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1

Stratigraphy of the Calvert Bluff Formation of the Wilcox Group, Brazos County, Texas  

E-print Network

, Calvert Bluff (including the Sabinetown shale), and Carizzo formations of the Wilcox Group. 3 Study area map showing major structural features: basins, fault zones, salt domes. . 7 4 Regional map of the Texas Gulf Coast showing the Wilcox outcrop... of the older structure. Three salt domes lie within or near this study area and include the Clay Creek dome to the south in Washington County, Millican dome in southern Brazos County, and Ferguson dome on the border between Brazos and Grimes counties...

May, Audrey Gail

2012-06-07

2

Hydrogeology and groundwater modeling of a Calvert Bluff aquifer  

E-print Network

HYDROGEOLOGY AND GROUNDWATER MODELING OF A CALVERT BLUFF AQUIFER A Thesis by JAMES LAWRENCE Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE... May 1989 Major Subject: Geology HYDROGEOLOGY AND GROUNDWATER MODELING OF A CALVERT BLUFF AQUIFER A Thesis by James Lawrence Approved as to style and content by: Patrick A. Domenico (Chair of Committee) Donald L. Reddell (Member) Robert R...

Lawrence, James

2012-06-07

3

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

USGS Publications Warehouse

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

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

1997-01-01

4

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

5

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

USGS Publications Warehouse

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

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

1998-01-01

6

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

7

The physical conditions indicated by the flora of the Calvert formation  

USGS Publications Warehouse

The object of the present paper is to give a summary of the small flora preserved in the Miocene diatomaceous beds of the Calvert formation in the District of Columbia and Virginia, and more especially to discuss its bearing on the physical conditions of the Calvert epoch. Subsequent to the middle Eocene the next abundant marine fauna preserved along the middle Atlantic coast is that of the Calvert formation of the Chesapeake group. Although Miocene faunas so low in the stratigraphic column are known south of Virginia only in the vicinity of Porters Landing, Savannah River, closely related but younger Miocene faunas extend southward at least as far as Florida, where the containing formation rests unconformably on beds in which occur the warmer-water faunas of the Apalachicola group.

Berry, Edward Wilber

1917-01-01

8

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

9

Wake Similarity and Vortex Formation for Two-Dimensional Bluff Bodies  

NASA Astrophysics Data System (ADS)

An experimental study of the flow around a cylinder with a single straight perturbation was conducted in a wind tunnel. With this bluff body, positioned in a uniform crossflow, the vortex shedding frequency and other flow characteristics could be manipulated. The Strouhal number has been shown to be a function of the perturbation angular position, theta _{rm p}, as well as the perturbation size and Reynolds number. As much as a 50% change in Strouhal number could be achieved, simply by changing theta _{rm p} by 1^ circ. The perturbation size compared to the boundary-layer thickness, delta, was varied from approximately 1delta to about 20delta. The Reynolds number was varied from 10,000 to 40,000. A detailed investigation of the characteristic Strouhal number variation has shown that varying theta_{rm p} had a significant influence on the boundary -layer separation and transition to turbulence. These significant changes occurring in the boundary-layer have been shown to cause variations in the spacing between the shear layers, base pressure, vortex formation length, drag, lift, and the longitudinal spacing between the vortices in the vortex street. The unique ability of the cylinder with a single straight perturbation to control the Strouhal number and other flow characteristics, was used to evaluate several previously proposed wake similarity concepts by Fage and Johansen(1927), Roshko(1955), Bearman(1967) and Griffin(1981). It was shown that these wake similarity concepts did not satisfactorily apply to the bluff body which was used in this study. The experimental results have shown that a wake similarity parameter, S_{rm M} = kf_{rm v}d*/U _infty has smaller variations from its mean values S_{rm Mo } = 0.39, when compared to previously proposed wake similarity parameters. The quantity, k, is the base pressure parameter, f_{rm v} , is the vortex shedding frequency, d*, is the spacing between the shear layers and U_infty , is the free stream velocity. The similarity parameter S_{rm M}, when applied to Fage and Johansen's measurements on a wide range of bluff bodies showed less variance and resulted in numbers near 0.39. The parameter, S_{rm M}, when used to evaluate the lateral-to-longitudinal stability of vortices in the vortex street was shown to favor von Karman's over Kronauer's wake stability criterion.

Nebres, Jose Luis Villafranca

10

Facies architecture of the upper Calvert Bluff Formation exposed in the highwall of Big Brown Mine, Fairfield, Texas  

E-print Network

be observed locally and occurrence of soft sediment deformation is rare (Figure 11). Prograding delta facies are recognized in subsurface logs by their low value, serrated gamma ray curve, high to medium density curve, and middle to high resistivity curve...-scale sedimentary structures were able to be observed. Delta top mud is identified in subsurface logs by a high but serrated gamma ray response, a moderately serrated average density response, and a variable resistivity whose deflections correspond directly...

Sturdy, Michael Dale

2006-10-30

11

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

12

Calvert: an historical geography  

E-print Network

, with attendant institutions of slavery and mono-crop production for export and profit. These Lower Southerners gradually dominated representatives of the Upper American South. A rail line reached Robertson County in 1869 and Calvert was founded where... the uplands merge into the alluvial floodplain of western Robertson County. As a rail terminus, the young town was soon marked by a sizeable population of merchants and settlers eager to take advantage of the results of use of the nearby fertile alluvial...

McMillan, Frank N

2012-06-07

13

Calvert Cliffs tiger beetle  

NSDL National Science Digital Library

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

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

2004-01-01

14

Calvert Cliffs tiger beetle  

NSDL National Science Digital Library

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

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

2004-01-01

15

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

...2014-07-01 false Security Zone; Calvert Cliffs Nuclear Power Plant, Chesapeake Bay, Calvert County, Maryland...District § 165.505 Security Zone; Calvert Cliffs Nuclear Power Plant, Chesapeake Bay, Calvert County,...

2014-07-01

16

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

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Security Zone; Calvert Cliffs Nuclear Power Plant, Chesapeake Bay, Calvert County, Maryland...District § 165.505 Security Zone; Calvert Cliffs Nuclear Power Plant, Chesapeake Bay, Calvert County,...

2010-07-01

17

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

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Security Zone; Calvert Cliffs Nuclear Power Plant, Chesapeake Bay, Calvert County, Maryland...District § 165.505 Security Zone; Calvert Cliffs Nuclear Power Plant, Chesapeake Bay, Calvert County,...

2011-07-01

18

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

Code of Federal Regulations, 2013 CFR

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

2013-07-01

19

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

Code of Federal Regulations, 2012 CFR

...2012-07-01 false Security Zone; Calvert Cliffs Nuclear Power Plant, Chesapeake Bay, Calvert County, Maryland...District § 165.505 Security Zone; Calvert Cliffs Nuclear Power Plant, Chesapeake Bay, Calvert County,...

2012-07-01

20

From Bluff to Backwater  

USGS Multimedia Gallery

This is an aerial view of Pool 7 of the Mississippi River south of Trempealeau, WI. This photo highlights the different habitats for plants and wildlife from the bluffs that parallel the river to its quiet backwaters. Balanced with that is the fact that the Mississippi River is a commercial highway ...

2010-08-18

21

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

22

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

23

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

Federal Register 2010, 2011, 2012, 2013

...50-317 and 50-318; NRC-2010-0337] Calvert Cliffs Nuclear Power Plant, LLC; Calvert Cliffs Nuclear Power Plant, Unit Nos. 1 and...the Commission) has granted the request of Calvert Cliffs Nuclear Power Plant, LLC, the...

2010-10-29

24

Ignition of bluff-body methane flames  

E-print Network

The movies show the ignition process following a spark in a bluff-body stabilised methane non-premixed flame. The flow is described in: S.F. Ahmed, R. Balachandran, T. Marchione, E. Mastorakos, Spark ignition of turbulent nonpremixed bluff...

Ahmed, Samer F; Marchione, Teresa; Balachandran, R; Mastorakos, Epaminondas; Triantafyllidis, A

2009-05-21

25

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

Federal Register 2010, 2011, 2012, 2013

...License Renewal for Calvert Cliffs Nuclear Power Plant, LLC's AGENCY: Nuclear...ISFSI) at the Calvert Cliffs Nuclear Power Plant site near Lusby, Maryland...September 17, 2010, Calvert Cliffs Nuclear Power Plant, LLC (CCNPP)...

2012-06-08

26

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

Federal Register 2010, 2011, 2012, 2013

...Release No. 29209; File No. 812-13718] Calvert Social Investment Fund, et al.; Notice...certain financial instruments. Applicants: Calvert Social Investment Fund (the ``Trust''), Calvert Asset Management Company, Inc....

2010-04-23

27

UNLV University Libraries Lance & Elena Calvert Undergraduate Research Award Scoring Rubric Essay (20 pts)  

E-print Network

UNLV University Libraries Lance & Elena Calvert Undergraduate Research Award Scoring Rubric 1 for evaluating #12;UNLV University Libraries Lance & Elena Calvert Undergraduate Research Award Scoring Rubric 2

Hemmers, Oliver

28

Aerodynamics of two-dimensional slotted bluff bodies  

SciTech Connect

Aerodynamic characteristics of two-dimensional, slotted bluff bodies were experimentally investigated. Flow visualizations, base pressure measurements, mean velocity vector measurements, and drag force measurements were conducted to analyze effects of spacing ratio (i.e., porosity), curvature, and vent. Low porosity model configurations produced stable near-wake patterns with enhanced vortex sheddings of overall wake formations. Model curvature reduced drag forces and weakened the vortex sheddings. Stabilizing effect of curvature on the near-wake patterns was also found. A vent combined with large model curvature was found to control drag force effectively, as well as suppressing vortex sheddings. 10 refs., 52 figs., 1 tab.

Takahashi, F.; Higuchi, H.

1988-04-30

29

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

USGS Publications Warehouse

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

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

1995-01-01

30

The recirculation dynamics of bluff body stabilized premixed combustion  

Microsoft Academic Search

Bluff body stabilized premixed combustion is present in many power generation and propulsion systems such as gas turbines and afterburners. In this environment, flow recirculation behind the bluff body provides low speed, hot products that act as an ignition source for the incoming reactants and help anchor the flame. Beyond this coarse phenomenological description, however, understanding of bluff body flame

Marios Soteriou

2005-01-01

31

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

32

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

Federal Register 2010, 2011, 2012, 2013

...CERCLA-04-2013-3751] LWD, Inc. Superfund Site; Calvert City, Marshall County, Kentucky; Notice of Settlement AGENCY: Environmental...the LWD, Inc., Superfund Site located in Calvert City, Marshall County, Kentucky. The settlement addresses costs from a...

2013-04-19

33

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

Federal Register 2010, 2011, 2012, 2013

...NRC-2011-0085] Calvert Cliffs Nuclear Power Plant, LLC Independent Spent Fuel...March 9, 2011, Calvert Cliffs Nuclear Power Plant (CCNPP), LLC, for the renewal of its Special Nuclear Material (SNM) License...

2011-04-25

34

75 FR 31835 - Environmental Impact Statement: Calvert and St. Mary's Counties, MD  

Federal Register 2010, 2011, 2012, 2013

...Administration Environmental Impact Statement: Calvert and St. Mary's Counties, MD AGENCY...widening and bridge replacement project in Calvert and St. Mary's Counties, Maryland...replacement of MD 4 from MD 2 to MD 235 in Calvert and St. Mary's Counties, a...

2010-06-04

35

Vortex phase-jitter in acoustically excited bluff body flames  

E-print Network

excitation on bluff body stabilized flames, specifically on the flow field characteristics. The Kelvin", manifested as cycle-to-cycle variation in flame and vorticity field at the same excitation phase. PhaseVortex phase-jitter in acoustically excited bluff body flames Santosh J. Shanbhogue, Michael

Lieuwen, Timothy C.

36

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

37

Site Visit to Calvert County, Maryland ARC Family Support Services.  

ERIC Educational Resources Information Center

The site visit report describes the Family Support Services program run by the Calvert County (Maryland) Association for Retarded Citizens. The program's goal is to prevent any person 21 years of age or younger from being institutionalized. It provides respite care services, specialized family support, and integrated day care for approximately 50…

Bersani, Hank A., Jr.

38

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

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

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

39

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

Federal Register 2010, 2011, 2012, 2013

...hour controls after the recovery period. Section 26...accommodations for restorative sleep. Calvert Cliffs is located...more of snow. 3.2 Recovery Exemption Immediately...conditions may require a recovery period. Also, high...period of restorative sleep for personnel. The...

2012-08-07

40

AOTV bluff body flow - Relaxation algorithm  

NASA Technical Reports Server (NTRS)

Preliminary investigations have led to the consideration of two classes of energy efficient aeroassisted orbital transfer vehicle (AOTV) concepts, with high and low L/D. The AOTV represent reentry space vehicles which are to fly hypersonically in the continuum upper reaches of the atmosphere. Problems arise in connection with convective and nonequilibrium radiative heating. As the possibilities for obtaining needed information by experimentation are limited, reliance must be placed on computational techniques to simulate testing of design concepts. A new relaxation algorithm for the compressible Navier-Stokes equations has been developed in the context of recent work with a conservative flux difference eigenvector split implicit upwind scheme CSCM (conservative supracharacteristics method). Attention is given to the CSCM implicit method, and early results for axisymmetric bluff body flow including complete forebody and base flow for a free flight range model drag brake AOTV.

Lombard, C. K.; Bardina, J.; Venkatapathy, E.

1985-01-01

41

Scotts Bluff: Shared Heritage Travel Itinerary  

NSDL National Science Digital Library

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

42

Conversations with Rep. Ken Calvert. Interview by Frank Sietzen Jr.  

PubMed

Rep. Calvert, chair of the House aeronautics and space subcommittee of the Science Committee, answers questions related to priorities for space in the current congressional session: the Vision for Space Exploration, development of the Crew Exploration Vehicle (CEV) and other heavy-lift launch vehicles, entrepreneurial alliances in the space transportation industry, the U.S. aerospace industry, space tourism, entrepreneurs and NASA, U.S. aeronautics research, a service mission to the Hubble Space Telescope, and priority military space programs. PMID:16044613

Calvert, Ken

2005-07-01

43

76 FR 12726 - DTE Calvert City, LLC; Supplemental Notice that Initial Market-Based Rate Filing Includes Request...  

Federal Register 2010, 2011, 2012, 2013

...Regulatory Commission [Docket No. ER11-2954-000] DTE Calvert City, LLC; Supplemental Notice that Initial Market- Based...supplemental notice in the above-referenced proceeding of DTE Calvert City, LLC's application for market-based rate...

2011-03-08

44

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

45

77 FR 10784 - Calvert Cliffs Nuclear Power Plant, LLC; Notice of Withdrawal of Application for Amendment to...  

Federal Register 2010, 2011, 2012, 2013

...50-317 and 50-318; NRC-2012-0045] Calvert Cliffs Nuclear Power Plant, LLC; Notice...Commission) has granted the request of Calvert Cliffs Nuclear Power Plant, LLC, the...License Nos. DPR-53 and DPR-69 for the Calvert Cliffs Nuclear Plant, Units 1 and...

2012-02-23

46

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

Federal Register 2010, 2011, 2012, 2013

...DOCKET NO. 52-016; NRC-2008-0250] Calvert Cliffs 3 Nuclear Project, LLC and Unistar...for the Combined License Application for Calvert Cliffs Nuclear Power Plant Unit 3 Notice...statement (EIS), NUREG- 1936, for the Calvert Cliffs Nuclear Power Plant...

2011-05-20

47

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

NASA Technical Reports Server (NTRS)

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

Chapman, R. S.

1977-01-01

48

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

of the Queen Formation is confined to the thick upper siliciclastic package. The lower half of the Queen Formation begins at the top of the first anhydrite beds, and ends at the base of the third siliciclastic bed (Fig. 5). The two siliciclastic members... of the Queen Formation is confined to the thick upper siliciclastic package. The lower half of the Queen Formation begins at the top of the first anhydrite beds, and ends at the base of the third siliciclastic bed (Fig. 5). The two siliciclastic members...

Harper, James Broox

2012-06-07

49

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

E-print Network

Field Course, or equivalent Rock I.D. flow charts Rock test kits (hardness test, acid test, grain size by the abundance of fossils, response to acid test, and hardness. 2. Show student different rock samples & pictures.e. acid test, silt size, hardness test). For example, show the difference between limestone and calk

Frank, Tracy D.

50

Disposal of chemical agents and munitions stored at Pine Bluff Arsenal, Pine Bluff, Arkansas  

SciTech Connect

The Pine Bluff Arsenal (PBA) near Pine Bluff, Arkansas, is one of eight continental United States (CONUS) Army installations where lethal unitary chemical agents and munitions are stored and where destruction of agents and munitions is proposed under the Chemical Stockpile Disposal Program (CSDP). The chemical agent inventory at PBA consists of approximately 12%, by weight, of the total US stockpile. The destruction of the stockpile is necessary to eliminate the risk to the public from continued storage and to dispose of obsolete and leaking munitions. In 1988 the US Army issued a Final Programmatic Environmental Impact Statement (FPEIS) for the CSDP that identified on-site disposal of agents and munitions as the environmentally preferred alternative (i.e., the alternative with the least potential to cause significant adverse impacts). The purpose of this report is to examine the proposed implementation of on-site disposal at PBA in light of more recent and more detailed data than those on which the FPEIS is based. New population data were used to compute fatalities using the same computation methods and values for all other parameters as in the FPEIS. Results indicate that all alternatives are indistinguishable when the potential health impacts to the PBA community are considered. However, risks from on-site disposal are in all cases equal to or less than risks from other alternatives. Furthermore, no unique resources with the potential to prevent or delay implementation of on-site disposal at PBA have been identified.

Ensminger, J.T.; Hillsman, E.L.; Johnson, R.D.; Morrisey, J.A.; Staub, W.P.; Boston, C.R.; Hunsaker, D.B.; Leibsch, E.; Rickert, L.W.; Tolbert, V.R.; Zimmerman, G.P.

1991-09-01

51

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

NASA Astrophysics Data System (ADS)

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

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

1993-12-01

52

Late Paleocene paleoenvironmental gradients in Wilcox Group strata, Big Brown Mine, Texas  

E-print Network

Wilcox Calvert Bluff Formation in and near the Texas Utilities' Big Brown Mine confirm that significant marine influence was present at the time of deposition. Most fine-grained sediments contain flaser, rippled, and laminated bedding, and palynological...

Klein, Jennifer Marie

2012-06-07

53

Bluff recession rates along the Lake Michigan shoreline in Illinois  

USGS Publications Warehouse

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

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

1992-01-01

54

Pressure field around three-dimensional bluff bodies  

Microsoft Academic Search

The pressure field on the ground plane around three-dimensional bluff bodies with varying relative dimensions has been obtained experimentally. The pressure measurements along the plane of symmetry are presented for the cases when the bodies are exposed to a uniform approach flow (without the presence of a horse-shoe vortex) and when the bodies are kept in a boundary layer. The

B. H. L. Gowda; H. J. Gerhardt; C. Kramer

1985-01-01

55

Measurements of aerodynamic forces on unsteadily moving bluff parachute canopies  

Microsoft Academic Search

Equations which describe the unsteady motion of bluff bodies through fluids contain certain components, termed added mass coefficients, which can only be determined by experiment. From the solutions to such equations the ways in which the shapes of parachute canopies influence the frequency of their oscillatory motion in pitch and their corresponding damping rates are required. Although a full-scale parachute

D. J. Cockrell; R. J. Harwood; C. Q. Shen

1987-01-01

56

Review of TRAC calculations for Calvert Cliffs PTS study  

SciTech Connect

Six selected transient calculations out of thirteen performed by LANL using the TRAC-PF1 code for the USNRC PTS study of the Calvert Cliffs Nuclear Power Plant have been reviewed in depth at BNL. Simple hand calculations based on the mass and energy balances have been performed to predict the temperature and pressure of the reactor system, and the results have been compared with those of TRAC. Comparison was also made between the TRAC and RETRAN calculations for two of these transients, which were performed by ENSA. In general, the results calculated by TRAC appear to be reasonable based on the comparison with RETRAN and hand calculations. 2 refs., 33 figs., 9 tabs.

Jo, J.H.; Rohatgi, U.S.

1985-04-01

57

Measurements of aerodynamic forces on unsteadily moving bluff parachute canopies  

NASA Astrophysics Data System (ADS)

Equations which describe the unsteady motion of bluff bodies through fluids contain certain components, termed added mass coefficients, which can only be determined by experiment. From the solutions to such equations the ways in which the shapes of parachute canopies influence the frequency of their oscillatory motion in pitch and their corresponding damping rates are required. Although a full-scale parachute canopy descends through air, oscillating in pitch as it does, experiments necessary to determine these added mass coefficients have been performed under water, using for this purpose a large ship tank from the towing carriage of which the model parachute canopies were suspended. These experiments showed that the added mass coefficients for bluff parachute canopies differed appreciably from their corresponding potential flow values. The latter were obtained from the analysis of inviscid, fluid flow around regular shapes which were representative of those parachute canopies. The significance for the prediction of the parachute's dynamic behavior in pitch is outlined.

Cockrell, D. J.; Harwood, R. J.; Shen, C. Q.

1987-06-01

58

Woody-Plant Succession in an Eastern Nebraska Bluff Forest  

Microsoft Academic Search

Woody plant composition of ridgetop old-fields abandoned at various times since 1800 suggest a successional pattern for an eastern Nebraska bluff forest. Sites abandoned for 24 years were dominated by elm (Ulmus spp.) and rough-leaved dogwood (Comus drummondii). Other sites, abandoned for76 years, were dominated by bitternut hickory (Cwya cordijormis), American linden (Tilia americana), and hop-hombeam (Ostrya virginiana), and those

Douglas E. Borland; Thomas B. Bragg; David M. Sutherland

1989-01-01

59

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

E-print Network

. At the locality studied (NE NW NW Sec. 22, T. 12 S, R. 18 S.; 13 km west of Lawrence, Kan- sas, on Interstate 70) the Rock Bluff Limestone is approximately 0.5 meters thick. It is massive, light gray to light bluish gray, and contains numerous vertical joints. A.... , 1967b, Isopod and limulid marks and trails in Tonganoxie Sandstone (Upper Pennsylvanian) of Kan- sas: Univ. Kansas Paleont. Contrib., Paper 19, 10 p. Billings, Elkanah, 1858, On the Asteridac of the Lower Silurian rocks of Canada: Geol. Survey Canada...

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

1976-01-15

60

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

E-print Network

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

Wesfreid, José Eduardo

61

Processes of coastal bluff erosion in weakly lithified sands, Pacifica, California, USA  

Microsoft Academic Search

Coastal bluff erosion and landsliding are currently the major geomorphic processes sculpting much of the marine terrace dominated coastline of northern California. In this study, we identify the spatial and temporal processes responsible for erosion and landsliding in an area of weakly lithified sand coastal bluffs located south of San Francisco, California. Using the results of a five year observational

Brian D. Collins; Nicholas Sitar

2008-01-01

62

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

63

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

64

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

65

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

66

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.

67

Piezoelectric energy harvesting from transverse galloping of bluff bodies  

NASA Astrophysics Data System (ADS)

The concept of harvesting energy from transverse galloping oscillations of a bluff body with different cross-section geometries is investigated. The energy is harvested by attaching a piezoelectric transducer to the transverse degree of freedom of the body. The power levels that can be generated from these vibrations and the variations of these levels with the load resistance, cross-section geometry, and freestream velocity are determined. A representative model that accounts for the transverse displacement of the bluff body and harvested voltage is presented. The quasi-steady approximation is used to model the aerodynamic loads. A linear analysis is performed to determine the effects of the electrical load resistance and the cross-section geometry on the onset of galloping, which is due to a Hopf bifurcation. The normal form of this bifurcation is derived to determine the type (supercritical or subcritical) of the instability and to characterize the effects of the linear and nonlinear parameters on the level of harvested power near the bifurcation. The results show that the electrical load resistance and the cross-section geometry affect the onset speed of galloping. The results also show that the maximum levels of harvested power are accompanied with minimum transverse displacement amplitudes for all considered (square, D, and triangular) cross-section geometries, which points to the need for performing a coupled analysis of the system.

Abdelkefi, A.; Hajj, M. R.; Nayfeh, A. H.

2013-01-01

68

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

USGS Publications Warehouse

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

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

1988-01-01

69

Blowoff dynamics of bluff body stabilized turbulent premixed flames  

SciTech Connect

This article concerns the flame dynamics of a bluff body stabilized turbulent premixed flame as it approaches lean blowoff. Time resolved chemiluminescence imaging along with simultaneous particle image velocimetry and OH planar laser-induced fluorescence were utilized in an axisymmetric bluff body stabilized, propane-air flame to determine the sequence of events leading to blowoff and provide a quantitative analysis of the experimental results. It was found that as lean blowoff is approached by reduction of equivalence ratio, flame speed decreases and the flame shape progressively changes from a conical to a columnar shape. For a stably burning conical flame away from blowoff, the flame front envelopes the shear layer vortices. Near blowoff, the columnar flame front and shear layer vortices overlap to induce high local stretch rates that exceed the extinction stretch rates instantaneously and in the mean, resulting in local flame extinction along the shear layers. Following shear layer extinction, fresh reactants can pass through the shear layers to react within the recirculation zone with all other parts of the flame extinguished. This flame kernel within the recirculation zone may survive for a few milliseconds and can reignite the shear layers such that the entire flame is reestablished for a short period. This extinction and reignition event can happen several times before final blowoff which occurs when the flame kernel fails to reignite the shear layers and ultimately leads to total flame extinguishment. (author)

Chaudhuri, Swetaprovo; Kostka, Stanislav; Renfro, Michael W.; Cetegen, Baki M. [Department of Mechanical Engineering, University of Connecticut, 191 Auditorium Road, U-3139, Storrs, CT 06269 (United States)

2010-04-15

70

Assessment of the safety implications of control at the Calvert Cliffs-1 Nuclear Plant. Volume 1  

Microsoft Academic Search

This study examined the consequences of possible control system malfunctions at the Calvert Cliffs-1 Nuclear Power Plant as technical support for an NRC program to assess the safety implications of nuclear power plant control systems. Plant systems capable of initiating plant overcooling and undercooling were identified, as well as those with potential for overfill events in the steam generators. The

P. N. Austin; S. J. Ball; R. E. Battle; S. J. Caruthers; N. E. Jr. Clapp; F. H. Clark; R. D. Dabbs; J. D. Freels; E. W. Hagen; K. M. Henry

1986-01-01

71

Disposal of chemical agents and munitions stored at Pine Bluff Arsenal, Pine Bluff, Arkansas. Final phase 1, Environmental report  

SciTech Connect

The Pine Bluff Arsenal (PBA) near Pine Bluff, Arkansas, is one of eight continental United States (CONUS) Army installations where lethal unitary chemical agents and munitions are stored and where destruction of agents and munitions is proposed under the Chemical Stockpile Disposal Program (CSDP). The chemical agent inventory at PBA consists of approximately 12%, by weight, of the total US stockpile. The destruction of the stockpile is necessary to eliminate the risk to the public from continued storage and to dispose of obsolete and leaking munitions. In 1988 the US Army issued a Final Programmatic Environmental Impact Statement (FPEIS) for the CSDP that identified on-site disposal of agents and munitions as the environmentally preferred alternative (i.e., the alternative with the least potential to cause significant adverse impacts). The purpose of this report is to examine the proposed implementation of on-site disposal at PBA in light of more recent and more detailed data than those on which the FPEIS is based. New population data were used to compute fatalities using the same computation methods and values for all other parameters as in the FPEIS. Results indicate that all alternatives are indistinguishable when the potential health impacts to the PBA community are considered. However, risks from on-site disposal are in all cases equal to or less than risks from other alternatives. Furthermore, no unique resources with the potential to prevent or delay implementation of on-site disposal at PBA have been identified.

Ensminger, J.T.; Hillsman, E.L.; Johnson, R.D.; Morrisey, J.A.; Staub, W.P.; Boston, C.R.; Hunsaker, D.B.; Leibsch, E.; Rickert, L.W.; Tolbert, V.R.; Zimmerman, G.P.

1991-09-01

72

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

E-print Network

, and its maximum storage capacity adjusted to sediment accumulation is estimated at 357 million m 3 (289,600 acre-ft.). Aside from the shortage of water entering the reservoir, high salinity has been a concern. This report was prepared with three main...-96 Red Bluff Reservoir above Dam Outflow EPA-TWC 13267 1972-96 Salt Creek near Reservoir Salt Creek EPA-TWC 13171 1989 1989 Red Bluff Reservoir 1/2 mile South of TX-NM border Inlet CRP-IBWC b 13269 1994-02 1994-02 Red Bluff Reservoir above Dam...

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

73

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

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  

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

75

Processes of coastal bluff erosion in weakly lithified sands, Pacifica, California, USA  

USGS Publications Warehouse

Coastal bluff erosion and landsliding are currently the major geomorphic processes sculpting much of the marine terrace dominated coastline of northern California. In this study, we identify the spatial and temporal processes responsible for erosion and landsliding in an area of weakly lithified sand coastal bluffs located south of San Francisco, California. Using the results of a five year observational study consisting of site visits, terrestrial lidar scanning, and development of empirical failure indices, we identify the lithologic and process controls that determine the failure mechanism and mode for coastal bluff retreat in this region and present concise descriptions of each process. Bluffs composed of weakly cemented sands (unconfined compressive strength - UCS between 5 and 30??kPa) fail principally due to oversteepening by wave action with maximum slope inclinations on the order of 65 at incipient failure. Periods of significant wave action were identified on the basis of an empirical wave run-up equation, predicting failure when wave run-up exceeds the seasonal average value and the bluff toe elevation. The empirical relationship was verified through recorded observations of failures. Bluffs composed of moderately cemented sands (UCS up to 400??kPa) fail due to precipitation-induced groundwater seepage, which leads to tensile strength reduction and fracture. An empirical rainfall threshold was also developed to predict failure on the basis of a 48-hour cumulative precipitation index but was found to be dependent on a time delay in groundwater seepage in some cases.

Collins, B. D.; Sitar, N.

2008-01-01

76

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

77

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

78

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

79

Late Wisconsinan sub-glacial clastic intrusive sheets along Lake Erie bluffs, at Bradtville, Ontario, Canada  

NASA Astrophysics Data System (ADS)

Numerous clastic intrusive sheets, a few decimetres to more than 16 m long, 1-120 cm thick, and extending one to more than 25 m laterally, occur along a 350 m long section of the late Wisconsinan Catfish Creek Drift in the Lake Erie bluffs at Bradtville, southwestern Ontario. Most of them are downglacier-dipping dikes, the largest one terminating in the underlying middle Wisconsinan Tyrconnell Formation. Most dikes strike NNE-SSW, at right angles to the local direction of glacier movement during the deposition of Catfish Creek Drift. The tops of some of them are truncated or displaced downglacier by shearing. The main concentration of clastic intrusive sheets is on the upglacier side of a glaciotectonically folded anticline of Tyrconnell Formation clays and silts underlying the Catfish Creek Drift. The host sediments are Catfish Creek till, gravel, sand and silt, and Tyrconnell Formation silt and clay. Most intrusive sheets, particularly the small to medium ones, consist of massive to crudely laminated sand and silt, intruded from below by a dewatering process. The largest dike reflects in its composition mainly the adjoining or higher-lying host-sediment materials, and its main part was formed by downward infilling, or by gravity flows into an open fracture. The large dike is flanked by small laminated silty sand sheets and several small apophyses, some of them injected downward and sideways, others upward by dewatering. The clastic intrusive sheets were formed under a moving glacier, the Erie lobe, probably both at the beginning and towards the end of the deposition of Catfish Creek till. Their location and position was predetermined by glaciotectonically induced listric planar structures and zones of weakness, mainly tension fractures, that strike transverse to glacier movement and dip downglacier and also by confinement of pore-water in a permeable sediment wedge between the less pervious Tyrconnell Formation and massive Catfish Creek basal till.

Dreimanis, Aleksis; Rappol, Martin

1997-07-01

80

Suppression of combustion instability by geometrical design of the bluff-body stabilizer  

SciTech Connect

Passive control methods were used to suppress combustion instability in a combustor with a bluff-body stabilizer. The instabilities in this combustor are excited by interaction between vortices shed downstream of the stabilizer and the combustion chamber acoustic modes. The passive control methodology was to change the geometrical design of the stabilizer in a manner that will disrupt the formation or reduce the coherence of the wake vortices, thus eliminating the source of the instability excitation. Two geometrical designs were tested and compared to the regular baseline disk stabilizer. The first was a corrugated stabilizer that promotes the shedding of longitudinal vortices from the stabilizer`s base. These vortices induce azimuthal instability in the axisymmetric wake vortices and accelerates their breakdown. The second configuration was a multistep cone that was shown to enhance the production of small-scale turbulence in the flow. Both methods were effective in the suppression of the pressure oscillations and reduced significantly the range of unstable combustion without adversely affecting the lean and rich flammability limits. The optimal configuration was the multistepped cone stabilizer. The orientation of the stabilizers and the effect of central ventilations were studied as well as the instability mode characteristics. 16 refs.

Gutmark, E.J.; Schadow, K.C.; Nina, M.N.R.; Pita, G.P.A. [Naval Air Warfare Cent, China Lake, CA (United States)

1995-05-01

81

Jackson Bluff Hydroelectric Project: Final operation and maintenance report  

SciTech Connect

The Jackson Bluff Hydroelectric Project is the first hydroelectric plant developed by the City of Tallahassee. The project is located on the Ochlockonee River approximately 66 miles upstream from its mouth at the Gulf of Mexico and approximately 20 miles west-southwest of the city of Tallahassee, Florida. The original hydroelectric generating facility with a total capacity of 8800 kw was retired in 1970. In the late seventies, the Department of Energy (DOE) classified the site as potential site for the Hydroelectric Demonstration Project. The City of Tallahassee submitted a proposal to DOE to reinstall generating equipment and operate the facility. The proposal was approved and after a feasibility study, the City was granted $1.75 million by DOE to meet approximately 15/percent/ of the total project cost. The existing powerhouse and intake serves to utilize three vertical-shaft turbines, two fixed blade and one adjustable blade propeller (Kaplan). The two fixed blade turbines drive a 4440 kw synchronous generator each and the adjustable blade propeller drives a 3438 kw synchronous generator. The plant design flow is 5200 cubic feet per second and the rated net head for the turbines is 32 feet. The runner diameters are 125.8 inches (fixed blade) and 104.7 inches (adjustable blade). In early 1983, with the proposal approved and the feasibility study completed, the City of Tallahassee took over the responsibility of the project. The rehabilitation work started in July 1983, and was completed in early 1986.

Hinton, J.; deMontmollin, F.

1988-03-01

82

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

83

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

84

Failure modes of thawing permafrost bluffs on the Chukchi Sea coast, Alaska  

NASA Astrophysics Data System (ADS)

Increasing Arctic temperatures from global climate change are well documented, however an understanding of their influences on specific geomorphic processes affecting arctic coastal bluff erosion are much less well understood. Coastal bluffs in natural settings typically erode through a suite of geomorphic processes including both marine (e.g. wave action) and terrestrial (e.g. groundwater seepage) forces. In arctic settings, thermal influences which affect both terrestrial and marine ice content also govern these processes and create additional inputs to instability and erosion. Here, we investigate the failure modes of coastal bluffs along a 10 km length of the Chukchi Sea in northwestern Alaska with the goal of identifying the predominant processes and their topographic signatures. We use high-resolution terrestrial lidar surveying, georeferenced simultaneously via geodetic-grade GPS measurements, to analyze cross-sections of the bluffs and compare these to observations of the predominant failure modes identified during recent field work. An effort is made to link the processes directly to the mapped stratigraphy of the bluffs. Our observations identify at least three different failure modes: (1) downward-driven spreads associated with thaw-slump activity in originally ice-bonded clay and sand, (2) topples of ice-wedge bounded, cantilevered ice-bonded peat and clay tundra blocks, and (3) retrogressive, steeply inclined translational ice-thawed sand landslides. All three failure modes are associated with warming air temperatures while the last two modes also appear to be initiated by thermal niching and/or wave action at the base of the bluff. Identification of the predominant failure modes along this coast will assist with further investigations aimed at predicting trends of both short- and long-term coastal erosion and their impact on local communities and wildlife habitats. Terrestrial lidar data collection of Arctic coastal bluff failure modes along the Chukchi Sea, Alaska

Collins, B. D.; Erikson, L. H.; Reiss, T.

2009-12-01

85

Godrap Girls, Draou Boys, and the Sexual Economy of the Bluff in Abidjan, Côte d'Ivoire  

Microsoft Academic Search

In Abidjan, both economic and sexual exchanges are structured around the bluff, a mimetic performance of modern urban identity that is both a form of deception and a means of social transformation. Men and women attempt to seduce each other through the bluff and exploit the relationship for material gain. While marriage is held up as an ideal, it is

Sasha Newell

2009-01-01

86

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

USGS Publications Warehouse

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

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

2009-01-01

87

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

88

UBC Social Ecological Economic Development Studies (SEEDS) Student Report Doug Mosher, Gabriel Patillo, Natassia Lynn, Travis Calvert  

E-print Network

will result in a diversion of nearly 31,340 tonnes of eCO2 annually, an increase in waste recycling activity Patillo, Natassia Lynn, Travis Calvert An Investigation into Waste Stream Tracking in the New SUB Building of a project/report". #12;An Investigation into Waste Stream Tracking in the New SUB Building Report Prepared

89

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

90

Factors Controlling Rates of Bluff Recession at Two Sites on Lake Michigan  

Microsoft Academic Search

Empirical relationships between recession rate of bluffs and precipitation, storm frequency, lake level, deep water wave power, and wave impact height are derived for two Lake Michigan shoreline reaches in Wisconsin. Recession rates are determined from digital orthophotos constructed using historical aerial photographs at least once every decade from the 1940s to present. The recession measurements represent spatial averages of

Elizabeth A. Brown; Chin H. Wu; David M. Mickelson; Tuncer B. Edil

2005-01-01

91

RESEARCH ARTICLE The use of plasma actuators for bluff body broadband  

E-print Network

the attention of communities that live near airports to the problem of noise pollution (Raman and Mc (Crighton 1991; Macaraeg 1998). Since airframe noise is normally caused by the interactions betweenRESEARCH ARTICLE The use of plasma actuators for bluff body broadband noise control Yong Li · Xin

Huang, Xun

92

CONTROL AND SUPPRESSION OF LAMINAR VORTEX SHEDDING OFF TWO-DIMENSIONAL BLUFF BODIES  

E-print Network

CONTROL AND SUPPRESSION OF LAMINAR VORTEX SHEDDING OFF TWO-DIMENSIONAL BLUFF BODIES A DISSERTATION #12;Abstract The focus of this research is on the control and suppression of vortex shedding of flow instabilities in the laminar shedding regime. Both bounded and unbounded flow conditions are examined

Stanford University

93

Comprehensive Housing Market Analysis: Omaha-Council Bluffs, Nebraska-Iowa As of December 1, 2013.  

National Technical Information Service (NTIS)

The Omaha-Council Bluffs Housing Market Area (HMA) is on the Nebraska-Iowa border, spanning the Missouri River. For purposes of this analysis, the HMA is divided into three submarkets: the Omaha submarket, comprising Douglas County, Nebraska; the Sarpy Co...

2013-01-01

94

Analyzing the vortex dynamics in bluff-body wakes by Helmholtz decomposition of the velocity field  

Microsoft Academic Search

The velocity field in the wake of a bluff body is calculated by a novel procedure for the Navier–Stokes equations in the vorticity–velocity formulation. The time evolution of the vorticity is solved as an ODE problem on each node of the spatial discretization, using at each step of the time discretization the spatial solution for the velocity field provided by

F. L. Ponta

2006-01-01

95

Analyzing the vortex dynamics in bluff-body wakes by Helmholtz decomposition of the velocity field  

Microsoft Academic Search

The velocity field in the wake of a bluff body is calculated by a novel procedure for the Navier-Stokes equations in the vorticity-velocity formulation. The time evolution of the vorticity is solved as an ODE problem on each node of the spatial discretization, using at each step of the time discretization the spatial solution for the velocity field provided by

F. L. Ponta

2006-01-01

96

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

NASA Astrophysics Data System (ADS)

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

Jardin, Thierry; Bury, Yannick

2014-06-01

97

78 FR 33121 - Staff Requirements-SECY-12-0168-Calvert Cliffs 3 Nuclear Project, LLC & UniStar Nuclear Operating...  

Federal Register 2010, 2011, 2012, 2013

...Services, LLC (Calvert Cliffs Nuclear Power Plant, Unit 3), Petition for...or domination of commercial nuclear power plants...domination (FOCD) of commercial nuclear power plants. The results and...

2013-06-03

98

Description of the larva of Argia chelata Calvert, 1902 (Odonata: Coenagrionidae).  

PubMed

The larva of Argia chelata is described and figured. It falls into the group of Argia larvae with a moderately prominent ligula and two palpal seta, but it differs from its closest relatives by having labial palp with 2 setae plus one basal setella; the length of the ligula is 30% of its maximum width; basal tergites (1-5) lacking long, fine setae, mainly on midline; S8-10 mostly dark brown; paraprocts with spiniform setae on basal 0.25 and 0.55 of dorsal and ventral borders, respectively. Larvae were found in 2nd to 4th order shallow streams in cloud forest, crawling among debris, fine sand and mud where the water flow is slow or still, close to the shoreline. The larva is compared with A. lacrimans (Hagen), A. pima Garrison, and A. tonto Calvert, species apparently closely related.  PMID:25113363

Novelo-Gutiérrez, Rodolfo

2013-01-01

99

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

100

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

SciTech Connect

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

101

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

102

Coccidioidomycosis in Northern California. An outbreak among archeology students near Red Bluff.  

PubMed

An outbreak of coccidioidomycosis occurred among 39 archeology students in the summer of 1972. The students excavated Indian ruins near Red Bluff in Tehama County, California, 20 miles north of the previously recognized northernmost limit of endemicity. At least 17 persons contracted an illness clinically compatible with a diagnosis of coccidioidomycosis. Coccidioidomycosis was documented by skin test conversion as well as by specific serologic reactions. Coccidioides immitis was also isolated from two soil samples taken at the excavation site. In light of its ecological requirements, it is doubtful that C. immitis will be recovered much farther north than Red Bluff. The occupational hazard of coccidioidomycosis to archeologists and others employed in known endemic areas remains a substantial threat to health. PMID:4733266

Werner, S B; Pappagianis, D

1973-09-01

103

Analysing fluid loadings on moving bluff bodies using proper orthogonal decomposition  

Microsoft Academic Search

Numerical simulations and experimental measurements of the fluid loadings on three typical fixed or moving bluff bodies are presented and analysed. The numerical approach is based on an efficient finite-element solver using an Arbitrary Lagrangian–Eulerian formulation for solving the two-dimensional incompressible Navier–Stokes equations with moving domains. Experimental tests consist of unsteady pressure measurements performed during sectional model tests. The Proper

X. Amandolèse; C. Crémona

2005-01-01

104

Low-Frequency Oscillation of a Non-Premixed Flame on a Bluff-Body Burner  

Microsoft Academic Search

The flickering characteristics of a non-premixed flame interacting with von Kármán vortex street on a bluff-body burner were investigated experimentally with varied velocities of the central fuel jet and annular air stream. Flow visualization in terms of a shadowgraph, planar laser-induced fluorescence of hydroxyl, and Mie scattering, which was obtained via PIV used to analyze the flow field, indicated that

Kuo-Long Pan; Chih-Chieh Li; Wen-Chi Juan; Jing-Tang Yang

2009-01-01

105

Simulation assessment of CO2 sequestration potential and enhanced methane recovery in low-rank coalbeds of the Wilcox Group, east-central Texas  

E-print Network

of low-rank coals of the Wilcox Group Lower Calvert Bluff (LCB) formation in east-central Texas are significant. Resources from LCB low-rank coals in the Wilcox Group in east-central Texas are estimated to be between 6.3 and 13.6 Tcf of methane, with a...

Hernandez Arciniegas, Gonzalo

2006-10-30

106

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

NASA Astrophysics Data System (ADS)

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

Vogt, P. R.; Parrish, M.

2009-12-01

107

Effect of nonharmonic forcing on bluff-body vortex dynamics.  

PubMed

Forced nonharmonic excitation of the two-dimensional flow about a circular cylinder is studied by numerical simulations at mean Reynolds numbers of 180 and 150. Moderate deviations of the forced inflow velocity waveform from a pure harmonic generate different modes of phase-locked vortex formation in the cylinder wake, involving combinations of single and/or pairs of vortices for the same forcing frequency and peak-to-peak amplitude. The dynamical response of the wake oscillator is studied by employing phase portraits of the drag and lift coefficients that display modified limit-cycle behavior due to nonharmonic excitation. It is further shown that changing solely the velocity waveform can incite transition from a quasiperiodic state to a phase-locked state. The findings demonstrate that the wake oscillator is admissible to an infinite number of phase-locked and/or modulated states characterized by a single point on the frequency-amplitude plane. PMID:19518288

Konstantinidis, E; Bouris, D

2009-04-01

108

Assessment of the safety implications of control at the Calvert Cliffs-1 Nuclear Plant. Volume 1  

SciTech Connect

This study examined the consequences of possible control system malfunctions at the Calvert Cliffs-1 Nuclear Power Plant as technical support for an NRC program to assess the safety implications of nuclear power plant control systems. Plant systems capable of initiating plant overcooling and undercooling were identified, as well as those with potential for overfill events in the steam generators. The first of the two major areas deals with the potential for steam generator overfill. Some postulated overfeed events require timely operator action, and if they are not terminated in time, the steam generator can overfill and inject liquid into the steam line. the second major sequence of interest is a critically sized small-break loss-of-coolant accident (SB-LOCA). An SB-LOCA can be initiated by control system malfunctions as well as by passive failure mechanisms such as steam generator tube ruptures. Our initial concern arose from the fact that the high-pressure safety injection (HPSI) system pumps can deliver coolant at a head of no more than 1275 psi, and that consequently there may be situations in which the primary coolant system pressure is high enough that the HPSI pumps cannot adequately make up for the net inventory loss, with the latter ultimately leading to core uncovery and fuel damage. Subsequent analyses indicated a very small probability of fuel damage for this scenario. 33 refs., 71 figs., 22 tabs.

Austin, P.N.; Ball, S.J.; Battle, R.E.; Caruthers, S.J.; Clapp, N.E. Jr.; Clark, F.H.; Dabbs, R.D.; Freels, J.D.; Hagen, E.W.; Henry, K.M.

1986-04-01

109

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

NASA Astrophysics Data System (ADS)

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

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

2001-11-01

110

Flow field behind a fixed bluff body in a vertical pipe simulating a wake of a Taylor bubble  

NASA Astrophysics Data System (ADS)

The hydrodynamic structure of the wake of an axisymmetric bluff body that simulates the shape of a moving elongated (Taylor) bubble in a vertical pipe was studied using Particle Image Velocimetry in laminar and turbulent background flows. The distribution of the mean axial and radial velocity components in the wake, as well as the spatial variation of the normal and shear stresses are presented and compared with the corresponding quantities in the wake of the gas bubble. The accumulated results enable estimates of the spatial variation of turbulent energy production term in the undeveloped separated flow in the wake of the bluff body.

Babin, V.; Barnea, D.; Shemer, L.

2013-10-01

111

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

Structure The Permian Basin of west Texas and southeastern New Mexico is a complex region of shelves, platforms, shelf margins, and basins that comprises an area of about 63, 000 miz (164, 000 kmz). The Permian Basin is bounded by four positive... Structure The Permian Basin of west Texas and southeastern New Mexico is a complex region of shelves, platforms, shelf margins, and basins that comprises an area of about 63, 000 miz (164, 000 kmz). The Permian Basin is bounded by four positive...

McKone, Charles Joseph

2012-06-07

112

Characteristics of the Axial and Tangential Velocities near a Rotating Bluff Body on a Platform  

NASA Astrophysics Data System (ADS)

Molecular Tagging Velocimetry (MTV) has been employed to obtain instantaneous axial and tangential velocity profiles at different vertical positions near a rotating bluff body on a platform. Measurements were made over a Reynolds number range from 4000 to 40000 based upon the characteristic body dimension and at angular accelerations varying two orders of magnitude. The evolution of the velocity profiles and flow statistics provide insights into the nature of the evolving flow field and the effect of acceleration on the global and local flow features. Our data show that the magnitude of the tangential velocity is largely independent of vertical position, is proportional to the instantaneous rotation rate and reaches a maximum value after acceleration has ceased. The magnitude of the axial velocity reaches a maximum at a fixed number of revolutions regardless of the acceleration rate and it is not proportional to the instantaneous rotation rate. Additionally, the axial velocity is in the direction of the platform for all Re and acceleration rates. These observed behavior along with previous data support a description of the evolving flow field around a rotating bluff body from start-up to steady state.

Maynes, Daniel; Robey, Harry; Klewicki, Joseph; McMurtry, Patrick

1997-11-01

113

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

USGS Publications Warehouse

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

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

1982-01-01

114

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.

115

Experiments to investigate direct containment heating phenomena with scaled models of the Calvert Cliffs Nuclear Power Plant  

SciTech Connect

The Surtsey Test Facility is used to perform scaled experiments simulating High Pressure Melt Ejection accidents in a nuclear power plant (NPP). The experiments investigate the effects of direct containment heating (DCH) on the containment load. The results from Zion and Surry experiments can be extrapolated to other Westinghouse plants, but predicted containment loads cannot be generalized to all Combustion Engineering (CE) plants. Five CE plants have melt dispersal flow paths which circumvent the main mitigation of containment compartmentalization in most Westinghouse PWRs. Calvert Cliff-like plant geometries and the impact of codispersed water were addressed as part of the DCH issue resolution. Integral effects tests were performed with a scale model of the Calvert Cliffs NPP inside the Surtsey test vessel. The experiments investigated the effects of codispersal of water, steam, and molten core stimulant materials on DCH loads under prototypic accident conditions and plant configurations. The results indicated that large amounts of coejected water reduced the DCH load by a small amount. Large amounts of debris were dispersed from the cavity to the upper dome (via the annular gap). 22 refs., 84 figs., 30 tabs.

Blanchat, T.K.; Pilch, M.M.; Allen, M.D.

1997-02-01

116

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

117

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

118

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 kΩ 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

119

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

USGS Publications Warehouse

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

Shideler, G.L.

1994-01-01

120

A New Species of Pinus Subgenus Pinus Subsection Contortae from Pliocene Sediments of Ch'ijee's Bluff, Yukon Territory, Canada  

Microsoft Academic Search

Three structurally preserved conifer ovulate cones are described from Pliocene sediments at Ch'ijee's Bluff on the Porcupine River, near Old Crow, Yukon Territory, Canada. Cones are ovoid to conical, symmetrical, 3.4-4.4 cm long and 2.8-3.4 cm wide, with helically arranged cone-scale complexes. Ovuliferous scales are thin at the base, expanded at the apex, 2 cm long and 1 cm wide,

Athena D. McKown; Ruth A. Stockey; Charles E. Schweger

2002-01-01

121

Terrestrial LIDAR investigation of the December 2003 and January 2007 activations of the Northridge Bluff landslide, Daly City, California  

USGS Publications Warehouse

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

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

2007-01-01

122

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

123

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

124

Ballography: A Billion Nanosecond History of the Bee Bluff Impact Crater of South Texas  

NASA Astrophysics Data System (ADS)

The Bee Bluff Structure of South Texas in Zavala County near Uvalde has been found to exhibit unusual features permitting study of impactites and meteorite impact processes from the standpoint of grain-level, nanosecond shock-compression science. The site is characterized by a thin cap of Carrizo Sandstone covering a thin hard Indio fm calcareous siltstone. A soft calcareous silt lies below the hard cap. Calculations based on the Earth Impact Effects web-based program indicate that the site is best described by a 60 m diameter iron meteorite striking the ground at 11 km/sec. Such an impact into sandstone is expected to produce a shock pressure of 250 GPa. A large release wave originates from the bottom of the hard target with upward moving melt-vaporization waves of solid, liquid and vapor products that become trapped at the impact interface. Numerous distinctive types of impactites result from this `bottom-up' release behavior. Evidence for hydrodynamic instabilities and resulting density gradients are abundant at the impact interface. An unusually valuable breccia sample called `The Uvalde Crater Rosetta Stone' contains at least seven types of impactites in a well defined arrangement that can be used to read the billion nanosecond history of the impact and identify scattered impactites relative to their place in that history.

Graham, R. A.

2006-07-01

125

Comparative study of micromixing models in transported scalar PDF simulations of turbulent nonpremixed bluff body flames  

SciTech Connect

Numerical simulation results are presented for turbulent jet diffusion flames with various levels of turbulence-chemistry interaction, stabilized behind a bluff body (Sydney Flames HM1-3). Interaction between turbulence and combustion is modeled with the transported joint-scalar PDF approach. The mass density function transport equation is solved in a Lagrangian manner. A second-moment-closure turbulence model is applied to obtain accurate mean flow and turbulent mixing fields. The behavior of two micromixing models is discussed: the Euclidean minimum spanning tree model and the modified Curl coalescence dispersion model. The impact of the micromixing model choice on the results in physical space is small, although some influence becomes visible as the amount of local extinction increases. Scatter plots and profiles of conditional means and variances of thermochemical quantities, conditioned on the mixture fraction, are discussed both within and downstream of the recirculation region. A distinction is made between local extinction and incomplete combustion, based on the CO species mass fraction. The differences in qualitative behavior between the micromixing models are explained and quantitative comparison to experimental data is made. (author)

Merci, Bart [Department of Flow, Heat and Combustion Mechanics, Ghent University-UGent, Ghent (Belgium); Roekaerts, Dirk [Department of Multi-Scale Physics, Delft University of Technology, Delft (Netherlands); Naud, Bertrand [CIEMAT, Madrid (Spain); Pope, Stephen B. [Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY (United States)

2006-07-15

126

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

SciTech Connect

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 elements in several structural-stratigraphic traps. However, most of the traps are controlled primarily by an updip facies change from porous, permeable sandstone to siltstone and shale. Most of the oil production is from the J/sub I/ Member, whose commercial production limits coincide with porous sandstone bodies at least 5 ft thick. Three fields have produced over 1,000,000 BO each. The J/sub I/ was deposited in elongate, elliptical, northwest-trending marine bars that are rhythmically separated by laterally equivalent shales. The central-bar facies, which includes most of the reservoir rock, grades into bioturbated bar-margin siltstones which, in turn, grade into interbar shales. Long-distance lateral petroleum migration probably occurred from thermally mature shales of the Dakota and Benton groups near the basin axis into the shallow reservoirs of the trend. Subsurface mapping indicates that recurrent movement along Precambrian basement faults has enhanced reservoir quality and localized oil migration, favoring oil accumulation along the trend. The trend is part of an extensive system of northeast-trending structural features along which movement has recurred. Recognition of the trend's characteristics will reduce exploration risk and help realize the area's considerable economic potential.

Silverman, M.R.

1988-07-01

127

Unsteady Euler/Lagrange simulation of a confined bluff-body gas-solid turbulent flow  

NASA Astrophysics Data System (ADS)

An unsteady Euler-Lagrangian approach is adopted to predict the gaseous carrier and disperse phases flow dynamics. The turbulence is captured using two different methods, i.e. the unsteady Reynolds averaging based numerical simulation (URANS) and the large eddy simulation (LES). In the latter one, the dynamic Smagorinsky approach is used to model the sub-grid scale stresses. The time-dependent solid particle and gas phase flow properties of a confined bluff-body turbulent flow including two-way coupling effects are evaluated through comparisons with experimental data. The configuration under study features an important recirculation zone and has a mass loading of 22%. So, collision effects are not considered while tracking the disperse phase that consists of glass beads. A thermodynamically consistent turbulence modulation approach is applied for the determination of the source terms that account for the effect of particles on the turbulence level of the carrier phase. Within the URANS technique the dispersion of particles is captured by the Markov sequence approach; this model is modified by integrating a drift factor term while modeling the pressure gradient. A particular emphasis is put on the disperse phase feedback on the carrier phase and coupling procedure within each Eulerian time step along with an unsteady coupling of both codes, the (Eulerian) FASTEST3D and the (Lagrangian) LAG3D codes. Quantitative results of the disperse phase properties as well as those of the carrier phase are presented at different positions around the recirculation zone. The numerical results using both, the LES and/or the URANS delivered comparable results that agree reasonably with experimental data. However, a slight advantage of LES over URANS could be observed.

Chrigui, Mouldi; Hidouri, Ammar; Sadiki, Amsini; Janicka, Johannes

2013-10-01

128

Review of thermal-hydraulic calculations for Calvert Cliffs and H. B. Robinson PTS study. [Pressurized thermal shock  

SciTech Connect

Thermal-hydraulic transient calculations performed by LANL using the TRAC-PF1 code and by INEL using the RELAP5 code for the USNRC pressurized thermal shock (PTS) study of the Calvert Cliffs and H.B. Robinson Nuclear Power Plants have been reviewed at BNL including the input decks and steady state calculations. Furthermore, six transients for each plant have been selected for the in-depth review. Simple hand calculations based on the mass and energy balances of the entire reactor system, have been performed to predict the temperature and pressure of the reactor system, and the results have been compared with those obtained by the code calculation. In general, the temperatures and pressures of the primary system calculated by the codes have been very reasonable. The secondary pressures calculated by TRAC appear to indicate that the codes have some difficulty with the condensation model and further work is needed to assess the code calculation of the U-tube steam generator pressure when the cold auxiliary feedwater is introduced to the steam generator. However, it is not expected that this uncertainty would affect the transient calculations significantly.

Jo, J.H.; Yuelys-Miksis, C.; Rohatgi, U.S.

1984-01-01

129

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

130

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

131

Three-dimensional calculations of transient fluid-thermal mixing in the downcomer of the Calvert Cliffs-1 plant using SOLA-PTS  

SciTech Connect

The SOLA-PTS code has been used to analyze transient fluid-thermal mixing in a 180/sup 0/ sector of the downcomer and a cold leg of the Calvert Cliffs-1 plant for three assumed accident scenarios. The inlet boundary conditions for these calculations were obtained from mass flow rates and temperatures that were computed in systems code studies. The results of the three-dimensional SOLA-PTS calculations indicated that a pressurized thermal shock risk was mitigated for these accident scenarios as the result of the particular circulation patterns that developed in the downcomer.

Daly, B.J.

1984-04-01

132

Habitat Quality and Recruitment Success of Cui-ui in the Truckee River Downstream of Marble Bluff Dam, Pyramid Lake, Nevada.  

National Technical Information Service (NTIS)

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 upst...

B. Harry, G. G. Scoppettone, J. A. Salgado, P. H. Rissler

2013-01-01

133

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

Microsoft Academic Search

This volume of the Technical Resource Document (TRD) for the Environmental Impact Statement (EIS) for the ''Design, Construction and Operation of One or More Pilot Test Facilities for Assembled Chemical Weapons Destruction Technologies at One or More Sites'' (PMACWA 2001g) pertains to the destruction of assembled chemical weapons (ACW) stored in the U.S. Army's unitary chemical stockpile at Pine Bluff

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

2001-01-01

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

Environmental radionuclide concentrations in the vicinity of the Calvert Cliffs Nuclear Power Plant and the Peach Bottom Atomic Power Station: 1996--1997. Final report  

SciTech Connect

The Maryland Power Plant Research Program monitors concentrations of natural, weapons, and power plant produced radionuclides in environmental samples collected from the Chesapeake Bay in the vicinity of the Calvert Cliffs Nuclear Power Plant (CCNPP) and from the Susquehanna River-Chesapeake Bay system in the vicinity of Peach Bottom Atomic Power Station (PBAPS). The purpose of this monitoring is to determine the fate, transport, and potential effects of power plant-produced radionuclides. This report contains a description of monitoring activities and data collected during the 1996 and 1997 calendar years. Radionuclide concentrations in shellfish, finfish, aquatic vegetation, and sediment were measured using high-resolution gamma spectrometry. Radionuclides in environmental samples originated from natural sources, historic atmospheric weapons testing, and normal operations of CCNPP and PBAPS.

McLean, R.I.; Jones, T.S.

1998-11-20

136

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

137

Preliminary assessment of the health and environmental impacts of incinerating M55 rockets stored at Pine Bluff Arsenal, Lexington-Blue Grass Depot Activity, and/or Anniston Army Depot at Pine Bluff Arsenal  

SciTech Connect

The purpose is to provide an assessment of the potential health and environmental impacts associated with converting and operating an incineration facility currently under construction at Pine Bluff Arsenal (PBA) in Arkansas. The plant is currently designed to dispose of the incapacitating agent BZ, and the converted plant would be designed to incinerate M55 rockets containing the nerve agent GB or VX. For the purposes of this study, the rockets to be incinerated at PBA are those currently stored at PBA and possibly those currently stored at Lexington-Blue Grass Depot Activity in Kentucky and/or at Anniston Army Depot in Alabama. The assessment considers impacts on air quality, ground and surface water, aquatic ecology, terrestrial ecology, human health, and cultural and socioeconomic resources at PBA and its host region. The assessment considers three basic scenarios during plant operations: normal operations, a minor spill of agent (i.e., the nerve-agent contents of one rocket being released to the biosphere), and an onsite transport accident (i.e., vaporization or aerosolization of the contents of two rockets and a spill of the remaining 13 rockets from an M55 rocket pallet) during disposal operations. For our assessment of accident impacts, we considered two separate sets of meteorological conditions: (1) conservative most likely and (2) worst-case.

Boyette, J.A.; Breck, J.E.; Coleman, P.R.; Griffin, G.D.; Hillsman, E.L.; Johnson, P.E.; Kornegay, F.C.; Schweitzer, M.; Sigal, L.L.; Thomas, G.A.

1986-03-01

138

A Study of Slender Bluff-Body Reacting Wakes Formed by Concurrent or Countercurrent Fuel Injection  

Microsoft Academic Search

The work presents an investigation of turbulent propane flames stabilized by planar injection across the span of a square cylinder, either from its leading face against the approach flow or directly into its vortex formation region. The non-premixed or partially premixed reacting wakes were studied by regulating the fuel injection level and position. Turbulent velocities, temperatures, CH*, flame images, and

P. Koutmos; K. Souflas

2012-01-01

139

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.

140

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

SciTech Connect

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

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

2009-12-15

141

Monitoring of populations and productivity of seabirds at St. George Island, Cape Peirce, and Bluff, Alaska, 1989. Final report  

SciTech Connect

In recent years, although descriptive studies have continued, the emphasis on population monitoring of seabirds has increased. Commercial uses of the Continental Shelf of the Bering and Chukchi Seas, including oil and gas development, subsurface placer mining, and commercial fishing, carry the potential for adverse pressures on seabird populations. Populations and productivity of seabirds were monitored in 1989 at three Bering Sea colonies: St. George, Cape Peirce, and Bluff. Murres and black-legged kittiwakes were monitored at all colonies to facilitate intercolony comparisons. These species were selected because they are relatively easy to study, numerous, sensitive to potential impacts of development, and widely distributed. Red legged kittiwakes also were monitored at St. George because of concern for the world status of the species. Methods were standardized among the three colonies to facilitate comparisons among colonies and years. Observations of productivity began at the time nests were established and continued until most young had fledged. Kittiwake nests and murre breeding sites used for estimation of productivity were mapped on photographs or sketches and the fate of each was recorded.

Mendenhall, V.M.

1991-04-01

142

Numerical study of a hydrodynamic instability excitation for bluff body wake control  

Microsoft Academic Search

Effects of spatially uniform and spanwise-discrete disturbances generated by steady suction on the surface of a cylinder are investigated. The wake flow was studied experimentally using flow visualization and hot-wire measurements, and numerically solving Navier-Stokes equations. The numerical and experimental results complement each other to overcome some of the limitations associated with each approach. The discrete perturbations cause the formation

Sunil Kumar Reddy Patil

2007-01-01

143

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

144

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

145

TRAC-PF1 analyses of potential pressurized-thermal-shock transients at Calvert Cliffs/Unit 1: a Combustion Engineering PWR  

SciTech Connect

Los Alamos National Laboratory participated in a program to assess the risk of a pressurized thermal shock (PTS) to the reactor vessel during a postulated overcooling transient in a pressurized water reactor (PWR). We provided the thermal-hydraulic analyses of three general accident categories: steamline breaks, runaway-feedwater transients, and small-break loss-of-coolant accidents. These postulated accidents included multiple operator and equipment failures. Results were provided to ORNL which plans to determine the probability of vessel failure and accident occurrence for an overall assessment of PTS risk. As specified by ORNL, the postulated overcooling transients were simulated for 7200 s (2 h) after the transient initiation. Our study was performed for a Combustion Engineering (C-E) PWR, Calvert Cliffs/Unit 1, using the Transient Reactor Analysis Code (TRAC-PF1). The analyses identified the phenomena important to the PTS issue. Flow stagnation in all reactor coolant loops, which occurred in one transient, could have severe consequences. We found the results to be very sensitive to the initial conditions of the plant. If the plant was initially at hot-zero power (compared to full power), the decay heat was much less, which made it possible for the same accident initiator to produce significantly lower downcomer temperatures. However, routine operator actions may reduce the consequences of any of these simulated accidents if the prescribed pressure-temperature relationships are followed.

Spriggs, G.D.; Koenig, J.E.; Smith, R.C.

1985-02-01

146

Aerodynamics of the flying snake Chrysopelea paradisi: how a bluff body cross-sectional shape contributes to gliding performance.  

PubMed

A prominent feature of gliding flight in snakes of the genus Chrysopelea is the unique cross-sectional shape of the body, which acts as the lifting surface in the absence of wings. When gliding, the flying snake Chrysopelea paradisi morphs its circular cross-section into a triangular shape by splaying its ribs and flattening its body in the dorsoventral axis, forming a geometry with fore-aft symmetry and a thick profile. Here, we aimed to understand the aerodynamic properties of the snake's cross-sectional shape to determine its contribution to gliding at low Reynolds numbers. We used a straight physical model in a water tunnel to isolate the effects of 2D shape, analogously to studying the profile of an airfoil of a more typical flyer. Force measurements and time-resolved (TR) digital particle image velocimetry (DPIV) were used to determine lift and drag coefficients, wake dynamics and vortex-shedding characteristics of the shape across a behaviorally relevant range of Reynolds numbers and angles of attack. The snake's cross-sectional shape produced a maximum lift coefficient of 1.9 and maximum lift-to-drag ratio of 2.7, maintained increases in lift up to 35 deg, and exhibited two distinctly different vortex-shedding modes. Within the measured Reynolds number regime (Re=3000-15,000), this geometry generated significantly larger maximum lift coefficients than many other shapes including bluff bodies, thick airfoils, symmetric airfoils and circular arc airfoils. In addition, the snake's shape exhibited a gentle stall region that maintained relatively high lift production even up to the highest angle of attack tested (60 deg). Overall, the cross-sectional geometry of the flying snake demonstrated robust aerodynamic behavior by maintaining significant lift production and near-maximum lift-to-drag ratios over a wide range of parameters. These aerodynamic characteristics help to explain how the snake can glide at steep angles and over a wide range of angles of attack, but more complex models that account for 3D effects and the dynamic movements of aerial undulation are required to fully understand the gliding performance of flying snakes. PMID:24477611

Holden, Daniel; Socha, John J; Cardwell, Nicholas D; Vlachos, Pavlos P

2014-02-01

147

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

148

Study of hydrocarbon miscible solvent slug injection process for improved recovery of heavy oil from Schrader Bluff Pool, Milne Point Unit, Alaska. Annual report, December 1, 1992--December 31, 1993  

SciTech Connect

The shallow Cretaceous sands of the Schrader Bluff Reservoir occur between depths of 4,000 and 4,800 feet below surface and are estimated to contain up to 1.5 billion barrels of oil in place. The field is currently under production by primary depletion. Initial production indicated that primary recovery will fall short of earlier estimates and waterflooding will have to be employed much earlier than expected. A large portion of the oil-in-place thus would still be left behind in this reservoir after primary and secondary recovery methods have been applied. Enhanced oil recovery (EOR) techniques will be needed to recover the additional portion of remaining oil in this huge reservoir and to add significant additional reserves. Slim tube displacement studies, PVT data and asphaltene precipitation studies are needed for Schrader Bluff heavy oil to define possible hydrocarbon solvent suitable for miscible solvent slug displacement process. Such studies are essential because the API gravity of the crude in Schrader Bluff reservoir varies significantly from well to well. Coreflood experiments are also needed to determine effect of solvent slug size, WAG ratio and solvent composition on the oil recovery and solvent breakthrough. A compositional reservoir simulation study will be conducted later to evaluate the complete performance of the hydrocarbon solvent slug process and to assess the feasibility of this process for improving recovery of heavy oil from Schrader Bluff reservoir. This report contains the following: reservoir description; slim tube displacement studies; and coreflood experiments.

Sharma, G.D.

1994-01-01

149

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

150

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 BMD and BMC values for the whole bone. The ftgnt leg bones were approximately 15, 2 cm (6 inches) long with an outside diameter of 2. 5 cm (1 inch). The size of the phantom closely approximated the average size of the sheep bones... considered significant if the coefficient of conelation exceeded 0. 80 and the P-value for the F-test exceeded 0. 95 which relates to a confidence interval of 95%. 28 CALCULATIONS The physical characteristics of the bones and phantoms used in this pmject...

Newsom, Douglas Floyd

2012-06-07

151

A Study of Slender Bluff Body Reacting Wakes Formed by ConCurrent or Counter-Current Fuel Injection  

Microsoft Academic Search

The work presents an investigation of turbulent propane flames stabilized by planar injection across the span of a square cylinder, either from its leading face against the approach flow or directly into its vortex formation region. The non- or partially- premixed reacting wakes were studied by regulating the fuel injection level and position. Turbulent velocities, temperatures, CH* and flame images

P. Koutmos; K. Souflas

2012-01-01

152

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

153

A comparison of RETRAN-02 and TRAC-PF1 simulations of a loss of off-site power cooldown to residual heat removal entry conditions at Calvert Cliffs Nuclear Power Plant  

SciTech Connect

As a part of the U.S. Nuclear Regulatory Commission's unresolved safety issue A-45 decay heat removal program, the Los Alamos National Laboratory (LANL) performed a TRAC-PF1 simulation of the Calvert Cliffs Unit 1 pressurized water reactor in a cooldown to residual heat removal (RHR) entry conditions after a loss of off-site power (LOSP). A detailed four-loop TRAC model developed for the A-49 pressurized thermal shock program was used. The LANL results indicated an inability to both cool down and depressurize the primary system sufficiently to meet RHR entry conditions using only the atmospheric dump valves and auxiliary pressurizer spray. A RETRAN-02/MOD3 analysis was performed for the same transient, using assumptions consistent with those in the LANL analysis. A fast-running one loop RETRAN model was selected because of the inherent symmetry of the transient. The RETRAN results compared well with sensitivity analyses indicating that the pressurizer model dominates the transient signatures. A best estimate RETRAN analysis of the cooldown was performed using a more accurate set of assumptions to better understand actual plant operational responses. These results indicate that RHR entry could be achieved after an LOSP using only existing plant equipment and procedures.

Cook, T.L.; Mirsky, S.M.

1987-01-01

154

Bluff and Bull in Education  

ERIC Educational Resources Information Center

Telling a lie, according to Harry G. Frankfurt, is different from engaging in bullshit because, while a lie is designed to insert a particular falsehood at a specific point in a set or system of beliefs in order to avoid the consequences of having that occupied by truth, bullshit neither misrepresents the state of affairs to which it refers nor…

Sassoon, David

2005-01-01

155

Alteration, mass conservation, and magmatic compositions of lavas of the Columbia River flood basalt province: Insights from the Sentinel Bluffs Member, Grande Ronde Basalt  

NASA Astrophysics Data System (ADS)

Understanding magmatic processes involved in flood basalt volcanism, and the ability to correlate flows within the voluminous, widespread lava fields requires accurate characterization of their magmatic geochemistry. Although evidence of alteration is widespread, modifications to lava chemistry by secondary processes are poorly understood. This results in uncertainty in the interpretation of geochemical analyses of Columbia River Basalt Group lava flows, particularly those of the Grande Ronde Basalt (GRB), in which chemical differences between the lavas are subtle. This problem is addressed here using major and trace element analyses (XRF) of samples of the Sentinel Bluffs Member (SB) of the GRB collected from multiple stratigraphic sections within the Columbia Plateau, Columbia River Gorge and Coast Ranges. Sixteen chemical groups, comprising 1-3 flows each, are recognized among multiple SB lava compositions. Flows assigned to three or four successive chemical groups are, in turn, assigned to more broadly defined chemical series based on shared characteristics such as immobile element ratios. Magmatic and alteration trends among SB compositions are clearly distinguished in Al-Ti variations. Magmatic trends are defined by inverse correlation of Al2O3 and TiO2. Alteration trends, extending from the magmatic array to higher abundances, are characterized by constant Al2O3/TiO2. Paired enrichments in Al and Ti, as well as other immobile elements, result from concentration in the residuum of altered rock that has lost mass due to soluble cation removal. Such enrichments are inversely proportional to mass loss. A mass conservation index (MCI), derived from Al-Ti systematics, quantifies mass retention and has multiple applications. MCI normalization eliminates residual concentration accompanying mass loss such that MCI-normalized immobile element abundances in altered rock agree with those in high-MCI rock. Compositions filtered to high-MCI values more closely reflect magmatic abundances of highly mobile elements, such as K and Ba, but some mobility not accounted by MCI normalization is evident. MCI-normalized abundances indicate which mobile elements have been enriched or depleted during alteration, and can characterize the composition of material removed. The slope of correlated MCI-normalized abundances and MCI corresponds to the weight fraction of total mass loss. That such correlations are observed indicates a consistent composition of material removed, which, in turn, suggests that alteration selectively affects particular phases. In SB lavas, depletions of Fe, Si, and Mg account for most mass loss; depletions in Ca are minor. The observed depletions indicate removal primarily of pyroxene and Fe-oxide. The MCI-based methodology provides a framework for quantifying effects of alteration on lava chemistry and clarifying magma compositions that provide a foundation for petrogenetic analysis. It is likely applicable to other lavas in this flood basalt province, as well as other volcanic rocks influenced by secondary processes.

Sawlan, M. G.

2013-12-01

156

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

157

Vadose-zone recharge and weathering in an Eocene sand deposit, East Texas, U.S.A.  

NASA Astrophysics Data System (ADS)

Weathering of terrigenous sand in the vadose zone of the Eocene Calvert Bluff Formation in Freestone County, Texas, appears to be controlled by vadose-water flow rate and kinetics of dissolution and precipitation of silicate minerals. Feldspar grains more commonly appear corroded by surface-reaction-controlled dissolution than argillized in situ. Kaolinite and smectite, which most likely precipitated from silica-rich vadose water, coat remaining framework grains. Where those grains are later dissolved, delicate clay molds remain. The relative abundances of feldspar and clay minerals are inversely related and vary with depth, reflecting the cumulative effect of feldspar weathering. Concentrations of dissolved and adsorbed cations generally are near massaction equilibrium. Recharge occurs from March to May (spring) and from October to November (autumn) when there is a net excess of water in the vadose zone. Dissolved ionic concentrations fluctuate seasonally with vadose-water residence time, suggesting that mass flux is close to mineral dissolution rate.

Dutton, A. R.

1990-03-01

158

Preliminary assessment of the health and environmental impacts of continuing to store M55 rockets at Lexington-Blue Grass Depot Activity, Anniston Army Depot, Umatilla Depot Activity, Pine Bluff Arsenal, and Tooele Army Depot  

SciTech Connect

The purpose is to provide an assessment of the potential health and environmental impacts of continuing to store M55 rockets filled with nerve agent GB or VX at their current storage locations at Anniston Army Depot in Alabama, Lexington-Blue Grass Depot Activity in Kentucky, Pine Bluff Arsenal in Arkansas, Tooele Army Depot in Utah, and Umatilla Depot Activity in Oregon. The assessment considers the possible impacts of (1) normal storage (with no release to the environment) and (2) two postulated accidents on the air quality, ground and surface water, aquatic ecology, terrestrial ecology, human health, and cultural and socioeconomic resources in and around the various storage depots. The analysis considers three basic scenarios during storage: (1) normal operations; (2) a minor spill of agent (the contents of one rocket released to the biosphere); and (3) a maximum credible event or MCE. The MCE is an igloo fire resulting in the aerosolization of a small (in the case of GB) or an extremely small (in the case of VX) percentage of the igloo's nerve agent contents to the biosphere. The extremely low probabilities of such accidents, which are reported elsewhere, are noted. Our assessments of the impacts of a minor spill and of an MCE consider two sets of meteorological conditions: conservative most likely and worst-case. In addition, we assume that an agent plume would travel toward the area of highest population density. 21 figs., 47 tabs.

Boyette, J.A.; Breck, J.E.; Coleman, P.R.; Griffin, G.D.; Hillsman, E.L.; Johnson, P.E.; Kornegay, F.C.; Ogles, M.R.; Schweitzer, M.; Sigal, L.L.

1986-03-01

159

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

NASA Astrophysics Data System (ADS)

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

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

1999-02-01

160

CO2 Sequestration Potential of Texas Low-Rank Coals  

SciTech Connect

Injection of CO{sub 2} in coalbeds is a plausible method of reducing atmospheric emissions of CO{sub 2}, and it can have the additional benefit of enhancing methane recovery from coal. Most previous studies have evaluated the merits of CO{sub 2} disposal in high-rank coals. The objective of this research was to determine the technical and economic feasibility of CO{sub 2} sequestration in, and enhanced coalbed methane (ECBM) recovery from, low-rank coals in the Texas Gulf Coast area. Our research included an extensive coal characterization program, including acquisition and analysis of coal core samples and well transient test data. We conducted deterministic and probabilistic reservoir simulation and economic studies to evaluate the effects of injectant fluid composition (pure CO{sub 2} and flue gas), well spacing, injection rate, and dewatering on CO{sub 2} sequestration and ECBM recovery in low-rank coals of the Calvert Bluff formation of the Texas Wilcox Group. Shallow and deep Calvert Bluff coals occur in two, distinct, coalbed gas petroleum systems that are separated by a transition zone. Calvert Bluff coals < 3,500 ft deep are part of a biogenic coalbed gas system. They have low gas content and are part of a freshwater aquifer. In contrast, Wilcox coals deeper than 3,500 ft are part of a thermogenic coalbed gas system. They have high gas content and are part of a saline aquifer. CO{sub 2} sequestration and ECBM projects in Calvert Bluff low-rank coals of East-Central Texas must be located in the deeper, unmineable coals, because shallow Wilcox coals are part of a protected freshwater aquifer. Probabilistic simulation of 100% CO{sub 2} injection into 20 feet of Calvert Bluff coal in an 80-acre 5-spot pattern indicates that these coals can store 1.27 to 2.25 Bcf of CO{sub 2} at depths of 6,200 ft, with an ECBM recovery of 0.48 to 0.85 Bcf. Simulation results of flue gas injection (87% N{sub 2}-13% CO{sub 2}) indicate that these same coals can store 0.34 to 0.59 Bcf of CO{sub 2} with an ECBM recovery of 0.68 to 1.20 Bcf. Economic modeling of CO{sub 2} sequestration and ECBM recovery indicates predominantly negative economic indicators for the reservoir depths (4,000 to 6,200 ft) and well spacings investigated, using natural gas prices ranging from $2 to $12 per Mscf and CO{sub 2} credits based on carbon market prices ranging from $0.05 to $1.58 per Mscf CO{sub 2} ($1.00 to $30.00 per ton CO{sub 2}). Injection of flue gas (87% N{sub 2} - 13% CO{sub 2}) results in better economic performance than injection of 100% CO{sub 2}. CO{sub 2} sequestration potential and methane resources in low-rank coals of the Lower Calvert Bluff formation in East-Central Texas are significant. The potential CO{sub 2} sequestration capacity of the coals ranges between 27.2 and 49.2 Tcf (1.57 and 2.69 billion tons), with a mean value of 38 Tcf (2.2 billion tons), assuming a 72.4% injection efficiency. Estimates of recoverable methane resources range between 6.3 and 13.6 Tcf, with a mean of 9.8 Tcf, assuming a 71.3% recovery factor. Moderate increases in gas prices and/or carbon credits could generate attractive economic conditions that, combined with the close proximity of many CO{sub 2} point sources near unmineable coalbeds, could enable commercial CO{sub 2} sequestration and ECBM projects in Texas low-rank coals. Additional studies are needed to characterize Wilcox regional methane coalbed gas systems and their boundaries, and to assess potential of other low-rank coal beds. Results from this study may be transferable to other low-rank coal formations and regions.

Duane McVay; Walter Ayers, Jr.; Jerry Jensen; Jorge Garduno; Gonzola Hernandez; Rasheed Bello; Rahila Ramazanova

2006-08-31

161

Palaeoenvironmental Indications of Enhanced Primary Productivity During Pliocene Sapropel Formation  

NASA Astrophysics Data System (ADS)

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

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

2001-12-01

162

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

SciTech Connect

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

Roehler, H.W.

1991-01-01

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

Bloor's bluff: Behaviourism and the strong programme  

Microsoft Academic Search

The accumulated case studies in the Sociology of Scientific Knowledge have been taken to establish the Strong Programme's thesis that beliefs have social causes in contradistinction to psychological ones. This externalism is essentially a commitment to the stimulus control of behaviour which was the principal tenet of orthodox Skinnerian Behaviorism. Offered as ‘straight forward scientific hypotheses’ these claims of social

Peter Slezak

1991-01-01

165

Planet formation  

Microsoft Academic Search

Models of planetary formation are developed using the present single example of a planetary system, supplemented by limited astrophysical observations of star-forming regions and circumstellar disks. The solar nebula theory and the planetesimal hypothesis are discussed. The latter is found to provide a viable theory of the growth of the terrestrial planets, the cores of the giant planets, and the

Jack J. Lissauer

1993-01-01

166

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

167

ANTIBODY FORMATION  

PubMed Central

The suppression of antibody formation by passively administered antibody is influenced by the dose and nature of the antigen, type of immunization procedure, ratio of antibody to antigen, species origin and characteristics of the antiserum used, as well as the species selected for immunization. In guinea pigs, diphtheria antitoxin formation can be effectively suppressed by an intravenous injection of excess homologous or heterologous antitoxin as long as 5 days after toxoid immunization and after delayed-type hypersensitivity to toxoid has developed. Following the period of antibody suppression which lasts 2 to 7 weeks, serum antibody can usually be demonstrated. It is proposed that this delayed immunization results from dissociation of antigen, since diphtheritic paralysis and death can be produced in guinea pigs and rabbits by the intravenous injection of toxin-antitoxin precipitates formed in antitoxin excess. This syndrome is prevented by injection of excess horse antitoxin 1 hour after injection of the toxin-antitoxin complexes. PMID:13779027

Uhr, Jonathan W.; Baumann, Joyce B.

1961-01-01

168

Cloud Formation  

NASA Astrophysics Data System (ADS)

Cloud formation is crucial to the heritage of modern physics, and there is a rich literature on this important topic. In 1927, Charles T.R. Wilson was awarded the Nobel Prize in physics for applications of the cloud chamber.2 Wilson was inspired to study cloud formation after working at a meteorological observatory on top of the highest mountain in Scotland, Ben Nevis, and testified near the end of his life, "The whole of my scientific work undoubtedly developed from the experiments I was led to make by what I saw during my fortnight on Ben Nevis in September 1894."3 To form clouds, Wilson used the sudden expansion of humid air.4 Any structure the cloud may have is spoiled by turbulence in the sudden expansion, but in 1912 Wilson got ion tracks to show up by using strobe photography of the chamber immediately upon expansion.5 In the interim, Millikan's study in 1909 of the formation of cloud droplets around individual ions was the first in which the electron charge was isolated. This study led to his famous oil drop experiment.6 To Millikan, as to Wilson, meteorology and physics were professionally indistinct. With his meteorological physics expertise, in WWI Millikan commanded perhaps the first meteorological observation and forecasting team essential to military operation in history.7 But even during peacetime meteorology is so much of a concern to everyone that a regular news segment is dedicated to it. Weather is the universal conversation topic, and life on land could not exist as we know it without clouds. One wonders then, why cloud formation is never covered in physics texts.

Graham, Mark Talmage

2004-05-01

169

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

170

P Formation  

NASA Astrophysics Data System (ADS)

The voids formed in the Ni3P layer during reaction between Sn-based solders and electroless Ni-P metallization is an important cause of rapid degradation of solder joint reliability. In this study, to suppress formation of the Ni3P phase, an electrolessly plated Ni-Sn-P alloy (6-7 wt.% P and 19-21 wt.% Sn) was developed to replace Ni-P. The interfacial microstructure of electroless Ni-Sn-P/Sn-3.5Ag solder joints was investigated after reflow and solid-state aging. For comparison, the interfacial reaction in electroless Ni-P/Sn-3.5Ag solder joints under the same reflow and aging conditions was studied. It was found that the Ni-Sn-P metallization is consumed much more slowly than the Ni-P metallization during soldering. After prolonged reaction, no Ni3P or voids are observed under SEM at the Ni-Sn-P/Sn-3.5Ag interface. Two main intermetallic compounds, Ni3Sn4 and Ni13Sn8P3, are formed during the soldering reaction. The reason for Ni3P phase suppression and the overall mechanisms of reaction at the Ni-Sn-P/Sn-3.5Ag interface are discussed.

Yang, Ying; Balaraju, J. N.; Huang, Yizhong; Tay, Yee Yan; Shen, Yiqiang; Tsakadze, Zviad; Chen, Zhong

2014-11-01

171

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

172

CO2 SEQUESTRATION POTENTIAL OF TEXAS LOW-RANK COALS  

SciTech Connect

The objectives of this project are to evaluate the feasibility of carbon dioxide (CO{sub 2}) sequestration in Texas low-rank coals and to determine the potential for enhanced coalbed methane (CBM) recovery as an added benefit of sequestration. there were two main objectives for this reporting period. first, they wanted to collect wilcox coal samples from depths similar to those of probable sequestration sites, with the objective of determining accurate parameters for reservoir model description and for reservoir simulation. The second objective was to pursue opportunities for determining permeability of deep Wilcox coal to use as additional, necessary data for modeling reservoir performance during CO{sub 2} sequestration and enhanced coalbed methane recovery. In mid-summer, Anadarko Petroleum Corporation agreed to allow the authors to collect Wilcox Group coal samples from a well that was to be drilled to the Austin Chalk, which is several thousand feet below the Wilcox. In addition, they agreed to allow them to perform permeability tests in coal beds in an existing shut-in well. Both wells are in the region of the Sam K. Seymour power station, a site that they earlier identified as a major point source of CO{sub 2}. They negotiated contracts for sidewall core collection and core analyses, and they began discussions with a service company to perform permeability testing. To collect sidewall core samples of the Wilcox coals, they made structure and isopach maps and cross sections to select coal beds and to determine their depths for coring. On September 29, 10 sidewall core samples were obtained from 3 coal beds of the Lower Calvert Bluff Formation of the Wilcox Group. The samples were desorbed in 4 sidewall core canisters. Desorbed gas samples were sent to a laboratory for gas compositional analyses, and the coal samples were sent to another laboratory to measure CO{sub 2}, CH{sub 4}, and N{sub 2} sorption isotherms. All analyses should be finished by the end of December. A preliminary report shows methane content values for the desorbed coal samples ranged between 330 and 388 scf/t., on ''as received'' basis. Residual gas content of the coals was not included in the analyses, which results in an approximate 5-10% underestimation of in-situ gas content. Coal maps indicate that total coal thickness is 40-70 ft in the Lower Calvert Bluff Formation of the Wilcox Group in the vicinity of the Sam K. Seymour power plant. A conservative estimate indicates that methane in place for a well on 160-acre spacing is approximately 3.5 Bcf in Lower Calvert Bluff coal beds. When they receive sorption isotherm data from the laboratory, they will determine the amount of CO{sub 2} that it may be possible to sequester in Wilcox coals. In December, when the final laboratory and field test data are available, they will complete the reservoir model and begin to simulate CO{sub 2} sequestration and enhanced CH{sub 4} production.

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

2004-11-01

173

The Format War.  

ERIC Educational Resources Information Center

Discussion of format changes in libraries focuses on managing change and phasing out older formats. Standardization is addressed, and five considerations regarding format shifts are examined: aesthetics, audience, compatibility, costs, and copyright. (MES)

Kreamer, Jean

1992-01-01

174

CO2 Sequestration Potential of Texas Low-Rank Coals  

SciTech Connect

The objectives of this project are to evaluate the feasibility of carbon dioxide (CO{sub 2}) sequestration in Texas low-rank coals and to determine the potential for enhanced coalbed methane (ECBM) recovery as an added benefit of sequestration. The main objectives for this reporting period were to (1) estimate the potential for CO{sub 2} sequestration in, and methane production from, low-rank coals of the Lower Calvert Bluff Formation of the Wilcox Group in the east-central Texas region, (2) quantify uncertainty associated with these estimates, (3) conduct reservoir and economic analyses of CO{sub 2} sequestration and ECBM production using horizontal wells, and (4) compare the results with those obtained from previous studies of vertical wells. To estimate the total volumes of CO{sub 2} that may be sequestered in, and total volumes of methane that can be produced from, the Wilcox Group low-rank coals in east-central Texas, we used data provided by Anadarko Petroleum Corporation, data obtained during this research, and results of probabilistic simulation modeling studies we conducted. For the analysis, we applied our base-case coal seam characteristics to a 2,930-mi{sup 2} (1,875,200-ac) area where Calvert Bluff coal seams range between 4,000 and 6,200 ft deep. Results of the probabilistic analysis indicate that potential CO{sub 2} sequestration capacity of the coals ranges between 27.2 and 49.2 Tcf (1.57 and 2.69 billion tons), with a mean value of 38 Tcf (2.2 billion tons), assuming a 72.4% injection efficiency. Estimates of recoverable methane resources, assuming a 71.3% recovery factor, range between 6.3 and 13.6 Tcf, with a mean of 9.8 Tcf. As part of the technology transfer for this project, we presented the paper SPE 100584 at the 2006 SPE Gas Technology Symposium held in Calgary, Alberta, Canada, on May 15-18, 2006. Also, we submitted an abstract to be considered for inclusion in a special volume dedicated to CO{sub 2} sequestration in geologic media, which is planned for publication by the American Association of Petroleum Geologists.

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

2006-07-01

175

Star formation - An overview  

NASA Technical Reports Server (NTRS)

Methods for studying star formation are reviewed. Stellar clusters and associations, as well as field stars, provide a fossil record of the star formation process. Regions of current star formation provide a series of snapshots of different epochs of star formation. A simplified picture of individual star formation as it was envisioned in the late 1970s is contrasted with the results of recent observations, in particular the outflow phenomenon.

Evans, N. J., II

1985-01-01

176

Index Sets of Computable Structures Wesley Calvert* Valentina S. Harizanov  

E-print Network

of A. We determine, using the arithmetical hierarchy and the difference hierarchy, the exact Ehrenfeucht theory. 1 Introduction One of the goals of computable structure theory is to study; For a given computable structure A, to calculate the precise com- plexity of I(A), we need a good

Calvert, Wesley

177

Estuarine stream piracy: Calvert County US Atlantic coastal plain  

SciTech Connect

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

Vogt, P.R. (Naval Research Lab., Washington, DC (United States))

1991-07-01

178

Postmodern Internetwork Architecture Bobby Bhattacharjee, Ken Calvert, Jim Griffioen,  

E-print Network

-known: various hacks, layering violations, and overloadings are introduced to enforce policies and attempt to get of scale offered by the unified Internet. We will use the postmodern architecture to explore basic. The Internet has fulfilled the potential of a complete generation of networking research by producing a global

Spring, Neil

179

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

180

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

NASA Astrophysics Data System (ADS)

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

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

181

Medical image file formats.  

PubMed

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

Larobina, Michele; Murino, Loredana

2014-04-01

182

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

USGS Publications Warehouse

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

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

2009-01-01

183

Planet formation in Binaries  

E-print Network

Spurred by the discovery of numerous exoplanets in multiple systems, binaries have become in recent years one of the main topics in planet formation research. Numerous studies have investigated to what extent the presence of a stellar companion can affect the planet formation process. Such studies have implications that can reach beyond the sole context of binaries, as they allow to test certain aspects of the planet formation scenario by submitting them to extreme environments. We review here the current understanding on this complex problem. We show in particular how each of the different stages of the planet-formation process is affected differently by binary perturbations. We focus especially on the intermediate stage of kilometre-sized planetesimal accretion, which has proven to be the most sensitive to binarity and for which the presence of some exoplanets observed in tight binaries is difficult to explain by in-situ formation following the "standard" planet-formation scenario. Some tentative solutions ...

Thebault, Ph

2014-01-01

184

Galaxy Formation and Evolution  

NASA Astrophysics Data System (ADS)

1. Introduction; 2. Observational facts; 3. Cosmological background; 4. Cosmological perturbations; 5. Gravitational collapse and collisionless dynamics; 6. Probing the cosmic density field; 7. Formation and structure of dark matter halos; 8. Formation and evolution of gaseous halos; 9. Star formation in galaxies; 10. Stellar populations and chemical evolution; 11. Disk galaxies; 12. Galaxy interactions and transformations; 13. Elliptical galaxies; 14. Active galaxies; 15. Statistical properties of the galaxy population; 16. The intergalactic medium; Appendices; References; Index.

Mo, Houjun; van den Bosch, Frank C.; White, Simon

2010-05-01

185

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

186

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

187

Analysis of bird formations  

Microsoft Academic Search

Birds in V formations are frequently observed and two main hypotheses have emerged in the biology\\/ornithology literature to explain this particular geometry: (i) it offers aerodynamic advantages and (ii) it is used to improve visual communication. Both explanations require a bird to track its predecessor. Observations of flocks suggest that this task is difficult for birds in large formations. We

Pete Seiler; Aniruddha Pant; Karl Hedrick

2002-01-01

188

Formative Evaluation Alternatives.  

ERIC Educational Resources Information Center

Discussion of formative evaluation highlights alternative formative evaluation methods and tools and explains their advantages, disadvantages, and applicable contexts. Methods described include two-on-one evaluation; think-aloud protocols; computer interviewing; self-evaluation; panel reviews; evaluation meetings; computer journals and networks;…

Tessmer, Martin

1994-01-01

189

Void formation in glasses  

Microsoft Academic Search

Void formation as a result of a single tightly focused femtosecond pulse irradiation has been systematically studied in commercial optical-grade glasses of different composition. Correlations between the composition, mass density, glass transition temperature and Young modulus of glass with the void formation threshold have been revealed. The pulse energy necessary to form a void was found reciprocal to the amount

Tomohiro Hashimoto; Saulius Juodkazis; Hiroaki Misawa

2007-01-01

190

School Formative Feedback Systems  

ERIC Educational Resources Information Center

Data-driven instructional improvement relies on developing coherent systems that allow school staff to generate, interpret, and act upon quality formative information on students and school programs. This article offers a formative feedback system model that captures how school leaders and teachers structure artifacts and practices to create…

Halverson, Richard

2010-01-01

191

Differentiated Teacher Evaluation.  

ERIC Educational Resources Information Center

Calvert County School District, Maryland, has developed a differentiated teacher evaluation system that promotes collaboration among supervisors and administrators in rating teacher performance. Methods involve informal observation, rating observation, and nonrating observation. Implementation is accompanied by extensive formative evaluation by…

Glatthorn, Allan A.; Holler, Richard L.

1987-01-01

192

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

E-print Network

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 (l3. 5 I b (4. 5 ) b SPART DEAD CREEK 22 were analyzed and were similar to those of the same units at Stone C1ty... 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 (l3. 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

193

Wood formation in Angiosperms.  

PubMed

Wood formation is a complex biological process, involving five major developmental steps, including (1) cell division from a secondary meristem called the vascular cambium, (2) cell expansion (cell elongation and radial enlargement), (3) secondary cell wall deposition, (4) programmed cell death, and (5) heartwood formation. Thanks to the development of genomic studies in woody species, as well as genetic engineering, recent progress has been made in the understanding of the molecular mechanisms underlying wood formation. In this review, we will focus on two different aspects, the lignification process and the control of microfibril angle in the cell wall of wood fibres, as they are both key features of wood material properties. PMID:20371107

Déjardin, Annabelle; Laurans, Françoise; Arnaud, Dominique; Breton, Christian; Pilate, Gilles; Leplé, Jean-Charles

2010-04-01

194

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.

Duc, P A; Braine, J; Brinks, E; Lisenfeld, U; Charmandaris, V; Duc, Pierre-Alain; Boquien, Meederic; Braine, Jonathan; Brinks, Elias; Lisenfeld, Ute; Charmandaris, Vassilis

2006-01-01

195

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

196

Format Monopolies: The Evolution of “Nationwide Format Oligopolies”  

Microsoft Academic Search

Almost ten years after the Telecommunications Act of 1996, 26 different radio station formats in Arbitron's 296 survey areas were examined in 2005 as a followup to Wirth's 2001 “Nationwide Format Oligopolies.” This longitudinal study sought to ascertain if format oligopolies (four companies reaching over 50% of a specific radio format's audience nationally) had evolved into format duopolies (two companies

Todd L. Wirth

2007-01-01

197

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

198

Violent Star Formation  

NASA Astrophysics Data System (ADS)

This volume deals with the most recent theories of violent star formation. It covers the formation and evolution of new stellar clusters, and explores all the possible consequences in a wide variety of objects where massive stellar bursts have occurred. It thus presents an alternative model to that which suggests supermassive black holes are the power houses of active glactic nuclei. In addition, it analyzes the impact of Wolf-Rayet stars, stellar winds and supernovae on their host galaxy, and provides evidence of massive superassociations and of supersonic velocity dispersions that result from photo-ionization by violent star formation. This book gives a valuable overview and a timely update on all aspects of violent star formation for graduate students and researchers in the field.

Tenorio-Tagle, G.

1995-01-01

199

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 & Co. Publishing

200

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

201

MARC Format Simplification.  

ERIC Educational Resources Information Center

Summarizes the feasibility of simplifying the MARC format for bibliographic records, including the benefits, disadvantages, and consequences. Five perspectives are given: history, standards, and codes; present purposes; computer operations; library operations; and online catalogs. There are four references. (RAA)

Gapen, D. Kaye

1981-01-01

202

Display formats manual  

NASA Technical Reports Server (NTRS)

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

Runnels, R. L.

1973-01-01

203

Intergalactic Star Formation  

Microsoft Academic Search

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

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

2006-01-01

204

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

205

Autonomous Formation Flight  

NASA Technical Reports Server (NTRS)

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

Schkolnik, Gerard S.; Cobleigh, Brent

2004-01-01

206

CONTROL OF FLOW PAST BLUFF BODIES USING ROTATING CONTROL CYLINDERS  

Microsoft Academic Search

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

S. Mittal

2001-01-01

207

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

208

Learned Individual Recognition and Deceptive Communication: Do Crayfish Bluff Opponents?  

E-print Network

likely to win encounters. · 16 female crayfish (Procambarus clarkii) were placed into 4 hierarchies based, L. (2004) Learning in Procambarus clarkii: the use of status and individual recognition. Calhoun by chemoreception in the red swamp crayfish, Procambarus clarkii. Journal of Chemical Ecology 25(4):781-793. Table 1

Childress, Michael J.

209

Some observations regarding steady laminar flows past bluff bodies.  

PubMed

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

Fornberg, Bengt; Elcrat, Alan R

2014-07-28

210

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

E-print Network

and the Wilberns forccatlon to the Cap Mountain foraatlon. He designated Cap Ncncntain ln XLanc County as the type Locality. Cloud, Barnaa, and Bridge (A/46) relocated the boundaries of taiga~a Cap Mountain forccatlon to include the calcareous sandstone... and the Wilberns forccatlon to the Cap Mountain foraatlon. He designated Cap Ncncntain ln XLanc County as the type Locality. Cloud, Barnaa, and Bridge (A/46) relocated the boundaries of taiga~a Cap Mountain forccatlon to include the calcareous sandstone...

Mangum, Charles Roland

2012-06-07

211

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

212

Constraints on Exomoon Formation  

NASA Astrophysics Data System (ADS)

It has been widely accepted that the Earth’s moon formed by a giant impact during the late stage of the planetary formation process. The giant impact led to the formation of a debris disk around the Earth from which the Moon accreted. This type of satellite formation is considered to be common not only in the solar system (e.g., the Pluto-Charon system) but also in extrasolar systems (e.g. Ogihara & Ida 2009). However, no detailed research has been conducted on impact-induced exomoon formation. Wada et al. (2006) suggest that a vapor-rich disk is dynamically unstable and that it may not be suitable for moon formation. If this is the case, the mass and composition of a planet may affect the satellite formation process. Here, we show results from giant impact simulations of planets with various masses and compositions. We use the model suggested by Nakajima & Stevenson (2014) to estimate the vapor mass fractions of the disks. We find that the more massive and the more ice-rich the planet is, the higher the vapor mass fraction of the disk becomes. This indicates there is an upper limit of the planetary mass to form an impact-induced moon and the limit depends on the planetary composition. This upper limit is a few Earth masses for a rocky planet, and about an Earth mass for an icy planet. These results are consistent with the models that Earth’s and Pluto’s satellites formed by impacts. Although no exomoon has been detected yet, our model may be used to predict whether an observed terrestrial exoplanet could potentially have one or multiple impact-induced exomoons.

Nakajima, Miki; Genda, Hidenori; Asphaug, Erik; Ida, Shigeru

2014-11-01

213

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

214

Isolating Triggered Star Formation  

SciTech Connect

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

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

2007-09-12

215

The stratigraphy and environment of deposition of productive Wilcox clays in west central Freestone and southeast Limestone Counties, Texas  

E-print Network

physiography, permits ground waters to penetrate deeply and form deep deposits of kaolin1te. Smectite and illite are formed from high concentrations of metal cat1ons and sil1ca. Parent rocks must be rich 1n calcium, magnesium, iron, and/or sodium... for the abundance of calcium smectite in the Calvert Bluff are: 1)the continental source was rich in calcium smectite which was transported directly to the site of deposition; Z)the continental source was the same as for the Simsboro with calcium smectite added...

Shelvey, Stephanie Anne

2012-06-07

216

Barrier cell sheath formation  

SciTech Connect

The solution for electrostatic potential within a simply modeled tandem mirror thermal barrier is seen to exhibit a sheath at each edge of the cell. The formation of the sheath requires ion collisionality and the analysis assmes that the collisional trapping rate into the barrier is considerably slower than the barrier pump rate.

Kesner, J

1980-04-01

217

Bacterial formate hydrogenlyase complex  

PubMed Central

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

2014-01-01

218

Bead lightning formation  

Microsoft Academic Search

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,

G. O. Ludwig; M. M. F. Saba

2005-01-01

219

Triglycerides and gallstone formation  

Microsoft Academic Search

Changes in bile acid (BA) metabolism and gallbladder function are critical factors in the pathogenesis of gallstones. Patients with hypertriglyceridemia (HTG) – often overweight and insulin resistant – are at risk for gallstone disease. The question arises whether HTG itself contributes to gallstone formation or whether gallstone disease only associates with this disorder.Triglycerides are formed in response to fluxes of

A. H. M. Smelt

2010-01-01

220

Formation of red sprites  

Microsoft Academic Search

The properties of red sprites that are generated in the ionosphere at an altitude of 100 km are considered. A process that leads to the formation of such plasma objects is proposed. It is demonstrated that sprites are generated by acoustic waves that give rise to vortices and gas breakdown in the presence of strong gradients of gas temperature and

A. R. Aramyan; G. A. Galechyan

2009-01-01

221

Specific Star Formation Rates  

E-print Network

We present results from a study to determine how star formation contributes to galaxy growth since redshift z=1.5. Using galaxies from the MUnich Near-Infrared Cluster Survey (MUNICS) and the FORS Deep Field (FDF), we investigate the specific star formation rate (SSFR, star formation rate [SFR] per unit galaxy stellar mass) as a function of galaxy stellar mass and redshift. We test the compatibility of our results with a sample drawn from a larger volume using the Sloan Digital Sky Survey. We find that the SSFR decreases as galaxy stellar mass increases, suggesting that star formation contributes more to the growth of low-mass galaxies than high-mass galaxies at all redshifts in this study. We also find a ridge in the SSFR that runs parallel to lines of constant SFR and decreases by a factor of 10 from z=1 to today, matching the results of the evolution in SFR density seen in the ``Lilly-Madau'' diagram. The ridge evolves independently of galaxy stellar mass to a particular turnover mass at the high mass end. Galaxies above the turnover mass show a sharp decrease in SSFR compared to the average at that epoch, and the turnover mass increases with redshift.

Amanda E. Bauer; Niv Drory; Gary J. Hill

2005-09-02

222

Oil Formation and Trapping  

NSDL National Science Digital Library

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

Marshak, Stephen; Company, W. W.

223

Technobabble: File Formats.  

ERIC Educational Resources Information Center

Considers the confusion of over 20 different kinds of graphics programs. Briefly distinguishes between some of the more popular graphics formats (Photoshop, TIFF, JPEG, GIF, PICT, and EPS), and describes the benefits and disadvantages of each in the context of journalism education. (SC)

Wilson, Bradley

1999-01-01

224

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...

225

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

226

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.

227

Mechanisms of Stone Formation  

Microsoft Academic Search

We have reviewed the general mechanisms involved in kidney stone formation, with reference to those composed of calcium oxalate\\u000a or phosphate, uric acid, and cystine. These processes include nucleation of individual crystals, aggregation or secondary\\u000a nucleation to produce small intrarenal multicrystalline aggregates, fixation within the kidney, and further aggregation and\\u000a secondary nucleation to produce the clinical stone. The factors regulating

Vishal N. Ratkalkar; Jack G. Kleinman

228

Formation of red sprites  

Microsoft Academic Search

The properties of red sprites that are generated in the ionosphere at an altitude of 100 km are considered. A process that\\u000a leads to the formation of such plasma objects is proposed. It is demonstrated that sprites are generated by acoustic waves\\u000a that give rise to vortices and gas breakdown in the presence of strong gradients of gas temperature and

A. R. Aramyan; G. A. Galechyan

2009-01-01

229

Formation of Transient Lamellipodia  

PubMed Central

Cell motility driven by actin polymerization is pivotal to the development and survival of organisms and individual cells. Motile cells plated on flat substrates form membrane protrusions called lamellipodia. The protrusions repeatedly appear and retract in all directions. If a lamellipodium is stabilized and lasts for some time, it can take over the lead and determine the direction of cell motion. Protrusions traveling along the cell perimeter have also been observed. Their initiation is in some situations the effect of the dynamics of the pathway linking plasma membrane receptors to actin filament nucleation, e.g. in chemotaxis. However, lamellipodia are also formed in many cells incessantly during motion with a constant state of the signaling pathways upstream from nucleation promoting factors (NPFs), or spontaneously in resting cells. These observations strongly suggest protrusion formation can also be a consequence of the dynamics downstream from NPFs, with signaling setting the dynamic regime but not initiating the formation of individual protrusions. A quantitative mechanism for this kind of lamellipodium dynamics has not been suggested yet. Here, we present a model exhibiting excitable actin network dynamics. Individual lamellipodia form due to random supercritical filament nucleation events amplified by autocatalytic branching. They last for about 30 seconds to many minutes and are terminated by filament bundling, severing and capping. We show the relevance of the model mechanism for experimentally observed protrusion dynamics by reproducing in very good approximation the repetitive protrusion formation measured by Burnette et al. with respect to the velocities of leading edge protrusion and retrograde flow, oscillation amplitudes, periods and shape, as well as the phase relation between protrusion and retrograde flow. Our modeling results agree with the mechanism of actin bundle formation during lamellipodium retraction suggested by Burnette et al. and Koestler et al. PMID:24505300

Zimmermann, Juliane; Falcke, Martin

2014-01-01

230

Compact toroid formation experiments  

Microsoft Academic Search

Summary form only given, as follows. A compact toroid (CT) formation experiment is discussed. The device has coaxial electrode diameters of 0.9 m (inner) and 1.25 m (outer) and an electrode length of ~1.2 m, including an expansion drift section. The CT is formed by a 0.1-0.2-T initial radial magnetic field embedded coaxial puff gas discharge. The gas puff is

J. H. Degnan; G. P. Baca; J. D. Beason; M. E. Dearborn; D. Dietz; K. E. Hackett; J. L. Holmes; B. W. Mullins; J. L. Mullins; E. L. Ruden; D. W. Price; C. R. Sovinec; D. Gale; J. D. Graham; D. Ralph; M. Scott; W. Sommars; G. Bird; S. K. Coffey; S. W. Seiler; G. F. Kiuttu; R. E. Peterkin; N. F. Roderick; P. Turchi

1990-01-01

231

The Star Formation Camera  

Microsoft Academic Search

The Star Formation Camera (SFC) is a wide-field (~15'x19, >280 arcmin^2), high-resolution (18x18 mas pixels) UV\\/optical dichroic camera designed for the Theia 4-m space-borne space telescope concept. SFC will deliver diffraction-limited images at lambda > 300 nm in both a blue (190-517nm) and a red (517-1075nm) channel simultaneously. Our aim is to conduct a comprehensive and systematic study of the

Paul A. Scowen; Rolf Jansen; Matthew Beasley; Daniela Calzetti; Steven Desch; Alex Fullerton; John Gallagher; Doug Lisman; Steve Macenka; Sangeeta Malhotra; Mark McCaughrean; Shouleh Nikzad; Robert O'Connell; Sally Oey; Deborah Padgett; James Rhoads; Aki Roberge; Oswald Siegmund; Stuart Shaklan; Nathan Smith; Daniel Stern; Jason Tumlinson; Rogier Windhorst; Robert Woodruff

2009-01-01

232

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

233

Cosmic Star Formation History  

E-print Network

Over the last decade and a half, an avalanche of new data from multiwavelength imaging and spectroscopic surveys has revolutionized our view of galaxy formation and evolution. Making sense of it all and fitting it together into a coherent picture remains one of astronomy's great challenges. Here we review the range of complementary techniques and theoretical tools that are allowing astronomers to map the cosmic history of star formation, heavy element production, and reionization of the universe from the cosmic "dark ages" to the present epoch. A consistent picture is emerging from modern galaxy surveys, whereby the star formation rate density peaked about 3.5 Gyr after the Big Bang, at redshift 1.9, and declined exponentially at later times, with an e-folding timescale of 3.9 Gyr. Half of the stellar mass observed today was formed before redshift 1.3. Less than 1% of today's stars formed during the epoch of reionization, at redshift greater than 6. Under the simple assumption of a universal initial mass func...

Madau, Piero

2014-01-01

234

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

235

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

236

The Star Formation Camera  

E-print Network

The Star Formation Camera (SFC) is a wide-field (~15'x19, >280 arcmin^2), high-resolution (18x18 mas pixels) UV/optical dichroic camera designed for the Theia 4-m space-borne space telescope concept. SFC will deliver diffraction-limited images at lambda > 300 nm in both a blue (190-517nm) and a red (517-1075nm) channel simultaneously. Our aim is to conduct a comprehensive and systematic study of the astrophysical processes and environments relevant for the births and life cycles of stars and their planetary systems, and to investigate and understand the range of environments, feedback mechanisms, and other factors that most affect the outcome of the star and planet formation process. This program addresses the origins and evolution of stars, galaxies, and cosmic structure and has direct relevance for the formation and survival of planetary systems like our Solar System and planets like Earth. We present the design and performance specifications resulting from the implementation study of the camera, conducted ...

Scowen, Paul A; Beasley, Matthew; Calzetti, Daniela; Desch, Steven; Fullerton, Alex; Gallagher, John; Lisman, Doug; Macenka, Steve; Malhotra, Sangeeta; McCaughrean, Mark; Nikzad, Shouleh; O'Connell, Robert; Oey, Sally; Padgett, Deborah; Rhoads, James; Roberge, Aki; Siegmund, Oswald; Shaklan, Stuart; Smith, Nathan; Stern, Daniel; Tumlinson, Jason; Windhorst, Rogier; Woodruff, Robert

2009-01-01

237

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

238

Liposome formation in microgravity  

NASA Astrophysics Data System (ADS)

Liposomes are artificial vesicles with a phospholipid bilayer membrane. The formation of liposomes is a self-assembly process that is driven by the amphipathic nature of phospholipid molecules and can be observed during the removal of detergent from phospholipids dissolved in detergent micelles. As detergent concentration in the mixed micelles decreases, the non-polar tail regions of phospholipids produce a hydrophobic effect that drives the micelles to fuse and form planar bilayers in which phospholipids orient with tail regions to the center of the bilayer and polar head regions to the external surface. Remaining detergent molecules shield exposed edges of the bilayer sheet from the aqueous environment. Further removal of detergent leads to intramembrane folding and membrane vesiculation, forming liposomes. We have observed that the formation of liposomes is altered in microgravity. Liposomes that were formed at 1-g did not exceed 150 nm in diameter, whereas liposomes that were formed during spaceflight exhibited diameters up to 2000 nm. Using detergent-stabilized planar bilayers, we determined that the stage of liposome formation most influenced by gravity is membrane vesiculation. In addition, we found that small, equipment-induced fluid disturbances increased vesiculation and negated the size-enhancing effects of microgravity. However, these small disturbances had no effect on liposome size at 1-g, likely due to the presence of gravity-induced buoyancy-driven fluid flows (e.g., convection currents). Our results indicate that fluid disturbances, induced by gravity, influence the vesiculation of membranes and limit the diameter of forming liposomes.

Claassen, D. E.; Spooner, B. S.

239

Adiabatic Halo Formation  

SciTech Connect

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

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

2005-06-08

240

Galaxy formation and evolution  

NASA Technical Reports Server (NTRS)

The presence of high-z quasars and radio galaxies indicates that galaxy formation began at z greater than 5, but leaves unanswered the question of when the bulk of galaxies formed. Recent near-infrared number counts of galaxies strongly favor a cosmological geometry with q0 = 0.5 and Lambda = 0. Such a model grossly underpredicts blue galaxy counts. Spectroscopy shows that the excess blue galaxies at B = 24 are dwarfs at z = 0.4, which are no longer seen at the present time. These dwarfs must contain a large amount of baryonic matter which is not included in current estimates of baryonic Omega.

Cowie, Lennox L.

1991-01-01

241

Galaxy formation and evolution  

NASA Technical Reports Server (NTRS)

The presence of high z quasars and radio galaxies tells us that galaxy formation began at z greater than 5, but leaves unanswered the question of when the bulk of galaxies formed. Recent near infrared number counts of galaxies strongly favor a cosmological geometry with q(sub 0) = 0.5 and lambda = 0. Such a model grossly underpredicts blue galaxy counts. Spectroscopy shows that the excess blue galaxies at B = 24 are dwarfs at z approximately equals 0.4 which are no longer seen at the present time. These dwarfs must contain a large amount of baryonic matter which is not included in current estimates of baryonic omega .

Cowie, Lennox L.

1991-01-01

242

Quantum Effects and Cluster Formation  

E-print Network

The causal interpretation of quantum mechanics is applied to the universe as a whole and the problem of cluster formation is studied in this framework. It is shown that the quantum effects be the source of the cluster formation.

Ali Shojai; Fatimah Shojai

2002-11-13

243

Star Formation in Irregular Galaxies.  

ERIC Educational Resources Information Center

Examines mechanisms of how stars are formed in irregular galaxies. Formation in giant irregular galaxies, formation in dwarf irregular galaxies, and comparisons with larger star-forming regions found in spiral galaxies are considered separately. (JN)

Hunter, Deidre; Wolff, Sidney

1985-01-01

244

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

245

Planet Formation - Overview  

NASA Technical Reports Server (NTRS)

Modern theories of star and planet formation are based upon observations of planets and smaller bodies within our own Solar System, exoplanets &round normal stars and of young stars and their environments. Terrestrial planets are believed to grow via pairwise accretion until the spacing of planetary orbits becomes large enough that the configuration is stable for the age of the system. Giant planets begin their growth as do terrestrial planets, but they become massive enough that they are able to accumulate substantial amounts of gas before the protoplanetary disk dissipates. These models predict that rocky planets should form in orbit about most single stars. It is uncertain whether or not gas giant planet formation is common, because most protoplanetary disks may dissipate before solid planetary cores can grow large enough to gravitationally trap substantial quantities of gas. A potential hazard to planetary systems is radial decay of planetary orbits resulting from interactions with material within the disk. Planets more massive than Earth have the potential to decay the fastest, and may be able to sweep up smaller planets in their path.

Lissauer, Jack J.

2005-01-01

246

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

247

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

248

Urbanization and slum formation.  

PubMed

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

Ooi, Giok Ling; Phua, Kai Hong

2007-05-01

249

Parametrising Star Formation Histories  

E-print Network

We examine the star formation histories (SFHs) of galaxies in smoothed particle hydrodynamics (SPH) simulations, compare them to parametric models that are commonly used in fitting observed galaxy spectral energy distributions, and examine the efficacy of these parametric models as practical tools for recovering the physical parameters of galaxies. The commonly used tau-model, with SFR ~ exp(-t/tau), provides a poor match to the SFH of our SPH galaxies, with a mismatch between early and late star formation that leads to systematic errors in predicting colours and stellar mass-to-light ratios. A one-parameter lin-exp model, with SFR ~ t*exp(-t/tau), is much more successful on average, but it fails to match the late-time behavior of the bluest, most actively star-forming galaxies and the passive, "red and dead" galaxies. We introduce a 4-parameter model, which transitions from lin-exp to a linear ramp after a transition time, which describes our simulated galaxies very well. We test the ability of these paramet...

Simha, Vimal; Conroy, Charlie; Dave, Romeel; Fardal, Mark; Katz, Neal; Oppenheimer, Benjamin D

2014-01-01

250

Simulating Cosmic Structure Formation  

E-print Network

We describe cosmological simulation techniques and their application to studies of cosmic structure formation, with particular attention to recent hydrodynamic simulations of structure in the high redshift universe. Collisionless N-body simulations with Gaussian initial conditions produce a pattern of sheets, filaments, tunnels, and voids that resembles the observed large scale galaxy distribution. Simulations that incorporate gas dynamics and dissipation form dense clumps of cold gas with sizes and masses similar to the luminous parts of galaxies. Models based on inflation and cold dark matter predict a healthy population of high redshift galaxies, including systems with star formation rates of 20 M_{\\sun}/year at z=6. At z~3, most of the baryons in these models reside in the low density intergalactic medium, which produces fluctuating Lyman-alpha absorption in the spectra of background quasars. The physical description of this ``Lyman-alpha forest'' is particularly simple if the absorption spectrum is viewed as a 1-dimensional map of a continuous medium instead of a collection of lines. The combination of superb observational data and robust numerical predictions makes the Lyman-alpha forest a promising tool for testing cosmological models.

David H. Weinberg; Neal Katz; Lars Hernquist

1997-08-22

251

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

252

Formation control for cooperative surveillance  

E-print Network

. The formation control scheme proposed in this work is based on a fusion of leader-follower and virtual reference approaches. This scheme gives a formation constraint representation that is independent of the number of agents in the formation and the resulting...

Woo, Sang-Bum

2009-05-15

253

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

254

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

255

Prominence Formation and Oscillations  

E-print Network

Prominences, or filaments, are a striking phenomenon in the solar atmosphere. Besides their own rich features and dynamics, they are related to many other activities, such as solar flares and coronal mass ejections (CMEs). In the past several years we have been investigating the prominence formation, oscillations, and eruptions through both data analysis and radiative hydrodynamic and magnetohydrodynamic (MHD) simulations. This paper reviews our progress on these topics, which includes: (1) With updated radiative cooling function, the coronal condensation becomes a little faster than previous work; (2) Once a seed condensation is formed, it can grow via siphon flow spontaneously even if the evaporation stops; (3) A scaling law was obtained to relate the length of the prominence thread to various parameters, indicating that higher prominences tend to have shorter threads, which is consistent with the fact that threads are long in active region prominences and short in quiescent prominences; (4) It was proposed...

Chen, P F

2014-01-01

256

Ferricyanide-humate formation  

NASA Astrophysics Data System (ADS)

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

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

2003-05-01

257

Germane vs. digermane formation.  

PubMed

Oxidative addition reactions of dialkylchalcogenanes R2E2 and [Me2Si(Nt-Bu)2]Ge 1 yielded bis(alkylchalcogeno)germanes Me2Si(Nt-Bu)2Ge(ER)2 (R = Et, E = S 2, Se 3; R = Me, E = Se 4) and digermanes [Me2Si(Nt-Bu)2Ge(EEt)]2 (E = S 5, Se 6). The reaction of 1 with Et2Te2 proceeds with formation of Me2Si(Nt-Bu)2Ge(TeEt)27, which slowly converts into the Te-bridged complex [Me2Si(Nt-Bu)2GeTe]28. 1-6 and 8 were characterized by single crystal X-ray diffraction. PMID:25354698

Steiniger, P; Bendt, G; Bläser, D; Wölper, C; Schulz, S

2014-12-18

258

Parametrically forced pattern formation.  

PubMed

Pattern formation in a nonlinear damped Mathieu-type partial differential equation defined on one space variable is analyzed. A bifurcation analysis of an averaged equation is performed and compared to full numerical simulations. Parametric resonance leads to periodically varying patterns whose spatial structure is determined by amplitude and detuning of the periodic forcing. At onset, patterns appear subcritically and attractor crowding is observed for large detuning. The evolution of patterns under the increase of the forcing amplitude is studied. It is found that spatially homogeneous and temporally periodic solutions occur for all detuning at a certain amplitude of the forcing. Although the system is dissipative, spatial solitons are found representing domain walls creating a phase jump of the solutions. Qualitative comparisons with experiments in vertically vibrating granular media are made. (c) 2001 American Institute of Physics. PMID:12779440

Armbruster, Dieter; George, Marguerite; Oprea, Iuliana

2001-03-01

259

Pattern Formation in Materials  

NASA Astrophysics Data System (ADS)

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

Karma, Alain

2011-04-01

260

Group Formation in Economics  

NASA Astrophysics Data System (ADS)

Broad and diverse ranges of activities are conducted within and by organized groups of individuals, including political, economic and social activities. These activities have recently become a subject of intense interest in economics and game theory. Some of the topics investigated in this collection are models of networks of power and privilege, trade networks, co-authorship networks, buyer-seller networks with differentiated products, and networks of medical innovation and the adaptation of new information. Other topics are social norms on punctuality, clubs and the provision of club goods and public goods, research and development and collusive alliances among corporations, and international alliances and trading agreements. While relatively recent, the literature on game theoretic studies of group formation in economics is already vast. This volume provides an introduction to this important literature on game-theoretic treatments of situations with networks, clubs, and coalitions, including some applications.

Demange, Gabrielle; Wooders, Myrna

2005-01-01

261

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

262

Dityrosine formation in calmodulin  

SciTech Connect

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

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

1987-02-10

263

Galaxy formation by dust  

NASA Technical Reports Server (NTRS)

It has been known since the early 1940's that radiation can cause an instability in the interstellar medium. Absorbing dust particles in an isotropic radiation field shadow each other by a solid angle which is inversely proportional to the square of the distance between the two particles, leading to an inverse-square attractive force - mock gravity. The effect is largest in an optically thin medium. Recently Hogan and White (HW, hereafter) proposed that if the pre-galactic universe contained suitable sources of radiation and dust, instability in the dust distribution caused by mock gravity may have led to the formation of galaxies and galaxy clusters. In their picture of a well-coupled dust-gas medium, HW show that mock gravity begins to dominate gravitational instability when the perturbation becomes optically thin, provided that the radiation field at the time is strong enough. The recent rocket observation of the microwave background at submillimeter wavelengths by Matsumoto et al. might be from pre-galactic stars, the consequence of the absorption of ultraviolet radiation by dust, and infrared reemission which is subsequently redshifted. HW's analysis omits radiative drag, incomplete collisional coupling of gas and dust, finite dust albedo, and finite matter pressure. These effects could be important. In a preliminary calculation including them, the authors have confirmed that mock gravitational instability is effective if there is a strong ultraviolet radiation at the time, but any galaxies that form would be substantially enriched in heavy elements because the contraction of the dust is more rapid than that of the gas. Moreover, since the dust moves with supersonic velocity through the gas soon after the perturbation becomes optically thin, the sputtering of dust particles by gas is significant, so the dust could disappear before the instability develops significantly. They conclude that the mock gravity by dust is not important in galaxy formations.

Wang, Boqi; Field, Goerge B.

1989-01-01

264

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

265

CO2 Sequestration Potential of Texas Low-Rank Coals  

SciTech Connect

The objectives of this project are to evaluate the feasibility of carbon dioxide (CO{sub 2}) sequestration in Texas low-rank coals and to determine the potential for enhanced coalbed methane (ECBM) recovery as an added benefit of sequestration. In this reporting period we revised all of the economic calculations, participated in technology transfer of project results, and began working on project closeout tasks in anticipation of the project ending December 31, 2005. In this research, we conducted five separate simulation investigations, or cases. These cases are (1) CO{sub 2} sequestration base case scenarios for 4,000-ft and 6,200-ft depth coal beds in the Lower Calvert Bluff Formation of east-central Texas, (2) sensitivity study of the effects of well spacing on sequestration, (3) sensitivity study of the effects of injection gas composition, (4) sensitivity study of the effects of injection rate, and (5) sensitivity study of the effects of coal dewatering prior to CO{sub 2} injection/sequestration. Results show that, in most cases, revenue from coalbed methane production does not completely offset the costs of CO{sub 2} sequestration in Texas low-rank coals, indicating that CO{sub 2} injection is not economically feasible for the ranges of gas prices and carbon credits investigated. The best economic performance is obtained with flue gas (13% CO{sub 2} - 87% N{sub 2}) injection, as compared to injection of 100% CO{sub 2} and a mixture of 50% CO{sub 2} and 50% N{sub 2}. As part of technology transfer for this project, we presented results at the West Texas Geological Society Fall Symposium in October 2005 and at the COAL-SEQ Forum in November 2005.

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

2006-03-01

266

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

267

Bead lightning formation  

NASA Astrophysics Data System (ADS)

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.

2005-09-01

268

Formation of "bound  

NASA Astrophysics Data System (ADS)

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

Nowak, K.; Kästner, M.; Miltner, A.

2009-04-01

269

Prominence formation and oscillations  

NASA Astrophysics Data System (ADS)

Prominences, or filaments, are a striking phenomenon in the solar atmosphere. Besides their own rich features and dynamics, they are related to many other activities, such as solar flares and coronal mass ejections (CMEs). In the past several years we have been investigating the prominence formation, oscillations, and eruptions through both data analysis and radiative hydrodynamic and magnetohydrodynamic (MHD) simulations. This paper reviews our progress on these topics, which includes: (1) With updated radiative cooling function, the coronal condensation becomes a little faster than previous work; (2) Once a seed condensation is formed, it can grow via siphon flow spontaneously even if the evaporation stops; (3) A scaling law was obtained to relate the length of the prominence thread to various parameters, indicating that higher prominences tend to have shorter threads, which is consistent with the fact that threads are long in active region prominences and short in quiescent prominences; (4) It was proposed that long-time prominence oscillations out of phase might serve as a precursor for prominence eruptions and CMEs; (5) An ensemble of oscillating prominence threads may explain the counter-streaming motion.

Chen, P. F.

270

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

271

Gaining Insight into Star Formation: Resolved Star Formation Laws  

NASA Astrophysics Data System (ADS)

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

Liebst, Kelley; Scowen, Paul A.

2014-06-01

272

Educational Products Videotapes (VHS format, other formats by  

E-print Network

Educational Products DVDs Videotapes (VHS format, other formats by special request) and DVDs (-R://sprott.physics.wisc.edu/wop.htm#videos The quality of the DVDs is much higher than what you see from the streamed version. Lecture Kit A kit = Adult M) For more information or to place an order for T-shirts, DVDs or Lecture Kits contact: (608) 262

Saffman, Mark

273

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

ERIC Educational Resources Information Center

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

Keeley, Page

2013-01-01

274

Medusae Fossae Formation  

NASA Technical Reports Server (NTRS)

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

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

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

1998-01-01

275

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

276

Star formation in the multiverse  

NASA Astrophysics Data System (ADS)

We develop a simple semianalytic model of the star formation rate as a function of time. We estimate the star formation rate for a wide range of values of the cosmological constant, spatial curvature, and primordial density contrast. Our model can predict such parameters in the multiverse, if the underlying theory landscape and the cosmological measure are known.

Bousso, Raphael; Leichenauer, Stefan

2009-03-01

277

Science Sampler: Formative assessment guideposts  

NSDL National Science Digital Library

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

Ayala, Carlos

2005-01-01

278

The Epoch of Galaxy Formation  

Microsoft Academic Search

We use a semianalytic model of galaxy formation in hierarchical clustering theories to interpret recent data on galaxy formation and evolution, focusing primarily on the recently discovered population of Lyman-break galaxies at z ~= 3. For a variety of cold dark matter (CDM) cosmologies, we construct mock galaxy catalogs subject to selection criteria identical to those applied to the real

C. M. Baugh; S. Cole; C. S. Frenk; C. G. Lacey

1998-01-01

279

Motivating Students through Formative Feedback  

ERIC Educational Resources Information Center

Technology tools that are used to help apply standards and benchmarks motivate physical educators to use new methods of teaching, and create new ways to provide students with direct formative feedback, the number one motivator for students. Direct formative feedback refers to verbal communication between the teacher and/or parent and student. The…

Mauch, Lois

2007-01-01

280

FORMATION OF SECONDARY ORGANIC AEROSOL  

EPA Science Inventory

(1) Gas-phase chemistry. With the clear and profound effect of the VOC/NOx ratio on SOA formation, we will augment gas-phase VOC oxidation mechanisms in atmospheric models to account for the effect of NOx level on the mechanism of SOA formation; (2) Revis...

281

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

282

Mechanism of tornado funnel formation  

Microsoft Academic Search

The mechanism of formation of a tornado funnel was observed in a specially designed facility for tornado simulation. In this facility, a tornado cyclone is first simulated at the exit of a vortex generator. Interaction of this vortex with a ground plane is found to be responsible for the funnel formation. Time-averaged velocity measurements indicate that a smaller, but highly

C. T. Hsu; B. Fattahi

1976-01-01

283

New Frontiers in Formative Assessment  

ERIC Educational Resources Information Center

"Formative assessment is a powerful learning tool that is too seldom, too haphazardly, and too ineffectively used in the United States," Pendred E. Noyce writes in the introduction to this volume. "The purpose of this book is to delve into why this is so and how it can be changed." Formative assessment involves constantly monitoring student…

Noyce, Pendred E., Ed.; Hickey, Daniel T., Ed.

2011-01-01

284

Formative Assessment: A Critical Review  

ERIC Educational Resources Information Center

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

Bennett, Randy Elliot

2011-01-01

285

VEHICLE NETWORKS: ACHIEVING REGULAR FORMATION  

Microsoft Academic Search

In this paper we will consider a network of vehicles exchanging information among themselves with the intention of achieving a specied polygonal formation. The network achieves the formation through decentralized feedback control, which is con- structed from the available information. Several information o w laws are considered in order to improve the performance of the vehicle network. A stochastic model

MADALENA CHAVES; ROBERT DAY; LUCIA GOMEZ-RAMOS; PARTHASARATHI NAG; ANCA WILLIAMS; WEI ZHANG

2002-01-01

286

The Apennine Bench Formation revisited  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

287

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

288

Formative Automated Computer Testing (FACT).  

ERIC Educational Resources Information Center

Describes the development of a tool, FACT (Formative Automated Computer Testing), to formatively assess information technology skills of college students in the United Kingdom. Topics include word processing competency; tests designed by tutors and delivered via a network; and results of an evaluation that showed students preferred automated…

Hunt, Nicoll; Hughes, Janet; Rowe, Glenn

2002-01-01

289

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 ...

290

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 w...

291

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

292

Galaxy formation and chemical evolution  

E-print Network

The manner the galaxy accretes matter along with the star formation rates at different epochs, influence the evolution of the stable isotopic inventories of the galaxy. A detailed analysis is presented here to study the dependence of the galactic chemical evolution on the accretion scenario of the galaxy along with the star formation rate during the early accretionary phase of the galactic thick disk and thin disk. Our results indicate that a rapid early accretion of the galaxy during the formation of the galactic thick disk along with an enhanced star formation rate in the early stages of the galaxy accretion could explain the majority of the galactic chemical evolution trends of the major elements. Further, we corroborate the recent suggestions regarding the formation of a massive galactic thick disk rather than the earlier assumed low mass thick disk.

Sahijpal, S

2014-01-01

293

Tubulogenesis during blood vessel formation  

PubMed Central

The ability to form and maintain a functional system of contiguous hollow tubes is a critical feature of vascular endothelial cells (ECs). Lumen formation, or tubulogenesis, occurs in blood vessels during both vasculogenesis and angiogenesis in the embryo. Formation of vascular lumens takes place prior to the establishment of blood flow and to vascular remodeling which results in a characteristic hierarchical vessel organization. While epithelial lumen formation has received intense attention in past decades, more recent work has only just begun to elucidate the mechanisms controlling the initiation and morphogenesis of endothelial lumens. Studies using in vitro and in vivo models, including zebrafish and mammals, are beginning to paint an emerging picture of how blood vessels establish their characteristic morphology and become patent. In this chapter, we review and discuss the molecular and cellular mechanisms driving the formation of vascular tubes, primarily in vivo, and we compare and contrast proposed models for blood vessel lumen formation. PMID:21624487

Xu, Ke; Cleaver, Ondine

2011-01-01

294

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

295

The Formation of Massive Stars  

E-print Network

Massive stars have a profound influence on the Universe, but their formation remains poorly understood. We review the current status of observational and theoretical research in this field, describing the various stages of an evolutionary sequence that begins with cold, massive gas cores and ends with the dispersal and ionization of gas by the newly-formed star. The physical processes in massive star formation are described and related to their observational manifestations. Feedback processes and the relation of massive stars to star cluster formation are also discussed. We identify key observational and theoretical questions that future studies should address.

H. Beuther; E. B. Churchwell; C. F. McKee; J. C. Tan

2006-02-01

296

Dissipative processes in galaxy formation.  

PubMed Central

A galaxy commences its life in a diffuse gas cloud that evolves into a predominantly stellar aggregation. Considerable dissipation of gravitational binding energy occurs during this transition. I review here the dissipative processes that determine the critical scales of luminous galaxies and the generation of their morphology. The universal scaling relations for spirals and ellipticals are shown to be sensitive to the history of star formation. Semiphenomenological expressions are given for star-formation rates in protogalaxies and in starbursts. Implications are described for elliptical galaxy formation and for the evolution of disk galaxies. PMID:11607396

Silk, J

1993-01-01

297

Holographic grating formation in photopolymers  

NASA Astrophysics Data System (ADS)

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

Piazzolla, Sabino; Jenkins, B. Keith

1996-07-01

298

Antihydrogen Formation using Cold Plasmas  

SciTech Connect

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

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

2004-10-20

299

Circumstellar disks and planetary formation  

NASA Astrophysics Data System (ADS)

Circumstellar disks are the the cradle of planetary systems. They are found around a large number of intermediate- and low-mass stellar objects in star forming regions and young clusters. Their study can provide important clues about the timescales and physical conditions for planet formation. In this paper, I review some properties of circumstellar disks that come from the analysis of multi-wavelength observational data, and that are important in the context of planet formation. In addition, I also present the first evidences of planetary formation within the so-called transitional disks.

Huélamo, N.

2013-05-01

300

Use-driven concept formation  

E-print Network

When faced with a complex task, humans often identify domain-specific concepts that make the task more tractable. In this thesis, I investigate the formation of domain-specific concepts of this sort. I propose a set of ...

Roberts, Jennifer M. (Jennifer Marie)

2010-01-01

301

Gas Behavior in Galaxy Formation  

NASA Astrophysics Data System (ADS)

This dissertation focuses on the topic of gas in galaxy formation from three different perspectives: spherical collapse, external radiative heating, and 3D collapse. The physics of galaxy formation is explored via a combination of 1D and 3D calculations. The 1D calculations, have been used to explore both simple analytic models as well as a large number of micro-physical processes (e.g., multi-species chemistry, full multi-spectrum radiative transfer, and the subsequent heating and cooling). The 3D calculations have looked at the effects of external torques and of a hierarchical gas structure, but in an environment with less micro-physics. Through this approach a variety of conclusions have drawn about the formation of bulges and disks; the absorption line signatures of mini-halos and multi-phase gas; and the role of hydrodynamics in simulating galaxy formation.

Kepner, Jeremy Victor

302

Constraining Corona Formation on Venus  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

303

The multifaceted planetesimal formation process  

E-print Network

Accumulation of dust and ice particles into planetesimals is an important step in the planet formation process. Planetesimals are the seeds of both terrestrial planets and the solid cores of gas and ice giants forming by core accretion. Left-over planetesimals in the form of asteroids, trans-Neptunian objects and comets provide a unique record of the physical conditions in the solar nebula. Debris from planetesimal collisions around other stars signposts that the planetesimal formation process, and hence planet formation, is ubiquitous in the Galaxy. The planetesimal formation stage extends from micrometer-sized dust and ice to bodies which can undergo run-away accretion. The latter ranges in size from 1 km to 1000 km, dependent on the planetesimal eccentricity excited by turbulent gas density fluctuations. Particles face many barriers during this growth, arising mainly from inefficient sticking, fragmentation and radial drift. Two promising growth pathways are mass transfer, where small aggregates transfer u...

Johansen, Anders; Tanaka, Hidekazu; Ormel, Chris; Bizzarro, Martin; Rickman, Hans

2014-01-01

304

Fuel spill reports-Format  

NSF Publications Database

... EAM NSF Org: OD / OPP Date : February 05, 1991 File : opp93022 DIVISION OF POLAR PROGRAMS OFFICE OF ... Reports/Format for Fuel Spill Reports) To: Files (S.7 - Environment) Accidents involving spillage of ...

305

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

306

The Epoch of Galaxy Formation  

Microsoft Academic Search

We use a semi-analytic model of galaxy formation in hierarchical clustering\\u000atheories to interpret recent data on galaxy formation and evolution, focussing\\u000aprimarily on the recently discovered population of Lyman-break galaxies at\\u000a$z\\\\simeq 3$. For a variety of cold dark matter (CDM) cosmologies we construct\\u000amock galaxy catalogues subject to identical selection criteria to those applied\\u000ato the real data.

C. M. Baugh; S. Cole; C. S. Frenk; C. G. Lacey

1997-01-01

307

The Formation of Stellar Clusters  

E-print Network

We review recent work that investigates the formation of stellar clusters, ranging in scale from globular clusters through open clusters to the small scale aggregates of stars observed in T associations. In all cases, recent advances in understanding have been achieved through the use of state of the art stellar dynamical and gas dynamical calculations, combined with the possibility of intercomparison with an increasingly large dataset on young clusters. Among the subjects that are highlighted are the frequency of cluster-mode star formation, the possible relationship between cluster density and the highest stellar mass, subclustering and the dynamical interactions that occur in compact aggregates, such as binary star formation. We also consider how the spectrum of stellar masses may be shaped by the process of competitive accretion in dense environments and how cluster properties, such as mass segregation and cluster morphology, can be used in conjunction with numerical simulations to investigate the initial conditions for cluster formation. Lastly, we contrast bottom-up and top-down scenarios for cluster formation and discuss their applicability to the formation of clusters on a range of scales.

Cathie J. Clarke; Ian A. Bonnell; Lynne A. Hillenbrand

1999-03-22

308

Treating tar sands formations with karsted zones  

SciTech Connect

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

309

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

310

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

311

Theories of Giant Planet Formation  

NASA Technical Reports Server (NTRS)

An overview of current theories of planetary formation, with emphasis on giant planets, is presented. The most detailed models are based upon observations of our own Solar System and of young stars and their environments. While these models predict that rocky planets should form around most single stars, the frequency of formation of gas giant planets is more difficult to predict theoretically. Terrestrial planets are believed to grow via pairwise accretion until the spacing of planetary orbits becomes large enough that the configuration is stable for the age of the system. Giant planets begin their growth as do terrestrial planets, but they become massive enough that they are able to accumulate substantial amounts of gas before the protoplanetary disk dissipates. Most models for extrasolar giant planets suggest that they formed as did Jupiter and Saturn (in nearly circular orbits, far enough from the star that ice could), and subsequently migrated to their current positions, although some models suggest in situ formation.

Lissauer, Jack J.; Young, Richard E. (Technical Monitor)

1998-01-01

312

Terrestrial versus giant planet formation  

NASA Technical Reports Server (NTRS)

Given a solar nebular surrounding the early protosun, containing dust grains that have already undergone growth through collisions to about centimeter-size, the question of the formation of the terrestrial and giant planets is considered. In contrast to the usual approach of emphasizing how well a problem is understood, the uncertainties and areas where more work needs to be done will be accentuated. Also, the emphasis will be on the dynamics of planetary formation, because profound problems still exist in this area, and because it seems most logical to concentrate first on the dynamical questions involved with assembling the planets before putting too much effort into the detailed chemical and geological consequences of certain formation mechanisms.

Boss, Alan P.

1988-01-01

313

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

2014-10-01

314

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

315

Structure formation in active networks  

E-print Network

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

Simone Köhler; Volker Schaller; Andreas R. Bausch

2011-03-18

316

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

317

Numerical simulations of galaxy formation  

E-print Network

The current status of numerical simulations of galaxy formation is reviewed. After a short description of the main numerical simulation techniques, three sample applications illustrate how numerical simulations have provided deeper insight in the galaxy formation process and how they have illuminated success and failure of the hierarchical galaxy formation paradigm: N-body simulations demonstrate that the density profiles of dark matter halos that form in hierarchical clustering scenarios follow a characteristic law. A comparison with the kinematics of disk galaxies however unravels that these density profiles are too concentrated. Hydrodynamical simulation show that the highly irregular velocity field of merging subclumps at redshift $z\\approx 3$ can easily account for the observed asymmetry in the absorption profiles of low ionization species in damped \\Lya absorption systems. The built-up of galaxies due to mergers is however also cause for one of the major inconsistencies of hierarchical structure formati...

Steinmetz, M

1999-01-01

318

Toward Understanding Massive Star Formation  

E-print Network

Although fundamental for astrophysics, the processes that produce massive stars are not well understood. Large distances, high extinction, and short timescales of critical evolutionary phases make observations of these processes challenging. Lacking good observational guidance, theoretical models have remained controversial. This review offers a basic description of the collapse of a massive molecular core and a critical discussion of the three competing concepts of massive star formation: - monolithic collapse in isolated cores - competitive accretion in a protocluster environment - stellar collisions and mergers in very dense systems We also review the observed outflows, multiplicity, and clustering properties of massive stars, the upper initial mass function and the upper mass limit. We conclude that high-mass star formation is not merely a scaled-up version of low-mass star formation with higher accretion rates, but partly a mechanism of its own, primarily owing to the role of stellar mass and radiation pressure in controlling the dynamics.

Hans Zinnecker; Harold W. Yorke

2007-07-09

319

Propellantless formation flight applications using electromagnetic satellite formations  

NASA Astrophysics Data System (ADS)

The alternative to using propellant for actuation of formation flying satellites is for each spacecraft to produce their own electromagnetic field that others in the formation can react against. This technique can be achieved by creating a steerable magnetic dipole and is called Electromagnetic Formation Flight (EMFF). EMFF can be implemented on a spacecraft by driving current through three orthogonal electromagnetic coils to create a steerable magnetic dipole in three dimensions. This paper investigates the applicability of EMFF as a means for attitude and translation control of multiple spacecraft maneuvering in close proximity. One example scenario is using two EMFF satellites as an inspector system to examine a non-EMFF satellite that is nearby. The results of the analysis show the design of the proximity guidance, navigation, and control laws that allow for rapid inspection scenarios. The primary role of EMFF is to impart forces and torques to maintain a satellite array. In addition, potential secondary roles of EMFF were investigated using EMFF in a multi-role sense. These included power transmission, passive, offensive capabilities, and use of the HTS coils as torque coils for geostationary satellites. The results of this paper show that EMFF is a promising propellantless formation flight technology.

Kwon, Daniel W.

2010-11-01

320

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

321

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

322

Formation of the first stars  

NASA Astrophysics Data System (ADS)

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 ˜106 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.

Bromm, Volker

2013-11-01

323

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

324

Cosmic Star-Formation History  

NASA Astrophysics Data System (ADS)

Over the past two decades, an avalanche of new data from multiwavelength imaging and spectroscopic surveys has revolutionized our view of galaxy formation and evolution. Here we review the range of complementary techniques and theoretical tools that allow astronomers to map the cosmic history of star formation, heavy element production, and reionization of the Universe from the cosmic “dark ages” to the present epoch. A consistent picture is emerging, whereby the star-formation rate density peaked approximately 3.5 Gyr after the Big Bang, at z?1.9, and declined exponentially at later times, with an e-folding timescale of 3.9 Gyr. Half of the stellar mass observed today was formed before a redshift z = 1.3. About 25% formed before the peak of the cosmic star-formation rate density, and another 25% formed after z = 0.7. Less than ˜1% of today's stars formed during the epoch of reionization. Under the assumption of a universal initial mass function, the global stellar mass density inferred at any epoch matches reasonably well the time integral of all the preceding star-formation activity. The comoving rates of star formation and central black hole accretion follow a similar rise and fall, offering evidence for coevolution of black holes and their host galaxies. The rise of the mean metallicity of the Universe to about 0.001 solar by z = 6, one Gyr after the Big Bang, appears to have been accompanied by the production of fewer than ten hydrogen Lyman-continuum photons per baryon, a rather tight budget for cosmological reionization.

Madau, Piero; Dickinson, Mark

2014-08-01

325

Hydrodynamic Simulations of Galaxy Formation  

E-print Network

We have developed an accurate, one-dimensional, spherically symmetric, Lagrangian hydrodynamics/gravity code, designed to study the effects of radiative cooling and photo-ionization on the formation of protogalaxies. We examine the ability of collapsing perturbations to cool within the age of the universe. In contrast to some studies based on order-of-magnitude estimates, we find that cooling arguments alone cannot explain the sharp upper cutoff observed in the galaxy luminosity function. We also look at the effect of a photoionizing background on the formation of low-mass galaxies.

A. A. Thoul

1994-12-09

326

Accretion processes in star formation.  

NASA Astrophysics Data System (ADS)

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 is covered at two levels. A descriptive narrative integrating both observational data and theoretical models is accessible to undergraduates or non-specialists. In addition, each topic is given a rigorous theoretical development with comparison to observations, and is appropriate for first-year graduate students.

Hartmann, L.

327

Dinoflagellate Cyst Biostratigraphy, Palynofacies and Paleoenvironmental Analysis of the Maastrichtian and Basal Danian, Brazon River, Texas  

E-print Network

in the Prairie Bluff Formation below the K-Pg boundary, including Trithyrodinium evittii (lowest), Palynodinium grallator, Thalassipora pelagica and 33 Table 2. Stratigraphic ranges of palynomorphs in the Brazos River Section. + represent species... in the Prairie Bluff Formation below the K-Pg boundary, including Trithyrodinium evittii (lowest), Palynodinium grallator, Thalassipora pelagica and 33 Table 2. Stratigraphic ranges of palynomorphs in the Brazos River Section. + represent species...

Aydin, Tuba

2013-06-17

328

Chevrons formation in laminar erosion  

NASA Astrophysics Data System (ADS)

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

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

2007-11-01

329

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

330

Signal Formation in Various Detectors  

E-print Network

In this write up we present the general theory of the signal formation in various detectors. We follow a pedagogical analysis and presentation such that the results could easily understood and applied by the interested reader to the different detector configurations. We include few applications to gaseous detectors, namely, Monitored Drift Tubes (MDT) and microstrip pattern detector of the micromegas type.

Manolis Dris; Theo Alexopoulos

2014-06-12

331

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

332

Mechanisms of polymeric film formation.  

PubMed

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

Felton, Linda A

2013-12-01

333

Formation Of Aldehydes During Ozonation  

Microsoft Academic Search

This study investigated the formation of aldehydes after ozonation of three real and three model waters reconstituted from hydrophobic organic material. The four main aldehyde species formaldehyde, acetaldehyde, glyoxal, and methyl glyoxal were analyzed. Formaldehyde was the dominant species formed as a result of ozonation. The different waters varied greatly with respect to aldehyde production under similar treatment conditions. Studies

Daniel S. Schechter; Philip C. Singer

1995-01-01

334

Cloud formation in substellar atmospheres  

E-print Network

Clouds seem like an every-day experience. But -- do we know how clouds form on brown dwarfs and extra-solar planets? How do they look like? Can we see them? What are they composed of? Cloud formation is an old-fashioned but still outstanding problem for the Earth atmosphere, and it has turned into a challenge for the modelling of brown dwarf and exo-planetary atmospheres. Cloud formation imposes strong feedbacks on the atmospheric structure, not only due to the clouds own opacity, but also due to the depletion of the gas phase, possibly leaving behind a dynamic and still supersaturated atmosphere. I summarise the different approaches taken to model cloud formation in substellar atmospheres and workout their differences. Focusing on the phase-non-equilibrium approach to cloud formation, I demonstrate the inside we gain from detailed micro-physical modelling on for instance the material composition and grain size distribution inside the cloud layer on a Brown Dwarf atmosphere. A comparison study on four different cloud approaches in Brown Dwarf atmosphere simulations demonstrates possible uncertainties in interpretation of observational data.

Christiane Helling

2008-09-26

335

Cloud Formation, Evolution and Destruction  

E-print Network

Chapter 4 Cloud Formation, Evolution and Destruction We now begin to trace the journey towards a star. How long does this take? The answer is surprisingly short: a good many clouds already contain new stars and these stars tend to be young. The typical cloud cannot spend long, if any time at all

Estalella, Robert

336

Audiences for Contemporary Radio Formats.  

ERIC Educational Resources Information Center

A radio audience survey of 110 sample geographic clusters in the Santa Barbara, California, area served a twofold purpose: the construction of a demographic profile of audience types according to radio format choices, and the identification and analysis of various audience subgroups. A skip interval technique of these geographic clusters resulted…

Lull, James T.; And Others

337

Brain gangliosides and memory formation  

Microsoft Academic Search

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

Hinrich Rahmann

1995-01-01

338

Biofilm formation in Streptococcus pneumoniae  

PubMed Central

Summary Biofilm?grown bacteria are refractory to antimicrobial agents and show an increased capacity to evade the host immune system. In recent years, studies have begun on biofilm formation by Streptococcus pneumoniae, an important human pathogen, using a variety of in vitro model systems. The bacterial cells in these biofilms are held together by an extracellular matrix composed of DNA, proteins and, possibly, polysaccharide(s). Although neither the precise nature of these proteins nor the composition of the putative polysaccharide(s) is clear, it is known that choline?binding proteins are required for successful biofilm formation. Further, many genes appear to be involved, although the role of each appears to vary when biofilms are produced in batch or continuous culture. Prophylactic and therapeutic measures need to be developed to fight S.?pneumoniae biofilm formation. However, much care needs to be taken when choosing strains for such studies because different S.?pneumoniae isolates can show remarkable genomic differences. Multispecies and in vivo biofilm models must also be developed to provide a more complete understanding of biofilm formation and maintenance. PMID:21906265

Domenech, Mirian; Garcia, Ernesto; Moscoso, Miriam

2012-01-01

339

Reflexive Expectation Formation Timo Ehrig  

E-print Network

Reflexive Expectation Formation Timo Ehrig J¨urgen Jost Abstract How do economic agents form expectations regarding asset prices and the development of macroeconomic quantities, when of expectations fold back to the realized economic process, and in particular, to the selection of one of multiple

Jost, Jürgen

340

Stereotype Formation: Biased by Association  

ERIC Educational Resources Information Center

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

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

2010-01-01

341

The Theory of Planetary Formation  

NSDL National Science Digital Library

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

Cassen, Patrick

2005-04-25

342

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

343

Machining -Chip Formation, Cutting Fluids,  

E-print Network

) continuous chip with large primary shear zone; (d) continuous chip with built-up edge; (e) segmented Discontinuous Continuous Catastrophic 50 100 Built-up edge Chip Shear localized hi Catastrophic shear Complete Prof. J.S. Colton © GIT 2009 10 ­ cracks extend into workpiece #12;Formation of Built up Edge (BUE

Colton, Jonathan S.

344

INTRAMURAL SOCCER RULES League Format  

E-print Network

INTRAMURAL SOCCER RULES League Format All players must complete the Sportsmanship Agreement soccer shoes or non-marking sneakers. Referees The authority of the referees starts upon entering. The team calling the time-out can only do so when their goalkeeper has control of the ball in his/her hands

Paulsson, Johan

345

Formation of the Giant Planets  

Microsoft Academic Search

The structure of a gaseous envelope surrounding a protoplanet has been investigated in connection with the formation of the giant planets. Under the assumptions of spherical symmetry and hydrostatic equilibrium, the structure has been calculated for the regions of Jupiter, Saturn, Uranus and Neptune. Energy transfer in the envelope has been taken into account precisely. When the core mass increases

Hiroshi Mizuno

1980-01-01

346

Informatique Nature de la formation  

E-print Network

opérationnelle, recouvrant ainsi tous les grands domaines de l'Informatique : Algorithmique et Programmation, les structures de données, les bases de données Simuler, expliquer un programme informatique, etInformatique Nature de la formation : Diplôme national de l'Enseignement Supérieur Durée des études

Sart, Remi

347

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

348

Heteronuclear Diatomic Molecular Orbital Formation  

NSDL National Science Digital Library

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

349

The formation of the Galaxy  

Microsoft Academic Search

A simple 'bottom-up' galaxy formation picture is discussed in which the Galaxy fits comfortably as the product of the collapse of material around an average density peak of somewhat less than three sigma amplitude in an initial density field with statistics similar to those expected in the cold dark matter\\/inflation scenario. The model, with the amplitude as the only adjustable

James E. Gunn

1987-01-01

350

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). ...

351

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

352

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

353

Mechanisms of plant spindle formation.  

PubMed

In eukaryotes, the formation of a bipolar spindle is necessary for the equal segregation of chromosomes to daughter cells. Chromosomes, microtubules and kinetochores all contribute to spindle morphogenesis and have important roles during mitosis. A unique property of flowering plant cells is that they entirely lack centrosomes, which in animals have a major role in spindle formation. The absence of these important structures suggests that plants have evolved novel mechanisms to assure chromosome segregation. In this review, we highlight some of the recent studies on plant mitosis and argue that plants utilize a variation of "spindle self-organization" that takes advantage of the early polarity of plant cells and accentuates the role of kinetochores in stabilizing the spindle midzone in prometaphase. PMID:21424324

Zhang, Han; Dawe, R Kelly

2011-04-01

354

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

355

Engineering biofilm formation and dispersal  

PubMed Central

Anywhere water is in the liquid state, bacteria will exist as biofilms, which are complex communities of cells cemented together. Although frequently associated with disease and biofouling, biofilms are also important for engineering applications, such as bioremediation, biocatalysis and microbial fuel cells. Here we review approaches to alter genetic circuits and cell signaling toward controlling biofilm formation, and emphasize utilizing these tools for engineering applications. Based on a better understanding of the genetic basis of biofilm formation, we find that biofilms may be controlled by manipulating extracellular signals and that they may be dispersed using conserved intracellular signals and regulators. Biofilms could also be formed at specific locations where they might be engineered to make chemicals or treat human disease. PMID:21131080

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

2011-01-01

356

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

357

Hydrodynamics of catheter biofilm formation  

E-print Network

A hydrodynamic model is proposed to describe one of the most critical problems in intensive medical care units: the formation of biofilms inside central venous catheters. The incorporation of approximate solutions for the flow-limited diffusion equation leads to the conclusion that biofilms grow on the internal catheter wall due to the counter-stream diffusion of blood through a very thin layer close to the wall. This biological deposition is the first necessary step for the subsequent bacteria colonization.

Sotolongo-Costa, Oscar; Rodriguez-Perez, Daniel; Martinez-Escobar, Sergio; Fernandez-Barbero, Antonio

2009-01-01

358

Protein engineering of formate dehydrogenase  

Microsoft Academic Search

NAD+-dependent formate dehydrogenase (FDH, EC 1.2.1.2) is one of the best enzymes for the purpose of NADH regeneration in dehydrogenase-based synthesis of optically active compounds. Low operational stability and high production cost of native FDHs limit their application in commercial production of chiral compounds. The review summarizes the results on engineering of bacterial and yeast FDHs aimed at improving their

Vladimir I. Tishkov; Vladimir O. Popov

2006-01-01

359

Contrail formation in aircraft wakes  

Microsoft Academic Search

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

Roberto Paoli; Jerome Hélie; Thierry Poinsot

2004-01-01

360

Kinetic models of opinion formation  

E-print Network

We introduce and discuss certain kinetic models of (continuous) opinion formation involving both exchange of opinion between individual agents and diffusion of information. We show conditions which ensure that the kinetic model reaches non trivial stationary states in case of lack of diffusion in correspondence of some opinion point. Analytical results are then obtained by considering a suitable asymptotic limit of the model yielding a Fokker-Planck equation for the distribution of opinion among individuals.

G. Toscani

2006-05-17

361

Pyrazines: occurrence, formation and biodegradation  

Microsoft Academic Search

Pyrazines are a class of compounds that occur almost ubiquitously in nature. Pyrazines can be synthesised chemically or biologically,\\u000a and are used as flavouring additives. The major formation of pyrazines occurs during heating of food. There is very little\\u000a information available on the degradation of these compounds. In humans and animals, pyrazines are excreted as glucuronates\\u000a or bound to glutathione

Rudolf Müller; Sugima Rappert

2010-01-01

362

Photophoresis boosts giant planet formation  

NASA Astrophysics Data System (ADS)

In the core accretion model of giant planet formation, a solid protoplanetary core begins to accrete gas directly from the nebula when its mass reaches ~5 M?. The protoplanet has at most a few million years to reach runaway gas accretion, as young stars lose their gas disks after 10 million years at the latest. Yet gas accretion also brings small dust grains entrained in the gas into the planetary atmosphere. Dust accretion creates an optically thick protoplanetary atmosphere that cannot efficiently radiate away the kinetic energy deposited by incoming planetesimals. A dust-rich atmosphere severely slows down atmospheric cooling, contraction, and inflow of new gas, in contradiction to the observed timescales of planet formation. Here we show that photophoresis is a strong mechanism for pushing dust out of the planetary atmosphere due to the momentum exchange between gas and dust grains. The thermal radiation from the heated inner atmosphere and core is sufficient to levitate dust grains and to push them outward. Photophoresis can significantly accelerate the formation of giant planets.

Teiser, J.; Dodson-Robinson, S. E.

2013-07-01

363

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

364

SCALE FORMATION IN CHRYSOPHYCEAN ALGAE  

PubMed Central

The cell wall of the marine chrysophycean alga Pleurochrysis scherfellii is composed of distinct wall fragments embedded in a gelatinous mass. The latter is a polysaccharide of pectic character which is rich in galactose and ribose. These wall fragments are identified as scales. They have been isolated and purified from the vegetative mother cell walls after zoospore formation. Their ultrastructure is described in an electron microscope study combining sectioning, freeze-etch, and negative staining techniques. The scales consist of a layer of concentrically arranged microfibrils (ribbons with cross-sections of 12 to 25 x 25 to 40 A) and underlying radial fibrils of similar dimensions. Such a network-plate is densely coated with particles which are assumed to be identical to the pectic component. The microfibrils are resistant to strong alkaline treatment and have been identified as cellulose by different methods, including sugar analysis after total hydrolysis, proton resonance spectroscopical examination (NMR spectroscopy) of the benzoylated product, and diverse histochemical tests. The formation and secretion of the scales can be followed along the maturing Golgi cisternae starting from a pronounced dilated "polymerization center" as a completely intracisternal process which ends in the exocytotic extrusion of the scales. The scales reveal the very same ultrastructure within the Golgi cisternae as they do in the cell wall. The present finding represents the first evidence on cellulose formation by the Golgi apparatus and is discussed in relation to a basic scheme for cellulose synthesis in plant cells in general. PMID:5513606

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

1970-01-01

365

The Formation of Close Binaries  

NASA Astrophysics Data System (ADS)

Binary stars produce an array of dramatic astrophysical phenomena. They allow us to probe stellar structure, nuclear physics, and gravitational wave physics. They also produce the powerful supernovae that allow us to measure the scale of the universe. Despite their importance and ubiquity, many questions remain unanswered as to how the star formation process produces the wide array of stellar multiples that we observe. A complete model for binary formation encompasses three main components. We must know: (1) the primordial population of systems, (2) the influence of the dynamical processes that reshape this distribution as stars form and natal clusters disperse, and (3) the role of binary stellar evolution. In this article, I review the most prominent theories for binary formation: turbulent core fragmentation, disc fragmentation, and competitive accretion. I argue that turbulent core fragmentation at all masses, with disc fragmentation added in at the upper end of the mass spectrum, might explain the trend towards increasing multiplicity for higher mass stars. In addition, I provide a brief overview of the observational statistics and of some of the important processes that modify the primordial distribution of stellar orbits.

Kratter, K. M.

2011-09-01

366

Gravity, Turbulence, and Star Formation  

NASA Astrophysics Data System (ADS)

The azimuthal power spectra of optical emission from star formation and dust in spiral galaxies resembles the azimuthal power spectra of HI emission from the LMC. These and other power spectra of whole galaxies all resemble that of velocity in incompressible Kolmogorov turbulence. The reasons for this are unknown but it could be simply that star and cloud formation are the result of a mixture of processes and each gives a power spectrum similar to Kolmogorov turbulence, within the observable errors. The important point is that star and cloud formation are not random but are correlated over large distances by forces that span several orders of magnitude in scale. These forces are probably the usual combination of self-gravity, turbulence, and compression from stellar winds and supernovae, but they have to work in concert to create the structures we see in galaxies. In addition, the identification of flocculant spirals with swing amplified instabilities opens the possibility that a high fraction of turbulence in the ISM is the result of self-gravity.

Elmegreen, B.

2004-12-01

367

Formation of Outer Planets: Overview  

NASA Technical Reports Server (NTRS)

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

Lissauer, Jack

2003-01-01

368

Calibration For Augmented Reality Experimental Testbeds Valerie A. Summers*& Kellogg S. Booth Tom Calvert  

E-print Network

Calibration For Augmented Reality Experimental Testbeds Valerie A. Summers*& Kellogg S. Booth Tom.3.7[ComputerGraphics]: Three-Dimensional GraphicsandRealism-virtual reality Keywords: augmentedreality "augment" theuser's view of thereal 3D world with computer-generatedvirtual objects. Thesevirtual

369

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

NASA Astrophysics Data System (ADS)

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

Vogt, Peter R.

1991-07-01

370

Formation mechanisms of metal colloids  

NASA Astrophysics Data System (ADS)

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

Halaciuga, Ionel

371

Core formation in silicate bodies  

NASA Astrophysics Data System (ADS)

Differentiation of a body into a metallic core and silicate mantle occurs most efficiently if temperatures are high enough to allow at least the metal to melt [1], and is enhanced if matrix deformation occurs [2]. Elevated temperatures may occur due to either decay of short-lived radio-isotopes, or gravitational energy release during accretion [3]. For bodies smaller than the Moon, core formation happens primarily due to radioactive decay. The Hf-W isotopic system may be used to date core formation; cores in some iron meteorites and the eucrite parent body (probably Vesta) formed within 1 My and 1-4~My of solar system formation, respectively [4]. These formation times are early enough to ensure widespread melting and differentiation by 26Al decay. Incorporation of Fe60 into the core, together with rapid early mantle solidification and cooling, may have driven early dynamo activity on some bodies [5]. Iron meteorites are typically depleted in sulphur relative to chondrites, for unknown reasons [6]. This depletion contrasts with the apparently higher sulphur contents of cores in larger planetary bodies, such as Mars [7], and also has a significant effect on the timing of core solidification. For bodies of Moon-size and larger, gravitational energy released during accretion is probably the primary cause of core formation [3]. The final stages of accretion involve large, stochastic collisions [8] between objects which are already differentiated. During each collision, the metallic cores of the colliding objects merge on timescales of a few hours [9]. Each collision will reset the Hf-W isotopic signature of both mantle and core, depending on the degree to which the impactor core re-equilibrates with the mantle of the target [10]. The re-equilibration efficiency depends mainly on the degree to which the impactor emulsifies [11], which is very uncertain. Results from N-body simulations [8,12] suggest that significant degrees of re- equilibration are required [4,10]. Re-equilibration is also suggested by mantle siderophile abundances [13], though simple partitioning models do not capture the likely complex P,T evolution during successive giant impacts. The timescale of Martian core formation is currently uncertain (0-10 My) [14], though it is clear that Martian core formation ended before that of the Earth. [1] Stevenson, in Origin of the Earth, 1990. [2] Groebner and Kohlstedt, EPSL 2006. [3] Rubie et al., Treatise Geophys. 2007. [4] Kleine et al., GCA submitted. [5] Weiss et al., LPSC 39, 2008. [6] Keil and Wilson, EPSL 1993 [7] Wanke and Dreibus, PTRSL, 1984. [8] Agnor et al. Icarus 1999 [9] Canup and Asphaug, Nature 2001 [10] Nimmo and Agnor, EPSL 2006. [11] Rubie et al., EPSL 2003 [12] O'Brien et al, Icarus 2006 [13] Righter, AREPS 2003. [14] Nimmo and Kleine, Icarus 2007.

Nimmo, F.; O'Brien, D. P.; Kleine, T.

2008-12-01

372

Process for stabilizing rock and coal formations by bonding these formations to themselves or other geological formations  

Microsoft Academic Search

The invention relates to a process for stabilizing rock and coal formations by bonding them to each other or to other geological formations. The bonding material is a reactive organic polyisocyanate-polyol mixture which may contain a catalyst.

D. Arndt; D. Hobein

1984-01-01

373

On-Going Galaxy Formation  

NASA Astrophysics Data System (ADS)

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

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

2002-07-01

374

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

375

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

376

Formation Flying and Deformable Instruments  

SciTech Connect

Astronomers have always attempted to build very stable instruments. They fight all that can cause mechanical deformation or image motion. This has led to well established technologies (autoguide, active optics, thermal control, tip/tilt correction), as well as observing methods based on the use of controlled motion (scanning, micro scanning, shift and add, chopping and nodding). Formation flying disturbs this practice. It is neither possible to reduce the relative motion to very small amplitudes, nor to control it at will. Some impacts on Simbol-X instrument design, and operation are presented.

Rio, Yvon [CEA/IRFU/Sap, CEA Saclay, 91191 Gif sur Yvette (France)

2009-05-11

377

Formation Flying and Deformable Instruments  

NASA Astrophysics Data System (ADS)

Astronomers have always attempted to build very stable instruments. They fight all that can cause mechanical deformation or image motion. This has led to well established technologies (autoguide, active optics, thermal control, tip/tilt correction), as well as observing methods based on the use of controlled motion (scanning, micro scanning, shift and add, chopping and nodding). Formation flying disturbs this practice. It is neither possible to reduce the relative motion to very small amplitudes, nor to control it at will. Some impacts on Simbol-X instrument design, and operation are presented.

Rio, Yvon

2009-05-01

378

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

379

Biomimetic stereoselective formation of methyllanthionine.  

PubMed

Fmoc-(2R,3S)-3-methyl-Se-phenylselenocysteine was used for the synthesis of dehydrobutyrine (Dhb)-containing peptides. Biomimetic cyclization via Michael addition of Cys to a Dhb yielded the B-ring of the lantibiotic subtilin as a single diastereomer. The methyllanthionine product was shown to have the natural configuration by preparation of the authentic stereoisomer. The formation of a single isomer suggests that the prepeptide has a strong intrinsic preference for the stereochemistry observed in lantibiotics. [reaction: see text] PMID:11950356

Zhou, Hao; van der Donk, Wilfred A

2002-04-18

380

Percolation-induced frost formation  

NASA Astrophysics Data System (ADS)

We report the observation of an unconventional mechanism for frost formation. On a smooth hydrophobic surface cooled much below the water freezing temperature (-9 °C), we find that, instead of the classical freezing of individual supercooled condensed droplets, frost can occur through a multi-step 2-dimensional percolation-driven mechanism. This in-plane propagation process provides a model to investigate more complex bulk phase transformations such as those occurring in atmospheric supercooled clouds. It can also lead to a new method to control and design in-plane solidification at a nanoscale level.

Guadarrama-Cetina, J.; Mongruel, A.; González-Viñas, W.; Beysens, D.

2013-01-01

381

Dark Matter and Galaxy Formation  

E-print Network

Abstract. The four lectures that I gave in the XIII Ciclo de Cursos Especiais at the National Observatory of Brazil in Rio in October 2008 were (1) a brief history of dark matter and structure formation in a ?CDM universe; (2) challenges to ?CDM on small scales: satellites, cusps, and disks; (3) data on galaxy evolution and clustering compared with simulations; and (4) semi-analytic models. These lectures, themselves summaries of much work by many people, are summarized here briefly. The slides [1] contain much more information.

Joel R. Primack A

382

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

383

Transcriptional regulation in wood formation.  

PubMed

Wood (i.e. xylem tissue) in trees is mainly composed of two types of cells, fibres and tracheary elements. Recent molecular studies of various trees, as well as the non-tree species Arabidopsis thaliana and Zinnia elegans, have revealed coordinated gene expression during differentiation of these cells in wood and the presence of several transcription factors that might govern the complex networks of transcriptional regulation. This article reviews recent findings concerning the regulation of genes by transcription factors involved in wood formation such as AUXIN RESPONSE FACTOR (ARF), CLASS III HOMEODOMAIN-LEUCINE ZIPPER (HD-ZIPIII), KANADI (KAN), MYB and NAM/ATAF/CUC (NAC). PMID:17224301

Demura, Taku; Fukuda, Hiroo

2007-02-01

384

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

385

Electrochemical formation of field emitters  

DOEpatents

Electrochemical formation of field emitters, particularly useful in the fabrication of flat panel displays. 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.

Bernhardt, Anthony F. (Berkeley, CA)

1999-01-01

386

49 CFR 563.8 - Data format.  

Code of Federal Regulations, 2011 CFR

...Transportation 6 2011-10-01 2011-10-01 false Data format. 563.8 Section 563.8 Transportation...ADMINISTRATION, DEPARTMENT OF TRANSPORTATION EVENT DATA RECORDERS § 563.8 Data format. Link to an amendment published at...

2011-10-01

387

49 CFR 563.8 - Data format  

Code of Federal Regulations, 2010 CFR

...Transportation 6 2010-10-01 2010-10-01 false Data format 563.8 Section 563.8 Transportation...ADMINISTRATION, DEPARTMENT OF TRANSPORTATION EVENT DATA RECORDERS § 563.8 Data format (a) The data elements listed in...

2010-10-01

388

49 CFR 563.8 - Data format.  

Code of Federal Regulations, 2013 CFR

...Transportation 6 2013-10-01 2013-10-01 false Data format. 563.8 Section 563.8 Transportation...ADMINISTRATION, DEPARTMENT OF TRANSPORTATION EVENT DATA RECORDERS § 563.8 Data format. (a) The data elements listed...

2013-10-01

389

Formation of the terrestrial planets from planetesimals  

NASA Technical Reports Server (NTRS)

Formation of the terrestrial planets from planetesimals is discussed. The following subject areas are covered: (1) formation of the original planetesimals; (2) growth of planetesimals into planetary embryos; and (3) growth of runaway planetary embryos into terrestrial planets.

Wetherill, George W.

1991-01-01

390

XML Format for SESAME and LEOS  

SciTech Connect

The objective of this document is to describe the XML format used by LLNL and LANL to represent the equation-of-state and related material information in the LEOS and SESAME data libraries. The primary purpose of this document is to describe a specific XML format for representing EOS data that is tailored to the nature of the underlying data and is amenable to conversion to both legacy SESAME and LEOS binary formats. The secondary purpose is to describe an XML format that lends itself to a 'natural' representation in a binary file format of the SESAME, pdb or hdf5 form so that this format and related tools can be used for the rapid and efficient development and implementation of prototype data structures. This document describes the XML format only. A working knowledge of LEOS and SESAME formats is assumed.

Durrenberger, J K; Neely, J R; Sterne, P A

2009-04-29

391

Formation damage in underbalanced drilling operations  

E-print Network

Formation damage has long been recognized as a potential source of reduced productivity and injectivity in both horizontal and vertical wells. From the moment that the pay zone is being drilled until the well is put on production, a formation...

Reyes Serpa, Carlos Alberto

2012-06-07

392

48 CFR 1315.204 - Contract format.  

Code of Federal Regulations, 2010 CFR

... CONTRACTING BY NEGOTIATION Solicitation and Receipt of Proposals and Information 1315.204 Contract format. The designee authorized to grant exemptions from the uniform contract format is set forth in CAM...

2010-10-01

393

48 CFR 1315.204 - Contract format.  

Code of Federal Regulations, 2011 CFR

... CONTRACTING BY NEGOTIATION Solicitation and Receipt of Proposals and Information 1315.204 Contract format. The designee authorized to grant exemptions from the uniform contract format is set forth in CAM...

2011-10-01

394

29 CFR 1960.38 - Committee formation.  

Code of Federal Regulations, 2012 CFR

... 2012-07-01 false Committee formation. 1960.38 Section 1960.38 Labor Regulations Relating to Labor (Continued...MATTERS Occupational Safety and Health Committees § 1960.38 Committee formation. (a) Upon...

2012-07-01

395

29 CFR 1960.38 - Committee formation.  

Code of Federal Regulations, 2011 CFR

... 2011-07-01 false Committee formation. 1960.38 Section 1960.38 Labor Regulations Relating to Labor (Continued...MATTERS Occupational Safety and Health Committees § 1960.38 Committee formation. (a) Upon...

2011-07-01

396

29 CFR 1960.38 - Committee formation.  

Code of Federal Regulations, 2010 CFR

... 2010-07-01 false Committee formation. 1960.38 Section 1960.38 Labor Regulations Relating to Labor (Continued...MATTERS Occupational Safety and Health Committees § 1960.38 Committee formation. (a) Upon...

2010-07-01

397

Dynamics and control of electromagnetic satellite formations  

E-print Network

Satellite formation flying is an enabling technology for many space missions, especially for space-based telescopes. Usually there is a tight formation-keeping requirement that may need constant expenditure of fuel or at ...

Ahsun, Umair, 1972-

2007-01-01

398

Structure formation: Models, Dynamics and Status  

E-print Network

The constraints on the models for the structure formation arising from various cosmological observations at different length scales are reviewed. The status of different models for structure formation is examined critically in the light of these observations.

T. Padmanabhan

1995-08-25

399

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.

400

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

401

Beaver assisted river valley formation  

USGS Publications Warehouse

We examined how beaver dams affect key ecosystem processes, including pattern and process of sediment deposition, the composition and spatial pattern of vegetation, and nutrient loading and processing. We provide new evidence for the formation of heterogeneous beaver meadows on riverine system floodplains and terraces where dynamic flows are capable of breaching in-channel beaver dams. Our data show a 1.7-m high beaver dam triggered overbank flooding that drowned vegetation in areas deeply flooded, deposited nutrient-rich sediment in a spatially heterogeneous pattern on the floodplain and terrace, and scoured soils in other areas. The site quickly de-watered following the dam breach by high stream flows, protecting the deposited sediment from future re-mobilization by overbank floods. Bare sediment either exposed by scouring or deposited by the beaver flood was quickly colonized by a spatially heterogeneous plant community, forming a beaver meadow. Many willow and some aspen seedlings established in the more heavily disturbed areas, suggesting the site may succeed to a willow carr plant community suitable for future beaver re-occupation. We expand existing theory beyond the beaver pond to include terraces within valleys. This more fully explains how beavers can help drive the formation of alluvial valleys and their complex vegetation patterns as was first postulated by Ruedemann and Schoonmaker in 1938. ?? 2010 John Wiley & Sons, Ltd.

Westbrook, C.J.; Cooper, D.J.; Baker, B.W.

2011-01-01

402

Possible mechanisms of macrolayer formation  

SciTech Connect

The high heat flux nucleate boiling region, also called the vapor mushroom region, has been shown to have a thin liquid layer on the heater surface under the large mushroom-shaped vapor bubbles that grow from the heater surface. The name given to this liquid layer is the macrolayer to differentiate it from the microlayer that exists under the discrete bubbles found at lower heat fluxes in the nucleate boiling region. Typical thicknesses of this macrolayer range from 50 to 500 {mu}m for water on a flat horizontal boiling surface and depend upon the heat flux. Thus, the macrolayer is thicker than the wedge-shaped microlayers, found under discrete bubbles, which range in thickness from 1 to 10 {mu}m. Although the mechanism of microlayer formation and its evaporation is conceptually simple that of the macrolayer is still not understood. This paper critically compares the potential mechanisms proposed for macrolayer formation. These mechanisms include the Helmholtz instability applied to the vapor stem above active nucleation sites, liquid trapped by lateral coalescence of discrete bubbles that initially form during the mushroom bubble`s waiting period, and the limitation of liquid resupply at mushroom departure as a result of vapor flow from the active nucleation sites.

Sadasivan, P.; Chappidi, P.R.; Unal, C.; Nelson, R.A.

1992-05-01

403

Possible mechanisms of macrolayer formation  

SciTech Connect

The high heat flux nucleate boiling region, also called the vapor mushroom region, has been shown to have a thin liquid layer on the heater surface under the large mushroom-shaped vapor bubbles that grow from the heater surface. The name given to this liquid layer is the macrolayer to differentiate it from the microlayer that exists under the discrete bubbles found at lower heat fluxes in the nucleate boiling region. Typical thicknesses of this macrolayer range from 50 to 500 {mu}m for water on a flat horizontal boiling surface and depend upon the heat flux. Thus, the macrolayer is thicker than the wedge-shaped microlayers, found under discrete bubbles, which range in thickness from 1 to 10 {mu}m. Although the mechanism of microlayer formation and its evaporation is conceptually simple that of the macrolayer is still not understood. This paper critically compares the potential mechanisms proposed for macrolayer formation. These mechanisms include the Helmholtz instability applied to the vapor stem above active nucleation sites, liquid trapped by lateral coalescence of discrete bubbles that initially form during the mushroom bubble's waiting period, and the limitation of liquid resupply at mushroom departure as a result of vapor flow from the active nucleation sites.

Sadasivan, P.; Chappidi, P.R.; Unal, C.; Nelson, R.A.

1992-01-01

404

Tube Formation in Nanoscale Materials  

PubMed Central

The formation of tubular nanostructures normally requires layered, anisotropic, or pseudo-layered crystal structures, while inorganic compounds typically do not possess such structures, inorganic nanotubes thus have been a hot topic in the past decade. In this article, we review recent research activities on nanotubes fabrication and focus on three novel synthetic strategies for generating nanotubes from inorganic materials that do not have a layered structure. Specifically, thermal oxidation method based on gas–solid reaction to porous CuO nanotubes has been successfully established, semiconductor ZnS and Nb2O5nanotubes have been prepared by employing sacrificial template strategy based on liquid–solid reaction, and an in situ template method has been developed for the preparation of ZnO taper tubes through a chemical etching reaction. We have described the nanotube formation processes and illustrated the detailed key factors during their growth. The proposed mechanisms are presented for nanotube fabrication and the important pioneering studies are discussed on the rational design and fabrication of functional materials with tubular structures. It is the intention of this contribution to provide a brief account of these research activities. PMID:20592945

2008-01-01

405

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

406

Globular Cluster Formation in Mergers  

E-print Network

Mergers of gas-rich galaxies lead to gravitationally driven increases in gas pressure that can trigger intense bursts of star and cluster formation. Although star formation itself is clustered, most newborn stellar aggregates are unbound associations and disperse. Gravitationally bound star clusters that survive for at least 10-20 internal crossing times (~20-40 Myr) are relatively rare and seem to contain <10% of all stars formed in the starbursts. The most massive young globular clusters formed in present-day mergers exceed omega Cen by an order of magnitude in mass, yet appear to have normal stellar initial mass functions. In the local universe, recent remnants of major gas-rich disk mergers appear as protoelliptical galaxies with subpopulations of typically 100-1000 young metal-rich globular clusters in their halos. The evidence is now strong that these "second-generation" globular clusters formed from giant molecular clouds in the merging disks, squeezed into collapse by large-scale shocks and high gas pressure rather than by high-velocity cloud-cloud collisions. Similarly, first- generation metal-poor globular clusters may have formed during cosmological reionization from low-metallicity giant molecular clouds squeezed by the universal reionization pressure.

Francois Schweizer

2006-06-01

407

Cooper Pair Formation in Acenes  

NASA Astrophysics Data System (ADS)

We have measured the ratio of doubly to singly charged molecular parent ions of benzene, naphthalene, anthracene, and pyrrole over a wide range of photon energies. About 40 eV above the double-ionization threshold, the first three of the above molecules exhibit a hump of very similar shape and magnitude in the double-to-single photoionization ratio, which we attribute to the formation and emission of an electron Cooper pair from a free molecule. Our results suggest that the de Broglie wave of this highly correlated pair of electrons forms a closed loop in the system of overlapping ? bonds with a wavelength that matches the distance between neighboring carbon atoms. Pyrrole with its pentagonal structure does not allow the formation of a closed de Broglie wave and, thus, does not exhibit a hump in the ratio. Photoelectron measurements indicate the break-up of the emitted Cooper pair by two electron peaks sitting on top of the mainly U-shaped double-ionization continuum in support of our interpretation.

Hartman, Tim; Jurani?, Pavle; Collins, Kelly; Reilly, Bethany; Appathurai, Narayana; Whitfield, Scott B.; Wehlitz, Ralf

2012-06-01

408

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

409

Dilatational band formation in bone  

PubMed Central

Toughening in hierarchically structured materials like bone arises from the arrangement of constituent material elements and their interactions. Unlike microcracking, which entails micrometer-level separation, there is no known evidence of fracture at the level of bone’s nanostructure. Here, we show that the initiation of fracture occurs in bone at the nanometer scale by dilatational bands. Through fatigue and indentation tests and laser confocal, scanning electron, and atomic force microscopies on human and bovine bone specimens, we established that dilatational bands of the order of 100 nm form as ellipsoidal voids in between fused mineral aggregates and two adjacent proteins, osteocalcin (OC) and osteopontin (OPN). Laser microdissection and ELISA of bone microdamage support our claim that OC and OPN colocalize with dilatational bands. Fracture tests on bones from OC and/or OPN knockout mice (OC?/?, OPN?/?, OC-OPN?/?;?/?) confirm that these two proteins regulate dilatational band formation and bone matrix toughness. On the basis of these observations, we propose molecular deformation and fracture mechanics models, illustrating the role of OC and OPN in dilatational band formation, and predict that the nanometer scale of tissue organization, associated with dilatational bands, affects fracture at higher scales and determines fracture toughness of bone. PMID:23129653

Poundarik, Atharva A.; Diab, Tamim; Sroga, Grazyna E.; Ural, Ani; Boskey, Adele L.; Gundberg, Caren M.; Vashishth, Deepak

2012-01-01

410

String Formatting Considered Harmful for Novice Programmers  

ERIC Educational Resources Information Center

In Java, "System.out.printf" and "String.format" consume a specialised kind of string commonly known as a format string. In our study of first-year students at the Ateneo de Manila University, we discovered that format strings present a substantial challenge for novice programmers. Focusing on their first laboratory we found that 8% of all the…

Hughes, Michael C.; Jadud, Matthew C.; Rodrigo, Ma. Mercedes T.

2010-01-01

411

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

412

FAINT RADIO SOURCES AND STAR FORMATION HISTORY  

E-print Network

FAINT RADIO SOURCES AND STAR FORMATION HISTORY Deborah B. Haarsma 1 , R. Bruce Partridge 1 , Ian the global history of star formation. Sensitive radio observations of the Hubble Deep Field and other fields important information about global star formation history. Sensitive radio observations of the Hubble Deep

Waddington, Ian

413

Cyclic Steam Stimulation With Formation Parting  

Microsoft Academic Search

Cyclic steam stimulation in highly viscous oil-bearing formations, such as those of Cold Lake, entails formation parting in many cases. This work presents a numeric treatment of the phenomena involved in this process, viz., fluid flow in cyclic steam stimulation, formation parting, fracture propagation, and closure. The latter part of the model involves the calculation of stresses and strains in

S. M. Farouq. Ali; J. Blunschi

1983-01-01

414

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.

415

Formative Constructs Implemented via Common Factors  

ERIC Educational Resources Information Center

Recently there has been a renewed interest in formative measurement and its role in properly specified models. Formative measurement models are difficult to identify, and hence to estimate and test. Existing solutions to the identification problem are shown to not adequately represent the formative constructs of interest. We propose a new two-step…

Treiblmaier, Horst; Bentler, Peter M.; Mair, Patrick

2011-01-01

416

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

417

Genome organization and species formation in vertebrates  

Microsoft Academic Search

Some years ago Wilson and co-workers proposed that the higher rates of karyotypic change and species formation of mammals compared to cold-blooded vertebrates are due to the formation of small demes, as favored by the social structuring and brain development of the former. Here, evidence is reviewed which indicates that mammals are more prone to karyotypic change and species formation

Giorgio Bernardi

1993-01-01

418

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

419

A new PICL trace file format  

Microsoft Academic Search

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.

P. H. Worley

1992-01-01

420

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

421

Experimental adipocere formation: implications for adipocere formation on buried bone.  

PubMed

Adipocere, or grave wax (adipo = fat, cere = wax), is a distinctive decomposition product composed primarily of fatty acids (FA) and their alkali salts. FA result from the bacterial enzymatic hydrolysis of body fats. Reactions with ammonia and alkali metals originating from body fluids and pore waters of the depositional environment produce alkali salts of FA (soap). Adipocere formation is generally associated with burial of corpses with ample adipose tissue available. No indications that adipocere can form on defleshed remains have been presented in the literature. At the termination of a long-term bone diagenesis experiment, several samples were found to possess growths of an unknown compound. Gas chromatography-mass spectrometry confirmed that the growths are adipocere. The results herein reveal that adipocere can indeed form on defleshed bones under the right conditions and that even residual adipose and lipids in defleshed bones are sufficient to produce adipocere growth on the surfaces of bone. PMID:22211839

Moses, Randolph J

2012-05-01

422

Early planet formation as a trigger for further planet formation  

E-print Network

Recent discoveries of extrasolar planets at small orbital radii, or with significant eccentricities, indicate that interactions between massive planets and the disks of gas and dust from which they formed are vital for determining the final shape of planetary systems. We show that if this interaction occurs at an early epoch, when the protoplanetary disc was still massive, then rapid planet growth through accretion causes an otherwise stable disc to fragment into additional planetary mass bodies when the planetary mass reaches 4-5 Jupiter masses. We suggest that such catastrophic planet formation could account for apparent differences in the mass function of massive planets and brown dwarfs, and the existence of young stars that appear to have dissipated their discs at an early epoch. Subsequent gravitational interactions will lead to planetary systems comprising a small number of massive planets in eccentric orbits.

Philip J. Armitage; Brad M. S. Hansen

1999-12-08

423

Evidence of Active Warm Based Neogene Glaciation in the Transantarctic Mountains  

Microsoft Academic Search

Interbedded diamictites, conglomerates, sandstones, and siltstones in the Meyer Desert Formation of the Transantarctic Mountains record a dynamic history of warm-based glacier advances and retreats during Neogene time. The Oliver Bluffs (85\\\\deg 80'S, 166\\\\deg 83'E) consist of near-vertical bluffs up to 85 m high that extend for 2 km along the flank of the Beardmore Glacier and reveal at least

S. R. Roof; A. C. Ashworth; D. J. Cantrill; J. E. Francis

2004-01-01

424

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

425

Reversible in situ catalyst formation.  

PubMed

Acid catalysts play a vital role in the industrial synthesis and production of a plethora of organic chemicals. But, their subsequent neutralization and disposal is also a giant source of waste. For example, for a Friedel-Crafts acylation with AlCl 3, a kilogram of product yields up to 20 kg of (contaminated) waste salt. Other processes are even worse, and this waste is both an environmental and economic shortcoming. Here we address this issue by showing a series of acid catalysts where the neutralization is "built in" to the system and thus eliminates waste. Clearly these will not replace all organic and mineral acid catalysts, but they can replace many. Further, we show how these self-neutralizing catalysts can often eliminate unwanted byproducts, improve selectivity, or elimination of mass transfer limitations by changing from heterogeneous to homogeneous systems. They readily facilitate separations and promote recycling, to promote both green chemistry and good economics. First is near-critical water, or liquid water under pressure, where the K W for dissociation goes up 3-4 decades between 0 degrees C and 250 degrees C, thus facilitating both acid and base catalysis. Moreover, as the exothermic hydrogen bonding diminishes, the dielectric constant goes down to the point at which both salts and organics are soluble in this very hot water. For example, toluene and water are completely miscible at 305 degrees C. This eliminates mass transfer limitations for the reactions, and postreaction cooling not only lowers the K W to neutralize the ions without waste but also results in facile separations from simple liquid-liquid immiscibility. Further, we show the formation of catalysts with alkylcarbonic acids from alcohols and CO2, analogous to carbonic acid from water and CO2. We show a number of applications for these self-neutralizing catalysts, including the formation of ketals, the formation of diazonium intermediates to couple with electron-rich aromatics to produce dye molecules, and the hydration of beta-pinene. Here also these systems often enhance phase behavior to cut mass transfer resistance. In an analogous application we show that peroxide and CO2 gives peroxycarbonic acid, also reversible upon the removal of the CO2, and we show application to epoxidation reactions. The bottom line is that these catalysts afford profound advantages for both green chemistry and improved economics. The methods outlined here have potential for abundant applications, and we hope that this work will motivate such opportunities. PMID:18251512

Hallett, Jason P; Pollet, Pamela; Liotta, Charles L; Eckert, Charles A

2008-03-01

426

Seismic Monitoring of Fracture Formation  

NASA Astrophysics Data System (ADS)

Seismically tracking fracture formation is an important step in the monitoring of subsurface sequestration reservoirs. In this paper we report on laboratory experiments that were performed to investigate seismic transmission across a slowly propagating fracture to monitor how fracture heterogeneity varied due to changing stress conditions. Experiments were performed on a cube of Pierre Blue limestone with dimensions 0.3 m by 0.3 m by 0.3 m in a tri-axial pressure machine consisting of three independent loading frames. Two seismic arrays were used to propagate compressional and shear waves through the sample prior to, during, and after fracturing. Each array was composed of sixteen piezoelectric transducers (eight compressional-mode and eight shear-mode) with a central frequency of 1 MHz. After the sample was removed from the triaxial frame, a laser profilometer was used to measure the geometry of the fracture surfaces. The seismic array data produced a time-dependent two-dimensional map of the propagating fracture tip and the resulting fracture. The transmitted signals showed a 5%-10% increase in amplitude as a precursor to the main fracturing event after which the transmitted energy decreased to 1%-15% of its original value. The observed increase in amplitude prior to major failure is caused by constructive interference from diffraction from the tip of the fracture before the fracture tip was even under the sensors. Numerical simulation shows that the precursory increase in amplitude is a function of the specific stiffness of the fracture tip and the frequency of the signal. Post-fracturing characterization of the fracture topology identified anisotropic features in the fracture aperture that correlated with the direction of fracture propagation observed in the seismic data. The seismic signal, combined with the fracture characterization, supports the hypothesis that seismic signals can provide specific information about fracture formation and the resulting fracture geometry. This work demonstrates the potential for developing seismic methods for characterizing time-dependent fracture formation and fracture properties. Acknowledgments: LJPN wishes to acknowledge the Geosciences Research Program, Office of Basic Energy Sciences US Department of Energy, the University Faculty Scholar program at Purdue University, and the Delft University of Technology

Pyrak-Nolte, L. J.; de Pater, C. J.; Jocker, J.

2005-12-01

427

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

428

Mud Volcanoes Formation And Occurrence  

NASA Astrophysics Data System (ADS)

Mud volcanoes are natural phenomena, which occur throughout the globe. They are found at a greater or lesser scale in Azerbaijan, Turkmenistan, Georgia, on the Kerch and Taman peninsulas, on Sakhalin Island, in West Kuban, Italy, Romania, Iran, Pakistan, India, Burma, China, Japan, Indonesia, Malaysia, New Zealand, Mexico, Colombia, Trinidad and Tobago, Venezuela and Ecuador. Mud volcanoes are most well-developed in Eastern Azerbaijan, where more than 30% of all the volcanoes in the world are concentrated. More than 300 mud volcanoes have already been recognized here onshore or offshore, 220 of which lie within an area of 16,000 km2. Many of these mud volcanoes are particularly large (up to 400 m high). The volcanoes of the South Caspian form permanent or temporary islands, and numerous submarine banks. Many hypotheses have been developed regarding the origin of mud volcanoes. Some of those hypotheses will be examined in the present paper. Model of spontaneous excitation-decompaction (proposed by Ivanov and Guliev, 1988, 2002). It is supposed that one of major factors of the movement of sedimentary masses and formation of hydrocarbon deposits are phase transitions in sedimentary basin. At phase transitions there are abnormal changes of physical and chemical parameters of rocks. Abnormal (high and negative) pressure takes place. This process is called as excitation of the underground environment with periodicity from several tens to several hundreds, or thousand years. The relationship between mud volcanism and the generation of hydrocarbons, particularly methane, is considered to be a critical factor in mud volcano formation. At high flow rates the gas and sediment develops into a pseudo-liquid state and as flow increases the mass reaches the "so-called hover velocity" where mass transport begins. The mass of fluid moves as a quasi-uniform viscous mass through the sediment pile in a piston like manner until expelled from the surface as a "catastrophic eruption". Model of buoyancy drive (by Brown, 1990). Brown's basic hypothesis is similar to Ivanov and Guliev and may be summarized briefly as follows: -in situations where rapid sedimentation is occurring mud may be driven to the surface by buoyancy forces due to bulk density contrasts between mud and overlying sediment cover. Such density contrasts may be simply the result of compaction -disequilibrium, but more importantly may be related to gas expansion when fluids are transported to shallower depths with lower pressure and temperature conditions. Synthetic model had been proposed by I.Lerche, E.Bagirov, I.Guliyev (1997). The model includes the following studies: The starting point of the mud volcanoes begins with the formation of a zone of decompaction as a consequence of a high rate of gas generation. The mud body starts to rise under buoyancy. The excess pressure inside the mud intrusion is less than in surrounding formation. As a result, fluid flow toward the body of mud volcanoes. The body of the mud volcanoes then grows, increasing the buoyancy forces, with further drive the mud. If the rate of gas generation more thôn gas flow, causing exsolving of gas to free-phase gas. If there are open faults and fractures which cross the body of mud volcanoes, then gas and mud can penetrate through the faults, and so from gryphons and salses on the surface. A mud volcanoes can be consider as a huge accumulation of gas, where as the oil is concentrated on the flanks of the mud body.

Guliyev, I. S.

2007-12-01

429

The Science of Galaxy Formation  

NASA Astrophysics Data System (ADS)

Our knowledge of the Universe remains discovery-led: in the absence of adequate physics-based theory, interpretation of new results requires a scientific methodology. Commonly, scientific progress in astrophysics is motivated by the empirical success of the “Copernican Principle”, that the simplest and most objective analysis of observation leads to progress. A complementary approach tests the prediction of models against observation. In practise, astrophysics has few real theories, and has little control over what we can observe. Compromise is unavoidable. Advances in understanding complex non-linear situations, such as galaxy formation, require that models attempt to isolate key physical properties, rather than trying to reproduce complexity. A specific example is discussed, where substantial progress in fundamental physics could be made with an ambitious approach to modelling: simulating the spectrum of perturbations on small scales.

Gilmore, Gerard

2009-03-01

430

Combuster. [low nitrogen oxide formation  

NASA Technical Reports Server (NTRS)

A combuster is provided for utilizing a combustible mixture containing fuel and air, to heat a load fluid such as water or air, in a manner that minimizes the formation of nitrogen oxide. The combustible mixture passes through a small diameter tube where the mixture is heated to its combustion temperature, while the load fluid flows past the outside of the tube to receive heat. The tube is of a diameter small enough that the combustible mixture cannot form a flame, and yet is not subject to wall quench, so that combustion occurs, but at a temperature less than under free flame conditions. Most of the heat required for heating the combustible mixture to its combustion temperature, is obtained from heat flow through the walls of the pipe to the mixture.

Mckay, R. A. (inventor)

1978-01-01

431

Sandpile formation by revolving rivers  

E-print Network

Experimental observation of a new mechanism of sandpile formation is reported. As a steady stream of dry sand is poured onto a horizontal surface, a pile forms which has a thin river of sand on one side flowing from the apex of the pile to the edge of its base. The river rotates about the pile, depositing a new layer of sand with each revolution, thereby growing the pile. For small piles the river is steady and the pile formed is smooth. For larger piles, the river becomes intermittent and the surface of the pile becomes undulating. The frequency of revolution of the river is measured as the pile grows and the results are explained with a simple scaling argument. The essential features of the system that produce the phenomena are discussed.

E. Altshuler; O. Ramos; A. J. Batista-Leyva; A. Rivera; K. E. Bassler

2002-06-25

432

Selective formation of tungsten nanowires  

PubMed Central

We report on a process for fabricating self-aligned tungsten (W) nanowires with polycrystalline silicon core. Tungsten nanowires as thin as 10 nm were formed by utilizing polysilicon sidewall transfer technology followed by selective deposition of tungsten by chemical vapor deposition (CVD) using WF6 as the precursor. With selective CVD, the process is self-limiting whereby the tungsten formation is confined to the polysilicon regions; hence, the nanowires are formed without the need for lithography or for additional processing. The fabricated tungsten nanowires were observed to be perfectly aligned, showing 100% selectivity to polysilicon and can be made to be electrically isolated from one another. The electrical conductivity of the nanowires was characterized to determine the effect of its physical dimensions. The conductivity for the tungsten nanowires were found to be 40% higher when compared to doped polysilicon nanowires of similar dimensions. PMID:21970543

2011-01-01

433

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

434

Polar Cap Formation on Ganymede  

NASA Technical Reports Server (NTRS)

Since thermal migration is not an effective mechanism for water transport in the polar regions at the Galilean satellites, some other process must be responsible for the formation of Ganymede's polar caps. It is proposed that Ganymede's polar caps are the optical manifestation of a process that began with the distribution of an ice sheet over the surface of Ganymede. The combined processes of impact gardening and thermal migration led, in regions at latitudes less than 40 to 45 deg., to the burial of some fraction of this ice, the migration of some to the polar caps margins, and a depletion of free ice in the optical surface. At higher latitudes, no process was effective in removing ice from the optical surface, so the remanants of the sheet are visible today.

Pilcher, C. B.; Shaya, E. J.

1985-01-01

435

Pattern formation in colloidal explosions  

E-print Network

We study the non-equilibrium pattern formation that emerges when magnetically repelling colloids, trapped by optical tweezers, are abruptly released, forming colloidal explosions. For multiple colloids in a single trap we observe a pattern of expanding concentric rings. For colloids individually trapped in a line, we observe explosions with a zigzag pattern that persists even when magnetic interactions are much weaker than those that break the linear symmetry in equilibrium. Theory and computer simulations quantitatively describe these phenomena both in and out of equilibrium. An analysis of the mode spectrum allows us to accurately quantify the non-harmonic nature of the optical traps. Colloidal explosions provide a new way to generate well-characterized non-equilibrium behaviour in colloidal systems.

Arthur V. Straube; Ard A. Louis; Jörg Baumgartl; Clemens Bechinger; Roel P. A. Dullens

2010-09-10

436

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

437

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

E-print Network

of the temperature dependence of the shear moduli. The high-temperature anomalies of defect formation volume, tracer at high temperatures [21, 22], assuming that the Schottky defect formation parameters determined to withinDefect pressure, formation volume, and temperature dependence of formation properties of point

Boyer, Edmond

438

Engram formation in psychiatric disorders.  

PubMed

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

439

Cataract formation following vitreoretinal procedures  

PubMed Central

Purpose To evaluate the incidence and prevalence of cataract formation, progression, and extraction in patients that underwent vitreoretinal procedures and to evaluate factors that can potentially predispose patients to postoperative cataracts. Materials and methods The medical records of consecutive patients who underwent vitreoretinal surgery at the Yale Eye Center with at least 6 months of follow-up and no prior intraocular surgery were obtained. Preoperative, intraoperative, and postoperative data were recorded and analyzed in this retrospective observational study. The main outcome measures were defined as cataract extraction, formation, and progression after vitreoretinal procedures. The lens status of the surgical eye was recorded preoperatively and at 1 month, 3 months, 6 months, 12 months, 24 months, and 36 months postoperatively. Results A total of 193 eyes of 180 patients fulfilled the inclusion criteria. The percentages of eyes with mild lens change were 96% after 20-gauge pars plana vitrectomy (PPV), 72% after small gauge (23- and 25-gauge) PPV, 38% after scleral buckle (SB), 38% after pneumatic retinopexy (PR), and 91% after PPV plus SB (PPV+SB). Posterior subcapsular and nuclear sclerotic cataracts were the most common with almost all developing within 24 months. There was no statistically significant difference (P=1.00) between the rate of cataract extraction after 20-gauge (41%) and small gauge PPV (42%), but there was a statistically significant difference between PPV and non-PPV (SB, 6%; PR, 7%; P<0.001) and PPV and PPV+SB groups (69%; P=0.0063). Conclusion Cataracts were common following PPV regardless of the gauge. SB and PR led to the lowest while PPV+SB led to the highest risk of postoperative cataracts.

Feng, Hao; Adelman, Ron A

2014-01-01

440

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

441

Fibril formation from pea protein and subsequent gel formation.  

PubMed

The objective of this study was to characterize fibrillar aggregates made using pea proteins, to assemble formed fibrils into protein-based gels, and to study the rheological behavior of these gels. Micrometer-long fibrillar aggregates were observed after pea protein solutions had been heated for 20 h at pH 2.0. Following heating of pea proteins, it was observed that all of the proteins were hydrolyzed into peptides and that 50% of these peptides were assembled into fibrils. Changes on a structural level in pea proteins were studied using circular dichroism, transmission electron microscopy, and particle size analysis. During the fibril assembly process, an increase in aggregate size was observed, which coincided with an increase in thioflavin T binding, indicating the presence of ?-sheet aggregates. Fibrils made using pea proteins were more branched and curly. Gel formation of preformed fibrils was induced by slow acidification from pH 7.0 to a final pH of around pH 5.0. The ability of pea protein-based fibrillar gels to fracture during an amplitude sweep was comparable to those of soy protein and whey protein-based fibrillar gels, although gels prepared from fibrils made using pea protein and soy protein were weaker than those of whey protein. The findings show that fibrils can be prepared from pea protein, which can be incorporated into protein-based fibrillar gels. PMID:24564788

Munialo, Claire Darizu; Martin, Anneke H; van der Linden, Erik; de Jongh, Harmen H J

2014-03-19

442

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

443

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

444

A model for fingerprint formation  

NASA Astrophysics Data System (ADS)

The uniqueness of fingerprints (epidermal ridges) has been recognized for over two thousand years. They have been studied scientifically for more than two hundred years. Yet, in spite of the accumulation of a wealth of empirical and experimental knowledge, no widely accepted explanation for the development of epidermal ridges on fingers, palms and soles has yet emerged. Informed by an extensive literature study we suggest that fingerprint patterns are created as the result of a buckling instability in the basal cell layer of the fetal epidermis. Analysis of the well-known von Karman equations informs us that the buckling direction is perpendicular to the direction of greatest stress in the basal layer. We propose that this stress is induced by resistance of furrows and creases to the differential growth of the basal layer and regression of the volar pads during the time of ridge formation. These theories have been tested by computer experiments. The results are in close harmony with observations. Specifically, they are consistent with the well-known observation that the pattern type depends on the geometry of the fingertip surface when fingerprint patterns are formed.

Kücken, M.; Newell, A. C.

2004-10-01

445

Stages of neuronal network formation  

NASA Astrophysics Data System (ADS)

Graph theoretical approaches have become a powerful tool for investigating the architecture and dynamics of complex networks. The topology of network graphs revealed small-world properties for very different real systems among these neuronal networks. In this study, we observed the early development of mouse retinal ganglion cell (RGC) networks in vitro using time-lapse video microscopy. By means of a time-resolved graph theoretical analysis of the connectivity, shortest path length and the edge length, we were able to discover the different stages during the network formation. Starting from single cells, at the first stage neurons connected to each other ending up in a network with maximum complexity. In the further course, we observed a simplification of the network which manifested in a change of relevant network parameters such as the minimization of the path length. Moreover, we found that RGC networks self-organized as small-world networks at both stages; however, the optimization occurred only in the second stage.

Woiterski, Lydia; Claudepierre, Thomas; Luxenhofer, Robert; Jordan, Rainer; Käs, Josef A.

2013-02-01

446

Cosmic vacuum and galaxy formation  

NASA Astrophysics Data System (ADS)

It is demonstrated that the protogalactic perturbations must enter the nonlinear regime before the red shift z? 1; otherwise they would be destroyed by the antigravity of the vacuum dark energy at the subsequent epoch of the vacuum domination. At the zrrV={M/[(8?/3)?V]}1/3, where M is the mass of a given over-density and ?V is the vacuum density. The criterion provides a new relation between the largest mass condensations and their spatial scales. All the real large-scale systems follow this relation definitely. It is also shown that a simple formula is possible for the key quantity in the theory of galaxy formation, namely the initial amplitude of the perturbation of the gravitational potential in the protogalactic structures. The amplitude is time independent and given in terms of the Friedmann integrals, which are genuine physical characteristics of the cosmic energies. The results suggest that there is a strong correspondence between the global design of the Universe as a whole and the cosmic structures of various masses and spatial scales.

Chernin, A. D.

2006-04-01

447

Laminin receptors for neurite formation.  

PubMed Central

Laminin, a basement membrane glycoprotein promotes both cell attachment and neurite outgrowth. Separate domains on laminin elicit these responses, suggesting that distinct receptors occur on the surface of cells. NG108-15 neuroblastoma-glioma cells rapidly extend long processes in the presence of laminin. We report here that 125I-labeled laminin specifically binds to these cells and to three membrane proteins of 67, 110, and 180 kDa. These proteins were isolated by affinity chromatography on laminin-Sepharose. The 67-kDa protein reacted with antibody to the previously characterized receptor for cell attachment to laminin. Antibodies to the 110-kDa and 180-kDa bands demonstrated that the 110-kDa protein was found in a variety of epithelial cell lines and in brain, whereas the 180-kDa protein was neural specific. Antibodies prepared against the 110-kDa and 180-kDa proteins inhibited neurite outgrowth induced by the neurite-promoting domain of laminin, whereas antibodies to the 67-kDa laminin receptor had no effect on neurite outgrowth. We conclude that neuronal cells have multiple cell-surface laminin receptors and that the 110-kDa and 180-kDa proteins are involved in neurite formation. Images PMID:2963341

Kleinman, H K; Ogle, R C; Cannon, F B; Little, C D; Sweeney, T M; Luckenbill-Edds, L

1988-01-01

448

Star Formation in Tadpole Galaxies  

E-print Network

Tadpole Galaxies look like a star forming head with a tail structure to the side. They are also named cometaries. In a series of recent works we have discovered a number of issues that lead us to consider them extremely interesting targets. First, from images, they are disks with a lopsided starburst. This result is firmly established with long slit spectroscopy in a nearby representative sample. They rotate with the head following the rotation pattern but displaced from the rotation center. Moreover, in a search for extremely metal poor (XMP) galaxies, we identified tadpoles as the dominant shapes in the sample- nearly 80% of the local XMP galaxies have a tadpole morphology. In addition, the spatially resolved analysis of the metallicity shows the remarkable result that there is a metallicity drop right at the position of the head. This is contrary to what intuition would say and difficult to explain if star formation has happened from gas processed in the disk. The result could however be understood if the ...

Munoz-Tunon, Casiana; Elmegreen, Debra M; Elmegreen, Bruce G

2014-01-01

449

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

450

Student use of formative assessments and progress charts of formative assessments in the 7th grade science class.  

E-print Network

??In this investigation formative assessments and a progress chart of formative assessments were implemented with the purpose of improving student engagement and learning. Formative assessments… (more)

McKenna, Emily Sue.

2011-01-01

451

Towards the Rosetta Stone of planet formation  

Microsoft Academic Search

Transiting exoplanets (TEPs) observed just about 10 Myrs after formation of\\u000atheir host systems may serve as the Rosetta Stone for planet formation\\u000atheories. They would give strong constraints on several aspects of planet\\u000aformation, e.g. time-scales (planet formation would then be possible within 10\\u000aMyrs), the radius of the planet could indicate whether planets form by\\u000agravitational collapse (being

G. Maciejewski; R. Neuhaeuser; R. Errmann; M. Mugrauer; Ch. Adam; A. Berndt; T. Eisenbeiss; S. Fiedler; Ch. Ginski; M. Hohle; U. Kramm; C. Marka; M. Moualla; T. Pribulla; St. Raetz; T. Roell; T. O. B. Schmidt; M. Seeliger; I. Spaleniak; N. Tetzlaff; L. Trepl

2010-01-01