Novel approach to thermal degradation kinetics of gypsum: application of peak deconvolution and Model-Free isoconversional method

Journal of Thermal Analysis and Calorimetry - In this work, we have reinvestigated the thermal degradation kinetics of synthetic gypsum (CaSO4·2H2O) using a novel approach based on peak...     

INFLUENCE OF THE POOL SIZE OF THE XANTHOPHYLL CYCLE ON THE EFFECTS OF LIGHT STRESS IN A DIATOM: COMPETITION BETWEEN PHOTOPROTECI'ION AND PHOTOINHIBITION

Abstract In a study of the relationship between nonphotochemical quenching of fluorescence and the xanthophyll cycle, we show that the diatom Phaeodactylum tricornutum exhibits several interesting characteristics. This xanthophyll cycle consists of only one reversible epoxidating/deepoxidating step (diadinoxanthiddiatoxanthin). Diadinoxan-thin, which increases from 8 to 17 molecules/100 chlorophyll a (Chl a ) during the ageing of the culture, was present as two separate pools, with a portion (of about 5 molecules/100 Chl a) which was never deepoxidated. Under a defined irradiance, the time necessary to abolish net photosynthesis increases with the pool size of diadinoxanthin available for deepoxidation. A close correlation is found between nonphotochemical quenching and the relative ratio of diatoxanthin until the photosytem II center is inactivated. The photoprotective effect of diadinoxanthin deepoxidation is limited to the phase during which quenching of the minimum fluorescence (F₀) develops.     

Zinc sulphide linear photodetector

Interband phototransitions and photoionization of coulombic centres allow linear detection of light intensity in Al/ZnS/Au photocells. The opposite spectral variations of photoconduction and apparent internal electric field lead to a maximum of spectral sensitivity of about 15A mW^–1 in the u.v. region for 500 Å sulphide thickness. Adequate simplified band models are proposed.