Soft-x-ray harmonic comb from relativistic electron spikes

We demonstrate a new high-order harmonic generation mechanism reaching the "water window" spectral region in experiments with multiterawatt femtosecond lasers irradiating gas jets. A few hundred harmonic orders are resolved, giving μJ/sr pulses. Harmonics are collectively emitted by an oscillating electron spike formed at the joint of the boundaries of a cavity and bow wave created by a relativistically self-focusing laser in underdense plasma. The spike sharpness and stability are explained by catastrophe theory. The mechanism is corroborated by particle-in-cell simulations.     

A model of the bursting process in non-newtonian fluids

A model for predicting the frequency of occurrence of sublayer bursts in non-Newtonian fluids is developed. The model is based on the similarity between turbulent pipe flow and a flat plate boundary layer at zero incidence. All parameters in the model are determined from hydrodynamic studies. The predicted bursting periods for Newtonian, power-law, and drag-reducing fluids are in reasonable agreement with previously published data and correlations.     

Novel ionic liquid electrolyte for electrochemical double layer capacitors

A novel oxygen containing spiro ammonium salt, oxazolidine-3-spiro-1’-pyrrolidinium tetrafluoroborate (OPBF₄) was synthesized using an innovative technique for use as electrolyte in electrochemical double layer capacitors (EDLC). Comparison of OPBF₄ with commercially available, tetraethyl ammonium tetrafluoroborate (TEABF₄) showed higher voltage window and higher capacitance for the OPBF₄ compound. Moreover, molarity of 3 M was produced with OPBF₄ as compared to a maximum of 1.5 M for TEABF₄ in acetonitrile (AN). This is especially important to enable the fabrication of higher energy density EDLC. This is the first report of testing OPBF₄ compound in an EDLC device, and it qualifies as a reasonable alternative to TEABF₄ for high performance ultracapacitors.     

Facile Syntheses of Some L-Sugar Derivatives from L-Quebrachitol

Abstract

Naturally occurring optically active cyclitol, L-quebrachitol (1) was transformed into 5-O-methyl L-manno- (5) and L-talofuranose derivatives (11) and methyl L-guluronate derivative (15) in short step reactions.     

Laser-induced fluorescence spectra of Ne- and Ar -aniline van der waals complexes in supersonic jets. Analysis of rotational structures

Laser-induced fluorescence spectra of Ne- and Ar -aniline complexes were observed with a resolution of 0.04 cm^?1. By a simulation analysis of the rotational structures, the distances between the rare-gas atom and the aromatic ring of aniline were found to be 3.35 ± 0.04 and 3.50 ± 0.04 A in the X?¹A₁ state of the Ne and Ar complexes, respectively, and about 0.05 A shorter when aniline was excited to the ùB₂ state.     

Equilibrium cyclotrimerization of n-butyraldehyde

n-Butyraldehyde was cyclotrimerized by using boron trifluoride etherate as an initiator at ?10 to 25°C under various conditions, e.g., in methylene chloride, in toluene, and without adding solvent. An equilibrium between the monomer and its cyclic trimer was observed, the equilibrium constant being highly dependent on not only the reaction temperature and the kind of solvents, but also the initial monomer concentration. A consistent interpretation for the results was obtained by the thermodynamic treatment of the equilibrium system as a nonideal solution composed of the monomer, its cyclic trimer, and solvent, in consideration of the intermolecular interactions between any two components.