13,784 research outputs found
Titanium alloy stress corrosion cracking in presence of dinitrogen tetroxide
Study resulting in a satisfactory stress corrosion cracking test with extremely consistent results produced six new analytical methods. Methods detect and determine differences in the minor constituent composition of different types of dinitrogen tetroxide
Velocity map imaging of the dynamics of the CH3 + HCl -> CH4 + Cl reaction using a dual molecular beam method
International audienceThe reactions CH3 + HCl → CH4 + Cl(<sup>2</sup>P<sub>3/2</sub>) and CD<sub>3</sub> + HCl → CD<sub>3</sub>H + Cl(<sup>2</sup>P<sub>3/2</sub>) have been studied by photo-initiation (by CH<sub>3</sub>I or CD<sub>3</sub>I photolysis at 266 nm) in a dual molecular beam apparatus. Product Cl(<sup>2</sup>P</sub>3/2</sub>) atoms were detected using resonance enhanced multi-photon ionisation and velocity map imaging, revealing product translational energy and angular scattering distributions in the centre-of-mass frame. Image analysis is complicated by the bimodal speed distribution of CH<sub>3</sub> (and CD<sub>3</sub>) radicals formed in coincidence with I(<sup>2</sup>P<sub>3/2</sub>) and I(<sup>2</sup>P<sub>1/2</sub>) atoms from CH<sub>3</sub>I (CD<sub>3</sub>I) photodissociation, giving overlapping Newton diagrams with displaced centre of mass velocities. The relative reactivities to form Cl atoms are greater for the slower CH<sub>3</sub> speed group than the faster group by factors of ~1.5 for the reaction of CH<sub>3</sub> and ~2.5 for the reaction of CD<sub>3</sub>, consistent with the greater propensity of the faster methyl radicals to undergo electronically adiabatic reactions to form Cl(<sup>2</sup>P<sub>1/2</sub>). The average fraction of the available energy becoming product translational energy is = 0.48 ± 0.05 and 0.50 ± 0.03 for reaction of the faster and slower sets of CH<sub>3</sub> radicals, respectively. The Cl atoms are deduced to be preferentially forward scattered with respect to the HCl reagents, but the angular distributions from the dual beam imaging experiments require correction for under-detection of forward scattered Cl products
Number of adaptive steps to a local fitness peak
We consider a population of genotype sequences evolving on a rugged fitness
landscape with many local fitness peaks. The population walks uphill until it
encounters a local fitness maximum. We find that the statistical properties of
the walk length depend on whether the underlying fitness distribution has a
finite mean. If the mean is finite, all the walk length cumulants grow with the
sequence length but approach a constant otherwise. Experimental implications of
our analytical results are also discussed
Searching for t-bar t Resonances at the Large Hadron Collider
Many new physics models predict resonances with masses in the TeV range which
decay into a pair of top quarks. With its large cross section, t-bar t
production at the Large Hadron Collider (LHC) offers an excellent opportunity
to search for such particles. We present a detailed study of the discovery
potential of the CERN Large Hadron Collider for Kaluza-Klein (KK) excitations
of the gluon in bulk Randall-Sundrum (RS) models in the t-bar t -> ell^+/- nu
b-bar bq-bar q' (ell=e, mu) final state. We utilize final states with one or
two tagged b-quarks, and two, three or four jets (including b-jets). Our
calculations take into account the finite resolution of detectors, the energy
loss due to b-quark decays, the expected reduced b-tagging efficiency at large
t-bar t invariant masses, and include the background originating from Wb-bar
b+jets, (Wb+W-bar b)+jets, W+jets, and single top + jets production. We derive
semi-realistic 5 sigma discovery limits for nine different KK gluon scenarios,
and compare them with those for KK gravitons, and a Z_H boson in the Littlest
Higgs model. We also analyze the capabilities of the LHC experiments to
differentiate between individual KK gluon models and measure the couplings of
KK gluons to quarks. We find that, for the parameters and models chosen, KK
gluons with masses up to about 4 TeV can be discovered at the LHC. The ability
of the LHC to discriminate between different bulk RS models, and to measure the
couplings of the KK gluons is found to be highly model dependent.Comment: revtex3, 27 pages, 5 tables, 6 figure
Letter from J. A. Orr to General W. S. Featherston. 20 May 1867
Letter sent from Columbus; regarding request for a character resolution on conduct during the Civil War, military bill, Congress, Republican Party.https://egrove.olemiss.edu/ciwar_corresp/1256/thumbnail.jp
Velocity map imaging of the dynamics of reactions of Cl atoms with neopentane and tetramethyl silane
Heat transfer to a gas containing a cloud of particles
Heat transfer to gas containing particle clou
Nonlinear optical response in doped conjugated polymers
Exciton effects on conjugated polymers are investigated in soliton lattice
states. We use the Su-Schrieffer-Heeger model with long-range Coulomb
interactions. The Hartree-Fock (HF) approximation and the single-excitation
configuration- interaction (single-CI) method are used to obtain optical
absorption spectra. The third-harmonic generation (THG) at off-resonant
frequencies is calculated as functions of the soliton concentration and the
chain length of the polymer. The magnitude of the THG at the 10 percent doping
increases by the factor about 10^2 from that of the neutral system. This is
owing to the accumulation of the oscillator strengths at the lowest exciton
with increasing the soliton concentration. The increase by the order two is
common for several choices of Coulomb interaction strengths.Comment: Accepted for publication in J. Phys.: Condens. Matte
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