A novel miniature superconducting converter for 1 kA magnets

A miniature full-wave converter to control the current of a superconducting magnet is developed and tested in our institutes. Typical design values of the device are: AC voltage of 35 V, current of 7 A, and frequency 50-60 Hz; DC voltage o f f 0.2 V, and current of * 1 kA. An efficiency is better than 97% and a ‘cold’ volume is less than 1 litre. The rectification is achieved by means of thermally controlled superconducting switches. The high reliability of the device is ensured by means of a mechanical switch. The device provides an efficient way to a fine control of the magnet current

Development of a 1 kA, 50 Hz Superconducting Converter

A single-phase, thermally switched superconducting power converter operating at mains frequency is being developed and tested by the authors. Typical design values of the device are: input voltage of 220 V; input current of 7 A; output voltage of 1 V; and output current of 1 kA. The average output power is about 750 VA, with an efficiency better than 96%. Test results of the full scale power converter while ramping up and down a superconducting magnet and a comparison with the theory are presented. The power converter will be installed as a part of a power supply system controlling the current of a separator magnet located in Ukraine for an iron ore recycling process

Electromagnetic and mechanical characteristaion of ITER CS-MC conductors affected by transverse cyclic loading, part 3: mechanical properties

The magnetic field and current of a coil wound with a cable-in-conduit conductor causes a transverse force pushing the cable to one side of the conduit. This load causes elastic and plastic deformation with friction as well as heating due to friction. A special cryogenic press has been built to study the mechanical and electrical properties of full-size ITER conductors under transverse mechanical loading. The cryogenic press can transmit at 4.2 K cyclic forces of 650 kN/m to conductor sections of 400 mm length representative of the peak load on a 50 kA conductor at 13 T. In order to transmit the force directly onto the cable, the conduit is opened partly to allow the cable deformation. The force acting on the cable as well as the displacement are monitored simultaneously in order to determine the mechanical heat generation due to friction. The mechanical loss under load is investigated for the Nb3Sn, 45 kA, 10 and 13 T, central solenoid model cell conductors (CSMC). The mechanical heat generation is determined from the hysteresis in the measured curves of displacement versus applied force. The first results of the effect of some 40 loading cycles are presented and the two conductors are compared. A significant decrease of the cable mechanical heat generation after loading cycles is observed

Collective Properties of Excitons in Presence of a Two-Dimensional Electron Gas

We have studied the collective properties of two-dimensional (2D) excitons immersed within a quantum well which contains 2D excitons and a two-dimensional electron gas (2DEG). We have also analyzed the excitations for a system of 2D dipole excitons with spatially separated electrons and holes in a pair of quantum wells (CQWs) when one of the wells contains a 2DEG. Calculations of the superfluid density and the Kosterlitz-Thouless (K-T) phase transition temperature for the 2DEG-exciton system in a quantum well have shown that the K-T transition temperature increases with increasing exciton density and that it might be possible to have fast long range transport of excitons. The superfluid density and the K-T transition temperature for dipole excitons in CQWs in the presence of a 2DEG in one of the wells increases with increasing inter-well separation.Comment: 10 pages, 1 figure. accepted by Solid State Communication

Trace Element Patterns in Shells of Mussels (Bivalvia) Allow to Distinguish between Fresh- and Brackish-Water Coastal Environments of the Subarctic and Boreal Zone

The accumulation of trace metals in the shells of bivalves allows quantitative assessments of environmental pollution and helps to reconstruct paleo aquatic environments. However, the understanding on how marine and freshwater mollusks control the level of trace elements in their shells remains very limited. Here, we compared the trace element composition of marine and freshwater bivalves from boreal and subarctic habitats, using examples of widely distributed species of marine (Mytilus edulis, M. trossulus) and freshwater (Anodonta anatina, Unio sp., Beringiana beringiana) mussels. Sizable differences in several trace element concentrations were detected between different species, depending on their environmental niches. A multiparametric statistical treatment of the shell’s elemental composition allowed to distinguish the impact of external factors (water and sediment chemical composition) from active metabolic (biological) control. In particular, the obtained results demonstrated that Ba:Ca and Pb:Ca ratios in mussels’ shells are closely related to the primary productivity of aquatic ecosystems. The Mn:Ca ratio allowed to constrain the environmental conditions of mussels’ species depending on the trophic state of inhabited waterbody. Overall, the marine mussels exhibited stronger biological control of trace element accumulation, whereas trace element pattern in shells of freshwater mussels was chiefly controlled by environmental factors. The obtained results might help to use the trace element composition of bivalves in distinguishing marine and freshwater habitats of mollusks in paleo environments

Seasonal dynamics of organic carbon and metals in thermokarst lakes from the discontinuous permafrost zone of western Siberia

Despite relatively good knowledge of the biogeochemistry of Siberian thermokarst lakes during summer base flow, their seasonal dynamics remains almost unexplored. This work describes the chemical composition of 130 thermokarst lakes ranging in size from a few m2 to several km2, located in the discontinuous permafrost zone. Lakes were sampled during spring flood, just after the ice break (early June), the end of summer (August), the beginning of ice formation (October) and during the full freezing season in winter (February). The lakes larger than 1000m2 did not exhibit any statistically significant control of the lake size on dissolved organic carbon (DOC), the major and trace element concentrations over three major open water seasons. On the annual scale, the majority of dissolved elements including organic carbon increased their concentration from 30 to 500 %, with a statistically significant (p summer>autumn>winter. The ice formation in October included several stages: first, surface layer freezing followed by crack (fissure) formation with unfrozen water from the deeper layers spreading over the ice surface. This water was subsequently frozen and formed layered ice rich in organic matter. As a result, the DOC and metal (Mn, Fe, Ni, Cu, Zn, As, Ba and Pb) concentrations were highest near the surface of the ice column (0 to 20 cm) and decreased by a factor of 2 towards the bottom. The main implications of discovered freeze-driven solute concentrations in thermokarst lake waters are enhanced colloidal coagulation and removal of dissolved organic matter and associated insoluble metals from the water column to the sediments. The measured distribution coefficients of a TE between amorphous organo-ferric coagulates and lake water (<0.45 μm) were similar to those reported earlier for Fe-rich colloids and low molecular weight (<1 kDa, or <1–2 nm) fractions of thermokarst lake waters, suggesting massive coprecipitation of TE with amorphous Fe oxyhydroxide stabilized by organic matter. Although the concentration of most elements was lowest in spring, this period of maximal water coverage of land created a significant reservoir of DOC and soluble metals in the water column that can be easily mobilized to the hydrological network. The highest DOC concentration observed in the smallest (<100m2) water bodies in spring suggests their strongly heterotrophic status and, therefore, a potentially elevated CO2 flux from the lake surface to the atmosphere

Genome-wide sequence analyses of ethnic populations across Russia

The Russian Federation is the largest and one of the most ethnically diverse countries in the world, however no centralized reference database of genetic variation exists to date. Such data are crucial for medical genetics and essential for studying population history. The Genome Russia Project aims at filling this gap by performing whole genome sequencing and analysis of peoples of the Russian Federation. Here we report the characterization of genome-wide variation of 264 healthy adults, including 60 newly sequenced samples. People of Russia carry known and novel genetic variants of adaptive, clinical and functional consequence that in many cases show allele frequency divergence from neighboring populations. Population genetics analyses revealed six phylogeographic partitions among indigenous ethnicities corresponding to their geographic locales. This study presents a characterization of population-specific genomic variation in Russia with results important for medical genetics and for understanding the dynamic population history of the world's largest country

Development and validation of HERWIG 7 tunes from CMS underlying-event measurements

This paper presents new sets of parameters (“tunes”) for the underlying-event model of the HERWIG7 event generator. These parameters control the description of multiple-parton interactions (MPI) and colour reconnection in HERWIG7, and are obtained from a fit to minimum-bias data collected by the CMS experiment at s=0.9, 7, and 13Te. The tunes are based on the NNPDF 3.1 next-to-next-to-leading-order parton distribution function (PDF) set for the parton shower, and either a leading-order or next-to-next-to-leading-order PDF set for the simulation of MPI and the beam remnants. Predictions utilizing the tunes are produced for event shape observables in electron-positron collisions, and for minimum-bias, inclusive jet, top quark pair, and Z and W boson events in proton-proton collisions, and are compared with data. Each of the new tunes describes the data at a reasonable level, and the tunes using a leading-order PDF for the simulation of MPI provide the best description of the dat

Measurement of the Splitting Function in &ITpp &ITand Pb-Pb Collisions at root&ITsNN&IT=5.02 TeV

Data from heavy ion collisions suggest that the evolution of a parton shower is modified by interactions with the color charges in the dense partonic medium created in these collisions, but it is not known where in the shower evolution the modifications occur. The momentum ratio of the two leading partons, resolved as subjets, provides information about the parton shower evolution. This substructure observable, known as the splitting function, reflects the process of a parton splitting into two other partons and has been measured for jets with transverse momentum between 140 and 500 GeV, in pp and PbPb collisions at a center-of-mass energy of 5.02 TeV per nucleon pair. In central PbPb collisions, the splitting function indicates a more unbalanced momentum ratio, compared to peripheral PbPb and pp collisions.. The measurements are compared to various predictions from event generators and analytical calculations.Peer reviewe

Measurement of prompt open-charm production cross sections in proton-proton collisions at root s=13 TeV

The production cross sections for prompt open-charm mesons in proton-proton collisions at a center-of-mass energy of 13TeV are reported. The measurement is performed using a data sample collected by the CMS experiment corresponding to an integrated luminosity of 29 nb(-1). The differential production cross sections of the D*(+/-), D-+/-, and D-0 ((D) over bar (0)) mesons are presented in ranges of transverse momentum and pseudorapidity 4 < p(T) < 100 GeV and vertical bar eta vertical bar < 2.1, respectively. The results are compared to several theoretical calculations and to previous measurements.Peer reviewe