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1.
J Chem Phys ; 150(18): 184905, 2019 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-31091931

RESUMO

Rectification of chiral active particles driven by transversal temperature difference is investigated in a two-dimensional periodic channel. Chiral active particles can be rectified by transversal temperature difference. Transport behaviors are qualitatively different for different wall boundary conditions. For the sliding boundary condition, the direction of transport completely depends on the chirality of particles. The average velocity is a peaked function of angular velocity or temperature difference. The average velocity increases linearly with the self-propulsion speed, while it decreases monotonically with the increase in the packing fraction. For randomized boundary condition, the transport behaviors become complex. When self-propulsion speed is small, in contrast with the sliding boundary condition, particles move in the opposite direction. However, for large self-propulsion speed, current reversals can occur by continuously changing the system parameters (angular velocity, temperature difference, packing fraction, and width of the channel).

2.
J Chem Phys ; 149(16): 164903, 2018 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-30384762

RESUMO

Transport of an inertial particle advected by a two-dimensional steady laminar flow is numerically investigated in the presence of a constant force and a periodic potential. Within particular parameter regimes, this system exhibits absolute negative mobility, which means that the particle can travel in a direction opposite to the constant force. It is found that the profile of the periodic potential plays an important role in the nonlinear response regime. Absolute negative mobility can be drastically enhanced by applying appropriate periodic potential, the parameter regime for this phenomenon becomes larger and the amplitude of negative mobility grows exceedingly large (giant negative mobility). In addition, giant positive mobility is also observed in the presence of appropriate periodic potential.

3.
Phys Rev E ; 95(1-1): 012116, 2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-28208376

RESUMO

Directed transport of self-propelled particles is numerically investigated in a three-dimensional asymmetric potential. Beside the steric repulsive forces, hydrodynamic interactions between particles have been taken into account in an approximate way. From numerical simulations, we find that hydrodynamic interactions can strongly affect the rectified transport of self-propelled particles. Hydrodynamic interactions enhance the performance of the rectified transport when particles can easily pass across the barrier of the potential, and reduce the rectified transport when particles are mainly trapped in the potential well.

4.
Soft Matter ; 11(19): 3852-9, 2015 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-25864888

RESUMO

Dynamics and separation of mixed chiral microswimmers are numerically investigated in a channel with regular arrays of rigid half-circle obstacles. For zero shear flow, transport behaviors are the same for different chiral particles: the average velocity decreases with increase of the rotational diffusion coefficient, the direction of the transport can be reversed by tuning the angular velocity, and there exists an optimal value of the packing fraction at which the average velocity takes its maximal value. However, when the shear flow is considered, different chiral particles show different behaviors. By suitably tailoring parameters, particles with different chiralities can move in different directions and can be separated. In addition, we also proposed a space separation method by introducing a constant load, where counterclockwise and clockwise particles stay in different regions of the channel.


Assuntos
Modelos Teóricos , Movimento (Física) , Difusão , Fenômenos Mecânicos , Estereoisomerismo
5.
J Chem Phys ; 141(19): 194111, 2014 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-25416878

RESUMO

Directed transport of interacting active (self-propelled) Brownian particles is numerically investigated in confined geometries (entropic barriers). The self-propelled velocity can break thermodynamical equilibrium and induce the directed transport. It is found that the interaction between active particles can greatly affect the ratchet transport. For attractive particles, on increasing the interaction strength, the average velocity first decreases to its minima, then increases, and finally decreases to zero. For repulsive particles, when the interaction is very weak, there exists a critical interaction at which the average velocity is minimal, nearly tends to zero, however, for the strong interaction, the average velocity is independent of the interaction.

6.
Artigo em Inglês | MEDLINE | ID: mdl-23767604

RESUMO

We study the interaction of both dense and sparse multiarmed spirals in bistable media modeled by equations of the FitzHugh-Nagumo type. A dense one-armed spiral is characterized by its fixed tip. For dense multiarmed spirals, when the initial distance between tips is less than a critical value, the arms collide, connect, and disconnect continuously as the spirals rotate. The continuous reconstruction between the front and the back drives the tips to corotate along a rough circle and to meander zigzaggedly. The rotation frequency of tip, the frequency of zigzagged displacement, the frequency of spiral, the oscillation frequency of media, and the number of arms satisfy certain relations as long as the control parameters of the model are fixed. When the initial distance between tips is larger than the critical value, the behaviors of individual arms within either dense or sparse multiarmed spirals are identical to that of corresponding one-armed spirals.


Assuntos
Modelos Teóricos , Dinâmica não Linear , Oscilometria/métodos , Simulação por Computador
7.
J Chem Phys ; 138(15): 154107, 2013 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-23614412

RESUMO

Transport of overdamped Brownian particles in a finite hydrodynamical channel is investigated in the presence of the ac driving force and the pressure-driven flow. The system is bounded by two particle reservoirs. With the help of the Fick-Jacobs method, we obtain the directed current of Brownian particles and the pumping capacity of the system. The directed transport is determined by the competitions among the asymmetry of the channel, the ac driving force, the pressure-driven flow, and the concentration difference. Their interplays can exhibit the peculiar properties. Remarkably, the particles can be pumped through the channel from the lower concentration reservoir to the higher concentration one, or from the lower pressure side to the higher pressure one. In addition, due to the existence of the pressure drop, ac driving force still plays the significant role on directed transport even in a completely symmetric channel. Our results could be implemented in constrained structures with narrow channels or pores where the particles are suspended in a solvent.


Assuntos
Entropia , Hidrodinâmica , Movimento (Física) , Simulação por Computador , Difusão , Modelos Químicos , Tamanho da Partícula , Pressão
8.
Artigo em Inglês | MEDLINE | ID: mdl-24483408

RESUMO

Rectification and diffusion of noninteracting self-propelled particles is numerically investigated in a two-dimensional corrugated channel. From numerical simulations, we obtain the average velocity and the effective diffusion coefficient. It is found that the self-propelled particles can be rectified by the self-propelled velocity. There exist optimal values of the parameters (the self-propelled velocity, the translational diffusion constant, and the height of the potential) at which the average velocity takes its maximal value. There exists an optimal translational diffusion at which the effective diffusion constant is maximal. The self-propelled velocity can strongly increase the effective diffusion, while the large rotational diffusion rate can strongly suppress the effective diffusion.

9.
Phys Rev E Stat Nonlin Soft Matter Phys ; 83(5 Pt 1): 051106, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21728489

RESUMO

Transport of Brownian particles interacting with each other via the Morse potential is investigated in the presence of an ac driving force applied locally at one end of the chain. By using numerical simulations, we find that the system can behave as a particle diode for both overdamped and underdamped cases. For low frequencies, the transport from the free end to the ac acting end is prohibited, while the transport from the ac acting end to the free end is permitted. However, the polarity of the particle diode will reverse for medium frequencies. There exists an optimal value of the well depth of the interaction potential at which the average velocity takes its maximum. The average velocity υ decreases monotonically with the system size N by a power law υ ∝ N(-1).


Assuntos
Modelos Teóricos , Movimento (Física) , Fenômenos Mecânicos , Fatores de Tempo
10.
J Chem Phys ; 133(11): 114507, 2010 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-20866145

RESUMO

Effects of time-delayed feedback on pattern formation are studied both numerically and theoretically in a bistable reaction-diffusion model. The time-delayed feedback applied to the activator and/or the inhibitor alters the behavior of the nonequilibrium Ising-Bloch (NIB) bifurcation. If the intensities of the feedbacks applied to the two species are identical, only the velocities of Bloch fronts are changed. If the intensities are different, both the critical point of the NIB bifurcation and the threshold of stability of front to transverse perturbations are changed. The effect of time-delayed feedback on the activator opposes the effect of time-delayed feedback on the inhibitor. When the time-delayed feedback is applied individually to one of the species, positive and negative feedbacks make the bifurcation point shift to different directions. The time-delayed feedback provides a flexible way to control the NIB bifurcation and the pattern formation.


Assuntos
Modelos Químicos , Difusão , Fatores de Tempo
11.
J Chem Phys ; 132(9): 094504, 2010 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-20210402

RESUMO

Transport of the Brownian particles driven by Lévy flights coexisting with subdiffusion in asymmetric periodic potentials is investigated in the absence of any external driving forces. Using the Langevin-type dynamics with subordination techniques, we obtain the group velocity which can measure the transport. It is found that the group velocity increases monotonically with the subdiffusive index and there exists an optimal value of the Lévy index at which the group velocity takes its maximal value. There is a threshold value of the subdiffusive index below which the ratchet effects will disappear. The nonthermal character of the Lévy flights and the asymmetry of the potential are necessary to obtain the directed transport. Some peculiar phenomena induced by the competition between Lévy flights and subdiffusion are also observed. The pseudonormal diffusion will appear on the level of the median.

12.
Phys Rev E Stat Nonlin Soft Matter Phys ; 82(6 Pt 1): 061102, 2010 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-21230639

RESUMO

Directed transport of overdamped Brownian particles driven by fractional Gaussian noises is investigated in asymmetrically periodic potentials. By using Langevin dynamics simulations, we find that rectified currents occur in the absence of any external driving forces. Unlike white Gaussian noises, fractional Gaussian noises can break thermodynamical equilibrium and induce directed transport. Remarkably, the average velocity for persistent fractional noise is opposite to that for antipersistent fractional noise. The velocity increases monotonically with Hurst exponent for the persistent case, whereas there exists an optimal value of Hurst exponent at which the velocity takes its maximal value for the antipersistent case.


Assuntos
Modelos Teóricos , Movimento (Física) , Algoritmos , Distribuição Normal
13.
Phys Rev E Stat Nonlin Soft Matter Phys ; 79(6 Pt 2): 066209, 2009 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-19658585

RESUMO

Suppression of spiral and turbulence in inhomogeneous media due to local heterogeneity with higher excitability is investigated numerically. When the inhomogeneity is small, control tactics by boundary periodic forcing (BPF) is effective against the existing spiral and turbulence. When the inhomogeneity of excitability is large, a rotating electric field (REF) is utilized to "smooth" regional heterogeneity based on driven synchronization. Consequently, a control approach combining BPF with REF is proposed to suppress the spiral and turbulence. The underlying mechanism of successful suppression is discussed in terms of dispersion relation.

14.
Zhonghua Wai Ke Za Zhi ; 45(22): 1565-8, 2007 Nov 15.
Artigo em Chinês | MEDLINE | ID: mdl-18282397

RESUMO

OBJECTIVE: To investigate bone defect healing by true bone ceramic complex carrying core binding factor a1 (Cbfa1) gene modified rabbit skin fibroblasts. METHODS: Transfect rabbit skin fibroblasts (RSF) with both eukaryotic expression vector pSG5 which could express Cbfa1 gene and pSG5. After being cultured for 48 h, the transfected RSF were seeded into true bone ceramic (TBC) of 2 cm in length and 4 mm in diameter to construct pSG5-Cbfa1/RSF/TBC complex and pSG5/RSF/TBC complex. Forty-eight bone defect model rabbits were randomized into four groups, each has 6 rabbits (12 radius), due to different treatment. group I: with pSG5-Cbfa1/RSF/TBC complex, group II: with pSG5/RSF/TBC complex, group III: with TBC, Group IV: empty control. After being seeded and cultured for about 24 h the complexes were implanted into 2 cm long bone defects in the middle of bilateral radius of rabbits. The radius were inspected by X-ray and then the specimens were collected at the end of the fourth and twelfth weeks after operation. Then, the specimens were decalcified and histologically investigated with Hematoxylin eosin staining and Masson staining methods. Newly synthesized trabecular bone was inspected by image analysis system and the strength of bone defect area treated with graft-implantation was tested with biomechanical method-three point bending test. RESULTS: In group I, trabecular bone was actively synthesized to generate a great amount of trabecular bone and osteon. Preliminary union and bone defect healing were completed with good biomechanical characteristics. There were no newly synthesized trabecular in the other three groups, and bone defect healing were not discovered. The amount of newly synthesized trabecular bone and the results of biomechanical testing differed significantly between group I and the other three (P < 0.01). The efficacy of group I was significantly better than that of the other three groups. CONCLUSION: True bone ceramic complex composed with Cbfa1 gene modified rabbit skin fibroblasts can effectively heal bone defect in rabbits.


Assuntos
Substitutos Ósseos , Subunidade alfa 1 de Fator de Ligação ao Core/genética , Fibroblastos/metabolismo , Rádio (Anatomia)/cirurgia , Animais , Regeneração Óssea , Transplante Ósseo , Células Cultivadas , Modelos Animais de Doenças , Fibroblastos/citologia , Plasmídeos/genética , Coelhos , Rádio (Anatomia)/lesões , Rádio (Anatomia)/fisiopatologia , Distribuição Aleatória , Pele/citologia , Engenharia Tecidual/métodos , Transfecção
15.
Guang Pu Xue Yu Guang Pu Fen Xi ; 26(5): 802-4, 2006 May.
Artigo em Chinês | MEDLINE | ID: mdl-16883840

RESUMO

Vibrational temperature of N2 (C 3IIu) molecules in dielectric barrier discharge (DBD) in argon/air at atmospheric pressure, in which the water electrodes were employed, was measured by using a method of spectrum diagnosis. Emission spectral lines of the N2 second positive band system(C 3IIu --> B 3IIg) and the sequences of vibrational bands with deltav = -1, deltav = -2 and deltav = -3 were used in the calculation. The experiment results show that the molecular vibrational temperature of N2 is in the range from 1 938 K to 2 720 K, and it increases almost linearly with increasing the air content in gas mixture. These results are of great importance to the study of plasma dynamics of DBD.

16.
Guang Pu Xue Yu Guang Pu Fen Xi ; 23(3): 607-8, 2003 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-12953556

RESUMO

The global light emission of dielectric barrier discharge with pattern mode in air was measured and compared with the global current obtained with a small resistor. The results show that the moments and the amplitudes of the pulses in light emission correspond to those in the global current, respectively. So the discharge current can be measured by optical methods. Further more, the temporal aspect of the microdischarges in dielectric barrier discharge was obtained by using this method. It is believed that the results are of great importance to the study of spatiotemporal dynamics in dielectric barrier discharge, and are valuable to the study of gas discharge as well.

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