3,596 research outputs found
Overview of the NASA YF-12 program
The history of NASA's interest in supersonic research and the agency's contribution to the development of the YF 12 aircraft is reviewed as well as the program designed to use that aircraft as a test bed for supersonic cruise research. Topics cover elements of the program, project organization, and major accomplishments
Improved Ar(II) transition probabilities
Precise Ar(II) branching ratios have been measured on a high current hollow cathode with a 1-m Fourier transform spectrometer. Absolute transition probabilities for 11 Ar(II) lines were calculated from these branching ratios and lifetime measurements published by Mohamed et al. For the prominent 4806 Å line, the present result is Aik = 7.12×107s-1 ±2.8%, which is in excellent agreement with recent literature data derived from pure argon diagnostics, two-wavelength-interferometry, and Hβ-diagnostics when using the theoretical data of Vidal et al
Oscillator strengths of Ti II from combined hook and emission measurements
It is demonstrated that a large set of accurate oscillator strengths of Ti II can be determined from a combination of hook and emission measurements without any assumption concerning the plasma state. Modified cascaded arcs and hollow cathode discharges have been used as plasma light sources for both hook and emission measurements. The relative f values have been converted to an absolute scale by means of literature data. The overall uncertainties of the f values are about 13-25%. Comparisons with other experimental and theoretical data are made which indicate excellent to fair agreement. Only for one of the published data sets has a wavelength-dependent discrepancy of up to a factor of two been found
Regular patterns, substitudes, Feynman categories and operads
We show that the regular patterns of Getzler (2009) form a 2-category biequivalent to the 2-category of substitudes of Day and Street (2003), and that the Feynman categories of Kaufmann and Ward (2013) form a 2-category biequivalent to the 2-category of coloured operads (with invertible 2-cells). These biequivalences induce equivalences between the corresponding categories of algebras. There are three main ingredients in establishing these biequivalences. The first is a strictification theorem (exploiting Power's General Coherence Result) which allows to reduce to the case where the structure maps are identity-on-objects functors and strict monoidal. Second, we subsume the Getzler and Kaufmann-Ward hereditary axioms into the notion of Guitart exactness, a general condition ensuring compatibility between certain left Kan extensions and a given monad, in this case the free-symmetric-monoidal-category monad. Finally we set up a biadjunction between substitudes and what we call pinned symmetric monoidal categories, from which the results follow as a consequence of the fact that the hereditary map is precisely the counit of this biadjunction
Monads in Double Categories
We extend the basic concepts of Street's formal theory of monads from the
setting of 2-categories to that of double categories. In particular, we
introduce the double category Mnd(C) of monads in a double category C and
define what it means for a double category to admit the construction of free
monads. Our main theorem shows that, under some mild conditions, a double
category that is a framed bicategory admits the construction of free monads if
its horizontal 2-category does. We apply this result to obtain double
adjunctions which extend the adjunction between graphs and categories and the
adjunction between polynomial endofunctors and polynomial monads.Comment: 30 pages; v2: accepted for publication in the Journal of Pure and
Applied Algebra; added hypothesis in Theorem 3.7 that source and target
functors preserve equalizers; on page 18, bottom, in the statement concerning
the existence of a left adjoint, "if and only if" was replaced by "a
sufficient condition"; acknowledgements expande
Double Adjunctions and Free Monads
We characterize double adjunctions in terms of presheaves and universal
squares, and then apply these characterizations to free monads and
Eilenberg--Moore objects in double categories. We improve upon our earlier
result in "Monads in Double Categories", JPAA 215:6, pages 1174-1197, 2011, to
conclude: if a double category with cofolding admits the construction of free
monads in its horizontal 2-category, then it also admits the construction of
free monads as a double category. We also prove that a double category admits
Eilenberg--Moore objects if and only if a certain parameterized presheaf is
representable. Along the way, we develop parameterized presheaves on double
categories and prove a double-categorical Yoneda Lemma.Comment: 52 page
Operational experiences and characteristics of the M2-F2 lifting body flight control system
M2-F2 lifting body flight control syste
Global trends in infectious diseases at the wildlife–livestock interface
The role and significance of wildlife–livestock interfaces in disease ecology has largely been neglected, despite recent interest in animals as origins of emerging diseases in humans. Scoping review methods were applied to objectively assess the relative interest by the scientific community in infectious diseases at interfaces between wildlife and livestock, to characterize animal species and regions involved, as well as to identify trends over time. An extensive literature search combining wildlife, livestock, disease, and geographical search terms yielded 78,861 publications, of which 15,998 were included in the analysis. Publications dated from 1912 to 2013 and showed a continuous increasing trend, including a shift from parasitic to viral diseases over time. In particular there was a significant increase in publications on the artiodactyls–cattle and bird–poultry interface after 2002 and 2003, respectively. These trends could be traced to key disease events that stimulated public interest and research funding. Among the top 10 diseases identified by this review, the majority were zoonoses. Prominent wildlife–livestock interfaces resulted largely from interaction between phylogenetically closely related and/or sympatric species. The bird–poultry interface was the most frequently cited wildlife–livestock interface worldwide with other interfaces reflecting regional circumstances. This review provides the most comprehensive overview of research on infectious diseases at the wildlife–livestock interface to date
Model independent analysis of nearly L\'evy correlations
A model-independent method for the analysis of the two-particle short-range
correlations is presented, that can be utilized to describe e.g. Bose-Einstein
(HBT), dynamical (ridge) or other correlation functions, that have a nearly
L\'evy or streched exponential shape. For the special case of L\'evy exponent
alpha = 1, the earlier Laguerre expansions are recovered, for the alpha = 2
special case, a new expansion method is obtained for nearly Gaussian
correlation functions. Multi-dimensional L\'evy expansions are also introduced
and their potential application to analyze rigde correlation data is discussed
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