The first synthesis of furazano[3,4‐b][1,6]naphthyridines

Reaction of 6‐acetyl‐7‐aminofurazano[3,4‐b]pyridines with DMFDMA afforded N,N‐dimethylformamidines that were cyclized to the novel furazan‐fused [1,6]naphthyridine system by treatment with sodium methylate in good yield. The tricyclic system is characterized by X‐ray crystallography.     

The first general synthesis of 3-iodo-4-R-furazans

The first general synthetic route has been developed for the convenient preparation of iodofurazans. The approach was accomplished by one-pot diazotization-iodation reaction of appropriate aminofurazans. A combination of sodium nitrite and iodine in organic solvent under anhydrous conditions as the reaction conditions allowed to solve problem in iodofurazans preparation. The investigation of the substituent's influence on NMR data of the iodofurazans has been carried out. The X-ray crystal structure of the 3-amino-4-iodofurazan 1d is reported. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:199–207, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20007     

A study of the feasibility of conducting the ELISE and EXL experiments at the ITEP accelerator complex

We report the results of a study into the feasibility of conducting the ELISE and EXL experiments on collisions of nuclei of radioactive fragments with electrons at the Institute for Theoretical and Experimental Physics (ITEP). A scheme for uranium ion acceleration in the ITEP accelerator complex is chosen, and it is shown that uranium ions may be accelerated with an intensity of ～1 × 10¹¹ ions/s as soon as the complex is modified and a new injector is constructed. The basic parameters of the modified complex are given, and a layout diagram indicating the positions of the target that serves to produce radioactive fragments, the separator, and the storage rings (CR, RESR, NESR, and ER) at the ITEP site is presented.     

Half-cycle pulses in the mid-infrared from a two-color laser-induced filament

Four-wave mixing (FWM) of femtosecond near-infrared laser pulses and its second harmonic in the filamentation regime is shown to give rise to ultrashort field waveforms in the mid-infrared with pulse widths as short as a half of the field cycle and produce ultrabroadband supercontinuum spectra stretching from the mid-IR to the terahertz region. Generation of 7-fs pulses centered at 4.35 μm is demonstrated by a two-color filamentation experiment, where the 25-fs, 800-nm fundamental-wavelength output of a Ti: Sapphire laser is mixed with its second harmonic. The spectral and temporal properties of the mid-IR waveforms, as well as their emission pattern, are consistent with the FWM scenario of frequency conversion generalized to include the Kerr effect and ionization-induced refractive-index modulation.     

Spin current in an electron waveguide tunnel-coupled to a topological insulator

We show that electron tunneling from edge states in a two-dimensional topological insulator into a parallel electron waveguide leads to the appearance of spin-polarized current in the waveguide. The spin polarization P can be very close to unity and the electron current passing through the tunnel contact splits in the waveguide into two branches flowing from the contact. The polarization essentially depends on the electron scattering by the contact and the electron-electron interaction in the one-dimensional edge states. The electron-electron interaction is treated within the Luttinger liquid model. The main effect of the interaction stems from the renormalization of the electron velocity, due to which the polarization increases with the interaction strength. Electron scattering by the contact leads to a decrease in P. A specific effect occurs when the bottom of the subbands in the waveguide crosses the Dirac point of the spectrum of edge states when changing the voltage or chemical potential. This leads to changing the direction of the spin current.     

Spatiotemporal dynamics of bumblebees foraging under predation risk

We analyze 3D flight paths of bumblebees searching for nectar in a laboratory experiment with and without predation risk from artificial spiders. For the flight velocities we find mixed probability distributions reflecting the access to the food sources while the threat posed by the spiders shows up only in the velocity correlations. The bumblebees thus adjust their flight patterns spatially to the environment and temporally to predation risk. Key information on response to environmental changes is contained in temporal correlation functions, as we explain by a simple emergent model.     

2,2‐Bis(methoxy‐NNO‐azoxy)ethyl Derivatives of 4,8‐Dihydro‐bis‐furazano[3,4‐b:3′4′‐e]pyrazine: The Synthesis and X‐ray Investigation

The first synthesis of 4,8‐dihydro‐bis‐furazano[3,4‐b:3′4′‐e]pyrazine bearing 2,2‐bis(methoxy‐NNO‐azoxy)ethyl groups has been developed. These compounds are obtained by aza‐Michael reaction of 1,1‐bis(methoxy‐NNO‐azoxy)ethene or its equivalents, such as 2,2‐bis(methoxy‐NNO‐azoxy)ethanol derivatives, with 4,8‐dihydro‐bis‐furazano[3,4‐b:3′4′‐e]pyrazine.     

Metric betweenness,Ptolemaic spaces,and isometric embeddings of pretangent spaces in ℝ

We study some properties of pretangent spaces describing the infinitesimal geometry of general metric spaces. The necessary and sufficient conditions characterizing Ptolemaic pretangent spaces and pretangent spaces, where every three points are situated “on a single straight line,” are found. As a corollary, we obtain a criterion of embeddability of pretangent spaces into the set ℝ of real numbers endowed by the natural metric.