Home About us Contact
|
Home About us Contact | ||
|
|
||
Spherical Structures (spherical + structure)
Selected AbstractsUltrastructural study of the precursor to fungiform papillae prior to the arrival of sensory nerves in the fetal ratJOURNAL OF MORPHOLOGY, Issue 3 2001Shin-ichi Iwasaki Abstract The structure of precursors to fungiform papillae without taste buds, prior to the arrival of sensory nerve fibers at the papillae, was examined in the fetal rat on embryonic day 13 (E13) and 16 (E16) by light and transmission electron microscopy in an attempt to clarify the mechanism of morphogenesis of these papillae. At E13, a row of rudiments of fungiform papillae was arranged along both sides of the median sulcus of the lingual dorsal surface, and each row consisted of about 10 rudiments. There was no apparent direct contact between papillae rudiments and sensory nerves at this time. Bilaterally towards the lateral side of the tongue, adjacent to these first rudiments of fungiform papillae, a series of cord-like invaginations of the dorsal epithelium of the tongue into the underlying connective tissue, representing additional papillary primordia parallel to the first row, was observed. The basal end of each invagination was enlarged as a round bulge, indented at its tip by a mound of fibroblasts protruding into the bulge. At E16 there was still no apparent direct contact between rudiments of fungiform papillae and sensory nerves. Each rudiment apically contained a spherical core of aggregating cells, which consisted of a dense assembly of large, oval cells unlike those in other areas of the lingual dorsal epithelium. The differentiation of these aggregated cells was unclear. The basal lamina was clearly recognizable between the epithelium of the rudiment of fungiform papillae and the underlying connective tissue. Spherical structures, which appeared to be sections of the cord-like invaginations of the lingual epithelium that appeared on E13, were observed within the connective tissue separated from the dorsal lingual epithelium. Transverse sections of such structures revealed four concentric layers of cells: a central core, an inner shell, an outer shell, and a layer of large cells. Bundles of fibers were arranged in the central core, and the diameters of bundles varied somewhat depending on the depth of the primordia within the connective tissue and their distance from the median sulcus. Ultrastructural features of cells in the outer shell differed significantly in rudiments close to the lingual epithelium as compared to those in deeper areas of connective tissue. Around the outer shell there was a large-cell layer consisting of one to three layers of radially elongated, oval cells that contained many variously sized, electron-dense, round granules. Large numbers of fibroblasts formed dense aggregates around each spherical rudiment, and were separated by the basal lamina from the large-cell epithelial layer. Progressing from deep-lying levels of the rudiments of the papillae to levels close to the lingual surface epithelium, the central core, inner shell, and outer shell gradually disappeared from the invaginated papillary cords. J. Morphol. 250:225,235, 2001. © 2001 Wiley-Liss, Inc. [source] PY181 Pigment Microspheres of Nanoplates Synthesized via Polymer-Induced Liquid PrecursorsADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Yurong Ma Abstract Organic pigments are important crystalline substances, and their properties and applications rely on size and shape control. Pigment Yellow 181 (PY181) is an industrial azo pigment that is light and weatherfast and suitable for high temperature processing. One disadvantage is its needle-like shape in the default , -phase, which makes the pigment difficult to process in industry, e.g., in polymer melts, where a spherical structure would be ideal. Here, we show for the first time, that polymer-induced liquid precursor structures can be formed even in association to a chemical reaction. Furthermore, it is demonstrated that biomineralization principles can be exploited for the generation of advanced functional materials, such as pigments with novel complex morphology and different properties. Stable PY181 microspheres of nanoplates in the , -phase were obtained in mixed solvents of water and isopropanol by direct azo coupling under the directing influence of a designed copolymer additive aminobenzoylaminobenzamide-acetoacetyl-poly(ethylene imine)- block -poly(ethylene glycol) (ABABA-acetoacetyl-PEI- b -PEG). [source] TiO2 -Coated Multilayered SnO2 Hollow Microspheres for Dye-Sensitized Solar CellsADVANCED MATERIALS, Issue 36 2009Jiangfeng Qian TiO2 -coated multilayered SnO2 hollow microspheres exhibit a high overall photoconversion efficiency of ,5.65% when used for dye-sensitized solar-cell photoelectrodes due to multiple reflecting and scattering of incident light in the hierarchical hollow spherical structure. [source] The substituent effects on the structure and surface morphology of polyanilineJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Mutlu Sahin Abstract In this work, poly(2-fluoroaniline), poly(2-chloroaniline), poly(2-methylaniline), and poly(N -ethylaniline) were prepared by a self-assembly method using an oxidizing system consisting of a dopant anion, p-toluene sulfonate with ammonium peroxydisulfate. The effects of substituents on the surface morphology, conductivity, molecular weight, spectral and thermal properties of the polymers were studied. SEM results revealed that the surface morphology of the resulting polymers changed from nanofiber to spherical structure by changing the substituent on the aniline monomers. The structure and properties of these conducting films were characterized by FTIR, UV-vis, elemental analysis, TGA, conductivity, and cyclic voltammetry. The polymer films show electroactivity in monomer free solution. Molecular weight of the polymers was determined by gel permeation chromatography. The dry electrical conductivity values of the substituted-polyanilines were found to be lower than that of PANI. The results revealed that the molecular structures of the polymers were similar to those of the emeraldine form of polyaniline. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Preparation of a Transparent Spherical Polymer Matrix Containing TiO2/SiO2 Hybrid MaterialsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 4 2008D.-H. Zhang Abstract A transparent spherical polymer matrix containing TiO2/SiO2 hybrid materials is prepared from the copolymerization reaction between TiO2/SiO2 hybrid materials containing vinyl groups and methyl methacrylate (MMA). Transparent TiO2/SiO2 hybrid materials are prepared from the reaction between nucleophilic agents and tetrabutyl titanate (TBT). Three reaction mechanisms leading to the formation of nanometer TiO2/SiO2 hybrid materials, including the single group coordination reaction mechanism (SGCRM), double group chelation reaction mechanism (DGCRM) and bridge coordination reaction mechanism (BCRM) are discussed in detail and confirmed by FT-IR spectroscopy. The sizes of the TiO2/SiO2 hybrid material nanoparticles are also characterized and calculated by TEM and range from 20,40,nm. The diameter of the particles in the transparent spherical polymer matrix is ca. 100,200,nm and their shape is a regular spherical structure from TEM observations. The transparent spherical polymer matrix containing TiO2/SiO2 hybrid materials could be used as holographic anti-counterfeiting materials. [source] Biomimetic Composites: Protein Localization in Silica Nanospheres Derived via Biomimetic Mineralization (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 18 2010Mater. Abstract Lysozyme-templated precipitation of silica synthesized by sol-gel chemistry produces a composite material with antimicrobial properties. This study investigates the structural properties of the composite material that allow for retention of the antimicrobial activity of lysozyme. Scanning (SEM) and transmission (TEM) electron microscopy reveal that the composite has a hierarchical structure composed of quasi-spherical structures (,450 nm diameter), which are in turn composed of closely packed spherical structures of ,8,10 nm in diameter. Using small-angle neutron scattering (SANS) with contrast variation, the scattering signatures of the lysozyme and silica within the composite were separated. It was determined that the lysozyme molecules are spatially correlated in the material and form clusters with colloidal silica particles. The size of the clusters determined by SANS agrees well with the structural architecture observed by TEM. BET analysis revealed that the surface area of the composite is relatively low (4.73 m2/g). However, after removal of the protein by heating to 200 °C, the surface area is increased by ,20%. In addition to demonstrating a well organized sol-gel synthesis which generates a functional material with antimicrobial applications, the analysis and modeling approaches described herein can be used for characterizing a wide range of mesoporous and ultrastructural materials. [source] Protein Localization in Silica Nanospheres Derived via Biomimetic MineralizationADVANCED FUNCTIONAL MATERIALS, Issue 18 2010Mateus B. Cardoso Abstract Lysozyme-templated precipitation of silica synthesized by sol-gel chemistry produces a composite material with antimicrobial properties. This study investigates the structural properties of the composite material that allow for retention of the antimicrobial activity of lysozyme. Scanning (SEM) and transmission (TEM) electron microscopy reveal that the composite has a hierarchical structure composed of quasi-spherical structures (,450 nm diameter), which are in turn composed of closely packed spherical structures of ,8,10 nm in diameter. Using small-angle neutron scattering (SANS) with contrast variation, the scattering signatures of the lysozyme and silica within the composite were separated. It was determined that the lysozyme molecules are spatially correlated in the material and form clusters with colloidal silica particles. The size of the clusters determined by SANS agrees well with the structural architecture observed by TEM. BET analysis revealed that the surface area of the composite is relatively low (4.73 m2/g). However, after removal of the protein by heating to 200 °C, the surface area is increased by ,20%. In addition to demonstrating a well organized sol-gel synthesis which generates a functional material with antimicrobial applications, the analysis and modeling approaches described herein can be used for characterizing a wide range of mesoporous and ultrastructural materials. [source] Morphological features of Murray Valley encephalitis virus infection in the central nervous system of swiss miceINTERNATIONAL JOURNAL OF EXPERIMENTAL PATHOLOGY, Issue 1 2000Vance Matthews We have examined the histological and ultrastructural features of CNS infection with Murray Valley encephalitis (MVE) virus in mice inoculated with a virulent parental strain (BH3479). Light microscopic examination revealed neuronal necrosis in the olfactory bulb and hippocampus of MVE-infected brains by 5 days post-infection (pi). Electron microscopy of these regions showed endoplasmic reticulum membrane proliferation, and tubular and spherical structures in the cisternae of the endoplasmic reticulum, Golgi complex and nuclear envelope. At seven to eight days pi, infected neurones exhibited chromatin condensation and extrusion, nuclear fragmentation, loss of segments of the nuclear envelope, reduced surface contact with adjacent cells and loss of cytoplasmic organelles. This cell injury was particularly noticeable in the proximal CA3 and distal CA1 regions of the hippocampus. The inflammatory cell profile consisted of macrophages, lymphocytes and especially neutrophils, and many of these inflammatory cells were apoptotic. High mortality rates in the BH3479-infected population of mice correlated with the intense polymorphonuclear and mononuclear leucocyte inflammatory infiltrate in the CNS. [source] Sonochemical Synthesis of CdSe Hollow Spherical Assemblies Via an In-Situ Template RouteADVANCED MATERIALS, Issue 2 2003J.J. Zhu CdSe hollow spherical assemblies composed of 5 nm nanoparticles have been synthesized sonochemically. During the process, amorphous Cd(OH)2, which acts as the in-situ template, directs the growth of primary CdSe nanoparticles on its surface and their assembly into hollow spherical structures. The Figure is a schematic of the proposed mechanism for the formation of the hollow chalcogenide spheres. [source] Synthesis and Self-Assembly of Novel Amphiphilic Six-Armed Star Copolymers TP[PDMAEMA -b- PSt]6MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 6 2009Kang Tao Abstract A triphenylene (TP)-based hexafunctional initiator was prepared and used in successive ATRP of DMAEMA and St. Well-defined six-armed star block copolymers TP[PDMAEMA -b- PSt]6 bearing hydrophilic backbones inside and hydrophobic blocks outside were successfully synthesized. The self-assembly behaviors of the novel amphiphilic copolymer were further investigated. Co-existing spherical and bowl-shaped aggregates were observed from their neutral aqueous solution, while large spherical structures with different dimensions were obtained from their diluted HCl and CF3COOH aqueous solution, respectively. Dynamic light scattering in different aqueous solutions were conducted to give further confirmation. The possible mechanism of the morphology formation was proposed. [source] Shape transition of medium-sized neutral silicon clustersPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2003A. Sieck Abstract Addressing the shape transition of silicon clusters, indicated by mobility experiments on silicon cluster cations with 24 to 30 atoms, we investigate the structure of low energy neutral silicon clusters with 25, 29, and 35 atoms within a density-functional based tight-binding approach. Since there is strong evidence for several nearly degenerate low-energy isomers for clusters of this size, we perform an extensive, but limited global search with Simulated Annealing and statistically analyze for each cluster size the 100 clusters with the lowest energy. We find different dominant shapes in the set of low energy clusters for each size. For neutral silicon clusters with 25 atoms, both prolate and spherical structures with low cohesive energies exist. For clusters containing 29 or 35 atoms, the low-energy isomers exhibit a spherical shape. For each cluster size several stable isomers with similar shapes, and hence similar mobilities, but different bonding patterns exist. The most stable 25 atom cluster resulting from our global search has the lowest energy within DFT-GGA known so far. Finally, we investigate the transition to diamond-like bonding patterns expected for larger silicon clusters. Clusters with up to 239 atoms resemble amorphous silicon rather than the diamond structure and contain several highly coordinated atoms. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Suppressed blinking in CdTe/CdSe core-shell quantum dotsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2009Viki Kloper Abstract CdTe/CdSe core-shell colloidal quantum dots (CQDs) were synthesized by a unique colloidal procedure permitting the growth of spherical structures with the highest emission quantum efficiency (,90%). The CQDs photoluminescence (PL) intensity shows only minor fluctuations (<10%) in time, revealing a blinking suppression in the CQDs, while the PL of a single CQD shows the occurrence of longer lived (ns) multiexcitons, important for the applications of CQDs also in gain devices. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Subzonal organization of olfactory sensory neurons projecting to distinct glomeruli within the mouse olfactory bulbTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 3 2003Olga Levai Abstract Olfactory sensory neurons located in the nasal neuroepithelium send their axons directly into the olfactory bulb, where they contact the dendrites of second-order neurons in specialized spherical structures called glomeruli; each sensory neuron projects to a single glomerulus. All neurons expressing the same odorant receptor gene are confined to distinct zones within the epithelium and converge their axons onto a small number of common glomeruli. In the present study, we analyzed transgenic mouse lines in which the projection of a neuron population expressing a particular receptor gene can be visualized as a result of axonal markers that are coexpressed. The target glomeruli could thus reproducibly be identified and allowed to deposit retrograde tracers precisely. After an appropriate incubation time, olfactory sensory neurons within distinct areas of the olfactory epithelium were labeled. The two subpopulations of neurons retrogradely stained by differently colored fluorescent dyes deposited at the dorsal and the dorsomedial glomerulus, respectively, were found to be segregated within distinct areas of the expression zone, where the cells expressing the same receptor type displayed a stochastic distribution. J. Comp. Neurol. 458:209,220, 2003. © 2003 Wiley-Liss, Inc. [source] | ||||||||||||||||||||||||||||