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Spreading and retraction dynamics of a dye doped smectic liquid crystal domain at the air-water interface
No full textRestricted Access.We have studied the spreading and retraction dynamics of a dye doped smectic multilayer domain in the collapsed state of a Langmuir monolayer at the air–water interface. We find that the domain undergoes shearing when excited with an appropriate wavelength in the epifluorescence setting of the microscope. The shearing leads to displacement of the stack of layers and results in asymmetric spreading of the domain. Eventually, due to line tension, the domain transforms into a circular shape. Here, the domain area was about twice that of the initial area. Under reflection setting of the microscope, with white light, we observe that the domain retracts to a smaller area. During the course of retraction, we find successive generation and evolution of edge dislocation loops leading to thickening of the domain. Our analysis on the variation of the normalized area of the domain with time yields different characteristic time constants for spreading and retraction. The spreading and retraction of the domain can be understood by invoking changes in interfacial tension due to photobleached surface active products and the depletion of photobleached products, respectively
Post-Newtonian prediction for the (2,2) mode of the gravitational wave emitted by compact binaries
No full textRestricted Access. Proceedings of 9th LISA Symposium Paris, France from 21-25 may 2012. Edited by Gerard Auger, Pierre Binétruy, and Eric Plagnol (We present our 3.5PN computation of the (2,2) mode of the gravitational wave amplitude emitted by compact binaries, on quasi-circular orbits and in the absence of spins. We use the multipolar post-Newtonian wave generation formalism, extending and building on previous works which computed the 3PN order. This calculation required the extension of the multipolar post-Minkowskian algorithm, as well as the computation of the mass source quadrupole at 3.5PN order. Our result will allow more accurate comparisons to numerical relativity, and is a first step towards the computation of the full 3.5PN waveform amplitude, which would improve the estimation of the source parameters by gravitational wave detector
Effects of disorder on the optical properties of CVD grown polycrystalline graphene
No full textRestricted AccessWe explore the effects of crystallite size (La) on the linear and non-linear optical properties of chemical vapor deposition grown polycrystalline graphene. The π-plasmon resonance present at [similar]4.75 eV ([similar]260 nm) in the optical absorption spectrum of graphene follows the empirical relationship λπ = 250.5 nm + 89.5 nm2/La, where λπ represents the π-plasmon wavelength. Furthermore, our Z-scan studies reveal that the crystallite size significantly changes the saturation intensity in CVD grown graphene. Notably, in comparison to epitaxial graphene layers grown on SiC wafers which exhibit a photogenerated carrier lifetime of few picoseconds, we find that the photogenerated carriers in our CVD grown graphene can exhibit lifetimes as long as nanoseconds
Bit slice addressing of fast switching bi-stable displays and multi-bit slice addressing of active matrix liquid crystal displays
No full textOpen AccessBit slice addressing (BSA) is useful to display grayscales in fast switchable bi-stable displays and active matrix liquid crystal displays (AMLCD). The display is used as a dynamic mask and intensity of light source that illuminates the display is controlled to be proportional to the bit-weight of the bit that was used to refresh the display. A viewing angle characteristic that is independent of grayscales, color purity of images, reduction of motion blur, wide voltage margin to switch the state of pixels, option to reduce power consumption of backlight and low hardware complexity of data drivers are some of the advantages of BSA. Multi-BSA is also proposed to drive the state-of-the-art active-matrix LCDs
Mean-field dynamo action in renovating shearing flows
No full textOpen AccessWe study mean-field dynamo action in renovating flows with finite and nonzero correlation time (τ) in the presence of shear. Previous results obtained when shear was absent are generalized to the case with shear. The question of whether the mean magnetic field can grow in the presence of shear and nonhelical turbulence, as seen in numerical simulations, is examined. We show in a general manner that, if the motions are strictly nonhelical, then such mean-field dynamo action is not possible. This result is not limited to low (fluid or magnetic) Reynolds numbers nor does it use any closure approximation; it only assumes that the flow renovates itself after each time interval τ. Specifying to a particular form of the renovating flow with helicity, we recover the standard dispersion relation of the α2Ω dynamo, in the small τ or large wavelength limit. Thus mean fields grow even in the presence of rapidly growing fluctuations, surprisingly, in a manner predicted by the standard quasilinear closure, even though such a closure is not strictly justified. Our work also suggests the possibility of obtaining mean-field dynamo growth in the presence of helicity fluctuations, although having a coherent helicity will be more efficient
Defect-mediated lamellar-isotropic transition of amphiphile bilayers
No full textRestricted Access.We report the observation of an isotropic phase of amphiphile bilayers, characterized by small average inter-bilayer spacing and short-range positional correlations. These bilayers form a weakly swollen lamellar (Lα) phase over a wide range of water content, which transforms into an isotropic (Li) phase on heating. This transition is not observed in samples without excess water, where the Lα phase is stable at higher temperatures. Small-angle X-ray scattering and ionic conductivity studies indicate that the Lα–Li transition is driven by the unbinding of edge dislocation loops, which has been shown to destroy the quasi-long-range positional order of the lamellar phase. Observation of similar behavior in other bilayer forming systems dominated by attractive inter-bilayer interactions suggests that this isotropic phase is generic to such systems
