Showing papers by "University of Rhode Island published in 1977"
844 citations
TL;DR: Injection of basic magma into acid magma causes superheating of the acid and vigorous convection as discussed by the authors, which can lead to an explosive acid eruption in volcanic edifices.
Abstract: Injection of basic magma into acid magma causes superheating of the acid magma and vigorous convection. Vesiculation induced by convection and increased magma pressure fractures the volcanic edifice triggering an explosive acid eruption. The 1875 plinian eruption of Askja, Iceland is an example of an explosive eruption triggered by magma mixing.
732 citations
TL;DR: In this paper, the authors developed surface electrical resistivity methods for estimating hydraulic conductivities in glacial outwash materials, using the results of Schlumberger electrical soundings at six sites in southern Rhode Island where pumping tests had previously been made.
Abstract: The objective of this study was to develop surface electrical resistivity methods for estimating hydraulic conductivities in glacial outwash materials Aquifer electrical resistivities were determined from the results of Schlumberger electrical soundings at six sites in southern Rhode Island where pumping tests had previously been made Hydraulic conductivities and transmissivities determined from pumping tests were then correlated with resistivities obtained from electrical soundings Results indicate that electrical resistivities determined from soundings can be used to predict aquifer hydraulic conductivities; an empirical relation between aquifer electrical resistivity and aquifer hydraulic conductivity was developed A semiempirical relation between aquifer formation factor and hydraulic conductivity was also developed
229 citations
TL;DR: In this article, the authors describe a mixture of hydrothermal, detrital, hydrogenous, and biogenous material for northwest Nazca plate sediments, and the distribution of each element is governed by supply from the four basic sources, including bottom currents moving east and then south across the northern East Pacific Rise and Bauer Deep to the Central Basin and moving west from the Peru Basin to the central Basin.
Abstract: Analytical data for northwest Nazca plate sediments can be described in terms of a mixture of hydrothermal, detrital, hydrogenous, and biogenous material. Fe, Mn, Cu, Zn, Ni, Ba, Si, and Al are more than 50 percent hydrothermal in East Pacific Rise samples from lat 10° to 25 °S. The first four elements are dominantly hydrothermal in the Bauer Deep and Central Basin as well. Seventy to 80 percent of the Ni, 60 to 80 percent of the Ba, and 30 to 60 percent of the Cu and Zn in Bauer Deep and Central Basin sediments are hydrogenous. Si, Ba, and Zn are dominantly biogenous on the northern East Pacific Rise crest, where more than one-third of the Cu also is derived from this source. Detrital Al and Si are dominant away from the rise crest, particularly in the Central Basin, where about 40 percent of the Fe and 15 percent of the Zn may also be detrital. Much of the hydrothermal Fe and biogenous Si have been transformed to an iron-rich smectite. The proportion of total Fe bound in this phase varies from less than 20 percent on the southern rise crest to about 40 percent in the Bauer Deep. The distribution of each element is governed by (1) supply from the four basic sources; (2) lateral transport by bottom currents moving east and then south across the northern East Pacific Rise and Bauer Deep to the Central Basin and moving west from the Peru Basin to the Central Basin; and (3) transformation of the unstable metalliferous hydroxides into more stable smectite and ferromanganese oxyhydroxides.
224 citations
TL;DR: A relatively precise and rapid method for the analysis of total dissolved monosaccharides at the concentrations that occur in seawater is described which uses 1-ml quantities for each analytical and control replicate.
196 citations
TL;DR: In this paper, chemical variations between the 15 larger volcanic islands of the Lesser Antilles island arc are examined in detail as type examples of this variation, i.e. Grenada (south), Dominica (centre), and St. Kitts (north).
193 citations
TL;DR: The Tropic Haze refers to turbid layers of air which are found regularly over the pack ice north of Alaska during periods of clear weather as mentioned in this paper, and can occur as single or multiple bands of different heights at nearly any level in the troposphere.
Abstract: ‘ARCTIC haze’ refers to turbid layers of air which are found regularly over the pack ice north of Alaska during periods of clear weather1. These layers are diffuse, hundreds to thousands of kilometres wide, 1–3 km thick, and can occur as single or multiple bands of different heights at nearly any level in the troposphere. They are invisible from the ground, but may limit horizontal and slant visibility within a layer to as little as 3–8 km. Their colour is grey–blue in the antisolar direction and reddish–brown in the solar direction, suggesting that they are true aerosol rather than ice crystals.
190 citations
TL;DR: In this article, a procedure is described which adds a hydrolysis step to the Johnson and Sieburth 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) assay for total dissolved monosaccharides.
187 citations
TL;DR: In this paper, surface water samples from the Sargasso Sea, the western North Atlantic, and the northeast Pacific all have manganese concentrations of about 0.1 ppb.
180 citations
TL;DR: In this paper, the first principal component is interpreted as being temperature-dependent based on the faunal assemblages associated with this component and on its close similarity to the oxygen isotope record.
154 citations
TL;DR: The distribution, number and movement of cyclonic Gulf Stream rings were estimated from an analysis of 50 000 temperature records obtained from the National Oceanographic Data Center and Fleet Numerical Weather Central as discussed by the authors.
Abstract: The distribution, number and movement of cyclonic Gulf Stream rings were estimated from an analysis of 50 000 temperature records obtained from the National Oceanographic Data Center and Fleet Numerical Weather Central. The data were taken from 1970 through September 1976 in the region bounded by 20–40°N and 50–80°W. Additional ring observations from other sources were also used. Twenty-five ring time series, together with 26 single ring observations were obtained; approximately 11 rings were found to exist at one time. Rings typically moved westward, turned southwest when close to the Gulf Stream and appeared to coalesce with the Stream near Florida. On the average, two rings per year moved down this path with a mean speed of 3 km day−1 and an estimated life span of 2–3 years. Although ring observations were concentrated in the northwestern Sargasso Sea, several were documented east of 60°W. In addition to cold core rings several warm eddies were found south of the Stream; they consisted of at l...
TL;DR: In this article, the authors examined the tempo of Cenozoic volcanism on opposite sides of the Pacific Ocean by compiling the numbers of radiometric dates reported for terrestrial volcanic sequences and the number of volcanic ash horizons recorded in Neogene deep-sea (DSDP) sedimentary sections.
TL;DR: In this paper, the ages determined for the polarity-interval boundaries in this study confirm recent estimates derived from analyses of marine magnetic anomalies using sea-floor-spreading assumptions.
Abstract: More than 400 successive lavas in Borgarfjordur, western Iceland, have been subjected to paleomagnetic and K-Ar age analysis. Volcanism in the region was virtually continuous between about 7.0 and 2 m.y. ago, during which time more than 3,500 m of volcanics and interbedded sediments accumulated. Regression analysis of the K-Ar age and aggregate thickness data demonstrates that the rate of growth of the lava pile was remarkably uniform at 730 m/m.y. throughout the whole period. The magnetostratigraphic and K-Ar data indicate a nearly complete record of the geomagnetic polarity history and extend the polarity time scale based upon data from subaerial volcanic rocks to about 6.5 m.y. ago. The boundaries of polarity epoch 5 are shown to be 5.34 and 5.83 m.y. Epoch 6 lies between about 6.54 and 5.83 m.y. ago, during which time three normal polarity events are recognized. The ages determined for the polarity-interval boundaries in this study confirm recent estimates derived from analyses of marine magnetic anomalies using sea-floor–spreading assumptions. The results show that it is possible to obtain reliable K-Ar ages on lavas that have undergone zeolite facies metamorphism at temperatures up to about 150°C by careful selection of samples that are well crystallized and have their original high-temperature mineralogy preserved. A revised estimate of 5.2 ± 0.1 m.y. is proposed for the age of the Miocene-Pliocene boundary.
TL;DR: In this article, carbon and oxygen isotopic determinations have been made of 29 species of Recent Indian Ocean planktonic foraminifera from 14 core-top samples and as many as 18 species were chosen from a single core top sample.
TL;DR: Initial settlement did not differ significantly among the experimental surfaces, but with time patterns in the distribution of these algal populations correlated with the surfaces beneath them, the season during which the substrata were introduced altered the patterns of development.
Abstract: Artificial substrata allow one to test a single factor in a complex environment. We wanted to determine whether surface particle size could regulate settlement and growth in marine macroalgae. Three grades of discrete monolayers of hard particles differing only in diameter (0.1 to 0.5 mm, 0.5 to 1.0 mm, 1.0 to 2.0 mm) were cemented to the surfaces of three quadrants on acrylic discs while the fourth was left smooth. All surfaces were painted with dissolved plastic to ensure chemical uniformity. At different times of the year, 25 plates were bolted directly to basement rock in the low intertidal zone on an exposed coast at the mouth of Narragansett Bay in Rhode Island (Fig. 1). Thirteen conspicuous species of macroalgae colonized the coated acrylic plates during the course of this investigation. Of these, the most abundant were Chondrus crispus, Corallina officinalis, Polysiphonia harveyi and Ulva lactuca, which were observed throughout the program. Initial settlement did not differ significantly among the experimental surfaces, but with time patterns in the distribution of these algal populations correlated with the surfaces beneath them. These differences were visually striking and not the same for each species. Most of the Chondrus crispus (79.5%) and U. lactuca (85.2%) appeared on the two largest particles, but only for C. crispus was the difference in populations within these grades significant (P<0.05). Populations were considerably smaller on the smallest grade (20.1 and 13.8% respectively), and on the smooth quadrants only a few individuals of these two species appeared (0.5 and 1.0%). The number of plants of P. harveyi, on the other hand, did not differ on the three particle sizes tested, but on the smooth surfaces only 2.9% appeared. Corallina officinalis showed optimal development on the smallest grade (44.8%). On smooth surfaces, where 8.4% of its population was observed, no upright articulated portions developed. The season during which the substrata were introduced altered the patterns of development. C. officinalis was the first macroalga to be seen in late spring, but on plates set out in the fall this species did not appear until the following late spring. P. harveyi covered some discs in fall, spring and summer, and on these surfaces Chondrus crispus was delayed up to 1 year. By the end of the experimental period (15 months), C. crispus was the most conspicuous macroalgal species on most of the plates.
TL;DR: Tri-octyl-amine-freon solutions can be used for the extraction of the acid from the solution if the concentration of the amine is carefully controlled.
Abstract: In preparing nucleotide extracts for HPLC analysis using microparticle, chemically bonded packings, tri-octyl-amine-freon solutions can be used for the extraction of the acid from the solution if the concentration of the amine is carefully controlled.
TL;DR: In this article, the anisotropy of magnetic susceptibility and mean particle size in the silt fraction have been measured in surface sediments and down selected cores from the Vema Channel.
TL;DR: The estimated denitrification rate in the study area suggests that pelagic sediments may be important sites of marineDenitrification, and nitrate concentrations and concentration gradients reflect zones of oxygen reduction, nitrate reduction, and sulfate reduction in the sediments.
Abstract: Pore-water nitrate concentrations in six pelagic eastern equatorial Atlantic cores increase from bottom water values (22 micromolar) to 40 micromolar at a depth of about 5 centimeters, then decrease to undetectable levels at depths as shallow as 40 centimeters. These nitrate concentrations and concentration gradients reflect zones of oxygen reduction, nitrate reduction, and sulfate reduction in the sediments. The estimated benthic flux of nitrate to the ocean from our data is much less than the total globalflux of nitrate to deep waters, even though these equatorial sediments underlie a productive upwelling zone. The estimated denitrification rate in our study area suggests that pelagic sediments may be important sites of marine denitrification.
TL;DR: In this article, the results of the first direct measurements of manganese in seawater near mid-ocean ridges, or in hydrothermal fluids emanating from these ridges were reported.
Abstract: HYDROTHERMAL emanations originating at mid-ocean ridges have been thought1–5 to provide a substantial source of manganese to the ocean but the evidence supporting this hypothesis has been indirect. Anomalous manganese concentrations have been measured in naturally occurring systems where seawater is in direct contact with lava flows6–8. Laboratory studies have shown that seawater tends to leach manganese from basalts at elevated temperatures and pressures9–11. Anomalously high manganese accumulation rates have also been determined for sediments adjacent to active ridge systems, most notably the East Pacific Rise12–14. No measurements of manganese concentrations in seawater near mid-ocean ridges, or in hydrothermal fluids emanating from these ridges, have yet been made, however. We report here the results of the first such direct measurements, which show that manganese is being injected into the deep sea by hydrothermal circulation of seawater through newly-formed oceanic crust.
TL;DR: Inverted echo Sounders (IES) were deployed at seven ocean bottom stations to acoustically monitor depth variations of the main thermocline as discussed by the authors, and the IES performs as a natural matched filter for the most fundamental internal displacement mode.
Abstract: Inverted Echo Sounders (IES) were deployed during MODE at seven ocean bottom stations to acoustically monitor depth variations of the main thermocline. The IES transmits pulses of 10 kHZ sound and records the time τ for the echo to return from the ocean surface; τ varies by a few milliseconds in response to vertical displacements of the temperature and salinity profiles in the water column. The acoustic travel time is inherently an integral measurement, which is insensitive to finestructure in the vertical but is dominantly influenced by vertical displacements which are coherent throughout the water column. Thus the IES performs as a natural “matched filter” for the most fundamental internal displacement mode. A perturbation analysis on the dynamic height (D), the total heat content (Q) and the acoustic travel time (τ) integrals shows that all three are dominated by displacements of the main thermocline. The proportionality is unique when a single mode of internal displacements is dominant. Compa...
TL;DR: IAA treatment of +B plants increased IAA oxidase activity of apical and subapical root sections and also inhibited root elongation and caused symptoms similar to -B treatments, demonstrating the earliest enzymic change for intact boron-deficient plants.
Abstract: The indoleacetic acid (IAA) oxidase activity of root tips of boron-sufficient, -deficient, recovering, and IAA-treated boron-sufficient squash plants (Cucurbita pepo L.) was determined. Apical and subapical root sections displayed an increase in IAA oxidase activity between 6 and 9 hours after boron was withheld, and after 24 hours the activity of the apical sections showed a 20-fold increase over +B controls. Root elongation of -B plants was inhibited before an increase in oxidase activity could be detected. Roots of plants subjected to 12 hours of -B treatment and then transferred to +B treatment for recovery regained normal elongation rates and oxidase activity within 18 to 20 hours. IAA treatment of +B plants increased IAA oxidase activity of apical and subapical root sections and also inhibited root elongation and caused symptoms similar to -B treatments.These results have demonstrated the earliest enzymic change for intact boron-deficient plants. The results are in agreement with the theory that boron deficiency symptoms may be the result of supraoptimal endogenous levels of IAA. These high levels of IAA may inhibit cell division and lead to an induction of the IAA oxidase enzyme.
TL;DR: The FAMOUS area lies in a geochemical transition zone between the Azores Plateau and normal ridge areas south of lat 33°N, and the LIL (large-ion-lithophile) and Sr-isotope geochemistry of FAMOUS basalts is thus influenced by the azores mantle plume.
Abstract: Ten basalt samples recovered from the FAMOUS area were selected so as to obtain representatives of a wide geographical and compositional range. The samples were analyzed for 87Sr/86Sr, K, Rb, Cs, Sr, Ba, and rare-earths. Sr-isotope ratios fall in the narrow range of 0.70288 to 0.70307, which implies that these samples were derived from an isotopically homogeneous source. The FAMOUS area lies in a geochemical transition zone between the Azores Plateau and “normal” ridge areas south of lat 33°N. The LIL (large-ion-lithophile) and Sr-isotope geochemistry of FAMOUS basalts is thus influenced by the Azores mantle plume; this results in higher Sr-isotope and LIL concentrations in these basalts than is typical of Mid-Atlantic Ridge basalts. Trace-element distributions in FAMOUS area basalts cannot be entirely accounted for by fractional crystallization models that are based on major-element chemistry. The LIL distribution in FAMOUS basalts could be due to variable extents of partial melting. Zonation within the magma chamber may result from incomplete mixing of successive batches of magma entering the chamber and could be further enhanced by fractional crystallization. The variation in partial melting would require significant increases in mantle temperature over a relatively short period of time. According to this model, the Mount Pluto magma represents the highest degree of partial melting and may mark the initiation of a new cycle of eruptive activity in the median valley.
TL;DR: Respiration and excretion rates were measured for a variety of sizes of Mnemiopsis leidyi over a temperature range of 10.3° to 24.5°C, and values are comparable to rates observed for small, active zooplankton.
Abstract: Respiration (dissolved oxygen and carbon dioxide) and excretion (dissolved organic carbon, inorganic and organic nitrogen and phosphorus) rates were measured for a variety of sizes of Mnemiopsis leidyi over a temperature range of 10.3° to 24.5°C. Both respiration and excretion rates were a direct linear function of animal weight and very temperature sensitive (Q10≊4). Oxygen uptake ranged from 155 to 489 μg at O/(g dry weight) day-1 and carbon dioxide release from 43 to 166 μM. Organic carbon made up about 38% of the total carbon released. Inorganic nitrogen excretion, exclusively in the form of ammonium, comprised 54% of the total nitrogen release and ranged from 10 to 36 μM NH4/(g dry weight) day-1. Average release of dissolved primary amines (expressed as glycine equivalents) equaled 43% of the organic nitrogen fraction. Inorganic phosphorus release ranged from 2.0 to 4.9 μM/(g dry weight) day-1 and made up about 72% of the total phosphorus loss. The turnover of elements in the body was calculated as 5 to 19% per day for carbon and nitrogen, depending on the temperature, and an even higher 20 to 48% per day for phosphorus. These values are comparable to rates observed for small, active zooplankton.
TL;DR: In general, nonneoplastic lesions, such as epithelial hyperplasia and accumulations of a orange-brown bodies, were more common in clams from polluted areas, but malignant neoplasms, based on their characteristic anaplastic appearance, invasiveness, metastasis, mitotic activity, associated tissue necrosis, and mortality, were less common.
Abstract: Neoplasia was a prevalent disease of the soft-shell clam and was found in widely geographically distinct sites in New England. Two types of neoplasms were recognized. Most were of hematopoietic origin, except in clams from Maine, which also had gonadal neoplasms. Both types were apparently malignant neoplasms, based on their characteristic anaplastic appearance, invasiveness, metastasis, mitotic activity, associated tissue necrosis, and mortality. Diagnosis of neoplasia in the living mollusk was achieved rapidly and accurately by cytologic examination of circulating blood. The etiology of the neoplasms was not identified. In general, nonneoplastic lesions, such as epithelial hyperplasia and accumulations of a orange-brown bodies, were more common in clams from polluted areas.
TL;DR: Gels arise from perforation plates, end-walls and pit membranes by a process of distension of primary wall and middle lamella constituents and represents one factor in the response of plants that provides for resistance to vascular infections.
Abstract: Vascular gels that coat the walk and fill the lumina of infected vessels were found in nine species of plants that had been inoculated with non-host-specific forms of Verticillium dahliae Kleb, or with Fusarium oxysporum Snyd. & Hans. Gel formation is therefore a general phenomenon and represents one factor in the response of plants that provides for resistance to vascular infections. Gels arise from perforation plates, end-walls and pit membranes by a process of distension of primary wall and middle lamella constituents. Swelling of these pre-formed constituents can account for complete occlusion of vessel lumina. A protective wall layer located between the plasmalemma and the pit membranes was observed in parenchyma cells that lined the perimeter of infected vessels in several species of plants.
TL;DR: Based on 16 cores (5 dated) from the crest and flanks of the East Pacific Rise and the Bauer Deep, the authors estimate that phosphorus is being deposited about 20 times faster in metalliferous sediments near the rise crest than in adjacent flank deposits, and about 40 times faster on the crest than on the Bauer deep.
TL;DR: By providing contingencies for the products of a child's classroom activities, rather than for being on task, the child will become more independent of the teacher's presence, and more under the control of the academic materials.
Abstract: Eight fifth- and sixth-grade children with behavior problems performed in a classroom under three conditions: (1) unreinforced baseline, (2) reinforcement for being on task, and (3) reinforcement for the accuracy and rate of math problems solved. The teacher was absent for a portion of the class session under each of these conditions. In the teacher's absence, on-task behavior declined markedly and disruption markedly increased, regardless of the reinforcement condition in operation. In addition, the teacher's absence resulted in fewer problems attempted and decreased accuracy. However, the extent to which the children became disruptive was reduced and the number of problems attempted increased when reinforcement was contingent on academic accuracy and rate, instead of being contingent on being on task. The results suggest that by providing contingencies for the products of a child's classroom activities, rather than for being on task, the child will become more independent of the teacher's presence, and more under the control of the academic materials.
TL;DR: The spin-Peierls transition is an unusual kind of magnetoelastic transition occurring (at least in in its simplest form) in a very limited number of quasi-one-dimensional insulating systems.
Abstract: The spin-Peierls transition is an unusual kind of magnetoelastic transition occurring (at least in in its simplest form) in a very limited number of quasi-one-dimensional insulating systems. It was predicted theoretically almost two decades ago, in the general context of physical chemistry and the properties of certain organic free radicals in particular. The first clear-cut experimental realization was not discovered until 1975.1,2 The discovery was made in the wake of a high level of interest which developed among physicists in the properties of quasi-one-dimensional organic conductors (organic metals), of which (tetrathiafulvalene)(7,7,8,8-tetracyano-p-quinodimethane), (TTF)(TCNQ), remains the best-known example. Typical programs proceeded by synthesis followed by conductivity measurements, and low-conductivity samples were routinely discarded. The program followed at General Electric involved combining organic donors (e.g., TTF) with metallo-organic planar acceptors called metal bisdithiolene (BDT) complexes, MBDT, where M is a metal atom, such as Cu, Au, or Pt. In the case of (TTF)(CuBDT), the system was found to be an excellent insulator; however, magnetization studies suggested low-dimensional behavior (quasi-one-dimensional behavior) with curious properties.
TL;DR: Foraminiferal cores from the Vema Channel and lower flanks of the Rio Grande Rise suggest the presence of episodic flow of deep and bottom water during the Late Pleistocene as discussed by the authors.