Orientation Of Columns Research Articles

Study of structure development of Titanium Nitride on inclined substrates

For magnetron sputter deposited coatings, the structure development during growth mostly depends on the mobility of the adatom over the substrate. The mobility is significantly affected by the orientation of the substrate with respect to the direction of the incident flux of sputtered atoms. The structural properties like crystallite size, crystallographic structure, column orientation, etc., are therefore influenced. This is relevant as the real work pieces over which the overlay functional coatings has to be applied are three dimensional in nature with the surfaces being off-normal to the incident flux. In the present investigation, the effect of incident angle on the various aspects of the structure development of Titanium Nitride coatings, having wide tribological applications, deposited on Si substrates by reactive magnetron sputter deposition was studied. A planar magnetron, with cathode diameter 75mm and mounted with pure Ti target was used and TiN was deposited in a mixture of argon and nitrogen gas. The deposition was done for different durations. The deposited coatings were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results indicate the formation of well defined columnar microstructure in the coatings. The column inclination is compared with the well known ‘Tangent rule’.

3D structure of nematic and columnar phases of hard colloidal platelets

We present small angle x-ray scattering data of single-domain nematic and columnar liquidcrystal phases in suspensions of sterically stabilized gibbsite platelets. The measurementsare performed with different sample orientations to obtain information about thethree-dimensional structure of the liquid crystalline phases. With the x-ray beam incidentalong the director of the nematic phase a strong correlation peak is observed correspondingto the side-to-side interparticle correlations, which suggests a columnar nematic structure.Upon sample rotation this side-to-side correlation peak of the nematic shifts to higherQ-values, suggesting the presence of strong fluctuations of small stacks of particles withdifferent orientations, while the overall particle orientation is constant. In the hexagonalcolumnar phase, clear Bragg intercolumnar reflections are observed. Upon rotation, theQ-value of these reflections remains constant while their intensity monotonically decreasesupon rotation. This indicates that the column orientation fluctuates together with theparticle director in the columnar phase. This difference between the behaviour of thecolumnar and the nematic reflections upon sample rotation is used to assign the liquidcrystal phase of a suspension consisting of larger platelets, where identification can beambiguous due to resolution limitations.

Processing-structure-property relationships in electron beam physical vapor deposited yttria stabilized zirconia coatings

The physical and mechanical properties of yttria stabilized zirconia (YSZ) coatings deposited by the electron beam physical vapor deposition technique have been investigated by varying the key process variables such as vapor incidence angle and sample rotation speed. The tetragonal zirconia coatings formed under varying process conditions employed were found to have widely different surface and cross-sectional morphologies. The porosity, phase composition, planar orientation, hardness, adhesion, and surface residual stresses in the coated specimens were comprehensively evaluated to develop a correlation with the process variables. Under transverse scratch test conditions, the YSZ coatings exhibited two different crack formation modes, depending on the magnitude of residual stress. The influence of processing conditions on the coating deposition rate, column orientation angle, and adhesion strength has been established. Key relationships between porosity, hardness, and adhesion are also presented.

Mesoporous silica hybrid membranes for precise size-exclusive separation of silver nanoparticles

One-dimensional (1D) nanomaterials have unique applications due to their inherent physical properties. In this study, hexagonally ordered mesoporous silica hybrid anodic alumina membranes (AAM) were synthesized using template-guided synthesis with a number of nonionic n-alkyl-oligo(ethylene oxide), Brij-type (C x EO y ), which are surfactants that have different molecular sizes and characteristics. The hexagonal mesoporous silicas are vertically aligned in the AAM channels with a predominantly columnar orientation. The hollow mesostructured silicas had tunable pore diameters varying from 3.7 to 5.1 nm. In this synthesis protocol, the surfactant molecular natures (corona/core features) are important for the controlled generation of ordered structures throughout AAM channels. The development of ultrafiltration membranes composed of silica mesostructures could be used effectively in separating silver nanoparticles (Ag NPs) in both aqueous and organic solution phases. This would be relevant to the production of well-defined Ag NPs with unique properties. To create a size-exclusive separation system of Ag NPs, we grafted hydrophobic trimethylsilyl (TMS) groups onto the inner pores of the mesoporous silica hybrid AAM. The immobilization of the TMS groups allowed the columnar mesoporous silica inside AAM to retain this inner pore order without distortion during the separation of solution-phase Ag NPs in organic solvents that may cause tortuous-pore membranes. Mesoporous TMS-silicas inside 1D AAM channels were applicable as a size-exclusive separation system to isolate organic solution-phase Ag NPs of uniform morphology and size.

Enhanced Biochemical and Biomechanical Properties of Scaffolds Generated by Flock Technology for Cartilage Tissue Engineering

Natural cartilage shows column orientation of cells and anisotropic direction of collagen fibers. However, matrices presently used in matrix-assisted autologous chondrocyte implantation do not show any fiber orientation. Our aim was to develop anisotropic scaffolds with parallel fiber orientation that were capable to support a cellular cartilaginous phenotype in vitro. Scaffolds were created by flock technology and consisted of a membrane of mineralized collagen type I as substrate, gelatine as adhesive, and parallel-oriented polyamide flock fibers vertically to the substrate. Confocal laser scan microscopy demonstrated that mesenchymal stem cells (MSCs) adhered and proliferated well in the scaffolds and cell vitality remained high over time. Articular chondrocytes seeded in a collagen type I gel into flock scaffolds deposited increasing amounts of proteoglycans and collagen type II over time. MSC-seeded flock scaffold constructs under chondrogenic conditions deposited significantly more proteoglycans and collagen type II than MSC collagen type I gel constructs only. Biomechanical testing revealed higher initial hardness of flock scaffolds than that of a clinically applied collagen type I/III scaffold combined with superior relaxation and an increasing hardness in MSC-loaded flock biocomposites during chondrogenesis. In conclusion, flock technology allows fabrication of scaffolds with anisotropic fiber orientation that mediates superior biomechanical and biochemical composition of tissue engineering constructs for cartilage repair.

Vibration analysis of pultruded FRP frames with semi-rigid connections

Vibration frequencies and mode shapes of pultruded FRP plane and space frames with semi-rigid joints are analyzed using two-node locking- free Hermitian finite elements. A nonlinear beam displacement field, accounting for shear deformation effects due to non-uniform bending and torsion, is adopted. The equation of motion is obtained via Hamilton’s principle, and the second-order work of initial stresses is included. Flexibility of three-dimensional joints is simulated by modifying the element stiffness matrix without introducing additional degrees of freedom. The first natural frequencies of portal frames, two-bay single-storey and single-bay two-storey frames are reported as a function of in-plane rotational joint stiffness, and a mode change between flexural and flexural–torsional vibrations is sometimes observed. Finally, a pultruded space frame is analyzed, which shows the effects of semi-rigid connections, column orientation and shear deformation on the natural frequencies.

Determination of diffusion coefficients by supercritical fluid chromatography: Effects of mobile phase mean velocity and column orientation

The supercritical fluid (SCF) chromatographic technique based on the Taylor dispersion theory has been widely applied in determination of diffusion coefficients of various organic compounds in SCFs. This study was aimed to understand impacts of mobile phase mean velocity (MPMV) and column orientation on diffusion coefficient measurements. The benzene/SCCO 2 system was investigated. Experiments were carried out at 40 and 60 °C and 9–15 MPa over a wide range of CO 2 densities at varying MPMV and repeated in two column orientations, vertical and horizontal. It was found that both MPMV and column orientation significantly affected measurements of diffusion coefficients in SCFs. When the column was installed vertically, apparent diffusion coefficients obtained at relatively low CO 2 density (<580 kg/m 3) increased with increasing MPMV over the entire velocity ranges. This results in a conclusion that diffusion coefficients cannot be accurately determined under these conditions using a vertically installed column. Under all other conditions, as MPMV increased, apparent diffusion coefficients initially increased, then remained constant, and finally increased again. The initial increase of apparent diffusion coefficients was associated with significant decline of curve-fitting errors, which indicates that the buoyancy effects are non-negligible and will cause larger errors. Accordingly, a new generalized D 12– U diagram comprised of three regions is proposed. Column orientation affected diffusion coefficient measurements mainly by enhancing or weakening the buoyancy effects. When the column was installed vertically, the buoyancy effects were enhanced, leading to lower apparent diffusion coefficients, especially when CO 2 density was relatively low. In addition, it was found that when CO 2 density was below ∼580 kg/m 3, diffusion coefficients obtained when the column was horizontally installed were higher than those obtained when the same column was vertically installed. When CO 2 density was above that value, opposite outcomes resulted. Finally, the horizontal orientation of a diffusion column is recommended for diffusion coefficient measurements by the SCF chromatographic technique, especially when densities of SCFs are relatively low.

Molybdenum Difluoride Dioxide, MoO2F2

MoO(2)F(2) is prepared by pyrolysis of (Na(+)H(2)O)(2) cis-MoO(2)F(4)(2-). A preliminary model of the structure is obtained from powder data: it has a triangular columnar structure with three fluorine bridges between the three molybdenum atoms and with oxygen bridges between the layers. (a = 1605, b = 384, c = 1395 pm, Pnma, Z = 12). The closest related structure is that of TiF(4), except that the orientation of the triangular columns is different.

Evaluation of the effect of column orientation in type-I high-speed counter-current chromatography

The performance of type-I high-speed counter-current chromatography was evaluated by changing the column inclination against the rotating centrifugal force field. The separations were performed with two different solvent systems composed of 1-butanol-acetic acid-water (4.75:0.25:5, v/v) (BAW) and hexane-ethyl acetate-methanol-0.1 M HCl (1:1:1:1, v/v) (HEMW) using dipeptides and DNP-amino acid as test samples, respectively. A set of short coiled columns connected in series is mounted around the holder hub in two different ways: in the parallel orientation, all column units are arranged in parallel to each other and mounted on the holder at various angles against the horizontal plane. In the zigzag configuration, the neighboring units of the same column are mounted symmetrically forming various angles apart. In the parallel configuration, for both the BAW and HEMW systems, Sf (the retention of stationary phase) first increased as the column angle decreased from 90 degrees to 60 degrees and then decreased, as the column angle further decreased from 60 degrees to 0 degrees, while Rs (peak resolution) continually declined over the entire column angle range from 90 degrees to 0 degrees. But, for both solvent systems, with the zigzag configuration, retention of stationary phase and resolution both decreased as the column angle decreased from 90 degrees to 0 degrees. In general, Sf and Rs for separation of dipeptides in the BAW system, from 90 degrees to 15 degrees, is better for the parallel orientation than for the zigzag configuration. However, at 0 degrees, Sf and Rs are better for the zigzag orientation. In the DNP-amino acid separation with the HEMW system, retention of the stationary phase and Rs for the parallel orientation is better than that for the zigzag orientation from 90 degrees to 30 degrees, whereas from 30 degrees to 0 degrees the results are opposite. Over all results of our studies revealed that the formally used column orientation at 90 degrees inclination yields the highest peak resolution in both solvent systems.

Orientational Packing of a Confined Discotic Mesogen in the Columnar Phase

The stacking of discotic molecules (hexakis(alkoxy)diquinoxalino[2,3-a:2′,3′-c]phenazines) in the columnar phase sandwiched between two flat glass substrates has been studied. The surface free energy of the substrates, measured by means of sessile drop technique, is found to have significant influence on the way that the discotic molecules anchor on the surface, and a steady thermal state of the system is crucial for a homogenous orientation of the discotic columns. On a surface of high free energy, the discotic molecules anchor with their disc-face toward the surface. A decrease in the surface free energy of the substrate causes the discotic columns to tilt away from the normal of the substrate.

Effect of Interface on the Orientation of the Liquid Crystalline Nickel Phthalocyanine Films

In this paper, the effect of interface oil the orientation of the film of two derivatives of tetra-substituted nickel phthalocyanines NiPcR4-1 (R = -OCH(CH2OC12H25)(2)) and NiPcR4-2 (R = -SCH(CH2(C1CH2CH2)(2)OC2H5)(2)) deposited oil one substrate and between two identical substrates is studied by the method of polarized Raman spectroscopy The methods of ultraviolet-visible (UV-vis) absorption spectroscopy and infrared (IR) spectroscopy were also used for the characterization of films deposited oil quartz and KBr substrates, respectively. The orientation of columns in films confined between two substrates is characterized by polarized optical microscopy It has been shown that the films of both compounds confined between two substrates are characterized by homeotropic alignment while no homeotropic alignments could be obtained with an air interface. The orientation is also independent of the type of substituents on the phthalocyanine ring.

Growth and characterisation on giant magnetoresistance property of metallic multilayers

Metallic multilayers with specific materials configurations have been shown to exhibit giant magnetoresistance effect at room temperature. In this study, microstructural analysis was carried out on magnetron sputtered Co/Cu multilayers using various diffraction and imaging techniques. Dominant characteristic features associated with the multilayers, such as lateral and vertical columnar grain orientations as well as layer undulation and regularity were identified. By deliberately introducing microstructural changes using a buffer layer and via heat treatment, detailed microstructural analysis carried out on the multilayers has provided an insight into the dependence of giant magnetoresistance on the observed microstructures. The present study shows that high giant magnetoresistance effect of the multilayers was associated with highly correlated interfacial profiles, sharp columnar grain boundaries and high degree of lateral coherency in columnar grain growth. While the introduction of iron buffer layer favoured the growth of these structural features that were responsible for large giant magnetoresistance effect, annealing led to deterioration of giant magnetoresistance property of the multilayers.

Serpentine Mineral Replacements of Natural Olivine and their Seismic Implications: Oceanic Lizardite versus Subduction-Related Antigorite

We report on microstructural data obtained by optical microscopy and transmission electron microscopy concerning the crystallographic relationships of serpentine minerals with their host olivine in two contrasting situations. In the first case, mesh-textured lizardite (liz) is developed in a standard 60% serpentinized oceanic harzburgite from the Oman ophiolite where olivine converts to columnar lizardite. The joined columns are perpendicular to the basal plane (001)liz, corresponding to the pseudofibres observed optically. The plane (001)liz is locally parallel to the narrow boundary ol–liz; thus column orientations register the interface of serpentinization. The ol–liz relationships are not strictly topotactic, but reflect preferred cracking orientations in olivine, parallel to (010)ol. In the second case, antigorite (atg) develops in a rare sample of antigorite schist in a kimberlite from Moses Rock (Colorado Plateau), representative of a suprasubduction-zone mantle wedge. High-resolution transmission electron microscopy (HRTEM) images along [010]atg show domains of very regular modulation with a 43·5 Å wavelength (m = 17, where m is the number of silicate tetrahedra along the wave), with few defects, indicative of HP–HT antigorite, and also heavily kinked regions as fingerprints of strong tectonic shear. TEM imaging and electron diffraction patterns reveal two topotactic relationships between antigorite and olivine: [100]atg//[010]ol and <100>atg//<100>ol; the planes in contact are (001)atg//(100)ol and (001)atg//(010)ol, respectively. The [010]atg//[001]ol and antigorite lamellae are parallel to the forsterite b-axis. In both cases, the topography of olivine–serpentine interfaces is controlled by open fluid pathways along microcracks oriented according to the anisotropy of the olivine aggregate. In the cases studied, the serpentine aggregate exhibits a preferred orientation inherited from that of the peridotite. These results have some relevance to the seismic anisotropy of serpentinized mantle. Anisotropy of propagation of seismic waves as a result of the olivine fabric is maintained and reinforced with the development of lizardite. Conversely, the development of antigorite produces a trench-parallel fast S-wave polarization and an anisotropy that is lowered at low degrees of serpentinization and then increased with increasing serpentinization.

Experimental and Numerical Investigations on the Seismic Behavior of Lightly Reinforced Concrete Beam-Column Joints

The experimental and analytical investigations carried out on lightly reinforced concrete beam-column joints subjected to seismic loading are presented in this paper. Five 3/4-scale reinforced concrete beam-column joints were tested to investigate the seismic behavior of the joints. The variables in the tested specimens include column orientations and the presence of slabs on the top of beams. The specimens were subjected to quasi-static load reversals to simulate earthquake loadings. Experimental results obtained include joint shear stresses, joint shear strains, observed cracking and initial stiffness. The test results provided some information about the seismic behavior of the specimens. However, due to the unique nature of the specimens, several key parameters could not be varied. Therefore, to elucidate further information, a numerical study consisting of three-dimensional nonlinear finite-element (FE) models was carried out. The FE models were then validated with the experimental results. This was followed by parametric studies, carried out to understand the effects of several critical factors, including column axial load, ratio of column depth to beam reinforcement bar diameter, and effective slab width, on the complex behavior of the joints.

Transplantation of free tibial periosteal grafts for the repair of articular cartilage defect: An experimental study.

Background:Articular chondrocytes have got a long lifespan but rarely divides after maturity. Thus, an articular cartilage has a limited capacity for repair. Periosteal grafts have chondrogenic potential and have been used to repair defects in the articular cartilage. The purpose of the present study is to investigate the differentiation of free periosteal grafts in the patellofemoral joint where the cambium layer faces the subchondral bone and to investigate the applicability of periosteal grafts in the reconstruction of articular surfaces.Materials and Methods:The study was carried out over a period of 1 year on 25 adult, male Indian rabbits after obtaining permission from the institutional animal ethical committee. A full-thickness osteochondral defect was created by shaving off the whole articular cartilage of the patella of the left knee. The defect thus created was grafted with free periosteal graft. The patella of the right knee was taken as a control where no grafting was done after shaving off the articular cartilage. The first animal was used to study the normal histology of the patellar articular cartilage and periosteum obtained from the medial surface of tibial condyle. Rest 24 animals were subjected to patellectomy, 4 each at serial intervals of 2, 4, 8, 16, 32 and 48 weeks and the patellar articular surfaces were examined macroscopically and histologically.Results:The grafts got adherent to the underlying patellar articular surface at the end of 4 weeks. Microscopically, graft incorporation could be appreciated at 4 weeks. Mesenchymal cells of the cambium layer were seen differentiating into chondrocytes by the end of 4 weeks in four grafts (100%) and they were arranged in a haphazard manner. Till the end of 8 weeks, the cellular arrangement was mostly wooly. At 16 weeks, one graft (25%) had wooly arrangement of chondrocytes and three grafts (75%) had columnar formation of cells. Same percentage was maintained at 32 weeks. Four grafts (100%) at 48 weeks showed columnar orientation. The control side showed no changes over the shaved off articular surface in all the rabbits. One rabbit at 4 weeks had a dislocation of the patella on the control side. None of the rabbits developed any infection or wound dehiscence.Conclusion:Autologous periosteal graft transplantation can be a promising substitute for articular cartilaginous defects.

Vertical Columnar Block-Copolymer-Templated Mesoporous Silica via Confined Phase Transformation

An efficient method is described for the preparation of phase-pure columnar mesoporous silica nanosystems within the channels of anodic alumina membranes (AAM) via evaporation-induced self-assembly (EISA). Upon the basis of a systematic investigation of the effects of interfacial interactions and different synthesis parameters on the resulting hierarchical mesophase, a salt-induced phase transformation was developed for efficient structural control. Samples with a columnar hexagonal 2D structure along the vertical channels of the AAM can be produced with ionic CTAB as template. However, when nonionic surfactants (Pluronic P123 and Brij 56) are used, samples with a circular hexagonal 2D structure perpendicular to the channels or phase mixtures of circular and columnar orientations are obtained. The behavior of ionic CTAB can be mimicked by adding inorganic salt to the nonionic template precursor solution, thus leading to a phase transformation toward columnar orientation. The distribution between the orientations was determined by means of small-angle X-ray scattering (SAXS) experiments. The effects of other synthesis parameters were also investigated, including temperature, surfactant: silica ratio, and salt composition. Strikingly, calcination-stable mesoporous materials with a columnar orientation exhibiting high mesoporosity and specific surface area were obtained for the first time with such structure directors. The salt-induced phase transformation is an efficient means for achieving a desired hierarchical mesostructure in the confined space of the AAM channels.

A Bayesian framework for cue integration in multistable grouping: Proximity, collinearity, and orientation priors in zigzag lattices

Integration of proximity and good continuation cues is analyzed as a probabilistic inference problem in contour grouping. A Bayesian framework was tested in a multistable dot lattice experiment. In rectangular lattices, distance ratio and global orientation of rows and columns were manipulated. Discollinearity was introduced by imposing zigzag in one orientation, by either fixed or stochastic displacement of elements. Results indicate that proximity and good continuation are generally treated as independent sources of information, added to prior orientation log-odds to produce the odds of grouping percepts. Distance likelihood is well captured by a power law, and discollinearity likelihoods by generalized Laplace distributions, with higher kurtosis for stochastic zigzag. While observers prefer vertical over horizontal orientations, the exact prior distribution is idiosyncratic. Perceptual grouping along cardinal axes is less affected by distance, but more by discollinearity, than along oblique orientations. Results are qualitatively and quantitatively compared to ecological statistics of contours (J. H. Elder & R. M. Goldberg, 2002). The potential of hierarchically extended Bayes models for a better understanding of principles in cue integration is discussed.

Photoalignment and patterning of a chromonic–silica nanohybrid on photocrosslinkable polymer thin films

We recently found that the chromonic mesophase structure of an azo dye can be immobilized by a silica network to form a chromonic–silica nanohybrid. This work reports the first demonstration of the macroscopic photoalignment and photopatterning of this nanohybrid via surface-mediated orientational transfer from a photocrosslinkable liquid crystalline polymer (PPLC). Irradiation with linearly polarized light (LPL) 300 nm above the PPLC film followed by an appropriate annealing process led to strong in-plane molecular orientation in the film. The precursor sol solution containing a chromonic forming azo dye and tetraethoxysilane in the presence of an anionic surfactant and 2-(2-aminoethoxy)ethanol was placed onto this aligned film by the static deposition or dipping method. After drying, the chromonic columns hybridized with silica were macroscopically oriented orthogonal to the LPL direction, namely the orientation of the dye molecule being parallel to it. In the dip coating process, a combination of photoalignment and flow induced orientation allowed clear micropatterning of the column orientations, which could be readily discerned when observed with a polarizing film.

Stacking of Main Chain-Crown Ether Polymers in Thin Films

Thin films (9-70 nm) of a series of polymers containing in the main chain dibenzo-18-crown-6 ether unit (DB18C6) linked to an aliphatic spacer of different length (10C and 14C) and nature have been prepared, from chloroform solutions, by spin coating on a silicon substrate. The quality and homogeneity of the polymer coatings was revealed by their reflectivity spectra and atomic force microscopy (AFM). The grazing incidence small-angle X-ray scattering (GISAXS) patterns show an out-of-plane structure correlation (interference maximum near the horizon) of scale size related to the polymer repeating unit length. Above this Bragg reflection, the shape of the scattering observed, in the GISAXS pattern, reveals an orientation of the stacked molecular columns in the coated polymer. A thermal treatment of the samples improves the nanostructure by increasing the lamellar coherence size (in y-direction) as well as the vertical orientation of the molecular columns.

Microfocus X-ray Diffraction Study of the Columnar Phase of Porphyrin-Based Mesogens

Porphyrin-based materials are prime candidates for solar energy harvesting applications. New compounds incorporating the porphyrin core, which exhibit the columnar liquid crystal (LC) phase, were synthesized as they offer a route to obtaining defect-free large area monodomain films. The structure of the phases exhibited by these materials has been probed by synchrotron X-ray diffraction with a microfocus (14 μm × 14 μm) beam. Exploiting the multidomain nature (i.e., having differently oriented crystal axes) of a thin glass cell, it was possible to obtain complete structural information without the need to have one single macroscopic crystal, which is normally difficult to obtain. The results confirmed the existence of the isotropic, discotic (columnar) LC, and discotic-ordered LC phases in these materials. The optical microscopic work demonstrates how macroscopic control of columnar orientations is achieved by manipulating the LC film thickness, substrate preparation, and the thermal annealing process.