Spectral intensities in the fundamental bands of HF and HCl

The transition intensities of the fundamental bands of natural isotopic HF and HCl vapors have been measured with Doppler-limited resolution using a tunable difference-frequency laser spectrometer. Precise values for the band intensities, vibrational moments and Herman-Wallis F factors have been obtained for H¹⁹F, H³⁵Cl and H³⁷Cl.     

Untersuchung von Luft und Dampf

Ohne Zusammenfassung     

Measurements of 3D velocity and scalar field for a film-cooled airfoil trailing edge

We present an experimental study of a supersonic nozzle with supersonic iodine injection. This nozzle simulates Chemical Oxygen Iodine Laser (COIL) flow conditions with non-reacting, cold flows. During the experiments, we used a laser sheet near 565 nm to excite fluorescence in iodine, which we imaged with an intensified and gated CCD camera. We captured streamwise and semi-spanwise (oblique-view) images, with fluorescence revealing the material injected into the flow. We identified the flow structures in the images, and produced quantitative characterizations of the flow morphology and of the mixing between the primary and injected flow. We considered four injection scenarios. The first scenario includes a single injector positioned downstream of the nozzle throat. To enhance the mixing between the flows, trip jets are placed in the wake of the single jet. The sonic trip jets, significantly smaller than the primary supersonic iodine jet, are intended to destabilize the counter-rotating vortex pair (CRVP) of the primary jet. We compare three different trip jet configurations for their ability to enhance mixing between the oxygen and iodine flows.     

Synthesis and characterization of poly(2‐ethylhexyl methacrylate) copolymers containing pendant,self‐complementary multiple‐hydrogen‐bonding sites

The synthesis and characterization of copolymers containing 2‐ethylhexyl methacrylate and a quadruple‐hydrogen‐bonding site, 2‐ureido‐4[1H]‐pyrimidone methacrylate (UPyMA), are described. An analogous dimeric hydrogen‐bond‐containing copolymer based on 2‐ethylhexyl methacrylate and methacrylic acid (PEHMA‐co‐MAA) was also synthesized for comparative purposes. The glass‐transition temperatures of the poly(2‐ethylhexyl methacrylate‐co‐2‐ureido‐4[1H]‐pyrimidone methacrylate) (PEHMA‐co‐UPyMA) series increased linearly with increasing UPyMA content. Creep compliance measurements as a function of temperature indicated a decrease in the creep compliance with increasing UPyMA content over the range of 1–10 mol % UPyMA. Melt rheological analysis also showed an increase and lengthening of the plateau modulus as a function of frequency with increasing UPyMA content, as well as increasing complex viscosity as a function of temperature. The analogous PEHMA‐co‐MAA copolymer, which contained 11 mol % methacrylic acid, showed, in the melt rheological analysis, behavior similar to that of the PEHMA‐co‐UPyMA copolymer containing only 1 mol % UPyMA units. The multiple‐hydrogen‐bond‐containing copolymers were successfully analyzed with time–temperature superposition for the construction of master curves. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4618–4631, 2005     

含油岩心显微荧光成像光谱研究

发展了一种显微荧光光谱成像技术,并将其应用于天然岩心进行显微荧光成像光谱研究。利用这种技术同时采集含油岩心表面的荧光光谱信息和空间信息．并对获得的光谱图像给予光谱学和地质学解释。结果表明,不但能显示岩心形貌和组分的大致趋势,而且能揭示其精细细节．为石油地质研究提供了一种新方法,为今后的石油勘探开发工作提供了一种先进的指导手段。     

On Numerical Solution of the Markov Renewal Equation: Tight Upper and Lower Kernel Bounds

We develop tight bounds and a fast parallel algorithm to compute the Markov renewal kernel. Knowledge of the kernel allows us to solve Markov renewal equations numerically to study non-steady state behavior in a finite state Markov renewal process. Computational error and numerical stability for computing the bounds in parallel are discussed using well-known results from numerical analysis. We use our algorithm and computed bounds to study the expected number of departures as a function of time for a two node overflow queueing network.     

Three-dimensional concentration field measurements in a mixing layer using magnetic resonance imaging

Magnetic resonance imaging (MRI) was used to measure the three-dimensional, time-averaged concentration distribution in a turbulent two-stream mixing layer. Test fluids and MRI scanning parameters were chosen to give good signal linearity, and a calibration/normalization procedure was developed to reduce the concentration measurement uncertainty. Plain deionized water mixing with a solution of 0.8% gadopentetate dimeglumine in deionized water were selected as test fluids. The concentration of the marked water was measured on an array of 220,000 0.69 mm³ voxels covering the entire flow apparatus. Planar laser-induced fluorescence experiments were performed on the flow centerplane to provide validation data. The uncertainty of a single voxel measurement was estimated to be less than 12% with the largest source of uncertainty being turbulent dephasing. Averaging two runs in which the marked water was switched between the two streams reduced the uncertainty to only 4%. The complete magnetic resonance concentration (MRC) procedure including the adjustment of scanning parameters, a background run, two reference/calibration runs, and multiple concentration measurement runs can be completed in 2–3 h. This work establishes MRC as a viable technique for studying the mixing in complex turbulent liquid flows.     

Multiple hydrogen bonding for reversible polymer surface adhesion

Specific and reversible adhesion of a terminal thymine-functionalized polystyrene (PS-thymine) was demonstrated for a silicon surface with complementary adenine recognition sites. A novel adenine-containing triethoxysilane (ADPTES), which was suitable for covalent attachment to silanol containing surfaces, was synthesized in one step from adenine and 3-isocyanatopropyl triethoxysilane (IPTES). 1H and 13C NMR spectroscopy and fast atom bombardment mass spectroscopy confirmed the chemical structure, and 29Si NMR spectroscopy indicated the absence of any premature hydrolysis of the alkoxysilane derivative. X-ray photoelectron spectroscopy (XPS) and water contact angle measurements indicated the attachment of PS-thymine to silicon surfaces that were modified with a mixture of ADPTES and 3-mercaptopropyl triethoxysilane (MPTES). PS-thymine attachment to surfaces that were modified with only MPTES was not observed. The exclusive attachment of PS-thymine to an ADPTES/MPTES-modified surface confirmed hydrogen bonding-mediated adenine-thymine association to silicon surfaces containing a sufficiently low concentration of adenine recognition sites. Although PS-thymine attachment to the ADPTES/MPTES-modified surfaces was insensitive to THF rinsing, the PS-thymine was completely removed from the surface upon DMSO rinsing because of the disruption of adenine-thymine hydrogen bonding with a more polar aprotic solvent. PS-thymine was successfully reattached to the ADPTES/MPTES-modified surface following the DMSO rinse, demonstrating the solvato-reversible nature of the adenine-thymine association.     

Long-term evolution in the tropospheric concentration of chlorofluorocarbon 12 (CCl2F2) derived from high-spectral resolution infrared solar absorption spectra: retrieval and comparison with in situ surface measurements

The average tropospheric volume mixing ratios of chlorofluorocarbon 12 (CCl₂F₂) have been retrieved from high-spectral resolution ground-based infrared solar-absorption spectra recorded from March 1982 to October 2003 with the McMath Fourier transform spectrometer at the US National Solar Observatory facility on Kitt Peak in southern Arizona (31.9°N, 111.6°W, 2.09 km altitude). The retrievals are based on fits to the unresolved ν₈ band Q-branches near using the SFIT2 retrieval algorithm. The annual increase rate was equal to (16.88±1.37) parts per trillion (10^-12) by volume at the beginning of the time series, March 1982, or (4.77±0.04)%, 1 sigma, declining progressively to (2.49±1.24) parts per trillion, by volume at the end, October 2003, or (0.46±0.24)%, 1 sigma. Average tropospheric mixing ratios from the solar spectra have been compared with average surface flask and in situ sampling measurements from the Climate Monitoring and Diagnostics Laboratory (CMDL) station at Niwot Ridge, CO, (USA) (40.0°N, 105.5°W, 3013 m altitude). The average ratio and standard deviation of the monthly means of the retrieved tropospheric mixing ratios relative to the CMDL surface mixing ratios is (1.01±0.03) for the overlapping time period. Both datasets demonstrate the progressive impact of the Montreal protocol and its strengthening amendments on the trend of CCl₂F₂, though a tropospheric decrease has yet to be observed.