Orientation Of Rods Research Articles

Diffuse reflectance of short-fiber-reinforced composites aligned by an electric field

This study aims to characterize the translucency of aligned, short-fiber composites by determining the effects of filler particle orientation on the Kubelka-Munk absorption and scattering coefficients. Rectangular composite specimens (n = 3) were filled with very short E-glass fibers. The fibers were oriented random, perpendicular, and parallel to the surface normal using an alternating electric field of 0.75 kV/mm. Diffuse reflectances of the composites on white and black backings were acquired with a spectrophotometer. The Kubelka-Munk model was then employed to calculate absorption and scattering coefficients. The ordering of the reflectances on a white backing is neither the same nor the reverse of the reflectances on the black backing. The effects of orientation were different for the absorption and scattering coefficients. Orientation parallel to the average light flux notably decreases the amount of absorption, while perpendicular orientation appreciably increases the amount of scattering. Since orientation affects the absorption and scattering coefficients differently, the ordering of the reflectances may be different when the backing is varied. This is because the translucency is composed of two parameters (absorption and scattering) and cannot be adequately summarized with one parameter such as transmittance or reflectance. Therefore, the use of a diffuse reflectance model, such as Kubelka-Munk, is essential to a quantitative understanding of the translucency effects of filler orientation. Understanding how the filler orientation affects diffuse reflectance of composites will yield insight as to how the orientation of enamel rods affects the diffuse reflectance in teeth by analogy.

Imaging properties of an elliptical-rod photonic-crystal slab lens

Imaging properties of a photonic-crystal (PC) slab lens consisting of a square lattice of elliptical dielectric rods in air are studied theoretically. The finite-difference time-domain technique is used to investigate the field patterns of a TM-polarized point source placed in the vicinity of the PC slab. A good-quality image can form in the opposite side of the slab in a frequency window located slightly below the fundamental band gap, but it is strongly confined in the near-field region irrespective of change of the slab thickness. We have changed the orientation of the elliptical rods with respect to the surface normal of the slab, and found that when the major or minor axis of the rods is not collinear with the surface normal, the image spot can show a vertical shift away from the horizontal line passing the point source. The simulation results are consistent with the equifrequency-surface contour analysis for these elliptical-rod photonic-crystal structures.

Effects of orientation and symmetry of rods on the complete acoustic band gap in two-dimensional periodic solid/gas systems

We study numerically the acoustic band structures of five different shapes of steel rods (regular triangle, square, hexagon, octagon prisms and columns) placed, respectively, in air with a square lattice. The dependences of the complete acoustic band gaps (CABGs) on the orientation of the above noncircular rods and the maximum of CABG on the rods' symmetry are discussed.

Strong Effect of Hydrodynamic Coupling on the Electric Dichroism of Bent Rods

The effect of hydrodynamic coupling on the spatial orientation of rigid bent rods in electric fields has been analyzed by Brownian dynamics simulations. Bead models for smoothly bent rods were constructed with dimensions of DNA double helices, and established simulation procedures were used to calculate their diffusion tensor, including the translational-rotational coupling tensor. The electric and optical parameters were assigned on the basis of known properties of double helices. Brownian dynamics simulations of the orientation of these models in electric fields showed that both transients and amplitudes of the calculated dichroism are very strongly dependent on translational-rotational coupling over a wide range of electric field strengths. For example, the stationary dichroism of a smoothly bent 179 bp DNA fragment calculated at low field strengths is positive in the presence and negative in the absence of hydrodynamic coupling. The transients are converted from a biphasic to a monophasic shape, when hydrodynamic coupling is turned off. The large changes resulting from hydrodynamic coupling were controlled by calculations based on analytical expressions derived for electrooptical response curves in the limit of low electric field strengths; the results obtained by this independent approach are in very satisfactory agreement with our Brownian dynamics simulations. The effect is strongly dependent on the electric dipole and on its direction. In the absence of any dipole the coupling effect was not observed. The coupling effect increases with the size of the bent rods. Because most macromolecular structures are known to have induced and/or permanent dipole moments, large effects of hydrodynamic coupling on both the amplitudes and the transients of the electric dichroism/birefringence must be expected in general for structures with nonsymmetric shape.

Large-scale Cd X ( X=S, Se) microtube arrays on glass substrate: transformation of CdOHCl microrod arrays by a simple template-sacrificing solution method

Large-scale arrayed Cd X ( X=S, Se) microtubes have been successfully prepared on glass substrate by a simple solution route. In this process, cadmium hydroxyl chloride (CdOHCl) microrod arrays, which could be directly grown on glass surface in solution of CdCl 2 and methenamine, were used not only as a source of cadmium but also as a new reactive template to fabricate these highly ordered cadmium chalcogenide tube arrays, and the orientation of CdOHCl microrods on glass substrate could be easily achieved by pretreating the glass surface with appropriate concentration of NaOH aqueous solution. The transformation from arrayed CdOHCl rods to CdS and CdSe microtube arrays were conducted in thioacetamide and Na 2SeSO 3 solution, respectively. The conversion was convenient, and no CdOHCl crystallites were detected in the final products measured by X-ray powder diffraction. The hexagonal prismatic morphology and orientation of CdOHCl rods were perfectly maintained in the as-prepared cadmium chalcogenide films according to scanning electron microscopy. Transmission electron microscopy was used to further characterize these microtube structures. The effect of NaOH pretreatment on CdOHCl orientation and the formation of tubular structures were also discussed.

Aqueous solution fabrication of large-scale arrayed obelisk-like zinc oxide nanorods with high efficiency

Two-dimensional (2D) arrays of obelisk-like zinc oxide nanorods were successfully synthesized with high efficiency on quartz and glass substrate on a large scale through a simple aqueous solution deposition method with zinc nitrate, ammonia, and ammonium chloride as the precursors. Characterized by XRD, EDS, TEM and SEM, the as-grown zinc oxide rods had a single crystalline obelisk-like hexagonal wurtzite structure with diameters of about 300–400 nm and length up to 5 μm. Both XRD and SEM studies revealed the orientation of ZnO rods, and the orientation of ZnO rods can be controlled easily by temperature, pH of the reaction system and the concentration of reactants.

Aqueous solution fabrication of large-scale arrayed obelisk-like zinc oxide nanorods with high efficiency

Two-dimensional (2D) arrays of obelisk-like zinc oxide nanorods were successfully synthesized with high efficiency on quartz and glass substrate on a large scale through a simple aqueous solution deposition method with zinc nitrate, ammonia, and ammonium chloride as the precursors. Characterized by XRD, EDS, TEM and SEM, the as-grown zinc oxide rods had a single crystalline obelisk-like hexagonal wurtzite structure with diameters of about 300–400 nm and length up to 5 μm. Both XRD and SEM studies revealed the orientation of ZnO rods, and the orientation of ZnO rods can be controlled easily by temperature, pH of the reaction system and the concentration of reactants.

Orientation, morphology and magnetostriction of a heat-treated 〈1 1 0〉 oriented TbDyFe alloy

〈1 1 0〉 oriented rods of a TbDyFe magnetostrictive alloy have been successfully prepared by zone melting unidirectional solidification. A homogenization annealing for 4 h or 48 h at 1000 °C has been carried out in a quartz cylinder under Ar 2 protection after pumping to 2×10 −3 Pa. The preferred orientation, morphologies and magnetostriction of the TbDyFe rods with directional solidification or annealing have been investigated. The 〈1 1 0〉 preferred orientation remains unchanged after annealing. The net-shaped pseudo-eutectic rare earth phase becomes discontinued and spheroidal after annealing for 4 h and shows spheroidal shape without the net-shaped morphology after annealing for 48 h. The magnetostriction slightly decreased after annealing without pre-stress, but increased drastically with pre-stress. An obvious magnetostriction jump effect was observed in the annealed samples. A satisfactory magnetostrictive property of 1970×10 −6 was obtained under 15 MPa pre-stress after 4 h heat treatment without a further improvement for 48 h annealing, which indicates that the heat treatment for 4 h at 1000 °C is proper for the present 〈1 1 0〉 oriented TbDyFe alloy.

Trabecular rod thickness by direct measurement from 3D SEM anaglyphs.

This study presents a methodology for measuring the thickness of trabecular rods directly from anaglyphs. Macerated sagittal slices of T12 vertebral bodies from 15 subjects were examined by scanning electron microscopy (SEM). Two digital images (the second image tilted 5 degrees ) were recorded, and a 3D anaglyph was created. The thickness of the trabecular rods (Tb.Th((rods))), and the anatomical orientation of the trabecular rods were measured using an image analyser. Conventional 2D histomorphometry was performed on adjacent bone slices. A total of 1559 rod measurements were made from the 15 vertebral bone slices, with a mean Tb.Th((rods)) of 123 +/- 36 microm. The rod thickness in males (128 +/- 34 microm) was significantly greater than that in females (119 +/- 37 microm, P < 0.001). Tb.Th((rods)) changed significantly with age in the males: the thicker rods in the younger men reduced with age to a thickness similar to that in women. 3D measurements were significantly larger than the 2D estimates, and there was no correlation between the two methods of measurement. An inverse correlation was found between the number of rods and the bone volume fraction (BV/TV), indicating that decreased BV/TV is associated with an increased number of rods. The vertical rods (132 +/- 39 microm) were significantly thicker than the horizontal rods (116 +/- 33 microm, P < 0.001). The determination of rod numbers, and their orientation and individual thicknesses enables a greater understanding of cancellous bone architecture in both individuals and populations, and will allow more reliable finite element modelling. Direct measurements from 3D anaglyphs of intact specimens provide new data that show previously unrecognised age- and sex-related changes.

Description of the state of deformation of ethylene-tetrafluoroethylene alternating copolymer films estimated by using a model proposed in terms of orientation of crystallites within a rod

To study the deformation mechanism of ethylene–tetrafluoroethylene alternating copolymer films caused by elongation, a model relating crystal orientation to the orientation of the rods was proposed. The orientation distribution of crystallites within the rod was given as the correlation with the rod orientation. The distribution functions of a given reciprocal lattice vector of the crystal plane were derived from the two functions of the crystallites and of rods with several parameters representing the orientation of rods and the rotation of crystallites within a rod. By choosing suitable values of the parameters, the calculated functions were in good agreement with the results of X-ray diffraction experiments. From the values of the parameters to give the best fit between calculated and observed results, it turned out that the characteristic orientation of the c-axis is mainly due to the preferential orientation of the rod with respect to a stretching direction and is hardly affected by the rotation of crystallites within the rod. Using the two orientation functions concerning rods and crystallites, Hv light scattering was formulated by introducing an interparticle interference effect of the rods. The calculated results assumed the characteristic profile of the observed patterns as the superposition of broadleaf lobes and a sharp pattern of streaks.

Controllable Orientation of Helical Poly(L-glutamic acid) Rods through Macrodipole Interaction on Gold Surfaces and Vectorial Electron Transfer

Controllable Orientation of Helical Poly(L-glutamic acid) Rods through Macrodipole Interaction on Gold Surfaces and Vectorial Electron Transfer

Molecular Orientation of Amphiphilic Block Copolymer of Poly (peptide-co-ethylene glycol) at Air-Water Interface.

An amphiphilic block copolymer of poly(L-leucine-co-ethylene glycol)(PLeu40-PEG114) was prepared and spread at an air-water interface to form a stable monolayer. α-helical conformation of PLeu segment of the block copolymer in the monolayer was confirmed by the circular dichroism (CD) and FT-IR measurements. The surface pressure-area (π-A) isotherm of the monolayer indicated that the α-helix rod of the PLeu segment oriented slightly normal to the air-water interface by increasing the surface pressure of the monolayer. The PLeu40-PEG114 monolayer could be transferred on the Au surface, and the molecular orientation of PLeu helix rods was estimated by FT-IR reflection absorption spectroscopy (FT-IR/RAS) measurements. As a result, it was also confirmed that α-helix rod of the block copolymer oriented slightly normal to the Au surface. Therefore, PEG segment in the block copolymer was essential for the tilting of the PLeu helix rod at the interface, however, which may act in turn as a fault for the further standing of helix rod by the additional compression of the monolayer.

Flow Studies of a Surfactant Hexagonal Mesophase

We utilize real-time scattering techniques to examine the mesoscopic and molecular response of a nonionic surfactant hexagonal mesophase to shear and extensional flows. These results are correlated with the rheological response in simple shear. During shear there is an initial modest orientation of the surfactant rods along the flow direction. This is followed by a progressive further increase in alignment over the next 500 shear units. This process of rod alignment corresponds to the progressive development of shear thinning, which might be anticipated from molecular theories developed for liquid crystalline polymer systems (LCPs). It is surprising, however, that equilibrium requires such large strains, not seen in LCPs, possibly due to a unique feature of the surfactant mesophase: the ability to rupture under stress and reform. This long structure induction time has clear implications for conventional rheology, which may rarely reach an equilibrium response. By contrast, in an extensional flow the orie...

Optical Properties of Aligned Rod-Shaped Gold Particles Dispersed in Poly(vinyl alcohol) Films

The polarization spectra of template-synthesized colloidal gold rods with aspect ratios ranging from L/d = 1.8 to 49 (and a diameter d = 15 nm) embedded in poly(vinyl alcohol) (PVA) films are studied as a function of the film elongation. Orientation of the colloidal gold rods is obtained by stretching the PVA films. The polarization absorbance spectra of aligned systems show only one resonance band instead of two absorbance bands as found for randomly distributed gold rods. The visible and near-infrared spectra reveal that the rods are completely oriented when the film is stretched 4−6 times its original length. No significant effect of the aspect ratio is observed on the film elongation required for complete alignment. The alignment of gold rods by the stretched-film method is visualized by reflection confocal scanning laser microscopy (CSLM). The CSLM micrographs also demonstrate the distribution of single gold rods in the film.

Ligand-induced association of helical polypeptides at the air–water interface. Orientation of helix rods on water

Download options Please wait... Article information DOI https://doi.org/10.1039/A706469A Article type Paper Download Citation J. Mater. Chem., 1998,8, 633-636 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Ligand-induced association of helical polypeptides at the air–water interface. Orientation of helix rods on water M. Niwa, T. Takada and N. Higashi, J. Mater. Chem., 1998, 8, 633 DOI: 10.1039/A706469A To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author Masazo Niwa Takeshi Takada Nobuyuki Higashi

Alpe Arami: a peridotite massif from the Mantle Transition Zone?

Petrologic discoveries made over the last ten years have shown that in regions of continent-continent collision, rocks of the continental crust can be subducted to much greater depths than previously considered reasonable. Documentation of such extreme subduction has come from discovery of diamond, coesite and other high pressure phases; in many cases these phases, metastable at the Earth's surface, are only preserved as inclusions in strong, refractory minerals that either have a broad pressure range of stability or exhibit very sluggish kinetics of reaction to low pressure forms. The Alpe Arami peridotite of the Swiss Alps displays extensive exsolution of FeTiO 3 rods in the oldest generation of olivine. The shape, orientation and abundance of the titanate rods provide strong indication that the phase originally exsolved was the orthorhombic pervoskite phase stable only at pressures greater than 10 GPa (300 km depth) at mantle temperatures. We show here that the dislocation substructure of the oldest generation of olivine is younger than the titanate rods and similar to that observed in peridotites the world over and in experiments; the slip systems represented are incapable of producing the unique and unexplained lattice preferred orientation (LPO) displayed by this generation of olivine. We also have conducted preliminary experiments to investigate the maximum solubility of FeTiO 3 in olivine. Our results suggest that the solubility of TiO 2 implied by the abundance of titanate precipitates may be impossible under any conditions of olivine stability. On the other hand, the measured solubility in wadsleyite (β-olivine) under the conditions of our experiments is comparable to that inferred for Alpe Arami olivine. This latter observation combined with the determination that the titanate rods and LPO of this generation of olivine are the oldest features yet identified in these rocks, leads us to speculate that this massif has been brought to the Earth's surface from within the mantle transition zone, at depths of 410–660 km. The only mechanism by which we can envision this to have been accomplished is for the Lepontine gneisses that now surround the massif to have been subducted to great depth following collision of Africa and Europe, and to have picked up the peridotite on their way back to the surface by buoyant upwelling.

Porous channels in the cuticle of the head-arrester system in dragon/damselflies (Insecta:Odonata).

The ultrastructure of the porous channels (PC) of the postcervical sclerite (SPC), which provides additional head fixation to the neck in adult odonates, was studied using TEM and high resolution SEM microscopy. Single chitin-protein microfibrils, about 0.14 micron thick, are arranged into channels with cylinder-like shapes. The axial rod of the chitin fiber (0.04 micron thick) is located in the center of the cylinder. The orientation of the axial rods was three-dimensionally demonstrated after dissolving the protein cover with NaOH. The PCs are arranged vertically to the surface and pass from the epidermal cells through all the cuticular layers to the surface of the cuticle. In the exo- and endocuticle, the PCs are usually oval in cross-section and about 0.3 micron thick. In the endocuticle, the cross-sectional area of the PCs varies widely, from 0.01-0.15 micron2. The shape of the PC is determined by the macromolecular organization of the chitin-protein microfibrils: the long axis of the channel is orientated parallel to the axis of the preferred orientation of the cuticular microfibrils. The microfibrils tend to follow the line of the channel very closely. In fractures orientated perpendicular to the surface, the PC resembles a ribbon-like construction, which was clearly demonstrated by casts. The strongly parallel orientation of PCs in the deep layers of the cuticle changes within the microtrichia (MT), and they begin to be curved. Numerous PCs pass through the microtrichium, and most of them end on its side wall. PCs usually contain channel filaments about 0.09 micron thick. Usually, a single channel contained one filament, but channels located in the deep layers of the endocuticle have from one to five single filaments. The filaments were observed in the intact cuticle and in the cuticle enzymatically treated with chitinase, while in the cuticle treated with NaOH filaments were absent. The porous channel system of the odonate arrester is interpreted as a device transporting adhesive excretions from the epidermal cells to the cuticular surface.

Porous channels in the cuticle of the head‐arrester system in dragon/damselflies (Insecta: Odonata)

The ultrastructure of the porous channels (PC) of the postcervical sclerite (SPC), which provides additional head fixation to the neck in adult odonates, was studied using TEM and high resolution SEM microscopy. Single chitin-protein microfibrils, about 0.14 μm thick, are arranged into channels with cylinder-like shapes. The axial rod of the chitin fiber (0.04 μm thick) is located in the center of the cylinder. The orientation of the axial rods was three-dimensionally demonstrated after dissolving the protein cover with NaOH. The PCs are arranged vertically to the surface and pass from the epidermal cells through all the cuticular layers to the surface of the cuticle. In the exo- and endocuticle, the PCs are usually oval in cross-section and about 0.3 μm thick. In the endocuticle, the cross-sectional area of the PCs varies widely, from 0.01–0.15 μm2. The shape of the PC is determined by the macromolecular organization of the chitin-protein microfibrils: the long axis of the channel is orientated parallel to the axis of the preferred orientation of the cuticular microfibrils. The microfibrils tend to follow the line of the channel very closely. In fractures orientated perpendicular to the surface, the PC resembles a ribbon-like construction, which was clearly demonstrated by casts. The strongly parallel orientation of PCs in the deep layers of the cuticle changes within the microtrichia (MT), and they begin to be curved. Numerous PCs pass through the microtrichium, and most of them end on its side wall. PCs usually contain channel filaments about 0.09 μm thick. Usually, a single channel contained one filament, but channels located in the deep layers of the endocuticle have from one to five single filaments. The filaments were observed in the intact cuticle and in the cuticle enzymatically treated with chitinase, while in the cuticle treated with NaOH filaments were absent. The porous channel system of the odonate arrester is interpreted as a device transporting adhesive excretions from the epidermal cells to the cuticular surface. Microsc. Res. Tech. 37:583–591, 1997. © 1997 Wiley-Liss, Inc.

Mathematical modeling and computer simulations of the flow, nematic phase orientation, and heat transfer in thermotropic liquid crystalline polymers

AbstractThis study includes a mathematical analysis and computer simulations of the injection molding of thermotropic liquid crystalline polymers (LCPs). The particular area of interest is the modeling and numerical evaluation of the orientation of the rigid rods in the nematic phase of LCPs during the filling stage of injection molding. The model is based on a continuum mechanics approach in order to derive the orientation distribution function of rigid rods for different orientation angles. Numerical distributions of average orientation factors are also derived. Computer simulations have been conducted in case studies that investigate the effects of changes in the processing conditions.

Directional solidification of TbDyFe magnetostrictive alloy

Grain-aligned rods of the huge magnetostrictive TbDyFe alloy have been prepared by directional solidification techniques. Axial grain orientation, phase spacing and elemental distribution of the alloy rods have been investigated. It was found that unseeded rods usually show a strong 〈112〉 orientation at higher growth rate regime. At lower growth rate regime, 〈110〉 axial grain orientation was often observed. In all the rods, a range of phase spacing existed. The average spacing was more sensitive to the temperature gradient than the growth rate. Large spacing was achieved with lower temperature gradient and lower growth rates. It was also found that different partition of Tb and Dy in the Laves phase and RE-rich phase existed, as well as the microsegregation of Tb and Dy. These led to a higher Tb/Dy atomic ratio in the RE-rich phase and a variation of the Tb/Dy ratio in the cellular Laves phase sheets. To explain the different axial grain orientations, a model was proposed. An orientation selection principle was adopted such that an orientation with a higher local interface temperature among competing orientations was preferred. The effects of the kinetic attachment anisotropy and the surface tension anisotropy were considered.