20,661 research outputs found
Research and development program on magnetic electrical conductor, electrical insulation, and bore seal materials - Electrical conductor and electrical insulation materials topical report
Electrical, mechanical, and thermo-physical properties of conductor and insulation materials for application to advanced space electric power system
Ultracold, radiative charge transfer in hybrid Yb ion - Rb atom traps
Ultracold hybrid ion-atom traps offer the possibility of microscopic
manipulation of quantum coherences in the gas using the ion as a probe.
However, inelastic processes, particularly charge transfer can be a significant
process of ion loss and has been measured experimentally for the Yb ion
immersed in a Rb vapour. We use first-principles quantum chemistry codes to
obtain the potential energy curves and dipole moments for the lowest-lying
energy states of this complex. Calculations for the radiative decay processes
cross sections and rate coefficients are presented for the total decay
processes. Comparing the semi-classical Langevin approximation with the quantum
approach, we find it provides a very good estimate of the background at higher
energies. The results demonstrate that radiative decay mechanisms are important
over the energy and temperature region considered. In fact, the Langevin
process of ion-atom collisions dominates cold ion-atom collisions. For spin
dependent processes \cite{kohl13} the anisotropic magnetic dipole-dipole
interaction and the second-order spin-orbit coupling can play important roles,
inducing couplingbetween the spin and the orbital motion. They measured the
spin-relaxing collision rate to be approximately 5 orders of magnitude higher
than the charge-exchange collision rate \cite{kohl13}. Regarding the measured
radiative charge transfer collision rate, we find that our calculation is in
very good agreement with experiment and with previous calculations.
Nonetheless, we find no broad resonances features that might underly a strong
isotope effect. In conclusion, we find, in agreement with previous theory that
the isotope anomaly observed in experiment remains an open question.Comment: 7 figures, 1 table accepted for publication in J. Phys. B: At. Mol.
Opt. Phys. arXiv admin note: text overlap with arXiv:1107.114
Endomorphisms and automorphisms of locally covariant quantum field theories
In the framework of locally covariant quantum field theory, a theory is
described as a functor from a category of spacetimes to a category of
*-algebras. It is proposed that the global gauge group of such a theory can be
identified as the group of automorphisms of the defining functor. Consequently,
multiplets of fields may be identified at the functorial level. It is shown
that locally covariant theories that obey standard assumptions in Minkowski
space, including energy compactness, have no proper endomorphisms (i.e., all
endomorphisms are automorphisms) and have a compact automorphism group.
Further, it is shown how the endomorphisms and automorphisms of a locally
covariant theory may, in principle, be classified in any single spacetime. As
an example, the endomorphisms and automorphisms of a system of finitely many
free scalar fields are completely classified.Comment: v2 45pp, expanded to include additional results; presentation
improved and an error corrected. To appear in Rev Math Phy
Thermal and Non-thermal Plasmas in the Galaxy Cluster 3C 129
We describe new Chandra spectroscopy data of the cluster which harbors the
prototypical "head tail" radio galaxy 3C 129 and the weaker radio galaxy 3C
129.1. We combined the Chandra data with Very Large Array (VLA) radio data
taken at 0.33, 5, and 8 GHz (archival data) and 1.4 GHz (new data). We also
obtained new HI observations at the Dominion Radio Astrophysical Observatory
(DRAO) to measure the neutral Hydrogen column density in the direction of the
cluster with arcminute angular resolution. The Chandra observation reveals
extended X-ray emission from the radio galaxy 3C 129.1 with a total luminosity
of 1.5E+41 erg/s. The X-ray excess is resolved into an extended central source
of ~2 arcsec (1 kpc) diameter and several point sources with an individual
luminosity up to 2.1E+40 erg/s. In the case of the radio galaxy 3C 129, the
Chandra observation shows, in addition to core and jet X-ray emission reported
in an earlier paper, some evidence for extended, diffuse X-ray emission from a
region east of the radio core. The 12 arcsec x 36 arcsec (6 kpc x 17 kpc)
region lies "in front" of the radio core, in the same direction into which the
radio galaxy is moving. We use the radio and X-ray data to study in detail the
pressure balance between the non-thermal radio plasma and the thermal Intra
Cluster Medium (ICM) along the tail of 3C 129 which extends over 15 arcmin (427
kpc). Depending on the assumed lower energy cutoff of the electron energy
spectrum, the minimum pressure of the radio plasma lies a factor of between 10
and 40 below the ICM pressure for a large part of the tail. We discuss several
possibilities to explain the apparent pressure mismatch.Comment: Accepted for publication in MNRAS. Refereed manuscript. 14 pages, 8
figures, additional panel of Fig. 3 shows asymmetric ICM distributio
EC71-799 Engineering the Irrigation Pumping Plant
Extension Circular 71-799: Engineering the irrigation pumping plant; pumps selection, pump drives, setting up the drives, power units, and direction for matching an electric motor to an irrigation pump
Organizing the innovation process : complementarities in innovation networking
This paper contributes to the developing literature on complementarities in organizational design. We test for the existence of complementarities in the use of external networking between stages of the innovation process in a sample of UK and German manufacturing plants. Our evidence suggests some differences between the UK and Germany in terms of the optimal combination of innovation activities in which to implement external networking. Broadly, there is more evidence of complementarities in the case of Germany, with the exception of the product engineering stage. By contrast, the UK exhibits generally strong evidence of substitutability in external networking in different stages, except between the identification of new products and product design and development stages. These findings suggest that previous studies indicating strong complementarity between internal and external knowledge sources have provided only part of the picture of the strategic dilemmas facing firms
Finding Z' bosons coupled preferentially to the third family at CERN LEP and the Fermilab Tevatron
Z' bosons that couple preferentially to the third generation fermions can
arise in models with extended weak (SU(2)xSU(2)) or hypercharge (U(1)xU(1))
gauge groups. We show that existing limits on quark-lepton compositeness set by
the LEP and Tevatron experiments translate into lower bounds of order a few
hundred GeV on the masses of these Z' bosons. Resonances of this mass can be
directly produced at the Tevatron. Accordingly, we explore in detail the limits
that can be set at Run II using the process p pbar -> Z' -> tau tau -> e mu. We
also comment on the possibility of using hadronically-decaying taus to improve
the limits.Comment: LaTeX2e, 24 pages (including title page), 13 figures; version 2:
corrected typographical errors and bad figure placement; version 3: added
references and updated introduction; version 4: changes to compensate for old
latex version on arXiv server; version 5: additional references, and embedded
fonts in eps files for PRD; version 6: corrected some minor typos to address
PRD referee's comment
Anthropomorphizing Science: How Does It Affect the Development of Evolutionary Concepts?
Despite the ubiquitous use of anthropomorphic language to describe biological change in both educational settings and popular science, little is known about how anthropomorphic language influences children’s understanding of evolutionary concepts. In an experimental study, we assessed whether the language used to convey evolutionary concepts influences children’s (5- to 12-year-olds; N = 88) understanding of evolutionary change. Language was manipulated by using three types of narrative, each describing animals’ biological change: (a) need-based narratives, which referenced animals’ basic survival needs; (b) desire-based or anthropomorphic narratives, which referenced animals’ mental states; and (c) scientifically accurate natural selection narratives. Results indicate that the language used to describe evolutionary change influenced children’s endorsement of and use of evolutionary concepts when interpreting that change. Narratives using anthropomorphic language were least likely to facilitate a scientifically accurate interpretation. In contrast, need-based and natural selection language had similar and positive effects, which suggests that need-based reasoning might provide a conceptual scaffold to an evolutionary explanation of biological origins. In sum, the language used to teach evolutionary change impacts conceptual understanding in children and has important pedagogical implications for science education
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