2,648 research outputs found
Steady-state expression of self-regulated genes
Motivation: Regulatory gene networks contain generic modules such as feedback loops that are essential for the regulation of many biological functions. The study of the stochastic mechanisms of gene regulation is instrumental for the understanding of how cells maintain their expression at levels commensurate with their biological role, as well as to engineer gene expression switches of appropriate behavior. The lack of precise knowledge on the steady-state distribution of gene expression requires the use of Gillespie algorithms and Monte-Carlo approximations. Methodology: In this study, we provide new exact formulas and efficient numerical algorithms for computing/modeling the steady-state of a class of self-regulated genes, and we use it to model/compute the stochastic expression of a gene of interest in an engineered network introduced in mammalian cells. The behavior of the genetic network is then analyzed experimentally in living cells. Results: Stochastic models often reveal counter-intuitive experimental behaviors, and we find that this genetic architecture displays a unimodal behavior in mammalian cells, which was unexpected given its known bimodal response in unicellular organisms. We provide a molecular rationale for this behavior, and we implement it in the mathematical picture to explain the experimental results obtained from this network. Contact: [email protected], [email protected] Supplementary information: Supplementary data are available at Bioinformatics onlin
Light-ion production in the interaction of 96 MeV neutrons with oxygen
Double-differential cross sections for light-ion (p, d, t, He-3 and alpha)
production in oxygen, induced by 96 MeV neutrons are reported. Energy spectra
are measured at eight laboratory angles from 20 degrees to 160 degrees in steps
of 20 degrees. Procedures for data taking and data reduction are presented.
Deduced energy-differential and production cross sections are reported.
Experimental cross sections are compared to theoretical reaction model
calculations and experimental data at lower neutron energies in the literature.
The measured proton data agree reasonably well with the results of the model
calculations, whereas the agreement for the other particles is less convincing.
The measured production cross sections for protons, deuterons, tritons and
alpha particles support the trends suggested by data at lower energies.Comment: 21 pages, 13 figures, submitted to Phys. Rev.
Study of timing characteristics of a 3 m long plastic scintillator counter using waveform digitizers
A plastic scintillator bar with dimensions 300 cm x 2.5 cm x 11 cm was
exposed to a focused muon beam to study its light yield and timing
characteristics as a function of position and angle of incidence. The
scintillating light was read out at both ends by photomultiplier tubes whose
pulse shapes were recorded by waveform digitizers. Results obtained with the
WAVECATCHER and SAMPIC digitizers are analyzed and compared. A discussion of
the various factors affecting the timing resolution is presented. Prospects for
applications of plastic scintillator technology in large-scale particle physics
detectors with timing resolution around 100 ps are provided in light of the
results
Light-ion Production And Fission Studies Using The Medley Facility At Tsl
oS(FNDA2006)001 © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence
95 MeV neutron scattering on hydrogen, deuterium, carbon, and oxygen
Three neutron-deuteron scattering experiments at 95 MeV have been performed recently at The Svedberg Laboratory in Uppsala. Subsets of the results of these experiments have been reported in two short articles, showing clear evidence for three-nucleon force effects. In this paper, we present a more detailed description of the experimental methods as well as further discussion of the results. In addition to neutron-deuteron scattering
data, neutron-proton and 12 C(n, n) elastic scattering data have been measured for normalization purposes, and 16 O (n, n) data have been obtained for the first time at this energy. It was possible to extract 12 C(n, n )and 16 O (n, n ) inelastic scattering cross sections to excited states below 12 MeV excitation energy. The inelastic scattering data (for both carbon and oxygen) are shown to have a significant impact on the determination ofnuclear recoil kerma coefficients
Scandal - A Facility For Elastic Neutron Scattering Studies in the 50-130 MeV Range
A facility for detection of scattered neutrons in the energy interval 50â130 MeV, SCANDAL (SCAttered Nucleon Detection AssembLy), is part of the standard detection system at the 20-180 MeV neutron beam facility of the The Svedberg Laboratory, Uppsala. It has primarily been used for studies of elastic neutron scattering, but it has been employed for (n,p) and (n,d) reaction experiments as well. Results of recent experiments are presented to illustrate the performance of the spectrometer. Recently, the facility has been upgraded to perform also (n,Xn') experiments. For this purpose, a new converter, CLODIA, has been developed and installed. Preliminary results of the commissioning of CLODIA will be presented
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