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Complex Morphology (complex + morphology)
Selected AbstractsSubmicrometer-Sized Vaterite Tubes Formed Through Nanobubble-Templated Crystal Growth,ADVANCED MATERIALS, Issue 19 2005W. Fan Electrolytic deposition is used to prepare submicrometer-sized vaterite (CaCO3) tubes (see Figure) in the absence of organic molecules, the presence of which was previously thought to be necessary for the growth of calcium carbonate crystals in complex morphologies. The mechanism of formation is shown experimentally to be hydrogen-nanobubble-templated crystal growth. [source] FROM EXOGENOUS TO ENDOGENOUS ECONOMIC NETWORKS: INTERNET APPLICATIONSJOURNAL OF ECONOMIC SURVEYS, Issue 5 2006Alessio D'Ignazio Abstract Economic agents' behaviour is affected by their position in a network, either exogenous or endogenous, in which they interact with a sub-set of neighbours only. The network's links, which may be generated by vertical and/or horizontal relations, or by more complex morphologies, may explain the transition between dynamic equilibria and the instability of economic aggregates. Moreover, networks shape strategic interaction among agents by determining their strategies; the problem of access and interconnection, particularly relevant in the Internet, is perhaps the best example. A two-way feedback between strategies and network structures arises instead when links are endogenous: those features are clearly shown in the mechanism underlying the formation of peering links and R & D networks. [source] Photoinitiated polymerization in bicontinuous microemulsions: Fluorescence monitoringJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2006C. Peinado Abstract The photopolymerization of bicontinuous microemulsions was simultaneously monitored with differential scanning calorimetry and fluorescence. The kinetics and mechanism of the reaction were studied throughout the entire photopolymerization reaction. The role played by the surfactant in the kinetics and morphology was studied. The nature of the surfactant changed the autoacceleration process and final conversion. The behavior was explained as a result of the differences in the interfacial properties. Anionic cetyltrimethylammonium bromide (CTAB) gave rise to a more flexible interfacial film than anionic sodium dodecyl sulfate (SDS), resulting in competition between the intramolecular and intermolecular reactions in the former systems. As cyclization did not contribute to the increase in the degree of crosslinking, SDS photopolymerization gave solids with a more rigid microstructure. Fluorescence methodology was applied to monitor bicontinuous microemulsion polymerization and to reveal the microstructure and morphology development during photopolymerization. The microemulsion composition was designed to prepare nanoporous, crosslinked materials. Even though the nanostructure of the precursor microemulsions was not retained because of phase separation during polymerization, mesoporous solids were obtained. Their morphologies depended on the nature of the surfactant, and membranes with open cells were successfully prepared with CTAB, whereas more complex morphologies resulted with SDS. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5291,5303, 2006 [source] Mesophase Separation of Diblock Copolymer Confined in a Cylindrical Tube Studied by Dissipative Particle DynamicsMACROMOLECULAR THEORY AND SIMULATIONS, Issue 9 2006Jian Feng Abstract Summary: The morphologies of diblock copolymers confined in a cylindrical tube have been investigated by the dissipative particle dynamics (DPD) method. Results indicate that the morphology depends on the volume ratio of the immiscible blocks, the diameter of the cylindrical tube and the interactions between the blocks and between the confinement wall and blocks. For symmetric diblock copolymers, when the tube wall is uniform toward the two blocks, perpendicular lamellae or a stacked disk morphology are generally formed except when the diameter of the cylindrical tube is very small; in that case, a special bi-helix morphology forms because of the entropy effect. When the tube wall is non-uniform, as the diameter of the tube increases, perpendicular lamellae are first formed, then changing to parallel lamellae and, finally, back to perpendicular lamellae again. An intermediate morphology characterizing the transition between perpendicular and parallel lamellae is observed. If the non-uniformity of the wall is further enhanced, only parallel lamellae can be found. In the case of asymmetric diblock copolymers, more complex morphologies can be obtained. Multi-cylindrical micro-domains and a multilayer helical phase as well as other complex pictures are observed. Generally, the morphologies obtained could find their counterparts from experiments or Monte Carlo simulations; however, differences do exist, especially in some cases of asymmetric diblock copolymers. Bi-helix and stacked disks morphologies of A5B5 diblock copolymer confined in two different neutral nanocylinders. [source] Palaeoecology Of A Late Devonian Back Reef: Canning Basin, Western AustraliaPALAEONTOLOGY, Issue 4 2000Rachel Wood Back-reef ecologies within the celebrated mixed carbonate-siliciclastic Late Devonian (late Frasnian) Pillara Limestone of Windjana Gorge, in the Canning Basin, Western Australia, are re-interpreted as being dominated by microbial communities. Proposed microbialites are expressed as weakly-laminated, fenestral micrite, that show unsupported primary voids, peloidal textures, disseminated bioclastic debris, and traces of microfilaments. These grew as either extensive free-standing mounds or columns, often intergrown with encrusting metazoans, or thick post-mortem encrustations upon skeletal benthos. In some cases, microbial encrustations are inferred to have developed in protected cavities formed by progressive burial of the reef. The calcimicrobe Shuguria also shows a preferentially cryptic habit, encrusting either primary cavities formed by skeletal benthos, microbialite, or the ceilings of mm-sized fenestrae within microbialite. A further calcimicrobe, Rothpletzella, formed columns up to 0.3 m high in areas enriched by very coarse siliciclastic sediment. Stromatoporoid sponges with a diverse range of morphologies also formed in situ growth fabrics. Monospecific thickets of closely-aggregating dendroid stromatoporoid sponges (Stachyodes costulata), and platy-laminar forms (?Hermatostroma spp.) were common, as were remarkably large stromatoporoids (Actinostroma spp.) that grew as isolated individuals up to 5 m in diameter. Such sponges showed impressive powers of regeneration from partial mortality, and individual clones may have been capable of substantial longevities of up to 500 years. Actinostroma spp. showed highly complex growth forms including platy-multicolumnar (A. windjanicum), and a hitherto undescribed inferred whorl-forming foliaceous morphology (Actinostroma sp.) reminiscent of the modern photosymbiotic coral Acropora palmata. These complex morphologies formed abundant primary cavities, previously thought to be only rarely developed in association with stromatoporoids.key words: Late Devonian, Canning Basin, reefs, palaeoecology, microbialite. [source] Extending the realm of membrane capacitance measurements to nerve terminals with complex morphologiesTHE JOURNAL OF PHYSIOLOGY, Issue 12 2010Mean-Hwan Kim No abstract is available for this article. [source] THE IMPORTANCE OF PREADAPTED GENOMES IN THE ORIGIN OF THE ANIMAL BODYPLANS AND THE CAMBRIAN EXPLOSIONEVOLUTION, Issue 5 2010Charles R. Marshall The genomes of taxa whose stem lineages branched early in metazoan history, and of allied protistan groups, provide a tantalizing outline of the morphological and genomic changes that accompanied the origin and early diversifications of animals. Genome comparisons show that the early clades increasingly contain genes that mediate development of complex features only seen in later metazoan branches. Peak additions of protein-coding regulatory genes occurred deep in the metazoan tree, evidently within stem groups of metazoans and eumetazoans. However, the bodyplans of these early-branching clades are relatively simple. The existence of major elements of the bilaterian developmental toolkit in these simpler organisms implies that these components evolved for functions other than the production of complex morphology, preadapting the genome for the morphological differentiation that occurred higher in metazoan phylogeny. Stem lineages of the bilaterian phyla apparently required few additional genes beyond their diploblastic ancestors. As disparate bodyplans appeared and diversified during the Cambrian explosion, increasing complexity was accommodated largely through changes in cis -regulatory networks, accompanied by some additional gene novelties. Subsequently, protein-coding genic richness appears to have essentially plateaued. Some genomic evidence suggests that similar stages of genomic evolution may have accompanied the rise of land plants. [source] Pigment Synthesis: PY181 Pigment Microspheres of Nanoplates Synthesized via Polymer-Induced Liquid Precursors (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Mater. A polymer-induced liquid precursor is used for a pigment yellow 181 crystal formed by chemical reaction in mixed solvents of water and isopropanol by direct azo coupling under the directing influence of a designed copolymer additive. This leads to a pigment with novel complex morphology and unusal properties, as shown by Cölfen et al. on page 2095. [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] Shaping Carbon Nanotubes and the Effects on Their Electrical and Mechanical Properties,ADVANCED FUNCTIONAL MATERIALS, Issue 11 2006S. Wang Abstract A method is developed and shown to be able to shape a carbon nanotube (CNT) into a desired morphology while maintaining its excellent electrical and mechanical properties. Single, freestanding nanotubes are bent by a scanning tunneling microscopy probe, and their morphology is fixed by electron-beam-induced deposition (inside a transmission electron microscope) of amorphous carbon on the bent area. It is shown that the mechanical strength of the bent CNT may be greatly enhanced by increasing the amount of carbon glue or the deposition area, and the electrical conduction of the nanotube shows hardly any dependence on the bending deformation or on the deposition of amorphous carbon. Our findings suggest that CNTs might be manipulated and processed as interconnections between electronic devices without much degradation in their electrical conductance, and be used in areas requiring complex morphology, such as nanometer-scale transport carriers and nanoelectromechanical systems. [source] Reentry in a Morphologically Realistic Atrial ModelJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2001EDWARD J. VIGMOND Ph.D. Reentry in Morphologically Realistic Atria.Introduction: Atrial fibrillation is the most common cardiac arrhythmia. In ablation procedures, identification of the reentrant pathways is vital. This has proven difficult because of the complex morphology of the atria. The purpose of this study was to ascertain the role of specific anatomic structures on reentry induction and maintenance. Method and Results: A computationally efficient, morphologically realistic, computer model of the atria was developed that incorporates its major structural features, including discrete electrical connections between the right and left atria, physiologic fiber orientation in three dimensions, muscle structures representing the crista terminalis (CT) and pectinate muscles, and openings for the veins and AV valves. Reentries were induced near the venous openings in the left and right atria, the mouth of the coronary sinus, and the free wall of the right atrium. The roles of certain muscular structures were ascertained by selectively removing the structures and observing how the propagation of activity was affected. Conclusion: (1) The muscular sheath of the coronary sinus acts as a pathway for a reentrant circuit and stabilizes any circuits that utilize the isthmus near the inferior vena cava. (2) Poor trans-CT coupling serves to stabilize flutter circuits. (3) Wall thickness is an important factor in the propagation of electrical activity, especially in the left atrium. (4) The openings of the inferior and superior venae cavae form natural anatomic anchors that make reentry easier to initiate by allowing for smaller ectopic beats to induce reentry. [source] Structural flyby characterization of nanoporosityPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2004R. R. Rosa Abstract Recently, Ferreira da Silva et al. [3] have performed a gradient pattern analysis of a canonical sample set (CSS) of scanning force microscopy (SFM) images of ,-Si. They applied the so-called Gradient Pattern Analysis to images of three typical ,-Si samples distinguished by different absorption energy levels and aspect ratios. Taking into account the measures of spatial asymmetric fluctuations they interpreted the global porosity not only in terms of the amount of roughness, but rather in terms of the structural complexity (e.g., walls and fine structures as slots). This analysis has been adapted in order to operate in a OpenGL flyby environment (the StrFB code), whose application give the numerical characterization of the structure during the flyby real time. Using this analysis we compare the levels of asymmetric fragmentation of active porosity related to different materials as ,-Si and "porous diamond-like" carbon. In summary we have shown that the gradient pattern analysis technique in a flyby environment is a reliable sensitive method to investigate, qualitatively and quantitatively, the complex morphology of active nanostructures. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A lithium ionomer of poly(ethylene-co-methacrylic acid) copolymer as compatibilizer for blends of poly(ethylene terephthalate) and high density polyethylenePOLYMER ENGINEERING & SCIENCE, Issue 11 2002A. Retolaza Blends of 75/25 poly(ethylene terephthalate) (PET)/high density polyethylene (HDPE) containing poly(ethylene-co-methacrylic acid) partially neutralized with lithium (PEMA-Li) were obtained by direct injection molding in an attempt (i) to ameliorate the poor performance of the binary blend and (ii) to find the best compatibilizer content. The presence of PEMA-Li caused a nucleation effect on PET, and a decrease in the crystalline content of HDPE. The compatibilizing effect of PEMA-Li was due to the combined effects of interaction at the interface and chemical reactions. The ternary blends showed a complex morphology, with two dispersed HDPE and PEMA-Li phases that contained a small internal dispersed phase, probably of PET. The compatibilizing effect of PEMA-Li was clearly shown by means of an impressive increase in the ductility and to a minor extent in the impact strength. The highest property improvement (ductility increase 1450%) appeared upon the addition of 45% PEMA-Li with respect to the HDPE phase, but taking into account the recycling interest, the ternary blend with the addition of roughly 22.5% PEMA-Li appears to be the most attractive. [source] | |||||||||||||||||||||||||