Size Of Ordered Domains Research Articles

Molecular Dynamics of Glycolipids in Liposomes.

Glycosphingolipids (GSLs) in the mammalian plasma membrane are essential for various biological events as they form glycolipid-rich membrane domains, such as lipid rafts. GSLs consist of a certain oligosaccharide head group and a ceramide tail with various lengths of acyl chains. The structure of the head group as well as the carbon number and degree of the unsaturation of the acyl chain are known to regulate the membrane distributions and interleaflet couplings of GSLs by altering physicochemical properties, such as dynamics, interactions, and cluster sizes. This chapter provides the detailed use of time-resolved fluorescence measurement for investigating the membrane properties of lactosylceramide (LacCer)-enriched domains in bilayer membranes. LacCer belongs to the neutral GSLs and is believedin forming a highly ordered phase in model membranes and biological membranes, while the details of the domain remain unclear. Here, we suggest using trans-parinaric acid (tPA) and tPA-LacCer fluorescent probes to reveal the dynamics and size of the GSL domains since they prefer to bedistributed in the GSL-rich ordered phase. The fluorescence lifetime in the nanosecond timescale reveals the difference in the surrounding membrane environments, which relates to hydrocarbon chain ordering, membrane hydration, and submicrometer domain size. The fluorescence lifetime of these probes can thus provide important information on submicron- to nano-scale small GSL domains not only in model membranes but also in biological membranes.

The evolution of structure and dielectric behavior of Pb(Sc0.5Ta0.5)O3 ceramics with various annealing times

Non-annealed and annealed Pb(Sc0.5Ta0.5)O3 ceramics were successfully prepared by using the traditional solid-state reaction method. The influence of annealing time on the structure and dielectric behavior was investigated. A pure-phase structure with a space group of Fm9m was obtained in all ceramics. As annealing time increased, both the degree of order and the ordered domain size increased. Superlattice reflection spots associated with B-site ordering arrangement were found in the long-time annealed ceramics by using selected area electron diffraction. The non-annealed sample exhibited clear relaxor ferroelectric behavior. Three unexpected peaks/jumps were observed in the dielectric-loss tangent curves of the annealed ceramics, in which each peak corresponded to a subtle dielectric change. X-ray powder diffraction analysis at −50, 10, and 50 °C performed on the 48-h annealed ceramics demonstrated that the degree of order and cell parameters barely changed. With increasing annealing time, the low-temperature dielectric transition weakened, the middle-temperature dielectric transition sharpened, and the transition temperature shifted toward high temperatures. At high temperatures, the dielectric transition increasingly strengthened with the increase in frequency. The unusual dielectric behavior was attributed to the inhomogeneous distribution of ordered and disordered regions in the ceramics. The low-temperature dielectric transition primarily originated from the disordered region, the middle-temperature dielectric transition was mainly attributed to the ordered region, and the dielectric transition at high temperatures was ascribed to the incommensurate structure that resulted from the intense competition of the ordered and disordered regions.

Ordered domain engineering and physical property modification of Ba(Co1/3Nb2/3)O3 complex perovskite ceramics

AbstractIn the present work, the physical properties modification by ordered domain engineering has been systematically investigated in Ba(Co1/3Nb2/3)O3 ceramics. The 1:2 ordered structure with an ordering degree up to 0.92 with uniform ordered domain size distribution is achieved in Ba(Co1/3Nb2/3)O3 ceramics after post‐densification annealing, where the significantly enhanced electric resistivity, thermal conductivity, and dielectric strength, and subsequently the superior energy storage characteristics are achieved. The dielectric strength increases from 618 kV cm–1 to 972 kV cm–1 in the present ceramics by such means of ordered domain engineering, while the energy storage density increases from 0.65 J cm–3 to 1.42 J cm–3. There are three primary parameters in ordered domain engineering: ordering degree, ordered domain size and its distribution, and ordered domain boundary type. The final physical properties are determined by these three parameters.

Effect of yttrium addition on the hot deformation behavior of Fe–6.5 wt%Si alloy

Due to its remarkable soft magnetic properties, the Fe–6.5 wt%Si alloy has shown potential in energy-saving and noise-reducing applications. However, the appearance of brittle-ordered structures hinders its production and utilization. It has been previously indicated that rare earth (RE) elements can be used as inclusion modificators as well as for purification of molten steel and microalloying. In the present work, the effects of yttrium (Y) on the hot deformation of the Fe–6.5 wt%Si alloy was studied by hot compression at temperatures of 600–900 °C at different strain rates. Moreover, the processing maps were established according to the dynamic materials models (DMM), which determined the range of optimal process conditions. The obtained results demonstrated that in the range of 600–900 °C, the activation energy for hot deformation of the Fe–6.5 wt%Si alloy was 428.68 kJ/mol, which is lower than that of the alloy containing 0.03 wt%Y (473.27 kJ/mol). It is speculated that Y decreases the unstable region and apparently reduces the occurrence of microcracks during the hot deformation process of the Fe–6.5 wt%Si alloy. In addition, the presence of this element leads to an increase in the dislocation density and causes segmentation of the ordered domain. Lastly, the addition of Y improves the ductility of the Fe–6.5 wt%Si alloy due to grain refinement and reduction of the ordered domain size.

Long-Range Order Self-Assembly of Conjugated Block Copolymers at Inclined Air-Liquid Interfaces.

Here, we report that long-range order, direction-controlled, ultrathin conjugated polymer films can be formed by the self-assembly of conjugated block copolymers (i.e., poly(3-hexylthiophene)-block-poly(ethylene glycol)) at inclined air-water interfaces. Structure analyses revealed well-aligned nanowire arrays of poly(3-hexylthiophene) with a dramatically increased ordered domain size compared to the polymer films formed on a flat water surface. The improved degree of order was attributed to the flow field created by the enhanced solvent evaporation at the top of the water contact line. Note that it is challenging to prepare such well-ordered and molecularly thin films of conjugated polymers by conventional fabrication methods. The long-range order polymer film showed hole mobility an order of magnitude higher than polymer films formed on a flat interface when implemented as an active layer of field-effect transistor devices. This study demonstrates that a simple interface modification can significantly impact the self-assembly process, structure, and function of polymer films formed at the air-liquid interface.

Further ordering structural investigation of Ba((Co,Zn,Mg)1/3Nb2/3)O3 perovskites by Raman spectroscopy

Correlations among the Raman vibration modes, ordering structures and dielectric properties have been established through further ordering structural investigation of Ba((Co0.6-x/2Zn0.4-x/2Mgx)1/3Nb2/3)O3 ceramics by Raman spectroscopy. Meanwhile an in-depth understanding of Raman spectroscopy for 1:2 ordered Ba(B′1/3B″2/3)O3 perovskites has been gained. An approximate 1:1 ordered structure composed of alternate Nb5+-rich and Nb5+-dificient layers is detected by transmission electron microscopy observation, confirming that the four main Raman peaks of 1:2 ordered structure arise from the nanoscale regions of 1:1 ordering in B-site sublattice. As x increases, Ba-related and Nb-related phonons show growing lifetime with the increase of ordering degree and Qf values. Simultaneously, oxygen vibration along c axis (Eg(4) (O) mode) is favored, while the vibration in ab plane (Eg(3) (O) mode) weakens since 1:2 ordering forms along the c-axis of ordered structure. The lifetime of the oxygen-octahedron stretch A1g(4) (O) mode (∼788 cm−1) is supposed not only influenced by the ordering domain size, but also the micro-defects such as ordering domain boundaries.

Characterization of micelle-templated silica nanotubes and nanotube bundles using tilt-series transmission electron microscopy

Pluronic-surfactant-templated silica and organosilica nanotubes, silica nanotube bundles and silicas with small ordered domains of cylindrical mesopores were characterized by using tilt-series transmission electron microscopy (TEM). In as-synthesized nanotube samples, three-dimensional (3-D) arrangements of long nanotubes, likely involving local cross-linking of nanotube pairs, were uncovered. As-synthesized silica nanotubes tended to be unstable during TEM observation, which appeared to stem from stretching and breaking of nanotubes whose parts belonged to two different nanotube aggregates, the latter undergoing shrinkage under TEM conditions. However, silica nanotubes hydrothermally treated at a sufficiently high temperature and methylene-bridged organosilica nanotubes did not undergo this kind of changes to any appreciable extent. Despite the observed instability of as-synthesized nanotubes, the calcined sample exhibited narrow pore size distribution, suggesting that if a similar degradation occurs during drying and calcination, it may merely fragment the nanotubes. Nanotube bundles were observed to exhibit 3-D structures with often curved bundle segments locally meeting one another and potentially forming loops. A junction within a seemingly continuous nanotube bundle was observed, where ends of two groups of nanotubes met. This feature is likely to have its counterparts in particles of materials with much larger ordered domain sizes. The imaging of a large-pore silica with 2-D hexagonal domains of small size revealed the presence of an impurity consisting of spheres encircled by nanotubes. These results demonstrate that the tilt-series TEM imaging is a powerful method for characterization of not only complicated 3-D morphologies of surfactant-templated materials, but also their softness and possible degradation modes.

Direct synthesis of a solid calcium-silicate-hydrate (C-S-H)

We present new results on solid (monolithic) synthetic C-S-H made at room temperature from easily obtainable calcium sources (calcium oxide, calcium hydroxide) and nanosilica (w/s = 2) with a 2 minute mixing time. Using synchrotron X-ray diffraction combined with TGA/DSC, 29Si NMR and synchrotron pair distribution function (PDF) data we show that the solid C-S-H is crystallographically similar to the more conventionally made synthetic C-S-H slurry. We show that C-S-H is present after 1 day curing (C/S = 0.81) and no X-ray visible portlandite is present at day 3. PDF data shows that the ordered domain size is 2.5 – 4.5 nm, depending on the fit chosen.

A selection rule of solvent for highly aligned diketopyrrolopyrrole-based conjugated polymer film for high performance organic field-effect transistors

Abstract Controlling the morphology of conjugated polymer film through careful selection of solvent is very important for facilitating charge transport in organic opto-electrical and electrical devices. In this report, we systematically study on a selection rule for optimum solvent choice to achieve highly aligned conjugated polymer chains with large ordered domain sizes for high performance organic field-effect transistors (OFETs) through various experimental analysis and Hansen solubility parameters. Three parameters: boiling point, solubility, and molecular interaction between conjugated polymer and solvents, are the most important to obtain optimum morphology. Similar molecular interaction values between solvent and conjugated polymer determined the formation of larger size ordered domain in films. High boiling point and relatively poor solubility solvents affect anisotropic film formation of conjugated polymer chains during off-center spin-coating. Considering these, large ordered domains with highly aligned diketopyrrolopyrrole thieno[3,2-b]thiophene (DPPT-TT) polymer chains were achieved by these important factors, and we demonstrate impressively high field-effect mobility ∼5.89 cm2 V−1 s−1 with low standard deviation (13%), which is the highest reported value so far for top-gate/bottom-contact DPPT-TT OFETs.

Improving thermal stability of organic photovoltaics via constructing interdiffused bilayer of polymer/fullerene

Abstract The thermal stability of organic photovoltaics (OPVs) is greatly enhanced by using an interdiffused polymer/fullerene bilayer (ID-BL) as a photoactive layer. The solutions of poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] (PCDTBT) and phenyl-C 71 -butyric-acid-methyl ester (PCBM) are sequentially deposited to form the ID-BL. For comparison, a single photoactive layer consisting of mixed domains of PCDTBT and PCBM (MX-SL) is prepared by depositing blended solution of PCDTBT and PCBM, which is the most widely used method for fabricating OPVs. After applying thermal stress at 80 °C for 10 days, the OPV utilizing the ID-BL photoactive layer maintained 97.2% of its initial efficiency, whereas the efficiency of the OPV utilizing the MX-SL photoactive layer decreased to 37.5% of its initial efficiency. The glazing angle X-ray diffraction (GIXRD) and Flory-Huggins interaction parameter analysis reveal that the ordered domain size of PCDTBT in ID-BL is greater than that of the MX-SL and the ordered domain is maintained after the thermal stress test. These findings imply that mixing of the PCDTBT and PCBM domains does not occur due to the enhanced ordering of PCDTBT in ID-BL during the thermal stress test. Meanwhile, the domain size of PCDTBT in MX-SL is reduced due to further mixing of the PCDTBT and PCBM domains during the thermal stress test, which deteriorates the optimized bulk heterojunction (BHJ) morphology. These results show that efficient and thermally stable OPVs can be realized by utilizing the ID-BL photoactive layer prepared by the sequential solution deposition.

Amorphous silicate nanoparticles with controlled Fe-Mg pyroxene compositions

The production of amorphous pyroxene nanoparticles (~20nm) with controlled Fe-Mg content is described. Homogenous particle compositions closely matching required target stoichiometries are obtained by drying a precursor gel under high vacuum conditions. The silicate nature of the particles is characterised using TEM, synchrotron radiation and FTIR. No oxide phase separation occurs, even at high Fe concentration. Structural domains exist within the nanoparticles that are typically ten times smaller than the physical particle size consistent with either a core-shell, or, random network with multiple embedded domains, particle structure. Thermal annealing below the crystallisation temperature allows the ordered domain size to be further reduced by a factor of ~2.

Temperature evolution of defects and atomic ordering in Si1−xGex islands on Si(001)

The observation of atomic ordering and signatures of defects in self-assembled Ge islands using x-ray diffraction techniques have been previously treated as unrelated subjects. However, mutual understanding can be achieved when both subjects are studied in a common frame. Here, we report on measurements and analysis of both defects and atomic ordering in Si1−xGex islands epitaxially grown on Si(001) substrates as a function of growth temperature. By using x-ray diffraction and mapping around a bulk forbidden reflection, defect sizes, and in-plane spacing between nearby dislocations are extracted and related to the composition of the islands. The results fit well with an independent determination using selective wet chemical etching and atomic force microscopy measurements. Moreover, the temperature dependence of the ordered domain size is discussed. Although both atomic ordering and defect formation take place independently in the system, it is found that the relaxation provided by the onset of defects does not affect the formation of ordered domains, recently pointed out to be stabilized by strain and surface equilibrium on islands facets.

Influence of Molecular Weight on Molecular Ordering and Proton Transport in Organized Sulfonated Polyimide Thin Films

The effect of molecular ordering and ordered domain size on molecular weight dependent proton conductivity in well-organized sulfonated polyimide (SPI) thin films has been investigated using both low molecular weight (LMw, Mw = 1.3 × 104) and high molecular weight samples (HMw, Mw = 2.6 × 105). Analyses of the films by grazing incidence small-angle X-ray scattering (GISAXS) revealed that the HMw SPI film exhibits the higher degree of inherent liquid crystalline-like lamellar ordering, and that it is consistent with a preferential in-plane main chain packing. Such molecular ordering and the in-plane oriented structure can have considerable influence on the proton transport characteristics in thin films. The larger ordered domains in the HMw SPI thin film with a thickness of approximately 500 nm shows the significant proton conductivity enhancement to a value of 2.6 × 10–1 S/cm (at 25 °C and 95% relative humidity), which is more than an order of magnitude higher value than that of the smaller ordered domain...

Tailoring the order–disorder transition and microwave dielectric properties of Ba[(Ni0.6Zn0.4)1/3Nb2/3]O3 ceramics by Mg-substitution

Effects of Mg-substitution on the structure, microstructure and microwave dielectric properties of Ba[(Ni0.6Zn0.4)1/3Nb2/3]O3 ceramics have been systematically investigated. Mg-substitution enhances the densification and promotes the homogenization of grain distribution. Single phase of 1:2 ordered complex perovskite structure forms in the entire composition range of Ba[(Ni0.6−x/2Zn0.4−x/2Mgx)1/3Nb2/3]O3 ceramics. Mg-substitution increases the 1:2 cations ordering degree and the ordering domain size. With increasing x, the Q × f value increases significantly, a slight decrease occurs in εr, and τf undergoes a small positive shift. Raman spectra reveal that Mg-substitution enhances the coherency of the A1g(O) vibration mode and thus improves the Q × f value. Post-densification annealing has been performed to further increase the cations ordering degree and improve the microwave dielectric properties for x = 0.3. With increasing the annealing temperature, the ordering degree increases monotonically, while the Q × f value increases first and then decreases, meanwhile εr decreases slightly and τf exhibits a negative shift. A good combination of microwave dielectric properties has been achieved for x = 0.3: εr = 32.0, Q × f = 56,500 GHz, τf = 8.4 ppm/°C.

Structure and microwave dielectric properties of Ba[(Mg1−xNix)1/3Nb2/3]O3 ceramics

The microwave dielectric characteristics of Ba[(Mg1−xNix)1/3Nb2/3]O3 ceramics have been investigated together with the microstructures. The microwave dielectric properties are deeply linked to the cations ordering, ordering domain, and Ni valence state. Ni-substitution for Mg promotes the homogenous nucleation of ordering domains but does not favor the domain growth, resulting in the decrease of domain size and ordering degree. τf is adjusted from positive to negative by Ni-substitution, a near-zero τf is obtained for x=0.6; ϵr decreases slightly with increasing x. The ordering degree and ordering domain size dominates the variations of Q×f values. After post-densification annealing, Q×f values increase significantly, while the ϵr and τf values undergo a negative shift. The Ni volatilization results in the oxidization of Ni2+ to Ni3+, affecting the cations ordering and microwave dielectric properties. The best combination of microwave dielectric properties is obtained for the composition with x=0.6: ϵr=29.5, Q×f=60,400GHz, τf=2.8ppm/°C.

Phase ordering in disordered and inhomogeneous systems.

We study numerically the coarsening dynamics of the Ising model on a regular lattice with random bonds and on deterministic fractal substrates. We propose a unifying interpretation of the phase-ordering processes based on two classes of dynamical behaviors characterized by different growth laws of the ordered domain size, namely logarithmic or power law, respectively. It is conjectured that the interplay between these dynamical classes is regulated by the same topological feature that governs the presence or the absence of a finite-temperature phase transition.

Donor–acceptor–π–acceptor based charge transfer chromophore as electron donors for solution processed small molecule organic bulk heterojunction solar cells

Two benzothiazole (BT) based donor–acceptor–π–acceptor (D–A–π–A) molecular system denoted as BT3 and BT4 have been designed, synthesized and their optical and electrochemical properties were investigated. The BT4 show wider absorption profile and lower bandgap as compared to BT3 due to the strong electron withdrawing ability of dicyanoquinodimethane (DCNQ) as compared to tetracyanobutadiene (TCBD). The solution processed bulk heterojunction solar cells were fabricated using BT3 and BT4 as electron donor and PC71BM as electron acceptor. The organic solar cells optimized dichloromethane (DCM) processed BT3:PC71BM (1:1) and BT4:PC71BM (1:1) showed PCE of 2.56% and 3.68%, respectively. The higher PCE of BT4:PC71BM is related to the wider absorption of the blend and better ordered domain sizes in the blend as compared to BT3:PC71BM. The devices processed with 1,8-diiodoctane (DIO) additives showed PCE of 3.77% and 5.27%, for BT3:PC71BM and BT4:PC71BM blends, respectively.

Les onychodystrophies en consultation externe de dermatologie au CHU/YO

The structure of the major protein constituent of photosynthetic membranes in higher plants, the chlorophyll a/b-light harvesting complex (LHC), was studied by x-ray diffraction and electron microscopy. The LHC was purified from Triton X-100 solubilized thylakoid membranes of the pea, and contained 6 mol of chlorophylls a and b per mole of a polypeptide of 27,000 molecular weight. X-ray diffraction showed that in the presence of 10 mM MgCl2, purified LHC forms planar aggregates that stack with a period of 51 A. Within each layer, LHC molecules pack with a center-to-center distance of 85 A but without long-range order. However, when LHC is incorporated into single-walled vesicles of plant lecithin, the addition of NaCl above 10 mM, or MgCl2 above 2 mM, led to the formation of plaques of hexagonal lattices, with a lattice constant of 125 A. The large domain size and high degree of order in the plane of the membrane are evident from the sharp lattice lines observed to 7 A resolution on the equator of the x-ray pattern. Freeze-fracture electron micrographs demonstrated an aligned stacking of the lattices in adjacent membranes, resulting in crystallinity in the third dimension over short distances. Micrographs of negatively stained membranes revealed a hexagonal lattice of the same lattice constant, formed by surface-exposed parts of the LHC molecules which are probably responsible for the ordered stacking of lattices. In both the LHC aggregates and in the reconstituted membrane lattices the diffracted x-ray intensities at 10-A spacing on the equator indicate that the LHC molecule contains paralled alpha-helices or beta-sheets that are oriented perpendicular to the planar arrays.

Hamartome folliculo-sébacé kystique : à propos de quatre cas

The structure of the major protein constituent of photosynthetic membranes in higher plants, the chlorophyll a/b-light harvesting complex (LHC), was studied by x-ray diffraction and electron microscopy. The LHC was purified from Triton X-100 solubilized thylakoid membranes of the pea, and contained 6 mol of chlorophylls a and b per mole of a polypeptide of 27,000 molecular weight. X-ray diffraction showed that in the presence of 10 mM MgCl2, purified LHC forms planar aggregates that stack with a period of 51 A. Within each layer, LHC molecules pack with a center-to-center distance of 85 A but without long-range order. However, when LHC is incorporated into single-walled vesicles of plant lecithin, the addition of NaCl above 10 mM, or MgCl2 above 2 mM, led to the formation of plaques of hexagonal lattices, with a lattice constant of 125 A. The large domain size and high degree of order in the plane of the membrane are evident from the sharp lattice lines observed to 7 A resolution on the equator of the x-ray pattern. Freeze-fracture electron micrographs demonstrated an aligned stacking of the lattices in adjacent membranes, resulting in crystallinity in the third dimension over short distances. Micrographs of negatively stained membranes revealed a hexagonal lattice of the same lattice constant, formed by surface-exposed parts of the LHC molecules which are probably responsible for the ordered stacking of lattices. In both the LHC aggregates and in the reconstituted membrane lattices the diffracted x-ray intensities at 10-A spacing on the equator indicate that the LHC molecule contains paralled alpha-helices or beta-sheets that are oriented perpendicular to the planar arrays.

Both Detergent Effects Upon Domain Size and Transmembrane Protein Length Effects Upon Domain Binding Suggest that Hydrophobic Mismatch can Control the Properties of Ordered Membrane Domains (“Rafts”)

Hydrophobic mismatch between co-existing domains potentially plays an important role in determining domain size and domain interaction with transmembrane proteins. We recently found that in bilayers with the potential to form co-existing Ld and Lo domains, the detergent Triton X-100 enlarges ordered domain size without perturbing ordered domain formation. This can be explained if the effect of detergent is greatest at the boundary between Lo and Ld domains, which would be the case if the main effect of detergent bound to the membranes is to alter the difference between Lo and Ld bilayer width. In other studies, we found that for a multi-transmembrane segment protein, perfringolysin O (PFO), altering the length of transmembrane sequences controls affinity of the protein for membranes domains in a fashion that is dependent upon domain bilayer width. In bilayers with co-existing Ld and Lo domains, PFO with shortened transmembrane segments preferred to partition into the membrane domains with a thin bilayer width, while PFO with lengthened transmembrane segments preferred to partition into domains forming a wider bilayer. PFO with intermediate length, wild type, transmembrane segments exhibited intermediate behavior. This relative bilayer width preference was the same whether the Lo domains were the thinner or wider membrane domains. The effect of transmembrane length upon domain localization was observed both in vesicles that have domains large enough to see by light microscopy and in vesicles with sub-microscopic domains, in which domain affinity was assayed with FRET. Thus, for both of detergent effects and protein-domain association experiments it is likely that hydrophobic mismatch is a key parameter.