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Measurements, Mechanisms, and Models of Heat Transport || A Macroscopic Model of Blackbody Emissions With Implications
摘要： Measurements of heat transfer in gas, pourable liquids, and nonmetallic solids point to diffusion of radiation being an essential component of heat transport (Chapter 5, Chapter 6 and Chapter 7). Diffusive radiation of heat is a direct outcome of a kinetic theory of gas that incorporates the inelastic nature of collisions (Chapter 5). Long ago, Lommel (1878) associated blackbody (BB) emissions from solids with inelastic losses, and specifically discussed damping of atomic vibrations (Kangro, 1976), but was unable to provide a formula for thermal emissions. His ideas were set aside in the early 1900s. Yet, strong theoretical support for inelasticity exists in the laws of thermodynamics, when these are framed in terms of the macroscopic behavior of light (Chapter 1 and Chapter 5). Fourier’s laws, which describe heat transfer as energy flowing through a medium (Chapter 3), are also consistent with diffusive of radiation explaining conduction in solids.
关键词： blackbody emissions,inelastic collisions,diffusive radiation,heat transfer,thermal emissions,kinetic theory,Fourier’s laws,thermodynamics
更新于2025-09-10 09:29:36
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Evaluation of a spectral line width for the Phillips spectrum by means of numerical simulation
摘要： The work aims to check one of the assumptions under which the kinetic equation for water waves was derived in order to understand whether it can be applied to the situations described by the Phillips spectrum. We evaluate a spectral line width of the spectrum from the simulations in the framework of primordial dynamical equations at different levels of nonlinearity in the system, corresponding to the weakly turbulent Kolmogorov–Zakharov spectra ω?4, Phillips spectra ω?5, and intermediate cases. The original motivation of the work was to check one of the assumptions under which the kinetic equation for water waves was derived in order to understand whether it can be applied to the Phillips spectrum. It is shown that, even in the case of relatively high average steepness, when the Phillips spectrum is present in the system, the spectral lines are still very narrow, at least in the region of the direct cascade spectrum. It allows us to state that, even in the case of the Phillips spectrum, one of the assumptions used for the derivation of the Hasselmann kinetic equation is still valid, at least in the case of moderate whitecapping.
关键词： numerical simulation,water waves,Phillips spectrum,spectral line width,kinetic equation
更新于2025-09-10 09:29:36
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Phase-field method for epitaxial kinetics on surfaces
摘要： We present a procedure for simulating epitaxial growth based on the phase-field method. We consider a basic model in which growth is initiated by a flux of atoms onto a heated surface. The deposited atoms diffuse in the presence of this flux and eventually collide to form islands which grow and decay by the attachment and detachment of migrating atoms at their edges. Our implementation of the phase-field method for this model includes uniform deposition, isotropic surface diffusion, and stochastic nucleation (in both space and time), which creates islands whose boundaries evolve as the surface atoms "condense" into and "evaporate" from the islands. Computations using this model in the submonolayer regime, prior to any appreciable coalescence of islands, agree with the results of kinetic Monte Carlo (KMC) simulations for the coverage-dependence of adatom and island densities and island-size distributions, for both reversible and irreversible growth. The scaling of the island density, as obtained from homogeneous rate equations, agrees with KMC simulations for irreversible growth and for reversible growth for varying deposition flux at constant temperature. For reversible growth with varying temperature but constant flux, agreement relies on an estimate of the formation energy of the critical cluster. Taken together, our results provide a comprehensive analysis of the phase-field method in the submonolayer regime of epitaxial growth, including the verification of the main scaling laws for adatoms and island densities and the scaling functions for island-size distributions, and point to the areas where the method can be extended and improved.
关键词： epitaxial growth,reversible and irreversible growth,kinetic Monte Carlo simulations,island-size distributions,phase-field method
更新于2025-09-10 09:29:36
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An optimized and automated approach to quantifying channelrhodopsin photocurrent kinetics
摘要： Channelrhodopsins are light-activated ion channels that enable targetable activation or inhibition of excitable cells with light. Ion conductance can generally be described by a four step photocycle, which includes two open and two closed states. While a complete understanding of channelrhodopsin function cannot be understood in the absence of kinetic modeling, model fitting requires manual fitting, which is laborious and technically complicated for non-experts. To enhance analysis of photocurrent data, this manuscript describes a fitting program where electrophysiology data can be automatically and quantitatively analyzed. Significant improvement in this program when compare to our previous version includes 1) the ability to automatically find the experiment start time using the derivative of the current signal, 2) utilizing the Object Oriented Programing (OPP) paradigm which is significantly more reliable if the code is used by people with little to no programming experience and 3) the distribution of the code is simplified to sharing a single MATLAB file, including rigorous comments throughout. To demonstrate the utility of this program, we show automated fitting of photocurrents from two member proteins: channelrhodopsin-2 and a chimera between channelrhodopsin-1 and channelrhodopsin-2 (C1C2).
关键词： neuroscience,channelrhodopsin,optogenetics,kinetic modeling,electrophysiology
更新于2025-09-10 09:29:36
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Precise sputtering of silicon dioxide by argon cluster ion beams
摘要： In this work, the sputtering yields of SiO2 by the argon cluster ion beam with incident angles 0° and 45° have been studied experimentally. The kinetic energy of the primary cluster ions was in the range of E = 5–23.5?keV, and the mean cluster size was Nmean = 100–1000 atom/cluster. It is found that, when the energy per cluster atom quantity E/N is comparable to the binding energy of the solid (of the order of several eV), the yields of atoms sputtered per primary atom Y/N, at the incident angle 45°, is 4 times greater than at normal incidence. Conversely, when energy E/N is significantly above the binding energy of the solid (~ 100?eV), the sputtering yields for the incident angles 0° and 45° have the same values.
关键词： kinetic energy,incident angles,argon cluster ion beam,sputtering yields,cluster size,silicon dioxide
更新于2025-09-10 09:29:36
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Theoretical Investigation of the Shubnikov-de Haas Magnetoresistance Oscillations in a Quantum well under the Influence of Confined Acoustic Phonons
摘要： The Shubnikov – de Haas magnetoresistance oscillations in the Quantum well (QW) under the influence of confined acoustic phonons, The theoretical results show that the conductivity tensor, the complex magnetic impedance of the magnetic field, the frequency, the amplitude of the laser radiation, the QW width, the temperature of the system and especially the quantum index m characterizes the confinement of the phonon. The amplitude of the oscillations of the Shubnikov-de Haas impedance decreases with the increase of the influence of the confined acoustic phonons. The results for bulk phonons in a QW could be achieved, when m goes to zero. We has been compared with other studies when perform the numerical calculations are also achieved for the GaAs/AlGaAs in the QW. Results show that The Shubnikov – de Haas magnetoresistance oscillations amplitude decrease when phonon confinement effect increasing and when width L of the QW increases to a certain value, The Shubnikov – de Haas magnetoresistance oscillations amplitude completely disappears can not be observed.
关键词： Quantum well and width L of quantum well,Confined acoustic phonons,Quantum kinetic equation,Laser radiation,Shubnikov–de Haas magnetoresistance oscillations
更新于2025-09-10 09:29:36
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Interaction of External Acoustic Waves - Confined Electrons - Internal Phonons in a Cylindrical Quantum Wire with an Infinite Potential in the Presence of an External Magnetic Field
摘要： Interaction of external acoustic waves - confined electrons - internal phonons in a cylindrical quantum wire with an infinite potential (CQWIP) has been theoretically studied via the quantum kinetic equation for electrons in the presence of an external magnetic field (EMF). The quantum kinetic equation for the distribution function of electrons interacting with internal and external acoustic phonons is obtained from the Heisenberg equation of motion and the model of CQWIP. The density of acoustomagnetoelectric (AME) current and the analytical expressions for the AME field in the CQWIP in the presence of the EMF are obtained. The theoretical results are numerically evaluated for the specific CQWIP of GaAs/GaAsAl. It is shown that the AME field strongly depends on the system temperature in both cases of the strong magnetic field and the weak magnetic field. However, the graph showing the relationship between the AME field and the system temperature has the peaks in case of the strong magnetic field. The reason may be due to movement of the electrons between the mini-bands. The AME field obtained in this work are then compared with those of bulk semiconductors, superlattices, quantum wells (QW) and rectangular quantum wire (RQW).
关键词： Cylindrical quantum wire,Acoustomagnetoelectric field,Kinetic equation method
更新于2025-09-10 09:29:36
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Theoretical Study of the Magneto-Thermoelectric Effect in Doped Semiconductor Superlattices under the Influence of an Electromagnetic Wave by Using a Quantum Kinetic Equation
摘要： By using a quantum kinetic equation for electrons, we studied magneto - thermoelectric effects in the doped semiconductor superlattice (DSSL) under the influence of electromagnetic waves (EMW). In case of the electron - acoustic phonon interaction, we have also figured out analytical expressions of the Ettingshausen coefficient (EC) in DSSL. These expressions are quite different from those which were obtained in the case of bulk semiconductors. The results are numerically calculated for the GaAs:Be/ GaAs:Si DSSL; we found that the EC depends on the characteristic parameters of EMW, temperature and the characteristic parameters of DSSL. The results are consistent with recently experimental observations but the EC is different from that in the bulk semiconductors or bismuth. In addition, the impact of the EMW on the Ettingshausen effect was also discovered. These are latest results which have been studied in terms of Ettingshausen effect in DSSL.
关键词： Semiconductor Superlattices,Doped Superlattices,Acoustomagnetoelectric field,Kinetic equation method
更新于2025-09-10 09:29:36
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Kinetic Modelling of Transient Photoluminescence from Thermally Activated Delayed Fluorescence
摘要： A simplified state model and associated rate equations are used to extract the reverse intersystem crossing and other key rate constants from transient photoluminescence measurements of two high performance thermally activated delayed fluorescence materials. The values of the reverse intersystem crossing rate constant are in close agreement with established methods, but do not require a priori assumption of exponential decay kinetics, nor any additional steady state measurements. The model is also applied to measurements at different temperatures and found to reproduce previously reported thermal activation energies for the thermally activated delayed fluorescence process. Transient absorption measurements provide independent confirmation that triplet decay channels (neglected here) have no adverse effect on the fitting.
关键词： Thermally Activated Delayed Fluorescence,Transient Photoluminescence,Reverse Intersystem Crossing,Kinetic Modelling
更新于2025-09-10 09:29:36
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High-Yield Formation of Graphdiyne Macrocycles Through On-Surface Assembling and Coupling Reaction
摘要： Rationally designed halogenated hydrocarbons are widely used building blocks to fabricate covalent-bonded carbon nanostructures on surface through a reaction pathway involving generation and dissociation of organometallic intermediates and irreversible covalent bond formation. Here we provide a comprehensive picture of the on-surface-assisted homocoupling reaction of 1,3-bis(2-bromoethynyl)benzene on Au(111), aiming for the synthesis of graphdiyne nanostructures. Submolecular resolution scanning tunneling microscopy and noncontact atomic force microscopy observations identify the organometallic intermediates and their self-assemblies formed in the dehalogenation process. The demetallization of the organometallic intermediates at elevated temperatures produces butadiyne moieties that spontaneously formed two different covalent structures, i.e. graphdiyne zigzag chains and macrocycles, whose ratio was found to depend on the initial coverage of organometallic intermediates. At the optimal condition, the stepwise demetallization and cyclization led to a high yield production of graphdiyne macrocycles up to 95 %. Statistical analysis and theoretical calculations suggested that the favored formation of macrocycles was resulted from the complex interplay between thermodynamic and kinetic processes involving the organometallic bonded intermediates and the covalently bonded butadiyne moieties.
关键词： on-surface reaction,graphdiyne macrocycle,organometallic intermediate,scanning tunneling microscopy,noncontact atomic force microscopy,thermodynamic and kinetic control
更新于2025-09-10 09:29:36