Resonant absorption of electromagnetic radiation in a quantum channel due to the scattering of electrons by impurities

We have found an analytical expression for the absorption coefficient of electromagnetic radiation in a quantum channel with a parabolic confinement potential. The calculation has been performed using the second-order perturbation theory taking into account the scattering of a quasi-one-dimensional electron gas by ionized impurities. We have analyzed the dependences of the absorption coefficient on the frequency of the electromagnetic radiation and the magnetic field. The appearance of additional resonant peaks, which are caused by scattering by impurities, has been found.     

Minimal Networks on the Regular n-Dimensional Simplex

The paper gives the proof of the following fact: all simple, i.e., having no nodes of degree 2, trees that span the vertices of the regular n-dimensional simplex can be realized as nondegenerate minimal parametric networks.     

A system for proton beam control during radiotherapy

A system for the on-line control of proton beam profiles and track has been designed and constructed to guarantee the quality assurance of radiotherapy carried out in the Medical-Technical Complex of the Joint Institute for Nuclear Research. To measure the horizontal and vertical profiles of the beam in the treatment room, a multiwire ionization chamber has been designed and constructed. The chamber consists of two anode and three cathode electrodes. Each anode electrode contains 30 wires 0.1 mm in diameter separated by 3 mm. To control the beam track, four industrial semiconductor diodes 2D212A designed for radio engineering application were used. The system is installed in front of the first collimator in the peripheral part of the beam, so that it does not disturb the operated part of the beam. Output signals from the ionization chamber and the diodes are processed by a specially constructed electronic device connected to a personal computer. It utilizes 64-channel 16-bit charge-current converters (TERA chip). One-years’s experience of the operation of the system in proton therapy treatment sessions has shown its high reliability and sensitivity to proton beam parameters. The accuracy of controlling the asymmetry of the beam profiles is 2% and the track deviations are equivalent to 0.2 mm of water.     

Nuclear Magnetic Resonance Spectra of Polyhydroxylated Fullerene C60(OH)n

Polyhydroxylated fullerene C₆₀(OH)_n (with an estimated number of hydroxyl groups n = 38–44) synthesized from pure fullerene by mixing a benzene solution of C₆₀ with a NaOH aqueous solution in the presence of a catalyst was studied with ¹H and ¹³C solid-state nuclear magnetic resonance. Possible features of the structure of a molecule shell were revealed from ¹H NMR data. The ¹³C spectrum showed a peak splitting with an increase in temperature, which is probably due to fullerenol isomers.

     

Universal Boundary Sets in the Generalized Steiner Problem

It is proved that every simple binary tree is realized by a nondegenerate minimal parametric network spanning the vertices of a regular simplex. Bibliography: 9 titles.