Multimodal nonlinear optical polarizing microscopy of long-range molecular order in liquid crystals

We demonstrate orientation-sensitive multimodal nonlinear optical polarizing microscopy capable of probing orientational, polar, and biaxial features of mesomorphic ordering in soft matter. This technique achieves simultaneous imaging in broadband coherent anti-Stokes Raman scattering, multiphoton excitation fluorescence, and multiharmonic generation polarizing microscopy modes and is based on the use of a single femtosecond laser and a photonic crystal fiber as sources of the probing light. We show the viability of this technique for mapping of three-dimensional patterns of molecular orientations and show that images obtained in different microscopy modes are consistent with each other.     

Multiobjective analog/RF circuit sizing using an improved brain storm optimization algorithm

This paper presents a multiobjective analog/RF circuit sizing tool using an improved brain storm optimization (IMBSO) algorithm with the purpose of analyzing the tradeoffs between competing performance specifications of analog/RF circuit block. A number of improvements are incorporated into IMBSO algorithm at different steps. At first, the clustering step of IMBSO algorithm is augmented with k-means\(++\) seeding technique to select the initial cluster centroids while clustering using k-means clustering technique. As a second improvement, the proposed IMBSO algorithm makes use of random probabilistic decision-making of river formation dynamics scheme to select optimal cluster centroids during population generation step. As a third improvement, an adaptive mutation operator is incorporated inside the IMBSO algorithm to generate new population. Finally, two separate constraint handling techniques are employed to handle both boundary and functional constraints during analog/RF circuit optimization. The performance of the proposed IMBSO algorithm is demonstrated in finding optimal Pareto fronts among different performance specifications of a two-stage operational amplifier circuit, a folded cascode amplifier circuit and a low noise amplifier circuit.     

Newtonian viscosity behavior of dilute to moderately concentrated solutions of cellulose acetate butyrate

The Newtonian viscosity behavior of dilute to moderately concentrated solutions of cellulose acetate butyrate in dioxane was investigated at different temperatures. The viscosity data were analyzed in terms of Martin's and Fedor's relationships and also generalized in terms of reduced variables. The rheological behavior of cellulose acetate butyrate solutions in the whole range of concentrations is determined by the parameter (K_MC [n]). The temperature dependence of viscosities was expressed by the Arrhenius-Frenkel-Eyring equation and the activation energy of viscous flow of polymer solutions (ΔGv) was calculated. ΔGv increases with concentration of polymer solution and is independent of temperature. The preexponential factor, A, related to activation entropy, decreases with concentration of polymer solution. The thermodynamic parameter of viscous flow for cellulose acetate butyrate (CAB)-dioxane solutions is indicative of moderately stiff structure for CAB in solutions.     

Restriction theorems for homogeneous bundles

We prove that for an irreducible representation , the associated homogeneous -vector bundle Wτ is strongly semistable when restricted to any smooth quadric or to any smooth cubic in , where k is an algebraically closed field of characteristic ≠2,3 respectively. In particular Wτ is semistable when restricted to general hypersurfaces of degree?2 and is strongly semistable when restricted to the generic hypersurface of degree?2.     

On the Construction of an Experimentally Based Set of Equations to Describe Cocurrent and Countercurrent, Two-Phase Flow of Immiscible Fluids Through Porous Media

Generalized flow equations developed for two-phase flow through porous media contain a second term that enables proper account to be taken of capillary coupling between the two flowing phases. In this study, a partition concept, together with a novel capillary pressure equation for countercurrent flow, have been introduced into Kalaydjian’s generalized flow equations to construct modified flow equations which enable a better understanding of the role of capillary coupling in horizontal, two-phase flow. With the help of these equations it is demonstrated that the reduced flux observed in countercurrent flow, as compared to cocurrent flow, can be explained by the reduction in the driving force per unit volume which comes about because of capillary coupling. Also, it is shown experimentally that, because fluids flow through a void space reduced in magnitude due to the presence of immobile irreducible and residual saturations, the capillary coupling parameter should be defined in terms of a reduced porosity, rather than in terms of porosity. Moreover, it is shown statistically that the countercurrent relative permeability curve is proportional to the cocurrent relative permeability curve, the constant of proportionality being the capillary coupling parameter. Finally it is suggested that one can eliminate the need to determine experimentally countercurrent relative permeability curves by making use of an equation constructed for predicting the magnitude of the capillary coupling parameter.     

High performing magnesium aluminate-coated separator for lithium batteries

A high performing and thermally stable magnesium aluminate (MgAl₂O₄) coated on both sides of Celgard 2320 for applications in lithium batteries was prepared. The MgAl₂O₄-coated membrane was thermally stable up to 440 °C and capable of up-taking electrolytes up to 250%. The contact angle of MgAl₂O₄-coated membrane was lower (21°) than that of uncoated membrane. The MgAl₂O₄-coated ceramic separator exhibited appreciable ionic conductivity and better compatibility with lithium metal anode. Finally, a 2032-type coin cell comprising Li/MgAl₂O₄-coated separator/LiFePO₄ was assembled and its charge-discharge behavior was analyzed at 0.1, 0.5, and 1 C-rates. A stable discharge capacity was achieved even at 1 C-rate which qualifies this MgAl₂O₄-coated membrane for lithium battery applications.

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Spectroscopy of Charge Transfer Complexes of Aniline Blue

Charge transfer (CT) complexes of aniline blue (AB) were prepared with standard organic acceptors such as TCNQ, TCNE, DDQ, and chloranil and studied with UV-VIS-NIR spectra showing σ→π* and π→π* transitions along with free-carrier absorption due to scattering of light particles which has been found involving phonon–photon, electron–photon, and electron–electron scattering. Infrared spectra contain half power beta density due to hopping conduction and an asymmetric band corresponding to A(k) = A₀k exp(?bk) as absorption associated with diffraction of IR light from the crystalline particles.     

Chern–Simons theory with vector fermion matter

We study three-dimensional conformal field theories described by U(N) Chern?CSimons theory at level k coupled to massless fermions in the fundamental representation. By solving a Schwinger?CDyson equation in light-cone gauge, we compute the exact planar free energy of the theory at finite temperature on ?² as a function of the ??t?Hooft coupling ??=N/k. Employing a dimensional reduction regularization scheme, we find that the free energy vanishes at |??|=1; the conformal theory does not exist for |??|>1. We analyze the operator spectrum via the anomalous conservation relation for higher spin currents, and in particular show that the higher spin currents do not develop anomalous dimensions at leading order in 1/N. We present an integral equation whose solution in principle determines all correlators of these currents at leading order in 1/N and present explicit perturbative results for all three-point functions up to two loops. We also discuss a light-cone Hamiltonian formulation of this theory where a W _?? algebra arises. The maximally supersymmetric version of our theory is ABJ model with one gauge group taken to be U(1), demonstrating that a pure higher spin gauge theory arises as a limit of string theory.     

Efficiency of diffusion controlled miscible displacement in fractured porous media

Experiments were performed to study the diffusion process between matrix and fracture while there is flow in fracture. 2-inch diameter and 6-inch length Berea sandstone and Indiana limestone samples were cut cylindrically. An artificial fracture spanning between injection and production ends was created and the sample was coated with heat-shrinkable teflon tube. A miscible solvent (heptane) was injected from one end of the core saturated with oil at a constant rate. The effects of (a) oil type (mineral oil and kerosene), (b) injection rates, (c) orientation of the core, (d) matrix wettability, (e) core type (a sandstone and a limestone), and (f) amount of water in matrix on the oil recovery performance were examined. The process efficiency in terms of the time required for the recovery as well as the amount of solvent injected was also investigated. It is expected that the experimental results will be useful in deriving the matrix–fracture transfer function by diffusion that is controlled by the flow rate, matrix and fluid properties.