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Start Over Coverage 207-215

1. Application of non-invasive spectroscopic and photoacoustic techniques in research on photosynthetic performance of intact leaves

Creator:
Vredenberg, W. J., Snel, J. F. H., Buurmeuer, W. F., and Boumans, H.
Format:
print
Type:
model:internalpart and TEXT
Language:
Multiple languages
Description:
The principles and application prospects of a set-up for simultaneous measurements of oxygen evolution and fluorescence in intact leaves on a fast (10 ms) time scale are descríbed. The oxygen evolution is measured with a photoacoustic technique. The method shows among other things (a) a direct deteimination of the intrinsic yield of 'open' reaction centres (RCs) of photosystem 2 (PS 2), and (b) ihe involvement of a 20-30 % firaction of PS 2 RCs with an apparent low oxygen yield in the light-adapted leaves. Double-flashPS 15 measurements in the light- and dark-adapted leaves have substantiated the absence of inactive RCs in leaves that were kept in the dark for more than 12 h.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2. Period and Q-factor of Free Core Nutation, based on different geophysical excitations and VLBI solutions

Creator:
Jan Vondrák and Cyril Ron
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
geofyzika, geophysics, rotation of the Earth, geophysical excitations, geomagnetic jerks, VLBI, celestial pole offsets, free core nutation, 7, and 551
Language:
English
Description:
Three variants of geophysical excitations and seven different VLBI solutions of celestial pole offsets (CPO) are used to determine period and Q-factor of Free Core Nutation (FCN). Brzeziński’s broad-band Liouville equations (Brzeziński, 1994) are numerically integrated to derive geophysical effects in nutation in time domain. Possible effect of geomagnetic jerks (GMJ) is also considered. Best-fitting values of FCN parameters are estimated by least-squares fit to observed CPO, corrected for the differences between the FCN parameters used in IAU 2000 model of nutation and newly estimated ones; MHB transfer function is used to compute these corrections. It is demonstrated that different VLBI solutions lead to FCN parameters that agree on the level of their formal uncertainties, but different models of geophysical excitations change the results more significantly. Using GMJ excitations always brings improvement of the fit between integrated and observed CPO. The obtained results show that the best fit is achieved when only GMJ excitations are used. Our conclusion is that GMJ are very probably more important for exciting FCN than the atmosphere and oceans. Empirical Sun-synchronous correction, introduced in the present IAU 2000 nutation model, cannot be explained by diurnal atmospheric tidal effects., Jan Vondrák and Cyril Ron., and Obsahuje bibliografii
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public