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Random Orientation (random + orientation)
Selected AbstractsThe Optimal Grain Sized Nanocrystalline Ni with High Strength and Good Ductility Fabricated by a Direct Current Electrodeposition,ADVANCED ENGINEERING MATERIALS, Issue 6 2008X. Shen In this work, six pure Ni specimen which mean grain sizes spans a broad range from ultra-fine to nanometer were fabricated by direct current electrodeposition and a coarse grain Ni was obtained by annealing. A gradual transition of the crystallographic preferred orientation of the deposited Ni from (200) texture to isotropic or random orientation with decreasing the mean grain size was revealed by XRD. [source] Canopy structure in savannas along a moisture gradient on Kalahari sandsGLOBAL CHANGE BIOLOGY, Issue 3 2004Robert J. Scholes Abstract Measurements of tree canopy architecture were made at six savanna sites on deep, sandy soils, along a gradient of increasing aridity. There was substantial variation in the leaf area estimated within each site, using the same sample frame, but different measurement techniques. The trends in canopy properties in relation to the aridity gradient were consistent, regardless of the technique used for estimating the properties. The effective plant area index for the tree canopy (the sum of the stem area index and the leaf area index (LAI)) declined from around 2 to around 0.8 m2 m,2 over a gradient of mean annual rainfall from 1000 to 350 mm. Stems contributed 2,5% of the tree canopy plant area index. Since the tree canopy cover decreased from 50% to 20% over this aridity range, the leaf area index within the area covered by tree canopies remained fairly constant at 3,4 m2 m,2. Tree leaves tended from a horizontal orientation to a more random orientation as the aridity increased. On the same gradient, the leaf minor axis dimension decreased from around 30 mm to around 3 mm, and the mean specific leaf area decreased from 14 to 5 m2 kgha,1. There was good agreement between LAI observed in the field using a line ceptometer and the LAI inferred by the MODIS sensor on the Terra satellite platform, 2 months later in the same season. [source] Effects of lithium carbonate on rat seminiferous tubules: an ultrastructural studyINTERNATIONAL JOURNAL OF ANDROLOGY, Issue 6 2006O. Zarnescu Summary Lithium salts are commonly used for treatment of bipolar disorder but prolonged treatment with therapeutic doses induces substantial toxic effects. In the present study we examined the effects of lithium carbonate on the ultrastructure of rat seminiferous tubules. Rats were exposed to lithium carbonate at doses of 35 mg/kg/day for 21 days. After lithium treatment, the tunica propria widened and folded together with convolutions of the basement membrane, myoid cells and lymphatic endothelium. In the seminiferous epithelium loss of germ cell attachment and appearance of expanded intercellular spaces between spermatogenic cells were observed. Early stages of spermatogenic cells showed nuclear protrusions or swellings because of an extensive enlargement of the outer nuclear membrane. Round spermatids exhibited abnormally shaped acrosomes and dilation of the subacrosomal space. Many abnormal, degenerated late spermatids with random orientation were seen towards the basal and adluminal compartments of the seminiferous epithelium. In addition, spermatids exhibited alteration in F-actin bundle ectoplasmic specialization and contained many mitochondria-associated granular bodies. [source] Promoted random orientation of the phenyl substituent of phenylhydroquinone,terephthalic acid polyesters prepared with a diphenyl chlorophosphate/pyridine condensing agentJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2001Fukuji Higashi Abstract The reaction of sterically hindered hydroxyl groups at the 2-position of methylhydroquinone and phenylhydroquinone (PhHQ) to form esters was largely promoted by their slow addition to benzoic acid activated by diphenyl chlorophosphate in pyridine. A modification of this reaction was applied to the preparation of thermotropic terephthalic acid/PhHQ and 2,5-dichloroterephthalic acid/PhHQ polymers with randomly oriented phenyl substituents, and the properties of the polymers were studied in terms of their transition temperatures, which were determined by differential scanning calorimetry and microscopic observation. The melting points were lowered by about 30,50 °C by the dropwise addition of PhHQ over 10,30 min. The molecular structures of the 2,5-dichloroterephthalic acid/PhHQ polymers were studied by 13C NMR. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1726,1732, 2001 [source] Formation of High-Quality, Epitaxial La2Zr2O7 Layers on Biaxially Textured Substrates by Slot-Die Coating of Chemical Solution PrecursorsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2007Sung-Hun Wee Crystallization studies were performed of epitaxial La2Zr2O7 (LZO) films on biaxially textured Ni,3at.%W substrates having thin Y2O3 (10 nm) seed layers. LZO films were deposited under controlled humid atmosphere using reel-to-reel slot-die coating of chemical solution precursors. Controlled crystallization under various processing conditions has revealed a broad phase space for obtaining high-quality, epitaxial LZO films without microcracks, with no degradation of crystallographic texture and with high surface crystallinity. Crack-free and strong c -axis aligned LZO films with no random orientation were obtained even at relatively low annealing temperatures of 850°,950°C in flowing one atmosphere gas mixtures of Ar,4% H2 with an effective oxygen partial pressure of P(O2),10,22 atm. Texture and reflection high-energy electron diffraction analyses reveal that low-temperature-annealed samples have strong cube-on-cube epitaxy and high surface crystallinity, comparable to those of LZO film annealed at high temperature of 1100°C. In addition, these samples have a smoother surface morphology than films annealed at higher temperatures. Ni diffusion rate into the LZO buffer film is also expected to be significantly reduced at the lower annealing temperatures. [source] Preferred Orientation of Bi4Ti3O12 Thick FilmJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2007Yoshiaki Kinemuchi The preferred orientation of thick films prepared by paste printing is rarely observed because of their bulky polycrystalline nature. We found that a Bi4Ti3O12 thick film with a thickness of ca. 20 ,m showed c -axis-preferred orientation. Initially, the texture of the screen-printed film was found to have a random orientation, which was attributed to the equiaxed particle shape of the raw powder synthesized by the co-precipitation method. During subsequent heating, c -axis orientation emerged in which the degree of orientation was proportional to the film density. Analysis of the orientation distribution revealed that the progress of texturing was attributed to the film deformation, indicating that anisotropic shrinkage and morphological changes in particles during heating influenced the preferred orientation. [source] Crystallographic Texture Development in Bismuth Sodium Titanate Prepared by Reactive-Templated Grain Growth MethodJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2004Toshio Kimura Bi0.5Na0.5TiO3 (BNT) and 0.94Bi0.5Na0.5TiO3·0.06BaTiO3 (BNT,BT) bulk ceramics with extensive ,100, texture were prepared by the reactive-templated grain growth method, using platelike Bi4Ti3O12 (BIT) particles as templates for BNT. Calcined compacts were composed of matrix grains with random orientation and ,100,-oriented grains transformed from aligned BIT particles, and the texture developed by the growth of oriented grains during sintering. Ceramics with extensive texture were obtained by using the starting mixture containing the maximum concentration of platelike BIT to form the maximum volume fraction of oriented grains. [source] Toughening by Multiple Mechanisms in Ceramic-Matrix Composites with Discontinuous Elongated ReinforcementsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2000Hongxiang Zhai The dependence of toughening mechanisms on reinforcement orientation and the toughening effect governed by multiple toughening mechanisms were characterized for ceramic-matrix composites (CMCs) with discontinuous elongated reinforcements. Two kinds of Si3N4 -based composites, with directionally oriented and randomly oriented SiC whiskers, respectively, were tested by the three-point bending of chevron-notched bars. Based on microscopic observations and micromechanical analyses, three mechanisms were confirmed to dominate the crack-bridging behavior: (1) bridging and breaking of long reinforcements, (2) frictional pullout and breaking of short reinforcements, and (3) local matrix spalling. Both the occurrence of the multiple mechanisms and their toughening effects were proved dependent on the reinforcement orientation. The combined effect of the multiple mechanisms correlated with random orientation thus was characterized by a statistical approach to solve for the crack-bridging stress function. The theoretical model was in good agreement with the experimental results. [source] A Simple Approximate Formula for the Aspect Ratio of Oblate ParticlesPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 6 2007Willi Pabst Abstract A simple approximative formula is derived, which can be used to quantify the shape of oblate particles or an average shape of the corresponding particle system, when the results of sedimentation analysis (Stokes equivalent diameters) are known and results from either microscopic image analysis (assuming stable orientation, i.e., with the plane perpendicular to the direction of observation) or laser diffraction (assuming random orientation) are available for the same sample. In the latter case Cauchy's stereological theorem is applied to account for random orientation. Furthermore, it is shown that for sufficiently large aspect ratios, this formula is very close to the well-known Jennings-Parslow relation and can replace this more complicated expression in many practical cases, e.g., in the routine characterization of ceramic raw materials (kaolins and oxide or non-oxide platelet powders). [source] Dynamic viscoelasticity of hybrid kevlar and glass fiber reinforced LLDPE in the molten statePOLYMER COMPOSITES, Issue 4 2002S. A. R. Hashmi Kevlar and glass fibers were used to reinforce linear low density polyethylene (LLDPE), and composite sheets of 0.8, 1.5 and 2.5 mm thicknesses were obtained by using a compression molding technique. Dynamic viscoelastic properties of non-hybrid and hybrid composites of various compositions at 200°C are evaluated. Storage modulus (G,) and loss modulus (G,) increase with angular frequency (,) and reinforcement. Replacement of glass fiber by Kevlar at constant loading of fibers in LLDPE increases the value of G,, G, and ,,. The fractured surface of composite shows the gradient orientation of fibers particularly in 2.5 mm thick sheet. Top and bottom layers show relatively two-dimensional orientation as compared to the middle layer, which shows random orientation. The orientation of fibers decreases G, and ,, of Kevlar fiber and hybrid fiber hybrid fiber reinforced LLDPE composites. The effect of change in distance between parallel plate of rheometer (change in strain amplitude) on dynamic rheological properties is studied and reported here. [source] Peptide microarrays for the characterization of antigenic regions of human chromogranin,APROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 14 2005Marcella Chiari Abstract Microarraying peptides is a powerful proteomics technique for studying molecular recognition events. Since peptides have small molecular mass, they are not easily accessible when adsorbed onto solid supports. Moreover, peptides can lack a well-defined three-dimensional structure, and therefore a correct orientation is essential to promote the interaction with their target. In this work, we investigated the suitability as a peptide array substrate of a glass slide coated with a copolymer of N,N -dimethylacrylamide, N,N -acryloyloxysuccinimide, and [3-(methacryloyl-oxy)propyl]trimethoxysilyl. This polymeric surface was used as substrate for peptides in the characterization of linear antigenic sites of human chromogranin,A, a useful tissue and serum marker for neuroendocrine tumors and a precursor of many biologically active peptides. The microarray support provided sufficient accessibility of the ligand, with no need for a spacer, as the polymer chains prevent interaction of immobilized peptides with substrate. In addition, the polymeric surface constitutes an aqueous micro-environment in which linear epitopes are freely exposed despite peptide random orientation. The results reported in this article are in accordance with those obtained in conventional ELISA assays using biotinylated and non-biotinylated peptides. [source] Isomerism of the right atrial appendages: Clinical, anatomical, and microscopic study of a long-surviving case with asplenia and ciliary abnormalitiesCLINICAL ANATOMY, Issue 3 2003R. Raman Abstract This study describes a case of isomerism of the right atrial appendages (bilateral morphologically right atrial appendages associated with complex congenital cardiac lesions) with ciliary abnormalities. Detailed investigation included gross anatomic dissection, review of the clinical history, and light, confocal, and electron microscopy. Clinically, this 40-year-old, long-surviving male patient had relatively good health until 4 years before death, which was due to cardiac failure. Surgical intervention consisted only of a Blalock-Taussig shunt (anastomosis of the right subclavian artery to the right pulmonary artery) at 6 years of age. Despite the presence of complex cardiac malformations and asplenia, his longevity may be attributed to the connection of the pulmonary veins to the atrium without pulmonary venous obstruction, pulmonary valvar stenosis rather than atresia, no significant atrioventricular valve regurgitation, and no serious infections during his life. Microscopic examination of bronchial epithelium revealed a narrow, disorganized epithelium with abundant goblet cells and short, angulated cilia with a random orientation and possibly an abnormal central microtubule doublet. These abnormalities were not present in controls, and have been noted in primary ciliary dyskinesia (PCD) or Kartagener's syndrome. Because this syndrome has classically been thought to cause random lateralization resulting in a mirror-imaged arrangement of the organs, the occurrence of truly isomeric patterns is not widely recognized. Whereas polysplenia and left bronchial isomerism have been reported to occur in immotile cilia syndrome, this is the first report to present detailed postmortem anatomic evidence of isomerism of the right atrial appendages, right bronchial isomerism, and asplenia in association with microscopy suggesting ciliary abnormalities. Clin. Anat. 16:269,276, 2003. © 2003 Wiley-Liss, Inc. [source] Precipitation of MgO·nAl2O3 in Mg-Doped ,-Al2O3 under Electron IrradiationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2003Kenji Kaneko A number of nanoscale precipitates with random orientations were produced by electron irradiation of polycrystalline Mg-doped ,-Al2O3. The precipitation behavior and microstructural changes were observed using in situ high-resolution transmission electron microscopy. A ring pattern corresponding to a polycrystalline fcc structure was obtained from the region of these precipitates by selected-area diffraction, and they were identified as nonstoichiometric MgO·nAl2O3. It is believed that Al2O3 with MgO(ss) and/or MgO at the grain boundaries is effectively stabilized by the electron irradiation process, forming the fundamental structure of MgO·nAl2O3. The average size of the precipitates is about 10 nm. [source] Phytochrome-mediated agravitropism in Arabidopsis hypocotyls requires GIL1 and confers a fitness advantageTHE PLANT JOURNAL, Issue 4 2006Trudie Allen Summary Plants use specialized photoreceptors to detect the amount, quality, periodicity and direction of light and to modulate their growth and development accordingly. These regulatory light signals often interact with other environmental cues. Exposure of etiolated Arabidopsis seedlings to red (R) or far-red (FR) light causes hypocotyls to grow in random orientations with respect to the gravitational vector, thus overcoming the signal from gravity to grow upwards. This light response, mediated by either phytochrome A or phytochrome B, represents a prime example of cross-talk between environmental signalling systems. Here, we report the isolation the mutant gil1 (for gravitropic in the light) in which hypocotyls continue to grow upwards after exposure of seedlings to R or FR light. The gil1 mutant displays no other phenotypic alterations in response to gravity or light. Cloning of GIL1 has identified a novel gene that is necessary for light-dependent randomization of hypocotyl growth orientation. Using gil1, we have demonstrated that phytochrome-mediated randomization of Arabidopsis hypocotyl orientation provides a fitness advantage to seedlings developing in patchy, low-light environments. [source] Sodium magnesium bis(vanadate) pyrovanadate: Na6Mg2(VO4)2(V2O7)ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2004Alexander Mitiaev The crystal structure of the new complex vanadium oxide Na6Mg2(VO4)2(V2O7) was solved from X-ray single-crystal data. The structure contains VO4 tetrahedra and MgO6 octahedra, linked by corners and forming a complex three-dimensional framework. A half of the VO4 tetrahedra are connected only to MgO6 octahedra, whereas the others are corner-sharing, forming V2O7 pyrovanadate groups with statistically random orientations. One unique Mg atom is located at an inversion centre, while the other Mg atom, one unique V atom and five unique O atoms lie on mirror planes. [source] | ||||||||||||||||