6,439 research outputs found
Anisotropic renormalized fluctuations in the microwave resistivity in YBCO
We discuss the excess conductivity above Tc due to renormalized
order-parameter fluctuations in YBCO at microwave frequencies. We calculate the
effects of the uniaxial anisotropy on the renormalized fluctuations in the
Hartree approximation, extending the isotropic theory developed by Dorsey
[Phys. Rev. B 43, 7575 (1991)]. Measurements of the real part of the microwave
resistivity at 24 and 48 GHz and of the dc resistivity are performed on
different YBCO films. The onset of the superconducting transition and the
deviation from the linear temperature behavior above Tc can be fully accounted
for by the extended theory. According to the theoretical calculation here
presented, a departure from gaussian toward renormalized fluctuations is
observed. Very consistent values of the fundamental parameters (critical
temperature, coherence lenghts, penetration depth) of the superconducting state
are obtained.Comment: RevTex, 8 pages with 5 figures included, to be published in Physical
Review
Mixed-state microwave response in superconducting cuprates
We report measurements of the magnetic-field induced microwave complex
resistivity in REBaCuO thin films, with RE = Y, Sm.
Measurements are performed at 48 GHz by means of a resonant cavity in the
end-wall-replacement configuration. The magnetic field dependence is
investigated by applying a moderate (0.8 T) magnetic field along the c-axis.
The measured vortex state complex resistivity in
YBaCuO and SmBaCuO is
analyzed within the well-known models for vortex dynamics. It is shown that
attributing the observed response to vortex motion alone leads to
inconsistencies in the as-determined vortex parameters (such as the vortex
viscosity and the pinning constant). By contrast, attributing the entire
response to field-induced pair breaking leads to a nearly quantitative
description of the data.Comment: 6 pages, 4 figures, to be published in J. Supercond. as proceedings
of 8th HTSHFF (May 26th-29th, 2004, Begur, Spain
Italy INAF Analysis Center Report
This report summarizes the activity of the Italian INAF VLBI Analysis Center. Our Analysis Center is located in Bologna, Italy and belongs to the Institute of Radioastronomy, which is part of the National Institute of Astrophysics. IRA runs the observatories of Medicina and Noto, where two 32-m VLBI AZ-EL telescopes are situated. This report contains the AC's VLBI data analysis activities and shortly outlines the investigations into the co-locations of space geodetic instruments
Italy INAF Data Center Report
This report summarizes the activities of the Italian INAF VLBI Data Center. Our Data Center is located in Bologna, Italy and belongs to the Institute of Radioastronomy, which is part of the National Institute of Astrophysics
Superoxide reductase from Giardia intestinalis: structural characterization of the first sor from a eukaryotic organism shows an iron centre that is highly sensitive to photoreduction
Superoxide reductase (SOR), which is commonly found in prokaryotic organisms, affords protection from oxidative stress by reducing the superoxide anion to hydrogen peroxide. The reaction is catalyzed at the iron centre, which is highly conserved among the prokaryotic SORs structurally characterized to date. Reported here is the first structure of an SOR from a eukaryotic organism, the protozoan parasite Giardia intestinalis (GiSOR), which was solved at 2.0 Ã… resolution. By collecting several diffraction data sets at 100 K from the same flash-cooled protein crystal using synchrotron X-ray radiation, photoreduction of the iron centre was observed. Reduction was monitored using an online UV-visible microspectrophotometer, following the decay of the 647 nm absorption band characteristic of the iron site in the glutamate-bound, oxidized state. Similarly to other 1Fe-SORs structurally characterized to date, the enzyme displays a tetrameric quaternary-structure arrangement. As a distinctive feature, the N-terminal loop of the protein, containing the characteristic EKHxP motif, revealed an unusually high flexibility regardless of the iron redox state. At variance with previous evidence collected by X-ray crystallography and Fourier transform infrared spectroscopy of prokaryotic SORs, iron reduction did not lead to dissociation of glutamate from the catalytic metal or other structural changes; however, the glutamate ligand underwent X-ray-induced chemical changes, revealing high sensitivity of the GiSOR active site to X-ray radiation damage
Household users cooperation to reduce cost in green mobile networks
The staggering mobile traffic growth is leading to a huge increase of operational costs for Mobile Operators (MOs) due to power supply. In a Smart Grid (SG) scenario, where Demand Response (DR) strategies are widely adopted to better balance the Demand-Supply mismatch, new opportunities arise for MOs, that can receive some monetary rewards for accomplishing the SG requests of periodically increasing or decreasing their energy consumption. This study considers a mobile network that exploits Renewable Energy (RE) to power the BSs and Resource on Demand (RoD) strategies to dynamically adapt the number of active radio resources to the varying traffic demand, in order to better react to the SG requests. On top of this, the purpose of this work is investigating the effects of the cooperation between Household Customers (HCs) engaged in the DR program and the mobile network. Based on a predefined agreement, HCs cooperate with the MO in order to increase its capability to accomplish the SG requests, receiving in return some benefits when stipulating the Internet provisioning contract with the MO. HCs can contribute to achieving the MO goals by means of two techniques. On the one hand, a fraction of the electric loads that are postponed by the HCs when the SG asks for a reduction of the energy consumption can be shifted on behalf of the mobile network, that will receive the corresponding monetary rewards (HC Trade - HCT). On the other hand, HCs can accept to handle some additional mobile traffic, that is moved to their own WiFi Access Points from the BSs, in order to reduce the energy load of the mobile network (WiFi Offloading - WO).Our results show that, although HCT alone provides limited saving in the energy bill due to the poor attitude of HCs to postpone their electric loads, up to 18% of cost saving can be achieved under full HCs cooperation when HCT is combined with WO. The effects of HCs cooperation can be further enhanced by installing larger sized RE generators, allowing to significantly reduce the energy bill up to more than 90%
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