Perceptual Fidelity for Digital Color Imagery

The problem of measuring the fidelity of digital color images in a manner that corresponds to human perceptual assessments is addressed. Experiments are performed to validate human visual system (HVS) models, which provide access to a \u27perceptual space\u27 in which visual distortions may be measured, and then a model is proposed for assessing the perceptual fidelity of digital color image. Color Mach bands are produced in the first experiment, demonstrating that, as in the brightness channel, low spatial frequency attenuation occurs in the chromatic channels of the HVS. In the second experiment, a correlation between the chromatic channels of the HVS model and color discrimination axes of color blind observers is demonstrated. Removing variation from one of the chromatic channels of a natural image produces a color-distorted image which the color blind subjects cannot distinguish from the original. Removing variation from the other chromatic channel produces an image that appears colorful to normally-sighted observers, but monochrome to the color blind observers. The third experiment shows that a Gabor filter-based HVS model produces illusory contours in several illusory contour stimuli. These results provide a unique validation of multiple-channel HVS models which process the image in multiple spatial frequency bands that are tuned to match measured sensitivities of neurons in the primary visual cortex of cats and monkeys. Finally, the multiple-channel processing used in the illusory contour experiment is combined with the color vision model from the first two experiments to produce a multiple-channel, color HVS model for measuring perceptual fidelity of color images. A demonstration of the model shows that the structure of the new model is correct. However, inaccurate parameter values for the multiple-channel processing of the chromatic channels cause over-prediction of visible differences in these channels

Narrow Line Cooling: Finite Photon Recoil Dynamics

We present an extensive study of the unique thermal and mechanical dynamics for narrow-line cooling on the 1S0 - 3P1 88Sr transition. For negative detuning, trap dynamics reveal a transition from the semiclassical regime to the photon-recoil-dominated quantum regime, yielding an absolute minima in the equilibrium temperature below the single-photon recoil limit. For positive detuning, the cloud divides into discrete momentum packets whose alignment mimics lattice points on a face-centered-cubic crystal. This novel behavior arises from velocity selection and "positive feedback" acceleration due to a finite number of photon recoils. Cooling is achieved with blue-detuned light around a velocity where gravity balances the radiative force.Comment: 4 pages, 3 figures, Phys. Rev. Lett., in pres

Energy Flow through the Marine Ecosystem of the Lancaster Sound Region, Arctic Canada

This paper synthesizes the trophic dynamics of a Canadian arctic marine ecosystem in so far as it is known, using new data on primary production, zooplankton, the bivalve Mya truncata, and arctic cod (Boreogadus saida), as well as literature values for marine mammals and seabirds. The 98,000 sq km region has a high rate of primary production relative to other parts of arctic Canada. About 60 g C/sq. m are fixed annually, of which approximately 90% is contributed by phytoplankton, 10% by ice algae, and 1% by kelp. Phytoplankton production is twofold higher along the south coast of Cornwallis Island than elsewhere in Barrow Strait. Four copepod species, of which Pseudocalanus acuspes is the most important energetically, graze about one-third of the phytoplankton production. Bivalves maintain high biomass but low energy flow, acting as sedimenting agents. Arctic cod is a major component, with 125,000 tonnes being consumed by marine mammals and 23,000 tonnes by seabirds annually. Our hydro-acoustic estimate for mean arctic cod density, 0.0022 fish/sq. m, is probably too low, partly because we have been unable to quantify dense aggregations of schooling fish. The ecological efficiency of ringed seal is near maximum, with 5% of ringed seal ingestion going to bears and man as seal flesh. The data on total kill and prey consumption in whales and birds is incomplete because they migrate out of the Lancaster Sound region in winter. The food chain is very long, with bears occupying the fifth trophic level; this is reflected by high biomagnification factors for persistent lipophilic pollutants such as PCBs. There are major data gaps for some zooplankton and most of the benthos, as well as for winter populations and energetics. This trophic analysis is therefore incomplete and efficiencies for entire trophic levels cannot be calculated.Key words: seals, whales, seabirds, benthos, zooplankton, phytoplankton, primary production, secondary production, harvest, yieldRÉSUMÉ. Cet article résume la dynamique trophique de l’écosystème marin dans le Canada arctique dans la mesure où il est connu, en utilisant de nouvelles données sur la production primaire, le zooplancton, le bivalve Mya truncata, et la morue polaire (Boreogadus saida), ainsi que les valeurs trouvées dans la documentation sur les mammifères et les oiseaux marins. Cette région d’une superficie de 98 000 km2 possède un taux élevé de production primaire par rapport à d’autres parties du Canada arctique. Environ 60 g C.m-2 sont fixés annuellement, dont environ 90 p. cent par le phytoplancton, 10 p. cent par les algues glaciaires et 1 p. cent par les laminaires. La production de phytoplancton est deux fois plus élevée le long de la côte méridionale de l’île Cornwallis qu’ailleurs dans le détroit de Barrow. Quatre espèces de copépodes, dont la Pseudocalanus acuspes est la plus importante du point de vue énergitique, utilisent environ un tiers de la production de phytoplancton pour se nourir. Les bivalves contribuent de façonimportante à la biomasse mais peu au flux énergétique, étant des agents de sédimentation. La morue arctique est une composante importante, étant consommée au taux annuel de 1250 00 tonnes par les mammifères marins et de 23 000 tonnes par les oiseaux marins. Notre estimation hydroacoustique pour la densité moyenne de la morue arctique, 0,002 poissons.m-2, est probablement trop faible, en partie parce que nous avons été incapables de quantifier les regroupements denses des poissons se rassemblant en bancs. L’efficacité écologique du phoque annelé est proche de son maximum, 5 p. cent de l’ingestion de cet animal allant à l’ours et à l’homme sous forme de chair de phoque. Les données sur le nombre d’animaux tués et sur laconsommation de proies chez les baleines et les oiseaux sont incomplètes en raison de leur migration hivernal à  l'extérieur du détroit de Lancaster. La chaine alimentaire est très longue, les ours occupant le cinquième niveau trophique; cela se traduit par des facteurs de bioamplification élevés en ce qui concerne les polluants lipophiles persistants tels que les BPC. Il existe des lacunes dans les données pour certains éléments du zooplancton et pour la plupart du benthos, ainsi que pour les populations et l’énergétique hivernales. Cette analyse trophique est donc incomplète et il n'est pas possible de calculer l’efficacité pour l’ensemble des niveaux trophiques.Mots clés: phoques, baleines, oiseaux marins, benthos, zooplancton, phytoplancton, production primaire, production secondaire, prélèvement, rendemen

Tracer concentration profiles measured in central London as part of the REPARTEE campaign

There have been relatively few tracer experiments carried out that have looked at vertical plume spread in urban areas. In this paper we present results from two tracer (cyclic perfluorocarbon) experiments carried out in 2006 and 2007 in central London centred on the BT Tower as part of the REPARTEE (Regent’s Park and Tower Environmental Experiment) campaign. The height of the tower gives a unique opportunity to study vertical dispersion profiles and transport times in central London. Vertical gradients are contrasted with the relevant Pasquill stability classes. Estimation of lateral advection and vertical mixing times are made and compared with previous measurements. Data are then compared with a simple operational dispersion model and contrasted with data taken in central London as part of the DAPPLE campaign. This correlates dosage with non-dimensionalised distance from source. Such analyses illustrate the feasibility of the use of these empirical correlations over these prescribed distances in central London

Quantum algorithm for the Boolean hidden shift problem

The hidden shift problem is a natural place to look for new separations between classical and quantum models of computation. One advantage of this problem is its flexibility, since it can be defined for a whole range of functions and a whole range of underlying groups. In a way, this distinguishes it from the hidden subgroup problem where more stringent requirements about the existence of a periodic subgroup have to be made. And yet, the hidden shift problem proves to be rich enough to capture interesting features of problems of algebraic, geometric, and combinatorial flavor. We present a quantum algorithm to identify the hidden shift for any Boolean function. Using Fourier analysis for Boolean functions we relate the time and query complexity of the algorithm to an intrinsic property of the function, namely its minimum influence. We show that for randomly chosen functions the time complexity of the algorithm is polynomial. Based on this we show an average case exponential separation between classical and quantum time complexity. A perhaps interesting aspect of this work is that, while the extremal case of the Boolean hidden shift problem over so-called bent functions can be reduced to a hidden subgroup problem over an abelian group, the more general case studied here does not seem to allow such a reduction.Comment: 10 pages, 1 figur

Key Articles and Guidelines Relative to Intensive Care Unit Pharmacotherapy: 2009 Update

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90162/1/phco.29.10.1228.pd

Key Articles and Guidelines Relative to Intensive Care Unit Pharmacology—2004

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90189/1/phco.25.4.585.61024.pd