Showing papers by "University of Maine published in 1991"

Point-set topological spatial relations

Abstract: Practical needs in geographic information systems (GIS) have led to the investigation of formal and sound methods of describing spatial relations. After an introduction to the basic ideas and notions of topology, a novel theory of topological spatial relations between sets is developed in which the relations are defined in terms of the intersections of the boundaries and interiors of two sets. By considering empty and non-empty as the values of the intersections, a total of sixteen topological spatial relations is described, each of which can be realized in R 2. This set is reduced to nine relations if the sets are restricted to spatial regions, a fairly broad class of subsets of a connected topological space with an application to GIS. It is shown that these relations correspond to some of the standard set theoretical and topological spatial relations between sets such as equality, disjointness and containment in the interior.

Reasoning about Binary Topological Relations

Abstract: A new formalism is presented to reason about topological relations. It is applicable as a foundation for an algebra over topological relations. The formalism is based upon the nine intersections of boundaries, interiors, and complements between two objects. Properties of topological relations are determined by analyzing the nine intersections to detect, for instance, symmetric topological relations and pairs of converse topological relations. Based upon the standard rules for the transitivity of set inclusion, the intersections of the composition of two binary topological relations are determined. These intersections are then matched with the intersections of the eight fundamental topological relations, giving an interpretation to the composition of topological relations.

Environmental effects on algal photosynthesis: temperature

Abstract: Three main aspects of the response of photosynthesis to temperature are reviewed: the short-term effect of temperature on photosynthetic metabolism, that is, the photosynthetic response when an alga is suddenly exposed to a higher or lower temperature, phenotypic changes in photosynthetic metabolism that occur in response to growth at different temperatures, and genetic differences in photosynthetic metabolism between algal species or ecotypes from different thermal environments

Qualitative Spatial Reasoning with Cardinal Directions

Abstract: Following reviews of previous approaches to spatial reasoning, a completely qualitative method for reasoning about cardinal directions, without recourse to analytical procedures, is introduced and a method is presented for a formal comparison with quantitative formulae. We use an algebraic method to formalize the meaning of cardinal directions. The standard directional symbols (N, S, E, W) are extended with a symbol 0 to denote an undecided case, which greatly increases the power of inference. Two examples of systems to determine and reason with cardinal directions are discussed in some detail and results from a prototype are given. The deduction rules for the coordination of directional symbols are formalized as equations; for inclusion in an expert system they can be coded as a look-up table (given in the text). The conclusions offer some direction for future work.

Retinohypothalamic tract in the female albino rat: a study using horseradish peroxidase conjugated to cholera toxin.

Abstract: There are several anatomically and functionally distinct retinofugal pathways, one of which is the retinohypothalamic tract (RHT). In this study, horseradish peroxidase conjugated to cholera toxin (CT-HRP), a sensitive neural tracer, was employed to describe the RHT in the female albino rat. Following uniocular injection of CT-HRP, both medial and lateral components of the RHT were evident. The medial component swept caudally into and through the suprachiasmatic nucleus (SCN) and dorsally to the subparaventricular zone. Terminal label was seen in the medial preoptic region, peri-SCN area, retrochiasmatic area, periventricular nucleus, anterior and central parts of the anterior hypothalamic area, and the subparaventricular zone. In contrast to the more focused and symmetrical medial component, the lateral component was diffuse with light terminal label in the lateral preoptic region, olfactory tubercle, lateral hypothalamus, supraoptic nucleus, and medial and posteroventral medial amygdaloid nuclei. The striking exception to this diffuse pattern of the lateral component was an extremely dense columnar terminal field over the dorsal border of the supraoptic nucleus. Whereas the intensity of label in terminal fields of the medial component was often similar on the sides ipsilateral and contralateral to the injection, the lateral component was consistently asymmetrical with greater labeling on the side contralateral to the injection. In addition, a light projection arrived at several thalamic nuclei by returning toward the thalamus from the tectal or pretectal areas via stria medullaris, and thus was not a part of the RHT. Implications for circadian as well as noncircadian photobiologic effects are discussed.

Punitive Attitudes Toward Criminals: Racial Consensus or Racial Conflict?

Abstract: A sizeable body of literature has found a surprising amount of agreement among racial and other demographic subgroups on punitive attitudes toward criminals. This consensus has been widely interpreted as evidence for functionalist views of crime and society. Challenging this interpretation, this paper argues that the similar attitudes between the races on punitiveness may in fact mask underlying hostilities and conflicting interests. Analyzing data from the 1987 National Opinion Research Center (NORC) General Social Survey, we find that the punitive attitudes of whites toward criminals are based partly on racial prejudice, while those of blacks are associated with their fear of crime. These results suggest that the consensus found in many previous studies between whites and blacks on punitiveness toward criminals may be apparent rather than real, and that their attitudes toward punitiveness reflect their disparate positions in the social and economic orders.

Protein functionality modification by extrusion cooking

Abstract: Cooking extruders process high-protein materials into palatable foods. New applications have been developed for protein extrusion during the past decade. Improvements in functional characteristics of proteins may be achieved through modification of temperature, screw speed, moisture content, and other extrusion parameters. Flavors and odors may be removed during expansion at the extruder die. Extrusion can improve the digestibility of proteins, while reducing gossypol, proteinase inhibitors, allergens, aflatoxins, and other undesirable compounds. In the future the use of extruders as chemical reactors for both animal and plant proteins will provide new food ingredients as well as novel, nutritious foods.

The photolysis of colloidal iron in the oceans

Abstract: THE extent to which iron limits primary production in open ocean waters depends not only on the aeolian supply1–3, but also on factors that control its availability for biological uptake. Although the marine chemistry of iron is poorly understood, much of it occurs in refractory participate1,2 and colloidal4 states—forms unavailable for direct assimilation by phytoplankton5,6. But iron availability depends on its chemical lability5, or ease of dissolution; hence processes that alter the lability of particulate and colloidal iron in sea water govern their availability to phytoplankton. Here we report that light increases the lability of colloidal iron in sea water of pH 8, with a photon-normalized spectral dependence that generally increases with decreasing wavelength from 400–300 nm. From optical modelling we predict that the incident solar spectrum, combined with the preferential attenuation of shorter ultraviolet wavelengths in sea water, will lead to a maximum depth-integrated photoreaction near 380–400 nm. Our results show that the photolysis of forms of solid iron may occur deep into the ocean's euphotic zone, and hence that the availability of iron to phytoplankton in the ocean may be much greater than previously thought.

The phttoconversion of colloidal iron oxyhydroxides in seawater

Abstract: The marine photochemistry of colloidal Fe oxyhydroxides was studied in order to determine its role in modifying the availability of Fe for phytoplankton. Using a new technique that measures a labile portion of total Fe in seawater, the lability of synthetic crystalline and non-crystalline colloidal Fe oxyhydroxides was found to increase in pH8 seawater upon irradiation with UV light, and simulated and natural full spectrum sunlight. The increased lability appeared to result from an organic-dependent Fe photoreduction followed by very rapid Fe(II) oxidation and Fe(III) reprecipitation as ferrihydrite. Aging in the dark caused significant reductions in the lability of the photoproduced ferrihydrites, with both synthetic iron oxides and natural iron from sunlit surface seawater. The results suggest that the lability of Fe in surface seawater varies in response to competing processes of photoredox and aging of Fe on oxyhydroxide surfaces. Because the lability of colloidal Fe correlates positively with its availability to marine algae, the photolysis of colloidal Fe has direct implications for phytoplankton.

Techniques for improving resolver-to-digital conversion accuracy

Abstract: Several methods for reducing the position error caused by the existence of imperfect resolver signal characteristics are introduced. The most straightforward method is simply to calibrate each resolver and resolver-to-digital (R/D) converter and then correct the R/D converter output in real time. Although this method corrects all errors, including those with an origin in the R/D converter, it is also the most time-consuming and labor-intensive. By appropriate signal processing, it is shown that quadrature error can be eliminated by simple algebraic manipulation of the resolver signals. Similarly, it is shown that all even harmonics in the resolver signals can be canceled if the resolver is constructed with complementary phases. It is shown that amplitude imbalance can be used to reduce the position error due to inductive harmonics. >

Temperature acclimation of respiration and photosynthesis in the brown alga Laminaria saccharina

Abstract: Sporophytes of the brown algaLaminaria saccharina (L.) Lamour grown at 15°C contained significantly more chlorophylla (chla) than did similar plants grown at 5°C. The increase in chla in 15°C plants was due to increased numbers of photosystem II reaction centes, and possibly to increased photosynthetic unit size, compared with 5°C plants. These changes were associated with increasedα values (photosynthetic efficiencies) in 15°C-grownL. saccharina relative to 5°C-grown plants. The changes inα together with reduced respiration rates allowed 15°C-grownL. saccharina to achieve net photosynthesis and light-saturated photosynthesis at a lower photon fluence rate (PFR) than 5°C plants when both groups were assayed at the same temperature (15°C). The photon fluence rates necessary to reach the compensation point and achieve light-saturated photosynthesis (I c andI k , respectively) increased with increasing incubation temperature inL. saccharina grown at both 5 and 15°C. However, acclimation responses to growth temperature compensated for the short-term effect of temperature onI c andI k . Consequently, plants grown at 5 and 15°C were able to achieve similar rates of light-limited photosynthesis, and similarI c andI k values at their respective growth temperatures. These responses are undoubtedly important for perennial seaweeds such asL. saccharina, which frequently grow in light-limited habitats and experience pronounced seasonal changes in water temperature.

A Formalization of Metaphors and Image-Schemas in User Interfaces

Abstract: Sound engineering approaches to user interface design require the formalization of key interaction concepts, one of them being metaphor. Work on interface metaphors has, however, been largely non-formal so far. The few existing formal theories of metaphor have been developed in the context of natural language understanding, learning, or reasoning. We propose to formalize interface metaphors by algebraic specifications. This approach provides a comprehensive formalization for the essential aspects of metaphorical user interfaces. Specifically, metaphor domains are being formalized by algebras, metaphorical mappings by morphisms, and image-schemas by categories. The paper explains these concepts and the approach, using examples of spatial and spatializing metaphors.

Peer Relationships and Adjustment in Children with Cancer

Abstract: Evaluated the psychosocial adaptations of children with cancer (n = 24, ages 8-18) as compared with same classroom controls on indices of (a) peer- and self-perceptions of sociability, aggression, and social isolation; (b) overall popularity; (c) mutual friendships; (d) feelings of loneliness; and (e) self-concept in multiple domains Although the peer report data showed that children with cancer had a social reputation as significantly more socially isolated, no significant differences were found for their popularity, number of mutual friends, loneliness, or self-worth Findings suggest that children with cancer have a reputation as more socially isolated, but differences were not found on measures of acceptance by peers, self-concept, or loneliness

Improved compensation for analog-to-digital converters

Abstract: Two changes are recommended for procedures used in building two-dimensional state-space error correction tables to compensate high-speed analog-to-digital converters (ADCs). The modifications require three frequencies to calibrate all states as well as extrapolation of estimated outputs to achieve a straight line input-output integral characteristic for the ADC. A simulated 6-bit ADC with only 35-dBc spurious free signal range is shown to be correctable to 53 dB over 80% of the Nyquist band when suggested changes are used to calibrate the ADC. >

Protein and Fiber Supplementation Effects on Extruded Cornmeal Snack Quality

Abstract: Cornmeal snacks containing blends of soy protein isolate (SPI) with cotton linter cellulose (CEL) or soy cotyledon fiber (SF) were produced with a twin screw extruder. SPI increased expansion and reduced collet bulk density. Samples containing soy materials were darker than those containing 10% CEL or only cornmeal. CEL reduced expansion and increased residual moisture. The effects of SF were intermediate between those of SPI and CEL. Samples containing either type fiber had slight increases in nitrogen solubility and higher losses of available lysine after extrusion. A sensory evaluation panel found samples with 15% SPI and 10% either fiber were tan and soft, with a nutty or grain flavor.

Spatial Relationships between Nesting Colonies and Foraging Areas of Great Blue Herons

Abstract: --I examined spatial relationships between nesting colonies of Great Blue Herons (Ardea herodias) and their aquatic foraging areas by synthesizing data from a survey of nesting colonies, a study of foraging Great Blue Herons, and a wetland inventory. I assessed whether Great Blue Herons gained energetically by nesting colonially at sites central to foraging areas versus solitarily and dispersed evenly over foraging areas. Nesting colonies (n = 29) were closer to local concentrations of foraging habitat and to points of minimum aggregate travel to all regional foraging areas than expected by chance. The number of nests per colony correlated positively with the availability of foraging habitat (in hectares) within commuting distance of a colony and negatively with foraging costs (km flown per ha wetland visited). Through computer simulations I found that an equally sized, hypothetical population of solitarily nesting herons dispersed evenly over foraging areas would experience higher foraging costs than colonially nesting herons. The spatial arrangement of wetlands upon the landscape of inland Maine limits the availability of sites with efficient access to heron foraging areas, and favors clumped nesting patterns. Received 2 October 1990, accepted 23 February 1991. COLONIAL birds often forage far from nesting or roosting sites (e.g. Hamilton et al. 1967), and species that depend on spatiotemporally clumped foods in theory benefit energetically by nesting in colonies central to the food distribution (Horn 1968, Wittenburger and Hunt 1985). My purpose was to evaluate two assumptions of Horn's (1968) geometrical model: (1) that colonies of a large, colonially nesting wading bird were located centrally to the food distribution, and (2) that energy expenditures were less for colony members than for an equally sized, hypothetical population distributed evenly over the same food distribution (Wittenburger and Hunt 1985). In Maine, Great Blue Herons (Ardea herodias) feed primarily in local and relatively permanent aquatic habitats (Palmer 1949) where food availability varies spatially and temporally (Krebs 1974). Thus, the distribution and abundance of nesting herons can be compared with that of various types of wetlands ranked according to their foraging profitability to herons. I compared the spatial configuration of aquatic foraging areas near (1) occupied colony sites and seemingly suitable-but unoccupied--sites, (2) nests of colonial breeders and nests of a hypothetical, equally : Present address: School of Forestry and Environmental Studies, Yale University, 205 Prospect Street, New Haven, Connecticut 06511 USA. 764 sized population of dispersed, solitarily nesting herons, and (3) nesting colonies of varying size.

Diffusion of geographic information innovations

Abstract: Appropriate diffusion of geographic information technologies is hampered by lack of systematic research on factors and processes affecting diffusion, utilization and impact assessment of the technologies and by a variety of conceptual and methodological problems. Diffusion of innovation principles developed in other fields, in combination with methods developed within the field of management information systems, provide an important beginning for improved understanding. This paper focuses on gaps in knowledge which might be addressed within the geographic information field by analysis techniques and research methodologies used in the diffusion of innovations.

The isolation and immunolocalization of iron-binding compounds produced by Gloeophyllum trabeum

Abstract: Low molecular weight iron-binding compounds are produced by the brown-rot fungus Gloeophyllum trabeum. These chelators may function in scavenging transition metals for fungal metabolism and extracellular enzyme production. Because of the low molecular mass of the chelate-metal complex (below 1000 Da), and the oxidizing potential of the bound transition metals, certain chelating compounds could also play a role in the early stages of cellulose depolymerization by brown-rot fungi. High-affinity iron-binding compounds were isolated and partially purified from both liquid cultures of the brown-rot Gloeophyllum trabeum and from infected wood. Chelating compounds purified by thin-layer chromatography were used to prepare specific antibodies. These antibodies were shown to detect the chelator in infected wood and liquid fungal cultures by enzyme-linked immunosorbent assay and could be used in immunotransmission electron microscopy to visualize the high-affinity iron-binding compounds in situ. Elucidating the physiological roles of fungal chelate-metal complexes and determining their function in lignocellulose depolymerization will help us to better understand the mechanism of wood biodegradation.

Cognitive and Linguistic Aspects of Geographic Space: An Introduction

Abstract: This volume contains papers presented or discussed at a NATO Advanced Study Institute on “Cognitive and Linguistic Aspects of Geographic Space,” held in Las Navas del Marques, Spain, July 8–20,1990. We organized the meeting as a place to discuss people’s understanding of space, specifically geographic space. An important subsidiary goal was to try to understand how such cognitive concepts of space relate to Geographic Information Systems (GISs). We invited researchers from a wide spectrum of disciplines, from geography and linguistics, psychology and anthropology, to mathematics and engineering. Each of the disciplines deals with some aspect of understanding space. Each discipline, and indeed each individual, views the problem in a different way and from a unique vantage point. The papers collected in this volume represent much of the breadth of this spectrum. Any such a collection of papers is of course influenced by the limitations of the size of the meeting, the availability of participants, and their ability to contribute to the topic. Despite this, we believe that the papers in this volume present a valuable perspective on our current understanding, and open5 a host of research avenues.