Showing papers by "University of Maine published in 1985"

Time perception and attention: The effects of prospective versus retrospective paradigms and task demands on perceived duration

Abstract: This research was designed to compare time judgments obtained under prospective conditions (in which subjects are instructed to attend to time) and retrospective conditions (in which subjects are unaware that they will be required to judge time). In Experiment 1, subjects prospectively or retrospectively judged the duration of intervals spent performing a perceptual-motor task at different levels of difficulty. The results showed that subjects tested under both research paradigms tended to give increasingly shorter and/or more inaccurate time judgments with increases in nontemporal task demands. Experiment 2 was designed to test the effects of attentional deployment on perceived time by comparing prospective and retrospective judgments under control, selective attention, and divided attention conditions. Both types of time judgments became increasingly inaccurate as attention was more broadly deployed. The results of these experiments are consistent with an attentional allocation model, and they suggest that nontemporal task demands disrupt or interfere with timing in both prospective and retrospective situations.

Au(110) (1×2)-to-(1×1) phase transition: A physical realization of the two-dimensional Ising model

Abstract: We report the first measurements of the critical exponents of a phase transition at the surface of a clean metal, the Au(110) (1 \ifmmode\times\else\texttimes\fi{} 2) \ensuremath{\leftrightarrow} (1 \ifmmode\times\else\texttimes\fi{} 1) transition. The exponents $\ensuremath{\beta}$, $\ensuremath{\gamma}$, and $\ensuremath{ u}$ and the amplitudes were measured by LEED and place the phase transition in the two-dimensional Ising universality class. The critical scattering is observed to peak above ${T}_{c}$, signaling the breakdown of the Ornstein-Zernike theory, and is in numerical accord with predictions of Fisher and Burford.

Separation of Carotenoids in Fruits and Vegetables by High Performance Liquid Chromatography

Abstract: Several isocratic high performance liquid chromatographic (HPLC) methods, including both normal and reversed-phase, have been developed to separate provitamin A compounds and other carotenoids - α-carotene, β-carotene, stereoisomers of β-carotene, γ-carotene, β-cryptoxanthin, canthaxanthin and lycopene- in fruits and vegetables. The normal phase systems used either an amino or alumina column with 99.5% isooctane and 0.5% tetrahydrofuran. Procedures employing reversed-phase used C18 columns- Vydac 201TP54, Vydac 218TP54, Zorbax ODS and NovaPak C18- with nonaqueous solvent systems comprised of various mixtures of acetonitrile, methanol, tetrahydrofuran and chloroform. All compounds were monitored at 470 nm or 450 nm. Each method has certain advantages and disadvantages for the analysis of carotenoids in fruits and vegetables.

Effect of Four Drying Methods on the Quality of Intermediate Moisture Lowbush Blueberries

Abstract: Lowbush blueberries have been processed by freeze dry, forced air, vacuum oven, and micro-convection methods to a moisture content of 16-25%. The drying effect on the product quality was evaluated. There were no significant differences in vitamin A and niacin retention except freeze dried berries had higher vitamin C retention. No significant differences occurred in retention of mineral content except higher sodium and lower magnesium were found in the micro-convection and freeze dry methods, respectively. Freeze dried and vacuum dried blueberries had higher soluble solids retention and were darker and redder than forced air or micro-convection dried berries. Freeze dried berries were found to have highest rehydration ratio and lowest bulk density.

Palaeolimnological evidence that lake acidification is accompanied by loss of organic matter

Abstract: The hypothesis that loss of dissolved organic matter from lake water accompanies acidification1,2 has been investigated palaeolimnologically for Hovvatn (pH 4.4; TOC (total organic carbon) 3.2 p.p.m.) and Holmvatn (pH 4.7; TOC 2.2 p.p.m.) in southern Norway. Regression equations3,4 that relate sedimentary diatom remains separately to pH and TOC were applied to diatom counts from 210Pb-dated cores from the lakes. The results indicate that in pre-industrial times both lakes were acidic (pH 4.9–5.1, no bicarbonate alkalinity) and relatively humic (TOC 6–9 p.p.m.). This acidification started about 1920 at Howatn and in the 1940s at Holmvatn, and was accompanied by TOC decreases of 3–6 p.p.m. This supports the hypothesis and suggests that the acidification of such lakes transformed them from organic weak acid dominated to mineral strong acid dominated. It also implies that acidification decreased the availability of organic ligands for binding potentially toxic aluminium.

Biological and granulometric controls on sedimentary organic matter of an intertidal mudflat

Abstract: A variety of measures of organic matter concentration and quality were made on samples collected from the top few mm of intertidal mudflat sediment over the course of a year, in order to assess the relative importance of biological and sedimentological influences on sedimentary organic matter. Winter and summer were times of relatively fine-grained sediment accumulation, caused by biological deposition or stabilization processes and resulting in higher organic matter concentrations. Stable carbon isotope and Br:C ratios indicated a planktonic source of bulk organic matter. Ratios of organic carbon to specific surface area of the sediments were consistent with an organic monolayer coverage of sediment grains. Correction for changing grain size during the year showed no change in the organic concentration per unit surface area, in spite of organic matter inputs by in situ primary production, buildup of heterotroph biomass and mucus coatings, and biodeposition of organic-rich seston. There were also no indications of changes in bulk organic quality, measured as hydrolyzable carbohydrates and amino acids, in response to these biological processes. It is concluded that biological processes on a seasonal time scale affect the bulk organic matter of these sediments via a modulation of grain size rather than creation or decay of organic matter.

Methods of pH calibration of sedimentary diatom remains for reconstructing history of pH in lakes

Abstract: The pH history of lakes can be inferred from diatom remains in dated sediment cores. To derive transfer functions for pH inference in acidic lakes, we counted diatoms in surface-sediment from 31 soft-water lakes in n. New England (NE) and 36 in Norway (N), covering pH 4.4–7.1. Cluster analysis of each data set indicates that pH 6 is an upper limit for a group of similar diatom assemblages. For each set, we developed multiple linear regressions to relate three versions of the diatom data to pH of surface-waters: (1) relative frequencies of selected diatom taxa, (2) the first principal component (1 PC) of these frequencies, and (3) the frequencies of Hustedt pH groups. Also, simple linear regressions were developed for two versions: (1) Index B and (2) Index Alpha, both based on pH groups. Regressions were run separately for lakes with pH ≤ 6; these are most relevant for pH inference in acidic lakes. The best regressions (N: taxa & 1 PC taxa) have r2 0.69–0.91 and Se 0.24–0.31 pH units, the worst (NE: log alpha) have r2 0.27–0.57 and Se 0.51. In all cases, errors for NE are greater than N, partly due to greater diversity of NE lakes. Regressions based on pH groups (directly & by indices) have smaller r2 and larger Se than those based on taxa and 1 taxa. The Index Alpha is least useful because its requirement for alkaline diatom units is unsatisfied at many acidic lakes. Regressions based on taxa may give erratic pH inferences due to sensitivity to unusual frequencies of individual taxa; this effect is reduced by using 1 PC taxa. Four regressions based on pH ≤ 6 lakes were used for inferring pH in a 210Pb dated core from Nedre Malmesvatn, N (now pH 4.6). There is good agreement among three of the four (not for the regression based directly on taxa) that there has been a decrease of ca. 0.6 pH units starting in the late 1800's.

Adaptations of Crustose Coralline Algae to Herbivory: Patterns in Space and Time

Abstract: Crustose coralline algae are among the most abundant organisms (plant or animal) to occupy hard substratum within the photic zone. In fact, the Holocene may be the “Age of Crustose Corallines,” since corallines are more diverse and abundant than ever before. This is also a period of maximum intensity of herbivory. The radiation of crustose corallines and coralline grazing herbivores are temporally correlated. Ecological and paleontological research suggests that crustose corallines and herbivores have “diffusely” coevolved to attain their current preeminance.

Oxygen detoxification in algal-invertebrate symbioses from the Great Barrier Reef

Abstract: Examination of 34 species of symbiotic invertebrates in four phyla has confirmed the generality of a direct relationship between chlorophyll concentration and the activities of superoxide dismutase and catalase, two enzymes involved in the detoxification of active oxygen. On a finer scale, activities of these enzymes also depend on the localization of the algal symbions (intracellular or extracellular) and hence on the extent to which photosynthetic O2 actually contacts animal cytoplasm, and on the solar irradiance experienced by the symbionts. Differences in SOD activity among organs of Tridacna crocea are not fully explained by local O2 levels but are further related to organ-specific retes of O2 consumption. This result is discussed in terms of known mechanisms of superoxide radical production in mitochondria and differences in O2 utilization concentrations among various organs in bivalve molluscs.

Denning Ecology and Movements of Coyotes in Maine during Pup Rearing

Abstract: Den attendance, movements, and home range of eight adult coyotes (Canis la- trans) attending pups were investigated during 1981-1983 in eastern Maine. Coyote families used several dens during pup rearing, and dens were frequently relocated following human disturbance. Six den entrances were oriented 120-236' from north. Two coyote families aban- doned dens when pups were 8-10 weeks of age. Males and females shared in the duties of pup raising, and both frequently attended pups. Movement rates and home ranges of adult coyotes increased from the nursing to weaning periods, but movements and home ranges of adults were greatest after pups became independent. Movements suggested that males centered their activities near den sites during the nursing period to supply food for mates and protection for pups. Females were more restricted than males during pup rearing because of nursing responsibilities.

Phase diagram of selenium adsorbed on the Ni(100) surface: A physical realization of the Ashkin-Teller model.

Abstract: We have used electron diffraction to study submonolayers of Se adsorbed on Ni(100); $p(2\ifmmode\times\else\texttimes\fi{}2)$, $c(2\ifmmode\times\else\texttimes\fi{}2)$, and disordered phases were observed and the boundaries between them located. Symmetry arguments indicate that the phase diagram belongs to the universality class of the Ashkin-Teller model and allow us to predict the critical behavior near the phase boundaries and at the multicritical point where they meet. Our lattice-gas-model calculations support these results. The predicted critical behavior, and thus the universality arguments, should be tested by additional experiments, in particular synchrotron-x-ray diffraction.

Non-specific cytotoxic activity of teleost leukocytes.

Abstract: The existence of lymphoid cells with “natural” killer activity in mammals and birds has been known for some time. Several previous reports have demonstrated similar activity in carp and catfish kidney leukocytes. However, the activity previously reported was directed towards established mammalian cell lines. In this report we confirm the existence of spontaneous killer activity in other species of teleosts, including salmonids. This spontaneous cytotoxic activity is directed towards several established teleost, as well as mammalian, cell lines. Cytotoxic activity appears to be optimal at 20°C in an 8 hour 51 Cr release assay. The RTG-2, AS, GS and EPC cell lines of teleost origin are susceptible to lysis by kidney, spleen, and blood leukocytes of Salmo salar , Salmo gairdneri , and Notemigonus crysoleucas . Furthermore, the susceptibility of the RTG-2 and AS teleost cell lines to killing by kidney leukocytes of both S . salar and S . gairdneri was significantly enhanced by preinfection of the target cells with infectious pancreatic necrosis virus.

Biogeochemical Influence of Vegetation and Soils in the ILWAS Watersheds

Abstract: The ILWAS catchments (Panther, Sagamore, and Woods) contain closely related variants of the northern hardwood-spruce-fir complex of the Adirondack Region. Dominant species in these watersheds are: American beech, sugar maple, red spruce, red maple, and yellow birch. On an areal basis, the watersheds contain 57 to 88% hardwood cover type and range in percent coniferous cover from 28% in Sagamore watershed to 5% in Woods catchment. Mean live basal area values range from 22 to 30 m2 ha-1 between catchments, while mean live stem densities range from 1400 to 1700 stems ha-1. Weighted average leaf area indices for the watersheds range from a low of 5.2 in Woods to a high of 7.2 in Sagamore. The higher leaf area in Sagamore watershed may enhance the collection of dry deposition and may explain the higher SO4 2- concentrations in surface waters within that system.

Comparative effects of precipitation acidity on three forest soils: carbon cycling responses

Abstract: This comparative soil microcosm study examined the effects of precipitation acidity on decomposition processes in three contrasting eastern North American forest soils: a Becket series Haplorthod, an Unadilla series Dystrochrept, and an Adams series Haplorthod. Results from all three soils showed that soil respiration is quantitatively unaffected by differences in precipitation acidity over the range of pH 5.7 to 3.5 (annual loading rates of 36 to 5,520 eq H+ · ha−1). Soil respiration did vary as a function of edaphic differences between soils. Data from all three soils also indicated that precipitation acidity (at pH≧3.5 and lime potential ≧1.11) had no consistent quantitative effect upon total dissolved organic carbon leaching. Again, differences in DOC flux were related to inter-soil edaphic variations. Carbon turnover budgets for the three soils indicated that 54–68% of the forest floor carbon loss occurred through respiration, while DOC leaching accounted for the remaining 32–46% of carbon loss. Finally, results from all three soils showed that increased inputs of strong acids to the forest floor caused distinct decreases in the hydrophobic acid (fulvic acid) content of leachate dissolved organic carbon.

The Maine Lobster Market: Between Market and Hierarchy

Abstract: Owners of firms in the Maine lobster industry exist in a complicated social milieu. They have one set of ties with firms from which they buy and to which they sell lobsters, which I call vertical ties. They have other ties with firms at the same level of the market, horizontal ties. Both, I shall argue, are necessary for economic success in the industry, although they are used for very different purposes. This paper examines how members of the lobster industry use their ties; the reasons for their evolution; and the effect of this social system on the way prices are established in the industry. The marketing system for lobsters in Maine is dominated by a large number of small, specialized firms which have developed long-term bilateral relationships. Fishermen, dealers, truckers, and wholesalers typically own their own small firms and buy and sell lobsters to each other. No vertically integrated firms have been developed which are involved in all phases of the business-from catching the lobsters to shipping them to distant markets. Yet the owners of these small firms do not act like the quintessential entrepreneur of the neoclassical model of economics, who responds only to market prices and buys and sells to the highest bidder with only economic optimization in mind. Rather, they buy and sell at the "established market price" to the same finite number of firms with whom they have developed ties. A fisherman ordinarily sells only to one lobster dealer; and the dealer usually sells only to a small number of pound operators, wholesalers, or other buyers. In this respect, the situation in Maine closely resembles the situation found in many other markets in the world where buyers and sellers have long-standing ties (Mintz; Geertz: 29ff.; Spoehr: 162ff; Wilson, 1980). However, there are differences as well.

Chemical Weathering and Solution Chemistry in Acid Forest Soils: Differential Influence of Soil Type, Biotic Processes, and H + Deposition

Abstract: In this investigation, weathering rates were calculated for three eastern North American forest soils using five separate estimation techniques. In addition, leaching experiments were performed to examine the influence of selected environmental variables on the weathering process. Weathering rates varied five-fold between soils, ranging from approximately 0.5 Keq ha–1 yr–1 in a sandy Adams Spodosol, to 1.2 Keq ha yr–1 in a sandy loam Becket Spodosol, to 2.7 Keq ha–1 yr–1 in a silty Unadilla Inceptisol. Inter-soil differences in weathering rate were inversely correlated with mean soil particle size and positively correlated with total exchangeable bases in the soil profile. Study results also demonstrated major differences in weathering rates between soil horizons.

The simply supported rectangular plate: An exact, three dimensional, linear elasticity solution

Abstract: An exact three dimensional solution for the problem of a transversely loaded, simply supported rectangular plate of arbitrary thickness is presented within the linear theory of elastostatics. The solution, obtained in a semi-inverse fashion, satisfies all the boundary conditions of the problem in a pointwise manner and is in the form of a double Fourier sine series. The classical Navier solution for the problem is shown to be the limit of the present solution as the plate thickness aspect ratio approaches zero. It is noted that the solution presented provides a benchmark against which approximate theories of transversely loaded plates may be measured. The new elasticity solution also provides a heuristic basis for a novel theory of thick plates of arbitrary planform and edge support recently given by the author.

Nitrogen fixation and respiration by root nodules of Alnus rubra Bong.: Effects of temperature and oxygen concentration*

Abstract: Using a root nodule cuvette and a continuous flow gas exchange system, we simultaneously measured the rates of carbon dioxide evolution, oxygen uptake and acetylene reduction by nodules of Alnus rubra. This system allowed us to measure the respiration rates of single nodules and to determine the effects of oxygen concentration and temperature on the energy cost of nitrogen fixation. Energy cost was virtually unchanged (2.8–3.5 moles of carbon dioxide or oxygen per mole of ethylene) from 16 to 26°C (pO2 = 20 kPa) while respiration and nitrogenase activity were highly temperature dependent. At temperatures below 16°C, nitrogenase activity decreased more than did respiration and as a result, energy cost rose sharply. Acetylene reduction ceased below 8°C. Inhibition of nitrogenase activity at low temperatures was rapidly reversed upon return to higher temperatures. At high temperatures (above 30°C) nitrogenase activity declined irreversibly, while respiration and energy cost increased.