Flight testing of a luminescent surface pressure sensor

NASA ARC has conducted flight tests of a new type of aerodynamic pressure sensor based on a luminescent surface coating. Flights were conducted at the NASA ARC-Dryden Flight Research Facility. The luminescent pressure sensor is based on a surface coating which, when illuminated with ultraviolet light, emits visible light with an intensity dependent on the local air pressure on the surface. This technique makes it possible to obtain pressure data over the entire surface of an aircraft, as opposed to conventional instrumentation, which can only make measurements at pre-selected points. The objective of the flight tests was to evaluate the effectiveness and practicality of a luminescent pressure sensor in the actual flight environment. A luminescent pressure sensor was installed on a fin, the Flight Test Fixture (FTF), that is attached to the underside of an F-104 aircraft. The response of one particular surface coating was evaluated at low supersonic Mach numbers (M = 1.0-1.6) in order to provide an initial estimate of the sensor's capabilities. This memo describes the test approach, the techniques used, and the pressure sensor's behavior under flight conditions. A direct comparison between data provided by the luminescent pressure sensor and that produced by conventional pressure instrumentation shows that the luminescent sensor can provide quantitative data under flight conditions. However, the test results also show that the sensor has a number of limitations which must be addressed if this technique is to prove useful in the flight environment

Singlet oxygen quantum yields from halogenated chlorins: potential new photodynamic therapy agents

Flash photolysis and photoacoustic calorimetry were used to measure the energy-transfer rates and singlet oxygen quantum yields originated by the triplet states of halogenated tetrakisphenylporphyrins and related chlorins in aerated toluene. The chlorins ([lambda]max[approximate]660 nm, [var epsilon][approximate]3×104 M-1 cm-1) have long-lived triplet states (>12 [mu]s) in the absence of molecular oxygen, and in its presence the singlet oxygen production quantum yields of the 2-chloro and 2,6-dichlorophenyl derivatives are 0.89±0.05 and 0.98±0.02, respectively. The high absorptivity in the red, the photostability and the efficiency of these chlorins in producing singlet oxygen suggests a ground for the development of better sensitisers for photodynamic therapy.http://www.sciencedirect.com/science/article/B6TGY-41YG70D-7/1/de6fc7896eaf9c58239551fa798e3e7

Self-Aggregation of Lipophilic Porphyrins in Reverse Micelles of Aerosol OT

The aggregation process of meso-tetra(4-aminosulfonylphenyl)porphyrin (PC0), of butyl and dodecyl derivatives (PC4 and PC12, respectively) in the presence of aerosol-OT (AOT) reversed micelles with different values of ω0 = [water]/[AOT] was investigated using steady-state extinction, fluorescence, and resonance light scattering (RLS) techniques. The scattering has been accounted for and the absorption spectra corrected from the extinction spectra. In homogeneous solutions, the porphyrins exist as a monomer showing the Soret band around 420 nm and emission bands at 650 and 716 nm. In reverse micelles, the spectra vary according to the chain length and the amount of solubilized water. Only PC12 is dissolved as a monomer at ω0 = 0, and PC4 shows some degree of aggregation. PC0 is present largely as an aggregate. At ω0 ≠ 0, a complete aggregation is observed for PC4 and PC12, whereas in PC0, some degree of disaggregation was detected. The extinction spectra of PC0 and PC4 in aggregate forms show a broad and red shifted Soret band indicating J aggregates. By contrast, the Soret band intensity of PC12 decreases and a new band around 376 nm appears with a broadening of the monomer Soret band which reflects H aggregates. RLS shows a strong signal for PC12 at red spectral region at high ω0 indicating J aggregate types. The fluorescence spectra showed the new band around 670 nm for PC0 and PC12, whereas in PC4, only blue shifted bands were observed with ω0 increase. The global fluorescence quantum yield of the PC12 aggregates is lower than the respective monomer. The aggregate sizes were followed by RLS measurements which showed an increase of intensity at around 440 nm. The aggregation dynamics is dependent on both the porphyrin concentration and ω0