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

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 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.

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

Diagnosing Spin at the LHC via Vector Boson Fusion

We propose a new technique for determining the spin of new massive particles that might be discovered at the Large Hadron Collider. The method relies on pair-production of the new particles in a kinematic regime where the vector boson fusion production mechanism is enhanced. For this regime, we show that the distribution of the leading jets as a function of their relative azimuthal angle can be used to distinguish spin-0 from spin-1/2 particles. We illustrate this effect by considering the particular cases of (i) strongly-interacting, stable particles and (ii) supersymmetric particles carrying color charge. We argue that this method should be applicable in a wide range of new physics scenarios.Comment: 5 pages, 4 figure