Light transmission through and its complete stoppage in an ultra slow wave optical medium

Light Wave transmission -- its compression, amplification, and the optical energy storage -- in an Ultra Slow Wave Medium (USWM) is studied analytically. Our phenomenological treatment is based entirely on the continuity equation for the optical energy flux, and the well known distribution-product property of Dirac delta-function. The results so obtained provide a clear understanding of some recent experiments on light transmission and its complete stoppage in an USWM. Keywords : Ultra slow light, stopped light, slow wave medium, EIT.Comment: (single-column 5pages PDF). Simple class-room phenomenological model of stopped light. Comments most welcom

Hydrodynamics of the Developing Region in Hydrophobic Microchannels: A Dissipative Particle Dynamics Study

Dissipative Particle Dynamics (DPD) is becoming a popular particle based method to study flow through microchannels due to the ease with which the presence of biological cells or DNA chains can be modeled. Many Lab-On-Chip (LOC) devices require the ability to manipulate the transport of cells or DNA chains in the fluid flow. Microchannel surfaces coated with combinations of hydrophilic and hydrophobic materials have been found useful for this purpose. In this work, we have numerically studied the hydrodynamics of a steady nonuniform developing flow between two infinite parallel plates with hydrophilic and hydrophobic surfaces using DPD for the first time. The hydrophobic and hydrophilic surfaces were modeled using partial-slip and no-slip boundary conditions respectively in the simulations. We also propose a new method to model the inflow and outflow boundaries for the DPD simulations. The simulation results of the developing flow match analytical solutions from continuum theory for no-slip and partial-slip surfaces to good accord. The entrance region constitutes a considerable fraction of the channel length in miniaturized devices. Thus it is desirable for the length of the developing region to be short as most microfluidic devices such as cell or DNA separators and mixers are designed for the developed flow field. We studied the effect of a hydrophilic strip near the inlet of a microchannel on the effective developing length. We find that the presence of the hydrophobic strip significantly reduces the developing length

Alignment, morphology and defect control of vertically aligned ZnO Nanorod array: competition between ‘surfactant’ and ‘stabilizer’ roles of the amine species and its photocatalytic properties

We demonstrate effective control of the morphology, defect content and vertical alignment of ZnO nanorod (NR) arrays grown by a solution method by simply varying the hexamine concentration during growth. We show that the amine acts both as a growth ‘stabilizer’ and ‘surfactant’ and controls both Zn release for ZnO formation and caps non-polar planes, respectively. Competition between these ‘stabilizer’ and ‘surfactant’ roles facilitates morphology, alignment and defect content control of 1D ZnO NR arrays. Well aligned, prismatic, defect (Zn interstitial) controlled ZnO NR arrays grown with a 1M amine concentration show higher photocatalytic degradation of Methylene Blue dye solutions under UV irradiation. Shallow donor zinc interstitials readily supply electrons which may increase the space charge near the nano-catalyst surface. The increased band bending associated with the interfacial electric field in the space charge region may then better facilitate the separation of photogenerated carriers and thus enhance the photocatalytic performance. Understanding the role of amine in the solution growth of 1D ZnO NR arrays holds great promise for tailoring ZnO NR functionalities for various potential applications

Crystal structure of 2-benzylamino-4-(4-bromo-phenyl)-6,7-dihydro-5H-cyclopenta[b]pyridine-3-carbonitrile

JS and RAN thank the management of The Madura College (Autonomous), Madurai, for their encouragement and support. RRK thanks the University Grants Commission, New Delhi, for funds through Major Research Project F. No. 42–242/2013 (SR).Peer reviewedPublisher PD