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1

Hydrogeology and groundwater modeling of a Calvert Bluff aquifer  

E-print Network

of a 8, 000 foot by 2, 500 foot crevasse splay-related sand deposit occurring within a lignite surface mine has documented the hydrogeology and ground- water behavior in a partially confined, partially uncon- fined aquifer of the Calvert Bluff... with a high moisture and volatile-matter content. It has a heating value of less than 8, 300 BTU/pound, and it is intermediate in coalification between peat and subbitu- minous coal. Most lignite contains clearly separable pieces of plant material...

Lawrence, James

1989-01-01

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.

Warwick, Peter D.; Crowley, Sharon S.

1995-01-01

4

Wind Erosion and Dune Formation on High Frozen Bluffs  

NASA Technical Reports Server (NTRS)

Frost penetration increases upslope on barren, windswept bluffs in cold environments. Along the south shore of Lake Superior, near the brow of 100 m high bluffs it typically exceeds 5 m. Frost increases the shear strength of damp sand to a level comparable to that of concrete, making winter slopes highly stable despite undercutting by waves and ground-water sapping along the footslope. Sublimation of interparticle ice in the slope face increases with wind speed and lower vapor pressures. The cold and dry winter winds of Lake Superior ablate these slopes through loss of binding ice. Wind erosion rates, based on measurements of sand accumulation on the forest floor downwind of the brow, show most airborne sand falls out within several meters of the brow, forming a berm 1 to 3 m high after many years. The spatial pattern of sand deposition, however, varies considerably over distances of several hundred meters along the top bluffs in response to frost conditions and the build-up of gravel lag on the slope face, sand exposure from mass movements, and local aerodynamics of the crest slope. The formation of perched sand dunes in the Great Lakes region is clearly related to wind erosion of sand from high bluffs in winter. Broadly similar processes may operate on Mars.

Marsh, W. M.; Marsh, B. D.

1984-01-01

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

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

7

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

8

Calvert: an historical geography  

E-print Network

-nineteenth century, when Anglo-Americans were firmly settled in the general area of Calvert, the most feared Indians were the Comanche. Tidwell Creek, which runs north and west of Calvert, was named for J. N. Tidwell who was killed by Indians while working his... of the Tonkawa Indians. The earliest documented European contact with the general area of the site is associated with efforts of the Spanish to establish a series of missions on the San Gabriel River, somewhat to the west of present-day Calvert. Anglo-American...

McMillan, Frank N

1984-01-01

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

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)

2004-01-01

11

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

Johns Hopkins University Center for Technology in Ecducation

2004-01-01

12

Large-scale vortex structures in turbulent wakes behind bluff bodies. I - Vortex formation processes. II - Far-wake structures  

Microsoft Academic Search

Phase-averaged vector fields and the associated streamline patterns are presented for flow in the nominal plane of symmetry of the near wake of some nominally two-dimensional bluff bodies. Patterns in the cavity region are produced using data obtained with reasonably high resolution for 16 phases of the vortex-shedding cycle. The flows encountered are always three-dimensional, and mean flow patterns in

A. E. Perry; T. R. Steiner

1987-01-01

13

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

14

The lithology, environment of deposition, and reservoir evaluation of sandstones in the Upper Queen Formation (Guadalupian, Permian) at Concho Bluff North and Jennifer Fields, Upton and Ector Counties, Texas  

E-print Network

completed on the shelf sandstones of this group. Unfortunately, this has left a large gap in our knowledge of clastic shelf sedimentation of the Permian Basin; consequently, bypassing an important potential for hydrocarbon exploitation. In a move...THE LI THOLOGY g ENVIRONMENT OF DEPOS ITION g AND RESERVOIR EVALUATION OF SANDSTONES IN THE UPPER QUEEN FORMATION (GUADALUPIAN, PERMIAN) AT CONCHO BLUFF NORTH AND JENNIFER F I ELDS g UPTON AND ECTOR COUNT I ES ~ TEXAS A Thesis by JAMES BROOX...

Harper, James Broox

2012-06-07

15

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

16

A model of tephra dispersal from an early Palaeogene shallow submarine Surtseyan-style eruption(s), the Red Bluff Tuff Formation, Chatham Island, New Zealand  

NASA Astrophysics Data System (ADS)

The Red Bluff Tuff Formation, an early Palaeogene volcano-sedimentary shallow marine succession from the Chatham Islands (New Zealand), provides a unique framework, in eastern 'Zealandia', to explore tephra dispersal processes associated with ancient small phreatomagmatic explosions (i.e. Surtseyan-style eruptions). Detailed sedimentological mapping, logging and sampling integrated with the results of extensive laboratory analyses (i.e. grain-size, componentry and applied palaeontological methods) elucidated the complex mechanisms of transport and deposition of nine identified resedimented fossiliferous volcaniclastic facies. These facies record the subaqueous reworking and deposition of tephra from the erosion and degradation of a proximal, entirely submerged ancient Surtseyan volcanic edifice (Cone II). South of this volcanic cone, the lowermost distal facies provides significant evidence of deposition as water-supported volcanic- or storm-driven mass flows (e.g. turbidity currents and mud/debris flows) of volcaniclastic and bioclastic debris, whereas the uppermost distal facies exhibit features of tractional sedimentary processes caused by shallow subaqueous currents. Further north, within the proximity of the volcanic edifice, the uppermost facies are represented by an abundant, diverse, large, and well preserved in situ fauna of shallow marine sessile invertebrates (e.g. corals and sponges) that reflect the protracted biotic stabiliszation and rebound following pulsed volcanic events. Over a period of time, these stable and wave-eroded volcanic platforms were inhabited by a flourishing and diversifying marine community of benthic and sessile pioneers (corals, bryozoans, molluscs, brachiopods, barnacles, sponges, foraminifera, etc.). This succession exhibits a vertical progression of sedimentary structures (i.e. density, cohesive and mass flows, and cross-bedding) and our interpretations indicate a shallowing upwards succession. This study reports for the first time mechanisms of degradation of a Surtseyan volcano on Chatham Islands and contributes to a better understanding of complex ancient volcano-sedimentary subaqueous terrains. This model of deposition (i.e. onlapping/overlapping features onto the remains of volcanic edifice(s), a vertical transition of structures from deeper- to shallower-marine environments, disaster faunas and subsequent preferential colonisation of diverse biota, including large in situ sessile invertebrates, on the summit), characterises an extraordinary example to be applied to other ancient subaqueous volcanic environments.

Sorrentino, Leonor; Stilwell, Jeffrey D.; Mays, Chris

2014-03-01

17

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

Code of Federal Regulations, 2010 CFR

...Plant, Chesapeake Bay, Calvert County, Maryland. 165.505 Section 165.505 ...Plant, Chesapeake Bay, Calvert County, Maryland. (a) Location. The following area is a security zone...Guard Captain of the Port, Baltimore, Maryland. (2) Persons...

2010-07-01

18

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

Code of Federal Regulations, 2013 CFR

...Plant, Chesapeake Bay, Calvert County, Maryland. 165.505 Section 165.505 ...Plant, Chesapeake Bay, Calvert County, Maryland. (a) Location. The following area is a security zone...Guard Captain of the Port, Baltimore, Maryland. (2) Persons...

2013-07-01

19

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

Code of Federal Regulations, 2011 CFR

...Plant, Chesapeake Bay, Calvert County, Maryland. 165.505 Section 165.505 ...Plant, Chesapeake Bay, Calvert County, Maryland. (a) Location. The following area is a security zone...Guard Captain of the Port, Baltimore, Maryland. (2) Persons...

2011-07-01

20

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

Code of Federal Regulations, 2012 CFR

...Plant, Chesapeake Bay, Calvert County, Maryland. 165.505 Section 165.505 ...Plant, Chesapeake Bay, Calvert County, Maryland. (a) Location. The following area is a security zone...Guard Captain of the Port, Baltimore, Maryland. (2) Persons...

2012-07-01

21

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

Code of Federal Regulations, 2014 CFR

...Plant, Chesapeake Bay, Calvert County, Maryland. 165.505 Section 165.505 ...Plant, Chesapeake Bay, Calvert County, Maryland. (a) Location. The following area is a security zone...Guard Captain of the Port, Baltimore, Maryland. (2) Persons...

2014-07-01

22

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

Federal Register 2010, 2011, 2012, 2013, 2014

...Federal Energy Regulatory Commission [Docket No. PR13-10-000] Moss Bluff Hub, LLC; Notice of Filing Take notice that on November 15, 2012, Moss Bluff Hub, LLC, (Moss Bluff) filed to revise its Statement of Operating Conditions...

2012-11-26

23

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, 2014

...Calvert Cliffs. Environmental Impacts of the Proposed...has completed its environmental assessment of the proposal...NRC- approved methods for the reload...significant radiological environmental impacts associated...

2011-01-10

24

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

Federal Register 2010, 2011, 2012, 2013, 2014

...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

25

Indicator tests for the creep of rock salt from borehole Moss Bluff 2, Moss Bluff Dome, Texas  

Microsoft Academic Search

Creep tests were performed on a representative sample of rock salt from borehole Moss Bluff 2 (MB2), Moss Bluff dome near Houston, Texas. Moss Bluff 2 is located at the site of a compressed gas storage cavern of Tejas Power Corporation. Four triaxial experiments were conducted at two values of principal stress difference and two representative temperatures. The minimum observed

Wawersik

1992-01-01

26

The Hydrogen Economy as a Technological Bluff  

ERIC Educational Resources Information Center

The hydrogen economy is a technological bluff in its implied assurance that, despite the accelerating pace at which we are depleting the remaining half of our fossil fuels, our energy future is secure. Elementary thermodynamic considerations are developed to show that a hydrogen economy is about as feasible as a perpetual motion machine. Hydrogen…

Vanderburg, Willem H.

2006-01-01

27

Calvert Cliffs RELAP5/MOD3/SCDAP plant deck  

SciTech Connect

This report documents the development of a RELAP5/MOD3/SCDAP input deck for the Calvert Cliffs nuclear power plant. Through the addition of SCDAP inputs, NPA interactive capabilities, and significant nodalization enhancements the range of applicability; of this input deck has been greatly increased.

Hendrix, C.E.; Determan, J.C.

1992-12-01

28

The Vascular Flora of Cove Point, Calvert County, Maryland  

Microsoft Academic Search

The vascular flora of the Cove Point Liquefied Natural Gas Limited Partner- ship property at Cove Point, Calvert County, Maryland was surveyed from 1996 to 1999. A voucher specimen was collected for each taxon discovered and deposited in the herbarium of the Cove Point Natural Heritage Trust. A total of 698 species (705 taxa) from 383 genera in 119 families

BRENT W. S TEURY

29

78 FR 21930 - Moss Bluff Hub, LLC; Notice of Filing  

Federal Register 2010, 2011, 2012, 2013, 2014

...DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. PR13-45-000] Moss Bluff Hub, LLC; Notice of Filing Take notice that on March 29, 2013, Moss Bluff Hub, LLC filed to revise its Statement of Operating Conditions to modify...

2013-04-12

30

GPU accelerated simulations of bluff body flows using vortex particle methods  

E-print Network

GPU accelerated simulations of bluff body flows using vortex particle methods Diego Rossinelli in press as: D. Rossinelli et al., GPU accelerated simulations of bluff body flows using vortex particle Penalization Bluff body flows a b s t r a c t We present a GPU accelerated solver for simulations of bluff body

Cottet, Georges-Henri

31

Evaluation of In Situ Combustion for Schrader Bluff  

SciTech Connect

The focus of this report is on the results related to evaluation of in situ combustion processes applied to Schrader Bluff. Initially, overall screening processes were applied to determine which of the EOR methods, were most appropriate for Schrader Bluff. In situ combustion was among the methods considered potentially favorable and was evaluated further. Laboratory scale tube runs were conducted to determine if the kinetic parameters for the crude oil were favorable. Additional sensitivity studies were conducted to evaluate the recovery potential. Described in this report are the results of the (1) initial screening,(2) experimental tube runs, and (3) simulation sensitivity studies as related to in situ combustion in Schrader Bluff.

Sarathi, P.; Strycker, A.; Wang, S.

1999-03-11

32

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

Federal Register 2010, 2011, 2012, 2013, 2014

...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

33

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

34

Nonpremixed bluff-body burner flow and flame imaging study  

Microsoft Academic Search

A nonpremixed bluff-body burner flow and flame have been studied using planar flow visualization and species concentration imaging techniques. The burner consists of a central jet of CH4 in a cylindrical bluff-body and an outer coflowing-air stream. Planar flow visualization, using Mie scattering from seed particles added to the fuel jet, Raman scattering from CH4 and laser-induced fluorescence of CH

M. Namazian; J. Kelly; R. W. Schefer; S. C. Johnston; M. B. Long

1989-01-01

35

Nonpremixed bluff-body burner flow and flame imaging study  

Microsoft Academic Search

A nonpremixed bluff-body burner flow and flame have been studied using planar flow visualization and species concentration imaging techniques. The burner consists of a central jet of CH 4 in a cylindrical bluff-body and an outer coflowing-air stream. Planar flow visualization, using Mie scattering from seed particles added to the fuel jet, Raman scattering from CH 4 and laser-induced fluorescence

M. Namazian; J. Kelly; R. W. Schefer; S. C. Johnston; M. B. Long

1989-01-01

36

Inside Interrogation: The Lie, The Bluff, and False Confessions  

Microsoft Academic Search

Using a less deceptive variant of the false evidence ploy, interrogators often use the bluff tactic, whereby they pretend\\u000a to have evidence to be tested without further claiming that it necessarily implicates the suspect. Three experiments were\\u000a conducted to assess the impact of the bluff on confession rates. Using the Kassin and Kiechel (Psychol Sci 7:125–128, 1996) computer crash paradigm,

Jennifer T. Perillo; Saul M. Kassin

2011-01-01

37

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

Federal Register 2010, 2011, 2012, 2013, 2014

...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

38

Ray Lemoine, Cedar Bluffs Public Schools, Cedar Bluffs, NE 2008 Understanding Geologic Formations  

E-print Network

guage) Background: Students should know the rock cycle and the three main types of rocks; sedimentary Materials: Bedded rock samples (or pictures) Fossilized rock samples (or pictures) Pictures from Geology Field Course, or equivalent Rock I.D. flow charts Rock test kits (hardness test, acid test, grain size

Frank, Tracy D.

39

Inside interrogation: the lie, the bluff, and false confessions.  

PubMed

Using a less deceptive variant of the false evidence ploy, interrogators often use the bluff tactic, whereby they pretend to have evidence to be tested without further claiming that it necessarily implicates the suspect. Three experiments were conducted to assess the impact of the bluff on confession rates. Using the Kassin and Kiechel (Psychol Sci 7:125-128, 1996) computer crash paradigm, Experiment 1 indicated that bluffing increases false confessions comparable to the effect produced by the presentation of false evidence. Experiment 2 replicated the bluff effect and provided self-reports indicating that innocent participants saw the bluff as a promise of future exoneration which, paradoxically, made it easier to confess. Using a variant of the Russano et al. (Psychol Sci 16:481-486, 2005) cheating paradigm, Experiment 3 replicated the bluff effect on innocent suspects once again, though a ceiling effect was obtained in the guilty condition. Results suggest that the phenomenology of innocence can lead innocents to confess even in response to relatively benign interrogation tactics. PMID:20734122

Perillo, Jennifer T; Kassin, Saul M

2011-08-01

40

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

41

78 FR 4467 - UniStar Nuclear Energy, Combined License Application for Calvert Cliffs Power Plant, Unit 3...  

Federal Register 2010, 2011, 2012, 2013, 2014

...52-016; NRC-2008-0250] UniStar Nuclear Energy, Combined License Application for Calvert...3, Exemption 1.0 Background UniStar Nuclear Energy (UNE), on behalf of Calvert Cliffs Nuclear Project, LLC and UniStar Nuclear...

2013-01-22

42

77 FR 1748 - Atomic Safety and Licensing Board; Calvert Cliffs 3 Nuclear Project, LLC, and UniStar Nuclear...  

Federal Register 2010, 2011, 2012, 2013, 2014

...COLA) by Calvert Cliffs 3 Nuclear Project, L.L.C., and UniStar Nuclear Operating Services, L.L...the existing Calvert Cliffs Nuclear Power Plant (CCNPP), Units...the public are requested to park in the offsite parking...

2012-01-11

43

Gosses bluff — diapir, crypto?volcanic structure or astrobleme?  

Microsoft Academic Search

Gosses Bluff, west of Alice Springs, Northern Territory, comprises a roughly circular rim of steeply dipping sandstone, locally overturned with downward facing folds, surrounding a topographically lower core of steeply dipping faulted sandstone, shale, and limestone. Abundant shattercones occur both in outcrop and to depths of 1,000 m. The structure lies on an’ anticlinal trend?Structural, gravity, seismic and drill hole

K. A. W. Crook; P. J. Cook

1966-01-01

44

A Bluff Model of Riverine Settlement in Prehistoric Amazonia  

Microsoft Academic Search

In Amazonia, prehistoric settlement was especially concentrated along the major rivers. This has been explained by the superior soil and wildlife resources of the floodplain (várzea) compared to the interfluve uplands (terra firme). However, the floodplain is a high-risk habitat because of regular and periodic extreme flooding of even the highest terrain. A bluff model is proposed arguing that most

William M. Denevan

1996-01-01

45

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

46

Stability Criterion for the Bluff-Body Stabilized Electrodeless Arc  

NASA Astrophysics Data System (ADS)

It has been found that the electrodeless arc can be stabilized in the presence of flow by placing a bluff body in the entrance stream. A two-stream boundary layer analysis, analogous to that used in combustion theory, is used to calculate an attachment length, the distance required to heat the entering stream to the arc temperature. The criterion for stability is that the attachment length is less than the length of the recirculation cell formed in the wake of the bluff body. Calculations are made for conditions typical of an atmospheric pressure arc in argon. It is found that the attachment length is approximately a linear function of the ratio of flow velocity to power density.

Martin, R. E.; Keefer, D. R.

1972-06-01

47

Bluff-body flameholder wakes - A simple numerical solution  

NASA Technical Reports Server (NTRS)

Numerical finite difference predictions are made of recirculation zones behind bluff-body flame stabilizers, showing quantitatively the effects of forebody geometry, blockage ratio, lateral position of the blockage and inlet swirl on the central recirculation zone. A simple transient Navier-Stokes solution algorithm and laminar flow simulation are used with 'free slip' and 'no slip' wall boundary conditions, thus illustrating how a basic approach may be used to solve a sophisticated fluid dynamic problem.

Vatistas, G. H.; Lin, S.; Kwok, C. K.; Lilley, D. G.

1982-01-01

48

76 FR 81994 - UniStar Nuclear Energy; Combined License Application for Calvert Cliffs Nuclear Power Plant, Unit...  

Federal Register 2010, 2011, 2012, 2013, 2014

...Calvert Cliffs Nuclear Power Plant...of the Atomic Energy Act of 1954...of the human environment, the NRC has...significant effect on the quality of the human environment. This exemption...issuance. For the Nuclear Regulatory...

2011-12-29

49

Characterizing Morphology and Erosional Trends of Permafrost Bluffs, Barter Island, Alaska  

NASA Astrophysics Data System (ADS)

Recession of coastal permafrost bluffs along portions of the North Slope of Alaska are highly variable, and recent studies have found increased retreat rates since the early 2000s along the western Beaufort Sea coastline, yet the mechanisms and processes driving the increased retreat rates remain poorly understood. The Native village of Kaktovik and adjacent U.S. Air Force radar site are situated on Barter Island and bound by an eroding coastal bluff where attempts to control bluff erosion with shore protection structures were undertaken more than a decade ago. In an effort to gain insight into the physical controls driving or limiting bluff recession in this region, a suite of field data was collected in August 2010 to characterize the beaches, bluffs, and nearshore setting. Data collected at 13 transect locations along the 3 km section of coastal bluffs include general bluff morphology and stratigraphy, detailed surveys of bluff edge and bluff face morphology, sediment grain size of the fronting beach, water/ice content and sediment grain size of the massive ice within the bluffs, and nearshore bathymetry. The bluffs here range in height from a few meters to more than ten meters and consist of a very complex sequence of material ranging from dense marine clay at the base, sands and gravel thought to be of fluvial origin, massive units of sand of unknown origin, massive ice which has recently been interpreted as buried glacial ice, wedge ice, thermokarst cave ice, aeolian silts and sands, and peat. At one site, thermistor arrays were installed to evaluate temperature gradients in response to solar radiation and heat flux transfers through characteristic bluff material. Aerial lidar DEMs obtained in 2009 (USGS) revealed a rise in bluff elevation across the central portion of the island where field observations of bluff stratigraphy showed multi-layered stratification. At the lower elevation outer flanks the exposed bluff face consisted of homogenous layers of sandy-silt below the surface peat layer. Comparison of historical bluff edge lines (1947, 1987, 2003), 2009 lidar derived bluff lines, and differential GPS surveys collected in August 2010 suggest increased erosion rates of the bluff top in recent years near the topographically-higher central portion of the island. Maximum beach widths were observed at the flanks of the island where east-west trending spits have formed, likely by way of longshore transport driven by variations in wave direction at the terminus of the spits. Beach width ranged from a maximum of 80 m at the eastern boundary of the bluffs to no beach in front of the former radar station landfill where shore protection structures are emplaced. Beach surface material consisted of fine sands in the back beach region and gravels to pebble-sized material in the mid-beach and swash zone areas. Primary failure modes of Barter Island bluffs appear to be a combination of thermal degradation and thawing of permafrost in the exposed bluff face, mechanical and thermal niching at the toe, followed by rotational slumping of the higher bluffs near the central portion of the island and block collapse of the lower bluffs at the flanks of the island.

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

2010-12-01

50

33 CFR 207.169 - Oklawaha River, navigation lock and dam at Moss Bluff, Fla.; use, administration, and navigation.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 false Oklawaha River, navigation lock and dam at Moss Bluff, Fla.; use, administration, and navigation...REGULATIONS § 207.169 Oklawaha River, navigation lock and dam at Moss Bluff, Fla.; use, administration, and...

2012-07-01

51

33 CFR 207.169 - Oklawaha River, navigation lock and dam at Moss Bluff, Fla.; use, administration, and navigation.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Oklawaha River, navigation lock and dam at Moss Bluff, Fla.; use, administration, and navigation...REGULATIONS § 207.169 Oklawaha River, navigation lock and dam at Moss Bluff, Fla.; use, administration, and...

2010-07-01

52

33 CFR 207.169 - Oklawaha River, navigation lock and dam at Moss Bluff, Fla.; use, administration, and navigation.  

Code of Federal Regulations, 2014 CFR

...2014-07-01 false Oklawaha River, navigation lock and dam at Moss Bluff, Fla.; use, administration, and navigation...REGULATIONS § 207.169 Oklawaha River, navigation lock and dam at Moss Bluff, Fla.; use, administration, and...

2014-07-01

53

33 CFR 207.169 - Oklawaha River, navigation lock and dam at Moss Bluff, Fla.; use, administration, and navigation.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Oklawaha River, navigation lock and dam at Moss Bluff, Fla.; use, administration, and navigation...REGULATIONS § 207.169 Oklawaha River, navigation lock and dam at Moss Bluff, Fla.; use, administration, and...

2011-07-01

54

33 CFR 207.169 - Oklawaha River, navigation lock and dam at Moss Bluff, Fla.; use, administration, and navigation.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Oklawaha River, navigation lock and dam at Moss Bluff, Fla.; use, administration, and navigation...REGULATIONS § 207.169 Oklawaha River, navigation lock and dam at Moss Bluff, Fla.; use, administration, and...

2013-07-01

55

Turbulence Structure Within and Above a Canopy of Bluff Elements  

NASA Astrophysics Data System (ADS)

Measurements of turbulence structure in a wind-tunnel model canopy of bluff elements show many of the features associated with vegetation canopies and roughness sublayers but also display features more characteristic of the inertial sublayer (ISL). Points of similarity include the existence of an inflexion point in the space-time averaged streamwise velocity at the canopy top, the variation with height of turbulent second moments and the departure of the turbulent kinetic energy budget from local equilibrium in and just above the canopy. Quadrant analysis shows characteristic dominance of sweep over ejection events within the canopy although sweeps are more frequent than usually seen in vegetation canopies. Points of difference are a u', w' correlation coefficient that is closer to the ISL value than to most canopy data, and a turbulent Prandtl number midway between canopy and ISL values. Within the canopy there is distinct spatial partitioning into two flow regimes, the wake and non-wake regions. Both time-mean and conditional statistics take different values in these different regions of the canopy flow. We explain many of these features by appealing to a modified version of the mixing-layer hypothesis that links the dominant turbulent eddies to the instability of the inflexion point at canopy top. However, it is evident that these eddies are perturbed by the quasi-coherent wakes of the bluff canopy elements. Based upon an equation for the instantaneous velocity perturbation, we propose a criterion for deciding when the eddies linked to the inflexion point will dominate flow structure and when that structure will be replaced by an array of superimposed element wakes. In particular, we show that the resemblance of some features of the flow to the ISL does not mean that ISL dynamics operate within bluff-body canopies in any sense.

Böhm, Margi; Finnigan, John J.; Raupach, Michael R.; Hughes, Dale

2013-03-01

56

Drag reduction of a bluff body using adaptive control methods Jean-Franois Beaudoina  

E-print Network

Drag reduction of a bluff body using adaptive control methods Jean-François Beaudoina Department 2006 A classical actuator is used to control the drag exerted on a bluff body at large Reynolds number a rotating cylinder at the edge. The slow fluctuations of the total drag are directly measured by means

Wesfreid, José Eduardo

57

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

E-print Network

RESEARCH ARTICLE Drag and lift reduction of a 3D bluff-body using active vortex generators Jean forces (drag and lift) induced on the bluff- body is investigated. The high sensitivity to many geo demonstrated. The maximum drag reduction is -12%, while the maximum global lift reduc- tion can reach more than

Wesfreid, José Eduardo

58

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

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false Federal Dam, Oklawaha River, Moss Bluff, Fla...NAVIGATION REGULATIONS § 207.170 Federal Dam, Oklawaha River, Moss Bluff, Fla...times of high water, the discharge past the dam shall be regulated in such manner as...

2012-07-01

59

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

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 false Federal Dam, Oklawaha River, Moss Bluff, Fla...NAVIGATION REGULATIONS § 207.170 Federal Dam, Oklawaha River, Moss Bluff, Fla...times of high water, the discharge past the dam shall be regulated in such manner as...

2011-07-01

60

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

Code of Federal Regulations, 2014 CFR

...2014-07-01 2014-07-01 false Federal Dam, Oklawaha River, Moss Bluff, Fla...NAVIGATION REGULATIONS § 207.170 Federal Dam, Oklawaha River, Moss Bluff, Fla...times of high water, the discharge past the dam shall be regulated in such manner as...

2014-07-01

61

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

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Federal Dam, Oklawaha River, Moss Bluff, Fla...NAVIGATION REGULATIONS § 207.170 Federal Dam, Oklawaha River, Moss Bluff, Fla...times of high water, the discharge past the dam shall be regulated in such manner as...

2010-07-01

62

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

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Federal Dam, Oklawaha River, Moss Bluff, Fla...NAVIGATION REGULATIONS § 207.170 Federal Dam, Oklawaha River, Moss Bluff, Fla...times of high water, the discharge past the dam shall be regulated in such manner as...

2013-07-01

63

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.

64

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.; Guy, D.E., Jr.

1988-01-01

65

On point vortex models of exotic bluff body wakes  

NASA Astrophysics Data System (ADS)

Exotic vortex wakes, in which three or more vortices are generated during each shedding cycle, are frequently found in the wake of an oscillating bluff body. Two common examples are P+S wakes (with 3 vortices) and 2P wakes (with 4 vortices). We consider mathematical models of these wakes consisting of N = 3 or 4 point vortices with constant strengths in an inviscid fluid that is otherwise at rest in a singly-periodic domain. By enforcing constraints on the vortex strengths and, in the case of N = 4, on the symmetry of the vortex locations, the mathematical models reduce to integrable Hamiltonian systems. We compare the point vortex trajectories with two exotic wake patterns reported in the literature. Results support the use of point vortex modeling to investigate vortex dynamics in exotic wakes and suggest the need for additional classification of experimental wake patterns.

Stremler, Mark A.; Basu, Saikat

2014-12-01

66

78 FR 20942 - Niobrara Confluence and Ponca Bluffs Conservation Areas, NE and SD; Draft Environmental Impact...  

Federal Register 2010, 2011, 2012, 2013, 2014

...the Great Plains to the Eastern deciduous forest. It drains one-sixth of the...also experience scenic bluffs, forests, grasslands, and traditional...natural floodplain and upland forest communities, pastureland,...

2013-04-08

67

40 CFR 81.50 - Metropolitan Omaha-Council Bluffs Interstate Air Quality Control Region.  

Code of Federal Regulations, 2010 CFR

...Metropolitan Omaha-Council Bluffs Interstate Air Quality Control Region. 81.50 Section 81...CONTINUED) DESIGNATION OF AREAS FOR AIR QUALITY PLANNING PURPOSES Designation of Air Quality Control Regions § 81.50...

2010-07-01

68

Physical model study of enlarged fish ladders for Red Bluff Diversion Dam. Appendix B. Data results. Final investigations. Red Bluff Diversion Dam. Fish passage program. Final report  

SciTech Connect

The Bureau of Reclamation, Water Resources Research Laboratory, conducted a physical model study to determine the potential of enlarged fish ladders to improve adult fish passage at Red Bluff Diversion Dam (RBDD). Ineffective fish passage at RBDD has been identified as a contributing factor in the decline of the anadramous fishery resource along the Sacramento River in California. This study was requested under the recently initiated Red Bluff Fish Passage Program (a combined effort of the Bureau of Reclamation, the US Fish and Wildlife Service, the National Marine Fisheries Service, and the California Department of Fish and Game). The results indicate that enlarged ladders have significant potential for generating improved near and far field attraction flow conditions in the diversion dam tailrace, compared with existing ladders. Furthermore, recommended diversion dam operating conditions associated with the proposed enlarged ladders have been identified. These results are intended for use in the development and implementation of solutions for improving fish passage at Red Bluff Diversion Dam.

Kubitschek, J.

1997-09-01

69

Physical model study of enlarged fish ladders for Red Bluff Diversion Dam. Appendix A. Data results, 1994 preliminary investigations. Red Bluff Diversion Dam, fish passage program. Final report  

SciTech Connect

The Bureau of Reclamation, Water Resources Research Laboratory, conducted a physical model study to determine the potential of enlarged fish ladders to improve adult fish passage at Red Bluff Division Dam (RBDD). Ineffective fish passage at RBDD has been identified as a contributing factor in the decline of the anadramous fishery resource along the Sacramento River in California. This study was requested under the recently initiated Red Bluff Fish Passage Program (a combined effort of the Bureau of Reclamation, the US Fish and Wildlife Service, the National Marine Fisheries Service, and the California Department of Fish and Game). The results indicate that enlarged ladders have significant potential for generating improved near and far field attraction flow conditions in the diversion dam tailrace, compared with existing ladders. Furthermore, recommended diversion dam operating conditions associated with the proposed enlarged ladders have been identified. These results are intended for use in the development and implementation of solutions for improving fish passage at Red Bluff Diversion Dam.

Kubitschek, J.

1997-09-01

70

Water Balance, Salt Loading, and Salinity Control Options of Red Bluff Reservoir, Texas  

E-print Network

TR- 298 2007 Water Balance, Salt Loading, and Salinity Control Options of Red Bluff Reservoir, Texas by S. Miyamoto, Fasong Yuan, and Shilpa Anand Agricultural Research and Extension Center at El Paso Texas... Agricultural Experiment Station The Texas A&M University System Texas Water Resources Institute Texas A&M University WATER BALANCE, SALT LOADING, AND SALINITY CONTROL OPTIONS OF RED BLUFF RESERVOIR, TEXAS S. Miyamoto, Fasong...

Miyamoto, S.; Yuan, Fasong; Anand, Shilpa

71

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); Sabari, Kambiz (Livermore, CA)

2005-12-27

72

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

73

Thermal Modeling of NUHOMS HSM-15 and HSM-1 Storage Modules at Calvert Cliffs Nuclear Power Station ISFSI  

SciTech Connect

As part of the Used Fuel Disposition Campaign of the Department of Energy (DOE), visual inspections and temperature measurements were performed on two storage modules in the Calvert Cliffs Nuclear Power Station’s Independent Spent Fuel Storage Installation (ISFSI). Detailed thermal models models were developed to obtain realistic temperature predictions for actual storage systems, in contrast to conservative and bounding design basis calculations.

Suffield, Sarah R.; Fort, James A.; Adkins, Harold E.; Cuta, Judith M.; Collins, Brian A.; Siciliano, Edward R.

2012-10-01

74

Physical model study of enlarged fish ladders for Red Bluff Diversion Dam. Appendix B. Data results. Final investigations. Red Bluff Diversion Dam. Fish passage program. Final report  

Microsoft Academic Search

The Bureau of Reclamation, Water Resources Research Laboratory, conducted a physical model study to determine the potential of enlarged fish ladders to improve adult fish passage at Red Bluff Diversion Dam (RBDD). Ineffective fish passage at RBDD has been identified as a contributing factor in the decline of the anadramous fishery resource along the Sacramento River in California. This study

Kubitschek

1997-01-01

75

Physical model study of enlarged fish ladders for Red Bluff Diversion Dam. Appendix A. Data results, 1994 preliminary investigations. Red Bluff Diversion Dam, fish passage program. Final report  

Microsoft Academic Search

The Bureau of Reclamation, Water Resources Research Laboratory, conducted a physical model study to determine the potential of enlarged fish ladders to improve adult fish passage at Red Bluff Division Dam (RBDD). Ineffective fish passage at RBDD has been identified as a contributing factor in the decline of the anadramous fishery resource along the Sacramento River in California. This study

Kubitschek

1997-01-01

76

Bluff Body Flow Control Using Dielectric Barrier Discharge Plasma Actuators  

NASA Astrophysics Data System (ADS)

The results of an experimental investigation involving the use of dielectric barrier discharge plasma actuators to control bluff body flow is presented. The motivation for the work is plasma landing gear noise control for commercial transport aircraft. For these flow control experiments, the cylinder in cross-flow is chosen for study since it represents a generic flow geometry that is similar in all essential aspects to a landing gear strut. The current work is aimed both at extending the plasma flow control concept to Reynolds numbers typical of landing approach and take-off and on the development of optimum plasma actuation strategies. The cylinder wake flow with and without actuation are documented in detail using particle image velocimetry (PIV) and constant temperature hot-wire anemometry. The experiments are performed over a Reynolds number range extending to ReD=10^5. Using either steady or unsteady plasma actuation, it is demonstrated that even at the highest Reynolds number Karman shedding is totally eliminated and turbulence levels in the wake decrease by more than 50%. By minimizing the unsteady flow separation from the cylinder and associated large-scale wake vorticity, the radiated aerodynamic noise is also reduced.

Thomas, Flint; Kozlov, Alexey

2008-11-01

77

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

78

Lean blowoff of bluff body stabilized flames: Scaling and dynamics Santosh J. Shanbhogue, Sajjad Husain, Tim Lieuwen*  

E-print Network

¨hler number Edge flames Extinction strain rate a b s t r a c t This paper overviews the dynamics of bluff body by an absolutely unstable, sinuous instability associated with vortex shedding from the bluff body/temporally localized extinction occurs sporadically on near blowoff flames, manifested as ``holes'' in the flame sheet

Lieuwen, Timothy C.

79

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

80

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

81

DNS of turbulent flow past a bluff body with a compliant tensegrity surface  

NASA Astrophysics Data System (ADS)

Direct numerical simulation (DNS) is used to study turbulent incompressible flow past a bluff body with a compliant surface. We use a 3D time-dependent coordinate transformation to account for the motion of the bluff body surface. Spatially, the flow domain is discretized using a dealiased pseudospectral method in the axial and azimuthal directions, while the radial (wall-normal) direction is discretized using a finite difference scheme. The grid is stretched in the azimuthal direction, which is handled spectrally. This leads to a unique challenge when solving the Poisson equation in the fractional step method for the time march, which we address with both multigrid and preconditioned BiCGStab algorithms. We are presently extending this flow code with a model for the compliant bluff body surface based on the ``tensegrity fabric'' paradigm which combines compressive members (bars) and tensile members (tendons) in a stable, flexible network.

Karandikar, Anish; Bewley, Thomas

2007-11-01

82

Alteration of volcaniclastic deposits at Minna Bluff: Geochemical insights on mineralizing environment and climate during the Late Miocene in Antarctica  

NASA Astrophysics Data System (ADS)

minerals in volcaniclastic deposits at Minna Bluff, a 45 km long peninsula in the Ross Sea, are used to infer processes of alteration and environmental conditions in the Late Miocene. Glassy volcaniclastic deposits are altered and contain phillipsite and chabazite, low to high-Mg carbonates, chalcedony, and clay. The ?18O of carbonates and chalcedony is variable, ranging from -0.50 to 21.53‰ and 0.68 to 10.37‰, respectively, and ?D for chalcedony is light (-187.8 to -220.6‰), corresponding to Antarctic meteoric water. A mean carbonate 87Sr/86Sr ratio of 0.70327 ± 0.0009 (1?, n = 12) is comparable to lava and suggests freshwater, as opposed to seawater, caused the alteration. Minerals were precipitated at elevated temperatures (91 and 104°C) based on quartz-calcite equilibrium, carbonate 13C-18C thermometry (?47 derived temperature = 5° to 43°C) and stability of zeolites in geothermal systems (>10 to ˜100°C). The alteration was a result of isolated, ephemeral events involving the exchange between heated meteoric water and glass during or soon after the formation of each deposit. Near-surface evaporative distillation can explain 18O-enriched compositions for some Mg-rich carbonates and chalcedony. The ?18Owater calculated for carbonates (-15.8 to -22.9‰) reveals a broad change, becoming heavier between ˜12 and ˜7 Ma, consistent with a warming climate. These findings are independently corroborated by the interpretation of Late Miocene sedimentary sequences recovered from nearby sediment cores. However, in contrast to a cold-based thermal regime proposed for ice flow at core sites, wet-based conditions prevailed at Minna Bluff; a likely consequence of high heat flow associated with an active magma system.

Antibus, Joanne V.; Panter, Kurt S.; Wilch, Thomas I.; Dunbar, Nelia; McIntosh, William; Tripati, Aradhna; Bindeman, Ilya; Blusztajn, Jerzy

2014-08-01

83

Petroleum geology and exploration of Scotts Bluff trend, northeastern Denver basin, Nebraska  

Microsoft Academic Search

Ten J Sandstone oil fields form a long, narrow, northeast-southwest trend in western Nebraska. Except for these fields, this area is nonproductive of oil and gas. It is proposed that this group of related fields be termed the Scotts Bluff trend. Subsurface mapping indicates that recurrent movement along Precambrian basement faults has enhanced reservoir quality and localized oil migration, favoring

Matthew R. Silverman

1984-01-01

84

Towards Large Eddy Simulations of a Bluff Body Burner Using an Unstructured Grid  

Microsoft Academic Search

A Large Eddy Simulation of a bluff body flame has been carried out using an unstructured grid. The flame, burning a methane-hydrogen fuel with de- tailed combustion chemistry (based on a mechanism of 18 species) is simulated using STAR-CD. The mix- ture fraction is used as a conserved scalar, and a sub- sequently temperature, density and species mass frac- tion

Shafiq R. Qureshi; Robert Prosser

2007-01-01

85

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

86

Investigating vortex streets behind real and virtual bluff bodies: An experiment for an advanced undergraduate laboratory  

E-print Network

1 Investigating vortex streets behind real and virtual bluff bodies: An experiment for an advanced there is no real body present in the fluid. The force field (virtual body) is created by a permanent magnet located above the surface of water in combination with electric current applied in the horizontal direction

deYoung, Brad

87

Return to Coalsack Bluff and the Permian Triassic boundary in Antarctica  

Microsoft Academic Search

Coalsack Bluff was the first discovery site in Antarctica for the latest Permian to earliest Triassic reptile Lystrosaurus. This together with discovery of Permian Glossopteris leaves during the heroic age of Antarctic exploration, indicated not only that Antarctica was part of Gondwanaland, but also that Antarctic rocks recorded faunas from the greatest of all mass extinctions at the Permian Triassic

Gregory J. Retallack; Tara Greaver; A. Hope Jahren

2007-01-01

88

Preventing Bluff Agent Invasions in Honest Societies Robert Lowe and Daniel Polani  

E-print Network

is the threat of an elevated punishment or cost. Statistics from the ``British Crime Survey 2000 capable of imposing a `punishment' cost on bluffer agents. We found that in order for honest signalling to be immune to invasion by a bluff strategy, the number of punishment enforcers in the society must be high

Polani, Daniel

89

Flow and mixing fields of turbulent bluff-body jets and flames  

Microsoft Academic Search

The mean structure of turbulent bluff-body jets and flames is presented. Measurements of the flow and mixing fields are compared with predictions made using standard turbulence models. It is found that two vortices exist in the recirculation zone; an outer vortex close to the air coflow and an inner vortex between the outer vortex and the jet. The inner vortex

D F Fletcherz

90

Experimental investigation of the aerodynamic noise radiated by a three-dimensional bluff body  

E-print Network

Experimental investigation of the aerodynamic noise radiated by a three-dimensional bluff body J.fischer@univ-poitiers.fr Proceedings of the Acoustics 2012 Nantes Conference 23-27 April 2012, Nantes, France 2335 #12;Aerodynamic. The present work is an experimental study of the aerodynamic noise radiated by a three-dimensional simplified

Paris-Sud XI, Université de

91

Twin solution calorimeter determines heats of formation of alloys at high temperatures  

NASA Technical Reports Server (NTRS)

Calvert-type, twin liquid metal solution calorimeter determines the heats of formation of transition metal alloys at high temperatures. The twin differential calorimeter measures the small heat effects generated over extended periods of time, has maximum operating temperature of 1073 degrees K and an automatic data recording system.

Darby, J. B., Jr.; Kleb, R.; Kleppa, O. J.

1968-01-01

92

Numerical analysis of high velocity flow field around the bluff body  

NASA Astrophysics Data System (ADS)

A finite-volume numerical analysis method for the solution of three-dimensional incompressible steady Navier-Stokes equations in a general curvilinear coordinate system is presented. The main solution algorithm of the method is an extension of SIMPLE algorithm to present general curvilinear coordinate formulation. The standard k-epsilon two equations turbulence model is used for the closure of the Reynolds equation. Numerical analysis are compared with experimental results for the flow field around the U-shaped gutter in a diffuser with fairly good agreement. This method is applied to the calculation of turbulent three-dimensional flows around the bluff body to obtain the velocity and temperature flow field. A feature of the velocity and temperature field around the bluff body was clarified.

Sato, Yukinori; Toh, Hidemi; Ando, Yasunori; Kawai, Masafumi

1988-12-01

93

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

94

Petroleum geology, paleotectonics, and sedimentation of the Scotts Bluff Trend, northeastern Denver Basin  

Microsoft Academic Search

Ten J Sandstone oil fields form a long, narrow, northeast-southwest trend in western Nebraska. Except for these fields, this area is non-productive of oil and gas. It is proposed that this group of related fields be named the Scotts Bluff trend. The Cretaceous J Sandstone dips gently southwest across the northeastern Denver basin. Low-relief closures and structural noses are critical

Silverman

1988-01-01

95

Numerical Investigation of a Bluff-Body Stabilised Nonpremixed Flame with Differential Reynolds-Stress Models  

Microsoft Academic Search

A numerical investigation of a bluff-body stabilised nonpremixedflame, and the corresponding nonreacting flow, has been performed withdifferential Reynolds-stress models (DRSMs). The equilibrium chemistry model is employed and an assumed-shape beta function PDFapproach is used to represent the interaction between turbulence andchemistry. The Reynolds flux of the mixture fraction is obtained from atransport equation, hence a full second moment closure is

Guoxiu Li; Bertrand Naud; Dirk Roekaerts

2003-01-01

96

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

97

Surface changes on a landslide affected high bluff in Dunaszekcs? (Hungary)  

NASA Astrophysics Data System (ADS)

This article presents results from the survey conducted on Dunaszekcs? loess bluff after the last major rotational sliding event in 2008. The study area is a region of 25×30 m located on loess bluff close to the recent scarp. The relative elevation change of the surface was surveyed in 2.5×5 m grid network in relation to a marked base point. The survey was conducted using simple equipment such as analogue theodolite and leveller with regular time interval during a year and control measurements were taken after six months. It was assumed that measurements to the nearest cm are sufficient to recognize vertical displacements of the surface. The study focused on identifying the pattern of general vertical movements for the study area by the relative movements of individual points. Our results show significant cm scale vertical displacements. Most of the grid points have a slow decreasing tendency, but close to the scarp a more significant displacement was found. The main character of the spatial pattern is subsidence, which is more definitive on southern part of the study area than the northern part. Our observations correlate with the broader geomorphological characteristics of loess bluffs along the Danube.

Bugya, Titusz; Fábián, Szabolcs Á.; Görcs, Noémi L.; Kovács, István P.; Radvánszky, Bertalan

2011-06-01

98

Scaling properties of two-dimensional turbulence in wakes behind bluff bodies B. Protas,1,2,* S. Goujon-Durand,2,3,  

E-print Network

Scaling properties of two-dimensional turbulence in wakes behind bluff bodies B. Protas,1,2,* S consideration is the turbulent wake behind a bluff body with a developed enstrophy cascade and reduced inverse turbulence obtained by means of numerical simulation using the vortex blob method. The flow under

Protas, Bartosz

99

Global mode analysis of axisymmetric bluff-body wakes: Stabilization by base bleed E. Sanmiguel-Rojas, A. Sevilla, C. Martnez-Bazn, and J.-M. Chomaz  

E-print Network

Global mode analysis of axisymmetric bluff-body wakes: Stabilization by base bleed E. Sanmiguel.1063/1.2909609 A note on the stabilization of bluff-body wakes by low density base bleed Phys. Fluids 18, 098102 (2006 instability and global bleed control Phys. Fluids 16, 3460 (2004); 10.1063/1.1773071 A coupled Landau model

Paris-Sud XI, Université de

100

230. CCC Camp NP21 was established at the Bluffs (Doughton ...  

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

230. CCC Camp NP-21 was established at the Bluffs (Doughton Park) located on what is now the Doughton Park Maintenance Area. It opened September 1, 1938 and was abandoned July 17, 1942. Crews were assigned to the first landscape development on the parkway in the Cumberland Knob Area. This work entailed removal of debris and downed wood, slope flattening and rounding, seeding shoulders and planting along the road, and improvement of fields and forest to the side of the roadway. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

101

Return to Coalsack Bluff and the Permian Triassic boundary in Antarctica  

NASA Astrophysics Data System (ADS)

Coalsack Bluff was the first discovery site in Antarctica for the latest Permian to earliest Triassic reptile Lystrosaurus. This together with discovery of Permian Glossopteris leaves during the heroic age of Antarctic exploration, indicated not only that Antarctica was part of Gondwanaland, but also that Antarctic rocks recorded faunas from the greatest of all mass extinctions at the Permian-Triassic boundary. Pinpointing the exact stratigraphic level of this life crisis has recently become possible using ? 13C values in terrestrial organic matter. Multiple, short-lived events of 13C depletion may reflect carbon cycle crises, with the isotopic change a measure of terrestrial and atmospheric disequilibrium. Additional evidence for ecosystem reorganization came from changes in paleosol types and their root traces. Such studies previously completed at the Antarctic localities of Graphite Peak, Mount Crean, Portal Mountain, Shapeless Mountain and Allan Hills, are here extended to Coalsack Bluff. Carbon isotopic values in Permian rocks at Coalsack Bluff average - 23.08 ± 0.25‰, but begin to decline within the last coal with leaves ( Glossopteris), roots ( Vertebraria) and permineralized stumps ( Araucarioxylon) of glossopterids. The low point in ä 13C values is - 27.19‰ at 5.6 m above the last coal, which is capped by unusually abundant pyrite, and a claystone breccia with common clasts of redeposited clayey soils. Above this are massive quartz-rich sandstones of braided streams, considered a geomorphic response to deforestation and soil erosion following the mass extinction. Distinctive berthierine-bearing paleosols (Dolores pedotype) within these sandstones have unoxidized iron taken as evidence of severe groundwater hypoxia. Other paleosols at this stratigraphic level are like those in other Early Triassic rocks of Antarctica, which indicate unusually warm and humid conditions for such high paleolatitude lowlands. Waterlogging is also indicated by newly discovered kinds of paleosol (Ernest pedotype) with groundwater calcretes. The lack of peat accumulation in such waterlogged lowlands, berthierine in paleosols and large negative carbon isotopic shift at Coalsack Bluff support the idea of atmospheric pollution with methane from submarine and permafrost clathrates as a cause for the Permian-Triassic mass extinction. Hypoxic soils would have killed lowland plants by preventing root respiration and hypoxic air would have challenged vertebrates with pulmonary edema. Causes for catastrophic methane release remain unclear. Flood basalt eruptions, dolerite intrusions into coal measures, submarine landslides, tectonic faulting, and bolide impact suggested for episodes of methane release at other times are also plausible for the Permian-Triassic boundary.

Retallack, Gregory J.; Greaver, Tara; Jahren, A. Hope

2007-01-01

102

Characterization of the turbulent bistable flow regime of a 2 D bluff body wake disturbed by a small control cylinder  

NASA Astrophysics Data System (ADS)

A small control cylinder placed in a turbulent wake of a much larger 2 D bluff body can cause a significant increase in drag fluctuations. These fluctuations occur on timescales longer than the timescales of the vortex shedding. The critical positions of the control cylinder are highly localized. Ensemble averages of PIV acquisitions and pressure measurements at the base of the bluff body reveal a bistable wake regime. Long duration hot-wire measurements are used to characterize the states and the transition process. The results show that a stochastic process is responsible for the transitions between the two stable states.

Parezanovi?, Vladimir; Monchaux, Romain; Cadot, Olivier

2015-01-01

103

The molluscan fauna of the Alum Bluff group of Florida, Part II, Astartacea, Carditacea, Chamacea  

USGS Publications Warehouse

The first of the series of papers upon the Mollusca of the Alum Bluff group covered the orders of the Prionodesmacea and the Anomalodesmacea. The Mollusca were by the beginning of Miocene time so far advances in development that the great majority are included under the highest of the three orders, the Teleodesmacea, characterized in the adult stages by the differentiation of the hinge teeth into distinct cardinals and laterals. This paper, the second of the series, covers the most primitive of the Teleodesmacea in the Alum Bluff group. All three of the superfamilies considered - the Astartacea, the Carditaeea, and the Chamacea-are included under Dall's group of the Diogenodonta, which is characterized in the normal forms by one or two laterals and not more than three cardinals. The Carditacea are very closely related to the Astartacea in hinge armature but differ in the development of a pronounced radial sculpture. The Chamacea have until recently been considered an offshooting group from the Carditacea that have been greatly modified by their sessile habit. Some doubt has been thrown upon this relationship by the late morphologic studies of Odhner.

Gardner, Julia

1926-01-01

104

The use of plasma actuators for bluff body broadband noise control  

NASA Astrophysics Data System (ADS)

Experiments were conducted using plasma actuators to control broadband noise generated by a bluff body flow. The motivation behind the study was to explore the potential of plasma actuators to reduce landing gear noise during approach phase of an aircraft. The control effectiveness of both dielectric barrier discharge and sliding discharge plasma actuators were tested in laboratory environment, using a representative bluff body consisting of a circular cylinder and an oblique strut. Noise measurements were taken in an anechoic chamber using a phased microphone array and far-field microphones. Results showed that the upstream directed plasma forcing, located at ±90 deg on the upstream cylinder with respect to the approaching flow, could effectively attenuate the broadband noise radiated from the wake flow interaction with the downstream strut. With the same AC electrical power consumption, the sliding discharge with additional DC voltage was found to be more effective due to its elongated plasma distribution and higher induced flow momentum. Measurements using particle image velocimetry suggested that the flow speed impinging on the downstream strut was reduced by the upstream plasma forcing, contributing to the reduced noise.

Li, Yong; Zhang, Xin; Huang, Xun

2010-08-01

105

The composition and diagenesis of the Upper Queen Formation (Guadalupian, Permian) at Concho Bluff North and Concho Bluff Queen Fields, Upton and Crane Counties, Texas  

E-print Network

dissolution voids (Figure 24H). Therefore, the aluminum and silicon released from feldspars within the sandflat facies probably served as the in situ primary source for precipitation of kaolinite. RESERVOIR PROPERTIES Reservoir horizons in the upper Queen...) potassium feldspar overgrowths, and (4) pore-filling anhydrite, dolomite, and halite cements during an early diagenetic phase. Subsequent dissolution of the anhydrite, dolomite, and halite by acidic pore-waters created high porosities (mean=15/o...

McKone, Charles Joseph

2012-06-07

106

The Illinois Natural Heritage Conservation Education Kit V. [Ecology and Management of Special Habitats: Dune, Cave, Cliff, Bluff, and Urban.  

ERIC Educational Resources Information Center

The ecology and management of special habitats is the theme of this instructional guide. It contains 24 activities designed to help teachers familiarize their students with dune, cave, cliff, bluff, and urban habitats in Illinois. Each activity (which is ready to be copied and given to students) includes an objective (called a mission) and…

Stone, Sally F.

107

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

108

Experimental investigation on longitudinal vortex control over a dihedral bluff body  

NASA Astrophysics Data System (ADS)

The present paper addresses an experimental investigation of the dynamic and the control of a longitudinal vortex emanating from the front pillar of a dihedral bluff body corresponding to a simplified geometry of an automotive vehicle. The control system is based on a thin rectangular slot located along the lateral edge of the windscreen and provides steady suction or blowing normal to the lateral face of the geometry. Qualitative results obtained with dye visualizations and Schlieren photos provide an overview of the impact of the control on the topology of the vortex flow. Quantitative Stereo-PIV measurements and unsteady forces measurements are used to characterize the interaction between the control and the longitudinal vortex. Controls that change significantly the topology of the vortex core and reduce aerodynamic drag are identified.

Lehugeur, Benjamin; Gilliéron, Patrick; Kourta, Azeddine

2010-01-01

109

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

110

Experimental investigation of galloping piezoelectric energy harvesters with square bluff bodies  

NASA Astrophysics Data System (ADS)

In this paper, both a baseline galloping piezoelectric energy harvester (GPEH) with a square bluff body and an improved GPEH with an impact bump stop are tested in a wind tunnel in order to determine the system damping, electrical response and limit cycle oscillation (LCO) amplitude. In the baseline GPEH, harvested voltage, LCO amplitude and damping ratio vary with wind velocity and electrical load. They all increase with increasing wind velocity under the same electrical load. Under each wind velocity, the damping ratio increases from the short circuit load, reaches a peak value at the electrical load resulting in a maximum voltage, and reduces the value at the open circuit load. The LCO amplitude shows the opposite trend compared to the damping case. It decreases as the electrical resistance load increases and reaches the minimum value when the damping ratio is highest. A resistance load of 100 k? yields a maximum peak power output. The impact stop is introduced to reduce bending stresses and improve the fatigue life of the baseline GPEH. The performance of the improved GPEH depends on the stop design parameters such as gap size, stop location and contact area. Comprehensive tests were conducted to investigate the effect of each parameter on the performance of the improved GPEH and an optimal bump stop configuration was determined. Compared to the expected proportional reduction in both electrical and structural responses, a maximum 70% reduction in LCO amplitude and only a maximum 20% reduction in harvested voltage are achieved in our optimal improved GPEH. The time variable and motion dependent aerodynamic forces acting on the bluff body could contribute to this. In summary, comprehensive experimental evaluations were conducted to characterize the performance of both baseline GPEHs and improved GPEHs. The baseline GPEH service life can be significantly improved by incorporating an impact bump stop. The improved GPEH design provides a practical solution to harvest electricity from wind-induced vibration.

Ewere, Felix; Wang, Gang; Cain, Brian

2014-10-01

111

A comparison of dispersion calculations in bluff body wakes using LES and unsteady RANS  

SciTech Connect

Accurate modeling of the dispersion behavior of sprays or particles is critical for a variety of problems including combustion, urban pollution or release events, and splash and spray transport around heavy vehicles. Bluff body wakes are particularly challenging since these flows are both highly separated and strongly unsteady. Attempting to model the dispersion of droplets or particles interacting with bluff body wakes is even more difficult since small differences in the flow field encountered by particles can lead to large differences in the dispersion behavior. Particles with finite inertia can exhibit additional complicating effects such as preferential concentration. In this preliminary study, we consider the dispersion of solid particles in the wake of a rectangular plane at a Reynolds number (Re) of 10000 and that of droplets in the wake of a simplified tractor-trailer geometry at Re = 2 x 10{sup 6} using both the Large Eddy Simulation (LES) and Unsteady Reynolds-Averaged Navier-Stokes (URANS) turbulence modeling approaches. The calculations were performed using identical meshes for both the LES and URANS models. Particle stresses are not backcoupled to the carrier fluid velocity solution. In the case of the rectangular plane wake, the LES calculation predicts a finer-scale and more persistent wake structure than the URANS one; the resulting particle dispersion is considerably ({approx} 40%) underpredicted for low inertia particles. For the case of the simplified tractor-trailer geometry, although the LES is underresolved, similar trends are observed with strong differences in the vertical and horizontal dispersion of the smallest particles. These results suggest that it may be necessary to use LES to accurately capture the dispersion behavior of small, low inertia particles or droplets, but that URANS may be sufficient for problems in which only large particles with substantial inertia are of primary concern.

Paschkewitz, J S

2006-01-19

112

Error analysis of large-eddy simulation of the turbulent non-premixed sydney bluff-body flame  

Microsoft Academic Search

A computational error analysis is applied to the large-eddy simulation of the turbulent non-premixed Sydney bluff-body flame, where the error is defined with respect to experimental data. The error-landscape approach is extended to heterogeneous compressible turbulence, which is coupled to combustion as described by a flamelet model. The Smagorinsky model formulation is used to model the unknown turbulent stresses. We

A. M. Kempf; B. J. Geurts; J. C. Oefelein

2011-01-01

113

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

114

Transported PDF Modelling of a High Velocity Bluff-Body Stabilised Flame (HM2) Using Detailed Chemistry  

Microsoft Academic Search

A transported probability density function (PDF) approach closed at the joint scalar level was used to model a bluff body\\u000a stabilised turbulent diffusion flame (HM2) investigated experimentally by Masri and co-workers. The current effort extends\\u000a a previous study of HM1 (Re?=?15,800) to a flame with a higher degree of local extinction (Re?=?23,900). The impact of an algebraic model that accounts

Konstantinos Gkagkas; R. Peter Lindstedt; Tek S. Kuan

2009-01-01

115

Boattail Plates With Non-Rectangular Geometries For Reducing Aerodynamic Base Drag Of A Bluff Body In Ground Effect  

DOEpatents

An apparatus for reducing the aerodynamic base drag of a bluff body having a leading end, a trailing end, a top surface, opposing left and right side surfaces, and a base surface at the trailing end substantially normal to a longitudinal centerline of the bluff body, with the base surface joined (1) to the left side surface at a left trailing edge, (2) to the right side surface at a right trailing edge, and (3) to the top surface at a top trailing edge. The apparatus includes left and right vertical boattail plates which are orthogonally attached to the base surface of the bluff body and inwardly offset from the left and right trailing edges, respectively. This produces left and right vertical channels which generate, in a flowstream substantially parallel to the longitudinal centerline, respective left and right vertically-aligned vortical structures, with the left and right vertical boattail plates each having a plate width defined by a rear edge of the plate spaced from the base surface. Each plate also has a peak plate width at a location between top and bottom ends of the plate corresponding to a peak vortex of the respective vertically-aligned vortical structures.

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

2006-03-07

116

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

117

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

118

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

119

Base pressure prediction in bluff-body potential-flow models  

NASA Astrophysics Data System (ADS)

In a recent study by Yeung & Parkinson (1997), a wake width was proposed which allowed the bluff-body potential-flow model by Parkinson & Jandali (1970) to be extended to include the flow around an oblique flat plate. By incorporating this wake width in the momentum equation originally derived by Eppler (1954) for separated flow, the drag of the plate is related to its inclination and base pressure through a simple analytical condition. It allows the base pressure, which is usually treated as an empirical input, to be determined theoretically and thus the model becomes self-contained. Predictions of the base pressure, drag and width of wake are found to be in reasonable agreement with the experimental data. When applied to the symmetrical flow around a wedge of arbitrary vertex angle, similar agreement with experimental measurements is obtained as well. It is also demonstrated that this condition is compatible with the free-streamline models by Wu (1962) and Wu & Wang (1964) such that the corresponding predictions are in good agreement with experiment.

Yeung, W. W. H.; Parkinson, G. V.

2000-11-01

120

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

121

Dynamical-systems analysis and unstable periodic orbits in reacting flows behind symmetric bluff bodies.  

PubMed

Dynamical systems analysis is performed for reacting flows stabilized behind four symmetric bluff bodies to determine the effects of shape on the nature of flame stability, acoustic coupling, and vortex shedding. The task requires separation of regular, repeatable aspects of the flow from experimental noise and highly irregular, nonrepeatable small-scale structures caused primarily by viscous-mediated energy cascading. The experimental systems are invariant under a reflection, and symmetric vortex shedding is observed throughout the parameter range. As the equivalence ratio-and, hence, acoustic coupling-is reduced, a symmetry-breaking transition to von Karman vortices is initiated. Combining principal-components analysis with a symmetry-based filtering, we construct bifurcation diagrams for the onset and growth of von Karman vortices. We also compute Lyapunov exponents for each flame holder to help quantify the transitions. Furthermore, we outline changes in the phase-space orbits that accompany the onset of von Karman vortex shedding and compute unstable periodic orbits (UPOs) embedded in the complex flows prior to and following the bifurcation. For each flame holder, we find a single UPO in flows without von Karman vortices and a pair of UPOs in flows with von Karman vortices. These periodic orbits organize the dynamics of the flow and can be used to reduce or control flow irregularities. By subtracting them from the overall flow, we are able to deduce the nature of irregular facets of the flows. PMID:24125348

Hua, Jia-Chen; Gunaratne, Gemunu H; Kostka, Stanislav; Jiang, Naibo; Kiel, Barry V; Gord, James R; Roy, Sukesh

2013-09-01

122

Detailed Ar-Ar Geochronology of Volcanism at Minna Bluff, Antarctica: Two-Phased Growth and Influence on Ross Ice Shelf  

NASA Astrophysics Data System (ADS)

Minna Bluff has been a significant topographic barrier to the flow of the Ross Ice Shelf since the mid-Miocene. Detailed Ar-Ar analyses of kaersutite and sanidine phenocrysts, and groundmass concentrates from volcanic units indicate an overall west to east progression of volcanic activity. Eruptions of basaltic to intermediate lavas, domes, and scoria cones started at ~12 Ma in at what is now the eastern most point of Minna Bluff, "Minna Hook." Activity was centered in this area for ~4 Ma, constructing a pre-Minna Bluff island. Multiple glacial unconformities found at Minna Hook suggest repeated interaction with large warm-based, erosive ice sheets. Activity migrated westward from Minna Bluff Island at 7-8 Ma closing the gap created by the island and the mainland. Significant edifice construction continued until 4-5 Ma with sporadic and parasitic scoria cone eruptions, possibly associated with Mt. Discovery activity, continuing until 2 Ma. The orientations of Minna Bluff's two major axes are strongly controlled by regional tectonic features. Minna Bluff's E-W axis, McIntosh Cliffs, is sub-parallel to the Radial Lineament and the N-S axis, Minna Hook, appears as extension of faulting bounding the Terror Rift. The constructional evolution of the 70km long volcanic complex has an important role in interpreting the climate signals recovered by the ANDRILL Project. Minna Bluff influenced the material delivered to the AND-1B drill site (ANDRILL MIS 2006-2007) in three critical ways: 1) Minna Bluff diverted upstream material, 2) provided a pinning and stabilizing point for the Ross Ice Shelf, possible controlling the calving line prior to the emergence of Ross Island, and 3) was a significant source of fresh volcanic material throughout much of the period recovered by ANDRILL MIS. For example, a kaersutite-bearing clast recovered from 822.78 mbsf in AND-1B yielded an age of 8.53±0.51 Ma, and was likely derived from Minna Bluff. The results from this study can be incorporated into detailed glacier and ice-sheet models of the McMurdo Sound region, a critical area in the Ross Ice Sheet and global climate system.

Ross, J. I.; McIntosh, W. C.; Wilch, T. I.

2012-12-01

123

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

124

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

125

Closed-loop bluff-body wake stabilization via fluidic excitation  

NASA Astrophysics Data System (ADS)

This article describes an experimental study aimed at stabilizing the wake of a shedding bluff-body by means of closed-loop active flow control at low Reynolds numbers. A D-shaped (6.5 mm thick) cylinder was used to allow a direct wake interaction rather than mixed wake-boundary-layer separation control. The fluidic actuators, installed inside the thin body, were ideally located at the separation locations, i.e., the trailing edges' upper and lower corners. The wake unsteadiness was monitored by a pair of hot wires (HWs), while a single surface-mounted hot-film (HF) sensor was used as a frequency and phase reference for closed-loop control. The HF signal was contaminated by noise. Hence, a technique for real-time tracking of a low signal-to-noise ratio (SNR) signal was necessary. This was achieved by means of a Phase-Locked Loop (PLL), common in communications systems. The closed-loop scheme was based on real-time measurement of the wake-state, using the surface-mounted HF sensor, and control authority imposed by the fluidic actuators. By using opposition control at frequencies close to the natural vortex shedding frequency (VSF), it was possible to significantly reduce the wake unsteadiness. Applying the same approach, but sensing the wake HW signal, rather than the surface-mounted HF signal, as the controller input did not result in wake stabilization. On the contrary, the unsteadiness increased at all the tested conditions. It is expected that a similar approach would work at much higher Reynolds numbers as well, as long as a clearly identifiable and nominally 2D vortex shedding occurs, even when the background flow is fully turbulent.

Stalnov, O.; Fono, I.; Seifert, A.

2011-06-01

126

Instantaneous and mean compositional structure of bluff-body stabilized nonpremixed flames  

SciTech Connect

Turbulent nonpremixed flames stabilized on an axisymmetric bluff-body burner are studied with fuels ranging from simple H{sub 2}/CO to complex H{sub 2}/CH{sub 4} and gaseous methanol. The fuel-jet velocity is varied to investigate the Damkoehler number effects on gas emissions, localized extinction (LE) in the neck zone, and the structure of the recirculation zone dependency on the flow field. Simultaneous, single-point measurements of temperature, major species, OH, and NO are made using the Raman/Rayleigh/Laser induced fluorescence (LIF) technique. The data are collected at different axial and radial locations along the full length of most flames and are presented in the form of ensemble means, root-mean-square (rms) fluctuations, scatter plots, and probability density functions (PDF). It is found that up to three mixing layers may exist in the recirculation zone, one on the air side of the outer vortex, one between the inner and the outer vortices, and one between the fuel jet and the inner vortex. With increasing jet momentum flux, the average mixture in the outer vortex loses its strength and the stoichiometric contour shifts closer to the fuel jet. The decay rate of the mixture fraction on the centerline exhibits similar trends to the ordinary jet flame downstream of the recirculation zone whereas different trends are found inside the recirculation zone. The laminar flame computations with constant mass diffusivities and Lewis number (Le) = 1 are found to better guides for the measured temperature and stable species mass fraction in the turbulent flames. The measured peak mass fractions of CO and H{sub 2} are similar to those reported earlier for pilot-stabilized flames of similar fuels. Hydroxyl radical and H{sub 2} are found not to be in superflamelet levels contrary to earlier findings in piloted flames.

Dally, B.B.; Masri, A.R. [Univ. of Sydney, New South Wales (Australia). Dept. of Mechanical and Mechatronic Engineering] [Univ. of Sydney, New South Wales (Australia). Dept. of Mechanical and Mechatronic Engineering; Barlow, R.S.; Fiechtner, G.J. [Sandia National Labs., Livermore, CA (United States). Combustion Research Facility] [Sandia National Labs., Livermore, CA (United States). Combustion Research Facility

1998-07-01

127

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.

128

Joint Scalar versus Joint Velocity-Scalar PDF Simulations of Bluff-Body Stabilized Flames with REDIM  

Microsoft Academic Search

Two transported PDF strategies, joint velocity-scalar PDF (JVSPDF) and joint scalar PDF (JSPDF), are investigated for bluff-body\\u000a stabilized jet-type turbulent diffusion flames with a variable degree of turbulence–chemistry interaction. Chemistry is modeled\\u000a by means of the novel reaction-diffusion manifold (REDIM) technique. A detailed chemistry mechanism is reduced, including\\u000a diffusion effects, with N\\u000a 2 and CO\\u000a 2 mass fractions as reduced

B. Merci; B. Naud; D. Roekaerts; U. Maas

2009-01-01

129

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

130

Properties of the mean recirculation region in the wakes of two-dimensional bluff bodies  

NASA Astrophysics Data System (ADS)

The properties of the time- and span-averaged mean wake recirculation region are investigated in separated flows over several different two-dimensional bluff bodies. Ten different cases are considered and they divide into two groups: cylindrical geometries of circular, elliptic and square cross-sections and the normal plate. A wide Reynolds number range from 250 to 140000 is considered, but in all the cases the attached portion of the boundary layer remains laminar until separation. The lower Reynolds number data are from direct numerical simulations, while the data at the higher Reynolds number are obtained from large-eddy simulation and the experimental work of Cantwell & Coles (1983), Krothapalli (1996, personal communication), Leder (1991) and Lyn et al. (1995). Unlike supersonic and subsonic separations with a splitter plate in the wake, in all the cases considered here there is strong interaction between the shear layers resulting in Kármán vortex shedding. The impact of this fundamental difference on the distribution of Reynolds stress components and pressure in relation to the mean wake recirculation region (wake bubble) is considered. It is observed that in all cases the contribution from Reynolds normal stress to the force balance of the wake bubble is significant. In fact, in the cylinder geometries this contribution can outweigh the net force from the shear stress, so that the net pressure force tends to push the bubble away from the body. In contrast, in the case of normal plate, owing to the longer wake, the net contribution from shear stress outweighs that from the normal stress. At higher Reynolds numbers, separation of the Reynolds stress components into incoherent contributions provides more insight. The behaviour of the coherent contribution, arising from the dominant vortex shedding, is similar to that at lower Reynolds numbers. The incoherent contribution to Reynolds stress, arising from small-scale activity, is compared with that of a canonical free shear layer. Based on these observations a simple extension of the wake model (Sychev 1982; Roshko 1993a, b) is proposed.

Balachandar, S.; Mittal, R.; Najjar, F. M.

1997-11-01

131

Scappoose Formation, Columbia County, Oregon: new evidence of age and relation to Columbia River basalt group  

SciTech Connect

The Scappoose Formation, considered to be late Oligocene to early Miocene in age, was originally believed to be disconformably separated from both the underlying Pittsburg Bluff Formation and the overlying Yakima subgroup of the Columbia River Basalt Group. Recent mapping and petrography show that it lies disconformably on both the Keasey and Pittsburg Bluff Formations, and interfingers with the Yakima Basalt. The Scappoose is composed of fluvial sandstone, conglomerate, and carbonaceous to coal-bearing mud rock, intertongued with shallow neritic to estuarine siltstone, mud rock, and minor sandstone. Chemistry of basalt clasts from fluvial conglomerates reveals that they are derived from the Yakima subgroup. Basalt conglomerate and palagonitic sediments in the upper part of the formation are intercalated with Grande Ronde basalt (Yakima subgroup) flows at many localities. Flows of Yakima Basalt are also invasive into originally wet, unconsolidated Scappoose sediment. Grande Ronde basalt and the Frenchman Springs Member of the Wanapum basalt overlie conglomerate of the Scappoose. In places, the Scappoose Formation is absent, and Yakima Basalt lies directly on the Pittsburg Bluff and Keasey Formations. The thickness of both the Scappoose Formation and the Columbia River Basalt Group varies widely, indicating that both were deposited over a paleotopography with a relief up to 800 ft (245 m). The definition of the boundaries of the Scappoose Formation should be revised, owing to the disconformable relation of the Scappoose to both the underlying Keasey and Pittsburg Bluff Formations and to the Scappoose's intercalation with the overlying Yakima Basalt. Definition of age must also be revised, inasmuch as sedimentation of the formation was coeval with Columbia River Basalt volcanism.

VanAtta, R.O.; Kelty, K.B.

1985-05-01

132

Large eddy simulation of bluff body stabilized premixed and partially premixed combustion  

NASA Astrophysics Data System (ADS)

Large Eddy Simulation (LES) of bluff body stabilized premixed and partially premixed combustion close to the flammability limit is carried out in this thesis. The main goal of the thesis is the study of the equivalence ratio effect on flame stability and dynamics in premixed and partially premixed flames. An LES numerical algorithm able to handle the entire range of combustion regimes and equivalence ratios is developed for this purpose. The algorithm has no ad-hoc adjustable model parameters and is able to respond automatically to variations in the inflow conditions, without user intervention. Algorithm validation is achieved by conducting LES of reactive and non-reactive flow. Comparison with experimental data shows good agreement for both mean and unsteady flow properties. In the reactive flow, two scalar closure models, Eddy Break-Up (EBULES) and Linear Eddy Mixing (LEMLES), are used and compared. Over important regions, the flame lies in the Broken Reaction Zone regime. Here, the EBU model assumptions fail. In LEMLES, the reaction-diffusion equation is not filtered, but resolved on a linear domain and the model maintains validity. The flame thickness predicted by LEMLES is smaller and the flame is faster to respond to turbulent fluctuations, resulting in a more significant wrinkling of the flame surface when compared to EBULES. As a result, LEMLES captures better the subtle effects of the flame-turbulence interaction, the flame structure shows higher complexity, and the far field spreading of the wake is closer to the experimental observations. Three premixed (? = 0.6, 0.65, and 0.75) cases are simulated. As expected, for the leaner case (? = 0.6) the flame temperature is lower, the heat release is reduced and vorticity is stronger. As a result, the flame in this case is found to be unstable. In the rich case (? = 0.75), the flame temperature is higher, and the spreading rate of the wake is increased due to the higher amount of heat release. The ignition delay in the lean case (? = 0.6) is larger when compared to the rich case (? = 0.75), in correlation with the instantaneous flame stretch. Partially premixed combustion is simulated for cases where the transverse profile of the inflow equivalence ratio is variable. The simulations show that for mixtures leaner in the core the vortical pattern tends towards anti-symmetry and the heat release decreases, resulting also in instability of the flame. For mixtures richer in the core, the flame displays sinusoidal flapping that results in larger wake spreading. The numerical simulations presented in this study employed simple, one-step chemical mechanisms. More accurate predictions of flame stability will require the use of detailed chemistry, raising the computational cost of the simulation. To address this issue, a novel algorithm for training Artificial Neural Networks (ANN) for prediction of the chemical source terms has been implemented and tested. Compared to earlier methods, such as reaction rate tabulation, the main advantages of the ANN method are in CPU time and disk space and memory reduction. The results of the testing indicate reasonable algorithm accuracy although some regions of the flame exhibit relatively significant differences compared to direct integration.

Porumbel, Ionut

133

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.

134

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

135

Strouhal-Reynolds number relationship for bluff-body flows numerically simulated by an artificial boundary method.  

PubMed

The incidence of the numerical resolution and the blockage effect are investigated in an embedding method for solving bidimensional bluff body flows. This method consists of using an artificial boundary instead of imposing exact conditions on the body surface. It requires us to define a blur frontier ratio and a blockage effect ratio. The blockage effect ratio is found using the mean flow of a circular cylinder directly. The blur frontier ratio is obtained by comparison of the present method with another numerical method where explicit boundary conditions on the body are imposed. For this ratio, the investigations are based on the flow past a square cylinder which discard the uncertainty on the surface of the body for the embedding method. Hence, the two factors allow the transformations of the Strouhal and the Reynolds numbers for the flow past a circular cylinder. The universal Strouhal-Reynolds number relationship of the circular cylinder is finally recovered. PMID:14682839

Ravoux, J F; Provansal, M; Nadim, A; Schouveiler, L

2003-11-01

136

Reconnaissance of Acid Drainage Sources and Preliminary Evaluation of Remedial Alternatives at the Copper Bluff Mine, Hoopa Valley Reservation, California  

USGS Publications Warehouse

Acidic drainage from the inactive Copper Bluff mine cascades down a steep embankment into the Trinity River, on the Hoopa Valley Reservation in northern California. The Copper Bluff mine produced about 100,000 tons of sulfide-bearing copper-zinc-gold-silver ore during 1957?1962. This report summarizes the results of a water-resources investigation begun by the U.S. Geological Survey in 1994 with the overall objective of gathering sufficient geochemical, hydrologic, and geologic information so that a sound remediation strategy for the Copper Bluff mine could be selected and implemented by the Hoopa Valley Tribe. This study had the following specific objectives: (1) monitor the quality and quantity of the mine discharge, (2) determine seasonal variability of metal concentrations and loads, (3) map and sample the underground mine workings to determine sources of flow and suitability of mine plugging options, and (4) analyze the likely consequences of various remediation and treatment options. Analysis of weekly water samples of adit discharge over parts of two wet seasons (January to July 1995 and October 1995 to May 1996) shows that dissolved copper (Cu) and zinc (Zn) concentrations (in samples filtered with 0.20-micrometer membranes) varied systematically in a seasonal pattern. Metal concentrations increased dramatically in response to the first increase in discharge, or first flush, early in the wet season. The value of Zn/Cu in the adit discharge exhibited systematic seasonal variations; an annual Zn/Cu cycle was observed, beginning with values between 3 and 5 during the main part of the wet season, rising to values between 6 and 10 during the period of lowest discharge late in the dry season, and then dropping dramatically to values less than 3 during the first-flush period. Values of pH were fairly constant in the range of 3.1 to 3.8 throughout the wet season and into the beginning of the dry season, but rose to values between 4.5 and 5.6 during the period of lowest discharge, from October to early December 1995. Underground reconnaissance was conducted once during dry-season conditions (September 1995) and twice during wet-season conditions (March 1995 and March 1996). The main tunnel was accessed to a distance of about 600 feet from the portal entrance. Water samples were collected at nine locations along the floor of the main tunnel and from several ore shoots to evaluate the contributions of water and dissolved constituents from different portions of the mine. Values of pH ranged from 2.5 to 6.4 at different underground locations, concentrations of copper ranged from 0.020 to 44 mg/L (milligram per liter), zinc from 6.3 to 160 mg/L, and cadmium from 0.010 to 0.47 mg/L. Discharge from the ore shoots ranged from less than 1 gallon per minute to more than 30 gallons per minute and was always a small component of the total mine flow compared with the tunnel floor drainage. During March 1996, the main flow originated in the northernmost portion of the underground workings (inaccessible) and mixed with an unknown quantity of water upwelling from flooded lower workings. High-water marks observed on the tunnel walls indicate that past blockages impounded more than 100,000 gallons of water. Sudden release of a large volume of metal-rich water could have serious effects on fish and other aquatic resources in the Trinity River. Because of the hydrogeologic setting, mine plugging is not likely to offer an effective long-term solution to the problem of acid mine drainage at the Copper Bluff mine. The underground workings are close to a state highway and underlie a 500-foot-high bluff with highly fractured rocks that seep during the wet season. Total plugging likely would result in additional uncontrolled seepage and could potentially destabilize the highway. Partial plugging to restrict flow during periods of highest discharge may provide benefits in terms of reduced risk of catastrophic release without the addi

Alpers, Charles N.; Hunerlach, Michael P.; Hamlin, Scott N.; Zierenberg, Robert A.

2003-01-01

137

Study of hydrocarbon miscible solvent slug injection process for improved recovery of heavy oil from Schrader Bluff Pool, Milne Point Unit, Alaska. Final report  

SciTech Connect

The National Energy Strategy Plan (NES) has called for 900,000 barrels/day production of heavy oil in the mid-1990s to meet our national needs. To achieve this goal, it is important that the Alaskan heavy oil fields be brought to production. Alaska has more than 25 billion barrels of heavy oil deposits. Conoco, and now BP Exploration have been producing from Schrader Bluff Pool, which is part of the super heavy oil field known as West Sak Field. Schrader Bluff reservoir, located in the Milne Point Unit, North Slope of Alaska, is estimated to contain up to 1.5 billion barrels of (14 to 21{degrees}API) oil in place. The field is currently under production by primary depletion; however, the primary recovery will be much smaller than expected. Hence, waterflooding will be implemented earlier than anticipated. The eventual use of enhanced oil recovery (EOR) techniques, such as hydrocarbon miscible solvent slug injection process, is vital for recovery of additional oil from this reservoir. The purpose of this research project was to determine the nature of miscible solvent slug which would be commercially feasible, to evaluate the performance of the hydrocarbon miscible solvent slug process, and to assess the feasibility of this process for improved recovery of heavy oil from Schrader Bluff reservoir. The laboratory experimental work includes: slim tube displacement experiments and coreflood experiments. The components of solvent slug includes only those which are available on the North Slope of Alaska.

NONE

1995-11-01

138

Analysis of river planforms in the New Madrid region and possible relations to tectonic warping across the loess bluffs and within the meander belt of the Mississippi River  

SciTech Connect

Stream channel planforms measured from such streams as the Hatchie (H), L'Anguille (LA), St. Francis, White (W) and Little Red (LR) rivers provide a way to study influences of topographic warping between the loess bluffs that bound the Mississippi river valley. Planforms are analyzed using sinuosity, Richardson analysis, and pattern. Pattern changes include transitions from braided to meandering and meandering to straight. Sinuosities of the W and LR rivers show a transition from low sinuosity, [1.3, 1.4] to higher sinuosity [2.6, 2.8], over a short distance, as they cross the bluffs from the uplands to the Western Lowlands. On the east, the Hatchie changes from a braided to meandering pattern upon crossing the bluffs. Its sinuosity varies from a low of about 1.4 to a high of 2.2, coincident with a marsh area. The LA river flows on the west side of Crowley's Ridge and is paralleled by the St. Francis river on the east. These rivers, with very different drainage areas and sinuosities, show matching meander bends at similar wavelengths along Crowley's Ridge. The bends are about 10 km in 1/2 wavelength suggesting some extraordinary influence on pattern perpendicular to the ridge. Richardson analysis indicates that features with a 1/2 wavelength of 2 km may control several rivers' bending patterns. These features are analyzed to determine their spatial relations with one another.

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

1993-03-01

139

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

140

Prediction of turbulent recirculating flow field behind a V-shaped bluff body using a nonlinear low Reynolds number k-epsilon model  

NASA Astrophysics Data System (ADS)

A new localized smoothing filter based on the least squares is proposed in this study. It has been found the use of an appropriate smoothing method is critical to the success of numerical prediction of separating flow problems with nonlinear turbulence models. The new smoothing filter effectively eliminated numerical fluctuations due to the nonlineality of the turbulence model and the higher order approximation. The efficiency of using this scheme is very attractive; less than 20% more CPU time is needed for the extra computation in simulations. Modification has been made to the nonlinear model to take into consideration of low Reynolds number effects. The two-dimensional turbulent recirculating flow field behind a V-shaped bluff body has been investigated numerically. Similar bluff bodies are used in combustion chambers for flame stabilization. The study helps to gain a comprehensive understanding of the mechanism of the flame stability and major factors that affect this stability, and thereby establishes a more reasonable physical model. The validation test of turbulent flow over a backward facing step shows that the modified nonlinear turbulence model significantly improved the overall prediction. Predicted results for both mean flow field and turbulence quantities agreed very well experimental results. The prediction error for the characteristic reattachment length has been reduced from 18% to 4% compared with the experimental data. The results of simulation of flow field behind the bluff body are also improved by using this model. The degree of improvement varies for different flow variables. Parametric investigation of the flow field by varying the shape and size of the bluff body is also performed. It has been found that the axial distributions of normalized reverse mass flow rate for different configurations are similar. The maximum reverse mass flow rate increases monotonically with the base height as well as with the included angle of the bluff body, but normalized axial location of the maximum reverse mass flow rate remains unchanged. Similarly, although the separation bubble length increases linearly rate remains unchanged. Similarly, although the separation bubble length increases linearly as the base height or included angle is increased, the normalized separation bubble length is almost the same for all cases.

Gu, Zhan

1998-09-01

141

Blowoff characteristics of bluff-body stabilized conical premixed flames with upstream spatial mixture gradients and velocity oscillations  

SciTech Connect

This experimental study concerns determination of blowoff equivalence ratios for lean premixed conical flames for different mixture approach velocities ranging from 5 to 16 m/s in the presence of spatial mixture gradients and upstream velocity modulation. Conical flames were anchored on a disk-shaped bluff body that was attached to a central rod in the burner nozzle. A combustible propane-air mixture flowed through a converging axisymmetric nozzle with a concentric insert, allowing radial mixture variation by tailoring the composition in the inner and outer parts of the nozzle. The radial mixture profiles were characterized near the location of the flame holder by laser Rayleigh light scattering. Additionally, a loudspeaker at the nozzle base allowed introduction of periodic velocity oscillations with an amplitude of 9% of the mean flow velocity up to a frequency of 350 Hz. The flame blowoff equivalence ratio was experimentally determined by continuously lowering the fuel flow rates and determining the flame detachment point from the flame holder. Flame detachment was detected by a rapid reduction of CH* emission from the flame base imaged by a photomultiplier detector. It was found that the flame blowoff is preceded by progressive narrowing of the flame cone for the case of higher inner jet equivalence ratios. In this case, the fuel-lean outer flow cannot sustain combustion, and clearly this is not a good way of operating a combustor. Nevertheless, the overall blowoff equivalence ratio is reduced by inner stream fuel enrichment. A possible explanation for this behavior is given based on the radial extent of the variable-equivalence-ratio mixture burning near the flame stabilization region. Fuel enrichment in the outer flow was found to have no effect on blowoff as compared to the case of uniform mixture. The results were similar for the whole range of mean flow velocities and upstream excitation frequencies. (author)

Chaudhuri, Swetaprovo; Cetegen, Baki M. [Mechanical Engineering Department, University of Connecticut, Storrs, CT 06269-3139 (United States)

2008-06-15

142

Two-stage growth of the Late Miocene Minna Bluff Volcanic Complex, Ross Embayment, Antarctica: implications for ice-sheet and volcanic histories  

NASA Astrophysics Data System (ADS)

Minna Bluff, a 45km long, 5km wide Late Miocene alkaline volcanic peninsula that extends SE into the Ross Ice Shelf, is a major obstruction to ice flow from the south into the McMurdo Sound region. Interpretations of the abundant paleoclimate and glacial history archives, including the ANDRILL records, need to account for the effects of paleogeography on past ice-flow configurations and sediment transport. Mapping and 40Ar/39Ar dating of volcanic sequences indicate that Minna Bluff was constructed between 12 and 4 Ma. The volcanic complex first emerged as an isolated island in the Ross Sea at about 12 Ma. The edifice, here named Minna Hook Island, was constructed between 12 and 8 Ma. During this first stage of growth, regional ice was able to flow through a ~40 km gap between the island and mainland. The second stage of volcanism built the main arm of Minna Bluff, now called McIntosh Cliffs, between 8 and 4 Ma. The second stage resulted in the eruption of exclusively subaerial cinder cones and lava flows. By approximately 5 Ma the peninsula had fully emerged above sea level, fully obstructing ice flow. Evidence for volcano-ice interaction is common in Minna Hook stratigraphic sequences. Well exposed cliff sections exhibit alternations between rocks erupted in subaerial and subaqueous conditions; these sequences are interpreted to represent syneruptive interactions between lava flows and glacial ice and provide evidence for periodic glaciations between 12 and 8 Ma. The lack of coherent horizontal passage zones between subglacial and subaerial lithofacies and the alternating nature of the deposits suggest that the eruptions did not occur in a large stable ice sheet but instead occurred in a more ephemeral local ice cap or rapidly drained ice sheet. At least two widespread, undulating glacial unconformities mantled by glacial and fluvial sediments are exposed near the base of the Minna Hook sequences. These unconformities record broad scale Antarctic Ice Sheet events between 10.46 and 10.31 Ma and between 9.81 and 9.46 Ma. The older of these widespread glaciations may correspond to Miocene Isotope Event 6 (Mi6), identified in marine sediment records. Eruptions and glacial overriding events at Minna Bluff occurred over the same time interval as sedimentation at the Andrill MIS and SMS core sites.

Wilch, T. I.; McIntosh, W. C.; Panter, K. S.; Dunbar, N. W.; Smellie, J.; Fargo, A. J.; Ross, J. I.; Antibus, J. V.; Scanlan, M. K.

2011-12-01

143

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

144

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

145

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

146

Experimental study of compressibility effects on entrainment and mixing in supersonic planar turbulent bluff-body wakes  

NASA Astrophysics Data System (ADS)

Understanding effects of compressibility on the entrainment and mixing properties of supersonic turbulent shear flows is a key to successful development of the next generation of high-speed airbreathing propulsion systems. Previous studies have focused largely on supersonic mixing layers, and have shown dramatic reductions in the entrainment and mixing rates with increasing compressibility which has been widely believed to be a generic effect of compressibility in supersonic turbulent shear flows. The present dissertation reports results from an experimental investigation of entrainment and mixing in supersonic, planar, turbulent, bluff-body wakes to clarify the generic effects of compressibility in turbulent shear flows. The experimental techniques, including conventional pressure measurements, shadowgraph and planar laser Mie scattering (PLMS) visualizations, and particle image velocimetry (PIV), were used to study instantaneous and mean velocity fields, scaling properties, turbulence statistics, and large-scale structure in instantaneous and phase-averaged vorticity fields over a range of relative Mach numbers. These were compared with corresponding results from incompressible wakes and from supersonic mixing layers. Results indicate that the classical vortex street-like large scale structure of incompressible planar turbulent wakes is recovered in supersonic wakes where the local relative Mach number Mr(x) has decreased to sufficiently small values, but no comparable large-scale organized structure is evident where the relative Mach number is large. Moreover, at downstream locations where Mr(x) is large, a reduction in the growth rate of the flow is observed due to compressibility, but this reduction is significantly smaller than that reported from studies of supersonic mixing layers. Results also show that the wake undergoes a self-induced forcing where it passes through reflected expansion waves produced by the wake generator. This local forcing alters the scaling constants for the wake, and affects the entrainment and mixing rate, only if the flow conditions produce a subsonic upstream path from the wave interaction point. However downstream of this point, the interaction leads to a dramatic increase in the growth rate and an attendant local increase in the entrainment rate, providing a means to increase the entrainment rate in supersonic turbulent shear flows.

Nakagawa, Masaki

2001-07-01

147

A revision of Metaleptobasis Calvert (Odonata: Coenagrionidae) with seven synonymies and the description of eighteen new species from South America.  

PubMed

Examination of over 1,400 specimens of the neotropical genus Metaleptobasis Calvert, 1907, including primary types or paratypes of 18 of the 20 currently available species names and large series of specimens including pairs in tandem and copula, allowed me to unequivocally associate older names with species, distinguish between specific and intraspecific variability, associate both sexes for each species, and recognize the existence of female polymorphism. As a result, seven names are found to be junior synonyms: Metaleptobasis mauritia Williamson, 1915 junior synonym of M. bicornis (Selys, 1877), M. manicaria Williamson, 1915 and M. fernandezi Rácenis, 1955 junior synonyms of M. diceras (Selys, 1877), M. westfalli Cumming, 1954 junior synonym of M. foreli Ris, 1915, and M. tetragena Calvert, 1947, M. weibezahni Rácenis, 1955, and M. incisula De Marmels, 1989 junior synonyms of M. brysonima Williamson, 1915. Lectotypes are designated for M. amazonica and Leptobasis diceras. Eighteen new species of Metaleptobasis are described: M. brevicauda (Holotype ?, Peru, Huánuco Dep., Shapajilla, jungle, 11 v 1939, F. Woytkowski leg., in UMMZ); M. falcifera (Holotype ?, Peru, Madre De Dios Dep., Pakitza, Reserved Zone, Manu National Park, T2 to R2 to T1 to base camp, 11°55'48''S, 71°15'18''W, 250 m, 17 ix 1989, J.A. Louton leg., in USNM); M. furcifera (Holotype ?, Peru, Loreto Dep., Iquitos, iii 1936, G.G. Klug leg., in BMNH); M. gabrielae (Holotype ?, Peru, Loreto Dep., Tamshiyacu-Tahuayo Reserve, forest interior (4°23'40''S, 73°14'56''W), 27 vii 2009, T. Faasen leg., in RMNH); M. guillermoi (Holotype ?, Peru, Loreto Dep., Yarinacocha, temporary forest stream (8°17'S, 74°37'W, 145 m), 2 vi 1972, D.L. Pearson leg., in FSCA); M. inermis (Holotype ?, Brazil, Pará State, Jacareacanga, vii 1969, F.R. Barbosa leg., in UMMZ); M. leniloba (Holotype ?, Peru, Loreto Dep., Pacaya-Samiria National Reserve, Santa Luisa trail (5°15'S, 74°40'W), 10 vi 2008, C. Beatty, A. Cordero & J. Hoffmann leg., in FSCA); M. longicauda (Holotype ?, Brazil, Mato Grosso State, C. Teles Pires, Alto Tapajos, 1-31 viii 1956,  Sick leg., in MNRJ); M. orthogonia (Holotype ?, Peru, Loreto Dep., San Juan, Río Amazonas, near Iquitos, viii 1939, J. Schunke leg., in FSCA); M. paludicola (Holotype ?, Peru, Loreto Dep., Tamshiyacu-Tahuayo Reserve, swamp, 4°23'49''S, 73°14'57''W, 27 ii 2009, T. Faasen leg., in RMNH); M. panguanae (Holotype ?, Peru, Huánuco Dep., Biological Station Panguana, E side Río Yuyapichis, 9°37'S, 74°57'W, 6-17 iv 2003, H.J. & E.-G. Burmeister leg., in ZSM); M. peltata (Holotype ?, Peru Loreto Dep., Tamshiyacu-Tahuayo Reserve, 4°21'22''S, 73°11'0''W, 19 ii 2010, T. Faasen leg., in RMNH); M. prostrata (Holotype ?, Peru, Junín Dep., Satipo, v 1945, P. Paprzycki leg., in UMMZ); M. silvicola (Holotype ?, Peru, Madre de Dios Dep., Explorer's Inn on Río Tambopata, 30 km SW Puerto Maldonado, main trail, 1 viii 1979, M. Perkins & P. Donahue leg., in FSCA); M. spatulata (Holotype ?, Peru, Huánuco Dep., 10 km N of Cucharas, confluence of Huallaga and Pacay rivers, viii 1954, F. Woytkowski leg., in UMMZ); M. tridentigera (Holotype ?, Brazil, Rondônia State, Porto Velho, Area Abunan, T11 Aleatorio, 8°46'S, 63°54'W, 86 m, 16 v 2010, Nogueira & Mendes leg., in MZUSP); M. truncata (Holotype ?, Brazil, Pará State, Jacareacanga, xi 1969, F.R. Barbosa leg., in UMMZ); and M. turbinata (Holotype ?, Peru, Loreto Dep., Tamshiyacu-Tahuayo Reserve, forest swamp (4°24'18''S, 73°14'38''W), 25 ii 2010, T. Fassen leg., in RMNH). Illustrations, keys, diagnoses, and distribution maps for all 31 currently known species are provided. Phylogenetic relationships within the genus Metaleptobasis are analyzed based on 33 adult morphological characters, including the 31 currently described species of Metaleptobasis and eleven outgroup taxa of other Coenagrionidae of the subfamily Teinobasinae. The cladistic analysis recovered Metaleptobasis as monophyletic, and as sister group of Aceratobasis Kennedy, a teinobasine genus s

Von Ellenrieder, Natalia

2013-01-01

148

High altitude flight test of a disk gap band parachute deployed behind a bluff body at a Mach number of 2.69  

NASA Technical Reports Server (NTRS)

A flight test was conducted with a 55-foot diameter disk-gap-band parachute located at a trailing distance of 4.4 forebody diameters behind a 15-foot diameter bluff-body planetary entry aeroshell and attached instrumented payload. At the time of parachute deployment the aeroshell-payload combination was oscillating through an angle-of-attack range of plus or minus 40 deg. Continued oscillatory motion of the aeroshell-payload combination and similar motion of the parachute caused rapid changes in parachute shape and loading which resulted in extensive cloth damage in the band and outer disk-edge areas of the parachute canopy. During steady-state descent the damage parachute provided an effective-drag coefficient of about 0.33 which was about 60 percent of that expected.

Eckstrom, C.; Branscome, D. R.

1972-01-01

149

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

150

Prediction of the Low-Reynolds Number Flows around the Airfoil andBluff Body Components of an Automotive Cooling Fan Module  

Microsoft Academic Search

A numerical model to assess the aerodynamic performance of typical\\u000d\\u000a\\u0009automotive cooling fan stators or support arms is presented. Under\\u000d\\u000a\\u0009real operating conditions, the flow over stators or support arms\\u000d\\u000a\\u0009resembles bluff body flow. Hence, the time and spatial resolution\\u000d\\u000a\\u0009are selected based on previous numerical simulations for the flow\\u000d\\u000a\\u0009around a normal flat plate. Turbulence modeling is based on

Ehab Abu-Ramadan; Behzad Ghafouri; Eric Savory; Chao Zhang; Robert J. Martinuzzi

2009-01-01

151

Water-resources appraisal of the Camp Swift lignite area, central Texas  

USGS Publications Warehouse

The Camp Swift area, Texas was studied to describe the hydrogeology and to provide baseline data of the groundwater and surface water resources that would be affected by the strip mining of lignite. The investigation was centered on the 18-square mile Camp Swift Military Reservation where a reported 80 to 100 million short tons of commercially mineable lignite occurs within 200 feet of the land surface. Groundwater data showed that water levels in observation wells changed only slightly and that the water quality in the Calvert Bluff Formation, which contains the lignite, and in the Simsboro Formation, which is the major aquifer beneath the Calvert Bluff, is suitable for most uses. Big Sandy Creek, which crosses Camp Swift generally has a base flow of less than 0.5 cu ft/sec and infrequently is dry. Dogwood Creek, which originates on Camp Swift, usually is dry. The flow of both streams changes rapidly in response to rainfall in the watersheds. The quality of the water in both streams generally is suitable for most uses. A lithologic examination of 255 feet of cored section that represents the overburden and the lignite showed cyclic layering of fine sand, silt, clay, and lignite. Chemical analyses indicate that the pyritic sulfur concentration is small but variable. (USGS)

Gaylord, J.L.; Slade, R.M.; Ruiz, L.M.; Welborn, C.T.; Baker, E.T.

1985-01-01

152

Hydrology, Water Quality, and Causes of Changes in Vegetation in the Vicinity of the Spring Bluff Nature Preserve, Lake County, Illinois, May 2007-August 2008  

USGS Publications Warehouse

Agriculture and urbanization have altered the hydrology and water quality of the coastal wetland complex along the shore of Lake Michigan at the Spring Bluff Nature Preserve and Illinois Beach State Park in northeastern Lake County, Ill., and the adjacent Chiwaukee Prairie State Natural Area in southeastern Wisconsin. Culverts, roads, ditches, and berms installed within the wetland complex have altered the natural directions of surface-water flow and likely have increased the natural hydroperiod in the Spring Bluff Nature Preserve and decreased it in the northern part of the Illinois Beach State Park. Relative to presettlement conditions, surface-water runoff into the wetlands likely is greater in quantity and higher in concentrations of several constituents, including chloride, nitrate, phosphorous, and suspended sediment. These constituent concentrations are affected by a variety of factors, including the amount of agricultural and urban land use in the watersheds. Hydrologic, chemical, and biologic processes within the wetland communities reduce the concentrations of these constituents in surface water before the water discharges to Lake Michigan by as much as 75 percent for chloride, 85 percent for nitrate, 66 percent for phosphorous, and more than an order of magnitude for suspended sediment. However, concentrations of phosphorous and suspended sediment in surface water increased within parts of the wetland complex. Given these changes, the floristic quality of these wetlands has been altered from the historic condition. Specifically, Typha spp. and Phragmites australis occur in greater numbers and over a larger area than in the past. The spread of Typha spp. and Phragmites australis appears to be enhanced by anthropogenic alterations within the wetland complex, such as increased water levels and duration of inundation and, possibly, increases in the total concentration of dissolved constituents in water.

Kay, Robert T.; Miner, James J.; Maurer, Debbie A.; Knight, Charles W.

2010-01-01

153

The lithology, environment of deposition, and reservoir properties of sandstones in the Upper Queen Formation (Guadalupian, Permian) at Concho Bluff Queen Field, Crane County, Texas  

E-print Network

total body BMD and calcium content information. The Texas AdtM University College of Veterinary Medicine provided bones &+a sheep for this study. Each sheep was slaughtered and dismembered. Four leg bones, one from each leg, were sent to the Texas A... be better measured by xelating bone strength to calcium content, a clearer understanding of bone diseases as related to calcium content will develop. Data from these expeximent showed a correlation between bone mineral density and calcium content in sheep...

Newsom, Douglas Floyd

1989-01-01

154

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

155

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

156

Sequential palynostratigraphy of the Queen City and Weches formations (Middle Eocene Claiborne Group), southeast central Texas  

SciTech Connect

Palynomorph sequences of several orders of magnitude were found in the Queen City and Weches formations respectively at Six Mile and Burleson bluffs on the Brazos River, Milam and Burleson counties, Texas. The long term development of the subtropical to tropical Claibornian palynoflora included Engelhardtia spp., Friedrichipollis claibornensis, Nudopollis terminalis, Pollenites laesius and Symplocoipollenites spp. Shorter term fluctuations in sea level were reflected by common herbaceous pollen in the Queen City, and common mangrove pollen in the Weches. Paleoenvironments were marginally to fully marine; dinocysts occurred throughout. The Wetzeliella group of dinocysts were present only in the Queen City at Six Mile Bluff. Late Paleocene to Early Eocene pollen, and Early Middle Eocene pollen with last effective occurrences near the Queen City and Weches boundary included Aesculiidites circumstriatus, Annona foveoreticulata and a new species of Platycarya. Five short term warmer-cooler couplet events were represented by successive abundance peaks of Juglandaceae followed by Ulmus; Alnus supports the three upper Ulmus peaks. One deep water event was recorded by an abundance of fresh water Pediastrum at the Queen City and Weches boundary. That boundary event was bracketed by two of the Alnus and Ulmus peaks.

Elsik, W.C. (MycoStrat Connection, Houston, TX (United States))

1993-02-01

157

Hydrogeochemistry of the vadose zone in unmined and reclaimed deposits at Big Brown Lignite Mine, East Texas  

SciTech Connect

Six sampling stations in the vadose zone - one in unmined mud, three in unmined sand, and two in reclaimed mud deposits - were operated from August 1979 to May 1981. The extent of seasonal variation in vadose-water content and in water chemical composition was studied by repeated sampling in each facies. Lithology, vadose-zone hydrology, and hydrochemistry were investigated by thin-section petrography, exchangeable-cation analysis, neutron-moisture geophysical logging, and water sampling using suction lysimeters. The author states that hydrogeochemistry of the vadose zone appears to be controlled by recharge rate, mineralogy, and history of each site. He concludes that low-permeability argillaceous deposits in the Calvert Bluff Formation most likely function as confining beds that retard vadose-water flow from reclaimed land to juxtaposed aquifiers, thus limiting the impact of mining on ground-water quality.

Dutton, A.R.

1986-01-01

158

High-resolution, paired geochemical-paleomagnetic stratigraphy of the Sentinel Bluffs Member of the Grande Ronde Basalt, Columbia River Basalt Group  

NASA Astrophysics Data System (ADS)

The Sentinel Bluffs Member (SB) of the Grande Ronde Basalt (GRB) is the youngest stratigraphic unit of the GRB, and is distinguished from other lava flows within the GRB's upper normal polarity magnetozone (N2) by its relatively high MgO content. We collected co-located samples in SB lava flows for major and trace element (XRF) geochemical and paleomagnetic analyses from 7 stratigraphic sections in the central and eastern Columbia River Gorge, on the southwestern Columbia Plateau, at Sentinel Gap on the western Plateau, and at Patrick Grade in the northern Blue Mountains of eastern WA. For the Sentinel Gap section we have adopted the paleomagnetic data from Coe et al. [1978, Rockwell Hanford report RHO-BWI-ST-2], except for our sampling of the Levering flow (not previously sampled) and resampling of their SB flow "H". Paleomagnetic directions for SB flows define 7 stratigraphically controlled groups (I-VII) varying primarily in inclination. Groups I, III, and V have moderate inclinations (means of 55°-57°), groups II and IV have steeper inclinations (67°-69°), and groups VI and VII have the steepest inclinations (72°-78°). SB lava flows exhibit relatively large chemical variations, spanning nearly 1 wt% MgO. Within this span, we recognize 11 discrete chemical groups (1-11, numbered in stratigraphic order) mainly on the basis of TiO2-MgO variations. Early SB eruptions include low- and high-Cr subgroups, and chemical groups 1 and 2 (paleomagnetic groups I-III) are subdivided on the basis of a ~2x difference in Cr abundances (e.g., 16-20 ppm Cr in groups 1a and 2a, 32-38 ppm Cr in groups 1b and 2b). Low-Cr flows are observed only in the lower parts of the SB stratigraphy. Three group 1 (I-II) lava flows that are the lowest SB flows in three sections have similar major element abundances, but differ from each other either in trace element abundances and/or paleomagnetic direction. We infer that the earliest SB flows have moderate inclinations (56°) and include both low-Cr and hi-Cr flows. Systematic decreases in TiO2 and increases in MgO are observed within groups 1-5 (I-III) and 9-11 (VI-VII) with decreasing age. Having similar MgO values, the younger flows of groups 9-11 have distinctly lower TiO2 relative to groups 1-5. Chemical groups 6-8 (IV-V) have relatively high MgO (~4.9-5.2 wt%), intermediate TiO2, and somewhat higher Cr (40-46 ppm) relative to lava flows within groups 1-5 and 9-11 having similar MgO values. With one exception, observed breaks between geochemical and paleomagnetic groups are not contemporaneous as shifts in paleomagnetic direction apparently occurred during eruption of flows within a single chemical group. A total of 22 SB flows are defined by geochemistry and physical flow boundaries. Accounting for differences in paleomagnetic directions within the chemical groups, as many as 29 flows are represented. We attribute the high resolution of our geochemical data to rigorous sampling and lab preparation protocols that minimized alteration products in the material analyzed. Our combined geochemical and paleomagnetic data enables correlation of individual flows or small flow packages (i.e. 2-4 flows) from locations separated by as much as 200 km. These results implicate a high degree of chemical homogeneity within individual SB flows.

Sawlan, M. G.; Hagstrum, J. T.

2012-12-01

159

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

160

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

161

Galaxy formation  

NASA Technical Reports Server (NTRS)

Implications of the isotropy of the cosmic microwave background on large and small angular scales for galaxy formation are reviewed. In primeval adiabatic fluctuations, a universe dominated by cold, weakly interacting nonbaryonic matter, e.g., the massive photino is postulated. A possible signature of photino annihilation in our galactic halo involves production of cosmic ray antiprotons. If the density is near its closure value, it is necessary to invoke a biasing mechanism for suppressing galaxy formation throughout most of the universe in order to reconcile the dark matter density with the lower astronomical determinations of the mean cosmological density. A mechanism utilizing the onset of primordial massive star formation to strip gaseous protogalaxies is described. Only the densest, early collapsing systems form luminous galaxies.

Silk, J.

1984-01-01

162

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. PMID:9419326

Peebles, P. J. E.

1998-01-01

163

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.

164

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

165

Ice Complex formation in arctic East Siberia during the MIS3 Interstadial  

NASA Astrophysics Data System (ADS)

A continuous 15 m long sequence of Ice Complex permafrost (Yedoma) exposed in a thermo-cirque at the southern coast of Bol'shoy Lyakhovsky Island (New Siberian Archipelago, Dmitry Laptev Strait) was studied to reconstruct past landscape and environmental dynamics. The sequence accumulated during the Marine Isotope Stage 3 (MIS3) Interstadial between >49 and 29 ka BP in an ice-wedge polygon. The frozen deposits were cryolithologically described and sampled on a vertical bluff between two ice wedges. According to sedimentological and geochronological data, the section is subdivided into three units which correlate with environmental conditions of the early, middle, and late MIS3 period. Palynological data support this stratification. The stable isotope signature of texture ice in the polygon structure reflects fractionation due to local freeze-thaw processes, while the signature of an approximately 5 m wide and more than 17 m high ice wedge fits very well into the regional stable-water isotope record. Regional climate dynamics during the MIS3 Interstadial and local landscape conditions of the polygonal patterned ground controlled the Ice Complex formation. The sequence presented here completes previously published MIS3 permafrost records in Northeast Siberia. Late Quaternary stadial-interstadial climate variability in arctic West Beringia is preserved at millennial resolution in the Ice Complex. A MIS3 climate optimum was revealed between 48 and 38 ka BP from the Ice Complex on Bol'shoy Lyakhovsky Island.

Wetterich, Sebastian; Tumskoy, Vladimir; Rudaya, Natalia; Andreev, Andrei A.; Opel, Thomas; Meyer, Hanno; Schirrmeister, Lutz; Hüls, Matthias

2014-01-01

166

Formatted: Footer, Left Formatted: Font: 10 pt  

E-print Network

Formatted: Footer, Left Formatted: Font: 10 pt Client Name RETI Stakeholder Steering Committee B Rd, Suite 490 Walnut Creek, CA 94597 Tel: (913) 458-2000 www.bv.com Formatted: Font: Arial, 16 pt Formatted: Space Before: 12 pt, Border: Bottom: (Single solid line, Auto, 0.5 pt Line width) Deleted:

167

Barrier Formation  

PubMed Central

Enamel fluorosis is an irreversible structural enamel defect following exposure to supraoptimal levels of fluoride during amelogenesis. We hypothesized that fluorosis is associated with excess release of protons during formation of hypermineralized lines in the mineralizing enamel matrix. We tested this concept by analyzing fluorotic enamel defects in wild-type mice and mice deficient in anion exchanger-2a,b (Ae2a,b), a transmembrane protein in maturation ameloblasts that exchanges extracellular Cl? for bicarbonate. Defects were more pronounced in fluorotic Ae2a,b ?/? mice than in fluorotic heterozygous or wild-type mice. Phenotypes included a hypermineralized surface, extensive subsurface hypomineralization, and multiple hypermineralized lines in deeper enamel. Mineral content decreased in all fluoride-exposed and Ae2a,b?/? mice and was strongly correlated with Cl?. Exposure of enamel surfaces underlying maturation-stage ameloblasts to pH indicator dyes suggested the presence of diffusion barriers in fluorotic enamel. These results support the concept that fluoride stimulates hypermineralization at the mineralization front. This causes increased release of protons, which ameloblasts respond to by secreting more bicarbonates at the expense of Cl? levels in enamel. The fluoride-induced hypermineralized lines may form barriers that impede diffusion of proteins and mineral ions into the subsurface layers, thereby delaying biomineralization and causing retention of enamel matrix proteins. PMID:24170372

Lyaruu, D.M.; Medina, J.F.; Sarvide, S.; Bervoets, T.J.M.; Everts, V.; DenBesten, P.; Smith, C.E.; Bronckers, A.L.J.J.

2014-01-01

168

Pattern Formation  

NASA Astrophysics Data System (ADS)

From the stripes of a zebra and the spots on a leopard's back to the ripples on a sandy beach or desert dune, regular patterns arise everywhere in nature. The appearance and evolution of these phenomena has been a focus of recent research activity across several disciplines. This book provides an introduction to the range of mathematical theory and methods used to analyse and explain these often intricate and beautiful patterns. Bringing together several different approaches, from group theoretic methods to envelope equations and theory of patterns in large-aspect ratio-systems, the book also provides insight behind the selection of one pattern over another. Suitable as an upper-undergraduate textbook for mathematics students or as a fascinating, engaging, and fully illustrated resource for readers in physics and biology, Rebecca Hoyle's book, using a non-partisan approach, unifies a range of techniques used by active researchers in this growing field. Accessible description of the mathematical theory behind fascinating pattern formation in areas such as biology, physics and materials science Collects recent research for the first time in an upper level textbook Features a number of exercises - with solutions online - and worked examples

Hoyle, Rebecca

2006-03-01

169

Ray Lemoine, Cedar Bluffs Public Schools, Cedar Bluffs, NE 2008 Mineral Identification  

E-print Network

several gypsum samples that are vastly different. One is rose colored massive, one is white fibrous, one is gray crystalline and one is red/yellow crystalline. They look vastly different but are all the same mineral. Then when I have the students identify the minerals, I throw in a red hematite sample, and a red

Frank, Tracy D.

170

77 FR 47121 - Calvert Cliffs Nuclear Power Plant, LLC; Calvert Cliffs Nuclear Power Plant, Units 1 and 2...  

Federal Register 2010, 2011, 2012, 2013, 2014

...Personnel Fatigue at Nuclear Power Plants...of the Atomic Energy Act of 1954...this focus on nuclear safety and security...a significant effect on the quality of the human environment. This exemption...2012. For the Nuclear Regulatory...

2012-08-07

171

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, 2014

...Nuclear Power Plant, LLC is owned by Constellation Energy Nuclear Group, LLC (CENG...one of CENG's parent companies, Constellation Energy Group, Inc (CEG). According...ownership by CEG of 100 percent of Constellation Nuclear, LLC and, indirectly,...

2011-07-07

172

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, P.P., Jr.; Miller, K.G.; Self-Trail J.M.; Kulpecz, A.A.; Elbra, T.

2009-01-01

173

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

174

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

175

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

176

layout formats sectioneight  

E-print Network

layout is based on the UCSF visual identity ­ a simple, structured format based on dividing the page Identity Standards WOMEN AND GENDER RESOURCES SEXUAL AND RELATIONSHIP VIOLENCE RESOURCES LESBIAN, GAY, BIlayout formats 69 sectioneight contents about the grid

Derisi, Joseph

177

Scenarios for galaxy formation  

NASA Technical Reports Server (NTRS)

The gravitational instability theory and its application to the origin of large scale structure are reviewed. The modeling of galaxy formation is described, from forwards and backwards perspectives. The emphasis is on the interactions between stellar and galactic formation.

Silk, Joseph

1997-01-01

178

Dublin, 11.09.2011 Star FormationStar FormationStar FormationStar Formation  

E-print Network

Dublin, 11.09.2011 Star FormationStar FormationStar FormationStar Formation An observational viewJ. Rowles, G. IoannidisJ. Rowles, G. Ioannidis #12;Dublin, 11.09.2011 Layout of the talkLayout of the talk on UWISH2 data #12;Dublin, 11.09.2011 GMCsGMCsGMCsGMCs Gravity and Turbulence dominate (maybe B

Froebrich, Dirk

179

The formation of galaxies  

NASA Technical Reports Server (NTRS)

Current models of galaxy formation are examined in a review of recent observational and theoretical studies. Observational data on elliptical galaxies, disk galaxies, luminosity functions, clustering, and angular fluctuations in the cosmic microwave background are summarized. Theoretical aspects discussed include the origin and early evolution of small fluctuations, matter and radiation fluctuations, the formation of large-scale structure, dissipationless galaxy formation, galaxy mergers, dissipational galaxy formation, and the implications of particle physics (GUTs, massive neutrinos, and gravitinos) for cosmology.

Efstathiou, G.; Silk, J.

1983-01-01

180

Bedrock geologic map of the Spring Valley, West Plains, and parts of the Piedmont and Poplar Bluff 30'x60' quadrangles, Missouri, including the upper Current River and Eleven Point River drainage basins  

USGS Publications Warehouse

Potentially economic mineral resources are present in the subsurface in the map area. Exploration drill-hole data indicate that anomalously high concentrations of base-metal sulfides locally occur within the Cambrian Bonneterre Formation. The geologic setting of these anomalous concentrations is similar to that found in the Viburnum Trend, part of the largest lead-mining district in the world. The southernmost part of the Viburnum Trend extends into the northern part of the map area and is exploited by the Sweetwater Mine. Undeveloped and potentially economic occurrences of base metals are known also beneath Blair Creek, a tributary to the Current River in the north-central part of the map area.

Weary, David J.; Harrison, Richard W.; Orndorff, Randall C.; Weems, Robert E.; Schindler, J. Stephen; Repetski, John E.; Pierce, Herbert A.

2015-01-01

181

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

182

GLOBAL STAR FORMATION REVISITED  

SciTech Connect

A general treatment of disk star formation is developed from a dissipative multiphase model, with the dominant dissipation due to cloud collisions. The Schmidt-Kennicutt (SK) law emerges naturally for star-forming disks and starbursts. We predict that there should be an inverse correlation between Tully-Fisher law and SK law residuals. The model is extended to include a multiphase treatment of supernova feedback that leads to a turbulent pressure-regulated generalization of the star formation law and is applicable to gas-rich starbursts. Enhanced pressure, as expected in merger-induced star formation, enhances star formation efficiency. An upper limit is derived for the disk star formation rate in starbursts that depends on the ratio of global ISM to cloud pressures. We extend these considerations to the case where the interstellar gas pressure in the inner galaxy is dominated by outflows from a central active galactic nucleus (AGN). During massive spheroid formation, AGN-driven winds trigger star formation, resulting in enhanced supernova feedback and outflows. The outflows are comparable to the AGN-boosted star formation rate and saturate in the super-Eddington limit. Downsizing of both SMBH and spheroids is a consequence of AGN-driven positive feedback. Bondi accretion feeds the central black hole with a specific accretion rate that is proportional to the black hole mass. AGN-enhanced star formation is mediated by turbulent pressure and relates spheroid star formation rate to black hole accretion rate. The relation between black hole mass and spheroid velocity dispersion has a coefficient (Salpeter time to gas consumption time ratio) that provides an arrow of time. Highly efficient, AGN-boosted star formation can occur at high redshift.

Silk, Joseph [Physics Department, University of Oxford, 1 Keble Road, Oxford OX1 3RH (United Kingdom); Norman, Colin [Physics Department, Johns Hopkins University, 2400 North Charles Street, Baltimore, MD 21218 (United States)], E-mail: silk@astro.ox.ac.uk, E-mail: norman@stsci.edu

2009-07-20

183

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

184

Tropical cyclone formation  

Microsoft Academic Search

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

Michael T. Montgomery; Brian F. Farrell

1993-01-01

185

Ice Formation on Wings  

NASA Technical Reports Server (NTRS)

This report makes use of the results obtained in the Gottingen ice tunnel in which the atmospheric conditions are simulated and the process of ice formation photographed. The effect of ice formation is threefold: 1) added weight to the airplane; 2) a change in the lift and drag forces; 3) a change in the stability characteristics.

Ritz, L

1939-01-01

186

Star formation Simon Goodwin  

E-print Network

Star formation Simon Goodwin Dept Physics & Astronomy, University of Sheffield, Hounsfield Road, Sheffield, S3 7RH, UK. s.goodwin@sheffield.ac.uk 1 Abstract Stars are one of the most important consituents of the Universe, and understanding their formation is crucial to many areas of astrophysics. Stars form from dense

Crowther, Paul

187

Formate production through biocatalysis  

PubMed Central

The generation of formate from CO2 provides a method for sequestration of this greenhouse gas as well as the production of a valuable commodity chemical and stabilized form of hydrogen fuel. Formate dehydrogenases are enzymes with the potential to catalyze this reaction; however they generally favor the reverse process, i.e., formate oxidation. By contrast, the formate dehydrogenase of the acetogen Clostridium carboxidivorans has been found to preferentially catalyze the reduction of CO2. This is in accord with its natural role to introduce CO2 as a carbon source in the Wood-Ljungdahl pathway. The direction of catalysis derives from the enzyme’s low affinity for formate. This enzyme is therefore an excellent candidate for biotechnological applications aimed at producing formic acid and derivative chemicals from CO2. PMID:23841981

Alissandratos, Apostolos; Kim, Hye-Kyung; Easton, Christopher J

2013-01-01

188

Intergalactic Star Formation  

E-print Network

Star formation in interacting systems may take place in various locations, from the dust--enshrouded core of Ultraluminous Infrared Galaxies to more unusual places such as the debris of colliding galaxies expelled into the intergalactic medium. Determining whether star-formation proceeds in the latter environment, far from the parent galaxies, in a similar way as in spiral disks has motivated the multi--wavelength study presented here. We collected VLA/HI, UV/GALEX, optical Halpha and MIR/Spitzer images of a few nearby interacting systems chosen for their prominent "intergalactic" star formation activity. Preliminary results on the spectacular collisional HI ring around NGC 5291 are presented.

Pierre-Alain Duc; Meederic Boquien; Jonathan Braine; Elias Brinks; Ute Lisenfeld; Vassilis Charmandaris

2006-10-13

189

Understanding Earth: Coal Formation  

NSDL National Science Digital Library

Supplementary material from Understanding Earth (4th ed.), this short animation guides viewers through the formation of coal and its pathway through different grades. The animation is annotated with labels.

W.H. Freeman & amp; Co. Publishing

190

Essays on Network Formation  

E-print Network

This dissertation contains two essays which examine the roles that individual incentives, competition, and information play in network formation. In the first essay, I examine a model in which two competing groups offer different allocation rules...

Mueller, William Graham

2012-10-19

191

Poplar wood formation.  

E-print Network

??Genotypical effects on wood formation in aspen (Populus tremula x tremuloides) have been studied at morphological, ultrastructural and micro-distributional levels. To characterize transgenically in­duced modifications,… (more)

Sandquist, David

2011-01-01

192

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.

Amber Morgan

2012-08-10

193

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

194

Format-Preserving Encryption  

NASA Astrophysics Data System (ADS)

Format-preserving encryption (FPE) encrypts a plaintext of some specified format into a ciphertext of identical format—for example, encrypting a valid credit-card number into a valid credit-card number. The problem has been known for some time, but it has lacked a fully general and rigorous treatment. We provide one, starting off by formally defining FPE and security goals for it. We investigate the natural approach for achieving FPE on complex domains, the “rank-then-encipher” approach, and explore what it can and cannot do. We describe two flavors of unbalanced Feistel networks that can be used for achieving FPE, and we prove new security results for each. We revisit the cycle-walking approach for enciphering on a non-sparse subset of an encipherable domain, showing that the timing information that may be divulged by cycle walking is not a damaging thing to leak.

Bellare, Mihir; Ristenpart, Thomas; Rogaway, Phillip; Stegers, Till

195

Gaussian entanglement of formation  

SciTech Connect

We introduce a Gaussian version of the entanglement of formation adapted to bipartite Gaussian states by considering decompositions into pure Gaussian states only. We show that this quantity is an entanglement monotone under Gaussian operations and provide a simplified computation for states of arbitrary many modes. For the case of one mode per site the remaining variational problem can be solved analytically. If the considered state is in addition symmetric with respect to interchanging the two modes, we prove additivity of the considered entanglement measure. Moreover, in this case and considering only a single copy, our entanglement measure coincides with the true entanglement of formation.

Wolf, M.M. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, Garching, D-85748 (Germany); Institut fuer Mathematische Physik, Mendelssohnstrasse. 3, D-38106 Braunschweig (Germany); Giedke, G. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, Garching, D-85748 (Germany); Institut fuer Quantenelektronik, ETH Zuerich, Wolfgang-Pauli-Strasse 16, CH-8093 Zurich (Switzerland); Krueger, O.; Werner, R. F. [Institut fuer Mathematische Physik, Mendelssohnstrasse. 3, D-38106 Braunschweig (Germany); Cirac, J.I. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, Garching, D-85748 (Germany)

2004-05-01

196

Formation of Galactic Disks  

E-print Network

We review progress in understanding the formation of galactic disks in the standard cosmogonic scenario involving gravitational clustering of baryons and dark matter and dissipative collapse of the baryons. This scenario accounts remarkably well for the observed properties of galactic disks if they have retained most of the specific angular momentum they acquired by tidal torques. Early simulations, which included cooling of the gas but not star formation and the associated feedback, indicated instead that most of the angular momentum of the baryons would be transferred to the dark matter. Recent simulations indicate that this angular-momentum problem can be solved partially, and in some cases entirely, by feedback and other effects.

S. Michael Fall

2002-03-27

197

Rosette formation in osteosarcoma.  

PubMed

Rosette formation is a rare, recently reported variation in osteogenic sarcoma and is thought to be associated with a poor prognosis. We report two cases of rosette forming osteosarcoma, one with poor response and other with total necrosis following chemotherapy. Pathologists should be aware of rosette formation in osteosarcoma to avoid misdiagnosis as other rosette forming tumors of bone especially PNET/Ewings sarcoma. In our opinion rosettes in an osteosarcoma should be documented both from a differential diagnostic point of view and also to elucidate definitive prognostic implications. PMID:15471138

Jambhekar, Nirmala A; Shet, Tanuja M; Das, Lolly

2004-01-01

198

The interaction of a bluff body with a vortex wake  

NASA Astrophysics Data System (ADS)

A theoretical, experimental and numerical study is presented of the interaction of a vortex-wake created by an upstream blade with a downstream prismatic block. The aim of the study is to investigate the fundamentals of force and noise generation for this type of flow and explain how inter-object spacing affects the far-field noise level. A theoretical model, based on a compact form of Curle's formulation, is developed and shows that acoustically constructive or destructive interference is determined by the amplitude and phase of the forces on each object. Experimental and two-dimensional, unsteady numerical results of the vortex-wake interaction case are presented for several blade-block separation distances. Using a combination of experimental and numerical data, the theoretical model is able to explain observed variations in far-field noise level with blade-block separation distance. The numerical model accurately predicts the phase relationship between the unsteady forces on each object.

Leclercq, D. J. J.; Doolan, C. J.

2009-07-01

199

Simulations of Bluff Body Flow Interaction for Noise Source Modeling  

NASA Technical Reports Server (NTRS)

The current study is a continuation of our effort to characterize the details of flow interaction between two cylinders in a tandem configuration. This configuration is viewed to possess many of the pertinent flow features of the highly interactive unsteady flow field associated with the main landing gear of large civil transports. The present effort extends our previous two-dimensional, unsteady, Reynolds Averaged Navier-Stokes computations to three dimensions using a quasilaminar, zonal approach, in conjunction with a two-equation turbulence model. Two distinct separation length-to-diameter ratios of L/D = 3.7 and 1.435, representing intermediate and short separation distances between the two cylinders, are simulated. The Mach 0.166 simulations are performed at a Reynolds number of Re = 1.66 105 to match the companion experiments at NASA Langley Research Center. Extensive comparisons with the measured steady and unsteady surface pressure and off-surface particle image velocimetry data show encouraging agreement. Both prominent and some of the more subtle trends in the mean and fluctuating flow fields are correctly predicted. Both computations and the measured data reveal a more robust and energetic shedding process at L/D = 3.7 in comparison with the weaker shedding in the shorter separation case of L/D = 1.435. The vortex shedding frequency based on the computed surface pressure spectra is in reasonable agreement with the measured Strouhal frequency.

Khorrami, Medi R.; Lockard David P.; Choudhari, Meelan M.; Jenkins, Luther N.; Neuhart, Dan H.; McGinley, Catherine B.

2006-01-01

200

Geology of the Little Bluff Creek Area, Mason County, Texas  

E-print Network

and schiats respectively. 2. 8. Terr {18/0) concluded Chat the pxesent drainage system in Cho ~no region was superimposed on the ancient Precaxguian and Paleosoic rocks dux ing Tertiary time. Pcige (1/11) named and described Che Cap Mountain... redefined by Paige (1912) who concluded Chat these units vere Algonkian (Proteroaoic) 1n age. Sellarda (l932, p. 33) defined the Packsaddle schist as a thick unit of metamorphosed sediments, ox'lginally con- sisting of ah?les w1th lesser amounts...

Mangum, Charles Roland

2012-06-07

201

Atmospheric flow over two-dimensional bluff surface obstructions  

NASA Technical Reports Server (NTRS)

The phenomenon of atmospheric flow over a two-dimensional surface obstruction, such as a building (modeled as a rectangular block, a fence or a forward-facing step), is analyzed by three methods: (1) an inviscid free streamline approach, (2) a turbulent boundary layer approach using an eddy viscosity turbulence model and a horizontal pressure gradient determined by the inviscid model, and (3) an approach using the full Navier-Stokes equations with three turbulence models; i.e., an eddy viscosity model, a turbulence kinetic-energy model and a two-equation model with an additional transport equation for the turbulence length scale. A comparison of the performance of the different turbulence models is given, indicating that only the two-equation model adequately accounts for the convective character of turbulence. Turbulence flow property predictions obtained from the turbulence kinetic-energy model with prescribed length scale are only insignificantly better than those obtained from the eddy viscosity model. A parametric study includes the effects of the variation of the characteristics parameters of the assumed logarithmic approach velocity profile. For the case of the forward-facing step, it is shown that in the downstream flow region an increase of the surface roughness gives rise to higher turbulence levels in the shear layer originating from the step corner.

Bitte, J.; Frost, W.

1976-01-01

202

Phase lag between vortex shedding from two tandem bluff bodies  

NASA Astrophysics Data System (ADS)

This paper presents a work on the phase lag (?) between vortex sheddings from two tandem cylinders of various shapes and its influence on fluctuating lift on the upstream cylinder. A differential equation of ?, d?=[4?fs/(2Vc-dVc)] dx, is derived, where fs is the vortex shedding frequency, Vc is the convective velocity of vortices, and x is the downstream distance from the upstream cylinder. Applying the condition ?=2? at L=Lc*, as obtained from experimental data, the equation yields ?=2.44? St(L-Lc*)+2?, where St is the Strouhal number, L is the normalized cylinder center-to-center spacing and Lc* is the critical spacing defined as the minimum L at which the upstream cylinder could shed vortices in the gap between the cylinders. This relationship agrees well with experimental data previously reported as well as presently measured.

Mahbub Alam, Md.; Zhou, Y.

2007-02-01

203

Trace fossils from the Rock Bluff Limestone (Pennsylvanian, Kansas)  

E-print Network

, Figures and descriptions, Canadian organic remains, p. 77-85. Branson, C. C., 1960, C.onostichus: Okla. Geol. Notes, v. 20, p. 195-207, pl. 1-4. Chamberlain, C. K., 1971, Morphology and ethology of trace fossils from the Ouachita Mountains, southeastern..., Figures and descriptions, Canadian organic remains, p. 77-85. Branson, C. C., 1960, C.onostichus: Okla. Geol. Notes, v. 20, p. 195-207, pl. 1-4. Chamberlain, C. K., 1971, Morphology and ethology of trace fossils from the Ouachita Mountains, southeastern...

Maerz, R. H., Jr.; Kaesler, R. L.; Hakes, W. G.

1976-01-15

204

Quasars and galaxy formation  

NASA Technical Reports Server (NTRS)

Observations of high redshift quasars provide direct information on the physical state of the universe at early epochs. The available data suggest well advanced structure formation even at the highest known quasar redshifts and are most easily understood in scenarios in which galaxies primarily formed at redshifts well above 5. Ten separate lines of argument supporting this general conclusion are summarized.

Turner, Edwin L.

1991-01-01

205

Formation of Language  

Microsoft Academic Search

PERMIT me to reply to your correspondent Mr. W. J. Stillman, on the ``Formation of Language'' (NATURE, March 26, p. 491). The interesting fact he records of the spontaneous invention and use of child-names for objects is not unknown to philologists. The phenomenon has been previously noticed, among others, by Miss Watson, of Boston, and Dr. E. R. Hun, of

Agnes Crane

1891-01-01

206

Bacterial formate hydrogenlyase complex.  

PubMed

Under anaerobic conditions, Escherichia coli can carry out a mixed-acid fermentation that ultimately produces molecular hydrogen. The enzyme directly responsible for hydrogen production is the membrane-bound formate hydrogenlyase (FHL) complex, which links formate oxidation to proton reduction and has evolutionary links to Complex I, the NADH:quinone oxidoreductase. Although the genetics, maturation, and some biochemistry of FHL are understood, the protein complex has never been isolated in an intact form to allow biochemical analysis. In this work, genetic tools are reported that allow the facile isolation of FHL in a single chromatographic step. The core complex is shown to comprise HycE (a [NiFe] hydrogenase component termed Hyd-3), FdhF (the molybdenum-dependent formate dehydrogenase-H), and three iron-sulfur proteins: HycB, HycF, and HycG. A proportion of this core complex remains associated with HycC and HycD, which are polytopic integral membrane proteins believed to anchor the core complex to the cytoplasmic side of the membrane. As isolated, the FHL complex retains formate hydrogenlyase activity in vitro. Protein film electrochemistry experiments on Hyd-3 demonstrate that it has a unique ability among [NiFe] hydrogenases to catalyze production of H2 even at high partial pressures of H2. Understanding and harnessing the activity of the FHL complex is critical to advancing future biohydrogen research efforts. PMID:25157147

McDowall, Jennifer S; Murphy, Bonnie J; Haumann, Michael; Palmer, Tracy; Armstrong, Fraser A; Sargent, Frank

2014-09-23

207

Queen's Garden Formations  

USGS Multimedia Gallery

Views along the Queen's Garden Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sands...

208

Terminology of Enzyme Formation  

Microsoft Academic Search

IT has been recognized for many years that in micro-organisms the formation of a large variety of enzymes can be specifically induced by exposing cells to compounds which are substrates for the enzymes in question. Recently, the same phenomenon has been demonstrated in a mammal1, and it will probably prove to be a general property of biological systems. Since a

M. Cohn; J. Monod; M. R. POLLOCK; S. SPIEGELMAN; R. Y. STANIER

1953-01-01

209

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.

Stephen Marshak

210

Hair follicle Formation of  

E-print Network

Hair follicle Formation of new follicles Bud Healed skin Hair bulge Open wound Epidermis a b Dermis 1950s and help to explain the controversy. What is the origin of the cells that make up these new hair follicles? Are they derived from existing hair follicles located at the wound edge

Chuong, Cheng-Ming

211

Isolating Triggered Star Formation  

E-print Network

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 select galaxy pairs that are isolated in their dark matter halos with respect to other massive subhalos (N=2 halos) and 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_Bj ~ 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. 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. (Abridged.)

Elizabeth J. Barton; Jacob A. Arnold; Andrew R. Zentner; James S. Bullock; Risa H. Wechsler

2007-08-21

212

Entropically Driven Helix Formation  

Microsoft Academic Search

The helix is a ubiquitous motif for biopolymers. We propose a heuristic, entropically based model that predicts helix formation in a system of hard spheres and semiflexible tubes. We find that the entropy of the spheres is maximized when short stretches of the tube form a helix with a geometry close to that found in natural helices. Our model could

Yehuda Snir; Randall D. Kamien

2005-01-01

213

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

214

FORMATION OF PHOTOCHEMICAL AEROSOLS  

EPA Science Inventory

The objective was to develop a better understanding of smog aerosol formation with particular reference to haze in the Southern California area. This study combined laboratory work with ambient air studies. Counting of particles by light scattering was the principle physical tech...

215

Formation in the Classroom  

ERIC Educational Resources Information Center

What is the relationship between the academic knowledge of the guild and the formation of students in the classroom? This Forum gathers four essays originally presented at a Special Topics Session at the 2009 conference of the American Academy of Religion (Atlanta, Georgia), with a brief introductory essay by Fred Glennon explaining the genesis of…

Glennon, Fred; Jacobsen, Douglas; Jacobsen, Rhonda Hustedt; Thatamanil, John J.; Porterfield, Amanda; Moore, Mary Elizabeth

2011-01-01

216

Pattern formation during vasculogenesis.  

PubMed

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. PMID:22692888

Czirok, Andras; Little, Charles D

2012-06-01

217

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

218

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. PMID:22692888

Czirok, Andras; Little, Charles D.

2012-01-01

219

Photochemical formation of intricarene.  

PubMed

Sunlight is the ultimate driver of biosynthesis but photochemical steps late in biosynthetic pathways are very rare. They appear to play a role in the formation of certain furanocembranoids isolated from Caribbean corals. One of these compounds, intricarene, has been suspected to arise from an intramolecular 1,3-dipolar cycloaddition involving an oxidopyrylium. Here we show, by a combination of experiments and theory, that the oxidopyrylium forms under photochemical conditions and that its cycloaddition occurs via a triplet state. The formation of a complex by-product can be rationalized by another photochemical step that involves a conical intersection. Our work raises the question whether intricarene is biosynthesized in the natural habitat of the corals or is an artefact formed during workup. It also demonstrates that the determination of exact irradiation spectra, in combination with quantum chemical calculations, enables the rationalization of complex reaction pathways that involve multiple excited states. PMID:25470600

Stichnoth, Desiree; Kölle, Patrick; Kimbrough, Thomas J; Riedle, Eberhard; de Vivie-Riedle, Regina; Trauner, Dirk

2014-01-01

220

Cosmic structure formation  

NASA Technical Reports Server (NTRS)

This article reviews the prevailing paradigm for how galaxies and larger structures formed in the universe: gravitational instability. Basic observational facts are summarized to motivate the standard cosmological framework underlying most detailed investigations of structure formation. The observed univers approaches spatial uniformity on scales larger than about 10(exp 26) cm. On these scales gravitational dynamics is almost linear and therefore relatively easy to relate to observations of large-scale structure. On smaller scales cosmic structure is complicated not only by nonlinear gravitational clustering but also by nonlinear nongravitational gas dynamical processes. The complexity of these phenomena makes galaxy formation one of the grand challenge problems of the physical sciences. No fully satisfactory theory can presently account in detail for the observed cosmic structure. However, as this article summarizes, significant progress has been made during the last few years.

Bertschinger, Edumund

1994-01-01

221

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.

222

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.

223

Hail Formation in Florida  

NASA Astrophysics Data System (ADS)

Hail poses a substantial threat to life and property in the state of Florida. These losses could be minimized through better understanding of the relationships between atmospheric variables that impact hail formation in Florida. Improving hail forecasting in Florida requires analyzing a number of meteorological parameters and synoptic data related to hail formation. NOAA archive data was retrieved to create a database that was used to categorize text files of hail days. The text files were entered into the National Oceanic and Atmospheric Administration Earth System Research Laboratory website to create National Centers for Environmental Prediction/National Center for Atmospheric Research Reanalysis maps of atmospheric variables for Florida hail days as well as days leading to the hail event. These data were then analyzed to determine the relationship between variables that affect hail formation, in general, across different regions and seasons in Florida using Statistical Product and Service Solutions. The reasoning for the differing factors affecting hail formation between regions, seasons and hail sizes were discussed, as well as forecasting suggestions relating to region and month in Florida. The study found that the majority of all hail that occurs in Florida is during the wet season. A low Lifted Index, high Precipitable Water and lower than average Sea Level Pressure, in most cases, is present during hail days in Florida. Furthermore, results show that Vector Wind magnitude increases as hail size increases. Additionally, several atmospheric variables useful to studying hail events, such as Lifted Index, Precipitable Water, Sea Level Pressure, Vector Wind and Temperature have significant correlations with each other depending on the region and season being observed. Strong correlations between low Lifted Index, high Precipitable Water values and the occurrence of hail events are discussed, as well as the relationship between temperature anomalies at various pressure levels and the occurrence of hail events.

Stanley, Matthew

224

Entropically driven helix formation.  

PubMed

The helix is a ubiquitous motif for biopolymers. We propose a heuristic, entropically based model that predicts helix formation in a system of hard spheres and semiflexible tubes. We find that the entropy of the spheres is maximized when short stretches of the tube form a helix with a geometry close to that found in natural helices. Our model could be directly tested with wormlike micelles as the tubes, and the effect could be used to self-assemble supramolecular helices. PMID:15718461

Snir, Yehuda; Kamien, Randall D

2005-02-18

225

Mesospheric cloud formations  

NASA Technical Reports Server (NTRS)

Formation of mesospheric clouds as a result of deposition of large amounts of H2O by the heavy lift launch vehicle (HLLV) of the solar power satellite system is discussed. The conditions which must be met in order to form and maintain clouds near the mesopause are described. The frequency and magnitude of H2O injections from the HLLV rocket exhaust are considered.

Forbes, J. M.

1980-01-01

226

Text formatting by demonstration  

Microsoft Academic Search

In text formatters such as troff, Scribe, and TEX, users write macro procedures to specify the desired visual appearance. In What-You-See-Is-What-You-Get text formatters, such as MacWrite and Microsoft Word, the formatting is specified by directly manipulating the text. However, some important functionality is lost in these systems since they are not programmable, For example, if the user wants to change

Brad A. Myers

1991-01-01

227

Mars brine formation experiment  

NASA Technical Reports Server (NTRS)

Evaporites, particularly carbonates, nitrates, and sulfates, may be major sinks of volatiles scavenged from the martian atmosphere. Mars is thought to have once had a denser, warmer atmosphere that permitted the presence of liquid surface water. The conversion of atmospheric CO2 into carbonate is hypothesized to have degraded the martian climate to its present state of a generally subfreezing, desiccated desert. The rate for such a conversion under martian conditions is poorly known, so the time scale of climate degradation by this process cannot be easily evaluated. If some models are correct, carbonate formation may have been fast at geological time scales. The experiments of Booth and Kieffer also imply fast (10(exp 6) - 10(exp 7) yr) removal of the missing CO2 inventory, estimated to be 1 - 5 bar, by means of carbonate formation. The timing of formation of many of the fluvial features observed on Mars is, in large part, dependent on when and how fast the atmosphere changed. A knowledge of the rate at which carbonates and nitrates formed is also essential for assessing the probability that life, or its chemical precursors, could have developed on Mars. No previous experiments have quantitatively evaluated the rate of solution for a suite of mobile anions and cations from unaltered minerals and atmospheric gases into liquid water under Mars-like conditions. Such experiments are the focus of this task.

Moore, Jeffrey M.; Bullock, Mark A.; Stoker, Carol R.

1992-01-01

228

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

229

Prediction of silicide formation and stability using heats of formation  

Microsoft Academic Search

The effective heat of formation (EHF) model is used to predict compound phase formation and stability in metal-silicon systems. The model defines an effective heat of formation ?H?, which is concentration dependent and shows a linear dependence on the concentration of the limiting element at the growth interface. For instance if CrSi2 (Cr0.33Si0.67) formation is considered and the effective concentration

R. Pretorius

1996-01-01

230

Flexible formation configuration for terrain following flight: Formation keeping constraints  

NASA Astrophysics Data System (ADS)

This work suggests a control method for the terrain-following formation motion of a group of communicating autonomous agents. The presented approach centers on defining a suitable set of constraints for formation keeping task that shall be fulfilled while agents are negotiating an unknown terrain toward the predefined goal location. It allows agents to maintain a general geometric formation shape, while allowing each individual formation member freedom of maneuver, required for terrain collision free motion. Formation structure is defined with the use of virtual leader. Formation keeping constraints are defined with plane surfaces, specified relative to position and navigation vector of the virtual leader. Formation navigation and guidance constraints are defined using navigation vectors of formation members and the virtual leader. Alternative designs for the constraints derived with parabolic, cone, and cylindrical surfaces are considered. Formation control is derived using the Udwadia-Kalaba equation, following corresponding approach to the development of control methods for constraint based dynamical systems, including leader-follower systems defined using geometric constraints. Approach to terrain following motion requiring agents to stay within bounds of cylindrical corridor volumes built around their respective navigation vectors is assumed. Individual formation primitives and multi-level, hierarchical, formation structures are considered. Simulations, based on three degrees of freedom nonlinear model of an agent, performed using Mathematica and specifically developed combined Maya-Mathematica modeling and simulation system, demonstrate that a flexible terrain following formation motion is achieved with the presented sets of constraints.

Latyshev, Simon

231

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

232

Cluster Formation and the ISM  

E-print Network

We review the physics of star formation, and its links with the state of the ISM in galaxies. Current obervations indicate that the preferred mode of star formation is clustered. Given that OB associations provide the dominant energy input into the ISM, deep links exist between the ISM and star formation. We present a multi-scale discussion of star formation, and attempt to create an integrated vision of these processes.

Ralph E. Pudritz; Jason D. Fiege

1999-05-12

233

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

234

Modeling Chondrule Formation  

NASA Astrophysics Data System (ADS)

Over the last several decades considerable data on chondrule sizes, compositions, and textures has been collected [1]; experimental studies have greatly improved our understanding of the conditions required to produce chondrule compositions and textures [2]; and models of energetic nebular processes have provided insight into mechanisms by which chondrules may have formed [3]. While much work remains in each of these areas, the information presently available is sufficient to allow the construction of simple numerical models of chondrule formation. We have constructed a computer algorithm to investigate the consequences of forming chondrules under a variety of conditions. Variables that are considered include: 1) the mechanism of heating (e.g., EM radiation, aerodynamic drag, collisions with energetic particles), 2) peak chondrule temperature, 3) heat-source geometry, 4) pre-chondrule dust aggregate size distributions, 5) dust aggregate compositional distributions, 6) chondrule solidus and liquidus temperatures, 7) kinetic barriers to melting, and 8) the duration of heating. Output includes the size distributions and relative abundances of PO, PP, POP, BO, and NP chondrules. Given the uncertainties in the input variables, the primary purpose of the code is not to construct a single (and necessarily somewhat arbitrary) model of chondrule formation, but rather to elucidate the differences in chondrule properties associated with various sets of formation conditions. Results from a number of simulations using a variety of input parameters illustrate the importance of both composition and peak temperature on the proportion of porphyritic to non-porphyritic chondrules produced. Also apparent is the influence of the mechanism of heating on the relative size distributions of chondrule textural types. Results indicate that specific heating mechanisms require unique sets of associated conditions to account for the observed properties of chondrules. These unique sets of conditions not only limit the range of plausible scenarios for chondrule formation, but provide a means of predicting as yet unmeasured chondrule properties. References: [1] Grossman J. N. et al. (1988) in Meteorites and the Early Solar System (J. F. Kerridge and M. S. Mathews, eds.), pp. 619-659, Univ. of Arizona, Tucson. [2] Hewins R. H. (1988) in Meteorites and the Early Solar System (J. F. Kerridge and M. S. Mathews, eds.), pp. 660-679, Univ. of Arizona, Tucson. [3] Hood L. L. and Kring D. A. (1995) in Chondrules and the Protoplanetary Disk (R. Hewins et al., eds.), Cambridge Univ., New York, in press.

Eisenhour, D. D.; Buseck, P. R.

1995-09-01

235

Formation of neutrino halos  

NASA Astrophysics Data System (ADS)

A fully general relativistic nonlinear model of the formation of massive neutrino halos in an Einstein-Straus universe was given by Fabbri, Jantzen and Ruffini (1982). The paper considers the role which a nonvanishing, repulsive cosmological constant Lambda greater than 0, admissible by observational limits, can have in the FJR model. The main conclusion is that the influence of Lambda is negligible in the FJR model for massive neutrinos with mass of about 10 eV, indicated by recent observations of SN 1987a. On the other hand, the cosmological constant is relevant in the model, if neutrinos have low mass, less than 0.2 eV.

Stuchlik, Zdenek

236

Large-format holography  

NASA Astrophysics Data System (ADS)

A review of the techniques and systems used and developed at Australian Holographics to make large format CW reflection (to 1.1. m X 1.1 m) and rainbow (to 1.1 m X 2.2 m) holograms will be given. Topics such as film holding, optical table design, optical schemes and geometries, the construction of large mirror towers, laser choice and installation, object choice and design, the use of unstable curtains, chemistry, drying and final product mounting will be covered. Pulsed holography as used by Australian Holographics will be briefly mentioned and its relative advantages and disadvantages compared to CW.

Ratcliffe, David

1998-02-01

237

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

238

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

239

CO{sub 2} 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 (CBM) recovery as an added benefit of sequestration. There were three main objectives for this reporting period, which related to obtaining accurate parameters for reservoir model description and modeling reservoir performance of CO{sub 2} sequestration and enhanced coalbed methane recovery. The first objective was to collect and desorb gas from 10 sidewall core coal samples from an Anadarko Petroleum Corporation well (APCL2 well) at approximately 6,200-ft depth in the Lower Calvert Bluff Formation of the Wilcox Group in east-central Texas. The second objective was to measure sorptive capacities of these Wilcox coal samples for CO{sub 2}, CH{sub 4}, and N{sub 2}. The final objective was to contract a service company to perform pressure transient testing in Wilcox coal beds in a shut-in well, to determine permeability of deep Wilcox coal. Bulk density of the APCL2 well sidewall core samples averaged 1.332 g/cc. The 10 sidewall core samples were placed in 4 sidewall core canisters and desorbed. Total gas content of the coal (including lost gas and projected residual gas) averaged 395 scf/ton on an as-received basis. The average lost gas estimations were approximately 45% of the bulk sample total gas. Projected residual gas was 5% of in-situ gas content. Six gas samples desorbed from the sidewall cores were analyzed to determine gas composition. Average gas composition was approximately 94.3% methane, 3.0% ethane, and 0.7% propane, with traces of heavier hydrocarbon gases. Carbon dioxide averaged 1.7%. Coal from the 4 canisters was mixed to form one composite sample that was used for pure CO{sub 2}, CH{sub 4}, and N{sub 2} isotherm analyses. The composite sample was 4.53% moisture, 37.48% volatile matter, 9.86% ash, and 48.12% fixed carbon. Mean vitrinite reflectance was 0.54%. Coal rank was high-volatile C to B bituminous. Comparison of the desorbed gas content (395 scf/ton, as received) at reservoir pressure (2,697 psi) with the sorption isotherm indicates that Lower Calvert Bluff coal at this well site is oversaturated, but lost gas may have been overestimated. This high gas content suggests that little or no depressurization would be required to initiate methane production. Sorption isotherms results indicate that the sorptive capacity of CO{sub 2} is about 2.5 times that of CH{sub 4} at 1,000 psia. This ratio is similar to that of higher rank bituminous coals from other basins (e.g., Carroll, and Pashin, 2003), and it is very low in comparison to results of other low-rank coals and to the values that we used in our preliminary reservoir modeling. If this value from the APCL2 well is representative, Wilcox coals in this area will sequester less CO{sub 2} on a per ton basis than we had earlier inferred. However, because measured methane contents are higher, enhanced coalbed methane production potential is greater than we earlier inferred. Pressure transient testing for determining coal fracture permeability will be conducted soon by Pinnacle Technologies. The data from these analyses will be used to finalize our coal model for the reservoir simulation phase of the project.

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

2005-02-01

240

Star Cluster Formation and Star Formation: The Role of Environment and Star Formation Efficiencies  

E-print Network

Analyzing global starburst properties in various kinds of starburst and post-starburst galaxies and relating them to the properties of the star cluster populations they form, I explore the conditions for the formation of massive, compact, long-lived star clusters. The aim is to find out whether the relative amount of star formation that goes into star cluster formation as opposed to field star formation, and into the formation of massive long-lived clusters in particular, is universal or scales with star formation rate, burst strength, star formation efficiency, galaxy or gas mass, and whether or not there are special conditions or some threshold for the formation of star clusters that merit to be called globular clusters a few gigayears later.

Uta Fritze

2008-01-15

241

Urbanization and Slum Formation  

PubMed Central

The formation of slums need not be inevitable with rapid urbanization. Such an argument appears to be contradicted by evidence of large slum populations in a large number of developing countries and particularly in rapidly urbanizing regions like Asia. The evidence discussed suggests that city authorities faced with rapid urban development lack the capacity to cope with the diverse demands for infrastructural provision to meet economic and social needs. Not only are strategic planning and intervention major issues in agenda to manage rapid urbanization, but city governments are not effectively linking the economic development trajectory to implications for urban growth and, hence, housing needs. In the following discussion, a case study is presented in support of the argument that city governments have to first recognize and then act to establish the link that is crucial between economic development, urban growth, and housing. This is the agendum that has been largely neglected by city and national governments that have been narrowly focused on economic growth with the consequent proliferation of slum formation as a housing solution. PMID:17387618

Phua, Kai Hong

2007-01-01

242

Explosions During Galaxy Formation  

NASA Astrophysics Data System (ADS)

As an idealized model of the effects of energy release by supernovae during galaxy formation, we consider an explosion at the center of a halo which forms at the intersection of filaments in the plane of a cosmological pancake by gravitational instability during pancake collapse. Such halos resemble the virialized objects found in N-body simulations in a CDM universe and, therefore, serve as a convenient, scale-free test-bed model for galaxy formation. ASPH/P3M simulations reveal that such explosions are anisotropic. The energy and metals are channeled into the low density regions, away from the pancake plane. The pancake remains essentially undisturbed, even if the explosion is strong enough to blow away all the gas located inside the halo at the onset of the explosion and reheat the IGM surrounding the pancake. Infall quickly replenishes this ejected gas and gradually restores the gas fraction as the halo mass continues to grow. Estimates of the collapse epoch and SN energy-release for galaxies of different mass in the CDM model can relate these results to scale-dependent questions of blow-out and blow-away and their implication for early IGM heating and metal enrichment and the creation of dark-matter-dominated dwarf galaxies.

Martel, H.; Shapiro, P. R.

2001-03-01

243

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

244

Egg Formation in Lepidoptera  

PubMed Central

Reproductive biology in the Twentieth Century produced comprehensive descriptions of the mechanisms of egg formation in most of the major orders of insects. While many general principles of ovarian development and physiology emerged, every order turned out to have a set of its own special motifs. Discovery of the lepidopteran motifs is summarized in this essay. The emphasis is on developmental mechanisms, beginning with the early growth and differentiation of female germ cells and ending, after many turns in morphogenesis, physiology and biosynthesis, with eggs that are filled with yolk and encased in chorions. Examples of uniquely lepidopteran traits include the cellular composition of ovarian follicles, the number of tubular ovarioles in which they mature, the functions of cell-to-cell junctional complexes in their maturation, their use of glycosaminoglycans to maintain intercellular patency during vitellogenesis, the role of proton and calcium pumps in their ion physiology, a separate postvitellogenic period of water and inorganic ion uptake, and the fine structure and protein composition of their chorions. Discovery of this combination of idiosyncracies was based on advances in the general concepts and techniques of cell and molecular biology and on insights borrowed from studies on other insects. The lepidopteran ovary in turn has contributed much to the understanding of egg formation in insects generally. PMID:20050770

Telfer, William H.

2009-01-01

245

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

246

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

247

Kinetics of ring formation  

NASA Astrophysics Data System (ADS)

We study reversible polymerization of rings. In this stochastic process, two monomers bond and, as a consequence, two disjoint rings may merge into a compound ring or a single ring may split into two fragment rings. This aggregation-fragmentation process exhibits a percolation transition with a finite-ring phase in which all rings have microscopic length and a giant-ring phase where macroscopic rings account for a finite fraction of the entire mass. Interestingly, while the total mass of the giant rings is a deterministic quantity, their total number and their sizes are stochastic quantities. The size distribution of the macroscopic rings is universal, although the span of this distribution increases with time. Moreover, the average number of giant rings scales logarithmically with system size. We introduce a card-shuffling algorithm for efficient simulation of the ring formation process and we present numerical verification of the theoretical predictions.

Ben-Naim, E.; Krapivsky, P. L.

2011-06-01

248

Cellular pattern formation  

NASA Astrophysics Data System (ADS)

This thesis studies the formation and evolution of cellular patterns in foams and living organisms using the extended large-Q Potts model. Specific problems include grain growth, foam drainage, foam rheology, and patterning and cell sorting in the mound phase of the slime mode Dictyostelium discoideum. In a wide range of cellular materials, surface-energy-driven diffusion leads to boundary motion which causes some grains to expend and others to shrink. Two-dimensional large-Q Potts model simulation of the evolution of a disordered cluster developed from a hexagonal grain array with a defect shows that abnormal grain growth can occur without strong anisotropy of surface energy. The grains at the boundary of the disordered cluster reach a special scaling state with no scale change. In three-dimensional liquid foams, drainage occurs due to gravity. Large-Q Potts model simulations, extended to include gravity in three dimensions, agree with both experimental and analytical results for various kinds of foam drainage, and also predict new phenomena. Foams exhibit a unique rheological transition from solid-like to fluid-like. Simulations using the large-Q Potts model, extended to apply shear to a two-dimensional foam, show three different types of hysteresis in foam's stress-strain relationship, which correspond to the elastic, viscoelastic and viscous fluid properties. This wide-ranging mechanical response depends on the structure and dynamics of local topological rearrangement of foam cells. Biological tissues resemble foams and the large-Q Potts model can also simulate sorting in biological cell aggregates. In Dictyostelium mound, two types of cells are initially randomly distributed. In time, one cell type sorts to form a tip. Simulations show that both differential adhesion and chemotaxis are required for sorted tip formation. With only differential adhesion, no tip forms. With only chemotaxis, a tip forms containing both cell types. Thus simulations can provide a method to determine the processes necessary for biological patterning.

Jiang, Yi

249

Medusae Fossae Formation  

NASA Technical Reports Server (NTRS)

(Released 16 April 2002) The Science This THEMIS visible image was acquired near 11o N, 159o W (201o E) and shows examples of the remarkable variations that can be seen in the erosion of the Medusae Fossae Formation. This Formation is a soft, easily eroded deposit that extends for nearly 1,000 km along the equator of Mars. In this region, like many others throughout the Medusae Fossae Formation, the surface has been eroded by the wind into a series of linear ridges called yardangs. These ridges generally point in direction of the prevailing winds that carved them, and demonstrate the power of martian winds to erode the landscape of Mars. The easily eroded nature of the Medusae Fossae Formation suggests that it is composed of weakly cemented particles, and was most likely formed by the deposition of wind-blown dust or volcanic ash. Within this single image it is possible to see differing amounts of erosion and stripping of layers in the Medusae Fossae Formation. Near the bottom (southern) edge of the image a rock layer with a relatively smooth upper surface covers much of the image. Moving upwards (north) in the image this layer becomes more and more eroded. At first there are isolated regions where the smooth unit has been eroded to produce sets of parallel ridges and knobs. Further north these linear knobs increase in number, and only small, isolated patches of the smooth upper surface remain. Finally, at the top of the image, even the ridges have been removed, exposing the remarkably smooth top of hard, resistant layer below. This sequence of layers with differing hardness and resistance to erosion is common on Earth and on Mars, and suggests significant variations in the physical properties, composition, particle size, and/or cementation of these martian layers. As is common throughout the Medusae Fossae Formation, very few impact craters are visible, indicating that the surface exposed is relatively young, and that the process of erosion may be active today. The Story 'Yardang!' Now, that may seem like a peculiar-sounding curse word, but nobody would get in trouble for using it. A yardang is one of the very cool-sounding words geologists use to describe long, irregular features like the ones seen in this image. Yardangs are grooved, furrowed ridges that form as the wind erodes away weakly cemented material in the region. Rippling across the surface, yardangs tell the story of how the powerful Martian wind carved the surface into such a gorgeous pattern over time. (Don't miss clicking on the above image to see a detailed view, in which the beauty and almost dance-like symmetry of the waving terrain pops out in highly compelling, three-dimensional texture.) It may be easy to see which way the wind blows in this area, since these streamlined features point in the direction of prevailing winds. But how can geologists understand the various kinds of terrain seen here? First, they have to study the different patterns of erosion, looking closely at how the wind has stripped off certain layers and not others. Want to be a geologist yourself? Start at the bottom of the image and scroll upward, and see how the relatively smooth, higher terrain toward the south gradually becomes more and more eroded. Moving up the image, at first you?ll see only a few, isolated regions of parallel ridges and knolls. Go a little farther north with your eyes (toward the center of the image), and you?ll see how these linear knobs really get going! Once you get to the top of the image, only patches of these grooved ridges remain, leaving an incredibly smooth, wind-scrubbed surface behind. You know this layer has to be made of pretty hard material, because it seems impervious to further erosion. Geologists studying Mars can compare these Martian yardangs to examples found on Earth, such as those in the Lut desert of Iran. Humans have even been known to use the wind as their inspiration, sculpting the shape of yardangs themselves. The famous sphynx at Giza in Egypt is thought to be a yardang that's been whittled

2002-01-01

250

Formation of Hydrogen and Formate by Ruminococcus albus  

PubMed Central

Radioisotopic growth studies with specifically labeled 14C-glucose confirmed that Ruminococcus albus, strain 7, ferments glucose mainly by the Embden-Myerhof-Parnas pathway to acetate, ethanol, formate, CO2, H2, and an unidentified product. Cell suspensions and extracts converted pyruvate to acetate, H2, CO2, and a small amount of ethanol. Formate was not produced from pyruvate and was not degraded to H2 and CO2, indicating that formate was not an intermediate in the production of H2 and CO2 from pyruvate. Cell extract and 14C-glucose growth studies showed that the H2-producing pyruvate lyase reaction is the major route of H2 and CO2 production. An active pyruvate-14CO2 exchange reaction was demonstrable with cell extracts. The 14C-glucose growth studies indicated that formate, as well as CO2, arises from the 3 and 4 carbon positions of glucose. A formate-producing pyruvate lyase system was not demonstrable either by pyruvate-14C-formate exchange or by net formate formation from pyruvate. Growth studies with unlabeled glucose and labeled 14CO2 or 14C-formate suggest that formate arises from the 3 and 4 carbon positions of glucose by an irreversible reduction of CO2. The results of the studies on the time course of formate production showed that formate production is a late function of growth, and the rate of production, as well as the total amount produced, increases as the glucose concentration available to the organism increases. PMID:4745433

Miller, Terry L.; Wolin, M. J.

1973-01-01

251

Binary stars - Formation by fragmentation  

NASA Technical Reports Server (NTRS)

Theories of binary star formation by capture, separate nuclei, fission and fragmentation are compared, assessing the success of theoretical attempts to explain the observed properties of main-sequence binary stars. The theory of formation by fragmentation is examined, discussing the prospects for checking the theory against observations of binary premain-sequence stars. It is concluded that formation by fragmentation is successful at explaining many of the key properties of main-sequence binary stars.

Boss, Alan P.

1988-01-01

252

Formation control for cooperative surveillance  

E-print Network

Unicycle model : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 15 5 Forming hexagonal formation. Gray shows initial conflguration of agents and black shows accomplished formation : : : : : : : : : : : : 21 6 All errors are stabilized... with point-mass type agents. In the 1990?s, formation control was researched via the virtual structure(VS) concept. In the latter a virtual reference point is computed by averaging the positions of all the agents as in [17], or a vir- tual reference frame can...

Woo, Sang-Bum

2009-05-15

253

“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. PMID:24926110

Dolnicar, Sara; Grün, Bettina

2013-01-01

254

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

255

Beach-cusp formation  

USGS Publications Warehouse

Field experiments on beach-cusp formation were undertaken to document how the cuspate form develops and to test the edge-wave hypothesis on the uniform spacing of cusps. These involved observations of cusps forming from an initially plane foreshore. The cuspate form was observed to be a product of swash modification of an intertidal beach ridge as follows. A ridge, cut by a series of channels quasi-equally spaced along its length, was deposited onto the lower foreshore. The ridge migrated shoreward with flood tide, while the longshore positions of the channels remained fixed. On ebb tide, changes in swash circulation over the ridge allowed the upwash to flow shoreward through the channels and the channel mouths were eroded progressively wider until adjacent mouths met, effecting a cuspate shape. Measured spacings of cusps, ranging in size from less than 1 m to more than 12 m, agree well with computed spacings due to either zero-mode subharmonic or zero-mode synchronous edge waves. Edge-wave-induced longshore variations in run up will cause water ponded behind a ridge to converge at points of low swash and flow seaward as relatively narrow currents eroding channels spaced at one edge-wave wavelength for synchronous edge waves or one half wavelength for subharmonic edge waves. The channels are subsequently modified into cusp troughs as described above.

Sallenger, A.H., Jr.

1979-01-01

256

Nuclear ``pasta'' formation  

NASA Astrophysics Data System (ADS)

The formation of complex nonuniform phases of nuclear matter, known as nuclear pasta, is studied with molecular dynamics (MD) simulations containing 51200 nucleons. A phenomenological nuclear interaction is used that reproduces the saturation binding energy and density of nuclear matter. Systems are prepared at an initial density of 0.10fm-3 and then the density is decreased by expanding the simulation volume at different rates to densities of 0.01fm-3 or less. An originally uniform system of nuclear matter is observed to form spherical bubbles (“swiss cheese”), hollow tubes, flat plates (“lasagna”), thin rods (“spaghetti”) and, finally, nearly spherical nuclei with decreasing density. We explicitly observe nucleation mechanisms, with decreasing density, for these different pasta phase transitions. Topological quantities known as Minkowski functionals are obtained to characterize the pasta shapes. Different pasta shapes are observed depending on the expansion rate. This indicates nonequilibrium effects. We use this to determine the best ways to obtain lower energy states of the pasta system from MD simulations and to place constraints on the equilibration time of the system.

Schneider, A. S.; Horowitz, C. J.; Hughto, J.; Berry, D. K.

2013-12-01

257

Bubble formation in microgravity  

NASA Technical Reports Server (NTRS)

An extensive experimental program was initiated for the purpose of understanding the mechanisms leading to bubble generation during fluid handling procedures in a microgravity environment. Several key fluid handling procedures typical for PCG experiments were identified for analysis in that program. Experiments were designed to specifically understand how such procedures can lead to bubble formation. The experiments were then conducted aboard the NASA KC-135 aircraft which is capable of simulating a low gravity environment by executing a parabolic flight attitude. However, such a flight attitude can only provide a low gravity environment of approximately 10-2go for a maximum period of 30 seconds. Thus all of the tests conducted for these experiments were designed to last no longer than 20 seconds. Several experiments were designed to simulate some of the more relevant fluid handling procedures during protein crystal growth experiments. These include submerged liquid jet cavitation, filling of a cubical vessel, submerged surface scratch, attached drop growth, liquid jet impingement, and geysering experiments. To date, four separate KC-135 flight campaigns were undertaken specifically for performing these experiments. However, different experiments were performed on different flights.

Antar, Basil N.

1996-01-01

258

The Principal as Formative Coach  

ERIC Educational Resources Information Center

Formative coaching, an approach that uses student work as the foundation for mentoring and professional development, can help principals become more effective instructional leaders. In formative coaching, teaches and coaches analyze student work to determine next steps for instruction. This article shows how a principal can use the steps of the…

Nidus, Gabrielle; Sadder, Maya

2011-01-01

259

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.

Carlos Ayala

2005-01-01

260

Sibling similarity in family formation.  

PubMed

Sibling studies have been widely used to analyze the impact of family background on socioeconomic and, to a lesser extent, demographic outcomes. We contribute to this literature with a novel research design that combines sibling comparisons and sequence analysis to analyze longitudinal family-formation trajectories of siblings and unrelated persons. This allows us to scrutinize in a more rigorous way whether sibling similarity exists in family-formation trajectories and whether siblings' shared background characteristics, such as parental education and early childhood family structure, can account for similarity in family formation. We use Finnish register data from 1987 through 2007 to construct longitudinal family-formation trajectories in young adulthood for siblings and unrelated dyads (N = 14,257 dyads). Findings show that family formation is moderately but significantly more similar for siblings than for unrelated dyads, also after controlling for crucial parental background characteristics. Shared parental background characteristics add surprisingly little to account for sibling similarity in family formation. Instead, gender and the respondents' own education are more decisive forces in the stratification of family formation. Yet, family internal dynamics seem to reinforce this stratification such that siblings have a higher probability to experience similar family-formation patterns. In particular, patterns that correspond with economic disadvantage are concentrated within families. This is in line with a growing body of research highlighting the importance of family structure in the reproduction of social inequality. PMID:25367282

Raab, Marcel; Fasang, Anette Eva; Karhula, Aleksi; Erola, Jani

2014-12-01

261

Organic chemistry of coke formation  

Microsoft Academic Search

The modes of formation of carbonaceous deposits (“coke”) during the transformation of organic compounds over acid and over bifunctional noble metal-acid catalysts are described. At low reaction temperatures, (350°C), the coke components are polyaromatic. Their formation involves hydrogen transfer (acid catalysts) and dehydrogenation (bifunctional catalysts) steps in addition to condensation and rearrangement steps. On microporous catalysts, the retention of coke

M Guisnet; P Magnoux

2001-01-01

262

SAS FORMATS: USES AND ABUSES  

EPA Science Inventory

SAS formats are a very powerful tool. They allow you to display the data in a more readable manner without modifying it. Formats can also be used to group data into categories for use in various procedures like PROC FREQ, PROC TTEST, and PROC MEANS (as a class variable). As ...

263

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

264

Accretion processes in star formation  

Microsoft Academic Search

This volume reviews our current knowledge of the processes governing the formation of stars, from the collapse and fragmentation of cold molecular gas clouds through the formation and evolution of disks which can form planets. It provides an especially timely reference for understanding recent discoveries of extrasolar planets and new direct evidence for protoplanetary disks around young stars. Each topic

Lee Hartmann

1998-01-01

265

ASDF: AUDIO SCENE DESCRIPTION FORMAT  

Microsoft Academic Search

The Audio Scene Description Format (ASDF) is an col- laboratively evolving format for the storage and inter- change of static, dynamic and interactive spatial audio content. This position paper briefly describes the current status and raises a list of open questions which shall be addressed in the panel discussion.

Matthias Geier; Sascha Spors

266

Double layer formation. [in plasma  

NASA Technical Reports Server (NTRS)

An investigation is conducted of the plasma processes which occur during the formation of a double layer in response to an applied initial electric field, when triggered by a current in the plasma. The important feature of the formation process was the creation of an ion-rich plasma-density cavity. The positive space charge of the cavity was shielded by induction of a negative space charge on the low potential side of the cavity, giving rise to the formation of a fully developed double layer. The shielding was complete only when the electron current from the low potential side exceeded the electron thermal current. It was found that during the formation of double layers counterstreaming electrons are generated. Moreover, transient double layers with reverse polarity also occur during this phase. Thus, the recurring formation of double layers can give rise to flickering double layers.

Singh, N.

1982-01-01

267

Physics of primordial star formation  

NASA Astrophysics Data System (ADS)

The study of primordial star formation has a history of nearly sixty years. It is generally thought that primordial stars are one of the key elements in a broad range of topics in astronomy and cosmology, from Galactic chemical evolution to the formation of super-massive blackholes. We review recent progress in the theory of primordial star formation. The standard theory of cosmic structure formation posits that the present-day rich structure of the Universe developed through gravitational amplification of tiny matter density fluctuations left over from the Big Bang. It has become possible to study primordial star formation rigorously within the framework of the standard cosmological model. We first lay out the key physical processes in a primordial gas. Then, we introduce recent developments in computer simulations. Finally, we discuss prospects for future observations of the first generation of stars.

Yoshida, Naoki

2012-09-01

268

Cyanide Formation by Chromobacterium violaceum  

PubMed Central

Michaels, Ruth (Columbia University, New York, N.Y.), and W. A. Corpe. Cyanide formation by Chromobacterium violaceum. J. Bacteriol. 89:106–112. 1965.—The formation of cyanide by a Chromobacterium violaceum strain was studied with growing cultures and with nonproliferating cells grown in complex and chemically defined media. Most of the cyanide was produced during the log-phase growth of the organism, and accumulated in the culture supernatant fluid. A synergistic effect of glycine and methionine on cyanide formation in a chemically defined medium was observed, and the amount of cyanide formed was found to be dependent on the concentrations of the two substances. Cyanide formation by nonproliferating cells was stimulated by preincubation with glycine and methionine. Cyanide formation by adapted cells in the presence of glycine and methionine was stimulated by succinate, malate, or fumarate, and depressed by azide and 2,4-dinitrophenol. Methionine could be replaced by betaine, dimethylglycine, and choline. PMID:14255648

Michaels, Ruth; Corpe, W. A.

1965-01-01

269

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

270

Liquid HEC formation damage potential  

SciTech Connect

Hydroxyethylcellulose (HEC) polymer is used extensively in completion/workover operations as a viscosifying agent for gravel-pack carrier fluid and fluid-loss-control pills. Formation damage potential of HEC gels is typically attributed to the presence of fisheyes or microgels. Potential for fisheye- and microgel-formation damage can be minimized by keeping powder dry to prevent water absorption and consequent hydration of the outer polymer layer that would prevent full polymer solution. To avoid problems in dry-powder storage and handling, HEC powder is sometimes pre-dispersed in alcohols, kerosene, diesel or mineral oil. These formulations are known as liquid HEC. Although they prevent premature powder hydration and consequent fisheye formation, they are not effective against formation damage because they contain microgels that are often pre-existing in the HEC powder used to prepare the slurry. In addition, these formulations may not be as clean as the HEC oilfield applications require, and may contain other additives which can, in some instances, react with the polymer. While the formation damage potential of HEC gels mixed in the field from HEC powder is well recognized, the damage potential of pre-mixed liquid HEC is less known. Hayatdavoudi, et al., noted that the gel prepared with liquid HEC contained as much microgels as those prepared using HEC powder. Chauveteau and Kohler reported that microgels can build up on the formation surface, as well as invade the formation and clog pores.

Ali, S.A.; Sketchler, B.C. (Chevron USA Production Co., New Orleans, LA (United States)); Hashemi, R. (Pall Corp., East Hills, NY (United States))

1994-11-01

271

An Assessment of the Cultural Practices Behind the Formation (or Not) of Amazonian Dark Earths in Marajo Island Archaeological Sites  

Microsoft Academic Search

For many decades, archaeologists working in Amazonia have looked for terra preta (black soil) areas in their search for ancient settlements. The typical Amazonian archaeological site is comprised of a combination\\u000a of black soil, ceramic sherds and some distinct vegetation species, which William Balée calls “cultural forests” (Balée 1989).\\u000a Sites are usually located in elevated terrains or riverine bluffs, pro

DP Schaan; DC Kern; FJL Frazão

272

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

273

Treating tar sands formations with karsted zones  

DOEpatents

Methods for treating a tar sands formation are described herein. The tar sands formation may have one or more karsted zones. Methods may include providing heat from one or more heaters to one or more karsted zones of the tar sands formation to mobilize fluids in the formation. At least some of the mobilized fluids may be produced from the formation.

Vinegar, Harold J. (Bellaire, TX); Karanikas, John Michael (Houston, TX)

2010-03-09

274

Formation of the First Star Clusters  

E-print Network

Formation of the First Star Clusters Ralf Klessen Zentrum für Astronomie der Universität Heidelberg-Hsu Wang ... many collaborators abroad! #12;First star formation agenda #12;Star cluster formation First of molecular clouds Star cluster formation First star formation Magnetic fields in the primordial universe

Klessen,Ralf

275

MISR Level 3 File Format  

Atmospheric Science Data Center

... MISR Level 3 products are in HDF-EOS format. Tools and other information about HDF-EOS are available from the  HDF-EOS Tools and Information Center  and  HDF Info . Detailed information about the ...

2015-01-08

276

Marmoryen Formation (marble) STORETVEIT GROUP  

E-print Network

) STORETVEIT GROUP Minor Bergen Arc Paradis Formation (green polymict congl.) Deformed saussurite gabbro, gabbro-pegmatite, basic/acidic dykes NORDÃ?SVATN COMPLEX Fine-grained amphibolite, mylonitic in most

Fossen, Haakon

277

Early Stage of Galaxy Formation  

E-print Network

We discuss on the early stage of galaxy formation based on recent deep surveys for very high-redshift galaxies, mostly beyond redshift of 6. These galaxies are observed to be strong Lyman$\\alpha$ emitters, indicating bursts of massive star formation in them. The fraction of such star-forming system appears to increase with increasing redshift. On the other hand, the star formation rate density derived from Lyman$\\alpha$ emitters tends to decrease with increasing redshift. It is thus suggested that the major epoch of initial starbursts may occur around $z \\sim$ 6 -- 7. In order to understand the early stage of galaxy formation, new surveys for galaxies beyond redshift of 7 will be important in near future.

Y. Taniguchi; T. Nagao; M. Ajiki; Y. Shioya; S. S. Sasaki; T. Murayama

2005-10-20

278

Sandstone Formations in Capitol Reef  

USGS Multimedia Gallery

Capitol Reef is primarily made up of sandstone formations within the Waterpocket Fold, monocline that extends nearly 100 miles. A monocline is a step-like fold in rock strata that can resemble an enormous wrinkle in the earth....

279

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

280

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

281

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

282

Methane formation in sewer systems  

Microsoft Academic Search

Methane formation and emission in sewer systems has not received as much attention as hydrogen sulphide formation. Through field measurements from two rising mains, with an average sewage temperature of 28.4 and 26.6°C, respectively, at the time of sampling, this study shows that a significant amount of methane can be produced in sewer systems, and that this production is positively

Albert Guisasola; David de Haas; Jurg Keller; Zhiguo Yuan

2008-01-01

283

Mechanisms of plant spindle formation  

Microsoft Academic Search

In eukaryotes, the formation of a bipolar spindle is necessary for the equal segregation of chromosomes to daughter cells.\\u000a Chromosomes, microtubules and kinetochores all contribute to spindle morphogenesis and have important roles during mitosis.\\u000a A unique property of flowering plant cells is that they entirely lack centrosomes, which in animals have a major role in spindle\\u000a formation. The absence of

Han Zhang; R. Kelly Dawe

2011-01-01

284

Zygospore formation in Mortierella capitata  

Microsoft Academic Search

A novel type of zygospore formation is described in the heterothallic speciesMortierella capitata, which was repeatedly isolated from soils inhabited by pillbugs (Armadillidium vulgare, Isopoda). Zygospore formation was induced on media containing sterilized arthropods. Anisogamy and colorless zygospore walls\\u000a are shared with other zygosporic species ofMortierella, but a unique feature ofM. capitata is the production of zygospores on elongated macrosuspensors

Yousuke Degawa; Seiji Tokumasu

1997-01-01

285

Carbothermic formation of boron nitride  

Microsoft Academic Search

Formation of boron nitride by reaction of boric oxide with carbon and nitrogen was studied. It was found from the results of experiments conducted by holding B2O3-activated C mixtures under a flowing nitrogen atmosphere that formation of boron nitride was complete in 120 min at 1500 °C. After cleaning the reaction product from the ash of the activated carbon and from

A. Aydo?du; N. Sevinç

2003-01-01

286

Dense cloud formation and star formation in a barred galaxy  

NASA Astrophysics Data System (ADS)

We investigate the properties of massive, dense clouds formed in a barred galaxy and their possible relation to star formation, performing a two-dimensional hydrodynamical simulation with the gravitational potential obtained from the 2MASS data from the barred spiral galaxy, M83. Since the environment for cloud formation and evolution in the bar region is expected to be different from that in the spiral arm region, barred galaxies are a good target to study the environmental effects on cloud formation and the subsequent star formation. Our simulation uses for an initial 80 Myr isothermal flow of non-self gravitating gas in the barred potential, then including radiative cooling, heating and self-gravitation of the gas for the next 40 Myr, during which dense clumps are formed. We identify many cold, dense gas clumps for which the mass is more than 104 M? (a value corresponding to the molecular clouds) and study the physical properties of these clumps. The relation of the velocity dispersion of the identified clump's internal motion with the clump size is similar to that observed in the molecular clouds of our Galaxy. We find that the virial parameters for clumps in the bar region are larger than that in the spiral arm region. From our numerical results, we estimate star formation in the bar and spiral arm regions by applying the simple model of Krumholz & McKee (2005). The mean relation between star formation rate and gas surface density agrees well with the observed Kennicutt-Schmidt relation. The star formation efficiency in the bar region is ˜60 per cent of the spiral arm region. This trend is consistent with observations of barred galaxies.

Nimori, M.; Habe, A.; Sorai, K.; Watanabe, Y.; Hirota, A.; Namekata, D.

2013-03-01

287

Significant melting of ice-wedges and formation of thermocirques on hill-slopes of thermokarst lakes in Central Yakutia (Siberia)  

NASA Astrophysics Data System (ADS)

On Earth, permafrost containing a high ice volume (referred as ice-rich) are sensible to climate change, they have been regionally degraded (thermokarst) during the early Holocene climatic optimum forming numerous thermokarst lakes in Central Yakutia (eastern Siberia). Recent temperature increases in the Arctic and Subarctic have been significantly greater than global averages. The frequency and magnitude of terrain disturbances associated with thawing permafrost are increasing in these regions and are thought to intensify in the future. Therefore, understand how is the current development of thermokarst is a critical question. Here, we describe the significant melting of ice-wedges on slopes of thermokarst lakes that leads to formation of amphitheatrical hollows referred as thermocirques. The evolution of thermocirques in Central Yakutia has been little studied and analyzing their formation could help to understand the recent thermokarst in relation to climate change in Central Yakutia. We studied the thermocirques at two scales: (i) field surveys of different thermocirques in July 2009-2010 and October 2012 to examine the processes and origin of melting of ice-wedges and; (ii) photo-interpretation of time series of satellite images (KH-9 Hexagon images of 6-9 m/pixel and GeoEye images of 50 cm/pixel) to study the temporal evolution of thermocirques. The melting of ground-ice on the scarp of thermocirque triggers falls and small mud-flows that induce the retreat of the scarp parallel to itself. Based on field studies and on GeoEye image comparison, we show that their rate of retrogressive growth is 1-2 m/year. On the hill-slopes of lakes, the thermokarst could be initiated by different processes that lead to the uncover and then melting of ice-wedges: thermal erosion by the waves of the ice-rich bluff; active-layer detachment (a form of slope failure linked to detachment of the seasonally thawed upper ground); flowing of water on the slope (precipitation) or; increase of near-surface temperature (insolation, summer temperature). We suggest that the preferential occurrence of thermocirques on south-facing slopes of lakes could emphasize the role of insolation as a factor controlling the preferential melting of ice-wedges. The air temperatures are shown to have increased in Central Yakutia over years and deciphering if ongoing climate warming could lead to an increased development of thermocirques along lake slopes in Central Yakutia is a question that we will address in future study.

Séjourné, Antoine; Costard, François; Gargani, Julien; Fedorov, Alexander; Skorve, Johnny

2013-04-01

288

Star formation in dwarf galaxies  

NASA Astrophysics Data System (ADS)

In this thesis, we examine the star formation history and stellar feedback effects of dwarf galaxies under the influence of extragalactic ultraviolet radiation, as well as the evolution of residual gas within tidally-limited dwarf galaxies and globular clusters. Previous work has indicated that the background UV flux can easily ionize the gas within typical dwarf galaxies, delaying or even preventing cooling and star formation within them. Many dwarf galaxies within the Local Group are, however, observed to contain multiple generations of stars, the oldest of which formed in the early epochs of cosmic evolution, when the background UV flux was intense. In order to address this paradox, we consider the dynamical evolution of gas in dwarf galaxies using a one-dimensional, spherically symmetric, Lagrangian numerical scheme which also computes the effects of radiative transfer and photoionization. We include in the scheme a physically-motivated star formation recipe and consider the effects of feedback. This scheme allows us to follow the history of the gas and of star formation within dwarf galaxies, as influenced by both external and internal UV radiation. Our results indicate that star formation in the severe environment of dwarf galaxies is a difficult and inefficient process. In potentials with total mass less than a few 106 M? , and velocity dispersion less than a few km s-1 , residual gas is efficiently photoionized by cosmic background UV radiation. For intermediate mass systems, such as the dSphs around the Galaxy, star formation can proceed within early cosmic epochs despite the intense background UV flux. Triggering processes such as merger events, collisions, and tidal disturbance can lead to density enhancements, reducing the recombination timescale, allowing gas to cool and star formation to proceed. However, the star formation and gas retention efficiency may vary widely in galaxies with similar dark matter potentials, because they depend on many factors, such as the baryonic fraction, external perturbation, IMF, and background UV intensity. We suggest that the presence of very old stars in these dwarf galaxies indicates that their initial baryonic to dark matter content was comparable to the cosmic value. This constraint suggests that the initial density fluctuation of baryonic matter may be correlated with that of the dark matter. For the more massive dwarf elliptical galaxies, the star formation efficiency and gas retention rate is much higher. Their mass to light ratio is regulated by star formation feedback, and is expected to be nearly independent of their absolute luminosity. The results of our theoretical models reproduce the observed M/L - Mupsilon correlation. (Abstract shortened by UMI.)

Dong, Shawfeng

289

The Dynamics of Latifundia Formation  

PubMed Central

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

290

Formation of Molecular Clouds and Global Conditions for Star Formation  

NASA Astrophysics Data System (ADS)

Giant molecular clouds (GMCs) are the primary reservoirs of cold, star-forming molecular gas in the Milky Way and similar galaxies, and thus any understanding of star formation must encompass a model for GMC formation, evolution, and destruction. These models are necessarily constrained by measurements of interstellar molecular and atomic gas and the emergent, newborn stars. Both observations and theory have undergone great advances in recent years, the latter driven largely by improved numerical simulations, and the former by the advent of large-scale surveys with new telescopes and instruments. This chapter offers a thorough review of the current state of the field.

Dobbs, C. L.; Krumholz, M. R.; Ballesteros-Paredes, J.; Bolatto, A. D.; Fukui, Y.; Heyer, M.; Low, M.-M. M.; Ostriker, E. C.; Vázquez-Semadeni, E.

291

Numerical Simulations of Galaxy Formation: Cooling, Heating, Star \\\\ Formation  

NASA Astrophysics Data System (ADS)

Formation of luminous matter in the Universe is a complicated process, which includes many processes and components. It is the vastly different scales involved in the process (from star formation on few parsec scales to galaxy clusters and superclusters on megaparsecs scales) and numerous ill-understood processes, which make the whole field a maze of unsolved, but exciting problems. We present new approximations for numerical treatment of multiphase ISM forming stars. The approximations were tested and calibrated using N-body+fluid numerical simulations. We specifically target issues related with effects of unresolved lumpinesses of the gas.

Klypin, A. A.

292

STAR FORMATION IN ATOMIC GAS  

SciTech Connect

Observations of nearby galaxies have firmly established, over a broad range of galactic environments and metallicities, that star formation occurs exclusively in the molecular phase of the interstellar medium (ISM). Theoretical models show that this association results from the correlation between chemical phase, shielding, and temperature. Interstellar gas converts from atomic to molecular only in regions that are well shielded from interstellar ultraviolet (UV) photons, and since UV photons are also the dominant source of interstellar heating, only in these shielded regions does the gas become cold enough to be subject to Jeans instability. However, while the equilibrium temperature and chemical state of interstellar gas are well correlated, the timescale required to reach chemical equilibrium is much longer than that required to reach thermal equilibrium, and both timescales are metallicity-dependent. Here I show that the difference in timescales implies that, at metallicities below a few percent of the solar value, well shielded gas will reach low temperatures and proceed to star formation before the bulk of it is able to convert from atomic to molecular. As a result, at extremely low metallicities, star formation will occur in a cold atomic phase of the ISM rather than a molecular phase. I calculate the observable consequences of this result for star formation in low-metallicity galaxies, and I discuss how some current numerical models for H{sub 2}-regulated star formation may need to be modified.

Krumholz, Mark R., E-mail: krumholz@ucolick.org [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)

2012-11-01

293

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. PMID:23197993

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

2012-01-01

294

Biofilm formation by Clostridium difficile  

PubMed Central

Clostridium difficile infection (CDI) is a major healthcare-associated disease worldwide. Recurring infections and increasing antibiotic resistance have complicated treatment of CDI. While C. difficile spores are important for transmission and persistence of CDI, other factors such as gut colonization and formation of bacterial communities in the gut may also contribute to pathogenesis and persistence, but have not been well investigated. Recently, we reported that important clinical C. difficile strains are able to form composite biofilms in vitro. C. difficile biofilm formation is a complex process, modulated by several different factors, including cell surface components and regulators. We also reported that bacteria within biofilms are more resistant to high concentrations of vancomycin, the antibiotic of choice for treatment of CDI. Here we summarize our recent findings and discuss the implications of biofilm formation by this anaerobic gut pathogen in disease pathogenesis and treatment. PMID:23892245

Dapa, Tanja; Unnikrishnan, Meera

2013-01-01

295

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. PMID:24339826

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

2013-01-01

296

Morphological study of penumbral formation  

NASA Astrophysics Data System (ADS)

Penumbrae are known to be areas of mainly horizontal magnetic field surrounding umbrae of relatively large and mature sunspots. In this paper, we observationally studied the formation of penumbrae in NOAA 10978, where several penumbral formations were observed in G-band images of the Solar Optical Telescope on board Hinode. Thanks to the continuous observation by Hinode, we could morphologically follow the evolution of sunspots and found that there are several paths to the penumbral formation: (1) active accumulation of magnetic flux, (2) rapid emergence of magnetic field, and (3) appearance of twisted or rotating magnetic tubes. In all of these cases, magnetic fields are expected to sustain high inclination at the edges of flux tube concentration longer than the characteristic growth time of downward magnetic pumping.

Kitai, Reizaburo; Watanabe, Hiroko; Otsuji, Ken'ichi

2014-12-01

297

Requirements for Hirano Body Formation  

PubMed Central

Hirano bodies are paracrystalline F-actin-rich structures associated with diverse conditions, including neurodegeneration and aging. Generation of model Hirano bodies using altered forms of Dictyostelium 34-kDa actin-bundling protein allows studies of their physiological function and mechanism of formation. We describe a novel 34-kDa protein mutant, E60K, with a point mutation within the inhibitory domain of the 34-kDa protein. Expression of E60K in Dictyostelium induces the formation of model Hirano bodies. The E60K protein has activated actin binding and is calcium regulated, unlike other forms of the 34-kDa protein that induce Hirano bodies and that have activated actin binding but lack calcium regulation. Actin filaments in the presence of E60K in vitro show enhanced resistance to disassembly induced by latrunculin B. Actin filaments in model Hirano bodies are also protected from latrunculin-induced depolymerization. We used nocodazole and blebbistatin to probe the role of the microtubules and myosin II, respectively, in the formation of model Hirano bodies. In the presence of these inhibitors, model Hirano bodies can form but are smaller than controls at early times of formation. The ultrastructure of model Hirano bodies did not reveal any major difference in structure and organization in the presence of inhibitors. In summary, these results support the conclusion that formation of model Hirano bodies is promoted by gain-of-function actin filament bundling, which enhances actin filament stabilization. Microtubules and myosin II contribute to but are not required for formation of model Hirano bodies. PMID:24632241

Griffin, Paul; Piggott, Cleveland; Maselli, Andrew; Fechheimer, Marcus

2014-01-01

298

Formation of the first stars.  

PubMed

Understanding the formation of the first stars is one of the frontier topics in modern astrophysics and cosmology. Their emergence signalled the end of the cosmic dark ages, a few hundred million years after the Big Bang, leading to a fundamental transformation of the early Universe through the production of ionizing photons and the initial enrichment with heavy chemical elements. We here review the state of our knowledge, separating the well understood elements of our emerging picture from those where more work is required. Primordial star formation is unique in that its initial conditions can be directly inferred from the ? cold dark matter (?CDM) model of cosmological structure formation. Combined with gas cooling that is mediated via molecular hydrogen, one can robustly identify the regions of primordial star formation, the so-called minihalos, having total masses of ~10(6) M? and collapsing at redshifts z ? 20-30. Within this framework, a number of studies have defined a preliminary standard model, with the main result that the first stars were predominantly massive. This model has recently been modified to include a ubiquitous mode of fragmentation in the protostellar disks, such that the typical outcome of primordial star formation may be the formation of a binary or small multiple stellar system. We will also discuss extensions to this standard picture due to the presence of dynamically significant magnetic fields, of heating from self-annihalating WIMP dark matter, or cosmic rays. We conclude by discussing possible strategies to empirically test our theoretical models. Foremost among them are predictions for the upcoming James Webb space telescope (JWST), to be launched ~2018, and for 'stellar archaeology', which probes the abundance pattern in the oldest, most-metal poor stars in our cosmic neighborhood, thereby constraining the nucleosynthesis inside the first supernovae. PMID:24168986

Bromm, Volker

2013-11-01

299

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

300

Implementing Protocols in Java: The Price of Portability \\Lambday Bobby Krupczak, Ken Calvert, Mostafa Ammar  

E-print Network

and deployment. Using insights from a Java­based protocol suite and supporting subsystem we have implemented, we by the traditional protocols (TCP/IP and UDP/IP). Unfortunately, the difficulty of designing, implementing new applications --- for example, multimedia conferencing --- could clearly benefit from such reusable

Ammar, Mostafa

301

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

Federal Register 2010, 2011, 2012, 2013, 2014

...limit with a maximum cooling time of seven years to be loaded. Raises the NUHOMS[supreg]-32P DSC neutron source to 4.175 x 10\\8\\ neutrons/sec/ assembly to support storage of the higher burnup fuel. 3. LCO 3.4.1.1,...

2010-09-29

302

77 FR 34093 - License Renewal for Calvert Cliffs Nuclear Power Plant, LLC's  

Federal Register 2010, 2011, 2012, 2013, 2014

...socioeconomics; air quality; water quality and use; geology and...on the NRC staff's evaluation, the potential environmental...significantly affect the quality of the human environment...which provides text and image files of NRC's...

2012-06-08

303

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

304

A comparison of differing techniques for the determination of mineral content in bone  

E-print Network

of sandstones within the Queen Formation that was started in 1983 at Texas A&M University. The environments of deposition for the siliciclastics of the Concho Bluff Queen Field will be addressed in this thesis. Currently, three contrasting models have been...THE LITHOLOGY, ENVIRONMENT OF DEPOSITION, AND RESERVOIR PROPERTIES OF SANDSTONES IN THE UPPER QUEEN FORMATION (GUADALUPIAN, PERMIAN) AT CONCHO BLUFF QUEEN FIELD, CRANE COUNTY, TEXAS A Thesis by Submitted to the Office of Graduate Studies...

Narrow, Samuel Everett

2012-06-07

305

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. PMID:24191107

Goehring, Lucas

2013-01-01

306

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

307

Enthalpy of formation of zircon  

Microsoft Academic Search

Using high-temperature solution calorimetry in molt 2PbO {center dot} BâOâ, the enthalpy of reaction of the formation of zircon, ZrSiOâ, from its constituent oxides has been determined: ÎâHâââ(ZrSiOâ) = -27.9 ({plus minus}1.9) kJ\\/mol. With previously reported data for the heat contents of ZrOâ SiOâ and ZrSiOâ and standard-state enthalpies of formation of ZrOâ and SiOâ, we obtain Î{sub f}Hâââ°. (ZrSiOâ)

Adam J. G. Ellison; Alexandra Navrotsky

1992-01-01

308

Intracellular starch formation in corynebacteria.  

PubMed

Carrier, E. Bernard (Louisiana State University, Baton Rouge, La.) and C. S. McCleskey. Intracellular starch formation in cor-yne bacteria. J. Bacteriol. 83:1029-1036. 1962.-Cor-ynebacterium tritici, C. striatum, C. renale, and C. pseudodiphtheriticum produce an intracellular starch-like material when grown on native starches; glucose-1-phosphate, mono-, di-, and trisaccharides do not serve as substrates for intracellular starch formation. C. pseudotuberculosis and C. kutscheri produce intracellular starch from starch substrates and glucose-1-phosphate. C. diphtheriae produces starch from glucose-1-phosphate only. PMID:13876866

CARRIER, E B; McCLESKEY, C S

1962-05-01

309

Optimal Reconfiguration of Tetrahedral Formations  

NASA Technical Reports Server (NTRS)

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 a nonlinear optimal control problem. In this research, this optimal control problem is solved using a spectral collocation method called the Gauss pseudospectral method. The objective of this research is to provide highly accurate minimum-fuel solutions to the MMS formation reconfiguration problem and to gain insight into the underlying structure of fuel-optimal trajectories.

Huntington, Geoffrey; Rao, Anil V.; Hughes, Steven P.

2004-01-01

310

Star formation and extinct radioactivities  

SciTech Connect

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. 36 references.

Cameron, A.G.W.

1984-11-01

311

INTRACELLULAR STARCH FORMATION IN CORYNEBACTERIA  

PubMed Central

Carrier, E. Bernard (Louisiana State University, Baton Rouge, La.) and C. S. McCleskey. Intracellular starch formation in cor-yne bacteria. J. Bacteriol. 83:1029–1036. 1962.—Cor-ynebacterium tritici, C. striatum, C. renale, and C. pseudodiphtheriticum produce an intracellular starch-like material when grown on native starches; glucose-1-phosphate, mono-, di-, and trisaccharides do not serve as substrates for intracellular starch formation. C. pseudotuberculosis and C. kutscheri produce intracellular starch from starch substrates and glucose-1-phosphate. C. diphtheriae produces starch from glucose-1-phosphate only. Images PMID:13876866

Carrier, E. Bernard; McCleskey, C. S.

1962-01-01

312

Tourism motivation and expectation formation  

Microsoft Academic Search

This theoretical study introduces a model of tourism motivation and expectation formation. It is based on a discussion and operationalization of both the behaviorist notion of drive reduction and the cognitivist constructs of attitudes and values. While the satisfaction of inner-directed values and motivations depends on classes of objects, outer-directed values target specific objects. In the case of trying to

Juergen Gnoth

1997-01-01

313

QGP formation and strange antibaryons  

Microsoft Academic Search

We explore, as function of the collision energy and stopping in relativistic nuclear collisions, the production yields of strange antibaryons, assuming formation of a deconfined thermal quark-gluon plasma (QGP) fireball which undergoes a sudden hadronisation. Aside of assumptions related to this reaction picture and QCD properties at this energy scale, our work does not contain (fitted) parameters.

Jean Letessier; Johann Rafelski; Ahmed Tounsi

1997-01-01

314

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

315

VEHICLE NETWORKS: ACHIEVING REGULAR FORMATION  

E-print Network

VEHICLE NETWORKS: ACHIEVING REGULAR FORMATION MADALENA CHAVES, ROBERT DAY, LUCIA GOMEZ a network of vehicles exchanging information among themselves with the intention of achieving a specified the performance of the vehicle network. A stochastic model for information flow is also considered, allowing

316

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

317

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

318

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

319

What's new in formation evaluation  

Microsoft Academic Search

Recent advances in formation evaluation techniques and tools are solving some previously difficult production engineering and operating problems. New approaches being used to attach long-standing difficulties include the following: (1) better, more informed use of data calculated from modern logs run in old wells; (2) small OD logging and caliper tools that can be pumped down drill pipe in directional

Timko

1968-01-01

320

Earth and Terrestrial Planet Formation  

E-print Network

The growth and composition of Earth is a direct consequence of planet formation throughout the Solar System. We discuss the known history of the Solar System, the proposed stages of growth and how the early stages of planet formation may be dominated by pebble growth processes. Pebbles are small bodies whose strong interactions with the nebula gas lead to remarkable new accretion mechanisms for the formation of planetesimals and the growth of planetary embryos. Many of the popular models for the later stages of planet formation are presented. The classical models with the giant planets on fixed orbits are not consistent with the known history of the Solar System, fail to create a high Earth/Mars mass ratio, and, in many cases, are also internally inconsistent. The successful Grand Tack model creates a small Mars, a wet Earth, a realistic asteroid belt and the mass-orbit structure of the terrestrial planets. In the Grand Tack scenario, growth curves for Earth most closely match a Weibull model. The feeding zon...

Jacobson, Seth A

2015-01-01

321

SAS FORMATS: USES AND ABUSES  

EPA Science Inventory

SAS formats are a very powerful tool. They allow you to display the data in a more readable manner without modifying the data. They can also be used to group data into categories for use in various procedures like PROC FREQ, PROC TTEST, and PROC MEANS (as a class variable). ...

322

Laser-assisted antihydrogen formation  

SciTech Connect

Laser-assisted antihydrogen (H) formation cross sections (differential and total) for collisions of antiprotons with positronium (Ps) are studied in the framework of the eikonal approximation for two geometries, when the field polarization is parallel (parallel{sup L}) or perpendicular (perpendicular{sup r}) to the incident Ps momentum. The variations of the H formation cross sections with respect to the field strength and the laser photon energy are studied for the multiphoton (absorption and emission) processes. The contribution of the atomic (both Ps and H) dressing terms to the enhancement of the H formation cross section is studied for both the geometries (parallel{sup L} and (perpendicular{sup r}). The most important prediction from the present work is the enhancement of the field-free (FF) H formation cross sections particularly at lower incident energies when the system (Ps+p) is irradiated by a single mode, linearly polarized laser, the enhancement being more pronounced for a wider range of incident energy in the perpendicular{sup r} geometry than in the parallel{sup L} one.

Chattopadhyay, A.; Sinha, C. [Department of Theoretical Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India)

2006-08-15

323

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

324

Peptide formation mediated by cyanate  

NASA Technical Reports Server (NTRS)

An investigation has been conducted to find out whether peptide formation can be enhanced by cyanate added to hydroxyapatite or orthophosphates. The results show that diglycine is formed when glycine is heated in the presence of apatite or orthophosphates. The addition of inorganic cyanate increases the yields of diglycine but its action as a condensing agent extends only to some of the orthophosphates studied.

Flores, J. J.; Leckie, J. O.

1973-01-01

325

Oligoadenosine Tracts Favor Nucleosome Formation  

Microsoft Academic Search

We have measured the ability of oligoadenosine tracts 25 base pairs in length to influence nucleosome formation. Such tracts can cause DNA to bind in nucleosomes at higher temperatures with a free energy up to 1 kcal\\/mol more favorable than heterogenous-sequence DNA. Furthermore, the position of the oligoadenosine tract affects the free energy of binding, with the most favorable position

Haleh Mahloogi; Michael J. Behe

1997-01-01

326

Batch calcination studies: melt formation  

Microsoft Academic Search

It is shown that the formation of a meltable calcine by batch calcination of an acidic waste solution containing primary sodium, iron, and aluminum sulfate and nitrate can be predicted. Calcine melting at temperatures less than 900°C can be correlated with the sodium to metal ion ratio and the sulfate to salt nitrate ratio. The minor constituents present in the

Shefcik

1961-01-01

327

A standard audit trail format  

SciTech Connect

The central role of audit trails, or (more properly) logs, in security monitoring needs little description, for it is too well known for any to doubt it. Auditing, or the analysis of logs, is a central part of security not only in computer system security but also in analyzing financial and other non-technical systems. As part of this process, it is often necessary to reconcile logs from different sources. This speaks of a need for a standard logging format. A standard log format robust enough to meet the needs of heterogeneity, transportability across various network protocols, and flexibility sufficient to meet a variety of needs in very different environments must satisfy two basic properties: extensibility and portability. This report presents the author`s proposed format for a standard log record. In section 3, he shows how and where the translation should be done, and in section 4 he demonstrates how log records from several disparate systems would be put into this format. Section 5 concludes with some observations and suggestions for future work.

Bishop, M. [Univ. of California, Davis, CA (United States). Dept. of Computer Science

1995-02-01

328

Computer simulation of bubble formation  

Microsoft Academic Search

Properties of liquid metals (Li, Pb, Na) containing nanoscale cavities were studied by atomistic Molecular Dynamics (MD). Two atomistic models of cavity simulation were developed that cover a wide area in the phase diagram with negative pressure. In the first model, the thermodynamics of cavity formation, stability and the dynamics of cavity evolution in bulk liquid metals have been studied.

Z. Insepov; T. Bazhirov; G. Norman; V. Stegailov

2007-01-01

329

Reverse hydrotropy by complex formation.  

PubMed

Self-aggregation of three di-N-alkylated diaza-18-crown-6 ethers (ACEs) was studied in non-polar solvents. The three ACEs differed by the length of the alkyl chain: n-decyl (ACE-10), n-hexadecyl (ACE-16) and n-tetracosane (ACE-24). From the previously reported interfacial tension isotherms, the formation of reverse micelles was expected above ACE concentrations of ?10(-3) M. However, the water content analysis in conjunction with Dynamic Light Scattering (DLS), Fluorescence Correlation Spectroscopy (FCS) and (1)H NMR Diffusion Ordered Spectroscopy (DOSY) do not provide any clear proof of the existence of aggregates. Only the Small Angle Neutron Scattering (SANS) of concentrated toluene ACE solutions reveals the existence of small reverse micelles (probably ACE dimers forming small cages hosting 1-2 water molecules). On the other hand, spectrophotometric and fluorescence dye dissolution studies using eosin Y, tropaeolin OO and methyl orange suggest that ACEs can dissolve these dyes without requiring the formation of aggregates. This discrepancy was interpreted assuming the dye-ACE complexation as the driving force for dye solubilisation, providing a possible mechanism of reverse hydrotropy ("lipotropy") in non-polar solvents. This example shows that special care should be taken when dye solubilisation is used to probe self-aggregation of an amphiphile in non-polar solvents. The amphiphile-dye complex formation might be responsible for false positive results and the aggregate formation should always be confirmed with other methods. PMID:25415596

Wojciechowski, Kamil; Gutberlet, Thomas; Raghuwanshi, Vikram Singh; Terry, Ann

2014-12-10

330

Controllability properties for aircraft formations  

Microsoft Academic Search

This paper studies the controllability of formations of n identical aircraft maintaining constant distances. Aircraft are modeled as a planar kinematic system with constant velocity and curvature bounds. The challenges of achieving controllability of such system are that it is an affine system with drift and its admissible controls are determined by its configuration variables. We begin with the study

Huifang Wang; Lucia Pallottino; Antonio Bicchi

2010-01-01

331

Formation of the terrestrial planets  

Microsoft Academic Search

The early phases of formation in the inner solar system were dominated by collisions and short-range dynamical interactions among planetesimals. But the later phases, which account for most of the differences among planets, are unsure because the dynamics are more subtle. Jupiter's influence became more important, leading to drastic clearing out of the asteroid belt and the stunting of Mars's

William M. Kaula

1994-01-01

332

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

333

The Black Hole Formation Probability  

NASA Astrophysics Data System (ADS)

A longstanding question in stellar evolution is which massive stars produce black holes (BHs) rather than neutron stars (NSs) upon death. It has been common practice to assume that a given zero-age main sequence (ZAMS) mass star (and perhaps a given metallicity) simply produces either an NS or a BH, but this fails to account for a myriad of other variables that may effect this outcome, such as spin, binarity, or even stochastic differences in the stellar structure near core collapse. We argue that instead a probabilistic description of NS versus BH formation may be better suited to account for the current uncertainties in understanding how massive stars die. Using the observed BH mass distribution from Galactic X-ray binaries, we investigate the probability that a star will make a BH as a function of its ZAMS mass. Although the shape of the black hole formation probability function is poorly constrained by current measurements, we believe that this framework is an important new step toward better understanding BH formation. We also consider some of the implications of this probability distribution, from its impact on the chemical enrichment from massive stars, to its connection with the structure of the core at the time of collapse, to the birth kicks that black holes receive. A probabilistic description of BH formation will be a useful input for future population synthesis studies that are interested in the formation of X-ray binaries, the nature and event rate of gravitational wave sources, and answering questions about chemical enrichment.

Clausen, Drew R.; Piro, Anthony; Ott, Christian D.

2015-01-01

334

Star Formation in Satellite Galaxies  

NASA Astrophysics Data System (ADS)

We present narrowband observations of the H? emission in a sample of 31 satellites orbiting isolated giant spiral galaxies. The sample studied spans the range -19 magformation rates are 0.68 and 3.66 Msolar yr-1, respectively. Maps of the spatial distribution of ionized gas are presented. The star-forming regions show a rich structure in which frequently discrete complexes are imposed over more diffuse structures. In general, the current star formation rates are smaller than the mean values in the past, obtained from the stellar content; this probably indicates a declining rate with time in the generation of new stars. However, the reserve of gas is enough to continue fueling the current levels of star formation activity for at least another Hubble time. Four of the objects (NGC 2718b, NGC 4541e, and NGC 5965a1 and NGC 5965a2) with higher current star formation rates show clear signs of interaction with close companions of comparable brightness at projected distances of 25, 20, and 2 kpc, respectively. The only two galaxies in our sample that do not show star formation activity are members of these interacting systems, and it is unclear if this is a consequence of intrinsic properties (both are early Hubble types) or if it is related to possible disruption of the external parts due to the interaction. In the case of the pair NGC 2718a-2718b there are indications of gas transport between the galaxies. Based on observations with the Vatican Advanced Technology Telescope: the Alice P. Lennon Telescope and the Thomas J. Bannan Astrophysics Facility.

Gutiérrez, C. M.; Alonso, M. S.; Funes, , J. G.; Ribeiro, M. B.

2006-08-01

335

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. PMID:18820078

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

2009-01-01

336

Peripheral Leptin Regulates Bone Formation  

PubMed Central

Substantial evidence does not support the prevailing view that leptin, acting through a hypothalamic relay, decreases bone accrual by inhibiting bone formation. To clarify the mechanisms underlying regulation of bone architecture by leptin, we evaluated bone growth and turnover in wild type (WT) mice, leptin receptor-deficient db/db mice, leptin-deficient ob/ob mice and ob/ob mice treated with leptin. We also performed hypothalamic leptin gene therapy to determine the effect of elevated hypothalamic leptin levels on osteoblasts. Finally, to determine the effects of loss of peripheral leptin signaling on bone formation and energy metabolism, we used bone marrow (BM) from WT or db/db donor mice to reconstitute the hematopoietic and mesenchymal stem cell compartments in lethally irradiated WT recipient mice. Decreases in bone growth, osteoblast-lined bone perimeter and bone formation rate were observed in ob/ob mice and greatly increased in ob/ob mice following subcutaneous administration of leptin. Similarly, hypothalamic leptin gene therapy increased osteoblast-lined bone perimeter in ob/ob mice. In spite of normal osteoclast-lined bone perimeter, db/db mice exhibited a mild but generalized osteopetrotic-like (calcified cartilage encased by bone) skeletal phenotype and greatly reduced serum markers of bone turnover. Tracking studies and histology revealed quantitative replacement of BM cells following BM transplantation. WT mice engrafted with db/db BM did not differ in energy homeostasis from untreated WT mice or WT mice engrafted with WT BM. Bone formation in WT mice engrafted with WT BM did not differ from WT mice, whereas bone formation in WT mice engrafted with db/db cells did not differ from the low rates observed in untreated db/db mice. In summary, our results indicate that leptin, acting primarily through peripheral pathways, increases osteoblast number and activity. PMID:22887758

Turner, Russell T.; Kalra, Satya P.; Wong, Carmen P.; Philbrick, Kenneth A.; Lindenmaier, Laurence B.; Boghossian, Stephane; Iwaniec, Urszula T.

2012-01-01

337

Galaxy formation through hierarchical clustering  

NASA Technical Reports Server (NTRS)

Analytic methods for studying the formation of galaxies by gas condensation within massive dark halos are presented. The present scheme applies to cosmogonies where structure grows through hierarchical clustering of a mixture of gas and dissipationless dark matter. The simplest models consistent with the current understanding of N-body work on dissipationless clustering, and that of numerical and analytic work on gas evolution and cooling are adopted. Standard models for the evolution of the stellar population are also employed, and new models for the way star formation heats and enriches the surrounding gas are constructed. Detailed results are presented for a cold dark matter universe with Omega = 1 and H(0) = 50 km/s/Mpc, but the present methods are applicable to other models. The present luminosity functions contain significantly more faint galaxies than are observed.

White, Simon D. M.; Frenk, Carlos S.

1991-01-01

338

Formation of quasiparallel Alfven solitons  

NASA Technical Reports Server (NTRS)

The formation of quasi-parallel Alfven solitons is investigated through the inverse scattering transformation (IST) for the derivative nonlinear Schroedinger (DNLS) equation. The DNLS has a rich complement of soliton solutions consisting of a two-parameter soliton family and a one-parameter bright/dark soliton family. In this paper, the physical roles and origins of these soliton families are inferred through an analytic study of the scattering data generated by the IST for a set of initial profiles. The DNLS equation has as limiting forms the nonlinear Schroedinger (NLS), Korteweg-de-Vries (KdV) and modified Korteweg-de-Vries (MKdV) equations. Each of these limits is briefly reviewed in the physical context of quasi-parallel Alfven waves. The existence of these limiting forms serves as a natural framework for discussing the formation of Alfven solitons.

Hamilton, R. L.; Kennel, C. F.; Mjolhus, E.

1992-01-01

339

Biofilm formation by Aspergillus fumigatus.  

PubMed

Aspergillus fumigatus is a well adapted, opportunistic fungus that causes a severe and commonly fatal disease, invasive pulmonary aspergillosis (IPA), in highly immunocompromised patients, aspergilloma in patients with lung cavities and allergic bronchopulmonary aspergillosis (ABPA) in hypersensitive individuals. Recent studies have suggested that biofilm formation by A. fumigatus may be one of the most important virulence factors in IPA and aspergilloma. Several fungal constituents may contribute to the formation of biofilm structures on host cells, including cell wall components, secondary metabolites and drug transporters. The biofilm phenotype of the fungus is refractory to most conventional antifungal treatment options. Thus, an in-depth analysis and understanding of A. fumigatus biofilms is necessary to devise newer and better antifungal targets for treating complex A. fumigatus biofilm-associated diseases. PMID:23962172

Kaur, Savneet; Singh, Shweta

2014-01-01

340

Biofilm Formation by Neisseria meningitidis  

PubMed Central

Biofilm formation by the human pathogen Neisseria meningitidis was analyzed. Biofilm-forming meningococcal strains were identified and quantitated by crystal violet staining. Laser scanning confocal microscopy of the meningococcal biofilm revealed variable layers up to 90 ?m in thickness. A total of 39 meningococcal isolates were studied; 23 were nasopharyngeal-carriage isolates, and 16 were invasive-disease isolates. Thirty percent of carriage isolates and 12.5% of invasive-disease isolates formed biofilms proficiently on a polystyrene surface. Generally, the strains that formed biofilms showed high-level cell surface hydrophobicity, characteristic of strains lacking a capsule. The inhibitory role of capsule in biofilm formation was further confirmed by comparing the biofilm-forming capabilities of a serogroup B wild-type strain of a disease-associated isolate to those of its capsule-deficient mutant (ctrA). Some strains of meningococci form biofilms, and this process is likely important in menigococcal colonization. PMID:15385518

Yi, Kyungcheol; Rasmussen, Andrew W.; Gudlavalleti, Seshu K.; Stephens, David S.; Stojiljkovic, Igor

2004-01-01

341

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

342

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

343

Shock Formation in Lovelock Theories  

E-print Network

We argue that Lovelock theories of gravity suffer from shock formation, unlike General Relativity. We consider the propagation of (i) a discontinuity in curvature, and (ii) weak, high frequency, gravitational waves. Such disturbances propagate along characteristic hypersurfaces of a "background" spacetime and their amplitude is governed by a transport equation. In GR the transport equation is linear. In Lovelock theories, it is nonlinear and its solutions can blow up, corresponding to the formation of a shock. We show that this effect is absent in some simple cases e.g. a flat background spacetime, and demonstrate its presence for a plane wave background. We comment on weak cosmic censorship, the evolution of shocks, and the nonlinear stability of Minkowski spacetime, in Lovelock theories.

Harvey S. Reall; Norihiro Tanahashi; Benson Way

2014-09-12

344

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

345

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

346

Hydrogen sulfide inhibits amyloid formation.  

PubMed

Amyloid fibrils are large aggregates of misfolded proteins, which are often associated with various neurodegenerative diseases such as Alzheimer's, Parkinson's, Huntington's, and vascular dementia. The amount of hydrogen sulfide (H2S) is known to be significantly reduced in the brain tissue of people diagnosed with Alzheimer's disease relative to that of healthy individuals. These findings prompted us to investigate the effects of H2S on the formation of amyloids in vitro using a model fibrillogenic protein hen egg white lysozyme (HEWL). HEWL forms typical ?-sheet rich fibrils during the course of 70 min at low pH and high temperatures. The addition of H2S completely inhibits the formation of ?-sheet and amyloid fibrils, as revealed by deep UV resonance Raman (DUVRR) spectroscopy and ThT fluorescence. Nonresonance Raman spectroscopy shows that disulfide bonds undergo significant rearrangements in the presence of H2S. Raman bands corresponding to disulfide (RSSR) vibrational modes in the 550-500 cm(-1) spectral range decrease in intensity and are accompanied by the appearance of a new 490 cm(-1) band assigned to the trisulfide group (RSSSR) based on the comparison with model compounds. The formation of RSSSR was proven further using a reaction with TCEP reduction agent and LC-MS analysis of the products. Intrinsic tryptophan fluorescence study shows a strong denaturation of HEWL containing trisulfide bonds. The presented evidence indicates that H2S causes the formation of trisulfide bridges, which destabilizes HEWL structure, preventing protein fibrillation. As a result, small spherical aggregates of unordered protein form, which exhibit no cytotoxicity by contrast with HEWL fibrils. PMID:25545790

Rosario-Alomar, Manuel F; Quiñones-Ruiz, Tatiana; Kurouski, Dmitry; Sereda, Valentin; Ferreira, Eduardo B; Jesús-Kim, Lorraine De; Hernández-Rivera, Samuel; Zagorevski, Dmitri V; López-Garriga, Juan; Lednev, Igor K

2015-01-29

347

Membrane adhesion and domain formation  

E-print Network

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 striking similarities to the pattern evolution observed during T cell adhesion.

Thomas R. Weikl; Reinhard Lipowsky

2007-09-23

348

The Black Hole Formation Probability  

NASA Astrophysics Data System (ADS)

A longstanding question in stellar evolution is which massive stars produce black holes (BHs) rather than neutron stars (NSs) upon death. It has been common practice to assume that a given zero-age main sequence (ZAMS) mass star (and perhaps a given metallicity) simply produces either an NS or a BH, but this fails to account for a myriad of other variables that may effect this outcome, such as spin, binarity, or even stochastic differences in the stellar structure near core collapse. We argue that instead a probabilistic description of NS versus BH formation may be better suited to account for the current uncertainties in understanding how massive stars die. We present an initial exploration of the probability that a star will make a BH as a function of its ZAMS mass, P BH(M ZAMS). Although we find that it is difficult to derive a unique P BH(M ZAMS) using current measurements of both the BH mass distribution and the degree of chemical enrichment by massive stars, we demonstrate how P BH(M ZAMS) changes with these various observational and theoretical uncertainties. We anticipate that future studies of Galactic BHs and theoretical studies of core collapse will refine P BH(M ZAMS) and argue that this framework is an important new step toward better understanding BH formation. A probabilistic description of BH formation will be useful as input for future population synthesis studies that are interested in the formation of X-ray binaries, the nature and event rate of gravitational wave sources, and answering questions about chemical enrichment.

Clausen, Drew; Piro, Anthony L.; Ott, Christian D.

2015-02-01

349

Equilibrium cluster formation and gelation  

E-print Network

We study the formation and growth of equilibrium clusters in a suspension of weakly-charged colloidal particles and small non-adsorbing polymers. The effective potential is characterised by a short-range attraction and a long-range repulsion. The size, shape and local structure of the clusters are studied using three-dimensional particle microscopy. We observe a rapid growth in the mean cluster size and the average number of nearest neighbours approaching the gel boundary.

Rodrigo Sanchez; Paul Bartlett

2005-06-22

350

Formation processes of framboidal pyrite  

Microsoft Academic Search

Pyrite framboid formation may be the result of four consecutive processes: (1) nucleation and growth of initial iron monosulfide microcrystals; (2) reaction of the microcrystals to greigite (Fe3S4; (3) aggregation of uniformly sized greigite microcrystals, i.e., framboid growth; and (4) replacement of greigite framboids by pyrite. The uniform morphology, uniform size range, and ordering of the microcrystals in individual framboids,

R. T. Wilkin; H. L. Barnes

1997-01-01

351

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

352

Dronedarone reduces arterial thrombus formation.  

PubMed

Dronedarone has been associated with a reduced number of first hospitalisation due to acute coronary syndromes. Whether this is only due to the reduction in ventricular heart rate and blood pressure or whether other effects of dronedarone may be involved is currently elusive. This study was designed to investigate the role of dronedarone in arterial thrombus formation. C57Bl/6 mice were treated with dronedarone and arterial thrombosis was investigated using a mouse photochemical injury model. Dronedarone inhibited carotid artery thrombus formation in vivo (P < 0.05). Thrombin- and collagen-induced platelet aggregation was impaired in dronedarone-treated mice (P < 0.05), and expression of plasminogen activator inhibitor-1 (PAI1), an inhibitor of the fibrinolytic system, was reduced in the arterial wall (P < 0.05). In contrast, the level of tissue factor (TF), the main trigger of the coagulation cascade, and that of its physiological inhibitor, TF pathway inhibitor, did not differ. Similarly, coagulation times as measured by prothrombin time and activated partial thromboplastin time were comparable between the two groups. Dronedarone inhibits thrombus formation in vivo through inhibition of platelet aggregation and PAI1 expression. This effect occurs within the range of dronedarone concentrations measured in patients, and may represent a beneficial pleiotropic effect of this drug. PMID:23052639

Breitenstein, Alexander; Sluka, Susanna H M; Akhmedov, Alexander; Stivala, Simona; Steffel, Jan; Camici, Giovanni G; Riem, Huy H; Beer, Hans-Jurg; Studt, Jan-Dirk; Duru, Firat; Luscher, Thomas F; Tanner, Felix C

2012-11-01

353

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

354

Galaxies within hierarchical structure formation  

NASA Astrophysics Data System (ADS)

While the structure of the Universe can typically be studied only by observing the light from luminous galaxies, the distribution of the galaxies themselves is ultimately a product of the formation of the dark matter halos that host them. This thesis explores the relationship between galaxies and the hierarchical growth of the cosmic web. Employing analytic and numerical techniques, we investigate the effects of the structure formation on observations of galaxies and use galaxy observations to constrain the underlying theoretical models. On large scales, the Lagrangian-based excursion-set formalism calculates the statistics of halos in a given survey volume, with any Eulerian evolution away from the Hubble flow described by the spherical collapse model. However, we also rely on high-resolution N-body simulations of dark matter to treat the nonlinear behavior on small-scales. We consider how the clustering of massive halos and the rapid evolution of their abundance with redshift informs the interpretation of high-redshift galaxy surveys with the Hubble Space Telescope. We further calculate the density and dynamics of the Shapley Supercluster from X-ray observations of galaxy clusters, primarily from the ROSAT satellite, and place constraints on reionization and the formation of first stars using Sloan Digital Sky Survey data from relics of the early Universe orbiting the Milky Way.

Munoz, Joseph Antonio

2010-12-01

355

[Molecular mechanisms for memory formation].  

PubMed

Excitatory synaptic transmission in the central nervous system (CNS) is mediated by the neurotransmitter glutamate and its receptors. Normal synaptic transmission is mediated mainly by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, whereas N-Methyl-D-aspartate (NMDA) receptors become functional during repetitive synaptic activation. Influx of calcium ions through NMDA receptors into the postsynaptic spine triggers biochemical processes associated with synaptic plasticity such as long-term potentiation (LTP), which is believed to underlie memory formation in the CNS including the hippocampus and amygdala. The increased calcium concentration in the spine activates key enzymes such as calcium/calmodulin-dependent protein kinase II (CaMKII), which eventually results in the enduring modulation of AMPA receptors. Thus, the modulation of NMDA receptor functions plays a critical role in the regulation of synaptic plasticity at the molecular and cellular levels as well as in memory formation at the level of the whole animal. Tyrosine phosphorylation of the NMDA receptors regulates its channel activity and localization of other functional molecules in the spine, such as CaMKII, and genetic modification of tyrosine phosphorylation of the NR2B subunit of NMDA receptors is shown to modulate the ability of some kinds of memory in mutant mice. In future studies, it will be important to detect molecular changes during memory formation in the brain of behaving animals in a more direct way. PMID:18646610

Manabe, Toshiya

2008-07-01

356

Rosette formation by peripheral lymphocytes  

PubMed Central

In preparations of human peripheral lymphocytes suspended in serum absorbed with sheep red cells, up to 30% of the lymphocytes may make rosettes with sheep erythrocytes. Washed lymphocytes suspended in Hanks' solution make many rosettes if tested without delay. Such lymphocytes rapidly lose their capacity to make rosettes, but it can be restored by adding the serum of man or of the horse, rabbit or guinea-pig. The lymphocytes of three newborn babies, and of one adult who had no detectable antisheep agglutinin in the serum, made rosettes with sheep cells. Rosette formation is uncorrelated with serum agglutinin levels. Many normal adults have far higher titres of agglutinins against the red cells of other animals than against sheep cells; yet their lymphocytes do not make rosettes with the cells of these other animals. Sodium cyanide (0·01 M) abolished rosette formation, and horse antihuman lymphocyte globulin inhibits it. It is concluded that sheep cell rosette formation by human peripheral lymphocytes is not due to humoral antibody or delayed hypersensitivity, because of the great proportion of lymphocytes that are capable of it. Its nature is obscure, but it is suggested that it may be due to a substance, not primarily an antibody, that is elaborated by a large proportion of circulating lymphocytes and cross-reacts with some red cell antigens as plant lectins do. Caution is advised in using the system to test antihuman lymphocyte serum until more is known about it. ImagesFig. 1Fig. 2 PMID:5477925

Brain, P.; Gordon, June; Willetts, W. A.

1970-01-01

357

Theory of Planetary System Formation  

NASA Technical Reports Server (NTRS)

Observations and theoretical considerations support the idea that the Solar System formed by the collapse of tenuous interstellar matter to a disk of gas and dust (the primitive solar nebula), from which the Sun and other components separated under the action of dissipative forces and by the coagulation of solid material. Thus, planets are understood to be contemporaneous byproducts of star formation. Because the circumstellar disks of new stars are easier to observe than mature planetary systems, the possibility arises that the nature and variety of planets might be studied from observations of the conditions of their birth. A useful theory of planetary system formation would therefore relate the properties of circumstellar disks both to the initial conditions of star formation and to the consequent properties of planets to those of the disk. Although the broad outlines of such a theory are in place, many aspects are either untested, controversial, or otherwise unresolved; even the degree to which such a comprehensive theory is possible remains unknown.

Cassen, Patrick

1996-01-01

358

NCI Best Case Summary Format-OCCAM  

Cancer.gov

The following is a sample Case Report Format used to submit BCS Case Summaries Please adhere to the suggestions below. You may alter the format but include as much of the indicated content as possible.

359

SAR polar format implementation with MATLAB.  

SciTech Connect

Traditional polar format image formation for Synthetic Aperture Radar (SAR) requires a large amount of processing power and memory in order to accomplish in real-time. These requirements can thus eliminate the possible usage of interpreted language environments such as MATLAB. However, with trapezoidal aperture phase history collection and changes to the traditional polar format algorithm, certain optimizations make MATLAB a possible tool for image formation. Thus, this document's purpose is two-fold. The first outlines a change to the existing Polar Format MATLAB implementation utilizing the Chirp Z-Transform that improves performance and memory usage achieving near realtime results for smaller apertures. The second is the addition of two new possible image formation options that perform a more traditional interpolation style image formation. These options allow the continued exploration of possible interpolation methods for image formation and some preliminary results comparing image quality are given.

Martin, Grant D.; Doerry, Armin Walter

2005-11-01

360

External Resource: The Formation of the Moon  

NSDL National Science Digital Library

This Windows to The Universe webpage explores the formation of the Moon. Topics: Moon surface, planetismals, Period of Late Heavy Bombardment, Moon core and mantle, lunar Maria, collisional ejection theory, capture theory, co-formation theory.

1900-01-01

361

Gas-Phase Infrared; JCAMP Format  

National Institute of Standards and Technology Data Gateway

SRD 35 NIST/EPA Gas-Phase Infrared; JCAMP Format (PC database for purchase)   This data collection contains 5,228 infrared spectra in the JCAMP-DX (Joint Committee for Atomic and Molecular Physical Data "Data Exchange") format.

362

49 CFR 563.8 - Data format.  

Code of Federal Regulations, 2013 CFR

...Data format. (a) The data elements listed in... Table III—Reported Data Element Format Data element Minimum range... Ignition cycle, crash 0 to 60,000 ±1...passenger On, Off, or Auto N/A On, Off,...

2013-10-01

363

Negative ion formation processes: A general review  

SciTech Connect

The principal negative ion formation processes will be briefly reviewed. Primary emphasis will be placed on the more efficient and universal processes of charge transfer and secondary ion formation through non-thermodynamic surface ionization. 86 refs., 20 figs.

Alton, G.D.

1990-01-01

364

Formative Assessment - Part I and Part II  

NSDL National Science Digital Library

In these podcasts, Kate Garrison, Manager of Products and services for Professional Development with Measured Progress, describes formative assessment as a verb, not a noun - a process whereby students and teachers maintain ongoing conversation about learning, formative assessment is key to student achievement. Kate Garrison debunks 5 myths about formative assessment in the first of this 2-part discussion. In the second, she discusses the culture of formative assessment.

2009-06-04

365

Treating nahcolite containing formations and saline zones  

DOEpatents

A method for treating a nahcolite containing subsurface formation includes removing water from a saline zone in or near the formation. The removed water is heated using a steam and electricity cogeneration facility. The heated water is provided to the nahcolite containing formation. A fluid is produced from the nahcolite containing formation. The fluid includes at least some dissolved nahcolite. At least some of the fluid is provided to the saline zone.

Vinegar, Harold J

2013-06-11

366

HISTONE METHYLATION REGULATES MEMORY FORMATION  

PubMed Central

It has been established that regulation of chromatin structure through post-translational modification of histone proteins, primarily histone H3 phosphorylation and acetylation, is an important early step in the induction of synaptic plasticity and formation of long-term memory. In this study, we investigated the contribution of another histone modification, histone methylation, to memory formation in the adult hippocampus. We found that tri-methylation of histone H3 at lysine 4 (H3K4), an active mark for transcription, is upregulated in hippocampus one hour following contextual fear conditioning. In addition, we found that di-methylation of histone H3 at lysine 9 (H3K9), a molecular mark associated with transcriptional silencing, is increased one hour after fear conditioning and decreased twenty-four hours after context exposure alone and contextual fear conditioning. Tri-methylated H3K4 levels returned to baseline levels at twenty-four hours. We also found that mice deficient in the H3K4-specific histone methyltransferase, Mll, displayed deficits in contextual fear conditioning relative to wildtype animals. This suggests that histone methylation is required for proper long-term consolidation of contextual fear memories. Interestingly, inhibition of histone deacetylases (HDACs) with sodium butyrate (NaB) resulted in increased H3K4 tri-methylation and decreased H3K9 di-methylation in hippocampus following contextual fear conditioning. Correspondingly, we found that fear learning triggered increases in H3K4 tri-methylation at specific gene promoter regions (Zif268 and bdnf) with altered DNA methylation and MeCP2 DNA binding. Zif268 DNA methylation levels returned to baseline at twenty-four hours. Together, these data demonstrate that histone methylation is actively regulated in the hippocampus and facilitates long-term memory formation. PMID:20219993

Gupta, Swati; Kim, Se Y.; Artis, Sonja; Molfese, David L.; Schumacher, Armin; Sweatt, J. David; Paylor, Richard E.; Lubin, Farah D.

2010-01-01

367

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. PMID:16348459

Greene, Anthony C.; Madgwick, John C.

1991-01-01

368

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

369

Pattern formation in geochemical systems  

NASA Astrophysics Data System (ADS)

Compositional patterns are extremely common in natural minerals. While, in many cases, variations in the solid mineral composition reflect the external changes in the environment at the time of the mineral formation, the role of self-organization is increasingly acknowledged. For example, in reaction-transport systems, the patterns may form spontaneously from an unpatterned state at the time of crystal growth and then become preserved by being "frozen" in the solid mineral. In this work, the pattern formation by self-organization is investigated by means of model construction and computer simulations in several minerals from different geologic environments. The impact of environmental noise is investigated on a model of oscillatory zoning in plagioclase feldspar. It is shown that environmental noise can lead to pattern formation such as oscillatory zoning, even when no deterministic periodic solutions exist. Coherence resonance close to the Hopf bifurcation is observed. Oscillatory zoning in barite-celestite system is simulated to quantitatively describe the results of the previously reported nucleation and growth experiments. The zoning is thought to be formed by autocatalytic growth from an aqueous solution. In addition to the description of the reaction-diffusion system in terns of partial and ordinary differential equations, a cellular automata model is proposed for the first time for this oscillatory crystallization type of problems. A quantitative model of banding in Mississippi Valley-type sphalerite is presented. Banded ring-like patterns are shown to arise due to a self-propagating sequence of growth and dissolution (coarsening wave). A two-dimensional model is presented for the first time and the conditions for the pattern generation and preservation are discussed. A number of time series analysis techniques are applied to characterize the compositional patterns observed in natural minerals as well as in the colored rythmites found in the marine clay sediments of the Ottawa Valley. Several caveats in interpreting the results of such analyses are outlined.

Katsev, Sergei

2002-08-01

370

The formation of interstellar jets  

NASA Technical Reports Server (NTRS)

The formation of interstellar jets by convergence of supersonic conical flows and the further dynamical evolution of these jets are investigated theoretically by means of numerical simulations. The results are presented in extensive graphs and characterized in detail. Strong radiative cooling is shown to result in jets with Mach numbers 2.5-29 propagating to lengths 50-100 times their original widths, with condensation of swept-up interstellar matter at Mach 5 or greater. The characteristics of so-called molecular outflows are well reproduced by the simulations of low-Mach-number and quasi-adiabatic jets.

Tenorio-Tagle, G.; Canto, J.; Rozyczka, M.

1988-01-01

371

Dust formation by failed supernovae  

NASA Astrophysics Data System (ADS)

We consider dust formation during the ejection of the hydrogen envelope of a red supergiant during a failed supernova (SN) creating a black hole. While the dense, slow moving ejecta are very efficient at forming dust, only the very last phases of the predicted visual transient will be obscured. The net grain production consists of Md ˜ 10- 2 M? of very large grains (10-1000 ?m). This means that failed SNe could be the source of the very large extrasolar dust grains possibly identified by Ulysses, Galileo and radar studies of meteoroid re-entry trails rather than their coming from an ejection process associated with protoplanetary or other discs.

Kochanek, C. S.

2014-11-01

372

Zonal flow as pattern formation  

SciTech Connect

Zonal flows are well known to arise spontaneously out of turbulence. We show that for statistically averaged equations of the stochastically forced generalized Hasegawa-Mima model, steady-state zonal flows, and inhomogeneous turbulence fit into the framework of pattern formation. There are many implications. First, the wavelength of the zonal flows is not unique. Indeed, in an idealized, infinite system, any wavelength within a certain continuous band corresponds to a solution. Second, of these wavelengths, only those within a smaller subband are linearly stable. Unstable wavelengths must evolve to reach a stable wavelength; this process manifests as merging jets.

Parker, Jeffrey B.; Krommes, John A. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)] [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)

2013-10-15

373

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

374

Jet Formation in MHD Simulations  

E-print Network

In this talk I review the current status of jet formation in direct numerical simulations of black-hole accretion disks and magnetospheres. I address the following critical questions: What constitutes the jet? What is the launching mechanism? Where is the launching point of the jet? What is the Lorentz factor? What is the opening angle? How is the jet collimated? Just as importantly, I also discuss how dependent the answers to the above questions are on factors such as the initial conditions of the simulation. I end by discussing possible future directions for this research.

P. Chris Fragile

2008-10-02

375

Emerging Principles of Galaxy Formation  

NASA Astrophysics Data System (ADS)

Until recently, the field of galaxy formation resembled that of stellar evolution after the discovery of the main sequence (in 1911) but before the discovery of nuclear energy generation (in the 1930's). In both cases, scaling laws were known, but there was not yet any theory for their origin. Now, new data on galaxies are revealing not only new scaling laws but finally (thanks to lookback studies) a glimmer at last of understanding. Interestingly, mass seems to be the leading variable for both stars and galaxies, but the physical reasons are entirely different.

Faber, Sandra

2007-12-01

376

Successful Student Writing through Formative Assessment  

ERIC Educational Resources Information Center

Use formative assessment to dramatically improve your students' writing. In "Successful Student Writing Through Formative Assessment", educator and international speaker Harry G. Tuttle shows you how to guide middle and high school students through the prewriting, writing, and revision processes using formative assessment techniques that work.…

Tuttle, Harry Grover

2010-01-01

377

A new PICL trace file format  

SciTech Connect

A trace file format is described that will be used in future releases of the Portable Instrumented Communication Library (PICL) and ParaGraph. The new format provides improved support for tracing and profiling PICL communication primitives and user-defined events. The new format is also easily extended and may be useful in other instrumentation packages and performance visualization tools.

Worley, P.H.

1992-10-01

378

Surfactant effects on gas hydrate formation  

Microsoft Academic Search

Micellar solutions were found to increase gas hydrate formation rate and alter formation mechanism for ethane and natural gas hydrates. A critical micellar concentration (CMC) of sodium dodecyl sulfate water solution was found to be 242 ppm at hydrate-forming conditions, where CMC was best determined by hydrate induction time. At surfactant concentrations above the CMC, hydrate formation rates in a

Y. Zhong; R. E. Rogers

2000-01-01

379

Brown dwarf formation in clusters Matthew Bate  

E-print Network

Brown dwarf formation in clusters Matthew Bate University of Exeter #12;· Bate, Bonnell & Bromm · Resolved binaries with · separations >1 AU · disc with radii >10 AU · Produced 23 stars & 27 brown dwarfs disc First cluster formation calculation to resolve brown dwarfs #12;Brown dwarf formation · How do

Joergens, Viki

380

Electromagnetic Formation Flight of Satellite Arrays  

E-print Network

Electromagnetic Formation Flight of Satellite Arrays Daniel W. Kwon and David W. Miller February 2005 SSL # 2-05 #12;#12;Electromagnetic Formation Flight of Satellite Arrays By DANIEL W. KWON S;#12;Electromagnetic Formation Flight of Satellite Arrays by DANIEL W. KWON Submitted to the Department of Aeronautics

381

Natural tracer profiles across argillaceous formations  

Microsoft Academic Search

Argillaceous formations generally act as aquitards because of their low hydraulic conductivities. This property, together with the large retention capacity of clays for cationic contaminants, has brought argillaceous formations into focus as potential host rocks for the geological disposal of radioactive and other waste. In several countries, programmes are under way to characterise the detailed transport properties of such formations

Martin Mazurek; Peter Alt-Epping; Adrian Bath; Thomas Gimmi; H. Niklaus Waber; Stéphane Buschaert; Pierre De Cannière; Mieke De Craen; Andreas Gautschi; Sébastien Savoye; Agnès Vinsot; Isabelle Wemaere; Laurent Wouters

2011-01-01

382

Derivational Word Formation Process In Kedah Malay  

Microsoft Academic Search

Previously word formation process in Malay Dialects and Standard Malay has been studied using structuralist method which capitalizes not only on forms but also on semantic classification. However, how the whole word formation process works in a paradigmatic yet interrelated manner and function escapes most generalizations. This paper looks at the word formation processes in Kedah Malay using Mark Aronoff's

Norizan Rajak

383

Star formation and the ages of stars  

NASA Astrophysics Data System (ADS)

In this contribution we illustrate how the knowledge of the ages of stars is important to constrain star formation processes. We focus on two specific cases: star formation around the supermassive black hole at the center of the Galaxy and triggered star formation on the borders of Hii regions.

Martins, F.

2014-11-01

384

Fault-tolerant formations of mobile robots  

Microsoft Academic Search

The goal of a robot formation control architecture is to get a number of robots into a specified form. To be effective and practical, the control architecture must be able to transition a group of robots from an initial swarm to a final formation. It must then be able to handle real-world events that could disrupt the formation, thus, requiring

Ross Mead; Robert Long; Jerry B. Weinberg

2009-01-01

385

Improving Foreign Language Speaking through Formative Assessment  

ERIC Educational Resources Information Center

Want a quick way to get your students happily conversing more in the target language? This practical book shows you how to use formative assessments to gain immediate and lasting improvement in your students' fluency. You'll learn how to: (1) Imbed the 3-minute formative assessment into every lesson with ease; (2) Engage students in peer formative

Tuttle, Harry Grover; Tuttle, Alan Robert

2012-01-01

386

Transfer of Training with Formation Flight Trainer.  

ERIC Educational Resources Information Center

The present research was conducted to determine transfer of practice from a formation simulator to actual aircraft flight for the wing aircraft component of the formation flying task. Evidence in support of positive transfer was obtained by comparing students trained in the formation simulator with students who were essentially untrained and with…

Reid, Gary B.; Cyrus, Michael L.

387

Microbubble formation from plasma polymers.  

PubMed

We document the formation of liquid-like particles in a toluene glow discharge that subsequently solidify via a process that releases hydrogen to form a solid microbubble with micrometer-size diameter, nanometer-size shell thickness, and high volume fraction, in excess of 90%. Liquid-like particles are produced in a toluene plasma under conditions that promote low degree of cross-linking (low power, high pressure). When these are transferred for observation in TEM, they are seen to transform under irradiation by the electron beam into solid bubbles with diameter of about 3 ?m. This transformation also takes place under laser irradiation of sufficient power and under heating. We present evidence that the formation of these microbubbles is due to solidification of the liquid-like precursor that is accompanied by release of hydrogen. This mechanism is supported by a geometric model that provides a quantitative description of the particle size before and after solidification. These unique stimuli-responsive particles exhibit the potential of using temperature, electron beam, or laser as a source to change their size and structure which may find application in thermal insulators, lightweight materials, and light scattering agents. PMID:22954230

Shahravan, Anaram; Yelamarty, Srinath; Matsoukas, Themis

2012-09-27

388

Montezuma Formation of Costa Rica  

SciTech Connect

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 Lower Pliocene (Globorotalia margaritae zones). Furthermore, benthic such as Bolivina interjuncta var. bicostata, Epistominella exigua, and E. pacifica indicate that the sedimentation occurred at depths no shallower than the outermost shelf. No drastic faunal turnovers are observed within the formation; a cluster analysis of various Neogene samples from the Nicoya Peninsula and other Pacific areas of Costa Rica demonstrate an overall uniformity of the Montezuma fauna. The frequency trends of certain species, particularly of Epistominella exigua, however, suggest a transgression, the assemblage in the upper part of the section definitely representing upper bathyal depths. Judging by the present elevation of Montezuma outcrops, this part of Costa Rica has been uplifted at least 300 meters in the past 5 m.y.

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

1985-01-01

389

Methane formation in sewer systems.  

PubMed

Methane formation and emission in sewer systems has not received as much attention as hydrogen sulphide formation. Through field measurements from two rising mains, with an average sewage temperature of 28.4 and 26.6 degrees C, respectively, at the time of sampling, this study shows that a significant amount of methane can be produced in sewer systems, and that this production is positively correlated with the hydraulic retention time of wastewater in these systems. The experimental results from a laboratory-scale sewer system fed with real sewage with a temperature of approximately 21 degrees C confirmed these field observations and further revealed that methanogenesis and sulphate reduction occur simultaneously in sewers, with methane production contributing considerably more to the loss of soluble COD in sewers than sulphate reduction. The production of methane in sewers at levels revealed by this study is a serious environmental concern as it potentially results in greenhouse emissions that is comparable to that caused by the energy consumption for the treatment of the same wastewater. Further, methane production in sewers influences sulphide production and its management due to the competition between methanogens and sulphate-reducing bacteria for potentially the same electron donors. The potential interactions between sulphate-reducing and methanogenic bacteria in sewer networks are discussed. PMID:17988709

Guisasola, Albert; de Haas, David; Keller, Jurg; Yuan, Zhiguo

2008-03-01

390

The Black Hole Formation Probability  

E-print Network

A longstanding question in stellar evolution is which massive stars produce black holes (BHs) rather than neutron stars (NSs) upon death. It has been common practice to assume that a given zero-age main sequence (ZAMS) mass star (and perhaps a given metallicity) simply produces either an NS or a BH, but this fails to account for a myriad of other variables that may effect this outcome, such as spin, binarity, or even stochastic differences in the stellar structure near core collapse. We argue that instead a probabilistic description of NS versus BH formation may be better suited to account for the current uncertainties in understanding how massive stars die. Using the observed BH mass distribution from Galactic X-ray binaries, we derive the probability that a star will make a BH as a function of its ZAMS mass, $P_{\\rm BH}(M_{\\rm ZAMS})$. We explore possible biases in the observed BH mass distribution and find that this sample is best suited for studying BH formation in stars with ZAMS masses in the range $12-...

Clausen, Drew; Ott, Christian D

2014-01-01

391

Airfoil tip vortex formation noise  

NASA Technical Reports Server (NTRS)

Spectral data are presented for the noise produced due to the turbulent three-dimensional vortex flow existing near the rounded tip of lifting airfoils. The results are obtained by the comparison of sets of two- and three-dimensional test data for different airfoil model sizes, angles of attack, and tunnel flow velocities. Microphone cross-correlation and cross-spectral methods were used to determine the radiated noise. Corrections were made for tunnel shear layer and source directivity effects. Interpretation of the results are aided by a three-dimensional flow analysis developed for this study which determines open tunnel and finite aspect ratio corrections heretofore neglected in tip vortex studies. Hot wire measurements were made in the tip vortex formation region for the specification of governing flow parameters. The spectral data is normalized in a format considered most useful for subsequent quantitative prediction of this noise mechanism for practical systems such as helicopter rotors. Comparison is made to the analysis of George and Chou. A recommended prediction method is given.

Brooks, T. F.; Marcolini, M. A.

1984-01-01

392

Coring in deep hardrock formations  

SciTech Connect

The United States Department of Energy is involved in a variety of scientific and engineering feasibility studies requiring extensive drilling in hard crystalline rock. In many cases well depths extend from 6000 to 20,000 feet in high-temperature, granitic formations. Examples of such projects are the Hot Dry Rock well system at Fenton Hill, New Mexico and the planned exploratory magma well near Mammoth Lakes, California. In addition to these programs, there is also continuing interest in supporting programs to reduce drilling costs associated with the production of geothermal energy from underground sources such as the Geysers area near San Francisco, California. The overall progression in these efforts is to drill deeper holes in higher temperature, harder formations. In conjunction with this trend is a desire to improve the capability to recover geological information. Spot coring and continuous coring are important elements in this effort. It is the purpose of this report to examine the current methods used to obtain core from deep wells and to suggest projects which will improve existing capabilities. 28 refs., 8 figs., 2 tabs.

Drumheller, D.S.

1988-08-01

393

Virialization Heating in Galaxy Formation  

SciTech Connect

In a hierarchical picture of galaxy formation virialization continually transforms gravitational potential energy into kinetic energies in the baryonic and dark matter. For the gaseous component the kinetic, turbulent energy is transformed eventually into internal thermal energy through shocks and viscous dissipation. Traditionally this virialization and shock heating has been assumed to occur instantaneously allowing an estimate of the gas temperature to be derived from the virial temperature defined from the embedding dark matter halo velocity dispersion. As the mass grows the virial temperature of a halo grows. Mass accretion hence can be translated into a heating term. We derive this heating rate from the extended Press Schechter formalism and demonstrate its usefulness in semi-analytical models of galaxy formation. Our method is preferable to the traditional approaches in which heating from mass accretion is only modeled implicitly through an instantaneous change in virial temperature. Our formalism can trivially be applied in all current semi-analytical models as the heating term can be computed directly from the underlying merger trees. Our analytic results for the first cooling halos and the transition from cold to hot accretion are in agreement with numerical simulations.

Wang, P. (KIPAC, Menlo Park); Abel, T. (Santa Barbara, KITP)

2007-01-17

394

Protostellar formation in rotating interstellar clouds. VIII - Inner core formation  

NASA Technical Reports Server (NTRS)

The results are presented of a variety of spherically symmetric one-dimensional (1D) calculations intended to determine the robustness of the dynamical hiccup phenomenon in protostellar cores. The 1D models show that the phenomenon is relatively insensitive to changes in the equations of state, numerical resolution, initial density and temperature, and the radiative transfer approximation. In 1D, the hiccup results in an explosive destruction of the entire inner protostellar core. Inner core formation is studied with a sequence of three-dimensional models which show that rapid inner core rotation stabilizes the hiccup instability. Instead, the inner core becomes quite flat and undergoes a cycle of binary fragmentation, binary decay into a single object surrounded by a bar, breakup of the bar into a binary, etc. When lesser amounts of rotation are involved, the inner core does hiccup somewhat, but mass is ejected in only a few directions, leading to several broad streams of ejecta.

Boss, Alan P.

1989-01-01

395

Protostellar formation in rotating interstellar clouds. VIII. Inner core formation  

SciTech Connect

The results are presented of a variety of spherically symmetric one-dimensional (1D) calculations intended to determine the robustness of the dynamical hiccup phenomenon in protostellar cores. The 1D models show that the phenomenon is relatively insensitive to changes in the equations of state, numerical resolution, initial density and temperature, and the radiative transfer approximation. In 1D, the hiccup results in an explosive destruction of the entire inner protostellar core. Inner core formation is studied with a sequence of three-dimensional models which show that rapid inner core rotation stabilizes the hiccup instability. Instead, the inner core becomes quite flat and undergoes a cycle of binary fragmentation, binary decay into a single object surrounded by a bar, breakup of the bar into a binary, etc. When lesser amounts of rotation are involved, the inner core does hiccup somewhat, but mass is ejected in only a few directions, leading to several broad streams of ejecta. 29 refs.

Boss, A.P. (Carnegie Institution of Washington, Washington, DC (USA))

1989-11-01

396

Heating tar sands formations while controlling pressure  

DOEpatents

Methods for treating a tar sands formation are described herein. Methods may include heating at least a section of a hydrocarbon layer in the formation from a plurality of heaters located in the formation. A pressure in the majority of the section may be maintained below a fracture pressure of the formation. The pressure in the majority of the section may be reduced to a selected pressure after the average temperature reaches a temperature that is above 240.degree. C. and is at or below pyrolysis temperatures of hydrocarbons in the section. At least some hydrocarbon fluids may be produced from the formation.

Stegemeier, George Leo (Houston, TX) [Houston, TX; Beer, Gary Lee (Houston, TX) [Houston, TX; Zhang, Etuan (Houston, TX) [Houston, TX

2010-01-12

397

Defect pressure, formation volume, and temperature dependence of formation properties of point defects in ionic solids  

E-print Network

dependence of the volume and the enthalpy of formation of equilibrium defects is understood in termsDefect pressure, formation volume, and temperature dependence of formation properties of point of the temperature dependence of the shear moduli. The high-temperature anomalies of defect formation volume, tracer

Boyer, Edmond

398

Formation Flying for Distributed InSAR  

NASA Technical Reports Server (NTRS)

We consider two spacecraft flying in formation to create interferometric synthetic aperture radar (InSAR). Several candidate orbits for such in InSar formation have been previously determined based on radar performance and Keplerian orbital dynamics. However, with out active control, disturbance-induced drift can degrade radar performance and (in the worst case) cause a collision. This study evaluates the feasibility of operating the InSAR spacecraft as a formation, that is, with inner-spacecraft sensing and control. We describe the candidate InSAR orbits, design formation guidance and control architectures and algorithms, and report the (Delta)(nu) and control acceleration requirements for the candidate orbits for several tracking performance levels. As part of determining formation requirements, a formation guidance algorithm called Command Virtual Structure is introduced that can reduce the (Delta)(nu) requirements compared to standard Leader/Follower formation approaches.

Scharf, Daniel P.; Murray, Emmanuell A.; Ploen, Scott R.; Gromov, Konstantin G.; Chen, Curtis W.

2006-01-01

399

Data Formats for SAR Archival and Distribution  

NASA Astrophysics Data System (ADS)

Synthetic Aperture Radar (SAR) data has historically been archived and distributed in the Committee on Earth Observation Satellite (CEOS) format. CEOS has some limitations, so future SAR missions are considering using the Hierarchical Data Format (HDF) format that is more compatible with other sensors supporting the Earth Observing System (EOS). With the adoption of HDF for SAR archival, the distribution formats of SAR data products are also under consideration. As SAR becomes more important in EOS, data formats compatible with geographic information systems (GIS) are needed and the GeoTIFF image format for the distribution of SAR data is the preferred choice. By moving into a more common data format, SAR data products may appeal to a larger audience. This paper summarizes the collaboration of the Alaska Satellite Facility, the National Snow and Ice Data Center, and the Oak Ridge National Laboratory to support the growing use of SAR for terrestrial ecology, resource management, and many other applications.

Cunningham, K.

2010-12-01

400

Formation of Coronal Shock Waves  

NASA Astrophysics Data System (ADS)

Magnetosonic wave formation driven by an expanding cylindrical piston is numerically simulated to obtain better physical insight into the initiation and evolution of large-scale coronal waves caused by coronal eruptions. Several very basic initial configurations are employed to analyze intrinsic characteristics of MHD wave formation that do not depend on specific properties of the environment. It turns out that these simple initial configurations result in piston/wave morphologies and kinematics that reproduce common characteristics of coronal waves. In the initial stage, the wave and the expanding source region cannot be clearly resolved; i.e. a certain time is needed before the wave detaches from the piston. Thereafter, it continues to travel as what is called a "simple wave." During the acceleration stage of the source region inflation, the wave is driven by the piston expansion, so its amplitude and phase-speed increase, whereas the wavefront profile steepens. At a given point, a discontinuity forms in the wavefront profile; i.e. the leading edge of the wave becomes shocked. The time/distance required for the shock formation is shorter for a more impulsive source-region expansion. After the piston stops, the wave amplitude and phase speed start to decrease. During the expansion, most of the source region becomes strongly rarefied, which reproduces the coronal dimming left behind the eruption. However, the density increases at the source-region boundary, and stays enhanced even after the expansion stops, which might explain stationary brightenings that are sometimes observed at the edges of the erupted coronal structure. Also, in the rear of the wave a weak density depletion develops, trailing the wave, which is sometimes observed as weak transient coronal dimming. Finally, we find a well-defined relationship between the impulsiveness of the source-region expansion and the wave amplitude and phase speed. The results for the cylindrical piston are also compared with the outcome for a planar wave that is formed by a one-dimensional piston, to find out how different geometries affect the evolution of the wave.

Luli?, S.; Vršnak, B.; Žic, T.; Kienreich, I. W.; Muhr, N.; Temmer, M.; Veronig, A. M.

2013-09-01

401

Adaptive Optics in Star Formation  

E-print Network

Over the past ten years, the concept of adaptive optics has evolved from early experimental stages to a standard observing tool now available at almost all major optical and near-infrared telescope facilities. Adaptive optics will also be essential in exploiting the full potential of the large optical/infrared interferometers currently under construction. Both observations with high-angular resolution and at high contrast, and with a high point source sensitivity are facilitated by adaptive optics. Among the areas which benefit most from the use of adaptive optics are studies of the circumstellar environment (envelopes, disks, outflows), substellar companions and multiple systems, and dense young stellar populations. This contribution highlights some of the recent advances in star formation studies facilitated by adaptive optics, and gives a brief tutorial on optimized observing and data reduction strategies.

Wolfgang Brandner

2003-09-29

402

The Formation of Lake Stars  

E-print Network

Star patterns, reminiscent of a wide range of diffusively controlled growth forms from snowflakes to Saffman-Taylor fingers, are ubiquitous features of ice covered lakes. Despite the commonality and beauty of these ``lake stars'' the underlying physical processes that produce them have not been explained in a coherent theoretical framework. Here we describe a simple mathematical model that captures the principal features of lake-star formation; radial fingers of (relatively warm) water-rich regions grow from a central source and evolve through a competition between thermal and porous media flow effects in a saturated snow layer covering the lake. The number of star arms emerges from a stability analysis of this competition and the qualitative features of this meter-scale natural phenomena are captured in laboratory experiments.

Tsai, Victor C

2007-01-01

403

Macromolecules Relevant to Stone Formation  

NASA Astrophysics Data System (ADS)

Despite years of research, no single macromolecule in kidney calculi or in urine has yet been shown to fulfill a specific function in stone pathogenesis. In this paper we briefly review papers investigating the urinary excretion of individual macromolecules, their effects on calcium oxalate (CaOx) crystallization and attachment of crystals to renal epithelial cells, and the influence of lithogenic conditions on their renal expression in cultured cells and animal models. Using prothrombin fragment 1 (PTF1) and human serum albumin as examples, we show the types of patterns resulting from the binding of a fluorescently tagged protein to a specific CaOx monohydrate (COM) crystal face and its incorporation into the crystal structure. Molecular modeling is also used to illustrate how PTF1 can align with the atomic array on a COM crystal surface. We conclude that although many macromolecules are, by strict definition, relevant to stone formation, very few are probably truly influential.

Ryall, Rosemary L.; Cook, Alison F.; Thurgood, Lauren A.; Grover, Phulwinder K.

2007-04-01

404

Polar frost formation on Ganymede  

NASA Technical Reports Server (NTRS)

Voyager photographs have shown the presence of polar frost on Ganymede, a satellite of Jupiter. A number of models have been proposed for the formation of this feature. The models are based on the transport of material from the equatorial to the polar regions. The present paper is concerned with a model regarding the origin and appearance of the Ganymede caps which does not depend on such a transport. The model is based on observations of the surficial changes produced by ion bombardment. It is pointed out that experiments on ion and electron bombardment of water ice at low temperatures have shown that these particles sputter significant quantities of water molecules. In addition, they also change the visual characteristics of the surface significantly. Ion bombardment competing with thermal reprocessing may be sufficient to explain the latitudinal differences observed on Ganymede.

Johnson, R. E.

1985-01-01

405

Statoconia formation in molluscan statocysts  

NASA Technical Reports Server (NTRS)

The gravity sensors of all molluscs phylogenetically below the cephalopods are spherical organs called statocysts. The wall of the sphere contains mechanosensory cells whose sensory cilia project into the lumen of the cyst. The lumen is filled with fluid and dense "stones", the statoconia or statoliths, which sink under the influence of gravity to load, and stimulate, those receptor cells which are at the bottom. The statoconia of Aplysia californica are shown to be calcified about a lamellar arrangement of membranes. Similar lamellar membrane arrangements are seen within the receptor cells, and their possible role in the formation of the statoconia is discussed. SEM of unfixed statoconia reveals plate-like crystallization on their surface. Elemental analysis shows a relatively high Sr content, which is of interest, since others have recently reported that Sr is required in the culture medium of several laboratory reared molluscs in order for the statoconia to develop.

Wiederhold, M. L.; Sheridan, C. E.; Smith, N. K.

1986-01-01

406

Modelling Star Formation in Ophiuchus  

NASA Astrophysics Data System (ADS)

We perform simulations of prestellar core collapse with initial conditions inferred from observations of Ophiuchus. The cores in Ophiuchus are mostly isolated, hence we run multiple simulations of individual cores. We statistically model the intrinsic shapes of cores as a population of triaxial ellipsoids with a single free parameter which is fitted to aspect ratio data. We assume a turbulent velocity field with modifications which add ordered radial and rotational motion. Mass, size and non-thermal velocity dispersion are drawn randomly from observational data. Preliminary results show a largely realistic IMF. Future work will explore solenoidal to compressive velocity mode ratios and the effects of accretion luminosity. Results will lead to inferences on quantities such as star formation efficiency in the region.

Lomax, Oliver; Whitworth, Anthony Peter; Cartwright, Annabel; Stamatellos, Dimitris; Walch, Stefanie K.

407

Supercoil formation in DNA denaturation  

E-print Network

We generalize the Poland-Scheraga (PS) model to the case of a circular DNA, taking into account the twisting of the two strains around each other. Guided by recent single-molecule experiments on DNA strands, we assume that the torsional stress induced by denaturation enforces formation of supercoils whose writhe absorbs the linking number expelled by the loops. Our model predicts that, when the entropy parameter of a loop satisfies $c \\le 2$, denaturation transition does not take place. On the other hand for $c>2$ a first-order denaturation transition is consistent with our model and may take place in the actual system, as in the case with no supercoils. These results are in contrast with other treatments of circular DNA melting where denaturation is assumed to be accompanied by an increase in twist rather than writhe on the bound segments.

A. Kabakcioglu; E. Orlandini; D. Mukamel

2009-06-04

408

Micromagnetic simulations of antivortex formation  

NASA Astrophysics Data System (ADS)

Magnetic vortices are fundamental magnetic structures that form in patterned ferromagnetic materials. The study of magnetic vortices is an active field of research at present, in part because of the potential for new technologies. In addition to vortices, so called antivortex states have been found in some particular geometries such as four connected rings and cross-like nanomagnets. Antivortices may be useful for nonvolatile data storage applications, and they are also expected to show unusual transport properties in an applied magnetic field, for example, a ``topological'' Hall effect. In order to make use of magnetic antivortices, it is important to first understand how to stabilize systems that contain only a single antivortex. Micromagnetic calculations have been performed with OOMMF and LLG software to explore how the geometry of the structure affects the formation and stability of the antivortex state and whether the field history can be used to reliably select the state.

Asmat-Uceda, Martin; Buchanan, Kristen

2011-10-01

409

ISAC's classification results file format.  

PubMed

Identifying homogenous sets of cell populations in flow cytometry is an important process for sorting and selecting populations of interests for further data acquisition and analysis. Many computational methods are now available to automate this process, with several algorithms partitioning cells based on high-dimensional separation versus the traditional pairwise two-dimensional visualization approach of manual gating. ISAC's classification results file format was developed to exchange the results of both manual gating and algorithmic classification approaches in a standardized way based on per event based classifications, including the potential for soft classifications expressed as the probability of an event being a member of a class. © 2014 International Society for Advancement of Cytometry. PMID:25407887

Spidlen, Josef; Bray, Chris; Brinkman, Ryan R

2015-01-01

410

Formation of primordia and phyllotaxy.  

PubMed

Leaves are made in an iterative pattern by the shoot apical meristem. The mechanism of this pattern formation has fascinated biologists, mathematicians and poets for centuries. Over the past year, fundamental insights into the molecular basis of this process have been gained. Patterns of auxin polar transport dictate when and where new leaf primordia are formed on the surface of the apical meristem. Subsequent events are still obscure but appear to involve both alteration of cell wall characteristics (to facilitate a new vector of growth) and a cascade of spatially co-ordinated transcription factor activity (to determine the fate of cells that are incorporated into new lateral organs). The co-ordinated signalling events involved in these processes are beginning to be elucidated. PMID:15653400

Fleming, Andrew J

2005-02-01

411

Electrochemical formation of field emitters  

DOEpatents

Electrochemical formation of field emitters, particularly useful in the fabrication of flat panel displays is disclosed. The fabrication involves field emitting points in a gated field emitter structure. Metal field emitters are formed by electroplating and the shape of the formed emitter is controlled by the potential imposed on the gate as well as on a separate counter electrode. This allows sharp emitters to be formed in a more inexpensive and manufacturable process than vacuum deposition processes used at present. The fabrication process involves etching of the gate metal and the dielectric layer down to the resistor layer, and then electroplating the etched area and forming an electroplated emitter point in the etched area. 12 figs.

Bernhardt, A.F.

1999-03-16

412

Sedimentary and faunal analysis of a marginal marine section, the Stone City Member (middle eocene), Crockett Formation, Burleson County, Texas  

E-print Network

Carbonaceous Matter Contacts: a = Abrupt g = Gradational b = Burrowed d = Distinct, gradational over a short distance 21 (4) 60- (6') (l. 5) (1. 5) 50L (4) (5) 40- (I') 0 IO 0 9 8 7 g 6 d 0 ROCKY CREEK (65 ) IO MEDIAN GRAIN SIZE 'vf... 30- (l4') (IO') 20- (8. 5 ) 3 0 2 q (8') IO (145) p (2. 5) '4' ?7 TONE CITY STENZEL et al. , (l957) SPARTA BLUFF (l 3. 5 I b (4. 5 ) b SPART DEAD CREEK 22 were analyzed and were similar to those of the same units at Stone C1ty...

Nelms, Katherine Currier

2012-06-07

413

Methanol Masers and Star Formation  

E-print Network

Methanol masers which are traditionally divided into two classes provide possibility to study important parts of the star forming regions: Class~II masers trace vicinities of the massive YSOs while class~I masers are likely to trace more distant parts of the outflows where newer stars can form. There are many methanol transitions which produce observed masers. This allows to use pumping analysis for estimation of the physical parameters in the maser formation regions and its environment, for the study of their evolution. Extensive surveys in different masing transitions allow to conclude on the values of the temperatures, densities, dust properties, etc. in the bulk of masing regions. Variability of the brightest masers is monitored during several years. In some cases it is probably caused by the changes of the dust temperature which follow variations in the brightness of the central YSO reflecting the character of the accretion process. A unified catalogue of the class II methanol masers consisting of more than 500 objects is compiled. Analysis of the data shows that: physical conditions within the usual maser source vary considerably; maser brightness is determined by parameters of some distinguished part of the object - maser formation region; class II methanol masers are formed not within the outflows but in the regions affected by their propagation. It is shown that the "near" solutions for the kinematic distances to the sources can be used for statistical analysis. The luminosity function of the 6.7 GHz methanol masers is constructed. It is shown that improvement of the sensitivity of surveys can increase number of detected maser sources considerably.

A. M. Sobolev; A. B. Ostrovskii; M. S. Kirsanova; O. V. Shelemei; M. A. Voronkov; A. V. Malyshev

2006-01-12

414

Drill cuttings mount formation study  

NASA Astrophysics Data System (ADS)

Oil, Gas and Energy sector has been identified as an essential driving force in the Malaysian Economic Transformation Programs (ETP). Recently confirmed discovery of many offshore oil and gas deposits in Malaysian waters has ignited new confidence in this sector. However, this has also spurred intense interest on safeguarding the health and environment of coastal waters in Malaysia from adverse impact resulting from offshore oil and gas production operation. Offshore discharge of spent drilling mud and rock cuttings is the least expensive and simplest option to dispose of large volumes of drilling wastes. But this onsite offshore disposal may have adverse environmental impacts on the water column and the seabed. It may also pose occupational health hazards to the workers living in the offshore platforms. It is therefore important to model the transport and deposition of drilling mud and rock cuttings in the sea to enable proper assessment of their adverse impacts on the environment and the workers. Further, accumulation of drill particles on the seabed may impede proper operation of pipelines on the seabed. In this paper, we present an in-house application model TUNA-PT developed to cater to local oil and gas industry needs to simulate the dispersion and mount formation of drill cuttings by offshore oil and gas exploration and production platforms. Using available data on Malaysian coastal waters, simulation analyses project a pile formation on the seabed with a maximum height of about 1 m and pile radius of around 30 to 50 m. Simulated pile heights are not sensitive to the heights of release of the cuttings as the sensitivity has been mitigated by the depth of water.

Teh, Su Yean; Koh, Hock Lye

2014-07-01

415

Bone formation in axial spondyloarthritis.  

PubMed

The success of targeted therapies directed against tumor necrosis factor for patients with spondyloarthritis has shifted the focus of physicians and scientists towards the prevention of structural damage to the involved structures, in particular the sacroiliac joints and the spine, to avoid loss of function and disability. Structural damage to the skeleton as witnessed by radiography mainly consists of new bone formation potentially progressively leading to spine or joint ankylosis. This important long-term outcome parameter has been difficult to study, not alone because the time window for change may be long but also because human tissues with direct translational relevance are rarely available. Data from rodent models have identified growth factor signaling pathways as relevant targets. Both human and animal studies have tried to understand the link between inflammation and new bone formation. At the current moment, most evidence points towards a strong link between both but with the question still lingering about the sequence of events, disease triggers, and the interdependence of both features of disease. New discoveries such as a masterswitch T cell population that carries the IL23 receptor and the analysis of auto-antibodies directed again noggin and sclerostin are contributing to innovative insights into the pathophysiology of disease. Long-term data with tumor necrosis factor (TNF) inhibitors also suggest that some window of opportunity may exist to inhibit structural disease progression. All these data provide support for a further critical analysis of the available datasets and boost research in the field. The introduction of novel disease definitions, in particular the characterization of non-radiographic axial spondyloarthritis patients, will likely be instrumental in our further understanding of structural damage. PMID:25488783

Lories, Rik J; Haroon, Nigil

2014-10-01

416

Biomineralization: mineral formation by organisms  

NASA Astrophysics Data System (ADS)

Organisms form many different types of minerals, with diverse shapes and sizes. These minerals fulfill a variety of functions. Inspired by the late H A Lowenstam, Steve Weiner and Lia Addadi have addressed many questions that relate to the mechanisms by which biological organisms produce these mineral phases and how their structures relate to their functions. Addadi and Weiner have explored the manner in which macromolecules extracted from mineralized tissues can interact with some crystal planes and not others, how these macromolecules can be occluded inside the forming crystals residing preferentially on specific crystal planes, and how they can induce one polymorph of calcium carbonate and not another to nucleate. Addadi and Weiner have also identified a novel strategy used by the sea urchin to form its smooth and convoluted mineralized skeletal elements. The strategy involves the initial production by cells of a highly disordered mineral precursor phase in vesicles, and then the export of this so-called amorphous phase to the site of skeletal formation, where it crystallizes. This strategy is now known to be used by many different invertebrate phyla, as well as by vertebrates to build bones and teeth. One of the major current research aims of the Weiner--Addadi group is to understand the biomineralization pathways whereby ions are extracted from the environment, are transported and deposited inside cells within vesicles, how these disordered phases are then transferred to the site of skeletal formation, and finally how the so-called amorphous phase crystallizes. Biology has clearly evolved unique strategies for forming crystalline minerals. Despite more than 300 years of research in this field, many challenging questions still remain unanswered.

Addadi, Lia; Weiner, Steve

2014-09-01

417

Engram formation in psychiatric disorders  

PubMed Central

Environmental factors substantially influence beginning and progression of mental illness, reinforcing or reducing the consequences of genetic vulnerability. Often initiated by early traumatic events, “engrams” or memories are formed that may give rise to a slow and subtle progression of psychiatric disorders. The large delay between beginning and time of onset (diagnosis) may be explained by efficient compensatory mechanisms observed in brain metabolism that use optional pathways in highly redundant molecular interactions. To this end, research has to deal with mechanisms of learning and long-term memory formation, which involves (a) epigenetic changes, (b) altered neuronal activities, and (c) changes in neuron-glia communication. On the epigenetic level, apparently DNA-methylations are more stable than histone modifications, although both closely interact. Neuronal activities basically deliver digital information, which clearly can serve as basis for memory formation (LTP). However, research in this respect has long time neglected the importance of glia. They are more actively involved in the control of neuronal activities than thought before. They can both reinforce and inhibit neuronal activities by transducing neuronal information from frequency-encoded to amplitude and frequency-modulated calcium wave patterns spreading in the glial syncytium by use of gap junctions. In this way, they serve integrative functions. In conclusion, we are dealing with two concepts of encoding information that mutually control each other and synergize: a digital (neuronal) and a wave-like (glial) computing, forming neuron-glia functional units with inbuilt feedback loops to maintain balance of excitation and inhibition. To better understand mental illness, we have to gain more insight into the dynamics of adverse environmental impact on those cellular and molecular systems. This report summarizes existing knowledge and draws some outline about further research in molecular psychiatry. PMID:24904262

Gebicke-Haerter, Peter J.

2014-01-01

418

Eye formation in the absence of retina  

PubMed Central

Eye development is a complex process that involves the formation of the retina and the lens, collectively called the eyeball, as well as the formation of auxiliary eye structures such as the eyelid, lacrimal gland, cornea and conjunctiva. The developmental requirements for the formation of each individual structure are only partially understood. We have shown previously that the homeobox-containing gene Rx is a key component in eye formation, as retinal structures do not develop and retina-specific gene expression is not observed in Rx-deficient mice. In addition, Rx?/? embryos do not develop any lens structure, despite the fact that Rx is not expressed in the lens. This demonstrates that during normal mammalian development, retina-specific gene expression is necessary for lens formation. In this paper we show that lens formation can be restored in Rx-deficient embryos experimentally, by the elimination of ?-catenin expression in the head surface ectoderm. This suggests that ?-catenin is involved in lens specification either through Wnt signaling or through its function in cell adhesion. In contrast to lens formation, we demonstrate that the development of auxiliary eye structures does not depend on retina-specific gene expression or retinal morphogenesis. These results point to the existence of two separate developmental processes involved in the formation of the eye and its associated structures. One involved in the formation of the eyeball and the second involved in the formation of the auxiliary eye structures. PMID:18675797

Swindell, Eric C.; Liu, Chaomei; Shah, Rina; Smith, April N.; Lang, Richard A.; Jamrich, Milan

2008-01-01

419

Formation temperatures of thermogenic and biogenic methane  

USGS Publications Warehouse

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.

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.

2014-01-01

420

Molecular hydrogen formation in the interstellar medium  

E-print Network

We have developed a model for molecular hydrogen formation under astrophysically relevant conditions. This model takes fully into account the presence of both physisorbed and chemisorbed sites on the surface, allows quantum mechanical diffusion as well as thermal hopping for absorbed H-atoms, and has been benchmarked versus recent laboratory experiments on H2 formation on silicate surfaces. The results show that H2 formation on grain surface is efficient in the interstellar medium up to some 300K. At low temperatures (<100K), H2 formation is governed by the reaction of a physisorbed H with a chemisorbed H. At higher temperatures, H2 formation proceeds through reaction between two chemisorbed H atoms. We present simple analytical expressions for H2 formation which can be adopted to a wide variety of surfaces once their surfaces characteristics have been determined experimentally.

S. Cazaux; A. G. G. M. Tielens

2002-07-01

421

Star formation in the most massive galaxies  

NASA Astrophysics Data System (ADS)

While the most massive galaxies typically have negligible ongoing star formation, there is a minority of massive galaxies that buck this trend. This includes Perseus A and Centaurus A, which are often used as illustrations of AGN feedback in galaxies.How often do massive galaxies undergo episodes of star formation? Can recent star formation contribute significantly to the growth of massive galaxies? Why does star formation occur in a minority of massive galaxies? To answer these questions, we have selected samples of low redshift massive galaxies from 245 X-ray selected galaxy clusters and from the 2MASS Redshift Survey field galaxy sample, and measured the star formation rates of these galaxies using WISE mid-infrared photometry. We find that Perseus A is an exceptional galaxy in the z<0.1 Universe, and only 1% of brightest cluster galaxies have comparable star formation rates.

Brown, Michael J. I.; Fraser-McKelvie, Amelia; Bonne, Nicolas

2015-01-01

422

Autonomous Formations of Multi-Agent Systems  

NASA Technical Reports Server (NTRS)

Autonomous formation control of multi-agent dynamic systems has a number of applications that include ground-based and aerial robots and satellite formations. For air vehicles, formation flight ("flocking") has the potential to significantly increase airspace utilization as well as fuel efficiency. This presentation addresses two main problems in multi-agent formations: optimal role assignment to minimize the total cost (e.g., combined distance traveled by all agents); and maintaining formation geometry during flock motion. The Kuhn-Munkres ("Hungarian") algorithm is used for optimal assignment, and consensus-based leader-follower type control architecture is used to maintain formation shape despite the leader s independent movements. The methods are demonstrated by animated simulations.

Dhali, Sanjana; Joshi, Suresh M.

2013-01-01

423

Molybdenum and tungsten-dependent formate dehydrogenases.  

PubMed

The prokaryotic formate metabolism is considerably diversified. Prokaryotes use formate in the C1 metabolism, but also evolved to exploit the low reduction potential of formate to derive energy, by coupling its oxidation to the reduction of numerous electron acceptors. To fulfil these varied physiological roles, different types of formate dehydrogenase (FDH) enzymes have evolved to catalyse the reversible 2-electron oxidation of formate to carbon dioxide. This review will highlight our present knowledge about the diverse physiological roles of FDH in prokaryotes, their modular structural organisation and active site structures and the mechanistic strategies followed to accomplish the formate oxidation. In addition, the ability of FDH to catalyse the reverse reaction of carbon dioxide reduction, a potentially relevant reaction for carbon dioxide sequestration, will also be addressed. PMID:25476858

Maia, Luisa B; Moura, José J G; Moura, Isabel

2014-12-01

424

Formation and Evolution of the Milky Way  

Microsoft Academic Search

\\u000a The problem of understanding the formation of the Galaxy is part of the problem of explaining galaxy formation in general.\\u000a In particular, we should try to understand the relative importance of mergers and dissipative collapse in the formation of\\u000a all galaxies, and whether the observational information about our Galaxy is enough to explain the timescales and the mechanisms\\u000a of its

Francesca Matteucci

425

Floating insulated conductors for heating subsurface formations  

DOEpatents

A heating system for a subsurface formation includes a conduit located in a first opening in the subsurface formation. Three electrical conductors are located in the conduit. A return conductor is located inside the conduit. The return conductor is electrically coupled to the ends of the electrical conductors distal from the surface of the formation. Insulation is located inside the conduit. The insulation electrically insulates the three electrical conductors, the return conductor, and the conduit from each other.

Burns, David; Goodwin, Charles R.

2014-07-29

426

Star Formation in Lynds 1641  

NASA Astrophysics Data System (ADS)

We conducted an extensive multi-wavelength study of the nearest giant molecular cloud, L1641, with the goal of characterizing its stellar populations. At a distance of approximately 500 pc, L1641 provides an excellent opportunity for studying star formation over the entire range of stellar masses, and the star formation history in a region thought representative of those dominating stellar production in the Milky Way. Our approach combines imaging surveys at optical and infrared wavelengths with spectroscopic surveys at ?? 6000-9000Å to measure stellar luminosities and effective temperatures. Stellar ages and masses are then estimated from comparison of L*, Teff with pre-main sequence evolutionary tracks. The stars for which we have obtained classifiable spectra as well as optical (R,I) and near-infrared and near-infrared (J,H,K) photometry number ~300, and are contained within four regions, each approximately 20' square (2.5 × 2.5 pc). Our 2.25micron images reveal both modest aggregates of several tens of stars and stars distributed at random across the face of the cloud; we find no evidence of rich (N gg 100 stars) clusters. The aggregate members appear to have formed within the past 1 Myr, while the distributed population contains both young stars (t < 1Myr) and stars ranging in age up to 30 Myr. From comparison of the fraction of the youngest stars forming in aggregates and in isolation, we conclude that stars born initially in aggregates comprise 25 - 50% of the total stars formed in L1641. The observed frequency distribution of stellar ages enables a discussion of the star-forming history of the cloud. The L1641 cloud has been producing stars for nearly 30 Myr and over the last 10 Myr, the SFR has been roughly constant. We explore the implications of this result for the ``off-cloud'' spatial distribution of young stars. Finally, we examine the circumstellar disk properties of stars in our spectroscopic sample. The frequency of disks, as inferred from infrared excess emission, is found to be higher for stars less massive than 1 Modot than for more massive stars. We also find that at least six stars in L1641 have apparently retained their accretion disks beyond an age of 3 Myr. The thesis is available on the World Wide Web at: http://decoy.phast.umass.edu/

Allen, Lori E.

1995-11-01

427

Pattern Formation in a Synthetic Multicellular System  

NASA Astrophysics Data System (ADS)

Pattern formation has been studied for a long history since the Turing's proposal for a reaction-diffusion system and been found in numerous physical, chemical and biological examples. However, experimental study about pattern formation advances slowly. Here we present an artificial pattern formation system. By engineering cellular communication in bacteria E. Coli and plating these engineered cells onto a solid-phase agarose plate, we are able to program the pattern formation of this multicellular system. The pattern changes dramatically with different levels of an external inducer IPTG. A simple model is developed to explain the experimental results.

Lu, Ting; Karig, David; Weiss, Ron

2008-03-01

428

GLOBULAR CLUSTER FORMATION WITHIN A COSMOLOGICAL CONTEXT  

SciTech Connect

We place constraints on the formation redshifts for blue globular clusters (BGCs), independent of the details of hydrodynamics and population III star formation. The observed radial distribution of BGCs in the Milky Way Galaxy suggests that they formed in biased dark matter halos at high redshift. As a result, simulations of a approx1 Mpc box up to z approx 10 must resolve BGC formation in LAMBDACDM. We find that most halo stars could be produced from destroyed BGCs and other low-mass clusters that formed at high redshift. We present a proof-of-concept simulation that captures the formation of globular-like star clusters.

Boley, Aaron C.; Lake, George; Read, Justin; Teyssier, Romain, E-mail: aaron.boley@gmail.co [Institute for Theoretical Physics, University of Zurich, Winterthurerstrasse 190, Zurich, CH-8057 (Switzerland)

2009-11-20

429

On the Formation of Brown Dwarfs  

E-print Network

The observational properties of brown dwarfs pose challenges to the theory of star formation. Because their mass is much smaller than the typical Jeans mass of interstellar clouds, brown dwarfs are most likely formed through secondary fragmentation processes, rather than through the direct collapse of a molecular cloud core. In order to prevent substantial post-formation mass accretion, young brown dwarfs must leave the high density formation regions in which they form. We propose here that brown dwarfs are formed in the circumbinary disks. Through post-formation dynamical interaction with their host binary stars, young brown dwarfs are either scattered to large distance or removed, with modest speed, from their cradles.

Ing-Guey Jiang; G. Laughlin; D. N. C. Lin

2003-09-19

430

Processes and problems in secondary star formation  

SciTech Connect

Recent developments relating the conditions in molecular clouds to star formation triggered by a prior stellar generation are reviewed. Primary processes are those that lead to the formation of a first stellar generation. The secondary processes that produce stars in response to effects caused by existing stars are compared and evaluated in terms of the observational data presently available. We discuss the role of turbulence to produce clumpy cloud structures and introduce new work on colliding inter-cloud gas flows leading to non-linear inhomogeneous cloud structures in an intially smooth cloud. This clumpy morphology has important consequences for secondary formation. The triggering processes of supernovae, stellar winds, and H II regions are discussed with emphasis on the consequences for radiation driven implosion as a promising secondary star formation mechanism. Detailed two-dimensional, radiation-hydrodynamic calculations of radiation driven implosion are discussed. This mechanism is shown to be highly efficient in synchronizing the formation of new stars in congruent to 1-3 x 10/sup 4/ years and could account for the recent evidence for new massive star formation in several UCHII regions. It is concluded that, while no single theory adequately explains the variety of star formation observed, a uniform description of star formation is likely to involve several secondary processes. Advances in the theory of star formation will require multiple dimensional calculations of coupled processes. The important non-linear interactions include hydrodynamics, radiation transport, and magnetic fields.

Klein, R.I.; Whitaker, R.W.; Sandford M.T. II

1984-03-01

431

The formation of ice on airplanes  

NASA Technical Reports Server (NTRS)

The present report examines the problem of ice formation from the point of view of the pilot and the meteorologist. Their experiences prove the ice deposit to be first and foremost a navigational problem and only secondarily a question of de-icing devices. With correct utilization of the meteorological information by the flyer, ice hazard can in many cases be minimized or avoided. Ice formation and the different types of ice deposits are listed and discussed. Weather formation during these ice deposits are also discussed as well as the effect of ice formation on aircraft.

Noth, H; Polte, W

1936-01-01

432

Heating systems for heating subsurface formations  

DOEpatents

Methods and systems for heating a subsurface formation are described herein. A heating system for a subsurface formation includes a sealed conduit positioned in an opening in the formation and a heat source. The sealed conduit includes a heat transfer fluid. The heat source provides heat to a portion of the sealed conduit to change phase of the heat transfer fluid from a liquid to a vapor. The vapor in the sealed conduit rises in the sealed conduit, condenses to transfer heat to the formation and returns to the conduit portion as a liquid.

Nguyen, Scott Vinh (Houston, TX); Vinegar, Harold J. (Bellaire, TX)

2011-04-26

433

Heating tar sands formations to visbreaking temperatures  

DOEpatents

Methods for treating a tar sands formation are described herein. Methods may include heating at least a section of a hydrocarbon layer in the formation from a plurality of heaters located in the formation. The heat may be controlled so that at least a majority of the section reaches an average temperature of between 200.degree. C. and 240.degree. C., which results in visbreaking of at least some hydrocarbons in the section. At least some visbroken hydrocarbon fluids may be produced from the formation.

Karanikas, John Michael (Houston, TX); Colmenares, Tulio Rafael (Houston, TX); Zhang, Etuan (Houston, TX); Marino, Marian (Houston, TX); Roes, Augustinus Wilhelmus Maria (Houston, TX); Ryan, Robert Charles (Houston, TX); Beer, Gary Lee (Houston, TX); Dombrowski, Robert James (Houston, TX); Jaiswal, Namit (Houston, TX)

2009-12-22

434

Dispersal, settling and layer formation.  

PubMed

Motivated by examples in developmental biology and ecology, we develop a model for convection-dominated invasion of a spatial region by initially motile agents which are able to settle permanently. The motion of the motile agents and their rate of settling are affected by the local concentration of settled agents. The model can be formulated as a nonlinear partial differential equation for the time-integrated local concentration of the motile agents, from which the instantaneous density of settled agents and its long-time limit can be extracted. In the limit of zero diffusivity, the partial differential equation is of first order; for application-relevant initial and boundary-value problems, shocks arise in the time-integrated motile agent density, leading to delta-function components in the motile agent density. Furthermore, there are simple solutions for a model of successive layer formation. In addition some analytic results for a one-dimensional system with non-zero diffusivity can also be obtained. A case study, both with and without diffusion, is examined numerically. Some important predictions of the model are insensitive to the specific settling law used and the model offers insight into biological processes involving layered growth or overlapping generations of colonization. PMID:21536053

Caffrey, James R; Hughes, Barry D; Landman, Kerry A

2011-07-01

435

Spheromak formation studies in SSPX  

SciTech Connect

We present results from the Sustained Spheromak Physics Experiment (SSPX) at LLNL, which has been built to study energy confinement in spheromak plasmas sustained for up to 2 ms by coaxial DC helicity injection. Peak toroidal currents as high as 600kA have been obtained in the 1m dia. (0.23m minor radius) device using injection currents between 200-400kA; these currents generate edge poloidal fields in the range of 0.2-0.4T. The internal field and current profiles are inferred from edge field measurements using the CORSICA code. Density and impurity control is obtained using baking, glow discharge cleansing, and titanium gettering, after which long plasma decay times ({tau} {ge} 1.5ms) are observed and impurity radiation losses are reduced from {approx}50% to <20% of the input energy. Thomson scattering measurements show peaked electron temperature and pressure profiles with T{sub e} (0){approx}120eV and {beta}{sub e}{approx}7%. Edge field measurements show the presence of n=1 modes during the formation phase, as has been observed in other spheromaks. This mode dies away during sustainment and decay so that edge fluctuation levels as low as 1% have been measured. These results are compared with numerical simulations using the NIMROD code.

Hill, D N; Bulmer, R H; Cohen, B L; Hooper, E B; LoDestro, L L; Mattor, N; McLean, H S; Moller, J; Pearlstein, L D; Ryutov, D D; Stallard, B W; Wood, R D; Woodruff, S; Holcomb, C T; Jarboe, T; Sovinec, C R; Wang, Z; Wurden, G

2000-09-29

436

Formation of the solar system  

NSDL National Science Digital Library

This exercise is designed as a lab, but can also be used as a classroom demonstration. It requires the use of the VPython programs which require Python and VPython to be installed on your computers (this software is free and has been made available on the default image for all computers on our campus). The models show the gravitational collapse of a set of particles to create a central "Sun" with other orbiting particles, a simple model to demonstrate elliptical orbits, a simple model of the solar system showing the planetary orbits (speeded up). The task is to assess one hypothesis about the formation of the solar system (from a dust and gas nebula) by comparing the computer simulation (model 1) to the shape and form of the actual solar system (model 3). Students can interact with the 3d models by, for example, selecting planetary objects to track, and changing perspectives in 3d space. In doing this students learn about the shapes of the planetary orbits (ellipticity etc) and reasons that they change.

Urbano, Lensyl

437

Dune formation under bimodal winds  

PubMed Central

The study of dune morphology represents a valuable tool in the investigation of planetary wind systems—the primary factor controlling the dune shape is the wind directionality. However, our understanding of dune formation is still limited to the simplest situation of unidirectional winds: There is no model that solves the equations of sand transport under the most common situation of seasonally varying wind directions. Here we present the calculation of sand transport under bimodal winds using a dune model that is extended to account for more than one wind direction. Our calculations show that dunes align longitudinally to the resultant wind trend if the angle ?w between the wind directions is larger than 90°. Under high sand availability, linear seif dunes are obtained, the intriguing meandering shape of which is found to be controlled by the dune height and by the time the wind lasts at each one of the two wind directions. Unusual dune shapes including the “wedge dunes” observed on Mars appear within a wide spectrum of bimodal dune morphologies under low sand availability. PMID:20018703

Parteli, Eric J. R.; Durán, Orencio; Tsoar, Haim; Schwämmle, Veit; Herrmann, Hans J.

2009-01-01

438

STAR FORMATION IN DENSE CLUSTERS  

SciTech Connect

A model of core-clump accretion with equally likely stopping describes star formation in the dense parts of clusters, where models of isolated collapsing cores may not apply. Each core accretes at a constant rate onto its protostar, while the surrounding clump gas accretes as a power of protostar mass. Short accretion flows resemble Shu accretion and make low-mass stars. Long flows resemble reduced Bondi accretion and make massive stars. Accretion stops due to environmental processes of dynamical ejection, gravitational competition, and gas dispersal by stellar feedback, independent of initial core structure. The model matches the field star initial mass function (IMF) from 0.01 to more than 10 solar masses. The core accretion rate and the mean accretion duration set the peak of the IMF, independent of the local Jeans mass. Massive protostars require the longest accretion durations, up to 0.5 Myr. The maximum protostar luminosity in a cluster indicates the mass and age of its oldest protostar. The distribution of protostar luminosities matches those in active star-forming regions if protostars have a constant birthrate but not if their births are coeval. For constant birthrate, the ratio of young stellar objects to protostars indicates the star-forming age of a cluster, typically {approx}1 Myr. The protostar accretion luminosity is typically less than its steady spherical value by a factor of {approx}2, consistent with models of episodic disk accretion.

Myers, Philip C., E-mail: pmyers@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2011-12-10

439

Pattern Formation and Complexity Emergence  

NASA Astrophysics Data System (ADS)

Success of nonlinear modelling of pattern formation and self-organization encourages speculations on informational and number theoretical foundations of complexity emergence. Pythagorean "unreasonable effectiveness of integers" in natural processes is perhaps extrapolatable even to universal emergence "out-of-nothing" (Leibniz, Wheeler). Because rational numbers (R = M/N) are everywhere dense on real axis, any digital string (hence any "book" from "Library of Babel" of J.L.Borges) is "recorded" infinitely many times in arbitrary many rationals. Furthermore, within any arbitrary small interval there are infinitely many Rs for which (either or both) integers (Ms and Ns) "carry" any given string of any given length. Because any iterational process (such as generation of fractal features of Mandelbrot Set) is arbitrary closely approximatable with rational numbers, the infinite pattern of integers expresses itself in generation of complexity of the world, as well as in emergence of the world itself. This "tunnelling" from Platonic World ("Platonia" of J.Barbour) to a real (physical) world is modern recast of Leibniz's motto ("for deriving all from nothing there suffices a single principle").

Berezin, Alexander A.

2001-03-01

440

Granitoid pluton formation by spreading of continental crust: the Wiley Glacier complex, northwest Palmer Land, Antarctica  

NASA Astrophysics Data System (ADS)

The emplacement mechanism, geometry, and isotope geochemistry of plutons of the Wiley Glacier complex suggest that new continental crust grew by multiple injection of tonalitic dykes during dextral transtension in the Antarctic Peninsula magmatic arc in Early Cretaceous times. The suggested mechanism is analogous to basalt dyke injection during sea-floor spreading. During normal-dextral shear, the Burns Bluff pluton, a sheeted, moderately east-dipping, syn-magmatically sheared tonalite-granodiorite intruded syn-magmatically sheared quartz diorite of the Creswick Gap pluton and 140 ± 5 Ma hornblende gabbro. U?Pb dating of zircon and Ar?Ar dating of hornblende and biotite suggest that both granite s.l. plutons were emplaced between 145 and 140 Ma, but that extensional shearing was active from the time of emplacement until ca. 127 Ma. The Burns Bluff pluton is chilled at its margin, and grades through mylonitised, porphyritic tonalite-granodiorite sheets and tonalite-granodiorite sheets with minor chilling, to a kilometre-scale body of coarse-grained, hypidiomorphic tonalite-granodiorite. Co-magmatic microdiorite forms dykes and abundant synplutonic mafic enclaves. These dykes opened as echelon veins during episodic dextral shear and were deformed to trains of enclaves during continued normal-dextral shear. Pluton-marginal porphyritic and hypidiomorphic tonalite-granodiorite forms large, fault-hosted sheets emplaced progressively under extension with minor dextral shear. Kinematic indicators from pluton-marginal granite s.l. dykes suggest that early in pluton accretion, intrusive sheets cooled rapidly, with simple shear prior to full crystallisation changing to ductile simple shear during cooling. Kinematic indicators towards the pluton core suggest that as the pluton grew, and cooled more slowly, emplacement switched from sheeting to in situ inflation with simple shear distributed across a broad zone prior to full crystallisation of magma. Cross-cutting relationships with the coeval, syn-extensional, Creswick Gap pluton suggest that the Burns Bluff pluton was emplaced in a steeper, second generation shear structure, like those in normal fault systems. This suggests that the Wiley Glacier complex was emplaced above the base of the brittle-ductile transition zone (15-18 km depth). The Burns Bluff pluton has Nd and Sr isotope values that range from mantle dominated ( ?Nd 141 = +3.8, {87Sr }/{86Sr 141} = 0.70468 ) to more crustally influenced ( ?Nd 141 = -1.7, {87Sr }/{86Sr 141} = 0.70652 ). This range probably represents different degrees of mixing between mantle-derived magma and lower crustal partial melts generated in the garnet-stability zone (40+ km depth). Addition of new crustal material by mafic underplating at the base of the crust and by redistribution of granitic s.l. and mafic, modified, underplated magma to mid-crustal levels along extensional shear zones as the arc 'spread' were the primary mechanisms of crustal growth.

Vaughan, Alan P. M.; Wareham, Christopher D.; Millar, Ian L.

1997-12-01

441

Pattern Formation in Complex Fluids  

NASA Astrophysics Data System (ADS)

Classical fluid instabilities -- such as the Saffman-Taylor instability in a Hele-Shaw cell -- are dramatically modified by using complex fluids. For example, polymeric liquids driven in a Hele-Shaw cell yield "dendritic" patterns with an apparent directional anisotropy. The dynamics of complex liquids can also lead to new instabilities and patterns, such as space-filling patterns formed by successive bucklings of growing "elastica" seen in the phase transition of a liquid crystalline material. Understanding such problems requires an interplay between physical modeling, mathematical analysis, and sophisticated nonlinear simulation. For the first problem, I will discuss a non-Newtonian version of Darcy's law for Hele-Shaw flow. This yields a free-boundary problem for the pattern formation, and requires the solution of a nonlinear elliptic equation in a time-dependent domain. This is pushing the development of adaptive grid methods that represent the geometry accurately and efficiently. Our simulations yield insight into how shear-thinning, as is evinced by polymeric liquids, can produce patterns reminiscent of experiment, with "dendritic fingers", side-branching, and reduced tip-splitting. In the second problem, a long filament in a smectic-A phase grows within an isotropic fluid. The splay deformation of the material gives this filament an elastic response. The macroscopic model describes the dynamics of a growing, elastic filament immersed in a Stokesian fluid. The model marries filament elasticity and tensile forces with a numerically tractable nonlocal slender-body theory. Analysis shows that growth of the filament, despite fluid drag, produces a buckling instability. When coupled to a nonlocal hydrodynamic self-interaction, our fully nonlinear simulations show that such instabilities iterate along the filament, and give "space-filling" patterns.

Shelley, Michael

2000-03-01

442

Formation of the giant planets  

NASA Technical Reports Server (NTRS)

The observed properties of giant planets, models of their evolution and observations of protoplanetary disks provide constraints on the formation of gas giant planets. The four largest planets in our Solar System contain considerable quantities of hydrogen and helium, which could not have condensed into solid planetesimals within the protoplanetary disk. All three (transiting) extrasolar giant planets with well determined masses and radii also must contain substantial amounts of these light gases. Jupiter and Saturn are mostly hydrogen and helium, but have larger abundances of heavier elements than does the Sun. Neptune and Uranus are primarily composed of heavier elements. HD 149026 b, which is slightly more massive than is Saturn, appears to have comparable quantities of light gases and heavy elements. HD 209458 b and TrES-1 are primarily hydrogen and helium, but may contain supersolar abundances of heavy elements. Spacecraft flybys and observations of satellite orbits provide estimates of the gravitational moments of the giant planets in our Solar System, which in turn provide information on the internal distribution of matter within Jupiter, Saturn, Uranus and Neptune. Atmospheric thermal structure and heat flow measurements constrain the interior temperatures of planets. Internal processes may cause giant planets to become more compositionally differentiated or alternatively more homogeneous; high-pressure laboratory .experiments provide data useful for modeling these processes. The preponderance of evidence supports the core nucleated gas accretion model. According to this model, giant planets begin their growth by the accumulation of small solid bodies, as do terrestrial planets. However, unlike terrestrial planets, the growing giant planet cores become massive enough that they are able to accumulate substantial amounts of gas before the protoplanetary disk dissipates. The primary questions regarding the core nucleated growth model is under what conditions planets with small cores/total heavy element abundances can accrete gaseous envelopes within the lifetimes of gaseous protoplanetary disks.

Lissauer, Jack J.

2006-01-01

443

Thermodynamics of ?-amyloid fibril formation  

NASA Astrophysics Data System (ADS)

Amyloid fibers are aggregates of proteins. They are built out of a peptide called ?-amyloid (A?) containing between 41 and 43 residues, produced by the action of an enzyme which cleaves a much larger protein known as the amyloid precursor protein (APP). X-ray diffraction experiments have shown that these fibrils are rich in ?-structures, whereas the shape of the peptide displays an ?-helix structure within the APP in its biologically active conformation. A realistic model of fibril formation is developed based on the 17 residues A?12-28 amyloid peptide, which has been shown to form fibrils structurally similar to those of the whole A? peptide. With the help of physical arguments and in keeping with experimental findings, the A?12-28 monomer is assumed to be in four possible states (i.e., native helix conformation, ?-hairpin, globular low-energy state, and unfolded state). Making use of these monomeric states, oligomers (dimers, tertramers, and octamers) were constructed. With the help of short, detailed molecular dynamics calculations of the three monomers and of a variety of oligomers, energies for these structures were obtained. Making use of these results within the framework of a simple yet realistic model to describe the entropic terms associated with the variety of amyloid conformations, a phase diagram can be calculated of the whole many-body system, leading to a thermodynamical picture in overall agreement with the experimental findings. In particular, the existence of micellar metastable states seem to be a key issue to determine the thermodynamical properties of the system.

Tiana, G.; Simona, F.; Broglia, R. A.; Colombo, G.

2004-05-01

444

The formation, structure, and evolution of plasmoids  

Microsoft Academic Search

The configuration and topology of the Earth's magnetotail is radically altered during geomagnetic substorms by the formation and subsequent ejection of large scale magnetic and plasma structures called plasmoids. The formation, structure, evolution and topology of plasmoids are studied by examining the magnetic and plasma data from the 1983 ISEE 3 Geotail Mission. This deep tail data set is combined

Mark Bela Santos Moldwin

1993-01-01

445

Learning Progressions that Support Formative Assessment Practices  

ERIC Educational Resources Information Center

Black, Wilson, and Yao (this issue) lay out a comprehensive vision for the way that learning progressions (or other "road maps") might be used to inform and coordinate formative and summative purposes of assessment. As Black, Wilson, and others have been arguing for over a decade, the effective use of formative assessment has great potential to…

Alonzo, Alicia C.

2011-01-01

446

A UNIMARC Bibliographic Format Database for ABCD  

ERIC Educational Resources Information Center

Purpose: ABCD is a web-based open and free software suite for library management derived from the UNESCO CDS/ISIS software technology. The first version was launched officially in December 2009 with a MARC 21 bibliographic format database. This paper aims to detail the building of the UNIMARC bibliographic format database for ABCD.…

Megnigbeto, Eustache

2012-01-01

447

Pattern formation in flowing electrorheological fluids.  

PubMed

A two-fluid continuum model is developed to describe mass transport in electro- and magnetorheological suspensions. The particle flux is related to the field-induced stresses. Solutions of the resulting mass balance show column formation in the absence of flow, and stripe formation when a suspension is subjected simultaneously to an applied electric field and shear flow. PMID:12005727

von Pfeil, Karl; Graham, Michael D; Klingenberg, Daniel J; Morris, Jeffrey F

2002-05-01

448

Flexible format, computer accessed telemetry system  

NASA Technical Reports Server (NTRS)

With this system, it is possible to sample and generate two or more simultaneous formats; one can be transmitted to ground station in real time, and other is stored for later transmission. Sensor output comparison data, plus information to control format, compression algorithm, and allowable degree of sensor activity, are stored in memory.

Easton, R. A.; Hilbert, E. E.

1973-01-01

449

Formation of $??$ atoms in $K_{?4} decay  

E-print Network

We derive the decay rate of $\\pi\\mu$ atom formation in $K_{\\mu 4}$ decay. Using the obtained expressions we calculate the decay rate of atom formation and point out that considered decay can give a noticeable contribution as a background to the fundamental decay $K^+\\to \\pi^+\

S. R. Gevorkyan; A. V. Tarasov; O. O. Voskresenskaya

2009-12-01

450

LARSPEC spectroradiometer-multiband radiometer data formats  

NASA Technical Reports Server (NTRS)

The data base software system, LARSPEC, is discussed and the data base format for agronomic, meteorological, spectroradiometer, and multiband radiometer data is described. In addition, the contents and formats of each record of data and the wavelength tables are listed and the codes used for some of the parameters are described.

Biehl, L. L.

1982-01-01

451

Mylonitic Breccia near the Gunsight Formation  

USGS Multimedia Gallery

Mylonitic breccia in alluvium of Little Deer Creek, downstream from a moderately west-dipping contact between biotitic quartzite of the Gunsight Formation, which is structurally overlain by garnet-chloritoid-bearing banded siltite of the banded siltite unit of the Apple Creek Formation. That structu...

452

Dynamics and Control of Electromagnetic Satellite Formations  

E-print Network

concept that uses superconducting electromagnetic coils to provide forces and torques between differentDynamics and Control of Electromagnetic Satellite Formations Umair Ahsun, David W. Miller June 2007 SSL # 12-07 #12;2 #12;Dynamics and Control of Electromagnetic Satellite Formations by Umair Ahsun B

453

GRAPH LAPLACIANS AND STABILIZATION OF VEHICLE FORMATIONS  

Microsoft Academic Search

Control of vehicle formations has emerged as a topic of signiflcant interest to the controls community. In this paper, we merge tools from graph theory and control theory to derive stability criteria for vehicle formations. The interconnection between vehicles (i.e., which vehicles are sensed by other vehicles) is modeled as a graph, and the eigenvalues of the Laplacian matrix of

J. Alexander Fa; Richard M. Murray

454

Soot Formation In Laminar Inverse Diffusion Flames  

Microsoft Academic Search

Soot formation in laminar ethylene inverse diffusion flames has been investigated experimentally and modeled. Soot volume fraction and temperature measurements have been made and compared to numerical predictions using a soot formation model previously applied to normal diffusion flames. The inverse flame configuration serves as a good test of the applicability of the model and is relevant to practical combustor

D. B. MAKEL; I. M. KENNEDY

1994-01-01

455

DISSERTATION FORMATION OF THE HURRICANE EYE  

E-print Network

DISSERTATION FORMATION OF THE HURRICANE EYE Submitted by Jonathan L. Vigh Department of Atmospheric OF THE HURRICANE EYE BE ACCEPTED AS FULFILLING IN PART REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY. Schubert Department Head: Richard H. Johnson ii #12;ABSTRACT OF DISSERTATION FORMATION OF THE HURRICANE EYE

Schubert, Wayne H.

456

An introduction to the ENDF formats  

SciTech Connect

The ENDF Evaluated Nuclear Data Formats are used all over the world to encode nuclear data evaluations for use in research and nuclear technology. This report is an introduction to the formats and how they are used in modern compilations of nuclear data.

NONE

1998-11-01

457

The New Galaxy: Signatures of Its Formation  

Microsoft Academic Search

The formation and evolution of galaxies is one of the great outstanding problems of astrophysics. Within the broad context of hierachical structure formation, we have only a crude picture of how galaxies like our own came into existence. A detailed physical picture where individual stellar populations can be associated with (tagged to) elements of the protocloud is far beyond our

Ken Freeman; Joss Bland-Hawthorn

2002-01-01

458

Star Formation in the Orion Nebula Cluster  

Microsoft Academic Search

We study the record of star formation activity within the dense cluster associated with the Orion Nebula. The bolometric luminosity function of 900 visible members is well matched by a simplified theoretical model for cluster formation. This model assumes that stars are produced at a constant rate and distributed according to the field-star initial mass function. Our best-fit age for

Francesco Palla; Steven W. Stahler

1999-01-01

459

Formation and evolution of the protoplanetary disk  

NASA Technical Reports Server (NTRS)

A disk formation model during collapse of the protosolar nebula, yielding a low-mass protoplanetary disk is presented. The following subject areas are covered: (1) circumstellar disks; (2) conditions for the formation of stars with disks; (3) early evolution of the protoplanetary disk; and (4) temperature conditions and the convection in the protoplanetary disk.

Ruzmaikina, Tamara V.; Makalkin, A. B.

1991-01-01

460

Methods for forming wellbores in heated formations  

DOEpatents

A method for forming a wellbore in a heated formation includes flowing liquid cooling fluid to a bottom hole assembly in a wellbore in a heated formation. At least a portion of the liquid cooling fluid is vaporized at or near a region to be cooled. Vaporizing the liquid cooling fluid absorbs heat from the region to be cooled.

Guimerans, Rosalvina Ramona; Mansure, Arthur James

2012-09-25