Suppression of vacancy formation and hydrogen isotope retention in irradiated tungsten by addition of chromium

2021 ◽  
pp. 153449
Author(s):  
Jing Wang ◽  
Yuji Hatano ◽  
Takeshi Toyama ◽  
Tomoaki Suzudo ◽  
Tatsuya Hinoki ◽  
...  
Keyword(s):  
Hydrogen Isotope ◽  
Vacancy Formation

Bringing Biocatalysis into the Deuteration Toolbox

2019 ◽  
Author(s):  
Jack Rowbotham ◽  
Oliver Lenz ◽  
Holly Reeve ◽  
Kylie Vincent
Keyword(s):  
Late Stage ◽  
Hydrogen Isotope ◽  
Reductive Amination ◽  
Mechanistic Studies ◽  
Ambient Conditions ◽  
Synthetic Pathway ◽  
Drug Candidates ◽  
Isotopic Selectivity ◽  
Reducing Equivalents

<p></p><p>Chemicals labelled with the heavy hydrogen isotope deuterium (<sup>2</sup>H) have long been used in chemical and biochemical mechanistic studies, spectroscopy, and as analytical tracers. More recently, demonstration of selectively deuterated drug candidates that exhibit advantageous pharmacological traits has spurred innovations in metal-catalysed <sup>2</sup>H insertion at targeted sites, but asymmetric deuteration remains a key challenge. Here we demonstrate an easy-to-implement biocatalytic deuteration strategy, achieving high chemo-, enantio- and isotopic selectivity, requiring only <sup>2</sup>H<sub>2</sub>O (D<sub>2</sub>O) and unlabelled dihydrogen under ambient conditions. The vast library of enzymes established for NADH-dependent C=O, C=C, and C=N bond reductions have yet to appear in the toolbox of commonly employed <sup>2</sup>H-labelling techniques due to requirements for suitable deuterated reducing equivalents. By facilitating transfer of deuterium atoms from <sup>2</sup>H<sub>2</sub>O solvent to NAD<sup>+</sup>, with H<sub>2</sub> gas as a clean reductant, we open up biocatalysis for asymmetric reductive deuteration as part of a synthetic pathway or in late stage functionalisation. We demonstrate enantioselective deuteration via ketone and alkene reductions and reductive amination, as well as exquisite chemo-control for deuteration of compounds with multiple unsaturated sites.</p><p></p>

New Particles

2018 ◽  
Author(s):  
Roger H. Stuewer
Keyword(s):  
Gamma Rays ◽  
Atomic Hydrogen ◽  
Nuclear Physics ◽  
Hydrogen Isotope ◽  
Alpha Particles ◽  
Cloud Chamber ◽  
Ernest Rutherford ◽  
James Chadwick ◽  
Theoretical Foundations ◽  
New Particles

In December 1931, Harold Urey discovered deuterium (and its nucleus, the deuteron) by spectroscopically detecting the faint companion lines in the Balmer spectrum of atomic hydrogen that were produced by the heavy hydrogen isotope. In February 1932, James Chadwick, stimulated by the claim of the wife-and-husband team of Irène Curie and Frédéric Joliot that polonium alpha particles cause the emission of energetic gamma rays from beryllium, proved experimentally that not gamma rays but neutrons are emitted, thereby discovering the particle whose existence had been predicted a dozen years earlier by Chadwick’s mentor, Ernest Rutherford. In August 1932, Carl Anderson took a cloud-chamber photograph of a positron traversing a lead plate, unaware that Paul Dirac had predicted the existence of the anti-electron in 1931. These three new particles, the deuteron, neutron, and positron, were immediately incorporated into the experimental and theoretical foundations of nuclear physics.

scholarly journals Unravelling the process of petroleum hydrocarbon biodegradation in different filter materials of constructed wetlands by stable isotope fractionation and labelling studies

2021 ◽  
Author(s):  
Andrea Watzinger ◽  
Melanie Hager ◽  
Thomas Reichenauer ◽  
Gerhard Soja ◽  
Paul Kinner
Keyword(s):  
Stable Isotope ◽  
Constructed Wetlands ◽  
Hydrogen Isotope ◽  
Petroleum Hydrocarbon ◽  
Isotope Fractionation ◽  
Isotope Effects ◽  
Filter Material ◽  
Hydrocarbon Biodegradation ◽  
Stable Isotope Fractionation ◽  
Filter Materials

AbstractMaintaining and supporting complete biodegradation during remediation of petroleum hydrocarbon contaminated groundwater in constructed wetlands is vital for the final destruction and removal of contaminants. We aimed to compare and gain insight into biodegradation and explore possible limitations in different filter materials (sand, sand amended with biochar, expanded clay). These filters were collected from constructed wetlands after two years of operation and batch experiments were conducted using two stable isotope techniques; (i) carbon isotope labelling of hexadecane and (ii) hydrogen isotope fractionation of decane. Both hydrocarbon compounds hexadecane and decane were biodegraded. The mineralization rate of hexadecane was higher in the sandy filter material (3.6 µg CO2 g−1 day−1) than in the expanded clay (1.0 µg CO2 g−1 day−1). The microbial community of the constructed wetland microcosms was dominated by Gram negative bacteria and fungi and was specific for the different filter materials while hexadecane was primarily anabolized by bacteria. Adsorption / desorption of petroleum hydrocarbons in expanded clay was observed, which might not hinder but delay biodegradation. Very few cases of hydrogen isotope fractionation were recorded in expanded clay and sand & biochar filters during decane biodegradation. In sand filters, decane was biodegraded more slowly and hydrogen isotope fractionation was visible. Still, the range of observed apparent kinetic hydrogen isotope effects (AKIEH = 1.072–1.500) and apparent decane biodegradation rates (k = − 0.017 to − 0.067 day−1) of the sand filter were low. To conclude, low biodegradation rates, small hydrogen isotope fractionation, zero order mineralization kinetics and lack of microbial biomass growth indicated that mass transfer controlled biodegradation.

Design for detecting recycling muon after muon-catalyzed fusion reaction in solid hydrogen isotope target

2021 ◽  
pp. 112712
Author(s):  
Kenichi Okutsu ◽  
Takuma Yamashita ◽  
Yasushi Kino ◽  
Ryota Nakashima ◽  
Konan Miyashita ◽  
...  
Keyword(s):  
Hydrogen Isotope ◽  
Fusion Reaction ◽  
Solid Hydrogen ◽  
Muon Catalyzed Fusion

Hydrogen isotope concentration enhancements at a blunt notch

1990 ◽  
Vol 24 (1) ◽  
pp. 111-115 ◽  
Author(s):  
S.L. Robinson ◽  
N.R. Moody ◽  
J.C. Costa ◽  
A.E. Pontau ◽  
W.W. Gerberich
Keyword(s):  
Hydrogen Isotope ◽  
Blunt Notch ◽  
Isotope Concentration

scholarly journals Are rate and selectivity correlated in iridium-catalysed hydrogen isotope exchange reactions?

2021 ◽  
Author(s):  
Daria S. Timofeeva ◽  
David M Lindsay ◽  
W. J. Kerr ◽  
David James Nelson
Keyword(s):  
Functional Groups ◽  
Hydrogen Isotope ◽  
Isotope Exchange ◽  
Reaction Rate ◽  
Exchange Reactions ◽  
Reaction Selectivity ◽  
Hydrogen Isotope Exchange ◽  
The Relationship

Herein we examine the relationship between reaction rate and reaction selectivity in iridium-catalysed hydrogen isotope exchange (HIE) reactions directed by Lewis basic functional groups. We have recently develped a directing...

Sign in / Sign up

Export Citation Format

Share Document