Investigating potential effects of heli-skiing on golden eagles in the Wasatch Mountains, Utah

Treesearch

Teryl G. Grubb; David K. Delaney; William W. Bowerman

2007-01-01

Implementing further research was beyond the scope of the U.S. Forest Service's 2004 Final Environmental Impact Statement (FEIS) and 2005 Wasatch Powderbird Guides (WPG) Special Use Permit Renewal process for heli-skiing in the Tri-Canyon Area in the Wasatch Mountains, just east of Salt Lake City, Utah. However, in their Record of Decision the Wasaatch-Cache (WCNF...

Climate during the Last Glacial Maximum in the Wasatch Mountains Inferred from Glacier Mass-Balance and Ice-Flow Modeling

NASA Astrophysics Data System (ADS)

Bash, E. A.; Laabs, B. J.

2006-12-01

The Wasatch Mountains of northern Utah contained numerous valley glaciers east and immediately downwind of Lake Bonneville during the Last Glacial Maximum (LGM). While the extent and chronology of glaciation in the Wasatch Mountains and the rise and fall of Lake Bonneville are becoming increasingly well understood, inferences of climatic conditions during the LGM for this area and elsewhere in the Rocky Mountains and northern Great Basin have yielded a wide range of temperature depression estimates. For example, previous estimates of temperature depression based on glacier and lake reconstructions in this region generally range from 7° to 9° C colder than modern. Glacier modeling studies for Little Cottonwood Canyon (northern Wasatch Mountains) suggest that such temperature depressions would have been accompanied by precipitation increases of about 3 to 1x modern, respectively (McCoy and Williams, 1985; Laabs et al., 2006). However, interpretations of other proxies suggest that temperature depression in this area may have been significantly greater, up to 13° C (e.g., Kaufman 2003), which would likely have been accompanied by less precipitation than modern. To address this issue, we reconstructed ice extent in the American Fork Canyon of the Wasatch Mountains and applied glacier modeling methods of Plummer and Phillips (2003) to infer climatic conditions during the LGM. Field mapping indicates that glaciers occupied an area of more than 20 km2 in the canyon and reached maximum lengths of about 9 km. To link ice extent to climatic changes, a physically based, two- dimensional numerical model of glacier mass balance and ice flow was applied to these valleys. The modeling approach allows the combined effects of temperature, precipitation and solar radiation on net mass balance of a drainage basin to be explored. Results of model experiments indicate that a temperature depression of less than 9° C in the American Fork Canyon would have been accompanied by greater

The Wasatch Plateau coal field, Utah

USGS Publications Warehouse

Spieker, Edmund M.

1931-01-01

The Wasatch Plateau, the northeasternmost of the great group of high plateaus in central and southern Utah, is underlain by a succession of Cretaceous rocks that, contain valuable coal beds, and the eastern part of the plateau, in which the coal is accessible, is generally known as the Wasatch Plateau coal field. This field and its continuation east of Price River the Book Cliffs coal field contain excellent coal of bituminous rank and together form the largest and most productive coal area in Utah. Coal from these fields has long been highly esteemed by users of western fuels and commands an important position in the fuel markets of the West.Mining of the coal began in a small way with the earliest settlements in this part of Utah. As population increased and transcontinental railroads were built, large mines were, opened and commercial development has advanced until at the present time most of the places accessible by existing railroads are the scenes of large mining enterprises, and the volume of coal passing out to the fuel-consuming centers of the West has reached an annual average of about 4,800,000 tons. The area now undergoing exploitation, however, is small compared with the part yet undeveloped, and the present examination of the field has shown clearly that the great bulk of its coal remains, constituting a reserve of many millions of tons.

Study of a prehistoric landslide using seismic reflection methods integrated with geological data in the Wasatch Mountains, Utah, USA

USGS Publications Warehouse

Tingey, B.E.; McBride, J.H.; Thompson, T.J.; Stephenson, W.J.; South, J.V.; Bushman, M.

2007-01-01

An integration of geological and geophysical techniques characterizes the internal and basal structure of a landslide along the western margin of the Wasatch Mountains in northern Utah, USA. The study area is within a region of planned and continuing residential development. The Little Valley Landslide is a prehistoric landslide as old as 13??ka B.P. Drilling and trenching at the site indicate that the landslide consists of chaotic and disturbed weathered volcanic material derived from Tertiary age volcanic rocks that comprise a great portion of the Wasatch Range. Five short high-resolution common mid-point seismic reflection profiles over selected portions of the site examine the feasibility of using seismic reflection to study prehistoric landslides in the Wasatch Mountain region. Due to the expected complexity of the near-surface geology, we have pursued an experimental approach in the data processing, examining the effects of muting first arrivals, frequency filtering, model-based static corrections, and seismic migration. The results provide a framework for understanding the overall configuration of the landslide, its basal (failure) surface, and the structure immediately underlying this surface. A glide surface or de??collement is interpreted to underlie the landslide suggesting a large mass movement. The interpretation of a glide surface is based on the onset of coherent reflectivity, calibrated by information from a borehole located along one of the seismic profiles. The glide surface is deepest in the center portion of the landslide and shallows up slope, suggesting a trough-like feature. This study shows that seismic reflection techniques can be successfully used in complex alpine landslide regions to (1) provide a framework in which to link geological data and (2) reduce the need for an extensive trenching and drilling program. ?? 2007 Elsevier B.V. All rights reserved.

Integration of paleoseismic data from multiple sites to develop an objective earthquake chronology: Application to the Weber segment of the Wasatch fault zone, Utah

USGS Publications Warehouse

DuRoss, Christopher B.; Personius, Stephen F.; Crone, Anthony J.; Olig, Susan S.; Lund, William R.

2011-01-01

We present a method to evaluate and integrate paleoseismic data from multiple sites into a single, objective measure of earthquake timing and recurrence on discrete segments of active faults. We apply this method to the Weber segment (WS) of the Wasatch fault zone using data from four fault-trench studies completed between 1981 and 2009. After systematically reevaluating the stratigraphic and chronologic data from each trench site, we constructed time-stratigraphic OxCal models that yield site probability density functions (PDFs) of the times of individual earthquakes. We next qualitatively correlated the site PDFs into a segment-wide earthquake chronology, which is supported by overlapping site PDFs, large per-event displacements, and prominent segment boundaries. For each segment-wide earthquake, we computed the product of the site PDF probabilities in common time bins, which emphasizes the overlap in the site earthquake times, and gives more weight to the narrowest, best-defined PDFs. The product method yields smaller earthquake-timing uncertainties compared to taking the mean of the site PDFs, but is best suited to earthquakes constrained by broad, overlapping site PDFs. We calculated segment-wide earthquake recurrence intervals and uncertainties using a Monte Carlo model. Five surface-faulting earthquakes occurred on the WS at about 5.9, 4.5, 3.1, 1.1, and 0.6 ka. With the exception of the 1.1-ka event, we used the product method to define the earthquake times. The revised WS chronology yields a mean recurrence interval of 1.3 kyr (0.7–1.9-kyr estimated two-sigma [2δ] range based on interevent recurrence). These data help clarify the paleoearthquake history of the WS, including the important question of the timing and rupture extent of the most recent earthquake, and are essential to the improvement of earthquake-probability assessments for the Wasatch Front region.

Integration of paleoseismic data from multiple sites to develop an objective earthquake chronology: Application to the Weber segment of the Wasatch fault zone, Utah

USGS Publications Warehouse

DuRoss, C.B.; Personius, S.F.; Crone, A.J.; Olig, S.S.; Lund, W.R.

2011-01-01

We present a method to evaluate and integrate paleoseismic data from multiple sites into a single, objective measure of earthquake timing and recurrence on discrete segments of active faults. We apply this method to the Weber segment (WS) of the Wasatch fault zone using data from four fault-trench studies completed between 1981 and 2009. After systematically reevaluating the stratigraphic and chronologic data from each trench site, we constructed time-stratigraphic OxCal models that yield site probability density functions (PDFs) of the times of individual earthquakes. We next qualitatively correlated the site PDFs into a segment-wide earthquake chronology, which is supported by overlapping site PDFs, large per-event displacements, and prominent segment boundaries. For each segment-wide earthquake, we computed the product of the site PDF probabilities in common time bins, which emphasizes the overlap in the site earthquake times, and gives more weight to the narrowest, best-defined PDFs. The product method yields smaller earthquake-timing uncertainties compared to taking the mean of the site PDFs, but is best suited to earthquakes constrained by broad, overlapping site PDFs. We calculated segment-wide earthquake recurrence intervals and uncertainties using a Monte Carlo model. Five surface-faulting earthquakes occurred on the WS at about 5.9, 4.5, 3.1, 1.1, and 0.6 ka. With the exception of the 1.1-ka event, we used the product method to define the earthquake times. The revised WS chronology yields a mean recurrence interval of 1.3 kyr (0.7-1.9-kyr estimated two-sigma [2??] range based on interevent recurrence). These data help clarify the paleoearthquake history of the WS, including the important question of the timing and rupture extent of the most recent earthquake, and are essential to the improvement of earthquake-probability assessments for the Wasatch Front region.

3D Dynamic Rupture Simulations along the Wasatch Fault, Utah, Incorporating Rough-fault Topography

NASA Astrophysics Data System (ADS)

Withers, Kyle; Moschetti, Morgan

2017-04-01

Studies have found that the Wasatch Fault has experienced successive large magnitude (>Mw 7.2) earthquakes, with an average recurrence interval near 350 years. To date, no large magnitude event has been recorded along the fault, with the last rupture along the Salt Lake City segment occurring 1300 years ago. Because of this, as well as the lack of strong ground motion records in basins and from normal-faulting earthquakes worldwide, seismic hazard in the region is not well constrained. Previous numerical simulations have modeled deterministic ground motion in the heavily populated regions of Utah, near Salt Lake City, but were primarily restricted to low frequencies ( 1 Hz). Our goal is to better assess broadband ground motions from the Wasatch Fault Zone. Here, we extend deterministic ground motion prediction to higher frequencies ( 5 Hz) in this region by using physics-based spontaneous dynamic rupture simulations along a normal fault with characteristics derived from geologic observations. We use a summation by parts finite difference code (Waveqlab3D) with rough-fault topography following a self-similar fractal distribution (over length scales from 100 m to the size of the fault) and include off-fault plasticity to simulate ruptures > Mw 6.5. Geometric complexity along fault planes has previously been shown to generate broadband sources with spectral energy matching that of observations. We investigate the impact of varying the hypocenter location, as well as the influence that multiple realizations of rough-fault topography have on the rupture process and resulting ground motion. We utilize Waveqlab3's computational efficiency to model wave-propagation to a significant distance from the fault with media heterogeneity at both long and short spatial wavelengths. These simulations generate a synthetic dataset of ground motions to compare with GMPEs, in terms of both the median and inter and intraevent variability.

78 FR 58158 - Establishment of Class E Airspace; Wasatch, UT

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-23

...., long. 111[deg]07'28'' W.; to Lat. 39[deg]03'55'' N., long. 110[deg]37'49'' W.; to Lat. 38[deg]28'51'' N... Aviation Administration (FAA), DOT. ACTION: Final rule. SUMMARY: This action establishes Class E airspace..., Wasatch, UT, to facilitate vectoring of Instrument Flight Rules (IFR) aircraft under control of Salt Lake...

76 FR 14372 - Uinta-Wasatch-Cache National Forest Resource Advisory Committee

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-16

... Street, Salt Lake City, Utah. Written comments should be sent to Loyal Clark, Uinta-Wasatch-Cache... open to the public. The following business will be conducted: (1) Review Forest Service project approval letter, (2) discuss travel budget, and (3) review new proposals. Persons who wish to bring related...

Hydrologic reconnaissance of the Wasatch Plateau-Book Cliffs coal-fields area, Utah

USGS Publications Warehouse

Waddell, Kidd M.; Contratto, P. Kay; Sumsion, C.T.; Butler, John R.

1981-01-01

Data obtained during a hydrologic reconnaissance in 1975-77 in the Wasatch Plateau-Book Cliffs coal-fields area of Utah were correlated with existing long-term data. Maps were prepared showing average precipitation, average streamflow, stream temperature, ground- and surface-water quality, sediment yield, and geology. Recommendations were made for additional study and suggested approaches for continued monitoring in the coalfields areas.moDuring the 1931-75 water years, the minimum discharges for the five major streams that head in the area ranged from about 12,000 to 26,000 acre-feet per year, and the maximum discharges ranged from about 59,000 to 315,000 acre-feet per year. Correlations indicate that 3 years of low-flow records at stream sites in the Wasatch Plateau would allow the development of relationships with long-term sites that can be used to estimate future low-flow records within a standard error of about 20 percent.Most water-quality degradation in streams occurs along the flanks of the Wasatch Plateau and Book Cliffs. In the uplands, dissolved-solids concentrations generally ranged from less than 100 to about 250 milligrams per liter, and in the lowlands, the concentrations ranged from about 250 to more than 6,000 milligrams per liter.Most springs in the Wasatch Plateau and Book Cliffs discharge from the Star Point Sandstone or younger formations, and the water generally contains less than about 1,000 milligrams per liter of dissolved solids. The discharges of 65 springs ranged from about 0.2 to 200 gallons per minute. The Blackhawk Formation, which is the principal coal-bearing formation, produces water in many of the mines. The dissolved-solids concentration in water discharging from springs and mines in the Blackhawk ranged from about 60 to 800 milligrams per liter.In the lowland areas, the Ferron Sandstone Member of the Maneos Shale appears to have the most potential for subsurface development of water of suitable chemical quality for human

Geologic setting and characteristic of mineral deposits in the central Wasatch Mountains, Utah

USGS Publications Warehouse

John, David A.

1997-01-01

Base- and precious-metal deposits in the central Wasatch Mountains southeast of Salt Lake City were mined for more than 100 years beginning in 1868. Deposits present in the Park City, Little Cottonwood, and Big Cottonwood mining districts include Ag-Pb-Zn ± Cu ± Au replacement and veins, a low-grade porphyry Cu-Au deposit, Cu-bearing skarns, a quartz monzonite-type (low F) porphyry Mo deposit, and high sulfidation (quartz-alunite) Au deposits. Most production came from polymetallic replacement and vein deposits in the Park City mining district, which has a recorded production of more than 1.4 million oz Au , 253 million oz Ag, 2.7 billion lbs Pb, 1.5 billion lbs Zn, and 129 million lbs Cu from 1872 to 1978. Production in the Little and Big Cottonwood districts, mostly from Pb-Ag replacement deposits, was much smaller. Most mineral deposits in the central Wasatch Mountains are genetically related to the Wasatch igneous belt, a series of high-K calc-alkaline stocks and cogenetic volcanic rocks that formed about 41(?) to 30 Ma. The mineral deposits mostly formed near the end of magmatic activity between about 36 to 31.4 Ma. A subeconomic porphyry Mo deposit in the Little Cottonwood stock is notably younger having formed about 26 to 23.5 Ma. The intrusive rocks were emplaced mostly along the westward extension of the west-trending Uinta arch during a period of NW-SE-directed extension, and much of the mineralization in the Park City district controlled by ENE-striking normal faults. About 15 degrees of eastward tilting of the central Wasatch Mountains during Late Cenozoic Basin and Range extension has resulted in progressively deeper levels of exposure from <1 km on the east to about 11 km on the west and in profound variations in the types of minerals deposits exposed in different parts of the range. Most deposits formed at paleodepths ≤5 km, and the most productive deposits in the Park City district formed at depths of 1 to 2 km. The prophyry Mo deposit in the

78 FR 2655 - Uinta-Wasatch-Cache National Forest; Utah; Ogden Travel Plan Project

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-14

...-Wasatch-Cache National Forest; Utah; Ogden Travel Plan Project AGENCY: Forest Service, USDA. ACTION... prepare a supplement to the Ogden Travel Plan Revision Final Supplemental Environmental Impact Statement (FSEIS). The Ogden Travel Plan Revision FSEIS evaluated six alternatives for possible travel management...

3D Dynamic Rupture Simulations along Dipping Faults, with a focus on the Wasatch Fault Zone, Utah

NASA Astrophysics Data System (ADS)

Withers, K.; Moschetti, M. P.

2017-12-01

We study dynamic rupture and ground motion from dip-slip faults in regions that have high-seismic hazard, such as the Wasatch fault zone, Utah. Previous numerical simulations have modeled deterministic ground motion along segments of this fault in the heavily populated regions near Salt Lake City but were restricted to low frequencies ( 1 Hz). We seek to better understand the rupture process and assess broadband ground motions and variability from the Wasatch Fault Zone by extending deterministic ground motion prediction to higher frequencies (up to 5 Hz). We perform simulations along a dipping normal fault (40 x 20 km along strike and width, respectively) with characteristics derived from geologic observations to generate a suite of ruptures > Mw 6.5. This approach utilizes dynamic simulations (fully physics-based models, where the initial stress drop and friction law are imposed) using a summation by parts (SBP) method. The simulations include rough-fault topography following a self-similar fractal distribution (over length scales from 100 m to the size of the fault) in addition to off-fault plasticity. Energy losses from heat and other mechanisms, modeled as anelastic attenuation, are also included, as well as free-surface topography, which can significantly affect ground motion patterns. We compare the effect of material structure and both rate and state and slip-weakening friction laws have on rupture propagation. The simulations show reduced slip and moment release in the near surface with the inclusion of plasticity, better agreeing with observations of shallow slip deficit. Long-wavelength fault geometry imparts a non-uniform stress distribution along both dip and strike, influencing the preferred rupture direction and hypocenter location, potentially important for seismic hazard estimation.

Using noble gases to investigate mountain-front recharge

USGS Publications Warehouse

Manning, A.H.; Solomon, D.K.

2003-01-01

Mountain-front recharge is a major component of recharge to inter-mountain basin-fill aquifers. The two components of mountain-front recharge are (1) subsurface inflow from the mountain block (subsurface inflow), and (2) infiltration from perennial and ephemeral streams near the mountain front (stream seepage). The magnitude of subsurface inflow is of central importance in source protection planning for basin-fill aquifers and in some water rights disputes, yet existing estimates carry large uncertainties. Stable isotope ratios can indicate the magnitude of mountain-front recharge relative to other components, but are generally incapable of distinguishing subsurface inflow from stream seepage. Noble gases provide an effective tool for determining the relative significance of subsurface inflow, specifically. Dissolved noble gas concentrations allow for the determination of recharge temperature, which is correlated with recharge elevation. The nature of this correlation cannot be assumed, however, and must be derived for the study area. The method is applied to the Salt Lake Valley Principal Aquifer in northern Utah to demonstrate its utility. Samples from 16 springs and mine tunnels in the adjacent Wasatch Mountains indicate that recharge temperature decreases with elevation at about the same rate as the mean annual air temperature, but is on average about 2??C cooler. Samples from 27 valley production wells yield recharge elevations ranging from the valley elevation (about 1500 m) to mid-mountain elevation (about 2500 m). Only six of the wells have recharge elevations less than 1800 m. Recharge elevations consistently greater than 2000 m in the southeastern part of the basin indicate that subsurface inflow constitutes most of the total recharge in this area. ?? 2003 Published by Elsevier Science B.V.

Assessment of watershed vulnerability to climate change for the Uinta-Wasatch-Cache and Ashley National Forests, Utah

Treesearch

Janine Rice; Tim Bardsley; Pete Gomben; Dustin Bambrough; Stacey Weems; Sarah Leahy; Christopher Plunkett; Charles Condrat; Linda A. Joyce

2017-01-01

Watersheds on the Uinta-Wasatch-Cache and Ashley National Forests provide many ecosystem services, and climate change poses a risk to these services. We developed a watershed vulnerability assessment to provide scientific information for land managers facing the challenge of managing these watersheds. Literature-based information and expert elicitation is used to...

Evaluation of undiscovered natural gas in the Upper Cretaceous Ferron Coal/Wasatch Plateau Total Petroleum System, Wasatch Plateau and Castle Valley, Utah

USGS Publications Warehouse

Henry, M.E.; Finn, T.M.

2003-01-01

The Total Petroleum System approach was used to estimate undiscovered gas potential of the Wasatch Plateau and Castle Valley, central Utah. The Ferron Coal/Wasatch Plateau Total Petroleum System was geologically defined and subdivided into seven assessment units, six of which were formally evaluated. Geologic data considered in defining the assessment unit boundaries included thermal maturity, coal presence and thickness, overburden thickness, and faulting intensity. Historical production data were also used to estimate volumes of gas from undrilled areas. The one conventional assessment unit includes almost the entire area of the petroleum system and is characterized by known accumulations that occur in structural or combination traps in sandstone reservoirs. The estimated undiscovered conventional producible gas that may be added to reserves of this unit ranges from a low (F95) of 14.8 billion cubic feet (BCFG) [419 million cubic meters (Mm3)] of gas to a high (F5) of 82 BCFG [2321 Mm3] and a mean value of 39.9 BCFG [1130 Mm3]. Continuous gas accumulations are those in which the entire assessment unit is considered to be gas-charged. Within these assessment units, there may be wells drilled that are not economic successes but all are expected to contain gas. Coalbed gas is in this continuous category. Mean estimates of undiscovered gas for the five continuous assessment units are: (1) Northern Coal Fairway/Drunkards Wash-752.3 BCFG [21,323 Mm3]; (2) Central Coal Fairway/Buzzard Bench-536.7 BCFG [15,194 Mm3]; (3) Southern Coal Fairway-152.6 BCFG [4320 Mm3]; (4) Deep (6000 feet plus) Coal and Sandstone-59.1 BCFG [1673 Mm3]; (5) Southern Coal Outcrop-10.6 BCFG [300 Mm3]; and Joes Valley and Musinia Grabens-not assessed.The mean estimate of undiscovered gas for the entire TPS is 1551.2 BCFG [43,914 Mm3]. There is a 95% chance that at least 855.7 BCFG [24,225 Mm3] and a 5% chance that at least 2504 BCFG [70,888 Mm3] of undiscovered producible gas remain in the TPS

A millennium-length reconstruction of Bear River stream flow, Utah

Treesearch

R. J. DeRose; M. F. Bekker; S.-Y. Wang; B. M. Buckley; R. K. Kjelgren; T. Bardsley; T. M. Rittenour; E. B. Allen

2015-01-01

The Bear River contributes more water to the eastern Great Basin than any other river system. It is also the most significant source of water for the burgeoning Wasatch Front metropolitan area in northern Utah. Despite its importance for water resources for the region’s agricultural, urban, and wildlife needs, our understanding of the variability of Bear River’s stream...

Composition of dust deposited to snow cover in the Wasatch Range (Utah, USA): Controls on radiative properties of snow cover and comparison to some dust-source sediments

USGS Publications Warehouse

Reynolds, Richard L.; Goldstein, Harland L.; Moskowitz, Bruce M.; Bryant, Ann C.; Skiles, S. McKenzie; Kokaly, Raymond F.; Flagg, Cody B.; Yauk, Kimberly; Berquó, Thelma S.; Breit, George N.; Ketterer, Michael; Fernandez, Daniel; Miller, Mark E.; Painter, Thomas H.

2014-01-01

of the DOS samples can be compared with sediments in a likely dust-source setting at the Milford Flat Fire (MFF) area about 225 km southwest of Salt Lake City. The MFF area represents geologically and physiographically similar and widespread dust sources west-southwest of the Wasatch Range and heavily populated Wasatch Front. The DOS layers and MFF sediments are similar in some textural, chemical, and magnetic properties, as well as in the common presence of goethite, hematite, magnetite-bearing basalt fragments, quartz, plagioclase, illite, and kaolinite. Textural and some chemical differences among these deposits can be explained by atmospheric sorting as well as by inputs from other settings, such as salt-crusted playas and contaminant sources.

The University of Utah Urban Undertaking (U4)

NASA Astrophysics Data System (ADS)

Lin, J. C.; Mitchell, L.; Bares, R.; Mendoza, D. L.; Fasoli, B.; Bowling, D. R.; Garcia, M. A.; Buchert, M.; Pataki, D. E.; Crosman, E.; Horel, J.; Catharine, D.; Strong, C.; Ehleringer, J. R.

2015-12-01

The University of Utah is leading efforts to understand the spatiotemporal patterns in both emissions and concentrations of greenhouse gases (GHG) and criteria pollutants within urban systems. The urbanized corridor in northern Utah along the Wasatch Front, anchored by Salt Lake City, is undergoing rapid population growth that is projected to double in the next few decades. The Wasatch Front offers multiple advantages as an unique "urban laboratory": urban regions in multiple valleys spanning numerous orders of magnitude in population, each with unique airsheds, well-defined boundary conditions along deserts and tall mountains, strong signals during cold air pool events, seasonal contrasts in pollution, and a legacy of productive partnerships with local stakeholders and governments. We will show results from GHG measurements from the Wasatch Front, including one of the longest running continuous CO2 records in urban areas. Complementing this record are comprehensive meteorological observations and GHG/pollutant concentrations on mobile platforms: light rail, helicopter, and research vans. Variations in the GHG and pollutant observations illustrate human behavior and the resulting "urban metabolism" taking place on hourly, weekly, and seasonal cycles, resulting in a coupling between GHG and criteria pollutants. Moreover, these observations illustrate systematic spatial gradients in GHG and pollutant distributions between and within urban areas, traced to underlying gradients in population, energy use, terrain, and land use. Over decadal time scales the observations reveal growth of the "urban dome" due to expanding urban development. Using numerical models of the atmosphere, we further link concentrations of GHG and air quality-relevant pollutants to underlying emissions at the neighborhood scale as well as urban planning considerations.

History of late Holocene earthquakes at the Willow Creek site on the Nephi segment, Wasatch fault zone, Utah

USGS Publications Warehouse

Crone, Anthony J.; Personius, Stephen F.; Duross, Christopher; Machette, Michael N.; Mahan, Shannon

2014-01-01

This 43-page report presents new data from the Willow Creek site that provides well-defined and narrow bounds on the times of the three youngest earthquakes on the southern strand of the Nephi segment, Wasatch Fault zone, and refines the time of the youngest earthquake to about 200 years ago. This is the youngest surface rupture on the entire Wasatch fault zone, which occurred about a century or less before European settles arrived in Utah. Two trenches at the Willow Creek site exposed three scarp-derived colluvial wedges that are evidence of three paleoearthquakes. OxCal modeling of ages from Willow Creek indicate that paleoearthquake WC1 occurred at 0.2 ± 0.1 ka, WC2 occurred at 1.2 ± 0.1 ka, and WC3 occurred at 1.9 ± 0.6 ka. Stratigraphic constraints on the time of paleoearthquake WC4 are extremely poor, so OxCal modeling only yields a broadly constrained age of 4.7 ± 1.8 ka. Results from the Willow Creek site significantly refine the times of late Holocene earthquakes on the Southern strand of the Nephi segment, and this result, when combined with a reanalysis of the stratigraphic and chronologic information from previous investigations at North Creek and Red Canyon, yield a stronger basis of correlating individual earthquakes between all three sites.

Holocene and latest Pleistocene paleoseismology of the Salt Lake City segment of the Wasatch Fault Zone, Utah, at the Penrose Drive Trench Site

USGS Publications Warehouse

DuRoss, Christopher B.; Hylland, Michael D.; McDonald, Greg N.; Crone, Anthony J.; Personius, Stephen F.; Gold, Ryan D.; Mahan, Shannon

2014-01-01

-Holocene earthquake chronology of the SLCS, and demonstrate that the SLCS has been a consistently active source of large-magnitude earthquakes since the latest Pleistocene. At least nine surface-faulting earthquakes (S1-S9) have occurred since the highstand of Lake Bonneville (~18 ka). Where the SLCS earthquake record is most complete (since ~14 ka), per-site estimates of mean recurrence are similar for the latest Pleistocene (post-Provo) (~1.6 kyr), Holocene (~1.6-1.9 kyr), and late Holocene (~1.2-1.4 kyr). These SLCS paleoearthquake data indicate an essentially stable rate of earthquake recurrence since the latest Pleistocene and are important for understanding the earthquake potential of the SLCS, clarifying the seismogenic relation between the SLCS and WVFZ, and forecasting the probabilities of future large-magnitude earthquake in the Wasatch Front region.

Selected hydrologic data, 1931-77, Wasatch Plateau-Book Cliffs coal-fields area, Utah

USGS Publications Warehouse

Waddell, K.M.; Vickers, H.L.; Upton, Robbin T.; Contratto, P. Kay

1978-01-01

The Wasatch Plateau-Book Cliffs coal-fields area in east-central Utah includes a significant part of the State's coal resources and is currently (1977) the most active coal-mining area in the State.This report presents data gathered by the U.S. Geological Survey as part of a hydrologic reconnaissance carried out during the period July 1975-September 1977 in cooperation with the U.S. Bureau of Land Management, as well as selected information for water-years 1931-75. The data were obtained in the field or from private, State, and other Federal agencies. The purpose of this report is to make the data available to those engaged in coal mining, to those assessing water resources that may possibly be affected by coal mining, and to supplement an interpretive report that will be published at a later date.

Petrologic and isotopic data from the Cretaceous (Campanian) Blackhawk Formation and Star Point Sandstone (Mesaverde Group), Wasatch Plateau, Utah

USGS Publications Warehouse

Fishman, Neil S.; Turner, Christine E.; Peterson, Fred

2013-01-01

The presence of discrete minerals associated with coal—whether (1) detrital or authigenic constituents of the coals or in thin mudstone or siltstone units interbedded with coals, or (2) authigenic phases that formed along cleats—might influence its utilization as an energy resource. The build-up of sintered ash deposits on the surfaces of heat exchangers in coal-fired power plants, due to the alteration of minerals during combustion of the coal, can seriously affect the functioning of the boiler and enhance corrosion of combustion equipment. In particular, the presence of sodium in coals has been considered a key factor in the fouling of boilers; however, other elements (such as calcium or magnesium) and the amount of discrete minerals burned with coal can also play a significant role in the inefficiency of and damage to boilers. Previous studies of the quality of coals in the Cretaceous (Campanian) Blackhawk Formation of the Wasatch Plateau, Utah, revealed that the sodium content of the coals varied across the region. To better understand the origin and distribution of sodium in these coals, petrologic studies were undertaken within a sedimentological framework to evaluate the timing and geochemical constraints on the emplacement of sodium-bearing minerals, particularly analcime, which previously had been identified in coals in the Blackhawk Formation. Further, the study was broadened to include not just coals in the Blackhawk Formation from various localities across the Wasatch Plateau, but also sandstones interbedded with the coals as well as sandstones in the underlying Star Point Sandstone. The alteration history of the sandstones in both formations was considered a key component of this study because it records the nature and timing of fluids passing through them and the associated precipitation of sodium-bearing minerals; thus, the alteration history could place constraints on the distribution and timing of sodium mineralization in the interbedded or

Earth Observations taken by Expedition 38 crewmember

NASA Image and Video Library

2013-12-12

ISS038-E-016506 (12 Dec. 2013) --- A nighttime view of Salt Lake City, Utah is featured in this image photographed by an Expedition 38 crew member on the International Space Station. The Salt Lake City metropolitan area is located along the western front of the Wasatch Range in northern Utah. Viewed at night from the vantage point of the space station, the regular north-south and east-west layout of street grids typical of western U.S. cities is clearly visible. Known as "the crossroads of the West", the headquarters of The Church of Jesus Christ of Latter-day Saints (also known as the LDS Church and informally as the Mormon Church), and the state capital of Utah, Salt Lake City was founded in 1847 by Brigham Young together with other followers of the Mormon faith. The Salt Lake City metropolitan area today is included in the larger urban Wasatch Front region of Utah which includes over two million people (approximately 80 percent of the population of the state). Both the color of the city lights and their density provide clues to the character of the urban fabric -- yellow gold lights generally indicate major roadways such as Interstate Highway 15 that passes through the center of the metropolitan area (center, left to right), while bright white clusters of lights are associated with city centers, commercial, and industrial areas. In contrast, residential and suburban areas are recognizable due to diffuse and relatively dim lighting (center left). The Wasatch Range to the east is largely dark, as are several large urban parks and golf courses located within the illuminated urban areas.

The Wasatch fault zone, utah-segmentation and history of Holocene earthquakes

USGS Publications Warehouse

Machette, M.N.; Personius, S.F.; Nelson, A.R.; Schwartz, D.P.; Lund, W.R.

1991-01-01

The Wasatch fault zone (WFZ) forms the eastern boundary of the Basin and Range province and is the longest continuous, active normal fault (343 km) in the United States. It underlies an urban corridor of 1.6 million people (80% of Utah's population) representing the largest earthquake risk in the interior of the western United States. We have used paleoseismological data to identify 10 discrete segments of the WFZ. Five are active, medial segments with Holocene slip rates of 1-2 mm a-1, recurrence intervals of 2000-4000 years and average lengths of about 50 km. Five are less active, distal segments with mostly pre-Holocene surface ruptures, late Quaternary slip rates of 6.5 have occurred since 1860. Although the time scale of the clustering is different-130 years vs 1100 years-we consider the central Nevada-eastern California Seismic Belt to be a historic analog for movement on the WFZ during the past 1500 years. We have found no evidence that surface-rupturing events occurred on the WFZ during the past 400 years, a time period which is twice the average intracluster recurrence interval and equal to the average Holocene recurrence interval. In particular, the Brigham City segment (the northernmost medial segment) has not ruptured in the past 3600 years-a period that is about three times longer than this segment's average recurrence interval during the early and middle Holocene. Although the WFZ's seismological record is one of relative quiescence, a comparison with other historic surface-rupturing earthquakes in the region suggests that earthquakes having moment magnitudes of 7.1-7.4 (or surface-wave magnitudes of 7.5-7.7)-each associated with tens of kilometers of surface rupture and several meters of normal dip slip-have occurred about every four centuries during the Holocene and should be expected in the future. ?? 1991.

Intraplate extensional tectonics of the eastern Basin-Range Inferencess on structural style from seismic reflection data, regional tectonics, and thermal-mechanical models of brittle-ductile deformation

NASA Technical Reports Server (NTRS)

Smith, R. B.; Bruhn, R. L.

1984-01-01

Using 1500 km of industry-released seismic reflection data, surface geology, velocity models from refraction data, and earthquake data, the large extensional structures in the crust of the eastern Basin-Range and its transition into the Middle Rocky Mountains and Colorado Plateau have been studied. It is suggested that the close spatial correlation between normal faults and thrust fault segmentation along the Wasatch Front reflects major east-trending structural and lithological boundaries inherited from tectonic processes associated with the evolution of the cordilleran miogeocline, which began in the Precambrian.

Earth Observations taken by the Expedition Seven crew

NASA Image and Video Library

2003-06-14

ISS007-E-07360 (14 June 2003) --- This regional view of Salt Lake City, Utah taken by an Expedition 7 crewmember onboard the International Space Station (ISS) shows the city and its suburbs nestled between the Wasatch Front and the Great Salt Lake. The core of Interstate Highway 15 runs North-South through the valley, with suburbs arrayed east and west of the highway. An important issue facing Salt Lake City’s growing population is preservation and allocation of water resources. Utah is in its fifth year of drought. One of the most dramatic effects of the drought visible in this picture is the fact that the lake levels are so low that Antelope Island is separated from the mainland by dry lakebed. Expansive productive wetlands occur where freshwater flows from the Wasatch Range and into the lake. The southern end of this network of wetlands can be seen in the image.

Fluctuations in fluvial style in the Wasatch Formation, Piceance Basin, Colorado: Climatic, tectonic, or sediment driven

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nadon, G.C.; Lorenz, J.C.; Lafrenier, L.

1996-01-01

The Molina Member of the Wasatch Formation is a primary objective for light gas sandstone production. The G-Sandstone unit of the Molina produces an average of 200 MCFGPD. The chert-rich sandstones and conglomerates of the Molina Member, which are exposed in two subparallel belts on the western and eastern sides of the basin, are strikingly different from the remainder of the Wasatch formation. The underlying Atwell Gulch Member and overlying Shire Member are composed of floodplain mudstones with well developed paleosols and rare, lenticular channel sandstones. Both units are interpreted as anastomosed fluvial deposits. The Molina Member, which varies frommore » 32-118 m thick and in places contains clasts >0.2 m, is more difficult to interpret. Different portions of individual sections contain significant proportions of parallel laminated sandstones up to 5 m thick and several hundred meters wide. These parallel laminated sandstones are most common to the north along the western outcrop bell. They are interbedded with sandstones and conglomerates that are typical of a braided fluvial deposit. The contact between the two fluvial styles is sharp but conformable. The Molina Member therefore represents a perturbation in fluvial style from suspended-load to bedload and back to suspended-load over a restricted time interval. This may be the product of a change in climate, i.e., a change in rainfall amount or timing in the source area, source rock, e.g., the unroofing of a Jurassic eolian sandstone, or an increase in the depositional slope due to uplift. The return to a mud-dominated depositional system in the Shire Member argues for either climatic or source-rock variations as the primary control of the fluvial style.« less

Fluctuations in fluvial style in the Wasatch Formation, Piceance Basin, Colorado: Climatic, tectonic, or sediment driven?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nadon, G.C.; Lorenz, J.C.; Lafrenier, L.

1996-12-31

The Molina Member of the Wasatch Formation is a primary objective for light gas sandstone production. The G-Sandstone unit of the Molina produces an average of 200 MCFGPD. The chert-rich sandstones and conglomerates of the Molina Member, which are exposed in two subparallel belts on the western and eastern sides of the basin, are strikingly different from the remainder of the Wasatch formation. The underlying Atwell Gulch Member and overlying Shire Member are composed of floodplain mudstones with well developed paleosols and rare, lenticular channel sandstones. Both units are interpreted as anastomosed fluvial deposits. The Molina Member, which varies frommore » 32-118 m thick and in places contains clasts >0.2 m, is more difficult to interpret. Different portions of individual sections contain significant proportions of parallel laminated sandstones up to 5 m thick and several hundred meters wide. These parallel laminated sandstones are most common to the north along the western outcrop bell. They are interbedded with sandstones and conglomerates that are typical of a braided fluvial deposit. The contact between the two fluvial styles is sharp but conformable. The Molina Member therefore represents a perturbation in fluvial style from suspended-load to bedload and back to suspended-load over a restricted time interval. This may be the product of a change in climate, i.e., a change in rainfall amount or timing in the source area, source rock, e.g., the unroofing of a Jurassic eolian sandstone, or an increase in the depositional slope due to uplift. The return to a mud-dominated depositional system in the Shire Member argues for either climatic or source-rock variations as the primary control of the fluvial style.« less

Evolution of fluvial styles in the Eocene Wasatch Formation, Powder River Basin, Wyoming

USGS Publications Warehouse

Warwick, Peter D.; Flores, Romeo M.; Ethridge, Frank G.; Flores, Romeo M.

1987-01-01

Vertical and lateral facies changes in the lower part of the Eocene Wasatch Formation in the Powder River Basin, Wyoming represent an evolution of fluvial systems that varied from meandering to anastomosing. The meandering facies in the lower part of the study interval formed in a series of broad meanderbelts in a northnorthwestflowing system. Upon abandonment this meanderbelt facies served as a topographic high on which a raised or ombrotrophic Felix peat swamp developed. Peat accumulated until compaction permitted encroachment of crevasse splays from an adjoining transitional facies which consists of deposits of a slightly sinuous fluvial system. Crevasse splays eventually prograded over the peat swamp that was partly covered by lakes. Bifurcation, reunification, and transformation of crevasse channels into major conduits produced an anastomosing system that was characterized by diverging and converging channels separated by floodbasins drowned by lakes and partly covered swamps.

Storms or cold fronts: what is really responsible for the extreme waves regime in the Colombian Caribbean coastal region?

NASA Astrophysics Data System (ADS)

Otero, L. J.; Ortiz-Royero, J. C.; Ruiz-Merchan, J. K.; Higgins, A. E.; Henriquez, S. A.

2016-02-01

The aim of this study is to determine the contribution and importance of cold fronts and storms to extreme waves in different areas of the Colombian Caribbean in an attempt to determine the extent of the threat posed by the flood processes to which these coastal populations are exposed. Furthermore, the study wishes to establish the actions to which coastal engineering constructions should be subject. In the calculation of maritime constructions, the most important parameter is the height of the wave. For this reason, it is necessary to establish the design wave height to which a coastal engineering structure should be resistant. This wave height varies according to the return period considered. The significant height values for the areas focused on in the study were calculated in accordance with Gumbel's extreme value methodology. The methodology was evaluated using data from the reanalysis of the spectral National Oceanic and Atmospheric Administration (NOAA) WAVEWATCH III® (WW3) model for 15 points along the 1600 km of the Colombian Caribbean coastline (continental and insular) between the years 1979 and 2009. The results demonstrated that the extreme waves caused by tropical cyclones and those caused by cold fronts have different effects along the Colombian Caribbean coast. Storms and hurricanes are of greater importance in the Guajira Peninsula (Alta Guajira). In the central area (consisting of Baja Guajira, and the cities of Santa Marta, Barranquilla, and Cartagena), the strong impact of cold fronts on extreme waves is evident. However, in the southern region of the Colombian Caribbean coast (ranging from the Gulf of Morrosquillo to the Gulf of Urabá), the extreme values of wave heights are lower than in the previously mentioned regions, despite being dominated mainly by the passage of cold fronts. Extreme waves in the San Andrés and Providencia insular region present a different dynamic from

Linking ShakeMap and Emergency Managers in the Utah Region

NASA Astrophysics Data System (ADS)

Pankow, K.; Bausch, D.; Carey, B.

2007-12-01

In 2001, the University of Utah Seismograph Stations (UUSS) locally customized and began producing automatic ShakeMaps in Utah's Wasatch Front urban corridor as part of a new real-time earthquake information system developed under the Advanced National Seismic System. In 2005, motivated by requests from Utah's Division of Homeland Security and FEMA, ShakeMap capabilities were expanded to cover the entire Utah region. Now in 2007, ShakeMap capabilities throughout the region will again be enhanced by increased station coverage. The increased station coverage comes both from permanent stations funded by a state initiative and from the temporary deployment of EarthScope USArray stations. The state initiative will add ~22 strong-motion instruments and ~10 broadband instruments to the UUSS network. The majority of these stations will be located in southwestern Utah--one of the fastest growing regions in the U.S. EarthScope will evenly distribute 70 broadband stations in the region during 2007 that will be removed after 18 to 24 months. In addition to the enhanced station coverage for producing ShakeMaps in the Utah region, the transfer of information to the emergency response community is also being enhanced. First, tools are being developed that will link ShakeMap data with HAZUS loss-estimation software in near-real-time for rapid impact assessment. Second, ShakeMap scenarios are being used in conjunction with HAZUS loss-estimation software to produce customized maps for planning and preparedness exercises and also for developing templates that can be used following a significant regional earthquake. With the improvements to ShakeMap and the improved dialogue with the emergency managers, a suite of maps and information products were developed based on scenario earthquakes for training and exercise purposes. These products will be available in a timely fashion following a significant earthquake in the Utah region.

Condensation Front Migration in a Protoplanetary Nebula

NASA Technical Reports Server (NTRS)

Davis, Sanford S.

2004-01-01

Condensation front dynamics are investigated in the mid-solar nebula region. A quasi-steady model of the evolving nebula is combined with equilibrium vapor pressure curves to determine evolutionary condensation fronts for selected species. These fronts are found to migrate inwards from the far-nebula to final positions during a period of 10(exp 7) years. The physical process governing this movement is a combination of local viscous heating and luminescent heating from the central star. Two luminescent heating models are used and their effects on the ultimate radial position of the condensation front are discussed. At first the fronts move much faster than the nebular accretion velocity, but after a time the accreting gas and dust overtakes the slowing condensation front.

Rossby waves, extreme fronts, and wildfires in southeastern Australia

NASA Astrophysics Data System (ADS)

Reeder, Michael J.; Spengler, Thomas; Musgrave, Ruth

2015-03-01

The most catastrophic fires in recent history in southern Australia have been associated with extreme cold fronts. Here an extreme cold front is defined as one for which the maximum temperature at 2 m is at least 17°C lower on the day following the front. An anticyclone, which precedes the cold front, directs very dry northerlies or northwesterlies from the interior of the continent across the region. The passage of the cold front is followed by strong southerlies or southwesterlies. European Centre for Medium-Range Weather Forecasts ERA-Interim Reanalyses show that this regional synoptic pattern common to all strong cold fronts, and hence severe fire conditions, is a consequence of propagating Rossby waves, which grow to large amplitude and eventually irreversibly overturn. The process of overturning produces the low-level anticyclone and dry conditions over southern Australia, while simultaneously producing an upper level trough and often precipitation in northeastern Australia.

Energy conversion at dipolarization fronts

NASA Astrophysics Data System (ADS)

Khotyaintsev, Yu. V.; Divin, A.; Vaivads, A.; André, M.; Markidis, S.

2017-02-01

We use multispacecraft observations by Cluster in the Earth's magnetotail and 3-D particle-in-cell simulations to investigate conversion of electromagnetic energy at the front of a fast plasma jet. We find that the major energy conversion is happening in the Earth (laboratory) frame, where the electromagnetic energy is being transferred from the electromagnetic field to particles. This process operates in a region with size of the order several ion inertial lengths across the jet front, and the primary contribution to E·j is coming from the motional electric field and the ion current. In the frame of the front we find fluctuating energy conversion with localized loads and generators at sub-ion scales which are primarily related to the lower hybrid drift instability excited at the front; however, these provide relatively small net energy conversion.

Receptor model source attributions for Utah’s Salt Lake City airshed and the impacts of wintertime secondary ammonium nitrate and ammonium chloride aerosol.

EPA Science Inventory

Communities along Utah’s Wasatch Front are currently developing strategies to reduce daily average PM2.5 levels to below National Ambient Air Quality Standards during wintertime, persistent, multi-day stable atmospheric conditions or cold-air pools. Speciated PM2.5 data from the ...

Subduction at upper ocean fronts by baroclinic instability

NASA Astrophysics Data System (ADS)

Verma, Vicky; Pham, Hieu T.; Radhakrishnan, Anand; Sarkar, Sutanu

2017-11-01

Large eddy simulations of upper ocean fronts that are initially in geostrophic balance show that the linear and subsequent nonlinear evolution of baroclinic intability are effective in restratifying the front. During the growth of baroclinic instability, the front develops thin regions with enhanced vertical vorticity, i.e., vorticity filaments. Moreover, the vorticity filaments organize into submesoscale eddies. The subsequent frontal dynamics is dominated by the vorticity filaments and the submesoscale eddies. Diagnosis of the horizontal force balance reveals that the regions occupied by these coherent structures have significantly large imbalance, and are characterized by large vertical velocity. High density fluid from the heavier side of the front is subducted by the vertical velocity to the bottom of the mixed layer. The process of subduction is illustrated by Lagrangian tracking of fluid particles released at a fixed depth.

Explosive-residue compounds resulting from snow avalanche control in the Wasatch Mountains of Utah

USGS Publications Warehouse

Naftz, David L.; Kanagy, Leslie K.; Susong, David D.; Wydoski, Duane S.; Kanagy, Christopher J.

2003-01-01

A snow avalanche is a powerful force of nature that can play a significant role in developing mountain landscapes (Perla and Martinelli, 1975). More importantly, loss of life can occur when people are caught in the path of snow avalanches (Grossman, 1999). Increasing winter recreation, including skiing, snowboarding, snowmobiling, snowshoeing, and climbing in mountainous areas, has increased the likelihood of people encountering snow avalanches (fig. 1). Explosives are used by most ski areas and State highway departments throughout the Western United States to control the release of snow avalanches, thus minimizing the loss of human life during winter recreation and highway travel (fig. 2).Common explosives used for snow avalanche control include trinitrotoluene (TNT), pentaerythritoltetranitrate (PETN), cyclotrimethylenetrinitramine (RDX), tetrytol, ammonium nitrate, and nitroglycerin (Perla and Martinelli, 1975). During and after snowfall or wind loading of potential avalanche slopes, ski patrollers and Utah Department of Transportation personnel deliver explosive charges onto predetermined targets to artificially release snow avalanches, thereby rendering the slope safer for winter activities. Explosives can be thrown by hand onto target zones or shot from cannons for more remote delivery of explosive charges. Hand-delivered charges typically contain about 2 pounds of TNT or its equivalent (Perla and Martinelli, 1975).Depending on the size of the ski area, acreage of potential avalanche terrain, and weather conditions, the annual quantity of explosives used during a season of snow avalanche control can be substantial. For example, the three ski areas of Alta, Snowbird, and Brighton, plus the Utah Department of Transportation, may use as many as 11,200 hand charges per year (Wasatch Powderbird Guides, unpub. data, 1999) for snow avalanche control in Big and Little Cottonwood Canyons (fig. 3). If each charge is assumed to weigh 2 pounds, this equates to about 22

Submesoscale-selective compensation of fronts in a salinity-stratified ocean.

PubMed

Spiro Jaeger, Gualtiero; Mahadevan, Amala

2018-02-01

Salinity, rather than temperature, is the leading influence on density in some regions of the world's upper oceans. In the Bay of Bengal, heavy monsoonal rains and runoff generate strong salinity gradients that define density fronts and stratification in the upper ~50 m. Ship-based observations made in winter reveal that fronts exist over a wide range of length scales, but at O(1)-km scales, horizontal salinity gradients are compensated by temperature to alleviate about half the cross-front density gradient. Using a process study ocean model, we show that scale-selective compensation occurs because of surface cooling. Submesoscale instabilities cause density fronts to slump, enhancing stratification along-front. Specifically for salinity fronts, the surface mixed layer (SML) shoals on the less saline side, correlating sea surface salinity (SSS) with SML depth at O(1)-km scales. When losing heat to the atmosphere, the shallower and less saline SML experiences a larger drop in temperature compared to the adjacent deeper SML on the salty side of the front, thus correlating sea surface temperature (SST) with SSS at the submesoscale. This compensation of submesoscale fronts can diminish their strength and thwart the forward cascade of energy to smaller scales. During winter, salinity fronts that are dynamically submesoscale experience larger temperature drops, appearing in satellite-derived SST as cold filaments. In freshwater-influenced regions, cold filaments can mark surface-trapped layers insulated from deeper nutrient-rich waters, unlike in other regions, where they indicate upwelling of nutrient-rich water and enhanced surface biological productivity.

Submesoscale-selective compensation of fronts in a salinity-stratified ocean

PubMed Central

Spiro Jaeger, Gualtiero; Mahadevan, Amala

2018-01-01

Salinity, rather than temperature, is the leading influence on density in some regions of the world’s upper oceans. In the Bay of Bengal, heavy monsoonal rains and runoff generate strong salinity gradients that define density fronts and stratification in the upper ~50 m. Ship-based observations made in winter reveal that fronts exist over a wide range of length scales, but at O(1)-km scales, horizontal salinity gradients are compensated by temperature to alleviate about half the cross-front density gradient. Using a process study ocean model, we show that scale-selective compensation occurs because of surface cooling. Submesoscale instabilities cause density fronts to slump, enhancing stratification along-front. Specifically for salinity fronts, the surface mixed layer (SML) shoals on the less saline side, correlating sea surface salinity (SSS) with SML depth at O(1)-km scales. When losing heat to the atmosphere, the shallower and less saline SML experiences a larger drop in temperature compared to the adjacent deeper SML on the salty side of the front, thus correlating sea surface temperature (SST) with SSS at the submesoscale. This compensation of submesoscale fronts can diminish their strength and thwart the forward cascade of energy to smaller scales. During winter, salinity fronts that are dynamically submesoscale experience larger temperature drops, appearing in satellite-derived SST as cold filaments. In freshwater-influenced regions, cold filaments can mark surface-trapped layers insulated from deeper nutrient-rich waters, unlike in other regions, where they indicate upwelling of nutrient-rich water and enhanced surface biological productivity. PMID:29507874

The Barents Sea Polar Front in summer

NASA Astrophysics Data System (ADS)

Parsons, A. Rost; Bourke, Robert H.; Muench, Robin D.; Chiu, Ching-Sang; Lynch, James F.; Miller, James H.; Plueddemann, Albert J.; Pawlowicz, Richard

1996-06-01

In August 1992 a combined physical oceanography and acoustic tomography experiment was conducted to describe the Barents Sea Polar Front (BSPF) and investigate its impact on the regional oceanography. The study area was an 80 × 70 km grid east of Bear Island where the front exhibits topographic trapping along the northern slope of the Bear Island Trough. Conductivity-temperature-depth, current meter, and acoustic Doppler current profiler (ADCP) data, combined with tomographic cross sections, presented a highly resolved picture of the front in August. All hydrographic measurements were dominated by tidal signals, with the strongest signatures associated with the M2 and S2 semidiurnal species. Mean currents in the warm saline water to the south of the front, derived from a current meter mooring and ADCP data, were directed to the southwest and may be associated with a barotropic recirculation of Norwegian Atlantic Water (NAW) within the Bear Island Trough. The geostrophic component of the velocity was well correlated with the measured southwestward mean surface layer flow north of the front. The frontal structure was retrograde, as the frontal isopleths sloped opposite to the bathymetry. The surface signature of the front was dominated by salinity gradients associated with the confluence of Atlantic and Arctic water masses, both warmed by insolation to a depth of about 20 m. The surface manifestation of the front varied laterally on the order of 10 km associated with tidal oscillations. Below the mixed layer, temperature and salinity variations were compensating, defining a nearly barotropic front. The horizontal scale of the front in this region was ˜3 km or less. At middepth beneath the frontal interface, tomographic cross sections indicated a high-frequency (˜16 cpd) upslope motion of filaments of NAW origin. The summertime BSPF was confirmed to have many of the general characteristics of a shelf-slope frontal system [Mooers et al., 1978] as well as a

Jet-front systems nearing strongly stratified region in differentially heated, rotating stratified annulus

NASA Astrophysics Data System (ADS)

Rolland, Joran; Achatz, Ulrich

2017-04-01

The differentially heated, rotating annulus configuration has been used for a long time as a model system of the earth troposphere. It can easily reproduce thermal wind and baroclinic waves in the laboratory. It has recently been shown numerically that provided the Rossby number, the rotation rate and the Brunt-Väisälä frequency were well chosen, this configuration also reproduces the spontaneous emission of gravity waves by jet front systems [1]. This offers a very practical configuration in which to study an important process of emission of atmospheric gravity waves. It has also been shown experimentally that this configuration can be modified in order to add the possibility for the emitted wave to reach a strongly stratified region [2]. It thus creates a system containing a model troposphere where gravity waves are spontaneously emitted and can propagate to a model stratosphere. For this matter a stratification was created using a salinity gradient in the experimental apparatus. Through double diffusion, this generates a strongly stratified layer in the middle of the flow (the model stratosphere) and two weakly stratified region in the top and bottom layers (the model troposphere). In this poster, we present simulations of this configuration displaying baroclinic waves in the top and bottom layers. We aim at creating jet front systems strong enough that gravity waves can be spontaneously emitted. This will thus offer the possibility of studying the wave characteristic and mechanisms in emission and propagation in details. References [1] S. Borchert, U. Achatz, M.D. Fruman, Spontaneous Gravity wave emission in the differentially heated annulus, J. Fluid Mech. 758, 287-311 (2014). [2] M. Vincze, I. Borcia, U. Harlander, P. Le Gal, Double-diffusive convection convection and baroclinic instability in a differentially heated and initially stratified rotating system: the barostrat instability, Fluid Dyn. Res. 48, 061414 (2016).

Chaos of radiative heat-loss-induced flame front instability.

PubMed

Kinugawa, Hikaru; Ueda, Kazuhiro; Gotoda, Hiroshi

2016-03-01

We are intensively studying the chaos via the period-doubling bifurcation cascade in radiative heat-loss-induced flame front instability by analytical methods based on dynamical systems theory and complex networks. Significant changes in flame front dynamics in the chaotic region, which cannot be seen in the bifurcation diagrams, were successfully extracted from recurrence quantification analysis and nonlinear forecasting and from the network entropy. The temporal dynamics of the fuel concentration in the well-developed chaotic region is much more complicated than that of the flame front temperature. It exhibits self-affinity as a result of the scale-free structure in the constructed visibility graph.

Wasatch fault zone, Utah - segmentation and history of Holocene earthquakes

USGS Publications Warehouse

Machette, Michael N.; Personius, Stephen F.; Nelson, Alan R.; Schwartz, David P.; Lund, William R.

1991-01-01

The Wasatch fault zone (WFZ) forms the eastern boundary of the Basin and Range province and is the longest continuous, active normal fault (343 km) in the United States. It underlies an urban corridor of 1.6 million people (80% of Utah's population) representing the largest earthquake risk in the interior of the western United States. The authors have used paleoseismological data to identify 10 discrete segments of the WFZ. Five are active, medial segments with Holocene slip rates of 1-2 mm a-1, recurrence intervals of 2000-4000 years and average lengths of about 50 km. Five are less active, distal segments with mostly pre-Holocene surface ruptures, late Quaternary slip rates of <0.5 mm a-1, recurrence intervals of ???10,000 years and average lengths of about 20 km. Surface-faulting events on each of the medial segments of the WFZ formed 2-4-m-high scarps repeatedly during the Holocene. Paleoseismological records for the past 6000 years indicate that a major surface-rupturing earthquake has occurred along one of the medial segments about every 395 ?? 60 years. However, between about 400 and 1500 years ago, the WFZ experienced six major surface-rupturing events, an average of one event every 220 years, or about twice as often as expected from the 6000-year record. Evidence has been found that surface-rupturing events occurred on the WFZ during the past 400 years, a time period which is twice the average intracluster recurrence interval and equal to the average Holocene recurrence interval.

Convective instabilities in traveling fronts of addition polymerization

NASA Technical Reports Server (NTRS)

Pojman, John A.; Jones, Chris E.; Khan, Akhtar M.

1993-01-01

An autocatalytic reaction in an unstirred vessel can support a constant velocity wavefront resulting from the coupling of diffusion to the chemical reaction. A flare front is a common example in which heat is the autocatalytic species that diffuses into unreacted regions stimulating a reaction that produces more heat. Traveling fronts were studied in synthetic polymerization reactions under high pressure by workers in the former USSR. More recently, propagating fronts of methacrylic acid polymerization were studied under ambient conditions, both with video techniques and by NMR.

Genome Sequences of 19 Novel Erwinia amylovora Bacteriophages

PubMed Central

Esplin, Ian N. D.; Berg, Jordan A.; Sharma, Ruchira; Allen, Robert C.; Arens, Daniel K.; Ashcroft, Cody R.; Bairett, Shannon R.; Beatty, Nolan J.; Bickmore, Madeline; Bloomfield, Travis J.; Brady, T. Scott; Bybee, Rachel N.; Carter, John L.; Choi, Minsey C.; Duncan, Steven; Fajardo, Christopher P.; Foy, Brayden B.; Fuhriman, David A.; Gibby, Paul D.; Grossarth, Savannah E.; Harbaugh, Kala; Harris, Natalie; Hilton, Jared A.; Hurst, Emily; Hyde, Jonathan R.; Ingersoll, Kayleigh; Jacobson, Caitlin M.; James, Brady D.; Jarvis, Todd M.; Jaen-Anieves, Daniella; Jensen, Garrett L.; Knabe, Bradley K.; Kruger, Jared L.; Merrill, Bryan D.; Pape, Jenny A.; Payne Anderson, Ashley M.; Payne, David E.; Peck, Malia D.; Pollock, Samuel V.; Putnam, Micah J.; Ransom, Ethan K.; Ririe, Devin B.; Robinson, David M.; Rogers, Spencer L.; Russell, Kerri A.; Schoenhals, Jonathan E.; Shurtleff, Christopher A.; Simister, Austin R.; Smith, Hunter G.; Stephenson, Michael B.; Staley, Lyndsay A.; Stettler, Jason M.; Stratton, Mallorie L.; Tateoka, Olivia B.; Tatlow, P. J.; Taylor, Alexander S.; Thompson, Suzanne E.; Townsend, Michelle H.; Thurgood, Trever L.; Usher, Brittian K.; Whitley, Kiara V.; Ward, Andrew T.; Ward, Megan E. H.; Webb, Charles J.; Wienclaw, Trevor M.; Williamson, Taryn L.; Wells, Michael J.; Wright, Cole K.; Breakwell, Donald P.; Hope, Sandra

2017-01-01

ABSTRACT Erwinia amylovora is the causal agent of fire blight, a devastating disease affecting some plants of the Rosaceae family. We isolated bacteriophages from samples collected from infected apple and pear trees along the Wasatch Front in Utah. We announce 19 high-quality complete genome sequences of E. amylovora bacteriophages. PMID:29146842

Simulating the Evolving Behavior of Secondary Slow Slip Fronts

NASA Astrophysics Data System (ADS)

Peng, Y.; Rubin, A. M.

2017-12-01

High-resolution tremor catalogs of slow slip events reveal secondary slow slip fronts behind the main front that repetitively occupy the same source area during a single episode. These repetitive fronts are most often observed in regions with high tremor density. Their recurrence intervals gradually increase from being too short to be tidally modulated (tens of minutes) to being close to tidal periods (about 12 or 24 hours). This could be explained by a decreasing loading rate from creep in the surrounding regions (with few or no observable tremor events) as the main front passes by. As the recurrence intervals of the fronts increase, eventually they lock in on the tidal periods. We attempt to simulate this numerically using a rate-and-state friction law that transitions from velocity-weakening at low slip speeds to velocity strengthening at high slip speeds. Many small circular patches with a cutoff velocity an order of magnitude higher than that of the background are randomly placed on the fault, in order to simulate the average properties of the high-density tremor zone. Preliminary results show that given reasonable parameters, this model produces similar propagation speeds of the forward-migrating main front inside and outside the high-density tremor zone, consistent with observations. We will explore the behavior of the secondary fronts that arise in this model, in relation to the local density of the small tremor-analog patches, the overall geometry of the tremor zone and the tides.

Structural analysis using thrust-fault hanging-wall sequence diagrams: Ogden duplex, Wasatch Range, Utah

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schirmer, T.W.

1988-05-01

Detailed mapping and cross-section traverses provide the control for structural analysis and geometric modeling of the Ogden duplex, a complex thrust system exposed in the Wasatch Mountains, east of Ogden, Utah. The structures consist of east-dipping folded thrust faults, basement-cored horses, lateral ramps and folds, and tear faults. The sequence of thrusting determined by means of lateral overlap of horses, thrust-splay relationships, and a top-to-bottom piggyback development is Willard thrust, Ogden thrust, Weber thrust, and Taylor thrust. Major decollement zones occur in the Cambrian shales and limestones. The Tintic Quartzite is the marker for determining gross geometries of horses. Thismore » exposed duplex serves as a good model to illustrate the method of constructing a hanging-wall sequence diagram - a series of longitudinal cross sections that move forward in time and space, and show how a thrust system formed as it moved updip over various footwall ramps. A hanging wall sequence diagram also shows the complex lateral variations in a thrust system and helps to locate lateral ramps, lateral folds, tear faults, and other features not shown on dip-oriented cross sections. 8 figures.« less

Tracking the Polar Front south of New Zealand using penguin dive data

NASA Astrophysics Data System (ADS)

Sokolov, Serguei; Rintoul, Stephen R.; Wienecke, Barbara

2006-04-01

Nearly 36,000 vertical temperature profiles collected by 15 king penguins are used to map oceanographic fronts south of New Zealand. There is good correspondence between Antarctic Circumpolar Current (ACC) front locations derived from temperatures sampled in the upper 150 m along the penguin tracks and front positions inferred using maps of sea surface height (SSH). Mesoscale features detected in the SSH maps from this eddy-rich region are also reproduced in the individual temperature sections based on dive data. The foraging strategy of Macquarie Island king penguins appears to be influenced strongly by oceanographic structure: almost all the penguin dives are confined to the region close to and between the northern and southern branches of the Polar Front. Surface chlorophyll distributions also reflect the influence of the ACC fronts, with the northern branch of the Polar Front marking a boundary between low surface chlorophyll to the north and elevated values to the south.

A Regional Survey of River-plume Sedimentation on the Mississippi River Delta Front

NASA Astrophysics Data System (ADS)

Courtois, A. J.; Bentley, S. J.; Xu, K.; Georgiou, I. Y.; Maloney, J. M.; Miner, M. D.; Chaytor, J. D.; Smith, J.

2017-12-01

Many studies of the Mississippi River and Delta (MRD) have shown historic declines in sediment load reaching the main river distributaries over the last few decades. Recent studies also reported that 50% of the suspended load during floods is sequestered within the delta. While the impact of declining sediment load on wetland loss is well documented, submarine sedimentary processes on the delta front during this recent period of declining sediment load are understudied. To better understand modern sediment dispersal and deposition across the Mississippi River Delta Front, 31 multicores were collected in June 2017 from locations extending offshore from Southwest Pass, South Pass, and Pass a Loutre (the main river outlets) in water depths of 25-280 m. Core locations were selected based on multibeam bathymetry and morphology collected by the USGS in May 2017; the timing of collection coincided with the end of annual peak discharge on the Mississippi River. This multi-agency survey is the first to study delta-front sedimentary processes regionally with such a wide suite of tools. Target locations for coring included the dominant depositional environments: mudflow lobes, gullies, and undisturbed prodelta. Cores were subsampled at 2 cm intervals and analyzed for Beryllium-7 activity via gamma spectrometry; in such settings, Be-7 can be used as a tracer of sediment recently delivered from fluvial origin. Results indicate a general trend of declining Be-7 activity with increasing distance from source, and in deeper water. Inshore samples near Southwest Pass show the deepest penetration depth of Be-7 into the sediment (24-26 cm), which is a preliminary indicator of rapid seasonal sedimentation. Nearshore samples from South Pass exhibited similar Be-7 penetration depths, with results near Pass a Loutre to 14-16 cm depth. Be-7 remains detectable to 2 cm in water 206 m deep, approximately 20 km from South Pass. Sediment dispersal remains impressive offshore from all three

Utah: Salt Lake Region

Atmospheric Science Data Center

2014-05-15

... scheduled events are at city (indoor) locations, and five in mountain (outdoor) facilities. All ten can be found within the area contained ... Lake City is surrounded by mountains including the Wasatch Range to the east, and the temperature difference between the Great Salt Lake ...

Riparian ecosystem consequences of water redistribution along the Colorado Front Range

Treesearch

John D. Wiener; Kathleen A. Dwire; Susan K. Skagen; Robert R. Crifasi; David Yates

2008-01-01

Water has shaped the American West. Nowhere is this more evident than along the Front Range of Colorado. At the west end of the famous Great Plains rainfall gradient, the Front Range extends most of the length of Colorado and is one of the fastest growing metropolitan regions in the nation. Annual precipitation along the Front Range averages about 16 inches, and...

Assessing the earthquake hazards in urban areas

USGS Publications Warehouse

Hays, W.W.; Gori, P.L.; Kockelman, W.J.

1988-01-01

Major urban areas in widely scattered geographic locations across the United States are a t varying degrees of risk from earthquakes. the locations of these urban areas include Charleston, South Carolina; Memphis Tennessee; St.Louis, Missouri; Salt Lake City, Utah; Seattle-Tacoma, Washington; Portland, Oregon; and Anchorage, Alaska; even Boston, Massachusetts, and Buffalo New York, have a history of large earthquakes. Cooperative research during the past decade has focused on assessing the nature and degree of the risk or seismic hazard i nthe broad geographic regions around each urban area. The strategy since the 1970's has been to bring together local, State, and Federal resources to solve the problem of assessing seismic risk. Successfl sooperative programs have been launched in the San Francisco Bay and Los Angeles regions in California and the Wasatch Front region in Utah. 

Revised Subsurface Stratigraphic Framework of the Fort Union and Wasatch Formations, Powder River Basin, Wyoming and Montana

USGS Publications Warehouse

Flores, Romeo M.; Spear, Brianne D.; Purchase, Peter A.; Gallagher, Craig M.

2010-01-01

Described in this report is an updated subsurface stratigraphic framework of the Paleocene Fort Union Formation and Eocene Wasatch Formation in the Powder River Basin (PRB) in Wyoming and Montana. This framework is graphically presented in 17 intersecting west-east and north-south cross sections across the basin. Also included are: (1) the dataset and all associated digital files and (2) digital files for all figures and table 1 suitable for large-format printing. The purpose of this U.S. Geological Survey (USGS) Open-File Report is to provide rapid dissemination and accessibility of the stratigraphic cross sections and related digital data to USGS customers, especially the U.S. Bureau of Land Management (BLM), to facilitate their modeling of the hydrostratigraphy of the PRB. This report contains a brief summary of the coal-bed correlations and database, and is part of a larger ongoing study that will be available in the near future.

Genome Sequences of 19 Novel Erwinia amylovora Bacteriophages.

PubMed

Esplin, Ian N D; Berg, Jordan A; Sharma, Ruchira; Allen, Robert C; Arens, Daniel K; Ashcroft, Cody R; Bairett, Shannon R; Beatty, Nolan J; Bickmore, Madeline; Bloomfield, Travis J; Brady, T Scott; Bybee, Rachel N; Carter, John L; Choi, Minsey C; Duncan, Steven; Fajardo, Christopher P; Foy, Brayden B; Fuhriman, David A; Gibby, Paul D; Grossarth, Savannah E; Harbaugh, Kala; Harris, Natalie; Hilton, Jared A; Hurst, Emily; Hyde, Jonathan R; Ingersoll, Kayleigh; Jacobson, Caitlin M; James, Brady D; Jarvis, Todd M; Jaen-Anieves, Daniella; Jensen, Garrett L; Knabe, Bradley K; Kruger, Jared L; Merrill, Bryan D; Pape, Jenny A; Payne Anderson, Ashley M; Payne, David E; Peck, Malia D; Pollock, Samuel V; Putnam, Micah J; Ransom, Ethan K; Ririe, Devin B; Robinson, David M; Rogers, Spencer L; Russell, Kerri A; Schoenhals, Jonathan E; Shurtleff, Christopher A; Simister, Austin R; Smith, Hunter G; Stephenson, Michael B; Staley, Lyndsay A; Stettler, Jason M; Stratton, Mallorie L; Tateoka, Olivia B; Tatlow, P J; Taylor, Alexander S; Thompson, Suzanne E; Townsend, Michelle H; Thurgood, Trever L; Usher, Brittian K; Whitley, Kiara V; Ward, Andrew T; Ward, Megan E H; Webb, Charles J; Wienclaw, Trevor M; Williamson, Taryn L; Wells, Michael J; Wright, Cole K; Breakwell, Donald P; Hope, Sandra; Grose, Julianne H

2017-11-16

Erwinia amylovora is the causal agent of fire blight, a devastating disease affecting some plants of the Rosaceae family. We isolated bacteriophages from samples collected from infected apple and pear trees along the Wasatch Front in Utah. We announce 19 high-quality complete genome sequences of E. amylovora bacteriophages. Copyright © 2017 Esplin et al.

Radiative thermal conduction fronts

NASA Technical Reports Server (NTRS)

Borkowski, Kazimierz J.; Balbus, Steven A.; Fristrom, Carl C.

1990-01-01

The discovery of the O VI interstellar absorption lines in our Galaxy by the Copernicus observatory was a turning point in our understanding of the Interstellar Medium (ISM). It implied the presence of widespread hot (approx. 10 to the 6th power K) gas in disk galaxies. The detection of highly ionized species in quasi-stellar objects' absorption spectra may be the first indirect observation of this hot phase in external disk galaxies. Previous efforts to understand extensive O VI absorption line data from our Galaxy were not very successful in locating the regions where this absorption originates. The location at interfaces between evaporating ISM clouds and hot gas was favored, but recent studies of steady-state conduction fronts in spherical clouds by Ballet, Arnaud, and Rothenflug (1986) and Bohringer and Hartquist (1987) rejected evaporative fronts as the absorption sites. Researchers report here on time-dependent nonequilibrium calculations of planar conductive fronts whose properties match well with observations, and suggest reasons for the difference between the researchers' results and the above. They included magnetic fields in additional models, not reported here, and the conclusions are not affected by their presence.

Radiative thermal conduction fronts

NASA Astrophysics Data System (ADS)

Borkowski, Kazimierz J.; Balbus, Steven A.; Fristrom, Carl C.

1990-07-01

The discovery of the O VI interstellar absorption lines in our Galaxy by the Copernicus observatory was a turning point in our understanding of the Interstellar Medium (ISM). It implied the presence of widespread hot (approx. 10 to the 6th power K) gas in disk galaxies. The detection of highly ionized species in quasi-stellar objects' absorption spectra may be the first indirect observation of this hot phase in external disk galaxies. Previous efforts to understand extensive O VI absorption line data from our Galaxy were not very successful in locating the regions where this absorption originates. The location at interfaces between evaporating ISM clouds and hot gas was favored, but recent studies of steady-state conduction fronts in spherical clouds by Ballet, Arnaud, and Rothenflug (1986) and Bohringer and Hartquist (1987) rejected evaporative fronts as the absorption sites. Researchers report here on time-dependent nonequilibrium calculations of planar conductive fronts whose properties match well with observations, and suggest reasons for the difference between the researchers' results and the above. They included magnetic fields in additional models, not reported here, and the conclusions are not affected by their presence.

Thiokol/Wasatch installation evaluation of the redesigned field joint protection system (concepts 1 and 3)

NASA Technical Reports Server (NTRS)

Cook, M.

1989-01-01

The procedures, performance, and results obtained from the Thiokol Corporation/Wasatch Redesigned Field Joint Protection System (FJPS) Installation Evaluation are documented. The purpose of the evaluation was to demonstrate and develop the procedures required to install two different concepts (referred to as Concepts 1 and 3) of the redesigned FJPS. The processing capability of each configuration was then evaluated and compared. The FJPS is installed on redesigned solid rocket motors (RSRM) to protect the field joints from rain intrusion and to maintain the joint temperature sensor measurement between 85 and 122 F while the boosters are on the launch pad. The FJPS is being redesigned to reduce installation timelines at KSC and to simplify or eliminate installation processing problems related to the present design of an EPDM moisture seal/extruded cork combination. Several installation techniques were evaluated, and a preferred method of application was developed for each concept. The installations were performed with the test article in the vertical (flight) position. Comparative timelines between the two concepts were also developed. An additional evaluation of the Concept 3 configuration was performed with the test article in the horizontal position, to simulate an overhead installation on a technical evaluation motor (TEM).

Liquid redistribution behind a drainage front in porous media imaged by neutron radiography

NASA Astrophysics Data System (ADS)

Hoogland, Frouke; Lehmann, Peter; Moebius, Franziska; Vontobel, Peter; Or, Dani

2013-04-01

Drainage from porous media is a highly dynamic process involving the motion of a displacement front with rapid pore scale interfacial jumps and phase entrapment, but also a more gradual host of liquid redistribution processes in the unsaturated region behind the front. Depending on the velocity of the drainage process, liquid properties and the permeability of the porous medium, redistribution lingers long after the main drainage process is stopped, until gravity and capillary forces regain equilibrium. The rapid and often highly inertial Haines jumps at the drainage front challenge the validity of Buckingham-Darcy law and thus representation of the process based on the foundation of Richards equation. To quantify front displacement and liquid reconfiguration and to test validity of Richards equation with respect to fast drainage dynamics, we carried out drainage experiments by withdrawing water from the bottom of initially saturated sand-filled Hele-Shaw cells at constant water flux (2.6 or 13.1 mm/minute). Water content distribution and evolution of drainage front were measured with neutron radiography at spatial and temporal resolutions of 0.1 mm and 3 seconds, respectively. Water pressure was measured above and below the front using pressure transducers and a tensiometer. After the pump was stopped (at a front depth around 100 mm), capillary pressure values in the unsaturated region (above the front) gradually converged to a new equilibrium. The pressure signal in the saturated region below the front reflected viscous losses during flow that were relaxed when the pump stopped. During pressure relaxation water was redistributed primarily downward in the unsaturated region. Pressure signals and dynamics of water content profiles for fast process (13.6 mm/minute) could not be reproduced with Richards equation based on hydraulic functions determined in preceding laboratory experiments. To explore if the deviations stem from inappropriate hydraulic functions we

Extreme weather caused by concurrent cyclone, front and thunderstorm occurrences

PubMed Central

Dowdy, Andrew J.; Catto, Jennifer L.

2017-01-01

Phenomena such as cyclones, fronts and thunderstorms can cause extreme weather in various regions throughout the world. Although these phenomena have been examined in numerous studies, they have not all been systematically examined in combination with each other, including in relation to extreme precipitation and extreme winds throughout the world. Consequently, the combined influence of these phenomena represents a substantial gap in the current understanding of the causes of extreme weather events. Here we present a systematic analysis of cyclones, fronts and thunderstorms in combination with each other, as represented by seven different types of storm combinations. Our results highlight the storm combinations that most frequently cause extreme weather in various regions of the world. The highest risk of extreme precipitation and extreme wind speeds is found to be associated with a triple storm type characterized by concurrent cyclone, front and thunderstorm occurrences. Our findings reveal new insight on the relationships between cyclones, fronts and thunderstorms and clearly demonstrate the importance of concurrent phenomena in causing extreme weather. PMID:28074909

The effects of variable front persistence and intensity on mesopelagic fish communities: a comparison of three fronts in the California Current Ecosystem

NASA Astrophysics Data System (ADS)

Netburn, A. N.; Koslow, J. A.

2016-02-01

Although the strong physical gradients at fronts are primarily realized in the epipelagic, the biological impacts of frontal ecosystems can extend into mesopelagic waters. In 2008, Lara-Lopez et al. (2012) observed a significant shift in total biomass and community composition of migrating mesopelagic fishes at a strong persistent front off of the Pt. Conception area of the southern California Current Ecosystem. Through the California Current Ecosystem Long-Term Ecological Research Program, two additional intensive sampling cruises have been conducted on frontal systems in the general region. In 2011 and 2012, paired day and night midwater Matsuda-Oozeki-Hu trawls were conducted at stations located on either side of the fronts and at the fronts themselves, a suite of concurrent observations of the physical environment measured, and lower trophic levels sampled. Using satellite imagery, we estimate front duration of each of the 2008, 2011, and 2012 fronts, and investigate changes to the relative abundance and community composition across these systems, comparing the resolved patterns in 2011 and 2012 to those published from 2008. Results of this work will help address the questions: (1) What are the timescales required for front presence to impact mesopelagic fish communities? (2) Do different types of frontal systems (e.g., an eddy front vs. a "classic" front) result in different patterns of mesopelagic fish abundance and community composition? These answers will provide insight into the mechanisms of accumulation of fishes at fronts. As many mesopelagic fishes are important forage species for oceanic predators, understanding their response to the high productivity frontal systems is key to understanding ecosystem-wide impacts of fronts.

Formation of temperature front in stably stratified turbulence

NASA Astrophysics Data System (ADS)

Kimura, Yoshifumi; Sullivan, Peter; Herring, Jackson

2016-11-01

An important feature of stably stratified turbulence is the significant influence of internal gravity waves which makes stably stratified turbulence unique compared to homogeneous isotropic turbulence. In this paper, we investigate the genesis of temperature fronts-a crucial subject both practically and fundamentally-in stably stratified turbulence using Direct Numerical Simulations (DNS) of the Navier-Stokes equation under the Boussinesq approximation with 10243 grid points. Vertical profiles of temperature fluctuations show almost vertically periodic sawtooth wavy structures with negative and positive layers stacked together with clear boundaries implying a sharp temperature fronts. The sawtooth waves consist of gradual decreasing temperature fluctuations with rapid recovery to a positive value as the frontal boundary is crossed vertically. This asymmetry of gradients comes from the structure that warm temperature region lies on top of cool temperature region, and can be verified in the skewed probability density function (PDF) of vertical temperature gradient. We try to extract the flow structures and mechanism for the formation and maintenance of the strong temperature front numerically.

Fault segmentation: New concepts from the Wasatch Fault Zone, Utah, USA

USGS Publications Warehouse

Duross, Christopher; Personius, Stephen F.; Crone, Anthony J.; Olig, Susan S.; Hylland, Michael D.; Lund, William R.; Schwartz, David P.

2016-01-01

The question of whether structural segment boundaries along multisegment normal faults such as the Wasatch fault zone (WFZ) act as persistent barriers to rupture is critical to seismic hazard analyses. We synthesized late Holocene paleoseismic data from 20 trench sites along the central WFZ to evaluate earthquake rupture length and fault segmentation. For the youngest (<3 ka) and best-constrained earthquakes, differences in earthquake timing across prominent primary segment boundaries, especially for the most recent earthquakes on the north-central WFZ, are consistent with segment-controlled ruptures. However, broadly constrained earthquake times, dissimilar event times along the segments, the presence of smaller-scale (subsegment) boundaries, and areas of complex faulting permit partial-segment and multisegment (e.g., spillover) ruptures that are shorter (~20–40 km) or longer (~60–100 km) than the primary segment lengths (35–59 km). We report a segmented WFZ model that includes 24 earthquakes since ~7 ka and yields mean estimates of recurrence (1.1–1.3 kyr) and vertical slip rate (1.3–2.0 mm/yr) for the segments. However, additional rupture scenarios that include segment boundary spatial uncertainties, floating earthquakes, and multisegment ruptures are necessary to fully address epistemic uncertainties in rupture length. We compare the central WFZ to paleoseismic and historical surface ruptures in the Basin and Range Province and central Italian Apennines and conclude that displacement profiles have limited value for assessing the persistence of segment boundaries but can aid in interpreting prehistoric spillover ruptures. Our comparison also suggests that the probabilities of shorter and longer ruptures on the WFZ need to be investigated.

Fluid front morphologies in gap-modulated Hele-Shaw cells

NASA Astrophysics Data System (ADS)

Díaz-Piola, Lautaro; Planet, Ramon; Campàs, Otger; Casademunt, Jaume; Ortín, Jordi

2017-09-01

We consider the displacement of an inviscid fluid (air) by a viscous fluid (oil) in a narrow channel with gap-thickness modulations. The interfacial dynamics of this problem is strongly nonlocal and exhibits competing effects from capillarity and permeability. We derive analytical predictions of steady-state front morphologies, which are exact at linear level in the case of a persistent modulation in the direction of front advancement. The theoretical predictions are in good agreement with experimental measurements of steady-state front morphologies obtained in a Hele-Shaw cell with modulations of the channel depth, consisting on three parallel tracks of reduced depth, for small gap modulations. The relative average distance between theoretical and experimental fronts in the region around the central track is smaller than about 4 % , provided that the height of the tracks is less than 13 % of the total channel depth and the local distortion of the front height h is small enough (|∇ h |<0.8 ) for the linear approximation to hold.

Speed of fast and slow rupture fronts along frictional interfaces

NASA Astrophysics Data System (ADS)

Trømborg, Jørgen Kjoshagen; Sveinsson, Henrik Andersen; Thøgersen, Kjetil; Scheibert, Julien; Malthe-Sørenssen, Anders

2015-07-01

The transition from stick to slip at a dry frictional interface occurs through the breaking of microjunctions between the two contacting surfaces. Typically, interactions between junctions through the bulk lead to rupture fronts propagating from weak and/or highly stressed regions, whose junctions break first. Experiments find rupture fronts ranging from quasistatic fronts, via fronts much slower than elastic wave speeds, to fronts faster than the shear wave speed. The mechanisms behind and selection between these fronts are still imperfectly understood. Here we perform simulations in an elastic two-dimensional spring-block model where the frictional interaction between each interfacial block and the substrate arises from a set of junctions modeled explicitly. We find that material slip speed and rupture front speed are proportional across the full range of front speeds we observe. We revisit a mechanism for slow slip in the model and demonstrate that fast slip and fast fronts have a different, inertial origin. We highlight the long transients in front speed even along homogeneous interfaces, and we study how both the local shear to normal stress ratio and the local strength are involved in the selection of front type and front speed. Last, we introduce an experimentally accessible integrated measure of block slip history, the Gini coefficient, and demonstrate that in the model it is a good predictor of the history-dependent local static friction coefficient of the interface. These results will contribute both to building a physically based classification of the various types of fronts and to identifying the important mechanisms involved in the selection of their propagation speed.

Analysis and selection of magnitude relations for the Working Group on Utah Earthquake Probabilities

USGS Publications Warehouse

Duross, Christopher; Olig, Susan; Schwartz, David

2015-01-01

Prior to calculating time-independent and -dependent earthquake probabilities for faults in the Wasatch Front region, the Working Group on Utah Earthquake Probabilities (WGUEP) updated a seismic-source model for the region (Wong and others, 2014) and evaluated 19 historical regressions on earthquake magnitude (M). These regressions relate M to fault parameters for historical surface-faulting earthquakes, including linear fault length (e.g., surface-rupture length [SRL] or segment length), average displacement, maximum displacement, rupture area, seismic moment (Mo ), and slip rate. These regressions show that significant epistemic uncertainties complicate the determination of characteristic magnitude for fault sources in the Basin and Range Province (BRP). For example, we found that M estimates (as a function of SRL) span about 0.3–0.4 units (figure 1) owing to differences in the fault parameter used; age, quality, and size of historical earthquake databases; and fault type and region considered.

Mesoscale ocean fronts enhance carbon export due to gravitational sinking and subduction

NASA Astrophysics Data System (ADS)

Stukel, Michael R.; Aluwihare, Lihini I.; Barbeau, Katherine A.; Chekalyuk, Alexander M.; Goericke, Ralf; Miller, Arthur J.; Ohman, Mark D.; Ruacho, Angel; Song, Hajoon; Stephens, Brandon M.; Landry, Michael R.

2017-02-01

Enhanced vertical carbon transport (gravitational sinking and subduction) at mesoscale ocean fronts may explain the demonstrated imbalance of new production and sinking particle export in coastal upwelling ecosystems. Based on flux assessments from 238U:234Th disequilibrium and sediment traps, we found 2 to 3 times higher rates of gravitational particle export near a deep-water front (305 mg Cṡm-2ṡd-1) compared with adjacent water or to mean (nonfrontal) regional conditions. Elevated particle flux at the front was mechanistically linked to Fe-stressed diatoms and high mesozooplankton fecal pellet production. Using a data assimilative regional ocean model fit to measured conditions, we estimate that an additional ˜225 mg Cṡm-2ṡd-1 was exported as subduction of particle-rich water at the front, highlighting a transport mechanism that is not captured by sediment traps and is poorly quantified by most models and in situ measurements. Mesoscale fronts may be responsible for over a quarter of total organic carbon sequestration in the California Current and other coastal upwelling ecosystems.

Mesoscale ocean fronts enhance carbon export due to gravitational sinking and subduction

PubMed Central

Stukel, Michael R.; Aluwihare, Lihini I.; Barbeau, Katherine A.; Chekalyuk, Alexander M.; Goericke, Ralf; Miller, Arthur J.; Ohman, Mark D.; Ruacho, Angel; Song, Hajoon; Stephens, Brandon M.; Landry, Michael R.

2017-01-01

Enhanced vertical carbon transport (gravitational sinking and subduction) at mesoscale ocean fronts may explain the demonstrated imbalance of new production and sinking particle export in coastal upwelling ecosystems. Based on flux assessments from 238U:234Th disequilibrium and sediment traps, we found 2 to 3 times higher rates of gravitational particle export near a deep-water front (305 mg C⋅m−2⋅d−1) compared with adjacent water or to mean (nonfrontal) regional conditions. Elevated particle flux at the front was mechanistically linked to Fe-stressed diatoms and high mesozooplankton fecal pellet production. Using a data assimilative regional ocean model fit to measured conditions, we estimate that an additional ∼225 mg C⋅m−2⋅d−1 was exported as subduction of particle-rich water at the front, highlighting a transport mechanism that is not captured by sediment traps and is poorly quantified by most models and in situ measurements. Mesoscale fronts may be responsible for over a quarter of total organic carbon sequestration in the California Current and other coastal upwelling ecosystems. PMID:28115723

Deciphering Front-Side Complex Formation in SN2 Reactions via Dynamics Mapping.

PubMed

Szabó, István; Olasz, Balázs; Czakó, Gábor

2017-07-06

Due to their importance in organic chemistry, the atomistic understanding of bimolecular nucleophilic substitution (S N 2) reactions shows exponentially growing interest. In this publication, the effect of front-side complex (FSC) formation is uncovered via quasi-classical trajectory computations combined with a novel analysis method called trajectory orthogonal projection (TOP). For both F - + CH 3 Y [Y = Cl,I] reactions, the lifetime distributions of the F - ···YCH 3 front-side complex revealed weakly trapped nucleophiles (F - ). However, only the F - + CH 3 I reaction features strongly trapped nucleophiles in the front-side region of the prereaction well. Interestingly, both back-side and front-side attack show propensity to long-lived FSC formation. Spatial distributions of the nucleophile demonstrate more prominent FSC formation in case of the F - + CH 3 I reaction compared to F - + CH 3 Cl. The presence of front-side intermediates and the broad spatial distribution in the back-side region may explain the indirect nature of the F - + CH 3 I reaction.

Concepts for a Muon Accelerator Front-End

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stratakis, Diktys; Berg, Scott; Neuffer, David

2017-03-16

We present a muon capture front-end scheme for muon based applications. In this Front-End design, a proton bunch strikes a target and creates secondary pions that drift into a capture channel, decaying into muons. A series of rf cavities forms the resulting muon beams into a series of bunches of differerent energies, aligns the bunches to equal central energies, and initiates ionization cooling. We also discuss the design of a chicane system for the removal of unwanted secondary particles from the muon capture region and thus reduce activation of the machine. With the aid of numerical simulations we evaluate themore » performance of this Front-End scheme as well as study its sensitivity against key parameters such as the type of target, the number of rf cavities and the gas pressure of the channel.« less

Geology of the Molina Member of the Wasatch Formation, Piceance Basin, Colorado

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lorenz, J.; Nadon, G.; LaFreniere, L.

1996-06-01

The Molina Member of the Wasatch Formation has been cored in order to assess the presence/absence and character of microbial communities in the deep subsurface. Geological study of the Molina Member was undertaken in support of the microbiological tasks of this project, for the purposes of characterizing the host strata and of assessing the potential for post-depositional introduction of microbes into the strata. The Molina Member comprises a sandy fluvial unit within a formation dominated by mudstones. Sandy to conglomeratic deposits of braided and meandering fluvial systems are present on the western and eastern margins of the basin respectively, althoughmore » the physical and temporal equivalence of these systems cannot be proven. Distal braided facies of planar-horizontal bedded sandstones are recognized on the western margin of the basin. Natural fractures are present in all Molina sandstones, commonly as apparent shear pairs. Core from the 1-M-18 well contains natural fractures similar to those found in outcrops, and has sedimentological affinities to the meandering systems of the eastern margin of the basin. The hydrologic framework of the Molina, and thus any potential post-depositional introduction of microbes into the formation, should have been controlled by approximately east-west flow through the natural fracture system, the geometries and extent of the sandstones in which the fractures occur, and hydraulic gradient. Migration to the well site, from outcropping recharge areas at the edge of the basin, could have started as early as 40 million years ago if the cored strata are connected to the eastern sedimentary system.« less

U.S. Geological Survey ground-water studies in Utah

USGS Publications Warehouse

Gates, Joseph S.

1988-01-01

Ground water is an important natural resource in Utah. In the basins west of the Wasatch Front, and in many other parts of Utah, ground water is the primary source of water. In many of the basins of the western desert and in parts of the Colorado Plateau, ground water is the only reliable source of water. Along the Wasatch Front to the north and south of Salt Lake City, in the Uinta Basin, and in the Sevier River drainage, surface water is the primary source of water. Ground-water sources supply about 20 percent of all water used in Utah and about 63 percent of the water for public supply. Of the total amount of ground water used, 44 percent is for irrigation, 35 percent is for public supply, 11 percent is for industry, 5 percent is for rural domestic supplies, and 5 percent is for livestock. The major issues related to ground water in Utah are: -Development of additional ground-water supplies while protecting existing water rights and minimizing effects on water levels, water quality, and streamflow, and-Protection of ground-water resources from contamination by pollutants from various types of land-use and waste-disposal practices.

Tectonic evolution of the central Brooks Range mountain front: Evidence from the Atigun Gorge region

USGS Publications Warehouse

Mull, C.G.; Glenn, R.K.; Adams, K.E.

1997-01-01

Atigun Gorge, at the northern front of the eastern Endicott Mountains, contains well-exposed rocks of the upper part of the Endicott Mountains allochthon and rocks of the structurally higher Picnic Creek or Ipnavik River allochthon. These allochthons contain rocks as young as Early Cretaceous (Valanginian) and are separated by a nearly vertical fault zone that contains exotic blocks of Triassic and Jurassic chert and silicified mudstone. Siliceous rocks of this type are not present in the Endicott Mountains allochthon but are characteristic of the Picnic Creek, Ipnavik River, and some of the other allochthons that structurally overlie the Endicott Mountains allochthon in the central and western Brooks Range. These exotic blocks, therefore indicate that structurally higher rocks of either the Picnic Creek or Ipnavik River allochthon were emplaced during the Early Cretaceous and are preserved along the northern flank of the eastern Endicott Mountains. The deformed thickness of this higher allochthon in the subsurface north of the mountains is unknown but probably exceeds 2 kilometers. Similar relations are mapped east of Atigun Gorge in an area of structural transition from the eastern Endicott Mountains into the northern Philip Smith Mountains, which are formed by the parautochthonous North Slope stratigraphic assemblage. The allochthonous rocks at the mountain front are regionally unconformably overlain by proximal Lower Cretaceous (Albian) foredeep conglomerate at the southern flank of the Colville basin, but at Atigun Gorge, the base of these deposits is interpreted as a possible back thrust at a triangle zone. Conglomerate clasts in the foredeep deposits are dominantly chert, mafic igneous rock, and other lithologies characteristic of the Picnic Creek and Ipnavik River allochthons and scattered clasts from the Endicott Mountains allochthon. The conglomerates show that the chert-rich allochthonous rocks and the Endicott Mountains allochthon were emplaced in the

Shelf sea tidal currents and mixing fronts determined from ocean glider observations

NASA Astrophysics Data System (ADS)

Sheehan, Peter M. F.; Berx, Barbara; Gallego, Alejandro; Hall, Rob A.; Heywood, Karen J.; Hughes, Sarah L.; Queste, Bastien Y.

2018-03-01

Tides and tidal mixing fronts are of fundamental importance to understanding shelf sea dynamics and ecosystems. Ocean gliders enable the observation of fronts and tide-dominated flows at high resolution. We use dive-average currents from a 2-month (12 October-2 December 2013) glider deployment along a zonal hydrographic section in the north-western North Sea to accurately determine M2 and S2 tidal velocities. The results of the glider-based method agree well with tidal velocities measured by current meters and with velocities extracted from the TPXO tide model. The method enhances the utility of gliders as an ocean-observing platform, particularly in regions where tide models are known to be limited. We then use the glider-derived tidal velocities to investigate tidal controls on the location of a front repeatedly observed by the glider. The front moves offshore at a rate of 0.51 km day-1. During the first part of the deployment (from mid-October until mid-November), results of a one-dimensional model suggest that the balance between surface heat fluxes and tidal stirring is the primary control on frontal location: as heat is lost to the atmosphere, full-depth mixing is able to occur in progressively deeper water. In the latter half of the deployment (mid-November to early December), a front controlled solely by heat fluxes and tidal stirring is not predicted to exist, yet a front persists in the observations. We analyse hydrographic observations collected by the glider to attribute the persistence of the front to the boundary between different water masses, in particular to the presence of cold, saline, Atlantic-origin water in the deeper portion of the section. We combine these results to propose that the front is a hybrid front: one controlled in summer by the local balance between heat fluxes and mixing and which in winter exists as the boundary between water masses advected to the north-western North Sea from diverse source regions. The glider observations

Planar microlens with front-face angle: design, fabrication, and characterization

NASA Astrophysics Data System (ADS)

Al Hafiz, Md. Abdullah; Michael, Aron; Kwok, Chee-Yee

2016-07-01

This paper studies the effect of microlens front-face angle on the performance of an optical system consisting of a planar-graded refractive index (GRIN) lens pair facing each other separated by a free-space region. The planar silica microlens pairs are designed to facilitate low-loss optical signal propagation in the free-space region between the opposing optical waveguides. The planar lens is fabricated from a 38-μm-thick fluorine-doped silica layer on a silicon substrate. It has a parabolic refractive index profile in the vertical direction, which is achieved by controlled fluorine incorporation in the silica film to collimate the optical beam in the vertical direction. Horizontal beam collimation is achieved by incorporating a horizontal curvature at the front face of the lens defined by deep oxide etch. A generalized 3×3 ABCDGH transformation matrix method has been derived to compute the coupling efficiency of such microlens pairs to take front-face angles that may be present due to fabrication variations or limitations and possible input/output optical fiber offset/tilt into considerations. Pairs of such planar GRIN lens with various free-space propagation distances between them ranging from 75 to 2500 μm and with front-face angles of 1.5 deg, 2 deg, and 4 deg have been fabricated and characterized. Beam propagation method simulations have been carried out to substantiate the theoretical and experimental results. The results indicate that the optical loss is reasonably low up to 1.5 deg of front-face angles and increases significantly with further increase in the front-face angle. Analysis shows that for a given system with specific microlens front-face angle, the optical loss can be significantly reduced by properly compensating the vertical position of the input and output fibers.

Characterization of intrabasin faulting and deformation for earthquake hazards in southern Utah Valley, Utah, from high-resolution seismic imaging

USGS Publications Warehouse

Stephenson, William J.; Odum, Jack K.; Williams, Robert A.; McBride, John H.; Tomlinson, Iris

2012-01-01

We conducted active and passive seismic imaging investigations along a 5.6-km-long, east–west transect ending at the mapped trace of the Wasatch fault in southern Utah Valley. Using two-dimensional (2D) P-wave seismic reflection data, we imaged basin deformation and faulting to a depth of 1.4 km and developed a detailed interval velocity model for prestack depth migration and 2D ground-motion simulations. Passive-source microtremor data acquired at two sites along the seismic reflection transect resolve S-wave velocities of approximately 200 m/s at the surface to about 900 m/s at 160 m depth and confirm a substantial thickening of low-velocity material westward into the valley. From the P-wave reflection profile, we interpret shallow (100–600 m) bedrock deformation extending from the surface trace of the Wasatch fault to roughly 1.5 km west into the valley. The bedrock deformation is caused by multiple interpreted fault splays displacing fault blocks downward to the west of the range front. Further west in the valley, the P-wave data reveal subhorizontal horizons from approximately 90 to 900 m depth that vary in thickness and whose dip increases with depth eastward toward the Wasatch fault. Another inferred fault about 4 km west of the mapped Wasatch fault displaces horizons within the valley to as shallow as 100 m depth. The overall deformational pattern imaged in our data is consistent with the Wasatch fault migrating eastward through time and with the abandonment of earlier synextensional faults, as part of the evolution of an inferred 20-km-wide half-graben structure within Utah Valley. Finite-difference 2D modeling suggests the imaged subsurface basin geometry can cause fourfold variation in peak ground velocity over distances of 300 m.

Shallow subsurface structure of the Wasatch fault, Provo segment, Utah, from integrated compressional and shear-wave seismic reflection profiles with implications for fault structure and development

USGS Publications Warehouse

McBride, J.H.; Stephenson, W.J.; Williams, R.A.; Odum, J.K.; Worley, D.M.; South, J.V.; Brinkerhoff, A.R.; Keach, R.W.; Okojie-Ayoro, A. O.

2010-01-01

Integrated vibroseis compressional and experimental hammer-source, shear-wave, seismic reflection profiles across the Provo segment of the Wasatch fault zone in Utah reveal near-surface and shallow bedrock structures caused by geologically recent deformation. Combining information from the seismic surveys, geologic mapping, terrain analysis, and previous seismic first-arrival modeling provides a well-constrained cross section of the upper ~500 m of the subsurface. Faults are mapped from the surface, through shallow, poorly consolidated deltaic sediments, and cutting through a rigid bedrock surface. The new seismic data are used to test hypotheses on changing fault orientation with depth, the number of subsidiary faults within the fault zone and the width of the fault zone, and the utility of integrating separate elastic methods to provide information on a complex structural zone. Although previous surface mapping has indicated only a few faults, the seismic section shows a wider and more complex deformation zone with both synthetic and antithetic normal faults. Our study demonstrates the usefulness of a combined shallow and deeper penetrating geophysical survey, integrated with detailed geologic mapping to constrain subsurface fault structure. Due to the complexity of the fault zone, accurate seismic velocity information is essential and was obtained from a first-break tomography model. The new constraints on fault geometry can be used to refine estimates of vertical versus lateral tectonic movements and to improve seismic hazard assessment along the Wasatch fault through an urban area. We suggest that earthquake-hazard assessments made without seismic reflection imaging may be biased by the previous mapping of too few faults. ?? 2010 Geological Society of America.

Mesopelagic fish assemblages across oceanic fronts: A comparison of three frontal systems in the southern California Current Ecosystem

NASA Astrophysics Data System (ADS)

Netburn, Amanda N.; Koslow, J. Anthony

2018-04-01

With strong horizontal gradients in physical properties, oceanic frontal regions can lead to disproportionately high biological productivity. We examined cross-frontal changes in mesopelagic fish assemblages at three separate frontal systems in the southern California Current Ecosystem (CCE) as part of the CCE Long Term Ecological Research program: the A-Front sampled in October 2008, the C-Front in June/July 2011, and the E-Front in July/August 2012. We analyzed the differential effects of front-associated regions on density and species composition of adult migratory and non-migratory fishes and larvae, and the larval to adult ratio (as a possible index of a population growth potential) for migratory and non-migratory species. The fronts did not have a strong effect on densities of any subset of the mesopelagic fish assemblage. The species composition of the vertical migratory fishes (and their larvae) was typically altered across fronts, with different assemblages present on either side of each front. The migratory assemblages at the fronts themselves were indistinguishable from those at the more productive side of the frontal system. In contrast, the assemblage composition of the non-migratory fishes was indistinguishable between regions across all three of the fronts. The differences between the Northern and Southern assemblages at the A-Front were primarily based on biogeographic provinces, while the assemblages at the E-Front were largely distinguishable by their oceanic or coastal-upwelling zone associations. These results generally confirm those of previous studies on frontal systems in the California Current Ecosystem and elsewhere. The ratio of larvae to adults, a potential index of population growth potential, was altered across two of the fronts for migratory species, elevated on the colder side of the A-Front and the warmer side of the E-Front. This finding suggests that fronts may be regions of enhanced reproduction. The larvae to adult ratio was

Wintertime Ambient Ammonia Concentrations in Northern Utah's Urban Valleys

NASA Astrophysics Data System (ADS)

Hammond, I. A.; Martin, R. S.; Silva, P.; Baasandorj, M.

2017-12-01

Many of the population centers in northern Utah are currently classified as non-attainment or serious non-attainment, Wasatch Front, for PM2.5 and previous studies have shown ammonium nitrate to often be the largest contributor to the particulate mass. Furthermore, measurements have shown several of the Wasatch Front cities and Cache Valley (UT/ID) consistently recorded some of the highest ambient ammonia (NH3) concentrations in the continental United States. As a part of the multi-organization 2017 Utah Winter Fine Particulate Study real-time NH3 concentrations were monitored in the Cache Valley at the Logan, UT site, collocated at an EPA sampling trailer near the Utah State University (USU) campus. A Picarro model G2508 was to used collect 5-sec averaged concentrations of NH3, carbon dioxide (CO2), and methane (CH4) from January 16th to February 14th, 2017. Parts of three inversion events, wherein the PM2.5 concentrations approached or exceeded the National Ambient Air Quality Standards, were captured during the sampling period, including a 10-day event from January 25th to February 4th. Concentrations of all three of the observed species showed significant accumulation during the events, with NH3 concentrations ranging from below the detection limit (<0.5 ppb) to >70 ppb. Preliminary analysis suggested the temporal NH3 changes tracked the increase in PM2.5 throughout the inversion events; however, a one-day period of NH3 depletion during the main inversion event was observed while PM2.5 continued to increase. Additionally, a network of passive NH3 samplers (Ogawa Model 3300) were arrayed at 25 sites throughout the Cache Valley and at 11 sites located along the Wasatch Front. These networks sampled for three 7-day periods, during the same study time frame. Ion chromatographic (IC) analyses of the sample pads are not yet finalized; however, preliminary results show concentrations in the tens of ppb and seemingly spatially correlate with previous studies showing

Heterogeneous porous media: Fronts and noise

NASA Astrophysics Data System (ADS)

Chaouchel, M.; Rakotomalala, N.; Salin, D.; Xu, B.; Yortsos, Y. C.

Capillary effects can be important in immiscible flows in heterogeneous media, particularly at low capillary numbers (Ca). We present experiments and simulations of slow drainage in 3-D porous media, either homogeneous and in the presence of buoyancy or heterogeneous and in its absence. An acoustic technique allows for an accurate study of the 3-D fronts and the cross-over region. Our results suggest that both cases can be described by invasion percolation in a gradient. Both front tails scale with the corresponding Bond numbers as σft≈B-47 in agreement with the theory. An analogous scaling for viscous effects is also given. The noise of these fronts are found correlated in the form of a fractional Brownian motion (fBm) of a Hurst exponent H≈.5. At higher Ca, experiments performed in 3-D porous media with sharp changes in permeability, exhibit a saturation profile response closely linked to the permeability variations. This viscous response to heterogeneity provides an opportunity to investigate and determine correlated (even at all scales, i.e. fBm), permeability fields.

Submesoscale CO2 variability across an upwelling front off Peru

NASA Astrophysics Data System (ADS)

Köhn, Eike E.; Thomsen, Sören; Arévalo-Martínez, Damian L.; Kanzow, Torsten

2017-12-01

As a major source for atmospheric CO2, the Peruvian upwelling region exhibits strong variability in surface fCO2 on short spatial and temporal scales. Understanding the physical processes driving the strong variability is of fundamental importance for constraining the effect of marine emissions from upwelling regions on the global CO2 budget. In this study, a frontal decay on length scales of 𝒪(10 km) was observed off the Peruvian coast following a pronounced decrease in down-frontal (equatorward) wind speed with a time lag of 9 h. Simultaneously, the sea-to-air flux of CO2 on the inshore (cold) side of the front dropped from up to 80 to 10 mmol m-2 day-1, while the offshore (warm) side of the front was constantly outgassing at a rate of 10-20 mmol m-2 day-1. Based on repeated ship transects the decay of the front was observed to occur in two phases. The first phase was characterized by a development of coherent surface temperature anomalies which gained in amplitude over 6-9 h. The second phase was characterized by a disappearance of the surface temperature front within 6 h. Submesoscale mixed-layer instabilities were present but seem too slow to completely remove the temperature gradient in this short time period. Dynamics such as a pressure-driven gravity current appear to be a likely mechanism behind the evolution of the front.

Hydrology of coal-resource areas in the southern Wasatch Plateau, central Utah

USGS Publications Warehouse

Danielson, T.W.; Sylla, D.A.

1982-01-01

The study defines the surface and groundwater hydrology of coal-resources areas in the Southern Wasatch Plateau in Central Utah and, where possible, predicts the hydrologic impacts of underground mining. Discharge data at four streamflow gaging stations indicated that from 5 to 29% of the average annual precipitation on a drainage runs off streams, mainly during the snowmelt period (spring and summer). Most of the base flow of streams originates as spring discharge in the higher altitudes of drainages. Peak flows, average 7-day flood flows, and flood depths were related to basin characteristics in order to develop flood equations for ungaged sites. Chemical quality of surface water was suitable for most uses. Dissolved-solids concentrations ranged from 97 to 835 milligrams per liter in 61 samples collected throughout the area. Data from wells and coal-test holes, and a comprehensive spring inventory indicate that groundwater occurs in all geologic units exposed in the study area. The coal-bearing Blackhawk Formation and underlying Star Point Sandstone are saturated in most areas. Some future mining operations would require dewatering of the Star Point-Blackhawk aquifer. Most of the springs issue from the Flagstaff Limestone and North Horn Formation above the Star Point-Blackhawk aquifer. It is not known whether water in the Flagstaff and North Horn is perched. Dissolved-solids concentrations in groundwater ranged from 105 to 1,080 milligrams per liter in 87 analyzed samples. Water levels in wells, the discharge of springs, benthic invertebrates in streams, and quantity and quality of mine effluents all need to be monitored in order to detect changes in the hydrologic system caused by coal mining. (USGS)

On the ability of human listeners to distinguish between front and back.

PubMed

Zhang, Peter Xinya; Hartmann, William M

2010-02-01

In order to determine whether a sound source is in front or in back, listeners can use location-dependent spectral cues caused by diffraction from their anatomy. This capability was studied using a precise virtual reality technique (VRX) based on a transaural technology. Presented with a virtual baseline simulation accurate up to 16 kHz, listeners could not distinguish between the simulation and a real source. Experiments requiring listeners to discriminate between front and back locations were performed using controlled modifications of the baseline simulation to test hypotheses about the important spectral cues. The experiments concluded: (1) Front/back cues were not confined to any particular 1/3rd or 2/3rd octave frequency region. Often adequate cues were available in any of several disjoint frequency regions. (2) Spectral dips were more important than spectral peaks. (3) Neither monaural cues nor interaural spectral level difference cues were adequate. (4) Replacing baseline spectra by sharpened spectra had minimal effect on discrimination performance. (5) When presented with an interaural time difference less than 200 micros, which pulled the image to the side, listeners still successfully discriminated between front and back, suggesting that front/back discrimination is independent of azimuthal localization within certain limits. Copyright 2009 Elsevier B.V. All rights reserved.

On the ability of human listeners to distinguish between front and back

PubMed Central

Zhang, Peter Xinya; Hartmann, William M.

2009-01-01

In order to determine whether a sound source is in front or in back, listeners can use location-dependent spectral cues caused by diffraction from their anatomy. This capability was studied using a precise virtual-reality technique (VRX) based on a transaural technology. Presented with a virtual baseline simulation accurate up to 16 kHz, listeners could not distinguish between the simulation and a real source. Experiments requiring listeners to discriminate between front and back locations were performed using controlled modifications of the baseline simulation to test hypotheses about the important spectral cues. The experiments concluded: (1) Front/back cues were not confined to any particular 1/3rd or 2/3rd octave frequency region. Often adequate cues were available in any of several disjoint frequency regions. (2) Spectral dips were more important than spectral peaks. (3) Neither monaural cues nor interaural spectral level difference cues were adequate. (4) Replacing baseline spectra by sharpened spectra had minimal effect on discrimination performance. (5) When presented with an interaural time difference less than 200 μs, which pulled the image to the side, listeners still successfully discriminated between front and back, suggesting that front/back discrimination is independent of azimuthal localization within certain limits. PMID:19900525

Gas, Water, and Oil Production from the Wasatch Formation, Greater Natural Buttes Field, Uinta Basin, Utah

USGS Publications Warehouse

Nelson, Philip H.; Hoffman, Eric L.

2009-01-01

Gas, oil, and water production data were compiled from 38 wells with production commencing during the 1980s from the Wasatch Formation in the Greater Natural Buttes field, Uinta Basin, Utah. This study is one of a series of reports examining fluid production from tight gas reservoirs, which are characterized by low permeability, low porosity, and the presence of clay minerals in pore space. The general ranges of production rates after 2 years are 100-1,000 mscf/day for gas, 0.35-3.4 barrel per day for oil, and less than 1 barrel per day for water. The water:gas ratio ranges from 0.1 to10 barrel per million standard cubic feet, indicating that free water is produced along with water dissolved in gas in the reservoir. The oil:gas ratios are typical of a wet gas system. Neither gas nor water rates show dependence upon the number of perforations, although for low gas-flow rates there is some dependence upon the number of sandstone intervals that were perforated. Over a 5-year time span, gas and water may either increase or decrease in a given well, but the changes in production rate do not exhibit any dependence upon well proximity or well location.

Turbulent transport model of wind shear in thunderstorm gust fronts and warm fronts

NASA Technical Reports Server (NTRS)

Lewellen, W. S.; Teske, M. E.; Segur, H. C. O.

1978-01-01

A model of turbulent flow in the atmospheric boundary layer was used to simulate the low-level wind and turbulence profiles associated with both local thunderstorm gust fronts and synoptic-scale warm fronts. Dimensional analyses of both type fronts provided the physical scaling necessary to permit normalized simulations to represent fronts for any temperature jump. The sensitivity of the thunderstorm gust front to five different dimensionless parameters as well as a change from axisymmetric to planar geometry was examined. The sensitivity of the warm front to variations in the Rossby number was examined. Results of the simulations are discussed in terms of the conditions which lead to wind shears which are likely to be most hazardous for aircraft operations.

Multiscale modeling of interfacial flow in particle-solidification front dynamics

NASA Astrophysics Data System (ADS)

Garvin, Justin

2005-11-01

Particle-solidification front interactions are important in many applications, such as metal-matrix composite manufacture, frost heaving in soils and cryopreservation. The typical length scale of the particles and the solidification fronts are of the order of microns. However, the force of interaction between the particle and the front typically arises when the gap between them is of the order of tens of nanometers. Thus, a multiscale approach is necessary to analyze particle-front interactions. Solving the Navier-Stokes equations to simulate the dynamics by including the nano-scale gap between the particle and the front would be impossible. Therefore, the microscale dynamics is solved using a level-set based Eulerian technique, while an embedded model is developed for solution in the nano-scale (but continuum) gap region. The embedded model takes the form of a lubrication equation with disjoining pressure acting as a body force and is coupled to the outer solution. A particle is pushed by the front when the disjoining pressure is balanced by the viscous drag. The results obtained show that this balance can only occur when the thermal conductivity ratio of the particle to the melt is less than 1.0. The velocity of the front at which the particle pushing/engulfment transition occurs is predicted. In addition, this novel method allows for an in-depth analysis of the flow physics that cause particle pushing/engulfment.

35. EAST FRONT OF POWERHOUSE AND CAR BARN: East front ...

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

35. EAST FRONT OF POWERHOUSE AND CAR BARN: East front of powerhouse and car barn. 'Annex' is right end of building. - San Francisco Cable Railway, Washington & Mason Streets, San Francisco, San Francisco County, CA

9. DETAIL OF INTERIOR OF FRONT PORCH SHOWING FRONT ENTRY ...

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

9. DETAIL OF INTERIOR OF FRONT PORCH SHOWING FRONT ENTRY (LEFT) AND BLANK WALL (CENTER) CORRESPONDING TO LOCATION OF INTERIOR VAULTS. VIEW TO SOUTHEAST. - Boise Project, Boise Project Office, 214 Broadway, Boise, Ada County, ID

3. VIEW NORTH, SOUTHWEST FRONT, SOUTHEAST SIDE Front and side ...

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

3. VIEW NORTH, SOUTHWEST FRONT, SOUTHEAST SIDE Front and side elevation. Note gasoline sign post added. Flush store window not altered, 1900 clapboard siding and panelling remaining. - 510 Central Avenue (Commercial Building), Ridgely, Caroline County, MD

Marine bird aggregations associated with the tidally-driven plume and plume fronts of the Columbia River

NASA Astrophysics Data System (ADS)

Zamon, Jeannette E.; Phillips, Elizabeth M.; Guy, Troy J.

2014-09-01

Freshwater discharge from large rivers into the coastal ocean creates tidally-driven frontal systems known to enhance mixing, primary production, and secondary production. Many authors suggest that tidal plume fronts increase energy flow to fish-eating predators by attracting planktivorous fishes to feed on plankton aggregated by the fronts. However, few studies of plume fronts directly examine piscivorous predator response to plume fronts. Our work examined densities of piscivorous seabirds relative to the plume region and plume fronts of the Columbia River, USA. Common murres (Uria aalge) and sooty shearwaters (Puffinus griseus) composed 83% of all birds detected on mesoscale surveys of the Washington and Oregon coasts (June 2003-2006), and 91.3% of all birds detected on fine scale surveys of the plume region less than 40 km from the river mouth (May 2003 and 2006). Mesoscale comparisons showed consistently more predators in the central plume area compared to the surrounding marine area (murres: 10.1-21.5 vs. 3.4-8.2 birds km-2; shearwaters: 24.2-75.1 vs. 11.8-25.9 birds km-2). Fine scale comparisons showed that murre density in 2003 and shearwater density in both 2003 and 2006 were significantly elevated in the tidal plume region composed of the most recently discharged river water. Murres tended to be more abundant on the north face of the plume. In May 2003, more murres and shearwaters were found within 3 km of the front on any given transect, although maximum bird density was not necessarily found in the same location as the front itself. Predator density on a given transect was not correlated with frontal strength in either year. The high bird densities we observed associated with the tidal plume demonstrate that the turbid Columbia River plume does not necessarily provide fish with refuge from visual predators. Bird predation in the plume region may therefore impact early marine survival of Pacific salmon (Oncorhynchus spp.), which must migrate through the

Identification, characteristics and seasonal evolution of surface thermal fronts in the Argentinean Continental Shelf

NASA Astrophysics Data System (ADS)

Rivas, Andrés L.; Pisoni, Juan Pablo

2010-01-01

The location and seasonal variability of surface thermal fronts along the Argentinean Continental Shelf (38-55°S) were studied using 18 years (1985-2002) of sea surface temperature (SST) satellite data. Monthly SST gradients were calculated and a threshold was used to identify frontal pixels. Frontal areas were classified into 4 zones according to their seasonal evolution and the main forcings leading to the front's formation were identified for each group. The shelf break front was easily detected due to the large number of frontal pixels in the region and its high mean gradient values. This front showed a marked annual cycle and relatively constant position associated to the bottom slope; it tended to be located where the core of the Malvinas current is closest to the shelf. Tidal fronts also showed a strong annual cycle, being detected in three well-defined regions during spring and summer. Along the coasts of Tierra del Fuego and Santa Cruz, the combination of strong tidal mixing and low-salinity coastal plumes led to semi-annual seasonal cycles of frontal intensity and persistence that showed a relative maximum in winter. A similar behavior (semi-annual) was found at the coast off the Buenos Aires Province. There, the coastal dilution and the bathymetric gradient generated near-coastal fronts that changed direction seasonally. In the northern mid-shelf, a front linked to the intrusion of warm waters formed in the San Matías Gulf was identified during the winter.

2. VIEW NORTHEAST, SOUTHWEST FRONT Front elevation. Note the altered ...

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

2. VIEW NORTHEAST, SOUTHWEST FRONT Front elevation. Note the altered center section where a storefront was removed. Note addition of a door for entrance to stairway to living quarters added to the second floor. - 510 Central Avenue (Commercial Building), Ridgely, Caroline County, MD

FACILITY 1042. FRONT OBLIQUE SHOWING ROYAL PALMS LINING FRONT WALK. ...

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

FACILITY 1042. FRONT OBLIQUE SHOWING ROYAL PALMS LINING FRONT WALK. VIEW FACING SOUTHEAST - U.S. Naval Base, Pearl Harbor, Naval Housing Area Hale Alii, Junior Officers' Quarters Type, 9-10 Hale Alii Avenue, 1-2 Eighth Street, Pearl City, Honolulu County, HI

VIEW OF FRONT, RECESSED ENTRY SHOWING FRONT WALK. VIEW FACING ...

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

VIEW OF FRONT, RECESSED ENTRY SHOWING FRONT WALK. VIEW FACING SOUTHWEST - Camp H.M. Smith and Navy Public Works Center Manana Title VII (Capehart) Housing, Three-Bedroom Single-Family Type 9, Birch Circle, Elm Drive, Elm Circle, and Date Drive, Pearl City, Honolulu County, HI

Modelling the Deformation Front of a Fold-Thrust Belt: the Effect of an Upper Detachment Horizon

NASA Astrophysics Data System (ADS)

Burberry, C. M.; Koyi, H.; Nilfouroushan, F.; Cosgrove, J. W.

2008-12-01

Structures found at the deformation fronts of fold-thrust belts are variable in type, geometry and spatial organisation, as can be demonstrated from comparisons between structures in the Zagros Fold-Thrust Belt, Iran and the Sawtooth Range, Montana. A range of influencing factors has been suggested to account for this variation, including the mechanical properties and distribution of any detachment horizons within the cover rock succession. A series of analogue models was designed to test this hypothesis, under conditions scaled to represent the Sawtooth Range, Montana. A brittle sand pack, containing an upper ductile layer with variable geometry, was shortened above a ductile base and the evolution of the deformation front was monitored throughout the deformation using a high-accuracy laser scanner. In none of the experiments did the upper detachment horizon cover the entire model. In experiments where it pinched out perpendicular to the shortening direction, a triangle zone was formed when the deformation front reached the pinch out. This situation is analogous to the Teton Canyon region structures in the Sawtooth Range, Montana, where the Cretaceous Colorado Shale unit pinches out at the deformation front, favouring the development of a triangle zone in this region. When the pinch out was oblique to the shortening direction, a more complex series of structures was formed. However, when shortening stopped before the detachment pinch out was reached, the deformation front structures were foreland-propagating and no triangle zone was observed. This situation is analogous to foreland-propagating thrust structures developed at the deformation front in the Swift Dam region of the Sawtooth Range, Montana and to the development of fault-bend folds at the deformation front of the Zagros Fold-Thrust Belt, Iran. We suggest that the presence of a suitable intermediate detachment horizon within a sediment pile can be invoked as a valid explanation for the development of

Ecosystem responses to biogeochemical fronts in the South Brazil Bight

NASA Astrophysics Data System (ADS)

Brandini, Frederico P.; Tura, Pedro M.; Santos, Pedro P. G. M.

2018-05-01

Here we described the general hydrography in the South Brazil Bight (23-28°S) with emphasis on frontal processes and their role in the structure and functioning of the regional shelf ecosystem. One of the key roles of fronts for ecosystem dynamics is the injection of nutrients into the euphotic zone increasing primary production. Frontal systems also affect plankton biodiversity and fisheries. Physical mechanisms behind frontogenesis in this region are similar in the analogous western side of oceanic basins; their magnitude and seasonal dynamics, however, may differ due to peculiarities in shelf morphology, wind field, tidal circulation and continental drainage. Here we provide a reassessment of earlier and recent ecological and hydrographic studies for a better evaluation of the spatial and temporal dynamics of fronts and their regional ecological implications. Albeit in a fragmented manner, we give a more detailed conceptual framework about the ecosystem responses to the complex frontal system in the South Brazil Bight.

Light-Front Holography, Light-Front Wavefunctions, and Novel QCD Phenomena

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins; de Teramond, Guy F.

2012-02-16

Light-Front Holography is one of the most remarkable features of the AdS/CFT correspondence. In spite of its present limitations it provides important physical insights into the nonperturbative regime of QCD and its transition to the perturbative domain. This novel framework allows hadronic amplitudes in a higher dimensional anti-de Sitter (AdS) space to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time. The model leads to an effective confining light-front QCD Hamiltonian and a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z inmore » AdS space is uniquely identified with a Lorentz-invariant coordinate {zeta} which measures the separation of the constituents within a hadron at equal light-front time and determines the off-shell dynamics of the bound-state wavefunctions, and thus the fall-off as a function of the invariant mass of the constituents. The soft-wall holographic model modified by a positive-sign dilaton metric, leads to a remarkable one-parameter description of nonperturbative hadron dynamics - a semi-classical frame-independent first approximation to the spectra and light-front wavefunctions of meson and baryons. The model predicts a Regge spectrum of linear trajectories with the same slope in the leading orbital angular momentum L of hadrons and the radial quantum number n. The hadron eigensolutions projected on the free Fock basis provides the complete set of valence and non-valence light-front Fock state wavefunctions {Psi}{sub n/H} (x{sub i}, k{sub {perpendicular}i}, {lambda}{sub i}) which describe the hadron's momentum and spin distributions needed to compute the direct measures of hadron structure at the quark and gluon level, such as elastic and transition form factors, distribution amplitudes, structure functions, generalized parton distributions and

The Wasatch fault zone, utah—segmentation and history of Holocene earthquakes

NASA Astrophysics Data System (ADS)

Machette, Michael N.; Personius, Stephen F.; Nelson, Alan R.; Schwartz, David P.; Lund, William R.

The Wasatch fault zone (WFZ) forms the eastern boundary of the Basin and Range province and is the longest continuous, active normal fault (343 km) in the United States. It underlies an urban corridor of 1.6 million people (80% of Utah's population) representing the largest earthquake risk in the interior of the western United States. We have used paleoseismological data to identify 10 discrete segments of the WFZ. Five are active, medial segments with Holocene slip rates of 1-2 mm a -1, recurrence intervals of 2000-4000 years and average lengths of about 50 km. Five are less active, distal segments with mostly pre-Holocene surface ruptures, late Quaternary slip rates of <0.5 mm a -1 recurrence intervals of ≥10,000 years and average lengths of about 20 km. Surface-faulting events on each of the medial segments of the WFZ formed 2-4-m-high scarps repeatedly during the Holocene; latest Pleistocene (14-15 ka) deposits commonly have scarps as much as 15-20 m in height. Segments identified from paleoseismological studies of other major late Quaternary normal faults in the northern Basin and Range province are 20-25 km long, or about half of that proposed for the medial segments of the WFZ. Paleoseismological records for the past 6000 years indicate that a major surface-rupturing earthquake has occurred along one of the medial segments about every 395 ± 60 years. However, between about 400 and 1500 years ago, the WFZ experienced six major surface-rupturing events, an average of one event every 220 years, or about twice as often as expected from the 6000-year record. This pattern of temporal clustering is similar to that of the central Nevada—eastern California Seismic Belt in the western part of the Basin and Range province, where 11 earthquakes of M > 6.5 have occurred since 1860. Although the time scale of the clustering is different—130 years vs 1100 years—we consider the central Nevada—eastern California Seismic Belt to be a historic analog for movement on

Investigation on the variability of East Asia Boreal Summer Front Frequency and Linkage between Tropical Air Temperature

NASA Astrophysics Data System (ADS)

Choi, Eunho; Lim, Gyu-Ho

2016-04-01

Summer time front is one of the most significant phenomena over East Asia including China, Korea and Japan. Many efforts have been established to understand the nature of front. However, there was no research conducting identifying East Asia summer time fronts objectively. We have established objective front recognition method. The method follows next procedures : 1) We calculate vorticity on 850-hPa surface. 2) Any grid point that have horizontal gradient of equivalent potential temperature (EPT hereafter) on 850-hPa surface less than 4 'c / 100km set to zero. 3) Next, we smooth this field using 9-point smoothing technique. 4) Finally we extract the main axis of closed contour correspond to vorticity of 1.5 10-5s-5. Voronoi diagram used to extract this axis. We define this axis as front on 850-hPa pressure surface. We have applied the method on 1981-2010 ERA-Interim dataset. From the result, front frequency maximums are in around of East China Sea (34N, 122E), north (38N, 136E) and south (34N, 140E) of main island of Japan. Below 30N and above 40N, front frequency tends to decrease maybe due to decrease in the magnitude of gradient of EPT and the frequency of cyclonic weather disturbance. Two main regions affect the variability of East Asia Front Frequency. One is equatorial positive region especially over Taiwan (25N, 120E). The other one is East Sea next to Korea (40N, 135E). Humid warm air transported from southern China (20N-30N, 100E-110E) and dry cold air transported from northern China (30N-40N, 100E-110E) compressed by clockwise high system over Taiwan and counter-clockwise low system over East Sea). This compressed precipitation-making system or front moves by extratropical westerly and transported out to north-western Pacific. It looks like geopotential over Taiwan affected by tropical activity, especially vertical integration of temperature (VIT hereafter) over tropical region (30S-30N). When VIT is higher than normal, geopotential over Taiwan also

Characteristics of high-latitude precursor flows ahead of dipolarization fronts

NASA Astrophysics Data System (ADS)

Li, Jia-Zheng; Zhou, Xu-Zhi; Runov, Andrei; Angelopoulos, Vassilis; Liu, Jiang; Pan, Dong-Xiao; Zong, Qiu-Gang

2017-05-01

Dipolarization fronts (DFs), earthward propagating structures in the magnetotail current sheet characterized by sharp enhancements of northward magnetic field, are capable of converting electromagnetic energy into particle kinetic energy. The ions previously accelerated and reflected at the DFs can contribute to plasma flows ahead of the fronts, which have been identified as DF precursor flows in both the near-equatorial plasma sheet and far from it, near the plasma sheet boundary. Using observations from the THEMIS (Time History of Events and Macroscale Interactions during Substorms) spacecraft, we show that the earthward particle and energy flux enhancements ahead of DFs are statistically larger farther away from the neutral sheet (at high latitudes) than in the near-equatorial region. High-latitude particle and energy fluxes on the DF dawnside are found to be significantly greater than those on the duskside, which is opposite to the dawn-dusk asymmetries previously found near the equatorial region. Using forward and backward tracing test-particle simulations, we then explain and reproduce the observed latitude-dependent characteristics of DF precursor flows, providing a better understanding of ion dynamics associated with dipolarization fronts.

MMS Observations of Protons and Heavy Ions Acceleration at Plasma Jet Fronts

NASA Astrophysics Data System (ADS)

Catapano, F.; Retino, A.; Zimbardo, G.; Cozzani, G.; Breuillard, H.; Le Contel, O.; Alexandrova, A.; Mirioni, L.; Cohen, I. J.; Turner, D. L.; Perri, S.; Greco, A.; Mauk, B.; Torbert, R. B.; Russell, C. T.; Khotyaintsev, Y. V.; Lindqvist, P. A.; Ergun, R.; Giles, B. L.; Fuselier, S. A.; Moore, T. E.; Burch, J.

2017-12-01

Plasma jet fronts in the Earth's magnetotail are kinetic-scale boundaries separating hot fast plasma jets, generally attributed to reconnection outflows, from colder ambient plasma. Jet fronts are typically associated with a sharp increase of the vertical component of the magnetic field Bz, an increase of the plasma temperature and a drop of plasma density. Spacecraft observations and numerical simulations indicate that jet fronts are sites of major ion acceleration. The exact acceleration mechanisms as well as the dependence of such mechanisms on ion composition are not fully understood, yet. Recent high-resolution measurements of ion distribution functions in the magnetotail allow for the first time to study the acceleration mechanisms in detail. Here, we show several examples of jet fronts and discuss ion acceleration therein. We show fronts that propagate in the mid-tail magnetotail both as isolated laminar boundaries and as multiple boundaries embedded in strong magnetic fluctuations and turbulence. We also show fronts in the near-Earth jet braking region, where they interact with the dipolar magnetic field and are significantly decelerated/diverted. Finally, we study the acceleration of different ion species (H+, He++, O+) at different types of fronts and we discuss possible different acceleration mechanisms and how they depend on the ion species.

Earth observation taken by the Expedition 11 crew

NASA Image and Video Library

2005-09-30

ISS011-E-13889 (30 September 2005) --- Wasatch Range, Utah is featured in this image photographed by an Expedition 11 crewmember on the international space station. The Wasatch Range forms an impressive backdrop to the Salt Lake City metropolitan area, and is a frequent destination for hikers, backpackers, and skiers. The range is considered to be the westernmost part of the Rocky Mountains, and rises to elevations of approximately 3600 meters (12,000 feet) above sea level. This photograph, taken at the end of September, captures red- (maple trees) and gold-mantled (aspen trees) hill slopes along the western mountain front to the south of Salt Lake City. Other common tree species at these elevations include pine, fir, spruce, willow, birch, and oak. A portion of Draper City is visible in the left half of the image. The elevation of Lone Peak, visible at upper right, is approximately 3410 meters (11,253 feet).

Estuarine density fronts and their effect on oil slicks

NASA Technical Reports Server (NTRS)

Klemas, V. (Principal Investigator); Polis, D. F.; Davis, G. R.

1976-01-01

The author has identified the following significant results. Estuarine fronts represent regions of extremely high gradient or discontinuity in various parameters of physical interest, the most important being the water velocity and density fields. Aircraft and boats were combined to study the behavior of different types of fronts in Delaware Bay and their effect on pollutants in order to provide a basis for improving an oil drift and spreading model. Imagery from the LANDSAT satellites provided the most effective means of determining the location and extent of frontal systems over all portions of the tidal cycle. This data is being used to modify the oil drift and spreading model.

DYNAMICS OF HIGH ENERGY IONS AT A STRUCTURED COLLISIONLESS SHOCK FRONT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gedalin, M.; Dröge, W.; Kartavykh, Y. Y., E-mail: gedalin@bgu.ac.il

2016-07-10

Ions undergoing first-order Fermi acceleration at a shock are scattered in the upstream and downstream regions by magnetic inhomogeneities. For high energy ions this scattering is efficient at spatial scales substantially larger than the gyroradius of the ions. The transition from one diffusive region to the other occurs via crossing the shock, and the ion dynamics during this crossing is mainly affected by the global magnetic field change between the upstream and downstream region. We study the effects of the fine structure of the shock front, such as the foot-ramp-overshoot profile and the phase-standing upstream and downstream magnetic oscillations. Wemore » also consider time dependent features, including reformation and large amplitude coherent waves. We show that the influence of the spatial and temporal structure of the shock front on the dependence of the transition and reflection on the pitch angle of the ions is already weak at ion speeds five times the speed of the upstream flow.« less

Cold Fronts in RegCM/HadGEM simulations over South America

NASA Astrophysics Data System (ADS)

Pampuch, Luana; Marcos de Jesus, Eduardo; Porfírio da Rocha, Rosmeri; Ambrizzi, Tércio

2017-04-01

Cold front is one of the most important systems that contribute for precipitation over South America. The representation of this system in climate models is important for a better representation of the precipitation. The Regional Climate Model RegCM is widely used for climate studies in South America, being important to understand how this model represents the cold fronts. A climatology (from 1979-2004) of the number of cold fronts in each season for RegCM4 simulations over South America CORDEX domain nested in HadGEM2-ES. The simulated climatology was compared with ERA-Interim reanalysis cold fronts climatology over the South America and adjacent South Atlantic Ocean. The cold fronts tracking for the model and the reanalysis were performed using an objective methodology based on decrease of air temperature in 925hPa, shift of meridional wind in 925hPa from northern to southern quadrant and increased in sea level pressure. The main differences were observed on summer and winter. On summer the model overestimate the number of cold fronts over southeastern South America and adjacent Atlantic Ocean; and underestimate it over central-south Argentina and Atlantic Ocean. On winter, the signs were opposite of that summer. On autumn and spring the differences were smaller and occurs mainly over all South Atlantic and north Argentina.

Front air bag nondeployments in frontal crashes fatal to drivers or right-front passengers.

PubMed

Braver, Elisa R; McCartt, Anne T; Sherwood, Christopher P; Zuby, David S; Blanar, Laura; Scerbo, Marge

2010-04-01

Public concern has arisen about the reliability of front air bags because Fatality Analysis Reporting System (FARS) data indicate many nondeployed air bags in fatal frontal crashes. However, the accuracy of air bag deployment, the variable in question, is uncertain. This study aimed to provide more certain estimates of nondeployment incidence in fatal frontal crashes. Fatally injured passenger vehicle drivers and right-front passengers in frontal crashes were identified in two U.S. databases for calendar years 1998-2006 and model years 1994-2006: FARS, a census of police-reported fatal crashes on public roads, and National Automotive Sampling System/Crashworthiness Data System (NASS/CDS), a probability sample of tow-away crashes. NASS/CDS contains subsets of fatal crashes in FARS and collects detailed data using crash investigators. Front air bag deployment coding for front-seat occupant fatalities was compared in FARS and NASS/CDS, and case reviews were conducted. Among FARS frontal deaths with available deployment status (N = 43,169), front air bags were coded as not deployed for 18 percent of front occupants. In comparison, NASS/CDS (N = 628) reported 9 percent (weighted estimate) nondeployment among front occupants killed. Among crashes common to both databases, NASS/CDS reported deployments for 45 percent of front occupant deaths for which FARS had coded nondeployments. Detailed case reviews of NASS/CDS crashes indicated highly accurate coding for deployment status. Based on this case review, 8 percent (weighted estimate) of front occupant deaths in frontal crashes appeared to involve air bag nondeployments; 1-2 percent of front occupant deaths represented potential system failures where deployments would have been expected. Air bag deployments appeared unwarranted in most nondeployments based on crash characteristics. FARS data overstate the magnitude of the problem of air bag deployment failures; steps should be taken to improve coding. There are inherent

Using Paleoseismic Trenching and LiDAR Analysis to Evaluate Rupture Propagation Through Segment Boundaries of the Central Wasatch Fault Zone, Utah

NASA Astrophysics Data System (ADS)

Bennett, S. E. K.; DuRoss, C. B.; Reitman, N. G.; Devore, J. R.; Hiscock, A.; Gold, R. D.; Briggs, R. W.; Personius, S. F.

2014-12-01

Paleoseismic data near fault segment boundaries constrain the extent of past surface ruptures and the persistence of rupture termination at segment boundaries. Paleoseismic evidence for large (M≥7.0) earthquakes on the central Holocene-active fault segments of the 350-km-long Wasatch fault zone (WFZ) generally supports single-segment ruptures but also permits multi-segment rupture scenarios. The extent and frequency of ruptures that span segment boundaries remains poorly known, adding uncertainty to seismic hazard models for this populated region of Utah. To address these uncertainties we conducted four paleoseismic investigations near the Salt Lake City-Provo and Provo-Nephi segment boundaries of the WFZ. We examined an exposure of the WFZ at Maple Canyon (Woodland Hills, UT) and excavated the Flat Canyon trench (Salem, UT), 7 and 11 km, respectively, from the southern tip of the Provo segment. We document evidence for at least five earthquakes at Maple Canyon and four to seven earthquakes that post-date mid-Holocene fan deposits at Flat Canyon. These earthquake chronologies will be compared to seven earthquakes observed in previous trenches on the northern Nephi segment to assess rupture correlation across the Provo-Nephi segment boundary. To assess rupture correlation across the Salt Lake City-Provo segment boundary we excavated the Alpine trench (Alpine, UT), 1 km from the northern tip of the Provo segment, and the Corner Canyon trench (Draper, UT) 1 km from the southern tip of the Salt Lake City segment. We document evidence for six earthquakes at both sites. Ongoing geochronologic analysis (14C, optically stimulated luminescence) will constrain earthquake chronologies and help identify through-going ruptures across these segment boundaries. Analysis of new high-resolution (0.5m) airborne LiDAR along the entire WFZ will quantify latest Quaternary displacements and slip rates and document spatial and temporal slip patterns near fault segment boundaries.

FRONT RIGHT OBLIQUE VIEW, SHOWING FRONT WALK/STEPS AND ROYAL PALM ...

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

FRONT RIGHT OBLIQUE VIEW, SHOWING FRONT WALK/STEPS AND ROYAL PALM IN FOREGROUND. VIEW FACING NORTH - Camp H.M. Smith and Navy Public Works Center Manana Title VII (Capehart) Housing, Four-Bedroom, Single-Family Type 10, Birch Circle, Elm Drive, Elm Circle, and Date Drive, Pearl City, Honolulu County, HI

Relativistic runaway ionization fronts.

PubMed

Luque, A

2014-01-31

We investigate the first example of self-consistent impact ionization fronts propagating at relativistic speeds and involving interacting, high-energy electrons. These fronts, which we name relativistic runaway ionization fronts, show remarkable features such as a bulk speed within less than one percent of the speed of light and the stochastic selection of high-energy electrons for further acceleration, which leads to a power-law distribution of particle energies. A simplified model explains this selection in terms of the overrun of Coulomb-scattered electrons. Appearing as the electromagnetic interaction between electrons saturates the exponential growth of a relativistic runaway electron avalanche, relativistic runaway ionization fronts may occur in conjunction with terrestrial gamma-ray flashes and thus explain recent observations of long, power-law tails in the terrestrial gamma-ray flash energy spectrum.

First-principles simulations of shock front propagation in liquid deuterium

NASA Astrophysics Data System (ADS)

Gygi, Francois; Galli, Giulia

2001-03-01

We present large-scale first-principles molecular dynamics simulations of the formation and propagation of a shock front in liquid deuterium. Molecular deuterium was subjected to supersonic impacts at velocities ranging from 10 to 30 km/s. We used Density Functional Theory in the local density approximation, and simulation cells containing 1320 deuterium atoms. The formation of a shock front was observed and its velocity was measured and compared with the results of laser-driven shock experiments [1]. The pressure and density in the compressed fluid were also computed directly from statistical averages in appropriate regions of the simulation cell, and compared with previous first-principles calculations performed at equilibrium [2]. Details of the electronic structure at the shock front, and their influence on the properties of the compressed fluid will be discussed. [1] J.W.Collins et al. Science 281, 1178 (1998). [2] G.Galli, R.Q.Hood, A.U.Hazi and F.Gygi, Phys.Rev. B61, 909 (2000).

Conjugate fracture pairs in the Molina Member of the Wasatch Formation, Piceance basin, Colorado: Implications for fracture origins and hydrocarbon production/exploration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lorenz, J.C.

1997-05-01

The sandstones of the Molina Member of the Wasatch Formation in the Piceance basin of northwestern Colorado contain a suite of fractures that have a conjugate-pair geometry. The fractures are vertical and intersect at an acute angle of between 20 and 40 degrees. Although direct evidence of shear is rare, the fracture surfaces commonly display small steps. The fracture geometries suggest that the maximum compressive stress during fracturing was in the plane of the acute angle of the conjugate fractures: the steps are interpreted as broken-face manifestations of very low angle en echelon fractures, formed within exceptionally narrow zones ofmore » incipient shear. In contrast to the highly anisotropic permeability enhancement created by subparallel vertical extension fractures in the underlying Mesaverde Formation, the conjugate pairs in the Molina sandstones should create a well connected and relatively isotropic mesh of fracture conductivity. Increases in stress magnitudes and anisotropy during production drawdown of reservoir pressures should cause shear offsets along the fractures, initially enhancing permeability.« less

Radiation hydrodynamical instabilities in cosmological and galactic ionization fronts

NASA Astrophysics Data System (ADS)

Whalen, Daniel J.; Norman, Michael L.

2011-11-01

Ionization fronts, the sharp radiation fronts behind which H/He ionizing photons from massive stars and galaxies propagate through space, were ubiquitous in the universe from its earliest times. The cosmic dark ages ended with the formation of the first primeval stars and galaxies a few hundred Myr after the Big Bang. Numerical simulations suggest that stars in this era were very massive, 25-500 solar masses, with H(II) regions of up to 30,000 light-years in diameter. We present three-dimensional radiation hydrodynamical calculations that reveal that the I-fronts of the first stars and galaxies were prone to violent instabilities, enhancing the escape of UV photons into the early intergalactic medium (IGM) and forming clumpy media in which supernovae later exploded. The enrichment of such clumps with metals by the first supernovae may have led to the prompt formation of a second generation of low-mass stars, profoundly transforming the nature of the first protogalaxies. Cosmological radiation hydrodynamics is unique because ionizing photons coupled strongly to both gas flows and primordial chemistry at early epochs, introducing a hierarchy of disparate characteristic timescales whose relative magnitudes can vary greatly throughout a given calculation. We describe the adaptive multistep integration scheme we have developed for the self-consistent transport of both cosmological and galactic ionization fronts.

Possible impacts of the pre-monsoon dry line and sea breeze front on nocturnal rainfall over northeast Bangladesh

NASA Astrophysics Data System (ADS)

Stiller-Reeve, Mathew; Toniazzo, Thomas; Kolstad, Erik; Spengler, Thomas

2017-04-01

The northeast region of Bangladesh receives a large amount of rainfall before the large-scale monsoon circulation begins. For example, in April (a "pre-monsoon" month) 2010, 804 mm of rain fell in the regional capital Sylhet. It was the second wettest month of the entire year. From our conversations with the local people, we know that this pre-monsoon rainfall is extremely important to their livelihoods. We therefore need to understand it's triggering mechanisms. Several theories have been published, all of which are likely to be at play. However, in this work we look more closely at how the sea breeze front and prominent pre-monsoonal dry line in this region may play a role. If these mechanisms play a role in the convection, then it is likely that they trigger convection further afield, and then the resulting systems then propagate towards northeast Bangladesh. We believe this because rainfall associated with dry line/sea-breeze front convection often occurs during the late afternoon, but the rainfall over northeast Bangladesh shows a clear late-night/early-morning maxima. At present, the temporal and spatial resolution of the regional observations is inappropriate for examining these possible mechanisms. We therefore use a numerical model (WRF) to investigate the possible links between the convection and the sea breeze front and dry line. We use April 2010 as a case study since it was such a wet pre-monsoon month. The simulation shows that a sea breeze circulation often develops during the day in the coastal zone of Bangladesh and northeast India. After sunset the sea breeze front propagates inland pushing back the hot, dry air over India. On several days during the simulation, convection is triggered along the sea breeze front, which then propagates towards northeast Bangladesh and intensifies across the topography surrounding the Sylhet region. From our simulations, it appears that nocturnal convection over northeast Bangladesh is triggered by several

Stratigraphy and structure of the Sevier thrust belt and proximal foreland-basin system in central Utah: A transect from the Sevier Desert to the Wasatch Plateau

USGS Publications Warehouse

Lawton, T.F.; Sprinkel, D.A.; Decelles, P.G.; Mitra, G.; Sussman, A.J.; Weiss, M.P.

1997-01-01

the Canyon Range thrust to growth strata deposited in the wedge-top depozone. Stops in the San Pitch Mountains illustrate deposits of the foredeep depozone and younger, superjacent wedge-top depozone. Stops in the Sanpete Valley and western part of the Wasatch Plateau examine the evolution of the foreland-basin system from foredeep to wedge-top during growth of a triangle zone near the front of the Gunnison thrust.

Can we observe the fronts of the Antarctic Circumpolar Current using GRACE OBP?

NASA Astrophysics Data System (ADS)

Makowski, J.; Chambers, D. P.; Bonin, J. A.

2014-12-01

The Antarctic Circumpolar Current (ACC) and the Southern Ocean remains one of the most undersampled regions of the world's oceans. The ACC is comprised of four major fronts: the Sub-Tropical Front (STF), the Polar Front (PF), the Sub-Antarctic Front (SAF), and the Southern ACC Front (SACCF). These were initially observed individually from repeat hydrographic sections and their approximate locations globally have been quantified using all available temperature data from the World Ocean and Climate Experiment (WOCE). More recent studies based on satellite altimetry have found that the front positions are more dynamic and have shifted south by up to 1° on average since 1993. Using ocean bottom pressure (OBP) data from the current Gravity Recovery and Climate Experiment (GRACE) we have measured integrated transport variability of the ACC south of Australia. However, differentiation of variability of specific fronts has been impossible due to the necessary smoothing required to reduce noise and correlated errors in the measurements. The future GRACE Follow-on (GFO) mission and the post 2020 GRACE-II mission are expected to produce higher resolution gravity fields with a monthly temporal resolution. Here, we study the resolution and error characteristics of GRACE gravity data that would be required to resolve variations in the front locations and transport. To do this, we utilize output from a high-resolution model of the Southern Ocean, hydrology models, and ice sheet surface mass balance models; add various amounts of random and correlated errors that may be expected from GFO and GRACE-II; and quantify requirements needed for future satellite gravity missions to resolve variations along the ACC fronts.

Persistent Urban Impacts on Surface Water Quality Mediated by Stormwater Recharge

NASA Astrophysics Data System (ADS)

Gabor, R. S.; Brooks, P. D.; Neilson, B. T.; Bowen, G. J.; Jameel, M. Y.; Hall, S. J.; Eiriksson, D.; Millington, M. R.; Gelderloos, A.

2016-12-01

Growing population centers along mountain watersheds put added stress on sensitive hydrologic systems and create water quality impacts downstream. We examined the mountain-to-urban transition in watersheds on Utah's Wasatch Front to identify mechanisms by which urbanization impacts water resources. Rivers in the Wasatch flow from the mountains directly into an urban landscape, where they are subject to channelization, stormwater runoff systems, and urban inputs to water quality from sources such as road salt and fertilizer. As part of an interdisciplinary effort within the iUTAH project, multiple synoptic surveys were performed and a variety of measurements were made, including basic water chemistry along with discharge, water isotopes, and nutrients. Red Butte Creek, a stream in Salt Lake City, does not show significant urban impact to water quality until several kilometers after it enters the city where concentrations of solutes such as chloride and nitrate more than triple in a gaining reach. Groundwater springs discharging to this gaining section demonstrate urban-impacted water chemistry, suggesting that during baseflow a contaminated alluvial aquifer significantly controls stream chemistry. By combining hydrometric and hydrochemical observations we were able to estimate that these groundwater springs were 17-20% urban runoff. We were then able to predict the chemistry of urban runoff that feeds into the alluvial aquifer. Samples collected from storm culverts, roofs, and asphalt during storms had chemistry values within the range of those predicted by the mixing model. This evidence that urbanization affects the water quality of baseflow through impacted groundwater suggests that stormwater mitigation may not be sufficient for protecting urban watersheds, and quantifying these persistent groundwater mediated impacts is necessary to evaluate the success of restoration efforts. By comparing these results from Red Butte Creek with similar studies from other

Nonlinear wave fronts and ionospheric irregularities observed by HF sounding over a powerful acoustic source

NASA Astrophysics Data System (ADS)

Blanc, Elisabeth; Rickel, Dwight

1989-06-01

Different wave fronts affected by significant nonlinearities have been observed in the ionosphere by a pulsed HF sounding experiment at a distance of 38 km from the source point of a 4800-kg ammonium nitrate and fuel oil (ANFO) explosion on the ground. These wave fronts are revealed by partial reflections of the radio sounding waves. A small-scale irregular structure has been generated by a first wave front at the level of a sporadic E layer which characterized the ionosphere at the time of the experiment. The time scale of these fluctuations is about 1 to 2 s; its lifetime is about 2 min. Similar irregularities were also observed at the level of a second wave front in the F region. This structure appears also as diffusion on a continuous wave sounding at horizontal distances of the order of 200 km from the source. In contrast, a third front unaffected by irregularities may originate from the lowest layers of the ionosphere or from a supersonic wave front propagating at the base of the thermosphere. The origin of these structures is discussed.

On the relationship between satellite-retrieved surface temperature fronts and chlorophyll a in the western South Atlantic

NASA Astrophysics Data System (ADS)

Saraceno, Martin; Provost, Christine; Piola, Alberto R.

2005-11-01

The time-space distribution of chlorophyll a in the southwestern Atlantic is examined using 6 years (1998-2003) of sea surface color images from Sea-viewing Wide Field of View Sensor (SeaWiFS). Chlorophyll a (chl a) distribution is confronted with sea surface temperature (SST) fronts retrieved from satellite imagery. Histogram analysis of the color, SST, and SST gradient data sets provides a simple procedure for pixel classification from which eight biophysical regions in the SWA are identified, including three new regions with regard to Longhurst (1998) work: Patagonian Shelf Break (PSB), Brazil Current Overshoot, and Zapiola Rise region. In the PSB region, coastal-trapped waves are suggested as a possible mechanism leading to the intraseasonal frequencies observed in SST and chl a. Mesoscale activity associated with the Brazil Current Front and, in particular, eddies drifting southward is probably responsible for the high chl a values observed throughout the Brazil Current Overshoot region. The Zapiola Rise is characterized by a local minimum in SST gradient magnitudes and shows chl a maximum values in February, 3 months later than the austral spring bloom of the surroundings. Significant interannual variability is present in the color imagery. In the PSB, springs and summers with high chl a concentrations seem associated with stronger local northerly wind speed, and possible mechanisms are discussed. Finally, the Brazil-Malvinas front is detected using both SST gradient and SeaWiFS images. The time-averaged position of the front at 54.2°W is estimated at 38.9°S and its alongshore migration of about 300 km.

Identifying Lagrangian fronts with favourable fishery conditions

NASA Astrophysics Data System (ADS)

Prants, S. V.; Budyansky, M. V.; Uleysky, M. Yu.

2014-08-01

Lagrangian fronts (LFs) in the ocean are defined as boundaries between surface waters with strongly different Lagrangian properties. They can be accurately detected in a given velocity field by computing synoptic maps for displacements of synthetic tracers and other Lagrangian indicators. We use Pacific saury catch and location data for a number of commercial fishery seasons in the region of the northwest Pacific with one of the richest fishery in the world. It is shown statistically that the saury fishing grounds with maximal catches are not randomly distributed over the region but located mainly along the sharp LFs where productive cold waters of the Oyashio Current, warmer waters of the southern branch of the Soya Current, and waters of warm-core Kuroshio rings converge. Computation of those fronts in altimetric geostrophic velocity fields both in the years with the First and Second Oyashio Intrusions shows that in spite of different oceanographic conditions LF locations may serve as good indicators of potential fishing grounds. Possible biophysical reasons for saury aggregation near sharp LFs are discussed. We propose a mechanism for effective export of nutrient rich waters based on stretching of material lines in the vicinity of hyperbolic objects in the ocean. The developed method, based on identifying LFs in any velocity fields, is quite general and may be applied to find potential fishing grounds for the other pelagic fish.

Dynamic stabilization of Rayleigh-Taylor instability: Experiments with Newtonian fluids as surrogates for ablation fronts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodriguez Prieto, G.; Piriz, A. R.; Lopez Cela, J. J.

2013-01-15

A previous theory on dynamic stabilization of Rayleigh-Taylor instability at interfaces between Newtonian fluids is reformulated in order to make evident the analogy of this problem with the related one on dynamic stabilization of ablation fronts in the framework of inertial confinement fusion. Explicit analytical expressions are obtained for the boundaries of the dynamically stable region which turns out to be completely analogue to the stability charts obtained for the case of ablation fronts. These results allow proposing experiments with Newtonian fluids as surrogates for studying the case of ablation fronts. Experiments with Newtonian fluids are presented which demonstrate themore » validity of the theoretical approach and encourage to pursue experimental research on ablation fronts to settle the feasibility of dynamic stabilization in the inertial confinement fusion scenario.« less

A fiber-resin micromechanics analysis of the delamination front in a DCB specimen

NASA Technical Reports Server (NTRS)

Crews, J. H.; Shivakumar, K. N.; Raju, I. S.

1988-01-01

A 3-D finite element model was developed to analyze the fiber-resin behavior near the delamination front in a graphite-epoxy double cantilever beam (DCB) specimen. The specimen interior was analyzed using a typical one-fiber slice, represented by a local 3-D fiber-resin model. The resin stresses were computed for the resin-rich layer at the ply interface as well as for the regions between the fibers close to the delamination front. However, the computed strain energy release rate G sub I along the delamination front varied by less than two percent, and was within about four percent of the plane-strain value. The von Mises yield criterion was used to estimate the extent of yielding near the delamination front. The yielding extended ahead of the delamination and also developed between the fibers. Although the fibers had only a negligible effect on G sub I, they caused yielding within the ply and therefore could influence delamination fracture toughness. The normal and shear stresses at the fiber-resin interface were computed near the delamination front. These results suggest that multi-axial stress criteria may be required to analyze fiber-resin interfaces.

Tracking the Recent and late Pleistocene Azores front by the distribution of planktic foraminifers

NASA Astrophysics Data System (ADS)

Schiebel, Ralf; Schmuker, Barbara; Alves, Mário; Hemleben, Christoph

2002-11-01

South of the Azores Islands, the population dynamics and sedimentation of planktic foraminifers are significantly influenced by the hydrography of the Azores Front Current System (AFCS). Planktic foraminifers collected from the water column during seasonal cruises across the Azores Front, record the temporal and spatial scale of hydrographic and faunal dynamics within this area. Surface sediment analysis reveals the presence of a large number of pteropod shells indicating preservation of aragonite and, therefore, little alteration of the calcitic foraminiferal tests. Consequently, most of the seasonal and spatial variability of the Azores Front is expected to be recorded by the planktic foraminiferal assemblages present within the surface sediment. In particular, Globorotalia scitula, a subsurface-dwelling species, decreases significantly in abundance to the south of the Azores Front, and shows fine-scale changes at the glacial/interglacial time scale. Enhanced faunal proportions of G. scitula in a sediment core that is located to the south of the modern Azores Current indicate a southward shift of the Azores Front Current System during the glacials and the presence of a transitional water mass at the Azores region.

Investigation of the influence of transport from oil and natural gas regions on elevated ozone levels in the northern Colorado front range.

PubMed

Evans, Jason M; Helmig, Detlev

2017-02-01

The Northern Colorado Front Range (NCFR) has been in exceedance of the ozone National Ambient Air Quality Standard (NAAQS) since 2004, which has led to much debate over the sources of ozone precursors to the region, as this area is home to both the Denver, CO, metropolitan area and the Denver-Julesburg Basin, which has experienced rapid growth of oil and natural gas (O&NG) operations and associated emissions. Several recent studies have reported elevated levels of atmospheric volatile organic compounds (VOCs) as a result of O&NG emissions and the potential for significant ozone production from these emissions, despite implementation of stricter O&NG VOC emissions regulations in 2008. Approximately 88% of 1-hr elevated ozone events (>75 ppbv) occur during June-August, indicating that elevated ozone levels are driven by regional photochemistry. Analyses of surface ozone and wind observations from two sites, namely, South Boulder and the Boulder Atmospheric Observatory, both near Boulder, CO, show a preponderance of elevated ozone events associated with east-to-west airflow from regions with O&NG operations in the N-ESE, and a relatively minor contribution of transport from the Denver Metropolitan area to the SE-S. Transport from upwind areas associated with abundant O&NG operations accounts for on the order of 65% (mean for both sites) of 1-hr averaged elevated ozone levels, while the Denver urban corridor accounts for 9%. These correlations contribute to mounting evidence that air transport from areas with O&NG operation has a significant impact on ozone and air quality in the NCFR. This article builds on several previous pieces of research that implied significant contributions from oil and natural gas emissions on ozone production in the Northern Colorado Front Range. By correlating increased ozone events with transport analyses we show that there is a high abundance of transport events with elevated ozone originating from the Denver-Julesburg oil and natural gas

Mineral exploration potential of ERTS-1 data

NASA Technical Reports Server (NTRS)

Brewer, W. A. (Principal Investigator); Erskine, M. C., Jr.; Prindle, R. O.

1973-01-01

The author has identified the following significant results. Further analysis of ERTS-1 MSS imagery of Arizona has led to division of the earlier reported three major regional fault/fracture systems into eight subdivisions. These are: System A - N40E to N50E; System B - N50W; System C - N35W; System D - N65E to N75E; System E - N-E; System F - N25W average; System G - N75W average; and System H - close to E-W. Their individual significance to known porphyry coppers and correlation to the Wasatch-Jerome and Front Orogens, the Texas Zone and Basin Range topography is postulated in the report. In this study area of Arizona the ERTS-1 mapped structural trends confirm and greatly extend some concepts of porphyry copper distribution based on prior geologic knowledge of major structural trends.

A beam-splitter-type 3-D endoscope for front view and front-diagonal view images.

PubMed

Kamiuchi, Hiroki; Masamune, Ken; Kuwana, Kenta; Dohi, Takeyoshi; Kim, Keri; Yamashita, Hiromasa; Chiba, Toshio

2013-01-01

In endoscopic surgery, surgeons must manipulate an endoscope inside the body cavity to observe a large field-of-view while estimating the distance between surgical instruments and the affected area by reference to the size or motion of the surgical instruments in 2-D endoscopic images on a monitor. Therefore, there is a risk of the endoscope or surgical instruments physically damaging body tissues. To overcome this problem, we developed a Ø7- mm 3-D endoscope that can switch between providing front and front-diagonal view 3-D images by simply rotating its sleeves. This 3-D endoscope consists of a conventional 3-D endoscope and an outer and inner sleeve with a beam splitter and polarization plates. The beam splitter was used for visualizing both the front and front-diagonal view and was set at 25° to the outer sleeve's distal end in order to eliminate a blind spot common to both views. Polarization plates were used to avoid overlap of the two views. We measured signal-to-noise ratio (SNR), sharpness, chromatic aberration (CA), and viewing angle of this 3-D endoscope and evaluated its feasibility in vivo. Compared to the conventional 3-D endoscope, SNR and sharpness of this 3-D endoscope decreased by 20 and 7 %, respectively. No significant difference was found in CA. The viewing angle for both the front and front-diagonal views was about 50°. In the in vivo experiment, this 3-D endoscope can provide clear 3-D images of both views by simply rotating its inner sleeve. The developed 3-D endoscope can provide the front and front-diagonal view by simply rotating the inner sleeve, therefore the risk of damage to fragile body tissues can be significantly decreased.

Front and pulse solutions for the complex Ginzburg-Landau equation with higher-order terms.

PubMed

Tian, Huiping; Li, Zhonghao; Tian, Jinping; Zhou, Guosheng

2002-12-01

We investigate one-dimensional complex Ginzburg-Landau equation with higher-order terms and discuss their influences on the multiplicity of solutions. An exact analytic front solution is presented. By stability analysis for the original partial differential equation, we derive its necessary stability condition for amplitude perturbations. This condition together with the exact front solution determine the region of parameter space where the uniformly translating front solution can exist. In addition, stable pulses, chaotic pulses, and attenuation pulses appear generally if the parameters are out of the range. Finally, applying these analysis into the optical transmission system numerically we find that the stable transmission of optical pulses can be achieved if the parameters are appropriately chosen.

Atmospheric fronts in current and future climates

NASA Astrophysics Data System (ADS)

Catto, J. L.; Nicholls, N.; Jakob, C.; Shelton, K. L.

2014-11-01

Atmospheric fronts are important for the day-to-day variability of weather in the midlatitudes. It is therefore vital to know how their distribution and frequency will change in a projected warmer climate. Here we apply an objective front identification method, based on a thermal front parameter, to 6-hourly data from models participating in Coupled Model Intercomparison Project phase 5. The historical simulations are evaluated against ERA-Interim and found to produce a similar frequency of fronts and with similar front strength. The models show some biases in the location of the front frequency maxima. Future changes are estimated using the high emissions scenario simulations (Representative Concentration Pathway 8.5). Projections show an overall decrease in front frequency in the Northern Hemisphere, with a poleward shift of the maxima of front frequency and a strong decrease at high latitudes where the temperature gradient is decreased. The Southern Hemisphere shows a poleward shift of the frequency maximum, consistent with previous storm track studies.

Unstructured viscous grid generation by advancing-front method

NASA Technical Reports Server (NTRS)

Pirzadeh, Shahyar

1993-01-01

A new method of generating unstructured triangular/tetrahedral grids with high-aspect-ratio cells is proposed. The method is based on new grid-marching strategy referred to as 'advancing-layers' for construction of highly stretched cells in the boundary layer and the conventional advancing-front technique for generation of regular, equilateral cells in the inviscid-flow region. Unlike the existing semi-structured viscous grid generation techniques, the new procedure relies on a totally unstructured advancing-front grid strategy resulting in a substantially enhanced grid flexibility and efficiency. The method is conceptually simple but powerful, capable of producing high quality viscous grids for complex configurations with ease. A number of two-dimensional, triangular grids are presented to demonstrate the methodology. The basic elements of the method, however, have been primarily designed with three-dimensional problems in mind, making it extendible for tetrahedral, viscous grid generation.

Analyzing and Post-modelling the High Speed Images of a Wavy Laser Induced Boiling Front

NASA Astrophysics Data System (ADS)

Matti, R. S.; Kaplan, A. F. H.

The boiling front in laser materials processing like remote fusion cutting, keyhole welding or drilling can nowadays be recorded by high speed imaging. It was recently observed that bright waves flow down the front. Several complex physical mechanisms are associated with a stable laser-induced boiling front, like beam absorption, shadowing, heating, ablation pressure, fluid flow, etc. The evidence of dynamic phenomena from high speed imaging is closely linked to these phenomena. As a first step, the directly visible phenomena were classified and analyzed. This has led to the insight that the appearance of steady flow of the bright front peaks is a composition of many short flashing events of 20-50 μs duration, though composing a rather constant melt film flow downwards. Five geometrical front shapes of bright and dark domains were categorized, for example long inclined dark valleys. In addition, the special top and bottom regions of the front are distinguished. As a second step, a new method of post-modelling based on the greyscale variation of the images was applied, to approximately reconstruct the topology of the wavy front and subsequently to calculate the absorption across the front. Despite certain simplifications this kind of analysis provides a variety of additional information, including statistical analysis. In particular, the model could show the sensitivity of front waves to the formation of shadow domains and the robustness of fiber lasers to keep most of an irradiated steel surface in an absorptivity window between 35 to 43%.

Salinity fronts in the tropical Pacific Ocean.

PubMed

Kao, Hsun-Ying; Lagerloef, Gary S E

2015-02-01

This study delineates the salinity fronts (SF) across the tropical Pacific, and describes their variability and regional dynamical significance using Aquarius satellite observations. From the monthly maps of the SF, we find that the SF in the tropical Pacific are (1) usually observed around the boundaries of the fresh pool under the intertropical convergence zone (ITCZ), (2) stronger in boreal autumn than in other seasons, and (3) usually stronger in the eastern Pacific than in the western Pacific. The relationship between the SF and the precipitation and the surface velocity are also discussed. We further present detailed analysis of the SF in three key tropical Pacific regions. Extending zonally around the ITCZ, where the temperature is nearly homogeneous, we find the strong SF of 1.2 psu from 7° to 11°N to be the main contributor of the horizontal density difference of 0.8 kg/m 3 . In the eastern Pacific, we observe a southward extension of the SF in the boreal spring that could be driven by both precipitation and horizontal advection. In the western Pacific, the importance of these newly resolved SF associated with the western Pacific warm/fresh pool and El Niño southern oscillations are also discussed in the context of prior literature. The main conclusions of this study are that (a) Aquarius satellite salinity measurements reveal the heretofore unknown proliferation, structure, and variability of surface salinity fronts, and that (b) the fine-scale structures of the SF in the tropical Pacific yield important new information on the regional air-sea interaction and the upper ocean dynamics.

Fluctuation-controlled front propagation

NASA Astrophysics Data System (ADS)

Ridgway, Douglas Thacher

1997-09-01

A number of fundamental pattern-forming systems are controlled by fluctuations at the front. These problems involve the interaction of an infinite dimensional probability distribution with a strongly nonlinear, spatially extended pattern-forming system. We have examined fluctuation-controlled growth in the context of the specific problems of diffusion-limited growth and biological evolution. Mean field theory of diffusion-limited growth exhibits a finite time singularity. Near the leading edge of a diffusion-limited front, this leads to acceleration and blowup. This may be resolved, in an ad hoc manner, by introducing a cutoff below which growth is weakened or eliminated (8). This model, referred to as the BLT model, captures a number of qualitative features of global pattern formation in diffusion-limited aggregation: contours of the mean field match contours of averaged particle density in simulation, and the modified mean field theory can form dendritic features not possible in the naive mean field theory. The morphology transition between dendritic and non-dendritic global patterns requires that BLT fronts have a Mullins-Sekerka instability of the wavefront shape, in order to form concave patterns. We compute the stability of BLT fronts numerically, and compare the results to fronts without a cutoff. A significant morphological instability of the BLT fronts exists, with a dominant wavenumber on the scale of the front width. For standard mean field fronts, no instability is found. The naive and ad hoc mean field theories are continuum-deterministic models intended to capture the behavior of a discrete stochastic system. A transformation which maps discrete systems into a continuum model with a singular multiplicative noise is known, however numerical simulations of the continuum stochastic system often give mean field behavior instead of the critical behavior of the discrete system. We have found a new interpretation of the singular noise, based on maintaining

QCD and Light-Front Dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.; de Teramond, Guy F.; /SLAC /Southern Denmark U., CP3-Origins /Costa Rica U.

2011-01-10

AdS/QCD, the correspondence between theories in a dilaton-modified five-dimensional anti-de Sitter space and confining field theories in physical space-time, provides a remarkable semiclassical model for hadron physics. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time. The result is a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate {zeta} which measures the separation of the constituents within a hadron at equalmore » light-front time and determines the off-shell dynamics of the bound state wavefunctions as a function of the invariant mass of the constituents. The hadron eigenstates generally have components with different orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless quarks has L = 0 and L = 1 light-front Fock components with equal probability. Higher Fock states with extra quark-anti quark pairs also arise. The soft-wall model also predicts the form of the nonperturbative effective coupling and its {beta}-function. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method to systematically include QCD interaction terms. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates. A method for computing the hadronization of quark and gluon jets at the amplitude level is outlined.« less

A practical implementation of wave front construction for 3-D isotropic media

NASA Astrophysics Data System (ADS)

Chambers, K.; Kendall, J.-M.

2008-06-01

Wave front construction (WFC) methods are a useful tool for tracking wave fronts and are a natural extension to standard ray shooting methods. Here we describe and implement a simple WFC method that is used to interpolate wavefield properties throughout a 3-D heterogeneous medium. Our approach differs from previous 3-D WFC procedures primarily in the use of a ray interpolation scheme, based on approximating the wave front as a `locally spherical' surface and a `first arrival mode', which reduces computation times, where only first arrivals are required. Both of these features have previously been included in 2-D WFC algorithms; however, until now they have not been extended to 3-D systems. The wave front interpolation scheme allows for rays to be traced from a nearly arbitrary distribution of take-off angles, and the calculation of derivatives with respect to take-off angles is not required for wave front interpolation. However, in regions of steep velocity gradient, the locally spherical approximation is not valid, and it is necessary to backpropagate rays to a sufficiently homogenous region before interpolation of the new ray. Our WFC technique is illustrated using a realistic velocity model, based on a North Sea oil reservoir. We examine wavefield quantities such as traveltimes, ray angles, source take-off angles and geometrical spreading factors, all of which are interpolated on to a regular grid. We compare geometrical spreading factors calculated using two methods: using the ray Jacobian and by taking the ratio of a triangular area of wave front to the corresponding solid angle at the source. The results show that care must be taken when using ray Jacobians to calculate geometrical spreading factors, as the poles of the source coordinate system produce unreliable values, which can be spread over a large area, as only a few initial rays are traced in WFC. We also show that the use of the first arrival mode can reduce computation time by ~65 per cent, with the

Shearlet-based edge detection: flame fronts and tidal flats

NASA Astrophysics Data System (ADS)

King, Emily J.; Reisenhofer, Rafael; Kiefer, Johannes; Lim, Wang-Q.; Li, Zhen; Heygster, Georg

2015-09-01

Shearlets are wavelet-like systems which are better suited for handling geometric features in multi-dimensional data than traditional wavelets. A novel method for edge and line detection which is in the spirit of phase congruency but is based on a complex shearlet transform will be presented. This approach to detection yields an approximate tangent direction of detected discontinuities as a byproduct of the computation, which then yields local curvature estimates. Two applications of the edge detection method will be discussed. First, the tracking and classification of flame fronts is a critical component of research in technical thermodynamics. Quite often, the flame fronts are transient or weak and the images are noisy. The standard methods used in the field for the detection of flame fronts do not handle such data well. Fortunately, using the shearlet-based edge measure yields good results as well as an accurate approximation of local curvature. Furthermore, a modification of the method will yield line detection, which is important for certain imaging modalities. Second, the Wadden tidal flats are a biodiverse region along the North Sea coast. One approach to surveying the delicate region and tracking the topographical changes is to use pre-existing Synthetic Aperture Radar (SAR) images. Unfortunately, SAR data suffers from multiplicative noise as well as sensitivity to environmental factors. The first large-scale mapping project of that type showed good results but only with a tremendous amount of manual interaction because there are many edges in the data which are not boundaries of the tidal flats but are edges of features like fields or islands. Preliminary results will be presented.

Front blind spot crashes in Hong Kong.

PubMed

Cheng, Yuk Ki; Wong, Koon Hung; Tao, Chi Hang; Tam, Cheok Ning; Tam, Yiu Yan; Tsang, Cheuk Nam

2016-09-01

In 2012-2014, our laboratory had investigated a total of 9 suspected front blind spot crashes, in which the medium and heavy goods vehicles pulled away from rest and rolled over the pedestrians, who were crossing immediately in front of the vehicles. The drivers alleged that they did not see any pedestrians through the windscreens or the front blind spot mirrors. Forensic assessment of the goods vehicles revealed the existence of front blind spot zones in 3 out of these 9 accident vehicles, which were attributed to the poor mirror adjustments or even the absence of a front blind spot mirror altogether. In view of this, a small survey was devised involving 20 randomly selected volunteers and their goods vehicles and 5 out of these vehicles had blind spots at the front. Additionally, a short questionnaire was conducted on these 20 professional lorry drivers and it was shown that most of them were not aware of the hazards of blind spots immediately in front of their vehicles, and many did not use the front blind spot mirrors properly. A simple procedure for quick measurements of the coverage of front blind spot mirrors using a coloured plastic mat with dimensional grids was also introduced and described in this paper. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Nonperturbative light-front Hamiltonian methods

NASA Astrophysics Data System (ADS)

Hiller, J. R.

2016-09-01

We examine the current state-of-the-art in nonperturbative calculations done with Hamiltonians constructed in light-front quantization of various field theories. The language of light-front quantization is introduced, and important (numerical) techniques, such as Pauli-Villars regularization, discrete light-cone quantization, basis light-front quantization, the light-front coupled-cluster method, the renormalization group procedure for effective particles, sector-dependent renormalization, and the Lanczos diagonalization method, are surveyed. Specific applications are discussed for quenched scalar Yukawa theory, ϕ4 theory, ordinary Yukawa theory, supersymmetric Yang-Mills theory, quantum electrodynamics, and quantum chromodynamics. The content should serve as an introduction to these methods for anyone interested in doing such calculations and as a rallying point for those who wish to solve quantum chromodynamics in terms of wave functions rather than random samplings of Euclidean field configurations.

A geophysical investigation of shallow deformation along an anomalous section of the Wasatch fault zone, Utah, USA

USGS Publications Warehouse

McBride, J.H.; Stephenson, W.J.; Thompson, T.J.; Harper, M.P.; Eipert, A.A.; Hoopes, J.C.; Tingey, D.G.; Keach, R.W.; Okojie-Ayoro, A. O.; Gunderson, K.L.; Meirovitz, C.D.; Hicks, T.C.; Spencer, C.J.; Yaede, J.R.; Worley, D.M.

2008-01-01

We report the results of a geophysical study of the Wasatch fault zone near the Provo and Salt Lake City segment boundary. This area is anomalous because the fault zone strikes more east-west than north-south. Vibroseis was used to record a common mid-point (CMP) profile that provides information to depths of ???500 m. A tomographic velocity model, derived from first breaks, constrained source and receiver static corrections; this was required due to complex terrain and significant lateral velocity contrasts. The profile reveals an ???250-m-wide graben in the hanging wall of the main fault that is associated with both synthetic and antithetic faults. Faults defined by apparent reflector offsets propagate upward toward topographic gradients. Faults mapped from a nearby trench and the seismic profile also appear to correlate with topographic alignments on LiDAR gradient maps. The faults as measured in the trench show a wide range of apparent dips, 20??-90??, and appear to steepen with depth on the seismic section. Although the fault zone is likely composed of numerous small faults, the broad asymmetric structure in the hanging wall is fairly simple and dominated by two inward-facing ruptures. Our results indicate the feasibility of mapping fault zones in rugged terrain and complex near-surface geology using low-frequency vibroseis. Further, the integration of geologic mapping and seismic reflection can extend surface observations in areas where structural deformation is obscured by poorly stratified or otherwise unmappable deposits. Therefore, the vibroseis technique, when integrated with geological information, provides constraints for assessing geologic hazards in areas of potential development.

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Methodology of automated ionosphere front velocity estimation for ground-based augmentation of GNSS

NASA Astrophysics Data System (ADS)

Bang, Eugene; Lee, Jiyun

2013-11-01

ionospheric anomalies occurring during severe ionospheric storms can pose integrity threats to Global Navigation Satellite System (GNSS) Ground-Based Augmentation Systems (GBAS). Ionospheric anomaly threat models for each region of operation need to be developed to analyze the potential impact of these anomalies on GBAS users and develop mitigation strategies. Along with the magnitude of ionospheric gradients, the speed of the ionosphere "fronts" in which these gradients are embedded is an important parameter for simulation-based GBAS integrity analysis. This paper presents a methodology for automated ionosphere front velocity estimation which will be used to analyze a vast amount of ionospheric data, build ionospheric anomaly threat models for different regions, and monitor ionospheric anomalies continuously going forward. This procedure automatically selects stations that show a similar trend of ionospheric delays, computes the orientation of detected fronts using a three-station-based trigonometric method, and estimates speeds for the front using a two-station-based method. It also includes fine-tuning methods to improve the estimation to be robust against faulty measurements and modeling errors. It demonstrates the performance of the algorithm by comparing the results of automated speed estimation to those manually computed previously. All speed estimates from the automated algorithm fall within error bars of ± 30% of the manually computed speeds. In addition, this algorithm is used to populate the current threat space with newly generated threat points. A larger number of velocity estimates helps us to better understand the behavior of ionospheric gradients under geomagnetic storm conditions.

Architecture and Channel-Belt Clustering in the Fluvial lower Wasatch Formation, Uinta Basin, Utah

NASA Astrophysics Data System (ADS)

Pisel, J. R.; Pyles, D. R.; Bracken, B.; Rosenbaum, C. D.

2013-12-01

The Eocene lower Wasatch Formation of the Uinta Basin contains exceptional outcrops of low net-sand content (27% sand) fluvial strata. This study quantitatively documents the stratigraphy of a 7 km wide by 300 meter thick strike-oriented outcrop in order to develop a quantitative data base that can be used to improve our knowledge of how some fluvial systems evolve over geologic time scales. Data used to document the outcrop are: (1) 550 meters of decimeter to half meter scale resolution stratigraphic columns that document grain size and physical sedimentary structures; (2) detailed photopanels used to document architectural style and lithofacies types in the outcrop; (3) thickness, width, and spatial position for all channel belts in the outcrop, and (4) directional measurements of paleocurrent indicators. Two channel-belt styles are recognized: lateral and downstream accreting channel belts; both of which occur as either single or multi-story. Floodplain strata are well exposed and consist of overbank fines and sand-rich crevasse splay deposits. Key upward and lateral characteristics of the outcrop documented herein are the following. First, the shapes of 243 channels are documented. The average width, thickness and aspect ratios of the channel belts are 110 m, 7 m, and 16:1, respectively. Importantly, the size and shape of channel belts does not change upward through the 300 meter transect. Second, channels are documented to spatially cluster. 9 clusters are documented using a spatial statistic. Key upward patterns in channel belt clustering are a marked change from non-amalgamated isolated channel-belt clusters to amalgamated channel-belt clusters. Critically, stratal surfaces can be correlated from mudstone units within the clusters to time-equivalent floodplain strata adjacent to the cluster demonstrating that clusters are not confined within fluvial valleys. Finally, proportions of floodplain and channel belt elements underlying clusters and channel belts

THE EFFECT OF ANISOTROPIC VISCOSITY ON COLD FRONTS IN GALAXY CLUSTERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

ZuHone, J. A.; Markevitch, M.; Kunz, M. W.

2015-01-10

Cold fronts—contact discontinuities in the intracluster medium (ICM) of galaxy clusters—should be disrupted by Kelvin-Helmholtz (K-H) instabilities due to the associated shear velocity. However, many observed cold fronts appear stable. This opens the possibility of placing constraints on microphysical mechanisms that stabilize them, such as the ICM viscosity and/or magnetic fields. We performed exploratory high-resolution simulations of cold fronts arising from subsonic gas sloshing in cluster cores using the grid-based Athena MHD code, comparing the effects of isotropic Spitzer and anisotropic Braginskii viscosity (expected in a magnetized plasma). Magnetized simulations with full Braginskii viscosity or isotropic Spitzer viscosity reduced bymore » a factor f ∼ 0.1 are both in qualitative agreement with observations in terms of suppressing K-H instabilities. The rms velocity of turbulence within the sloshing region is only modestly reduced by Braginskii viscosity. We also performed unmagnetized simulations with and without viscosity and find that magnetic fields have a substantial effect on the appearance of the cold fronts, even if the initial field is weak and the viscosity is the same. This suggests that determining the dominant suppression mechanism of a given cold front from X-ray observations (e.g., viscosity or magnetic fields) by comparison with simulations is not straightforward. Finally, we performed simulations including anisotropic thermal conduction, and find that including Braginskii viscosity in these simulations does not significantly affect the evolution of cold fronts; they are rapidly smeared out by thermal conduction, as in the inviscid case.« less

Characterizing the Response of Fluvial Systems to Extreme Global Warming During the Early Eocene Climatic Optimum: An Analysis of the Wasatch and Green River Formations, Uinta Basin, UT

NASA Astrophysics Data System (ADS)

Jones, E. R.; Plink-Bjorklund, P.

2013-12-01

The Wasatch and Green River Formations in the Uinta Basin, UT contain fluvial sandstones that record changes in terrestrial sedimentation coincident with Paleocene-Eocene Thermal Maximum (PETM) and at least six post-PETM hyperthermal climate change events. While proxies for chemical weathering rates during the PETM have been developed using the marine osmium isotope record, to date there has been little research on chemical weathering rates in proximal terrestrial depocenters. This work is one part of a multi-proxy research effort combining quantitative petrographic analysis, the stable carbon isotope record, and a high-resolution stratigraphic and sedimentologic framework across the southern margin of the Uinta Basin. Relative tectonic quiescence in the Uinta Basin during the Early Eocene suggests that climate is the forcing mechanism controlling fluvial architecture and composition, and gradual basin subsidence has preserved at least six pulses of greenhouse climate change during the Early Eocene Climatic Optimum (EECO). Terrestrial records of PETM climate do not support a humid climate with increased precipitation as previously suggested from marine proxies of climate change. Instead, terrestrial records of the PETM climate show evidence of prolonged drought punctuated by intense terrestrial flooding events in mid-latitude continental interiors. Increases in chemical weathering rates during the PETM due to increased temperature and average precipitation is cited as a key carbon sink to initiate a recovery phase where atmospheric CO2 returned to normal concentrations. If terrestrial records of chemical weathering rates differ substantially from marine proxies the carbon-cycle dynamics active during the EECO must be reconsidered. Initial results of this study show that these peak hyperthermal climate change conditions in the Uinta Basin preserve more compositionally and texturally immature sediments due to extremely high erosion and deposition rates, and subdued

Predicting driver from front passenger using only the postmortem pattern of injury following a motor vehicle collision.

PubMed

Curtin, Eleanor; Langlois, Neil E I

2007-10-01

This study aimed to establish whether post-mortem injury patterns can assist in distinguishing drivers from front seat passengers among victims of motor vehicle collisions without regard to collision type, vehicle type or if safety equipment had been used. Injuries sustained by 206 drivers and 91 front seat passengers were catalogued from post-mortem reports. Injuries were coded for the body region, depth and location of the injury. Statistical analysis was used to detect injuries capable of discriminating between driver and passenger. Drivers were more likely to sustain the following injuries: brain injury; fractures to the right femur, right posterior ribs, base of skull, right humerus and right shoulder; and superficial wounds at the right lateral and posterior thigh, right face, right and left anterior knee, right anterior shoulder, lateral right arm and forearm and left anterior thigh. Front passengers were more vulnerable to splenic injury; fractures to the left posterior and anterior ribs, left shoulder and left femur; and superficial wounds at the left anterior shoulder region and left lateral neck. Linear discriminant analysis generated a model for predicting seating position based on the presence of injury to certain regions of the body; the overall predictive accuracy of the model was 69.3%. It was found that driver and front passenger fatalities receive different injury patterns from motor vehicle collisions, regardless of collision type. A larger study is required to improve the predictive accuracy of this model and to ascertain its value to forensic medicine.

Automated detection of secondary slip fronts in Cascadia

NASA Astrophysics Data System (ADS)

Bletery, Q.; Thomas, A.; Krogstad, R. D.; Hawthorne, J. C.; Skarbek, R. M.; Rempel, A. W.; Bostock, M. G.

2016-12-01

Slow slip events (SSEs) in subduction zones propagate along the plate interface at velocities on the order of 5 km/day and are largely confined to the region known as the transition zone, located down-dip of the seismogenically locked zone. As SSEs propagate, small on-fault asperities capable of generating seismic radiation fail in earthquake-like events known as low-frequency earthquakes. Recently, low-frequency earthquakes have been used to image smaller scale secondary slip fronts (SSFs) that occur within the actively slipping region of the fault after the main front associated with the SSE has passed. SSFs appear to occur over several different length and timescales and propagate both along dip and along strike. To date, most studies that have documented SSFs have relied on subjective methods, such as visual selection, to identify them. While such approaches have met with considerable success, it is likely that many small-scale fronts remain unidentifiable by visual inspection alone. We implement an algorithm to automatically detect SSFs from 2009 to 2015 along the Cascadia subduction zone. We also apply our algorithm to three large SSEs that were detected by campaign seismic instrumentation in the Vancouver Island area between 2003 and 2005. We find numerous SSFs at different time scales (from 30 min to 32 h duration). We provide a catalog of 1076 SSFs in Cascadia, including time, location, duration, area, propagation velocity, moment, stress drop, slip, slip velocity, and fracture energy for each of the detected SSFs. Analysis of their basic features indicate a wide spectra of stress drops, slip velocities, and fracture energy, as well as an intriguing relationship between SSF direction and duration that could potentially help discriminate between the different physical models proposed to explain slow slip phenomena.

[Effects on the regional homogeneity of resting-state brain function in the healthy subjects of gastric distention treated with acupuncture at the front-mu and back-shu points of the stomach, Weishu (BL 21) and Zhongwan (CV 12)].

PubMed

Cai, Ronglin; Guan, Yuanyuan; Wu, Hongli; Xu, Chunsheng; Li, Chuanfu; Hu, Ling; Shen, Guoming

2018-04-12

To observe the regional homogeneity (ReHo) of resting-state brain function in the healthy subjects of gastric distention treated with acupuncture at the back- shu and front- mu points of the stomach, Weishu (BL 21) and Zhongwan (CV 12) and the correlation with gastric motility so as to explore the mechanism on the central integration of the front- mu and back- shu points of the stomach. The crossover test design was adopted. Twenty-four healthy subjects were assigned to a Weishu group, a Zhongwan group and a combined-point group separately, 8 cases in each one in each of the three times. Totally, 24 subjects were included in each group. Under the water load condition, the subjects received acupuncture at Weishu (BL 21), Zhongwan (CV 12) and the combined Weishu (BL 21) and Zhongwan (CV 12). Before and after each acupuncture, the resting-state brain functional magnetic resonance imaging (fMRI) scan and electrogastrogram (EGG) test were applied. The ReHo value was calculated in the collected fMRI imaging data. The changes in ReHo values were analyzed and compared before and after acupuncture in each group, as well as among the groups. The gastric motility was analyzed before and after acupuncture. Additionally, the correlative analysis was conducted between the gastric motility and ReHo changes before and after acupuncture. (1) After acupuncture, EGG amplitudes in the subjects of each group were lower remarkably as compared with those before acupuncture (all P <0.01). The EGG frequencies were not different significantly as compared with those before acupuncture (all P >0.05). The EGG amplitudes in the Weishu group and the Zhongwan group were higher than those in the combined-point group (both P <0.05). (2) As compared with the conditions before acupuncture, acupuncture at the combined front- mu and the back- shu points as well as Weishu (BL 21) and Zhongwan (CV 12) separately all induced the changes in the brain ReHo. Acupuncture at the combined front- mu and the back

Relating precipitation to fronts at a sub-daily basis

NASA Astrophysics Data System (ADS)

Hénin, Riccardo; Ramos, Alexandre M.; Liberato, Margarida L. R.; Gouveia, Célia

2017-04-01

High impact events over Western Iberia include precipitation extremes that are cause for concern as they lead to flooding, landslides, extensive property damage and human casualties. These events are usually associated with low pressure systems over the North Atlantic moving eastward towards the European western coasts (Liberato and Trigo, 2014). A method to detect fronts and to associate amounts of precipitation to each front is tested, distinguishing between warm and cold fronts. The 6-hourly ERA-interim 1979-2012 reanalysis with 1°x1° horizontal resolution is used for the purpose. An objective front identification method (the Thermal Method described in Shemm et al., 2014) is applied to locate fronts all over the Northern Hemisphere considering the equivalent potential temperature as thermal parameter to use in the model. On the other hand, we settled a squared search box of tuneable dimension (from 2 to 10 degrees long) to look for a front in the neighbourhood of a grid point affected by precipitation. A sensitivity analysis is performed and the optimal dimension of the box is assessed in order to avoid over(under) estimation of precipitation. This is performed in the light of the variability and typical dynamics of warm/cold frontal systems in the Western Europe region. Afterwards, using the extreme event ranking over Iberia proposed by Ramos et al. (2014) the first ranked extreme events are selected in order to validate the method with specific case studies. Finally, climatological and trend maps of frontal activity are produced both on annual and seasonal scales. Trend maps show a decrease of frontal precipitation over north-western Europe and a slight increase over south-western Europe, mainly due to warm fronts. REFERENCES Liberato M.L.R. and R.M. Trigo (2014) Extreme precipitation events and related impacts in Western Iberia. Hydrology in a Changing World: Environmental and Human Dimensions. IAHS Red Book No 363, 171-176. ISSN: 0144-7815. Ramos A.M., R

Seasonal and Interannual Variability of the Brazil - Malvinas Front: an Altimetry Perspective

NASA Astrophysics Data System (ADS)

Saraceno, M.; Valla, D.; Pelegrí, J. L.; Piola, A. R.

2016-02-01

The Brazil and Malvinas Confluence in the Southwestern Atlantic is one of the most energetic regions of the world ocean. Using recent measurements of sub-surface velocity currents, collected along 2348 nautical miles with a vessel mounted acoustic Doppler profiler onboard R/V BIO Hespérides, we validate geostrophic velocities derived from gridded fields of sea surface height (SSH). A remarkable correspondence between in-situ surface hydrographic data collected from the vessel and satellite sea surface temperature (SST), color and altimetry data allows selecting a specific SSH contour to track the position of the Brazil-Malvinas front. We then use 22 years of SSH data distributed by AVISO to show that the Brazil-Malvinas front shows a NS orientation in winter and a NE-SW orientation in summer, in good agreement with results based on the analysis of SST gradients. Furthermore, a clear southward migration of the front during the 22 year period is observed. The migration is associated with the southward shift of the South Atlantic high-pressure system that is in turn related to large climate changes in the southern portion of the South American continent. The seasonal variability in the orientation of the front is related to the Brazil and Malvinas encountering currents.

Adaptive two-regime method: Application to front propagation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robinson, Martin, E-mail: martin.robinson@maths.ox.ac.uk; Erban, Radek, E-mail: erban@maths.ox.ac.uk; Flegg, Mark, E-mail: mark.flegg@monash.edu

2014-03-28

The Adaptive Two-Regime Method (ATRM) is developed for hybrid (multiscale) stochastic simulation of reaction-diffusion problems. It efficiently couples detailed Brownian dynamics simulations with coarser lattice-based models. The ATRM is a generalization of the previously developed Two-Regime Method [Flegg et al., J. R. Soc., Interface 9, 859 (2012)] to multiscale problems which require a dynamic selection of regions where detailed Brownian dynamics simulation is used. Typical applications include a front propagation or spatio-temporal oscillations. In this paper, the ATRM is used for an in-depth study of front propagation in a stochastic reaction-diffusion system which has its mean-field model given in termsmore » of the Fisher equation [R. Fisher, Ann. Eugen. 7, 355 (1937)]. It exhibits a travelling reaction front which is sensitive to stochastic fluctuations at the leading edge of the wavefront. Previous studies into stochastic effects on the Fisher wave propagation speed have focused on lattice-based models, but there has been limited progress using off-lattice (Brownian dynamics) models, which suffer due to their high computational cost, particularly at the high molecular numbers that are necessary to approach the Fisher mean-field model. By modelling only the wavefront itself with the off-lattice model, it is shown that the ATRM leads to the same Fisher wave results as purely off-lattice models, but at a fraction of the computational cost. The error analysis of the ATRM is also presented for a morphogen gradient model.« less

An explanation of unstable wetting fronts in soils

NASA Astrophysics Data System (ADS)

Steenhuis, Tammo; Parlange, Jean-Yves; Kung, Samuel; Stoof, Cathelijne; Baver, Christine

2016-04-01

Despite the findings of Raats on unstable wetting front almost a half a century ago, simulating wetting fronts in soils is still an area of active research. One of the critical questions currently is whether Darcy law is valid at the wetting front. In this talk, we pose that in many cases for dry soils, Darcy's law does not apply because the pressure field across the front is not continuous. Consequently, the wetting front pressure is not dependent on the pressure ahead of the front but is determined by the radius of water meniscuses and the dynamic contact angle of the water. If we further assume since the front is discontinuous, that water flows at one pore at the time, then by using the modified Hoffman relationship - relating the dynamic contact angle to the pore water velocity - we find the elevated pressures at the wetting front typical for unstable flows that are similar to those observed experimentally in small diameter columns. The theory helps also explain the funnel flow phenomena observed in layered soils.

Advanced RF Front End Technology

NASA Technical Reports Server (NTRS)

Herman, M. I.; Valas, S.; Katehi, L. P. B.

2001-01-01

The ability to achieve low-mass low-cost micro/nanospacecraft for Deep Space exploration requires extensive miniaturization of all subsystems. The front end of the Telecommunication subsystem is an area in which major mass (factor of 10) and volume (factor of 100) reduction can be achieved via the development of new silicon based micromachined technology and devices. Major components that make up the front end include single-pole and double-throw switches, diplexer, and solid state power amplifier. JPL's Center For Space Microsystems - System On A Chip (SOAC) Program has addressed the challenges of front end miniaturization (switches and diplexers). Our objectives were to develop the main components that comprise a communication front end and enable integration in a single module that we refer to as a 'cube'. In this paper we will provide the latest status of our Microelectromechanical System (MEMS) switches and surface micromachined filter development. Based on the significant progress achieved we can begin to provide guidelines of the proper system insertion for these emerging technologies. Additional information is contained in the original extended abstract.

Flux front penetration in disordered superconductors.

PubMed

Zapperi, S; Moreira, A A; Andrade, J S

2001-04-16

We investigate flux front penetration in a disordered type-II superconductor by molecular dynamics simulations of interacting vortices and find scaling laws for the front position and the density profile. The scaling can be understood by performing a coarse graining of the system and writing a disordered nonlinear diffusion equation. Integrating numerically the equation, we observe a crossover from flat to fractal front penetration as the system parameters are varied. The value of the fractal dimension indicates that the invasion process is described by gradient percolation.

Geophysical Studies in the Vicinity of the Warner Mountains and Surprise Valley, Northeast California, Northwest Nevada, and Southern Oregon

USGS Publications Warehouse

Ponce, David A.; Glen, Jonathan M.G.; Egger, Anne E.; Bouligand, Claire; Watt, Janet T.; Morin, Robert L.

2009-01-01

From May 2006 to August 2007, the U.S. Geological Survey (USGS) collected 793 gravity stations, about 102 line-kilometers of truck-towed and ground magnetometer data, and about 325 physical-property measurements in northeastern California, northwestern Nevada, and southern Oregon. Gravity, magnetic, and physical-property data were collected to study regional crustal structures and geology as an aid to understanding the geologic framework of the Surprise Valley geothermal area and, in general, geothermal systems throughout the Great Basin. The Warner Mountains and Surprise Valley mark the transition from the extended Basin and Range province to the unextended Modoc Plateau. This transition zone, in the northwestern corner of the Basin and Range, is relatively diffuse compared to other, more distinct boundaries, such as the Wasatch front in Utah and the eastern Sierran range front. In addition, this transition zone is the site of a geothermal system with potential for development, and previous studies have revealed a complex structural setting consisting of several obliquely oriented fault sets. As a result, this region has been the subject of several recent geological and geophysical investigations. The gravity and magnetic data presented here support and supplement those studies, and although the study area is composed predominantly of Tertiary volcanic rocks of the Modoc Plateau rocks, the physical properties of these and others rocks create a distinguishable pattern of gravity and magnetic anomalies that can be used to infer subsurface geologic structure.

Role of lower hybrid waves in ion heating at dipolarization fronts

NASA Astrophysics Data System (ADS)

Greco, A.; Artemyev, A.; Zimbardo, G.; Angelopoulos, V.; Runov, A.

2017-05-01

One of the important sources of hot ions in the magnetotail is the bursty bulk flows propagating away from the reconnection region and heating the ambient plasma. Charged particles interact with nonlinear magnetic field pulses (dipolarization fronts, DFs) embedded into these flows. The convection electric fields associated with DF propagation are known to reflect and accelerate ambient ions. Moreover, a wide range of waves is observed within/near these fronts, the electric field fluctuations being dominated by the lower hybrid drift (LHD) instability. Here we investigate the potential role of these waves in the further acceleration of ambient ions. We use a LHD wave emission profile superimposed on the leading edge of a two-dimensional model profile of a DF and a test particle approach. We show that LHD waves with realistic amplitudes can significantly increase the upper limit of energies gained by ions. Wave-particle interaction near the front is more effective in producing superthermal ions than in increasing the flux of thermal ions. Comparison of test particle simulations and Time History of Events and Macroscale Interactions during Substorms observations show that ion acceleration by LHD waves is more important for slower DFs.

Surface properties of ocean fronts

NASA Technical Reports Server (NTRS)

Wolff, P. M.; Hubert, W. E.

1976-01-01

Background information on oceanic fronts is presented and the results of several models which were developed to study the dynamics of oceanic fronts and their effects on various surface properties are described. The details of the four numerical models used in these studies are given in separate appendices which contain all of the physical equations, program documentation and running instructions for the models.

Convection induced by thermal gradients on thin reaction fronts

NASA Astrophysics Data System (ADS)

Ruelas Paredes, David R. A.; Vasquez, Desiderio A.

2017-09-01

We present a thin front model for the propagation of chemical reaction fronts in liquids inside a Hele-Shaw cell or porous media. In this model we take into account density gradients due to thermal and compositional changes across a thin interface. The front separating reacted from unreacted fluids evolves following an eikonal relation between the normal speed and the curvature. We carry out a linear stability analysis of convectionless flat fronts confined in a two-dimensional rectangular domain. We find that all fronts are stable to perturbations of short wavelength, but they become unstable for some wavelengths depending on the values of compositional and thermal gradients. If the effects of these gradients oppose each other, we observe a range of wavelengths that make the flat front unstable. Numerical solutions of the nonlinear model show curved fronts of steady shape with convection propagating faster than flat fronts. Exothermic fronts increase the temperature of the fluid as they propagate through the domain. This increment in temperature decreases with increasing speed.

Wintertime sea surface temperature fronts in the Taiwan Strait

NASA Astrophysics Data System (ADS)

Chang, Yi; Shimada, Teruhisa; Lee, Ming-An; Lu, Hsueh-Jung; Sakaida, Futoki; Kawamura, Hiroshi

2006-12-01

We present wintertime variations and distributions of sea surface temperature (SST) fronts in the Taiwan Strait by applying an entropy-based edge detection method to 10-year (1996-2005) satellite SST images with grid size of 0.01°. From climatological monthly mean maps of SST gradient magnitude in winter, we identify four significant SST fronts in the Taiwan Strait. The Mainland China Coastal Front is a long frontal band along the 50-m isobath near the Chinese coast. The sharp Peng-Chang Front appears along the Peng-Hu Channel and extends northward around the Chang-Yuen Ridge. The Taiwan Bank Front evolves in early winter. As the winter progresses, the front becomes broad and moves toward the Chinese coast, connecting to the Mainland China Coastal Front. The Kuroshio Front extends northeastward from the northeastern tip of Taiwan with a semicircle-shape curving along the 100-m isobath.

A CloudSat-CALIPSO View of Cloud and Precipitation Properties Across Cold Fronts over the Global Oceans

NASA Technical Reports Server (NTRS)

Naud, Catherine M.; Posselt, Derek J.; van den Heever, Susan C.

2015-01-01

The distribution of cloud and precipitation properties across oceanic extratropical cyclone cold fronts is examined using four years of combined CloudSat radar and CALIPSO lidar retrievals. The global annual mean cloud and precipitation distributions show that low-level clouds are ubiquitous in the post frontal zone while higher-level cloud frequency and precipitation peak in the warm sector along the surface front. Increases in temperature and moisture within the cold front region are associated with larger high-level but lower mid-/low level cloud frequencies and precipitation decreases in the cold sector. This behavior seems to be related to a shift from stratiform to convective clouds and precipitation. Stronger ascent in the warm conveyor belt tends to enhance cloudiness and precipitation across the cold front. A strong temperature contrast between the warm and cold sectors also encourages greater post-cold-frontal cloud occurrence. While the seasonal contrasts in environmental temperature, moisture, and ascent strength are enough to explain most of the variations in cloud and precipitation across cold fronts in both hemispheres, they do not fully explain the differences between Northern and Southern Hemisphere cold fronts. These differences are better explained when the impact of the contrast in temperature across the cold front is also considered. In addition, these large-scale parameters do not explain the relatively large frequency in springtime post frontal precipitation.

Characterizing Ion Flows Across a Dipolarization Front

NASA Astrophysics Data System (ADS)

Arnold, H.; Drake, J. F.; Swisdak, M.

2017-12-01

In light of the Magnetospheric Multiscale Mission (MMS) moving to study predominately symmetric magnetic reconnection in the Earth's magnetotail, it is of interest to investigate various methods for determining the relative location of the satellites with respect to the x line or a dipolarization front. We use a 2.5 dimensional PIC simulation to explore the dependence of various characteristics of a front, or flux bundle, on the width of the front in the dawn-dusk direction. In particular, we characterize the ion flow in the x-GSM direction across the front. We find a linear relationship between the width of a front, w, and the maximum velocity of the ion flow in the x-GSM direction, Vxi, for small widths: Vxi/VA=w/di*1/2*(mVA2)/Ti*Bz/Bxwhere m, VA, di, Ti, Bz, and Bx are the ion mass, upstream Alfven speed, ion inertial length, ion temperature, and magnetic fields in the z-GSM and x-GSM directions respectively. However, once the width reaches around 5 di, the relationship gradually approaches the well-known theoretical limit for ion flows, the upstream Alfven speed. Furthermore, we note that there is a reversal in the Hall magnetic field near the current sheet on the positive y-GSM side of the front. This reversal is most likely due to conservation of momentum in the y-GSM direction as the ions accelerate towards the x-GSM direction. This indicates that while the ions are primarily energized in the x-GSM direction by the front, they transfer energy to the electromagnetic fields in the y-GSM direction. The former energy transfer is greater than the latter, but the reversal of the Hall magnetic field drags the frozen-in electrons along with it outside of the front. These simulations should better able researchers to determine the relative location of a satellite crossing a dipolarization front.

Ammonium Nitrate Formation near the Colorado Front Range

NASA Astrophysics Data System (ADS)

Middlebrook, A. M.; Bahreini, R.; Brock, C. A.; Brown, S. S.; Cozic, J.; Frost, G. J.; Langford, A. O.; Lerner, B. M.; Matthew, B.; McKeen, S. A.; Neuman, J.; Nowak, J. B.; Peischl, J. W.; Quinn, P.; Ryerson, T. B.; Schultz, K.; Stark, H.; Trainer, M.; Wagner, N.; Williams, E. J.; Wollny, A. G.

2009-12-01

A significant air quality issue during wintertime temperature inversions along the Colorado Front Range urban corridor is the infamous “Brown Cloud” which is dominated by ammonium nitrate particles. Aerosol composition, size distribution, and gas phase measurements were obtained along with meteorology in Boulder-based ground studies during the winters of 2005 and 2009 and in an airborne survey over the Colorado Front Range urban corridor and northeastern Colorado on April 1, 2008. New in these campaigns was the fast time response data which showed that nitric acid was partitioned mainly into the aerosol phase as ammonium nitrate. During the survey flight, ammonium nitrate mass concentrations were highest on the west side of the urban corridor whereas nitrogen oxide concentrations were highest directly west and south of Denver. Nitric acid concentrations were highest south of the city. The calculated equilibrium gas phase ammonia was highest close to the ground directly around large feed lots near Brush and west of Greeley. These differences are consistent with what is known about the locations of emission sources, the predominant flow during the experiments, and the chemistry. Indeed, the ammonia emissions in the northern part of the region are sufficiently high to cause ammonium nitrate formation to be limited by nitric acid whereas in the southern part of the region ammonium nitrate formation was limited by low ammonia emissions. Although NOx (NO + NO2) emissions in the region are much larger than those for ammonia, NOx must be converted into nitric acid in order for ammonium nitrate to form. In the survey data, aerosol nitrate was correlated with the daytime nitric acid production rate but with higher slopes in the northern parts of the region. In the longer Boulder datasets, the calculated daytime production rate was slow and comparable to nighttime heterogeneous production via N2O5 hydrolysis. During periods of low aerosol surface area, daytime and

Pareto-front shape in multiobservable quantum control

NASA Astrophysics Data System (ADS)

Sun, Qiuyang; Wu, Re-Bing; Rabitz, Herschel

2017-03-01

Many scenarios in the sciences and engineering require simultaneous optimization of multiple objective functions, which are usually conflicting or competing. In such problems the Pareto front, where none of the individual objectives can be further improved without degrading some others, shows the tradeoff relations between the competing objectives. This paper analyzes the Pareto-front shape for the problem of quantum multiobservable control, i.e., optimizing the expectation values of multiple observables in the same quantum system. Analytic and numerical results demonstrate that with two commuting observables the Pareto front is a convex polygon consisting of flat segments only, while with noncommuting observables the Pareto front includes convexly curved segments. We also assess the capability of a weighted-sum method to continuously capture the points along the Pareto front. Illustrative examples with realistic physical conditions are presented, including NMR control experiments on a 1H-13C two-spin system with two commuting or noncommuting observables.

Comparing methods for modelling spreading cell fronts.

PubMed

Markham, Deborah C; Simpson, Matthew J; Maini, Philip K; Gaffney, Eamonn A; Baker, Ruth E

2014-07-21

Spreading cell fronts play an essential role in many physiological processes. Classically, models of this process are based on the Fisher-Kolmogorov equation; however, such continuum representations are not always suitable as they do not explicitly represent behaviour at the level of individual cells. Additionally, many models examine only the large time asymptotic behaviour, where a travelling wave front with a constant speed has been established. Many experiments, such as a scratch assay, never display this asymptotic behaviour, and in these cases the transient behaviour must be taken into account. We examine the transient and the asymptotic behaviour of moving cell fronts using techniques that go beyond the continuum approximation via a volume-excluding birth-migration process on a regular one-dimensional lattice. We approximate the averaged discrete results using three methods: (i) mean-field, (ii) pair-wise, and (iii) one-hole approximations. We discuss the performance of these methods, in comparison to the averaged discrete results, for a range of parameter space, examining both the transient and asymptotic behaviours. The one-hole approximation, based on techniques from statistical physics, is not capable of predicting transient behaviour but provides excellent agreement with the asymptotic behaviour of the averaged discrete results, provided that cells are proliferating fast enough relative to their rate of migration. The mean-field and pair-wise approximations give indistinguishable asymptotic results, which agree with the averaged discrete results when cells are migrating much more rapidly than they are proliferating. The pair-wise approximation performs better in the transient region than does the mean-field, despite having the same asymptotic behaviour. Our results show that each approximation only works in specific situations, thus we must be careful to use a suitable approximation for a given system, otherwise inaccurate predictions could be made

Discrete modelling of front propagation in backward piping erosion

NASA Astrophysics Data System (ADS)

Tran, Duc-Kien; Prime, Noémie; Froiio, Francesco; Callari, Carlo; Vincens, Eric

2017-06-01

A preliminary discrete numerical model of a REV at the front region of an erosion pipe in a cohesive granular soil is briefly presented. The results reported herein refer to a simulation carried out by coupling the Discrete Element Method (DEM) with the Lattice Boltzmann Method (LBM) for the representation of the granular and fluid phases, respectively. The numerical specimen, consisiting of bonded grains, is tested under fully-saturated conditions and increasing pressure difference between the inlet (confined) and the outlet (unconfined) flow regions. The key role of compression arches of force chains that transversely cross the sample and carry most part of the hydrodynamic actions is pointed out. These arches partition the REV into an upstream region that remains almost intact and a downstream region that gradually degrades and is subsequently eroded in the form of a cluster. Eventually, the collapse of the compression arches causes the upstream region to be also eroded, abruptly, as a whole. A complete presentation of the numerical model and of the results of the simulation can be found in [12].

Supersymmetric Properties of Hadron Physics from Light-Front Holography and Superconformal Algebra and other Advances in Light-Front QCD

NASA Astrophysics Data System (ADS)

Brodsky, Stanley J.

2018-05-01

Light-front holography, together with superconformal algebra, have provided new insights into the physics of color confinement and the spectroscopy and dynamics of hadrons. As shown by de Alfaro, Fubini and Furlan, a mass scale can appear in the equations of motion without affecting the conformal invariance of the action if one adds a term to the Hamiltonian proportional to the dilatation operator or the special conformal operator. If one applies the procedure of de Alfaro et al. to the frame-independent light-front Hamiltonian, it leads uniquely to a confining q \\bar{q} potential κ ^4 ζ ^2, where ζ ^2 is the light-front radial variable related in momentum space to the q \\bar{q} invariant mass. The same result, including spin terms, is obtained using light-front holography—the duality between the front form and AdS_5, the space of isometries of the conformal group—if one modifies the action of AdS_5 by the dilaton e^{κ ^2 z^2} in the fifth dimension z. When one generalizes this procedure using superconformal algebra, the resulting light-front eigensolutions lead to a a unified Regge spectroscopy of meson, baryon, and tetraquarks, including supersymmetric relations between their masses and their wavefunctions. One also predicts hadronic light-front wavefunctions and observables such as structure functions, transverse momentum distributions, and the distribution amplitudes. The mass scale κ underlying confinement and hadron masses can be connected to the parameter Λ_{\\overline{MS}} in the QCD running coupling by matching the nonperturbative dynamics to the perturbative QCD regime. The result is an effective coupling α _s(Q^2) defined at all momenta. The matching of the high and low momentum transfer regimes determines a scale Q_0 which sets the interface between perturbative and nonperturbative hadron dynamics. I also discuss a number of applications of light-front phenomenology.

Estimated effects of projected ground-water withdrawals on movement of the saltwater front in the Floridan aquifer, 1976-2000, west-central Florida

USGS Publications Warehouse

Wilson, William Edward

1982-01-01

Maps of observed 1976 and simulated 2000 potentiometric surfaces were used to estimate rates of saltwater encroachment and theoretical predevelopment equilibrium positions of the saltwater-freshwater interface in west-central Florida. The observed saltwater front, defined by the 19,000 milligrams-per-liter line of equal chloride concentration in the lower part of the Floridan aquifer, corresponds closely to a theoretical predevelopment equilibrium position of a saltwater-freshwater interface. The interface position was computed by the Ghyben-Herzberg method, using heads from a map of the predevelopment potentiometric surface. In maps of both the observed May 1976 and simulated May 2000 potentiometric surface, the saltwater front was within a large seasonal cone of depression in parts of Hillsborough, Manatee, and Sarasota Counties. Average landward flow rate of the front was computed to be 0.30 foot per day in May 1976 and 0.36 foot per day in May 2000. Seaward potentiometric-surface gradient under simulated October 2000 conditions averaged 8.8 x 10-5 foot per foot less than under observed September 1976 conditions. Regional observation wells are desirable for monitoring potentiometric-level changes in western Hardee County and eastern Manatee County and for monitoring water-quality changes along the saltwater front, on its landward side, from mid-Sarasota County northward to Hillsborough County. Net landward movement of the saltwater front in the lower part of the Floridan aquifer is probably occurring under existing conditions. Pumping during 1976-2000 would probably increase slightly the rate of movement. However, rates are so slow that on a regional basis saltwater encroachment under existing and projected conditions is not presently a threat to the existing freshwater resources. The maximum projected regional landward movement, under 'worst case' conditions, of the saltwater front between 1976 and 2000 is estimated to be about one-half mile. Significant local

Chemical consequences of compaction within the freezing front of a crystallizing magma ocean

NASA Astrophysics Data System (ADS)

Hier-Majumder, S.; Hirschmann, M. M.

2013-12-01

The thermal and compositional evolution of planetary magma oceans have profound influences on the early development and differentiation of terrestrial planets. During crystallization, rejection of elements incompatible in precipitating solids leads to petrologic and geochemical planetary differentiation, including potentially development of a compositionally stratified early mantle and evolution of thick overlying atmospheres. In cases of extremely efficient segregation of melt and crystals, solidified early mantles can be nearly devoid of key incompatible species including heat-producing (U, Th, K) and volatile (H,C,N,& noble gas) elements. A key structural component of a crystallizing magma ocean is the partially molten freezing front. The dynamics of this region influences the distribution of incompatible elements between the earliest mantle and the initial surficial reservoirs. It also can be the locus of heating owing to the dissipation of large amounts of tidal energy potentially available from the early Moon. The dynamics are influenced by the solidification rate, which is coupled to the liberation of volatiles owing to the modulating greenhouse effects in the overlying thick atmosphere. Compaction and melt retention in the freezing front of a magma ocean has received little previous attention. While the front advances during the course of crystallization, coupled conservation of mass, momentum, and energy within the front controls distribution and retention of melt within this layer. Due to compaction within this layer, melt distribution is far from uniform, and the fraction of melt trapped within this front depends on the rate of freezing of the magma ocean. During phases of rapid freezing, high amount of trapped melt within the freezing front retains a larger quantity of dissolved volatiles and the reverse is true during slow periods of crystallization. Similar effects are known from inferred trapped liquid fractions in layered mafic intrusions. Here we

End Joining-Mediated Gene Expression in Mammalian Cells Using PCR-Amplified DNA Constructs that Contain Terminator in Front of Promoter.

PubMed

Nakamura, Mikiko; Suzuki, Ayako; Akada, Junko; Tomiyoshi, Keisuke; Hoshida, Hisashi; Akada, Rinji

2015-12-01

Mammalian gene expression constructs are generally prepared in a plasmid vector, in which a promoter and terminator are located upstream and downstream of a protein-coding sequence, respectively. In this study, we found that front terminator constructs-DNA constructs containing a terminator upstream of a promoter rather than downstream of a coding region-could sufficiently express proteins as a result of end joining of the introduced DNA fragment. By taking advantage of front terminator constructs, FLAG substitutions, and deletions were generated using mutagenesis primers to identify amino acids specifically recognized by commercial FLAG antibodies. A minimal epitope sequence for polyclonal FLAG antibody recognition was also identified. In addition, we analyzed the sequence of a C-terminal Ser-Lys-Leu peroxisome localization signal, and identified the key residues necessary for peroxisome targeting. Moreover, front terminator constructs of hepatitis B surface antigen were used for deletion analysis, leading to the identification of regions required for the particle formation. Collectively, these results indicate that front terminator constructs allow for easy manipulations of C-terminal protein-coding sequences, and suggest that direct gene expression with PCR-amplified DNA is useful for high-throughput protein analysis in mammalian cells.

40 CFR 81.345 - Utah.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Wasatch Mountain Range (and this includes the Cities of Provo and Orem) with an eastern boundary for Utah.../Attainment Nonattainment. The area of Weber County that lies west of the Wasatch Mountain Range with an... of the Wasatch Mountain Range (and this includes the Cities of Provo and Orem) with an eastern...

Quantifying atmospheric nitrogen outflow from the Front Range of Colorado

NASA Astrophysics Data System (ADS)

Neuman, J. A.; Eilerman, S. J.; Brock, C. A.; Brown, S. S.; Dube, W. P.; Herndon, S. C.; Holloway, J. S.; Nowak, J. B.; Roscioli, J. R.; Ryerson, T. B.; Sjostedt, S. J.; Thompson, C. R.; Trainer, M.; Veres, P. R.; Wild, R. J.

2015-12-01

Reactive nitrogen emitted to the atmosphere from urban, industrial, and agricultural sources can be transported and deposited far from the source regions, affecting vegetation, soils, and water of sensitive ecosystems. Mitigation of atmospheric nitrogen deposition requires emissions characterization and quantification. Ammonia (NH3), a full suite of gas-phase oxidized nitrogen compounds, and particulate matter were measured from an aircraft that flew downwind from concentrated animal feeding operations, oil and gas extraction facilities, and urban areas along the Colorado Front Range in March and April 2015, as part of the Shale Oil and Natural Gas Nexus (SONGNEX) field study. Additionally, NH3 measurements from a fully instrumented aircraft that flew over the same region in July and August 2014 as part of the Front Range Air Pollution and Photochemistry Experiment (FRAPPE) are used to examine atmospheric nitrogen emission and transport. Cross-wind plume transects and altitude profiles were performed over the source regions and 60-240 km downwind. Plumes were transported in the boundary layer with large NH3 mixing ratios (typically 20-100 ppbv) and were tens of km wide. The NH3 in these plumes provided an atmospheric nitrogen burden greater than 0.2 kg N/ha. Nitrogen oxides and their oxidation products and particulate matter were also enhanced in the plumes, but with concentrations substantially less than NH3. With efficient transport followed by wet deposition, these plumes have the potential to provide a large nitrogen input to the neighboring Rocky Mountain National Park, where nitrogen deposition currently exceeds the ecological critical load of 1.5 kg N/ha/yr.

Analysis of nucleon electromagnetic form factors from light-front holographic QCD: The spacelike region

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sufian, Raza Sabbir; de Teramond, Guy F.; Brodsky, Stanley J.

We present a comprehensive analysis of the space-like nucleon electromagnetic form factors and their flavor decomposition within the framework of light-front holographic QCD. We show that the inclusion of the higher Fock componentsmore » $$|{qqqq\\bar{q}}$$ has a significant effect on the spin-flip elastic Pauli form factor and almost zero effect on the spin-conserving Dirac form factor. We present light-front holographic QCD results for the proton and neutron form factors at any momentum transfer range, including asymptotic predictions, and show that our results agree with the available experimental data with high accuracy. In order to correctly describe the Pauli form factor we need an admixture of a five quark state of about 30$$\\%$$ in the proton and about 40$$\\%$$ in the neutron. We also extract the nucleon charge and magnetic radii and perform a flavor decomposition of the nucleon electromagnetic form factors. The free parameters needed to describe the experimental nucleon form factors are very few: two parameters for the probabilities of higher Fock states for the spin-flip form factor and a phenomenological parameter $r$, required to account for possible SU(6) spin-flavor symmetry breaking effects in the neutron, whereas the Pauli form factors are normalized to the experimental values of the anomalous magnetic moments. As a result, the covariant spin structure for the Dirac and Pauli nucleon form factors prescribed by AdS$$_5$$ semiclassical gravity incorporates the correct twist scaling behavior from hard scattering and also leads to vector dominance at low energy.« less

Analysis of nucleon electromagnetic form factors from light-front holographic QCD: The spacelike region

DOE PAGES

Sufian, Raza Sabbir; de Teramond, Guy F.; Brodsky, Stanley J.; ...

2017-01-10

We present a comprehensive analysis of the space-like nucleon electromagnetic form factors and their flavor decomposition within the framework of light-front holographic QCD. We show that the inclusion of the higher Fock componentsmore » $$|{qqqq\\bar{q}}$$ has a significant effect on the spin-flip elastic Pauli form factor and almost zero effect on the spin-conserving Dirac form factor. We present light-front holographic QCD results for the proton and neutron form factors at any momentum transfer range, including asymptotic predictions, and show that our results agree with the available experimental data with high accuracy. In order to correctly describe the Pauli form factor we need an admixture of a five quark state of about 30$$\\%$$ in the proton and about 40$$\\%$$ in the neutron. We also extract the nucleon charge and magnetic radii and perform a flavor decomposition of the nucleon electromagnetic form factors. The free parameters needed to describe the experimental nucleon form factors are very few: two parameters for the probabilities of higher Fock states for the spin-flip form factor and a phenomenological parameter $r$, required to account for possible SU(6) spin-flavor symmetry breaking effects in the neutron, whereas the Pauli form factors are normalized to the experimental values of the anomalous magnetic moments. As a result, the covariant spin structure for the Dirac and Pauli nucleon form factors prescribed by AdS$$_5$$ semiclassical gravity incorporates the correct twist scaling behavior from hard scattering and also leads to vector dominance at low energy.« less

Deuteron electromagnetic form factors with the light-front approach

NASA Astrophysics Data System (ADS)

Sun, Bao-dong; Dong, Yu-bing

2017-01-01

The electromagnetic form factors and low-energy observables of the deuteron are studied with the help of the light-front approach, where the deuteron is regarded as a weakly bound state of a proton and a neutron. Both the S and D wave interacting vertexes among the deuteron, proton, and neutron are taken into account. Moreover, the regularization functions are also introduced. In our calculations, the vertex and the regularization functions are employed to simulate the momentum distribution inside the deuteron. Our numerical results show that the light-front approach can roughly reproduce the deuteron electromagnetic form factors, like charge G 0, magnetic G 1, and quadrupole G 2, in the low Q 2 region. The important effect of the D wave vertex on G 2 is also addressed. Supported by National Natural Science Foundation of China (10975146, 11475192), The fund provided by the Sino-German CRC 110 “Symmetries and the Emergence of Structure in QCD" project is also appreciated, YBD thanks FAPESP grant 2011/11973-4 for funding his visit to ICTP-SAIFR

Lag-driven motion in front propagation

NASA Astrophysics Data System (ADS)

Amor, Daniel R.; Fort, Joaquim

2013-10-01

Front propagation is a ubiquitous phenomenon. It arises in physical, biological and cross-disciplinary systems as diverse as flame propagation, superconductors, virus infections, cancer spread or transitions in human prehistory. Here we derive a single, approximate front speed from three rather different time-delayed reaction-diffusion models, suggesting a general law. According to our approximate speed, fronts are crucially driven by the lag times (periods during which individuals or particles do not move). Rather surprisingly, the approximate speed is able to explain the observed spread rates of completely different biophysical systems such as virus infections, the Neolithic transition in Europe, and postglacial tree recolonizations.

Hindrances to bistable front propagation: application to Wolbachia invasion.

PubMed

Nadin, Grégoire; Strugarek, Martin; Vauchelet, Nicolas

2018-05-01

We study the biological situation when an invading population propagates and replaces an existing population with different characteristics. For instance, this may occur in the presence of a vertically transmitted infection causing a cytoplasmic effect similar to the Allee effect (e.g. Wolbachia in Aedes mosquitoes): the invading dynamics we model is bistable. We aim at quantifying the propagules (what does it take for an invasion to start?) and the invasive power (how far can an invading front go, and what can stop it?). We rigorously show that a heterogeneous environment inducing a strong enough population gradient can stop an invading front, which will converge in this case to a stable front. We characterize the critical population jump, and also prove the existence of unstable fronts above the stable (blocking) fronts. Being above the maximal unstable front enables an invading front to clear the obstacle and propagate further. We are particularly interested in the case of artificial Wolbachia infection, used as a tool to fight arboviruses.

Development of regional earthquake early warning and structural health monitoring system and real-time ground motion forecasting using front-site waveform data (Invited)

NASA Astrophysics Data System (ADS)

Motosaka, M.

2009-12-01

This paper presents firstly, the development of an integrated regional earthquake early warning (EEW) system having on-line structural health monitoring (SHM) function, in Miyagi prefecture, Japan. The system makes it possible to provide more accurate, reliable and immediate earthquake information for society by combining the national (JMA/NIED) EEW system, based on advanced real-time communication technology. The author has planned to install the EEW/SHM system to the public buildings around Sendai, a million city of north-eastern Japan. The system has been so far implemented in two buildings; one is in Sendai, and the other in Oshika, a front site on the Pacific Ocean coast for the approaching Miyagi-ken Oki earthquake. The data from the front-site and the on-site are processed by the analysis system which was installed at the analysis center of Disaster Control Research Center, Tohoku University. The real-time earthquake information from JMA is also received at the analysis center. The utilization of the integrated EEW/SHM system is addressed together with future perspectives. Examples of the obtained data are also described including the amplitude depending dynamic characteristics of the building in Sendai before, during, and after the 2008/6/14 Iwate-Miyagi Nairiku Earthquake, together with the historical change of dynamic characteristics for 40 years. Secondary, this paper presents an advanced methodology based on Artificial Neural Networks (ANN) for forward forecasting of ground motion parameters, not only PGA, PGV, but also Spectral information before S-wave arrival using initial part of P-waveform at a front site. The estimated ground motion information can be used as warning alarm for earthquake damage reduction. The Fourier Amplitude Spectra (FAS) estimated before strong shaking with high accuracy can be used for advanced engineering applications, e.g. feed-forward structural control of a building of interest. The validity and applicability of the method

Cloud Front

NASA Technical Reports Server (NTRS)

2006-01-01

[figure removed for brevity, see original site] Context image for PIA02171 Cloud Front

These clouds formed in the south polar region. The faintness of the cloud system likely indicates that these are mainly ice clouds, with relatively little dust content.

Image information: VIS instrument. Latitude -86.7N, Longitude 212.3E. 17 meter/pixel resolution.

Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

AIRS Storm Front Approaching California (animation)

NASA Technical Reports Server (NTRS)

2005-01-01

[figure removed for brevity, see original site] Click on the image for the AIRS Storm Front Approaching California Animation

NASA's Atmospheric Infrared Sounder instrument is able to peel back cloud cover to reveal 3-D structure of a storm's water vapor content, information that can be used to improve weather forecast models.

In this animation the initial visible cloud image series shows a front moving toward the West Coast of the United States as a low pressure area moves into the Pacific Northwest. The 'Pineapple Express,' a stream of moisture that originates in the tropics South of Hawaii and usually crosses Mexico to enter New Mexico and Texas, has shifted Westward and is also visible moving into Baja California. The area preceding the front appears to be relatively clear in the visible images.

As the view shifts from the visible to the infrared wavelengths which highlight water vapor, we see both cloud areas contain heavy burdens of moisture. The area which appears clear in the visible images is seen to contain water vapor near the coastline as well. The viewpoint then rotates so that we can see the vertical cross section of the fronts. The variability of the vertical extent of water vapor and the amount is now clearly visible. The storm moving in from the Gulf of Alaska is more heavily laden with water vapor than that moving in from the Southwest. The moisture is concentrated in the lower atmosphere. The colors indicate the amount of water vapor present. Blue areas denote low water vapor content; green areas are medium water vapor content; red areas signify high water vapor content. The vertical grid for the final frame ranges from 250 millibar pressure at the top to 1000 millibar pressure at the bottom. The top is about 10 km (6.2 miles) above the surface of the Earth.

The Atmospheric Infrared Sounder Experiment, with its visible, infrared, and microwave detectors, provides a three-dimensional look at Earth's weather. Working in

SLOW PATCHY EXTREME-ULTRAVIOLET PROPAGATING FRONTS ASSOCIATED WITH FAST CORONAL MAGNETO-ACOUSTIC WAVES IN SOLAR ERUPTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Y.; Ding, M. D.; Chen, P. F., E-mail: guoyang@nju.edu.cn

2015-08-15

Using the high spatiotemporal resolution extreme ultraviolet (EUV) observations of the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, we conduct a statistical study of the observational properties of the coronal EUV propagating fronts. We find that it might be a universal phenomenon for two types of fronts to coexist in a large solar eruptive event. It is consistent with the hybrid model of EUV propagating fronts, which predicts that coronal EUV propagating fronts consist of both a fast magneto-acoustic wave and a nonwave component. We find that the morphologies, propagation behaviors, and kinematic features of the two EUVmore » propagating fronts are completely different from each other. The fast magneto-acoustic wave fronts are almost isotropic. They travel continuously from the flaring region across multiple magnetic polarities to global distances. On the other hand, the slow nonwave fronts appear as anisotropic and sequential patches of EUV brightening. Each patch propagates locally in the magnetic domains where the magnetic field lines connect to the bottom boundary and stops at the magnetic domain boundaries. Within each magnetic domain, the velocities of the slow patchy nonwave component are an order of magnitude lower than that of the fast-wave component. However, the patches of the slow EUV propagating front can jump from one magnetic domain to a remote one. The velocities of such a transit between different magnetic domains are about one-third to one-half of those of the fast-wave component. The results show that the velocities of the nonwave component, both within one magnetic domain and between different magnetic domains, are highly nonuniform due to the inhomogeneity of the magnetic field in the lower atmosphere.« less

Transition fronts of time periodic bistable reaction-diffusion equations in RN

NASA Astrophysics Data System (ADS)

Sheng, Wei-Jie; Guo, Hong-Jun

2018-09-01

This paper is concerned with the existence and qualitative properties of transition fronts for time periodic bistable reaction-diffusion equations in RN. We first show that any almost-planar transition front is actually planar, regardless of the number of transition layers. Then we prove that all transition fronts admit a global mean speed γ and it holds γ = | c |, where c is the speed of the planar traveling front. Finally we establish the existence of a transition front in RN that is not a standard traveling front. Such a front behaves like three moving time periodic planar fronts as time goes to -∞ and like a time periodic V-shaped traveling front as time goes to ∞.

Revealing the timing of ocean stratification using remotely-sensed ocean fronts: links with marine predators

NASA Astrophysics Data System (ADS)

Miller, P. I.; Loveday, B. R.

2016-02-01

Stratification is of critical importance to the mixing and productivity of the ocean, though currently it can only be measured using in situ sampling, profiling buoys or underwater autonomous vehicles. Stratification is understood to affect the surface aggregation of pelagic fish and hence the foraging behaviour and distribution of their predators such as seabirds and cetaceans. Satellite Earth observation sensors cannot directly detect stratification, but can observe surface features related to the presence of stratification, for example shelf-sea fronts that separate tidally-mixed water from seasonally stratified water. This presentation describes a novel algorithm that accumulates evidence for stratification from a sequence of oceanic front maps, and in certain regions can reveal the timing of the seasonal onset and breakdown of stratification. Initial comparisons will be made with seabird locations acquired through GPS tagging. If successful, a remotely-sensed stratification timing index would augment the ocean front metrics already developed at PML, that have been applied in over 20 journal articles relating marine predators to ocean fronts. The figure below shows a preliminary remotely-sensed 'stratification' index, for 25-31 Jul. 2010, where red indicates water with stronger evidence for stratification.

Boundary-layer effects on cold fronts at a coastline

NASA Astrophysics Data System (ADS)

Garratt, J. R.

1986-07-01

The present note discusses one physical mechanism which may contribute to cold air channelling, manifest as a frontal bulge on a surface-analysis chart, in the coastal region of Victoria in southeast Australia. This involves the modification of boundary-layer air in both offshore (prefrontal) and onshore (postfrontal) flow, and the effect on cross-frontal thermal contrast. The problem is discussed in terms of a north-south-oriented cold front behaving as an atmospheric gravity current, propagating along an east-west-oriented coastline, in the presence of a prefrontal offshore stream.

Fine-scale planktonic habitat partitioning at a shelf-slope front revealed by a high-resolution imaging system

NASA Astrophysics Data System (ADS)

Greer, Adam T.; Cowen, Robert K.; Guigand, Cedric M.; Hare, Jonathan A.

2015-02-01

Ocean fronts represent productive regions of the ocean, but predator-prey interactions within these features are poorly understood partially due to the coarse-scale and biases of net-based sampling methods. We used the In Situ Ichthyoplankton Imaging System (ISIIS) to sample across a front near the Georges Bank shelf edge on two separate sampling days in August 2010. Salinity characterized the transition from shelf to slope water, with isopycnals sloping vertically, seaward, and shoaling at the thermocline. A frontal feature defined by the convergence of isopycnals and a surface temperature gradient was sampled inshore of the shallowest zone of the shelf-slope front. Zooplankton and larval fishes were abundant on the shelf side of the front and displayed taxon-dependent depth distributions but were rare in the slope waters. Supervised automated particle counting showed small particles with high solidity, verified to be zooplankton (copepods and appendicularians), aggregating near surface above the front. Salps were most abundant in zones of intermediate chlorophyll-a fluorescence, distinctly separate from high abundances of other grazers and found almost exclusively in colonial form (97.5%). Distributions of gelatinous zooplankton differed among taxa but tended to follow isopycnals. Fine-scale sampling revealed distinct habitat partitioning of various planktonic taxa, resulting from a balance of physical and biological drivers in relation to the front.

Combined effects of inversion and feature removal on N170 responses elicited by faces and car fronts

PubMed Central

Kloth, Nadine; Itier, Roxane J.; Schweinberger, Stefan R.

2014-01-01

The face-sensitive N170 is typically enhanced for inverted compared to upright faces. Itier, Alain, Sedore, and McIntosh (2007) recently suggested that this N170 inversion effect is mainly driven by the eye region which becomes salient when the face configuration is disrupted. Here we tested whether similar effects could be observed with non-face objects that are structurally similar to faces in terms of possessing a homogeneous within-class first-order feature configuration. We presented upright and inverted pictures of intact car fronts, car fronts without lights, and isolated lights, in addition to analogous face conditions. Upright cars elicited substantial N170 responses of similar amplitude to those evoked by upright faces. In strong contrast to face conditions however, the car-elicited N170 was mainly driven by the global shape rather than the presence or absence of lights, and was dramatically reduced for isolated lights. Overall, our data confirm a differential influence of the eye region in upright and inverted faces. Results for car fronts do not suggest similar interactive encoding of eye-like features and configuration for non-face objects, even when these objects possess a similar feature configuration as faces. PMID:23485023

End-Users, Front Ends and Librarians.

ERIC Educational Resources Information Center

Bourne, Donna E.

1989-01-01

The increase in end-user searching, the advantages and limitations of front ends, and the role of the librarian in end-user searching are discussed. It is argued that librarians need to recognize that front ends can be of benefit to themselves and patrons, and to assume the role of advisors and educators for end-users. (37 references) (CLB)

Smoldering wave-front velocity in fiberboard

Treesearch

John J. Brenden; Erwin L. Schaffer

1980-01-01

In fiberboard, the phenomena of smoldering can be visualized as decomposition resulting from the motion of a thermal wave-front through the material. The tendency to smolder is then directly proportional to the velocity of the front. Velocity measurements were made on four fiberboards and were compared to values given in the literature for several substances....

Storms or cold fronts? What is really responsible for the extreme waves regime in the Colombian Caribbean coast

NASA Astrophysics Data System (ADS)

Otero, L. J.; Ortiz-Royero, J. C.; Ruiz-Merchan, J. K.; Higgins, A. E.; Henriquez, S. A.

2015-05-01

On Friday, 7 March 2009, a 200 m-long section of the tourist pier in Puerto Colombia collapsed under the impact of the waves generated by a cold front in the area. The aim of this study is to determine the contribution and importance of cold fronts and storms on extreme waves in different areas of the Colombian Caribbean to determine the degree of the threat posed by the flood processes to which these coastal populations are exposed and the actions to which coastal engineering constructions should be subject. In the calculation of maritime constructions, the most important parameter is the wave's height; therefore, it is necessary to definitively know the design wave height to which a coastal engineering structure should be resistant. This wave height varies according to the return period considered. Using Gumbel's extreme value methodology, the significant height values for the study area were calculated. The methodology was evaluated using data from the re-analysis of the spectral NOAA Wavewatch III (WW3) model for 15 points along the 1600 km of the Colombia Caribbean coast (continental and insular) of the last 15 years. The results demonstrated that the extreme waves caused by tropical cyclones and cold fronts have different effects along the Colombian Caribbean coast. Storms and hurricanes are of greater importance in the Guajira Peninsula (Alta Guajira). In the central area formed by Baja Guajira, Santa Marta, Barranquilla, and Cartagena, the strong influence of cold fronts on extreme waves is evident. On the other hand, in the southern region of the Colombian Caribbean coast, from the Gulf of Morrosquillo to the Gulf of Urabá, even though extreme waves are lower than in the previous regions, extreme waves are dominated mainly by the passage of cold fronts. Extreme waves in the San Andrés and Providencia insular region present a different dynamic from that in the continental area due to its geographic location. The wave heights in the extreme regime are

Time-delayed reaction-diffusion fronts

NASA Astrophysics Data System (ADS)

Isern, Neus; Fort, Joaquim

2009-11-01

A time-delayed second-order approximation for the front speed in reaction-dispersion systems was obtained by Fort and Méndez [Phys. Rev. Lett. 82, 867 (1999)]. Here we show that taking proper care of the effect of the time delay on the reactive process yields a different evolution equation and, therefore, an alternate equation for the front speed. We apply the new equation to the Neolithic transition. For this application the new equation yields speeds about 10% slower than the previous one.

Fronts and Thermohaline Structure of the Brazil Current Confluence System

NASA Astrophysics Data System (ADS)

Severov, Dimitri

and Thermohaline Structure of the Brazil Current Confluence System (BCCS) are stud-ied from climatic data, "Marathon Exp. Leg.8, 1984"data, and two Sea surface temperature (SST) data bases: "Meteor satellite"(1989-1994) and "ds277-Reynolds" (1981-2000).The South Atlantic Central Water (SACW) is divided in two main types: tropical (TW) and subtropical water (ST). Water masses, fronts, inter-frontal and frontal zones are analysed and classified: a) the water masses: Tropical Low-Salinity Water, Tropical Surface Water, Tropical Tropospheric Water, Subtropical Low-Salinity Water, Subtropical Surface Water, Subtropical Tropospheric Water. T,S characteristics of intermediate, deep and bottom water defined by different authors are confirmed and completed; b) the Inter-frontal Zones: Tropical/Brazil Current Zone, Sub-tropical Zone and Subantarctic Zone; c) the Frontal Zones: Subtropical, Subantarctic and Polar, and d) the Fronts: Subtropical Front of the Brazil Current, Principal Subtropical Front, North Subtropical Front, Subtropical Surface Front, South Subtropical Front, Subantarctic Surface Front, Subantarctic Front and Polar Front. Several stable T-S relationships are found below the friction layer and at the Fronts. The maximum gradient of the oceanographic characteris-tics occurs at the Brazil Current Front, which can be any of the subtropical fronts, depending on season. Minimum mean depth of the pycnocline coincides with the fronts of the BCCS, indicating the paths of low-salinity shelf waters into the open ocean. D. N. Severov (a) , V. Pshennikov (b) and A.V. Remeslo (c) a -Sección Oceanologé Facultad de Ciencia, Universidad de la Republica, Igué 4225, 11400 ıa, a Montevideo, Uruguay. Tel. (598-2) 525-8618, Fax (598-2) 525-8617, mail: dima@fcien.edu.uy b -Instituto de Física, Facultad de Ciencias, Universidad de la Republica, Igué 4225, 11400 Mon-a tevideo, Uruguay, mail: seva@fisica.edu.uy c -Atlantic Research Inst. For Fisheries Oceanology (Atlant

Wideband monolithically integrated front-end subsystems and components

NASA Astrophysics Data System (ADS)

Mruk, Joseph Rene

This thesis presents the analysis, design, and measurements of passive, monolithically integrated, wideband recta-coax and printed circuit board front-end components. Monolithic fabrication of antennas, impedance transformers, filters, and transitions lowers manufacturing costs by reducing assembly time and enhances performance by removing connectors and cabling between the devices. Computational design, fabrication, and measurements are used to demonstrate the capabilities of these front-end assemblies. Two-arm wideband planar log-periodic antennas fed using a horizontal feed that allows for filters and impedance transformers to be readily fabricated within the radiating region of the antenna are demonstrated. At microwave frequencies, low-cost printed circuit board processes are typically used to produce planar devices. A 1.8 to 11 GHz two-arm planar log-periodic antenna is designed with a monolithically integrated impedance transformer. Band rejection methods based on modifying the antenna aperture, use of an integrated filter, and the application of both methods are investigated with realized gain suppressions of over 25 dB achieved. The ability of standard circuit board technology to fabricate millimeter-wave devices up to 110 GHz is severely limited. Thin dielectrics are required to prevent the excitation of higher order modes in the microstrip substrate. Fabricating the thin line widths required for the antenna aperture also becomes prohibitively challenging. Surface micro-machining typically used in the fabrication of MEMS devices is capable of producing the extremely small features that can be used to fabricate antennas extending through W-band. A directly RF fed 18 to 110 GHz planar log-periodic antenna is developed. The antenna is fabricated with an integrated impedance transformer and additional transitions for measurement characterization. Singly terminated low-loss wideband millimeter-wave filters operating over V- and W- band are developed. High

Ion Transport and Acceleration at Dipolarization Fronts: High-Resolution MHD/Test-Particle Simulations

NASA Astrophysics Data System (ADS)

Ukhorskiy, A. Y.; Sorathia, K.; Merkin, V. G.; Sitnov, M. I.; Mitchell, D. G.; Wiltberger, M. J.; Lyon, J.

2017-12-01

Much of plasma heating and transport from the magnetotail into the inner magnetosphere occurs in the form of mesoscale discrete injections associated with sharp dipolarizations of magnetic field (dipolarization fronts). In this study we investigate the mechanisms of ion acceleration at dipolarization fronts in a high-resolution global magnetospheric MHD model (LFM). We use large-scale three-dimensional test-particle simulations (CHIMP) to address the following science questions: 1) what are the characteristic scales of dipolarization regions that can stably trap ions? 2) what role does the trapping play in ion transport and acceleration? 3) how does it depend on particle energy and distance from Earth? 4) to what extent ion acceleration is adiabatic? High-resolution LFM was run using idealized solar wind conditions with fixed nominal values of density and velocity and a southward IMF component of -5 nT. To simulate ion interaction with dipolarization fronts, a large ensemble of test particles distributed in energy, pitch-angle, and gyrophase was initialized inside one of the LFM dipolarization channels in the magnetotail. Full Lorentz ion trajectories were then computed over the course of the front inward propagation from the distance of 17 to 6 Earth radii. A large fraction of ions with different initial energies stayed in phase with the front over the entire distance. The effect of magnetic trapping at different energies was elucidated with a correlation of the ion guiding center and the ExB drift velocities. The role of trapping in ion energization was quantified by comparing the partial pressure of ions that exhibit trapping to the pressure of all trapped ions.

Distribution of whitemouth croaker ( Micropogonias furnieri, Desmarest 1823) larvae in the Río de la Plata estuarine front

NASA Astrophysics Data System (ADS)

Braverman, Mara S.; Acha, E. Marcelo; Gagliardini, Domingo A.; Rivarossa, Martín

2009-05-01

Whitemouth croaker ( Micropogonias furnieri) larvae obtained and hydrographic data collected in the Rio de la Plata estuary (35°S-56°W) between 1987 and 2000 were used to explore the early life stages spatial and temporal distribution patterns and their relation to oceanographic features. The spatial distribution, restricted to a band in the inner part of the estuary, coincided with the bottom salinity front and the maximum turbidity zone (MTZ, turbidity front). Larvae were present during the warmest months (October through May) within a range of 14-24.5 °C temperature and 0.9-33 salinity. A vertically stratified sampling performed in the region where the largest abundance was found (December 2005 and March 2006) was used to test the hypothesis that larvae retention occurs in the bottom salinity front. The vertically stratified sampling showed larvae throughout the water column with high predominance in the river-estuary transition zone. A positive correlation between abundance and the bottom salinity horizontal gradient was found. The size analysis showed that the largest individuals (>10 mm SL), probably undergoing the settlement process, inhabited near the bottom and that the smallest (<10 mm SL) were present in the whole water column. Length distribution along the front showed no trend. Results support the estuarine retention hypothesis of previous studies on whitemouth croaker gravid females, eggs distribution and outcomes from a numerical simulation model. Retention in the salinity front/MTZ would allow larvae to benefit from food accumulation in the region, the high turbidity level provide shelter against predators and retention in the estuary secure closeness to the main nursery ground.

Supersymmetric Properties of Hadron Physics from Light-Front Holography and Superconformal Algebra and other Advances in Light-Front QCD

DOE PAGES

Brodsky, Stanley J.

2018-03-06

Here, light-front holography, together with superconformal algebra, have provided new insights into the physics of color confinement and the spectroscopy and dynamics of hadrons. As shown by de Alfaro, Fubini and Furlan, a mass scale can appear in the equations of motion without affecting the conformal invariance of the action if one adds a term to the Hamiltonian proportional to the dilatation operator or the special conformal operator. If one applies the procedure of de Alfaro et al. to the frame-independent light-front Hamiltonian, it leads uniquely to a confining qq¯ potential κ 4ζ 2, where ζ 2 is the light-frontmore » radial variable related in momentum space to the qq¯ invariant mass. The same result, including spin terms, is obtained using light-front holography—the duality between the front form and AdS 5, the space of isometries of the conformal group—if one modifies the action of AdS 5 by the dilaton e κ2 z2 in the fifth dimension z. When one generalizes this procedure using superconformal algebra, the resulting light-front eigensolutions lead to a a unified Regge spectroscopy of meson, baryon, and tetraquarks, including supersymmetric relations between their masses and their wavefunctions. One also predicts hadronic light-front wavefunctions and observables such as structure functions, transverse momentum distributions, and the distribution amplitudes. The mass scale κ underlying confinement and hadron masses can be connected to the parameter Λ MS¯ in the QCD running coupling by matching the nonperturbative dynamics to the perturbative QCD regime. The result is an effective coupling α s(Q 2) defined at all momenta. The matching of the high and low momentum transfer regimes determines a scale Q 0 which sets the interface between perturbative and nonperturbative hadron dynamics. I also discuss a number of applications of light-front phenomenology.« less

Supersymmetric Properties of Hadron Physics from Light-Front Holography and Superconformal Algebra and other Advances in Light-Front QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.

Here, light-front holography, together with superconformal algebra, have provided new insights into the physics of color confinement and the spectroscopy and dynamics of hadrons. As shown by de Alfaro, Fubini and Furlan, a mass scale can appear in the equations of motion without affecting the conformal invariance of the action if one adds a term to the Hamiltonian proportional to the dilatation operator or the special conformal operator. If one applies the procedure of de Alfaro et al. to the frame-independent light-front Hamiltonian, it leads uniquely to a confining qq¯ potential κ 4ζ 2, where ζ 2 is the light-frontmore » radial variable related in momentum space to the qq¯ invariant mass. The same result, including spin terms, is obtained using light-front holography—the duality between the front form and AdS 5, the space of isometries of the conformal group—if one modifies the action of AdS 5 by the dilaton e κ2 z2 in the fifth dimension z. When one generalizes this procedure using superconformal algebra, the resulting light-front eigensolutions lead to a a unified Regge spectroscopy of meson, baryon, and tetraquarks, including supersymmetric relations between their masses and their wavefunctions. One also predicts hadronic light-front wavefunctions and observables such as structure functions, transverse momentum distributions, and the distribution amplitudes. The mass scale κ underlying confinement and hadron masses can be connected to the parameter Λ MS¯ in the QCD running coupling by matching the nonperturbative dynamics to the perturbative QCD regime. The result is an effective coupling α s(Q 2) defined at all momenta. The matching of the high and low momentum transfer regimes determines a scale Q 0 which sets the interface between perturbative and nonperturbative hadron dynamics. I also discuss a number of applications of light-front phenomenology.« less

Improved Discretization of Grounding Lines and Calving Fronts using an Embedded-Boundary Approach in BISICLES

NASA Astrophysics Data System (ADS)

Martin, D. F.; Cornford, S. L.; Schwartz, P.; Bhalla, A.; Johansen, H.; Ng, E.

2017-12-01

Correctly representing grounding line and calving-front dynamics is of fundamental importance in modeling marine ice sheets, since the configuration of these interfaces exerts a controlling influence on the dynamics of the ice sheet. Traditional ice sheet models have struggled to correctly represent these regions without very high spatial resolution. We have developed a front-tracking discretization for grounding lines and calving fronts based on the Chombo embedded-boundary cut-cell framework. This promises better representation of these interfaces vs. a traditional stair-step discretization on Cartesian meshes like those currently used in the block-structured AMR BISICLES code. The dynamic adaptivity of the BISICLES model complements the subgrid-scale discretizations of this scheme, producing a robust approach for tracking the evolution of these interfaces. Also, the fundamental discontinuous nature of flow across grounding lines is respected by mathematically treating it as a material phase change. We present examples of this approach to demonstrate its effectiveness.

Cold fronts in the Colombian Caribbean Sea and their relationship to extreme wave events

NASA Astrophysics Data System (ADS)

Ortiz-Royero, J. C.; Otero, L. J.; Restrepo, J. C.; Ruiz, J.; Cadena, M.

2013-11-01

Extreme ocean waves in the Caribbean Sea are commonly related to the effects of storms and hurricanes during the months of June through November. The collapse of 200 m of the Puerto Colombia pier in March 2009 revealed the effects of meteorological phenomena other than storms and hurricanes that may be influencing the extreme wave regime in the Colombian Caribbean. The marked seasonality of these atmospheric fronts was established by analyzing the meteorological-marine reports of the Instituto de Hidrología, Meteorología y Estudios Ambientales of Colombia (IDEAM, based on its initials in Spanish) and the Centro de Investigación en Oceanografía y Meteorología of Colombia (CIOH, based on its initials in Spanish) during the last 16 yr. The highest number of cold fronts was observed during the months of January, February, and March, with 6 fronts occurring per year. An annual trend was observed and the highest number of fronts occurred in 2010 (20 in total); moreover, an annual strong relationship between the maximum average wave values and the cold fronts in the central zone of the Colombian Caribbean during the first three months of the year was established. In addition, the maximum values of the significant height produced by the passage of cold fronts during the last 16 yr were identified. Although the Colombian Caribbean has been affected by storms and hurricanes in the past, this research allows us to conclude that there is a strong relationship between cold fronts and the largest waves in the Colombian Caribbean during the last 16 yr, which have caused damage to coastal infrastructure. We verified that the passage of a cold front corresponded to the most significant extreme wave event of the last two decades in the Colombian Caribbean, which caused the structural collapse of the Puerto Colombia pier, located near the city of Barranquilla, between 5 and 10 March 2009. This information is invaluable when evaluating average and extreme wave regimes for the

Light-front Ward-Takahashi identity for two-fermion systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marinho, J. A. O.; Frederico, T.; Pace, E.

We propose a three-dimensional electromagnetic current operator within light-front dynamics that satisfies a light-front Ward-Takahashi identity for two-fermion systems. The light-front current operator is obtained by a quasipotential reduction of the four-dimensional current operator and acts on the light-front valence component of bound or scattering states. A relation between the light-front valence wave function and the four-dimensional Bethe-Salpeter amplitude both for bound or scattering states is also derived, such that the matrix elements of the four-dimensional current operator can be fully recovered from the corresponding light-front ones. The light-front current operator can be perturbatively calculated through a quasipotential expansion, andmore » the divergence of the proposed current satisfies a Ward-Takahashi identity at any given order of the expansion. In the quasipotential expansion the instantaneous terms of the fermion propagator are accounted for by the effective interaction and two-body currents. We exemplify our theoretical construction in the Yukawa model in the ladder approximation, investigating in detail the current operator at the lowest nontrivial order of the quasipotential expansion of the Bethe-Salpeter equation. The explicit realization of the light-front form of the Ward-Takahashi identity is verified. We also show the relevance of instantaneous terms and of the pair contribution to the two-body current and the Ward-Takahashi identity.« less

High expression of A-type lamin in the leading front is required for Drosophila thorax closure.

PubMed

Kosakamoto, Hina; Fujisawa, Yuya; Obata, Fumiaki; Miura, Masayuki

2018-05-05

Tissue closure involves the coordinated unidirectional movement of a group of cells without loss of cell-cell contact. However, the molecular mechanisms controlling the tissue closure are not fully understood. Here, we demonstrate that Lamin C, the sole A-type lamin in Drosophila, contributes to the process of thorax closure in pupa. High expression of Lamin C was observed at the leading front of the migrating wing imaginal discs. Live imaging analysis revealed that knockdown of Lamin C in the thorax region affected the coordinated movement of the leading front, resulting in incomplete tissue fusion required for formation of the adult thorax. The closure defect due to knockdown of Lamin C correlated with insufficient accumulation of F-actin at the front. Our study indicates a link between A-type lamin and the cell migration behavior during tissue closure. Copyright © 2018 Elsevier Inc. All rights reserved.

Fronts and frontogenesis as revealed by high time resolution data

NASA Technical Reports Server (NTRS)

Frank, A. E.; Barber, D. A.

1977-01-01

Upper air sounding are used to examine a cold front of average intensity. Vertical cross sections of potential temperature and wind, and horizontal analyses were compared and adjusted for consistency. These analyses were then used to study the evolution of the front, found to consist of a complex system of fronts occurring at all levels of the troposphere. Low level fronts were strongest at the surface and rapidly weakened with height. Fronts in the midddle troposphere were much more intense. The warm air ahead of the fronts was nearly barotropic, while the cold air behind was baroclinic through deep layers. A deep mixed layer was observed to grow in this cold air.

Revealing the timing of ocean stratification using remotely sensed ocean fronts

NASA Astrophysics Data System (ADS)

Miller, Peter I.; Loveday, Benjamin R.

2017-10-01

Stratification is of critical importance to the circulation, mixing and productivity of the ocean, and is expected to be modified by climate change. Stratification is also understood to affect the surface aggregation of pelagic fish and hence the foraging behaviour and distribution of their predators such as seabirds and cetaceans. Hence it would be prudent to monitor the stratification of the global ocean, though this is currently only possible using in situ sampling, profiling buoys or underwater autonomous vehicles. Earth observation (EO) sensors cannot directly detect stratification, but can observe surface features related to the presence of stratification, for example shelf-sea fronts that separate tidally-mixed water from seasonally stratified water. This paper describes a novel algorithm that accumulates evidence for stratification from a sequence of oceanic front maps, and discusses preliminary results in comparison with in situ data and simulations from 3D hydrodynamic models. In certain regions, this method can reveal the timing of the seasonal onset and breakdown of stratification.

Dynamic stabilization of Rayleigh-Taylor instability in an ablation front

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piriz, A. R.; Di Lucchio, L.; Rodriguez Prieto, G.

2011-01-15

Dynamic stabilization of Rayleigh-Taylor instability in an ablation front is studied by considering a modulation in the acceleration that consists of sequences of Dirac deltas. This allows obtaining explicit analytical expressions for the instability growth rate as well as for the boundaries of the stability region. As a general rule, it is found that it is possible to stabilize all wave numbers above a certain minimum value k{sub m}, but the requirements in the modulation amplitude and frequency become more exigent with smaller k{sub m}. The essential role of compressibility is phenomenologically addressed in order to find the constraint itmore » imposes on the stability region. The results for some different wave forms of the acceleration modulation are also presented.« less

The Majorana Low-noise Low-background Front-end Electronics

NASA Astrophysics Data System (ADS)

Abgrall, N.; Aguayo, E.; Avignone, F. T.; Barabash, A. S.; Bertrand, F. E.; Boswell, M.; Brudanin, V.; Busch, M.; Byram, D.; Caldwell, A. S.; Chan, Y.-D.; Christofferson, C. D.; Combs, D. C.; Cuesta, C.; Detwiler, J. A.; Doe, P. J.; Efremenko, Yu.; Egorov, V.; Ejiri, H.; Elliott, S. R.; Fast, J. E.; Finnerty, P.; Fraenkle, F. M.; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guiseppe, V. E.; Gusev, K.; Hallin, A. L.; Hazama, R.; Hegai, A.; Henning, R.; Hoppe, E. W.; Howard, S.; Howe, M. A.; Keeter, K. J.; Kidd, M. F.; Kochetov, O.; Konovalov, S. I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J.; Leviner, L. E.; Loach, J. C.; MacMullin, J.; MacMullin, S.; Martin, R. D.; Meijer, S.; Mertens, S.; Nomachi, M.; Orrell, J. L.; O'Shaughnessy, C.; Overman, N. R.; Phillips, D. G.; Poon, A. W. P.; Pushkin, K.; Radford, D. C.; Rager, J.; Rielage, K.; Robertson, R. G. H.; Romero-Romero, E.; Ronquest, M. C.; Schubert, A. G.; Shanks, B.; Shima, T.; Shirchenko, M.; Snavely, K. J.; Snyder, N.; Suriano, A. M.; Thompson, J.; Timkin, V.; Tornow, W.; Trimble, J. E.; Varner, R. L.; Vasilyev, S.; Vetter, K.; Vorren, K.; White, B. R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Young, A. R.; Yu, C.-H.; Yumatov, V.

The MAJORANA DEMONSTRATOR will search for the neutrinoless double beta decay (ββ(0ν)) of the isotope 76Ge with a mixed array of enriched and natural germanium detectors. In view of the next generation of tonne-scale germanium-based ββ(0ν)-decay searches, a major goal of the MAJORANA DEMONSTRATOR is to demonstrate a path forward to achieving a background rate at or below 1 cnt/(ROI-t-y) in the 4 keV region of interest (ROI) around the 2039-keV Q-value of the 76Ge ββ(0ν)-decay. Such a requirement on the background level significantly constrains the design of the readout electronics, which is further driven by noise and energy resolution performances. We present here the low-noise low- background front-end electronics developed for the low-capacitance p-type point contact (P-PC) germanium detectors of the MAJORANA DEMONSTRATOR. This resistive-feedback front-end, specifically designed to have low mass, is fabricated on a radioassayed fused-silica substrate where the feedback resistor consists of a sputtered thin film of high purity amorphous germanium and the feedback capacitor is based on the capacitance between gold conductive traces.

Observations of a tidal intrusion front in a tidal channel

NASA Astrophysics Data System (ADS)

Lu, Shasha; Xia, Xiaoming; Thompson, Charlie E. L.; Cao, Zhenyi; Liu, Yifei

2017-11-01

A visible front indicated by a surface colour change, and sometimes associated with foam or debris lines, was observed in a tidal channel during neap tide. This is an example of a tidal intrusion front occurring in the absence of sudden topographical changes or reversing flows, typically reported to be associated with such fronts. Detailed Acoustic Doppler Current Profiler and conductivity/temperature/depth measurements were taken on repeated transects both with fronts apparent and with fronts absent. The results indicated that the front occurred as a result of stratification, which was sustained by the buoyancy flux and the weak tide-induced mixing during neap ebb tide. The stronger tide-induced mixing during spring tide restrained stratification, leading to the absence of a front. The mechanism of the frontogenesis was the density gradient between the stratified water formed during neap ebb tide, and the more mixed seawater during neap flood tide; thus, the water on the landward (southwestern) side of the front was stratified, and that on the seaward side (northeastern) of the front was vertically well mixed. Gradient Richardson number estimates suggest that the flow between the stratified and mixed water was near the threshold 0.25 for shear instability. Meanwhile, the density gradient would provide an initial baroclinic contribution to velocity convergence, which is indicated by the accumulation of buoyant matter such as foam, grass, and debris into a sharply defined line along the surface. The front migrates with the flood current, with a local maximum towards the eastern side of the channel, leading to an asymmetrical shape with the eastern side of the front driven further into the Tiaozhoumen tidal channel.

Detection of the Tawahka reserve colonization front: Sub-pixel TM analysis using linear mixing models La Mosquitia, Honduras

DOE Office of Scientific and Technical Information (OSTI.GOV)

Portigal, F.P.; Harrill, R.W.

1996-08-01

Disregard for environmental issues, rising population and the ravages of war have left Honduras with an environmental catastrophe. Vast regions of southern Honduras have been denuded of vegetation causing rapid desertification. This has resulted in decreasing rainfall, falling agricultural yields and food shortages. Deforestation is accelerating in La Mosquitia, a vast region virtually without roads in the northeast extending into Nicaragua. This is the home of the indigenous Garifuna, Miskito, Pech and Tawahkan people and is the largest unbroken tropical forest in Central America. Increasing demand for resources, incursion by Ladino peasant settlers, poverty and the cattle industry are pushingmore » the colonization fronts deeper into La Mosquitia. Linear mixing models are used to identify subtle evidence of the forward fringes of the Tawahka Reserve colonization front.« less

Paleoseismology of the Nephi Segment of the Wasatch Fault Zone, Juab County, Utah - Preliminary Results From Two Large Exploratory Trenches at Willow Creek

USGS Publications Warehouse

Machette, Michael N.; Crone, Anthony J.; Personius, Stephen F.; Mahan, Shannon; Dart, Richard L.; Lidke, David J.; Olig, Susan S.

2007-01-01

In 2004, we identified a small parcel of U.S. Forest Service land at the mouth of Willow Creek (about 5 km west of Mona, Utah) that was suitable for trenching. At the Willow Creek site, which is near the middle of the southern strand of the Nephi segment, the WFZ has vertically displaced alluvial-fan deposits >6-7 m, forming large, steep, multiple-event scarps. In May 2005, we dug two 4- to 5-m-deep backhoe trenches at the Willow Creek site, identified three colluvial wedges in each trench, and collected samples of charcoal and A-horizon organic material for AMS (acceleration mass spectrometry) radiocarbon dating, and sampled fine-grained eolian and colluvial sediment for luminescence dating. The trenches yielded a stratigraphic assemblage composed of moderately coarse-grained fluvial and debris-flow deposits and discrete colluvial wedges associated with three faulting events (P1, P2, and P3). About one-half of the net vertical displacement is accommodated by monoclinal tilting of fan deposits on the hanging-wall block, possibly related to massive ductile landslide deposits that are present beneath the Willow Creek fan. The timing of the three surface-faulting events is bracketed by radiocarbon dates and results in a much different fault chronology and higher slip rates than previously considered for this segment of the Wasatch fault zone.

From the front

DOE Office of Scientific and Technical Information (OSTI.GOV)

Price, Stephen

The causes of recent dynamic thinning of Greenland's outlet glaciers have been debated. Realistic simulations suggest that changes at the marine fronts of these glaciers are to blame, implying that dynamic thinning will cease once the glaciers retreat to higher ground. For the last decade, many outlet glaciers in Greenland that terminate in the ocean have accelerated, thinned, and retreated. To explain these dynamic changes, two hypotheses have been discussed. Atmospheric warming has increased surface melting and may also have increased the amount of meltwater reaching the glacier bed, increasing lubrication at the base and hence the rate of glaciermore » sliding. Alternatively, a change in the delicate balance of forces where the glacier fronts meet the ocean could trigger the changes. Faezeh Nick and colleagues5 present ice-sheet modeling experiments that mimic the observations on Helheim glacier, East Greenland, and suggest that the dynamic behaviour of outlet glaciers follows from perturbations at their marine fronts. Greenland's ice sheet loses mass partly through surface melting and partly through fast flowing outlet glaciers that connect the vast plateau of inland ice with the ocean. Earlier ice sheet models have failed to reproduce the dynamic variability exhibited by ice sheets over time. It has therefore not been possible to distinguish with confidence between basal lubrication from surface meltwater and changes at the glaciers' marine fronts as causes for the observed changes on Greenland's outlet glaciers. But this distinction bears directly on future sea-level rise, the raison d'etre of much of modern-day glaciology: If the recent dynamic mass loss Greenland's outlet glaciers is linked to changing atmospheric temperatures, it may continue for as long as temperatures continue to increase. On the other hand, if the source of the dynamic mass loss is a perturbation at the ice-ocean boundary, these glaciers will lose contact with that perturbation after

Bathymetrically controlled velocity-shear front at a tidal river confluence

NASA Astrophysics Data System (ADS)

Blain, Cheryl Ann; Mied, Richard P.; McKay, Paul; Chen, Wei; Rhea, W. Joseph

2015-08-01

Nonbuoyant front formation at the confluence of Nanjemoy Creek and the main Potomac River (MD) channel is examined. Terra satellite ASTER imagery reveals a sediment color front emerging from Nanjemoy Creek when the Potomac is near maximum ebb. Nearly contemporaneous ASTER and Landsat ETM+ imagery are used to extract surface velocities, which suggest a velocity shear front is collocated with the color front. In situ velocities (measured by RiverRay traverses near the Nanjemoy Creek mouth) confirm the shear front's presence. A finite-element simulation (using ADCIRC) replicates the observed velocity-shear front and is applied to decipher its physics. Three results emerge: (1) the velocity-shear front forms, confined to a shoal downstream of the creek-river confluence for most of the tidal cycle, (2) a simulation with a flat bottom in Nanjemoy Creek and Potomac River (i.e., no bathymetry variation) indicates the velocity-shear front never forms, hence the front cannot exist without the bathymetry, and (3) an additional simulation with a blocked-off Creek entrance demonstrates that while the magnitude of the velocity shear is largely unchanged without the creek, shear front formation is delayed in time. Without the Creek, there is no advection of the M6 tidal constituent (generated by nonlinear interaction of the flow with bottom friction) onto the shoals, only a locally generated contribution. A tidal phase difference between Nanjemoy and Potomac causes the ebbing Nanjemoy Creek waters to intrude into the Potomac as far south as its deep channel, and draw from a similar location in the Potomac during Nanjemoy flood.

Changes in nutrient dynamics of midcontinent greater white-fronted geese during spring migration

USGS Publications Warehouse

Pearse, Aaron T.; Alisauskas, Ray T.; Krapu, Gary L.; Cox, Robert R.

2011-01-01

Waterfowl and other migratory birds commonly store nutrients at traditional staging areas during spring for later use during migration and reproduction. We investigated nutrient-storage dynamics in the midcontinent population of greater white-fronted geese (Anser albifrons; hereafter white-fronted geese) at spring staging sites in the Rainwater Basin of Nebraska during February-April and in southern Saskatchewan during April-May, 1998 and 1999. In Nebraska, lipid content of white-fronted geese did not increase, and protein content changed little over time for most age and sex categories. In Saskatchewan, lipids increased 11.4 g/day (SE = 1.7) and protein content increased 1.6 g/day (SE = 0.6) in the sample of adult geese collected over a 3-week period. A study conducted during 1979-1980 in the Rainwater Basin reported that white-fronted geese gained 8.8-17.7 g of lipids per day during spring, differing greatly from our results 2 decades later. In addition, lipid levels were less in the 1990s compared to spring 1980 for adult geese nearing departure from staging sites in Saskatchewan. This shift in where geese acquired nutrient stores from Nebraska to more northern staging sites coincided with a decrease in availability of waste corn in Nebraska, their primary food source while staging at that stopover site, and an increase in cultivation of high-energy pulse crops in Saskatchewan. White-fronted geese exhibited flexibility in nutrient dynamics during spring migration, likely in response to landscape-level variation in food availability caused by changes in agricultural trends and practices. Maintaining a wide distribution of wetlands in the Great Plains may allow springstaging waterfowl to disperse across the region and facilitate access to high-energy foods over a larger cropland base.

Combined effects of inversion and feature removal on N170 responses elicited by faces and car fronts.

PubMed

Kloth, Nadine; Itier, Roxane J; Schweinberger, Stefan R

2013-04-01

The face-sensitive N170 is typically enhanced for inverted compared to upright faces. Itier, Alain, Sedore, and McIntosh (2007) recently suggested that this N170 inversion effect is mainly driven by the eye region which becomes salient when the face configuration is disrupted. Here we tested whether similar effects could be observed with non-face objects that are structurally similar to faces in terms of possessing a homogeneous within-class first-order feature configuration. We presented upright and inverted pictures of intact car fronts, car fronts without lights, and isolated lights, in addition to analogous face conditions. Upright cars elicited substantial N170 responses of similar amplitude to those evoked by upright faces. In strong contrast to face conditions however, the car-elicited N170 was mainly driven by the global shape rather than the presence or absence of lights, and was dramatically reduced for isolated lights. Overall, our data confirm a differential influence of the eye region in upright and inverted faces. Results for car fronts do not suggest similar interactive encoding of eye-like features and configuration for non-face objects, even when these objects possess a similar feature configuration as faces. Copyright © 2013 Elsevier Inc. All rights reserved.

Firing up the front line.

PubMed

Katzenbach, J R; Santamaria, J A

1999-01-01

For many organizations, achieving competitive advantage means eliciting superior performance from employees on the front line--the burger flippers, hotel room cleaners, and baggage handlers whose work has an enormous effect on customers. That's no easy task. Front line workers are paid low wages, have scant hope of advancement, and--not surprisingly--often care little about the company's performance. But then how do some companies succeed in engaging the emotional energy of rank-and-file workers? A team of researchers at McKinsey & Company and the Conference Board recently explored that question and discovered that one highly effective route is demonstrated by the U.S. Marine Corps. The Marines' approach to motivation follows the "mission, values, and pride" path, which researchers say is practical and relevant for the business world. More specifically, the authors say the Marines follow five practices: they over-invest in cultivating core value; prepare every person to lead, including front line supervisors; learn when to create teams and when to create single-leader work groups; attend to all employees, not just the top half; and encourage self-discipline as a way of building pride. The authors admit there are critical differences between the Marines and most businesses. But using vivid examples from companies such as KFC and Marriott International, the authors illustrate how the Marines' approach can be translated for corporate use. Sometimes, the authors maintain, minor changes in a company's standard operating procedure can have a powerful effect on front line pride and can result in substantial payoffs in company performance.

Frozen reaction fronts in steady flows: A burning-invariant-manifold perspective

NASA Astrophysics Data System (ADS)

Mahoney, John R.; Li, John; Boyer, Carleen; Solomon, Tom; Mitchell, Kevin A.

2015-12-01

The dynamics of fronts, such as chemical reaction fronts, propagating in two-dimensional fluid flows can be remarkably rich and varied. For time-invariant flows, the front dynamics may simplify, settling in to a steady state in which the reacted domain is static, and the front appears "frozen." Our central result is that these frozen fronts in the two-dimensional fluid are composed of segments of burning invariant manifolds, invariant manifolds of front-element dynamics in x y θ space, where θ is the front orientation. Burning invariant manifolds (BIMs) have been identified previously as important local barriers to front propagation in fluid flows. The relevance of BIMs for frozen fronts rests in their ability, under appropriate conditions, to form global barriers, separating reacted domains from nonreacted domains for all time. The second main result of this paper is an understanding of bifurcations that lead from a nonfrozen state to a frozen state, as well as bifurcations that change the topological structure of the frozen front. Although the primary results of this study apply to general fluid flows, our analysis focuses on a chain of vortices in a channel flow with an imposed wind. For this system, we present both experimental and numerical studies that support the theoretical analysis developed here.

Flame front propagation in a channel with porous walls

NASA Astrophysics Data System (ADS)

Golovastov, S. V.; Bivol, G. Yu

2016-11-01

Propagation of the detonation front in hydrogen-air mixture was investigated in rectangular cross-section channels with sound-absorbing boundaries. The front of luminescence was detected in a channel with acoustically absorbing walls as opposed to a channel with solid walls. Flame dynamics was recorded using a high-speed camera. The flame was observed to have a V-shaped profile in the acoustically absorbing section. The possible reason for the formation of the V-shaped flame front is friction under the surface due to open pores. In these shear flows, the kinetic energy of the flow on the surface can be easily converted into heat. A relatively small disturbance may eventually lead to significant local stretching of the flame front surface. Trajectories of the flame front along the axis and the boundary are presented for solid and porous surfaces.

Small-scale zooplankton aggregations at the front of a Kuroshio warm-core ring

NASA Astrophysics Data System (ADS)

Yamamoto, Tamiji; Nishizawa, Satoshi

1986-11-01

A Longhurst-Hardy Plankton Recorder was used to study the small-scale zooplankton distribution across the front of a Kuroshio warm-core ring in June 1979. Zooplankton were strongly aggregated in the frontal region; patches of zooplankton and phytoplankton were spatially separated. A major part of the zooplankton assemblage consisted of neritic forms such as cladocerans and indicator species of the cold Oyashio water. This implies that lateral entrainment of coastal waters, which is directly influenced by the Oyashio, was an important factor in the formation of the aggregations at the Kuroshio warm-core ring front. Variation in the distribution of abundance peaks of individual zooplankton species was also observed. Futhermore, zooplankton showed more intensive non-randomness (aggregation) than phytoplankton and non-motile euphausiid's eggs. Thus, biological processes, such as motility and prey-predator interaction, also appeared to be regulating the patchiness.

Summertime sea surface temperature fronts associated with upwelling around the Taiwan Bank

NASA Astrophysics Data System (ADS)

Lan, Kuo-Wei; Kawamura, Hiroshi; Lee, Ming-An; Chang, Yi; Chan, Jui-Wen; Liao, Cheng-Hsin

2009-04-01

It is well known that upwelling of subsurface water is dominant around the Taiwan Bank (TB) and the Penghu (PH) Islands in the southern Taiwan Strait in summertime. Sea surface temperature (SST) frontal features and related phenomena around the TB upwelling and the PH upwelling were investigated using long-term AVHRR (1996-2005) and SeaWiFS (1998-2005) data received at the station of National Taiwan Ocean University. SST and chlorophyll-a (Chl-a) images with a spatial resolution of 0.01° were generated and used for the monthly SST and Chl-a maps. SST fronts were extracted from each SST images and gradient magnitudes (GMs); the orientations were derived for the SST fronts. Monthly maps of cold fronts where the cooler SSTs were over a shallower bottom were produced from the orientation. Areas with high GMs (0.1-0.2 °C/km) with characteristic shapes appeared at geographically fixed positions around the TB/PH upwelling region where SSTs were lower than the surrounding waters. The well-shaped high GMs corresponded to cold fronts. Two areas with high Chl-a were found around the TB and PH Islands. The southern border of the high-Chl-a area in the TB upwelling area was outlined by the high-GM area. Shipboard measurements of snapshot vertical sections of temperature (T) and salinity (S) along the PH Channel showed a dome structure east of PH Islands, over which low SST and high GM in the maps of the corresponding month were present. Clear evidence of upwelling (vertically uniform distributions of T and S) was indicated at the TB edge in the T and S sections close to TB upwelling. This case of upwelling may be caused by bottom currents ascending the TB slope as pointed out by previous studies. The position of low SSTs in the monthly maps matched the upwelling area, and the high GMs corresponded to the area of eastern surface fronts in the T/S sections.

Changes in zooplankton habitat, behavior, and acoustic scattering characteristics across glider-resolved fronts in the Southern California Current System

NASA Astrophysics Data System (ADS)

Powell, Jesse R.; Ohman, Mark D.

2015-05-01

We report cross-frontal changes in the characteristics of plankton proxy variables measured by autonomous Spray ocean gliders operating within the Southern California Current System (SCCS). A comparison of conditions across the 154 positive frontal gradients (i.e., where density of the surface layer decreased in the offshore direction) identified from six years of continuous measurements showed that waters on the denser side of the fronts typically showed higher Chl-a fluorescence, shallower euphotic zones, and higher acoustic backscatter than waters on the less dense side. Transitions between these regions were relatively abrupt. For positive fronts the amplitude of Diel Vertical Migration (DVM), inferred from a 3-beam 750 kHz acoustic Doppler profiler, increased offshore of fronts and covaried with optical transparency of the water column. Average interbeam variability in acoustic backscatter also changed across many positive fronts within 3 depth strata (0-150 m, 150-400 m, and 400-500 m), revealing a front-related change in the acoustic scattering characteristics of the assemblages. The extent of vertical stratification of distinct scattering assemblages was also more pronounced offshore of positive fronts. Depth-stratified zooplankton samples collected by Mocness nets corroborated the autonomous measurements, showing copepod-dominated assemblages and decreased zooplankton body sizes offshore and euphausiid-dominated assemblages with larger median body sizes inshore of major frontal features.

Bioconvection and front formation of Paramecium tetraurelia

NASA Astrophysics Data System (ADS)

Kitsunezaki, So; Komori, Rie; Harumoto, Terue

2007-10-01

We have investigated the bioconvection of Paramecium tetraurelia in high-density suspensions made by centrifugal concentration. When a suspension is kept at rest in a Hele-Shaw cell, a crowded front of paramecia is formed in the vicinity of the bottom and it propagates gradually toward the water-air interface. Fluid convection occurs under this front, and it is driven persistently by the upward swimming of paramecia. The roll structures of the bioconvection become turbulent with an increase in the depth of the suspension; they also change rapidly as the density of paramecia increases. Our experimental results suggest that lack of oxygen in the suspension causes the active individual motions of paramecia to induce the formation of this front.

Finite-time barriers to reaction front propagation

NASA Astrophysics Data System (ADS)

Locke, Rory; Mahoney, John; Mitchell, Kevin

2015-11-01

Front propagation in advection-reaction-diffusion systems gives rise to rich geometric patterns. It has been shown for time-independent and time-periodic fluid flows that invariant manifolds, termed burning invariant manifolds (BIMs), serve as one-sided dynamical barriers to the propagation of reaction front. More recently, theoretical work has suggested that one-sided barriers, termed burning Lagrangian Coherent structures (bLCSs), exist for fluid velocity data prescribed over a finite time interval, with no assumption on the time-dependence of the flow. In this presentation, we use a time-varying fluid ``wind'' in a double-vortex channel flow to demonstrate that bLCSs form the (locally) most attracting or repelling fronts.

Optimal back-to-front airplane boarding.

PubMed

Bachmat, Eitan; Khachaturov, Vassilii; Kuperman, Ran

2013-06-01

The problem of finding an optimal back-to-front airplane boarding policy is explored, using a mathematical model that is related to the 1+1 polynuclear growth model with concave boundary conditions and to causal sets in gravity. We study all airplane configurations and boarding group sizes. Optimal boarding policies for various airplane configurations are presented. Detailed calculations are provided along with simulations that support the main conclusions of the theory. We show that the effectiveness of back-to-front policies undergoes a phase transition when passing from lightly congested airplanes to heavily congested airplanes. The phase transition also affects the nature of the optimal or near-optimal policies. Under what we consider to be realistic conditions, optimal back-to-front policies lead to a modest 8-12% improvement in boarding time over random (no policy) boarding, using two boarding groups. Having more than two groups is not effective.

Turbulence spectra measured during fire front passage

Treesearch

Daisuke Seto; Craig B. Clements; Warren E. Heilman

2013-01-01

Four field experiments were conducted over various fuel and terrain to investigate turbulence generation during the passage of wildland fire fronts. Our results indicate an increase in horizontal mean winds and friction velocity, horizontal and vertical velocity variances as well as a decreased degree of anisotropy in TKE during fire front passage (FFP) due to fire-...

Reaction fronts of the autocatalytic hydrogenase reaction

NASA Astrophysics Data System (ADS)

Gyevi-Nagy, László; Lantos, Emese; Gehér-Herczegh, Tünde; Tóth, Ágota; Bagyinka, Csaba; Horváth, Dezső

2018-04-01

We have built a model to describe the hydrogenase catalyzed, autocatalytic, reversible hydrogen oxidation reaction where one of the enzyme forms is the autocatalyst. The model not only reproduces the experimentally observed front properties, but also explains the found hydrogen ion dependence. Furthermore, by linear stability analysis, two different front types are found in good agreement with the experiments.

Research fronts analysis : A bibliometric to identify emerging fields of research

NASA Astrophysics Data System (ADS)

Miwa, Sayaka; Ando, Satoko

Research fronts analysis identifies emerging areas of research through observing co-clustering in highly-cited papers. This article introduces the concept of research fronts analysis, explains its methodology and provides case examples. It also demonstrates developing research fronts in Japan by looking at the past winners of Thomson Reuters Research Fronts Awards. Research front analysis is currently being used by the Japanese government to determine new trends in science and technology. Information professionals can also utilize this bibliometric as a research evaluation tool.

Study of the Río de la Plata turbidity front, Part 1: spatial and temporal distribution

NASA Astrophysics Data System (ADS)

Framiñan, Mariana B.; Brown, Otis B.

1996-08-01

The Río de la Plata is a riverine system located on the east coast of South America at 35°S. It covers 35,000 km 2, it is 320 km long and 230 km wide at the mouth. The Río de la Plata drains the second largest basin in South America with an average discharge of 22,000 m 3 s -1. The processes associated with the interaction of the fresh river water and the saline shelf water and tidal stirring generate a turbidity front in the outer region, which is clearly defined in the satellite images as a strong gradient in reflectance and a sharp change in water color. We use a 4 yr span of NOAA-AVHRR daily images, from September 1986 to August 1990, to determine the spatial and temporal distribution of the turbidity front. Channels 1 and 2 (visible and near-infrared) are used to digitize the fronts, and channel 4 and sea surface temperature are used as complementary information for cloud detection. From a total of 2578 images, 1274 daytime images allowed us to determine 333 positions of the front. This information is used to estimate the distribution of the frontal density, a probabilistic measure of frontal occurrence. Monthly, seasonal and annual analyses were performed. The relation of the turbidity front patterns to bathymetry, tidal dynamics, river discharge and winds were investigated. A comparison between the frontal density distribution and stratification parameters is presented. The results show a high degree of variability of the frontal distribution at the northern coast of the estuary. In this region, the frontal position varies between 57°W and 54°12'W. The westernmost location occurs in the summer months, which is coincident with minimum river discharge, predominance of easterly winds and minimum occurrence of southwesterlies. The easternmost location occurs during the spring, with strong winds from the southwest. At the southern coast the modal position of the front coincides with the 5 m isobath, although great variations to this position have been

Year 1 Field Work Report: Utah Bat Monitoring Protocol

DTIC Science & Technology

2010-01-28

Plateau shrublands, Great Basin shrub steppe, Wasatch and Uinta montane forests, Mojave Desert and Wyoming Basin shrub steppe. A total 65, 20 x 20 km... Basin shrub steppe, Wasatch and Uinta montane forests) each harbored 20 sampling cells, while the limited size of the Mojave Desert and Wyoming Basin ...Wasatch and Uinta montane forest and Wyoming Basin shrub steppe). Site # A unique identifier between 1 and 20 within each ecoregion. UTM The

11. VIEW NORTH, SOUTH FRONT OF MAIN OFFICE UNIT (BUILDING ...

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

11. VIEW NORTH, SOUTH FRONT OF MAIN OFFICE UNIT (BUILDING I, 2); SOUTH AND EAST FRONTS OF SEED STORAGE BUILDING (BUILDING 21); EAST FRONT OF GREENHOUSE #1 (BUILDING 5) - U.S. Plant Introduction Station, 11601 Old Pond Road, Glenn Dale, Prince George's County, MD

Discovery of a Molecular Collision Front in Interacting Galaxies NGC 4567/4568 with ALMA

NASA Astrophysics Data System (ADS)

Kaneko, Hiroyuki; Kuno, Nario; Saitoh, Takayuki R.

2018-06-01

We present results of 12CO(J = 1–0) imaging observations of NGC 4567/4568, a galaxy pair in a close encounter, with the Atacama Large Millimeter/Submillimeter Array (ALMA). For the first time, we find clear evidence of a molecular collision front with a velocity dispersion that is 16.8 ± 1.4 km s‑1 at the overlapping region, owing to high spatial and velocity resolution. By integrating over the velocity width that corresponds to the molecular collision front, we find a long filamentary structure with a size of 1800 pc × 350 pc at the collision front. This filamentary molecular structure spatially coincides with a dark lane seen in the R-band image. We find four molecular clouds in the filament, each with a radius of 30 pc and mass of 106 M ⊙ the radii matching a typical value for giant molecular clouds (GMCs) and the masses corresponding to those between GMCs and giant molecular associations (GMAs). All four clouds are gravitationally bound. The molecular filamentary structure and its physical conditions are similar to the structure expected via numerical simulation. The filament could be a progenitor of super star clusters.

[The general practitioners in front of reforms: the reactions of the sample group of liberal physicians of the region PACA].

PubMed

Videau, Yann; Ventelou, Bruno; Combes, Jean-Baptiste; Verger, Pierre; Paraponaris, Alain

2007-05-01

The general practitioners in front of reforms: the reactions of the sample group of liberal physicians of the region PACA This article intends to analyse the opinion of general practioners (GPs) about the two laws of July 2004, relating to the health insurance reform and to public health planning. We used a panel data sample of 528 GPs practising in Provence Alpes Côte d'Azur in order to analyse the determinants of physicians' adherence to the reform, using multinomial logistic regression models. The results show that GPs do not seem to be fully convinced by this reform (45% agree with it, whereas 48% don't): this mistrustful opinion is more marked for young physicians and appears little correlated with their practices. 75% of the GPs are favourable to the Personal Medical File (Dossier Médical Personnel in french) and 76% estimate that they should draw a better attention to the public health dimension of their practice. Two barriers concerning GPs' adherence to the < preferred doctor > reform (réforme du < médecin traitant >) seem relevant: the burden of administrative tasks and the disadvantage of young physicians who have not already fixed their own clientele.

Southern elephant seal trajectories, fronts and eddies in the Brazil/Malvinas Confluence

NASA Astrophysics Data System (ADS)

Campagna, Claudio; Piola, Alberto R.; Rosa Marin, Maria; Lewis, Mirtha; Fernández, Teresita

2006-12-01

This study describes the association between transient, mesoscale hydrographic features along the axis of the Brazil-Malvinas Confluence, in the SW Atlantic, and the foraging behavior of 2-3-year-old (focal) juvenile southern elephant seals, Mirounga leonina, from Península Valdés, Argentina. Departing from the dominant pattern of foraging on predictable bathymetric fronts on the Patagonian shelf and slope, three females out of 12 satellite-tracked juveniles remained at the edge of young warm-core eddies and near the outer core of cold-core eddies, coinciding with the most productive areas of these temperature fronts. Seal trajectories along high-temperature gradients were always consistent with the speed and direction of surface currents inferred from the temperature distribution and confirmed by surface drifters. Movements of foraging seals were compared with those of surface drifters, coinciding in time and space and yielding independent and consistent data on regional water circulation parameters. The diving pattern recorded for one focal seal yielded shallower dives and a loose diel pattern in the eddy, and a marked diurnal cycle compatible with foraging on vertically migrating prey in the cold waters of the Malvinas Current. Pre-reproductive females that use the mesoscale fronts of the Argentine Basin as an alternative foraging area would benefit from lower competition with more experienced seals and with other top predators that reproduce along the coast of Patagonia.

CMOS Ultralow Power Brain Signal Acquisition Front-Ends: Design and Human Testing.

PubMed

Karimi-Bidhendi, Alireza; Malekzadeh-Arasteh, Omid; Lee, Mao-Cheng; McCrimmon, Colin M; Wang, Po T; Mahajan, Akshay; Liu, Charles Yu; Nenadic, Zoran; Do, An H; Heydari, Payam

2017-08-01

Two brain signal acquisition (BSA) front-ends incorporating two CMOS ultralow power, low-noise amplifier arrays and serializers operating in mosfet weak inversion region are presented. To boost the amplifier's gain for a given current budget, cross-coupled-pair active load topology is used in the first stages of these two amplifiers. These two BSA front-ends are fabricated in 130 and 180 nm CMOS processes, occupying 5.45 mm 2 and 0.352 mm 2 of die areas, respectively (excluding pad rings). The CMOS 130-nm amplifier array is comprised of 64 elements, where each amplifier element consumes 0.216 μW from 0.4 V supply, has input-referred noise voltage (IRNoise) of 2.19 μV[Formula: see text] corresponding to a power efficiency factor (PEF) of 11.7, and occupies 0.044 mm 2 of die area. The CMOS 180 nm amplifier array employs 4 elements, where each element consumes 0.69 μW from 0.6 V supply with IRNoise of 2.3 μV[Formula: see text] (corresponding to a PEF of 31.3) and 0.051 mm 2 of die area. Noninvasive electroencephalographic and invasive electrocorticographic signals were recorded real time directly on able-bodied human subjects, showing feasibility of using these analog front-ends for future fully implantable BSA and brain- computer interface systems.

Seasonal Atmospheric Argon Variability Measured in the Equatorial Region of Mars by the Mars Exploration Rover Alpha Particle X-Ray Spectrometers: Evidence for an Annual Argon-Enriched Front

NASA Astrophysics Data System (ADS)

VanBommel, S. J.; Gellert, R.; Clark, B. C.; Ming, D. W.

2018-02-01

The Mars Exploration Rover Opportunity (MER-B) has been exploring the surface of Mars since landing in 2004. Its Alpha Particle X-ray Spectrometer (APXS) is primarily used to interrogate the chemical composition of rocks and soil samples in situ. Additionally, the APXS has measured the atmosphere of Mars with a regular cadence, monitoring the change in relative atmospheric argon density. Atmospheric measurements with the MER-B APXS span over six Mars years providing an unprecedented level of statistics for careful study of the ubiquitous APXS spectral background. Several models were applied to high-frequency long-duration Spirit rover atmospheric APXS measurements. The most stable model with the least uncertainty was applied to the MER-B data set. Seasonal variation of 10-15% in equatorial atmospheric argon density was observed - in agreement with existing literature and global climate models. Unseen in previous work and global climate models, an abrupt deviation from the model-predicted annual mixing ratio was measured by the MER-B APXS around Ls 150. The sharp change, 10% over 10° Ls, provides strong evidence for a northward migrating front, enriched in argon, sourced from the south pole at the end of southern winter. A similar weaker front is possibly observed around Ls 325, sourced from the northern polar region.

The Majorana low-noise low-background front-end electronics

DOE PAGES

Abgrall, N.; Aguayo, E.; Avignone, III, F. T.; ...

2015-03-24

The Majorana Demonstrator will search for the neutrinoless double beta decay (ββ(0ν)) of the isotope ⁷⁶Ge with a mixed array of enriched and natural germanium detectors. In view of the next generation of tonne-scale germanium-based ββ(0ν)-decay searches, a major goal of the Majorana Demonstrator is to demonstrate a path forward to achieving a background rate at or below 1 cnt/(ROI-t-y) in the 4 keV region of interest (ROI) around the 2039-keV Q-value of the ⁷⁶Ge ββ(0ν)-decay. Such a requirement on the background level significantly constrains the design of the readout electronics, which is further driven by noise and energy resolutionmore » performances. We present here the low-noise low-background front-end electronics developed for the low-capacitance p-type point contact (P-PC) germanium detectors of the Majorana Demonstrator. This resistive-feedback front-end, specifically designed to have low mass, is fabricated on a radioassayed fused-silica substrate where the feedback resistor consists of a sputtered thin film of high purity amorphous germanium and the feedback capacitor is based on the capacitance between gold conductive traces.« less

Growth and gravitational collapse of a mountain front of the Eastern Cordillera of Colombia

NASA Astrophysics Data System (ADS)

Kammer, Andreas; Montana, Jorge; Piraquive, Alejandro

2016-04-01

The Eastern Cordillera of Colombia is bracketed between the moderately east-dipping flank of the Central Cordillera on its western and the gently bent Guayana shield on its eastern side. It evolved as a response to a considerable displacement transfer from the Nazca to the Southamerican plate since the Oligocene break-up of the Farallon plate. One of its distinctive traits refers to its significant shortening by penetrative strain at lower and folding at higher structural levels, approximating a wholesale pure-shear in analogy to a vice model or a crustal welt sandwiched between rigid buttresses. This contrasting behavior may be explained by the spatial coincidence between Neogene mountain belt and a forebulge that shaped the foreland trough during a Cretaceous subduction cycle and was very effective in localizing a weakening of the backarc region comprised between two basin margin faults. In this paper we examine a two-phase evolution of the Eastern mountain front. Up to the late Miocene deformation was restrained by the inherited eastern basin margin fault and as the cordilleran crust extruded, a deformation front with an amplitude similar the present structural relief of up to 10.000 m may have built up. In the Pliocene convergence changed from a roughly strike-perpendicular to an oblique E-W direction and caused N-S trending faults to branch off from the deformation front. This shortening was partly driven by a gravitational collapse of the Miocene deformation front, that became fragmented by normal faults and extruded E on newly formed Pliocene thrust faults. Normal faults display displacements of up to 3000 m and channelized hydrothermal fluids, leading to the formation of widely distributed fault breccias and giving rise to a prolific Emerald mineralization. In terms of wedge dynamics, the Pliocene breaching of the early formed deformation front helped to establish a critical taper.

Miscellaneous High-Resolution Seismic Imaging Investigations in Salt Lake and Utah Valleys for Earthquake Hazards

USGS Publications Warehouse

Stephenson, W.J.; Williams, R.A.; Odum, J.K.; Worley, D.M.

2007-01-01

Introduction In support of earthquake hazards and ground motion studies by researchers at the Utah Geological Survey, University of Utah, Utah State University, Brigham Young University, and San Diego State University, the U.S. Geological Survey Geologic Hazards Team Intermountain West Project conducted three high-resolution seismic imaging investigations along the Wasatch Front between September 2003 and September 2005. These three investigations include: (1) a proof-of-concept P-wave minivib reflection imaging profile in south-central Salt Lake Valley, (2) a series of seven deep (as deep as 400 m) S-wave reflection/refraction soundings using an S-wave minivib in both Salt Lake and Utah Valleys, and (3) an S-wave (and P-wave) investigation to 30 m at four sites in Utah Valley and at two previously investigated S-wave (Vs) minivib sites. In addition, we present results from a previously unpublished downhole S-wave investigation conducted at four sites in Utah Valley. The locations for each of these investigations are shown in figure 1. Coordinates for the investigation sites are listed in Table 1. With the exception of the P-wave common mid-point (CMP) reflection profile, whose end points are listed, these coordinates are for the midpoint of each velocity sounding. Vs30 and Vs100, also shown in Table 1, are defined as the average shear-wave velocities to depths of 30 and 100 m, respectively, and details of their calculation can be found in Stephenson and others (2005). The information from these studies will be incorporated into components of the urban hazards maps along the Wasatch Front being developed by the U.S. Geological Survey, Utah Geological Survey, and numerous collaborating research institutions.

The Store Front School.

ERIC Educational Resources Information Center

Forrest, Barbara

1986-01-01

Describes the Store Front School project, a program of cooperative education aimed at rekindling students' interest in school and helping them earn their diplomas. The school conducts classes in an office in a shopping mall where the students work. (ABB)

Rapid acceleration of protons upstream of earthward propagating dipolarization fronts

PubMed Central

Ukhorskiy, AY; Sitnov, MI; Merkin, VG; Artemyev, AV

2013-01-01

[1] Transport and acceleration of ions in the magnetotail largely occurs in the form of discrete impulsive events associated with a steep increase of the tail magnetic field normal to the neutral plane (Bz), which are referred to as dipolarization fronts. The goal of this paper is to investigate how protons initially located upstream of earthward moving fronts are accelerated at their encounter. According to our analytical analysis and simplified two-dimensional test-particle simulations of equatorially mirroring particles, there are two regimes of proton acceleration: trapping and quasi-trapping, which are realized depending on whether the front is preceded by a negative depletion in Bz. We then use three-dimensional test-particle simulations to investigate how these acceleration processes operate in a realistic magnetotail geometry. For this purpose we construct an analytical model of the front which is superimposed onto the ambient field of the magnetotail. According to our numerical simulations, both trapping and quasi-trapping can produce rapid acceleration of protons by more than an order of magnitude. In the case of trapping, the acceleration levels depend on the amount of time particles stay in phase with the front which is controlled by the magnetic field curvature ahead of the front and the front width. Quasi-trapping does not cause particle scattering out of the equatorial plane. Energization levels in this case are limited by the number of encounters particles have with the front before they get magnetized behind it. PMID:26167430

A downslope propagating thermal front over the continental slope

NASA Astrophysics Data System (ADS)

van Haren, Hans; Hosegood, Phil J.

2017-04-01

In the ocean, internal frontal bores above sloping topography have many appearances, depending on the local density stratification, and on the angle and source of generation of the carrier wave. However, their common characteristics are a backward breaking wave, strong sediment resuspension, and relatively cool (denser) water moving more or less upslope underneath warm (less dense) water. In this paper, we present a rare example of a downslope moving front of cold water moving over near-bottom warm water. Large backscatter is observed in the downslope moving front's trailing edge, rather than the leading edge as is common in upslope moving fronts. Time series observations have been made during a fortnight in summer, using a 101 m long array of high-resolution temperature sensors moored with an acoustic Doppler current profiler at 396 m depth in near-homogeneous waters, near a small canyon in the continental slope off the Malin shelf (West-Scotland, UK). Occurring between fronts that propagate upslope with tidal periodicity, the rare downslope propagating one resembles a gravity current and includes strong convective turbulence coming from the interior rather than the more usual frictionally generated turbulence arising from interaction with the seabed. Its turbulence is 3-10 times larger than that of more common upslope propagating fronts. As the main turbulence is in the interior with a thin stratified layer close to the bottom, little sediment is resuspended by a downslope propagating front. The downslope propagating front is suggested to be generated by oblique propagation of internal (tidal) waves and flow over a nearby upstream promontory.

Fibre laser cutting stainless steel: Fluid dynamics and cut front morphology

NASA Astrophysics Data System (ADS)

Pocorni, Jetro; Powell, John; Deichsel, Eckard; Frostevarg, Jan; Kaplan, Alexander F. H.

2017-01-01

In this paper the morphology of the laser cut front generated by fibre lasers was investigated by observation of the 'frozen' cut front, additionally high speed imaging (HSI) was employed to study the fluid dynamics on the cut front while cutting. During laser cutting the morphology and flow properties of the melt film on the cut front affect cut quality parameters such as cut edge roughness and dross (residual melt attached to the bottom of the cut edge). HSI observation of melt flow down a laser cutting front using standard cutting parameters is experimentally problematic because the cut front is narrow and surrounded by the kerf walls. To compensate for this, artificial parameters are usually chosen to obtain wide cut fronts which are unrepresentative of the actual industrial process. This paper presents a new experimental cutting geometry which permits HSI of the laser cut front using standard, commercial parameters. These results suggest that the cut front produced when cutting medium section (10 mm thick) stainless steel with a fibre laser and a nitrogen assist gas is covered in humps which themselves are covered by a thin layer of liquid. HSI observation and theoretical analysis reveal that under these conditions the humps move down the cut front at an average speed of approximately 0.4 m/s while the covering liquid flows at an average speed of approximately 1.1 m/s, with an average melt depth at the bottom of the cut zone of approximately 0.17 mm.

Light-front holographic QCD and emerging confinement

DOE PAGES

Brodsky, Stanley J.; de Téramond, Guy F.; Dosch, Hans Günter; ...

2015-05-21

In this study we explore the remarkable connections between light-front dynamics, its holographic mapping to gravity in a higher-dimensional anti-de Sitter (AdS) space, and conformal quantum mechanics. This approach provides new insights into the origin of a fundamental mass scale and the physics underlying confinement dynamics in QCD in the limit of massless quarks. The result is a relativistic light-front wave equation for arbitrary spin with an effective confinement potential derived from a conformal action and its embedding in AdS space. This equation allows for the computation of essential features of hadron spectra in terms of a single scale. Themore » light-front holographic methods described here give a precise interpretation of holographic variables and quantities in AdS space in terms of light-front variables and quantum numbers. This leads to a relation between the AdS wave functions and the boost-invariant light-front wave functions describing the internal structure of hadronic bound-states in physical spacetime. The pion is massless in the chiral limit and the excitation spectra of relativistic light-quark meson and baryon bound states lie on linear Regge trajectories with identical slopes in the radial and orbital quantum numbers. In the light-front holographic approach described here currents are expressed as an infinite sum of poles, and form factors as a product of poles. At large q 2 the form factor incorporates the correct power-law fall-off for hard scattering independent of the specific dynamics and is dictated by the twist. At low q 2 the form factor leads to vector dominance. The approach is also extended to include small quark masses. We briefly review in this report other holographic approaches to QCD, in particular top-down and bottom-up models based on chiral symmetry breaking. We also include a discussion of open problems and future applications.« less

Turbulent premixed combustion in V-shaped flames: Characteristics of flame front

NASA Astrophysics Data System (ADS)

Kheirkhah, S.; Gülder, Ö. L.

2013-05-01

Flame front characteristics of turbulent premixed V-shaped flames were investigated experimentally using the Mie scattering and the particle image velocimetry techniques. The experiments were performed at mean streamwise exit velocities of 4.0, 6.2, and 8.6 m/s, along with fuel-air equivalence ratios of 0.7, 0.8, and 0.9. Effects of vertical distance from the flame-holder, mean streamwise exit velocity, and fuel-air equivalence ratio on statistics of the distance between the flame front and the vertical axis, flame brush thickness, flame front curvature, and angle between tangent to the flame front and the horizontal axis were studied. The results show that increasing the vertical distance from the flame-holder and the fuel-air equivalence ratio increase the mean and root-mean-square (RMS) of the distance between the flame front and the vertical axis; however, increasing the mean streamwise exit velocity decreases these statistics. Spectral analysis of the fluctuations of the flame front position depicts that the normalized and averaged power-spectrum-densities collapse and show a power-law relation with the normalized wave number. The flame brush thickness is linearly correlated with RMS of the distance between the flame front and the vertical axis. Analysis of the curvature of the flame front data shows that the mean curvature is independent of the experimental conditions tested and equals to zero. Values of the inverse of the RMS of flame front curvature are similar to those of the integral length scale, suggesting that the large eddies in the flow make a significant contribution in wrinkling of the flame front. Spectral analyses of the flame front curvature as well as the angle between tangent to the flame front and the horizontal axis show that the power-spectrum-densities feature a peak. Value of the inverse of the wave number pertaining to the peak is larger than that of the integral length scale.

Polarization and wavelength diversities of Gulf Stream fronts imaged by AIRSAR

NASA Technical Reports Server (NTRS)

Lee, J. S.; Jansen, R. W.; Marmorino, G. O.; Chubb, S. R.

1995-01-01

During the 1990 Gulf Stream Experiment, NASA/JPL AIRSAR imaged the north edge of the Gulf Stream near the coast of Virginia. Simultaneous in-situ measurements of currents, temperatures, salinities, etc. were made for several crossings of the north edge by the R/V Cape Henlopen. Measurements identified two fronts with shearing and converging flows. The polarimetric SAR images from the fronts showed two bright linear features. One of them corresponds to the temperature front, which separated the warm Gulf Stream water to the south from a cool, freshwater filament to the north. The other line, located about 8 km north of the temperature front, is believed to correspond to the velocity front between the filament and the slope water. At these fronts, wave-current interactions produced narrow bands of steep and breaking waves manifesting higher radar returns in polarimetric SAR images. In general, our AIRSAR imagery shows that the signal-to-clutter ratio of radar cross sections for the temperature front is higher than that of the velocity front. In this paper, we study the polarization and wavelength diversities of radar response of these two fronts using the P-, L-, and C-Band Polarimetric SAR data. The north-south flight path of the AIRSAR crossed the temperature front several times and provided valuable data for analysis. Three individual passes are investigated. We found that for the temperature front, the cross-pol (HV) responses are much higher than co-pol responses (VV and HH), and that P-Band HV has the highest signal to clutter ratio. For the velocity front, the ratio is the strongest in P-Band VV, and it is indistinguishable for all polarizations in C-Band. The radar cross sections for all three polarization (HH, HV, and VV) and for all three bands are modelled using an ocean wave model and a composite Bragg scattering model. In our initial investigations, the theoretical model agrees qualitatively with the AIRSAR observations.

5-D interpolation with wave-front attributes

NASA Astrophysics Data System (ADS)

Xie, Yujiang; Gajewski, Dirk

2017-11-01

Most 5-D interpolation and regularization techniques reconstruct the missing data in the frequency domain by using mathematical transforms. An alternative type of interpolation methods uses wave-front attributes, that is, quantities with a specific physical meaning like the angle of emergence and wave-front curvatures. In these attributes structural information of subsurface features like dip and strike of a reflector are included. These wave-front attributes work on 5-D data space (e.g. common-midpoint coordinates in x and y, offset, azimuth and time), leading to a 5-D interpolation technique. Since the process is based on stacking next to the interpolation a pre-stack data enhancement is achieved, improving the signal-to-noise ratio (S/N) of interpolated and recorded traces. The wave-front attributes are determined in a data-driven fashion, for example, with the Common Reflection Surface (CRS method). As one of the wave-front-attribute-based interpolation techniques, the 3-D partial CRS method was proposed to enhance the quality of 3-D pre-stack data with low S/N. In the past work on 3-D partial stacks, two potential problems were still unsolved. For high-quality wave-front attributes, we suggest a global optimization strategy instead of the so far used pragmatic search approach. In previous works, the interpolation of 3-D data was performed along a specific azimuth which is acceptable for narrow azimuth acquisition but does not exploit the potential of wide-, rich- or full-azimuth acquisitions. The conventional 3-D partial CRS method is improved in this work and we call it as a wave-front-attribute-based 5-D interpolation (5-D WABI) as the two problems mentioned above are addressed. Data examples demonstrate the improved performance by the 5-D WABI method when compared with the conventional 3-D partial CRS approach. A comparison of the rank-reduction-based 5-D seismic interpolation technique with the proposed 5-D WABI method is given. The comparison reveals that

Null geodesics and wave front singularities in the Gödel space-time

NASA Astrophysics Data System (ADS)

Kling, Thomas P.; Roebuck, Kevin; Grotzke, Eric

2018-01-01

We explore wave fronts of null geodesics in the Gödel metric emitted from point sources both at, and away from, the origin. For constant time wave fronts emitted by sources away from the origin, we find cusp ridges as well as blue sky metamorphoses where spatially disconnected portions of the wave front appear, connect to the main wave front, and then later break free and vanish. These blue sky metamorphoses in the constant time wave fronts highlight the non-causal features of the Gödel metric. We introduce a concept of physical distance along the null geodesics, and show that for wave fronts of constant physical distance, the reorganization of the points making up the wave front leads to the removal of cusp ridges.

Plasma flow in peripheral region of detached plasma in linear plasma device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayashi, Y., E-mail: hayashi-yuki13@ees.nagoya-u.ac.jp; Ohno, N.; Kajita, S.

2016-01-15

A plasma flow structure is investigated using a Mach probe under detached plasma condition in a linear plasma device NAGDIS-II. A reverse flow along the magnetic field is observed in a steady-state at far-peripheral region of the plasma column in the upstream side from the recombination front. These experimental results indicate that plasma near the recombination front should strongly diffuse across the magnetic field, and it should be transported along the magnetic field in the reverse flow direction. Furthermore, bursty plasma density fluctuations associated with intermittent convective plasma transport are observed in the far-peripheral region of the plasma column inmore » both upstream and downstream sides from the recombination front. Such a nondiffusive transport can contribute to the intermittent reverse plasma flow, and the experimental results indicate that intermittent transports are frequently produced near the recombination front.« less

A NASA/University Joint Venture in Space Science (JOVE)

NASA Technical Reports Server (NTRS)

Vaughn, Danny M.

1997-01-01

Several papers have been given to national level meeting and a paper has been published in an international journal. Several additional papers have been co-author by students. The initial research project on the Atchafalaya Delta seems to have died in part due to a transfer of the NASA colleague to another location and subsequent reassigment to another job title. I have continued to include credit to NASA for many of my papers presented and published: A major debris flow along the Wasatch front in Northern Ogden; Spatial and volumetric changes in the Atchafalaya delta, Louisiana; An analysis of prehistoric Greenstone artifact in northern Alabama; An assessment of surfacing algorithm; Analysis of georeferencing algorithms to assess spatial accuracy.

Advances in Light-Front QCD: Supersymmetric Properties of Hadron Physics from Light-Front Holography and Superconformal Algebra

NASA Astrophysics Data System (ADS)

Brodsky, Stanley J.

2017-05-01

A remarkable feature of QCD is that the mass scale κ which controls color confinement and light-quark hadron mass scales does not appear explicitly in the QCD Lagrangian. However, de Alfaro, Fubini, and Furlan have shown that a mass scale can appear in the equations of motion without affecting the conformal invariance of the action if one adds a term to the Hamiltonian proportional to the dilatation operator or the special conformal operator. If one applies the same procedure to the light-front Hamiltonian, it leads uniquely to a confinement potential κ ^4 ζ ^2 for mesons, where ζ ^2 is the LF radial variable conjugate to the q \\bar{q} invariant mass. The same result, including spin terms, is obtained using light-front holography—the duality between the front form and AdS_5, the space of isometries of the conformal group—if one modifies the action of AdS_5 by the dilaton e^{κ ^2 z^2} in the fifth dimension z. When one generalizes this procedure using superconformal algebra, the resulting light-front eigensolutions predict a unified Regge spectroscopy of meson, baryon, and tetraquarks, including remarkable supersymmetric relations between the masses of mesons and baryons of the same parity. One also predicts observables such as hadron structure functions, transverse momentum distributions, and the distribution amplitudes defined from the hadronic light-front wavefunctions. The mass scale κ underlying confinement and hadron masses can be connected to the parameter Λ _{\\overline{MS}} in the QCD running coupling by matching the nonperturbative dynamics to the perturbative QCD regime. The result is an effective coupling α _s(Q^2) defined at all momenta. The matching of the high and low momentum transfer regimes determines a scale Q_0 which sets the interface between perturbative and nonperturbative hadron dynamics. The use of Q_0 to resolve the factorization scale uncertainty for structure functions and distribution amplitudes, in combination with the

Advances in Light-Front QCD: Supersymmetric Properties of Hadron Physics from Light-Front Holography and Superconformal Algebra

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.

A remarkable feature of QCD is that the mass scalemore » $k$ which controls color confinement and light-quark hadron mass scales does not appear explicitly in the QCD Lagrangian. However, de Alfaro, Fubini, and Furlan have shown that a mass scale can appear in the equations of motion without affecting the conformal invariance of the action if one adds a term to the Hamiltonian proportional to the dilatation operator or the special conformal operator. If one applies the same procedure to the light-front Hamiltonian, it leads uniquely to a confinement potential κ 4ζ 2 for mesons, where ζ 2 is the LF radial variable conjugate to the $$q\\bar{q}$$ invariant mass. The same result, including spin terms, is obtained using light-front holography$-$the duality between the front form and AdS 5, the space of isometries of the conformal group$-$if one modifies the action of AdS 5 by the dilaton e $κ^2z^2$ in the fifth dimension z. When one generalizes this procedure using superconformal algebra, the resulting light-front eigensolutions predict a unified Regge spectroscopy of meson, baryon, and tetraquarks, including remarkable supersymmetric relations between the masses of mesons and baryons of the same parity. One also predicts observables such as hadron structure functions, transverse momentum distributions, and the distribution amplitudes defined from the hadronic light-front wavefunctions. The mass scale κκ underlying confinement and hadron masses can be connected to the parameter Λ $$\\overline{MS}$$ in the QCD running coupling by matching the nonperturbative dynamics to the perturbative QCD regime. The result is an effective coupling α s (Q 2) defined at all momenta. The matching of the high and low momentum transfer regimes determines a scale Q 0 which sets the interface between perturbative and nonperturbative hadron dynamics. The use of Q 0 to resolve the factorization scale uncertainty for structure functions and distribution amplitudes, in combination with

Advances in Light-Front QCD: Supersymmetric Properties of Hadron Physics from Light-Front Holography and Superconformal Algebra

DOE PAGES

Brodsky, Stanley J.

2017-04-19

A remarkable feature of QCD is that the mass scalemore » $k$ which controls color confinement and light-quark hadron mass scales does not appear explicitly in the QCD Lagrangian. However, de Alfaro, Fubini, and Furlan have shown that a mass scale can appear in the equations of motion without affecting the conformal invariance of the action if one adds a term to the Hamiltonian proportional to the dilatation operator or the special conformal operator. If one applies the same procedure to the light-front Hamiltonian, it leads uniquely to a confinement potential κ 4ζ 2 for mesons, where ζ 2 is the LF radial variable conjugate to the $$q\\bar{q}$$ invariant mass. The same result, including spin terms, is obtained using light-front holography$-$the duality between the front form and AdS 5, the space of isometries of the conformal group$-$if one modifies the action of AdS 5 by the dilaton e $κ^2z^2$ in the fifth dimension z. When one generalizes this procedure using superconformal algebra, the resulting light-front eigensolutions predict a unified Regge spectroscopy of meson, baryon, and tetraquarks, including remarkable supersymmetric relations between the masses of mesons and baryons of the same parity. One also predicts observables such as hadron structure functions, transverse momentum distributions, and the distribution amplitudes defined from the hadronic light-front wavefunctions. The mass scale κκ underlying confinement and hadron masses can be connected to the parameter Λ $$\\overline{MS}$$ in the QCD running coupling by matching the nonperturbative dynamics to the perturbative QCD regime. The result is an effective coupling α s (Q 2) defined at all momenta. The matching of the high and low momentum transfer regimes determines a scale Q 0 which sets the interface between perturbative and nonperturbative hadron dynamics. The use of Q 0 to resolve the factorization scale uncertainty for structure functions and distribution amplitudes, in combination with

Ground based mobile isotopic methane measurements in the Front Range, Colorado

NASA Astrophysics Data System (ADS)

Vaughn, B. H.; Rella, C.; Petron, G.; Sherwood, O.; Mielke-Maday, I.; Schwietzke, S.

2014-12-01

Increased development of unconventional oil and gas resources in North America has given rise to attempts to monitor and quantify fugitive emissions of methane from the industry. Emission estimates of methane from oil and gas basins can vary significantly from one study to another as well as from EPA or State estimates. New efforts are aimed at reconciling bottom-up, or inventory-based, emission estimates of methane with top-down estimates based on atmospheric measurements from aircraft, towers, mobile ground-based vehicles, and atmospheric models. Attributing airborne measurements of regional methane fluxes to specific sources is informed by ground-based measurements of methane. Stable isotopic measurements (δ13C) of methane help distinguish between emissions from the O&G industry, Confined Animal Feed Operations (CAFO), and landfills, but analytical challenges typically limit meaningful isotopic measurements to individual point sampling. We are developing a toolbox to use δ13CH4 measurements to assess the partitioning of methane emissions for regions with multiple methane sources. The method was applied to the Denver-Julesberg Basin. Here we present data from continuous isotopic measurements obtained over a wide geographic area by using MegaCore, a 1500 ft. tube that is constantly filled with sample air while driving, then subsequently analyzed at slower rates using cavity ring down spectroscopy (CRDS). Pressure, flow and calibration are tightly controlled allowing precise attribution of methane enhancements to their point of collection. Comparisons with point measurements are needed to confirm regional values and further constrain flux estimates and models. This effort was made in conjunction with several major field campaigns in the Colorado Front Range in July-August 2014, including FRAPPÉ (Front Range Air Pollution and Photochemistry Experiment), DISCOVER-AQ, and the Air Water Gas NSF Sustainability Research Network at the University of Colorado.

Fronts in extended systems of bistable maps coupled via convolutions

NASA Astrophysics Data System (ADS)

Coutinho, Ricardo; Fernandez, Bastien

2004-01-01

An analysis of front dynamics in discrete time and spatially extended systems with general bistable nonlinearity is presented. The spatial coupling is given by the convolution with distribution functions. It allows us to treat in a unified way discrete, continuous or partly discrete and partly continuous diffusive interactions. We prove the existence of fronts and the uniqueness of their velocity. We also prove that the front velocity depends continuously on the parameters of the system. Finally, we show that every initial configuration that is an interface between the stable phases propagates asymptotically with the front velocity.

AdS/QCD and Applications of Light-Front Holography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins; Cao, Fu-Guang

2012-02-16

Light-Front Holography leads to a rigorous connection between hadronic amplitudes in a higher dimensional anti-de Sitter (AdS) space and frame-independent light-front wavefunctions of hadrons in 3 + 1 physical space-time, thus providing a compelling physical interpretation of the AdS/CFT correspondence principle and AdS/QCD, a useful framework which describes the correspondence between theories in a modified AdS5 background and confining field theories in physical space-time. To a first semiclassical approximation, where quantum loops and quark masses are not included, this approach leads to a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spinmore » and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate {zeta} which measures the separation of the constituents within a hadron at equal light-front time. The internal structure of hadrons is explicitly introduced and the angular momentum of the constituents plays a key role. We give an overview of the light-front holographic approach to strongly coupled QCD. In particular, we study the photon-to-meson transition form factors (TFFs) F{sub M{gamma}}(Q{sup 2}) for {gamma}{gamma}* {yields} M using light-front holographic methods. The results for the TFFs for the {eta} and {eta}' mesons are also presented. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates. A method for computing the hadronization of quark and gluon jets at the amplitude level is outlined.« less

A study on the consumer's perception of front-of-pack nutrition labeling

PubMed Central

Kim, Woo Kyoung

2009-01-01

The goal of this research is to investigate the present situation for front of pack labeling in Korea and the perception of consumers for the new system of labeling, front of pack labeling, based on the consumer survey. We investigated the number of processed foods with front of pack labeling in one retailer in Youngin-si. And we also surveyed 1,019 participants nationwide whose ages were from 20 to 49; the knowledge of nutrition labeling, the knowledge of 'front of pack labeling', and the opinion about the labeling system. The data were analyzed using SAS statistics program. The results were as follows: 13.4% of processed foods had front of pack labeling, and 16.8% of the consumers always checked the nutrition labeling, while 32.7% of the consumers seldom checked it. In addition, 44.3% of the consumers think that 'front of pack labeling' is necessary, and 58.3% of the consumers think it is important to show the percentage of daily value as a way of 'front of pack labeling'. However, 32% of the consumer think the possibility of 'front of pack labeling' is slim. Meanwhile, 58.3% of the consumers think that it is important to have the color difference according to contents. The number of favorite nutrients in the front of pack was four or five. It seems that the recognition of current nutrition labeling has the influence on the willingness of using the future 'front of pack labeling'. Along with our study, the policy for 'front of pack labeling' has to be updated and improved constantly since 'front of pack labeling' helps consumer understand nutrition facts. PMID:20098583

The Parkes front-end controller and noise-adding radiometer

NASA Technical Reports Server (NTRS)

Brunzie, T. J.

1990-01-01

A new front-end controller (FEC) was installed on the 64-m antenna in Parkes, Australia, to support the 1989 Voyager 2 Neptune encounter. The FEC was added to automate operation of the front-end microwave hardware as part of the Deep Space Network's Parkes-Canberra Telemetry Array. Much of the front-end hardware was refurbished and reimplemented from a front-end system installed in 1985 by the European Space Agency for the Uranus encounter; however, the FEC and its associated noise-adding radiometer (NAR) were new Jet Propulsion Laboratory (JPL) designs. Project requirements and other factors led to the development of capabilities not found in standard Deep Space Network (DSN) controllers and radiometers. The Parkes FEC/NAR performed satisfactorily throughout the Neptune encounter and was removed in October 1989.

Surgeon preparedness for mass casualty events: Adapting essential military surgical lessons for the home front.

PubMed

Remick, Kyle N; Shackelford, Stacy; Oh, John S; Seery, Jason M; Grabo, Daniel; Chovanes, John; Gross, Kirby R; Nessen, Shawn C; Tai, Nigel Rm; Rickard, Rory F; Elster, Eric; Schwab, C W

2016-01-01

Military surgeons have gained familiarity and experience with mass casualty events (MCEs) as a matter of routine over the course of the last two conflicts in Afghanistan and Iraq. Over the same period of time, civilian surgeons have increasingly faced complex MCEs on the home front. Our objective is to summarize and adapt these combat surgery lessons to enhance civilian surgeon preparedness for complex MCEs on the home front. The authors describe the unique lessons learned from combat surgery over the course of the wars in Afghanistan and Iraq and adapt these lessons to enhance civilian surgical readiness for a MCE on the home front. Military Damage Control Surgery (mDCS) combines the established concept of clinical DCS (cDCS) with key combat situational awareness factors that enable surgeons to optimally care for multiple, complex patients, from multiple simultaneous events, with limited resources. These additional considerations involve the surgeon's role of care within the deployed trauma system and the battlefield effects. The proposed new concept of mass casualty DCS (mcDCS) similarly combines cDCS decisions with key factors of situational awareness for civilian surgeons faced with complex MCEs to optimize outcomes. The additional considerations for a civilian MCE include the surgeon's role of care within the regional trauma system and the incident effects. Adapting institutionalized lessons from combat surgery to civilian surgical colleagues will enhance national preparedness for complex MCEs on the home front.

Energy conversion and dissipation at dipolarization fronts: Theory, modeling and MMS observations

NASA Astrophysics Data System (ADS)

Sitnov, M. I.; Motoba, T.; Merkin, V. G.; Ohtani, S.; Cohen, I. J.; Mauk, B.; Vines, S. K.; Anderson, B. J.; Moore, T. E.; Torbert, R. B.; Giles, B. L.; Burch, J. L.

2017-12-01

Magnetic reconnection is one of the most important energy conversion mechanisms in space plasmas. In the classical picture it converts the energy of antiparallel magnetic fields into the kinetic and thermal energy of accelerated plasma particles in reconnection exhausts. It also involves energy dissipation near the X-line. This classical picture may be substantially modified in real space plasma configurations, such as the dayside magnetopause and the magnetotail. In particular, in the magnetotail the flows of accelerated particles may be strongly asymmetric along the tail with the domination of earthward flows. At the same time, strong energy conversion and even dissipation may occur away from the X-line, in particular, at dipolarization fronts. Here we present a theoretical picture of spontaneous magnetotail reconnection based on 3-D PIC simulations with the focus on plasma bulk flows, energy conversion and dissipation. This picture is compared with some observations from the MMS tail season. An important finding from these observations is that dipolarizations fronts may not only be regions of the total energy conversion with jE>0, but they may also be the sites of energy dissipation, both positive (jE'>0, E' is the electric field E in the system moving with one of the plasma species) and negative (jE'<0). Observations are further compared with theory and modeling that predict the specific location and sign of the energy dissipation at fronts depending on their evolution phase (e.g., formation, propagation, braking).

Flow patterns and bathymetric signatures on the delta front of a prograding river delta

NASA Astrophysics Data System (ADS)

Shaw, J.; Mohrig, D. C.; Wagner, R. W.

2016-02-01

The transition of water between laterally confined channels and the unchannelized delta front controls the growth pattern of river deltas, but is difficult to measure on field-scale deltas. We quantify flow patterns, bathymetry and bathymetric evolution for the subaqueous delta front on the Wax Lake Delta (WLD), a rapidly prograding delta in coastal Louisiana. The flow direction field, mapped using streaklines composed of biogenic slicks on the water surface, shows that a significant portion of flow ( 59%) departs subaqueous channels laterally over the subaqueous margins of the channel seaward of the shoreline. Synoptic datasets of bathymetry and flow direction allow spatial changes in flow velocity to be quantified. Most lateral flow divergence and deceleration occurs within 3-8 channel widths outboard of subaqueous channel margins, rather than downstream of channel tips. In interdistributary bays, deposit elevation decreases with a basinward slope of 2.4 x 10-4 with distance from a channel margin along any flow path. Flow patterns and this slope produce constructional features called interdistributary troughs - topographic lows in the center of interdistributary bays. These data show that flow patterns and bathymetry on the delta front are coupled both at the transition from channelized to unchannelized flow and in the depositional regions outside the distributary network.

Open Boundary Particle-in-Cell Simulation of Dipolarization Front Propagation

NASA Technical Reports Server (NTRS)

Klimas, Alex; Hwang, Kyoung-Joo; Vinas, Adolfo F.; Goldstein, Melvyn L.

2014-01-01

First results are presented from an ongoing open boundary 2-1/2D particle-in-cell simulation study of dipolarization front (DF) propagation in Earth's magnetotail. At this stage, this study is focused on the compression, or pileup, region preceding the DF current sheet. We find that the earthward acceleration of the plasma in this region is in general agreement with a recent DF force balance model. A gyrophase bunched reflected ion population at the leading edge of the pileup region is reflected by a normal electric field in the pileup region itself, rather than through an interaction with the current sheet. We discuss plasma wave activity at the leading edge of the pileup region that may be driven by gradients, or by reflected ions, or both; the mode has not been identified. The waves oscillate near but above the ion cyclotron frequency with wavelength several ion inertial lengths. We show that the waves oscillate primarily in the perpendicular magnetic field components, do not propagate along the background magnetic field, are right handed elliptically (close to circularly) polarized, exist in a region of high electron and ion beta, and are stationary in the plasma frame moving earthward. We discuss the possibility that the waves are present in plasma sheet data, but have not, thus far, been discovered.

Wave-front propagation in a discrete model of excitable media

NASA Astrophysics Data System (ADS)

Feldman, A. B.; Chernyak, Y. B.; Cohen, R. J.

1998-06-01

correspondence between the shapes of the RD and CA spiral arms in the region away from the tip where kinematic theory applies. Our analysis suggests that only four physical parameters control the behavior of wave fronts in excitable media.

Desirable forest structures for a restored Front Range

Treesearch

Yvette L. Dickinson; Rob Addington; Greg Aplet; Mike Babler; Mike Battaglia; Peter Brown; Tony Cheng; Casey Cooley; Dick Edwards; Jonas Feinstein; Paula Fornwalt; Hal Gibbs; Megan Matonis; Kristen Pelz; Claudia Regan

2014-01-01

As part of the federal Collaborative Forest Landscape Restoration Program administered by the US Forest Service, the Colorado Front Range Collaborative Forest Landscape Restoration Project (FR-CFLRP, a collaborative effort of the Front Range Roundtable1 and the US Forest Service) is required to define desired conditions for lower montane ponderosa pine (Pinus ponderosa...

A Satellite View of a Back-door Cold Front

NASA Image and Video Library

2014-05-29

A "backdoor cold front" is bringing April temperatures to the U.S. northeast and Mid-Atlantic today, May 29. The backdoor cold front brings relief to the Mid-Atlantic after temperatures in Washington, D.C. hit 92F on Tuesday, May 27 and 88F on Wednesday, May 28 at Reagan National Airport, according to the National Weather Service (NWS). NWS forecasters expect the high temperature for May 29 to only reach 60F in the District of Columbia. NOAA's GOES-East satellite captured a view of the clouds associated with the backdoor cold front that stretch from southern Illinois to North Carolina. The National Weather Service forecast expects the backdoor cold front to bring showers to the Midwest, Northeast, and Mid-Atlantic today, May 29. According to the National Oceanic and Atmospheric Administration, a backdoor cold front is a cold front moving south or southwest along the Atlantic seaboard and Great Lakes; these are especially common during the spring months. This visible image was taken by NOAA's GOES-East satellite on May 29 at 12:30 UTC (8:30 a.m. EDT). The image was created at NASA/NOAA's GOES Project at NASA's Goddard Space Flight Center in Greenbelt, Maryland. In addition to the backdoor cold front clouds, the GOES-East image shows clouds circling around a low pressure area located in eastern Texas. That low pressure area is expected to bring rain from Texas eastward over the southeastern U.S. According to NOAA's National Weather Service, the slow-moving low pressure area in the Deep South "will bring heavy showers and thunderstorms from Louisiana to Alabama through Thursday. This area is already saturated from previous rainfall, so flash flooding will be possible." Image: NASA/NOAA GOES Project Caption: NASA Goddard/Rob Gutro

Case study of mesospheric front dissipation observed over the northeast of Brazil

NASA Astrophysics Data System (ADS)

Fragoso Medeiros, Amauri; Paulino, Igo; Wrasse, Cristiano Max; Fechine, Joaquim; Takahashi, Hisao; Valentin Bageston, José; Paulino, Ana Roberta; Arlen Buriti, Ricardo

2018-03-01

On 3 October 2005 a mesospheric front was observed over São João do Cariri (7.4° S, 36.5° W). This front propagated to the northeast and appeared in the airglow images on the west side of the observatory. By about 1.5 h later, it dissipated completely when the front crossed the local zenith. Ahead of the front, several ripple structures appeared during the dissipative process of the front. Using coincident temperature profile from the TIMED/SABER satellite and wind profiles from a meteor radar at São João do Cariri, the background of the atmosphere was investigated in detail. On the one hand, it was noted that a strong vertical wind shear in the propagation direction of the front produced by a semidiunal thermal tide was mainly responsible for the formation of duct (Doppler duct), in which the front propagated up to the zenith of the images. On the other hand, the evolution of the Richardson number as well as the appearance of ripples ahead of the main front suggested that a presence of instability in the airglow layer that did not allow the propagation of the front to the other side of the local zenith.

Front contact solar cell with formed electrically conducting layers on the front side and backside

DOEpatents

Cousins, Peter John

2012-06-26

A bipolar solar cell includes a backside junction formed by a silicon substrate and a first doped layer of a first dopant type on the backside of the solar cell. A second doped layer of a second dopant type makes an electrical connection to the substrate from the front side of the solar cell. A first metal contact of a first electrical polarity electrically connects to the first doped layer on the backside of the solar cell, and a second metal contact of a second electrical polarity electrically connects to the second doped layer on the front side of the solar cell. An external electrical circuit may be electrically connected to the first and second metal contacts to be powered by the solar cell.

How Do Density Fronts Interact with Zooplankton Distributions to Create Baleen Whale Prey-Fields in Roseway Basin?

NASA Astrophysics Data System (ADS)

Ruckdeschel, G.; Ross, T.; Davies, K. T. A.

2016-02-01

On the Scotian Shelf in the northwest Atlantic, Roseway Basin is a feeding ground for several species of large baleen whales, including the highly endangered North Atlantic right whale. In this habitat, aggregations of zooplankton must be present at concentrations high enough for baleen whales to obtain an energetic benefit. Regions of highly concentrated zooplankton are formed within the habitat through various biophysical interactions, such as fontal accumulation and retention. In Roseway Basin, humpback and fin whales prey on accumulated euphausiids, while right and sei whales forage for deep layers of Calanoid copepods. Right whales are found most often along the southeastern basin margin in Roseway, and this is also where density fronts occur and are associated with zooplankton patches that can form and disaggregate at tidal scales. The temporal persistence and biophysical mechanisms behind the observed interactions of zooplankton and frontal features have not been assessed. To understand how density fronts impact zooplankton distributions at the scale of feeding whales, we deployed Slocum gliders equipped with conductivity-temperature-depth sensors and echosounders in a series of cross-isobath transects along the sloped southeastern margin of Roseway Basin during August to November 2015. By looking for the presence of density fronts that are also regions of elevated acoustic backscatter (primarily from copepods and euphausiids) and quantifying their persistence over time, we aim to determine how these biophysical interactions create whale prey-fields.

Speed of pulled fronts with a cutoff

NASA Astrophysics Data System (ADS)

Benguria, R. D.; Depassier, M. C.

2007-05-01

We study the effect of a small cutoff γ on the velocity of a pulled front in one dimension by means of a variational principle. We obtain a lower bound on the speed dependent on the cutoff, for which the two leading order terms correspond to the Brunet-Derrida expression. To do so we cast a known variational principle for the speed of propagation of fronts in different variables which makes it more suitable for applications.

Stability of a Shock-Decelerated Ablation Front

DTIC Science & Technology

2009-01-01

the target through the ablation front. Our experiments on the Nike laser at the Naval Research Laboratory (NRL) are aimed at obtaining...separated from the CH foil by a 100-120 μm wide vacuum gap. The front side of the plastic foil is irradiated by 37 overlapping beams of the Nike ...krypton fluoride laser ( 248=Lλ nm) [19]. The Nike laser produces a very uniform irradiation with a time-averaged rms non-uniformity ɘ.3% in a central

2. EXTERIOR FRONT (SOUTHEAST) SIDE OF BUILDING 117 SHOWING MAIN ...

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

2. EXTERIOR FRONT (SOUTHEAST) SIDE OF BUILDING 117 SHOWING MAIN RESIDENTIAL STREET IN LOWER FOREGROUND, CEMENT-LAID ROCK RETAINING WALL IN FRONT OF HOUSE, AND CONCRETE STEPS AND WALKWAY TO FRONT PORCH AND DOOR. NOTE SLIDING GLASS DOOR REPLACEMENT FOR ORIGINAL DOOR WHICH HAS SUBSEQUENTLY BEEN REMODELED BACK TO A SINGLE ENTRY DOOR. VIEW TO NORTHWEST. - Bishop Creek Hydroelectric System, Plant 4, Worker Cottage, Bishop Creek, Bishop, Inyo County, CA

How Obstacles Perturb Population Fronts and Alter Their Genetic Structure.

PubMed

Möbius, Wolfram; Murray, Andrew W; Nelson, David R

2015-12-01

As populations spread into new territory, environmental heterogeneities can shape the population front and genetic composition. We focus here on the effects of an important building block of heterogeneous environments, isolated obstacles. With a combination of experiments, theory, and simulation, we show how isolated obstacles both create long-lived distortions of the front shape and amplify the effect of genetic drift. A system of bacteriophage T7 spreading on a spatially heterogeneous Escherichia coli lawn serves as an experimental model system to study population expansions. Using an inkjet printer, we create well-defined replicates of the lawn and quantitatively study the population expansion of phage T7. The transient perturbations of the population front found in the experiments are well described by a model in which the front moves with constant speed. Independent of the precise details of the expansion, we show that obstacles create a kink in the front that persists over large distances and is insensitive to the details of the obstacle's shape. The small deviations between experimental findings and the predictions of the constant speed model can be understood with a more general reaction-diffusion model, which reduces to the constant speed model when the obstacle size is large compared to the front width. Using this framework, we demonstrate that frontier genotypes just grazing the side of an isolated obstacle increase in abundance, a phenomenon we call 'geometry-enhanced genetic drift', complementary to the founder effect associated with spatial bottlenecks. Bacterial range expansions around nutrient-poor barriers and stochastic simulations confirm this prediction. The effect of the obstacle on the genealogy of individuals at the front is characterized by simulations and rationalized using the constant speed model. Lastly, we consider the effect of two obstacles on front shape and genetic composition of the population illuminating the effects expected from

How Obstacles Perturb Population Fronts and Alter Their Genetic Structure

PubMed Central

Möbius, Wolfram; Murray, Andrew W.; Nelson, David R.

2015-01-01

As populations spread into new territory, environmental heterogeneities can shape the population front and genetic composition. We focus here on the effects of an important building block of heterogeneous environments, isolated obstacles. With a combination of experiments, theory, and simulation, we show how isolated obstacles both create long-lived distortions of the front shape and amplify the effect of genetic drift. A system of bacteriophage T7 spreading on a spatially heterogeneous Escherichia coli lawn serves as an experimental model system to study population expansions. Using an inkjet printer, we create well-defined replicates of the lawn and quantitatively study the population expansion of phage T7. The transient perturbations of the population front found in the experiments are well described by a model in which the front moves with constant speed. Independent of the precise details of the expansion, we show that obstacles create a kink in the front that persists over large distances and is insensitive to the details of the obstacle’s shape. The small deviations between experimental findings and the predictions of the constant speed model can be understood with a more general reaction-diffusion model, which reduces to the constant speed model when the obstacle size is large compared to the front width. Using this framework, we demonstrate that frontier genotypes just grazing the side of an isolated obstacle increase in abundance, a phenomenon we call ‘geometry-enhanced genetic drift’, complementary to the founder effect associated with spatial bottlenecks. Bacterial range expansions around nutrient-poor barriers and stochastic simulations confirm this prediction. The effect of the obstacle on the genealogy of individuals at the front is characterized by simulations and rationalized using the constant speed model. Lastly, we consider the effect of two obstacles on front shape and genetic composition of the population illuminating the effects

Evolution of the shock front and turbulence structures in the shock/turbulence interaction

NASA Technical Reports Server (NTRS)

Kevlahan, N.; Mahesh, K.; Lee, S.

1992-01-01

The interaction of a weak shock front with isotropic turbulence has been investigated using Direct Numerical Simulation (DNS). Two problems were considered: the ability of the field equation (the equation for a propagating surface) to model the shock; and a quantitative study of the evolution of turbulence structure using the database generated by Lee et al. Field equation model predictions for front shape have been compared with DNS results; good agreement is found for shock wave interaction with 2D turbulence and for a single steady vorticity wave. In the interaction of 3D isotropic turbulence with a normal shock, strong alignment of vorticity with the intermediate eigenvector of the rate of strain tensor (S(sup *)(sub ij) = S(sub ij) - (1/3)(delta(sub ij))(S(sub kk))) is seen to develop upstream of the shock and to be further amplified on passage through the shock. Vorticity tends to align at 90 deg to the largest eigenvector, but there is no preferred alignment with the smallest eigenvector. Upstream of the shock, the alignments continue to develop even after the velocity derivative skewness saturates. There is a significant tendency, which increases with time throughout the computational domain, for velocity to align with vorticity. The alignment between velocity and vorticity is strongest in eddy regions and weakest in convergence regions.

Have pedestrian subsystem tests improved passenger car front shape?

PubMed

Li, Guibing; Wang, Fang; Otte, Dietmar; Cai, Zhihua; Simms, Ciaran

2018-06-01

Subsystem impactor tests are the main approaches for evaluation of safety performance of vehicle front design for pedestrian protection in legislative regulations. However, the main aspects of vehicle safety for pedestrians are shape and stiffness, and though it is clear that subsystem impact tests encourage lower vehicle front stiffness, it is unclear whether they promote improved vehicle front shapes for pedestrian protection. The purpose of this paper is therefore to investigate the effects of European pedestrian safety regulations on passenger car front shape and pedestrian injury risk using recent German In-Depth Accident Study (GIDAS) pedestrian collision data and numerical simulations. Firstly, a sample of 579 pedestrian collision cases involving 190 different car models between 2000-2015 extracted from the GIDAS was used to compare front-end shapes of passenger cars manufactured before and after the legislative pedestrian safety regulations were introduced in Europe. The focus was on changes in passenger car front shape and differences in pedestrian AIS2+ (Abbreviated Injury Scale at least level 2) leg, pelvis/femur and head injury risk observed in collisions. Multi-body simulations were also used to assess changes in vehicle aggressivity due to the observed changes in vehicle shape. The results show that newer passenger cars tend to have a flatter and wider bumper, higher bonnet leading edge, shorter and steeper bonnet and a shallower windscreen. Both the collision data and the numerical simulations indicate that newer passenger car front bumper designs are significantly safer for pedestrians' legs. However, the results also show that the higher bonnet leading edge in newer passenger cars is poor for pedestrian pelvis/femur protection, even though newer cars show an obviously lower AIS2+ injury risk to younger pedestrians in collisions. Newer cars have a lower AIS2+ head injury risk for pedestrians in collisions, but the numerical analysis indicate that

Multiple stable isotope fronts during non-isothermal fluid flow

NASA Astrophysics Data System (ADS)

Fekete, Szandra; Weis, Philipp; Scott, Samuel; Driesner, Thomas

2018-02-01

Stable isotope signatures of oxygen, hydrogen and other elements in minerals from hydrothermal veins and metasomatized host rocks are widely used to investigate fluid sources and paths. Previous theoretical studies mostly focused on analyzing stable isotope fronts developing during single-phase, isothermal fluid flow. In this study, numerical simulations were performed to assess how temperature changes, transport phenomena, kinetic vs. equilibrium isotope exchange, and isotopic source signals determine mineral oxygen isotopic compositions during fluid-rock interaction. The simulations focus on one-dimensional scenarios, with non-isothermal single- and two-phase fluid flow, and include the effects of quartz precipitation and dissolution. If isotope exchange between fluid and mineral is fast, a previously unrecognized, significant enrichment in heavy oxygen isotopes of fluids and minerals occurs at the thermal front. The maximum enrichment depends on the initial isotopic composition of fluid and mineral, the fluid-rock ratio and the maximum change in temperature, but is independent of the isotopic composition of the incoming fluid. This thermally induced isotope front propagates faster than the signal related to the initial isotopic composition of the incoming fluid, which forms a trailing front behind the zone of transient heavy oxygen isotope enrichment. Temperature-dependent kinetic rates of isotope exchange between fluid and rock strongly influence the degree of enrichment at the thermal front. In systems where initial isotope values of fluids and rocks are far from equilibrium and isotope fractionation is controlled by kinetics, the temperature increase accelerates the approach of the fluid to equilibrium conditions with the host rock. Consequently, the increase at the thermal front can be less dominant and can even generate fluid values below the initial isotopic composition of the input fluid. As kinetics limit the degree of isotope exchange, a third front may

Charged Particle Distribution near the Shock Front in a Glow Discharge

NASA Astrophysics Data System (ADS)

Baryshnikov, A. S.; Basargin, I. V.; Bezverkhnii, N. O.; Bobashev, S. V.; Monakhov, N. A.; Popov, P. A.; Sakharov, V. A.; Chistyakova, M. V.

2018-02-01

The charged particle distribution near the front of a shock wave propagating in the glow discharge plasma has been investigated. It has been found that the ion concentration before the front varies nonmonotonically. Behind the shock front, the charged particle concentration varies smoothly in contrast to the neutral component density.

Varying Indian crustal front in the southern Tibetan Plateau as revealed by magnetotelluric data

NASA Astrophysics Data System (ADS)

Xie, Chengliang; Jin, Sheng; Wei, Wenbo; Ye, Gaofeng; Zhang, Letian; Dong, Hao; Yin, Yaotian

2017-10-01

In the southern Tibetan plateau, which is considered to be the ongoing India-Eurasia continental collision zone, tracing of the Indian crustal front beneath Tibet is still controversial. We conducted deep subsurface electrical modeling in southern Tibet and discuss the geometry of the front of the Indian crust. Three areas along the Yarlung-Zangbo river zone for which previous magnetotelluric (MT) data are available were inverted independently using a three-dimensional MT inversion algorithm ModEM. Electrical horizontal slices at different depths and north-south oriented cross sections at different longitudes were obtained to provide a geoelectrical perspective for deep processes beneath the Tethyan Himalaya and Lhasa terrane. Horizontal slices at depths greater than - 15 km show that the upper crust is covered with resistive layers. Below a depth of - 20 km, discontinuous conductive distributions are primarily concentrated north of the Yarlung-Zangbo sutures (YZS) and could be imaged from mid- to lower crust. The results show that the maximum depth to which the resistive layers extend is over - 20 km, while the mid- to lower crustal conductive zones extend to depths greater than - 50 km. The results indicate that the conductive region in the mid- to lower crust can be imaged primarily from the YZS to south of the Bangong-Nujiang sutures in western Tibet and to 31°N in eastern Tibet. The northern front of the conductive zones appears as an irregular barrier to the Indian crust from west to east. We suggest that a relatively less conductive subsurface in the northern portion of the barrier indicates a relatively cold and strong crust and that the front of the Indian crust might be halted in the south of the barrier. We suggest that the Indian crustal front varies from west to east and has at least reached: 33.5°N at 80°E, 31°N at 85°E, and 30.5°N at 87°E and 92°E.[Figure not available: see fulltext.

Kinetics of a plasma streamer ionization front

NASA Astrophysics Data System (ADS)

Taccogna, Francesco; Pellegrini, Fabrizio

2018-02-01

A streamer is a non-linear and non-local gas breakdown mode. Its large-scale coherent structures, such as the ionization front, are the final results of a hierarchical cascade starting from the single particle dynamics. Therefore, this phenomenon covers, by definition, different space and time scales. In this study, we have reproduced the ionization front formation and development by means of a particle-based numerical methodology. The physical system investigated concerns of a high-voltage ns-pulsed surface dielectric barrier discharge. Different reduced electric field regimes ranging from 50 to 500 Td have been considered for two gases: pure atomic Ar and molecular N2. Results have shown the detailed structure of the negative streamer: the leading edge, the head, the interior and the tail. Its dynamical evolution and the front propagation velocity have been calculated for the different cases. Finally, the deviation of the electron energy distribution function from equilibrium behavior has been pointed out as a result of a fast and very localized phenomenon.

Observations of phytoplankton spring bloom onset triggered by a density front in NW Mediterranean

NASA Astrophysics Data System (ADS)

Olita, A.; Sparnocchia, S.; Cusí, S.; Fazioli, L.; Sorgente, R.; Tintoré, J.; Ribotti, A.

2013-09-01

Phytoplankton bloom in NW Mediterranan sea is a seasonal event that mainly occurrs in a limited area (Gulf of Lyon and Provençal basin) where this phenomenon is promoted by a cyclonic circulation, strong wind-driven mixing and subsequent spring restratification. At the southern boundary of this area a density front (North Balearic Front) separating denser waters from the lighter Modified Atlantic Waters reservoir at south is suspected to trigger weaker and earlier (late winter) blooms by (a) enhanced pumping of nutrients into the euphotic layer and (b) promoting an early restratification of the water column (by frontal instabilities). A multisensor glider round trip, equipped with CTD and fluorimeter, crossing the frontal area in February-March 2013, allowed to observe the bloom triggering after the decrease of intense wind-driven turbulent convection and mixing. Satellite imagery supports and confirms in-situ observations. It was shown that frontal activity has a relevant role in the promotion and acceleration of the dynamical restratification, with a consequent biological response in terms of primary production. Restratification is necessary preconditioning factor for bloom triggering in frontal area, net of other involved mechanism promoting the bloom as the enhanced biological pump. So, like for high-latitude fronts (Taylor and Ferrari, 2011a), also for this mid-latitude oligotrophic region front seems to promote new production by dynamically enahnced restratification inhibiting mixing. Finally, we argued that Sverdrup's Critical Depth criterion seems to apply in the northern well-mixed area, where the zeroing of heat fluxes (and related turbulent convection) does not correspond to a prompt onset of the bloom (which appeared 1 month later).

Age Appropriate Restraints for the Right Front Passenger

PubMed Central

Augenstein, J; Perdeck, E.; Digges, K.; Bahouth, G.

2007-01-01

This study applies NASS/CDS, GES and FARS data to examine occupant exposure plus injury and fatality rates for belted occupants in frontal crashes by seating position, age and gender. The NASS data was used to examine the distributions by crash severity. The GES data showed that when two elderly occupants (age 65+) were present, the female occupied the right front passenger position 73% of the time. A paired comparison analysis using FARS data showed that, for elderly occupants (age 65+), the fatality risk for elderly right front passengers is 42% higher than for elderly drivers. The NASS/CDS analysis found 74% of the seriously injured vulnerable passengers with MAIS 3+ injuries were in crashes less severe than 26 mph. This group of injured occupants was made up of 43% aged 50 and older and 42% younger females. The injury rates for the older (age 50+) right front passengers were 1.8 times the rates for the elderly drivers. These results suggest the need for more benign safety systems for the right front passenger that are appropriate for the lower injury tolerance of the predominant occupants of that seating position. PMID:18184503

The split in the ancient cold front in the Perseus cluster

NASA Astrophysics Data System (ADS)

Walker, Stephen A.; ZuHone, John; Fabian, Andy; Sanders, Jeremy

2018-04-01

Sloshing cold fronts in clusters, produced as the dense cluster core moves around in the cluster potential in response to in-falling subgroups, provide a powerful probe of the physics of the intracluster medium and the magnetic fields permeating it1,2. These sharp discontinuities in density and temperature rise gradually outwards with age in a characteristic spiral pattern, embedding into the intracluster medium a record of the minor merging activity of clusters: the further from the cluster centre a cold front is, the older it is. Recently, it was discovered that these cold fronts can survive out to extremely large radii in the Perseus cluster3. Here, we report on high-spatial-resolution Chandra observations of the large-scale cold front in Perseus. We find that rather than broadening through diffusion, the cold front remains extremely sharp (consistent with abrupt jumps in density) and instead is split into two sharp edges. These results show that magnetic draping can suppress diffusion for vast periods of time—around 5 Gyr—even as the cold front expands out to nearly half the cluster virial radius.

5. AERIAL VIEW, FROM NORTH, SHOWING ROOF OF CARPENTER'S FRONT ...

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

5. AERIAL VIEW, FROM NORTH, SHOWING ROOF OF CARPENTER'S FRONT STORE AND CARPENTER'S HALL IN CENTER BACKGROUND - Carpenters' Company, Front Store, 322 Chestnut Street & Carpenters' Court, Philadelphia, Philadelphia County, PA

Sequential deconvolution from wave-front sensing using bivariate simplex splines

NASA Astrophysics Data System (ADS)

Guo, Shiping; Zhang, Rongzhi; Li, Jisheng; Zou, Jianhua; Xu, Rong; Liu, Changhai

2015-05-01

Deconvolution from wave-front sensing (DWFS) is an imaging compensation technique for turbulence degraded images based on simultaneous recording of short exposure images and wave-front sensor data. This paper employs the multivariate splines method for the sequential DWFS: a bivariate simplex splines based average slopes measurement model is built firstly for Shack-Hartmann wave-front sensor; next, a well-conditioned least squares estimator for the spline coefficients is constructed using multiple Shack-Hartmann measurements; then, the distorted wave-front is uniquely determined by the estimated spline coefficients; the object image is finally obtained by non-blind deconvolution processing. Simulated experiments in different turbulence strength show that our method performs superior image restoration results and noise rejection capability especially when extracting the multidirectional phase derivatives.

A Detailed Analysis of Frontal Precipitation in a Decadal Convection-Resolving Regional Climate Simulation over Europe

NASA Astrophysics Data System (ADS)

Ruedisuehli, S.; Sprenger, M.; Leutwyler, D.; Schar, C.; Wernli, H.

2017-12-01

We study fronts and precipitation in a decadal continental-scale convection-resolving (2.2 km) regional climate simulation over Europe, which has been conducted using a GPU-enabled version of the COSMO model. Resolving convection substantially improves the representation of precipitation, e.g., the diurnal cycle of summer convection or organization of convection along fronts, while the large domain is able to represent most synoptic fronts affecting Europe with their full spatial extent. Studying nine years of the simulation, we present climatological results of how precipitation relates to fronts both structurally and quantitatively, and address seasonal, regional, and diurnal effects. Cold and warm fronts are identified at hourly intervals based on horizontal gradients of equivalent potential temperature on 850 hPa. We track the frontal areas using a new feature tracking algorithm, which accounts for mergings and splittings and supports complex tracks.Based on track properties, we separate synoptic and local fronts. The latter mostly form along orography and coasts during summer. While the resulting front climatology is already valuable, we exploit the full potential of the simulation by relating fronts to precipitation. We subdivide the domain at every timestep into pre-, at-, post-, and non-frontal areas by considering at every grid point the time since the latest and until the next frontal passage (separately for cold and warm fronts). This allows, for the first time, to disaggregate the precipitation field into front-related components, and to quantify the influence of fronts on both regular and extreme precipitation throughout the domain. To investigate the average structure of precipitation across fronts, we composite precipitation relative to the time of frontal passage. This approach reveals characteristic properties of the precipitation distribution across fronts. The Figure shows the mean across-front distribution of precipitation, separated into

Resident Front Office Experience: A Systems-Based Practice Activity

PubMed Central

Sutkin, Gary; Aronoff, Christine K.

2008-01-01

Purpose: We set out to create and evaluate a systems-based practice experience designed to introduce residents to front office responsibilities and stimulate suggestions for front office improvements. Methods: On two occasions in 2002 and 2006, each resident in the Obstetrics and Gynecology Department was trained by a front office staff member for one day. The residents completed pre- and post-experience surveys, answered open-ended questions about their experience, and volunteered suggestions for improving the front office staff, and were evaluated by their precepting staff member. Results: All but two of 23 particpating residents participated enthusiastically. These residents perceived experiencing the staff as vital to the success of the practice, reported an increased sense of appreciation for the training of staff personnel, and were evaluated favorably. Conclusion: This program gave our residents an appreciation for the training and responsibilities of pivotal office staff and an opportunity to suggest improvements. This program also satisfied ACGME resident education requirements regarding systems-based practice. PMID:20165536

Modelling larval transport in a axial convergence front

NASA Astrophysics Data System (ADS)

Robins, P.

2010-12-01

Marine larvae exhibit different vertical swimming behaviours, synchronised by factors such as tidal currents and daylight, in order to aid retention near the parent populations and hence promote production, avoid predation, or to stimulate digestion. This paper explores two types of larval migration in an estuarine axial convergent front which is an important circulatory mechanism in many coastal regions where larvae are concentrated. A parallelised, three-dimensional, ocean model was applied to an idealised estuarine channel which was parameterised from observations of an axial convergent front which occurs in the Conwy Estuary, U.K. (Nunes and Simpson, 1985). The model successfully simulates the bilateral cross-sectional recirculation of an axial convergent front, which has been attributed to lateral density gradients established by the interaction of the lateral shear of the longitudinal currents with the axial salinity gradients. On the flood tide, there is surface axial convergence whereas on the ebb tide, there is (weaker) surface divergence. Further simulations with increased/decreased tidal velocities and with stronger/weaker axial salinity gradients are planned so that the effects of a changing climate on the secondary flow can be understood. Three-dimensional Lagrangian Particle Tracking Models (PTMs) have been developed which use the simulated velocity fields to track larvae in the estuarine channel. The PTMs take into account the vertical migrations of two shellfish species that are commonly found in the Conwy Estuary: (i) tidal migration of the common shore crab (Carcinus maenas) and (ii), diel (daily) migration of the Great scallop (Pecten maximus). These migration behaviours are perhaps the most widespread amongst shellfish larvae and have been compared with passive (drifting) particles in order to assess their relative importance in terms of larval transport. Preliminary results suggest that the net along-estuary dispersal over a typical larval

Characterization and effects of cold fronts in the Colombian Caribbean Coast and their relationship to extreme wave events

NASA Astrophysics Data System (ADS)

Ortiz-Royero, J. C.; Otero, L. J.; Restrepo, J. C.; Ruiz, J.; Cadena, M.

2013-07-01

Extreme ocean waves in the Caribbean Sea are commonly related to the effects of storms and hurricanes during the months of June through November. The collapse of 200 m of the Puerto Colombia pier in March 2009 revealed the effects of meteorological phenomena other than storms and hurricanes that may be influencing the extreme wave regime in the Colombian Caribbean. The marked seasonality of these atmospheric fronts was established by analyzing the meteorological-marine reports of Instituto de Hidrología, Meteorología y Estudios Ambientales of Colombia (IDEAM, based on its initials in Spanish) and Centro de Investigación en Oceanografía y Meteorología of Colombia (CIOH, based on its initials in Spanish). The highest occurrences were observed during the months of January, February, and March, with 6 fronts occurring per year. An annual trend was not observed, although the highest number of fronts occurred in 2010 (20 in total). An annual strong relationship between the maximum average wave values and the cold fronts, in the central zone of the Colombian Caribbean during the first three months of the year was established. In addition, the maximum values of the significant height produced by the passage of cold fronts during the last 16 yr were identified. Although the Colombian Caribbean has been affected by storms and hurricanes in the past, this research allows us to conclude that, there is a strong relationship between cold fronts and the largest waves in the Colombian Caribbean during the last 16 yr, which have caused damage to coastal infrastructure. We verified that the passage of a cold front corresponded to the most significant extreme wave event of the last two decades in the Colombian Caribbean, which caused the structural collapse of the Puerto Colombia pier, located near the city of Barranquilla, between 5 and 10 March 2009. This information is invaluable when evaluating average and extreme wave regimes for the purpose of informing the design of

Influence of the tidal front on the three-dimensional distribution of spring phytoplankton community in the eastern Yellow Sea.

PubMed

Choi, Byoung-Ju; Lee, Jung A; Choi, Jae-Sung; Park, Jong-Gyu; Lee, Sang-Ho; Yih, Wonho

2017-04-01

Hydrographic observation and biological samplings were conducted to assess the distribution of phytoplankton community over the sloping shelf of the eastern Yellow Sea in May 2012. The concentration of chlorophyll a was determined and phytoplankton was microscopically examined to conduct quantitative and cluster analyses. A cluster analysis of the phytoplankton species and abundance along four observation lines revealed the three-dimensional structure of the phytoplankton community distribution: the coastal group in the mixed region, the offshore upper layer group preferring stable water column, and the offshore lower layer group. The subsurface maximum of phytoplankton abundance and chlorophyll a concentration appeared as far as 64 km away from the tidal front through the middle layer intrusion. The phytoplankton abundance was high in the shore side of tidal front during the spring tide. The phytoplankton abundance was relatively high at 10-m depth in the mixed region while the concentration of chlorophyll a was high below the depth. The disparity between the profiles of the phytoplankton abundance and the chlorophyll a concentration in the mixed region was related to the depth-dependent species change accompanied by size-fraction of the phytoplankton community. Copyright © 2017 Elsevier Ltd. All rights reserved.

Use of Glacial Fronts by Narwhals (Monodon monoceros) in West Greenland

NASA Astrophysics Data System (ADS)

Laidre, K. L.

2015-12-01

Glacial fronts in Greenland are known to be important summer habitat for narwhals (Monodon monoceros), as freshwater runoff and sediment discharge may aggregate prey at the terminus. We investigated the importance of glacial habitat characteristics in determining narwhal visitation. Narwhals (n=18) were instrumented with satellite transmitters in September 1993-1994 and 2006-2007 in Melville Bay, West Greenland. Daily narwhal locations were interpolated using a correlated random walk based on observed filtered locations and associated positional error. We also compiled a database on physical features of 41 glaciers along the northwest Greenland coast. This covered the entire coastal region with narwhal activity. Parameters included glacier ice velocity (km/yr) from radar satellite data, glacier front advance and retreat, and glacier width (km) at the ice-ocean interface derived using front position data digitized from 20-100m resolution radar image mosaics and Landsat imagery. We also quantified relative volumes and extent of glacial ice discharge, thickness of the glacial ice at the terminus (m), and water depth at the terminus (m) from gravity and airborne radar data, sediment flux from satellite-based analysis, and freshwater runoff from a regional atmospheric climate model (RACMO2.3). We quantified whale visits to glaciers at three distances (5, 7, and 10 km) and conducted proximity analyses on annual and monthly time steps. We estimated 1) narwhal presence or absence, 2) the number of 24 h periods spent at glaciers, and 3) the fraction of study animals that visited each glacier. The use of glacial habitat by narwhals expanded to the north and south between the 1990s (n=9 unique glaciers visited) and the 2000s (n=30 visited), likely due to loss of summer fast ice and later fall freeze-up trends (3.5 weeks later since 1979). We used a generalized linear mixed effects framework to quantify the glacier and fjord habitat characteristics preferred by narwhals.

Holocene behavior of the Brigham City segment: implications for forecasting the next large-magnitude earthquake on the Wasatch fault zone, Utah

USGS Publications Warehouse

Personius, Stephen F.; DuRoss, Christopher B.; Crone, Anthony J.

2012-01-01

The Brigham City segment (BCS), the northernmost Holocene‐active segment of the Wasatch fault zone (WFZ), is considered a likely location for the next big earthquake in northern Utah. We refine the timing of the last four surface‐rupturing (~Mw 7) earthquakes at several sites near Brigham City (BE1, 2430±250; BE2, 3490±180; BE3, 4510±530; and BE4, 5610±650 cal yr B.P.) and calculate mean recurrence intervals (1060–1500  yr) that are greatly exceeded by the elapsed time (~2500  yr) since the most recent surface‐rupturing earthquake (MRE). An additional rupture observed at the Pearsons Canyon site (PC1, 1240±50 cal yr B.P.) near the southern segment boundary is probably spillover rupture from a large earthquake on the adjacent Weber segment. Our seismic moment calculations show that the PC1 rupture reduced accumulated moment on the BCS about 22%, a value that may have been enough to postpone the next large earthquake. However, our calculations suggest that the segment currently has accumulated more than twice the moment accumulated in the three previous earthquake cycles, so we suspect that additional interactions with the adjacent Weber segment contributed to the long elapse time since the MRE on the BCS. Our moment calculations indicate that the next earthquake is not only overdue, but could be larger than the previous four earthquakes. Displacement data show higher rates of latest Quaternary slip (~1.3  mm/yr) along the southern two‐thirds of the segment. The northern third likely has experienced fewer or smaller ruptures, which suggests to us that most earthquakes initiate at the southern segment boundary.

Dr. von Braun In Front of a Display of Missiles

NASA Technical Reports Server (NTRS)

1960-01-01

In this photo, Director of the US Army Ballistic Missile Agency (ABMA) Development Operations Division, Dr. Wernher von Braun, is standing before a display of Army missiles celebrating ABMA's Fourth Open House. The missiles in the background include (left to right) a satellite on a Juno II shroud with a Nike Ajax pointing left in front of a Jupiter missile. The Lacrosse is in front of the Juno II. The Nike Hercules points skyward in front of the Juno II and the Redstone.

EVIDENCE OF FAST PEBBLE GROWTH NEAR CONDENSATION FRONTS IN THE HL TAU PROTOPLANETARY DISK

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Ke; Blake, Geoffrey A.; Bergin, Edwin A., E-mail: kzhang@astro.caltech.edu

2015-06-10

Water and simple organic molecular ices dominate the mass of solid materials available for planetesimal and planet formation beyond the water snow line. Here we analyze ALMA long baseline 2.9, 1.3 and 0.87 mm continuum images of the young star HL Tau, and suggest that the emission dips observed are due to rapid pebble growth around the condensation fronts of abundant volatile species. Specifically, we show that the prominent innermost dip at 13 AU is spatially resolved in the 0.87 mm image, and its center radius is coincident with the expected mid-plane condensation front of water ice. In addition, twomore » other prominent dips, at distances of 32 and 63 AU, cover the mid-plane condensation fronts of pure ammonia or ammonia hydrates and clathrate hydrates (especially with CO and N{sub 2}) formed from amorphous water ice. The spectral index map of HL Tau between 1.3 and 0.87 mm shows that the flux ratios inside the dips are statistically larger than those of nearby regions in the disk. This variation can be explained by a model with two dust populations, where most of the solid mass resides in a component that has grown to decimeter size scales inside the dips. Such growth is in accord with recent numerical simulations of volatile condensation, dust coagulation, and settling.« less

Light-front field theory in the description of hadrons

NASA Astrophysics Data System (ADS)

Ji, Chueng-Ryong

2017-03-01

We discuss the use of light-front field theory in the descriptions of hadrons. In particular, we clarify the confusion in the prevailing notion of the equivalence between the infinite momentum frame and the light-front dynamics and the advantage of the light-front dynamics in hadron physics. As an application, we present our recent work on the flavor asymmetry in the proton sea and identify the presence of the delta-function contributions associated with end-point singularities arising from the chiral effective theory calculation. The results pave the way for phenomenological applications of pion cloud models that are manifestly consistent with the chiral symmetry properties of QCD.

Synoptic-to-planetary scale wind variability enhances phytoplankton biomass at ocean fronts

NASA Astrophysics Data System (ADS)

Whitt, D. B.; Taylor, J. R.; Lévy, M.

2017-06-01

In nutrient-limited conditions, phytoplankton growth at fronts is enhanced by winds, which drive upward nutrient fluxes via enhanced turbulent mixing and upwelling. Hence, depth-integrated phytoplankton biomass can be 10 times greater at isolated fronts. Using theory and two-dimensional simulations with a coupled physical-biogeochemical ocean model, this paper builds conceptual understanding of the physical processes driving upward nutrient fluxes at fronts forced by unsteady winds with timescales of 4-16 days. The largest vertical nutrient fluxes occur when the surface mixing layer penetrates the nutricline, which fuels phytoplankton in the mixed layer. At a front, mixed layer deepening depends on the magnitude and direction of the wind stress, cross-front variations in buoyancy and velocity at the surface, and potential vorticity at the base of the mixed layer, which itself depends on past wind events. Consequently, mixing layers are deeper and more intermittent in time at fronts than outside fronts. Moreover, mixing can decouple in time from the wind stress, even without other sources of physical variability. Wind-driven upwelling also enhances depth-integrated phytoplankton biomass at fronts; when the mixed layer remains shallower than the nutricline, this results in enhanced subsurface phytoplankton. Oscillatory along-front winds induce both oscillatory and mean upwelling. The mean effect of oscillatory vertical motion is to transiently increase subsurface phytoplankton over days to weeks, whereas slower mean upwelling sustains this increase over weeks to months. Taken together, these results emphasize that wind-driven phytoplankton growth is both spatially and temporally intermittent and depends on a diverse combination of physical processes.

Security Station and Front Entrance to hospital property, looking northeast ...

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

Security Station and Front Entrance to hospital property, looking northeast - U.S. Veterans Hospital, Jefferson Barracks, Security Station & Front Gate, VA Medical Center, Jefferson Barracks Division 1 Jefferson Barracks Drive, Saint Louis, Independent City, MO

Multidimensional stability of traveling fronts in combustion and non-KPP monostable equations

NASA Astrophysics Data System (ADS)

Bu, Zhen-Hui; Wang, Zhi-Cheng

2018-02-01

This paper is concerned with the multidimensional stability of traveling fronts for the combustion and non-KPP monostable equations. Our study contains two parts: in the first part, we first show that the two-dimensional V-shaped traveling fronts are asymptotically stable in R^{n+2} with n≥1 under any (possibly large) initial perturbations that decay at space infinity, and then, we prove that there exists a solution that oscillates permanently between two V-shaped traveling fronts, which implies that even very small perturbations to the V-shaped traveling front can lead to permanent oscillation. In the second part, we establish the multidimensional stability of planar traveling front in R^{n+1} with n≥1.

Reduction of front-metallization grid shading in concentrator cells through laser micro-grooved cover glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

García-Linares, Pablo, E-mail: pablo.garcia-linares@cea.fr; Voarino, Philippe; Besson, Pierre

2015-09-28

Concentrator solar cell front-grid metallizations are designed so that the trade-off between series resistance and shading factor (SF) is optimized for a particular irradiance. High concentrator photovoltaics (CPV) typically requires a metallic electrode pattern that covers up to 10% of the cell surface. The shading effect produced by this front electrode results in a significant reduction in short-circuit current (I{sub SC}) and hence, in a significant efficiency loss. In this work we present a cover glass (originally meant to protect the cell surface) that is laser-grooved with a micrometric pattern that redirects the incident solar light towards interfinger regions andmore » away from the metallic electrodes, where they would be wasted in terms of photovoltaic generation. Quantum efficiency (QE) and current (I)-voltage (V) characterization under concentration validate the proof-of-concept, showing great potential for CPV applications.« less

Virulence evolution at the front line of spreading epidemics.

PubMed

Griette, Quentin; Raoul, Gaël; Gandon, Sylvain

2015-11-01

Understanding and predicting the spatial spread of emerging pathogens is a major challenge for the public health management of infectious diseases. Theoretical epidemiology shows that the speed of an epidemic is governed by the life-history characteristics of the pathogen and its ability to disperse. Rapid evolution of these traits during the invasion may thus affect the speed of epidemics. Here we study the influence of virulence evolution on the spatial spread of an epidemic. At the edge of the invasion front, we show that more virulent and transmissible genotypes are expected to win the competition with other pathogens. Behind the front line, however, more prudent exploitation strategies outcompete virulent pathogens. Crucially, even when the presence of the virulent mutant is limited to the edge of the front, the invasion speed can be dramatically altered by pathogen evolution. We support our analysis with individual-based simulations and we discuss the additional effects of demographic stochasticity taking place at the front line on virulence evolution. We confirm that an increase of virulence can occur at the front, but only if the carrying capacity of the invading pathogen is large enough. These results are discussed in the light of recent empirical studies examining virulence evolution at the edge of spreading epidemics. © 2015 The Author(s). Evolution © 2015 The Society for the Study of Evolution.

Burning invariant manifolds for reaction fronts in three-dimensional fluid flows

NASA Astrophysics Data System (ADS)

Mitchell, Kevin; Solomon, Tom

2017-11-01

The geometry of reaction fronts that propagate in fully three-dimensional (3D) fluid flows is studied using the tools of dynamical systems theory. The evolution of an infinitesimal front element is modeled as a six-dimensional ODE-three dimensions for the position of the front element and three for the orientation of its unit normal. This generalizes an earlier approach to understanding front propagation in two-dimensional (2D) fluid flows. As in 2D, the 3D system exhibits prominent burning invariant manifolds (BIMs). In 3D, BIMs are two-dimensional dynamically defined surfaces that form one-way barriers to the propagation of reaction fronts within the fluid. Due to the third dimension, BIMs in 3D exhibit a richer topology than their cousins in 2D. In particular, whereas BIMs in both 2D and 3D can originate from fixed points of the dynamics, BIMs in 3D can also originate from limit cycles. Such BIMs form robust tube-like channels that guide and constrain the evolution of the front within the bulk of the fluid. Supported by NSF Grant CMMI-1201236.

Patterns of LGM precipitation in the U.S. Rocky Mountains: results from regional application of a glacier mass/energy balance and flow model

NASA Astrophysics Data System (ADS)

Leonard, E. M.; Laabs, B. J.; Refsnider, K. A.; Plummer, M. A.; Jacobsen, R. E.; Wollenberg, J. A.

2010-12-01

Global climate model (GCM) simulations of the last glacial maximum (LGM) in the western United States predict changes in atmospheric circulation and storm tracks that would have resulted in significantly less-than-modern precipitation in the Northwest and northern Rockies, and significantly more-than-modern precipitation in the Southwest and southern Rockies. Model simulations also suggest that late Pleistocene pluvial lakes in the intermontane West may have modified local moisture regimes in areas immediately downwind. In this study, we present results of the application of a coupled energy/mass balance and glacier-flow model (Plummer and Phillips, 2003) to reconstructed paleoglaciers in Rocky Mountains of Utah, New Mexico, Colorado, and Wyoming to assess the changes from modern climate that would have been necessary to sustain each glacier in mass-balance equilibrium at its LGM extent. Results demonstrate that strong west-to-east and north-to-south gradients in LGM precipitation, relative to present, would be required if a uniform LGM temperature depression with respect to modern is assumed across the region. At an assumed 7oC temperature depression, approximately modern precipitation would have been necessary to support LGM glaciation in the Colorado Front Range, significantly less than modern precipitation to support glaciation in the Teton Range, and almost twice modern precipitation to sustain glaciers in the Wasatch and Uinta ranges of Utah and the New Mexico Sangre de Cristo Range. The observed west-to-east (Utah-to-Colorado) LGM moisture gradient is consistent with precipitation enhancement from pluvial Lake Bonneville, decreasing with distance downwind from the lake. The north-to-south (Wyoming-to-New Mexico) LGM moisture gradient is consistent with a southward LGM displacement of the mean winter storm track associated with the winter position of the Pacific Jet Stream across the western U.S. Our analysis of paleoglacier extents in the Rocky Mountain

The immature thrust belt of the northern front of the Tianshan

NASA Astrophysics Data System (ADS)

Chen, Ke; Gumiaux, Charles; Augier, Romain; Chen, Yan; Wang, Qingchen

2010-05-01

The modern Tianshan (central Asia), which extends east-west on about 2500 km long with an average of more than 2000 m in altitude, is considered as a direct consequence of the reactivation of a Paleozoic belt due to the India - Asia collision. At first order, the finite structure of this range obviously displays a significant uprising of Paleozoic "basement" rocks - as a crustal-scale ‘pop-up' - surrounded by two Cenozoic foreland basins. In order to characterize the coupling history of this Cenozoic orogeny with its northern foreland basin (Junggar basin), a detailed structural field work has been carried out on the northern piedmont of Tianshan. From Wusu to Urumqi, on about 250 km long, the thrusting of the Paleozoic basement on the Mesozoic or Cenozoic sedimentary series of the basin is remarkably exposed along several river valleys. In contrast, in other sections, the Triassic to Jurassic sedimentary series can be followed from the basin to the range where they unconformably overlie on the Carboniferous basement. These series are only gently folded along the "range front". These features imply that, at regional-scale, the Cenozoic reactivation of the Tianshan has not produced important deformation along its contact with the juxtaposed Junggar basin. The shortening ascribed to the Cenozoic intra-continental collision would either be localized in the range, mostly accommodated by reactivated Paleozoic structures or faults in the basement units, or in the distal parts of the Junggar basin, by folds and faults within the Cenozoic sedimentary series. Alternative hypothesis would be that the Tianshan uplift and the movements associated with along its northern front structures, which are traditionally assigned to its Cenozoic reactivation, might be reduced. Such characteristic significantly differs from other well-known orogenic ranges, such as the Canadian Rocky Mountains, the Appalachians, the Pyrenees which display highly folded foreland basins and thrust belts

Post-modelling of images from a laser-induced wavy boiling front

NASA Astrophysics Data System (ADS)

Matti, R. S.; Kaplan, A. F. H.

2015-12-01

Processes like laser keyhole welding, remote fusion laser cutting or laser drilling are governed by a highly dynamic wavy boiling front that was recently recorded by ultra-high speed imaging. A new approach has now been established by post-modelling of the high speed images. Based on the image greyscale and on a cavity model the three-dimensional front topology is reconstructed. As a second step the Fresnel absorptivity modulation across the wavy front is calculated, combined with the local projection of the laser beam. Frequency polygons enable additional analysis of the statistical variations of the properties across the front. Trends like shadow formation and time dependency can be studied, locally and for the whole front. Despite strong topology modulation in space and time, for lasers with 1 μm wavelength and steel the absorptivity is bounded to a narrow range of 35-43%, owing to its Fresnel characteristics.

Measurement of the shock front velocity produced in a T-tube

DOE Office of Scientific and Technical Information (OSTI.GOV)

Djurović, S.; Mijatović, Z.; Vujičić, B.

2015-01-15

A set of shock front velocity measurements is described in this paper. The shock waves were produced in a small electromagnetically driven shock T-tube. Most of the measurements were performed in hydrogen. The shock front velocity measurements in other gases and the velocity of the gas behind the shock front were also analyzed, as well as the velocity dependence on applied input energy. Some measurements with an applied external magnetic field were also performed. The used method of shock front velocity is simple and was shown to be very reliable. Measured values were compared with the calculated ones for themore » incident and reflected shock waves.« less

Align the Front End First.

ERIC Educational Resources Information Center

Perry, Jim

1995-01-01

Discussion of management styles and front-end analysis focuses on a review of Douglas McGregor's theories. Topics include Theories X, Y, and Z; leadership skills; motivational needs of employees; intrinsic and extrinsic rewards; and faulty implementation of instructional systems design processes. (LRW)

Iterative wave-front reconstruction in the Fourier domain.

PubMed

Bond, Charlotte Z; Correia, Carlos M; Sauvage, Jean-François; Neichel, Benoit; Fusco, Thierry

2017-05-15

The use of Fourier methods in wave-front reconstruction can significantly reduce the computation time for large telescopes with a high number of degrees of freedom. However, Fourier algorithms for discrete data require a rectangular data set which conform to specific boundary requirements, whereas wave-front sensor data is typically defined over a circular domain (the telescope pupil). Here we present an iterative Gerchberg routine modified for the purposes of discrete wave-front reconstruction which adapts the measurement data (wave-front sensor slopes) for Fourier analysis, fulfilling the requirements of the fast Fourier transform (FFT) and providing accurate reconstruction. The routine is used in the adaptation step only and can be coupled to any other Wiener-like or least-squares method. We compare simulations using this method with previous Fourier methods and show an increase in performance in terms of Strehl ratio and a reduction in noise propagation for a 40×40 SPHERE-like adaptive optics system. For closed loop operation with minimal iterations the Gerchberg method provides an improvement in Strehl, from 95.4% to 96.9% in K-band. This corresponds to ~ 40 nm improvement in rms, and avoids the high spatial frequency errors present in other methods, providing an increase in contrast towards the edge of the correctable band.

Sidewall crystallization and saturation front formation in silicic magma chambers

NASA Astrophysics Data System (ADS)

Lake, E. T.

2012-12-01

The cooling and crystallization style of silicic magma bodies in the upper crust falls on a continuum between whole-chamber processes of convection, crystal settling, and cumulate formation and interface driven processes of conduction and crystallization front migration. In the former case, volatile saturation occurs uniformly chamber wide, in the latter volatile saturation occurs along an inward propagating front. Ambient thermal gradient primarily controls the propagation rate; warm (> 30 °C / km) geothermal gradients promote 1000m+ thick crystal mush zones but slow crystallization front propagation. Cold geothermal gradients support the opposite. Magma chamber geometry plays a second order role in controlling propagation rates; bodies with high surface to magma ratio and large Earth's surface parallel faces exhibit more rapid propagation and smaller mush zones. Crystallization front propagation occurs at speeds of up to 6 cm/year (rhyolitic magma, thin sill geometry, 10 °C / km geotherm), far faster than diffusion of volatiles in magma and faster than bubbles can nucleate and ascend under certain conditions. Saturation front propagation is fixed by pressure and magma crystal content; above certain modest initial water contents (4.4 wt% in a dacite) mobile magma above 10 km depth always contains a saturation front. Saturation fronts propagate down from the magma chamber roof at lower water contents (3.3 wt% in a dacite at 5 km depth), creating an upper saturated interface for most common (4 - 6 wt%) magma water contents. This upper interface promotes the production of a fluid pocket underneath the apex of the magma chamber. Magma de-densification by bubble nucleation promotes convection and homogenization in dacitic systems. If the fluid pocket grew rapidly without draining, hydro-fracturing and eruption would result. The combination of fluid escape pathways and metal scavenging would generate economic vein or porphyry deposits.

On the Importance of "Front-Side Mechanics" in Athletics Sprinting.

PubMed

Haugen, Thomas; Danielsen, Jørgen; Alnes, Leif Olav; McGhie, David; Sandbakk, Øyvind; Ettema, Gertjan

2018-05-16

Practitioners have, for many years, argued that athletic sprinters should optimize front-side mechanics (leg motions occurring in front of the extended line through the torso) and minimize back-side mechanics. This study aimed to investigate if variables related to front- and back-side mechanics can be distinguished from other previously highlighted kinematic variables (spatiotemporal variables and variables related to segment configuration and velocities at touchdown) in how they statistically predict performance. A total of 24 competitive sprinters (age: 23.1 [3.4] y, height: 1.81 [0.06] m, body mass: 75.7 [5.6] kg, and 100-m personal best: 10.86 [0.22] s) performed two 20-m starts from block and 2 to 3 flying sprints over 20 m. Kinematics were recorded in 3D using a motion tracking system with 21 cameras at a 250 Hz sampling rate. Several front- and back-side variables, including thigh (r = .64) and knee angle (r = .51) at lift-off and maximal thigh extension (r = .66), were largely correlated (P < .05) with accelerated running performance, and these variables displayed significantly higher correlations (P < .05) to accelerated running performance than nearly all the other analyzed variables. However, the relationship directions for most front- and back-side variables during accelerated running were opposite in comparison to how the theoretical concept has been described. Horizontal ankle velocity, contact time, and step rate displayed significantly higher correlation values to maximal velocity sprinting than the other variables (P < .05), and neither of the included front- and back-side variables were significantly associated with maximal velocity sprinting. Overall, the present findings did not support that front-side mechanics were crucial for sprint performance among the investigated sprinters.

2. VIEW SOUTHEAST, WEST FRONT OF BUILDINGS 25. 26; NORTH ...

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

2. VIEW SOUTHEAST, WEST FRONT OF BUILDINGS 25. 26; NORTH FRONT OF BUILDING 24: ROOF GABLE OF BUILDING 27 - U.S. Plant Introduction Station, Soil Conservation Service Cluster, 11601 Old Pond Road, Glenn Dale, Prince George's County, MD

1. VIEW SOUTHWEST, EAST FRONT OF GREENHOUSE #1 (BUILDING 5), ...

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

1. VIEW SOUTHWEST, EAST FRONT OF GREENHOUSE #1 (BUILDING 5), WITH NORTH FRONT OF SHED (BUILDING 20) IN DISTANCE - U.S. Plant Introduction Station, Greenhouse Nos. 1 & 2, 11601 Old Pond Road, Glenn Dale, Prince George's County, MD

Radar observation of an along-front jet and transverse flow convergence associated with a North Sea front

NASA Astrophysics Data System (ADS)

Matthews, J. P.; Fox, A. D.; Prandle, D.

1993-01-01

This paper describes the first synoptic mapping of surface currents across a strong and stable tidal mixing front by HF radar. The radar deployment took place along the coast of northeast England during August and early September 1988 in parallel with extensive ship based CTD density and ADCP (Acoustic Doppler Current Profiler) measurements which provided data in the vertical plane to complement those of the HF radar. We describe two main results. Firstly, during a spring-tide period of strengthening inshore density gradients, an along-front jet with speeds of up to 14 cm s -1 was detected in the long term IIF radar residual field. The location and spatial form of this jet correspond with estimates of geostrophic currents derived from the measured density field. Secondly, a transverse "double-sided" surface flow convergence centred close to the frontal boundary and of net magnitude 4 cm s -1 accompanied the large along-front jet. Such a weaker cross-frontal component has been anticipated on theoretical grounds but never previously observed in this detailed fashion. The experiment underlines the power of a synergistic approach, based on HF remote sensing radar and ADCP, for the study of frontal circulation in coastal zones.

Angular momentum conservation law in light-front quantum field theory

DOE PAGES

Chiu, Kelly Yu-Ju; Brodsky, Stanley J.

2017-03-31

We prove the Lorentz invariance of the angular momentum conservation law and the helicity sum rule for relativistic composite systems in the light-front formulation. We explicitly show that j 3, the z -component of the angular momentum remains unchanged under Lorentz transformations generated by the light-front kinematical boost operators. The invariance of j 3 under Lorentz transformations is a feature unique to the front form. Applying the Lorentz invariance of the angular quantum number in the front form, we obtain a selection rule for the orbital angular momentum which can be used to eliminate certain interaction vertices in QED andmore » QCD. We also generalize the selection rule to any renormalizable theory and show that there exists an upper bound on the change of orbital angular momentum in scattering processes at any fixed order in perturbation theory.« less

Angular momentum conservation law in light-front quantum field theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chiu, Kelly Yu-Ju; Brodsky, Stanley J.

We prove the Lorentz invariance of the angular momentum conservation law and the helicity sum rule for relativistic composite systems in the light-front formulation. We explicitly show that j 3, the z -component of the angular momentum remains unchanged under Lorentz transformations generated by the light-front kinematical boost operators. The invariance of j 3 under Lorentz transformations is a feature unique to the front form. Applying the Lorentz invariance of the angular quantum number in the front form, we obtain a selection rule for the orbital angular momentum which can be used to eliminate certain interaction vertices in QED andmore » QCD. We also generalize the selection rule to any renormalizable theory and show that there exists an upper bound on the change of orbital angular momentum in scattering processes at any fixed order in perturbation theory.« less

Angular momentum conservation law in light-front quantum field theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chiu, Kelly Yu-Ju; Brodsky, Stanley J.

We prove the Lorentz invariance of the angular momentum conservation law and the helicity sum rule for relativistic composite systems in the light-front formulation. We explicitly show that j 3 , the z -component of the angular momentum remains unchanged under Lorentz transformations generated by the light-front kinematical boost operators. The invariance of j 3 under Lorentz transformations is a feature unique to the front form. Applying the Lorentz invariance of the angular quantum number in the front form, we obtain a selection rule for the orbital angular momentum which can be used to eliminate certain interaction vertices in QEDmore » and QCD. We also generalize the selection rule to any renormalizable theory and show that there exists an upper bound on the change of orbital angular momentum in scattering processes at any fixed order in perturbation theory.« less

40 CFR 63.487 - Batch front-end process vents-reference control technology.

Code of Federal Regulations, 2010 CFR

2010-07-01

... § 63.487 Batch front-end process vents—reference control technology. (a) Batch front-end process vents... 40 Protection of Environment 9 2010-07-01 2010-07-01 false Batch front-end process vents-reference control technology. 63.487 Section 63.487 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY...

Curved fronts in the Belousov-Zhabotinskii reaction-diffusion systems in R2

NASA Astrophysics Data System (ADS)

Niu, Hong-Tao; Wang, Zhi-Cheng; Bu, Zhen-Hui

2018-05-01

In this paper we consider a diffusion system with the Belousov-Zhabotinskii (BZ for short) chemical reaction. Following Brazhnik and Tyson [4] and Pérez-Muñuzuri et al. [45], who predicted V-shaped fronts theoretically and discovered V-shaped fronts by experiments respectively, we give a rigorous mathematical proof of their results. We establish the existence of V-shaped traveling fronts in R2 by constructing a proper supersolution and a subsolution. Furthermore, we establish the stability of the V-shaped front in R2.

Existence and non-existence of transition fronts in mixed ignition-monostable media

NASA Astrophysics Data System (ADS)

Graham, Cole; Shean Lim, Tau; Ma, Andrew; Weber, David

2018-02-01

We study transition fronts for one-dimensional reaction-diffusion equations with compactly-perturbed ignition-monostable reactions. We establish an almost sharp condition on reactions which characterizes the existence and non-existence of fronts. In particular, we prove that a strong inhomogeneity in the reaction prevents formation of transition fronts, while a weak inhomogeneity gives rise to a front. Our work extends the results and methods introduced in Nolen et al 2012 (Arch. Ration. Mech. Anal. 203 217-46), which studied the same question in inhomogeneous KPP media.

Apennine Front revisited - Diversity of Apollo 15 highland rock types

NASA Technical Reports Server (NTRS)

Lindstrom, Marilyn M.; Marvin, Ursula B.; Vetter, Scott K.; Shervais, John W.

1988-01-01

The Apollo 15 landing site is geologically the most complex of the Apollo sites, situated at a mare-highland interface within the rings of two of the last major basin-forming impacts. Few of the Apollo 15 samples are ancient highland rocks derived from the early differentiation of the moon, or impact melts from major basin impacts. Most of the samples are regolith breccias containing abundant clasts of younger volcanic mare and KREEP basalts. The early geologic evolution of the region can be understood only by examining the small fragments of highland rocks found in regolith breccias and soils. Geochemical and petrologic studies of clasts and matrices of three impact melt breccias and four regolith breccias are presented. Twelve igneous and metamorphic rocks show extreme diversity and include a new type of ferroan norite. Twenty-five samples of highland impact melt are divided into groups based on composition. These impact melts form nearly a continuum over more than an order of magnitude in REE concentrations. This continuum may result from both major basin impacts and younger local events. Highland rocks from the Apennine Front include most of the highland rock types found at all of the other sites. An extreme diversity of highland rocks is a fundamental characteristic of the Apennine Front and is a natural result of its complex geologic evolution.

Magnetohydrodynamical Effects on Nuclear Deflagration Fronts in Type Ia Supernovae

NASA Astrophysics Data System (ADS)

Hristov, Boyan; Collins, David C.; Hoeflich, Peter; Weatherford, Charles A.; Diamond, Tiara R.

2018-05-01

This article presents a study of the effects of magnetic fields on non-distributed nuclear burning fronts as a possible solution to a fundamental problem for the thermonuclear explosion of a Chandrasekhar mass ({M}Ch}) white dwarf (WD), the currently favored scenario for the majority of Type Ia SNe. All existing 3D hydrodynamical simulations predict strong global mixing of the burning products due to Rayleigh–Taylor (RT) instabilities, which contradicts observations. As a first step toward studying the flame physics, we present a set of computational magnet-hydrodynamic models in rectangular flux tubes, resembling a small inner region of a WD. We consider initial magnetic fields up to {10}12 {{G}} of various orientations. We find an increasing suppression of RT instabilities starting at about {10}9 {{G}}. The front speed tends to decrease with increasing magnitude up to about {10}11 {{G}}. For even higher fields new small-scale, finger-like structures develop, which increase the burning speed by a factor of 3 to 4 above the field-free RT-dominated regime. We suggest that the new instability may provide sufficiently accelerated energy production during the distributed burning regime to go over the Chapman–Jougey limit and trigger a detonation. Finally, we discuss the possible origins of high magnetic fields during the final stage of the progenitor evolution or the explosion.

Shock wave and flame front induced detonation in a rapid compression machine

NASA Astrophysics Data System (ADS)

Wang, Y.; Qi, Y.; Xiang, S.; Mével, R.; Wang, Z.

2018-05-01

The present study focuses on one mode of detonation initiation observed in a rapid compression machine (RCM). This mode is referred to as shock wave and flame front-induced detonation (SWFID). Experimental high-speed imaging and two-dimensional numerical simulations with skeletal chemistry are combined to unravel the dominant steps of detonation initiation under SWFID conditions. It is shown that the interaction between the shock wave generated by the end-gas auto-ignition and the spherical flame creates a region of high pressure and temperature which enables the acceleration of the flame front and the detonation onset. The experimental observation lacks adequate spatial and temporal resolution despite good reproducibility of the detonation onset. Based on the numerical results, phenomenological interpretation of the event within the framework of shock wave refraction indicates that the formation of a free-precursor shock wave at the transition between regular and irregular refraction may be responsible for detonation onset. The present results along with previous findings on shock wave reflection-induced detonation in the RCM indicate that super-knock occurs after the interaction of the shock wave generated by end-gas auto-ignition with the RCM walls, preignition flame, or another shock wave.

Barriers to front propagation in laminar, three-dimensional fluid flows

NASA Astrophysics Data System (ADS)

Doan, Minh; Simons, J. J.; Lilienthal, Katherine; Solomon, Tom; Mitchell, Kevin A.

2018-03-01

We present experiments on one-way barriers that block reaction fronts in a fully three-dimensional (3D) fluid flow. Fluorescent Belousov-Zhabotinsky reaction fronts are imaged with laser-scanning in a laminar, overlapping vortex flow. The barriers are analyzed with a 3D extension to burning invariant manifold (BIM) theory that was previously applied to two-dimensional advection-reaction-diffusion processes. We discover tube and sheet barriers that guide the front evolution. The experimentally determined barriers are explained by BIMs calculated from a model of the flow.

26. EXCAVATION OF EAST (FRONT) BASEMENT WELL AND DRAINAGE SYSTEM, ...

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

26. EXCAVATION OF EAST (FRONT) BASEMENT WELL AND DRAINAGE SYSTEM, WITH ARCHED ENTRY INTO BASEMENT UNDER FRONT ENTRY IN BACKGROUND, LOOKING NORTH (NOTE GALLETING IN BRICK FOUNDATION) - Belair, Tulip Grove Drive, Belair-at-Bowie, Bowie, Prince George's County, MD

TRACES OF ORIGINAL PARTITIONS AT JUNCTURE OF FRONT ROOM, REAR ...

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

TRACES OF ORIGINAL PARTITIONS AT JUNCTURE OF FRONT ROOM, REAR ROOM AND HALL, SECOND FLOOR. ALSO SHOWS ORIGINAL STUCCO CORNICE OF FRONT AND REAR ROOMS (LEFT) AND HALL (RIGHT) - Kid-Chandler House, 323 Walnut Street, Philadelphia, Philadelphia County, PA

2. LAUNCH CONTROL SUPPORT BUILDING WEST FRONT AND VEHICLE STORAGE ...

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

2. LAUNCH CONTROL SUPPORT BUILDING WEST FRONT AND VEHICLE STORAGE BUILDING SOUTHWEST FRONT. VIEW TO EAST. - Minuteman III ICBM Launch Control Facility November-1, 1.5 miles North of New Raymer & State Highway 14, New Raymer, Weld County, CO

On the existence of stationary reaction fronts in precipitation-dissolution systems

NASA Astrophysics Data System (ADS)

Kondratiuk, Paweł; Nizinkiewicz, Hanna; Ladd, Anthony JC; Szymczak, Piotr

2014-05-01

Coupled precipitation-dissolution processes are ubiquitous in hydrogeochemical systems which are out of chemical equilibrium. However, as already remarked by Ortoleva et al. [1], the precipitation front will in general move with a velocity different form that of a dissolution front; thus the distance between them will increase in time. However, there are a number of systems where the both fronts appear to move with the same velocity. One example is the terra rossa formation process [2], in which kaolinite precipitation produces hydrogen ions that dissolve the underlying calcite. In this case the velocities of the dissolution and precipitation front agree to within 1%, which does not seem accidental. In this communication, we propose a possible mechanism of such a front synchronization, and study its further implications for the dynamics of the system. [1] P. Ortoleva et al., Physica D: 19, 334 (1986) [2] E. Merino and A. Banjerjee, J. Geol., 116, 62 (2008)

Supra Arcade Downflows with XRT Informed by Dipolarization Fronts with THEMIS

NASA Technical Reports Server (NTRS)

Kobelski, Adam; Savage, Sabrina Leah; Malaspina, David

2016-01-01

Magnetic reconnection can rapidly reconfigure the magnetic field of the corona, accelerating plasma through the site of reconnection. Ambiguities due to the nature of remote sensing have complicated the interpretation of observations of the inflowing and outflowing plasma in reconnecting regions. In particular, the interpretation of sunward moving density depletions above flare arcades (known as Supra Arcade Downflows - SADs) is still debated. Hinode/XRT has provided a wealth of observations for SADs and helped inform our current understanding of these structures. SADs have been interpreted as wakes behind newly reconnected and outflowing loops (Supra Arcade Downflowing Loops - SADLs). Models have shown the plausibility of this interpretation, though this interpretation has not yet been fully accepted. We present here observations of newly reconnected outflowing loops observed via in situ instruments in the magnetosphere. These observations, provided by five THEMIS spacecraft, show that around retracting loops (dipolarization fronts in this context) similar dynamic temperature and density structures are found as seen in SADs. We compare data from multiple SADs and dipolarization fronts to show that the observational signatures implied in the corona can be directly observed in similar plasma regimes in the magnetosphere, strongly favoring the interpretation of SADs as wakes behind retracting loops.

4. VIEW NORTHWEST, NORTH FRONT OF SOIL CONSERVATION SERVICE CLUSTER ...

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

4. VIEW NORTHWEST, NORTH FRONT OF SOIL CONSERVATION SERVICE CLUSTER (BUILDINGS 24, 25, 26); NORTH FRONT OF QUARANTINE HEADHOUSE (BUILDING 27) - U.S. Plant Introduction Station, Soil Conservation Service Cluster, 11601 Old Pond Road, Glenn Dale, Prince George's County, MD

8. INTERIOR OF FRONT SCREENEDIN PORCH SHOWING PORCH ENTRY DOOR ...

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

8. INTERIOR OF FRONT SCREENED-IN PORCH SHOWING PORCH ENTRY DOOR AT PHOTO CENTER AND FRONT ENTRY DOOR TO LIVING ROOM AT PHOTO LEFT. VIEW TO NORTHWEST. - Bishop Creek Hydroelectric System, Plant 4, Worker Cottage, Bishop Creek, Bishop, Inyo County, CA

2. VIEW OF PARK SIGNAGE AT FRONT ROYAL. SIGN SAYS: ...

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

2. VIEW OF PARK SIGNAGE AT FRONT ROYAL. SIGN SAYS: "NORTH ENTRANCE SHENANDOAH NATIONAL PARK." LOCATED ON EXIT SIDE OF ROAD. LOOKING SOUTHWEST, MILE 0.0. - Skyline Drive, From Front Royal, VA to Rockfish Gap, VA , Luray, Page County, VA

Are Hydrostatic Models Still Capable of Simulating Oceanic Fronts

DTIC Science & Technology

2016-11-10

Coriolis effect is added to the model momentum equations...nonhydrostatic (NH) models to address the relevance of NH effects on the evolution of density fronts and the development of meso- and submeso-scale vertical...nonhydrostatic (NH) models to address the relevance of NH effects on the evolution of density fronts and the development of meso- and submeso-scale vertical

WPC Product Legends - Surface fronts and precipitation areas/symbols

Science.gov Websites

, etc...) drawn on each segment. For example, the image below shows a forming cold front. Frontolysis is other segment. Below is an example of a dissipating warm front. Precipitation Areas and Symbols Areas of an example) Below are symbols found on our short range forecasts that represent categories (and in

Implementation of a gust front head collapse scheme in the WRF numerical model

NASA Astrophysics Data System (ADS)

Lompar, Miloš; Ćurić, Mladjen; Romanic, Djordje

2018-05-01

Gust fronts are thunderstorm-related phenomena usually associated with severe winds which are of great importance in theoretical meteorology, weather forecasting, cloud dynamics and precipitation, and wind engineering. An important feature of gust fronts demonstrated through both theoretical and observational studies is the periodic collapse and rebuild of the gust front head. This cyclic behavior of gust fronts results in periodic forcing of vertical velocity ahead of the parent thunderstorm, which consequently influences the storm dynamics and microphysics. This paper introduces the first gust front pulsation parameterization scheme in the WRF-ARW model (Weather Research and Forecasting-Advanced Research WRF). The influence of this new scheme on model performances is tested through investigation of the characteristics of an idealized supercell cumulonimbus cloud, as well as studying a real case of thunderstorms above the United Arab Emirates. In the ideal case, WRF with the gust front scheme produced more precipitation and showed different time evolution of mixing ratios of cloud water and rain, whereas the mixing ratios of ice and graupel are almost unchanged when compared to the default WRF run without the parameterization of gust front pulsation. The included parameterization did not disturb the general characteristics of thunderstorm cloud, such as the location of updraft and downdrafts, and the overall shape of the cloud. New cloud cells in front of the parent thunderstorm are also evident in both ideal and real cases due to the included forcing of vertical velocity caused by the periodic collapse of the gust front head. Despite some differences between the two WRF simulations and satellite observations, the inclusion of the gust front parameterization scheme produced more cumuliform clouds and seem to match better with real observations. Both WRF simulations gave poor results when it comes to matching the maximum composite radar reflectivity from radar

Travelling Fronts and Entire Solutionsof the Fisher-KPP Equation in N

NASA Astrophysics Data System (ADS)

Hamel, François; Nadirashvili, Nikolaï

This paper is devoted to time-global solutions of the Fisher-KPP equation in N: where f is a C2 concave function on [0,1] such that f(0)=f(1)=0 and f>0 on (0,1). It is well known that this equation admits a finite-dimensional manifold of planar travelling-fronts solutions. By considering the mixing of any density of travelling fronts, we prove the existence of an infinite-dimensional manifold of solutions. In particular, there are infinite-dimensional manifolds of (nonplanar) travelling fronts and radial solutions. Furthermore, up to an additional assumption, a given solution u can be represented in terms of such a mixing of travelling fronts.

Seabird diving behaviour reveals the functional significance of shelf-sea fronts as foraging hotspots

NASA Astrophysics Data System (ADS)

Cox, S. L.; Miller, P. I.; Embling, C. B.; Scales, K. L.; Bicknell, A. W. J.; Hosegood, P. J.; Morgan, G.; Ingram, S. N.; Votier, S. C.

2016-09-01

Oceanic fronts are key habitats for a diverse range of marine predators, yet how they influence fine-scale foraging behaviour is poorly understood. Here, we investigated the dive behaviour of northern gannets Morus bassanus in relation to shelf-sea fronts. We GPS (global positioning system) tracked 53 breeding birds and examined the relationship between 1901 foraging dives (from time-depth recorders) and thermal fronts (identified via Earth Observation composite front mapping) in the Celtic Sea, Northeast Atlantic. We (i) used a habitat-use availability analysis to determine whether gannets preferentially dived at fronts, and (ii) compared dive characteristics in relation to fronts to investigate the functional significance of these oceanographic features. We found that relationships between gannet dive probabilities and fronts varied by frontal metric and sex. While both sexes were more likely to dive in the presence of seasonally persistent fronts, links to more ephemeral features were less clear. Here, males were positively correlated with distance to front and cross-front gradient strength, with the reverse for females. Both sexes performed two dive strategies: shallow V-shaped plunge dives with little or no active swim phase (92% of dives) and deeper U-shaped dives with an active pursuit phase of at least 3 s (8% of dives). When foraging around fronts, gannets were half as likely to engage in U-shaped dives compared with V-shaped dives, independent of sex. Moreover, V-shaped dive durations were significantly shortened around fronts. These behavioural responses support the assertion that fronts are important foraging habitats for marine predators, and suggest a possible mechanistic link between the two in terms of dive behaviour. This research also emphasizes the importance of cross-disciplinary research when attempting to understand marine ecosystems.

Near-surface Stratification and Submesoscale Fronts in the north Bay of Bengal during Summer Monsoon of 2014 and 2015.

NASA Astrophysics Data System (ADS)

Sengupta, D.; Jarugula, S. L.; D'Asaro, E. A.; Chaudhuri, D.; S, S.; Tandon, A.; M, R.; Lucas, A.; Simmons, H. L.

2016-02-01

The north bay of Bengal is characterised by a shallow layer of fresh water from monsoon rainfall and river discharge, with very strong stratification at its base, and a warm subsurface layer. The thermodynamic structure of the ocean has significant influence on air-sea interaction. We conducted two research cruises of ORV Sagar Nidhi in August-September 2014 and 2015, to study the physical processes that maintain the shallow fresh layer. We collected a total of about 4000 kilometers of underway Conductivity-Temperature-Depth (uCTD) and Acoustic Doppler Current Profiler (ADCP) data. The vertical resolution of the data is 1-2 m; at ship speeds of 4-5 knots, the horizontal resolution is 300-1500 m, sufficient to resolve submesoscale (1-20 km) features. It is known that dynamical instability of submesoscale fronts can lead to slumping of heavier water under lighter water, enhancing vertical stratification. We identified 35 major salinity-dominated near-surface density fronts along the ship track, with surface density gradient exceeding 0.03 kg/m3 per kilometer, and density difference exceeding 0.3 kg/m3. The largest gradients in the open ocean, between fresh water of riverine origin and ambient seawater, exceeded 10 psu in 40 km and 6 psu in 50 km; the spatial scales of the other fronts range from 1 to 25 km. At several submesoscale fronts, the surface mixed layer is shallower directly under the front than on either side, suggesting active restratification. ADCP observations reveal a region of confluence and narrow jets associated with some fronts, consistent with frontal slumping. In addition, wind-driven Ekman transport can enhance near-surface stratification by carrying lighter water over denser water. We discuss the relevance of these two mechanisms in observations and model simulations.

Sources and Coverage of Medical News on Front Pages of US Newspapers

PubMed Central

Lai, William Y. Y.; Lane, Trevor; Jones, Alison

2009-01-01

Background Medical news that appears on newspaper front pages is intended to reach a wide audience, but how this type of medical news is prepared and distributed has not been systematically researched. We thus quantified the level of visibility achieved by front-page medical stories in the United States and analyzed their news sources. Methodology Using the online resource Newseum, we investigated front-page newspaper coverage of four prominent medical stories, and a high-profile non-medical news story as a control, reported in the US in 2007. Two characteristics were quantified by two raters: which newspaper titles carried each target front-page story (interrater agreement, >96%; kappa, >0.92) and the news sources of each target story (interrater agreement, >94%; kappa, >0.91). National rankings of the top 200 US newspapers by audited circulation were used to quantify the extent of coverage as the proportion of the total circulation of ranked newspapers in Newseum. Findings In total, 1630 front pages were searched. Each medical story appeared on the front pages of 85 to 117 (67.5%–78.7%) ranked newspaper titles that had a cumulative daily circulation of 23.1 to 33.4 million, or 61.8% to 88.4% of all newspapers. In contrast, the non-medical story achieved front-page coverage in 152 (99.3%) newspaper titles with a total circulation of 41.0 million, or 99.8% of all newspapers. Front-page medical stories varied in their sources, but the Washington Post, Los Angeles Times, New York Times and the Associated Press together supplied 61.7% of the total coverage of target front-page medical stories. Conclusion Front-page coverage of medical news from different sources is more accurately revealed by analysis of circulation counts rather than of newspaper titles. Journals wishing to widen knowledge of research news and organizations with important health announcements should target at least the four dominant media organizations identified in this study. PMID:19724643

Bibliography of Research on Ocean Fronts, 1964-1984

DTIC Science & Technology

1985-08-01

water masses which exhibit notable differences in temperature, salinity , chlorophyll and other properties. One example of an ocean front is the...Phil. Trans. R. Soc. Lond. A302: 617-634. Amos, A.F., M.G. Langseth and R.G. Markl. 1972. Visible oceanic saline fronts, p. 49-62. In A.L. Gordon...On the mechanism of the deep mixed layer formation during MEDOC 1969. Cahiers Oceanogr. XXII: 427-442. Anderson, F.E. 1980. The variation in

Consumer preferences for front-of-pack calories labelling.

PubMed

van Kleef, Ellen; van Trijp, Hans; Paeps, Frederic; Fernández-Celemín, Laura

2008-02-01

In light of the emerging obesity pandemic, front-of-pack calories labels may be an important tool to assist consumers in making informed healthier food choices. However, there is little prior research to guide key decisions on whether caloric content should be expressed in absolute terms or relative to recommended daily intake, whether it should be expressed in per serving or per 100 g and whether the information should be further brought alive for consumers in terms of what the extra calorie intake implies in relation to activity levels. The present study aimed at providing more insight into consumers' appreciation of front-of-pack labelling of caloric content of food products and their specific preferences for alternative execution formats for such information in Europe. For this purpose, eight executions of front-of-pack calorie flags were designed and their appeal and information value were extensively discussed with consumers through qualitative research in four different countries (Germany, The Netherlands, France and the UK). The results show that calories are well-understood and that participants were generally positive about front-of-pack flags, particularly when flags are uniform across products. The most liked flags are the simpler flags depicting only the number of calories per serving or per 100 g, while more complex flags including references to daily needs or exercise and the flag including a phrase referring to balanced lifestyle were least preferred. Some relevant differences between countries were observed. Although participants seem to be familiar with the notion of calories, they do not seem to fully understand how to apply them. From the results, managerial implications for the design and implementation of front-of-pack calorie labelling as well as important directions for future research are discussed.

Consumer preferences for front-of-pack calories labelling

PubMed Central

van Kleef, Ellen; van Trijp, Hans; Paeps, Frederic; Fernández-Celemín, Laura

2008-01-01

Objective In light of the emerging obesity pandemic, front-of-pack calories labels may be an important tool to assist consumers in making informed healthier food choices. However, there is little prior research to guide key decisions on whether caloric content should be expressed in absolute terms or relative to recommended daily intake, whether it should be expressed in per serving or per 100 g and whether the information should be further brought alive for consumers in terms of what the extra calorie intake implies in relation to activity levels. The present study aimed at providing more insight into consumers’ appreciation of front-of-pack labelling of caloric content of food products and their specific preferences for alternative execution formats for such information in Europe. Design For this purpose, eight executions of front-of-pack calorie flags were designed and their appeal and information value were extensively discussed with consumers through qualitative research in four different countries (Germany, The Netherlands, France and the UK). Results The results show that calories are well-understood and that participants were generally positive about front-of-pack flags, particularly when flags are uniform across products. The most liked flags are the simpler flags depicting only the number of calories per serving or per 100 g, while more complex flags including references to daily needs or exercise and the flag including a phrase referring to balanced lifestyle were least preferred. Some relevant differences between countries were observed. Although participants seem to be familiar with the notion of calories, they do not seem to fully understand how to apply them. Conclusion From the results, managerial implications for the design and implementation of front-of-pack calorie labelling as well as important directions for future research are discussed. PMID:17601362

Sharp-front wave of strong magnetic field diffusion in solid metal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Bo; Gu, Zhuo-wei; Kan, Ming-xian

When a strong magnetic field diffuses into a solid metal, if the metal's resistance possesses an abrupt rise at some critical temperature and the magnetic field strength is above some critical value, the magnetic field will diffuse into the metal in the form of a sharp-front wave. Formulas for the critical conditions under which a sharp-front magnetic diffusion wave emerges and a formula for the wave-front velocity are derived in this work.

Influence of wave-front sampling in adaptive optics retinal imaging

PubMed Central

Laslandes, Marie; Salas, Matthias; Hitzenberger, Christoph K.; Pircher, Michael

2017-01-01

A wide range of sampling densities of the wave-front has been used in retinal adaptive optics (AO) instruments, compared to the number of corrector elements. We developed a model in order to characterize the link between number of actuators, number of wave-front sampling points and AO correction performance. Based on available data from aberration measurements in the human eye, 1000 wave-fronts were generated for the simulations. The AO correction performance in the presence of these representative aberrations was simulated for different deformable mirror and Shack Hartmann wave-front sensor combinations. Predictions of the model were experimentally tested through in vivo measurements in 10 eyes including retinal imaging with an AO scanning laser ophthalmoscope. According to our study, a ratio between wavefront sampling points and actuator elements of 2 is sufficient to achieve high resolution in vivo images of photoreceptors. PMID:28271004

Transient behavior of flare-associated solar wind. II - Gas dynamics in a nonradial open field region

NASA Technical Reports Server (NTRS)

Nagai, F.

1984-01-01

Transient behavior of flare-associated solar wind in the nonradial open field region is numerically investigated, taking into account the thermal and dynamical coupling between the chromosphere and the corona. A realistic steady solar wind is constructed which passes through the inner X-type critical point in the rapidly diverging region. The wind speed shows a local maximum at the middle, O-type, critical point. The wind's density and pressure distributions decrease abruptly in the rapidly diverging region of the flow tube. The transient behavior of the wind following flare energy deposition includes ascending and descending conduction fronts. Thermal instability occurs in the lower corona, and ascending material flows out through the throat after the flare energy input ceases. A local density distribution peak is generated at the shock front due to the pressure deficit just behind the shock front.

Formation of a katabatic induced cold front at the east Andean slopes

NASA Astrophysics Data System (ADS)

Trachte, K.; Nauss, T.,; Rollenbeck, R.; Bendix, J.

2009-04-01

Within the DFG research unit 816, climate dynamics in a tropical mountain rain forest in the national reserve of the Reserva Biósfera de San Francisco in South Ecuador are investigated. Precipitation measurements in the mountain environment of the Estación Científica de San Francisco (ECSF) with a vertical rain radar profiler have been made over the last seven years. They reveal unexpected constant early morning rainfall events. On the basis of cloud top temperatures from corresponding GOES satellite imageries, a Mesoscale Convective System could be derived. Its formation region is located south-east of the ECSF in the Peruvian Amazon basin. The generation of the MCS is assumed to results from an interaction of both local and mesoscale conditions. Nocturnal drainage air from the Andean slopes and valleys confluences in the Amazon basin due to the concave lined terrain. This cold air converges with the warm-moist air of the Amazon inducing a local cold front. This process yields to deep convection resulting in a MCS. With the numerical model ARPS the hypothesized formation of a cloud cluster due to a katabatic induced cold front is shown in an ideal case study. Therefor an ideal terrain model representing the features of the Andes in the target area has been used. The simplification of the oprography concerns a concave lined slope and a valley draining into the basin. It describes the confluence of the cold drainage air due to the shape of the terrain. Inside the basin the generation of a local cold front is shown, which triggers the formation of a cloud cluster.

Kinematics of the Horsehead Nebula and IC 434 Ionization Front in CO and C+

NASA Astrophysics Data System (ADS)

Bally, John; Chambers, Ed; Guzman, Viviana; Keto, Eric; Mookerjea, Bhaswati; Sandell, Goran; Stanke, Thomas; Zinnecker, Hans

2018-02-01

Stratospheric Observatory for Infrared Astronomy [C II] 157 μm, APEX 860 μm J = 3‑2 CO, and archival James Clerk Maxwell Telescope J = 2‑1 CO and 13CO observations of the Horsehead Nebula are presented. The photon-dominated region (PDR) between the Orion B molecular cloud and the adjacent IC 434 H II region is used to study the radial velocity structure of the region and the feedback impacts of UV radiation. Multiple west-facing cloud edges are superimposed along the line of sight with radial velocities that differ by a few kilometers per second. The Horsehead lies in the foreground blueshifted portion of the Orion B molecular cloud and is predominantly illuminated from the rear. The mean H2 density of the Horsehead, ∼ 6× {10}3 {{cm}}-3, results in a spatially thin PDR where the photoablation flow has compressed the western cloud edge to an H2 density of (2{--}6)× {10}4 {{cm}}-3. The associated [C II] 157 μm layer has a width L < 0.05 pc. The background parts of the Orion B cloud in the imaged field consist of a clumpy medium surrounded by molecular gas with H2 densities lower by one to two orders of magnitude. Along the straight part of the IC 434 ionization front, the PDR layer probed by [C II] 157 μm emission is much thicker with L ∼ 0.5 pc. A possible model for the formation and evolution of this edge-on ionization front and PDR is presented. The [C II] data were independently analyzed and published by Pabst et al.

The Front-End System For MARE In Milano

NASA Astrophysics Data System (ADS)

Arnaboldi, Claudio; Pessina, Gianluigi

2009-12-01

The first phase of MARE consists of 72 μ-bolometers composed each of a crystal of AgReO4 readout by Si thermistors. The spread in the thermistor characteristics and bolometer thermal coupling leads to different energy conversion gains and optimum operating points of the detectors. Detector biasing levels and voltage gains are completely remote-adjustable by the front end system developed, the subject of this paper, achieving the same signal range at the input of the DAQ system. The front end consists of a cold buffer stage, a second pseudo differential stage followed by a gain stage, an antialiasing filter, and a battery powered detector biasing set up. The DAQ system can be used to set all necessary parameters of the electronics remotely, by writing to a μ-controller located on each board. Fiber optics are used for the serial communication between the DAQ and the front end. To suppress interference noise during normal operation, the clocked devices of the front end are maintained in sleep-mode, except during the set-up phase of the experiment. An automatic DC detector characterization procedure is used to establish the optimum operating point of every detector of the array. A very low noise level has been achieved: about 3nV/□Hz at 1 Hz and 1 nV/□Hz for the white component, high frequencies.

View of front (north) and east walls of the Office, ...

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

View of front (north) and east walls of the Office, Childs power plant. Rock cairn in front frames the 1976 National Historic Mechanical Engineering plaque. Looking southeast - Childs-Irving Hydroelectric Project, Childs System, Office, Forest Service Road 708/502, Camp Verde, Yavapai County, AZ

Pareto fronts for multiobjective optimization design on materials data

NASA Astrophysics Data System (ADS)

Gopakumar, Abhijith; Balachandran, Prasanna; Gubernatis, James E.; Lookman, Turab

Optimizing multiple properties simultaneously is vital in materials design. Here we apply infor- mation driven, statistical optimization strategies blended with machine learning methods, to address multi-objective optimization tasks on materials data. These strategies aim to find the Pareto front consisting of non-dominated data points from a set of candidate compounds with known character- istics. The objective is to find the pareto front in as few additional measurements or calculations as possible. We show how exploration of the data space to find the front is achieved by using uncer- tainties in predictions from regression models. We test our proposed design strategies on multiple, independent data sets including those from computations as well as experiments. These include data sets for Max phases, piezoelectrics and multicomponent alloys.

Front-End Analysis Cornerstone of Logistics

NASA Technical Reports Server (NTRS)

Nager, Paul J.

2000-01-01

The presentation provides an overview of Front-End Logistics Support Analysis (FELSA), when it should be performed, benefits of performing FELSA and why it should be performed, how it is conducted, and examples.

Automated Detection of Fronts using a Deep Learning Convolutional Neural Network

NASA Astrophysics Data System (ADS)

Biard, J. C.; Kunkel, K.; Racah, E.

2017-12-01

A deeper understanding of climate model simulations and the future effects of global warming on extreme weather can be attained through direct analyses of the phenomena that produce weather. Such analyses require these phenomena to be identified in automatic, unbiased, and comprehensive ways. Atmospheric fronts are centrally important weather phenomena because of the variety of significant weather events, such as thunderstorms, directly associated with them. In current operational meteorology, fronts are identified and drawn visually based on the approximate spatial coincidence of a number of quasi-linear localized features - a trough (relative minimum) in air pressure in combination with gradients in air temperature and/or humidity and a shift in wind, and are categorized as cold, warm, stationary, or occluded, with each type exhibiting somewhat different characteristics. Fronts are extended in space with one dimension much larger than the other (often represented by complex curved lines), which poses a significant challenge for automated approaches. We addressed this challenge by using a Deep Learning Convolutional Neural Network (CNN) to automatically identify and classify fronts. The CNN was trained using a "truth" dataset of front locations identified by National Weather Service meteorologists as part of operational 3-hourly surface analyses. The input to the CNN is a set of 5 gridded fields of surface atmospheric variables, including 2m temperature, 2m specific humidity, surface pressure, and the two components of the 10m horizontal wind velocity vector at 3-hr resolution. The output is a set of feature maps containing the per - grid cell probabilities for the presence of the 4 front types. The CNN was trained on a subset of the data and then used to produce front probabilities for each 3-hr time snapshot over a 14-year period covering the continental United States and some adjacent areas. The total frequencies of fronts derived from the CNN outputs matches

Bacterial properties of rainwater associated with cyclones, stationary fronts and typhoons in southwestern Japan

NASA Astrophysics Data System (ADS)

Zhang, D.; Hu, W.; Niu, H.

2016-12-01

The activities and role of bioaerosols in aerosol-cloud-precipitation links are important but unresolved issues in atmospheric and microbiological sciences. Bacteria, a main part of bioaerosols, are ubiquitous in atmospheric water. They are considered to be involved in the processes of cloud condensation and ice nuclei formation. However, to date, little information on rainwater bacteria is available. Rainwater samples were collected at a suburban site in southwestern Japan during October 2014 to September 2015. Results show that the cell concentration of rainwater bacteria was 2.3±1.5×104 cells ml-1, with a viability of 80±10% on average. The bacterial abundance and viability systematically differed with the weather systems causing rain. In cold-front-derived rain, the average bacterial concentration was the highest (3.5±1.6×104 cells ml-1), with the lowest viability as 75%. In the stationary-front-derived rain during Meiyu period and typhoon rain, the average bacterial concentrations were lower, but with higher viability. In stationary-front-derived rain during non-Meiyu period, the average abundance was higher (2.4±1.6×104 cells ml-1), while the viability was lower (78%) than those during Meiyu period. It was suggested that clouds produced by air mass from ocean areas carried fewer bacteria but with higher viability than those originated from continental regions. Bacterial concentrations in rainwater did not show good correlations with the ratios of total and decreased airborne particle concentrations to rainfall. Combining the univariate and factorial analysis of chemical compositions and bacterial abundance, we found that bacteria in rainwater were mainly associated with nss-SO42-, nss-Ca2+, and NO3-, which can act as nuclei or be produced within clouds. The cultured heterotrophic marine bacteria were of much higher abundance in stationary-front-derived rain than those in cold-front-derived rain. Bacterial genera containing ice nucleation active

Neotectonics and structure of the Himalayan deformation front in the Kashmir Himalaya, India: Implication in defining what controls a blind thrust front in an active fold-thrust belt

NASA Astrophysics Data System (ADS)

Gavillot, Y. G.; Meigs, A.; Yule, J. D.; Rittenour, T. M.; Malik, M. O. A.

2014-12-01

Active tectonics of a deformation front constrains the kinematic evolution and structural interaction between the fold-thrust belt and most-recently accreted foreland basin. In Kashmir, the Himalayan Frontal thrust (HFT) is blind, characterized by a broad fold, the Suruin-Mastargh anticline (SMA), and displays no emergent faults cutting either limb. A lack of knowledge of the rate of shortening and structural framework of the SMA hampers quantifying the earthquake potential for the deformation front. Our study utilized the geomorphic expression of dated deformed terraces on the Ujh River in Kashmir. Six terraces are recognized, and three yield OSL ages of 53 ka, 33 ka, and 0.4 ka. Vector fold restoration of long terrace profiles indicates a deformation pattern characterized by regional uplift across the anticlinal axis and back-limb, and by fold limb rotation on the forelimb. Differential uplift across the fold trace suggests localized deformation. Dip data and stratigraphic thicknesses suggest that a duplex structure is emplaced at depth along the basal décollement, folding the overlying roof thrust and Siwalik-Muree strata into a detachment-like fold. Localized faulting at the fold axis explains the asymmetrical fold geometry. Folding of the oldest dated terrace, suggest that rock uplift rates across the SMA range between 2.0-1.8 mm/yr. Assuming a 25° dipping ramp for the blind structure on the basis of dip data constraints, the shortening rate across the SMA ranges between 4.4-3.8 mm/yr since ~53 ka. Of that rate, ~1 mm/yr is likely absorbed by minor faulting in the near field of the fold axis. Given that Himalaya-India convergence is ~18.8-11 mm/yr, internal faults north of the deformation front, such as the Riasi thrust absorbs more of the Himalayan shortening than does the HFT in Kashmir. We attribute a non-emergent thrust at the deformation front to reflect deformation controlled by pre-existing basin architecture in Kashmir, in which the thick succession

Morphological variation and zoogeography of racers (Coluber constrictor) in the central Rocky Mountains

USGS Publications Warehouse

Corn, Paul Stephen; Bury, R. Bruce

1986-01-01

We examined 63 specimens of Coluber constrictor from Colorado and Utah using eight external morphological characters that have been used to distinguish C. c. mormon from C. c. flaviventris. We grouped the snakes into three Operational Taxonomic Units (OTU's) in a transect across the Rocky Mountains: the eastern Front Range foothills in Colorado; the inter-mountain region (western slope of Colorado and northeastern Utah); and the western foothills of the Wasatch Mountains in Utah. Statistically significant variation among the OTU's was discovered for ration of tail length to total length, number of central and subcaudal scales, and number of dentary teeth. However, variation is clinal with nearly complete overlap from one end f the transect to the other for each character, suggesting a wide zone of intergradiation in the inter-mountain region. We do not believe reported differences in reproductive parameters between Great Plains and Great Basin racers are sufficient grounds for recognition of species, because clutch size is both geographically variable and dependent on the environment. The distribution of C. constrictor is similar to that of other reptiles with transmontane distributions in the western United States, and we suggest two possible routes of dispersal across the Continental Divide in southwestern Wyoming. Thus, elevation of C. c. mormon to species status is not supported by morphological, reproductive, or zoogeographic evidence.

Magnetotelluric Imaging of Lower Crustal Melt and Lithospheric Hydration in the Rocky Mountain Front Transition Zone, Colorado, USA

NASA Astrophysics Data System (ADS)

Feucht, D. W.; Sheehan, A. F.; Bedrosian, P. A.

2017-12-01

We present an electrical resistivity model of the crust and upper mantle from two-dimensional (2-D) anisotropic inversion of magnetotelluric data collected along a 450 km transect of the Rio Grande rift, southern Rocky Mountains, and High Plains in Colorado, USA. Our model provides a window into the modern-day lithosphere beneath the Rocky Mountain Front to depths in excess of 150 km. Two key features of the 2-D resistivity model are (1) a broad zone ( 200 km wide) of enhanced electrical conductivity (<20 Ωm) in the midcrust to lower crust that is centered beneath the highest elevations of the southern Rocky Mountains and (2) hydrated lithospheric mantle beneath the Great Plains with water content in excess of 100 ppm. We interpret the high conductivity region of the lower crust as a zone of partially molten basalt and associated deep-crustal fluids that is the result of recent (less than 10 Ma) tectonic activity in the region. The recent supply of volatiles and/or heat to the base of the crust in the late Cenozoic implies that modern-day tectonic activity in the western United States extends to at least the western margin of the Great Plains. The transition from conductive to resistive upper mantle is caused by a gradient in lithospheric modification, likely including hydration of nominally anhydrous minerals, with maximum hydration occurring beneath the Rocky Mountain Front. This lithospheric "hydration front" has implications for the tectonic evolution of the continental interior and the mechanisms by which water infiltrates the lithosphere.

Influence of viscoelastic nature on the intermittent peel-front dynamics of adhesive tape

NASA Astrophysics Data System (ADS)

Kumar, Jagadish; Ananthakrishna, G.

2010-07-01

We investigate the influence of viscoelastic nature of the adhesive on the intermittent peel front dynamics by extending a recently introduced model for peeling of an adhesive tape. As time and rate-dependent deformation of the adhesives are measured in stationary conditions, a crucial step in incorporating the viscoelastic effects applicable to unstable intermittent peel dynamics is the introduction of a dynamization scheme that eliminates the explicit time dependence in terms of dynamical variables. We find contrasting influences of viscoelastic contribution in different regions of tape mass, roller inertia, and pull velocity. As the model acoustic energy dissipated depends on the nature of the peel front and its dynamical evolution, the combined effect of the roller inertia and pull velocity makes the acoustic energy noisier for small tape mass and low-pull velocity while it is burstlike for low-tape mass, intermediate values of the roller inertia and high-pull velocity. The changes are quantified by calculating the largest Lyapunov exponent and analyzing the statistical distributions of the amplitudes and durations of the model acoustic energy signals. Both single and two stage power-law distributions are observed. Scaling relations between the exponents are derived which show that the exponents corresponding to large values of event sizes and durations are completely determined by those for small values. The scaling relations are found to be satisfied in all cases studied. Interestingly, we find only five types of model acoustic emission signals among multitude of possibilities of the peel front configurations.

Great Basin cold desert shrublands and the Desert Experimental Range

Treesearch

Stanley G. Kitchen; Stephanie L. Carlson

2008-01-01

The Great Basin is a vast, internally drained region of the Western United States, bounded by the Sierra Nevada and southern Cascade Mountain ranges to the west and the Wasatch Mountains and western rim of the Colorado Plateau to the east. Although less discrete, northern and southern boundaries are generally defined by the drainages of the Columbia and Colorado Rivers...

Cold Front Cools the Eastern U.S.

NASA Image and Video Library

2014-07-16

Summertime heat and humidity in the U.S. East Coast is on hold for a couple of days thanks to a cold front and that brought clouds, showers, thunderstorms, and some severe weather on July 16 to the coast. The National Oceanic and Atmospheric Administration (NOAA) noted that the dip in the jet stream will create below normal temperatures for most of the Central and Eastern U.S. for the next couple of days. NOAA's GOES-East satellite captured an image of the clouds associated with the cold front on July 16 at 1630 UTC (12:30 p.m. EDT).The clouds follow the front which stretches from the Florida panhandle, across Florida and up the U.S. East Coast into eastern Canada. Along the front lie two areas of low pressure, one over eastern New England, and the other offshore from South Carolina. Both of those low pressure areas are associated with additional cloudiness along the front. GOES satellites are managed by NOAA. The image was created by the NASA/NOAA GOES Project at NASA's Goddard Space Flight Center in Greenbelt, Maryland. GOES satellites provide the kind of continuous monitoring necessary for intensive data analysis. Geostationary describes an orbit in which a satellite is always in the same position with respect to the rotating Earth. This allows GOES to hover continuously over one position on Earth's surface, appearing stationary. As a result, GOES provide a constant vigil for the atmospheric "triggers" for severe weather conditions such as tornadoes, flash floods, hail storms and hurricanes. For updated information about the storm system, visit NOAA's National Weather Service website: www.weather.gov For more information about GOES satellites, visit: www.goes.noaa.gov/ or goes.gsfc.nasa.gov/ Image Credit: NASA/NOAA GOES Project, Text: Rob Gutro NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in

Three-dimensional hybrid grid generation using advancing front techniques

NASA Technical Reports Server (NTRS)

Steinbrenner, John P.; Noack, Ralph W.

1995-01-01

A new 3-dimensional hybrid grid generation technique has been developed, based on ideas of advancing fronts for both structured and unstructured grids. In this approach, structured grids are first generate independently around individual components of the geometry. Fronts are initialized on these structure grids, and advanced outward so that new cells are extracted directly from the structured grids. Employing typical advancing front techniques, cells are rejected if they intersect the existing front or fail other criteria When no more viable structured cells exist further cells are advanced in an unstructured manner to close off the overall domain, resulting in a grid of 'hybrid' form. There are two primary advantages to the hybrid formulation. First, generating blocks with limited regard to topology eliminates the bottleneck encountered when a multiple block system is used to fully encapsulate a domain. Individual blocks may be generated free of external constraints, which will significantly reduce the generation time. Secondly, grid points near the body (presumably with high aspect ratio) will still maintain a structured (non-triangular or tetrahedral) character, thereby maximizing grid quality and solution accuracy near the surface.

Transverse tectonic structural elements across Himalayan mountain front, eastern Arunachal Himalaya, India: Implication of superposed landform development on analysis of neotectonics

NASA Astrophysics Data System (ADS)

Bhakuni, S. S.; Luirei, Khayingshing; Kothyari, Girish Ch.; Imsong, Watinaro

2017-04-01

Structural and morphotectonic signatures in conjunction with the geomorphic indices are synthesised to trace the role of transverse tectonic features in shaping the landforms developed along the frontal part of the eastern Arunachal sub-Himalaya. Mountain front sinuosity (Smf) index values close to one are indicative of the active nature of the mountain front all along the eastern Arunachal Himalaya, which can be directly attributed to the regional uplift along the Himalayan Frontal Thrust (HFT). However, the mountain front is significantly sinusoidal around junctions between HFT/MBT (Main Boundary Thrust) and active transverse faults. The high values of stream length gradient (SL) and stream steepness (Ks) indices together with field evidence of fault scarps, offset of terraces, and deflection of streams are markers of neotectonic uplift along the thrusts and transverse faults. This reactivation of transverse faults has given rise to extensional basins leading to widening of the river courses, providing favourable sites for deposition of recent sediments. Tectonic interactions of these transverse faults with the Himalayan longitudinal thrusts (MBT/HFT) have segmented the mountain front marked with varying sinuosity. The net result is that a variety of tectonic landforms recognized along the mountain front can be tracked to the complex interactions among the transverse and longitudinal tectonic elements. Some distinctive examples are: in the eastern extremity of NE Himalaya across the Dibang River valley, the NW-SE trending mountain front is attenuated by the active Mishmi Thrust that has thrust the Mishmi crystalline complex directly over the alluvium of the Brahmaputra plains. The junction of the folded HFT and Mishmi Thrust shows a zone of brecciated and pulverized rocks along which transverse axial planar fracture cleavages exhibit neotectonic activities in a transverse fault zone coinciding with the Dibang River course. Similarly, the transverse faults cut the

OBLIQUE/EXTERIOR VIEW, SIDE AND FRONT ELEVATIONS, FOUR ROOMPYRAMIDAL ROOF COTTAGE ...

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

OBLIQUE/EXTERIOR VIEW, SIDE AND FRONT ELEVATIONS, FOUR ROOM-PYRAMIDAL ROOF COTTAGE (AT 328 CAMILLE) WITH FRONT YARD LANDSCAPING. - Mulga Community, Off AL 269 at I-20-59, Birmingham, Jefferson County, AL

Temperature in subsonic and supersonic radiation fronts measured at OMEGA

NASA Astrophysics Data System (ADS)

Johns, Heather; Kline, John; Lanier, Nick; Perry, Ted; Fontes, Chris; Fryer, Chris; Brown, Colin; Morton, John

2017-10-01

Propagation of heat fronts relevant to astrophysical plasmas is challenging in the supersonic regime. Plasma Te changes affect opacity and equation of state without hydrodynamic change. In the subsonic phase density perturbations form at material interfaces as the plasma responds to radiation pressure of the front. Recent experiments at OMEGA studied this transition in aerogel foams driven by a hohlraum. In COAX, two orthogonal backlighters drive x-ray radiography and K-shell absorption spectroscopy to diagnose the subsonic shape of the front and supersonic Te profiles. Past experiments used absorption spectroscopy in chlorinated foams to measure the heat front; however, Cl dopant is not suitable for higher material temperatures at NIF. COAX has developed use of Sc and Ti dopants to diagnose Te between 60-100eV and 100-180eV. Analysis with PrismSPECT using OPLIB tabular opacity data will evaluate the platform's ability to advance radiation transport in this regime.

Effectively Transparent Front Contacts for Optoelectronic Devices

DOE PAGES

Saive, Rebecca; Borsuk, Aleca M.; Emmer, Hal S.; ...

2016-06-10

Effectively transparent front contacts for optoelectronic devices achieve a measured transparency of up to 99.9% and a measured sheet resistance of 4.8 Ω sq-1. These 3D microscale triangular cross-section grid fingers redirect incoming photons efficiently to the active semiconductor area and can replace standard grid fingers as well as transparent conductive oxide layers in optoelectronic devices. Optoelectronic devices such as light emitting diodes, photodiodes, and solar cells play an important and expanding role in modern technology. Photovoltaics is one of the largest optoelectronic industry sectors and an ever-increasing component of the world's rapidly growing renewable carbon-free electricity generation infrastructure. Inmore » recent years, the photovoltaics field has dramatically expanded owing to the large-scale manufacture of inexpensive crystalline Si and thin film cells and modules. The current record efficiency (η = 25.6%) Si solar cell utilizes a heterostructure intrinsic thin layer (HIT) design[1] to enable increased open circuit voltage, while more mass-manufacturable solar cell architectures feature front contacts.[2, 3] Thus improved solar cell front contact designs are important for future large-scale photovoltaics with even higher efficiency.« less

Taking charge: front-line nurse leadership development.

PubMed

Schwarzkopf, Ruth; Sherman, Rose O; Kiger, Anna J

2012-04-01

The recent Institute of Medicine (2010) report, The Future of Nursing: Leading Change, Advancing Health, included a recommendation that nurses at all levels should be prepared and enabled to lead change to advance health care in the United States. Historically, in most organizations, nursing leadership development programs have focused on nurses in management or executive roles rather than those working in front-line leadership roles. This article describes a front-line leadership development initiative developed by Tenet Healthcare Corporation and attended by 400 charge nurses. Program development, evaluation, and lessons learned that can be applied in other organizations are discussed. Copyright 2012, SLACK Incorporated.

Water masses, ocean fronts, and the structure of Antarctic seabird communities: putting the eastern Bellingshausen Sea in perspective

USGS Publications Warehouse

Ribic, Christine A.; Ainley, David G.; Ford, R. Glenn; Fraser, William R.; Tynan, Cynthia T.; Woehler, Eric J.

2015-01-01

Waters off the western Antarctic Peninsula (i.e., the eastern Bellingshausen Sea) are unusually complex owing to the convergence of several major fronts. Determining the relative influence of fronts on occurrence patterns of top-trophic species in that area, therefore, has been challenging. In one of the few ocean-wide seabird data syntheses, in this case for the Southern Ocean, we analyzed ample, previously collected cruise data, Antarctic-wide, to determine seabird species assemblages and quantitative relationships to fronts as a way to provide context to the long-term Palmer LTER and the winter Southern Ocean GLOBEC studies in the eastern Bellingshausen Sea. Fronts investigated during both winter (April–September) and summer (October–March) were the southern boundary of the Antarctic Circumpolar Current (ACC), which separates the High Antarctic from the Low Antarctic water mass, and within which are embedded the marginal ice zone and Antarctic Shelf Break Front; and the Antarctic Polar Front, which separates the Low Antarctic and the Subantarctic water masses. We used clustering to determine species' groupings with water masses, and generalized additive models to relate species' densities, biomass and diversity to distance to respective fronts. Antarctic-wide, in both periods, highest seabird densities and lowest species diversity were found in the High Antarctic water mass. In the eastern Bellingshausen, seabird density in the High Antarctic water mass was lower (as low as half that of winter) than found in other Antarctic regions. During winter, Antarctic-wide, two significant species groups were evident: one dominated by Adélie penguins (Pygoscelis adeliae) (High Antarctic water mass) and the other by petrels and prions (no differentiation among water masses); in eastern Bellingshausen waters during winter, the one significant species group was composed of species from both Antarctic-wide groups. In summer, Antarctic-wide, a High Antarctic group

The dynamics of oceanic fronts. Part 1: The Gulf Stream

NASA Technical Reports Server (NTRS)

Kao, T. W.

1970-01-01

The establishment and maintenance of the mean hydrographic properties of large scale density fronts in the upper ocean is considered. The dynamics is studied by posing an initial value problem starting with a near surface discharge of buoyant water with a prescribed density deficit into an ambient stationary fluid of uniform density. The full time dependent diffusion and Navier-Stokes equations for a constant Coriolis parameter are used in this study. Scaling analysis reveals three independent length scales of the problem, namely a radius of deformation or inertial length scale, Lo, a buoyance length scale, ho, and a diffusive length scale, hv. Two basic dimensionless parameters are then formed from these length scales, the thermal (or more precisely, the densimetric) Rossby number, Ro = Lo/ho and the Ekman number, E = hv/ho. The governing equations are then suitably scaled and the resulting normalized equations are shown to depend on E alone for problems of oceanic interest. Under this scaling, the solutions are similar for all Ro. It is also shown that 1/Ro is a measure of the frontal slope. The governing equations are solved numerically and the scaling analysis is confirmed. The solution indicates that an equilibrium state is established. The front can then be rendered stationary by a barotropic current from a larger scale along-front pressure gradient. In that quasisteady state, and for small values of E, the main thermocline and the inclined isopycnics forming the front have evolved, together with the along-front jet. Conservation of potential vorticity is also obtained in the light water pool. The surface jet exhibits anticyclonic shear in the light water pool and cyclonic shear across the front.

Seasonal variability of thermal fronts in the northern South China Sea from satellite data

NASA Astrophysics Data System (ADS)

Wang, Dongxiao; Liu, Yun; Qi, Yiquan; Shi, Ping

The 8-year (1991-1998) Pathfinder sea surface temperature data have been applied here to produce the objectively derived seasonality of the oceanic thermal fronts in the northern South China Sea from 17°N to 25°N. Several fronts have been clearly distinguished, namely, Fujian and Guangdong Coastal Water, Pear River Estuary Coastal, Taiwan Bank, Kuroshio Intrusion, Hainan Island East Coast and Tonkin Gulf Coastal fronts. The frontal patterns in winter, spring and summer are quite similar, whereas individual fronts display different modes of seasonal variability due to different mechanisms favoring those fronts.

Macroscopic response to microscopic intrinsic noise in three-dimensional Fisher fronts.

PubMed

Nesic, S; Cuerno, R; Moro, E

2014-10-31

We study the dynamics of three-dimensional Fisher fronts in the presence of density fluctuations. To this end we simulate the Fisher equation subject to stochastic internal noise, and study how the front moves and roughens as a function of the number of particles in the system, N. Our results suggest that the macroscopic behavior of the system is driven by the microscopic dynamics at its leading edge where number fluctuations are dominated by rare events. Contrary to naive expectations, the strength of front fluctuations decays extremely slowly as 1/logN, inducing large-scale fluctuations which we find belong to the one-dimensional Kardar-Parisi-Zhang universality class of kinetically rough interfaces. Hence, we find that there is no weak-noise regime for Fisher fronts, even for realistic numbers of particles in macroscopic systems.

The thermodynamic and dynamical features of double front structures during 21 31 July 1998 in China

NASA Astrophysics Data System (ADS)

Zhou, Yushu; Deng, Guo; Lei, Ting; Ju, Jianhua

2005-11-01

The daily 1° × 1° data of the Aviation (AVN) model, the black body temperature (TBB) data of cloud top, and cloud images by geostationary meteorological satellite (GMS) are used to identify a dew-point front near the periphery of the western Pacific subtropical high (WPSH). The results clearly demonstrate the existence of the dew-point front, and its thermodynamic and dynamic structural characteristics are analyzed in detail. The dew-point front is a transitional belt between the moist southwest monsoon flow and the dry adiabatic sinking flow near the WPSH, manifested by a large horizontal moisture gradient in the mid-lower troposphere and conjugated with the mei-yu front to form a predominant double-front structure associated with intense rainfall in the mei-yu period. The mei-yu front is located between 30° and 35°N, vertically extends from the ground level to the upper level and shifts northward. The dew-point front is to the south of the mei-yu front and lies up against the periphery of the WPSH. Generally, it is located between 850 hPa and 500 hPa. On the dew-point front side, the southwesterly prevails at the lower level and the northeasterly at the upper level; this wind distribution is different from that on the mei-yu front side. Vertical ascending motion exists between the two fronts, and there are descending motions on the north side of the mei-yu front and on the south side of the dew-point front, which form a secondary circulation. The dynamics of the double fronts also have some interesting features. At the lower level, positive vertical vorticity and obvious convergence between the two fronts are clearly identified. At the mid-lower level, negative local change of the divergence (corresponding to increasing convergence) is often embedded in the two fronts or against the mei-yu front. Most cloud clusters occur between the two fronts and propagate down stream in a wave-like manner.

Front propagation in one-dimensional spatially periodic bistable media

NASA Astrophysics Data System (ADS)

Löber, Jakob; Bär, Markus; Engel, Harald

2012-12-01

Front propagation in heterogeneous bistable media is studied using the Schlögl model as a representative example. Spatially periodic modulations in the parameters of the bistable kinetics are taken into account perturbatively. Depending on the ratio L/l (L is the spatial period of the heterogeneity, l is the front width), appropriate singular perturbation techniques are applied to derive an ordinary differential equation for the position of the front in the presence of the heterogeneities. From this equation, the dependence of the average propagation speed on L/l as well as on the modulation amplitude is calculated. The analytical results obtained predict velocity overshoot, different cases of propagation failure, and the propagation speed for very large spatial periods in quantitative agreement with the results of direct numerical simulations of the underlying reaction-diffusion equation.

The Mesozoic palaeo-relief and immature front belt of northern Tianshan

NASA Astrophysics Data System (ADS)

Chen, K.; Gumiaux, C.; Augier, R.; Chen, Y.; Wang, Q.

2012-04-01

Tianshan displays as very uncylindrical with rapid lateral transitions from one type to the other. This study shows that the Cenozoic reactivation of the Tianshan range has not yielded important deformation along its contact with the juxtaposed Junggar basin, into the studied segment. Besides, the topography of the current northern Tianshan area can not be considered as the unique consequence of Cenozoic reactivation. Finally, from a compilation of structural field observations with available seismic geophysical data, regional cross sections show only moderate shortening in the deformed belt of the northern piedmont of Tianshan. Structure of the fold-and-thrust belt looks controlled by several basement thrusts faults separating rigid blocks. This study suggests that the northern front of the intra-continental Tianshan range may be considered as an immature thrust belt and is still at an early developing stage of its orogenic evolution.

The forearc crustal evolution of Izu-Bonin (Ogasawara) region obtained by seismic reflection and refraction surveys

NASA Astrophysics Data System (ADS)

Yamashita, M.; Kodaira, S.; Takahashi, N.; Tatsumi, Y.; Kaneda, Y.

2009-12-01

The Izu-Bonin (Ogasawara)-Mariana (IBM) arc is known to the typical oceanic island arc, and it is the most suitable area to understand the growth process of island arc. By previous seismic survey and deep sea drilling, convex basements are distributed along North-South direction in present forearc region. The convex basements are reported to be formed during Oligocene and Eocene (Taylor, 1992). In IBM forearc region, the middle crust with 6 km/s is recognized by seismic survey using OBSs. In IBM region, four IODP drilling sites are proposed in order to understand comprehensive growth process of arc and continental crust evolution. Two of them are located in forearc region. Japan Agency for Marine-Earth Science and Technology (JAMSTEC) carried out multi-channel seismic reflection survey using 7,800/12,000 cu.in. air gun and 5-6 km streamer with 444/204 ch hydrophones in the IBM region since 2004. We investigate the crustal structure beneath the Izu-Bonin forearc region for contribution of IBM drilling site along five long survey lines, which are across from present volcanic front to forearc basin. Seismic refraction survey is also conducted across forearc region using 84 OBSs every 1 km interval. Shallow crustal structure can be classified four units including basement which compared between previous drilling results and obtained seismic profiles. In IBM forearc region, thick sedimentary basin distribute from east side of volcanic front. Two convex basement peaks are indicated in across profile of forearc region. These peaks are estimated the top of paleoarc (Oligocene and Eocene) by previous ODP drilling. The half graben structure with major displacement is identified from west side of present volcanic front to the top of Oligocene arc. On the other hand, there is no displacement of sediments between the Oligocene arc and Eocene arc. This result shows the same origin of basement between the present volcanic front and Oligocene arc. There is long time difference of

Assessing Attentional Prioritization of Front-of-Pack Nutrition Labels using Change Detection

PubMed Central

Becker, Mark W.; Sundar, Raghav Prashant; Bello, Nora; Alzahabi, Reem; Weatherspoon, Lorraine; Bix, Laura

2015-01-01

We used a change detection method to evaluate attentional prioritization of nutrition information that appears in the traditional “Nutrition Facts Panel” and in front-of-pack nutrition labels. Results provide compelling evidence that front-of-pack labels attract attention more readily than the Nutrition Facts Panel, even when participants are not specifically tasked with searching for nutrition information. Further, color-coding the relative nutritional value of key nutrients within the front-of-pack label resulted in increased attentional prioritization of nutrition information, but coding using facial icons did not significantly increase attention to the label. Finally, the general pattern of attentional prioritization across front-of-pack designs was consistent across a diverse sample of participants. Our results indicate that color-coded, front-of-pack nutrition labels increase attention to the nutrition information of packaged food, a finding that has implications for current policy discussions regarding labeling change. PMID:26851468

Simulation based comparative analysis of photoresponse in front- and back-illuminated GaN P-I-N ultraviolet photodetectors

NASA Astrophysics Data System (ADS)

Wang, Jun; Guo, Jin; Xie, Feng; Wang, Guosheng; Wu, Haoran; Song, Man; Yi, Yuanyuan

2016-10-01

This paper presents the comparative analysis of influence of doping level and doping profile of the active region on zero bias photoresponse characteristics of GaN-based p-i-n ultraviolet (UV) photodetectors operating at front- and back-illuminated. A two dimensional physically-based computer simulation of GaN-based p-i-n UV photodetectors is presented. We implemented GaN material properties and physical models taken from the literature. It is shown that absorption layer doping profile has notable impacts on the photoresponse of the device. Especially, the effect of doping concentration and distribution of the absorption layer on photoresponse is discussed in detail. In the case of front illumination, comparative to uniform n-type doping, the device with n-type Gaussian doping profiles at absorption layer has higher responsivity. Comparative to front illumination, back illuminated detector with p-type doping profiles at absorption layer has higher maximum photoresponse, while the Gaussian doping profiles have a weaker ability to enhance the device responsivity. It is demonstrated that electric field distribution, mobility degradation, and recombinations are jointly responsible for the variance of photoresponse. Our work enriches the understanding and utilization of GaN based p-i-n UV photodetectors.

Characterisation of the Interaction between Toroidal Vortex Structures and Flame Front Propagation

NASA Astrophysics Data System (ADS)

Long, E. J.; Hargrave, G. K.; Jarvis, S.; Justham, T.; Halliwell, N.

2006-07-01

Experimental laser diagnostic data is presented for flame characterisation during interactions with toroidal vortices generated in the wake of an annular obstacle. A novel twin section combustion chamber has been utilised to allow the controlled formation of stable eddy structures into which a flame front can propagate. High speed laser sheet visualisation was employed to record the flow field and flame front temporal development and high-speed digital particle image velocimetry was used to quantify the velocity field of the unburnt mixture ahead of the flame front. Results provide characterisation of the toroidal vortex/flame front interaction for a range of vortex scales of and recirculation strengths.

Motivation and Front-End Analysis.

ERIC Educational Resources Information Center

Harless, Joe

1978-01-01

Relates Front-End Analysis (FEA) to motivation by categorizing it as either Diagnostic FEA or Planning FEA. The former is used to diagnose existing problems and prescribe motivational programs; the latter assumes that motivational programs must be implemented, along with other programs, to build the optimum environment to support the performance.…

Intense deformation field at oceanic front inferred from directional sea surface roughness observations

NASA Astrophysics Data System (ADS)

Rascle, Nicolas; Molemaker, Jeroen; Marié, Louis; Nouguier, Frédéric; Chapron, Bertrand; Lund, Björn; Mouche, Alexis

2017-06-01

Fine-scale current gradients at the ocean surface can be observed by sea surface roughness. More specifically, directional surface roughness anomalies are related to the different horizontal current gradient components. This paper reports results from a dedicated experiment during the Lagrangian Submesoscale Experiment (LASER) drifter deployment. A very sharp front, 50 m wide, is detected simultaneously in drifter trajectories, sea surface temperature, and sea surface roughness. A new observational method is applied, using Sun glitter reflections during multiple airplane passes to reconstruct the multiangle roughness anomaly. This multiangle anomaly is consistent with wave-current interactions over a front, including both cross-front convergence and along-front shear with cyclonic vorticity. Qualitatively, results agree with drifters and X-band radar observations. Quantitatively, the sharpness of roughness anomaly suggests intense current gradients, 0.3 m s-1 over the 50 m wide front. This work opens new perspectives for monitoring intense oceanic fronts using drones or satellite constellations.

Targeting NCK-Mediated Endothelial Cell Front-Rear Polarity Inhibits Neovascularization.

PubMed

Dubrac, Alexandre; Genet, Gael; Ola, Roxana; Zhang, Feng; Pibouin-Fragner, Laurence; Han, Jinah; Zhang, Jiasheng; Thomas, Jean-Léon; Chedotal, Alain; Schwartz, Martin A; Eichmann, Anne

2016-01-26

Sprouting angiogenesis is a key process driving blood vessel growth in ischemic tissues and an important drug target in a number of diseases, including wet macular degeneration and wound healing. Endothelial cells forming the sprout must develop front-rear polarity to allow sprout extension. The adaptor proteins Nck1 and 2 are known regulators of cytoskeletal dynamics and polarity, but their function in angiogenesis is poorly understood. Here, we show that the Nck adaptors are required for endothelial cell front-rear polarity and migration downstream of the angiogenic growth factors VEGF-A and Slit2. Mice carrying inducible, endothelial-specific Nck1/2 deletions fail to develop front-rear polarized vessel sprouts and exhibit severe angiogenesis defects in the postnatal retina and during embryonic development. Inactivation of NCK1 and 2 inhibits polarity by preventing Cdc42 and Pak2 activation by VEGF-A and Slit2. Mechanistically, NCK binding to ROBO1 is required for both Slit2- and VEGF-induced front-rear polarity. Selective inhibition of polarized endothelial cell migration by targeting Nck1/2 prevents hypersprouting induced by Notch or Bmp signaling inhibition, and pathological ocular neovascularization and wound healing, as well. These data reveal a novel signal integration mechanism involving NCK1/2, ROBO1/2, and VEGFR2 that controls endothelial cell front-rear polarity during sprouting angiogenesis. © 2015 American Heart Association, Inc.

Conceptual design of front ends for the advanced photon source multi-bend achromats upgrade

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jaski, Y., E-mail: jaskiy@aps.anl.gov; Westferro, F., E-mail: westferr@aps.anl.gov; Lee, S. H., E-mail: shlee@aps.anl.gov

2016-07-27

The proposed Advanced Photon Source (APS) upgrade from a double-bend achromats (DBA) to multi-bend achromats (MBA) lattice with ring energy change from 7 GeV to 6 GeV and beam current from 100 mA to 200 mA poses new challenges for front ends. All front ends must be upgraded to fulfill the following requirements: 1) handle the high heat load from two insertion devices in either inline or canted configuration, 2) include a clearing magnet in the front end to deflect and dump any electrons in case the electrons escape from the storage ring during swap-out injection with the safety shuttersmore » open, 3) incorporate the next generation x-ray beam position monitors (XBPMs) into the front end to meet the new stringent beam stability requirements. This paper presents the evaluation of the existing APS front ends and standardizes the insertion device (ID) front ends into two types: one for the single beam and one for the canted beams. The conceptual design of high heat load front end (HHLFE) and canted undulator front end (CUFE) for APS MBA upgrade is presented.« less

Conceptual Design of Front Ends for the Advanced Photon Source Multi-bend Achromats Upgrade

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jaski, Y.; Westferro, F.; Lee, S. H.

2016-07-27

The proposed Advanced Photon Source (APS) upgrade from a double-bend achromats (DBA) to multi-bend achromats (MBA) lattice with ring energy change from 7 GeV to 6 GeV and beam current from 100 mA to 200 mA poses new challenges for front ends. All front ends must be upgraded to fulfill the following requirements: 1) handle the high heat load from two insertion devices in either inline or canted configuration, 2) include a clearing magnet in the front end to deflect and dump any electrons in case the electrons escape from the storage ring during swap-out injection with the safety shuttersmore » open, 3) incorporate the next generation x-ray beam position monitors (XBPMs) into the front end to meet the new stringent beam stability requirements. This paper presents the evaluation of the existing APS front ends and standardizes the insertion device (ID) front ends into two types: one for the single beam and one for the canted beams. The conceptual design of high heat load front end (HHLFE) and canted undulator front end (CUFE) for APS MBA upgrade is presented.« less

Incorporating seepage losses into the unsteady streamflow equations for simulating intermittent flow along mountain front streams

USGS Publications Warehouse

Niswonger, R.G.; Prudic, David E.; Pohll, G.; Constantz, J.

2005-01-01

Seepage losses along numerous mountain front streams that discharge intermittently onto alluvial fans and piedmont alluvial plains are an important source of groundwater in the Basin and Range Province of the Western United States. Determining the distribution of seepage loss along mountain front streams is important when assessing groundwater resources of the region. Seepage loss along a mountain front stream in northern Nevada was evaluated using a one-dimensional unsteady streamflow model. Seepage loss was incorporated into the spatial derivatives of the streamflow equations. Because seepage loss from streams is dependent on stream depth, wetted perimeter, and streambed properties, a two-dimensional variably saturated flow model was used to develop a series of relations between seepage loss and stream depth for each reach. This method works when streams are separated from groundwater by variably saturated sediment. Two periods of intermittent flow were simulated to evaluate the modeling approach. The model reproduced measured flow and seepage losses along the channel. Seepage loss in the spring of 2000 was limited to the upper reaches on the alluvial plain and totaled 196,000 m3, whereas 64% of the seepage loss in the spring of 2004 occurred at the base of the alluvial plain and totaled 273,000 m3. A greater seepage loss at the base of the piedmont alluvial plain is attributed to increased streambed hydraulic conductivity caused by less armoring of the channel. The modeling approach provides a method for quantifying and distributing seepage loss along mountain front streams that cross alluvial fans or piedmont alluvial plains. Copyright 2005 by the American Geophysical Union.

Instant-Form and Light-Front Quantization of Field Theories

NASA Astrophysics Data System (ADS)

Kulshreshtha, Usha; Kulshreshtha, Daya Shankar; Vary, James

2018-05-01

In this work we consider the instant-form and light-front quantization of some field theories. As an example, we consider a class of gauged non-linear sigma models with different regularizations. In particular, we present the path integral quantization of the gauged non-linear sigma model in the Faddeevian regularization. We also make a comparision of the possible differences in the instant-form and light-front quantization at appropriate places.

Wind modulation of upwelling at the shelf-break front off Patagonia: Observational evidence

NASA Astrophysics Data System (ADS)

Carranza, M. M.; Gille, S. T.; Piola, A. R.; Charo, M.; Romero, S. I.

2017-03-01

The South-Atlantic Patagonian shelf is the largest chlorophyll-a (Chl-a) hot spot in Southern Ocean color images. While a persistent 1500 km long band of high Chl-a along the shelf-break front (SBF) is indicative of upwelling, the mechanisms that drive it are not entirely known. Along-front wind oscillations can enhance upwelling and provide a nutrient pumping mechanism at shelf-break fronts of western boundary currents. Here we assess wind-induced upwelling at the SBF off Patagonia from daily satellite Chl-a and winds, historical hydrographic observations, cross-shelf Chl-a fluorescence transects from two cruises, and in situ winds and water column structure from a mooring site. Satellite Chl-a composites segregated by along-front wind direction indicate that surface Chl-a is enhanced at the SBF with southerly winds and suppressed with northerly winds. Northerly winds also result in enhanced Chl-a further offshore (˜25-50 km). Synoptic transects as well as mean hydrographic sections segregated by along-front winds show isopycnals tilted upward for southerly winds. Spring observations from the mooring also suggest that southerly winds destratify the water column and northerly winds restratify, in agreement with Ekman transport interacting with the front. Moreover, changes in water column temperature lag along-front wind forcing by 2-4 days. Our results suggest that oscillations in along-front winds, on timescales typical of atmospheric storms (2-10 days), can significantly modulate the upwelling and Chl-a concentrations at the SBF off Patagonia, revealing the importance of wind-induced upwelling for shelf-slope exchange at shelf-break fronts of western boundary currents.

Passive microwave detection of river-plume fronts in the German Bight

NASA Technical Reports Server (NTRS)

Blume, H.-J. C.

1982-01-01

The NASA P-3 aircraft with the L- and S-band radiometer system on board participated in the MARSEN experiments carried out between August 30 and September 23, 1979. Measurements of surface temperature and salinity were concentrated on freshwater outflows of the Rivers Weser and Elbe in the German Bight. Three missions were carried out, on September 19, 22, and 23. The values of salinity are plotted as a function of geographic position, and contour maps of the salinity distribution are generated from the value plots. It is noted that on September 22, during a noon flood-tide, two river-plume salinity fronts were detected when a body of water with higher salinity existed in front of the Weser delta near Bremerhaven generating with the river outflow of lower saline waters a front of delta-S equals 5 per thousand. Another pocket of lower saline waters was found in front of the Elbe delta at Cuxhaven, which in turn set up a strong front of delta-S equals 6 per thousand. The morning low tide of September 23 did not exhibit this extreme condition.

Optimal front light design for reflective displays under different ambient illumination

NASA Astrophysics Data System (ADS)

Wang, Sheng-Po; Chang, Ting-Ting; Li, Chien-Ju; Bai, Yi-Ho; Hu, Kuo-Jui

2011-01-01

The goal of this study is to find out the optimal luminance and color temperature of front light for reflective displays in different ambient illumination by conducting series of psychophysical experiments. A color and brightness tunable front light device with ten LED units was built and been calibrated to present 256 luminance levels and 13 different color temperature at fixed luminance of 200 cd/m2. The experiment results revealed the best luminance and color temperature settings for human observers under different ambient illuminant, which could also assist the e-paper manufacturers to design front light device, and present the best image quality on reflective displays. Furthermore, a similar experiment procedure was conducted by utilizing new flexible e-signage display developed by ITRI and an optimal front light device for the new display panel has been designed and utilized.

Front fingering and complex dynamics driven by the interaction of buoyancy and diffusive instabilities.

PubMed

D'Hernoncourt, J; Merkin, J H; De Wit, A

2007-09-01

Traveling fronts can become transversally unstable either because of a diffusive instability arising when the key variables diffuse at sufficiently different rates or because of a buoyancy-driven Rayleigh-Taylor mechanism when the density jump across the front is statically unfavorable. The interaction between such diffusive and buoyancy instabilities of fronts is analyzed theoretically for a simple model system. Linear stability analysis and nonlinear simulations show that their interplay changes considerably the stability properties with regard to the pure Rayleigh-Taylor or diffusive instabilities of fronts. In particular, an instability scenario can arise which triggers convection around statically stable fronts as a result of differential diffusion. Moreover, spatiotemporal chaos can be observed when both buoyancy and diffusive effects cooperate to destabilize the front. Experimental conditions to test our predictions are suggested.

Long, Strong Eastern U.S. Cold Front Brings Changes

NASA Image and Video Library

2013-12-23

A long, strong, cold front draped over the eastern U.S. is marking a stark change from record-warmth to very cold temperatures. This NOAA GOES-East satellite image from December 23 at 1515 UTC/10:15 a.m. EST shows a powerful cold front covering the U.S. East Coast and stretching into the central and southwestern Gulf of Mexico. According to the National Weather Service, that front is bringing rain and embedded thunderstorms over the Mid-Atlantic and Southeastern U.S. The same system is bringing lingering wintry precipitation to northern New England and upstate New York. Behind the cold front, much colder and dry Canadian air will filter in under high pressure and bring sunshine over the eastern U.S. in time for Christmas. The image was created by the NASA GOES Project at NASA's Goddard Space Flight Center, Greenbelt, Md. Rob Gutro NASA Goddard Space Flight Center NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Slow Progress in Dune (Left Front Wheel)

NASA Technical Reports Server (NTRS)

2005-01-01

The left front wheel of NASA's Mars Exploration Rover Opportunity makes slow but steady progress through soft dune material in this movie clip of frames taken by the rover's front hazard identification camera over a period of several days. The sequence starts on Opportunity's 460th martian day, or sol (May 10, 2005) and ends 11 days later. In eight drives during that period, Opportunity advanced a total of 26 centimeters (10 inches) while spinning its wheels enough to have driven 46 meters (151 feet) if there were no slippage. The motion appears to speed up near the end of the clip, but that is an artifact of individual frames being taken less frequently.

The density compression ratio of shock fronts associated with coronal mass ejections

NASA Astrophysics Data System (ADS)

Kwon, Ryun-Young; Vourlidas, Angelos

2018-02-01

We present a new method to extract the three-dimensional electron density profile and density compression ratio of shock fronts associated with coronal mass ejections (CMEs) observed in white light coronagraph images. We demonstrate the method with two examples of fast halo CMEs (˜2000 km s-1) observed on 2011 March 7 and 2014 February 25. Our method uses the ellipsoid model to derive the three-dimensional geometry and kinematics of the fronts. The density profiles of the sheaths are modeled with double-Gaussian functions with four free parameters, and the electrons are distributed within thin shells behind the front. The modeled densities are integrated along the lines of sight to be compared with the observed brightness in COR2-A, and a χ2 approach is used to obtain the optimal parameters for the Gaussian profiles. The upstream densities are obtained from both the inversion of the brightness in a pre-event image and an empirical model. Then the density ratio and Alfvénic Mach number are derived. We find that the density compression peaks around the CME nose, and decreases at larger position angles. The behavior is consistent with a driven shock at the nose and a freely propagating shock wave at the CME flanks. Interestingly, we find that the supercritical region extends over a large area of the shock and lasts longer (several tens of minutes) than past reports. It follows that CME shocks are capable of accelerating energetic particles in the corona over extended spatial and temporal scales and are likely responsible for the wide longitudinal distribution of these particles in the inner heliosphere. Our results also demonstrate the power of multi-viewpoint coronagraphic observations and forward modeling in remotely deriving key shock properties in an otherwise inaccessible regime.

The CF6 jet engine performance improvement: New front mount

NASA Technical Reports Server (NTRS)

Fasching, W. A.

1979-01-01

The New Front Mount was evaluated in component tests including stress, deflection/distortion and fatigue tests. The test results demonstrated a performance improvement of 0.1% in cruise sfc, 16% in compressor stall margin and 10% in compressor stator angle margin. The New Front Mount hardware successfully completed 35,000 simulated flight cycles endurance testing.

The DIRC front-end electronics chain for BaBar

NASA Astrophysics Data System (ADS)

Bailly, P.; Beigbeder, C.; Bernier, R.; Breton, D.; Bonneaud, G.; Caceres, T.; Chase, R.; Chauveau, J.; Del Buono, L.; Dohou, F.; Ducorps, A.; Gastaldi, F.; Genat, J. F.; Hrisoho, A.; Imbert, P.; Lebbolo, H.; Matricon, P.; Oxoby, G.; Renard, C.; Roos, L.; Sen, S.; Thiebaux, C.; Truong, K.; Tocut, V.; Vasileiadis, G.; Va'Vra, J.; Verderi, M.; Warner, D.; Wilson, R. J.; Wormser, G.; Zhang, B.; Zomer, F.

2000-12-01

Recent results from the Front-End electronics of the Detector of Internally Reflected Cerenkov light (DIRC) for the BaBar experiment at SLAC (Stanford, USA) are presented. It measures to better than 1 ns the arrival time of Cerenkov photoelectrons detected in a 11000 phototubes array and their amplitude spectra. It mainly comprises 64-channel DIRC Front-End Boards (DFB) equipped with eight full-custom analog chips performing zero-cross discrimination with 2 mV threshold and pulse shaping, four full-custom digital time to digital chips (TDC) for timing measurements with 500 ps binning and a readout logic selecting hits in the trigger window, and DIRC Crate Controller cards (DCC) serializing the data collected front up to 16 DFBs onto a 1.2 Gb/s optical link. Extensive test results of the pre-production chips are presented, as well as system tests.

Bifurcating fronts for the Taylor-Couette problem in infinite cylinders

NASA Astrophysics Data System (ADS)

Hărăguş-Courcelle, M.; Schneider, G.

We show the existence of bifurcating fronts for the weakly unstable Taylor-Couette problem in an infinite cylinder. These fronts connect a stationary bifurcating pattern, here the Taylor vortices, with the trivial ground state, here the Couette flow. In order to show the existence result we improve a method which was already used in establishing the existence of bifurcating fronts for the Swift-Hohenberg equation by Collet and Eckmann, 1986, and by Eckmann and Wayne, 1991. The existence proof is based on spatial dynamics and center manifold theory. One of the difficulties in applying center manifold theory comes from an infinite number of eigenvalues on the imaginary axis for vanishing bifurcation parameter. But nevertheless, a finite dimensional reduction is possible, since the eigenvalues leave the imaginary axis with different velocities, if the bifurcation parameter is increased. In contrast to previous work we have to use normalform methods and a non-standard cut-off function to obtain a center manifold which is large enough to contain the bifurcating fronts.

Multi-Material Front Contact for 19% Thin Film Solar Cells.

PubMed

van Deelen, Joop; Tezsevin, Yasemin; Barink, Marco

2016-02-06

The trade-off between transmittance and conductivity of the front contact material poses a bottleneck for thin film solar panels. Normally, the front contact material is a metal oxide and the optimal cell configuration and panel efficiency were determined for various band gap materials, representing Cu(In,Ga)Se₂ (CIGS), CdTe and high band gap perovskites. Supplementing the metal oxide with a metallic copper grid improves the performance of the front contact and aims to increase the efficiency. Various front contact designs with and without a metallic finger grid were calculated with a variation of the transparent conductive oxide (TCO) sheet resistance, scribing area, cell length, and finger dimensions. In addition, the contact resistance and illumination power were also assessed and the optimal thin film solar panel design was determined. Adding a metallic finger grid on a TCO gives a higher solar cell efficiency and this also enables longer cell lengths. However, contact resistance between the metal and the TCO material can reduce the efficiency benefit somewhat.

Ice Front at Venable Ice Shelf

NASA Image and Video Library

2013-06-13

This photo, taken onboard the Chilean Navy P3 aircraft, shows the ice front of Venable Ice Shelf, West Antarctica, in October 2008. It is an example of a small-size ice shelf that is a large melt water producer.

9. INTERIOR OF LIVING ROOM SHOWING OPEN 6LIGHT FRONT ENTRY ...

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

9. INTERIOR OF LIVING ROOM SHOWING OPEN 6-LIGHT FRONT ENTRY DOOR AND TWO 6-LIGHT OVER 1-LIGHT SASH WINDOWS OVERLOOKING FRONT ENTRY STEPS. VIEW TO NORTHEAST. - Rush Creek Hydroelectric System, Clubhouse Cottage, Rush Creek, June Lake, Mono County, CA

Observation of ionization fronts in low density foam targets

NASA Astrophysics Data System (ADS)

Hoarty, D.; Willi, O.; Barringer, L.; Vickers, C.; Watt, R.; Nazarov, W.

1999-05-01

Ionization fronts have been observed in low density chlorinated foam targets and low density foams confined in gold tubes using time resolved K-shell absorption spectroscopy. The front was driven by an intense pulse of soft x-rays produced by high power laser irradiation. The density and temperature profiles inferred from the radiographs provided detailed measurement of the conditions. The experimental data were compared to radiation hydrodynamics simulations and reasonable agreement was obtained.

Nesting habitat of the Tule Greater White-fronted Goose Anser albifrons elgasi

USGS Publications Warehouse

Densmore, R.V.; Ely, Craig R.; Bollinger, K.S.; Kratzer, S.; Udevitz, M.S.; Fehringer, D.J.; Rothe, T.C.

2006-01-01

This paper presents the first information on the availability and use of nesting habitat by the rare Tule Greater White-fronted Goose Anser albifrons elgasi. The breeding range was sampled by marking geese with radio transmitters on wintering and moulting areas, and tracking them to nest sites in Alaska. Nesting habitat was described at the scales of ecoregion, wetland ecosystem (National Wetlands Inventory (NWI) maps), vegetation type within wetland (Alaska Vegetation Classification (AVC) maps based on satellite imagery), and nest site. Tule Greater White-fronted Goose nests were located in boreal forest wetlands in the upper Cook Inlet Basin ecoregion. Nesting Tule Greater White-fronted Geese selected NWT Palustrine Seasonally Flooded wetlands and used NWI Palustrine Saturated wetlands in proportion to availability. Within these wetlands, Tule Greater White-fronted Geese used Needleleaf Forest, Low Shrub and Herbaceous (mostly graminoid) AVC classes for nest sites in proportion to availability Most (93%) Tule Greater White-fronted Geese nested > 75 m from open water ponds or lakes, and many nested in wetlands with little or no open water. Tule Greater White-fronted Geese nest only in a small breeding area near the most human-impacted area of the state, and continued development may limit the use of suitable nesting habitat.

Front propagation in a regular vortex lattice: Dependence on the vortex structure.

PubMed

Beauvier, E; Bodea, S; Pocheau, A

2017-11-01

We investigate the dependence on the vortex structure of the propagation of fronts in stirred flows. For this, we consider a regular set of vortices whose structure is changed by varying both their boundary conditions and their aspect ratios. These configurations are investigated experimentally in autocatalytic solutions stirred by electroconvective flows and numerically from kinematic simulations based on the determination of the dominant Fourier mode of the vortex stream function in each of them. For free lateral boundary conditions, i.e., in an extended vortex lattice, it is found that both the flow structure and the front propagation negligibly depend on vortex aspect ratios. For rigid lateral boundary conditions, i.e., in a vortex chain, vortices involve a slight dependence on their aspect ratios which surprisingly yields a noticeable decrease of the enhancement of front velocity by flow advection. These different behaviors reveal a sensitivity of the mean front velocity on the flow subscales. It emphasizes the intrinsic multiscale nature of front propagation in stirred flows and the need to take into account not only the intensity of vortex flows but also their inner structure to determine front propagation at a large scale. Differences between experiments and simulations suggest the occurrence of secondary flows in vortex chains at large velocity and large aspect ratios.

Aggregate supply and demand modeling using GIS methods for the front range urban corridor, Colorado

NASA Astrophysics Data System (ADS)

Karakas, Ahmet; Turner, Keith

2004-07-01

The combined use of allocation modeling and geographical information system (GIS) technologies for providing quantitative assessments of aggregate supply and demand is evaluated using representative data for the Front Range Urban Corridor (FRUC) in Colorado. The FRUC extends from the Colorado-Wyoming border to south of Colorado Springs, and includes Denver and the major urban growth regions of Colorado. In this area, aggregate demand is high and is increasing in response to population growth. Neighborhood opposition to the establishment of new pits and quarries and the depletion of many deposits are limiting aggregate supplies. Many sources are already covered by urban development or eliminated from production by zoning. Transport of aggregate by rail from distant resources may be required in the future. Two allocation-modeling procedures are tested in this study. Network analysis procedures provided within the ARC/INFO software, are unsatisfactory. Further aggregate allocation modeling used a model specifically designed for this task; a modified version of an existing Colorado School of Mines allocation model allows for more realistic market analyses. This study evaluated four scenarios. The entire region was evaluated with a scenario reflecting the current market and by a second scenario in which some existing suppliers were closed down and new potential suppliers were activated. The conditions within the Denver metropolitan area were studied before and after the introduction of three possible rail-to-truck aggregate distribution centers. GIS techniques are helpful in developing the required database to describe the Front Range Urban Corridor aggregate market conditions. GIS methods allow the digital representation of the regional road network, and the development of a distance matrix relating all suppliers and purchasers.

Laboratory Study of Wave Generation Near Dipolarization Fronts

NASA Astrophysics Data System (ADS)

Tejero, E. M.; Enloe, C. L.; Amatucci, B.; Crabtree, C. E.; Ganguli, G.; Malaspina, D.

2017-12-01

Experiments conducted in the Space Physics Simulation Chamber at the Naval Research Laboratory (NRL) create plasma equilibria that replicate those found in dipolarization fronts. These experiments were designed to study the dynamics of boundary layers, such as dipolarization fronts, and it was found that there are instabilities generated by highly inhomogeneous plasma flows. It has previously been shown that these highly inhomogeneous flows can generate waves in the lower hybrid frequency range. Analysis of satellite observations indicate that the sheared flows are a plausible explanation for the observed lower hybrid waves at dipolarization fronts since they can generate longer wavelengths compared to the electron gyroradius, which is consistent with observations. Recent experiments at NRL have demonstrated that these flows can also generate electromagnetic waves in the whistler band. These waves are large amplitude, bursty waves that exhibit frequency chirps similar to whistler mode chorus. Recent results from these experiments and comparisons to in situ observations will be presented. * Work supported by the Naval Research Laboratory Base Program and NASA Grant No. NNH17AE70I.

10. WEST FRONT OF SOUTH WING OF TECHWOOD DORMITORY, SHOWING ...

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

10. WEST FRONT OF SOUTH WING OF TECHWOOD DORMITORY, SHOWING MAIN ENTRANCE INTO SOUTH WING. ORIGINAL DOUBLE DOORS HAVE BEEN REPLACED WITH A SINGLE, WIDER DOOR. DOOR IS RECESSED AND HAS AN ELABORATE SURROUND LIKE THAT OF THE MAIN ENTRANCE (WEST FRONT) INTO THE NORTH WING. - Techwood Homes, McDaniel Dormitory, 581-587 Techwood Drive, Atlanta, Fulton County, GA

Dynamics of curved fronts in systems with power-law memory

NASA Astrophysics Data System (ADS)

Abu Hamed, M.; Nepomnyashchy, A. A.

2016-08-01

The dynamics of a curved front in a plane between two stable phases with equal potentials is modeled via two-dimensional fractional in time partial differential equation. A closed equation governing a slow motion of a small-curvature front is derived and applied for two typical examples of the potential function. Approximate axisymmetric and non-axisymmetric solutions are obtained.

Slow slip and the transition from fast to slow fronts in the rupture of frictional interfaces

PubMed Central

Trømborg, Jørgen Kjoshagen; Sveinsson, Henrik Andersen; Scheibert, Julien; Thøgersen, Kjetil; Amundsen, David Skålid; Malthe-Sørenssen, Anders

2014-01-01

The failure of the population of microjunctions forming the frictional interface between two solids is central to fields ranging from biomechanics to seismology. This failure is mediated by the propagation along the interface of various types of rupture fronts, covering a wide range of velocities. Among them are the so-called slow fronts, which are recently discovered fronts much slower than the materials’ sound speeds. Despite intense modeling activity, the mechanisms underlying slow fronts remain elusive. Here, we introduce a multiscale model capable of reproducing both the transition from fast to slow fronts in a single rupture event and the short-time slip dynamics observed in recent experiments. We identify slow slip immediately following the arrest of a fast front as a phenomenon sufficient for the front to propagate further at a much slower pace. Whether slow fronts are actually observed is controlled both by the interfacial stresses and by the width of the local distribution of forces among microjunctions. Our results show that slow fronts are qualitatively different from faster fronts. Because the transition from fast to slow fronts is potentially as generic as slow slip, we anticipate that it might occur in the wide range of systems in which slow slip has been reported, including seismic faults. PMID:24889640

Quality in Higher Education: Perspectives from Front-Line Faculty in the United States

ERIC Educational Resources Information Center

Hall, Molly Reas

2015-01-01

The purpose of this study was to explore perceptions of front-line faculty members in the United States related to quality and quality management in higher education. The study's three research questions were: (1) How do front-line faculty members in the United States define quality in higher education? (2) How do front-line faculty members in the…

Water resources in the Great Basin

Treesearch

Jeanne C. Chambers

2008-01-01

The Great Basin Watershed covers 362,600 km (140,110 mi2) and extends from the Sierra Nevada Range in California to the Wasatch Range in Utah, and from southeastern Oregon to southern Nevada (NBC Weather Plus Website). The region is among the driest in the nation and depends largely on winter snowfall and spring runoff for its water supply. Precipitation may be as much...

Pentan isomers compound flame front structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mansurov, Z.A.; Mironenko, A.W.; Bodikov, D.U.

1995-08-13

The fuels (hexane, pentane, diethyl ether) and conditions investigated in this study are relevant to engine knock in spark- ignition engines. A review is provided of the field of low temperature hydrocarbon oxidation. Studies were made of radical and stable intermediate distribution in the front of cool flames: Maximum concentrations of H atoms and peroxy radicals were observed in the luminous zone of the cool flame front. Peroxy radicals appear before the luminous zone at 430 K due to diffusion. H atoms were found in cool flames of butane and hexane. H atoms diffuses from the luminous zone to themore » side of the fresh mixture, and they penetrate into the fresh mixture to a small depth. Extension of action sphear of peroxy radicals in the fresh mixture is much greater than that of H atoms due to their small activity and high concentrations.« less

DESIGN OF MEDICAL RADIOMETER FRONT-END FOR IMPROVED PERFORMANCE

PubMed Central

Klemetsen, Ø.; Birkelund, Y.; Jacobsen, S. K.; Maccarini, P. F.; Stauffer, P. R.

2011-01-01

We have investigated the possibility of building a singleband Dicke radiometer that is inexpensive, small-sized, stable, highly sensitive, and which consists of readily available microwave components. The selected frequency band is at 3.25–3.75 GHz which provides a reasonable compromise between spatial resolution (antenna size) and sensing depth for radiometry applications in lossy tissue. Foreseen applications of the instrument are non-invasive temperature monitoring for breast cancer detection and temperature monitoring during heating. We have found off-the-shelf microwave components that are sufficiently small (< 5 mm × 5 mm) and which offer satisfactory overall sensitivity. Two different Dicke radiometers have been realized: one is a conventional design with the Dicke switch at the front-end to select either the antenna or noise reference channels for amplification. The second design places a matched pair of low noise amplifiers in front of the Dicke switch to reduce system noise figure. Numerical simulations were performed to test the design concepts before building prototype PCB front-end layouts of the radiometer. Both designs provide an overall power gain of approximately 50 dB over a 500 MHz bandwidth centered at 3.5 GHz. No stability problems were observed despite using triple-cascaded amplifier configurations to boost the thermal signals. The prototypes were tested for sensitivity after calibration in two different water baths. Experiments showed superior sensitivity (36% higher) when implementing the low noise amplifier before the Dicke switch (close to the antenna) compared to the other design with the Dicke switch in front. Radiometer performance was also tested in a multilayered phantom during alternating heating and radiometric reading. Empirical tests showed that for the configuration with Dicke switch first, the switch had to be locked in the reference position during application of microwave heating to avoid damage to the active components

Co-ordinated spatial propagation of blood plasma clotting and fibrinolytic fronts

PubMed Central

Zhalyalov, Ansar S.; Panteleev, Mikhail A.; Gracheva, Marina A.; Ataullakhanov, Fazoil I.

2017-01-01

Fibrinolysis is a cascade of proteolytic reactions occurring in blood and soft tissues, which functions to disintegrate fibrin clots when they are no more needed. In order to elucidate its regulation in space and time, fibrinolysis was investigated using an in vitro reaction-diffusion experimental model of blood clot formation and dissolution. Clotting was activated by a surface with immobilized tissue factor in a thin layer of recalcified blood plasma supplemented with tissue plasminogen activator (TPA), urokinase plasminogen activator or streptokinase. Formation and dissolution of fibrin clot was monitored by videomicroscopy. Computer systems biology model of clot formation and lysis was developed for data analysis and experimental planning. Fibrin clot front propagated in space from tissue factor, followed by a front of clot dissolution propagating from the same source. Velocity of lysis front propagation linearly depended on the velocity clotting front propagation (correlation r2 = 0.91). Computer model revealed that fibrin formation was indeed the rate-limiting step in the fibrinolysis front propagation. The phenomenon of two fronts which switched the state of blood plasma from liquid to solid and then back to liquid did not depend on the fibrinolysis activator. Interestingly, TPA at high concentrations began to increase lysis onset time and to decrease lysis propagation velocity, presumably due to plasminogen depletion. Spatially non-uniform lysis occurred simultaneously with clot formation and detached the clot from the procoagulant surface. These patterns of spatial fibrinolysis provide insights into its regulation and might explain clinical phenomena associated with thrombolytic therapy. PMID:28686711

A virtual test system representing the distribution of pedestrian impact configurations for future vehicle front-end optimization.

PubMed

Li, Guibing; Yang, Jikuang; Simms, Ciaran

2016-07-03

The purpose of this study is to define a computationally efficient virtual test system (VTS) to assess the aggressivity of vehicle front-end designs to pedestrians considering the distribution of pedestrian impact configurations for future vehicle front-end optimization. The VTS should represent real-world impact configurations in terms of the distribution of vehicle impact speeds, pedestrian walking speeds, pedestrian gait, and pedestrian height. The distribution of injuries as a function of body region, vehicle impact speed, and pedestrian size produced using this VTS should match the distribution of injuries observed in the accident data. The VTS should have the predictive ability to distinguish the aggressivity of different vehicle front-end designs to pedestrians. The proposed VTS includes 2 parts: a simulation test sample (STS) and an injury weighting system (IWS). The STS was defined based on MADYMO multibody vehicle to pedestrian impact simulations accounting for the range of vehicle impact speeds, pedestrian heights, pedestrian gait, and walking speed to represent real world impact configurations using the Pedestrian Crash Data Study (PCDS) and anthropometric data. In total 1,300 impact configurations were accounted for in the STS. Three vehicle shapes were then tested using the STS. The IWS was developed to weight the predicted injuries in the STS using the estimated proportion of each impact configuration in the PCDS accident data. A weighted injury number (WIN) was defined as the resulting output of the VTS. The WIN is the weighted number of average Abbreviated Injury Scale (AIS) 2+ injuries recorded per impact simulation in the STS. Then the predictive capability of the VTS was evaluated by comparing the distributions of AIS 2+ injuries to different pedestrian body regions and heights, as well as vehicle types and impact speeds, with that from the PCDS database. Further, a parametric analysis was performed with the VTS to assess the sensitivity of the

Front End Software for Online Database Searching. Part 2: The Marketplace.

ERIC Educational Resources Information Center

Levy, Louise R.; Hawkins, Donald T.

1986-01-01

This article analyzes the front end software marketplace and discusses some of the complex forces influencing it. Discussion covers intermediary market; end users (library customers, scientific and technical professionals, corporate business specialists, consumers); marketing strategies; a British front end development firm; competitive pressures;…

8. INTERIOR OF LIVING ROOM SHOWING 6LIGHT FRONT ENTRY DOOR ...

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

8. INTERIOR OF LIVING ROOM SHOWING 6-LIGHT FRONT ENTRY DOOR AND TWO 6-LIGHT OVER 1-LIGHT SASH WINDOWS TO PHOTO RIGHT OF FRONT DOOR OVERLOOKING PORCH. VIEW TO NORTHEAST. - Rush Creek Hydroelectric System, Worker Cottage, Rush Creek, June Lake, Mono County, CA

Observational evidence for thermal wave fronts in solar flares

NASA Technical Reports Server (NTRS)

Rust, D. M.; Simnett, G. M.; Smith, D. F.

1985-01-01

Images in 3.5-30 keV X-rays obtained during the first few minutes of seven solar flares show rapid motions. In each case X-ray emission first appeared at one end of a magnetic field structure, and then propagated along the field at a velocity between 800 and 1700 km/s. The observed X-ray structures were 45,000-230,000 km long. Simultaneous H-alpha images were available in three cases; they showed brightenings when the fast-moving fronts arrived at the chromosphere. The fast-moving fronts are interpreted as electron thermal conduction fronts since their velocities are consistent with conduction at the observed temperatures of 1-3 x 10 to the 7th K. The inferred conductive heat flux of up to 10-billion ergs/s sq cm accounts for most of the energy released in the flares, implying that the flares were primarily thermal phenomena.

Wave front sensing for next generation earth observation telescope

NASA Astrophysics Data System (ADS)

Delvit, J.-M.; Thiebaut, C.; Latry, C.; Blanchet, G.

2017-09-01

High resolution observations systems are highly dependent on optics quality and are usually designed to be nearly diffraction limited. Such a performance allows to set a Nyquist frequency closer to the cut off frequency, or equivalently to minimize the pupil diameter for a given ground sampling distance target. Up to now, defocus is the only aberration that is allowed to evolve slowly and that may be inflight corrected, using an open loop correction based upon ground estimation and refocusing command upload. For instance, Pleiades satellites defocus is assessed from star acquisitions and refocusing is done with a thermal actuation of the M2 mirror. Next generation systems under study at CNES should include active optics in order to allow evolving aberrations not only limited to defocus, due for instance to in orbit thermal variable conditions. Active optics relies on aberration estimations through an onboard Wave Front Sensor (WFS). One option is using a Shack Hartmann. The Shack-Hartmann wave-front sensor could be used on extended scenes (unknown landscapes). A wave-front computation algorithm should then be implemented on-board the satellite to provide the control loop wave-front error measure. In the worst case scenario, this measure should be computed before each image acquisition. A robust and fast shift estimation algorithm between Shack-Hartmann images is then needed to fulfill this last requirement. A fast gradient-based algorithm using optical flows with a Lucas-Kanade method has been studied and implemented on an electronic device developed by CNES. Measurement accuracy depends on the Wave Front Error (WFE), the landscape frequency content, the number of searched aberrations, the a priori knowledge of high order aberrations and the characteristics of the sensor. CNES has realized a full scale sensitivity analysis on the whole parameter set with our internally developed algorithm.

Is particulate air pollution at the front door a good proxy of residential exposure?

PubMed

Zauli Sajani, Stefano; Trentini, Arianna; Rovelli, Sabrina; Ricciardelli, Isabella; Marchesi, Stefano; Maccone, Claudio; Bacco, Dimitri; Ferrari, Silvia; Scotto, Fabiana; Zigola, Claudia; Cattaneo, Andrea; Cavallo, Domenico Maria; Lauriola, Paolo; Poluzzi, Vanes; Harrison, Roy M

2016-06-01

The most advanced epidemiological studies on health effects of air pollution assign exposure to individuals based on residential outdoor concentrations of air pollutants measured or estimated at the front-door. In order to assess to what extent this approach could cause misclassification, indoor measurements were carried out in unoccupied rooms at the front and back of a building which fronted onto a major urban road. Simultaneous measurements were also carried out at adjacent outdoor locations to the front and rear of the building. Two 15-day monitoring campaigns were conducted in the period June-December 2013 in a building located in the urban area of Bologna, Italy. Particulate matter metrics including PM2.5 mass and chemical composition, particle number concentration and size distribution were measured. Both outdoor and indoor concentrations at the front of the building substantially exceeded those at the rear. The highest front/back ratio was found for ultrafine particles with outdoor concentration at the front door 3.4 times higher than at the rear. A weak influence on front/back ratios was found for wind direction. Particle size distribution showed a substantial loss of particles within the sub-50 nm size range between the front and rear of the building and a further loss of this size range in the indoor data. The chemical speciation data showed relevant reductions for most constituents between the front and the rear, especially for traffic related elements such as Elemental Carbon, Iron, Manganese and Tin. The main conclusion of the study is that gradients in concentrations between the front and rear, both outside and inside the building, are relevant and comparable to those measured between buildings located in high and low traffic areas. These findings show high potential for misclassification in the epidemiological studies that assign exposure based on particle concentrations estimated or measured at subjects' home addresses. Copyright © 2016 Elsevier

Analysis of moving surface structures at a laser-induced boiling front

NASA Astrophysics Data System (ADS)

Matti, R. S.; Kaplan, A. F. H.

2014-10-01

Recently ultra-high speed imaging enabled to observe moving wave patterns on metal melts that experience laser-induced boiling. In laser materials processing a vertical laser-induced boiling front governs processes like keyhole laser welding, laser remote fusion cutting, laser drilling or laser ablation. The observed waves originate from temperature variations that are closely related to the melt topology. For improved understanding of the essential front mechanisms and of the front topology, for the first time a deeper systematic analysis of the wave patterns was carried out. Seven geometrical shapes of bright or dark domains were distinguished and categorized, in particular bright peaks of three kinds and dark valleys, often inclined. Two categories describe special flow patterns at the top and bottom of the front. Dynamic and statistical analysis has revealed that the shapes often combine or separate from one category to another when streaming down the front. The brightness of wave peaks typically fluctuates during 20-50 μs. This variety of thermal wave observations is interpreted with respect to the accompanying surface topology of the melt and in turn for governing local mechanisms like absorption, shadowing, boiling, ablation pressure and melt acceleration. The findings can be of importance for understanding the key process mechanisms and for optimizing laser materials processing.

The influence of atmospheric cold fronts on larval supply and settlement of intertidal invertebrates: Case studies in the Cabo Frio coastal upwelling system (SE Brazil)

NASA Astrophysics Data System (ADS)

de Azevedo Mazzuco, Ana Carolina; Christofoletti, Ronaldo Adriano; Coutinho, Ricardo; Ciotti, Áurea Maria

2018-07-01

Atmospheric fronts such as cold fronts are dynamic mesoscale systems with potential effects on the ecology of marine communities. In this study, larval dynamics in subtropical rocky shore communities were evaluated under the influence of atmospheric frontal systems. The hypothesis is that these systems may promote favorable conditions for larval supply and settlement regardless of taxa or site, and that supply and settlement vary in association with fluctuations of meteorological and oceanographic conditions driven by the fronts. This study was carried out in the Southeastern Brazil littoral region under the influence of coastal upwelling events (Cabo Frio) and subject to weekly atmospheric frontal systems, cold polar fronts. The spatial and temporal variability of larvae and settlers of barnacles and mussels were assessed by collecting daily samples at three sites before, during and after atmospheric cold fronts, and the atmospheric and pelagic conditions were monitored. Contrasts among rates, events and sites were tested using discriminant function analysis, analyses of variance and correlation analysis. Atmospheric frontal systems were considered to influence the sites when wind direction changed to SW-S-SE and persisted for at least a day, and waves from SW-SW-SE increased in height. The results corroborate the hypothesis that cold fronts are important regulators of larval dynamics and intertidal communities on rocky shores of the studied area. Both larval supply and settlement were highly correlated with fluctuations in wind speed and direction. Higher settlement rates of barnacles occurred one-day prior, or on the onset of cold fronts. Mussels species tended to settle during all conditions, but on average, settlement rates were higher during the cold fronts. Some temporal trends were site specific and variability was detected among taxa and larval stages. Our findings suggest that mesoscale oceanographic/atmospheric systems are particularly relevant on the

Test of ATLAS RPCs Front-End electronics

NASA Astrophysics Data System (ADS)

Aielli, G.; Camarri, P.; Cardarelli, R.; Di Ciaccio, A.; Di Stante, L.; Liberti, B.; Paoloni, A.; Pastori, E.; Santonico, R.

2003-08-01

The Front-End Electronics performing the ATLAS RPCs readout is a full custom 8 channels GaAs circuit, which integrates in a single die both the analog and digital signal processing. The die is bonded on the Front-End board which is completely closed inside the detector Faraday cage. About 50 000 FE boards are foreseen for the experiment. The complete functionality of the FE boards will be certificated before the detector assembly. We describe here the systematic test devoted to check the dynamic functionality of each single channel and the selection criteria applied. It measures and registers all relevant electronics parameters to build up a complete database for the experiment. The statistical results from more than 1100 channels are presented.

Front contact solar cell with formed emitter

DOEpatents

Cousins, Peter John

2014-11-04

A bipolar solar cell includes a backside junction formed by an N-type silicon substrate and a P-type polysilicon emitter formed on the backside of the solar cell. An antireflection layer may be formed on a textured front surface of the silicon substrate. A negative polarity metal contact on the front side of the solar cell makes an electrical connection to the substrate, while a positive polarity metal contact on the backside of the solar cell makes an electrical connection to the polysilicon emitter. An external electrical circuit may be connected to the negative and positive metal contacts to be powered by the solar cell. The positive polarity metal contact may form an infrared reflecting layer with an underlying dielectric layer for increased solar radiation collection.

Front contact solar cell with formed emitter

DOEpatents

Cousins, Peter John [Menlo Park, CA

2012-07-17

A bipolar solar cell includes a backside junction formed by an N-type silicon substrate and a P-type polysilicon emitter formed on the backside of the solar cell. An antireflection layer may be formed on a textured front surface of the silicon substrate. A negative polarity metal contact on the front side of the solar cell makes an electrical connection to the substrate, while a positive polarity metal contact on the backside of the solar cell makes an electrical connection to the polysilicon emitter. An external electrical circuit may be connected to the negative and positive metal contacts to be powered by the solar cell. The positive polarity metal contact may form an infrared reflecting layer with an underlying dielectric layer for increased solar radiation collection.

Internal papillomatosis with intrahepatic cholangiocarcinoma and gastrointestinal adenocarcinoma in a peach-fronted conure (Aratinga aurea).

PubMed

Gibbons, Paul M; Busch, Martin D; Tell, Lisa A; Graham, Jennifer E; Lowenstine, Linda J

2002-01-01

A 17-yr-old pet female peach-fronted conure (Aratinga aurea) was presented with the chief complaints of mild lethargy and weight loss with increased appetite. Antemortem diagnostics included complete blood count, plasma biochemistry, and radiography. Abnormal findings included elevated inflammatory parameters (hyperfibrinogenemia) and a space-occupying mass in the region of the liver. Histologic examination of a liver biopsy sample indicated bile duct hyperplasia leading to a presumptive diagnosis of hepatoxicosis. The bird initially showed moderate improvement with supportive care, but its condition declined 9 days after the liver biopsy. Supportive care was attempted a second time, but the bird did not improve and euthanasia was elected. Abnormal gross necropsy findings were confined to the liver, which contained multiple tan nodules that exuded yellowish fluid on cut section. Histopathologic examination revealed multicentric bile duct hyperplasia and cholangiocarcinoma as well as segmental papillary hyperplasia and adenocarcinoma in the proventriculus, ventriculus, and throughout the intestinal tract. This is the first report of concurrent internal papillomatosis, gastrointestinal adenocarcinoma, and cholangiocarcinoma in a peach-fronted conure.

Subnanosecond measurements of detonation fronts in solid high explosives

NASA Astrophysics Data System (ADS)

Sheffield, S. A.; Bloomquist, D. D.; Tarver, C. M.

1984-04-01

Detonation fronts in solid high explosives have been examined through measurements of particle velocity histories resulting from the interaction of a detonation wave with a thin metal foil backed by a water window. Using a high time resolution velocity-interferometer system, experiments were conducted on three explosives—a TATB (1,3,5-triamino-trinitrobenzene)-based explosive called PBX-9502, TNT (2,4,6-Trinitrotoluene), and CP (2-{5-cyanotetrazolato} pentaamminecobalt {III} perchlorate). In all cases, detonation-front rise times were found to be less than the 300 ps resolution of the interferometer system. The thermodynamic state in the front of the detonation wave was estimated to be near the unreacted state determined from an extrapolation of low-pressure unreacted Hugoniot data for both TNT and PBX-9502 explosives. Computer calculations based on an ignition and growth model of a Zeldovich-von Neumann-Doering (ZND) detonation wave show good agreement with the measurements. By using the unreacted Hugoniot and a JWL equation of state for the reaction products, we estimated the initial reaction rate in the high explosive after the detonation wave front interacted with the foil to be 40 μs-1 for CP, 60 μs-1 for TNT, and 80 μs-1 for PBX-9502. The shape of the profiles indicates the reaction rate decreases as reaction proceeds.

40 CFR 63.491 - Batch front-end process vents-recordkeeping requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... CATEGORIES National Emission Standards for Hazardous Air Pollutant Emissions: Group I Polymers and Resins § 63.491 Batch front-end process vents—recordkeeping requirements. (a) Group determination records for...) through (a)(6) of this section for each batch front-end process vent subject to the group determination...

40 CFR 63.491 - Batch front-end process vents-recordkeeping requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... CATEGORIES National Emission Standards for Hazardous Air Pollutant Emissions: Group I Polymers and Resins § 63.491 Batch front-end process vents—recordkeeping requirements. (a) Group determination records for...) through (a)(6) of this section for each batch front-end process vent subject to the group determination...

40 CFR 63.491 - Batch front-end process vents-recordkeeping requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

... CATEGORIES National Emission Standards for Hazardous Air Pollutant Emissions: Group I Polymers and Resins § 63.491 Batch front-end process vents—recordkeeping requirements. (a) Group determination records for...) through (a)(6) of this section for each batch front-end process vent subject to the group determination...

40 CFR 63.491 - Batch front-end process vents-recordkeeping requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... CATEGORIES National Emission Standards for Hazardous Air Pollutant Emissions: Group I Polymers and Resins § 63.491 Batch front-end process vents—recordkeeping requirements. (a) Group determination records for...) through (a)(6) of this section for each batch front-end process vent subject to the group determination...

40 CFR 81.345 - Utah.

Code of Federal Regulations, 2012 CFR

2012-07-01

... area of Utah County that lies west of the Wasatch Mountain Range (and this includes the Cities of Provo... Weber County that lies west of the Wasatch Mountain Range with an eastern boundary for Weber County to... within Utah: Township 15 North Range 1 East; Township 14 North Range 1 East; Township 13 North Range 1...

40 CFR 81.345 - Utah.

Code of Federal Regulations, 2013 CFR

2013-07-01

... area of Utah County that lies west of the Wasatch Mountain Range (and this includes the Cities of Provo... Weber County that lies west of the Wasatch Mountain Range with an eastern boundary for Weber County to... within Utah: Township 15 North Range 1 East; Township 14 North Range 1 East; Township 13 North Range 1...

Golden eagle indifference to heli-skiing and military helicopters in northern Utah

Treesearch

Teryl G. Grubb; David K. Delaney; William W. Bowerman; Michael R. Wierda

2010-01-01

In 2006-2007, during Wasatch Powderbird Guides (WPG) permit renewal for heli-skiing in the Tri-Canyon Area (TCA) of the Wasatch Mountains, Utah, USA, we recorded 303 helicopter passes between 0 m and 3,000 m (horizontal distance) near >30 individual golden eagles (Aquila chrysaetos) in 22 nesting territories, through passive observation and active experimentation...

Biophysical Interactions Control the Size and Abundance of Large Phytoplankton Chains at the Ushant Tidal Front

PubMed Central

Landeira, José M.; Ferron, Bruno; Lunven, Michel; Morin, Pascal; Marié, Louis; Sourisseau, Marc

2014-01-01

Phytoplankton blooms are usually dominated by chain-forming diatom species that can alter food pathways from primary producers to predators by reducing the interactions between intermediate trophic levels. The food-web modifications are determined by the length of the chains; however, the estimation is biased because traditional sampling strategies damage the chains and, therefore, change the phytoplankton size structure. Sedimentological studies around oceanic fronts have shown high concentrations of giant diatom mats (>1 cm in length), suggesting that the size of diatom chains is underestimated in the pelagic realm. Here, we investigate the variability in size and abundance of phytoplankton chains at the Ushant tidal front (NW France) using the Video Fluorescence Analyzer (VFA), a novel and non-invasive system. CTD and Scanfish profiling characterized a strong temperature and chlorophyll front, separating mixed coastal waters from the oceanic-stratified domain. In order to elucidate spring-neap variations in the front, vertical microstructure profiler was used to estimate the turbulence and vertical nitrate flux. Key findings were: (1) the VFA system recorded large diatom chains up to 10.7 mm in length; (2) chains were mainly distributed in the frontal region, with maximum values above the pycnocline in coincidence with the maximum chlorophyll; (3) the diapycnal fluxes of nitrate enabled the maintenance of the bloom in the frontal area throughout the spring-neap tidal cycle; (4) from spring to neap tide the chains length was significantly reduced; (5) during neap tide, the less intense vertical diffusion of nutrients, as well as the lower turbulence around the chains, intensified nutrient-depleted conditions and, thus, very large chains became disadvantageous. To explain this pattern, we suggest that size plasticity is an important ecological trait driving phytoplankton species competition. Although this plasticity behavior is well known from experiments in the

Investigation of the Loads on a Conventional Front and Rear Sliding Canopy

NASA Technical Reports Server (NTRS)

Dexter, Howard E.; Rickey, Edward A.

1947-01-01

As one phase of a comprehensive canopy load investigation, conventional front and rear sliding canopies which are typified by installation on the SB2C-4E airplane, were tested in the Langley full-scale tunnel to determine the pressure distributions and the aerodynamic loads on the canopies. A preliminary analysis of the results of these tests is presented in this report. Plots are presented that show the distribution of pressure at four longitudinal stations through each canopy for a range of conditions selected to determine the effects of varying canopy position, yaw, lift coefficient, and power. The results indicate that the maximum loads, based on the external-internal pressure differential, for the front and rear canopies were obtained with the airplane simulating the high speed flight condition. The highest loading on the front canopy was in the exploding direction for the configuration with the front and rear canopies closed. The highest loads on the rear canopy were in the crushing direction with the front canopy open and the rear canopy closed. For most of the simulated flight conditions, the highest loads on the front canopy, per unit area, were over twice as great as the highest loads on the rear canopy when the comparison was made for the most critical canopy configuration in each case. The external pressure distribution over the front and rear canopies, which were fairly symmetrical to 0 degree angle of yaw, were greatly distorted at other yaw attitudes, particularly for the propeller operating conditions. These distorted pressure distributions resulted in local exploding and crushing loads on both canopies which were often considerably higher than the average canopy loads.

Loran digital phase-locked loop and RF front-end system error analysis

NASA Technical Reports Server (NTRS)

Mccall, D. L.

1979-01-01

An analysis of the system performance of the digital phase locked loops (DPLL) and RF front end that are implemented in the MINI-L4 Loran receiver is presented. Three of the four experiments deal with the performance of the digital phase locked loops. The other experiment deals with the RF front end and DPLL system error which arise in the front end due to poor signal to noise ratios. The ability of the DPLLs to track the offsets is studied.

46 CFR 111.30-4 - Circuit breakers removable from the front.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 4 2011-10-01 2011-10-01 false Circuit breakers removable from the front. 111.30-4 Section 111.30-4 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Switchboards § 111.30-4 Circuit breakers removable from the front...

46 CFR 111.30-4 - Circuit breakers removable from the front.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 4 2014-10-01 2014-10-01 false Circuit breakers removable from the front. 111.30-4 Section 111.30-4 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Switchboards § 111.30-4 Circuit breakers removable from the front...

46 CFR 111.30-4 - Circuit breakers removable from the front.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 4 2012-10-01 2012-10-01 false Circuit breakers removable from the front. 111.30-4 Section 111.30-4 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Switchboards § 111.30-4 Circuit breakers removable from the front...

46 CFR 111.30-4 - Circuit breakers removable from the front.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 4 2013-10-01 2013-10-01 false Circuit breakers removable from the front. 111.30-4 Section 111.30-4 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Switchboards § 111.30-4 Circuit breakers removable from the front...

46 CFR 111.30-4 - Circuit breakers removable from the front.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 4 2010-10-01 2010-10-01 false Circuit breakers removable from the front. 111.30-4 Section 111.30-4 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Switchboards § 111.30-4 Circuit breakers removable from the front...

Granular-front formation in free-surface flow of concentrated suspensions

NASA Astrophysics Data System (ADS)

Leonardi, Alessandro; Cabrera, Miguel; Wittel, Falk K.; Kaitna, Roland; Mendoza, Miller; Wu, Wei; Herrmann, Hans J.

2015-11-01

A granular front emerges whenever the free-surface flow of a concentrated suspension spontaneously alters its internal structure, exhibiting a higher concentration of particles close to its front. This is a common and yet unexplained phenomenon, which is usually believed to be the result of fluid convection in combination with particle size segregation. However, suspensions composed of uniformly sized particles also develop a granular front. Within a large rotating drum, a stationary recirculating avalanche is generated. The flowing material is a mixture of a viscoplastic fluid obtained from a kaolin-water dispersion with spherical ceramic particles denser than the fluid. The goal is to mimic the composition of many common granular-fluid materials, such as fresh concrete or debris flow. In these materials, granular and fluid phases have the natural tendency to separate due to particle settling. However, through the shearing caused by the rotation of the drum, a reorganization of the phases is induced, leading to the formation of a granular front. By tuning the particle concentration and the drum velocity, it is possible to control this phenomenon. The setting is reproduced in a numerical environment, where the fluid is solved by a lattice-Boltzmann method, and the particles are explicitly represented using the discrete element method. The simulations confirm the findings of the experiments, and provide insight into the internal mechanisms. Comparing the time scale of particle settling with the one of particle recirculation, a nondimensional number is defined, and is found to be effective in predicting the formation of a granular front.

Granular-front formation in free-surface flow of concentrated suspensions.

PubMed

Leonardi, Alessandro; Cabrera, Miguel; Wittel, Falk K; Kaitna, Roland; Mendoza, Miller; Wu, Wei; Herrmann, Hans J

2015-11-01

A granular front emerges whenever the free-surface flow of a concentrated suspension spontaneously alters its internal structure, exhibiting a higher concentration of particles close to its front. This is a common and yet unexplained phenomenon, which is usually believed to be the result of fluid convection in combination with particle size segregation. However, suspensions composed of uniformly sized particles also develop a granular front. Within a large rotating drum, a stationary recirculating avalanche is generated. The flowing material is a mixture of a viscoplastic fluid obtained from a kaolin-water dispersion with spherical ceramic particles denser than the fluid. The goal is to mimic the composition of many common granular-fluid materials, such as fresh concrete or debris flow. In these materials, granular and fluid phases have the natural tendency to separate due to particle settling. However, through the shearing caused by the rotation of the drum, a reorganization of the phases is induced, leading to the formation of a granular front. By tuning the particle concentration and the drum velocity, it is possible to control this phenomenon. The setting is reproduced in a numerical environment, where the fluid is solved by a lattice-Boltzmann method, and the particles are explicitly represented using the discrete element method. The simulations confirm the findings of the experiments, and provide insight into the internal mechanisms. Comparing the time scale of particle settling with the one of particle recirculation, a nondimensional number is defined, and is found to be effective in predicting the formation of a granular front.

Last Passage Percolation and Traveling Fronts

NASA Astrophysics Data System (ADS)

Comets, Francis; Quastel, Jeremy; Ramírez, Alejandro F.

2013-08-01

We consider a system of N particles with a stochastic dynamics introduced by Brunet and Derrida (Phys. Rev. E 70:016106, 2004). The particles can be interpreted as last passage times in directed percolation on {1,…, N} of mean-field type. The particles remain grouped and move like a traveling front, subject to discretization and driven by a random noise. As N increases, we obtain estimates for the speed of the front and its profile, for different laws of the driving noise. As shown in Brunet and Derrida (Phys. Rev. E 70:016106, 2004), the model with Gumbel distributed jumps has a simple structure. We establish that the scaling limit is a Lévy process in this case. We study other jump distributions. We prove a result showing that the limit for large N is stable under small perturbations of the Gumbel. In the opposite case of bounded jumps, a completely different behavior is found, where finite-size corrections are extremely small.

2. EXTERIOR OF FRONT (EAST SIDE) OF BUILDING 105 SHOWING ...

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

2. EXTERIOR OF FRONT (EAST SIDE) OF BUILDING 105 SHOWING RECESSED PORCH FRAMED BY CRISS-CROSS WOOD BALUSTRADE, STONE FACING ALONG ORIGINAL PORTION OF HOUSE FRONT, AND ORIGINAL PLANK DOOR TO PORCH BASEMENT AT LOWER PHOTO CENTER. WELDED STEEL PORCH RAILINGS VISIBLE AT PHOTO LEFT CENTER WERE ADDED IN 1972. VIEW TO NORTHWEST. - Rush Creek Hydroelectric System, Worker Cottage, Rush Creek, June Lake, Mono County, CA

Landslides in the northern Colorado Front Range caused by rainfall, September 11-13, 2013

USGS Publications Warehouse

Godt, Jonathan W.; Coe, Jeffrey A.; Kean, Jason W.; Baum, Rex L.; Jones, Eric S.; Harp, Edwin L.; Staley, Dennis M.; Barnhart, William D.

2014-01-01

During the second week of September 2013, nearly continuous rainfall caused widespread landslides and flooding in the northern Colorado Front Range. The combination of landslides and flooding was responsible for eight fatalities and caused extensive damage to buildings, highways, and infrastructure. Three fatalities were attributed to a fast moving type of landslide called debris flow. One fatality occurred in Jamestown, and two occurred in the community of Pinebrook Hills immediately west of the City of Boulder. All major canyon roads in the northern Front Range were periodically closed between September 11 and 13, 2013. Some canyon closures were caused by undercutting of roads by landslides and flooding, and some were caused by debris flows and rock slides that deposited material on road surfaces. Most of the canyon roads, with the exceptions of U.S. Highway 6 (Clear Creek Canyon), State Highway 46/Jefferson Co. Rd. 70 (Golden Gate Canyon), and Sunshine Canyon in Boulder County, remained closed at the end of September 2013. A review of historical records in Colorado indicates that this type of event, with widespread landslides and flooding occurring over a very large region, in such a short period of time, is rare.

The Relationship Between Propulsive Force in Tethered Swimming and 200-m Front Crawl Performance.

PubMed

Santos, Karini B; Bento, Paulo C B; Pereira, Gleber; Rodacki, André L F

2016-09-01

Santos, KB, Bento, PCB, Pereira, G, and Rodacki, ALF. The relationship between propulsive force in tethered swimming and 200-m front crawl performance. J Strength Cond Res 30(9): 2500-2507, 2016-The aims of this study were to determine whether propulsive force (peak force, mean force, impulse, and rate of force development) and stroke rate change during 2 minutes of front crawl tethered swimming and to correlate them with the stroke rate and swimming velocity in 200-m front crawl swimming. Twenty-one swimmers (21.6 ± 4.8 years, 1.78 ± 0.06 m, 71.7 ± 8.1 kg), with 200-m front crawl swimming performance equivalent to 78% of the world record (140.4 ± 10.1 seconds), were assessed during 2 minutes of maximal front crawl tethered swimming (propulsive forces and stroke rate) and 200-m front crawl swimming (stroke rate and clean velocity). Propulsive forces decreased between the beginning and the middle instants (∼20%; p ≤ 0.05) but remained stable between the middle and the end instants (∼6%; p > 0.05). The peak force was positively correlated with the clean velocity in the 200-m front crawl swimming (mean r = 0.61; p < 0.02). The stroke rates of the tethered swimming and 200-m front crawl swimming were positively correlated (r = 45; p≤ 0.01) at the middle instant. Therefore, the propulsive force and stroke rate changed throughout the 2 minutes of tethered swimming, and the peak force is the best propulsive force variable tested that correlated with 200-m front crawl swimming performance.

Crash characteristics and injury patterns of restrained front seat occupants in far-side impacts.

PubMed

Yoganandan, Narayan; Arun, Mike W J; Halloway, Dale E; Pintar, Frank A; Maiman, Dennis J; Szabo, Aniko; Rudd, Rodney W

2014-01-01

The study was conducted to determine the association between vehicle-, crash-, and demographic-related factors and injuries to front seat far-side occupants in modern environments. Field data were obtained from the NASS-CDS database for the years 2009-2012. Inclusion factors included the following: adult restrained front outboard-seated occupants, no ejection or rollovers, and vehicle model years less than 10 years old at the time of crash. Far-side crashes were determined by using collision deformation classification. Injuries were scored using the Abbreviated Injury Scale (AIS). Injuries (MAIS 2+, MAIS 3+, M denotes maximum score) were examined based on demographics, change in velocity, vehicle type, direction of force, extent zone, collision partner, and presence of another occupant in the front seat. Only weighted data were used in the analysis. Injuries to the head and face, thorax, abdomen, pelvis, and upper and lower extremity regions were studied. Odds ratios and upper and lower confidence intervals were estimated from multivariate analysis. Out of 519,195 far-side occupants, 17,715 were MAIS 2+ and 4,387 were MAIS 3+ level injured occupants. The mean age, stature, total body mass, and body mass index (BMI) were 40.7 years, 1.7 m, 77.2 kg, and 26.8 kg/m2, respectively. Of occupants with MAIS 2+ injuries, 51% had head and 19% had thorax injuries. Of occupants with MAIS 3+ injuries, 50% had head and 69% had thorax injuries. The cumulative distribution of changes in velocities at the 50th percentile for the struck vehicle for all occupants and occupants with MAIS 2+ and MAIS 3+ injuries were 19, 34, and 42 km/h, respectively. Furthermore, 73% of MAIS 2+ injuries and 86% of MAIS 3+ injuries occurred at a change in velocity of 24 km/h or greater. Odds of sustaining MAIS 2+ and MAIS 3+ injuries increased with each unit increase in change in velocity, stature, and age, with one exception. Odds of sustaining injuries were higher with the presence of an occupant in

Crash characteristics and injury patterns of restrained front seat occupants in far-side impacts

PubMed Central

Yoganandan, Narayan; Arun, Mike W. J.; Halloway, Dale E.; Pintar, Frank A.; Maiman, Dennis J.; Szabo, Aniko; Rudd, Rodney W.

2015-01-01

STRUCTURED ABSTRACT Objective The study was conducted to determine the association between vehicle-, crash- and demographic-related factors and injuries to front seat far-side occupants in modern environments. Methods Field data were obtained from the United States (US) National Automotive Sampling System – Crashworthiness Data System (NASS-CDS) database, for the years 2009–2012. Inclusion factors: adult restrained front outboard seated occupants, no ejection or rollovers, and vehicle model years less than 10 years old at the time of crash. Far-side crashes were determined by using collision deformation classification. Injuries were scored using the Abbreviated Injury Scale (AIS). Injuries (MAIS2+, MAIS3+, M denotes maximum score) were examined based on demographics, change in velocity, vehicle type, direction of force, extent zone, collision partner and presence of another occupant in the front seat. Only weighted data were used in the analysis. Injuries to the head and face, thorax, abdomen, pelvis, upper extremity and lower extremity regions were studied. Odds ratios and upper and lower confidence intervals were estimated from multivariate analysis. Results Out of 519,195 far-side occupants, 17,715 were MAIS2+ and 4,387 were MAIS3+ level injured occupants. The mean age, stature, total body mass, and BMI were 40.7 years, 1.7 m, 77.2 kg, and 26.8 kg/m2, respectively. Of occupants with MAIS2+ injuries, 51% had head and 19% had thorax injuries. Of occupants with MAIS 3+ injuries, 50% had head and 69% had thorax injuries. The cumulative distribution of changes in velocities at the 50th percent level for the struck vehicle for all occupants and, MAIS2+ and MAIS3+ occupants were 19, 34 and 42 km/h, respectively. Furthermore, 73% of MAIS2+ injuries and 86% of MAIS3+ injuries occurred at a change in velocity of 24 km/h or greater. Odds of sustaining MAIS2+ and MAIS3+ injuries increased with unit increase in change in velocity, stature and age, with one exception

Propagation of transition fronts in nonlinear chains with non-degenerate on-site potentials

NASA Astrophysics Data System (ADS)

Shiroky, I. B.; Gendelman, O. V.

2018-02-01

We address the problem of transition front propagation in chains with a bi-stable nondegenerate on-site potential and a nonlinear gradient coupling. For generic nonlinear coupling, one encounters a special regime of transitions, characterized by extremely narrow fronts, far supersonic velocities of the front propagation, and long waves in the oscillatory tail. This regime can be qualitatively associated with a shock wave. The front propagation can be described with the help of a simple reduced-order model; the latter delivers a kinetic law, which is almost not sensitive to the fine details of the on-site potential. Besides, it is possible to predict all main characteristics of the transition front, including its velocity, as well as the frequency and the amplitude of the oscillatory tail. Numerical results are in good agreement with the analytical predictions. The suggested approach allows one to consider the effects of an external pre-load, the next-nearest-neighbor coupling and the on-site damping. When the damping is moderate, it is possible to consider the shock propagation in the damped chain as a perturbation of the undamped dynamics. This approach yields reasonable predictions. When the damping is high, the transition front enters a completely different asymptotic regime of a subsonic kink. The gradient nonlinearity generically turns negligible, and the propagating front converges to the regime described by a simple exact solution for a continuous model with linear coupling.

Improving client-centred care and services: the role of front/back-office configurations.

PubMed

Broekhuis, Manda; de Blok, Carolien; Meijboom, Bert

2009-05-01

This paper is a report of a study conducted to explore the application of designing front- and back-office work resulting in efficient client-centred care in healthcare organizations that supply home care, welfare and domestic services. Front/back-office configurations reflect a neglected domain of design decisions in the development of more client-centred processes and structures without incurring major cost increases. Based on a literature search, a framework of four front/back-office configurations was constructed. To illustrate the usefulness of this framework, a single, longitudinal case study was performed in a large organization, which provides home care, welfare and domestic services for a sustained period (2005-2006). The case study illustrates how front/back-office design decisions are related to the complexity of the clients' demands and the strategic objectives of an organization. The constructed framework guides the practical development of front/back-office designs, and shows how each design contributes differently to such performance objectives as quality, speed and efficiency. The front/back-office configurations presented comprise an important first step in elaborating client-centred care and service provision to the operational level. It helps healthcare organizations to become more responsive and to provide efficient client-centred care and services when approaching demand in a well-tuned manner. In addition to its applicability in home care, we believe that a deliberate front/back-office configuration also has potential in other fields of health care.

Instability of an infiltration-driven dissolution-precipitation front with a nonmonotonic porosity profile

NASA Astrophysics Data System (ADS)

Kondratiuk, Paweł; Dutka, Filip; Szymczak, Piotr

2016-04-01

Infiltration of a rock by an external fluid very often drives it out of chemical equilibrium. As a result, alteration of the rock mineral composition occurs. It does not however proceed uniformly in the entire rock volume. Instead, one or more reaction fronts are formed, which are zones of increased chemical activity, separating the altered (product) rock from the yet unaltered (primary) one. The reaction fronts propagate with velocities which are usually much smaller than those of the infiltrating fluid. One of the simplest examples of such alteration is the dissolution of some of the minerals building the primary rock. For instance, calcium carbonate minerals in the rock matrix can be dissolved by infiltrating acidic fluids. In such a case the product rock has higher porosity and permeability than the primary one. Due to positive feedbacks between the reactant transport, fluid flow, and porosity generation, the reaction fronts in porosity-generating replacement systems are inherently unstable. An arbitrarily small protrusion of the front gets magnified and develops into a highly porous finger-like or funnel-like structure. This feature of dissolution fronts, dubbed the "reactive-infiltration instability" [1], is responsible for the formation of a number of geological patterns, such as solution pipes or various karst forms. It is also of practical importance, since spontaneous front breakup and development of localized highly porous flow paths (a.k.a. "wormholes") is favourable by petroleum engineers, who apply acidization to oil-bearing reservoirs in order to increase their permeability. However, more complex chemical reactions might occur during infiltration of a rock by a fluid. In principle, the products of dissolution might react with other species present either in the fluid or in the rock and reprecipitate [2]. The dissolution and precipitation fronts develop and and begin to propagate with equal velocities, forming a single dissolution-precipitation front

FRED, a Front End for Databases.

ERIC Educational Resources Information Center

Crystal, Maurice I.; Jakobson, Gabriel E.

1982-01-01

FRED (a Front End for Databases) was conceived to alleviate data access difficulties posed by the heterogeneous nature of online databases. A hardware/software layer interposed between users and databases, it consists of three subsystems: user-interface, database-interface, and knowledge base. Architectural alternatives for this database machine…

Targeting NCK-Mediated Endothelial Cell Front-Rear Polarity Inhibits Neo-Vascularization

PubMed Central

Dubrac, Alexandre; Genet, Gael; Ola, Roxana; Zhang, Feng; Pibouin-Fragner, Laurence; Han, Jinah; Zhang, Jiasheng; Thomas, Jean-Léon; Chedotal, Alain; Schwartz, Martin A.; Eichmann, Anne

2015-01-01

Background Sprouting angiogenesis is a key process driving blood vessel growth in ischemic tissues and an important drug target in a number of diseases, including wet macular degeneration and wound healing. Endothelial cells forming the sprout must develop front-rear polarity to allow sprout extension. The adaptor proteins Nck1 and 2 are known regulators of cytoskeletal dynamics and polarity, but their function in angiogenesis is poorly understood. Here we show that the Nck adaptors are required for endothelial cell front-rear polarity and migration downstream of the angiogenic growth factors VEGF-A and Slit2. Methods and Results Mice carrying inducible, endothelial-specific Nck1/2 deletions fail to develop front-rear polarized vessel sprouts and exhibit severe angiogenesis defects in the postnatal retina and during embryonic development. Inactivation of NCK1 and 2 inhibits polarity by preventing Cdc42 and Pak2 activation by VEGF-A and Slit2. Mechanistically, NCK binding to ROBO1 is required for both Slit2 and VEGF induced front-rear polarity. Selective inhibition of polarized endothelial cell migration by targeting Nck1/2 prevents hypersprouting induced by Notch or Bmp signaling inhibition, as well as pathological ocular neovascularization and wound healing. Conclusions These data reveal a novel signal integration mechanism involving NCK1/2, ROBO1/2 and VEGFR2 that controls endothelial cell front-rear polarity during sprouting angiogenesis. PMID:26659946

Front of the Werenskiold Glacier (Svalbard) - changes in years 1957-2013

NASA Astrophysics Data System (ADS)

Ciężkowski, Wojciech; Głowacki, Tadeusz; Grudzińska, Katarzyna K.; Kasza, Damian; Zagożdżon, Paweł P.

2018-01-01

Werenskiold Glacier in the Isle of Spitsbergen is one of the polygons on which evaluation of the rate of glacier recession is performed. Location of the glacier front is precisely presented in the specialist literature since the mid. 30. of 20th century. Article presents results of studies about changes in the position of Werenskiold Glacier based on selected archival data and own research conducted in 2012-2013. The initial location of the glacier front was described by the topographical map in the scale 1:5000 elaborated in the year 1961 on the basis of data from the years 1957-1959 by the Polish Army Topographic Service. Moreover, as comparative data on location of glacier front in the later years there were applied results of photogrammetrical images from the year 1973 and a orthophotomap from 1990. These data together with the author's GPS measurements were transformed into the uniform coordinate system. Thus, prepared data made it possible to evaluate the rate of recession of Werenskiold Glacier front in the three epochs from the years 1957-2013. It was found that during the 56 years the glacier front was moved by ca. 1200 m, which gives the mean recession value of 25 m/year as well as the mean yearly loss of the glacier surface of the order of 5 ha.

Particle versus density models in spark formation: X-rays from pulled fronts?

NASA Astrophysics Data System (ADS)

Ebert, Ute

2008-03-01

Streamer discharges govern the early stages of sparks and lightning, of spark-like phenomena in water, oil, and semiconductors, in industrial corona reactors, or in gigantic sprite discharges above thunderclouds [1,2]. Thunderstorms recently have been found to emit terrestrial gamma-ray flashes or X-rays towards satellites and towards the ground. These emissions might be explained by particle models of ``pulled'' streamer ionization fronts. In general, the growing discharge channel has an inner structure with multiple scales [1-3]. While the largest part of this channel can be treated in a density approximation for the electrons and ions, the dynamics of the ionization front is that of a pulled front; it is determined in the leading edge where the density approach eventually breaks down. We therefore investigate a realistic MC particle model for the motion of single electrons in a discharge in pure nitrogen. The particle model not only incorporates particle fluctuations, but also shows that the electron energies are systematically larger in the leading edge of the front than in the corresponding density model, and that the ionization level behind the front is higher as well, while the front velocity hardly changes [3]. These effects increase with increasing applied electric field and might actually cause the recently observed X-ray emission from lightning through rare very energetic runaway electrons in the tail of the distribution. Comparing the leading edge of the particle front with a linear particle avalanche, the avalanche shows the same mean density gradient and energy overshoot in its leading edge as the nonlinear front; hence the pulled front concept in this sense applies to discrete particle models as well [3]. This gives a key to understanding the above effects through analytical approximations and to develop efficient numerical methods coupling particle and density models in space.[1] U. Ebert et al., Plasma Sources Sci. Techn. 15, S118 (2006) (ar

Structure of the detonation wave front in a mixture of nitromethane with acetone

NASA Astrophysics Data System (ADS)

Buravova, S. N.

2012-09-01

It is shown that the leading front of an inhomogeneous detonation wave is a shock wave in which wave structures of the type of triple shock configurations are moving. It was experimentally found that the reaction in these inhomogeneities occurs in oblique shock waves. The reaction sites at the wave front are ring-shaped. In a 75: 25 mixture of nitromethane with acetone, up to 70% of the front surface is occupied by the reaction at the sites in the wave front. Measurements of the mass velocity profile indicate that afterburning takes place in the unloading area behind the Jouguet plane. Calculations of the heat release in the reaction mixture with a decrease in the mass velocity indicate that the material that have not reacted in the inhomogeneities can be ignited in the induction zone. It is suggested that the adiabatic flashes are a mechanism that generates inhomogeneities in the detonation wave front.

Phytoplankton response to a plume front in the northern South China Sea

NASA Astrophysics Data System (ADS)

Li, Qian P.; Zhou, Weiwen; Chen, Yinchao; Wu, Zhengchao

2018-04-01

Due to a strong river discharge during April-June 2016, a persistent salinity front, with freshwater flushing seaward on the surface but seawater moving landward at the bottom, was formed in the coastal waters west of the Pearl River estuary (PRE) over the northern South China Sea (NSCS) shelf. Hydrographic measurements revealed that the salinity front was influenced by both the river plume and coastal upwelling. On shipboard nutrient-enrichment experiments with size-fractionation chlorophyll a measurements were taken on both sides of the front as well as in the frontal zone to diagnose the spatial variations of phytoplankton physiology across the frontal system. We also assessed the size-fractionated responses of phytoplankton to the treatment of plume water at the frontal zone and the sea side of the front. The biological impact of vertical mixing or upwelling was further examined by the response of surface phytoplankton to the addition of local bottom water. Our results suggested that there was a large variation in phytoplankton physiology on the sea side of the front, driven by dynamic nutrient fluxes, although P limitation was prevailing on the shore side of the front and at the frontal zone. The spreading of plume water at the frontal zone would directly improve the growth of microphytoplankton, while nano- and picophytoplankton growths could have become saturated at high percentages of plume water. Also, the mixing of bottom water would stimulate the growth of surface phytoplankton on both sides of the front by altering the surface N/P ratio to make it closer to the Redfield stoichiometry. In summary, phytoplankton growth and physiology could be profoundly influenced by the physical dynamics in the frontal system during the spring-summer of 2016.

Social perceptions versus meteorological observations of snow and winter along the Front Range

NASA Astrophysics Data System (ADS)

Milligan, William James, IV

This research aims to increase understanding of Front Range residents' perceptions of snow, winter and hydrologic events. This study also investigates how an individual's characteristics may shape perceptions of winter weather and climate. A survey was administered to determine if perceptions of previous winters align with observed meteorological data. The survey also investigated how individual characteristics influence perceptions of snow and winter weather. The survey was conducted primarily along the Front Range area of the state of Colorado in the United States of America. This is a highly populated semi-arid region that acts as an interface between the agricultural plains to the east that extend to the Mississippi River and the Rocky Mountains to the west. The climate is continental, and while many people recreate in the snowy areas of the mountains, most live where annual snowfall amounts are low. Precipitation, temperature, and wind speed datasets from selected weather stations were analyzed to determine correct survey responses. Survey analysis revealed that perceptions of previous winters do not necessarily align with observed meteorological data. The mean percentage of correct responses to all survey questions was 36.8%. Further analysis revealed that some individual characteristics (e.g. winter recreation, source of winter weather information) did influence correct responses to survey questions.

Cold Front Driven Flows Through Multiple Inlets of Lake Pontchartrain Estuary

NASA Astrophysics Data System (ADS)

Huang, Wei; Li, Chunyan

2017-11-01

With in situ observations using acoustic Doppler current profilers (ADCPs) and numerical experiments using the Finite Volume Coastal Ocean Model (FVCOM), this study investigates atmospheric cold front induced exchange of water between Lake Pontchartrain Estuary and coastal ocean through multiple inlets. Results show that the subtidal hydrodynamic response is highly correlated with meteorological parameters. Northerly and westerly winds tend to push water out of Lake Pontchartrain, while south and east winds tend to produce currents flowing into it. For most cases, the subtidal water level is inversely correlated with the east wind, with the correlation coefficient being ˜0.8. The most important finding of this work is that, contrary to intuition, the cold front induced remote wind effect has the greatest contribution to the overall water level variation, while the local wind stress determines the surface slope inside the estuary. It is found that wind driven flow is roughly quasi steady state: the surface slope in the north-south direction is determined by the north-south wind stress, explaining ˜83% of the variability but less so in the east-west direction (˜43%). In other words, the north-south local wind stress determines the water level gradient in that direction in the estuary while the overall water level change is pretty much controlled by the open boundary which is the "remote wind effect," a regional response that can be illustrated only by a numerical model for a much larger area encompassing the estuary.

An 8.4-GHz dual-maser front-end system for Parkes reimplementation

NASA Technical Reports Server (NTRS)

Trowbridge, D. L.; Loreman, J. R.; Brunzie, T. J.; Quinn, R.

1990-01-01

An 8.4-GHz front-end system consisting of a feedhorn, a waveguide feed assembly, dual masers, and downconverters was reimplemented at Parkes as part of the Parkes Canberra Telemetry Array for the Voyager Neptune encounter. The front-end system was originally assembled by the European Space Agency and installed on the Parkes antenna for the Giotto project. It was also used on a time-sharing basis by the Deep Space Network as part of the Parkes Canberra Telemetry Array to enhance the data return from the Voyager Uranus encounter. At the conclusion of these projects in 1986, part of the system was then shipped to JPL on loan for reimplementation at Parkes for the Voyager Neptune encounter. New design and implementation required to make the system operable at Parkes included new microwave front-end control cabinets, closed-cycle refrigeration monitor system, noise-adding radiometer system, front-end controller assembly, X81 local oscillator multiplier, and refurbishment of the original dual 8.4-GHz traveling-wave masers and waveguide feed system. The front-end system met all requirements during the encounter and was disassembled in October 1989 and returned to JPL.

The influence of cricket fast bowlers' front leg technique on peak ground reaction forces.

PubMed

Worthington, Peter; King, Mark; Ranson, Craig

2013-01-01

High ground reaction forces during the front foot contact phase of the bowling action are believed to be a major contributor to the high prevalence of lumbar stress fractures in fast bowlers. This study aimed to investigate the influence of front leg technique on peak ground reaction forces during the delivery stride. Three-dimensional kinematic data and ground reaction forces during the front foot contact phase were captured for 20 elite male fast bowlers. Eight kinematic parameters were determined for each performance, describing run-up speed and front leg technique, in addition to peak force and time to peak force in the vertical and horizontal directions. There were substantial variations between bowlers in both peak forces (vertical 6.7 ± 1.4 body weights; horizontal (braking) 4.5 ± 0.8 body weights) and times to peak force (vertical 0.03 ± 0.01 s; horizontal 0.03 ± 0.01 s). These differences were found to be linked to the orientation of the front leg at the instant of front foot contact. In particular, a larger plant angle and a heel strike technique were associated with lower peak forces and longer times to peak force during the front foot contact phase, which may help reduce the likelihood of lower back injuries.

The Colorado Front Range Ecosystem Management Research Project: Accomplishments to date

Treesearch

Brian Kent; Wayne D. Shepperd; Deborah J. Shields

2000-01-01

This article briefly describes the goals and objectives for the Colorado Front Range Ecosystem Management Project (FREM). Research under this project has addressed both biophysical and human dimensions problems relating to ecosystem management in the Colorado Front Range. Results of completed work are described, and the status of the ongoing demonstration project at...

27. EXCAVATION OF EAST (FRONT) BASEMENT WELL AND DRAINAGE SYSTEM, ...

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

27. EXCAVATION OF EAST (FRONT) BASEMENT WELL AND DRAINAGE SYSTEM, WITH ARCHED ENTRY INTO BASEMENT UNDER FRONT ENTRY IN BACKGROUND, LOOKING NORTH (NOTE GALLETING IN BRICK FOUNDATION) BUT CLOSER RANGE SHOWING BRICK STRUCTURE WHICH CARRIED WATER FROM THE GUTTER DRAIN PIPE INTO THE BRICK DRAIN ALONG THE GROUND AND AWAY FROM THE FOUNDATION OF THE HOUSE - Belair, Tulip Grove Drive, Belair-at-Bowie, Bowie, Prince George's County, MD

On the formation and expansion of H II regions

NASA Technical Reports Server (NTRS)

Franco, Jose; Tenorio-Tagle, Guillermo; Bodenheimer, Peter

1990-01-01

The evolution of H II regions in spherical clouds with small, constant-density cores and power-law density distributions r exp -w outside the core is described analytically. It is found that there is a critical exponent above which the cloud becomes completely ionized. Its value in the formation phase depends on the initial conditions, but it has a well-defined value w(crit) = 3/2 during the expansion phase. For w less than w(crit), the radius of the H II region grows at a given rate, while neutral mass accumulates in the interphase between the ionization and shock fronts. For w = w(crit), the fronts move together without mass accumulation. Cases with w greater than w(crit) lead to the champagne phase: once the cloud is fully ionized, the expansion becomes supersonic. For self-gravitating disks without magnetic fields, the main features include a new 'variable-size' stage. The initial shape of the H II region has a critical point beyond which the disk becomes completely ionized.

Comparing the Records of Calving Front Position, Elevation, and Velocity for Neighboring Glaciers in Sermilik Fjord

NASA Astrophysics Data System (ADS)

Goliber, S. A.; Allwes, K.; Roberts, C.; Csatho, B. M.

2016-12-01

The southeast region of the Greenland Ice Sheet has thinned at a high rate compared to the rest of the Ice Sheet over the last decade and is characterized by a high diversity of outlet glacier behaviors (Csatho et al., 2014). While the entire region has experienced an overall mass loss from a warming climate, some major outlet glaciers exhibit varying amounts of thinning and thickening attributed to changes in ice dynamics. From 1980 to 2016, Helheim, Fenris, and Midgard glaciers (all located in the Sermilik fjord system) have shown dissimilar thinning and thickening patterns, retreat rates, and velocity changes despite their close geographic proximity. To understand why these glaciers behave so differently, detailed calving front and trimline reconstructions were created from historical maps, aerial photographs, and satellite imagery. Additionally, we measured elevation changes from Airborne Topographic Mapper (ATM) laser altimetry data and DEMs derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Satellite Pour l'Observation de la Terre (SPOT) stereo imagery. The presentation compares the elevation and velocity records with the timing of calving front changes of Helheim, Fenris and Midgard glaciers. Helheim Glacier has retreated a net distance of 7 km since 1972 and exhibited a thinning-thickening- thickening pattern from 2003-2009. It retreated to its maximum inland position in 2005, followed by a re-advance to a new equilibrium position by 2007. The calving front then oscillated around a relatively stable position from 2007 to 2014. However, in 2015, it again retreated to within 2 km of its 2005 position. Contrastingly, Midgard Glacier has experienced decelerated thinning from 2003-2009, followed by an acceleration of thinning. Midgard Glacier retreated a total of 15 km between 1972 and 2015, behind its confluence with a former tributary. While Fenris Glacier exhibits a thinning-thickening-thinning pattern similar to Helheim

A Multistep Algorithm for the Radiation Hydrodynamical Transport of Cosmological Ionization Fronts and Ionized Flows

NASA Astrophysics Data System (ADS)

Whalen, Daniel; Norman, Michael L.

2006-02-01

Radiation hydrodynamical transport of ionization fronts (I-fronts) in the next generation of cosmological reionization simulations holds the promise of predicting UV escape fractions from first principles as well as investigating the role of photoionization in feedback processes and structure formation. We present a multistep integration scheme for radiative transfer and hydrodynamics for accurate propagation of I-fronts and ionized flows from a point source in cosmological simulations. The algorithm is a photon-conserving method that correctly tracks the position of I-fronts at much lower resolutions than nonconservative techniques. The method applies direct hierarchical updates to the ionic species, bypassing the need for the costly matrix solutions required by implicit methods while retaining sufficient accuracy to capture the true evolution of the fronts. We review the physics of ionization fronts in power-law density gradients, whose analytical solutions provide excellent validation tests for radiation coupling schemes. The advantages and potential drawbacks of direct and implicit schemes are also considered, with particular focus on problem time-stepping, which if not properly implemented can lead to morphologically plausible I-front behavior that nonetheless departs from theory. We also examine the effect of radiation pressure from very luminous central sources on the evolution of I-fronts and flows.

Fisher waves and front roughening in a two-species invasion model with preemptive competition.

PubMed