Showing papers by "University of Rhode Island published in 1987"

Multi-channel seismic imaging of a crustal magma chamber along the East Pacific Rise

Abstract: A reflection observed on multi-channel seismic profiles along and across the East Pacific Rise between 8°50′ N and 13°30′ N is interpreted to arise from the top of a crustal magma chamber located 1.2–2.4 km below the sea floor. The magma chamber is quite narrow (<4 – 6 km wide), but can be traced as a nearly continuous feature for tens of kilometres along the rise axis.

The Cenomanian-Turonian Oceanic Anoxic Event, II. Palaeoceanographic controls on organic-matter production and preservation

Abstract: Correlation of the δ13C spike with the well dated occurrences of strata rich in organic carbon detailed in Schlanger et al. (this volume), indicates that a global episode of intense organic carbon (orgC) burial took place during the latest Cenomanian-earliest Turonian ‘Oceanic Anoxic Event’ (OAE) (A. plenus through I. labiatus macrofossil zones and upper R. cushmani TRZ through W. archecretacea PRZ foraminiferal zones) over a period of no more than 1 million years (m.y.). The shape of the δ13C curve indicates that rates of orgC burial gradually increased in the early part of the late Cenomanian, increased more rapidly in the later Cenomanian, and levelled off at peak values in latest Cenomanian-early Turonian time during the maximum rate of orgC burial. The δ13C values decreased nearly to pre-late Cenomanian levels in the early to middle Turonian. The decrease in δ13C reflects decreasing rates of orgC burial following the Cenomanian-Turonian ‘oceanic anoxic event’ as well as the probable oxidation and return of significant amounts of orgC to the oceans following regression and re-oxygenation of much of the deeper water masses in contact with the seafloor.

Routh-Hurwitz criterion in the examination of eigenvalues of a system of nonlinear ordinary differential equations.

Abstract: In stability analysis of nonlinear systems, the character of the eigenvalues of the Jacobian matrix (i.e., whether the real part is positive, negative, or zero) is needed, while the actual value of the eigenvalue is not required. We present a simple algebraic procedure, based on the Routh-Hurwitz criterion, for determining the character of the eigenvalues without the need for evaluating the eigenvalues explicitly. This procedure is illustrated for a system of nonlinear ordinary differential equations we have studied previously. This procedure is simple enough to be used in computer code, and, more importantly, makes the analysis possible even for those cases where the secular equation cannot be solved.

Along-axis variations in seafloor spreading in the MARK area

Abstract: Recent investigations with the manned submersible Alvin and the Angus deep-towed camera sled greatly extended the known range of variations in the style of seafloor spreading along the axis of the Mid-Atlantic Ridge. Five transects of the spreading centre at intervals of10–20 km south of the Kane Fracture Zone at 24° N latitude demonstrate dramatic changes in the style and magnitude of tectonic extension, development of the neovolcanic zone, expression of hydrothermal venting, types oflithologic exposures and morphology of the median valley.

Simple Parallel Hierarchical and Relaxation Algorithms for Segmenting Noncausal Markovian Random Fields

Abstract: The modeling and segmentation of images by MRF's (Markov random fields) is treated. These are two-dimensional noncausal Markovian stochastic processes. Two conceptually new algorithms are presented for segmenting textured images into regions in each of which the data are modeled as one of C MRF's. The algorithms are designed to operate in real time when implemented on new parallel computer architectures that can be built with present technology. A doubly stochastic representation is used in image modeling. Here, a Gaussian MRF is used to model textures in visible light and infrared images, and an autobinary (or autoternary, etc.) MRF to model a priori information about the local geometry of textured image regions. For image segmentation, the true texture class regions are treated either as a priori completely unknown or as a realization of a binary (or ternary, etc.) MRF. In the former case, image segmentation is realized as true maximum likelihood estimation. In the latter case, it is realized as true maximum a posteriori likelihood segmentation. In addition to providing a mathematically correct means for introducing geometric structure, the autobinary (or ternary, etc.) MRF can be used in a generative mode to generate image geometries and artificial images, and such simulations constitute a very powerful tool for studying the effects of these models and the appropriate choice of model parameters. The first segmentation algorithm is hierarchical and uses a pyramid-like structure in new ways that exploit the mutual dependencies among disjoint pieces of a textured region.

Distribution of VA mycorrhizal fungi along a latitudinal temperature gradient

Abstract: Spores of Gigaspora and Scutellospora species predominated in the root zones of three major plant species growing in the barrier dunes extending from northern New Jersey to Virginia. Similarity in edaphic factors, vegetation, daylength during the growing season, and precipitation along a 355 km transect permitted study of the composition of the VAM fungal community in response to temperature. Twenty-three species of VAM fungi were recovered. Dominant species along the transect were G. gigantea, Acaulospora scrobiculata, and S. dipapillosa. Some species were more abundant in the northern (cooler) regions of the transect and others were more abundant in the southern regions. Average VAM fungal species richness was positively correlated with distance south along the transect and with temperature parameters. Temperature effects on the VAM fungal community may be separated into two components, a direct effect on the fungi and an indirect effect mediated through the host plant. Plots of rank/log Importance Value depicted the structure of the VAM fungal community and were of use in identifying severe habitats where heat stress appeared to be the controlling factor. Dominance by a single fungal species was inversely correlated with distance south and with temperature parameters. It was most pronounced in northern sites and in the root zones of heat-stressed Ammophila breviligulata plants growing near the species' southern limit.

Referent selection in determining equity perceptions: differential effects on behavioral and attitudinal outcomes

Abstract: The concept of differential equity allows individuals to have different perceptions of equity depending on the pay referent used. Different pay referents should result in different tactics to reduce inequities. To test this hypothesis, equity perceptions with respect to seven different referents were compared as to their relationship to pay satisfaction, intent to remain with a company, and frequency of extra-role behavior. Findings suggest that the various types of inequity relate differentially to each of the three outcome variables.

A comparison of four methods for determining planktonic community production1

Abstract: Samples from two coastal experimental ecosystems were incubated in vitro and sampled over 24 h. Production rates were measured by the 14C method, the O2 and CO, light-dark bottle methods, and the I80 method. 0, production in the experimental enclosures (volume - 1.3 x lo4 liters) was also measured directly. Photosynthetic and respiratory quotients were close to 1 .O. Gross production values determined by 0, light-dark experiments, CO2 light-dark experiments, and I80 were similar. 14C production ranged from 60 to 100% of gross production measured in CO, light-dark experiments, indicating that 14C uptake is not precisely fixed with respect to other measures of community metabolism. There was no evidence that 14C or any other method underestimated the rate of primary production in vitro by more than 40%. Productivities in vitro ranged from 35 to 100% of those in the mesocosm at similar light intensities. In samples from one of the ecosystems, the rate of respiration in the light (calculated from I80 data) was an order of magnitude greater than the rate in the dark. This difference may be ascribed to either photorespiration or light enhancement of mitochondrial respiration.

A Mathematical Model to Predict the Thermal Response of Decomposing, Expanding Polymer Composites

Abstract: A one-dimensional transient thermal model has been developed to predict the thermal response of a decomposing, expanding polymer composite exposed to high temperatures. Both the decomposition and t...

Measurement of free cupric ion concentration in seawater by a ligand competition technique involving copper sorption onto C18 SEP-PAK cartridges1

Abstract: Knowledge of ion speciation and free ion concentrations is important in predicting the biological availability and geochemical behavior of trace metals. Here we describe a new technique for measuring free cupric ion concentration in seawater based on sorption of copper onto SEP-PAK C,, cartridges and internal free cupric ion calibration. Calibration was achieved by adding cupric ion buffers, consisting of copper and excess concentrations of synthetic chelator, ethylenediaminetetraacetic acid (EDTA). EDTA competes with natural organic ligands for copper complexation, but its copper chelate is not retained by the C,, cartridges. This latter property allows EDTA to bc used for free cupric ion calibration. Titrations in seawater utilizing the new technique revealed that copper was highly complexed. Fret cupric ion concentrations in three samples of seawater from lower Narragansett Bay, Rhode Island, and one from off the coast of Peru were measured to be 10-12.3, 10 -120, 10 12.L, and 1O-“.5 M at total dissolved copper concentrations of 26.7, 16.5, 19.4, and 3.7 nM. From these values and from computed and experimental values for inorganic complexation, we compute that only 0.03-2% of the dissolved copper can be accounted for as inorganic species (Cu2+, CuCO,, CuOH’, etc.). The remainder, 99.97-98%, appears to bc organically complexed. These results are in general agreement with several other recent studies, using several techniques, of copper complexation in seawater.

Who Participates, Who Does Not, and Why? An Analysis of Voluntary Neighborhood Organizations in the United States and Israel

Abstract: Lack of participation in voluntary associations and the associated issues of why people do or do not participate are major areas of interest in the research literature concerning citizen participation. The present study used three types of variables (demographic, social psychological, and costs/benefits) to investigate the characteristics of participants and nonparticipants in neighborhood-type organizations in the United States and Israel. Findings from analysis of the demographic variables show some cross-cultural similarities (including a surprising lack of race/ethnic and education differences between participants and nonparticipants). There were striking cross-cultural similarities using the social psychological variables. The data from the Israel sample provide important information on the costs and benefits of participation. A discriminant analysis points to the predictive strength of social psychological and cost/benefit variables in comparison to demographic variables. Implications of these results for explanatory and predictive purposes are discussed.

Temporal variations in column height and magma discharge rate during the 79 A.D. eruption of Vesuvius

Abstract: The 79 A.D. plinian eruption of Vesuvius ejected ∼4 km3 (ORE) of phonolitic magma over a period of ∼19 hr. A change in magma composition during the eruption is marked by a sharp transition from white, evolved phonolitic pumice to denser, overlying gray pumice, at mid-level within the fall deposit. Deposition of the upper, gray pumice fall was interrupted six times by the emplacement of pyroclastic surges and flows. Reverse size grading is conspicuous in the fall deposit. Measurements of maximum pumice and lithic diameters have been used to construct isopleths for eight chronostratigraphic levels within the fall deposit. The temporal evolution of eruption column height and magma discharge rate have been evaluated from these isopleths, using a theoretical model of pyroclast dispersal from explosive eruptions. During ejection of the white pumice, the column height rose from 14 to 26 km, as the magma discharge rate increased to 7.7 × 107 kg/s. Shortly after onset of the gray pumice fall, the column reached its maximum altitude of 32 km, with a discharge rate of 1.5 × 108 kg/s. Subsequent generation of surges and pyroclastic flows was associated with fluctuations in column height, supporting an origin by column collapse. At the white-gray boundary in the fall deposit, pumice density increases abruptly from 0.60 g/cm3 in the white pumice to 1.10 g/cm3 at the base of the gray pumice. Higher in the gray fall, the density decreases continuously to 0.60 g/cm3. The variation in pumice density is attributed primarily to differences in volatile content of two magmas which were tapped and mixed in varying proportions during ascent and eruption.

Mammal sounds and motivation-structural rules: a test of the hypothesis

Abstract: We tested if mammal sounds given in aggressive and fearful/friendly contexts showed acoustic design characteristics in accordance with the Motivation-Structural (MS) rule hypothesis (Morton, 1977). Our data were taken from literature and consist of 76 aggressive sounds and 75 fearful/friendly sounds from 50 species of mammals. Aggressive sounds are of low-frequency and wide bandwidth and thus support MS rule predictions. Fearful/friendly sounds show a trend toward conforming to MS rule design expectations (high-frequency and tonal) but exhibit considerable variation. This variation may be due to the existence of acoustic parameters other than frequency or bandwidth that might convey motivation information in fearful/friendly contexts. In addition, fear and friendliness represent two very different motivation states in mammals and MS rules may not apply to both.

Long-range transport of terrestrially derived lipids in aerosols from the south Pacific

Abstract: Terrestrially produced participate organic matter can be transported relatively fast in the atmosphere, long distances over the ocean. It has been hypothesized that this atmospheric transport may be an important way of quickly introducing continentally-derived organic material to the surface waters of the open ocean1–11. After rapid transport through the water column to the sediment surface12, these terrestrial organic substances could account for an important fraction of the organic carbon found in the sedimentary record13. The atmospheric fluxes of these organic substances are large enough to have a major potential impact on the inventory of terrestrially derived lipid material, originating from vascular plant waxes, found in deep-sea sediments13. We present here the first use of organic compound biological source marker information in conjunction with long-range meteorological trajectory analysis to elucidate specific terrestrial source regions and to determine the transport pathways of organic material through the atmosphere to remote marine locations.

A whole-core squeezer for interfacial pore-water sampling1

Abstract: The “whole-core squeezer” is a simple pore-water sampler dcsigncd for millimeter depth rcsolution near the sediment-water interface. Various tests have been done to determine how accurately true gradients are reproduced by whole-core squeezing. Tracer studies show that any mixing associated with squeezing dots not smear the profiles by more than a few millimeters. Benthic fluxes of SiO, calculated from interfacial concentration gradients resolved with the whole-core squeezer in San Clcmente Basin are in good agreement with “beil-jar” values measured with the benthic chambers of a bottom lander. Oxygen profiles determined with the whole-core squeezer are very similar to values determined with an oxygen microelectrode. These comparisons confirm that intcrfacial gradients and (by calculation from models) fluxes of 02, N03-, SiO,, and other particle-unreactive ions and molecules can be determined with the instrument. On the other hand, the composition of squeezed pore waters is very susceptible to rapid alteration by solid-solution reactions. Therefore the method is not suitable for determining port-water profiles of trace metals and other particle-reactive chemicals.

A depositional model for outwash, sediment sources, and hydrologic characteristics, Malaspina Glacier, Alaska: A modern analog of the southeastern margin of the Laurentide Ice Sheet

Abstract: The Malaspina Glacier on the southern coast of Alaska is a partial analog of the late Wisconsinan Laurentide Ice Sheet that occupied New England and adjacent areas. Ice lobes of the Malaspina are similar in size to end moraine lobes in southern New England and Long Island. Estimated ablation rates, surface slopes, and meltwater discharge per unit of surface area for the Laurentide Ice Sheet are comparable to measured ablation rates, surface slopes, and meltwater discharge rates for the Malaspina Glacier. Meltwater moves from the surface of the Malaspina down-glacier and toward the bed of the glacier along intercrystalline pathways and through a series of tunnels. Regolith beneath the glacier, which is eroded and transported to the margin of the glacier by subglacial and englacial streams, is the source of essentially all fluvial and lacustrine deposits on the Malaspina Foreland. By analogy, a similar hydrologic system existed at the southeastern margin of the Laurentide Ice Sheet. Subglacial regolith, which was eroded from beneath the ice sheet by meltwater, was the source of most stratified sediment deposited in New England and adjacent areas during the late Wisconsinan. Similarly, Wisconsinan ice-contact landforms in New England were built by the same processes that are constructing landforms composed of stratified sediments in contact with the Malaspina Glacier. For the Malaspina Glacier and the Laurentide Ice Sheet, therefore, we reject the concept of the “dirt machine” by which debris near the base of the glacier is carried to the surface of the glacier along shear planes and then washed off the surface to form ice-contact stratified deposits.

The first methane-oxidizing bacterium from the upper mixing layer of the deep ocean: Methylomonas pelagica sp. nov.

Abstract: Methane enrichment of twenty-three 100-ml portions of seawater from three stations in the Sargasso Sea yielded the same obligate type I methanotroph. It is pigmented white, requires NaCl, grows well in seawater with either methane or methanol, but not on other C1 compounds nor on C−C bonded organic matter, and it uses either ammonia or nitrate but not dinitrogen as a nitrogen source. Formaldehyde is produced in marked amounts from methanol. Growth occurs at 20° and 30°C but not at 10°C and is inhibited in natural sunlight. Representative isolates from each hydrographic station assimilate one-carbon units via the ribulose monophosphate pathway for formaldehyde fixation, and have a DNA base composition of 49 mol% guanine plus cytosine. The type strain, NCMB 2265, has been namedMethylomonas pelagica sp. nov. This upper ocean methanotroph may obtain its C1 substrates in situ from particles of algal debris that become anoxic, ferment, and accumulate in the thermocline to form a false benthos.

Methylamines in the marine atmosphere

Abstract: There is growing recognition of the possible importance of organic nitrogen compounds in the global atmospheric nitrogen cycle. Concentrations of gaseous methylamines (MAs) have been measured for the first time in the atmosphere of two non urban regions-coastal Hawaii and Rhode Island. In Hawaii gaseous MA concentrations were as follows: monomethylamine (MMA), 11±5 pmol/m³ dimethylamine (DMA), 93±51 pmol/m³ and trimethylamine (TMA), 30±19 pmol/m³. Concentrations of these compounds were also measured in coastal seawater in Hawaii and Massachusetts and in rainwater from Rhode Island. Calculations of the fluxes of MAs across the air-sea interface indicate that the oceans are a source for MMA and TMA but may be a sink for dimethylamine (DMA). The concentrations of MAs observed in rain can largely be explained by scavenging of gaseous MAs. Another important removal process for atmospheric MAs appears to be oxidation by OH radicals. Wet and dry removal combined with OH oxidation appear to balance oceanic production of MMA and TMA in the Hawaii region. Significant uncertainties remain about the cycling of DMA.

Thyroxine content of eggs and larvae of coho salmon, Oncorhynchus kisutch

Abstract: The whole-animal content of the thyroid hormone thyroxine (T4) was measured in embryonic and larval coho salmon (Oncorhynchus kisutch) by radioimmunoassay following the validation of an extraction method. The embryonic yolk, at 20 days after fertilization and 10 days before hatching, was found to have 5.3 ± 0.3 ng T4 (mean ± SEM). At hatching, the total T4 content decreased to 4.4 ± 0.3 ng, of which 96% remained in the yolk and 4% was distributed in the larva. T4 content decreased to 1.5 ± 0.1 ng during the 30 days of larval development. The first increases in T4 were detected within 2 weeks following emergence from the substrate of the actively feeding juvenile; the newly emerged salmon responds significantly to bovine TSH. The presence and clearance of T4 from the yolk suggest that T4 may be critical to normal larval morphogenesis, that initially the T4 is of maternal origin, and that the hypothalamo-adenohypophysial-thyroid axis begins to function independently at or near the time of emergence.

The 1982 eruptions of El Chichon volcano, Mexico (3): Physical properties of pyroclastic surges

Abstract: Two major pyroclastic surges generated during the 4 April 1982 eruption of El Chichon devastated an area of 153 km2 with a quasi-radial distribution around the volcano. The hot surge clouds carbonized wood throughout their extent and were too hot to allow accretionary lapilli formation by vapor condensation. Field evidence indicates voidage fraction of 0.99 in the surge cloud with extensive entrainment of air. Thermal calculations indicate that heat content of pyroclasts can heat entrained air and maintain high temperatures in the surge cloud. The dominant bed form of the surge deposits are sand waves shaped in dune forms with vertical form index of 10–20, characterized by stoss-side erosion and lee-side deposition of 1–10 cm reversely graded laminae. A systematic decrease in maximum lithic diameter with distance from source is accompanied by decrease in wavelength and amplitude. Modal analysis indicates fractionation of glass and pumice from the surge cloud relative to crystals, resulting in loss of at least 10%–25% of the cloud mass due to winnowing out of fines during surge emplacement. Greatest fractionation from the −1.0–0.0−∅ grain sizes reflects relatively lower pumice particle density in this range and segregation in the formative stages of the surge cloud. Extensive pumice rounding indicates abrasion during bed-load transport. Flow of pyroclastic debris in the turbulent surge cloud was by combination of bed-load and suspended-load transport. The surges are viewed as expanding pyroclastic gravity flows, which entrain and mix with air during transport. The balance between sedimentation at the base of the surge cloud and expansion due to entrainment of air contributed to low cloud density and internal turbulence, which persisted to the distal edge of the surge zone.

Effect of starch of textural properties of surimi gel

Abstract: The proportion of amylose and amylopectin, and the rheological behavior of eight starches were correlated with the textural properties of starch-containing surimi gels. Findings included the following: increased firmness and cohesiveness with increases in water-holding ability and viscosity of the starch; increased expressible moisture and penetration force with an increase in the amylose fraction due to increased retrogradation: increased tensile force with an increase in the amylopectin fraction: and increased cohesiveness and chewiness after refrigerated storage for all starches with a greater increase for high amylose starches. Surimi gels containing potato starch were the firmest and most cohesive. The textural properties of starch-containing surimi gel correlated well (r = 0.90 to 0.97, P>0.05) with the viscosity of starch paste if 100% amylopectin-containing and pregelatinized starches were excluded from the correlation.