450 research outputs found
Role of the cyclic lipopeptide massetolide A in biological control of Phytophthora infestans and in colonization of tomato plants by Pseudomonas fluorescens
Pseudomonas strains have shown promising results in biological control of late blight caused by Phytophthora infestans. However, the mechanism(s) and metabolites involved are in many cases poorly understood. Here, the role of the cyclic lipopeptide massetolide A of Pseudomonas fluorescens SS101 in biocontrol of tomato late blight was examined. Pseudomonas fluorescens SS101 was effective in preventing infection of tomato (Lycopersicon esculentum) leaves by P. infestans and significantly reduced the expansion of existing late blight lesions. Massetolide A was an important component of the activity of P. fluorescens SS101, since the massA-mutant was significantly less effective in biocontrol, and purified massetolide A provided significant control of P. infestans, both locally and systemically via induced resistance. Assays with nahG transgenic plants indicated that the systemic resistance response induced by SS101 or massetolide A was independent of salicylic acid signalling. Strain SS101 colonized the roots of tomato seedlings significantly better than its massA-mutant, indicating that massetolide A was an important trait in plant colonization. This study shows that the cyclic lipopeptide surfactant massetolide A is a metabolite with versatile functions in the ecology of P fluorescens SS101 and in interactions with tomato plants and the late blight pathogen P. infestans
Experimental Study of CO2 Gasification of Biomethanation Waste
Gasification is one of prominent thermochemical processes generally used to convert organic feedstock to combustible syngas (CO and H2). An experimental study of biomass gasification using carbon dioxide as an gasifying medium was carried out in a fixed bed gasifier. The main aim of this study was to determine the effect of temperature on the output syngas. The present study reported the results for producing syngas with CO2 as gasification agent and biomass (rice husk and bio-methanation waste) as raw material. The gasification was performed at 700-900°C respectively and CO2 flow rate was maintained at 0.5 lpm. Maximum syngas
production found at high temperature (900°C). The syngas analysis showed higher hydrogen yield at higher temperatures
Demonstration and Comparison of Operation of Photomultiplier Tubes at Liquid Argon Temperature
Liquified noble gases are widely used as a target in direct Dark Matter
searches. Signals from scintillation in the liquid, following energy deposition
from the recoil nuclei scattered by Dark Matter particles (e.g. WIMPs), should
be recorded down to very low energies by photosensors suitably designed to
operate at cryogenic temperatures. Liquid Argon based detectors for Dark Matter
searches currently implement photo multiplier tubes for signal read-out. In the
last few years PMTs with photocathodes operating down to liquid Argon
temperatures (87 K) have been specially developed with increasing Quantum
Efficiency characteristics. The most recent of these, Hamamatsu Photonics Mod.
R11065 with peak QE up to about 35%, has been extensively tested within the R&D
program of the WArP Collaboration. During these testes the Hamamatsu PMTs
showed superb performance and allowed obtaining a light yield around 7
phel/keVee in a Liquid Argon detector with a photocathodic coverage in the 12%
range, sufficient for detection of events down to few keVee of energy
deposition. This shows that this new type of PMT is suited for experimental
applications, in particular for new direct Dark Matter searches with LAr-based
experiments
Design and Performance of the XENON10 Dark Matter Experiment
XENON10 is the first two-phase xenon time projection chamber (TPC) developed
within the XENON dark matter search program. The TPC, with an active liquid
xenon (LXe) mass of about 14 kg, was installed at the Gran Sasso underground
laboratory (LNGS) in Italy, and operated for more than one year, with excellent
stability and performance. Results from a dark matter search with XENON10 have
been published elsewhere. In this paper, we summarize the design and
performance of the detector and its subsystems, based on calibration data using
sources of gamma-rays and neutrons as well as background and Monte Carlo
simulations data. The results on the detector's energy threshold, energy and
position resolution, and overall efficiency show a performance that exceeds
design specifications, in view of the very low energy threshold achieved (<10
keVr) and the excellent energy resolution achieved by combining the ionization
and scintillation signals, detected simultaneously
Исследование микроструктуры безобжиговых периклазоуглеродистых огнеупоров при использовании в качестве заполнителя различного вида периклаза
У статті представлено результати досліджень мікроструктури периклазовуглецевих зразків, у яких в якості наповнювача використовували різні види периклазу. Петрографічні дослідження показали, що зразки щільні та міцні, як на плавленому, так і на спеченому периклазі.In clause the results of researches of microstructure magnesia-carbon refractors are submitted, at which in quality filler used different kind magnesia. Microstructures of samples strong and dense, both on melted, and on sintered periclase have shown, that
Experimental Bounds on Masses and Fluxes of Nontopological Solitons
We have re-analyzed the results of various experiments which were not
originally interested as searches for the Q-ball or the Fermi-ball. Based on
these analyses, in addition to the available data on Q-balls, we obtained
rather stringent bounds on flux, mass and typical energy scale of Q-balls as
well as Fermi-balls. In case these nontopological solitons are the main
component of the dark matter of the Galaxy, we found that only such solitons
with very large quantum numbers are allowed. We also estimate how sensitive
future experiments will be in the search for Q-balls and Fermi-balls.Comment: 19 pages, 7 eps figures, RevTeX, psfig.st
The scintillation and ionization yield of liquid xenon for nuclear recoils
XENON10 is an experiment designed to directly detect particle dark matter. It
is a dual phase (liquid/gas) xenon time-projection chamber with 3D position
imaging. Particle interactions generate a primary scintillation signal (S1) and
ionization signal (S2), which are both functions of the deposited recoil energy
and the incident particle type. We present a new precision measurement of the
relative scintillation yield \leff and the absolute ionization yield Q_y, for
nuclear recoils in xenon. A dark matter particle is expected to deposit energy
by scattering from a xenon nucleus. Knowledge of \leff is therefore crucial for
establishing the energy threshold of the experiment; this in turn determines
the sensitivity to particle dark matter. Our \leff measurement is in agreement
with recent theoretical predictions above 15 keV nuclear recoil energy, and the
energy threshold of the measurement is 4 keV. A knowledge of the ionization
yield \Qy is necessary to establish the trigger threshold of the experiment.
The ionization yield \Qy is measured in two ways, both in agreement with
previous measurements and with a factor of 10 lower energy threshold.Comment: 8 pages, 9 figures. To be published in Nucl. Instrum. Methods
Self-shielding effect of a single phase liquid xenon detector for direct dark matter search
Liquid xenon is a suitable material for a dark matter search. For future
large scale experiments, single phase detectors are attractive due to their
simple configuration and scalability. However, in order to reduce backgrounds,
they need to fully rely on liquid xenon's self-shielding property. A prototype
detector was developed at Kamioka Observatory to establish vertex and energy
reconstruction methods and to demonstrate the self-shielding power against
gamma rays from outside of the detector. Sufficient self-shielding power for
future experiments was obtained.Comment: 8 pages, 8 figure
Selected reactive oxygen species and antioxidant enzymes in common bean after Pseudomonas syringae pv. phaseolicola and Botrytis cinerea infection
Phaseolus vulgaris cv. Korona plants were
inoculated with the bacteria Pseudomonas syringae pv.
phaseolicola (Psp), necrotrophic fungus Botrytis cinerea
(Bc) or with both pathogens sequentially. The aim of the
experiment was to determine how plants cope with multiple
infection with pathogens having different attack strategy.
Possible suppression of the non-specific infection with
the necrotrophic fungus Bc by earlier Psp inoculation was
examined. Concentration of reactive oxygen species
(ROS), such as superoxide anion (O2
-) and H2O2 and
activities of antioxidant enzymes such as superoxide dismutase
(SOD), catalase (CAT) and peroxidase (POD) were
determined 6, 12, 24 and 48 h after inoculation. The
measurements were done for ROS cytosolic fraction and
enzymatic cytosolic or apoplastic fraction. Infection with
Psp caused significant increase in ROS levels since the
beginning of experiment. Activity of the apoplastic
enzymes also increased remarkably at the beginning of
experiment in contrast to the cytosolic ones. Cytosolic
SOD and guaiacol peroxidase (GPOD) activities achieved
the maximum values 48 h after treatment. Additional forms
of the examined enzymes after specific Psp infection were
identified; however, they were not present after single Bc
inoculation. Subsequent Bc infection resulted only in
changes of H2O2 and SOD that occurred to be especially
important during plant–pathogen interaction. Cultivar Korona
of common bean is considered to be resistant to Psp and mobilises its system upon infection with these bacteria.
We put forward a hypothesis that the extent of defence
reaction was so great that subsequent infection did not
trigger significant additional response
New constraint on the existence of the mu+-> e+ gamma decay
The analysis of a combined data set, totaling 3.6 \times 10^14 stopped muons
on target, in the search for the lepton flavour violating decay mu^+ -> e^+
gamma is presented. The data collected by the MEG experiment at the Paul
Scherrer Institut show no excess of events compared to background expectations
and yield a new upper limit on the branching ratio of this decay of 5.7 \times
10^-13 (90% confidence level). This represents a four times more stringent
limit than the previous world best limit set by MEG.Comment: 5 pages, 3 figures, a version accepted in Phys. Rev. Let
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