Long-range Orientation Research Articles

Controlled Orientation and Alignment in Films of Single-Walled Carbon Nanotubes Using Inkjet Printing

An inkjet printing procedure for depositing films of carbon nanotubes (CNTs) that exhibit a very high degree of long-range mutual alignment as well as a controlled orientation with respect to the printed geometry is presented. CNT self-assembly was induced by the intrinsic lyotropic liquid crystallinity of CNT suspensions. Sufficient concentrations are reached by matching the inkjet deposition rate to the numerically modeled local evaporation rate of the printed feature and enable the CNT suspension to be printed using standard inkjet printing. Surface alignment was verified using scanning electron microscopy (SEM) and polarized light microscopy. In addition, the bulk morphology was investigated and found to be composed of stacked planar layers that did not necessarily have the same long-range orientation found on the surface. The bulk morphology was characterized by removing layers through an elastomeric peeling process and by observing cross sections of the films using SEM. CNT concentration and length were spanned experimentally, and it was found that very short and very long CNTs as well as low concentration suspensions did not yield long-range alignment.

Long-range orientation correlation in liquids

Strong short-range intermolecular interactions result in position and orientation correlations between nearest neighbour molecules in isotropic liquids, and it is generally assumed that such correlations extend at most a few molecular diameters. This assumption is contradicted by results from second harmonic light scattering experiments presented here, which reveal long-range orientation correlations in several isotropic liquids including water. These experiments measure the polarization dependence of the scattered light, and the observations are interpreted in terms of transverse and longitudinal polar collective modes, as well as simple explicit models. The results revise our understanding of the structure of molecular liquids and provide a test of computational simulations.

Ordering and Large-Scale Relaxation Properties of Macromolecules in Ferroelectric Polymer Films

Dynamical equations for transverse and longitudinal mean projections of elastic-deformed kinetic chain units (Gaussian subchains) with anisotropic local intra- and interchain orientation interactions of dipolar type and spectra of relaxation times for large-scale motions of the chains in an isotropic and ordered state were obtained. The long-range orientation planar order in the 3D-layered systems leads to an anisotropy of large-scale relaxation properties of the chains (relative to the axis perpendicular to layers). The anisotropy increases with increase of the chain bending rigidity, the strength of interchain interactions and decrease of the scale of its motion. It disappears for most large-scale motions of chains.

Classification of Textures and Microstructure Stability in Rolled F.C.C. Metals with Grain Interactions

A novel experimental investigation of both high and medium stacking fault energy bi-crystals of aluminum and copper, respectively, show that orientation, grain interaction and material are all key factors in the stability of some ideal rolling texture components. Ideal {110} or {112} orientations obtained from high purity aluminum or copper single crystals were embedded within a {110} crystal orientation of the same material and reduced 60 percent by channel die compression at room temperature. Spatial misorientations developed inside the deformation bands were analyzed using SEM-based EBSD. The presence of long-range orientation gradients in some of the crystals revealed the interacting nature of polycrystalline deformation. From the results it is proposed that f.c.c. polycrystalline grains can be classified according to their stability and susceptibility to deformation: (i) stable and interacting; (ii) unstable and interacting; (iii) stable and non-interacting; (iv) unstable and non-interacting.

A directional MAC protocol with long-range communication ability in ad hoc networks

To address the problem that long-range communication capability in ad hoc networks using directional antenna is not generally utilized, a directional media access control (DMAC) protocol with long-range communication (LRC) capability in ad hoc networks is proposed. In the LRC-DMAC, the intermediate node uses a long-range orientation (LRO) algorithm to help the transmitter obtain the directional information of the receiver which is two hops away. Consequently, the long-range link between such two hops nodes can be set up. According to whether the received power information is available or not, we propose two types of LRO algorithm: without the received power information, a basic LRO obtains the approximate directional information of the long-range receiver by a geometric relationship; however, the LRO-PI can calculate the accurate directional information of the long-range receiver using the received power. Performance analysis indicates that the LRO algorithm achieves high accuracy when the relevant parameters are properly chosen. Simulation results show that the establishment of long-range links can effectively improve the network throughput and reduce the end-to-end delay.

Study on mechanism of photocatalytic performance of La-doped TiO 2/Ti photoelectrodes by theoretical and experimental methods

TiO 2 photoelectrodes with various nanostructures have been successfully prepared by the anodization method. The morphology, microstructure and optical properties of as-prepared photoelectrodes were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), ultraviolet/visible light diffuse reflectance spectra (UV/vis/DRS), surface photovoltage spectroscopy (SPS) and photocurrent. The electronic structure and optical properties of La doped/undoped TiO 2 photoelectrodes with different crystal structures were calculated by the density function theory. The photocatalytic and photoelectrocatalytic activities of as-prepared photoelectrodes were evaluated. The results showed that the anodization potentials played a crucial role in the surface morphology and microstructure. Both results of theoretical calculations and experimental tests demonstrated that La-doped photoelectrodes were more sensitive to light than undoped one. The difference of photoelectrodes performance was ascribed to the crystal configuration, impurity energy levels and long-range orientation moving of photogenerated carriers.

Ad Hoc 网络中具有远距离通信能力的方向性MAC 协议

To address the problem that long-range communication capability in ad hoc networks using direc- tional antenna is not generally utilized, a directional media access control (DMAC) protocol with long-range communication (LRC) capability in ad hoc networks is proposed. In the LRC-DMAC, the intermediate node uses a long-range orientation (LRO) algorithm to help the transmitter obtain the directional information of the receiver which is two hops away. Consequently, the long-range link between such two hops nodes can be set up. According to whether the received power information is available or not, we propose two types of LRO algorithm: without the received power information, a basic LRO obtains the approximate directional information of the long-range receiver by a geometric relationship; however, the LRO-PI can calculate the accurate directional information of the long-range receiver using the received power. Performance analysis indicates that the LRO algorithm achieves high accuracy when the relevant parameters are properly chosen. Simulation results show that the establishment of long-range links can effectively improve the network throughput and reduce the end-to-end delay.

Liquid-Crystalline Polymer Composites with CdS Nanorods: Structure and Optical Properties

We report on the structure, uniaxial orientation, and photoluminescent properties of CdS nanorods that form stable nanocomposites with smectic C hydrogen-bonded polymers from the family of poly(4-(n-acryloyloxyalkoxy)benzoic acids. TEM analysis of microtomed films of nanocomposites reveals that CdS nanorods form small domains that are homogeneously distributed in the LC polymer matrix. They undergo long-range orientation with the formation of one-dimensional aggregates of rods when the composite films are uniaxially deformed. The Stokes photoluminescence was observed from CdS NRs/LC polymer composites with emission peak located almost at the same wavelength as that of NRs solution in heptane. An anti-Stokes photoluminescence (ASPL) in polymer nanocomposites was found under the excitation below the nanoparticles ground state. The mechanism of ASPL was interpreted in terms of thermally populated states that are involved in the excitation process. These nanocomposites represent an unusual material in which the optical properties of anisotropic semiconductor nanostructures can be controlled by mechanical deformation of liquid-crystalline matrix.

Self-Assembly and Orientation of Hydrogen-Bonded Oligothiophene Polymorphs at Liquid–Membrane–Liquid Interfaces

One of the challenges in organic systems with semiconducting function is the achievement of molecular orientation over large scales. We report here on the use of self-assembly kinetics to control long-range orientation of a quarterthiophene derivative designed to combine intermolecular π-π stacking and hydrogen bonding among amide groups. Assembly of these molecules in the solution phase is prevented by the hydrogen-bond-accepting solvent tetrahydrofuran, whereas formation of H-aggregates is facilitated in toluene. Rapid evaporation of solvent in a solution of the quarterthiophene in a 2:1:1 mixture of 1,4-dioxane/tetrahydrofuran/toluene leads to self-assembly of kinetically trapped mats of bundled fibers. In great contrast, slow drying in a toluene atmosphere leads to the homogeneous nucleation and growth of ordered structures shaped as rhombohedra or hexagonal prisms depending on concentration. Furthermore, exceedingly slow delivery of toluene from a high molecular weight polymer solution into the system through a porous aluminum oxide membrane results in the growth of highly oriented hexagonal prisms perpendicular to the interface. The amide groups of the compound likely adsorb onto the polar aluminum oxide surface and direct the self-assembly pathway toward heterogeneous nucleation and growth to form hexagonal prisms. We propose that the oriented prismatic polymorph results from the synergy of surface interactions rooted in hydrogen bonding on the solid membrane and the slow kinetics of self-assembly. These observations demonstrate how self-assembly conditions can be used to guide the supramolecular energy landscape to generate vastly different structures. These fundamental principles allowed us to grow oriented prismatic assemblies on transparent indium-doped tin oxide electrodes, which are of interest in organic electronics.

Mathematical study of the formation of long-range horizontal connections and orientation maps in the primary visual cortex

Mathematical study of the formation of long-range horizontal connections and orientation maps in the primary visual cortex

Polarization-Based Long-Range Communication Directional MAC Protocol for Cognitive Ad Hoc Networks

Utilizing available channels to improve the network performance is one of the most important targets for the cognitive MAC protocol design. Using antenna technologies is an efficient way to reach this target. Therefore, in this paper, we propose a novel cognitive MAC protocol, called Polarization-based Long-range Communication Directional MAC Protocol (PLRC-DMAC), for Cognitive Ad Hoc Networks (CAHNs). The proposed protocol uses directional antennas to acquire better spatial reuse and establish long-range communication links, which can support more nodes to access the same channel simultaneously. Moreover, the PLRC-DMAC also uses polarization diversity to allow nodes in the CAHN to share the same channel with Primary Users (PUs). Furthermore, we also propose a Long-range Orientation (LRO) algorithm to orient the long-range nodes. Simulation results show that the LRO algorithm can accurately orient the long-range nodes, and the PLRC-DMAC can significantly increase the network throughput as well as reduce the end-to-end delay.

Orienting Periodic Organic−Inorganic Nanoscale Domains Through One-Step Electrodeposition

One of the challenges in the synthesis of hybrid materials with nanoscale structure is to precisely control morphology across length scales. Using a one-step electrodeposition process on indium tin oxide (ITO) substrates followed by annealing, we report here the preparation of materials with preferentially oriented lamellar domains of electron donor surfactants and the semiconductor ZnO. We found that either increasing the concentration of surfactant or the water to dimethyl sulfoxide ratio of solutions used resulted in the suppression of bloomlike morphologies and enhanced the density of periodic domains on ITO substrates. Furthermore, by modifying the surface of the ITO substrate with the conductive polymer blend poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), we were able to alter the orientation of these electrodeposited lamellar domains to be perpendicular to the substrate. The long-range orientation achieved was characterized by 2D grazing incidence small-angle X-ray scattering. This high degree of orientation in electronically active hybrids with alternating nanoscale p-type and n-type domains is of potential interest in photovoltaics or thermoelectric materials.

Correlation functions and optical effects in surface layers of polymer films

The calculated dependences of the quadrupole orientation order parameter on the Kuhn segment length adequately describe the experimental data obtained by the birefringence method for multilayer polymer films. The transverse orientation correlations of chain segments decrease according to a power law, like in 2d infinite systems. The fluctuations of the 3d long-range orientation order in the layer plane increase with the increasing anisotropy of interactions in the system.

Correlation Functions and Optical Effects in Surface Layers of Polymer Films

The calculated dependences of the quadrupole orientation order parameter on the Kuhn statistical segment length properly describe the experimental data, obtained by the film birefringence method for different multilayer polymer films. Transverse orientation correlations of chains segments decrease according to a power law, as in the case of infinite two-dimensional systems. The fluctuations of three-dimensional long-range orientation order in the plane of the layers are observed. These fluctuations are enhanced when the anisotropy of intra- and interchain interactions increase in the film.

Flying the Fly: Long-range Flight Behavior of Drosophila melanogaster to Attractive Odors

The fruit fly, Drosophila melanogaster Meigen (Diptera: Drosophilidae), is a model for how animals sense, discriminate, and respond to chemical signals. However, with D. melanogaster our knowledge of the behavioral activity of olfactory receptor ligands has relied largely on close-range attraction, rather than on long-range orientation behavior. We developed a flight assay to relate chemosensory perception to behavior. Headspace volatiles from vinegar attracted 62% of assayed flies during a 15-min experimental period. Flies responded irrespective of age, sex, and mating state, provided they had been starved. To identify behaviorally relevant chemicals from vinegar, we compared the responses to vinegar and synthetic chemicals. Stimuli were applied by a piezoelectric sprayer at known and constant release rates. Re-vaporized methanol extracts of Super Q-trapped vinegar volatiles attracted as many flies as vinegar. The main volatile component of vinegar, acetic acid, elicited significant attraction as a single compound. Two other vinegar volatiles, 2-phenyl ethanol and acetoin, produced a synergistic effect when added to acetic acid. Geosmin, a microbiological off-flavor, diminished attraction to vinegar. This wind tunnel assay based on a conspicuous and unambiguous behavioral response provides the necessary resolution for the investigation of physiologically and ecologically relevant odors and will become an essential tool for the functional analysis of the D. melanogaster olfactory system.

Electrophysiological, Flight Orientation and Oviposition Responses of Three Species of Mosquito Vectors to Hexadecyl Pentanoate: Residual Oviposition Repellent Activity

Understanding on the chemical ecology of mosquito behavior is of paramount importance in developing control programs employing attractants and repellents. Several workers focused on topical repellents and oviposition attractants of mosquitoes, however, only limited work has been accomplished on mosquito oviposition repellents. The present systematic investigation provides evidence on the effectiveness of a C21 fatty acid ester- hexadecyl pentanoate, to stimulate antennal olfactory receptors of Aedes aegypti (L.), Ae. albopictus (Skuse), and Anopheles stephensi (Liston) that mediate their long-range olfaction guided flight orientation behavior by repelling the gravid females of these mosquito vectors in the olfactometer. The compound loaded onto an effervescent tablet retained its repellent property in the treated substrates for up to 1 wk at 10 mg/L. In places, where the mosquito breeding habitats are near to human habitations, could be treated with hexadecyl pentanoate to repel the ovipositing gravid females as a component of the integrated approach for mosquito management by disrupting the mosquito life cycle and population growth.

Thermodynamic investigation of mixed monolayers of trans-dehydrocrotonin and phospholipids

The thermodynamic behavior of mixed floating monolayers of zwitterionic phospholipids and trans-dehydrocrotonin (t-DCTN) at different molar fractions ( x) of the diterpene has been investigated by measuring the surface pressure and surface potential Langmuir isotherms. Excess Gibbs energies of mixing have been calculated for different compositions of the floating monolayer at varying surface pressure values. Spreading of pure t-DCTN molecules at the air–water interface resulted in a compressed-type isotherm. For the t-DCTN/DBPC and t-DCTN/DOPC binary systems, the maximum stability was obtained at x t-DCTN = 0.375 and 0.500 at a surface pressure of 15 mN/m, with a minimum ΔG M value equal to −1.7 kJ/mol. The analyses of the obtained thermodynamic parameters such as excess areas, excess free energies and free energy of mixing confirmed the miscibility of the phospholipids and t-DCTN in the binary systems. In these mixed monolayers, the phospholipid molecules seemed to exhibit higher long-range orientation order for intermediary values of t-DCTN molar fractions. As a whole, the above observations suggest that the t-DCTN molecules exert a condensing effect on the monolayers when mixed with the phospholipids.

Mechanical Properties of Regenerated Bombyx mori Silk Fibers and Recombinant Silk Fibers Produced by Transgenic Silkworms

Regenerated silk fibroin fibers from the cocoons of silkworm, Bombyx mori, were prepared with hexafluoro solvents, 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) or hexafluoroacetone-trihydrate (HFA), as dope solvents and methanol as coagulation solvent. The regenerated fiber prepared from the HFIP solution showed slightly larger tensile strength when the draw ratio is 1:3 than that of native silk fiber, but the strength of the regenerated fiber with draw ratio 1:3 from the HFA solution is much lower than that of native silk fiber. This difference in the tensile strength of the regenerated silk fibers between two dope solvents comes from the difference in the long-range orientation of the crystalline region rather than that of short-range structural environment such as the fraction of β-sheet structure. The increase in the biodegradation was observed for the regenerated silk fiber compared with native silk fiber. Preparations of regenerated silk fibroin fibers containing spider silk sequences were obtained by mixing silk fibroins and silk-like proteins with characteristic sequences from a spider, Naphila clavipes, to produce drag-line silk in E. coli in the fluoro solvents. A small increase in the tensile strength was obtained by adding 5% (w/w) of the silk-like protein to the silk fibroin. The production of silk fibroin fibers with these spider silk sequences was also performed with transgenic silkworms. Small increase in the tensile strength of the fibers was obtained without significant change in the elongation-at-break.

Phase Transitions and Structures of 5-{[(4’-Pentyloxy-4-biphenylyl)carbonyl]oxy}-1-pentyne

Phase transitions and structures of the monomer of side-chain liquid crystalline polyacetylene containing biphenyl mesogen,namely,5-{[(4'-pentyloxy-4-biphenylyl)carbonyl]oxy}-1-pentyne (A3EO5) were investigated by differential scanning calorimetry (DSC),one dimensional (1D) wide angle X-ray diffraction (WAXD),and polarized light microscopy equipped with hot-stage (PLM-hot stage).DSC and 1D-WAXD results show that A3EO5 forms an enantiotropic liquid crystal and displays four transitions during the cooling and subsequent heating processes.Upon cooling from isotropic phase to room temperature,the sample forms smectic A phase and then leads to smectic B phase with pseudo long-range orientation within the layer structure,further lowering the temperature,A3EO5 forms smectic E phase with orthorhombic packing within the smectic layer and enters crystal phase.PLM results show that the sample forms spherulitic texture,focal conic texture and concentric arcs texture during the cooling process.

10.1007/s11498-008-3013-8

Two types of anisotropic polymer systems were studied in the spherical approximation used in the classical theory of ferromagnetism. These were a three-dimensional system composed of weakly interacting layers with isotropic interactions between chain segments in the layer planes and thin quasi-two-dimensional polymer films possessing intra-and interchain interaction anisotropy, whose behavior is close to that of two-dimensional systems. Laws that govern a change in the temperature T cr of phase transition from the long-range order state to a disordered state depending on the magnitude of anisotropy and the size of the layers were established. For systems of the former type in which interlayer interactions is weakened, T cr tends to zero, being inversely proportional to lng, where g is the ratio of the interaction constant between the layers to that of inplane interaction in a layer. For systems of the latter type, the transition temperature T cr → 0 according to the T cr ∼ √ɛ law, where ɛ is the parameter that characterizes the anisotropy of intra-and interchain interactions. The number of layers required for the systems to be considered three-dimensional was estimated. Regardless of the type of boundary conditions for finite systems, the number of layers increases with enhancement of interaction anisotropy (a decrease in g and ɛ) and an increase in the number of chains in the layers, especially for systems of the former type. Transverse orientational correlations of chain segments with respect to the arrangement of the layers decrease according to a power law, as in the case of infinite two-dimensional systems. There are fluctuations of three-dimensional long-range orientation order in the plane of the layers, the fluctuations are enhanced with an increase in the anisotropy of interactions in the system.