scholarly journals Numerical Simulation of Small Radius Polaron in a Chain with Random Perturbations

2019 ◽  
Vol 14 (2) ◽  
pp. 406-419
Author(s):  
N.S. Fialko ◽  
V.D. Lakhno
Keyword(s):  
Computational Experiment ◽  
Center Of Mass ◽  
Small Radius ◽  
Large Radius ◽  
Zero Temperature ◽  
Time Intervals ◽  
Holstein Model ◽  
A Chain ◽  
Charge Transfer In Dna ◽  
Thermodynamic Equilibrium State

We consider the dynamics of polaron in a chain using computational experiment. The temperature, which is simulated by random Langevin-type perturbations, and influence of external electric field are taking into account. In a sufficiently long unperturbed chain, the displacement of the center of mass of the polaron and its velocity does not depend on its length. In the semiclassical Holstein model, which is applied for simulations of charge transfer in DNA, the region of polaron existence in the thermodynamic equilibrium state depends not only on temperature, but also on the chain length. Therefore, when modeling dynamics from polaron initial data, the time dependences of the average displacement of the charge mass center at the same temperature are different for chains of different lengths. According to the results of computational experiment, for polaron of large radius the time dependence of the “average polaron displacement”, which takes into account only the polaron peak and its position, for chains of different lengths behaves almost equally at time intervals until the polaron will destroyed. The same slope of the polaron displacement allows us to estimate the average polaron velocity. The results of calculations demonstrate that in Holstein model at zero temperature, the mobility value of the large radius polaron is small but non-zero.

scholarly journals Charge diffusion in homogeneous molecular chains based on the analysis of generalized frequency spectra in the framework of the Holstein model

2019 ◽  
Vol 27 (3) ◽  
pp. 217-230
Author(s):  
Dmitry A Tikhonov ◽  
Egor V Sobolev ◽  
Victor D Lakhno
Keyword(s):  
Diffusion Coefficient ◽  
Charge Distribution ◽  
Dna Sequences ◽  
Mean Square Displacement ◽  
Frequency Spectra ◽  
Velocity Autocorrelation ◽  
Holstein Model ◽  
Quantum Chemical Methods ◽  
A Chain ◽  
Charge Transfer In Dna

We analyzed numerically computed velocity autocorrelation functions and generalized frequency spectra of charge distribution in homogeneous DNA sequences at finite temperature. The autocorrelation function and generalized frequency spectrum (frequency-dependent diffusion coefficient) are phenomenologically introduced based on the functional of mean-square displacement of the charge in DNA. The charge transfer in DNA was modeled in the framework of the semi-classical Holstein model. In this model, DNA is represented by a chain of oscillators placed into thermostat at a given temperature that is provided by the additional Langevin term. Correspondence to the real DNA is provided by choice of the force parameters, which are calculated with quantum-chemical methods. We computed the diffusion coefficient for all homogenous DNA chains with respect to the temperature and found a special scaling of independent variables that the temperature dependence of the diffusion coefficient for different homogenous DNA is almost similar. Our calculations suggest that for all the sequences, only one parameter of the system is mainly responsible for the charge kinetics. The character of individual motions contributing to the charge mobility and temperature-dependent regimes of charge distribution is determined.

scholarly journals Charge diffusion in homogeneous molecular chains based on the analysis of generalized frequency spectra in the framework of the Holstein model

2019 ◽  
Vol 27 (3) ◽  
pp. 217-230
Author(s):  
Dmitry A. Tikhonov ◽  
Egor V. Sobolev ◽  
Victor D. Lakhno
Keyword(s):  
Diffusion Coefficient ◽  
Charge Distribution ◽  
Dna Sequences ◽  
Mean Square Displacement ◽  
Frequency Spectra ◽  
Velocity Autocorrelation ◽  
Holstein Model ◽  
Quantum Chemical Methods ◽  
A Chain ◽  
Charge Transfer In Dna

We analyzed numerically computed velocity autocorrelation functions and generalized frequency spectra of charge distribution in homogeneous DNA sequences at finite temperature. The autocorrelation function and generalized frequency spectrum (frequency-dependent diffusion coefficient) are phenomenologically introduced based on the functional of mean-square displacement of the charge in DNA. The charge transfer in DNA was modeled in the framework of the semi-classical Holstein model. In this model, DNA is represented by a chain of oscillators placed into thermostat at a given temperature that is provided by the additional Langevin term. Correspondence to the real DNA is provided by choice of the force parameters, which are calculated with quantum-chemical methods. We computed the diffusion coefficient for all homogenous DNA chains with respect to the temperature and found a special scaling of independent variables that the temperature dependence of the diffusion coefficient for different homogenous DNA is almost similar. Our calculations suggest that for all the sequences, only one parameter of the system is mainly responsible for the charge kinetics. The character of individual motions contributing to the charge mobility and temperature-dependent regimes of charge distribution is determined.

scholarly journals Charge diffusion in homogeneous molecular chains based on the analysis of generalized frequency spectra in the framework of the Holstein model

2019 ◽  
Vol 27 (3) ◽  
pp. 217-230
Author(s):  
Dmitry A. Tikhonov ◽  
Egor V. Sobolev ◽  
Victor D. Lakhno
Keyword(s):  
Diffusion Coefficient ◽  
Charge Distribution ◽  
Dna Sequences ◽  
Mean Square Displacement ◽  
Frequency Spectra ◽  
Velocity Autocorrelation ◽  
Holstein Model ◽  
Quantum Chemical Methods ◽  
A Chain ◽  
Charge Transfer In Dna

We analyzed numerically computed velocity autocorrelation functions and generalized frequency spectra of charge distribution in homogeneous DNA sequences at finite temperature. The autocorrelation function and generalized frequency spectrum (frequency-dependent diffusion coefficient) are phenomenologically introduced based on the functional of mean-square displacement of the charge in DNA. The charge transfer in DNA was modeled in the framework of the semi-classical Holstein model. In this model, DNA is represented by a chain of oscillators placed into thermostat at a given temperature that is provided by the additional Langevin term. Correspondence to the real DNA is provided by choice of the force parameters, which are calculated with quantum-chemical methods. We computed the diffusion coefficient for all homogenous DNA chains with respect to the temperature and found a special scaling of independent variables that the temperature dependence of the diffusion coefficient for different homogenous DNA is almost similar. Our calculations suggest that for all the sequences, only one parameter of the system is mainly responsible for the charge kinetics. The character of individual motions contributing to the charge mobility and temperature-dependent regimes of charge distribution is determined.

Coexistence of large-radius and small-radius polaron states in a quantum wire

1995 ◽  
Vol 17 (11-12) ◽  
pp. 1723-1728
Author(s):  
Y. Shinozuka ◽  
N. Ishida
Keyword(s):  
Quantum Wire ◽  
Small Radius ◽  
Large Radius

scholarly journals Triple Oxygen Isotope Measurements by Multi-Collector Secondary Ion Mass Spectrometry

2021 ◽  
Vol 8 ◽  
Author(s):  
Nordine Bouden ◽  
Johan Villeneuve ◽  
Yves Marrocchi ◽  
Etienne Deloule ◽  
Evelyn Füri ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Oxygen Isotope ◽  
Spatial Resolution ◽  
Secondary Ion Mass Spectrometry ◽  
Small Radius ◽  
Large Radius ◽  
Ion Mass Spectrometry ◽  
Secondary Ion ◽  
Isotope Measurements

Secondary ion mass spectrometry (SIMS) is a powerful technique for in situ triple oxygen isotope measurements that has been used for more than 30 years. Since pioneering works performed on small-radius ion microprobes in the mid-80s, tremendous progress has been made in terms of analytical precision, spatial resolution and analysis duration. In this respect, the emergence in the mid-90s of the large-radius ion microprobe equipped with a multi-collector system (MC-SIMS) was a game changer. Further developments achieved on CAMECA MC-SIMS since then (e.g., stability of the electronics, enhanced transmission of secondary ions, automatic centering of the secondary ion beam, enhanced control of the magnetic field, 1012Ω resistor for the Faraday cup amplifiers) allow nowadays to routinely measure oxygen isotopic ratios (18O/16O and 17O/16O) in various matrices with a precision (internal error and reproducibility) better than 0.5‰ (2σ), a spatial resolution smaller than 10 µm and in a few minutes per analysis. This paper focuses on the application of the MC-SIMS technique to the in situ monitoring of mass-independent triple oxygen isotope variations.

scholarly journals Disk Structure in U Geminorum

1977 ◽  
Vol 42 ◽  
pp. 313-321
Author(s):  
J. Madej ◽  
B. Paczyński
Keyword(s):  
Angular Momentum ◽  
Hot Spot ◽  
Outer Part ◽  
Tangential Velocity ◽  
Radial Component ◽  
Small Radius ◽  
Large Radius ◽  
Disk Structure ◽  
Orbital Periods ◽  
The Difference

AbstractA hot spot at the outer rim of the accretion disk dominates the light of U Geminorum at minimum light. We take this as evidence that there is no accretion from the disk onto the white dwarf between the eruptions, and we assume there is no viscosity in the disk at that time. The hot spot is produced by dissipation of the radial component of velocity of stream falling from the inner Lagrangian point. Angular momentum per unit massis smaller in the stream than it is in the outer parts of the disk. This leads to angular momentum redistribution in the outer part of the disk. The difference of tangential velocity between the stream and the disk is dissipated in few orbital periods. These processes make the outer parts of the disk look like a torus. We calculated the structure of the torus in U Geminorum between the eruptions and we obtained the following oarameters: mass of the torus: 10-9 - 10-8 M⊙ (assumed), its optical thickness: 106, the large radius (i.e. the radius of the disk): 0.5 R⊙ (assumed), the small radius (i.e. the half thickness of the outer parts of the disk): 0.05 R⊙. Conditions at the surface of the torus are similar as on the solar surface.

scholarly journals Charge Transfer in Dimer with Dissipation

2019 ◽  
Vol 224 ◽  
pp. 03006
Author(s):  
Nadezhda Fialko ◽  
Maxim Olshevets ◽  
Victor Lakhno
Keyword(s):  
Charge Transfer ◽  
Charged Particle ◽  
Computer Modeling ◽  
Electron Energy ◽  
Small Radius ◽  
Memory Devices ◽  
Charge Motion ◽  
Transfer Processes ◽  
Holstein Model ◽  
Charge Tunneling

The study of the charge transfer processes in biomacromolecules such as DNA is essential for the development of nanobioelectronics, design and construction of DNA-based nanowires, memory devices, logical elements, etc. Mathematical and computer modeling of charge transfer in biopolymer chains is an important part of these investigations. Some properties of charge transfer can be demonstrated by modeling of two-site chain. Based on the semi-classical Holstein model we consider a system of two sites and charged particle (electron or hole) in which the oscillations of the first site are not related to the charge motion, and the parameters of the second site correspond to a small-radius polaron. The system steady states depending on the electron energy H at the second site are studied numerically. The dynamics of the charge initially localized at the first site is modeled. Various modes depending on H are demonstrated: charge tunneling, resonant transfer, and lack of transfer.

Intershield geochemical differences among Hawaiian volcanoes: implications for source compositions, melting process and magma ascent paths

1993 ◽  
Vol 342 (1663) ◽  
pp. 121-136 ◽  
Keyword(s):  
Melting Process ◽  
Isotope Ratios ◽  
Magma Ascent ◽  
Small Radius ◽  
Element Abundance ◽  
Isotopic Ratios ◽  
Large Radius ◽  
Major Element Composition ◽  
Mauna Loa ◽  
Melt Segregation

As Hawaiian volcanoes develop, their lavas systematically change in composition and isotopic ratios of Sr, Nd and Pb. These trends provide important constraints for understanding plume-related volcanism as a volcano migrates away from the hotspot. There are also geochemical differences between Hawaiian shields. In particular, lavas from adjacent shields such as Kilauea and Mauna Loa on Hawaii and Koolau and Waianae on Oahu have significant differences in abundances of some major and incompatible elements and isotopic ratios of Sr, Nd and Pb. Some incompatible element abundance ratios, such as Zr/Nb and Sr/Nb, are correlated with intershield differences in Sr and Nd isotope ratios, but these isotopic ratios are not correlated with intershield differences in major element composition, or even parent/daughter abundance ratios such as Rb/Sr and Sm/Nd. Moreover, at Kilauea and Mauna Loa the intershield differences have apparently persisted for a relatively long time, perhaps 100 ka. These intershield geochemical differences provide important constraints on plume volcanism. Specifically, (i) each volcano must have distinct magma ascent paths from the region of melt segregation; (ii) the 25-50 km distance between adjacent, but geochemically distinct, shields requires that the sources vary on a similar scale, and that the melt production region is similarly restricted. The absence of correlations between lava compositions and radiogenic isotope ratios provides evidence for significant differences in melting process such as each shield forming by a different mean extent of melting with melt segregation at different mean pressures. Two types of models are consistent with the intershield geochemical differences: (i) a relatively large radius, ca . 40 km, plume conduit with a systematic spatial distribution of geochemical heterogeneities; or (ii) a small radius, less than 20 km, plume conduit composed of geochemically distinct diapirs. Because relatively small radius diapirs of limited vertical extent are too small to create the large Hawaiian shields, a possible alternative is a continuous conduit containing solitary waves which transport geochemically distinct packets of material.

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