128 research outputs found
Simulations of secondary Farley-Buneman instability driven by a kilometer-scale primary wave: anomalous transport and formation of flat-topped electric fields
Since the 1950s, high frequency and very high frequency radars near the magnetic equator have frequently detected strong echoes caused ultimately by the FarleyâBuneman instability (FBI) and the gradient drift instability (GDI). In the 1980s, coordinated rocket and radar campaigns made the astonishing observation of flatâtopped electric fields coincident with both meterâscale irregularities and the passage of kilometerâscale waves. The GDI in the daytime E region produces kilometerâscale primary waves with polarization electric fields large enough to drive meterâscale secondary FBI waves. The meterâscale waves propagate nearly vertically along the largeâscale troughs and crests and act as VHF tracers for the largeâscale dynamics. This work presents a set of hybrid numerical simulations of secondary FBIs, driven by a primary kilometerâscale GDIâlike wave. Meterâscale density irregularities develop in the crest and trough of the kilometerâscale wave, where the total electric field exceeds the FBI threshold, and propagate at an angle near the direction of total Hall drift determined by the combined electric fields. The meterâscale irregularities transport plasma across the magnetic field, producing flatâtopped electric fields similar to those observed in rocket data and reducing the largeâscale wave electric field to just above the FBI threshold value. The selfâconsistent reduction in driving electric field helps explain why echoes from the FBI propagate near the plasma acoustic speed.NSF grants PHY-1500439 and AGS-1755350 and NASA grant NNX14AI13G supported the research presented in this work. This work used TACC and XSEDE computational resources supported by the National Science Foundation grant ACI-1053575. This paper did not use any data; simulation runs are archived on the TACC Ranch system. The authors thank one anonymous reviewer for helpful comments. (PHY-1500439 - NSF; AGS-1755350 - NSF; NNX14AI13G - NASA; ACI-1053575 - National Science Foundation)Published version2019-07-0
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
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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Factorization of absolutely continuous polynomials
In this paper we study the ideal of dominated
(p,s)-continuous polynomials, that extend
the nowadays well known ideal of
p-dominated polynomials to the more general setting
of the interpolated ideals of polynomials. We give the polynomial version of Pietsch s
factorization Theorem for this new ideal. Our factorization theorem requires new techniques inspired in the theory of Banach lattices.The authors thank the referee for his/her suggestions. D. Achour acknowledges with thanks the support of the Ministere de l'Enseignament Superieur et de la Recherche Scientifique (Algeria) under project PNR 8-U28-181. E. Dahia acknowledges with thanks the support of the Ministere de l'Enseignament Superieur et de la Recherche Scientifique (Algeria) under grant 170/PGRS/C.U.K.M(2012) for short term stage. 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.Achour, D.; Dahia, E.; Rueda, P.; SĂĄnchez PĂ©rez, EA. (2013). Factorization of absolutely continuous polynomials. Journal of Mathematical Analysis and Applications. 405:259-270. https://doi.org/10.1016/j.jmaa.2013.03.063S25927040
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A creative destruction approach to replication: implicit work and sex morality across cultures
How can we maximize what is learned from a replication study? In the creative destruction approach to replication, the original hypothesis is compared not only to the null hypothesis, but also to predictions derived from multiple alternative theoretical accounts of the phenomenon. To this end, new populations and measures are included in the design in addition to the original ones, to help determine which theory best accounts for the results across multiple key outcomes and contexts. The present pre-registered empirical project compared the Implicit Puritanism account of intuitive work and sex morality to theories positing regional, religious, and social class differences; explicit rather than implicit cultural differences in values; self-expression vs. survival values as a key cultural fault line; the general moralization of work; and false positive effects. Contradicting Implicit Puritanism's core theoretical claim of a distinct American work morality, a number of targeted findings replicated across multiple comparison cultures, whereas several failed to replicate in all samples and were identified as likely false positives. No support emerged for theories predicting regional variability and specific individual-differences moderators (religious affiliation, religiosity, and education level). Overall, the results provide evidence that work is intuitively moralized across cultures
Creative destruction in science
Drawing on the concept of a gale of creative destruction in a capitalistic economy, we argue that initiatives to assess the robustness of findings in the organizational literature should aim to simultaneously test competing ideas operating in the same theoretical space. In other words, replication efforts should seek not just to support or question the original findings, but also to replace them with revised, stronger theories with greater explanatory power. Achieving this will typically require adding new measures, conditions, and subject populations to research designs, in order to carry out conceptual tests of multiple theories in addition to directly replicating the original findings. To illustrate the value of the creative destruction approach for theory pruning in organizational scholarship, we describe recent replication initiatives re-examining culture and work morality, working parents\u2019 reasoning about day care options, and gender discrimination in hiring decisions.
Significance statement
It is becoming increasingly clear that many, if not most, published research findings across scientific fields are not readily replicable when the same method is repeated. Although extremely valuable, failed replications risk leaving a theoretical void\u2014 reducing confidence the original theoretical prediction is true, but not replacing it with positive evidence in favor of an alternative theory. We introduce the creative destruction approach to replication, which combines theory pruning methods from the field of management with emerging best practices from the open science movement, with the aim of making replications as generative as possible. In effect, we advocate for a Replication 2.0 movement in which the goal shifts from checking on the reliability of past findings to actively engaging in competitive theory testing and theory building.
Scientific transparency statement
The materials, code, and data for this article are posted publicly on the Open Science Framework, with links provided in the article
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