Phase identification in a series of liquid crystalline TPP polyethers and copolyethers having highly ordered mesophase structures. 6. Structure changes from smectic to columnar phases in a series of copolyethers containing odd and even numbers of methylene units in equal molar composition

A series of liquid crystalline copolyethers has been synthesized from 1-(4-hydroxy-4'-biphenyl)-2-(4-hydroxyphenyl)propane and different alpha,omega-dibromoalkanes [coTPP(n/m)]. In this report, coTPPs having n = 5, 7, 9, 11 and m = 12 are studied, which represent copolyethers having both varying odd number and a fixed even number of methylene units. The compositions were fixed at an equal molar ratio (50/50). These coTPPs(nlm) show multiple phase transitions during cooling and heating in differential scanning calorimetry experiments. The undercooling dependence of these transitions is found to be small, indicating that these transitions are close to equilibrium, Although the coTPPs possess a high-temperature nematic (N) phase, the periodicity order along the chain direction is increasingly disturbed when the length of the odd-numbered methylene units decreases from n 11 to 5. in the coTPPs(5/12, 7/12, and 9/12), wide-angle X-ray diffraction experiments at different temperatures show that, shortly after the N phase formation during cooling, the lateral molecular packing improves toward a hexagonal lattice, as evidenced by a gradual narrowing of the scattering halo. This process represents the possible existence of an exotic N phase, which serves as a precursor to the columnar (Phi(H)) phase. A further decrease in temperature leads to a (PH phase having a long-range ordered, two-dimensional hexagonal lattice. In coTPP(11/12), the phase structures are categorized as highly ordered and tilted, smectic and smectic crystal phases, similar to homoTPPs, such as the smectic F (S-F) and smectic crystal G (SCG) phases. An interesting observation is found for coTPP(9/12), wherein a structural change from the high-temperature Phi(H) phase to the low-temperature S-F phase occurs. It can be proven that, upon heating, the well-defined layer structure disappears and the lateral packing remains hexagonal. The overall structural differences in this series of coTPPs between those of the columnar and highly ordered smectic phases are related to the disorders introduced into the layer structure by the dissimilarity of the methylene unit lengths in the comonomers.

Columnar-to-disk structural transition in nanoscale (SiO2)(N) clusters

Bromley, S. T., Flikkema, E. (2005) 'Columnar-to-disk structural transition in nanoscale (SiO2)(N) clusters'. Physical Review Letters 95 (18), article no: 185505 RAE2008

Columnar aerosol properties in a northeastern atlantic site (plymouth united kingdom) by means of ground based skyradiometer data during years 2000-2008.

Between 2000 and 2008, columnar optical and radiative properties were measured at the Plymouth Marine Laboratory (PML), UK (50° 21.95′N, 4° 8.85′W) using an automatic Prede POM01L sun–sky photometer. The database was analyzed for aerosol optical properties using the SKYRAD radiative inversion algorithm and calibrated using the in situ SKYIL calibration method. Retrievals include aerosol optical depth, Ångström wavelength exponent, aerosol volume distribution, refractive index and single scattering albedo. The results show that the Plymouth site is characterized by low values of aerosol optical depth with low variability (0.18 ± 0.08 at 500 nm) and a mean annual Ångström exponent of 1.03 ± 0.21. The annual mean of the single scattering albedo is 0.97, indicative of non-absorbing aerosols. The aerosol properties were classified in terms of air mass back trajectories: the area is mainly affected by Atlantic air masses and the dominant aerosol type is a mixture of maritime particles, present in low burdens with variable size. The maritime air masses were defined by annual mean values for the AOD (at 500 nm) of 0.13–0.14 and a wavelength exponent of 0.96–1.03. Episodic anthropogenic and mineral dust intrusions occasionally occur, but they are sporadic and dilute (AOD at 500 nm about 0.20). Tropical continental air masses were characterized by the highest AOD at 500 nm (0.34) and the lowest wavelength exponent (0.83), although they were the least represented in the analysis.

Lack of RUNX3 inactivation in columnar cell lesions of breast

Aims:

Fabrication of thin films and nano columnar structures of Fe-Ni amorphous alloys and modification of its surface properties by thermal annealing and swift heavy ion irradiation for tailoring the magnetic properties

Department of Physics, Cochin University of Science and Technology

Nematic and columnar ordering of a PEG-peptide conjugate in aqueous solution

The self-assembly in aqueous solution of a PEG-peptide conjugate is studied by spectroscopy, electron microscopy, rheology and small-angle Xray and neutron scattering (SAXS and SANS). The peptide fragment, FFKLVFF is based on fragment KLVFF of the amyloid beta-peptide, A beta(16-20), extended by two hydrophobic phenylalanine units. This is conjugated to PEG which confers water solubility and leads to distinct self-assembled structures. Small-angle scattering reveals the formation of cylindrical fibrils comprising a peptide core and PEG corona. This constrained structure leads to a model parallel beta-sheet self-assembled structure with a radial arrangement of beta sheets. Oil increasing concentration, successively nematic and hexagonal columnar phases are formed. The flow-induced alignment of both structures was studied in situ by SANS using a Couette cell. Shear-induced alignment is responsible for the shear thinning behaviour observed by dynamic shear rheometry. Incomplete recovery of moduli after cessation of shear is consistent with the observation from SANS of retained orientation in the sample.

Columnar translation: an ancient interpretive tool that the Romans gave the Greeks

Among the more peculiar literary papyri uncovered in the past century are numerous bilingual texts of Virgil and Cicero, with the Latin original and a Greek translation arranged in distinctive narrow columns. These materials, variously classified as texts with translations or as glossaries, were evidently used by Greek-speaking students when they first started to read Latin literature. They thus provide a unique window into the experience of the first of many groups of non-native Latin speakers to struggle with reading the classics of Latin literature.

Columnar joints in the Patino Formation sandstones, Eastern Paraguay: a dynamic interaction between dyke intrusion, quartz dissolution and cooling-induced fractures

The Patino Formation sandstones, which crop out in Aregua neighborhood in Eastern Paraguay and show columnar joints near the contact zone with a nephelinite dyke, have as their main characteristics the high proportion of syntaxial quartz overgrowth and a porosity originated from different processes, initially by dissolution and later by partial filling and fracturing. Features like the presence of floating grains in the syntaxial cement, the transitional interpenetrative contact between the silica-rich cement and grains as well as the intense fracture porosity are strong indications that the cement has been formed by dissolution and reprecipitation of quartz from the framework under the effect of thermal expansion followed by rapid contraction. The increase of the silica-rich cement towards the dyke in association with the orthogonal disposition of the columns relative to dyke walls are indicative that the igneous body may represent the main heat source for the interstitial aqueous solutions previously existing in the sediments. At macroscopic scale, the increasing of internal tensions in the sandstones is responsible for the nucleation of polygons, leading to the individualization of prisms, which are interconnected by a system of joints, formed firstly on isotherm surfaces of low temperature and later on successive adjacent planes towards the dyke heat source.

Sequencing of Spodoptera frugiperda midgut trehalases and demonstration of secretion of soluble trehalase by midgut columnar cells

Both soluble (SfTre1) and membrane-bound (SfTre2) trehalases occur along the midgut of Spodoptera frugiperda larvae. Released SfTre2 was purified as a 67 kDa protein. Its K(m) (1.6 mM) and thermal stability (half life 10 min at 62 degrees C) are different from the previously isolated soluble trehalase (K(m) = 0.47 mM; 100% stable at 62 degrees C). Two cDNAs coding for S. frugiperda trehalases have been cloned using primers based on consensus sequences of trehalases and having as templates a cDNA library prepared from total polyA-containing RNA extracted from midguts. One cDNA codes for a trehalase that has a predicted transmembrane sequence and was defined as SfTre2. The other, after being cloned and expressed, results in a recombinant trehalase with a K(m) value and thermal stability like those of native soluble trehalase. This enzyme was defined as SfTre1 and, after it was used to generate antibodies, it was immunolocalized at the secretory vesicles and at the glycocalyx of columnar cells. Escherichia coli trehalase 3D structure and sequence alignment with SfTre1 support a proposal regarding the residue modulating the pKa value of the proton donor.

Columnar microstructure of nanocrystalline Ga1-xMnxN films deposited by reactive sputtering

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Vortex lattice of a long superconducting wire with a columnar defect

In the present work we study a long superconducting wire with a columnar defect in the presence of an applied magnetic field. The cross section of the cylinder is assumed to be circular. The field is taken uniform and parallel to the cylinder axis. We use the London theory to investigate the vortex lattice inside the wire. Although this theory is valid in the limit of low vortex density, that is, when the nearest neighbor vortex distance is much larger than the coherence length, we can obtain a reasonable qualitative description of lattice properties. We calculate: (1) the vortex lattice structure using the simulated annealing technique; (2) the magnetization curve as a function of the applied field.

Vortices in superconductors with a columnar defect: Finite size effects

In the present work we investigate the behavior of a vortex in a long superconducting cylinder near to a columnar defect at the center. The derivations of the local magnetic field distribution and the Gibbs free energy will be carried out for a cylinder and a cavity of arbitrary sizes. From the general expressions, it is considered two particular limits: one in which the radius of the cavity is very small but the radius of the superconducting cylinder is kept finite; and one in which the radius of the superconducting cylinder is taken very large (infinite) but the radius of the cavity is kept finite. In both cases the maximum number of vortices which are allowed in the cavity is determined. In addition, the surface barrier field for flux entrance into the cavity is calculated. (c) 2005 Elsevier B.V. All rights reserved.