scholarly journals Universal Protoplanetary Disk Size under Complete Nonideal Magnetohydrodynamics: The Interplay between Ion-neutral Friction, Hall Effect, and Ohmic Dissipation

2021 ◽  
Vol 922 (1) ◽  
pp. 36
Author(s):  
Yueh-Ning Lee ◽  
Pierre Marchand ◽  
Yu-Hsuan Liu ◽  
Patrick Hennebelle
Keyword(s):  
Hall Effect ◽  
Initial Conditions ◽  
Early Stage ◽  
Small Disk ◽  
Ohmic Dissipation ◽  
Vertical Field ◽  
Disk Size ◽  
Wide Range ◽  
Parallel Configuration

Abstract The role of nonideal magnetohydrodynamics has been proven critical during the formation of protoplanetary disks, particularly in regulating their sizes. We provide a simple model to predict the disk size under the interplay among ambipolar diffusion, the Hall effect, and ohmic dissipation. The model predicts a small disk size of around 20 au that depends only sublinearly on disk parameters, for a wide range of initial conditions of subsolar mass and moderate magnetization. It is able to explain phenomena manifested in existing numerical simulations, including the bimodal disk behavior under parallel and antiparallel alignment between the rotation and magnetic field. In the parallel configuration, the disk size decreases and eventually disappears. In the antiparallel configuration, the disk has an outer partition (or pseudodisk), which is flat, shrinking, and short-lived, as well as an inner partition, which grows slowly with mass and is long-lived. Even with significant initial magnetization, the vertical field in the disk can only dominate at the early stage when the mass is low, and the toroidal field eventually dominates in all disks.

scholarly journals Understanding the Impacts of Soil Moisture Initial Conditions on NWP in the Context of Land–Atmosphere Coupling

2019 ◽  
Vol 20 (5) ◽  
pp. 793-819 ◽  
Author(s):  
Joseph A. Santanello Jr. ◽  
Patricia Lawston ◽  
Sujay Kumar ◽  
Eli Dennis
Keyword(s):  
Soil Moisture ◽  
High Resolution ◽  
Land Surface ◽  
Initial Conditions ◽  
Land Surface Model ◽  
Surface Model ◽  
Coupled Models ◽  
Wide Range ◽  
Soil Moisture Initialization

Abstract The role of soil moisture in NWP has gained more attention in recent years, as studies have demonstrated impacts of land surface states on ambient weather from diurnal to seasonal scales. However, soil moisture initialization approaches in coupled models remain quite diverse in terms of their complexity and observational roots, while assessment using bulk forecast statistics can be simplistic and misleading. In this study, a suite of soil moisture initialization approaches is used to generate short-term coupled forecasts over the U.S. Southern Great Plains using NASA’s Land Information System (LIS) and NASA Unified WRF (NU-WRF) modeling systems. This includes a wide range of currently used initialization approaches, including soil moisture derived from “off the shelf” products such as atmospheric models and land data assimilation systems, high-resolution land surface model spinups, and satellite-based soil moisture products from SMAP. Results indicate that the spread across initialization approaches can be quite large in terms of soil moisture conditions and spatial resolution, and that SMAP performs well in terms of heterogeneity and temporal dynamics when compared against high-resolution land surface model and in situ soil moisture estimates. Case studies are analyzed using the local land–atmosphere coupling (LoCo) framework that relies on integrated assessment of soil moisture, surface flux, boundary layer, and ambient weather, with results highlighting the critical role of inherent model background biases. In addition, simultaneous assessment of land versus atmospheric initial conditions in an integrated, process-level fashion can help address the question of whether improvements in traditional NWP verification statistics are achieved for the right reasons.

scholarly journals Growth of Magnetorotational Instability in Circumstellar Disks around Class 0 Protostars

2021 ◽  
Author(s):  
Yoshihiro Kawasaki ◽  
Shunta Koga ◽  
Masahiro N Machida
Keyword(s):  
Magnetic Field ◽  
Hall Effect ◽  
Diffusion Coefficients ◽  
Early Stage ◽  
Circumstellar Disks ◽  
Linear Growth Rate ◽  
Magnetorotational Instability ◽  
Ionization Degree ◽  
Ohmic Dissipation ◽  
Disk Model

Abstract We investigate the possibility of the growth of magnetorotational instability (MRI) in disks around Class 0 protostars. We construct a disk model and calculate the chemical reactions of neutral and charged atoms, molecules and dust grains to derive the abundance of each species and the ionization degree of the disk. Then, we estimate the diffusion coefficients of non-ideal magnetohydrodynamics effects such as ohmic dissipation, ambipolar diffusion and the Hall effect. Finally, we evaluate the linear growth rate of MRI in each area of the disk. We investigate the effect of changes in the strength and direction of the magnetic field in our disk model and we adopt four different dust models to investigate the effect of dust size distribution on the diffusion coefficients. Our results indicate that an MRI active region possibly exists with a weak magnetic field in a region far from the protostar where the Hall effect plays a role in the growth of MRI. On the other hand, in all models the disk is stable against MRI in the region within <20 au from the protostar on the equatorial plane. Since the size of the disks in the early stage of star formation is limited to ≲ 10–20 au, it is difficult to develop MRI-driven turbulence in such disks.

The Role of the External Audit in Assessing Continuity of Companies under the Financial Crisis: An Applied Study in the Iraqi Banks Listed in the Iraq Stock Exchange for the Period 2016-2019

2021 ◽  
Vol 39 (11) ◽  
Author(s):  
Sallama Ibrahim Ali ◽  
Hakeem Hammood Flayyih
Keyword(s):  
Financial Crisis ◽  
Financial Analysis ◽  
Stock Exchange ◽  
Early Stage ◽  
International Standards ◽  
Financial Ratios ◽  
External Audit ◽  
Energy Company ◽  
Wide Range

In the first decade of the third millennium, shareholding companies faced several crises, with four major crises affecting financial markets, beginning with the collapses of a group of large companies following the Enron Energy company and similar companies in various countries, followed by the financial crisis and the collapse of global oil prices, which quickly ended until the sta As a result, the purpose of this study is to shed light on the role of external audit in assessing bank continuity, as Iraqi banks are among the first institutions and companies to move toward the application of international standards as well as being committed to accounting principles and assumptions, and they face a wide range of risks, the most dangerous of which is financial instability. Furthermore, the Kida model has been adopted in assessing the stability of banks and their ability to meet their obligations and perform their duties through a set of financial ratios that distinguish successful banks from those whose ability is suspect and vulnerable to financial failure, as well as trying to identify the nature of their activities at an early stage. However, using financial ratios, Kida's model was applied to a sample of three Iraqi banks, and the research concluded that the external auditor should use financial analysis models to know and evaluate the banks' continuity in terms of anticipating financial collapse.

scholarly journals Role of Surface Enthalpy Fluxes in Idealized Simulations of Tropical Depression Spinup

2018 ◽  
Vol 75 (6) ◽  
pp. 1811-1831 ◽  
Author(s):  
Varun S. Murthy ◽  
William R. Boos
Keyword(s):  
Wind Speed ◽  
Initial Conditions ◽  
Early Stage ◽  
Three Dimensional ◽  
Surface Fluxes ◽  
Tropical Cyclogenesis ◽  
Radial Gradient ◽  
Tropical Depression ◽  
Surface Enthalpy

AbstractAn idealized, three-dimensional, cloud-system-resolving model is used to investigate the influence of surface enthalpy flux variations on tropical depression (TD) spinup, an early stage of tropical cyclogenesis in which the role of surface fluxes remains incompletely understood. A range of simulations supports the hypothesis that a negative radial gradient of surface enthalpy flux outside the storm center is necessary for TD spinup but can arise from multiple mechanisms. The negative radial gradient is typically created by the wind speed dependence of surface enthalpy fluxes, consistent with some previous theories for tropical cyclone intensification. However, when surface enthalpy fluxes are prescribed to be independent of wind speed, spinup still occurs, albeit more slowly, with the negative radial gradient of surface enthalpy flux maintained by an enhanced air–sea thermodynamic disequilibrium beneath the cold core of the incipient vortex. Surface enthalpy flux variations seem more important for intensification than initial conditions. For example, a vortex forms and intensifies even from a state of rest when the center of the domain is initialized to be nearly saturated with water vapor, but this intensification is modest in amplitude and transient, lasting less than 12 h, without interactive surface enthalpy flux. Sustained spinup on time scales longer than a day does not occur when surface enthalpy fluxes are horizontally homogeneous or constant, even when fixed at the high value of 200 W m−2. In the ensemble of simulations presented here, the vortex intensification rate scales linearly with the storm-scale surface enthalpy flux anomaly relative to the undisturbed environment.

scholarly journals Lyapunov function and global asymptotic stability for a new multiscale viral dynamics model incorporating the immune system response: Implemented upon HCV

PLoS ONE ◽  
2021 ◽  
Vol 16 (10) ◽  
pp. e0257975
Author(s):  
Hesham A. Elkaranshawy ◽  
Hossam M. Ezzat ◽  
Nermeen N. Ibrahim
Keyword(s):  
Immune System ◽  
Equilibrium Point ◽  
Reproduction Number ◽  
Initial Conditions ◽  
Equilibrium Points ◽  
System Response ◽  
Viral Dynamics ◽  
Wide Range ◽  
Immune System Response

In this paper, a new mathematical model is formulated that describes the interaction between uninfected cells, infected cells, viruses, intracellular viral RNA, Cytotoxic T-lymphocytes (CTLs), and antibodies. Hence, the model contains certain biological relations that are thought to be key factors driving this interaction which allow us to obtain precise logical conclusions. Therefore, it improves our perception, that would otherwise not be possible, to comprehend the pathogenesis, to interpret clinical data, to control treatment, and to suggest new relations. This model can be used to study viral dynamics in patients for a wide range of infectious diseases like HIV, HPV, HBV, HCV, and Covid-19. Though, analysis of a new multiscale HCV model incorporating the immune system response is considered in detail, the analysis and results can be applied for all other viruses. The model utilizes a transformed multiscale model in the form of ordinary differential equations (ODE) and incorporates into it the interaction of the immune system. The role of CTLs and the role of antibody responses are investigated. The positivity of the solutions is proven, the basic reproduction number is obtained, and the equilibrium points are specified. The stability at the equilibrium points is analyzed based on the Lyapunov invariance principle. By using appropriate Lyapunov functions, the uninfected equilibrium point is proven to be globally asymptotically stable when the reproduction number is less than one and unstable otherwise. Global stability of the infected equilibrium points is considered, and it has been found that each equilibrium point has a specific domain of stability. Stability regions could be overlapped and a bistable equilibria could be found, which means the coexistence of two stable equilibrium points. Hence, the solution converges to one of them depending on the initial conditions.

The Problem of Identifying and Modeling the Relationship between Monetary Factor and Inflation in the Russian Economy

2008 ◽  
pp. 61-76
Author(s):  
A. Porshakov ◽  
A. Ponomarenko
Keyword(s):  
Money Supply ◽  
Money Demand ◽  
Russian Economy ◽  
Long Run ◽  
Complex Approach ◽  
Wide Range ◽  
Long Time ◽  
The Relationship ◽  
Supply Side Factors

The role of monetary factor in generating inflationary processes in Russia has stimulated various debates in social and scientific circles for a relatively long time. The authors show that identification of the specificity of relationship between money and inflation requires a complex approach based on statistical modeling and involving a wide range of indicators relevant for the price changes in the economy. As a result a model of inflation for Russia implying the decomposition of inflation dynamics into demand-side and supply-side factors is suggested. The main conclusion drawn is that during the recent years the volume of inflationary pressures in the Russian economy has been determined by the deviation of money supply from money demand, rather than by money supply alone. At the same time, monetary factor has a long-run spread over time impact on inflation.

Introduction: Emotion, History and the Arts

2018 ◽  
Vol 7 (2) ◽  
pp. 117-128 ◽  
Author(s):  
Erin Sullivan ◽  
Marie Louise Herzfeld-Schild
Keyword(s):  
Historical Change ◽  
Carson Mccullers ◽  
Emotional Life ◽  
Review Section ◽  
The Arts ◽  
Wide Range ◽  
War Correspondents ◽  
History Of ◽  
Johan Huizinga

This introduction surveys the rise of the history of emotions as a field and the role of the arts in such developments. Reflecting on the foundational role of the arts in the early emotion-oriented histories of Johan Huizinga and Jacob Burkhardt, as well as the concerns about methodological impressionism that have sometimes arisen in response to such studies, the introduction considers how intensive engagements with the arts can open up new insights into past emotions while still being historically and theoretically rigorous. Drawing on a wide range of emotionally charged art works from different times and places—including the novels of Carson McCullers and Harriet Beecher-Stowe, the private poetry of neo-Confucian Chinese civil servants, the photojournalism of twentieth-century war correspondents, and music from Igor Stravinsky to the Beatles—the introduction proposes five ways in which art in all its forms contributes to emotional life and consequently to emotional histories: first, by incubating deep emotional experiences that contribute to formations of identity; second, by acting as a place for the expression of private or deviant emotions; third, by functioning as a barometer of wider cultural and attitudinal change; fourth, by serving as an engine of momentous historical change; and fifth, by working as a tool for emotional connection across communities, both within specific time periods but also across them. The introduction finishes by outlining how the special issue's five articles and review section address each of these categories, while also illustrating new methodological possibilities for the field.

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