Coarse Component Research Articles

Continental slope sedimentation adjacent to an ice margin. III. The upper Labrador Slope

The upper Labrador Slope is the key area for sediment transfer from the northeastern margin of the Pleistocene Laurentide ice sheets (LIS) to the deep basin. It is subdivided from north to south into 8 sectors based on relief differences and echo-character on 750 line-km of continuous sleeve-gun and 3.5 kHz seismic profiles. High- to moderate-relief sectors 2 and 4 and, in part, 6 and 8 are seismically transparent and well stratified with continuous individual high-amplitude reflections and deep penetration; low-relief sectors 1, 3, 5 and 7 show strong bottom reflections and, with the exception of sector 1, low seismic penetration, poor stratification, and low-amplitude, if any, subbottom reflections. The lateral distribution of these alternating high- to moderate- and low-relief sectors reflects fundamental differences in the sediment transfer mechanisms through outlets from the LIS onto the slope. Low-relief slope sectors represent debrite and turbidite slopes and are located in front of ice-outlets on the slope and adjacent regions to the north. They originate from mass wasting on the upper slope of glacial detritus with a significant coarse component originally delivered as englacial or subglacial material and deposited in (end-) moraines or as bedload by subglacial or supraglacial rivers. High- to moderate-relief sectors originate from fall-out of suspended sediment from turbid surface-plumes (TSP) and preferentially occur off the southern half of outlets and south of major outlets, as exemplified by sector 2 south of the Hudson Strait outlet. This asymmetry is caused by the south-flowing Labrador Current, which entrains the buoyantly rising turbid meltwater-plumes at the glacier front. The present high-relief topography, which shows a dendritic pattern of upslope canyon branching, is the result of retrograde, headward canyon erosion by mass-wasting processes of an originally much smoother mud-blanket surface. The sediment is remobilized by slumping and entrained in debris flows and turbidity currents. The occurrence of TSP deposits on the high- to moderate-relief upper-slope sectors requires a summer sea surface not frozen over during major parts of the Pleistocene, including glacial maxima. TPS deposition on the upper slope, ice-rafting, and a plethora of ice-margin depositional phenomena, many of which give rise to mass-wasting and mass-flow phenomena, are the main features that make high-latitude continental slopes adjacent to continental ice-sheets different from their lower-latitude counterparts.

Mobilization of Iron from Coal Fly Ash Was Dependent upon the Particle Size and the Source of Coal

Particulate air pollution, including coal fly ash, contains iron, and some of the pathological effects after inhalation may be due to reactive oxygen species produced by iron-catalyzed reactions. The objective of this study was to determine whether iron, present in coal fly ash, was mobilized, leading to ferritin induction in human airway epithelial cells, and whether the size of the particles affected the amount of iron mobilized. Three types of coal were used to generate the three size fractions of fly ash collected. The Utah coal fly ash was generated from a bituminous b coal, the Illinois coal fly ash from a bituminous c coal, and the North Dakota coal fly ash from a lignite a coal. Three size fractions were studied to compare the amount of iron mobilized in human airway epithelial (A549) cells and by citrate in cell-free suspensions. The size fractions selected were fine (<2.5 microm) and coarse (2.5-10 microm) components of PM10, airborne particulate matter <10 microm in diameter, and the fraction greater than 10 microm. Coal fly ash samples were incubated with 1 mM citrate to determine if iron associated with coal fly ash could be mobilized. Iron was mobilized by citrate from all three size fractions of all three coal types to levels as high as 56.7 nmol of Fe/mg of coal fly ash after 24 h. With all three coal types, more iron was mobilized by citrate from the <2.5 microm fraction than from the >2.5 microm fractions. Further, the mobilized iron was in the Fe(III) form. To determine if iron associated with the coal fly ash could be mobilized by A549 cells, cells were treated with coal fly ash, and the amount of the iron storage protein ferritin was determined after 24 h. Ferritin levels were increased by as much as 11.9-fold in cells treated with coal fly ash. With two of the three types of coal studied, more ferritin was induced in cells treated with the <2.5 microm fraction than with the >2.5 microm fractions. Further, inhibition of the endocytosis of the coal fly ash by the cells resulted in ferritin levels that were near that of the untreated cells, suggesting that iron was mobilized intracellularly, not in the culture medium. The results of this study suggest that differences in particle size and speciation of iron may affect the release of iron in human airway epithelial cells.

Latest Pleistocene ice‐rafting events on the Scotian Margin (eastern Canada) and their relationship to Heinrich events

Piston cores from the continental margin off Nova Scotia show up to four discrete intervals of “brick‐red sandy mud,” which are up to 20 cm thick. The ages of these intervals are bracketed by several radiocarbon dates, and three fall in the range 12.5–14.1 ka (radiocarbon years with −0.4 kyr reservoir correction). The youngest dates from ∼10.4 ka, placing it within the Younger Dryas. The distribution of the beds and their petrographic character indicate a source in the Gulf of Saint Lawrence. The grain size of these beds suggests that they comprise a coarse component transported by ice rafting that diminishes distally and a fine component that represents suspension fallout from a surface plume and resulting nepheloid layers. Graded brick‐red beds in some cores were probably redeposited from turbidity currents. The lowermost bed on the Laurentian Fan and East Scotian Rise is immediately overlain by a carbonate‐rich interval that can be identified all around the margin of the Grand Banks. This interval is correlated with detrital carbonate bed DC‐1 in the Labrador Sea and Heinrich event H1 in the North Atlantic. The sequential occurrence of the two beds suggests that they may be a response to the same trigger, probably sea level rise, but that the Gulf of Saint Lawrence source was more easily destabilized.

Fine Particles and Coarse Particles: Concentration Relationships Relevant to Epidemiologic Studies

Fine particles and coarse particles are defined in terms of the modal structure of particle size distributions typically observed in the atmosphere. Differences between the various mdes are discussed. The fractions of fine and coarse particles collected in specific size ranges, such as total suspended particulate matter (TSP), PM10, PM2.5, and PM(10-2.5), are shown. Correlations of 24-h concentrations of PM2.5, PM10, and PM(10-2.5) at the same site show that, in Philadelphia and St. Louis, PM2.5 is highly correlated with PM10 but poorly correlated with PM(10-2.5). Among sites distributed across these urban areas, the site–to–site correlations of 24– PM concentrations are high for PM2.5 but not for PM(10–2.5). This indicates that a PM measurement at a central monitor can serve as a better indicator of the community–wide concentration of fine particles than of coarse particles. The fraction of ambient outdoor particles found suspended indoors is greater for fine particles than for coarse particles because of the difference in indoor lifetimes. Consideration of these relationships leads to the hypothesis that the statistical associations found between daily PM indicators and health outcomes may be the result of variations in the fine particle component of the atmospheric aerosol, not of variations in the coarse component. As a result, epidemiologic studies using PM10 or TSP may provide more useful information on the acute health effects of fine particles than coarse particles. Fine and coarse particles are separate classes of pollutants and should be measured separately in research and epidemiologic studies. PM2.5 and PM(10–2.5) are indicators or surrogates, but not measurements, of fine and coarse particles.

Simultaneous presence of orbital inclination and eccentricity in proxy climate records from Ocean Drilling Program Site 806

Ocean Drilling Program Site 806 in the western Pacific shows evidence of a remarkably constant average sedimentation rate. This feature allows us to analyze ancient climate proxies without the need for “orbital tuning,” a standard procedure in prior work, but one that can lead to biased results. Spectral analysis of stable oxygen isotope ratios at this site, a proxy for global ice volume, shows a single narrow peak with a period ≈ 100 k.y., a result that supports our model which links glacial cycles to variations in the inclination of the Earth's orbit. In contrast, spectral analysis of the coarse component fraction of the sediment (primarily foraminifera) shows a structure characteristic of standard Milankovitch theory, with a triplet of peaks with periods near those expected from the Earth's eccentricity: 95, 125, and 400 k.y. Bispectral analysis confirms these linkages but suggests that orbital inclination also plays some role in the coarse fraction. From the clear presence of both signals in different proxies at the same site, we conclude that although eccentricity affected the local climate, it is orbital inclination that drove the variations in the global ice volume for the past million years.

Multigrid convergence for convection-diffusion problems on composite grids

We study the convergence behavior of the FAC (fast adaptive composite) multigrid method as applied to the solution of convection-diffusion equations discretized on composite grids in one and two dimensions. Analysis of the one-dimensional problem leads to the interpretation of two-level FAC as a direct solver. This analysis also provides important insight into the behavior of the method for the two-dimensional problem that has its flow velocity oriented in a single coordinate direction. For the latter problem we consider the use of standard upwind differencing on the coarse component of the grid, and allow the discretization type to vary on the fine component. When centered differencing is used on this fine region, we show that the behavior is very similar to that predicted by the analysis in one dimension. With a higher-order upwinding scheme used on this component, we show how to modify the discretization at the coarse-grid level in order to preserve the attractive convergence behavior predicted by the analysis.

Thermodynamische Berechnung der Phasengleichgewichte für Schnellarbeitsstähle

This paper reports Thermo-Calc computations of phase equilibria in the six-component system Fe-Cr-Mo-W-V-C which provide a quantitative understanding of the microstructures of three important high speed steels, AISI T1, M2 and M7. Compositions and volume fractions of the phases in equilibrium during austenitization are reproduced with good accuracy, and so are the temperatures of the liquidus line and the peritectic reaction. The influence of the individual alloying elements such as Mo, W, V and C is presented. Since the volume fractions and compositions of the matrix and of the blocky carbides MC and MaC do not change during quenching and tempering, the Thermo-Calc computations provide exact predictions of all the coarse components of the microstrncture, allowing computertailoring of microstructures

Multiresolution wavelet analysis of evoked potentials.

Neurological injury, such as from cerebral hypoxia, appears to cause complex changes in the shape of evoked potential (EP) signals. To characterize such changes we analyze EP signals with the aid of scaling functions called wavelets. In particular, we consider multiresolution wavelets that are a family of orthonormal functions. In the time domain, the multiresolution wavelets analyze EP signals at coarse or successively greater levels of temporal detail. In the frequency domain, the multiresolution wavelets resolve the EP signal into independent spectral bands. In an experimental demonstration of the method, somatosensory EP signals recorded during cerebral hypoxia in anesthetized cats are analyzed. Results obtained by multiresolution wavelet analysis are compared with conventional time-domain analysis and Fourier series expansions of the same signals. Multiresolution wavelet analysis appears to be a different, sensitive way to analyze EP signal features and to follow the EP signal trends in neurologic injury. Two characteristics appear to be of diagnostic value: the detail component of the MRW displays an early and a more rapid decline in response to hypoxic injury while the coarse component displays an earlier recovery upon reoxygenation.

The nature and origin of nodules in Podzolic soils from Alberta

A common pedological feature in Podzols and Podzolic-like soils in the forest region of Hinton, Alberta is the presence of nodules in the Bf horizons with diameters of 1—20 cm. The nature of these nodules was investigated through physical, chemical, mineralogical and micromorphological examinations. Results showed that the nodule microstructure is mainly bridged-grain type compared to dominantly pellicular type for the soil matrixes. The basic building blocks are (a) coarse components (&gt; 5 μm): quartz, feldspars mainly albite, pseudo sands, sand-sized chlorites and small quantities of anthophyllite, sillimanite, andalusite and lithogenic hematite; (b) fine components (&lt; μm): phyllosilicates (mainly hydroxy interlayered vermiculite, kaolinite, vermiculite, and small amounts of chlorite), quartz and organic matter. Imogolite is present in the very fine clays. The similarity in the mineral suites and the porphyric related distribution pattern between the Bf horizons and the nodules indicate an authigenic origin for the nodules through an eluviation/illuviation process. Fungal hyphae provide a framework for nodule aggregation. In situ XRD determinations revealed that sand-sized Fe concretions are goethite alone or in association with hematite. The omnipresence of quartz in infillings, coatings and opaque coarse components was also evident. Key words: Micromorphology, related distribution pattern, in situ mineral determination

Generation of Sedimentary Fabrics and Facies by Repetitive Excavation and Storm Infilling of Burrow Networks, Holocene of South Florida and Caicos Platform, B.W.I.

Excavation of deep, open burrow networks and subsequent infilling with sediment from the surface produces an entirely new sedimentary deposit and results in obliteration to severe diagenetic transformation of precursor depositional facies. Repetitive excavation and infilling is responsible for creating the preserved depositional facies of many marine deposits. Excavating burrowers occur from intertidal to abyssal depths, and are important throughout the Phanerozoic. The repetitive coupling of deep, open burrow excavation with subsequent storm sediment infilling of open burrow networks is a gradual process that ultimately results in the loss of the original deposit and the generation of new lithologies, fabrics and facies. The new lithologies are produced in the subsurface and possess fabrics, textures and skeletal assemblages that are not a direct reflection of either precursor facies or the surficial depositional conditions. Sedimentary facies generated by repetitive burrow excavation and infilling commonly are massively bedded and generally are mottled skeletal packstones. Skeletal grains usually are well-preserved and coarser components are concentrated in burrow networks, pockets and patches. The coarse skeletal components of burrow-generated facies are a mixture of coarse bioclasts from the precursor facies and both the coarse and fine skeletal material introduced from the sediment surface. Many so-called bioturbatedmore » or massive facies may, in fact, be primary depositional facies generated in the subsurface and represent severe diagenetic transformation of originally deposited sequences. In addition, mudstones and wackestones mottled with packstone patches may record storm sedimentation.« less

Automated thin-film analyses of anhydrous interplanetary dust particles in the analytical electron microscope

An analytical electron microscope (AEM) equipped with digital beam control was used to obtain quantitative point count analyses from thin-sections of eight anhydrous chondritic interplanetary dust particles (IDPs). The electron beam was rastered on a two-dimensional grid over each thin-section. A preset video threshold was used to locate chondritic material. Between 200 and 500 X-ray analyses were collected from each thin-section with a total of 2804 spectra from the eight IDPs. Each spectrum was analyzed for Mg, Al, Si, S, Ca, Cr, Mn, Fe, and Ni using a Cliff-Lorimer thin-film correction procedure. Cluster analysis was used to identify major and minor mineral phases and their relative abundances. Petrographic features of each thin-section were determined from brightfield and darkfield images. Two types of anhydrous chondritic aggregates were observed in the eight IDPs. One was highly porous with an average grain size < 10 2 nm and the other was less porous with grains between 10 2 and 10 3 nm. Most IDPs were dominated either by the fine- or coarse-grained aggregates and there was a tendency towards enstatite enrichment in the fine, and olivine enrichment in the coarse components. One IDP contained both fine- and coarse-grained aggregates. Pyroxene and olivine in the fine-grained aggregates usually contain < 5 mole % Fe while those in the coarse aggregates contain up to 30 mole % Fe. The eight anhydrous IDPs are mixtures of fine- and coarse-grained aggregates, large ( > 10 3 nm) mineral grains, glass, and carbonaceous material. On a scale of less than a micrometer, elemental concentrations follow those of solar abundances, suggesting that they are chemically pristine and unperturbed by aqueous alteration. Using an automated AEM and cluster analysis we are able to rapidly characterise IDP thin-sections. It now appears possible to develop an IDP classification scheme based on AEM data.

Resolution of ionic components of late winter arctic aerosols

A total of 69 size fractionated aerosol samples was taken day and night, 16 March–6 May 1986, in Barrow, Alaska, during the AGASP-II project in order to identify components of the Arctic haze and their likely sources. Samples were taken sequentially, 12 ionic species in the samples were measured, and multivariate principal component analysis was used to resolve different components. The samples were analyzed by ion chromatography for SO 2− 4, Cl −, Br −, NO − 3, methanesulfonate, formate, acetate, propionate, pyruvate, K +, Na + and NH + 4. The temporal variabilities in measured concentrations were fit to a linear physical mixing model by principal component analysis of the data. Coarse and fine aerosol components exhibited both similarities and differences. Most of the coarse concentration variability is described by three components that explain 80% of total variance in the data set: sea salt contaminated with non-sea salt (nss) SO 2− 4 and nss K +, a carboxylic acid anion component and a component containing most of Br − 3, NO 3 − and methanesulfonate. Ion balances between cations and anions in all three components are close to neutrality, consistent with these components being internally mixed aerosols. The large amounts of nss K + in the first coarse component suggest a combustion origin at lower latitudes. The second component consists of carboxylic acid anions and some sea salt, and may represent reaction between the acids and sea salt. The third component of Br −, NO − 3 and methanesulfonate could be the product of gas phase reactions of marine organic compounds. Some independent aerosol occurrences, consisting of seven coarse samples of highest acetate and sea salt concentrations, is identified by the combination of linear regression and absolute principal component analysis (APCA) and does not belong to the communality of the rest of the data. In the fine fraction four components explain 86% of total variance in the data set, with compositions that differ somewhat from their coarse fraction counterparts. The first component is mainly a mixture of carboxylic acid anions with additional NH + 4 and Na +, which resembles the second coarse component in composition. The second is a contaminated sea salt component similar in composition to the contaminated sea salt in the coarse fraction. However, it contains smaller amounts of nss SO 2− 4 and is not as deficient in Cl −. The third component is defined and contains most of the Br −, NO − 3 and methanesulfonate, and has a similar composition to the third coarse component. The fourth component is mainly nss SO 2− 4 plus significant amounts of NO − 3 and NH + 4.

Thin surface soil layers attributable to rain‐flow transportation on low‐angle slopes: An example from semi‐arid tropical Queensland, Australia

AbstractParticle‐size analyses have been made on surface soils and a thin, overlying sandy pavement at 16 sites along a gently sloping transect at Torrens Creek in North Queensland. The transect is 1590 m long and has a maximum gradient of 0.018 (less than 1°). The sandy pavement is enriched in coarse components due to the sorting and differential downslope transport of the finer soil fractions. Particle movement is ascribed to the action of raindrops impacting very shallow, flowing water. The process, referred to as ‘rain‐flow transportation’, is active wherever overland flow is too weak to generate rills and channels and occurs in areas of very low slope with permeable surface soils that allow rapid infiltration during storms. Rain‐flow transportation is discussed with particular reference to the development of soil profiles in an old, subdued landscape of semi‐arid tropical Australia.

Discharge composition and concentration profiles in a continuously operating spouted bed

AbstractThe cause of segregation at the discharge in a continuously operating spouted bed has been investigated. Radial concentration profiles of the coarse component have been detected in a two‐component mixture of glass ballotini at different spouting regimes, at different bed levels and discharging from openings at several bed depths. The annulus of a spouted bed has been shown to move in a fashion close to a plug flow without altering the concentration gradients existing below the bed free surface. Consistent with previous results, percolation induced segregation was negligible under these experimental conditions. The concentration existing at the column wall has been shown to be identical to that in the outgoing stream of solids and segregation phenomena at the outlet cannot explain a discharge composition different from the mean concentration in the bed. The particle trajectories in the fountain are believed to be responsible for the radial concentration gradient in the annulus of the spouted bed.

Distribution of some trace metals and their fluxes in the Genesee River, NY

Total and particulate metal concentrations, measured during intensive synoptic studies of the Genesee River, NY, correlated with suspended-sediment concentration and river discharge. Dissolved metal concentrations, on the other hand, showed little systematic variation over the length of the river. Metal and sediment fluxes for two elevated-discharged periods peaked at a midbasin sampling site. For most metals at most sampling sties particulate materials comprised over one-half of the total material. Comparison of particulate material metal concentrations, normalized to the measured suspended-sediment concentrations had with basinwide average values shows that sites having low suspended-sediment concentrations had high particulate material metal contents relative to the basin averages, while sites with high suspended-sediment concentration had low metal contents. These results are consistent with a metal transport mechanism in the Genesee River involving (1) a nearly constant dissolved component, (2) a fine acid-soluble component, and (3) a coarse component that is effectively a neutral diluent in the sediment. Chemical factors, such as sediment organic content, also appear to affect metal transport in the Genesee River.

Mining and preparation of aggregates for concrete at the construction site of the Inguri hydroelectric station

1. The use of the dredge complex under conditions of heavy, dense boulder-filled saturated gravel-sand deposits is a reliable, efficient, and rational means for obtaining concrete aggregates at large construction projects. 2. The elimination on the dredge of the coarse component — boulders and gravel larger than 120 mm — and the separation of the useful mass into the 5–120 mm fraction and sand of the 0.10–5.0 mm fraction thereafter greatly facilitates the entire process of preparing the aggregates and in many respects simplifies their transportation, processing, and concentration; however, the loss of the coarse component reduces the effectiveness of using the dredge complex. 3. The creation of reserve stockpiles of sand and gravel, which makes the operation of both the dredge complex and the sand classification and gravel grading plant independent, is the most technologically efficient solution. In this case the effectiveness of using the equipment is increased considerably. 4. Preliminary thickening of the slurry being fed to the sand classifier reduces the number of classifiers and improved the quality of classification.

Density regulation by choice of fractions in vibratory shaping

It has been established by experiment that for fine powders of angular particle shape maximum density in two-fraction mixtures is attained at a coarse component content of 60% (the density is the higher, the larger the ratio between the particle sizes of the coarse and fine fractions). The density of such a mixture may exceed the densities of the starting fractions by 26–37%. A simple method of calculation has been developed enabling the densities of mixtures with different combinations of starting fraction contents to be determined from the optimum densities of the fractions and from the result of a single control experiment. The same method can be employed for calculating two probable ratios between the amounts of starting components at which any given mixture density will be attained. Experiments have shown that a three-component system has a dome-shaped density diagram with a maximum density of more than 80% of theoretical; any given density (lower than maximum) can be obtained at various combinations of starting fraction contents, but the lower this density, the larger is the number of possible composition combinations.

Coarse Components in Surface Sediments of the Panama Basin, Eastern Equatorial Pacific

The abundance and distribution of biogenic, terrigenous, and volcanic particles in the Panama Basin are markedly dependent on bottom topography and dissolution of calcite in the deeper parts of the basin. Of the coarse fraction (> 62µ), foraminiferal tests and acidic volcanic glass shards are concentrated on the Cocos and Carnegie Ridges as lag deposits. Foraminiferal fragments found on these ridge flanks and on the Malpelo Ridge are caused by the winnowing of bottom currents and by dissolution of calcite with increasing depth. The hydrodynamically light radiolarian skeletons are concentrated by bottom currents in the basin adjacent to the ridges. The foraminiferal calcite compensation depth in the basin is 3,400 m. This relatively shallow depth is probably a consequence of the high biologic productivity in the cold, nutrient-rich surface waters over the basin. The pattern of productivity, however, is not reflected in the pattern of biogenic sediments. Acidic volcanic glass appears to have been carried into the basin from Costa Rica, Colombia, and Ecuador by easterly winds at altitudes of 1,500-6,000 m. Basaltic shards from the Galapagos Islands have been dispersed only over short distances to the west. Terrigenous sand-sized material is found on the edge of the continental shelf, where associated glauconite points to a relict origin, and along the northern Cocos Ridge, where contour currents may act as the dispersal mechanism.

Some effects of vibration upon powder segregation during die filling

The mechanism of segregation during die filling with a 10–35 mesh lead mixture using a vibrating die is one of filtration of fines down through the moving powder mass. This mechanism is modified by other mechanisms which occur in the powder as a result of the vibratory conditions. The vibration conditions used varied between 0–0.6 inches amplitude and 1–100 c.p.s. frequency. At low amplitude and frequency the powder mass is quiescent. At high amplitude, the powder bounces in the die. At intermediate amplitudes over the frequency range 1–100 c.p.s., a marked churning of the powder mass occurs. During conditions of churning, radial segregation is reduced (i.e., more fines locate in the bottom of the die cavity). Less vertical segregation is observed when churning is absent. The results indicate that in the bottom zone of the die, for conditions of churning, increasing the time of vibration tends to allow some mixing to occur which causes a moderate reduction in the vertical segregation. In the case of the fine (80–325) mesh system, there is an apparent anomaly in the vertical segregation observed, in that the coarse component tends to locate in the bottom zone of the die during vibratory die filling.

Precision analog to digital converter with coarse components

The application of automatic correction to the null-detector zero-level and to the linearly-varying voltage slope in electronic scanning analog to digital voltage converters reduces their error to hundredths of one percent with less stringent requirements for all the constituent components of the device and a very small complication of the circuit.