Because fusicoccin (FC) has the capacity to promote solute uptake, a selective procedure for isolating mutants of Arabidopsis thaliana with a reduced response to the toxin has been developed. The ...procedure is based on the incubation of A. thaliana seedlings in a solution containing the cation Paraquat (Pq) at a concentration that per se does not produce bleaching of the leaves upon illumination but does in the presence of FC because of the increased uptake of the toxic cation. Using this procedure, we identified, among the progenies of 2010 M1 ethyl methanesulfonate-mutagenized plants, two mutants that stay green after exposure to FC and Pq. Some properties and inheritance of one of the two mutants (5-2) are described. Morphology of mutant plants is almost indistinguishable from that of the wild type. However, 5-2 seeds germinate and produce viable seedlings in the presence of FC plus the aminoglycoside antibiotic hygromycin B: plants of the mutant do not wilt when exposed to FC and stomata do not open or open only partially. in the presence of FC, the mutant appears less responsive than the wild type as far as the increment in fresh weight, the enlargement of leaf disc area, or the stimulation of H+ extrusion is concerned. Inheritance of the trait is monogenic dominant or semidominant, depending on the test used
A comparative study on the isolated chlorosomes from Chloroflexus aurantiacus, a green filamentous photosynthetic bacterium and Chlorobium tepidum, a green sulfur photosynthetic bacterium, was done ...by ODMR (optically detected magnetic resonance). Correlation between the results obtained by fluorescence and absorption detection is shown to be a source of information about the functional interactions among pigments. Analogies and differences are pointed out between the light-harvesting systems of the two species. Triplet states are easily detected in both bacteria at 1.8 K under steady-state illumination and are assigned to BChl c, BChl a, and carotenoid molecules. Carotenoids are found to be able to quench BChl a triplet states, but no evidence of BChl c triplet states quenching by this triplet−triplet transfer mechanism is found in both systems. Then from the data it appears that some carotenoids are in close contact with BChl a molecules. The relevance of this finding to the localization of carotenoids in the chlorosomes is discussed. In Cb. tepidum three different pools of BChl c oligomers connected to BChl a were found by detection of their triplet state, while only one pool of BChl c was evidenced in Cf. aurantiacus. The latter appears to be unconnected, at least at 1.8 K, to BChl a. On the other hand, heterogeneity in the BChl a triplet population was detected in Cf. aurantiacus. Even though the two bacteria show common features in the way the light excitation induces triplet formation at low temperature, the detected triplet states show spectroscopic properties that strongly depend on the system. The results clearly indicate that differences in pigment organization exist both in the core and in the baseplate of the chlorosomes from the two different bacteria.
The electronics for the AMS-02 calorimeter Cervelli, F.; Di Falco, S.; Incagli, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2007, Letnik:
572, Številka:
1
Journal Article
Recenzirano
AMS-02 is an astroparticle experiment that will operate on board of the ISS for a period of about three years. The main scientific goals of the experiment are the search for antimatter and dark ...matter and the study of gamma rays. In AMS-02 the Electromagnetic Calorimeter (ECAL) plays a key role for its high capability to measure
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and gamma spectra and to discriminate electromagnetic showers from hadronic cascades C. Adloff, et al., Performance of a 3D imaging electromagnetic calorimeter for the AMS02 space experiment, Proceedings of Calor 2004, Perugia, Italy.
1. All the electronics of the detector has been designed following stringent requirements on mechanical and thermal stability, power consumption, radiation hardness and double redundancy. The system has successfully gone through the space qualification tests and the full production will start soon.
We report the results of two beam tests performed in July and September 1995 at CERN using silicon microstrip detectors of various types: single sided, double sided with small-angle stereo strips, ...double sided with orthogonal strips, double sided with pads. For the read-out electronics, use was made of Preshape32, Premux 128 and VA1 chips. The signal-to-noise ratio and the resolution of the detectors was studied at different incident angles of the incoming particles and for different values of the detector bias voltage. The goal of these tests was to check and improve the performances of the prototypes for the CMS Central Detector.
Four different associations between ciliates of the family Euplotidae and bacteria have been studied. The ectosymbiotic relationship between ciliates of the genus Euplotidium and epixenosomes, ...(bacteria related to Verrucomicrobia), offers cues for ecological and evolutionary studies. Epixenosomes, although not vital for their host, confer on them a selective advantage, i.e. defense against predation. Epixenosomes have a compartmentalized cell and possess microtubule-like structures. Interestingly, the presence of two tubulin-like genes has been reported in members of the free-living verrucomicrobial genus Prosthecobacter. We obtained evidence that well-known Polynucleobacter bacteria, upon which a group of fresh-water Euplotes species depends, interfere with the glycogen metabolism of their hosts. Euplotes magicirratus is no longer able to digest food-organisms and is destined to die, once deprived of its specific prokaryotic endosymbiont, likely a new species of the alpha-proteobacterial genus Devosia. A further intriguing finding is the regular presence of rickettsiae in the cytoplasm of a marine Diophrys species. This is the first report of these bacteria in protozoa. This short list suggests that specialized mutualism is more widespread in the phylum than so far supposed.
An original theoretical model has been devised to simulate mass flow over hill slopes due to gravitational sliding. The sliding mass is discretized into a sequence of contiguous blocks which are ...subjected to gravitational forces, to bottom friction and to surface resistance stresses that are generally negligible for subaerial flows, but are relevant for submarine slides. The blocks interact with each other while sliding down the hill flanks because of internal forces that dissipate mechanical energy and produce a momentum exchange between the individual blocks, yet conserving the total momentum of the mass. Internal forces are expressed in terms of interaction coefficients depending on the instantaneous distance between the block centers of mass, which is a measure of the deformation experienced by the blocks: the functional dependence includes three parameters, namely the interaction intensity ¯λ, the deformability parameter σ and the shape parameter γ, by means of which a wide range of interaction types can be fully accounted for. The time integration is performed numerically by solving the equations for the block velocities and positions at any time ti by means of the block accelerations at the previous time t^sub i-1^, and by subsequently updating the block accelerations, which allows to proceed iteratively to the following times. The model has been tested against laboratory results available from literature and by means of several numerical experiments involving a simplified geometry both for the sliding body and the basal surface, with the purpose of clarifying the influence of the model parameters on the slide dynamics. The model improves the performance of the existing kinematic models for slides, moreover preserving an equivalent numerical simplicity. Future applications and possible improvements of this model are suggested.PUBLICATION ABSTRACT
Some biological activities of Azotobacter chroococcum, strain Azcap 1, (spontaneous mutant, captan resistant up to 300 micrograms/ml) were assayed on RM medium with and without the presence of the ...fungicide. Comparisons were also carried out with Az. chroococcum sensitive strains Azwt, Azcan 10 and 14. The hydrolysis of captan, incorporated in agar plates of RM at 100 micrograms/ml, was rapid, since on 4-day plates, no effect was found on the strain Azwt, while on freshly prepared ones its growth was completely blocked. As for Azcap 1, grown on RM only, the behaviour was similar to that of sensitive strains, whereas when grown on captan the results of experiments showed: (i) a lag of approximately 12 h to reach the maximum nitrogen-fixing activity; (ii) delay of 12-24 h in the full consumption of glucose present in the medium, although the invertase activity did not present differences; (iii) high ATP culture content during the 50 h of the experiment; (iv) approximately 6-10-fold lower production of PHB (poly-B-hydroxybutyrate); (v) lack of typical encystment phase, for the tested 96 h and reduced viability in developing colonies on agar RM medium. In contrast, when captan was added to cultural medium at sublethal concentration, 50 micrograms/ml for sensitive strain Azwt and 200 micrograms/ml for Azcap 1, the amount of glutathione produced (to remove the fungicide toxicity) was several times higher for the former.
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