Synthesis and Scintillation of Single Crystal and Polycrystalline Rare-Earth-Activated Lutetium Aluminum Garnet

Single crystals with composition Lu3Al5O12 were synthesized using Czochralski and micro-pulling-down melt growth techniques. Polycrystalline ceramics of the same composition were synthesized by vacuum annealing of powders prereacted using a citrate-nitrate combustion technique and by spark-plasma-sintering of powders prereacted using a flame-spray-pyrolysis technique. Single crystals and polycrystalline ceramics are activated with Ce3+ or Pr3+ or doubly activated with Ce3+ and Tb3+ ions. Cerium-doped Czochralski-grown single crystals were compared to cerium-terbium codoped Czochralski-grown and micro-pulling down single crystals. Cerium-terbium codoped single crystals are also compared to similarly-activated polycrystalline ceramics sintered under vacuum using combustion-synthesized prereacted powders. X-ray diffraction analysis and fluorescence characterization were used to determine successful formation of single-phase LuAG and successful incorporation of doping species. Absorbance, fluorescence, radioluminescence, and scintillation decay analyses were used to compare synthesis processes and activator selection

Consumption inequality and income uncertainty

This paper places the debate over using consumption or income in studies of inequality growth in a formal intertemporal setting. It highlights the importance of permanent and transitory income uncertainty in the evaluation of growth in consumption inequality. We derive conditions under which the growth of variances and covariances of income and consumption can be used to separately identify the growth in the variance of permanent and transitory income shocks. Household data from Britain for the period 1968-1992 are used to show a strong growth in transitory inequality toward the end of this period, while younger cohorts are shown to face significantly higher levels of permanent inequality

Development of a Dual-Pump CARS System for Measurements in a Supersonic Combusting Free Jet

This work describes the development of a dual-pump CARS system for simultaneous measurements of temperature and absolute mole fraction of N2, O2 and H2 in a laboratory scale supersonic combusting free jet. Changes to the experimental set-up and the data analysis to improve the quality of the measurements in this turbulent, high-temperature reacting flow are described. The accuracy and precision of the instrument have been determined using data collected in a Hencken burner flame. For temperature above 800 K, errors in absolute mole fraction are within 1.5, 0.5, and 1% of the total composition for N2, O2 and H2, respectively. Estimated standard deviations based on 500 single shots are between 10 and 65 K for the temperature, between 0.5 and 1.7% of the total composition for O2, and between 1.5 and 3.4% for N2. The standard deviation of H2 is ~10% of the average measured mole fraction. Results obtained in the jet with and without combustion are illustrated, and the capabilities and limitations of the dual-pump CARS instrument discussed

Price Drops, Fluctuations, and Correlation in a Multi-Agent Model of Stock Markets

In this paper we compare market price fluctuations with the response to fundamental price drops within the Lux-Marchesi model which is able to reproduce the most important stylized facts of real market data. Major differences can be observed between the decay of spontaneous fluctuations and of changes due to external perturbations reflecting the absence of detailed balance, i.e., of the validity of the fluctuation-dissipation theorem. We found that fundamental price drops are followed by an overshoot with a rather robust characteristic time.Comment: 11 pages, 5 figures, 2 tables; submitted to Physica

Multi-Point Interferometric Rayleigh Scattering using Dual-Pass Light Recirculation

This paper describes for the first time an interferometric Rayleigh scattering system using dual-pass light recirculation (IRS-LR) capable of simultaneously measuring at multiple points two orthogonal components of flow velocity in combustion flows using single shot laser probing. An additional optical path containing the interferometer input mirror, a quarter-wave plate, a polarization dependent beam combiner, and a high reflectivity mirror partially recirculates the light that is rejected by the interferometer. Temporally- and spatially-resolved acquisitions of Rayleigh spectra in a large-scale combustion-heated supersonic axi-symmetric jet were performed to demonstrate the technique. Recirculating of Rayleigh scattered light increases the number of photons analyzed by the system up to a factor of 1.8 compared with previous configurations. This is equivalent to performing measurements with less laser energy or performing measurements with the previous system in gas flows at higher temperatures

Spatially and Temporally-Resolved Multi-Parameter Interferometric Rayleigh Scattering

A novel approach to simultaneously measure the translational temperature, bulk velocity, and density in gases by collecting, referencing, and analyzing nanosecond time-scale Rayleigh scattered light from molecules is described. A narrow-band pulsed laser source is used to probe two largely separated measurement locations, one of which is used for reference. The elastically scattered photons containing information from both measurement locations are collected at the same time and analyzed spectrally using a planar Fabry - Perot interferometer. A practical means of referencing the measurement of velocity using the laser frequency, and the density and temperature using the information from the reference measurement location maintained at constant properties is described. To demonstrate the technique single-shot spectra of elastic scattered light are obtained in a near zero velocity H2-air Hencken burner flame and simultaneously in an N2-filled gas cell. A simplified Gaussian distribution model to the scattered light spectra is used to obtain the flame properties. Corrections to this model are applied at lower gas temperatures when the simplified Gaussian approximation is no longer suitable. The near-zero measured velocity as a function of the measured flame temperature, and a comparison of the measured flame density and temperature with the perfect gas law are presented

Beam Shaping for CARS Measurements in Turbulent Environments

This paper describes a new technique to mitigate the effect of beam steering on CARS measurements in turbulent, variable density environments. The new approach combines Planar BOXCARS phase-matching with elliptical shaping of one of the beams to generate a signal insensitive to beam steering, while keeping the same spatial resolution. Numerical and experimental results are provided to demonstrate the effectiveness of this approach. One set of experiments investigated the effect of beam shaping in the presence of a controlled and well quantified displacement of the beams at the focal plane. Another set of experiments, more qualitative, proved the effectiveness of the technique in the presence of severe beam steering due to turbulence

The expression of Na, K-ATPase in the Madin-Darby canine kidney (MDCK) cell line

The efficiency of a number of experimental techniques for the extraction of total RNA from various cells and tissues (including MDCK strain I cells) was assessed, and the optimal conditions for hybridisation of Na,K-ATPase isoform-specific DNA probes to this RNA were determined. The specificity of hybridisation of DNA probes for the Na,K-ATPase al, a2, a3, and beta1 isoforms was assessed using RNA isolated from rat tissues. The relative abundance of isoform mRNA's in rat kidney, brain, lung, and myocardial tissues was determined by Northern blotting. The abundance of Na,K-ATPase isoforms was also determined in the myocardial tissues of the Milan rat, a hypertensive animal model. Significant differences between the abundance of Na,K-ATPase isoform mRNA's in hypertensive rats and their age and sex matched controls were found. The relative abundance (per ng of total RNA) of al, a3, and beta1 mRNA's in left ventricle and, that of a1, and beta1 mRNA's in right ventricle were significantly decreased in hypertensive rats. The relative abundance (per mug of total RNA) of a2 and beta1 mRNA's in atria was significantly increased in hypertensive rats. These differences found in ventricles and atria were further accentuated by expression of the results per gram wet weight of tissue. The results from ventricular tissues were in contrast to those previously reported by Herrera et al. (1988) who found either increases or no change in the abundance of a1 and beta1 mRNA's in hypertensive rat aorta, skeletal muscle and left ventricle. The differences between these results may be related to the deoxy-corticosterone treatment and high salt diet of the hypertensive rat model used by Herrera et al. (1988). Na,K-ATPase isoform-specific DNA restriction endonuclease fragments were used to investigate the expression of the isoform mRNA's in MDCK strain I cells. Only a1 and beta1 mRNA's was detected on Northern blots, with no detectable a2 or a3 isoform mRNA signals being found in this cell line. [3H]-ouabain binding to cells was used, as an estimate of the cell surface expression of Na,K-ATPase. Possible factors affecting the expression of Na,K-ATPase during the normal cell growth of MDCK strain I cells were investigated. Factors such as cell seeding density, cell growth substrate and the volume of growth medium used, were all found to affect both the level and pattern of expression of Na,K-ATPase during the normal cell growth or culturing cycle. After 2 days of culture the large increases in the expression of Na,K-ATPase assayed in low density compared to high density seeded cells, were not correlated with concomitant changes in the relative abundance of Na,K-ATPase a subunit mRNA. These results indicate that the large changes in cell surface expression of Na,K- ATPase found during cell growth are probably controlled by post transcriptional processes. The effect of certain hormones or their agonists (aldosterone, deoxy-corticosterone, corticosterone, dexamethasone, and tri-iodo thyronine), on the expression of Na,K-ATPase in MDCK strain I cells was also briefly investigated. Under the conditions used, hormone treatment was not found to induce any measurable expression of a2 or a3 mRNA's. The mineralocorticoid aldosterone, and the glucocorticoid corticosterone, both produced small but significant increases in the level of Na,K-ATPase present on the cell membrane, however these increases were not correlated with similar increases in the abundance of both Na,K-ATPase a1 and beta1 mRNA's. The small size of increases in Na,K-ATPase enzyme abundance after hormone treatments and the inability of those treatments to induce consistent increases in Na,K-ATPase mRNA's further suggests that changes in the cell surface expression of Na,K-ATPase in MDCK cells is the result of regulation at a post transcriptional level

Spatially-and Temporally-Resolved Multi-Parameter Interferometric Rayleigh Scattering System and Method

A system that simultaneously measures the translational temperature, bulk velocity, and density in gases by collecting, referencing, and analyzing nanosecond time-scale Rayleigh scattered light from molecules is described. A narrow-band pulsed laser source is used to probe two largely separated measurement locations, one of which is used for reference. The elastically scattered photons containing information from both measurement locations are collected at the same time and analyzed spectrally using a planar Fabry-Perot interferometer. A practical means of referencing the measurement of velocity using the laser frequency, and the density and temperature using the information from the reference measurement location maintained at constant properties is provided