4,736 research outputs found
Topographic Shear and the Relation of Ocular Dominance Columns to Orientation Columns in Prime and Cat Visual Cortex
Shear has been known to exist for many years in the topographic structure of prirnary visual cortex, but has received little attention in the modeling literature. Although the topographic map of V1 is largely conformal (i.e. zero shear), several groups have observed topographic shear in the region of the V1/V2 border. Furthennore, shear has also been revealed by anisotropy of cortical magnification factor within a single ocular dominance colunm. In the present paper, we make a functional hypothesis: the major axis of the topographic shear tensor provides cortical neurons with a preferred direction of orientation tuning. We demonstrate that isotropic neuronal summation of a sheared topographic map, in the presence of additional random shear can provide the major features of corlical functional architecture with the ocular dominance column system acting as the principal source of the shear tensor. The major principal axis of the shear tensor determines the direction and its eigenvalues the relative strength of cortical orientation preference. This hypothesis is then shown to be qualitatively consistent with a variety of experimental results on cat and monkey orientation column properties obtained from optical recording and from other anatomical and physiological techniques. In addition, we show that a recent result of (Das and Gilbert, 1997) is consistent with an infinite set of parameterized solutions for the cortical map. We exploit this freedom to choose a particular instance of the Das-Gilbert solution set which is consistent with the full range of local spatial structure in V1. These results suggest that further relationships between ocular dominance columns, orientation columns, and local topography may be revealed by experimental testing
Effects of Chronic Waterborne Nickle Exposure on Two Successive Generations of \u3cem\u3eDaphnia Magna\u3c/em\u3e
In a 21-d chronic toxicity test in which an F0 generation of Daphnia magna were exposed to waterborne Ni, the noobservable-effect concentration (for survival, reproduction, and growth) was 42 μg Ni L-1, or 58% of the measured 21-d median lethal concentration (LC50) of 71.9 μg Ni L-1 (95% confidence interval, 56.5–95.0). Chronic exposure to 85 μg Ni L-1 caused marked decreases in survival, reproduction, and growth in F0 animals. In the F1 generation (daphnids born of mothers from the chronically exposed F0 generation), animals chronically exposed to 42 μg Ni L-1 for 11 d weighed significantly less (20%) than controls, indicating increased sensitivity of F1 animals. Additionally, in this successive generation, significant decreases in whole-body levels of metabolites occurred following exposure to both 42 μg Ni L-1 (decreased glycogen and adenosine triphosphate [ATP]) and 21 μg Ni L-1 (decreased ATP). No significant changes were observed in whole-body total lipid, total protein, and lactate levels at any concentration. Whereas F1 neonates with mothers that were exposed to 21 μg Ni L-1 showed increased resistance to acute Ni challenge, as measured by a significant (83%) increase in the acute (48-h) LC50, F1 neonates with mothers that were exposed to 42 μg Ni L-1 were no more tolerant of acute Ni challenge than control animals were. Nickel accumulations in F1 animals chronically exposed to 21 and 42 μg Ni L-1 were 11- and 18-fold, respectively, above control counterparts. The data presented suggest that chronic Ni exposure to two successive generations of D. magna lowered the overall energy state in the second generation. Whereas the quantity of neonates produced was not affected, the quality was; thus, environmentally meaningful criteria for regulating waterborne Ni concentrations in freshwater require consideration of possible multigenerational effects
Perceptions of Division I Athletic Director Career Paths
There is increased information about the profile of current collegiate athletic directors as it relates to education, age, race, and gender. However, there is a gap in the knowledge of the career paths of the modern day Division I collegiate athletic director position compared to the athletic directors studied over 20 years ago. There is also a gap in the knowledge of the skills necessary to be an effective athletic director from the perspective of Division I athletic directors. The purpose of this study was to use the Perceptions of Division I Athletic Director Career Paths (PADCP) scale to determine their career paths. The goal was to not only understand the career paths of today’s athletic directors but to compare the experiences with those from the 1994 foundational study conducted by Fitzgerald et al. (1994). This research is beneficial to aspiring and entry-level collegiate athletics administrators because the landscape of college athletics has changed significantly over the past 20 years. It is important for them to know the common experiences and required skill sets in order to navigate their path to the top
Private sector engagement in public sector education in England, 1997-2005: an analysis of New Labour's policy with a focus on modernisation, competitiveness and the Private Finance Initiative
This thesis examines the philosophical drivers behind the education policy agenda pursued by the New Labour Government and will test the assertion that:
Mrs Thatcher had a project. Blair's historic project is adjusting us to it. (Hall, S. 1998.14. p 28)
The research considers the legislative policy, practice and continuities between Conservative and New Labour governments and critically analyses the 'Third Way'with particular reference to modernisation, competition and the restructuring of the welfare state in response to globalisation. The thesis also examines the growth of the private sector in state education, the development of the Private Finance Initiative in both policy and operational terms and draws conclusions about the implications for the governance of education of the trend towards a 'liberal state', where individual choice is perceived to be more effective and efficient than a model of governance based upon social values.
The qualitative nature of this thesis includes consideration of the issues involved in the changing concepts of citizenship and consumerism within the evolving, redefined welfare state; examines the assertion by Marquand (2000) that incessant marketisation has generated a culture of distrust which has corroded the values of professionalism, citizenship, equity and public service and draws conclusions about accountabilities within a modern social democracy.
The study includes an analysis of education legislation and a critique of policy intent in the broader context of societal impact. This incorporates an analysis of primary texts, government policy statements as well as Green and White Papers, compared and evaluated with contemporary research literature.
Coupled with a case study of the Private Finance Initiative in Stoke-on-Trent the theoretical triangulation (Denzin, 1970) is combined with witness accounts of the 4 complex phenomena' associated with a Private Finance Initiative' (Adelman, 1980) and enabled cross cutting perspectives to be illuminated and the knowledge and understanding of modernisation extended. Such triangulation extends knowledge by clarifying meaning by the identification of different ways in which modernisation is perceived in both theoretical and practical terms (Silverman, 1993; Flick, 1998). The thesis considers within the reality of the case study the importance of the local democratic voice and local political actions in educational governance, including the political/professional/public interface. This leads to conclusions about the need for a modern social democracy to explore the concept of accountability to the citizen as well as the consumer of services within a framework of evolving local policy networks and emergent patterns of governance within state education.
In essence this thesis examines whether it is a superficial assertion to equate the 'Third Way'with neo-liberalism (Marquand, 2000; Driver and Martell, 1998,2000; Giddens, 1998,2000) or that the plurality of 'Third Ways' have translated into operational definition, legislation and policies within a model of education which lacks a coherent and identifiable national drive and is therefore critically dependent upon local interpretation and local political response. It also reaches conclusions about the citizen - state relationship, the validity of the concept of the 'social investment state' and suggests constituent elements of a 'fourth way' as a contribution to the issue posed by Whitty, (2000), 'how can education best help reconstruct the social fabric and new concepts of citizenship - and who shall influence its design? (p 8)
Fermipy: An open-source Python package for analysis of Fermi-LAT Data
Fermipy is an open-source python framework that facilitates analysis of data
collected by the Fermi Large Area Telescope (LAT). Fermipy is built on the
Fermi Science Tools, the publicly available software suite provided by NASA for
the LAT mission. Fermipy provides a high-level interface for analyzing LAT data
in a simple and reproducible way. The current feature set includes methods for
extracting spectral energy distributions and lightcurves, generating test
statistic maps, finding new source candidates, and fitting source position and
extension. Fermipy leverages functionality from other scientific python
packages including NumPy, SciPy, Matplotlib, and Astropy and is organized as a
community-developed package following an open-source development model. We
review the current functionality of Fermipy and plans for future development.Comment: Proc. 35th ICRC, Busan, South Korea, PoS(ICRC2017)82
Research into the influence of spatial variability and scale on the parameterization of hydrological processes
The objectives of the research were as follows: (1) Extend the Representative Elementary Area (RE) concept, first proposed and developed in Wood et al, (1988), to the water balance fluxes of the interstorm period (redistribution, evapotranspiration and baseflow) necessary for the analysis of long-term water balance processes. (2) Derive spatially averaged water balance model equations for spatially variable soil, topography and vegetation, over A RANGE OF CLIMATES. This is a necessary step in our goal to derive consistent hydrologic results up to GCM grid scales necessary for global climate modeling. (3) Apply the above macroscale water balance equations with remotely sensed data and begin to explore the feasibility of parameterizing the water balance constitutive equations at GCM grid scale
Heterogeneity and scaling land-atmospheric water and energy fluxes in climate systems
The effects of small-scale heterogeneity in land surface characteristics on the large-scale fluxes of water and energy in land-atmosphere system has become a central focus of many of the climatology research experiments. The acquisition of high resolution land surface data through remote sensing and intensive land-climatology field experiments (like HAPEX and FIFE) has provided data to investigate the interactions between microscale land-atmosphere interactions and macroscale models. One essential research question is how to account for the small scale heterogeneities and whether 'effective' parameters can be used in the macroscale models. To address this question of scaling, three modeling experiments were performed and are reviewed in the paper. The first is concerned with the aggregation of parameters and inputs for a terrestrial water and energy balance model. The second experiment analyzed the scaling behavior of hydrologic responses during rain events and between rain events. The third experiment compared the hydrologic responses from distributed models with a lumped model that uses spatially constant inputs and parameters. The results show that the patterns of small scale variations can be represented statistically if the scale is larger than a representative elementary area scale, which appears to be about 2 - 3 times the correlation length of the process. For natural catchments this appears to be about 1 - 2 sq km. The results concerning distributed versus lumped representations are more complicated. For conditions when the processes are nonlinear, then lumping results in biases; otherwise a one-dimensional model based on 'equivalent' parameters provides quite good results. Further research is needed to fully understand these conditions
Simulation of Boreal Ecosystem Carbon and Water Budgets: Scaling from Local to Regional Extents
A coupled water and energy balance model is developed. This model can predict the partitioning of water and energy between major source, sink and storage elements within the Boreal-Ecosystem-Atmospheric Study (BOREAS) areas. The results of testing the model against data collected at BOREAS tower sites during Intensive Field Campaigns and remotely sensed data collected across the BOREAS region are presented
Scaling Water and Energy Fluxes in Climate Systems: Three Land-Atmospheric Modeling Experiments
The effects of small-scale heterogeneity in land-surface characteristics on the large-scale fluxes of water and energy in the land-atmosphere system have become a central focus of many of the climatology research experiments. The acquisition of high-resolution land-surface data through remote sensing and intensive land-climatology field experiments(like HAPEX and EIFE) has provided data to investigate the interactions between microscale land-atmosphere interactions and macroscale models. One essential research question is how to account for the small-scale heterogeneities and whether `effective\u27 parameters can be used in the macroscale models. To address this question ofscaling, three modeling experiments were performed and are reviewed in the paper. The first is concerned with the land-surface hydrology during rain events and between rain events. The second experiment applies the Simple Biosphere Model (SiB) to a heterogeneous domain and the spatial and temporal latent beat flux is analyzed. The third experiment uses thermatic mapper (TM) data to look at the scaling of the normalized vegetation index (NDVI), latent heat flux, and sensible heat flux through either scaling of the TM-derived fields using the TM data or the fields derived from aggregated TM data.In all three experiments it was found that the surface fluxes and land characteristics can be sealed, and that macroscale models based on elective parameters are sufficient to account for the small-scale heterogeneities investigated. The paper also suggests that the scale at which a macroscale model becomes valid, the representative elementary scale (REA), is on the order 1.5-3 correlation lengths, which for land processes investigated appears to be about 1000-1500 m. At scales less than the REA scale, exact patterns of subgrid heterogeneities are needed for accurate small-scale modeling
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