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排序方式: 共有135条查询结果,搜索用时 15 毫秒
91.
Dr. Lorenzo Moro Dr. Matteo di Giosia Dr. Matteo Calvaresi Dr. Evangelos Bakalis Prof. Francesco Zerbetto 《Chemphyschem》2014,15(9):1834-1840
A general framework is provided that makes possible the estimation of time‐dependent properties of a stochastic system moving far from equilibrium. The process is investigated and discussed in general terms of nonequilibrium thermodynamics. The approach is simple and can be exploited to gain insight into the dynamics of any molecular‐level machine. As a case study, the dynamics of an artificial molecular rotary motor, similar to the inversion of a helix, which drives the motor from a metastable state to equilibrium, are examined. The energy path that the motor walks was obtained from the results of atomistic calculations. The motor undergoes unidirectional rotation and its entropy, internal energy, free energy, and net exerted force are given as a function of time, starting from the solution of Smoluchowski’s equation. The rather low value of the organization index, that is, the ratio of the work done by the particle against friction during the unidirectional motion per available free energy, reveals that the motion is mainly subject to randomness, and the amount of energy converted to heat due to the directional motion is very small. 相似文献
92.
We derive the explicit analytic expression for the Stokes' drift in one dimension in the presence of a dichotomic Markov forcing. For small amplitudes of the forcing, the drift is enhanced, but the enhancement is reduced with increasing frequency of the forcing. On the other hand, a reduction of the drift or even a flux reversal can be induced at larger amplitudes, while the flux is now found to be an increasing function of the perturbation frequency. 相似文献
93.
Aluminum combustion in a solid rocket motor environment 总被引:5,自引:0,他引:5
A model for prediction of particle radius and oxide cap size/shape versus time for an aluminum particle tracking a stream-tube through a solid rocket motor port has been developed. Following preliminary calculations leading to a postulated flame structure, a quasi-steady model to predict instantaneous consumption of aluminum and generation of condensed oxide (both as a cap on the aluminum particle and as smoke) as a function of instantaneous particle size, ambient conditions, and cumulative amount of oxide in the cap was developed. Finally, this model was imbedded into a framework tracking evolution of particle size, oxide cap size, and ambient conditions, which change as the particle travels along a stream-tube consuming oxidizer and releasing heat. Qualitative agreement was found between predictions and limited observations. 相似文献
94.
Biomolecular motors are tiny engines that transport materials at the microscopic level within biological cells. In recent years, Elston and Peskin et al have investigated the effect of the elastic properties of the tether that connects the motor to its cargo at the speed of the
motor. In this paper we extend their work and present a tether in the form of symmetric linear potential.Our results show that when the driving mechanism is an imperfect Brownian ratchet, the
average speed decreases as the stiffness of the tether increases in the limit of large motor diffusion coefficient, which is similar to the results of Elston and Peskin.However, a threshold for the stiffness of the tether connecting the motor to its cargo is found in our model. Only when the tether is stiffer than the threshold can the motor and its cargo function co-operatively, otherwise, the motor and its cargo depart from each other. This result is more realistic than that of the spring model of Elston and Peskin. 相似文献
95.
K. Wagner B. Pfeil F. Brutschin R. Lenz G. Ostermay 《Isotopes in environmental and health studies》2013,49(8):269-271
Es wird über die Fortführung von Verschleiβuntersuchungen mit 110mAg-markierten Graphit- und Kupfer-Graphit-Bürsten auf nicht markierten Kohle- und Metallrotoren und über neuerdings begonnene Verschleiβexperimente mit radioaktiv markierten Kohle-(110mAg) und Rotguβrotoren (64Cu, 65Zn, 113Sn, 117mSn) berichtet. 相似文献
96.
Lehn JM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(23):5910-5915
Compounds containing the C==N group, such as imines and their derivatives, may undergo syn-anti isomerization by two different routes: 1) photochemically, by out-of-plane rotation around the carbon-nitrogen double bond through a "perpendicular" form, and 2) thermally, by in-plane nitrogen inversion through a "linear" transition state. When the two interconversions occur in sequence, a full, closed process is accomplished, restoring the initial state of the system along two different steps. In a chiral imine-type compound, for example, with an asymmetric center next to the C==N function, photoinduced rotation may be expected to occur in one sense in preference to the opposite one. Thus, photoisomerization followed by thermal isomerization in a chiral imine compound generates unidirectional molecular motion. Generally, imine-type compounds represent unidirectional molecular photomotors converting light energy into mechanical motion. As they are also able to undergo exchange of the carbonyl and amine partners, they present constitutional dynamics. Thus, imine-type compounds are double dynamic, motional, and constitutional devices. 相似文献
97.
Raishma Krishnan 《Physica A》2010,389(24):5563-5572
Previous works have shown that time asymmetric forcing on the one hand, as well as non-Gaussian noises on the other, can separately enhance the efficiency and current of a Brownian motor. Here, we study the result of subjecting a Brownian motor to both effects simultaneously. Our results have been compared with those obtained for the Gaussian white noise regime in the adiabatic limit. We find that, although the inclusion of the time asymmetry parameter increases the efficiency value up to a certain extent, for the present case this increase is much less appreciable than in the white noise case. We also present a comparative study of the transport coherence in the context of colored noise. Though the efficiency in some cases becomes higher for the non-Gaussian case, the Péclet number is always higher in the Gaussian colored noise case than in the white noise as well as non-Gaussian colored noise cases. 相似文献
98.
99.
The growing interest in the design and fabrication of novel autonomous micro‐ and nanoparticles is motivated by the vast advances in their motion efficiency and their further implementation in both biomedical and environmental fields. The present review covers the motion principle and fabrication procedures of synthetic and hybrid particle‐like micromotors reported to date to give a comprehensive view of the key design parameters and different approaches for optimal motor guidance. The applications of self‐propelled micro‐ and nanoparticles in different fields are classified accordingly to clarify not only the latest advances but also the current challenges and constraints in the field. This review aims to provide clues to develop more efficient and biocompatible autonomous microparticles in the future, with advanced multitasking and sensing capabilities while being able to perform cooperative work. 相似文献
100.
ABSTRACTThe nanomaterials based on the In2O3 molecule are widely used as catalysts and sensors among other applications. In the present study, we discuss the possibility of using nanoclusters of In2O3 as molecular photomotors. A comparative analysis of the electronic structure of the In2O3 molecule in the free state and in the crystal is performed. For the free In2O3 molecule the geometry of its lowest structures, V-shape and linear, was optimised at the CCSD(T) level, which is the most precise computational method applied up to date to study In2O3. Using experimental crystallographic data, we determined the geometry of In2O3 in the crystal. It has a zigzag, not symmetric structure and possesses a dipole moment with magnitude slightly smaller than that of the V-structure of the free molecule (the linear structure due to its symmetry has no dipole moment). According to the Natural Atomic population analysis, the chemical structure of the linear In2O3 can be represented as O = In?O?In = O; the V-shaped molecule has the similar double- and single-bond structure. The construction of nanoclusters from ?bricks? of In2O3 with geometry extracted from crystal (or nanoclusters extracted directly from crystal) and their use as photo-driven molecular motors are discussed. 相似文献