Transverse electrokinetic and microfluidic effects in micro-patterned channels: lubrication analysis for slab geometries

Off-diagonal (transverse) effects in micro-patterned geometries are predicted and analyzed within the general frame of linear response theory, relating applied presure gradient and electric field to flow and electric current. These effects could contribute to the design of pumps, mixers or flow detectors. Shape and charge density modulations are proposed as a means to obtain sizeable transverse effects, as demonstrated by focusing on simple geometries and using the lubrication approximation.Comment: 9 pages, 7 figure

Hitchhiking transport in quasi-one-dimensional systems

In the conventional theory of hopping transport the positions of localized electronic states are assumed to be fixed, and thermal fluctuations of atoms enter the theory only through the notion of phonons. On the other hand, in 1D and 2D lattices, where fluctuations prevent formation of long-range order, the motion of atoms has the character of the large scale diffusion. In this case the picture of static localized sites may be inadequate. We argue that for a certain range of parameters, hopping of charge carriers among localization sites in a network of 1D chains is a much slower process than diffusion of the sites themselves. Then the carriers move through the network transported along the chains by mobile localization sites jumping occasionally between the chains. This mechanism may result in temperature independent mobility and frequency dependence similar to that for conventional hopping.Comment: a few typos correcte

Coral relocation in Chabahar Bay, the North-east of Oman Sea

Corals are marine benthic animals typically living in compact colonies of many identical individual polyps (Barnes, 1987; Gateno et al., 1996; Sumich, 1996). Coral reefs are important for many reasons including: a) Most importantly, they provide protection and shelter for many different species of fish. b) They turn surplus carbon dioxide in the water into a limestone shell. Without coral, the amount of carbon dioxide in the water would increase dramatically and that would affect all living things on Earth. c) Similar to a barrier, the coral reefs protect coasts from strong currents and waves by slowing down the water before it gets to the shore. d) Coral reef ecosystems support a variety of human needs such as fisheries and tourism (James and Spurgeon, 1992; Moberg and Folke, 1999; Cesar, 2000). Therefore, the conservation of coral colonies is very vital for marine organisms and human. In Chabahar Bay, the coral reefs are in danger of destruction due to the development program of Shahid Beheshti Port. Since the corals are very sensitive to turbidity and suspended sediments from land reclamation and dredging projects, therefore appropriate measures should be conducted for conservation and recovery of them. At present, the coral relocation is suggested as a good method for recovery of coral reefs after a disturbance in condition of their native habitats. In our project, over 28,000 hard corals were transported to coast of Hotel Lipar (Fig. 1), an area at a distance of 3.5 km far from Shahid Beheshti Port. Also, the new techniques were used for coral reattachment and transportation

Quantization and Corrections of Adiabatic Particle Transport in a Periodic Ratchet Potential

We study the transport of an overdamped particle adiabatically driven by an asymmetric potential which is periodic in both space and time. We develop an adiabatic perturbation theory after transforming the Fokker-Planck equation into a time-dependent hermitian problem, and reveal an analogy with quantum adiabatic particle transport. An analytical expression is obtained for the ensemble average of the particle velocity in terms of the Berry phase of the Bloch states. Its time average is shown to be quantized as a Chern number in the deterministic or tight-binding limit, with exponentially small corrections. In the opposite limit, where the thermal energy dominates the ratchet potential, a formula for the average velocity is also obtained, showing a second order dependence on the potential.Comment: 8 page

Topological Measure Locating the Effective Crossover between Segregation and Integration in a Modular Network

We introduce an easily computable topological measure which locates the effective crossover between segregation and integration in a modular network. Segregation corresponds to the degree of network modularity, while integration is expressed in terms of the algebraic connectivity of an associated hyper-graph. The rigorous treatment of the simplified case of cliques of equal size that are gradually rewired until they become completely merged, allows us to show that this topological crossover can be made to coincide with a dynamical crossover from cluster to global synchronization of a system of coupled phase oscillators. The dynamical crossover is signaled by a peak in the product of the measures of intra-cluster and global synchronization, which we propose as a dynamical measure of complexity. This quantity is much easier to compute than the entropy (of the average frequencies of the oscillators), and displays a behavior which closely mimics that of the dynamical complexity index based on the latter. The proposed toplogical measure simultaneously provides information on the dynamical behavior, sheds light on the interplay between modularity vs total integration and shows how this affects the capability of the network to perform both local and distributed dynamical tasks

Cooperative Transport of Brownian Particles

We consider the collective motion of finite-sized, overdamped Brownian particles (e.g., motor proteins) in a periodic potential. Simulations of our model have revealed a number of novel cooperative transport phenomena, including (i) the reversal of direction of the net current as the particle density is increased and (ii) a very strong and complex dependence of the average velocity on both the size and the average distance of the particles.Comment: 4 pages, 5 figure

Effective interactions between inclusions in complex fluids driven out of equilibrium

The concept of fluctuation-induced effective interactions is extended to systems driven out of equilibrium. We compute the forces experienced by macroscopic objects immersed in a soft material driven by external shaking sources. We show that, in contrast with equilibrium Casimir forces induced by thermal fluctuations, their sign, range and amplitude depends on specifics of the shaking and can thus be tuned. We also comment upon the dispersion of these shaking-induced forces, and discuss their potential application to phase ordering in soft-materials.Comment: 10 pages, 8 figures, to appear in PR

Casimir Torques between Anisotropic Boundaries in Nematic Liquid Crystals

Fluctuation-induced interactions between anisotropic objects immersed in a nematic liquid crystal are shown to depend on the relative orientation of these objects. The resulting long-range ``Casimir'' torques are explicitely calculated for a simple geometry where elastic effects are absent. Our study generalizes previous discussions restricted to the case of isotropic walls, and leads to new proposals for experimental tests of Casimir forces and torques in nematics.Comment: 4 pages, 1 figur