Collective modes of two-dimensional classical Coulomb fluids

Molecular dynamics simulations have been performed to investigate in detail collective modes spectra of two-dimensional Coulomb fluids in a wide range of coupling. The obtained dispersion relations are compared with theoretical approaches based on quasi-crystalline approximation (QCA), also known as the quasi-localized charge approximation (QLCA) in the plasma-related context. An overall satisfactory agreement between theory and simulations is documented for the longitudinal mode at moderate coupling and in the long-wavelength domain at strong coupling. For the transverse mode, satisfactory agreement in the long-wavelength domain is only reached at very strong coupling, when the cutoff wave-number below which shear waves cannot propagate becomes small. The dependence of the cutoff wave-number for shear waves on the coupling parameter is obtained.Comment: 10 pages, 6 figure

Application of High-Power Electrical Sparks for Dynamic Compaction of Soil

The paper describes an electrical discharge technology, applied for soil compaction around a borehole, filled with hardening grout, in operations for erection of micropiles, cast piles, soil anchors and soil nails. The technology consists in that 150-250 microsecond long electrical sparks are generated with 6-second period in borehole. The sparks have 30-40 kJ energy, which is roughly of the same order of magnitude as a pile drop hammer. But a single electrical spark has 200-250 MW because of its short duration. Such pulses compact the contact layer of soil and thus increase bearing capacity of piles, anchors or soil nails times 1.5-2.0. Electrical spark in soil is a practically non-observable event, prohibiting any instrumentation near it, which so far can only allow its qualitative investigation in water rather than in soil. The experiments in water were staged in lab on a set-up, generating 5 kJ sparks, with electronic registration of time-dependent registration of pulse behavior. It was found that longer pulse efficiency is higher and can be increased by addition of special admixtures. Full-size bored piles, micropiles and soil anchors were tested in-situ on construction sites, having various soil conditions. The test data yielded that pile (anchor, nail) bearing capacity could be increased times 1.5-2.0 by high-energy electrical spark treatment, as compared to conventional technology (without electrical spark treatment)

Remote atomic clock synchronization via satellites and optical fibers

In the global network of institutions engaged with the realization of International Atomic Time (TAI), atomic clocks and time scales are compared by means of the Global Positioning System (GPS) and by employing telecommunication satellites for two-way satellite time and frequency transfer (TWSTFT). The frequencies of the state-of-the-art primary caesium fountain clocks can be compared at the level of 10e-15 (relative, 1 day averaging) and time scales can be synchronized with an uncertainty of one nanosecond. Future improvements of worldwide clock comparisons will require also an improvement of the local signal distribution systems. For example, the future ACES (atomic clock ensemble in space) mission shall demonstrate remote time scale comparisons at the uncertainty level of 100 ps. To ensure that the ACES ground instrument will be synchronized to the local time scale at PTB without a significant uncertainty contribution, we have developed a means for calibrated clock comparisons through optical fibers. An uncertainty below 50 ps over a distance of 2 km has been demonstrated on the campus of PTB. This technology is thus in general a promising candidate for synchronization of enhanced time transfer equipment with the local realizations of UTC . Based on these experiments we estimate the uncertainty level for calibrated time transfer through optical fibers over longer distances. These findings are compared with the current status and developments of satellite based time transfer systems, with a focus on the calibration techniques for operational systems

High capacity in G protein-coupled receptor signaling.

G protein-coupled receptors (GPCRs) constitute a large family of receptors that activate intracellular signaling pathways upon detecting specific extracellular ligands. While many aspects of GPCR signaling have been uncovered through decades of studies, some fundamental properties, like its channel capacity-a measure of how much information a given transmission system can reliably transduce-are still debated. Previous studies concluded that GPCRs in individual cells could transmit around one bit of information about the concentration of the ligands, allowing only for a reliable on or off response. Using muscarinic receptor-induced calcium response measured in individual cells upon repeated stimulation, we show that GPCR signaling systems possess a significantly higher capacity. We estimate the channel capacity of this system to be above two, implying that at least four concentration levels of the agonist can be distinguished reliably. These findings shed light on the basic principles of GPCR signaling

Practical thermodynamics of Yukawa systems at strong coupling

Simple practical approach to estimate thermodynamic properties of strongly coupled Yukawa systems, in both fluid and solid phases, is presented. The accuracy of the approach is tested by extensive comparison with direct computer simulation results (for fluids and solids) and the recently proposed shortest-graph method (for solids). Possible applications to other systems of softly repulsive particles are briefly discussed.Comment: Published in J. Chem. Phy

The relationship between reaction to a moving object with concentrations of biogenic amines and kynematic-dynamic parameters of complex coordination movement in elite alpine skiers

Aim of the study: to identify mutual interaction between the reaction to a moving object with functional state of the central nervous system and kinematic-dynamic parameters of complex coordination movement.Materials and methods: 9 elite alpine skiers were participated in this study. Visual-motor coordination variables were assessed by computer complex for psychophysiological testing NS-Psychotest (Neurosoft, Russia). Dynamic parameters of complex coordination movement during counter movement jump were registered on the MuscleLab Force Plate (Ergotest Innovation A.S., Norway). Quantitation of hormones — adrenaline and noradrenaline as well as neurotransmitters — dopamine and serotonin in blood samples was performed using ultra-high performance liquid chromatograph combined with triple quadrupole mass analyzer LCMS-8060 (Shimadzu, Japan).Results: a significant negative relationship between the maximum output of motor efforts during counter movement jump, mean reaction time and the number of negative reactions recorded within visual-motor coordination testing was documented. A reliable positive relationship between excitation processes, jump power and jump time was established. Increases in noradrenaline and serotonin concentrations are positively associated with the number of accurate reactions, whereas dopamine level was positively correlated with jump altitude.Conclusion: the predominance of excitation over inhibition processes in the central nervous system had a positive effect on reducing the time spent on counter moving and increasing the maximum power of movement. As applied to alpine skiers we registered the following relationship: the higher the speeds of signal perception and muscle activation when solving a visual-motor task, the higher the power of working efforts, the shorter the time of the eccentric phase and total time spent on performing counter movement jump

Scanning Electron Microscopy Study of Drilling Cuttings in Tomsk Oblast Sites

The research is focused on determining mineralogical composition of drilling cuttings by scanning electron microscope as well as imaging the sample surface of high resolution that allows studying the structural characteristics of the site. In addition, a number of other techniques permit obtaining information on chemical composition of sample in near-surface layers. The study in drilling cuttings by means of scanning microscopy has revealed the presence of titanium, iron, zirconium oxides, iron sulphide, barium sulphate. The former is a mineral that concentrates rare-earth elements, presumably monocyte, as well as uranium silicate, etc. The results obtained confirm the data of previous X-ray structural analysis, i.e. the study samples consist of alumosilicate matrix. Apart from silicon and aluminium oxides, the matrix includes such elements as Na, K, Mg. Such a composition corresponds to rock-forming minerals: quartz, albite, microcline, clinochlore, muscovite, anorthoclase

The Minimum-Uncertainty Squeezed States for for Atoms and Photons in a Cavity

We describe a six-parameter family of the minimum-uncertainty squeezed states for the harmonic oscillator in nonrelativistic quantum mechanics. They are derived by the action of corresponding maximal kinematical invariance group on the standard ground state solution. We show that the product of the variances attains the required minimum value 1/4 only at the instances that one variance is a minimum and the other is a maximum, when the squeezing of one of the variances occurs. The generalized coherent states are explicitly constructed and their Wigner function is studied. The overlap coefficients between the squeezed, or generalized harmonic, and the Fock states are explicitly evaluated in terms of hypergeometric functions. The corresponding photons statistics are discussed and some applications to quantum optics, cavity quantum electrodynamics, and superfocusing in channeling scattering are mentioned. Explicit solutions of the Heisenberg equations for radiation field operators with squeezing are found.Comment: 27 pages, no figures, 174 references J. Phys. B: At. Mol. Opt. Phys., Special Issue celebrating the 20th anniversary of quantum state engineering (R. Blatt, A. Lvovsky, and G. Milburn, Guest Editors), May 201

A transverse current rectification in graphene superlattice

A model for energy spectrum of superlattice on the base of graphene placed on the striped dielectric substrate is proposed. A direct current component which appears in that structure perpendicularly to pulling electric field under the influence of elliptically polarized electromagnetic wave was derived. A transverse current density dependence on pulling field magnitude and on magnitude of component of elliptically polarized wave directed along the axis of a superlattice is analyzed.Comment: 12 pages, 6 figure