35,952 research outputs found
Long baseline vector determinations and intercomparisons
The East Coast very long baseline interferometry (VLBI) group has performed about 60 experiments over the last 10 years in the process of developing and exploiting advanced VLBI techniques. Of those, the most recent 14 experiments are briefly described
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The effect of pitch span on intonational plateaux
Previous research has indicated that the H (high) of a nuclear accent may be realized as a flat stretch of contour rather than as a single turning point. Both the duration of this plateau and its alignment within the accented syllable are affected by the segmental and prosodic structure of the utterance. The present work investigates whether a non-structural variable, namely pitch span, also affects the realization of the plateau. Speakers replicated all-sonorant utterances in different pitch spans. Results show that both the duration and alignment of the plateau vary with pitch span but in ways different from the way they vary with prosodic structure. Importantly, results also indicate that, when using a proportional measure of alignment, the end of the plateau is anchored within the syllable for each speaker and may be a marker of linguistic structure
The Sinkhorn-Knopp algorithm : convergence and applications
As long as a square nonnegative matrix A contains sufficient nonzero elements, then the Sinkhorn-Knopp algorithm can be used to balance the matrix, that is, to find a diagonal scaling of A that is doubly stochastic. It is known that the convergence is linear, and an upper bound has been given for the rate of convergence for positive matrices. In this paper we give an explicit expression for the rate of convergence for fully indecomposable matrices. We describe how balancing algorithms can be used to give a measure of web page significance. We compare the measure with some well known alternatives, including PageRank. We show that, with an appropriate modi. cation, the Sinkhorn-Knopp algorithm is a natural candidate for computing the measure on enormous data sets
Continued DDT Persistence in Mississippi River Delta Streams: A Case Study
Fish samples representative of several trophic levels were taken from the Wolf and Loosahatchie Rivers of western Tennessee during the early 1980s. Results indicate that DDT, with metabolites DDD and DDE, remains common in fish tissues in these areas and approaches the levels recommended as maxima for human consumption by the U.S. Food and Drug Administration. Samples of top carnivores and forage fishes, particularly the gizzard shad, Dorosoma cepedlanum, commonly exceeded 500 ppb DDE. The results are discussed in light of sediment disturbing activities
Chemical Reactivity of Hydrogen, Nitrogen and Oxygen Atoms at Temperatures Below 100 deg K Semiannual report, 1 Jul. - 31 Dec. 1966
Chemical reactivity of hydrogen, nitrogen, and oxygen atoms at temperatures below 100 deg
Higher Spin Alternating Sign Matrices
We define a higher spin alternating sign matrix to be an integer-entry square
matrix in which, for a nonnegative integer r, all complete row and column sums
are r, and all partial row and column sums extending from each end of the row
or column are nonnegative. Such matrices correspond to configurations of spin
r/2 statistical mechanical vertex models with domain-wall boundary conditions.
The case r=1 gives standard alternating sign matrices, while the case in which
all matrix entries are nonnegative gives semimagic squares. We show that the
higher spin alternating sign matrices of size n are the integer points of the
r-th dilate of an integral convex polytope of dimension (n-1)^2 whose vertices
are the standard alternating sign matrices of size n. It then follows that, for
fixed n, these matrices are enumerated by an Ehrhart polynomial in r.Comment: 41 pages; v2: minor change
The Properties of the Hot Gas in Galaxy Groups and Clusters from 1-D Hydrodynamical Simulations -- I. Cosmological Infall Models
We report the results of 1-D hydrodynamical modelling of the evolution of gas
in galaxy clusters. We have incorporated many of the effects missing from
earlier 1-D treatments: improved modelling of the dark matter and galaxy
distributions, cosmologically realistic evolution of the cluster potential, and
the effects of a multiphase cooling flow. The model utilises a fairly standard
1-D Lagrangian hydrodynamical code to calculate the evolution of the
intracluster gas. This is coupled to a theoretical model for the growth of dark
matter density perturbations. The main advantages of this treatment over 3-D
codes are (1) improved spatial resolution within the cooling flow region, (2)
much faster execution time, allowing a fuller exploration of parameter space,
and (3) the inclusion of additional physics.
In the present paper, we explore the development of infall models -- in which
gas relaxes into a deepening potential well -- covering a wide range of cluster
mass scales. We find that such simple models reproduce many of the global
properties of observed clusters. Very strong cooling flows develop in these 1-D
cluster models. In practice, disruption by major mergers probably reduces the
cooling rate in most clusters. The models overpredict the gas fraction in low
mass systems, indicating the need for additional physical processes, such as
preheating or galaxy winds, which become important on small mass scales.Comment: 38 pages, 21 encapsulated postscript figures, accepted for
publication in MNRA
Using a theory of mind to find best responses to memory-one strategies
Memory-one strategies are a set of Iterated Prisoner's Dilemma strategies
that have been praised for their mathematical tractability and performance
against single opponents. This manuscript investigates best response memory-one
strategies with a theory of mind for their opponents. The results add to the
literature that has shown that extortionate play is not always optimal by
showing that optimal play is often not extortionate. They also provide evidence
that memory-one strategies suffer from their limited memory in multi agent
interactions and can be out performed by optimised strategies with longer
memory. We have developed a theory that has allowed to explore the entire space
of memory-one strategies. The framework presented is suitable to study
memory-one strategies in the Prisoner's Dilemma, but also in evolutionary
processes such as the Moran process, Furthermore, results on the stability of
defection in populations of memory-one strategies are also obtained
The Distribution of \u3ci\u3eCorydalus Cornutus\u3c/i\u3e (Linnaeus) and \u3ci\u3eNigronia Serricornis (Say) (Megaloptera: Corydalidae) in Michigan
(excerpt)
The distribution of the hellgrammite [Corydalus cornutus (Linnaeus)] and the sawcombed fishfly [Nigronia serricornis (Say)] in Michigan was determined as part of an investigation of the biology of these large Megalopterans (Knight and Simmons, 1975a, 1975b). Megalopteran larvae are some of the largest aquatic insects, with a maximum length of approximately 84 mm. They are robust larvae with paired lateral abdominal appendages on segments 1-8 and a pair of anal prolegs bearing two strong hooks. They are fiercely predaceous and generally insectivorous, feeding chiefly on larvae of Simulium, Cheumatopsyche, Hydropsyche and Chironomidae, but eating almost anything they can subdue, including their own kind (Chandler, 1956; Stewart et al., 1973)
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