scholarly journals Organofluorine chemistry: Difluoromethylene motifs spaced 1,3 to each other imparts facial polarity to a cyclohexane ring

2016 ◽  
Vol 12 ◽  
pp. 2823-2827 ◽  
Author(s):  
Mathew J Jones ◽  
Ricardo Callejo ◽  
Alexandra M Z Slawin ◽  
Michael Bühl ◽  
David O'Hagan
Keyword(s):  
Solid State ◽  
Design Strategy ◽  
Chair Conformation ◽  
Axial Orientation ◽  
Solution Nmr ◽  
Cyclohexane Ring ◽  
X Ray

2,2-Dimethyl-5-phenyl-1,1,3,3-tetrafluororocyclohexane has been prepared and characterised as an example of a facially polarised cyclohexane containing 1,3 related CF2 groups. The dipolar nature of the ring arises from the axial orientation of two of the C–F bonds pointing in the same direction, and set by the chair conformation of the cyclohexane. This electrostatic profile is revealed experimentally both in the solid-state (X-ray) packing of the rings and by solution (NMR) in different solvents. A computationally derived electrostatic profile of this compound is consistent with a more electronegative and a more electropositive face of the cyclohexane ring. This placing of CF2 groups 1,3 to each other in a cyclohexane ring is introduced as a new design strategy which could be applicable to the preparation of polar hydrophobic cyclohexane motifs.

Magnetic orientation of snow buntings (Plectrophenax nivalis), a species breeding in the high Arctic: passage migration through temperate-zone areas

1996 ◽  
Vol 199 (9) ◽  
pp. 1899-1905
Author(s):  
R Sandberg ◽  
J Pettersson
Keyword(s):  
Magnetic Fields ◽  
High Arctic ◽  
Temperate Zone ◽  
Axial Orientation ◽  
Magnetic Orientation ◽  
Directional Information ◽  
Clear Sky ◽  
Migratory Orientation ◽  
Plectrophenax Nivalis ◽  
Auxiliary Source

Orientation tests were conducted with snow buntings (Plectrophenax nivalis) exposed to artificially manipulated magnetic fields, during both spring and autumn migration. Experiments were run under clear sunset skies and under simulated complete overcast. The birds closely followed experimental shifts of the magnetic fields during both seasons regardless of whether they had access to celestial cues. Clear-sky tests in vertical magnetic fields resulted in a significant bimodal orientation, the directionality of which was almost identical during spring and autumn. When the snow buntings were deprived of celestial directional information and tested in vertical magnetic fields, they failed to show any statistically significant mean directions in either spring or autumn. The results demonstrate that snow buntings possess a magnetic compass and suggest that magnetic cues are of primary importance for their migratory orientation while on passage through temperate-zone areas. However, the axial orientation in vertical magnetic fields under clear skies may indicate an involvement of celestial cues as an auxiliary source of directional information.

The Formation of Tracheae and Tracheoles in Rhodnius prolixus

1958 ◽  
Vol s3-99 (45) ◽  
pp. 29-46
Author(s):  
M. LOCKE
Keyword(s):  
Axial Compression ◽  
Wall Thickness ◽  
Tube Wall ◽  
Rhodnius Prolixus ◽  
Axial Orientation ◽  
Tube Wall Thickness ◽  
Walled Cylinder ◽  
Tangential Orientation

The formation of tracheae in Rhodnius is described by the hypothesis of expansion and buckling. The cuticulin lining is at first a smooth-walled cylinder. Later it expands equally in each direction, increasing in diameter but buckling in the axis. An engineering expression describing symmetrical buckling in a cylinder under uniform axial compression has been applied to this process. Agreement was obtained between the expected and observed values for buckling frequency and tube-wall thickness. The taenidia are formed within the buckles, their amplitude being proportional to the increase in diameter. The axial orientation of the chitin micelles in the lining membrane and the tangential orientation in the taenidia are consistent with their being oriented by the stresses expected during expansion and buckling. The formation of tracheoles may also be described by the expansion and buckling hypothesis.

Study of Garnets by ALCHEMI

2001 ◽  
Vol 7 (S2) ◽  
pp. 358-359
Author(s):  
János L. Lábár ◽  
Lajos Tόth ◽  
István Dόdony ◽  
Jerzy Morgiel
Keyword(s):  
Crystal Structure ◽  
Chemical Composition ◽  
High Sensitivity ◽  
Unit Cell ◽  
Previous Literature ◽  
The Other ◽  
Axial Orientation ◽  
Partial Substitution ◽  
X Ray ◽  
Oxygen Atoms

Garnets were one of the first materials in which an occupation of separate lattice sites by different atomic species was determined with an ALCHEMI technique proposed by Spence and Tafto in l982. The reason of so much interest in this material was twofold, i.e. first its known high sensitivity of X-ray generation depending on orientation especially in the axial orientation and second its complicated crystal structure allowing different atomic arrangements in the unit cell depending on its chemical composition. The dodecahedral (X), octahedral (Y) and tetrahedral (Z) sites between the relatively large oxygen atoms can be filled with a variety of small cations in accordance with the formula X3Y2Z3O12. Partial substitution of one cation with another is common in this structure. The results presented in the previous literature indicated that ALCHEMI can only separate the Y-sites from the sum of the other two (X+Z), while the latter has to remain unresolved.

scholarly journals A study on the use of planarity for quick identification of potential landslide hazard

2015 ◽  
Vol 15 (5) ◽  
pp. 997-1009 ◽  
Author(s):  
M. H. Baek ◽  
T. H. Kim
Keyword(s):  
Hazard Assessment ◽  
Ground Surface ◽  
Landslide Hazard ◽  
Axial Orientation ◽  
Orientation Data ◽  
Landslide Hazard Assessment ◽  
Geotechnical Monitoring ◽  
Digital Elevation ◽  
Elevation Model ◽  
Geomorphological Features

Abstract. In this study we focused on identifying a geomorphological feature that controls the location of landslides. The representation of the feature is based on a high-resolution digital elevation model derived from the airborne laser altimetry (LiDAR) and evaluated by the statistical analysis of axial orientation data. The main principle of this analysis is generating eigenvalues from axial orientation data and comparing them. The planarity, a ratio of eigenvalues, would tell the degree of irregularity on the ground surface based on their ratios. Results are compared to the recent landslide case in Korea in order to evaluate the feasibility of the proposed methodology in identifying the potential landslide hazard. The preliminary landslide hazard assessment based on the planarity analysis discriminates features between stable and unstable domain in the study area well, especially in the landslide initiation zones. Results also show it is beneficial to build the landslide hazard inventory mapping, especially where no information on historical records of landslides exists. By combining other physical procedures such as geotechnical monitoring, the landslide hazard assessment using geomorphological features promises a better understanding of landslides and their mechanisms and provides an enhanced methodology to evaluate their hazards and appropriate actions.

The effect of uni-axial orientation on macroporous membrane structure

2006 ◽  
Vol 13 (1) ◽  
pp. 61-72 ◽  
Author(s):  
Jason A. Morehouse ◽  
Leah S. Worrel ◽  
Dana L. Taylor ◽  
Douglas R. Lloyd ◽  
Benny D. Freeman ◽  
...  
Keyword(s):  
Membrane Structure ◽  
Axial Orientation

scholarly journals Synthesis and stereochemistry of some new 1,3,5-tris(1,3-dioxan-2-yl)-benzene derivatives

2006 ◽  
Vol 4 (4) ◽  
pp. 808-821 ◽  
Author(s):  
Maria Florian ◽  
Monica Cîrcu ◽  
Loïc Toupet ◽  
Anamaria Terec ◽  
Ion Grosu ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Single Crystal ◽  
Axial Orientation ◽  
Benzene Derivatives ◽  
Aryl Group ◽  
X Ray

AbstractThe synthesis and the stereochemistry of new 1,3,5-tris(1,3-dioxan-2-yl)-benzene derivatives are reported. The anancomeric structure and the axial orientation of the aryl group with respect to all 1,3-dioxane rings, and the cis-trans isomerism of some of the compounds are revealed. The data are supported by NMR investigations and by the molecular structure of one compound determined by single crystal X-ray diffractometry.

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