potential fluctuations
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2021 ◽  
Author(s):  
Norbert Ankri ◽  
Dominique Debanne

Abstract Channel noise results from rapid transitions of protein channels from closed to open state and is generally considered as the most dominant source of electrical noise causing membrane-potential fluctuations even in the absence of synaptic inputs. The simulation of a realistic channel noise remains a source of possible error. Although the Markovian method is considered as the golden standard for appropriate description of channel noise, its computation time increasing exponentially with numbers of channels, it is poorly suitable to simulate realistic features. We describe here a novel algorithm for simulating ion channel noise based on Markov chains (MC). Although this new algorithm refers to a Monte-Carlo process, it only needs few random numbers whatever the number of channels involved. Our fast MC (FMC) model does not exhibit the drawbacks due to approximations based on stochastic differential equations. In fact, we show here, that these drawbacks can be highlighted even for a high number of channels.


2021 ◽  
Vol 923 (1) ◽  
pp. 103
Author(s):  
C. Krafft ◽  
A. S. Volokitin

Abstract Solar coronal and wind plasmas often contain density fluctuations of various scales and amplitudes. The scattering of Langmuir wave turbulence on these inhomogeneities modifies the properties of the radiated electromagnetic emissions traveling from the Sun to the Earth. This paper shows the similarities between the physical results obtained by (i) a model based on the Zakharov equations, describing the self-consistent dynamics of Langmuir wave turbulence spectra in a plasma with external density fluctuations, and (ii) a modeling, within the framework of geometric optics approximation, of quasi-particles (representing plasmon quanta) moving in a fluctuating potential. It is shown that the dynamics of the Langmuir spectra is governed by anomalous diffusion processes, as a result of multiple scattering of waves on the density fluctuations; the same dynamics are observed in the momenta distributions of quasi-particles moving in potential structures with random inhomogeneities. These spectra and distributions are both characterized by a fast broadening during which energy is transported to larger wavevectors and momenta, exhibiting nonlinear time dependence of the average squares of wavevectors and quasi-particle momenta as well as non-Gaussian tails in the asymptotic stage. The corresponding diffusion coefficients depend on the time and are proportional to the square of the average level of density (or potential) fluctuations. It appears that anomalous transport and superdiffusion phenomena are responsible for the spectral broadening.


2021 ◽  
Vol 2086 (1) ◽  
pp. 012104
Author(s):  
N A Talnishnikh ◽  
E I Shabunina ◽  
N M Shmidt ◽  
A E Ivanov

Abstract The obtained experimental results allow us to clarify the nature of mechanisms related to the presence of cations in disordered InGaN alloy and hetero-interfaces. The capture of charge carriers by cations reduces the external quantum efficiency (EQE) in green MQWs at j < 10 A/cm2. The EQE droop phenomenon caused by smoothed out lateral potential fluctuations occurs at j > 10 A/cm2. At j > 40 A/cm2 the droop associated with interactions between charge carriers and dislocations and grain boundaries takes place.


2021 ◽  
Author(s):  
Josh Miller ◽  
Mitja Back ◽  
Donald Lynam ◽  
Aidan G.C. Wright

Narcissism is of great interest to behavioral scientists and the lay public. Research across the last 20 years has led to substantial progress in the conceptualization, measurement, and study of narcissism. The present paper reviews the current state of the field, identifying recent advances and outlining future directions. Advances include hierarchical conceptualizations of narcissism across one (narcissism), two (grandiose vs. vulnerable narcissism), and three factor levels (agentic extraversion, antagonism, narcissistic neuroticism), the development of measures to assess the components of narcissism, clarification of the relations between narcissism and self-esteem, an understanding of the behavioral and motivational dynamics underlying narcissistic actions and social outcomes, and insight regarding potential fluctuations between narcissistic states. Future directions point in general to increased research using the lower levels of the narcissism hierarchy, especially the three-factor level. At this level, more research is required on the etiology, heritability, stability, and centrality of the three components.


2021 ◽  
pp. 127521
Author(s):  
K. Jayaprakash ◽  
Prince Alex ◽  
A. Saravanan ◽  
M. Perumal ◽  
Thangjam Rishikanta Singh ◽  
...  

Author(s):  
Francisco J Mercado ◽  
James S Bullock ◽  
Michael Boylan-Kolchin ◽  
Jorge Moreno ◽  
Andrew Wetzel ◽  
...  

Abstract We explore the origin of stellar metallicity gradients in simulated and observed dwarf galaxies. We use FIRE-2 cosmological baryonic zoom-in simulations of 26 isolated galaxies as well as existing observational data for 10 Local Group dwarf galaxies. Our simulated galaxies have stellar masses between 105.5 and 108.6M⊙. Whilst gas-phase metallicty gradients are generally weak in our simulated galaxies, we find that stellar metallicity gradients are common, with central regions tending to be more metal-rich than the outer parts. The strength of the gradient is correlated with galaxy-wide median stellar age, such that galaxies with younger stellar populations have flatter gradients. Stellar metallicty gradients are set by two competing processes: (1) the steady “puffing” of old, metal-poor stars by feedback-driven potential fluctuations, and (2) the accretion of extended, metal-rich gas at late times, which fuels late-time metal-rich star formation. If recent star formation dominates, then extended, metal-rich star formation washes out pre-existing gradients from the “puffing” process. We use published results from ten Local Group dwarf galaxies to show that a similar relationship between age and stellar metallicity-gradient strength exists among real dwarfs. This suggests that observed stellar metallicity gradients may be driven largely by the baryon/feedback cycle rather than by external environmental effects.


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