Planar rings in nano-Saturns and related complexes

2019 ◽  
Vol 55 (25) ◽  
pp. 3650-3653 ◽  
Author(s):  
Steven M. Bachrach
Keyword(s):  
Flat Ring ◽  
Nitrogen Substitution ◽  
Ribbon Structures

Nitrogen substitution into the ortho positions in polyaryl macrocycles creates planar or ribbon structures leading to such structures as this nano-Saturn with a flat ring.

Distortion of steel flat ring products during the production cycle∗

2013 ◽  
Vol 68 (2) ◽  
pp. 97-102
Author(s):  
D. Česnik ◽  
V. Bratuš ◽  
M. Bizjak
Keyword(s):  
Production Cycle ◽  
Flat Ring

Boron insertion into alkyl ether bonds via zinc/nickel tandem catalysis

Science ◽  
2021 ◽  
Vol 372 (6538) ◽  
pp. 175-182
Author(s):  
Hairong Lyu ◽  
Ilia Kevlishvili ◽  
Xuan Yu ◽  
Peng Liu ◽  
Guangbin Dong
Keyword(s):  
Nickel Catalyst ◽  
Bioactive Compounds ◽  
Cyclic Ethers ◽  
Alkyl Ether ◽  
Tandem Catalysis ◽  
Mechanistic Studies ◽  
Alkyl Ethers ◽  
Nitrogen Substitution ◽  
Zinc Nickel

Mild methods to cleave the carbon-oxygen (C−O) bond in alkyl ethers could simplify chemical syntheses through the elaboration of these robust, readily available precursors. Here we report that dibromoboranes react with alkyl ethers in the presence of a nickel catalyst and zinc reductant to insert boron into the C−O bond. Subsequent reactivity can effect oxygen-to-nitrogen substitution or one-carbon homologation of cyclic ethers and more broadly streamline preparation of bioactive compounds. Mechanistic studies reveal a cleavage-then-rebound pathway via zinc/nickel tandem catalysis.

scholarly journals WASP: a software package for correctly characterizing the topological development of ribbon structures

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Zachary Sierzega ◽  
Jeff Wereszczynski ◽  
Chris Prior
Keyword(s):  
Software Package ◽  
Helical Structure ◽  
Optical Tweezer ◽  
Application Software ◽  
Not Given ◽  
Magnetic Flux Ropes ◽  
Additional Information ◽  
Non Local ◽  
Alternative Approaches ◽  
Ribbon Structures

AbstractWe introduce the Writhe Application Software Package (WASP) which can be used to characterisze the topology of ribbon structures, the underlying mathematical model of DNA, Biopolymers, superfluid vorticies, elastic ropes and magnetic flux ropes. This characterization is achieved by the general twist–writhe decomposition of both open and closed ribbons, in particular through a quantity termed the polar writhe. We demonstrate how this decomposition is far more natural and straightforward than artificial closure methods commonly utilized in DNA modelling. In particular, we demonstrate how the decomposition of the polar writhe into local and non-local components distinctly characterizes the local helical structure and knotting/linking of the ribbon. This decomposition provides additional information not given by alternative approaches. As example applications, the WASP routines are used to characterise the evolving topology (writhe) of DNA minicircle and open ended plectoneme formation magnetic/optical tweezer simulations, and it is shown that the decomponsition into local and non-local components is particularly important for the detection of plectonemes. Finally it is demonstrated that a number of well known alternative writhe expressions are actually simplifications of the polar writhe measure.

scholarly journals Effect of Nitrogen on the Growth of (100)-, (110)-, and (111)-Oriented Diamond Films

2020 ◽  
Vol 11 (1) ◽  
pp. 126
Author(s):  
Jen-Chuan Tung ◽  
Tsung-Che Li ◽  
Yen-Jui Teseng ◽  
Po-Liang Liu
Keyword(s):  
Growth Mechanism ◽  
Density Functional ◽  
Film Growth ◽  
Hydrogen Abstraction ◽  
Diamond Films ◽  
Activation Energies ◽  
Diamond Surface ◽  
Nitrogen Doped ◽  
Nitrogen Substitution ◽  
Diamond Film Growth

The aim of this research is the study of hydrogen abstraction reactions and methyl adsorption reactions on the surfaces of (100), (110), and (111) oriented nitrogen-doped diamond through first-principles density-functional calculations. The three steps of the growth mechanism for diamond thin films are hydrogen abstraction from the diamond surface, methyl adsorption on the diamond surface, and hydrogen abstraction from the methylated diamond surface. The activation energies for hydrogen abstraction from the surface of nitrogen-undoped and nitrogen-doped diamond (111) films were −0.64 and −2.95 eV, respectively. The results revealed that nitrogen substitution was beneficial for hydrogen abstraction and the subsequent adsorption of methyl molecules on the diamond (111) surface. The adsorption energy for methyl molecules on the diamond surface was generated during the growth of (100)-, (110)-, and (111)-oriented diamond films. Compared with nitrogen-doped diamond (100) films, adsorption energies for methyl molecule adsorption were by 0.14 and 0.69 eV higher for diamond (111) and (110) films, respectively. Moreover, compared with methylated diamond (100), the activation energies for hydrogen abstraction were by 0.36 and 1.25 eV higher from the surfaces of diamond (111) and (110), respectively. Growth mechanism simulations confirmed that nitrogen-doped diamond (100) films were preferred, which was in agreement with the experimental and theoretical observations of diamond film growth.

Calculation of flat ring frames of constant stiffness in arbitrary static loading

1993 ◽  
Vol 29 (1) ◽  
pp. 30-32
Author(s):  
L. V. Popov ◽  
A. V. Gusev ◽  
S. R. Kalimulin
Keyword(s):  
Static Loading ◽  
Constant Stiffness ◽  
Flat Ring

scholarly journals Injective modules under faithfully flat ring extensions

2015 ◽  
Vol 144 (3) ◽  
pp. 1015-1020 ◽  
Author(s):  
Lars Winther Christensen ◽  
Fatih Köksal
Keyword(s):  
Injective Modules ◽  
Flat Ring ◽  
Ring Extensions

scholarly journals Additive Manufacturing of Bulk Nanocrystalline FeNdB Based Permanent Magnets

Micromachines ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 538
Author(s):  
Dagmar Goll ◽  
Felix Trauter ◽  
Timo Bernthaler ◽  
Jochen Schanz ◽  
Harald Riegel ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Melt Spinning ◽  
Permanent Magnets ◽  
Maximum Energy ◽  
Laser Melting ◽  
Powder Bed ◽  
Melt Pool ◽  
Bulk Nanocrystalline ◽  
Ribbon Structures ◽  
Nanocrystalline Ribbon

Lab scale additive manufacturing of Fe-Nd-B based powders was performed to realize bulk nanocrystalline Fe-Nd-B based permanent magnets. For fabrication a special inert gas process chamber for laser powder bed fusion was used. Inspired by the nanocrystalline ribbon structures, well-known from melt-spinning, the concept was successfully transferred to the additive manufactured parts. For example, for Nd16.5-Pr1.5-Zr2.6-Ti2.5-Co2.2-Fe65.9-B8.8 (excess rare earth (RE) = Nd, Pr; the amount of additives was chosen following Magnequench (MQ) powder composition) a maximum coercivity of µ0Hc = 1.16 T, remanence Jr = 0.58 T and maximum energy density of (BH)max = 62.3 kJ/m3 have been achieved. The most important prerequisite to develop nanocrystalline printed parts with good magnetic properties is to enable rapid solidification during selective laser melting. This is made possible by a shallow melt pool during laser melting. Melt pool depths as low as 20 to 40 µm have been achieved. The printed bulk nanocrystalline Fe-Nd-B based permanent magnets have the potential to realize magnets known so far as polymer bonded magnets without polymer.

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