67 research outputs found
Deterministic and stochastic descriptions of gene expression dynamics
A key goal of systems biology is the predictive mathematical description of
gene regulatory circuits. Different approaches are used such as deterministic
and stochastic models, models that describe cell growth and division explicitly
or implicitly etc. Here we consider simple systems of unregulated
(constitutive) gene expression and compare different mathematical descriptions
systematically to obtain insight into the errors that are introduced by various
common approximations such as describing cell growth and division by an
effective protein degradation term. In particular, we show that the population
average of protein content of a cell exhibits a subtle dependence on the
dynamics of growth and division, the specific model for volume growth and the
age structure of the population. Nevertheless, the error made by models with
implicit cell growth and division is quite small. Furthermore, we compare
various models that are partially stochastic to investigate the impact of
different sources of (intrinsic) noise. This comparison indicates that
different sources of noise (protein synthesis, partitioning in cell division)
contribute comparable amounts of noise if protein synthesis is not or only
weakly bursty. If protein synthesis is very bursty, the burstiness is the
dominant noise source, independent of other details of the model. Finally, we
discuss two sources of extrinsic noise: cell-to-cell variations in protein
content due to cells being at different stages in the division cycles, which we
show to be small (for the protein concentration and, surprisingly, also for the
protein copy number per cell) and fluctuations in the growth rate, which can
have a significant impact.Comment: 23 pages, 5 figures; Journal of Statistical physics (2012
Measurement of the Atmospheric Muon Spectrum from 20 to 3000 GeV
The absolute muon flux between 20 GeV and 3000 GeV is measured with the L3
magnetic muon spectrometer for zenith angles ranging from 0 degree to 58
degree. Due to the large exposure of about 150 m2 sr d, and the excellent
momentum resolution of the L3 muon chambers, a precision of 2.3 % at 150 GeV in
the vertical direction is achieved.
The ratio of positive to negative muons is studied between 20 GeV and 500
GeV, and the average vertical muon charge ratio is found to be 1.285 +- 0.003
(stat.) +- 0.019 (syst.).Comment: Total 32 pages, 9Figure
Response to Lawrence DJ: The global summit on the efficacy and effectiveness of spinal manipulative therapy for the prevention and treatment of non-musculoskeletal disorders: A systematic review of the literature
Thank you for the opportunity to respond to the Letter to the Editor by Dana J. Lawrence. In his letter, Lawrence states that the results of our systematic review may be due to bias. However, he does not adequately substantiate his claims..
Molecular detection of hepatitis E virus in feces and slurry from swine farms, Rio Grande do Sul, Southern Brazil
Techniques for measuring aerosol attenuation using the Central Laser Facility at the Pierre Auger Observatory
The Pierre Auger Observatory in MalargĂŒe, Argentina, is designed to study the properties of ultra-high energy cosmic rays with energies above 10(18) eV. It is a hybrid facility that employs a Fluorescence Detector to perform nearly calorimetric measurements of Extensive Air Shower energies. To obtain reliable calorimetric information from the FD, the atmospheric conditions at the observatory need to be continuously monitored during data acquisition. In particular, light attenuation due to aerosols is an important atmospheric correction. The aerosol concentration is highly variable, so that the aerosol attenuation needs to be evaluated hourly. We use light from the Central Laser Facility, located near the center of the observatory site, having an optical signature comparable to that of the highest energy showers detected by the FD. This paper presents two procedures developed to retrieve the aerosol attenuation of fluorescence light from CLF laser shots. Cross checks between the two methods demonstrate that results from both analyses are compatible, and that the uncertainties are well understood. The measurements of the aerosol attenuation provided by the two procedures are currently used at the Pierre Auger Observatory to reconstruct air shower data
The rapid atmospheric monitoring system of the Pierre Auger Observatory
The Pierre Auger Observatory is a facility built to detect air showers produced by cosmic rays above 10(17) eV. During clear nights with a low illuminated moon fraction, the UV fluorescence light produced by air showers is recorded by optical telescopes at the Observatory. To correct the observations for variations in atmospheric conditions, atmospheric monitoring is performed at regular intervals ranging from several minutes (for cloud identification) to several hours (for aerosol conditions) to several days (for vertical profiles of temperature, pressure, and humidity). In 2009, the monitoring program was upgraded to allow for additional targeted measurements of atmospheric conditions shortly after the detection of air showers of special interest, e. g., showers produced by very high-energy cosmic rays or showers with atypical longitudinal profiles. The former events are of particular importance for the determination of the energy scale of the Observatory, and the latter are characteristic of unusual air shower physics or exotic primary particle types. The purpose of targeted (or 'rapid') monitoring is to improve the resolution of the atmospheric measurements for such events. In this paper, we report on the implementation of the rapid monitoring program and its current status. The rapid monitoring data have been analyzed and applied to the reconstruction of air showers of high interest, and indicate that the air fluorescence measurements affected by clouds and aerosols are effectively corrected using measurements from the regular atmospheric monitoring program. We find that the rapid monitoring program has potential for supporting dedicated physics analyses beyond the standard event reconstruction
Antennas for the detection of radio emission pulses from cosmic-ray induced air showers at the Pierre Auger Observatory
The Pierre Auger Observatory is exploring the potential of the radio detection technique to study extensive air showers induced by ultra-high energy cosmic rays. The Auger Engineering Radio Array (AERA) addresses both technological and scientific aspects of the radio technique. A first phase of AERA has been operating since September 2010 with detector stations observing radio signals at frequencies between 30 and 80 MHz. In this paper we present comparative studies to identify and optimize the antenna design for the final configuration of AERA consisting of 160 individual radio detector stations. The transient nature of the air shower signal requires a detailed description of the antenna sensor. As the ultra-wideband reception of pulses is not widely discussed in antenna literature, we review the relevant antenna characteristics and enhance theoretical considerations towards the impulse response of antennas including polarization effects and multiple signal reflections. On the basis of the vector effective length we study the transient response characteristics of three candidate antennas in the time domain. Observing the variation of the continuous galactic background intensity we rank the antennas with respect to the noise level added to the galactic signal
The Rapid Atmospheric Monitoring System of the Pierre Auger Observatory
The Pierre Auger Observatory is a facility built to detect air showers
produced by cosmic rays above 10^17 eV. During clear nights with a low
illuminated moon fraction, the UV fluorescence light produced by air showers is
recorded by optical telescopes at the Observatory. To correct the observations
for variations in atmospheric conditions, atmospheric monitoring is performed
at regular intervals ranging from several minutes (for cloud identification) to
several hours (for aerosol conditions) to several days (for vertical profiles
of temperature, pressure, and humidity). In 2009, the monitoring program was
upgraded to allow for additional targeted measurements of atmospheric
conditions shortly after the detection of air showers of special interest,
e.g., showers produced by very high-energy cosmic rays or showers with atypical
longitudinal profiles. The former events are of particular importance for the
determination of the energy scale of the Observatory, and the latter are
characteristic of unusual air shower physics or exotic primary particle types.
The purpose of targeted (or "rapid") monitoring is to improve the resolution of
the atmospheric measurements for such events. In this paper, we report on the
implementation of the rapid monitoring program and its current status. The
rapid monitoring data have been analyzed and applied to the reconstruction of
air showers of high interest, and indicate that the air fluorescence
measurements affected by clouds and aerosols are effectively corrected using
measurements from the regular atmospheric monitoring program. We find that the
rapid monitoring program has potential for supporting dedicated physics
analyses beyond the standard event reconstruction
Description of Atmospheric Conditions at the Pierre Auger Observatory using the Global Data Assimilation System (GDAS)
Atmospheric conditions at the site of a cosmic ray observatory must be known
for reconstructing observed extensive air showers. The Global Data Assimilation
System (GDAS) is a global atmospheric model predicated on meteorological
measurements and numerical weather predictions. GDAS provides
altitude-dependent profiles of the main state variables of the atmosphere like
temperature, pressure, and humidity. The original data and their application to
the air shower reconstruction of the Pierre Auger Observatory are described. By
comparisons with radiosonde and weather station measurements obtained on-site
in Malarg\"ue and averaged monthly models, the utility of the GDAS data is
shown
Estruturas secretoras de mucilagem em Hibiscus pernambucensis Arruda (Malvaceae): distribuição, caracterização morfoanatĂŽmica e histoquĂmica
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