Showing papers by "University of Maine published in 1979"

Importance of classical diffusion in NMR studies of water in biological cells

Abstract: Nuclear-magnetic-resonance measurements of the proton-spin relaxation for water in biological cells are known to exhibit a multiexponential decay. A theory, based on the diffusion equation using the bulk diffusivity of water, is developed to explain this phenomenon. It is shown that multiexponential decay arises simply as a consequence of an eigenvalue problem associated with the size and shape of the cell and that this multiexponential decay can only be observed for samples whose size is of the order of a biological cell. As an example, the theory is applied to a previously published data for rat gastronemius cells. Excellent agreement is obtained, and furthermore, the size of the cell is calculated by fitting the theory to the experiment.

The Dynamics of Marine Ice Sheets

Abstract: Marine ice sheets rest on land that, for the most part, is below sea-level. Ice that flows across the grounding line, where the ice sheet becomes afloat, either calves into icebergs or forms a floating ice shelf joined to the ice sheet. At the grounding line there is a transition from ice-sheet dynamics to ice-shelf dynamics, and the creep-thinning rate in this region is very sensitive to sea depth; rising sea-level causes increased thinning-rates and grounding-line retreat, falling sea-level has the reverse effect. If the bedrock slopes down towards the centre of the ice sheet there may be only two stable modes: a freely-floating ice shelf or a marine ice sheet that extends to the edge of the continental shelf. Once started, collapse of such an ice sheet to form an ice shelf may take place extremely rapidly. Ice shelves which form in embayments of a marine ice sheet, or which are partially grounded, have a stabilizing influence since ice flowing across the grounding line has to push the ice shelf past its sides. Retreat of the grounding line tends to enlarge the ice shelf, which ultimately may become large enough to prevent excessive outflow from the ice sheet so that a new equilibrium grounding line is established; removal of the ice shelf would allow retreat to continue. During the late-Wisconsin glacial maximum there may have been marine ice sheets in the northern hemisphere but the only current example is the West Antarctic ice sheet. This is buttressed by the Ross and Ronne Ice Shelves, and if climatic warming were to prohibit the existence of these ice shelves then the ice sheet would collapse. Field observations suggest that, at present, the ice sheet may be advancing into parts of the Ross Ice Shelf. Such advance, however, would not ensure the security of the ice sheet since ice streams that drain to the north appear to flow directly into the sea with little or no ice shelf to buttress them. If these ice streams do not flow over a sufficiently high bedrock sill then they provide the most likely avenues for ice-sheet retreat.

Effect of climatic warming on the west Antarctic ice sheet

Abstract: Climatic warming could cause increased melting from Antarctic ice shelves. Continued weakening of the ice shelves in this way would result in the ultimate collapse of most of the West Antarctic ice sheet. For complete removal of the ice shelves collapse of the ice sheet and a 5 m rise in world sea level could occur in <100 yr. More realistically, ice-shelf deterioration is likely to be a rather slow process, and even for a major and sustained warming trend ice-sheet collapse would take several hundred years, with most of the associated rise in sea level occurring during the final century. However, little is known about the glaciers that drain the northern part of the ice sheet. These glaciers have little or no protective fringe of ice shelf and, unless they flow over sufficiently high bedrock sills, they may show a more rapid response to increased temperatures.

Strategic, Tactical and Organizational Dilemmas of the Protest Movement Against Nuclear Power

Abstract: Recent research has recognized that social movements face several dilemmas in simultaneously mobilizing the many resources that are necessary for their success. This study examines some of the problems that have confronted the contemporary protest movement against the construction and operation of nuclear power plants. Its emphasis is on differences within the antinuclear movement over four strategic, tactical, or organizational matters: (1) the single-issue focus; (2) the definition of nonviolence; (3) the intent of the civil disobedience committed by protesters; and (4) the use of affinity groups and a consensus style of decisionmaking. Some of the tactical problems that antinuclear protesters have encountered in the criminal courts are also identified, and implications for the resource mobilization perspective discussed. Social movements face many tough questions of strategy and tactics. A particular course of action may help achieve one goal but make it more difficult to achieve another. The organizational pattern of movement groups also matters, as a lack of effective organization may frustrate their efforts to change existing conditions. Movements throughout American history have had to resolve these ongoing dilemmas of protest group activity. The abolitionist movement of the nineteenth century, for example, was divided by differences over tactics. In the women's suffrage movement a few decades later, the wisdom of extending the movement's focus beyond the suffrage issue was debated at length. More recently, the southern civil rights movement was often beset by arguments over the possible benefits and disadvantages of various marches and rallies. And several Vietnam antiwar groups developed centralized structures of authority that permitted quick decisionmaking but also led to frustration among those denied any real influence on courses of action. In this paper I examine a number of strategic, tactical, and organizational dilemmas that have characterized the contemporary protest movement against nuclear power. These difficulties derive from the number of issues the movement has chosen to emphasize, its commitment to nonviolent civil disobedience as a primary method of protest, and its novel consensus style of decisionmaking using affinity groups. I also discuss the legal and political dilemmas confronting antinuclear protesters who have faced criminal prosecution for committing civil disobedience. In concentrating on some of the problems of this particular movement, I hope to contribute to

Late Quaternary extent of the West Antarctic ice sheet: New evidence from Ross Sea cores

Abstract: Ross Sea cores contain diatom floras and have sediment characteristics which suggest that grounded ice filled the Ross Sea embayment to the continental shelf margin during the last, and previous, glacial advances. Each successive advance reworked sediments from the previous interglacial period with older material and compressed them into a firm deposit with reworked (mixed and fractured) microfossils. As the grounding line retreated past each core location, subglacial meltwater, tidal pumping, and marine bottom-water flow winnowed light, less heavily silicified diatoms, leaving a lag of Eucampia balaustium in well-sorted, sandy sediment. Warm-water, open-marine conditions initially prevailed after deglaciation on the northern part of the continental shelf during summers. Open-marine conditions were gradually replaced by the pack-ice cover that today characterizes the Ross Sea continental shelf region.

Fish, crustaceans, and the sea floor under the ross ice shelf.

Abstract: Baited traps and a camera lowered through the Ross Ice Shelf, Antarctica, at a point 475 kilometers from the open Ross Sea and to 597 meters below sea level revealed the presence of fish, many amphipods, and one isopod. Biological or current markings were not evident on a soft bottom littered with subangular lumps. A fish was caught through a crevasse 80 kilometers from the shelf edge.

Ice Shelves: A Review

Abstract: Ice shelves form where ice flows off the Antarctic ice sheet onto the sea to produce rather flat slabs of floating ice which, for the theoretician, are the simplest of all large ice masses. Boundary conditions are well defined, conditions change very slowly over distances that are large compared with ice thickness, and horizontal velocities are independent of depth. Unconfined ice shelves can be used as giant creep machines to investigate the ice flow law at low stresses. Further inland, where movement is hampered by obstructions such as grounded ice rises and by shear between the ice shelf and its sides, the ice shelf transmits a backpressure which tends to restrict drainage from the ice sheets that feed it. Wastage from ice shelves is principally by calving and by bottom melting. There has been no direct measurement of bottom-melting rates, but indirect evidence suggests that, near the seaward edges of ice shelves, bottom-melting rates may exceed one metre per year, with significant melting within about 100 km of the ice front. Further inland there may be bottom freezing, and analysis of cores taken from the Amery Ice Shelf indicate that bottom-freezing rates average 0.5 m a–1 over a distance of 200 km. Such high freezing-rates are probably exceptional, and, beneath the Ross Ice Shelf, freezing appears to be insignificant even at a distance of 400 km from the ice front. Because of their accessibility ice shelves have been studied in considerable detail, but many problems remain. In particular we need to improve our understanding of basal flux, ice-shelf dynamics near the grounding line, the calving of icebergs, and the state of equilibrium of ice rises. In addition there is a clear need for basic data from the Filchner-Ronne ice shelf.

Seasonal succession and breeding cycles of three species of Acartia (Copepoda: Calanoida) in a maine estuary

Abstract: Seasonal succession of three species of Acartia in a Maine estuary was examined. The well-defined successional pattern, in which A. tonsa is replaced, by A. clausi in winter and early spring, is well-documented in the middle Atlantic estuaries, but was not observed in this northern New England estuary. Instead, both species increased in their abundance at the same time on most occasions. In general, A. clausi was present throughout the year and produced three generations from March to November. A. longiremis had two or three generations between May and November, and disappeared during late summer. A. tonsa was present from May through December and was most abundant in early fall. A. clausi and A. tonsa were generally most numerous upstream, and A. longiremis downstream. Adult and copepodite V sex ratios varied among species, stations, and seasons. Seasonal patterns of Acartia populations in estuaries of the north Atlantic coast and their possible relationships to environmental factors were also compared and discussed.

WAIS performance for different age groups of hypertensive and control subjects during the administration of a diuretic.

Abstract: This study examined the effects of age and hypertension on WAIS performance. Previous studies have reported that hypertension adversely affects cognitive functioning, but few have considered the influence of hypertension on discrete age groups. Hypertension was found to be negatively associated with WAIS Verbal scores for younger (21 to 39 years) but not older (45 to 65 years) subjects. Further, younger subjects attained higher WAIS Performance scores than did older subjects. Medication history was not associated with performance levels for hypertensives, nor was performance of controls influenced by whether or not they were tested while on a diuretic. When WAIS Performance scores were analyzed for subjects matched on WAIS Verbal scores across age (21 to 39 vs 45 to 65 years) and blood pressure (normotensive vs hypertensive), a significant age by blood pressure interaction was found. The effect of blood pressure on Performance scores was found to be greater for younger than for older subjects. The association between plasma renin activity (PRA) level and WAIS Performance scores was also examined. Contrary to previous findings PRA was not related to Performance scores. The results are discussed in the context of previous hypertension research and their implications for comparisons across age levels.

Polyploid Mosaics Induced by Cytochalasin B in Landlocked Atlantic Salmon Salmo salar

Abstract: Polyploid mosaicism was induced in landlocked Atlantic salmon by treatment of fertilized eggs with 10 mg/liter solution of cytochalasin B. On the basis of nuclear size in 3,025 erythrocytes and chromosome counts we judged the treated fish to be polyploid mosaics of diploid, triploid, and tetraploid cells. The dominant polyploid cell type in test fish was triploid rather than tetraploid, in contrast to previous reports of Atlantic salmon exposed to cytochalasin B. Control groups had mainly diploid cells but a few triploid cells were measured in most individuals.

Distinctive features of cilia in metazoans and their significance for systematics

Abstract: A comparative study of epidermal cilia in the Turbellaria and Nemertea has revealed features in these organelles that are specific to certain taxonomic groups. Turbellarians of the order Acoela, in particular, have a characteristic pattern of axonemal filament termination in the distal tips of their cilia and a characteristic ciliary rootlet system that is not seen in other turbellarian orders nor in other metazoans. Each epidermal cilium in acoels has a typical 9 + 2 axonemal pattern through the main part of its length, but near its distal tip there is an abrupt shelf-like narrowing at which filaments 4–7 terminate; filaments 1, 2, 3, 8 and 9 continue into the thinner distal-most part of the shaft along with the singlet microtubules from the axonemal center. The rootlet system in acoel cilia involves an interconnecting pattern with lateral connectives. The unique structure of these cilia has systematic and phylogenetic significance for the Acoela, and it is argued that ultrastructural characters in general, including characters of organelles, can be validly applied to the phylogeny and systematics of the Metazoa.

p -Cresol: an Oviposition Attractant of Aedes triseriatus

Abstract: Aqueous infusions of decayed paper birch, Betula papyrifera (Marsh), are shown to contain an oviposition attractant for the tree-hole mosquito Aedes triseriatus (Say) in laboratory experiments. The attractive material is proved to be volatile and soluble in pentane. p -Cresol is shown to be an active component of this extract. Further experiments demonstrate that contact of ovipositing mosquitoes with p -cresol odor alone suffices to induce significantly increased oviposition. Trapping experiments show that p -cresol solutions attract significantly more mosquitoes, both male and female, than does distilled water alone.

Hinge morphogenesis in the shells of larval and early post-larval mussels (Mytilus edulis L. and Modiolus modiolus (L.))

Abstract: Scanning electron and optical microscopic examination of the hinge apparatus and primary ligament pit of two Recent mytilids (Mytilus edulis and Modiolus modiolus) revealed a similar sequence of ontogenetic changes in both species from the prodissoconch I stage through metamorphosis. Hinge-line dentition was absent at the prodissoconch I stage. Provinculum length and complexity increased throughout larval development with progressive lateral thickening characteristic of the family Mytilidae.

Androgyny: Some Audacious Assertions Toward Its Coming of Age

Abstract: It is proposed that the field of research on psychological androgyny has entered a crucial period during which its development will not be optimal unless the following problems are recognized and corrected for: (a) the dangers of too rigidly held values; (b) the prevalence of dubious definitional assumptions; (c) the pervasity of diffuse and/or atheoretical research directions; and (d) alienation from certain basic concerns in “mainstream” personality research. The origins and nature of each of these problems are discussed, and in each case recommendations for future research are made. Finally, broad outlines are proposed for an idiographic model of sex roles designed to increase the predictive utility of assessment in the area of androgyny research.

Feeding Ecology and Development of Juvenile Black Ducks in Maine

Abstract: -Data from 41 juvenile Black Ducks (Anas rubripes) collected in the Penobscot River valley of Maine from June through August 1974-76 were used to estimate the proportion of aquatic invertebrates in the prefledging diet and the allometric growth rates of the tarsi, flight muscles, and alimentary system. The proportion of aquatic invertebrates in the diet of downy and partially feathered juveniles averaged 88 and 91% of dry weight, but decreased to 43% for fully feathered young. The most important invertebrate food organisms for juvenile Black Ducks were asellid isopods, molluscs, nymphs of Ephemeroptera and Odonata, and larvae of Coleoptera, Trichoptera, and Diptera. A high proportion of invertebrates was consumed during the period of fastest absolute and relative growth. Estimation of allometric growth rates with the power formula (Y = a X&) showed that (1) the legs were relatively large at hatching and developed slowly; (2) the flight muscles, which were relatively small at hatching, grew slowly until the 4-week period preceding fledging, when they increased as the 4.75 power of body weight; and (3) growth of the liver and gizzard was approximately proportional to body weight. The data support Ricklefs' thesis that delayed functional maturity of the wings permits an increase in the overall growth rate of waterfowl. Received 12 January 1979, accepted 6 August 1979. BECAUSE the components of avian reproductive strategy (e.g. nest site, clutch size, mode of development) are interdependent, it is necessary to consider the requirements of the young with those of the parent birds (Cody 1971: 473). The same is true of energy relationships; adults and young must be treated as a single unit during the period of parental care (Ricklefs 1974: 268). These concepts have stimulated increased interest in the growth and energy requirements of young birds (e.g. Ricklefs 1975). Before such a holistic approach is possible for the Black Duck (Anas rubripes) or other waterfowl, additional data must be collected. Information on the food requirements and development of the young is essential. Early reports on the foods used by juvenile waterfowl were based on limited collections (Collias and Collias 1963) or on techniques biased toward the less digestible food items (Swanson and Bartonek 1970). Nevertheless, the importance of aquatic invertebrates for the young of several species of dabbling (Anatini) and diving (Aythyini) ducks has been established (Bartonek and Hickey 1969, Sugden 1973). Limited data available for juvenile Black Ducks suggest that aquatic invertebrates may be an important food (Mendall 1949: 82-83), but the timing and extent of invertebrate use are unknown. The objectives of the present paper are to quantify the proportion of freshwater invertebrates in the diet of juvenile Black Ducks and to describe the allometric growth of the tarsi, wing musculature, and alimentary system. STUDY AREA AND METHODS Juvenile Black Ducks were collected in the lower Penobscot River valley, within 55 km of Orono, Maine. Undeveloped areas of the Penobscot valley currently support spruce-fir and maple-beech-birch 1 Migratory Bird and Habitat Research Laboratory, U.S. Fish and Wildlife Service, Laurel, Maryland 20811 USA. 737 The Auk 96: 737-745. October 1979 This content downloaded from 157.55.39.253 on Wed, 08 Jun 2016 06:23:48 UTC All use subject to http://about.jstor.org/terms 738 KENNETH J. REINECKE [Auk, Vol. 96 forest types (Ferguson and Kingsley 1972). The soils of this area developed in a stony till of variable thickness overlying relatively insoluble Paleozoic rocks (Doyle 1967). As a result, waters of the lakes and ponds are dilute, and total alkalinities rarely exceed 20 ppm (as CaCO3) (Mairs 1966). Approximately 25 beaver ponds and sedge-meadow streams were used as collection sites during the study. These wetlands are classified as Types 3 and 4 (Martin et al. 1953), or as subclasses of deep and shallow marsh associated with seasonal flats, shrub swamps, and bogs (Golet and Larson 1974). Although I tried to observe a period of feeding activity before each collection (Swanson and Bartonek 1970), this was at times impossible because of low Black Duck densities and poor visibility in Maine wetlands. Of the 41 juveniles collected from June through August 1974-76, 88% contained more than 5 food items in the esophagus and were included in the analysis. Approximately equal numbers (n = 13, 12, 11) of downy (class I), partially feathered (class II), and fully feathered (class III) juveniles were collected. The class III sample included both flying and flightless young because flighted juveniles were impossible to distinguish when feeding. The food from each esophagus was preserved in 75% ETOH in the field, and the carcasses frozen. In the laboratory, I identified the food items using Martin and Barkley (1961), Pennak (1953), and a reference seed collection. The dry weight of each food was measured to the nearest 0.1 mg after drying for 48 h in a convection oven at 50-55?C. I chose dry weight as the principal measure of food importance in this study because differences in the moisture content of seeds and invertebrates bias volumetric and wet weight data (Sugden 1973), and because dry weight has a more direct nutritional and energetic interpretation. Statistical treatment of food-use data is often difficult; an alternative is to present the results in several formats, each of which reduces certain biases. For this study I calculated food importance as (1) percentage occurrence, (2) aggregate percentage, and (3) aggregate dry weight. Swanson et al. (1974b) reviewed the use of these terms. Aggregate dry weight is the total weight of a food item in a sample of birds divided by the weight of all such food items; aggregate percentage is the proportion of a given food item in each bird averaged over all birds in a sample. Specimens frozen during the summer were later dissected. The age of each bird was estimated by reference to plumage descriptions (Gollop and Marshall 1954). To quantify juvenile development, I obtained wet weights to the nearest 0. 1 g for the gizzard, liver, flight muscles (pectoralis, coracobrachialis, and supracoracoideus), and whole body. I compared the differential growth of organs and tissues with allometric growth constants as described by Ricklefs (1975) and Brody (1945: Ch. 15). RESULTS AND DISCUSSION Juvenile food use.-The importance of aquatic invertebrates for three age classes of juvenile Black Ducks is summarized in Table 1. Of the three statistics, percentage occurrence is least informative because of the use of both animal and plant foods by nearly all birds. Agreement between the aggregate percentage and aggregate dry weight estimates suggests that the analysis has not been seriously biased by large food volumes in a small number of birds. All three statistics show a transition from consistently high invertebrate consumption in classes I and II to a diet of mixed composition during class III. The significance of the decline in the aggregate percentage use of invertebrates during class III was tested with a one-way ANOVA. The F-statistic was significant (F = 9.55, df = 2,33, P < 0.001), and a Student-Newman-Keuls test (Sokal and Rohlf 1969: 239) showed that invertebrate usage by class III young was less (P < 0.01) than that of classes I and II; 95% confidence limits for invertebrate consumption were: class I, 83.6-100%; class II, 87.4-100%; and class III, 10.3-80.6%. Important invertebrate foods consumed by class I birds were Diptera, Trichoptera, and Ephemeroptera (Table 2). The dipterans were larval, pupal, and adult midges (Chironomidae) and mosquitoes (Culicinae). For about 10 days after the ducklings hatched, most of their prey were adult or emerging insects captured at or above the water surface. Dry weight consumption of trichopteran larvae and ephemeropteran nymphs This content downloaded from 157.55.39.253 on Wed, 08 Jun 2016 06:23:48 UTC All use subject to http://about.jstor.org/terms October 1979] Juvenile Black Duck Feeding Ecology 739 TABLE 1. The importance of aquatic invertebrates in the diet of juvenile Black Ducks collected in Maine.

Monomial gorenstein curves in A4 as set-theoretic complete intersections

Abstract: It is shown that if the prime ideal\(P(S) \subseteq k[x_1 , \cdots ,x_4 ]\),⋯, x4], k an arbitrary field, has generic zero xi=tni, ni positive integers with g.c.d. equal l, l ≤ i ≤ 4, then P(S) is a set-theoretic complete intersection if the numerical semigroup S= is symmetric (i.e. if the extension of P(S) in k[[x1,⋯, x4]] is a Gorenstein ideal).