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.     

Multifrequency EPR of four triarylmethyl radicals

Continuous-wave spectra at W-band of four triarylmethyl (trityl) radicals at 100 K in 1∶1 water-glycerol exhibit rhombic electron paramagnetic resonance spectra. The rigid-lattice line widths at W-band are only 3 to 5 times larger than at X-band or S-band, and fluid-solution line widths are much narrower than those for rigid lattice, which indicates that unresolved anisotropic nuclear hyperfine couplings make significant contributions to the rigid-lattice line widths. Spin-flip lines are observed in glassy-solution spectra at X-band and S-band, but not at W-band or 250 MHz. At 100 KT _m is dominated by spin diffusion of solvent protons and is independent of microwave frequency. Between about 130 and 170 K, 1/T _m for trityl-CH₃ is enhanced by rotation of the methyl groups at a rate comparable to inequivalences in the hyperfine interaction. Motional averaging of anisotropic interactions enhances spin echo dephasing between about 200 and 300 K. The temperature dependence of 1/T ₁ is similar for the four radicals and is consistent with assignment of the Raman process and a local mode as the dominant relaxation processes. The similarity inT ₁ values at W-band and X-band supports this assignment.     

ARACHIDONIC ACID PEROXIDATION, PROSTAGLANDIN SYNTHESIS AND PLATELET FUNCTION

Abstract— The initial oxygenation or peroxidation of arachidonic acid seems to be an essential step for the synthesis of cyclic endoperoxides and prostaglandins. There has been some evidence and considerable interest in the role of superoxide anion, hydroxyl radicals or singlet oxygen as a source of oxygen in the formation of the active species (free radicals). A test capable of detecting active intermediates of lipid peroxidation and useful for studying the role of free radicals has been developed. The test resulted from the discovery that vitamin E markedly enhanced the reduction of nitroblue tetrazolium (NBT) during arachidonic acid peroxidation. Intact platelets, microsomes, sheep vesicular gland enzymes or peroxidases could provide essential enzyme activity. NBT and vitamin E when added to platelet microsomes inhibited the conversion of ¹⁴C arachidonic acid to HETE, HHT and thromboxanes. The combination also inhibited aggregation of platelets stimulated by collagen, thrombin, ADP and epinephrine. Prolonged incubation with these agents at the highest concentrations used in the study caused no change in morphology and had no deleterious effect on platelet levels of adenine nucleotides and serotonin. Results of our preliminary studies suggest that NBT and vitamin E can detect intermediates of lipid peroxidation, inhibit the conversion of arachidonic acid, prevent platelet aggregation and the release reaction without damaging the platelets morphologically or biochemically. As both the agents are scavengers of free radicals and in combination exert synergistic effects, the test system may serve as a probe in various free radical mediated events and may offer some degree of protection against free radical mediated pathological processes.     

The vibrational force field of halogenated aromatic molecules: In-plane vibrations of benzene and fluorobenzenes

The force fields for the in-plane vibrations of benzene and its fluoro derivatives are determined using the overlay technique. Between 36 and 39 parameters were allowed to vary in different fields and in all cases convergence on the experimental frequencies was smooth and rapid. Only one solution could be found. This solution agrees extremely well with the benzene field of Duinker and Mills. The variation of diagonal force constants in an internal valence coordinate basis set with fluorine substitution in the coordinate environment is determined. The variation in certain force constants is considerable. Thus for the CF stretching constant it is 12% for replacement of two hydrogens by two fluorines. Attempts are made to interpret these variations. Various aspects of the force constant problem for benzene are discussed.     

The function of Shp2 tyrosine phosphatase in the dispersal of acetylcholine receptor clusters

Background

Tone languages such as Thai and Mandarin Chinese use differences in fundamental frequency (F₀, pitch) to distinguish lexical meaning. Previous behavioral studies have shown that native speakers of a non-tone language have difficulty discriminating among tone contrasts and are sensitive to different F₀ dimensions than speakers of a tone language. The aim of the present ERP study was to investigate the effect of language background and training on the non-attentive processing of lexical tones. EEG was recorded from 12 adult native speakers of Mandarin Chinese, 12 native speakers of American English, and 11 Thai speakers while they were watching a movie and were presented with multiple tokens of low-falling, mid-level and high-rising Thai lexical tones. High-rising or low-falling tokens were presented as deviants among mid-level standard tokens, and vice versa. EEG data and data from a behavioral discrimination task were collected before and after a two-day perceptual categorization training task.

Results

Behavioral discrimination improved after training in both the Chinese and the English groups. Low-falling tone deviants versus standards elicited a mismatch negativity (MMN) in all language groups. Before, but not after training, the English speakers showed a larger MMN compared to the Chinese, even though English speakers performed worst in the behavioral tasks. The MMN was followed by a late negativity, which became smaller with improved discrimination. The High-rising deviants versus standards elicited a late negativity, which was left-lateralized only in the English and Chinese groups.

Conclusion

Results showed that native speakers of English, Chinese and Thai recruited largely similar mechanisms when non-attentively processing Thai lexical tones. However, native Thai speakers differed from the Chinese and English speakers with respect to the processing of late F₀ contour differences (high-rising versus mid-level tones). In addition, native speakers of a non-tone language (English) were initially more sensitive to F₀ onset differences (low-falling versus mid-level contrast), which was suppressed as a result of training. This result converges with results from previous behavioral studies and supports the view that attentive as well as non-attentive processing of F₀ contrasts is affected by language background, but is malleable even in adult learners.