WorldWideScience

Sample records for splash snow gliding

  1. Electrical charging of skis gliding on snow.

    Science.gov (United States)

    Colbeck, S C

    1995-01-01

    Ski charging was measured using giant-slalom style skis as gliding capacitors. The voltage measured across the plates was proportional to the charge on the base. While resting on dry snow or suspended in the air, the voltage was slowly reduced by the data logger itself. On wet snow the decay was much faster. While stationary on powder snow the ski developed a slightly negative voltage, showed a small, transient positive peak when motion began, rapidly dropped to negative values, and then assumed a quasi-steady climb to positive voltages. A great deal of noise was superimposed on the general features of the signal when skiing on hard or bumpy surfaces. Thus, the accumulation of charge to high levels was only possible with long runs in deep powder. The rate of charging increased with speed but was not affected by use of one "antistatic" wax, and another such wax actually increased the measured voltage over that of an unwaxed base.

  2. Wet and full-depth glide snow avalanche onset monitoring and detection with ground based Ku-band radar

    Science.gov (United States)

    Lucas, Célia; Bühler, Yves; Leinss, Silvan; Hajnsek, Irena

    2017-04-01

    Wet and full-depth glide snow avalanches can be of considerable danger for people and infrastructure in alpine regions. In Switzerland avalanche hazard predictions are performed by the Institute for Snow and Avalanche Research SLF. However these predictions are issued on regional scale and do not yield information about the current status of particular slopes of interest. To investigate the potential of radar technology for avalanche prediction on the slope scale, we performed the following experiment. During the winter seasons 2015/2016 and 2016/2017, a ground-based Ku-band radar was placed in the vicinity of Davos (GR) in order to monitor the Dorfberg slope with 4-minute measurement intervals [1]. With Differential Interferometry [2] line of sight movements on the order of a fraction of the radar wavelength (1.7 cm) can be measured. Applying this technique to the Dorfberg scenario, it was possible to detect snowpack displacement of up to 0.4 m over 3 days in the avalanche release area prior to a snow avalanche event. A proof of concept of this approach was previously made by [3-5]. The analysis of the snowpack displacement history of such release areas shows that an avalanche is generally released after several cycles of acceleration and deceleration of a specific area of the snowpack, followed by an abrupt termination of the movement at the moment of the avalanche release. The acceleration and deceleration trends are related to thawing and refreezing of the snowpack induced by the daily temperature variations. The proposed method for the detection of snowpack displacements as indication for potential wet and full-depth glide snow avalanches is a promising tool to increase avalanche safety on specific slopes putting infrastructure or people at risk. The identification of a singular signature to discriminate the time window immediately prior to the release is still under investigation, but the ability to monitor snowpack displacement allows for mapping of zones

  3. SPLASH'13 workshops summary

    DEFF Research Database (Denmark)

    Balzer, S.; Schultz, U. P.

    2013-01-01

    Following its long-standing tradition, SPLASH 2013 will host 19 high-quality workshops, allowing their participants to meet and discuss research questions with peers, to mature new and exciting ideas, and to build up communities and start new collaborations. SPLASH workshops complement the main t...

  4. Standardization of splash device

    Science.gov (United States)

    Fernández Raga, María; Peters, Piet

    2017-04-01

    The erosion is a complex process that has been studied extensively by numerous researchers, requiring a prolongued time effort and a large economic investment. To be effective, the measurements of erosion should be precise, controlled and replicable, and to assure efectiveness, measurement devices of erosion should be properly designed, constructed, well calibrated and also they should be operated by a trained person (Stroosnijder, 2005). Because researchers try to improve old devices, the equipment is constantly being redesigned, making the measurements not comparable and furthermore, producing a lack of available standarized device. The lack of standardization of erosion equipment is more obvious in the case of the local splash erosion, where the nature of the process makes very difficult to isolate its effects. In this article we compare the results obtained from five of the most common splash erosion devices (selected from more than 16 different currently types), under the same rain conditions, with the objective of facilitate the standardization of the method that will be more easy to build, minimizing the error. A set of six splash devices were setted in well known positions under simulated rain, to measured the differences, among devices and the accuracy of the data recovered after 10 minutes of rainfall simulation under different intensities (from 60 to 130 mm/h). The rainfall simulator of Wageningen was used, using sand as splash erosion source. Differences in the infiltration were also measured, and a calibration of sizes and speeds of the raindrops was done using the photography method (Hamidreza-Sadeghi et al., 2013). The splash devices selected for this study were unbounded splash devices (like the funnel, the cup (Fernandez-Raga et al., 2010) and the splash flume (Jomaa et al., 2010)), and bounded devices that allow the calculation of splash rate, (like the new cup (Scholten et al., 2011) and the Morgan tray). The behaviour of different splash devices

  5. Splash erosion. A bibliometric Review

    Science.gov (United States)

    Fernández Raga, M. B.

    2012-04-01

    Ellison (1944) developed the splash board as a system for measuring splash erosion that was both cheap and reliable. Bollinne (1975), Morgan (1978, 1981). Mutchler (1967) described another different type of splash detectors according to whether they were passive or could register data. In the study mentioned above these authors included bottles, funnels, glasses, photography, markers. After that several devices has been made up like the splash sampler (Leguedois et al., 2005), soil tray (Van Dijk et al., 2002), splash funnel (Terry, 1989) and several rain cups (Fernandez-Raga et al., 2010; Molina and Llinares, 1996; Torri et al., 1987). Splash erosion research has materialized in the form of a number of papers published in international journals. The database of bibliographic references employed has been one of the most prestigious ones: theWeb of Science (ISI). The search was carried out on January 27th 2012. Among the 3x10^8 scholarly documents included in the Science Citation Index Expanded (SCI-EXPANDED) 1899 to present , the searching engine located 439 containing the word "splash erosion*", where the asterisk acts as a wildcard for any letter or group of letters. Of these, 383 were classified as articles, 87 as proceeding papers, 5 as editorial material, 2 as notes and 1 as correction. These documents have been published in 163 different journals, although four are particularly recurrent: Earth surface processes and Landforms, Catena, Soil Science Society of America Journal and Hydrological processes, with 41, 35, 35 and 26 published documents respectively. A geographic analysis of these articles has been carried out in an attempt to determine in what parts of the world research projects were making use of splash erosion. The results are that anglo-saxon countries, as USA, England and Australia dominate, particularly USA, with 130 articles. China and Japan are large communities of researches too, and some Central European countries as Belgium, France Germany

  6. The making of a splash

    KAUST Repository

    Thoroddsen, Sigurdur T.

    2011-12-20

    The splash resulting from the impact of a drop onto a pool is a particularly beautiful manifestation of a canonical problem, where a mass of fluid breaks up into smaller pieces. Despite over a century of experimental study, the splashing mechanics have eluded full description, the details often being obscured by the very rapid motions and small length scales involved. Zhang et al. (J. Fluid Mech., vol. 690, 2012, pp. 515) introduce a powerful new tool to the experimental arsenal, when they apply X-ray imaging to study the fine ejecta sheets which emerge during the earliest contact of the drop. Their images reveal hidden details and complex underlying dynamics, which will directly affect the size and velocity of the splashing droplets. © 2011 Cambridge University Press.

  7. Bouncing, splashing and disintegrating nanodrops

    Science.gov (United States)

    Koplik, Joel; Zhang, Rui

    2012-11-01

    The impact of nanometer-sized drops on solid surfaces is studied by molecular dynamics simulations. The surfaces are atomically smooth, dry and non-wetting, and both volatile and non-volatile liquids are considered. At low impact velocities drops distort on contact but bounce off the surface and relax back to a spherical shape. At higher velocities drops form a prompt splash on impact and subsequently disintegrate, while at still higher velocities drops disintegrate immediately on impact. In contrast to macroscopic drops, the presence or absence of vapor plays no role at all in nanodrop splashing.

  8. Assessing the importance of terrain parameters on glide avalanche release

    Science.gov (United States)

    Peitzsch, Erich H.; Hendrikx, Jordy; Fagre, Daniel B.

    2014-01-01

    Glide snow avalanches are dangerous and difficult to predict. Despite recent research there is still a lack of understanding regarding the controls of glide avalanche release. Glide avalanches often occur in similar terrain or the same locations annually and observations suggest that topography may be critical. Thus, to gain an understanding of the terrain component of these types of avalanches we examined terrain parameters associated with glide avalanche release as well as areas of consistent glide crack formation but no subsequent avalanches. Glide avalanche occurrences visible from the Going-to-the-Sun Road corridor in Glacier National Park, Montana from 2003-2013 were investigated using an avalanche database derived of daily observations each year from April 1 to June 15. This yielded 192 glide avalanches in 53 distinct avalanche paths. Each avalanche occurrence was digitized in a GIS using satellite, oblique, and aerial imagery as reference. Topographical parameters such as area, slope, aspect, elevation and elevation were then derived for the entire dataset utilizing GIS tools and a 10m DEM. Land surface substrate and surface geology were derived from National Park Service Inventory and Monitoring maps and U.S. Geological Survey surface geology maps, respectively. Surface roughness and glide factor were calculated using a four level classification index. . Then, each avalanche occurrence was aggregated to general avalanche release zones and the frequencies were compared. For this study, glide avalanches released in elevations ranging from 1300 to 2700 m with a mean aspect of 98 degrees (east) and a mean slope angle of 38 degrees. The mean profile curvature for all glide avalanches was 0.15 and a plan curvature of -0.01, suggesting a fairly linear surface (i.e. neither convex nor concave). The glide avalanches occurred in mostly bedrock made up of dolomite and limestone slabs and talus deposits with very few occurring in alpine meadows. However, not all glide

  9. Drop splashing is independent of substrate wetting

    Science.gov (United States)

    Latka, Andrzej; Boelens, Arnout M. P.; Nagel, Sidney R.; de Pablo, Juan J.

    2018-02-01

    A liquid drop impacting a dry solid surface with sufficient kinetic energy will splash, breaking apart into numerous secondary droplets. This phenomenon shows many similarities to forced wetting, including the entrainment of air at the contact line. Because of these similarities and the fact that forced wetting has been shown to depend on the wetting properties of the surface, existing theories predict splashing to depend on wetting properties as well. However, using high-speed interference imaging, we observe that at high capillary numbers wetting properties have no effect on splashing for various liquid-surface combinations. Additionally, by fully resolving the Navier-Stokes equations at length and time scales inaccessible to experiments, we find that the shape and motion of the air-liquid interface at the contact line/edge of the droplet are independent of wettability. We use these findings to evaluate existing theories and to compare splashing with forced wetting.

  10. Snow Fun.

    Science.gov (United States)

    Finlay, Joy

    1988-01-01

    Describes several learning activities that can be done with children in the snow. Includes shake paintings, snow sculpture, snow "snakes," snow-ball contests, an igloo experience, and how to make snowshoes. (TW)

  11. Boundary-layer effects in droplet splashing

    Science.gov (United States)

    Riboux, Guillaume; Gordillo, Jose Manuel

    2017-11-01

    A drop falling onto a solid substrate will disintegrate into smaller parts when its impact velocity exceeds the so called critical velocity for splashing. Under these circumstances, the very thin liquid sheet ejected tangentially to the solid after the drop touches the substrate, lifts off as a consequence of the aerodynamic forces exerted on it and finally breaks into smaller droplets, violently ejected radially outwards, provoking the splash. Here, the tangential deceleration experienced by the fluid entering the thin liquid sheet is investigated making use of boundary layer theory. The velocity component tangent to the solid, computed using potential flow theory provides the far field boundary condition as well as the pressure gradient for the boundary layer equations. The structure of the flow permits to find a self similar solution of the boundary layer equations. This solution is then used to calculate the boundary layer thickness at the root of the lamella as well as the shear stress at the wall. The splash model presented in, which is slightly modified to account for the results obtained from the boundary layer analysis, provides a very good agreement between the measurements and the predicted values of the critical velocity for the splash.

  12. The Physics of Hang Gliding

    Science.gov (United States)

    Hewett, Lionel D.

    2008-03-01

    Dr. Hewett has received both national and international awards from the hang gliding community for his contributions to the safety of towing hang gliders. These contributions were a consequence of his applying his knowledge of physics to the sport of hang gliding. This lecture illustrates how these and other applications of the fundamental principles of physics have influenced the historical evolutions of hang gliding and paragliding from the earliest flights of Otto Lilienthal in 1891 through the more recent record breaking flights of more than 430 miles from Zapata Texas.

  13. Boundary-layer effects in droplet splashing

    Science.gov (United States)

    Riboux, Guillaume; Gordillo, José Manuel

    2017-07-01

    A drop falling onto a solid substrate will disintegrate into smaller parts when its impact velocity V exceeds the so-called critical velocity for splashing, i.e., when V >V* . Under these circumstances, the very thin liquid sheet, which is ejected tangentially to the solid after the drop touches the substrate, lifts off as a consequence of the aerodynamic forces exerted on it. Subsequently, the growth of capillary instabilities breaks the toroidal rim bordering the ejecta into smaller droplets, violently ejected radially outward, provoking the splash [G. Riboux and J. M. Gordillo, Phys. Rev. Lett. 113, 024507 (2014)], 10.1103/PhysRevLett.113.024507. In this contribution, the effect of the growth of the boundary layer is included in the splash model presented in Phys. Rev. Lett. 113, 024507 (2014), 10.1103/PhysRevLett.113.024507, obtaining very good agreement between the measured and the predicted values of V* for wide ranges of liquid and gas material properties, atmospheric pressures, and substrate wettabilities. Our description also modifies the way at when the liquid sheet is first ejected, which can now be determined in a much more straightforward manner than that proposed in Phys. Rev. Lett. 113, 024507 (2014), 10.1103/PhysRevLett.113.024507.

  14. Numerical Study of Splash Detail Due to Grain Impact on Granular Bed

    Science.gov (United States)

    Tanabe, Takahiro; Niiya, Hirofumi; Awazu, Akinori; Nishimori, Hiraku

    2017-04-01

    Massive sediment transport phenomena, such as sand storm and drifting snow, pose a considerable threat to human life. Further, the formation of geomorphological patterns on sand-desert and snowfield surfaces as a result of sediment transport, such as dunes and ripples, is of considerable research interest. Because the major component of the grain entrainment into the air is caused by both the collision and ejection, it is necessary to focus on the collisions between wind-blown grains and surface of sand field along with the resultant ejection grains from the surfaces, which processes are, as a whole, called a splash process. However, because of complexity of jumping grains over the ground surface, detailed measurement is very hard. Therefore, to investigate the splash process, we simulate detailed process of splash caused by 1-grain impact onto a randomly packed granular bed using discrete element method. As a result, we obtained good correspondence between our numerical results and the findings of previous experiments for the movement of ejected grains. Furthermore, the distributions of the ejection angle and the vertical ejection speed for individual grains vary depending on the relative timing at which the grains are ejected after the initial impact. Obvious differences are observed between the distributions of grains ejected during the earlier and later splash periods: the form of the vertical ejection-speed distribution varies from a power-law form to a lognormal form with time, and this difference is related to the grain trajectory after ejection [1]. In addition, we focus on the bulk dynamics inside the granular bed to relate the ejected grains behavior to the force propagations from the first impact to the ejection of each grain. [1] T. Tanabe, T. Shimada, N. Ito, and, H. Nishimori, (submitted)

  15. Assessment of the Performance of Several Roadway Mixes under Rain, Snow, and Winter Maintenance Activities

    OpenAIRE

    Flintsch, Gerardo W.

    2004-01-01

    The purpose of this study was to assess the relative functional performance, including skid resistance and splash and spray, of five hot-mix-asphalt (HMA) surfaces and a tinned portland cement concrete highway surface during controlled wet and wintry weather events. The study compared the way that these surfaces respond to various deicing and anti-icing snow removal and ice control techniques under artificial wintry conditions. In addition, the splash and spray characteristics of the surfaces...

  16. ATLAS Splash event - 6 April 2018

    CERN Multimedia

    ATLAS Collaboration

    2018-01-01

    The image shows a visualization of experimental data coming from the 'beam splash' tests run in April 2018 as part of the restart process of the LHC accelerator, after the winter break for maintenance. The image shows the hits of part of the tracking detector (in red, at the center), the energy deposits in the electromagnetic calorimeter (in green), and those in the hadronic calorimeter (in yellow). The semi-transparent azure volumes are part of the hadronic calorimeter, while the grey outer structure is part of the muon spectrometer.

  17. Effects of Crop Canopies on Rain Splash Detachment

    Science.gov (United States)

    Ma, Bo; Yu, Xiaoling; Ma, Fan; Li, Zhanbin; Wu, Faqi

    2014-01-01

    Crops are one of the main factors affecting soil erosion in sloping fields. To determine the characteristics of splash erosion under crop canopies, corn, soybean, millet, and winter wheat were collected, and the relationship among splash erosion, rainfall intensity, and throughfall intensity under different crop canopies was analyzed through artificial rainfall experiments. The results showed that, the mean splash detachment rate on the ground surface was 390.12 g/m2·h, which was lower by 67.81% than that on bare land. The inhibiting effects of crops on splash erosion increased as the crops grew, and the ability of the four crops to inhibit splash erosion was in the order of winter wheat>corn>soybeans>millet. An increase in rainfall intensity could significantly enhance the occurrence of splash erosion, but the ability of crops to inhibit splash erosion was 13% greater in cases of higher rainfall intensity. The throughfall intensity under crop canopies was positively related to the splash detachment rate, and this relationship was more significant when the rainfall intensity was 40 mm/h. Splash erosion tended to occur intensively in the central row of croplands as the crop grew, and the non-uniformity of splash erosion was substantial, with splash erosion occurring mainly between the rows and in the region directly under the leaf margin. This study has provided a theoretical basis for describing the erosion mechanisms of cropland and for assisting soil erosion prediction as well as irrigation and fertilizer management in cultivated fields. PMID:24992386

  18. Influence of surface structure and chemistry on water droplet splashing.

    Science.gov (United States)

    Koch, Kerstin; Grichnik, Roland

    2016-08-06

    Water droplet splashing and aerosolization play a role in human hygiene and health systems as well as in crop culturing. Prevention or reduction of splashing can prevent transmission of diseases between animals and plants and keep technical systems such as pipe or bottling systems free of contamination. This study demonstrates to what extent the surface chemistry and structures influence the water droplet splashing behaviour. Smooth surfaces and structured replicas of Calathea zebrina (Sims) Lindl. leaves were produced. Modification of their wettability was done by coating with hydrophobizing and hydrophilizing agents. Their wetting was characterized by contact angle measurement and splashing behaviour was observed with a high-speed video camera. Hydrophobic and superhydrophilic surfaces generally showed fewer tendencies to splash than hydrophobic ones. Structuring amplified the underlying behaviour of the surface chemistries, increasing hydrophobic surfaces' tendency to splash and decreasing splash on hydrophilic surfaces by quickly transporting water off the impact point by capillary forces. The non-porous surface structures found in C. zebrina could easily be applied to technical products such as plastic foils or mats and coated with hydrophilizing agents to suppress splash in areas of increased hygiene requirements or wherever pooling of liquids is not desirable.This article is part of the themed issue 'Bioinspired hierarchically structured surfaces for green science'. © 2016 The Author(s).

  19. Characterizing wet slab and glide slab avalanche occurrence along the Going-to-the-Sun Road, Glacier National Park, Montana, USA

    Science.gov (United States)

    Peitzsch, Erich H.; Hendrikx, Jordy; Fagre, Daniel B.; Reardon, Blase

    2010-01-01

    Wet slab and glide slab snow avalanches are dangerous and yet can be particularly difficult to predict. Both wet slab and glide slab avalanches are thought to depend upon free water moving through the snowpack but are driven by different processes. In Glacier National Park, Montana, both types of avalanches can occur in the same year and affect the Going-to-the-Sun Road (GTSR). Both wet slab and glide slab avalanches along the GTSR from 2003-2010 are investigated. Meteorological data from two high-elevation weather stations and one SNOTEL site are used in conjunction with an avalanche database and snowpit profiles. These data were used to characterize years when only glide slab avalanches occurred and those years when both glide slab and wet slab avalanches occurred. Results of 168 glide slab and 57 wet slab avalanches along the GTSR suggest both types of avalanche occurrence depend on sustained warming periods with intense solar radiation (or rain on snow) to produce free water in the snowpack. Differences in temperature and net radiation metrics between wet slab and glide slab avalanches emerge as one moves from one day to seven days prior to avalanche occurrence. On average, a more rapid warming precedes wet slab avalanche occurrence. Glide slab and wet slab avalanches require a similar amount of net radiation. Wet slab avalanches do not occur every year, while glide slab avalanches occur annually. These results aim to enhance understanding of the required meteorological conditions for wet slab and glide slab avalanches and aid in improved wet snow avalanche forecasting.

  20. Snow Leopard

    Indian Academy of Sciences (India)

    the Central Asian mountains and the Indian Himalayan re- gion. Owing to their ... ographical range and associated ecological, social, and cultural ... Central Asia. Snow Leopard: Morphology. The ability of snow leopards to camouflage with the surrounding landscape of rocks, sparse low vegetation, and snow is crucial for.

  1. Droplet Splashing by a Slingshot Mechanism

    KAUST Repository

    Thoroddsen, Sigurdur T.

    2011-01-18

    When a drop impacts onto a liquid pool, it ejects a thin horizontal sheet of liquid, which emerges from the neck region connecting the two liquid masses. The leading section of this ejecta bends down to meet the pool liquid. When the sheet touches the pool, at an “elbow,” it ruptures and sends off microdroplets by a slingshot mechanism, driven by surface tension. High-speed imaging of the splashing droplets suggests the liquid sheet is of submicron thickness, as thin as 300 nm. Experiments in partial vacuum show that air resistance plays the primary role in bending the sheet. We identify a parameter regime where this slingshot occurs and also present a simple model for the sheet evolution, capable of reproducing the overall shape.

  2. Micro-splashing by drop impacts

    KAUST Repository

    Thoroddsen, Sigurdur T.

    2012-07-18

    We use ultra-high-speed video imaging to observe directly the earliest onset of prompt splashing when a drop impacts onto a smooth solid surface. We capture the start of the ejecta sheet travelling along the solid substrate and show how it breaks up immediately upon emergence from the underneath the drop. The resulting micro-droplets are much smaller and faster than previously reported and may have gone unobserved owing to their very small size and rapid ejection velocities, which approach 100 m s-1, for typical impact conditions of large rain drops. We propose a phenomenological mechanism which predicts the velocity and size distribution of the resulting microdroplets. We also observe azimuthal undulations which may help promote the earliest breakup of the ejecta. This instability occurs in the cusp in the free surface where the drop surface meets the radially ejected liquid sheet. © 2012 Cambridge University Press.

  3. First beam splashes at the LHC

    CERN Multimedia

    CERN Bulletin

    2015-01-01

    After a two-year shutdown, the first beams of Run 2 circulated in the LHC last Sunday. On Tuesday, the LHC operators performed dedicated runs to allow some of the experiments to record their first signals coming from particles splashed out when the circulating beams hit the collimators. Powerful reconstruction software then transforms the electronic signals into colourful images.     “Splash” events are used by the experiments to test their numerous subdetectors and to synchronise them with the LHC clock. These events are recorded when the path of particles travelling in the LHC vacuum pipe is intentionally obstructed using collimators – one-metre-long graphite or tungsten jaws that are also used to catch particles that wander too far from the beam centre and to protect the accelerator against unavoidable regular and irregular beam losses. The particles sprayed out of the collision between the beam and the collimators are mostly muons. ATLAS and CMS&...

  4. Examining spring wet slab and glide avalanche occurrence along the Going-to-the-Sun Road corridor, Glacier National Park, Montana, USA

    Science.gov (United States)

    Peitzsch, Erich H.; Hendrikx, Jordy; Fagre, Daniel B.; Reardon, Blase

    2012-01-01

    Wet slab and glide snow avalanches are dangerous and yet can be particularly difficult to predict. Wet slab and glide avalanches are presumably triggered by free water moving through the snowpack and the subsequent interaction with layer or ground interfaces, and typically occur in the spring during warming and subsequent melt periods. In Glacier National Park (GNP), Montana, both types of avalanches can occur in the same year and affect the spring opening operations of the Going-to-the-Sun Road (GTSR).

  5. Preventive medicine oversight of splash pads on military installations.

    Science.gov (United States)

    Hardcastle, Lisa Raysby; Perry, Matthew; Browne, Ashley

    2015-01-01

    Over the past several years, an increasing number of military installations have installed splash pads that provide fun, recreational water entertainment for Soldiers and their families. The addition of splash pads brings added responsibilities for medical treatment facility preventive medicine oversight and installation facilities maintenance to ensure a safe and healthy environment. Currently, there are no consistent standards or detailed guidance for military installations to follow when installing and maintaining splash pads. The central issues associated with splash pads on military installations are water quality and risk for waterborne illnesses, responsibility for safety and health oversight, and federal energy and water sustainability mandates. This article examines the importance of implementing a standard for design and oversight to ensure the health and safety of Soldiers and their families.

  6. Radial gravitational gliding on passive margins

    Science.gov (United States)

    Cobbold, P. R.; Szatmari, P.

    1991-03-01

    Gravitational gliding of uppermost sediments down a passive margin is possible if there is a basal layer of evaporite or other soft material to allow detachment. In examples from the Gulf of Mexico and the Brazilian margin, gliding has produced three main structural domains: an uppermost domain of downdip extension; an intermediate domain of rigid gliding; and a lowermost domain of downdip contraction. Domain boundaries are established by changes in slope. In this paper, we examine three kinds of gravitational gliding, depending on the paths followed by material particles. In ideal parallel gliding, particle paths are parallel straight lines, trending downslope. This should occur where the margin is perfectly straight. In ideal radial gliding, particle paths are radii of a circle and the margin is shaped like a circular cone. Natural margins will not have ideal shapes; but divergent gliding will tend to occur off coastal salients; convergent gliding, off coastal re-entrants. A simple kinematic model based on ductile behaviour illustrates some essential features of radial gliding. Changes in radius during divergent gliding produce strike-parallel extension; during convergent gliding, they produce strike-parallel contraction. Vertical strains also differ. Divergent gliding produces an uppermost domain of strong vertical thinning, balanced by extensions in all horizontal directions. Similarly, convergent gliding produces a lowermost domain of strong vertical thickening, balanced by contractions in all horizontal directions. These deformed states cannot be restored by simple techniques based on section balancing. We have done three experiments using analogue materials: sand, to model the brittle behaviour of sediments; silicone putty, to model the ductile behaviour of basal layers of evaporite. The experiments were properly scaled to account for gravitational forces. Experiment I reproduced convergent gliding above a basement with a conical upper surface. Strike

  7. Snow Matters

    DEFF Research Database (Denmark)

    Gyimóthy, Szilvia; Jensen, Martin Trandberg

    2018-01-01

    attribute of high altitude mountain destinations. Hitherto, researchers mostly engaged with snowclad landscapes as a backstage; trying to deconstruct the complex symbolism and representational qualities of this elusive substance. Despite snow being a strategically crucial condition for tourism in the Alps......This chapter explores the performative potential of snow for Alpine tourism, by drawing attention to its material and nonrepresentational significance for tourism practices. European imagination has been preoccupied with snow since medieval times and even today, snow features as the sine que non...

  8. Drop splashing: the role of surface wettability and liquid viscosity

    Science.gov (United States)

    Almohammadi, Hamed; Amirfazli, Alidad; -Team

    2017-11-01

    There are seemingly contradictory results in the literature about the role of surface wettability and drop viscosity for the splashing behavior of a drop impacting onto a surface. Motivated by such issues, we conducted a systematic experimental study where splashing behavior for a wide range of the liquid viscosity (1-100 cSt) and surface wettability (hydrophilic to hydrophobic) are examined. The experiments were performed for the liquids with both low and high surface tensions ( 20 and 72 mN/m). We found that the wettability affects the splashing threshold at high or low contact angle values. At the same drop velocity, an increase of the viscosity (up to 4 cSt) promotes the splashing; while, beyond such value, any increase in viscosity shows the opposite effect. It is also found that at a particular combination of liquid surface tension and viscosity (e.g. silicone oil, 10 cSt), an increase in the drop velocity changes the splashing to spreading. We relate such behaviors to the thickness, shape, and the velocity of the drop's lamella. Finally, to predict the splashing, we developed an empirical correlation which covers all of the previous reported data, hence clarifying the ostensible existing contradictions.

  9. Splash Safety During Dermatologic Procedures Among US Dermatology Residents.

    Science.gov (United States)

    Korta, Dorota Z; Chapman, Lance W; Lee, Patrick K; Linden, Kenneth G

    2017-07-01

    Dermatologists are at potential risk of acquiring infections from contamination of the mucous membranes by blood and body fluids. However, there are little data on splash safety during procedural dermatology. To determine dermatology resident perceptions about splash risk during dermatologic procedures and to quantify the rate of protective equipment use. An anonymous on-line survey was sent to 108 United States ACGME-approved dermatology residency programs assessing frequency of facial protection during dermatologic procedures, personal history of splash injury, and, if applicable, reasons for not always wearing facial protection. A total of 153 dermatology residents responded. Rates of facial protection varied by procedure, with the highest rates during surgery and the lowest during local anesthetic injection. Over 54% of respondents reported suffering facial splash while not wearing facial protection during a procedure. In contrast, 88.9% of respondents correctly answered that there is a small risk of acquiring infection from mucosal splash. Residency program recommendations for facial protection seem to vary by procedure. The authors' results demonstrate that although facial splash is a common injury, facial protection rates and protective recommendations vary significantly by procedure. These data support the recommendation for enhanced facial protection guidelines during procedural dermatology.

  10. Drop impact splashing and air entrapment

    KAUST Repository

    Thoraval, Marie-Jean

    2013-03-01

    Drop impact is a canonical problem in fluid mechanics, with numerous applications in industrial as well as natural phenomena. The extremely simple initial configuration of the experiment can produce a very large variety of fast and complex dynamics. Scientific progress was made in parallel with major improvements in imaging and computational technologies. Most recently, high-speed imaging video cameras have opened the exploration of new phenomena occurring at the micro-second scale, and parallel computing allowed realistic direct numerical simulations of drop impacts. We combine these tools to bring a new understanding of two fundamental aspects of drop impacts: splashing and air entrapment. The early dynamics of a drop impacting on a liquid pool at high velocity produces an ejecta sheet, emerging horizontally in the neck between the drop and the pool. We show how the interaction of this thin liquid sheet with the air, the drop or the pool, can produce micro-droplets and bubble rings. Then we detail how the breakup of the air film stretched between the drop and the pool for lower impact velocities can produce a myriad of micro-bubbles.

  11. Glide performance and aerodynamics of non-equilibrium glides in northern flying squirrels (Glaucomys sabrinus).

    Science.gov (United States)

    Bahlman, Joseph W; Swartz, Sharon M; Riskin, Daniel K; Breuer, Kenneth S

    2013-03-06

    Gliding is an efficient form of travel found in every major group of terrestrial vertebrates. Gliding is often modelled in equilibrium, where aerodynamic forces exactly balance body weight resulting in constant velocity. Although the equilibrium model is relevant for long-distance gliding, such as soaring by birds, it may not be realistic for shorter distances between trees. To understand the aerodynamics of inter-tree gliding, we used direct observation and mathematical modelling. We used videography (60-125 fps) to track and reconstruct the three-dimensional trajectories of northern flying squirrels (Glaucomys sabrinus) in nature. From their trajectories, we calculated velocities, aerodynamic forces and force coefficients. We determined that flying squirrels do not glide at equilibrium, and instead demonstrate continuously changing velocities, forces and force coefficients, and generate more lift than needed to balance body weight. We compared observed glide performance with mathematical simulations that use constant force coefficients, a characteristic of equilibrium glides. Simulations with varying force coefficients, such as those of live squirrels, demonstrated better whole-glide performance compared with the theoretical equilibrium state. Using results from both the observed glides and the simulation, we describe the mechanics and execution of inter-tree glides, and then discuss how gliding behaviour may relate to the evolution of flapping flight.

  12. Glide performance and aerodynamics of non-equilibrium glides in northern flying squirrels (Glaucomys sabrinus)

    Science.gov (United States)

    Bahlman, Joseph W.; Swartz, Sharon M.; Riskin, Daniel K.; Breuer, Kenneth S.

    2013-01-01

    Gliding is an efficient form of travel found in every major group of terrestrial vertebrates. Gliding is often modelled in equilibrium, where aerodynamic forces exactly balance body weight resulting in constant velocity. Although the equilibrium model is relevant for long-distance gliding, such as soaring by birds, it may not be realistic for shorter distances between trees. To understand the aerodynamics of inter-tree gliding, we used direct observation and mathematical modelling. We used videography (60–125 fps) to track and reconstruct the three-dimensional trajectories of northern flying squirrels (Glaucomys sabrinus) in nature. From their trajectories, we calculated velocities, aerodynamic forces and force coefficients. We determined that flying squirrels do not glide at equilibrium, and instead demonstrate continuously changing velocities, forces and force coefficients, and generate more lift than needed to balance body weight. We compared observed glide performance with mathematical simulations that use constant force coefficients, a characteristic of equilibrium glides. Simulations with varying force coefficients, such as those of live squirrels, demonstrated better whole-glide performance compared with the theoretical equilibrium state. Using results from both the observed glides and the simulation, we describe the mechanics and execution of inter-tree glides, and then discuss how gliding behaviour may relate to the evolution of flapping flight. PMID:23256188

  13. Snow Leopard

    Indian Academy of Sciences (India)

    Owing to their secretive nature and inaccessible habitat,little is known about its ecology and distribution. Due toits endangered status and high aesthetic value, the snow leopardis considered as an 'umbrella species' for wildlife conservationin the Indian Himalayas. This article summarizes thecurrent knowledge on snow ...

  14. Snow Leopard

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 22; Issue 7. Snow Leopard: Ecology and Conservation Issues in India. Abhishek Ghoshal. General Article Volume 22 Issue 7 July 2017 pp 677- ... Keywords. Ecology, carnivore, conservation, Himalayas, mammal, snow leopard, Panthera uncia, wildlife.

  15. Impact splash chondrule formation during planetesimal recycling

    Science.gov (United States)

    Lichtenberg, Tim; Golabek, Gregor J.; Dullemond, Cornelis P.; Schönbächler, Maria; Gerya, Taras V.; Meyer, Michael R.

    2018-03-01

    Chondrules, mm-sized igneous-textured spherules, are the dominant bulk silicate constituent of chondritic meteorites and originate from highly energetic, local processes during the first million years after the birth of the Sun. So far, an astrophysically consistent chondrule formation scenario explaining major chemical, isotopic and textural features, in particular Fe,Ni metal abundances, bulk Fe/Mg ratios and intra-chondrite chemical and isotopic diversity, remains elusive. Here, we examine the prospect of forming chondrules from impact splashes among planetesimals heated by radioactive decay of short-lived radionuclides using thermomechanical models of their interior evolution. We show that intensely melted planetesimals with interior magma oceans became rapidly chemically equilibrated and physically differentiated. Therefore, collisional interactions among such bodies would have resulted in chondrule-like but basaltic spherules, which are not observed in the meteoritic record. This inconsistency with the expected dynamical interactions hints at an incomplete understanding of the planetary growth regime during the lifetime of the solar protoplanetary disk. To resolve this conundrum, we examine how the observed chemical and isotopic features of chondrules constrain the dynamical environment of accreting chondrite parent bodies by interpreting the meteoritic record as an impact-generated proxy of early solar system planetesimals that underwent repeated collision and reaccretion cycles. Using a coupled evolution-collision model we demonstrate that the vast majority of collisional debris feeding the asteroid main belt must be derived from planetesimals which were partially molten at maximum. Therefore, the precursors of chondrite parent bodies either formed primarily small, from sub-canonical aluminum-26 reservoirs, or collisional destruction mechanisms were efficient enough to shatter planetesimals before they reached the magma ocean phase. Finally, we outline the

  16. Stability of alternating current gliding arcs

    DEFF Research Database (Denmark)

    Kusano, Yukihiro; Salewski, Mirko; Leipold, Frank

    2014-01-01

    on Ohm’s law indicates that the critical length of alternating current (AC) gliding arc discharge columns can be larger than that of a corresponding direct current (DC) gliding arc. This finding is supported by previously published images of AC and DC gliding arcs. Furthermore, the analysis shows...... that the critical length can be increased by increasing the AC frequency, decreasing the serial resistance and lowering the gas flow rate. The predicted dependence of gas flow rate on the arc length is experimentally demonstrated. The gap width is varied to study an optimal electrode design, since the extended non...

  17. Observation of gliding arc surface treatment

    DEFF Research Database (Denmark)

    Kusano, Yukihiro; Zhu, Jiajian; Ehn, A.

    2015-01-01

    . Water contact angle measurements indicate that the treatment uniformity improves significantly when the AC gliding arc is tilted to the polymer surface. Thickness reduction of the gas boundary layer, explaining the improvement of surface treatment, by the ultrasonic irradiation was directly observed...... surfaces. A gap was observed between the polymer surface and the luminous region of the plasma column, indicating the existence of a gas boundary layer. The thickness of the gas boundary layer is smaller at higher gas flow-rates or with ultrasonic irradiation to the AC gliding arc and the polymer surface......An alternating current (AC) gliding arc can be conveniently operated at atmospheric pressure and efficiently elongated into the ambient air by an air flow and thus is useful for surface modification. A high speed camera was used to capture dynamics of the AC gliding arc in the presence of polymer...

  18. Snow clearance

    CERN Multimedia

    Mauro Nonis

    2005-01-01

    In reply to the numerous questions received, we should like to inform you of the actions and measures taken in an effort to maintain the movements of vehicles and pedestrians since the heavy snow fall on Sunday 23 January. Our contractor's employees began clearing the snow during the morning of Sunday 23 January on the main CERN sites (Meyrin, Prévessin), but an accident prevented them from continuing. The vehicle in question was repaired by Monday morning when two other vehicles joined it to resume snow clearing; priority was given to access points to the main sites and the LHC sites, as well as to the main roads inside the sites. The salt sprinklers were also brought into action that same day; the very low temperature during the night from Monday to Tuesday prevented the snow from melting and compacted the ice; the continuing cold during the day on Tuesday (-6°C at 10:00 on the Meyrin site) meant that all efforts to remove the ice were doomed to failure. In order to ensure more efficie...

  19. Snow Matters

    DEFF Research Database (Denmark)

    Gyimóthy, Szilvia; Jensen, Martin Trandberg

    2018-01-01

    attribute of high altitude mountain destinations. Hitherto, researchers mostly engaged with snowclad landscapes as a backstage; trying to deconstruct the complex symbolism and representational qualities of this elusive substance. Despite snow being a strategically crucial condition for tourism in the Alps...

  20. Snow Leopard

    Indian Academy of Sciences (India)

    around the same time in Kinnaur district. Studies on snow leop- ard habitats over the past two decades show that the economy of the region has rapidly shifted from traditional agro-pastoralism to market-driven agriculture. Consequently, human population growth, agricultural expanse, and excessive livestock grazing (Fig-.

  1. New gliding mammaliaforms from the Jurassic

    Science.gov (United States)

    Meng, Qing-Jin; Grossnickle, David M.; Liu, Di; Zhang, Yu-Guang; Neander, April I.; Ji, Qiang; Luo, Zhe-Xi

    2017-08-01

    Stem mammaliaforms are Mesozoic forerunners to mammals, and they offer critical evidence for the anatomical evolution and ecological diversification during the earliest mammalian history. Two new eleutherodonts from the Late Jurassic period have skin membranes and skeletal features that are adapted for gliding. Characteristics of their digits provide evidence of roosting behaviour, as in dermopterans and bats, and their feet have a calcaneal calcar to support the uropagatium as in bats. The new volant taxa are phylogenetically nested with arboreal eleutherodonts. Together, they show an evolutionary experimentation similar to the iterative evolutions of gliders within arboreal groups of marsupial and placental mammals. However, gliding eleutherodonts possess rigid interclavicle-clavicle structures, convergent to the avian furculum, and they retain shoulder girdle plesiomorphies of mammaliaforms and monotremes. Forelimb mobility required by gliding occurs at the acromion-clavicle and glenohumeral joints, is different from and convergent to the shoulder mobility at the pivotal clavicle-sternal joint in marsupial and placental gliders.

  2. Performance analysis of jump-gliding locomotion for miniature robotics.

    Science.gov (United States)

    Vidyasagar, A; Zufferey, Jean-Christohphe; Floreano, Dario; Kovač, M

    2015-03-26

    Recent work suggests that jumping locomotion in combination with a gliding phase can be used as an effective mobility principle in robotics. Compared to pure jumping without a gliding phase, the potential benefits of hybrid jump-gliding locomotion includes the ability to extend the distance travelled and reduce the potentially damaging impact forces upon landing. This publication evaluates the performance of jump-gliding locomotion and provides models for the analysis of the relevant dynamics of flight. It also defines a jump-gliding envelope that encompasses the range that can be achieved with jump-gliding robots and that can be used to evaluate the performance and improvement potential of jump-gliding robots. We present first a planar dynamic model and then a simplified closed form model, which allow for quantification of the distance travelled and the impact energy on landing. In order to validate the prediction of these models, we validate the model with experiments using a novel jump-gliding robot, named the 'EPFL jump-glider'. It has a mass of 16.5 g and is able to perform jumps from elevated positions, perform steered gliding flight, land safely and traverse on the ground by repetitive jumping. The experiments indicate that the developed jump-gliding model fits very well with the measured flight data using the EPFL jump-glider, confirming the benefits of jump-gliding locomotion to mobile robotics. The jump-glide envelope considerations indicate that the EPFL jump-glider, when traversing from a 2 m height, reaches 74.3% of optimal jump-gliding distance compared to pure jumping without a gliding phase which only reaches 33.4% of the optimal jump-gliding distance. Methods of further improving flight performance based on the models and inspiration from biological systems are presented providing mechanical design pathways to future jump-gliding robot designs.

  3. Dispersal of seeds from splash-cup plants

    Science.gov (United States)

    Pepper, Rachel

    2017-11-01

    Splash cup plants disperse their seeds with the help of raindrops. The seeds sit in a small (mm-scale) conical cup and are ejected upon drop impact. The seeds are ejected at velocities up to five times the impact speed of the raindrop, and are dispersed up to 1 m away from the parent plant, which is only a few cm high. Previous work investigating the mechanism of this remarkable dispersal predicted an optimum cup opening angle of around 40°, which matched reasonably well with experiments performed with 3D-printed splash cup models. Those experiments were done with off-center drop impacts on initially empty cups with no seeds. We discuss similar experiments for cups that are not initially empty, but rather contain seed mimics, water, or both seeds and water. For some of these realistic initial states results are strikingly different from empty cups. Connections to theory will also be discussed.

  4. Origin and dynamics of vortex rings in drop splashing.

    Science.gov (United States)

    Lee, Ji San; Park, Su Ji; Lee, Jun Ho; Weon, Byung Mook; Fezzaa, Kamel; Je, Jung Ho

    2015-09-04

    A vortex is a flow phenomenon that is very commonly observed in nature. More than a century, a vortex ring that forms during drop splashing has caught the attention of many scientists due to its importance in understanding fluid mixing and mass transport processes. However, the origin of the vortices and their dynamics remain unclear, mostly due to the lack of appropriate visualization methods. Here, with ultrafast X-ray phase-contrast imaging, we show that the formation of vortex rings originates from the energy transfer by capillary waves generated at the moment of the drop impact. Interestingly, we find a row of vortex rings along the drop wall, as demonstrated by a phase diagram established here, with different power-law dependencies of the angular velocities on the Reynolds number. These results provide important insight that allows understanding and modelling any type of vortex rings in nature, beyond just vortex rings during drop splashing.

  5. How swifts control their glide performance with morphing wings

    NARCIS (Netherlands)

    Lentink, D.; Muller, U. K.; Stamhuis, E. J.; de Kat, R.; van Gestel, W.; Veldhuis, L. L. M.; Henningsson, P.; Hedenstrom, A.; Videler, J. J.

    2007-01-01

    Gliding birds continually change the shape and size of their wings(1-6), presumably to exploit the profound effect of wing morphology on aerodynamic performance(7-9). That birds should adjust wing sweep to suit glide speed has been predicted qualitatively by analytical glide models(2,10), which

  6. Underlying and derived glides in Middle High German

    Directory of Open Access Journals (Sweden)

    Tracy Alan Hall

    2017-05-01

    Full Text Available The present study investigates the phonology of glides in Middle High German. On the basis of surface contrasts between prevocalic nuclear glides in syllable-final position ([VG.V] and postvocalic glides in onset position ([V.GV], it is argued that the latter were underlying glides (e.g. the /w/ in [le.wə] ‘lion’ and that the former were glides derived from vowels (e.g. the offglide [o̯] in the diphthong [uo̯] from /uo/. Underlying glides are argued to be [+consonantal], while nuclear glides ‒ like the vowels from which they derive ‒ are [‒consonantal]. The analysis of Middle High German bears on several debates involving glides in the theoretical literature. First, a treatment with an underlying glide in /VGV/ cannot be reanalyzed by treating the vowels as peaks (e.g. Harris & Kaisse 1999 for Argentinian Spanish. Second, the treatment of underlying glides as [+consonantal] is to be preferred over alternatives which analyze those sounds as [‒vocalic] (e.g. Nevins & Chitoran 2008 for several languages. Third, an analysis of nuclear structure is adopted (from Harris & Kaisse 1999 which enables one to interpret which element in a complex nucleus is the peak and which is the nonpeak without stipulation. Fourth, the contrastive syllabification of surface glides (i.e. [VG.V] vs. [V.GV] is shown to be a diagnostic of underlying glide languages that has not been discussed in the literature to date.

  7. Are splash plumes the origin of minor hotspots?

    Science.gov (United States)

    Davies, J. H.; Bunge, H.-P.

    2006-05-01

    It has been claimed that focused hot cylindrical upwelling plumes cause many of the surface volcanic hotspots on Earth. It has also been argued that they must originate from thermal boundary layers. In this paper, we present spherical simulations of mantle circulation at close to Earth-like vigor with significant internal heating. These show, in addition to thermal boundary layer plumes, a new class of plumes that are not rooted in thermal boundary layers. These plumes develop as instabilities from the edge of bowls of hot mantle, which are produced by cold downwelling material deforming hot sheets of mantle. The resulting bowl and plume structure can look a bit like the “splash” of a water droplet. These splash plumes might provide an explanation for some hotspots that are not underlain by thermal boundary layer sourced plumes and not initiated by large igneous provinces. We suggest that in Earth's mantle, lithospheric instabilities or small pieces of subducting slab could play the role of the model downwelling material in initiating splash plumes. Splash plumes would have implications for interpreting ocean-island basalt geochemistry, plume fixity, excess plume temperature, and estimating core heat flux. Improved seismic imaging will ultimately test this hypothesis.

  8. User manual for SPLASH (Single Panel Lamp and Shroud Helper).

    Energy Technology Data Exchange (ETDEWEB)

    Larsen, Marvin Elwood

    2006-02-01

    The radiant heat test facility develops test sets providing well-characterized thermal environments, often representing fires. Many of the components and procedures have become standardized to such an extent that the development of a specialized design tool to determine optimal configurations for radiant heat experiments was appropriate. SPLASH (Single Panel Lamp and Shroud Helper) is that tool. SPLASH is implemented as a user-friendly, Windows-based program that allows a designer to describe a test setup in terms of parameters such as number of lamps, power, position, and separation distance. This document is a user manual for that software. Any incidental descriptions of theory are only for the purpose of defining the model inputs. The theory for the underlying model is described in SAND2005-2947 (Ref. [1]). SPLASH provides a graphical user interface to define lamp panel and shroud designs parametrically, solves the resulting radiation enclosure problem for up to 2500 surfaces, and provides post-processing to facilitate understanding and documentation of analyzed designs.

  9. Effect of Seed Density on Splash Cup Seed Dispersal

    Science.gov (United States)

    Wigger, Patrick; Pepper, Rachel

    2017-11-01

    Splash cup plants are plants that utilize a small, mm-sized cup filled with seeds as a method of seed dispersal. The cup uses kinetic energy of an incident raindrop in order to project the seeds away from the plant up to 1 meter. The dispersal distance is important to ensure the offspring are not clustered too tightly to the parent plant. It has previously been found that a cup angle of 40 degrees to the horizontal is optimal for maximum dispersal of water from cups with no seeds. In this study we examine if the 40 degree cup is optimal for cups containing seeds with varying densities. We released uniform water drops above 5.0 mm 3D printed models of splash cups, using 1.0 mm plastic and glass microspheres of varying densities to simulate seeds. We observed the dispersal characteristics of each bead type by measuring the final seed locations after each splash, and by recording high speed video to determine the angle and velocity of the seeds as they exited the cup.

  10. Roughness influence on human blood drop spreading and splashing

    Science.gov (United States)

    Smith, Fiona; Buntsma, Naomi; Brutin, David

    2017-11-01

    The impact behaviour of complex fluid droplets is a topic that has been extensively studied but with much debate. The Bloodstain Pattern Analysis (BPA) community is encountering this scientific problem with daily practical cases since they use bloodstains as evidence in crime scene reconstruction. We aim to provide fundamental explanations in the study of blood drip stains by investigating the influence of surface roughness and wettability on the splashing limit of droplets of blood, a non-Newtonian colloidal fluid. Droplets of blood impacting perpendicularly different surfaces at different velocities were recorded. The recordings were analysed as well as the surfaces characteristics in order to find an empirical solution since we found that roughness plays a major role in the threshold of the splashing/non-splashing behaviour of blood compared to the wettability. Moreover it appears that roughness alters the deformation of the drip stains. These observations are key in characterising features of drip stains with the impacting conditions, which would answer some forensic issues.

  11. Investigation of gliding flight by flying fish

    Science.gov (United States)

    Park, Hyungmin; Jeon, Woo-Pyung; Choi, Haecheon

    2006-11-01

    The most successful flight capability of fish is observed in the flying fish. Furthermore, despite the difference between two medium (air and water), the flying fish is well evolved to have an excellent gliding performance as well as fast swimming capability. In this study, flying fish's morphological adaptation to gliding flight is experimentally investigated using dry-mounted darkedged-wing flying fish, Cypselurus Hiraii. Specifically, we examine the effects of the pectoral and pelvic fins on the aerodynamic performance considering (i) both pectoral and pelvic fins, (ii) pectoral fins only, and (iii) body only with both fins folded. Varying the attack angle, we measure the lift, drag and pitching moment at the free-stream velocity of 12m/s for each case. Case (i) has higher lift-to-drag ratio (i.e. longer gliding distance) and more enhanced longitudinal static stability than case (ii). However, the lift coefficient is smaller for case (i) than for case (ii), indicating that the pelvic fins are not so beneficial for wing loading. The gliding performance of flying fish is compared with those of other fliers and is found to be similar to those of insects such as the butterfly and fruitfly.

  12. Hypergravity effects on glide arc plasma

    NARCIS (Netherlands)

    Šperka, J.; Souček, P.; van Loon, J.J.W.A.; Dowson, A.; Schwarz, C.; Krause, J.; Kroesen, G.; Kudrle, V.

    2013-01-01

    The behaviour of a special type of electric discharge - the gliding arc plasma - has been investigated in hypergravity (1g-18g) using the Large Diameter Centrifuge (LDC) at ESA/ESTEC. The discharge voltage and current together with the videosignal from a fast camera have been recorded during the

  13. Upside-down gliding of Lymnaea.

    Science.gov (United States)

    Aono, Kanako; Fusada, Ayachika; Fusada, Yorichika; Ishii, Wataru; Kanaya, Yuji; Komuro, Mami; Matsui, Kanae; Meguro, Satoru; Miyamae, Ayumi; Miyamae, Yurie; Murata, Aya; Narita, Shizuka; Nozaka, Hiroe; Saito, Wakana; Watanabe, Ayumi; Nishikata, Kaori; Kanazawa, Akira; Fujito, Yutaka; Yamagishi, Miki; Abe, Takashi; Nagayama, Masafumi; Uchida, Tsutomu; Gohara, Kazutoshi; Lukowiak, Ken; Ito, Etsuro

    2008-12-01

    The pond snail Lymnaea stagnalis can often be observed moving upside down on its back just below the surface of the water. We have termed this form of movement "upside-down gliding." To elucidate the mechanism of this locomotion, we performed a series of experiments involving behavioral analyses and microscopic observations. These experiments were designed (1) to measure the speed of this locomotion; (2) to determine whether the mucus secreted from the foot of Lymnaea repels water, thereby allowing the snail to exploit the surface tension of the water for upside-down gliding; and (3) to observe the beating of foot cilia in this behavior. The beating of these cilia is thought to be the primary driving force for upside-down gliding. Our results demonstrate that upside-down gliding is an efficient active process involving the secretion of mucus that floats up to the water surface to serve as a substrate upon which cilia beat to cause locomotion at the underside of the water surface.

  14. Improved docking of polypeptides with Glide.

    Science.gov (United States)

    Tubert-Brohman, Ivan; Sherman, Woody; Repasky, Matt; Beuming, Thijs

    2013-07-22

    Predicting the binding mode of flexible polypeptides to proteins is an important task that falls outside the domain of applicability of most small molecule and protein-protein docking tools. Here, we test the small molecule flexible ligand docking program Glide on a set of 19 non-α-helical peptides and systematically improve pose prediction accuracy by enhancing Glide sampling for flexible polypeptides. In addition, scoring of the poses was improved by post-processing with physics-based implicit solvent MM-GBSA calculations. Using the best RMSD among the top 10 scoring poses as a metric, the success rate (RMSD ≤ 2.0 Å for the interface backbone atoms) increased from 21% with default Glide SP settings to 58% with the enhanced peptide sampling and scoring protocol in the case of redocking to the native protein structure. This approaches the accuracy of the recently developed Rosetta FlexPepDock method (63% success for these 19 peptides) while being over 100 times faster. Cross-docking was performed for a subset of cases where an unbound receptor structure was available, and in that case, 40% of peptides were docked successfully. We analyze the results and find that the optimized polypeptide protocol is most accurate for extended peptides of limited size and number of formal charges, defining a domain of applicability for this approach.

  15. Optical diagnostics of a gliding arc

    DEFF Research Database (Denmark)

    Sun, Z.W.; Zhu, J.J.; Li, Z.S.

    2013-01-01

    triggered by Townsend breakdown between the two legs of the gliding arc. The emission from the plasma column is shown to pulsate at a frequency of 62.5 kHz, i.e., twice the frequency of the AC power supply. Optical emission spectra of the plasma radiation show the presence of excited N2, NO and OH radicals......Dynamic processes in a gliding arc plasma generated between two diverging electrodes in ambient air driven by 31.25 kHz AC voltage were investigated using spatially and temporally resolved optical techniques. The life cycles of the gliding arc were tracked in fast movies using a high-speed camera...... with framing rates of tens to hundreds of kHz, showing details of ignition, motion, pulsation, short-cutting, and extinction of the plasma column. The ignition of a new discharge occurs before the extinction of the previous discharge. The developed, moving plasma column often short-cuts its current path...

  16. SPLASH-SXDF Multi-wavelength Photometric Catalog

    Science.gov (United States)

    Mehta, Vihang; Scarlata, Claudia; Capak, Peter; Davidzon, Iary; Faisst, Andreas; Hsieh, Bau Ching; Ilbert, Olivier; Jarvis, Matt; Laigle, Clotilde; Phillips, John; Silverman, John; Strauss, Michael A.; Tanaka, Masayuki; Bowler, Rebecca; Coupon, Jean; Foucaud, Sébastien; Hemmati, Shoubaneh; Masters, Daniel; McCracken, Henry Joy; Mobasher, Bahram; Ouchi, Masami; Shibuya, Takatoshi; Wang, Wei-Hao

    2018-04-01

    We present a multi-wavelength catalog in the Subaru/XMM-Newton Deep Field (SXDF) as part of the Spitzer Large Area Survey with Hyper-Suprime-Cam (SPLASH). We include the newly acquired optical data from the Hyper-Suprime-Cam Subaru Strategic Program, accompanied by IRAC coverage from the SPLASH survey. All available optical and near-infrared data is homogenized and resampled on a common astrometric reference frame. Source detection is done using a multi-wavelength detection image including the u-band to recover the bluest objects. We measure multi-wavelength photometry and compute photometric redshifts as well as physical properties for ∼1.17 million objects over ∼4.2 deg2, with ∼800,000 objects in the 2.4 deg2 HSC-Ultra-Deep coverage. Using the available spectroscopic redshifts from various surveys over the range of 0 catalog is a valuable, publicly available resource, perfectly suited for studying galaxies in the early universe and tracing their evolution through cosmic time.

  17. Splash-like marine biodiversity additions after the cambrian

    Directory of Open Access Journals (Sweden)

    Ruban Dmitry A.

    2015-01-01

    Full Text Available Some Phanerozoic biotic radiations in the marine realm led to marine biodiversity additions, i.e., increases in the global number of genera to unprecedented levels. Each of the two alternative biodiversity curves implies five post-Cambrian events of this kind, which coincided with parts of the biotic radiations. However, differences between these curves do not allow to find coherent marine biodiversity additions with the only exception of those occurred at the interval of the Great Ordovician Biodiversification. The attempted interpretations indicate that the marine biodiversity additions increased the number of marine genera by 10-30 % (from the previous unprecedented level to that new. All additions were relatively brief and occurred as splashes throughout the Phanerozoic. Peculiar intrinsic and extrinsic factors, as well as the speed of diversification should be considered when triggers of these events are looked for. Undoubtedly, splash-like marine biodiversity additions played an important role in the evolution of life in the sea, but a lot of research is required in order to understand their true nature.

  18. Splash Dynamics of Watercolors on Dry, Wet, and Cooled Surfaces

    Science.gov (United States)

    Baron, David; Vaidya, Ashwin; Su, Haiyan

    2015-11-01

    In his classic study in 1908, A.M. Worthington gave a thorough account of splashes and their formation through visualization experiments. In more recent times, there has been renewed interest in this subject, and much of the underlying physics behind Worthington's experiments has now been clarified. One specific set of such recent studies, which motivates this paper, concerns the fluid dynamics behind Jackson Pollock's drip paintings. The physical processes and the mathematical structures hidden in his works have received serious attention and made the scientific pursuit of art a compelling area of exploration. Our work explores the interaction of watercolors with watercolor paper. Specifically, we conduct experiments to analyze the settling patterns of droplets of watercolor paint on wet and frozen paper. Variations in paint viscosity, paper roughness, paper temperature, and the height of a released droplet are examined from time of impact, through its transient stages, until its final, dry state. Observable phenomena such as paint splashing, spreading, fingering, branching, rheological deposition, and fractal patterns are studied in detail and classified in terms of the control parameters.

  19. Investigation of the pathway of contaminated soil transported to plant surfaces by raindrop splash

    International Nuclear Information System (INIS)

    Dreicer, M.; Hakonson, T.E.; Whicker, F.W.; White, G.C.

    1983-01-01

    The environmental transport pathway of soil-borne radioisotopes to vegetation surfaces via raindrop splash was studied. The data show that soil can significantly contribute to the contamination found on plants. Further detailed study is needed to calculate the rate constant for the raindrop splash and retention pathways. 8 references, 1 figure

  20. Health risk assessment for splash parks that use rainwater as source water

    NARCIS (Netherlands)

    De Man, H.; Bouwknegt, M.; van Heijnsbergen, E.; Leenen, E. J T M; van Knapen, F.; de Roda Husman, A. M.

    2014-01-01

    In the Netherlands, rainwater becomes more and more popular as an economic and environmentally sustainable water source for splash parks, however, the associated public health risk and underlying risk factors are unknown. Since splash parks have been associated with outbreaks of infectious diseases,

  1. Risk of blood splashes to the eye during surgery | De Silva | South ...

    African Journals Online (AJOL)

    Background. With the advent of a new infectious era involving the HIV and hepatitis B and C viruses, concern has arisen about transmission of these viruses through ocular blood splashes during surgery. The purpose of the study was to determine the risk of ocular blood splashes to surgeons and their assistants during ...

  2. Particle tracking velocimetry of a gliding arc discharge

    DEFF Research Database (Denmark)

    Zhu, Jiajian; Gao, Jinlong; Ehn, Andreas

    2014-01-01

    A 35 kHz AC gliding arc discharge at atmospheric pressure is generated between two diverging electrodes and extended by an air flow. The gas flow velocity is measured by particle tracking velocimetry (PTV) while the moving velocity of the plasma column of the gliding arc discharge is measured...... by analyzing the movie taken by a high-speed camera. The two-dimensional velocity vector of the gas flow and of the gliding arc in the imaging plane was determined....

  3. Aerodynamics of gliding flight in common swifts.

    Science.gov (United States)

    Henningsson, P; Hedenström, A

    2011-02-01

    Gliding flight performance and wake topology of a common swift (Apus apus L.) were examined in a wind tunnel at speeds between 7 and 11 m s(-1). The tunnel was tilted to simulate descending flight at different sink speeds. The swift varied its wingspan, wing area and tail span over the speed range. Wingspan decreased linearly with speed, whereas tail span decreased in a nonlinear manner. For each airspeed, the minimum glide angle was found. The corresponding sink speeds showed a curvilinear relationship with airspeed, with a minimum sink speed at 8.1 m s(-1) and a speed of best glide at 9.4 m s(-1). Lift-to-drag ratio was calculated for each airspeed and tilt angle combinations and the maximum for each speed showed a curvilinear relationship with airspeed, with a maximum of 12.5 at an airspeed of 9.5 m s(-1). Wake was sampled in the transverse plane using stereo digital particle image velocimetry (DPIV). The main structures of the wake were a pair of trailing wingtip vortices and a pair of trailing tail vortices. Circulation of these was measured and a model was constructed that showed good weight support. Parasite drag was estimated from the wake defect measured in the wake behind the body. Parasite drag coefficient ranged from 0.30 to 0.22 over the range of airspeeds. Induced drag was calculated and used to estimate profile drag coefficient, which was found to be in the same range as that previously measured on a Harris' hawk.

  4. ESA GlobSnow Snow Water Equivalent (SWE)

    Data.gov (United States)

    National Aeronautics and Space Administration — The European Space Agency (ESA) Global Snow Monitoring for Climate Research (GlobSnow) snow water equivalent (SWE) v2.0 data record contains snow information derived...

  5. Splash of a liquid drop on a dry solid surface

    Science.gov (United States)

    Mishra, Shruti; Mandre, Shreyas; Rycroft, Chris; Brenner, Michael

    2015-11-01

    We study the early-time fluid mechanical phenomena of the splash of a liquid drop on a solid surface, focusing on the dynamics before contact through the intervening air layer. Previous theoretical work (e.g. Mani, Mandre and Brenner) on this problem neglected viscous effects in the liquid. However, a set of recent experiments show definitively that even at early times viscous effects in the liquid are important, and in particular have the ability to dramatically change the shape of the interface before contact. We describe a set of computations aimed to reproduce these experimental features. The simulations couple lubrication flow in the gas layer with nonsteady Stokes flow in the liquid, and surface tension at the liquid-air interface.

  6. 14 CFR 23.71 - Glide: Single-engine airplanes.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Glide: Single-engine airplanes. 23.71... AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Flight Performance § 23.71 Glide: Single-engine airplanes. The maximum horizontal distance traveled in still air, in nautical miles...

  7. A distributed snow-evolution modeling system (SnowModel)

    Science.gov (United States)

    Glen E. Liston; Kelly. Elder

    2006-01-01

    SnowModel is a spatially distributed snow-evolution modeling system designed for application in landscapes, climates, and conditions where snow occurs. It is an aggregation of four submodels: MicroMet defines meteorological forcing conditions, EnBal calculates surface energy exchanges, SnowPack simulates snow depth and water-equivalent evolution, and SnowTran-3D...

  8. Modelling of snow exceedances

    Science.gov (United States)

    Jordanova, Pavlina K.; Sadovský, Zoltán; Stehlík, Milan

    2017-07-01

    Modelling of snow exceedances is of great importance and interest for ecology, civil engineering and general public. We suggest the favorable fit for exceedances related to the exceptional snow loads from Slovakia, assuming that the data is driven by Generalised Pareto Distribution or Generalized Extreme Value Distribution. Further, the statistical dependence between the maximal snow loads and the corresponding altitudes is studied.

  9. Snow snake performance monitoring.

    Science.gov (United States)

    2008-12-01

    A recent study, Three-Dimensional Roughness Elements for Snow Retention (FHWA-WY-06/04F) (Tabler 2006), demonstrated : positive evidence for the effectiveness of Snow Snakes, a new type of snow fence suitable for use within the highway right-of...

  10. SWFSC/MMTD/AK: Structure of Populations, Level of Abundance, and Status of Humpbacks (SPLASH) 2004

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This project was part of a larger international project (SPLASH) designed to estimate the abundance and determine the population structure for humpback whales...

  11. Kelvin-Helmholtz instability in an ultrathin air film causes drop splashing on smooth surfaces.

    Science.gov (United States)

    Liu, Yuan; Tan, Peng; Xu, Lei

    2015-03-17

    When a fast-moving drop impacts onto a smooth substrate, splashing will be produced at the edge of the expanding liquid sheet. This ubiquitous phenomenon lacks a fundamental understanding. Combining experiment with model, we illustrate that the ultrathin air film trapped under the expanding liquid front triggers splashing. Because this film is thinner than the mean free path of air molecules, the interior airflow transfers momentum with an unusually high velocity comparable to the speed of sound and generates a stress 10 times stronger than the airflow in common situations. Such a large stress initiates Kelvin-Helmholtz instabilities at small length scales and effectively produces splashing. Our model agrees quantitatively with experimental verifications and brings a fundamental understanding to the ubiquitous phenomenon of drop splashing on smooth surfaces.

  12. Simulation of thermally activated dislocation glide

    International Nuclear Information System (INIS)

    Roennpagel, D.; Mohles, V.

    1994-01-01

    Solid solution hardening was investigated by simulating the motion of a flexible dislocation in thermal equilibrium while overcoming obstacles by thermal activation. In a first approach, the waiting times before activation were analysed at several temperatures, external stresses and segment lengths. From statistical studies of such activation event, the effective attack frequency, Gibb's free enthalpy of activation and the activation volume were derived in strict analogy to the analysis of experimental data. As a second approach the average velocity of a dislocation gliding over an infinite row of equidistant obstacles was calculated by simulation. The temperature dependence of this speed significantly differs from that of the waiting times, indicating that kinetic effects must not be neglected even at high at high temperatures where dislocation motion is said to be 'overdamped'. (au)

  13. Beam Splashes seen by the CMS detector #RestartLHC 2017 (end of April 2017)

    CERN Multimedia

    Mc Cauley, Thomas; Zevi Della Porta, Giovanni

    2017-01-01

    CMS event display from LHC beam splash on Saturday, 29th April 2017. This is the first time the full detector has seen particles produced since the beginning of the Extended Year-End Technical Stop (EYETS) 2017. In contrast to proton-proton collisions where the particles come from the center of the detector, in splash events, particles traverse the detector horizontally from one side to the other.

  14. Beam Splashes seen by the CMS detector #RestartLHC 2018 (end of Mar 2018)

    CERN Multimedia

    Mc Cauley, Thomas; Olivito, Dominick

    2018-01-01

    CMS event displays from LHC beam splash on Friday, 30th March 2018. In contrast to proton-proton collisions where the particles come from the center of the detector, in splash events, particles traverse the detector horizontally from one side to the other. The time sampling for the picture, which is optimized for collisions at the center of the detector, amplifies the appearance of an asymmetric energy deposit in the end that the particles traverse last.

  15. Ash wettability conditions splash erosion in the postfire

    Science.gov (United States)

    Gordillo-Rivero, Ángel J.; de Celis, Reyes; García-Moreno, Jorge; Jiménez-Compán, Elizabeth; Alanís, Nancy; Cerdà, Artemi; Pereira, Paulo; Zavala, Lorena M.; Jordán, Antonio

    2015-04-01

    à and Doerr, 2008; Woods and Balfour, 2008; Zavala et al., 2009). The presence of an ash layer may be ephemeral, as it often is quickly removed or redistributed by water and wind erosion, animals or traffic (Zavala et al., 2009a). Many authors have observed that the capacity of ash to protect soil depends on properties as the topography, the meteorological conditions and the thickness of ash coverage (Cerdà and Doerr, 2008; Pereira et al., 2013; Woods and Balfour, 2010; Zavala et al., 2009). Taking this into account, in this study we hypothesized that the wettability / hydrophobicity of the ash layer may have a significant effect on the soil response to splash erosion. Therefore, the aim of this study is to evaluate the dispersion of sediments produced by the impact of raindrops in function of ash wettability after a prescribed fire at plot scale. 2. MATERIAL AND METHODS In 20 November 2012, a prescribed fire was carried out in an area located in the public mount "Las Navas", near Almaden de la Plata, Sevilla (approx. 37° 50' 44.44'' N / 6° 3' 7.44''W and 428 masl). Soils are acidic and shallow, developed from acidic metamorphic rocks (schists, slates and pyrophyllites). Vegetation is dominated by shrub legumes (Calicotome villosa and several species of Ulex and Genista). The experimental area was framed and plowed to eliminate the risk of fire spreading during the experiment. Previously to burn, level staffs were installed for determination of flame height. The temperature reached in the soil was monitored during the fire by a set of six thermocouples which were buried in soil (2 cm depth) and connected to a data-logger for monitoring the topsoil temperature every 60 s. The environmental conditions were also monitored during the experiment by a mobile weather station. At the moment of the ignition, the temperature was around 20 °C and the wind speed was near 0.0 m/s. After ignition, the experimental area was allowed to burn during 2.5 h. During burning, flames

  16. Negatively charged nanoparticles produced by splashing of water

    Directory of Open Access Journals (Sweden)

    H. Tammet

    2009-01-01

    Full Text Available The production of splashing-generated balloelectric intermediate ions was studied by means of mobility spectrometry in the atmosphere during the rain and in a laboratory experiment simulating the heavy rain. The partial neutralization of intermediate ions with cluster ions generated by beta rays suppressed the space charge of intermediate ions but preserved the shape of the mobility distribution. The balloelectric ions produced from the waterworks water of high TDS (Total Dissolved Solids had about the same mobilities as the ions produced from the rainwater of low TDS. This suggests that the balloelectric ions can be considered as singly charged water nanoparticles. By different measurements, the diameter mode of these particles was 2.2–2.7 nm, which is close to the diameter of 2.5 nm of the Chaplin's 280-molecule magic icosahedron superclusters. The measurements can be explained by a hypothesis that the pressure of saturated vapor over the nanoparticle surface is suppressed by a number of magnitudes due to the internal structure of the particles near the size of 2.5 nm. The records of the concentration bursts of balloelectric ions in the atmosphere are formally similar to the records of the nucleation bursts but they cannot be qualified as nucleation bursts because the particles are not growing but shrinking.

  17. ACCURATE OH MASER POSITIONS FROM THE SPLASH PILOT REGION

    Energy Technology Data Exchange (ETDEWEB)

    Qiao, Hai-Hua; Shen, Zhi-Qiang [Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai, 200030 (China); Walsh, Andrew J.; Jordan, Christopher H. [International Centre for Radio Astronomy Research, Curtin University, GPO Box U1987, Perth WA 6845 (Australia); Green, James A. [CSIRO Astronomy and Space Science, Australia Telescope National Facility, PO Box 76, Epping, NSW 2121 (Australia); Breen, Shari L. [Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, NSW 2006 (Australia); Dawson, J. R. [Department of Physics and Astronomy and MQ Research Centre in Astronomy, Astrophysics and Astrophotonics, Macquarie University, NSW 2109 (Australia); Ellingsen, Simon P. [School of Physical Sciences, Private Bag 37,University of Tasmania, Hobart 7001, TAS (Australia); Gómez, José F. [Instituto de Astrofísica de Andalucía, CSIC, Glorieta de la Astronomía s/n, E-18008, Granada (Spain); Lowe, Vicki; Jones, Paul A., E-mail: qiaohh@shao.ac.cn [Department of Astrophysics and Optic, School of Physics, University of New South Wales, Sydney, NSW 2052 (Australia)

    2016-12-01

    We report on high spatial resolution observations, using the Australia Telescope Compact Array (ATCA), of ground-state OH masers. These observations were carried out toward 196 pointing centers previously identified in the Southern Parkes Large-Area Survey in Hydroxyl (SPLASH) pilot region, between Galactic longitudes of 334° and 344° and Galactic latitudes of −2° and +2°. Supplementing our data with data from the MAGMO (Mapping the Galactic Magnetic field through OH masers) survey, we find maser emission toward 175 of the 196 target fields. We conclude that about half of the 21 nondetections were due to intrinsic variability. Due to the superior sensitivity of the followup ATCA observations, and the ability to resolve nearby sources into separate sites, we have identified 215 OH maser sites toward the 175 fields with detections. Among these 215 OH maser sites, 111 are new detections. After comparing the positions of these 215 maser sites to the literature, we identify 122 (57%) sites associated with evolved stars (one of which is a planetary nebula), 64 (30%) with star formation, two sites with supernova remnants, and 27 (13%) of unknown origin. The infrared colors of evolved star sites with symmetric maser profiles tend to be redder than those of evolved star sites with asymmetric maser profiles, which may indicate that symmetric sources are generally at an earlier evolutionary stage.

  18. Distributed calibrating snow models using remotely sensed snow cover information

    Science.gov (United States)

    Li, H.

    2015-12-01

    Distributed calibrating snow models using remotely sensed snow cover information Hongyi Li1, Tao Che1, Xin Li1, Jian Wang11. Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China For improving the simulation accuracy of snow model, remotely sensed snow cover data are used to calibrate spatial parameters of snow model. A physically based snow model is developed and snow parameters including snow surface roughness, new snow density and critical threshold temperature distinguishing snowfall from precipitation, are spatially calibrated in this study. The study region, Babaohe basin, located in northwestern China, have seasonal snow cover and with complex terrain. The results indicates that the spatially calibration of snow model parameters make the simulation results more reasonable, and the simulated snow accumulation days, plot-scale snow depth are more better than lumped calibration.

  19. Liquid/glide zero alternation in Chitonga: an optimality analysis*

    African Journals Online (AJOL)

    ach-i-a 'leave to someone' ach-il-i-a. 'pardon' fika 'arrive' fik-i-a 'reach someone' fik-il-i-a 'get right here'. In other analyses for example, Mkochi (2004), liquid, glide and zero alternations have been treated as cases of glide and liquid epenthesis. Mkochi. (2004:27) states: "What determines whether it is a liquid that is inserted ...

  20. Basic Snow Pressure Calculation

    Science.gov (United States)

    Hao, Shouzhi; Su, Jian

    2018-03-01

    As extreme weather rising in recent years, the damage of large steel structures caused by weather is frequent in China. How to consider the effect of wind and snow loads on the structure in structural design has become the focus of attention in engineering field. In this paper, based on the serious snow disasters in recent years and comparative analysis of some scholars, influence factors and the value of the snow load, the probability model are described.

  1. Glide back booster wind tunnel model testing

    Science.gov (United States)

    Pricop, M. V.; Cojocaru, M. G.; Stoica, C. I.; Niculescu, M. L.; Neculaescu, A. M.; Persinaru, A. G.; Boscoianu, M.

    2017-07-01

    Affordable space access requires partial or ideally full launch vehicle reuse, which is in line with clean environment requirement. Although the idea is old, the practical use is difficult, requiring very large technology investment for qualification. Rocket gliders like Space Shuttle have been successfullyoperated but the price and correspondingly the energy footprint were found not sustainable. For medium launchers, finally there is a very promising platform as Falcon 9. For very small launchers the situation is more complex, because the performance index (payload to start mass) is already small, versus medium and heavy launchers. For partial reusable micro launchers this index is even smaller. However the challenge has to be taken because it is likely that in a multiyear effort, technology is going to enable the performance recovery to make such a system economically and environmentally feasible. The current paper is devoted to a small unitary glide back booster which is foreseen to be assembled in a number of possible configurations. Although the level of analysis is not deep, the solution is analyzed from the aerodynamic point of view. A wind tunnel model is designed, with an active canard, to enablea more efficient wind tunnel campaign, as a national level premiere.

  2. Loropetalum chinense 'Snow Panda'

    Science.gov (United States)

    A new Loropetalum chinense, ‘Snow Panda’, developed at the U.S. National Arboretum is described. ‘Snow Panda’ (NA75507, PI660659) originated from seeds collected near Yan Chi He, Hubei, China in 1994 by the North America-China Plant Exploration Consortium (NACPEC). Several seedlings from this trip w...

  3. FORMING CHONDRULES IN IMPACT SPLASHES. II. VOLATILE RETENTION

    Energy Technology Data Exchange (ETDEWEB)

    Dullemond, Cornelis Petrus; Harsono, Daniel; Stammler, Sebastian Markus [Institute for Theoretical Astrophysics, Heidelberg University, Albert-Ueberle-Strasse 2, D-69120 Heidelberg (Germany); Johansen, Anders [Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, SE-22100 Lund (Sweden)

    2016-11-20

    Solving the mystery of the origin of chondrules is one of the most elusive goals in the field of meteoritics. Recently, the idea of planet(esimal) collisions releasing splashes of lava droplets, long considered out of favor, has been reconsidered as a possible origin of chondrules by several papers. One of the main problems with this idea is the lack of quantitative and simple models that can be used to test this scenario by directly comparing to the many known observables of chondrules. In Paper I of this series, we presented a simple thermal evolution model of a spherically symmetric expanding cloud of molten lava droplets that is assumed to emerge from a collision between two planetesimals. The production of lava could be either because the two planetesimals were already in a largely molten (or almost molten) state due to heating by {sup 26}Al, or due to impact jetting at higher impact velocities. In the present paper, number II of this series, we use this model to calculate whether or not volatile elements such as Na and K will remain abundant in these droplets or whether they will get depleted due to evaporation. The high density of the droplet cloud (e.g., small distance between adjacent droplets) causes the vapor to quickly reach saturation pressure and thus shuts down further evaporation. We show to what extent, and under which conditions, this keeps the abundances of these elements high, as is seen in chondrules. We find that for most parameters of our model (cloud mass, expansion velocity, initial temperature) the volatile elements Mg, Si, and Fe remain entirely in the chondrules. The Na and K abundances inside the droplets will initially stay mostly at their initial values due to the saturation of the vapor pressure, but at some point start to drop due to the cloud expansion. However, as soon as the temperature starts to decrease, most or all of the vapor recondenses again. At the end, the Na and K elements retain most of their initial abundances, albeit

  4. GLobal Integrated Design Environment (GLIDE): A Concurrent Engineering Application

    Science.gov (United States)

    McGuire, Melissa L.; Kunkel, Matthew R.; Smith, David A.

    2010-01-01

    The GLobal Integrated Design Environment (GLIDE) is a client-server software application purpose-built to mitigate issues associated with real time data sharing in concurrent engineering environments and to facilitate discipline-to-discipline interaction between multiple engineers and researchers. GLIDE is implemented in multiple programming languages utilizing standardized web protocols to enable secure parameter data sharing between engineers and researchers across the Internet in closed and/or widely distributed working environments. A well defined, HyperText Transfer Protocol (HTTP) based Application Programming Interface (API) to the GLIDE client/server environment enables users to interact with GLIDE, and each other, within common and familiar tools. One such common tool, Microsoft Excel (Microsoft Corporation), paired with its add-in API for GLIDE, is discussed in this paper. The top-level examples given demonstrate how this interface improves the efficiency of the design process of a concurrent engineering study while reducing potential errors associated with manually sharing information between study participants.

  5. Constraints on the Formation of M31’s Stellar Halo from the SPLASH Survey

    Directory of Open Access Journals (Sweden)

    Karoline Gilbert

    2017-09-01

    Full Text Available The SPLASH (Spectroscopic and Photometric Landscape of Andromeda’s Stellar Halo Survey has observed fields throughout M31’s stellar halo, dwarf satellites, and stellar disk. The observations and derived measurements have either been compared to predictions from simulations of stellar halo formation or modeled directly in order to derive inferences about the formation and evolution of M31’s stellar halo. We summarize some of the major results from the SPLASH survey and the resulting implications for our understanding of the build-up of M31’s stellar halo.

  6. 77 FR 23120 - Special Local Regulations; Lowcountry Splash Open Water Swim, Wando River and Cooper River, Mount...

    Science.gov (United States)

    2012-04-18

    ...-AA08 Special Local Regulations; Lowcountry Splash Open Water Swim, Wando River and Cooper River, Mount... Special Local Regulations; Lowcountry Splash Open Water Swim, Wando River and Cooper River, Mount Pleasant... water swim, starts at Hobcaw Yacht Club on the Wando River, in approximate position 32[deg]49'19'' N, 79...

  7. Mechanics of gliding in birds with special reference to the influence of the ground effect.

    Science.gov (United States)

    Blake, R W

    1983-01-01

    A model of the mechanics of gliding without loss of altitude (horizontal gliding) is developed. The model can be employed to assess the influence of the principal drag components (induced, profile and parasite drag), choice of initial and final glide velocities and height above the ground on glide distance. For birds gliding near to the ground the ground effect acts to decrease the induced drag and increase the lift to drag ratio of the wings. Minimum drag speed is reduced for birds gliding near to the ground. The model is applied to the gliding flight of the black skimmer (Rhyncops nigra). Glide distances for given initial and final velocities are significantly increased in the influence of the ground effect over out of ground effect values.

  8. Effects of Surface Passivation on Gliding Motility Assays

    Science.gov (United States)

    2011-06-03

    vitro motility studies use two different methods to investigate the kinesin and microtubule system. In one method, microtubules are fixed to a coverglass... catalase Casein Effects on Gliding Motility Assays PLoS ONE | www.plosone.org 2 June 2011 | Volume 6 | Issue 6 | e19522 (Sigma C9322) and 20% (v/v) of 2...Letters 466(1): 59–62. doi: 10.1016/S0014-5793(99)01757-3. 11. Böhm KJ, Stracke R, Unger E (1999) Speeding up kinesin-driven microtubule gliding in vitro

  9. Sound absorption of snow

    OpenAIRE

    Maysenhölder, W.; Schneebeli, M.; Zhou, X.; Zhang, T.; Heggli, M.

    2008-01-01

    Recently fallen snow possesses good sound-absorbing properties. This fact is well-known and confirmed by measurements. Is the filigree structure of snowflakes decisive? In principle we know that the sound-absorbing capacity of a porous material is dependent on its structure. But until now the question as to which structural characteristics are significant has been insufficiently answered. Detailed investigations of snow are to explain this fact by precise measurements of the sound absorption,...

  10. Is splash erosion potential species specific? Measuring of splash erosion potential under forest in different succession stages along a biodiversity gradient in the humid subtropics

    Science.gov (United States)

    Geißler, C.; Kühn, P.; Scholten, T.

    2009-04-01

    It is widely accepted that (forest) vegetation is a key control for the type and intensity of soil erosion. The current paradigm is that natural or quasi-natural vegetation protects the soil from erosion and that agricultural vegetation or land use generally enhances erosion. The latter was in focus of most research during the last decades and less interest was paid on natural systems, which are more difficult to study. Nevertheless, afforestation is widely used as a measure of soil protection against soil erosion. Rainfall can be highly erosive particularly in the humid subtropics. Regarding climate change, also precipitation regime may change in direction to even more severe storms and higher rainfall intensities; it is a research field of growing importance. Key mechanisms of a vegetation cover in reducing or enhancing erosion are modifications of drop-size distribution, retention of raindrop impact on the soil and changes in amount and spatial distribution of rainfall at the ground surface. Controlling determinants are rainfall intensity, drop size distribution, drop fall velocity, height of the canopy as well as density of the canopy, crown and leaf traits, LAI and coverage by a litter layer. Large drops are supposed to be significant sources of splash detachment in forests (Brandt 1989; Vis 1986). However, the mechanisms of reducing (or enhancing?) splash detachment under forest in relation to species richness and species composition are not well understood. Some studies indicate that raindrop impact is species specific (Calder 2001; Nanko et al. 2006) and some neglect the effects of species specific impacts (Foot & Morgan 2005). Our research uses different methods of rainfall characterization (splash cups, tipping-bucket rain gauge, laser distrometer) to reveal the described mechanisms from the canopy through different vegetation layers to the ground. First results of splash cup measurements (revised after Ellison 1947) show that sand loss under vegetation

  11. Effects of Rainfall Intensity and Slope Angle on Splash Erosion in ...

    African Journals Online (AJOL)

    Global Journal of Pure and Applied Sciences ... Soil erosion is a critical global environmental problem, especially in the developing countries including Nigeria. In the humid and ... Factors of slope angle, rainfall amount, and intensity, and total kinetic energy were regressed against directional components of splash.

  12. The Effects of Mulch Cover on Splash Erosion in Makurdi Town ...

    African Journals Online (AJOL)

    Soil erosion has continued to be a serious environmental problem, particularly among the farming communities. In Benue State, the dominant economic activity is subsistence farming which is done under sub humid rainfall conditions. Splash erosion resulting from intense rainfall therefore poses severe problems that can be ...

  13. Degradation of Verapamil hydrochloride in water by gliding arc discharge

    Czech Academy of Sciences Publication Activity Database

    Krishna, S.; Mašláni, Alan; Izdebski, T.; Horáková, M.; Klementová, Š.; Špatenka, P.

    2016-01-01

    Roč. 152, June (2016), s. 47-54 ISSN 0045-6535 Institutional support: RVO:61389021 Keywords : Gliding arc discharge * Emission spectroscopy * Pharmaceuticals * Half-life * Degradation mechanism Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 4.208, year: 2016 http://www.sciencedirect.com/science/article/pii/S0045653516302442

  14. Kick, Glide, Pole! Cross-Country Skiing Fun (Part II)

    Science.gov (United States)

    Duoos, Bridget A.

    2012-01-01

    Part I of Kick, Glide, Pole! Cross-Country Skiing Fun, which was published in last issue, discussed how to select cross-country ski equipment, dress for the activity and the biomechanics of the diagonal stride. Part II focuses on teaching the diagonal stride technique and begins with a progression of indoor activities. Incorporating this fun,…

  15. Dislocation glide in non-compact crystal planes in copper

    Czech Academy of Sciences Publication Activity Database

    Orlová, Alena

    2002-01-01

    Roč. 93, č. 1 (2002), s. 72-75 ISSN 0044-3093 R&D Projects: GA AV ČR IBS2041001; GA AV ČR IAA2041504 Institutional research plan: CEZ:AV0Z2041904 Keywords : copper * noncompact glide * slip pattern Subject RIV: JG - Metallurgy Impact factor: 0.636, year: 2002

  16. Hypergravity synthesis of graphitic carbon nanomaterial in glide arc plasma

    NARCIS (Netherlands)

    Šperka, J.; Soucek, P.; van Loon, J.J.W.A.; Dowson, A.; Schwarz, C.; Krause, J.; Butenko, Y.; Kroesen, G.; Kudrle, V.

    2014-01-01

    A nanostructured carbon material was synthesized using a methane/helium glide arc plasma under standard and increased gravity. Material analysis performed on samples collected from an effluent gas filter showed that the deposited material was present in the form of carbon nanoparticles. They

  17. A global safety deficiency : False glide slope capture affecting aircraft

    NARCIS (Netherlands)

    Schuurman, M.J.

    2016-01-01

    A serious incident occurred at Eindhoven Airport (Netherlands) in May 2013. A Boeing 737-800 performed a go-around while using the Instrument Landing System (ILS). The flight crew reported a False Glide Slope capture as the reason for the go-around.
    At first the occurrence report did not really

  18. Gliding swifts attain laminar flow over rough wings.

    Directory of Open Access Journals (Sweden)

    David Lentink

    Full Text Available Swifts are among the most aerodynamically refined gliding birds. However, the overlapping vanes and protruding shafts of their primary feathers make swift wings remarkably rough for their size. Wing roughness height is 1-2% of chord length on the upper surface--10,000 times rougher than sailplane wings. Sailplanes depend on extreme wing smoothness to increase the area of laminar flow on the wing surface and minimize drag for extended glides. To understand why the swift does not rely on smooth wings, we used a stethoscope to map laminar flow over preserved wings in a low-turbulence wind tunnel. By combining laminar area, lift, and drag measurements, we show that average area of laminar flow on swift wings is 69% (n = 3; std 13% of their total area during glides that maximize flight distance and duration--similar to high-performance sailplanes. Our aerodynamic analysis indicates that swifts attain laminar flow over their rough wings because their wing size is comparable to the distance the air travels (after a roughness-induced perturbation before it transitions from laminar to turbulent. To interpret the function of swift wing roughness, we simulated its effect on smooth model wings using physical models. This manipulation shows that laminar flow is reduced and drag increased at high speeds. At the speeds at which swifts cruise, however, swift-like roughness prolongs laminar flow and reduces drag. This feature gives small birds with rudimentary wings an edge during the evolution of glide performance.

  19. Recent research in snow hydrology

    Science.gov (United States)

    Dozier, Jeff

    1987-01-01

    Recent work on snow-pack energy exchange has involved detailed investigations on snow albedo and attempts to integrate energy-balance calculations over drainage basins. Along with a better understanding of the EM properties of snow, research in remote sensing has become more focused toward estimation of snow-pack properties. In snow metamorphism, analyses of the physical processes must now be coupled to better descriptions of the geometry of the snow microstructure. The dilution method now appears to be the best direct technique for measuring the liquid water content of snow; work on EM methods continues. Increasing attention to the chemistry of the snow pack has come with the general focus on acid precipitation in hydrology.

  20. Snow, ice and solar radiation

    NARCIS (Netherlands)

    Kuipers Munneke, P.

    2009-01-01

    The snow-covered ice sheets of Antarctica and Greenland reflect most of the incoming solar radiation. The reflectivity, commonly called the albedo, of snow on these ice sheets has been observed to vary in space and time. In this thesis, temporal and spatial changes in snow albedo is found to depend

  1. LHC Beam Splash seen by the ATLAS detector, 7 Apr 2015 - Run 260466 - event 22425

    CERN Multimedia

    Adam Bourdarios, Claire

    2015-01-01

    Event display of one of the collimator "splash" event seen by the ATLAS experiment in LHC Run-2 , on Tuesday April the 7th : event 22425, run 260466. The collimator position is 140m in front of the ATLAS interaction point. The spray of particles enters ATLAS from the left hand side of the picture. The length of the yellow bars indicates the energy deposited in the ATLAS calorimeter.

  2. The shape and dynamics of the generation of the splash forms in single-phase systems after drop hitting

    Science.gov (United States)

    Sochan, Agata; Beczek, Michał; Mazur, Rafał; RyŻak, Magdalena; Bieganowski, Andrzej

    2018-02-01

    The splash phenomenon is being increasingly explored with the use of modern measurement tools, including the high-speed cameras. Recording images at a rate of several thousand frames per second facilitates parameterization and description of the dynamics of splash phases. This paper describes the impact of a single drop of a liquid falling on the surface of the same liquid. Three single-phase liquid systems, i.e., water, petrol, and diesel fuel, were examined. The falling drops were characterized by different kinetic energy values depending on the height of the fall, which ranged from 0.1 to 7.0 m. Four forms, i.e., waves, crowns, semi-closed domes, and domes, were distinguished depending on the drop energy. The analysis of the recorded images facilitated determination of the static and dynamic parameters of each form, e.g., the maximum height of each splash form, the width of the splash form at its maximum height, and the rate of growth of the splash form. We, Re, Fr, and K numbers were determined for all analyzed liquid systems. On the basis of the obtained values of dimensionless numbers, the areas of occurrence of characteristic splash forms were separated.

  3. Investigation of Aerodynamic Capabilities of Flying Fish in Gliding Flight

    Science.gov (United States)

    Park, H.; Choi, H.

    In the present study, we experimentally investigate the aerodynamic capabilities of flying fish. We consider four different flying fish models, which are darkedged-wing flying fishes stuffed in actual gliding posture. Some morphological parameters of flying fish such as lateral dihedral angle of pectoral fins, incidence angles of pectoral and pelvic fins are considered to examine their effect on the aerodynamic performance. We directly measure the aerodynamic properties (lift, drag, and pitching moment) for different morphological parameters of flying fish models. For the present flying fish models, the maximum lift coefficient and lift-to-drag ratio are similar to those of medium-sized birds such as the vulture, nighthawk and petrel. The pectoral fins are found to enhance the lift-to-drag ratio and the longitudinal static stability of gliding flight. On the other hand, the lift coefficient and lift-to-drag ratio decrease with increasing lateral dihedral angle of pectoral fins.

  4. Circular random motion in diatom gliding under isotropic conditions

    International Nuclear Information System (INIS)

    Gutiérrez-Medina, Braulio; Maldonado, Ana Iris Peña; Guerra, Andrés Jiménez; Rubio, Yadiralia Covarrubias; Meza, Jessica Viridiana García

    2014-01-01

    How cells migrate has been investigated primarily for the case of trajectories composed by joined straight segments. In contrast, little is known when cellular motion follows intrinsically curved paths. Here, we use time-lapse optical microscopy and automated trajectory tracking to investigate how individual cells of the diatom Nitzschia communis glide across surfaces under isotropic environmental conditions. We find a distinct kind of random motion, where trajectories are formed by circular arcs traveled at constant speed, alternated with random stoppages, direction reversals and changes in the orientation of the arcs. Analysis of experimental and computer-simulated trajectories show that the circular random motion of diatom gliding is not optimized for long-distance travel but rather for recurrent coverage of limited surface area. These results suggest that one main biological role for this type of diatom motility is to efficiently build the foundation of algal biofilms. (paper)

  5. Two mechanisms of droplet splashing on a solid substrate

    KAUST Repository

    Jian, Zhen

    2017-11-29

    We investigate droplet impact on a solid substrate in order to understand the influence of the gas in the splashing dynamics. We use numerical simulations where both the liquid and the gas phases are considered incompressible in order to focus on the gas inertial and viscous contributions. We first confirm that the dominant gas effect on the dynamics is due to its viscosity through the cushioning of the gas layer beneath the droplet. We then describe an additional inertial effect that is directly related to the gas density. The two different splashing mechanisms initially suggested theoretically are observed numerically, depending on whether a jet is created before or after the impacting droplet wets the substrate. Finally, we provide a phase diagram of the drop impact outputs as the gas viscosity and density vary, emphasizing the dominant effect of the gas viscosity with a small correction due to the gas density. Our results also suggest that gas inertia influences the splashing formation through a Kelvin–Helmholtz-like instability of the surface of the impacting droplet, in agreement with former theoretical works.

  6. Acti-Glide: a simple method of applying compression hosiery.

    Science.gov (United States)

    Hampton, Sylvie

    2005-05-01

    Compression hosiery is often worn to help prevent aching legs and swollen ankles, to prevent ulceration, to treat venous ulceration or to treat varicose veins. However, patients and nurses may experience problems applying hosiery and this can lead to non-concordance in patients and possibly reluctance from nurses to use compression hosiery. A simple solution to applying firm hosiery is Acti-Glide from Activa Healthcare.

  7. NASA Airborne Snow Observatory: Measuring Spatial Distribution of Snow Water Equivalent and Snow Albedo

    Science.gov (United States)

    Joyce, M.; Painter, T. H.; Bormann, K. J.; Berisford, D. F.; Lai-Norling, J.

    2017-12-01

    The two most critical properties for understanding snowmelt runoff and timing are the spatial and temporal distributions of snow water equivalent (SWE) and snow albedo. Despite their importance in controlling volume and timing of runoff, snowpack albedo and SWE are still largely unquantified in the US and not at all in most of the globe, leaving runoff models poorly constrained. NASA Jet Propulsion Laboratory, in partnership with the California Department of Water Resources, has developed the Airborne Snow Observatory (ASO), an imaging spectrometer and scanning LiDAR system, to quantify SWE and snow albedo, generate unprecedented knowledge of snow properties for cutting edge cryospheric science, and provide complete, robust inputs to water management models and systems of the future. This poster will describe the NASA Airborne Snow Observatory, its outputs and their uses and applications, along with recent advancements to the system and plans for the project's future. Specifically, we will look at how ASO uses its imaging spectrometer to quantify spectral albedo, broadband albedo, and radiative forcing by dust and black carbon in snow. Additionally, we'll see how the scanning LiDAR is used to determine snow depth against snow-free acquisitions and to quantify snow water equivalent when combined with in-situ constrained modeling of snow density.

  8. Connection between electrodes shape and plasma flow of the gliding discharge

    International Nuclear Information System (INIS)

    Slama, J.; Pichal, J.; Pichal, J.

    2011-01-01

    Contribution deals with form of electrodes and corresponding shape of plasma flow in the gliding discharge reactor. Gliding discharge sustained in air at atmospheric pressure and room temperature. There were studied three elemental electrodes configuration. Plasma was investigated by means of its visible spectral lines for identification of the most reactive plasma region in the flow. Results can be helpful in shaping of the gliding discharge reactor ionized gas region.

  9. Introduction to snow rheology

    International Nuclear Information System (INIS)

    Montmollin, Vincent de

    1978-01-01

    The tests described in the thesis are rotating shearing tests, with rotational constant speed ranging between 0.00075 rpm and 0.75 rpm. The results obtained are similar to those observed with compression tests at constant speed, except that shearing tests are carried out with densities nearly constant. So, we show three different domains when the rotation speed increases: 1) viscous (without failure) 2) brittle of first type (cycles of brittle failures) and 3) brittle of second type (only one brittle failure and solid friction). These results show clearly that the fundamental mechanism that rules the mechanisms of snow, is fast metamorphosis of bonds, binding ice grains: this metamorphosis is important when solicitation speeds are low (permanent rate of shearing in viscous domain, regeneration of the failure surfaces in the brittle domain of the first type) and this metamorphosis does not exist when speed increases (only one failure and solid friction in the brittle domain of second type). It is also included an important bibliographic analysis of the snow mechanics, and an experimental and theoretical study about shock wave propagation in natural snow covers. (author) [fr

  10. The effectiveness of detection of splashed particles using a system of three integrated high-speed cameras

    Science.gov (United States)

    Ryżak, Magdalena; Beczek, Michał; Mazur, Rafał; Sochan, Agata; Bieganowski, Andrzej

    2017-04-01

    The phenomenon of splash, which is one of the factors causing erosion of the soil surface, is the subject of research of various scientific teams. One of efficient methods of observation and analysis of this phenomenon are high-speed cameras to measure particles at 2000 frames per second or higher. Analysis of the phenomenon of splash with the use of high-speed cameras and specialized software can reveal, among other things, the number of broken particles, their speeds, trajectories, and the distances over which they were transferred. The paper presents an attempt at evaluation of the efficiency of detection of splashed particles with the use of a set of 3 cameras (Vision Research MIRO 310) and software Dantec Dynamics Studio, using a 3D module (Volumetric PTV). In order to assess the effectiveness of estimating the number of particles, the experiment was performed on glass beads with a diameter of 0.5 mm (corresponding to the sand fraction). Water droplets with a diameter of 4.2 mm fell on a sample from a height of 1.5 m. Two types of splashed particles were observed: particle having a low range (up to 18 mm) splashed at larger angles and particles of a high range (up to 118 mm) splashed at smaller angles. The detection efficiency the number of splashed particles estimated by the software was 45 - 65% for particles with a large range. The effectiveness of the detection of particles by the software has been calculated on the basis of comparison with the number of beads that fell on the adhesive surface around the sample. This work was partly financed from the National Science Centre, Poland; project no. 2014/14/E/ST10/00851.

  11. Experimental study of snow friction

    Science.gov (United States)

    Cohen, Caroline; Canale, Luca; Siria, Alessandro; Quere, David; Bocquet, Lyderic; Clanet, Christophe

    2017-11-01

    Snow friction results from the interplay of different physical processes: solid friction of granular material, phase change and lubrication, heat transport, capillarity, elasticity and plasticity. The multiple conditions of temperature, humidity and density of the snow result in different regimes of friction. In particular, there is an optimal amount of melted water to lubricate the contact between the ski sole and the snow grains. The thickness of the water layer depends on temperature, speed... A huge variety of waxes have been empirically developed to adapt the amount of water to the conditions of skiing, but remain mysterious. In these study, we investigate experimentally the mechanisms of snow friction at different scales: first, the friction of a ski on snow is measured on a test bench, depending on the snow characteristics and for different waxes. Then microscopic experiments are led in order to understand the friction at the ice crystals scale.

  12. MODIS Snow-Cover Products

    Science.gov (United States)

    Hall, Dorothy K.; Riggs, George A.; Salomonson, Vincent V.; DiGirolamo, Nicole E.; Bayr, Klaus J.; Houser, Paul R. (Technical Monitor)

    2002-01-01

    On December 18, 1999, the Terra satellite was launched with a complement of five instruments including the Moderate Resolution Imaging Spectroradiometer (MODIS). Many geophysical products are derived from MODIS data including global snow-cover products. MODIS snow and ice products have been available through the National Snow and Ice Data Center (NSIDC) Distributed Active Archive Center (DAAC) since September 13, 2000. MODIS snow-cover products represent potential improvement to or enhancement of the currently-available operational products mainly because the MODIS products are global and 500-m resolution, and have the capability to separate most snow and clouds. Also the snow-mapping algorithms are automated which means that a consistent data set may be generated for long-term climate studies that require snow-cover information. Extensive quality assurance (QA) information is stored with the products. The MODIS snow product suite begins with a 500-m resolution, 2330-km swath snow-cover map which is then gridded to an integerized sinusoidal grid to produce daily and 8-day composite tile products. The sequence proceeds to a climate-modeling grid (CMG) product at about 5.6-km spatial resolution, with both daily and 8-day composite products. Each pixel of the CMG contains fraction of snow cover from 40 - 100%. Measured errors of commission in the CMG are low, for example, on the continent of Australia in the spring, they vary from 0.02 - 0.10%. Near-term enhancements include daily snow albedo and fractional snow cover. A case study from March 6, 2000, involving MODIS data and field and aircraft measurements, is presented to show some early validation work.

  13. Effects of Polyacrylamide in Controlling of Splash Erosion from a Soil induced Freeze-Thaw Cycle

    Directory of Open Access Journals (Sweden)

    S.H.R. Sadeghi

    2016-09-01

    Full Text Available Introduction: The capability of a soil to resist erosion depends on soil-particle size and distribution, soil structure and structural stability, soil permeability, water content, organic matter content, and mineral and chemical constituents. Among many affecting factors on aforesaid characteristics, the freezing-thawing processes may considerably affects. Freeze–thaw fluctuation is a natural phenomenon that is frequently encountered by soils in the higher latitude and altitude regions in late autumn and early spring. Effects of freezing and freezing-thawing phenomena on soil erosion and sediment yield are important. Nevertheless, soil conservation under these phenomena by using different methods as well as soil amendments has not been yet considered. Surface application of anionic polyacrylamide (PAM in solution has been found to be very effective in decreasing seal formation, runoff, and erosion.PAM stabilizes soil structure due to the ability of the polymer chains to adsorb onto clay particles and bridge them together forming stable domains. This adsorption can be a result of interactions between the negatively-charged functional groups of the PAM molecules and the positively-charged edges of clay minerals, orexchangeable polycations (mainly Ca2+ acting as ‘bridges’ between the negative charges of the PAM's functional groups and the negatively- charged planar surfaces of the clay. The PAM is adsorbed on the external surfaces of the aggregates and binds soil particles far apart together, thereby were shorter and evidently less effective in enhancing increasing their resistance to splash by raindrop impact and detachment by runoff. A lot of research work focused on freezing effects in soils on aggregation or increase aggregate stability and emphasis corresponding effects. But the effects of application of soil amendments on soil induced freeze and thaw cycle have not been studied yet. Materials and Methods: The present study evaluated the

  14. Timing of wet snow avalanche activity: An analysis from Glacier National Park, Montana, USA.

    Science.gov (United States)

    Peitzsch, Erich H.; Hendrikx, Jordy; Fagre, Daniel B.

    2012-01-01

    Wet snow avalanches pose a problem for annual spring road opening operations along the Going-to-the-Sun Road (GTSR) in Glacier National Park, Montana, USA. A suite of meteorological metrics and snow observations has been used to forecast for wet slab and glide avalanche activity. However, the timing of spring wet slab and glide avalanches is a difficult process to forecast and requires new capabilities. For the 2011 and 2012 spring seasons we tested a previously developed classification tree model which had been trained on data from 2003-2010. For 2011, this model yielded a 91% predictive rate for avalanche days. For 2012, the model failed to capture any of the avalanche days observed. We then investigated these misclassified avalanche days in the 2012 season by comparing them to the misclassified days from the original dataset from which the model was trained. Results showed no significant difference in air temperature variables between this year and the original training data set for these misclassified days. This indicates that 2012 was characterized by avalanche days most similar to those that the model struggled with in the original training data. The original classification tree model showed air temperature to be a significant variable in wet avalanche activity which implies that subsequent movement of meltwater through the snowpack is also important. To further understand the timing of water flow we installed two lysimeters in fall 2011 before snow accumulation. Water flow showed a moderate correlation with air temperature later in the season and no synchronous pattern associated with wet slab and glide avalanche activity. We also characterized snowpack structure as the snowpack transitioned from a dry to a wet snowpack throughout the spring. This helped to assess potential failure layers of wet snow avalanches and the timing of avalanches compared to water moving through the snowpack. These tools (classification tree model and lysimeter data), combined with

  15. Cyclic fatigue of instruments for endodontic glide path.

    Science.gov (United States)

    Gambarini, Gianluca; Plotino, Gianluca; Sannino, GianPaolo; Grande, Nicola Maria; Giansiracusa, Alessio; Piasecki, Lucila; da Silva Neto, Ulisses Xavier; Al-Sudani, Dina; Testarelli, Luca

    2015-01-01

    Endodontic glide path is the creation of a smooth patency from canal orifice to apex, which can be performed manually or with small tapered NiTi rotary instruments. The use of stainless steel (SS) hand K-files inserted in a reciprocating handpiece can be a possible alternative to create a mechanical glide path. The aim of this study was to compare the cyclic fatigue resistance between SS K-files used in a reciprocating motion and NiTi rotary instruments in artificial curved canals. Ten SS size 15 K-files used with the M4 handpiece (SybronEndo, Glendora, CA, USA) and ten PathFiles (Maillefer-Dentsply, Ballaigues, CH, Switzerland) NiTi rotary instruments size 16, 0.02 taper were tested for resistance to cyclic fatigue. The time to fracture inside an artificial curved canal was recorded for each instrument. Data were analyzed by one-way ANOVA and Tukey HSD test. Mean time (and SD) to failure was 464 s (±40.4) for the Group PF (NiTi rotary PathFile), and 1049 s (±24.8) for the Group M4 (SS K-files reciprocating) with a statistically significant difference between the two groups (p = 0.033). The SS 15 K-files used with the M4 handpiece showed a significant greater resistance to cyclic fatigue when compared to the NiTi rotary PathFiles. Therefore, the use of small size SS files in a reciprocating motion might be a rational choice for the creation of a mechanical endodontic glide path in curved root canals.

  16. Assessment of the Implementation of GNSS into Gliding

    Directory of Open Access Journals (Sweden)

    Tomáš Kubáč

    2017-11-01

    Full Text Available Global navigation satellite systems are increasingly part of our lives and many industries including aviation. Glider flying is no exception in this trend. Global navigation satellite systems were part of gliding since the early 1990s. First as official recording devices for simple evidence of sporting performances, then as navigation systems, anti-collision systems and emergency location transmitters. Development of recording application was initiated and supported by International Gliding Commission of World Air Sports Federation in way of certifications for flight recorders. The use of navigation and other modern instruments in gliders has brought many benefits but also risks. However, the advantages outweigh the disadvantages and these systems are now integral part of gliding. With this wide usage of global navigation satellite systems devices, there is great many possibilities how and in which way one can use these systems. Pilots must orient themselves in varied selection of products, which they can use to choose one solution, that fits him. Therefore, to find out how and if pilots use these devices, we created questionnaire survey among 143 Czech glider pilots. We found out, that 84% of them are using global navigation satellite systems devices for official record of flight and for navigation as well. More than half of pilots is using free, not built-in devices. Most common devices are mobile phones up to 5 inches of screen diagonal in combination with approved flight recorder without display. If pilots use mobile device for navigation, 52% of them is using one with Windows Mobile operating system, 33% use Android. Navigational software on these mobile devices is then almost tied between SeeYou Mobile, XCSoar and LK8000. Knowledge about usage preference of global navigation systems devices should help pilots with selection and overall orientation in subject.

  17. Radiation-Enhanced Dislocation Glide: The Current Status of Research

    Science.gov (United States)

    Maeda, Koji

    Dislocations in most semiconductors exhibit radiation-enhanced dislocation glide (REDG) which is a cause of serious degradation in bipolar devices under forward biasing. Phenomenologically, REDG is characterized by the remarkable reduction of activation energy for glide velocity and the pre-exponential factor controlled by radiation intensity. Although the REDG shares features common with similar effects in point defects known as the recombination-enhanced defect reaction (REDR) that is well interpreted in terms of the phonon kick mechanism, it is not as yet established whether the REDG and the REDR share or not the same microscopic mechanism due to the lack of knowledge concerning electronic levels associated with the dislocations showing the REDG. Recent progress, however, has been achieved by studies of REDG in 4H-silicon carbide (4H-SiC) in which the dislocation component that exhibits the REDG is identified as 30°-Si(g) partial dislocation. Nevertheless, the driving force for the REDG in 4H-SiC is not the mechanical stress as in usual cases but an anomalous reversal of the sign of the Shockley stacking-fault (SSF) energy depending on the radiation intensity. An attempt was made in our recent experiments of photoinduced REDG to separate the intensity-dependent REDG effect and also the intensity-dependent driving force by simultaneous measurements of SSF expansion velocity (hence, the glide velocity of 30°-Si(g) partials) and the intensity of photoluminescence from the same SSFs (the latter allows us to deduce the driving force for the SSF expansion and hence the REDG). A comment, inspired by the studies of REDG in 4H-SiC, is given also to the mechanism of radiation-enhanced dislocation climb, another cause of degradation induced by minority-carrier injection.

  18. Investigation and prevention of droplet splashing during operation of a sodium free jet flow

    Energy Technology Data Exchange (ETDEWEB)

    Stoppel, L.; Gordeev, S.; Wetzel, T.; Fellmoser, F.; Daubner, M. [Karlsruhe Institute of Technology (KIT), Karlsruhe (Germany). KALLA Lab.; Stieglitz, R. [Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen (DE). Inst. for Neutron Physics and Reactor Technology (INR)

    2010-05-15

    Many accelerator application concepts consider liquid metal as a windowless target, at which the particle beam does directly hit the liquid. One of such concepts is studied in the European project ''DIRAC-Secondary beams - Design Study''. This project is focused on the preliminary research work for construction of a new international particle accelerator - Facility for Antiproton and Ion Research (FAIR) in Darmstadt. The planned accelerator is aimed to work with high-energy heavy-ions, such as U{sup 238}. One of the key elements of the FAIR facility is a liquid-metal-target, made in the form of a rectangular shaped Lithium jet aligned with the gravity vector. In the course of preliminary investigations the theoretical and practical conditions for a stable liquid-metal-jet conforming to the FAIR-requirements have been studied in the Karlsruhe Liquid Metal Laboratory (KALLA) sodium facility. The acquired scientific and technological results can be transferred to liquid-metal targets in nuclear applications, for example, the IFMIF-Target for the study of fusion reactor materials and the Myrrah/XT-ADS target. The main goals of the KALLA-part of the project were to design and build a facility for experimental research on hydrodynamic phenomena of the free surface liquid metal flow as well as to look at technological problems influencing the hydrodynamic stability of such flows. One of such problems emerged already during the startup of the facility: Splashing of liquid metal drops in the vacuum volume of the target box. As a result of such splashing process, liquid metal droplets are accumulated on various internal constructional elements of the target box, for example, on the inspection windows. This effect prohibits long term operation with the facility. The present paper describes the methods used to reduce the splashing to a minimum. (orig.)

  19. Antarctic snow and global climate

    International Nuclear Information System (INIS)

    Granberg, H.B.

    2001-01-01

    Global circulation models (GCM) indicate that global warming will be most pronounced at polar regions and high latitudes, causing concern about the stability of the Antarctic ice cap. A project entitled the Seasonal Snow in Antarctica examined the properties of the near surface snow to determine the current conditions that influence snow cover development. The goal was to assess the response of the snow cover in Queen Maud Land (QML) to an increased atmospheric carbon dioxide content. The Antarctic snow cover in QML was examined as part of the FINNARP expeditions in 1999 and 2000 which examined the processes that influence the snow cover. Its energy and mass balance were also assessed by examining the near surface snow strata in shallow (1-2 m) pits and by taking measurements of environmental variables. This made it possible to determine if the glacier is in danger of melting at this northerly location in the Antarctic. The study also made it possible to determine which variables need to change and by how much, for significant melting to occur. It was shown that the Antarctic anticyclone creates particular conditions that protect the snow cover from melting. The anticyclone brings dry air from the stratosphere during most of the year and is exempt from the water vapour feedback. It was concluded that even a doubling of atmospheric carbon dioxide will not produce major snow melt runoff. 8 refs

  20. Gliding motility of Babesia bovis merozoites visualized by time-lapse video microscopy.

    Directory of Open Access Journals (Sweden)

    Masahito Asada

    Full Text Available BACKGROUND: Babesia bovis is an apicomplexan intraerythrocytic protozoan parasite that induces babesiosis in cattle after transmission by ticks. During specific stages of the apicomplexan parasite lifecycle, such as the sporozoites of Plasmodium falciparum and tachyzoites of Toxoplasma gondii, host cells are targeted for invasion using a unique, active process termed "gliding motility". However, it is not thoroughly understood how the merozoites of B. bovis target and invade host red blood cells (RBCs, and gliding motility has so far not been observed in the parasite. METHODOLOGY/PRINCIPAL FINDINGS: Gliding motility of B. bovis merozoites was revealed by time-lapse video microscopy. The recorded images revealed that the process included egress of the merozoites from the infected RBC, gliding motility, and subsequent invasion into new RBCs. The gliding motility of B. bovis merozoites was similar to the helical gliding of Toxoplasma tachyzoites. The trails left by the merozoites were detected by indirect immunofluorescence assay using antiserum against B. bovis merozoite surface antigen 1. Inhibition of gliding motility by actin filament polymerization or depolymerization indicated that the gliding motility was driven by actomyosin dependent process. In addition, we revealed the timing of breakdown of the parasitophorous vacuole. Time-lapse image analysis of membrane-stained bovine RBCs showed formation and breakdown of the parasitophorous vacuole within ten minutes of invasion. CONCLUSIONS/SIGNIFICANCE: This is the first report of the gliding motility of B. bovis. Since merozoites of Plasmodium parasites do not glide on a substrate, the gliding motility of B. bovis merozoites is a notable finding.

  1. Snow and SMOW

    International Nuclear Information System (INIS)

    1967-01-01

    In the midst of Vienna's hottest weather spell this year, members of the Agency's headquarters laboratory staff found themselves unpacking a consignment of fresh snow from the Antarctic. It had been sent by air through Los Angeles, not for cooling purposes, but to assist in making more accurate measurements as part of the study of the world's water distribution and movement. The same research also involves SMOW (Standard Mean Ocean Water) and samples of water from the mid-Pacific will also soon arrive for scientific examination

  2. 'Snow White' in Color

    Science.gov (United States)

    2008-01-01

    This color image taken by the Surface Stereo Imager on NASA's Phoenix Mars Lander shows the trench dubbed 'Snow White,' after further digging on the 25th Martian day, or sol, of the mission (June 19, 2008). The lander's solar panel is casting a shadow over a portion of the trench. The trench is about 5 centimeters (2 inches) deep and 30 centimeters (12 inches) long. The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  3. Evaluation of forest snow processes models (SnowMKIP2)

    Science.gov (United States)

    Nick Rutter; Richard Essery; John Pomeroy; Nuria Altimir; Kostas Andreadis; Ian Baker; Alan Barr; Paul Bartlett; Aaron Boone; Huiping Deng; Herve Douville; Emanuel Dutra; Kelly Elder; others

    2009-01-01

    Thirty-three snowpack models of varying complexity and purpose were evaluated across a wide range of hydrometeorological and forest canopy conditions at five Northern Hemisphere locations, for up to two winter snow seasons. Modeled estimates of snow water equivalent (SWE) or depth were compared to observations at forest and open sites at each location. Precipitation...

  4. SnowClim: Snow climate monitoring for Europe

    Science.gov (United States)

    Bissolli, P.; Maier, U.

    2009-09-01

    Snow cover, particularly its depth and its frequency, is a very essential climate element. It influences the earth's surface radiation budget considerably due to its reflectivity properties and also it has large impact on economy and daily life (e.g. traffic, tourism). Although a lot of research and many national activities of snow monitoring have been done, there are very few products describing an integrated snow monitoring for whole Europe. In the light of a foreseen future Regional Climate Centre on Climate Monitoring (RCC-CM), the German Meteorological Service (Deutscher Wetterdienst, DWD) has established some first operational snow climate monitoring activities for the WMO Region VI (Europe and the Middle East). First selected key elements are the number of snowdays with a snow cover > 1 cm, the mean and the maximum snow depth per month. Results are presented in form of monthly and climatological maps, tables and diagrams of time series starting in 1981. Data presently are taken from observations at synoptical stations, received by the Global Telecommunication System. A first quality control based on threshold tests has been developed. The snow climate monitoring products are currently under further development. New evaluations will be carried out also on a daily data basis, additional satellite data, and also the quality control procedure will be extended. Some operational SnowClim products are available on the DWD web site: www.dwd.de/snowclim

  5. Snow Plow Activity (2015-2016)

    Data.gov (United States)

    Allegheny County / City of Pittsburgh / Western PA Regional Data Center — Snow Plow data from the the City of Pittsburgh's Snow Plow Tracker. These data are collected from the Snow Plow Tracker's Fusion Table and converted to geoJSON....

  6. Evolution of gliding in Southeast Asian geckos and other vertebrates is temporally congruent with dipterocarp forest development.

    Science.gov (United States)

    Heinicke, Matthew P; Greenbaum, Eli; Jackman, Todd R; Bauer, Aaron M

    2012-12-23

    Gliding morphologies occur in diverse vertebrate lineages in Southeast Asian rainforests, including three gecko genera, plus frogs, snakes, agamid lizards and squirrels. It has been hypothesized that repeated evolution of gliding is related to the dominance of Asian rainforest tree floras by dipterocarps. For dipterocarps to have influenced the evolution of gliding in Southeast Asian vertebrates, gliding lineages must have Eocene or later origins. However, divergence times are not known for most lineages. To investigate the temporal pattern of Asian gliding vertebrate evolution, we performed phylogenetic and molecular clock analyses. New sequence data for geckos incorporate exemplars of each gliding genus (Cosymbotus, Luperosaurus and Ptychozoon), whereas analyses of other vertebrate lineages use existing sequence data. Stem ages of most gliding vertebrates, including all geckos, cluster in the time period when dipterocarps came to dominate Asian tropical forests. These results demonstrate that a gliding/dipterocarp correlation is temporally viable, and caution against the assumption of early origins for apomorphic taxa.

  7. Plasma-liquid system with rotational gliding discharge with liquid electrode

    International Nuclear Information System (INIS)

    Nedybaliuk, O.A.; Solomenko, O.V; Martysh, E.V.; Fedirchuk, I.I.

    2014-01-01

    Plasma-liquid system based on rotational gliding discharge with one liquid electrode was developed. Emission spectra of plasma of rotational gliding discharge with one liquid electrode were investigated. Discovered effective mechanism of controlling non-isothermal level of plasma in dynamic plasma-liquid systems. Major mechanism of expulsion of metal anode material from plasma-liquid systems with rotational discharges was shown.

  8. The Gcm/Glide molecular and cellular pathway: new actors and new lineages.

    Science.gov (United States)

    Laneve, Pietro; Delaporte, Claude; Trebuchet, Guillaume; Komonyi, Orban; Flici, Hakima; Popkova, Anna; D'Agostino, Giuseppe; Taglini, Francesca; Kerekes, Irene; Giangrande, Angela

    2013-03-01

    In Drosophila, the transcription factor Gcm/Glide plays a key role in cell fate determination and cellular differentiation. In light of its crucial biological impact, major efforts have been put for analyzing its properties as master regulator, from both structural and functional points of view. However, the lack of efficient antibodies specific to the Gcm/Glide protein precluded thorough analyses of its regulation and activity in vivo. In order to relieve such restraints, we designed an epitope-tagging approach to "FLAG"-recognize and analyze the functional protein both in vitro (exogenous Gcm/Glide) and in vivo (endogenous protein). We here (i) reveal a tight interconnection between the small RNA and the Gcm/Glide pathways. AGO1 and miR-1 are Gcm/Glide targets whereas miR-279 negatively controls Gcm/Glide expression (ii) identify a novel cell population, peritracheal cells, expressing and requiring Gcm/Glide. Peritracheal cells are non-neuronal neurosecretory cells that are essential in ecdysis. In addition to emphasizing the importance of following the distribution and the activity of endogenous proteins in vivo, this study provides new insights and a novel frame to understand the Gcm/Glide biology. Copyright © 2012 Elsevier Inc. All rights reserved.

  9. Effortful Pitch Glide: A Potential New Exercise Evaluated by Dynamic MRI

    Science.gov (United States)

    Miloro, Keri Vasquez; Pearson, William G., Jr.; Langmore, Susan E.

    2014-01-01

    Purpose: The purpose of this study was to compare the biomechanics of the effortful pitch glide (EPG) with swallowing using dynamic MRI. The EPG is a combination of a pitch glide and a pharyngeal squeeze maneuver for targeting laryngeal and pharyngeal muscles. The authors hypothesized that the EPG would elicit significantly greater structural…

  10. Spatiotemporally resolved characteristics of a gliding arc discharge in a turbulent air flow at atmospheric pressure

    DEFF Research Database (Denmark)

    Zhu, Jiajian; Gao, Jinlong; Ehn, Andreas

    2017-01-01

    A gliding arc discharge was generated in a turbulent air flow at atmospheric pressure driven by a 35 kHz alternating current (AC) electric power. The spatiotemporally resolved characteristics of the gliding arc discharge, including glow-type discharges, spark-type discharges, short-cutting events...

  11. Improving efficiency of heat pumps by use of zeotropic mixtures for different temperature glides

    DEFF Research Database (Denmark)

    Zühlsdorf, Benjamin; Jensen, Jonas Kjær; Cignitti, Stefano

    2017-01-01

    The present study demonstrates the optimization of a heat pump for an application with a large temperature glide on the sink and a smaller temperature glide on the source side. The study includes a simulation of a heat pump cycle for all possible binary mixtures from a list of 14 natural...

  12. 14 CFR 121.360 - Ground proximity warning-glide slope deviation alerting system.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 3 2010-01-01 2010-01-01 false Ground proximity warning-glide slope... Equipment Requirements § 121.360 Ground proximity warning-glide slope deviation alerting system. (a) No person may operate a turbine-powered airplane unless it is equipped with a ground proximity warning...

  13. Plastic deformation of tubular crystals by dislocation glide.

    Science.gov (United States)

    Beller, Daniel A; Nelson, David R

    2016-09-01

    Tubular crystals, two-dimensional lattices wrapped into cylindrical topologies, arise in many contexts, including botany and biofilaments, and in physical systems such as carbon nanotubes. The geometrical principles of botanical phyllotaxis, describing the spiral packings on cylinders commonly found in nature, have found application in all these systems. Several recent studies have examined defects in tubular crystals associated with crystalline packings that must accommodate a fixed tube radius. Here we study the mechanics of tubular crystals with variable tube radius, with dislocations interposed between regions of different phyllotactic packings. Unbinding and separation of dislocation pairs with equal and opposite Burgers vectors allow the growth of one phyllotactic domain at the expense of another. In particular, glide separation of dislocations offers a low-energy mode for plastic deformations of solid tubes in response to external stresses, reconfiguring the lattice step by step. Through theory and simulation, we examine how the tube's radius and helicity affects, and is in turn altered by, the mechanics of dislocation glide. We also discuss how a sufficiently strong bending rigidity can alter or arrest the deformations of tubes with small radii.

  14. Gliding arc in tornado using a reverse vortex flow

    International Nuclear Information System (INIS)

    Kalra, Chiranjeev S.; Cho, Young I.; Gutsol, Alexander; Fridman, Alexander; Rufael, Tecle S.

    2005-01-01

    The present article reports a new gliding arc (GA) system using a reverse vortex flow ('tornado') in a cylindrical reactor (gliding arc in tornado, or GAT), as used to preserve the main advantages of traditional GA systems and overcome their main drawbacks. The primary advantages of traditional GA systems retained in the present GAT are the possibility to generate transitional plasma and to avoid considerable electrode erosion. In contrast to a traditional GA, the new GAT system ensures much more uniform gas treatment and has a significantly larger gas residence time in the reactor. The present article also describes the design of the new reactor and its stable operation regime when the variation of GAT current is very small. These features are understood to be very important for most viable applications. Additionally the GAT provides near-perfect thermal insulation from the reactor wall, indicating that the present GAT does not require the reactor wall to be constructed of high-temperature materials. The new GAT system, with its unique properties such as a high level of nonequilibrium and a large residence time, looks very promising for many industrial applications including fuel conversion, carbon dioxide conversion to carbon monoxide and oxygen, surface treatment, waste treatment, flame stabilization, hydrogen sulfide treatment, etc

  15. Amoeboid cells use protrusions for walking, gliding and swimming.

    Directory of Open Access Journals (Sweden)

    Peter J M Van Haastert

    Full Text Available Amoeboid cells crawl using pseudopods, which are convex extensions of the cell surface. In many laboratory experiments, cells move on a smooth substrate, but in the wild cells may experience obstacles of other cells or dead material, or may even move in liquid. To understand how cells cope with heterogeneous environments we have investigated the pseudopod life cycle of wild type and mutant cells moving on a substrate and when suspended in liquid. We show that the same pseudopod cycle can provide three types of movement that we address as walking, gliding and swimming. In walking, the extending pseudopod will adhere firmly to the substrate, which allows cells to generate forces to bypass obstacles. Mutant cells with compromised adhesion can move much faster than wild type cells on a smooth substrate (gliding, but cannot move effectively against obstacles that provide resistance. In a liquid, when swimming, the extending pseudopods convert to side-bumps that move rapidly to the rear of the cells. Calculations suggest that these bumps provide sufficient drag force to mediate the observed forward swimming of the cell.

  16. The glide of screw dislocations in bcc Fe: Atomistic static and dynamic simulations

    International Nuclear Information System (INIS)

    Chaussidon, Julien; Fivel, Marc; Rodney, David

    2006-01-01

    We present atomic-scale simulations of screw dislocation glide in bcc iron. Using two interatomic potentials that, respectively, predict degenerate and non-degenerate core structures, we compute the static 0 K dependence of the screw dislocation Peierls stress on crystal orientation and show strong boundary condition effects related to the generation of non-glide stress components. At finite temperatures we show that, with a non-degenerate core, glide by nucleation/propagation of kink-pairs in a {1 1 0} glide plane is obtained at low temperatures. A transition in the twinning region, towards an average {1 1 2} glide plane, with the formation of debris loops is observed at higher temperatures

  17. Strongly gliding harmonic tremor during the 2009 eruption of Redoubt Volcano

    Science.gov (United States)

    Hotovec, Alicia J.; Prejean, Stephanie G.; Vidale, John E.; Gomberg, Joan S.

    2013-01-01

    During the 2009 eruption of Redoubt Volcano, Alaska, gliding harmonic tremor occurred prominently before six nearly consecutive explosions during the second half of the eruptive sequence. The fundamental frequency repeatedly glided upward from harmonic tremor is not uncommon at volcanoes, tremor at such high frequencies is a rare observation. These frequencies approach or exceed the plausible upper limits of many models that have been suggested for volcanic tremor. We also analyzed the behavior of a swarm of repeating earthquakes that immediately preceded the first instance of pre-explosion gliding harmonic tremor. We find that these earthquakes share several traits with upward gliding harmonic tremor, and favor the explanation that the gliding harmonic tremor at Redoubt Volcano is created by the superposition of increasingly frequent and regular, repeating stick–slip earthquakes through the Dirac comb effect.

  18. Director gliding in a nematic liquid crystal layer: Quantitative comparison with experiments

    Science.gov (United States)

    Mema, E.; Kondic, L.; Cummings, L. J.

    2018-03-01

    The interaction between nematic liquid crystals and polymer-coated substrates may lead to slow reorientation of the easy axis (so-called "director gliding") when a prolonged external field is applied. We consider the experimental evidence of zenithal gliding observed by Joly et al. [Phys. Rev. E 70, 050701 (2004), 10.1103/PhysRevE.70.050701] and Buluy et al. [J. Soc. Inf. Disp. 14, 603 (2006), 10.1889/1.2235686] as well as azimuthal gliding observed by S. Faetti and P. Marianelli [Liq. Cryst. 33, 327 (2006), 10.1080/02678290500512227], and we present a simple, physically motivated model that captures the slow dynamics of gliding, both in the presence of an electric field and after the electric field is turned off. We make a quantitative comparison of our model results and the experimental data and conclude that our model explains the gliding evolution very well.

  19. Impact induced splash and spill in a quasi-confided granular medium

    Science.gov (United States)

    Ogale, S. B.

    2005-03-01

    Dissipation of the energy of impact in a granular medium and its effects has been a subject of considerable scientific for quite some time. In this work we have explored and analyzed the splash and spill effects caused by the impact of a ball dropped from a height into a granular medium in a open container. Three different granular media, namely rice, mustard seeds, and cream of wheat were used. The amount of spilled-over granular matter was measured as a function of the ball-drop height. Digital pictures of the splash process were also recorded. The quantity of spilled granular matter varies linearly with the impact energy. However additional step like structures are also noted. Specifically, a distinct and large jump is seen in the spilled quantity at a specific impact energy in the case of mustard seeds, which also exhibit obvious charging effects and repulsion. Although the parameters such as mass per grain and packing density for the case of mustard seeds are intermediate between those for rice and cream of wheat, the spill quantity for comparable impact energy is considerably higher. These data will be presented and discussed.

  20. Impact-induced splash and spill in a quasi-confined granular medium

    Science.gov (United States)

    Ogale, S. B.; Shinde, S. R.; Karve, P. A.; Ogale, Abhijit S.; Kulkarni, A.; Athawale, A.; Phadke, A.; Thakurdas, R.

    2006-05-01

    The splash and spill effects caused by the impact of a ball dropped from a height into a granular medium held in a small open container are examined. Different granular media, namely rice, mustard seeds, cream of wheat and plastic beads are used. The quantity of spilled-over granular matter ( W, grams) is measured as a function of the ball-drop height and compared for different cases. Digital pictures of the splash process are also recorded. The quantity W is seen to vary approximately linearly with the energy of impact. Interestingly, a distinct upward jump is seen in the spilled quantity at specific impact energy in the case of mustard seeds, which have spherical shape and also exhibit some charging effects. Similar jump was also confirmed for the case of plastic beads with broadly similar properties. Although the parameters such as mass per grain and packing density for the case of mustard seeds are intermediate between those for rice and cream of wheat, the spill quantity for comparable impact energy is considerably higher in the former case. The possible reasons for this non-monotonicity of behavior are discussed in terms of the differences in grain shapes and properties. Experiments are also performed using plastic beads of the same type but with four different sizes to explore the dependence of spilled quantity on bead size. The container size dependence is also examined for various bead types. Interesting systematics are seen, which are discussed qualitatively.

  1. The value of snow cover

    Science.gov (United States)

    Sokratov, S. A.

    2009-04-01

    Snow is the natural resource, like soil and water. It has specific properties which allow its use not just for skiing but also for houses cooling in summer (Swedish experience), for air fields construction (Arctic and Antarctic), for dams (north of Russia), for buildings (not only snow-houses of some Polar peoples but artistic hotel attracting tourists in Sweden), and as art material (Sapporo snow festival, Finnish events), etc. "Adjustment" of snow distribution and amount is not only rather common practice (avalanche-protection constructions keeping snow on slopes) but also the practice with long history. So-called "snow irrigation" was used in Russia since XIX century to protect winter crop. What is now named "artificial snow production", is part of much larger pattern. What makes it special—it is unavoidable in present climate and economy situation. 5% of national income in Austria is winter tourism. 50% of the economy in Savoy relay on winter tourism. In terms of money this can be less, but in terms of jobs and income involved this would be even more considerable in Switzerland. As an example—the population of Davos is 14000 in Summer and 50000 in Winter. Skiing is growing business. In present time you can find ski slopes in Turkey and Lebanon. To keep a cite suitable for attracting tourists you need certain amount of sunny days and certain amount of snow. The snow cannons are often the only way to keep a place running. On the other hand, more artificial snow does not necessary attract more tourists, while heavy natural snowfall does attract them. Artificial snow making is costly and requires infrastructure (ponds and electric lines) with very narrow range of weather conditions. Related companies are searching for alternatives and one of them can be "weather regulation" by distribution of some chemical components in clouds. It did not happen yet, but can happen soon. The consequences of such interference in Nature is hardly known. The ski tourism is not the

  2. High Order Large Eddy Simulation (LES) of Gliding Snake Aerodynamics: Effect of 3D Flow on Gliding Performance

    Science.gov (United States)

    Delorme, Yann; Hassan, Syed Harris; Socha, Jake; Vlachos, Pavlos; Frankel, Steven

    2014-11-01

    Chrysopelea paradisi are snakes that are able to glide over long distances by morphing the cross section of their bodies from circular to a triangular airfoil, and undulating through the air. Snake glide is characterized by relatively low Reynolds number and high angle of attack as well as three dimensional and unsteady flow. Here we study the 3D dynamics of the flow using an in-house high-order large eddy simulation code. The code features a novel multi block immersed boundary method to accurately and efficiently represent the complex snake geometry. We investigate the steady state 3-dimensionality of the flow, especially the wake flow induced by the presence of the snake's body, as well as the vortex-body interaction thought to be responsible for part of the lift enhancement. Numerical predictions of global lift and drag will be compared to experimental measurements, as well as the lift distribution along the body of the snake due to cross sectional variations. Comparisons with previously published 2D results are made to highlight the importance of 3-dimensional effects. Additional efforts are made to quantify properties of the vortex shedding and Dynamic Mode Decomposition (DMD) is used to analyse the main modes responsible for the lift and drag forces.

  3. Myxococcus xanthus gliding motors are elastically coupled to the substrate as predicted by the focal adhesion model of gliding motility.

    Science.gov (United States)

    Balagam, Rajesh; Litwin, Douglas B; Czerwinski, Fabian; Sun, Mingzhai; Kaplan, Heidi B; Shaevitz, Joshua W; Igoshin, Oleg A

    2014-05-01

    Myxococcus xanthus is a model organism for studying bacterial social behaviors due to its ability to form complex multi-cellular structures. Knowledge of M. xanthus surface gliding motility and the mechanisms that coordinated it are critically important to our understanding of collective cell behaviors. Although the mechanism of gliding motility is still under investigation, recent experiments suggest that there are two possible mechanisms underlying force production for cell motility: the focal adhesion mechanism and the helical rotor mechanism, which differ in the biophysics of the cell-substrate interactions. Whereas the focal adhesion model predicts an elastic coupling, the helical rotor model predicts a viscous coupling. Using a combination of computational modeling, imaging, and force microscopy, we find evidence for elastic coupling in support of the focal adhesion model. Using a biophysical model of the M. xanthus cell, we investigated how the mechanical interactions between cells are affected by interactions with the substrate. Comparison of modeling results with experimental data for cell-cell collision events pointed to a strong, elastic attachment between the cell and substrate. These results are robust to variations in the mechanical and geometrical parameters of the model. We then directly measured the motor-substrate coupling by monitoring the motion of optically trapped beads and find that motor velocity decreases exponentially with opposing load. At high loads, motor velocity approaches zero velocity asymptotically and motors remain bound to beads indicating a strong, elastic attachment.

  4. Myxococcus xanthus gliding motors are elastically coupled to the substrate as predicted by the focal adhesion model of gliding motility.

    Directory of Open Access Journals (Sweden)

    Rajesh Balagam

    2014-05-01

    Full Text Available Myxococcus xanthus is a model organism for studying bacterial social behaviors due to its ability to form complex multi-cellular structures. Knowledge of M. xanthus surface gliding motility and the mechanisms that coordinated it are critically important to our understanding of collective cell behaviors. Although the mechanism of gliding motility is still under investigation, recent experiments suggest that there are two possible mechanisms underlying force production for cell motility: the focal adhesion mechanism and the helical rotor mechanism, which differ in the biophysics of the cell-substrate interactions. Whereas the focal adhesion model predicts an elastic coupling, the helical rotor model predicts a viscous coupling. Using a combination of computational modeling, imaging, and force microscopy, we find evidence for elastic coupling in support of the focal adhesion model. Using a biophysical model of the M. xanthus cell, we investigated how the mechanical interactions between cells are affected by interactions with the substrate. Comparison of modeling results with experimental data for cell-cell collision events pointed to a strong, elastic attachment between the cell and substrate. These results are robust to variations in the mechanical and geometrical parameters of the model. We then directly measured the motor-substrate coupling by monitoring the motion of optically trapped beads and find that motor velocity decreases exponentially with opposing load. At high loads, motor velocity approaches zero velocity asymptotically and motors remain bound to beads indicating a strong, elastic attachment.

  5. Snow farming: conserving snow over the summer season

    Science.gov (United States)

    Grünewald, Thomas; Wolfsperger, Fabian; Lehning, Michael

    2018-01-01

    Summer storage of snow for tourism has seen an increasing interest in the last years. Covering large snow piles with materials such as sawdust enables more than two-thirds of the initial snow volume to be conserved. We present detailed mass balance measurements of two sawdust-covered snow piles obtained by terrestrial laser scanning during summer 2015. Results indicate that 74 and 63 % of the snow volume remained over the summer for piles in Davos, Switzerland and Martell, Italy. If snow mass is considered instead of volume, the values increase to 83 and 72 %. The difference is attributed to settling and densification of the snow. Additionally, we adapted the one-dimensional, physically based snow cover model SNOWPACK to perform simulations of the sawdust-covered snow piles. Model results and measurements agreed extremely well at the point scale. Moreover, we analysed the contribution of the different terms of the surface energy balance to snow ablation for a pile covered with a 40 cm thick sawdust layer and a pile without insulation. Short-wave radiation was the dominant source of energy for both scenarios, but the moist sawdust caused strong cooling by long-wave emission and negative sensible and latent heat fluxes. This cooling effect reduces the energy available for melt by up to a factor of 12. As a result only 9 % of the net short-wave energy remained available for melt. Finally, sensitivity studies of the parameters thickness of the sawdust layer, air temperature, precipitation and wind speed were performed. We show that sawdust thickness has a tremendous effect on snow loss. Higher air temperatures and wind speeds increase snow ablation but less significantly. No significant effect of additional precipitation could be found as the sawdust remained wet during the entire summer with the measured quantity of rain. Setting precipitation amounts to zero, however, strongly increased melt. Overall, the 40 cm sawdust provides sufficient protection for mid

  6. Snow farming: conserving snow over the summer season

    Directory of Open Access Journals (Sweden)

    T. Grünewald

    2018-01-01

    Full Text Available Summer storage of snow for tourism has seen an increasing interest in the last years. Covering large snow piles with materials such as sawdust enables more than two-thirds of the initial snow volume to be conserved. We present detailed mass balance measurements of two sawdust-covered snow piles obtained by terrestrial laser scanning during summer 2015. Results indicate that 74 and 63 % of the snow volume remained over the summer for piles in Davos, Switzerland and Martell, Italy. If snow mass is considered instead of volume, the values increase to 83 and 72 %. The difference is attributed to settling and densification of the snow. Additionally, we adapted the one-dimensional, physically based snow cover model SNOWPACK to perform simulations of the sawdust-covered snow piles. Model results and measurements agreed extremely well at the point scale. Moreover, we analysed the contribution of the different terms of the surface energy balance to snow ablation for a pile covered with a 40 cm thick sawdust layer and a pile without insulation. Short-wave radiation was the dominant source of energy for both scenarios, but the moist sawdust caused strong cooling by long-wave emission and negative sensible and latent heat fluxes. This cooling effect reduces the energy available for melt by up to a factor of 12. As a result only 9 % of the net short-wave energy remained available for melt. Finally, sensitivity studies of the parameters thickness of the sawdust layer, air temperature, precipitation and wind speed were performed. We show that sawdust thickness has a tremendous effect on snow loss. Higher air temperatures and wind speeds increase snow ablation but less significantly. No significant effect of additional precipitation could be found as the sawdust remained wet during the entire summer with the measured quantity of rain. Setting precipitation amounts to zero, however, strongly increased melt. Overall, the 40 cm sawdust provides

  7. Rain or snow?

    Science.gov (United States)

    Richman, Barbara T.

    It's easy to look out the window and decide whether it's raining, snowing, or hailing, right? Well, not always—especially when the region of interest isn't directly outside your window. To help discern the difference, the National Oceanic and Atmospheric Administration (NOAA) has developed a laser beam device that differentiates between the precipitation types.The laser weather identifier produces different signals when raindrops, snowflakes, or hailstones pass through the laser's beam, according to Ting-i Wang—until recently a scientist at NOAA's Environmental Research Laboratories in Boulder, Colo. These signature signals can be read by computer and integrated into present weather networks. ‘It can eliminate human error or negligence, and can be cost effective by constantly observing and monitoring the weather,’ Wang noted. Wang and his colleagues are developing several of the laser instruments for evaluation by NOAA's National Weather Service. The first of these is scheduled to be installed in 1984.

  8. Water treatment by the AC gliding arc air plasma

    Science.gov (United States)

    Gharagozalian, Mehrnaz; Dorranian, Davoud; Ghoranneviss, Mahmood

    2017-09-01

    In this study, the effects of gliding arc (G Arc) plasma system on the treatment of water have been investigated experimentally. An AC power supply of 15 kV potential difference at 50 Hz frequency was employed to generate plasma. Plasma density and temperature were measured using spectroscopic method. The water was contaminated with staphylococcus aureus (Gram-positive) and salmonella bacteria (Gram-negative), and Penicillium (mold fungus) individually. pH, hydrogen peroxide, and nitride contents of treated water were measured after plasma treatment. Decontamination of treated water was determined using colony counting method. Results indicate that G Arc plasma is a powerful and green tool to decontaminate water without producing any byproducts.

  9. Gliding and Saccadic Gaze Gesture Recognition in Real Time

    DEFF Research Database (Denmark)

    Rozado, David; San Agustin, Javier; Rodriguez, Francisco

    2012-01-01

    paradigm in the context of human-machine interaction as low-cost gaze trackers become more ubiquitous. The viability of gaze gestures as an innovative way to control a computer rests on how easily they can be assimilated by potential users and also on the ability of machine learning algorithms...... to discriminate intentional gaze gestures from typical gaze activity performed during standard interaction with electronic devices. In this work, through a set of experiments and user studies, we evaluate the performance of two different gaze gestures modalities, gliding gaze gestures and saccadic gaze gestures......, and their corresponding real-time recognition algorithms, Hierarchical Temporal Memory networks and the Needleman-Wunsch algorithm for sequence alignment. Our results show how a specific combination of gaze gesture modality, namely saccadic gaze gestures, and recognition algorithm, Needleman-Wunsch, allows for reliable...

  10. Leaping shampoo glides on a lubricating air layer

    KAUST Repository

    Lee, S.

    2013-06-10

    When a stream of shampoo is fed onto a pool in one\\'s hand, a jet can leap sideways or rebound from the liquid surface in an intriguing phenomenon known as the Kaye effect. Earlier studies have debated whether non-Newtonian effects are the underlying cause of this phenomenon, making the jet glide on top of a shear-thinning liquid layer, or whether an entrained air layer is responsible. Herein we show unambiguously that the jet slides on a lubricating air layer. We identify this layer by looking through the pool liquid and observing its rupture into fine bubbles. The resulting microbubble sizes suggest this air layer is of submicron thickness. This thickness estimate is also supported by the tangential deceleration of the jet during the rebounding.

  11. Numerical Investigation of Swimmer's Gliding Stage with 6-DOF Movement.

    Science.gov (United States)

    Li, Tianzeng; Cai, Wenhao; Zhan, Jiemin

    2017-01-01

    The purpose of this study is to analyze the motion status of swimmers during their gliding stage using a numerical simulation method. This simulation strategy is conducted by solving the 3D incompressible Navier-Stokes equations using the Realizable k-ε turbulence closure equations in combination with the Six Degrees of Freedom (6-DOF) method. The uneven mass distribution of a swimmer and the roughness of the surface of the body are taken into consideration. The hydrodynamic characteristics and movement characteristics of the swimmers at different launch speeds were analyzed. The calculated results suggest that an optimal instant for starting propulsive movement is when the velocity of the swimmer decreases by 1.75 m/s to 2.0 m/s from an initial horizontal velocity of 3.1 m/s to 3.5 m/s.

  12. Employment of hypersonic glide vehicles: Proposed criteria for use

    Energy Technology Data Exchange (ETDEWEB)

    Olguin, Abel [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-07-01

    Hypersonic Glide Vehicles (HGVs) are a type of reentry vehicle that couples the high speed of ballistic missiles with the maneuverability of aircraft. The HGV has been in development since the 1970s, and its technology falls under the category of Conventional Prompt Global Strike (CPGS) weapons. As noted by James M. Acton, a senior associate in the Nuclear Policy Program at the Carnegie Endowment, CPGS is a “missile in search of a mission.” With the introduction of any significant new military capability, a doctrine for use—including specifics regarding how, when and where it would be used, as well as tactics, training and procedures—must be clearly defined and understood by policy makers, military commanders, and planners. In this paper, benefits and limitations of the HGV are presented. Proposed criteria and four scenarios illustrate a possible method for assessing when to use an HGV.

  13. Non-equilibrium trajectory dynamics and the kinematics of gliding in a flying snake

    International Nuclear Information System (INIS)

    Socha, John J; Jafari, Farid; Miklasz, Kevin; Vlachos, Pavlos P

    2010-01-01

    Given sufficient space, it is possible for gliding animals to reach an equilibrium state with no net forces acting on the body. In contrast, every gliding trajectory must begin with a non-steady component, and the relative importance of this phase is not well understood. Of any terrestrial animal glider, snakes exhibit the greatest active movements, which may affect their trajectory dynamics. Our primary aim was to determine the characteristics of snake gliding during the transition to equilibrium, quantifying changes in velocity, acceleration, and body orientation in the late phase of a glide sequence. We launched 'flying' snakes (Chrysopelea paradisi) from a 15 m tower and recorded the mid-to-end portion of trajectories with four videocameras to reconstruct the snake's body position with mm to cm accuracy. Additionally, we developed a simple analytical model of gliding assuming only steady-state forces of lift, drag and weight acting on the body and used it to explore effects of wing loading, lift-to-drag ratio, and initial velocity on trajectory dynamics. Despite the vertical space provided to transition to steady-state gliding, snakes did not exhibit equilibrium gliding and in fact displayed a net positive acceleration in the vertical axis, an effect also predicted by the analytical model.

  14. Non-equilibrium trajectory dynamics and the kinematics of gliding in a flying snake

    Energy Technology Data Exchange (ETDEWEB)

    Socha, John J; Jafari, Farid [Engineering Science and Mechanics, Virginia Tech, Blacksburg, VA 24061 (United States); Miklasz, Kevin [Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950 (United States); Vlachos, Pavlos P, E-mail: jjsocha@vt.ed [Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA 24061 (United States)

    2010-12-15

    Given sufficient space, it is possible for gliding animals to reach an equilibrium state with no net forces acting on the body. In contrast, every gliding trajectory must begin with a non-steady component, and the relative importance of this phase is not well understood. Of any terrestrial animal glider, snakes exhibit the greatest active movements, which may affect their trajectory dynamics. Our primary aim was to determine the characteristics of snake gliding during the transition to equilibrium, quantifying changes in velocity, acceleration, and body orientation in the late phase of a glide sequence. We launched 'flying' snakes (Chrysopelea paradisi) from a 15 m tower and recorded the mid-to-end portion of trajectories with four videocameras to reconstruct the snake's body position with mm to cm accuracy. Additionally, we developed a simple analytical model of gliding assuming only steady-state forces of lift, drag and weight acting on the body and used it to explore effects of wing loading, lift-to-drag ratio, and initial velocity on trajectory dynamics. Despite the vertical space provided to transition to steady-state gliding, snakes did not exhibit equilibrium gliding and in fact displayed a net positive acceleration in the vertical axis, an effect also predicted by the analytical model.

  15. Corrosion Behavior of Low-C Medium-Mn Steel in Simulated Marine Immersion and Splash Zone Environment

    Science.gov (United States)

    Zhang, Dazheng; Gao, Xiuhua; Su, Guanqiao; Du, Linxiu; Liu, Zhenguang; Hu, Jun

    2017-05-01

    The corrosion behavior of low-C medium-Mn steel in simulated marine immersion and splash zone environment was studied by static immersion corrosion experiment and wet-dry cyclic corrosion experiment, respectively. Corrosion rate, corrosion products, surface morphology, cross-sectional morphology, elemental distribution, potentiodynamic polarization curves and electrochemical impedance spectra were used to elucidate the corrosion behavior of low-C medium-Mn steel. The results show that corrosion rate in immersion zone is much less than that in splash zone owing to its relatively mild environment. Manganese compounds are detected in the corrosion products and only appeared in splash zone environment, which can deteriorate the protective effect of rust layer. With the extension of exposure time, corrosion products are gradually transformed into dense and thick corrosion rust from the loose and porous one in these two environments. But in splash zone environment, alloying elements of Mn appear significant enrichment in the rust layer, which decrease the corrosion resistance of the steel.

  16. LHC Beam Splash seen by the ATLAS detector - 5 Apr 2015 - Run 260272 - LB 240 - event 5879

    CERN Multimedia

    ATLAS EXPERIMENT

    2015-01-01

    Event display of first collimator "splash" event seen by the ATLAS experiment in LHC Run-2 , on Sunday April the 5th : event 5879, run 260272. The collimator position is 140m in front of the ATLAS interaction point. The spray of particles enters ATLAS from the right hand side of the picture.

  17. Unexpected Patterns in Snow and Dirt

    Science.gov (United States)

    Ackerson, Bruce J.

    2018-01-01

    For more than 30 years, Albert A. Bartlett published "Thermal patterns in the snow" in this journal. These are patterns produced by heat sources underneath the snow. Bartlett's articles encouraged me to pay attention to patterns in snow and to understanding them. At winter's end the last snow becomes dirty and is heaped into piles. This…

  18. Palatalization and glide strengthening as competing repair strategies: Evidence from Kirundi

    Directory of Open Access Journals (Sweden)

    Alexei Kochetov

    2016-07-01

    Full Text Available Alternations involving place-changing palatalization (e.g. t+j → ʧ in spirit – spiritual are very common and have been a focus of much generative phonological work since Chomsky & Halle’s (1968 ‘Sound Pattern of English’. The interest in palatalization and its mechanisms (see e.g. Sagey 1990; Chen 1996; Bateman 2007 has somewhat obscured the question of how these processes fit into a wider typology of segmental alternations. What happens when palatalization fails to apply? Do other processes take its place and apply under the same circumstances? In this paper, I argue for a close functional and formal affinity between place-changing palatalization and one such process, palatal glide strengthening (e.g. p+j → pc. As evidence I present data from Kirundi (Bantu on the realization of consonant + palatal and velar glide sequences within and across morphemes. As will be shown, palatalization and glide strengthening in Kirundi work in parallel, affecting different subsets of consonants. Specifically, palatalization targets C+j sequences with laryngeals, velars, nasal coronals, and – across morpheme boundaries – non-nasal coronals. In contrast, glide strengthening targets C+j sequences with labials and – within morphemes – non-nasal coronals. In addition, glide strengthening applies to within- and across-morpheme consonant + velar glide sequences, producing a set of outputs (e.g. m+w → mŋ similar to C+j sequences. I further present a unified Optimality Theoretic (Prince & Smolensky 1993/2004 account of these seemingly disparate phenomena as both arising from different rankings of constraints prohibiting consonant + glide sequences (parameterized by place and/or manner and various feature-specific agreement and faithfulness constraints. Finally, I explore typological predictions of this account, reviewing several remarkably similar cases of C + glide resolution patterns from other languages, and outlining questions for further

  19. Application of X-ray computed microtomography to soil craters formed by raindrop splash

    Science.gov (United States)

    Beczek, Michał; Ryżak, Magdalena; Lamorski, Krzysztof; Sochan, Agata; Mazur, Rafał; Bieganowski, Andrzej

    2018-02-01

    The creation of craters on the soil surface is part of splash erosion. Due to the small size of these craters, they are difficult to study. The main aim of this paper was to test X-ray computed microtomography to investigate craters formed by raindrop impacts. Measurements were made on soil samples moistened to three different levels corresponding with soil water potentials of 0.1, 3.16 and 16 kPa. Using images obtained by X-ray microtomography, geometric parameters of the craters were recorded and analysed. X-ray computed microtomography proved to be a useful and efficient tool for the investigation of craters formed on the soil surface after the impact of water drops. The parameters of the craters changed with the energy of the water drops and were dependent on the initial moisture content of the soil. Crater depth is more dependent on the increased energy of the water drop than crater diameter.

  20. Translational, rotational and vibrational temperatures of a gliding arc discharge at atmospheric pressure air

    DEFF Research Database (Denmark)

    Zhu, Jiajian; Gao, Jinlong; Ehn, Andreas

    2014-01-01

    Gliding arc discharges have generally been used to generate non-equilibrium plasma at atmospheric pressure. Temperature distributions of a gliding arc are of great interest both for fundamental plasma research and for practical applications. In the presented studies, translational, rotational...... and vibrational temperatures of a gliding arc generated at atmospheric pressure air are investigated. Translational temperatures (about 1100 K) were measured by laser-induced Rayleigh scattering, and two-dimensional temperature imaging was performed. Rotational and vibrational temperatures (about 3600 K and 6700...

  1. Debris extrusion by glide-path establishing endodontic instruments with different geometries

    Directory of Open Access Journals (Sweden)

    Jung-Hong Ha

    2016-06-01

    Conclusion: Creating the glide-path using nickel-titanium rotary files produced lower amounts of debris extrusion than using manual stainless-steel files. The progressive taper design of ProGlider, the center-off cross-section of One G, and the alternative-pitch design of ScoutRace may have increased the efficiencies of debris removal with minimal extrusion during glide-path preparation. Glide-path preparation using NiTi rotary files have better clinical efficiency than the manual stainless-steel file.

  2. Parallel glide: flow of dislocations with internal stress source/sink distribution

    Directory of Open Access Journals (Sweden)

    Karlo T Raić

    2008-01-01

    Full Text Available The unexpected glide of dislocations on a plane parallel to the film/substrate interface in ultrathin copper films, which has been called parallel glide (Balk et al 2003 Acta Metall. 51 447, is described using an analytical model. The phenomenon is observed as a problem involving inlet/outlet flow from different positions of a grain boundary into the grain channel. In this sense, parallel glide is presented as the flow of dislocations with an internal stress source/sink distribution.

  3. Cultivar architecture modulates spore dispersal by rain splash: A new perspective to reduce disease progression in cultivar mixtures.

    Directory of Open Access Journals (Sweden)

    Tiphaine Vidal

    Full Text Available Cultivar mixtures can be used to improve the sustainability of disease management within farming systems by growing cultivars that differ in their disease resistance level in the same field. The impact of canopy aerial architecture on rain-splash dispersal could amplify disease reduction within mixtures. We designed a controlled conditions experiment to study single splash-dispersal events and their consequences for disease. We quantified this impact through the spore interception capacities of the component cultivars of a mixture. Two wheat cultivars, differing in their aerial architecture (mainly leaf area density and resistance to Septoria tritici blotch, were used to constitute pure stands and mixtures with 75% of resistant plants that accounted for 80% of the canopy leaf area. Canopies composed of 3 rows of plants were exposed to standardized spore fluxes produced by splashing calibrated rain drops on a linear source of inoculum. Disease propagation was measured through spore fluxes and several disease indicators. Leaf susceptibility was higher for upper than for lower leaves. Dense canopies intercepted more spores and mainly limited horizontal spore transfer to the first two rows. The presence of the resistant and dense cultivar made the mixed canopy denser than the susceptible pure stand. No disease symptoms were observed on susceptible plants of the second and third rows in the cultivar mixture, suggesting that the number of spores intercepted by these plants was too low to cause disease symptoms. Both lesion area and disease conditional severity were significantly reduced on susceptible plants within mixtures on the first row beside the inoculum source. Those reductions on one single-splash dispersal event, should be amplified after several cycle over the full epidemic season. Control of splash-dispersed diseases within mixtures could therefore be improved by a careful choice of cultivars taking into consideration both resistance and

  4. Snow density climatology across the former USSR

    Science.gov (United States)

    Zhong, X.; Zhang, T.; Wang, K.

    2014-04-01

    Snow density is one of the basic properties used to describe snow cover characteristics, and it is a key factor for linking snow depth and snow water equivalent, which are critical for water resources assessment and modeling inputs. In this study, we used long-term data from ground-based measurements to investigate snow density (bulk density) climatology and its spatiotemporal variations across the former Soviet Union (USSR) from 1966 to 2008. The results showed that the long-term monthly mean snow density was approximately 0.22 ± 0.05 g cm-3 over the study area. The maximum and minimum monthly mean snow density was about 0.33 g cm-3 in June, and 0.14 g cm-3 in October, respectively. Maritime and ephemeral snow had the highest monthly mean snow density, while taiga snow had the lowest. The higher values of monthly snow density were mainly located in the European regions of the former USSR, on the coast of Arctic Russia, and the Kamchatka Peninsula, while the lower snow density occurred in central Siberia. Significant increasing trends of snow density from September through June of the next year were observed, however, the rate of the increase varied with different snow classes. The long-term (1966-2008) monthly and annual mean snow densities had significant decreasing trends, especially during the autumn months. Spatially, significant positive trends in monthly mean snow density lay in the southwestern areas of the former USSR in November and December and gradually expanded in Russia from February through April. Significant negative trends mainly lay in the European Russia and the southern Russia. There was a high correlation of snow density with elevation for tundra snow and snow density was highly correlated with latitude for prairie snow.

  5. MODIS Snow Cover Mapping Decision Tree Technique: Snow and Cloud Discrimination

    Science.gov (United States)

    Riggs, George A.; Hall, Dorothy K.

    2010-01-01

    Accurate mapping of snow cover continues to challenge cryospheric scientists and modelers. The Moderate-Resolution Imaging Spectroradiometer (MODIS) snow data products have been used since 2000 by many investigators to map and monitor snow cover extent for various applications. Users have reported on the utility of the products and also on problems encountered. Three problems or hindrances in the use of the MODIS snow data products that have been reported in the literature are: cloud obscuration, snow/cloud confusion, and snow omission errors in thin or sparse snow cover conditions. Implementation of the MODIS snow algorithm in a decision tree technique using surface reflectance input to mitigate those problems is being investigated. The objective of this work is to use a decision tree structure for the snow algorithm. This should alleviate snow/cloud confusion and omission errors and provide a snow map with classes that convey information on how snow was detected, e.g. snow under clear sky, snow tinder cloud, to enable users' flexibility in interpreting and deriving a snow map. Results of a snow cover decision tree algorithm are compared to the standard MODIS snow map and found to exhibit improved ability to alleviate snow/cloud confusion in some situations allowing up to about 5% increase in mapped snow cover extent, thus accuracy, in some scenes.

  6. Translational, rotational, vibrational and electron temperatures of a gliding arc discharge

    DEFF Research Database (Denmark)

    Zhu, Jiajian; Ehn, Andreas; Gao, Jinlong

    2017-01-01

    the instantaneous length of the plasma column, the discharge voltage and the translational temperature, from which the electron temperature (Te) of the gliding arc discharge was estimated. The uncertainties of the translational, rotational, vibrational and electron temperatures were analyzed. The relations......Translational, rotational, vibrational and electron temperatures of a gliding arc discharge in atmospheric pressure air were experimentally investigated using in situ, non-intrusive optical diagnostic techniques. The gliding arc discharge was driven by a 35 kHz alternating current (AC) power source...... and operated in a glow-type regime. The two-dimensional distribution of the translational temperature (Tt) of the gliding arc discharge was determined using planar laser-induced Rayleigh scattering. The rotational and vibrational temperatures were obtained by simulating the experimental spectra. The OH A–X (0...

  7. Adhesion improvement of glass-fibre-reinforced polyester composites by gliding arc discharge treatment

    DEFF Research Database (Denmark)

    Kusano, Yukihiro; Sørensen, Bent F.; Løgstrup Andersen, Tom

    2013-01-01

    A gliding arc is a plasma that can be operated at atmospheric pressure and applied for plasma surface treatment for adhesion improvement. In the present work, glass-fibre-reinforced polyester plates were treated using an atmospheric pressure gliding arc discharge with an air flow to improve...... adhesion with a vinylester adhesive. The treatment improved wettability and increased the polar component of the surface energy and the density of oxygen-containing polar functional groups at the surfaces. Double cantilever beam specimens were prepared for fracture mechanics characterisation (fracture...... resistance as a function of nominal mode mixity) of the laminate adhesive interface. It was found that gliding arc treatment significantly increases the interfacial fracture energy and fracture resistance in comparison with a standard peel ply treatment, although the mixed mode fracture energy of the gliding...

  8. Effects of Fire on Soil Splash Erosion in Semi-steppe Rangelandof Karsanak Region,Chaharmahal and Bakhtiari

    Directory of Open Access Journals (Sweden)

    D. Baharlooi

    2016-02-01

    Full Text Available Introduction: The detachment process can be conceptually divided in two sub-processes included aggregate breakdown (Le Bissonnais, 1996 and movement initiation of breakdown products(Kinnell, 2005. soil detachment depends on raindrop size and mass(Elison, 1944; Bisal, 1960, drop velocity(Elison, 1944; Bisal, 1960, intensity rainfall (Ting et al, 2008, kinetic energy (Kinnell, 2003; Fernandez- Raga et al, 2010, runoff depth(Torri et al, 1987; Kinnell,1991 and 2005, crop covers(Bancy, 1994; Ghahremani et al, 2011, wind speed( Erpul et al, 2000 and experimental area (cup size (Leguedois et al, 2005; Luk, 1979; Torri and poesen, 1988. Many of studies have been conducted to evaluate the relationship between splash and slope (Bryan, 1979; Torri and Poesen, 1992; Wan et al, 1996.Torri and Poesen (1992 expressed that in steep slope the gravity force adds to the drop detaching force and decreases of soil resistance, consequently increases splash erosion rate with increasing slope. Soil splash erosion is also strongly influenced by soil properties including soil particles size distribution (Mazurak and Mosher, 1968; Legout et al, 2005; fan and li, 1993, soil shear strength(Cruse and Larson, 1977; Al-Durrah and Bradford,1981; Ekwue and ohi; 1990 , soil cohesion(Torri et al, 1987, soil organic matter content and aggregate size (Ekwue and Maiduguri, 1991; Qinjuan et al, 2008, soil aggregates stability(Qinjuan et al, 2008, surface crust (Qinjuan et al, 2008. Fire, play an important role in splash erosion. The absence of vegetation cover in disturbed lands accelerates splash erosion rates by as much as several folds compared to undisturbed sites (Lal, 2001; Thomaz and luiz, 2012.The detachment of soil particles by splash depends on several raindrop characteristics, including raindrop size and mass, drop velocity, kinetic energy, and water drop impact angle (Sharma et al., 1993; Singer and Le Bissonnais, 1998; Cruse et al., 2000, Bhattacharyya et al., 2010

  9. Dislocation glide velocity in creep of Mg alloys derived from dip tests

    Czech Academy of Sciences Publication Activity Database

    Eisenlohr, P.; Blum, W.; Milička, Karel

    510-511, Sp. Iss. (2009), s. 393-397 ISSN 0921-5093. [Creep 2008. Bayreuth, 04.05.2008-09.05.2008] R&D Projects: GA ČR GA106/06/1354 Institutional research plan: CEZ:AV0Z20410507 Keywords : Dislocation glide velocity * Temperature dependence * Solute drag * Forest cutting * Prismatic glide Subject RIV: JG - Metallurgy Impact factor: 1.901, year: 2009

  10. Efficiency of lift production in flapping and gliding flight of swifts.

    Directory of Open Access Journals (Sweden)

    Per Henningsson

    Full Text Available Many flying animals use both flapping and gliding flight as part of their routine behaviour. These two kinematic patterns impose conflicting requirements on wing design for aerodynamic efficiency and, in the absence of extreme morphing, wings cannot be optimised for both flight modes. In gliding flight, the wing experiences uniform incident flow and the optimal shape is a high aspect ratio wing with an elliptical planform. In flapping flight, on the other hand, the wing tip travels faster than the root, creating a spanwise velocity gradient. To compensate, the optimal wing shape should taper towards the tip (reducing the local chord and/or twist from root to tip (reducing local angle of attack. We hypothesised that, if a bird is limited in its ability to morph its wings and adapt its wing shape to suit both flight modes, then a preference towards flapping flight optimization will be expected since this is the most energetically demanding flight mode. We tested this by studying a well-known flap-gliding species, the common swift, by measuring the wakes generated by two birds, one in gliding and one in flapping flight in a wind tunnel. We calculated span efficiency, the efficiency of lift production, and found that the flapping swift had consistently higher span efficiency than the gliding swift. This supports our hypothesis and suggests that even though swifts have been shown previously to increase their lift-to-drag ratio substantially when gliding, the wing morphology is tuned to be more aerodynamically efficient in generating lift during flapping. Since body drag can be assumed to be similar for both flapping and gliding, it follows that the higher total drag in flapping flight compared with gliding flight is primarily a consequence of an increase in wing profile drag due to the flapping motion, exceeding the reduction in induced drag.

  11. The novel echo-guided ProGlide technique during percutaneous transfemoral transcatheter aortic valve implantation.

    Science.gov (United States)

    Honda, Yohsuke; Araki, Motoharu; Yamawaki, Masahiro; Tokuda, Takahiro; Tsutumi, Masakazu; Mori, Shinsuke; Sakamoto, Yasunari; Kobayashi, Norihiro; Hirano, Keisuke; Ito, Yoshiaki

    2018-04-01

    The aim of this study was to assess clinical benefit of the Echo-guided ProGlide technique in patients undergoing percutaneous transfemoral transcatheter aortic valve implantation (TF-TAVI). The efficacy of the Echo-guided ProGlide technique during percutaneous TF-TAVI was not previously clarified. A total of 121 consecutive patients who underwent percutaneous TF-TAVI at our institution between February 2014 and July 2017 were enrolled in this study. According to the introduction of this novel technique in March 2016, patients were divided into two groups (echo-guided group who underwent TAVI from March 2016 to July 2017, n = 63; not echo-guided group who underwent TAVI from February 2014 to February 2016, n = 58). The incidence of major vascular complications, defined per the Valve Academic Research Consortium-2 criteria, and ProGlide complications including acute femoral artery stenosis or occlusion and bleeding requiring any intervention. The incidence of major vascular complication and ProGlide complication were significantly lower in the echo-guided group than in not echo-guided group (1.6% vs 17.2%, P guided ProGlide technique was independently associated with prevention of ProGlide complications (odds ratio, 0.11; 95% confidential interval, 0.01-0.76; P = 0.03). This novel Echo-guided ProGlide technique was associated with a lower rate of major vascular complications, particularly ProGlide complications during percutaneous TF-TAVI. © 2017, Wiley Periodicals, Inc.

  12. Politics of Snow

    Science.gov (United States)

    Burko, D.

    2012-12-01

    In a 2010 catalog introduction for my exhibition titled: POLITICS OF SNOW, Eileen Claussen, President of the Pew Center on Global Climate Change wrote the following: "Climate change has been taken over by politics…We are awash in talking points, briefing papers, scientific studies, and communiqués from national governments… Diane Burko's paintings remind us that all these words can often obscure or even obstruct our view of what is truly happening …..There is only so much you can do with words. People need to see that the world is changing before our eyes. When we look at Diane's images of the effects of climate change, we connect to something much deeper and more profound (and more moving) than the latest political pitch from one side or another in this debate…These paintings also connect us to something else. Even as Diane documents how things are changing, she also reminds us of the stunning beauty of nature - and, in turn, the urgency of doing everything in our power to protect it." The creation of this body of work was made possible because of the collaboration of many glacial geologists and scientists who continually share their visual data with me. Since 2006 I've been gathering repeats from people like Bruce Molnia (USGS) and Tad Pfeffer of Alaskan glaciers, from Daniel Fagre (USGS) of Glacier National Park and Lonnie Thompson and Jason Box (Ohio University's Byrd Polar Center) about Kilimanjaro, Qori Kalis and Petermann glaciers as well as from photographer David Breashears on the disappearing Himalayan glaciers. In my practice, I acknowledge the photographers, or archive agencies, such as USGS, NASA or Snow and Ice Center, in the title and all printed material. As a landscape painter and photographer my intent is to not reproduce those images but rather use them as inspiration. At first I used the documentary evidence in sets of diptychs or triptychs. Since 2010 I have incorporated geological charts of recessional lines, graphs, symbols and

  13. Black carbon aerosol size in snow.

    Science.gov (United States)

    Schwarz, J P; Gao, R S; Perring, A E; Spackman, J R; Fahey, D W

    2013-01-01

    The effect of anthropogenic black carbon (BC) aerosol on snow is of enduring interest due to its consequences for climate forcing. Until now, too little attention has been focused on BC's size in snow, an important parameter affecting BC light absorption in snow. Here we present first observations of this parameter, revealing that BC can be shifted to larger sizes in snow than are typically seen in the atmosphere, in part due to the processes associated with BC removal from the atmosphere. Mie theory analysis indicates a corresponding reduction in BC absorption in snow of 40%, making BC size in snow the dominant source of uncertainty in BC's absorption properties for calculations of BC's snow albedo climate forcing. The shift reduces estimated BC global mean snow forcing by 30%, and has scientific implications for our understanding of snow albedo and the processing of atmospheric BC aerosol in snowfall.

  14. Assimilation of snow cover and snow depth into a snow model to estimate snow water equivalent and snowmelt runoff in a Himalayan catchment

    Directory of Open Access Journals (Sweden)

    E. E. Stigter

    2017-07-01

    Full Text Available Snow is an important component of water storage in the Himalayas. Previous snowmelt studies in the Himalayas have predominantly relied on remotely sensed snow cover. However, snow cover data provide no direct information on the actual amount of water stored in a snowpack, i.e., the snow water equivalent (SWE. Therefore, in this study remotely sensed snow cover was combined with in situ observations and a modified version of the seNorge snow model to estimate (climate sensitivity of SWE and snowmelt runoff in the Langtang catchment in Nepal. Snow cover data from Landsat 8 and the MOD10A2 snow cover product were validated with in situ snow cover observations provided by surface temperature and snow depth measurements resulting in classification accuracies of 85.7 and 83.1 % respectively. Optimal model parameter values were obtained through data assimilation of MOD10A2 snow maps and snow depth measurements using an ensemble Kalman filter (EnKF. Independent validations of simulated snow depth and snow cover with observations show improvement after data assimilation compared to simulations without data assimilation. The approach of modeling snow depth in a Kalman filter framework allows for data-constrained estimation of snow depth rather than snow cover alone, and this has great potential for future studies in complex terrain, especially in the Himalayas. Climate sensitivity tests with the optimized snow model revealed that snowmelt runoff increases in winter and the early melt season (December to May and decreases during the late melt season (June to September as a result of the earlier onset of snowmelt due to increasing temperature. At high elevation a decrease in SWE due to higher air temperature is (partly compensated by an increase in precipitation, which emphasizes the need for accurate predictions on the changes in the spatial distribution of precipitation along with changes in temperature.

  15. Loop formation of microtubules during gliding at high density

    International Nuclear Information System (INIS)

    Liu, Lynn; Ross, Jennifer L; Tuezel, Erkan

    2011-01-01

    The microtubule cytoskeleton, including the associated proteins, forms a complex network essential to multiple cellular processes. Microtubule-associated motor proteins, such as kinesin-1, travel on microtubules to transport membrane bound vesicles across the crowded cell. Other motors, such as cytoplasmic dynein and kinesin-5, are used to organize the cytoskeleton during mitosis. In order to understand the self-organization processes of motors on microtubules, we performed filament-gliding assays with kinesin-1 motors bound to the cover glass with a high density of microtubules on the surface. To observe microtubule organization, 3% of the microtubules were fluorescently labeled to serve as tracers. We find that microtubules in these assays are not confined to two dimensions and can cross one other. This causes microtubules to align locally with a relatively short correlation length. At high density, this local alignment is enough to create 'intersections' of perpendicularly oriented groups of microtubules. These intersections create vortices that cause microtubules to form loops. We characterize the radius of curvature and time duration of the loops. These different behaviors give insight into how crowded conditions, such as those in the cell, might affect motor behavior and cytoskeleton organization.

  16. LHC Beam Splash seen by the ATLAS detector - 7 Apr 2015 - Run 260466 - LB 731 - Event 16848

    CERN Multimedia

    ATLAS, EXPERIMENT

    2015-01-01

    Event display of a collimator "splash" event seen by the ATLAS experiment in LHC Run-2, on Tuesday April the 7th 2015: event 16848, run 260466. The collimator position is 140m in front of the ATLAS interaction point. The figure on the left shows an axial view of the various components of the ATLAS detector. The figure on the right shows the energy deposits in the cells of the ATLAS calorimeter.

  17. Potential Use of BEST® Sediment Trap in Splash - Saltation Transport Process by Simultaneous Wind and Rain Tests.

    Directory of Open Access Journals (Sweden)

    Mustafa Basaran

    Full Text Available The research on wind-driven rain (WDR transport process of the splash-saltation has increased over the last twenty years as wind tunnel experimental studies provide new insights into the mechanisms of simultaneous wind and rain (WDR transport. The present study was conducted to investigate the efficiency of the BEST® sediment traps in catching the sand particles transported through the splash-saltation process under WDR conditions. Experiments were conducted in a wind tunnel rainfall simulator facility with water sprayed through sprinkler nozzles and free-flowing wind at different velocities to simulate the WDR conditions. Not only for vertical sediment distribution, but a series of experimental tests for horizontal distribution of sediments was also performed using BEST® collectors to obtain the actual total sediment mass flow by the splash-saltation in the center of the wind tunnel test section. Total mass transport (kg m-2 were estimated by analytically integrating the exponential functional relationship using the measured sediment amounts at the set trap heights for every run. Results revealed the integrated efficiency of the BEST® traps at 6, 9, 12 and 15 m s-1 wind velocities under 55.8, 50.5, 55.0 and 50.5 mm h-1 rain intensities were, respectively, 83, 106, 105, and 102%. Results as well showed that the efficiencies of BEST® did not change much as compared with those under rainless wind condition.

  18. Numerical analysis of splashing fluid using hybrid method of mesh-based and particle-based modelings

    International Nuclear Information System (INIS)

    Tanaka, Nobuatsu; Ogawara, Takuya; Kaneda, Takeshi; Maseguchi, Ryo

    2009-01-01

    In order to simulate splashing and scattering fluid behaviors, we developed a hybrid method of mesh-based model for large-scale continuum fluid and particle-based model for small-scale discrete fluid particles. As for the solver of the continuum fluid, we adopt the CIVA RefIned Multiphase SimulatiON (CRIMSON) code to evaluate two phase flow behaviors based on the recent computational fluid dynamics (CFD) techniques. The phase field model has been introduced to the CRIMSON in order to solve the problem of loosing phase interface sharpness in long-term calculation. As for the solver of the discrete fluid droplets, we applied the idea of Smoothed Particle Hydrodynamics (SPH) method. Both continuum fluid and discrete fluid interact each other through drag interaction force. We verified our method by applying it to a popular benchmark problem of collapse of water column problems, especially focusing on the splashing and scattering fluid behaviors after the column collided against the wall. We confirmed that the gross splashing and scattering behaviors were well reproduced by the introduction of particle model while the detailed behaviors of the particles were slightly different from the experimental results. (author)

  19. Unexpected Patterns in Snow and Dirt

    Science.gov (United States)

    Ackerson, Bruce J.

    2018-01-01

    For more than 30 years, Albert A. Bartlett published "Thermal patterns in the snow" in this journal. These are patterns produced by heat sources underneath the snow. Bartlett's articles encouraged me to pay attention to patterns in snow and to understanding them. At winter's end the last snow becomes dirty and is heaped into piles. This snow comes from the final clearing of sidewalks and driveways. The patterns observed in these piles defied my intuition. This melting snow develops edges where dirt accumulates, in contrast to ice cubes, which lose sharp edges and become more spherical upon melting. Furthermore, dirt absorbs more radiation than snow and yet doesn't melt and round the sharp edges of snow, where dirt accumulates.

  20. Correlation and prediction of snow water equivalent from snow sensors

    Science.gov (United States)

    Bruce J. McGurk; David L. Azuma

    1992-01-01

    Since 1982, under an agreement between the California Department of Water Resources and the USDA Forest Service, snow sensors have been installed and operated in Forest Service-administered wilderness areas in the Sierra Nevada of California. The sensors are to be removed by 2005 because of the premise that sufficient data will have been collected to allow "...

  1. Effects of Glide Path on the Centering Ability and Preparation Time of Two Reciprocating Instruments

    Science.gov (United States)

    Coelho, Marcelo Santos; Fontana, Carlos Eduardo; Kato, Augusto Shoji; de Martin, Alexandre Sigrist; da Silveira Bueno, Carlos Eduardo

    2016-01-01

    Introduction: The aim of this in vitro study was to evaluate the effects of establishing glide path on the centering ability and preparation time of two single-file reciprocating systems in mesial root canals of mandibular molars. Methods and Materials: Sixty extracted mandibular molars with curvatures of 25-39 degrees and separate foramina for the mesiobuccal and mesiolingual canals, were divided into four groups (n=15); WaveOne+glide path; WaveOne; Reciproc+glide path and Reciproc. Non-patent canals were excluded and only one canal in each tooth was instrumented. A manual glide path was established in first and third groups with #10, 15 and 20 hand K-files. Preparation was performed with reciprocating in-and-out motion, with a 3-4 mm amplitude and slight apical pressure. Initial and final radiographs were taken to analyze the amount of dentin removed in the instrumented canals. The radiographs were superimposed with an image editing software and examined to assess discrepancies at 3-, 6- and 9-mm distances from the apex. The Kruskal-Wallis test was used for statistical analysis. The level of significance was set at 0.05. Results: Preparation in groups without glide paths was swifter than the other groups (P=0.001). However, no difference was observed regarding centering ability. Conclusion: Establishing a glide path increased the total instrumentation time for preparing curved canals with WaveOne and Reciproc instruments. Glide path had no influence on the centering ability of these systems. PMID:26843875

  2. Internal Stellar Kinematics of M32 from the SPLASH Survey: Dark Halo Constraints

    Science.gov (United States)

    Howley, K. M.; Guhathakurta, P.; van der Marel, R.; Geha, M.; Kalirai, J.; Yniguez, B.; Kirby, E.; Cuillandre, J.-C.; Gilbert, K.

    2013-03-01

    As part of the SPLASH survey of the Andromeda (M31) system, we have obtained Keck/DEIMOS spectra of the compact elliptical (cE) satellite M32. This is the first resolved-star kinematical study of any cE galaxy. In contrast to most previous kinematical studies that extended out to r information to account statistically for M31 contamination. The rotation curve and velocity dispersion profile extend well beyond the radius (r ~ 150'') where the isophotes are distorted. Unlike NGC 205, another close dwarf companion of M31, M32's kinematics appear regular and symmetric and do not show obvious sharp gradients across the region of isophotal elongation and twists. We interpret M31's kinematics using three-integral axisymmetric dynamical equilibrium models constructed using Schwarzschild's orbit superposition technique. Models with a constant mass-to-light ratio can fit the data remarkably well. However, since such a model requires an increasing tangential anisotropy with radius, invoking the presence of an extended dark halo may be more plausible. Such an extended dark halo is definitely required to bind a half-dozen fast-moving stars observed at the largest radii, but these stars may not be an equilibrium component of M32. Data herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  3. [Snow cover pollution monitoring in Ufa].

    Science.gov (United States)

    Daukaev, R A; Suleĭmanov, R A

    2008-01-01

    The paper presents the results of examining the snow cover polluted with heavy metals in the large industrial town of Ufa. The level of man-caused burden on the snow cover of the conventional parts of the town was estimated and compared upon exposure to a wide range of snow cover pollutants. The priority snow cover pollutants were identified among the test heavy metals.

  4. [Posterior lamellar keratoplasty with DSEK technique and use of the Tan EndoGlide - short-term results].

    Science.gov (United States)

    Kałuiny, Bartłomiej J; Piotrowiak, Ilona; Sołdańska, Beata; Grzybek, Katarzyna; Czajkowska, Monika; Galas, Małgorzata; Malukiewicz, Grazyna

    2013-01-01

    To present the differences in surgical technique of DSEK (Descemet's Stripping Endothelial Keratoplasty) with the use of Tan EndoGlide (Coronet, UK) and Busin Glide (Moria, FR). Short-term results will also be presented, DSEK was performed in 24 eyes, in 8 cases the surgery was combined with cataract phacoemulsification and lOL implantation. Surgery course and 6 months postoperative results of first 12 eyes performed with the use of Tan EndoGlide were compared with 12 consecutive eyes preformed with Busin Glide. Tan EndoGlide provided much more stable anterior chamber, donor tissue unfolding process was better controlled but the incision was wider incision. Surgically induced mean refractory cylinder 6. months after the surgery was 1.56 - 1.15 Dsph in Tan EndoGlide group and 1.18 +/- 1.10 Dsph in Busin Glide group (P 0.05). Mean CDVA was 0.65+/- 0.27 and 0.63 +/- 0.25, respectively (P>0,05). Statistically significant differences in intra- and post-operative complications between both groups were not found. The Tan EndoGlide used during posterior lamellar keratoplasty with DSEK technique is a good alternative to currently used methods. It provides better stabilization of the anterior chamber, however its use is linked with higher postoperative astigmatism in comparison with Busin Glide. The visual outcomes and endothelial cell loss 6 months after the surgery were similar in both groups.

  5. Utilizing Multiple Datasets for Snow Cover Mapping

    Science.gov (United States)

    Tait, Andrew B.; Hall, Dorothy K.; Foster, James L.; Armstrong, Richard L.

    1999-01-01

    Snow-cover maps generated from surface data are based on direct measurements, however they are prone to interpolation errors where climate stations are sparsely distributed. Snow cover is clearly discernable using satellite-attained optical data because of the high albedo of snow, yet the surface is often obscured by cloud cover. Passive microwave (PM) data is unaffected by clouds, however, the snow-cover signature is significantly affected by melting snow and the microwaves may be transparent to thin snow (less than 3cm). Both optical and microwave sensors have problems discerning snow beneath forest canopies. This paper describes a method that combines ground and satellite data to produce a Multiple-Dataset Snow-Cover Product (MDSCP). Comparisons with current snow-cover products show that the MDSCP draws together the advantages of each of its component products while minimizing their potential errors. Improved estimates of the snow-covered area are derived through the addition of two snow-cover classes ("thin or patchy" and "high elevation" snow cover) and from the analysis of the climate station data within each class. The compatibility of this method for use with Moderate Resolution Imaging Spectroradiometer (MODIS) data, which will be available in 2000, is also discussed. With the assimilation of these data, the resolution of the MDSCP would be improved both spatially and temporally and the analysis would become completely automated.

  6. Performance evaluation of snow and ice plows.

    Science.gov (United States)

    2015-11-01

    Removal of ice and snow from road surfaces is a critical task in the northern tier of the United States, : including Illinois. Highways with high levels of traffic are expected to be cleared of snow and ice quickly : after each snow storm. This is ne...

  7. Photopolarimetric Retrievals of Snow Properties

    Science.gov (United States)

    Ottaviani, M.; van Diedenhoven, B.; Cairns, B.

    2015-01-01

    Polarimetric observations of snow surfaces, obtained in the 410-2264 nm range with the Research Scanning Polarimeter onboard the NASA ER-2 high-altitude aircraft, are analyzed and presented. These novel measurements are of interest to the remote sensing community because the overwhelming brightness of snow plagues aerosol and cloud retrievals based on airborne and spaceborne total reflection measurements. The spectral signatures of the polarized reflectance of snow are therefore worthwhile investigating in order to provide guidance for the adaptation of algorithms currently employed for the retrieval of aerosol properties over soil and vegetated surfaces. At the same time, the increased information content of polarimetric measurements allows for a meaningful characterization of the snow medium. In our case, the grains are modeled as hexagonal prisms of variable aspect ratios and microscale roughness, yielding retrievals of the grains' scattering asymmetry parameter, shape and size. The results agree with our previous findings based on a more limited data set, with the majority of retrievals leading to moderately rough crystals of extreme aspect ratios, for each scene corresponding to a single value of the asymmetry parameter.

  8. Velocity distribution in snow avalanches

    Science.gov (United States)

    Nishimura, K.; Ito, Y.

    1997-12-01

    In order to investigate the detailed structure of snow avalanches, we have made snow flow experiments at the Miyanomori ski jump in Sapporo and systematic observations in the Shiai-dani, Kurobe Canyon. In the winter of 1995-1996, a new device to measure static pressures was used to estimate velocities in the snow cloud that develops above the flowing layer of avalanches. Measurements during a large avalanche in the Shiai-dani which damaged and destroyed some instruments indicate velocities increased rapidly to more than 50 m/s soon after the front. Velocities decreased gradually in the following 10 s. Velocities of the lower flowing layer were also calculated by differencing measurement of impact pressure. Both recordings in the snow cloud and in the flowing layer changed with a similar trend and suggest a close interaction between the two layers. In addition, the velocity showed a periodic change. Power spectrum analysis of the impact pressure and the static pressure depression showed a strong peak at a frequency between 4 and 6 Hz, which might imply the existence of either ordered structure or a series of surges in the flow.

  9. Changes in Snow Albedo Resulting from Snow Darkening Caused by Black Carbon

    Science.gov (United States)

    Engels, J.; Kloster, S.; Bourgeois, Q.

    2014-12-01

    We investigate the potential impact of snow darkening caused by pre-industrial and present-day black carbon (BC) emissions on snow albedo and subsequently climate. To assess this impact, we implemented the effect of snow darkening caused by BC emitted from natural as well as anthropogenic sources into the Max Planck Institute for Meteorology Earth System Model (MPI-M ESM). Considerable amounts of BC are emitted e.g. from fires and are transported through the atmosphere for several days before being removed by rain or snow precipitation in snow covered regions. Already very small quantities of BC reduce the snow reflectance significantly, with consequences for snow melting and snow spatial coverage. We implemented the snow albedo reduction caused by BC contamination and snow aging in the one layer land surface component (JSBACH) of the atmospheric general circulation model ECHAM6, developed at MPI-M. For this we used the single-layer simulator of the SNow, Ice, and Aerosol Radiation (SNICAR-Online (Flanner et al., 2007); http://snow.engin.umich.edu) model to derive snow albedo values for BC in snow concentrations ranging between 0 and 1500 ng(BC)/g(snow) for different snow grain sizes for the visible (0.3 - 0.7 μm) and near infrared range (0.7 - 1.5 μm). As snow grains grow over time, we assign different snow ages to different snow grain sizes (50, 150, 500, and 1000 μm). Here, a radius of 50 μm corresponds to new snow, whereas a radius of 1000 μm corresponds to old snow. The deposition rates of BC on snow are prescribed from previous ECHAM6-HAM simulations for two time periods, pre-industrial (1880-1889) and present-day (2000-2009), respectively. We perform a sensitivity study regarding the scavenging of BC by snow melt. To evaluate the newly implemented albedo scheme we will compare the modeled black carbon in snow concentrations to observed ones. Moreover, we will show the impact of the BC contamination and snow aging on the simulated snow albedo. The

  10. Use of the Perclose ProGlide device with the 9 French Merci retrieval system

    Energy Technology Data Exchange (ETDEWEB)

    Layton, Kennith F.; Cloft, Harry J.; Kallmes, David F. [Mayo Clinic, Department of Radiology, Rochester, MN (United States); White, J. Bradley [Mayo Clinic, Department of Neurosurgery, Rochester, MN (United States)

    2006-05-15

    Closure devices are commonly used in neurointerventional procedures to achieve groin hemostasis. These devices are particularly useful in procedures requiring anticoagulation and larger catheters. The suture-mediated Perclose ProGlide device is intended for use with 5F to 8F sheaths. We describe the use of the ProGlide device with 9F sheaths in acute stroke treatment using the Merci retrieval device. The ProGlide device is advanced over a wire until the wire exit port is at the skin surface. The wire is removed and the device is advanced until pulsatile blood flow is encountered. The footplates are opened and the stitch is deployed. The footplates are then closed and the device is removed. After advancing the suture to the vessel, it is locked and trimmed. Firm pressure is necessary during deployment to prevent oozing around the device. If continued bleeding is encountered, direct manual pressure is used to achieve hemostasis. We have successfully used the Perclose ProGlide device in four patients following the Merci retriever without groin or extremity complication. The Perclose ProGlide device can be successfully used after placement of a 9F system in patients who have undergone mechanical thrombectomy. (orig.)

  11. Polycomb controls gliogenesis by regulating the transient expression of the Gcm/Glide fate determinant.

    Directory of Open Access Journals (Sweden)

    Anna Popkova

    Full Text Available The Gcm/Glide transcription factor is transiently expressed and required in the Drosophila nervous system. Threshold Gcm/Glide levels control the glial versus neuronal fate choice, and its perdurance triggers excessive gliogenesis, showing that its tight and dynamic regulation ensures the proper balance between neurons and glia. Here, we present a genetic screen for potential gcm/glide interactors and identify genes encoding chromatin factors of the Trithorax and of the Polycomb groups. These proteins maintain the heritable epigenetic state, among others, of HOX genes throughout development, but their regulatory role on transiently expressed genes remains elusive. Here we show that Polycomb negatively affects Gcm/Glide autoregulation, a positive feedback loop that allows timely accumulation of Gcm/Glide threshold levels. Such temporal fine-tuning of gene expression tightly controls gliogenesis. This work performed at the levels of individual cells reveals an undescribed mode of Polycomb action in the modulation of transiently expressed fate determinants and hence in the acquisition of specific cell identity in the nervous system.

  12. Lubrication of dislocation glide in MgO by hydrous defects

    Science.gov (United States)

    Skelton, Richard; Walker, Andrew M.

    2018-02-01

    Water-related defects, principally in the form of protonated cation vacancies, are potentially able to weaken minerals under high-stress or low-temperature conditions by reducing the Peierls stress required to initiate dislocation glide. In this study, we use the Peierls-Nabarro (PN) model to determine the effect of protonated Mg vacancies on the 1/2{110} and 1/2{100} slip systems in MgO. This PN model is parameterized using generalized stacking fault energies calculated using plane-wave density functional theory, with and without protonated Mg vacancies present at the glide plane. It found that these defects increase dislocation core widths and reduce the Peierls stress over the entire pressure range 0-125 GPa. Furthermore, 1/2{110} slip is found to be more sensitive to the presence of protonated vacancies which increases in the pressure at which {100} becomes the easy glide plane for 1/2 screw dislocations. These results demonstrate, for a simple mineral system, that water-related defects can alter the deformation behavior of minerals in the glide-creep regime by reducing the stress required to move dislocations by glide. (Mg, Fe)O is the most anisotropic mineral in the Earth's lower mantle, so the differential sensitivity of the major slip systems in MgO to hydrous defects has potential implications for the interpretation of the seismic anisotropy in this region.

  13. A cyclic GMP signalling module that regulates gliding motility in a malaria parasite.

    Directory of Open Access Journals (Sweden)

    Robert W Moon

    2009-09-01

    Full Text Available The ookinete is a motile stage in the malaria life cycle which forms in the mosquito blood meal from the zygote. Ookinetes use an acto-myosin motor to glide towards and penetrate the midgut wall to establish infection in the vector. The regulation of gliding motility is poorly understood. Through genetic interaction studies we here describe a signalling module that identifies guanosine 3', 5'-cyclic monophosphate (cGMP as an important second messenger regulating ookinete differentiation and motility. In ookinetes lacking the cyclic nucleotide degrading phosphodiesterase delta (PDEdelta, unregulated signalling through cGMP results in rounding up of the normally banana-shaped cells. This phenotype is suppressed in a double mutant additionally lacking guanylyl cyclase beta (GCbeta, showing that in ookinetes GCbeta is an important source for cGMP, and that PDEdelta is the relevant cGMP degrading enzyme. Inhibition of the cGMP-dependent protein kinase, PKG, blocks gliding, whereas enhanced signalling through cGMP restores normal gliding speed in a mutant lacking calcium dependent protein kinase 3, suggesting at least a partial overlap between calcium and cGMP dependent pathways. These data demonstrate an important function for signalling through cGMP, and most likely PKG, in dynamically regulating ookinete gliding during the transmission of malaria to the mosquito.

  14. MODIS Snow and Sea Ice Products

    Science.gov (United States)

    Hall, Dorothy K.; Riggs, George A.; Salomonson, Vincent V.

    2004-01-01

    In this chapter, we describe the suite of Earth Observing System (EOS) Moderate-Resolution Imaging Spectroradiometer (MODIS) Terra and Aqua snow and sea ice products. Global, daily products, developed at Goddard Space Flight Center, are archived and distributed through the National Snow and Ice Data Center at various resolutions and on different grids useful for different communities Snow products include binary snow cover, snow albedo, and in the near future, fraction of snow in a 5OO-m pixel. Sea ice products include ice extent determined with two different algorithms, and sea ice surface temperature. The algorithms used to develop these products are described. Both the snow and sea ice products, available since February 24,2000, are useful for modelers. Validation of the products is also discussed.

  15. Rabi, Snow, and "The Two Cultures"

    Science.gov (United States)

    Day, Michael A.

    2003-04-01

    John Rigden in his biography of I. I. Rabi, "Rabi: Scientist and Citizen" (1987, 2000 with a new preface) includes an intriguing footnote concerning Rabi's influence on C. P. Snow. According to the footnote, when Snow and his son were visiting the Rabis in New York City, Rabi's wife heard Snow tell his son that Rabi was "the man who gave me [Snow] the idea for the two cultures." In this talk, after a brief overview of Rabi's views on science and society, the mutual influence between Rabi and Snow is explored. On the basis of chronology and an interpretation of Rabi's works (published and unpublished) as well as letters between Rabi and Snow, a case is made that Rabi could very well have been the man who gave Snow the idea for "The Two Cultures."

  16. Gliding arc surface treatment of glass-fiber-reinforced polyester enhanced by ultrasonic irradiation

    DEFF Research Database (Denmark)

    Kusano, Yukihiro; Norrman, Kion; Drews, Joanna Maria

    2011-01-01

    . The efficiency of such a plasma treatment at atmospheric pressure can be further improved by ultrasonic irradiation onto the surface during the treatment. In the present work glass fiber reinforced polyester (GFRP) plates are treated using an atmospheric pressure gliding arc with and without ultrasonic...... that ultrasonic irradiation reduced the OH rotational temperature of the gliding arc. The wettability of the GFRP surface was significantly improved by the plasma treatment without ultrasonic irradiation, and tended to improve furthermore at higher power to the plasma. Ultrasonic irradiation during the plasma......A gliding arc is a plasma generated between diverging electrodes and extended by a high speed gas flow. It can be operated in air at atmospheric pressure. It potentially enables selective chemical processing with high productivity, and is useful for adhesion improvement of material surfaces...

  17. Effect of 2H and 18O water isotopes in kinesin-1 gliding assay

    Directory of Open Access Journals (Sweden)

    Andy Maloney

    2014-03-01

    Full Text Available We show for the first time the effects of heavy-hydrogen water (2H2O and heavy-oxygen water (H218O on the gliding speed of microtubules on kinesin-1 coated surfaces. Increased fractions of isotopic waters used in the motility solution decreased the gliding speed of microtubules by a maximum of 21% for heavy-hydrogen and 5% for heavy-oxygen water. We also show that gliding microtubule speed returns to its original speed after being treated with heavy-hydrogen water. We discuss possible interpretations of these results and the importance for future studies of water effects on kinesin and microtubules. We also discuss the implication for using heavy waters in biomolecular devices incorporating molecular motors.

  18. Two-leg Su-Schrieffer-Heeger chain with glide reflection symmetry

    Science.gov (United States)

    Zhang, Shao-Liang; Zhou, Qi

    2017-06-01

    The Su-Schrieffer-Heeger (SSH) model lays the foundation of many important concepts in quantum topological matters. Here, we show that a spin-dependent double-well optical lattice allows one to couple two topologically distinct SSH chains in the bulk and realize a glided-two-leg SSH model that respects the glide reflection symmetry. Such a model gives rise to intriguing quantum phenomena beyond the paradigm of a traditional SSH model. It is characterized by Wilson lines that require non-Abelian Berry connections, and the interplay between the glide symmetry and interaction automatically leads to charge fractionalization without jointing two lattice potentials at an interface. Our work demonstrates the versatility of ultracold atoms to create new theoretical models for studying topological matters.

  19. Benzoxazinones as Human Peroxisome Proliferator Activated Receptor Gamma (PPARγ) Agonists: A Docking Study Using Glide.

    Science.gov (United States)

    Das, N; Dhanawat, M; Shrivastava, S K

    2011-03-01

    The purpose of the present study is to undertake a docking study of some benzoxazinone derivatives on human peroxisome proliferator activated receptor co-crystallized with an alpha-aryloxyphenylacetic acid agonist using Glide 4.5. The QikProp program was used to obtain the absorption, distribution, metabolism and excretion properties of the analogues. The intermolecular hydrogen bonding interaction of the best-fit ligands were found to be associated with Tyr473, Ser289, Hie 449, Hip 323, Ser 342 and Gly 284 amino acid residue at the receptor active site. Among all the observed interaction with similar binding pattern, the presence of methyl carboxypentyl side chain (Lig. No. 21) showed additional interaction with Ser 342 and the affinity was increased by carboxyl oxygen (as hydrogen bond acceptor) with a best Glide score of -14.54 as compared to the co-crystallized aryloxyphenyl acetic acid which achieved a glide score of -12.50.

  20. Aerodynamic consequences of wing morphing during emulated take-off and gliding in birds.

    Science.gov (United States)

    Klaassen van Oorschot, Brett; Mistick, Emily A; Tobalske, Bret W

    2016-10-01

    Birds morph their wings during a single wingbeat, across flight speeds and among flight modes. Such morphing may allow them to maximize aerodynamic performance, but this assumption remains largely untested. We tested the aerodynamic performance of swept and extended wing postures of 13 raptor species in three families (Accipitridae, Falconidae and Strigidae) using a propeller model to emulate mid-downstroke of flapping during take-off and a wind tunnel to emulate gliding. Based on previous research, we hypothesized that (1) during flapping, wing posture would not affect maximum ratios of vertical and horizontal force coefficients (C V :C H ), and that (2) extended wings would have higher maximum C V :C H when gliding. Contrary to each hypothesis, during flapping, extended wings had, on average, 31% higher maximum C V :C H ratios and 23% higher C V than swept wings across all biologically relevant attack angles (α), and, during gliding, maximum C V :C H ratios were similar for the two postures. Swept wings had 11% higher C V than extended wings in gliding flight, suggesting flow conditions around these flexed raptor wings may be different from those in previous studies of swifts (Apodidae). Phylogenetic affiliation was a poor predictor of wing performance, due in part to high intrafamilial variation. Mass was only significantly correlated with extended wing performance during gliding. We conclude that wing shape has a greater effect on force per unit wing area during flapping at low advance ratio, such as take-off, than during gliding. © 2016. Published by The Company of Biologists Ltd.

  1. Plastic deformation of crystals: analytical and computer simulation studies of dislocation glide

    Energy Technology Data Exchange (ETDEWEB)

    Altintas, S.

    1978-05-01

    The plastic deformation of crystals is usually accomplished through the motion of dislocations. The glide of a dislocation is impelled by the applied stress and opposed by microstructural defects such as point defects, voids, precipitates and other dislocations. The planar glide of a dislocation through randomly distributed obstacles is considered. The objective of the present research work is to calculate the critical resolved shear stress (CRSS) for athermal glide and the velocity of the dislocation at finite temperature as a function of the applied stress and the nature and strength of the obstacles. Dislocation glide through mixtures of obstacles has been studied analytically and by computer simulation. Arrays containing two kinds of obstacles as well as square distribution of obstacle strengths are considered. The critical resolved shear stress for an array containing obstacles with a given distribution of strengths is calculated using the sum of the quadratic mean of the stresses for the individual obstacles and is found to be in good agreement with the computer simulation data. Computer simulation of dislocation glide through randomly distributed obstacles containing up to 10/sup 6/ obstacles show that the CRSS decreases as the size of the array increases and approaches a limiting value. Histograms of forces and of segment lengths are obtained and compared with theoretical predictions. Effects of array shape and boundary conditions on the dislocation glide are also studied. Analytical and computer simulation results are compared with experimental results obtained on precipitation-, irradiation-, forest-, and impurity cluster-hardening systems and are found to be in good agreement.

  2. Plastic deformation of crystals: analytical and computer simulation studies of dislocation glide

    International Nuclear Information System (INIS)

    Altintas, S.

    1978-05-01

    The plastic deformation of crystals is usually accomplished through the motion of dislocations. The glide of a dislocation is impelled by the applied stress and opposed by microstructural defects such as point defects, voids, precipitates and other dislocations. The planar glide of a dislocation through randomly distributed obstacles is considered. The objective of the present research work is to calculate the critical resolved shear stress (CRSS) for athermal glide and the velocity of the dislocation at finite temperature as a function of the applied stress and the nature and strength of the obstacles. Dislocation glide through mixtures of obstacles has been studied analytically and by computer simulation. Arrays containing two kinds of obstacles as well as square distribution of obstacle strengths are considered. The critical resolved shear stress for an array containing obstacles with a given distribution of strengths is calculated using the sum of the quadratic mean of the stresses for the individual obstacles and is found to be in good agreement with the computer simulation data. Computer simulation of dislocation glide through randomly distributed obstacles containing up to 10 6 obstacles show that the CRSS decreases as the size of the array increases and approaches a limiting value. Histograms of forces and of segment lengths are obtained and compared with theoretical predictions. Effects of array shape and boundary conditions on the dislocation glide are also studied. Analytical and computer simulation results are compared with experimental results obtained on precipitation-, irradiation-, forest-, and impurity cluster-hardening systems and are found to be in good agreement

  3. Gliding arc surface modification of carrot nanofibre coating - perspective for composite processing

    DEFF Research Database (Denmark)

    Kusano, Yukihiro; Berglund, L; Aitomäki, Y

    2016-01-01

    Surfaces of carrot nanofibre coatings were modified by a gliding arc in atmospheric pressure air. The treatment strengthened wetting of deionized water and glycerol, increased an oxygen content, C-O and C=O, and moderately roughened the surfaces. In the perspective of composite materials......, these changes to the nanofibres can potentially improve their processability when they are to be impregnated with a polymeric matrix. However, longer exposure to the gliding arc reduced oxidation and roughness of the surface, and thus there exists an optimum condition to achieve good wetting to solvents....

  4. Snow and ice: Chapter 3

    Science.gov (United States)

    Littell, Jeremy; McAfee, Stephanie A.; O'Neel, Shad; Sass, Louis; Burgess, Evan; Colt, Steve; Clark, Paul; Hayward, Gregory D.; Colt, Steve; McTeague, Monica L.; Hollingsworth, Teresa N.

    2017-01-01

    Temperature and precipitation are key determinants of snowpack levels. Therefore, climate change is likely to affect the role of snow and ice in the landscapes and hydrology of the Chugach National Forest region.Downscaled climate projections developed by Scenarios Network for Alaska and Arctic Planning (SNAP) are useful for examining projected changes in snow at relatively fine resolution using a variable called “snowday fraction (SDF),” the percentage of days with precipitation falling as snow.We summarized SNAP monthly SDF from five different global climate models for the Chugach region by 500 m elevation bands, and compared historical (1971–2000) and future (2030–2059) SDF. We found that:Snow-day fraction and snow-water equivalent (SWE) are projected to decline most in late autumn (October to November) and at lower elevations.Snow-day fraction is projected to decrease 23 percent (averaged across five climate models) from October to March, between sea level and 500 m. Between sea level and 1000 m, SDF is projected to decrease by 17 percent between October and March.Snow-water equivalent is projected to decrease most in autumn (October and November) and at lower elevations (below 1500 m), an average of -26 percent for the 2030–2059 period compared to 1971– 2000. Averaged across the cool season and the entire domain, SWE is projected to decrease at elevations below 1000 m because of increased temperature, but increase at higher elevations because of increased precipitation.Compared to 1971–2000, the percentage of the landscape that is snowdominant in 2030–2059 is projected to decrease, and the percentage in which rain and snow are co-dominant (transient hydrology) is projected to increase from 27 to 37 percent. Most of this change is at lower elevations.Glaciers on the Chugach National Forest are currently losing about 6 km3 of ice per year; half of this loss comes from Columbia Glacier (Berthier et al. 2010).Over the past decade, almost all

  5. Spatial Distribution And Synoptic Conditions Of Snow Accumulation And Snow Ablation In The West Siberian Plain

    Directory of Open Access Journals (Sweden)

    Bednorz Ewa

    2015-09-01

    Full Text Available The mean duration of snow coverage in the West Siberian Plain is approximately eight months in the north to about five months in the south. While the period of intense snow melting is short (one or two months between March and May, snow accumulation persists for most of the cold season. Snow accumulation is associated with negative anomalies of sea level pressure, which means increased cyclonal activity and weaker than normal Siberian High. Much lower anomalies of sea level pressure occur during snow ablation. This suggests smaller influence of air circulation on snow cover reduction in spring.

  6. Everywhere and nowhere: snow and its linkages

    Science.gov (United States)

    Hiemstra, C. A.

    2017-12-01

    Interest has grown in quantifying higher latitude precipitation change and snow-related ecosystem and economic impacts. There is a high demand for creating and using snow-related datasets, yet available datasets contain limitations, aren't scale appropriate, or lack thorough validation. Much of the uncertainty in snow estimates relates to ongoing snow measurement problems that are chronic and pervasive in windy, Arctic environments. This, coupled with diminishing support for long-term snow field observations, creates formidable hydrologic gaps in snow dominated landscapes. Snow touches most aspects of high latitude landscapes and spans albedo, ecosystems, soils, permafrost, and sea ice. In turn, snow can be impacted by disturbances, landscape change, ecosystem, structure, and later arrival of sea or lake ice. Snow, and its changes touch infrastructure, housing, and transportation. Advances in snow measurements, modeling, and data assimilation are under way, but more attention and a concerted effort is needed in a time of dwindling resources to make required advances during a time of rapid change.

  7. Storing snow for the next winter: Two case studies on the application of snow farming.

    Science.gov (United States)

    Grünewald, Thomas; Wolfsperger, Fabian

    2016-04-01

    Snow farming is the conservation of snow during the warm half-year. This means that large piles of snow are formed in spring in order to be conserved over the summer season. Well-insulating materials such as chipped wood are added as surface cover to reduce melting. The aim of snow farming is to provide a "snow guaranty" for autumn or early winter - this means that a specific amount of snow will definitively be available, independent of the weather conditions. The conserved snow can then be used as basis for the preparation of winter sports grounds such as cross-country tracks or ski runs. This helps in the organization of early winter season sport events such as World Cup races or to provide appropriate training conditions for athletes. We present a study on two snow farming projects, one in Davos (Switzerland) and one in the Martell valley of South Tyrol. At both places snow farming has been used for several years. For the summer season 2015, we monitored both snow piles in order to assess the amount of snow conserved. High resolution terrestrial laser scanning was performed to measure snow volumes of the piles at the beginning and at the end of the summer period. Results showed that only 20% to 30 % of the snow mass was lost due to ablation. This mass loss was surprisingly low considering the extremely warm and dry summer. In order to identify the most relevant drivers of snow melt we also present simulations with the sophisticated snow cover models SNOWPACK and Alpine3D. The simulations are driven by meteorological input data recorded in the vicinity of the piles and enable a detailed analysis of the relevant processes controlling the energy balance. The models can be applied to optimize settings for snow farming and to examine the suitability of new locations, configurations or cover material for future snow farming projects.

  8. [The research of the relationship between snow properties and the bidirectional polarized reflectance from snow surface].

    Science.gov (United States)

    Sun, Zhong-Qiu; Wu, Zheng-Fang; Zhao, Yun-Sheng

    2014-10-01

    In the context of remote sensing, the reflectance of snow is a key factor for accurate inversion for snow properties, such as snow grain size, albedo, because of it is influenced by the change of snow properties. The polarized reflectance is a general phenomenon during the reflected progress in natural incident light In this paper, based on the correct measurements for the multiple-angle reflected property of snow field in visible and near infrared wavelength (from 350 to 2,500 nm), the influence of snow grain size and wet snow on the bidirectional polarized property of snow was measured and analyzed. Combining the results measured in the field and previous conclusions confirms that the relation between polarization and snow grain size is obvious in infrared wavelength (at about 1,500 nm), which means the degree of polarization increasing with an increase of snow grain size in the forward scattering direction, it is because the strong absorption of ice near 1,500 nm leads to the single scattering light contributes to the reflection information obtained by the sensor; in other word, the larger grain size, the more absorption accompanying the larger polarization in forward scattering direction; we can illustrate that the change from dry snow to wet snow also influences the polarization property of snow, because of the water on the surface of snow particle adheres the adjacent particles, that means the wet snow grain size is larger than the dry snow grain size. Therefore, combining the multiple-angle polarization with reflectance will provide solid method and theoretical basis for inversion of snow properties.

  9. Nimbus-7 SMMR Derived Monthly Global Snow Cover and Snow Depth

    Data.gov (United States)

    National Aeronautics and Space Administration — The data set consists of monthly global snow cover and snow depth derived from Nimbus-7 SMMR data for 1978 through 1987. The SMMR data are interpolated for spatial...

  10. SnowEx17 SnowMicroPen (SMP) Raw Penetration Force Profiles V001

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains raw penetration force profiles measured at snow pits and along linear transects at Grand Mesa, Colorado using the SnowMicroPen (SMP), a...

  11. Nimbus-7 SMMR Derived Monthly Global Snow Cover and Snow Depth, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — The data set consists of monthly global snow cover and snow depth derived from Nimbus-7 SMMR data for 1978 through 1987. The SMMR data are interpolated for spatial...

  12. Flight modes in migrating European bee-eaters: heart rate may indicate low metabolic rate during soaring and gliding.

    Directory of Open Access Journals (Sweden)

    Nir Sapir

    Full Text Available BACKGROUND: Many avian species soar and glide over land. Evidence from large birds (m(b>0.9 kg suggests that soaring-gliding is considerably cheaper in terms of energy than flapping flight, and costs about two to three times the basal metabolic rate (BMR. Yet, soaring-gliding is considered unfavorable for small birds because migration speed in small birds during soaring-gliding is believed to be lower than that of flapping flight. Nevertheless, several small bird species routinely soar and glide. METHODOLOGY/PRINCIPAL FINDINGS: To estimate the energetic cost of soaring-gliding flight in small birds, we measured heart beat frequencies of free-ranging migrating European bee-eaters (Merops apiaster, m(b∼55 g using radio telemetry, and established the relationship between heart beat frequency and metabolic rate (by indirect calorimetry in the laboratory. Heart beat frequency during sustained soaring-gliding was 2.2 to 2.5 times lower than during flapping flight, but similar to, and not significantly different from, that measured in resting birds. We estimated that soaring-gliding metabolic rate of European bee-eaters is about twice their basal metabolic rate (BMR, which is similar to the value estimated in the black-browed albatross Thalassarche (previously Diomedea melanophrys, m(b∼4 kg. We found that soaring-gliding migration speed is not significantly different from flapping migration speed. CONCLUSIONS/SIGNIFICANCE: We found no evidence that soaring-gliding speed is slower than flapping flight in bee-eaters, contradicting earlier estimates that implied a migration speed penalty for using soaring-gliding rather than flapping flight. Moreover, we suggest that small birds soar and glide during migration, breeding, dispersal, and other stages in their annual cycle because it may entail a low energy cost of transport. We propose that the energy cost of soaring-gliding may be proportional to BMR regardless of bird size, as theoretically deduced by

  13. Gravity effects on a gliding arc in four noble gases: from normal to hypergravity

    NARCIS (Netherlands)

    Potocnakova, L.; Sperka, J.; Zikan, P.; van Loon, J.J.W.A.; Beckers, J.; Kudrle, V.

    2015-01-01

    A gliding arc in four noble gases (He, Ne, Ar, Kr) has been studied under previously unexplored conditions of varying artificial gravity, from normal 1 g gravity up to 18 g hypergravity. Significant differences, mainly the visual thickness of the plasma channel, its maximum elongation and general

  14. An in vitro comparison of root canal transportation by reciproc file with and without glide path.

    Directory of Open Access Journals (Sweden)

    Kiumars Nazarimoghadam

    2014-10-01

    Full Text Available The aim of ideal canal preparation is to prevent iatrogenic aberrations such as transportation. The aim of this study was to evaluate the root canal transportation by Reciproc file with and without glide path.Thirty acrylic-resin blocks with a curvature of 60° and size#10 (2% taper were assigned into two groups (n= 15. In group 1, the glide path was performed using stainless steel k-files size#10 and 15 at working length In group 2, canals were prepared with Reciproc file system at working length. By using digital imaging software (AutoCAD 2008, the pre-instrumentation and post-instrumentation digital images were superimposed over, taking the landmarks as reference points. Then the radius of the internal and external curve of the specimens was calculated at three α, β and γ points (1mm to apex as α, 3mm to apex as β, and 5mm to apex as γ. The data were statically analyzed using the independent T-test and Mann-Whitney U test by SPSS version 16.Glide path was found significant for only external curve in the apical third of the canal; that is, 5mm to apex (P=0.005. But in the other third, canal modification was not significant (P> 0.008.Canal transportation in the apical third of the canal seems to be significantly reduced when glide path is performed using reciprocating files.

  15. Sustained diffusive alternating current gliding arc discharge in atmospheric pressure air

    DEFF Research Database (Denmark)

    Zhu, Jiajian; Gao, Jinlong; Li, Zhongshan

    2014-01-01

    Rapid transition from glow discharge to thermal arc has been a common problem in generating stable high-power non-thermal plasmas especially at ambient conditions. A sustained diffusive gliding arc discharge was generated in a large volume in atmospheric pressure air, driven by an alternating...

  16. Measurements of 3D slip velocities and plasma column lengths of a gliding arc discharge

    NARCIS (Netherlands)

    Zhu, J.; Gao, J.; Ehn, A.; Alden, M.; Li, Z.; Moseev, D.; Kusano, Y.; Salewski, M.; Alpers, A.; Gritzmann, P.; Schwenk, M.

    2015-01-01

    A non-thermal gliding arc discharge was generated at atmospheric pressure in an air flow. The dynamics of the plasma column and tracer particles were recorded using two synchronized highspeed cameras. Whereas the data analysis for such systems has previously been performed in 2D (analyzing the

  17. Vocoid-driven processes: Palatalization and glide hardening in Greek and its dialects

    Directory of Open Access Journals (Sweden)

    Mary Baltazani

    2016-07-01

    Full Text Available The point of departure of this article is the processes that front vocoids induce as triggers in language. We start with a description of 'palatalization', using Standard Modern Greek and other Greek dialects as an empirical basis. We then introduce a new, so far undescribed type of palatalization, dubbed 'strengthened palatalization'. Despite its similarity to 'secondary palatalization', we argue that it is a different process because it is triggered by an unrealized high front /i/, unlike secondary palatalization, where the high vocoid is alongside the preceding consonant as a secondary gesture. Furthermore, the output of strengthened palatalization is different because it lacks the primary cue of secondary palatalization, that is, F2 raising in VC sequences. Next, we examine 'glide hardening', a process complementary to palatalization because it is also triggered by a high front vocoid. However, in glide hardening the glide is maintained as a separate segment and is strengthened into a palatal fricative (or even a stop. By focusing on the 'triggers '– rather than the 'outputs', we attain a unified account of both palatalization and glide hardening as enhancement processes that aim at strengthening the phonetic cues of their targets for reasons of perceptual salience.

  18. The 3D CFD study of gliding swimmer on passive hydrodynamics drag

    Directory of Open Access Journals (Sweden)

    Vishveshwar Rajendra Mantha

    2014-04-01

    Full Text Available The aim of this study was to analyze the effect of depth on the hydrodynamic drag coefficient during the passive underwater gliding after the starts and turns. The swimmer hydrodynamics performance was studied by the application of computational fluid dynamics (CFD method. The steady-state CFD simulations were performed by the application of k - omega turbulent model and volume of fluid method to obtain two-phase flow around a three-dimensional swimmer model when gliding near water surface and at different depths from the water surface. The simulations were conducted for four different swimming pool size, each with different depth, i.e., 1.0, 1.5, 2.0 and 3.0 m for three different velocities, i.e., 1.5, 2.0 and 2.5 m/s, with swimmer gliding at different depths with intervals of 0.25 m, each starting from the water surface, respectively. The numerical results of pressure drag and total coefficients at individual average race velocities were obtained. The results showed that the drag coefficient decreased as depth increased, with a trend toward reduced fluctuation after 0.5m depth from the water surface. The selection of the appropriate depth during the gliding phase should be a main concern of swimmers and coaches.

  19. Use of glide-ins in CMS for production and analysis

    International Nuclear Information System (INIS)

    Bradley, D; Gutsche, O; Holzman, B; Sfiligoi, I; Vaandering, E; Hahn, K; Padhi, S; Pi, H; Wuerthwein, F; Spiga, D

    2010-01-01

    With the evolution of various grid federations, the Condor glide-ins represent a key feature in providing a homogeneous pool of resources using late-binding technology. The CMS collaboration uses the glide-in based Workload Management System, glideinWMS, for production (ProdAgent) and distributed analysis (CRAB) of the data. The Condor glide-in daemons traverse to the worker nodes, submitted via Condor-G. Once activated, they preserve the Master-Worker relationships, with the worker first validating the execution environment on the worker node before pulling the jobs sequentially until the expiry of their lifetimes. The combination of late-binding and validation significantly reduces the overall failure rate visible to CMS physicists. We discuss the extensive use of the glideinWMS since the computing challenge, CCRC-08, in order to prepare for the forthcoming LHC data-taking period. The key features essential to the success of large-scale production and analysis on CMS resources across major grid federations, including EGEE, OSG and NorduGrid are outlined. Use of glide-ins via the CRAB server mechanism and ProdAgent, as well as first hand experience of using the next generation CREAM computing element within the CMS framework is discussed.

  20. A Jurassic gliding euharamiyidan mammal with an ear of five auditory bones

    Science.gov (United States)

    Han, Gang; Mao, Fangyuan; Bi, Shundong; Wang, Yuanqing; Meng, Jin

    2017-11-01

    Gliding is a distinctive locomotion type that has been identified in only three mammal species from the Mesozoic era. Here we describe another Jurassic glider that belongs to the euharamiyidan mammals and shows hair details on its gliding membrane that are highly similar to those of extant gliding mammals. This species possesses a five-boned auditory apparatus consisting of the stapes, incus, malleus, ectotympanic and surangular, representing, to our knowledge, the earliest known definitive mammalian middle ear. The surangular has not been previously identified in any mammalian middle ear, and the morphology of each auditory bone differs from those of known mammals and their kin. We conclude that gliding locomotion was probably common in euharamiyidans, which lends support to idea that there was a major adaptive radiation of mammals in the mid-Jurassic period. The acquisition of the auditory bones in euharamiyidans was related to the formation of the dentary-squamosal jaw joint, which allows a posterior chewing movement, and must have evolved independently from the middle ear structures of monotremes and therian mammals.

  1. Evaluation of the GlideScope Direct: A New Video Laryngoscope for Teaching Direct Laryngoscopy

    Directory of Open Access Journals (Sweden)

    Darwin Viernes

    2012-01-01

    Full Text Available Background. Teaching direct laryngoscopy is limited by the inability of the instructor to simultaneously view the airway with the laryngoscopist. Our primary aim is to report our initial use of the GlideScope Direct, a video-enabled, Macintosh laryngoscope intended primarily as a training tool in direct laryngoscopy. Methods. The GlideScope Direct was made available to anyone who planned on performing direct laryngoscopy as the primary technique for intubation. Novices were those who had performed <30 intubations. Results. The GlideScope Direct was used 123 times as primarily a direct laryngoscope while the instructor viewed the intubation on the monitor. It was highly successful as a direct laryngoscope (93% success. Salvage by indirect laryngoscopy occurred in 7/9 remaining patients without changing equipment. Novices performed 28 intubations (overall success rate of 79%. In 6 patients, the instructor took over and successfully intubated the patient. Instructors used the video images to guide the operator in 16 (57% of those patients. Seven different instructors supervised the 28 novices, all of who subjectively felt advantaged by having the laryngoscopic view available. Conclusions. The GlideScope Direct functions similarly to a Macintosh laryngoscope and provides the instructor subjective reassurance, while providing the ability to guide the trainee laryngoscopist.

  2. Note on the glide of a bird with wings bent downwards

    NARCIS (Netherlands)

    Sparenberg, J. A.

    This note considers the influence of the bending down of the wings of a bird on the performance of its glide. The induced drag of bent wings is compared with the induced drag of a corresponding straight wing. Numerical results are given.

  3. Boundary layer physics over snow and ice

    OpenAIRE

    Anderson, P. S.; Neff, W. D.

    2008-01-01

    Observations of the unique chemical environment over snow and ice in recent decades, particularly in the polar regions, have stimulated increasing interest in the boundary layer processes that mediate exchanges between the ice/snow interface and the atmosphere. This paper provides a review of the underlying concepts and examples from recent field studies in polar boundary layer meteorology, which will generally apply to atmospheric flow over snow and ice surfaces. It forms a companion paper t...

  4. Snow cover as a source of technogenic pollution of surface water during the snow melting period

    OpenAIRE

    Labuzova Olga; Noskova Tatyana; Lysenko Maria; Ovcharenko Elena; Papina Tatyana

    2016-01-01

    The study of pollutants in melt water of snow cover and snow disposal sites in the city of Barnaul showed that during the snow melting period the surface water is not subjected to significant technogenic impact according to a number of studied indices. The oils content is an exception: it can exceed MAC more than 20 times in river- water due to the melting of city disposal sites. Environmental damage due to an oils input into water resources during the snow melting period...

  5. Snow Water Equivalent SAR and Radiometer

    Data.gov (United States)

    National Aeronautics and Space Administration — After nearly four decades of international effort developing remote sensing techniques, measurement of land surface snow remains a significant challenge. Developing...

  6. Supporting Snow Research: SnowEx Data and Services at the NASA National Snow and Ice Data Center DAAC

    Science.gov (United States)

    Leon, A.; Tanner, S.; Deems, J. S.

    2017-12-01

    The National Snow and Ice Data Center Distributed Active Archive Center (NSIDC DAAC), part of the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder, will archive and distribute all primary data sets collected during the NASA SnowEx campaigns. NSIDC DAAC's overarching goal for SnowEx data management is to steward the diverse SnowEx data sets to provide a reliable long-term archive, to enable effective data discovery, retrieval, and usage, and to support end user engagement. This goal will be achieved though coordination and collaboration with SnowEx project management and investigators. NSIDC DAAC's core functions for SnowEx data management include: Data Creation: Advise investigators on data formats and structure as well as metadata creation and content to enable preservation, usability, and discoverability. Data Documentation: Develop comprehensive data set documentation describing the instruments, data collection and derivation methods, and data file contents. Data Distribution: Provide discovery and access through NSIDC and NASA data portals to make SnowEx data available to a broad user community Data & User Support: Assist user communities with the selection and usage of SnowEx data products. In an effort to educate and broaden the SnowEx user community, we will present an overview of the SnowEx data products, tools, and services which will be available at the NSIDC DAAC. We hope to gain further insight into how the DAAC can enable the user community to seamlessly and effectively utilize SnowEx data in their research and applications.

  7. Modeling of falling snow properties for snowpack models: towards a better link between falling snow and snow on the ground

    Science.gov (United States)

    Vionnet, Vincent; Milbrandt, Jason; Yamaguchi, Satoru; Morrison, Hugh

    2017-04-01

    Falling snow is made of different types of solid hydrometeors including single ice crystals, aggregates at different riming stages and graupel. This variability results from complex in-cloud processes (deposition, riming and aggregation) and sub-cloud processes (melting and sublimation). It has consequences for the properties of fresh fallen snow accumulating on the ground including density and specific surface area (SSA). These properties strongly affect the evolution of snow on the ground by modifying for example the albedo and the thermal conductivity. Detailed snowpack models such as Crocus or SNOWPACK use near-surface wind speed, air temperature and humidity to compute the density and SSA of falling snow. The shape, size and degree of riming of falling solid hydrometeors are not directly taken into account, which limit the accurate determination of properties of fresh fallen snow. An alternative is offered by new bulk cloud microphysics schemes implemented in numerical weather prediction system that can be used to drive snowpack model. In particular, the scheme P3 (Predicted Particle Properties) proposes an innovative representation of all ice-phase particles by predicting several physical properties (e.g. size, rime fraction, rime density …). In this study, we first theoretically analyze the strengths and limitations of P3 to represent the density and SSA of falling snow. Parameterizations are then proposed to derive density and SSA from P3 output. Finally, P3 implemented in the Canadian Global Environmental Multiscale (GEM) weather prediction model is used to simulate snowfall events observed at the Falling Snow Observatory (Nagoaka, Japan). Model predictions are compared with (i) observations of the type of falling snow particles derived from disdrometer data and (ii) manual measurements of fresh fallen snow density and SSA. This study is a first step towards the development of a more integrated approach between falling snow and snow on the ground.

  8. Surface energy balance of seasonal snow cover for snow-melt ...

    Indian Academy of Sciences (India)

    This study describes time series analysis of snow-melt, radiation data and energy balance for a seasonal snow cover at Dhundi field station of SASE, which lies in Pir Panjal range of the. N–W Himalaya, for a winter season from 13 January to 12 April 2005. The analysis shows that mean snow surface temperature remains ...

  9. Nitrogen Fixation by Gliding Arc Plasma: Better Insight by Chemical Kinetics Modelling.

    Science.gov (United States)

    Wang, Weizong; Patil, Bhaskar; Heijkers, Stjin; Hessel, Volker; Bogaerts, Annemie

    2017-05-22

    The conversion of atmospheric nitrogen into valuable compounds, that is, so-called nitrogen fixation, is gaining increased interest, owing to the essential role in the nitrogen cycle of the biosphere. Plasma technology, and more specifically gliding arc plasma, has great potential in this area, but little is known about the underlying mechanisms. Therefore, we developed a detailed chemical kinetics model for a pulsed-power gliding-arc reactor operating at atmospheric pressure for nitrogen oxide synthesis. Experiments are performed to validate the model and reasonable agreement is reached between the calculated and measured NO and NO 2 yields and the corresponding energy efficiency for NO x formation for different N 2 /O 2 ratios, indicating that the model can provide a realistic picture of the plasma chemistry. Therefore, we can use the model to investigate the reaction pathways for the formation and loss of NO x . The results indicate that vibrational excitation of N 2 in the gliding arc contributes significantly to activating the N 2 molecules, and leads to an energy efficient way of NO x production, compared to the thermal process. Based on the underlying chemistry, the model allows us to propose solutions on how to further improve the NO x formation by gliding arc technology. Although the energy efficiency of the gliding-arc-based nitrogen fixation process at the present stage is not comparable to the world-scale Haber-Bosch process, we believe our study helps us to come up with more realistic scenarios of entering a cutting-edge innovation in new business cases for the decentralised production of fertilisers for agriculture, in which low-temperature plasma technology might play an important role. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Ancient phylogenetic divergence of the enigmatic African rodent Zenkerella and the origin of anomalurid gliding

    Directory of Open Access Journals (Sweden)

    Steven Heritage

    2016-08-01

    Full Text Available The “scaly-tailed squirrels” of the rodent family Anomaluridae have a long evolutionary history in Africa, and are now represented by two gliding genera (Anomalurus and Idiurus and a rare and obscure genus (Zenkerella that has never been observed alive by mammalogists. Zenkerella shows no anatomical adaptations for gliding, but has traditionally been grouped with the glider Idiurus on the basis of craniodental similarities, implying that either the Zenkerella lineage lost its gliding adaptations, or that Anomalurus and Idiurus evolved theirs independently. Here we present the first nuclear and mitochondrial DNA sequences of Zenkerella, based on recently recovered whole-body specimens from Bioko Island (Equatorial Guinea, which show unambiguously that Zenkerella is the sister taxon of Anomalurus and Idiurus. These data indicate that gliding likely evolved only once within Anomaluridae, and that there were no subsequent evolutionary reversals. We combine this new molecular evidence with morphological data from living and extinct anomaluromorph rodents and estimate that the lineage leading to Zenkerella has been evolving independently in Africa since the early Eocene, approximately 49 million years ago. Recently discovered fossils further attest to the antiquity of the lineage leading to Zenkerella, which can now be recognized as a classic example of a “living fossil,” about which we know remarkably little. The osteological markers of gliding are estimated to have evolved along the stem lineage of the Anomalurus–Idiurus clade by the early Oligocene, potentially indicating that this adaptation evolved in response to climatic perturbations at the Eocene–Oligocene boundary (∼34 million years ago.

  11. Influence of GlideScope assisted endotracheal intubation on intraocular pressure in ophthalmic patients

    Directory of Open Access Journals (Sweden)

    Nauman Ahmad

    2015-01-01

    Full Text Available Background: Traditional Macintoch laryngoscopy is known to cause a rise in intraocular pressure (IOP, tachycardia and hypertension. These changes are not desirable in patients with glaucoma and open globe injury. GlideScope is a video laryngoscope that functions independent of the line of sight, reduces upward lifting forces for glottic exposure and requires less cervical neck movement for intubation, making it less stimulating than Macintosh laryngoscopy. Aim: The aim was to assess the variations in IOP and hemodynamic changes after GlideScope assisted intubation. Materials and Methods: After approval of the local Institutional Research and Ethical Board and informed patient consent, 50 adult American Society of Anesthesiologist I and II patients with normal IOP were enrolled in a prospective, randomized study for ophthalmic surgery requiring tracheal intubation. In all patients, trachea was intubated using either GlideScope or Macintoch laryngoscope. IOP of nonoperated eye, heart rate and blood pressure were measured as baseline, 1 min after induction, 1 min and 5 min after tracheal intubation. Results: IOP was not significantly different between groups before and after anesthetic induction and 5 min after tracheal intubation (P = 0.217, 0.726, and 0.110 respectively. The only significant difference in IOP was at 1 min after intubation (P = 0.041. No significant difference noted between groups in mean arterial pressure (P = 0.899, 0.62, 0.47, 0.82 respectively and heart rate (P = 0.21, 0.72, 0.07, 0.29, respectively at all measurements. Conclusion: GlideScope assisted tracheal intubation shown lesser rise in IOP at 1 min after intubation in comparison to Macintoch laryngoscope, suggesting that GlideScope may be preferable to Macintosh laryngoscope.

  12. Comparison of patellar distraction with patellar glides in female patients with patellofemoral pain syndrom

    International Nuclear Information System (INIS)

    Syed, S.; Chaudhary, M.A.; Noor, R.; Bashir, M.S.; Manzoor, B.

    2017-01-01

    To analyse effectiveness of patellar glides and patellar distraction in the patients with patellofemoral pain syndrome (PFPS). Methodology: This longitudinal interventional comparative study was conducted at Physiotherapy Department, Mayo Hospital Lahore, Pakistan from September 2015 to March 2016. A total of 70 patients were divided into 2 groups randomly; group A received hot pack, quadriceps strengthening exercises and patellar distraction whereas group B received hot pack, quadriceps strengthening exercises and patellar glides. Age of the female patients was 18-40 years. Visual Analogue Scale (VAS) and Knee Injury and osteoarthritis outcome score (KOOS) questionnaire were used to compare the effectiveness of both treatments. The data were analysed using SPSS v. 21.0. Results: There was reduction in pain at VAS and KOOS showed improvement in function as well as the range of motion also increased in both groups. Both treatment techniques were effective in reducing pain in PFPS (P <0.005). Pre-treatment KOOS score in patellar glides group was 34.77+10.84 and post-treatment KOOS score was 62.155+15.75 and for patellar distraction group pre-treatment KOOS score was 35.42+10.07 that increased to 55.77+14.66 after treatment which showed that patellar glides had better effect on PFPS. Conclusion: Both treatments were effective in managing PFPS in terms of decreasing pain and increasing ROM as there was no significant difference between two techniques, however patellar glides were superior as compared to patellar distraction in decreasing pain and increasing ROM. (author)

  13. Performance study of protective clothing against hot water splashes: from bench scale test to instrumented manikin test.

    Science.gov (United States)

    Lu, Yehu; Song, Guowen; Wang, Faming

    2015-03-01

    Hot liquid hazards existing in work environments are shown to be a considerable risk for industrial workers. In this study, the predicted protection from fabric was assessed by a modified hot liquid splash tester. In these tests, conditions with and without an air spacer were applied. The protective performance of a garment exposed to hot water spray was investigated by a spray manikin evaluation system. Three-dimensional body scanning technique was used to characterize the air gap size between the protective clothing and the manikin skin. The relationship between bench scale test and manikin test was discussed and the regression model was established to predict the overall percentage of skin burn while wearing protective clothing. The results demonstrated strong correlations between bench scale test and manikin test. Based on these studies, the overall performance of protective clothing against hot water spray can be estimated on the basis of the results of the bench scale hot water splashes test and the information of air gap size entrapped in clothing. The findings provide effective guides for the design and material selection while developing high performance protective clothing. Published by Oxford University Press on behalf of the British Occupational Hygiene Society 2014.

  14. Measurement of gliding resistance of the extensor pollicis longus and extensor digitorum communis II tendons within the extensor retinaculum.

    Science.gov (United States)

    Kutsumi, Keiji; Amadio, Peter C; Zhao, Chunfeng; Zobitz, Mark E; An, Kai-Nan

    2004-03-01

    The etiology of spontaneous extensor pollicis longus (EPL) tendon rupture is still largely unknown. It is possible that friction within the sheath may play a role. The purposes of this study were to compare gliding resistance of the EPL tendon with that of the extensor digitorum communis tendon of the index finger (EDC II) and to find the wrist position that gives the EPL tendon the lowest gliding resistance. Fifteen fresh-frozen cadavers were used. Gliding resistance was measured directly in 7 different wrist positions. The mean gliding resistance of the EPL tendon was 0.16 +/- 0.08 N and that of the EDC II tendon was 0.11 +/- 0.06 N. This difference was significant. There was also a significant effect on gliding resistance due to wrist position. For the EPL tendon, the gliding resistance was significantly greater in 60 degrees wrist flexion compared with all other wrist positions tested. Additionally the gliding resistance of the EPL in 30 degrees flexion, 60 degrees extension, and 15 degrees radial deviation was significantly higher than wrist positions of 30 degrees extension, neutral, and 30 degrees ulnar deviation. Positioning the wrist close to neutral flexion/extension and in some ulnar deviation minimizes the friction within the EPL sheath. Such positions may be advantageous for splinting patients at risk for EPL rupture.

  15. Water losses during technical snow production

    Science.gov (United States)

    Grünewald, Thomas; Wolfsperger, Fabian

    2017-04-01

    These days, the production of technical snow can be seen as a prerequisite for winter tourism. Huge amounts of water are used for technical snow production by ski resorts, especially in the beginning of the winter season. The aim is to guarantee an appropriate amount of snow to reliably provide optimal ski runs until the date of season opening in early December. Technical snow is generated by pumping pressurized water through the nozzles of a snow machine and dispersing the resulting spray of small water droplets which freeze during their travel to the ground. Cooling and freezing of the droplets can only happen if energy is emitted to the air mass surrounding the droplets. This heat transfer is happening through convective cooling and though evaporation and sublimation of water droplets and ice particles. This means that also mass is lost from the droplets and added in form of vapor to the air. It is important to note that not all water that is pumped through the snow machine is converted to snow distributed on the ground. Significant amounts of water are lost due to wind drift, sublimation and evaporation while droplets are traveling through the air or to draining of water which is not fully frozen when arriving at the ground. Studies addressing this question are sparse and the quantity of the water losses is still unclear. In order to assess this question in more detail, we obtained several systematic field observations at a test site near Davos, Switzerland. About a dozen of snow making tests had been performed during the last winter seasons. We compare the amount of water measured at the intake of the snow machine with the amount of snow accumulating at the ground during a night of snow production. The snow mass was calculated from highly detailed repeated terrestrial laser scanning measurements in combination with manually gathered snow densities. In addition a meteorological station had been set up in the vicinity observing all relevant meteorological

  16. How to determine wet-snow instability

    Science.gov (United States)

    Reiweger, Ingrid; Mitterer, Christoph

    2017-04-01

    Processes leading to wet-snow instability are very complex and highly non-linear in time and space. Infiltrating water changes wet-snow strength and other mechanical properties. A high liquid water content presumably favors fracture propagation, which consequently has an influence on the formation of wet slab avalanches. The weakening of snow due to liquid water within the snowpack might be gradual (melt event) or sudden (rain-on-snow event). There are several feedback mechanisms between liquid water and snow stratigraphy, making the weakening process complex. We used modelled stability indices to determine periods with high wet-snow instability. These indices were either based on energy and mass balances indicating critical amounts of water within the snowpack or on simple hydro-mechanical relationships. In addition to the modelled indices, preliminary field studies investigated the fracture initiation and fracture propagation propensity within wet snowpacks. We therefore performed Rutschblock and propagation saw tests in faceted weak layers with different volumetric liquid water contents. Results of simulations and field experiments showed that a critical amount of liquid water combined with a pre-critical snow stratigraphy were relevant for wet-snow instability. The critical amount of water was assumed to drive both failure initiation and fracture propagation. The simulated indices and observed stability tests indicated a high wet-snow instability when the volumetric liquid water content within faceted weak layers exceeded 3. Within our propagation saw test measurements crack propagation propensity even slightly decreased at very low liquid water contents compared to completely dry conditions, presumably due to capillary forces. For liquid water contents higher than 3-4%, however, crack propagation propensity strongly increased, which we assume was due to the weakening of bonds between grains within the increasingly wet weak snow layer. Our results could be used

  17. Central Asian Snow Cover from Hydrometeorological Surveys, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides observations of end of month snow depth, snow density, and snow water equivalent from three river basins in Central Asia: Amu Darya, Sir...

  18. Quantifying the impacts of snow on surface energy balance through assimilating snow cover fraction and snow depth

    Science.gov (United States)

    Meng, Chunlei

    2017-10-01

    Seasonal snow plays an important part in Earth's climate system. Snow cover regulates the land surface energy balance through altering the albedo of the land surface. To utilize the satellite-retrieved snow cover fraction (SCF) and snow depth (SD) data sufficiently and avoid inconsistency, this paper developed a very simple but robust quality control method to assimilate Fengyun satellite-retrieved SCF and SD simultaneously. The results show that the assimilation method which this paper implemented can not only utilize the satellite-retrieved SCF and SD data sufficiently but also avoid the inconsistency of them. Two experiments were designed and performed to quantify the impacts of snow on land surface energy balance using the integrated urban land model. With the increase of the SCF and SD, the net radiation decreased significantly during the day and increased a little at night; the sensible heat flux decreased significantly during the day; the evapotranspiration and ground heat flux decreased during the day too.

  19. Brilliant Colours from a White Snow Cover

    Science.gov (United States)

    Vollmer, Michael; Shaw, Joseph A

    2013-01-01

    Surprisingly colourful views are possible from sparkling white snow. It is well known that similarly colourful features can exist in the sky whenever appropriate ice crystals are around. However, the transition of light reflection and refraction from ice crystals in the air to reflection and refraction from those in snow on the ground is not…

  20. Cold, Ice, and Snow Safety (For Parents)

    Science.gov (United States)

    ... And protect your kids' faces with sunscreen. The idea of a sunburn in January can seem odd, but snow can reflect up to 85% of the sun's ultraviolet rays . Kids should dress warmly in layers of clothes. If the top layer gets wet from snow or freezing rain, they can peel off some clothes down to ...

  1. Prevent Snow from Blocking your Tailpipe

    Centers for Disease Control (CDC) Podcasts

    2014-12-11

    If it's snowing, make sure your vehicle’s tailpipe is clear of snow before starting the engine to prevent carbon monoxide poisoning.  Created: 12/11/2014 by National Center for Environmental Health (NCEH).   Date Released: 12/11/2014.

  2. Modelling stable atmospheric boundary layers over snow

    NARCIS (Netherlands)

    Sterk, H.A.M.

    2015-01-01

    Thesis entitled:

    Modelling Stable Atmospheric Boundary Layers over Snow

    H.A.M. Sterk

    Wageningen, 29th of April, 2015

    Summary

    The emphasis of this thesis is on the understanding and forecasting of the Stable Boundary Layer (SBL) over snow-covered surfaces. SBLs

  3. Comments on Nancy Snow, "Generativity and Flourishing"

    Science.gov (United States)

    Kamtekar, Rachana

    2015-01-01

    In her rich and wide-ranging paper, Nancy Snow argues that there is a virtue of generativity--an other-regarding desire to invest one's substance in forms of life and work that will outlive the self (p. 10). By "virtue" Snow means not just a desirable or praiseworthy quality of a person, but more precisely, as Aristotle defined it, a…

  4. Modelling stable atmospheric boundary layers over snow

    NARCIS (Netherlands)

    Sterk, H.A.M.

    2015-01-01

    Thesis entitled: Modelling Stable Atmospheric Boundary Layers over Snow H.A.M. Sterk Wageningen, 29th of April, 2015 Summary The emphasis of this thesis is on the understanding and forecasting of the Stable Boundary Layer (SBL) over snow-covered surfaces. SBLs typically form at night and in polar

  5. Major ions in spitsbergen snow samples

    International Nuclear Information System (INIS)

    Semb, A.; Braekkan, R.; Joranger, E.

    1984-01-01

    Chemical analysis of Spitsbergen snow cores sampled in spring 1983, reveals a spatial pattern consistent with orographic deposition of major anthropogenic pollutants with air movements from southeast towards northwest. The highest concentrations of pollutant species were found at an altitude of 700 metres above sea level, and are higher than for any other recorded snow samples from the Arctic

  6. Regime shift of snow days in Switzerland

    Science.gov (United States)

    Marty, Christoph

    2008-06-01

    The number of days with a snow depth above a certain threshold is the key factor for winter tourism in an Alpine country like Switzerland. An investigation of 34 long-term stations between 200 and 1800 m asl (above sea level) going back for at least the last 60 years (1948-2007) shows an unprecedented series of low snow winters in the last 20 years. The signal is uniform despite high regional differences. A shift detection analysis revealed a significant step-like decrease in snow days at the end of the 1980's with no clear trend since then. This abrupt change resulted in a loss of 20% to 60% of the total snow days. The stepwise increase of the mean winter temperature at the end of the 1980's and its close correlation with the snow day anomalies corroborate the sensitivity of the mid-latitude winter to the climate change induced temperature increase.

  7. Surface decontamination using dry ice snow

    International Nuclear Information System (INIS)

    Ryu, Jungdong; Park, Kwangheon; Lee, Bumsik; Kim Yangeun

    1999-01-01

    An adjustable nozzle for controlling the size of dry ice snow was developed. The converging/diverging nozzle can control the size of snows from sub-microns to 10 micron size. Using the nozzle, a surface decontamination device was made. The removal mechanisms of surface contaminants are mechanical impact, partial dissolving and evaporation process, and viscous flow. A heat supply system is added for the prevention of surface ice layer formation. The cleaning power is slightly dependent on the size of snow. Small snows are the better in viscous flow cleaning, while large snows are slightly better in dissolving and sublimation process. Human oils like fingerprints on glass were easy to remove. Decontamination ability was tested using a contaminated pump-housing surface. About 40 to 80% of radioactivity was removed. This device is effective in surface-decontamination of any electrical devices like detector, controllers which cannot be cleaned in aqueous solution. (author)

  8. The Snow Data System at NASA JPL

    Science.gov (United States)

    Horn, J.; Painter, T. H.; Bormann, K. J.; Rittger, K.; Brodzik, M. J.; Skiles, M.; Burgess, A. B.; Mattmann, C. A.; Ramirez, P.; Joyce, M.; Goodale, C. E.; McGibbney, L. J.; Zimdars, P.; Yaghoobi, R.

    2017-12-01

    The Snow Data System at NASA JPL includes data processing pipelines built with open source software, Apache 'Object Oriented Data Technology' (OODT). Processing is carried out in parallel across a high-powered computing cluster. The pipelines use input data from satellites such as MODIS, VIIRS and Landsat. They apply algorithms to the input data to produce a variety of outputs in GeoTIFF format. These outputs include daily data for SCAG (Snow Cover And Grain size) and DRFS (Dust Radiative Forcing in Snow), along with 8-day composites and MODICE annual minimum snow and ice calculations. This poster will describe the Snow Data System, its outputs and their uses and applications. It will also highlight recent advancements to the system and plans for the future.

  9. Boundary layer physics over snow and ice

    Directory of Open Access Journals (Sweden)

    P. S. Anderson

    2008-07-01

    Full Text Available Observations of the unique chemical environment over snow and ice in recent decades, particularly in the polar regions, have stimulated increasing interest in the boundary layer processes that mediate exchanges between the ice/snow interface and the atmosphere. This paper provides a review of the underlying concepts and examples from recent field studies in polar boundary layer meteorology, which will generally apply to atmospheric flow over snow and ice surfaces. It forms a companion paper to the chemistry review papers in this special issue of ACP that focus on processes linking halogens to the depletion of boundary layer ozone in coastal environments, mercury transport and deposition, snow photochemistry, and related snow physics. In this context, observational approaches, stable boundary layer behavior, the effects of a weak or absent diurnal cycle, and transport and mixing over the heterogeneous surfaces characteristic of coastal ocean environments are of particular relevance.

  10. Past and future of the Austrian snow cover - results from the CC-Snow project

    Science.gov (United States)

    Strasser, Ulrich; Marke, Thomas; Hanzer, Florian; Ragg, Hansjörg; Kleindienst, Hannes; Wilcke, Renate; Gobiet, Andreas

    2013-04-01

    This study has the goal to simulate the evolution of the Austrian snow cover from 1971 to 2050 by means of a coupled modelling scheme, and to estimate the effect of climate change on the evolution of the natural snow cover. The model outcomes are interepreted with focus on both the future natural snow conditions, and the effects on winter skiing tourism. Therefore the regional temperature-index snow model SNOWREG is applied, providing snow maps with a spatial resolution of 250 m. The model is trained by means of assimilating local measurements and observed natural snow cover patterns. Meteorological forcing consists of the output of four realizations of the ENSEMBLES project for the A1B emission scenario. The meteorological variables are downscaled and error corrected with a quantile based empirical-statistical method on a daily time basis. The control simulation is 1971-2000, and the scenario simulation 2021-2050. Spatial interpolation is performed on the basis of parameter-elevation relations. We compare the four different global/regional climate model combinations and their effect on the snow modelling, and we explain the patterns of the resulting snow cover by means of regional climatological characteristics. The provinces Tirol and Styria serve as test regions, being typical examples for the two climatic subregions of Austria. To support the interpretation of the simulation results we apply indicators which enable to define meaningful measures for the comparison of the different periods and regions. Results show that the mean duration of the snow cover will decrease by 15 to 30 days per winter season, mostly in elevations between 2000 and 2500 m. Above 3000 m the higher winter precipitation can compensate this effect, and mean snow cover duration may even slightly increase. We also investigate the local scale by application of the physically based mountain snow model AMUNDSEN. This model is capable of producing 50 m resolution output maps for indicators

  11. Water-cooled non-thermal gliding arc for adhesion improvement of glass-fibre-reinforced polyester

    DEFF Research Database (Denmark)

    Kusano, Yukihiro; Sørensen, Bent F.; Løgstrup Andersen, Tom

    2013-01-01

    A non-equilibrium quenched plasma is prepared using a gliding-arc discharge generated between diverging electrodes and extended by a gas flow. It can be operated at atmospheric pressure and applied to plasma surface treatment to improve adhesion properties of material surfaces. In this work, glass......-fibre-reinforced polyester plates were treated using an atmospheric pressure gliding-arc discharge with air flow to improve adhesion with a vinylester adhesive. The electrodes were water-cooled so as to operate the gliding arc continually. The treatment improved wettability and increased the density of oxygen......-containing polar functional groups on the surfaces. Double cantilever beam specimens were prepared for fracture mechanic characterization of the laminate adhesive interface. It was found that gliding-arc treatment significantly increases the fracture resistance in comparison with a standard peel-ply treatment....

  12. Improvement of a snow albedo parameterization in the Snow-Atmosphere-Soil Transfer model: evaluation of impacts of aerosol on seasonal snow cover

    Science.gov (United States)

    Zhong, Efang; Li, Qian; Sun, Shufen; Chen, Wen; Chen, Shangfeng; Nath, Debashis

    2017-11-01

    The presence of light-absorbing aerosols (LAA) in snow profoundly influence the surface energy balance and water budget. However, most snow-process schemes in land-surface and climate models currently do not take this into consideration. To better represent the snow process and to evaluate the impacts of LAA on snow, this study presents an improved snow albedo parameterization in the Snow-Atmosphere-Soil Transfer (SAST) model, which includes the impacts of LAA on snow. Specifically, the Snow, Ice and Aerosol Radiation (SNICAR) model is incorporated into the SAST model with an LAA mass stratigraphy scheme. The new coupled model is validated against in-situ measurements at the Swamp Angel Study Plot (SASP), Colorado, USA. Results show that the snow albedo and snow depth are better reproduced than those in the original SAST, particularly during the period of snow ablation. Furthermore, the impacts of LAA on snow are estimated in the coupled model through case comparisons of the snowpack, with or without LAA. The LAA particles directly absorb extra solar radiation, which accelerates the growth rate of the snow grain size. Meanwhile, these larger snow particles favor more radiative absorption. The average total radiative forcing of the LAA at the SASP is 47.5 W m-2. This extra radiative absorption enhances the snowmelt rate. As a result, the peak runoff time and "snow all gone" day have shifted 18 and 19.5 days earlier, respectively, which could further impose substantial impacts on the hydrologic cycle and atmospheric processes.

  13. Spatial and temporal variability in seasonal snow density

    KAUST Repository

    Bormann, Kathryn J.

    2013-03-01

    Snow density is a fundamental physical property of snowpacks used in many aspects of snow research. As an integral component in the remote sensing of snow water equivalent and parameterisation of snow models, snow density may be used to describe many important features of snowpack behaviour. The present study draws on a significant dataset of snow density and climate observations from the United States, Australia and the former Soviet Union and uses regression-based techniques to identify the dominant climatological drivers for snow densification rates, characterise densification rate variability and estimate spring snow densities from more readily available climate data. Total winter precipitation was shown to be the most prominent driver of snow densification rates, with mean air temperature and melt-refreeze events also found to be locally significant. Densification rate variance is very high at Australian sites, very low throughout the former Soviet Union and between these extremes throughout much of the US. Spring snow densities were estimated using a statistical model with climate variable inputs and best results were achieved when snow types were treated differently. Given the importance of snow density information in many snow-related research disciplines, this work has implications for current methods of converting snow depths to snow water equivalent, the representation of snow dynamics in snow models and remote sensing applications globally. © 2013 Elsevier B.V.

  14. The effects of one-dimensional glide on the reaction kinetics of interstitial clusters

    DEFF Research Database (Denmark)

    Heinisch, H.L.; Singh, B.N.; Golubov, S.I.

    2000-01-01

    is therefore 'mixed 1D/3D migration' along a 3D path consisting of 1D segments, The defect reaction kinetics under mixed 1D/3D diffusion are different from pure 1D diffusion and pure 3D diffusion, both of which can be formulated within analytical rate theory models of microstructure evolution under irradiation....... Atomic-scale kinetic Monte Carlo (kMC) defect migration simulations are used to investigate the effects of mixed 1D/3D migration on defect reaction kinetics as a guide for implementing mixed 1D/3D migration into the analytical rate theory. The functional dependence of the sink strength on the size......Collision cascades in metals produce small interstitial clusters and perfect dislocation loops that glide in thermally activated one-dimensional (1D) random walks. These gliding defects can change their Burgers vectors by thermal activation or by interactions with other defects. Their migration...

  15. Pulsating-gliding transition in the dynamics of levitating liquid nitorgen droplets.

    Energy Technology Data Exchange (ETDEWEB)

    Snezhko, A.; Jacob, E. B.; Aranson, I. S.; Materials Science Division; Tel-Aviv Univ.

    2008-04-21

    Hot surfaces can cause levitation of small liquid droplets if the temperature is kept above the Leidenfrost point (220 C for water) due to the pressure formed because of rapid evaporation. Here, we demonstrate a new class of pulsating-gliding dynamic transitions in a special setting of the Leidenfrost effect at room temperatures and above a viscous fluid for droplets of liquid nitrogen. A whole range of highly dynamic patterns unfolds when droplets of liquid nitrogen are poured on the surface of another, more viscous liquid at room temperature. We also discovered that the levitating droplets induce vortex motion in the supporting viscous liquid. Depending on the viscosity of the supporting liquid, the nitrogen droplets either adopt an oscillating (pulsating) star-like shape with different azimuthal symmetries (from 2-9 petals) or glide on the surface with random trajectories. Thus, by varying the viscosity of the supporting liquid, we achieve controlled morphology and dynamics of Leidenfrost droplets.

  16. Pulsating-gliding transition in the dynamics of levitating liquid nitrogen droplets

    Energy Technology Data Exchange (ETDEWEB)

    Snezhko, Alexey; Aranson, Igor S [Materials Science Division, Argonne National Laboratory, 9700 S Cass Avenue, Argonne, IL 60439 (United States); Jacob, Eshel Ben [School of Physics and Astronomy, 69978 Tel Aviv University, Tel Aviv (Israel)], E-mail: aranson@msd.anl.gov

    2008-04-15

    Hot surfaces can cause levitation of small liquid droplets if the temperature is kept above the Leidenfrost point (220 {sup 0}C for water) due to the pressure formed because of rapid evaporation. Here, we demonstrate a new class of pulsating-gliding dynamic transitions in a special setting of the Leidenfrost effect at room temperatures and above a viscous fluid for droplets of liquid nitrogen. A whole range of highly dynamic patterns unfolds when droplets of liquid nitrogen are poured on the surface of another, more viscous liquid at room temperature. We also discovered that the levitating droplets induce vortex motion in the supporting viscous liquid. Depending on the viscosity of the supporting liquid, the nitrogen droplets either adopt an oscillating (pulsating) star-like shape with different azimuthal symmetries (from 2-9 petals) or glide on the surface with random trajectories. Thus, by varying the viscosity of the supporting liquid, we achieve controlled morphology and dynamics of Leidenfrost droplets.

  17. Relationship between the electronic structure and the glide in the hexagonal close packed metals

    International Nuclear Information System (INIS)

    Legrand, B.; Le Hazif, R.

    1983-06-01

    In all hexagonal close-packed metals (HCP), deformation is performed by slip on a mean glide system (MGS) and on several secondary systems. There are no reliable predictions of the MGS choice. In this paper is shown the role played by the electronic structure on the choice of glide system in HCP metals. MGS is basal for all normal metals and is a function of the electron number in HCP transition metals. The different SFE's were calculated using appropriate total energy models, for different metals. Thus pseudopotentials were used (or empirical pair potentials) for normal metals, and a tight-binding model for transition metals. The most important results are the following: prismatic SFE (PSFE) is smaller than basal SFE (BSFE) for Y, Ti, Zr, Hf, Ru and Os; BSFE is smaller than PSFE for Co and all normal metals; BSFE and PSFe and about the same for RE and Tc

  18. Estimating Snow Water Storage in North America Using CLM4, DART, and Snow Radiance Data Assimilation

    Science.gov (United States)

    Kwon, Yonghwan; Yang, Zong-Liang; Zhao, Long; Hoar, Timothy J.; Toure, Ally M.; Rodell, Matthew

    2016-01-01

    This paper addresses continental-scale snow estimates in North America using a recently developed snow radiance assimilation (RA) system. A series of RA experiments with the ensemble adjustment Kalman filter are conducted by assimilating the Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) brightness temperature T(sub B) at 18.7- and 36.5-GHz vertical polarization channels. The overall RA performance in estimating snow depth for North America is improved by simultaneously updating the Community Land Model, version 4 (CLM4), snow/soil states and radiative transfer model (RTM) parameters involved in predicting T(sub B) based on their correlations with the prior T(sub B) (i.e., rule-based RA), although degradations are also observed. The RA system exhibits a more mixed performance for snow cover fraction estimates. Compared to the open-loop run (0.171m RMSE), the overall snow depth estimates are improved by 1.6% (0.168m RMSE) in the rule-based RA whereas the default RA (without a rule) results in a degradation of 3.6% (0.177mRMSE). Significant improvement of the snow depth estimates in the rule-based RA as observed for tundra snow class (11.5%, p < 0.05) and bare soil land-cover type (13.5%, p < 0.05). However, the overall improvement is not significant (p = 0.135) because snow estimates are degraded or marginally improved for other snow classes and land covers, especially the taiga snow class and forest land cover (7.1% and 7.3% degradations, respectively). The current RA system needs to be further refined to enhance snow estimates for various snow types and forested regions.

  19. Which stresses affect the glide of screw dislocations in bcc metals?

    Czech Academy of Sciences Publication Activity Database

    Gröger, Roman

    2014-01-01

    Roč. 94, č. 18 (2014), s. 2021-2030 ISSN 1478-6435 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068 Grant - others:Marie Curie Actions(CZ) 247705 MesoPhysDel Institutional support: RVO:68081723 Keywords : Peierls stress * screw dislocation * bcc metal * non-glide stress * yield criterion Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.825, year: 2014

  20. Can Road-Crossing Structures Improve Population Viability of an Urban Gliding Mammal?

    Directory of Open Access Journals (Sweden)

    Brendan D. Taylor

    2009-12-01

    Full Text Available Tree-dwelling mammals are potentially highly vulnerable to discontinuities in habitat created by roads. We used population modeling to assess the viability of a metapopulation of Australia's largest gliding marsupial, the greater glider (Petauroides volans, occurring in forest remnants in the fastest-urbanizing region of Australia, where habitat is dissected by major roads. Crossing structures for arboreal mammals (consisting of a land bridge with wooden poles for gliding and adjacent rope canopy bridges have been installed over an arterial road that separates two of these remnants (one large, one small. It is currently unknown whether this species will use the crossing structures, but available tree height and spacing do not allow a glide crossing, and fences with metal flashing prevent access to the road by terrestrial and arboreal mammals. Our modeling reveals that even a relatively low rate of dispersal facilitated by these structures would substantially reduce the probability of extinction of the smaller subpopulation. This rate of dispersal is plausible given the small distance involved (about 55 m. The inclusion of wildfire as a catastrophe in our model suggests that these two remnants may encounter an undesirable level of extinction risk. This can be reduced to an acceptable level by including inter-patch movement via dispersal among other forest remnants. However, this requires connection to a very large remnant 8 km away, through a set of remnants that straddle two motorways. These motorways create discontinuities in forest cover that are beyond the gliding ability of this species. Crossing structures will be required to enable inter-patch movement. A priority for future research should be whether the greater glider will use road-crossing structures. Loss of habitat and habitat connections is continuing in this landscape and is likely to have dire consequences for wildlife if land managers are unable to retain appropriate habitat cover

  1. Using physical models to study the gliding performance of extinct animals.

    Science.gov (United States)

    Koehl, M A R; Evangelista, Dennis; Yang, Karen

    2011-12-01

    Aerodynamic studies using physical models of fossil organisms can provide quantitative information about how performance of defined activities, such as gliding, depends on specific morphological features. Such analyses allow us to rule out hypotheses about the function of extinct organisms that are not physically plausible and to determine if and how specific morphological features and postures affect performance. The purpose of this article is to provide a practical guide for the design of dynamically scaled physical models to study the gliding of extinct animals using examples from our research on the theropod dinosaur, †Microraptor gui, which had flight feathers on its hind limbs as well as on its forelimbs. Analysis of the aerodynamics of †M. gui can shed light on the design of gliders with large surfaces posterior to the center of mass and provide functional information to evolutionary biologists trying to unravel the origins of flight in the dinosaurian ancestors and sister groups to birds. Measurements of lift, drag, side force, and moments in pitch, roll, and yaw on models in a wind tunnel can be used to calculate indices of gliding and parachuting performance, aerodynamic static stability, and control effectiveness in maneuvering. These indices permit the aerodynamic performance of bodies of different shape, size, stiffness, texture, and posture to be compared and thus can provide insights about the design of gliders, both biological and man-made. Our measurements of maximum lift-to-drag ratios of 2.5-3.1 for physical models of †M. gui suggest that its gliding performance was similar to that of flying squirrels and that the various leg postures that might have been used by †M. gui make little difference to that aspect of aerodynamic performance. We found that body orientation relative to the movement of air past the animal determines whether it is difficult or easy to maneuver.

  2. McKenzie treatment versus mulligan sustained natural apophyseal glides for chronic mechanical low back pain

    OpenAIRE

    Waqqar, Saira; Shakil-ur-Rehman, Syed; Ahmad, Shakeel

    2016-01-01

    Background and Objective: Chronic mechanical low back pain is common among different age groups and genders. Different manual therapy techniques combined with exercise therapy and electrotherapy modalities play an important role in its management. Our objective was to compare the effects of McKenzie extension exercisesprogram (EEP) versus Mulligan Sustained Natural Apophyseal Glides (SNAGs) for chronic mechanical low back pain (CMLBP). Methods: This randomized control trial (RCT) was conducte...

  3. Bonfils fiberscope vs GlideScope for awake intubation in morbidly obese patients with expected difficult airways.

    Science.gov (United States)

    Nassar, Mahmoud; Zanaty, Ola M; Ibrahim, Mohamed

    2016-08-01

    To assess the efficacy of both Bonfils and GlideScope in obese patient with difficult airways for bariatric surgery using awake intubation. Comparative study. Operating room. The study was carried out on 60 patients, for laparoscopic bariatric surgery, after approval of the Medical Ethics Committee and having an informed written consent from each patient. Patients were randomly categorized into 2 equal groups 30 patients in each group. Awake intubation with either Retromolar Bonfils or GlideScope. Time to visualize the laryngeal inlet, time of intubation, time of scope manipulation, success rate at each attempt, the lowest oxygen saturation, hemodynamic parameters, and any complication. Regarding intubation criteria, GlideScope achieves shorter times compared with Retromolar for visualization of the vocal cords and intubation, in addition to less intubation attempts, but both without a statistically significant difference. Retromolar shows better patient satisfaction than does GlideScope, with statistically significant difference. Both Bonfils fiberscope and the GlideScope can be successfully used for awake intubation in morbidly obese patients with expected difficult airways. Bonfils intubating fiberscope was more tolerated by patients with statistical difference; on the other hand, GlideScope provided shorter intubation time and less intubation attempts but not statistically significant. Copyright © 2016 Elsevier Inc. All rights reserved.

  4. Shape optimization of blended-wing-body underwater glider by using gliding range as the optimization target

    Directory of Open Access Journals (Sweden)

    Chunya Sun

    2017-11-01

    Full Text Available Blended-Wing-Body Underwater Glider (BWBUG, which has excellent hydrodynamic performance, is a new kind of underwater glider in recent years. In the shape optimization of BWBUG, the lift to drag ratio is often used as the optimization target. However this results in lose of internal space. In this paper, the energy reserve is defined as the direct proportional function of the internal space of BWBUG. A motion model, which relates gliding range to steady gliding motion parameters as well as energy consumption, is established by analyzing the steady-state gliding motion. The maximum gliding range is used as the optimization target instead of the lift to drag ratio to optimizing the shape of BWBUG. The result of optimization shows that the maximum gliding range of initial design is increased by 32.1% though an Efficient Global Optimization (EGO process. Keywords: Blended-wing-body underwater glider, Shape optimization, Gliding range, Energy consumption model, Lift to drag ratio

  5. Anteroposterior glide versus rotating platform low contact stress (LCS knee arthroplasty: a randomised controlled trial

    Directory of Open Access Journals (Sweden)

    Wynn-Jones Charles

    2007-08-01

    Full Text Available Abstract Background Fifty thousand knee replacements are performed annually in the UK at an estimated cost of £150 million. Post-operative improvement depends on a number of factors including implant design and patient associated factors. To our knowledge there are no published study's comparing the results of AP glide and rotating platform designs of LCS knee arthroplasty. Therefore we feel that a study is required to investigate and compare the effects of two types of LCS total knee arthroplasty on joint proprioception and range of motion. Methods/Design Patients will be randomised to receive either a LCS AP glide or Rotating platform prosthesis. Clinical scores (Oxford knee score, American knee society score, EuroQol, range of motion and proprioception will be assessed prior to and at 3,6, 12 and 24 months after the operation. Proprioception will be assessed in terms of absolute error angle (mean difference between the target angle and the response angle. Knee angles will be measured in degrees using an electromagnetic tracking device, Polhemus 3Space Fastrak that detects positions of sensors placed on the test limb. Student's t-test will be used to compare the mean of two groups. Discussion Evidence is lacking concerning the best prosthesis to use for patients undergoing total knee replacement. This pragmatic randomised trial will test the null hypothesis that anteroposterior glide LCS knee arthroplasty does not result in better post operative knee motion and proprioception as compared to rotating platform LCS knee. Trial Registration ISRCTN52943804

  6. Use of glide-ins in CMS for production and analysis

    CERN Document Server

    Bradley, D; Hahn, K; Holzman, B; Padhi, S; Pi, H; Spiga, D; Sfiligoi, I; Vaandering, E; Würthwein, F

    2010-01-01

    With the evolution of various grid federations, the Condor glide-ins represent a key feature in providing a homogeneous pool of resources using late-binding technology. The CMS collaboration uses the glide-in based Workload Management System, glideinWMS, for production (ProdAgent) and distributed analysis (CRAB) of the data. The Condor glide-in daemons traverse to the worker nodes, submitted via Condor-G. Once activated, they preserve the Master-Worker relationships, with the worker first validating the execution environment on the worker node before pulling the jobs sequentially until the expiry of their lifetimes. The combination of late-binding and validation significantly reduces the overall failure rate visible to CMS physicists. We discuss the extensive use of the glideinWMS since the computing challenge, CCRC-08, in order to prepare for the forthcoming LHC data-taking period. The key features essential to the success of large-scale production and analysis on CMS resources across major grid federations,...

  7. A theoretical analysis of pitch stability during gliding in flying snakes.

    Science.gov (United States)

    Jafari, Farid; Ross, Shane D; Vlachos, Pavlos P; Socha, John J

    2014-06-01

    Flying snakes use their entire body as a continuously morphing 'wing' to produce lift and shallow their glide trajectory. Their dominant behavior during gliding is aerial undulation, in which lateral waves are sent posteriorly down the body. This highly dynamic behavior, which is unique among animal gliders, should have substantial effects on the flight dynamics and stability of the snakes, resulting from the continuous redistribution of mass and aerodynamic forces. In this study, we develop two-dimensional theoretical models to assess the stability characteristics of snakes in the pitch direction. Previously measured force coefficients are used to simulate aerodynamic forces acting on the models, and undulation is simulated by varying mass. Model 1 is a simple three-airfoil representation of the snake's body that possesses a passively stable equilibrium solution, whose basin of stability contains initial conditions observed in experimental gliding trajectories. Model 2 is more sophisticated, with more degrees of freedom allowing for postural changes to better represent the snake's real kinematics; in addition, a restoring moment is added to simulate potential active control. The application of static and dynamic stability criteria show that Model 2 is passively unstable, but can be stabilized with a restoring moment. Overall, these models suggest that undulation does not contribute to stability in pitch, and that flying snakes require a closed-loop control system formed around a passively stable dynamical framework.

  8. A theoretical analysis of pitch stability during gliding in flying snakes

    International Nuclear Information System (INIS)

    Jafari, Farid; Ross, Shane D; Socha, John J; Vlachos, Pavlos P

    2014-01-01

    Flying snakes use their entire body as a continuously morphing ‘wing’ to produce lift and shallow their glide trajectory. Their dominant behavior during gliding is aerial undulation, in which lateral waves are sent posteriorly down the body. This highly dynamic behavior, which is unique among animal gliders, should have substantial effects on the flight dynamics and stability of the snakes, resulting from the continuous redistribution of mass and aerodynamic forces. In this study, we develop two-dimensional theoretical models to assess the stability characteristics of snakes in the pitch direction. Previously measured force coefficients are used to simulate aerodynamic forces acting on the models, and undulation is simulated by varying mass. Model 1 is a simple three-airfoil representation of the snake’s body that possesses a passively stable equilibrium solution, whose basin of stability contains initial conditions observed in experimental gliding trajectories. Model 2 is more sophisticated, with more degrees of freedom allowing for postural changes to better represent the snake’s real kinematics; in addition, a restoring moment is added to simulate potential active control. The application of static and dynamic stability criteria show that Model 2 is passively unstable, but can be stabilized with a restoring moment. Overall, these models suggest that undulation does not contribute to stability in pitch, and that flying snakes require a closed-loop control system formed around a passively stable dynamical framework. (papers)

  9. Prosodic effects on glide-vowel sequences in three Romance languages

    Science.gov (United States)

    Chitoran, Ioana

    2004-05-01

    Glide-vowel sequences occur in many Romance languages. In some they can vary in production, ranging from diphthongal pronunciation [ja,je] to hiatus [ia,ie]. According to native speakers' impressionistic perceptions, Spanish and Romanian both exhibit this variation, but to different degrees. Spanish favors glide-vowel sequences, while Romanian favors hiatus, occasionally resulting in different pronunciations of the same items: Spanish (b[j]ela, ind[j]ana), Romanian (b[i]ela, ind[i]ana). The third language, French, has glide-vowel sequences consistently (b[j]elle). This study tests the effect of position in the word on the acoustic duration of the sequences. Shorter duration indicates diphthong production [jV], while longer duration, hiatus [iV]. Eleven speakers (4 Spanish, 4 Romanian, 3 French), were recorded. Spanish and Romanian showed a word position effect. Word-initial sequences were significantly longer than word-medial ones (p0.05). In the Spanish and Romanian sentences, V in the sequence bears pitch accent, but not in French. It is therefore possible that duration is sensitive not to the presence/absence of the word boundary, but to its position relative to pitch accent. The results suggest that the word position effect is crucially enhanced by pitch accent on V.

  10. Dragonfly flight. I. Gliding flight and steady-state aerodynamic forces.

    Science.gov (United States)

    Wakeling, JM; Ellington, CP

    1997-02-01

    The free gliding flight of the dragonfly Sympetrum sanguineum was filmed in a large flight enclosure. Reconstruction of the glide paths showed the flights to involve accelerations. Where the acceleration could be considered constant, the lift and drag forces acting on the dragonfly were calculated. The maximum lift coefficient (CL) recorded from these glides was 0.93; however, this is not necessarily the maximum possible from the wings. Lift and drag forces were additionally measured from isolated wings and bodies of S. sanguineum and the damselfly Calopteryx splendens in a steady air flow at Reynolds numbers of 700-2400 for the wings and 2500-15 000 for the bodies. The maximum lift coefficients (CL,max) were 1.07 for S. sanguineum and 1.15 for C. splendens, which are greater than those recorded for all other insects except the locust. The drag coefficient at zero angle of attack ranged between 0.07 and 0.14, being little more than the Blassius value predicted for flat plates. Dragonfly wings thus show exceptional steady-state aerodynamic properties in comparison with the wings of other insects. A resolved-flow model was tested on the body drag data. The parasite drag is significantly affected by viscous forces normal to the longitudinal body axis. The linear dependence of drag on velocity must thus be included in models to predict the parasite drag on dragonflies at non-zero body angles.

  11. Spinless Weyl semimetals and Z2 topological crystalline insulator with glide symmetry

    Science.gov (United States)

    Kim, Heejae; Murakami, Shuichi

    A topological crystalline insulator (TCI) is one of the symmetry protected topological phases protected by crystalline symmetries such as rotational symmetry, mirror symmetry etc. In recent works, a new class of three-dimensional (3D) Z2 TCI with a nonsymmorphic glide plane symmetry is theoretically predicted both for spinless and spinfull systems. Our study shows that a spinless Weyl semimetal (WSM) phase always emerges between a normal insulator (NI) and TCI phases transition in general glide symmetric spinless systems. In particular, we find how the Z2 topological invariant is changed by pair creations and pair annihilations of Weyl nodes in general phase transition. To confirm this scenario, we introduce a simple spinless tight-binding model on a 3D rectangular lattice with two sublattices and two orbitals with glide plane symmetry. Using this model, we show that the spinless WSM phase emerges between the NI and TCI phases, and the changing of Z2 topological invariant comes from the behavior of Weyl nodes. Our numerical calculation also shows that surface Fermi arcs in the spinless WSM phase evolve into a surface Dirac cone in the TCI phase.

  12. Dynamic Modeling & Stability Analysis of a Generic UAV in Glide Phase

    Directory of Open Access Journals (Sweden)

    Mir Imran

    2017-01-01

    Full Text Available In this paper, we present dynamic modelling and stability analysis of a generic UAV in the glide phase under engine failure condition. When such extreme phenomena occurs, the most desirable requirement is to survive that stage by keeping the vehicle controllable by maintaining its orientation and to glide the vehicle towards the intended direction with maximum extended range. This study investigates the stability aspects of one such aerial vehicle under engine failure condition. In the proposed architecture, a six degree of freedom vehicle dynamic simulation model is implemented through a set of coupled non-linear differential equations. The aerodynamic forces and moments encountered by the UAV during various phases of the flight are ascertained through empirical / non-empirical techniques. Non-linear constrained optimization technique is employed to evaluate the steady state values of the optimized trajectory for the complete flight regime. Results from dynamical systems theory are applied to investigate local stability characteristics of UAV around the steady state. Complete set of dynamic modes of UAV throughout the glide phase are evaluated and mode content in each of the motion variable is determined using modal decomposition technique. The dynamic characteristics of the open-loop configuration are assessed to generate adequate benchmark performance for closed-loop controller design

  13. Mac OS X Snow Leopard pocket guide

    CERN Document Server

    Seiblod, Chris

    2009-01-01

    Whether you're new to the Mac or a longtime user, this handy book is the quickest way to get up to speed on Snow Leopard. Packed with concise information in an easy-to-read format, Mac OS X Snow Leopard Pocket Guide covers what you need to know and is an ideal resource for problem-solving on the fly. This book goes right to the heart of Snow Leopard, with details on system preferences, built-in applications, and utilities. You'll also find configuration tips, keyboard shortcuts, guides for troubleshooting, lots of step-by-step instructions, and more. Learn about new features and changes s

  14. Distribution of Snow and Maximum Snow Water Equivalent Obtained by LANDSAT Data and Degree Day Method

    Science.gov (United States)

    Takeda, K.; Ochiai, H.; Takeuchi, S.

    1985-01-01

    Maximum snow water equivalence and snowcover distribution are estimated using several LANDSAT data taken in snowmelting season over a four year period. The test site is Okutadami-gawa Basin located in the central position of Tohoku-Kanto-Chubu District. The year to year normalization for snowmelt volume computation on the snow line is conducted by year to year correction of degree days using the snowcover percentage within the test basin obtained from LANDSAT data. The maximum snow water equivalent map in the test basin is generated based on the normalized snowmelt volume on the snow line extracted from four LANDSAT data taken in a different year. The snowcover distribution on an arbitrary day in snowmelting of 1982 is estimated from the maximum snow water equivalent map. The estimated snowcover is compared with the snowcover area extracted from NOAA-AVHRR data taken on the same day. The applicability of the snow estimation using LANDSAT data is discussed.

  15. Estimation of snow cover distribution in Beas basin, Indian Himalaya ...

    Indian Academy of Sciences (India)

    of snow cover in the study area are snow under vegetation, contaminated snow and patchy snow. To overcome these problems, ... using planetary reflectance), NIR band reflectance and forest/vegetation cover information. The satellite estimated ... exerts an influence on hydropower generation sys- tem, water management ...

  16. (NDSI) and Normalised Difference Principal Component Snow Index

    African Journals Online (AJOL)

    Phila Sibandze

    overview of some the common remote sensing datasets and methods used in snow mapping. One of the most successful image based snow mapping techniques is the Normalized Difference Snow. Index (NDSI) proposed Hall et al. (2001). This technique exploits the ratio between snow's high reflectance and strong ...

  17. Spatiotemporal variability of snow cover and snow water equivalent in the last three decades over Eurasia

    Science.gov (United States)

    Zhang, Yinsheng; Ma, Ning

    2018-04-01

    Changes in the extent and amount of snow cover in Eurasia are of great interest because of their vital impacts on the global climate system and regional water resource management. This study investigated the spatial and temporal variability of the snow cover extent (SCE) and snow water equivalent (SWE) of the continental Eurasia using the Northern Hemisphere Equal-Area Scalable Earth Grid (EASE-Grid) Weekly SCE data for 1972-2006 and the Global Monthly EASE-Grid SWE data for 1979-2004. The results indicated that, in general, the spatial extent of snow cover significantly decreased during spring and summer, but varied little during autumn and winter over Eurasia in the study period. The date at which snow cover began to disappear in spring has significantly advanced, whereas the timing of snow cover onset in autumn did not vary significantly during 1972-2006. The snow cover persistence period declined significantly in the western Tibetan Plateau as well as partial area of Central Asia and northwestern Russia, but varied little in other parts of Eurasia. "Snow-free breaks" (SFBs) with intermittent snow cover in the cold season were principally observed in the Tibetan Plateau and Central Asia, causing a low sensitivity of snow cover persistence period to the timings of snow cover onset and disappearance over the areas with shallow snow. The averaged SFBs were 1-14 weeks during the study period and the maximum intermittence could even reach 25 weeks in certain years. At a seasonal scale, SWE usually peaked in February or March, but fell gradually since April across Eurasia. Both annual mean and annual maximum SWE decreased significantly during 1979-2004 in most parts of Eurasia except for eastern Siberia as well as northwestern and northeastern China. The possible cross-platform inconsistencies between two passive microwave radiometers may cause uncertainties in the detected trends of SWE here, suggesting an urgent need of producing a long-term, more homogeneous SWE

  18. Simulating snow maps for Norway: description and statistical evaluation of the seNorge snow model

    Directory of Open Access Journals (Sweden)

    T. M. Saloranta

    2012-11-01

    Full Text Available Daily maps of snow conditions have been produced in Norway with the seNorge snow model since 2004. The seNorge snow model operates with 1 × 1 km resolution, uses gridded observations of daily temperature and precipitation as its input forcing, and simulates, among others, snow water equivalent (SWE, snow depth (SD, and the snow bulk density (ρ. In this paper the set of equations contained in the seNorge model code is described and a thorough spatiotemporal statistical evaluation of the model performance from 1957–2011 is made using the two major sets of extensive in situ snow measurements that exist for Norway. The evaluation results show that the seNorge model generally overestimates both SWE and ρ, and that the overestimation of SWE increases with elevation throughout the snow season. However, the R2-values for model fit are 0.60 for (log-transformed SWE and 0.45 for ρ, indicating that after removal of the detected systematic model biases (e.g. by recalibrating the model or expressing snow conditions in relative units the model performs rather well. The seNorge model provides a relatively simple, not very data-demanding, yet nonetheless process-based method to construct snow maps of high spatiotemporal resolution. It is an especially well suited alternative for operational snow mapping in regions with rugged topography and large spatiotemporal variability in snow conditions, as is the case in the mountainous Norway.

  19. Modeling the influence of snow cover temperature and water content on wet-snow avalanche runout

    Science.gov (United States)

    Valero, Cesar Vera; Wever, Nander; Christen, Marc; Bartelt, Perry

    2018-03-01

    Snow avalanche motion is strongly dependent on the temperature and water content of the snow cover. In this paper we use a snow cover model, driven by measured meteorological data, to set the initial and boundary conditions for wet-snow avalanche calculations. The snow cover model provides estimates of snow height, density, temperature and liquid water content. This information is used to prescribe fracture heights and erosion heights for an avalanche dynamics model. We compare simulated runout distances with observed avalanche deposition fields using a contingency table analysis. Our analysis of the simulations reveals a large variability in predicted runout for tracks with flat terraces and gradual slope transitions to the runout zone. Reliable estimates of avalanche mass (height and density) in the release and erosion zones are identified to be more important than an exact specification of temperature and water content. For wet-snow avalanches, this implies that the layers where meltwater accumulates in the release zone must be identified accurately as this defines the height of the fracture slab and therefore the release mass. Advanced thermomechanical models appear to be better suited to simulate wet-snow avalanche inundation areas than existing guideline procedures if and only if accurate snow cover information is available.

  20. The significance of vertical moisture diffusion on drifting snow sublimation near snow surface

    Science.gov (United States)

    Huang, Ning; Shi, Guanglei

    2017-12-01

    Sublimation of blowing snow is an important parameter not only for the study of polar ice sheets and glaciers, but also for maintaining the ecology of arid and semi-arid lands. However, sublimation of near-surface blowing snow has often been ignored in previous studies. To study sublimation of near-surface blowing snow, we established a sublimation of blowing snow model containing both a vertical moisture diffusion equation and a heat balance equation. The results showed that although sublimation of near-surface blowing snow was strongly reduced by a negative feedback effect, due to vertical moisture diffusion, the relative humidity near the surface does not reach 100 %. Therefore, the sublimation of near-surface blowing snow does not stop. In addition, the sublimation rate near the surface is 3-4 orders of magnitude higher than that at 10 m above the surface and the mass of snow sublimation near the surface accounts for more than half of the total snow sublimation when the friction wind velocity is less than about 0.55 m s-1. Therefore, the sublimation of near-surface blowing snow should not be neglected.

  1. Measured Black Carbon Deposition on the Sierra Nevada Snow Pack and Implication for Snow Pack Retreat

    Energy Technology Data Exchange (ETDEWEB)

    Hadley, O.L.; Corrigan, C.E.; Kirchstetter, T.W.; Cliff, S.S.; Ramanathan, V.

    2010-01-12

    Modeling studies show that the darkening of snow and ice by black carbon deposition is a major factor for the rapid disappearance of arctic sea ice, mountain glaciers and snow packs. This study provides one of the first direct measurements for the efficient removal of black carbon from the atmosphere by snow and its subsequent deposition to the snow packs of California. The early melting of the snow packs in the Sierras is one of the contributing factors to the severe water problems in California. BC concentrations in falling snow were measured at two mountain locations and in rain at a coastal site. All three stations reveal large BC concentrations in precipitation, ranging from 1.7 ng/g to 12.9 ng/g. The BC concentrations in the air after the snow fall were negligible suggesting an extremely efficient removal of BC by snow. The data suggest that below cloud scavenging, rather than ice nuclei, was the dominant source of BC in the snow. A five-year comparison of BC, dust, and total fine aerosol mass concentrations at multiple sites reveals that the measurements made at the sampling sites were representative of large scale deposition in the Sierra Nevada. The relative concentration of iron and calcium in the mountain aerosol indicates that one-quarter to one-third of the BC may have been transported from Asia.

  2. Snow cover as a source of technogenic pollution of surface water during the snow melting period

    Directory of Open Access Journals (Sweden)

    Labuzova Olga

    2016-10-01

    Full Text Available The study of pollutants in melt water of snow cover and snow disposal sites in the city of Barnaul showed that during the snow melting period the surface water is not subjected to significant technogenic impact according to a number of studied indices. The oils content is an exception: it can exceed MAC more than 20 times in river- water due to the melting of city disposal sites. Environmental damage due to an oils input into water resources during the snow melting period can be more than 300000 thousand rubles.

  3. Central Asian Snow Cover from Hydrometeorological Surveys

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Central Asian Snow Cover from Hydrometeorological Surveys data are based on observations made by personnel for three river basins: Amu Darya, Sir Darya, and...

  4. Mount Everest snow plume: A case study

    Science.gov (United States)

    Moore, G. W. K.

    2004-11-01

    A plume of snow blowing from the summit of Mount Everest is one of the most iconic images of the world's highest mountain. Its presence provides evidence of the strong jet stream winds that can buffet the mountain. In January 2004, astronauts onboard the International Space Station (ISS) observed a 15 to 20 km long snow plume emanating from the summit of Mount Everest. Remarkably little is known about these plumes and the role that they play in the redistribution of snow in the high Himalaya. In this paper we use a variety of meteorological datasets to show that the observed plume was the combination of high winds associated with the East Asian Jet Stream (EAJS) and a heavy snowfall that had occurred over the Himalaya during the preceding week. A simple model of a blown snow plume is shown to be consistent with the observations made from the ISS.

  5. Optimization of snow removal in Vermont.

    Science.gov (United States)

    2013-08-01

    The purpose of this report is to document the research activi : ties performed under project SPR : - : RAC : - : 727 for the : State of Vermont, Agency of Transportation, Materials & Research Section entitled Optimization of Snow Removal : in Verm...

  6. Rand Corporation Mean Monthly Global Snow Depth

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — All available monthly snow depth climatologies were integrated by the Rand Corporation, in the early 1980s, into one global (excluding Africa and South America)...

  7. CLPX-Ground: ISA Snow Pit Measurements

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set consists of snow pit data from nine study areas, within three larger-scale areas in northern Colorado (Fraser, North Park, and Rabbit Ears Meso-cell...

  8. CLPX-Ground: ISA Snow Depth Transects

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set is part of the NASA Cold Land Processes Field Experiment (CLPX). Parameters include snow depth, surface wetness, surface roughness, canopy, and soil...

  9. SNOW CLEARING SERVICE WINTER 2001-2002

    CERN Multimedia

    ST-HM Group; Tel. 72202

    2001-01-01

    As usual at this time of the year, the snowing clearing service, which comes under the control of the Transport Group (ST-HM), is preparing for the start of snow-clearing operations (timetable, stand-by service, personnel responsible for driving vehicles and machines, preparation of useful and necessary equipment, work instructions, etc.) in collaboration with the Cleaning Service (ST-TFM) and the Fire Brigade (TIS-FB). The main difficulty for the snow-clearing service is the car parks, which cannot be properly cleared because of the presence of CERN and private vehicles parked there overnight in different parts of the parking areas. The ST-HM Transport Group would therefore like to invite you to park vehicles together in order to facilitate the access of the snow ploughs, thus allowing the car parks to be cleared more efficiently before the personnel arrives for work in the mornings.

  10. Spectral reflectance characteristics of different snow and snow-covered land surface objects and mixed spectrum fitting

    Science.gov (United States)

    Zhang, J.-H.; Zhou, Z.-M.; Wang, P.-J.; Yao, F.-M.; Yang, L.

    2011-01-01

    The field spectroradiometer was used to measure spectra of different snow and snow-covered land surface objects in Beijing area. The result showed that for a pure snow spectrum, the snow reflectance peaks appeared from visible to 800 nm band locations; there was an obvious absorption valley of snow spectrum near 1030 nm wavelength. Compared with fresh snow, the reflection peaks of the old snow and melting snow showed different degrees of decline in the ranges of 300~1300, 1700~1800 and 2200~2300 nm, the lowest was from the compacted snow and frozen ice. For the vegetation and snow mixed spectral characteristics, it was indicated that the spectral reflectance increased for the snow-covered land types(including pine leaf with snow and pine leaf on snow background), due to the influence of snow background in the range of 350~1300 nm. However, the spectrum reflectance of mixed pixel remained a vegetation spectral characteristic. In the end, based on the spectrum analysis of snow, vegetation, and mixed snow/vegetation pixels, the mixed spectral fitting equations were established, and the results showed that there was good correlation between spectral curves by simulation fitting and observed ones(correlation coefficient R2=0.9509).

  11. Frontal Dynamics of Powder Snow Avalanches

    Science.gov (United States)

    Louge, M. Y.; Carroll, C. S.; Turnbull, B.

    2012-04-01

    We model the dynamics of the head of dilute powder snow avalanches sustained by a massive frontal blow-out, arising as a weakly cohesive snow cover is fluidized by the very pore pressure gradients that the avalanche induces within the snow pack. Such material eruption just behind the front acts as a source of denser fluid thrust into a uniform ambient air flow at high Reynolds number. In such "eruption current", fluidization depth is inversely proportional to a bulk Richardson number representing avalanche height. By excluding situations in which the snow cover is not fluidized up to its free surface, we derive a criterion combining snow pack friction and density indicating which avalanches can produce a sustainable powder cloud. A mass balance involving snow cover and powder cloud sets avalanche height and mean density. By determining which solution of the mass balance is stable, we find that avalanches reach constant growth and acceleration rates for fixed slope and avalanche width. Under these conditions, we calculate the fraction of the fluidized cover that is actually scoured and blown-out into the cloud, and deduce from a momentum balance on the head that the avalanche accelerates at a rate only 14% of the gravitational component along the flow. We also calculate how far a powder cloud travels until its mean density becomes constant. Finally, we show that the dynamics of powder snow avalanches are crucially affected by the rate of change of their width, for example by reaching an apparent steady speed as their channel widens. If such widening is rapid, or if slope inclination vanishes, we calculate where and how powder clouds collapse. Predictions agree well with observations of powder snow avalanches carried out at the Vallee de la Sionne (Switzerland).

  12. Erosion dynamics of powder snow avalanches - Observations

    Science.gov (United States)

    Sovilla, Betty; Louge, Michel

    2013-04-01

    Powder snow avalanches (PSA) entrain massive amounts of material from the underlying snow cover by erosion mechanisms that are not fully understood. Despite their inherent diversity, PSAs have recognizable flow features: they are fast, reaching velocity up to 80 m/s, they develop a tall, low density powder cloud and, at the same time, they can exert impact pressure with similar magnitudes of high density flow. In this talk, we report observations that underscore the interplay between entrainment and flow dynamics qualitatively shared by several PSAs at the Vallée de la Sionne test site in Switzerland. Measurements include time-histories of snow pack thickness with buried FMCW radar and time-histories of particle velocity using optical sensors, cloud density and cluster size using capacitance probes, and impact pressure measured at several elevations on a pylon. Measurements show that, at the avalanche front, a layer of light, cold and cohesionless snow is rapidly entrained, creating a turbulent and stratified head region with intermittent snow clusters. Fast and localized entrainment of deeper and warmer snow layers may also occur well behind the front, up to a distance of hundreds of meters, where pronounced stratification appears and snow clusters grow larger. In the avalanche head, impact pressure strongly fluctuates and is larger near the ground. Velocity profiles change throughout the avalanche head, with more abrupt changes localized where rapid entrainment occurs. A basal, continuous dense layer forms as deeper, warmer and denser snow cover is entrained and as suspended material starts to deposit. The thickness of the basal layer progressively increases toward the avalanche tail where, finally, deposition occurs en masse. Toward the avalanche tail, velocity profiles tend to become uniform, impact pressures are lower and nearly constant, while entrainment processes are negligible. These observations underscore the relevance of entrainment location and the

  13. Snow management practices in French ski resorts

    Science.gov (United States)

    Spandre, Pierre; Francois, Hugues; George-Marcelpoil, Emmanuelle; Morin, Samuel

    2016-04-01

    Winter tourism plays a fundamental role in the economy of French mountain regions but also in other countries such as Austria, USA or Canada. Ski operators originally developed grooming methods to provide comfortable and safe skiing conditions. The interannual variability of snow conditions and the competition with international destinations and alternative tourism activities encouraged ski resorts to mitigate their dependency to weather conditions through snowmaking facilities. However some regions may not be able to produce machine made snow due to inadequate conditions and low altitude resorts are still negatively impacted by low snow seasons. In the meantime, even though the operations of high altitude resorts do not show any dependency to the snow conditions they invest in snowmaking facilities. Such developments of snowmaking facilities may be related to a confused and contradictory perception of climate change resulting in individualistic evolutions of snowmaking facilities, also depending on ski resorts main features such as their altitude and size. Concurrently with the expansion of snowmaking facilities, a large range of indicators have been used to discuss the vulnerability of ski resorts such as the so-called "100 days rule" which was widely used with specific thresholds (i.e. minimum snow depth, dates) and constraints (i.e. snowmaking capacity). The present study aims to provide a detailed description of snow management practices and major priorities in French ski resorts with respect to their characteristics. We set up a survey in autumn 2014, collecting data from 56 French ski operators. We identify the priorities of ski operators and describe their snowmaking and grooming practices and facilities. The operators also provided their perception of the ski resort vulnerability to snow and economic challenges which we could compare with the actual snow conditions and ski lift tickets sales during the period from 2001 to 2012.

  14. Snow darkening caused by black carbon emitted from fires

    Science.gov (United States)

    Engels, Jessica; Kloster, Silvia; Bourgeois, Quentin

    2014-05-01

    We implemented the effect of snow darkening caused by black carbon (BC) emitted from forest fires into the Max Planck Institute for Meteorology Earth System Model (MPI-M ESM) to estimate its potential climate impact of present day fire occurrence. Considerable amounts of black carbon emitted from fires are transported into snow covered regions. Already very small quantities of black carbon reduce the snow reflectance, with consequences for snow melting and snow spatial coverage. Therefore, the SNICAR (SNow And Ice Radiation) model (Flanner and Zender (2005)) is implemented in the land surface component (JSBACH) of the atmospheric general circulation model ECHAM6, developed at the MPI-M. The SNICAR model includes amongst other processes a complex calculation of the snow albedo depending on black carbon in snow and snow grain growth depending on water vapor fluxes for a five layer snow scheme. For the implementation of the SNICAR model into the one layer scheme of ECHAM6-JSBACH, we used the SNICAR-online version (http://snow.engin.umich.edu). This single-layer simulator provides the albedo of snow for selectable combinations of impurity content (e.g. black carbon), snow grain size, and incident solar flux characteristics. From this scheme we derived snow albedo values for black carbon in snow concentrations ranging between 0 and 1500 ng(BC)/g(snow) and for different snow grain sizes for the visible (0.3 - 0.7 µm) and near infrared range (0.7 - 1.5 µm). As snow grains grow over time, we assign different snow ages to different snow grain sizes (50, 150, 500, and 1000 µm). Here, a radius of 50 µm corresponds to new snow, whereas a radius of 1000 µm corresponds to old snow. The required snow age is taken from the BATS (Biosphere Atmosphere Transfer Scheme, Dickinson et al. (1986)) snow albedo implementation in ECHAM6-JSBACH. Here, we will present an extended evaluation of the model including a comparison of modeled black carbon in snow concentrations to observed

  15. Volcanic deposits in Antarctic snow and ice

    Science.gov (United States)

    Delmas, Robert J.; Legrand, Michel; Aristarain, Alberto J.; Zanolini, FrançOise

    1985-12-01

    Major volcanic eruptions are able to spread large amounts of sulfuric acid all over the world. Acid layers of volcanic origin were detected for the first time a few years ago by Hammer in Greenland ice. The present paper deals with volcanic deposits in the Antarctic. The different methods that can be used to find volcanic acid deposits in snow and ice cores are compared: electrical conductivity, sulfate, and acidity measurements. Numerous snow and ice samples collected at several Antarctic locations were analyzed. The results reveal that the two major volcanic events recorded by H2SO4, fallout in Antarctic ice over the last century are the eruptions of Krakatoa (1883) and Agung (1963), both located at equatorial latitudes in the southern hemisphere. The volcanic signals are found to be particularly well defined at central Antarctic locations apparently in relation to the low snow accumulation rates in these areas. It is demonstrated that volcanic sulfuric acid in snow is not even partially neutralized by ammonia. The possible influence of Antarctic volcanic activity on snow chemistry is also discussed, using the three recent eruptions of the Deception Island volcano as examples. Only one of them seems to have had a significant effect on the chemistry of snow at a location 200 km from this volcano. It is concluded that Antarctic volcanic ice records are less complicated than Greenland records because of the limited number of volcanos in the southern hemisphere and the apparently higher signal to background ratio for acidity in Antarctica than in Greenland.

  16. Snow as a habitat for microorganisms

    Science.gov (United States)

    Hoham, Ronald W.

    1989-01-01

    There are three major habitats involving ice and snow, and the microorganisms studied from these habitats are most eukaryotic. Sea ice is inhabited by algae called diatoms, glacial ice has sparse populations of green algai cal desmids, and the temporary and permanent snows in mountainous regions and high latitudes are inhabited mostly by green algal flagellates. The life cycle of green algal flagellates is summarized by discussing the effects of light, temperature, nutrients, and snow melts. Specific examples of optimal conditions and environmental effects for various snow algae are given. It is not likely that the eukaryotic snow algae presented are candidated for life on the planet Mars. Evolutionally, eukaryotic cells as know on Earth may not have had the opportunity to develop on Mars (if life evolved at all on Mars) since eukaryotes did not appear on Earth until almost two billion years after the first prokaryotic organisms. However, the snow/ice ecosystems on Earth present themselves as extreme habitats were there is evidence of prokaryotic life (eubacteria and cyanbacteria) of which literally nothing is known. Any future surveillances of extant and/or extinct life on Mars should include probes (if not landing sites) to investigate sites of concentrations of ice water. The possibility of signs of life in Martian polar regions should not be overlooked.

  17. Monitoring and projecting snow on Hawaii Island

    Science.gov (United States)

    Zhang, Chunxi; Hamilton, Kevin; Wang, Yuqing

    2017-05-01

    The highest mountain peaks on Hawaii Island are snow covered for part of almost every year. This snow has aesthetic and recreational value as well as cultural significance for residents and visitors. Thus far there have been almost no systematic observations of snowfall, snow cover, or snow depth in Hawaii. Here we use satellite observations to construct a daily index of Hawaii Island snow cover starting from 2000. The seasonal mean of our index displays large interannual variations that are correlated with the seasonal mean freezing level and frequency of trade wind inversions as determined from nearby balloon soundings. Our snow cover index provides a diagnostic for monitoring climate variability and trends within the extensive area of the globe dominated by the North Pacific trade wind meteorological regime. We have also conducted simulations of the Hawaii climate with a regional atmospheric model. Retrospective simulations for 1990-2015 were run with boundary conditions prescribed from gridded observational analyses. Simulations for the end of 21st century employed boundary conditions based on global climate model projections that included standard scenarios for anticipated anthropogenic climate forcing. The future projections indicate that snowfall will nearly disappear by the end of the current century.

  18. Snow model design for operational purposes

    Science.gov (United States)

    Kolberg, Sjur

    2017-04-01

    A parsimonious distributed energy balance snow model intended for operational use is evaluated using discharge, snow covered area and grain size; the latter two as observed from the MODIS sensor. The snow model is an improvement of the existing GamSnow model, which is a part of the Enki modelling framework. Core requirements for the new version have been: 1. Reduction of calibration freedom, motivated by previous experience of non-identifiable parameters in the existing version 2. Improvement of process representation based on recent advances in physically based snow modelling 3. Limiting the sensitivity to forcing data which are poorly known over the spatial domain of interest (often in mountainous areas) 4. Preference for observable states, and the ability to improve from updates. The albedo calculation is completely revised, now based on grain size through an emulation of the SNICAR model (Flanner and Zender, 2006; Gardener and Sharp, 2010). The number of calibration parameters in the albedo model is reduced from 6 to 2. The wind function governing turbulent energy fluxes has been reduced from 2 to 1 parameter. Following Raleigh et al (2011), snow surface radiant temperature is split from the top layer thermodynamic temperature, using bias-corrected wet-bulb temperature to model the former. Analyses are ongoing, and the poster will bring evaluation results from 16 years of MODIS observations and more than 25 catchments in southern Norway.

  19. Perception of visual apparent motion is modulated by a gap within concurrent auditory glides, even when it is illusory

    Science.gov (United States)

    Wang, Qingcui; Guo, Lu; Bao, Ming; Chen, Lihan

    2015-01-01

    Auditory and visual events often happen concurrently, and how they group together can have a strong effect on what is perceived. We investigated whether/how intra- or cross-modal temporal grouping influenced the perceptual decision of otherwise ambiguous visual apparent motion. To achieve this, we juxtaposed auditory gap transfer illusion with visual Ternus display. The Ternus display involves a multi-element stimulus that can induce either of two different percepts of apparent motion: ‘element motion’ (EM) or ‘group motion’ (GM). In “EM,” the endmost disk is seen as moving back and forth while the middle disk at the central position remains stationary; while in “GM,” both disks appear to move laterally as a whole. The gap transfer illusion refers to the illusory subjective transfer of a short gap (around 100 ms) from the long glide to the short continuous glide when the two glides intercede at the temporal middle point. In our experiments, observers were required to make a perceptual discrimination of Ternus motion in the presence of concurrent auditory glides (with or without a gap inside). Results showed that a gap within a short glide imposed a remarkable effect on separating visual events, and led to a dominant perception of GM as well. The auditory configuration with gap transfer illusion triggered the same auditory capture effect. Further investigations showed that visual interval which coincided with the gap interval (50–230 ms) in the long glide was perceived to be shorter than that within both the short glide and the ‘gap-transfer’ auditory configurations in the same physical intervals (gaps). The results indicated that auditory temporal perceptual grouping takes priority over the cross-modal interaction in determining the final readout of the visual perception, and the mechanism of selective attention on auditory events also plays a role. PMID:26042055

  20. [Was Snow White a transsexual?].

    Science.gov (United States)

    Michel, A; Mormont, C

    2002-01-01

    modalities in the transsexual dynamics. Nevertheless, one can ask oneself about the possibility of a request based on a desire rather than on a defense, or even on the existence of a defensive process diametrically opposed to the counter-phobic attitude and which, instead of actively provoking the dreaded reality, would privilege its avoidance and the search of passivity. This latter hypothesis has the advantage of being rather easy to explore with the Rorschach because, according to Exner, the predominance of passive compared to active human movement responses (which he terms the Snow White Syndrome) indicates the propensity to escape into passive fantasies and the tendency to avoid the initiative for behaviour or decision-making, if other people can do it in the subject's place (12). Our results largely confirmed the hypothesis of the existence of an opposite mechanism, as a third of subjects (n = 26) presented Snow White Syndrome. According to Exner, these transsexuals are typically characterized by hiding into a world of make believe, avoiding all responsibility, as well as any decision-making. This passivity in our Snow White Syndrome group was all the more remarkable in that, on the whole, it infiltrated into all the movement responses and seemed to define a rigid style of thinking and mental elaboration, in addition to a suggestive content of passivity. However, this condition cannot be associated with a general lack of dynamism or energy. In fact, the treatment of information, which provides data concerning the motivation to treat a stimulus field of the stimulus--whether this concerns the capture (L) of the stimulus or the elaboration (DQ+) of the response--displayed a sufficient amount of motivation. Furthermore, internal resources (EA) were considerable and were brought into play whenever it was necessary to adopt a behaviour or make a decision. Furthermore, based on these Rorschach findings, we note that in transsexuals with Snow White Syndrome, there is a

  1. Evaluation of SNODAS snow depth and snow water equivalent estimates for the Colorado Rocky Mountains, USA

    Science.gov (United States)

    Clow, David W.; Nanus, Leora; Verdin, Kristine L.; Schmidt, Jeffrey

    2012-01-01

    The National Weather Service's Snow Data Assimilation (SNODAS) program provides daily, gridded estimates of snow depth, snow water equivalent (SWE), and related snow parameters at a 1-km2 resolution for the conterminous USA. In this study, SNODAS snow depth and SWE estimates were compared with independent, ground-based snow survey data in the Colorado Rocky Mountains to assess SNODAS accuracy at the 1-km2 scale. Accuracy also was evaluated at the basin scale by comparing SNODAS model output to snowmelt runoff in 31 headwater basins with US Geological Survey stream gauges. Results from the snow surveys indicated that SNODAS performed well in forested areas, explaining 72% of the variance in snow depths and 77% of the variance in SWE. However, SNODAS showed poor agreement with measurements in alpine areas, explaining 16% of the variance in snow depth and 30% of the variance in SWE. At the basin scale, snowmelt runoff was moderately correlated (R2 = 0.52) with SNODAS model estimates. A simple method for adjusting SNODAS SWE estimates in alpine areas was developed that uses relations between prevailing wind direction, terrain, and vegetation to account for wind redistribution of snow in alpine terrain. The adjustments substantially improved agreement between measurements and SNODAS estimates, with the R2 of measured SWE values against SNODAS SWE estimates increasing from 0.42 to 0.63 and the root mean square error decreasing from 12 to 6 cm. Results from this study indicate that SNODAS can provide reliable data for input to moderate-scale to large-scale hydrologic models, which are essential for creating accurate runoff forecasts. Refinement of SNODAS SWE estimates for alpine areas to account for wind redistribution of snow could further improve model performance. Published 2011. This article is a US Government work and is in the public domain in the USA.

  2. Testing a blowing snow model against distributed snow measurements at Upper Sheep Creek, Idaho, United States of America

    Science.gov (United States)

    Rajiv Prasad; David G. Tarboton; Glen E. Liston; Charles H. Luce; Mark S. Seyfried

    2001-01-01

    In this paper a physically based snow transport model (SnowTran-3D) was used to simulate snow drifting over a 30 m grid and was compared to detailed snow water equivalence (SWE) surveys on three dates within a small 0.25 km2 subwatershed, Upper Sheep Creek. Two precipitation scenarios and two vegetation scenarios were used to carry out four snow transport model runs in...

  3. Quantification of uncertainties in snow accumulation, snowmelt, and snow disappearance dates

    Science.gov (United States)

    Raleigh, Mark S.

    Seasonal mountain snowpack holds hydrologic and ecologic significance worldwide. However, observation networks in complex terrain are typically sparse and provide minimal information about prevailing conditions. Snow patterns and processes in this data sparse environment can be characterized with numerical models and satellite-based remote sensing, and thus it is essential to understand their reliability. This research quantifies model and remote sensing uncertainties in snow accumulation, snowmelt, and snow disappearance as revealed through comparisons with unique ground-based measurements. The relationship between snow accumulation uncertainty and model configuration is assessed through a controlled experiment at 154 snow pillow sites in the western United States. To simulate snow water equivalent (SWE), the National Weather Service SNOW-17 model is tested as (1) a traditional "forward" model based primarily on precipitation, (2) a reconstruction model based on total snowmelt before the snow disappearance date, and (3) a combination of (1) and (2). For peak SWE estimation, the reliability of the parent models was indistinguishable, while the combined model was most reliable. A sensitivity analysis demonstrated that the parent models had opposite sensitivities to temperature that tended to cancel in the combined model. Uncertainty in model forcing and parameters significantly controlled model accuracy. Uncertainty in remotely sensed snow cover and snow disappearance in forested areas is enhanced by canopy obstruction but has been ill-quantified due to the lack of sub-canopy observations. To better quantify this uncertainty, dense networks of near-surface temperature sensors were installed at four study areas (≤ 1 km2) with varying forest cover in the Sierra Nevada, California. Snow presence at each sensor was detected during periods when temperature was damped, which resulted from snow cover insulation. This methodology was verified using time-lapse analysis and

  4. Contact- and Protein Transfer-Dependent Stimulation of Assembly of the Gliding Motility Machinery in Myxococcus xanthus.

    Directory of Open Access Journals (Sweden)

    Beata Jakobczak

    2015-07-01

    Full Text Available Bacteria engage in contact-dependent activities to coordinate cellular activities that aid their survival. Cells of Myxococcus xanthus move over surfaces by means of type IV pili and gliding motility. Upon direct contact, cells physically exchange outer membrane (OM lipoproteins, and this transfer can rescue motility in mutants lacking lipoproteins required for motility. The mechanism of gliding motility and its stimulation by transferred OM lipoproteins remain poorly characterized. We investigated the function of CglC, GltB, GltA and GltC, all of which are required for gliding. We demonstrate that CglC is an OM lipoprotein, GltB and GltA are integral OM β-barrel proteins, and GltC is a soluble periplasmic protein. GltB and GltA are mutually stabilizing, and both are required to stabilize GltC, whereas CglC accumulate independently of GltB, GltA and GltC. Consistently, purified GltB, GltA and GltC proteins interact in all pair-wise combinations. Using active fluorescently-tagged fusion proteins, we demonstrate that GltB, GltA and GltC are integral components of the gliding motility complex. Incorporation of GltB and GltA into this complex depends on CglC and GltC as well as on the cytoplasmic AglZ protein and the inner membrane protein AglQ, both of which are components of the gliding motility complex. Conversely, incorporation of AglZ and AglQ into the gliding motility complex depends on CglC, GltB, GltA and GltC. Remarkably, physical transfer of the OM lipoprotein CglC to a ΔcglC recipient stimulates assembly of the gliding motility complex in the recipient likely by facilitating the OM integration of GltB and GltA. These data provide evidence that the gliding motility complex in M. xanthus includes OM proteins and suggest that this complex extends from the cytoplasm across the cell envelope to the OM. These data add assembly of gliding motility complexes in M. xanthus to the growing list of contact-dependent activities in bacteria.

  5. Snow Monitoring Using Remote Sensing Data: Modification of Normalized Difference Snow Index

    Science.gov (United States)

    Kaplan, G.; Avdan, U.

    2016-12-01

    Snow cover is an important part of the Earth`s climate system so its continuous monitoring is necessary to map snow cover in high resolution. Satellite remote sensing can successfully fetch land cover and land cover changes. Although normalized difference snow index NDSI has quite good accuracy, topography shadow, water bodies and clouds can be easily misplaced as snow. Using Landsat TM, +ETM and TIRS/OLI satellite images, the NDSI was modified for more accurate snow mapping. In this paper, elimination of the misplaced water bodies was made using the high reflectance of the snow in the blue band. Afterwards, the modified NDSI (MNDSI) was used for estimating snow cover through the years on the highest mountains in Republic of Macedonia. The results from this study show that the MNDSI accuracy is bigger than the NDSI`s, totally eliminating the misplaced water bodies, and partly the one caused from topography and clouds. Also, it was noticed that the snow cover in the study area has been lowered through the years. For future studies, the MNDSI should be validated on different study areas with different characteristics.

  6. Snow measurement system for airborne snow surveys (GPR system from helicopter) in high mountian areas.

    Science.gov (United States)

    Sorteberg, Hilleborg K.

    2010-05-01

    In the hydropower industry, it is important to have precise information about snow deposits at all times, to allow for effective planning and optimal use of the water. In Norway, it is common to measure snow density using a manual method, i.e. the depth and weight of the snow is measured. In recent years, radar measurements have been taken from snowmobiles; however, few energy supply companies use this method operatively - it has mostly been used in connection with research projects. Agder Energi is the first Norwegian power producer in using radar tecnology from helicopter in monitoring mountain snow levels. Measurement accuracy is crucial when obtaining input data for snow reservoir estimates. Radar screening by helicopter makes remote areas more easily accessible and provides larger quantities of data than traditional ground level measurement methods. In order to draw up a snow survey system, it is assumed as a basis that the snow distribution is influenced by vegetation, climate and topography. In order to take these factors into consideration, a snow survey system for fields in high mountain areas has been designed in which the data collection is carried out by following the lines of a grid system. The lines of this grid system is placed in order to effectively capture the distribution of elevation, x-coordinates, y-coordinates, aspect, slope and curvature in the field. Variation in climatic conditions are also captured better when using a grid, and dominant weather patterns will largely be captured in this measurement system.

  7. Energy consumption of ProTaper Next X1 after glide path with PathFiles and ProGlider.

    Science.gov (United States)

    Berutti, Elio; Alovisi, Mario; Pastorelli, Michele Angelo; Chiandussi, Giorgio; Scotti, Nicola; Pasqualini, Damiano

    2014-12-01

    Instrument failure caused by excessive torsional stress can be controlled by creating a manual or mechanical glide path. The ProGlider single-file system (Dentsply Maillefer, Ballaigues, Switzerland) was recently introduced to perform a mechanical glide path. This study was designed to compare the effect of a glide path performed with PathFiles (Dentsply Maillefer) and ProGlider on torque, time, and pecking motion required for ProTaper Next X1 (Dentsply Maillefer) to reach the full working length in simulated root canals. Forty Endo Training Blocks (Dentsply Maillefer) were used. Twenty were prepared with a mechanical glide path using PathFiles 1 and 2 (the PathFile group), and 20 were prepared with a mechanical glide path using a ProGlider single file (the ProGlider group). All samples were shaped with ProTaper Next X1 driven by an endodontic motor connected to a digital wattmeter. The required torque for root canal instrumentation was analyzed by evaluating the electrical power consumption of the endodontic engine. Electric power consumption (mW/h), elapsed time (seconds), and number of pecking motions required to reach the full working length with ProTaper Next X1 were calculated. Differences among groups were analyzed with the parametric Student t test for independent data (P path and preliminary middle and coronal preflaring. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  8. MotAB-like machinery drives the movement of MreB filaments during bacterial gliding motility.

    Science.gov (United States)

    Fu, Guo; Bandaria, Jigar N; Le Gall, Anne Valérie; Fan, Xue; Yildiz, Ahmet; Mignot, Tâm; Zusman, David R; Nan, Beiyan

    2018-03-06

    MreB is a bacterial actin that is important for cell shape and cell wall biosynthesis in many bacterial species. MreB also plays crucial roles in Myxococcus xanthus gliding motility, but the underlying mechanism remains unknown. Here we tracked the dynamics of single MreB particles in M. xanthus using single-particle tracking photoactivated localization microscopy. We found that a subpopulation of MreB particles moves rapidly along helical trajectories, similar to the movements of the MotAB-like gliding motors. The rapid MreB motion was stalled in the mutants that carried truncated gliding motors. Remarkably, M. xanthus MreB moves one to two orders of magnitude faster than its homologs that move along with the cell wall synthesis machinery in Bacillus subtilis and Escherichia coli , and this rapid movement was not affected by the inhibitors of cell wall biosynthesis. Our results show that in M. xanthus , MreB provides a scaffold for the gliding motors while the gliding machinery drives the movement of MreB filaments, analogous to the interdependent movements of myosin motors and actin in eukaryotic cells.

  9. Iron snow in the Martian core?

    Science.gov (United States)

    Davies, Christopher J.; Pommier, Anne

    2018-01-01

    The decline of Mars' global magnetic field some 3.8-4.1 billion years ago is thought to reflect the demise of the dynamo that operated in its liquid core. The dynamo was probably powered by planetary cooling and so its termination is intimately tied to the thermochemical evolution and present-day physical state of the Martian core. Bottom-up growth of a solid inner core, the crystallization regime for Earth's core, has been found to produce a long-lived dynamo leading to the suggestion that the Martian core remains entirely liquid to this day. Motivated by the experimentally-determined increase in the Fe-S liquidus temperature with decreasing pressure at Martian core conditions, we investigate whether Mars' core could crystallize from the top down. We focus on the "iron snow" regime, where newly-formed solid consists of pure Fe and is therefore heavier than the liquid. We derive global energy and entropy equations that describe the long-timescale thermal and magnetic history of the core from a general theory for two-phase, two-component liquid mixtures, assuming that the snow zone is in phase equilibrium and that all solid falls out of the layer and remelts at each timestep. Formation of snow zones occurs for a wide range of interior and thermal properties and depends critically on the initial sulfur concentration, ξ0. Release of gravitational energy and latent heat during growth of the snow zone do not generate sufficient entropy to restart the dynamo unless the snow zone occupies at least 400 km of the core. Snow zones can be 1.5-2 Gyrs old, though thermal stratification of the uppermost core, not included in our model, likely delays onset. Models that match the available magnetic and geodetic constraints have ξ0 ≈ 10% and snow zones that occupy approximately the top 100 km of the present-day Martian core.

  10. Monitoring Forsmark. Snow depth, snow water content and ice cover during the winter 2010/2011

    International Nuclear Information System (INIS)

    Wass, Eva

    2011-07-01

    Snow depth and ice cover have been measured and observed during the winter 2010/2011. This type of measurements started in the winter 2002/2003 and has been ongoing since then. In addition to these parameters, the water content of the snow was calculated at each measurement occasion from the weight of a snow sample. Measurements and observations were conducted on a regular basis from the beginning of November 2010 until the middle of April 2011. A persistent snow cover was established in the end of November 2010 and remained until the beginning of April 2011 at the station with longest snow cover duration. The period of ice cover was 160 days in Lake Eckarfjaerden, whereas the sea bay at SFR was ice covered for 135 days

  11. Bacterial gliding fluid dynamics on a layer of non-Newtonian slime: Perturbation and numerical study.

    Science.gov (United States)

    Ali, N; Asghar, Z; Anwar Bég, O; Sajid, M

    2016-05-21

    Gliding bacteria are an assorted group of rod-shaped prokaryotes that adhere to and glide on certain layers of ooze slime attached to a substratum. Due to the absence of organelles of motility, such as flagella, the gliding motion is caused by the waves moving down the outer surface of these rod-shaped cells. In the present study we employ an undulating surface model to investigate the motility of bacteria on a layer of non-Newtonian slime. The rheological behavior of the slime is characterized by an appropriate constitutive equation, namely the Carreau model. Employing the balances of mass and momentum conservation, the hydrodynamic undulating surface model is transformed into a fourth-order nonlinear differential equation in terms of a stream function under the long wavelength assumption. A perturbation approach is adopted to obtain closed form expressions for stream function, pressure rise per wavelength, forces generated by the organism and power required for propulsion. A numerical technique based on an implicit finite difference scheme is also employed to investigate various features of the model for large values of the rheological parameters of the slime. Verification of the numerical solutions is achieved with a variational finite element method (FEM). The computations demonstrate that the speed of the glider decreases as the rheology of the slime changes from shear-thinning (pseudo-plastic) to shear-thickening (dilatant). Moreover, the viscoelastic nature of the slime tends to increase the swimming speed for the shear-thinning case. The fluid flow in the pumping (generated where the organism is not free to move but instead generates a net fluid flow beneath it) is also investigated in detail. The study is relevant to marine anti-bacterial fouling and medical hygiene biophysics. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Interaction of gliding motion of bacteria with rheological properties of the slime.

    Science.gov (United States)

    Asghar, Z; Ali, N; Sajid, M

    2017-08-01

    Bacteria which do not have organelles of motility, such as flagella, adopt gliding as a mode of locomotion. In gliding motility bacterium moves under its own power by secreting a layer of slime on the substrate. The exact mechanism by which a glider achieves motility is yet in controversy but there are evidences which support the wave-like undulation on the surface of the organism, as a possible mechanism of motility. Based on this observation, a model of undulating sheet over a layer of slime is examined as a possible model of the gliding motion of a bacterium. Three different non-Newtonian constitutive equations namely, finite extendable nonlinear elastic-peterline (FENE-P), Simplified Phan-Thien-Tanner (SPTT) and Rabinowitsch equations are used to capture the rheological properties of the slime. It is found that the governing equation describing the fluid mechanics of the model under lubrication approximation is same for all the considered three constitutive equations. In fact, it involves a single non-Newtonian parameter which assumes different values for each of the considered constitutive relations. This differential equation is solved using both perturbation and semi-analytic procedure. The perturbation solution is exploited to get an estimate of the speed of the glider for different values of the non-Newtonian parameter. The solution obtained via semi-analytic procedure is used to investigate the important features of the flow field in the layer of the slime beneath the glider when the glider is held fixed. The expression of forces generated by the organism and power required for propulsion are also derived based on the perturbation analysis. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Effect of repetitive pecking at working length for glide path preparation using G-file

    Directory of Open Access Journals (Sweden)

    Jung-Hong Ha

    2015-05-01

    Full Text Available Objectives Glide path preparation is recommended to reduce torsional failure of nickel-titanium (NiTi rotary instruments and to prevent root canal transportation. This study evaluated whether the repetitive insertions of G-files to the working length maintain the apical size as well as provide sufficient lumen as a glide path for subsequent instrumentation. Materials and Methods The G-file system (Micro-Mega composed of G1 and G2 files for glide path preparation was used with the J-shaped, simulated resin canals. After inserting a G1 file twice, a G2 file was inserted to the working length 1, 4, 7, or 10 times for four each experimental group, respectively (n = 10. Then the canals were cleaned by copious irrigation, and lubricated with a separating gel medium. Canal replicas were made using silicone impression material, and the diameter of the replicas was measured at working length (D0 and 1 mm level (D1 under a scanning electron microscope. Data was analysed by one-way ANOVA and post-hoc tests (p = 0.05. Results The diameter at D0 level did not show any significant difference between the 1, 2, 4, and 10 times of repetitive pecking insertions of G2 files at working length. However, 10 times of pecking motion with G2 file resulted in significantly larger canal diameter at D1 (p < 0.05. Conclusions Under the limitations of this study, the repetitive insertion of a G2 file up to 10 times at working length created an adequate lumen for subsequent apical shaping with other rotary files bigger than International Organization for Standardization (ISO size 20, without apical transportation at D0 level.

  14. Destruction of tributylphosphate by cold plasma. Use of a gliding arc reactor

    International Nuclear Information System (INIS)

    Moussa, David

    1999-01-01

    The nuclear industry uses the Purex process for reprocessing spent nuclear fuel by plutonium and uranium separation. This process uses complexing properties of tributylphosphate. This solvent is aged by the high radioactivity and acidity of the medium and loses its extracting properties. Thus it becomes an highly radioactive liquid organic waste and it must be degraded before its conditioning. We have elaborated a new method for mineralizing TBP by exposure to the plasma produced by a wet air gliding arc. Electric discharges in wet air give rise to very reactive species like excited molecules and radicals. Such species can accelerate oxidation and degradation of organic compounds. The gliding arc discharge is obtained by applying high voltage between two divergent metal electrodes disposed around a blowing nozzle. The arc formed between the electrodes is blown by the air flow with growing in length. Thus a quenched wet air plasma trail is formed and licks an upper layer of TBP while the lower layer is water. Our device can degrade almost 40 percent of the treated TBP. The main degradation product is phosphoric acid for which we have monitored the production kinetics and suggested a model of a surface oxidation process to explain it. Another part of the TBP is converted into a phosphate layer found on the electrodes and phosphorus oxide white smokes present in exhaust fumes. By means of chromatography and spectroscopic analysis we have found the dibutyl-phosphoric acid as the main partial degradation product. The gliding arc device presents several advantages towards other plasma processes which are a low cost and especially for the present task i.e. an easy building and use, operating at atmospheric pressure and moderate temperature, and the possibility to use high powers (several kW for one unit). (author) [fr

  15. Evidence and characterization of a glide-vowel distinction in American English

    Directory of Open Access Journals (Sweden)

    Zachary Scott Jaggers

    2018-02-01

    Full Text Available This study tests whether native speakers of American English exhibit a glide-vowel distinction ([j]-[i] in a speech elicitation experiment. When reading sentences out loud, participants’ pronunciations of 4 near-minimal pairs of pre-existing lexical items (e.g., 'Eston'[iə] vs. 'pneumon'[jə] exhibit significant differences when acoustically measured, confirming the presence of a [j]-[i] distinction. This distinction is also found to be productively extended to the production of 20 near-minimal pairs of nonce words (e.g., 'Súmia '→ [sumiə] vs. 'Fímya '→ [fimjə], diversified and balanced along different phonologically relevant factors of the surrounding environment. Multiple acoustic measurements are compared to test what aspects most consistently convey the distinction: F2 (frontness, F1 (height, intensity, vocalic sequence duration, transition earliness, and transition speed. This serves the purpose of documenting the distinction’s acoustic phonetic realization. It also serves in the comparison of phonological representations. Multiple types of previously proposed phonological representations are considered along with the competing predictions they generate regarding the acoustic measurements performed. Results suggest that the primary and most consistent characteristic of the distinction is earliness of transition into the following vowel, with results also suggesting that the [j] glide has a greater degree of constriction. The [j] glide is found to have a significantly 'less 'anterior articulation, challenging the application of a representation based on place or articulator differences that would predict [j] to be 'more 'anterior.

  16. The Effects of One-Dimensional Glide on the Reaction Kinetics of Interstitial Clusters

    International Nuclear Information System (INIS)

    Heinisch, Howard L.; Singh, B N.; Golubov, S I.

    2000-01-01

    Collision cascades in metals produce small interstitial clusters and perfect dislocation loops that glide in thermally activated one-dimensional (1D) random walks. These gliding defects can change their Burgers vectors by thermal activation or by interactions with other defects. Their migration is therefore''mixed 1D/3D migration'' along a 3D path consisting of 1D segments. The defect reaction kinetics under mixed 1D/3D diffusion are different from pure 1D diffusion and pure 3D diffusion, both of which can be formulated within analytical rate theory models of microstructure evolution under irradiation. Atomic-scale kinetic Monte Carlo (kMC) defect migration simulations are used to investigate the effects of mixed 1D/3D migration on defect reaction kinetics as a guide for implementing mixed 1D/3D migration into the analytical rate theory. The functional dependence of the sink strength on the sixe and concentration of sinks under mixed 1D/3D migration is shown to lie between that for pure 1D and pure 3D migration and varies with L, the average distance between direction changes of the gliding defects. It is shown that the sink strength in simulations for spherical sinks of radius R under mixed 1D/3D migration for values of L greater than R can be approximated by an expression that varies directly as R2. For small L, the form of the transition from mixed 1D/3D to pure 3D diffusion as L decreases is demonstrated in the simulations, the results of which can be used in the future development of an analytical expression describing this transition region

  17. The barrier to misfit dislocation glide in continuous, strained, epitaxial layers on patterned substrates

    International Nuclear Information System (INIS)

    Watson, G.P.; Ast, D.G.; Anderson, T.J.; Pathangey, B.

    1993-01-01

    In a previous report [G. P. Watson, D. G. Ast, T. J. Anderson, and Y. Hayakawa, Appl. Phys. Lett. 58, 2517 (1991)] we demonstrated that the motion of misfit dislocations in InGaAs, grown by organometallic vapor phase epitaxy on patterned GaAs substrates, can be impeded even if the strained epitaxial layer is continuous. Trenches etched into GaAs before growth are known to act as a barrier to misfit dislocation propagation [E. A. Fitzgerald, G. P. Watson, R. E. Proano, D. G. Ast, P. D. Kirchner, G. D. Pettit, and J. M. Woodall, J. Appl. Phys. 65, 2220 (1989)] when those trenches create discontinuities in the epitaxial layers; but even shallow trenches, with continuous strained layers following the surface features, can act as barriers. By considering the strain energy required to change the length of the dislocation glide segments that stretch from the interface to the free surface, a simple model is developed that explains the major features of the unique blocking action observed at the trench edges. The trench wall angle is found to be an important parameter in determining whether or not a trench will block dislocation glide. The predicted blocking angles are consistent with observations made on continuous 300 and 600 nm thick In 0.04 Ga 0.96 As films on patterned GaAs. Based on the model, a structure is proposed that may be used as a filter to yield misfit dislocations with identical Burgers vectors or dislocations which slip in only one glide plane

  18. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Dynamics of splashing of molten metals during irradiation with single CO2 laser pulses

    Science.gov (United States)

    Arutyunyan, R. V.; Baranov, V. Yu; Bol'shov, Leonid A.; Dolgov, V. A.; Malyuta, D. D.; Mezhevov, V. S.; Semak, V. V.

    1988-03-01

    An experimental investigation was made of the dynamics of the loss of the melt as a result of interaction with single-mode CO2 laser radiation pulses of 5-35 μs duration. The dynamics of splashing of the melt during irradiation with short pulses characterized by a Gaussian intensity distribution differed from that predicted by models in which the distribution of the vapor pressure was assumed to be radially homogeneous.

  19. [Use of a new video-laryngoscope (GlideScope) in patients with a difficult airway].

    Science.gov (United States)

    Hirabayashi, Yoshihiro; Hakozaki, Takahiro; Fujisawa, Koji; Sata, Naho; Kataoka, Sachiko; Okada, Osamu; Yamada, Masaki; Hotta, Kunihisa; Seo, Norimasa; Ikeda, Kaori

    2007-07-01

    We describe the clinical use of a new video-laryngoscope (GlideScope, GS) in patients with a difficult airway and morbid obesity. In 4 patients with a difficult airway, showing a Cormack-Lehane grade III view with Macintosh direct laryngoscope, the glottic opening (Cormack-Lehane grade I or II) was visualized with GS. In 2 patients, showing a Cormack-Lehane grade IV view with Macintosh direct laryngoscope, Cormack-Lehane grade II view of the glottic opening was obtained. GS also provided a good view of glottic opening in a patient with morbid obesity. GS will have a profound impact on the management of the difficult airway.

  20. Gliding arc discharge — Application for adhesion improvement of fibre reinforced polyester composites

    DEFF Research Database (Denmark)

    Kusano, Yukihiro; Teodoru, Steluta; Leipold, Frank

    2008-01-01

    production, and surface treatment. However, the application for adhesion improvement of structural materials has been rarely reported. In the present work, glass fibre reinforced polyester plates were treated using atmospheric pressure gliding arcs with high speed air flow for adhesion improvement...... with vinylester resin. It is found that the treatment increased the density of oxygen-containing polar functional groups at the composite surfaces, the polar component of the surface energy, and adhesive strength with a vinylester resin. The treatment effect highly depended on the temperatures of the electrodes...

  1. In situ TEM study on elastic interaction between a prismatic loop and a gliding dislocation

    International Nuclear Information System (INIS)

    Matsukawa, Yoshitaka; Liu, Grace S.

    2012-01-01

    In situ straining in a transmission electron microscope was performed in order to investigate dislocation interactions with a prismatic loop, which as a mobile obstacle is expected to be displaced by the strain-field of dislocation prior to physical contact. It was found that when a gliding dislocation approached a critical distance, the prismatic loop was certainly attracted to the dislocation. The captured loop disrupted the dislocation motion and was not dragged along with the mobile dislocation. Instead, the dislocation bypassed the loop via cross-slip to another slip plane with a resolved shear stress estimated to be 40% lower than that of the original plane.

  2. John Snow: the first hired gun?

    Science.gov (United States)

    Lilienfeld, D E

    2000-07-01

    The 1854 English cholera outbreak led to reform of Victorian public health legislation, including the Nuisances Removal and Diseases Prevention Act. The reforms threatened the closure of many factories whose fumes were considered hazardous to the public's health. The second witness to appear before the Parliamentary committee considering the reforms was Dr. John Snow. Snow testified on behalf of the manufacturers threatened by the reforms. He stated that the fumes from such establishments were not hazardous. He contended that the workers in these factories did not become ill as a result of their exposures, and therefore these fumes could not be a hazard to the general public's health. Snow also presented data from the 1854 cholera outbreak as the basis for his belief that epidemic diseases were transmitted by water, not air. Although the data concerned cholera, Snow extended the inference to all epidemic diseases. When the committee's report was published, The Lancet chastised Snow in a stinging editorial. Parliament subsequently revised the bill in favor of the manufacturers and passed it into law. The implications of this particular episode in the history of epidemiology are discussed.

  3. Differential recognition of pitch patterns in discrete and gliding stimuli in congenital amusia: evidence from Mandarin speakers.

    Science.gov (United States)

    Liu, Fang; Xu, Yi; Patel, Aniruddh D; Francart, Tom; Jiang, Cunmei

    2012-08-01

    This study examined whether "melodic contour deafness" (insensitivity to the direction of pitch movement) in congenital amusia is associated with specific types of pitch patterns (discrete versus gliding pitches) or stimulus types (speech syllables versus complex tones). Thresholds for identification of pitch direction were obtained using discrete or gliding pitches in the syllable /ma/ or its complex tone analog, from nineteen amusics and nineteen controls, all healthy university students with Mandarin Chinese as their native language. Amusics, unlike controls, had more difficulty recognizing pitch direction in discrete than in gliding pitches, for both speech and non-speech stimuli. Also, amusic thresholds were not significantly affected by stimulus types (speech versus non-speech), whereas controls showed lower thresholds for tones than for speech. These findings help explain why amusics have greater difficulty with discrete musical pitch perception than with speech perception, in which continuously changing pitch movements are prevalent. Copyright © 2012 Elsevier Inc. All rights reserved.

  4. Assessment of Northern Hemisphere Snow Water Equivalent Datasets in ESA SnowPEx project

    Science.gov (United States)

    Luojus, Kari; Pulliainen, Jouni; Cohen, Juval; Ikonen, Jaakko; Derksen, Chris; Mudryk, Lawrence; Nagler, Thomas; Bojkov, Bojan

    2016-04-01

    Reliable information on snow cover across the Northern Hemisphere and Arctic and sub-Arctic regions is needed for climate monitoring, for understanding the Arctic climate system, and for the evaluation of the role of snow cover and its feedback in climate models. In addition to being of significant interest for climatological investigations, reliable information on snow cover is of high value for the purpose of hydrological forecasting and numerical weather prediction. Terrestrial snow covers up to 50 million km² of the Northern Hemisphere in winter and is characterized by high spatial and temporal variability. Therefore satellite observations provide the best means for timely and complete observations of the global snow cover. There are a number of independent SWE products available that describe the snow conditions on multi-decadal and global scales. Some products are derived using satellite-based information while others rely on meteorological observations and modelling. What is common to practically all the existing hemispheric SWE products, is that their retrieval performance on hemispherical and multi-decadal scales are not accurately known. The purpose of the ESA funded SnowPEx project is to obtain a quantitative understanding of the uncertainty in satellite- as well as model-based SWE products through an internationally coordinated and consistent evaluation exercise. The currently available Northern Hemisphere wide satellite-based SWE datasets which were assessed include 1) the GlobSnow SWE, 2) the NASA Standard SWE, 3) NASA prototype and 4) NSIDC-SSM/I SWE products. The model-based datasets include: 5) the Global Land Data Assimilation System Version 2 (GLDAS-2) product 6) the European Centre for Medium-Range Forecasts Interim Land Reanalysis (ERA-I-Land) which uses a simple snow scheme 7) the Modern Era Retrospective Analysis for Research and Applications (MERRA) which uses an intermediate complexity snow scheme; and 8) SWE from the Crocus snow scheme, a

  5. Converting Snow Depth to SWE: The Fusion of Simulated Data with Remote Sensing Retrievals and the Airborne Snow Observatory

    Science.gov (United States)

    Bormann, K.; Marks, D. G.; Painter, T. H.; Hedrick, A. R.; Deems, J. S.

    2015-12-01

    Snow cover monitoring has greatly benefited from remote sensing technology but, despite their critical importance, spatially distributed measurements of snow water equivalent (SWE) in mountain terrain remain elusive. Current methods of monitoring SWE rely on point measurements and are insufficient for distributed snow science and effective management of water resources. Many studies have shown that the spatial variability in SWE is largely controlled by the spatial variability in snow depth. JPL's Airborne Snow Observatory mission (ASO) combines LiDAR and spectrometer instruments to retrieve accurate and very high-resolution snow depth measurements at the watershed scale, along with other products such as snow albedo. To make best use of these high-resolution snow depths, spatially distributed snow density data are required to leverage SWE from the measured snow depths. Snow density is a spatially and temporally variable property that cannot yet be reliably extracted from remote sensing techniques, and is difficult to extrapolate to basin scales. However, some physically based snow models have shown skill in simulating bulk snow densities and therefore provide a pathway for snow depth to SWE conversion. Leveraging model ability where remote sensing options are non-existent, ASO employs a physically based snow model (iSnobal) to resolve distributed snow density dynamics across the basin. After an adjustment scheme guided by in-situ data, these density estimates are used to derive the elusive spatial distribution of SWE from the observed snow depth distributions from ASO. In this study, we describe how the process of fusing model data with remote sensing retrievals is undertaken in the context of ASO along with estimates of uncertainty in the final SWE volume products. This work will likely be of interest to those working in snow hydrology, water resource management and the broader remote sensing community.

  6. The Effect of Surface Modification on Gliding Ability of Decellularized Flexor Tendon in a Canine Model In Vitro

    Science.gov (United States)

    Ozasa, Yasuhiro; Amadio, Peter C.; Thoreson, Andrew R.; An, Kai-Nan; Zhao, Chunfeng

    2013-01-01

    Purpose To investigate the gliding ability and mechanical properties of decellularized intrasynovial tendons without and with surface modification designed to reduce gliding resistance. Methods Thirty-three canine flexor digitorum profundus tendons were randomly assigned to one of 3 groups: untreated fresh tendons, to serve as a control; tendons decellularized with trypsin and Triton X-100; and tendons decellularized as in group 2 with surface modification using carbodiimide-derivatized hyaluronic acid and gelatin (cd- HA-gelatin). Tendons were subjected to cyclic friction testing for 1000 cycles with subsequent tensile stiffness testing. The surface roughness after 1000 cycles was qualitatively evaluated using scanning electron microscopy. Results The gliding resistance of the decellularized group was significantly higher than that of both the control and cd-HA-gelatin tendons (0.20N, 0.09N and 0.11N after the first cycle, 0.41N, 0.09N and 0.14N after 1000 cycles, respectively).Gliding resistance between the control and cd-HA-gelatin groups was not significantly different. The Young modulus was not significantly different between the 3 groups. The surfaces of the control and cd-HA-gelatin treated tendons appeared smooth after 1000 cycles, while those of the decellularized tendons appeared rougher under scanning electron microscopy observation. Conclusions Decellularization with trypsin and Triton X-100 did not change tendon stiffness. However, this treatment, while effective in removing cells, adversely altered the tendon surface, both in appearance and gliding resistance. Surface modification with cd- HA-gelatin improved the tendon surface smoothness and significantly decreased the gliding resistance. Clinical Relevance The combination of decellularization and surface modification may improve the function of tendon allografts when used clinically. PMID:23849733

  7. Dislocation glide in Ni-Al solid solutions from the atomic scale up: a molecular dynamics study

    International Nuclear Information System (INIS)

    Rodary, E.

    2003-01-01

    The glide of an edge dislocation in solid solutions is studied by molecular dynamics, at fixed temperature and imposed external stress. We have optimized an EAM potential for Ni(1 a 8% A1): it well reproduces the lattice expansion, local atomic order, stacking fault energy as a function of composition, as well as the elastic properties of the γ' phase with L1 2 structure. On increasing the stress, the dislocation is first immobile, then glides with a velocity proportional to the stress and the velocity saturates on reaching the transverse sound velocity. However, only beyond a static threshold stress, σ s , does the dislocation glide a distance large enough to allow macroscopic shear; the linear part of the velocity-stress curve extrapolates to zero at a dynamical threshold stress, σ d , The friction coefficient, and the threshold stresses (σ s and σ d ), increase with the A1 concentration and decrease with temperature (300 and 500 K). Close to the critical shear stress, σ s , the dislocation glide is analysed with a 'stop and go' model. The latter yields the flight velocity between obstacles, the mean obstacle density and the distribution of the waiting time on each obstacle as a function of stress, composition and temperature. The obstacle to the glide is proposed to be the strong repulsion between Al atoms brought into nearest neighbour position by the glide process, and not the dislocation-solute interaction. The microscopic parameters so defined are introduced into a micro-mechanical model, which well reproduces the known behaviour of nickel base solid solutions. (author)

  8. Andes Mountain Snow Distribution, Properties, and Trend: 1979-2014

    Science.gov (United States)

    Mernild, Sebastian H.; Liston, Glen E.; Hiemstra, Christopher A.

    2015-04-01

    Andes snow presence, absence, properties, and water amount are key components of Earth's changing climate system that incur far-reaching physical ramifications. Modeling developments permit relatively high-resolution (4-km horizontal grid; 3-h time step) Andes snow estimates for 1979-2014. SnowModel, in conjunction with land cover, topography, and 35-years of NASA Modern-Era Retrospective Analysis for Research and Applications (MERRA) atmospheric reanalysis data, was used to create a spatially distributed, time-evolving, snow-related dataset that included air temperature, snow precipitation, snow-season timing and length, maximum snow water equivalent depth, and average snow density. Regional variability is a dominant feature of the modeled snow-property trends from an area northeast of Quito (latitude: 2.65°S to 0.23°N) to Patagonia (latitude: 52.15°S to 46.44°S). For example, the Quito area annual snow cover area changed -45%, -43% around Cusco (latitude: 14.75°S to 12.52°S), -5% east of Santiago (including the Olivares Basin), and 25% in Patagonia. The annual snow covered area for the entire Andes decreased 13%, mainly in the elevation band between 4,000-5,000 m a.s.l. In spite of strong regional variability, the data clearly show a general positive trend in mean annual air temperature and precipitation, and a decreasing trend in snow precipitation, snow precipitation days, and snow density. Also, the snow-cover onset is later and the snow-cover duration - the number of snow cover days - decreased.

  9. Building a Cloud-based Global Snow Observatory

    Science.gov (United States)

    Li, X.; Coll, J. M.

    2016-12-01

    Snow covers some 40 percent of Earth's land masses year in and year out and constitutes a vitally important variable for the planet's climate, hydrology, and biosphere due to its high albedo and insulation. It affects atmospheric circulation patterns, permafrost, glacier mass balance, river discharge, and groundwater recharge (Dietz et al. 2015). Snow is also nature's igloo where species from microscopic fungi to 800-pound moose survive the winter each in its own way (Pauli et al. 2013; Petty et al. 2015). Many studies have found that snow in high elevation regions is particularly sensitive to global climate change and is considered as sentinel of change. For human beings, about one-sixth of the world's population depends on seasonal snow and glaciers for their water supply (Barnett et al. 2005) and more than 50% of mountainous areas have an essential or supportive role for downstream regions (Viviroli et al. 2007). Large snowstorms also have a major impact on society in terms of human life, economic loss, and disruption (Squires et al. 2014). Remote sensing provides a practical approach of monitoring global snow and ice cover change. Based on our comprehensive validation and assessment on MODIS snow products, we build a cloud-based Global Snow Observatory (GSO) using Google Earth Engine (GEE) to serve as a platform for global researchers and the general public to access, visualize, and analyze snow data and to build snowmelt runoff models for mountain watersheds. Specifically, we build the GSO to serve global MODIS daily snow cover data and their analyses through GEE on Google App Engine. The GSO provides users the functions of accessing and extracting cloud-gap-filled snow data and interactive snow cover change exploration. In addition to snow cover frequency (SCF), we also plan to develop several other snow cover parameters, including snow cover duration/days, snow cover onset dates, and snow cover melting dates, and to study the shift and trend of global snow

  10. Deriving Snow Cover Metrics for Alaska from MODIS

    Directory of Open Access Journals (Sweden)

    Chuck Lindsay

    2015-09-01

    Full Text Available Moderate Resolution Imaging Spectroradiometer (MODIS daily snow cover products provide an opportunity for determining snow onset and melt dates across broad geographic regions; however, cloud cover and polar darkness are limiting factors at higher latitudes. This study presents snow onset and melt dates for Alaska, portions of western Canada and the Russian Far East derived from Terra MODIS snow cover daily 500 m grid data (MOD10A1 and evaluates our method for filling data gaps caused by clouds or polar darkness. Pixels classified as cloud or no data were reclassified by: spatial filtering using neighboring pixel values; temporal filtering using pixel values for days before/after cloud cover; and snow-cycle filtering based on a time series assessment of a pixel’s position within snow accumulation, cover or melt periods. During the 2012 snow year, these gap-filling methods reduced cloud pixels from 27.7% to 3.1%. A total of 12 metrics (e.g., date of first and last snow, date of persistent snow cover and periods of intermittence for each pixel were calculated by snow year. A comparison of MODIS-derived snow onset and melt dates with in situ observations from 244 weather stations generally showed an early bias in MODIS-derived dates and an effect of increasing cloudiness exacerbating bias. Our results show that mean regional duration of seasonal snow cover is 179–311 days/year and that snow cover is often intermittent, with 41% of the area experiencing ≥2 snow-covered periods during a snow season. Other regional-scale patterns in the timing of snow onset and melt are evident in the yearly 500 m gridded products publically available at http://static.gina.alaska.edu/NPS_products/MODIS_snow/.

  11. Snow Precipitation and Snow Cover Climatic Variability for the Period 1971–2009 in the Southwestern Italian Alps: The 2008–2009 Snow Season Case Study

    Directory of Open Access Journals (Sweden)

    Simona Fratianni

    2010-10-01

    Full Text Available Snow cover greatly influences the climate in the Alpine region and is one of the most relevant parameters for the climate change analysis. Nevertheless, snow precipitation variability is a relatively underexplored field of research because of the lack of long-term, continuous and homogeneous time series. After a historical research aiming to recover continuous records, three high quality time series of snow precipitation and snow depth recorded in the southwestern Italian Alps were analyzed. The comparison between the climatological indices over the 30 years reference period 1971–2000 and the decade 2000–2009 outlined a general decrease in the amount of snow precipitation, and a shift in the seasonal distribution of the snow precipitation in the most recent period. In the analysis of the last decade snow seasons characteristics, the attention was focused on the heavy snowfalls that occurred in Piedmont during the 2008–2009 snow season: MODerate resolution Imager Spectroradiometer (MODIS snow cover products were used to evaluate snow cover extension at different times during the snow season, and the results were set in relation to the temperatures.

  12. Linking snowfall and snow accumulation to generate spatial maps of SWE and snow depth

    Science.gov (United States)

    Broxton, Patrick D.; Dawson, Nicholas; Zeng, Xubin

    2016-06-01

    It is critically important but challenging to estimate the amount of snow on the ground over large areas due to its strong spatial variability. Point snow data are used to generate or improve (i.e., blend with) gridded estimates of snow water equivalent (SWE) by using various forms of interpolation; however, the interpolation methodologies often overlook the physical mechanisms for the snow being there in the first place. Using data from the Snow Telemetry and Cooperative Observer networks in the western United States, we show that four methods for the spatial interpolation of peak of winter snow water equivalent (SWE) and snow depth based on distance and elevation can result in large errors. These errors are reduced substantially by our new method, i.e., the spatial interpolation of these quantities normalized by accumulated snowfall from the current or previous water years. Our method results in significant improvement in SWE estimates over interpolation techniques that do not consider snowfall, regardless of the number of stations used for the interpolation. Furthermore, it can be used along with gridded precipitation and temperature data to produce daily maps of SWE over the western United States that are comparable to existing estimates (which are based on the assimilation of much more data). Our results also show that not honoring the constraint between SWE and snowfall when blending in situ data with gridded data can lead to the development and propagation of unrealistic errors.

  13. A systematic review on the safety of Prostar XL versus ProGlide after TAVR and EVAR

    Energy Technology Data Exchange (ETDEWEB)

    Maniotis, Christos [2nd Cardiology Department, Hellenic Red Cross Hospital of Athens, Athens (Greece); Andreou, Constantinos; Karalis, Ioannis [Interventional Cardiology Department, University Hospital of Leiden, Leiden (Netherlands); Koutouzi, Giasemi [Interventional Radiology Department, Sahlgrenska University Hospital, Gothenburg (Sweden); Agelaki, Maria [2nd Cardiology Department, Hellenic Red Cross Hospital of Athens, Athens (Greece); Koutouzis, Michael, E-mail: koutouzismike@yahoo.gr [2nd Cardiology Department, Hellenic Red Cross Hospital of Athens, Athens (Greece)

    2017-03-15

    Background: Endovascular aortic aneurysm repair (EVAR) and transfemoral transcatheter aortic valve replacement (TAVR) are widely spreading minimally invasive procedures performed mainly through the femoral artery. Prostar XL and ProGlide vascular closure devices are used in clinical practice for the hemostasis in these procedures and they have been shown to be safe and effective. Purpose: The aim of our systematic review is to compare the safety of these two devices for percutaneous closure of large arteriotomies in patients undergoing TAVR and EVAR. Methods: We searched PubMed, EMBASE, Google Scholar and the Cochrane Central Register of Controlled Trials for all randomized and observational published studies that compared Prostar XL vs. ProGlide. Relative risk was calculated by random-effects model. Review Manager 5.1 was used for statistical analysis. Results: A total number of 2909 patients were included in our analysis. The rate of overall vascular complications did not differ between Prostar XL and ProGlide {RR 1.35 (0.80–2.29), p = 0.27}. In contrary, the risk ratio of all bleeding complications with Prostar XL compared to ProGlide was 1.82 (1.47–2.24, p < 0.001) and for major and life-threatening bleeding complications was 2.48 (1.65–3.73, p < 0001, suggesting a lower bleeding risk with ProGlide). No statistical difference was found between groups for end-stage acute kidney injury (AKI), with a risk ratio of 2.14 (0.81–5.66), p = 0.05. Finally, there were no differences in in-hospital and 30-days mortality rate between the two groups (1.41, 0.56–3.54, p = 0.46 and 1.43, 0.55–3.73, p = 0.47, respectively). Conclusions: Prostar XL is associated with greater risk of any bleeding as well as life threatening bleeding compared to the ProGlide device. However, no significant differences were observed in the rate of overall vascular complications, end stage AKI and in-hospital and 30-days mortality. - Highlights: • We present a systematic review

  14. A protein secretion system linked to bacteroidete gliding motility and pathogenesis

    Science.gov (United States)

    Sato, Keiko; Naito, Mariko; Yukitake, Hideharu; Hirakawa, Hideki; Shoji, Mikio; McBride, Mark J.; Rhodes, Ryan G.; Nakayama, Koji

    2009-01-01

    Porphyromonas gingivalis secretes strong proteases called gingipains that are implicated in periodontal pathogenesis. Protein secretion systems common to other Gram-negative bacteria are lacking in P. gingivalis, but several proteins, including PorT, have been linked to gingipain secretion. Comparative genome analysis and genetic experiments revealed 11 additional proteins involved in gingipain secretion. Six of these (PorK, PorL, PorM, PorN, PorW, and Sov) were similar in sequence to Flavobacterium johnsoniae gliding motility proteins, and two others (PorX and PorY) were putative two-component system regulatory proteins. Real-time RT-PCR analysis revealed that porK, porL, porM, porN, porP, porT, and sov were down-regulated in P. gingivalis porX and porY mutants. Disruption of the F. johnsoniae porT ortholog resulted in defects in motility, chitinase secretion, and translocation of a gliding motility protein, SprB adhesin, to the cell surface, providing a link between a unique protein translocation system and a motility apparatus in members of the Bacteroidetes phylum. PMID:19966289

  15. Instantaneous imaging of ozone in a gliding arc discharge using photofragmentation laser-induced fluorescence

    Science.gov (United States)

    Larsson, Kajsa; Hot, Dina; Gao, Jinlong; Kong, Chengdong; Li, Zhongshan; Aldén, Marcus; Bood, Joakim; Ehn, Andreas

    2018-04-01

    Ozone vapor, O3, is here visualized in a gliding arc discharge using photofragmentation laser-induced fluorescence. Ozone is imaged by first photodissociating the O3 molecule into an O radical and a vibrationally hot O2 fragment by a pump photon. Thereafter, the vibrationally excited O2 molecule absorbs a second (probe) photon that further transits the O2-molecule to an excited electronic state, and hence, fluorescence from the deexcitation process in the molecule can be detected. Both the photodissociation and excitation processes are achieved within one 248 nm KrF excimer laser pulse that is formed into a laser sheet and the fluorescence is imaged using an intensified CCD camera. The laser-induced signal in the vicinity of the plasma column formed by the gliding arc is confirmed to stem from O3 rather than plasma produced vibrationally hot O2. While both these products can be produced in plasmas a second laser pulse at 266 nm was utilized to separate the pump- from the probe-processes. Such arrangement allowed lifetime studies of vibrationally hot O2, which under these conditions were several orders of magnitude shorter than the lifetime of plasma-produced ozone.

  16. Decolorization of Acid Orange 7 solution by gas-liquid gliding arc discharge plasma.

    Science.gov (United States)

    Du, ChangMing; Shi, TaiHong; Sun, YuWei; Zhuang, XiaoFeng

    2008-06-15

    The decolorization of 180 microM aqueous solutions of Acid Orange 7 (AO7) by means of a non-thermal plasma technique (i.e., the gas-liquid gliding arc discharge, which is generated between at least two metal electrodes with AC high voltage) was investigated in this paper. The effects of the plasma treatment time and the type of feeding gas, including air, oxygen, nitrogen and argon of the dye removal were determined. It is found that the voltage cycles of the gas-liquid gliding arc discharge are characterized by a moderate increase in the tension which is represented by a peak followed by an abrupt decrease and a current peak in the half period (10 ms); the concentration of AO7 solution decreases exponentially to reach 58.9, 77.4, 89.1, 95.1 and 99% in 25, 50, 75, 100 and 125 min, respectively, and the ln(Ct/C0) varies linearly with the treatment time t, indicating that decolorization reaction follow first pseudo-order kinetics with a constant rate of 0.03327 min(-1) when air was used as feeding gas; the decolorization rate during the plasma treatment is the greatest for oxygen as the feeding gas, in turn followed by air and argon, and was the least when using nitrogen. The variations of pH and conductivity and the formations of hydrogen peroxide and ozone are measured.

  17. Glide-symmetric locomotion reinforcement in patients with multiple sclerosis by visual feedback.

    Science.gov (United States)

    Baram, Yoram; Miller, Ariel

    2010-01-01

    To compare the effects of gait training with distinct glide-symmetric visual feedback cues, adapted to the geometry of human locomotion, to the effects of training with visual cues of no distinct symmetry, on the walking abilities of subjects with gait disorders due to multiple sclerosis (MS). Ten patients trained with transverse lines while 11 patients trained with checkerboard tiles, both provided by a wearable virtual reality device. Baseline performance (walking speed and stride length along a 10 m straight track) was measured before device use. Following 20 min training with the device and 10 min rest, performance without the device was measured again and compared to the baseline performance. The average improvement in the group using the visual cue of transverse lines was 7.79% +/- 4.24% in walking speed and 7.20% +/- 3.92% in stride length. The average improvement in the group using the visual cue of checkerboard tiles was 21.09% +/- 18.39% in walking speed and 12.99% +/- 1.72% in stride length. Patients with gait disorders due to MS, training with a glide-symmetric visual feedback cue, showed a significantly higher improvement in their gait parameters than patients training with a visual feedback cue of no without distinct symmetry.

  18. Fine-scale genetic response to landscape change in a gliding mammal.

    Directory of Open Access Journals (Sweden)

    Ross L Goldingay

    Full Text Available Understanding how populations respond to habitat loss is central to conserving biodiversity. Population genetic approaches enable the identification of the symptoms of population disruption in advance of population collapse. However, the spatio-temporal scales at which population disruption occurs are still too poorly known to effectively conserve biodiversity in the face of human-induced landscape change. We employed microsatellite analysis to examine genetic structure and diversity over small spatial (mostly 1-50 km and temporal scales (20-50 years in the squirrel glider (Petaurus norfolcensis, a gliding mammal that is commonly subjected to a loss of habitat connectivity. We identified genetically differentiated local populations over distances as little as 3 km and within 30 years of landscape change. Genetically isolated local populations experienced the loss of genetic diversity, and significantly increased mean relatedness, which suggests increased inbreeding. Where tree cover remained, genetic differentiation was less evident. This pattern was repeated in two landscapes located 750 km apart. These results lend support to other recent studies that suggest the loss of habitat connectivity can produce fine-scale population genetic change in a range of taxa. This gives rise to the prediction that many other vertebrates will experience similar genetic changes. Our results suggest the future collapse of local populations of this gliding mammal is likely unless habitat connectivity is maintained or restored. Landscape management must occur on a fine-scale to avert the erosion of biodiversity.

  19. Designing, developing and implementing a living snow fence program for New York state.

    Science.gov (United States)

    2015-07-01

    Living snow fences (LSF) are a form of passive snow control designed to mitigate blowing and drifting snow problems : on roadways. Blowing and drifting snow can increase the cost of highway maintenance and create hazardous driving : conditions when s...

  20. CLPX-Ground: Snow Measurements at the Local Scale Observation Site (LSOS), Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set presents snow depth, snow water equivalence (SWE), snow wetness data, and snow pit data from two pine sites and a small clearing at the Local Scale...

  1. CLPX-Ground: Snow Measurements at the Local Scale Observation Site (LSOS)

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set presents snow depth, snow water equivalence (SWE), snow wetness data, and snow pit data from two pine sites and a small clearing at the Local Scale...

  2. Merging datasets from NASA SnowEx to better understand how snow falls and moves.

    Science.gov (United States)

    Gongora, J. A.; Marshall, H. P.; Glenn, N. F.

    2017-12-01

    A modelers ability to estimated snow depth and snow water equivalent (SWE) for mountain snow depends strongly on their understanding of snowpack spatial distribution and the soundness of the models initial conditions. This work focuses on the application of data science and efficient algorithms to find optimal locations in mountainous terrain to act as initital conditions for machine driven interpolation methods. By using graphs, collections of pairwise relationships between objects, to describe our data we were able to efficiently search, partition, and understand snowpack from the persepetive of this data structure.

  3. Integration of snow management practices into a detailed snow pack model

    Science.gov (United States)

    Spandre, Pierre; Morin, Samuel; Lafaysse, Matthieu; Lejeune, Yves; François, Hugues; George-Marcelpoil, Emmanuelle

    2016-04-01

    The management of snow on ski slopes is a key socio-economic and environmental issue in mountain regions. Indeed the winter sports industry has become a very competitive global market although this economy remains particularly sensitive to weather and snow conditions. The understanding and implementation of snow management in detailed snowpack models is a major step towards a more realistic assessment of the evolution of snow conditions in ski resorts concerning past, present and future climate conditions. Here we describe in a detailed manner the integration of snow management processes (grooming, snowmaking) into the snowpack model Crocus (Spandre et al., Cold Reg. Sci. Technol., in press). The effect of the tiller is explicitly taken into account and its effects on snow properties (density, snow microstructure) are simulated in addition to the compaction induced by the weight of the grooming machine. The production of snow in Crocus is carried out with respect to specific rules and current meteorological conditions. Model configurations and results are described in detail through sensitivity tests of the model of all parameters related to snow management processes. In-situ observations were carried out in four resorts in the French Alps during the 2014-2015 winter season considering for each resort natural, groomed only and groomed plus snowmaking conditions. The model provides realistic simulations of the snowpack properties with respect to these observations. The main uncertainty pertains to the efficiency of the snowmaking process. The observed ratio between the mass of machine-made snow on ski slopes and the water mass used for production was found to be lower than was expected from the literature, in every resort. The model now referred to as "Crocus-Resort" has been proven to provide realistic simulations of snow conditions on ski slopes and may be used for further investigations. Spandre, P., S. Morin, M. Lafaysse, Y. Lejeune, H. François and E. George

  4. ISLSCP II Northern Hemisphere Monthly Snow Cover Extent

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This ISLSCP data set is derived from the National Snow and Ice Data Center (NSIDC) Northern Hemisphere EASE-Grid Weekly Snow Cover and Sea Ice Extent...

  5. Meltater Flow Through Snow from Plot to Baisn Scale

    National Research Council Canada - National Science Library

    Williams, Mark

    2000-01-01

    ... research instrumentation award. Near-infrared photographs of melting snow were analyzed using a moving windows procedure that can be used to define the correlation lengths in the snow reflectance surface...

  6. Rand Corporation Mean Monthly Global Snow Depth, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides monthly snow depth for the entire globe (excluding Africa and South America) from 1950 to 1976. All available monthly snow depth climatologies...

  7. Heavy metals in the snow pack of Semey town

    International Nuclear Information System (INIS)

    Panin, M.S.; Esenzholova, A.Zh.; Toropov, A.S.

    2008-01-01

    The data about the maintenance of heavy metals in the snow pack in various zones of Semey and biogeochemical operation factors of snow pack in Semey are presented in this work. Also the correlation connection between elements is calculated.

  8. Russian Federation Snow Depth and Ice Crust Surveys

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Russian Federation Snow Depth and Ice Crust Surveys, dataset DSI-9808, contains routine snow surveys that run throughout the cold season every 10 days (every five...

  9. Estonian Mean Snow Depth and Duration (1891-1994)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains the number of days of snow cover in days per year, and three 10-day snow depth means per month in centimeters from stations across Estonia....

  10. Canadian Meteorological Centre (CMC) Daily Snow Depth Analysis Data

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set consists of Northern Hemisphere snow depth analysis data processed by the Canadian Meteorological Centre (CMC). Snow depth data obtained from surface...

  11. ISLSCP II Northern Hemisphere Monthly Snow Cover Extent

    Data.gov (United States)

    National Aeronautics and Space Administration — This ISLSCP data set is derived from the National Snow and Ice Data Center (NSIDC) Northern Hemisphere EASE-Grid Weekly Snow Cover and Sea Ice Extent product which...

  12. Western Italian Alps Monthly Snowfall and Snow Cover Duration

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set consists of snow observations for 18 stations in the western Italian Alps. Two types of data are included: monthly snowfall amounts and monthly snow...

  13. [Characteristics of chemical pollution of snow cover in Aktobe areas].

    Science.gov (United States)

    Iskakov, A Zh

    2010-01-01

    The paper gives data on the nature of snow cover pollution in the urbanized areas in relation to the remoteness from the basic sources of ambient air pollution. The total snow content of carcinogens has been estimated.

  14. GPM GROUND VALIDATION GCPEX SNOW MICROPHYSICS CASE STUDY V1

    Data.gov (United States)

    National Aeronautics and Space Administration — The GPM Ground Validation GCPEX Snow Microphysics Case Study characterizes the 3-D microphysical evolution and distribution of snow in context of the thermodynamic...

  15. Estimation of snow cover distribution in Beas basin, Indian Himalaya ...

    Indian Academy of Sciences (India)

    areas of Himalaya, which is at high altitude,. Keywords. Snow cover monitoring; NDSI; AWiFS; reflectance; topographic corrections. J. Earth Syst. Sci. 118, No. 5, October 2009, pp. ... characteristics of snow and vegetation to reduce the errors caused ...... Thakur N and Manoj 2002a Effect of global warming on snow ablation ...

  16. Snow instability patterns at the scale of a small basin

    Science.gov (United States)

    Reuter, Benjamin; Richter, Bettina; Schweizer, Jürg

    2016-02-01

    Spatial and temporal variations are inherent characteristics of the alpine snow cover. Spatial heterogeneity is supposed to control the avalanche release probability by either hindering extensive crack propagation or facilitating localized failure initiation. Though a link between spatial snow instability variations and meteorological forcing is anticipated, it has not been quantitatively shown yet. We recorded snow penetration resistance profiles with the snow micropenetrometer at an alpine field site during five field campaigns in Eastern Switzerland. For each of about 150 vertical profiles sampled per day a failure initiation criterion and the critical crack length were calculated. For both criteria we analyzed their spatial structure and predicted snow instability in the basin by external drift kriging. The regression models were based on terrain and snow depth data. Slope aspect was the most prominent driver, but significant covariates varied depending on the situation. Residual autocorrelation ranges were shorter than the ones of the terrain suggesting external influences possibly due to meteorological forcing. To explore the causes of the instability patterns we repeated the geostatistical analysis with snow cover model output as covariate data for one case. The observed variations of snow instability were related to variations in slab layer properties which were caused by preferential deposition of precipitation and differences in energy input at the snow surface during the formation period of the slab layers. Our results suggest that 3-D snow cover modeling allows reproducing some of the snow property variations related to snow instability, but in future work all relevant micrometeorological spatial interactions should be considered.

  17. [Analysis of influencing factors of snow hyperspectral polarized reflections].

    Science.gov (United States)

    Sun, Zhong-Qiu; Zhao, Yun-Sheng; Yan, Guo-Qian; Ning, Yan-Ling; Zhong, Gui-Xin

    2010-02-01

    Due to the need of snow monitoring and the impact of the global change on the snow, on the basis of the traditional research on snow, starting from the perspective of multi-angle polarized reflectance, we analyzed the influencing factors of snow from the incidence zenith angles, the detection zenith angles, the detection azimuth angles, polarized angles, the density of snow, the degree of pollution, and the background of the undersurface. It was found that these factors affected the spectral reflectance values of the snow, and the effect of some factors on the polarization hyperspectral reflectance observation is more evident than in the vertical observation. Among these influencing factors, the pollution of snow leads to an obvious change in the snow reflectance spectrum curve, while other factors have little effect on the shape of the snow reflectance spectrum curve and mainly impact the reflection ratio of the snow. Snow reflectance polarization information has not only important theoretical significance, but also wide application prospect, and provides new ideas and methods for the quantitative research on snow using the remote sensing technology.

  18. Estimation of snow cover distribution in Beas basin, Indian Himalaya ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 118; Issue 5 ... The satellite estimated snow or non-snow pixel information using proposed methodology was validated with the snow cover information collected at three observatory locations and it was found that the algorithm classify all the sample points correctly ...

  19. Collaborative Research: Snow Accumulation and Snow Melt in a Mixed Northern Hardwood-Conifer Forest, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains snow depth, Snow Water Equivalent (SWE), and forest cover characteristics for sites at the Hubbard Brook Experimental Forest in northern New...

  20. Assessment and placement of living snow fences to reduce highway maintenance costs and improve safety (living snow fences).

    Science.gov (United States)

    2015-05-01

    Living snow fences (LSF) are designed plantings of trees and/or shrubs and native grasses along highways, roads : and ditches that create a vegetative buffer that traps and controls blowing and drifting snow. These strategically : placed fences have ...

  1. Enhancement of the MODIS Daily Snow Albedo Product

    Science.gov (United States)

    Hall, Dorothy K.; Schaaf, Crystal B.; Wang, Zhuosen; Riggs, George A.

    2009-01-01

    The MODIS daily snow albedo product is a data layer in the MOD10A1 snow-cover product that includes snow-covered area and fractional snow cover as well as quality information and other metadata. It was developed to augment the MODIS BRDF/Albedo algorithm (MCD43) that provides 16-day maps of albedo globally at 500-m resolution. But many modelers require daily snow albedo, especially during the snowmelt season when the snow albedo is changing rapidly. Many models have an unrealistic snow albedo feedback in both estimated albedo and change in albedo over the seasonal cycle context, Rapid changes in snow cover extent or brightness challenge the MCD43 algorithm; over a 16-day period, MCD43 determines whether the majority of clear observations was snow-covered or snow-free then only calculates albedo for the majority condition. Thus changes in snow albedo and snow cover are not portrayed accurately during times of rapid change, therefore the current MCD43 product is not ideal for snow work. The MODIS daily snow albedo from the MOD10 product provides more frequent, though less robust maps for pixels defined as "snow" by the MODIS snow-cover algorithm. Though useful, the daily snow albedo product can be improved using a daily version of the MCD43 product as described in this paper. There are important limitations to the MOD10A1 daily snow albedo product, some of which can be mitigated. Utilizing the appropriate per-pixel Bidirectional Reflectance Distribution Functions (BRDFs) can be problematic, and correction for anisotropic scattering must be included. The BRDF describes how the reflectance varies with view and illumination geometry. Also, narrow-to-broadband conversion specific for snow on different surfaces must be calculated and this can be difficult. In consideration of these limitations of MOD10A1, we are planning to improve the daily snow albedo algorithm by coupling the periodic per-pixel snow albedo from MCD43, with daily surface ref|outanoom, In this paper, we

  2. "Snow Soup" Students Take on Animation Creation

    Science.gov (United States)

    Nikirk, Martin

    2009-01-01

    This article describes the process of producing "Snow Soup"--the 2009 Adobe Flash animation produced by the Computer Game Development and Animation seniors of Washington County Technical High School in Hagerstown, Maryland, for libraries in their area. In addition to the Flash product, the students produced two related Game Maker games, a printed…

  3. Snow and ice control at extreme temperatures.

    Science.gov (United States)

    2011-04-25

    As expected, most state and provincial DOTs that we spoke with are using traditional methods to prevent and : remove snow and ice at very low temperatures. In addition to a review of current research, we spoke with six winter : maintenance profession...

  4. Evaluation of alternative snow plow cutting edges.

    Science.gov (United States)

    2009-05-01

    With approximately 450 snow plow trucks, the Maine Department of Transportation (MaineDOT) uses in : excess of 10,000 linear feet of plow cutting edges each winter season. Using the 2008-2009 cost per linear : foot of $48.32, the Departments total co...

  5. Snow as an accumulator of air pollutants

    Science.gov (United States)

    Robert T. Brown

    1976-01-01

    Using simple analytical techniques, the amounts of air pollutants accumulated in winter snow were determined and the results correlated with lichen survival on trees. Pollutants measured were particulate matter, sulfate, and chloride. An inverse relationship was found between amounts of each of these pollutants and the abundance of various lichens.

  6. Combining snow depth and innovative skier flow measurements in order to improve snow grooming techniques

    Science.gov (United States)

    Carmagnola, Carlo Maria; Albrecht, Stéphane; Hargoaa, Olivier

    2017-04-01

    In the last decades, ski resort managers have massively improved their snow management practices, in order to adapt their strategies to the inter-annual variability in snow conditions and to the effects of climate change. New real-time informations, such as snow depth measurements carried out on the ski slopes by grooming machines during their daily operations, have become available, allowing high saving, efficiency and optimization gains (reducing for instance the groomer fuel consumption and operation time and the need for machine-made snow production). In order to take a step forward in improving the grooming techniques, it would be necessary to keep into account also the snow erosion by skiers, which depends mostly on the snow surface properties and on the skier attendance. Today, however, most ski resort managers have only a vague idea of the evolution of the skier flows on each slope during the winter season. In this context, we have developed a new sensor (named Skiflux) able to measure the skier attendance using an infrared beam crossing the slopes. Ten Skiflux sensors have been deployed during the 2016/17 winter season at Val Thorens ski area (French Alps), covering a whole sector of the resort. A dedicated software showing the number of skier passages in real time as been developed as well. Combining this new Skiflux dataset with the snow depth measurements from grooming machines (Snowsat System) and the snow and meteorological conditions measured in-situ (Liberty System from Technoalpin), we were able to create a "real-time skiability index" accounting for the quality of the surface snow and its evolution during the day. Moreover, this new framework allowed us to improve the preparation of ski slopes, suggesting new strategies for adapting the grooming working schedule to the snow quality and the skier attendance. In the near future, this work will benefit from the advances made within the H2020 PROSNOW project ("Provision of a prediction system allowing

  7. Use of Landsat multispectral imagery in estimating snow areal extent and snow water content cost-effectively

    Science.gov (United States)

    Khorram, S.

    1977-01-01

    Landsat color composites are used in conjunction with a limited amount of aerial survey data and ground-truth measurements in order to estimate snow areal extent and snow water content. The snow water content estimations are based on the inexpensive Landsat data and the much more expensively obtained information on ground snow courses. A cost-effectiveness analysis of the procedures showed the expenses involved in obtaining confidence intervals of 80, 90, 95 and 99% for the estimates.

  8. Iron snow in the Martian Core?

    Science.gov (United States)

    Davies, C. J.; Pommier, A.

    2017-12-01

    The decline of Mars' global magnetic field some 3.8-4.1 billion years ago is thought to reflect the demise of the dynamo that operated in its liquid core. The termination of the dynamo is intimately tied to the thermochemical evolution of the core-mantle system and therefore to the present-day physical state of the Martian core. The standard model predicts that the Martian dynamo failed because thermal convection stopped and the core remained entirely liquid until the present. Here we consider an alternative hypothesis that the Martian core crystallized from the top down in the so-called iron snow regime. We derive energy-entropy equations describing the long-timescale thermal and magnetic evolution of the core that incorporate the self-consistent formation of a snow layer that freezes out pure iron and is assumed to be on the liquidus; the iron sinks and remelts in the deeper core, acting as a possible source for magnetic field generation. Compositions are in the FeS system, with a sulfur content up to 16 wt%. The values of the different parameters (core radius, density and CMB pressure) are varied within bounds set by recent internal structure models that satisfy existing geodetic constraints (planetary mass, moment of inertia and tidal Love number). The melting curve and adiabat, CMB heat flow and thermal conductivity were also varied, based on previous experimental and numerical works. We observe that the formation of snow zones occurs for a wide range of interior and thermal structure properties and depends critically on the initial sulfur concentration. Gravitational energy release and latent heat effects arising during growth of the snow zone do not generate sufficient entropy to restart the dynamo unless the snow zone occupies a significant fraction of the core. Our results suggest that snow zones can be 1.5-2 Gyrs old, though thermal stratification of the uppermost core, not included in our model, likely delays onset. Models that match the available

  9. GlideScope videolaryngoscope vs. Macintosh direct laryngoscope for intubation of morbidly obese patients: a randomized trial

    DEFF Research Database (Denmark)

    Andersen, L H; Rovsing, Marie Louise; Olsen, K S

    2011-01-01

    Morbidly obese patients are at increased risk of hypoxemia during tracheal intubation because of increased frequency of difficult and impossible intubation and a decreased apnea tolerance. In this study, intubation with the GlideScope videolaryngoscope (GS) was compared with the Macintosh direct...

  10. Estimating intratidal nonlinearity of respiratory system mechanics: a model study using the enhanced gliding-SLICE method

    International Nuclear Information System (INIS)

    Schumann, Stefan; Burcza, Boris; Guttmann, Josef; Haberthür, Christoph; Lichtwarck-Aschoff, Michael

    2009-01-01

    In the clinical situation and in most research work, the analysis of respiratory system mechanics is limited to the estimation of single-value compliances during static or quasi-static conditions. In contrast, our SLICE method analyses intratidal nonlinearity under the dynamic conditions of mechanical ventilation by calculating compliance and resistance for six conjoined volume portions (slices) of the pressure–volume loop by multiple linear regression analysis. With the gliding-SLICE method we present a new approach to determine continuous intratidal nonlinear compliance. The performance of the gliding-SLICE method was tested both in computer simulations and in a physical model of the lung, both simulating different intratidal compliance profiles. Compared to the original SLICE method, the gliding-SLICE method resulted in smaller errors when calculating the compliance or pressure course (all p 2 O s L −1 to 0.8 ± 0.3 cmH 2 O s L −1 (mathematical model) and from 7.2 ± 3.9 cmH 2 O s L −1 to 0.4 ± 0.2 cmH 2 O s L −1 (physical model) (all p < 0.001). We conclude that the new gliding-SLICE method allows detailed assessment of intratidal nonlinear respiratory system mechanics without discontinuity error

  11. Differential Recognition of Pitch Patterns in Discrete and Gliding Stimuli in Congenital Amusia: Evidence from Mandarin Speakers

    Science.gov (United States)

    Liu, Fang; Xu, Yi; Patel, Aniruddh D.; Francart, Tom; Jiang, Cunmei

    2012-01-01

    This study examined whether "melodic contour deafness" (insensitivity to the direction of pitch movement) in congenital amusia is associated with specific types of pitch patterns (discrete versus gliding pitches) or stimulus types (speech syllables versus complex tones). Thresholds for identification of pitch direction were obtained using discrete…

  12. Colony analysis and deep learning uncover 5-hydroxyindole as an inhibitor of gliding motility and iridescence in Cellulophaga lytica.

    Science.gov (United States)

    Chapelais-Baron, Maylis; Goubet, Isabelle; Péteri, Renaud; Pereira, Maria de Fatima; Mignot, Tâm; Jabveneau, Apolline; Rosenfeld, Eric

    2018-03-01

    Iridescence is an original type of colouration that is relatively widespread in nature but has been either incompletely described or entirely neglected in prokaryotes. Recently, we reported a brilliant 'pointillistic' iridescence in agar-grown colony biofilms of Cellulophaga lytica and some other marine Flavobacteria that exhibit gliding motility. Bacterial iridescence is created by a unique self-organization of sub-communities of cells, but the mechanisms underlying such living photonic crystals are unknown. In this study, we used Petri dish assays to screen a large panel of potential activators or inhibitors of C. lytica's iridescence. Derivatives potentially interfering with quorum-sensing and other communication or biofilm formation processes were tested, as well as metabolic poisons or algal exoproducts. We identified an indole derivative, 5-hydroxyindole (5HI, 250 µM) which inhibited both gliding and iridescence at the colonial level. 5HI did not affect growth or cell respiration. At the microscopic level, phase-contrast imaging confirmed that 5HI inhibits the gliding motility of cells. Moreover, the lack of iridescence correlated with a perturbation of self-organization of the cell sub-communities in both the WT and a gliding-negative mutant. This effect was proved using recent advances in machine learning (deep neuronal networks). In addition to its effect on colony biofilms, 5HI was found to stimulate biofilm formation in microplates. Our data are compatible with possible roles of 5HI or marine analogues in the eco-biology of iridescent bacteria.

  13. An analysis of snow cover changes in the Himalayan region using MODIS snow products and in-situ temperature data

    NARCIS (Netherlands)

    Maskey, S.; Uhlenbrook, S.; Ojha, S.

    2011-01-01

    Amidst growing concerns over the melting of the Himalayas’ snow and glaciers, we strive to answer some of the questions related to snow cover changes in the Himalayan region covering Nepal and its vicinity using Moderate Resolution Imaging Spectroradiometer (MODIS) snow cover products from 2000 to

  14. Variability of snow line elevation, snow cover area and depletion in the main Slovak basins in winters 2001–2014

    Directory of Open Access Journals (Sweden)

    Krajčí Pavel

    2016-03-01

    Full Text Available Spatial and temporal variability of snow line (SL elevation, snow cover area (SCA and depletion (SCD in winters 2001–2014 is investigated in ten main Slovak river basins (the Western Carpathians. Daily satellite snow cover maps from MODIS Terra (MOD10A1, V005 and Aqua (MYD10A1, V005 with resolution 500 m are used.

  15. Estimation of the condition of snow cover in Voronezh according to the chemical analysis of water from melted snow

    OpenAIRE

    Prozhorina Tatyana Ivanovna; Bespalova Elena Vladimirovna; Yakunina Nadezhda

    2014-01-01

    Snow cover possesses high sorption ability and represents informative object to identify technogenic pollution of an urban environment. In this article the investigation data of a chemical composition of snow fallen in Voronezh during the winter period of 2014 are given. Relationships between existence of pollutants in snow and the level of technogenic effect are analyzed.

  16. Planetesimal formation starts at the snow line

    Science.gov (United States)

    Drążkowska, J.; Alibert, Y.

    2017-12-01

    Context. The formation stage of planetesimals represents a major gap in our understanding of the planet formation process. Late-stage planet accretion models typically make arbitrary assumptions about planetesimal and pebble distribution, while dust evolution models predict that planetesimal formation is only possible at some orbital distances. Aims: We wish to test the importance of the water snow line in triggering the formation of the first planetesimals during the gas-rich phase of a protoplanetary disk, when cores of giant planets have to form. Methods: We connected prescriptions for gas disk evolution, dust growth and fragmentation, water ice evaporation and recondensation, the transport of both solids and water vapor, and planetesimal formation via streaming instability into a single one-dimensional model for protoplanetary disk evolution. Results: We find that processes taking place around the snow line facilitate planetesimal formation in two ways. First, because the sticking properties between wet and dry aggregates change, a "traffic jam" inside of the snow line slows the fall of solids onto the star. Second, ice evaporation and outward diffusion of water followed by its recondensation increases the abundance of icy pebbles that trigger planetesimal formation via streaming instability just outside of the snow line. Conclusions: Planetesimal formation is hindered by growth barriers and radial drift and thus requires particular conditions to take place. The snow line is a favorable location where planetesimal formation is possible for a wide range of conditions, but not in every protoplanetary disk model, however. This process is particularly promoted in large cool disks with low intrinsic turbulence and an increased initial dust-to-gas ratio. The movie attached to Fig. 3 is only available at http://www.aanda.org

  17. MODIS Snow Cover Recovery Using Variational Interpolation

    Science.gov (United States)

    Tran, H.; Nguyen, P.; Hsu, K. L.; Sorooshian, S.

    2017-12-01

    Cloud obscuration is one of the major problems that limit the usages of satellite images in general and in NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) global Snow-Covered Area (SCA) products in particular. Among the approaches to resolve the problem, the Variational Interpolation (VI) algorithm method, proposed by Xia et al., 2012, obtains cloud-free dynamic SCA images from MODIS. This method is automatic and robust. However, computational deficiency is a main drawback that degrades applying the method for larger scales (i.e., spatial and temporal scales). To overcome this difficulty, this study introduces an improved version of the original VI. The modified VI algorithm integrates the MINimum RESidual (MINRES) iteration (Paige and Saunders., 1975) to prevent the system from breaking up when applied to much broader scales. An experiment was done to demonstrate the crash-proof ability of the new algorithm in comparison with the original VI method, an ability that is obtained when maintaining the distribution of the weights set after solving the linear system. After that, the new VI algorithm was applied to the whole Contiguous United States (CONUS) over four winter months of 2016 and 2017, and validated using the snow station network (SNOTEL). The resulting cloud free images have high accuracy in capturing the dynamical changes of snow in contrast with the MODIS snow cover maps. Lastly, the algorithm was applied to create a Cloud free images dataset from March 10, 2000 to February 28, 2017, which is able to provide an overview of snow trends over CONUS for nearly two decades. ACKNOWLEDGMENTSWe would like to acknowledge NASA, NOAA Office of Hydrologic Development (OHD) National Weather Service (NWS), Cooperative Institute for Climate and Satellites (CICS), Army Research Office (ARO), ICIWaRM, and UNESCO for supporting this research.

  18. Water and life from snow: A trillion dollar science question

    Science.gov (United States)

    Sturm, Matthew; Goldstein, Michael A.; Parr, Charles

    2017-05-01

    Snow provides essential resources/services in the form of water for human use, and climate regulation in the form of enhanced cooling of the Earth. In addition, it supports a thriving winter outdoor recreation industry. To date, the financial evaluation of the importance of snow is incomplete and hence the need for accelerated snow research is not as clear as it could be. With snow cover changing worldwide in several worrisome ways, there is pressing need to determine global, regional, and local rates of snow cover change, and to link these to financial analyses that allow for rational decision making, as risks related to those decisions involve trillions of dollars.

  19. Snow observations in Mount Lebanon (2011–2016

    Directory of Open Access Journals (Sweden)

    A. Fayad

    2017-08-01

    Full Text Available We present a unique meteorological and snow observational dataset in Mount Lebanon, a mountainous region with a Mediterranean climate, where snowmelt is an essential water resource. The study region covers the recharge area of three karstic river basins (total area of 1092 km2 and an elevation up to 3088 m. The dataset consists of (1 continuous meteorological and snow height observations, (2 snowpack field measurements, and (3 medium-resolution satellite snow cover data. The continuous meteorological measurements at three automatic weather stations (MZA, 2296 m; LAQ, 1840 m; and CED, 2834 m a.s.l. include surface air temperature and humidity, precipitation, wind speed and direction, incoming and reflected shortwave irradiance, and snow height, at 30 min intervals for the snow seasons (November–June between 2011 and 2016 for MZA and between 2014 and 2016 for CED and LAQ. Precipitation data were filtered and corrected for Geonor undercatch. Observations of snow height (HS, snow water equivalent, and snow density were collected at 30 snow courses located at elevations between 1300 and 2900 m a.s.l. during the two snow seasons of 2014–2016 with an average revisit time of 11 days. Daily gap-free snow cover extent (SCA and snow cover duration (SCD maps derived from MODIS snow products are provided for the same period (2011–2016. We used the dataset to characterize mean snow height, snow water equivalent (SWE, and density for the first time in Mount Lebanon. Snow seasonal variability was characterized with high HS and SWE variance and a relatively high snow density mean equal to 467 kg m−3. We find that the relationship between snow depth and snow density is specific to the Mediterranean climate. The current model explained 34 % of the variability in the entire dataset (all regions between 1300 and 2900 m a.s.l. and 62 % for high mountain regions (elevation 2200–2900 m a.s.l.. The dataset is suitable for

  20. Improved MPSP Method-based Cooperative Re-entry Guidance for Hypersonic Gliding Vehicles

    Directory of Open Access Journals (Sweden)

    Chu Haiyan

    2017-01-01

    Full Text Available A computationally sufficient technique is used to solve the 3-D cooperative re-entry guidance problem for hypersonic gliding vehicles. Due to the poor surrounding adaptive ability of the traditional cooperative guidance methods, a novel methodology, named as model predictive static programming (MPSP, is used to solve a class of finite-horizon optimal control problems with hard terminal constraints. The main feature of this guidance law is that it is capable of hitting the target with high accuracy for each one of the cooperative vehicles at the same time. In addition, it accurately satisfies variable constraints. Performance of the proposed MPSP-based guidance is demonstrated in 3-D nonlinear dynamics scenario. The numerical simulation results show that the proposed cooperative re-entry guidance methodology has the advantage of computational efficiency and better robustness against the perturbations.

  1. Treatment by gliding arc of epoxy resin: preliminary analysis of surface modifications

    Science.gov (United States)

    Faubert, F.; Wartel, M.; Pellerin, N.; Pellerin, S.; Cochet, V.; Regnier, E.; Hnatiuc, B.

    2016-12-01

    Treatments with atmospheric pressure non-thermal plasma are easy to implement and inexpensive. Among them gliding arc (GlidArc) remains rarely used in surface treatment of polymers. However, it offers economic and flexible way to treat quickly large areas. In addition the choice of carrier gas makes it possible to bring the active species and other radicals allowing different types of grafting and functionalization of the treated surfaces, for example in order to apply for anti-biofouling prevention. This preliminary work includes analysis of the surface of epoxy resins by infrared spectroscopy: the different affected chemical bonds were studied depending on the duration of treatment. The degree of oxidation (the C/O ratio) is obtained by X-ray microanalysis and contact angle analysis have been performed to determinate the wettability properties of the treated surface. A spectroscopic study of the plasma allows to determine the possible active species in the different zones of the discharge.

  2. Measurements of 3D slip velocities and plasma column lengths of a gliding arc discharge

    DEFF Research Database (Denmark)

    Zhu, Jiajian; Gao, Jinlong; Ehn, Andreas

    2015-01-01

    A non-thermal gliding arc discharge was generated at atmospheric pressure in an air flow. The dynamics of the plasma column and tracer particles were recorded using two synchronized high-speed cameras. Whereas the data analysis for such systems has previously been performed in 2D (analyzing...... the single camera image), we provide here a 3D data analysis that includes 3D reconstructions of the plasma column and 3D particle tracking velocimetry based on discrete tomography methods. The 3D analysis, in particular, the determination of the 3D slip velocity between the plasma column and the gas flow......, gives more realistic insight into the convection cooling process. Additionally, with the determination of the 3D slip velocity and the 3D length of the plasma column, we give more accurate estimates for the drag force, the electric field strength, the power per unit length, and the radius...

  3. Measurements of 3D slip velocities and plasma column lengths of a gliding arc discharge

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Jiajian; Gao, Jinlong; Ehn, Andreas; Aldén, Marcus; Li, Zhongshan, E-mail: zhongshan.li@forbrf.lth.se, E-mail: alpers@ma.tum.de [Division of Combustion Physics, Lund University, P.O. Box 118, S-221 00 Lund (Sweden); Moseev, Dmitry [Max-Planck-Institut für Plasmaphysik, D-85748 Garching bei München (Germany); FOM Institute DIFFER, 3430 BE Nieuwegein (Netherlands); Kusano, Yukihiro [Department of Wind Energy, Section for Composites and Materials Mechanics, Technical University of Denmark, Risø Campus, Frederiksborgvej 399, DK-4000 Roskilde (Denmark); Salewski, Mirko [Department of Physics, Section for Plasma Physics and Fusion Energy, Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark); Alpers, Andreas, E-mail: zhongshan.li@forbrf.lth.se, E-mail: alpers@ma.tum.de; Gritzmann, Peter; Schwenk, Martin [Zentrum Mathematik, Technische Universität München, D-85747 Garching bei München (Germany)

    2015-01-26

    A non-thermal gliding arc discharge was generated at atmospheric pressure in an air flow. The dynamics of the plasma column and tracer particles were recorded using two synchronized high-speed cameras. Whereas the data analysis for such systems has previously been performed in 2D (analyzing the single camera image), we provide here a 3D data analysis that includes 3D reconstructions of the plasma column and 3D particle tracking velocimetry based on discrete tomography methods. The 3D analysis, in particular, the determination of the 3D slip velocity between the plasma column and the gas flow, gives more realistic insight into the convection cooling process. Additionally, with the determination of the 3D slip velocity and the 3D length of the plasma column, we give more accurate estimates for the drag force, the electric field strength, the power per unit length, and the radius of the conducting zone of the plasma column.

  4. Gliding locomotion of manta rays, killer whales and swordfish near the water surface.

    Science.gov (United States)

    Zhan, Jie-Min; Gong, Ye-Jun; Li, Tian-Zeng

    2017-03-24

    The hydrodynamic performance of the locomotive near the water surface is impacted by its geometrical shape. For marine animals, their geometrical shape is naturally selective; thus, investigating gliding locomotion of marine animal under the water surface may be able to elucidate the influence of the geometrical shape. We investigate three marine animals with specific geometries: the killer whale is fusiform shaped; the manta ray is flat and broad-winged; and the swordfish is best streamlined. The numerical results are validated by the measured drag coefficients of the manta ray model in a towing tank. The friction drag of the three target models are very similar; the body shape affected form drag coefficient is order as swordfish killer whale killer whale and swordfish. These bio-inspired observations provide a new and in-depth understanding of the shape effects on the hydrodynamic performances near the free surface.

  5. Gliding arc surface treatment of glass fibre reinforced polyester enhanced by ultrasonic irradiation

    DEFF Research Database (Denmark)

    Kusano, Yukihiro; Singh, Shailendra Vikram; Bardenshtein, Alexander

    2010-01-01

    that polar functional groups were introduced at the surface by the gliding arc treatment, and that the treatment efficiency was enhanced by the ultrasonic irradiation, indicating that the adhesive property would be improved. The results are extensively discussed in terms of the plasma conditions......During atmospheric pressure plasma surface treatment, reactive species generated in the plasma diffuse through a boundary gas layer which sticks at the material surface. Due to the short lifetime of these species only a small fraction can reach the surface, limiting the surface treatment efficiency...... of approximately 150 dB were introduced vertically to the GFRP surface through a cylindrical waveguide. The water contact angle of the GFRP surface dropped markedly with no ultrasonic irradiation, and tended to decrease furthermore at higher power. Ultrasonic irradiation during the plasma treatment consistently...

  6. The Glide/Gcm fate determinant controls initiation of collective cell migration by regulating Frazzled.

    Science.gov (United States)

    Gupta, Tripti; Kumar, Arun; Cattenoz, Pierre B; VijayRaghavan, K; Giangrande, Angela

    2016-10-14

    Collective migration is a complex process that contributes to build precise tissue and organ architecture. Several molecules implicated in cell interactions also control collective migration, but their precise role and the finely tuned expression that orchestrates this complex developmental process are poorly understood. Here, we show that the timely and threshold expression of the Netrin receptor Frazzled triggers the initiation of glia migration in the developing Drosophila wing. Frazzled expression is induced by the transcription factor Glide/Gcm in a dose-dependent manner. Thus, the glial determinant also regulates the efficiency of collective migration. NetrinB but not NetrinA serves as a chemoattractant and Unc5 contributes as a repellant Netrin receptor for glia migration. Our model includes strict spatial localization of a ligand, a cell autonomously acting receptor and a fate determinant that act coordinately to direct glia toward their final destination.

  7. Impact of the snow cover scheme on snow distribution and energy budget modeling over the Tibetan Plateau

    Science.gov (United States)

    Xie, Zhipeng; Hu, Zeyong; Xie, Zhenghui; Jia, Binghao; Sun, Genhou; Du, Yizhen; Song, Haiqing

    2018-02-01

    This paper presents the impact of two snow cover schemes (NY07 and SL12) in the Community Land Model version 4.5 (CLM4.5) on the snow distribution and surface energy budget over the Tibetan Plateau. The simulated snow cover fraction (SCF), snow depth, and snow cover days were evaluated against in situ snow depth observations and a satellite-based snow cover product and snow depth dataset. The results show that the SL12 scheme, which considers snow accumulation and snowmelt processes separately, has a higher overall accuracy (81.8%) than the NY07 (75.8%). The newer scheme performs better in the prediction of overall accuracy compared with the NY07; however, SL12 yields a 15.1% underestimation rate while NY07 overestimated the SCF with a 15.2% overestimation rate. Both two schemes capture the distribution of the maximum snow depth well but show large positive biases in the average value through all periods (3.37, 3.15, and 1.48 cm for NY07; 3.91, 3.52, and 1.17 cm for SL12) and overestimate snow cover days compared with the satellite-based product and in situ observations. Higher altitudes show larger root-mean-square errors (RMSEs) in the simulations of snow depth and snow cover days during the snow-free period. Moreover, the surface energy flux estimations from the SL12 scheme are generally superior to the simulation from NY07 when evaluated against ground-based observations, in particular for net radiation and sensible heat flux. This study has great implications for further improvement of the subgrid-scale snow variations over the Tibetan Plateau.

  8. Simulations of snow distribution and hydrology in a mountain basin

    Science.gov (United States)

    Hartman, M.D.; Baron, Jill S.; Lammers, R.B.; Cline, D.W.; Band, L.E.; Liston, G.E.; Tague, C.

    1999-01-01

    We applied a version of the Regional Hydro-Ecologic Simulation System (RHESSys) that implements snow redistribution, elevation partitioning, and wind-driven sublimation to Loch Vale Watershed (LVWS), an alpine-subalpine Rocky Mountain catchment where snow accumulation and ablation dominate the hydrologic cycle. We compared simulated discharge to measured discharge and the simulated snow distribution to photogrammetrically rectified aerial (remotely sensed) images. Snow redistribution was governed by a topographic similarity index. We subdivided each hillslope into elevation bands that had homogeneous climate extrapolated from observed climate. We created a distributed wind speed field that was used in conjunction with daily measured wind speeds to estimate sublimation. Modeling snow redistribution was critical to estimating the timing and magnitude of discharge. Incorporating elevation partitioning improved estimated timing of discharge but did not improve patterns of snow cover since wind was the dominant controller of areal snow patterns. Simulating wind-driven sublimation was necessary to predict moisture losses.

  9. Objective Characterization of Snow Microstructure for Microwave Emission Modeling

    Science.gov (United States)

    Durand, Michael; Kim, Edward J.; Molotch, Noah P.; Margulis, Steven A.; Courville, Zoe; Malzler, Christian

    2012-01-01

    Passive microwave (PM) measurements are sensitive to the presence and quantity of snow, a fact that has long been used to monitor snowcover from space. In order to estimate total snow water equivalent (SWE) within PM footprints (on the order of approx 100 sq km), it is prerequisite to understand snow microwave emission at the point scale and how microwave radiation integrates spatially; the former is the topic of this paper. Snow microstructure is one of the fundamental controls on the propagation of microwave radiation through snow. Our goal in this study is to evaluate the prospects for driving the Microwave Emission Model of Layered Snowpacks with objective measurements of snow specific surface area to reproduce measured brightness temperatures when forced with objective measurements of snow specific surface area (S). This eliminates the need to treat the grain size as a free-fit parameter.

  10. Analysis of snow feedbacks in 14 general circulation models

    Science.gov (United States)

    Randall, D. A.; Cess, R. D.; Blanchet, J. P.; Chalita, S.; Colman, R.; Dazlich, D. A.; Del Genio, A. D.; Keup, E.; Lacis, A.; Le Treut, H.; Liang, X.-Z.; McAvaney, B. J.; Mahfouf, J. F.; Meleshko, V. P.; Morcrette, J.-J.; Norris, P. M.; Potter, G. L.; Rikus, L.; Roeckner, E.; Royer, J. F.; Schlese, U.; Sheinin, D. A.; Sokolov, A. P.; Taylor, K. E.; Wetherald, R. T.; Yagai, I.; Zhang, M.-H.

    1994-10-01

    Snow feedbacks produced by 14 atmospheric general circulation models have been analyzed through idealized numerical experiments. Included in the analysis is an investigation of the surface energy budgets of the models. Negative or weak positive snow feedbacks occurred in some of the models, while others produced strong positive snow feedbacks. These feedbacks are due not only to melting snow, but also to increases in boundary temperature, changes in air temperature, changes in water vapor, and changes in cloudiness. As a result, the net response of each model is quite complex. We analyze in detail the responses of one model with a strong positive snow feedback and another with a weak negative snow feedback. Some of the models include a temperature dependence of the snow albedo, and this has significantly affected the results.

  11. Soot in the atmosphere and snow surface of Antarctica

    International Nuclear Information System (INIS)

    Warren, S.G.; Clarke, A.D.

    1990-01-01

    Samples of snow collected near the south pole during January and February 1986 were analyzed for the presence of light-absorbing particles by passing the melted snow through a nuclepore filter. Transmission of light through the filter showed that snow far from the station contains the equivalent of 0.1-0.3 ng of carbon per gram of snow (ng/g). Samples of ambient air were filtered and found to contain about 1-2 ng of carbon per kilogram of air, giving a scavenging ratio of about 150. The snow downwind of the station exhibited a well-defined plume of soot due to the burning of diesel fuel, but even in the center of the plume 1 km downwind, the soot concentration was only 3 ng/g, too small to affect snow albedo significantly. Measurements of snow albedo near large inland stations are therefore probably representative of their surrounding regions

  12. Spatiotemporally resolved characteristics of a gliding arc discharge in a turbulent air flow at atmospheric pressure

    Science.gov (United States)

    Zhu, Jiajian; Gao, Jinlong; Ehn, Andreas; Aldén, Marcus; Larsson, Anders; Kusano, Yukihiro; Li, Zhongshan

    2017-01-01

    A gliding arc discharge was generated in a turbulent air flow at atmospheric pressure driven by a 35 kHz alternating current (AC) electric power. The spatiotemporally resolved characteristics of the gliding arc discharge, including glow-type discharges, spark-type discharges, short-cutting events and transitions among the different types of discharges, were investigated using simultaneously optical and electrical diagnostics. The glow-type discharge shows sinusoidal-like voltage and current waveforms with a peak current of hundreds of milliamperes. The frequency of the emission intensity variation of the glow-type discharge is the same as that of the electronic power dissipated in the plasma column. The glow-type discharge can transfer into a spark discharge characterized by a sharp peak current of several amperes and a sudden increase of the brightness in the plasma column. Transitions can also be found to take place from spark-type discharges to glow-type discharges. Short-cutting events were often observed as the intermediate states formed during the spark-glow transition. Three different types of short-cutting events have been observed to generate new current paths between two plasma channel segments, and between two electrodes, as well as between the channel segment and the electrodes, respectively. The short-cut upper part of the plasma column that was found to have no current passing through can be detected several hundreds of microseconds after the short-cutting event. The voltage recovery rate, the period of AC voltage-driving signal, the flow rates and the rated input powers were found to play an important role in affecting the transitions among the different types of discharges.

  13. Mechanical Properties of Glide Path Preparation Instruments with Different Pitch Lengths.

    Science.gov (United States)

    Al Raeesi, Dana; Kwak, Sang Won; Ha, Jung-Hong; Sulaiman, Sameh; El Abed, Rashid; Kim, Hyeon-Cheol

    2018-03-20

    This study compared the effects of pitch length on the torsional resistance and cyclic fatigue resistance of glide path preparation instruments. G-File (G1 and G2; Micro-Mega, Besançon, France) and new generation G-File (NG1 and NG2, Micro-Mega) instruments were compared to evaluate the effects of the shorter pitch of the latter (25% shorter than G-File). G1 and NG1 have a #12 tip size, whereas G2 and NG2 have a #17 tip size. All the files have the same taper of 3%. For comparing the torsional resistances (n = 15), the file was fixed at 4 mm from the tip, and the clockwise rotation at a constant rotational speed of 2 rpm was adjusted until the file fractured. The maximum torsional load and distortion angle at fracture were recorded. For comparing the cyclic fatigue resistances (n = 15), the files were freely rotated in a simulated canal (radius, 3 mm; curvature, 90°) at a speed of 300 rpm in a dynamic mode. When the file fractured, the time elapsed was recorded using a chronometer. The number of cycles to failure was calculated by multiplying the total time to failure by the rotation rate. Fractured fragments were examined under the scanning electron microscope. The NG2 instruments had significantly higher fatigue resistance and torsional strength than the G2 instruments (P < .05) and showed approximately the same fatigue resistance as the G1. Scanning electron microscopic examinations revealed the typical appearances of 2 failure modes. A shorter pitch design increased cyclic fatigue resistance and torsional strength of the glide path instruments. Copyright © 2018 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  14. Prevalence and factors associated with percutaneous injuries and splash exposures among health-care workers in a provincial hospital, Kenya, 2010

    Science.gov (United States)

    Mbaisi, Everline Muhonja; Ng'ang'a, Zipporah; Wanzala, Peter; Omolo, Jared

    2013-01-01

    Introduction Accidental occupational exposure of healthcare workers to blood and body fluids after skin injury or mucous membrane contact constitutes a risk for transmission of blood-borne pathogens. Such pathogens include Human Immunodeficiency Virus (HIV), Hepatitis B virus (HBV) and Hepatitis C virus (HCV). We conducted a study to determine the prevalence and associated factors for percutaneous injuries and splash exposures among health-care workers in Rift Valley provincial hospital. Methods A cross-sectional study was carried out from October to November 2010. Self reported incidents, circumstances surrounding occupational exposure and post-exposure management were sought by use of interviewer administered questionnaire. Descriptive, bivariate and multiple logistic regression (forward stepwise procedure) analyses were performed. The level of significance was set at 0.05. Results Twenty five percent of health-care workers interviewed (N = 305) reported having been exposed to blood and body fluids in the preceding 12 months. Percutaneous injuries were reported by 19% (n = 305) and splash to mucous membrane by 7.2%. Higher rates of percutaneous injuries were observed among nurses (50%), during stitching (30%), and in obstetric and gynecologic department (22%). Health workers aged below 40 years were more likely to experience percutaneous injuries (OR= 3.7; 95% CI = 1.08-9.13) while previous training in infection prevention was protective (OR= 0.52; 95% CI = 0.03-0.90). Forty eight percent (n = 83) reported the incidents with 20% (n = 83) taking PEP against HIV. Conclusion Percutaneous injuries and splashes are common in Rift Valley Provincial hospital. Preventive measures remain inadequate. Health institutions should have policies, institute surveillance for occupational risks and enhance training of health care workers. PMID:23504245

  15. Role of Tibetan Buddhist monasteries in snow leopard conservation.

    Science.gov (United States)

    Li, Juan; Wang, Dajun; Yin, Hang; Zhaxi, Duojie; Jiagong, Zhala; Schaller, George B; Mishra, Charudutt; McCarthy, Thomas M; Wang, Hao; Wu, Lan; Xiao, Lingyun; Basang, Lamao; Zhang, Yuguang; Zhou, Yunyun; Lu, Zhi

    2014-02-01

    The snow leopard (Panthera uncia) inhabits the rugged mountains in 12 countries of Central Asia, including the Tibetan Plateau. Due to poaching, decreased abundance of prey, and habitat degradation, it was listed as endangered by the International Union for Conservation of Nature in 1972. Current conservation strategies, including nature reserves and incentive programs, have limited capacities to protect snow leopards. We investigated the role of Tibetan Buddhist monasteries in snow leopard conservation in the Sanjiangyuan region in China's Qinghai Province on the Tibetan Plateau. From 2009 to 2011, we systematically surveyed snow leopards in the Sanjiangyuan region. We used the MaxEnt model to determine the relation of their presence to environmental variables (e.g., elevation, ruggedness) and to predict snow leopard distribution. Model results showed 89,602 km(2) of snow leopard habitat in the Sanjiangyuan region, of which 7674 km(2) lay within Sanjiangyuan Nature Reserve's core zones. We analyzed the spatial relation between snow leopard habitat and Buddhist monasteries and found that 46% of monasteries were located in snow leopard habitat and 90% were within 5 km of snow leopard habitat. The 336 monasteries in the Sanjiangyuan region could protect more snow leopard habitat (8342 km(2) ) through social norms and active patrols than the nature reserve's core zones. We conducted 144 household interviews to identify local herders' attitudes and behavior toward snow leopards and other wildlife. Most local herders claimed that they did not kill wildlife, and 42% said they did not kill wildlife because it was a sin in Buddhism. Our results indicate monasteries play an important role in snow leopard conservation. Monastery-based snow leopard conservation could be extended to other Tibetan Buddhist regions that in total would encompass about 80% of the global range of snow leopards. © 2013 Society for Conservation Biology.

  16. Snow bedforms: A review, new data, and a formation model

    Science.gov (United States)

    Filhol, Simon; Sturm, Matthew

    2015-09-01

    Snow bedforms, like sand bedforms, consist of various shapes that form under the action of wind on mobile particles. Throughout a year, they can cover up to 11% of the Earth surface, concentrated toward the poles. These forms impact the local surface energy balance and the distribution of precipitation. Only a few studies have concentrated on their genesis. Their size ranges from 2 cm (ripple marks) to 2.5 m tall (whaleback dunes). We counted a total of seven forms that are widely recognized. Among them sastrugi, an erosional shape, is the most widespread. From laser scans, we compared scaling of snow versus sand barchan morphology. We found that both have proportionally the same footprint, but snow barchans are flatter. The key difference is that snow can sinter, immobilizing the bedform and creating an erodible material. Using a model, we investigated the effect of sintering on snow dune dynamics. We found that sintering limits their size because it progressively hardens the snow and requires an ever-increasing wind speed to maintain snow transport. From the literature and results from this model, we have reclassified snow bedforms based on two parameters: wind speed and snow surface conditions. The new data show that snow dune behavior mirrors that of sand dunes, with merging, calving, and collision. However, isolated snow barchans are rare, with most of the snow surfaces encountered in the field consisting of several superimposed bedforms formed sequentially during multiple weather events. Spatially variable snow properties and geometry can explain qualitatively these widespread compound snow surfaces.

  17. Winter survival of Scots pine seedlings under different snow conditions.

    Science.gov (United States)

    Domisch, Timo; Martz, Françoise; Repo, Tapani; Rautio, Pasi

    2018-04-01

    Future climate scenarios predict increased air temperatures and precipitation, particularly at high latitudes, and especially so during winter. Soil temperatures, however, are more difficult to predict, since they depend strongly on the fate of the insulating snow cover. 'Rain-on-snow' events and warm spells during winter can lead to thaw-freeze cycles, compacted snow and ice encasement, as well as local flooding. These adverse conditions could counteract the otherwise positive effects of climatic changes on forest seedling growth. In order to study the effects of different winter and snow conditions on young Scots pine (Pinus sylvestris L.) seedlings, we conducted a laboratory experiment in which 80 1-year-old Scots pine seedlings were distributed between four winter treatments in dasotrons: ambient snow cover (SNOW), compressed snow and ice encasement (ICE), flooded and frozen soil (FLOOD) and no snow (NO SNOW). During the winter treatment period and a 1.5-month simulated spring/early summer phase, we monitored the needle, stem and root biomass of the seedlings, and determined their starch and soluble sugar concentrations. In addition, we assessed the stress experienced by the seedlings by measuring chlorophyll fluorescence, electric impedance and photosynthesis of the previous-year needles. Compared with the SNOW treatment, carbohydrate concentrations were lower in the FLOOD and NO SNOW treatments where the seedlings had almost died before the end of the experiment, presumably due to frost desiccation of aboveground parts during the winter treatments. The seedlings of the ICE treatment showed dead needles and stems only above the snow and ice cover. The results emphasize the importance of an insulating and protecting snow cover for small forest tree seedlings, and that future winters with changed snow patterns might affect the survival of tree seedlings and thus forest productivity.

  18. Snow and Vegetation Interactions at Boundaries in Alaska's Boreal Forest

    Science.gov (United States)

    Hiemstra, C. A.; Sturm, M.

    2012-12-01

    There has been increased attention on snow-vegetation interactions in Arctic tundra because of rapid climate-driven changes affecting that snow-dominated ecosystem. Yet, far less attention is paid to boreal forest snow-vegetation interactions even though climatic conditions are changing there as well. Further, it is the prevalent terrestrial biome on the planet. The forest is a variable patchwork of trees, shrubs, grasses, and forbs shaped by wind, fire, topography, water drainage, and permafrost. These patches and their boundaries have a corresponding effect on boreal snow distributions; however, measurements characterizing boreal snow are sparse and focus within patches (vs. between patches). Unfortunately, remote sensing approaches in such forested areas frequently fall short due to coarse footprint size and dense canopy cover. Over the last several years we have been examining the characteristics of snow cover within and across boundaries in the boreal forest, seeking to identify gradients in snow depth due to snow-vegetation interactions as well identifying methods whereby boreal forest surveys could be improved. Specifically, we collected end-of-season snow measurements in the Alaska boreal forest during long-distance traverses in the Tanana Basin in 2010 (26 sites) and within the Yukon Flats National Wildlife Refuge in 2011 (26 sites). At each site (all relatively flat), hundreds of snow depths were collected using a GPS-equipped Magnaprobe, which is an automated tool for measuring and locating individual snow depths. Corresponding canopy properties included NDVI determined from high-resolution satellite imagery; canopy properties were variable among the 1ha sites and some areas had recently burned. Among sites, NDVI had the largest correlation with snow depths; elevation was not significant. Vegetation transition zones play important roles in explaining observed snow depth. Similar to treeline work showing nutrient and energy gradients are influenced by

  19. A probabilistic model for snow avalanche occurrence

    Science.gov (United States)

    Perona, P.; Miescher, A.; Porporato, A.

    2009-04-01

    Avalanche hazard forecasting is an important issue in relation to the protection of urbanized environments, ski resorts and of ski-touring alpinists. A critical point is to predict the conditions that trigger the snow mass instability determining the onset and the size of avalanches. On steep terrains the risk of avalanches is known to be related to preceding consistent snowfall events and to subsequent changes in the local climatic conditions. Regression analysis has shown that avalanche occurrence indeed correlates to the amount of snow fallen in consecutive three snowing days and to the state of the settled snow at the ground. Moreover, since different type of avalanches may occur as a result of the interactions of different factors, the process of snow avalanche formation is inherently complex and with some degree of unpredictability. For this reason, although several models assess the risk of avalanche by accounting for all the involved processes with a great detail, a high margin of uncertainty invariably remains. In this work, we explicitly describe such an unpredictable behaviour with an intrinsic noise affecting the processes leading snow instability. Eventually, this sets the basis for a minimalist stochastic model, which allows us to investigate the avalanche dynamics and its statistical properties. We employ a continuous time process with stochastic jumps (snowfalls), deterministic decay (snowmelt and compaction) and state dependent avalanche occurrence (renewals) as a minimalist model for the determination of avalanche size and related intertime occurrence. The physics leading to avalanches is simplified to the extent where only meteorological data and terrain data are necessary to estimate avalanche danger. We explore the analytical formulation of the process and the properties of the probability density function of the avalanche process variables. We also discuss what is the probabilistic link between avalanche size and preceding snowfall event and

  20. Satellite Snow-Cover Mapping: A Brief Review

    Science.gov (United States)

    Hall, Dorothy K.

    1995-01-01

    Satellite snow mapping has been accomplished since 1966, initially using data from the reflective part of the electromagnetic spectrum, and now also employing data from the microwave part of the spectrum. Visible and near-infrared sensors can provide excellent spatial resolution from space enabling detailed snow mapping. When digital elevation models are also used, snow mapping can provide realistic measurements of snow extent even in mountainous areas. Passive-microwave satellite data permit global snow cover to be mapped on a near-daily basis and estimates of snow depth to be made, but with relatively poor spatial resolution (approximately 25 km). Dense forest cover limits both techniques and optical remote sensing is limited further by cloudcover conditions. Satellite remote sensing of snow cover with imaging radars is still in the early stages of research, but shows promise at least for mapping wet or melting snow using C-band (5.3 GHz) synthetic aperture radar (SAR) data. Observing System (EOS) Moderate Resolution Imaging Spectroradiometer (MODIS) data beginning with the launch of the first EOS platform in 1998. Digital maps will be produced that will provide daily, and maximum weekly global snow, sea ice and lake ice cover at 1-km spatial resolution. Statistics will be generated on the extent and persistence of snow or ice cover in each pixel for each weekly map, cloudcover permitting. It will also be possible to generate snow- and ice-cover maps using MODIS data at 250- and 500-m resolution, and to study and map snow and ice characteristics such as albedo. been under development. Passive-microwave data offer the potential for determining not only snow cover, but snow water equivalent, depth and wetness under all sky conditions. A number of algorithms have been developed to utilize passive-microwave brightness temperatures to provide information on snow cover and water equivalent. The variability of vegetative Algorithms are being developed to map global snow

  1. Snow specific surface area simulation using the one-layer snow model in the Canadian LAnd Surface Scheme (CLASS

    Directory of Open Access Journals (Sweden)

    A. Roy

    2013-06-01

    Full Text Available Snow grain size is a key parameter for modeling microwave snow emission properties and the surface energy balance because of its influence on the snow albedo, thermal conductivity and diffusivity. A model of the specific surface area (SSA of snow was implemented in the one-layer snow model in the Canadian LAnd Surface Scheme (CLASS version 3.4. This offline multilayer model (CLASS-SSA simulates the decrease of SSA based on snow age, snow temperature and the temperature gradient under dry snow conditions, while it considers the liquid water content of the snowpack for wet snow metamorphism. We compare the model with ground-based measurements from several sites (alpine, arctic and subarctic with different types of snow. The model provides simulated SSA in good agreement with measurements with an overall point-to-point comparison RMSE of 8.0 m2 kg–1, and a root mean square error (RMSE of 5.1 m2 kg–1 for the snowpack average SSA. The model, however, is limited under wet conditions due to the single-layer nature of the CLASS model, leading to a single liquid water content value for the whole snowpack. The SSA simulations are of great interest for satellite passive microwave brightness temperature assimilations, snow mass balance retrievals and surface energy balance calculations with associated climate feedbacks.

  2. A triple-moment blowing snow-atmospheric model and its application in computing the seasonal wintertime snow mass budget

    Directory of Open Access Journals (Sweden)

    J. Yang

    2010-06-01

    Full Text Available Many field studies have shown that surface sublimation and blowing snow transport and sublimation have significant influences on the snow mass budget in many high latitude regions. We developed a coupled triple-moment blowing snow-atmospheric modeling system to study the influence of these processes on a seasonal time scale over the Northern Hemisphere. Two simulations were performed. The first is a 5 month simulation for comparison with snow survey measurements over a Saskatchewan site to validate the modeling system. The second simulation covers the 2006/2007 winter period to study the snow mass budget over the Northern Hemisphere. The results show that surface sublimation is significant in Eurasian Continent and the eastern region of North America, reaching a maximum value of 200 mm SWE (Snow Water Equivalent. Over the Arctic Ocean and Northern Canada, surface deposition with an average value of 30 mm SWE was simulated. Blowing snow sublimation was found to return up to 50 mm SWE back to the atmosphere over the Arctic Ocean, while the divergence of blowing snow transport contributes only a few mm SWE to the change in snow mass budget. The results were further stratified in 10 degree latitudinal bands. The results show that surface sublimation decreases with an increase in latitude while blowing snow sublimation increases with latitude. Taken together, the surface sublimation and blowing snow processes was found to distribute 23% to 52% of winter precipitation over the three month winter season.

  3. Comparison of the Truview PCD™ and the GlideScope(®) video laryngoscopes with direct laryngoscopy in pediatric patients: a randomized trial.

    Science.gov (United States)

    Riveros, Ricardo; Sung, Wai; Sessler, Daniel I; Sanchez, Ivan Parra; Mendoza, Maria L; Mascha, Edward J; Niezgoda, Julie

    2013-05-01

    The GlideScope(®) video laryngoscope has a 60° angled blade and the blade of the Truview PCD™ video laryngoscope has an optical lens that provides a 46° refraction of the viewing angle. Despite successful results using the GlideScope in adults, few studies have been published regarding its use in pediatric patients. We therefore tested our joint primary hypothesis that the GlideScope and the Truview PCD video laryngoscopes provide superior visualization to direct laryngoscopy and are non-inferior regarding time to intubation. One hundred thirty-four patients (neonate to ten years of age, American Society of Anesthesiologists physical status I-III) scheduled for general surgical procedures were randomized to tracheal intubation using the Truview PCD or GlideScope video laryngoscope or direct laryngoscopy (Macintosh blade). The laryngoscopic view was scored using the Cormack-Lehane scale. Time to intubation (defined as the time from the moment the device entered the patient's mouth until end-tidal CO2 was detected) and the number of attempts were recorded. The Cormack-Lehane views attained using the GlideScope (P > 0.99) and Truview PCD (P = 0.18) were not superior to the views attained with direct laryngoscopy. Furthermore, the view attained using the GlideScope was significantly worse than that attained using direct laryngoscopy (P Cormack-Lehane grade I views with the GlideScope than with the Truview PCD (14% vs 82%, respectively; 95% confidence interval [CI] -91% to -46%). The observed median [Q1, Q3] times to intubation were: 39 [31, 59] sec, 44 [28, 62] sec, and 23 [21, 28] sec with the GlideScope, Truview PCD, and direct laryngoscopy, respectively, with median differences of 14 sec (95% CI 7 to 26, GlideScope - direct laryngoscopy) and 17 sec (95% CI 6 to 28, Truview PCD - direct laryngoscopy). The Cormack-Lehane views attained using the GlideScope and the Truview PCD video laryngoscopes were not superior to views attained using direct laryngoscopy

  4. Surface decontamination using dry ice snow cleaning

    International Nuclear Information System (INIS)

    Lu, J.D.; Park, K.H.; Lee, B.S.; Kim, Y.E.

    1999-01-01

    The water washing and steam blast cleaning method are currently used in nuclear power plants in decontamination. These methods produce lots of secondary wastes and tend to damage the work surface. A dry ice snow cleaning device with an adjustable nozzle was developed for the decontamination purpose. Glass with finger prints and scratched acrylic plastics surface with adsorbed oil-dust mixture were tested to see the cleaning ability of the developed device. Traces of finger prints and oil-dust mixture could not be detected after cleaning. The radioactivity of pump housing in a primary system of Wolsung Nuclear Power Plant was also tested. The maximum of 82% of radioactivity was reduced after dry ice snow cleaning. This device is expected to be used in decontamination of expensive electronic and optical instruments and detectors that cannot be decontaminated by water

  5. Estimating Snow Depth and Snow Water Equivalence Using Repeat-Pass Interferometric SAR in the Northern Piedmont Region of the Tianshan Mountains

    OpenAIRE

    Li, Hui; Wang, Zuo; He, Guangjun; Man, Wang

    2017-01-01

    Snow depth and Snow Water Equivalence (SWE) are important parameters for hydrological applications. In this application, a theoretical method of snow depth estimation with repeat-pass InSAR measurements was proposed, and a preliminary sensitivity analysis of snow phase changes versus the incident angle and snow density was developed. Moreover, the snow density and incident angle parameters were analyzed and calibrated, and the local incident angle was used as a substitute for the satellite in...

  6. Evaluation of snow cover and snow depth on the Qinghai–Tibetan Plateau derived from passive microwave remote sensing

    Directory of Open Access Journals (Sweden)

    L. Dai

    2017-08-01

    Full Text Available Snow cover on the Qinghai–Tibetan Plateau (QTP plays a significant role in the global climate system and is an important water resource for rivers in the high-elevation region of Asia. At present, passive microwave (PMW remote sensing data are the only efficient way to monitor temporal and spatial variations in snow depth at large scale. However, existing snow depth products show the largest uncertainties across the QTP. In this study, MODIS fractional snow cover product, point, line and intense sampling data are synthesized to evaluate the accuracy of snow cover and snow depth derived from PMW remote sensing data and to analyze the possible causes of uncertainties. The results show that the accuracy of snow cover extents varies spatially and depends on the fraction of snow cover. Based on the assumption that grids with MODIS snow cover fraction > 10 % are regarded as snow cover, the overall accuracy in snow cover is 66.7 %, overestimation error is 56.1 %, underestimation error is 21.1 %, commission error is 27.6 % and omission error is 47.4 %. The commission and overestimation errors of snow cover primarily occur in the northwest and southeast areas with low ground temperature. Omission error primarily occurs in cold desert areas with shallow snow, and underestimation error mainly occurs in glacier and lake areas. With the increase of snow cover fraction, the overestimation error decreases and the omission error increases. A comparison between snow depths measured in field experiments, measured at meteorological stations and estimated across the QTP shows that agreement between observation and retrieval improves with an increasing number of observation points in a PMW grid. The misclassification and errors between observed and retrieved snow depth are associated with the relatively coarse resolution of PMW remote sensing, ground temperature, snow characteristics and topography. To accurately understand the variation in snow

  7. Evaluation of a New SnowPaver at McMurdo Station, Antarctica

    Science.gov (United States)

    2014-09-01

    3.2.1 Rammsonde Snow Penetrometer ......................................................................................... 19 3.2.2 Clegg Impact...Figure 11. SnowPaver operating in untracked (soft) snow. 3.2 Snow strength and density measurements A Rammsonde Snow Penetrometer and a Clegg...the density profile for each snow pavement. ERDC/CRREL TR-14-16 19 3.2.1 Rammsonde Snow Penetrometer To determine strength relationships with

  8. Planetesimal formation starts at the snow line

    OpenAIRE

    Drążkowska, J; Alibert, Y

    2017-01-01

    Context. The formation stage of planetesimals represents a major gap in our understanding of the planet formation process. Late-stage planet accretion models typically make arbitrary assumptions about planetesimal and pebble distribution, while dust evolution models predict that planetesimal formation is only possible at some orbital distances. Aims. We wish to test the importance of the water snow line in triggering the formation of the first planetesimals during the gas-rich phase of a p...

  9. Planetesimal formation starts at the snow line

    OpenAIRE

    Drazkowska, Joanna; Alibert, Yann

    2017-01-01

    Planetesimal formation stage represents a major gap in our understanding of the planet formation process. The late-stage planet accretion models typically make arbitrary assumptions about planetesimals and pebbles distribution while the dust evolution models predict that planetesimal formation is only possible at some orbital distances. We want to test the importance of water snow line for triggering formation of the first planetesimals during the gas-rich phase of protoplanetary disk, when c...

  10. The Snow Must Go On: Ground Ice Encasement, Snow Compaction and Absence of Snow Differently Cause Soil Hypoxia, CO2 Accumulation and Tree Seedling Damage in Boreal Forest.

    Directory of Open Access Journals (Sweden)

    Françoise Martz

    Full Text Available At high latitudes, the climate has warmed at twice the rate of the global average with most changes observed in autumn, winter and spring. Increasing winter temperatures and wide temperature fluctuations are leading to more frequent rain-on-snow events and freeze-thaw cycles causing snow compaction and formation of ice layers in the snowpack, thus creating ice encasement (IE. By decreasing the snowpack insulation capacity and restricting soil-atmosphere gas exchange, modification of the snow properties may lead to colder soil but also to hypoxia and accumulation of trace gases in the subnivean environment. To test the effects of these overwintering conditions changes on plant winter survival and growth, we established a snow manipulation experiment in a coniferous forest in Northern Finland with Norway spruce and Scots pine seedlings. In addition to ambient conditions and prevention of IE, we applied three snow manipulation levels: IE created by artificial rain-on-snow events, snow compaction and complete snow removal. Snow removal led to deeper soil frost during winter, but no clear effect of IE or snow compaction done in early winter was observed on soil temperature. Hypoxia and accumulation of CO2 were highest in the IE plots but, more importantly, the duration of CO2 concentration above 5% was 17 days in IE plots compared to 0 days in ambient plots. IE was the most damaging winter condition for both species, decreasing the proportion of healthy seedlings by 47% for spruce and 76% for pine compared to ambient conditions. Seedlings in all three treatments tended to grow less than seedlings in ambient conditions but only IE had a significant effect on spruce growth. Our results demonstrate a negative impact of winter climate change on boreal forest regeneration and productivity. Changing snow conditions may thus partially mitigate the positive effect of increasing growing season temperatures on boreal forest productivity.

  11. Limitations of modeling snow in ski resorts

    Science.gov (United States)

    Steiger, Robert; Abegg, Bruno

    2016-04-01

    The body of literature on snow modeling in a ski area operations context has been growing over the last decades in an accelerating speed. The majority of snow model applications for ski areas can be found in the climate change impacts literature. These studies differ in many aspects: the type of model used; the meteorological variables used in the models; the spatial and temporal resolution of the meteorological variables; the method how the climate change signal is derived and applied in the model concept; the number of climate models and emission scenarios used and consequently the handling of uncertainties; the indicators used to interpret the impacts for the skiing tourism industry; the incorporation of adaptation measures (e.g. snowmaking); and the geographical scale of analysis. In this contribution we will present a review of approaches used for modeling snow conditions in a ski area context. The major limitations both from a scientific as well as from a users' perspective will be discussed and solutions for shortcomings of existing approaches will be presented.

  12. Toward mountains without permanent snow and ice

    Science.gov (United States)

    Huss, M.; Bookhagen, B.; Huggel, C.; Jacobsen, D.; Bradley, R. S.; Clague, J. J.; Vuille, M.; Buytaert, W.; Cayan, D. R.; Greenwood, G.; Mark, B. G.; Milner, A. M.; Weingartner, R.; Winder, M.

    2017-05-01

    The cryosphere in mountain regions is rapidly declining, a trend that is expected to accelerate over the next several decades due to anthropogenic climate change. A cascade of effects will result, extending from mountains to lowlands with associated impacts on human livelihood, economy, and ecosystems. With rising air temperatures and increased radiative forcing, glaciers will become smaller and, in some cases, disappear, the area of frozen ground will diminish, the ratio of snow to rainfall will decrease, and the timing and magnitude of both maximum and minimum streamflow will change. These changes will affect erosion rates, sediment, and nutrient flux, and the biogeochemistry of rivers and proglacial lakes, all of which influence water quality, aquatic habitat, and biotic communities. Changes in the length of the growing season will allow low-elevation plants and animals to expand their ranges upward. Slope failures due to thawing alpine permafrost, and outburst floods from glacier- and moraine-dammed lakes will threaten downstream populations. Societies even well beyond the mountains depend on meltwater from glaciers and snow for drinking water supplies, irrigation, mining, hydropower, agriculture, and recreation. Here, we review and, where possible, quantify the impacts of anticipated climate change on the alpine cryosphere, hydrosphere, and biosphere, and consider the implications for adaptation to a future of mountains without permanent snow and ice.

  13. Monitoring Areal Snow Cover Using NASA Satellite Imagery

    Science.gov (United States)

    Harshburger, Brian J.; Blandford, Troy; Moore, Brandon

    2011-01-01

    The objective of this project is to develop products and tools to assist in the hydrologic modeling process, including tools to help prepare inputs for hydrologic models and improved methods for the visualization of streamflow forecasts. In addition, this project will facilitate the use of NASA satellite imagery (primarily snow cover imagery) by other federal and state agencies with operational streamflow forecasting responsibilities. A GIS software toolkit for monitoring areal snow cover extent and producing streamflow forecasts is being developed. This toolkit will be packaged as multiple extensions for ArcGIS 9.x and an opensource GIS software package. The toolkit will provide users with a means for ingesting NASA EOS satellite imagery (snow cover analysis), preparing hydrologic model inputs, and visualizing streamflow forecasts. Primary products include a software tool for predicting the presence of snow under clouds in satellite images; a software tool for producing gridded temperature and precipitation forecasts; and a suite of tools for visualizing hydrologic model forecasting results. The toolkit will be an expert system designed for operational users that need to generate accurate streamflow forecasts in a timely manner. The Remote Sensing of Snow Cover Toolbar will ingest snow cover imagery from multiple sources, including the MODIS Operational Snowcover Data and convert them to gridded datasets that can be readily used. Statistical techniques will then be applied to the gridded snow cover data to predict the presence of snow under cloud cover. The toolbar has the ability to ingest both binary and fractional snow cover data. Binary mapping techniques use a set of thresholds to determine whether a pixel contains snow or no snow. Fractional mapping techniques provide information regarding the percentage of each pixel that is covered with snow. After the imagery has been ingested, physiographic data is attached to each cell in the snow cover image. This data

  14. Small scale variability of snow properties on Antarctic sea ice

    Science.gov (United States)

    Wever, Nander; Leonard, Katherine; Paul, Stephan; Jacobi, Hans-Werner; Proksch, Martin; Lehning, Michael

    2016-04-01

    Snow on sea ice plays an important role in air-ice-sea interactions, as snow accumulation may for example increase the albedo. Snow is also able to smooth the ice surface, thereby reducing the surface roughness, while at the same time it may generate new roughness elements by interactions with the wind. Snow density is a key property in many processes, for example by influencing the thermal conductivity of the snow layer, radiative transfer inside the snow as well as the effects of aerodynamic forcing on the snowpack. By comparing snow density and grain size from snow pits and snow micro penetrometer (SMP) measurements, highly resolved density and grain size profiles were acquired during two subsequent cruises of the RV Polarstern in the Weddell Sea, Antarctica, between June and October 2013. During the first cruise, SMP measurements were done along two approximately 40 m transects with a horizontal resolution of approximately 30 cm. During the second cruise, one transect was made with approximately 7.5 m resolution over a distance of 500 m. Average snow densities are about 300 kg/m3, but the analysis also reveals a high spatial variability in snow density on sea ice in both horizontal and vertical direction, ranging from roughly 180 to 360 kg/m3. This variability is expressed by coherent snow structures over several meters. On the first cruise, the measurements were accompanied by terrestrial laser scanning (TLS) on an area of 50x50 m2. The comparison with the TLS data indicates that the spatial variability is exhibiting similar spatial patterns as deviations in surface topology. This suggests a strong influence from surface processes, for example wind, on the temporal development of density or grain size profiles. The fundamental relationship between variations in snow properties, surface roughness and changes therein as investigated in this study is interpreted with respect to large-scale ice movement and the mass balance.

  15. Parallel Splash Belief Propagation

    Science.gov (United States)

    2010-08-01

    Service, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of...heaps: An alternative to Fibonacci heaps with applications to parallel computation. Communications of the ACM, 31:1343–1354, 1988. G. Elidan, I. Mcgraw

  16. The Airborne Snow Observatory: fusion of scanning lidar, imaging spectrometer, and physically-based modeling for mapping snow water equivalent and snow albedo

    Science.gov (United States)

    Snow cover and its melt dominate regional climate and water resources in many of the world’s mountainous regions. Snowmelt timing and magnitude in mountains tend to be controlled by absorption of solar radiation and snow water equivalent, respectively, and yet both of these are very poorly known ev...

  17. Simple process-led algorithms for simulating habitats (SPLASH v.1.0): robust indices of radiation, evapotranspiration and plant-available moisture

    Science.gov (United States)

    Davis, Tyler W.; Prentice, I. Colin; Stocker, Benjamin D.; Thomas, Rebecca T.; Whitley, Rhys J.; Wang, Han; Evans, Bradley J.; Gallego-Sala, Angela V.; Sykes, Martin T.; Cramer, Wolfgang

    2017-02-01

    Bioclimatic indices for use in studies of ecosystem function, species distribution, and vegetation dynamics under changing climate scenarios depend on estimates of surface fluxes and other quantities, such as radiation, evapotranspiration and soil moisture, for which direct observations are sparse. These quantities can be derived indirectly from meteorological variables, such as near-surface air temperature, precipitation and cloudiness. Here we present a consolidated set of simple process-led algorithms for simulating habitats (SPLASH) allowing robust approximations of key quantities at ecologically relevant timescales. We specify equations, derivations, simplifications, and assumptions for the estimation of daily and monthly quantities of top-of-the-atmosphere solar radiation, net surface radiation, photosynthetic photon flux density, evapotranspiration (potential, equilibrium, and actual), condensation, soil moisture, and runoff, based on analysis of their relationship to fundamental climatic drivers. The climatic drivers include a minimum of three meteorological inputs: precipitation, air temperature, and fraction of bright sunshine hours. Indices, such as the moisture index, the climatic water deficit, and the Priestley-Taylor coefficient, are also defined. The SPLASH code is transcribed in C++, FORTRAN, Python, and R. A total of 1 year of results are presented at the local and global scales to exemplify the spatiotemporal patterns of daily and monthly model outputs along with comparisons to other model results.

  18. Observations of distributed snow depth and snow duration within diverse forest structures in a maritime mountain watershed

    Science.gov (United States)

    Dickerson-Lange, Susan E.; Lutz, James A.; Gersonde, Rolf; Martin, Kael A.; Forsyth, Jenna E.; Lundquist, Jessica D.

    2015-11-01

    Spatially distributed snow depth and snow duration data were collected over two to four snow seasons during water years 2011-2014 in experimental forest plots within the Cedar River Municipal Watershed, 50 km east of Seattle, Washington, USA. These 40 × 40 m forest plots, situated on the western slope of the Cascade Range, include unthinned second-growth coniferous forests, variable density thinned forests, forest gaps in which a 20 m diameter (approximately equivalent to one tree height) gap was cut in the middle of each plot, and old-growth forest. Together, this publicly available data set includes snow depth and density observations from manual snow surveys, distributed snow duration observations from ground temperature sensors and time-lapse cameras, meteorological data collected at two open locations and three forested locations, and forest canopy data from airborne light detection and ranging (LiDAR) data and hemispherical photographs. These colocated snow, meteorological, and forest data have the potential to improve understanding of forest influences on snow processes, and provide a unique model-testing data set for hydrological analyses in a forested, maritime watershed. We present empirical snow depletion curves within forests to illustrate an application of these data to improve subgrid representation of snow cover in distributed modeling.

  19. Deriving Snow-Cover Depletion Curves for Different Spatial Scales from Remote Sensing and Snow Telemetry Data

    Science.gov (United States)

    Fassnacht, Steven R.; Sexstone, Graham A.; Kashipazha, Amir H.; Lopez-Moreno, Juan Ignacio; Jasinski, Michael F.; Kampf, Stephanie K.; Von Thaden, Benjamin C.

    2015-01-01

    During the melting of a snowpack, snow water equivalent (SWE) can be correlated to snow-covered area (SCA) once snow-free areas appear, which is when SCA begins to decrease below 100%. This amount of SWE is called the threshold SWE. Daily SWE data from snow telemetry stations were related to SCA derived from moderate-resolution imaging spectro radiometer images to produce snow-cover depletion curves. The snow depletion curves were created for an 80,000 sq km domain across southern Wyoming and northern Colorado encompassing 54 snow telemetry stations. Eight yearly snow depletion curves were compared, and it is shown that the slope of each is a function of the amount of snow received. Snow-cover depletion curves were also derived for all the individual stations, for which the threshold SWE could be estimated from peak SWE and the topography around each station. A stations peak SWE was much more important than the main topographic variables that included location, elevation, slope, and modelled clear sky solar radiation. The threshold SWE mostly illustrated inter-annual consistency.

  20. A novel linear physical model for remote sensing of snow wetness and snow density using the visible and infrared bands

    Science.gov (United States)

    Varade, D. M.; Dikshit, O.

    2017-12-01

    Modeling and forecasting of snowmelt runoff are significant for understanding the hydrological processes in the cryosphere which requires timely information regarding snow physical properties such as liquid water content and density of snow in the topmost layer of the snowpack. Both the seasonal runoffs and avalanche forecasting are vastly dependent on the inherent physical characteristics of the snowpack which are conventionally measured by field surveys in difficult terrains at larger impending costs and manpower. With advances in remote sensing technology and the increase in the availability of satellite data, the frequency and extent of these surveys could see a declining trend in future. In this study, we present a novel approach for estimating snow wetness and snow density using visible and infrared bands that are available with most multi-spectral sensors. We define a trapezoidal feature space based on the spectral reflectance in the near infrared band and the Normalized Differenced Snow Index (NDSI), referred to as NIR-NDSI space, where dry snow and wet snow are observed in the left diagonal upper and lower right corners, respectively. The corresponding pixels are extracted by approximating the dry and wet edges which are used to develop a linear physical model to estimate snow wetness. Snow density is then estimated using the modeled snow wetness. Although the proposed approach has used Sentinel-2 data, it can be extended to incorporate data from other multi-spectral sensors. The estimated values for snow wetness and snow density show a high correlation with respect to in-situ measurements. The proposed model opens a new avenue for remote sensing of snow physical properties using multi-spectral data, which were limited in the literature.

  1. Sierra Nevada, California, U.S.A., Snow Algae: Snow albedo changes, algal-bacterial interrelationships and ultraviolet radiation effects

    International Nuclear Information System (INIS)

    Thomas, W.H.; Duval, B.

    1995-01-01

    In the Tioga Pass area (upper LeeVining Creek watershed) of the Sierra Nevada (California), snow algae were prevalent in the early summers of 1993 and 1994. Significant negative correlations were found between snow water content. However, red snow caused by algal blooms did not decrease mean albedos in representative snowfields. This was due to algal patchiness; mean albedos would not decrease over the whole water catchment basin; and water supplies would not be affected by the presence of algae. Albedo was also reduced by dirt on the snow, and wind-blown dirt may provide a source of allochthonous organic matter for snow bacteria. However, several observations emphasize the importance of an autochthonous source for bacterial nutrition. Bacterial abundances and production rates were higher in red snow containing algae than in noncolored snow. Bacterial production was about two orders-of-magnitude lower than photosynthetic algal production. Bacteria were also sometimes attached to algal cells. In experiments where snow algae were contained in UV-transmitting quartz tubes, ultraviolet radiation inhibited red snow (collected form open, sunlit areas) photosynthesis about 25%, while green snow (collected from forested, shady locations) photosynthesis was inhibited by 85%. Methanol extracts of red snow algae had greater absorbances in blue and UV spectral regions than did algae from green snow. These differences in UV responses and spectra may be due to habitat (sun vs shade) differences, or may be genetic, since different species were found in the two snow types. However, both habitat and genetic mechanisms may be operating together to cause these differences. 53 refs., 5 figs., 5 tabs

  2. A Bayesian spatial assimilation scheme for snow coverage observations in a gridded snow model

    Directory of Open Access Journals (Sweden)

    S. Kolberg

    2006-01-01

    Full Text Available A method for assimilating remotely sensed snow covered area (SCA into the snow subroutine of a grid distributed precipitation-runoff model (PRM is presented. The PRM is assumed to simulate the snow state in each grid cell by a snow depletion curve (SDC, which relates that cell's SCA to its snow cover mass balance. The assimilation is based on Bayes' theorem, which requires a joint prior distribution of the SDC variables in all the grid cells. In this paper we propose a spatial model for this prior distribution, and include similarities and dependencies among the grid cells. Used to represent the PRM simulated snow cover state, our joint prior model regards two elevation gradients and a degree-day factor as global variables, rather than describing their effect separately for each cell. This transformation results in smooth normalised surfaces for the two related mass balance variables, supporting a strong inter-cell dependency in their joint prior model. The global features and spatial interdependency in the prior model cause each SCA observation to provide information for many grid cells. The spatial approach similarly facilitates the utilisation of observed discharge. Assimilation of SCA data using the proposed spatial model is evaluated in a 2400 km2 mountainous region in central Norway (61° N, 9° E, based on two Landsat 7 ETM+ images generalized to 1 km2 resolution. An image acquired on 11 May, a week before the peak flood, removes 78% of the variance in the remaining snow storage. Even an image from 4 May, less than a week after the melt onset, reduces this variance by 53%. These results are largely improved compared to a cell-by-cell independent assimilation routine previously reported. Including observed discharge in the updating information improves the 4 May results, but has weak effect on 11 May. Estimated elevation gradients are shown to be sensitive to informational deficits occurring at high altitude, where snowmelt has not started

  3. Engineering Circular Gliding of Actin Filaments Along Myosin-Patterned DNA Nanotube Rings To Study Long-Term Actin-Myosin Behaviors.

    Science.gov (United States)

    Hariadi, Rizal F; Appukutty, Abhinav J; Sivaramakrishnan, Sivaraj

    2016-09-27

    Nature has evolved molecular motors that are critical in cellular processes occurring over broad time scales, ranging from seconds to years. Despite the importance of the long-term behavior of molecular machines, topics such as enzymatic lifetime are underexplored due to the lack of a suitable approach for monitoring motor activity over long time periods. Here, we developed an "O"-shaped Myosin Empowered Gliding Assay (OMEGA) that utilizes engineered micron-scale DNA nanotube rings with precise arrangements of myosin VI to trap gliding actin filaments. This circular gliding assay platform allows the same individual actin filament to glide over the same myosin ensemble (50-1000 motors per ring) multiple times. First, we systematically characterized the formation of DNA nanotubes rings with 4, 6, 8, and 10 helix circumferences. Individual actin filaments glide along the nanotube rings with high processivity for up to 12.8 revolutions or 11 min in run time. We then show actin gliding speed is robust to variation in motor number and independent of ring curvature within our sample space (ring diameter of 0.5-4 μm). As a model application of OMEGA, we then analyze motor-based mechanical influence on "stop-and-go" gliding behavior of actin filaments, revealing that the stop-to-go transition probability is dependent on motor flexibility. Our circular gliding assay may provide a closed-loop platform for monitoring long-term behavior of broad classes of molecular motors and enable characterization of motor robustness and long time scale nanomechanical processes.

  4. Mesocell study area snow distributions for the Cold Land Processes Experiment (CLPX)

    Science.gov (United States)

    Glen E. Liston; Christopher A. Hiemstra; Kelly Elder; Donald W. Cline

    2008-01-01

    The Cold Land Processes Experiment (CLPX) had a goal of describing snow-related features over a wide range of spatial and temporal scales. This required linking disparate snow tools and datasets into one coherent, integrated package. Simulating realistic high-resolution snow distributions and features requires a snow-evolution modeling system (SnowModel) that can...

  5. Some relationships among air, snow, and soil temperatures and soil frost

    Science.gov (United States)

    George Hart; Howard W. Lull

    1963-01-01

    Each winter gives examples of the insulating properties of snow cover. Seeds and soil fauna are protected from the cold by snow. Underground water pipes are less likely to freeze under snow cover. And, according to many observers, the occurrence, penetration, and thaw of soil frost are affected by snow cover. The depth of snow necessary to protect soil from freezing...

  6. Influence of snow-cover properties on avalanche dynamics

    Science.gov (United States)

    Steinkogler, W.; Sovilla, B.; Lehning, M.

    2012-04-01

    Snow avalanches with the potential of reaching traffic routes and settlements are a permanent winter threat for many mountain communities. Snow safety officers have to take the decision whether to close a road, a railway line or a ski slope. Those decisions are often very difficult as they demand the ability to interpret weather forecasts, to establish their implication for the stability and the structure of the snow cover and to evaluate the influence of the snow cover on avalanche run-out distances. In the operational programme 'Italy-Switzerland, project STRADA' we focus on the effects of snow cover on avalanche dynamics, and thus run-out distance, with the aim to provide a better understanding of this influence and to ultimately develop tools to support snow safety officers in their decision process. We selected five avalanches, measured at the Vallée de la Sionne field site, with similar initial mass and topography but different flow dynamics and run-out distances. Significant differences amongst the individual avalanches could be observed for front and internal velocities, impact pressures, flow regimes, deposition volumes and run-out distances. For each of these avalanches, the prevailing snow conditions at release were reconstructed using field data from local snowpits or were modeled with SNOWPACK. Combining flow dynamical data with snow cover properties shows that erodible snow depth, snow density and snow temperature in the snow pack along the avalanche track are among the decisive variables that appear to explain the observed differences. It is further discussed, how these influencing factors can be quantified and used for improved predictions of site and time specific avalanche hazard.

  7. Remote sensing of snow albedo for determination of dustfall.

    Science.gov (United States)

    Sydor, M; Sorensen, J A; Shuter, V

    1979-11-01

    Changes in snow reflectivity as a function of dustfall were used to measure dust deposition rates in terms of satellite reflectivity data. The results show that for dry snow conditions, snow reflectivity can be approximated by Kubelka-Munk theory. Dustfall above threshold values of 10 microg/cm(2) can be detected using Landsat computer tape data. Determination of dust deposition over ice-covered lakes and harbors appears in good agreement with sampling measurements.

  8. Large-scale simulations of snow albedo masking by forests

    OpenAIRE

    Essery, Richard

    2013-01-01

    Comparisons between climate models have found large differences in predictions for the albedo of forested regions with snow cover, leading to uncertainty in the strength of snow albedo feedbacks on climate change predicted by these models. To explore this uncertainty, three commonly used methods for calculating the albedo of vegetated surfaces are compared, taking observed snow and vegetation distributions as inputs. Surprisingly, all three methods produce similar results and compare reasonab...

  9. Validation of MODIS snow cover images over Austria

    Directory of Open Access Journals (Sweden)

    J. Parajka

    2006-01-01

    Full Text Available This study evaluates the Moderate Resolution Imaging Spectroradiometer (MODIS snow cover product over the territory of Austria. The aims are (a to analyse the spatial and temporal variability of the MODIS snow product classes, (b to examine the accuracy of the MODIS snow product against in situ snow depth data, and (c to identify the main factors that may influence the MODIS classification accuracy. We use daily MODIS grid maps (version 4 and daily snow depth measurements at 754 climate stations in the period from February 2000 to December 2005. The results indicate that, on average, clouds obscured 63% of Austria, which may significantly restrict the applicability of the MODIS snow cover images to hydrological modelling. On cloud-free days, however, the classification accuracy is very good with an average of 95%. There is no consistent relationship between the classification errors and dominant land cover type and local topographical variability but there are clear seasonal patterns to the errors. In December and January the errors are around 15% while in summer they are less than 1%. This seasonal pattern is related to the overall percentage of snow cover in Austria, although in spring, when there is a well developed snow pack, errors tend to be smaller than they are in early winter for the same overall percent snow cover. Overestimation and underestimation errors balance during most of the year which indicates little bias. In November and December, however, there appears to exist a tendency for overestimation. Part of the errors may be related to the temporal shift between the in situ snow depth measurements (07:00 a.m. and the MODIS acquisition time (early afternoon. The comparison of daily air temperature maps with MODIS snow cover images indicates that almost all MODIS overestimation errors are caused by the misclassification of cirrus clouds as snow.

  10. Small scale variability of snow density on Antarctic sea ice

    Science.gov (United States)

    Wever, N.; Leonard, K. C.; Paul, S.; Jacobi, H. W.; Proksch, M.; Lehning, M.

    2016-12-01

    Snow on sea ice plays an important role in air-ice-sea interactions. For example, snow may smooth the ice surface when snow drift is occurring, while at the same time it may also generate roughness elements by interactions with the wind. Snow density is a key property in many processes, for example by influencing the thermal conductivity of the snow layer, radiative transfer inside the snow as well as the effects of aerodynamic forcing on the snowpack. We present data from an in-situ measurement campaign in the Weddell Sea during two subsequent cruises of RV Polarstern. By comparing snow density from snow pits and snow micro penetrometer (SMP) measurements, augmented by terrestrial laser scanning (TLS) on an area of 50x50 m2, highly resolved density profiles and surface topology were acquired at a horizontal resolution of approximately 30 cm. Average snow densities are about 280 kg/m3, but the analysis also reveals a high spatial variability in snow density on sea ice in both horizontal and vertical direction, ranging from roughly 170 to 360 kg/m3. This variability is expressed by coherent snow structures over several meters, which disappear over larger distances. A comparison with TLS data indicates that the spatial variability is related to deviations in surface topology. This suggests a strong influence from surface processes, for example wind, on the temporal development of density profiles. The fundamental relationship between density variations, surface roughness and changes therein as investigated in this study are interpreted with respect to larger-scale ice-movement and the ice mass balance.

  11. Improving the snow physics of WEB-DHM and its point evaluation at the SnowMIP sites

    Directory of Open Access Journals (Sweden)

    M. Shrestha

    2010-12-01

    Full Text Available In this study, the snow physics of a distributed biosphere hydrological model, referred to as the Water and Energy Budget based Distributed Hydrological Model (WEB-DHM is significantly improved by incorporating the three-layer physically based energy balance snowmelt model of Simplified Simple Biosphere 3 (SSiB3 and the Biosphere-Atmosphere Transfer Scheme (BATS albedo scheme. WEB-DHM with improved snow physics is hereafter termed WEB-DHM-S. Since the in-situ observations of spatially-distributed snow variables with high resolution are currently not available over large regions, the new distributed system (WEB-DHM-S is at first rigorously tested with comprehensive point measurements. The stations used for evaluation comprise the four open sites of the Snow Model Intercomparison Project (SnowMIP phase 1 with different climate characteristics (Col de Porte in France, Weissfluhjoch in Switzerland, Goose Bay in Canada and Sleepers River in USA and one open/forest site of the SnowMIP phase 2 (Hitsujigaoka in Japan. The comparisons of the snow depth, snow water equivalent, surface temperature, snow albedo and snowmelt runoff at the SnowMIP1 sites reveal that WEB-DHM-S, in general, is capable of simulating the internal snow process better than the original WEB-DHM. Sensitivity tests (through incremental addition of model processes are performed to illustrate the necessity of improvements over WEB-DHM and indicate that both the 3-layer snow module and the new albedo scheme are essential. The canopy effects on snow processes are studied at the Hitsujigaoka site of the SnowMIP2 showing that the snow holding capacity of the canopy plays a vital role in simulating the snow depth on ground. Through these point evaluations and sensitivity studies, WEB-DHM-S has demonstrated the potential to address basin-scale snow processes (e.g., the snowmelt runoff, since it inherits the distributed hydrological framework from the WEB-DHM (e.g., the slope-driven runoff

  12. Poor visualization during direct laryngoscopy and high upper lip bite test score are predictors of difficult intubation with the GlideScope videolaryngoscope.

    Science.gov (United States)

    Tremblay, Marie-Hélène; Williams, Stephan; Robitaille, Arnaud; Drolet, Pierre

    2008-05-01

    The GlideScope videolaryngoscope allows equal or superior glottic visualization compared with direct laryngoscopy, but predictive features for difficult GlideScope intubation have not been identified. We undertook this prospective study to identify patient characteristics associated with difficult GlideScope intubation. Demographic and morphometric factors were recorded preoperatively for 400 patients undergoing anesthesia with endotracheal intubation. After induction, direct laryngoscopy was performed in all patients to assess the Cormack and Lehane grade of glottic visualization followed by GlideScope intubation. The number of attempts and time needed for intubation were recorded. Univariate and multivariate analyses were performed to identify the characteristics associated with difficult GlideScope intubation. Intubation required 1, 2, and 3 attempts in 342, 48, and 9 participants, respectively, with one failure. Mean time for intubation was 21 +/- 14 s. After univariate analysis, the following characteristics were significantly correlated (P Cormack and Lehane grade during direct laryngoscopy. However, after introducing these variables in nominal logistic and proportional hazard multiple regression models, only high Cormack and Lehane grade during direct laryngoscopy, high upper lip bite test score, and short sternothyroid distance were significantly associated with multiple attempts or lengthier intubations. Despite a high success rate, intubation with the GlideScope is likely to be more challenging in patients with high Cormack and Lehane grade during direct laryngoscopy, high upper lip bite test score, or short sternothyroid distance.

  13. Direct observation of gliding dislocations interactions with defects in irradiated niobium single crystals by means of the high voltage electronic microscopy (HVEM)

    International Nuclear Information System (INIS)

    Otero, M.P.

    1985-01-01

    The interactions of gliding dislocations with defects in irradiated niobium that result in the formation of dislocations channels. The effects in the mechanical behaviour of [941]- and [441]- oriented Nb single crystals due to oxygen addition, neutron and electron irradiation was observed either by macroscopic deformation in a Instron machine or 'in-situ' deformation in the HVEM-High Voltage Electron Microscope. Some specimens were irradiated at IPNS-Intense Pulsed Neutron Source, at 325 K, with 5 x 10 17 n/cm 2 , others were irradiated with electrons in the HVEM. The interactions between gliding dislocations with clusters point defects and dislocations were observed. The primary mechanism for removal of the clusters by the gliding dislocations was the 'sweeping' of the clusters along with the gliding dislocations. As to the point defects, they were 'swept' by the gliding dislocations and left as aligned loops close to the intersections of the gliding dislocations with the upper and lower specimen surfaces. For the illustration of this phenomena, a schematic drawing was made. The mechanism of 'bowing-out' interaction of dislocations with defect clusters was also observed. The reported anomalous slip observed to operate in the [941]- oriented Nb was also directly observed and a qualitive explanation along with a schematic drawing was proposed. This would explain the softenig observed after the yield stress in the [941]- oriented Nb deformed in the Instron machine. (Author) [pt

  14. View Angle Effects on MODIS Snow Mapping in Forests

    Science.gov (United States)

    Xin, Qinchuan; Woodcock, Curtis E.; Liu, Jicheng; Tan, Bin; Melloh, Rae A.; Davis, Robert E.

    2012-01-01

    Binary snow maps and fractional snow cover data are provided routinely from MODIS (Moderate Resolution Imaging Spectroradiometer). This paper investigates how the wide observation angles of MODIS influence the current snow mapping algorithm in forested areas. Theoretical modeling results indicate that large view zenith angles (VZA) can lead to underestimation of fractional snow cover (FSC) by reducing the amount of the ground surface that is viewable through forest canopies, and by increasing uncertainties during the gridding of MODIS data. At the end of the MODIS scan line, the total modeled error can be as much as 50% for FSC. Empirical analysis of MODIS/Terra snow products in four forest sites shows high fluctuation in FSC estimates on consecutive days. In addition, the normalized difference snow index (NDSI) values, which are the primary input to the MODIS snow mapping algorithms, decrease as VZA increases at the site level. At the pixel level, NDSI values have higher variances, and are correlated with the normalized difference vegetation index (NDVI) in snow covered forests. These findings are consistent with our modeled results, and imply that consideration of view angle effects could improve MODIS snow monitoring in forested areas.

  15. Research of Snow-Melt Process on a Heated Platform

    Directory of Open Access Journals (Sweden)

    Vasilyev Gregory P.

    2016-01-01

    Full Text Available The article has shown the results of experimental researches of the snow-melt on a heated platform-near building heat-pump snow-melt platform. The near-building (yard heat pump platforms for snow melt with the area up to 10-15 m2 are a basis of the new ideology of organization of the street cleaning of Moscow from snow in the winter period which supposes the creation in the megalopolis of the «distributed snow-melt system» (DSMS using non-traditional energy sources. The results of natural experimental researches are presented for the estimation of efficiency of application in the climatic conditions of Moscow of heat pumps in the snow-melt systems. The researches were conducted on a model sample of the near-building heat-pump platform which uses the low-potential thermal energy of atmospheric air. The conducted researches have confirmed experimentally in the natural conditions the possibility and efficiency of using of atmospheric air as a source of low-potential thermal energy for evaporation of the snow-melt heat pump systems in the climatic conditions of Moscow. The results of laboratory researches of snow-melt process on a heated horizontal platform are presented. The researches have revealed a considerable dependence of efficiency of the snow-melt process on its piling mode (form-building and the organization of the process of its piling mode (form-building and the organization of the process of its (snow mass heat exchange with the surface of the heated platform. In the process of researches the effect of formation of an «ice dome» under the melting snow mass called by the fact that in case of the thickness of snow loaded on the platform more than 10 cm the water formed from the melting snow while the contact with the heating surface don’t spread on it, but soaks into the snow, wets it due to capillary effect and freezes. The formation of «ice dome» leads to a sharp increase of snow-melt period and decreases the operating

  16. Effect of snow cover on soil frost penetration

    Science.gov (United States)

    Rožnovský, Jaroslav; Brzezina, Jáchym

    2017-12-01

    Snow cover occurrence affects wintering and lives of organisms because it has a significant effect on soil frost penetration. An analysis of the dependence of soil frost penetration and snow depth between November and March was performed using data from 12 automated climatological stations located in Southern Moravia, with a minimum period of measurement of 5 years since 2001, which belong to the Czech Hydrometeorological institute. The soil temperatures at 5 cm depth fluctuate much less in the presence of snow cover. In contrast, the effect of snow cover on the air temperature at 2 m height is only very small. During clear sky conditions and no snow cover, soil can warm up substantially and the soil temperature range can be even higher than the range of air temperature at 2 m height. The actual height of snow is also important - increased snow depth means lower soil temperature range. However, even just 1 cm snow depth substantially lowers the soil temperature range and it can therefore be clearly seen that snow acts as an insulator and has a major effect on soil frost penetration and soil temperature range.

  17. Snow reliability in ski resorts considering artificial snowmaking

    Science.gov (United States)

    Hofstätter, M.; Formayer, H.; Haas, P.

    2009-04-01

    Snow reliability is the key factor to make skiing on slopes possible and to ensure added value in winter tourism. In this context snow reliability is defined by the duration of a snowpack on the ski runs of at least 50 mm snow water equivalent (SWE), within the main season (Dec-Mar). Furthermore the snowpack should form every winter and be existent early enough in season. In our work we investigate the snow reliability of six Austrian ski resorts. Because nearly all Austrian resorts rely on artificial snowmaking it is of big importance to consider man made snow in the snowpack accumulation and ablation in addition to natural snow. For each study region observed weather data including temperature, precipitation and snow height are used. In addition we differentiate up to three elevations on each site (valley, intermediate, mountain top), being aware of the typical local winter inversion height. Time periods suitable for artificial snow production, for several temperature threshold (-6,-4 or -1 degree Celsius) are calculated on an hourly base. Depending on the actual snowpack height, man made snow can be added in the model with different defined capacities, considering different technologies or the usage of additives. To simulate natural snowpack accumulation and ablation we a simple snow model, based on daily precipitation and temperature. This snow model is optimized at each site separately through certain parameterization factors. Based on the local observations and the monthly climate change signals from the climate model REMO-UBA, we generate long term time series of temperature and precipitation, using the weather generator LARS. Thereby we are not only able to simulate the snow reliability under current, but also under future climate conditions. Our results show significant changes in snow reliability, like an increase of days with insufficient snow heights, especially at mid and low altitudes under natural snow conditions. Artificial snowmaking can partly

  18. Snow hydrology in Mediterranean mountain regions: A review

    Science.gov (United States)

    Fayad, Abbas; Gascoin, Simon; Faour, Ghaleb; López-Moreno, Juan Ignacio; Drapeau, Laurent; Page, Michel Le; Escadafal, Richard

    2017-08-01

    Water resources in Mediterranean regions are under increasing pressure due to climate change, economic development, and population growth. Many Mediterranean rivers have their headwaters in mountainous regions where hydrological processes are driven by snowpack dynamics and the specific variability of the Mediterranean climate. A good knowledge of the snow processes in the Mediterranean mountains is therefore a key element of water management strategies in such regions. The objective of this paper is to review the literature on snow hydrology in Mediterranean mountains to identify the existing knowledge, key research questions, and promising technologies. We collected 620 peer-reviewed papers, published between 1913 and 2016, that deal with the Mediterranean-like mountain regions in the western United States, the central Chilean Andes, and the Mediterranean basin. A large amount of studies in the western United States form a strong scientific basis for other Mediterranean mountain regions. We found that: (1) the persistence of snow cover is highly variable in space and time but mainly controlled by elevation and precipitation; (2) the snowmelt is driven by radiative fluxes, but the contribution of heat fluxes is stronger at the end of the snow season and during heat waves and rain-on-snow events; (3) the snow densification rates are higher in these regions when compared to other climate regions; and (4) the snow sublimation is an important component of snow ablation, especially in high-elevation regions. Among the pressing issues is the lack of continuous ground observation in high-elevation regions. However, a few years of snow depth (HS) and snow water equivalent (SWE) data can provide realistic information on snowpack variability. A better spatial characterization of snow cover can be achieved by combining ground observations with remotely sensed snow data. SWE reconstruction using satellite snow cover area and a melt model provides reasonable information that

  19. Scales of snow depth variability in high elevation rangeland sagebrush

    Science.gov (United States)

    Tedesche, Molly E.; Fassnacht, Steven R.; Meiman, Paul J.

    2017-09-01

    In high elevation semi-arid rangelands, sagebrush and other shrubs can affect transport and deposition of wind-blown snow, enabling the formation of snowdrifts. Datasets from three field experiments were used to investigate the scales of spatial variability of snow depth around big mountain sagebrush ( Artemisia tridentata Nutt.) at a high elevation plateau rangeland in North Park, Colorado, during the winters of 2002, 2003, and 2008. Data were collected at multiple resolutions (0.05 to 25 m) and extents (2 to 1000 m). Finer scale data were collected specifically for this study to examine the correlation between snow depth, sagebrush microtopography, the ground surface, and the snow surface, as well as the temporal consistency of snow depth patterns. Variograms were used to identify the spatial structure and the Moran's I statistic was used to determine the spatial correlation. Results show some temporal consistency in snow depth at several scales. Plot scale snow depth variability is partly a function of the nature of individual shrubs, as there is some correlation between the spatial structure of snow depth and sagebrush, as well as between the ground and snow depth. The optimal sampling resolution appears to be 25-cm, but over a large area, this would require a multitude of samples, and thus a random stratified approach is recommended with a fine measurement resolution of 5-cm.

  20. Cyclic fatigue resistance of R-Pilot, WaveOne Gold Glider, and ProGlider glide path instruments.

    Science.gov (United States)

    Keskin, Cangül; İnan, Uğur; Demiral, Murat; Keleş, Ali

    2018-02-17

    The aim of the present study was to compare the cyclic fatigue resistance of R-Pilot (VDW; Munich, Germany) with ProGlider (Denstply Sirona; Ballaigues, Switzerland) and WaveOne Gold Glider (Denstply Sirona; Ballaigues, Switzerland) glide path instruments. R-Pilot, ProGlider, and WaveOne Gold Glider instruments were collected (n = 15) and tested in a dynamic cyclic fatigue test device, which has an artificial canal with 60° angle of curvature and a 5-mm radius of curvature. All instruments were operated until fracture occurred, and both time to fracture (TF) and the lengths of the fractured fragments were recorded. Mean and standard deviations of TF and fragment length were calculated for each reciprocating system. TF data and fractured fragment length data were subjected to one-way ANOVA and post-hoc Tukey tests (P  0.05). Weibull analysis revealed that WaveOne Gold Glider showed the highest predicted TF value for 99% survival rate, which was followed by R-Pilot and ProGlider. Regarding the length of the fractured tips, there were no significant differences among the instruments (P > 0.05). The reciprocating WaveOne Gold Glider and R-Pilot instruments had significantly higher cyclic fatigue resistance than rotary ProGlider instruments. This study reported that novel reciprocating glide path instruments exhibited higher cyclic fatigue resistance than rotating glide path instrument.

  1. CR TKA UHMWPE Wear Tested after Artificial Aging of the Vitamin E Treated Gliding Component by Simulating Daily Patient Activities

    Directory of Open Access Journals (Sweden)

    Jens Schwiesau

    2014-01-01

    Full Text Available The wear behaviour of total knee arthroplasty (TKA is dominated by two wear mechanisms: the abrasive wear and the delamination of the gliding components, where the second is strongly linked to aging processes and stress concentration in the material. The addition of vitamin E to the bulk material is a potential way to reduce the aging processes. This study evaluates the wear behaviour and delamination susceptibility of the gliding components of a vitamin E blended, ultra-high molecular weight polyethylene (UHMWPE cruciate retaining (CR total knee arthroplasty. Daily activities such as level walking, ascending and descending stairs, bending of the knee, and sitting and rising from a chair were simulated with a data set received from an instrumented knee prosthesis. After 5 million test cycles no structural failure of the gliding components was observed. The wear rate was with 5.62±0.53 mg/million cycles falling within the limit of previous reports for established wear test methods.

  2. Use of GlideScope for double lumen endotracheal tube insertion in an awake patient with difficult airway.

    Science.gov (United States)

    Onrubia, X; Lluch-Oltra, A; Armero, R; Baldó, J

    2014-01-01

    There is scientific evidence that an anticipated difficult airway must be managed with the patient being awake. The GlideScope has been proven to be a useful device to intubate the trachea in some instances when difficult airway is present, and particularly in the awake patient. It has also been used for double lumen tube (DLT) in the anaesthetized patient, but its use with DLT in both circumstances, awake patients with difficult airway has not been described. GlideScope enabled us to achieve accurate local anesthetic spraying and a successful endotracheal intubation with a double lumen tube (DLT) in an awake patient with predicted difficult airway and bronchoaspiration risk. Different ways to resolve cases like this can be found in the anesthetic literature, but we think this could be another option to bear in mind. We also describe a new variation in the maneuver of introducing a DLT into the trachea under GlideScope view as DLT presents with some difficulties when introduced under normal circumstances. This option could add some risk for the patients when used in inexperienced hands and there is not sufficient scientific evidence in the literature to recommend it for all cases. Copyright © 2013 Sociedad Española de Anestesiología, Reanimación y Terapéutica del Dolor. Published by Elsevier España. All rights reserved.

  3. Modelling technical snow production for skiing areas in the Austrian Alps with the physically based snow model AMUNDSEN

    Science.gov (United States)

    Hanzer, F.; Marke, T.; Steiger, R.; Strasser, U.

    2012-04-01

    Tourism and particularly winter tourism is a key factor for the Austrian economy. Judging from currently available climate simulations, the Austrian Alps show a particularly high vulnerability to climatic changes. To reduce the exposure of ski areas towards changes in natural snow conditions as well as to generally enhance snow conditions at skiing sites, technical snowmaking is widely utilized across Austrian ski areas. While such measures result in better snow conditions at the skiing sites and are important for the local skiing industry, its economic efficiency has also to be taken into account. The current work emerges from the project CC-Snow II, where improved future climate scenario simulations are used to determine future natural and artificial snow conditions and their effects on tourism and economy in the Austrian Alps. In a first step, a simple technical snowmaking approach is incorporated into the process based snow model AMUNDSEN, which operates at a spatial resolution of 10-50 m and a temporal resolution of 1-3 hours. Locations of skiing slopes within a ski area in Styria, Austria, were digitized and imported into the model environment. During a predefined time frame in the beginning of the ski season, the model produces a maximum possible amount of technical snow and distributes the associated snow on the slopes, whereas afterwards, until to the end of the ski season, the model tries to maintain a certain snow depth threshold value on the slopes. Due to only few required input parameters, this approach is easily transferable to other ski areas. In our poster contribution, we present first results of this snowmaking approach and give an overview of the data and methodology applied. In a further step in CC-Snow, this simple bulk approach will be extended to consider actual snow cannon locations and technical specifications, which will allow a more detailed description of technical snow production as well as cannon-based recordings of water and energy

  4. Silvering substrates after CO2 snow cleaning

    Science.gov (United States)

    Zito, Richard R.

    2005-09-01

    There have been some questions in the astronomical community concerning the quality of silver coatings deposited on substrates that have been cleaned with carbon dioxide snow. These questions center around the possible existence of carbonate ions left behind on the substrate by CO2. Such carbonate ions could react with deposited silver to produce insoluble silver carbonate, thereby reducing film adhesion and reflectivity. Carbonate ions could be produced from CO2 via the following mechanism. First, during CO2 snow cleaning, a small amount of moisture can condense on a surface. This is especially true if the jet of CO2 is allowed to dwell on one spot. CO2 gas can dissolve in this moisture, producing carbonic acid, which can undergo two acid dissociations to form carbonate ions. In reality, it is highly unlikely that charged carbonate ions will remain stable on a substrate for very long. As condensed water evaporates, Le Chatelier's principle will shift the equilibrium of the chain of reactions that produced carbonate back to CO2 gas. Furthermore, the hydration of CO2 reaction of CO2 with H20) is an extremely slow process, and the total dehydrogenation of carbonic acid is not favored. Living tissues that must carry out the equilibration of carbonic acid and CO2 use the enzyme carbonic anhydrase to speed up the reaction by a factor of one million. But no such enzymatic action is present on a clean mirror substrate. In short, the worst case analysis presented below shows that the ratio of silver atoms to carbonate radicals must be at least 500 million to one. The results of chemical tests presented here support this view. Furthermore, film lift-off tests, also presented in this report, show that silver film adhesion to fused silica substrates is actually enhanced by CO2 snow cleaning.

  5. A Cost-Effective Tracking Algorithm for Hypersonic Glide Vehicle Maneuver Based on Modified Aerodynamic Model

    Directory of Open Access Journals (Sweden)

    Yu Fan

    2016-10-01

    Full Text Available In order to defend the hypersonic glide vehicle (HGV, a cost-effective single-model tracking algorithm using Cubature Kalman filter (CKF is proposed in this paper based on modified aerodynamic model (MAM as process equation and radar measurement model as measurement equation. In the existing aerodynamic model, the two control variables attack angle and bank angle cannot be measured by the existing radar equipment and their control laws cannot be known by defenders. To establish the process equation, the MAM for HGV tracking is proposed by using additive white noise to model the rates of change of the two control variables. For the ease of comparison several multiple model algorithms based on CKF are presented, including interacting multiple model (IMM algorithm, adaptive grid interacting multiple model (AGIMM algorithm and hybrid grid multiple model (HGMM algorithm. The performances of these algorithms are compared and analyzed according to the simulation results. The simulation results indicate that the proposed tracking algorithm based on modified aerodynamic model has the best tracking performance with the best accuracy and least computational cost among all tracking algorithms in this paper. The proposed algorithm is cost-effective for HGV tracking.

  6. The Glide/Gcm fate determinant controls initiation of collective cell migration by regulating Frazzled

    Science.gov (United States)

    Gupta, Tripti; Kumar, Arun; Cattenoz, Pierre B.; VijayRaghavan, K; Giangrande, Angela

    2016-01-01

    Collective migration is a complex process that contributes to build precise tissue and organ architecture. Several molecules implicated in cell interactions also control collective migration, but their precise role and the finely tuned expression that orchestrates this complex developmental process are poorly understood. Here, we show that the timely and threshold expression of the Netrin receptor Frazzled triggers the initiation of glia migration in the developing Drosophila wing. Frazzled expression is induced by the transcription factor Glide/Gcm in a dose-dependent manner. Thus, the glial determinant also regulates the efficiency of collective migration. NetrinB but not NetrinA serves as a chemoattractant and Unc5 contributes as a repellant Netrin receptor for glia migration. Our model includes strict spatial localization of a ligand, a cell autonomously acting receptor and a fate determinant that act coordinately to direct glia toward their final destination. DOI: http://dx.doi.org/10.7554/eLife.15983.001 PMID:27740455

  7. T-S Fuzzy Modelling and H∞ Attitude Control for Hypersonic Gliding Vehicles

    Directory of Open Access Journals (Sweden)

    Weidong Zhang

    2017-01-01

    Full Text Available This paper addresses the T-S fuzzy modelling and H∞ attitude control in three channels for hypersonic gliding vehicles (HGVs. First, the control-oriented affine nonlinear model has been established which is transformed from the reentry dynamics. Then, based on Taylor’s expansion approach and the fuzzy linearization approach, the homogeneous T-S local modelling technique for HGVs is proposed. Given the approximation accuracy and controller design complexity, appropriate fuzzy premise variables and operating points of interest are selected to construct the T-S homogeneous submodels. With so-called fuzzy blending, the original plant is transformed into the overall T-S fuzzy model with disturbance. By utilizing Lyapunov functional approach, a state feedback fuzzy controller has been designed based on relaxed linear matrix inequality (LMI conditions to stable the original plants with a prescribed H∞ performance of disturbance. Finally, numerical simulations are performed to demonstrate the effectiveness of the proposed H∞ T-S fuzzy controller for the original attitude dynamics; the superiority of the designed T-S fuzzy controller compared with other local controllers based on the constructed fuzzy model is shown as well.

  8. PIV-based study of the gliding osprey aerodynamics in a wind tunnel

    Science.gov (United States)

    Gurka, Roi; Liberzon, Alex; Kopp, Gregory; Kirchhefer, Adam; Weihs, Daniel

    2009-11-01

    The hunting flight of an osprey consists of periods where the bird glides while foraging for prey. High quality measurements of aerodynamics in this flight mode are needed in order to estimate the daily energy expenditure of the bird accurately. An experimental study of an osprey model in a wind tunnel (BLWTL, UWO) was performed in order to characterize the aerodynamic forces using particle image velocimetry (PIV). The model was a stuffed osprey with mechanical joints allowing control of the the wing (angle of attack, tilt) and tail orientation. Two-dimensional velocity realizations in the streamwise-normal plane were obtained simultaneously in the two fields of view: above the wing and in the wake of the wing. Mean and turbulent flow characteristics are presented as function of angle of attack based on measurements taken at 4 different angles of attack at three different locations over the wingspan. The main outcome is the accurate estimate of the drag from the measurements of momentum thickness in the turbulent boundary layer of the osprey wing. Moreover, the gradient of the momentum thickness method was applied to identify the separation point in the boundary layer. This estimate has been compared to the total drag calculated from measurements in the wake of the wing and with a theoretical prediction.

  9. Musicians demonstrate experience-dependent brainstem enhancement of musical scale features within continuously gliding pitch.

    Science.gov (United States)

    Bidelman, Gavin M; Gandour, Jackson T; Krishnan, Ananthanarayan

    2011-10-10

    In contrast to language, where pitch patterns consist of continuous and curvilinear contours, musical pitch consists of relatively discrete, stair-stepped sequences of notes. Behavioral and neurophysiological studies suggest that both tone-language and music experience enhance the representation of pitch cues associated with a listener's domain of expertise, e.g., curvilinear pitch in language, discrete scale steps in music. We compared brainstem frequency-following responses (FFRs) of English-speaking musicians (musical pitch experience) and native speakers of Mandarin Chinese (linguistic pitch experience) elicited by rising and falling tonal sweeps that are exemplary of Mandarin tonal contours but uncharacteristic of the pitch patterns typically found in music. In spite of musicians' unfamiliarity with such glides, we find that their brainstem FFRs show enhancement of the stimulus where the curvilinear sweep traverses discrete notes along the diatonic musical scale. This enhancement was note specific in that it was not observed immediately preceding or following the scale tone of interest (passing note). No such enhancements were observed in Chinese listeners. These findings suggest that the musician's brainstem may be differentially tuned by long-term exposure to the pitch patterns inherent to music, extracting pitch in relation to a fixed, hierarchical scale. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  10. Surface energy balance of seasonal snow cover for snow-melt ...

    Indian Academy of Sciences (India)

    ... surface at this station received a mean short wave radiation of 430 W m−2, out of which 298 W m−2 was re flected back by the snow surface with mean albedo value of 0.70. The high average temperature and more absorption of solar radiation resulted in higher thermal state of the snowpack which was further responsible ...

  11. Snow instability evaluation in skier-triggered snow slab avalanches: combining failure initiation and crack propagation

    Science.gov (United States)

    Gaume, Johan; Reuter, Benjamin

    2017-04-01

    Dry-snow slab avalanches start with a local failure in a weak snowpack layer buried below cohesive snow slab layers. If the size of the failed zone exceeds a critical size, rapid crack propagation occurs possibly followed by slab release if the slope is steep enough. The probability of skier-triggering a slab avalanche is generally characterized by classical stability indices that do not account for crack propagation. In this study, we propose a new model to evaluate the conditions for the onset of crack propagation in skier-triggered slab avalanches. For a given weak layer, the critical crack length characterizing crack propagation propensity was compared to the size of the area where the skier-induced stress exceeds the shear strength of the weak layer. The ratio between both length scales yields a stability criterion combining the processes of failure initiation and crack propagation. The critical crack length was calculated from a recently developed model based on numerical simulations. The skier-induced stress was computed from analytical solutions and finite element simulations to account for slab layering. A detailed sensitivity analysis was performed for simplified snow profiles to characterize the influence of snowpack properties and slab layering on crack propagation propensity. Finally, we applied our approach for manually observed snow profiles and compared our results to rutschblock stability tests.

  12. Translating Chicana Rap: Snow Tha Product

    Directory of Open Access Journals (Sweden)

    Adriana Onita

    2017-06-01

    Full Text Available This project examines rap lyrics, interviews, and music videos by Chicana artist Snow Tha Product to show how rap has been culturally translated, performed, and appropriated by females in order to “flip the script,” or subvert the dichotomous model of female sexuality that has been imposed upon them. Weaving insights from three academic fields (cultural translation, Chican@ studies, and hip-hop feminism, this paper also aims to creatively expand the definition of translation by positioning rap music as a performative language in its own right, capable of encoding and translating complex cultural issues related to race, gender, and sexuality.

  13. Second International Conference on Snow Engineering.

    Science.gov (United States)

    1992-12-01

    Papers of Annual Meeting, Architectural Institute of Japan, 451 -452, October 1990 (in Japanese). Watanabe, M. and Hirai, K. (1991) "Study on Snow Sliding...visitor center facility: "Washington Pass experiences temperatures from minus 30 degrees Farenheit (minus 34 degrees Centigrade) to 90 degrees Farenheit ...Comparison of drift loads by 4 C s8 12 m NBCC and ASCE for Lu =75m Figure 4 Comparison of drift loads by ASCE and ISO 451 TORONTO ASCE . _ =228 m USSR kPa 4

  14. Take control of upgrading to Snow Leopard

    CERN Document Server

    Kissell, Joe

    2009-01-01

    Installing a major new version of Mac OS X should be exciting and fun, but without proper guidance you may find it nerve-wracking or even risk losing valuable files. Fortunately, many thousands of people have upgraded Mac OS X calmly and successfully with Joe Kissell's previous best-selling Take Control of Upgrading... titles. Joe's friendly, expert steps-developed over innumerable test installations-help you to avoid trouble, understand what's going on when you install Snow Leopard, and easily recover from problem

  15. Simulation of Seasonal Snow Microwave TB Using Coupled Multi-Layered Snow Evolution and Microwave Emission Models

    Science.gov (United States)

    Brucker, Ludovic; Royer, Alain; Picard, Ghislain; Langlois, Alex; Fily, Michel

    2014-01-01

    The accurate quantification of SWE has important societal benefits, including improving domestic and agricultural water planning, flood forecasting and electric power generation. However, passive-microwave SWE algorithms suffer from variations in TB due to snow metamorphism, difficult to distinguish from those due to SWE variations. Coupled snow evolution-emission models are able to predict snow metamorphism, allowing us to account for emissivity changes. They can also be used to identify weaknesses in the snow evolution model. Moreover, thoroughly evaluating coupled models is a contribution toward the assimilation of TB, which leads to a significant increase in the accuracy of SWE estimates.

  16. [Research on the Thermal Infrared Polarization Properties of Fresh Snow].

    Science.gov (United States)

    Wang, Ting-ting; Li, Zhao-liang; Tang, Bo-hui; Sun, Wei-qi; Zhao, Yun-sheng

    2015-07-01

    Snow can directly affect the surface energy balance and climate change and has a significant impact on human life and production. It is therefore of great significance to study the fresh snow emission spectroscopy properties by using the thermal infrared Polarization technique. This can provide a basis for quantitative thermal infrared remote sensing monitoring of snow as well as a deeper understanding of global warming and appropriate countermeasures. This paper focuses on the investigation of the thermal infrared polarization properties of the fresh snow. The results show that the thermal emissive polarization properties of fresh snow depend significantly on the wavelengths (channels) and view angles used to measure them. Four channels are considered in this study, their spectral response ranges are 8-14 microm for channel 1 (CH1), 11.5-12.5 microm for channel 2 (CH2), 10.3-11.5 microm for channel 3 (CH) and 8.2-9.2 microm for channel 4 (CH4). The snow polarized radiance (L) and its polarized brightness temperature (T) manifest as L(CH1) >L(CH3) > L(CH4) > L(CH2) and T(CH4) > T(CH1) > T(CH2) > TCH3, respectively, while the degree of polarization (P) manifests as P0 > P30 > P40 > P20 > P0 > P50 where the subscript of P denotes the view angle. The maximum of both L and T occurs at the view angle of 50 degree and polarization angle of 90 degree while their minimum appears at the view angle of 30 degree and polarization angle of 75 degree for each channel. In addition, the results show that: CH3 is more appropriate for better investigation of the emissive polarization properties of snow. Linear relationship is found between the fresh snow polarized T and the polarization angle with the coefficient of determination larger than 0.77 for all four channels. The polarized brightness temperature of the fresh snow is found to be increased about 0.003 K per polarization angle within 0-135 degree. The degree of polarization of snow is almost independent of the channels we

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

    Science.gov (United States)

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

    2014-02-01

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

  18. Impact of climate change in Switzerland on socioeconomic snow indices

    Science.gov (United States)

    Schmucki, Edgar; Marty, Christoph; Fierz, Charles; Weingartner, Rolf; Lehning, Michael

    2017-02-01

    Snow is a key element for many socioeconomic activities in mountainous regions. Due to the sensitivity of the snow cover to variations of temperature and precipitation, major changes caused by climate change are expected to happen. We analyze the evolution of some key snow indices under future climatic conditions. Ten downscaled and postprocessed climate scenarios from the ENSEMBLES database have been used to feed the physics-based snow model SNOWPACK. The projected snow cover has been calculated for 11 stations representing the diverse climates found in Switzerland. For the first time, such a setup is used to reveal changes in frequently applied snow indices and their implications on various socioeconomic sectors. Toward the end of the twenty-first century, a continuous snow cover is likely only guaranteed at high elevations above 2000 m a.s.l., whereas at mid elevations (1000-1700 m a.s.l.), roughly 50 % of all winters might be characterized by an ephemeral snow cover. Low elevations (below 500 m a.s.l.) are projected to experience only 2 days with snowfall per year and show the strongest relative reductions in mean winter snow depth of around 90 %. The range of the mean relative reductions of the snow indices is dominated by uncertainties from different GCM-RCM projections and amounts to approximately 30 %. Despite these uncertainties, all snow indices show a clear decrease in all scenario periods and the relative reductions increase toward lower elevations. These strong reductions can serve as a basis for policy makers in the fields of tourism, ecology, and hydropower.

  19. Airborne Surveys of Snow Depth over Arctic Sea Ice

    Science.gov (United States)

    Kwok, R.; Panzer, B.; Leuschen, C.; Pang, S.; Markus, T.; Holt, B.; Gogineni, S.

    2011-01-01

    During the spring of 2009, an ultrawideband microwave radar was deployed as part of Operation IceBridge to provide the first cross-basin surveys of snow thickness over Arctic sea ice. In this paper, we analyze data from three approx 2000 km transects to examine detection issues, the limitations of the current instrument, and the regional variability of the retrieved snow depth. Snow depth is the vertical distance between the air \\snow and snow-ice interfaces detected in the radar echograms. Under ideal conditions, the per echogram uncertainty in snow depth retrieval is approx 4 - 5 cm. The finite range resolution of the radar (approx 5 cm) and the relative amplitude of backscatter from the two interfaces limit the direct retrieval of snow depths much below approx 8 cm. Well-defined interfaces are observed over only relatively smooth surfaces within the radar footprint of approx 6.5 m. Sampling is thus restricted to undeformed, level ice. In early April, mean snow depths are 28.5 +/- 16.6 cm and 41.0 +/- 22.2 cm over first-year and multiyear sea ice (MYI), respectively. Regionally, snow thickness is thinner and quite uniform over the large expanse of seasonal ice in the Beaufort Sea, and gets progressively thicker toward the MYI cover north of Ellesmere Island, Greenland, and the Fram Strait. Snow depth over MYI is comparable to that reported in the climatology by Warren et al. Ongoing improvements to the radar system and the utility of these snow depth measurements are discussed.

  20. Daily Snow Depth and SWE from GPS Signal-to-Noise Ratios, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set consists of daily snow depths and snow-water equivalents (SWEs) estimated from GPS signal-to-noise ratios (SNRs). Snow depth is determined by...

  1. Early results from NASA's SnowEx campaign

    Science.gov (United States)

    Kim, Edward; Gatebe, Charles; Hall, Dorothy; Misakonis, Amy; Elder, Kelly; Marshall, Hans Peter; Hiemstra, Chris; Brucker, Ludovic; Crawford, Chris; Kang, Do Hyuk; De Marco, Eugenia; Beckley, Matt; Entin, Jared

    2017-04-01

    SnowEx is a multi-year airborne snow campaign with the primary goal of addressing the question: How much water is stored in Earth's terrestrial snow-covered regions? Year 1 (2016-17) focuses on the distribution of snow-water equivalent (SWE) and the snow energy balance in a forested environment. The year 1 primary site is Grand Mesa and the secondary site is the Senator Beck Basin, both in western, Colorado, USA. Ten core sensors on four core aircraft will make observations using a broad suite of airborne sensors including active and passive microwave, and active and passive optical/infrared sensing techniques to determine the sensitivity and accuracy of these potential satellite remote sensing techniques, along with models, to measure snow under a range of forest conditions. SnowEx also includes an extensive range of ground truth measurements—in-situ samples, snow pits, ground based remote sensing measurements, and sophisticated new techniques. A detailed description of the data collected will be given and some early results will be presented. Seasonal snow cover is the largest single component of the cryosphere in areal extent (covering an average of 46M km2 of Earth's surface (31 % of land areas) each year). This seasonal snow has major societal impacts in the areas of water resources, natural hazards (floods and droughts), water security, and weather and climate. The only practical way to estimate the quantity of snow on a consistent global basis is through satellites. Yet, current space-based techniques underestimate storage of snow water equivalent (SWE) by as much as 50%, and model-based estimates can differ greatly vs. estimates based on remotely-sensed observations. At peak coverage, as much as half of snow-covered terrestrial areas involve forested areas, so quantifying the challenge represented by forests is important to plan any future snow mission. Single-sensor approaches may work for certain snow types and certain conditions, but not for others

  2. Snow and Dust over Inner Mongolia

    Science.gov (United States)

    2002-01-01

    A severe snow-and-sand storm hit an 80,000 square-mile (205,000-square-km) stretch of the Chinese province of Mongolia on New Year's Eve, killing 21 people and leaving thousands of people to face possible starvation. The affected area is located about 250 miles (400 km) northwest of Beijing. It is the worst snowstorm to hit the region in more than 50 years. Lasting about 3 days, the storm dumped 24 inches (60 cm) of snow mixed with sand from the Gobi Desert, stranding many residents in deep drifts. The Chinese Red Cross reports that almost 1 million people were affected by the storm and at least 10,000 head of livestock are confirmed dead. As many as 120,000 residents are in need of food and other supplies. The Sea-viewing Wide Field-of-view Sensor (SeaWiFS), flying aboard the OrbView-2 satellite, acquired this image of the storm on January 2, 2001, as it approached China's eastern provinces. You can see storm clouds (white pixels) and windblown dust (brownish pixels) crossing the Yellow Sea and East China Sea toward Japan and the western Pacific. Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  3. Detection of Oil in Ice and Snow

    Directory of Open Access Journals (Sweden)

    Merv Fingas

    2013-11-01

    Full Text Available The response to a major oil spill can be challenging in temperate climates and with good weather conditions. By contrast, a major spill in or under ice and snow, presents a whole new series of challenges. This paper reviews detection technologies for these challenging situations. A number of acoustic techniques have been tried in test tank situations and it was found that acoustic detection of oil was possible because oil behaves as a solid in acoustic terms and transmits shear waves. Laboratory tests have been carried out and a prototype was built and tested in the field. Radio frequency methods, such as ground penetrating radar (GPR, have been tested for both oil-under-ice and oil-under-snow. The GPR method does not provide sufficient discrimination for positive oil detection in actual spills. Preliminary tests on the use of Nuclear Magnetic Resonance for detecting oil, in and under ice, shows promise and further work on this is being done at this time. A number of other oil-in-ice detection technologies have been tried and evaluated, including standard acoustic thickness probes, fluorosensor techniques, and augmented infrared detection. Each of these showed potential in theory during tank tests. Further testing on these proposed methods is required.

  4. Kinetic Friction of Sport Fabrics on Snow

    Directory of Open Access Journals (Sweden)

    Werner Nachbauer

    2016-03-01

    Full Text Available After falls, skiers or snowboarders often slide on the slope and may collide with obstacles. Thus, the skier’s friction on snow is an important factor to reduce incidence and severity of impact injuries. The purpose of this study was to measure snow friction of different fabrics of ski garments with respect to roughness, speed, and contact pressure. Three types of fabrics were investigated: a commercially available ski overall, a smooth downhill racing suit, and a dimpled downhill racing suit. Friction was measured for fabrics taped on a short ski using a linear tribometer. The fabrics’ roughness was determined by focus variation microscopy. Friction coefficients were between 0.19 and 0.48. Roughness, friction coefficient, and friction force were highest for the dimpled race suit. The friction force of the fabrics was higher for the higher contact pressure than for the lower one at all speeds. It was concluded that the main friction mechanism for the fabrics was dry friction. Only the fabric with the roughest surface showed friction coefficients, which were high enough to sufficiently decelerate a sliding skier on beginner and intermediate slopes.

  5. The Snow Data System at NASA JPL

    Science.gov (United States)

    Laidlaw, R.; Painter, T. H.; Mattmann, C. A.; Ramirez, P.; Bormann, K.; Brodzik, M. J.; Burgess, A. B.; Rittger, K.; Goodale, C. E.; Joyce, M.; McGibbney, L. J.; Zimdars, P.

    2014-12-01

    NASA JPL's Snow Data System has a data-processing pipeline powered by Apache OODT, an open source software tool. The pipeline has been running for several years and has successfully generated a significant amount of cryosphere data, including MODIS-based products such as MODSCAG, MODDRFS and MODICE, with historical and near-real time windows and covering regions such as the Artic, Western US, Alaska, Central Europe, Asia, South America, Australia and New Zealand. The team continues to improve the pipeline, using monitoring tools such as Ganglia to give an overview of operations, and improving fault-tolerance with automated recovery scripts. Several alternative adaptations of the Snow Covered Area and Grain size (SCAG) algorithm are being investigated. These include using VIIRS and Landsat TM/ETM+ satellite data as inputs. Parallel computing techniques are being considered for core SCAG processing, such as using the PyCUDA Python API to utilize multi-core GPU architectures. An experimental version of MODSCAG is also being developed for the Google Earth Engine platform, a cloud-based service.

  6. [An overview of snow-boarding injuries].

    Science.gov (United States)

    Biasca, N; Battaglia, H; Simmen, H P; Disler, P; Trentz, O

    1995-01-01

    Snowboarding is increasing dramatically in popularity in Switzerland as well as other countries. Work aimed at improving the design of the boards and of the boots and bindings has also increased rapidly during recent years. Most injured snowboarders are fit young men and boys who describe themselves as beginners and have had a minimal amount of instruction at an officially approved training centre. Appropriate snowboard training has mostly been quite inadequate, and protective devices (e.g. waterproofed support gloves). The anatomical distribution and the types of injuries sustained in snowboarding differ from those in alpine skiing. The wrist (and forearm) and the ankle are the most frequent locations of injuries (23%) as against the knee and thumb in alpine skiing. Sprains and strains were the most frequent types of injuries (46%), followed by fractures (28%) and contusions (13.5%). The snowboard injury rate was higher than in alpine skiing (1.7-8/1000 snowboard days versus 2-4/1000 ski days). Falling forward on the slope was the major mechanism of injury (80%), and torsion the next most frequent (20%). Snowboarding injuries were sustained most often on ice and hardpacked snow, compared with soft powder snow for alpine skiing injuries. Appropriate preseason conditioning, snowboarding lessons from a certified instructor, appropriate selection of rigorously tested equipment and use of protective devices are the main steps that must be taken to prevent injuries.

  7. Energy and dissipated work in snow avalanches

    Science.gov (United States)

    Bartelt, P.; Buser, O.

    2004-12-01

    Using the results of large scale avalanche experiments at the Swiss Vallée de la Sionne test site, the energy balance of several snow avalanches is determined. Avalanches convert approximately one-seventh of their potential energy into kinetic energy. The total potential energy depends strongly on the entrained snowcover, indicating that entrainment processes cannot be ignored when predicting terminal velocities and runout distances. We find energy dissipation rates on the order of 1 GW. Fluidization of the fracture slab can be identified in the experiments as an increase in dissipation rate, thereby explaining the initial and rapid acceleration of avalanches after release. Interestingly, the dissipation rates appear to be constant along the track, although large fluctuations in internal velocity exist. Thus, we can demonstrate within the context of non-equilibrium thermodynamics that -- in space -- granular snow avalanches are irreversible, dissipative systems that minimize entropy production because they appear to reach a steady-state non-equilibrium. A thermodynamic analysis reveals that fluctuations in velocity depend on the roughness of the flow surface and viscosity of the granular system. We speculate that this property explains the transition from flowing avalanches to powder avalanches.

  8. [Characteristics of mercury exchange flux between soil and atmosphere under the snow retention and snow melting control].

    Science.gov (United States)

    Zhang, Gang; Wang, Ning; Ai, Jian-Chao; Zhang, Lei; Yang, Jing; Liu, Zi-Qi

    2013-02-01

    Jiapigou gold mine, located in the upper Songhua River, was once the largest mine in China due to gold output, where gold extraction with algamation was widely applied to extract gold resulting in severe mercury pollution to ambient environmental medium. In order to study the characteristics of mercury exchange flux between soil (snow) and atmosphere under the snow retention and snow melting control, sampling sites were selected in equal distances along the slope which is situated in the typical hill-valley terrain unit. Mercury exchange flux between soil (snow) and atmosphere was determined with the method of dynamic flux chamber and in all sampling sites the atmosphere concentration from 0 to 150 cm near to the earth in the vertical direction was measured. Furthermore, the impact factors including synchronous meteorology, the surface characteristics under the snow retention and snow melting control and the mercury concentration in vertical direction were also investigated. The results are as follows: During the period of snow retention and melting the air mercury tends to gather towards valley bottom along the slope and an obvious deposit tendency process was found from air to the earth's surface under the control of thermal inversion due to the underlying surface of cold source (snow surface). However, during the period of snow melting, mercury exchange flux between the soil and atmosphere on the surface of the earth with the snow being melted demonstrates alternative deposit and release processes. As for the earth with snow covered, the deposit level of mercury exchange flux between soil and atmosphere is lower than that during the period of snow retention. The relationship between mercury exchange flux and impact factors shows that in snow retention there is a remarkable negative linear correlation between mercury exchange flux and air mercury concentration as well as between the former and the air temperature. In addition, in snow melting mercury exchange

  9. Chemistry of snow and lake water in Antarctic region

    Indian Academy of Sciences (India)

    Surface snow and lake water samples were collected at different locations around Indian station at Antarctica, Maitri, during December 2004-March 2005 and December 2006-March 2007.Samples were analyzed for major chemical ions. It is found that average pH value of snow is 6.1. Average pH value of lake water with ...

  10. Chemistry of snow and lake water in Antarctic region

    Indian Academy of Sciences (India)

    Surface snow and lake water samples were collected at different locations around Indian station at. Antarctica, Maitri, during December 2004–March 2005 and December 2006–March 2007. Samples were analyzed for major chemical ions. It is found that average pH value of snow is 6.1. Average pH value of lake water with ...

  11. Bacterial diversity in snow on North Pole ice floes

    DEFF Research Database (Denmark)

    Hauptmann, Aviaja Zenia Edna Lyberth; Stibal, Marek; Bælum, Jacob

    2014-01-01

    The microbial abundance and diversity in snow on ice floes at three sites near the North Pole was assessed using quantitative PCR and 454 pyrosequencing. Abundance of 16S rRNA genes in the samples ranged between 43 and 248 gene copies per millilitre of melted snow. A total of 291,331 sequences we...

  12. Prevent Snow from Blocking your Tailpipe PSA (:30)

    Centers for Disease Control (CDC) Podcasts

    2014-12-11

    If it's snowing, make sure your vehicle’s tailpipe is clear of snow before starting the engine to prevent carbon monoxide poisoning.  Created: 12/11/2014 by National Center for Environmental Health (NCEH).   Date Released: 12/11/2014.

  13. Consistent seasonal snow cover depth and duration variability over ...

    Indian Academy of Sciences (India)

    Decline in consistent seasonal snow cover depth, duration and changing snow cover build- up pattern over the WH in recent decades indicate that WH has undergone considerable climate change and winter weather patterns are changing in the WH. 1. Introduction. Mountainous regions around the globe are storehouses.

  14. Consistent seasonal snow cover depth and duration variability over ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 125; Issue 7. Consistent seasonal ... Consistent seasonal snow cover depth and duration, delay days and early melt days of consistent seasonal snow cover at 11 stations spread across different mountain ranges over the WH were analyzed. Mean, maximum and ...

  15. A comparison of Normalised Difference Snow Index (NDSI) and ...

    African Journals Online (AJOL)

    As an alternative, thematic cover–types based on remotely sensed data-sets are becoming popular. In this study we hypothesise that the reduced dimensionality using Principal Components Analysis (PCA) in concert Normalized Difference Snow Index (NDSI) is valuable for improving the accuracy of snow cover maps.

  16. Spectral characterization of soil and coal contamination on snow ...

    Indian Academy of Sciences (India)

    Snow is a highly reflecting object found naturally on the Earth and its albedo is highly influenced by the amount and type of contamination. In the present study, two major types of contaminants (soil and coal) have been used to understand their effects on snow reflectance in the Himalayan region. These con- taminants were ...

  17. Spectral characterization of soil and coal contamination on snow ...

    Indian Academy of Sciences (India)

    Crystal gauge with magnifying glass was used for estimating grain size of snow. Thermometer was used for snow skin temperature and air temperature measurements. 4. Methodology. In the present study, two types of contaminants – soil and coal – were used in varying amount of contamination in two categories during the ...

  18. Seasonal snow accumulation in the mid-latitude forested catchment

    Czech Academy of Sciences Publication Activity Database

    Šípek, Václav; Tesař, Miroslav

    2014-01-01

    Roč. 69, č. 11 (2014), s. 1562-1569 ISSN 0006-3088 R&D Projects: GA TA ČR TA02021451 Institutional support: RVO:67985874 Keywords : snow depth * snow water equivalent * forested catchment Subject RIV: DA - Hydrology ; Limnology Impact factor: 0.827, year: 2014

  19. Monitoring and evaluation of seasonal snow cover in Kashmir valley ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 118; Issue 6 ... Different geographical parameters of these regions were studied to evaluate the influence on snow cover and it was observed that altitude and position of region with respect to mountain range are the deciding factors for retaining the seasonal snow ...

  20. Chemical compositions of snow from Mt. Yulong, southeastern ...

    Indian Academy of Sciences (India)

    snowpits formed over recent years. 2. Sampling methods. Fresh snow samples were collected immediately ... because of contamination problems. Snow samples were packed into insulated and cleaned polyethy- lene bottles ..... climbers or tourists to the glacier. The upper rope- way station where tourists gather to enjoy the.

  1. Monitoring and evaluation of seasonal snow cover in Kashmir valley ...

    Indian Academy of Sciences (India)

    in Kashmir valley using remote sensing, GIS and ancillary data. H S Negi∗, N K Thakur, Rajeev Kumar and Manoj Kumar. Snow and Avalanche Study Establishment, Him Parisar, Sector-37A, Chandigarh 160 036, India. ∗ e-mail: negi−hs@yahoo.com. Seasonal snow cover is a vital natural resource in the Himalaya.

  2. Spectral characterization of soil and coal contamination on snow

    Indian Academy of Sciences (India)

    Snow is a highly reflecting object found naturally on the Earth and its albedo is highly influenced by the amount and type of contamination. In the present study, two major types of contaminants (soil and coal) have been used to understand their effects on snow reflectance in the Himalayan region. These contaminants were ...

  3. Modeling Snow Regime in Cores of Small Planetary Bodies

    Science.gov (United States)

    Boukaré, C. E.; Ricard, Y. R.; Parmentier, E.; Parman, S. W.

    2017-12-01

    Observations of present day magnetic field on small planetary bodies such as Ganymede or Mercury challenge our understanding of planetary dynamo. Several mechanisms have been proposed to explain the origin of magnetic fields. Among the proposed scenarios, one family of models relies on snow regime. Snow regime is supported by experimental studies showing that melting curves can first intersect adiabats in regions where the solidifying phase is not gravitationaly stable. First solids should thus remelt during their ascent or descent. The effect of the snow zone on magnetic field generation remains an open question. Could magnetic field be generated in the snow zone? If not, what is the depth extent of the snow zone? How remelting in the snow zone drive compositional convection in the liquid layer? Several authors have tackled this question with 1D-spherical models. Zhang and Schubert, 2012 model sinking of the dense phase as internally heated convection. However, to our knowledge, there is no study on the convection structure associated with sedimentation and phase change at planetary scale. We extend the numerical model developped in [Boukare et al., 2017] to model snow dynamics in 2D Cartesian geometry. We build a general approach for modeling double diffusive convection coupled with solid-liquid phase change and phase separation. We identify several aspects that may govern the convection structure of the solidifying system: viscosity contrast between the snow zone and the liquid layer, crystal size, rate of melting/solidification and partitioning of light components during phase change.

  4. DISCOVERY OF A TRANSITING PLANET NEAR THE SNOW-LINE

    DEFF Research Database (Denmark)

    Kipping, D. M.; Torres, G.; Buchhave, L. A.

    2014-01-01

    In most theories of planet formation, the snow-line represents a boundary between the emergence of the interior rocky planets and the exterior ice giants. The wide separation of the snow-line makes the discovery of transiting worlds challenging, yet transits would allow for detailed subsequent ch...

  5. Consistent seasonal snow cover depth and duration variability over ...

    Indian Academy of Sciences (India)

    of biodiversity, global ecosystem and global hydro- logical cycle (Robinson ... climate change impacts assessment, water resources ...... Brown R D and Braaten R O 1998 Spatial and temporal vari- ability of Canadian monthly snow depths; Atmos. Ocean. 36 37–54. Cayan D R 1996 Interannual climate variability and snow.

  6. Electron microprobe analysis (WDS EPMA) of Zhamanshin glass reveals the impactor and a common role of accretion in the origin of splash-form impact glass

    International Nuclear Information System (INIS)

    Vetvicka, I; Frank, J; Drtina, J

    2010-01-01

    Impact glass samples collected during expeditions to the Zhamashin and Lonar craters were subjected to a morphology survey and compared to Wabar, Henbury and Darwin impact glasses to reveal that the accretion of fibres and spherules is not exclusive for irghizites but occurs in other splash form glasses over the world. WDS EPMA and LA-ICP-MS assays of Zhamanshin and Lonar glasses enabled the definition of akmurynites as Zhamanshin glass of specific morphology, chemistry and absence of extraterrestrial contamination. However, extraterrestrial contamination in irghizites was verified and further WDS EPMA analyses led to the conclusion that the Zhamanshin crater had been formed by the impact of a primitive achondrite of Lodran chemistry.

  7. Partitioning washoff of manure-borne fecal indicators (Escherichia coli and stanols) into splash and hydraulic components: field rainfall simulations in a tropical agro-ecosystem.

    Science.gov (United States)

    Ribolzi, Olivier; Rochelle-Newall, Emma J.; Janeau, Jean-Louis; Viguier, Marion; Jardé, Emilie; Latsachack, Keooudone; Henri-Des-Tureaux, Thierry; Thammahacksac, Chanthamousone; Mugler, Claude; Valentin, Christian; Sengtaheuanghoung, Oloth

    2017-04-01

    Overland flow from manured fields and pastures is known to be an important mechanism by which organisms of faecal origin are transferred to streams in rural watersheds. In the tropical montane areas of South-East Asia, recent changes in land use have induced increased runoff, soil erosion, in-stream suspended sediment loads resulting in increased microbial pathogen dissemination and contamination of stream waters. The majority of enteric and environmental bacteria in aquatic systems are associated with particles such as sediments which can strongly influence their survival and transport characteristics. Escherichia coli (E. coli) has emerged as one of the most appropriate microbial indicators of faecal contamination of natural waters, with the presence of E. coli indicating that faecal contamination is present. In association with E. coli, faecal stanols can also be used as microbial source tracking tool for the identification of the origin of the faecal contamination (e.g. livestock, human, etc). Field rain simulations were used to examine how E.coli and stanols are exported from the surface of upland, agricultural soils during overland flow events. The objectives were to characterize the loss dynamics of these indicators from agricultural soils contaminated with livestock waste, and to partition total detachment into the splash and hydraulic components. Nine 1m2 microplots were divided in triplicated treatment groups: (a) controls with no amendments, (b) amended with pig manure or (c) poultry manure. Each plot was divided into two 0.5m2 rectangular subplots. For each simulation, one subplot was designated as a rain splash treatment; the other was covered with 2-mm grid size wire screen 10 cm above the soil surface to break the raindrops into fine droplets, thus drastically reducing their kinetic energy. E. coli concentrations in overland flow were estimated for both the attached and free living fractions and stanols were measured on the particulate matter washed

  8. A COMPARISON OF OBSERVATION WITH MODELING FOR ALBEDO AND TRANSMITTANCE OF SNOW

    OpenAIRE

    アオキ, テルオ; セコ, カツモト; アオキ, タダオ; フカボリ, マサシ; Teruo, AOKI; Katsumoto, SEKO; Tadao, AOKI; Masashi, FUKABORI

    1994-01-01

    Snow surface albedo and transmittance inside the snow have been investigated by observation and modeling. Observations were taken by a grating type spectrometer at Tokamachi in March 1993. The observed snow was old and very wet. Microscope photo-graphs of snow grains taken at this time indicate that snow grain is spherical particles with size of about 1.0μm. Surface albedo and transmittance of snow by a multiple scattering model for the atmosphere-snow system with pure snow grain size of 1.0μ...

  9. High Resolution Insights into Snow Distribution Provided by Drone Photogrammetry

    Science.gov (United States)

    Redpath, T.; Sirguey, P. J.; Cullen, N. J.; Fitzsimons, S.

    2017-12-01

    Dynamic in time and space, New Zealand's seasonal snow is largely confined to remote alpine areas, complicating ongoing in situ measurement and characterisation. Improved understanding and modeling of the seasonal snowpack requires fine scale resolution of snow distribution and spatial variability. The potential of remotely piloted aircraft system (RPAS) photogrammetry to resolve spatial and temporal variability of snow depth and water equivalent in a New Zealand alpine catchment is assessed in the Pisa Range, Central Otago. This approach yielded orthophotomosaics and digital surface models (DSM) at 0.05 and 0.15 m spatial resolution, respectively. An autumn reference DSM allowed mapping of winter (02/08/2016) and spring (10/09/2016) snow depth at 0.15 m spatial resolution, via DSM differencing. The consistency and accuracy of the RPAS-derived surface was assessed by comparison of snow-free regions of the spring and autumn DSMs, while accuracy of RPAS retrieved snow depth was assessed with 86 in situ snow probe measurements. Results show a mean vertical residual of 0.024 m between DSMs acquired in autumn and spring. This residual approximated a Laplace distribution, reflecting the influence of large outliers on the small overall bias. Propagation of errors associated with successive DSMs saw snow depth mapped with an accuracy of ± 0.09 m (95% c.l.). Comparing RPAS and in situ snow depth measurements revealed the influence of geo-location uncertainty and interactions between vegetation and the snowpack on snow depth uncertainty and bias. Semi-variogram analysis revealed that the RPAS outperformed systematic in situ measurements in resolving fine scale spatial variability. Despite limitations accompanying RPAS photogrammetry, this study demonstrates a repeatable means of accurately mapping snow depth for an entire, yet relatively small, hydrological basin ( 0.5 km2), at high resolution. Resolving snowpack features associated with re-distribution and preferential

  10. What controls the isotopic composition of Greenland surface snow?

    Directory of Open Access Journals (Sweden)

    H. C. Steen-Larsen

    2014-02-01

    Full Text Available Water stable isotopes in Greenland ice core data provide key paleoclimatic information, and have been compared with precipitation isotopic composition simulated by isotopically enabled atmospheric models. However, post-depositional processes linked with snow metamorphism remain poorly documented. For this purpose, monitoring of the isotopic composition (δ18O, δD of near-surface water vapor, precipitation and samples of the top (0.5 cm snow surface has been conducted during two summers (2011–2012 at NEEM, NW Greenland. The samples also include a subset of 17O-excess measurements over 4 days, and the measurements span the 2012 Greenland heat wave. Our observations are consistent with calculations assuming isotopic equilibrium between surface snow and water vapor. We observe a strong correlation between near-surface vapor δ18O and air temperature (0.85 ± 0.11‰ °C−1 (R = 0.76 for 2012. The correlation with air temperature is not observed in precipitation data or surface snow data. Deuterium excess (d-excess is strongly anti-correlated with δ18O with a stronger slope for vapor than for precipitation and snow surface data. During nine 1–5-day periods between precipitation events, our data demonstrate parallel changes of δ18O and d-excess in surface snow and near-surface vapor. The changes in δ18O of the vapor are similar or larger than those of the snow δ18O. It is estimated using the CROCUS snow model that 6 to 20% of the surface snow mass is exchanged with the atmosphere. In our data, the sign of surface snow isotopic changes is not related to the sign or magnitude of sublimation or deposition. Comparisons with atmospheric models show that day-to-day variations in near-surface vapor isotopic composition are driven by synoptic variations and changes in air mass trajectories and distillation histories. We suggest that, in between precipitation events, changes in the surface snow isotopic composition are driven by these changes in near

  11. Observations of atmospheric chemical deposition to high Arctic snow

    Science.gov (United States)

    Macdonald, Katrina M.; Sharma, Sangeeta; Toom, Desiree; Chivulescu, Alina; Hanna, Sarah; Bertram, Allan K.; Platt, Andrew; Elsasser, Mike; Huang, Lin; Tarasick, David; Chellman, Nathan; McConnell, Joseph R.; Bozem, Heiko; Kunkel, Daniel; Duan Lei, Ying; Evans, Greg J.; Abbatt, Jonathan P. D.

    2017-05-01

    Rapidly rising temperatures and loss of snow and ice cover have demonstrated the unique vulnerability of the high Arctic to climate change. There are major uncertainties in modelling the chemical depositional and scavenging processes of Arctic snow. To that end, fresh snow samples collected on average every 4 days at Alert, Nunavut, from September 2014 to June 2015 were analyzed for black carbon, major ions, and metals, and their concentrations and fluxes were reported. Comparison with simultaneous measurements of atmospheric aerosol mass loadings yields effective deposition velocities that encompass all processes by which the atmospheric species are transferred to the snow. It is inferred from these values that dry deposition is the dominant removal mechanism for several compounds over the winter while wet deposition increased in importance in the fall and spring, possibly due to enhanced scavenging by mixed-phase clouds. Black carbon aerosol was the least efficiently deposited species to the snow.

  12. The Infrared Sensor Suite for SnowEx 2017

    Science.gov (United States)

    Hall, D. K.; Chickadel, C. C.; Crawford, C. J.; DeMarco, E. L.; Jennings, D. E.; Jhabvala, M. D.; Kim, E. J.; Lundquist, J. D.; Lunsford, A. W.

    2017-01-01

    SnowEx is a winter airborne and field campaign designed to measure snow-water equivalent in forested landscapes. A major focus of Year 1 (2016-17) of NASA's SnowEx campaign will be an extensive field program involving dozens of participants from U.S. government agencies and from many universities and institutions, both domestic and foreign. Along with other instruments, two infrared (IR) sensors will be flown on a Naval Research Laboratory P-3 aircraft. Surface temperature is a critical input to hydrologic models and will be measured during the SnowEx mission. A Quantum Well Infrared Photodetector (QWIP) IR imaging camera system will be flown along with a KT-15 remote thermometer to aid in the calibration of the IR image data. Together, these instruments will measure surface temperature of snow and ice targets to an expected accuracy of less than 1C.

  13. Inorganic carbon addition stimulates snow algae primary productivity.

    Science.gov (United States)

    Hamilton, Trinity L; Havig, Jeff R

    2018-01-29

    Earth has experienced glacial/interglacial oscillations accompanied by changes in atmospheric CO 2 throughout much of its history. Today over 15 million square kilometers of Earth's land surface is covered in ice including glaciers, ice caps, and ice sheets. Glaciers are teeming with life and supraglacial snow and ice surfaces are often darkened by the presence of photoautotrophic snow algae, resulting in accelerated melt due to lowered albedo. Few studies report the productivity of snow algal communities and the parameters which constrain their growth on supraglacial surfaces-key factors for quantifying biologically induced albedo effects (bio-albedo). We demonstrate that snow algae primary productivity is stimulated by the addition of inorganic carbon. Our results indicate a positive feedback between increasing CO 2 and snow algal primary productivity, underscoring the need for robust climate models of past and present glacial/interglacial oscillations to include feedbacks between supraglacial primary productivity, albedo, and atmospheric CO 2 .

  14. Bacterial diversity in snow on North Pole ice floes

    DEFF Research Database (Denmark)

    Hauptmann, Aviaja Zenia Edna Lyberth; Stibal, Marek; Bælum, Jacob

    2014-01-01

    sites clustered together when compared to the underlying environments of sea ice and ocean water. The Shannon indices ranged from 2.226 to 3.758, and the Chao1 indices showed species richness between 293 and 353 for the three samples. The relatively low abundances and diversity found in the samples......The microbial abundance and diversity in snow on ice floes at three sites near the North Pole was assessed using quantitative PCR and 454 pyrosequencing. Abundance of 16S rRNA genes in the samples ranged between 43 and 248 gene copies per millilitre of melted snow. A total of 291,331 sequences were...... indicate a lower rate of microbial input to this snow habitat compared to snow in the proximity of terrestrial and anthropogenic sources of microorganisms. The differences in species composition and diversity between the sites show that apparently similar snow habitats contain a large variation...

  15. Variability in snow depth time series in the Adige catchment

    Directory of Open Access Journals (Sweden)

    Giorgia Marcolini

    2017-10-01

    New hydrological insights for the region: Stations located above and below 1650 m a.s.l. show different dynamics, with the latter experiencing in the last decades a larger reduction of average snow depth and snow cover duration, than the former. Wavelet analyses show that snow dynamics change with elevation and correlate differently with climatic indices at multiple temporal scales. We also observe that starting from the late 1980s snow cover duration and mean seasonal snow depth are below the average in the study area. We also identify an elevation dependent correlation with the temperature. Moreover, correlation with the Mediterranean Oscillation Index and with the North Atlantic Oscillation Index is identified.

  16. Estimating Snow Depth and Snow Water Equivalence Using Repeat-Pass Interferometric SAR in the Northern Piedmont Region of the Tianshan Mountains

    Directory of Open Access Journals (Sweden)

    Hui Li

    2017-01-01

    Full Text Available Snow depth and Snow Water Equivalence (SWE are important parameters for hydrological applications. In this application, a theoretical method of snow depth estimation with repeat-pass InSAR measurements was proposed, and a preliminary sensitivity analysis of snow phase changes versus the incident angle and snow density was developed. Moreover, the snow density and incident angle parameters were analyzed and calibrated, and the local incident angle was used as a substitute for the satellite incident angle to improve the snow depth estimation. From the results, the coherence images showed that a high degree of coherence can be found for dry snow, and, apart from the effect of snow, land use/cover change due to a long temporal baseline and geometric distortion due to the rugged terrain were the main constraints for InSAR technique to measure snow depth and SWE in this area. The result of snow depth estimation between July 2008 and February 2009 demonstrated that the average snow depth was about 20 cm, which was consistent with the field survey results. The areal coverage of snow distribution estimated from the snow depth and SWE results was consistent with snow cover obtained from HJ-1A CCD optical data at the same time.

  17. An ensemble-based subgrid snow data assimilation framework

    Science.gov (United States)

    Aalstad, K.; Westermann, S.; Bertino, L.

    2016-12-01

    Snow, with high albedo, low thermal conductivity and large water storing capacity strongly modulates the surface energy and water balance. At the same time, the estimation of the seasonal snow cycle at the kilometer scale is a major hydrometeorological challenge and thus represents a significant source of uncertainty in land surface schemes. To constrain this uncertainty we are developing a modular ensemble-based subgrid snow data assimilation framework (ESSDA) for satellite-era snow distribution (SD) reanalyses. ESSDA makes use of an ensemble Kalman smoother (EnKS) approach to assimilate MODIS and LandSat retrievals of snow cover fraction into the subgrid snow distribution submodel (SSNOWD). Our problem is particularly challenging as snow cover is doubly bounded in physical space, which violates the Gaussian error assumption in the EnKS and thus compromises the performance of the reanalysis. In an attempt to alleviate this issue we make use of the technique of analytical Gaussian anamorphosis (GA) and apply the EnKS in a transformed space. The potential of the framework is presented through both synthetic (twin) and real experiments. The latter are carried out for the Bayelva catchment near Ny Ålelsund (79°N, Svalbard, Norway) where independent and accurate ground-based observations of snow cover and snow depth distributions are available. Our ensuing evaluation demonstrates that ESSDA provides robust estimates of the evolution of the SD over almost a decade long validation period. The use of GA, and our emphasis on the subgrid SD, is what sets ESSDA apart from previously proposed snow reanalysis frameworks. ESSDA has been developed to aid in satellite-based permafrost mapping efforts. Nonetheless, being modular and given the improved error treatment through GA, the ESSDA approach may also prove valuable for broader hydrometeorological reanalysis and forecast initialization efforts.

  18. SWEAT: Snow Water Equivalent with AlTimetry

    Science.gov (United States)

    Agten, Dries; Benninga, Harm-Jan; Diaz Schümmer, Carlos; Donnerer, Julia; Fischer, Georg; Henriksen, Marie; Hippert Ferrer, Alexandre; Jamali, Maryam; Marinaci, Stefano; Mould, Toby JD; Phelan, Liam; Rosker, Stephanie; Schrenker, Caroline; Schulze, Kerstin; Emanuel Telo Bordalo Monteiro, Jorge

    2017-04-01

    To study how the water cycle changes over time, satellite and airborne remote sensing missions are typically employed. Over the last 40 years of satellite missions, the measurement of true water inventories stored in sea and land ice within the cryosphere have been significantly hindered by uncertainties introduced by snow cover. Being able to determine the thickness of this snow cover would act to reduce such error, improving current estimations of hydrological and climate models, Earth's energy balance (albedo) calculations and flood predictions. Therefore, the target of the SWEAT (Snow Water Equivalent with AlTimetry) mission is to directly measure the surface Snow Water Equivalent (SWE) on sea and land ice within the polar regions above 60°and below -60° latitude. There are no other satellite missions currently capable of directly measuring SWE. In order to achieve this, the proposed mission will implement a novel combination of Ka- and Ku-band radioaltimeters (active microwave sensors), capable of penetrating into the snow microstructure. The Ka-band altimeter (λ ≈ 0.8 cm) provides a low maximum snow pack penetration depth of up to 20 cm for dry snow at 37 GHz, since the volume scattering of snow dominates over the scattering caused by the underlying ice surface. In contrast, the Ku-band altimeter (λ ≈ 2 cm) provides a high maximum snowpack penetration depth of up to 15 m in high latitudes regions with dry snow, as volume scattering is decreased by a factor of 55. The combined difference in Ka- and Ku-band signal penetration results will provide more accurate and direct determination of SWE. Therefore, the SWEAT mission aims to improve estimations of global SWE interpreted from passive microwave products, and improve the reliability of numerical snow and climate models.

  19. Design of an optimal snow observation network to estimate snowpack

    Science.gov (United States)

    Juan Collados Lara, Antonio; Pardo-Iguzquiza, Eulogio; Pulido-Velazquez, David

    2016-04-01

    Snow is an important water resource in many river basins that must be taken into account in hydrological modeling. Although the snow cover area may be nowadays estimated from satellite data, the snow pack thickness must be estimated from experimental data by using some interpolation procedure or hydrological models that approximates snow accumulation and fusion processes. The experimental data consist of hand probes and snow samples collected in a given number of locations that constitute the monitoring network. Assuming that there is an existing monitoring network, its optimization may imply the selection of an optimal network as a subset of the existing network (decrease of the existing network in the case that there are no funds for maintaining the full existing network) or to increase the existing network by one or more stations (optimal augmentation problem). In this work we propose a multicriterion approach for the optimal design of a snow network. These criteria include the estimation variance from a regression kriging approach for estimating thickness of the snowpack (using ground and satellite data), to minimize the total snow volume and accessibility criteria. We have also proposed a procedure to analyze the sensitivity of the results to the non-snow data deduced from the satellite information. We intent to minimize the uncertities in snowpack estimation. The methodology has been applied to estimation of the snow cover area and the design of the optimal snow observation network in Sierra Nevada mountain range in the Southern of Spain. Acknowledgments: This research has been partially supported by the GESINHIMPADAPT project (CGL2013-48424-C2-2-R) with Spanish MINECO funds. We would also like to thank ERHIN program and NASA DAAC for the data provided for this study.

  20. Assessing the controls of the snow energy balance and water available for runoff in a rain-an-snow environment

    Science.gov (United States)

    Adam B. Mazurkiewicz; David G. Callery; Jeffrey J. McDonnell

    2008-01-01

    Rain-on-snow (ROS) melt production and its contribution to water available for runoff is poorly understood. In the Pacific Northwest (PNW) of the USA, ROS drives many runoff events with turbulent energy exchanges dominating the snow energy balance (EB). While previous experimental work in the PNW (most notably the H.J. Andrews Experimental Forest (HJA» has quantified...