3,442 research outputs found
Vertices and the CJT Effective Potential
The Cornwall-Jackiw-Tomboulis effective potential is modified to include a
functional dependence on the fermion-gauge particle vertex, and applied to a
quark confining model of chiral symmetry breaking.Comment: 10 pages (latex), PURD-TH-93-1
Flexible and practical modeling of animal telemetry data: hidden Markov models and extensions
We discuss hidden Markov-type models for fitting a variety of multistate random walks to wildlife movement data. Discrete-time hidden Markov models (HMMs) achieve considerable computational gains by focusing on observations that are regularly spaced in time, and for which the measurement error is negligible. These conditions are often met, in particular for data related to terrestrial animals, so that a likelihood-based HMM approach is feasible. We describe a number of extensions of HMMs for animal movement modeling, including more flexible state transition models and individual random effects (fitted in a non-Bayesian framework). In particular we consider so-called hidden semi-Markov models, which may substantially improve the goodness of fit and provide important insights into the behavioral state switching dynamics. To showcase the expediency of these methods, we consider an application of a hierarchical hidden semi-Markov model to multiple bison movement paths
The Temporal and Spatial Scale of Microevolution: Fine-scale Color Pattern Variation in the Lake Erie Watersnake
Question: What is the temporal and spatial scale of microevolution?
Hypotheses: The combined effects of natural selection and gene flow result in variation in
heritable traits on fine spatial and geographic scales.
Organism: The Lake Erie watersnake, Nerodia sipedon insularum.
Field site: US and Canadian islands in western Lake Erie.
Methods: We tested for variation in colour pattern frequency within islands, among islands,
and over time using data from nearly annual censuses conducted since 1980, museum
specimens, and published sources. We compared FST for a presumptive major colour pattern
locus to FST for allozyme loci to determine whether spatial variation exceeded that expected by
chance. We computed effective population size (Ne) based on temporal frequency changes in
presumptive colour pattern alleles to determine whether temporal variation exceeded that
expected by chance (Ne significantly less than ∞).
Conclusions: Morph frequencies did not differ significantly within islands or between
islands separated by short distances. Morph frequencies did sometimes differ significantly
among distant islands and among sampling periods from 1980 to the present, but no more than
expected by chance. In contrast, a marked change in morph frequency occurred between
historic (prior to 1961) and recent (1980–2003) samples. Possible mechanisms include changes
in the strength of selection (due to changes in predator assemblages and visual environments)
and rates of gene flow (due to changes in island watersnake population size)
The actively controlled jet in crossflow
This study quantifies the dynamics of actuation for the temporally forced, round gas jet injected transversely into a crossflow, and incorporates these dynamics in developing a methodology for open loop jet control. A linear model for the dynamics of the forced jet actuation is used to develop a dynamic compensator for the actuator. When the compensator is applied, it allows the jet to be forced in a manner which results in a more precisely prescribed, temporally varying exit velocity, the RMS amplitude of perturbation of which can be made independent of the forcing frequency. Use of the compensator allows straightforward comparisons among different conditions for jet excitation. Clear identification can be made of specific excitation frequencies and characteristic temporal pulse widths which optimize transverse jet penetration and spread through the formation of distinct, deeply penetrating vortex structures
A pearl on SAT solving in Prolog
A succinct SAT solver is presented that exploits the control provided by delay declarations to implement watched literals and unit propagation. Despite its brevity the solver is surprisingly powerful and its elegant use of Prolog constructs is presented as a programming pearl
Livestock water needs in pastoral Africa in relation to climate and forage
Discusses livestock water needs and the variation of water dependence in dif. circumstance, mentioning body water functions; physiological aspects of water balance; channels of gain & loss; and factors affecting water balance, particularly energy production, thermoregulation and water availability. Examines energy and water use, as well as water & livestock development in pastoral areas of Africa
Microarray analyses demonstrate the involvement of type i interferons in psoriasiform pathology development in D6-deficient mice
The inflammatory response is normally limited by mechanisms regulating its resolution. In the absence of resolution, inflammatory pathologies can emerge, resulting in substantial morbidity and mortality. We have been studying the D6 chemokine scavenging receptor, which played an indispensable role in the resolution phase of inflammatory responses and does so by facilitating removal of inflammatory CC chemokines. In D6-deficient mice, otherwise innocuous cutaneous inflammatory stimuli induce a grossly exaggerated inflammatory response that bears many similarities to human psoriasis. In the present study, we have used transcriptomic approaches to define the molecular make up of this response. The data presented highlight potential roles for a number of cytokines in initiating and maintaining the psoriasis-like pathology. Most compellingly, we provide data indicating a key role for the type I interferon pathway in the emergence of this pathology. Neutralizing antibodies to type I interferons are able to ameliorate the psoriasis-like pathology, confirming a role in its development. Comparison of transcriptional data generated from this mouse model with equivalent data obtained from human psoriasis further demonstrates the strong similarities between the experimental and clinical systems. As such, the transcriptional data obtained in this preclinical model provide insights into the cytokine network active in exaggerated inflammatory responses and offer an excellent tool to evaluate the efficacy of compounds designed to therapeutically interfere with inflammatory processes
Search for Lepton Flavour Violation in the Decay tau -> mu gamma
A search for the lepton flavour violating decay tau -> mu gamma has been
performed using 221.4/fb of data collected at an e+e- centre-of-mass energy of
10.58 GeV with the BABAR detector at the PEP-II storage ring. The search has an
efficiency of (7.45+/-0.65)% for an expected background level of 6.2+/-0.5
events. In the final sample 4 candidate events are selected. As there is no
evidence for a signal in this data, for this preliminary result we set an upper
limit of BR(tau -> mu gamma) < 9 x 10^-8 at 90%CL using the method of Feldman
and Cousins.Comment: 7 pages, 3 encapsulated postscript figures, uses espcrc2.st
Enigma of ultraluminous X-ray sources may be resolved by 3D-spectroscopy (MPFS data)
The ultraluminous X-ray sources (ULXs) were isolated in external galaxies for
the last 5 years. Their X-ray luminosities exceed 100-10000 times those of
brightest Milky Way black hole binaries and they are extremely variable. There
are two models for the ULXs, the best black hole candidates. 1. They are
supercritical accretion disks around a stellar mass black hole like that in
SS433, observed close to the disk axes. 2. They are Intermediate Mass Black
Holes (of 100-10000 solar masses). Critical observations which may throw light
upon the ULXs nature come from observations of nebulae around the ULXs. We
present results of 3D-spectroscopy of nebulae around several ULXs located in
galaxies at 3-6 Mpc distances. We found that the nebulae to be powered by their
central black holes. The nebulae are shocked and dynamically perturbed probably
by jets. The nebulae are compared with SS433 nebula (W50).Comment: Proceedings of the ESO and Euro3D Workshop "Science Perspectives for
3D Spectroscopy", Garching (Germany), October 10-14, 2005. M. Kissler-Patig,
M.M. Roth and J.R. Walsh (eds.
Ab-initio simulation of high-temperature liquid selenium
Ab initio molecular dynamics simulation is used to investigate the structure
and dynamics of liquid Se at temperatures of 870 and 1370~K. The calculated
static structure factor is in excellent agreement with experimental data. The
calculated radial distribution function gives a mean coordination number close
to 2, but we find a significant fraction of one-fold and three-fold atoms,
particularly at 1370~K, so that the chain structure is considerably disrupted.
The self-diffusion coefficient has values (~m~s)
typical of liquid metals.Comment: 10 pages, 4 Poscript figures, uses REVTE
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