scholarly journals Hydrogen molecular ions for improved determination of fundamental constants

2016 ◽  
Vol 94 (5) ◽  
Author(s):  
J.-Ph. Karr ◽  
L. Hilico ◽  
J. C. J. Koelemeij ◽  
V. I. Korobov
Keyword(s):  
Molecular Ions ◽  
Fundamental Constants

Heuristic determination of the cosmological constant

2021 ◽  
pp. 2150114
Author(s):  
Manuel Urueña Palomo ◽  
Fernando Pérez Lara
Keyword(s):  
Field Theory ◽  
Energy Density ◽  
Cosmological Constant ◽  
Accelerated Expansion ◽  
Fundamental Constants ◽  
Quantum Field ◽  
Brute Force ◽  
Expansion Of The Universe ◽  
The Universe

The vacuum catastrophe results from the disagreement between the theoretical value of the energy density of the vacuum in quantum field theory and the estimated one observed in cosmology. In a similar attempt in which the ultraviolet catastrophe was solved, we search for the value of the cosmological constant by brute-force through computation. We explore combinations of the fundamental constants in physics performing a dimensional analysis, in search of an equation resulting in the measured energy density of the vacuum or cosmological constant that is assumed to cause the accelerated expansion of the universe.

scholarly journals 4-t-Butylbenzylation of carboxylic acid for GC–MS analysis

2020 ◽  
Vol 2 (5) ◽  
Author(s):  
Shinji Tsunoi ◽  
Nao Yamamoto ◽  
Tomohiro Yasuhisa ◽  
Riko Akehi ◽  
Itaru Suzuki ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Carboxylic Acids ◽  
Water Samples ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Good Sensitivity ◽  
Good Reproducibility ◽  
Methyl Radical ◽  
Microwave Reactor

Abstract We report a 4-t-butylbenzyl derivatization for the analysis of carboxylic acids by GC–MS (EI). Carboxylic acids were analyzed as a 4-t-butylbenzyl ester after the derivatization with 4-t-butylbenzyl bromide. On the mass spectra of 4-t-butylbenzyl ester, [M-15]+ ions were observed with high intensity. These ions were tertiary benzyl cations generated by the elimination of a methyl radical from molecular ions. After optimization of the 4-t-butylbenzyl derivatization conditions using microwave reactor, we established a method for the determination of the carboxylic acids in water samples. The method showed good sensitivity and good reproducibility, and was successfully applied to the analysis of rain water samples.

Determination of Twenty-one Chloroanisoles in Water and Sediment Samples

1988 ◽  
Vol 71 (4) ◽  
pp. 803-807
Author(s):  
Hing-Biu Lee
Keyword(s):  
Molecular Ions ◽  
Sediment Samples ◽  
Mass Selective Detector ◽  
Water And Sediment ◽  
Soxhlet Apparatus ◽  
Selective Detector ◽  
Electron Impact Mass ◽  
Impact Mass ◽  
Water And Sediment Samples

Abstract A simple and sensitive method for the determination of 19 chloroanisoles and 2 chloromethylanisoles was developed for water; another method was developed for sediment samples. Water samples were extracted with dichloromethane; sediments were extracted with a mixture of hexane and acetone in a Soxhlet apparatus. The extracts were concentrated on a Snyder column and then were cleaned up on an activated Florisil column. The anisoles were separated by either an OV-1 or SPB-5 capillary column and were detected by an electroncapture or a mass selective detector. Recoveries of chloroanisoles in fortified water and sediment samples generally ranged between 70 and 85%. The method detection limits were 0.02 /tg/L and 0.002 Mg/g for mono- and di-chloroanisoles in water and sediments and 0.002 jug/L and better than 0.001 jig/g for tri-, tetra-, and pentachloroanisoles in those matrixes. The electron-impact mass spectra of all chloroanisoles exhibited intense peaks for the molecular ions (M+ ), as well as (M - 43)+ and either (M - 15)+ or (M - 30)+ fragments. These masses were used as characteristic ions for quantitative and confirmation purposes.

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