1,579 research outputs found
Analysis of expression of aquaporins and Na+/H+ transporters in tomato colonized by arbuscular mycorrhizal fungi and affected by salt stress
Evaluation of two thermal neutron detection units consisting of ZnS/LiF scintillating layers with embedded WLS fibers read out with a SiPM
Two single channel detection units for thermal neutron detection are
investigated in a neutron beam. They consist of two ZnS/LiF scintillating
layers sandwiching an array of WLS fibers. The pattern of this units can be
repeated laterally and vertically in order to build up a one dimensional
position sensitive multi-channel detector with the needed sensitive surface and
with the required neutron absorption probability. The originality of this work
arises from the fact that the WLS fibers are read out with SiPMs instead of the
traditionally used PMTs or MaPMTs. The signal processing system is based on a
photon counting approach. For SiPMs with a dark count rate as high as 0.7 MHz,
a trigger efficiency of 80% is achieved together with a system background rate
lower than Hz and a dead time of 30 s. No change of
performance is observed for neutron count rates of up to 3.6 kHz.Comment: Submitted to Nuclear Instruments and Methods
Complex span versus updating tasks of working memory : the gap is not that deep
How to best measure working memory capacity is an issue of ongoing debate. Besides established complex span tasks, which combine short-term memory demands with generally unrelated secondary tasks, there exists a set of paradigms characterized by continuous and simultaneous updating of several items in working memory, such as the n-back, memory updating, or alpha span tasks. With a latent variable analysis (N = 96) based on content-heterogeneous operationalizations of both task families, the authors found a latent correlation between a complex span factor and an updating factor that was not statistically different from unity (r = .96). Moreover, both factors predicted fluid intelligence (reasoning) equally well. The authors conclude that updating tasks measure working memory equally well as complex span tasks. Processes involved in building, maintaining, and updating arbitrary bindings may constitute the common working memory ability underlying performance on reasoning, complex span, and updating tasks
Studies of aging and HV break down problems during development and operation of MSGC and GEM detectors for the Inner Tracking System of HERA-B
The results of five years of development of the inner tracking system of the
HERA-B experiment and first experience from the data taking period of the year
2000 are reported. The system contains 184 chambers, covering a sensitive area
of about 20 * 20 cm2 each. The detector is based on microstrip gas counters
(MSGCs) with diamond like coated (DLC) glass wafers and gas electron
multipliers (GEMs). The main problems in the development phase were gas
discharges in intense hadron beams and aging in a high radiation dose
environment. The observation of gas discharges which damage the electrode
structure of the MSGC led to the addition of the GEM as a first amplification
step. Spurious sparking at the GEM cannot be avoided completely. It does not
affect the GEM itself but can produce secondary damage of the MSGC if the
electric field between the GEM and the MSGC is above a threshold depending on
operation conditions. We observed that aging does not only depend on the dose
but also on the spot size of the irradiated area. Ar-DME mixtures had to be
abandoned whereas a mixture of 70% Ar and 30% CO2 showed no serious aging
effects up to about 40 mC/cm deposited charge on the anodes. X-ray measurements
indicate that the DLC of the MSGC is deteriorated by the gas amplification
process. As a consequence, long term gain variations are expected. The Inner
Tracker has successfully participated in the data taking at HERA-B during
summer 2000.Comment: 29 pages, 22 figure
Research Proposal for an Experiment to Search for the Decay {\mu} -> eee
We propose an experiment (Mu3e) to search for the lepton flavour violating
decay mu+ -> e+e-e+. We aim for an ultimate sensitivity of one in 10^16
mu-decays, four orders of magnitude better than previous searches. This
sensitivity is made possible by exploiting modern silicon pixel detectors
providing high spatial resolution and hodoscopes using scintillating fibres and
tiles providing precise timing information at high particle rates.Comment: Research proposal submitted to the Paul Scherrer Institute Research
Committee for Particle Physics at the Ring Cyclotron, 104 page
Precision calculation of within chiral perturbation theory
The reaction is calculated up to order in
chiral perturbation theory, where denotes the ratio of the pion to the
nucleon mass. Special emphasis is put on the role of nucleon--recoil
corrections that are the source of contributions with fractional power in
. Using the known near threshold production amplitude for as the only input, the total cross section for
is described very well. A conservative estimate suggests that the theoretical
uncertainty for the transition operator amounts to 3 % for the computed
amplitude near threshold.Comment: 28 page
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