A probabilistic concept of accessibility for access structures

In this paper we introduce the concept of weighted accessibility for access structures. In some sense, it represents a measure of how difficult or how easy is to recover the secret. We give also a numerical measure of accessibility for each participant depending on his position in the access structure. Both concepts, the accessibility of the access structure and the accessibility of the participants are closely related. We also provide an axiomatic characterization of the weighted accessibility for access structures based on four simple properties

Access Structures in a Standard Translation Dictionary

The access structure is the primary guide structure in the central texts of any standard translation dictionary. The metalexicographical term "guide structures" refers to the set of structures that provides a framework within which the accessibility and availability of information types in the dictionary can be evaluated. The access structure is, however, not a singular entity. It includes certain substructures, of which the outer and inner access structures are the most important. In this article the status quo with regard to access structures in standard translation dictionaries with Afrikaans and English as treated language pair will be evaluated. Suggestions will then be made as to possible improvements. In the discussion of the outer access structure it is suggested that the rapid outer access structure be improved by using an elementary thumb index and that the current system of running heads be retained. For the standard outer access structure a better planned and motivated system of ordering homonyms, as welI as a more consistent initial alphabetical ordering is suggested. The focus in the discussion of the inner access structure will be on improving the rapid inner access structure by an innovative use of typographical and non-typographical structural markers. Better systems of ordering information subtypes within information categories are suggested as an innovation in the standard inner access structure. Broad guidelines are therefore given to improve dictionary accessibility and enhance userfriendliness through improved access structures.Keywords: Access structure, dictionary, dictionary accessibiuty, homonymy, Inner access structure, inner search path, lexicography, metalexicography, Outer access structure, outer search path, polysemy, Rapid inner access structure, rapid outer access structure, standard Inner access structure, standard outer access structure, standard Translation dictionary, structural marker, user-friendlines

A decision support system to improve service quality in multimodal rapid rail systems: A bayesian perspective

Copyright @ 2011 International Conference on Computers and Industrial EngineeringIn this study, the accessibility of the rail transit stations in a multimodal network formed by a trunk line and its feeder lines are defined. Connectivity between lines and the accessibility of the nodes identify the overall spatial structure of the network. The factors influencing the access choices of rail transit stations and satisfaction of transit travelers in rapid rail transit systems are investigated in order to gain insights into the factors and their interrelationships. The quantitative indications of the relationships are produced and the complexity of evaluating the performance of transit services is exhibited. As the interrelationships are mainly stochastic, the problem on hand is treated as a Bayesian Belief Network (BBN). A BBN approach that presents a learning mechanism is employed and is used as an alternative decision making tool to analyze the rapid rail transit services and identify policies to improve the traveler’s level of service

Evaluation of the European Policies in Support of Ultraperipheric Regions, Azores, Madeira, Canarias, Guadalupe, Martinique, Guyane and Reunion

The paper looks at the development of the EU's outermost regions. We develop a model not only to explain the effects caused by peripherality but also to evaluate the European policies towards ultra peripheral regions. Ultra-peripherality is an economic and social phenomenon associated to a geographical structure characterised by two attributes: size and access. The structure of the model to analyse size, or supply performance, can be represented in three interrelated blocks: i) the first block explains the effect on the population of driving activities in island economies: exports, external aid for employment and external subsidies; ii) the second block establishes the relationships between population and activities associated to the provision of goods and services not receiving external aid; iii) the third block estimates the product and the income of the region by multiplying the quantity of each type of activity, measured in terms of the number of jobs involved. The structure of the model for access, or demand performance, is in a way implicit in the model of size through the population indicator; however, the population indicator does not clearly translate variations of accessibility to the region being. The present study uses the demographic potential to arrive at an accessibility indicator that uses easily accessible statistical data: the population and the traffic of passengers. We conclude that the impact of ultra-peripheral policies are weaker in the regions more dependent on external public transferences, the connection with neighbour countries can produce important effects in the economy, the elimination of the "sea rights" in most of the regions could generate important impacts in the respective development process, the effective liberalisation of air transportation will lead to a strong increase in the accessibility and the development process based on import substitution and external public transferences can led to a big increase in the population and created a great dependence on the "sea rights".

The spatial effect of intra-metropolitan agglomeration economies

This study deals with the role of spatial accessibility to agglomeration economies in the change in spatial structure of industrial employment for the case of the Barcelona Metropolitan Region of Barcelona (BMR). Using the growth in gross density of municipal employment between 1986 and 1996 for seven manufacturing industries as an indicator of changes in the spatial structure of employment, an exploration is made of the spatial impact of agglomeration economies operating on a local scale – the municipality and three areas 5, 8 and 12 kilometres away surrounding the municipality itself - , agglomeration economies emerging from CBD and the main specialised subcentres in the region, and the network economies associated with the total jobs in the region, access to which depends on the distance from the main transport infrastructuresAgglomeration economies, industrial employment growth, intra-metropolitan localisation, spatial structure.

What Europe? Fortress, different speeds, coloniser or archipelago

The paper starts with the introduction of a simple analytical tool that classifies regions according to their scale and accessibility. Those indicators are closely related to the strategies of European expansion and European integration and at the same time translate paradigmatic outcomes of those combined strategies; they are usually labelled as fortress Europe, different speeds Europe, coloniser Europe and, adding one more, an archipelago of European Regions. The paper then uses European regional statistics in order to access the structure and evolution of the Europe that has being built.

Spatially Characterizing Effective Timber Supply

The structure of a computer-oriented cartographic model for assessing roundwood supply for generation of base load electricity is discussed. The model provides an analytical procedure for coupling spatial information of harvesting economics and owner willingness to sell stumpages. Supply is characterized in terms of standing timber; of accessibility considering various harvesting and hauling factors; and of availability as affected by ownership and residential patterns. Factors governing accessibility to timber include effective harvesting distance to haulic roads as modified by barriers and slopes. Haul distance is expressed in units that take into account the relative ease of travel along various road types to a central processing facility. Areas of accessible timber are grouped into spatial units, termed 'timbersheds', of common access to particular haul road segments that belong to unique 'transport zones'. Timber availability considerations include size of ownership parcels, housing density and excluded areas. The analysis techniques are demonstrated for a cartographic data base in western Massachusetts

High-speed railway developments and corporate location decisions. The role of accessibility

Accessibility is a major factor that determines the effects of transport infrastructure developments on corporate location decisions. High-speed railways have an impact on accessibility by reducing travel times and increasing comfort. However, little research on its effects on location choices has been carried out so far. Still, high-speed railway infrastructure development is advocated for these effects on regional economy. This research uses interviews among corporate decision makers to determine how a change in accessibility due to new high-speed rail infrastructure is perceived by these corporate decision makers and what impact HST infrastructure has on the location choices of firm branches. Firstly, in-dept interviews are held among recently (re)located firm branches to identify accessibility related factors that play a role in the location decision process. For the in-dept interviews we start from the assumption that for firms three aspects of accessibility by passenger transport systems are of importance: access and accessibility for (1) current and potential employees, (2) current and potential business partners, and (3) current and potential customers. Furthermore, corporate decision makers perceive different transport modes in a distinct way. Hereby for example, the level of comfort of the transport mode can be of importance ? it might be of more importance for business trips than for commuting. In this paper special attention is given to how the accessibility by high-speed trains is perceived. The perception of the accessibility of a certain place will differ among firms, because distinct firms appreciate the several facets of accessibility differently. This depends on the activities that take place in the firm branch, for example how often face-to-face contact with (international) business partners occurs, and on the cost structure of the firm. An improved accessibility will reduce transport costs, but on the other hand better accessible locations are likely to have higher prices of real estate. Probably for firms a trade off exists between these opposite cost effects, based on their characteristics. But beside these ?objective? factors, subjective properties of accessibility might also be of importance to corporate decision makers. Being settled on good accessible transport hubs can contribute to the firm?s image. The interviews shed light on how new high-speed rail infrastructure affects the perception of accessibility by corporate decision makers. By questioning different firm types and sizes it is made clear what types of firms are mostly influenced by this change in accessibility. In a later stage of the research, these factors will be quantified by means of stated preference interviews. The results of these interviews will then be used to improve the way accessibility is embedded in land-use transport interaction models, an important instrument for the ex ante evaluation of transport infrastructure.

If Alonso was Right: Residual Land Price, Accessibility and Urban Attraction

This study investigates whether accessibility shapes the attractiveness of residential land as predicted by theory. A spatial hedonic analysis is conducted for the metropolitan area of Berlin, Germany, using a large set of georeferenced property transactions and micro-level data. We find that the nuclei of residential land price and employment density gradients are separated by approx. 10 km, which essentially contradicts theoretical implications. Also, environmental externalities arising from the residential composition or the building structure and density in the neighborhood are more important determinants than access to the city center, which, if at all, impacts negatively on residential land prices. Moreover, a new gravity-based accessibility indicator is employed that incorporates the effective distribution of employment as well as the rapid transit network architecture in order to disentangle the effects of proximity to employment opportunities from a more general urban attraction effect. After controlling for accessibility, we find a negative effect of urban attraction, respectively an effect of urban repulsion, indicating a relatively higher attractiveness of peripheral locations. This effect is partially counterbalanced by the benefits arising from access to employment opportunities that are, although relatively dispersed, more concentrated within downtown areas. In the tension between both forces, the land price gradient tends to be, if at all significant, positive. After all, we conclude that if transport costs are very low, commuting costs lose their role as the most striking determinant of land price. These results are robust to spatial dependency.Accessibility, gradient inversion, land price, urban attraction, Berlin

H2A.Z facilitates access of active and repressive complexes to chromatin in embryonic stem cell self-renewal and differentiation.

SummaryChromatin modifications have been implicated in the self-renewal and differentiation of embryonic stem cells (ESCs). However, the function of histone variant H2A.Z in ESCs remains unclear. We show that H2A.Z is highly enriched at promoters and enhancers and is required for both efficient self-renewal and differentiation of murine ESCs. H2A.Z deposition leads to an abnormal nucleosome structure, decreased nucleosome occupancy, and increased chromatin accessibility. In self-renewing ESCs, knockdown of H2A.Z compromises OCT4 binding to its target genes and leads to decreased binding of MLL complexes to active genes and of PRC2 complex to repressed genes. During differentiation of ESCs, inhibition of H2A.Z also compromises RA-induced RARα binding, activation of differentiation markers, and the repression of pluripotency genes. We propose that H2A.Z mediates such contrasting activities by acting as a general facilitator that generates access for a variety of complexes, both activating and repressive