bluuebunny/crossref_metadata_2025 huggingface dataset:
Using GIS-Based Continuous Methods for Assessing Agricultural Land-Use Potential in Sloping Areas
Authors: Baja Sumbangan , Chapman David M , Dragovich Deirdre
Published: August 2002

The dynamic nature of land qualities both in space and in time suggests that, whatever the stages of the development of an area, it is always crucial to assess land qualities in terms of their potential and suitability for specific kinds of land use on a sustainable basis. In this paper we demonstrate an integrated method of biophysical land-suitability assessment, which combines two basic land-evaluation principles: allowing trade-offs among evaluation criteria, and a limiting condition approach. Decision criteria consist mainly of biophysical parameters, based on internal and external groups of land properties. Internal variables include various physical and chemical characteristics of soils, whereas external variables are those of topographic attributes. A fuzzy set methodology was employed to calculate values of a membership function, MF (0 ⩽ MF ⩽ 1.0), of each land variable. These fuzzy membership values were then combined to produce land-suitability indices, LSIs (0 ⩽ LSIs ⩽ 1.0), which can be used to assess the potential of land for a nominated land-use type. The analysis procedure implements a convex combination, which permits trade-offs between criteria of the same group, and a multiplicative function, which takes no account of compensation between groups (internal and external variables). A limiting condition approach is also incorporated in this system to resolve shortcomings found when using a convex combination technique alone. The results show that LSIs are consistent with categorical classes generated from applying the well-established method based on the Food and Agriculture Organisation framework for land evaluation. However, the LSIs, as derived from a cell-by-cell operation, produce more detailed subdivisions of land in terms of their potential for a given purpose. The main advantages of using this model include: (1) it minimises subjectivity in the evaluation procedure; (2) it takes into account the combined effects of the factors considered, while preserving information on biophysical constraints for a given purpose; and (3) it is amenable to further computer-based applications, especially for use in geographical information systems.
Graph-Cellular Automata: A Generalised Discrete Urban and Regional Model
Authors: O'Sullivan David
Published: August 2002

A new type of dynamic spatial model is described: graph-cellular automatoa (graph-CA). First, the proximal model of space and geo-algebra are briefly introduced. Then, the graph-CA model is described, with an emphasis on understanding it as a reworking of the proximal model of space and also of geo-algebra. It is shown that graph-CA with particular structural properties defined in terms of the relationships between subsets of cells are a useful generalisation of traditional cellular automaton (CA) which enable meaningful descriptions of model structure to be developed. This enables further development of novel types of model in the same ‘family’ while retaining links to simpler, better understood examples. It is further argued that the derivation of the graph-CA from both the graph and CA formalisms permits the simultaneous use of well-developed ways of describing model structure and process dynamics, and that this could form the basis of a research programme into the elusive relations between the two. The relationship of graph-CA to other discrete models is briefly discussed, and a classification scheme which indicates the particular geographical interest of such models is suggested.
Characterization of the Street Networks in the Traditional Turkish Urban Form
Authors: Asami Yasushi , Kubat Ayse Sema , Istek Cihangir
Published: August 2002

In this paper, we use the question “what is the true nature of traditional street networks in Turkish cities?” to test different quantitative methods of urban morphological analysis. Traditional Turkish street networks are characterized by discriminant functions of several space-syntax-related indices, as well as by image-analysis and graph-theoretical indices. A set of space-syntactic indices is found to be powerful enough to distinguish the traditional street network among others, particularly axial ringiness, implying that the formation of large blocks is a typical feature. The relative abundance of closed-end edges is found to be another important feature of the traditional street network.
Effects of Zoning Structure and Network Detail on Traffic Demand Modeling
Authors: Chang Kang-Tsung , Khatib Zaher , Ou Yanmei
Published: August 2002

By using traffic analysis zones (TAZs), centroids, and a road network as the inputs, traffic demand modeling aggregates trips from the locations of individual tripmakers to TAZ centroids and estimates trips generated between TAZs on the network. Like spatial analysis, traffic demand modeling is subject to the modifiable areal unit problem (MAUP). In this paper we report the findings of a simulation study, which uses eleven zoning structures and two levels of network detail to assess the effects of TAZs, centroids, and network detail on statewide traffic demand modeling in Idaho. First, trips generated between smaller TAZs have shorter trip lengths, higher proportions of interzonal trips, more accurate estimated volume-to-ground-count ratios, and lower percentage root mean square errors ( ERMS) between estimated volumes and ground counts. Second, the effect of centroid locations is mixed and generally slight with small TAZs. Third, the level of network detail impacts ERMS values in two ways: larger TAZs produce lower ERMS values than smaller TAZs on the less detailed network, and the detailed network outperforms the less detailed network, regardless of the size of TAZs.
Internet GIS for Public Participation
Authors: Peng Zhong-Ren
Published: August 2002

Internet GIS, serving spatial data and GIS functionality on the web, offers a special and potentially important means to facilitate public participation in the planning and decision-making process. In this paper I discuss a framework for the design of a web-based public participation system (WPPS) that integrates Internet GIS, Internet communications, and scenario-building tools. The design framework is based on a taxonomy that is created to describe the level of services in serving public participation according to the information content, level of user interactivity, and system functionality. The system is designed to enhance public participation in the planning and decision-making process by providing the general public with data, analysis tools, and a forum to explore knowledge, express opinion, and discuss issues. The unique feature of the WPPS using Internet GIS is that it provides users not only the option of evaluating, commenting, and selecting alternatives, but also the capability of forming their own alternatives. I also discuss system components and design issues in the WPPS.
Participatory Planning and GIS: A PSS to Bridge the Gap
Authors: Geertman Stan
Published: August 2002

The fields of spatial planning, geographical information systems (GIS), and information and communication technology (ICT) are all developing at their own pace and in different directions, thereby obstructing the widespread acceptance of GIS as an integral part of planning practice. In this paper I take a closer look at their divergence and outline the role that a planning support system (PSS) can play in bridging this growing gap. I consider the benefits of participatory planning and show how my prototype of a PSS can contribute to its success. To that end, the functionality of this PSS is described in the context of the initial experience with its application in a diversity of planning circumstances. Some conclusions are then drawn on how a PSS can overcome some of the barriers to GIS support within planning practice.
Anticoverage Models for Obnoxious Material Transportation
Authors: Marianov Vladimir , ReVelle Charles , Shih Sam
Published: August 2002

We present models for the design of routes for transportation of loads that might become hazardous or obnoxious to the population living along these routes. We take into consideration the fact that the values of the properties that are close to the roads used for the transportation may decrease as a consequence of this activity. As opposed to the traditional approach, of minimizing the population along the routes, we propose to include a compensation cost as a direct cost of choosing the routes. This compensation could include, for instance, a reduction in property tax rates. Two formulations are presented, covering different patterns of effects on property values. As an example of application of the models, we provide some computational experience.
Valuing Locational Externalities: A GIS and Multilevel Modelling Approach
Authors: Orford Scott
Published: August 2002

Hedonic house price modelling has been used extensively in the valuation of locational externalities. However, the theory of how locational externalities impact upon house prices is not reflected in the traditional measurements of location used in these studies. The result is that many hedonic house price models suffer from parameter estimates that are either insignificant or counterintuitive. In this paper I attempt to move towards a more realistic valuation of locational externalities by examining the effects of location upon house prices from a geographical as opposed to a purely economic perspective. A multilevel conceptualisation is presented, which takes into account the spatial effects of locational externalities upon house prices. A location-sensitive GIS of Cardiff and a multilevel specification of the hedonic model is then used to model these effects. I conclude that a more realistic treatment of location is required if locational externalities are to be valued successfully.
Neighbourhood Regeneration and New Labour's Third Way
Authors: Tiesdell Steven , Allmendinger Philip
Published: August 2002

In the Unted Kingdom New Labour has claimed to be pursuing a ‘third way’, with policy implications intended to break away from and/or move beyond established debates and policy alternatives. In this paper we explore, identify, and discuss what New Labour's third way means with regard to neighbourhood regeneration in England. The paper has two main aims: first, to review developments in neighbourhood regeneration policy and, second, to assess New Labour's third way in respect of neighbourhood regeneration. The paper is in four main parts. The first provides a broad-brush review of the New Right approach to neighbourhood regeneration in the form of the Thatcher and Major governments. This provides the point of departure for the second part, which discusses the Blair government's neighbourhood regeneration policies in terms of policy change or continuity in four substantive areas: welfare policy, housing policy, regeneration, and the institutional context for regeneration. The third part identifies some of the key themes in New Labour's approach and the final part draws some overarching conclusions.
Taking Care of Business: Aftercare and the State — Multinational Enterprise Nexus in Wales
Authors: Phelps Nicholas A , Fuller Cris
Published: August 2002

In this paper the authors examine the nature of relationships between multinational enterprise (MNE) affiliates and local institutions of governance. They begin by identifying a number of key themes regarding the efficacy and nature of local institutional support for the attraction and embedding of MNE affiliates. The growing interest of governments in embedding MNE affiliates begs questions not only of the rational organisation of government as a distinct set of institutions but, more significantly, of the increasingly indistinct boundaries between the state and firms. Governments adopt different stances toward MNEs, and the credibility of these stances rests crucially on some degree of partnership with MNEs at the local level. These partnerships and associated potential for oneway or mutual forms of capture highlight the increasingly politicised nature of the local state—MNE nexus. The authors illustrate these themes through a study of the relationship between local institutions and some of the most important MNEs in Wales—a ‘region’ noted for its proactive stance in the attraction and, more recently, the development of MNE affiliates. Finally, the authors offer some conclusions regarding the increasingly politicised nature of state—MNE relations at the local scale.
A Novel Approach to the Appraisal of Technological Risk: A Multicriteria Mapping Study of a Genetically Modified Crop
Authors: Stirling Andy , Mayer Sue
Published: August 2002

The recent controversy over genetically modified (GM) foods amply demonstrates the general difficulties encountered in the social appraisal of technological risk. Existing procedures for regulatory appraisal neglect many possible forms of impact and routinely exclude important cultural and social dimensions of risk. A narrow, expert, ‘science-based’ approach is now widely acknowledged to be insufficient. There is a need for new approaches that are more broadly based, transparent, pluralistic and ready to acknowledge uncertainty as well as being practically feasible and robust. The authors investigate the potential for a novel ‘multicriteria mapping’ (MCM) method as one such possible tool. Drawing on a variety of perspectives in the current UK debate, a range of agricultural strategies for the production of oilseed rape, including both GM and non-GM options were explored in this MCM pilot exercise. The results demonstrate the general feasibility and positive potential of this type of approach, with specific findings providing modest insights for policymaking in this difficult area.
Writing Travel/Travelling Writing: Roland Barthes Detours the Orient
Authors: Sharp Joanne P
Published: August 2002

This paper offers a contribution to the recent emergence in geography of studies of travel writers and the production of other representations of the non-Western world. I consider a rather different text to those normally studied in that the book, Empire of Signs by Barthes, purports not to represent any real place. A number of writers, influenced by Said's pathbreaking work Orientalism, have considered whether Barthes perpetuates Orientalist images. Rather than structure my argument around the binary of Orientalist/not-Orientalist I will consider the ways that Barthes subverts the structure of Orientalism from within. Barthes counterfeits travel: playing with the concept of ‘wonder’ which halted the representational language of more conventional travellers. Through the construction of his own ‘hyper-Orientalist’ account, Barthes produces a poststructural ethics which I argue offers some important reflections on the politics of representation both of travel writing and of academic critiques of it.
Automobility—A Social Problem and Theoretical Concept
Authors: Beckmann Jörg
Published: August 2002

In this paper, I explore automobility as the dominant type of contemporary everyday mobility. I critically review recent attempts to conceptualise the social role of cars and subsequently suggest a three-dimensional model to theorise automobility further as a modern mobility paradigm. This theory of automobility assigns central importance to the subjects, the vehicles, and the spatiotemporalities that are involved in, and produced by, the car-system. For the purpose of outlining the content and internal dependencies of this three-dimensional model, I make use of theoretical assumptions gleaned from transport geography, modernisation theory, as well as the sociology of technology. Furthermore, I argue that a somewhat orthodox form of automobilisation has become reflexive in the course of a growing public recognition of the inherent threats of the car to culture and nature. Under reflexive automobilisation almost all ‘auto-subjects’ are engaged in defining, interpreting, and responding to ‘auto-risks’. They do not necessarily do this, however, in a self-critical fashion. Instead of fostering the rise of a different, postautomotive mobility paradigm, their responses often merely lead to a reproduction of traditional ‘auto-scapes’.
Baudrillard Unwound: The Duplicity of Post-Marxism and Deconstruction
Authors: Smith Richard G , Doel Marcus A
Published: August 2002

The paper comprises two readings of the work of Jean Baudrillard. The first, by Richard Smith, locates itself amid the polarization of debate between Marxism, postmodernism, and poststructuralism, which he claims is both ill-judged and unproductive. In contrast to this standoff Smith argues the case for a ‘transgenic’ or ‘transversal’ post-Marxism by demonstrating that the oft-repeated claims for an ‘epistemological break’ between an early, Marxian Baudrillard and a later, postmodern Baudrillard are not borne out by the evidence. Rather, Smith foregrounds the continuity of Baudrillard's work by highlighting how an antagonistic entwining of the semiotic and the symbolic structures Baudrillard's oeuvre. Crucially, Smith suggests that the possibilities of post-Marxism will only come into clear view once the semiotic logic at the heart of ‘the general political economy of the sign’ is freed from the Utopian mystique of symbolic exchange. In the second series of readings, Marcus Doel engages with the spacing at play with Baudrillard's and Smith's texts in an attempt to demonstrate that they are perpetually turning against themselves. By way of a series of angled, slanted, curvaceous, and suspended readings drawn from Althusser, Baudrillard, Deleuze, Derrida, and Lyotard, Doel deconstructs Smith's post-Marxism in order to affirm the irreducible, aleatory drift of Baudrillard's spiralling texts.
Other Domains of Democratic Theory: Space, Power, and the Politics of Democratization
Authors: Slater David
Published: August 2002

Located in the analysis of spatial power and democratic politics, this paper brings together three guiding questions. First, given the fact that inside the West much theorization of power and social relations has assumed a geohistorical context that is intrinsically Western, to what extent and in what ways does this particularity constrain the conceptual and thematic effectiveness of the perspectives employed and especially in relation to the politics of democratization? Second, as it is most appropriate to argue that power shapes social identities, and that democratic politics cannot dispense with power, a key question becomes how to generate relations of power that are compatible with democratic values and opposed to ethnocentric privilege. Third, how can we open up a discussion of democratic politics so that the geographies of democratization can be explored in a way that might broaden our vision of power and geopolitics? These questions are pursued in the context of the coloniality of power and an exploration of the territoriality of democratization in the Peruvian and Bolivian cases. The overall objective is to go beyond the limits of a Euro—Americanist frame and open up the analysis of the complex and dynamic geographies of democracy.
Immigration Research in the Politics of an Anxious Nation
Authors: Fincher Ruth
Published: August 2002

In this paper I examine the closure of the national government-funded Bureau of Immigration Research in 1996, soon after the election of a conservative political coalition to power in Australia. The Bureau's abolition is treated as a defining event in the profound shift that has been observable over the last five years in the forms of evidence produced and publicly aired about immigration. I seek both to form an explanation for the demise of this successful research institution and to provide examples of the research about immigration that was produced during the time of the Bureau, and after its closure. Using evidence primarily from a reading of contemporary media texts, government reports, and statistics, the analysis is made with reference to three themes. First, immigration as a contested ‘issue’, and the style of research done about it, is situated in the context of the new politics of nationhood emerging from the recent shift in federal governments. Second, views of the ‘facts’ of immigration that were publicly prevalent in the days of the Bureau's operation, are contrasted with those now dominant. Third, particular representations of immigration found in these contrasting accounts are examined.
As a City Besieged: Place, Zionism, and the Deforestation of Jerusalem
Authors: Cohen Shaul E
Published: August 2002

Environmental disputes in Israel reflect the pervasive metanarrative of Zionism, and are frequently about friction over symbols of national identity and meaning. Currently, actors engaged in a conflict over a small forest at the margins of Jerusalem harness nationalism/Zionism, and ‘other’ their opponents, as they seek to enlist support beyond their natural constituency. Fieldwork with Green groups and an analysis of their public and internal documents show that municipal officials who are converting the area of the forest to commercial development are cast as (Arab) attackers of the city. Municipal officials also tap national tropes and a security discourse, and claim to be defending Jewish control of Jerusalem. In this paper I show that theories of space, place, and resistance must be supplemented with a contextual and rounded analysis of the master cultural narratives that form the symbolic grounds of these conflicts. It also reveals the complexity of resistance narratives, as the weak seek to benefit from discourses they share with their opponents.
Social Balance and Mixed Neighbourhoods in Britain since 1979: A Review of Discourse and Practice in Social Housing
Authors: Goodchild Barry , Cole Ian
Published: August 2002

In Britain, current interest in social balance has arisen partly as a response to increased management difficulties in social housing and partly in response to the concepts of the underclass and social exclusion. Social balance is now endorsed in some, but not all, the relevant urban policy statements of the New Labour government elected in 1997. A modified form of poststructural discourse analysis offers the best way of understanding the term and its implications. The approach focuses on different levels of social reality—the level of a national policy, the level of management and estate upgrading, and the level of the social experience of residents. In doing this, the approach reveals the varied and occasionally contradictory meanings of the term ‘social balance’; it highlights the increasingly common attempts by social housing agencies to control the characteristics of their tenants; and it enables a sceptical assessment of the practical significance of mixed housing estates for poor individuals and households.
Till Death do us Part: Masculinity, Friendship, and Nationalism in Belfast, Northern Ireland
Authors: Dowler Lorraine
Published: August 2002

Inherent to the conflict in Northern Ireland has been the spatial segregation of men from women, whereby men go to prison and women are left to support and take care of their families. As a result of this segregation, a power relationship has been established that informs men's relationships both with women and with other men. While in prison, Irish men developed highly charged political friendships which reinforced the exclusion of women from the body politic. The eradication of women from the political discourses of the prison has been reincarnated years later in the spaces of Nationalist clubs. The private spaces of Long Kesh gave birth to a third space which is constructed from the traditional characteristics of both the private and the public spheres. This third space, unlike the impenetrable walls of the prison, represents an opening up of space whereby men no longer had to mirror the unrealistic image of the superhero. Instead this space represented a homeplace where these men could simply be themselves.
An Empirical Study of the Traditional Mach Card Effect
Authors: Bloj Marina G , Hurlbert Anya C
Published: August 2002

The traditional achromatic Mach card effect is an example of lightness inconstancy and a demonstration of how shape and lightness perception interact. We present a quantitative study of this phenomenon and explore the conditions under which it occurs. The results demonstrate that observers show lightness constancy only when sufficient information is available about the light-source position, and the perceptual task required of them is surface identification rather than direct colour-appearance matching. An analysis and comparison of these results with the chromatic Mach card effect (Bloj et al 1999 Nature402 877–879) demonstrate that the luminance effects of mutual illumination do not account for the change in lightness perception in the traditional Mach card.
The Influence of Chromatic and Achromatic Variability on Chromatic Induction and Perceived Colour
Authors: Brenner Eli , Cornelissen Frans W
Published: August 2002

Judgments of the colour of a surface are influenced by the colour of the surrounding. To determine whether only the average colour of the surrounding matters, or also the chromatic variability, judgments in colourful scenes are often compared with ones in which a target is surrounded by a plain background that provides the same average physical illumination of the retina as the colourful scene. The variability sometimes makes a difference (eg Shevell and Wei, 1998 Vision Research38 1561–1566), and sometimes it does not (eg Brenner and Cornelissen, 1998 Vision Research38 1789–1793). Is this because of the nonlinearity in cone responses? We designed scenes that stimulated the cones in an equivalent manner, both on average and in terms of variability, and yet differed markedly in chromatic variability. The more colourful surroundings had considerably less influence on subjects' colour judgments. We conclude that early cone-specific regulation of sensitivity cannot be responsible for the change in perceived colour, and deduce that chromatic induction takes place after contrast gain control.
Scene Articulation: Dependence of Illuminant Estimates on Number of Surfaces
Authors: Linnell Karina J , Foster David H
Published: August 2002

The ability of observers to detect changes in illuminant over two scenes containing different random samples of reflecting surfaces was determined in an experiment with Mondrian-like patterns containing different numbers of coloured patches. Performance was found to improve as the number of patches increased from 9 to 49. In principle, observers could have used space-average scene colour as the cue (‘grey-world’ hypothesis) or the colour of the brightest surface in the scene (‘bright-is-white’ hypothesis), as the two cues generally covary. In a second experiment, observers matched illuminants across different patterns in which the space-average cue and the brightest-patch cue were independently manipulated. The articulation of the patterns was varied: the number of patches increased from 49 (patch width 1 deg visual angle) to over 50 000 (patch width 0.03 deg), while the gamut of colours was held constant. Space-average colour was found to be the dominant cue with all patterns except for those with the largest patches.
Surface-Illuminant Ambiguity and Color Constancy: Effects of Scene Complexity and Depth Cues
Authors: Kraft James M , Maloney Shannon I , Brainard David H
Published: August 2002

Two experiments were conducted to study how scene complexity and cues to depth affect human color constancy. Specifically, two levels of scene complexity were compared. The low-complexity scene contained two walls with the same surface reflectance and a test patch which provided no information about the illuminant. In addition to the surfaces visible in the low-complexity scene, the high-complexity scene contained two rectangular solid objects and 24 paper samples with diverse surface reflectances. Observers viewed illuminated objects in an experimental chamber and adjusted the test patch until it appeared achromatic. Achromatic settings made under two different illuminants were used to compute an index that quantified the degree of constancy. Two experiments were conducted: one in which observers viewed the stimuli directly, and one in which they viewed the scenes through an optical system that reduced cues to depth. In each experiment, constancy was assessed for two conditions. In the valid-cue condition, many cues provided valid information about the illuminant change. In the invalid-cue condition, some image cues provided invalid information. Four broad conclusions are drawn from the data: (a) constancy is generally better in the valid-cue condition than in the invalid-cue condition; (b) for the stimulus configuration used, increasing image complexity has little effect in the valid-cue condition but leads to increased constancy in the invalid-cue condition; (c) for the stimulus configuration used, reducing cues to depth has little effect for either constancy condition; and (d) there is moderate individual variation in the degree of constancy exhibited, particularly in the degree to which the complexity manipulation affects performance.
Detecting Anticipatory Events in Handwriting Movements
Authors: Kandel Sonia , Orliaguet Jean-Pierre , Boë Louis-Jean
Published: August 2002

We investigated how visual processes exploit specific anticipatory movements observed in handwriting gestures. Previous research has shown that the kinematic information contained in the downstroke of an l is exploited to predict the identity of the forthcoming letter. Here, we determined the moment at which prediction takes place. Two between-letter effects were examined: changes in size ( ll vs le) and changes in rotation direction ( le vs ln). Results show that with only 75% of the l downstroke trajectory (or 60% of the downstroke time) subjects are already capable of predicting the identity of the letter following the l, that is well before the end of the downstroke. Analysis also reveals that identification takes place after the presentation of the movement acceleration phase. The visual perception of motor anticipation seems to involve the detection of motor events.
Visual Metrics: Discriminative Power through Flexibility
Authors: Janssen Timotheus J W M , Blommaert Frans J J
Published: August 2002

An important stage in visual processing is the quantification of optical attributes of the outside world. We argue that the metrics used for this quantification are flexible, and that this flexibility is exploited to optimise the discriminative power of the metrics. We derive mathematical expressions for such optimal metrics and show that they exhibit properties resembling well-known visual phenomena. To conclude, we discuss some of the implications of flexible metrics for visual identification.
Cross-Modal Interaction between Vision and Touch: The Role of Synesthetic Correspondence
Authors: Martino Gail , Marks Lawrence E
Published: August 2002

At each moment, we experience a melange of information arriving at several senses, and often we focus on inputs from one modality and ‘reject’ inputs from another. Does input from a rejected sensory modality modulate one's ability to make decisions about information from a selected one? When the modalities are vision and hearing, the answer is “yes”, suggesting that vision and hearing interact. In the present study, we asked whether similar interactions characterize vision and touch. As with vision and hearing, results obtained in a selective attention task show cross-modal interactions between vision and touch that depend on the synesthetic relationship between the stimulus combinations. These results imply that similar mechanisms may govern cross-modal interactions across sensory modalities.
Overestimation of Heights in Virtual Reality is Influenced more by Perceived Distal Size than by the 2-D versus 3-D Dimensionality of the Display
Authors: Dixon Melissa W , Proffitt Dennis R
Published: August 2002

One important aspect of the pictorial representation of a scene is the depiction of object proportions. Yang, Dixon, and Proffitt (1999 Perception28 445–467) recently reported that the magnitude of the vertical – horizontal illusion was greater for vertical extents presented in three-dimensional (3-D) environments compared to two-dimensional (2-D) displays. However, because all of the 3-D environments were large and all of the 2-D displays were small, the question remains whether the observed magnitude differences were due solely to the dimensionality of the displays (2-D versus 3-D) or to the perceived distal size of the extents (small versus large). We investigated this question by comparing observers' judgments of vertical relative to horizontal extents on a large but 2-D display compared to the large 3-D and the small 2-D displays used by Yang et al (1999). The results confirmed that the magnitude differences for vertical over-estimation between display media are influenced more by the perceived distal object size rather than by the dimensionality of the display.
Depth Discrimination from Shading under Diffuse Lighting
Authors: Langer Michael S , Bülthoff Heinrich H
Published: August 2002

The human visual system has a remarkable ability to interpret smooth patterns of light on a surface in terms of 3-D surface geometry. Classical studies of shape-from-shading perception have assumed that surface irradiance varies with the angle between the local surface normal and a collimated light source. This model holds, for example, on a sunny day. One common situation in which this model fails to hold, however, is under diffuse lighting such as on a cloudy day. Here we report on the first psychophysical experiments that address shape-from-shading under a uniform diffuse-lighting condition. Our hypothesis was that shape perception can be explained with a perceptual model that “dark means deep”. We tested this hypothesis by comparing performance in a depth-discrimination task to performance in a brightness-discrimination task, using identical stimuli. We found a significant correlation between responses in the two tasks, supporting a dark-means-deep model. However, overall performance in the depth-discrimination task was superior to that predicted by a dark-means-deep model. This implies that humans use a more accurate model than dark-means-deep to perceive shape-from-shading under diffuse lighting.
An Oblique Effect of Chromatic Gratings Measured by Color-Mixture Thresholds
Authors: Krebs William K , Essock Edward A , Buttrey Samuel E , Sinai Michael J , McCarley Jason S
Published: August 2002

Contrast sensitivity is lower for obliquely oriented achromatic gratings than for vertical or horizontal gratings at high spatial and low temporal frequencies. Although this response is suggestive of mediation by P-pathway cortical correlates, no clear sensory (ie class 1) oblique effect has been demonstrated with isoluminant chromatic stimuli. In the present experiment, a two-alternative forced-choice detection task was used to measure observers' sensitivity to spatio-temporal sinusoids varying in orientation and color contrast. A maximum-likelihood method fit ellipses to the thresholds, with the length of each ellipse taken as a measure of chromatic contrast sensitivity at isoluminance, and the width as luminance contrast threshold. A chromatic oblique effect was observed at about 3 cycles deg−1 suggesting an orientation bias within the cortical stream conveying P-cell activity.
Can Attention Select Only a Fixed Number of Objects at a Time?
Authors: Davis Greg , Welch Victoria L , Holmes Amanda , Shepherd Alex
Published: August 2002

Several previous studies have suggested that we may attend only a fixed number of ‘objects’ at a time. However, whereas findings from two-target experiments suggest that we can attend only one object at a time, other results from object-tracking and enumeration paradigms point instead to a four-object limit. Here, we note that in these previous studies the number of objects covaried with the overall size and complexity of the stimulus, such that apparent one-object or four-object limits in those tasks may reflect changes in the complexity of attended stimuli, rather than the number of objects per se. Accordingly, in the current experiments we employ stimuli in which the number of objects varies, while overall size and complexity are held constant. Using these refined measures of object-based effects, we find no evidence for a one-object or four-object limit on attention. Indeed, we conclude that the number of attended objects does not affect how efficiently we can attend a given stimulus. We propose and test an alternative approach to object-based attention limitations based on within-object and between-object feature-binding mechanisms in human vision.
Separating Perception Time from Response Time: The Slope Transition Paradigm
Authors: Matin Ethel , Nofer David C , Gische Lisa
Published: August 2002

This paper describes the slope transition paradigm (STP), a variant of rapid serial visual presentation (RSVP) that separates early (perceptual) processing time from total response time. The paradigm is based on a very simple idea: provide varying amounts of time for perceptual processing and find the moment when the subject begins to waste time waiting for more data. That moment is a measure of how much time was actually needed. The method was used in two experiments. Results are discussed in relation to set-size effects, perceptual capacity limits, attentional dwell times, and some related neurophysiological findings. The method appears to tap aspects of information processing that differ from those tapped in studies of the psychological refractory period, the attentional blink, and repetition blindness.
Perceptual Assignment of Opacity to Translucent Surfaces: The Role of Image Blur
Authors: Singh Manish , Anderson Barton L
Published: August 2002

In constructing the percept of transparency, the visual system must decompose the light intensity at each image location into two components—one for the partially transmissive surface, the other for the underlying surface seen through it. Theories of perceptual transparency have typically assumed that this decomposition is defined quantitatively in terms of the inverse of some physical model (typically, Metelli's ‘episcotister model’). In previous work, we demonstrated that the visual system uses Michelson contrast as a critical image variable in assigning transmittance to transparent surfaces—not luminance differences as predicted by Metelli's model [F Metelli, 1974 Scientific American230(4) 90–98]. In this paper, we study the contribution of another variable in determining perceived transmittance, namely, the image blur introduced by the light-scattering properties of translucent surfaces and materials. Experiment 1 demonstrates that increasing the degree of blur in the region of transparency leads to a lowering in perceived transmittance, even if Michelson contrast remains constant in this region. Experiment 2 tests how this addition of blur affects apparent contrast in the absence of perceived transparency. The results demonstrate that, although introducing blur leads to a lowering in apparent contrast, the magnitude of this decrease is relatively small, and not sufficient to explain the decrease in perceived transmittance observed in experiment 1. The visual system thus takes the presence of blur in the region of transparency as an additional image cue in assigning transmittance to partially transmissive surfaces.
Effect of fruit maturity on the response of 'Kensington' mango fruit to heat treatment
Authors: Jacobi K. K. , MacRae E. A. , Hetherington S. E.
Published: August 2002

The effects of conditioning and hot water treatments on immature and mature
‘Kensington’ mangoes were examined. A hot water treatment of
47°C fruit core temperature held for 15 min increased weight loss
(50%), fruit softness (15%), disrupted starch hydrolysis and
interacted with maturity to reduce the skin yellowness (40–51%)
of early harvested fruit. Immature fruit were more susceptible to hot water
treatment-induced skin scalding, starch layer and starch spot injuries and
disease. Conditioning fruit at 40°C for up to 16 h before hot water
treatment accelerated fruit ripening, as reflected in higher total soluble
solids and lower titratable acidity levels. As fruit maturity increased, the
tolerance to hot water treatment-induced skin scalding and the retention of
starch layers and starch spots increased and susceptibility to lenticel
spotting decreased. A conditioning treatment of either 22° or
40°C before hot water treatment could prevent the appearance of
cavities at all maturity levels. The 40°C conditioning temperature was
found to be more effective in increasing fruit heat tolerance than the
22°C treatment; the longer the time of conditioning at 40°C,
the more effective the treatment (16 v. 4 h). For
maximum fruit quality, particularly for export markets, it is recommended that
mature fruit are selected and conditioned before hot water treatment to reduce
the risk of heat damage.
Environmental effects on stunting and the expression of a tiller inhibition (tin) gene in wheat
Authors: Duggan Brian L. , Richards Richard A. , Tsuyuzaki Hiroshi
Published: August 2002

A recessive gene (tin) that inhibits tillering in wheat
(Triticum aestivum L.), and that may be important in the
redirection of assimilate from unproductive to productive tillers, has been
reported. However, this gene has also been associated with a fatal condition
known as ‘stunting’. The severity of this phenomenon has been
shown to increase when plants are grown under long photoperiods and at low
temperatures. The objectives of this study were to observe how the expression
of the tin gene varied in different genetic backgrounds,
in addition to obtaining a better understanding of environmental factors that
may affect both tillering and stunting in lines with the
tin gene. Plants were grown outdoors in Canberra,
Australia, at various times throughout the year, as well as under controlled
conditions where photoperiod, temperature and light intensity were varied. The
inhibition of tillers resulting from the presence of the
tin gene was most extreme in summer, autumn and spring
(up to 90% reduction in tillering). However, when sown in late autumn
and winter, tillering was reduced by between 30–50% for the
tin lines compared with their near-isogenic parents.
Reduced tillering in the tin lines was due to an earlier cessation of
tillering rather than a reduced rate. Stunting was frequently observed in some
lines more than others when plants were grown under long days and when
temperatures were low. The daily minimum temperature, rather than the average
daily temperature, was associated with stunting. The duration of the dark
period also influenced stunting, with a longer dark period reducing the
incidence of stunting from almost 100% to 0%. In all experiments
where irradiance was increased, stunting also increased. In addition, elevated
CO2 also increased growth characteristics associated
with stunting. It is concluded that stunting is associated with a high
assimilate supply to the main stem shoot apex before the time of floral
initiation. This is caused by an inhibition of tillering and a high
photothermal quotient. Leaf length was found to be a good indicator of
stunting severity, with stunted plants producing shorter leaves than those
plants which failed to stunt. Measurements of leaf length indicated that
stunting is induced when the second leaf is expanding.
Figuring out the figs: the Ficus obliqua-Ficus rubiginosa Complex (Moraceae: Urostigma sect. Malvanthera)
Authors: Dixon Dale J. , Jackes B. R. , Bielig L. M.
Published: August 2002

A revision of the
Ficus obliqua—F. rubiginosa
complex (Moraceae: Urostigma sect.
Malvanthera Corner) is presented. A phenetic analysis of
morphometric characters using clustering techniques and multidimensional
scaling was used to identify the taxa in this complex. Three taxa are
recognised, F. obliqua G.Forst.,
F. rubiginosa Desf. ex Vent. f.
rubiginosa and F. rubiginosa f.
glabrescens (F.M.Bailey) D.J.Dixon. Each taxon is
redescribed. The epithet glabrescens of F. rubiginosa f.
glabrescens is resurrected with a change in status. The
data from the pollinator wasps strongly supports the taxonomy, with
F. obliqua pollinated by
Pleistodontes greenwoodi (Grandi) and
F. rubiginosa sens lat. pollinated by
P. imperialis Saunders. A key to the species and
infraspecific taxa of F. rubiginosa as well as notes and
distribution maps are provided for both species.
Australian boletes: their diversity and possible origins
Authors: Watling Roy
Published: August 2002

The distributions of the major components of the Australian bolete mycota are
considered and suggestions made as to their possible mycogeography. The final
number of species of bolete in Australia is likely to be well over 250 taxa.
CONNECTIVITY PROPERTIES IN RANDOM REGULAR GRAPHS WITH EDGE FAULTS
Authors: NIKOLETSEAS S. , PALEM K. , SPIRAKIS P. , YUNG M.
Published: August 2002

We introduce a new model of random graphs, that of random regular graphs with edge faults (which we denote by [Formula: see text]), obtained by selecting the edges of a random member of the set of all regular graphs of degree r independently and with probability p. We can thus represent a communication network in which the links fail independently and with probability f =1-p.

In order to deal with this new model, we extend the notion of configurations and the translation lemma between configurations and random regular graphs provided by B. Bollobás, by introducing the concept of random configurations, to account for edge faults, and by providing an extended translation lemma between random configurations and [Formula: see text] graphs.

We investigate important connectivity properties of [Formula: see text] by estimating the ranges of r, f for which, with high probability, [Formula: see text] graphs a) are highly connected b) become disconnected and c) admit a giant connected component of small diameter.
COVER OF THE BROWNIAN BRIDGE AND STOCHASTIC SYMPLECTIC ACTION
Authors: LÉANDRE R.
Published: August 2002

We define the universal cover of the Brownian bridge of a symplectic manifold. This allows us to define a non-trivial functional over it called the stochastic symplectic action, and to define local Sobolev spaces over the universal cover, such that the symplectic action belong to them. This is done in the purpose of an analytical Morse theory in the sense of Witten over the loop space associated to this symplectic action. In this purpose, a stochastic Witten complex is constructed over the universal cover of the loop space, and modulo some weights, it is shown that its cohomology is equal to the stochastic cohomology of the universal cover.
THE GLOBAL MINIMUM OF THE EFFECTIVE POTENTIAL OF THE MANY-ELECTRON SYSTEM WITH DELTA-INTERACTION
Authors: LEHMANN DETLEF
Published: August 2002

We prove that the global minimum of the real part of the full effective potential of the many electron system with attractive delta interaction is in fact given by the BCS mean field configuration. This is a consequence of a simple bound which is obtained by applying Hadamard's inequality to the functional determinant. The second order Taylor expansion around the minimum is computed.
ON BRIDGE NUMBERS OF COMPOSITE RIBBON KNOTS
Authors: Tanaka Toshifumi
Published: August 2002

Bleiler and Eudave-Muñoz showed that composite ribbon number one knots have two-bridge summands. In this paper, we show that there exists an infinite family of composite ribbon number one knots which have arbitrary large bridge numbers.