An algorithm for correction of two-axes laser mount direction and gates in case of atmospheric drag induces diviations from the predicted satellite motion is described. Results of numerical simulations are shown.
A relatively high rate of mortality among engorged females of Ornithodoros moubata (Murray, 1877) was observed in our laboratory colony. The general aim of the study was to identify the causative agent responsible for this mortality. The diagnostic tests were performed by Yeast Identification Service (CBS-Delft, Netherlands) and the pathogen was identified as the yeast Candida haemulonii (van Uden et Kolipinski, 1962) Meyer et Yarrovi, 1978. The artificial infection study was performed by intrahaemocoelic inoculation of yeast suspension, resulting in a mortality of 37%. The maximum mortality of ticks infected per os by contaminated blood meal was 13%. Re-isolated yeast cells from haemolymph of dead and paralysed ticks were apparently identical with primary yeast cells, without loosing reproductive abilities. An occasional formation of elongated chains of yeast cells (pseudomycelium) was recorded. The majority of ticks infected in both experiments mentioned above survived and displayed no evident symptoms of the infection. The presence of yeast cells in the haemolymph of surviving ticks was not detected. The in vitro phagocytosis assay performed with FITC-labelled yeast cells showed that about 4% of tick haemocytes were phagocytically active against the pathogenic yeast cells. Thus phagocytosis seems to be a potent defence reaction against spreading and multiplying of the yeast C. haemulonii within the tick haemocoel.
For Tunisian olive tree orchards, nitrogen deficiency is an important nutritional problem, in addition to the availability of water. Establishment of relationships between nutrients such as nitrogen and ecophysiological parameters is a promising method to manage fertilisation at orchard level. Therefore, a nitrogen stress experiment with one-year-old olive trees (Olea europaea L. 'Koroneiki' and 'Meski') was conducted with trees respectively subjected to four nitrogen supply regimes (23.96 meq l-1, 9.58 meq l-1, 4.79 meq l-1 and 0 meq l-1 NO3-).
The current paper focuses on the use of the SPAD-502 portable chlorophyll (Chl) meter, a nondestructive method for fertilisation management under nitrogen stress conditions of olive trees. Maximum net photosynthetic assimilation rates, chlorophyll fluorescence parameters and the SPAD Chl index were therefore measured simultaneously and the Chl and nitrogen content of the leaves were analysed. Significant correlations were established in the olive tree leaves between SPAD-502 readings on the one hand and Chl content, nitrogen content, photosynthetic assimilation rate, and Chl fluorescence parameters (ΦPSII and ETR) on the other hand. and O. Boussadia ... [et al.].
The parasitic copepod fauna of 182 specimens of Mustelus schmitti Springer from the coast of Mar del Plata, Argentina was investigated. Three species of parasitic copepods were identified: Nessipus orientalis Heller, 1865 from the buccal cavity, Perissopus oblongus (Wilson, 1908) from the edge of pectoral, pelvic, dorsal, anal and caudal fins and in claspers, and Lernaeopoda galei К rayer, 1837 from the base of the pectoral fins. N. orientalis was most common being present the entire year, while P. oblongus and L. galei occurred seasonally with low prevalence and mean intensity. There were differences in the site of infection by these copepods and variations in the relationship between prevalence and mean intensity and host size and seasonality. These parameters were unrelated to host sex. Our data suggest that the structure of this parasite community is a result of a complex of biotic and abiotic factors, such as temperature, spawning and breeding preferences of the host, and overlapping in the distribution of different shark species. This is the first report of N. orientalis in Argentinean waters.
Tolerance of Festuca rupicola Heuff., Botriochloa ischaemum (L.) Keng., and Salvia nemorosa L. to co-occurring drought, high air temperature and high irradiance were investigated in stands representing different degree of degradation. Air and leaf temperatures were higher for the stands in the advanced degradation stage. The net photosynthetic rate was not significantly lower and WUE was depressed in the degraded stands as compared to the intact stands. Carbon fixation type seems to have outstanding importance in the outcome of degradation processes in semiarid temperate grasslands.
A theory of spectra and excitation dynamics in antenna based on the notion of exciton interactions in the cyclic structures of light-harvesting pigments is reported. The theory provides an explanation for the picosecond absorbance difference spectra, the induced absorption anisotropy decay, the anomalously high bleaching valné, as well as for the fluorescence spectra, kinetics and depolarizatio