Direct Triple Annulations: A Way to Design Large Triazastarphenes with Intertwined Hexagonal Packing

Dual porosity fibrous media are important in a number of applications, ranging from bioreactor design and transport in living systems to composites manufacturing. In the present study we are concerned with the development of predictive models for the hydraulic permeability ( Kp) of various arrays of fibre bundles. For this we carry out extensive computations for viscous flow through arrays of fibre bundles using the Boundary Element Method (BEM) implemented on a multi-processor computer. Up to 350 individual filaments, arranged in square or hexagonal packing within bundles, which are also arranged in square of hexagonal packing, are included in each simulation. These are simple but not trivial models for fibrous preforms used in composites manufacturing – dual porosity systems characterised by different inter- and intra-tow porosities. The way these porosities affect the hydraulic permeability of such media is currently unknown and is elucidated through our simulations. Following numerical solution of the governing equations, ( Kp) is calculated from the computed flowrate through Darcy's law and is expressed as function of the inter- and intra-tow porosities (φ, φt) and of the filament radius ( Rf). Numerical results are also compared to analytical models. The latter form the starting point in the development of a dimensionless correlation for the permeability of such dual porosity media. It is found that the numerically computed permeabilities follow that correlation for a wide range of φ i, φt and Rf.

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1,1′-Biadamantane-3,3′-diol: a two-dimensional network supported by a `hexameric alcohol cluster' supramolecular synthon

Acta Crystallographica Section C Crystal Structure Communications ◽

10.1107/s0108270112051785 ◽

2013 ◽

Vol 69 (2) ◽

pp. 175-178 ◽

Cited By ~ 2

Author(s):

Konstantin V. Domasevitch

Keyword(s):

Title Compound ◽

Chair Conformation ◽

The Other ◽

Two Dimensional ◽

Supramolecular Synthon ◽

Hexagonal Packing ◽

Compound C ◽

Dimensional Network ◽

Grid Topology ◽

Independent Molecules

In the title compound, C20H30O2, one of the two crystallographically independent molecules lies across a centre of inversion and the other resides in a general position (Z′ = 1.5). The supramolecular structure exists as an unusual two-dimensional network incorporating centrosymmetric hexameric hydrogen-bonded alcohol (OH)6clusters [O...O = 2.6637 (12)–2.6993 (12) Å] as the net nodes. The hexamers adopt a chair conformation [O...O...O = 106.55 (4)–115.81 (4)°] and are connected into a network with a square-grid topology (44) by a combination of single and double 1,1′-biadamantanediyl links. The bulky aliphatic groups appear to require specific hexagonal packing and so generate distinct noncovalent hydrophobic layers, which are essential for the stabilization of the hexameric alcohol array rather than the formation of the more commonly encountered tetramer-based arrays.

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Crystal structure of chloridobis[(1,2,5,6-η)-cycloocta-1,5-diene]iridium(I)

Acta Crystallographica Section E Crystallographic Communications ◽

10.1107/s2056989017000809 ◽

2017 ◽

Vol 73 (2) ◽

pp. 273-277 ◽

Cited By ~ 1

Author(s):

A. K. Fazlur Rahman ◽

Miles Wilklow-Marnell ◽

William W. Brennessel ◽

William D. Jones

Keyword(s):

Title Complex ◽

Asymmetric Unit ◽

Large Excess ◽

Orthorhombic Space Group ◽

Slow Cooling ◽

Hexagonal Packing ◽

Trigonal Bipyramidal ◽

Chloride Ligand ◽

Packing Arrangement ◽

Coordinate Geometry

The title complex, [IrCl(C8H12)2], was synthesized directly from the reaction of IrCl3·3H2O with a large excess of cod (cod = cycloocta-1,5-diene) in alcoholic solvent. Large yellow needles were obtained by the slow cooling of a hot solution. Based on the positions of the chloride ligand and the mid-points of the four C=C bonds, the molecule adopts a five-coordinate geometry that is midway between square pyramidal and trigonal bipyramidal. The material crystallizes in the orthorhombic space groupPbcawith one molecule per asymmetric unit in a general position and shows no significant intermolecular interactions. Individual molecules are aligned along [010], and these rows form a pseudo-hexagonal packing arrangement.

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Heart gap junction preparations reveal hemiplaques by atomic force microscopy

AJP Cell Physiology ◽

10.1152/ajpcell.1995.268.4.c968 ◽

1995 ◽

Vol 268 (4) ◽

pp. C968-C977 ◽

Cited By ~ 52

Author(s):

R. Lal ◽

S. A. John ◽

D. W. Laird ◽

M. F. Arnsdorf

Keyword(s):

Gap Junctions ◽

Gap Junction ◽

Long Range ◽

Connexin 43 ◽

Plasma Membranes ◽

Aqueous Media ◽

Freeze Fracture ◽

Isolated Rat Heart ◽

Hexagonal Packing ◽

Atomic Force

Current structural models of gap junctions indicate two apposed plasma membranes with hexagonally packed hemichannels in each membrane aligning end to end. These channels connect the cytoplasms of contacting cells. Images of isolated rat heart gap junctions have been made with the atomic force microscope in aqueous media. We show that native cardiac gap junctions have a thickness of 25 +/- 0.6 nm. This decreases to 17 nm when they are treated with trypsin, which is known to remove some cytoplasmic components of connexin 43. Imaging shows subunits with a center to center spacing of approximately 9-10 nm and long range hexagonal packing, measurements in agreement with studies using freeze-fracture and negative-stain electron microscopy. In addition to gap junctions, we imaged structures that had all the characteristics of native gap junctions except their thickness was limited to 9-11 nm. They also show long range hexagonal packing and center to center spacing of 9-10 nm. These structures decrease in thickness, to 6-9 nm, when treated with trypsin. We have called these structures hemiplaques. They appear to be present endogenously in the preparation, as we have ruled out their being an artifact of imaging by AFM. However, it remains to be determined if they are a consequence of the procedure used in isolating gap junctions or a possible intermediary in gap junction formation.

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DNA in Human and Stallion Spermatozoa Forms Local Hexagonal Packing with Twist and Many Defects

Journal of Structural Biology ◽

10.1006/jsbi.2001.4365 ◽

2001 ◽

Vol 134 (1) ◽

pp. 76-81 ◽

Cited By ~ 47

Author(s):

Nathalie Sartori Blanc ◽

Alfred Senn ◽

Amélie Leforestier ◽

Françoise Livolant ◽

Jacques Dubochet

Keyword(s):

Hexagonal Packing

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THE USE OF ACOUSTIC LOGS IN THE EVALUATION OF SANDSTONE RESERVOIRS

Geophysics ◽

10.1190/1.1438691 ◽

1960 ◽

Vol 25 (1) ◽

pp. 250-274 ◽

Cited By ~ 12

Author(s):

G. R. Pickett

Keyword(s):

Acoustic Velocity ◽

Pressure Differential ◽

Well Bore ◽

Laboratory Measurements ◽

Theoretical Relation ◽

Hexagonal Packing ◽

Empirical Relations ◽

Borehole Logs ◽

Acoustic Velocities ◽

Self Potential

It is shown that acoustic velocities in sandstones are primarily dependent on porosity, shaliness, and pressure differential between overburden and fluid pressures. Although there are undoubtedly other variables which have some effect on acoustic velocities in sandstones, usable porosity predictions can be made from acoustic borehole logs if measured velocities are corrected for effects of pressure differential and shaliness. A theoretical relation between acoustic velocity and pressure differential in a hexagonal packing of spheres has been empirically extended by correlation of laboratory measurements on cores with actual well‐bore measurements. A system of empirical relations among acoustic velocity, porosity, and self potential of sandstones is developed. Further, it appears that the resistivity of water in permeable rocks can be estimated from the velocity and resistivity of adjoining shales. When this is possible, the SP log can then be used to estimate the shaliness of a sandstone in order to correct velocities for porosity estimates.

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Studies on the formation of Graphite-Ferric Chloride complexes: Kinetics of Formation

Australian Journal of Chemistry ◽

10.1071/ch9530302 ◽

1953 ◽

Vol 6 (3) ◽

pp. 302 ◽

Cited By ~ 17

Author(s):

JA Barker ◽

RC Croft

Keyword(s):

Particle Size ◽

Diffusion Coefficients ◽

Small Difference ◽

Critical Concentration ◽

Activation Energies ◽

Ferric Ions ◽

Chloride Complexes ◽

Hexagonal Packing ◽

Kinetics Of Formation ◽

Kinetics Of

A study has been made of the kinetics of the diffusion of anhydrous FeC1, in graphite. I t was found that this process can be represented for stages between 50 and 100 per cent. saturation of the graphite and at temperatures in the range 200 to 360 OC by a relation of the type δc/δt = D(δ2c/δr2 + δc/δ/r), providing the diffusion coefficient D is assigned several values for concentrations of occluded FeCl3 above and below a critical concentration. The value of the latter was found to be about two-thirds the saturation concentration of FeCl3 in graphite, this value apparently being the point at which open hexagonal packing of intercalated ferric ions is complete and a closer hexagonal packing commences. Values of the activation energies of occlusion for concentrations above and below two-thirds saturation were found from the relations of corresponding values of diffusion coefficients to temper- ature. The small difference between these activation energies which were of the order of 2 to 3 kcal is attributed to a cancelling of effects, thus the energy necessary to separate carbon lamellae in early stages of occlusion is offset in later stages by hindrance imposed on diffusing molecules by those already occluded. Reduction of particle size of graphite accelerated the occlusion of FeCl3.

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