Lithiation and electrophilic substitution of 8-chlorodibenz[b,f][1,4]-oxazepine-10-tert-butylcarbamate: The preparation of novel fused heterocyclic derivatives of 8-chlorodibenzoxazepine

Lithiation of 8-chlorodibenz[b,f][1,4]oxazepine-10-tert-butylcarbamate ( 1 ) is described. Electrophilic substitution of the resulting N-Boc dibenzoxazepine α- lithioamine 2 with ketones, aldehydes, nitriles, iso-cyanates and imines, followed by an in-situ cyclization, gave fused carbamates 5–26 , fused 2H-imidazol-2-ones 27–29 , fused hydantoins 30–32 , and fused ureas 33–35 , respectively, in 11–66% yield.     

Measurement and simulation of the rates of threshold reactions in a W—Na target bombarded with 0.8-GeV protons

The results of experimental measurement and numerical simulation of 979 rates of threshold reactions in 142 samples of ²⁰⁹Bi, ¹⁹⁷Au, ¹⁸¹Ta, ¹⁶⁹Tm, ¹¹⁵In, ⁹³Nb, ⁶⁵Cu, ⁶⁴Zn, ⁶³Cu, ⁵⁹Co, ²⁷Al, ¹⁹F, and ¹²C placed inside and outside of a “thick” W-Na target irradiated with 0.8-GeV protons are reported. The reaction rates are measured by the method of γ spectrometry using Ge and GeLi semiconductor detectors. The numerical calculations were performed using the LAHET code package together with the EXFOR database and the evaluated data libraries MENDL2N, MENDL2P, and IEAF2001. The experimental and calculated results are compared and the most significant discrepancies are analyzed.     

The procedure and results of calculations of the equilibrium isotopic composition of a demonstration subcritical molten salt reactor

A subcritical molten salt reactor with an external neutron source is studied computationally as a facility for incineration and transmutation of minor actinides from spent nuclear fuel of reactors of VVER-1000 type and for producing ²³³U from ²³²Th. The reactor configuration is chosen, the requirements to be imposed on the external neutron source are formulated, and the equilibrium isotopic composition of heavy nuclides and the key parameters of the fuel cycle are calculated.     

A 19F NMR Study of the Transmissive Ability of Boron-Containing Bridged Systems with Three- and Four-Coordinated Boron Atoms

Two series of model compounds, Ar₂BOC₆H₄F-4 and Ar₂B(Py)OC₆H₄F-4, containing three-and four-coordinated boron atoms, have been synthesized. It was established by ¹⁹F NMR technique that both systems possess a similar transmissive ability that is in intermolecular coordination with pyridine does not influence the transmissive properties of the boron-oxygen binuclear bridging group. The solvent polarity does not influence the electron transmission in the boron complexes studied.     

An analytical formula for ring artefact suppression in X-ray tomography

A method of ring artefact suppression in X-ray computerised tomography (CT) reconstructions is proposed. The method is based on the assumption that a sinogram is a smooth function along the horizontal spatial coordinate. Methods based on the theory of ill-posed problems are applied to find a regularised solution. An analytical formula for the solution is proposed allowing fast ring artefact suppression. Its performance is demonstrated for parallel beam synchrotron X-ray tomography.     

Structure and evolution of shock waves in relativistic magnetohydrodynamics

We derive the existence conditions for relativistic shock waves propagating in a perfectly conducting fluid with a general equation of state that guarantees that the stationary wave has a continuous profile in the presence of weak viscosity. To this end we study the one-dimensional solutions of the magnetohydrodynamic equations with a relativistic viscosity tensor. We allow for anomalous regions of thermodynamic variables and do not use the well-known condition for the convexity of Poisson adiabats. The results lead to relationships among the velocities of magnetoacoustic, Alfvén, and shock waves in front of and behind the discontinuity that prove to be more stringent than the corollaries of the evolution conditions. In the nonrelativistic case and in parallel and perpendicular shock waves, any difference between the two conditions disappears. Zh. éksp. Teor. Fiz. 114, 881–891 (September 1998)     

Nuclear level densities in <Superscript>208</Superscript>Bi and <Superscript>209</Superscript>Po from the neutron spectra in the (<Emphasis Type="Italic">p,n</Emphasis>) reactions on <Superscript>208</Superscript>Pb and <Superscript>209</Superscript>Bi nuclei

The spectra of neutrons from the (p, n) reactions on the ²⁰⁸Pb and ²⁰⁹Bi nuclei were measured in the proton-energy range 8–11 MeV. These measurements were performed by using a time-of-flight spectrometer of fast neutrons on the basis of the pulsed tandem accelerator EGP-15 of the Institute of Physics and Power Engineering (Obninsk, Russian Federation). A high resolution and stability of the time-of-flight spectrometermade it possible to identify reliably low-lying discrete levels alongwith the continuum section of the neutron spectra. The measured data were analyzed on the basis of the statistical equilibrium and preequilibrium models of nuclear reactions. The respective calculations were performed by using the precise formalism of Hauser-Feshbach statistical theory together with the generalizedmodel of a superfluid nucleus and the back-shifted Fermi gas model for the nuclear-level density. The nuclear-level densities in ²⁰⁸Bi and ²⁰⁹Po were determined along with their energy dependences and model parameters. Our results are discussed together with available experimental data and recommendations of model systematics.