Showing papers by "University of Maine published in 1984"
TL;DR: The first major horizon of ice-rafting occurred at about 2.4 Myr, and was preceded by a minor pulse of icerafting at 2.5 Myr as discussed by the authors, and the carbon isotope record shows that the site has been bathed by a water mass of similar characteristics to present-day North Atlantic deep water at least since 3.5
Abstract: We report here that DSDP Site 552A, cored with the hydraulic piston corer on the west flank of Rockall Bank, recovered an undisturbed sequence of alternating white deep-sea carbonate oozes and dark-coloured layers that are rich in glacial debris. Oxygen isotope analysis of the sequence together with detailed nannofossil and palaeomagnetic stratigraphy shows that the first major horizon of ice-rafting occurred at about 2.4 Myr, and was preceded by a minor pulse of ice-rafting at about 2.5 Myr. The carbon isotope record shows that the site has been bathed by a water mass of similar characteristics to present-day North Atlantic deep water at least since 3.5 Myr.
1,027 citations
Journal Article•
422 citations
TL;DR: The final effort of the CLIMAP project was a study of the last interglaciation, a time of minimum ice volume some 122,000 yr ago coincident with the Substage 5e oxygen isotopic minimum.
382 citations
211 citations
TL;DR: In this paper, deep-water sediment cores from 32 Scandinavian and 19 northern New England, U.S.A., lakes were analyzed for 137Cs; 210Pb was analyzed in cores from 16 and 14 of these lakes, respectively.
199 citations
TL;DR: In this article, surface oxygen uptake, sulfate reduction and total sediment metabolism were measured in sediments (0-30 cm) supporting stands of short Spartina alterniflora in a New England salt marsh.
Abstract: Surface oxygen uptake, sulfate reduction and total sediment metabolism were measured in sediments (0-30 cm) supporting stands of short Spartina alterniflora in a New England salt marsh. Surface oxygen uptake varied seasonally and was highly correlated with total sediment metabolism. Rates of oxygen uptake ranged from about 75 to 121 mmol/sq m/day during winter to a maximum in August of 363. Total carbon dioxide production followed the same trend with a winter low of 65 mmol/sq m/day and a maximum in August of 415. The sulfate concentration in porewater from the 0-2 cm interval was about that expected from seawater at the salinity of the interstitial water. Below this depth sulfate decreased to values of about 21.6 mmol/liter. Time-course experiments using carbon dioxide production and sulfate reduction indicate that the aqua regia technique is not reliable for measuring sulfate reaction and that the rate of sulfate reduction is much less than previously reported for this marsh. Carbon mineralization is estimated to average about 180 mmol C/sq m/day, among the highest measured for marine sediments. Simultaneous measurements of oxygen uptake, carbon dioxide production and sulfate reduction suggest that at least half of this decomposition occurs via sulfate reduction. 54 references, 7more » figures.« less
186 citations
TL;DR: The hypothesis that the presence of quaternary amines can mediate the coexistence of sulfate reduction and methanogenesis in marine surface sediments is supported and the activities of fermenters, methanogens, and sulfate reducers were all required to effect complete mineralization.
Abstract: The response of methanogenesis and sulfate reduction to trimethylamine, choline, and glycine betaine was examined in surface sediments from the intertidal region of Lowes Cove, Maine Addition of these substrates markedly stimulated methanogenesis in the presence of active sulfate reduction, whereas addition of other substrates, including glucose, acetate, and glycine, had no effect on methane production Sulfate reduction was stimulated simultaneously with methanogenesis by the various quaternary amines and all other substrates examined Incubation of exogenous trimethylamine, choline, or glycine betaine with either bromoethane sulfonic acid or sodium molybdate was used to establish pathways of degradation of the substrates Methanogenesis dominated the metabolism of trimethylamine, although limited nonmethanogenic activity, perhaps by sulfate-reducing bacteria, was observed Acetate was oxidized primarily by sulfate reducers Both choline and glycine betaine were fermented stoichiometrically to acetate and trimethylamine; apparently, neither substrate could be utilized directly by methanogens or sulfate reducers, and the activities of fermenters, methanogens, and sulfate reducers were all required to effect complete mineralization These observations support the hypothesis that the presence of quaternary amines can mediate the coexistence of sulfate reduction and methanogenesis in marine surface sediments; they also implicate methanogens in the nitrogen cycle of marine sediments containing quaternary amines
180 citations
161 citations
TL;DR: One hypothesis explaining the coexistence of sulfate reduction and methanogenesis in marine sediments is that methanogens use substrates for which competition is minimal or nonexistent.
Abstract: Methanogenesis occurs at low rates in many marine sediments containing sulfate, in spite of an unfavorable thermodynamic and kinetic environment. One hypothesis explaining the coexistence of sulfate reduction and methanogenesis in marine sediments is that methanogens use substrates for which competition is minimal or nonexistent. Methylamines and methanol in particular have been suggested as “noncompetitive”; substrates. Data from studies of the physiology of recently isolated marine methanogens and studies using radiotracers at in situ concentrations support the notion that methylamines are important methane precursors in surface sediments. In contrast, sulfate‐reducing bacteria appear to outcompete methanogens for methanol at low concentrations (μ?), while the reverse is true at higher concentrations (e.g., > 1 mM). At present, sources of methyl‐amines are the subject of some speculation; several have been suggested, including trimethylamine oxide, choline, and glycine betaine. Of these, glycin...
157 citations
TL;DR: Because heterozygosity was higher in oysters created during meiosis I than in other groups, the increased growth must be due toheterozygosity rather than to triploidy per se.
131 citations
TL;DR: This article showed that outlet glaciers of a local ice cap carved primary valley systems on both flanks of the Transantarctic Mountains, while coeval alpine glaciers eroded exposed intervalley mountain ranges.
Abstract: Data from the Dry Valleys, Antarctica, suggest that outlet glaciers of a local ice cap carved primary valley systems on both flanks of the Transantarctic Mountains, while coeval alpine glaciers eroded exposed intervalley mountain ranges. Subsequently, a thick ice sheet overrode the Transantarctic Mountains at least twice, flowing northeastward across major pre-existing valleys. The youngest overriding episode postdated and the older episode antedated middle to early late Miocene time. We think that an extensive ice sheet covered East and West Antarctica during overriding episodes.
TL;DR: Senkirkine, a pyrrolizidine alkaloid, is to the authors' knowledge the first member of this class of compounds shown to have feeding deterrent activity in Lepidoptera.
Abstract: Sixth instars of the spruce budworm, Choristoneura fumiferana (Clemens), were exposed to an ethanol extract of roots of the composite coltsfoot, Tussilago farfara L., in a laboratory feeding bioassay. The extract had feeding deterrent activity, and the active ingredient, senkirkine, was isolated. Senkirkine, a pyrrolizidine alkaloid, is to our knowledge the first member of this class of compounds shown to have feeding deterrent activity in Lepidoptera. Thirteen additional pyrrolizidine alkaloids were bioassayed to determine possible structure-activity correlations. Most of the pyrrolizidine alkaloids tested were inactive, and high levels of feeding deterrence were not observed in those compounds lacking lactone or diester side chains. The most active compounds, senkirkine and lasiocarpine, bore α, β unsaturation in the side chain.
Journal Article•
TL;DR: It appears reasonable to assume that cold-induced rises in the concentration of enzymes in fish muscle reflect changes in organellar densities–changes which may serve primarily to ameliorate the effect of temperature on diffusive exchange between mitochondria and cytoplasm rather than solely to overcome catalytic limitation as is widely assumed.
Abstract: Transmission electron microscopy of myotomal muscle from goldfish (Carassius auratus L.) reveals significant differences in distribution and density of mitochondria in animals acclimated to cold temperature (5°C) as compared to those acclimated to warm temperature (25°C). Micrographs of red and white muscle from these animals have been analyzed quantitatively for the stereological parameters Vv (volume density), Sv (surface density), and S/V (specific surface); and diffusion distances between mitochondria have been calculated as the harmonic mean of spacings between clusters of mitochondria (τh). The most dramatic differences occur in Vv, Sv, and τh of red muscle, Vv and Sv being significantly greater in cold-acclimated animals and τh being smaller. In white muscle, Vv is significantly greater for cold-acclimated animals than warm-acclimated animals, but other parameters are not significantly different. Using our values of Sv as estimates of the surface area through which exchange of metabolites occurs and our values of τh as estimates of the distance over which diffusion occurs, we calculate that the diffusivity constant in the one-dimensional diffusion equation for metabolites may be reduced in cold-acclimated animals to as low as 0.29 that of warm-acclimated animals while still maintaining absolute rates of diffusive flux between cytoplasm and mitochondria. It appears reasonable to assume that cold-induced rises in the concentration of enzymes in fish muscle reflect changes in organellar densities–changes which may serve primarily to ameliorate the effect of temperature on diffusive exchange between mitochondria and cytoplasm rather than solely to overcome catalytic limitation as is widely assumed.
TL;DR: In this article, the authors examined the relationship between creativity and left-hemisphere and righthemisphere EEG activity and found that highly-creative people exhibit greater right-hemispheres than left hemispheres EEG activity during creative performance.
TL;DR: The authors investigated several possible sources of these stereotypes, including parental stereotypes, parental reinforcement practices, television programming, and actual sex-differences in emotionality, and found that each of these sources may potentially contribute to children's stereotypes about emotionality.
Abstract: Contemporary preschool-aged children have pronounced sex-role stereotypes about emotionality. They feel that anger is a male characteristic, while fear, sadness, and happiness are female characteristics. Four studies investigated several possible sources of these stereotypes, including parental stereotypes, parental reinforcement practices, television programming, and actual sex-differences in emotionality. The results suggest that each of these sources may potentially contribute to children's stereotypes about emotionality.
TL;DR: The majority of triploid scallops failed to ripen during the summer months, while diploidScallops ripened and spawned, and the indexes of weight and glycogen content of the adductor muscle were significantly greater in triploids at the end of the growing season.
01 Jan 1984
TL;DR: This article found that conservatives derogated the victim's character to a greater extent than liberals in two experiments conducted with liberal and conservative university students (so designated on the basis of their scores on Tomkins' Polarity Scale).
Abstract: In the first of two experiments conducted with liberal and conservative university students (so designated on the basis of their scores on Tomkins' Polarity Scale) men and women made attributions of responsibility to a welfare client. Overall, conservatives blamed the victim more than liberals. The second study extended this finding to the victim of a theft. Liberals were particularly lenient when the victim was described as emotionally upset, supporting Tomkins' ideas about left-right affective differences. In both studies, conservatives derogated the victim's character to a greater extent than liberals.
Journal Article•
TL;DR: Thematic Mapper Simulator data were collected over a 23,200 hectare forested area near Baxter State Park in north-central Maine as discussed by the authors, where waveband discriminant analyses were used to generate training statistics and test pixel accuracies.
Abstract: Thematic Mapper Simulator data were collected over a 23,200 hectare forested area near Baxter State Park in north-central Maine. Photointerpreted ground reference information was used to drive a stratified random sampling procedure for waveband discriminant analyses and to generate training statistics and test pixel accuracies. Stepwise discriminant analyses indicated that the following bands best differentiated the thirteen level II - III cover types (in order of entry): near infrared (0.77 to 0.90 micron), blue (0.46 0.52 micron), first middle infrared (1.53 to 1.73 microns), second middle infrared (2.06 to 2.33 microsn), red (0.63 to 0.69 micron), thermal (10.32 to 12.33 microns). Classification accuracies peaked at 58 percent for thirteen level II-III land-cover classes and at 65 percent for ten level II classes.
TL;DR: Sedimentologic and biologic evidence indicates soil instability and relatively high soil erosion rates from the watersheds during the late-glacial period accounts for the abundance of Glomus in late- glacial sediments, and the reduced abundance of the fungus in Holocene sediments is attributed to a decrease in the rate of soil erosion after the est...
Abstract: Specimens of the vesicular–arbuscular mycorrhizal fungal Glomus fasciculatum complex have been identified from lake sediment cores from Gould Pond (central Maine) and Upper South Branch Pond (north central Maine). The fungus became established with tundra vegetation on newly developing soils soon after the melting of Wisconsin ice. This is the first record of such an occurrence for North America. The earliest specimens from Gould Pond were deposited in sediment dated at about 13 000 years old and those at Upper South Branch Pond between about 12 500 and 11 000 years old. This is at least 1000 years prior to the arrival of trees in those areas. Sedimentologic and biologic evidence indicates soil instability and relatively high soil erosion rates from the watersheds during the late-glacial period. Thus erosion probably accounts for the abundance of Glomus in late-glacial sediments. The reduced abundance of the fungus in Holocene sediments is attributed to a decrease in the rate of soil erosion after the est...
TL;DR: The profitability of a limited increase of average herd life was insensitive to increased feed price, poor management, decreased salvage value, trend of improving management, but high salvage value and low feed price significantly decreased profitability of extended herd life.
TL;DR: The cichlid fishes of the Great Lakes of Africa are the most spectacular examples ofspeciation and adaptive radiation within a single vertebrate family and the number of species in each rift valley lake is still unknown, as many undescribed species are being discovered in newly explored areas.
Abstract: The cichlid fishes of the Great Lakes of Africa are the most spectacular examples ofspeciation and adaptive radiation within a single vertebrate family. In each of the lakes-Malawi, Tanganyika and Victoria-more species offish coexist than in any other lake outside ofthe rift valley region. The exact number of species in each rift valley lake is still unknown, as many undescribed species are being discovered in newly explored areas (Eccles and Lewis, 1977, 1978; van Oijen et aI., 1981; Witte, 1981; Witte and Witte-Maas, 198 I; Lewis, 1982; MeKaye and Mackenzie, 1982; Ribbink, unpubI.). van Oijen et ai. (1979), and Barel and Witte (pers. comm.), for example, report that in the Mwanza Gulf of southern Lake Victoria approximately 200 cichlid species coexist, and in Lake Malawi it is estimated that over 500 species are present (consensus of ichthyologists working in Malawi). Further, many of the \"species\" earlier described are now being recognized to be polyspecific aggregates (Holzberg, 1978; van Oijen et aI., 1979; Schroder, 1980; Hoogerhoudand Witte, 1981; Marsh et al., 1981; McKaye et aI., 1982). Other outstanding examples of fish speciation in lacustrine environment-the 18 endemic cottids of Lake Baikal (Brooks, 1950; Koshov, 1963), the 18 cyprinids ofLake Lanao (Herre, 1933), and the 14 endemic cyprinodontid species ofthe genus Orestias of Lake Titicaca (Tchernavin, I944)-achieve but 1I20th of the species diversity of cichlids in Lake Malawi. However, the high diversity of African cichlid species has been questioned by an electrophoretic study of three trophically specialized Mexican cichlids (Sage and Selander, 1975). This study has often been cited to cast doubt upon the reported species richness of the African cichlids (Kirkpatrick and Selander, 1979; Graves and Rosenblatt, 1980). Electrophoretic data from other fishes such as goodeids \"suggest that the number of biological species evolved in several extreme radiations of trophic diversity, most notably those of the cichlids in the African Rift lakes ... may have been seriously overestimated by morphological references\" (Turner and Grosse, 1980). Besides this skepticism over the total number of species within these lakes, a controversy exists over the modes of speciation responsible for the evolution of these fishes. Fryer (1959, 1977) and Fryer Revised February 22, 1983
TL;DR: Stomach content data and laboratory studies indicate that O. victoriae utilizes a variety of feeding methods but not suspension feeding, which indicates this species is an opportunistic generalist with high diet plasticity.
Abstract: The diet and feeding behavior of the brittle star Ophionotus victoriae were studied in 1981–1983. Frequency-of-occurrence and points methods were used to examine stomach contents of 2475 specimens from 19 stations representing seven general localities along the Antarctic Peninsula and South Sandwich Islands. Results of the two methods were in agreement and indicated this species is an opportunistic generalist with high diet plasticity. The most abundant component of the stomach contents was sediment but the diet derived from at least 13 phyla. Crustaceans, notably euphausiids and amphipods, were most important at some locations. Diet composition varied significantly between locations and years, but did not differ among brittle star size groups. Stomach content data and laboratory studies indicate that O. victoriae utilizes a variety of feeding methods but not suspension feeding.
TL;DR: In this article, the authors studied the relationship between the zero scheme of a section of a rank two bundle on iP3 and the ideal I(C) of a curve C c P3 if and only if C is ideally the intersection of three suraces and C is arithmetically Cohen-Macaulay (noncomplete intersection).
01 Jan 1984
TL;DR: In this paper, a combined experimental and analytical study of the cracked-lap-shear specimen subjected to constant-amplitude cyclic loading was undertaken, and the fatigue failure was in the form of cyclic debonding with some 0°fiber pulloff from the strap adherend.
Abstract: To analyze the fatigue behavior of a simple composite-to-composite bonded joint, a combined experimental and analytical study of the cracked-lap-shear specimen subjected to constant-amplitude cyclic loading was undertaken. Two bonded systems were studied: T300/5208 graphite/epoxy adherends bonded with adhesives EC 3445 and with FM-300. For each bonded system, two specimen geometries were tested: (1) a strap adherend of 16 plies bonded to a lap adherend of 8 plies, and (2) a strap adherend of 8 plies bonded to a lap adherend of 16 plies. In all specimens tested, the fatigue failure was in the form of cyclic debonding with some 0°fiber pull-off from the strap adherend. The debond always grew in the region of adhesive that had the highest mode I (peel) loading and that region was close to the adhesive-strap interface. Furthermore, the measured cyclic debond growth rates correlated well with total strain energy release rates GT as well as with its components GI (peel) and GII (shear) for the mixed-mode loading in the present study.