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Long-range Order (long-range + order)
Selected AbstractsPhotoinduced Formation of Wrinkled Microstructures with Long-Range Order in Thin Oxide Films,ADVANCED MATERIALS, Issue 24 2007M. Takahashi Thin oxide films with long-range ordered microstructures were fabricated by a wrinkling process initiated by photopolymerization. The faster polymerization of the film surface generates a buckling effect to create patterns in the films. The removal of the organic polymer by thermal treatment leaves titania microstructures having long-range order. This method of producing micropatterned structures can find several applications in photonics. [source] Studying natural structural protein fibers by solid-state nuclear magnetic resonanceCONCEPTS IN MAGNETIC RESONANCE, Issue 1 2009Alexandre A. Arnold Abstract As a consequence of evolutionary pressure, various organisms have developed structural fibers displaying a range of exceptional mechanical properties adapted specifically to their functions. An understanding of these properties at the molecular level requires a detailed description of local structure, orientation with respect to the fiber and size of constitutive units, and dynamics on various timescales. The size and lack of long-range order in these protein systems constitute an important challenge to classical structural techniques such as high-resolution NMR and X-ray diffraction. Solid-state NMR overcomes these constraints and is uniquely suited to the study of these inherently disordered systems. Solid-state NMR experiments developed or applied to determine structure, orientation, and dynamics of these complex proteins will be reviewed and illustrated through examples of their applications to fibers such as spider and silkworm silks, collagen, elastin, and keratin. © 2009 Wiley Periodicals, Inc. Concepts Magn Reson Part A 34A: 24,27, 2009. [source] EuIII -Doping of Lamellar Bilayer and Amorphous Mono-Amide Cross-Linked Alkyl/Siloxane HybridsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2010Silvia C. Nunes Abstract Two structurally different but chemically similar families of alkyl/siloxane mono-amidosil hosts, represented by m-A(x) [where x = 14 or 8 represents the number of CH2 groups of the pendant alkyl chains directly bonded to the carbonyl group of the amide cross-link] have been doped with a wide range of concentrations of Eu(CF3SO3)3. Mono-amidosils m-A(x)nEu(CF3SO3)3 with n,,,10 (where n is the molar ratio of carbonyl groups per Eu3+ ion) have been analyzed. The m-A(8)nEu(CF3SO3)3 mono-amidosils are transparent and amorphous films, in which the alkyl chains adopt gauche conformations. In contrast, the m-A(14)nEu(CF3SO3)3 mono-amidosils are solid powders; here the lamellar bilayer hierarchical structure of m-A(14) coexists with a new lamellar phase in which the Eu3+ ions are bonded to carbonyl oxygen atoms of the amide groups. At n = 10 the hydrogen-bonded associations formed are highly ordered and considerably stronger than those found in the less concentrated hybrids and in the nondoped matrices. "Free" and weakly coordinated triflate ions occur in all the mono-amidosil samples. The hybrids are white light emitters (maximum quantum yield: 0.08,±,0.01), presenting a broad emission band in the blue/purplish-blue spectral region (ascribed to the hybrid host) superimposed on the 5D0,7F0,4 Eu3+ intra-4f6 transitions. Two Eu3+ local coordination sites (named A and B) have been discerned in both systems. Site A is attributed to weakly coordinated Eu3+/CF3SO3, ion pairs, whereas site B involves Eu3+ coordination to the oxygen atoms of the C=O groups, of the CF3SO3, ions and of the water molecules. For site B, the long-range order of the hybrid host induces distinct features in the energy of the 5D0,7F0,4 transitions, the 5D0 lifetime and the degree of covalency of the Eu3+,first-ligand bonds. [source] Bio-mimetic scaling of mechanical behavior of thin films, coatings, and surfaces by Laser Interference MetallurgyADVANCED ENGINEERING MATERIALS, Issue 9 2005C. Daniel Biological solutions to enhance strength and stability often use hierarchical composite structures. The effect is not based on large chemical variations, but instead is realized by structural composites with long-range order. Laser Interference Metallurgy is a newly developed technique that utilizes this biological approach to optimize the mechanical properties of surfaces and thin films. The possibility of scaling mechanical properties is quantitatively analyzed and compared with the biological approach. [source] Transistor Paint: Environmentally Stable N -alkyldithienopyrrole and Bithiazole-Based Copolymer Thin-Film Transistors Show Reproducible High Mobilities without AnnealingADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Junying Liu Abstract New solution processable 4-(2-hexyldecan)- 4H -bisthieno[2,3- d:3,,2,- b]pyrrole and 4,4,-dialkyl-2,2,-bithiazole-based copolymers (PBTzDTPs) are synthesized with excellent FET performance. These novel copolymers have considerable potential in printable electronics as they have high charge carrier mobilities, excellent air stability, good solution processibility, and no requirement for post-deposition thermal annealing, all requirements for this field of application. The thin film transistors fabricated from PBTzDTPs achieve field effect mobilities as high as 0.14,cm2 V,1 s,1 with current on/off ratios up to 106 without thermal annealing. In addition, the devices exhibit stable performance in air, showing no significant degradation over 60 days. Moreover, the polymers described here provide an excellent example of the systems in which higher mobility performance does not require higher crystalline, long-range ordered structures. Such a system appears to be particularly promising for rapid fabrication techniques, where kinetic conditions usually prevent the development of long-range order. [source] Swelling-Induced Surface Patterns in Hydrogels with Gradient Crosslinking DensityADVANCED FUNCTIONAL MATERIALS, Issue 19 2009Murat Guvendiren Abstract Hydrogels with controlled surface patterns are useful for a range of applications, including in microdevices, sensors, coatings, and adhesives. In this work, a simple and robust method to generate a wide range of osmotically driven surface patterns, including random, lamellar, peanut, and hexagonal structures is developed. This method does not require the use of organic solvents for swelling, pre-patterning of the film surface, or coating of a second layer on the gel. The patterns are fabricated by exposing a photocurable formulation to light while open to air and then swelling, using oxygen inhibition of the radical polymerization at the surface to create a gradient of crosslinking with depth, which was confirmed by measuring the double bond conversion at the surface, surface mechanics, and molecule diffusion into the network. The modulus gradient, and hence osmotic pressure, is controlled by the crosslinker concentration, and the characteristic size of the patterns is determined by the initial film thickness. The patterns are stable in both swollen and dry states, creating a versatile approach that is useful for diverse polymers to create complex patterns with long-range order. [source] Nucleation-Governed Reversible Self-Assembly of an Organic Semiconductor at Surfaces: Long-Range Mass Transport Forming Giant Functional Fibers,ADVANCED FUNCTIONAL MATERIALS, Issue 18 2007G. De, Luca Abstract The use of solvent-vapor annealing (SVA) to form millimeter-long crystalline fibers, having a sub-micrometer cross section, on various solid substrates is described. Thin films of a perylene-bis(dicarboximide) (PDI) derivative, with branched alkyl chains, prepared from solution exhibit hundreds of nanometer-sized PDI needles. Upon exposure to the vapors of a chosen solvent, tetrahydrofuran (THF), the needles re-organize into long fibers that have a remarkably high aspect ratio, exceeding 103. Time- and space-resolved mapping with optical microscopy allows the self-assembly mechanism to be unravelled; the mechanism is found to be a nucleation-governed growth, which complies with an Avrami-type of mechanism. SVA is found to lead to self-assembly featuring i),long-range order (up to the millimeter scale), ii),reversible characteristics, as demonstrated through a series of assembly and disassembly steps, obtained by cycling between THF and CHCl3 as solvents, iii),remarkably high mass transport because the PDI molecular motion is found to occur at least over hundreds of micrometers. Such a detailed understanding of the growth process is fundamental to control the formation of self-assembled architectures with pre-programmed structures and physical properties. The versatility of the SVA approach is proved by its successful application using different substrates and solvents. Kelvin probe force microscopy reveals that the highly regular and thermodynamically stable fibers of PDI obtained by SVA exhibit a greater electron-accepting character than the smaller needles of the drop-cast films. The giant fibers can be grown in,situ in the gap between microscopic electrodes supported on SiOx, paving the way towards the application of SVA in micro- and nanoelectronics. [source] Highly Ordered, Millimeter-Scale, Continuous, Single-Crystalline Graphene Monolayer Formed on Ru (0001)ADVANCED MATERIALS, Issue 27 2009Yi Pan A single-crystalline graphene monolayer is grown on a Ru(0001) surface by thermal annealing of a ruthenium single crystal containing carbon. The layer is highly ordered, continuous, and exhibits perfect crystallinity, with good long-range order on the order of millimeters (see figure). These findings offer high-quality graphene layers for fundamental research as well as large-scale graphene wafers for device fabrication and integration. [source] The Influence of Morphology on High-Performance Polymer Field-Effect TransistorsADVANCED MATERIALS, Issue 2 2009Hoi Nok Tsao The influence of molecular packing on the performance of polymer organic field-effect transistors is illustrated in this work. Both close ,-stacking distance and long-range order are important for achieving high mobilities. By aligning the polymers from solution, long-range order is induced, yielding hole mobilities of up to µsat,=,1.4,cm2 V,1 s,1 and current on/off ratios Ion/Ioff of 105. [source] Photoinduced Formation of Wrinkled Microstructures with Long-Range Order in Thin Oxide Films,ADVANCED MATERIALS, Issue 24 2007M. Takahashi Thin oxide films with long-range ordered microstructures were fabricated by a wrinkling process initiated by photopolymerization. The faster polymerization of the film surface generates a buckling effect to create patterns in the films. The removal of the organic polymer by thermal treatment leaves titania microstructures having long-range order. This method of producing micropatterned structures can find several applications in photonics. [source] Thomas,Fermi approximation for the quasi-two-dimensional electron gasINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 6 2001M. Moreno Abstract To take into account static correlation effects in the quasi-two-dimensional electron gas a screened Coulombic interaction between particles is studied. The Thomas,Fermi approximation is used and the potential screening appears as a function of the Wigner,Seitz density parameter rs and the effective width t of the system. With the self-consistent field theory applied to the modified deformable jellium, the ground-state energy per particle and the conditions for electron localization are obtained in terms of the interparticle distance and the screening parameter ,. A critical minimum characteristic width tc is obtained; below tc no long-range order is obtained. For larger widths a stable localized state is predicted at finite densities. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 82: 269,276, 2001 [source] The effect of disorder on the chemical reactivity of an organic solid, tetraglycine methyl ester: Change of the reaction mechanismJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 2 2002Evgenyi Shalaev Abstract Many drugs undergo chemical changes in the solid state, and understanding chemical reactivity of organic crystals is a critical factor in the drug development process. In this report, the impact of milling on the thermal chemical reactivity of an organic solid, tetraglycine methyl ester, was studied using DSC, isothermal calorimetry, chemical analysis (HPLC and insoluble residue determination), and powder X-ray diffraction. Significant changes in both X-ray diffraction patterns and DSC curves were detected after very brief milling (5 s). The changes were interpreted as the formation of a disordered phase. The disordered phase was tentatively identified as a crystal mesophase that combines properties of both crystalline (i.e., long-range order) and amorphous (i.e., glass transition) states. In the disordered material, the reaction mechanism changed from the methyl transfer reaction, which was observed in the intact crystal, to a polycondensation reaction when the reaction was performed at 165°C. Such changes in the reaction mechanism occurred in materials milled for >,30 s. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:584,593, 2002 [source] Annealed crystallization of ultrafine amorphous NiB alloy studied by XAFSJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2001Shiqiang Wei XAFS has been used to investigate the local structure evolutions of ultrafine amorphous NiB alloy during the annealed crystal-lization process. A nanocrystalline Ni phase with the local structure of crystalline Ni-like and a crystalline Ni3B, have been produced for ultrafine amorphous NiB alloy under the annealed temperature of 573 K. The results rule out Rojo et al.'s devitrification mechanism of Ni80B20 amorphous alloy in which they considered that an amorphous pure Ni phase is formed in the first exothermic process. However, our results are almost identical with Riveiro et al.'s conclusion in which the intermediate state is interpreted as two metastable crystalline phases of Ni3B and Ni-rich NiB alloy. With the annealed temperature going onto 773 K, the ultrafine NiB sample is further decomposed and crystallized into crystalline Ni with long-range order. [source] Kinetics of coupled ordering and segregation in antiphase domainsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2009K. Gumennyk Abstract We study a multi-domain ordering kinetics in solid solutions under simultaneous diffusion of solute atoms. By the example of a binary bcc alloy a system of kinetic equations is derived, describing the coupled relaxation of occupancies of the two sublattices, building a bcc lattice, by A and B atomic species. Such an approach supplemented by the simplest mean-field approximation proves sufficient to describe both the establishing of long-range order and the segregation processes occurring in antiphase domains. An interaction and interrelation between evolution of the conserved and non-conserved order parameter fields are elucidated. Asymptotical and numerical analysis of the obtained evolution equations reveals a multi-stage scenario of the alloy relaxation: first comes the quick development of long-range order which is then followed by the slow redistribution of local alloy concentration, so that the majority atoms segregate towards the region of an antiphase boundary. The alloy exhibits a distinct tendency to form a multi-domain structure out of a solitary long-range order parameter fluctuation of a certain sign. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] AFM study of crystalline cellulose in the cell walls of strawPOLYMER INTERNATIONAL, Issue 1 2006Wan Li Abstract Crystalline cellulose in the cell walls of straw was studied by atomic force microscopy (AFM). The samples were first treated and then observed by AFM under dimethylsulfoxide (DMSO). The crystalline regions were located and two allomorphs of crystalline cellulose, triclinic I, and monoclinic I, phases, were identified. In most crystalline regions, the I, and I, phases are intimately associated, with the I, phase more abundant than the I, phase. In some small domains only one phase with long-range order was observed. It was demonstrated that in these one-phase domains, I, phase crystals always have their (010) plane lying parallel to the cell wall surface and I, phase crystals with (110) plane lying parallel. Copyright © 2005 Society of Chemical Industry [source] Quasiperiodicity in decagonal phases forced by inclined net planes?ACTA CRYSTALLOGRAPHICA SECTION A, Issue 3 2001Walter Steurer It is generally assumed that decagonal quasicrystals show periodically arranged atomic layers only on net planes perpendicular to the tenfold axis and quasiperiodically arranged ones parallel to it. However, there also do exist only slightly puckered atomic layers that are periodically arranged and inclined to the tenfold axis. They coincide with the net planes of the periodic average structures of the decagonal phase and are related to the strongest Bragg reflections. Since they link quasiperiodic and periodic directions, inclined net planes may play a crucial role for growth and stabilization of decagonal quasicrystals. In fact, it is shown how ideal quasiperiodic long-range order and inflation symmetry allow for the existence of inclined net planes with small corrugation and reinforce the relation with the periodic average structures. [source] The anionic coordination polymer {K2[PtII2AgI8(2,2,-bipyridine)2(O2CCF3)14]}nACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2009Zachary M. Hudson The trimetallic compound catena -poly[dipotassium(I) [bis(2,2,-bipyridine)di-,3 -trifluoroacetato-dodeca-,2 -trifluoroacetato-diplatinum(II)octasilver(I)]], K2[Pt2Ag8(C2F3O2)14(C10H8N2)2], forms an extended structure in the solid state. Electrostatic interactions involving the K+ ions play a key role in the formation of the extended structure in three dimensions. The AgI ions form one-dimensional coordination polymers, with alternating Ag2 and Ag6 units linked by CF3CO2, ligands. Pt...Pt interactions perpendicular to the one-dimensional polymerization axis provide another element of long-range order, and electrostatic interactions with K+ ions provide connectivity between adjacent polymeric structures. [source] Influence of organotin compounds on phosphatidylserine membranesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 3 2004José A. Teruel Abstract Organotin compounds are widely distributed toxicants. They are membrane-active molecules with broad biological toxicity. We have studied the interaction of tributyltin and triphenyltin with phosphatidylserine model membranes using differential scanning calorimetry, infrared spectroscopy and X-ray diffraction techniques. Organotin compounds produced a broadening of the gel to the liquid-crystalline phase transition of the phospholipid and a shifting of the phase transition temperature to lower values. Infrared spectroscopy experiments showed that tributyltin exerted a fluidizing effect on the apolar part of the bilayer, and that both tributyl- and triphenyltin interact with the interfacial region of the bilayer, making the carbonyl groups less accessible to water. As seen by X-ray diffraction experiments, organotin compounds were unable to change the bilayer macroscopic organization of the phospholipid, but they were able to reduce the long-range order of the multibilayer system and to disorder the packing of the phospholipid molecules. The observed interaction between organotin compounds and phosphatidylserine membranes promotes physical perturbations that could affect membrane function and may mediate some of their toxic effects. Copyright © 2004 John Wiley & Sons, Ltd. [source] | |||||||||||||