Space-charge lens for focusing negative ion beams by means of an additional electron ionizer

A space-charge lens created at the Institute of Physics, National Academy of Sciences of Ukraine, to focus negative ion beams using an additional electron ionizer is investigated. In the previous version of the lens, in which the gas was ionized by the ion beam itself, the focal power was quite high (the focal length was ? ≤ 20 cm) but the gas pressure was too great (P ～ 10^?3 torr), which resulted in significant charge-exchange losses of the beam ions. The experimental and theoretical study reported here shows that the use of a 100-eV electron beam as an auxiliary ionizer allows the working pressure in the lens to be significantly reduced. As a result, a simple, inexpensive, and efficient lens has been developed that can be used in systems for transportation of negative ion beams.     

Sterilization of medical productsin low-pressure glow discharges

Results are presented from experimental and theoretical studies of the sterilization of medical products by the plasmas of dc glow discharges in different gas media. The sterilization efficiency is obtained as a function of discharge parameters. The plasma composition in discharges in N₂ and O₂ is investigated under the operating conditions of a plasma sterilizer. It is shown that free surfaces of medical products are sterilized primarily by UV radiation from the discharge plasma, while an important role in sterilization of products with complicated shapes is played by such chemically active particles as oxygen atoms and electronically excited O₂ molecules.     

Genome-wide association study and scan for signatures of selection point to candidate genes for body temperature maintenance under the cold stress in Siberian cattle populations

Background

Design of new highly productive livestock breeds, well-adapted to local climatic conditions is one of the aims of modern agriculture and breeding. The genetics underlying economically important traits in cattle are widely studied, whereas our knowledge of the genetic mechanisms of adaptation to local environments is still scarce. To address this issue for cold climates we used an integrated approach for detecting genomic intervals related to body temperature maintenance under acute cold stress. Our approach combined genome-wide association studies (GWAS) and scans for signatures of selection applied to a cattle population (Hereford and Kazakh Whiteheaded beef breeds) bred in Siberia. We utilized the GGP HD150K DNA chip containing 139,376 single nucleotide polymorphism markers.

Results

We detected a single candidate region on cattle chromosome (BTA)15 overlapping between the GWAS results and the results of scans for selective sweeps. This region contains two genes, MSANTD4 and GRIA4. Both genes are functional candidates to contribute to the cold-stress resistance phenotype, due to their indirect involvement in the cold shock response (MSANTD4) and body thermoregulation (GRIA4).

Conclusions

Our results point to a novel region on BTA15 which is a candidate region associated with the body temperature maintenance phenotype in Siberian cattle. The results of our research and the follow up studies might be used for the development of cattle breeds better adapted to cold climates of the Russian Federation and other Northern countries with similar climates.

     

Modern problems of drug allergy to antibiotics in the clinical aspects of skin and venereal diseases]

Allergic dermatoses induced by antibiotics amounted to 45.2 per cent of all determined drug reactions according to the data of the Kharkov Research Institute of Dermatology and Venerology. The data on the factors favouring development of the drug dermatoses are presented. Difficulties in differential diagnosis by means of clinical and laboratory methods are indicated. The modern immunological tests of etiological diagnosis of drug resistance and the results of studying non-specific reactivity in patients with medicamentous dermatoses were analyzed. The principles of therapy and prophylaxis are summarized.     

Investigation of the electron energy distribution function in hollow-cathode glow discharges in nitrogen and oxygen

The mechanism for the formation of the inverse electron distribution function is proposed and realized experimentally in a nitrogen plasma of a hollow-cathode glow discharge. It is shown theoretically and experimentally that, for a broad range of the parameters of an N₂ discharge, it is possible to form a significant dip in the profile of the electron distribution function in the energy range ε=2–4 eV and, accordingly, to produce the inverse distribution with df(ε)/d?>0. The formation of a dip is associated with both the vibrational excitation of N₂ molecules and the characteristic features of a hollow-cathode glow discharge. In such a discharge, the applied voltage drops preferentially across a narrow cathode sheath. In the main discharge region, the electric field E is weak (E<0.1 V/cm at a pressure of about p～0.1 torr) and does not heat the discharge plasma. The gas is ionized and the ionization-produced electrons are heated by a beam of fast electrons (with an energy of about 400 eV) emitted from the cathode. A high-energy electron beam plays an important role in the formation of a dip in the profile of the electron distribution function in the energy range in which the cross section for the vibrational excitation of nitrogen molecules is maximum. A plasma with an inverted electron distribution function can be used to create a population inversion in which more impurity molecules and atoms will exist in electronically excited states.     

Space-charge lens for focusing a negative-ion beam

Results are presented from experimental and theoretical studies of a space-charge lens for focusing a negative-ion beam. The space-charge field and the beam ion trajectories are numerically calculated for the lens used in the experiments. The results of calculations are compared with the experimental data. It is shown theoretically and experimentally that the proposed device allows one to achieve the main operating conditions of the space-charge lens: the inertial confinement of positive ions and the removal of electrons by an external electric field. The focusing field of the lens attains ～100 V/cm, which provides a focal length of <20 cm.     

Space charge lens for focusing negative-ion beams

A space charge lens is proposed to focus intense beams of negative hydrogen ions. The focal length of the lens is determined as a function of the parameters of the beam and the gas medium. It is demonstrated experimentally that the lens efficiently focuses H-ion beams with currents of up to ～30 mA and energies of ～10 keV. The measured focal lengths are in good agreement with the calculated ones.