Simultaneous quantification of reduced and oxidized glutathione in plasma using a two-dimensional chromatographic system with parallel porous graphitized carbon columns coupled with fluorescence and coulometric electrochemical detection

A method for the simultaneous quantification of reduced and oxidized glutathione in human plasma employing a two-dimensional chromatographic system with parallel porous graphitized carbon (PGC) columns coupled with fluorescence (FLD) and coulometric electrochemical detection (ED) has been developed. Post-sampling oxidation of reduced glutathione (GSH) was prevented by derivatizing the -SH group with monobromobimane (MBB) and the glutathione-bimane adduct (GSMB) was detected by FLD. Oxidized glutathione (GSSG) was detected by ED optimized to give lowest possible limits of detection (LOD). The method is fully validated and is currently used for determination of GSH, GSSG and its redox potential in different clinical studies.     

A revisit to the bending problem of a thin elliptic aelotropic plate with simply supported edge and uniform lateral load

The complex solution method of Okubo for the deflection of a thin circular aelotropic plate with simply supported edge and uniform lateral load was extended to an elliptic plate by Ohasi. In his work however several inconsistencies appear, of which at least one disqualifies a central part. From a revisit to the works of Okubo and Ohasi a new solution for the deflection of a thin elliptic aelotropic plate with simply supported edge and uniform lateral load emerged. The solution is a generalisation of Okubo’s solution and is valid for any angle between material and geometric principal axes. Previously known solutions, including those for circular plates, are reproduced as special cases of the new solution and results of numerical calculations in new situations appear reasonable.     

GELATION KINETICS OF POLYMERS CONFINED IN WATER/ OIL-SATURATED POROUS MATERIALS PROBED BY NMR

Abstract

The gelation of polyvinylalcohol with glutaraldehyde confined in a water/ oil (= 3/1 in volume ratio) saturated sandstone (Bentheimer) was characterized by H NMR spin-lattice relaxation rate (1/ T)measurements and Pulse Field Gradient (PFG) NMR diffusion measurements. The gelation rate was found to be (12.8 ± 1.3) 10^?1 5^?1 at 340 K, which is approximately an order of magnitude faster than in bulk solution. In comparison, the gelation rate within the same porous material containing no oil phase was even faster, by a factor of 2.     

In Situ Studies on Reaction Mechanisms in Atomic Layer Deposition

During the past decade, atomic layer deposition (ALD) has become an important thin-film deposition method in microelectronics industry, and it has also gained a lot of interest in many other areas, such as nanotechnology. The success of ALD is built on proper surface reactions. In this paper, in situ reaction mechanism studies on ALD processes are reviewed with the aim of building a general understanding on similarities and differences exhibited by various processes and process groups. Also, levels of understanding reaction mechanisms in ALD are discussed. The main methods used to study ALD chemistry in situ under typical process conditions are quadrupole mass spectrometry (QMS), quartz crystal microbalance (QCM), and infrared (IR) spectrometry. These are presented in detail in the review. Various other optical methods, ellipsometry in particular, have been used to study ALD processes too, but they provide little information about the reaction mechanisms. Competent in situ investigations solve the ALD reaction mechanism as balanced equations for the ALD half-reactions. The majority of ALD processes are exploiting ligand exchange reactions, where the ligands of the metal precursor are eliminated by bonding to the Lewis acids of the nonmetal precursors, most commonly hydrogen. These volatile byproducts are usually released during both precursor pulses, and determining their relative amounts is the important task in reaction mechanism studies of such processes. These processes are mechanistically fairly well understood, though some of these also display side-reactions to the ligand exchange reactions. There are also whole groups of processes that are using chemistry almost entirely different from the ligand exchange reactions. The most important such processes involve combustion chemistry, with oxygen, oxygen plasma, or ozone as a precursor or co-reactant. The mechanisms of these processes are complicated and less understood compared with the mechanisms of the ligand exchange reaction processes.     

Parallel systems under two sequential attacks with contest intensity variation

Single and double attacks against a system of parallel elements are analyzed. The vulnerability of each element depends on an attacker-defender contest success function. The contest intensity may change from the first to the second attack as determined by a contest intensity variation factor. The defender allocates its resource between deploying elements to provide redundancy, and protecting each element. The attacker allocates its resource optimally across the two attacks, may attack a subset of the elements in the first attack, observes which elements are destroyed in the first attack, and attacks all surviving elements in the second attack. A minmax two period game is analyzed where the defender moves first and the attacker moves second. The paper shows how the contest intensity variation factor affects the defense and attack strategies.     

Numerical Simulation with an Extinction Database for Use with the Eddy Dissipation Concept for Turbulent Combustion

A Local Extinction approach for treating chemical reaction kinetics within the Eddy Dissipation Concept (EDC) has been examined. It applies a database of pre-calculated chemical time scales, which contains the influence of chemical kinetics that is otherwise time-consuming to calculate. The approach was evaluated against experimental data for two piloted diffusion flames (Sandia/TNF Flame D and Flame E) and a piloted lean-premixed jet burner (PPJB). Results were also compared to the EDC with Fast Chemistry and with full Detailed Chemistry (GRI-Mech 3.0). All validation simulations were carried out using a standard k???ε turbulence model and the open-source CFD-toolbox OpenFOAM. The Local Extinction approach showed significantly better results than the Fast Chemistry approach while having a comparably small computational cost. For Flame D and the PPJB, the reactions along centerline and in the mixing layer near the nozzle, the reactions were reduced. For Flame E, the Local Extinciton model predicted some lift off of the flame. The Detailed Chemistry approach gave the best predictions compared to the experimental data, however the calculation effort was orders of magnitude higher.     

Analytic analysis of irregular discrete universes

In this work we investigate the dynamics of cosmological models with spherical topology containing up to 600 Schwarzschild black holes arranged in an irregular manner. We solve the field equations by tessellating the 3-sphere into eight identical cells, each having a single edge which is shared by all cells. The shared edge is enforced to be locally rotationally symmetric, thereby allowing for solving the dynamics to high accuracy along this edge. Each cell will then carry an identical (up to parity) configuration which can however have an arbitrarily random distribution. The dynamics of such models is compared to that of previous works on regularly distributed black holes as well as with the standard isotropic dust models of the FLRW type. The irregular models are shown to have richer dynamics than that of the regular models. The randomization of the distribution of the black holes is done both without bias and also with a certain clustering bias. The geometry of the initial configuration of our models is shown to be qualitatively different from the regular case in the way it approaches the isotropic model.