A detailed chemical kinetic mechanism has been developed and used to study the oxidation of cyclohexane at both low and high temperatures. Reaction rate constant rules are developed for the low temperature combustion of cyclohexane. These rules can be used for in chemical kinetic mechanisms for other cycloalkanes. Since cyclohexane produces only one type of cyclohexyl radical, much of the low temperature chemistry of cyclohexane is described in terms of one potential energy diagram showing the reaction of cyclohexyl radical + O{sub 2} through five, six and seven membered ring transition states. The direct elimination of cyclohexene and HO{sub 2} from RO{sub 2} is included in the treatment using a modified rate constant of Cavallotti et al. Published and unpublished data from the Lille rapid compression machine, as well as jet-stirred reactor data are used to validate the mechanism. The effect of heat loss is included in the simulations, an improvement on previous studies on cyclohexane. Calculations indicated that the production of 1,2-epoxycyclohexane observed in the experiments can not be simulated based on the current understanding of low temperature chemistry. Possible 'alternative' H-atom isomerizations leading to different products from the parent O{sub 2}QOOH radical were included in the low temperature …

Alloy 22 (N06022) is highly resistant to localized corrosion. Under aggressive environmental conditions Alloy 22 may be susceptible to crevice corrosion in hot chloride (Cl{sup -}) solutions. The objective of the present work was to explore the environmental and geometrical conditions for crevice corrosion to occur. Electrochemical tests were performed using PCA and prismatic mill annealed Alloy 22 specimens in chloride solutions. Crevice corrosion current density was found to be a function of applied potential. i{sub CREV} values ranged from 40 {micro}A/cm{sup 2} to 20 mA/cm{sup 2}. Such low values of current density explained the absence of pitting corrosion in Alloy 22 at any potential. Decreasing of the effective diffusion distance in a propagating crevice is thought to cause crevice corrosion stifling or repassivation after long anodic polarization. Crevice corrosion breakdown potential is expected to decrease with potential scan rate, approaching repassivation potential for low scan rates. The lowest corrosion potential of Alloy 22 in hydrochloric acid solutions at which active corrosion exists was proposed as the lowest possible repassivation potential for crevice corrosion.

Researchers at Lawrence Livermore National Laboratory conducted a field study to evaluate the deposition of an explosively dispersed radionuclide surrogate (CsCl) on grime and non-grime containing urban surfaces. An additional objective of this study was to evaluate several laboratory surface contamination techniques for the preparation of mock urban surfaces in order to determine the method that most closely mimics surface contamination following an RDD event. The field study was conducted at the LLNL Site 300 Contained Firing Facility (CFF). For our study, we detonated a mock RDD made using C4 and non-radioactive CsCl. Lab prepared concrete samples (3.8 cm x 7.6 cm cylinders) were made using 4 different conditioning regimes to mimic a range of conditions that may be encountered during an RDD event. This sample set included dry, wet, carbonated and non-carbonated cores with and without the application of urban grime. In addition, concreted samples (13 cm x 13 cm x 5 cm) removed from an urban surface were placed inside the CFF chamber. The samples were placed inside the firing chamber at 3 different distances from the mock RDD device. Following the detonation of the mock RDD, the samples were removed from the firing chamber and selected cores …

The Fourier transform of the deeply virtual Compton scattering amplitude (DVCS) with respect to the skewness parameter {zeta} = Q{sup 2}/2p {center_dot} q can be used to provide an image of the target hadron in the boost-invariant variable {sigma}, the coordinate conjugate to light-front time {tau} = t + z/c. As an illustration, we construct a consistent covariant model of the DVCS amplitude and its associated generalized parton distributions using the quantum fluctuations of a fermion state at one loop in QED, thus providing a representation of the light-front wavefunctions of a lepton in {sigma} space. A consistent model for hadronic amplitudes can then be obtained by differentiating the light-front wavefunctions with respect to the bound-state mass. The resulting DVCS helicity amplitudes are evaluated as a function of {sigma} and the impact parameter {rvec b}{sub {perpendicular}}, thus providing a light-front ''photograph'' of the target hadron in a frame-independent three-dimensional light-front coordinate space. We find that in the models studied, the Fourier transform of the DVCS amplitudes exhibit diffraction patterns. The results are analogous to the diffractive scattering of a wave in optics where the distribution in {sigma} measures the physical size of the scattering center in a one-dimensional system.

The existence of flux-ratio anomalies between fold and cusp images in galaxy-scale strong-lens systems has led to an interpretation based on the presence of a high mass-fraction of cold-dark-matter (CDM) substructures around galaxies, as predicted by numerical N-body simulations. These substructures can cause large perturbations of the image magnifications, leading to changes in the image flux ratios. The flux-ratio anomaly is particularly evident in the radio-loud quadruple gravitational lens system CLASS B2045+265. In this paper, new high-resolution radio, optical, and infrared imaging of B2045+265 is presented which sheds more light on this anomaly and its possible causes. First, deep Very Long Baseline Array observations show very compact images, possibly with a hint of a jet, but with no evidence for differential scattering or scatter broadening. Hence, the flux-ratio anomaly is unlikely to be caused by refractive scattering in either the Milky Way or the lens galaxy. Second, optical and infrared observations with the Hubble Space Telescope and through Adaptive-Optics imaging with the W. M. Keck Telescope, show a previously undiscovered object--interpreted as a (tidally disrupted) dwarf satellite based on its colors and slight extension--between the main lens galaxy and the three anomalous flux-ratio images. Third, color variations in the early-type …

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