176 research outputs found
An inhibitory effect of D-Mannoheptulose on lactate formation in human whole blood in vitro
NumeraciĂłn errĂłnea en el original
Effects of electrojet turbulence on a magnetosphere-ionosphere simulation of a geomagnetic storm
Ionospheric conductance plays an important role in regulating the response of the magnetosphereâionosphere system to solar wind driving. Typically, models of magnetosphereâionosphere coupling include changes to ionospheric conductance driven by extreme ultraviolet ionization and electron precipitation. This paper shows that effects driven by the FarleyâBuneman instability can also create significant enhancements in the ionospheric conductance, with substantial impacts on geospace. We have implemented a method of including electrojet turbulence (ET) effects into the ionospheric conductance model utilized within geospace simulations. Our particular implementation is tested with simulations of the LyonâFedderâMobarry global magnetosphere model coupled with the Rice Convection Model of the inner magnetosphere. We examine the impact of including ETâmodified conductances in a case study of the geomagnetic storm of 17 March 2013. Simulations with ET show a 13% reduction in the cross polar cap potential at the beginning of the storm and up to 20% increases in the Pedersen and Hall conductance. These simulation results show better agreement with Defense Meteorological Satellite Program observations, including capturing features of subauroral polarization streams. The fieldâaligned current (FAC) patterns show little differences during the peak of storm and agree well with Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) reconstructions. Typically, the simulated FAC densities are stronger and at slightly higher latitudes than shown by AMPERE. The inner magnetospheric pressures derived from TsyganenkoâSitnov empirical magnetic field model show that the inclusion of the ET effects increases the peak pressure and brings the results into better agreement with the empirical model.This material is based upon work supported by NASA grants NNX14AI13G, NNX13AF92G, and NNX16AB80G. The National Center for Atmospheric Research is sponsored by the National Science Foundation. This work used the XSEDE and TACC computational facilities, supported by National Science Foundation grant ACI-1053575. We would like to acknowledge high-performance computing support from Yellowstone (ark:/85065/d7wd3xhc) provided by NCAR's Computational and Information Systems Laboratory, sponsored by the National Science Foundation. We thank the AMPERE team and the AMPERE Science Center for providing the Iridium derived data products. All model output, simulation codes, and analysis routines are being preserved on the NCAR High-Performance Storage System and will be made available upon written request to the lead author of this publication. (NNX14AI13G - NASA; NNX13AF92G - NASA; NNX16AB80G - NASA; National Science Foundation; ACI-1053575 - National Science Foundation
Propagation of gamma rays and production of free electrons in air
A new concept of remote detection of concealed radioactive materials has been
recently proposed \cite{Gr.Nusin.2010}-\cite{NusinSprangle}. It is based on the
breakdown in air at the focal point of a high-power beam of electromagnetic
waves produced by a THz gyrotron. To initiate the avalanche breakdown, seed
free electrons should be present in this focal region during the
electromagnetic pulse. This paper is devoted to the analysis of production of
free electrons by gamma rays leaking from radioactive materials. Within a
hundred meters from the radiation source, the fluctuating free electrons appear
with the rate that may exceed significantly the natural background ionization
rate. During the gyrotron pulse of about 10 microsecond length, such electrons
may seed the electric breakdown and create sufficiently dense plasma at the
focal region to be detected as an unambiguous effect of the concealed
radioactive material.Comment: 27 pages, 10 figure
A fibered description of the vector-valued spectrum
For Banach spaces X and Y we study the vector-valued spectrum (Formula presented.), that is the set of non null algebra homomorphisms from (Formula presented.) to (Formula presented.), which is naturally projected onto the closed unit ball of (Formula presented.). The aim of this article is to describe the fibers defined by this projection, searching for analytic balls and considering Gleason parts.Fil: Dimant, Veronica Isabel. Universidad de San AndrĂ©s. Departamento de MatemĂĄticas y Ciencias; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Singer, JoaquĂn Camilo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de MatemĂĄtica; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Ciudad Universitaria. Instituto de Investigaciones MatemĂĄticas "Luis A. SantalĂł". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones MatemĂĄticas "Luis A. SantalĂł"; Argentin
The mediating effect of task presentation on collaboration and children's acquisition of scientific reasoning
There has been considerable research concerning peer interaction and the acquisition of children's scientific reasoning. This study investigated differences in collaborative activity between pairs of children working around a computer with pairs of children working with physical apparatus and related any differences to the development of children's scientific reasoning. Children aged between 9 and 10 years old (48 boys and 48 girls) were placed into either same ability or mixed ability pairs according to their individual, pre-test performance on a scientific reasoning task. These pairs then worked on either a computer version or a physical version of Inhelder and Piaget's (1958) chemical combination task. Type of presentation was found to mediate the nature and type of collaborative activity. The mixed-ability pairs working around the computer talked proportionally more about the task and management of the task; had proportionally more transactive discussions and used the record more productively than children working with the physical apparatus. Type of presentation was also found to mediated children's learning. Children in same ability pairs who worked with the physical apparatus improved significantly more than same ability pairs who worked around the computer. These findings were partially predicted from a socio-cultural theory and show the importance of tools for mediating collaborative activity and collaborative learning
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Direct detection of alpha synuclein oligomers in vivo
Background: Rat models of Parkinsonâs disease are widely used to elucidate the mechanisms underlying disease etiology or to investigate therapeutic approaches. Models were developed using toxins such as MPTP or 6-OHDA to specifically target dopaminergic neurons resulting in acute neuronal loss in the substantia nigra or by using viral vectors to induce the specific and gradual expression of alpha synuclein in the substantia nigra. The detection of alpha- synuclein oligomers, the presumed toxic species, in these models and others has been possible using only indirect biochemical approaches to date. Here we coinjected AAVs encoding alpha-synuclein fused to the N- or C-terminal half of VenusYFP in rat substantia nigra pars compacta and describe for the first time a novel viral vector rodent model with the unique ability to directly detect and track alpha synuclein oligomers ex vivo and in vivo. Results: Viral coinjection resulted in widespread VenusYFP signal within the nigrostriatal pathway, including cell bodies in the substantia nigra and synaptic accumulation in striatal terminals, suggestive of in vivo alpha-synuclein oligomers formation. Transduced rats showed alpha-synuclein induced dopaminergic neuron loss in the substantia nigra, the appearance of dystrophic neurites, and gliosis in the striatum. Moreover, we have applied in vivo imaging techniques in the living mouse to directly image alpha-synuclein oligomers in the cortex. Conclusion: We have developed a unique animal model that provides a tool for the Parkinsonâs disease research community with which to directly detect alpha- synuclein oligomers in vivo and screen therapeutic approaches targeting alpha-synuclein oligomers
Comparison of predictive estimates of highâlatitude electrodynamics with observations of globalâscale Birkeland currents
Two of the geomagnetic storms for the Space Weather Prediction Center Geospace Environment Modeling challenge occurred after data were first acquired by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). We compare Birkeland currents from AMPERE with predictions from four models for the 4â5 April 2010 and 5â6 August 2011 storms. The four models are the Weimer (2005b) fieldâaligned current statistical model, the LyonâFedderâMobarry magnetohydrodynamic (MHD) simulation, the Open Global Geospace Circulation Model MHD simulation, and the Space Weather Modeling Framework MHD simulation. The MHD simulations were run as described in Pulkkinen et al. (2013) and the results obtained from the Community Coordinated Modeling Center. The total radial Birkeland current, ITotal, and the distribution of radial current density, Jr, for all models are compared with AMPERE results. While the total currents are well correlated, the quantitative agreement varies considerably. The Jr distributions reveal discrepancies between the models and observations related to the latitude distribution, morphologies, and lack of nightside current systems in the models. The results motivate enhancing the simulations first by increasing the simulation resolution and then by examining the relative merits of implementing more sophisticated ionospheric conductance models, including ionospheric outflows or other omitted physical processes. Some aspects of the system, including substorm timing and location, may remain challenging to simulate, implying a continuing need for realâtime specification.Key PointsPresents the first comparison between observed fieldâaligned currents and models previously evaluated for space weather operational useThe model and observed integrated currents are well correlated, but the ratio between them ranges from 1/3 to 3The 2âD current densities are weakly correlated with observations implying significant areas for improvements in the modelsPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136469/1/swe20415_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136469/2/swe20415.pd
Modeling Ionospheric Absorption Modified by Anomalous Heating During Substorms
Abstract. Riometers monitor the changes in ionospheric conductivity by measuring the absorption of very high frequency radio noise of galactic origin passing through the ionosphere. In this Letter the absorption of radio signals by a thin layer of ionospheric plasma, produced by ionization due to energetic precipitating electrons, is modeled by taking into account strong turbulent heating caused by instabilities. The precipitating electron population is obtained from a global MHD simulation of the magnetosphere, along with the electric fields which excite the Farley-Buneman instability and lead to turbulent electron heating. A comparison, the first of its kind, of the data from polar and sub-auroral riometers for the magnetic cloud event of January 10, 1997 shows good agreement. The ionospheric conductance modified by turbulent electron heating can be used to improve the magnetosphereionosphere coupling in the current global MHD models
Surveying the spirit of absolute summability on multilinear operators and homogeneous polynomials
[EN] We draw a fundamental compendium of the most valuable results of the theory
of summing linear operators and detail those that are not shared by known multilinear and
polynomial extensions of absolutely summing linear operators. The lack of such results in the
theory of non-linear summing operators justifies the introduction of a class of polynomials
and multilinear operators that satisfies at once all related non-linear results. Surprisingly
enough, this class, defined by means of a summing inequality, happens to be the well known
ideal of composition with a summing operator.D. Pellegrino acknowledges with thanks the support of CNPq Grant 401735/2013-3-PVE (Linha 2)-Brazil. P. Rueda acknowledges with thanks the support of the Ministerio de Economia y Competitividad (Spain) MTM2011-22417. E. A. Sanchez Perez acknowledges with thanks the support of the Ministerio de Economia y Competitividad (Spain) MTM2012-36740-C02-02.Pellegrino, D.; Rueda, P.; SĂĄnchez PĂ©rez, EA. (2016). Surveying the spirit of absolute summability on multilinear operators and homogeneous polynomials. Revista de la Real Academia de Ciencias Exactas FĂsicas y Naturales Serie A MatemĂĄticas. 110(1):285-302. https://doi.org/10.1007/s13398-015-0224-8S2853021101Achour, D., Dahia, E., Rueda, P., SĂĄnchez-PĂ©rez, E.A.: Factorization of absolutely continuous polynomials. J. Math. Anal. Appl. 405(1), 259â270 (2013)Albiac, F., Kalton, N.: Topics in Banac Space Theory. 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