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121.
A series of NOx–air irradiations, with trace amounts of propane and propene present to monitor OH radical concentrations, have been carried out in a 5800-L evacuable environmental chamber to investigate radical levels and sources during such irradiations. The data obtained show conclusively that unknown radical sources are present, and that photolysis of initial nitrous acid can be, at best, only a minor source of radicals after ~30–60 min of irradiation. 相似文献
122.
Laser induced fluorescence of C2O is observed following the 266 nm laser photodissociation Of C3O2. Excitation spectra of C2O(Ã3Πi?-~X3Σ? are consistent with previous absorption studies of C2O. A number of new transitions are identified and assigned. Fluorescence spectra have been recorded following single vibrational level laser excitation. Bands are assigned to ground state vibrational progressions. Values of 1967 and 1063 cm?1 are found for υ1″ and υ3″ stretching vibrations in the X?3Σ ? state. A subband structure in the fluorescence spectrum is observed and discussed. 相似文献
123.
The fluorescence decay and bimolecular electronic quenching behavior of C2O (3Πi) is reported. C2O(3Σ?) is produced by laser photolysis of C3O2 at 266 nm and is subsequently excited by a tunable flashlamp pumped dye laser. The fluorescence decay is highly nonexponential and dominated by both short (≈ 15 μs) and long (50–250 μs) decay components. The long-lived emission, itself, is nonexponential. The fluorescence decay is modeled as the sum of three exponential components. The short-lived emission is quenched by C3O2 at higher than the gas kinetic rate while the long-lived fluorescence is quenched much less efficiently. Fluorescence quenching measurements are also reported for collisions with Ar, N2 and O2. 相似文献
124.
Considerable recent work has explored the queueing impact of different properties of the input process to a buffer. The authors confine their attention to the effects of variation in service time distribution; the motivation for this being the need to calculate accurate delay bounds in the presence of variable length IP packets, and specifically to assess the impact of a small proportion of large packets on the delay performance. An analytical result is developed into which any distribution of packet size can be substituted easily, and in the process the value of better queueing models for arbitrary packet length distributions is shown 相似文献
125.
A formula is presented for the `equivalent capacity' required to support a given cell loss probability in an ATM buffer fed by a single on/off source. This formula can be applied as a component in connection admission control and bandwidth management algorithms in ATM telecommunications networks 相似文献
126.
Roger Atkinson William P. L. Carter Sara M. Aschmann Arthur M. Winer James N. Pitts 《国际化学动力学杂志》1984,16(4):469-481
Relative rate constants for the reaction of OH radicals with a series of branched alkanes have been determined at 297 ± 2 K, using methyl nitrite photolysis in air as a source of OH radicals. Using a rate constant for the reaction of OH radicals with n-butane of 2.58 × 10?12 cm3/molecule · s, the rate constants obtained are (× 1012 cm3/molecule · s): isobutane, 2.29 ± 0.06; 2-methylbutane, 3.97 ± 0.11; 2,2-dimethylbutane, 2.66 ± 0.08; 2-methylpentane, 5.68 ± 0.24; 3-methylpentane, 5.78 ± 0.11; 2,2,3-trimethylbutane, 4.21 ± 0.08; 2,4-dimethylpentane, 5.26 ± 0.11; methylcyclohexane, 10.6 ± 0.3; 2,2,3,3-tetramethylbutane, 1.06 ± 0.08; and 2,2,4-trimethylpentane, 3.66 ± 0.16. Rate constants for 2,2-dimethylbutane, 2,4-dimethylpentane, and methylclohexane have been determined for the first time, while those for the other branched alkanes are in generally good agreement with the literature data. Primary, secondary, and tertiary group rate constants at room temperature have been derived from these and previous data for alkanes and unstrained cycloalkanes, with the secondary and tertiary group rate constants depending in a systematic manner on the identity of the neighboring groups. The use of these group rate constants, together with a previous determination of the effect of ring strain energy on the OH radical rate constants for a series of cycloalkanes, allows the a priori estimation of OH radical rate constants for alkanes and cycloalkanes at room temperature. 相似文献
127.
Absolute rate constants are reported for reactions of C2O(3Σ?) under pseudo-first-order decay conditions. C2O is generated by laser photodissociation of C3O2 at 266 nm, and detected by dye-laser induced fluorescence on the 3Πi-3Σ? transition. Rate constants of (433 ± 12), (3.30 ± 0.12) and (1.12 ± 0.05) × 10?13 cm3 molecule?1 s?1 are reported for reactions with NO, O2 and isobutene. The NO value is approximate due to an apparent dark reaction between NO and C3O2. Upper limits of 1 × 10?14 cm3 molecule?1 s?1 are reported for reactions with H2, CO2, C3H2 and C2H4. The C2O + C3O2 reaction does not follow pseudo-first-order decay kinetics. Two explanations are proposed to explain this observation. Results are compared with previous relative rate measurements and are discussed in terms of their relevance to combustion chemistry. 相似文献
128.
Rate constants for the reaction of O(3P) atoms with CH2 = CHF,CH2 = CHCl,and CH2 = CHBr at 298 ± 2°K
Absolute rate constants for the reaction of O(3P) atoms with CH2 = CHF, CH2 = CHCl, and CH2 = CHBr have been obtained at 298 ± 2°K using a modulation phase shift technique. The rate constants (k2 × 10?8 l./mole · sec) obtained are: CH2 = CHF (1.61 ± 0.20), CH2 = CHCl (2.54 ± 0.26), and CH2 = CHBr (2.45 ± 0.25). These rate constants are lower than those determined by discharge flow techniques, but that for CH2 = CHF is in good agreement with relative rate measurements. 相似文献
129.
Zapata-Velandia A Ng SS Brennan RF Simonsen NR Gastanaduy M Zabaleta J Lentz JJ Craver RD Correa H Delgado A Pitts AL Himel JR Udall JN Schmidt-Sommerfeld E Brown RF Athas GB Keats BB Mannick EE 《Journal of immune based therapies and vaccines》2004,2(1):6-8
BACKGROUND: Polymorphisms in several genes (NOD2, MDR1, SLC22A4) have been associated with susceptibility to Crohn's disease. Identification of the remaining Crohn's susceptibility genes is essential for the development of disease-specific targets for immunotherapy. Using gene expression analysis, we identified a differentially expressed gene on 5q33, the colony stimulating factor 1 receptor (CSF1R) gene, and hypothesized that it is a Crohn's susceptibility gene. The CSF1R gene is involved in monocyte to macrophage differentiation and in innate immunity. METHODS: Patients provided informed consent prior to entry into the study as approved by the Institutional Review Board at LSU Health Sciences Center. We performed forward and reverse sequencing of genomic DNA from 111 unrelated patients with Crohn's disease and 108 controls. We also stained paraffin-embedded, ileal and colonic tissue sections from patients with Crohn's disease and controls with a polyclonal antibody raised against the human CSF1R protein. RESULTS: A single nucleotide polymorphism (A2033T) near a Runx1 binding site in the eleventh intron of the colony stimulating factor 1 receptor was identified. The T allele of this single nucleotide polymorphism occurred in 27% of patients with Crohn's disease but in only 13% of controls (X2 = 6.74, p < 0.01, odds ratio (O.R.) = 2.49, 1.23 < O.R. < 5.01). Using immunohistochemistry, positive staining with a polyclonal antibody to CSF1R was observed in the superficial epithelium of ileal and colonic tissue sections. CONCLUSIONS: We conclude that the colony stimulating factor receptor 1 gene may be a susceptibility gene for Crohn's disease. 相似文献
130.
Experiments on edge turbulence in the TCV tokamak have been performed for the first time at the beginning of 2003. This paper presents an overview of some of the results obtained, concentrating in particular on two areas: universality of density fluctuations and the dynamical coupling between radial turbulent-driven fluxes and parallel flows.Plasma fluctuations in the edge of the TCV tokamak have been found to exhibit statistical properties which are universal across a broad range of discharge conditions. Analysis of the time series of density fluctuations in the entire scrape-off layer (SOL) region from just inside the magnetic separatrix to the plasma-wall interface, yields a probability distribution function (PDF) of density which conforms closely to a Gamma distribution. In the wall vicinity, the density fluctuations exhibit clear evidence of self-similarity and are characterised by a PDF with universal shape and with a standard deviation proportional to the mean density. It is also found that radial particle-flux fluctuations scale solely with the mean density. Such findings indicate that it may be possible to improve the prediction of transport in the critical plasma-wall interaction region of future large-scale tokamaks.Recent experiments on JET [C. Hidalgo et al.: Phys. Rev. Lett. 91 (2003) 065001] have investigated a possible link between turbulent transport and the parallel flows. Similar experiments have been performed on TCV for a variety of plasma conditions and flow magnitudes. Although correlations have been found as seen on JET, especially in the wall vicinity, it appears that the magnitude of the coupling is insufficient to drive any significant flow.Presented at the Workshop Electric Fields Structures and Relaxation in Edge Plasmas, Nice, France, October 26–27, 2004. 相似文献