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1

The origin and distribution of HAPs elements in relation to maceral composition of the A1 lignite bed (Paleocene, Calvert Bluff Formation, Wilcox Group), Calvert mine area, east-central Texas  

USGS Publications Warehouse

The origin and distribution of twelve potentially Hazardous Air Pollutants (HAPs; As, Be, Cd, Cr, Co, Hg, Mn, Ni, Pb Sb, Se, and U) identified in the 1990 Clean Air Act Amendments were examined in relation to the maceral composition of the A1 bed (Paleocene, Calvert Bluff Formation, Wilcox Group) of the Calvert mine in east-central Texas. The 3.2 m-thick A1 bed was divided into nine incremental channel samples (7 lignite samples and 2 shaley coal samples) on the basis of megascopic characteristics. Results indicate that As, Cd, Cr, Ni, Pb, Sb, and U are strongly correlated with ash yield and are enriched in the shaley coal samples. We infer that these elements are associated with inorganic constituents in the coal bed and may be derived from a penecontemporaneous stream channel located several kilometers southeast of the mining block. Of the HAPs elements studied, Mn and Hg are the most poorly correlated to ash yield. We infer an organic association for Mn; Hg may be associated with pyrite. The rest of the trace elements (Be, Co, and Se) are weakly correlated with ash yield. Further analytical work is necessary to determine the mode of occurrence for these elements. Overall, concentrations of the HAPs elements are generally similar to or less than those reported in previous studies of lignites of the Wilcox Group, east-central region, Texas. Petrographic analysis indicates the following ranges in composition for the seven lignite samples: liptinites (5-8%), huminites (88-95%), and inertinites (trace amounts to 7%). Samples from the middle portion of the A1 bed contain abundant crypto-eugelinite compared to the rest of the samples; this relationship suggests that the degradation of plant material was an important process during the development of the peat mire. With the exception of Hg and Mn, relatively low levels of the HAPs elements studied are found in the samples containing abundant crypto-eugelinite. We infer that the peat-forming environment for this portion of the coal bed was very wet with minimal detrital input. Relatively high concentrations of crypto-humotelinite were found in samples from the top and base of the coal bed. The presence of abundant crypto-humotelinite in this part of the coal bed suggests the accumulation of wood-rich peat under conditions conducive to a high degree of tissue preservation in the peat mire. Although several of the trace elements (Be, Co, Ni, and Sb) exhibit enrichment in these samples, they are not necessarily chemically associated with humotelinite. We infer that these elements, with the exception of Be, are possibly associated with deposition of the roof and floor rock of the coal bed; however, further analytical work would be necessary to confirm this hypothesis. Beryllium may have an organic origin. ?? 1997 Elsevier Science B.V.

Crowley, S. S.; Warwick, P. D.; Ruppert, L. F.; Pontolillo, J.

1997-01-01

2

Slope evolution at the Calvert Cliffs, Maryland -- measuring the change from eroding bluffs to stable slopes  

USGS Publications Warehouse

Despite a long history of geomorphic studies, it is difficult to ascertain the time required for slopes to change from near vertical exposures to relatively stable slopes due to inadequate age control. Actively eroding coastal bluffs along the western shore of the Chesapeake Bay provide a key for understanding the centennial-scale development of stable slopes from eroding bluff faces. The Calvert Cliffs are composed of sandy silts, silty sands, and clayey silts of Miocene-age. Active wave erosion at the bluff toes encourages rapid sloughing from bluff faces and maintains slope angles of 70-80 degrees and relatively constant bluff-retreat rates. Naturally stabilized slopes are preserved as a fossil bluff line inland from a prograding cuspate foreland at Cove Point. The foreland is migrating southward at a rate of ca. 1.5 m/yr. As it moves south, it progressively protects bluffs from wave action as new beaches are deposited at their toes. Wave erosion is reinitiated at the northern end of the complex as the landform passes. An incremental record of slope change is preserved along the fossil bluff line. 14C dating of swales between beach ridges shows the complex to span 1700 years of progressive migration history. We hypothesized that slopes would change from steep, eroding faces to low-angle slopes covered with vegetation and sought to document the rate of change. Our team measured slope angles at intervals along the fossil bluff line and dated profiles by interpolating 14C ages of adjacent beach ridges. There was no progressive decrease in slope with age. All slopes along the fossil bluff line were 30-40 degrees with a mean of 35 degrees. Constancy in slope angle suggests that steep, actively eroding bluffs were quickly changed to stable slopes by landslides and slumping once they were protected. Given the accuracy of our age control, we conclude that the time required to attain a stable slope under natural processes is less than one century. This indicates that once toe erosion is ended (naturally or through engineering) slopes are reduced to 35-degrees over a period of decades and not centuries.

Herzog, Martha; Larsen, Curtis E.; McRae, Michele

2002-01-01

3

Coal geology of the Paleocene-Eocene Calvert Bluff Formation (Wilcox Group) and the Eocene Manning Formation (Jackson Group) in east-central Texas; field trip guidebook for the Society for Organic Petrology, Twelfth Annual Meeting, The Woodlands, Texas, August 30, 1995  

USGS Publications Warehouse

The Jackson and Wilcox Groups of eastern Texas (fig. 1) are the major lignite producing intervals in the Gulf Region. Within these groups, the major lignite-producing formations are the Paleocene-Eocene Calvert Bluff Formation (Wilcox) and the Eocene Manning Formation (Jackson). According to the Keystone Coal Industry Manual (Maclean Hunter Publishing Company, 1994), the Gulf Coast basin produces about 57 million short tons of lignite annually. The state of Texas ranks number 6 in coal production in the United States. Most of the lignite is used for electric power generation in mine-mouth power plant facilities. In recent years, particular interest has been given to lignite quality and the distribution and concentration of about a dozen trace elements that have been identified as potential hazardous air pollutants (HAPs) by the 1990 Clean Air Act Amendments. As pointed out by Oman and Finkelman (1994), Gulf Coast lignite deposits have elevated concentrations of many of the HAPs elements (Be, Cd, Co, Cr, Hg, Mn, Se, U) on a as-received gm/mmBtu basis when compared to other United States coal deposits used for fuel in thermo-electric power plants. Although regulations have not yet been established for acceptable emissions of the HAPs elements during coal burning, considerable research effort has been given to the characterization of these elements in coal feed stocks. The general purpose of the present field trip and of the accompanying collection of papers is to investigate how various aspects of east Texas lignite geology might collectively influence the quality of the lignite fuel. We hope that this collection of papers will help future researchers understand the complex, multifaceted interrelations of coal geology, petrology, palynology and coal quality, and that this introduction to the geology of the lignite deposits of east Texas might serve as a stimulus for new ideas to be applied to other coal basins in the U.S. and abroad.

edited by Warwick, Peter D.; Crowley, Sharon S.

1995-01-01

4

Frequency of effective wave activity and the recession of coastal bluffs: Calvert Cliffs, Maryland  

USGS Publications Warehouse

The Calvert Cliffs, Chesapeake Bay, Maryland, USA, erode by direct wave undercutting or by freeze/thaw erosion accompanied by wave removal of slope debris. Directly undercut slopes recede more rapidly, with long-term rates exceeding 1.0 m/yr; freeze/thaw slopes recede at rates approaching 0.5 m/yr. The frequency of wave height and water level at the shoreline is estimated for eleven sites based on a 37-year wind record, estimates of storm surge, offshore wave geometry, nearshore wave transformation, and breaking wave type. Locations experiencing the largest slope recession are not uniformly those with the largest cumulative wave energy; the resistance to erosion of the slope toe must also be accounted for. An index of relative wave strength is defined as the ratio of wave pressure T and the cohesive strength S of the slope material. For the Calvert Cliffs, a minimum relative wave strength for initiating erosion of intact material is 0.05 < T/S < 0.1. A cumulative duration of ???50 hours per year for T/S ??? 0.1 distinguishes undercut and nonundercut slopes and recession rates greater or lesser than 0.5 m/yr. The relative wave strength index may be used to identify sites at risk of increased erosion. At one site with a small historical erosion rate, the loss of a protective beach and associated decrease in toe elevation caused a positive shift in the frequency of large T/S. Direct wave undercutting and increased slope recession may be anticipated at this site, as indicated by the development of an undercut notch during the course of the study.

Wilcock, P. R.; Miller, D. S.; Shea, R. H.; Kerkin, R. T.

1998-01-01

5

Stratigraphy and Facies of Cretaceous Schrader Bluff and Prince Creek Formations in Colville River Bluffs, North Slope, Alaska  

USGS Publications Warehouse

Stratigraphic and sedimentologic studies of facies of the Upper Cretaceous rocks along the Colville River Bluffs in the west-central North Slope of Alaska identified barrier shoreface deposits consisting of vertically stacked, coarsening-upward parasequences in the Schrader Bluff Formation. This vertical stack of parasequence deposits represents progradational sequences that were affected by shoaling and deepening cycles caused by fluctuations of sea level. Further, the vertical stack may have served to stabilize accumulation of voluminous coal deposits in the Prince Creek Formation, which formed braided, high-sinuosity meandering, anastomosed, and low-sinuosity meandering fluvial channels and related flood plain deposits. The erosional contact at the top of the uppermost coarsening-upward sequence, however, suggests a significant drop of base level (relative sea level) that permitted a semiregional subaerial unconformity to develop at the contact between the Schrader Bluff and Prince Creek Formations. This drop of relative sea level may have been followed by a relative sea-level rise to accommodate coal deposition directly above the unconformity. This rise was followed by a second drop of relative sea level, with formation of incised valley topography as much as 75 ft deep and an equivalent surface of a major marine erosion or mass wasting, or both, either of which can be traced from the Colville River Bluffs basinward to the subsurface in the west-central North Slope. The Prince Creek fluvial deposits represent late Campanian to late Maastrichtian depositional environments that were affected by these base level changes influenced by tectonism, basin subsidence, and sea-level fluctuations.

Flores, Romeo M.; Myers, Mark D.; Houseknecht, David W.; Stricker, Gary D.; Brizzolara, Donald W.; Ryherd, Timothy J.; Takahashi, Kenneth I.

2007-01-01

6

Stratigraphy and Facies of Cretaceous Schrader Bluff and Prince Creek Formations in Colville River Bluffs, North Slope, Alaska.  

National Technical Information Service (NTIS)

Stratigraphic and sedimentologic studies of facies of the Upper Cretaceous rocks along the Colville River Bluffs in the west-central North Slope of Alaska identified barrier shoreface deposits consisting of vertically stacked, coarsening-upward parasequen...

2007-01-01

7

Pumice in the interglacial Whidbey Formation at Blowers Bluff, central Whidbey Island, WA, USA  

USGS Publications Warehouse

A new 40Ar/39Ar age of 128??9 ka and chemical analyses of pumice layers from interglacial alluvium at Blowers Bluff, Whidbey Island, WA, show that the deposits are part of the Whidbey Formation, a widespread, mainly subsurface unit. Glass chemistry of the dated dacitic pumice does not match any analyzed northern Cascade source, but upper Pleistocene dacites from Glacier Peak and early Pleistocene silicic rocks from the Kulshan caldera are chemically similar. The chemistry of pumiceous dacite in younger units, including the latest Pleistocene Partridge Gravel, is similar to that of the dated material. The deep troughs of the modern northern Puget lowland must have been filled during deposition of the Whidbey Formation, allowing volcanic-rich sediment to reach what is now Whidbey Island. Topographic analysis of LIDAR images demonstrates that extensive erosion occurred during latest Pleistocene ice retreat. The Partridge Gravel likely records subglacial fluvial erosion along an ice tunnel and ice-marginal deposition into adjacent marine waters. Pumice in the Partridge Gravel probably was reworked from stratigraphically and topographically lower deposits, including those at Blowers Bluff. ?? 2007 Elsevier Ltd and INQUA.

Dethier, D. P.; Dragovich, J. D.; Sarna-Wojcicki, A. M.; Fleck, R. J.

2008-01-01

8

Sentinel Hill Core Test 1: Facies Descriptions and Stratigraphic Reinterpretations of the Prince Creek and Schrader Bluff Formations, North Slope, Alaska  

USGS Publications Warehouse

The Sentinel Hill Core Test 1 well penetrated an intertonguing sequence of (1) the marine Schrader Bluff Formation in the depth intervals 950?1,180 ft and 690?751 ft, which consists of shoreface and offshore deposits that accumulated along a storm-dominated, barred shoreline; and (2) the nonmarine Prince Creek Formation in the depth intervals 751?950 ft and surface to 690 ft, which consists of fluvial channel, crevasse splay, backswamp, and ash fall deposits. The strata range in age from early Campanian to early Maastrichtian. An erosional contact at a depth of 690 ft at the base of the upper unit of the Prince Creek Formation is interpreted as a major regional sequence boundary, and the overlying conglomeratic fluvial channel deposits are interpreted to have accumulated in a paleovalley. In its more proximal reaches along the Colville River, channels of this paleovalley cut down 75 ft into the lowermost Prince Creek Formation and the uppermost Schrader Bluff Formation. Farther offshore, the equivalent surface to the aforementioned paleovalley appears to be a subtle discontinuity between middle and lower Schrader Bluff Formation shelfal marine strata. Still farther offshore, the equivalent paleovalley surface is interpreted as a marine mass-wasting surface that locally cuts through the lowermost Schrader Bluff Formation and into the underlying Seabee Formation.

Flores, Romeo M.; Stricker, Gary D.; Decker, Paul L.; Myers, Mark D.

2007-01-01

9

Bluff evolution along coastal drumlins: Boston Harbor Islands, Massachusetts  

USGS Publications Warehouse

A series of partially drowned drumlins forms the backbone of the inner islands within Boston Harbor. The shoreline of these rounded glacial deposits is composed of actively retreating bluffs formed by continual wave attack. Comparisons of bluffs reveal variability in their height and lateral extent, as well as in the dominant mechanism causing their retreat. Two processes are responsible for bluff erosion and yield distinct bluff morphologies: (1) wave attack undercuts the bluff and causes episodic slumping, yielding planar bluff slopes, and (2) subaerial processes such as rainfall create irregular slopes characterized by rills and gullies. We propose a model of drumlin bluff evolution that is based on processes of erosion and physical characteristics such as bluff height, slope morphology, and the orientation of the bluff with respect to the long axis of the drumlin and its topographic crest. The four phases of drumlin bluff evolution consist of (1) initial formation of bluff, with retreat dominated by wave notching and slumping processes; (2) rill and gully development as bluff heights exceed 10 m and slumped sediment at bluff base inhibits wave attack; (3) return of wave notching and slumping as bluff heights decrease; and (4) final development of boulder retreat lag as last remnants of drumlin are eroded by wave action. These phases capture the important physical processes of drumlin evolution in Boston Harbor and could apply to other eroding coastal drumlin deposits.

Himmelstoss, E. A.; FitzGerald, D. M.; Rosen, P. S.; Allen, J. R.

2006-01-01

10

Bluff body aerodynamics in wind engineering  

Microsoft Academic Search

Most of the man made structures are bluff bodies. Therefore, the subject of this conference is central to the subject of wind engineering. One of the most obvious features of the flow around bluff bodies is the formation of strong large vortices in their wakes. These have a large impact on the wind loading of tall buildings and bridges, particularly

Peter A. Irwin

2008-01-01

11

Hemiacodon engardae, a new species of omomyid primate from the earliest Uintan Turtle Bluff Member of the Bridger Formation, southwestern Wyoming, USA.  

PubMed

In this paper, we describe a new species of Hemiacodon known only from University of Colorado Museum Loc. 92189 (Donna's Locality) in the Turtle Bluff Member of the Bridger Formation, Green River Basin, southwestern Wyoming. Donna's locality has yielded a diverse mostly small-bodied mammalian assemblage of Bridgerian and first appearance Uintan mammalian taxa, as well as range-through taxa. Together with H. engardae sp. nov., the faunal assemblage from Donna's Locality and more recently discovered localities in the same stratigraphic interval provides the first conclusive paleontological evidence of an earliest Uintan age (Ui1A biochron) for the Turtle Bluff Member of the Bridger Formation. The new species is represented by a sample of 11 specimens consisting of well-preserved upper and lower premolars and lower molars. H. engardae is distinct from H. gracilis on the basis of overall larger size as well as a combination of features of the premolars and molars related to a greater development of shearing crests. This suggests that H. engardae may have incorporated more foliage into its diet than the Bridgerian species, H. gracilis. PMID:19625072

Murphey, Paul C; Dunn, Rachel H

2009-08-01

12

Observations of Permafrost Bluff Failure Processes, Barter Island, NE Alaska  

NASA Astrophysics Data System (ADS)

Arctic coast permafrost bluffs are extremely vulnerable to increased thaw, erosion, and landward retreat in a warming climate. Here, we report on permafrost bluff retreat processes based on field observations of bluff geology and morphology during the summers of 2010 and 2011 combined with historical analyses of bluff retreat rates from the mid 1940s to the present for Barter Island, NE Alaska. Field data collected included GPS surveys of bluff position and morphology, geologic mapping including stratigraphy, sediment size and composition, ice content, nearshore bathymetry, and temperature gradients recorded by thermistor arrays. Failure mechanisms are the direct causes of failures and include wave action, water flow (both surface and groundwater), freeze/thaw impacts, and surficial weathering. Failure modes are the processes by which the failures occur such as undercutting (notching) and oversteepening of the bluff face, retrogressive thaw slumping, rotational failures, block falls, and gullying. Processes of failure observed along the Barter Island bluffs vary both temporally with seasonal changes in temperature and sea-ice conditions, and spatially associated with variations in bluff height and composition. In the spring and early summer, sediment-entrained land-fast ice recedes, removing and reworking sediment from the bluff and foreshore. Snow melt induces surface runoff and gullying, and is accompanied by thawing of the bluff face which begins to produce debris avalanches and small alluvial fans at the base of the bluffs where a backbeach is present. During the summer months, when sea-ice has retreated from the coast, thermo-erosional niching and mechanical notch formation occurs due to small storm waves and elevated water levels in response to winds and pressure differences. As bluff-face thawing continues large thaw slump failures and block falls begin to develop. In late summer and fall, before the sea ice returns, extra-tropical storms lead to increased niching, notching, and dispersal of protective failure blocks by longshore sediment transport. Large storms can result in significant bluff retreat in a matter of days. Bluffs that feature segregated ice layers, large niche formations typically occur in response to thawing from incoming solar radiation, and/or contact with seawater. Greater bluff ice content typically results in higher retreat rates and thick layers are often accompanied by cantilever beam-type failures. Ice-wedges near the bluff edge are zones of weakness and act to facilitate block falls. Interactions between failure modes, such as block failure followed by enhanced thaw slumping, may result in amplification of bluff retreat.

Erikson, L. H.; Richmond, B. M.; Gibbs, A.; Jones, B.

2011-12-01

13

Calvert Cliffs tiger beetle  

NSDL National Science Digital Library

This video clip, viewable in RealPlayer, introduces students to the rare puritan tiger beetles that live in Maryland's Calvert Cliffs. The two and a half-minute clip addresses the beetle's lifecycle, focusing on its dependence on the area's beachside cliffs. A discussion of the beetle's reproduction and feeding behaviors is accompanied by footage of adult beetles on the shore and of larvae tunneling holes into the cliffs. An entomologist lists the conservation actions that need to be taken to remove the beetle from the state list of endangered species. Copyright 2005 Eisenhower National Clearinghouse

Ecducation, Johns H.; Maryland Public Television (MPT)

2004-01-01

14

Calvert Cliffs tiger beetle  

NSDL National Science Digital Library

This video clip, viewable in Windows Media Player, introduces students to the rare puritan tiger beetles that live in Maryland's Calvert Cliffs. The two and a half-minute clip addresses the beetle's lifecycle, focusing on its dependence on the area's beachside cliffs. A discussion of the beetle's reproduction and feeding behaviors is accompanied by footage of adult beetles on the shore and of larvae tunneling holes into the cliffs. An entomologist lists the conservation actions that need to be taken to remove the beetle from the state list of endangered species. Copyright 2005 Eisenhower National Clearinghouse

Johns Hopkins University. Center for Technology in Education (CTE); Maryland Public Television (MPT)

2004-01-01

15

33 CFR 165.505 - Security Zone; Calvert Cliffs Nuclear Power Plant, Chesapeake Bay, Calvert County, Maryland.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Security Zone; Calvert Cliffs Nuclear Power Plant, Chesapeake Bay, Calvert County, Maryland...Guard District § 165.505 Security Zone; Calvert Cliffs Nuclear Power Plant, Chesapeake Bay, Calvert County,...

2013-07-01

16

Historic bluff retreat and stabilization at Flag Harbor, Chesapeake Bay, Maryland  

USGS Publications Warehouse

Studies of bluff erosion and slope stability along the western shore of Chesapeake Bay suggest relative evolution from steep, eroding coastal bluffs to stable slopes at angles of repose ca. 35 degrees over decades. Because of the dating methods in those studies, it was impossible to precisely define rates of change. The present study provides historic age control. A pair of small harbor structures were constructed in the early 1950's at Chesapeake Beach, MD to maintain a dredged channel to a small marina occupying a ravine in the Calvert Cliffs. Prior to construction, this section of shoreline was comprised of eroding steep bluffs cut into Miocene-age sediments. Downdrift erosion is now apparent south of the structures as is updrift deposition behind the northern jetty. Since construction the updrift sand body has prograded northward and progressively deposited protective beaches along the toes of the bluffs. Former eroding bluffs nearest the harbor are now stable, vegetated slopes at angles near 35 degrees. Slope angles widen to the north and to the northern limit of the sand body. Beyond this are eroding bluffs standing at angles of 70-80 degrees. The relative time required for eroding bluffs to reach stability is estimated by interpolating the distance and time for the sand body to prograde northward since harbor construction. We measured slope angles at intervals northward from the updrift structure for a distance of 2000 feet. A least squares regression of slope angle vs distance showed progressive decrease in angle from north to south. Actively eroding 70-80 degree bluffs gave way to vegetated, but slumping slopes, and finally to stable 35-degree slopes at the harbor. A relationship between time and distance along the shore allowed us to estimate a stabilization time for this location of 35-40 years. The shortness of this time scale allows us to suggest that attempts to artificially stabilize eroding bluffs along this coast is not a simple task of protecting the toes of slopes from wave action. Once shoreline retreat ends, sloughing of sediment from bluff faces gives way to longer-term landslide processes. The bluff top recedes until a stable 35-degree slope is attained. Thus, simple shoreline protection methods may not preserve property at the bluff edge.

Clark, Inga; Larsen, Curtis E.; McRae, Michele

2002-01-01

17

6. SOUTHEAST ABUTMENT AT CALVERT STREET, SHOWING LEON HERMANT ALLEGORICAL ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

6. SOUTHEAST ABUTMENT AT CALVERT STREET, SHOWING LEON HERMANT ALLEGORICAL RELIEF OF TRANSPORTATION BY AUTOMOBILE - Calvert Street Bridge, Spanning Rock Creek & Potomac Parkway, Washington, District of Columbia, DC

18

Gosses Bluff impact structure, Australia.  

NASA Technical Reports Server (NTRS)

A comprehensive study has been carried out of the Gosses Bluff structure in Central Australia, which is a typical cryptoexplosion structure. The study included detailed geologic mapping, and seismic reflection and refraction, gravity, aeromagnetic, and ground magnetic surveys. It is concluded that the structure is an eroded crater formed by a single nearly instantaneous shock event, and that the event can be explained only by impact.

Milton, D. J.; Barlow, B. C.; Brown, A. R.; Glikson, A. Y.; Manwaring, E. A.; Moss, F. J.; Sedmik, E. C. E.; Van Son, J.; Brett, R.; Young, G. A.

1972-01-01

19

Industrial Sites Study: Poplar Bluff, Missouri.  

National Technical Information Service (NTIS)

The study is to determine the most appropriate site for expansion of Poplar Bluff's municipal industrial park. Consideration is given to existing park, as well as, potential sites throughout the urban area. Several factors will determine most advantageous...

1972-01-01

20

Geohydrology and simulation of ground-water flow in the aquifer system near Calvert City, Kentucky  

USGS Publications Warehouse

The U.S. Geological Survey, in cooperation with the Kentucky Natural Resources and Environmental Protection Cabinet, constructed a two-dimensional, steady-state ground-water-flow model to estimate hydraulic properties, contributing areas to discharge boundaries, and the average linear velocity at selected locations in an aquifer system near Calvert City, Ky. Nonlinear regression was used to estimate values of model parameters and the reliability of the parameter estimates. The regression minimizes the weighted difference between observed and calculated hydraulic heads and rates of flow. The calibrated model generally was better than alternative models considered, and although adding transmissive faults in the bedrock produced a slightly better model, fault transmissivity was not estimated reliably. The average transmissivity of the aquifer was 20,000 feet squared per day. Recharge to two outcrop areas, the McNairy Formation of Cretaceous age and the alluvium of Quaternary age, were 0.00269 feet per day (11.8 inches per year) and 0.000484 feet per day (2.1 inches per year), respectively. Contributing areas to wells at the Calvert City Water Company in 1992 did not include the Calvert City Industrial Complex. Since completing the fieldwork for this study in 1992, the Calvert City Water Company discontinued use of their wells and began withdrawing water from new wells that were located 4.5 miles east-southeast of the previous location; the contributing area moved farther from the industrial complex. The extent of the alluvium contributing water to wells was limited by the overlying lacustrine deposits. The average linear ground-water velocity at the industrial complex ranged from 0.90 feet per day to 4.47 feet per day with a mean of 1.98 feet per day.

Starn, J. J.; Arihood, L. D.; Rose, M. F.

1995-01-01

21

The Interaction Vortex Flow Around Two Bluff Cylinders  

NASA Astrophysics Data System (ADS)

In this study, the interaction vortex flow features around a pair of parallel arranged bluff cylinders were observed by visualizing water flow experiment at the range of the gap ratio G/d=0~3. It was obtained that the result of established wind tunnel test and the result of this water tank test agreed about the characteristics of vortex shedding when varying the distance of circular cylinder gap. The flow pattern and vortex shedding frequency of another type bluff cylinder (triangular and square cylinder) were also investigated. As a result of the experiment, it was shown that the flow pattern of wake flow was divided into three kinds (coupled vortex streets, biased gap flow and single vortex street) regardless of the cylinder section shape and cylinder size. Then, the region of the appearance of flow pattern was shown about each case. In the case where two each other independent vortex streets were formed, three typical flow patterns of vortex formation (in-phase coupled vortex streets, out-of-phase coupled vortex streets and complication coupled vortex streets) were observed. It was known that three configuration of vortex formation appear intermittently and alternatively.

Yokoi, Y.; Hirao, K.

2013-04-01

22

VORTEX SHEDDING OF BLUFF BODIES: A REVIEW  

Microsoft Academic Search

In this paper the various types of vortex generation and the related response characteristics of bluff bodies are described. The vortices are, in general, generated by a certain stimulation, leading to one- or two-shear layer instability; the related unsteady forces could excite flexible structures such as tall towers, tall buildings and long-span bridges. Karman vortex shedding is well known as

M. Matsumoto

1999-01-01

23

75 FR 21372 - Calvert Social Investment Fund, et al.; Notice of Application  

Federal Register 2010, 2011, 2012, 2013

...29209; File No. 812-13718] Calvert Social Investment Fund, et al.; Notice of...financial instruments. Applicants: Calvert Social Investment Fund (the ``Trust...calling (202) 551-8090. Applicants' Representations 1. The Trust is organized as a...

2010-04-23

24

75 FR 65230 - Drawbridge Operation Regulation; Arkansas Waterway, Pine Bluff, AR  

Federal Register 2010, 2011, 2012, 2013

...Operation Regulation; Arkansas Waterway, Pine Bluff, AR AGENCY: Coast Guard, DHS...the Arkansas Waterway at Mile 67.4 at Pine Bluff, Arkansas. Vessel operators shall...Operation Regulation; Arkansas Waterway, Pine Bluff, AR in the Federal Register...

2010-10-22

25

1. SOUTH END OF CALVERT STATION. FREIGHT HOUSE IS GABLED ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

1. SOUTH END OF CALVERT STATION. FREIGHT HOUSE IS GABLED STRUCTURE ON RIGHT. FIRST FLOOR FACADE ADDED IN 1946 WHEN THE PASSENGER TERMINAL SOUTH OF CENTRE STREET WAS DEMOLISHED AND ALL IT ACTIVITIES WERE TRANSFERRED TO THE FREIGHT SHED. - North Central Railroad, Baltimore Freight House, Guilford & Centre Streets, Baltimore, Independent City, MD

26

Evaluation of previous remedial construction along the Duquesne Bluff  

Microsoft Academic Search

The Boulevard of the Allies is a major four lane roadway in Pittsburgh, Pennsylvania that is constructed atop a near vertical, 35 meter high rock slope known locally as the Duquesne Bluff. Stratigraphic relief observed on the bluff consists of alternating sequences of flat lying sedimentary deposits of sandstone, siltstone, shale, carbonaceous shale, claystone and limestone. Expsoure of alternating sequences

J. W. Kovacs; W ADAMSJR

1997-01-01

27

VORTEX SHEDDING FROM BLUFF BODIES AND A UNIVERSAL STROUHAL NUMBER  

Microsoft Academic Search

Experiments on vortex shedding from bluff bodies were conducted in a wind tunnel, with emphasis on finding the effects of afterbody shape on the vortex-shedding frequency. It is found that the Strouhal number of a bluff body with afterbody decreases initially with increasing side ratio, with a reduction that is not dependent on the details of afterbody shape but only

Y. Nakamura

1996-01-01

28

Bluff Body Flow Control Using Plasma Actuators  

NASA Astrophysics Data System (ADS)

In this study, the use of single dielectric barrier discharge plasma actuators for the control of bluff body flow separation is investigated. In particular, surface mounted plasma actuators are used to reduce both drag and unsteady vortex shedding from circular cylinders in cross-flow. It is demonstrated that the plasma-induced surface blowing gives rise to a local Coanda effect that promotes the maintenance of flow attachment. Large reductions in vortex shedding and drag are demonstrated for Reynolds numbers ˜ 10^410^5. Both steady and unsteady plasma-induced surface blowing is explored. Results are presented from experiments involving both two and four surface mounted actuators.

Thomas, Flint

2005-11-01

29

Scotts Bluff: Shared Heritage Travel Itinerary  

NSDL National Science Digital Library

Located along the North Platte River Valley in Nebraska, the Scotts Bluff region is rich in history. The area was traversed by settlers on their way West throughout the 19th century, and it is the subject of this Shared Heritage Travel Itinerary created by the National Park Service. This Itinerary was produced in cooperation with the city of Scottsbluff, the city of Gering, the Nebraska State Historic Preservation Office, and the National Conference of State Historic Preservation Officers. As with the other itineraries in the series, this one includes a "List of Sites" (complete with information about their significance), maps, and thematic essays like "Trappers, Traders, and Travelers" and "Cultivation, Irrigation, and Urbanization". There are many highlights here, but visitors shouldn't miss the sections on the Morrill County Courthouse or the Marquis Opera House in Scottsbluff.

30

Interaction of a two-dimensional bluff body and incompressible jet and annulus flows  

NASA Astrophysics Data System (ADS)

A particular interaction of bluff body and jet flows was studied using two dimensional slot jet (aspect ratio = 50) surrounded by a two dimensional bluff body. The coflowing system used air in the annulus and nitrogen in the jet. Flow visualization identified flow patterns containing large vortex structures. These were observed as jet velocities changed. Laser Doppler Anenometry measurements of instantaneous velocities were examined to characterize the flowfield details, and high speed movies provided qualitative insight into flow dynamics. The concept of jet and annulus fields is introduced. The jet field is the region above the bluff body that extends six or seven slot widths downstream, and the annulus field is the region above the jet field. The annulus flow dictates the flowfield dynamics in the annulus field up to jet-to-annulus velocity ratios of 1.45. The jet is responsible for the formation of the large-scale structures and dominates the flow in the jet field. Jet domination of the entire flowfield is seen at velocity ratios of 1.45 and above. Mie scattering was used to determine shedding frequencies of the large structures.

Boedicker, Christopher A.

1987-12-01

31

Panoramic view from bluff south of Grand Coulee Dam; this ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Panoramic view from bluff south of Grand Coulee Dam; this segment of the panorama shows the westernmost extend of Franklin D. Roosevelt Lake and part of Grand Coulee Dam, looking north. - Columbia Basin Project, Grand Coulee, Grant County, WA

32

15. GENERAL VEW FROM SOUTHWEST SHOWING BLUFF, COAST GUARD'S HOUSE, ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

15. GENERAL VEW FROM SOUTHWEST SHOWING BLUFF, COAST GUARD'S HOUSE, WARDEN'S HOUSE AND RUBBLE IN FOREGROUND - Alcatraz, Cell House, Alcatraz Island, San Francisco Bay, San Francisco, San Francisco County, CA

33

76 FR 10581 - Moss Bluff Hub, LLC; Notice of Filing  

Federal Register 2010, 2011, 2012, 2013

...Bluff Hub, LLC filed to revise its Statement of General Terms and Standard Operating Conditions to reflect the addition of Bobcat Gas Storage to the list of entities whose service agreements constitute a Valid Service Agreement as more fully described...

2011-02-25

34

Overview from bluff east of facility. Note buildings #35 (left). ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Overview from bluff east of facility. Note buildings #35 (left). #33 (center), and #31 A (right) VIEW WEST - Department of Energy, Grand Junction Office, 2597 B3/4 Road, Grand Junction, Mesa County, CO

35

An Investigation into the Flow around Axisymmetric Bluff Bodies.  

National Technical Information Service (NTIS)

The flows around three types of axisymmetric bluff bodies compounded from the upper and lower halves of the Westland Wisp basic body shape were investigated. The investigation had three methods of attack: flow visualization; a static pressure distribution...

P. W. Churms R. K. Harris

1978-01-01

36

76 FR 29279 - Calvert Cliffs 3 Nuclear Project, LLC and Unistar Nuclear Operating Services, LLC; Notice of...  

Federal Register 2010, 2011, 2012, 2013

...52-016; NRC-2008-0250] Calvert Cliffs 3 Nuclear Project, LLC and Unistar Nuclear...Combined License Application for Calvert Cliffs Nuclear Power Plant Unit 3 Notice is hereby...EIS), NUREG- 1936, for the Calvert Cliffs Nuclear Power Plant (CCNPP), Unit...

2011-05-20

37

Variation in composition and abundance of Miocene shark teeth from Calvert Cliffs, Maryland  

Microsoft Academic Search

Shark teeth are the most common vertebrate fossils found along the western shore of Chesapeake Bay at Calvert Cliffs in Maryland. The stratigraphic distribution of teeth within the cliffs has not yet been documented. We utilized museum collections of in situ teeth to access their distribution within stratigraphic beds and a large selection of float teeth retrieved from Calvert County

Christy C. Visaggi; Stephen J. Godfrey

2010-01-01

38

78 FR 23563 - LWD, Inc. Superfund Site; Calvert City, Marshall County, Kentucky; Notice of Settlement  

Federal Register 2010, 2011, 2012, 2013

...CERCLA-04-2013-3751] LWD, Inc. Superfund Site; Calvert City, Marshall County...past costs concerning the LWD, Inc., Superfund Site located in Calvert City, Marshall...your comments by Site name LWD, Inc., Superfund Site by one of the following...

2013-04-19

39

75 FR 60147 - Calvert Cliffs Nuclear Power Plant, LLC; Independent Spent Fuel Storage Installation; Notice of...  

Federal Register 2010, 2011, 2012, 2013

...Calvert Cliffs Nuclear Power Plant, LLC; Independent...Installation; Notice of Issuance of Amendment...Transportation, Office of Nuclear Material Safety...Calvert Cliffs Nuclear Power Plant, LLC (CCNPP...the identification of each failure and the...requester's/petitioner's belief. In addition,...

2010-09-29

40

Particle size and X-ray analysis of Feldspar, Calvert, Ball, and Jordan soils  

NASA Technical Reports Server (NTRS)

Pipette analysis and X-ray diffraction techniques were employed to characterize the particle size distribution and clay mineral content of the feldspar, calvert, ball, and jordan soils. In general, the ball, calvert, and jordan soils were primarily clay size particles composed of kaolinite and illite whereas the feldspar soil was primarily silt-size particles composed of quartz and feldspar minerals.

Chapman, R. S.

1977-01-01

41

Paleotemperatures versus sea level: Oxygen isotope signal from fish bone phosphate of the Miocene Calvert Cliffs, Maryland  

NASA Astrophysics Data System (ADS)

The use of skeletal oxygen isotopic records for use in paleotemperature reconstruction has been hampered by the lack of independent evidence for ocean water oxygen isotopic composition. The ?18O record from homeothermic cetaceans has provided an independent estimate of ocean ?18O values represented by the Calvert and Choptank formations of Maryland. Fish teeth and bones (especially shark and ray teeth) were also collected from these sediments and provide the basis for paleotemperature estimates for represented time slices of the middle Miocene. Trends in ?18O values of the fish phosphate throughout the Calvert Formation are of opposite polarity to the trends from the cetacean bone phosphate. Paleotemperatures calculated using the cetacean proxies for ocean ?18O values sharpen the already present trend, indicating that ocean temperatures increased during episodes of greater glaciation and decreased during periods of lesser or no glaciation. When using modern average ocean values of 0‰ SMOW in the paleotemperature calculation, however, corrected paleotemperatures for the Choptank Formation do not alter the existing pattern of temperatures.

Barrick, Reese E.; Fischer, Alfred G.; Bohaska, David J.

1993-12-01

42

33 CFR 207.170 - Federal Dam, Oklawaha River, Moss Bluff, Fla.; pool level.  

Code of Federal Regulations, 2013 CFR

...Federal Dam, Oklawaha River, Moss Bluff, Fla.; pool level. 207.170 Section 207.170 Navigation and...Federal Dam, Oklawaha River, Moss Bluff, Fla.; pool level. (a) The level of the pool shall normally be maintained at...

2013-07-01

43

75 FR 36313 - Drawbridge Operation Regulation; Arkansas Waterway, Pine Bluff, AR  

Federal Register 2010, 2011, 2012, 2013

...Operation Regulation; Arkansas Waterway, Pine Bluff, AR AGENCY: Coast Guard, DHS...the Arkansas Waterway at mile 67.4 at Pine Bluff, AR be revised in the Code of Federal...the Rob Roy Drawbridge, mile 67.4, at Pine Bluff, AR is maintained in the...

2010-06-25

44

Bluff recession rates along the Lake Michigan shoreline in Illinois  

USGS Publications Warehouse

For two time periods, 1872-1937 and 1937-1987, rates of retreat vary from 10 to 75 cm/yr between discrete segments of bluffs (defined by lithology) and between time periods for a given bluff segment. The average retreat rates for the entire area, however, do not vary significantly between the two time periods and are approximately 20-25 cm/yr. The temporally constant regional retreat rates and the regular shape of the local shoreline indicate that a long-term uniform rate of retreat prevails and that local variations in rates balance out through time to produce long-term parallel (in map view) bluff retreat in the area. -from Authors

Jibson, R. W.; Staude, J. -M.

1992-01-01

45

Monitoring stream bluff erosion using repeat terrestrial laser scanning  

NASA Astrophysics Data System (ADS)

Terrestrial laser scanning (TLS) technology provides high-resolution topographic data that can be used to detect geomorphic change in fluvial environments. In this study, we utilize successive terrestrial laser scans to investigate the relationship between peak flow rates and stream bluff erosion in the Amity Creek watershed in Duluth, Minnesota. We also combine TLS scan results with bluff inventories from airborne lidar to estimate the volume of sediment erosion from bluffs in the watershed, which is an important source of fine sediment contributing to the creek's turbidity impairment. We selected nine study bluffs to conduct terrestrial laser scans on after all significant flood events over a two-year time period. The study employs a Faro Focus 3D phase-shift laser to collect data. Post-processing of the TLS-point cloud data sets involves: (1) removal of vegetation and objects other than the erosional surface of interest; (2) decimation of the point cloud in PC Tools and extraction of zmin values to produce a data set manageable in GIS; (3) creation of a bare earth digital elevation model (DEM) for each set of scans using ArcMap; and (4) utilization of Geomorphic Change Detection (GCD) software to generate DEMs of Difference (DODs) from subsequent terrestrial laser scans. Preliminary results from three flooding events indicate significant erosional activity at all field sites. Slumps were observed at two bluffs following spring melt and freeze/thaw cycling. Two major precipitation events in late spring and early summer provided a unique opportunity to observe the impact of extreme high flow events on bluff erosion throughout the watershed using TLS technology. 4.75 inches of intermittent rain over a six-day period in late May 2012 (May 23-28) resulted in slumping at many bluffs and one major failure. The ?100-year flood that occurred on June 19-20 (7.25 inches), 2012 was powerful enough to induce considerable channel change. Slumps occurred at six study sites, and at some locations, channel centerlines were permanently shifted by up to four to six meters. Additionally, all rebar control points were removed at four sites making post-flood data analysis challenging. Fortunately, adequate control remained at many bluffs, providing unique insight into geomorphic change that occurs in a fluvial setting during such a dramatic event.

Neitzel, G.; Gran, K. B.

2012-12-01

46

Dynamics of perturbed exothermic bluff-body flow-fields  

NASA Astrophysics Data System (ADS)

This thesis describes research on acoustically excited bluff body flow-fields, motivated by the problem of combustion instabilities in devices utilizing these types of flame-holders. Vortices/convective-structures play a dominant role in perturbing the flame during these combustion instabilities. This thesis addresses a number of issues related to the origin, evolution and the interaction of these structures with the flame. The first part of this thesis reviews the fluid mechanics of non-reacting and reacting bluff body flows. The second part describes the spatio/temporal characteristics of bluff-body flames responding to excitation. The key processes controlling the flame response have been identified as (1) the anchoring of the flame at the bluff body, (2) the excitation of flame-front wrinkles by the oscillating velocity field and (3) flame propagation normal to itself at the local flame speed. The first two processes control the growth of the flame response and the last process controls the decay. The third part of this thesis describes the effect of acoustic excitation on the velocity field of reacting bluff body flows. Acoustic disturbances excite the Kelvin-Helmholtz (KH) instability of the reacting shear layer. This leads to a spatially decaying vorticity field downstream of the bluff body in the shear layers. The length over which the decay occurs was shown to scale with the length of the recirculation zone of the bluff body, i.e. the length over which the velocity profile transitions from shear layer to wake. The flame influences this decay process in two ways. Gas expansion across the flame reduces the extent of shear by reducing the magnitude of negative velocities within the recirculation zone. This combined with the higher product diffusivity reduces the length of the recirculation zone, thereby further augmenting the decay of the vorticity fluctuations. Lastly, these results also revealed the phase jitter - a cycle-to-cycle variation in the position of the rolled-up vortices. Close to the bluff-body, phase jitter is very low but increases monotonically in the downstream direction. This leads to significant differences between instantaneous and ensemble averaged flow fields and, in particular, the decay rate of the vorticity in the downstream direction.

Shanbhogue, Santosh Janardhan

47

76 FR 22935 - Calvert Cliffs Nuclear Power Plant, LLC Independent Spent Fuel Storage Installation; Notice of...  

Federal Register 2010, 2011, 2012, 2013

...NUCLEAR REGULATORY COMMISSION [Docket No. 72-8; NRC-2011-0085] Calvert Cliffs Nuclear Power Plant, LLC Independent Spent Fuel...Opportunity for a Hearing for Renewal of Special Nuclear Materials License No.-2505...

2011-04-25

48

3. IRONWOOD BLUFFS BRIDGE MISSISSIPPI, ITAWAMBA CO. One mile W ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

3. IRONWOOD BLUFFS BRIDGE MISSISSIPPI, ITAWAMBA CO. One mile W of Ms. 25 on dirt road 2.5 mi. N of Bull Mtn. Cr. View from S side of E approach. Sarcone Photography, Columbus, Ms. September 1978. - Bridges of the Upper Tombigbee River Valley, Columbus, Lowndes County, MS

49

4. IRONWOOD BLUFFS BRIDGE MISSISSIPPI, ITAWAMBA CO. One mile W ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

4. IRONWOOD BLUFFS BRIDGE MISSISSIPPI, ITAWAMBA CO. One mile W of Ms. 25 on dirt road 2.5 mi. N of Bull Mtn. Cr. View from N, wide angle. Sarcone Photography, Columbus, Ms. September 1978. - Bridges of the Upper Tombigbee River Valley, Columbus, Lowndes County, MS

50

1. IRONWOOD BLUFFS BRIDGE Tombigbee R. MISSISSIPPI, ITAWAMBA CO. One ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

1. IRONWOOD BLUFFS BRIDGE Tombigbee R. MISSISSIPPI, ITAWAMBA CO. One mile W of Ms. 25 on dirt road 2.5 mi. N of Bull Mtn. Cr. Detail of upper panel point, showing components of members. Sarcone Photography, Columbus, Ms. September 1978. - Bridges of the Upper Tombigbee River Valley, Columbus, Lowndes County, MS

51

5. IRONWOOD BLUFFS BRIDGE MISSISSIPPI, ITAWAMBA CO. One mile W ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

5. IRONWOOD BLUFFS BRIDGE MISSISSIPPI, ITAWAMBA CO. One mile W of Ms. 25 on dirt road 2.5 mi. N of Bull Mtn. Cr. View of underside from NE shore, showing lower panel point, lateral bracing. Sarcone Photography, Columbus, Ms. September 1978. - Bridges of the Upper Tombigbee River Valley, Columbus, Lowndes County, MS

52

2. IRONWOOD BLUFFS BRIDGE MISSISSIPPI, ITAWAMBA CO. One mile W ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

2. IRONWOOD BLUFFS BRIDGE MISSISSIPPI, ITAWAMBA CO. One mile W of Ms. 25 on dirt road 2.5 mi. N of Bull Mtn. Cr. Oblique view of N truss from E end. Sarcone Photography, Columbus, Ms. September 1978. - Bridges of the Upper Tombigbee River Valley, Columbus, Lowndes County, MS

53

Vortex phase-jitter in acoustically excited bluff body flames  

Microsoft Academic Search

This paper describes an experimental study of the effect of acoustic excitation on bluff body stabilized flames, specifically on the flow field characteristics. The Kelvin-Helmholtz (KH) instability of the shear layer is excited due to the incident acoustics. In turn, the KH instability imposes a convecting, harmonic excitation on the flame, which leads to spatially periodic flame wrinkling and heat-release

Santosh J. Shanbhogue; Michael Seelhorst; Tim Lieuwen

2009-01-01

54

Overview of the Grand Junction Office from Bluff east of ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Overview of the Grand Junction Office from Bluff east of facility. Note Buildings #35. #33 and #31A in lower left of photograph. VIEW WEST - Department of Energy, Grand Junction Office, 2597 B3/4 Road, Grand Junction, Mesa County, CO

55

Lichens and Related Fungi of Pine Bluff Arsenal, Arkansas  

Microsoft Academic Search

A total of 161 taxa of lichens and related fungi were documented from Pine Bluff Arsenal in Jefferson County, on the Gulf Coastal Plain in south-central Arkansas. Constrained time entitations in five natural area units within the arsenal revealed a high degree of similarity among the lichen biota of the units. Crustose lichens are the most common growth form, comprising

DOUGLAS LADD

56

Some observations on the state of bluff-body aeroelasticity  

Microsoft Academic Search

The paper comments in general upon the state of the art in bluff-body aerodynamics and aeroelasticity, nothing particularly the continuing requirements for improving the data obtained in reduced-scale experiments. While certain existing theoretical response models are gaining in sophistication - as demonstrated by theories of long-span bridge response to wind - some of the gaps to be filled therein are

Robert H. Scanlan

1997-01-01

57

The flow past bluff bodies by a vortex method  

Microsoft Academic Search

A review of the literature on vortex methods for the representation of vortex sheets and the literature in two dimensional viscous incompressible flow past bluff bodies, mainly the circular cylinder, both experimental and numerical, with emphasis on the use of vortex methods, is presented. An algorithm for the transport of vorticity in two dimensional incompressible flow past a circular cylinder

Andrew P. Burrows

1990-01-01

58

Panoramic view from bluff south of Grand Coulee Dam; this ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Panoramic view from bluff south of Grand Coulee Dam; this segment of the panorama shows the western end of Crescent Bay Lake (in the foreground), the western limits of the town of Grand Coulee, part of Grand Coulee's transformer yard (center in the distance), and the concrete-lined feeder canal that extends to Banks Lake, looking northwest. - Columbia Basin Project, Grand Coulee, Grant County, WA

59

Aerodynamic modification of flow over bluff objects by plasma actuation  

Microsoft Academic Search

Particle image velocimetry and smoke visualization are used to study the alteration of the flow field in the wake of a bluff body by use of an alternating current (AC) surface dielectric barrier discharge. Staggered, surface, and buried electrodes were positioned on the downstream side of circular cylinders at conditions of Re\\u000a \\u000a D \\u000a = 1 × 104?4 × 104 configured to impose a force due

Y. Sung; W. Kim; M. G. Mungal; M. A. Cappelli

2006-01-01

60

Bluff Body Fluid Interactions Modelling for Micro Energy Harvesting Application  

NASA Astrophysics Data System (ADS)

In this paper, we have presented a MEMS-based piezoelectric fluid-flow based micro energy harvester. The design and modelling of the energy harvester structure was based on a piezoelectric cantilever affixed to a bluff-body. In a cross fluid flow, pressure in the flow channel, in the wake of the bluff body, fluctuates with the same frequency as the pressure variation caused by the Kármán Vortex Street. This fluctuation of pressure in the flow channel causes the piezoelectric cantilever, trailing the bluff-body, to vibrate in a direction normal to the fluid flow direction. COMSOL finite element analysis software are used for the evaluation of various mechanical analysis of the micro energy harvester structure like, physical the Stress and Strain state in the cantilever structures, Eigen frequency Analysis, Transient analysis to demonstrate the feasibility of the design. Detailed steps of modelling and simulation results of the uniform cantilever were explained. The results confirm the probability of the fluid flow based MEMS energy harvester.

Bhuyan, M. S.; Majlis, B. Y.; Othman, M.; Ali, Sawal H. Md; Kalaivani, C.; Islam, S.

2013-04-01

61

Morphologic characteristics of upland bluffs east and west of Crowley's Ridge in the New Madrid area  

SciTech Connect

Although presumed to be purely erosional in origin, the development of the bluffs bounding the Mississippi River may be ultimately influenced by tectonic processes. Quantitative morphologic characterization of the bluffs may provide insights to their erosional history and possible tectonic impacts on their evolution. Characterization consists of digitizing topographic planforms of the bluffs, valley floor morphology, and calculation of such parameters as sinuosity (S), valley floor/valley height ratios (Vf) and stream gradient indices for streams cutting the bluffs. Bluff planforms vary in sinuosity from nearly straight, S = 1.3, to highly sinuous, S = 8.2. Sinuosity appears to primarily reflect the size of the streams that dissect the bluffs. On the west side of the river, sinuosities are systematically higher than on the east side, reflecting the consequences of larger streams which effectively embay the bluffs. Interestingly, the lowest sinuosities in the area studied are geographically juxtaposed to the highest ones, both found on the east side of the river. The low sinuosities are due to the near coincidence of the drainage divide with the bluffs themselves resulting in east flowing drainage away from the bluffs. Vf ratios show a geographic pattern similar to that of sinuosity.

Church, A.; Mayer, L. (Miami Univ., Oxford, OH (United States). Dept. of Geology)

1993-03-01

62

Phenomena and modelling of flow-induced vibrations of bluff bodies  

Microsoft Academic Search

A detailed treatment is undertaken of the transverse vibrations of single long bodies of bluff section in steady incident flow normal to their span. 'Bluff section' is understood to refer to one from which the flow separates, producing two shear layers that bound a relatively broad wake. The transverse vibrations are galloping and vortex-induced. Galloping is a self-excited vibration in

Geoffrey Parkinson

1989-01-01

63

33 CFR 207.170 - Federal Dam, Oklawaha River, Moss Bluff, Fla.; pool level.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Federal Dam, Oklawaha River, Moss Bluff, Fla.; pool level. 207.170 Section 207.170 Navigation... § 207.170 Federal Dam, Oklawaha River, Moss Bluff, Fla.; pool level. (a) The level of the pool...

2010-07-01

64

33 CFR 207.170 - Federal Dam, Oklawaha River, Moss Bluff, Fla.; pool level.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 false Federal Dam, Oklawaha River, Moss Bluff, Fla.; pool level. 207.170 Section 207.170 Navigation... § 207.170 Federal Dam, Oklawaha River, Moss Bluff, Fla.; pool level. (a) The level of the pool...

2009-07-01

65

Secondary sulfate minerals from Alum Cave Bluff: Microscopy and microanalysis  

SciTech Connect

Microcrystals of secondary sulfate minerals from Alum Cave Bluff, Great Smoky Mountains National Park, were examined by scanning electron microscopy and identified by X-ray fluorescence (XRF) in the SEM. Among the samples the author discovered three new rare-earth sulfates: coskrenite-(Ce), levinsonite-(Y), and zugshunstite-(Ce). Other minerals illustrated in this report include sulfur, tschermigite, gypsum, epsomite, melanterite, halotrichite, apjohnite, jarosite, slavikite, magnesiocopiapite, and diadochite. Additional specimens whose identification is more tentative include pickeringite, aluminite, basaluminite, and botryogen. Alum Cave is a ``Dana locality`` for apjohnite and potash alum, and is the first documented North American occurrence of slavikite.

Lauf, R.J.

1997-07-01

66

Seepage erosion of Arctic coastal bluffs driven by thawing permafrost in Northwest Alaska  

NASA Astrophysics Data System (ADS)

On the forefront of transient landscapes is the Arctic. Air and sea surface temperatures have increased significantly in the last 50 years due to anthropogenic warming, and have been blamed for observed accelerations in coastal erosion rates and the formation of thermokarst features. The controls that permafrost exerts on landforms and sediment transport are largely unknown, but may be elucidated by examining landscape response to permafrost thaw. Using current and historical aerial photos of Northwest Alaska we identified an area of coastal bluffs experiencing increased erosion. What makes this portion of the coast unusual is that erosion is not driven by thermomechanical action from waves, however waves are important in the removal of material from the base of the slump. Instead, retrogressive slump failures - which have seen accelerated growth in the 1900s - initiated the growth of headward cutting alcoves that have now penetrated up to a hundred meters inland. Our field topographic surveys reveal that slumps decrease in slope and increase in circularity with increasing size, suggesting a temporal growth progression toward an asymptotic quasi-circular planform shape. Morphometric scaling relationships suggest that groundwater seepage erosion may be driving alcove growth. Junction angles of alcoves, and the trajectories of headcutting measured from repeat aerial photography, also support a model of ground water competition as the primary mechanism of continued growth. Coastal erosion rates do not depend on solar radiation flux; we propose therefore that seepage water is derived from a vertical lowering of the permafrost table, by thaw resulting from increased ambient air temperatures. Slump features such as those observed here are expected to become more numerous on Arctic coastal and river bluffs in the approaching decades as mean summer air temperatures continue to rise. Thawing of permafrost shows how the Arctic landscape is out of equilibrium, eroding as a result of a geologically-rapid change in boundary conditions.

Phillips, C. B.; Jerolmack, D. J.; Crosby, B. T.

2010-12-01

67

Coastal erosion: Processes, timing and magnitudes at the bluff toe  

USGS Publications Warehouse

Five Lake Erie bluffs (one interlaminated clay and silt, three clay-rich diamicts and one shale) were surveyed at about 2-week intervals and after wind storms for up to 5 years. Erosion of the bluff toes along this low-energy coast occurred during northeast wind storms, which produced surges of up to 1 m and surf-zone waves of up to 1.2 m. Wave impact and/or uprush caused quarrying, which removed most of the toe material, and abrasion. There were from 1 to 23 erosion events/sites, with maximum magnitudes of erosion ranging from 12 to 55 cm/event. Timing and magnitude were linked to erodibility, maximum water level, storm surge, storm duration and beach width. A threshold maximum water level and a threshold surge were necessary for erosion. At these thresholds, the beach was submerged and wave energy was directly expended on the toe. Erosion did not take place when there was shorefast ice or when debris slopes shielded the toe from waves. The originally cohesive toe materials are easily eroded when they weather to an essentially noncohesive state. Wave erosion is the crucial erosion process; removal of material from the toe prevents the development of a stable slope. ?? 1988.

Carter, C. H.; E. , Guy, Jr. , D.

1988-01-01

68

Plasma actuators for bluff body flow control  

NASA Astrophysics Data System (ADS)

The aerodynamic plasma actuators have shown to be efficient flow control devices in various applications. In this study the results of flow control experiments utilizing single dielectric barrier discharge plasma actuators to control flow separation and unsteady vortex shedding from a circular cylinder in cross-flow are reported. This work is motivated by the need to reduce landing gear noise for commercial transport aircraft via an effective streamlining created by the actuators. The experiments are performed at Re D = 20,000...164,000. Circular cylinders in cross-flow are chosen for study since they represent a generic flow geometry that is similar in all essential aspects to a landing gear oleo or strut. The minimization of the unsteady flow separation from the models and associated large-scale wake vorticity by using actuators reduces the radiated aerodynamic noise. Using either steady or unsteady actuation at ReD = 25,000, Karman shedding is totally eliminated, turbulence levels in the wake decrease significantly and near-field sound pressure levels are reduced by 13.3 dB. Unsteady actuation at an excitation frequency of St D = 1 is found to be most effective. The unsteady actuation also has the advantage that total suppression of shedding is achieved for a duty cycle of only 25%. However, since unsteady actuation is associated with an unsteady body force and produces a tone at the actuation frequency, steady actuation is more suitable for noise control applications. Two actuation strategies are used at ReD = 82,000: spanwise and streamwise oriented actuators. Near field microphone measurements in an anechoic wind tunnel and detailed study of the near wake using LDA are presented in the study. Both spanwise and streamwise actuators give nearly the same noise reduction level of 11.2 dB and 14.2 dB, respectively, and similar changes in the wake velocity profiles. The contribution of the actuator induced noise is found to be small compared to the natural shedding noise. A tandem cylinder configuration with the plasma actuation on the upstream cylinder is investigated using surface dynamic pressure sensors. As a result of the plasma actuation, the surface pressure fluctuations on the downstream cylinder are reduced by about two times at the free-stream velocity of 40 m/s (ReD = 164,000). In addition, this study presents the results of a parametric experimental investigation aimed at optimizing the body force produced by single dielectric barrier discharge (SDBD) plasma actuators used for aerodynamic flow control. A primary goal of the study is the improvement of actuator authority for flow control applications at higher Reynolds number than previously possible. The study examines the effects of dielectric material and thickness, applied voltage amplitude and frequency, voltage waveform, exposed electrode geometry, covered electrode width and multiple actuator arrays. The metric used to evaluate the performance of the actuator in each case is the measured actuator-induced thrust which is proportional to the total body force. It is demonstrated that actuators constructed with thick dielectric material of low dielectric constant and operated at low frequency AC voltage produce a body force that is an order of magnitude larger than that obtained by the Kapton-based actuators used in many previous plasma flow control studies. These actuators allow operation at much higher applied voltages without the formation of discrete streamers which lead to body force saturation.

Kozlov, Alexey V.

69

Point vortex model for asymmetric inviscid wakes past bluff bodies  

NASA Astrophysics Data System (ADS)

Wakes past bluff bodies are modeled by means of point vortices standing in equilibrium. The consistency of the adopted model is discussed with respect to the asymptotic model proposed by Batchelor. It is shown that, in general, when symmetry is broken, the wake configuration may be neither closed, as for the Batchelor model, nor open, as for the Kirchhoff model. The proposed model has three degrees of freedom, which reduce to one when the locations of separation are prescribed. A further condition has been established for the closure of the wake which reduces the degrees of freedom to zero as for the asymptotic Batchelor model. The existence of multiple solutions, suggestive for real world phenomena, is discussed.

Elcrat, A.; Ferlauto, M.; Zannetti, L.

2014-06-01

70

PIV measurement of flow around an irregularly rotating disk with bluff bodies  

NASA Astrophysics Data System (ADS)

Flow structure interaction between a rotating disk with bluff bodies and surrounding flow has been evaluated by using a tomographic PIV. To examine the dynamics of disks and the fluid flow simultaneously, fluorescence tracer particles and long pass filters were used. Particles and a marked surface pattern were separated by an image processing. The geometries of the bluff bodies and the disk were then obtained by analyzing the marked pattern. Subsequently, a particle volume was reconstructed by MLOS-SMART. The particle displacement was then calculated by the PIV algorithm from the reconstructed particle volume. Rotating disk dynamics and fluid flow were discussed with variety of bluff body shapes and arrangements. Furthermore, the influence of bluff bodies on the flow field was also considered.

Im, Sunghyuk; Jeon, Young Jin; Sung, Hyung Jin

2011-11-01

71

Omaha-Council Bluffs, NE-IA National Compensation Survey State and Local Government, April 2008.  

National Technical Information Service (NTIS)

This summary provides results of an April 2008 survey of occupational pay in the Omaha-Council Bluffs, NEIA, Metropolitan Statistical Area (MSA). The MSA consists of Cass, Douglas, Sarpy, Saunders, and Washington Counties, NE; and Harrison, Mills, and Pot...

2009-01-01

72

Energy Engineering Analysis Program. Lighting survey of selected buildings, Pine Bluff Arsenal, Pine Bluff, Arkansas. Executive summary. Final report  

SciTech Connect

The Energy Engineering Analysis Program (EEAP), Lighting Survey of Selected Buildings at Pine Bluff, Arsenal, was authorized by the U.S. Army, Little Rock District, Corps of Engineers, under Contract Number DACAO1-94-D-0038. Delivery Order Number 0001, dated 29 September 1994. The objectives of this Delivery Order (D.O.) are as follows: (A) Perform a site survey of 45 buildings selected by Arsenal personnel. The purpose of the site survey is to gather sufficient data to permit evaluation of possible Energy Conservation Opportunities (ECOs). (B) Evaluate possible and new ECOs. (C) Combine ECOs into recommended projects. (D) Prepare a comprehensive report to document the work performed, the results and the recommendations. The final report is to contain funds programming documentation.

NONE

1995-06-01

73

Extreme rates of riverbank erosion of the high bluff formed by the ice-rich syngenetic permafrost (yedoma), Itkillik River, Northern Alaska  

NASA Astrophysics Data System (ADS)

Riverbank erosion in areas underlain by ice-rich permafrost is strongly affected by the processes of thawing of ground ice, which include (1) thermal erosion, and (2) thermal denudation. Thermal erosion is a process of combined thermal and mechanical action of moving water, which results in simultaneous thawing of frozen soil and its removal by water. Thermal erosion can cause block collapse of eroded banks. Thermal denudation is a process of thawing of frozen soils exposed in the bluff due to solar energy and consequent removal of thawed soils by gravity. Studies of riverbank and coastal erosion revealed that the highest rates of erosion are typical of bluffs composed by yedoma (ice- and organic-rich syngenetically frozen silty deposits). Yedoma deposits can be up to 50 m thick, and they contain huge ice wedges up to 10 m wide. Since 2006, we have studied the process of riverbank erosion of the 35 m high exposure of yedoma along the Itkillik River in northern Alaska. Based on five measurements of the areas occupied by wedge ice in panoramic photographs taken in 2006, 2007, 2011, and 2012, the average wedge-ice volume makes 61% of the entire exposed bluff. The total volumetric ground ice content of the Itkillik yedoma, including wedge, segregated and pore ice, is 85%. We detect three main stages of the riverbank erosion for the study site and other similar sites in the areas of ice-rich permafrost: (1) thermal erosion combined with thermal denudation, (2) thermal denudation, and (3) slope stabilization. The first stage includes formation of thermoerosional niches; development of sub-vertical cracks and block-fall collapse of cornices; and thawing and disintegration of blocks of ground ice and frozen soil in the water. All these processes are accompanied by thermal denudation of the exposed bluff. On August 16, 2007, a big portion of the bluff fell down along the crack sub-parallel to the bluff. As a result, the vertical wall more than 65 m long entirely formed by the wedge ice was exposed. This block-fall affected the area of approximately 800 m2, and the volume of frozen soil and ice involved in the block-fall was about 15,000 m3. The riverbank retreat due to thermal erosion and/or thermal denudation, measured from August 2007 to August 2011, varied from less than 10 to almost 100 m. An estimated retreat rate average for the whole 680 m long bluff was 11.4 m/year, but for the most actively eroded central part of the bluff (150 m long) it was 20.3 m/year, ranging from 16 to 24 m/year. During these 4 years, about 650,000 m3 of ice and organic-rich frozen soil were transported to the river from the retreating bank (more than 160,000 m3/year). Analysis of aerial photographs (1948-1979) and satellite images (1974-2013) showed that the riverbank was relatively stable till July 1995, when the Itkillik River changed its course and triggered extremely active thermal erosion. The total retreat of the riverbank in 1995-2010 varied from 180 to 280 m, which means that the average retreat rate for the most actively eroded part of the riverbank reached almost 19 m/year. Such a high rate of riverbank erosion over a long time period has not been reported before for any permafrost regions of Eurasia and North America.

Kanevskiy, M. Z.; Shur, Y.; Fortier, D.; Jorgenson, T.; Stephani, E.; Strauss, J.

2013-12-01

74

Investigations of impingement of aquatic organisms at the Calvert Cliffs Nuclear Power Plant, 1975–1995  

Microsoft Academic Search

The Calvert Cliffs Nuclear Power Plant (CCNPP) in Maryland began commercial operation in 1975. The once-through cooling system pumps Chesapeake Bay water at a maximum rate of 73 m3\\/s (2.4×106 gallons per min) to the condensers, a total equal to 0.7% of the average tidal flow in the area.From 1975 to 1995, impingement monitoring was conducted at CCNPP. The 21-year record

T. G Ringger

2000-01-01

75

Apparatus And Method For Reducing Drag Of A Bluff Body In Ground Effect Using Counter-Rotating Vortex Pairs  

DOEpatents

An aerodynamic base drag reduction apparatus and method for bluff bodies, such as tractor-trailer trucks, utilizing a pair of lift surfaces extending to lift surface tips and located alongside the bluff body such as on opposing left and right side surfaces. In a flowstream substantially parallel to the longitudinal centerline of the bluff body, the pair of lift surfaces generate a pair of counter-rotating trailing vortices which confluence together in the wake of the bluff body in a direction orthogonal to the flowstream. The confluence draws or otherwise turns the flowstream, such as the flowstream passing over a top surface of the bluff body, in and around behind a trailing end of the bluff body to raise the pressure on a base surface at the trailing end and thereby reduce the aerodynamic base drag.

Ortega, Jason M. (Pacifica, CA) [Pacifica, CA; Sabari, Kambiz (Livermore, CA) [Livermore, CA

2005-12-27

76

Apparatus And Method For Reducing Drag Of A Bluff Body In Ground Effect Using Counter-Rotating Vortex Pairs  

DOEpatents

An aerodynamic base drag reduction apparatus and method for bluff bodies, such as tractor-trailer trucks, utilizing a pair of lift surfaces extending to lift surface tips and located alongside the bluff body such as on opposing left and right side surfaces. In a flowstream substantially parallel to the longitudinal centerline of the bluff body, the pair of lift surfaces generate a pair of counter-rotating trailing vortices which confluence together in the wake of the bluff body in a direction orthogonal to the flowstream. The confluence draws or otherwise turns the flowstream, such as the flowstream passing over a top surface of the bluff body, in and around behind a trailing end of the bluff body to raise the pressure on a base surface at the trailing end and thereby reduce the aerodynamic base drag.

Ortega, Jason M. (Pacifica, CA); Salari, Kambiz (Livermore, CA)

2005-08-09

77

Experimental aerodynamic study of a car-type bluff body  

NASA Astrophysics Data System (ADS)

The Ahmed body is used as a reference model for fundamental studies of car-type bluff body aerodynamics, in particular focused on the influence of the rear slant angle on the drag coefficient. The objectives of the present work are to obtain reliable drag coefficient comparable to the literature and to explain, based on the nature of the flow, its variation when changing the rear slant angle from 10° to 40°. The drag coefficients measured in both an open and a closed test sections differ by less than 0.5% which proves the reliability and reproducibility of the results. The sensitivity of the drag coefficient to some parameters such as the model roughness or the oncoming boundary layer and the lack of precise information on these parameters in the literature could explain the difference observed with the Ahmed drag coefficient data. The various types of measurement techniques used in the study underline their complementarity. The combination of particle image velocimetry and oil visualization provides a deeper understanding of the flow behaviour around the Ahmed body and a physical interpretation of the drag coefficient evolution.

Conan, Boris; Anthoine, Jérôme; Planquart, Philippe

2011-05-01

78

Short-Term Bluff Recession Behavior Along Pennsylvania's Great Lakes Coastline, USA  

NASA Astrophysics Data System (ADS)

Coastal bluff retreat is a common problem along the world's unconsolidated coastlines. On the Great Lakes coast of Pennsylvania, Quaternary clay-rich glacial till, paleo-lake plain, and sandy strandplain sequences overlie Devonian bedrock. These Quaternary strata are subject to subaerial and lacustrine erosional processes that cause permanent coastal land loss at spatially variable rates, with the former (runoff, slumping, groundwater focusing, etc) dominating over the latter (wave and current scour, abrasion, etc). Land loss is of concern to environmental agencies because land-use planning should account for spatial and temporal variability in land-loss rates, and because bluff erosion contributes to a temporary degradation in coastal water quality. The goal of this study is to evaluate spatial variability in bluff retreat rates along a 20 km sector of Pennsylvania's short Great Lakes coast. High resolution LiDAR data covering a one-decade time frame (1998-2007) permit bluff-crest mapping on two comparable data sets that captures change within a timeframe similar to CZM planning intervals. Short-term recession data can be more useful, cost-effective, and accurate than long-term analyses that use lower-resolution field measurements, T-sheets, and historical aerial photography. Bluffs along the 20 km coastal study site consist of up to 26 m of unlithified Quaternary sediments overlying a 1-4 m ledge of sub-horizontal Devonian shale and sandstone. Bluff slopes range from 20-90 degrees, beaches are narrow (<8 m wide) or absent, and the bluffs are seasonally shielded by ground-freeze and lake ice. DEMs, hillshades, and slope and contour maps were generated from bare-earth 1998 and 2007 LiDAR data, and checked against 2005 aerial ortho-photography. Maps were analyzed at a scale of 1:120 in ArcGIS and the bluff crest was identified primarily by the visual-break-in-slope method. Rates of bluff retreat derived using DSAS vary from unresolvable to as much as 2.2 m/yr, averaging less than 0.3 m/yr which is consistent with known long-term rates. Very-short term rates of recession can locally exceed 11 m/yr. In general, bluffs retreat relatively linearly where poorly-vegetated glacial till dominates the bluff stratigraphy, while along higher-elevation strandplain-capped bluff sections, rotational earth slumps (<100 m diameter) are well developed. Retreat rates are highest at slump areas and at 1st - 2nd order ravines (100-300 m in length). Both of these settings are associated with focused groundwater discharge from thin lake plain and strandplain aquifers in particular. Other factors do influence bluff retreat temporally, but are not important at the scale of this study.

Foyle, A. M.; Naber, M. D.; Pluta, M. J.

2011-12-01

79

The bluff body stabilized premixed flame in an acoustically resonating tube: combustion CFD and measured pressure field  

Microsoft Academic Search

The resulting limit cycle amplitude and frequency spectrum of a flame placed in a combustor of rectangular cross section is investigated. The partially premixed flame is stabilized on a bluff body placed in the upstream half of the combustor. The bluff body is an equilateral triangular wedge with one of the edges pointing in upstream direction. Acoustically there is an

Jim Kok; Salvatore Matarazzo; Artur Pozarlik

2009-01-01

80

Drag reduction of a bluff body using adaptive control methods  

NASA Astrophysics Data System (ADS)

A classical actuator is used to control the drag exerted on a bluff body at large Reynolds number (Re=20000). The geometry is similar to a backward-facing step whose separation point is modified using a rotating cylinder at the edge. The slow fluctuations of the total drag are directly measured by means of strain gauges. As shown by visualizations, the actuator delays the separation point. The size of the low-pressure region behind the body is decreased and the drag reduced. It is found that the faster the rotation of the cylinder, the lower the drag. In a first study, the goal of the control is for the system to reach a drag consign predetermined by the experimentalist. The control loop is closed with a proportional integral correction. This adaptive method is shown to be efficient and robust in spite of the large fluctuations of the drag. In the second method, the system finds itself its optimal set point. It is defined as the lowest cost of global energy consumption of the system (drag reduction versus energy used by the actuator). For this purpose, an extremum seeking control method is applied in order to deal with the large background noise due to turbulence. It consists in a synchronous detection of the response measured in the drag measurements to a modulation of the actuator. The phase shift and amplitude of the modulation estimate the local gradient of the total energy function. With this gradient estimation, the system goes to the minimum of global power consumption by itself. The system is found to be also robust and reacts successfully to changes of the external mean flow. This experiment attests to the real efficiency of local active control in reducing autonomously the global energy consumption of a system under turbulent flow.

Beaudoin, Jean-François; Cadot, Olivier; Aider, Jean-Luc; Wesfreid, José-Eduardo

2006-08-01

81

Real-time monitoring of bluff stability at Woodway, Washington, USA  

USGS Publications Warehouse

On January 15, 1997, a landslide of approximately 100,000-m3 from a coastal bluff swept five cars of a freight train into Puget Sound at Woodway, Washington, USA, 25 km north of downtown Seattle. The landslide resulted from failure of a sequence of dense sands and hard silts of glacial and non-glacial origin, including the Lawton Clay, a hard, jointed clayey silt that rarely fails in natural slopes. Joints controlled ground-water seepage through the silt and break-up of the landslide mass. During September of 1997, the US Geological Survey began measuring rainfall, ground-water pressures, and slope movement at the bluff where the landslide occurred. Data are collected every 15 minutes and updated hourly on the World-Wide-Web. Pore pressures observed from September 1997 to February 1998 generally were low and pressures near the bluff face, in the upper few meters of the hard clayey silt, increased gradually.

Baum, R. L.; Harp, E. L.; Likos, W. J.; Powers, P. S.; Lahusen, R. G.

1998-01-01

82

Study of motion of flexible eel from the wake of bluff body in a cross flow  

NASA Astrophysics Data System (ADS)

In this research, interaction between eel and vortex shedding behind a bluff body is studied numerically, aiming to optimize the oscillation of eels by coupling with the altering vertices. Effects of different factors such as length of eel, width of bluff body and flow speed on vibration of eels are also aimed to be investigated. A 2-dimensional Fluid-Structure Interaction Model that simulates the motion of eel under vortex shedding behind a bluff body is constructed by using the computational fluid dynamics (CFD) software - COMSOL Multiphysics. Simulations based on laminar flow regime are performed and the results show that undulating motion of the eel is successfully modeled with the Fluid-Structure Interaction Model along with Arbitrary Lagrangian-Eulerian (ALE) method.

Sin, Vai Kuong; Deng, Wen Yue; Xiao, Wei Hang

2012-09-01

83

National Assessment of Historical Shoreline Change: A Pilot Study of Historical Coastal Bluff Retreat in the Great Lakes, Erie, Pennsylvania  

USGS Publications Warehouse

Coastal bluff retreat is a chronic problem along many high-relief coastlines in the United States. As coastal populations continue to grow and community infrastructures are threatened by erosion, there is increased demand for accurate information regard-ing trends and rates of bluff retreat. There is also a need for a comprehensive analysis that is consistent from one coastal region to another. To address these national needs, the U.S. Geological Survey (USGS), as part of the National Assessment of Coastal Change Hazards Project, conducted a pilot study of bluff retreat along the Lake Erie, Pa., coastline to assess the feasibility of undertaking a larger, multi-state analysis in the Great Lakes region. This report provides an overview of the pilot-study location and bluff geomorphology, the data sources and methodology, results of the analysis, and a discussion of the feasibility of undertaking a similar analysis along eroding bluffs in other Great Lakes states. This pilot study is part of an ongoing effort by the USGS to provide a comprehensive analysis of historical shoreline change and cliff and bluff retreat along open-ocean coastlines of the conterminous United States and parts of Hawaii, Alaska, and the Great Lakes. One purpose of the work is to develop standard, repeatable methods for mapping and analyzing coastal change so that systematic and consistent periodic updates of coastal erosion can be made nationally. Bluff-retreat evaluations are conducted by comparing the location of a historical bluff edge digitized from aerial photographs with those of recent bluff edges interpreted from both aerial photographs and lidar topographic surveys. The historical bluff edge is from 1938, whereas the more recent bluff edges are from 1998 and 2006 lidar data. Long-term (68-year) rates of retreat are calculated using the available bluff-edge data. The rates of retreat presented in this report represent conditions from the 1930s to 1998/2006, and are not intended for predicting future bluff-edge positions or rates of retreat. The report presents bluff-retreat rates for 32 km of a 60-km stretch along the Lake Erie, Pa., coastline. Data are discontinuous due to gaps in source data and lack of continuous bluffs. The average rate of coastal bluff retreat for the Lake Erie, Pa., bluffs was -0.3 +- 0.1 m/yr (retreat rates are presented as negative numbers in this report), based on rates averaged from 1,595 individual transects. Retreat rates generally were lowest where bedrock outcrops are exposed as the basal unit in the bluff. The highest rates are associated with anthropogenic activities, including jetties that trap littoral sediment, depleting a source of material for the natural replenishment of protective beaches downcoast, and extensive irrigation of farmlands on the tops of the bluffs, which can destabilize bluffs by enhancing ground-water outflow.

Hapke, Cheryl J.; Malone, Shamus; Kratzmann, Meredith

2009-01-01

84

Wall effect on fluid-structure interactions of a tethered bluff body  

NASA Astrophysics Data System (ADS)

Wind tunnel experiments have shown an unexplained amplification of the free motion of a tethered bluff body in a small wind tunnel relative to that in a large wind tunnel. The influence of wall proximity on fluid-structure interaction is explored using a compound pendulum motion in the plane orthogonal to a steady freestream with a doublet model for aerodynamic forces. Wall proximity amplifies a purely symmetric single degree of freedom oscillation with the addition of an out-of-phase force. The success of this simple level of simulation enables progress to develop metrics for unsteady wall interference in dynamic testing of tethered bluff bodies.

Sharma, Sumant; Raghav, Vrishank; Komerath, Narayanan; Smith, Marilyn

2013-11-01

85

Attenuated basin?margin sequence stratigraphy of the Palaeoproterozoic Calvert and Isa Superbasins: The Fickling Group, southern Murphy Inlier, Queensland  

Microsoft Academic Search

Sedimentary rocks of the Palaeoproterozoic Calvert and Isa Superbasins are exposed across a large area of northern Australia. Despite the extent of the exposures there is little to indicate the nature of the basin margins as most outcrop boundaries are structurally or erosionally defined, or the margins, where preserved, are concealed beneath younger basins. The Murphy Inlier, which forms the

B. E. Bradshaw; J. F. Lindsay; A. A. Krassay; A. T. Wells

2000-01-01

86

Superfund Record of Decision (EPA Region 4): Airco, Calvert City, Marshall County, Kentucky (First Remedial Action), June 1988.  

National Technical Information Service (NTIS)

The Airco site is a 2.7-acre industrial waste landfill located outside the zoned area of Calvert City, Marshall County, Kentucky. By 1971, 18,000 tons of caustics, acids, VOCs, zinc and mercuric acetate, and mercuric chloride reportedly were disposed at t...

1988-01-01

87

Distributed forcing of the flow past a blunt-based axisymmetric bluff body  

NASA Astrophysics Data System (ADS)

In this paper, we address the influence of a blowing-/suction-type distributed forcing on the flow past a blunt-based axisymmetric bluff body by means of direct numerical simulations. The forcing is applied via consecutive blowing and suction slots azimuthally distributed along the trailing edge of the bluff body. We examine the impact of the forcing wavelength, amplitude and waveform on the drag experienced by the bluff body and on the occurrence of the reflectional symmetry preserving and reflectional symmetry breaking wake modes, for Reynolds numbers 800 and 1,000. We show that forcing the flow at wavelengths inherent to the unforced flow drastically damps drag oscillations associated with the vortex shedding and vorticity bursts, up to their complete suppression. The overall parameter analysis suggests that this damping results from the surplus of streamwise vorticity provided by the forcing that tends to stabilize the ternary vorticity lobes observed at the aft part of the bluff body. In addition, conversely to a blowing-type or suction-type forcing, the blowing-/suction-type forcing involves strong nonlinear interactions between locally decelerated and accelerated regions, severely affecting both the mean drag and the frequencies representative of the vortex shedding and vorticity bursts.

Jardin, Thierry; Bury, Yannick

2013-10-01

88

Omaha-Council Bluffs Metropolitan Area Comprehensive Plan. Phase II. Housing Study and Economic Base Survey.  

National Technical Information Service (NTIS)

Phase Two of the areawide comprehensive plan for the Omaha-Council Bluffs three-county SMSA consists of a housing study and economic base survey. The housing study presents a current housing inventory for the SMSA, housing condition analysis, and an analy...

1970-01-01

89

Distributed forcing of the flow past a blunt-based axisymmetric bluff body  

NASA Astrophysics Data System (ADS)

In this paper, we address the influence of a blowing-/suction-type distributed forcing on the flow past a blunt-based axisymmetric bluff body by means of direct numerical simulations. The forcing is applied via consecutive blowing and suction slots azimuthally distributed along the trailing edge of the bluff body. We examine the impact of the forcing wavelength, amplitude and waveform on the drag experienced by the bluff body and on the occurrence of the reflectional symmetry preserving and reflectional symmetry breaking wake modes, for Reynolds numbers 800 and 1,000. We show that forcing the flow at wavelengths inherent to the unforced flow drastically damps drag oscillations associated with the vortex shedding and vorticity bursts, up to their complete suppression. The overall parameter analysis suggests that this damping results from the surplus of streamwise vorticity provided by the forcing that tends to stabilize the ternary vorticity lobes observed at the aft part of the bluff body. In addition, conversely to a blowing-type or suction-type forcing, the blowing-/suction-type forcing involves strong nonlinear interactions between locally decelerated and accelerated regions, severely affecting both the mean drag and the frequencies representative of the vortex shedding and vorticity bursts.

Jardin, Thierry; Bury, Yannick

2014-06-01

90

The effects of turbulence and unsteadiness on vortex shedding from sharp-edged bluff bodies  

Microsoft Academic Search

Motivated by a desire to evaluate vortex shedding flow meters for measuring velocity in unsteady turbulent flow applications, the objective of the work was to study the effects of flow disturbances on vortex shedding from sharp-edged bluff bodies. In particular, the combined effects of turbulence and unsteadiness were examined, as well as their separate effects using controlled wind tunnel tests.

M. C. Wolochuk; M. W. Plesniak; J. E. Braun

1996-01-01

91

National Compensation Survey: State and Local Government, Omaha-Council Bluffs, NE-IA, April 2009.  

National Technical Information Service (NTIS)

This summary provides results of an April 2009 survey of occupational pay in the Omaha-Council Bluffs, NE-IA, Metropolitan Statistical Area (MSA). The MSA consists of Cass, Douglas, Sarpy, Saunders, and Washington Counties, NE; and Harrison, Mills, and Po...

2010-01-01

92

Comprehensive Housing Market Analysis: Omaha-Council Bluffs, Nebraska-Iowa As of October 1, 2009.  

National Technical Information Service (NTIS)

The Omaha-Council Bluffs, Nebraska-Iowa Housing Market Area (HMA) is located on the Iowa-Nebraska border, spanning the Missouri River. The HMA consists of Cass, Douglas, Sarpy, Saunders, and Washington Counties in Nebraska and Harrison, Mills, and Pottawa...

2009-01-01

93

Mechanical Response of Dry Reid-Bedford Model Sand and Saturated Misers Bluff Sand.  

National Technical Information Service (NTIS)

This report presents a collection of data from laboratory mechanical property tests on dry Reid-Bedford Model sand and saturated MISERS BLUFF sand which were conducted by the US Army Engineer Waterways Experiment Station in support of a variety of project...

B. R. Phillips

1986-01-01

94

Effects of Acoustic Excitation on Bluff-body Stabilized Premixed Reacting Flows  

Microsoft Academic Search

Bluff body stabilized flames are used in numerous combustion applications to enable stable burning at high speeds. These confined flames are susceptible to acoustic excitation arising due to the confinement that can lead to thermoacoustic instabilities which are detrimental to the operability of the combustion device. In this study, we formulate a computational approach for the simulation of this phenomenon

Vaidyanathan Sankaran; Robert Erickson; Marios Soteriou

2009-01-01

95

Drag reduction on a bluff body at yaw angles to 30 degrees  

NASA Technical Reports Server (NTRS)

The base separation alleviation and drag reduction effectiveness of transverse rectangular grooves and longitudinal v-grooves in the afterbody shoulder region of a bluff body is investigated for body yaw angles of 0-30 deg. The grooves are found to be beneficial in reducing both freestream and axial drag coefficients at yaw angles of up to 25 deg.

Howard, Floyd G.; Goodman, Wesley L.

1987-01-01

96

Results of the Misers Bluff II Aircraft Dust Particle Sampling Experiments.  

National Technical Information Service (NTIS)

Dust clouds generated from two high explosive detonations of 100 and 600 tons (TNT equivalent) in the Misers Bluff II Experiment were sampled with an instrumented aircraft to determine the size and number density of particulates from 0.1 to 10,000 microme...

R. G. Knollenberg

1979-01-01

97

Council Bluff Reservoir, Potosi Ranger District, Clark National Forest, Iron County, Missouri.  

National Technical Information Service (NTIS)

The Council Bluff Reservoir Project in Clark National Forest proposes to build a 100 ft dam containing a 440 acre lake. The project is located at mile 134.5 on the Big River in Iron County, Missouri. Approximately two miles of stream and related ecosystem...

1971-01-01

98

Large eddy simulation of forced ignition of an annular bluff-body burner  

Microsoft Academic Search

The optimization of the ignition process is a crucial issue in the design of many combustion systems. Large eddy simulation (LES) of a conical shaped bluff-body turbulent nonpremixed burner has been performed to study the impact of spark location on ignition success. This burner was experimentally investigated by Ahmed et al. [Combust. Flame 151 (2007) 366–385]. The present work focuses

V. Subramanian; P. Domingo; L. Vervisch

2010-01-01

99

Large eddy simulation of forced ignition of an annular bluff-body burner  

Microsoft Academic Search

The optimization of the ignition process is a crucial issue in the design of many combustion systems. Large eddy simulation (LES) of a conical shaped bluff-body turbulent nonpremixed burner has been performed to study the impact of spark location on ignition success. This burner was experimentally investigated by Ahmed et al. [Combust. Flame 151 (2007) 366-385]. The present work focuses

V. Subramanian; P. Domingo; L. Vervisch

2010-01-01

100

Maastrichtian ammonites chiefly from the Prairie Bluff Chalk in Alabama and Mississippi  

USGS Publications Warehouse

The Prairie Bluff Chalk of Alabama and Mississippi yields a diverse ammonite fauna of Maastrichtian age. Twenty-eight species, of which three are new, are recorded. The bulk of the fauna can be referred to a Discoscaphites conradi assemblage zone, but some elements in the fauna are significantly older. -Authors

Cobban, W. A.; Kennedy, W. J.

1995-01-01

101

Wave–mean flow interaction in an MHD wake behind bluff body  

Microsoft Academic Search

Experimental studies of the effect of constant magnetic field on the process of mean velocity profile stabilization in a wake behind a bluff body are described. To interpret the obtained results, a theoretical model is proposed explaining the scheme of wave-mean flow interaction. We assume that the stabilization process is based on the injection of energy of respective turbulent modes

H. Branover; A. Eidelman; E. Golbraikh; A. Kapusta; B. Mikhailovich

2004-01-01

102

A new giant python from the Pliocene Bluff Downs Local Fauna of northeastern Queensland  

Microsoft Academic Search

Liasis dubudingala n. sp., described on the basis of isolated vertebrae from the Early Pliocene Bluff Downs Local Fauna, is the largest snake known from Australia. Dependance of vertebral proportions on intracolumnar position indicates that the fossil taxon can be excluded from the Morelia\\/Python clade. High neural spines suggest possible affinity with Liasis olivacea, whereas a posterior dentary fragment with

John D. Scanlon; Brian S. Mackness

2001-01-01

103

Volcanic and Glacial Geology of the Miocene Minna Bluff Volcanic Complex, Antarctica  

NASA Astrophysics Data System (ADS)

Minna Bluff is a 45-km long, 5-km wide Miocene alkaline volcanic peninsula that extends SE into the Ross Ice Shelf from the Mt. Discovery stratovolcano. Minna Bluff is a significant topographic barrier that has effectively blocked the Ross Ice Shelf and former grounded marine ice sheets from flowing southward into McMurdo Sound. In the late Miocene, Minna Bluff likely was a terminal pinning point for the Ross Ice Shelf. The peninsula is composed of many overlapping volcanic centers and is intensely eroded along south facing McIntosh Cliffs and east-facing Minna Hook cliffs, providing well-exposed 1000-m-thick stratigraphic sections. Mapping and sampling during 2006-7 and 2007-8 field seasons provide records of pulsating volcanism, glacial erosion, and glacial deposition in the Ross Embayment during the construction of Minna Bluff between 12 and 8 Ma. The volcanic stratigraphy along the Minna Hook cliffs contrasts markedly with the stratigraphy of McIntosh Cliffs. Stratigraphic alternations between subaerial lava and breccia and thin subaqueous pillow lava and hyaloclastite are concentrated in the lower parts of the Minna Hook sections. These alternations are interpreted as representing syneruptive interactions between lava flows and ephemeral local ice. The lower parts of the Minna Hook sequences also include widespread, undulating unconformities mantled by glacial and fluvial sediments. These unconformities and associated sediment record at least two broader scale grounded ice sheet events which are tightly constrained by 40Ar/39Ar ages (see Fargo et al, this volume). Upper parts of the Minna Hook sections resemble the McIntosh Cliff sequences, in being dominated by subaerial lava, breccia, and vent complexes and lacking subaqueous volcanic lithofacies, sedimentary rocks, and unconformities. More than 50 partially eroded, subaerially erupted domes and cinder cones were mapped and are preserved on the bluff top. An explosively erupted hydrovolcanic deposit forms a small nunatak in the saddle between Mt. Discovery and Minna Bluff. Minna Bluff rocks form a basanite to phonolite alkaline volcanic lineage. Phonolite and tephriphonolite domes are common in the lower third of the Minna Hook cliff sections and along the top of the Minna Hook, basanite to phonotephrite lavas are the dominant lithologies overall. Ongoing geochronology, geochemistry, and lithofacies analysis of more than 500 samples will provide a detailed glacial and volcanic record of this important region.

Wilch, T. I.; McIntosh, W. C.; Panter, K. S.; Dunbar, N. W.; Smellie, J. L.; Fargo, A.; Scanlan, M.; Zimmerer, M. J.; Ross, J.; Bosket, M. E.

2008-12-01

104

Spatial and Temporal Distribution of Sacramento Pikeminnow and Striped Bass at the Red Bluff Diversion Complex, Including the Research Pumping Plant, Sacramento, California: January 1997 to August 1998. Red Bluff Research Pumping Plant Report Series. Volume 10.  

National Technical Information Service (NTIS)

Red Bluff Research Pumping Plant (RPP) is being evaluated by the Bureau of Reclamation (Reclamation) to determine if pumping water through Archimedes or internal helical pumps is a viable method for meeting water delivery requirements to the Tehama-Colusa...

2003-01-01

105

Plasma Cortisol Levels and Behavioral Stress Responses of Juvenile Chinook Salmon Passed Through Archimedes Lifts and an Internal Helical Pump at Red Bluff Research Pumping Plant, Sacramento River, California. Red Bluff Research Pumping Plant Report Series. Volume 8.  

National Technical Information Service (NTIS)

We examined plasma cortisol levels and behavioral stress-responses of juvenile chinook salmon (Oncorhynchus tshawyacha) passed through the Archimedes lifts and internal helical pump at Red Bluff Research Pumping Plant (RBRPP). If juvenile chinook salmon a...

2000-01-01

106

Laboratory measurements of upwelled radiance and reflectance spectra of Calvert, Ball, Jordan, and Feldspar soil sediments  

NASA Technical Reports Server (NTRS)

An effort to investigate the potential of remote sensing for monitoring nonpoint source pollution was conducted. Spectral reflectance characteristics for four types of soil sediments were measured for mixture concentrations between 4 and 173 ppm. For measurements at a spectral resolution of 32 mm, the spectral reflectances of Calvert, Ball, Jordan, and Feldspar soil sediments were distinctly different over the wavelength range from 400 to 980 nm at each concentration tested. At high concentrations, spectral differences between the various sediments could be detected by measurements with a spectral resolution of 160 nm. At a low concentration, only small differences were observed between the various sediments when measurements were made with 160 nm spectral resolution. Radiance levels generally varied in a nonlinear manner with sediment concentration; linearity occurred in special cases, depending on sediment type, concentration range, and wavelength.

Whitlock, C. H.; Usry, J. W.; Witte, W. G.; Gurganus, E. A.

1977-01-01

107

Environmental Assessment of the Gering-Stegall 115-kV Transmission Line Consolidation Project, Scotts Bluff County, Nebraska.  

National Technical Information Service (NTIS)

The Department of Energy (DOE), Western Area Power Administration (Western) proposes to consolidate segments of two transmission lines near the Gering Substation in Gering, Nebraska. The transmission lines are both located in Scotts Bluff County, Nebraska...

1995-01-01

108

National Assessment of Historical Shoreline Change: A Pilot Study of Historical Coastal Bluff Retreat in the Great Lakes, Erie, Pennsylvania.  

National Technical Information Service (NTIS)

Coastal bluff retreat is a chronic problem along many high-relief coastlines in the United States. As coastal populations continue to grow and community infrastructures are threatened by erosion, there is increased demand for accurate information regardin...

C. J. Hapke M. Kratzmann S. Malone

2009-01-01

109

Flow-Induced Vibrations of Three-Dimensional Bluff Bodies in a Cross Flow, an Annotated Bibliography.  

National Technical Information Service (NTIS)

Literature on flow-induced vibrations of spheres, spheroids, short cylinders and other three-dimensional bluff bodies has been reviewed. Information considered pertinent to the analysis and design of large submerged cable structures subjected to currents ...

R. D. Rail B. E. Hafen D. J. Meggitt

1977-01-01

110

Confinement Effects on Flows Past an In-Duct Rectangular Bluff Body with Semi-Circular Leading Edge  

NASA Astrophysics Data System (ADS)

This paper reports a numerical study of a two-dimensional time-dependent viscous flow past a rectangular bluff body with a Reynolds number Re = 6 073 based on bluff body height installed in a flow duct. The leading edge of the bluff body takes a semi-circular profile. The governing equations of the flow are solved with large-eddy simulation (LES) using a commercial computational fluid dynamics software FLUENT. The focus of the present study is to explore the effects of the ratio of the height of the bluff body H and the separation D between the bluff body and the duct wall surface. The numerical simulations are validated with the results obtained from a separate wind-tunnel experiment. Numerical simulations with various D/H are carried out. The numerical results show that the mean and instantaneous flow quantities are strongly dependent on the ratio D/H. The suppression effects of vortex shedding by the neighboring duct wall are highlighted by comparing the unsteady flow structure topology, dominant Strouhal number, lift and drag forces, etc. The mechanism for the suppression of vortex shedding suppression and its variation with D/H are analyzed, and its relevance to generation of flow inducing noise by a bluff body in a flow duct is discussed.

Yu, K. F.; Leung, R. C. K.; Lu, Z. B.; Cheng, L.; Chan, H. Y. H.

2011-09-01

111

Large eddy simulation of flows around ground vehicles and other bluff bodies.  

PubMed

A brief review of large eddy simulation (LES) applications for different bluff-body flows performed by the author and his co-workers is presented. Examples of flows range from simple cube flows characterized by sharp edge separation over a three-dimensional hill where LES relies on good near-wall resolution, to complex flows of a tall, finite cylinder that contains several flow regimes that cause different challenges to LES. The second part of the paper is devoted to flows around ground vehicles at moderate Reynolds numbers. Although the present review proves the applicability of LES for various bluff-body flows, an increase of the Reynolds number towards the operational speeds of ground vehicles requires accurate near-wall modelling for a successful LES. PMID:19531512

Krajnovic, Sinisa

2009-07-28

112

Large eddy simulation of flows after a bluff body: Coherent structures and mixing properties  

NASA Astrophysics Data System (ADS)

This paper performs large eddy simulations (LES) to investigate coherent structures in the flows after the Sydney bluff-body burner, a circular bluff body with an orifice at its center. The simulations are validated by comparison to existing experimental data. The Q function method is used to visualize the instantaneous vortex structures. Three kinds of structures are found, a cylindrical shell structure in the outer shear layer, a ring structure and some hairpin-like structures in the inner shear layer. An eduction scheme is employed to investigate the coherent structures in this flow. Some large streaks constituted by counter-rotating vortices are found in the outer shear layer and some well-organized strong structures are found in the inner shear layer. Finally, the influences of coherent structures on scalar mixing are studied and it is shown that scalar in the recirculation region is transported outward by coherent structures.

Zhang, Pei; Han, Chao; Chen, Yiliang

2013-10-01

113

Aerodynamic drag reduction apparatus for gap-divided bluff bodies such as tractor-trailers  

DOEpatents

An apparatus for reducing the aerodynamic drag of a bluff-bodied vehicle such as a tractor-trailer in a flowstream, the bluff-bodied vehicle of a type having a leading portion, a trailing portion connected to the leading portion, and a gap between the leading and trailing portions defining a recirculation zone. The apparatus is preferably a baffle assembly, such as a vertical panel, adapted to span a width of the gap between the leading and trailing portions so as to impede cross-flow through the gap, with the span of the baffle assembly automatically adjusting for variations in the gap width when the leading and trailing portions pivot relative to each other.

Ortega, Jason M. (Pacifica, CA); Salari, Kambiz (Livermore, CA)

2006-07-11

114

Vortex shedding from bluff bodies in a shear flow - A review  

Microsoft Academic Search

This paper examines the effects of velocity shear on vortex shedding from stationary and vibrating bluff bodies. Experiments with circular cylindrical bodies and other cross sections such as D-section cylinders and rectangular cylinders, which were limited to conditions with length\\/diameter ratios less than L\\/D = 15 to 20, have shown that the spanwise cellular structure of the vortex shedding is

O. M. Griffin

1985-01-01

115

Modeling erosion of ice-rich permafrost bluffs along the Alaskan Beaufort Sea coast  

NASA Astrophysics Data System (ADS)

The Arctic climate is changing, inducing accelerating retreat of ice-rich permafrost coastal bluffs. Along Alaska's Beaufort Sea coast, erosion rates have increased roughly threefold from 6.8 to 19 m yr-1 since 1955 while the sea ice-free season has increased roughly twofold from 45 to 100 days since 1979. We develop a numerical model of bluff retreat to assess the relative roles of the length of sea ice-free season, sea level, water temperature, nearshore wavefield, and permafrost temperature in controlling erosion rates in this setting. The model captures the processes of erosion observed in short-term monitoring experiments along the Beaufort Sea coast, including evolution of melt notches, topple of ice wedge-bounded blocks, and degradation of these blocks. Model results agree with time-lapse imagery of bluff evolution and time series of ocean-based instrumentation. Erosion is highly episodic with 40% of erosion is accomplished during less than 5% of the sea ice-free season. Among the formulations of the submarine erosion rate we assessed, we advocate those that employ both water temperature and nearshore wavefield. As high water levels are a prerequisite for erosion, any future changes that increase the frequency with which water levels exceed the base of the bluffs will increase rates of coastal erosion. The certain increases in sea level and potential changes in storminess will both contribute to this effect. As water temperature also influences erosion rates, any further expansion of the sea ice-free season into the midsummer period of greatest insolation is likely to result in an additional increase in coastal retreat rates.

Barnhart, Katherine R.; Anderson, Robert S.; Overeem, Irina; Wobus, Cameron; Clow, Gary D.; Urban, Frank E.

2014-05-01

116

The numerical study of separated laminar and turbulent flows past bluff bodies of arbitrary shape  

Microsoft Academic Search

The flow motion and heat transfer of separated laminar and turbulent flows past an arbitrarily shaped bluff body is numerically investigated. The turbulent flows are characterized using time-averaged Reynolds equations and a two-equation. The computational approach uses a body-fitted coordinate system to account for irregularities in the flow domain. The modified strongly implicit (MSI) iteration method is applied to solve

Shih-Shan Wei; Selcuk I. Guceri

1987-01-01

117

Driftwood dropstones in mid-Miocene shallow marine strata (Calvert Cliffs, Maryland Coastal Plain): An erratic lithic pebble des not necessarily a cold paleoclimate make  

NASA Astrophysics Data System (ADS)

Erratic lithic pebbles recovered from marine sediments are routinely identified as Ice-Rafted Debris (IRD), transported by icebergs, sea ice, or river ice discharged into the sea. We suggest this is not always the transport mechanism--especially when other paleoclimatologic proxies indicate relatively warm climates and extensive forests in the pebble provenance regions. Rivers could transport significant amounts of pebbbles as driftwood dropstones, trapped in the roots of trees and later uprooted in floods and carried out to sea. To illustrate a likely example of Tree-Rafted Detritus (TRD), we analyzed a collection of lithic erratics collected from three beds in eroding (5-10 cm/a) mid-Miocene (Serravalian)shallow marine deposits (upper Calvert Formation,Chesapeake Bay, southern Maryland), which predate the ca. 13.9 Ma global cooling and expansion of the East Antarctic Ice Sheet. The ca. 220 specimens (1-10 cm in diameter) are extremely variable in lithology and degree of roundness. The great majority are evidently of Piedmont provenance and were probably rafted ca. 120 km to the collection site from the paleo-mouth of the Susquehanna River, floated out to sea and carried south by the Miocene Coastal Current. River ice can probably be ruled out as the transport mechanism, given the prevailing warm temperate to subtropical climates. Common carbonized wood fragments (typically 2 x 10 cm in outcrop dimensions) in the same strata containing the erratics support driftwood transport. The lithic erratics may serve as independent tracers for terrestrial vertebrate fossils, transported into the Calvert Sea (Atlantic Ocean) by the 'float and bloat' mechanism.(Allowance has to be made for ca. 20 m/Ma post-middle Miocene source region denudation). However,only 3% of the clasts (mostly quartz diorite gneiss)could be readily related to a specific outcrop--the Port Deposit Gneiss near the modern mouth of the Susquehanna River. We suggest that driftwood transport be considered as a possibly significant alternative source of lithic erratics found in e.g. Middle Eocene Arctic Basin sediments--especially given that this basin was largely enclosed and fed by large rivers draining vast forests.

Vogt, P. R.; Parrish, M.

2009-12-01

118

Drag and lift reduction of a 3D bluff-body using active vortex generators  

NASA Astrophysics Data System (ADS)

In this study, a passive flow control experiment on a 3D bluff-body using vortex generators (VGs) is presented. The bluff-body is a modified Ahmed body (Ahmed in J Fluids Eng 105:429-434 1983) with a curved rear part, instead of a slanted one, so that the location of the flow separation is no longer forced by the geometry. The influence of a line of non-conventional trapezoïdal VGs on the aerodynamic forces (drag and lift) induced on the bluff-body is investigated. The high sensitivity to many geometric (angle between the trapezoïdal element and the wall, spanwise spacing between the VGs, longitudinal location on the curved surface) and physical (freestream velocity) parameters is clearly demonstrated. The maximum drag reduction is -12%, while the maximum global lift reduction can reach more than -60%, with a strong dependency on the freestream velocity. For some configurations, the lift on the rear axle of the model can be inverted (-104%). It is also shown that the VGs are still efficient even downstream of the natural separation line. Finally, a dynamic parameter is chosen and a new set-up with motorized vortex generators is proposed. Thanks to this active device. The optimal configurations depending on two parameters are found more easily, and a significant drag and lift reduction (up to -14% drag reduction) can be reached for different freestream velocities. These results are then analyzed through wall pressure and velocity measurements in the near-wake of the bluff-body with and without control. It appears that the largest drag and lift reduction is clearly associated to a strong increase of the size of the recirculation bubble over the rear slant. Investigation of the velocity field in a cross-section downstream the model reveals that, in the same time, the intensity of the longitudinal trailing vortices is strongly reduced, suggesting that the drag reduction is due to the breakdown of the balance between the separation bubble and the longitudinal vortices. It demonstrates that for low aspect ratio 3D bluff-bodies, like road vehicles, the flow control strategy is much different from the one used on airfoils: an early separation of the boundary layer can lead to a significant drag reduction if the circulation of the trailing vortices is reduced.

Aider, Jean-Luc; Beaudoin, Jean-François; Wesfreid, José Eduardo

2010-05-01

119

Feedback shear layer control for bluff body drag reduction  

Microsoft Academic Search

Drag reduction strategies for the turbulent flow around a D-shaped body are examined experimentally and theoretically. A reduced-order vortex model describes the inter- action between the shear layer and wake dynamics and guides a path to an efficient feedback control design. The derived feedback controller desynchronizes shear-layer and wake dynamics, thus postponing vortex formation. This actuation is tested in a

GILEAD T ADMOR

2008-01-01

120

Energy Engineering Analysis Program. Lighting survey of selected buildings, Pine Bluff Arsenal, Pine Bluff, Arkansas. Volume I, narrative report. Final report  

SciTech Connect

The Energy Engineering Analysis Program (EEAP), Lighting Survey of Selected Buildings at Pine Bluff, Arsenal, was authorized by the U.S. Army, Little Rock District, Corps of Engineers, under Contract Number DACAOl-94-D-0038. Delivery Order Number 0001, dated 29 September 1994. Objectives The objectives of this Delivery Order (D.O.), as shown in the Detailed Scope of Work (Appendix A, Volume II) are as follows: (A) Perform a site survey of 45 buildings selected by Arsenal personnel. The purpose of the site survey is to gather sufficient data to permit evaluation of possible Energy Conservation Opportunities (ECOs). (B) Evaluate possible and new ECOs. (C) Combine ECOs into recommended projects. (D) Prepare a comprehensive report to document the work performed, the results and the recommendations. The final report is to contain funds programming documentation.

NONE

1995-06-01

121

Water-Quality and Ground-Water Hydrology of the Columbia/Eagle Bluffs Wetland Complex, Columbia, Missouri, 1992-99.  

National Technical Information Service (NTIS)

In an effort to restore riverine wetlands along the Missouri River, the Missouri Department of Conservation constructed the 2,700-acre Eagle Bluffs Conservation Area. The primary water source for managing 1,200 wetland acres on the Eagle Bluffs Conservati...

J. M. Richards

2002-01-01

122

Finite Elemente Large Eddy Simulation of Flows Past Bluff Bodies with Active Flow Control  

NASA Astrophysics Data System (ADS)

A semi-implicit fractional step finite element large eddy simulation (LES) method for unstructured grids has been developed. The turbulence models implemented into the code are the constant and dynamic coefficient Smagorinsky models as well as the stress similarity model of Liu et al. The technique was applied to analyzing the effects of active flow control by massless oscillatory blowing from a slot. Especially flows past bluff bodies (e.g. circular cylinder; download on a tiltrotor wing) were investigated. Numerical optimization was used to find optimum parameters such as slot location, slot angle, frequency, etc. The numerical results are compared with experimental PIV (Particle Image Velocimetry) and pressure measurements.

Kjellgren, Per; Taubert, Lutz; Wygnanski, I. J.

2001-11-01

123

Power production locality of bluff body flutter mills using fully coupled 2D direct numerical simulation  

NASA Astrophysics Data System (ADS)

Two-dimensional, fully coupled direct numerical simulations (DNS) are conducted to examine the local energy dynamics of a flexible cantilevered plate in the wake of a two-dimensional circular cylinder. The motion of the cantilevered plate is described using a finite element formulation and a fully compressible, finite volume Navier Stokes solver is used to compute the flow field. A sharp interface level set method is employed in conjunction with a ghost fluid method to describe the immersed boundaries of the bluff body and flexible plate. DNS is first conducted to validate the numerical methodology and compared with previous studies of flexible cantilevered plates and flow over bluff bodies; excellent agreement with previous results is observed. A newly defined power production/loss geometry metric is introduced based on surface curvature and plate velocity. The metric is found to be useful for determining which sections of the plate will produce energy based on curvature and deflection rate. Scatter plots and probability measures are presented showing a high correlation between the direction of energy transfer (i.e., to or from the plate) and the sign of the newly defined curvature-deflection-rate metric. The findings from this study suggest that a simple local geometry/kinematic based metric can be devised to aid in the development and design of flexible wind energy harvesting flutter mills.

Kuhl, J. M.; Desjardin, P. E.

2012-01-01

124

Vortex shedding from bluff bodies in a shear flow - A review  

NASA Astrophysics Data System (ADS)

This paper examines the effects of velocity shear on vortex shedding from stationary and vibrating bluff bodies. Experiments with circular cylindrical bodies and other cross sections such as D-section cylinders and rectangular cylinders, which were limited to conditions with length/diameter ratios less than L/D = 15 to 20, have shown that the spanwise cellular structure of the vortex shedding is dependent upon end conditions. The vortex shedding also is influenced strongly by the shear flow steepness parameter which is based upon the incident flow velocity gradient. Experimental evidence is available to show that moderate shear levels of practical importance (a shear flow steepness parameter ranging from 0.01 to 0.015) do not appreciably decrease the probability of occurrence of vortex-excited oscillations for flexible structures and cables. The effects of incident shear on vortex shedding from stationary and vibrating bluff structures in both fluid media should be investigated further for long cylinders which have minimal end boundary effects. More definitive bounds for and details of this fluid-structure interaction are needed for applications in the wind engineering design of buildings and structures, and in the design of marine structures and cable systems.

Griffin, O. M.

1985-09-01

125

Characteristics of suspended sediment in the San Juan River near Bluff, Utah  

USGS Publications Warehouse

Fluvial-sediment data were collected for the San Juan River near Bluff beginning in 1914 and terminating in 1980. A double-mass curve showed a change in relationship between annual suspended-sediment discharge and annual stream discharge between the water years 1941-44 and 73. Possible causes for these changes in laboratory procedures, and unusually large runoff that occurred in 1941 and 1972. An unknown or unidentified factor may also be involved. The actual reason for this change in relationship may never be fully understood. Navajo Dam apparently has had no significant effect on fluvial sediment at the sampling site. Mean annual suspended sediment discharge in the San Juan River near Bluff was about 25,410,000 tons ranging from 3,234,000 tons in 1978 to 112,400,000 tons in 1941. The use of annual stream discharge to predict annual suspended-sediment discharge at the site will produce poor results because of size and diversity of the basin and the quality of records available. A positive correlation exists between sand concentration and stream discharge at this site, however, considerable variability is evident. This relationship does not exist when stream discharge exceeds 6,000 cubic feet per second. It is recommended that if collection of suspended-sediment records be resumed in this reach of the river an alternative sampling site should be selected and the use of pumping samplers considered because of the remoteness of the area. (USGS)

Thompson, K. R.; Mundorff, J. C.

1982-01-01

126

Fluctuating wind forces measured on a bluff body extending from a cavity  

NASA Astrophysics Data System (ADS)

The effect of wind forces measured on a bluff body extending from a cavity was investigated. This was accomplished by measuring wind induced vibratory inputs to a plexiglas bluff body model. The model extended from a ground board cavity installed in the AFIT 5-Foot Wind Tunnel. Forces and moments were measured from an 8 element load cell unit built and installed in the base of a plexiglas model. Three different size cavity openings were tested for both a no-rotation and 45 degree rotation referenced to the wind. Data was taken at individual speed points between 55 ft/s and 180 ft/s, producing Reynolds number based on model width in the range of 1.5 x 10 to the 5th power to 5.0 x 10 to the 5th power. Baseline data for a closed cavity configuration was collected and compared to previous studies conducted at the USAF Academy. Force and moment coefficient data are presented, comparing cavity opening and model rotation effects. Results of shedding frequency analysis are presented based on transient data recorded.

King, Brian W.

1989-12-01

127

Numerical aerodynamic analysis of bluff bodies at a high Reynolds number with three-dimensional CFD modeling  

NASA Astrophysics Data System (ADS)

This paper focuses on numerical simulations of bluff body aerodynamics with three-dimensional CFD (computational fluid dynamics) modeling, where a computational scheme for fluid-structure interactions is implemented. The choice of an appropriate turbulence model for the computational modeling of bluff body aerodynamics using both two-dimensional and three-dimensional CFD numerical simulations is also considered. An efficient mesh control method which employs the mesh deformation technique is proposed to achieve better simulation results. Several long-span deck sections are chosen as examples which were stationary and pitching at a high Reynolds number. With the proposed CFD method and turbulence models, the force coefficients and flutter derivatives thus obtained are compared with the experimental measurement results and computed values completely from commercial software. Finally, a discussion on the effects of oscillation amplitude on the flutter instability of a bluff body is carried out with extended numerical simulations. These numerical analysis results demonstrate that the proposed three-dimensional CFD method, with proper turbulence modeling, has good accuracy and significant benefits for aerodynamic analysis and computational FSI studies of bluff bodies.

Bai, YuGuang; Yang, Kai; Sun, DongKe; Zhang, YuGuang; Kennedy, David; Williams, Fred; Gao, XiaoWei

2013-02-01

128

Drag reduction by closed-loop control of a separated flow over a bluff body with a blunt trailing edge  

Microsoft Academic Search

The present investigation focuses on the drag reduction of a bluff body with a blunt trailing edge in wind tunnel experiments. Two different approaches of closed-loop control are presented. First, a robust controller based on a family of linear black-box models is designed to suppress the vortex shedding by controlling the base pressure. To reduce the conservatism of this approach,

Lars Henning; Rudibert King

2005-01-01

129

Operational experience with a superconducting magnetic energy storage device at Owens Corning Vinyl Operations, Fair Bluff, North Carolina  

Microsoft Academic Search

This paper presents the operational and power quality monitoring results for 21 months operating experience of a superconducting magnetic energy storage (SMES) device used to mitigate power quality disturbances at the Owens Coming Vinyl Operations in Fair Bluff, North Carolina, USA, a vinyl siding manufacturer. The SMES unit at Owens Coming provides sag and momentary interruption ride-through for the plant's

John Cerulli; G. Melotte; S. Peele

1999-01-01

130

Time-resolved blowoff transition measurements for two-dimensional bluff body-stabilized flames in vitiated flow  

Microsoft Academic Search

Flame holding and blowoff characteristics of bluff-body stabilized, turbulent flames were measured in an enclosed rectangular duct with a triangular flame holder in vitiated, premixed flows. Blowoff stability margins were characterized with chemiluminescence measurements performed by high-speed imaging to capture flame dynamics during the approach to flame blow off. As the equivalence ratio was decreased, local extinctions along the flames

Steven G. Tuttle; Swetaprovo Chaudhuri; Stanislav Kostka; Kristin M. Kopp-Vaughan; Trevor R. Jensen; Baki M. Cetegen; Michael W. Renfro

131

Alteration and geochemical zoning in Bodie Bluff, Bodie mining district, eastern California  

USGS Publications Warehouse

Banded, epithermal quartz-adularia veins have produced about 1.5 million ounces of gold and 7 million ounces of silver from the Bodie mining district, eastern California. The veins cut dacitic lava flows, pyroclastic rocks and intrusions. Sinter boulders occur in a graben structure at the top of Bodie Bluff and fragments of sinter and mineralized quartz veins occur in hydrothermal breccias nearby. Explosive venting evidently was part of the evolution of the ore-forming geothermal systems which, at one time, must had reached the paleosurface. Previous reconnaissance studies at Bodie Bluff suggested that the geometry of alteration mineral assemblages and distribution of some of the major and trace elements throughout the system correspond to those predicted by models of hot-spring, volcanic rock hosted precious metal deposits (Silberman, 1982; Silberman and Berger, 1985). The current study was undertaken to evaluate these sugestions further. About 500 samples of quartz veins and altered rocks, including sinter, collected over a vertical extent of 200 meters within Bodie Bluff were petrographically examined and chemically analyzed for trace elements by emission spectrographic and atomic absorption methods. Sixty-five samples were analyzed for major elements by X-ray fluorescence methods. The results of these analyses showed that, in general, alteration mineral assemblage and vertical geochemical zoning patterns follow those predicted for hot-spring deposits, but that geochemical zoning patterns for sinter and quartz veins (siliceous deposits), and altered wall rocks are not always similar. The predicted depth-concentration patterns for some elements, notably Au, Ag, Hg, and Tl in quartz veins, and Hg, As and Ag in wall rocks were not as expected, or were perturbed by the main ore producing zone. For both quartz veins and altered wall rocks, the main ore zone had elevated metal contents. Increased concentration of many of these elements could indicate proximity to this zone. However, irregularities in the distribution of some key elements, such as Au and Ag, relative to the predictive models suggest that a larger suite of elements be considered for exploration for ore zones within the district. ?? 1993.

Herrera, P. A.; Closs, L. G.; Silberman, M. L.

1993-01-01

132

3-D Slope Stability of Coastal Bluffs Incorporating 3-D Pore-Water Pressures, Seattle, WA  

NASA Astrophysics Data System (ADS)

Coastal landsliding can dramatically alter both subaerial and subaqueous environments. The stability of coastal bluffs is controlled by the interplay of 3-D variations in gravitational stress, strength, and pore-water pressure. We have developed a 3-D slope-stability analysis, SCOOPS, that allows us to search a high-resolution digital-elevation model and quantify the relative stability of all parts of the landscape by computing the stability and volume of millions of potential spherical failure surfaces. Many types of landsliding, including large, deep-seated slides, affect the steep coastal bluffs of Puget Sound in Seattle, WA. Most of the larger failures occur in glacially deposited Vashon Advance Outwash; some failures extend into the underlying mechanically weaker Lawton Clay. We use our 3-D analysis to examine the destabilizing influences of topographic form, variations in material strength, and changes in pore-water pressures created by 3-D groundwater flow fields for a coastal bluff in Seattle. By assuming homogeneous material properties without pore pressures, we can examine the effects of topography. In this scenario, the least stable areas are located on the steepest slopes or headland morphologies. However, some of these locations do not coincide with historical landslide locations. When we add heterogeneous material properties as defined by stratigraphy, the least stable areas shift to the steepest parts of the weak Lawton Clay, a result also inconsistent with historical locations. The low hydraulic conductivity of the Lawton Clay impedes groundwater flow, and elevates pore pressures at the base of the Vashon Advance Outwash, thereby increasing the potential for deep-seated landslides. We use the groundwater flow model, MODFLOW, to generate a 3-D pore-pressure field. We obtain a more realistic scenario by combining 3-D pore pressures with heterogeneous strength properties; here, areas of elevated pore pressure reflect the influence of a perched groundwater table in the Outwash as well as groundwater convergence in the coastal re-entrants. This scenario places the least stable areas in the Vashon Advance Outwash where pore pressures are locally elevated. These results agree with records of historic landslides.

Brien, D. L.; Reid, M. E.

2001-12-01

133

Drag reduction of a 3D bluff body using coherent streamwise streaks  

NASA Astrophysics Data System (ADS)

Separation on the rear-end of an Ahmed body is suppressed by means of large-scale coherent streaks forced on the roof of the model. These streaks originate from an array of suitably shaped cylindrical roughness elements and are amplified by the mean shear through the lift-up effect. Interacting with the mean velocity field at leading order, they induce a strong controlled spanwise modulation. The resulting streaky base flow is observed to sustain the adverse pressure gradient since PIV measurements as well as static wall pressure distributions show that the re-circulation bubble completely vanishes. These modifications of the topology of the flow are associated with a substantial drag reduction, which can be of about 10% when the roughness array is optimally placed on the roof of the bluff body.

Pujals, G.; Depardon, S.; Cossu, C.

2010-11-01

134

Drag and lift reduction of a 3D bluff body using flaps  

NASA Astrophysics Data System (ADS)

We present an experimental study on flow control over a classic 3D bluff-body used in automotive aerodynamics (Ahmed 1983). Flow control is achieved through moving flaps fixed on every edge around the two rear flat surfaces of the model. Different pairs of flaps, with variable angle compared to the walls, are tested. Parametric studies show that the most efficient configuration for the flaps is along the side edges of the rear slant, i.e. in the region where longitudinal vortices are created, and also at the junction between the roof and the rear slant, where the flow separates. We also explore the combinations of different flap configurations. We find interesting results showing cumulative effects between some configurations leading to -25% drag reduction and -105% lift reduction. Finally, particle image velocimetry measurements show that one of the key effects is the control of the longitudinal vortices created at the side edges of the rear slant.

Beaudoin, Jean-François; Aider, Jean-Luc

2008-04-01

135

High-Speed Linear Raman Spectroscopy for Instability Analysis of a Bluff Body Flame  

NASA Technical Reports Server (NTRS)

We report a high-speed laser diagnostics technique based on point-wise linear Raman spectroscopy for measuring the frequency content of a CH4-air premixed flame stabilized behind a circular bluff body. The technique, which primarily employs a Nd:YLF pulsed laser and a fast image-intensified CCD camera, successfully measures the time evolution of scalar parameters (N2, O2, CH4, and H2O) in the vortex-induced flame instability at a data rate of 1 kHz. Oscillation of the V-shaped flame front is quantified through frequency analysis of the combustion species data and their correlations. This technique promises to be a useful diagnostics tool for combustion instability studies.

Kojima, Jun; Fischer, David

2013-01-01

136

Investigation of the near and far wake of a bluff airfoil model with trailing edge modifications using time-resolved particle image velocimetry  

NASA Astrophysics Data System (ADS)

Experimental investigations on the topology and the structure of the near and far wake of a quasi-2D blunt NACA0012 airfoil cut at 80 % of the original chord length c master have been performed by means of time-resolved particle image velocimetry. The experiments took place in a closed-loop water tunnel at a model-thickness H-based Reynolds number of Re H = 44,000. The periodic and alternating vortex formation process at the base of the bluff model with a dimensionless frequency of Sr h = 0.2 (relating to the trailing edge height h) was investigated in detail. Subsequently, four modifications of the trailing edge geometry (broken trailing edge, square-wave base, stepped afterbody and extension of the reference model by ? c/c_master = 7.5 %) have been investigated in order to mitigate the periodic vortex formation and the alternating shedding process. In the far wake, a considerable decrease in momentum loss and resulting drag force in the range of 29 % has been achieved for this specific Reynolds number. Investigations of the time-resolved flow field proved that the periodic, alternating flow separation can be attenuated resulting in an optimized recirculation region and a low-loss wake. It can be inferred that passive flow control means like modifications of the rear end geometry of quasi-2D blunt models are a capable method to improve the flow field with respect to a minimization of momentum losses in the wake.

Krentel, Daniel; Nitsche, Wolfgang

2013-07-01

137

Sedimentological indicators of paleoenvironments and siliciclastic stratigraphic sequences in some Miocene deposits of the Calvert Cliffs, southern Maryland  

USGS Publications Warehouse

Middle Miocene siliciclastic deposits comprising the Calvert Cliffs section at the Baltimore Gas and Electric Company's (BG&E) nuclear power plant site in southern Maryland were analyzed in terms of lithostratigraphy, sedimentary structures, and granulometric parameters, to interprete paleo-environments within a sequence-stratigraphic framework. In terms of sequence-stratigraphic models, the BG&E section can be interpreted as consisting of two genetic stratigraphic sequences (Galloway model), namely, a shelf sequence and an overlying deltaic sequence. Using the Exxon model, the section consists of two third-order (1-5 m.y. duration) depositional sequences. The stratigraphic sequences of the BG&E section reflect both relatively short-term eustatic transgressive events, as well as a long-term regressive trend with associated local deltation and coastal progradation. The regression probably signified a regional basinward shift of depocenters within the Salisbury embayment during Miocene time. -from Author

Shideler, G. L.

1994-01-01

138

Theoretical analysis and experimental verification on valve-less piezoelectric pump with hemisphere-segment bluff-body  

NASA Astrophysics Data System (ADS)

Existing researches on no-moving part valves in valve-less piezoelectric pumps mainly concentrate on pipeline valves and chamber bottom valves, which leads to the complex structure and manufacturing process of pump channel and chamber bottom. Furthermore, position fixed valves with respect to the inlet and outlet also makes the adjustability and controllability of flow rate worse. In order to overcome these shortcomings, this paper puts forward a novel implantable structure of valve-less piezoelectric pump with hemisphere-segments in the pump chamber. Based on the theory of flow around bluff-body, the flow resistance on the spherical and round surface of hemisphere-segment is different when fluid flows through, and the macroscopic flow resistance differences thus formed are also different. A novel valve-less piezoelectric pump with hemisphere-segment bluff-body (HSBB) is presented and designed. HSBB is the no-moving part valve. By the method of volume and momentum comparison, the stress on the bluff-body in the pump chamber is analyzed. The essential reason of unidirectional fluid pumping is expounded, and the flow rate formula is obtained. To verify the theory, a prototype is produced. By using the prototype, experimental research on the relationship between flow rate, pressure difference, voltage, and frequency has been carried out, which proves the correctness of the above theory. This prototype has six hemisphere-segments in the chamber filled with water, and the effective diameter of the piezoelectric bimorph is 30mm. The experiment result shows that the flow rate can reach 0.50 mL/s at the frequency of 6 Hz and the voltage of 110 V. Besides, the pressure difference can reach 26.2 mm H2O at the frequency of 6 Hz and the voltage of 160 V. This research proposes a valve-less piezoelectric pump with hemisphere-segment bluff-body, and its validity and feasibility is verified through theoretical analysis and experiment.

Ji, Jing; Zhang, Jianhui; Xia, Qixiao; Wang, Shouyin; Huang, Jun; Zhao, Chunsheng

2014-05-01

139

Terrestrial LIDAR Investigation of the December 2003 and January 2007 Activations of the Northridge Bluff Landslide, Daly City, California  

USGS Publications Warehouse

Introduction On December 20, 2003 and again on January 1, 2007, landslides occurred along the coastal bluff that forms the west boundary of Daly City, California sending debris as far as 290 meters downhill and 90 meters into the ocean. This area is known for large landslide events where 150-meter tall coastal bluffs extend southward along the west boundary of San Francisco and San Mateo Counties (Fig. 1). The 2003 and 2007 landslide events occurred west of Northridge Drive in Daly City and just south of Avalon Canyon, which bisects the bluffs in this area (Fig. 2). Residential development, utility lines and roads occupy the land immediately east of this location. As part of a comprehensive project to investigate the failure mechanisms of coastal bluff landslides in weakly lithified sediments along the west coast of the United States, members of the U.S. Geologic Survey (USGS) Coastal and Marine Geology (CMG) Program performed reconnaissance mapping of these landslide events including collection of high-resolution topographic data using CMG's terrestrial LIDAR laser scanning system. This report provides a brief background on each landslide event and presents topographic datasets collected following each event. Downloadable contour data, images, and FGDC-compliant metadata of the surfaces generated from the LIDAR data are also provided. LIDAR data collection and processing techniques used to generate the datasets are outlined. Geometric and volumetric measurements are also presented along with high-resolution cross-sections through various areas of the slide masses and discussion concerning the slides present (2007) configuration is provided.

Collins, Brian D.; Kayen, Robert; Reiss, Thomas; Sitar, Nicholas

2007-01-01

140

Large eddy simulation of the flow around bluff body with drag reduction device  

NASA Astrophysics Data System (ADS)

This thesis focuses on the use of LES to simulate the flow around elliptical bluff body with blunt trailing edge fitted with open base cavity. The main objective of this study is to determine the effects of the cavity on the drag of the body. A secondary but important objective is to demonstrate that LES can provide accurate representation of the flow around this bluff body. Moreover, LES results can complement the available experimental results in order to provide a much better understanding of the flow. The simulations were carried out at a Reynolds number of 2.6×104 based on the height of the body using Spalart-Allmaras RANS model while the LES were performed using Smagorinsky dynamic model. A grid-independence test was conducted using three grids which contain 0.85M, 1.3M and 1.7M cells, respectively. This test shows that the results are grid-independent. The LES results predicted the mean flow field in the near wake with good accuracy as compared to the experimental mean flow field obtained. The base pressure results show that the base pressure coefficient for the base model was around -0.56, which agrees well with the experimental results .By attaching the cavity, the base pressure has increased. The increase in base pressure coefficient was around 44% using 1/3 h cavity and this agrees well with the experimental measurements. The RANS predicted drag coefficient of 0.56 for the base model and 0.471 for the cavity model. This represents a difference of 8% for the base model and 34% for the cavity model when compared with experiment drag coefficients (0.61 for the base model and 0.35 for the cavity model). For the LES, the drag coefficient of the base model was around 0.65 (6.5% difference) and using the cavity, the drag coefficient was reduced to around 0.37 (5.74% difference). Details of the mean velocity components have been compared with experimental data at various locations in the wake region of the flow. Observation on the comparison between LES and RANS shows that LES predicted the mean flow field more accurately than RANS particularly downstream the recirculation regions. The length of the recirculation region was over predicted by RANS compared to LES. The prediction of this length by LES was in excellent agreement with experimental measurement.

Al-Anazi, Khalid Qaied

141

Vortex Methods for High-Resolution Simulations of Viscous Flow Past Bluff Bodies of General Geometry  

NASA Astrophysics Data System (ADS)

Recent contributions to the 2-D vortex method are presented. A technique to accurately redistribute particles in the presence of bodies of general geometry is developed. The particle strength exchange (PSE) scheme for diffusion is modified for particles in the vicinity of the solid boundaries to avoid a spurious vorticity flux during the convection/PSE step. The scheme used to enforce the no-slip condition through the vorticity flux at the boundary is modified in a way that is more accurate than in the previous method. Finally, to perform simulations with nonuniform resolution, a mapping of the redistribution lattice is also used. In that case, the PSE is still done in the physical domain, using a symmetrized, conservative scheme. The quadratic convergence of this scheme is proved mathematically, and numerical tests are shown to support the proof. These elements are all validated on the benchmark problem of the flow past an impulsively started cylinder. High-resolution, long-time simulations of the flow past other bluff bodies are also presented: the case of a square and of a capsule at angle of attack.

Ploumhans, P.; Winckelmans, G. S.

2000-12-01

142

Large eddy simulation of forced ignition of an annular bluff-body burner  

SciTech Connect

The optimization of the ignition process is a crucial issue in the design of many combustion systems. Large eddy simulation (LES) of a conical shaped bluff-body turbulent nonpremixed burner has been performed to study the impact of spark location on ignition success. This burner was experimentally investigated by Ahmed et al. [Combust. Flame 151 (2007) 366-385]. The present work focuses on the case without swirl, for which detailed measurements are available. First, cold-flow measurements of velocities and mixture fractions are compared with their LES counterparts, to assess the prediction capabilities of simulations in terms of flow and turbulent mixing. Time histories of velocities and mixture fractions are recorded at selected spots, to probe the resolved probability density function (pdf) of flow variables, in an attempt to reproduce, from the knowledge of LES-resolved instantaneous flow conditions, the experimentally observed reasons for success or failure of spark ignition. A flammability map is also constructed from the resolved mixture fraction pdf and compared with its experimental counterpart. LES of forced ignition is then performed using flamelet fully detailed tabulated chemistry combined with presumed pdfs. Various scenarios of flame kernel development are analyzed and correlated with typical flow conditions observed in this burner. The correlations between, velocities and mixture fraction values at the sparking time and the success or failure of ignition, are then further discussed and analyzed. (author)

Subramanian, V.; Domingo, P.; Vervisch, L. [CORIA-CNRS and INSA de Rouen, Technopole du Madrillet, BP 8, 76801 Saint-Etienne-du-Rouvray (France)

2010-03-15

143

Measurements on a wind turbine wake: 3D effects and bluff body vortex shedding  

NASA Astrophysics Data System (ADS)

The velocity field in the wake of a two-bladed wind turbine model (diameter 180 mm) has been studied under different conditions using a two-component hot wire. All three velocity components were measured both for the turbine rotor normal to the oncoming flow as well as with the turbine inclined to the freestream direction (the yaw angle was varied from 0° to 20°). The measurements showed, as expected, a wake rotation in the opposite direction to that of the turbine. A yawed turbine is found to clearly deflect the wake flow to the side, showing the potential of controlling the wake by yawing the turbine. An unexpected feature of the flow was that spectra from the time signals showed the appearance of a low-frequency fluctuation both in the wake and in the flow outside the wake. This fluctuation was found both with and without freestream turbulence and also with a yawed turbine. The frequency expressed as a Strouhal number was shown to be independent of the freestream velocity or turbulence level, but the low frequency was only observed when the tip speed ratio (or equivalently the drag coefficient) was high. The shedding frequency changed also with the yaw angle. This is in agreement with the idea that the turbine sheds structures as a bluff body. The phenomenon, noticeable in all the velocity components, was further investigated using two-point cross-correlations of the velocity signals. Copyright

Medici, D.; Alfredsson, P. H.

2006-05-01

144

The Mechanism and Prediction of Bluff Body Flame Blow-Out  

NASA Astrophysics Data System (ADS)

Premixed flame blow-out downstream of a bluff body has to be thoroughly understood for accurate prediction and design of high performance gas turbine combustors and augmentors. Many complex issues are at play, such as the role of a large number of intermediate and minor species, detailed chemistry, the inherent unsteadiness of the problem, and vortex-combustion interaction. To partially address this problem, we carry out large eddy simulations within the framework of premixed flamelet modeling. After an analysis of the factors upon which the LES and flamelet models depend, we carry out a parametric study with the incoming stream equivalent ratio, turbulence intensity, and the flame-holder geometry, and investigate the local values of various parameters, including the equivalence ratio, temperature, heat flux, turbulent flame speed, strain rate, turbulence intensity, and the terms in the energy equation. The occurrence of blow-out is related to these parameters, with the hope that some cause-effect relationships can be established. The progress along these lines will be reported at the meeting.

Ladeinde, Foluso; Cai, Xiaodan; Kiel, Barry; Sekar, Balu

2004-11-01

145

A rotating bluff-body disc for reduced variability in wind tunnel aerosol studies.  

PubMed

A rotating bluff-body disc (RBD) was developed to reduce spatiotemporal variability associated with sampling supermicron aerosol in low-velocity wind tunnels. The RBD is designed to rotate eight personal aerosol samplers around a circular path in a forward-facing plane aligned with the wind tunnel cross section. Rotation of the RBD allows each sampler to traverse an identical path about the wind tunnel cross section, which reduces the effects of spatial heterogeneity associated with dispersing supermicron aerosol in low-velocity wind tunnels. Samplers are positioned on the face of the RBD via sampling ports, which connect to an air manifold on the back of the disc. Flow through each sampler was controlled with a critical orifice or needle valve, allowing air to be drawn through the manifold with a single pump. A metal tube, attached to this manifold, serves as both the axis of rotation and the flow conduction path (between the samplers and the vacuum source). Validation of the RBD was performed with isokinetic samplers and 37-mm cassettes. For facing-the-wind tests, the rotation of the RBD significantly decreased intra-sampler variability when challenged with particle diameters from 1 to 100 ?m. The RBD was then employed to determine the aspiration efficiency of Institute of Occupational Medicine (IOM) personal samplers under a facing-the-wind condition. Operation of IOM samplers on the RBD reduced the between-sampler variability for all particle sizes tested. PMID:21097990

Koehler, Kirsten A; Anthony, T Renee; van Dyke, Michael; Volckens, John

2011-01-01

146

Quartz and Hydrous Iron Oxides from the Bee Bluff Structure of South Texas  

NASA Astrophysics Data System (ADS)

There is substantial information showing that the Bee Bluff structure is an impact site and that a residual crater can be identified. The thin hard cap of Carrizo Sandstone, Indio fm calcareous silt and a thin layer of iron-rich siltstone leads to impact processes in which the high pressure release wave proceeds promptly upward leading to a trapping of metamorphic products at the impact interface, a `bottom-up' pressure release. Release of water from goethite binder in the sandstone and from the iron-rich siltstone results in supersaturated steam in mixtures with iron and quartz compounds. Samples with quartz and hydrous iron oxide features are examined with optical microscopy, SEM, EDX and XRD. A quartz grain is found with a well defined PDF set. There is widespread amorphous quartz including lechatleriete. Nanocrystals of ?-goethite in the acicular form are common. A condensation sphere from the `Uvalde Crater Rosetta Stone' shows a complex mixture of hematite, goethite, and alpha quartz with a trace of trydimite. Numerous samples are yet to be analyzed. The crater appears to have features that can serve as an Earth analog to Mars craters. A companion paper in the present proceedings summarizes prior work, adds new site detail, reports impact-loading analysis, and describes overall features of impactite samples from the site.

Graham, R. A.; Martin, M.; Thadhani, N. N.; Morosin, B.

2006-07-01

147

Scaling properties of two-dimensional turbulence in wakes behind bluff bodies  

SciTech Connect

This paper contains an analysis of the scaling properties of two-dimensional (2D) turbulence obtained by means of numerical simulation using the {ital vortex blob} method. The flow under consideration is the turbulent wake behind a bluff body with a developed enstrophy cascade and reduced inverse energy cascade. The concept of {ital extended self-similarity} (ESS) and the associated {ital relative} scaling exponents {bar {zeta}}{sub m,n}={zeta}{sub n}/{zeta}{sub m} are invoked within the framework of 2D turbulence. The scaling exponents in the enstrophy range are found to systematically vary with the downstream distance from the obstacle, thus revealing their nonuniqueness. In terms of the {ital relative} exponents, the present results quantitatively agree with recent laboratory experiments of Gaudin {ital et al.} [PMMH-ESPCI Report No. A 96/57, 1996 (unpublished)]. Error bars and the accuracy of the ESS scaling are carefully checked. {copyright} {ital 1997} {ital The American Physical Society}

Protas, B. [Department of Aerodynamics, Institute of Aeronautics and Applied Mechanics, Warsaw University of Technology, ul. Nowowiejska 24, 00-665 Warsaw (Poland)] [Department of Aerodynamics, Institute of Aeronautics and Applied Mechanics, Warsaw University of Technology, ul. Nowowiejska 24, 00-665 Warsaw (Poland); [Laboratoire de Physique et Mecanique des Milieux Heterogenes, CNRS URA 857, Ecole Superieure de Physique et Chimie Industrielles, 10 rue Vauquelin, 75231 Paris Cedex 05 (France); Goujon-Durand, S. [Laboratoire de Physique et Mecanique des Milieux Heterogenes, CNRS URA 857, Ecole Superieure de Physique et Chimie Industrielles, 10 rue Vauquelin, 75231 Paris Cedex 05 (France)] [Laboratoire de Physique et Mecanique des Milieux Heterogenes, CNRS URA 857, Ecole Superieure de Physique et Chimie Industrielles, 10 rue Vauquelin, 75231 Paris Cedex 05 (France); [Faculte de Sciences et Technologie, Universite Paris XII-Val de Marne, 61 avenue du General de Gaulle, 94010 Creteil Cedex (France); Wesfreid, J.E. [Faculte de Sciences et Technologie, Universite Paris XII-Val de Marne, 61 avenue du General de Gaulle, 94010 Creteil Cedex (France)] [Faculte de Sciences et Technologie, Universite Paris XII-Val de Marne, 61 avenue du General de Gaulle, 94010 Creteil Cedex (France)

1997-04-01

148

Erosional history of Cape Halkett and contemporary monitoring of bluff retreat, Beaufort Sea coast, Alaska  

USGS Publications Warehouse

Cape Halkett is located along the Beaufort Sea at the end of a low-lying tundra landscape. The area has been subject to major modifications over the last century as a result of erosion and migration of the coastline inland. Long-term mean annual erosion rates (1955-2009) for the entire cape are 7.6 m/yr, with a gradual increase in rates over the first five time periods of remotely sensed imagery analyzed and a large increase during the most recent time period. Division of the cape into three distinct coastal zones shows very different erosional patterns: the northeast-facing segment (Zone 1) showing a consistent and large increase; the southeast-facing segment (Zone 3) showing a gradual increase with recent, heightened erosion rates; and the east-facing segment (Zone 2) showing decreased rates due to the reformation of a sand and gravel spit. Monitoring of bluff erosion with time-lapse photography, differential GPS surveys, terrestrial and bathymetric surveys, and water level, sea and permafrost temperature data provide insights into the processes driving contemporary patterns of erosion and will provide valuable information for the prediction of future shoreline positions.

Jones, Benjamin M.; Arp, Christopher D.; Beck, Richard A.; Grosse, Guido; Webster, James M.; Urban, Frank E.

2009-01-01

149

Paleomagnetic and 40Ar/39Ar results from the Grant intrusive breccia and coparison to the Permian Downeys Bluff Sill; evidence for Permian igneous activity at Hicks Dome, southern Illinois Basin  

USGS Publications Warehouse

Igneous processes at Hicks dome, a structural upwarp at lat 37.5 degrees N., long 88.4 degrees W. in the southern part of the Illinois Basin, may have thermally affected regional basinal fluid flow and may have provided fluorine for the formation of the Illinois-Kentucky Fluorspar district. The timing of both igneous activity and mineralization is poorly known. For this reason, we have dated an intrusive breccia at Hicks dome, the Grant intrusion, using 40Ar/39Ar geochronometric and paleomagnetic methods. Concordant plateau dates, giving Permian ages, were obtained from amphibole (272.1+or-0.7 [1 sigma] Ma) and phlogopite (272.7+or-0.7 [1 sigma] Ma). After alternating-field (AF) demagnetization, specimens that contain titanomagnetite-bearing igneous rock fragments give a mean remanent direction of declination (D)=168.4 degrees; inclination (I)=-8 degrees; alpha 95=8.6 degrees; number of specimens (N)=10; this direction yields a virtual geomagnetic pole (VGP) at lat 54.8 degrees N., long 119.0 degrees E., delta p=4.4 degrees, delta m=8.7 degrees, near the late Paleozoic part of the North American apparent pole wander path. A nearly identical magnetization was found for the nearby Downeys Bluff sill (previously dated at about 275+or-24 Ma by the Rb-Sr method), in southern Illinois. Both AF and thermal demagnetization isolated shallow, southeasterly remanent directions carried by magnetite in the sill and from pyrrhotite in the baked contact of the Upper Mississippian Downeys Bluff Limestone: D=158.6 degrees; I=-11.8 degrees; alpha 95=3.8 degrees; N=15, yielding a VGP at lat 53.0 degrees N., long 128.7 degrees E., delta p=2.0 degrees, delta m=3.9 degrees. The paleomagnetic results, isotopic dates, and petrographic evidence thus favor the acquisition of thermal remanent magnetization by the Grant breccia and the Downeys Bluff sill during the Permian. The isotopic dates record rapid cooling from temperatures greater than 550 degrees C to less than 300 degrees C (the closure temperatures for diffusion of 40Ar in amphibole and phlogopite, respectively) after emplacement during the Permian. The results further indicate that individual clasts of the Grant breccia were emplaced at temperatures greater than about 550 degrees C, the magnetization-blocking temperature of the titanomagnetite in the breccia, and that it cooled very rapidly,within less than 1-2 m.y. After cooling, the breccia was not affected by thermal perturbations greater than about 300 degrees C.

Reynolds, Richard L.; Goldhaber, Martin B.; Snee, Lawrence W.

1997-01-01

150

Mixing enhancement of jets and drag reduction in manipulated bluff body wakes  

NASA Astrophysics Data System (ADS)

In the first part of this work a direct numerical simulation of the approach is employed in the study of a planar jet immersed in a co-flowing stream. An aerodynamic vectoring effect on the jet is achieved by the application of asymmetrically distributed suction at the lips of the exit nozzle. An optimal suction distribution for maximum lift generation is located and used in conjunction with time-dependent stimulation to enhance the mixing characteristics of the jet. The dynamic behavior of the system in the phase plane is explored and a regime of suction parameters for maximum mixing enhancement is revealed. The attractor selection sensitivity to initial conditions of the system is also investigated. The second part of this dissertation used direct numerical simulation in the study of the flow dynamics in the near wake of a two dimensional rectangular bluff body. The suppression of the global mode of instability via base suction or bleed is investigated and the ventilation coefficient cvent , a non-dimensional measure of the ventilation mass flux, is identified as a major scaling parameter in the determination of the structural characteristics and suppression of the global mode of via base bleed. Aerodynamic drag reduction is pursued by modifying the base pressure component of the drag. Boat-tails (blocks and plates) are attached at the trailing edge of the rectangular forebody and an optimal aspect ratio for boat-tail notches at the separation point is identified. The use of boat-tailing in conjunction with base bleed is also investigated and the common underlying mechanism leading to elevated base pressure in different configurations is revealed.

Arcas, Diego Rodriguez

151

Blowoff behavior of bluff body stabilized flames in vitiated and partially premixed flows  

NASA Astrophysics Data System (ADS)

Turbulent flame holding and blowoff characteristics of bluff body stabilized flames were measured in an enclosed rectangular duct with a triangular flame holder in vitiated, premixed and unvitiated, asymmetrically stratified flows. Blowoff stability margins were characterized, with chemiluminescence measurements performed by high-speed imaging to capture flame dynamics during blow off. As the equivalence ratio was decreased, local extinction along the shear layer flames occurred with greater frequency and proximity to the wake stagnation zone. Decreased equivalence ratio resulted in extinction events at the trailing edge of the stagnation zone, where reactants were convected into the recirculation zone and burned. Eventually, increasing reactant dilution of the recirculation zone either increased the ignition time scale or the lowered the strain tolerance of the propagating flames in the flame anchoring region, resulting in lift-off or extinction, and the near field shear layer flames convected to the wake stagnation zone, where they continued to propagate. From there, the flames were convected upstream into the recirculation zone, where they were eventually quenched. Simultaneous PIV and OH PLIF measurements captured the flame edge location and aerodynamic behavior as blowoff was approached. Two-dimensional hydrodynamic stretch alone the flame front and flow field vorticity maps were extracted from the combined PIV/OH PLIF data. The distribution of flame stretch shifted to greater values as the equivalence ratio decreased. Asymmetric fuel distributions, measured with acetone LW, were found to increase the equivalence ratio at blow off from that found with uniformly-fueled flows. This was attributed to the greater wake instability and extinction of the lean-side flames. The asymmetrically fueled flames were more susceptible to thermoacoustic instabilities when the shedding frequency was near an acoustic eigenmode of the exhaust duct, due to the decreased attenuation of the Benard-Von Karman vortex shedding instability on the lean side of the wake.

Tuttle, Steven G.

152

On the flame-generated vorticity dynamics of bluff-body stabilized premixed flames  

NASA Astrophysics Data System (ADS)

This investigation considers the dynamics of the flame-generated vorticity for a premixed, submerged bluff-body stabilized flame. Digital particle image velocimetry (DPIV) is used to obtain mean and instantaneous velocity and vorticity fields in four streamwise locations, capturing nearly the entire combustion chamber. The Mie scattering images which are collected for DPIV prove useful in determining the approximate location of the flame as indicated by a stark difference in seeding particle density caused by volumetric expansion. Examining the location of the flame fronts in relation to the mean velocity, mean vorticity, and corresponding instantaneous fields provides useful information about the interaction of the flame and the flow. Experiments characterize the far-field region in particular with a level of detail not previously afforded to this type of flow. The unique nature of the velocity and vorticity fields, as well as a change in rotation of the flame structures observed in the Mie scattering images, are explained by appealing to the baroclinic generation of vorticity. The baroclinic mechanism is activated when non-parallel pressure and density gradients are present. Mean static pressure measurements at the combustion chamber wall allow inferences about the pressure field to be made. The coupling that exists among pressure, heat release, and baroclinic generation is also acknowledged and will influence strategies for control of the baroclinic mechanism. Particular details of the coupling remain unclear, nevertheless improved understanding can lead to advancements in combustion efficiency. Simple scaling of the problem allows a prediction of baroclinic vorticity generation to be obtained. Further insight into the dynamics in the region of interest are provided using CH* filtered and unfiltered chemiluminescence images.

Caramella, Lucia

153

Monitoring channel morphology and bluff erosion at two installations of flow-deflecting vanes, North Fish Creek, Wisconsin, 2000-03  

USGS Publications Warehouse

Flow-deflecting vanes were installed in the streambed along two meander bends with eroding bluffs in 2000 and 2001 in the upper main stem of North Fish Creek, a tributary to Lake Superior in Wisconsin. About 45 vanes were arranged in 15 arrays at each site to deflect the flow away from the eroding toe or base of the bluff (outside of a bend) and toward the point bar (inside of a bend). Channel cross-section and bluff-erosion surveys were done and streamflow and stage were measured before, during, and after vane installation to monitor changes in channel morphology and bluff erosion in the context of hydrologic conditions. There were two large floods in the study area in spring 2001 (recurrence interval of approximately 100 years) and in spring 2002 (recurrence intervals of approximately 50 years). Some maintenance and replacement of vanes were needed after the floods. Most of the channel-morphology changes resulted from the large floods, and fewer changes resulted from near-bankfull or at-bankfull flows (one in October 2002 and four in April and May 2003). At the bluff located 16.4 river miles upstream of the creek mouth (site 16.4), the vanes deflected flow and caused the channel to migrate away from the base of the bluff and toward the point bar, allowing sediment to deposit along the bluff base. The 361-foot reach at site 16.4 had a net gain of 6,740 cubic feet of sediment over the entire monitoring period (2000?03). Deposition (10,660 cubic feet) occurred mainly along the base of the bluff in the downstream part of the bend. Erosion occurred at site 16.4 along the streambed, the point bar side of the channel, and along a midchannel bar (1,220, 1,610, and 1,090 cubic feet, respectively). Less channel migration was observed during 2001-03 at another bluff located 12.2 river miles upstream of the creek mouth (site 12.2), which had a net loss of sediment through the 439-foot reach of 2,800 cubic feet over the monitored time period. The main volume of sediment was lost from the bluff toe in the downstream part of the bend (7,100 cubic feet). Monitored channel-morphology changes at site 12.2 were less than at site 16.4, most likely because installation was done after the April 2001 flood, which caused major changes in channel morphology at site 16.4, and because the monitoring period was shorter than at site 16.4. Bluff-erosion data from both sites indicate that mass wasting and block failures from the bluff top occur episodically and will continue to occur for decades or more.

Fitzpatrick, Faith A.; Peppler, Marie C.; Schwar, Heather E.; Hoopes, John A.; Diebel, Matthew W.

2005-01-01

154

Evidence for Complex Mixing Processes Controlling the Composition of a Wide Range of Alkaline Volcanic Rocks at Minna Bluff, Antarctica.  

NASA Astrophysics Data System (ADS)

Minna Bluff, a 45-km-long chain of coalesced volcanic centers formed by a wide range of alkaline magmatic compositions. Compositions between basanite and phonolite are represented and these form volcanic features ranging from small, primitive, cinder cones to large, evolved domes. Abundant stacked lava flows (subaerial to subglacial), feeder dikes, and vent complexes are exposed in cliffs up to ~1000 m in height. A notable field feature of many of the volcanic rocks at Minna Bluff is the presence of large (up to 5 cm) amphibole and feldspar megacrysts, which are found in rocks of a range of compositions and eruptive styles. Microprobe analysis shows that many lavas exhibit strikingly common disequilibrium textures, consisting primarily of phenocrystic kaersutitic to ferro-kaersutitic amphibole that is either partially, or fully, broken down to a combination of plagioclase, pyroxene and magnetite. The extent to which breakdown has occurred varies from crystal to crystal. In some cases, a breakdown rim of only a few 10s of microns thickness is present, whereas in other parts of the sample, mm-scale kaersutites are almost completely reacted. Although individual phenocrysts are compositionally uniform, a range of kaersutite compositions are present (even within a single sample) with FeO and MgO contents between 9.5-18 and 7.5-13.5 wt. percent respectively. Approximately the same compositional range of kaersutite (as well as the same disequilibrium textures) is observed in samples with a range of bulk compositions. Some of the same samples contain feldspar phenocrysts with relatively evolved plagioclase (andesine) cores and more primitive (labradorite) rims. Amphibole-related disequilibrium textures are observed in basanitic lavas containing olivine with Mg- rich cores (Fo87). The textural and compositional characteristics of the Minna Bluff volcanic rocks suggest that, for many, mixing between one or more magmatic sources, shortly before the eruption process, controls the final bulk magmatic composition. Two possible mixing endmembers would be a hydrous, evolved, kaersutite-rich magma and a second, hotter, more primitive melt, and the relative abundance of the two endmembers may influence the final composition of erupted lava. These observations suggest that the mixing processes outlined by Scanlan et al., (this volume) for a single example of inclusion-rich lava at Minna Bluff may be important over a much larger part of the volcanic complex.

Dunbar, N. W.; Panter, K.; Scanlan, M. K.; Fargo, A.; McIntosh, W. C.; Wilch, T. I.

2008-12-01

155

Environmental Assessment of the Gering-Stegall 115-kV Transmission Line Consolidation Project, Scotts Bluff County, Nebraska  

SciTech Connect

The Department of Energy (DOE), Western Area Power Administration (Western) proposes to consolidate segments of two transmission lines near the Gering Substation in Gering, Nebraska. The transmission lines are both located in Scotts Bluff County, Nebraska. The transmission lines are both located in Scotts Bluff County, Nebraska, within the city of Gering. Presently, there are three parallel 115-kilovolt (kV) transmission lines on separate rights-of-way (ROW) that terminate at the Gering Substation. The project would include dismantling the Archer-Gering wood-pole transmission line and rebuilding the remaining two lines on single-pole steel double circuit structures. The project would consolidate the Gering-Stegall North and Gering-Stegall South 115-kV transmission lines on to one ROW for a 1.33-mile segment between the Gering Substation and a point west of the Gering Landfill. All existing wood-pole H-frame structures would be removed, and the Gering-Stegall North and South ROWs abandoned. Western is responsible for the design, construction, operation, and maintenance of the line. Western prepared an environmental assessment (EA) that analyzed the potential environmental impacts of the proposed construction, operation, and maintenance of the 115-kV transmission line consolidation. Based on the analyses in the EA, the DOE finds that the proposed action is not a major Federal action significantly affecting the quality of the human environment, within the meaning of the National Environmental Policy Act of 1969 (NEPA).

NONE

1995-05-01

156

Calculations of the flow past bluff bodies, including tilt-rotor wing sections at alpha = 90 deg  

NASA Technical Reports Server (NTRS)

An attempt was made to model in two dimensions the effects of rotor downwash on the wing of the tilt-rotor aircraft and to compute the drag force on airfoils at - 90 deg angle of attack, using a well-established Navier-Stokes code. However, neither laminar nor turbulent calculations agreed well with drag and base-pressure measurements at high Reynolds numbers. Therefore, further efforts were concentrated on bluff-body flows past various shapes at low Reynolds numbers, where a strong vortex shedding is observed. Good results were obtained for a circular cylinder, but the calculated drag of a slender ellipse at right angles to the freestream was significantly higher than experimental values reported in the literature for flat plates. Similar anomalous results were obtained on the tilt-rotor airfoils, although the qualitative effects of flap deflection agreed with the wind tunnel data. The ensemble of results suggest that there may be fundamental differences in the vortical wakes of circular cylinders and noncircular bluff bodies.

Raghavan, V.; Mccroskey, W. J.; Baeder, J. D.; Van Dalsem, W. R.

1990-01-01

157

Monitoring Channel Morphology and Bluff Erosion at Two Installations of Flow-Deflecting Vanes, North Fish Creek, Wisconsin, 2000-03.  

National Technical Information Service (NTIS)

Flow-deflecting vanes were installed in the streambed along two meander bends with eroding bluffs in 2000 and 2001 in the upper main stem of North Fish Creek, a tributary to Lake Superior in Wisconsin. About 45 vanes were arranged in 15 arrays at each sit...

F. A. Fitzpatrick M. C. Peppler H. E. Schwar J. A. Hoopes M. W. Diebel

2004-01-01

158

Blowoff Characteristics of Bluff-Body Stabilized Conical Premixed Flames in a Duct with Upstream Spatial Mixture Gradients and Velocity Oscillations  

Microsoft Academic Search

An experimental study of flame blowoff phenomenon in a bluff body stabilized flame confined in a cylindrical duct is presented. Blowoff equivalence ratios were determined for two approach velocities and three different upstream equivalence ratio profiles (uniform, inner, and outer fuel enrichment) in the absence and presence of imposed upstream velocity oscillations. The results were compared with those for the

Swetaprovo Chaudhuri; Baki M. Cetegen

2009-01-01

159

Estimating the Abundance of Sacramento River Juvenile Winter Chinook Salmon with Comparisons to Adult Escapement. Final Report Red Bluff Research Pumping Plant Report Series. Volume 5.  

National Technical Information Service (NTIS)

We developed in-river quantitative methodologies for indexing juvenile winter chinook production (JPI) in the upper Sacramento River using data collected by rotary-screw traps at Red Bluff Diversion Dam. These indices were used in conjunction with and in ...

2001-01-01

160

Coherent structure statistics in the wake of a sharp-edged bluff body placed vertically in a shallow channel  

NASA Astrophysics Data System (ADS)

Proper orthogonal decomposition and closed-streamline-based vortex identification algorithm has been applied to extract information on coherent structures downstream of a sharp-edged bluff body, placed vertically in a shallow open channel flow. The friction effect of the bed was found to reduce the size and strength of the coherent structures close to the bed. The free surface weakly decreases the size and strength of the prevalent coherent structures. The population trends of coherent structure statistics with downstream distance indicate the phenomenon of merging and spatial growth of coherent structures with time and space. But the rates of merging and growth were found to be different at different vertical locations over the flow depth. The distribution functions of the location, size and strength in the transverse direction were examined to shed light on the dynamics of these structures.

Singha, Arindam; Balachandar, Ram

2011-10-01

161

Vortex dynamics and scalar transport in the wake of a bluff body driven through a steady recirculating flow  

NASA Astrophysics Data System (ADS)

The air ventilation system in wide-body aircraft cabins provides passengers with a healthy breathing environment. In recent years, the increase in global air traffic has amplified contamination risks by airborne flu-like diseases and terrorist threats involving the onboard release of noxious materials. In particular, passengers moving through a ventilated cabin may transport infectious pathogens in their wake. This paper presents an experimental investigation of the wake produced by a bluff body driven through a steady recirculating flow. Data were obtained in a water facility using particle image velocimetry and planar laser induced fluorescence. Ventilation attenuated the downward convection of counter-rotating vortices produced near the free-end corners of the body and decoupled the downwash mechanism from forward entrainment, creating stagnant contaminant regions.

Poussou, Stephane B.; Plesniak, Michael W.

2012-09-01

162

Technology resource document for the assembled chemical weapons assessment environmental impact statement. Vol. 3 : assembled systems for weapons destruction at Pine Bluff Arsenal.  

SciTech Connect

This volume of the Technical Resource Document (TRD) for the Environmental Impact Statement (EIS) for the ''Design, Construction and Operation of One or More Pilot Test Facilities for Assembled Chemical Weapons Destruction Technologies at One or More Sites'' (PMACWA 2001g) pertains to the destruction of assembled chemical weapons (ACW) stored in the U.S. Army's unitary chemical stockpile at Pine Bluff Arsenal (PBA), located outside Pine Bluff, Arkansas. This volume presents technical and process information on each of the destruction technologies applicable to treatment of the specific ACW stored at PBA. The destruction technologies described are those that have been demonstrated as part of the Assembled Chemical Weapons Assessment (ACWA) selection process (see Volume 1).

Kimmell, T.; Folga, S., Frey, G.; Molberg, J.; Kier, P.; Templin, B.; Goldberg, M.

2001-05-04

163

Calvert Marine Museum  

NSDL National Science Digital Library

Facility in Solomons, MD, interprets regional paleontology, estuarine ecosystem, maritime history. Natural history exhibits: shark, whale and other fossils; aquariums, displays and outdoor trails introducing life of marshes, oyster bars, the Patuxent River and Chesapeake Bay. Maritime history exhibits include woodcarving and boatbuilding shed, oyster house, lighthouse, and traditional Chesapeake Bay wooden sailing vessel. Educational programs for school groups, Elderhostel and the public include: field trips, lectures, cruises, classes, and demonstrations. Admission and program fees apply.

164

Large Eddy Simulations of forced ignition of a non-premixed bluff-body methane flame with Conditional Moment Closure  

SciTech Connect

Large Eddy Simulations (LES) of forced ignition of a bluff-body stabilised non-premixed methane flame using the Conditional Moment Closure (CMC) turbulent combustion model have been performed. The aim is to investigate the feasibility of the use of CMC/LES for ignition problems and to examine which, if any, of the characteristics already observed in related experiments could be predicted. A three-dimensional formulation of the CMC equation was used with simple and detailed chemical mechanisms, and sparks with different parameters (location, size) were used. It was found that the correct pattern of flame expansion and overall flame appearance were predicted with reasonable accuracy with both mechanisms, but the detailed mechanism resulted in expansion rates closer to the experiment. Moreover, the distribution of OH was predicted qualitatively accurately, with patches of high and low concentration in the recirculation zone during the ignition transient, consistent with experimental data. The location of the spark relative to the recirculation zone was found to determine the pattern of the flame propagation and the total time for the flame stabilisation. The size was also an important parameter, since it was found that the flame extinguishes when the spark is very small, in agreement with expectations from experiment. The stabilisation mechanism of the flame was dominated by the convection and sub-grid scale diffusion of hot combustion products from the recirculation zone to the cold gases that enter the burner, as revealed by analysis of the CMC equation. (author)

Triantafyllidis, A.; Mastorakos, E. [Hopkinson Laboratory, Department of Engineering, University of Cambridge, Cambridge CB2 1PZ (United Kingdom); Eggels, R.L.G.M. [Rolls Royce Deutschland, Blankenfelde-Mahlow (Germany)

2009-12-15

165

A non-uniform vortex method for 3-D bluff body flows using parallelized multipole tree codes  

NASA Astrophysics Data System (ADS)

Direct numerical simulations of 3-D bluff body flows are performed using a vortex method. These simulations require a high number of vortex particles (N=O(10^5 - 10^6)) and a high number of surface elements (M=O(10^4 - 10^5)). The fast multipole tree-code running on a parallel computer leads to efficient Biot-Savart evaluation (velocity and its gradient). The boundary integral problem (used to enforce the no-slip boundary condition through the vorticity flux) is solved iteratively, each iteration using the parallel multipole method to achieve an efficient ``matrix-vector'' multiply. The non-uniform particle redistribution technique, here designed for intersection with general body shapes, is also used. Viscous diffusion by the particle strength exchange scheme is still done in physical space; the method is shown, both theoretically and numerically, to be second order accurate. Simulations of the flow past a sphere at Re=300 and Re=1000 will be presented, together with the evaluation of the unsteady forces. The case of a vehicule-like body (the Ahmed body) will also be presented.

Ploumhans, Paul; Winckelmans, Gregoire S.; Salmon, John K.; Warren, Michael S.

2000-11-01

166

Seepage erosion of Arctic coastal bluffs driven by thawing permafrost in Northwest Alaska  

Microsoft Academic Search

On the forefront of transient landscapes is the Arctic. Air and sea surface temperatures have increased significantly in the last 50 years due to anthropogenic warming, and have been blamed for observed accelerations in coastal erosion rates and the formation of thermokarst features. The controls that permafrost exerts on landforms and sediment transport are largely unknown, but may be elucidated

C. B. Phillips; D. J. Jerolmack; B. T. Crosby

2010-01-01

167

Petrology of Inclusion-Rich Lavas at Minna Bluff, Antarctica: Implications for Magma Origin, Differentiation and Eruption Dynamics  

NASA Astrophysics Data System (ADS)

Inclusion-bearing lava, dome and cinder cone deposits are distributed along the top of Minna Bluff, a 45 km long volcanic peninsula located in the southern Ross Sea. One deposit, informally named Xeno Ridge, consists of phonolitic lavas that host a diversity of inclusion types that vary in size (<1 to 25 cm), shape (angular to teardrop), texture (porphyritic to granular) and composition (mafic to felsic). The dominate types include salt and peppered colored enclaves (nepheline-bearing syenite and kaersutite-rich diorite) that have granular textures and sharp contact margins with the host lava indicating that they were fully solidified when entrained. Others are dark, highly vesicular, amphibole-rich phonotephrite inclusions with fluidal forms and crenulate contact margins with the host lava indicating magma comingling. All amphibole is kaersutite and phenocrysts within the host lava are often mantled by thick fine-grained rims of diopside, plagioclase and magnetite formed by devolatilization and reaction with the surrounding melt at shallow depth. Semi- quantitative thermobarometric results for kaersutite and clinopyroxene indicate P-T conditions for crystallization of hydrous magmas within the lower crust and upper mantle (5-9 kbars, ~ 15-27 km depth; >= 1000°C). High water contents caused early crystallization of amphibole and clinopyroxene and suppression of plagioclase, which crystallized later with magnetite at lower pressures. The magmatic history of Xeno Ridge is summarized as follows: first, phonolitic magmas rise into the upper crust, stagnate and devolatilize; second, replenishing mafic magmas mix with phonolite and trigger eruption; third, the mixed magmas entrain crystalline selvages from conduit walls on ascent to the surface.

Scanlan, M.; Panter, K. S.; Wilch, T. I.; Dunbar, N. W.; McIntosh, W. C.

2008-12-01

168

Study of hydrocarbon miscible solvent slug injection process for improved recovery of heavy oil from Schrader Bluff pool, Milne Point Unit, Alaska. Quarterly report, October 1, 1993--December 31, 1993  

SciTech Connect

The ultimate objective of this three-year research project is to evaluate the performance of the hydrocarbon miscible solvent slug process and to assess the feasibility of this process for improving recovery of heavy oil from Schrader Bluff reservoir. This will be accomplished through measurement of PVT and fluid properties of Schrader Bluff oil, determination of phase behavior of Schrader Bluff oil solvent mixtures, asphaltene precipitation tests, slim tube displacement tests, core flood experiments and reservoir simulation studies. The expected results from this project include: determination of optimum hydrocarbon solvent composition suitable for hydrocarbon miscible solvent slug displacement process, optimum slug sizes of solvent needed, solvent recovery factor, solvent requirements, extent and timing of solvent recycle, displacement and sweep efficiency to be achieved and oil recovery.

Sharma, G.D.

1993-12-31

169

Ground-water conditions in the Dutch Flats area, Scotts Bluff and Sioux Counties, Nebraska, with a section on chemical quality of the ground water  

USGS Publications Warehouse

The U.S. Department of the Interior (DOI) studied contamination induced by irrigation drainage in 26 areas of the Western United States during 1986-95. Comprehensive compilation, synthesis, and evaluation of the data resulting from these studies were initiated by DOI in 1992. Soils and ground water in irrigated areas of the West can contain high concentrations of selenium because of (1) residual selenium from the soil's parent rock beneath irrigated land; (2) selenium derived from rocks in mountains upland from irrigated land by erosion and transport along local drainages, and (3) selenium brought into the area in surface water imported for irrigation. Application of irrigation water to seleniferous soils can dissolve and mobilize selenium and create hydraulic gradients that cause the discharge of seleniferous ground water into irrigation drains. Given a source of selenium, the magnitude of selenium contamination in drainage-affected aquatic ecosystems is strongly related to the aridity of the area and the presence of terminal lakes and ponds. Marine sedimentary rocks and deposits of Late Cretaceous or Tertiary age are generally seleniferous in the Western United States. Depending on their origin and history, some Tertiary continental sedimentary deposits also are seleniferous. Irrigation of areas associated with these rocks and deposits can result in concentrations of selenium in water that exceed criteria for the protection of freshwater aquatic life. Geologic and climatic data for the Western United States were evaluated and incorporated into a geographic information system (GIS) to produce a map identifying areas susceptible to irrigation-induced selenium contamination. Land is considered susceptible where a geologic source of selenium is in or near the area and where the evaporation rate is more than 2.5 times the precipitation rate. In the Western United States, about 160,000 square miles of land, which includes about 4,100 square miles (2.6 million acres) of land irrigated for agriculture, has been identified as being susceptible. Biological data were used to evaluate the reliability of the map. In 12 of DOI's 26 study areas, concentrations of selenium measured in bird eggs were elevated sufficiently to significantly reduce hatchability of the eggs. The GIS map identifies 9 of those 12 areas. Deformed bird embryos having classic symptoms of selenium toxicosis were found in four of the study areas, and the map identifies all four as susceptible to irrigation-induced selenium contamination. The report describes the geography, geology, and ground-water resources of the Dutch Flats area in Scotts Bluff and Sioux Counties, Nebr. The area comprises about 60 square miles and consists predominantly of relatively flat-lying terraces. Farming is the principal occupation in the area. The farm lands are irrigated largely from surface water; ground water is used only as a supplementary supply during drought periods. The climate in the area is semiarid, and the mean annual precipitation is about 16 inches. The rocks exposed in the Dutch Flats area are of Tertiary sad Quaternary age. A map showing the areas of outcrop of the rock formations is included in the report. Sufficient unconfined ground water for irrigation supplies is contained in the deposits of the .third terrace, and wells that yield 1,000 to 2,000 gallons a minute probably could be developed. The depth to water in the area ranges from a few feet to about 80 feet sad averages about 30 feet. The depth to water varies throughout the year; it is least in the late summer when the recharge from irrigation is greatest, sad it is greatest in the early spring before irrigation is begun. A map showing the depth to water in September 1949 is included in the report. The ground-water reservoir is recharged by seepage from irrigation canals and laterals, by seepage from irrigation water applied to the farms, and, to a much lesser extent, by precipitation. In the area b

Babcock, H. M.; Visher, F. N.; Durum, W. H.

1951-01-01

170

Laboratory measurements of selected optical, physical, chemical, and remote-sensing properties of five water mixtures containing Calvert clay and a nonfluorescing dye  

NASA Technical Reports Server (NTRS)

Total suspended solids concentrations ranged from 6.1 ppm to 24.3 ppm and sizes ranged between 1.5 micrometers and 10 micrometers with the most frequently occurring size less than 2 micrometers. Iron concentration was less than 1 percent of the total suspended solids. Nonfluorescing dye concentrations of the two mixtures were 20 ppm and 40 ppm. Attenuation coefficient for the five mixtures ranged from 4.8/m to 21.3/m. Variations in volume scattering function with phase angle were typical. Variations in attenuation and absorption coefficient with wavelength were similar for the mixtures without the dye. Attenuation coefficient of the mixtures with the dye increased for wavelengths less than 600 nm due to the dye's strong absorption peak near 500 nm. Reflectance increased as the concentration of Calvert clay increased and peaked near 600 nm. The nonfluorescent dye decreased the magnitude of the peak, but had practically no effect on the variation for wavelengths greater than 640 nm. At wavelengths less than 600 nm, the spectral variations of the mixtures with the dye were significantly different from those mixtures without the dye.

Usry, J. W.; Whitlock, C. H.; Poole, L. R.; Witte, W. G., Jr.

1981-01-01

171

Paleoenvironment of the Ogallala (Neogene) Formation in west-central Kansas  

SciTech Connect

At Lake Scott (Scott County) in west-central Kansas, the Ogallala Formation unconformably overlies the Niobrara Formation (Cretaceous) and forms the bluffs of the north-trending Ladder Creek valley. Two sections (Devil's Backbone, 23 m thick; Suicide Bluff, 45 m thick) contain fluvial sands that grade upward into probable eolian sands. The lower sections contain poorly cemented, moderately sorted, arkosic sand, some mud gravel, and poorly defined fluvial channels. In the lower part of Devil's Backbone, cross-bedded sand is capped by mud drapes. At Suicide Bluff, beds of cross-bedded and better sorted sand occur high in the section. Paleosols and secondary calcite and opal dominate the sections. Pedogenic calcretes with more than 52% CaCO[sub 3] are especially abundant and range up to morphologic Stage VI. The [delta][sup 13]C and [delta][sup 18]O in the calcretes range from [minus]4.8 to [minus]6.5 and [minus]8.2 to [minus]6.7 per mil (PDB), respectively. Opal-A has replaced most rhizoliths of the Ogallala. Silicified fossil seeds (Celtis sp., Biorbia sp.) and probable fossil mammal burrows also occur in the sections. Rhyolitic tephra, about 10 Ma, occurs 12 m below the calcrete caprock of Suicide Bluff. A massive layer of opal occurs about 8 m above the tephra and below a diatomaceous bed. Siliceous cement occurs throughout each section, possibly originating from opal phytoliths, tephra, and/or diatoms. These sections afford the potential for understanding the stratigraphic succession and paleoclimate during the late Miocene to possibly early Pliocene in the central High Plains region.

Twiss, P.C.; McCahon, T.J.; Oviatt, C.G. (Kansas State Univ., Manhattan, KS (United States). Geology Dept.)

1993-02-01

172

Interglacial Extension of the Boreal Forest Limit in the Noatak Valley, Northwest Alaska: Evidence from an Exhumed River-Cut Bluff and Debris Apron  

USGS Publications Warehouse

Numerous exposures of Pleistocene sediments occur in the Noatak basin, which extends for 130 km along the Noatak River in northwestern Alaska. Nk-37, an extensive bluff exposure near the west end of the basin, contains a record of at least three glacial advances separated by interglacial and interstadial deposits. An ancient river-cut bluff and associated debris apron is exposed in profile through the central part of Nk-37. The debris apron contains a rich biotic record and represents part of an interglaciation that is probably assignable to marine-isotope stage 5. Pollen spectra from the lower part of the debris apron closely resemble modern samples taken from the Noatak floodplain in spruce gallery forest, and macrofossils of spruce are also present at this level. Fossil bark beetles and carpenter ants occur higher in the debris apron. Mutual Climatic Range (MCR) estimates from the fossil beetles suggest temperatures similar to or warmer than today. Together, these fossils indicate the presence of an interglacial spruce forest in the western part of the Noatak Basin, which lies about 80 km upstream of the modern limit of spruce forest.

Edwards, M. E.; Hamilton, T. D.; Elias, S. A.; Bigelow, N. H.; Krumhardt, A. P.

2003-01-01

173

Three-dimensional topology and dynamical modelling of vortex shedding from finite surface-mounted bluff bodies  

NASA Astrophysics Data System (ADS)

While the dynamically rich behaviour of fully turbulent wakes is very high dimensional, the most energetic, large scale coherent structures generated through instability processes are typically low dimensional and are thereby conducive to reduced order modeling procedures. These large scale eddies associated with the flow instability have the most anisotropic and geometry dependent topology and act as a source of kinetic energy in the cascade process, making them the most important to characterize. Dissipative small scale structure can then be modelled with reasonable accuracy by traditional means. The present study experimentally educes the coherent structures in the complex three-dimensional wake of a wall-mounted finite square-cross-section cylinder of aspect ratio h/d = 4 and 8 immersed in boundary layers of thickness delta/d = 0.72 and 2.6 at a Reynolds number of 12,000. Coherent structure eduction is carried out using phase averaging and a novel generalized phase averaging technique that incorporates proper orthogonal decomposition (POD) modes that are most important in the nonlinear instability saturation process. Global flow estimation and mode construction is undertaken using linear pressure-POD coefficient correlations, applicable to experimental investigations where practicality demands that subdomains of the global field are measured asynchronously. The large-scale coherent structures of the wakes investigated are analyzed in terms of their topology, their turbulent kinetic energy (amounting to roughly half the total fluctuation energy), and their influence on turbulence production. The educed coherent vortical structures are found to have either full-loop or half-loop topological structure depending on the boundary layer thickness, showing vortical connector strands connecting alternately shed vortices from either side of the obstacle. The structure provides an explanation of the dipole and quadrupole distributions of streamwise vorticity that have previously been observed in these types of three-dimensional wakes. The reduced order nonlinear Galerkin models derived for the dynamics of the coherent structures using the generalized phase average are shown to successfully account for the slow base flow transients, the instability saturation mechanism, and the excitation of the second harmonic modes. KEYWORDS: Full-loop vortex shedding, Half-loop vortex shedding, Finite wall-mounted bluff-bodies, Coherent structures, Trailing vortices, Reduced order modelling, Proper orthogonal decomposition, Linear stochastic estimation, Particle image velocimetry.

Bourgeois, Jason A.

174

Study of hydrocarbon miscible solvent slug injection process for improved recovery of heavy oil from Schrader Bluff Pool, Milne Point Unit, Alaska. Annual report, January 1, 1994--December 31, 1994  

SciTech Connect

Alaska is the second largest oil producing state in the nation and currently contributes nearly 24% of the nations oil production. It is imperative that Alaskan heavy oil fields be brought into production. Schrader Bluff reservoir, located in the Milne Point Unit, which is part of the heavy oil field known as West Sak is estimated to contain 1.5 billion barrels of (14 to 21 degree API) oil-in-place. The field is currently under production by primary depletion. The eventual implementation of enhanced oil recovery (EOR) techniques will be vital for the recovery of additional oil from this reservoir. The availability of hydrocarbon gases (solvents) on the Alaska North Slope make the hydrocarbon miscible solvent injection process an important consideration for the EOR project in Schrader Bluff reservoir. Since Schrader Bluff oil is heavy and viscous, a water-alternating-gas (WAG) type of process for oil recovery is appropriate since such a process tends to derive synergetic benefits from both water injection (which provides mobility control and improvement in sweep efficiency) and miscible gas injection (which provides improved displacement efficiency). A miscible solvent slug injection process rather than continuous solvent injection is considered appropriate. Slim tube displacement studies, PVT data and asphaltene precipitation studies are needed for Schrader bluff heavy oil to define possible hydrocarbon solvent suitable for miscible solvent slug displacement process. Coreflood experiments are also needed to determine the effect of solvent slug size, WAG ratio and solvent composition on the recovery and solvent breakthrough. A compositional reservoir simulation study will be conducted later to evaluate the complete performance of the hydrocarbon solvent slug process and to assess the feasibility of this process for improving recovery of heavy oil from Schrader Bluff reservoir.

Sharma, G.D.

1995-07-01

175

The Knowledge Bluff  

ERIC Educational Resources Information Center

Our knowledge "system" is built up from disciplines and specialties as its components, which are "wired" by patterns of collaboration that constitute its organization. The intellectual autonomy of these components prevents this knowledge system from adequately accounting for what we have gradually discovered during the past 50 years: In human…

Vanderburg, Willem H.

2007-01-01

176

Cavitating flows around a NACA0015 hydrofoil and a bluff body. The effect of cavitation on turbulent structure of the flows  

NASA Astrophysics Data System (ADS)

In the work, cavitating flows around a two-dimensional foil of NACA0015 series and a bluff symmetrical body were studied experimentally by means of PIV/LIF technique and high-speed imaging. The flows were investigated for different angles of incidence (from 0° up to 9°) and cavitation numbers (from 0,7 to 2,4), which allowed to register various patterns of partial cavities. Cavitation inception and development were of a particular interest in this study. As a result, instantaneous velocity and vorticity fields were measured and an analysis of instantaneous structure and evolution of partial cavities was performed. Finally, the full set of statistical moments of turbulent fluctuations (including the thirdorder ones) was calculated for cavitation and cavitation-free conditions. The paper reports the effects of body shape and cavitation pattern on the turbulent structure of the flows.

Kravtsova, A. Yu.; Markovich, D. M.; Pervunin, K. S.; Timoshevskiy, M. V.

2012-03-01

177

Study of hydrocarbon miscible solvent slug injection process for improved recovery of heavy oil from Schrader Bluff Pool, Milne Point Unit, Alaska. [Quarterly] report, January 1, 1994--March 31, 1994  

SciTech Connect

The ultimate objective of this three-year research project is to evaluate the performance of the hydrocarbon miscible solvent slug process and to assess the feasibility of this process for improving recovery of heavy oil from Schrader Bluff reservoir. This will be accomplished through measurement of PVT and fluid properties of Schrader Bluff oil, determination of phase behavior of Schrader Bluff oil solvent mixtures, asphaltene precipitation tests, slim tube displacement tests, core flood experiments and reservoir simulation studies. The expected results from this project include: determination of optimum hydrocarbon solvent composition suitable for hydrocarbon miscible solvent slug displacement process, optimum slug sizes of solvent needed, solvent recovery factor, solvent requirements, extent and timing of solvent recycle, displacement and sweep efficiency to be achieved and oil recovery. During this quarter, more displacement experiments in slim tube and miscible coreflood experiments have been conducted. Also, work has been initiated to match the slim tube displacement results using GEM, a compositional simulator developed by Computer Modelling Group.

Sharma, G.D.

1994-06-01

178

Study of hydrocarbon miscible solvent slug injection process for improved recovery of heavy oil from Schrader Bluff Pool, Milne Point Unit, Alaska. [Quarterly] report, January 1, 1993--March 31, 1993  

SciTech Connect

The ultimate objective of this three-year research project is to evaluate the performance of the hydrocarbon miscible solvent slug process and to assess the feasibility of this process for improving recovery of heavy oil from Schrader Bluff reservoir. This will be accomplished through measurement of PVT and fluid properties of Schrader Bluff oil, determination of phase behavior of Schrader Bluff oil solvent mixtures, asphaltene precipitation tests, slim tube displacement tests, core flood experiments and reservoir simulation studies. The expected results from this project include: determination of optimum hydrocarbon solvent composition suitable for hydrocarbon miscible solvent slug displacement process, optimum slug sizes of solvent needed, solvent recovery factor, solvent requirements, extent and timing of solvent recycle, displacement and sweep efficiency to be achieved and oil recovery. Work performed during quarter includes preliminary reservoir fluid characterization and multiple contact test runs using equation-of-state (EOS) simulator. Reservoir fluid samples are being acquired from Conoco Inc., and the process is expected to continue through the next quarter. Also, the experimental apparatus for the displacement study was set up.

Sharma, G.D.

1993-06-01

179

Structural geology of the Mesozoic Miers Bluff Formation and crosscutting Paleogene dikes (Livingston Island, South Shetland Islands, Antarctica) – Insights into the geodynamic history of the northern Antarctic Peninsula  

Microsoft Academic Search

The Antarctic Peninsula has been part of a magmatic arc since at least Jurassic times. The South Shetland Islands archipelago forms part of this arc, but it was separated from the Peninsula following the Pliocene opening of the Bransfield Strait. Dikes are widespread throughout the archipelago and are particularly accessible on the Hurd Peninsula of Livingston Island. The host rocks

S. Kraus; H. Miller; D. Dimov; E. Hegner; M. McWilliams; Z. Pecskay

2008-01-01

180

Superfund Record of Decision (EPA Region 7): Mid-America Tanning site, Sergeant bBluff, IA. (First remedial action), September 1991  

SciTech Connect

The 98.7-acre Mid-America Tanning site is a former leather tannery in Sergeant Bluff, Woodbury County, Iowa. Surrounding land use is mixed industrial and agricultural. A portion of the site is bordered by Oxbow Lake and lies within the 100-year floodplain. The Missouri River is approximately 1.5 miles to the southwest of the site and receives discharges from Oxbow Lake. The facility began onsite processing of animal hides in 1970. In 1980, the State confirmed the onsite burial of chromium-containing sludge in trenches, and the company was cited for permit violations. A 1985 EPA investigation identified excessive chromium contamination in onsite soil, sediment, and ground water. In 1990, EPA conducted a removal action that included excavating and consolidating onsite 1,290 cubic yards of sludge from the trench disposal area. The Record of Decision (ROD) addresses the contaminated soil, impoundment sediment and water, and the excavated trench material. A future ROD will address onsite ground water contamination. The primary contaminant of concern affecting the soil, sediment, debris, sludge, and surface water are metals including chromium and lead. The selected remedial action for the site is included.

Not Available

1991-09-24

181

Habitat quality and recruitment success of cui-ui in the Truckee River downstream of Marble Bluff Dam, Pyramid Lake, Nevada  

USGS Publications Warehouse

We compared cui-ui (Chasmistes cujus) recruitment from two reaches of the Truckee River with histories of severe erosional downcutting caused by a decline in Pyramid Lake surface elevation. In 1975, Marble Bluff Dam (MBD) was constructed 5 kilometers upstream of the extant mouth of the Truckee River to stabilize the upstream reach of the river; the downstream reach of the river remained unstable and consequently unsuitable for cui-ui recruitment. By the early 2000s, there was a decrease in the Truckee River’s slope from MBD to Pyramid Lake after a series of wet years in the 1990s. This was followed by changes in river morphology and erosion abatement. These changes led to the question as to cui-ui recruitment potential in the Truckee River downstream of MBD. In 2012, more than 7,000 cui-ui spawners were passed upstream of MBD, although an indeterminate number of cui-ui spawned downstream of MBD. In this study, we compared cui-ui recruitment upstream and downstream of MBD during a Truckee River low-flow year (2012). Cui-ui larvae emigration to Pyramid Lake began earlier and ended later downstream of MBD. A greater number of cui-ui larvae was produced downstream of MBD than upstream. This also was true for native Tahoe sucker (Catostomus tahoensis) and Lahontan redside (Richardsonius egregius). The improved Truckee River stability downstream of MBD and concomitant cui-ui recruitment success is attributed to a rise in Pyramid Lake's surface elevation. A decline in lake elevation may lead to a shift in stream morphology and substrate composition to the detriment of cui-ui reproductive success as well as the reproductive success of other native fishes.

Scoppettone, G. Gary; Rissler, Peter H.; Salgado, J. Antonio; Harry, Beverly

2013-01-01

182

Invertebrate fossils (Insecta: Trichoptera, Diptera, Coleoptera) from the Pleistocene Scarborough Formation at Toronto, Ontario, and their paleoenvironmental significance  

NASA Astrophysics Data System (ADS)

Larval caddisfly, chironomid, and beetle remains have been recovered from the Pleistocene Scarborough Formation in the Toronto region of southern Ontario. Three stratigraphic levels were sampled at the northeastern end of the Scarborough Bluffs; the youngest horizon yielded 16 chironomid taxa, 33 caddisfly taxa, and 28 beetle taxa, whereas the two older levels yielded somewhat less diverse assemblages. Only one taxon in each of the caddisfly and chironomid groups was identified from the presumed correlative beds at Woodbridge, Ontario, but numerous beetle fragments were recovered, several of which have been specifically identified and match species found previously in the upper part of the Scarborough Formation. The youngest sampled assemblage in the Scarborough Formation at the northeastern end of the Scarborough Bluffs is interpreted as indicating cool climatic conditions in a boreal forest environment, given the present-day distributions and feeding habits of these river, lake, and terrestrial taxa. The mean July temperature at this time was probably about 15°C, as compared to the present-day value of 20.5°C. The forest was poorer in deciduous species during deposition of the older part of the formation as preserved here. These results agree well with previous interpretations based on plant remains. We suggest that both aquatic and terrestrial insects are good indicators of macroclimate.

Williams, Nancy E.; Westgate, John A.; Williams, D. Dudley; Morgan, Anne; Morgan, Alan V.

1981-09-01

183

Quaternary geology of the Duck Hawk Bluffs, southwest Banks Island, Arctic Canada: a re-investigation of a critical terrestrial type locality for glacial and interglacial events bordering the Arctic Ocean  

NASA Astrophysics Data System (ADS)

Duck Hawk Bluffs, southwest Banks Island, is a primary section (8 km long and 60 m high) in the western Canadian Arctic Archipelago exposing a long record of Quaternary sedimentation adjacent to the Arctic Ocean. A reinvestigation of Duck Hawk Bluffs demonstrates that it is a previously unrecognized thrust-block moraine emplaced from the northeast by Laurentide ice. Previous stratigraphic models of Duck Hawk Bluffs reported a basal unit of preglacial fluvial sand and gravel (Beaufort Fm, forested Arctic), overlain by a succession of three glaciations and at least two interglacials. Our observations dismiss the occurrence of preglacial sediments and amalgamate the entire record into three glacial intervals and one prominent interglacial. The first glacigenic sedimentation is recorded by an ice-contact sandur containing redeposited allochthonous organics previously assigned to the Beaufort Fm. This is overlain by fine-grained sediments with ice wedge pseudomorphs and well-preserved bryophyte assemblages corresponding to an interglacial environment similar to modern. The second glacial interval is recorded by ice-proximal mass flows and marine rhythmites that were glacitectonized when Laurentide ice overrode the site from Amundsen Gulf to the south. Sediments of this interval have been reported to be magnetically reversed (>780 ka). The third interval of glacigenic sedimentation includes glacifluvial sand and gravel recording the arrival of Laurentide ice that overrode the site from the northeast (island interior) depositing a glacitectonite and constructing the thrust block moraine that comprises Duck Hawk Bluffs. Sediments of this interval have been reported to be magnetically normal (<780 ka). The glacitectonite contains a highly deformed melange of pre-existing sediments that were previously assigned to several formally named, marine and interglacial deposits resting in an undeformed sequence. In contrast, the tectonism associated with the thrust block moraine imparted pervasive deformation throughout all underlying units, highlighted by a previously unrecognized raft of Cretaceous bedrock. During this advance, Laurentide ice from the interior of Banks Island coalesced with an ice stream in Amundsen Gulf, depositing the interlobate Sachs Moraine that contains shells as young as ?24 cal ka BP (Late Wisconsinan). During deglaciation, meltwater emanating from these separating ice lobes deposited outwash that extended to deglacial marine limit (11 m asl) along the west coast of Banks Island. Our new stratigraphic synthesis fundamentally revises and simplifies the record of past Quaternary environments preserved on southwest Banks Island, which serves as a key terrestrial archive for palaeoenvironmental change.

Evans, David J. A.; England, John H.; La Farge, Catherine; Coulthard, Roy D.; Lakeman, Thomas R.; Vaughan, Jessica M.

2014-05-01

184

Shatter Complex Formation in the Twin Craters Lava Flow, Zuni-Bandera Field, New Mexico  

NASA Astrophysics Data System (ADS)

Lava channels, tubes and sheets are transport structures that deliver flowing lava to a flow front. The type of structure can vary within a flow field and evolve throughout an eruption. The 18.0 × 1.0 ka Twin Craters lava flow in the Zuni-Bandera lava field provides a unique opportunity to study morphological changes of a lava flow partly attributable to interaction with a topographic obstacle. Facies mapping and airborne image analysis were performed on an area of the Twin Craters flow that includes a network of channels, lava tubes, shatter features, and disrupted pahoehoe flows surrounding a 45 m tall limestone bluff. The bluff is 1000 m long (oriented perpendicular to flow.) The general flow characteristics upstream from the bluff include smooth, lobate pahoehoe flows and a >2.5 km long lava tube (see Samuels et al., this meeting.) Emplacement characteristics change abruptly where the flow encountered the bluff, to include many localized areas of disrupted pahoehoe and several pahoehoe-floored depressions. Each depression is fully or partly surrounded by a raised rim of blocky material up to 4 m higher than the surrounding terrain. The rim is composed of 0.05 - 4 m diameter blocks, some of which form a breccia that is welded by lava, and some of which exhibit original flow textures. The rim-depression features are interpreted as shatter rings based on morphological similarity to those described by Orr (2011.Bul Volcanol.73.335-346) in Hawai';i. Orr suggests that shatter rings develop when fluctuations in the lava supply rate over-pressurize the tube, causing the tube roof to repeatedly uplift and subside. A rim of shattered blocks and breccias remains surrounding the sunken tube roof after the final lava withdraws from the system. One of these depressions in the Twin Craters flow is 240 m wide and includes six mounds of shattered material equal in height to the surrounding undisturbed terrain. Several mounds have depressed centers floored with rubbly pahoehoe. Prominent ';a';a channels travel around the bluff, leaving a 'wake' of uncovered ground on the downstream side. We interpret this shatter area to have been a branching tube network within an active sheet. The limestone bluff acted as an obstacle that caused a backup of lava within the tubes, driving episodes of shattering. The mounds likely represent earlier solidified sections between active, possibly braided, tube branches, which remained as mounds within the shatter area after the adjacent crust subsided. When lava broke out from the pressurized sheet-like lobe, it formed the ';a';a channels. This section of the flow field is interpreted using inferences from shatter ring formation, but is perhaps better termed a shatter sheet or shatter complex. This study has implications for understanding lava flow dynamics at constriction points, as well as the evolution and morphology of shatter rings.

von Meerscheidt, H. C.; Bleacher, J. E.; Brand, B. D.; deWet, A.; Samuels, R.; Hamilton, C.; Garry, W. B.; Bandfield, J. L.

2013-12-01

185

Torsional flutter of bluff bodies  

Microsoft Academic Search

This paper describes the torsional flutter mechanism of 2D rectangular cylinders and 2D H-shaped cylinders based upon unsteady pressure measurements under forced torsional vibration. For some cylinders with certain side ratio (BD, B: chord length, D: cylinder thickness), such as BD = 5 to BD = 12.5, in the high reduced velocity range, that is V\\/f B> 10 (f: torsional

Masaru Matsumoto; Yoshiyuki Daito; Fumitaka Yoshizumi; Yasuo Ichikawa; Tadahiro Yabutani

1997-01-01

186

Formation of lunar basin rings  

USGS Publications Warehouse

The origin of the multiple concentric rings that characterize lunar impact basins, and the probable depth and diameter of the transient crater have been widely debated. As an alternative to prevailing "megaterrace" hypotheses, we propose that the outer scarps or mountain rings that delineate the topographic rims of basins-the Cordilleran at Orientale, the Apennine at Imbrium, and the Altai at Nectaris-define the transient cavities, enlarged relatively little by slumping, and thus are analogous to the rim crests of craters like Copernicus; inner rings are uplifted rims of craters nested within the transient cavity. The magnitude of slumping that occurs on all scarps is insufficient to produce major inner rings from the outer. These conclusions are based largely on the observed gradational sequence in lunar central uplifts:. from simple peaks through somewhat annular clusters of peaks, peak and ring combinations and double ring basins, culminating in multiring structures that may also include peaks. In contrast, belts of slump terraces are not gradational with inner rings. Terrestrial analogs suggest two possible mechanisms for producing rings. In some cases, peaks may expand into rings as material is ejected from their cores, as apparently occurred at Gosses Bluff, Australia. A second process, differential excavation of lithologically diverse layers, has produced nested experimental craters and is, we suspect, instrumental in the formation of terrestrial ringed impact craters. Peak expansion could produce double-ring structures in homogeneous materials, but differential excavation is probably required to produce multiring and peak-in-ring configurations in large lunar impact structures. Our interpretation of the representative lunar multiring basin Orientale is consistent with formation of three rings in three layers detected seismically in part of the Moon-the Cordillera (basin-bounding) ring in the upper crust, the composite Montes Rook ring in the underlying, more coherent "heald" crust, and an innermost, 320-km ring at the crust-mantle interface. Depth-diameter ratios of 1 10to 1 15 are consistent with this interpretation and suggest that volumes of transient cavities and hence of basin ejecta may be considerably greater than commonly assumed. ?? 1978.

Hodges, C. A.; Wilhelms, D. E.

1978-01-01

187

Ab initio studies of the formation of a Y1-xNi2 superstructure with ordered Y vacancies  

NASA Astrophysics Data System (ADS)

Ab initio total-energy calculations have been performed to study the structural stability of Y1-xNi2. In the literature (Villars P and Calvert L D 1985 Pearson's Handbook of Crystallographic Data for Intermetallic Phases (Materials Park, OH: American Society for Metals)) YNi2 is often considered to show the cubic Laves phase structure, but x-ray diffraction experiments of Latroche et al ( J. Less-Common Met. 161 L27) showed that YNi2 crystallizes in a superstructure of C15 with ordered Y vacancies with a stoichiometry of approximately Y0.95Ni2. The total-energy calculations for the superstructure and for the ideal C15 structure, as well as for the neighbouring phases in the Y-Ni phase diagram YNi and YNi3, confirm that the formation of the superstructure with Y vacancies is favoured against the formation of the pure C15 compound YNi2. The calculated relaxation of the atoms around the vacancies is also in good agreement with the experimental results (Latroche et al), demonstrating that the relaxation of strains in the Y sublattice is the driving mechanism for formation of vacancies. In addition, the electronic properties of the vacancy superstructure have been examined.

Lindbaum, A.; Hafner, J.; Gratz, E.

1999-02-01

188

Vortices induced in a stagnation region by wakes - Their incipient formation and effects on heat transfer from cylinders  

NASA Technical Reports Server (NTRS)

Horseshoe-like vortices, induced by wakes in the stagnation region of bluff bodies, are proposed as an efficient mechanism for augmentation of convective heat transfer. The vortex 'flow module' induced by single or multiple wakes, which had not been observed previously, was first documented and the resulting flow field was studied using various visualization techniques and hot-wire anemometry. In an attempt to understand the driving force behind this flow module, the conditions at which incipient formation of the vortices occurs were investigated. Existence of such a threshold is essential and was hitherto an open question in analytical studies of stability of flow in stagnation region. Finally, effects of the flow module on heat transfer from a cylinder were measured.

Nagib, H. M.; Hodson, P. R.

1977-01-01

189

Palaeoenvironmental Indications of Enhanced Primary Productivity During Pliocene Sapropel Formation  

NASA Astrophysics Data System (ADS)

Cores taken during the Ocean Drilling Program (ODP) Leg 160 in the eastern Mediterranean basin revealed periodic, laminated intervals with high organic contents, i.e. sapropels (Emeis et al., 1996). These include Pliocene sediments showing cyclic variations in organic matter deposition strongly correlated to the precession cyclicity of the Earth's orbit (e.g. Rossignol-Strick, 1985; Lourens et al., 1996a). The two main causes for sapropel formation are either climate-related enhanced organic matter productivity and/or increased preservation due to oxygen depletion of the bottom waters (e.g. Calvert et al., 1992; Canfield, 1994). Increased productivity is suggested to be the driving force in generating euxinic conditions leading to sapropel deposition (e.g. Passier et al., 1999). Photic zone euxinia was most probably triggered by large-scale input of nutrients from the Nile and other rivers leading to enhanced primary productivity and consequently high organic matter fluxes. This was based on concentrations of isorenieratene, a biomarker of photic zone euxinia, studied in three lateral time-equivalent Pliocene sapropels (subm. Menzel et al., 2001). Photic zone euxinia was more pronounced at the central and western part of the eastern Mediterranean basin, when compared with the most eastern part, where a deepening of the chemocline resulted from the increased delivery of fresh water. Using additional biomarkers will provide detailed insights in palaeoenvironmental changes that caused high organic matter deposition. The quantitative analysis of compounds specific for phytoplankton classes, e.g. isololiolides and loliolides reflecting Bacillariophyta, C37 - C39 alkenones indicative of Prymnesiophyta etc., will result in reconstruction of compositions of the standing crop and changes thereof at the time of deposition. The quantitative analysis of long-chain n-alkanes, indicating higher land plants, could reveal river input into the basin. Carbon isotope compositions of these alkanes may provide signatures in vegetation transition between C4/C3 land plants at periods of sapropel and non-sapropel formation. Changes in primary productivity conditions will be investigated using carbon isotope analyses of alkenones, reflecting the fractionation effect during CO2 assimilation. Simultaneously, the Uk'37 of C37 alkenones will be used to reconstruct climate-related sea surface temperature changes in the basin. References: Calvert, S.E. Nielsen, B. and Fontugne, M.R., 1992. Nature, 359: 223-225. Canfield, D.E., 1994. Chem. Geol., 114: 315-329. Emeis, K.C., Robertson, A.H.F., Richter, C. et al., 1996. Proceedings of the Ocean Drilling Program, 160 (initial reports, Mediterranean 1, College Station, TX). Lourens L.J., Antonarakou, A., Hilgen, F.J., van Hoof, A.A.M., Vergnaud-Grazzine, C. and Zachariasse, W.J., 1996a. Palaeoceanography, 11: 391-413. Menzel, D., Hopmans, E.C., van Bergen, P.F., de Leeuw, J.W. and Sinninghe Damste, J.S. subm. 2001. Passier, H.F., Bosch, H.J., Nijenhuis, I.A., Lourens, L.J., Boettcher, M.E., Leenders, A., Sinninghe Damste, J.S., de Lange, G.J. and de Leeuw, J.W., 1999. Nature, 397: 146-149.

Menzel, D.; Hopmans, E. C.; Schouten, S.; van Bergen, P. F.; Sinninghe Damste, J. S.

2001-12-01

190

Drop Formation  

NSDL National Science Digital Library

This site from the University of BristolâÂÂs Mathematics department contains an explanation of drop formation and its applications. A description of studies of drop separation and its applications in medicine and technology are provided. The site also contains photographs, including a series of images showing the formation of a satellite drop.

2010-03-25

191

Soil Formation  

NSDL National Science Digital Library

Humans use soil for their daily needs but do not sufficiently take account of its slow formation and fast loss. Discover the amazing geology of soil formation and the basic rock and soil types.Although soil seems the end product from weathering rocks, it is merely a stage in the gigantic cycle of mineral recycling by the movement of tectonic plates.

2008-07-24

192

Regolith Formation  

NSDL National Science Digital Library

In this three-part activity, learners use food to determine the effects of wind, sandblasting and water on regolith (dust) formation and deposition on Earth. Then, learners simulate regolith formation on the Moon by meteorite bombardment, an activity best completed outdoors.

Nasa

1997-01-01

193

Godiva Rim Member: A new stratigraphic unit of the Green River Formation in southwest Wyoming and northwest Colorado. Geology of the Eocene Wasatch, Green River, and Bridger (Washakie) Formations, Greater Green River Basin, Wyoming, Utah, and Colorado. Professional paper  

SciTech Connect

The report names and describes the Godiva Rim Member of the Green River Formation in the eastern part of the Washakie basin in southwest Wyoming and the central part of the Sand Wash basin in northwest Colorado. The Godiva Rim Member comprises lithofacies of mixed mudflat and lacustrine origin situated between the overlying lacustrine Laney Member of the Green River Formation and the underlying fluvial Cathedral Bluffs Tongue of the Wasatch Formation. The Godiva Rim Member is laterally equivalent to and grades westward into the LaClede Bed of the Laney Member. The Godiva Rim Member of the Green River Formation was deposited along the southeast margins of Lake Gosiute and is correlated to similar lithologic units that were deposited along the northeast margins of Lake Uinta in the Parachute Creek Member of the Green River Formation. The stratigraphic data presented provide significant evidence that the two lakes were periodically connected around the east end of the Uinta Mountains during the middle Eocene.

Roehler, H.W.

1991-01-01

194

Star Formation  

NASA Astrophysics Data System (ADS)

Stars are one of the most important constituents of the Universe, and understanding their formation is crucial to many areas of astrophysics. Stars form from dense molecular gas, and they tend not to form in isolation. Stars often form in binary and multiple systems, and these systems tend to form in clusters with 102-105 members. Stars also form with a wide range of masses, from substellar brown dwarfs with masses < 0. 1 M ? to massive stars > 100 M ?, and wherever stars form the distribution of their masses seems always to be the same. This chapter will review our current understanding of star formation from cold gas to young star clusters.

Goodwin, Simon

195

Vortex equilibrium in flows past bluff bodies  

NASA Astrophysics Data System (ADS)

The equilibrium conditions of a point vortex in the separated flow past a locally deformed wall is studied in the framework of the two-dimensional potential flow. Equilibrium locations are represented as fixed points of the vortex Hamiltonian contour line map. Their pattern is ascribable to the Poincaré Birkhoff fixed-point theorem. An ‘equilibrium manifold’, representing the generalization of the Föppl curve for circular cylinders, is defined for arbitrary bodies. The property partialomega/partialskew3tildepsi {=} 0 holds on it, with skew3tildepsi being the stream function and omega the streamline slope of the pure potential flow.

Zannetti, Luca

2006-09-01

196

Prescribed Burn at Pine Bluff Arsenal.  

National Technical Information Service (NTIS)

Previous to the establishment of the arsenal in 1941 the area was a mix of farms and forest. The area was cutover for timber before 1920. The flat areas were cultivated and steeper area used as woodlots and grazing for cattle and hogs. Abandoned fields gr...

L. Peacock D. Zollber S. Simon

2000-01-01

197

Identifying Fossils: Exploring the Mississippi River Bluffs  

NSDL National Science Digital Library

This activity is a geology lab where students learn about fossils found in sedimentary rocks and show their understanding by writing a literary nonfiction paper from the perspective of one of those fossils.

198

Planet Formation  

NASA Astrophysics Data System (ADS)

1. Historical notes on planet formation Bodenheimer; 2. The formation and evolution of planetary systems Bouwman et al.; 3. Destruction of protoplanetary disks by photoevaporation Richling, Hollenbach and Yorke; 4. Turbulence in protoplanetary accretion disks Klahr, Rozyczka, Dziourkevitch, Wunsch and Johansen; 5. The origin of solids in the early solar system Trieloff and Palme; 6. Experiments on planetesimal formation Wurm and Blum; 7. Dust coagulation in protoplanetary disks Henning, Dullemond, Wolf and Dominik; 8. The accretion of giant planet cores Thommes and Duncan; 9. Planetary transits: direct vision of extrasolar planets Lecavelier des Etangs and Vidal-Madjar; 10. The core accretion - gas capture model Hubickyj; 11. Properties of exoplanets Marcy, Fischer, Butler and Vogt; 12. Giant planet formation: theories meet observations Boss; 13. From hot Jupiters to hot Neptures … and below Lovis, Mayor and Udry; 14. Disk-planet interaction and migration Masset and Kley; 15. The Brown Dwarf - planet relation Bate; 16. From astronomy to astrobiology Brandner; 17. Overview and prospective Lin.

Klahr, Hubert; Brandner, Wolfgang

2011-02-01

199

Formation Control  

Microsoft Academic Search

This paper deals with vision-based localization for leader- follower formation control. Each unicycle robot is equipped with a panoramic camera that only provides the view angle to the other robots. The localization problem is studied using a new observability condition valid for general nonlinear systems and based on the extended output Jacobian. This allows us to identify those robot motions

Gian Luca Mariottini; Fabio Morbidi; Domenico Prattichizzo; Nicholas Vander Valk; Nathan Michael; George Pappas; Kostas Daniilidis

200

Water-Quality Data, 1999-2005, and Ground-Water Level Data, 2004-2005, for McBaine Bottoms, Including the Eagle Bluffs Conservation Area, Columbia, Missouri  

USGS Publications Warehouse

The U.S. Geological Survey, in cooperation with the city of Columbia, Missouri, and the Missouri Department of Conservation, collected ground-water quality data from June 1999 through August 2005, surface-water quality data from August 1999 through August 2003, and water-level data from February 2004 through August 2005 in McBaine Bottoms, southwest of Columbia. McBaine Bottoms, adjacent to the Missouri River, is the location of the municipal-supply well field for the city of Columbia, the city of Columbia wastewater-treatment wetlands, and the Missouri Department of Conservation Eagle Bluffs Conservation Area. This report presents water-quality data, which include water-quality analyses of samples collected from 36 water-quality sampling sites (31 were wells and 5 were surface-water sites), and ground-water level data, which include water-level measurements from more than 80 wells. Water samples were analyzed for physical properties, inorganic chemical constituents, nutrients, and dissolved iron. Selected samples were analyzed for trace elements, wastewater organic compounds, and pesticides. In samples from monitoring wells, chloride concentrations ranged from 2.41 to 259 mg/L (milligrams per liter), sodium concentrations ranged from 1.08 to 175 mg/L, and sulfate concentrations ranged from less than 0.2 to 271 mg/L (all concentrations were dissolved). Dissolved nitrite plus nitrate as nitrogen concentrations ranged from less than 0.05 to 0.46 mg/L. Total phosphorous concentrations ranged from less than 0.04 to 1.68 mg/L, dissolved phosphorous concentrations ranged from less than 0.04 to 1.50 mg/L, and dissolved orthophosphorous concentrations ranged from less than 0.01 to 1.83 mg/L. Dissolved iron concentrations ranged from less than 6 to 42,900 g/L (micrograms per liter). Dissolved arsenic concentrations in samples from two monitoring wells ranged from 11 to 37 g/L. In samples from surface-water sampling sites, chloride concentrations ranged from 8.67 to 289 mg/L, sodium concentrations ranged from 6.18 to 219 mg/L, and sulfate concentrations ranged from 33.4 to 119 mg/L. All of the minimum concentrations were detected in samples from Perche Creek. Dissolved nitrite plus nitrate as nitrogen concentrations ranged from less than 0.05 to 1.53 mg/L. Total phosphorous concentrations ranged from 0.07 to 3.06 mg/L, dissolved phosphorous concentrations ranged from less than 0.05 to 2.88 mg/L, and dissolved orthophosphorous concentrations ranged from less than 0.01 to 2.86 mg/L. Most of the maximum concentrations were detected in samples from the city outflow. More than 35 wastewater organic compounds and pesticides were detected in samples from the city outflow. However, most concentrations were estimated or their presence verified, but not quantified. Water levels in monitoring wells ranged from 548.54 to 576.55 ft (feet) above the National Geodetic Vertical Datum of 1929 (NGVD 29). The difference in water levels from February 2004 to August 2005 ranged from 0.13 ft to 10.97 ft.

Smith, Brenda J.; Richards, Joseph M.

2006-01-01

201

Galaxy formation  

PubMed Central

It is argued that within the standard Big Bang cosmological model the bulk of the mass of the luminous parts of the large galaxies likely had been assembled by redshift z ? 10. Galaxy assembly this early would be difficult to fit in the widely discussed adiabatic cold dark matter model for structure formation, but it could agree with an isocurvature version in which the cold dark matter is the remnant of a massive scalar field frozen (or squeezed) from quantum fluctuations during inflation. The squeezed field fluctuations would be Gaussian with zero mean, and the distribution of the field mass therefore would be the square of a random Gaussian process. This offers a possibly interesting new direction for the numerical exploration of models for cosmic structure formation.

Peebles, P. J. E.

1998-01-01

202

ANTIBODY FORMATION  

PubMed Central

Injection of a sufficient dose of bacteriophage ?X 174 into guinea pigs results in the formation of rapidly sedimenting antibody molecules (19S), and later, slowly sedimenting molecules (7S). Above a threshold dose of antigen, the relative rate of 19S formation is maximal and dose-independent; below this dose, slower relative rates are obtained. The time for doubling the serum 19S level is as short as 6 to 8 hours, suggesting that the absolute rate of antibody formation per cell is increasing in addition to proliferation of antibody-producing cells. Synthesis of 19S after injection of 1010 ?X virtually ceases at 10 days after which 19S antibody activity disappears from the circulation with a half-life of approximately 24 hours. A second injection of ?X on day 5 or 9 prolongs 19S synthesis, indicating that antigen not only can regulate the relative rate, but also is essential for continued synthesis of 19S. 19S synthesis is also prolonged in guinea pigs by injection of ?X with endotoxin or by 400 r whole body x-irradiation 24 hours after injection of phage into rabbits. The primary 7S response is not detected until approximately 1 week after immunization and relative rates are antigen-dependent. Primary 7S synthesis can continue for many months and leads to preparation for a secondary antibody response (immunological memory) during which only 7S is detected. In contrast, in animals that form precipitating 19S without detectable 7S, a second injection of phage 1 month later results in a second 19S response which closely resembles the first. These findings have led to the suggestion that formation of 19S does not lead to persisting immunological memory.

Uhr, Jonathan W.; Finkelstein, Martin S.

1963-01-01

203

Fossil formation  

NSDL National Science Digital Library

The National Science Education Standards Life Science Content Standard mentions that fossils indicate extinct species and contribute to an understanding of evolution and diversity. The Earth and Space Sciences Content Standard tells us they provide clues about past environments. But what is a fossil? How does it form? The processes can be complex. An understanding of fossil formation will enable accurate student conceptions of related science concepts including methods of science in geology, paleontology, and evolution.

University, Staff A.

2008-03-07

204

Treatment of sandstone formations  

Microsoft Academic Search

A method of treating a subterranean sandstone formation with an aqueous acid solution containing hydrofluoric acid is described. The reaction rate of the acid with the formation is retarded and substantial penetration of the formation with active acid results. When the hydrofluoric acid solution contacts the sandstone formation, siliceous minerals and clay in the formation are dissolved, thereby increasing the

J. A. Knox; R. M. Lasater

1974-01-01

205

Low-frequency unsteadiness in the vortex formation region of a circular cylinder  

NASA Astrophysics Data System (ADS)

The presence of low-frequency fluctuations in the wake of bluff bodies have been observed in several investigations. Even though the flow past a circular cylinder at Re = 3900 (Re = UrefD/?) has been the object of several experimental and numerical investigations, there is a large scattering in the average statistics in the near wake. In the present work, the flow dynamics of the near wake region behind a circular cylinder has been investigated by means of direct numerical simulations and statistics have been computed for more than 858 shedding cycles. The analysis of instantaneous velocity signals of several probes located in the vortex formation region, point out the existence of a low-frequency fluctuation at the non-dimensional frequency of fm = 0.0064. This large-scale almost periodic motion seems to be related with the modulation of the recirculation bubble which causes its shrinking and enlargement over the time. Two different configurations have been identified: (i) a high-energy mode with larger fluctuations in the shear-layer and in the vortex formation region (Mode H) and (ii) a low-energy mode with weaker fluctuations in the shear layer (Mode L). The influence of such a low-frequency in the wake topology has been studied not only by means of the phase-average flow field for each mode, but also by the analysis of the time-average first- and second-order statistics of each wake mode. The results are compared with the long-term averaged solution and with results in the existing literature.

Lehmkuhl, O.; Rodríguez, I.; Borrell, R.; Oliva, A.

2013-08-01

206

Pollen analysis of a late pliocene and early pleistocene section from the Gubik Formation of Arctic Alaska  

USGS Publications Warehouse

A 14-m-thick section of marine and nonmarine sediments of the Gubik Formation of northern Alaska, exposed in bluffs near Ocean Point on the Colville River, has been studied by means of pollen analysis. Pollen from the marine sediments, of probable late Pliocene age, records a boreal forest of spruce and birch with minor amounts of alder in the adjacent terrestrial vegetation. Pine and perhaps true fir were probably at or near their northern limit here, but hemlocks and hardwoods were absent. The suggested environment for the Arctic Slope during the time represented by the marine sediments is similar to that of present-day Anchorage. Pollen floras from the overlying fluvial strata, of early or middle Pleistocene age, record predominantly herbaceous taxa indicating tundra conditions probably more severe than those of the present day. These deposits were most likely contemporaneous with glacial conditions in the Brooks Range to the south. Pollen of woody taxa (spruce, alder, birch, heaths) is rare through most of the section, although birch and alder percentages similar to those found in modern river sediments indicate an interstadial or interglacial warming in midsection. Inland climates during glacial episodes may have been similar to those of the present Arctic coast. ?? 1985.

Nelson, R. E.; Carter, L. D.

1985-01-01

207

Hydrologic and geochemical data for the Big Brown lignite mine area, Freestone County, Texas  

USGS Publications Warehouse

Lignite mining in east and east-central Texas is increasing in response to increased energy needs throughout the State. Associated with the increase in mining activities is a greater need to know the effects of mining activities on the water quantity and quality of near surface aquifers. The near surface lignite beds mined at the Big Brown Lignite Mine are from the Calvert Bluff Formation of the Wilcox Group of Eocene age, which is a minor aquifer generally having water suitable for all uses, in eastern Freestone County, Texas. One of the potential hydrologic effects of surface coal mining is a change in the quality of groundwater associated with replacement of aquifer materials by mine spoils. The purpose of this report is to compile and categorize geologic, mineralogic, geochemical, and hydrologic data for the Big Brown Lignite Mine and surrounding area in east-central Texas. Included are results of paste-extract analyses, constituent concentrations in water from batch-mixing experiments, sulfur analyses, and minerals or mineral groups detected by X-ray diffraction in 12 spoil material samples collected from 3 locations at the mine site. Also, common-constituent and trace-constituent concentrations in water from eight selected wells, located updip and downdip from the mine, are presented. Dissolved solids concentrations in water from batch-mixing experiments vary from 12 to 908 mg/L. Water from selected wells contains dissolved solids concentrations ranging from 75 to 510 mg/L. (Author 's abstract)

Dorsey, M. E.

1985-01-01

208

Depositional facies and eustatic effects in Upper Cretaceous (Maastrichtian) Ripley Formation, central and eastern Alabama  

SciTech Connect

In eastern and central Alabama, the Upper Cretaceous Ripley Formation (40-175 m thick) is comprised of five depositional facies. Facies 1 (barrier-island shoreface and tidal-inlet fill) is a medium to coarse, intraclastic quartzose sand that is planar and trough cross-stratified and has abundant Ophiomorpha traces. Facies 2 (back-barrier lagoon or marsh) is a bioturbated, micaceous, carbonaceous silt that contains macerated plant debris and bivalve molds and impressions. Interbedded with facies 2 is facies 3 (storm-washover deposits), a hummocky cross-stratified, micaceous fine sand. Facies 4 (back-barrier tidal flat) is a micaceous silty clay lacking body fossils and plant debris. Facies 5 (lower shoreface) is a glauconitic, clayey and micaceous, fine to medium sand that is highly bioturbated and commonly has abundant marine macrofauna. The Ripley is divided into two genetic packages of facies; the genetic packages are bounded by stratigraphic breaks or discontinuities. The package-bounding breaks are correlated biostratigraphically with discrete third-order eustatic drops on the world sea level curve. The basal Ripley break is correlated with the end of Campanian (about 74 Ma) eustatic drop, and the middle Ripley break (separating the two genetic packages) marks the mid-Maastrichtian (71 Ma) sea level drop. The basal and middle Ripley breaks are low-relief surfaces marked by sharp facies discontinuities (correlatable across 130 km) and terminal coarsening-upward cycles (5 m thick); the estimated eustatic sea level fall in both instances was about 50 m. The break at the top of the Ripley has 70 m of erosional relief and a bone bed up to 80 cm thick. This break represents a late Maastrichtian (about 68 Ma) sea level fall estimated to have been nearly 95 m. Facies of the superjacent Prairie Bluff Chalk and Providence Sand overlie the erosional surface.

Skotnicki, M.C.; King, D.T. Jr. (Auburn Univ., AL (USA))

1989-09-01

209

Geologic columns for the ICDP-USGS Eyreville A and C cores, Chesapeake Bay impact structure: Postimpact sediments, 444 to 0 m depth  

USGS Publications Warehouse

A 443.9-m-thick, virtually undisturbed section of postimpact deposits in the Chesapeake Bay impact structure was recovered in the Eyreville A and C cores, Northampton County, Virginia, within the "moat" of the structure's central crater. Recovered sediments are mainly fine-grained marine siliciclastics, with the exception of Pleistocene sand, clay, and gravel. The lowest postimpact unit is the upper Eocene Chickahominy Formation (443.9-350.1 m). At 93.8 m, this is the maximum thickness yet recovered for deposits that represent the return to "normal marine" sedimentation. The Drummonds Corner beds (informal) and the Old Church Formation are thin Oligocene units present between 350.1 and 344.7 m. Above the Oligocene, there is a more typical Virginia coastal plain succession. The Calvert Formation (344.7-225.4 m) includes a thin lower Miocene part overlain by a much thicker middle Miocene part. From 225.4 to 206.0 m, sediments of the middle Miocene Choptank Formation, rarely reported in the Virginia coastal plain, are present. The thick upper Miocene St. Marys and Eastover Formations (206.0-57.8 m) appear to represent a more complete succession than in the type localities. Correlation with the nearby Kiptopeke core indicates that two Pliocene units are present: Yorktown (57.8-32.2 m) and Chowan River Formations (32.2-18.3 m). Sediments at the top of the section represent an upper Pleistocene channel-fill and are assigned to the Butlers Bluff and Occohannock Members of the Nassawadox Formation (18.3-0.6 m). ?? 2009 The Geological Society of America.

Edwards, L. E.; Powars, D. S.; Browning, J. V.; McLaughlin, Jr. , P. P.; Miller, K. G.; Self-Trail, J. M.; Kulpecz, A. A.; Elbra, T.

2009-01-01

210

Structure Formation in Astrophysics  

NASA Astrophysics Data System (ADS)

Part I. Physical Processes and Numerical Methods Common to Structure Formations in Astrophysics: 1. The physics of turbulence E. Levêque; 2. The numerical simulation of turbulence W. Schmidt; 3. Numerical methods for radiation magnetohydrodynamics in astrophysics R. Klein and J. Stone; 4. The role of jets in the formation of planets, stars, and galaxies R. Banerjee, R. Pudritz and R. Ouyed; 5. Advanced numerical methods in astrophysical fluid dynamics A. Hujeirat and F. Heitsch; Part II. Structure and Star Formation in the Primordial Universe: 6. New frontiers in cosmology and galaxy formation challenges for the future R. Ellis and J. Silk; 7. Galaxy formation physics T. Abel, G. Bryan and R. Teyssier; 8. First stars formation, evolution, feedback effects V. Bromm, A. Ferrara and A. Heger; Part III. Contemporary Star and Brown Dwarf Formation: a) Cloud Formation and Fragmentation: 9. Diffuse interstellar medium and the formation of molecular clouds P. Hennebelle, M. Mac Low and E. Vazquez-Semadeni; 10. The formation of distributed and clustered stars in molecular clouds T. Megeath, Z. -Y. Li and A. Nordlund; b) Core Fragmentation and Star Formation: 11. The formation and evolution of prestellar cores P. André, S. Basu and S. Inutsuka; 12. Models for the formation of massive stars; Part IV. Protoplanetary Disks and Planet Formation M. Krumholz and I. Bonnell: 13. Observational properties of disks and young stellar objects G. Duchêne, F. Ménard, J. Muzzerolle and S. Mohanty; 14. Structure and dynamics of protoplanetary disks C. Dullemond, R. Durisen and J. Papaloizou; 15. Planet formation and evolution theory and observation Y. Alibert, I. Baraffe, W. Benz, G. Laughlin and S. Udry; 16. Planet formation assembling the puzzle G. Wurm and T. Guillot; Part V. Summary: 17. Open issues in small- and large-scale structure formation R. Klessen and M. Mac Low; 18. Final word E. Salpeter.

Chabrier, Gilles

2011-02-01

211

Structure Formation in Astrophysics  

NASA Astrophysics Data System (ADS)

Part I. Physical Processes and Numerical Methods Common to Structure Formations in Astrophysics: 1. The physics of turbulence E. Levêque; 2. The numerical simulation of turbulence W. Schmidt; 3. Numerical methods for radiation magnetohydrodynamics in astrophysics R. Klein and J. Stone; 4. The role of jets in the formation of planets, stars, and galaxies R. Banerjee, R. Pudritz and R. Ouyed; 5. Advanced numerical methods in astrophysical fluid dynamics A. Hujeirat and F. Heitsch; Part II. Structure and Star Formation in the Primordial Universe: 6. New frontiers in cosmology and galaxy formation challenges for the future R. Ellis and J. Silk; 7. Galaxy formation physics T. Abel, G. Bryan and R. Teyssier; 8. First stars formation, evolution, feedback effects V. Bromm, A. Ferrara and A. Heger; Part III. Contemporary Star and Brown Dwarf Formation: a) Cloud Formation and Fragmentation: 9. Diffuse interstellar medium and the formation of molecular clouds P. Hennebelle, M. Mac Low and E. Vazquez-Semadeni; 10. The formation of distributed and clustered stars in molecular clouds T. Megeath, Z. -Y. Li and A. Nordlund; b) Core Fragmentation and Star Formation: 11. The formation and evolution of prestellar cores P. André, S. Basu and S. Inutsuka; 12. Models for the formation of massive stars; Part IV. Protoplanetary Disks and Planet Formation M. Krumholz and I. Bonnell: 13. Observational properties of disks and young stellar objects G. Duchêne, F. Ménard, J. Muzzerolle and S. Mohanty; 14. Structure and dynamics of protoplanetary disks C. Dullemond, R. Durisen and J. Papaloizou; 15. Planet formation and evolution theory and observation Y. Alibert, I. Baraffe, W. Benz, G. Laughlin and S. Udry; 16. Planet formation assembling the puzzle G. Wurm and T. Guillot; Part V. Summary: 17. Open issues in small- and large-scale structure formation R. Klessen and M. Mac Low; 18. Final word E. Salpeter.

Chabrier, Gilles

2009-01-01

212

Humidity effects on photochemical aerosol formation in the SO 2-NO-C 3H 6-air system  

NASA Astrophysics Data System (ADS)

In order to investigate the effects of humidity on the gas-phase oxidation of SO 2 in polluted air and on the subsequent aerosol formation process, photoirradiation experiments were carried out by means of a 4-m 3 chamber, in which mixtures containing SO 2, NO and C 3H 6 with concentrations in the ppm range were exposed to simulated solar radiation in different relative humidity (r.h.) conditions. The total amount of oxidized SO 2 was quantified from the SO 42- yield determined by the chemical analysis of the aerosol product, and a part due to the oxidation by the OH radical was evaluated by estimating the OH concentration from the decay rate of C 3H 6. The remaining part was assigned to the oxidation by the Criegee intermediate, as it had a good correlation with the progress of the O 3 + C 3H 6 reaction. The contributions of the two oxidizing species to the total conversion and the oxidation rate of SO 2 were measured as functions of r.h. As a result, experimental evidence was obtained for the prediction of Calvert and Stockwell's (1983, Envir. Sci. Technol. 17, 428A-443A) simulation that the oxidation due to the Criegee intermediate was retarded by the increase in humidity. The OH contribution, on the other hand, was almost independent of r.h. It was observed consequently that the total oxidized amount of SO 2 considerably decreased as r.h. was higher. The humidity effect on the aerosol formation process was found to be more complicated than the effect on the gas-phase chemistry. The maximum rate of increase in the particle number concentration rose linearly with increasing r.h., but the number concentration itself measured at its maximum or at the end of the irradiation reached a ceiling value around r.h. = 30% and went down for higher r.h. The average panicle size in the final stage of the reaction showed a minimum around the same r.h. at which the number concentration was maximum. The H 2SO 4 concentration in the mist particles, however, decreased monotonically as r.h. got higher. It was suggested that these different responses against the increase in humidity resulted from the cooperation of several processes such as the H 2SO 4 monomer formation, the H 2O condensation, the particle coagulation, etc., which had different dependences on r.h.

Izumi, Katsuyuki; Mizuochi, Motoyuki; Murano, Kentaro; Fukuyama, Tsutomu

213

76 FR 4391 - Calvert Cliffs Nuclear Power Plant, LLC, Calvert Cliffs Nuclear Power Plant, Unit Nos. 1 and 2...  

Federal Register 2010, 2011, 2012, 2013

...and orders of the Nuclear Regulatory Commission...for light- water nuclear power reactors...pressurized light-water nuclear power reactor fueled...that the rate of energy release, hydrogen...the metal/water reaction shall be calculated...design consists of low enriched...

2011-01-25

214

75 FR 66802 - Calvert Cliffs Nuclear Power Plant, LLC; Calvert Cliffs Nuclear Power Plant, Unit Nos. 1 and 2...  

Federal Register 2010, 2011, 2012, 2013

...gov. Dated at Rockville, Maryland, this 19th day of October 2010. For the Nuclear Regulatory Commission. Douglas V. Pickett, Senior Project Manager, Plant Licensing Branch I-1, Division of Operating Reactor Licensing, Office of Nuclear...

2010-10-29

215

76 FR 1469 - Calvert Cliffs Nuclear Power Plant, LLC; Calvert Cliffs Nuclear Power Plant, Unit Nos. 1 and 2...  

Federal Register 2010, 2011, 2012, 2013

...gov. Dated at Rockville, Maryland, this 3rd day of January 2011. For the Nuclear Regulatory Commission. Douglas V. Pickett, Senior Project Manager, Plant Licensing Branch I-1, Division of Operating Reactor Licensing, Office of Nuclear...

2011-01-10

216

76 FR 39908 - Calvert Cliffs Nuclear Power Plant, LLC; Calvert Cliffs Nuclear Power Plant, Unit Nos. 1 and 2...  

Federal Register 2010, 2011, 2012, 2013

...FURTHER INFORMATION CONTACT: Douglas Pickett, Senior Project Manager, Plant Licensing...301-415-1364; e-mail: Douglas.Pickett@nrc.gov. The U.S. Nuclear Regulatory...Nuclear Regulatory Commission. Douglas V. Pickett, Senior Project Manager, Plant...

2011-07-07

217

Star Formation in Galaxies  

NASA Technical Reports Server (NTRS)

Topics addressed include: star formation; galactic infrared emission; molecular clouds; OB star luminosity; dust grains; IRAS observations; galactic disks; stellar formation in Magellanic clouds; irregular galaxies; spiral galaxies; starbursts; morphology of galactic centers; and far-infrared observations.

1987-01-01

218

Advanced Formation Flight Control.  

National Technical Information Service (NTIS)

In this thesis, the formation flight control problem is continued from four previous theses. Automatic formation flight involves controlling multiple aircraft equipped with standard Mach-hold, altitude hold, and heading-hold autopilots to maintain a desir...

M. J. Veth

1994-01-01

219

Optimal Formation Flight Control.  

National Technical Information Service (NTIS)

Automatic formation flight involves controlling multiple wing aircraft equipped with standard Mach-hold, altitude-hold, and heading-hold autopilots in order to maintain a desired position relative to a lead aircraft throughout formation maneuvers. Changes...

S. B. McCamish

1995-01-01

220

The Format Dilemma.  

ERIC Educational Resources Information Center

Reports results of a survey of public libraries that investigated trends in audiovisual materials. Highlights include format issues; audiobooks; media budgets for various formats; video collections; DVDs; circulation; collection sizes; music CDs; and future possibilities. (LRW)

Oder, Norman

2002-01-01

221

Close Formation Flight Control.  

National Technical Information Service (NTIS)

In this research the close formation flight control problem is addressed. The formation consists of a lead and wing aircraft, where the wing flies in close formation with the lead, such that the lead's vortices produce aerodynamic coupling effects, and a ...

A. W. Proud

1999-01-01

222

Autonomous formation flight  

Microsoft Academic Search

This article describes an approach to close-formation flight of autonomous aircraft. A standard LQ-based structure was synthesized for each vehicle and for formation position error control using linearized equations of motion and a lifting line model of the aircraft wake. We also consider the definition of a formation management structure, capable of dealing with a variety of generic transmission and

F. Giulietti; L. Pollini; M. Innocenti

2000-01-01

223

Medical image file formats.  

PubMed

Image file format is often a confusing aspect for someone wishing to process medical images. This article presents a demystifying overview of the major file formats currently used in medical imaging: Analyze, Neuroimaging Informatics Technology Initiative (Nifti), Minc, and Digital Imaging and Communications in Medicine (Dicom). Concepts common to all file formats, such as pixel depth, photometric interpretation, metadata, and pixel data, are first presented. Then, the characteristics and strengths of the various formats are discussed. The review concludes with some predictive considerations about the future trends in medical image file formats. PMID:24338090

Larobina, Michele; Murino, Loredana

2014-04-01

224

Tropical cyclone formation  

SciTech Connect

The physics of tropical cyclone formation is not well understood, and more is known about the mature hurricane than the formative mechanisms that produce it. It is believed part of the reason for this can be traced to insufficient upper-level atmospheric data. Recent observations suggest that tropical cyclones are initiated by asymmetric interactions associated with migratory upper-level potential vorticity disturbances and low-level disturbances. Favored theories of cyclones formation, however, focus on internal processes associated with cumulus convection and/or air-sea interaction. This work focuses on external mechanisms of cyclone formation and, using both a two- and three-dimensional moist geostrophic momentum model, investigates the role of upper-level potential vorticity disturbances on the formation process. A conceptual model of tropical cyclone formation is proposed, and implications of the theory are discussed. 71 refs., 5 figs., 1 tab.

Montgomery, M.T.; Farrell, B.F. (Harvard Univ., Cambridge, MA (United States))

1993-01-15

225

DBP formation during chloramination  

Microsoft Academic Search

Batch experiments were conducted on three diverse water sources to study the formation of dissolved organic halogen (DOX), trihalomethanes (THMs), haloacetic acids (HAAs), and cyanogen halides (CNX) during chloramination. The authors used preformed chloramines to examine the effect of pH, mass ratio of chlorine to ammonia-nitrogen (Cl? to N), and bromide concentration on disinfection by-product (DBP) formation. Formation of specific

Alicia C. Diehl; Gerald E. Speitel Jr.; James M. Symons; Stuart W. Krasner; Cordelia J. Hwang; Sylvia E. Barrett

2000-01-01

226

Flash Open File Format  

NSDL National Science Digital Library

Macromedia has released the file format specification for its Flash (discussed in the April 11, 1997 Scout Report) multimedia web tool. Flash allows web developers to create vector based graphics and animation. By making the format (.swf) available, Macromedia hopes to establish it as a standard for vector graphics and animation. The company claims it will "submit the format specification to a recognized Internet standards organization." In addition to providing the file format specification, the site provides Flash related news releases, a Flash FAQ, and a vector graphics white paper.

227

Three Dimensional Formation Flight Control.  

National Technical Information Service (NTIS)

Automating the control of an aircraft flying in formation necessitates the extension of the theory of formation flight control to allow for three dimensional maneuvers. The formation was modeled as a two-aircraft, leader and wingspan, formation. Both airc...

J. K. Hall

2000-01-01

228

Entering the Formative Years  

ERIC Educational Resources Information Center

This article discusses formative assessment--classroom strategies that ensure students are understanding music concepts. Unlike summative assessments (end-of-process evaluations like final exams, SATs, or auditions), formative assessments need to be non-threatening, helpful, and most of all, effective. The process starts with a teacher…

Powers, Keith

2011-01-01

229

Ribbed moraine formation  

Microsoft Academic Search

Ribbed (Rogen) moraines are conspicuous landforms found in interior parts of formerly glaciated areas. Two major theories for ribbed moraine formation have been suggested in recent years: (i) the shear and stack theory, which explains ribbed moraine formation by shearing and stacking of till slabs or englacially entrained material during compressive flow, followed by basal melt-out of transverse moraine ridges,

Clas Hättestrand; Johan Kleman

1999-01-01

230

Formative Assessment Probes  

ERIC Educational Resources Information Center

Formative assessment probes can be effective tools to help teachers build a bridge between students' initial ideas and scientific ones. In this article, the authors describe how using two formative assessment probes can help teachers determine the extent to which students make similar connections between developing a concept of matter and a…

Eberle, Francis; Keeley, Page

2008-01-01

231

Delayed ettringite formation  

Microsoft Academic Search

Delayed ettringite formation (DEF) can damage concrete that has experienced a temperature above about 70°C. Claims that slow release of sulfate from the clinker can have a similar effect in concrete not thus heated are unsupported. Chemical and microstructural aspects of DEF are reviewed. Expansion results from formation of ettringite crystals of submicrometre size in the paste, the larger crystals

H. F. W Taylor; C Famy; K. L Scrivener

2001-01-01

232

Formation of giant planets  

NASA Astrophysics Data System (ADS)

We present calculations of giant planet formation based on extended core-accretion planet formation models taking into account disk structure and evolution and migration of the protoplanet. We show that these models lead to giant planet formation timescales compatible with disk lifetimes. Using these models, we show that we can reproduce the bulk internal structure of Jupiter and Saturn, as well as the enrichment in volatile species measured in situ by the Galileo probe (for Jupiter), and from the Earth (for Saturn). We then apply these models to the formation of the three Neptune mass planet system recently discovered by the HARPS collaboration (Lovis et al. 2006), and show that the two outer planets are likely to have accreted large amounts of water ice during their formation. Finally, the comparison with the extrasolar planets will be presented by C. Mordasini (this meeting, abstract EPSC2006-A-00672) using a Monte-Carlo approach.

Alibert, Y.; Mordasini, C.; Benz, W.

233

Complex caddisfly-dominated bioherms from the Eocene Green River Formation  

NASA Astrophysics Data System (ADS)

Complex, caddisfly-dominated (Insecta: Trichoptera) carbonate mounds up to 9 m tall and 40 m in diameter formed in the nearshore environment of Eocene Lake Gosiute. The mounds outcrop for 70 km in reef-like geometries along the northern margin of Lake Gosiute in Wyoming. The relationships among the caddisfly larvae, the benthic microbial mat and physicochemical nearshore processes of Eocene Lake Gosiute resulted in unique external and internal carbonate mound morphology. Externally, the large carbonate mounds are formed by the lateral and vertical coalescence of several layers of smaller columns. The smaller columns are generally 1-2 m tall and are 0.5-1 m in diameter. Each layer or generation of smaller columns tends to have a unique external morphology. This suggests that variable paleoenvironmental conditions produced subtle differences in tufa and stromatolite morphology. Internally, each of the smaller columns is composed of a core of caddisfly larval cases surrounded by layers of tufa and stromatolites. The smaller column cores are characterized by centimeter thick microbial-caddisfly couplets in which layers or packets of calcified caddisfly larval cases are covered by microbial mat-mediated, microlaminated carbonate. The microbial-caddisfly couplets suggest that both metazoans and microbes were responsible for column height and shape. In this paper, we propose a mechanism for the growth of these caddisfly-dominated mounds. The base of the Laney Member of the Green River Formation records a freshwater lacustrine transgression over the surrounding floodplains and mudflats of the Cathedral Bluffs Tongue of the Wasatch Formation. In nearshore areas of the lake's northern margin, carbonate hardgrounds developed in some areas of the softer, carbonate-rich, bottom muds. These hardgrounds provided nucleation sites for the carbonate mounds and columns by providing a stable substrate for the benthic microbial mat and for caddisfly larval case attachment during pupation. The larval cases became calcified, and became a new stable substrate for the benthic microbial mat during, or shortly after, pupation. The microbial-caddisfly couplets may record a yearly cycle in which caddisfly pupation and aggregation behavior regularly interrupted the microbial mat-mediated carbonate buildups in these unique carbonate mounds.

Leggitt, V. Leroy; Cushman, Robert A.

2001-12-01

234

Formation of Planetesimals.  

National Technical Information Service (NTIS)

Formation of planetesimals is discussed. The following subject areas are covered: (1) nebular structure; (2) aerodynamics of the solid bodies in the nebula; (3) problems with gravitational instability; (4) particle growth by coagulation; properties of fra...

S. J. Weidenschilling

1991-01-01

235

Formation of Hurricanes  

NSDL National Science Digital Library

This is a picture inquiry based lesson for students to explore the formation of hurricanes. Groups of three students will observe and explain trends found in a picture and share ideas with their peers.

Morgan, Amber

2012-08-10

236

Plant Formate Dehydrogenase  

SciTech Connect

The research in this study identified formate dehydrogenase, an enzyme that plays a metabolic role on the periphery of one-carbon metabolism, has an unusual localization in Arabidopsis thaliana and that the enzyme has an unusual kinetic plasticity. These properties make it possible that this enzyme could be engineered to attempt to engineer plants with an improved photosynthetic efficiency. We have produced transgenic Arabidopsis and tobacco plants with increased expression of the formate dehydrogenase enzyme to initiate further studies.

John Markwell

2005-01-10

237

Display formats manual  

NASA Technical Reports Server (NTRS)

The standards and procedures for the generation of operational display formats to be used in the Mission Control Center (MCC) display control system are presented. The required effort, forms, and fundamentals for the design, specifications, and production of display formats are identified. The principles of display design and system constraints controlling the creation of optimum operational displays for mission control are explained. The basic two types of MCC display systems for presenting information are described.

Runnels, R. L.

1973-01-01

238

Autonomous Formation Flight  

NASA Technical Reports Server (NTRS)

NASA's Strategic Plan for the Aerospace Technology Enterprise includes ambitious objectives focused on affordable air travel, reduced emissions, and expanded aviation-system capacity. NASA Dryden Flight Research Center, in cooperation with NASA Ames Research Center, the Boeing Company, and the University of California, Los Angeles, has embarked on an autonomous-formation-flight project that promises to make significant strides towards these goals. For millions of years, birds have taken advantage of the aerodynamic benefit of flying in formation. The traditional "V" formation flown by many species of birds (including gulls, pelicans, and geese) enables each of the trailing birds to fly in the upwash flow field that exists just outboard of the bird immediately ahead in the formation. The result for each trailing bird is a decrease in induced drag and thus a reduction in the energy needed to maintain a given speed. Hence, for migratory birds, formation flight extends the range of the system of birds over the range of birds flying solo. The Autonomous Formation Flight (AFF) Project is seeking to extend this symbiotic relationship to aircraft.

Schkolnik, Gerard S.; Cobleigh, Brent

2004-01-01

239

Some observations regarding steady laminar flows past bluff bodies.  

PubMed

Steady laminar flows past simple objects, such as a cylinder or a sphere, have been studied for well over a century. Theoretical, experimental and numerical methods have all contributed fundamentally towards our understanding of the resulting flows. This article focuses on developments during the past few decades, when mostly numerical and asymptotical advances have provided insights also for steady, although unstable, high-Reynolds-numbers flow regimes. PMID:24936017

Fornberg, Bengt; Elcrat, Alan R

2014-07-28

240

Computing Bluff Body Flows Using Commercial CFD Software  

NASA Astrophysics Data System (ADS)

Commercial CFD codes are increasingly being used to simulate complex engineering flows. Three commercial codes: CFD-ACE v2004, Fluent 6.2.16 and CFX 5.7.1 are examined for their ability to compute the separated flow over a square cylinder. Large Eddy Simulation (LES) results are presented using four SGS models implemented in these commercial codes: the Smagorinsky's model, the dynamic model (Germano et al., 1991), the localized dynamic model (Kim and Menon, 1995) and the WALE model (Nicoud and Ducros, 1999). Global simulation results, time averaged quantities and phase averaged quantities are benchmarked against the experimental results of Lyn and Rodi (Journal of Fluid Mechanics, 1994). All simulations predict the Strouhal number accurately, and simulations employing the dynamic model are excellent in predicting the mean recirculation length and the r.m.s. of the lift coefficient on the cylinder. In terms of flow fluctuations, all simulations over-predict the streamwise component, but under-predict the vertical component. Velocity fluctuations in the wake correlate well with the fluctuation of forces on the cylinder. An examination of the streamlines of the flow indicates that CFD-ACE and Fluent's implementation of the dynamic model offers the best prediction of the vertical displacement of the wake and the size of the shed vortex. Finally, the addition of 10% upwind differencing to the convective terms is also investigated.

Kirpekar, Sujit

2005-11-01

241

Bluff Body Flow Simulation Using a Vortex Element Method  

SciTech Connect

Heavy ground vehicles, especially those involved in long-haul freight transportation, consume a significant part of our nation's energy supply. it is therefore of utmost importance to improve their efficiency, both to reduce emissions and to decrease reliance on imported oil. At highway speeds, more than half of the power consumed by a typical semi truck goes into overcoming aerodynamic drag, a fraction which increases with speed and crosswind. Thanks to better tools and increased awareness, recent years have seen substantial aerodynamic improvements by the truck industry, such as tractor/trailer height matching, radiator area reduction, and swept fairings. However, there remains substantial room for improvement as understanding of turbulent fluid dynamics grows. The group's research effort focused on vortex particle methods, a novel approach for computational fluid dynamics (CFD). Where common CFD methods solve or model the Navier-Stokes equations on a grid which stretches from the truck surface outward, vortex particle methods solve the vorticity equation on a Lagrangian basis of smooth particles and do not require a grid. They worked to advance the state of the art in vortex particle methods, improving their ability to handle the complicated, high Reynolds number flow around heavy vehicles. Specific challenges that they have addressed include finding strategies to accurate capture vorticity generation and resultant forces at the truck wall, handling the aerodynamics of spinning bodies such as tires, application of the method to the GTS model, computation time reduction through improved integration methods, a closest point transform for particle method in complex geometrics, and work on large eddy simulation (LES) turbulence modeling.

Anthony Leonard; Phillippe Chatelain; Michael Rebel

2004-09-30

242

Flow Past a Bluff Body with a Wavy Stagnation Face  

NASA Astrophysics Data System (ADS)

Numerical investigations have been performed to study the flow past square-section cylinders with a spanwise geometric deformation leading to a stagnation face with a sinusoidal waviness. The computations were performed using a spectral/hp element solver over a range of Reynolds numbers from 10 to 500. Starting from fully developed shedding past a straight cylinder at a Reynolds number of 100, a sufficiently high waviness is impulsively introduced resulting in the stabilization of the the near-wake to a time-independent state. The steady nature of the near-wake is associated with a reduction in total drag of about 16% at a Reynolds number of 100 as compared with a straight, non-wavy cylinder. Further increases in the amplitude of the waviness lead to the emergence of hairpin vortices from the near-wake region, similar to the wake of a sphere at low Reynolds numbers. At higher Reynolds numbers, the drag reduction increases substantially, e.g. at a Reynolds number of 500 it is 34%, principally due to the increase in drag of the nonwavy cylinder. Alternative methods based on three-dimensional forms of bleed are investigated to suppress the von-Kármán vortex street of a straight, non-wavy cylinder.

Darekar, R. M.; Sherwin, S. J.

2001-04-01

243

On vortex shedding from bluff bodies with base cavities  

NASA Astrophysics Data System (ADS)

In an extension of a previous drag reduction study via geometric shaping, this paper describes a numerical study of a quasistreamlined body in which the trailing edge is modified to form a base cavity. Here, we seek to establish if any synergistic merits exist through a combination of a spanwise wavy trailing edge with a straight-edged base cavity. Both two-dimensional and three-dimensional (3D) simulations are conducted to assess the effect of Reynolds number, streamwise cavity length and spanwise waviness on the flow. Two dimensional simulations examining a variation in Reynolds number for a cavity of constant length reveal the presence of three different general wake patterns: the steady wake, the Karman wake, and an asymmetric, deflected wake. Most critically, the origins of the deflected wake pattern are traced to the presence of a vortex which resides within the base cavity. Similarly, for a constant Reynolds number the influence of the cavity length on the flow is also intricately related to this cavity vortex, giving rise to wake topologies which bear a strong resemblance to the above three shedding processes. Reductions in drag are observed for all the investigated cavity configurations and additionally it is found that the magnitude of the reduction obeys a direct relationship with the length of the cavity up to a certain asymptotic value. The results of the 3D simulations reveal that the current base-cavity arrangement appears to yield a potential for further reduction in form drag as compared to earlier studies where the entire base region is modified in the shape of a wave. However, for a fixed cavity length, introducing spanwise waviness reduces the fluctuation intensity of the form drag but offers no obvious added benefit in terms of the time-averaged values. We anticipate that the presence of the straight-edged cavity causes a loss of spanwise coherence of these structures such that further enhancements due to the introduction of waviness are of less consequence.

Cai, Jinsheng; Chng, Tat Loon

2009-03-01

244

77 FR 70431 - Moss Bluff Hub, LLC; Notice of Filing  

Federal Register 2010, 2011, 2012, 2013

[Federal Register Volume 77, Number...DEPARTMENT OF ENERGY Federal Energy Regulatory Commission...Operating Conditions (SOC) to reflect, among other...or intervention to the Federal Energy Regulatory...

2012-11-26

245

78 FR 41397 - Moss Bluff Hub, LLC; Notice of Filing  

Federal Register 2010, 2011, 2012, 2013

[Federal Register Volume 78...DEPARTMENT OF ENERGY Federal Energy Regulatory...Operating Conditions (SOC) pursuant to sections...states the revised SOC reflects modifications...intervention to the Federal Energy...

2013-07-10

246

Permian fossils from the Greenhills group, Bluff, Southland, New Zealand  

Microsoft Academic Search

Rare fossils including the gastropod Peruvispira aff. imbricata Waterhouse and the bivalve Atomodesma aff. marwicki Waterhouse indicate a late Lower Permian age for the middle part of the Greenhills Group. Plerophyllum aff. timorense Gerth occurs in a lower horizon of the Greenhills Group. Bands of marble containing shell prisms, rare radiolarians, and other microfossils occur in the upper part of

David J. Mossman; Lucy M. Force

1969-01-01

247

CONTROL OF FLOW PAST BLUFF BODIES USING ROTATING CONTROL CYLINDERS  

Microsoft Academic Search

Computational results for control of flow past a circular cylinder using small rotating cylinders are presented. A well-proven stabilized finite-element method, that has been applied to various flow problems earlier, is utilized to solve the incompressible Navier–Stokes equations in the primitive variables formulation. The formulation is first applied to study flow past an isolated rotating cylinder. Excellent match with experimental

S. Mittal

2001-01-01

248

Formation of the earth  

NASA Technical Reports Server (NTRS)

The origin of the earth is discussed in the context of the formation of the sun and the planets, and a standard model for such a formation assuming gravitational instability in a dense interstellar molecular cloud is outlined, along with the most significant variant of the model in which the loss of the nebular gas occurred after the formation of the earth. The formation of the sun and solar nebulae is addressed, and the coagulation of grains and the formation of small planetesimals are covered, along with the gravitational accumulation of planetesimals into planetary embryos and final stages of accumulation - embryos of planets. It is pointed out that the final stage of accumulation consists of the collision of these embryos; because of their large size, particularly after their further growth, these collisions represent giant impacts. It is concluded that the earth was initially an extremely hot and melted planet, surrounded by a fragile atmosphere and subject to violent impacts by bodies of the size of Ceres and even the moon.

Wetherill, George W.

1990-01-01

249

Family formation and urbanization.  

PubMed

"This article will deal with two stages in the family life course: formation of the couple through marriage, and the birth of successive children.... We shall investigate whether migration into or out of a metropolitan area modifies the formation of the family, and conversely whether the different stages in family formation modify migration behaviour....First, using a nonparametric approach, we shall consider the sequence of events throughout an individual's life-course, and thereby demonstrate how the occurrence of one life-event alters the probability of the occurrence of others." Next, a semiparametric approach is used to analyze the impact of variables such as educational level, occupational level, and social class on marriage, fertility, and migration. The geographic focus is on France. PMID:12157901

Courgeau, D

1989-09-01

250

Neoproterozoic banded iron formations  

Microsoft Academic Search

Two epochs of the formation of ferruginous quartzites—Archean-Paleoproterozoic (3.2–1.8 Ga) and Neoproterozoic (0.85–0.7 Ga)—are\\u000a distinguished in the Precambrian. They are incommensurable in scale: the Paleoproterozoic Kursk Group of the Kursk Magnetic\\u000a Anomaly (KMA) extends over 1500 km, whereas the extension of Neoproterozoic banded iron formations (BIF) beds does not exceed\\u000a a few tens of kilometers. Their thickness is up to

A. V. Ilyin

2009-01-01

251

Primary Radiation Damage Formation  

SciTech Connect

The physical processes that give rise to changes in the microstructure, and the physical and mechanical properties of materials exposed to energetic particles are initiated by essentially elastic collisions between atoms in what has been called an atomic displacement cascade. The formation and evolution of this primary radiation damage mechanism are described to provide an overview of how stable defects are formed by displacement cascades, as well as the nature and morphology of the defects themselves. The impact of the primary variables cascade energy and irradiation temperature are discussed, along with a range of secondary factors that can influence damage formation.

Stoller, Roger E [ORNL

2012-01-01

252

Wotsit's File Format Collection  

NSDL National Science Digital Library

Wotsit's File Format Collection, provided by Paul Oliver, features a very large number of file formats. These include JPEG image files, wave sound files, Rich Text files, and common database and word-processing files such as Paradox and Wordperfect. Documents collected or linked at the site are primarily either original specifications from the creator or an improved version of the original. All of the specifications are very technical and are directed towards programmers. Users can subscribe to a mailing list for notification of site updates.

253

Isolating Triggered Star Formation  

SciTech Connect

Galaxy pairs provide a potentially powerful means of studying triggered star formation from galaxy interactions. We use a large cosmological N-body simulation coupled with a well-tested semi-analytic substructure model to demonstrate that the majority of galaxies in close pairs reside within cluster or group-size halos and therefore represent a biased population, poorly suited for direct comparison to 'field' galaxies. Thus, the frequent observation that some types of galaxies in pairs have redder colors than 'field' galaxies is primarily a selection effect. We use our simulations to devise a means to select galaxy pairs that are isolated in their dark matter halos with respect to other massive subhalos (N= 2 halos) and to select a control sample of isolated galaxies (N= 1 halos) for comparison. We then apply these selection criteria to a volume-limited subset of the 2dF Galaxy Redshift Survey with M{sub B,j} {le} -19 and obtain the first clean measure of the typical fraction of galaxies affected by triggered star formation and the average elevation in the star formation rate. We find that 24% (30.5 %) of these L* and sub-L* galaxies in isolated 50 (30) h{sup -1} kpc pairs exhibit star formation that is boosted by a factor of {approx}> 5 above their average past value, while only 10% of isolated galaxies in the control sample show this level of enhancement. Thus, 14% (20 %) of the galaxies in these close pairs show clear triggered star formation. Our orbit models suggest that 12% (16%) of 50 (30) h{sup -1} kpc close pairs that are isolated according to our definition have had a close ({le} 30 h{sup -1} kpc) pass within the last Gyr. Thus, the data are broadly consistent with a scenario in which most or all close passes of isolated pairs result in triggered star formation. The isolation criteria we develop provide a means to constrain star formation and feedback prescriptions in hydrodynamic simulations and a very general method of understanding the importance of triggered star formation in a cosmological context.

Barton, Elizabeth J.; Arnold, Jacob A.; /UC, Irvine; Zentner, Andrew R.; /KICP, Chicago /Chicago U., EFI; Bullock, James S.; /UC, Irvine; Wechsler, Risa H.; /KIPAC, Menlo Park /SLAC

2007-09-12

254

Cave Formation: Kane Cave  

NSDL National Science Digital Library

This video documents an experiment conducted in Kane Cave, Wyoming, to see if microbes that inhabit the cave could actually be contributing to the cave-formation process. Adapted from a NOVA broadcast, the segment is four minutes and twelve seconds in length.

2010-11-25

255

Oil Formation and Trapping  

NSDL National Science Digital Library

This animation shows the successive stages in the formation of an oil reserve. In View 1, organic material settles, is buried, and is transformed by heat and pressure into oil. In View 2 an oil trap is formed: the area folds into an anticline, and oil migrates and accumulates in the anticline crest.

Marshak, Stephen; Company, W. W.

256

Formation of planetesimals  

NASA Technical Reports Server (NTRS)

Formation of planetesimals is discussed. The following subject areas are covered: (1) nebular structure; (2) aerodynamics of the solid bodies in the nebula; (3) problems with gravitational instability; (4) particle growth by coagulation; properties of fractal aggregates; and (5) coagulation and settling of fractal aggregates.

Weidenschilling, Stuart J.

1991-01-01

257

Promoting habit formation  

Microsoft Academic Search

Habits are automatic behavioural responses to environmental cues, thought to develop through repetition of behaviour in consistent contexts. When habit is strong, deliberate intentions have been shown to have a reduced influence on behaviour. The habit concept may provide a mechanism for establishing new behaviours, and so healthy habit formation is a desired outcome for many interventions. Habits also however

Phillippa Lally; Benjamin Gardner

2011-01-01

258

Wound-Periderm Formation  

Microsoft Academic Search

Herbivores, and particularly chewing insects, cause substantial damage to the plant. In addition to lost tissue, there are great concerns of pathogen invasion and water loss at the site of the attack. One of the plant’s defense strategies is the formation of wound periderm at the boundaries of the invaded or damaged region to isolate it from non-wounded healthy tissue.

Idit Ginzberg

259

Localized Bluetooth Scatternet Formation  

Microsoft Academic Search

This paper addresses the problem of scatternet formation algorithm for multi-hop Bluetooth based personal area and ad hoc network, with minimal communication overhead. Nodes are assumed to know their position and are able to establish connections with any of the neighboring nodes. We first pro- pose a new sparse subgraph, namely, partial Delaunay triangulation (PDT), which can be constructed efficiently

XIANG-YANG LI

260

Supernova induced star formation  

Microsoft Academic Search

The evidence for the triggering of star formation by shocks from expanding supernova shells is examined with special emphasis on the solar system. It is shown that the recently discovered isotopic anomalies, mainly in Ti, can serve as the best signature for this purpose. It is suggested that the discovery of correlated anomalies in Ti, Fe, and Ca will give

S. Ramadurai

1986-01-01

261

The Formation of Trihalomethanes.  

ERIC Educational Resources Information Center

Reviewed are a number of factors important in the formation of trihalomethanes (THM) including the nature of aquatic humus and the influences of preozonation, bromide, pH, and chlorine. A brief investigation is also conducted into the kinetics of the THM reaction. Several major research needs are represented. (CS)

Trussell, R. Rhodes; Umphres, Mark D.

1978-01-01

262

Energetics of Core Formation  

Microsoft Academic Search

The loss of gravitational energy on core formation is calculated for the case of simple unmixing of two components, whose equations of state are found from the present density distribution. Without allowance for thermal expansion, the mean energy available for heating is 600 eal\\/g; with an approximate allowance for thermal expansion, this is re- dueed to 400 eal\\/g, which is

Francis Birch

1965-01-01

263

Formation of Giant Planets.  

National Technical Information Service (NTIS)

Under the support of NASA Origins grant, we studied the formation of gaps in protoplanetary disks due the tidal interaction between a fully grown protoplanet and protostellar disk. The result of this study is published in the Astrophysical Journal, (vol 5...

D. Lin

1999-01-01

264

Document Format Recognition.  

National Technical Information Service (NTIS)

This study is primarily concerned with methods for analyzing the format of pages from technical journals, and means for automatically processing the textual and graphic material on these pages for input to a computer which is to perform textual data proce...

S. B. Gray

1965-01-01

265

Computational Star Formation (IAU S270)  

NASA Astrophysics Data System (ADS)

1. Historical introduction; 2. Individual star formation: observations; 3. Low-mass star formation: observations; 4. Individual star formation: theory; 5. Formation of clusters: observations; 6. Formation of clusters: theory; 7. Numerical methods: MHD; 8. Numerical methods: radiative dynamics; 9. Local star formation processes; 10. Star formation feedback; 11. Star formation on galactic scales; 12. Special purpose hardware; 13. Computational methods; 14. Radiation diagnostics of star formation; 15. Large scale star formation; 16. Cosmological star formation; 17. Computational star formation: Summary; Index.

Alves, João.; Elmegreen, Bruce G.; Girart, Josep M.; Trimble, Virginia

2011-05-01

266

Pattern formation during vasculogenesis  

PubMed Central

Vasculogenesis, the assembly of the first vascular network, is an intriguing developmental process that yields the first functional organ system of the embryo. In addition to being a fundamental part of embryonic development, vasculogenic processes also have medical importance. To explain the organizational principles behind vascular patterning, we must understand how morphogenesis of tissue level structures can be controlled through cell behavior patterns that, in turn, are determined by biochemical signal transduction processes. Mathematical analyses and computer simulations can help conceptualize how to bridge organizational levels and thus help in evaluating hypotheses regarding the formation of vascular networks. Here we discuss the ideas that have been proposed to explain the formation of the first vascular pattern: cell motility guided by extracellular matrix alignment (contact guidance), chemotaxis guided by paracrine and autocrine morphogens, and sprouting guided by cell-cell contacts.

Czirok, Andras; Little, Charles D.

2012-01-01

267

Tetrahedron Formation Control  

NASA Technical Reports Server (NTRS)

This paper considers the preliminary development of a general optimization procedure for tetrahedron formation control. The maneuvers are assumed to be impulsive and a multi-stage optimization method is employed. The stages include (1) targeting to a fixed tetrahedron location and orientation, and (2) rotating and translating the tetrahedron. The number of impulsive maneuvers can also be varied. As the impulse locations and times change, new arcs are computed using a differential corrections scheme that varies the impulse magnitudes and directions. The result is a continuous trajectory with velocity discontinuities. The velocity discontinuities are then used to formulate the cost function. Direct optimization techniques are employed. The procedure is applied to the NASA Goddard Magnetospheric Multi-Scale (MMS) mission to compute preliminary formation control fuel requirements.

Petruzzo, Charles; Guzman, Jose

2004-01-01

268

Cosmological structure formation  

NASA Technical Reports Server (NTRS)

A summary of the current forefront problem of physical cosmology, the formation of structures (galaxies, clusters, great walls, etc.) in the universe is presented. Solutions require two key ingredients: (1) matter; and (2) seeds. Regarding the matter, it now seems clear that both baryonic and non-baryonic matter are required. Whether the non-baryonic matter is hot or cold depends on the choice of seeds. Regarding the seeds, both density fluctuations and topological defects are discussed. The combination of isotropy of the microwave background and the recent observations indicating more power on large scales have severly constrained, if not eliminated, Gaussian fluctuations with equal power on all scales, regardless of the eventual resolution of both the matter and seed questions. It is important to note that all current structure formation ideas require new physics beyond SU(3) x SU(2) x U(1).

Schramm, David N.

1991-01-01

269

Formation of bacterial nanocells  

NASA Astrophysics Data System (ADS)

Existence of nanobacteria received increasing attention both in environmental microbiology/geomicro-biology and in medical microbiology. In order to study a production of nanoforms by typical bacterial cells. Effects of different physical factors were investigated. Treatment of bacterial cultures with microwave radiation, or culturing in field of electric current resulted in formation a few types of nanocells. The number and type of nanoforms were determined with type and dose of the treatment. The produced nanoforms were: i) globules, ii) clusters of the globules--probably produced by liaison, iii) nanocells coated with membrane. The viability of the globules is an object opened for doubts. The nanocells discovered multiplication and growth on solidified nutrient media. The authors suggest that formation of nanocells is a common response of bacteria to stress-actions produced by different agents.

Vainshtein, Mikhail; Kudryashova, Ekaterina; Suzina, Natalia; Ariskina, Elena; Voronkov, Vadim

1998-07-01

270

Cave Formation: Biogeochemical Cycles  

NSDL National Science Digital Library

This video explores the role of biogeochemical cycles in the formation of caves. It discusses a radical new theory that identifies sulfuric acid as a cave-forming agent. The video, adapted from a NOVA broadcast, identifies the source of the sulfuric acid, which, unlike carbonic acid, the typical cave-forming agent, does not readily form in nature. The segment is 5 minutes and forty seconds in length.

2011-07-28

271

Drumlin Formation Library Work  

NSDL National Science Digital Library

Students will individually produce a written introduction for a paper about the presence of drumlins on Mars - this introduction describes different models for drumlin formation on earth. To prepare for this assignment, students work in groups to do library research to find and read articles. The groups summarize their findings for each other. Each student then writes an introduction incorporating material from all the groups. Designed for a geomorphology course Uses geomorphology to solve problems in other fields

Anders, Alison M.

272

Nicotine and amyloid formation  

Microsoft Academic Search

The major protein constituents of amyloid deposits in Alzheimer’s disease (AD) are the 40-residue ?-amyloid (A?) (1–40) peptide and the 42-residue A?(1–42) peptide. The A?(1–42) is more pathogenic and produced in greater quantities in familial forms of AD. A major goal of research is to uncover a suitable inhibitor that either slows down or inhibits A? formation (?-amyloidosis). During ?-amyloidosis,

Hong Zeng; Yongbo Zhang; Li-Jun Peng; Haiyan Shao; Nanda K. Menon; Jing Yang; Arthur R. Salomon; Robert P. Freidland; Michael G. Zagorski

2001-01-01

273

Cave Formation: Biogeochemical Cycles  

NSDL National Science Digital Library

This video explores the role of biogeochemical cycles in the formation of caves. It discusses a radical new theory that identifies sulfuric acid as a cave-forming agent. The video, adapted from a NOVA broadcast, identifies the source of the sulfuric acid, which, unlike carbonic acid, the typical cave-forming agent, does not readily form in nature. The segment is 5 minutes and forty seconds in length.

274

Terrestrial planet formation.  

PubMed

Advances in our understanding of terrestrial planet formation have come from a multidisciplinary approach. Studies of the ages and compositions of primitive meteorites with compositions similar to the Sun have helped to constrain the nature of the building blocks of planets. This information helps to guide numerical models for the three stages of planet formation from dust to planetesimals (~10(6) y), followed by planetesimals to embryos (lunar to Mars-sized objects; few 10(6) y), and finally embryos to planets (10(7)-10(8) y). Defining the role of turbulence in the early nebula is a key to understanding the growth of solids larger than meter size. The initiation of runaway growth of embryos from planetesimals ultimately leads to the growth of large terrestrial planets via large impacts. Dynamical models can produce inner Solar System configurations that closely resemble our Solar System, especially when the orbital effects of large planets (Jupiter and Saturn) and damping mechanisms, such as gas drag, are included. Experimental studies of terrestrial planet interiors provide additional constraints on the conditions of differentiation and, therefore, origin. A more complete understanding of terrestrial planet formation might be possible via a combination of chemical and physical modeling, as well as obtaining samples and new geophysical data from other planets (Venus, Mars, or Mercury) and asteroids. PMID:21709256

Righter, K; O'Brien, D P

2011-11-29

275

[Synapse formation and regeneration].  

PubMed

Synapse formation is probably the key process in neural development allowing signal transmission between nerve cells. As an interesting model of synapse maturation, we considered first the neuromuscular junction (NMJ), whose development is particularly dependent on intercellular interactions between the motor nerve and the skeletal muscle. Nerve and muscle have distinct roles in synaptic compartment differentiation. The initial steps of this differentiation and motor endplate formation require several postsynaptic molecular agents including agrin, the tyrosine kinase receptor MuSK and rapsyn. The agrin or motoneuron dependence of this process continues to be debated while the following steps of axonal growth and postsynaptic apparatus maintenance essentially depend on neuronal agrin and a neuron-specific signal dispersing ectopic AChR aggregate remainders, possibly mediated by acetylcholine itself. Neuregulin is essentially involved in Schwann's cell survival and guidance for axonal growth. In this paper, we will discuss the similarities between Central Nervous System (CNS) synaptic formation and Motor innervation. The limited ability of the CNS to create new synapses after nervous system injury will be then discussed with a final consideration of some new strategies elaborated to circumvent the limitations of lesion extension processes. PMID:19230939

d'Houtaud, S; Sztermer, E; Buffenoir, K; Giot, J-P; Wager, M; Bauche, S; Lapierre, F; Rigoard, P

2009-03-01

276

Flocks and Formations  

NASA Astrophysics Data System (ADS)

Given a large number (the "flock") of moving physical objects, we investigate physically reasonable mechanisms of influencing their orbits in such a way that they move along a prescribed course and in a prescribed and fixed configuration (or "in formation"). Each agent is programmed to see the position and velocity of a certain number of others. This flow of information from one agent to another defines a fixed directed (loopless) graph in which the agents are represented by the vertices. This graph is called the communication graph. To be able to fly in formation, an agent tries to match the mean position and velocity of his neighbors (his direct antecedents on the communication graph) to his own. This operation defines a (directed) Laplacian on the communication graph. A linear feedback is used to ensure stability of the coherent flight patterns. We analyze in detail how the connectedness of the communication graph affects the coherence of the stable flight patterns and give a characterization of these stable flight patterns. We do the same if in addition the flight of the flock is guided by one or more leaders. Finally we use this theory to develop some applications. Examples of these are: flight guided by external controls, flocks of flocks, and some results about flocks whose formation is always oriented along the line of flight (such as geese).

Veerman, J. J. P.; Lafferriere, G.; Caughman, J. S.; Williams, A.

2005-12-01

277

Tetrahedron Formation Control  

NASA Technical Reports Server (NTRS)

Spacecraft flying in tetrahedron formations are excellent instrument platforms for electromagnetic and plasma studies. A minimum of four spacecraft - to establish a volume - is required to study some of the key regions of a planetary magnetic field. The usefulness of the measurements recorded is strongly affected by the tetrahedron orbital evolution. This paper considers the preliminary development of a general optimization procedure for tetrahedron formation control. The maneuvers are assumed to be impulsive and a multi-stage optimization method is employed. The stages include targeting to a fixed tetrahedron orientation, rotating and translating the tetrahedron and/or varying the initial and final times. The number of impulsive maneuvers citn also be varied. As the impulse locations and times change, new arcs are computed using a differential corrections scheme that varies the impulse magnitudes and directions. The result is a continuous trajectory with velocity discontinuities. The velocity discontinuities are then used to formulate the cost function. Direct optimization techniques are employed. The procedure is applied to the Magnetospheric Multiscale Mission (MMS) to compute preliminary formation control fuel requirements.

Guzman, Jose J.

2003-01-01

278

Ribbed moraine formation  

NASA Astrophysics Data System (ADS)

Ribbed (Rogen) moraines are conspicuous landforms found in interior parts of formerly glaciated areas. Two major theories for ribbed moraine formation have been suggested in recent years: (i) the shear and stack theory, which explains ribbed moraine formation by shearing and stacking of till slabs or englacially entrained material during compressive flow, followed by basal melt-out of transverse moraine ridges, and (ii) the fracturing theory, according to which ribbed moraines form by fracturing of frozen pre-existing till sheets, at the transition from cold- to warm-based conditions under deglaciating ice sheets. In this paper, we present new data on the distribution of ribbed moraines and their close association with areas of frozen-bed conditions under ice sheets. In addition, we show examples of ribbed moraine ridges that fit together like a jig-saw puzzle. These observations indicate that fracturing and extension of a pre-existing till sheet may be a predominant process in ribbed moraine formation. In summary, we conclude that all described characteristics of ribbed moraines are compatible with the fracturing theory, while the shear and stack theory is hampered by an inability to explain many conspicuous features in the distribution pattern and detailed morphology of ribbed moraines. One implication of the fracturing theory is that the distribution of ribbed moraines can be used to reconstruct the extent of areas that underwent a change from frozen-bed to thawed-bed conditions under former ice sheets.

Hättestrand, Clas; Kleman, Johan

279

Terrestrial planet formation  

PubMed Central

Advances in our understanding of terrestrial planet formation have come from a multidisciplinary approach. Studies of the ages and compositions of primitive meteorites with compositions similar to the Sun have helped to constrain the nature of the building blocks of planets. This information helps to guide numerical models for the three stages of planet formation from dust to planetesimals (?106 y), followed by planetesimals to embryos (lunar to Mars-sized objects; few × 106 y), and finally embryos to planets (107–108 y). Defining the role of turbulence in the early nebula is a key to understanding the growth of solids larger than meter size. The initiation of runaway growth of embryos from planetesimals ultimately leads to the growth of large terrestrial planets via large impacts. Dynamical models can produce inner Solar System configurations that closely resemble our Solar System, especially when the orbital effects of large planets (Jupiter and Saturn) and damping mechanisms, such as gas drag, are included. Experimental studies of terrestrial planet interiors provide additional constraints on the conditions of differentiation and, therefore, origin. A more complete understanding of terrestrial planet formation might be possible via a combination of chemical and physical modeling, as well as obtaining samples and new geophysical data from other planets (Venus, Mars, or Mercury) and asteroids.

Righter, K.; O'Brien, D. P.

2011-01-01

280

77 FR 28703 - Endangered and Threatened Wildlife and Plants; Threatened Status for Eriogonum codium (Umtanum...  

Federal Register 2010, 2011, 2012, 2013

...Ringold Formation, a sedimentary formation made up of soft Pliocene lacustrine deposits of clay, sand, and silt (Newcomb 1958...the White Bluffs, beginning with periodic high-recharge, Ice Age flood events. Since the Pleistocene Epoch,...

2012-05-15

281

Model of kimberlite formation  

NASA Astrophysics Data System (ADS)

The critical goals in recognizing the nature of kimberlites are to find out: (1) the primary composition of melt of these rocks and (2) the principal processes of evolution of primary composition of kimberlites while ascending from mantle depth towards earth surface. Suppose, that the primary composition of kimberlite melt-fluid was in fact the composition of asthenosphere melt geochemically being close to alkaline-basalt (Hi-µ) saturated with high CO2. The genetic relation of kimberlites with basaltoids is indicated by a spatial and temporal affinity of their formation (Carlson et al, 2006; Lehmann et al, 2010; Tappe et al, 2012), similarity of the pattern of incompatible elements distribution, presence of megacryst minerals in alkaline basaltoids, Pyr-Alm garnet included, and finally, model calculation of parent melt composition for low-Cr megacryst minerals; it showed this composition to be typical for the alkaline basaltoid (Jones, 1980). At the asthenosphere level there was differentiation of basaltoid melt-fluid which was responsible for formation of its different parts with varying melt to fluid ratio and possibly varying content of alkalis (K2O). The outbreak of asthenosphere substance through lithosphere mantle proceeded by different scenarios: (a) With a noticeable dominance of fluid component kimberlites were formed by the capture and contamination of high-Mg, high-Cr rocks of lithosphere mantle that caused formation of high-Mg kimberlites. That corresponds to model of Russell (2012). (b) With a considerable proportion of melt phase depending on saturation in fluid there formed magnesium-ferriferous and ferriferous-titaniferous petrochemical types of kimberlites. There is no doubt that in formation of these kimberlite types the contamination of lithosphere material was the case, at the much lower level than in formation of high-Mg kimberlites. This model logically explains steady differences of petrochemistry of kimberlites making up clusters of different pipes, fields of pipes and even province. The model clarifies presence or absence of low-Cr, high-Ti megacryst association of minerals, with its crystallization proceeding in the melt phase of asthenosphere source of kimberlites. The role of hybridism in kimberlite emplacement is vivid in considering the features of composition of breccias and massive kimberlites composing pipe and dyke bodies of Kuoiksky field, in particular Obnazhennaya pipe. The former compared to massive varieties the kimberlites show much higher contents of SiO2, MgO and much lower CaO and CO2. Massive varieties of kimberlites are more ferriferous and titaniferous. The onset of breccias formation should evidently be attributed to the time of passing kimberlite melt-fluid through the lithosphere mantle. It is triggered by the processes of disintegration and capture of its rocks. Considering the composition of mantle xenoliths captured by the ascending flow of kimberlite mantle-fluid, the onset of the hybridization process should be referred to the boundary of asthenosphere and mantle lithosphere. The most deep-seated xenoliths are deformed lherzolites, which experienced the direct metasomatic effect of asthenosphere melt (Nixon, Boyd, 1973; Burgess & Harte, 2004). The hybrid nature of kimberlites assumes both the mechanic capture of fragmented material of lithosphere mantle and its inevitable partial assimilation causing a significant change of primary melt composition.

Kostrovitsky, Sergey; Fiveyskaya, Lyudmila

2013-04-01

282

Ultrarelativistic black hole formation.  

PubMed

We study the head-on collision of fluid particles well within the kinetic energy dominated regime (? = 8 to 12) by numerically solving the Einstein-hydrodynamic equations. We find that the threshold for black hole formation is lower (by a factor of a few) than simple hoop conjecture estimates, and, moreover, near this threshold two distinct apparent horizons first form postcollision and then merge. We argue that this can be understood in terms of a gravitational focusing effect. The gravitational radiation reaches luminosities of 0.014 c(5)/G, carrying 16 ± 2% of the total energy. PMID:23521246

East, William E; Pretorius, Frans

2013-03-01

283

Adiabatic Halo Formation  

SciTech Connect

In a high intensity circular accelerator the synchrotron dynamics introduces a slow modulation in the betatronic tune due to the space-charge tune depression. When the transverse motion is non-linear due to the presence of multipolar effects, resonance islands move in the phase space and change their amplitude. This effect introduces the trapping and detrapping phenomenon and a slow diffusion in the phase space. We apply the neo-adiabatic theory to describe this diffusion mechanism that can contribute to halo formation.

Bazzani, A.; Turchetti, G.; Benedetti, C.; Rambaldi, S.; Servizi, G. [Physics Department University of Bologna, INFN Bologna, via Irnerio 46 40126 Bologna Italy (Italy)

2005-06-08

284

Interstellar chemistry: polycyanoacetylene formation  

SciTech Connect

Two opposing views are given for the formation of interstellar polycyanoacetylenes. One theory states that the carbon chains are formed by ion-molecule reactions in the gas phase. The opposing theory is that the polycyanoacetylenes are produced by fragmentation of polymerized cyanoacetylenes formed on grains. Each author states his reasons why he believes in his theory over the opposing theory. However, both authors agree that cyanopolyacetylenes are produced in nature in the absence of ion-molecule chemistry, i.e., the star IRC +10216. (SC)

Anders, E. (Univ. of Chicago, IL); Hayatsu, R.

1981-11-06

285

Modeling river delta formation  

PubMed Central

A model to simulate the time evolution of river delta formation process is presented. It is based on the continuity equation for water and sediment flow and a phenomenological sedimentation/erosion law. Different delta types are reproduced by using different parameters and erosion rules. The structures of the calculated patterns are analyzed in space and time and compared with real data patterns. Furthermore, our model is capable of simulating the rich dynamics related to the switching of the mouth of the river delta. The simulation results are then compared with geological records for the Mississippi River.

Seybold, Hansjorg; Andrade, Jose S.; Herrmann, Hans J.

2007-01-01

286

Particle Formation in Dextran Solutions.  

National Technical Information Service (NTIS)

The study indicated that temperature variation and the isolation of droplets of solution predispose to particle formation in bottled dextran solutions. Particle formation induced by temperature variation during short storage periods can be prevented by si...

R. A. Ewald, A. A. Young, W. H. Crosby

1964-01-01

287

Fuel spill reports-Format  

NSF Publications Database

Title : Fuel spill reports-Format Type : Antarctic EAM NSF Org: OD / OPP Date : February 05, 1991 ... Action Memorandum (Threshold for Fuel Spill Reports/Format for Fuel Spill Reports) To: Files (S.7 - ...

288

Automation of Formation Flight Control.  

National Technical Information Service (NTIS)

The research contained in this thesis explores the concepts of Automated Formation Flight Control documented in three previous AFIT theses. The generic formation analyzed consists of a Leader and Wingman, with the Wingman referencing its maneuvers off of ...

V. P. Reyna

1994-01-01

289

CO2 Sequestration Potential of Texas Low-Rank Coals  

SciTech Connect

The objectives of this project are to evaluate the feasibility of carbon dioxide (CO{sub 2}) sequestration in Texas low-rank coals and to determine the potential for enhanced coalbed methane (ECBM) recovery as an added benefit of sequestration. The main objectives for this reporting period were to (1) determine the effects of permeability anisotropy on performance of CO{sub 2} sequestration and ECBM production in the Lower Calvert Bluff Formation (LCB) of the Wilcox Group coals in east-central Texas, and (2) begin reservoir and economic analyses of CO{sub 2} sequestration and ECBM production using horizontal wells. To evaluate the effects of permeability anisotropy on CO{sub 2} sequestration and ECBM in LCB coal beds, we conducted deterministic reservoir modeling studies of 100% CO{sub 2} gas injection for the 6,200-ft depth base case (Case 1b) using the most likely values of the reservoir parameters. Simulation results show significant differences in the cumulative volumes of CH{sub 4} produced and CO{sub 2} injected due to permeability anisotropy, depending on the orientation of injection patterns relative to the orientation of permeability anisotropy. This indicates that knowledge of the magnitude and orientation of permeability anisotropy will be an important consideration in the design of CO{sub 2} sequestration and ECBM projects. We continued discussions with Anadarko Petroleum regarding plans for additional coal core acquisition and laboratory work to further characterize Wilcox low-rank coals. As part of the technology transfer for this project, we submitted the paper SPE 100584 for presentation at the 2006 SPE Gas Technology Symposium to be held in Calgary, Alberta, Canada on May 15-18, 2006.

Duane A. McVay; Walter B. Ayers, Jr; Jerry L. Jensen

2006-05-01

290

Method for measuring pollutant formation  

NASA Technical Reports Server (NTRS)

Diagnostic methods for determining an instantaneous rate of pollutant formation in a combustion system are based on measurement of chemiluminescence intensity generated simultaneously with the formation of the pollutant. The chemiluminescent signal is generated by an analog reaction which occurs in parallel with a key step in the formation of a specific pollutant of interest. The connection between the analog reaction and the pollution reaction is such that the chemiluminescent signal indicates the local, instantaneous formation rate of the pollutant of interest.

Annen, Kurt (Inventor); Stickler, David B. (Inventor)

2001-01-01

291

Formative Assessment: Simply, No Additives  

ERIC Educational Resources Information Center

Among the types of assessment the closest to daily reading instruction is formative assessment. In contrast to summative assessment, which occurs after instruction, formative assessment involves forming judgments frequently in the flow of instruction. Key features of formative assessment include identifying gaps between where students are and…

Roskos, Kathleen; Neuman, Susan B.

2012-01-01

292

Bone formation by cancer metastases  

Microsoft Academic Search

The formation of heterotopic bone tissue in malignant tumors or in their metastases is extremely rare. In a 60 years old male patient with bronchogenic carcinoma (adenocarcinoma) extensive bone formation was observed within multiple metastases in the skeletal muscles. On the basis of the microscopic findings, the mechanism of bone formation by malignant tumors is discussed. Obviously, proliferation of local

U. Bettendorf; W. Remmele; H. Laaff

1976-01-01

293

Formative assessment: a critical review  

Microsoft Academic Search

This paper covers six interrelated issues in formative assessment (aka, ‘assessment for learning’). The issues concern the definition of formative assessment, the claims commonly made for its effectiveness, the limited attention given to domain considerations in its conceptualisation, the under?representation of measurement principles in that conceptualisation, the teacher?support demands formative assessment entails, and the impact of the larger educational system.

Randy Elliot Bennett

2011-01-01

294

Star formation and molecular clouds  

NASA Technical Reports Server (NTRS)

Several differnt stages can be discerned within the star formation process. Star formation can be considered to start when a molecular cloud fragments into many clumps. Many different physical processes are likely to play an important role in star formation, including self-gravity, magnetic fields, rotation, winds, and radiation transport. The current knowledge on some of these processes are reviewed.

Tielens, Alexander G. G. M.

1988-01-01

295

Biofilm formation by haloarchaea.  

PubMed

A fluorescence-based live-cell adhesion assay was used to examine biofilm formation by 20 different haloarchaea, including species of Halobacterium, Haloferax and Halorubrum, as well as novel natural isolates from an Antarctic salt lake. Thirteen of the 20 tested strains significantly adhered (P-value ?< 0.05) to a plastic surface. Examination of adherent cell layers on glass surfaces by differential interference contrast, fluorescence and confocal microscopy showed two types of biofilm structures. Carpet-like, multi-layered biofilms containing micro- and macrocolonies (up to 50 ?m in height) were formed by strains of Halobacterium salinarum and the Antarctic isolate t-ADL strain DL24. The second type of biofilm, characterized by large aggregates of cells adhering to surfaces, was formed by Haloferax volcanii DSM 3757T and Halorubrum lacusprofundi DL28. Staining of the biofilms formed by the strongly adhesive haloarchaeal strains revealed the presence of extracellular polymers, such as eDNA and glycoconjugates, substances previously shown to stabilize bacterial biofilms. For Hbt. salinarum DSM 3754T and Hfx. volcanii DSM 3757T , cells adhered within 1 day of culture and remained viable for at least 2 months in mature biofilms. Adherent cells of Hbt. salinarum DSM 3754T showed several types of cellular appendages that could be involved in the initial attachment. Our results show that biofilm formation occurs in a surprisingly wide variety of haloarchaeal species. PMID:23057712

Fröls, Sabrina; Dyall-Smith, Mike; Pfeifer, Felicitas

2012-12-01

296

Collagen fibril formation.  

PubMed Central

Collagen is most abundant in animal tissues as very long fibrils with a characteristic axial periodic structure. The fibrils provide the major biomechanical scaffold for cell attachment and anchorage of macromolecules, allowing the shape and form of tissues to be defined and maintained. How the fibrils are formed from their monomeric precursors is the primary concern of this review. Collagen fibril formation is basically a self-assembly process (i.e. one which is to a large extent determined by the intrinsic properties of the collagen molecules themselves) but it is also sensitive to cell-mediated regulation, particularly in young or healing tissues. Recent attention has been focused on "early fibrils' or "fibril segments' of approximately 10 microns in length which appear to be intermediates in the formation of mature fibrils that can grow to be hundreds of micrometers in length. Data from several laboratories indicate that these early fibrils can be unipolar (with all molecules pointing in the same direction) or bipolar (in which the orientation of collagen molecules reverses at a single location along the fibril). The occurrence of such early fibrils has major implications for tissue morphogenesis and repair. In this article we review the current understanding of the origin of unipolar and bipolar fibrils, and how mature fibrils are assembled from early fibrils. We include preliminary evidence from invertebrates which suggests that the principles for bipolar fibril assembly were established at least 500 million years ago.

Kadler, K E; Holmes, D F; Trotter, J A; Chapman, J A

1996-01-01

297

Deep water formation  

NASA Technical Reports Server (NTRS)

Some simple arguments on plumes of dense water and filling boxes were given. What determines the time for a large-scale environment to be modified by the injection of dense water at its edge is the mass flux, not the buoyancy flux. However, it is the denser buoyancy flux, when there are several competing plumes (e.g., the Mediterranean outflow versus the Denmark Strait outflow) that determines which plume will provide the bottom water for that ocean basin. It was noted that the obvious laboratory experiment (rotate a pie-shaped annulus, and heat/cool it on the surface) had never been performed. Thus, to some extent our belief that deep convection is somehow automatic at high latitudes to close off some ill-defined meridional circulation has never been tested. A summary of deep convection was given. The two fundamental formation mechanisms were shown. Of the two, it is open-ocean convection which forms the water which supplies the Denmark Strait overflow -- in all likelihood, as formation in the Greenland Sea remains stubbornly unobserved. But it is the slope convection which finally creates North Atlantic deep water, following the Denmark Strait overspill.

Killworth, P. D.

1984-01-01

298

Granular Crater Formation  

NASA Astrophysics Data System (ADS)

This project characterizes crater formation in a granular material by a jet of gas impinging on a granular material, such as a retro-rocket landing on the moon. We have constructed a 2D model of a planetary surface, which consists of a thin, clear box partially filled with granular materials (sand, lunar and Mars simulants...). A metal pipe connected to a tank of nitrogen gas via a solenoid valve is inserted into the top of the box to model the rocket. The results are recorded using high-speed video. We process these images and videos in order to test existing models and develop new ones for describing crater formation. A similar set-up has been used by Metzger et al.footnotetextP. T. Metzger et al. Journal of Aerospace Engineering (2009) We find that the long-time shape of the crater is consistent with a predicted catenary shape (Brandenburg). The depth and width of the crater both evolve logarithmically in time, suggesting an analogy to a description in terms of an activated process: dD/dt = A (-aD) (D is the crater depth, a and A constants). This model provides a useful context to understand the role of the jet speed, as characterized by the pressure used to drive the flow. The box width also plays an important role in setting the width of the crater.

Clark, Abe; Behringer, Robert; Brandenburg, John

2009-11-01

299

Bubble formation in microgravity  

NASA Technical Reports Server (NTRS)

Two KC-135 flight campaigns have been conducted to date which are specifically dedicated to study bubble formation in microgravity. The first flight was conducted during March 14-18, 1994, and the other during June 20-24, 1994. The results from the June 1994 flight have not been analyzed yet, while the results from the March flight have been partially analyzed. In the first flight three different experiments were performed, one with the specific aim at determining whether or not cavitation can take place during any of the fluid handling procedures adopted in the shuttle bioprocessing experiments. The other experiments were concerned with duplicating some of the procedures that resulted in bubble formation, namely the NCS filling procedure and the needle scratch of a solid surface. The results from this set of experiments suggest that cavitation did not take place during any of the fluid handling procedures. The results clearly indicate that almost all were generated as a result of the breakup of the gas/liquid interface. This was convincingly demonstrated in the scratch tests as well as in the liquid fill tests.

Antar, Basil N.

1994-01-01

300

LISA satellite formation control  

NASA Astrophysics Data System (ADS)

The joint ESA-NASA Laser Interferometer Space Antenna (LISA) mission consists of a triangular formation of three satellites aiming at detecting gravitational waves. In linear approximation the LISA satellites describe a circle around a reference point, maintaining a fixed position with respect to each other. The reference point, the center of the triangle, orbits the Sun in a circular orbit, trailing the Earth at twenty degrees. In reality the distance between the satellites will vary by about one to two percent and the angle between the arms of the antenna will vary by about 0.5° over the course of one year for the nominal LISA satellite configuration. For measurement accuracy it is desirable that the pointing offset of the telescopes be kept small. This makes it necessary to actuate the telescopes or to control the formation. It was assumed that the LISA satellites are equipped with six ?N engines that would allow to keep the two cubical proof masses within each satellite in almost perfect free fall. It was found that control forces up to about 700 ?N are required for maintaining the absolute triangular LISA formation, leading to unacceptable excursions of the proof masses from free fall. However, these forces compensate predominantly very low frequency variations of the arm lengths and angles of the triangle, which are then to be compensated by the telescope actuators. The variations are outside the aimed LISA measurement bandwidth (10 -4-0.1 Hz). In addition, the effect of thruster noise, orbit determination errors and orbit injection errors was examined. The effect of these error sources on the arm lengths and orientation angles between the LISA satellites was assessed both in open loop and in closed loop, where the closed loop was based on a proportional-derivative (PD) controller. It was found that orbit determination errors of the order of a few km in position and a few mm/s in velocity lead to negligible closed loop control forces. In addition, orbit injection errors of the order of 10 km in position and 1 cm/s in velocity could be eliminated after a few days when thrusting at levels of 200-500 ?N. Even for a high estimated level of thruster noise below 10 -4 Hz (equivalent to about 2 ?N random thrusts once an hour), the closed loop controller effectively reduced the effect on the angles of the triangle to below 30 nrad.

Bik, J. J. C. M.; Visser, P. N. A. M.; Jennrich, O.

301

Ferricyanide-humate formation  

NASA Astrophysics Data System (ADS)

We studied the complexation of ferricyanide ion by humic substances (HS) at acidic, neutral and basic pH by means of cyclic voltammetry (CV) and UV-visible spectroscopy. The CV measurements carried out at pH 3.5 and 7 showed that the first addition of HS (0.05 mg mL^{-1} of organic carbon) to ferricyanide solution caused a shift of both cathodic and anodic peak potentials together with a depression of the corresponding peak currents. After successive addition of HS further depression of peak currents were observed. Experiments perfonned at pH 12.5 showed no changes in peak current and peak potential after addition of HS. These results suggested the formation of ferricyanide-HS complexes at pH 3.5 and 7 and were confirmed by UV-Vis spectra recorded in concomitance to voltammetric measurements.

Leita, L.; Petruzzelli, G.; Fornasier, F.

2003-05-01

302

Glass formation in microgravity  

NASA Technical Reports Server (NTRS)

An account is given of containerless glass-forming experiments conducted aboard the Space Shuttle in 1985, using a single-axis acoustic levitator furnace apparatus. An attempt was made to obtain quantitative evidence for the suppression of heterogeneous nucleation/crystallization in containerless melts under microgravity conditions, as well as to study melt homogenization in the absence of gravity-driven convection and assess the feasibility of laser fusion target glass microsphere preparation with a microgravity apparatus of the present type. A ternary calcia-gallia-silica glass thus obtained indicated a 2-3-fold increase in glass-formation tendency for this material composition in microgravity, by comparison with 1g.

Ray, C. S.; Day, D. E.

1987-01-01

303

Pattern Formation in Materials  

NASA Astrophysics Data System (ADS)

Pattern formation is ubiquitous in nature, from sand ripples formed by wind to the development of a complex biological organism with different organs and a central nervous system. In the realm of materials, patterns are formed invariably when matter is transformed between different solid, liquid or gaseous states far from thermodynamic equilibrium. Material failure is itself mediated by the propagation of cracks that form intricate patterns. Understanding how patterns form and evolve is key to design materials with desired properties and to optimize their performance and safety. This talk will discuss recent progress made to understand three distinct class of patterns including the highly branched snow-flake-like dendritic patterns formed during the solidification process, polycrystalline patterns shaped by grain boundaries, and crack patterns.

Karma, Alain

2011-04-01

304

Dust Formation in Macronovae  

NASA Astrophysics Data System (ADS)

We examine dust formation in macronovae (as known as kilonovae), which are the bright ejecta of neutron star binary mergers and one of the leading sites of r-process nucleosynthesis. In light of information about the first macronova candidate associated with GRB 130603B, we find that dust grains of r-process elements have difficulty forming because of the low number density of the r-process atoms, while carbon or elements lighter than iron can condense into dust if they are abundant. Dust grains absorb emission from ejecta with an opacity even greater than that of the r-process elements, and re-emit photons at infrared wavelengths. Such dust emission can potentially account for macronovae without r-process nucleosynthesis as an alternative model. This dust scenario predicts a spectrum with fewer features than the r-process model and day-scale optical-to-ultraviolet emission.

Takami, Hajime; Nozawa, Takaya; Ioka, Kunihito

2014-07-01

305

Chorionic Villi Formation  

NSDL National Science Digital Library

This FlashTM animation depicts morphogenesis of chorionic villi. It begins by displaying a cross section through the three layers of the chorion, with a maternal sinusoid expanding through the syncyciotrophoblast. Clicking causes the lesson to progress through a stepwise display of the formation of stem, terminal, primary, secondary and tertiary villi, with the intervillous space and outer trophoblastic shell. The lesson ends with an explanation of how the chorionic villi of the placenta mediate diffusion between the fetal and maternal circulatory systems. A back button allows users to jump to previous scenes, a rate button allows them to toggle between fast and slow modes, and a text button allows them to toggle explanatory text on and off.

PhD Jack D Thatcher (West Virginia School of Osteopathic Medicine Structural Biology)

2010-11-29

306

Pine Island Iceberg Formation  

NSDL National Science Digital Library

This animation is a sequence showing the formation of the Pine Island iceberg and the glacial seaward flow upstream from the crack. It is a series of MISR images from the Terra satellite on top of the continental Radarsat view of Antarctica. The Pine Island Glacier is the largest discharger of ice in Antarctica and the continents fastest moving glacier. Even so, when a large crack formed across the glacier in mid 2000, it was surprising how fast the crack expanded, 15 meters per day, and how soon the resulting iceberg broke off, mid-November, 2001. This iceberg, called B-21, is 42 kilometers by 17 kilometers and contains seven years of glacier outflow released to the sea in a single event.

Perkins, Lori; Bindschadler, Bob; Diner, Dave

2002-01-10

307

Dityrosine formation in calmodulin  

SciTech Connect

Ultraviolet (280-nm) irradiation of bovine brain calmodulin results in calcium-dependent changes in its fluorescence emission spectrum. These consist of a decline in the intrinsic tyrosine fluorescence of the protein and the appearance of a new emission maximum at 400 nm. Chromatography of irradiated calmodulin, using Ultrogel AcA 54 and phenyl-agarose columns, yields several distinctive fractions. One of these, representing 2.8% of the total recovered protein and 53% of the total fluorescence emission at 400 nm, was selected for detailed characterization. Analyses performed on acid hydrolysates reveal the presence of dityrosine, a derivative of tyrosine known for its fluorescence near 400 nm, at the level of 0.59-0.89 mol per 16,700 g of protein. Sodium dodecyl sulfate gel electrophoresis experiments demonstrate two components of apparent molecular weights 14,000 (80%) and 16,000 (20%). Observations on the effects of UV irradiation on the thrombic fragments of calmodulin and on related calcium binding proteins (rabbit skeletal muscle troponin C, bovine cardiac troponin C, and parvalbumin) support the interpretation that dityrosine formation in calmodulin results from the intramolecular cross-linking of Tyr-99 and Tyr-138. The dityrosine-containing photoproduct of calmodulin is unable to stimulate the p-nitrophenyl phosphatase activity of calcineurin under standard assay conditions. Smooth muscle myosin light chain kinase binds the derivative about 280-fold less effectively than it binds native calmodulin. Of several metal ions tested, only Cd/sup 2 +/ approaches Ca/sup 2 +/ in its ability to promote the appearance of the 400-nm emission band during UV irradiation of calmodulin. Mn/sup 2 +/ and Cu/sup 2 +/ appear to inhibit dityrosine formation.

Malencik, D.A.; Anderson, S.R.

1987-02-10

308

Gas formation. Formation temperatures of thermogenic and biogenic methane.  

PubMed

Methane is an important greenhouse gas and energy resource generated dominantly by methanogens at low temperatures and through the breakdown of organic molecules at high temperatures. However, methane-formation temperatures in nature are often poorly constrained. We measured formation temperatures of thermogenic and biogenic methane using a "clumped isotope" technique. Thermogenic gases yield formation temperatures between 157° and 221°C, within the nominal gas window, and biogenic gases yield formation temperatures consistent with their comparatively lower-temperature formational environments (<50°C). In systems where gases have migrated and other proxies for gas-generation temperature yield ambiguous results, methane clumped-isotope temperatures distinguish among and allow for independent tests of possible gas-formation models. PMID:24970083

Stolper, D A; Lawson, M; Davis, C L; Ferreira, A A; Santos Neto, E V; Ellis, G S; Lewan, M D; Martini, A M; Tang, Y; Schoell, M; Sessions, A L; Eiler, J M

2014-06-27

309

Star formation in elliptical galaxies  

NASA Astrophysics Data System (ADS)

In this paper we anticipate part of the results of a recent study by the Padova group to cast light on the formation and evolution of elliptical galaxies by means of N-body TSPH simulations including star formation, feed-back and chemical evolution. Particular attention is paid here to the case of dwarf spheroidals of the Local Group which, thanks to their proximity and modern ground-based and space instrumentation, can be resolved into single stars so that independent determinations of their age and star formation history can be derived. Dwarf galaxies are known to exhibit complicated histories of star formation ranging from a single very old episode to a series of bursts over most of the Hubble time. By understanding the physical process driving star formation in these objects, we might be able to infer the mechanism governing star formation in more massive elliptical galaxies.

Chiosi, Cesare

310

Gaining Insight into Star Formation: Resolved Star Formation Laws  

NASA Astrophysics Data System (ADS)

Until recently astronomers have used star formation laws to measure the star formation rate and star formation efficiency of galaxies only on global scales because of the poor resolution of available data. What I am now capable of producing is a spatially resolved star formation law that can provide direct insight into the physical processes that govern star formation and assess the short-term nature of bursts of star formation and the longer-term nature of larger-scale events that can dictate the global distribution of stars and the ultimate fate of a galaxy as a whole. I am using exquisite narrowband optical data from a variety of sources, including the Hubble Space Telescope, and Kitt Peak National Observatory, etc., in conjunction with infrared data from the Spitzer Infrared Nearby Galaxy Survey and the Spitzer Local Volume Legacy survey, neutral gas data from The HI Nearby Galaxy Survey, and molecular gas data from the Berkeley-Illinois-Maryland Association Survey of Nearby Galaxies, to provide star formation rates and star formation efficiencies on previously inaccessible small spatial scales across a suite of galaxies that represent a range of star formation environments and scales. My sample includes 18 spiral galaxies ranging from 2.1 to 15.1 Mpc in distance and offers a large range of morphological types (i.e. a large range of star formation environments). I am using these data to test different models of star formation modes under a variety of physical conditions and relate the variations I observe to the known local physical conditions and the associated star formation histories for each locale within each galaxy.This is the heart of the matter - that the nature and evolution of the local physical environment intimately influences how stars can form, how quickly and how massive those stars are allowed to form, and as a result how they shape the local conditions for subsequent star formation. It is this tracking of the stellar ecology that is vital for insight into the star formation process, but also to understand the conditions that can result in star and planet formation, or conversely what conditions prevent this. Such an analysis is only possible with the kind of datasets I am producing.

Liebst, Kelley; Scowen, Paul A.

2014-06-01

311

Bead lightning formation  

SciTech Connect

Formation of beaded structures in triggered lightning discharges is considered in the framework of both magnetohydrodynamic (MHD) and hydrodynamic instabilities. It is shown that the space periodicity of the structures can be explained in terms of the kink and sausage type instabilities in a cylindrical discharge with anomalous viscosity. In particular, the fast growth rate of the hydrodynamic Rayleigh-Taylor instability, which is driven by the backflow of air into the channel of the decaying return stroke, dominates the initial evolution of perturbations during the decay of the return current. This instability is responsible for a significant enhancement of the anomalous viscosity above the classical level. Eventually, the damping introduced at the current channel edge by the high level of anomalous viscous stresses defines the final length scale of bead lightning. Later, during the continuing current stage of the lightning flash, the MHD pinch instability persists, although with a much smaller growth rate that can be enhanced in a M-component event. The combined effect of these instabilities may explain various aspects of bead lightning.

Ludwig, G.O.; Saba, M.M.F. [Associated Plasma Laboratory, National Space Research Institute, 12227-010, Sao Jose dos Campos, SP (Brazil); Division of Space Geophysics, National Space Research Institute, 12227-010, Sao Jose dos Campos, SP (Brazil)

2005-09-15

312

ARTIST tape output formats  

NASA Astrophysics Data System (ADS)

The format of the ARTIST data and raw data records written to magnetic tape are described. The contents of each record type are fully explained making possible an unpacking of the data for subsequent analysis. A new generation of modern ionosondes is now being deployed world wide. These are the University of Lowell Center for Atmospheric Research (ULCAR) Digisonde 256 and AN/FMQ-12 DISS systems. The Digisonde 256 network will provide a consistent data set of ionospheric parameters that are automatically scaled in real time. The automated stations output the standard ionospheric parameters, the h'N(f) traces with amplitudes and Doppler frequencies, and the electron density profiles. There are currently 32 systems in operation or are close to being installed. The global station distribution is very uneven, the majority of sites lying in the northern hemisphere, and there are no equatorial stations. Nevertheless this network provides an extensive data base of ionospheric parameters in digital form, making it easy to process and analyze the data in terms of average diurnal variations, storms, and irregularities. This data base will be invaluable for the testing of global ionosphere models.

Tang, Jane; Dozois, Claude G.; Gamache, Robert R.

1990-07-01

313

Formation of "bound  

NASA Astrophysics Data System (ADS)

During degradation of organic pollutants in soil, metabolites, microbial biomass, CO2and "bound" residues ("non-extractable" residues in soil organic matter) are formed. Enhanced transformation of these contaminants into "bound" residues has been proposed as an alternative remediation method for polluted soils. However, this kind of residues may pose a potential risk for the environment due to their chemical structure and possible remobilization under different conditions. Therefore particular attention is given actually to "bound" residues. Part of these non-extractable residues may be "biogenic," because microorganisms use the carbon from the pollutant to form their biomass components (fatty acids, amino acids, amino sugars), which subsequently may be incorporated into soil organic matter. Furthermore, the CO2 originating from mineralization of xenobiotics, can be re-assimilated by microorganisms and also incorporated into "biogenic residue". The hazard posed by "bound" residues may be overestimated because they are "biogenic" (contain microbial fatty acids and amino acids). The knowledge about the pathways of "biogenic residue" formation is necessary for a proper assessment of the fate of tested pollutants and their turnover in the soil environment. Moreover, these data are needed to establish the realistic degradation rates of the contaminants in soil. The main objectives of this study are: to quantify the extent of "biogenic residue" (fatty acids, amino acids, amino sugars) formation during the degradation of a model pollutant (2,4-dichlorophenoxyacetic acid = 2,4-D) and during CO2 assimilation by microorganisms and to evaluate which components are mainly incorporated into "bound" residues. To investigate the extent of "biogenic residue" formation in soil during the degradation of 2,4-D, experiments with either 14C-U-ring and 13C6-2,4-D or carboxyl-14C 2,4-D were performed. The incubation experiments were performed according to OECD test guideline 307, in the dark, at constant temp 20Ë? C (+/-2Ë? C) and with intermittent aeration. During incubation, the mineralization was quantified and soil samples were analyzed for the presence of both "biogenic residues" and remaining 2,4-D. Mineralization of 2,4-D in both experiments was very high. However, the 14CO2 evolution was higher from carboxyl-14C 2,4-D than from 14C-ring 2,4-D. After 7 days of incubation, 30% of initial amount of 14C in soil contaminated with 14C-ring 2,4-D was mineralized, whereas 40% of total radioactivity was evolved as CO2after 4 days from soil incubated with 14C-carboxyl 2,4-D. The amount of extractable 2,4-D residues was very low in both experiments (14C-ring 2,4-D: 2% and 14C-carboxyl 2,4-D: 1%). The soil incubated with 14C-ring 2,4-D contained 60% of "non-extractable" residues of 2,4-D after 7 days, while the amount of these residues in soil contaminated with 14C-carboxyl 2,4-D reached 50% of the initial radioactivity in the tested system 4 days after application. More "biogenic residues" were formed in soil spiked with 14C-U-ring 2,4-D (10%) than in soil with carboxyl 14C 2,4-D (7%). Both 2,4-D and CO2-derived C were incorporated mainly into microbial amino acids (9.5% at day 7 and 7.0% at day 4, respectively). After 7 days of incubation, 0.5% of initial applied radioactivity in system was found in microbial lipids in the soil contaminated with 14C-ring 2,4-D. Only 0.1% of the total radioactivity was incorporated into lipids in soil treated with 14C-carboxyl 2,4-D on day 4 after application. Thin Layer Chromatography identified the microbial lipids containing the radioactivity as phosphatidylethanolamine, a phospholipid typical for microorganisms. The amount of microbial lipids (which corresponds to phospholipids) in both cases decreased with time; this can be explained by the death of the microbial biomass. To the best of our knowledge, this is the first report on the formation of &qu

Nowak, K.; Kästner, M.; Miltner, A.

2009-04-01

314

Large Format Radiographic Imaging  

SciTech Connect

Radiographic imaging continues to be a key diagnostic in many areas at Los Alamos National Laboratory (LANL). Radiographic recording systems have taken on many form, from high repetition-rate, gated systems to film recording and storage phosphors. Some systems are designed for synchronization to an accelerator while others may be single shot or may record a frame sequence in a dynamic radiography experiment. While film recording remains a reliable standby in the radiographic community, there is growing interest in investigating electronic recording for many applications. The advantages of real time access to remote data acquisition are highly attractive. Cooled CCD camera systems are capable of providing greater sensitivity with improved signal-to-noise ratio. This paper begins with a review of performance characteristics of the Bechtel Nevada large format imaging system, a gated system capable of viewing scintillators up to 300 mm in diameter. We then examine configuration alternatives in lens coupled and fiber optically coupled electro-optical recording systems. Areas of investigation include tradeoffs between fiber optic and lens coupling, methods of image magnification, and spectral matching from scintillator to CCD camera. Key performance features discussed include field of view, resolution, sensitivity, dynamic range, and system noise characteristics.

J. S. Rohrer; Lacey Stewart; M. D. Wilke; N. S. King; S. A Baker; Wilfred Lewis

1999-08-01

315

Galactic and extragalactic star formation  

SciTech Connect

This book present new technology that allows the linking of the physics of local star forming regions to the global star forming properties of galaxies. Galactic star formation and examination of the processes of formation of nearby stars are addressed. Focus is on bipolar outflows and circumstellar disks. Larger scale phenomena in molecular clouds are then discussed, followed by reviews of star formation across the Milky Way.

Pudritz, R.E. (Minnesota Univ., Minneapolis, MN (USA). Heat Transfer Lab.); Fich, M. (Waterloo Univ., ON (Canada))

1988-01-01

316

Energy saving in flight formation.  

PubMed

Many species of large bird fly together in formation, perhaps because flight power demands and energy expenditure can be reduced when the birds fly at an optimal spacing, or because orientation is improved by communication within groups. We have measured heart rates as an estimate of energy expenditure in imprinted great white pelicans (Pelecanus onocrotalus) trained to fly in 'V' formation, and show that these birds save a significant amount of energy by flying in formation. This advantage is probably a principal reason for the evolution of flight formation in large birds that migrate in groups. PMID:11607019

Weimerskirch, H; Martin, J; Clerquin, Y; Alexandre, P; Jiraskova, S

2001-10-18

317

"Translating" between survey answer formats?  

PubMed Central

Survey research remains the most popular source of market knowledge, yet researchers have not yet established one consistent technique for measuring responses. Some market research companies offer respondents two answer options; others five or seven. Some answer formats use middle points on the answer scales, others do not. Some formats verbalize all answer options, some only the endpoints. The wide variety of answer formats that market research companies and academic researchers use makes comparing results across studies virtually impossible. This study offers guidance for market researchers by presenting empirical translations for the answer formats they most commonly use, thus enabling easier comparisons of results.

Dolnicar, Sara; Grun, Bettina

2013-01-01

318

Formative Assessment Probes: Is It a Rock? Continuous Formative Assessment  

ERIC Educational Resources Information Center

A lesson plan is provided for a formative assessment probe entitled "Is It a Rock?" This probe is designed for teaching elementary school students about rocks through the use of a formative assessment classroom technique (FACT) known as the group Frayer Model. FACT activates students' thinking about a concept and can be used to…

Keeley, Page

2013-01-01

319

Medusae Fossae Formation  

NASA Technical Reports Server (NTRS)

An exotic terrain of wind-eroded ridges and residual smooth surfaces are seen in one of the highest resolution images ever taken of Mars from orbit. The Medusae Fossae formation is believed to be formed of the fragmental ejecta of huge explosive volcanic eruptions. When subjected to intense wind-blasting over hundreds of millions of years, this material erodes easily once the uppermost tougher crust is breached. In the Mars Orbiter Camera (MOC) image shown on the right, the crust, or cap rock, can be seen in the upper right part of the picture. The finely-spaced ridges are similar to features on Earth called yardangs, which are formed by intense winds plucking individual grains from, and by wind-driven sand blasting particles off, sedimentary deposits.

The MOC image was taken on October 30, 1997 at 11:05 AM PST, shortly after the Mars Global Surveyor spacecraft's 31st closest approach to Mars. The image covers an area 3.6 X 21.5 km (2.2 X 13.4 miles) at 3.6 m (12 feet) per picture element--craters only 11 m (36 feet, about the size of a swimming pool) across can be seen. The context image (left; the best Viking view of the area; VO 1 387S34) has a resolution of 240 m/pixel, or 67 times lower resolution than the MOC frame.

Malin Space Science Systems (MSSS) and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

1998-01-01

320

Feasible formations of multi-agent systems  

Microsoft Academic Search

Formations of multi-agent systems, such as satellites and aircraft, require that individual agents satisfy their kinematic equations while constantly maintaining inter-agent constraints. In this paper, we develop a systematic framework for studying formations of multiagent systems. In particular, we consider undirected formations for centralized formations and directed formations for decentralized formations. In each case, we determine differential geometric conditions that

Paulo Tabuada; George J. Pappas; Pedro Lima

2001-01-01

321

Science Sampler: Formative assessment guideposts  

NSDL National Science Digital Library

A formative assessment can provide a snapshot of what a student knows and is able to do. Use this approach to close the gap between what is known and what needs to be known through informative feedback. Explore the use of formative assessments with navigational help from these six guideposts.

Ayala, Carlos

2005-01-01

322

Mediating Among Diverse Data Formats.  

National Technical Information Service (NTIS)

The growth of the Internet and other global networks has made large quantities of data available in a wide variety of formats. Unfortunately, most programs are only able to interpret a small number of formats, and cannot take advantage of data in unfamili...

J. Ockerbloom

1998-01-01

323

Information-Theoretic Image Formation  

Microsoft Academic Search

The emergent role of information theory in image formation is surveyed. Unlike the subject of information-theoretic communication theory, information-theoretic imaging is far from a mature subject. The possible role of information theory in prob- lems of image formation is to provide a rigorous framework for defining the imaging problem, for defining measures of optimality used to form estimates of images,

Joseph A. O'sullivan; Richard E. Blahut; Donald L. Snyder

1998-01-01

324

Formative Assessment: A Critical Review  

ERIC Educational Resources Information Center

This paper covers six interrelated issues in formative assessment (aka, "assessment for learning"). The issues concern the definition of formative assessment, the claims commonly made for its effectiveness, the limited attention given to domain considerations in its conceptualisation, the under-representation of measurement principles in that…

Bennett, Randy Elliot

2011-01-01

325

Morse theory and formation control  

Microsoft Academic Search

Formation shape control for a collection of point agents is concerned with devising decentralized control laws which will ensure that the formation will move so that certain inter-agent distances assume prescribed values. A number of algorithms based on steepest descent of an error function have been suggested for various problems, and all display the existence of incorrect equilibria, though often

Brian D. O. Anderson

2011-01-01

326

Formation of the solar system  

Microsoft Academic Search

The overall evolution of the solar system is discussed in terms of what is called the Kyoto model. Starting from the formation of the solar nebula, a multistep process is followed in detail, including growth and sedimentation of dust grains in the nebula, formation of planetesimals due to fragmentation of a dust layer, radial migration and accumulation of planetesimals to

C. Hayashi; K. Nakazawa; Y. Nakagawa

1985-01-01

327

Tooth formation - delayed or absent  

MedlinePLUS

Delayed or absent tooth formation; Teeth - delayed or absent formation ... The timing of the first appearance of teeth varies. Most infants get their first tooth between 6 and 9 months, although earlier or later eruption may be normal. In some cases, ...

328

Pattern Formation Using Multiple Robots  

Microsoft Academic Search

Pattern formation is one of typical problems in the field of multi-robot cooperation. It can be applied to complex application scenarios such as region coverage and path exploration. Compare to traditional multi-robot coordination algorithm, the method based on swarm robots to solve the issue of pattern formation has better scalability and dynamic adaptability and robustness. In this demo, we propose

Jun Zeng; Daoyong Liu; Alei Liang; Haibing Guan

2009-01-01

329

Professional Development through Formative Evaluation  

ERIC Educational Resources Information Center

Formative evaluation and its associated methodology of reflection on practice are used extensively in academic staff development. In reflecting on formative evaluation processes in both more traditional and newer programmes conducted at a university of technology, a number of variables reported in the literature were observed to have influenced…

Nsibande, Rejoice; Garraway, James

2011-01-01

330

Pellicle formation in Shewanella oneidensis  

PubMed Central

Background Although solid surface-associated biofilm development of S. oneidensis has been extensively studied in recent years, pellicles formed at the air-liquid interface are largely overlooked. The goal of this work was to understand basic requirements and mechanism of pellicle formation in S. oneidensis. Results We demonstrated that pellicle formation can be completed when oxygen and certain cations were present. Ca(II), Mn(II), Cu(II), and Zn(II) were essential for the process evidenced by fully rescuing pellicle formation of S. oneidensis from the EDTA treatment while Mg (II), Fe(II), and Fe(III) were much less effective. Proteins rather than DNA were crucial in pellicle formation and the major exopolysaccharides may be rich in mannose. Mutational analysis revealed that flagella were not required for pellicle formation but flagellum-less mutants delayed pellicle development substantially, likely due to reduced growth in static media. The analysis also demonstrated that AggA type I secretion system was essential in formation of pellicles but not of solid surface-associated biofilms in S. oneidensis. Conclusion This systematic characterization of pellicle formation shed lights on our understanding of biofilm formation in S. oneidensis and indicated that the pellicle may serve as a good research model for studying bacterial communities.

2010-01-01

331

Formation of the Outer Planets  

Microsoft Academic Search

Models of the origins of gas giant planets and ‘ice’ giant planets are discussed and related to formation theories of both smaller objects (terrestrial planets) and larger bodies (stars). The most detailed models of planetary formation are based upon observations of our own Solar System, of young stars and their environments, and of extrasolar planets. Stars form from the collapse,

Jack J. Lissauer

2005-01-01

332

Galaxy Collisions and Star Formation  

Microsoft Academic Search

We present a brief overview of some recent observations of colliding galaxies and relevant numerical simulations. These are compared, and details of the locations and history of collision induced star formation are explored, with possible application to star formation at earlier epochs.

Susan A. Lamb; Nathan C. Hearn

2000-01-01

333

Galaxy Collisions and Star Formation  

Microsoft Academic Search

We present a brief overview of some recent observations of colliding galaxies\\u000aand relevant numerical simulations. These are compared, and details of the\\u000alocations and history of collision induced star formation are explored, with\\u000apossible application to star formation at earlier epochs.

Susan A. Lamb; Nathan C. Hearn

2000-01-01

334

The Apennine Bench Formation revisited  

NASA Technical Reports Server (NTRS)

The Apennine Bench Formation consists of pre-mare light plains materials that crop out south of the crater Archimedes, inside the Imbrium basin. This material was ascribed to either impact or volcanic origins. The characteristics of Apollo 15 KREEP basalts and the Apennine Bench Formation are reviewed to determine whether their characteristics are compatible with a volcanic origin.

Spudis, P. D.; Hawke, B. R.

1985-01-01

335

Formation of interstellar anions  

NASA Astrophysics Data System (ADS)

Formation of interstellar anions: M.L. Senent. The recent detection of negative charged species in the ISM1 has instigated enthusiasm for anions in the astrophysical community2. Many of these species are new and entail characterization. How they are formed in astrophysical sources is a question of major relevance. The anion presence in ISM was first predicted theoretically on the basis of electron affinities and on the negative linear chain molecular stabilities. Although very early, they were considered in astrochemical models3-4, their discovery is so recent because their abundances seem to be relatively low. These have to be understood in terms of molecular stabilities, reaction probabilities and radiative and collisional excitations. Then, we present our theoretical work on even carbon chains type Cn and CnH (n=2,4,6) focused to the understanding of anion abundances. We use highly correlated ab initio methods. We performed spectroscopic studies of various isomers that can play important roles as intermediates5-8. In previous papers9-10, we compared C2H and C2H- collisional rates responsible for observed line intensities. Actually, we study hydrogen attachment (Cn +H ? CnH and Cn- +H ? CnH-) and associative detachment processes (Cn- +H ? CnH +e-) for 2, 4 and 6 carbon atom chains11. [1] M.C.McCarthy, C.A.Gottlieb, H.Gupta, P.Thaddeus, Astrophys.J, 652, L141 (2006) [2] V.M.Bierbaum, J.Cernicharo, R.Bachiller, eds., 2011, pp 383-389. [3] A. Dalgarno, R.A. Mc Cray, Astrophys.J,, 181, 95 (1973) [4] E. Herbst E., Nature, 289, 656 (1981); [5] H.Massó, M.L.Senent, P.Rosmus, M.Hochlaf, J.Chem.Phys., 124, 234304 (2006) [6] M.L.Senent, M.Hochlaf, Astrophys. J. , 708, 1452(2010) [7] H.Massó, M.L.Senent, J.Phys.Chem.A, 113, 12404 (2009) [8] D. Hammoutene, M.Hochlaf, M.L.Senent, submitted. [9] A. Spielfiedel, N. Feautrier, F. Najar, D. ben Abdallah, F. Dayou, M.L. Senent, F. Lique, Mon.Not.R.Astron.Soc., 421, 1891 (2012) [10] F.Dumouchel, A, Spielfieldel , M.L.Senent, N.Feautrier, Chem. Phys. Lett., 533, 6 (2012) [11] M.L.Senent, M.Hochlaf, submitted

Senent, Maria Luisa

2012-05-01

336

The formation of Pangea  

NASA Astrophysics Data System (ADS)

The making of Pangea is the result of large-scale amalgamation of continents and micro-continents, which started at the end of the Neoproterozoic with the formation of Gondwana. As pieces were added to Gondwana on its South-American, Antarctica and Australia side, ribbon-like micro-continents were detached from its African and South-Chinese side: Cadomia in the late Neoproterozoic, Avalonia and Hunia in the Ordovician, Galatia in the Devonian and Cimmeria in the Permian. Cadomia was re-accreted to Gondwana, but the other ribbon-continents were accreted to Baltica, North-China, Laurussia or Laurasia. Finding the origin of these numerous terranes is a major geological challenge. Recently, a global plate tectonic model was developed together with a large geological/geodynamic database, at the Lausanne University, covering the last 600 Ma of the Earth's history. Special attention was given to the placing of Gondwana derived terranes in their original position, using all possible constraints. We propose here a solution for the Variscan terranes, another paper deals with the Altaids. The Galatian super-terrane was detached from Gondwana in the Devonian, during the opening of Paleotethys, and was quickly separated into four sub-terranes that started to by-pass each other. The leading terranes collided at the end of the Devonian with the Hanseatic terrane detached from Laurussia. In the Carboniferous, Gondwana started to impinge onto the amalgamated terranes, creating the Variscan chain and the Pangean super-continent. East of Spain Paleotethys remained opened until the Triassic, subducting northward under Laurasia. Roll-back of the Paleotethyan slab triggered the collapse of most of the European Variscan orogen, which was replaced by series of Permian rifts, some of them becoming oceanized back-arc basins during the Triassic. Major force changes at the Pangean plate limits at the end of the Triassic provoked its break-up, through the opening of the proto-Caribbean, central-Atlantic, Alpine-Tethys oceanic seaways.

Stampfli, G. M.; Hochard, C.; Vérard, C.; Wilhem, C.; vonRaumer, J.

2013-05-01

337

Star formation rates and starbursts  

NASA Astrophysics Data System (ADS)

Understanding star formation rates in galaxies requires understanding both the rate at which molecular clouds form and the efficiency of star formation in these clouds. The efficiency of star formation is probably limited mainly by the destruction of star-forming clouds by ionization, and molecular clouds probably form by a combination of large-scale gravitational instabilities and cloud accretion processes. These hypotheses lead to quantitative predictions that agree well with observational estimates of both the efficiency of star formation and the timescale for converting gas into stars. The predicted timescale depends mainly on the surface density of gas in a galaxy, and the predicted star formation rate per unit area is proportional to the square of the gas surface density, similar to the original Schmidt law. A burst of star formation requires an exceptionally high gas surface density; this results in both a short timescale and a high efficiency for star formation. The gas feeding a starburst must be assembled rapidly into the starburst region, and this requires a violent large-scale disturbance to the interstellar medium in a galaxy, such as that produced by a tidal interaction or merger with another galaxy.

Larson, Richard B.

338

Euromech 160 on Periodic Flow and Wake Phenomena  

NASA Astrophysics Data System (ADS)

Several areas of periodic flow and wake phenomena are addressed including vortex shedding, oscillator model theory, unsteady pressure, velocity fields, vortex formation, bluff body wakes, and wind induced vibrations.

339

Antihydrogen Formation using Cold Plasmas  

SciTech Connect

Antihydrogen, the antimatter counterpart of the hydrogen atom, can be formed by mixing cold samples of antiprotons and positrons. In 2002 the ATHENA collaboration succeeded in the first production of cold antihydrogen. By observing and imaging the annihilation products of the neutral, non-confined, antihydrogen atoms annihilating on the walls of the trap we can observe the production in quasi-real-time and study the dynamics of the formation mechanism. The formation mechanism strongly influences the final state of the formed antihydrogen atoms, important for future spectroscopic comparison with hydrogen. This paper briefly summarizes the current understanding of the antihydrogen formation in ATHENA.

Madsen, N.; Bowe, P.D.; Hangst, J.S. [Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark); Amoretti, M.; Carraro, C.; Macri, M.; Testera, G.; Variola, A. [Istituto Nazionale di Fisica Nucleare, Sezione di Genova, I-16146 Genova (Italy); Amsler, C.; Johnson, I.; Pruys, H.; Regenfus, C. [Physik-Institut, Zuerich University, CH-8057 Zurich (Switzerland); Bonomi, G.; Bouchta, A.; Doser, M.; Kellerbauer, A.; Landua, R. [PH Department, CERN, Geneva (Switzerland); Cesar, C.L. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21945-970 (Brazil); Charlton, M.; Joergensen, L.V. [Department of Physics, University of Wales Swansea, Swansea SA2 8PP (United Kingdom)] [and others

2004-10-20

340

Dynamics of rock varnish formation  

SciTech Connect

Our studies of rock varnish from the southwestern United States suggest that the Mn-phase in rock varnish has neither the chemistry nor the crystal structure of birnessite. Rather, the Mn-rich phase is non-crystalline and contains Ba, Ca, Fe, Al, and P. Unknowns concerning the formation of this non-crystalline Mn phase must be resolved before researchers are able to define chemical parameters of rock varnish formation based upon conditions of formation of the Mn phase. 6 refs., 9 figs.

Raymond, R. Jr.; Reneau, S.L.; Guthrie, G.D. Jr.; Bish, D.L.; Harrington, C.D.

1991-01-01

341

Holographic grating formation in photopolymers  

NASA Astrophysics Data System (ADS)

We introduce a model describing real-time grating formation in holographic photopolymers, assuming that the diffusion of free monomers is much faster than the grating formation. This model, which combines polymerization kinetics with results from coupled-wave theory, indicates that the grating formation time depends sublinearly on the average holographic recording intensity and the beam intensity ratio controls the grating index modulation at saturation. We validate the model by comparing its predictions with the results of experiments in which DuPont HRF-150X001 photopolymer was used.

Piazzolla, Sabino; Jenkins, B. Keith

1996-07-01

342

Amyloid beta mediates memory formation  

PubMed Central

The amyloid precursor protein (APP) undergoes sequential cleavages to generate various polypeptides, including the amyloid ? (1–42) peptide (A?[1–42]), which is believed to play a major role in amyloid plaque formation in Alzheimer's disease (AD). Here we provide evidence that, in contrast with its pathological role when accumulated, endogenous A? in normal hippocampi mediates learning and memory formation. Furthermore, hippocampal injection of picomolar concentrations of exogenous A?(1–42) enhances memory consolidation. Correlative data suggest that A? peptides may exert their function via nicotinic acethylcoline receptors. Hence, A? peptides, including A?(1–42), play an important physiological role in hippocampal memory formation.

Garcia-Osta, Ana; Alberini, Cristina M.

2009-01-01

343

The physics of planetesimal formation  

NASA Technical Reports Server (NTRS)

Physical processes involved in the planetesimal formation are discussed with special attention given to the nature of aerodynamic interactions between solid bodies and gas in the solar nebula. It is emphasized that the model of planetesimal formation by gravitational instability of a dust layer yields predictions that are simple but almost certainly wrong. It is suggested instead that the formation of planetesimals began with the process of coagulation of grains into larger aggregates, and that gravitational forces became more important than gas drag only after objects as large as many meters in diameter had formed.

Weidenschilling, Stuart J.; Donn, Bertram D.; Meakin, Paul

1989-01-01

344

Energetic condition for carbyne formation  

NASA Astrophysics Data System (ADS)

Although hypothesized in the carbon phase diagram, a general criterion to explain the formation of sp bonded carbon chains (carbynes) is lacking. We propose an energetic approach to explain carbyne formation in two conceptually simple configurations in which impact events play a major role, namely, in ancient meteorite craters and in the synthesis of cluster-assembled carbon films. For both configurations the calculated energies per particle equal each other. In one case pressure and temperature values match the carbyne region in the carbon phase diagram. A threshold range of 130-180 eV particle -1 is suggested as an energetic condition for carbyne formation.

Lamperti, A.; Ossi, P. M.

2003-07-01

345

Dissipative processes in galaxy formation.  

PubMed Central

A galaxy commences its life in a diffuse gas cloud that evolves into a predominantly stellar aggregation. Considerable dissipation of gravitational binding energy occurs during this transition. I review here the dissipative processes that determine the critical scales of luminous galaxies and the generation of their morphology. The universal scaling relations for spirals and ellipticals are shown to be sensitive to the history of star formation. Semiphenomenological expressions are given for star-formation rates in protogalaxies and in starbursts. Implications are described for elliptical galaxy formation and for the evolution of disk galaxies.

Silk, J

1993-01-01

346

Germline cyst formation in Drosophila.  

PubMed

In a wide variety of organisms, gametes develop within clusters of interconnected germline cells called cysts. Four major principles guide the construction of most cysts: synchronous division, a maximally branched pattern of interconnection between cells, specific changes in cyst geometry, and cyst polarization. The fusome is a germline-specific organelle that is associated with cyst formation in many insects and is likely to play an essential role in these processes. This review examines the cellular and molecular processes that underlie fusome formation and cyst initiation, construction, and polarization in Drosophila melanogaster. The studies described here highlight the importance of cyst formation to the subsequent development of functional gametes. PMID:9442902

de Cuevas, M; Lilly, M A; Spradling, A C

1997-01-01

347

Constraining Corona Formation on Venus  

NASA Astrophysics Data System (ADS)

We model the formation of off-rift coronae at Parga Chasma in order to understand how Venus loses its heat. We find the data required to make proper comparisons between models and observations is lacking.

Piskorz, D.; Elkins-Tanton, L. T.; Smrekar, S. E.

2014-05-01

348

Full Capability Formation Flight Control.  

National Technical Information Service (NTIS)

The subject of automatic formation flight control is of current interest to the development of Unmanned Aerial Vehicles (UAV). Previous control approaches have been refined in this work to allow more robust maneuvering and to include a fourth control para...

R. K. Osteroos

2005-01-01

349

Formation of the Solar System  

NSDL National Science Digital Library

This chapter from an online astronomy course briefly describes the formation of the solar system from an accretionary disk. Links to additional resources, a homework assignment, and a quiz are included.

Barnes, Joshua

350

Metamorphism and Metamorphic Formation & Deformation  

NSDL National Science Digital Library

This presentation on metamorphis and metamorphic formation was created by Martin Streck of Portland State University. The lesson provides an overview on the deformation of metamorphic rocks and minerals and includes helpful diagrams and images.

Streck, Martin

2008-04-25

351

Optimal Reconfiguration of Tetrahedral Formations.  

National Technical Information Service (NTIS)

The problem of minimum-fuel formation reconfiguration for the Magnetospheric Multi- Scale (MMS) mission is studied. This reconfiguration trajectory optimization problem can be posed as B nonlinear optimal control problem. In this research, this optimal co...

G. Huntington S. P. Hughes

2003-01-01

352

Method for treating underground formations  

SciTech Connect

Disclosed is a method for treating subterranean formations such as underground petroleum-containing formations penetrated by a well, and particularly a formation penetrated by a producing well which formation contain a plurality of zones, one or more of which are producing petroleum and one or more of which are producing water. The treatment selectively reduces the permeability of the water-producing intervals without adversely affecting the permeability of the oil producing intervals, thereby reducing the production of water and reducing the water-oil ratio of the fluid being produced from the well. The treatment method involves introducing an effective amount of a liquid comprising a hydrocarbon having dispersed therein an unhydrated water swellable clay such as bentonite, a sodium montmorillonite. The clay swells on contacting water in the water-producing intervals and plugs or reduces the permeability of the flow channels in the water-producing intervals.

Noles, J.R.; Walker, C.O.; White, N.F.

1981-04-14

353

Vertical formations demand unique treatments  

SciTech Connect

In the US midcontinent area, major thrust faults trap large quantities of hydrocarbons in the down-thrown fault block. As exploration of these thrust fault structures continues, the application of extended reach and horizontal well bores will increase. Formations in deep structures are apt to have lower porosity and permeability than the currently developed thrust faults and thus, require fracture stimulation. In addition, the portion of the formation closest to the fault may be subjected to folding resulting in a vertical formation penetrated by a horizontal well bore. Low porosity and vertical bedding were encountered in the City of Lawton No. 1-34, an 18,088-ft wildcat (14,627-ft TVD) in Caddo County, Oklahoma. This article details methods to overcome the obstacles that well bore and formation geometry present to fracture stimulation operations in the 17,714-ft (14,614-ft TVD) Britt sand.

Fairchild, K. [Fina Oil and Chemical Co., Midland, TX (United States)

1996-04-01

354

Cosmic strings and galaxy formation  

NASA Technical Reports Server (NTRS)

The cosmogonical model proposed by Zel'dovich and Vilenkin (1981), in which superconducting cosmic strings act as seeds for the origin of structure in the universe, is discussed, summarizing the results of recent theoretical investigations. Consideration is given to the formation of cosmic strings, the microscopic structure of strings, gravitational effects, cosmic string evolution, and the formation of galaxies and large-scale structure. Simulation results are presented in graphs, and several outstanding issues are listed and briefly characterized.

Bertschinger, Edmund

1989-01-01

355

Flight Formation of Multiple UAVs  

Microsoft Academic Search

\\u000a To conclude the whole monograph, we feature respectively in Chaps. 10 and 11 the applications of the unmanned rotorcraft systems constructed. More specifically, in Chap. 10, we present some basic results\\u000a on flight formation and collision avoidance of multiple unmanned systems. We adopt the leader-follower pattern to maintain\\u000a a fixed geometrical formation while navigating the unmanned rotorcraft following certain trajectories. In order

Guowei Cai; Ben M. Chen; Tong Heng Lee

356

Thiol isomerases in thrombus formation.  

PubMed

Protein disulfide isomerase (PDI), ERp5, and ERp57, among perhaps other thiol isomerases, are important for the initiation of thrombus formation. Using the laser injury thrombosis model in mice to induce in vivo arterial thrombus formation, it was shown that thrombus formation is associated with PDI secretion by platelets, that inhibition of PDI blocked platelet thrombus formation and fibrin generation, and that endothelial cell activation leads to PDI secretion. Similar results using this and other thrombosis models in mice have demonstrated the importance of ERp5 and ERp57 in the initiation of thrombus formation. The integrins, ?IIb?3 and ?V?3, play a key role in this process and interact directly with PDI, ERp5, and ERp57. The mechanism by which thiol isomerases participate in thrombus generation is being evaluated using trapping mutant forms to identify substrates of thiol isomerases that participate in the network pathways linking thiol isomerases, platelet receptor activation, and fibrin generation. PDI as an antithrombotic target is being explored using isoquercetin and quercetin 3-rutinoside, inhibitors of PDI identified by high throughput screening. Regulation of thiol isomerase expression, analysis of the storage, and secretion of thiol isomerases and determination of the electron transfer pathway are key issues to understanding this newly discovered mechanism of regulation of the initiation of thrombus formation. PMID:24677236

Furie, Bruce; Flaumenhaft, Robert

2014-03-28

357

Paleoenvironmental and paleoclimatic significance of freshwater bivalves in the Upper Jurassic Morrison Formation, Western Interior, USA  

NASA Astrophysics Data System (ADS)

Freshwater unionid bivalves are spatially and temporally distributed throughout the Morrison depositional basin, and locally dominate the biomass of many aquatic depositional environments. Two bivalve assemblages are identified. Within-channel assemblages are death assemblages that have been transported and may represent mixed assemblages from multiple communities. These assemblages are predominately disarticulated, in current stable orientations, and composed of higher stream velocity ecophenotypes (medium size, lanceolate form, and very thick shells). The floodplain-pond assemblages are disturbed neighborhood assemblages in the mudstones inhabited during life. The bivalves are predominately articulated, variable in size, and composed of low stream velocity ecophenotypes (large maximum sizes, ovate shell shapes, and thinner shells). The glochidial parasitic larval stage of unionid bivalves provides an effective means of dispersing species throughout drainage basins. These larvae attach to fish and are carried through the fluvial drainage where the larvae detach and establish new bivalve communities. Preliminary paleobiogeographic analyses are drawn at the genus level because of the need to reevaluate bivalve species of the Morrison. Unio spp. and Vetulonaia spp. are widespread throughout the Morrison depositional basin, but Hadrodon spp. are restricted to the eastern portion of the Colorado Plateau during Salt Wash Member deposition, suggesting that Salt Wash drainage was isolated from other contemporaneous regions of the basin. Bivalves from five localities in the Morrison Formation were thin-sectioned for growth band analysis. Growth bands of modern unionid bivalves are produced when the valves are forced to close. Closure can produce annual growth bands in response to seasonal variation, such as temperature-induced hibernation, or precipitation-induced aestivation or turbidity. Pseudoannual growth bands form from non-cyclical events such as predation attacks or isolated storm turbidity. Vetulonaia sp. from the Tidwell Member, Green River, Utah, and from Tidwell-equivalent beds at Como Bluff, Wyoming, exhibits continuous growth with no annual banding, suggesting that seasonality of climate and discharge did not vary appreciable during the year. Hadrodon sp. from the Salt Wash Member in Colorado National Monument, Colorado, exhibits annual banding with subequal light and dark bands indicating seasonal cyclicity. Vetulonaia sp. from the Cleveland-Lloyd locality, Utah, exhibits complex banding that indicates a combination of annual and pseudoannual bands. This suggests seasonal cyclicity and intermittent periods of environmental stress (predation, storm-produced turbidity and/or volcanic ash falls). Specimens of Vetulonaia sp. from Dinosaur National Monument, Utah, are replaced by chert with faint ghosts of bands that are too poorly preserved for environmental interpretations. Preliminary growth band studies suggest a change from a uniform optimum habitat in the Tidwell Member to strongly developed annual growth banding in the Salt Wash Member, suggesting cyclic annual precipitation, and finally to irregular banding produced by a complex interaction of weakly developed annual growth bands and pseudoannual bands in the Brushy Basin Member.

Good, Steven C.

2004-05-01

358

The dynamics of latifundia formation.  

PubMed

Land tenure inequity is a major social problem in developing nations worldwide. In societies, where land is a commodity, inequities in land tenure are associated with gaps in income distribution, poverty and biodiversity loss. A common pattern of land tenure inequities through the history of civilization has been the formation of latifundia [Zhu?ngyuán in chinese], i.e., a pattern where land ownership is concentrated by a small fraction of the whole population. Here, we use simple Markov chain models to study the dynamics of latifundia formation in a heterogeneous landscape where land can transition between forest, agriculture and recovering land. We systematically study the likelihood of latifundia formation under the assumption of pre-capitalist trade, where trade is based on the average utility of land parcels belonging to each individual landowner during a discrete time step. By restricting land trade to that under recovery, we found the likelihood of latifundia formation to increase with the size of the system, i.e., the amount of land and individuals in the society. We found that an increase of the transition rate for land use changes, i.e., how quickly land use changes, promotes more equitable patterns of land ownership. Disease introduction in the system, which reduced land profitability for infected individual landowners, promoted the formation of latifundia, with an increased likelihood for latifundia formation when there were heterogeneities in the susceptibility to infection. Finally, our model suggests that land ownership reforms need to guarantee an equitative distribution of land among individuals in a society to avoid the formation of latifundia. PMID:24376597

Chaves, Luis Fernando

2013-01-01

359

Isolated star formation: from cloud formation to core collapse.  

PubMed

The formation of stars is one of the most fundamental problems in astrophysics, as it underlies many other questions, on scales from the formation of galaxies to the formation of the solar system. The physical processes involve the turbulent behavior of a partially ionized medium containing a non-uniform magnetic field. Current debate centers around the time taken for turbulence to decay and the relative importance of the roles played by magnetic fields and turbulence. Technological advances such as millimeter-wave cameras have made possible observations of the temperature and density profiles, and statistical calculations of the lifetimes, of objects collapsing under their own self-gravity and those on the verge of collapse. Increased computing power allows more complex models to be made that include magnetic and turbulent effects. No current model can reproduce all of the observations. PMID:11778038

Ward-Thompson, Derek

2002-01-01

360

An XML portable chart format.  

PubMed

The clinical chart remains the fundamental record of outpatient clinical care. As this information migrates to electronic form, there is an opportunity to create standard formats for transmitting these charts. This paper describes work toward a Portable Chart Format (PCF) that can represent the relevant aspects of an outpatient chart. The main goal of the format is to provide a packaging medium for outpatient clinical charts in a transfer of care scenario. A secondary goal is to support the aggregation of comparable clinical data for outcomes analysis. The syntax used for PCF is Extended Markup Language (XML), a W3C standard. The structure of the PCF is based on a clinically relevant view of the data. The data definitions and nomenclature used are based primarily on existing clinical standards. PMID:9929315

Chueh, H C; Raila, W F; Berkowicz, D A; Barnett, G O

1998-01-01

361

Granuloma Formation in Pulmonary Sarcoidosis  

PubMed Central

Sarcoidosis is a granulomatous disorder of unknown cause, affecting multiple organs, but mainly the lungs. The exact order of immunological events remains obscure. Reviewing current literature, combined with careful clinical observations, we propose a model for granuloma formation in pulmonary sarcoidosis. A tight collaboration between macrophages, dendritic cells, and lymphocyte subsets, initiates the first steps toward granuloma formation, orchestrated by cytokines and chemokines. In a substantial part of pulmonary sarcoidosis patients, granuloma formation becomes an on-going process, leading to debilitating disease, and sometimes death. The immunological response, determining granuloma sustainment is not well understood. An impaired immunosuppressive function of regulatory T cells has been suggested to contribute to the exaggerated response. Interestingly, therapeutical agents commonly used in sarcoidosis, such as glucocorticosteroids and anti-TNF agents, interfere with granuloma integrity and restore the immune homeostasis in autoimmune disorders. Increasing insight into their mechanisms of action may contribute to the search for new therapeutical targets in pulmonary sarcoidosis.

Broos, Caroline E.; van Nimwegen, Menno; Hoogsteden, Henk C.; Hendriks, Rudi W.; Kool, Mirjam; van den Blink, Bernt

2013-01-01

362

Deposit formation in hydrocarbon fuels  

NASA Technical Reports Server (NTRS)

The hydrocarbon fuels RP-1, commercial-grade propane, JP-7 and chemically pure propane were subjected to tests in a high pressure fuel coking apparatus in order to evaluate their thermal decomposition limits and carbon deposition rates in heated copper tubes. A fuel thermal stability parametric evaluation was conducted at 136-340 atmospheres, bulk fuel velocities of 6-30 m/sec, and tube wall temperatures of 422-811 K, and the effect of inside wall material on deposit formation was evaluated in tests using nickel-plated tubes. Results show RP-1 deposit formation at wall temperatures between 600 and 800 K, with peak deposit formation near 700 K. Substitution of deoxygenated JP-7 for RP-1 showed no improvement, and the carbon deposition rates for propane fuels were found to be higher than those of either of the kerosene fuels. Nickel plating of the tube walls significantly reduced RP-1 carbon deposition rates.

Roback, R.; Szetela, E. J.; Spadaccini, L. J.

1982-01-01

363

Structure formation in active networks  

NASA Astrophysics Data System (ADS)

Structure formation and constant reorganization of the actin cytoskeleton are key requirements for the function of living cells. Here we show that a minimal reconstituted system consisting of actin filaments, crosslinking molecules and molecular-motor filaments exhibits a generic mechanism of structure formation, characterized by a broad distribution of cluster sizes. We demonstrate that the growth of the structures depends on the intricate balance between crosslinker-induced stabilization and simultaneous destabilization by molecular motors, a mechanism analogous to nucleation and growth in passive systems. We also show that the intricate interplay between force generation, coarsening and connectivity is responsible for the highly dynamic process of structure formation in this heterogeneous active gel, and that these competing mechanisms result in anomalous transport, reminiscent of intracellular dynamics.

Köhler, Simone; Schaller, Volker; Bausch, Andreas R.

2011-06-01

364

Computational Modeling of Microabscess Formation  

PubMed Central

Bacterial infections can be of two types: acute or chronic. The chronic bacterial infections are characterized by being a large bacterial infection and/or an infection where the bacteria grows rapidly. In these cases, the immune response is not capable of completely eliminating the infection which may lead to the formation of a pattern known as microabscess (or abscess). The microabscess is characterized by an area comprising fluids, bacteria, immune cells (mainly neutrophils), and many types of dead cells. This distinct pattern of formation can only be numerically reproduced and studied by models that capture the spatiotemporal dynamics of the human immune system (HIS). In this context, our work aims to develop and implement an initial computational model to study the process of microabscess formation during a bacterial infection.

Pigozzo, Alexandre Bittencourt; Macedo, Gilson Costa; Weber dos Santos, Rodrigo; Lobosco, Marcelo

2012-01-01

365

Mathematical Models for Somite Formation  

PubMed Central

Somitogenesis is the process of division of the anterior–posterior vertebrate embryonic axis into similar morphological units known as somites. These segments generate the prepattern which guides formation of the vertebrae, ribs and other associated features of the body trunk. In this work, we review and discuss a series of mathematical models which account for different stages of somite formation. We begin by presenting current experimental information and mechanisms explaining somite formation, highlighting features which will be included in the models. For each model we outline the mathematical basis, show results of numerical simulations, discuss their successes and shortcomings and avenues for future exploration. We conclude with a brief discussion of the state of modeling in the field and current challenges which need to be overcome in order to further our understanding in this area.

Baker, Ruth E.; Schnell, Santiago; Maini, Philip K.

2009-01-01

366

Formation Flying In Highly Elliptical Orbits Initializing the Formation  

NASA Technical Reports Server (NTRS)

In this paper several methods are examined for initializing formations in which all spacecraft start in a common elliptical orbit subsequent to separation from the launch vehicle. The tetrahedron formation used on missions such as the Magnetospheric Multiscale (MMS), Auroral Multiscale Midex (AMM), and Cluster is used as a test bed Such a formation provides full three degrees-of-freedom in the relative motion about the reference orbit and is germane to several missions. The type of maneuver strategy that can be employed depends on the specific initial conditions of each member of the formation. Single-impulse maneuvers based on a Gaussian variation-of-parameters (VOP) approach, while operationally simple and intuitively-based, work only in a limited sense for a special class of initial conditions. These 'tailored' initial conditions are characterized as having only a few of the Keplerian elements different from the reference orbit. Attempts to achieve more generic initial conditions exceed the capabilities of the single impulse VOP. For these cases, multiple-impulse implementations are always possible but are generally less intuitive than the single-impulse case. The four-impulse VOP formalism discussed by Schaub is examined but smaller delta-V costs are achieved in our test problem by optimizing a Lambert solution.

Mailhe, Laurie; Schiff, Conrad; Hughes, Steven

2000-01-01

367

Conductive Anodic Filament (CAF) Formation  

NASA Astrophysics Data System (ADS)

Conductive anodic filament (CAF) is a failure mode in printed wiring boards (PWBs) which occurs under high humidity and high voltage gradient conditions. The filament, a copper salt, grows from anode to cathode along the epoxy-glass interface. Ready and Turbini (2000) identified this copper salt as the Cu 2(OH)3Cl, atacamite compound. This work has investigated the influence of polyethylene glycol (PEG) and polyethylene propylene glycol (PEPG) fluxing agents on the chemical nature of CAF. For coupons processed with PEPG flux, with and without chloride, a copper-chloride containing compound was formed in the polymer matrix. This compound was characterized using x-ray photoelectron spectroscopy (XPS) as CuCl and an electrochemical mechanism for the formation of the chloride-containing CAF has been proposed. For PEG flux, with and without chloride, it has been shown that CAF only formed, but no copper containing compound formed in the matrix. It appears for PEG fluxed coupons, a PEG-Cu-Cl complex forms, binds the available Cu and acts as a barrier to the formation of CuCl in the polymer matrix. Meeker and Lu Valle (1995) have previously proposed that CAF failure is best represented by two competing reactions -- the formation of a copper chloride corrosion compound (now identified as Cu2(OH)3Cl) and the formation of innocuous trapped chlorine compounds. Since no evidence of any trapped chloride compounds has been found, we propose that the formation of CAF is best represented by a single non-reversible reaction. For coupons processed with a high bromide-containing flux, bromide containing CAF was created and characterized using transmission electron microscopy (TEM) to be Cu2(OH)3Br. In addition, a copper-containing compound was formed in the polymer matrix and characterized using XPS as CuBr. An electrochemical mechanism for the formation of bromide-containing CAF has been proposed based on the XPS data.

Caputo, Antonio

368

Pattern formation in the geosciences  

PubMed Central

Pattern formation is a natural property of nonlinear and non-equilibrium dynamical systems. Geophysical examples of such systems span practically all observable length scales, from rhythmic banding of chemical species within a single mineral crystal, to the morphology of cusps and spits along hundreds of kilometres of coastlines. This article briefly introduces the general principles of pattern formation and argues how they can be applied to open problems in the Earth sciences. Particular examples are then discussed, which summarize the contents of the rest of this Theme Issue.

Goehring, Lucas

2013-01-01

369

Adaptive Optics and Star Formation  

NASA Astrophysics Data System (ADS)

In this contribution I will briefly review the growing impact adaptive optics is having on the field of star formation. The volume of interesting scientific papers published to date is by far too large for this paper to be even close to be a complete review (but see Ménard, Lai & Dumas 2004). Instead, I will present a few recent results to show topics in star formation where adaptive optics has had a significant impact lately. These selected topics include the search and characterisation of accretion disks, the surveys to measure the binary fraction among the various pre-main sequence populations, and the search for low-mass and substellar companions.

Ménard, François

370

Star formation and extinct radioactivities  

NASA Technical Reports Server (NTRS)

An assessment is made of the evidence for the existence of now-extinct radioactivities in primitive solar system material, giving attention to implications for the early stages of sun and solar system formation. The characteristics of possible disturbances in dense molecular clouds which can initiate the formation of cloud cores is discussed, with emphasis on these disturbances able to generate fresh radioactivities. A one-solar mass red giant star on the asymptotic giant branch appears to have been the best candidate to account for the short-lived extinct radioactivities in the early solar system.

Cameron, A. G. W.

1984-01-01

371

Star formation across galactic environments  

NASA Astrophysics Data System (ADS)

I present here parallel investigations of star formation in typical and extreme galaxies. The typical galaxies are selected to be free of active galactic nuclei (AGN), while the extreme galaxies host quasars (the most luminous class of AGN). These two environments are each insightful in their own way; quasars are among the most violent objects in the universe, literally reshaping their host galaxies, while my sample of AGN-free star-forming galaxies ranges from systems larger than the Milky Way to small galaxies which are forming stars at unsustainably high rates. The current paradigm of galaxy formation and evolution suggests that extreme circumstances are key stepping stones in the assembly of galaxies like our Milky Way. To test this paradigm and fully explore its ramifications, this dual approach is needed. My sample of AGN-free galaxies is drawn from the KPNO International Spectroscopic Survey. This Halpha-selected, volume-limited survey was designed to detect star-forming galaxies without a bias toward continuum luminosity. This type of selection ensures that this sample is not biased toward galaxies that are large or nearby. My work studies the KISS galaxies in the mid- and far-infrared using photometry from the IRAC and MIPS instruments aboard the Spitzer Space Telescope. These infrared bands are particularly interesting for star formation studies because the ultraviolet light from young stars is reprocessed into thermal emission in the far-infrared (24mum MIPS) by dust and into vibrational transitions features in the mid-infrared (8.0mum IRAC) by polycyclic aromatic hydrocarbons (PAHs). The work I present here examines the efficiencies of PAH and thermal dust emission as tracers of star-formation rates over a wide range of galactic stellar masses. I find that the efficiency of PAH as a star-formation tracer varies with galactic stellar mass, while thermal dust has a highly variable efficiency that does not systematically depend on galactic stellar mass. Complementing this study of normal star-forming galaxies, my study of quasar host galaxies utilizes narrow- and medium-band images of eight Palomar-Green (PG) quasars from the WFPC2 and NICMOS instruments aboard the Hubble Space Telescope. Using images of a point-spread function (PSF) star in the same filters, I subtract the PSF of the quasar from each of the target images. The residual light images clearly show the host galaxies of the respective quasars. The narrow-band images were chosen to be centered on the Hbeta, [O II ], [O III], and Paalpha emission lines, allowing the use of line ratios and luminosities to create extinction and star formation maps. Additionally, I utilize the line-ratio maps to distinguish AGN-powered line emission from star formation powered line emission with line-diagnostic diagrams. I find star formation in each of the eight quasar host galaxies in my study. The bulk star-formation rates are lower than expected, suggesting that quasar host galaxies may be dynamically more advanced than previously believed. Seven of the eight quasar host galaxies in this study have higher-than-typical mass-specific star-formation rates. Additionally, I see evidence of shocked gas, supporting the hypotheses presented in earlier works that suggest that AGN activity quenches star formation in its host galaxy by disrupting its gas reservoir.

Young, Jason

372

Massive star formation: new results  

NASA Astrophysics Data System (ADS)

In the past year several new observations with important implications for massive star formation (MSF) have been obtained. Among these were the detection of UC H II region precursor candidates at 350 ?m and the discovery of many hard X-ray point sources in the Orion and W3 MSF region. These observations are summarized below.

Churchwell, Ed

373

Study of Yttrium Hydroxide Formation.  

National Technical Information Service (NTIS)

A study was made of yttrium hydroxide formation in sulphuric acid, chlorine and nitric acid solutions by means of the solubility method, measurement of pH and equilibrium solution electroconductivity, apparent residue volume, and x-ray phase analysis. It ...

I. M. Polyashkov N. V. Mal'kevich I. A. Grishin

1973-01-01

374

The Theory of Planetary Formation  

NSDL National Science Digital Library

This website offers an audio of a lecture on the theory of planetary formation. There is also an option to use a viewgraph if you do not have real audio player. The site also provides a detailed written summary of the audio lecture.

Cassen, Patrick

2010-08-06

375

Coalition Formation Among Autonomous Agents  

Microsoft Academic Search

Coalitions of agents can work more effectively than individual agents in many multi-agent settings. Determining which coalitions should form (i.e., what agents should work together) is a difficult problem that is typically solved by some kind of centralised planner. As the number of agents grows, however, reliance on a central authority becomes increasingly impractical. This paper formalises the coalition formation

Steven P. Ketchpel

1993-01-01

376

Amyloid Beta Mediates Memory Formation  

ERIC Educational Resources Information Center

The amyloid precursor protein (APP) undergoes sequential cleavages to generate various polypeptides, including the amyloid [beta] (1-42) peptide (A[beta][1-42]), which is believed to play a major role in amyloid plaque formation in Alzheimer's disease (AD). Here we provide evidence that, in contrast with its pathological role when accumulated,…

Garcia-Osta, Ana; Alberini, Cristina M.

2009-01-01

377

Geometric Cooperative Control of Formations.  

National Technical Information Service (NTIS)

Robots in a team are modeled as particles which obey simple, second order dynamics. The whole team can be viewed as a deformable body with changing shape and orientation. Jacobi shape theory is applied to model such a formation. The configuration space of...

F. Zhang

2004-01-01

378

Formation of Clastic Sedimentary Rocks  

NSDL National Science Digital Library

This animation traces the formation of sedimentary rock. It starts at a beach environment where sea water minerals cement sand grains together. The animation concludes with a real microscopic image of sandstone showing both mineral grains and cement. The animation can be paused and rewound to stress important points.

2010-01-01

379

Montezuma Formation of Costa Rica  

Microsoft Academic Search

The Montezuma Formation of the Nicoya Peninsula is one of the better known Neogene stratigraphic units of the Pacific side of Costa Rica. Past workers have reported its age to be Miocene-Pliocene or Miocene-Quaternary, and its environment of deposition to be inner shelf. The planktonic foraminiferal record of the unit in the type locality, however, places it firmly in the

W. H. McKee; B. K. Sen Gupta

1985-01-01

380

Technology Enhanced Distributive Formative Evaluation  

ERIC Educational Resources Information Center

Quality assurance in instructional development demands an exhaustive formative evaluation effort and applied testing. Unfortunately, this process is expensive and requires large numbers of user testers with characteristics similar to the intended audience. This article presents a procedure for increasing the efficiency of quality assurance efforts…

Moore, David Richard

2008-01-01

381

CCF: The Common Communication Format.  

ERIC Educational Resources Information Center

The purpose of the Common Communication Format (CCF) is to provide a detailed and structured method for recording a number of mandatory and optional data elements in a computer-readable bibliographic record for exchange purposes between two or more computer-based systems. However, it can also be useful within non-computerized bibliographic…

Simmons, Peter, Ed.; Hopkinson, Alan, Ed.

382

Electrodeposit Formation in Solid Electrolytes  

Microsoft Academic Search

Devices based on polarity-dependent switching in solid electrolytes show great promise as next generation memory and perhaps even logic devices. These elements operate by the formation of robust but reversible electrodeposited conducting pathways which can be grown and dissolved at low voltage and current. Although such devices have been well characterized, little has been presented on the exact growth mechanism

Michael N. Kozicki; Cynthia Ratnakumar; Maria Mitkova

2006-01-01

383

Pattern formation during fracture dissolution  

Microsoft Academic Search

A number of experimental and numerical studies of dissolution in fractured and porous rocks have established that the evolving topography of the pore space depends strongly on the fluid flow and mineral dissolution rates. Remarkably, there exists a wide parameter range in which positive feedback between fluid transport and mineral dissolution leads to the spontaneous formation of pronounced channels, frequently

P. Szymczak; T. Ladd

2009-01-01

384

Stereotype Formation: Biased by Association  

Microsoft Academic Search

We propose that biases in attitude and stereotype formation might arise as a result of learned differences in the extent to which social groups have previously been predictive of behavioral or physical properties. Experiments 1 and 2 demonstrate that differences in the experienced predictiveness of groups with respect to evaluatively neutral information influence the extent to which participants later form

Mike E. Le Pelley; Stian J. Reimers; Guglielmo Calvini; Russell Spears; Tom Beesley; Robin A. Murphy

2010-01-01

385

Formation of artificial ionospheric ducts  

Microsoft Academic Search

It is well known that strong electron heating by a powerful HF-facility can lead to the formation of electron and ion density perturbations that stretch along the magnetic field line. Those density perturbations can serve as ducts for ELF waves, both of natural and artificial origin. This paper presents the first experimental evidence of plasma modifications associated with ion outflows

G. M. Milikh; K. Papadopoulos; H. Shroff; C. L. Chang; T. Wallace; E. V. Mishin; M. Parrot; J. J. Berthelier

2008-01-01

386

Formation control with collision avoidance  

Microsoft Academic Search

We present a formation flight control strategy featuring a collision avoidance scheme. The control algorithm is based on a Sliding Mode controller. The controller sliding surfaces account for aircraft maneuvering limitations, restricting the required velocities to a feasible set. Further, the relative position between vehicles affects the sliding surfaces shape, enabling collision avoidance. The control method derivation is based on

Ricardo Bencatel; Mariam Faied; Joao Sousa; Anouck R. Girard

2011-01-01

387

A Bluetooth scatternet formation algorithm  

Microsoft Academic Search

A Bluetooth ad hoc network can be formed by interconnecting piconets into scatternets. The constraints and properties of Bluetooth scatternets present special challenges in forming an ad hoc network efficiently. We present and analyse a new randomized distributed algorithm for Bluetooth scatternet formation. We prove that our algorithm achieves O(log n) time complexity and O(n) message complexity. We show that:

Ching Law; Kai-Yeung Siu

2001-01-01

388

Distributed Bluetooth scatternet formation algorithm  

Microsoft Academic Search

Bluetooth is a short range communication technology in which devices communicate in a master-slave fashion within a piconet. Several piconets interconnect via gateway devices to form a scatternet. This paper introduces a greedy approach to scatternet tree and mesh formation which tries to minimize the number of piconets at each iterative step. The protocol is distributed, rapidly converging and incurs

Vikas P. Verma; Amit A. Chandak

2003-01-01

389

Formative Assessment: A Cybernetic Viewpoint  

ERIC Educational Resources Information Center

This paper considers alternative assessment, feedback and cybernetics. For more than 30 years, debates about the bi-polarity of formative and summative assessment have served as surrogates for discussions about the workings of the mind, the social implications of assessment and, as important, the role of instruction in the advancement of learning.…

Roos, Bertil; Hamilton, David

2005-01-01

390

Pattern formation outside of equilibrium  

Microsoft Academic Search

A comprehensive review of spatiotemporal pattern formation in systems driven away from equilibrium is presented, with emphasis on comparisons between theory and quantitative experiments. Examples include patterns in hydrodynamic systems such as thermal convection in pure fluids and binary mixtures, Taylor-Couette flow, parametric-wave instabilities, as well as patterns in solidification fronts, nonlinear optics, oscillatory chemical reactions and excitable biological media.

M. C. Cross; P. C. Hohenberg

1993-01-01

391

Biofilm Formation by Candida dubliniensis  

Microsoft Academic Search

Candida dubliniensis is an opportunistic yeast closely related to Candida albicans that has been recently implicated in oropharyngeal candidiasis in human immunodeficiency virus-infected patients. Most manifes- tations of candidiasis are associated with biofilm formation, with cells in biofilms displaying properties dramatically different from free-living cells grown under normal laboratory conditions. Here, we report on the development of in vitro models

GORDON RAMAGE; KACY VANDE WALLE; BRIAN L. WICKES

2001-01-01

392

Formation of the outer planets  

Microsoft Academic Search

A discussion is given of a number of physical processes which were probably important during the formation of the outer planets if these formed from a gaseous solar nebula in which magnetic effects were not important. Arguments are given that large-scale gravitational instabilities in the solar nebula did not occur. Qualitative consideration is given to the conditions in which dynamical

A. G. W. Cameron

1973-01-01

393

Brain gangliosides and memory formation  

Microsoft Academic Search

It is generally accepted that the process of molecular facilitation of neuronal circuits by means of stabilization of synaptic contacts represents the structural basis for memory formation. At the distinct zone of synaptic contact the following basic events occur: alterations of the electrical field strength at the outer surface of synaptic membranes, conformational changes of membrane-bound functional proteins (ion channels,

Hinrich Rahmann

1995-01-01

394

Mechanisms of polymeric film formation.  

PubMed

Polymeric films are applied to solid dosage forms for decorative, protective, and functional purposes. These films are generally applied by a spray atomization process, where the polymer is sprayed onto the solid substrate. The mechanism by which films are formed is dependent on whether the polymer is in the dissolved or dispersed state. For solutions, film formation occurs as the solvent evaporates, since the polymer chains are intimately mixed. Film formation from polymeric dispersions, however, requires the coalescence of individual polymer spheres and interpenetration of the polymer chains. Films prepared from polymeric dispersions exhibit a minimum film forming temperature and processing conditions must exceed this temperature in order to form the film. In addition, these systems generally require post-coating storage in temperature and humidity controlled environments to ensure complete polymer coalescence. Incomplete coalescence can lead to significant changes in drug release over time. This review article highlights the basic science principles involved in film formation from both polymeric solutions and dispersions and the variables that influence these film formation processes. PMID:23305867

Felton, Linda A

2013-12-01

395

Vertical formations demand unique treatments  

Microsoft Academic Search

In the US midcontinent area, major thrust faults trap large quantities of hydrocarbons in the down-thrown fault block. As exploration of these thrust fault structures continues, the application of extended reach and horizontal well bores will increase. Formations in deep structures are apt to have lower porosity and permeability than the currently developed thrust faults and thus, require fracture stimulation.

1996-01-01

396

VLBI Data Interchange Format (VDIF).  

National Technical Information Service (NTIS)

One important outcome of the 7th International e-VLBI Workshop in Shanghai in June 2008 was the creation of a task force to study and recommend a universal VLBI data format that is suitable for both on-the-wire e-VLBI data transfer, as well as direct disk...

A. Whitney C. Phillips M. Kettenis M. Sekido

2010-01-01

397

Chevrons formation in laminar erosion  

NASA Astrophysics Data System (ADS)

When eroded by laminar free-surface flows, granular substrates may generate a rich variety of natural patterns. Among them are dunes, similar to the ones observed by Charru and Hinch in a Couette cell (Charru F, Hinch EJ ; Ripple formation on a particle bed sheared by a viscous liquid. Part 1. Steady flow ; JOURNAL OF FLUID MECHANICS 550: 111-121 MAR 10 2006). Chevron-shaped instabilities as those found on the sea-shore, can also be observed, sometimes in competition against dunes formation. These were first pointed out by Daerr et al. when pulling a plate covered with granular material out of a bath of water (Daerr A, Lee P, Lanuza J, et al. ; Erosion patterns in a sediment layer ; PHYSICAL REVIEW E 67 (6): Art. No. 065201 Part 2 JUN 2003). Both instabilities can grow in laminar open-channel flows, an experimental set-up which is more easily controlled. The mechanisms leading to the formation of these patterns are investigated and compared. Whereas dunes formation requires vertical inertia effects, we show that chevrons may result from the non-linear evolution of bars instability, which may grow even in purely viscous flows.

Devauchelle, Olivier; Josserand, Christophe; Lagree, Pierre-Yves; Zaleski, Stephane; Nguyen, Khanh-Dang; Malverti, Luce; Lajeunesse, Eric

2007-11-01

398

Stereotype Formation: Biased by Association  

ERIC Educational Resources Information Center

We propose that biases in attitude and stereotype formation might arise as a result of learned differences in the extent to which social groups have previously been predictive of behavioral or physical properties. Experiments 1 and 2 demonstrate that differences in the experienced predictiveness of groups with respect to evaluatively neutral…

Le Pelley, Mike E.; Reimers, Stian J.; Calvini, Guglielmo; Spears, Russell; Beesley, Tom; Murphy, Robin A.

2010-01-01

399

Pattern Formation in Active Fluids  

Microsoft Academic Search

We discuss pattern formation in active fluids in which active stress is regulated by diffusing molecular components. Nonhomogeneous active stress profiles create patterns of flow which transport stress regulators by advection. Our work is motivated by the dynamics of the actomyosin cell cortex in which biochemical pathways regulate active stress. We present a mechanism in which a single diffusing species

Justin S. Bois; Frank Jülicher; Stephan W. Grill

2011-01-01

400

Heteronuclear Diatomic Molecular Orbital Formation  

NSDL National Science Digital Library

Here is a set of movies that demonstrates heteronuclear diatomic molecular orbital formation. The orbitals start at a distance where there is little or no interatomic interaction and move to the appropriate bond distance. Orbital phase is shown by the different colors.

401

Memory formation by neuronal synchronization.  

PubMed

Cognitive functions not only depend on the localization of neural activity, but also on the precise temporal pattern of activity in neural assemblies. Synchronization of action potential discharges provides a link between large-scale EEG recordings and cellular plasticity mechanisms. Here, we focus on the role of neuronal synchronization in different frequency domains for the subsequent stages of memory formation. Recent EEG studies suggest that synchronized neural activity in the gamma frequency range (around 30-100 Hz) plays a functional role for the formation of declarative long-term memories in humans. On the cellular level, gamma synchronization between hippocampal and parahippocampal regions may induce LTP in the CA3 region of the hippocampus. In order to encode spatial locations or sequences of multiple items and to guarantee a defined temporal order of memory processing, synchronization in the gamma frequency range has to be accompanied by a stimulus-locked phase reset of ongoing theta oscillations. Simultaneous gamma- and theta-dependent plasticity leads to complex learning rules required for realistic declarative memory formation. Subsequently, consolidation of declarative memories may occur via replay of newly acquired patterns in so-called sharp wave-ripple complexes, predominantly during slow-wave sleep. These irregular bursts induce longer lasting forms of synaptic plasticity in output regions of the hippocampus and in the neocortex. In summary, synchronization of neural assemblies in different frequency ranges induces specific forms of cellular plasticity during subsequent stages of memory formation. PMID:16545463

Axmacher, Nikolai; Mormann, Florian; Fernández, Guillen; Elger, Christian E; Fell, Juergen

2006-08-30

402

Biofilm Formation by Pneumocystis spp.? †  

PubMed Central

Pneumocystis spp. can cause a lethal pneumonia in hosts with debilitated immune systems. The manner in which these fungal infections spread throughout the lung, the life cycles of the organisms, and their strategies used for survival within the mammalian host are largely unknown, due in part to the lack of a continuous cultivation method. Biofilm formation is one strategy used by microbes for protection against environmental assaults, for communication and differentiation, and as foci for dissemination. We posited that the attachment and growth of Pneumocystis within the lung alveoli is akin to biofilm formation. An in vitro system comprised of insert wells suspended in multiwell plates containing supplemented RPMI 1640 medium supported biofilm formation by P. carinii (from rat) and P. murina (from mouse).Dramatic morphological changes accompanied the transition to a biofilm. Cyst and trophic forms became highly refractile and produced branching formations that anastomosed into large macroscopic clusters that spread across the insert. Confocal microscopy revealed stacking of viable organisms enmeshed in concanavalin A-staining extracellular matrix. Biofilms matured over a 3-week time period and could be passaged. These passaged organisms were able to cause infection in immunosuppressed rodents. Biofilm formation was inhibited by farnesol, a quorum-sensing molecule in Candida spp., suggesting that a similar communication system may be operational in the Pneumocystis biofilms. Intense staining with a monoclonal antibody to the major surface glycoproteins and an increase in (1,3)-?-d-glucan content suggest that these components contributed to the refractile properties. Identification of this biofilm process provides a tractable in vitro system that should fundamentally advance the study of Pneumocystis.

Cushion, Melanie T.; Collins, Margaret S.; Linke, Michael J.

2009-01-01

403

Dust Formation in Brown Dwarfs  

NASA Astrophysics Data System (ADS)

Brown Dwarfs provide favorable conditions for the gas-solid phase transition since in its atmosphere low temperatures with high densities are combined. Observations of unexpectedly weak molecular absorption bands indicate the existence of dust in their atmospheres. Considering stability arguments, high temperature compounds like CaTiO3, Fe2-xSixO4 or Al2O_3 are expected to form first. Another argument for the formation of heterogeneous dust is given by the wide variety of molecular species of comparable abundances in an oxygen-rich gas. The description of the formation of such heterogeneous particles, however, is still a matter of debate since the nominal molecules are only present in negligible amounts or even completely absent in the gas phase. Furthermore, the formation of solid particles has to proceed via the formation of seed particles which is followed by the growth towards macroscopic sizes. Thereby, a large supersaturation has to be achieved which results in a considerable gap between typical nucleation temperatures and the sublimation temperatures of plane solid. Promising astrophysical seed candidates are (TiO2N and (Fe)N clusters which appears in appropriate amounts in oxygen-rich gases; Fe seeds maybe even more favorable in the densest regions of the atmospheres (nH > 1019cm-3). In this presentation, the efficiency of nucleation and the stability of solid compounds are examined for a typical atmosphere of a Brown Dwarf in comparison to M dwarfs and Jupiter-like planets. We additionally present first results of numerical calculations for Brown Dwarf atmospheres including a detailed time-dependent, phase non-equilibrium description of the formation of core-mantel grains. Dust properties like the amount and the sizes of the solid particles are thereby a result of the calculation.

Lüttke, M.; Helling, Ch.; John, M.; Jeong, K. S.; Woitke, P.; Sedlmayr, E.

404

Sedimentary pyrite formation: An update  

NASA Astrophysics Data System (ADS)

Sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time. The amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter, dissolved sulfate, and reactive detrital iron minerals. Organic matter appears to be the major control on pyrite formation in normal (non-euxinic) terrigenous marine sediments where dissolved sulfate and iron minerals are abundant. By contrast, pyrite formation in non-marine, freshwater sediments is severely limited by low concentrations of sulfate and this characteristic can be used to distinguish ancient organic-rich fresh water shales from marine shales. Under marine euxinic conditions sufficient H 2S is produced that the dominant control on pyrite formation is the availability of reactive iron minerals. Calculations, based on a sulfur isotope model, indicate that over Phanerozoic time the worldwide average organic carbon-to-pyrite sulfur ratio of sedimentary rocks has varied considerably. High C/S ratios during Permo-Carboniferous time can be explained by a shift of major organic deposition from the oceans to the land which resulted in the formation of vast coal swamps at that time. Low C/S ratios, compared to today, during the early Paleozoic can be explained in terms of a greater abundance of euxinic basins combined with deposition of a more reactive type of organic matter in the remaining oxygenated portions of the ocean. The latter could have been due to lower oceanic oxygen levels and/or a lack of transportation of refractory terrestrial organic matter to the marine environment due to the absence of vascular land plants at that time.

Berner, Robert A.

1984-04-01

405

Method of fracturing a geological formation  

DOEpatents

An improved method of fracturing a geological formation surrounding a well bore is disclosed. A relatively small explosive charge is emplaced in a well bore and the bore is subsequently hydraulically pressurized to a pressure less than the formation breakdown pressure and preferably greater than the fracture propagation pressure of the formation. The charge is denoted while the bore is so pressurized, resulting in the formation of multiple fractures in the surrounding formation with little or no accompanying formation damage. Subsequent hydraulic pressurization can be used to propagate and extend the fractures in a conventional manner. The method is useful for stimulating production of oil, gas and possibly water from suitable geologic formations.

Johnson, James O. (2679-B Walnut, Los Alamos, NM 87544)

1990-01-01

406

Formation of Molecular Clouds and Initial Conditions of Star Formation  

NASA Astrophysics Data System (ADS)

Using three-dimensional magnetohydrodynamic simulations, including the effects of radiative cool- ing/heating, chemical reactions, self-gravity and thermal conduction, we investigate the formation of molecular clouds in the multi-phase interstellar medium. We consider the formation of molecular clouds due to accretion of HI clouds as suggested by recent observations. Our simulations show that the initial HI medium is piled up behind the shock waves induced by accretion flows. Since the accreting medium is highly inhomogeneous as a consequence of thermal instability, a newly formed molecular cloud becomes very turbulent owing to the development of the Richtmyer-Meshkov instability. The kinetic energy of the turbulence dominates the thermal, magnetic, and gravitational energies. However, the kinetic energy measured using CO-fraction-weighted density is comparable to the other energies, once the CO molecules are sufficiently formed as a result of UV shielding. This suggests that the true kinetic energy of turbulence in molecular clouds as a whole can be much larger than the kinetic energy of turbulence estimated by using line widths of molecular emission. We find that dense clumps in the molecular cloud show the following evolution: the typical plasma beta of the clumps is roughly constant; the size-?locity dispersion relation follows Larson's law, irrespective of the density; and the clumps evolve into magnetically supercritical cores by clump-clump collisions. These statistical properties would represent the initial conditions of star formation.

Inoue, Tsuyoshi

2013-07-01

407

Test fuel rod irradiation in 14 x 14 assemblies at Calvert Cliffs 1. Final report  

SciTech Connect

In a 10-year demonstration that included destructive and nondestructive testing, standard 14 x 14 fuel proved reliable to burnups in excess of 54 MWd/kgU. This major study produced an extremely well characterized data base to support the licensing of 14 x 14 fuel reloads to high burnups. As a result, Baltimore Gas and Electric Company expects to save $10 million yearly in the operating-cycle costs of two PWRs.

Ruzauskas, E.J.; Garde, A.M.; Pati, S.R.; Corsetti, L.V.

1985-09-01

408

Estuarine stream piracy: Calvert County, U.S. Atlantic coastal plain  

NASA Astrophysics Data System (ADS)

The topography of Maryland's western shore of the Chesapeake Bay shows that five streams now flowing eastward into the bay comprise the pirated (and inverted) headwaters of streams previously flowing westward from a vanished Pliocene upland now occupied by the central Chesapeake. Estuarine shoreline erosion during Pleistocene interglaciations removed the upland, exposing the upper reaches of west-flowing stream valleys. Headward (westward) erosion by east-flowing streams then occurred along existing valleys, facilitated by steep eastward gradients and easily eroded valley-floor sediments. Stream inversion may be more common than previously recognized, since any eroding shoreline causes consumption of seaward-draining watershed and steepening of gradients, thus setting the stage for eventual stream inversion.

Vogt, Peter R.

1991-07-01

409

Laser beam pulse formatting method  

DOEpatents

A method for formatting a laser beam pulse using one or more delay loops is disclosed. The delay loops have a partially reflective beam splitter and a plurality of highly reflective mirrors arranged such that the laser beam pulse enters into the delay loop through the beam splitter and circulates therein along a delay loop length defined by the mirrors. As the laser beam pulse circulates within the delay loop a portion thereof is emitted upon each completed circuit when the laser beam pulse strikes the beam splitter. The laser beam pulse is thereby formatted into a plurality of sub-pulses. The delay loops are used in combination to produce complex waveforms by combining the sub-pulses using additive waveform synthesis. 8 figs.

Daly, T.P.; Moses, E.I.; Patterson, R.W.; Sawicki, R.H.

1994-08-09

410

Laser beam pulse formatting method  

DOEpatents

A method for formatting a laser beam pulse (20) using one or more delay loops (10). The delay loops (10) have a partially reflective beam splitter (12) and a plurality of highly reflective mirrors (14) arranged such that the laser beam pulse (20) enters into the delay loop (10) through the beam splitter (12) and circulates therein along a delay loop length (24) defined by the mirrors (14). As the laser beam pulse (20) circulates within the delay loop (10) a portion thereof is emitted upon each completed circuit when the laser beam pulse (20) strikes the beam splitter (12). The laser beam pulse (20) is thereby formatted into a plurality of sub-pulses (50, 52, 54 and 56). The delay loops (10) are used in combination to produce complex waveforms by combining the sub-pulses (50, 52, 54 and 56) using additive waveform synthesis.

Daly, Thomas P. (Livermore, CA); Moses, Edward I. (Livermore, CA); Patterson, Ralph W. (Livermore, CA); Sawicki, Richard H. (Danville, CA)

1994-01-01

411

Rapid gas hydrate formation process  

DOEpatents

The disclosure provides a method and apparatus for forming gas hydrates from a two-phase mixture of water and a hydrate forming gas. The two-phase mixture is created in a mixing zone which may be wholly included within the body of a spray nozzle. The two-phase mixture is subsequently sprayed into a reaction zone, where the reaction zone is under pressure and temperature conditions suitable for formation of the gas hydrate. The reaction zone pressure is less than the mixing zone pressure so that expansion of the hydrate-forming gas in the mixture provides a degree of cooling by the Joule-Thompson effect and provides more intimate mixing between the water and the hydrate-forming gas. The result of the process is the formation of gas hydrates continuously and with a greatly reduced induction time. An apparatus for conduct of the method is further provided.

Brown, Thomas D.; Taylor, Charles E.; Unione, Alfred J.

2013-01-15

412

Exospore formation in Methylosinus trichosporium.  

PubMed Central

Formation of exospores in Methylosinus trichosporium was examined by electron microscopy; serial sectioning was used to visualize the shape and location of the developing exospore in relation to the vegetative cell. The initial stage was the formation of a budlike enlargement on one end of the vegetative cell. The enlargement was surrounded by the exospore capsule, and the cell wall was continuous around both the cell and the developing exospore. A constriction occurred in the area where the budlike structure was attached to the vegetative cell, and the constriction continued to form until the immature exospore was detached from the vegetative cell. The cup-shaped immature exospore was surrounded by the exospore capsule, which appeared to hold the exospore close to the vegetative cell. After separation from the vegetative cell, the immature exospore developed further by forming the exospore wall and by becoming spherical. Images

Titus, J A; Reed, W M; Pfister, R M; Dugan, P R

1982-01-01

413

The dynamics of city formation*  

PubMed Central

This paper examines city formation in a country whose urban population is growing steadily over time, with new cities required to accommodate this growth. In contrast to most of the literature there is immobility of housing and urban infrastructure, and investment in these assets is taken on the basis of forward-looking behavior. In the presence of these fixed assets cities form sequentially, without the population swings in existing cities that arise in current models, but with swings in house rents. Equilibrium city size, absent government, may be larger or smaller than is efficient, depending on how urban externalities vary with population. Efficient formation of cities with internalization of externalities involves local government intervention and borrowing to finance development. The paper explores the institutions required for successful local government intervention.

Henderson, J. Vernon; Venables, Anthony J.

2013-01-01

414

Engineering biofilm formation and dispersal  

PubMed Central

Anywhere water is in the liquid state, bacteria will exist as biofilms, which are complex communities of cells cemented together. Although frequently associated with disease and biofouling, biofilms are also important for engineering applications, such as bioremediation, biocatalysis and microbial fuel cells. Here we review approaches to alter genetic circuits and cell signaling toward controlling biofilm formation, and emphasize utilizing these tools for engineering applications. Based on a better understanding of the genetic basis of biofilm formation, we find that biofilms may be controlled by manipulating extracellular signals and that they may be dispersed using conserved intracellular signals and regulators. Biofilms could also be formed at specific locations where they might be engineered to make chemicals or treat human disease.

Wood, Thomas K.; Hong, Seok Hoon; Ma, Qun

2011-01-01

415

Cycling Behavior and Memory Formation  

PubMed Central

Circadian research has spent considerable effort in the determining clock output pathways, including identifying both physiological and behavioral processes that demonstrate significant time-of-day variation. Memory formation and consolidation represent notable processes shaped by endogenous circadian oscillators. To date, very few studies on memory mechanisms have considered potential confounding effects of time-of-day and the organism’s innate activity cycles (e.g., nocturnal, diurnal, or crepuscular). The following studies highlight recent work describing this interactive role of circadian rhythms and memory formation, and were presented at a minisymposium at the 2009 annual meeting of the Society for Neuroscience. The studies illustrate these time-of-day observations in a variety of behavioral paradigms and model organisms, including olfactory avoidance conditioning in Drosophila, long-term sensitization in Aplysia, active-avoidance conditioning in Zebrafish, and classical fear conditioning in rodents, suggesting that the circadian influence on memory behavior is highly conserved across species. Evidence also exists for a conserved mechanistic relationship between specific cycling molecules and memory formation, and the extent to which proper circadian cycling of these molecules is necessary for optimal cognitive performance. Studies describe the involvement of the core clock gene period, as well as vasoactive intestinal peptide, melatonin, and the cAMP/MAPK (cAMP/mitogen-activated protein kinase) cascade. Finally, studies in humans describe evidence for alterations in cognitive performance based on an interaction between sleep–wake homeostasis and the internal circadian clock. Conservation of a functional relationship between circadian rhythms with learning and memory formation across species provides a critical framework for future analysis of molecular mechanisms underlying complex behavior.

Gerstner, Jason R.; Lyons, Lisa C.; Wright, Kenneth P.; Loh, Dawn H.; Rawashdeh, Oliver; Eckel-Mahan, Kristin L.; Roman, Gregg W.

2014-01-01

416

Union formation in fragile families  

Microsoft Academic Search

In this article, we use data from a new longitudinal survey—the Fragile Families and Child Wellbeing Study—to examine union\\u000a formation among unmarried parents who have just had a child together. We used multinomial logistic regression to estimate\\u000a the effects of economic, cultural\\/interpersonal, and other factors on whether (relative to having no romantic relationship)\\u000a parents are romantically involved and living apart,

Marcia Carlson; Sara Mclanahan; Paula England

2004-01-01

417

Biofilm formation on oral piercings  

Microsoft Academic Search

Summary  PURPOSE: Biofilms on oral piercings might serve as a bacterial reservoir in the host and lead to bacteraemia and even septic\\u000a complications. The use of piercing materials less susceptible to biofilm accumulation could contribute to alleviation of problems.\\u000a The present study aimed to assess biofilm formation on four commercially available, surface characterized piercing materials\\u000a in vitro (polytetrafluoroethylene, titanium, stainless steel,

Ines Kapferer; Christoph Steiner; Ulrike Beier; Natalia Schiefermeier; Markus Nagl; Frederik Klauser

2010-01-01

418

Crystal sedimentation and stone formation  

Microsoft Academic Search

Mechanisms of crystal collision being the first step of aggregation (AGN) were analyzed for calcium oxalate monohydrate (COM)\\u000a directly produced in urine. COM was produced by oxalate titration in urine of seven healthy men, in solutions of urinary macromolecules\\u000a and in buffered distilled water (control). Crystal formation and sedimentation were followed by a spectrophotometer and analyzed\\u000a by scanning electron microscopy.

Johannes Markus Baumann; Beat Affolter; Rolf Meyer

2010-01-01

419

Molecular mechanisms of memory formation  

Microsoft Academic Search

Studies with neonate chicks, trained on a passive avoidance task, suggest that at least two shorter-term memory stages precede\\u000a long-term, protein synthesis-dependent memory consolidation. Posttetanic neuronal hyperpolarization arising from two distinct\\u000a mechanisms is postulated to underlie formation of these two early memory stages. Maintenance of the second of these stages\\u000a may involve a prolonged period of hyperpolarization brought about by

K. T. Ng; M. E. Gibbs; S. F. Crowe; G. L. Sedman; F. Hua; W. Zhao; B. O'Dowd; N. Rickard; C. L. Gibbs; E. Syková; J. Svoboda; P. Jendelová

1991-01-01

420

Contrail formation in aircraft wakes  

Microsoft Academic Search

The process of the formation and early evolution of a condensation trail (`contrail') in the near field of an aircraft wake was numerically studied by means of a mixed Eulerian\\/Lagrangian two-phase flow approach. Large-eddy simulations were used for the carrier phase, while, for the dispersed phase, a Lagrangian particle tracking method was used, coupled with a microphysics model to account

Roberto Paoli; Jerome Hélie; Thierry Poinsot

2004-01-01

421

Central control of bone formation  

Microsoft Academic Search

Vertebrates constantly remodel bone to maintain a constant bone mass. Bone remodeling comprises two phases: bone resorption\\u000a by the osteoclasts followed by bone formation by the osteoblasts. Although the prevailing view about the control of bone remodeling\\u000a is that it is an autocrine\\/paracrine phenomenon, the bone resorption arm of bone remodeling is under a tight endocrine control.\\u000a To date little

Shu Takeda; Gerard Karsenty

2001-01-01

422

Membrane adhesion and domain formation  

Microsoft Academic Search

We review theoretical results for the adhesion-induced phase behavior of biomembranes. The focus is on models in which the membranes are represented as discretized elastic sheets with embedded adhesion molecules. We present several mechanism that lead to the formation of domains during adhesion, and discuss the time-dependent evolution of domain patterns obtained in Monte-Carlo simulations. The simulated pattern dynamics has

Thomas R. Weikl; Reinhard Lipowsky

2007-01-01

423

Pattern formation in optical resonators  

NASA Astrophysics Data System (ADS)

We review pattern formation in optical resonators. The emphasis is on 'particle-like' structures such as vortices or spatial solitons. On the one hand, similarities impose themselves with other fields of physics (condensed matter, phase transitions, particle physics, fluds/super fluids). On the other hand the feedback is led by the resonator mirrors to bi- and multi-stability of the spatial field structure, which is the basic ingredient for optical information processing. The spatial dimension or the 'parallelism' is the strength of optics compared to electronics (and will have to be employed to fully use the advantages optics offers in information processing). But even in the 'serial' processing tasks of telecoms (e.g. information buffering) spatial resonator solitons can do better than the schemes proposed so far—including 'slow light'. Pattern formation in optical resonators will likely be the key to brain-like information processing like cognition, learning and association; to complement the precise but limited algorithmic capabilities of electronic processing. But even in the short term it will be useful for solving serial optical processing problems. The prospects for technical uses of pattern formation in resonators are one motivation for this research. The fundamental similarities with other fields of physics, on the other hand, inspire transfer of concepts between fields; something that has always proven fruitful for gaining deeper insights or for solving technical problems.

Weiss, C. O.; Larionova, Ye

2007-02-01

424

Clumpy disc and bulge formation  

NASA Astrophysics Data System (ADS)

We present a set of hydrodynamical/N-body controlled simulations of isolated gas-rich galaxies that self-consistently include supernova (SN) feedback and a detailed chemical evolution model, both tested in cosmological simulations. The initial conditions are motivated by the observed star-forming galaxies at z ˜ 2-3. We find that the presence of a multiphase interstellar media in our models promotes the growth of disc instability favouring the formation of clumps which, in general, are not easily disrupted on time-scales compared to the migration time. We show that stellar clumps migrate towards the central region and contribute to form a classical-like bulge with a Sérsic index, n > 2. Our physically motivated SN feedback has a mild influence on clump survival and evolution, partially limiting the mass growth of clumps as the energy released per SN event is increased, with the consequent flattening of the bulge profile. This regulation does not prevent the building of a classical-like bulge even for the most energetic feedback tested. Our SN feedback model is able to establish self-regulated star formation, producing mass-loaded outflows and stellar age spreads comparable to observations. We find that the bulge formation by clumps may coexist with other channels of bulge assembly such as bars and mergers. Our results suggest that galactic bulges could be interpreted as composite systems with structural components and stellar populations storing archaeological information of the dynamical history of their galaxy.

Perez, Josefa; Valenzuela, Octavio; Tissera, Patricia B.; Michel-Dansac, Leo

2013-11-01

425

Stellar Metallicity and Planet Formation  

NASA Astrophysics Data System (ADS)

We describe results from two independent analyses of the [Fe/H] abundance of stars in two separate planet search programs. For the Keck, AAT, and Lick (KAL) planet search program, we determined stellar parameters spectroscopically. Results for the CORALIE and KAL both show a similar steep increase in the fraction of stars with known planets as stellar [Fe/H] increase. This planet metallicity correlation is a key observational constraint on the formation and evolution of giant planets. We rule out changes in velocity precision as the cause of the correlation. By comparing stars with different convection zone depths (along and off the main-sequence), we rule out chemical enrichment by accretion as the origin of the correlation. Most known planets have migrated inwards since formation. The end point of migration does not depend on stellar [Fe/H], but it is still possible that migration occurs only above some metallicity threshold. The planet-metallicity correlation is consistent with core-accretion scenarios of giant planet formation.

Valenti, J.; Fischer, D.

2008-04-01

426

Rock Cycle: Environments of Formation  

NSDL National Science Digital Library

This Science Object is the second of four Science Objects in the Rocks SciPack. It provides an in-depth exploration of the conditions and environment required during the formation of igneous, sedimentary, and metamorphic rocks. Igneous rock forms from the cooling and crystallization of magma. Sometimes the magma reaches Earth's surface and cools quickly; sometimes it does not reach the surface and thus cools slowly. Rocks at Earth's surface are subjected to processes of weathering and erosion, producing sediments as they are broken down. Sedimentary rock is formed when sediments are buried and solidified through various processes. Sedimentary rock buried deep enough may be transformed into metamorphic rock or melted down to magma. Rock formed deep within the crust (either igneous or metamorphic) may be forced up again to become land surface and even mountains by the forces that drive the motion of Earth's plates. Subsequently, this new rock too will erode. Learning Outcomes:� Realize that different rocks have specific origins, and that they are the product of any number of processes.� Identify the processes through which igneous, sedimentary, and metamorphic rock form.� Explain the role of intermediary materials such as sediment and magma in the formation of different kinds of rock.� Provide an overarching description of the steps in the rock cycle, the formation of sedimentary rock, the re-forming of rock by heat and pressure, and the process by which re-formed rock can return to the surface.

National Science Teachers Association (NSTA)

2006-11-01

427

Formation of Outer Planets: Overview  

NASA Technical Reports Server (NTRS)

An overview of current theories of planetary formation, with emphasis on giant planets is presented. The most detailed models are based upon observation of our own Solar System and of young stars and their environments. Terrestrial planets are believe to grow via pairwise accretion until the spacing of planetary orbits becomes large enough that the configuration is stable for the age of the system. According to the prevailing core instability model, giant planets begin their growth by the accumulation of small solid bodies, as do terrestrial planets. However, unlike terrestrial planets, the growing giant cores become massive enough that they are able to accumulate substantial amounts of gas before the protoplanetary disk disspates. The primary questions regarding the core instability model is whether planets with small cores can accrete gaseous enveloples within the lifetimes of gaseous protoplanetary disks. The main alternative giant planet formation model is the disk instability model, in which gaseous planets form directly via gravitational instabilities within protoplanetary disks. Formation of giant planets via gas instability has never been demonstrated for realistic disk conditions. Moreover, this model has difficulty explaining the supersolar abundances of heavy elements in Jupiter and Saturn, and it does not explain the orgin of planets like Uranus and Neptune.

Lissauer, Jack

2003-01-01

428

SCALE FORMATION IN CHRYSOPHYCEAN ALGAE  

PubMed Central

The cell wall of the marine chrysophycean alga Pleurochrysis scherfellii is composed of distinct wall fragments embedded in a gelatinous mass. The latter is a polysaccharide of pectic character which is rich in galactose and ribose. These wall fragments are identified as scales. They have been isolated and purified from the vegetative mother cell walls after zoospore formation. Their ultrastructure is described in an electron microscope study combining sectioning, freeze-etch, and negative staining techniques. The scales consist of a layer of concentrically arranged microfibrils (ribbons with cross-sections of 12 to 25 x 25 to 40 A) and underlying radial fibrils of similar dimensions. Such a network-plate is densely coated with particles which are assumed to be identical to the pectic component. The microfibrils are resistant to strong alkaline treatment and have been identified as cellulose by different methods, including sugar analysis after total hydrolysis, proton resonance spectroscopical examination (NMR spectroscopy) of the benzoylated product, and diverse histochemical tests. The formation and secretion of the scales can be followed along the maturing Golgi cisternae starting from a pronounced dilated "polymerization center" as a completely intracisternal process which ends in the exocytotic extrusion of the scales. The scales reveal the very same ultrastructure within the Golgi cisternae as they do in the cell wall. The present finding represents the first evidence on cellulose formation by the Golgi apparatus and is discussed in relation to a basic scheme for cellulose synthesis in plant cells in general.

Brown, R. Malcolm; Franke, Werner W.; Kleinig, Hans; Falk, Heinz; Sitte, Peter

1970-01-01

429

Modeling of Dynamic FRC Formation  

NASA Astrophysics Data System (ADS)

We have developed a 2-D resistive MHD code, Lamy Ridge, to simulate the entire FRC formation process in Tri Alpha's C2 device, including initial formation, translation, merging and settling into equilibrium. Two FRC's can be created simultaneously, and then translated toward each other so that they merge into a single FRC. The code couples the external circuits around the formation tubes to the partially ionized plasma inside. Plasma and neutral gas are treated as two fluids. Dynamic and energetic equations, which take into account ionization and charge exchange, are solved in a time advance manner. The geometric shape of the vessel is specified by a set of inputs that defines the boundaries, which are handled by a cut-cell algorithm in the code. Multiple external circuits and field coils can be easily added, removed or relocated through individual inputs. The design of the code is modular and flexible so that it can be applied to future devices. The results of the code are in reasonable agreement with experimental measurements on the C2 device.

Mok, Yung; Barnes, Dan; Dettrick, Sean

2010-11-01

430

Supernova Feedback in Galaxy Formation  

NASA Astrophysics Data System (ADS)

The hierarchical model of galaxy formation is known to suffer from the ``over-cooling'' problem: the high efficiency of radiative cooling results in too much baryonic matter in a condensed phase (namely, cold gas or stars) when compared to observations. A solution proposed by many authors (see Springel & Hernquist 2003; Fujita et al. 2004; Rasera & Teyssier 2005) is feedback due to supernova (SN) driven winds or active galactic nuclei. Modeling SN feedback by direct injection of thermal energy usually turns out to be inefficient in galaxy-scale simulations, due to the quasi-instantaneous radiation of the SN energy. To avoid this effect, we have developed a new method to incorporate SN feedback in cosmological simulations: using temporary test particles, we reproduce explicitly a local Sedov blast wave solution in the gas distribution. We have performed several self-consistent runs of isolated Navarro, Frenk, & White (1996, hereafter NFW) halos with radiative cooling, star formation, SN feedback and metal enrichment using the adaptive mesh refinement code RAMSES (Teyssier 2002). We have explored the influence of SN feedback on the formation and the evolution of galaxies with different masses. We have studied the efficiency of the resulting galactic winds, as a function of the mass of the parent halo.

Dubois, Y.; Teyssier, R.

2008-06-01

431

Formate auxotroph of Methanobacterium thermoautotrophicum Marburg.  

PubMed Central

A formate-requiring auxotroph of Methanobacterium thermoautotrophicum Marburg was isolated after hydroxylamine mutagenesis and bacitracin selection. The requirement for formate is unique and specific; combined pools of other volatile fatty acids, amino acids, vitamins, and nitrogen bases did not substitute for formate. Compared with those of the wild type, cell extracts of the formate auxotroph were deficient in formate dehydrogenase activity, but cells of all of the strains examined catalyzed a formate-carbon dioxide exchange activity. All of the strains examined took up a small amount (200 to 260 mumol/liter) of formate (3 mM) added to medium. The results of the study of this novel auxotroph indicate a role for formate in biosynthetic reactions in this methanogen. Moreover, because methanogenesis from H2-CO2 is not impaired in the mutant, free formate is not an intermediate in the reduction of CO2 to CH4.

Tanner, R S; McInerney, M J; Nagle, D P

1989-01-01

432

Outlook: Testing Planet Formation Theories  

NASA Astrophysics Data System (ADS)

The discovery of the first planetary companion to a solar-type star by Mayor and Queloz (1995) launched the extrasolar planetary systems era. Observational and theoretical progress in this area has been made at a breathtaking pace since 1995, as evidenced by this workshop. We now have a large and growing sample of extrasolar gas giant planets with which to test our theories of their formation and evolution. The two competing theories for the formation of gas giant planets, core accretion and disk instability, appear to have testable predictions: (i) Core accretion seems to require exceptionally long-lived disks, implying that gas giants should be somewhat rare, while disk instability can occur in even the shortest-lived disk, implying that gas giants should be abundant. The ongoing census of gas giants by the spectroscopic search programs will determine the frequency of gas giants on Jupiter-like orbits within the next decade. (ii) Core accretion takes millions of years to form gas giants, while disk instability forms gaseous protoplanets in thousands of years. Determining the epoch of gas giant planet formation by searching for astrometric wobbles indicative of gas giant companions around young stars with a range of ages (˜ 0.1 Myr to ˜ 10 Myr) should be possible with the Space Interferometry Mission (SIM). (iii) Core accretion would seem to be bolstered by a higher ratio of dust to gas, whereas disk instability occurs equally well for a range of dust opacities. Determining whether a high primordial metallicity is necessary for gas giant planet formation can be accomplished by spectroscopic and astrometric searches for gas giants around metal-poor stars. Eventually, ice giant planets will be detectable as well. If ice giants are found to be much more frequent that gas giants, this may imply that core accretion occurs, but usually fails to form a gas giant. Terrestrial planets will be detected through photometry by Kepler and Eddington, astrometry by SIM, and imaging by Terrestrial Planet Finder and Darwin. Ultimately these detections will clarify the process of Earth formation by collisional accumulation, the only contending theory.

Boss, A. P.

433

Formation mechanisms of metal colloids  

NASA Astrophysics Data System (ADS)

Highly dispersed uniform metallic particles are widely used in various areas of technology and medicine and are likely to be incorporated into many other applications in the future. It is commonly accepted that size, shape and composition of the particles represent critical factors in most applications. Thus, understanding the mechanisms of formation of metal particles and the ways to control the physical (e.g. shape, size) and chemical (e.g. composition) properties is of great importance. In the current research, the formation of uniform silver spheres is investigated experimentally. The parameters that influence the formation of silver particles when concentrated iso-ascorbic acid and silver-polyamine complex solutions are rapidly mixed were studied in the absence of dispersants. We found that by varying the nature of the amine, temperature, concentration of reactants, silver/amine molar ratio, and the nature of the silver salt, the size of the resulting silver particles can be varied in a wide range (0.08--1.5 microm). The silver particles were formed by aggregation of nanosize subunits as substantiated by both electron microscopy and X-ray diffraction techniques and by the vivid rapid color changes during the chemical precipitation process. From the practical standpoint, the goal of this research was to prepare well dispersed spherical silver particles having a relatively smooth surface and a diameter of about 1 microm to satisfy the demands of the current electronic materials market. A two stage particle growth model previously developed to explain the narrow size distribution occurring in synthesis of gold spheres was applied to the present experimental system, and the parameters that control the size distribution characteristics were identified. The kinetic parameter required to match the final particle size was found to be in agreement with the one used previously in modeling formation of gold spheres, suggesting that similar kinetics governs the aggregation process. Furthermore, the two-stage particle growth model was used to account for the effects of solvent viscosity and temperature on the particle properties, particularly their size. As an application of the above mentioned study, the aggregation process that led to the formation of large silver spheres was used to deposit in a controlled manner layers of silver and other metals (Ni, Au) onto various metallic and non-metallic substrates. In the final section of this thesis methods to form nanosized primary particle strictly through diffusional growth are described. The highly crystalline metallic particles of various sizes and composition prepared provide performance characteristics that are complementary to the polycrystalline metallic particles described in the preceding sections.

Halaciuga, Ionel

434

Formation of the hurricane eye  

NASA Astrophysics Data System (ADS)

This dissertation consists of three distinct studies which investigate aspects of eye formation. The first study reviews eye phenomenon in a variety of vortices ranging from simple vortices to the menagerie of geophysical vortices, emphasizing similarities and differences to the eyes formed in hurricanes. The hurricane eye is found to be a paradoxical structure imposed by conservation of angular momentum and the boundaries of the vortex. A comprehensive definition for hurricane eye formation is proposed and various eye formation mechanisms are summarized. The next study presents a simple theoretical argument to isolate the conditions under which a tropical cyclone can rapidly develop a warm-core thermal structure and subsequently approach a steady state. The theoretical argument is based on the balanced vortex model and, in particular, on the associated transverse circulation equation and the geopotential tendency equation. The transverse circulation and the temperature tendency in a tropical vortex depend not only on the diabatic forcing, but also on the spatial distributions of the static stability, the baroclinity, and the inertial stability. The vortex response to diabatic heating depends critically on whether the heating occurs in the low inertial stability region outside the radius of maximum wind or in the high inertial stability region inside the radius of maximum wind. This result suggests that rapid intensification is favored for storms which have at least some of the eyewall convection inside the radius of maximum wind. The development of an eye partially removes diabatic heating from the high inertial stability region of the storm center, yet rapid intensification may continue if the eyewall heating continues to become more efficient. As the warm core matures and static stability increases over the inner core, conditions there become less favorable for deep upright convection and the storm tends to approach a steady state. The final study characterizes the kinematic and thermodynamic changes that occur before, during, and after the initial eye formations of a broad set of Atlantic tropical cyclones. To obtain the requisite structure and intensity parameters, a new data set has been synthesized from the Vortex Data Messages transmitted by routine aircraft reconnaissance from 1989--2008. Intensity ranges are determined for the times when the eye/eyewall structure first appears in aircraft radar and infrared satellite imagery. The mean intensity at which an eye is first observed in both aircraft or satellite imagery is found to be 58 kt, somewhat lower than reported in previous studies. Changes about the time of eye formation are examined for intensity, the radius of maximum winds, the minimum Rossby radius of deformation, eye temperature and dew point temperature depression. Storms are found to intensify most rapidly near the time of eye formation, especially when a persistent eye is observed in infrared satellite imagery. Many storms which are forming eyes are found to undergo a substantial and rapid contraction in the radius of maximum winds during the 24-h period before the eye is observed; once the eye is present, this contraction slows or ceases. Strong warming at lower levels (850 or 700 hPa) of the eye is not observed to correlate well with the time in which the eye is first observed. Finally, observations suggest that the dynamical heating efficiency of the resulting eyewall increases even as the physical scale of the efficient heating region decreases. This allows the storm to continue intensifying even though the total inner core diabatic heating may decrease. The answer to why some storms fail to form eyes may shed light on whether eye formation is a stochastic process involving constructive and destructive mesoscale interactions---or whether it is a manifold attractor of the system sometimes stymied by an unfavorable environment.

Vigh, Jonathan L.

435

Energy Engineering Analysis Program. Lighting survey of selected buildings, Pine Bluff Arsenal, Pine Bluff, Arkansas. Volume 2a: Appendices. Final report  

SciTech Connect

The Architect-Engineer shall: (1) perform site survey of specific buildings or areas to collect all data required to evaluate the list of possible ECOs provided in Annex A; (2) Evaluate new ECOs discovered by the AE in his site survey to verify their energy savings potential and economic feasibility; (3) Provide project administrative/technical documentation (DD Form 1391 and Project Development Brochure (PDB)) for qualifying Energy Conservation Investment Program (ECIP) projects as detailed herein. See Annex C for required documentation; (4) Prepare a comprehensive report to document all work (site surveys, evaluations, etc.) performed, the results and all recommendations.

NONE

1995-06-01

436

Basin scale evolution of formation waters: a diagenetic and formation water study of the Triassic Chaunoy Formation, Paris Basin  

Microsoft Academic Search

Formation waters and their movements within basins are commonly attributed with responsibility for patterns of cementation and porosity-loss within reservoirs and aquifers. It is thus important to understand when and how waters move in the subsurface. We have studied the evolution and movement of formation water in the Triassic Chaunoy Formation of the Paris Basin, NW Europe to define the

R. H Worden; M. L Coleman; J-M Matray

1999-01-01

437

The formation of cluster galaxies  

NASA Astrophysics Data System (ADS)

In this work I sought to understand the formation and evolution of galaxies. Specifically, I studied three key aspects of galaxy formation: star formation, mass assembly, and structural evolution. Past research has shown that the formation of a galaxy is strongly coupled to its local environment (i.e. the local galaxy density). Therefore, I studied the evolution of cluster galaxies because clusters are the highest density environments that exist in the universe. In turn, the observational results found herein form a foundation upon which to test theories of galaxy formation in the densest environments. I used the latest sample of galaxy clusters from the Bootes region to measure the near-infrared luminosity function (NIR LF) of cluster galaxies from 0 < z < 2 and estimate the primary epoch of star formation for massive cluster galaxies. I found that massive cluster galaxies formed the bulk of their stars at zf ˜ 2.5, that they evolved passively at z ? 1.3, and that they deviated from passive evolution at higher redshifts. This latter observation suggested that massive cluster galaxies were actively assembling their final stellar masses at z > 1.3. I used deeper IRAC imaging to study the NIR LF of high redshift cluster galaxies (1 < z < 1.5) with focus on the properties of faint (i.e. low mass) galaxies. I found no evidence for evolution of the LF for low mass cluster galaxies out to the highest redshifts studied, which suggested that the cluster galaxy population was in place at high redshift. Finally, I calculated the evolution of the size-mass relationship (SMR) of cluster galaxies as a function of morphology for the high redshift cluster sample. I found that apparent evolution of the SMR can be partially explained by the progenitor bias, but that there was a missing population of large, massive cluster galaxies. These galaxies were either be accreted by clusters at lower redshifts, or the cluster galaxy population underwent size-evolution to account for their presence at low redshift. I developed two new programs to aid in my research as well as future research in this field. I created EzGal, a program which extracts observables (magnitudes, k-corrections, stellar masses, mass-to-light ratios, etc...) from standard stellar population synthesis (SPS) models. This simplified comparisons of observations to many different model sets, and simplified comparison of different model sets to each other. I used EzGal to quantitatively compare various model sets and estimate SPS model uncertainty, and recovered the well known result that SPS models agree best in the optical for old stellar populations, but disagree substantially for intermediate age stellar populations in the NIR. The latter uncertainty was caused by the presence of thermally pulsating AGB stars, which are poorly understood observationally but contribute substantially to the NIR light of a stellar population. I also created the Python Galaxy Fitter (PyGFit), a program which measures PSF matched photometry from crowded imaging with disparate PSFs and resolutions. This enabled accurate measurement of spectral energy distributions (SEDs) in crowded cluster fields.

Mancone, Conor L.

438

On-Going Galaxy Formation  

NASA Astrophysics Data System (ADS)

We investigate the process of galaxy formation as can be observed in the only currently forming galaxies - the so-called Tidal Dwarf Galaxies, hereafter TDGs - through observations of the molecular gas detected via its CO (Carbon Monoxide) emission. These objects are formed of material torn off of the outer parts of a spiral disk due to tidal forces in a collision between two massive galaxies. Molecular gas is a key element in the galaxy formation process, providing the link between a cloud of gas and a bona fide galaxy. We have detected CO in 8 TDGs (Braine, Lisenfeld, Duc and Leon, 2000: Nature 403, 867; Braine, Duc, Lisenfeld, Charmandaris, Vallejo, Leon and Brinks: 2001, A&A 378, 51), with an overall detection rate of 80%, showing that molecular gas is abundant in TDGs, up to a few 108 M ?. The CO emission coincides both spatially and kinematically with the HI emission, indicating that the molecular gas forms from the atomic hydrogen where the HI column density is high. A possible trend of more evolved TDGs having greater molecular gas masses is observed, in accord with the transformation of HI into H2. Although TDGs share many of the properties of small irregulars, their CO luminosity is much greater (factor ˜ 100) than that of standard dwarf galaxies of comparable luminosity. This is most likely a consequence of the higher metallicity (?sim 1/3 solar) of TDGs which makes CO a good tracer of molecular gas. This allows us to study star formation in environments ordinarily inaccessible due to the extreme difficulty of measuring the molecular gas mass. The star formation efficiency, measured by the CO luminosity per H? flux, is the same in TDGs and full-sized spirals. CO is likely the best tracer of the dynamics of these objects because some fraction of the HI near the TDGs may be part of the tidal tail and not bound to the TDG. Although uncertainties are large for individual objects, as the geometry is unknown, our sample is now of eight detected objects and we find that the ‘dynamical’ masses of TDGs, estimated from the CO line widths, seem not to be greater than the ‘visible’ masses (HI + H2 + a stellar component). Although higher spatial resolution CO (and HI) observations would help reduce the uncertainties, we find that TDGs require no dark matter, which would make them the only galaxy-sized systems where this is the case. Dark matter in spirals should then be in a halo and not a rotating disk. Most dwarf galaxies are dark matter-rich, implying that they are not of tidal origin. We provide strong evidence that TDGs are self-gravitating entities, implying that we are witnessing the ensemble of processes in galaxy formation: concentration of large amounts of gas in a bound object, condensation of the gas, which is atomic at this point, to form molecular gas and the subsequent star formation from the dense molecular component.

Braine, Jonathan; Duc, P.-A.; Lisenfeld, U.; Charmandaris, V.; Vallejo, O.; Leon, S.; Brinks, E.

2002-07-01

439

Micelle formation of sodium hyodeoxycholate.  

PubMed

Sodium hyodeoxycholate (NaHDC) is the main component of hog bile salts, which play a role in the absorption of sparingly soluble materials in the intestinal solution. The biosurfactant has an amphiphilic molecular structure, similar to that of ursodeoxycholate from bear gallbladder. Micelle formation from hyodeoxycholate was studied at 308.2K using pyrene fluorescence probe to determine critical micelle concentrations (cmc) at various NaCl concentrations. The change in the fluorescence spectrum peak ratios with NaHDC concentration indicated two steps for bile salt aggregation. The first step was the formation of small micelles (cmc) at 5mM, and the second step was the formation of stable aggregates at 14 mM in aqueous solution. The aggregation of hyodeoxycholate, analyzed using the stepwise association model, was found to grow its aggregation number from 4 to 7 with increasing concentration. The aggregation number in aqueous solution was also confirmed by the static light scattering method. The average measured aggregation number of the micelles was 6.7. The micellar size was relatively small as measured by either method, but it was covered by general aggregation number of human bile salts. The degree of counterion binding to the micelles, determined using a sodium ion-selective electrode, was ca. 0.5 for the NaHDC micelles. This value was relatively high among typical bile salts. Moreover, the solubilization capacity of the NaHDC micelles was assessed using cholesterol. It became clear that NaHDC micelles hardly solubilized cholesterol compared to typical human bile salts. The maximum solubilization by NaHDC was equivalent only to that by sodium ursodeoxycholate. PMID:23665117

Matsuoka, Keisuke; Takagi, Kaede; Honda, Chikako

2013-01-01

440

Sequential star formation in Cassiopeia  

NASA Astrophysics Data System (ADS)

Massive stars (M ? 9 M_{?}) are usually formed in OB associations, consisting of one or more not very massive open clusters and a halo of scattered young stars. The study of these open clusters can provide clues about how stellar formation proceeds from the parent molecular clouds. We present first results on a project to understand sequential star formation mechanisms in OB associations. We have chosen associations Cas OB4, Cas OB5 and Cas OB7, close to the Cassiopeia constellation, at l = 110°-125°. Previous determinations of their distance provided very similar values for them all, and placed them on the Perseus Arm. This study aims at improved distance and age determinations using new spectroscopic observations and existing photometry. The goal is to investigate whether the clusters in Cas OB4, Cas OB5 and Cas OB7 are separate entities or can be enclosed in a global common OB association. If associated,we will check for evidence of induced star formation. We preselected about 100 stars from 12 clusters, based on photometric criteria. Long-slit spectra were taken with the Intermediate Dispersion Spectrograph at the Isaac Newton Telescope (2.5 m), located in La Palma's Observatorio del Roque de los Muchachos. We used the R632V grating, to achieve a spectral coverage between 3500 Å and 5500 Å and spectral resolution of 0.90 Å px^{-1}. The observed spectra have been used to determine the spectral type and luminosity class of the sample stars. The spectral classification yields the stellar properties (from calibrations), and will enable the reconstruction of the HR-diagram. We present in this poster newly discovered B-type stars in two selected clusters.

Velasco, S.; García, M.; Negueruela, I.

2013-05-01

441

Microbial Formation of Manganese Oxides  

PubMed Central

Microbial manganese oxidation was demonstrated at high Mn2+ concentrations (5 g/liter) in bacterial cultures in the presence of a microalga. The structure of the oxide produced varied depending on the bacterial strain and mode of culture. A nonaxenic, acid-tolerant microalga, a Chlamydomonas sp., was found to mediate formation of manganite (?-MnOOH). Bacteria isolated from associations with crude cultures of this alga grown in aerated bioreactors formed disordered ?-MnO2 from Mn2+ at concentrations of 5 g/liter over 1 month, yielding 3.3 g of a semipure oxide per liter. All algal-bacterial cultures removed Mn2+ from solution, but only those with the highest removal rates formed an insoluble oxide. While the alga was an essential component of the reaction, a Pseudomonas sp. was found to be primarily responsible for the formation of a manganese precipitate. Medium components—algal biomass and urea—showed optima at 5.7 and 10 g/liters, respectively. The scaled-up culture (50 times) gave a yield of 22.3 g (53 mg/liter/day from a 15-liter culture) of semipure disordered ?-MnO2, identified by X-ray diffraction and Fourier transform infrared (FTIR) spectroscopy, and had a manganese oxide O/Mn ratio of 1.92. The Mn(IV) content in the oxide was low (30.5%) compared with that of mined or chemically formed ?-MnO2 (ca. 50%). The shortfall in the bacterial oxide manganese content was due to biological and inorganic contaminants. FTIR spectroscopy, transmission electron microscopy, and electron diffraction studies have identified manganite as a likely intermediate product in the formation of disordered ?-MnO2.

Greene, Anthony C.; Madgwick, John C.

1991-01-01

442

Digital Formats for Content Reproductions  

NSDL National Science Digital Library

This small document, though designed mainly to aid entrants in the Library of Congress/Ameritech Digital Library Competition, is also an updated inside look at the procedures used to create the digital images in LOC's National Digital Library Program, particularly its famous American Memory digital collection. The report details the standards used by the Library in digitization of images, text, maps, sound files, and movies. While these are not necessarily universal standards, few institutions or individuals have more experience than LOC in these endeavors. Digital Formats will be of great value to anyone interested in digitizing library collections.

443

Petrophysical evaluation of subterranean formations  

DOEpatents

Methods and systems are provided for evaluating petrophysical properties of subterranean formations and comprehensively evaluating hydrate presence through a combination of computer-implemented log modeling and analysis. Certain embodiments include the steps of running a number of logging tools in a wellbore to obtain a variety of wellbore data and logs, and evaluating and modeling the log data to ascertain various petrophysical properties. Examples of suitable logging techniques that may be used in combination with the present invention include, but are not limited to, sonic logs, electrical resistivity logs, gamma ray logs, neutron porosity logs, density logs, NRM logs, or any combination or subset thereof.

Klein, James D; Schoderbek, David A; Mailloux, Jason M

2013-05-28

444