142 research outputs found
Igor Germanovich Levichev (in connection with the 70th anniversary)
No full textOctober 6, 2015 Igor Germanovich Levichev, Ph. D., Senior Researcher of the Herbarium of the Komarov Botanical Institute of Russian Academy of Sciences, celebrated his 70th birthday. He is widely known monograph of the large genus Gagea and its related genera as well as the author of the original hypothesis in the evolution of morphological structures of monocots. His scientific career began with expeditions to Chukotka, Kamchatka, in the Trans-Baikal region, Kyzylkum (Uzbekistan), Badkhyz Nature Reserve (Turkmenistan, 1972). Since the autumn of 1972, I. G. Levichev worked in Chatkal nature reserve (Uzbekistan), where he created the basis for the monitoring of vegetation changes in two key areas of relatively little changed Uzbek part of the Western Tien Shan. He worked on the creation of “The Red Book of Uzbek SSR” (1984), “Guide to the Plants of Central Asia. Critical synopsis of Flora “(1987). In 1996 he defended his thesis on the topic “Genus Gagea Salisb. of Western Tien Shan “. In collaboration with colleges from German, Italian and other countries I. G. Levichev published a number of interesting results of molecular phylogenetic studies of the genus Gagea (and its related genera). He also described a new genus – Kharkevichia Levichev of Lloydia – Gagea relationship (the family Liliaceae.). Igor Germanovich is the author of over 120 scientific (scientific and popular) works, 53 of them are in fact of Gagea species.</p
Electron dynamics for high-intensity hollow electron beams
No full textHollow Electron Lenses (HEL) will be installed at the High Luminosity Large Hadron Collider to provide a continuous and controlled depletion of beam halo particles by interaction with a superimposed hollow electron beam, of intensity as high as 5 A, and radii 1.1–2.2 mm for 7 TeV LHC operations. In this paper, issues related to the propagation of high intensity hollow electron beams are discussed and the simulations of the electron beam dynamics with feedback to the HEL design are presented. The main results are the rise of the electron beam accelerating voltage from 10 kV, as in the initial proposal, to 15 kV and the validation of the 5 T magnetic field at the main solenoids as being sufficient to guarantee a stable electron beam
Isotopic composition (δ18O, δ2H) of the snow cover in Karelia
Get PDFFor the first time, a regional study of the isotopic composition (δ18O and δ2 H) of the snow cover in Karelia was performed using a sub-meridional and two sub-latitudinal profiles (March 2016). Snow nutrition does generally prevail here in the river and underground runoff. Integral snow samples were taken at 45 sites, three horizons were studied at 39 of them. Monitoring of the isotopic composition of atmospheric precipitation is carried out in the Petrozavodsk city from 2012 to the present. The isotopic composition of snow on the territory of Karelia varied through the following range: for δ18O it is from −15.7 to −21.1 ‰, and for δ2 H – from −118 to −158 ‰, which is significantly less than the isotopic composition of atmospheric precipitation for the same period: δ18O = −8.7 ÷ −30.9 ‰, δ2 H = −77 ÷ −239 ‰. The exception is snow in the valleys of the large Shuya and Suna rivers with light isotopes δ18O (down to −21 ‰). According to two sublatitudinal profiles in southern and central Karelia, there were no obvious trends in the isotopic composition of snow. The decrease in the contents of deuterium (δ2 H) and oxygen-18 (δ18O) in the sections of snow cover corresponds to an almost complete loss of snow at the beginning of winter due to the December thaws of 2015 and its intensive accumulation in abnormally cold January 2016. According to trajectory analysis data, air masses containing isotopically heavy moisture come mainly from the west and southwest, and those containing isotopically light moisture come from the north and east. The results of this research demonstrate that the reconstruction of the isotopic composition of winter precipitation can be approximately performed by the isotopic composition of snow cover
QTG quadrupole magnets for the CNGS transfer line
No full textThe QTG quadrupole magnets will be a part of the CERN Neutrino to Gran Sasso (CNGS) transfer line. 23 QTG magnets will be used as lattice and matching quadrupoles. They are being produced in the framework of a German in-kind contribution via DESY to CNGS. The QTG magnets have a maximum gradient of 40 T/m at the 530 A excitation current and are manufactured from laminated steel cores. The yoke length is 2.2 m and the inscribed radius is 22.5 mm. The excitation coils are made of vacuum impregnated hollow copper conductor. The main design aspects and the results of the acceptance tests including mechanical, electrical and magnetic field measurements are described
Alternative design of the CLIC Damping Ring Lattice
No full textAn original design of the CLIC damping ring demonstrates the parameters required for the linear collider together with the highly compact lattice (the circumference of the ring is only about 365 m). However, this design can hardly be implemented in a real machine because of such drawbacks as the lack of space between the magnetic elements to accommodate other accelerator components, serious problems with the evacuation of the high radiation power from damping wigglers and strong gradient of quadrupoles and sextupoles, which can hardly be achieved in the frame of the existing magnet technology. From this point of view this design can be considered as an ideal solution and an aim to be approached. In this paper we explore a possibility to design alternative solutions although with a larger size but with the same performance and with the realistic technical parameters
THERMAL STABILITY OF ENERGY-EMISSION FROM <font>CdTe</font> NANOCRYSTALS EMBEDDED IN <font>SiO</font><sub>2</sub> THIN FILMS
No full text CdTe -doped SiO 2 thin films were produced by RF magnetron co-sputtering technique. Presence of CdTe nanocrystals inside the silica matrix was confirmed by Raman spectroscopy and grazing incidence X-ray diffraction. The samples demonstrate size dependent photoluminescence. Temperature dependent photoluminescence measurements were carried out in the temperature range 15–295 K and revealed energy-emission thermal stability. This feature can be usefully applied in a production of light-emitting diodes with wavelength stability in a wide temperature range. </jats:p
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