Demonstrator of continuous-detonation air-breathing ramjet: Wind tunnel data

First experimental investigations were carried out into the detonation combustion of hydrogen in a demonstrator of an original-design air-breathing ramjet while blowing with an air flow at Mach 4 to 8 in an impulse wind tunnel, and for the first time under these conditions, continuous spin and longitudinal pulsed modes of detonation combustion of hydrogen in an annular combustor were detected.     

Selective precipitation of rare earth orthophosphates with hydrogen peroxide from phosphoric acid solutions

It has been shown for the first time that the use of hydrogen peroxide allows precipitation of rare earth orthophosphates (La–Tb) from phosphoric acid solutions at temperatures below 100°C. Either anhydrous or hydrated orthophosphates with monazite or rhabdophane structure, respectively, can be obtained depending on rare earth element position in lanthanide series and precipitation conditions (orthophosphoric acid and hydrogen peroxide concentration). Hydrated orthophosphates with rhabdophane structure can be prepared by precipitation with hydrogen peroxide for all studied rare earth elements.     

Aminomethylation of substituted pyrroles and 4,5,6,7-tetrahydroindoles with biogenic cyclic amines

Aminomethylation of 2-methyl(aryl)-, 2-aryl-3-alkylpyrroles, 4,5,6,7-tetrahydroindole and its 1-vinyl- and 1-benzyl-substituted derivatives with a mixture of 5% water-ethanol solution of formaldehyde and cyclic amine (pyrrolidine, piperazine, and morpholine) without catalyst at room temperature leads to the formation of the corresponding 2-aminomethylpyrroles and 2-aminomethyl-4,5,6,7-tetrahydroindoles in up to 92% yields. In reaction of 1-vinyl-4,5,6,7-tetrahydroindole with formaldehyde water solution and piperazine in a 60% yield 1,4-bis(1-vinyl-4,5,6,7-tetrahydroindol-2-yl)piperazine was obtained, a promising bifunctional monomer and a building block for the synthesis of new indole derivatives, in particular, of biologically active polymers. In the reaction of 2-methylpyrrole and 4,5,6,7-tetrahydroindole with formaldehyde and morpholine along with the С²-aminomethylation the 1-hydroxymethylation of the pyrrole ring was observed.     

Thermodynamic Properties of Alloys of the Sn–Yb System

Thermochemical properties of liquid alloys of the Sn–Yb system are studied via calorimetry at 1110–1310 K over the ranges of concentrations 0 < x_Yb < 0.47 and 0.82 < x_Yb < 1. Considerable negative heat effects of the mixing of these alloys are identified. Activities of the components, the Gibbs energies and entropies of mixing, and the liquidus curve of the phase diagram of this system are calculated using the ideal associated solution (IAS) model and agree with data from the literature.     

From 1/f noise to multifractal cascades in heartbeat dynamics

We explore the degree to which concepts developed in statistical physics can be usefully applied to physiological signals. We illustrate the problems related to physiologic signal analysis with representative examples of human heartbeat dynamics under healthy and pathologic conditions. We first review recent progress based on two analysis methods, power spectrum and detrended fluctuation analysis, used to quantify long-range power-law correlations in noisy heartbeat fluctuations. The finding of power-law correlations indicates presence of scale-invariant, fractal structures in the human heartbeat. These fractal structures are represented by self-affine cascades of beat-to-beat fluctuations revealed by wavelet decomposition at different time scales. We then describe very recent work that quantifies multifractal features in these cascades, and the discovery that the multifractal structure of healthy dynamics is lost with congestive heart failure. The analytic tools we discuss may be used on a wide range of physiologic signals. (c) 2001 American Institute of Physics.     

Alkoxylation of 1,2-Bis(methylchlorosilyl)ethylenes and -Acetylenes

Reactions of a series of 1,2-bis(methylchlorosilyl)ethylenes and -acetylenes Me_nCl_{3 - n}Si-Z-SiCl_{3 - n}Me_n (Z = CH = CH, CC; n = 0-2) with ethanol and acetoxime were studied. Novel alkoxy- and isopropylideneaminooxysilanes were obtained and characterized. A relation was found between the activity of Si-Cl bonds in the reactions studied and the structure of the carbon-carbon bridge.     

Effect of Organic Compounds and Salts on the Tris(2,2"-Bipyridyl)Ruthenium(II)-Photosensitized Substitution of the Sulfo Group for Halogen in Halogenated Naphthalenes in Aqueous Solutions

The effect of the addition of organic compounds and salts on the occurrence of the chain radical-ion reaction of replacement of halogen by sulfo group in halogenated hydroxynaphthalenes in a sodium sulfite aqueous solution, which was photosensitized by a tris(2,2"-bipyridyl)ruthenium(II) complex, was studied. It was shown that both organic compounds and salts in small concentrations increase the quantum yield of the substitution reaction. The kinetic scheme of the reaction is discussed.     

Effect of Nitrate Ions on the Chain Photochemical Reaction of Sulfo Group Substitution for Bromine in 1-Bromo-2-Hydroxynaphthalene upon Sensitized and Direct Photolysis

The influence of nitrate ion admixtures on the proceeding of the radical-ion chain reaction of sulfo group substitution for halogen in halogenated hydroxynaphthalenes in an aqueous sodium sulfite solution was studied upon both direct and tris(2,2-bipyridyl)ruthenium(II)-sensitized photolysis. It was found that nitrate ions increase the quantum yields of the photosensitized substitution reaction and decrease the quantum yields of the reaction in the direct photolysis. Based on an analysis of kinetic schemes of the reaction, it was shown that nitrate ions affect the photoinitiation step in sensitized photolysis or the termination step in the direct photolysis.     

Computational studies on pseudorotaxanes by molecular dynamics and free energy perturbation simulations

A computational scheme that comprises the utilization of the AMBER force field with RESP charges and an explicit solvent model for acetonitrile proved to be useful for studying the structures and energetics of pseudorotaxanes of benzidine and 4,4'-biphenol with cyclobis(paraquat-p-phenylene). The scheme can be further utilized for modeling [2]rotaxanes.