排序方式: 共有57条查询结果,搜索用时 15 毫秒
21.
The overdamped Langevin dynamics has been employed to study the directional transport of particles driven in a tilted rocking ratchet potential. The system subjected to a constant direct force undergoes an asymmetrical dynamic transition from a static state to a sliding state at two different critical forces that are consistent with the predicted values. When an additional alternating force is applied to the system, the time-averaged velocity shows several steps of equal height as the direct force increases. These steps are similar to the Shapiro steps in an rf-driven Josephson junction, and appear whenever the system's natural frequency given by the direct force matches an integer multiple of the applied frequency. When the alternating force exceeds a certain critical value which can be also estimated for a slow rocking, a directional motion known as the rectification effect occurs even at zero direct force. 相似文献
22.
Molecular motors are proteins or protein complexes which
function as transporting engines in biological cells. This paper
models the tether between motor and its cargo as a symmetric linear
potential. Different from Elston and Peskin's work for which
performance of the system was discussed only in some limiting cases,
this study produces analytic solutions of the problem for general
cases by simplifying the transport system into two physical states,
which makes it possible to discuss the dynamics of the motor--cargo
system in detail. It turns out that the tether strength between
motor and cargo should be greater than a threshold or the motor will
fail to transport the cargo, which was not discussed by former
researchers yet. Value of the threshold depends on the diffusion
coefficients of cargo and motor and also on the strength of the
Brownian ratchets dragging the system. The threshold approaches a
finite constant when the strength of the ratchet tends to infinity. 相似文献
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24.
FANG Jian-Shu ZHANG Xiang-Ping 《理论物理通讯》2008,50(12):1355-1360
The chaotic ratchet effect for Bos-Einstein condensed atoms in an optical lattice is investigated. By using the direct perturbation method we obtain the chaotic solution of the condensed system. Theoretical analysis reveals that the transport of the condensed atoms in the ratchet potential is a chaotic one, and corresponding numerical results agree well with the theoretical results. 相似文献
25.
Ricardo Ortiz Domin Koh Dai Hyun Kim Mohammad Towshif Rabbani Cesar Anguaya Velasquez Mukul Sonker Edgar A. Arriaga Alexandra Ros 《Electrophoresis》2022,43(12):1283-1296
Heterogeneity in organelle size has been associated with devastating human maladies such as neurodegenerative diseases or cancer. Therefore, assessing the size-based subpopulation of organelles is imperative to understand the biomolecular foundations of these diseases. Here, we demonstrated a ratchet migration mechanism using insulator-based dielectrophoresis in conjunction with a continuous flow component that allows the size-based separation of submicrometer particles. The ratchet mechanism was realized in a microfluidic device exhibiting an array of insulating posts, tailoring electrokinetic and dielectrophoretic transport. A numerical model was developed to elucidate the particle migration and the size-based separation in various conditions. Experimentally, the size-based separation of a mixture of polystyrene beads (0.28 and 0.87 m) was accomplished demonstrating good agreement with the numerical model. Furthermore, the size-based separation of mitochondria was investigated using a mitochondria mixture isolated from HepG2 cells and HepG2 cells carrying the gene Mfn-1 knocked out, indicating distinct size-related migration behavior. With the presented continuous flow separation device, larger amounts of fractionated organelles can be collected in the future allowing access to the biomolecular signature of mitochondria subpopulations differing in size. 相似文献
26.
Kulrattanarak T van der Sman RG Schroën CG Boom RM 《Advances in colloid and interface science》2008,142(1-2):53-66
Membrane processes are well-known for separating and fractionating suspensions in many industries, but suffer from particle accumulation on the membrane surface. Currently, there are new developments using microfluidic devices for cell/DNA sorting and fractionation. We anticipate these devices are also applicable to fractionation of polydisperse and concentrated suspensions (e.g. foods), and may potentially have fewer problems with particle accumulation compared to membranes. This review article presents an overview of relevant microfluidic devices. We focus on their performance with respect to concentrated suspensions, as one finds in food industry. We give quantitative estimates on their yield, selectivity, and the potential for large-scale application. From this evaluation follows that deterministic ratchets seem most promising. 相似文献
27.
A flashing ratchet model of a two-headed molecular motor in a two-dimensional potential is proposed to simulate the hand-over-hand motion of kinesins. Extensive Langevin simulations of the model are performed. We discuss the dependences of motion and efficiency on the model parameters, including the external force and the temperature. A good qualitative agreement with the expected behavior is observed. 相似文献
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29.
We presented a detailed investigation on the movement of two-headed Brownian motors in an asymmetric potential under a feedback control.By numerical simulations the direct current is obtained.The current is periodic in the initial length of spring.There is an optimal value of the spring constant.And the dependence of the current on the opposing force is reversed.Then we found that when the change of the temperature and the opposing force have optimal values,the Brownian motors can also obtain the optimal efficiency. 相似文献
30.
分子马达是一类将化学能转化为机械能的微小机器. 对二维模型的研究表明, 非保守力在体系与外界能量交换中发挥重要作用. 四态模型较好地反映了马达力学化学过程的各个状态及相应的构象变化. Motor protein is a kind of small machines that convert chemical energy to mechanical works. It is revealed from the study of the two dimensional model that the non conservative impulsive force plays a significant role in the exchanging process of energy. A four state model characterizing the coupling of mechanical and chemical processes of molecular motor is also discussed. 相似文献