Crystal supramolecularity: hexagonal arrays of sextuple phenyl embraces amongst chemically diverse compounds

1998 ◽  
pp. 329-344 ◽  
Author(s):  
Marcia Scudder ◽  
Ian Dance
Keyword(s):  
Crystal Supramolecularity ◽  
Hexagonal Arrays

The low-resolution 3D-structure of porin, a channel-forming protein in E. coliouter membranes

1983 ◽  
Vol 41 ◽  
pp. 440-441
Author(s):  
A. Engel ◽  
D.L. Dorset ◽  
A. Massalski ◽  
J.P. Rosenbusch
Keyword(s):  
Crystal Packing ◽  
3D Structure ◽  
Gram Negative Bacteria ◽  
Protein Ratio ◽  
Crystal Forms ◽  
Large Molecules ◽  
Functional Studies ◽  
Voltage Dependent ◽  
Planar Membranes ◽  
Hexagonal Arrays

Porins represent a group of channel forming proteins that facilitate diffusion of small solutes across the outer membrane of Gram-negative bacteria, while excluding large molecules (>650 Da). Planar membranes reconstituted from purified matrix porin (OmpF protein) trimers and phospholipids have allowed quantitative functional studies of the voltage-dependent channels and revealed concerted activation of triplets. Under the same reconstitution conditions but using high protein concentrations porin aggregated to 2D lattices suitable for electron microscopy and image processing. Depending on the lipid-to- protein ratio three different crystal packing arrangements were observed: a large (a = 93 Å) and a small (a = 79 Å) hexagonal and a rectangular (a = 79 Å b = 139 Å) form with p3 symmetry for the hexagonal arrays. In all crystal forms distinct stain filled triplet indentations could be seen and were found to be morphologically identical within a resolution of (22 Å). It is tempting to correlate stain triplets with triple channels, but the proof of this hypothesis requires an analysis of the structure in 3 dimensions.

Observations on the Structure of Ta2O5

1972 ◽  
Vol 30 ◽  
pp. 540-541
Author(s):  
P. S. Kotval ◽  
C. J. Dewit
Keyword(s):  
Electron Microscope ◽  
Structural Features ◽  
Amorphous Structure ◽  
Polished Surface ◽  
Distilled Water ◽  
Anodic Films ◽  
Amorphous Films ◽  
Beam Heating ◽  
Diffraction Patterns ◽  
Hexagonal Arrays

The structure of Ta2O5 has been described in the literature in several different crystallographic forms with varying unit cell lattice parameters. Earlier studies on films of Ta2O5 produced by anodization of tantalum have revealed structural features which are not consistent with the parameters of “bulk” Ta2O5 crystalsFilms of Ta2O5 were prepared by anodizing a well-polished surface of pure tantalum sheet. The anodic films were floated off in distilled water, collected on grids, dried and directly examined in the electron microscope. In all cases the films were found to exhibit diffraction patterns representative of an amorphous structure. Using beam heating in the electron microscope, recrystallization of the amorphous films can be accomplished as shown in Fig. 1. As suggested by earlier work, the recrystallized regions exhibit diffraction patterns which consist of hexagonal arrays of main spots together with subsidiary rows of super lattice spots which develop as recrystallization progresses (Figs. 2a and b).

Evolutionary algorithms based synthesis of low sidelobe hexagonal arrays

2018 ◽  
Vol 38 ◽  
pp. 139-157 ◽  
Author(s):  
Sudipta Das ◽  
Rajesh Bera ◽  
Durbadal Mandal ◽  
Sakti Prasad Ghoshal ◽  
Rajib Kar
Keyword(s):  
Evolutionary Algorithms ◽  
Low Sidelobe ◽  
Hexagonal Arrays

Large Scale Monodisperse Hexagonal Arrays of Superparamagnetic Iron Oxides Nanodots: A Facile Block Copolymer Inclusion Method

2012 ◽  
Vol 24 (18) ◽  
pp. 2390-2397 ◽  
Author(s):  
Tandra Ghoshal ◽  
Tuhin Maity ◽  
Jeffrey F. Godsell ◽  
Saibal Roy ◽  
Michael A. Morris
Keyword(s):  
Block Copolymer ◽  
Iron Oxides ◽  
Large Scale ◽  
Superparamagnetic Iron Oxides ◽  
Inclusion Method ◽  
Hexagonal Arrays

Hexagonal arrays of grain-boundary dislocations in coherent twin boundaries

1986 ◽  
Vol 53 (3) ◽  
pp. L31-L34 ◽  
Author(s):  
C. T. Forwood ◽  
L. M. Clarebrough
Keyword(s):  
Grain Boundary ◽  
Twin Boundaries ◽  
Hexagonal Arrays

Simulation of the Organization of Heteroepitaxial Monolayer Islands Under Anisotropic Conditions

2004 ◽  
Vol 854 ◽  
Author(s):  
Gajendra Pandey ◽  
Robert V. Kukta
Keyword(s):  
Point Defects ◽  
Surface Stress ◽  
Lattice Mismatch ◽  
Finite Size ◽  
Source Model ◽  
Crystalline Material ◽  
Elastic Fields ◽  
High Anisotropy ◽  
Degree Of Anisotropy ◽  
Hexagonal Arrays

ABSTRACTThis paper addresses the effect of anisotropy on the organization of epitaxial islands deposited on a substrate. Focus is on in-plane anisotropies in surface stress and lattice mismatch between the film and substrate materials. Starting from a configuration where island sizes and position are random, evolution towards equilibrium through mass transport via condensation/evaporation is simulated. The effect of the degree of anisotropy is investigated. An efficient numerical method is obtained by reducing a model of square monolayer islands of finite size to point defects that interact through their elastic fields. Models for both the kinetics and energetics of the system are obtained by this reduction. It is found that the point source model is accurate for island separations larger than about 3 times the width of an island. Under isotropic conditions islands tend to form into hexagonal arrays, and as there is no preferred orientation of these arrays, defects analogous to grain boundaries in a crystalline material tend to arise. With anisotropy islands tend to align in particular directions. This is found to enhance organization in cases of modest anisotropy and cause islands to form into zigzagged lines in cases of high anisotropy.

Hexagonal arrays of Pt nanocylinders on the top surface of PAA membranes using low vacuum sputter coating technique

Vacuum ◽  
2019 ◽  
Vol 161 ◽  
pp. 259-267 ◽  
Author(s):  
Mohamed Shaban ◽  
Mona Ali ◽  
Kamal Abdelhady ◽  
Aftab Aslam Parwaz Khan ◽  
Hany Hamdy
Keyword(s):  
Coating Technique ◽  
Sputter Coating ◽  
Hexagonal Arrays

Hexagonal arrays and rectangular blocks

1976 ◽  
Vol 5 (3) ◽  
pp. 353-381 ◽  
Author(s):  
Gift Siromoney ◽  
Rani Siromoney
Keyword(s):  
Hexagonal Arrays
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