منابع مشابه
Readily accessible chiral at nitrogen cage structures.
The reaction of glycine-N-methyl amide with paraformaldehyde in the presence of ytterbium triflate (1 mol%) leads to a novel cage structure 6 which is chiral at nitrogen. Single crystal X-ray analysis and DFT calculations suggest this cage structure is rigid and adopts a single low energy conformation. Use of single enantiomer α-amino amides results in two diastereomeric tertiary amines that di...
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The embedding of a given point set with non-crystallographic symmetry into higher-dimensional space is reviewed, with special emphasis on the Minkowski embedding known from number theory. This is a natural choice that does not require an a priori construction of a lattice in relation to a given symmetry group. Instead, some elementary properties of the point set in physical space are used, and ...
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deployable scissor type structures are composed of the so-called scissor-like elements (sles), which are connected to each other at an intermediate point through a pivotal connection and allow them to be folded into a compact bundle for storage or transport. several sles are connected to each other in order to form units with regular polygonal plan views. the sides and radii of the polygons are...
On Some Limits of Lattice and Lifting Structures
We discuss the relation between lattice and ladder structures for two-channel lter banks. It is wellknown that both lattice and ladder steps are powerful enough to generate all perfect reconstructing lter banks provided that the lter coe cients may take arbitrary values in a eld. However, we will show that the two concept di er in general. We relate the two concepts by looking at three properti...
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New instruments and techniques expand the reach of crystallography, making it more efficient and/or accessible to the greater scientific community. However, despite technological improvements, crystallography still faces outstanding challenges. As an example, structure determination from sub-micron crystals remains largely out of reach for conventional crystallography. In this issue of Acta Cry...
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ژورنال
عنوان ژورنال: Journal of Topology
سال: 2019
ISSN: 1753-8416,1753-8424
DOI: 10.1112/topo.12123