF) are secreted proteins involved in reactivation of dormant actinobacteria, including Mycobacterium tuberculosis. They have been considered as prospective targets for the development of new antituberculosis drugs preventing reactivation of dormant tubercle bacilli, generally associated with latent tuberculosis. However, no inhibitors of Rpf activity have been reported so far. The goal of this study was to find low molecular weight compounds inhibiting the enzymatic and biological activities of Rpfs. Methodology/Principal Findings: Here we describe a novel class of 2-nitrophenylthiocyanates (NPT) compounds that inhibit muralytic activity of Rpfs with IC50 1–7 mg/ml. Fluorescence studies revealed interaction of active NPTs with the internal regions of the Rpf molecule. Candidate inhibitors of Rpf enzymatic activity showed a bacteriostatic effect on growth of Micrococcus luteus (in which Rpf is essential for growth protein) at concentrations close to IC50. The candidate compounds suppressed resuscitation of dormant (‘‘non-culturable’’) cells of M. smegmatis at 1 mg/ml or delayed resuscitation of dormant M. tuberculosis obtained in laboratory conditions at 10 mg/ml. However, they did not inhibit growth of active mycobacteria under these concentrations. Conclusions/Significance: NPT are the first example of low molecular weight compounds that inhibit the enzymatic an

A preliminary numerical model of the Geminid meteoroid stream

A pilot numerical model of the Geminid meteoroid stream is presented. This model implies cometary origin of the stream. Ejection of relatively small amount of particles (90 000 test meteoroids with masses 0.02, 0.003 and 0.0003 g) from the asteroid (3200) Phaethon (the parent body) was simulated, and their evolution was followed till the present time. The particles close to the Earth orbit were considered as the ‘shower’. It was found that the width of the model shower is at least twice less comparatively the real shower. The maximum activity of the model shower is dislocated and occurs about one day late. The most probable reason for both discrepancies is the drastic transformation of the parent body orbit during rapid release of the volatiles in the process of the stream initial formation. The dispersion of the model stream was evaluated in terms of the Southworth–Hawkins D-criterion

The Geminid meteor shower radiant: a mathematical model

The origin of the Geminid meteoroid stream and its parent body the asteroid (3200) Phaethon is still under discussion. The observed bimodal activity profile of the Geminid shower agrees with a cometary scheme of the stream formation. We show that the radiant areas for meteors of different magnitudes may also be used to provide arguments supporting or undermining the cometary hypothesis. We used semi-analytic and numerical models of the stream. The resulting model radiants for meteors of various magnitudes (masses) have peculiar patterns that might be detected in a real shower

Mathematical modelling of meteoroid streams

Modern computer power and high-precision observational data have greatly improved the reliability of meteoroid stream models. At present, scientific research calls for two kinds of models: precise ones for individual streams, and statistically averaged ones for Solar System dust distribution models. Thus, there is a wide field of study open to stream modellers. This brief describes step-by-step computer simulations of meteoroid stream formation and evolution. Detailed derivations of relevant formulae are given, along with plenty of helpful, digestible figures explaining the subtleties of the method. Each theoretical section ends with examples aimed to help readers practice and master the material. Most of the examples are based on the Geminid meteoroid stream model, which has been developed by the author in the last 30 years. The book is intended for researchers interested in meteor astronomy and mathematical modelling, and it is also accessible to physics and astrophysics students

On mean motion resonances in the Geminid meteoroid stream

Analysing numerical models of the Geminid meteoroid stream for particle masses 0.00003–0.3 g we found evidence of several mean motion resonances: 1:2, 2:5, 3:7, 3:8 and 4:9 with Venus, 2:3 and 5:7 with the Earth and 7:1 with Jupiter. The resonant particles form dust trails located far from the Earth's orbit. Indeed, there is no observational support for resonant effects in the observed Geminid meteor shower. The trails are stable and compact, and consist of large (0.003–0.3 g) meteoroids

The force model for asteroid (3200) Phaethon

Asteroid (3200) Phaethon is an Apollo asteroid having very small (0.14 au) perihelion distance. We analyze the influence of various perturbing factors on the asteroid motion. Most of them were studied on the base of (O–C) residuals and/or the orbital evolution. This set of estimated perturbing accelerations contains: gravitational perturbations from all major planets, Pluto, the Moon, Ceres, Pallas, Vesta; the Earth, the Sun and Jupiter oblateness, the relativistic effects of the Sun and the solar radiation pressure. The perturbation estimation was done by five various methods. The purpose was to classify the perturbing accelerations as powerful, medium or weak ones, and the criteria for classification were built on the value of the mean accuracy of positional observations from the Earth. All five methods showed a good consistency. We found that the solar radiation pressure exerts a weak influence on the Phaethon motion, while the relativistic effects of the Sun and the Sun oblateness could be classified as medium perturbations. For the most complete and correct description of (3200) Phaethon motion we recommend to include gravitational influence from the planets and the Moon, the relativistic effects of the Sun and the Sun oblateness in the force model. Some other factors we considered separately. They are the recoil acceleration from the recurrent mass loss at perihelia, the Yarkovsky acceleration and relativistic effects of planets, Pluto and the Moon. It was obtained that their contributions to the total acceleration are negligible. We analyzed the next close encounter of Phaethon with the Earth in 2017 and found that neglecting gravitational perturbations from Neptune and Pluto, the Earth and Jupiter oblateness give an error less than 100 km in the asteroid position. Gravitational perturbations from the inner planets (including the Moon) and Jupiter are the strongest and neglecting one of them results in the asteroid position error 104–106 km