Abstract.We have undertaken a thorough dynamical investigation of five extrasolar planetary systems using extensive numerical experiments. The systems Gl 777 A, HD 72659, Gl 614, 47 Uma and HD 4208 were examined concerning the question of whether they could host terrestrial-like planets in their habitable zones (HZ). First we investigated the mean motion resonances between fictitious terrestrial planets and the existing gas giants in these five extrasolar systems. Then a fine grid of initial conditions for a potential terrestrial planet within the HZ was chosen for each system, from which the stability of orbits was then assessed by direct integrations over a time interval of 1 million years. For each of the five systems the 2-dimensional grid of initial conditions contained 80 eccentricity points for the Jovian planet and up to 160 semimajor axis points for the fictitious planet. The computations were carried out using a Lie-series integration method with an adaptive step size control. This integration method achieves machine precision accuracy in a highly efficient and robust way, requiring no special adjustments when the orbits have large eccentricities. The stability of orbits was examined with a determination of the Rényi entropy, estimated from recurrence plots, and with a more straightforward method based on the maximum eccentricity achieved by the planet over the 1 million year integration. Additionally, the eccentricity is an indication of the habitability of a terrestrial planet in the HZ; any value of e > 0.2 produces a significant temperature difference on a planet's surface between apoapse and periapse. The results for possible stable orbits for terrestrial planets in habitable zones for the five systems are: for Gl 777 A nearly the entire HZ is stable, for 47 Uma, HD 72659 and HD 4208 terrestrial planets can survive for a sufficiently long time, while for Gl 614 our results exclude terrestrial planets moving in stable orbits within the HZ. Studies such as this one are of primary interest to future space missions dedicated to finding habitable terrestrial planets in other stellar systems. Assessing the likelihood of other habitable planets, and more generally the possibility of other life, is the central question of astrobiology today. Our investigation indicates that, from the dynamical point of view, habitable terrestrial planets seem to be compatible with many of the currently discovered extrasolar systems. they could host additional terrestrial-like planets in their habitable zones (=HZ).Since the discovery of the first extrasolar planetary system about 10 years ago (Mayor & Queloz 1995), a major point of dynamical investigations has been the determination of stable regions in extrasolar planetary systems, where additional planets on stable orbits could exist. Today we know about 105 planetary systems with 120 planets, where 13 systems have more than one planet (both confirmed and unconfirmed cases).Article published by EDP Sciences and available at
A number of studies in the recent past have proposed a variety of scaling relationships among the penetration depth at the bottom of a convective region, the vertical velocity of the Ñuid and theWhile a relationship of the form has been proposed by Schmitt and coworkers (F b ). * d P V z 3@2 on the basis of the equations of motion for buoyant plumes, Zahn proposed a similar relationship based on scaling arguments. The relationships involving and the input Ñux are based on recent two-* d , V z , dimensional numerical simulations by Hurlburt and coworkers. All these scalings were recently looked into by Singh, Roxburgh, & Chan, who performed full three-dimensional simulations of turbulent compressible convection for a stable-unstable-stable sandwich conÐguration. In the present study, we numerically solve the full set of Navier-Stokes equations in three dimensions in order to study the behavior of convective motions penetrating into the bottom stable layer. We take up a series of models di †ering in resolution or mesh size and aspect ratio with a view to examine, in greater detail, the scaling relationships between the penetration distance and other Ñow parameters.
The present study reports the antibacterial properties of flower-shaped ZnO (FZnO) microstructures and its comparison with that of hexagon-shaped bulk ZnO (BZnO) nanostructures. The samples are prepared successfully by wet chemical method and the surface morphologies, structures and size of the ZnO samples are characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), BET adsorption isotherm, and Photoluminescence (PL) Spectroscopy. The SEM and TEM images of the sample have confirmed flower-shaped structure of the ZnO. The materials are also analyzed by using an innovative tool called Lacunarity, a nonlinear dynamical (NLD) tool for proper understanding of the inherent surface properties of the particles formed, comparing the results estimated with the BET results obtained, thereby confirming our proposition to use it as an important parameter in predictive models. In this new approach, geometry of the surface structure is being associated with biological properties, in order to come up with easier ways to identify materials for any such applications where rich surface structure is desired. The photocatalytic activity of the flower-shaped material is carried out to find out its optical properties as another marker for confirming the antimicrobial activities. It has been reported for the first time that the prominent antibacterial activities are favoured by the FZnO microstructure having lesser Lacunarity, significantly better than its bulk counterpart, for inhibiting gram negative-Escherichia coli microorganism. Nanotechnology, at present, pertains to creation of useful materials, devices, and systems through appropriate manipulation of matter. A significant number of researchers have reported that formation of ZnO nanostructures in different shapes, such as, nanorod, nanoplates, nanowire 1 , flower-shaped ZnO microstructures 2 , etc. In the present work, two important attributes, capping and molarity, are used to control the particle size and their agglomeration 3. It is reported in W Yu et al. (2016), that photo-generated electrons in ZnO are much lighter than their corresponding holes, which indicates that it belongs to the n-type semiconductor 4. This result paves the way for obtaining excitation energy of electrons in ZnO that determines its optical property. ZnO materials are good inhibitors of microorganisms, and it is believed that this activity is enhanced in case of ZnO due to its high surface morphology. The capped ZnO usually shows up higher antibacterial activity than the uncapped one 5. In the present work, flower-shaped ZnO (FZnO) microstructures in PVP matrix and uncapped hexagon-shaped bulk ZnO (BZnO) nanostructures are synthesized for the study of their antimicrobial properties. The as-prepared samples are characterized by X-ray diffraction (XRD) 6 , Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) to find their size and shape 7,8. Further, the FZnO are characterized by UV-spectra, Photoluminescence (PL) Spec...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.