Enamines of 1,3-dimethylbarbiturates and their symmetrical palladium(II) complexes: synthesis,characterization and biological activity

Transition Metal Chemistry - Three 1,3-dimethylbarbiturate-enamine derivatives and their symmetrical palladium(II) complexes were prepared and characterized by spectroscopic methods. In addition,...     

Bayesian demand updating in the lost sales newsvendor problem: A two-moment approximation

We consider Bayesian updating of demand in a lost sales newsvendor model with censored observations. In a lost sales environment, where the arrival process is not recorded, the exact demand is not observed if it exceeds the beginning stock level, resulting in censored observations. Adopting a Bayesian approach for updating the demand distribution, we develop expressions for the exact posteriors starting with conjugate priors, for negative binomial, gamma, Poisson and normal distributions. Having shown that non-informative priors result in degenerate predictive densities except for negative binomial demand, we propose an approximation within the conjugate family by matching the first two moments of the posterior distribution. The conjugacy property of the priors also ensure analytical tractability and ease of computation in successive updates. In our numerical study, we show that the posteriors and the predictive demand distributions obtained exactly and with the approximation are very close to each other, and that the approximation works very well from both probabilistic and operational perspectives in a sequential updating setting as well.     

Phase-sensitive specular neutron reflectometry for imaging the nanometer scale composition depth profile of thin-film materials

Neutron reflectometry is a powerful method for probing the molecular scale structure of both hard and soft condensed matter films. Moreover, the phase-sensitive methods which have been developed make it possible for specular neutron reflectometry to be effectively employed as an imaging device of the composition depth profile of thin film materials with a spatial resolution approaching a fraction of a nanometer. The image of the cross-sectional distribution of matter in the film obtained in such a way can be shown to be, in most cases, unambiguous to a degree limited primarily by the range and statistical uncertainty of the reflectivity data available. The application of phase-sensitive neutron reflectometry (PSNR) to the study of several types of soft matter thin film systems are illustrated by a number of specific examples from recent studies. In addition, new software tools available to the researcher to apply PSNR methods and analysis are discussed.     

Carbon Nano-Flakes Produced by an Inductively Coupled Thermal Plasma System for Catalyst Applications

Carbon material was produced using an inductively coupled thermal plasma torch system of 35 kW and a conical shape reactor. The carbon nanopowders were obtained by plasma decomposition of methane at various flow rates and show a uniform microstructure throughout the reactor. The product has a crystalline graphitic structure, with a stacking of between 6 and 16 planes and a nano-flake morphology with particles dimensions of approximately 100 nm long, 50 nm wide and 5 nm thick. Nitrogen was also introduced in some synthesis experiments along with the methane precursor using flow rates of 0.1 and 0.2 slpm. The resulting product has the same structural properties and the nitrogen is incorporated into the graphitic structure through pyridinic type bonds.     

Intense geodesic acousticlike modes driven by suprathermal ions in a tokamak plasma

Intense axisymmetric oscillations driven by suprathermal ions injected in the direction counter to the toroidal plasma current are observed in the DIII-D tokamak. The modes appear at nearly half the ideal geodesic acoustic mode frequency, in plasmas with comparable electron and ion temperatures and elevated magnetic safety factor (q_{min}>or=2). Strong bursting and frequency chirping are observed, concomitant with large (10%-15%) drops in the neutron emission. Large electron density fluctuations (n[over ]_{e}/n_{e} approximately 1.5%) are observed with no detectable electron temperature fluctuations, confirming a dominant compressional contribution to the pressure perturbation as predicted by kinetic theory. The observed mode frequency is consistent with a recent theoretical prediction for the energetic-particle-driven geodesic acoustic mode.     

Biodistribution of GdCl3 and Gd-DTPA and their influence on proton magnetic relaxation in rat tissues

The biodistribution and relative molar effectiveness of the ionic (GdCl3) and chelated (Gd-DTPA) forms of gadolinium (Gd) to enhance proton relaxation rates in rat kidney, liver and spleen were evaluated. Rats were given intravenous injections of either GdCl3 (100 mumol/kg) or Gd-DTPA (178 mumol/kg). Gd-DTPA was primarily contained in the vascular compartment and was quickly accumulated in the kidney after injection with a relaxivity of 4.3 sec-1 (mumol/g kidney)-1. It was eliminated quickly from the body with only 2% of the injected dose remaining after 120 min. After GdCl3 injection, Gd was found primarily in liver and spleen. It accumulated continuously reaching 72% of the injected does in these two tissues after 120 min. Despite this continuous increase in tissue Gd concentration, the relaxation rates showed saturation in liver and spleen. The results suggest that after GdCl3 was injected it distributed either in a protein bound form that was effective at causing relaxation or in a colloid form that was not effective. The biodistribution of GdCl3 was such that it was determined by the phagocytic action of the recticuloendothelial system on a colloid. The biodistribution and tissue relaxivity of Gd-DTPA suggest it will be a useful vascular MRI contrast agent. However, the usefulness of GdCl3 as an MRI contrast agent is limited not only by its acute toxicity but also by its saturable effect on tissue relaxation rates. Consequently, GdCl3 has only a modest influence on tissue relaxivity.     

Supplier diversification under binomial yield

We consider supplier diversification in an EOQ type inventory setting with multiple suppliers and binomial yields. We characterize the optimal policy for the model and show that, in this case, it does not pay to diversify, in contrast to previous results in the random yield literature.