2,018 research outputs found
Developing Infrastructure Adaptation Pathways to Combat Hurricane Intensification: A Coupled Storm Simulation and Economic Modeling Framework for Coastal Installations
Climate change projections suggest intensification of extreme weather events, including hurricanes, is expected throughout the 21st century. This will lead to increased destruction for coastal military bases unless infrastructure resiliency and adaptation measures are implemented. This research focuses on examining the simulation of probabilistic, climate-intensified hurricane events at Eglin Air Force Base. FEMA Hazus models are combined with climate projections for wind Intensity, tide, and sea-level rise to produce an assessment of losses to the installation. Damage estimates and hurricane intensity outputs are downscaled to the facility-level so that climate adaptation signals can be identified. The facility losses and climate signals are used as inputs for a dynamic adaptation pathway model. Utilizing a variety of infrastructure investment strategies, the pathway model is used to calculate the expected benefits, risks, and costs associated with adaptation. Such pathways can be used to inform campus and installation master plans and are vital to reducing coastal bases vulnerability to future hurricane events
Pattern integration in the normal and abnormal human visual system
The processing conducted by the visual system requires the combination of signals that are detected at different locations in the visual field. The processes by which these signals are combined are explored here using psychophysical experiments and computer modelling. Most of the work presented in this thesis is concerned with the summation of contrast over space at detection threshold. Previous investigations of this sort have been confounded by the inhomogeneity in contrast sensitivity across the visual field. Experiments performed in this thesis find that the decline in log contrast sensitivity with eccentricity is bilinear, with an initial steep fall-off followed by a shallower decline. This decline is scale-invariant for spatial frequencies of 0.7 to 4 c/deg. A detailed map of the inhomogeneity is developed, and applied to area summation experiments both by incorporating it into models of the visual system and by using it to compensate stimuli in order to factor out the effects of the inhomogeneity. The results of these area summation experiments show that the summation of contrast over area is spatially extensive (occurring over 33 stimulus carrier cycles), and that summation behaviour is the same in the fovea, parafovea, and periphery. Summation occurs according to a fourth-root summation rule, consistent with a “noisy energy” model. This work is extended to investigate the visual deficit in amblyopia, finding that area summation is normal in amblyopic observers. Finally, the methods used to study the summation of threshold contrast over area are adapted to investigate the integration of coherent orientation signals in a texture. The results of this study are described by a two-stage model, with a mandatory local combination stage followed by flexible global pooling of these local outputs. In each study, the results suggest a more extensive combination of signals in vision than has been previously understood
The attenuation surface for contrast sensitivity has the form of a witch’s hat within the central visual field
Over the full visual field, contrast sensitivity is fairly well described by a linear decline in log sensitivity as a function of eccentricity (expressed in grating cycles). However, many psychophysical studies of spatial visual function concentrate on the central ±4.5 deg (or so) of the visual field. As the details of the variation in sensitivity have not been well documented in this region we did so for small patches of target contrast at several spatial frequencies (0.7–4 c/deg), meridians (horizontal, vertical, and oblique), orientations (horizontal, vertical, and oblique), and eccentricities (0–18 cycles). To reduce the potential effects of stimulus uncertainty, circular markers surrounded the targets. Our analysis shows that the decline in binocular log sensitivity within the central visual field is bilinear: The initial decline is steep, whereas the later decline is shallow and much closer to the classical results. The bilinear decline was approximately symmetrical in the horizontal meridian and declined most steeply in the superior visual field. Further analyses showed our results to be scale-invariant and that this property could not be predicted from cone densities. We used the results from the cardinal meridians to radially interpolate an attenuation surface with the shape of a witch's hat that provided good predictions for the results from the oblique meridians. The witch's hat provides a convenient starting point from which to build models of contrast sensitivity, including those designed to investigate signal summation and neuronal convergence of the image contrast signal. Finally, we provide Matlab code for constructing the witch's hat
GOES-R Algorithms: A Common Science and Engineering Design and Development Approach for Delivering Next Generation Environmental Data Products
GOES-R, the next generation of the National Oceanic and Atmospheric Administration’s (NOAA) Geostationary Operational Environmental Satellite (GOES) System, represents a new technological era in operational geostationary environmental satellite systems. GOES-R will provide advanced products that describe the state of the atmosphere, land, oceans, and solar/ space environments over the western hemisphere. The Harris GOES-R Ground Segment team will provide the software, based on government-supplied algorithms, and engineering infrastructures designed to produce and distribute these next-generation data products. The Harris GOES-R Team has adopted an integrated applied science and engineering approach that combines rigorous system engineering methods, with modern software design elements to facilitate the transition of algorithms for Level 1 and 2+ products to operational software. The Harris Team GOES-R GS algorithm framework, which includes a common data model interface, provides general design principles and standardized methods for developing general algorithm services, interfacing to external data, generating intermediate and L1b and L2 products and implementing common algorithm features such as metadata generation and error handling.
This work presents the suite of GOES-R products, their properties and the process by which the related requirements are maintained during the complete design/development life-cycle. It also describes the algorithm architecture/engineering approach that will be used to deploy these algorithms, and provides a preliminary implementation road map for the development of the GOES-R GS software infrastructure, and a view into the integration of the framework and data model into the final design
The Equilibrium Existence Duality: Equilibrium with Indivisibilities & Income Effects
We show that, with indivisible goods, the existence of competitive
equilibrium fundamentally depends on agents' substitution effects, not their
income effects. Our Equilibrium Existence Duality allows us to transport
results on the existence of competitive equilibrium from settings with
transferable utility to settings with income effects. One consequence is that
net substitutability---which is a strictly weaker condition than gross
substitutability---is sufficient for the existence of competitive equilibrium.
We also extend the ``demand types'' classification of valuations to settings
with income effects and give necessary and sufficient conditions for a pattern
of substitution effects to guarantee the existence of competitive equilibrium.Comment: 46 pages, 1 figur
A possible feature of thermal matter in relativistic jets of radio-loud quasars
It has been suggested that relativistic jets in quasars may contain a
considerable amount of thermal matter. In this paper, we explore the
possibility that the K-alpha line from the thermal matter may appear at tens of
keV due to a high Doppler blue-shift. In the jet comoving frame, the energy
density of photons originally emitted by the accretion disk and reflected off
the broad line region clouds dominates over that of photons of other origin. We
discuss the photoionization states of the thermal matter and find that the
irons elements are neutral. The high metallicity in quasars enhances the
possibility to detect the thermal matter in the relativistic jet in some
radio-loud quasars. A highly Doppler blue-shifted K-alpha line may be detected.
We make a rediction for 3C 273, in which the K-alpha line luminosity might be
of the order erg/s with an equivalent width of 2.4 keV.
Such a line could be detected in a future mission.Comment: 4 pages, 1 Figur
Stellar Envelopes as Sources of Broad Line Region Emission: New Possibilities Allowed
In Active Galactic Nuclei (AGNs) the presence of a star cluster around the
central black hole can have several effects on the dynamics and the emission of
the global system. In this paper we analyze the interaction of stellar
atmospheres with a wind outflowing from the central region of the AGN nucleus.
Even a small mass loss from stars, as well as possible star collisions, can
give a non-negligible contribution in feeding matter into the AGN nuclear wind.
Moreover, stellar mass loss can produce envelopes surrounding stars that turn
out to be suitable for reproducing the observed emission from the Broad Line
Region (BLR). In this framework, the envelope can be confined by the bow shock
arising from the interaction between the expanding stellar atmosphere and the
AGN nuclear wind.Comment: 21 pages, Latex, accepted for publication in A&
Evaluation of a Waistband for Attaching External Radiotransmitters to Anurans
Radiotelemetry provides fine-scale temporal and spatial information about an individual\u27s movements and habitat use; however, its use for monitoring amphibians has been restricted by transmitter mass and lack of suitable attachment techniques. We describe a novel waistband for attaching external radiotransmitters to anurans and evaluate the percentages of resulting abrasions, lacerations, and shed transmitters. We used radiotelemetry to monitor movements and habitat use of wood frogs (Lithobates sylvaticus) in 2006 and 2011–2013 in Maine, USA; American toads (Anaxyrus americanus) in 2012 in North Carolina, USA; and, wood frogs, southern leopard frogs (L. sphenocephalus), and green frogs (L. clamitans) in 2012 in South Carolina, USA. We monitored 172 anurans for 1–365 days (56.4 ± 59.4) in a single year and 1–691 days (60.5 ± 94.1) across years. Our waistband resulted in an injury percentage comparable to 7 alternative anuran waistband attachment techniques; however, 12.5% fewer anurans shed their waistband when attached with our technique. Waistband retention facilitates longer monitoring periods and, thus, provides a greater quantity of data per radiotagged individual. © 2015 The Wildlife Society
Axonal transport defects are a common phenotype in Drosophila models of ALS
Amyotrophic lateral sclerosis (ALS) is characterized by the degeneration of motor neurons resulting in a catastrophic loss of
motor function. Current therapies are severely limited owing to a poor mechanistic understanding of the pathobiology.
Mutations in a large number of genes have now been linked to ALS, including SOD1, TARDBP (TDP-43), FUS and C9orf72.
Functional analyses of these genes and their pathogenic mutations have provided great insights into the underlying disease
mechanisms. Defective axonal transport is hypothesized to be a key factor in the selective vulnerability of motor nerves due
to their extraordinary length and evidence that ALS occurs as a distal axonopathy. Axonal transport is seen as an early
pathogenic event that precedes cell loss and clinical symptoms and so represents an upstream mechanism for therapeutic
targeting. Studies have begun to describe the impact of a few pathogenic mutations on axonal transport but a broad survey
across a range of models and cargos is warranted. Here, we assessed the axonal transport of different cargos in multiple
Drosophila models of ALS. We found that axonal transport defects are common across all models tested, although they often
showed a differential effect between mitochondria and vesicle cargos. Motor deficits were also common across the models
and generally worsened with age, though surprisingly there was not a clear correlation between the severity of axonal
transport defects and motor ability. These results further support defects in axonal transport as a common factor in models
of ALS that may contribute to the pathogenic process
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