A secretory phospholipase A2-mediated neuroprotection and anti-apoptosis

Background  

Phospholipase A₂ liberates free fatty acids and lysophospholipids upon hydrolysis of phospholipids and these products are often associated with detrimental effects such as inflammation and cerebral ischemia. The neuroprotective effect of neutral phospholipase from snake venom has been investigated.     

Quantum ergodicity and the wigner distribution

A quantum ergodic analysis is developed based on comparison of Wigner phase-space densities of quantum eigenstates to classical densities. The technique is applied to the two-dimensional Henon-Heiles system. Analysis of quantum densities as a function of energy is found to clearly display the regular to ergodic transition.     

Onset of buckling in drying droplets of colloidal suspensions

Minute concentrations of suspended particles can dramatically alter the behavior of a drying droplet. After a period of isotropic shrinkage, similar to droplets of a pure liquid, these droplets suddenly buckle like an elastic shell. While linear elasticity is able to describe the morphology of the buckled droplets, it fails to predict the onset of buckling. Instead, we find that buckling is coincident with a stress-induced fluid to solid transition in a shell of particles at a droplet's surface, occurring when attractive capillary forces overcome stabilizing electrostatic forces between particles.     

The microwave-assisted Dötz benzannulation process

Chromium carbene-mediated D?tz benzannulation has been shown to proceed remarkably rapidly and with enhanced efficiency under developed microwave-assisted conditions.     

Second order theory of excitations in trapped bose condensates at finite temperatures

We present a finite temperature field theory for collective excitations of trapped Bose condensates which includes the dynamics of the thermal cloud. In spherical traps we show that excitations couple strongly to a small number of modes, giving resonance structure in their frequency spectra. Where possible, we derive energy shifts and lifetimes of excitations. For the l = 0 mode we show that the simple picture of a decay rate fails, which should be observable in suitable experiments. It also suggests a possible explanation for the anomalous behavior of the m = 0 mode observed in anisotropic traps.     

Quantitative gas sensing by backscatter-absorption measurements of a pseudorandom code modulated lambda ~ 8-microm quantum cascade laser

We have demonstrated quantitative chemical vapor detection with a multimode quantum cascade (QC) laser. Experiments incorporated pseudorandom code (PRC) modulation of the laser intensity to permit sensitive absorption measurements of isopropanol vapor at 8.0micro . The demonstration shows the practicality of one technical approach for implementing low-peak-power QC lasers in the transmitter portion of a differential absorption lidar (DIAL) system. With a 31-chip, 300-ns/chip PRC sequence, the measured isopropanol detection limit was 12 parts in 10(6) by volume times meters (~3x10(-3) absorption) for a simple backscatter-absorption measurement configuration.     

High-power, continuous-wave, current-tunable, single-mode quantum-cascade distributed-feedback lasers at lambda - 5.2 and lambda - 7.95 mum

Quantum-cascade distributed-feedback lasers with high-power, continuous-wave (cw), tunable, single-mode emission are reported. The emission wavelengths are near 5.2 and 7.95 mum. The lasers are operated at liquid-nitrogen temperature and above. A maximum output power of >100 mW is obtained per facet at 80 K for both wavelengths, which is the result of careful positioning of the peak gain with respect to the Bragg wavelength. Continuous tuning with either heat-sink temperature or cw current is demonstrated. The tuning coefficients are 0.35 nm/K (5.2 mum) and 0.51 nm/K(7.95 mum) for thermal tuning and vary from 20 to 40 nm/A for tuning with current. The lasers are being used in high-resolution and high-sensitivity gas-sensing applications.     

Cavity ringdown spectroscopy using mid-infrared quantum-cascade lasers

Cavity ringdown spectra of ammonia at 10 parts in 10(9) by volume (ppbv) and higher concentrations were recorded by use of a 16-mW continuous-wave quantum-casacde distributed-feedback laser at 8.5 mum whose wavelength was continuously temperature tuned over 15 nm. A sensitivity (noise-equivalent absorbance) of 3.4x10(-9) cm(-1) Hz(-1/2) was achieved for ammonia in nitrogen at standard temperature and pressure, which corresponds to a detection limit of 0.25 ppbv.     

Reactions of substituted phenacyl bromides with various bases. o- and p-nitrophenacyl bromide. I

The products obtained from the reaction of o- and p-nitrophenacyl bromide with various bases is described.     

Model theory via set theory

We develop a technique for applying models of set theory to obtain results in the model theory of infinitary languages. Some results on Δ-logics are also discussed.