NUMERICAL STUDY OF THE TWO-DIMENSIONAL SPRUCE BUDWORM REACTION-DIFFUSION EQUATION WITH DENSITY DEPENDENT DIFFUSION

The spruce budworm model is one of the interesting single species reaction-diffusion problems describing insect dispersal behavior. In this paper, we investigate a two-dimensional model with linear diffusion dependence and a convective wind. This system has been successfully solved using an operator splitting method for various domains and initial conditions. The numerical results show that populations can grow and diffuse in such a way as to produce steady state outbreak populations or steady state inhomogeneous spatial patterns in which they aggregate with low population densities.     

Synthesis of 7-hydroxythioridazine and 7-hydroxysulforidazine

The thioridazine metabolites 7-hydroxythioridazine (2a) and 7-hydroxysulforidazine (2b) were synthesized. Commercial 4-chloro-3-nitrophenylmethylsulfone was converted to the corresponding 4-thiol through an intermediate xanthate ester. Subsequent zinc metal reduction provided the 3-amino thiolate. This salt was condensed with chloroquinone to yield 7-hydroxy-2-methylsulfonylphenothiazine which was then protected as the isopropyl ether. N-Alkylation with 2-(2-chloroethyl)-1-methylpiperidine using sodium hydroxide, then ether cleavage, afforded 2b . The N-alkylation followed by reduction with diisobutylaluminum hydride and deblocking yielded 2a . These reference standards will assist in an exploration of the potential role of meta-bolically formed 2a and 2b in the neuroleptic response to thioridazine.     

Mixed micelle behavior of poly(ethylene glycol) alkyl ethers with series of monomeric cationic, phosphonium cationic, and zwitterionic surfactant

The steady state fluorescence measurements have been carried out for the binary mixtures of poly(ethylene glycol) alkyl ethers (C _i E _j ) with series of monomeric cationic (MC), zwitterionic (ZI), and phosphonium cationic (PC) surfactants over the whole mole fraction range by using pyrene as fluorescence probe. The cmc values for all the binary mixtures, thus, determined have been further evaluated by using the regular solution theory. The various micellar parameters such as regular solution interaction parameter (β), micropolarity (I ₁/I ₃), and mean micelle aggregation number (N _agg) have been determined. A strong influence of hydrophobicity of both nonionic as well as cosurfactant (CS) components has been observed on the nature of mixed micelles. The presence of bulky head groups of PC surfactants significantly contributes towards the unfavorable mixing.     

Mechanisms of edge-localized-mode mitigation by external-magnetic-field perturbations

Particle and energy transport in the tokamak edge transport barrier is analyzed in the presence of magnetic field perturbations from external resonant coils. In recent experiments such coils have been verified as an effective tool for mitigation of the edge-localized modes of type I. The observed reduction of the density in plasmas of low collisionality is explained by the generation of charged particle flows along perturbed field lines. The increase of the electron and ion temperatures in the barrier is interpreted by the reduction of perpendicular neoclassical transport with decreasing density and nonlocality of parallel heat transport. The found modification of the pressure gradient implies the stabilization of ballooning-peeling MHD modes responsible for type I ELMs.     

Enhanced magneto-electrical properties and room temperature magnetoresistance in lightly doped manganite thin films

We report the effect of compressive strain on magnetic and magneto-electrical properties of lightly doped manganite La_0.88Sr_0.12MnO₃ thin films. Films, having 5-60 nm thickness, were grown on (001) LaAlO₃ and (001) SrTiO₃ substrate by DC-magnetron sputtering. These films show a magnetoresistance as high as ∼65% at room temperature and insulator-metal transition temperature . Further, we demonstrate that a small variation in strain causes significant changes in their properties. We have discussed the possible origin of these features and compared with the reported literature.     

On the representation of the interaction energy between two polar molecules

Summary An attempt has been made to represent the interaction energy between two polar molecules by using an effective relative orientation of the pair of the colliding molecules. Calculations made for gaseous ammonia show fairly satisfactory results.     

Temperature and strain measurement by combining ILFE and bragg grating optical fiber sensors

This paper presents two optical fiber sensor configurations that are capable of simultaneously measuring temperature and strain. These sensor configurations use serial and parallel combinations of in-line fiber etalon (ILFE) and in-fiber Bragg grating sensors, along with wavelength division multiplexing concepts. The results obtained while simultaneously varying the temperature over 130°C and strain field over 1500 με showed favorable agreement with thermistors and resistance strain gages.     

Viscoelastic characterization of selected foods over an extended frequency range

Three disparate food systems (gummy candy, Mozzarella cheese, and cooked ham) were characterized for their viscoelastic behavior under isothermal conditions over an extended frequency range of 10⁻³ to 10⁴ Hz using broadband viscoelastic spectroscopy (BVS). The materials were tested for any stress-induced fluid flow. However, no evidence of fluid flow was found under the tested frequency range. Validity of time–temperature superposition for the selected materials was also tested and compared with data from BVS.     

Boundary conditions for stokes flows near a porous membrane

A theoretical development is carried out to model the boundary conditions for Stokes flows near a porous membrane, which, in general, allows non-zero slip as well as normal flow at the surface. Two types of models are treated: an infinitesimally thin plate with a periodic array of circular apertures and a series of parallel slits. For Stokes flows, the mean normal flux and slip velocity are proportional to the pressure difference across the membrane and the average shear stress at the membrane, respectively. The appropriate proportionality constants which depend on the membrane geometry are calculated as functions of the porosity. An interesting feature of the results is that the slip at the membrane has, in general, a direction different from that of the applied shear for these models.     

Micromotor‐Based Energy Generation

A micromotor‐based strategy for energy generation, utilizing the conversion of liquid‐phase hydrogen to usable hydrogen gas (H₂), is described. The new motion‐based H₂‐generation concept relies on the movement of Pt‐black/Ti Janus microparticle motors in a solution of sodium borohydride (NaBH₄) fuel. This is the first report of using NaBH₄ for powering micromotors. The autonomous motion of these catalytic micromotors, as well as their bubble generation, leads to enhanced mixing and transport of NaBH₄ towards the Pt‐black catalytic surface (compared to static microparticles or films), and hence to a substantially faster rate of H₂ production. The practical utility of these micromotors is illustrated by powering a hydrogen–oxygen fuel cell car by an on‐board motion‐based hydrogen and oxygen generation. The new micromotor approach paves the way for the development of efficient on‐site energy generation for powering external devices or meeting growing demands on the energy grid.