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Lateral Dimensions (lateral + dimension)
Selected AbstractsMorphological, structural and optical study of quasi-1D SnO2 nanowires and nanobeltsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10-11 2005D. Calestani Abstract 0.1,0.3 mm thick entanglements of quasi-one-dimensional semiconducting Tin dioxide nanocrystals, in form of nanowires and nanobelts, are successfully grown by low cost Chemical Vapour Deposition directly on large area (100 mm2) Al2O3, SiO2 and Si substrates. Their lateral size ranges from 50 to 700 nm and their length can achieve several hundreds of micrometers. Transmission Electron Microscopy reveals either the nanowires and the nanobelts grow in the tetragonal Rutile structure. Diffraction contrast analyses and selected area diffraction investigations show the nanowires are single crystals without defects while the nanobelts sometimes present twins inside. An almost cylindrical shape and an average diameter of about 30,50 nm for the smallest nanowires is reported. X-ray diffraction investigations exclude the presence of spurious phases. A broad band structured in two emissions peaked at about 450 nm and 560 nm is revealed by large area Cathotoluminescence, while single nanocrystal spectroscopy shows that the reduction of the lateral dimension of the nanobelts from 1000 nm to 50 nm blue-shifts the main emission band at 560 nm of about 40 nm (at room temperature). These preliminary results suggest a possible role of oxygen vacancies and of the surface/volume ratio on the origin and the blue shift of Cathodoluminescence spectra. The near band edge emission, typical of bulk tin dioxide (,320 nm), is not found in nanobelts narrower than 1000 nm. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Macroscopically Aligned Ionic Self-Assembled Perylene-Surfactant Complexes within a Polymer Matrix,ADVANCED FUNCTIONAL MATERIALS, Issue 13 2008Ari Laiho Abstract Ionic self-assembled (ISA) surfactant complexes present a facile concept for self-assembly of various functional materials. However, no general scheme has been shown to allow their overall alignment beyond local polydomain-like order. Here we demonstrate that ionic complexes forming a columnar liquid-crystalline phase in bulk can be aligned within polymer blends upon shearing, taken that the matrix polymers have sufficiently high molecular weight. We use an ISA complex of N,N,-bis(ethylenetrimethylammonium)perylenediimide/bis(2-ethylhexyl) phosphate (Pery-BEHP) blended with different molecular weight polystyrenes (PS). Based on X-ray scattering studies and transmission electron microscopy the pure Pery-BEHP complex was found to form a two-dimensional oblique columnar phase where the perylene units stack within the columns. Blending the complex with PS lead to high aspect ratio Pery-BEHP aggregates with lateral dimension in the mesoscale, having internal columnar liquid-crystalline order similar to the pure Pery-BEHP complex. When the Pery-BEHP/PS blend was subjected to a shear flow field, the alignment of perylenes can be achieved but requires sufficiently high molecular weight of the polystyrene matrix. The concept also suggests a simple route for macroscopically aligned nanocomposites with conjugated columnar liquid-crystalline functional additives. [source] Effects of Individual Layer Thickness on the Microstructure and Optoelectronic Properties of Sol,Gel-Derived Zinc Oxide Thin FilmsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2008Noureddine Bel Hadj Tahar Zinc oxide (ZnO) thin films were prepared under different conditions on glass substrates using a sol,gel process. The microstructure of ZnO films was investigated by means of diffraction analysis, and plan-view and cross-sectional scanning electron microscopy. It was found that the preparation conditions strongly affected the structure and the optoelectronic properties of the films. A structural evolution in morphology from spherical to columnar growth was observed. The crystallinity of the films was improved and columnar film growth became more dominant as the zinc concentration and the substrate withdrawal speed decreased. The individual layer thickness for layer-by-layer homoepitaxy growth that resulted in columnar grains was <20 nm. The grain columns are grown through the entire film with a nearly unchanged lateral dimension through the full film thickness. The columnar ZnO grains are c -axis oriented perpendicular to the interface and possess a polycrystalline structure. Optical transmittance up to 90% in the visible range and electrical resistivity as low as 6.8 × 10,3·,·cm were obtained under optimal deposition conditions. [source] Probing the Building Blocks of Eumelanins Using Scanning Electron MicroscopyPIGMENT CELL & MELANOMA RESEARCH, Issue 3 2000J. BRIAN NOFSINGER Scanning electron microscopy (SEM) is used to examine the structure of natural and synthetic melanins. Eumelanin from Sepia officinalis and synthetic eumelanin are found to be structurally dissimilar. The natural sample has a significant structural order with subunits that have a lateral dimension of ,15 nm. The synthetic samples, on the other hand, appear to be amorphous solids. These results lend support for the existence of fundamental structural units proposed from the analyses of wide-angle X-ray diffraction measurements and previous mass-spectrometry results. These findings also provide insight into the disparate photophysical behavior of Sepia and synthetic eumelanin. [source] Airway Assessment by Volumetric Computed Tomography in Snorers and Subjects With Obstructive Sleep Apnea in a Far-East Asian Population (Chinese)THE LARYNGOSCOPE, Issue 4 2002Ning-Hung Chen MD Abstract Objectives To evaluate the airway dimension of simple snorers and subjects with obstructive sleep apnea (OSA) in a Far-East Asian population (Chinese). Study Design Prospective study of 117 near-consecutive patients evaluated for snoring and possible OSA from January 1998 to December 1998 in a sleep laboratory. Overnight polysomnography (PSG) was performed on all patients and the sleep parameters, including respiratory disturbance index (RDI), snoring index, minimal oxygen saturation (min O2), percentage of slow wave sleep (SWS), and rapid eye movement (REM) were recorded. Three-dimensional computerized tomography (CT) during awake periods was performed. The anteroposterior (AP) and the lateral distance of the retropalatal (RP) region in the oropharynx, the smallest area of RP, and retroglossal (RG) regions, and the total volume of the oropharynx were measured. Result Ninety-eight patients were diagnosed with OSA (mean RDI, 41.48 ± 26.45 events per hour; min O2, 72.82 ± 12.86%), whereas 19 were simple snorers. The AP and the lateral distance of the RP region, as well as the smallest area of the RP region, are significantly smaller in subjects with OSA. However, no differences in the RG region and the total volume of the oropharynx were found between the two groups. Linear regression analysis demonstrated that the lateral dimension and the smallest RP area in overweight subjects inversely correlated with the RDI, but only the AP dimension of the RP area was found to have an inverse correlation with the RDI in the underweight subjects. Conclusion In Far-East Asians (Chinese), the RP airway was found to be the primary site of narrowing in subjects with OSA, and the narrowest RP area was inversely correlated with RDI. Furthermore, weight may influence the pattern of RP narrowing by contributing to lateral collapse. [source] Protein-Enabled Synthesis of Monodisperse Titania Nanoparticles On and Within Polyelectrolyte MatricesADVANCED FUNCTIONAL MATERIALS, Issue 14 2009Eugenia Kharlampieva Abstract Here, the results of a study of the mechanism of bio-enabled surface-mediated titania nanoparticle synthesis with assistance of polyelectrolyte surfaces are reported. By applying atomic force microscopy, surface force spectroscopy, circular dichroism, and in situ attenuated total reflection Fourier-transform infrared spectroscopy, structural changes of rSilC-silaffin upon its adsorption to polyelectrolyte surfaces prior to and during titania nanoparticle growth are revealed. It is demonstrated that the adhesion of rSilC-silaffin onto polyelectrolyte surfaces results in its reorganization from a random-coil conformation in solution into a mixed secondary structure with both random coil and , -sheet structures presented. Moreover, the protein forms a continuous molecularly thin layer with well-defined monodisperse nanodomains of lateral dimensions below 20,nm. It is also shown that rSilC embedded inside the polylelectrolyte matrix preserves its titania formation activity. It is suggested that the surface-mediated, bio-enabled synthesis of nanostructured materials might be useful to develop general procedures for controlled growth of inorganic nanomaterials on reactive organic surfaces, which opens new perspectives in the design of tailored, in situ grown, hybrid inorganic,organic nanomaterials. [source] Electroaddressing of Cell Populations by Co-Deposition with Calcium Alginate HydrogelsADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Xiao-Wen Shi Abstract Electroaddressing of biological components at specific device addresses is attractive because it enlists the capabilities of electronics to provide spatiotemporally controlled electrical signals. Here, the electrodeposition of calcium alginate hydrogels at specific electrode addresses is reported. The method employs the low pH generated at the anode to locally solubilize calcium ions from insoluble calcium carbonate. The solubilized Ca2+ can then bind alginate to induce this polysaccharide to undergo a localized sol-gel transition. Calcium alginate gel formation is shown to be spatially controlled in the normal and lateral dimensions. The deposition method is sufficiently benign that it can be used to entrap the bacteria E. coli. The entrapped cells are able to grow and respond to chemical inducers in their environment. Also, the entrapped cells can be liberated from the gel network by adding sodium citrate that can compete with alginate for Ca2+ binding. The capabilities of calcium alginate electrodeposition is illustrated by entrapping reporter cells that can recognize the quorum sensing autoinducer 2 (AI-2) signaling molecule. These reporter cells were observed to recognize and respond to AI-2 generated from an external bacterial population. Thus, calcium alginate electrodeposition provides a programmable method for the spatiotemporally controllable assembly of cell populations for cell-based biosensing and for studying cell-cell signaling. [source] Influence of Point-Defect Reaction Kinetics on the Lattice Parameter of Ce0.8Gd0.2O1.9ADVANCED FUNCTIONAL MATERIALS, Issue 4 2009Anna Kossoy Abstract The kinetics of point-defect association/dissociation reactions in Ce0.8Gd0.2O1.9 and their influence on the crystal lattice parameter are investigated by monitoring thermally induced stress and strain in substrate- and self-supported thin films. It is found that, in the temperature range of 100,180,°C, the lattice parameter of the substrate-supported films and the lateral dimensions of annealed, self-supported films both exhibit a hysteretic behavior consistent with dissociation/association of oxygen vacancy,aliovalent dopant complexes. This leads to strong deviation from linear elastic behavior, denoted in the authors' previous work as the "chemical strain" effect. At room temperature, the equilibrium state of the point defects is reached within a few months. During this period, the lattice parameter of the substrate-supported films spontaneously increases, while the self-supported films are observed to transform from the flat to the buckled state, indicating that formation of the dopant,vacancy complex is associated with a volume increase. The unexpectedly slow kinetics of establishing the defect equilibrium at room temperature can explain the fact that, depending on the sample history, the "observable" lattice parameters of Ce0.8Gd0.2O1.9, as reported in the literature, may differ from one another by a few tenths of a percent. These findings strongly suggest that the lattice parameter of the materials with a large concentration of interacting point defects is a strong function of time and material preparation route. [source] Cover Picture: Photolithographic Route to the Fabrication of Micro/Nanowires of III,V Semiconductors (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 1 2005Mater. Abstract The cover shows a patterned assembly of GaAs nanowires with their ends tethered to a bulk single-crystal wafer as described on p.,30 by Rogers and co-workers. These wires, which have triangular cross-sections, were fabricated via a top,down process that combines photolithography and anisotropic chemical etching. Nano/microwires of semiconducting materials (e.g., GaAs and InP) with triangular cross-sections can be fabricated by "top,down" approaches that combine lithography of high-quality bulk wafers (using either traditional photolithography or phase-shift optical lithography) with anisotropic chemical etching. This method gives good control over the lateral dimensions, lengths, and morphologies of free-standing wires. The behaviors of many different resist layers and etching chemistries are presented. It is shown how wire arrays with highly ordered alignments can be transfer printed onto plastic substrates. This "top,down" approach provides a simple, effective, and versatile way of generating high-quality single-crystalline wires of various compound semiconductors. The resultant wires and wire arrays have potential applications in electronics, optics, optoelectronics, and sensing. [source] Shaped Films of Ionotropic Hydrogels Fabricated Using Templates of Patterned PaperADVANCED MATERIALS, Issue 4 2009Paul J. Bracher Patterned paper wet with multivalent cations can template the production of films of ionotropic hydrogels in topologically complex shapes such as Möbius strips and interlocking rings (see figure). The films have lateral dimensions as low as 2mm, and range in thickness from 0.2 to 1.3mm. The films are magnetically responsive when cross-linked by Ho3+ or Gd3+. [source] Topography Mediated Patterning of Inorganic Materials by Spray Pyrolysis,ADVANCED MATERIALS, Issue 22 2006D. Beckel Microstructured ceramic thin films are produced by spray pyrolysis of metal salt solutions onto micromachined substrates. The ceramic structures built on the substrate result from preferential assembly of particles on the edge of the initially micromachined structures, leading to smaller lateral dimensions (1,2 ,m in width) than the initial structures on the substrate (see figure). The assembly process amplifies the height of the initial structures by a factor of approximately thirty, resulting in features with an aspect ratio of three. [source] Registered Deposition of Nanoscale Ferroelectric Grains by Template-Controlled Growth,ADVANCED MATERIALS, Issue 11 2005S. Clemens Regular patterns of ferroelectric PbTiO3 nanostructures (see Figure) with lateral dimensions down to 30,60,nm have been grown onto platinized Si substrates by chemical solution deposition. The high registration of the grains is achieved by "top,down"-generated templates of TiO2 dots as seeds for their deposition. Ferroelectricity was verified by piezoresponse force microscopy. [source] Hierarchical Pattern Replication by Polymer Demixing,ADVANCED MATERIALS, Issue 9 2003M. Sprenger Structures with a lateral size of ,,100 nm have been created using a new replication method based on the demixing of a ternary polymer mixture during spin-coating. The technique, which relies on the interfacial wetting of one of the polymer components at the interface of the other two, produces structures (see Figure) that are significantly smaller than the lateral dimensions of the substrate prepattern. [source] In-plane polarization of GaN-based heterostructures with arbitrary crystal orientationPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2010Q. Y. Wei Abstract The total polarization fields of pseudomorphic InxGa1,xN/GaN and AlxGa1,xN/GaN heterostructures with 0,,,x,,,0.4 have been calculated as a function of the crystal orientation. Especial attention is placed on the direction and magnitude of in-plane piezoelectric polarization, which is not negligible for the non-polar and semi-polar growth. For an arbitrary crystal orientation, the piezoelectric polarization prevails in the InGaN/GaN system while the spontaneous polarization prevails in the AlGaN/GaN system. The in-plane potential due to polarization fields in non-polar epilayers is found to depend on the degree of planarity of the heterojunctions, and on the respective lateral dimensions. [source] Preface: phys. stat. sol. (c) 1/8PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2004Markus C. Amann In this special issue of physica status solidi (c) we have included 10 invited papers reviewing the current state-of-the-art and the progress achieved in materials science, semiconductor theory, novel physical mechanisms and advanced device concepts in the field of nanostructured electronic and optoelectronic semiconductor devices. All of these papers were written by previous members of the Collaborative Research Centre 348 "Nanometer-Halbleiterbauelemente: Grundlagen , Konzepte , Realisierungen" (Nanometer Semiconductor Devices: Fundamentals , Concepts , Realisations), which was funded by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) during the period from 1991 to 2003. In these twelve years, the researchers in this programme have carried an intense activity directed towards two main objectives. First of all, Fundamentals and Concepts of nanostructure devices and their technology were explored theoretically and experimentally including the effects of low-dimensional structures on carrier transport, optical properties and spin, as well as the enabling epitaxial and nanostructure technologies such as the cleaved-edge-overgrowth technique and the self-assembled growth of quantum dots. A second field of interest was focused towards the design and development of Novel Semiconductor Devices exploiting nanostructure technology. This comprises optical detectors and memories with nanometer lateral dimensions, microwave detectors and sources up to the 300 GHz regime, innovative tunable and surface-emitting semiconductor lasers for the wavelength range 0.9 to 2 ,m, and nitride-based resonant tunnelling diodes. Some of the device innovations have meanwhile become commercial products proving also the practical importance of this research area. The articles in this special issue relate to the projects of the last three-years' funding period from 2000 to 2003 and are organized along these two topical areas. We would like to thank the numerous reviewers for their valuable comments and the editorial staff of physica status solidi (c) for their extremely helpful support. The funding by the German Research Foundation over the full project time and the continued monitoring and advice by its representatives Dr. Klaus Wehrberger and Dr. Peter Heil are gratefully acknowledged by all previous members and co-workers of this Collaborative Research Centre. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Complex attributes of the magnetic signal for multiple sources: Application to signals from buried ditchesARCHAEOLOGICAL PROSPECTION, Issue 2 2010Christian M. Milea Abstract Complex attributes of the magnetic signal are computed using a multiple source approach. Polygonal bodies are considered and the attributes of each corner are summed to produce the overall response; that is a decomposition of the polygonal body into magnetized steps to simulate the vertices. The method is tested on synthetic examples of buried ditches, as well as on real magnetic data. This type of target was selected because it comprises a common objective in ,archaeological geophysics'. The resolution of the method in detecting the edges of the buried ditches depends on their lateral dimensions with respect to the sampling interval used. In general, the signal of the shallowest edges of the buried targets obscures the signal from the deeper corners, thus prohibiting their detection. In some extreme cases, the signals from the deeper corners posed a recognizable signature. The analytic signal may be seen as an anomaly rectification technique. In this context, it is suitable for the presentation of ,archaeological prospection' data since it provides an image that resembles the plane view of the buried antiquities better than the total field anomaly itself. Copyright © 2010 John Wiley & Sons, Ltd. [source] Open-magnet MR defaecography compared with evacuation proctography in the diagnosis and management of patients with rectal intussusceptionCOLORECTAL DISEASE, Issue 1 2004L. S. Dvorkin Abstract Objective The aim of this study was to determine whether open-magnet magnetic resonance (MR) defaecography could provide more useful clinical information than evacuation proctography (EP) alone in the evaluation of a cohort of patients with full-thickness rectal intussusception and could assist in decisions concerning management. Methods Ten patients (4 male; median age 43, range 30,65) with symptomatic circumferential rectal intussusception diagnosed on EP, underwent open-magnet MR defaecography. Pathologies visible with each technique were recorded and 12 parameters of anorectal configuration and morphology measured and compared. Results There was discordance in the diagnosis of rectal intussusception in three cases. In another two patients, MR defaecography demonstrated mucosal descent only. Measurements of anorectal configuration and morphology were similar between techniques; only rectal size and lateral dimensions of the rectocoele were significantly different, being smaller on MR defaecography than EP. Two patients were shown on MR defaecography to have significant bladder descent and two female patients had significant vaginal descent. Conclusion EP remains the first line investigation for the diagnosis of rectal intussusception, but may not distinguish mucosal from full-thickness descent. MR defaecography further complements EP by giving information on movements of the whole pelvic floor, 30% of the patients studied having associated abnormal anterior and/or middle pelvic organ descent. If surgery is planned for patients with rectal intussusception, MR defaecography provides useful information regarding the presence and degree of anterior pelvic compartment descent that may need to be addressed if a good functional outcome is to be achieved. [source] | ||||||||||||||||