29 research outputs found
Recommended from our members
Possible photoacoustic detection of cyclic electron transport around Photosystem II in photoinhibited thylakoid preparations
This study was undertaken to compare the kinetics of chlorophyll
a fluorescence, of Photosystem II and Photosystem I electron transport activity, of the number of atrazine-binding sites, and of the photoacoustic signal during photoinhibition of rye (
Secale cereale L.) thylakoids. Once all Photosystem II activity and all chlorophyll
a variable fluorescence (
F
v) were lost, a substantial amount of energy was still stored in thylakoid membranes, suggesting photosynthetic activity. A significant fraction of atrazine-binding sites remained functional. Both the number of atrazine-binding sites and the amount of energy stored in the thylakoids showed a slow decrease once all Photosystem II activity was lost. The remaining energy storage is suggested to measure photosynthetic activity in Photosystem II β centres, once all Photosystem II α centres are inactivated. These Photosystem II β centres could store energy via a cyclic electron pathway involving cytochrome
b-559
STUDY OF THE ORGANISATION AND GENESIS OF RANDALL'S PLAQUES BY PHYSICAL TECHNIQUES OF CHARACTERISATION
Habitat use of an artificial wetland by the invasive catfish Ameiurus melas.
This study examined the distribution and habitat selection of the invasive black bullhead [Ameiurus melas (Rafinesque)] in the ditches and surrounded temporary flooded habitats of an artificial wetland in western France. A multiscale approach was used to quantify patterns of A. melas abundance in relation to physical habitat characteristics in the ditch network. Young-of-the-year (YOY) and adult A. melas largely dominated the local fish assemblage but were highly variable among sites. Although we found evidence for some fine-scale habitat differences for YOY and adult individuals, the abundance of A. melas was positively and consistently related to the dominance of reed beds. Furthermore, A. melas preferentially used reed beds as opposed to marsh meadows during the flooding period. The results from this study suggest that the invasion of A. melas has been facilitated by the expansion of reed beds associated with the diminution of agricultural pressure in recent decades. This study represents an unusual example where human activities can have had an unexpected effect by facilitating an invasive fish species
Saccharomyces cerevisiae strains AWRI 838, Lalvin EC1118 and Maurivin PDM do not produce excessive sulfur dioxide in white wine fermentations
Correlation of reefal Oxfordian episodes and climatic implications in the eastern Paris Basin (France)
Classifying chalk microtextures: Sedimentary versus diagenetic origin (Cenomanian-Santonian, Paris Basin, France)
International audienceMicrotexture describes the type of particles and their arrangement in matrix samples at scanning electron microscopy scale. Although a microtexture classification exists for micritic limestone, it cannot be directly applied to chalk. This study therefore proposes a classification of chalk microtextures and discusses the origin of microtexture variability. Chalk was sampled at thirteen spatio-temporal locations along the coastline of northern France (Cenomanian-Santonian). Four criteria are defined to describe, characterize and determine chalk matrix microtexture: (i) mineralogical content; (ii) biogenic fraction; (iii) micritic fraction; and (iv) cement fraction. From these criteria, two major groups are defined: Pure Chalk Microtexture Group, with seven classes, and Impure Chalk Microtexture Group, divided into two subgroups: Argillaceous Microtexture with four classes and Siliceous Microtexture with two classes. Microtexture variability is related both to initial sedimentation and to diagenesis. Sedimentological conditions (for example, climate and distance from shore) affect chalk composition (carbonate content and type of insoluble particles), thus influencing microtexture. Changes in Pure Chalk Microtexture are the result of increasing diagenetic intensity. This classification can also be used to characterize the microtexture of subsurface chalk reservoirs. Reservoir quality depends on the petrophysical and mechanical properties of reservoir rocks, which can be better understood by exploring their sedimentary and diagenetic history, revealed by the study of chalk microtexture variability