Showing papers by "University of Maine published in 1992"

Teachers' Sense of Efficacy and Commitment to Teaching

Abstract: The present study examined the degree to which teachers' sense of efficacy, as well as other hypothesized influences on commitment to teaching, predicted 170 teachers' responses to the question, “Suppose you had it to do all over again: In view of your present knowledge, would you become a teacher?” General and personal efficacy emerged as the two strongest predictors of teaching commitment, along with teacher-student ratio, school climate, and sex. In short, greater teaching commitment tended to be expressed by those teachers who were higher in both general and personal efficacy; who taught in schools with fewer students per teacher; and who worked under a principal regarded positively in the areas of instructional leadership, school advocacy, decision making, and relations with students and staff. Teaching commitment also was higher for female teachers.

Reasoning about Gradual Changes of Topological Relationships

Abstract: Geographic objects and phenomena may gradually change their location, orientation, shape, and size over time. A qualitative change occurs if the deformation of an object affects its topological relationship with respect to another object. The observation of such changes is particularly interesting, because qualitative changes frequently require different decisions or trigger new actions. Investigations of a closed set of mutually exclusive binary topological relationships led to a formal model to determine for each topological relationship the relationships closest to it. Applied to the entire set of binary topological relationships between spatial regions, this model describes a partial order over topological relationships and provides a measure to assess how far two relationships are apart from each other. The changes to the binary topological relationship caused by such deformations as translation, rotation, reduction, and expansion of an object are mapped onto this graph. The graphs show characteristic traverses for each kind of deformation. Using these characteristic traverses as knowledge about deformations, one can infer from multiple observations the kind of deformation that caused the change and predict the next topological relationship. Particularly, it provides answers to three kinds of qualitative space-time inferences: (1) Given a process and a state, what is the next most likely state? (2) Given an ordered pair of states, what process may have occurred? (3) Given an ordered pair of states and a process, in what states must the two objects have been in between?

Simultaneous miocene extension and shortening in the himalayan orogen.

Abstract: The South Tibetan detachment system separates the high-grade metamorphic core of the Himalayan orogen from its weakly metamorphosed suprastructure It is thought to have developed in response to differences in gravitational potential energy produced by crustal thickening across the mountain front Geochronologic data from the Rongbuk Valley, north of Qomolangma (Mount Everest) in southern Tibet, demonstrate that at least one segment of the detachment system was active between 19 and 22 million years ago, an interval characterized by large-scale crustal thickening at lower structural levels These data suggest that decoupling between an extending upper crust and a converging lower crust was an important aspect of Himalayan tectonics in Miocene time

Is density an indicator of breeding success

Abstract: -A new method of measuring reproductive success was used to test Van Horne's (1983) contention that reliance on population density as a measure of habitat quality can produce misleading results. None of the three emberizine sparrows in this study showed a clear correlation between high territory density and high reproductive success. Grasshopper Sparrows (Ammodramus savannarum) were most successful in medium-density plots, and did poorly when territory density was low. Savannah Sparrows (Passerculus sandwichensis) were significantly more successful at low density, and were least successful at high density. Vesper Sparrows (Pooecetes gramineus) were the only species whose reproductive success was unaffected by territory density and, thus, for which density would have been a reasonable measure of habitat quality. These results lend support to Van Horne's thesis that the singular use of density may be a poor indicator of habitat quality and that additional factors should be considered. Received 5 March 1991, accepted 10 February 1992. POPULATION DENSITY frequently is used as an indicator of a habitat's quality, because a greater number of individuals within a given area is generally thought to reflect larger amounts of the necessary resources to sustain a species (Van Horne 1983). By extension, it often is assumed that concentration of resources allowing a high population density also will be reflected in greater reproductive success, or other indices of fitness. Because density is easier to measure than fitness, Flood et al. (1977) and others who model habitat relationships have used density to make inferences about habitat quality, although not necessarily with a high degree of predictive success (Lancia et al. 1982, Bart et al. 1984, Maurer 1986). Van Horne (1983) questioned the singular reliance on density as an indicator of habitat quality and suggested that inferences about which habitats support individuals with the highest fitness often may be false. She suggested that, from a populationviability and management perspective, it is preferable to define habitat quality as a product of density and reproductive success. To test the hypothesis that density is a reasonable index of nesting habitat quality for three grassland sparrows, we examined the relationship between 3Present address: Conservation Department, Massachusetts Audubon Society, Lincoln, Massachusetts 01773, USA. 4Present address: Department of Natural Resources, Field of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York 14853, USA. breeding densities and reproductive success for each species. METHODS The study site was located on a sandplain grassland in Kennebunk, York County, Maine (43024'N, 70?59'W). We studied three emberizine sparrows: Vesper Sparrow (Pooecetes gramineus); Savannah Sparrow (Passerculus sandwichensis); Grasshopper Sparrow (Ammodramus savannarum). Vickery et al. (1992) provided additional information on site and methods. The site was managed for commercial blueberry production with one-half of the area mowed and burned on a biennial rotation. This management created profound year-to-year changes in the vegetation structure with a concomitant influence on habitat quality. These habitat manipulations allowed us to measure the avian response to these year-to-year changes in each plot. To examine the relationship between territory density and reproductive success, territories were "spot mapped" (International Bird Census Committee 1970) using eight replicate censuses on eight plots (8-24 ha) for three years (1984-1986). For each species, plots were assigned to a class depending on territory density: low, '2.5 territories per 10 ha; medium, >2.5 to <3.5 territories per 10 ha; high, 23.5 territories per 10 ha. There were at least four plots for each density category. The reproductive-index rank (Vickery et al. 1992) for each territory was assigned to the appropriate density category. We then used the KruskalWallis test (Conover 1980:229) to determine if there were differences in the reproductive-index rankings within each density classification. We measured percent cover for nine vegetation features for high-success and low-success Grasshopper, Savannah and Vesper sparrows, and also measured the same parameters on the unoccupied habitat in each plot. To evaluate whether Savannah Sparrows

Ecological Aspects of Methane Oxidation, a Key Determinant of Global Methane Dynamics

Abstract: Methane oxidation became a subject of scientific inquiry when Alessandro Volta observed in 1776 that gas bubbles collected from a pond were combustible. Methane was subsequently exploited as a source of heat and light. However, in spite of its commercial significance, the biological and ecological aspects of methane oxidation were largely ignored until the pioneering work of Sohngen (1906), who first isolated methane-oxidizing bacteria (MOB). [Quayle (1987) notes that Lowe probably isolated the first MOB in 1892 without recognizing their ability to oxidize methane.] Little additional progress was made until the 1960s, at which time the systematic efforts of several groups provided methodological tools and details on the taxonomy, physiology, and biochemistry of C1 metabolism. Aside from purely academic motivations, this work was stimulated by: (1) the potential use of methanotrophic bacteria as sources of “single cell protein”; (2) the role of methylotrophic bacteria in food spoilage; (3) the possible use of methanotrophs in the bioremediation of certain halogenated organic pollutants or as agents for commercial biotransformations (Higgins et al., 1980). Ecological studies were slower in development, but a number of important observations established the ubiquity of methanotrophs, the impact of methane oxidation in freshwater and some marine systems, and the potential for anaerobic as well as aerobic methane oxidation (see Hanson, 1980, and Rudd and Taylor, 1980, for earlier reviews).

Recruitment and mortality of early post-settlement stages of benthic algae

Abstract: Four transitional life history stages are generally recognized for benthic marine algae. On the basis of differences in size, we propose two more: young germlings and young juveniles. Three of these (spores or zygotes, young germlings, and germlings) are considered early post-settlement (EPS) stages. Many of the available data on recruitment and mortality were not collected with EPS stages specifically in mind, and considerable extrapolation and inference are required to interpret effects on early phases. Data on EPS stages, and grazing in particular, are based on the disappearance of early stages (laboratory or field experiments, including outplantings), on indirect information on mortality from manipulations of grazers or juvenile stages, and combinations of observation and manipulation. We also provide original data on the effects of water motion and canopy sweeping on zygote mortality. The most notable finding is the variability in, and multiplicity of, factors preventing successful recruitment of ear...

Effects of Temperature on Methane Consumption in a Forest Soil and in Pure Cultures of the Methanotroph Methylomonas rubra.

Abstract: Methane oxidation in soil cores from a mixed hardwood-coniferous forest varied relatively little as a function of incubation temperatures from −1 to 30°C. The increase in oxidation rate was proportional to T2.4 (in kelvins). This relationship was consistent with limitation of methane transport through a soil gas phase to a subsurface zone of consumption by diffusion. The Q10 for CO2 production, 3.4, was substantially higher than that for methane oxidation, 1.1, and indicated that the response of soil respiration to temperature was limited by enzymatic processes and not diffusion of either organic substrates or molecular oxygen. When grown under conditions of phase-transfer limitation, cultures of Methylomonas rubra showed a minimal response to temperature changes between 19 and 38°C, as indicated by methane oxidation rates; in the absence of phase-transfer limitations, M. rubra oxidized methane at rates strongly dependent on temperature.

Oxygen radical production in the sea anemone Anthopleura elegantissima and its endosymbiotic algae

Abstract: Host animals in algal-invertebrate endosymbiotic associations are exposed to photosynthetically generated hyperoxia while in sunlight, conditions conducive to photodynamic excitations and production of cytotoxic oxygen-derived radicals such as the superoxide anion (O2−) and the hydroxyl radical (OH). All previous vidence of oxyradical production in symbiotic associations has been circumstantial. We here present direct evidence, from electron paramagnetic resonance studies on tissue homogenates of the photosymbiont-containing sea anemone Anthopleura elegantissima (Brandt), of substantial light-dependent OH and O2 production that is abolished by dichlorophenyldimethylurea (DCMU), an inhibitor of photosynthesis. Shade-adapted A. elegantissima lacking endosymbiotic algae likewise show OH production upon illumination. The latter flux is not dependent on photosynthesis, and DCMU has no effect. Rather, OH production in apozooxanthellate anemones is via direct photoexcitations. The selective reaction of dimethyl sulfoxide (DMSO) with OH to form methane sulfinic acid allows quantification of OH produced in vivo . Such in vivo measurements confirm the production of OH in both host and algae in illuminated zooxanthellate anemones, where the amount of OH in the zooxanthellae is disproportionately large relative to their fractional contribution to the biomass of the symbiosis. In vivo studies using DMSO also suggest a photochemical production of OH in apozooxanthellate anemones exposed to simulated sunlight enriched in ultraviolet (UV) wavelengths, and the enhancement by UV light of OH production in zooxanthellate individuals. Such chronic radical exposure necessitates defenses

A Conceptual Model of Wayfinding Using Multiple Levels of Abstraction

Abstract: Wayfinding is part of everyday life. This study concentrates on the development of a conceptual model of human navigation in the U.S. Interstate Highway Network. It proposes three different levels of conceptual understanding that constitute the cognitive map: the Planning Level, the Instructional Level, and the Driver Level. This paper formally defines these three levels and examines the conceptual objects that comprise them. The problem treated here is a simpler version of the open problem of planning and navigating a multi-mode trip. We expect the methods and preliminary results found here for the Interstate system to apply to other systems such as river transportation networks and railroad networks.

Strategic Issues Management: An Integration of Issue Life Cycle Perspectives

Abstract: This paper explores, in depth models of issues management and uses public policy, corporate strategy, process models and multiple perspectives to understand the evolution of issues management and how organizations can strategically respond to, and manage, issues. The paper concludes with empirical considerations and a research agenda for the future.

Use of a New Reproductive Index to Evaluate Relationship Between Habitat Quality and Breeding Success

Abstract: -A new method of measuring reproductive success is proposed that uses a composite of breeding-behavior observations (for behaviors that reflect different stages in the reproductive cycle) as an index of fitness. This reproductive index does not rely on discovery of nests, but is comprehensive in that it includes information on all monitored territories. The reproductive index was applied to three co-occurring grassland emberizine sparrows, two of which required special care because of their regional rarity. Ranks derived from this reproductive index were used to distinguish territories of birds of known high success (i.e. those that fledged young in at least one brood) from territories of birds with known low success (unpaired males), and were compared with findings for "spot-mapped" territories. Principal-components analyses of habitat measurements for these territory types revealed a similar pattern for all three species: spot-mapped territories overlapped broadly with nonterritory (unoccupied) plots, whereas high-success territories formed a discrete, isolated cluster within the spot-map matrix. Univariate analyses revealed that high-success territories were described by 15 vegetation features that differed (P < 0.01) from nonterritory values, whereas in spot-mapped territories only 8 vegetation measures differed and in lowsuccess territories only 2 differed. The ability to distinguish high-success territories allowed us to identify a greater number of habitat features that were correlated with reproductive success. If we had relied on the spot-mapping method, we would have been unable to identify many of these important habitat features. Yet, the ability to make such discriminations is likely to be critical in the management of threatened species. Received 5 March 1991, accepted 7 April 1992. THE DIFFICULTY of being able to gather detailed reproductive information about a bird 3Present address: Conservation Department, Massachusetts Audubon Society, Lincoln, Massachusetts 01773, USA. 4 Present address: Department of Natural Resources, Field of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York 14853, USA. population or community in a time-efficient manner has frequently limited avian-community research (e.g. Wiens 1973). Techniques for quantifying avian reproductive activity usually fall into two general categories. The simplest method, territory mapping, allows the researcher to define the location of individual male territories for a species or group of co-occurring species (Kendeigh 1944, International Bird Cen-

RGB-NDVI colour composites for visualizing forest change dynamics

Abstract: The study presents a simple and logical technique to display and quantify forest change using three dates of satellite imagery The normalized difference vegetation index (NDVI) was computed for each date of imagery to define high and low vegetation biomass Color composites were generated by combining each date of NDVI with either the red, green, or blue (RGB) image planes in an image display monitor Harvest and regeneration areas were quantified by applying a modified parallelepiped classification creating an RGB-NDVI image with 27 classes that were grouped into nine major forest change categories Aerial photographs and stand history maps are compared with the forest changes indicated by the RGB-NDVI image The utility of the RGB-NDVI technique for supporting forest inventories and updating forest resource information systems are presented and discussed

The effect of television day part on gender portrayals in television commercials: A content analysis

Abstract: Gender portrayals in 2,209 network television commercials were content analyzed. To compare differences between three day parts, the sample was chosen from three time periods: daytime, when the audience is mostly women; evening prime time, when the sex of the audience is more evenly distributed; and weekend afternoon sportscasts, when men are a large percentage of the audience. The results indicate large and consistent differences in the way men and women are portrayed in these three day parts, with almost all comparisons reaching significance at the .05 level. Although ads in all day parts tended to portray men in stereotypical roles of authority and dominance, those on weekends tended to emphasize escape from home and family. The findings of earlier studies which did not consider day part differences may now have to be reevaluated.

Glacial deposits in Great Britain and Ireland

Abstract: With the increasing awareness of environmental problems, there is a growing desire for a de--tailed understanding of superficial deposits in general, and glacial deposits in particular. This is because these sediments have a profound influence on groundwater protection, waste management and nature conservation. They are also of vital importance to civil engineering, because they provide the foundation for, as well as the materials extracted to build our roads and buildings. The greater part of the British Isles was glaciated, at least once, during the Quater--nary Era. In the regions subjected to glaciation, glacial deposits underlie much of the present land surface. Although there have been many recent publica--tions on various Quaternary geological topics, the present volume is the first dedicated to a detailed assessment of the glacial deposits of Britain and Ireland. After introductory chapters presenting the glacial history, the sedimentary sequences in 24 critical regions are discussed. These regions include all of Ireland, the gla--ciated area of Great Britain, and the adjoining offshore region of the North Sea. The controver--sial evolution of the Irish Sea Basin during the Last Glaciation is discussed from various view--points. A collection of 'critical topics' presented in the later part of the book range from the classification of glacigenic landforms and de--posits to the results of geophysical, geotechnical and geochemical analyses. The book includes 368 figures, 40 tables and 51 colour photographs, a detailed index and a list of over 1000 references. With 45 contributions by 48 scientists, this volume represents a truly contemporary view of this field of research. To--gether with its companion volume the Glacial deposits in North-West Europe, this book pro--vides an excellent textbook for the advanced student or the amateur, as well as an indispen--sible source- and guidebook for the professional scientist.

The influence of nearest neighbors on the rate and pattern of spontaneous point mutations.

Abstract: The numbers and local sequence environments of the two types of substitution mutation plus additions and deletions have been obtained directly in this study from differences between a large number of extant primate gene and pseudogene sequences. A total of 3786 mutations were scored in regions where similarities between pseudogene and corresponding gene sequences is ≥ 85%, comprising ∼30% of the pseudogene database of 80,584 bp. The pattern of mutations obtained in this fashion is almost identical to that obtained by Li et al. (1984) using a slightly different, more direct approach and with a smaller database. When mutations were scored, the neighbor pairs on the 5′ and 3′ sides were also noted, leading to a large 16 × 12 matrix of transitions and transversions. Biases of varying magnitude are found in the rates of substitution of the same base pair in different local sequence environments. The overall order for the effect of the 5′ neighbor on the rates of substitution mutation of a pyrimidine is A > C ≫ T > G, and G > A > T > C for the 3′ neighbor; where these results represent the average of substitution rates for the complement purine with complement neighbors of bases ordered above. The order for the 3′ neighbor is essentially the same for the two transitions and most of the four transversions as well; however, the order for the 5′ neighbor is more variable. The overall rate for the C · G → T · A transition is not unusual, however the presence of a 3′ neighboring G · C pair boosts the rate substantially, presumably due to specific cytosine methylation of the CG doublet in primate DNAs. The rate of the T · A → C · G transition is also well above average when the 3′ neighbor is an A · T, and to a lesser extent a G · C, pair. The latter bias is typical in that it reflects the association of alternating pyrimidine-purine sequences with increasing mutation rates. The substitution of the pyrimidine in a 5′ purine-pyrimi-dine-purine3′ sequence generally occurs much faster than in a pyrimidine tract and points to the local conformation as a major determining factor of the substitution rate. An apparent inverse relationship is found between starting and product doublet frequencies of base pairs undergoing mutations with specific 3′ neighbors, indicating that differences in intrinsic substitution rates of base pairs with specific neighbors are a key factor in producing the familiar biases of nearest-neighbor frequencies.

High-pressure viscosity and density of n -alkanes

Abstract: High-pressure viscosities and densities of n-butane, n-pentane, n-hexane, and n-octane have been measured with a specially designed falling cylinder viscometer. Data cover the pressure range from 10 to 70 MPa at temperatures from 310 to 450 K. When the viscosity is plotted as a function of density, the data at all temperatures and pressures are shown to reduce to a single curve for each alkane. An exponential relationship of the form η = B 1 x exp(B 2xρ) + B 3 is used to describe the density dependence of viscosity. The logarithmic viscosity of the alkanes changes linearly with the inverse temperature at all pressures. The density shows a linear dependence on temperature.

Gametogenesis, gametes and zygotes: An ecological perspective on sexual reproduction in the algae

Abstract: Ecological aspects of sexual reproduction in freshwater and marine algae are reviewed in the context of reproductive seasonality, gamete release, pheromones, fertilization success, polyspermy, part

Fertilization in natural populations of the dioecious brown alga Fucus ceranoides and the importance of the polyspermy block

Abstract: The brown alga Fucus ceranoides L. was studied in several estuaries on the Isle of Man (Great Britain) in the summers of 1989 and 1990. The objective were to determine the success of natural fertilization in a dioecious organism with external fertilization and to contribute to our understanding of processes such as polyspermy blocks and propagule settlement under natural conditions. Gamete release occurred on a semilunar cycle near full and new moons; at such times, settlement densities of 500 zygotes cm-2 d-1 were common. Gamete release was largely restricted to daytime high tides. Fertilization success was high: about 95 to 100% of all eggs released were fertilized, and 1 to 9% of these zygotes were polyspermic. The incidence of polyspermy increased towards the upper limit of F. ceranoides in the estuary of the river Neb; this may be significant in the context of the Na+-dependent block against polyspermy. Levels of polyspermy were not related to fertilization success (R2=0.06). Rates of pronuclear migration and karyogamy determined in the laboratory were used as an internal clock to estimate when eggs were fertilized in the field. Most eggs were fertilized 30 to 120 min after plants were immersed by the incoming tide, which corresponded to the period 60 min before to 30 min after high tide. The high success of fertilization suggests that polyspermy blocks are important in nature, and, in combination with the high settlement of zygotes, shows that population size in F. ceranoides is determined by post-settlement mortality, not by propagule availability.

A structural analysis of the Main Central Thrust zone, Langtang National Park, central Nepal Himalaya

Abstract: The Main Central Thrust (MCT) is one of the most tectonically significant structures in the Himalayan orogen. Detailed geologic mapping and structural analysis of the MCT in the Langtang National Park region of central Nepal reveals that this segment of the fault zone experienced multiple episodes of south-directed movement, under both brittle and ductile conditions, during the Tertiary period. Early (mid-Miocene) movement resulted in the development of mylonitic fabrics synchronous with amphibolite-facies metamorphism. The mean orientation of the dominant mylonitic foliation is N28°W, 38°NE. An associated mineral/stretching lineation plunges 40° to N40°E. Kinematic indicators suggest hanging-wall movement to the southwest relative to the footwall along the north-dipping fault. It is not possible to constrain the magnitude of high-temperature displacement on the MCT at the longitude of Langtang. Late-stage structures in the MCT zone at Langtang include a series of imbricate, brittle thrust faults that separate different lithostratigraphic units and correspond to metamorphic discontinuities. We interpret this fault system as a duplex structure. Muscovite 40 Ar/ 39 Ar cooling ages from the MCT zone range from 8.9-6.9 Ma. Because the nominal closure temperature of Ar diffusion in muscovite (approximately 625 K) is higher than the apparent temperature conditions under which late brittle deformation occurred, we suggest that brittle deformation was a latest Miocene-Pliocene phenomenon. Another major Himalayan fault, the Main Boundary Thrust (MBT), was developing to the south of Langtang at approximately the same time. We speculate that brittle faulting within the MCT zone may have initiated as the MCT zone was transported over a ramp in the MBT.

Consequences of dropping out of school: Findings from high school and beyond.

Abstract: The dropout problem has recently been the focus of considerable concern and the subject of much research. Nevertheless, the lack of a careful and systematic assessment of the consequences of dropping out still exists. The purpose of the present study was to examine the personal, social, and economic consequences of dropping out of school. The High School and Beyond (HS&B) data base was used to investigate the experiences of dropouts and high school graduates in 1986, 4 years after the projected date of graduation. Specifically, dropouts and graduates with no postsecondary education were compared on (a) self-esteem, (b) alcohol use, (c) political/social participation measures, (d) work satisfaction, (e) salary of current job, (f) periods of unemployment, and (g) number of jobs. Multiple-regression analyses were used to determine the degree to which dropping out explained variance in those measures when race, urbanicity, geographic region, socioeconomic status, and academic achievement were held co...

Fossil-pollen evidence for abrupt climate changes during the past 18 000 years in eastern North America

Abstract: A quantitative measure of the rate at which fossil-pollen abundances changed over the last 18 000 years at 18 sites spread across eastern North America distinguishes local from regionally synchronous changes. Abrupt regional changes occurred at most sites in late-glacial time (at ≈13700, ≈ 12 300, and ≈ 10000 radiocarbon yr BP) and during the last 1000 years. The record of abrupt late-glacial vegetation changes in eastern North America correlates well with abrupt global changes in ice-sheet volume, mountain snow-lines, North Atlantic deep-water production, atmospheric CO2, and atmospheric dust, although the palynological signal varies from site to site. Changes in vegetation during most of the Holocene, although locally significant, were not regionally synchronous. The analysis reveals non-alpine evidence for Neoglacial/Little Ice Age climate change during the last 1000 years, which was the only time during the Holocene when climate change was of sufficient magnitude to cause a synchronous vegetational response throughout the subcontinent. During the two millennia preceding this widespread synchronous change, the rate of change at all sites was low and the average rate of change was the lowest of the Holocene.

Electrocatalytic reduction of carbon dioxide based on 2,2'-bipyridyl complexes of osmium

Abstract: The complex cis-[Os(bpy) 2 (CO)H] + (bpy is 2,2'-bipyridine) has been found to be an electrocatalyst for the reduction of CO 2 in CH 3 CN containing 0.1 M tetra-n-butylammonium hexafluorophosphate at glassy carbon or Pt electrodes. Under anhydrous conditions CO is the dominant product, but addition of water results in up to 22% formate anion.