Initiation and propagation of detonation waves in combustible high speed flows

The initiation and propagation of detonation waves in combustible high speed flows were studied experimentally. A planar detonation wave traveling in an initiation tube was transmitted into a test section where a combustible high speed flow was induced by an incident shock wave generated in a shock tube. In this study, the flow Mach numbers were obtained as 0.9 and 1.2. The experimental results show that depending on the flow velocity, the apparent propagation velocity of a detonation wave is higher in the upstream and lower in the downstream direction than the CJ velocity. Smoked plate records reveal cellular patterns deformed in the flow direction, and the calculated aspect ratios of the cell were found to agree well with the experimental ones on the basis of the assumption that the velocity of the transverse wave is not affected by the flowing mixture. By analyzing the shock-wave diffraction at the position where there is an abrupt change in the area, on the basis of Whitham’s theory, it was deduced that in the present experimental set-up, the detonation was initiated by the reflection of the diffracted shock waves on the sidewalls of the test section. The agreement between the experimental and calculated results regarding the position of the cellular patterns on the smoked plate record indicated that the position of detonation initiation in high speed flows is shifted downstream due to the flow velocity.     

Kondo effect in a quantum antidot

We report Kondo-like behavior in a quantum antidot (a submicron depleted region in a two-dimensional electron gas) in the quantum-Hall regime. When both spins of the lowest Landau level are present all around the antidot, the resonances between extended edge states via antidot bound states show an abnormal feature in alternate Coulomb-blockaded regions. The feature becomes suppressed when the temperature or source-drain bias is raised as for Kondo resonances in quantum dots. Although the exact mechanism is unknown, Kondo-like correlated tunneling may arise from a Skyrmion-type edge reconstruction. This observation demonstrates the generality of the Kondo phenomenon.     

New bis- and tris-annulation reagents for the syntheses of CD rings of steroids,bearing a functionalized 18-methyl group,by the palladium-catalyzed cyclization

2-Substituted 2-alkoxycarbonyl-3-vinylcyclopentanones (2), easily prepared by the palladium-catalyzed cyclization of 2-substituted 3-oxo-8-phenoxy-6-octenoates (1), are very suitable building blocks for CD rings of steroids, bearing particularly a functionalized 18-methyl group.     

The convergence of a new iteration process for the solution of nonlinear functional equations in banach space

A new iteration process is used to prove several theorems concerning the existence of solutions of the functional equation F(x)=0 where F(x) is a nonlinear functional in Banach space. An advantage of the process under consideration over analogous process using tangential parabolas and tangential hyperbolas, which have rates of convergence of the same order, is the fact that in it second-order Frechet derivatives do not have to be calculated.Translated from Matematicheskie Zametki, Vol. 4, No. 3, pp. 313–322, September, 1968.     

Transverse instability of solitary waves in the generalized kadomtsev-petviashvili equation

The linear stability of planar solitary waves with respect to long-wavelength transverse perturbations is studied in the framework of the generalized Kadomtsev-Petviashvili equation. It is newly discovered that for some nonlinearities in this family, the solitary waves could be transversely unstable even in a medium with negative dispersion. In the case of positive dispersion, they are found to be always unstable.     

Switching by pulse electric field of the elevated enzymatic reaction in the core of polyion complex micelles

Polyion complex micelles entrapping enzyme molecules in the core provide a unique reaction field inducing a remarkable elevation of enzymatic reactivity through a drastic change in the binding specificity between the enzyme and substrate. On-off switching of this enhanced effect was achieved through the destabilization of the core domain by applying a pulse electric field.     

Palladium-catalyzed synthesis of terminal acetals via highly selective anti-Markovnikov nucleophilic attack of pinacol on vinylarenes, allyl ethers, and 1,5-dienes

A palladium-catalyzed reaction of vinylarenes, allyl ethers, and 1,5-dienes with pinacol proceeded via a selective anti-Markovnikov nucleophilic attack to afford corresponding terminal acetals as major products. The bulkiness of pinacol was found to be critical in controlling the regioselectivity.     

Rational design of smart supramolecular assemblies for gene delivery: chemical challenges in the creation of artificial viruses

Polymeric materials have been extensively developed as a delivery vehicle for nucleic acids over the past two decades. Many previous studies have demonstrated that synthetic delivery vehicles can be highly functionalized by chemical approaches to overcome biological barriers in nucleic acid delivery, similar to viruses. Based on our current knowledge, this tutorial review describes rational strategies in the design of polymeric materials to achieve construction of the versatile vehicles, that is "artificial viruses", for successful gene therapy, especially focusing on the chemical structures with the minimal adverse effects.     

Determination of daidzein and genistein in soybean foods by automated on-line in-tube solid-phase microextraction coupled to high-performance liquid chromatography

An automated on-line method for the determination of the isoflavones, daidzein and genistein, was developed using in-tube solid-phase microextraction coupled to high-performance liquid chromatography (in-tube SPME-HPLC). In-tube SPME is a new extraction technique for organic compounds in aqueous samples, in which analytes are extracted from the sample directly into an open tubular capillary by repeated draw/eject cycles of sample solution. Daidzein, genistein and their glucosides tested in this study were clearly separated within 8 min by HPLC using an XDB-C8 column with diode array detection. In order to optimize the extraction of these compounds, several in-tube SPME parameters were examined. The glucosides daidzin and genistin were analyzed as aglycones after hydrolysis because the glucosides were not concentrated by in-tube SPME. The optimum extraction conditions for daidzein and genistein were obtained with 20 draw/eject cycles of 40 microl of sample using a Supel-Q porous layer open tubular capillary column. The extracted compounds were easily desorbed from the capillary by mobile phase flow, and carryover was not observed. Using the in-tube SPME-HPLC method, the calibration curves of these compounds were linear in the range 5-200 ng/ml, with a correlation coefficient above 0.9999 (n = 18), and the detection limits (S/N = 3) were 0.4-0.5 ng/ml. This method was successfully applied to the analysis of soybean foods without interference peaks. The recoveries of aglycones and glucosides spiked into food samples were above 97%.