Reactive Burgers model for detonation propagation in a non-uniform medium

In this work we analyze, within the framework of the reactive Burgers model (Kasimov et al., 2013), the propagation of detonation in a periodically varying medium. We investigate the role of the amplitude and the wavelength of the variations on the dynamics of both stable and unstable detonations. It is found that: (1) the periodic upstream can lead to the amplification of the detonation oscillations, i.e., there is a resonance, and (2) the detonation dynamics exhibits mode locking whereby the dynamics is “enslaved” by the upstream variations.     

Synthesis of methyl(ethyl) pyrazolo[4,3-b]pyridine-6-carboxylates and their conversion to tert-butyl 4,5,6,7-tetrahydropyrazolo-[4,3-b]pyridine-6-carboxylates

Chemistry of Heterocyclic Compounds - N-Boc-4-aminopyrazole-5-carbaldehydes react with methyl 3,3-dimethoxypropanoate or β-keto esters in acetic acid under reflux to form methyl(ethyl)...     

The synthesis of a 2-azabicyclo[3.1.0]hexane by rearrangement of a spirocyclic epoxide

An unusual rearrangement of a 1-oxa-6-azaspiro[2.5]octane derivative giving access to novel 5-substituted 2-azabicyclo[3.1.0]hexanes is described. The synthetic application of the reaction is demonstrated by the synthesis of N-Boc-2,3-methano-β-proline. The amino acid was prepared through a three-step synthesis from easily available reagents in an overall yield of 15%.     

Dynamics of an anharmonic oscillator with a periodic perturbation

We study the features of the stochastic dynamics of a Hamiltonian system with the potential x ²ⁿ subjected to an external monochromatic perturbation. Three regimes of stochastic diffusion, which differ in the value of the amplitude of the external perturbation, are detected. We demonstrate the possibility of chaotic regimes manifesting themselves in pendulum vibrations of the well of a water-moderated and-cooled nuclear power reactor as an application of the model being investigated. Finally, we propose a method of simple proportional control, which makes it possible to control the chaotic vibrations of the anharmonic oscillator. Zh. éksp. Teor. Fiz. 115, 361–377 (January 1999)     

Excited State Intramolecular Proton Transfer and Photophysics of a New Fluorenyl Two‐Photon Fluorescent Probe

The steady‐state photophysical, NMR, and two‐photon absorption (2PA) properties of a new fluorene derivative ( 1 ) containing the 2‐(2′‐hydroxyphenyl)benzothiazole (HBT) terminal construct is investigated for use as a fluorescence probe in bioimaging. A comprehensive analysis of the linear spectral properties reveals inter‐ and intramolecular hydrogen bonding and excited state intramolecular proton transfer (ESIPT) processes in the HBT substituent. A specific electronic model with a double minimum potential energy surface is consistent with the observed spectral properties. The 2PA spectra are obtained using a standard two‐photon induced fluorescence method with a femtosecond kHz laser system, affording a maximum 2PA cross section of ～600 GM, a sufficiently high value for two‐photon fluorescence imaging. No dependence of two‐photon absorption efficiency on solvent properties and hydrogen bonding in the HBT substituent is observed. The potential use of this fluorenyl probe in bioimaging is demonstrated via one‐ and two‐photon fluorescence imaging of COS‐7 cells.