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Substituent Effects in the ortho Position: Model Compounds with a Removed Reaction Centre

100%

Böhm S. , Exner O.

Polish Journal of Chemistry

2007

tom Vol. 81, nr 5-6

993-1006

2' -Substituted phenylpropynoic acids 1 and - in less details - 2' -substituted (E)-phenyliminoacetic acids 3 were investigated theoretically as model for theortho substitution, in which direct steric interaction is prevented by the extended side chain bearing the reaction centre. Energies of the acid molecules and of their deprotonated forms were calculated within the framework of the density functional theory at the level B3LYP/6- 311+G(d,p)//B3LYP/6-311+G(d,p). The substituent effects were evaluated in terms of isodesmic reactions, on the one hand for the acidity, on the other separately for the acid molecules or for the anions. Contrary to the expectation, the steric interaction of the substituent with the side chain is rather strong. The substituent effects represent a blend of polar and steric effects, and cannot serve for deriving any set of standard ortho substituent constants free of proximity effects as it was originally believed.

Complex demodulation in monitoring Earth rotation by VLBI: testing the algorithm by analysis of long periodic EOP components

80%

Wielgosz A. , Brzeziński A. , Böhm S.

Artificial Satellites : Journal of Planetary Geodesy

2016

tom Vol. 51, No. 4

135--147

The complex demodulation (CD) algorithm is an efficient tool for extracting the diurnal and subdiurnal components of Earth rotation from the routine VLBI observations (Brzeziński, 2012). This algorithm was implemented by Böhm et al (2012b) into a dedicated version of the VLBI analysis software VieVs. The authors processed around 3700 geodetic 24-hour observing sessions in 1984.0-2010.5 and estimated simultaneously the time series of the long period components as well as diurnal, semidiurnal, terdiurnal and quarterdiurnal components of polar motion (PM) and universal time UT1. This paper describes the tests of the CD algorithm by checking consistency of the low frequency components of PM and UT1 estimated by VieVS CD and those from the IERS and IVS combined solutions. Moreover, the retrograde diurnal component of PM demodulated from VLBI observations has been compared to the celestial pole offsets series included in the IERS and IVS solutions. We found for all three components a good agreement of the results based on the CD approach and those based on the standard parameterization recommended by the IERS Conventions (IERS, 2010) and applied by the IERS and IVS. We conclude that an application of the CD parameterization in VLBI data analysis does not change those components of EOP which are included in the standard adjustment, while enabling simultaneous estimation of the high frequency components from the routine VLBI observations. Moreover, we deem that the CD algorithm can also be implemented in analysis of other space geodetic observations, like GNSS or SLR, enabling retrieval of subdiurnal signals in EOP from the past data.