Precision Quantum Hall Resistance Measurement on Epitaxial Graphene Device in Low Magnetic Field

Precision quantum Hall resistance (QHR) measurements were performed on large-area epitaxial graphene device at low magnetic fields (B = 2 T - 8 T) at temperature T = 1.5 K. Hall resistance was measured using Cryogenic Current Comparator resistance bridge with high biasing current Isd = 40 micro ampere. The results showed that at B = 8 T the relative deviation of Hall resistance from the expected quantized value h/2e2 is within experimental uncertainty of 3.5 parts in 108 and remained below 0.35 parts per million (ppm) down to B = 3 T

Structure and operational properties of porous cermets on the basis of alloyed steel scale

Compositions of batches for obtaining porous cermets on the basis of alloyed steel scale with addition of ferrosilicon have been developed. Roentgenograms of the obtained alloys were shown, mechanical durability and porosity of the obtained materials were investigated. The model of formation of porous cermets was offere

Towards a Graphene-Based Quantum Impedance Standard

Precision measurements of the quantum Hall resistance with alternating current (ac) in the kHz range were performed on epitaxial graphene in order to assess its suitability as a quantum standard of impedance. The quantum Hall plateaus measured with alternating current were found to be flat within one part in 10^7. This is much better than for plain GaAs quantum Hall devices and shows that the magnetic-flux-dependent capacitive ac losses of the graphene device are less critical. The observed frequency dependence of about -8x10^-8/kHz is comparable in absolute value to the positive frequency dependence of plain GaAs devices, but the negative sign is attributed to stray capacitances which we believe can be minimized by a careful design of the graphene device. Further improvements thus may lead to a simpler and more user-friendly quantum standard for both resistance and impedance

Magnetically operated nanorelay based on two single-walled carbon nanotubes filled with endofullerenes Fe@C20

Structural and energy characteristics of the smallest magnetic endofullerene Fe@C20 have been calculated using the density functional theory approach. The ground state of Fe@C20 is found to be a septet state, and the magnetic moment of Fe@C20 is estimated to be 8 Bohr magnetons. Characteristics of an (8,8) carbon nanotube with a single Fe@C20 inside are studied in the framework of the semiempirical approach. The scheme of a magnetic nanorelay based on cantilevered nanotubes filled with magnetic endofullerenes is elaborated. The proposed nanorelay is turned on as a result of bending of nanotubes by a magnetic force. Operational characteristics of such a nanorelay based on (8,8) and (21,21) nanotubes fully filled with Fe@C20 are estimated and compared to the ones of a nanorelay made of a (21,21) nanotube fully filled with experimentally observed (Ho3N)@C80 with the magnetic moment of 21 Bohr magnetons. Room temperature operation of (21,21) nanotube based nanorelays is shown.Comment: 18 pages, 9 figure

Some features of the bioelectric activity of the muscles with prolonged hypokinesia

The effects of prolonged hypokinesia, brought on by confinement to bed and the attendant lack of motor activity, on the bioelectric activity of muscles are studied. Electromyographic measurements of amplitude and frequency indicators of muscular bioelectric activity were analyzed

Species of Fungi in the Root System of Woody Plants in Urban Plantations

The features of the species composition of microscopic fungi in the root system and rhizosphere soil of woody plants in connection with the level of soil contamination have not been studied sufficiently. This article presents the results of studying the species composition of fungi in the root system and soil of three species of woodyplants (Acer negundo L., Acer platanoides L., and Betula pendula Roth.) growing in urban plantations of various ecological categories with different levels of heavy metal soil contamination. The study was carried out in a large industrial center of the Urals region, Izhevsk. When studying the species composition of fungi, microscopyand molecular genetic analysis were used. Isolates of endotrophic fungi from the root system of plants were isolated, and systematic membership was determined by molecular genetic analysis. The results showed that in soils with a high level of contamination, the DNA of endotrophic mycorrhiza-forming fungi was found in theroots of woody plants in a good living state. Keywords: fungi, heavy metals, plantations, urban environment, resistanc

Childhood environmental health concerns in Russia

Environmental Health Centre (EHC) is one of the few Russian organisations responsible for the development of environmental epidemiology and health risk assessment methodologies in Russia. Being a WELL resource centre network partner we considered the possibilities for environmental interventions to address major causes of child mortality and morbidity and environmental health concerns in Russia. It was based on the results of the preliminary scoping studies carried out by our Centre during May – October 2002. The scoping studies themselves were based on published and unpublished literature and on consultations with key stakeholders