Neutral oxygen atom density in the MESOX air plasma solar furnace facility

The density of neutral oxygen atoms in the MESOX set-up, one device of the PROMES-CNRS solar facilities, was determined by a fiber-optics catalytic probe (FOCP). Plasma was created in a flowing air within a quartz tube with the outer diameter of 5 cm by a 2.45 GHz microwave generator with the output power up to 1000 W. The flow of air was varied between 4 and 20 l/h. The O-atom density was found to increase monotonously with the increasing discharge power, and it decreased with the increasing flow rate. The degree of dissociation of oxygen molecules in the plasma column depended largely on the flow rate. At the air flow of 4 l/h it was about 80% but it decreased to about 20% at the flow of 20 l/h.     

Chain and Ring Phosphorus Compounds—Analogies between Phosphorus and Carbon Chemistry

Up to about 15 years ago compounds with a skeleton of phosphorus chains or rings were regarded as “exotic” in the field of nonmetal chemistry. Aside from a number of examples of molecules with two P atoms directly bonded to each other and a few sporadically discovered monocyclic ring compounds, only solids of undefined composition and structure were known. Since then the state of our knowledge in this sector has made considerable progress: between PH₃ and its derivatives on the one hand, and the high-molecular modifications of elementary phosphorus on the other, an unexpected variety of well defined compounds have been discovered, showing many similarities to the analogous compounds of carbon. However, surprises can still occur even with “small” phosphorus-containing molecules, as shown by the likewise recently discovered field of phosphorus three-membered ring compounds.     

Novel binding of beryllium to dicarboxyimidazole-based model compounds and polymers

The ligand 4,5-dicarboxyimidazole (H(2)DCI) and its methyl derivative 1-methyl-4,5-dicarboxyimidazole (H(2)MDCI) have been shown to bind to Be(II) forming a zwitterionic species that has been structurally characterized. A new dicarboxyimidazole-based polymer has been prepared and its Be-binding properties have been studied using NMR ((1)H and (9)Be) and fluorescence spectroscopy; it represents a rare example of beryllium binding to a polymer. Models of the mononuclear and polymeric Be(II)-binding sites have been studied using density functional theory (DFT), and the (9)Be NMR chemical shifts of these model materials have been calculated for the purpose of direct comparison to experimentally observed values. Differences in the binding modes of the mononuclear and polymeric species are discussed.     

Crystal structure and spectroscopic characterization of K8(VO)2O(SO4)6

Red and yellow dichroistic crystals of a vanadium(V) compound, potassium (mu-oxo, di-mu-sulfato)bis(oxodisulfatovanadate), K(8)(VO)(2)O(SO(4))(6), have been obtained from the ternary catalytic model melt system K(2)S(2)O(7)[bond]K(2)SO(4)[bond]V(2)O(5). By slow cooling of the melt from 420 to 355 degrees C, crystal growth occurred, using solid V(2)O(5) crystals present in the melt as nucleation promoter. The compound crystallizes in the monoclinic space group P2(l) with a = 13.60(9) A, b = 13.93(9) A, c = 14.05(9) A, beta = 90.286(10) degrees, and Z = 2. It contains two VO(6) octahedra linked together by a mu-oxo and two mu-sulfato bridges. Furthermore, each octahedron has two monodentate sulfate ligands, making the dimeric entity coordinatively saturated. IR spectroscopy shows bands arising from V[bond]O[bond]V and V[double bond]O stretches as well as splitting of sulfate bands due to the different degrees of freedom present for different conformations of sulfate ligands. The coordination of vanadium in K(8)(VO)(2)O(SO(4))(6) is discussed in relation to the reaction mechanism of SO(2) oxidation catalysis.     

Computerized, comprehensive databases of cellular and secreted proteins from normal human embryonic lung MRC-5 fibroblasts: identification of transformation and/or proliferation sensitive proteins

Databases of protein information from human embryonal lung fibroblasts (MRC-5) have been established using computer analyzed two-dimensional gel electrophoresis. One thousand four hundred and eighty-two cellular proteins (1060 with isoelectric focusing and 422 with nonequilibrium pH gradient electrophoresis, in the first dimension) ranging in molecular mass between 8 and 234 kDa were separated and numbered. Information entered in the database (in most cases for major proteins) includes: protein name, HeLa protein catalog number, mouse protein catalog number, proteins matched in transformed human epithelial amnion cells (AMA) and peripheral blood mononuclear cells (PBMC), transformation and/or proliferation sensitive proteins, synthesis in quiescent cells, cell cycle regulated proteins, mitochondrial and heat shock proteins, cytoskeletal proteins and proteins whose synthesis is affected by interferons. Additional information entered for a few transformation-sensitive proteins that have been selected for future studies includes levels of synthesis and amounts in fetal human tissues. A total of four hundred and seventy-six [35S]methionine labeled polypeptides (258 isoelectric focusing; 218, nonequilibrium pH gradient electrophoresis) secreted by MRC-5 fibroblasts were separated and recorded (J. E. Celis et al., Leukemia 1987, 1, 707-717). Information entered in this database includes molecular weight and transformation sensitive proteins. These databases, as well as those of epithelial and lymphoid cell proteins (J. E. Celis et al., Leukemia 1988, 9, 561-601), represent the initial stages of a systematic effort to establish comprehensive databases of human protein information. In the long run, these databases are expected to offer a useful framework in which to focus the human genome sequencing effort.     

Surface tension of quantum fluids from molecular simulations

We present the first molecular simulations of the vapor-liquid surface tension of quantum liquids. The path integral formalism of Feynman was used to account for the quantum mechanical behavior of both the liquid and the vapor. A replica-data parallel algorithm was implemented to achieve good parallel performance of the simulation code on at least 32 processors. We have computed the surface tension and the vapor-liquid phase diagram of pure hydrogen over the temperature range 18-30 K and pure deuterium from 19 to 34 K. The simulation results for surface tension and vapor-liquid orthobaric densities are in very good agreement with experimental data. We have computed the interfacial properties of hydrogen-deuterium mixtures over the entire concentration range at 20.4 and 24 K. The calculated equilibrium compositions of the mixtures are in excellent agreement with experimental data. The computed mixture surface tension shows negative deviations from ideal solution behavior, in agreement with experimental data and predictions from Prigogine's theory. The magnitude of the deviations at 20.4 K are substantially larger from simulations and from theory than from experiments. We conclude that the experimentally measured mixture surface tension values are systematically too high. Analysis of the concentration profiles in the interfacial region shows that the nonideal behavior can be described entirely by segregation of H(2) to the interface, indicating that H(2) acts as a surfactant in H(2)-D(2) mixtures.     

Physicochemical Investigations on the Interaction of Surfactants and Salts with Polyvinylpyrrolidone in Aqueous Medium

Microcalorimetric investigations have been carried out onthe interaction of the surfactants sodium cholate, sodium deoxycholate, tetradecyltrimethylammonium bromide, cetyl(hexadecyl)trimethylammonium bromide, and p-tert-octylphenoxy polyoxy-ethylene ether (Triton X-100) and the salts potassium iodide, sodium benzoate, sodium bromide, and sodium salicylate with the neutral polymer polyvinylpyrrolidone (PVP). The enthalpy of dilution of the surfactants has been measured in the absence and presence of the polymer and the results are compared to determine the effect of PVP on the micellization of the surfactants and the energetics of the process. As well, the micellization activity of the surfactants in the presence of the polymer has been studied by conductometric and fluorimetric methods. The enthalpy of dilution of the salts has been measured to provide an understanding of the nature and magnitude of their interaction with PVP. Copyright 2001 Academic Press.     

Electrocatalytic oxidation of ascorbic acid and voltammetric determination with a ferrocene-modified platinum electrode

Ferrocene attached to the surface of a platinum electrode catalyses the electrochemical oxidation of ascorbic acid in acidic buffer solutions. The overpotential for ascorbic acid oxidation is decreased by 150 mV at pH 2.2 compared with reaction at bare platinum; and an increase in anodic current and decrease in cathodic current for the redox reaction of ferrocene occurs on addition of ascorbic acid to the solution. The ferrocene-modified electrode is useful for the voltammetric determination of ascorbic acid in natural fruit juices. The advantages result from the electrocatalytic effect and from the prevention of adsorption of inhibitory substances from solution.