Principal component analysis calibration method for dual-luminophore oxygen and temperature sensor films: application to luminescence imaging

Oxygen sensor films are frequently used to image air-pressure distributions on surfaces in aerodynamic wind tunnels. In this application, the sensor film is referred to as a pressure-sensitive paint (PSP). A Stern-Volmer calibration is used to relate the emission intensity ratio of a long-lifetime luminescent dye (the pressure-sensitive luminophore, PSL) to surface air pressure. A major problem in PSP measurements arises because the Stern-Volmer calibration of the PSL's emission varies with temperature. To correct for the temperature dependence, a second luminescent dye that has an emission that varies with temperature (the temperature-sensitive luminophore, TSL) is incorporated into the sensor film. With such a dual-luminophore PSP (DL-PSP), it is possible to measure the surface-temperature distribution with the TSL emission, and this information is then used to correct the temperature dependence of the PSL's pressure response. In the present article, we report the application of a DL-PSP to obtain high-resolution air-pressure distributions on a surface that is subjected to a 20 degrees C temperature gradient. Two different calibration methods are used to generate surface-temperature and air-pressure distributions from the luminescence imaging data, and a quantitative comparison of the results obtained from the two methods is provided. The first method is based on an intensity-ratio calibration that uses luminescence images collected at two wavelengths, one corresponding to the TSL emission and the second corresponding to the PSL emission. The second method is based on principal component analysis (PCA) of luminescence images obtained at four wavelengths throughout the spectral region of the TSL and PSL emission (hyperspectral imaging, 550-750 nm). The results demonstrate that the PCA method allows the measurement of surface air pressure with higher accuracy and precision compared to those of the intensity-ratio method. The improvement is especially significant at pressures near 1 atm, where the temperature interference is most pronounced. Surface-pressure distributions are measured with comparable accuracy and precision with the two methods.     

Carba-acyclonucleoside antiherpetic agents

Ganciclovir 2 and 2′-carba-ganciclovir 5a are anti-viral agents differing structurally only in the replacement of an oxygen by a methylene group and yet expressing their biological properties along mechanistically independent pathways. Methoxy, hydroxy and fluoro derivatives of 2′-carba-ganciclovir were prepared to examine the effect of re-introducing a binding site close to that in the original oxa side chain. The cyclic phosphate of carba-ganciclovir was also prepared.     

A facile one-pot synthesis of acyclic β-enamino ketones, an important class of versatile synthetic intermediates

A one-pot sequential process consisting of nucleophilic substitution of the lithiated acetylides with Weinreb amides followed by a Michael reaction of the extruded N-methoxy-N-methylamine after quenching with saturated NH₄Cl, provided β-enamino ketones in high yield and in a single geometrical isomeric form. It has been demonstrated that this method is applicable to a wide variety of such amides and to different acetylides.     

Theory and numerical evaluation of oddoids and evenoids: Oscillatory cuspoid integrals with odd and even polynomial phase functions

The properties of oscillating cuspoid integrals whose phase functions are odd and even polynomials are investigated. These integrals are called oddoids and evenoids, respectively (and collectively, oddenoids). We have studied in detail oddenoids whose phase functions contain up to three real parameters. For each oddenoid, we have obtained its Maclaurin series representation and investigated its relation to Airy–Hardy integrals and Bessel functions of fractional orders. We have used techniques from singularity theory to characterise the caustic (or bifurcation set) associated with each oddenoid, including the occurrence of complex whiskers. Plots and short tables of numerical values for the oddenoids are presented. The numerical calculations used the software package CUSPINT [N.P. Kirk, J.N.L. Connor, C.A. Hobbs, An adaptive contour code for the numerical evaluation of the oscillatory cuspoid canonical integrals and their derivatives, Comput. Phys. Commun. 132 (2000) 142–165].     

Gun tunnel flow calibration: defining input conditions for hypersonic flow computations

The procedures used to calibrate a hypersonic gun tunnel nozzle flow are described. The values obtained using these methods are then used as input conditions for computations of hypersonic flow over a long slender test body. Only by completely specifying the flow field, including the effects of nozzle flow angularity, can the best agreement between experiment and computations be achieved. Received 18 February 2000 / Accepted 7 July 2000