Results 1 - 10 of 1523
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[en] Complete text of publication follows. A major new research infrastructure is being planned to be constructed in Northern Scandinavia. The new EISCAT 3D radar system has a design goal of ten times higher temporal and spatial resolution than the present radars. The modular construction is aimed at a final configuration consisting of several very large phased-array transmitters/ receivers with multiple receiver arrays. Some arrays are very large, up to the scale of 30000 individual antenna elements. The receiver arrays will be located at 50-150 km distance from the illuminators, so that the total system will comprise in the order of 100 000 elements. The volumetric radar imaging capability in an extended spatial area with simultaneous full-vector drift velocities, continuous operation modes, built-in short baseline interferometry capability for imaging sub-beam width scales, real-time data access for applications and extensive data archiving and analysis solutions will provide an unprecedented science and technology application opportunity, well beyond the traditional ground-based ionospheric remote sensing role of the old incoherent scatter radars. EISCAT 3D was accepted on the European Roadmap for Research Infrastructures by the European Strategy Forum on Research Infrastructures in December 2008. The facility will be constructed as a modular concept by year 2015. The first design study of the facility was conducted recently, during 2005-2009 by EISCAT Scientific Association, University of Tromso, Lulea University of Technology, Swedish Institute of Space Physics, Rutherford Appleton Laboratory, and supported by EU FP6 funding. EISCAT Scientific Association operates currently three incoherent scatter radars in Northern Scandinavia on behalf of its associate members in Finland, China, Germany, Japan, Norway, Sweden and United Kingdom, as well as currently supporting partners in France, Russia and Ukraine.
[en] We show that any incoherent qubit channel could be decomposed into four incoherent Kraus operators. The proof consists in showing existence of four incoherent Kraus operators by decomposing the corresponding Choi–Jamiołkowski–Sudarshan matrix. We mention some applications of this optimal decomposition. We also show that the Kraus rank and incoherent rank are different even for qubit channel. (paper)
[en] This paper is devoted to the consideration of neutron scattering on the crystal nuclei based on multiple scattering theories with application of the optical potential. In the approximation of the heavy nucleus the formula is derived for the distribution of the intensity of the scattered incoherent wave. The obtained results are applied to the calculation of the angle of deflection of a neutron in multiple scattering on nucleons of the nucleus.
[en] Using Geant4 toolkit, the differential cross-section and the atomic form factor for coherent scattering of 25.2 heV photons in some tissue - equivalent compounds at 90 degree were calcuated. The results gave good agreement with those calculated theoretically. (author).
[en] Complete text of publication follows. This paper presents an investigation of the subauroral and mid-latitude ionosphere variations in the north eastern region of Asia during stratospheric warming in 2008 and 2009. We used the data from network of vertical and oblique-incidence sounding ionosondes, Irkutsk incoherent scatter (IS) radar and optic instruments of ISTP SB RAS. Irkutsk chirp-sounder and IS radar ran every 1 minute on 24-hour basis from the 18th January until the 17th February, 2008 and from the 22nd January until the 21st February, 2008 to study small-scale and medium-scale disturbances. Observation of airglow near Irkutsk was provided by the zenith photometer that measured intensities of 557.7 nm and 630.0 nm atomic oxygen emissions. Airglow observations were conducted over 2 weeks off the new moon. The experiments on the radio paths Magadan-Irkutsk and Norilsk -Irkutsk were conducted every 4 minutes on 24-hour basis on January 22 - February 21, 2009. The frequency range was from 4 to 30 MHz, the sweep rate used 500 kHz/sec.Vertical sounding stations operated in standard regime. To identify the stratospheric warming events the Berlin Meteorological University data (http://strat-www.met.fu-berlin.de) on stratospheric warming at standard isobaric levels and the atmospheric temperature height profiles measured by the Microwave Limb Sounder (MLS) aboard the EOS Aura spacecraft were used. The increase of wave activity recorded both in low and in upper ionosphere during sudden stratospheric warming. Spectrums of multi-scale variations were derived from the data obtained during the prolonged experiments. We used the spectral analysis based on a modified Fourier transform with varying upper limit. The possible reasons of the ionospheric disturbances and their intensity spatial distribution are discussed. This work was supported by Russian Foundation for Basic Research (grant 08-05-00658).
[en] Myelin is a multilayered proteolipid membrane structure surrounding selected axons in the vertebrate nervous system, which allows the rapid saltatory conduction of nerve impulses. Deficits in myelin formation and maintenance may lead to chronic neurological disease. P2 is an abundant myelin protein from peripheral nerves, binding between two apposing lipid bilayers. We studied the dynamics of the human myelin protein P2 and its mutated P38G variant in hydrated powders using elastic incoherent neutron scattering. The local harmonic vibrations at low temperatures were very similar for both samples, but the mutant protein had increased flexibility and softness close to physiological temperatures. The results indicate that a drastic mutation of proline to glycine at a functional site can affect protein dynamics, and in the case of P2, they may explain functional differences between the two proteins. (authors)
[en] Complete text of publication follows. One of the controversial questions relating to the α-relaxation in glass forming systems is whether this process is of heterogeneous or homogeneous nature or equivalently whether the relaxation function results from a superposition of single exponential processes or is intrinsically non-exponential. In this work this question is discussed using the information provided by incoherent neutron scattering techniques in glass-forming polymers. The results obtained in more than 10 different polymers show that the incoherent intermediate scattering function is well described by a Kohlrausch-Williams-Watts function with a constant shape parameter. Moreover, the Q-dependence of this function approximately follows the Gaussian approximation . These results do not agree with those expected from the heterogeneous picture usually invoked as the origin of the non-exponential behavior of the α-process. It seems that the apparent stretching of the α-relaxation function in glass forming polymers relates dominantly to sublinear diffusion, at least in the mesoscopic timescale covered by neutron scattering . (author)
[en] The thermal self-focusing instability, which manifests itself in the formation of density striations in the ionosphere, is studied. Two separate ionospheric modification experiments were conducted at the National Astronomy and Ionosphere Center (NAIC) in Arecibo, P.R. for the purpose of discerning the spatial dependence of the striations on incident HF power flux and angle between kHF and B. Both experiments made use of the HF heating facility in Islote, P.R., which operated at 5.1 MHz in the O-mode. The ionosphere was overdense to 5.1 MHz in both experiments. The orientation of the striations with respect to the HF heater beam and the earth's magnetic field is also considered. The first experiment was a two part campaign in which maps of the HF heated volume electric field intensity were made. The HF beam was vertical for the first part and tilted 12 degrees to the north for the second part, which allowed for the experimental variation of θ (the angle between kHF and B). The second experiment was the AA-3A rocket of the CR-RES campaign. This rocket injected three clouds of barium into the heated ionosphere, each 20 km apart in altitude, centered on the middle of the HF heated volume. Incoherent Scatter Radar plasma line data and CCD optical data was taken to study the geometry of the evolution of the striations. Ray tracing, ionization modeling, and thermal self-experimental data. Conclusions were made that suggest that the striations are aligned with the HF beam below the HF reflection height and are B field aligned above reflection due to thermal conduction. The experimental data supports Perkins ampersand Valeo's and Cragin ampersand Fejer's theories which both state that minimum striation width decreases with increasing incident power flux. It is also concluded that the barium cloud acts as a divergent lens which focuses HF energy away from the area centered above the cloud