scholarly journals Influence of growth on dust settling and migration in protoplanetary discs

2010 ◽  
Vol 6 (S276) ◽  
pp. 405-406
Author(s):  
Elisabeth Crespe ◽  
Jean-Francois Gonzalez ◽  
Guillaume Laibe ◽  
Sarah T. Maddison ◽  
Laure Fouchet
Keyword(s):  
Growth Rate ◽  
Central Star ◽  
Constant Growth Rate ◽  
Grain Growth Model ◽  
Dust Dynamics ◽  
And Migration ◽  
Dust Distribution ◽  
Constant Growth ◽  
Gas Drag ◽  
Protoplanetary Discs

AbstractTo form meter-sized pre-planetesimals in protoplanetary discs, dust aggregates have to decouple from the gas at a distance far enough from the central star so they are not accreted. Dust grains are affected by gas drag, which results in a vertical settling towards the mid-plane, followed by radial migration. To have a better understanding of the influence of growth on the dust dynamics, we use a simple grain growth model to determine the dust distribution in observed discs. We implement a constant growth rate into a gas+dust hydrodynamics SPH code and vary the growh rate to study the resulting effect on dust distribution. The growth rate allows us to determine the relative importance between friction and growth.We show that depending on the growth rate, a range of dust distribution can result. For large enough growth rates, grains can decouple from the gas before being accreted onto the central star, thus contributing as planetary building rocks.

scholarly journals Inner dusty regions of protoplanetary discs – II. Dust dynamics driven by radiation pressure and disc winds

2020 ◽  
Vol 500 (1) ◽  
pp. 506-519
Author(s):  
Dejan Vinković ◽  
Miljenko Čemeljić
Keyword(s):  
Radiation Pressure ◽  
Stationary Solutions ◽  
Density Distributions ◽  
Dust Dynamics ◽  
Dust Distribution ◽  
Porous Grains ◽  
Gas Drag ◽  
Dust Flow ◽  
Radiation Pressure Force ◽  
Protoplanetary Discs

ABSTRACT We explore dust flow in the hottest parts of protoplanetary discs using the forces of gravity, gas drag, and radiation pressure. Our main focus is on the optically thin regions of dusty disc, where the dust is exposed to the most extreme heating conditions and dynamical perturbations: the surface of optically thick disc and the inner dust sublimation zone. We utilize results from two numerically strenuous fields of research. The first is the quasi-stationary solutions on gas velocity and density distributions from mangetohydrodynamical (MHD) simulations of accretion discs. This is critical for implementing a more realistic gas drag impact on dust movements. The second is the optical depth structure from a high-resolution dust radiation transfer. This step is critical for a better understanding of dust distribution within the disc. We describe a numerical method that incorporates these solutions into the dust dynamics equations. We use this to integrate dust trajectories under different disc wind models and show how grains end up trapped in flows that range from simple accretion on to the star to outflows into outer disc regions. We demonstrate how the radiation pressure force plays one of the key roles in this process and cannot be ignored. It erodes the dusty disc surface, reduces its height, resists dust accretion on to the star, and helps the disc wind in pushing grains outwards. The changes in grain size and porosity significantly affect the results, with smaller and porous grains being influenced more strongly by the disc wind and radiation pressure.

scholarly journals Breeding records of Leptotila rufaxilla (Aves: Columbidae) in southwestern Brazilian Amazon with notes on nesting in some regions of occurrence

2021 ◽  
Vol 28 (3) ◽  
pp. e18793
Author(s):  
Jônatas Lima ◽  
Railene Almeida ◽  
Edson Guilherme
Keyword(s):  
Growth Rate ◽  
Brazilian Amazon ◽  
Nesting Success ◽  
Daily Survival Rate ◽  
Forest Fragment ◽  
Lowland Forest ◽  
Constant Growth Rate ◽  
Nestling Period ◽  
Constant Growth ◽  
Southwestern Amazonia

We present new aspects of breeding biology of Gray-fronted Dove Leptotila rufaxilla, from five nests found between 2012 and 2014 in a lowland forest fragment in southwestern Brazil. The nests simple/platform shape were built at a mean height of 1.90 m above ground. The clutch size was two eggs white and elliptic, incubated for 15 days (based on three nests). We recorded predation in two nests still in incubation phase. Minimum hatch weight of nestlings was 10 g and young fledged with a mean mass of 56 g. The constant growth rate (K) of nestlings was 0.40 with a growth asymptote of 60.7 g. Daily survival rate, Mayfield and apparent nesting success in the incubation period was 90, 20 and 56%, respectively, while in the nestling period were all 100%. Our data and the contribution of citizen science showed that L. rufaxilla breeds over the year, mainly in the rainy season, both in southwestern Amazonia and in other regions of occurrence.

Growth and Evaluation of [AFeOx/REFeO3] (A=Ca, Sr, RE=La, Bi) Superlattices by Pulsed Laser Deposition Method Using High Density Targets Prepared by Pechini Method

2012 ◽  
Vol 1454 ◽  
pp. 161-166 ◽  
Author(s):  
Nobuyuki Iwata ◽  
Yuta Watabe ◽  
Yoshito Tsuchiya ◽  
Kento. Norota ◽  
Takuya Hashimoto ◽  
...  
Keyword(s):  
Growth Rate ◽  
Flat Surface ◽  
Pechini Method ◽  
Laser Deposition ◽  
Growth Constant ◽  
Constant Growth Rate ◽  
X Ray ◽  
Flat Interface ◽  
Reference Layer ◽  
Constant Growth

ABSTRACTThe LaFeO3 and CaFeOX layers are grown using highly dense target prepared by Pechini method, with which accurate growth rate is achieved. Since the LaFeO3demonstrates the obvious RHEED oscillation until the end of growth, constant growth rate, and the step-terraces structure, the LFO is employed as a buffer and/or reference layer to determine the required pulses to deposit the thickness we desire in the superlattice. Superlattices show the clear satellite peaks and Laue oscillation in the XRD spectra as well as the oscillations caused by the film thickness with a flat surface and superstructure with a flat interface in the x-ray reflection spectrum. The streaky RHEED patterns and step-terraces surface are consistent with the results of spectra using x-ray.

scholarly journals Constant Growth Rate Can Be Supported by Decreasing Energy Flux and Increasing Aerobic Glycolysis

Cell Reports ◽  
2014 ◽  
Vol 7 (3) ◽  
pp. 705-714 ◽  
Author(s):  
Nikolai Slavov ◽  
Bogdan A. Budnik ◽  
David Schwab ◽  
Edoardo M. Airoldi ◽  
Alexander van Oudenaarden
Keyword(s):  
Growth Rate ◽  
Energy Flux ◽  
Aerobic Glycolysis ◽  
Constant Growth Rate ◽  
Constant Growth

scholarly journals General formulation of Luria-Delbrück distribution of the number of mutants

2015 ◽  
Author(s):  
bahram houchmandzadeh
Keyword(s):  
Growth Rate ◽  
Evolutionary Theory ◽  
Growth Function ◽  
Considerable Effort ◽  
Constant Growth Rate ◽  
Stochastic Growth ◽  
The Subject ◽  
Constant Growth

Abstract The Luria-Delbrück experiment is a cornerstone of evolutionary theory, demonstrating the randomness of mutations before selection. The distribution of the number of mutants in this experiment has been the subject of intense investigation during the last 70 years. Despite this considerable effort, most of the results have been obtained under the assumption of constant growth rate, which is far from the experimental condition. We derive here the properties of this distribution for arbitrary growth function, for both the deterministic and stochastic growth of the mutants. The derivation we propose is surprisingly simple and versatile, allowing many generalizations to be taken easily into account.

scholarly journals Hybrid systems approach to modeling stochastic dynamics of cell size

2016 ◽  
Author(s):  
Cesar Augusto Vargas-Garcia ◽  
Abhyudai Singh
Keyword(s):  
Growth Rate ◽  
Cell Size ◽  
Size Variation ◽  
Model Parameters ◽  
Constant Growth Rate ◽  
Division Rate ◽  
Size Dependent ◽  
Daughter Cells ◽  
Constant Growth ◽  
Over Time

A ubiquitous feature of all living cells is their growth over time followed by division into two daughter cells. How a population of genetically identical cells maintains size homeostasis, i.e., a narrow distribution of cell size, is an intriguing fundamental problem. We model size using a stochastic hybrid system, where a cell grows exponentially over time and probabilistic division events are triggered at discrete time intervals. Moreover, whenever these events occur, size is randomly partitioned among daughter cells. We first consider a scenario, where a timer (i.e., cell-cycle clock) that measures the time since the last division event regulates cellular growth and the rate of cell division. Analysis reveals that such a timer-driven system cannot achieve size homeostasis, in the sense that, the cell-to-cell size variation grows unboundedly with time. To explore biologically meaningful mechanisms for controlling size we consider three different classes of models: i) a size-dependent growth rate and timer-dependent division rate; ii) a constant growth rate and size-dependent division rate and iii) a constant growth rate and division rate that depends both on the cell size and timer. We show that each of these strategies can potentially achieve bounded intercellular size variation, and derive closed-form expressions for this variation in terms of underlying model parameters. Finally, we discuss how different organisms have adopted the above strategies for maintaining cell size homeostasis.

Re-normalized quasi-linear approximation of plasma turbulence: Part 3. Collective binary correlations and turbulent de-trapping.

1975 ◽  
Vol 13 (3) ◽  
pp. 429-436 ◽  
Author(s):  
J. H. Misguich ◽  
R. Balescu
Keyword(s):  
Growth Rate ◽  
Linear Approximation ◽  
Plasma Turbulence ◽  
Constant Growth Rate ◽  
Average Function ◽  
Constant Growth

Collective binary correlations are deduced from the re-normalized quasi-linear (RQL) equation describing the evolution of the singlet average function. For a constant growth rate, a crude calculation suggests that generalized Dupree damping could seriously reduce the trapping of resonant particles.

scholarly journals Migrating low-mass planets in inviscid dusty protoplanetary discs

2020 ◽  
Vol 497 (2) ◽  
pp. 2425-2441
Author(s):  
He-Feng Hsieh ◽  
Min-Kai Lin
Keyword(s):  
Central Star ◽  
Small Scale ◽  
Dust Trapping ◽  
Drag Forces ◽  
Planetary Cores ◽  
Planet Migration ◽  
Low Mass ◽  
Future Work ◽  
Gas Drag ◽  
Protoplanetary Discs

ABSTRACT Disc-driven planet migration is integral to the formation of planetary systems. In standard, gas-dominated protoplanetary discs, low-mass planets or planetary cores undergo rapid inwards migration and are lost to the central star. However, several recent studies indicate that the solid component in protoplanetary discs can have a significant dynamical effect on disc–planet interaction, especially when the solid-to-gas mass ratio approaches unity or larger and the dust-on-gas drag forces become significant. As there are several ways to raise the solid abundance in protoplanetary discs, for example through disc winds and dust trapping in pressure bumps, it is important to understand how planets migrate through a dusty environment. To this end, we study planet migration in dust-rich discs via a systematic set of high-resolution, two-dimensional numerical simulations. We show that the inwards migration of low-mass planets can be slowed down by dusty dynamical corotation torques. We also identify a new regime of stochastic migration applicable to discs with dust-to-gas mass ratios of ≳0.3 and particle Stokes numbers ≳0.03. In these cases, disc–planet interaction leads to the continuous development of small-scale, intense dust vortices that scatter the planet, which can potentially halt or even reverse the inwards planet migration. We briefly discuss the observational implications of our results and highlight directions for future work.

Sign in / Sign up

Export Citation Format

Share Document