Science.gov

Sample records for frost layer presence

  1. 1D Transient Model for Frost Heave in PEFCs III. Heat Transfer, Microporous Layer, and Cycling Effects

    E-print Network

    Mench, Matthew M.

    -5,11-16 To determine the root cause of freeze/thaw dam- age, a frost heave thermal model has been developed layer CL , which would typically not cause dam- age upon shutdown to freezing in an unconstrained. In soils, frost heaved sur- faces are cracked and elevated. Specifically, an ice lens can continue

  2. Frost Growth and Densification in Laminar Flow Over Flat Surfaces

    NASA Technical Reports Server (NTRS)

    Kandula, Max

    2011-01-01

    One-dimensional frost growth and densification in laminar flow over flat surfaces has been theoretically investigated. Improved representations of frost density and effective thermal conductivity applicable to a wide range of frost circumstances have been incorporated. The validity of the proposed model considering heat and mass diffusion in the frost layer is tested by a comparison of the predictions with data from various investigators for frost parameters including frost thickness, frost surface temperature, frost density and heat flux. The test conditions cover a range of wall temperature, air humidity ratio, air velocity, and air temperature, and the effect of these variables on the frost parameters has been exemplified. Satisfactory agreement is achieved between the model predictions and the various test data considered. The prevailing uncertainties concerning the role air velocity and air temperature on frost development have been elucidated. It is concluded that that for flat surfaces increases in air velocity have no appreciable effect on frost thickness but contribute to significant frost densification, while increase in air temperatures results in a slight increase the frost thickness and appreciable frost densification.

  3. Crushed aggregates for roads and their properties for frost protection

    NASA Astrophysics Data System (ADS)

    Kuznetsova, Elena; Willy Danielsen, Svein

    2015-04-01

    Crushed aggregates for roads and their properties for frost protection Elena Kuznetsova, NTNU and Svein Willy Danielsen, SINTEF With natural (fluvial, glaciofluvial) sand/gravel resources being rapidly depleted in many countries, the last decade has seen a significant trend towards using more alternative materials for construction purpose. In Norway the development and implementation of crushed aggregate technology has been the most important way to get around the problem with increased resource scarcity. Today Norway is one the European countries with the highest percentage of crushed/manufactured aggregates. A crushed product will reveal a different particle size distribution, a sharper, more angular particle shape, and not least - a significantly different mineral composition. The latter may often be characterised by more polymineral composition, and it will also much more depend on the local bedrock. When handled with care and knowledge, these differences can give the user a lot of new opportunities relating to materials design. Norwegian road construction practice has changed significantly during the last 40 years due to the replacement of gravel by crushed rock materials in the granular layers of the pavements. The use of non-processed rock materials from blasting was allowed in the subbase layer until 2012. This was a reason for a lot of problems with frost heaving due to inhomogeneity of this material, and in practice it was difficult to control the size of large stones. Since 2012 there is a requirement that rock materials for use in the subbase layer shall be crushed (Handbook N200, 2014). During the spring 2014 The Norwegian Public Roads Administration introduced a new handbook with requirements for roads construction in Norway, including new specifications for the frost protection layer. When pavements are constructed over moist and/or frost susceptible soils in cold and humid environments, the frost protection layer also becomes a very important part of the road system. According to new specification; the size of large stones for this layer should be maximum 0.5 m (longest edge) or ½ layer thickness. And minimum 30% of stones should be less than 90 mm. Fines content (<0.063 mm) should be maximum 15% of the material less than 22.4 mm. Analysing these new requirements, several questions are arising. First of all how this materials size will affect heat exchange in the layer, secondly - if the allowable fines content will make the materials frost susceptible. For calculations of frost protection layer thickness the knowledge of thermal conductivity of the aggregate layers is required. Handbook for geotechnical investigations of the soils provides this data for natural gravel which is limited by 0.7 - 1.3 W/mK. But when it comes to the crushed rocks, it can be significantly increased due to the higher conductivity of minerals (especially if they contain high amount of quartz), as well as due to higher effective conductivity. In rock-fill materials, i.e. materials with large particles and low degree of saturation, convection and radiation are the predominant heat transfer mechanisms. Convection and radiation can increase the effective conductivity by factor 2-10. Lebeau and Konrad (2007) showed that convection heat transfer could lead to the formation of undesirable permafrost conditions in toe drains of embankment dams located in Northern Quebec, i.e. in areas where there are no naturally occurring permafrost soils. In a frost design method the required parameter values of crushed rock aggregates are thermal conductivity, density and water content. The heat transfer during the freezing of natural soils is assumed proportional to thermal conductivity of the material. In a coarse-grained material with abundant pore space, convective heat transfer and radiation may be a considerable factor, sometimes even more significant than conduction. Specifications used by pavement engineers in most countries are solely based on grain size distribution and allowable fines content. The presence of fines in these layers can

  4. Frost formation with salt

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    The formation of frost in presence of salt (NaCl) crystal is experimentally investigated on a hydrophobic surface. It presents several remarkable features due to the interplay of salty-water saturation pressure evolution, initially lower than the saturation pressure of ice and water, and the percolating propagation of ice dendrites from defects throughout the supercooled water droplet pattern. In particular, it is remarkable that nucleation of supercooled water and/or ice is prevented around the salty drop in a region of inhibited condensation where the substrate remains dry. As condensation proceeds, salt concentration decreases to eventually become lower than ice's, allowing ice dendrites to hit the salty drop. Salty water then melts ice but eventually freezes as an effect of dilution.

  5. A model for nocturnal frost formation on a wing section: Aircraft takeoff performance penalties

    NASA Technical Reports Server (NTRS)

    Dietenberger, M. A.

    1983-01-01

    The nocturnal frost formation on a wing section, to explain the hazard associated with frost during takeoff was investigated. A model of nocturnal frost formation on a wing section which predicts when the nocturnal frost will form and also its thickness and density as a function of time was developed. The aerodynamic penalities as related to the nocturnal frost formation properties were analyzed to determine how much the takeoff performance would be degraded by a specific frost layer. With an aircraft takeoff assuming equations representing a steady climbing flight, it is determined that a reduction in the maximum gross weight or a partial frost clearance and a reduction in the takeoff angle of attack is needed to neutralize drag and life penalities which are due to frost. Atmospheric conditions which produce the most hazardous frost buildup are determined.

  6. Tints, Shades and Frost

    ERIC Educational Resources Information Center

    Sterling, Joan

    2009-01-01

    This article describes a classroom art project inspired by the work of Robert Frost, one of the most acclaimed and beloved American poets of all time. Using tints and shades in a composition, this project demonstrates how quality literature may be incorporated into elementary art lessons in a very useful way, making art an important complement to…

  7. Frost Forecasting for Fruitgrowers

    NASA Technical Reports Server (NTRS)

    Martsolf, J. D.; Chen, E.

    1983-01-01

    Progress in forecasting from satellite data reviewed. University study found data from satellites displayed in color and used to predict frost are valuable aid to agriculture. Study evaluated scheme to use Earth-temperature data from Geostationary Operational Environmental Satellite in computer model that determines when and where freezing temperatures endanger developing fruit crops, such as apples, peaches and cherries in spring and citrus crops in winter.

  8. Water frost on Charon

    NASA Technical Reports Server (NTRS)

    Buie, Marc W.; Cruikshank, Dale P.; Lebofsky, Larry A.; Tedesco, Edward F.

    1987-01-01

    New spectra of the Pluto-Charon system taken just before and during a total eclipse of the satellite are presented. The spectrum of Charon extracted from the data reveals the signature of water ice. There is no evidence for any methane or ammonia frost on the surface of Charon. The significance of these findings for the evolution of the Pluto-Charon system are discussed.

  9. Free magnetohydrodynamic shear layers in the presence of rotation and magnetic fielda)

    E-print Network

    Ji, Hantao

    Free magnetohydrodynamic shear layers in the presence of rotation and magnetic fielda) E. J. Spence and numerical study of hydrodynamic and magnetohydrodynamic free shear layers and their stability. We first typically reach zero velocity at the bounding wall. A shear layer is called "free" when it exists

  10. Winter Frost and Fog

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This somewhat oblique blue wide angle Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the 174 km (108 mi) diameter crater, Terby, and its vicinity in December 2004. Located north of Hellas, this region can be covered with seasonal frost and ground-hugging fog, even in the afternoon, despite being north of 30oS. The subtle, wavy pattern is a manifestation of fog.

    Location near: 28oS, 286oW Illumination from: upper left Season: Southern Winter

  11. Seeing through Frost on Enceladus

    NASA Astrophysics Data System (ADS)

    Helfenstein, P.

    2012-12-01

    It is now well-established that active cryovolcanism on Enceladus populates the E-ring with icy dust grains, that re-accreting E-ring particles bombard and globally modify the surfaces of Enceladus and its satellite neighbors (cf. Verbiscer et al. 2007, Science 315, pp. 815; Kempf et al. 2010, Icarus 206, 446-457), and that direct fallout from eruptive plumes creates distinct, predicable broad-scale regional patterns of albedo and color on the surface of Enceladus (Schenk et al. 2010, Icarus 211, 740-757). However, at present it is not clearly established how thickly that plume fallout mantles the surface from location to location, how the presence of plume fallout affects the appearance and detection of underlying geological features, how rapidly the deposits accumulate, how long they have been accumulating, or how plume fallout, E-ring bombardment, and endogenic processes like thermal annealing and seismic shaking, for example near active tiger stripe rifts, compete and combine to modify the shape of geological structures at size-scales of kilometers or less that are much smaller than those that are represented in the regional albedo patterns found by Schenk et al. (2010). Early Cassini Narrow Angle Camera (NAC) images of Enceladus' Western Hemisphere (leading-side) that were obtained at relatively large phase angles (?>90°) and spatial resolutions better than about 1 km/pixel clearly identify peculiar circular albedo structures with diameters of tens of kilometers. One feature (here called P1) at 9.1°S, 83.0°W is conspicuously darker than its surroundings, while an adjacent feature (P2) at 24.1°S, 73.5°W is comparable in brightness to its surroundings except for a relatively bright diffuse patch that appears to be ejecta from a superposed small impact crater. The subdued circular surface relief of these features and overprinting by quasi-linear tectonic features suggest that they may be palimpsest-like structures or else surface expressions of diapirism (cf. Spencer et al. 2009, In "Saturn after Cassini-Huygens", Springer-Verlag. 683-724; Helfenstein et al. 2010; American Geophysical Union, Fall Meeting 2010, abstract #P23C-04). More recent Cassini high-resolution imaging of the region over a wide range of illumination geometry reveals a systematic change in the appearance of the circular albedo features as the phase angle decreases from ?=124° to ?=31° -- the circular albedo features that are so clearly visible at large phase angles are completely masked at small phase angles. The decrease in the albedo contrast with decreasing phase angle is dramatic: The average albedo contrast between the circular P1 and P2 features diminishes from 27±3% at phase ?=124° to only 1.3±0.2% at ?=31°. A likely explanation for this photometric behavior is that it reveals a top layer of frost or snow that scatters light strongly at relatively small phase angles, but which becomes more transparent as phase angles increase allowing Cassini to see through to underlying features. It is also possible that the changing photometric contrasts arise from terrain-dependent differences in regolith properties like surface roughness or regolith grain-size.

  12. Modeling the effects of martian surface frost on ice table depth

    NASA Astrophysics Data System (ADS)

    Williams, K. E.; McKay, Christopher P.; Heldmann, J. L.

    2015-11-01

    Ground ice has been observed in small fresh craters in the vicinity of the Viking 2 lander site (48°N, 134°E). To explain these observations, current models for ground ice invoke levels of atmospheric water of 20 precipitable micrometers - higher than observations. However, surface frost has been observed at the Viking 2 site and surface water frost and snow have been shown to have a stabilizing effect on Antarctic subsurface ice. A snow or frost cover provides a source of humidity that should reduce the water vapor gradient and hence retard the sublimation loss from subsurface ice. We have modeled this effect for the Viking 2 landing site with combined ground ice and surface frost models. Our model is driven by atmospheric output fields from the NASA Ames Mars General Circulation Model (MGCM). Our modeling results show that the inclusion of a thin seasonal frost layer, present for a duration similar to that observed by the Viking Lander 2, produces ice table depths that are significantly shallower than a model that omits surface frost. When a maximum frost albedo of 0.35 was permitted, seasonal frost is present in our model from Ls = 182° to Ls = 16°, resulting in an ice table depth of 64 cm - which is 24 cm shallower than the frost-free scenario. The computed ice table depth is only slightly sensitive to the assumed maximum frost albedo or thickness in the model.

  13. Seasonal Frost in Terra Sirenum

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This image of the Terra Sirenum region of Mars was taken by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) at 0918 UTC (4:18 a.m. EST) on Nov. 25, 2006, near 38.9 degrees south latitude, 195.9 degrees east longitude. CRISM's image was taken in 544 colors covering 0.36-3.92 micrometers, and shows features as small as 18 meters (60 feet) across.

    At this time, Mars' southern hemisphere was experiencing mid-winter. During Martian southern winter, the southern polar cap is covered and surrounded by carbon dioxide frost and water frost. This is unlike Earth, whose frozen winter precipitation is made up of only one volatile -- water. The carbon dioxide frost evaporates, or sublimates, at a lower temperature than water frost. So, during spring, the carbon dioxide ice evaporates first and leaves a residue of water frost, which later sublimates as well.

    The image shown here covers part of a crater rim, which is illuminated from the upper left. North is at the top. The topography creates a cold microenvironment on the south side of the rim that is partially protected from solar illumination. That cold surface contains an outlier of the southern seasonal frost about 15 degrees of latitude closer to the equator than the average edge of the frost at this season.

    The top image was constructed from three infrared wavelengths that highlight the bluer color of frost than the background rock and soil. Note that the frost occurs both on sunlit and shaded surfaces on the south side of the rim. The shaded areas are still visible because they are illuminated indirectly by the Martian sky.

    The bottom image was constructed by measuring the depths of spectral absorption bands due to water frost and carbon dioxide frost, and displaying the results in image form. Blue shows strength of an absorption due to water frost near 1.50 micrometers, and green shows strength of an absorption due to carbon dioxide frost near 1.45 micrometers. Red shows brightness of the surface at 1.33 micrometers -- outside of the frost absorption bands -- in order to show the relationship of frost to the illuminated crater rim.

    In comparing the top and bottom images, note that water frost occurs in many locations on the south-facing side of the crater rim, both in sunlit and shaded areas. Because it faces away from the sun, this side of the crater rim is colder than the north, sun-facing side. This favors the formation of frost. In contrast, carbon dioxide frost occurs only in the coldest, most shaded areas.

    CRISM's mission: Find the spectral fingerprints of aqueous and hydrothermal deposits and map the geology, composition and stratigraphy of surface features. The instrument will also watch the seasonal variations in Martian dust and ice aerosols, and water content in surface materials -- leading to new understanding of the climate.

    The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) is one of six science instruments on NASA's Mars Reconnaissance Orbiter. Led by The Johns Hopkins University Applied Physics Laboratory, the CRISM team includes expertise from universities, government agencies and small businesses in the United States and abroad.

  14. Free magnetohydrodynamic shear layers in the presence of rotation and magnetic field

    SciTech Connect

    Spence, E. J.; Roach, A. H.; Edlund, E. M.; Sloboda, P.; Ji, H.

    2012-05-15

    We present an experimental and numerical study of hydrodynamic and magnetohydrodynamic free shear layers and their stability. We first examine the experimental measurement of globally unstable hydrodynamic shear layers in the presence of rotation and their range of instability. These are compared to numerical simulations, which are used to explain the modification of the shear layer, and thus the critical Rossby number for stability. Magnetic fields are then applied to these scenarios and globally unstable magnetohydrodynamic shear layers generated. These too are compared to numerical simulations showing behavior consistent with the hydrodynamic case and previously reported measurements.

  15. Free MHD Shear Layers In The Presence Of Rotation And Magnetic Field

    SciTech Connect

    Spence, E. J.; Roach, A. H.; Edlund, E. M.; Sloboda, P.; Ji, H.

    2012-03-20

    We present an experimental and numerical study of hydrodynamic and magnetohydrodynamic free shear layers and their stability. We first examine the experimental measurement of globally unstable hydrodynamic shear layers in the presence of rotation, and their range of instability. These are compared to numerical simulations, which are used to explain the modification of the shear layer and thus the critical Rossby number for stability. Magnetic fields are then applied to these scenarios, and globally unstable magnetohydrodynamic shear layers generated. These too are compared to numerical simulations, showing behavior consistent with the hydrodynamic case and previously reported measurements.

  16. Accretion onto neutron stars with the presence of a double layer

    NASA Technical Reports Server (NTRS)

    Williams, A. C.; Weisskopf, M. C.; Elsner, R. F.; Darbro, W.; Sutherland, P. G.

    1986-01-01

    It is known from laboratory experiments that double layers can form in plasmas, usually in the presence of an electric current. It is argued that a double layer may be present in the accretion column of a neutron star in a binary system. It is suggested that the double layer may be the predominant deceleration mechanism for the accreting ions, especially for sources with X-ray luminosities of less than about 10 to the 37th erg/s. Previous models have involved either a collisionless shock or an assumed gradual deceleration of the accreting ions to thermalize the energy of the infalling matter.

  17. Accretion onto neutron stars with the presence of a double layer

    NASA Technical Reports Server (NTRS)

    Williams, A. C.; Weisskopf, M. C.; Elsner, R. F.; Darbro, W.; Sutherland, P. G.

    1987-01-01

    It is known, from laboratory experiments, that double layers will form in plasmas, usually in the presence of an electric current. It is argued that a double layer may be present in the accretion column of a neutron star in a binary system. It is suggested that the double layer may be the predominant deceleration mechanism for the accreting ions, especially for sources with X-ray luminosities of less than about 10 to the 37th erg/s. Previous models have involved either a collisionless shock or an assumed gradual deceleration of the accreting ions to thermalize the energy of the infalling matter.

  18. Experimental strategies for frost analysis

    NASA Astrophysics Data System (ADS)

    Janssen, Daniel D.

    An area of increasing importance in the field of refrigeration is the study of frosting and defrosting. Frosting poses a concern to many refrigeration systems, as frost growth both obstructs airflow through low temperature heat exchangers and increases heat transfer resistance. Drastic decreases in system efficiency result from the compounding of these problems, and because it is difficult to prevent the frosting process, refrigeration systems must be defrosted periodically to restore optimal operating conditions. A deeper understanding of the complex physical processes of frosting and defrosting will lead to more efficient refrigeration system designs; an idea which has driven a rise in frost growth research over recent decades. Although research has shown great progress, there remain significant challenges associated with predicting the frosting and defrosting processes accurately under wide ranges of conditions. The equations governing such behavior still remain insoluble by exact analytical methods. Numerical approaches have shown the most promising results, but are yet in an early stage of development. Most research has instead been concerned with developing correlations for frost properties and growth, though few are applicable to varying conditions. The most commonly used correlations are shown to have widely different results, perhaps owing to different experimental methods used to acquire data and a lack of deeper level analysis. A new thickness correlation is proposed which attempts to reconcile to some degree the gap between theory and application. Broader ranges of data are used for fitment which enables the application of the correlation to a wider range of conditions. To improve the consistency of results in frost research, it is suggested that new forms of data acquisition be explored. Proposed alternative methods utilize high magnification imaging equipment in combination with computer based measurements, which are shown to be capable of improving accuracy by an order of magnitude in some areas (specifically frost thickness measurement) when calibrated appropriately. In addition to improving measurement accuracy such methods make possible the rapid calculation of droplet geometry during defrosting, an area which has seen little research until recently. The influence of the experimental apparatus on results is also investigated, and a variety of different setups used in past and recent research are categorized according to capability and functionality. Pros and cons of related parameters are discussed with an emphasis on goals. Opportunities for future work include the further development of computer based measurement methods, the acquisition of data over wider ranges of conditions and improvements on the experimental apparatus required to achieve those conditions reliably. It is clear from this research that frost growth is a developing field where much progress is yet to be made. Experimental setups of types ranging from small enclosed tests to wind tunnels on industrial evaporators have provided a clearer understanding of the phenomenon in many aspects. Research presented in this thesis shows that small scale experiments are preferable at this point in time to reach deeper understanding of the frost growth process. It is shown here that many current methods of measurement for important frost growth parameters can be greatly improved upon by the use of computer based algorithms. Faster and more accurate measurement opportunities mean that larger data sets spread across wider ranges of testing conditions can be obtained, setting the stage for more advanced correlation development. Currently, most correlations are only applicable to specific conditions and are still not highly accurate. An attempt is made to show that larger collections of reliable data can be used to develop more robust correlations. To do so a new correlation is proposed which fits a wide range of conditions well. Finally it is shown that the defrosting process may be understood more fully by the use of digital analysis of visual data du

  19. Three-dimensional shock-wave/boundary-layer interaction at the presence of entropy layer

    NASA Astrophysics Data System (ADS)

    Borovoy, V.; Egorov, I.; Maximenko, A.; Mosharov, V.; Radchenko, V.; Skuratov, A.; Struminskaya, I.

    2013-06-01

    An experimental and numerical investigation of a gas flow on a flat plate near a single fin and a fin pair, generating crossings shocks, is performed. The study is focused on the plate bluntness influence on the flow field and the heat transfer in the interaction region. The experiments are carried out in a short duration wind tunnel at Mach numbers M = 5, 6, and 8 and Reynolds numbers Re?L up to 27·106. Luminescent substances are used for heat flux and pressure distribution measurements and for the surface flow visualization. In addition, the heat flux is measured with thermocouple sensors. For a numerical flow simulation, the three-dimensional (3D) Reynolds-averaged Navier-Stokes (RANS) equations are solved using the q-? turbulence model. It is found that even a small plate blunting affects heat transfer and pressure distributions significantly. Moreover, in the case of crossing shocks, it can cause a global transformation of the flow structure in the area of the interaction between the shock waves and the boundary layer.

  20. Presence and function of a thick mucous layer rich in polysaccharides around Bacillus subtilis spores.

    PubMed

    Faille, Christine; Ronse, Annette; Dewailly, Etienne; Slomianny, Christian; Maes, Emmanuel; Krzewinski, Frédéric; Guerardel, Yann

    2014-01-01

    This study was designed to establish the presence and function of the mucous layer surrounding spores of Bacillus subtilis. First, an external layer of variable thickness and regularity was often observed on B. subtilis spores. Further analyses were performed on B. subtilis 98/7 spores surrounded by a thick layer. The mechanical removal of the layer did not affect their resistance to heat or their ability to germinate but rendered the spore less hydrophilic, more adherent to stainless steel, and more resistant to cleaning. This layer was mainly composed of 6-deoxyhexoses, ie rhamnose, 3-O-methyl-rhamnose and quinovose, but also of glucosamine and muramic lactam, known also to be a part of the bacterial peptidoglycan. The specific hydrolysis of the peptidoglycan using lysozyme altered the structure of the required mucous layer and affected the physico-chemical properties of the spores. Such an outermost mucous layer has also been seen on spores of B. licheniformis and B. clausii isolated from food environments. PMID:25115519

  1. Device for determining frost depth and density

    NASA Astrophysics Data System (ADS)

    Huneidi, F.

    1983-08-01

    A hand held device having a forward open window portion adapted to be pushed downwardly into the frost on a surface, and a rear container portion adapted to receive the frost removed from the window area are described. A graph on a side of the container enables an observer to determine the density of the frost from certain measurements noted. The depth of the frost is noted from calibrated lines on the sides of the open window portion.

  2. Field measurements of frost penetration into a landfill cover that uses a paper sludge barrier

    SciTech Connect

    Moo-Young, H.K.; LaPlante, C.; Zimmie, T.F.; Quiroz, J.

    1999-07-01

    Frost penetration is a major environmental concern in landfill design. Freezing and thawing cycles may deteriorate the permeability of the liner or cap. In this study, the depth of frost penetration into a landfill cover that uses paper sludge as the impermeable barrier (the Hubbardston landfill in Massachusetts) was measured using a frost measurement system. A thermistor probe measured the temperature at various depths. Although temperature measurements are important, soil resistivity measurements are required to accurately predict the freezing level, since soil resistivity increases greatly upon freezing. A conductivity probe measured the half-bridge voltage between conductivity rings and a ground rod. Data were collected in data loggers. The data collected from 1992--1996 showed that the frost level did not penetrate the paper sludge capping layer. Heavy snow cover throughout the winters decreased the depth of frost penetration by insulating the landfill. The high water content in the sludge also contributed to the lack of freezing.

  3. Doctoral Defense "Frost Deterioration in Concrete Due to Deicer Salt Exposure

    E-print Network

    Kamat, Vineet R.

    Doctoral Defense "Frost Deterioration in Concrete Due to Deicer Salt Exposure: Mechanism in the presence of a deicer salt solution is considered a severe concrete exposure condition. Prolonged exposure

  4. With Robert Frost in Tesolonia.

    ERIC Educational Resources Information Center

    Welninski, Virginia

    A teacher's guide and exercises for teaching poetry by Robert Frost to English as a second language students are presented. Suggestions are presented for developing meanings for words and other meaningful units through the use of realia, pictures, demonstrations, definitions, context clues, paraphrasing, completion exercises, solving and creating…

  5. Frost heave Alan W. REMPEL

    E-print Network

    Rempel, Alan W.

    investigations into Frost's `some- thing': the forces exerted by growing crystals and the `needle-like ice liquid transport towards growing ice lenses, early investigators predicted their occurrence and noted migration that supplies growing ice lenses (Taber, 1929, 1930). The precise mechanisms respon- sible

  6. Cave development by frost weathering

    NASA Astrophysics Data System (ADS)

    Oberender, Pauline; Plan, Lukas

    2015-01-01

    This paper deals with the description and genesis of a special type of shelter cave. In German they are termed Auswitterungshöhlen which goes back to the 19th century and the genesis is supposed to be related to frost weathering, but to our knowledge, detailed studies are missing so far. This type of cave is very common in the area of investigation that comprises pre-Alpine and Alpine regions in the north-eastern part of the Eastern Alps: They make up 32% of the 5138 registered caves but surprisingly they entirely developed in carbonate rocks. Although most of them are smaller than a dozen metres, some have lengths of more than 50 m and entrances can be more than 100 m wide or similarly high. Besides general observations that lead to a list of characteristics for these caves, two of them in a pre-Alpine setting were studied in-depth. A detailed map, descriptions, and measurements concerning cave morphology, host rock geology, and climate are given. The thickness and composition of clastic sediments were investigated by small trenches and electric resistivity measurements. Sediment thicknesses reach up to 2 m inside the caves and below the entrances. For one year nets were installed to measure rockfall in both caves. In warm periods generally less than 5 g/month of debris could be collected, but a few 100 g/month for frost periods. This strong correlation and the significant amount of debris together with other observations suggest that frost weathering is an on-going and very important process for the formation of these caves. Grain-size distribution of the collected debris argues for the activity of both microgelivation and ice segregation. Therefore we suggest that the term frost weathering caves should be used for shelter caves whose genesis is related to frost weathering. As dissolution seems to be of marginal importance for the genesis they are a paradox as they develop in karstic rock but have pseudokarst features.

  7. Developing a numerical model of frost boils dynamics.

    NASA Astrophysics Data System (ADS)

    Nicolsky, D. J.; Tipenko, G. S.; Romanovsky, V. E.

    2003-12-01

    The research was initiated as a part of biocomplexity project, which investigates cryoturbation in continuous permafrost regions in the Arctic. The project explores influence of climate (mean annual and summer temperatures, and snow cover depth and density), vegetation layer composition and physical properties, soil textures and moisture content on evolution of frost boils. The work deals with analysis of temperature regimes and moisture distribution and dynamics during seasonal cycles of freezing and thawing. The research focuses on the development of a computational approach to the study of frost boils as a self-organized system. The model is calibrated using temperature and moisture content data collected from a field experiment at two study sites. A thermo-mechanical model of the frost boil phenomena based on principles of macroscopic thermodynamics and continuum mechanics will be presented. The model includes the energy and mass conservation equations, continuity equation, the Clausius-Claiperon equation, and an empirical formula which relates unfrozen water content to temperature. The complete system is reduced to a computationally convenient set of coupled equations for temperature, pore water pressure and porosity in a two-dimensional domain. A finite element method and an implicit scheme in time were utilized to construct a non-linear system of equations, which was solved iteratively. The model describes dynamics of frost boils and helps to explain geometric form and size of distinctly visible patterned ground north of the Alaska's Brook Range.

  8. Ground level air convection produces frost damage patterns in turfgrass

    NASA Astrophysics Data System (ADS)

    Ackerson, Bruce J.; Beier, Richard A.; Martin, Dennis L.

    2015-11-01

    Frost injury patterns are commonly observed on the warm-season turfgrass species bermudagrass ( Cynodon species Rich.), zoysiagrass ( Zoysia species Willd.), and buffalograss [ Bouteloua dactyloides (Nutt.) J.T. Columbus] in cool-temperate and subtropical zones. Qualitative observations of these injury patterns are presented and discussed. A model for the formation of such patterns based on thermal instability and convection of air is presented. The characteristic length scale of the observed frost pattern injury requires a temperature profile that decreases with height from the soil to the turfgrass canopy surface followed by an increase in temperature with height above the turfgrass canopy. This is justified by extending the earth temperature theory to include a turf layer with atmosphere above it. Then the theory for a thermally unstable layer beneath a stable region by Ogura and Kondo is adapted to a turf layer to include different parameter values for pure air, as well as for turf, which is treated as a porous medium. The earlier porous medium model of Thompson and Daniels proposed to explain frost injury patterns is modified to give reasonable agreement with observed patterns.

  9. Ground level air convection produces frost damage patterns in turfgrass.

    PubMed

    Ackerson, Bruce J; Beier, Richard A; Martin, Dennis L

    2015-11-01

    Frost injury patterns are commonly observed on the warm-season turfgrass species bermudagrass (Cynodon species Rich.), zoysiagrass (Zoysia species Willd.), and buffalograss [Bouteloua dactyloides (Nutt.) J.T. Columbus] in cool-temperate and subtropical zones. Qualitative observations of these injury patterns are presented and discussed. A model for the formation of such patterns based on thermal instability and convection of air is presented. The characteristic length scale of the observed frost pattern injury requires a temperature profile that decreases with height from the soil to the turfgrass canopy surface followed by an increase in temperature with height above the turfgrass canopy. This is justified by extending the earth temperature theory to include a turf layer with atmosphere above it. Then the theory for a thermally unstable layer beneath a stable region by Ogura and Kondo is adapted to a turf layer to include different parameter values for pure air, as well as for turf, which is treated as a porous medium. The earlier porous medium model of Thompson and Daniels proposed to explain frost injury patterns is modified to give reasonable agreement with observed patterns. PMID:25796203

  10. Frost resistance in alpine woody plants.

    PubMed

    Neuner, Gilbert

    2014-01-01

    This report provides a brief review of key findings related to frost resistance in alpine woody plant species, summarizes data on their frost resistance, highlights the importance of freeze avoidance mechanisms, and indicates areas of future research. Freezing temperatures are possible throughout the whole growing period in the alpine life zone. Frost severity, comprised of both intensity and duration, becomes greater with increasing elevation and, there is also a greater probability, that small statured woody plants, may be insulated by snow cover. Several frost survival mechanisms have evolved in woody alpine plants in response to these environmental conditions. Examples of tolerance to extracellular freezing and freeze dehydration, life cycles that allow species to escape frost, and freeze avoidance mechanisms can all be found. Despite their specific adaption to the alpine environment, frost damage can occur in spring, while all alpine woody plants have a low risk of frost damage in winter. Experimental evidence indicates that premature deacclimation in Pinus cembra in the spring, and a limited ability of many species of alpine woody shrubs to rapidly reacclimate when they lose snow cover, resulting in reduced levels of frost resistance in the spring, may be particularly critical under the projected changes in climate. In this review, frost resistance and specific frost survival mechanisms of different organs (leaves, stems, vegetative and reproductive over-wintering buds, flowers, and fruits) and tissues are compared. The seasonal dynamics of frost resistance of leaves of trees, as opposed to woody shrubs, is also discussed. The ability of some tissues and organs to avoid freezing by supercooling, as visualized by high resolution infrared thermography, are also provided. Collectively, the report provides a review of the complex and diverse ways that woody plants survive in the frost dominated environment of the alpine life zone. PMID:25520725

  11. Frost resistance in alpine woody plants

    PubMed Central

    Neuner, Gilbert

    2014-01-01

    This report provides a brief review of key findings related to frost resistance in alpine woody plant species, summarizes data on their frost resistance, highlights the importance of freeze avoidance mechanisms, and indicates areas of future research. Freezing temperatures are possible throughout the whole growing period in the alpine life zone. Frost severity, comprised of both intensity and duration, becomes greater with increasing elevation and, there is also a greater probability, that small statured woody plants, may be insulated by snow cover. Several frost survival mechanisms have evolved in woody alpine plants in response to these environmental conditions. Examples of tolerance to extracellular freezing and freeze dehydration, life cycles that allow species to escape frost, and freeze avoidance mechanisms can all be found. Despite their specific adaption to the alpine environment, frost damage can occur in spring, while all alpine woody plants have a low risk of frost damage in winter. Experimental evidence indicates that premature deacclimation in Pinus cembra in the spring, and a limited ability of many species of alpine woody shrubs to rapidly reacclimate when they lose snow cover, resulting in reduced levels of frost resistance in the spring, may be particularly critical under the projected changes in climate. In this review, frost resistance and specific frost survival mechanisms of different organs (leaves, stems, vegetative and reproductive over-wintering buds, flowers, and fruits) and tissues are compared. The seasonal dynamics of frost resistance of leaves of trees, as opposed to woody shrubs, is also discussed. The ability of some tissues and organs to avoid freezing by supercooling, as visualized by high resolution infrared thermography, are also provided. Collectively, the report provides a review of the complex and diverse ways that woody plants survive in the frost dominated environment of the alpine life zone. PMID:25520725

  12. Frost flowers growing in the Arctic ocean-atmosphere-sea ice-snow interface: 1. Chemical composition

    NASA Astrophysics Data System (ADS)

    Douglas, Thomas A.; Domine, Florent; Barret, Manuel; Anastasio, Cort; Beine, Harry J.; Bottenheim, Jan; Grannas, Amanda; Houdier, Stephan; Netcheva, Stoyka; Rowland, Glenn; Staebler, Ralf; Steffen, Alexandra

    2012-07-01

    Frost flowers, intricate featherlike crystals that grow on refreezing sea ice leads, have been implicated in lower atmospheric chemical reactions. Few studies have presented chemical composition information for frost flowers over time and many of the chemical species commonly associated with Polar tropospheric reactions have never been reported for frost flowers. We undertook this study on the sea ice north of Barrow, Alaska to quantify the major ion, stable oxygen and hydrogen isotope, alkalinity, light absorbance by soluble species, organochlorine, and aldehyde composition of seawater, brine, and frost flowers. For many of these chemical species we present the first measurements from brine or frost flowers. Results show that major ion and alkalinity concentrations, stable isotope values, and major chromophore (NO3- and H2O2) concentrations are controlled by fractionation from seawater and brine. The presence of these chemical species in present and future sea ice scenarios is somewhat predictable. However, aldehydes, organochlorine compounds, light absorbing species, and mercury (part 2 of this research and Sherman et al. (2012)) are deposited to frost flowers through less predictable processes that probably involve the atmosphere as a source. The present and future concentrations of these constituents in frost flowers may not be easily incorporated into future sea ice or lower atmospheric chemistry scenarios. Thinning of Arctic sea ice will likely present more open sea ice leads where young ice, brine, and frost flowers form. How these changing ice conditions will affect the interactions between ice, brine, frost flowers and the lower atmosphere is unknown.

  13. Mixed Layer Formation and Restratification in the Presence of Mesoscale and Submesoscale Turbulence

    NASA Astrophysics Data System (ADS)

    Couvelard, X.; Tréguier, A. M.; Dumas, F.; Garnier, V.; Ponte, A.

    2014-12-01

    Recent realistic high resolution modeling studies show a net increase of submesoscale activity in fall and winter when the Mixed Layer Depth (hereafter MLD) is at its maximum. This submesoscale activity is associated with the shallowing of the MLD when compared to similar model configurations at lower resolution. Both phenomena can be related to the development of Mixed Layer Instabilities (MLIs), which by slumping the horizontal density gradient in the mixed layer convert Available Potential Energy into submesoscale Eddy Kinetic Energy and contribute to a fast restratification. While parameterizations of the shallowing of the mixed layer by MLIs have been proposed they are based on idealized configurations and are not yet fully tested in realistically forced simulations. In the present work, the ML formation and restratification is studied by uniformly cooling a fully turbulent zonal jet in a periodic channel at different resolutions (eddy resolving (10km) to submesoscale permitting (2km)). The effect of horizontal resolution is quantified in terms of MLD, restratification rate, buoyancy fluxes, and conversion of Available Potential Energy in Eddy Kinetic Energy. At the highest resolution when submesoscale is active the MLD formed during the surface cooling is shallower by about 30% and the total restratification almost three times faster. Such differences between low and high resolution models are explained by the submesoscale vertical buoyancy flux which compensates the convection during the formation phase and accelerates the restratification once the surface cooling stops. These findings are robust and the uncertainties are quantified by ensemble experiments. The most common parameterization of MLIs has been implemented and tested in our coarse resolution configuration, leading as expected to a slightly faster restratification, but the shallowing of the MLD is not represented, suggesting a caveat in such parameterization in presence of strong convection.

  14. Frost flowers on young Arctic sea ice: The climatic, chemical, and microbial significance of an emerging ice type

    NASA Astrophysics Data System (ADS)

    Barber, D. G.; Ehn, J. K.; Pu?ko, M.; Rysgaard, S.; Deming, J. W.; Bowman, J. S.; Papakyriakou, T.; Galley, R. J.; Søgaard, D. H.

    2014-10-01

    Ongoing changes in Arctic sea ice are increasing the spatial and temporal range of young sea ice types over which frost flowers can occur, yet the significance of frost flowers to ocean-sea ice-atmosphere exchange processes remains poorly understood. Frost flowers form when moisture from seawater becomes available to a cold atmosphere and surface winds are low, allowing for supersaturation of the near-surface boundary layer. Ice grown in a pond cut in young ice at the mouth of Young Sound, NE Greenland, in March 2012, showed that expanding frost flower clusters began forming as soon as the ice formed. The new ice and frost flowers dramatically changed the radiative and thermal environment. The frost flowers were about 5°C colder than the brine surface, with an approximately linear temperature gradient from their base to their upper tips. Salinity and ?18O values indicated that frost flowers primarily originated from the surface brine skim. Ikaite crystals were observed to form within an hour in both frost flowers and the thin pond ice. Average ikaite concentrations were 1013 µmol kg-1 in frost flowers and 1061 µmol kg-1 in the surface slush layer. Chamber flux measurements confirmed an efflux of CO2 at the brine-wetted sea ice surface, in line with expectations from the brine chemistry. Bacteria concentrations generally increased with salinity in frost flowers and the surface slush layer. Bacterial densities and taxa indicated that a selective process occurred at the ice surface and confirmed the general pattern of primary oceanic origin versus negligible atmospheric deposition.

  15. Shock induced Richtmyer-Meshkov instability in the presence of a wall boundary layer

    NASA Astrophysics Data System (ADS)

    Jourdan, G.; Billiotte, M.; Houas, L.

    1996-06-01

    An experimental investigation on gaseous mixing zones originated from the Richtmyer-Meshkov instability has been undertaken in a square cross section shock tube. Mass concentration fields, of one of the two mixing constituents, have been determined within the mixing zone when the shock wave passes from the heavy gas to the light one, from one gas to an other of close density, and from the light gas to the heavy one. Results have been obtained before and after the coming back of the reflected shock wave. The diagnostic method is based on the infrared absorption of one of the two constituents of the mixing zone. It is shown that the mixing zone is strongly deformed by the wall boundary layer. The consequence is the presence of strong gradients of concentration in the direction perpendicular to the shock wave propagation. Finally, it is pointed out that the mixing goes more homogeneous when the Atwood number tends to zero.

  16. Frost formation and ice adhesion on superhydrophobic surfaces

    E-print Network

    Varanasi, Kripa K.

    We study frost formation and its impact on icephobic properties of superhydrophobic surfaces. Using an environmental scanning electron microscope, we show that frost nucleation occurs indiscriminately on superhydrophobic ...

  17. Robert Frost and the Poetry of Physics.

    ERIC Educational Resources Information Center

    Coletta, W. John; Tamres, David H.

    1992-01-01

    Examines five poems by Robert Frost that illustrate Frost's interest in science. The poems include allusions to renowned physicists, metaphoric descriptions of some famous physics experiments, explorations of complementarity as enunciated by Bohr, and poetic formulations of Heisenberg's uncertainty principle. (20 references) (MDH)

  18. FROST CONTROL IN THE PACIFIC NORTHWEST

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The basic physics of frost protection in orchards and vineyard in the Pacific Northewest USA are presented. Various frost protection techniques are discussed and compared. Potential emerging technologies in cold temperature modification are also discussed for potential applications in New Zealand k...

  19. Micropropagation of Frost-Resistant Eucalyptus1

    E-print Network

    Micropropagation of Frost-Resistant Eucalyptus1 Michel Boulay2 For 10 years now, AFOCEL has at the Workshop on Eucalyptus in California, June 14-16, 1983, Sacramento, California. 2 Head of the in vitro lab, AFOCEL, Nangis, France. 102 Abstract: A method for the in vitro propagation of frost resistant eucalyptus

  20. Galilean satellites - Identification of water frost.

    NASA Technical Reports Server (NTRS)

    Pilcher, C. B.; Mccord, T. B.; Ridgway, S. T.

    1972-01-01

    Water frost absorptions have been detected in the infrared reflectivities of Jupiter's Galilean satellites JII (Europa) and JIII (Ganymede). We have determined the percentage of frost-covered surface area to be 50 to 100 percent for JII, 20 to 65 percent for JIII, and possibly 5 to 25 percent for JIV (Callisto). The leading side of JIII has 20 percent more frost cover than the trailing side, which explains the visible geometric albedo differences between the two sides. The reflectivity of the material underlying the frost on JII, JIII, and JIV resembles that of silicates. The surface of JI (Io) may be covered by frost particles much smaller than those on JII and JIII.

  1. Evolution of symmetric reconnection layer in the presence of parallel shear flow

    SciTech Connect

    Lu Haoyu; Cao Jinbin

    2011-07-15

    The development of the structure of symmetric reconnection layer in the presence of a shear flow parallel to the antiparallel magnetic field component is studied by using a set of one-dimensional (1D) magnetohydrodynamic (MHD) equations. The Riemann problem is simulated through a second-order conservative TVD (total variation diminishing) scheme, in conjunction with Roe's averages for the Riemann problem. The simulation results indicate that besides the MHD shocks and expansion waves, there exist some new small-scale structures in the reconnection layer. For the case of zero initial guide magnetic field (i.e., B{sub y0} = 0), a pair of intermediate shock and slow shock (SS) is formed in the presence of the parallel shear flow. The critical velocity of initial shear flow V{sub zc} is just the Alfven velocity in the inflow region. As V{sub z{infinity}} increases to the value larger than V{sub zc}, a new slow expansion wave appears in the position of SS in the case V{sub z{infinity}} < V{sub zc}, and one of the current densities drops to zero. As plasma {beta} increases, the out-flow region is widened. For B{sub y0} {ne} 0, a pair of SSs and an additional pair of time-dependent intermediate shocks (TDISs) are found to be present. Similar to the case of B{sub y0} = 0, there exists a critical velocity of initial shear flow V{sub zc}. The value of V{sub zc} is, however, smaller than the Alfven velocity of the inflow region. As plasma {beta} increases, the velocities of SS and TDIS increase, and the out-flow region is widened. However, the velocity of downstream SS increases even faster, making the distance between SS and TDIS smaller. Consequently, the interaction between SS and TDIS in the case of high plasma {beta} influences the property of direction rotation of magnetic field across TDIS. Thereby, a wedge in the hodogram of tangential magnetic field comes into being. When {beta}{yields}{infinity}, TDISs disappear and the guide magnetic field becomes constant.

  2. Io - Longtudinal distribution of sulfur dioxide frost

    NASA Technical Reports Server (NTRS)

    Nelson, R. M.; Lane, A. L.; Matson, D. L.; Fanale, F. P.; Nash, D. B.; Johnson, T. V.

    1980-01-01

    A longitudinal variation in the distribution of SO2 frost on Io is examined. Twenty spectra of Io (0.26 to 0.33 micrometer) are presented and a strong ultraviolet absorption is found shortward of 0.33 micrometer. The abundance of frost is greatest at orbital longitudes 72 to 137 degrees. Longitudes 250 to 323 degrees are least abundant in SO2. Comparisons are made with a Voyager color relief map, which suggest that SO2 frost is in greatest concentration in the white areas of Io and other sulfurous materials are in greatest concentration in the red areas.

  3. Dissecting the genetic architecture of frost tolerance in Central European winter wheat

    PubMed Central

    Reif, Jochen C.

    2013-01-01

    Abiotic stress tolerance in plants is pivotal to increase yield stability, but its genetic basis is still poorly understood. To gain insight into the genetic architecture of frost tolerance, this work evaluated a large mapping population of 1739 wheat (Triticum aestivum L.) lines and hybrids adapted to Central Europe in field trials in Germany and fingerprinted the lines with a 9000 single-nucleotide polymorphism array. Additive effects prevailed over dominance effects. A two-dimensional genome scan revealed the presence of epistatic effects. Genome-wide association mapping in combination with a robust cross-validation strategy identified one frost tolerance locus with a major effect located on chromosome 5B. This locus was not in linkage disequilibrium with the known frost loci Fr-B1 and Fr-B2. The use of the detected diagnostic markers on chromosome 5B, however, does not allow prediction of frost tolerance with high accuracy. Application of genome-wide selection approaches that take into account also loci with small effect sizes considerably improved prediction of the genetic variation of frost tolerance in wheat. The developed prediction model is valuable for improving frost tolerance because this trait displays a wide variation in occurrence across years and is therefore a difficult target for conventional phenotypic selection. PMID:24006418

  4. Extension of Humidity Standards to Frost Point

    NASA Astrophysics Data System (ADS)

    Choi, B. I.; Lee, S.-W.; Kim, J. C.; Woo, S. B.

    2015-08-01

    The KRISS low frost-point humidity generator which has been operated by the two-temperature method in the frost-point range from to since 2006 is reformed to a two-temperature, two-pressure type, in order to extend the calibration capability to a frost point of . The temperature and pressure of the saturator were controlled to and 1 MPa, respectively. The water-vapor mole ratio generated by the upgraded humidity generator reached . The uncertainty of the generator was estimated by calculations as well as a series of experiments including the stability of the generated frost point, the saturation efficiency with a varied gas flow rate, and the change of water-vapor mole ratio in the tubing line. The standard uncertainty of the generator is less than at the frost point of and is increased to at the frost point of . The increase in uncertainty is mainly due to the water adsorption/desorption on the internal surface of tubing from the saturator to the hygrometer.

  5. Quasi-two-layer finite-volume scheme for modeling shallow water flows with the presence of external forces

    E-print Network

    K. V. Karelsky; A. S. Petrosyan; A. G. Slavin

    2011-08-19

    Finite-volume numerical method for study shallow water flows over an arbitrary bed profile in the presence of external force is proposed. This method uses the quasi-two-layer model of hydrodynamic flows over a stepwise boundary with advanced consideration of the flow features near the step. A distinctive feature of the suggested model is a separation of a studied flow into two layers in calculating flow quantities near each step, and improving by this means approximation of depth-averaged solutions of the initial three-dimensional Euler equations. We are solving the shallow-water equations for one layer, introducing the fictitious lower layer only as an auxiliary structure in setting up the appropriate Riemann problems for the upper layer. Besides quasi-two-layer approach leads to appearance of additional terms in one-layer finite-difference representation of balance equations. These terms provide the mechanical work made by nonhomogeneous bed interacting with flow. A notable advantage of the proposed method is the consideration of the properties of the process of the waterfall, namely the fluid flow on the step in which the fluid does not wet part of the vertical wall of the step. The presence of dry zones in the vertical part of the step indicates violation of the conditions of hydrostatic flow. The quasi-two-layer approach determines the size of the dry zone of the vertical component of the step. Consequently it gives an opportunity to figure out the amount of flow kinetic energy dissipation on complex boundary. Numerical simulations are performed based on the proposed algorithm of various physical phenomena, such as a breakdown of the rectangular fluid column over an inclined plane, large-scale motion of fluid in the gravity field in the presence of Coriolis force over an mounted obstacle on underlying surface.

  6. Subharmonic excitation in amplitude modulation atomic force microscopy in the presence of adsorbed water layers

    SciTech Connect

    Santos, Sergio; Barcons, Victor; Verdaguer, Albert; Chiesa, Matteo

    2011-12-01

    In ambient conditions, nanometric water layers form on hydrophilic surfaces covering them and significantly changing their properties and characteristics. Here we report the excitation of subharmonics in amplitude modulation atomic force microscopy induced by intermittent water contacts. Our simulations show that there are several regimes of operation depending on whether there is perturbation of water layers. Single period orbitals, where subharmonics are never induced, follow only when the tip is either in permanent contact with the water layers or in pure noncontact where the water layers are never perturbed. When the water layers are perturbed subharmonic excitation increases with decreasing oscillation amplitude. We derive an analytical expression which establishes whether water perturbations compromise harmonic motion and show that the predictions are in agreement with numerical simulations. Empirical validation of our interpretation is provided by the observation of a range of values for apparent height of water layers when subharmonic excitation is predicted.

  7. Laminar-specific distribution of zinc: Evidence for presence of layer IV in forelimb motor cortex in the rat

    PubMed Central

    Alaverdashvili, Mariam; Hackett, Mark J.; Pickering, Ingrid J.; Paterson, Phyllis G.

    2015-01-01

    The rat is the most widely studied pre-clinical model system of various neurological and neurodegenerative disorders affecting hand function. Although brain injury to the forelimb region of the motor cortex in rats mostly induces behavioral abnormalities in motor control of hand movements, behavioral deficits in the sensory-motor domain are also observed. This questions the prevailing view that cortical layer IV, a recipient of sensory information from the thalamus, is absent in rat motor cortex. Because zinc-containing neurons are generally not found in pathways that run from the thalamus, an absence of zinc (Zn) in a cortical layer would be suggestive of sensory input from the thalamus. To test this hypothesis, we used synchrotron micro X-ray fluorescence imaging to measure Zn distribution across cortical layers. Zn maps revealed a heterogeneous layered Zn distribution in primary and secondary motor cortices of the forelimb region in the adult rat. Two wider bands with elevated Zn content were separated by a narrow band having reduced Zn content, and this was evident in two rat strains. The Zn distribution pattern was comparable to that in sensorimotor cortex, which is known to contain a well demarcated layer IV. Juxtaposition of Zn maps and the images of brain stained for Nissl bodies revealed a “Zn valley” in primary motor cortex, apparently starting at the ventral border of pyramidal layer III and ending at the close vicinity of layer V. This finding indicates the presence of a conspicuous cortical layer between layers III and V, i.e. layer IV, the presence of which previously has been disputed. The results have implications for the use of rat models to investigate human brain function and neuropathology, such as after stroke. The presence of layer IV in the forelimb region of the motor cortex suggests that therapeutic interventions used in rat models of motor cortex injury should target functional abnormalities in both motor and sensory domains. The finding is also critical for future investigation of the biochemical mechanisms through which therapeutic interventions can enhance neural plasticity, particularly through Zn dependent pathways. PMID:25192655

  8. Effect of sodium monofluorophosphate treatment on microstructure and frost salt scaling durability of slag cement paste

    SciTech Connect

    Copuroglu, O. . E-mail: o.copuroglu@citg.tudelft.nl; Fraaij, A.L.A.; Bijen, J.M.J.M.

    2006-08-15

    Sodium-monofluorophosphate (Na-MFP) is currently in use as a surface applied corrosion inhibitor in the concrete industry. Its basic mechanism is to protect the passive layer of the reinforcement steel against disruption due to carbonation. Carbonation is known as the most detrimental environmental effect on blast furnace slag cement (BFSC) concrete with respect to frost salt scaling. In this paper the effect of Na-MFP on the microstructure and frost salt scaling resistance of carbonated BFSC paste is presented. The results of electron microscopy, mercury intrusion porosimetry (MIP) and X-ray diffraction (XRD) are discussed. It is found that the treatment modifies the microstructure and improves the resistance of carbonated BFSC paste against frost salt attack.

  9. Enhanced interlayer trapping of a tetracycline antibiotic within montmorillonite layers in the presence of Ca and Mg.

    PubMed

    Aristilde, Ludmilla; Lanson, Bruno; Miéhé-Brendlé, Jocelyne; Marichal, Claire; Charlet, Laurent

    2016-02-15

    The formation of a ternary antibiotic-metal-clay complex is hypothesized as the primary adsorption mechanism responsible for the increased adsorption of tetracycline antibiotics on smectites in the presence of divalent metal cations under circumneutral and higher pH conditions. To evaluate this hypothesis, we conducted a spectroscopic investigation of oxytetracycline (OTC) interacting with Na-montmorillonite in the presence and absence of Ca or Mg salts at pH 6 and pH 8. Despite a two-fold increase in OTC adsorbed in the presence of Ca or Mg, both solid-state nuclear magnetic resonance and infrared signatures of the OTC functional groups involved in metal complexation implied that the formation of an inner-sphere ternary complexation was not significant in stabilizing the adsorbate structures. The spectroscopic data further indicated that the positively-charged amino group mediated the OTC adsorption both in the absence and presence of the divalent metal cations. Focusing on the experiments with Mg, X-ray diffraction analysis revealed that the metal-promoted adsorption was coupled with an increased intercalation of OTC within the montmorillonite layers. The resulting interstratified clay layers were characterized by simulating X-ray diffraction of theoretical stacking compositions using molecular dynamics-optimized montmorillonite layers with and without OTC. The simulations uncovered the evolution of segregated interstratification patterns that demonstrated how increased access to smectite interlayers in the presence of the divalent metal cations enhanced adsorption of OTC. Our findings suggest that specific aqueous structures of the clay crystallites in response to the co-presence of Mg and OTC in solution served as precursors to the interlayer trapping of the antibiotic species. Elucidation of these structures is needed for further insights on how aqueous chemistry influences the role of smectite clay minerals in trapping organic molecules in natural and engineered soil particles. PMID:26613334

  10. Measurements of thermal infrared spectral reflectance of frost, snow, and ice

    NASA Technical Reports Server (NTRS)

    Salisbury, John W.; D'Aria, Dana M.; Wald, Andrew

    1994-01-01

    Because much of Earth's surface is covered by frost, snow, and ice, the spectral emissivities of these materials are a significant input to radiation balance calculations in global atmospheric circulation and climate change models. Until now, however, spectral emissivities of frost and snow have been calculated from the optical constants of ice. We have measured directional hemispherical reflectance spectra of frost, snow, and ice from which emissivities can be predicted using Kirchhoff's law (e = 1-R). These measured spectra show that contrary to conclusions about the emissivity of snow drawn from previously calculated spectra, snow emissivity departs significantly from blackbody behavior in the 8-14 micrometer region of the spectrum; snow emissivity decreases with both increasing particle size and increasing density due to packing or grain welding; while snow emissivity increases due to the presence of meltwater.

  11. Evaluation of fin staging methods for minimizing coil frost accumulation 

    E-print Network

    Watters, Richard J.

    2001-01-01

    Frost formation on heat pump evaporators is a source of degradation in the performance of heat pumps during heating mode operation. This research sought to determine whether staged fins on outdoor evaporators could slow the growth of frost...

  12. Electronic structure and layer-resolved transmission of bilayer graphene nanoribbon in the presence of vertical fields

    NASA Astrophysics Data System (ADS)

    Rostami, Habib; Asgari, Reza

    2013-07-01

    Electronic properties of bilayer graphene are distinct from both the conventional two dimensional electron gas and monolayer graphene due to its particular chiral properties and excitation charge carrier dispersions. We study the effect of strain on the electronic structure, the edge states and charge transport of bilayer graphene nanoribbon at zero temperature. We demonstrate a valley polarized quantum Hall effect in biased bilayer graphene when the system is subjected to a perpendicular magnetic field. In this system a topological phase transition from a quantum valley Hall to a valley polarized quantum Hall phase can occur by tuning the interplanar strain. Furthermore, we study the layer-resolved transport properties by calculating the layer polarized quantity by using the recursive Green's function technique and show that the resulting layer polarized value confirms the obtained phases. These predictions can be verified by experiments, and our results demonstrate the possibility for exploiting strained bilayer graphene in the presence of external fields for electronics and valleytronics devices.

  13. Insulator (Heat and Frost). Occupational Analyses Series.

    ERIC Educational Resources Information Center

    McRory, Aline; Ally, Mohamed

    This analysis covers tasks performed by an insulator, an occupational title some provinces and territories of Canada have also identified as heat and frost insulator. A guide to analysis discusses development, structure, and validation method; scope of the occupation; trends; and safety. To facilitate understanding the nature of the occupation,…

  14. Everett Frost Biochemistry 118Q Final Paper

    E-print Network

    Brutlag, Doug

    Everett Frost Biochemistry 118Q Final Paper November 30, 2010 The Blood-Brain Barrier and Innovative Technology for Increasing Absorption of Medicine into Brain Tissue Three Blood-Brain Barriers The main blood-brain barrier is a system of zonula occludens that form an impermeable barrier between

  15. Latest results from FROST at Jefferson Lab

    SciTech Connect

    Ritchie, Barry G.

    2014-06-01

    The spectrum of broad and overlapping nucleon excitations can be greatly clarified by use of a polarized photon beam incident on a polarized target in meson photoproduction experiments. At Jefferson Lab, a program of such measurements has made use of the Jefferson Lab FROzen Spin Target (FROST). An overview of preliminary results are presented.

  16. Summer Boundary Layer structure and circulations in the presence of a large man made lake

    NASA Astrophysics Data System (ADS)

    Salgado, Rui; Soares, Pedro; Policarpo, Carlos; Le Moigne, Patrick; Miranda, Pedro; Potes, Miguel

    2015-04-01

    The evolution of the thermodynamic structure of the atmospheric boundary layer over and in the vicinity of the Alqueva reservoir, a 250 km2 man made lake in south Portugal, is studied using mesoscale simulations and observations. The Observations were carried out during the intensive period (IOP) of the ALqueva hydro-meteorological Experiment, ALEX 2014 (www.alex2014.cge.uevora.pt), which took place between 22 and 24 July 2014. Twomodels were used, and the results have been inter-compared: The Weather Research and Forecasting, WRF, andthe non-hydrostatic Meso-NH. During the ALEX 2014 IOP, radiosondes were launched every tree hours and the near surface fluxes of energy, vapor and momentum were measured using an eddy covariance system installed on a floating platform in the lake. The ALEX field campaign includes also several surface meteorological stations, over water and land in order to characterize the local horizontal structure of the surface layer. The simulations, validated by the observations, allows the study of the effects of the lake in the boundary layer and on the atmospheric flow.

  17. Distribution of Sulfur Dioxide Frost on Io

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Sulfur dioxide, normally a gas at room temperatures, is known to exist on Io's surface as a frost, condensing there from the hot gases emanating from the Io volcanoes. However, the deposition patterns and relation of the frost distribution to the volcanic activity is unknown, since prior measurements lacked the spatial resolution to accurately map the surface frost.

    The Galileo Near Infrared Mapping Spectrometer (NIMS) obtained relatively high spatial and spectral resolution images during the C3 orbit, and the characteristic infrared absorptions of sulfur dioxide frost appearing in the spectra were used to produce the SO2 frost map shown on the right. The comparison image on the left (from 1979 Voyager measurements) shows the same view and indicates the surface brightness as seen in visible light.

    The frost map shows maximum SO2 concentration as white, lesser amounts as blue coloration, and areas with little or no SO2 as black. The resolution of this map is about 120 km (75 miles), which spans the latitude range 120 W to 270 W.

    It is interesting to compare this frost distribution with regions of volcanic activity. Volcanic hotspots identified from NIMS and SSI images occur in many of the dark - low SO2 - areas, a reasonable finding since sulfur dioxide would not condense on such hot regions. The Pele region (to the lower left), N. Colchis hot spots (upper center) and S. Volund (upper right) are good examples of hot spot areas depleted in sulfur dioxide. Much of the rest of this hemisphere of Io has varying amounts of sulfur dioxide present. The most sulfur dioxide-rich area is Colchis Regio, the white area to the right of center.

    Of particular interest is the dark area to the south of Colchis Regio. From the study of other NIMS images, it is seen that this region does not have any large, obvious hotspots. However, it is depleted in sulfur dioxide.

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov.

  18. The Management of Extracellular Ice by Petioles of Frost-resistant Herbaceous Plants

    PubMed Central

    McCULLY, M. E.; CANNY, M. J.; HUANG, C. X.

    2004-01-01

    • Background and Aims Some frost-tolerant herbaceous plants droop and wilt during frost events and recover turgor and posture on thawing. It has long been known that when plant tissues freeze, extracellular ice forms. Distributions of ice and water in frost-frozen and recovered petioles of Trifolium repens and Escholschzia californica were visualized. • Methods Petioles of intact plants were cryo-fixed, planed to smooth transverse faces, and examined in a cryo-SEM. • Key Results With frost-freezing, parenchyma tissues shrank to approx. one-third of their natural volume with marked cytorrhysis of the cells, and massive blocks of extracellular icicles grew under the epidermis (poppy) or epidermis and subepidermis (clover), leaving these layers intact but widely separated from the parenchyma except at specially structured anchorages overlying vascular bundles. On thawing, the extracellular ice was reabsorbed by the expanding parenchyma, and surface tissues again contacted the internal tissues at weak junctions (termed faults). These movements of water into and from the fault zones occurred repeatedly at each frost/thaw event, and are interpreted to explain the turgor changes that led to wilting and recovery. Ice accumulations at tri-cellular junctions with intercellular spaces distended these spaces into large cylinders, especially large in clover. Xylem vessels of frozen petioles were nearly all free of gas; in thawed petioles up to 20 % of vessels were gas-filled. • Conclusions The occurrence of faults and anchorages may be expected to be widespread in frost-tolerant herbaceous plants, as a strategy accommodating extracellular ice deposits which prevent intracellular freezing and consequent membrane disruption, as well as preventing gross structural damage to the organs. The developmental processes that lead to this differentiation of separation of sheets of cells firmly cemented at determined regions at their edges, and their physiological consequences, will repay detailed investigation. PMID:15355865

  19. Alternate dipping preparation of biomimetic apatite layers in the presence of carbonate ions.

    PubMed

    Chatelain, Grégory; Bourgeois, Damien; Ravaux, Johann; Averseng, Olivier; Vidaud, Claude; Meyer, Daniel

    2014-02-01

    The classical simulated body fluids method cannot be employed to prepare biomimetic apatites encompassing metallic ions that lead to very stable phosphates. This is the case for heavy metals such as uranium, whose presence in bone mineral after contamination deserves toxicological study. We have demonstrated that existing methods, based on alternate dipping into calcium and phosphate ions solutions, can be adapted to achieve this aim. We have also especially studied the impact of the presence of carbonate ions in the medium as these are necessary to avoid hydrolysis of the contaminating metallic cations. Both the apatite-collagen complex method and a standard chemical (STD) method employing only mineral solutions lead to biomimetic apatites when calcium and carbonate ions are introduced simultaneously. The obtained materials were fully characterized and we established that the STD method tolerates the presence of carbonate ions much better, and this leads to homogeneous samples. Emphasis was set on the repeatability of the method to ensure the relevancy of further work performed on series of samples. Finally, osteoblasts cultured on these samples also proved a similar yield and standard-deviation in their adenosine triphosphate content when compared to commercially available substrates designed to study of such cell cultures. PMID:24343417

  20. Polymerization of microtubules in the presence of diffusing tubulins: a boundary layer analysis

    NASA Astrophysics Data System (ADS)

    Yadav, Vandana; Mukherji, Sutapa

    2015-02-01

    Microtubules are biopolymers with an interesting growth dynamics that alternates between persistent phases of polymerization and depolymerization. The growth dynamics is expected to be influenced by the dynamics of the tubulin molecules around the microtubule. In this paper, we present a boundary layer based method that allows us to study systematically a nonlinear growth model coupling the growth dynamics of microtubule and the diffusive dynamics of free tubulins in the neighboring environment. Following previous experimental studies, we consider the growth and the rescue rates to be dependent on the tubulin density in the neighborhood of the microtubule tip. Considering the effect of various regulatory proteins that facilitate the motion of tubulin molecules along the direction of growth, we incorporate an effective biased diffusion of tubulin molecules. Based on the values of the bias velocity and other parameters, the boundary layer analysis shows two regions with distinct nature of microtubule length distributions. In order to show the wider applicability of the method, we briefly discuss the case of tubulin density dependent catastrophe rate. Some of our results are supported by numerical simulations.

  1. Method and apparatus for detecting the presence and thickness of carbon and oxide layers on EUV reflective surfaces

    DOEpatents

    Malinowski, Michael E.

    2005-01-25

    The characteristics of radiation that is reflected from carbon deposits and oxidation formations on highly reflective surfaces such as Mo/Si mirrors can be quantified and employed to detect and measure the presence of such impurities on optics. Specifically, it has been shown that carbon deposits on a Mo/Si multilayer mirror decreases the intensity of reflected HeNe laser (632.8 nm) light. In contrast, oxide layers formed on the mirror should cause an increase in HeNe power reflection. Both static measurements and real-time monitoring of carbon and oxide surface impurities on optical elements in lithography tools should be achievable.

  2. Kinetic Alfven wave in the presence of kappa distribution function in plasma sheet boundary layer

    NASA Astrophysics Data System (ADS)

    Shrivastava, G.; Shrivastava, J.; Ahirwar, G.

    2015-07-01

    The particle aspect approach is adopted to investigate the trajectories of charged particles in the electromagnetic field of kinetic Alfven wave. Expressions are found for the dispersion relation, damping/growth rate and associated currents in the presence of kappa distribution function. Kinetic effect of electrons and ions are included to study kinetic Alfven wave because both are important in the transition region. It is found that the ratio ? of electron thermal energy density to magnetic field energy density and the ratio of ion to electron thermal temperature (Ti/Te), and kappa distribution function affect the dispersion relation, damping/growth rate and associated currents in both cases(warm and cold electron limit).The treatment of kinetic Alfven wave instability is based on assumption that the plasma consist of resonant and non resonant particles. The resonant particles participate in an energy exchange process, whereas the non resonant particles support the oscillatory motion of the wave.

  3. Synthesis of layered zinc hydroxide chlorides in the presence of Al(III)

    SciTech Connect

    Ishikawa, Tatsuo . E-mail: ishikawa@cc.osaka-kyoiku.ac.jp; Matsumoto, Kumi; Kandori, Kazuhiko; Nakayama, Takenori

    2006-04-15

    Zinc hydroxide chloride particles were synthesized by hydrolysis of ZnCl{sub 2} solutions dissolving AlCl{sub 3} at different atomic Al/Zn ratios from 0 to 1.0 and characterized by various techniques. Increasing Al/Zn ratio changed the crystal phases of the products as ZnO{sup {yields}}ZnO+ZHC (Zn{sub 5}(OH){sub 8}Cl{sub 2}.H{sub 2}O){sup {yields}}ZHC{sup {yields}}LDH (layered double hydroxides, Zn-Al-Cl) and the particle morphology as agglomerates (ZnO){sup {yields}}fine particles (ZnO){sup {yields}}plates (ZHC)+rods (ZnO){sup {yields}}plates (ZHC){sup {yields}}plates (LDH). The atomic Cl/Zn ratios of LDH particles formed at Al/Zn{>=}0.3 were ca. 0.3 despite the increase of Al/Zn ratio, being due to the intercalation of CO{sub 3} {sup 2-} into the LDH crystal. The OH{sup -} content of LDH estimated by TG was reduced by the deprotonation of OH{sup -} to counteract the excess positive charge produced by replacing Zn(II) with Al(III). ZHC exhibited a high adsorption selectivity of H{sub 2}O.

  4. Tail-ion transport and Knudsen layer formation in the presence of magnetic fields

    NASA Astrophysics Data System (ADS)

    Schmit, Paul; Molvig, Kim

    2013-10-01

    The impact of magnetic fields on Knudsen layer formation in ICF-relevant plasma is investigated for the first time. Magnetic fields change the energy scaling of the ion diffusivity in a way that eliminates the preferential losses of fast ions compared to thermal ions. Simple threshold criteria give conditions such that the restoration of the ion tail distribution is sufficient to recover much of the lost fusion reactivity. The tail-ion kinetic equations are solved for hot fuel bounded by a cold, nonreacting wall using a numerical stochastic differential equation solver, and the modified fusion reactivities are calculated. We find that modest magnetic fields too weak to magnetize thermal ions are still sufficient to restore much of the lost reactivity, consistent with the threshold conditions. We also find that the Maxwell-averaged fusion reactivities are recovered more fully in cylindrical targets compared to spherical targets. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  5. GTD analysis of airborne antennas radiating in the presence of lossy dielectric layers

    NASA Technical Reports Server (NTRS)

    Rojas-Teran, R. G.; Burnside, W. D.

    1981-01-01

    The patterns of monopole or aperture antennas mounted on a perfectly conducting convex surface radiating in the presence of a dielectric or metal plate are computed. The geometrical theory of diffraction is used to analyze the radiating system and extended here to include diffraction by flat dielectric slabs. Modified edge diffraction coefficients valid for wedges whose walls are lossy or lossless thin dielectric or perfectly conducting plates are developed. The width of the dielectric plates cannot exceed a quarter of a wavelength in free space, and the interior angle of the wedge is assumed to be close to 0 deg or 180 deg. Systematic methods for computing the individual components of the total high frequency field are discussed. The accuracy of the solutions is demonstrated by comparisons with measured results, where a 2 lambda by 4 lambda prolate spheroid is used as the convex surface. A jump or kink appears in the calculated pattern when higher order terms that are important are not included in the final solution. The most immediate application of the results presented here is in the modelling of structures such as aircraft which are composed of nonmetallic parts that play a significant role in the pattern.

  6. A coupled thermo-mechanical model of the differential frost heave

    NASA Astrophysics Data System (ADS)

    Nicolsky, D. J.; Tipenko, G. S.; Romanovsky, V.; Walker, D. A.

    2004-12-01

    Research investigates cryoturbation processes in the Arctic tundra, and mechanisms that cause differential frost heave in the active layer. The project explores the influence of seasonal freeze/thaw cycles on the dynamics of frost boils north of the Alaska's Brook Range. The main question to be addressed is, "How changes in surface conditions such as vegetation, snow cover and climate affect the seasonal dynamics of water and heat within frost-boil systems?" A coupled thermo-mechanical model of the frost boil phenomena based on principles of thermodynamic equilibrium and continuum mechanics will be presented. The soil is treated as a heterogeneous fully saturated mixture of ice, water and soil particles, which obeys laws of elasticity for slow deformations in a porous media. The pore water migration towards the freezing zone and its consequent freezing are the main driving forces of the soil deformation. The model includes the heat and mass conservation laws, continuity equation, the Claiperon equation, and an empirical formula, which relates unfrozen water content to temperature. The basic system of equations is reduced to a computationally convenient set of coupled equations for temperature, liquid water pressure, porosity, and the velocity of soil particles in a three-dimensional domain with an assumption of cylindrical symmetry. A finite element method and an implicit scheme in time are utilized to construct a non-linear system of equations, which are solved iteratively.

  7. Algorithm for Estimating the Plume Centerline Temperature and Ceiling Jet Temperature in the Presence of a Hot Upper Layer

    NASA Technical Reports Server (NTRS)

    Davis, William D.; Notarianni, Kathy A.; Tapper, Phillip Z.

    1998-01-01

    The experiments were designed to provide insight into the behavior of jet fuel fires in aircraft hangars and to study the impact of these fires on the design and operation of a variety of fire protection systems. As a result, the test series included small fires designed to investigate the operation of UV/IR detectors and smoke detectors as well as large fires which were used to investigate the operation of ceiling mounted heat detectors and sprinklers. The impact of the presence or absence of draft curtains was also studied in the 15 m hangar. It is shown that in order to predict the plume centerline temperature within experimental uncertainty, the entrainment of the upper layer gas must be modeled. For large fires, the impact of a changing radiation fraction must also be included in the calculation. The dependence of the radial temperature profile of the ceiling jet as a function of layer development is demonstrated and a ceiling jet temperature algorithm which includes the impact of a growing layer is developed.

  8. The periglacial engine of mountain erosion - Part 1: Rates of frost cracking and frost creep

    NASA Astrophysics Data System (ADS)

    Andersen, J. L.; Egholm, D. L.; Knudsen, M. F.; Jansen, J. D.; Nielsen, S. B.

    2015-04-01

    With accelerating climate cooling in the late Cenozoic, glacial and periglacial erosion became more widespread on the surface of the Earth. The resultant shift in erosion patterns significantly changed the large-scale morphology of many mountain ranges worldwide. Whereas the glacial fingerprint is easily distinguished by its characteristic fjords and U-shaped valleys, the periglacial fingerprint is more subtle but potentially prevailing in some landscape settings. Previous models have advocated a frost-driven control on debris production on steep headwalls and glacial valley sides. Here we investigate the important role that periglacial processes also play in less steep parts of mountain landscapes. Understanding the influences of frost-driven processes in low-relief areas requires a focus on the consequences of an accreting soil-mantle, which characterizes such surfaces. In this paper, we present a new model that quantifies two key physical processes: frost cracking and frost creep, as a function of both temperature and sediment thickness. Our results yield new insights to how climate and sediment transport properties combine to scale the intensity of periglacial processes. The thickness of the soil-mantle strongly modulates the relation between climate and the intensity of mechanical weathering and sediment flux. Our results also point to an offset between the conditions that promote frost cracking and those that promote frost creep, indicating that a stable climate can only provide optimal conditions for one of those processes at a time. Finally, quantifying these relations also opens the possibility of including periglacial processes in large-scale, long-term landscape evolution models, as demonstrated in a companion paper.

  9. The periglacial engine of mountain erosion - Part 1: Rates of frost cracking and frost creep

    NASA Astrophysics Data System (ADS)

    Andersen, J. L.; Egholm, D. L.; Knudsen, M. F.; Jansen, J. D.; Nielsen, S. B.

    2015-10-01

    With accelerating climate cooling in the late Cenozoic, glacial and periglacial erosion became more widespread on the surface of the Earth. The resultant shift in erosion patterns significantly changed the large-scale morphology of many mountain ranges worldwide. Whereas the glacial fingerprint is easily distinguished by its characteristic fjords and U-shaped valleys, the periglacial fingerprint is more subtle but potentially prevails in some mid- to high-latitude landscapes. Previous models have advocated a frost-driven control on debris production at steep headwalls and glacial valley sides. Here we investigate the important role that periglacial processes also play in less steep parts of mountain landscapes. Understanding the influences of frost-driven processes in low-relief areas requires a focus on the consequences of an accreting soil mantle, which characterises such surfaces. We present a new model that quantifies two key physical processes: frost cracking and frost creep, as a function of both temperature and sediment thickness. Our results yield new insights into how climate and sediment transport properties combine to scale the intensity of periglacial processes. The thickness of the soil mantle strongly modulates the relation between climate and the intensity of mechanical weathering and sediment flux. Our results also point to an offset between the conditions that promote frost cracking and those that promote frost creep, indicating that a stable climate can provide optimal conditions for only one of those processes at a time. Finally, quantifying these relations also opens up the possibility of including periglacial processes in large-scale, long-term landscape evolution models, as demonstrated in a companion paper.

  10. Mathematical model of frost heave and thaw settlement in pavements

    NASA Astrophysics Data System (ADS)

    Guymon, Gary L.; Berg, Richard L.; Hromadka, Theodore V.

    1993-04-01

    Since 1975 the U.S. Army Corps of Engineers, the Federal Highway Administration and the Federal Aviation Administration have been working cooperatively to develop a mathematical model to estimate frost heave and thaw weakening under various environmental conditions and for various pavement designs. A model has been developed. It is a one-dimensional representation of vertical heat and moisture flux. It is based on a numerical solution technique termed the nodal domain integration method, and it estimates frost heave and frost penetration reasonably well for a variety of situations. The model is now ready for additional field evaluation and implementation in appropriate cases. The main objectives of this report are: (1) to describe the model, FROST, including modeling uncertainties and errors; (2) to summarize recent comparisons between measured and computed values for frost heave and frost penetration; and (3) to describe parameters necessary for input into the model.

  11. Presence of an iron-rich nanophase material in the upper layer of the Cretaceous-Tertiary boundary clay

    NASA Astrophysics Data System (ADS)

    Wdowiak, Thomas J.; Armendarez, Lawrence P.; Agresti, David G.; Wade, Manson L.; Wdowiak, Suzanne Y.; Claeys, Philippe; Izett, Glenn

    2001-01-01

    We report new geochemical evidence from ten Cretaceous-Tertiary boundary sites in North America and Europe, indicating the presence of a material remnant of a large asteroid or comet that struck the Earth at 65.0 Ma. Mössbauer spectroscopic data reveals that a ubiquitous iron-rich nanophase material exists at the uppermost part of the K-T boundary layer in the Western Hemisphere and in Europe in marine and continental fine-grained sedimentary rock. The high surface-to-volume ratio of nanophase material suggests that it may be the carrier of the iridium abundance enhancement that marks the K-T boundary. Even more provocative is the possibility that the discovered nanophase material is, for the most part, composed of the vaporized impactor after the impact-generated high-temperature vapor plume rose and cooled above the atmosphere.

  12. Transition Components of the Frost Center, a Model Program Background: The Frost Center and Its Students.

    ERIC Educational Resources Information Center

    Mosso, Janet L.

    The Frost Center (Rockville, Maryland) is a private, nonprofit school and therapeutic day program that serves adolescents with emotional, learning, and behavioral disabilities and their families. Approximately two-thirds of each student's day is spent in academic classes, acquiring the skills and behavior necessary for a return to a less…

  13. Application of Satellite SAR Imagery in Mapping the Active Layer of Arctic Permafrost

    NASA Technical Reports Server (NTRS)

    Zhang, Ting-Jun; Li, Shu-Sun

    2003-01-01

    The objective of this project is to map the spatial variation of the active layer over the arctic permafrost in terms of two parameters: (i) timing and duration of thaw period and (ii) differential frost heave and thaw settlement of the active layer. To achieve this goal, remote sensing, numerical modeling, and related field measurements are required. Tasks for the University of Colorado team are to: (i) determine the timing of snow disappearance in spring through changes in surface albedo (ii) simulate the freezing and thawing processes of the active layer and (iii) simulate the impact of snow cover on permafrost presence.

  14. Geophysical Implications of Enceladus' CO2 Frost

    NASA Astrophysics Data System (ADS)

    Matson, D.; Davies, A. G.; Johnson, T. V.; Castillo, J. C.; Lunine, J. I.

    2013-12-01

    CO2 frost has been reported on the surface of Enceladus [1]. We suggest that the frost originated from shallow gas pockets below the surface. These pockets are a natural consequence of the ocean water circulation hypothesis [2]. They are different from the plume chambers [3] and would constitute a previously unrecognized structure in the surface. The oceanic circulation uses gas bubbles to make seawater buoyant and bring up water, chemicals, and heat from a warm ocean at depth [2]. The ocean water rises through the icy crust and near the surface it spreads out laterally beneath a relatively thin ice cap, following the pattern indicated by the thermal anomalies identified in Cassini data [4,5]. Topography on the bottom of this cap ice is conducive to the formation of gas pockets. As the ocean water flows horizontally, the gas bubbles in it continue to rise vertically. Even though their vertical migration may be slow and even if the flow is relatively turbulent, some bubbles reach recesses in the bottom of the ice cap and, over time, pop and form gas pockets. The gas pockets are envisioned as being ruptured by the regular fissuring of ice in the South Polar Region. Hurford et al. [6] have modelled the tidally controlled openings of rifts in the SPR. If one of these rifts reaches a gas pocket, CO2 gas may come to the surface. The tortuosity and other properties of its route will determine if it vents as a seep or a jet. If enough gas is vented and the molecules in the transient cloud have many collisions, some of them will be scattered to the surface and freeze. It was noted by Brown, et al. [1] that the frost deposits may not be permanent and that an active replenishment processes might be necessary. Studies of CO2 frost on Iapetus suggest that migration can be significant [7]. This work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. al., Science 311, 1425-1428, 2006. [2] Matson D. L. et al., Icarus 221, 53-62, 2012. (also see Matson et al. LPS 44 Abstract 1371, 2013). [3] Schmidt J. et al., Nature 451, 685-688, 2008. [4] Spencer J. R. et al., Science 311, 1401-1405, 2006. [5] Howett C. et al., JGR 116, E03003, 2011. [6] Hurford T. A. et al., Nature 447, 292-294, 2007. [7] Palmer E. E. and Brown R. H. Icarus 195, 434-446, 2008.

  15. A Laboratory Study of the Effect of Frost Flowers on C Band Radar Backscatter from Sea Ice

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Martin, S.; Perovich, D. K.; Kwok, R.; Drucker, R.; Gow, A. J.

    1997-01-01

    C band images of Arctic sea ice taken by the ERS 1 synthetic aperture radar show transitory regions of enhanced radar backscatter from young sea ice. Published field observations associate this increase with frost flower growth and the capture of blowing snow by the flowers. To investigate the first part of this phenomenon, we carried out a laboratory experiment on the response of C band radar backscatter to frost flowers growing on the surface of newly formed saline ice. The experiment took place in a 5 m by 7 m by 1.2 m deep saline water pool located in a two-story indoor refrigerated facility at the Cold Regions Research and Engineering Laboratory. Sodium chloride ice was grown in this pool at an air temperature of -28 C. The frost flowers first appeared on the ice surface as dendrites and then changed to needles as the ice sheet grew thicker and the surface temperatures became colder. The frost flowers reached to a height of 10-15 mm, and beneath each cluster of frost flowers a slush layer formed to a thickness of approximately 4 mm. Far-field radar measurements of the backscatter from the ice were made at incident angles from 20 to 40 deg and at approximately 6-hour intervals throughout the 3-day period of the experiment. A backscatter minimum occurred early in the flower growth at the time coincident with an abrupt doubling in the ice surface salinity. Once the full flower coverage was achieved, we removed first the crystal flowers and then the slush layer from the ice surface. The results for these cases show that the crystals have little impact on the backscatter, while the underlying slush patches yield a backscatter increase of 3-5 dB over that of bare ice. The laboratory results suggest that this relative backscatter increase of approximately 5 dB can be used as an index to mark the full area coverage of frost flowers.

  16. Simulated frost effects on cool-season grass carbohydrate levels

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Anecdotal observations suggest increased incidences of metabolic problems in horses on pasture after a frost. The speculation is that frost increases the level of nonstructural carbohydrates (NSC) in cool-season grasses, which have been implicated in horse metabolic problems (e.g., laminitis). We co...

  17. The distribution of water frost on Charon

    NASA Technical Reports Server (NTRS)

    Buie, Marc W.; Shriver, Scott K.

    1994-01-01

    We present high-spatial-resolution imaging observations of the Pluto-Charon system taken with ProtoCAM on the Infrared Telescope Facility (IRTF). Our dataset consists of measurements from eight nights at widely separated rotational longitudes and covering five wavelengths -- standard J, H, and K, plus two special narrow band filters at 1.5 and 1.75 microns. The relative flux contributions of Pluto and Charon were extracted, when possible, by fitting a two-source Gaussian image model to the observed images. At K, we find the Charon-Pluto magnitude difference to be on average 1.8 mag, somewhat less than the value of 2.2 mag found by Bosh et al. (1992). The average differential magnitude at 1.5 and 1.75 microns is 2.0 and 1.6, respectively. The larger magnitude difference at 1.5 microns is due to a water-frost absorption band on the surface of Charon. Our observations are consistent with a surface of Charon dominated by water frost at all longitudes.

  18. Specific surface area, density and microstructure of frost flowers

    NASA Astrophysics Data System (ADS)

    Domine, Florent; Taillandier, Anne Sophie; Simpson, William R.; Severin, Ken

    2005-07-01

    Frost flowers often grow on new sea ice. They are thought to have a high specific surface area (SSA) that provides sites for heterogeneous reactions. We have measured the SSA of frost flowers using CH4 adsorption at 77 K and obtained a value of 185 (+80 -50) cm2/g, much lower than inferred by others. Their density is 0.02 g/cm3. We calculate that the total surface area of frost flowers is 1.4 m2 per m2 of ice surface, so that they do not increase the ice surface area significantly. Their role as sites for enhanced heterogeneous reactions should be reconsidered. Frost flowers also commonly grow on fresh water and the saline brine seen on young sea ice is not necessary for their growth. Photo- and electro-micrographs reveal hollow and concave structures, typical of very fast growing crystals. The brine that wicks up frost flowers considerably perturbs their growth.

  19. Evaluation of Apical Leakage in Root Canals Obturated with Three Different Sealers in Presence or Absence of Smear Layer

    PubMed Central

    Mokhtari, Hadi; Shahi, Shahriar; Janani, Maryam; Reyhani, Mohammad Frough; Mokhtari Zonouzi, Hamid Reza; Rahimi, Saeed; Sadr Kheradmand, Hamid Reza

    2015-01-01

    Introduction: Microleakage can result in failure of endodontic treatment. An important characteristic of endodontic sealer is sealing ability. The aim of this experimental study was to compare the apical leakage of teeth obturated with gutta-percha and three different sealers (resin- and zinc oxide eugenol-based) with/without smear layer (SL). Materials and Methods: In this study, 100 single-rooted teeth were used after cutting off their crowns. Cleaning and shaping was carried out with step-back technique and the samples were randomly divided into three groups (n=30) which were then divided into two subgroups (n=15) according to the presence/absence of SL. Two negative and positive control groups (n=5) were also prepared. In the various groups, the canals were obturated with gutta-percha and either of the test sealers (AH-26, Adseal or Endofill). The samples were submerged in India ink for 72 h. Then they were longitudinally sectioned and observed under a stereomicroscope at 20× magnification. Data were analyzed with descriptive statistical methods and one-way ANOVA. The significance level was set at 0.05. Results: The mean penetration length of dye in AH-26, Adseal and Endofill samples were 2.53, 2.76 and 3.03 mm, respectively. The differences between three groups were not significant (P>0.05); also, the mean dye penetration in AH-26, Adseal and Endofill samples in presence or absence of the SL was not significantly different. Conclusion: AH-26, Adseal and Endofill were similarly effective in prevention of apical microleakage. Differences in the mean dye penetration between the groups with/without the SL were not statistically significant. PMID:25834599

  20. One: Microphysics of frost metamorphism: Applications to Triton and Mars. Two: A global analysis of the ozone deficit in the upper stratosphere and lower mesosphere. Three: The diabatic circulation in the stratosphere as diagnosed from Microwave Limb Sounder data

    SciTech Connect

    Eluszkiewicz, J.B.

    1993-01-01

    The present thesis is devoted to two broad subjects, planetary frost metamorphism and the terrestrial middle atmosphere, and consists of three papers. Paper 1 considers frost metamorphism on the surfaces of Triton and Mars. Based on an analysis of the microphysical processes involved in the pressureless sintering, it is concluded that fine-grained nitrogen and carbon dioxide frosts can undergo seasonal metamorphism into semitransparent layers on the surface of Triton and in the Martian seasonal polar caps, respectively. The presence of such layers explains a host of facts about Triton's surface and about the Martian seasonal caps. Paper 2 is devoted to elucidating a long-standing issue in the terrestrial middle atmosphere chemistry, the so-called 'ozone deficit problem.' Based on an analysis of data acquired by the Limb Infrared Monitor of the Stratosphere (LIMS) instrument between October 1978 and May 1979, it is concluded that current photochemical models systematically underestimate observed ozone abundances in the upper stratosphere and lower mesosphere. Three modifications to the accepted photochemical scheme, capable of providing a global solution to this problem, are proposed and discussed. Paper 3 differs from the other two in that it reports on results from an ongoing research effort. It considers the diabatic circulation in the stratosphere and lower mesosphere, using ozone and temperature measurements acquired by the Microwave Limb Sounder (MLS) instrument onboard the Upper Atmosphere Research Satellite (UARS). The present study extends past analyses of the diabatic circulation by considering a full annual cycle, November 1991-November 1992, and by taking advantage of the high vertical resolution of MLS data. In the tropical upper stratosphere and lower mesosphere, a semiannual oscillation (SAO) is observed in the computed circulation, with the region of downwelling reaching maximum spatial extent approximately 1 month before the equinox.

  1. On turbulence modulation due to the presence of sediment in the bottom boundary layer - a numerical investigation

    NASA Astrophysics Data System (ADS)

    Hsu, T.; Yu, X.; Ozdemir, C. E.; Balachandar, S.

    2013-05-01

    One of the most intriguing issues in fine sediment transport, including turbidity currents, tidal-driven transport and wave-driven transport, is that the presence of sediments may lead to attenuation of flow turbulence. Depending on the level of turbulence suppression, it may lead to the formation of lutocline (a sharp negative sediment concentration) and an enhanced gravity flow; or it may cause catastrophic collapse of turbulence and sediment deposition. Through laboratory observations and numerical simulations, prior studies have established that these transitions can be caused by various degree of sediment-induced stable density stratification. However, when sediment concentration becomes larger, inter-particle (or inter-floc) interactions may lead to enhanced viscosity through rheological stress and its role on turbulence modulation is unclear. Through turbulence-resolving simulations, this study further investigates turbulence suppression due to enhanced effective viscosity via two simple Newtonian rheological closures in a steady channel flow and in an oscillatory bottom boundary layer. Assuming a small Stokes number, the Equilibrium approximation to the Eulerian two-phase flow equations is adopted. The resulting simplified equations are solved with a high-accuracy hybrid spectral-compact finite difference scheme in an idealized channel. The numerical approach extends an earlier pseudo-spectral model for direct numerical simulation (DNS) of turbulent flows with a sixth-order compact finite difference scheme in the wall-normal direction on Chebyshev grid points. The compact finite difference scheme allows easy implementation of concentration-dependent viscosity. Simulation results reveal that when rheological stress is incorporated, the enhanced effective viscosity can further attenuate flow turbulence in addition to the well-known sediment-induced stable density stratification. Through the enhanced viscosity, velocity gradient very near the bed is significantly reduced, which leads to much weaker turbulent production and the onset of laminarization. This mechanism is different from the sediment-induced density stratification that typically damps turbulence in the middle of the boundary layer where the lutocline is located. Our preliminary finding shows that rheology encourages laminarization may explain why large attenuation of surface waves over muddy seabed is ubiquitous and the highest dissipation rate is often observed during the waning stage of a storm.

  2. Study of Potential Sub-Micrometer-Thick Frost Events and Soil Water Content at Gale Crater

    NASA Astrophysics Data System (ADS)

    Martinez, G.; Fischer, E.; Renno, N. O.; De La Torre Juarez, M.; Meslin, P. Y.; Kemppinen, O.; Genzer, M.; Harri, A. M.; Ramos, M.; Borlina, C.; Schröder, S.; Gómez-Elvira, J.

    2014-12-01

    We analyze the highest confidence measurements of relative humidity [1] and ground temperature [2] to identify potential frost events at the surface of Gale Crater during the first 600 sols of the MSL mission. We find that between 4 and 6 am on sols 533, 535, 555, 557, 559 and 560 the ground temperature falls below the calculated frost point. Order-of-magnitude estimate for the thickness of the frost layer indicates that it is of the order of micrometers or less. Additionally, we analyze the relation between water vapor pressure and ground temperature to provide additional constraints on potential frost events and to quantify the exchange of adsorbed water between the surface and the atmosphere. Adsorbed water could be forced into liquid-like state at the of Gale because van der Waals forces between water ice molecules and mineral surfaces reduces the freezing point [3]. This form of liquid water is relevant to habitability because microorganisms could survive in liquid-like adsorbed water [4].References: [1] Harri, Ari-Matti et al., Mars Science Laboratory Relative Humidity Observations - Initial Results (2014), JGR (in press). [2] Martínez, G. M. et al., Surface Energy Budget and Thermal Inertia at Gale Crater: Calculations from Ground-Based Measurements (2014), JGR (in press). [3] Möhlmann, D., The influence of van der Waals forces on the state of water in the shallow subsurface of Mars (2008), Icarus 195 (1), 131-139. [4] Rivkina, E. M. et al., Metabolic activity of permafrost bacteria below the freezing point (2000), Appl. Environ. Microbiol., 66(8), 3230-3233.

  3. Spring frost vulnerability of sweet cherries under controlled conditions

    NASA Astrophysics Data System (ADS)

    Matzneller, Philipp; Götz, Klaus-P.; Chmielewski, Frank-M.

    2015-05-01

    Spring frost is a significant production hazard in nearly all temperate fruit-growing regions. Sweet cherries are among the first fruit varieties starting their development in spring and therefore highly susceptible to late frost. Temperatures at which injuries are likely to occur are widely published, but their origin and determination methods are not well documented. In this study, a standardized method was used to investigate critical frost temperatures for the sweet cherry cultivar `Summit' under controlled conditions. Twigs were sampled at four development stages ("side green," "green tip," "open cluster," "full bloom") and subjected to three frost temperatures (-2.5, -5.0, -10.0 °C). The main advantage of this method, compared to other approaches, was that the exposition period and the time interval required to reach the target temperature were always constant (2 h). Furthermore, then, the twigs were placed in a climate chamber until full bloom, before the examination of the flowers and not further developed buds started. For the first two sampling stages (side green, green tip), the number of buds found in open cluster, "first white," and full bloom at the evaluation date decreased with the strength of the frost treatment. The flower organs showed different levels of cold hardiness and became more vulnerable in more advanced development stages. In this paper, we developed four empirical functions which allow calculating possible frost damages on sweet cherry buds or flowers at the investigated development stages. These equations can help farmers to estimate possible frost damages on cherry buds due to frost events. However, it is necessary to validate the critical temperatures obtained in laboratory with some field observations.

  4. Delayed Frost Growth on Jumping-Drop Superhydrophobic Surfaces

    SciTech Connect

    Boreyko, Jonathan B; Collier, Pat

    2013-01-01

    Self-propelled jumping drops are continuously removed from a condensing superhydrophobic surface to enable a micrometric steady-state drop size. Here, we report that subcooled condensate on a chilled superhydrophobic surface are able to repeatedly jump off the surface before heterogeneous ice nucleation occurs. Frost still forms on the superhydrophobic surface due to ice nucleation at neighboring edge defects, which eventually spreads over the entire surface via an inter-drop frost wave. The growth of this inter-drop frost front is shown to be up to three times slower on the superhydrophobic surface compared to a control hydrophobic surface, due to the jumping-drop effect dynamically minimizing the average drop size and surface coverage of the condensate. A simple scaling model is developed to relate the success and speed of inter-drop ice bridging to the drop size distribution. While other reports of condensation frosting on superhydrophobic surfaces have focused exclusively on liquid-solid ice nucleation for isolated drops, these findings reveal that the growth of frost is an inter-drop phenomenon that is strongly coupled to the wettability and drop size distribution of the surface. A jumping-drop superhydrophobic condenser was found to be superior to a conventional dropwise condenser in two respects: preventing heterogeneous ice nucleation by continuously removing subcooled condensate, and delaying frost growth by minimizing the success of interdrop ice bridge formation.

  5. Coagulation of particles in Saturn's rings - Measurements of the cohesive force of water frost

    SciTech Connect

    Hatzes, A.P.; Bridges, F.; Lin, D.N.C.; Sachtjen, S. McDonald Observatory, Austin, TX )

    1991-01-01

    Experimental data are presented on the sticking force of water ice particles which are indicative of the role that the cohesive properties of such particles could play in the dynamics of Saturn ring particles. Sticking forces are dependent on particle impact velocities; a Velcro model is devised to describe the surface structure involved in sticking. The data indicate that below the critical impact velocity of about 0.03 cm/sec, particle cohesion always occurs. Due to the optical depth of micron-sized grains in the Saturn rings, particles are hypothesized to be coated with a layer of frost which will render cohesion an important ring-dynamics process. 14 refs.

  6. Coagulation of particles in Saturn's rings - Measurements of the cohesive force of water frost

    NASA Technical Reports Server (NTRS)

    Hatzes, A. P.; Bridges, F.; Lin, D. N. C.; Sachtjen, S.

    1991-01-01

    Experimental data are presented on the sticking force of water ice particles which are indicative of the role that the cohesive properties of such particles could play in the dynamics of Saturn ring particles. Sticking forces are dependent on particle impact velocities; a 'Velcro' model is devised to describe the surface structure involved in sticking. The data indicate that below the critical impact velocity of about 0.03 cm/sec, particle cohesion always occurs. Due to the optical depth of micron-sized grains in the Saturn rings, particles are hypothesized to be coated with a layer of frost which will render cohesion an important ring-dynamics process.

  7. (abstract) A Polarimetric Model for Effects of Brine Infiltrated Snow Cover and Frost Flowers on Sea Ice Backscatter

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Kwok, R.; Yueh, S. H.

    1995-01-01

    A polarimetric scattering model is developed to study effects of snow cover and frost flowers with brine infiltration on thin sea ice. Leads containing thin sea ice in the Artic icepack are important to heat exchange with the atmosphere and salt flux into the upper ocean. Surface characteristics of thin sea ice in leads are dominated by the formation of frost flowers with high salinity. In many cases, the thin sea ice layer is covered by snow, which wicks up brine from sea ice due to capillary force. Snow and frost flowers have a significant impact on polarimetric signatures of thin ice, which needs to be studied for accessing the retrieval of geophysical parameters such as ice thickness. Frost flowers or snow layer is modeled with a heterogeneous mixture consisting of randomly oriented ellipsoids and brine infiltration in an air background. Ice crystals are characterized with three different axial lengths to depict the nonspherical shape. Under the covering multispecies medium, the columinar sea-ice layer is an inhomogeneous anisotropic medium composed of ellipsoidal brine inclusions preferentially oriented in the vertical direction in an ice background. The underlying medium is homogeneous sea water. This configuration is described with layered inhomogeneous media containing multiple species of scatterers. The species are allowed to have different size, shape, and permittivity. The strong permittivity fluctuation theory is extended to account for the multispecies in the derivation of effective permittivities with distributions of scatterer orientations characterized by Eulerian rotation angles. Polarimetric backscattering coefficients are obtained consistently with the same physical description used in the effective permittivity calculation. The mulitspecies model allows the inclusion of high-permittivity species to study effects of brine infiltrated snow cover and frost flowers on thin ice. The results suggest that the frost cover with a rough interface significantly increases the backscatter from thin saline ice and the polarimetric signature becomes closer to the isotropic characteristics. The snow cover also modifies polarimetric signatures of thin sea ice depending on the snow mixture and the interface condition.

  8. Control of boundary layer transition location and plate vibration in the presence of an external acoustic field

    NASA Technical Reports Server (NTRS)

    Maestrello, L.; Grosveld, F. W.

    1991-01-01

    The experiment is aimed at controlling the boundary layer transition location and the plate vibration when excited by a flow and an upstream sound source. Sound has been found to affect the flow at the leading edge and the response of a flexible plate in a boundary layer. Because the sound induces early transition, the panel vibration is acoustically coupled to the turbulent boundary layer by the upstream radiation. Localized surface heating at the leading edge delays the transition location downstream of the flexible plate. The response of the plate excited by a turbulent boundary layer (without sound) shows that the plate is forced to vibrate at different frequencies and with different amplitudes as the flow velocity changes indicating that the plate is driven by the convective waves of the boundary layer. The acoustic disturbances induced by the upstream sound dominate the response of the plate when the boundary layer is either turbulent or laminar. Active vibration control was used to reduce the sound induced displacement amplitude of the plate.

  9. On the Effective Thermal Conductivity of Frost Considering Mass Diffusion and Eddy Convection

    NASA Technical Reports Server (NTRS)

    Kandula, Max

    2010-01-01

    A physical model for the effective thermal conductivity of water frost is proposed for application to the full range of frost density. The proposed model builds on the Zehner-Schlunder one-dimensional formulation for porous media appropriate for solid-to-fluid thermal conductivity ratios less than about 1000. By superposing the effects of mass diffusion and eddy convection on stagnant conduction in the fluid, the total effective thermal conductivity of frost is shown to be satisfactorily described. It is shown that the effects of vapor diffusion and eddy convection on the frost conductivity are of the same order. The results also point out that idealization of the frost structure by cylindrical inclusions offers a better representation of the effective conductivity of frost as compared to spherical inclusions. Satisfactory agreement between the theory and the measurements for the effective thermal conductivity of frost is demonstrated for a wide range of frost density and frost temperature.

  10. Forecast of Frost Days Based on Monthly Temperatures

    NASA Astrophysics Data System (ADS)

    Castellanos, M. T.; Tarquis, A. M.; Morató, M. C.; Saa-Requejo, A.

    2009-04-01

    Although frost can cause considerable crop damage and mitigation practices against forecasted frost exist, frost forecasting technologies have not changed for many years. The paper reports a new method to forecast the monthly number of frost days (FD) for several meteorological stations at Community of Madrid (Spain) based on successive application of two models. The first one is a stochastic model, autoregressive integrated moving average (ARIMA), that forecasts monthly minimum absolute temperature (tmin) and monthly average of minimum temperature (tminav) following Box-Jenkins methodology. The second model relates these monthly temperatures to minimum daily temperature distribution during one month. Three ARIMA models were identified for the time series analyzed with a stational period correspondent to one year. They present the same stational behavior (moving average differenced model) and different non-stational part: autoregressive model (Model 1), moving average differenced model (Model 2) and autoregressive and moving average model (Model 3). At the same time, the results point out that minimum daily temperature (tdmin), for the meteorological stations studied, followed a normal distribution each month with a very similar standard deviation through years. This standard deviation obtained for each station and each month could be used as a risk index for cold months. The application of Model 1 to predict minimum monthly temperatures showed the best FD forecast. This procedure provides a tool for crop managers and crop insurance companies to asses the risk of frost frequency and intensity, so that they can take steps to mitigate against frost damage and estimated the damage that frost would cost. This research was supported by Comunidad de Madrid Research Project 076/92. The cooperation of the Spanish National Meteorological Institute and the Spanish Ministerio de Agricultura, Pesca y Alimentation (MAPA) is gratefully acknowledged.

  11. Scaled experimental models show that the pres-ence of a viscous layer, such as salt, facilitates the

    E-print Network

    (Withjack et al., 1989, 1990). In these three regions, the presence of subsurface evaporites facili- tated and identifying the small-scale structures within them, however, can be difficult. Typically, the evaporitic

  12. Zwitter-wettability and antifogging coatings with frost-resisting capabilities.

    PubMed

    Lee, Hyomin; Alcaraz, Maria L; Rubner, Michael F; Cohen, Robert E

    2013-03-26

    Antifogging coatings with hydrophilic or even superhydrophilic wetting behavior have received significant attention due to their ability to reduce light scattering by film-like condensation. However, under aggressive fogging conditions, these surfaces may exhibit frost formation or excess and nonuniform water condensation, which results in poor optical performance of the coating. In this paper, we show that a zwitter-wettable surface, a surface that has the ability to rapidly absorb molecular water from the environment while simultaneously appearing hydrophobic when probed with water droplets, can be prepared by using hydrogen-bonding-assisted layer-by-layer (LbL) assembly of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA). An additional step of functionalizing the nano-blended PVA/PAA multilayer with poly(ethylene glycol methyl ether) (PEG) segments produced a significantly enhanced antifog and frost-resistant behavior. The addition of the PEG segments was needed to further increase the nonfreezing water capacity of the multilayer film. The desirable high-optical quality of these thin films arises from the nanoscale control of the macromolecular complexation process that is afforded by the LbL processing scheme. An experimental protocol that not only allows for the exploration of a variety of aggressive antifogging challenges but also enables quantitative analysis of the antifogging performance via real-time monitoring of transmission levels as well as image distortion is also described. PMID:23360374

  13. Frost sensor for use in defrost controls for refrigeration

    DOEpatents

    French, Patrick D. (ADA Technologies, Inc. 8100 Shaffer Pkwy., Suite 130, Littleton, CO 80127-4107); Butz, James R. (ADA Technologies, Inc. 8100 Shaffer Pkwy., Suite 130, Littleton, CO 80127-4107); Veatch, Bradley D. (ADA Technologies, Inc. 8100 Shaffer Pkwy., Suite 130, Littleton, CO 80127-4107); O'Connor, Michael W. (ADA Technologies, Inc. 8100 Shaffer Pkwy., Suite 130, Littleton, CO 80127-4107)

    2002-01-01

    An apparatus and method for measuring the total thermal resistance to heat flow from the air to the evaporative cooler fins of a refrigeration system. The apparatus is a frost sensor that measures the reduction in heat flow due to the added thermal resistance of ice (reduced conduction) as well as the reduction in heat flow due to the blockage of airflow (reduced convection) from excessive ice formation. The sensor triggers a defrost cycle when needed, instead of on a timed interval. The invention is also a method for control of frost in a system that transfers heat from air to a refrigerant along a thermal path. The method involves measuring the thermal conductivity of the thermal path from the air to the refrigerant, recognizing a reduction in thermal conductivity due to the thermal insulation effect of the frost and due to the loss of airflow from excessive ice formation; and controlling the defrosting of the system.

  14. The role of phenology in assessing risks of frost damage

    NASA Astrophysics Data System (ADS)

    Menzel, Annette; Estrella, Nicole

    2013-04-01

    Climate warming in temperate regions has been shown to lengthen the summer growing season, both at the spring and autumn side, and shorten the winter season. Spring phenology, e.g. bud burst and leafing, is mainly triggered by forcing temperatures in order to maximize growing season during favorable conditions. Winter chilling and / or photoperiodic requirements prevent too early plant development related to a higher risk of damage by late spring frosts. The questions how risks of late spring frosts have been altered in the past and will change under future warming are discussed controversially in the current literature. In this paper we will take this classical example of vegetation - atmosphere interaction to demonstrate that traits of the species studied, the (partially) neglected status of the vegetation and regional climatic conditions may account for these differences reported. We suggest a methodology based on extreme value theory (EVT) to assess the frost risks and present results for continental Europe.

  15. FROST - FREEDOM OPERATIONS SIMULATION TEST VERSION 1.0

    NASA Technical Reports Server (NTRS)

    Deshpande, G. K.

    1994-01-01

    The Space Station Freedom Information System processes and transmits data between the space station and the station controllers and payload operators on the ground. Components of the system include flight hardware, communications satellites, software and ground facilities. FROST simulates operation of the SSF Information System, tracking every data packet from generation to destination for both uplinks and downlinks. This program collects various statistics concerning the SSF Information System operation and provides reports of these at user-specified intervals. Additionally, FROST has graphical display capability to enhance interpretation of these statistics. FROST models each of the components of the SSF Information System as an object, to which packets are generated, received, processed, transmitted, and/or dumped. The user must provide the information system design with specified parameters and inter-connections among objects. To aid this process, FROST supplies an example SSF Information System for simulation, but this example must be copied before it is changed and used for further simulation. Once specified, system architecture and parameters are put into the input file, named the Test Configuration Definition (TCD) file. Alternative system designs can then be simulated simply by editing the TCD file. Within this file the user can define new objects, alter object parameters, redefine paths, redefine generation rates and windows, and redefine object interconnections. At present, FROST does not model every feature of the SSF Information System, but it is capable of simulating many of the system's important functions. To generate data messages, which can come from any object, FROST defines "windows" to specify when, what kind, and how much of that data is generated. All messages are classified by priority as either (1)emergency (2)quick look (3)telemetry or (4)payload data. These messages are processed by all objects according to priority. That is, all priority 1 (emergency) messages are processed and transmitted before priority 2 messages, and so forth. FROST also allows for specification of "pipeline" or "direct" links. Pipeline links are used to broadcast at constant intervals, while direct links transmit messages only when packets are ready for transmission. FROST allows the user substantial flexibility to customize output for a simulation. Output consists of tables and graphs, as specified in the TCD file, to be generated at the specified interval. These tables may be generated at short intervals during the run to produce snapshots as simulation proceeds, or generated after the run to give a summary of the entire run. FROST is written in SIMSCRIPT II.5 (developed by CACI) for DEC VAX series computers running VMS. FROST was developed on a VAX 8700 and is intended to be run on large VAXes with at least 32Mb of memory. The main memory requirement for FROST is dependent on the number of processors used in the simulation and the event time. The standard distribution medium for this package is a 9-track 1600 BPI DEC VAX BACKUP Format Magnetic Tape. An executable is included on the tape in addition to the source code. FROST was developed in 1990 and is a copyrighted work with all copyright vested in NASA. DEC, VAX and VMS are registered trademarks of Digital Equipment Corporation. IBM PC is a trademark of International Business Machines. SIMSCRIPT II.5 is a trademark of CACI.

  16. Frost-weathering on Mars - Experimental evidence for peroxide formation

    NASA Technical Reports Server (NTRS)

    Huguenin, R. L.; Miller, K. J.; Harwood, W. S.

    1979-01-01

    The weathering of silicates by frost is investigated in relation to the formation of surface peroxides to which Viking biology experiment results have been attributed. Samples of the minerals olivine and pyroxene were exposed to water vapor at -11 to -22 C and resultant gas evolution and pH were monitored. Experiments reveal the formation of an acidic oxidant upon interaction of the mineral and H2O frost at subfreezing temperatures, which chemical indicators have suggested to be chemisorbed hydrogen peroxide. A model for the formation of chemisorbed peroxide based on the chemical reduction of the mineral by surface frost is proposed, and it is predicted that the perioxide would decay at high temperatures to H2O and adsorbed O, consistent with the long-term storage and sterilization behavior of the soil oxidants observed in the Viking Gas Exchange and Labeled Release experiments.

  17. A Laboratory Study of the Effect of Frost Flowers on C Band Radar Backscatter from Sea Ice

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Martin, S.; Perovich, D. K.; Kwok, R.; Drucker, R.; Gow, A. J.

    1997-01-01

    C band images of Arctic sea ice taken by the ERS 1 synthetic aperture radar show transitory regions of enhanced radar backscatter from young sea ice. Published field observations associate this increase with frost flower growth and the capture of blowing snow by the flowers. To investigate the first part of this phenomenon, we carried out a laboratory experiment on the response of C band radar backscatter to frost flowers growing on the surface of newly formed saline ice. The experiment took place in a 5 m by 7 m by 1.2 m deep saline water pool located in a two-story indoor refrigerated facility at the Cold Regions Research and Engineering Laboratory. Sodium chloride ice was grown in this pool at an air temperature of -28 C. The frost flowers first appeared on the ice surface as dendrites and then changed to needles as the ice sheet grew thicker and the surface temperatures became colder. The frost flowers reached to a height of 10-15 mm, and beneath each cluster of frost flowers a slush layer formed to a thickness of approximately 4 mm. Far-field radar measurements of the backscatter from the ice were made at incident angles from 20 C to 40 C and at approximately 6-hour intervals throughout the 3-day period of the experiment. A backscatter minimum occurred early in the flower growth at the time coincident with an abrupt doubling in the ice surface salinity. Once the full flower coverage was achieved, we removed first the crystal flowers and then the slush layer from the ice surface. The results for these cases show that the crystals have little impact on the backscatter, while the underlying slush patches yield a backscatter increase of 3-5 dB over that o f bare ice. The laboratory results suggest that this relative backscatter increase of approximately 5 dB can be used as an index to mark the full areal coverage of frost flowers.

  18. Seasonally active frost-dust avalanches on a north polar scarp of Mars captured by HiRISE

    USGS Publications Warehouse

    Russell, P.; Thomas, N.; Byrne, S.; Herkenhoff, K.; Fishbaugh, K.; Bridges, N.; Okubo, C.; Milazzo, M.; Daubar, I.; Hansen, C.; McEwen, A.

    2008-01-01

    North-polar temporal monitoring by the High Resolution Imaging Science Experiment (HiRISE) orbiting Mars has discovered new, dramatic examples that Mars1 CO2-dominated seasonal volatile cycle is not limited to quiet deposition and sublimation of frost. In early northern martian spring, 2008, HiRISE captured several cases of CO2 frost and dust cascading down a steep, polar scarp in discrete clouds. Analysis of morphology and process reveals these events to be similar to terrestrial powder avalanches, sluffs, and falls of loose, dry snow. Potential material sources and initiating mechanisms are discussed in the context of the Martian polar spring environment and of additional, active, aeolian processes observed on the plateau above the scarp. The scarp events are identified as a trigger for mass wasting of bright, fractured layers within the basal unit, and may indirectly influence the retreat rate of steep polar scarps in competing ways. Copyright 2008 by the American Geophysical Union.

  19. Correlation of Water Frost Porosity in Laminar Flow over Flat Surfaces

    NASA Technical Reports Server (NTRS)

    Kandula, Max

    2011-01-01

    A dimensionless correlation has been proposed for water frost porosity expressing its dependence on frost surface temperature and Reynolds number for laminar forced flow over a flat surface. The correlation is presented in terms of a dimensionless frost surface temperature scaled with the cold plate temperature, and the freezing temperature. The flow Reynolds number is scaled with reference to the critical Reynolds number for laminar-turbulent transition. The proposed correlation agrees satisfactorily with the simultaneous measurements of frost density and frost surface temperature covering a range of plate temperature, ambient air velocity, humidity, and temperature. It is revealed that the frost porosity depends primarily on the frost surface and the plate temperatures and the flow Reynolds number, and is only weakly dependent on the relative humidity. The results also point out the general character of frost porosity displaying a decrease with an increase in flow Reynolds number.

  20. Far-infrared spectra of CO2 clathrate hydrate frosts

    NASA Technical Reports Server (NTRS)

    Landry, J. C.; England, A. W.

    1993-01-01

    As a product of our interest in remote sensing of planetary ices, frost samples of CO2 clathrate hydrate were grown by depositing water vapor on a cooled surface and pressurizing the resulting water frost with CO2 gas. At pressures above the dissociation pressure of the clathrate, the samples exhibit an absorption peak at 75 cm (sup -1). At pressures below the dissociation pressure, the peak disappears. Since the free CO2 molecule does not have rotational or vibrational absorption in this region, the absorption is attributed to a CO2 rattling mode within a clathrate cage.

  1. Long term spatial and temporal trends in frost day indices in Kansas, USA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Frost day indices such as number of frost days (nFDs), frost free days (nFFDs), last spring freeze (LSF), first fall freeze (FFF), and growing-season length (GSL), were calculated using daily minimum air temperature (Tmin) values from 23 centennial weather stations spread across Kansas during four t...

  2. Accuracy of tropospheric and stratospheric water vapor measurements by the cryogenic frost point hygrometer

    E-print Network

    Vömel, Holger

    Accuracy of tropospheric and stratospheric water vapor measurements by the cryogenic frost point] The cryogenic frost point hygrometer (CFH), currently built at the University of Colorado, is a new balloon of tropospheric and stratospheric water vapor measurements by the cryogenic frost point hygrometer: Instrumental

  3. Soret-driven convection of binary mixture in a horizontal porous layer in the presence of a heat or concentration source

    SciTech Connect

    Goldobin, D. S. Lyubimov, D. V.

    2007-05-15

    Soret-driven convection of a binary mixture in a shallow porous layer is analyzed. The analysis focuses on the behavior of the system in the presence of a concentration or heat source. In the long-wavelength limit, regimes are found in which the flow regions near the source and at the periphery are separated by narrow annular transition regions. It is also shown that the outward concentration flux from the source is dominated by convection, whereas heat can be transferred from the source both by convection and by diffusion. Multistability between these two regimes is possible.

  4. Genetic Architecture of Winter Hardiness and Frost Tolerance in Triticale

    PubMed Central

    Liu, Wenxin; Maurer, Hans Peter; Li, Guoliang; Tucker, Matthew R.; Gowda, Manje; Weissmann, Elmar A.; Hahn, Volker; Würschum, Tobias

    2014-01-01

    Abiotic stress experienced by autumn-sown crops during winter is of great economic importance as it can have a severe negative impact on yield. In this study, we investigated the genetic architecture of winter hardiness and frost tolerance in triticale. To this end, we used a large mapping population of 647 DH lines phenotyped for both traits in combination with genome-wide marker data. Employing multiple-line cross QTL mapping, we identified nine main effect QTL for winter hardiness and frost tolerance of which six were overlapping between both traits. Three major QTL were identified on chromosomes 5A, 1B and 5R. In addition, an epistasis scan revealed the contribution of epistasis to the genetic architecture of winter hardiness and frost tolerance in triticale. Taken together, our results show that winter hardiness and frost tolerance are complex traits that can be improved by phenotypic selection, but also that genomic approaches hold potential for a knowledge-based improvement of these important traits in elite triticale germplasm. PMID:24927281

  5. Salt Frost Deterioration in Concrete Pavement --Causes and Mitigation

    E-print Network

    Salt Frost Deterioration in Concrete Pavement --Causes and Mitigation Zhichao Liu, Will Hansen and special effects such as surface tension and osmotic effect (salt solution). ·Below the nucleation the surface contains a salt solution, pore suction attracts surface liquid and additional ice growth may

  6. Genetic architecture of winter hardiness and frost tolerance in triticale.

    PubMed

    Liu, Wenxin; Maurer, Hans Peter; Li, Guoliang; Tucker, Matthew R; Gowda, Manje; Weissmann, Elmar A; Hahn, Volker; Würschum, Tobias

    2014-01-01

    Abiotic stress experienced by autumn-sown crops during winter is of great economic importance as it can have a severe negative impact on yield. In this study, we investigated the genetic architecture of winter hardiness and frost tolerance in triticale. To this end, we used a large mapping population of 647 DH lines phenotyped for both traits in combination with genome-wide marker data. Employing multiple-line cross QTL mapping, we identified nine main effect QTL for winter hardiness and frost tolerance of which six were overlapping between both traits. Three major QTL were identified on chromosomes 5A, 1B and 5R. In addition, an epistasis scan revealed the contribution of epistasis to the genetic architecture of winter hardiness and frost tolerance in triticale. Taken together, our results show that winter hardiness and frost tolerance are complex traits that can be improved by phenotypic selection, but also that genomic approaches hold potential for a knowledge-based improvement of these important traits in elite triticale germplasm. PMID:24927281

  7. Heritability of frost-seeded red clover establishment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In the colder parts of the United States, in late winter after disappearance of snow cover, red clover (Trifolium pratense) is often broadcast seeded into forage legume-depleted grass pastures to increase pasture forage quality. This method of establishment is referred to as frost seeding. However...

  8. Inhibition of Condensation Frosting by Arrays of Hygroscopic Antifreeze Drops.

    PubMed

    Sun, Xiaoda; Damle, Viraj G; Uppal, Aastha; Linder, Rubin; Chandrashekar, Sriram; Mohan, Ajay R; Rykaczewski, Konrad

    2015-12-29

    The formation of frost and ice can have negative impacts on travel and a variety of industrial processes and is typically addressed by dispensing antifreeze substances such as salts and glycols. Despite the popularity of this anti-icing approach, some of the intricate underlying physical mechanisms are just being unraveled. For example, recent studies have shown that in addition to suppressing ice formation within its own volume, an individual salt saturated water microdroplet forms a region of inhibited condensation and condensation frosting (RIC) in its surrounding area. This occurs because salt saturated water, like most antifreeze substances, is hygroscopic and has water vapor pressure at its surface lower than water saturation pressure at the substrate. Here, we demonstrate that for macroscopic drops of propylene glycol and salt saturated water, the absolute RIC size can remain essentially unchanged for several hours. Utilizing this observation, we demonstrate that frost formation can be completely inhibited in-between microscopic and macroscopic arrays of propylene glycol and salt saturated water drops with spacing (S) smaller than twice the radius of the RIC (?). Furthermore, by characterizing condensation frosting dynamics around various hygroscopic drop arrays, we demonstrate that they can delay complete frosting over of the samples 1.6 to 10 times longer than films of the liquids with equivalent volume. The significant delay in onset of ice nucleation achieved by dispensing propylene glycol in drops rather than in films is likely due to uniform dilution of the drops driven by thermocapillary flow. This transport mode is absent in the films, leading to faster dilution, and with that facilitated homogeneous nucleation, near the liquid-air interface. PMID:26651017

  9. Frost heave susceptibility of saturated soil under constant rate of freezing

    SciTech Connect

    Ryokai, K.; Iguro, M.; Yoneyama, K.

    1982-01-01

    Introduced are the results of experiments carried out to quantitatively obtain the frost heave pressure and displacement of soil subjected to artificial freezing or freezing around in-ground liquefied natural gas storage tanks. This experiment is conducted to evaluate the frost heave susceptibility of saturated soil under overconsolidation. In other words, this experiment was carried out to obtain the relation of the over-burden pressure and freezing rate to the frost heave ratio by observing the frost heave displacement and freezing time of specimens by freezing the specimens at a constant freezing rate under a constant overburden pressure, while letting water freely flow in and out of the system. Introduced are the procedures for frost heave test required to quantitatively obtain the frost heave displacement and pressure of soil. Furthermore, the relation between the frost heave susceptibility and physical properties of soil obtained by this test is reported.

  10. Layers

    NASA Astrophysics Data System (ADS)

    Hong, K. J.; Jeong, T. S.; Youn, C. J.

    2014-09-01

    The temperature-dependent photoresponse characteristics of MnAl2S4 layers have been investigated, for the first time, by use of photocurrent (PC) spectroscopy. Three peaks were observed at all temperatures. The electronic origin of these peaks was associated with band-to-band transitions from the valence-band states ?4( z), ?5( x), and ?5( y) to the conduction-band state ?1( s). On the basis of the relationship between PC-peak energy and temperature, the optical band gap could be well expressed by the expression E g( T) = E g(0) - 2.80 × 10-4 T 2/(287 + T), where E g(0) was estimated to be 3.7920 eV, 3.7955 eV, and 3.8354 eV for the valence-band states ?4( z), ?5( x), and ?5( y), respectively. Results from PC spectroscopy revealed the crystal-field and spin-orbit splitting were 3.5 meV and 39.9 meV. The gradual decrease of PC intensity with decreasing temperature can be explained on the basis of trapping centers associated with native defects in the MnAl2S4 layers. Plots of log J ph, the PC current density, against 1/ T, revealed a dominant trap level in the high-temperature region. By comparing PC and the Hall effect results, we confirmed that this trap level is a shallow donor 18.9 meV below the conduction band.

  11. Frost trends and their estimated impact on yield in the Australian wheatbelt

    PubMed Central

    Zheng, Bangyou; Chapman, Scott C.; Christopher, Jack T.; Frederiks, Troy M.; Chenu, Karine

    2015-01-01

    Radiant spring frosts occurring during reproductive developmental stages can result in catastrophic yield loss for wheat producers. To better understand the spatial and temporal variability of frost, the occurrence and impact of frost events on rain-fed wheat production was estimated across the Australian wheatbelt for 1957–2013 using a 0.05 ° gridded weather data set. Simulated yield outcomes at 60 key locations were compared with those for virtual genotypes with different levels of frost tolerance. Over the last six decades, more frost events, later last frost day, and a significant increase in frost impact on yield were found in certain regions of the Australian wheatbelt, in particular in the South-East and West. Increasing trends in frost-related yield losses were simulated in regions where no significant trend of frost occurrence was observed, due to higher mean temperatures accelerating crop development and causing sensitive post-heading stages to occur earlier, during the frost risk period. Simulations indicated that with frost-tolerant lines the mean national yield could be improved by up to 20% through (i) reduced frost damage (~10% improvement) and (ii) the ability to use earlier sowing dates (adding a further 10% improvement). In the simulations, genotypes with an improved frost tolerance to temperatures 1 °C lower than the current 0 °C reference provided substantial benefit in most cropping regions, while greater tolerance (to 3 °C lower temperatures) brought further benefits in the East. The results indicate that breeding for improved reproductive frost tolerance should remain a priority for the Australian wheat industry, despite warming climates. PMID:25922479

  12. Frost trends and their estimated impact on yield in the Australian wheatbelt.

    PubMed

    Zheng, Bangyou; Chapman, Scott C; Christopher, Jack T; Frederiks, Troy M; Chenu, Karine

    2015-06-01

    Radiant spring frosts occurring during reproductive developmental stages can result in catastrophic yield loss for wheat producers. To better understand the spatial and temporal variability of frost, the occurrence and impact of frost events on rain-fed wheat production was estimated across the Australian wheatbelt for 1957-2013 using a 0.05 ° gridded weather data set. Simulated yield outcomes at 60 key locations were compared with those for virtual genotypes with different levels of frost tolerance. Over the last six decades, more frost events, later last frost day, and a significant increase in frost impact on yield were found in certain regions of the Australian wheatbelt, in particular in the South-East and West. Increasing trends in frost-related yield losses were simulated in regions where no significant trend of frost occurrence was observed, due to higher mean temperatures accelerating crop development and causing sensitive post-heading stages to occur earlier, during the frost risk period. Simulations indicated that with frost-tolerant lines the mean national yield could be improved by up to 20% through (i) reduced frost damage (~10% improvement) and (ii) the ability to use earlier sowing dates (adding a further 10% improvement). In the simulations, genotypes with an improved frost tolerance to temperatures 1 °C lower than the current 0 °C reference provided substantial benefit in most cropping regions, while greater tolerance (to 3 °C lower temperatures) brought further benefits in the East. The results indicate that breeding for improved reproductive frost tolerance should remain a priority for the Australian wheat industry, despite warming climates. PMID:25922479

  13. Partial oxidation of liquid hydrocarbons in the presence of oxygen-conducting supports: Effect of catalyst layer deposition

    SciTech Connect

    Smith, M.; Berry, D.; Shekhawt, D.; Haynes, D.; Spivey, J.

    2010-01-01

    Ni-substituted barium hexaaluminate (BNHA) catalysts supported onto gadolinium-doped ceria (GDC), an oxygen-conductor, were prepared using two different methods: (1) conventional incipient wetness impregnation (IWI), in which a non-porous GDC support was impregnated in the conventional manner with aqueous precursors, then dried and calcined to form a supported hexaaluminate, and (2) solid-state mixing (SSM), in which solid hexaaluminate and GDC particles were mechanically ground together and thermally treated to produce a final catalyst. These catalysts were compared to bulk, unsupported BNHA; 3 wt% Ni/alumina; and 3 wt% Ni/GDC (the latter two prepared by conventional impregnation) for the partial oxidation (POX) of n-tetradecane. The reaction studies included examining the effect of 50 ppm S as dibenzothiophene (DBT) and 5 wt% 1-methylnaphthalene (MN) on the product yield under POX conditions. Temperature programmed oxidation (TPO) was used to characterize carbon formation in the reactor. The materials were characterized by BET, ICP-OES, XRD, and SEM/EDS prior to the reaction tests. Characterization of the two GDC-supported BNHA catalysts prior to the reaction studies indicated no significant differences in the bulk composition, surface area, and crystal structure. However, SEM images showed a larger amount of exposed GDC support surface area for the material prepared by IWI. Both of the GDC-supported BNHA materials demonstrated greatly reduced deactivation, with significantly reduced carbon formation compared to bulk BNHA. This was attributed to the oxygen-conducting property of the GDC, which reduced the rate of deactivation of the reaction sites by DBT and MN. The material prepared by IWI demonstrated more stable hydrogen and carbon monoxide yield than the material prepared by SSM. Although both catalysts deactivated in the presence of DBT and MN, the activity of the catalyst prepared by IWI recovered activity more quickly after the contaminants were removed. This material also maintained >50% of its initial hydrogen yield for more than 4 h after exposure to DBT and MN, while the hydrogen for the material prepared by SSM dropped to this same level within 2 h. Incipient wetness impregnation appears to provide a higher degree of interaction between the oxygenconducting GDC support and the hexaaluminate, resulting in less rapid deactivation, which appears to be due primarily to carbon deposition.

  14. High-resolution topography and albedo of the south polar layered deposits on Mars

    SciTech Connect

    Herkenhoff, K.E.; Murray, B.C. )

    1990-08-30

    Using a new photoclinometric technique with high-resolution Mariner 9 images, maximum slopes of 10{degree}-20{degree} are found to occur on an exposure of layered deposits within the south polar residual cap of Mars. Stereophotogrammetry is used to constrain the photoclinometric solutions, which resolve layer thicknesses of 100-300 m. Albedo variations are correlated with slope, indicating that frost is present on level areas. There is evidence for temporal changes in frost distribution in the 7 days (4{degree} of L{sub 8}) between the two images used in this study. The magnitude of the slopes derived here and consideration of the stability of water ice at the surface of the layered deposits strongly suggest the presence of a competent weathering rind. The weathered surface may be composed of dark filamentary sublimation residue particles that protect the underlying ice from solar heating. This hypothesis is consistent with previous studies of the regional color and albedo of the layered deposits, which indicate that the deposits are slightly darker and less red than the bright dust that mantles much of the south polar region. Furthermore, the proposed weathering mechanism provides a plausible source of dark, saltating material for the Martian polar dune fields.

  15. Large quasi-circular features beneath frost on Triton

    NASA Technical Reports Server (NTRS)

    Helfenstein, Paul; Veverka, Joseph; Mccarthy, Derek; Lee, Pascal; Hillier, John

    1992-01-01

    Specially processed Voyager 2 images of Neptune's largest moon, Triton, reveal three large quasi-circular features ranging in diameter from 280 to 935 km within Triton's equatorial region. The largest of these features contains a central irregularly shaped area of comparatively low albedo about 380 km in diameter, surrounded by crudely concentric annuli of higher albedo materials. None of the features exhibit significant topographic expression, and all appear to be primarily albedo markings. The features are located within a broad equatorial band of anomalously transparent frost that renders them nearly invisible at the large phase angles (alpha greater than 90 deg) at which Voyager obtained its highest resolution coverage of Triton. The features can be discerned at smaller phase angles (alpha = 66 deg) at which the frost only partially masks underlying albedo contrasts. The origin of the features is uncertain but may have involved regional cryovolcanic activity.

  16. Effects of environmental factors and management practices on microclimate, winter physiology, and frost resistance in trees

    PubMed Central

    Charrier, Guillaume; Ngao, Jérôme; Saudreau, Marc; Améglio, Thierry

    2015-01-01

    Freezing stress is one of the most important limiting factors determining the ecological distribution and production of tree species. Assessment of frost risk is, therefore, critical for forestry, fruit production, and horticulture. Frost risk is substantial when hazard (i.e., exposure to damaging freezing temperatures) intersects with vulnerability (i.e., frost sensitivity). Based on a large number of studies on frost resistance and frost occurrence, we highlight the complex interactive roles of environmental conditions, carbohydrates, and water status in frost risk development. To supersede the classical empirical relations used to model frost hardiness, we propose an integrated ecophysiologically-based framework of frost risk assessment. This framework details the individual or interactive roles of these factors, and how they are distributed in time and space at the individual-tree level (within-crown and across organs). Based on this general framework, we are able to highlight factors by which different environmental conditions (e.g., temperature, light, flood, and drought), and management practices (pruning, thinning, girdling, sheltering, water aspersion, irrigation, and fertilization) influence frost sensitivity and frost exposure of trees. PMID:25972877

  17. Chemical frost weathering of olivine: Experimental study and implications

    NASA Technical Reports Server (NTRS)

    Harris, S. L.; Huguenin, R. L.

    1987-01-01

    New experimental results are reported on the frost weathering of olivine. After first weathering, a decrease in Fe sup 2(+)M(2) absorption bands were noted. This decrease is related to the protonation of O(+) in the mineral. It is contented that this reaction may result in the regolith storage of 100 to 1000 m of H(sub 2) over the history of Mars.

  18. Frost Induces Respiration and Accelerates Carbon Depletion in Trees.

    PubMed

    Sperling, Or; Earles, J Mason; Secchi, Francesca; Godfrey, Jessie; Zwieniecki, Maciej A

    2015-01-01

    Cellular respiration depletes stored carbohydrates during extended periods of limited photosynthesis, e.g. winter dormancy or drought. As respiration rate is largely a function of temperature, the thermal conditions during such periods may affect non-structural carbohydrate (NSC) availability and, ultimately, recovery. Here, we surveyed stem responses to temperature changes in 15 woody species. For two species with divergent respirational response to frost, P. integerrima and P. trichocarpa, we also examined corresponding changes in NSC levels. Finally, we simulated respiration-induced NSC depletion using historical temperature data for the western US. We report a novel finding that tree stems significantly increase respiration in response to near freezing temperatures. We observed this excess respiration in 13 of 15 species, deviating 10% to 170% over values predicted by the Arrhenius equation. Excess respiration persisted at temperatures above 0°C during warming and reoccurred over multiple frost-warming cycles. A large adjustment of NSCs accompanied excess respiration in P. integerrima, whereas P. trichocarpa neither excessively respired nor adjusted NSCs. Over the course of the years included in our model, frost-induced respiration accelerated stem NSC consumption by 8.4 mg (glucose eq.) cm-3 yr-1 on average in the western US, a level of depletion that may continue to significantly affect spring NSC availability. This novel finding revises the current paradigm of low temperature respiration kinetics. PMID:26629819

  19. Morning Frost in Trench Dug by Phoenix, Sol 113

    NASA Technical Reports Server (NTRS)

    2008-01-01

    This image from the Surface Stereo Imager on NASA's Phoenix Mars Lander shows morning frost inside the 'Snow White' trench dug by the lander, in addition to subsurface ice exposed by use of a rasp on the floor of the trench.

    The camera took this image at about 9 a.m. local solar time during the 113th Martian day of the mission (Sept. 18, 2008). Bright material near and below the four-by-four set of rasp holes in the upper half of the image is water-ice exposed by rasping and scraping in the trench earlier the same morning. Other bright material especially around the edges of the trench, is frost. Earlier in the mission, when the sun stayed above the horizon all night, morning frost was not evident in the trench.

    This image is presented in approximately true color.

    The trench is 4 to 5 centimeters (about 2 inches) deep, about 23 centimeters (9 inches) wide.

    Phoenix landed on a Martian arctic plain on May 25, 2008. The mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is led by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development was by Lockheed Martin Space Systems, Denver.

  20. CRYOLINK: Monitoring of permafrost and seasonal frost in southern Norway

    NASA Astrophysics Data System (ADS)

    Farbrot, Herman; Hipp, Tobias; Etzelmüller, Bernd; Humlum, Ole; Isaksen, Ketil; Strand Ødegârd, Rune

    2010-05-01

    The modern southern boundary for Scandinavian permafrost is located in the mountains of Southern Norway. Permafrost and seasonal frost are considered key components of the cryosphere, and the climate-permafrost relation has acquired added importance with the increasing awareness and concern of rising air temperatures. The three-year research project CRYOLINK ("Permafrost and seasonal frost in southern Norway") aims at improving knowledge on past and present ground temperatures, seasonal frost, and distribution of mountain permafrost in Southern Norway by addressing the fundamental problem of heat transfer between the atmosphere and the ground surface. Hence, several shallow boreholes have been drilled in August 2008 in three areas (Juvvass, Jetta and Tron) situated along a west-east transect. On most borehole sites air and ground temperatures are measured. Further, vertical arrays of Miniature Temperature Dataloggers (MTDs; Thermochron iBottons®) at fixed heights above the ground surface have been installed to roughly determine the snow depths at the sites, which is also indicated by digital cameras providing daily pictures of snow and weather conditions. In addition individual MTDs have been placed out to measure ground surface temperature at different aspects and snow settings. This presentation will focus on the field set up and give examples of data obtained from the sites.

  1. Frost Induces Respiration and Accelerates Carbon Depletion in Trees

    PubMed Central

    Sperling, Or; Earles, J. Mason; Secchi, Francesca; Godfrey, Jessie; Zwieniecki, Maciej A.

    2015-01-01

    Cellular respiration depletes stored carbohydrates during extended periods of limited photosynthesis, e.g. winter dormancy or drought. As respiration rate is largely a function of temperature, the thermal conditions during such periods may affect non-structural carbohydrate (NSC) availability and, ultimately, recovery. Here, we surveyed stem responses to temperature changes in 15 woody species. For two species with divergent respirational response to frost, P. integerrima and P. trichocarpa, we also examined corresponding changes in NSC levels. Finally, we simulated respiration-induced NSC depletion using historical temperature data for the western US. We report a novel finding that tree stems significantly increase respiration in response to near freezing temperatures. We observed this excess respiration in 13 of 15 species, deviating 10% to 170% over values predicted by the Arrhenius equation. Excess respiration persisted at temperatures above 0°C during warming and reoccurred over multiple frost-warming cycles. A large adjustment of NSCs accompanied excess respiration in P. integerrima, whereas P. trichocarpa neither excessively respired nor adjusted NSCs. Over the course of the years included in our model, frost-induced respiration accelerated stem NSC consumption by 8.4 mg (glucose eq.) cm-3 yr-1 on average in the western US, a level of depletion that may continue to significantly affect spring NSC availability. This novel finding revises the current paradigm of low temperature respiration kinetics. PMID:26629819

  2. Unsteady MHD boundary layer stagnation point flow with heat and mass transfer in nanofluid in the presence of mass fluid suction and thermal radiation

    NASA Astrophysics Data System (ADS)

    Salem, A. M.; Ismail, Galal; Fathy, Rania

    2015-06-01

    The unsteady boundary layer stagnation point flow of heat and mass transfer in a nanofluid with magnetic field and thermal radiation is theoretically investigated. The resulting governing equations are nondimensionalized and are transformed using a similarity transformation and then solved numerically by the shooting method. Comparison with the previously published work is presented and the results are found to be in good agreement. The effects of unsteadiness parameter A , solid volume fraction , magnetic field M, radiation parameter R, Schmidit number Sc and suction parameter w on the fluid flow, heat and mass transfer characteristic are discussed. Dual similarity solutions for the velocity, temperature and concentration profiles are obtained for some negative values of the unsteadiness parameter. It is found that the critical values of A for which the dual solution exists depend on the values of solid volume fraction parameter in the presence of the Schmidit number. Also, the magnetic field parameter as well as the mass fluid suction widen the range of A for which the solution exists. The results also indicate that momentum, thermal and concentration boundary layer thickness for the first solution are thinner than that of the second solution.

  3. Influence of Salt Stress on Growth and Frost Resistance of Three Winter Cereals

    NASA Astrophysics Data System (ADS)

    Matuszak-Slamani, Renata; Brzóstowicz, Aleksander

    2015-04-01

    This paper presents results of a study on the influence of 0-150 mmol NaCl dm-3 Hoagland solution on growth, chlorophyll content, photosynthesis and frost resistance of seedlings of three winter cereals: wheat - cv. Almari, rye - cv. Amilo, and triticale - cv. Tornado. Sodium chloride at 25 mmol dm-3 caused better growth of wheat shoots and roots, both of fresh and dry matter. Higher concentrations of NaCl in the medium decreased the biomass of the tested seedlings. The influence of NaCl on the chlorophyll content in the seedlings varied. The conductometry method showed that the resistance of the cell walls of wheat and rye to low temperature decreased in the presence of NaCl in the growth medium. Luminescence has shown that seedlings that grew in NaCl-containing medium indicated an impediment of electron flow at a lower temperature than the control plants.

  4. Numerical Analysis of the Channel Wheel Fresh Air Ventilator Under Frosting Conditions 

    E-print Network

    Gao, B.; Dong, Z.; Cheng, Z.; Luo, E.

    2006-01-01

    , China HVAC Technologies for Energy Efficiency Vol.IV-4-4 Numerical Analysis of the Channel Wheel Fresh Air Ventilator Under Frosting Conditions Bo Gao Zhongcheng Dong Zhigang Cheng Ercang Luo Doctoral Master....IV-4-4 first term represents the amount of water vapor condensed contributing to the increase of frost thickness, andthesecond term to the increase of frost density. Yang Yao [12] used the following expression for themass...

  5. Martian Seasonal CO2 Frost Indicating Decameter-Scale Variability in Buried Water Ice

    NASA Astrophysics Data System (ADS)

    Mellon, M. T.; Hansen, C. J.; Cull, S.; Arvidson, R. E.; Searls, M.

    2011-12-01

    Several new lines of evidence indicate that subsurface water ice (ground ice) on Mars is more complexly distributed, and in variable concentrations, than had been previously envisioned. Understanding the current distribution of ground ice is a fundamental part of understanding how this ice was emplaced and the recent past climate conditions under which icy deposits formed and subsequently evolved. In this work we examine the seasonal defrosting of CO2 observed by HiRISE as an indicator of decameter-scale ground-ice heterogeneity. It is well known that CO2 dry ice accumulates on the martian surface in winter. The amount of dry ice and the time it spends on the ground depends strongly on surface properties. A readily observable attribute is the "crocus date", the season (Ls) when CO2 completely sublimates, exposing the soil surface. Many factors can affect the crocus date, but perhaps most important are the properties of CO2 frost and of the surface soil. We examine HiRISE observations, spanning more than a martian year, for decameter-scale patterns of CO2 frost and the crocus date. Year-to-year repeatability of CO2 ice patterns, both in polygon troughs and decameter-size patches, along with a lack of topography nor aeolian redistribution, suggests that differences in the surface substrate is the root cause for these patterns. In addition, only CO2 slab ice (solid, non-porous dry ice) is indicated throughout the observed seasons and at all spatial scales (down to meter scale), as evidenced by albedo (HiRISE and TES) and IR spectra (CRISM). In addition, the low emissivity and high albedo of fine-grained particulate CO2 frost would result in a crocus date much earlier than even the earliest observed. We present two scenarios of substrate differences which explain the observations: (i) the ice-table depth varies away from atmospheric equilibrium, such that a thicker "dry-soil" layer occurs in disequilibrium where the CO2 ice lingers longest; and (ii) the H2O concentration at the ice table and below is less than pore filling (or that subsurface pure-water-ice deposits contain substantial open porosity) in these same lingering CO2-ice locations. In the later case these CO2 ice patches may be outlining deposits of the light-toned, friable, pure water ice as was discovered by Phoenix. Neither of these two ground-ice scenarios is predicted by the current models of ground ice stability and dynamics. These results indicate substantial decameter-scale heterogeneity in the ground ice distribution and local disequilibrium with the current martian climate.

  6. Ice/frost/debris assessment for space shuttle Mission STS-32 (61-C)

    NASA Technical Reports Server (NTRS)

    Stevenson, Charles G.; Katnik, Gregory N.; Speece, Robert F.

    1986-01-01

    An Ice/Frost/Debris assessment was conducted for Space Shuttle Mission STS-32 (61-C). This assessment begins with debris inspections of the flight elements and launch facilities before and after launch. Ice/Frost formations are calculated during cryogenic loading of the external tank followed by an on-pad assessment of the Shuttle vehicle and pad at T-3 hours in the countdown. High speed films are reviewed after launch to identify Ice/Frost/Debris sources and investigate potential vehicle damage. The Ice/Frost/Debris conditions and their effects on the Space Shuttle are documented.

  7. Experimental assessment on the frost sensitivity during leaf development of juvenile Fagus sylvatica L.

    NASA Astrophysics Data System (ADS)

    Estrella, Nicole; Menzel, Annette

    2014-05-01

    Late frost events in spring shape species distribution as well as reduce productivity. Till now, it is still not clear if future warming will lead to more frequent / stronger / more harmful frost damages in forestry and agriculture or not. Since the variability of extremes is increasing it seems that the risk of late frost damages in many regions may not decrease, even if the mean air temperature in general is increasing. A late frost event is only harmful if plants have initiated their leaf / flower development. Closed buds are usually very frost tolerant. However, once leaves develop after mild and warm spring periods, the new tissue is especially sensitive to freezing temperatures. Therefore not only the date of the last frost but also the weather history of the late winter / early spring determines if a frost event might result in frost damage or not. Tissue sensitivity to frost varies among species, but even within species there might be differences in frost tolerance during the different stages in leaf development. We set up an experiment to identify the frost risk in connection with the developmental stage of the leaves of juvenile beech. In order to vary the timing of frost events, we placed 1-year old potted beech trees 7times overnight in a climate chamber, in which the air temperature was cooled down to - 3° for five hours. For each tree the phenological stages were observed before and after the frost, the percent of damage was estimated after two days; additionally phenology of the damaged plants was observed weekly to document the recovery of their damage till May 23, 2013. Only about 30% of the plants were damaged. In general it can be stated if damage occurred it was a severe damage, only very few plants sustained little damage. We observed dependence on the date of the freezing event, rather than on specific phenological phases - the later the frost was applied the more plants were damaged. Damaged plants recovered relatively rapidly from the frost damage; three to six weeks after the event most of the damage plants were foliated equally to non-damaged plants. Only a few plants did not recover at all from the frost event.

  8. Linking the Presence of Surfactant Associated Bacteria on the Sea Surface and in the Near Surface Layer of the Ocean to Satellite Imagery

    NASA Astrophysics Data System (ADS)

    Hamilton, Bryan; Dean, Cayla; Kurata, Naoko; Soloviev, Alex; Tartar, Aurelien; Shivji, Mahmood; Perrie, William; Lehner, Susanne

    2015-04-01

    Several genera of bacteria residing on the sea surface and in the near-surface layer of the ocean have been found to be involved in the production and decay of surfactants. Under low wind speed conditions, these surfactants can suppress short gravity capillary waves at the sea surface and form natural sea slicks. These features can be observed with both airborne and satellite-based synthetic aperture radar (SAR). We have developed a new method for sampling the sea surface microlayer that has reduced contamination from the boat and during lab handling of samples. Using this new method, a series of experiments have been conducted to establish a connection between the presence of surfactant-associated bacteria in the upper layer of the ocean and sea slicks. DNA analysis of in situ samples taken during a RADARSAT-2 satellite overpass in the Straits of Florida during the 2010 Deepwater Horizon oil spill showed a higher abundance of surfactant-associated bacterial genera in the slick area as compared to the non-slick area. These genera were found to be more abundant in the subsurface water samples collected as compared to samples taken from the sea surface. The experiment was repeated in the Straits of Florida in September 2013 and was coordinated with TerraSAR-X satellite overpasses. The observations suggest that the surfactants contributing to sea slick formation are produced by marine bacteria in the organic matter-rich water column and move to the sea surface by diffusion or advection. Thus, within a range of wind-wave conditions, the organic materials present in the water column (such as dissolved oil spills) can be monitored with SAR satellite imagery. In situ sampling was also performed in the Gulf of Mexico in December 2013 during RADARSAT-2 and TerraSAR-X satellite overpasses. Areas near natural oil seeps identified from archived TerraSAR-X imagery were targeted for in situ sampling. A number of samples from this location have been analyzed to determine the presence and relative abundance levels of one genus of surfactant-associated bacteria. Determining the effect of surfactant-associated bacteria on the state of the sea surface may help provide a more complete global picture of biophysical processes at the air-sea interface and uptake of greenhouse gases by the ocean.

  9. Ice barriers promote supercooling and prevent frost injury in reproductive buds, flowers and fruits of alpine dwarf shrubs throughout the summer?

    PubMed Central

    Kuprian, Edith; Briceño, Verónica F.; Wagner, Johanna; Neuner, Gilbert

    2014-01-01

    Over-wintering reproductive buds of many woody plants survive frost by supercooling. The bud tissues are isolated from acropetally advancing ice by the presence of ice barriers that restrict ice growth. Plants living in alpine environments also face the risk of ice formation in summer months. Little knowledge exists, how reproductive structures of woody alpine plants are protected from frost injury during episodic summer frosts. In order to address this question, frost resistance of three common dwarf shrubs, Calluna vulgaris, Empetrum hermaphroditum and Loiseleuria procumbens was measured and ice formation and propagation were monitored in twigs bearing reproductive shoots during various stages of reproductive development (bud, anthesis, and fruit) throughout the alpine summer. Results indicated that, in the investigated species, ice barriers were present at all reproductive stages, isolating the reproductive shoots from ice advancing from the subtending vegetative shoot. Additionally, in the reproductive stems ice nucleating agents that are active at warm, sub-zero temperatures, were absent. The ice barriers were 100% effective, with the exception of L. procumbens, where in 13% of the total observations, the ice barrier failed. The ice barriers were localized at the base of the pedicel, at the anatomical junction of the vegetative and reproductive shoot. There, structural aspects of the tissue impede or prevent ice from advancing from the frozen stem into the pedicel of the reproductive shoot. Under the experimental conditions used in this study, ice nucleation initially occurred in the stem of the vegetative shoot at species-specific mean temperatures in the range of ?4.7 to ?5.8 °C. Reproductive shoots, however, remained supercooled and ice free down to a range of ?7.2 to ?18.2 °C or even below ?22 °C, the lowest temperature applied in the study. This level of supercooling is sufficient to prevent freezing of reproductive structures at the lowest air temperature occurring at the altitude of the upper distribution boundary of the natural habitat of the investigated species which is between ?8 and ?10 °C in summer. Frost resistance assays indicated that reproductive shoots are much less frost resistant than vegetative stems, and in contrast to vegetative shoots, are not ice tolerant. Supercooling of reproductive shoots in alpine, woody plant species is an effective mechanism that protects developing offspring from potential frost damage resulting from episodic summer freezing events. PMID:25284910

  10. GIVRE: A Protection Against Frost Deposit on Polar Instruments

    NASA Astrophysics Data System (ADS)

    Durand, G.; Cadelis, L.; Minier, V.; Veyssière, C.; Walter, C.; Pierre, A.; Agabi, A.; Fossat, E.; Jeanneaux, F.

    The CEA, in coordination with IPEV and LUAN, will prepare an experiment to study frost formation on surfaces in radiative cooling in the winter. This experiment has been shipped to be installed at Concordia before the 2007 winter period. It will be controlled from Concordia winterover personal, through PC server that will locally archive data from WEBcams and several local heat regulators. This experiment will be used to give recipes on the way to compensate with heaters the radiative cooling from the sky and maintain instrument surfaces at temperature just above icing conditions. The individual regulators proposed in this experiment will be usable as standalone ice protection systems for existing and future telescopes.

  11. A search for transient water frost at the lunar poles using LOLA

    NASA Astrophysics Data System (ADS)

    Lemelin, M.; Lucey, P. G.; Song, E.; Paige, D. A.; Greenhagen, B. T.; Siegler, M. A.; Hayne, P. O.; Mazarico, E.; Neumann, G.; Smith, D. E.; Zuber, M. T.

    2014-12-01

    The possibility of lunar polar ice has been considered since suggested by Harold Urey in the 1950's, and has likely been directly detected at the north pole of Mercury by MESSENGER. That detection was based on the presence of reflectance anomalies seen by the Mercury Laser Altimeter that occurred only where models of the surface temperature allow long-duration preservation of water ice against sublimation (Paige et al., 2013; Neumann et al., 2013). Similar characteristics are seen at the poles of the Moon, though the higher lunar albedo complicates the detection. In this study we seek evidence for transient water frost on polar surfaces using data from the Lunar Orbiter Laser Altimeter. The Lunar Orbiter Laser Altimeter (LOLA) measures the backscattered energy of the returning altimetric laser pulse at its wavelength of 1064 nm, and these data are used to map the reflectivity of the Moon at zero-phase angle with a photometrically uniform data set. Global maps have been produced at 4 pixels per degree (about 8 km at the equator) and 2 km resolution within 20° latitude of each pole. The zero-phase geometry is insensitive to lunar topography and enables the characterization of subtle variations in lunar albedo, even at high latitudes where such measurements are not possible with the Sun as the illumination source. We are currently searching the data set for evidence of transient surface frost by looking for changes in reflectance as a function of temperature based on the Diviner radiometer measurements and models. Thus far one candidate region has been identified, and we are refining the calibration to ensure that this and other detections are reliable.

  12. Impacts of future climate change on soil frost in the midwestern United States

    E-print Network

    Sinha, Tushar

    Click Here for Full Article Impacts of future climate change on soil frost in the midwestern United: Sinha, T., and K. A. Cherkauer (2010), Impacts of future climate change on soil frost in the midwestern winter may lead to colder soil temperatures in the future. Cumulatively, these changes will affect cold

  13. Past and future changes in frost day indices on Catskill Mountains region of New York

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Changes in frost indices in New York's Catskill Mountains region, the location of water supply reservoirs for New York City, have potentially important implications. Frost day is defined as a day with Tmin < 0 deg C. The objective of this study was to investigate past and predicted changes in minimu...

  14. Minimal Spray Strategy for Frosted Apple Trees Nikki Rothwell, District Fruit IPM Educator

    E-print Network

    1 Minimal Spray Strategy for Frosted Apple Trees Nikki Rothwell, District Fruit IPM Educator Amy Irish-Brown, District Fruit IPM Educator Jim Nugent, District Horticulturist 2006 After the early morning frost of Saturday, May 6th , many apples in the northwest region were affected. Based on some

  15. Simulating Snowmelt and Soil Frost Depth by an Energy Budget Approach

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The occurrence of snow and soil frost influences hydrology and, in turn, the mechanics of soil erosion processes in cold regions. For these regions, reliably modeling the dynamics of snow accumulation and melt, and soil frost formation and melt, is necessary prior to accurately predicting runoff an...

  16. Prediction of soil frost penetration depth in northwest of Iran using air freezing indices

    NASA Astrophysics Data System (ADS)

    Mohammadi, H.; Moghbel, M.; Ranjbar, F.

    2015-08-01

    Information about soil frost penetration depth can be effective in finding appropriate solutions to reduce the agricultural crop damage, transportations, and building facilities. Amongst proper methods to achieve this information are the statistical and empirical models capable of estimating soil frost penetration depth. Therefore, the main objective of this research is to calculate soil frost penetration depth in northwest of Iran during the year 2007-2008 to validate two different models accuracy. To do so, the relationship between air and soil temperature in different depths (5-10-20-30-50-100 cm) at three times of the day (3, 9, and 15 GMT) for 14 weather stations over 7 provinces was analyzed using linear regression. Then, two different air freezing indices (AFIs) including Norwegian and Finn AFI was implemented. Finally, the frost penetration depth was calculated by McKeown method and the accuracy of models determined by actual soil frost penetration depth. The results demonstrated that there is a significant correlation between air and soil depth temperature in all studied stations up to the 30 cm under the surface. Also, according to the results, Norwegian index can be effectively used for determination of soil frost depth penetration and the correlation coefficient between actual and estimated soil frost penetration depth is r = 0.92 while the Finn index overestimates the frost depth in all stations with correlation coefficient r = 0.70.

  17. Past and future changes in frost day indices on Catskill Mountain Region of New York

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Changes in frost indices in the New York’s Catskill Mountains region, the location of water supply reservoirs for New York City, have potentially important implications. Frost day is defined as a day with Tmin < 0ºC. The objective of this study was to investigate past and predicted changes in minimu...

  18. Dew and frost chemistry at a midcontinent site, United States

    SciTech Connect

    Wagner, G.H.; Steele, K.F. ); Peden, M.E. )

    1992-12-20

    Little national effort is being devoted to appraising the importance of dew in the research on acid rain and atmospheric pollutants. Because dew lingers directly on plants and is perhaps more concentrated than rain, especially during its evaporation, it may overshadow certain rain effects which work mainly through the soil. From July 1989 to July 1990 a total of 98 dew and 9 frost samples were collected at the University of Arkansas Agricultural Experiment Station, Fayetteville. The total water flux from dews and frosts per year was less than 2% of that from rains. Acid and nutrient fluxes were also much lower in dew. In the following series of ions the number in parentheses gives the percent of the yearly flux of the ion in dew compared to rain for the same time period: H[sup +] (0.06), Ca[sup 2+] (25), Mg[sup 2+] (11), K[sup +] (21), Na[sup +] (4), NH[sub 4][sup +] (10), Cl[sup [minus

  19. Importance of soil frost and winter climate for dissolved organic carbon (DOC) in northern boreal soils

    NASA Astrophysics Data System (ADS)

    Haei, M.; Öquist, M.; Laudon, H.

    2011-12-01

    In many northern latitude regions, riparian soils are significant sources of DOC to the adjacent streams and exert a major control on stream water chemistry. As the winter climate in northern regions is predicted to be particularly affected by climate change, it is important to investigate the sensitivity of DOC in riparian soils. We conducted an eight year field-scale soil frost manipulation experiment (deep soil frost, shallow soil frost and control) to investigate the impacts of soil frost and winter conditions on the concentration and quality of DOC in riparian soil water in a boreal forest of northern Sweden. The effect of soil freezing on DOC was further investigated in a laboratory experiment on the riparian soil samples. In the laboratory experiment, we studied several combinations of four freezing related factors: low experiment temperature, water content, experiment duration and frequency of freeze-thaw cycles. Deeper and longer soil frost significantly increased the soil water DOC concentrations (up to twice) and lability in the upper soil horizons, compared to shallower and shorter soil frost. In the laboratory experiment, similar responses of soil water DOC were observed in which the highest concentration and lability were observed in the samples incubated in the lowest temperatures (-12°C). Furthermore, fungal growth rate and soil basal respiration responded positively to soil frost induced increase in DOC concentration. The frequency of freeze-thaw cycle did not appear to be an influential factor in the laboratory experiment. Several significant interactions of the factors were also detected. In addition, we studied the alterations in soil water DOC concentrations as the soil frost expanded downwards in a mire profile during the soil frost season (Nov-May). As the soil frost deepened from Nov to Feb, the soil water DOC concentrations below the ice increased. At soil frost thaw in May, the DOC concentrations decreased to the initial levels measured at the onset of soil frost formation. In a complementary freeze-out experiment in the laboratory, we observed that DOC concentrations in the unfrozen water enhanced as the frozen proportion of the sample increased, so that the DOC concentrations doubled when 75% of the sample was frozen. Here we highlight the importance of soil frost regime and winter climatic conditions for regulating DOC in riparian forest soils and in mires in seasonally frozen soils. However, to assess the sensitivity of soil DOC to climate change, the complex interactions of air temperature, snow depth and soil frost together with changes in hydrology and soil microbial community should be taken into account.

  20. Activating the Microscale Edge Effect in a Hierarchical Surface for Frosting Suppression and Defrosting Promotion

    PubMed Central

    Chen, Xuemei; Ma, Ruiyuan; Zhou, Hongbo; Zhou, Xiaofeng; Che, Lufeng; Yao, Shuhuai; Wang, Zuankai

    2013-01-01

    Despite extensive progress, current icephobic materials are limited by the breakdown of their icephobicity in the condensation frosting environment. In particular, the frost formation over the entire surface is inevitable as a result of undesired inter-droplet freezing wave propagation initiated by the sample edges. Moreover, the frost formation directly results in an increased frost adhesion, posing severe challenges for the subsequent defrosting process. Here, we report a hierarchical surface which allows for interdroplet freezing wave propagation suppression and efficient frost removal. The enhanced performances are mainly owing to the activation of the microscale edge effect in the hierarchical surface, which increases the energy barrier for ice bridging as well as engendering the liquid lubrication during the defrosting process. We believe the concept of harnessing the surface morphology to achieve superior performances in two opposite phase transition processes might shed new light on the development of novel materials for various applications. PMID:23981909

  1. Managing Potato Biodiversity to Cope with Frost Risk in the High Andes: A Modeling Perspective

    PubMed Central

    Condori, Bruno; Hijmans, Robert J.; Ledent, Jean Francois; Quiroz, Roberto

    2014-01-01

    Austral summer frosts in the Andean highlands are ubiquitous throughout the crop cycle, causing yield losses. In spite of the existing warming trend, climate change models forecast high variability, including freezing temperatures. As the potato center of origin, the region has a rich biodiversity which includes a set of frost resistant genotypes. Four contrasting potato genotypes –representing genetic variability- were considered in the present study: two species of frost resistant native potatoes (the bitter Solanum juzepczukii, var. Luki, and the non-bitter Solanum ajanhuiri, var. Ajanhuiri) and two commercial frost susceptible genotypes (Solanum tuberosum ssp. tuberosum var. Alpha and Solanum tuberosum ssp. andigenum var. Gendarme). The objective of the study was to conduct a comparative growth analysis of four genotypes and modeling their agronomic response under frost events. It included assessing their performance under Andean contrasting agroecological conditions. Independent subsets of data from four field experiments were used to parameterize, calibrate and validate a potato growth model. The validated model was used to ascertain the importance of biodiversity, represented by the four genotypes tested, as constituents of germplasm mixtures in single plots used by local farmers, a coping strategy in the face of climate variability. Also scenarios with a frost routine incorporated in the model were constructed. Luki and Ajanhuiri were the most frost resistant varieties whereas Alpha was the most susceptible. Luki and Ajanhuiri, as monoculture, outperformed the yield obtained with the mixtures under severe frosts. These results highlight the role played by local frost tolerant varieties, and featured the management importance –e.g. clean seed, strategic watering- to attain the yields reported in our experiments. The mixtures of local and introduced potatoes can thus not only provide the products demanded by the markets but also reduce the impact of frosts and thus the vulnerability of the system to abiotic stressors. PMID:24497912

  2. Arctic organic aerosol measurements show particles from mixed combustion in spring haze and from frost flowers in winter

    E-print Network

    combustion in spring haze and from frost flowers in winter P. M. Shaw,1 L. M. Russell,1 A. Jefferson,2 and P of the Northwest Territories of Canada. Frost flowers with organicsalt coatings that arise by brine rejection in spring haze and from frost flowers in winter, Geophys. Res. Lett., 37, L10803, doi:10.1029/2010GL042831

  3. Early spring, severe frost events, and drought induce rapid carbon loss in high elevation meadows.

    PubMed

    Arnold, Chelsea; Ghezzehei, Teamrat A; Berhe, Asmeret Asefaw

    2014-01-01

    By the end of the 20th century, the onset of spring in the Sierra Nevada mountain range of California has been occurring on average three weeks earlier than historic records. Superimposed on this trend is an increase in the presence of highly anomalous "extreme" years, where spring arrives either significantly late or early. The timing of the onset of continuous snowpack coupled to the date at which the snowmelt season is initiated play an important role in the development and sustainability of mountain ecosystems. In this study, we assess the impact of extreme winter precipitation variation on aboveground net primary productivity and soil respiration over three years (2011 to 2013). We found that the duration of snow cover, particularly the timing of the onset of a continuous snowpack and presence of early spring frost events contributed to a dramatic change in ecosystem processes. We found an average 100% increase in soil respiration in 2012 and 2103, compared to 2011, and an average 39% decline in aboveground net primary productivity observed over the same time period. The overall growing season length increased by 57 days in 2012 and 61 days in 2013. These results demonstrate the dependency of these keystone ecosystems on a stable climate and indicate that even small changes in climate can potentially alter their resiliency. PMID:25207640

  4. Early Spring, Severe Frost Events, and Drought Induce Rapid Carbon Loss in High Elevation Meadows

    PubMed Central

    Arnold, Chelsea; Ghezzehei, Teamrat A.; Berhe, Asmeret Asefaw

    2014-01-01

    By the end of the 20th century, the onset of spring in the Sierra Nevada mountain range of California has been occurring on average three weeks earlier than historic records. Superimposed on this trend is an increase in the presence of highly anomalous “extreme” years, where spring arrives either significantly late or early. The timing of the onset of continuous snowpack coupled to the date at which the snowmelt season is initiated play an important role in the development and sustainability of mountain ecosystems. In this study, we assess the impact of extreme winter precipitation variation on aboveground net primary productivity and soil respiration over three years (2011 to 2013). We found that the duration of snow cover, particularly the timing of the onset of a continuous snowpack and presence of early spring frost events contributed to a dramatic change in ecosystem processes. We found an average 100% increase in soil respiration in 2012 and 2103, compared to 2011, and an average 39% decline in aboveground net primary productivity observed over the same time period. The overall growing season length increased by 57 days in 2012 and 61 days in 2013. These results demonstrate the dependency of these keystone ecosystems on a stable climate and indicate that even small changes in climate can potentially alter their resiliency. PMID:25207640

  5. Balloon borne observations of backscatter, frost point and ozone in polar stratospheric clouds at the South Pole

    SciTech Connect

    Rosen, J.M.; Kjome, N.T. ); Oltmans, S.J. )

    1991-02-01

    Concurrent backscatter and ozone measurements were made with near-simultaneous frost point soundings over the South Pole when the center of the 1990 winter vortex was at or very near that location. The initial water vapor concentration in the stratosphere was {approximately}5ppmv and decreased to {approximately}1.5-2.0 ppmv as cooling took place. By mid-July the stratospheric temperature had decreased to the frost point and heavy polar stratospheric cloud (PSC) activity was observed presumably due to the condensation of water vapor. The lowest water vapor concentrations observed correspond to saturated air at the lowest temperatures encountered. The slow recovery of the water vapor concentration during spring warming indicates that the 12 to 22 km altitude region in the vortex is not readily penetrated by outside air. The observed large decrease in PSC backscatter above {approximately}14 km before the stratosphere began to warm is consistent with loss of particles by sedimentation leading to significant dehydration and denitrification. The region of PSC activity in July is noted to be in the same region in which ozone depletion and the persistent dehydration is observed later in the year. At the end of August heavy PSC activity was observed in the lower stratosphere and upper troposphere, consistent with earlier observations from NASA aircraft. These lower clouds were in a region that apparently was still experiencing cooling. No compelling evidence was found surrounding earlier claims that PSC layers are anti-correlated with ozone inside the vortex.

  6. Characterization of frost susceptibility of soils by mercury porosimetry

    SciTech Connect

    Haiying Fu; Dash, J.G. . Dept. of Physics)

    1993-09-01

    Mercury porosimetry is described as a method for rapid and detailed prediction of the water-ice phase fraction in porous media. The mercury volume-intrusion pressure approximates the functional dependence of the ice volume-temperature curve in the range most important for frost heave, i.e., within a few degrees of the transition. The method was tested by comparing porosimetry-based predicted freezing curves against direct measurements of the ice-water ratio by time domain reflectometry, for several types of artificial powders and natural soils. The technique includes a simple method of correction for tile effects of solutes in the dilute range. Except for compression effects produced in powders of very fine particles, the soil freezing curve (SFC) predicted on the basis of mercury porosimetry is found to be in very good agreement with the directly measured freezing curves.

  7. Seasonal frost effects on the dynamic behavior of a twenty-story office building

    USGS Publications Warehouse

    Yang, Z.; Dutta, U.; Xiong, F.; Biswas, N.; Benz, H.

    2008-01-01

    Studies have shown that seasonal frost can significantly affect the seismic behavior of a bridge foundation system in cold regions. However, little information could be found regarding seasonal frost effects on the dynamic behavior of buildings. Based on the analysis of building vibration data recorded by a permanent strong-motion instrumentation system, the objective of this paper is to show that seasonal frost can impact the building dynamic behavior and the magnitude of impact may be different for different structures. Ambient noise and seismic data recorded on a twenty-story steel-frame building have been analyzed to examine the building dynamic characteristics in relationship to the seasonal frost and other variables including ground shaking intensity. Subsequently, Finite Element modeling of the foundation-soil system and the building superstructure was conducted to verify the seasonal frost effects. The Finite Element modeling was later extended to a reinforced-concrete (RC) type building assumed to exist at a similar site as the steel-frame building. Results show that the seasonal frost has great impact on the foundation stiffness in the horizontal direction and a clear influence on the building dynamic behavior. If other conditions remain the same, the effects of seasonal frost on structural dynamic behavior may be much more prominent for RC-type buildings than for steel-frame buildings. ?? 2007 Elsevier B.V. All rights reserved.

  8. Quasi-two-layer finite-volume scheme for modeling shallow water flows over an arbitrary bed in the presence of external force

    E-print Network

    1 Quasi-two-layer finite-volume scheme for modeling shallow water flows over an arbitrary bed. G. Slavin). Finite-volume numerical method for study shallow water flows over an arbitrary bed in one-layer finite-difference representation of balance equations. These terms provide the mechanical

  9. Habitat characteristics of adult frosted elfins (Callophrys irus) in sandplain communities of southeastern Massachusetts, USA

    USGS Publications Warehouse

    Albanese, G.; Vickery, P.D.; Sievert, P.R.

    2007-01-01

    Changes to land use and disturbance frequency threaten disturbance-dependent Lepidoptera within sandplain habitats of the northeastern United States. The frosted elfin (Callophrys irus) is a rare and declining monophagous butterfly that is found in xeric open habitats maintained by disturbance. We surveyed potential habitat for adult frosted elfins at four sites containing frosted elfin populations in southeastern Massachusetts, United States. Based on the survey data, we used kernel density estimation to establish separate adult frosted elfin density classes, and then used regression tree analysis to describe the relationship between density and habitat features. Adult frosted elfin density was greatest when the host plant, wild indigo (Baptisia tinctoria), density was >2.6 plants/m2 and tree canopy cover was <29%. Frosted elfin density was inversely related to tree cover and declined when the density of wild indigo was <2.6 plants/m2 and shrub cover was ???16%. Even small quantities of non-native shrub cover negatively affected elfin densities. This effect was more pronounced when native herbaceous cover was <36%. Our results indicate that management for frosted elfins should aim to increase both wild indigo density and native herbaceous cover and limit native tree and shrub cover in open sandplain habitats. Elimination of non-native shrub cover is also recommended because of the negative effects of even low non-native shrub cover on frosted elfin densities. The maintenance of patches of early successional sandplain habitat with the combination of low tree and shrub cover, high host plant densities, and the absence of non-native shrubs appears essential for frosted elfin persistence, but may also be beneficial for a number of other rare sandplain insects and plant species. ?? 2006 Elsevier Ltd. All rights reserved.

  10. Ice/frost/debris assessment for space shuttle mission STS-26R

    NASA Technical Reports Server (NTRS)

    Stevenson, Charles G.; Katnik, Gregory N.; Higginbotham, Scott A.

    1988-01-01

    An Ice/Frost/Debris Assessment was conducted for Space Shuttle Mission STS-26R. Debris inspections of the flight elements and launch pad are performed before and after launch. Ice/Frost conditions are assessed by use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by an on-pad visual inspection. High speed photography is viewed after launch to identify ice/debris sources and evaluate potential vehicle damage. The Ice/Frost/Debris conditions of Mission 26R and their effect on the Space Shuttle Program is documented.

  11. Stability of polar frosts in spherical bowl-shaped craters on the moon, Mercury, and Mars

    NASA Technical Reports Server (NTRS)

    Ingersoll, Andrew P.; Svitek, Tomas; Murray, Bruce C.

    1992-01-01

    A model of spherical bowl-shaped craters is described and applied to the moon, Mercury, and Mars. The maximum temperature of permanently shadowed areas are calculated using estimates of the depth/diameter ratios of typical lunar bowl-shaped craters and assuming a saturated surface in which the craters are completely overlapping. For Mars, two cases are considered: water frost in radiative equilibrium and subliming CO2 frost in vapor equilibrium. Energy budgets and temperatures are used to determine whether a craterlike depression loses mass faster or slower than a flat horizontal surface. This reveals qualitatively whether the frost surface becomes rougher or smoother as it sublimes.

  12. KSC ice/frost/debris assessment for Space Shuttle Mission STS-30R

    NASA Technical Reports Server (NTRS)

    Stevenson, Charles G.; Katnik, Gregory N.; Higginbotham, Scott A.

    1989-01-01

    An ice/frost/debris assessment was conducted for Space Shuttle Mission STS-30R. Debris inspections of the flight elements and launch pad are performed before and after launch. Ice/frost conditions on the external tank are assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by an on-pad visual inspection. High speed photography is analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage. The ice/frost/debris conditions of Mission STS-30R and their overall effect on the Space Shuttle Program is documented.

  13. KSC ice/frost/debris assessment for space shuttle mission STS-29R

    NASA Technical Reports Server (NTRS)

    Stevenson, Charles G.; Katnik, Gregory N.; Higginbotham, Scott A.

    1989-01-01

    An ice/frost/debris assessment was conducted for Space Shuttle Mission STS-29R. Debris inspections of the flight elements and launch pad are performed before and after launch. Ice/frost conditions on the external tank are assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by an on-pad visual inspection. High speed photography is analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage. The ice/frost/debris conditions of Mission STS-29R and their effect on the Space Shuttle Program are documented.

  14. The influence of vegetation on frost dynamics, infiltration rate and surface stability in Icelandic Andisolic rangelands 

    E-print Network

    Orradottir, Berglind

    2002-01-01

    of Icelandic rangelands. Specific objectives were to characterize and quantify soil temperature and frost dynamics, water infiltration, and surface stability in contrasting land cover types. The modulating influence of vegetation on soil temperature...

  15. Laboratory studies of the diffuse reflectance spectra of frosts and minerals occurring on astronomical objects

    NASA Technical Reports Server (NTRS)

    Glaser, F. M.

    1978-01-01

    A vacuum monochromator was integrated into the system and optics chosen to increase data collection in the infrared spectral region. Using a InSb detector, good reflectance data was obtained to 5.5 micron from a variety of samples including magnesium oxide, barium sulfate, water frost and Bloedite. Magnesium oxide was found to be a poorer reflector than the barium sulfate throughout the visible and near infrared region. The barium sulfate material was shown to be a Lambert reflector in the visible region and over an angular range of 60 deg. Several samples of water frost were prepared and in reflectance measured from 0.3 micron to 5.5 microm. The fine grained frosts were better reflectors than the coarse grained frosts, usually by 20 percent or more, over the entire spectral range. The minerals Bloedite and sulfur were also investigated further.

  16. CO_2 Frost Halos on the South Polar Residual Cap of Mars

    NASA Astrophysics Data System (ADS)

    Becerra, P.; Byrne, S.; HiRISE Team

    2012-03-01

    We present observational analysis, and a numerical model to explain the formation of bright CO_2 frost halos seen by HiRISE on the edges of scarps and "swiss cheese" features in the south polar residual cap of Mars.

  17. 9/7/2004 Penumadu, Prashant, and Frost. EM-2004 1 A VIRTUAL TRIAXIAL COMPRESSION

    E-print Network

    Prashant, Amit

    , TN, USA Amit Prashant: Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN, USA David J. Frost: Department of Civil and Environmental Engineering, Georgia Institute Dayakar Penumadu: Department of Civil and Environmental Engineering, University of Tennessee, Knoxville

  18. Infrared spectroscopy of Comet Kohoutek. [and reflection studies of frost spectra

    NASA Technical Reports Server (NTRS)

    Fink, U.

    1975-01-01

    Interferometry observations from 90-in. and 61-in. telescopes tracking the Comet Kohoutek are summarized. Laboratory reflection studies of ices potentially useful for future cometary work were conducted. The frosts studied included: H2O, CO2 NH3, H2S, CH4, NH4HS, and ammonia polysulfide. The frost spectra show remarkable changes with the temperatures, particularly in the case of hydrogen sulfide. Additional analysis found the variation in the H2S ice spectrum to be due to a phase change from a low temperature tetragonal unit cube to a higher temperature face-centered cubic structure. The spectra data indicate that if frost spectra are required for comparison with observed cometary or planetary absorption, the temperature of the frost must be matched.

  19. Mariner 9 observations of the south polar cap of Mars - Evidence for residual CO2 frost

    NASA Technical Reports Server (NTRS)

    Paige, D. A.; Herkenhoff, K. E.; Murray, B. C.

    1990-01-01

    The first spacecraft observations of the south residual polar cap of Mars were obtained by the Mariner 9 orbiter during the Martian southern summer season, 1971-1972. Analyses of Viking orbiter observations obtained 3 Mars years later have shown that residual carbon dioxide frost was present at the south polar cap in 1977. In this study, Mariner 9 infrared interferometer spectrometer spectra and television camera images are used in conjuction with multispectral thermal emission models to constrain the temperatures of dark bare ground and bright frost regions within the south residual cap. The results provide strong evidence that carbon dioxide frost was present throughout the summer season despite the fact that the residual frost deposits observed by Mariner 9 were less extensive than those observed by Viking.

  20. Reconstructing patterns of temperature, phenology, and frost damage over 124 years: spring damage risk is increasing.

    PubMed

    Augspurger, Carol K

    2013-01-01

    Climate change, with both warmer spring temperatures and greater temperature fluctuations, has altered phenologies, possibly leading to greater risk of spring frost damage to temperate deciduous woody plants. Phenological observations of 20 woody species from 1993 to 2012 in Trelease Woods, Champaign County, Illinois, USA, were used to identify years with frost damage to vegetative and reproductive phases. Local temperature records were used in combination with the phenological observations to determine what combinations of the two were associated with damage. Finally, a long-term temperature record (1889-1992) was evaluated to determine if the frequency of frost damage has risen in recent decades. Frost < or = -1.7 degrees C occurred after bud-break in 14 of the 20 years of observation. Frost damage occurred in five years in the interior and in three additional years at only the forest edge. The degree of damage varied with species, life stage, tissue (vegetative or reproductive), and phenological phase. Common features associated with the occurrence of damage to interior plants were (1) a period of unusual warm temperatures in March, followed by (2) a frost event in April with a minimum temperature < or = -6.1 degrees C with (3) a period of 16-33 days between the extremes. In the long-term record, 10 of 124 years met these conditions, but the yearly probability of frost damage increased significantly, from 0.03 during 1889-1979 to 0.21 during 1980-2012. When the criteria were "softened" to < or = -1.7 degrees C in April and an interval of 16-37 days, 31 of 124 years met the conditions, and the yearly damage probability increased significantly to 0.19 for 1889-1979 and 0.42 for 1980-2012. In this forest, the combination of warming trends and temperature variability (extremes) associated with climate change is having ecologically important effects, making previously rare frost damage events more common. PMID:23600239

  1. Decreased frost hardiness of Vaccinium vitis-idaea in reponse to UV-A radiation.

    PubMed

    Taulavuori, Kari; Keränen, Johanna; Suokanerva, Hanne; Lakkala, Kaisa; Huttunen, Satu; Laine, Kari; Taulavuori, Erja

    2012-08-01

    The aim of this study was to investigate plant frost hardiness responses to ultraviolet (UV) radiation, since the few results reported are largely contradictory. It was hypothesized that functional adaptation of life forms could explain these contradictions. Dwarf shrubs and tree seedlings, representing both evergreen and deciduous forms, were tested (Vaccinium vitis-idaea, Vaccinium myrtillus, Pinus sylvestris, Betula pubescens and its red form f. rubra). The research was performed in Sodankylä, Northern Finland (67°N), with enhanced UV-B- and UV-A-radiation treatments between 2002 and 2009. Plant frost hardiness was determined using the freeze-induced electrolyte leakage method in early autumn, during the onset of the frost hardening process. Additional physiological variables (malondialdehyde, glutathione, total phenols, C and N contents) were analyzed in V. vitis-idaea to explain the possible responses. These variables did not respond significantly to UV-radiation treatments, but explained the frost hardiness well (r² = 0.678). The main finding was that frost hardiness decreased in the evergreen shrub V. vitis-idaea, particularly with enhanced UV-A radiation. No significant responses were observed with the other plants. Therefore, this study does not support the idea that enhanced UV radiation could increase plant frost hardiness. PMID:22182287

  2. Frost resistance of concrete surfaces coated with waterproofing materials

    NASA Astrophysics Data System (ADS)

    Klovas, A.; Dauksys, M.; Ciuprovaite, G.

    2015-03-01

    Present research lays emphasis on the problem of concrete surface exposed to aggressive surrounding quality. The test was conducted with concrete surfaces coated with different waterproofing materials exposed in solution of 3 % of sodium sulphate. Research was performed according to LST EN 1338:2003 standard requirements. Technological properties of concrete mixture as well as physical-mechanical properties of formed concrete specimens were established. The resistance of concrete to freezing - thawing cycles was prognosticated according to the porosity parameters established by the kinetic of water absorption. Five different waterproofing materials (coatings) such as liquid bitumen-rubber based, elastic fiber-strengthened, silane-siloxane based emulsion, mineral binder based and liquid rubber (caoutchouc) based coatings were used. Losses by mass of coating materials and specimens surface fractures were calculated based on the results of frost resistance test. Open code program "ImageJ" was used for visual analysis of concrete specimens. Based on the results, aggressive surrounding did not influence specimens coated with elastic, fibre-strengthened, mineral materials. On the other hand, specimens coated with liquid rubber (caoutchouc) based material were greatly influenced by aggressive surrounding. The biggest losses of specimen surface concrete (fractures) were obtained with silane-siloxane based emulsion coating. Generally, specimens coated with waterproofing materials were less influenced by aggressive surrounding compared with those without.

  3. Statistical Evaluation of Potential Damage to the Al(OH)3 Layer on nTiO2 Particles in the Presence of Swimming Pool and Seawater

    EPA Science Inventory

    Nanosized TiO2 particles (nTiO2) are usually coated with an Al(OH)3 layer when used in sunscreen to shield against the harmful effects of free radicals that are generated when these particles are exposed to UV radiation. Therefore, it is vital to ...

  4. Cell shape and localisation of ice in leaves of overwintering wheat during frost stress in the field.

    PubMed

    Pearce, R S; Ashworth, E N

    1992-10-01

    Wheat leaf pieces were excised and freeze-fixed in the field, preparatory to low-temperature scanning electron microscopy to study distribution of ice within leaf blades, and associated cell shapes, during natural frosts. Pieces of leaf blades from wheat plants (Triticum aestivum L. 7942H1-20-8) overwintering in Indiana, USA (January, 1991), were excised and immediately freeze-fixed by manually plunging in melting freon. Cells in controls were turgid and extracellular ice was absent. The leaves of the frost-stressed plants froze at about - 2.4° C, and at that temperature extracellular ice was mainly located sub-epidermally, including in the substomatal cavity, and occupied about 14% of the fracture faces. The frequency of ice particles per unit leaf area in two specimens was 14 and 210 · mm(-2) (about 140 and 2100 · g(-1) leaf fresh-weight basis). At -9.0° C, ice filled the extracellular spaces, occupying 61% of the fracture faces. Cells were somewhat collapsed at -2.4° C and were much more collapsed at -9.0° C. The epidermal cells were more collapsed than the mesophyll cells. Tissue structure (connections with adjacent cells), wall flexibility, and ice growth may all have influenced the shapes of the collapsing cells. The experiments demonstrate the feasibility of freeze-fixation in the field. The sub-epidermal location of most ice indicates that in the field either (i) ice is nucleated sub-epidermally (implying both the presence of nucleators and the presence of liquid water in the sub-epidermal spaces) or (ii) ice is nucleated on the leaf surface, then propagates into the leaf probably through stomata. PMID:24178321

  5. Intramolecular vibrational energy redistribution from a high frequency mode in the presence of an internal rotor: Classical thick-layer diffusion and quantum localization

    NASA Astrophysics Data System (ADS)

    Manikandan, Paranjothy; Keshavamurthy, Srihari

    2007-08-01

    We study the effect of an internal rotor on the classical and quantum intramolecular vibrational energy redistribution (IVR) dynamics of a model system with three degrees of freedom. The system is based on a Hamiltonian proposed by Martens and Reinhardt [J. Chem. Phys. 93, 5621 (1990)] to study IVR in the excited electronic state of para-fluorotoluene. We explicitly construct the state space and show, confirming the mechanism proposed by Martens and Reinhardt, that an excited high frequency mode relaxes via diffusion along a thick layer of chaos created by the low frequency-rotor interactions. However, the corresponding quantum dynamics exhibits no appreciable relaxation of the high frequency mode. We attribute the quantum suppression of the classical thick-layer diffusion to the rotor selection rules and, possibly, dynamical localization effects.

  6. Increasing frost risk associated with advanced citrus flowering dates in Kerman and Shiraz, Iran: 1960-2010

    NASA Astrophysics Data System (ADS)

    Fitchett, Jennifer M.; Grab, Stefan W.; Thompson, Dave I.; Roshan, Gholamreza

    2014-10-01

    Flowering dates and the timing of late season frost are both driven by local ambient temperatures. However, under climatic warming observed over the past century, it remains uncertain how such impacts affect frost risk associated with plant phenophase shifts. Any increase in frost frequency or severity has the potential to damage flowers and their resultant yields and, in more extreme cases, the survival of the plant. An accurate assessment of the relationship between the timing of last frost events and phenological shifts associated with warmer climate is thus imperative. We investigate spring advances in citrus flowering dates (orange, tangerine, sweet lemon, sour lemon and sour orange) for Kerman and Shiraz, Iran from 1960 to 2010. These cities have experienced increases in both T max and T min, advances in peak flowering dates and changes in last frost dates over the study period. Based on daily instrumental climate records, the last frost dates for each year are compared with the peak flowering dates. For both cities, the rate of last frost advance lags behind the phenological advance, thus increasing frost risk. Increased frost risk will likely have considerable direct impacts on crop yields and on the associated capacity to adapt, given future climatic uncertainty.

  7. Increasing frost risk associated with advanced citrus flowering dates in Kerman and Shiraz, Iran: 1960-2010.

    PubMed

    Fitchett, Jennifer M; Grab, Stefan W; Thompson, Dave I; Roshan, Gholamreza

    2014-10-01

    Flowering dates and the timing of late season frost are both driven by local ambient temperatures. However, under climatic warming observed over the past century, it remains uncertain how such impacts affect frost risk associated with plant phenophase shifts. Any increase in frost frequency or severity has the potential to damage flowers and their resultant yields and, in more extreme cases, the survival of the plant. An accurate assessment of the relationship between the timing of last frost events and phenological shifts associated with warmer climate is thus imperative. We investigate spring advances in citrus flowering dates (orange, tangerine, sweet lemon, sour lemon and sour orange) for Kerman and Shiraz, Iran from 1960 to 2010. These cities have experienced increases in both T max and T min, advances in peak flowering dates and changes in last frost dates over the study period. Based on daily instrumental climate records, the last frost dates for each year are compared with the peak flowering dates. For both cities, the rate of last frost advance lags behind the phenological advance, thus increasing frost risk. Increased frost risk will likely have considerable direct impacts on crop yields and on the associated capacity to adapt, given future climatic uncertainty. PMID:24429704

  8. A Community Frost/Freeze Susceptibility Operational Guidance Tool

    NASA Astrophysics Data System (ADS)

    Hall, B. L.; Curtis, A.; Timlin, M.; Woloszyn, M.; Zaloudek, Z.; Hilberg, S.; Guinan, P.; Andresen, J.; Longstroth, M.; Wolf, R.; Shanklin, R.; Spoden, P.

    2013-12-01

    In response to historical costly and damaging freeze events in the north-central United States, the Midwestern Regional Climate Center (MRCC) has teamed up with the National Weather Service (NWS), State Climatologists, and land grant university Extension agricultural and horticultural specialists to develop an operational online guidance tool to help monitor, assess, and mitigate these extreme weather phenomena. The Vegetation Impact Program (VIP), hosted by the MRCC, was established in spring 2013 to provide a partnership opportunity among these stakeholders of vegetation and climate monitoring and assessment. It offers an online portal to operational assessment tools, a means of communicating status of vegetative growth and climate conditions in the region, and multiple methods of communicating between sectors and stakeholders. The Frost/Freeze Project is the first impact monitoring project within VIP and was inspired by NWS forecasters requesting help attaining decision-making assistance and guidance tools both within the NWS community and the community of vegetation experts. Early accomplishments have included: (1) the development of daily, operational climate monitoring maps based upon in situ atmospheric observations from the cooperative network (Co-op), (2) development of online guidance and impact reporting forms for VIP subscribers to submit their observations from both the field and forecasting offices, and (3) an email listserv for the VIP community to share general information. Future plans include expanding the spatial domain of the project to the 48 states, incorporating hourly observations from both national and local/state mesonets, and integrating digital forecast data real-time to provide vegetation susceptibility and risk guidance tools.

  9. Structural Analysis of the Redesigned Ice/Frost Ramp Bracket

    NASA Technical Reports Server (NTRS)

    Phillips, D. R.; Dawicke, D. S.; Gentz, S. J.; Roberts, P. W.; Raju, I. S.

    2007-01-01

    This paper describes the interim structural analysis of a redesigned Ice/Frost Ramp bracket for the Space Shuttle External Tank (ET). The proposed redesigned bracket consists of mounts for attachment to the ET wall, supports for the electronic/instrument cables and propellant repressurization lines that run along the ET, an upper plate, a lower plate, and complex bolted connections. The eight nominal bolted connections are considered critical in the summarized structural analysis. Each bolted connection contains a bolt, a nut, four washers, and a non-metallic spacer and block that are designed for thermal insulation. A three-dimensional (3D) finite element model of the bracket is developed using solid 10-node tetrahedral elements. The loading provided by the ET Project is used in the analysis. Because of the complexities associated with accurately modeling the bolted connections in the bracket, the analysis is performed using a global/local analysis procedure. The finite element analysis of the bracket identifies one of the eight bolted connections as having high stress concentrations. A local area of the bracket surrounding this bolted connection is extracted from the global model and used as a local model. Within the local model, the various components of the bolted connection are refined, and contact is introduced along the appropriate interfaces determined by the analysts. The deformations from the global model are applied as boundary conditions to the local model. The results from the global/local analysis show that while the stresses in the bolts are well within yield, the spacers fail due to compression. The primary objective of the interim structural analysis is to show concept viability for static thermal testing. The proposed design concept would undergo continued design optimization to address the identified analytical assumptions and concept shortcomings, assuming successful thermal testing.

  10. Growth and densification of frost around a circular cylinder under humid air on cross flow

    NASA Astrophysics Data System (ADS)

    Madrid, Victor; Sanchez, Fausto; Martinez, Simon; Morales, Arturo

    2015-03-01

    Formation, growth and densification of frost around a circular cylinder under humid air on cross flow at different Reynolds numbers has been numerically studied using the finite volume method. The frost formation phenomenon takes place when humidity goes through a desublimation phase change at a temperature lower than its solidification point. Continuity, momentum, energy and mass transport equations have been solved for a whole domain including both phases, gas and solid, and the two components in the gas phase, i.e. dry air and humidity. The mass of water that goes from the gas to the solid phase is used as a source term in the mass conservation equation for solid phase and as a sink for the gas phase, affecting source terms in all the other conservation equations (energy and momentum) also. A volume of fraction conservation equation for solid phase is used to obtain local fractions of ice droplets, considering formally as frost those fraction values greater than a critical value. Once those local fractions are known, local frost properties such as density and thermal conductivity can be calculated as functions of the phase fraction allowing to compute the evolution of growth and local properties of frost. Authors aknowledge financial support from CONACYT through Project 221993.

  11. Keeping a surface ice/frost free with electro-conducting water-repellent coatings

    NASA Astrophysics Data System (ADS)

    Das, Arindam; Kapatral, Shreyas; Megaridis, Constantine M.

    2013-11-01

    Ice/frost formation on aircraft, wind turbines, power grids, marine vessels, telecommunication devices, etc. has propelled scientific research on surfaces that facilitate the removal of the water solid phase or retard its formation. Superhydrophobic, self-cleaning surfaces have been investigated recently (Jung et al., Langmuir 2011) for their passive anti-icing properties. Although superhydrophobic surfaces have been shown to delay the onset of frosting and icing, they cannot prevent it entirely. Hence active deicing/defrosting approaches are required to keep surfaces free of ice/frost. Defrosting experiments have been carried out on glass substrates coated with textured polymeric nanocomposite films of different surface wettability, porosity and roughness. A strong influence of these parameters on condensation, condensation frosting and defrosting was observed. The coatings are electro-conducting, thus allowing skin heating at the interface between ice and the substrate. Sustained ice- and frost-free operation is demonstrated at substrate temperatures well below the freezing point and in humid ambient atmospheres. Supported by NSF Grant CBET-1066426.

  12. Greenhouse gas fluxes in a drained peatland forest during spring frost-thaw event

    NASA Astrophysics Data System (ADS)

    Pihlatie, M. K.; Kiese, R.; Brüggemann, N.; Butterbach-Bahl, K.; Kieloaho, A.-J.; Laurila, T.; Lohila, A.; Mammarella, I.; Minkkinen, K.; Penttilä, T.; Schönborn, J.; Vesala, T.

    2010-05-01

    Fluxes of greenhouse gases (GHG) carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) were measured during a two month campaign at a drained peatland forest in Finland by the eddy covariance (EC) technique (CO2 and N2O), and automatic and manual chambers (CO2, CH4 and N2O). In addition, GHG concentrations and soil parameters (mineral nitrogen, temperature, moisture content) in the peat profile were measured. The aim of the measurement campaign was to quantify the GHG fluxes during freezing and thawing of the top-soil, a time period with potentially high GHG fluxes, and to compare different flux measurement methods. The forest was a net CO2 sink during the two months and the fluxes of CO2 dominated the GHG exchange. The peat soil was a small sink of atmospheric CH4 and a small source of N2O. Both CH4 oxidation and N2O production took place in the top-soil whereas CH4 was produced in the deeper layers of the peat, which were unfrozen throughout the measurement period. During the frost-thaw events of the litter layer distinct peaks in CO2 and N2O emissions were observed. The CO2 peak followed tightly the increase in soil temperature, whereas the N2O peak occurred with a delay after the thawing of the litter layer. CH4 fluxes did not respond to the thawing of the peat soil. The CO2 and N2O emission peaks were not captured by the manual chambers and hence we conclude that high time-resolution measurements with automatic chambers or EC are necessary to quantify fluxes during peak emission periods. Sub-canopy EC measurements and chamber-based fluxes of CO2 and N2O were comparable, although the fluxes of N2O measured by EC were close to the detection limit of the system. We conclude that if fluxes are high enough, i.e. greater than 5-10 ?g N m-2 h-1, the EC method is a good alternative to measure N2O and CO2 fluxes at ecosystem scale, thereby minimizing problems with chamber enclosures and spatial representativeness of the measurements.

  13. Sensitivity of Soil Carbon Balances to Changes in the Extent and Duration of Soil Frost in a Boreal Forest

    NASA Astrophysics Data System (ADS)

    Oquist, M. G.; Haei, M.; Laudon, H.

    2008-12-01

    Climate change is likely to alter soil frost depth and duration in the boreal zone in the future. Soil frost can influence biogeochemical soil processes directly, for instance by altering rates of microbial decomposition of soil organic matter (SOM) and by increasing root mortality. In addition, soil frost controls hydrologic flow paths, which in turn determines export of carbon from soils to surface waters, primarily during high-flood events associated with snow melt and soil thawing. Nonetheless, to what extent changes in soil frost regimes influences the soil C dynamics is poorly understood. Here we present results from a field manipulation investigation with three soil frost treatments (deep soil frost, shallow soil frost and ambient controls; n = 3) that has been in operation for 7 years. Increased soil frost depth results in decreased soil CO2 concentrations and soil respiration rates during the following growing season. We see a strong correlation between the maximum soil frost depth during winter and the amount of C lost from the system by soil respiration (R = 0.99) suggesting that average soil respiration rates during the growing season will decrease by ca 0.01 g CO2 m-2 day-1 for every 1 cm increase in soil frost depth. This corresponds to up to 0.5% of the estimated annual net ecosystem productivity. Because year-to-year variation in soil frost depth at the site varies by up to 60 cm, we conclude that it can constitute an important control on soil C balances. Results also show a significant effect on the pool of dissolved organic carbon (DOC) in the soil during spring thaw and early summer, where deep soil frost treatments show up to twice the amount of DOC, as compared to shallow soil frost treatments. In addition, laboratory incubations suggest that alterations in winter soil temperatures and soil frost distribution also affects the composition of the DOC pool altering its aromaticity, with potential effects on its bioavailability. Thus, a change in soil frost regime has implications for both the amount and the composition of C exported from soils to surface waters.

  14. Modified Ion-Acoustic Shock Waves and Double Layers in a Degenerate Electron-Positron-Ion Plasma in Presence of Heavy Negative Ions

    NASA Astrophysics Data System (ADS)

    Hossen, M. A.; Hossen, M. R.; Mamun, A. A.

    2014-12-01

    A general theory for nonlinear propagation of one dimensional modified ion-acoustic waves in an unmagnetized electron-positron-ion (e-p-i) degenerate plasma is investigated. This plasma system is assumed to contain relativistic electron and positron fluids, non-degenerate viscous positive ions, and negatively charged static heavy ions. The modified Burgers and Gardner equations have been derived by employing the reductive perturbation method and analyzed in order to identify the basic features (polarity, width, speed, etc.) of shock and double layer (DL) structures. It is observed that the basic features of these shock and DL structures obtained from this analysis are significantly different from those obtained from the analysis of standard Gardner or Burgers equations. The implications of these results in space and interstellar compact objects (viz. non-rotating white dwarfs, neutron stars, etc.) are also briefly mentioned.

  15. An effective field theory study of layering transitions in Blume-Capel thin films in the presence of quenched random crystal fields

    NASA Astrophysics Data System (ADS)

    Yüksel, Yusuf

    2014-02-01

    In the presence of quenched random crystal fields, phase transitions in magnetic thin films described by the spin-1 Blume-Capel model have been investigated using effective field theory (EFT). Crystal field disorder has been sampled by introducing dilute and trimodal random crystal fields. For dilute crystal fields, in the highly anisotropic limit (D??), we have found that the critical value of the surface to bulk ratio of exchange interactions (Rc) at which the second-order transition temperature becomes independent of the film thickness is a spin-dependent property of thin magnetic films. Moreover, as a percolation problem, we have performed detailed calculations in the limit D?-?, and it has been shown that a novel feature emerges in the presence of enhanced surfaces. Besides, for trimodal random crystal fields, the variation of the special point Rc as a function of the random field parameters has been elucidated. Finally, in the limit D??, based on the numerical data provided by EFT, we have introduced an analytical expression for the variation of Rc as a function of the randomness parameter p of the trimodal distribution.

  16. North Polar Surfaces of the Uranian Moons: Coated with CO2 Frost?

    NASA Astrophysics Data System (ADS)

    Cartwright, Richard; Emery, Joshua; Rivkin, Andy; Trilling, David; Pinilla-Alonso, Noemi

    2014-12-01

    We propose to investigate the near-surface composition of the Uranian moons Ariel, Umbriel, Titania, and Oberon by using the Infrared Array Camera (IRAC) onboard the Spitzer Space Telescope. Previous IRAC observations of these objects in Program 71 (2003 - 2005) indicate that the surfaces of their southern hemispheres are dominated by pure water ice (sub-observer latitudes 7 - 18 degree S). The observations we propose here are of these objects' now observable northern hemispheres (sub-observer latitudes 25 - 33 degree N). Unlike the Program 71 observations, which collected data near the end of southern summer when any seasonal CO2 frost would have migrated to the winter hemisphere, we are proposing to observe these moons at the beginning of northern summer when seasonal CO2 frost should still be present. Therefore, the 2015 - 2016 Cycle 11 opportunity window represents an ideal time frame to search for seasonal CO2 frost on these objects.

  17. Frosted branch angiitis as ocular manifestation of Behçet's disease: unusual case report and literature review.

    PubMed

    Kwon, Soon Jae; Park, Dong Ho; Shin, Jae Pil

    2013-12-01

    We report an unusual case of unilateral frosted branch angiitis associated with Behçet's disease, including a review of previously reported cases. A 39-year-old male with history of recurrent oral and genital ulcers presented with visual loss in his left eye. Fundus findings demonstrated occlusive retinal vasculitis resembling acute frosted branch angiitis. Laboratory examinations including viral markers revealed no abnormal findings except positive HLA-B51. The patient was treated with systemic steroid and cyclosporine. Six months after presentation, new oral ulcers and pseudofolliculitis appeared, and he was diagnosed with Behçet's disease following rheumatology consultation. During follow-up, there was no change in visual acuity of hand movement, and disc neovascularization developed even after complete panretinal photocoagulation. Ocular manifestations of Behçet's disease can present as unilateral frosted branch angiitis, and may consecutively involve in both eyes. Early immunosuppressive treatment is recommended. PMID:24311935

  18. Is Frost Cracking By Segregation Ice Growth One of the Mechanisms That Erode Bedrock River Margins?

    NASA Astrophysics Data System (ADS)

    Alden, L. L.; Sklar, L. S.

    2014-12-01

    Rivers cut vertically and laterally into bedrock. However, control on the width of bedrock rivers is an unsolved problem. In alpine settings, frost cracking is one of the mechanisms that break down bedrock. Segregation ice drives growth of ice lenses within rock masses. When the temperature of the rock is within the "frost cracking window" of -3 to -8 °C, ice lenses can attract liquid water. Expanding ice lenses can exert sufficient pressure to fracture the rock. We hypothesize that alpine rivers may promote segregation ice growth at the river margin by supplying water, but also may inhibit frost cracking by supplying heat. We find support for this hypothesis in data collected along the Tuolumne and Mokelumne rivers in the Sierra Nevada, California. A 1D heat flow model predicts that frost cracking should occur above 2325 masl in this area. To test for a river effect, we measured fracture density along the Tuolumne River at ~2600 masl, finding that density at the river margin is significantly greater than on adjacent hillslopes in the Cathedral Peak granodiorite. We then deployed data loggers on the Mokelumne River (at 2486 masl) over the winter of 2013/2014 to record water, surface and subsurface rock temperatures at varying depths and distances from the river. Temperatures within the frost cracking window were only recorded at a distance of ~5 m from the river, suggesting an insulating effect from the river and snow cover. Rock temperatures 1 m deep equilibrated at ~ 2 °C, significantly colder than predicted by the 1D model. Ongoing work includes terrestrial LIDAR scans to detect erosion of the river bank at the Mokelumne site, and development of a 2D heat flow model to predict subsurface rock temperatures for varying surface boundary conditions and channel morphology. We expect that further analysis will reveal systematic relationships between the surface boundary conditions and rock temperature at depth, enabling predictive modeling of frost cracking intensity at the river margin.

  19. STUDY OF FROST GROWTH ON HEAT EXCHANGERS USED AS OUTDOOR COILS IN AIR SOURCE HEAT PUMP SYSTEMS

    E-print Network

    STUDY OF FROST GROWTH ON HEAT EXCHANGERS USED AS OUTDOOR COILS IN AIR SOURCE HEAT PUMP SYSTEMS OF FROST GROWTH ON HEAT EXCHANGERS USED AS OUTDOOR COILS IN AIR SOURCE HEAT PUMP SYSTEMS Dissertation like to acknowledge the technical and financial support from Heat Transfer Center of Excellence

  20. Intercomparisons of Stratospheric Water Vapor Sensors: FLASH-B and NOAA/CMDL Frost-Point Hygrometer

    E-print Network

    Vömel, Holger

    Intercomparisons of Stratospheric Water Vapor Sensors: FLASH-B and NOAA/CMDL Frost-Point Hygrometer and Diagnostics Laboratory (CMDL) frost-point hygrometer and the Fluorescent Advanced Stratospheric Hygrometer for Balloon (FLASH-B) Lyman-alpha hygrometer is reported. Both instruments were part of a small balloon

  1. Validation of Aura Microwave Limb Sounder water vapor by balloon-borne Cryogenic Frost point Hygrometer measurements

    E-print Network

    Vömel, Holger

    Validation of Aura Microwave Limb Sounder water vapor by balloon- borne Cryogenic Frost point extensive observations of stratospheric and upper tropospheric water vapor using the balloon-borne Cryogenic vapor by balloon-borne Cryogenic Frost point Hygrometer measurements, J. Geophys. Res., 112, D24S37, doi

  2. A study of heat pump fin staged evaporators under frosting conditions 

    E-print Network

    Yang, Jianxin

    2004-09-30

    -by-section evaluation scheme was combined with the tube- by-tube approach to model the mass transfer process in the frost formation module. The two-dimensional fin surface was divided into a number of parallel non-overlapping sections. Each of the sections... STUDY OF HEAT PUMP FIN STAGED EVAPORATORS UNDER FROSTING CONDITIONS A Dissertation by JIANXIN YANG Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY May...

  3. A nano-frost array technique to prepare nanoporous PVDF membranes

    NASA Astrophysics Data System (ADS)

    Lee, Min Kyung; Lee, Jonghwi

    2014-07-01

    Frost, the solid deposition of water vapor from humid air, forms on the surface of a solid substrate when its temperature drops below the freezing point of water. In this study, we demonstrate how this natural phenomenon can be applied to develop novel nanoporous materials. The solvent annealing of polyvinylidene fluoride (PVDF) infiltrated into nanopores induced template-directed dewetting thus preparing nanoembossing films. Then, water nanodroplets formed on the cold polymer nanopatterned surfaces following the embossing patterns, similar to dew formation on the ground. Subsequently, the nanodroplets were frozen and then removed by freeze-drying. This nano-frost array technique produced nanoporous PVDF membranes with an average thickness of 250 (+/-48) nm. It was revealed that the nanopatterned surface formed by solvent annealing played an important role in achieving a nano-frost array with an adjustable size. Additionally, the freezing process led to significant changes of the PVDF crystallinity and polymorphism. Our results prove that the nano-frost array technique can be broadly used to design ordered nanoporous structures and provide new prospects in nanomaterial fields.Frost, the solid deposition of water vapor from humid air, forms on the surface of a solid substrate when its temperature drops below the freezing point of water. In this study, we demonstrate how this natural phenomenon can be applied to develop novel nanoporous materials. The solvent annealing of polyvinylidene fluoride (PVDF) infiltrated into nanopores induced template-directed dewetting thus preparing nanoembossing films. Then, water nanodroplets formed on the cold polymer nanopatterned surfaces following the embossing patterns, similar to dew formation on the ground. Subsequently, the nanodroplets were frozen and then removed by freeze-drying. This nano-frost array technique produced nanoporous PVDF membranes with an average thickness of 250 (+/-48) nm. It was revealed that the nanopatterned surface formed by solvent annealing played an important role in achieving a nano-frost array with an adjustable size. Additionally, the freezing process led to significant changes of the PVDF crystallinity and polymorphism. Our results prove that the nano-frost array technique can be broadly used to design ordered nanoporous structures and provide new prospects in nanomaterial fields. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr00951g

  4. Frost hardiness of mycorrhizal and non-mycorrhizal Scots pine under two fertilization treatments.

    PubMed

    Korhonen, Anna; Lehto, Tarja; Repo, Tapani

    2015-07-01

    Survival and functioning of mycorrhizal associations at low temperatures are not known well. In an earlier study, ectomycorrhizas did not affect the frost hardiness of Scots pine (Pinus sylvestris L.) roots, but here we studied whether differential nutrient availability would change the result and additionally, alter frost hardiness aboveground. The aim in this experiment was to compare the frost hardiness of roots and needles of mycorrhizal (Hebeloma sp.) and non-mycorrhizal Scots pine seedlings raised using two fertilization treatments and two cold-hardening regimes. The fertilization treatments were low (LF) and high (HF) application of a complete nutrient solution. Three hundred mycorrhizal and non-mycorrhizal seedlings were cultivated in growth chambers in four blocks for 16 weeks. For the first 9 weeks, the seedlings grew in long-day and high-temperature (LDHT) with low fertilization and then they were raised for 3 weeks in LDHT with either low or high fertilization. After this, half of the plants in each treatment combination remained in LDHT, and half were transferred to short-day and low-temperature (SDLT) conditions to cold acclimatize. The frost hardiness of the roots and needles was assessed using controlled freezing tests followed by electrolyte leakage tests (REL). Mycorrhizal roots were slightly more frost hardy than non-mycorrhizal roots, but only in the growing-season conditions (LDHT) in low-nutrient treatment. In LDHT and LF, the frost hardiness of the non-mycorrhizal roots was about -9 °C, and that of the non-mycorrhizal HF roots and the mycorrhizal roots in both fertilization levels was about -11 °C. However, no difference was found in the roots within the SDLT regime, and in needles, there was no difference between mycorrhizal and fertilization treatments. The frost hardiness of needles increased by SDLT treatment, being -8.5 and -14.1 °C in LDHT and SDLT, respectively. The dry mass of roots, stems, and needles was lower in LF than in HF and lower in SDLT than in LDHT. Mycorrhizal treatment did not affect the dry mass or its allocation. Although the mycorrhizal roots were slightly more frost hardy in the growing-season conditions, this is not likely to have significance in the field. PMID:25404213

  5. Io meteorology - How atmospheric pressure is controlled locally by volcanos and surface frosts

    NASA Technical Reports Server (NTRS)

    Ingersoll, Andrew P.

    1989-01-01

    The present modification of the Ingersoll et al. (1985) hydrodynamic model of the SO2 gas sublimation-driven flow from the day to the night side of Io includes the effects of nonuniform surface properties noted in observational studies. Calculations are conducted for atmospheric pressures, horizontal winds, sublimation rates, and condensation rates for such surface conditions as patchy and continuous frost cover, volcanic venting, surface temperature discontinuities, subsurface cold trapping, and the propagation of insolation into the frost. While pressure is found to follow local vapor pressure away from the plumes, it becomes higher inside them.

  6. Frosted branch angiitis caused by Varicella Zoster virus in an immunocompetent patient

    PubMed Central

    Talebi-Taher, Mahshid; Javadzadeh, Ali; Hedayatfar, Alireza; Rahmani, Shahrzad; Ghanooni, Amir Hossein; Mahmoodian, Reihaneh

    2015-01-01

    Introduction: Frosted branch angiitis(FBA) is a panuveitis with sheating of all retinal vesssels. Case presentation: Herein we report an immunocompetent person who presented with fever, headache, atypical rash, and hazy vision. Ophthalmoscopy of both eyes revealed perivascular sheathing with frosted branch angiitis pattern in veins, patchy retinal hemorrhages. Aqueous PCR analysis turned positive for VZV. Discussion: This case illustrates that VZV should be considered in the differential diagnosis of retinal perivasculitis. Since a rapid and accurate diagnosis is crucial for prompt administration of antiviral therapy, PCR-based analysis of aqueous humor is a valuable tool for detecting viruses. PMID:26622973

  7. In live interaction, does familiarity promote attraction or contempt? Reply to Norton, Frost, and Ariely (2011).

    PubMed

    Reis, Harry T; Maniaci, Michael R; Caprariello, Peter A; Eastwick, Paul W; Finkel, Eli J

    2011-09-01

    In this reply, we address and refute each of Norton, Frost, and Ariely's (see record 2011-18560-001) specific objections to the conclusion that, ceteris paribus, familiarity breeds liking in live interaction. In particular, we reiterate the importance of studying live interaction rather than decontextualized processes. These rebuttals notwithstanding, we concur with Norton et al.'s call for an integrative model that encompasses both Norton, Frost, and Ariely's (see record 2006-23056-008) results and ours (see record 2011-04644-001), and we point readers toward a description of a possible model presented in our original article. PMID:21859228

  8. The influence of thermal inertia on temperatures and frost stability on Triton

    NASA Technical Reports Server (NTRS)

    Spencer, John R.; Moore, Jeffrey M.

    1992-01-01

    It is presently argued, in view of (1) a thermal inertia model for the surface of Triton which (like previous ones) predicts a monotonic recession of permanent N2 deposits toward the poles and very little seasonal N2 frost in the southern hemisphere, and (2) new spectroscopic evidence for nonvolatile CO2 on Triton's bright southern hemisphere, that much of that bright southern material is not N2. Such bright southern hemisphere volatiles may allow the formation of seasonal frosts, thereby helping to explain the observed spectroscopic changes of Triton during the last decade.

  9. Fracture Mechanical Analysis of Frost Wedging in Ice Shelves as Break-Up Mechanism

    NASA Astrophysics Data System (ADS)

    Plate, Carolin; Humbert, Angelika; Gross, Dietmar; Müller, Ralf

    2013-04-01

    Disintegration events in ice shelves have been the subject of extensive investigations in the past years, however comprehensive explanations applicable to a majority of events are still missing. A popular assumption made by Scambos et al. (2000) [1] links disintegration events to a general thinning of the ice shelf in conjunction with growing melt-water ponds leading to hydro fractures. This explanation seems reasonable for break-up events that happened in Antarctic summers. Large parts of the Wilkins Ice Shelf, however broke-up in fall and winter periods. Therefore, the aim of the present study is to analyse the possibility of frost wedging of water filled surface crevasses in an ice shelf as a source of break-up events. Configurational forces are used to assess crack criticality. The simulations are performed on a 2-dimensional single crack with a mode-I type load, body forces and additional crack-face pressure due to freezing of the water. Depth-dependent density profiles are considered. The relevant parameters, Young's modulus, Poisson's ratio and external loading are obtained from literature, remote sensing data analysis and modelling of the ice dynamics. The investigation is performed using the finite element software COMSOL. The simulations show that in comparison to water filled crevasses without ice, thin layers of frozen water may lead to a decreasing criticality at the crack tip as long as the ice 'bridge' is allowed to take tensile loads. An increasing crack criticality can be seen for thicker layers of ice. The results are compared to findings from previous finite element analyses of dry and water filled cracks as presented in Plate et al. (2012) [2]. [1] Scambos, T., Hulbe, C., Fahnestock, M., & Bohlander, J. (2000). The link between climate warming and break-up of ice shelves in the Antarctic Peninsula. Journal of Glaciology, 46(154), 516-530. [2] Plate, C., Müller, R., Humbert, A., & Gross, D. (2012). Evaluation of the criticality of cracks in ice shelves using finite element simulations. The Cryosphere, 6(5), 973-984.

  10. Hyperthermostable surface layer protein tetrabrachion from the archaebacterium Staphylothermus marinus: evidence for the presence of a right-handed coiled coil derived from the primary structure.

    PubMed

    Peters, J; Baumeister, W; Lupas, A

    1996-04-19

    The scaffold of the surface layer covering the hyperthermophilic archaebacterium Staphylothermus marinus is formed by an extended filiform glycoprotein complex, tetrabrachion, which is anchored in the cell membrane at one end of a 70 nm stalk and branches at the other end into four arms of 24 nm length. The arms from a canopy-like meshwork by end-to-end contacts, enclosing a "quasi-periplasmic space". The primary structure of the complex, obtained by an approach based entirely on the polymerase chain reaction, shows that the light and the heavy chains are encoded in this order in a single gene and are generated by internal proteolytic cleavage. One light chain associates with the N-terminal part of a heavy chain to form one of the four arms of the complex, comprising about 1000 residues. Following a glycine-rich linker of about ten residues, the C-terminal 500 residues of the four heavy chains converge to form a four-stranded parallel coiled coil, which ends in a transmembrane segment. The sequence of the coiled coil is exceptional in that the heptad repeat of hydrophobic residues typical for left-handed coiled coils shifts to an undecad repeat after an internal proline residue, indicating that the C-terminal part of the sequence forms a right-handed coiled coil. Such a periodicity has not been detected in coiled coils to date. The almost flawless pattern of aliphatic residues, mainly leucine and isoleucine, throughout the hydrophobic core of the stalk provide one explanation for its exceptional stability. PMID:8632466

  11. Metabolite profiling during cold acclimation of Lolium perenne genotypes distinct in the level of frost tolerance.

    PubMed

    Bocian, Aleksandra; Zwierzykowski, Zbigniew; Rapacz, Marcin; Koczyk, Grzegorz; Ciesio?ka, Danuta; Kosmala, Arkadiusz

    2015-11-01

    Abiotic stresses, including low temperature, can significantly reduce plant yielding. The knowledge on the molecular basis of stress tolerance could help to improve its level in species of relatively high importance to agriculture. Unfortunately, the complex research performed so far mainly on model species and also, to some extent, on cereals does not fully cover the demands of other agricultural plants of temperate climate, including forage grasses. Two Lolium perenne (perennial ryegrass) genotypes with contrasting levels of frost tolerance, the high frost tolerant (HFT) and the low frost tolerant (LFT) genotypes, were selected for comparative metabolomic research. The work focused on the analysis of leaf metabolite accumulation before and after seven separate time points of cold acclimation. Gas chromatography-mass spectrometry (GC/MS) was used to identify amino acids (alanine, proline, glycine, glutamic and aspartic acid, serine, lysine and asparagine), carbohydrates (fructose, glucose, sucrose, raffinose and trehalose) and their derivatives (mannitol, sorbitol and inositol) accumulated in leaves in low temperature. The observed differences in the level of frost tolerance between the analysed genotypes could be partially due to the time point of cold acclimation at which the accumulation level of crucial metabolite started to increase. In the HFT genotype, earlier accumulation was observed for proline and asparagine. The increased amounts of alanine, glutamic and aspartic acids, and asparagine during cold acclimation could be involved in the regulation of photosynthesis intensity in L. perenne. Among the analysed carbohydrates, only raffinose revealed a significant association with the acclimation process in this species. PMID:26025228

  12. Susceptibility of provenances and families of Pinus maximinoi and Pinus tecunumanii to frost in South Africa

    E-print Network

    Susceptibility of provenances and families of Pinus maximinoi and Pinus tecunumanii to frost+Business Media B.V. 2012 Abstract The future of South Africa's most important pine species, Pinus patula, is threatened by the pitch canker fungus, Fusarium circinatum. Pinus maximinoi and P. tecunumanii represent two

  13. Cross-Cultural Validity of the Frost Multidimensional Perfectionism Scale in Korea

    ERIC Educational Resources Information Center

    Lee, Dong-gwi; Park, Hyun-joo

    2011-01-01

    This study with 213 South Korean college students (113 men) examined the cross-cultural generalizability of (a) the factor structure of the Frost Multidimensional Perfectionism Scale (F-MPS) and (b) the existence of adaptive perfectionists, maladaptive perfectionists, and nonperfectionists. A confirmatory factor analysis did not support the…

  14. Selective inverted sink efficiency for spring frost protection in almond orchards northwest of Isfahan, Iran

    NASA Astrophysics Data System (ADS)

    Yazdanpanah, H.; Stigter, C. J.

    2011-08-01

    A so-called selective inverted sink (SIS) was validated in frost protection of a 20-ha almond orchard. Daily counts of flower buds were made for two branches of some selected almond trees in every plot to determine frost damage percentage. Temperatures increased due to the SIS system, but there was an average gradient of temperature decrease of about 0.4°C per 100 m with distance from the SIS. The minimum air temperature increased from 0.5 to 2.8°C, with the highest increase closest to the SIS. The percent of frost-damaged flower buds of almond relative to the control plot with distance to the SIS system had its maximum gradient (8% per 100 m ) in 100-200-m distance from the SIS, but this gradient decreased to a minimum (4% per 100 m) in 500-700-m distance from the SIS. The ANOVA and Duncan's multiple-range test of air temperature and frost damage data confirm that the significant influence zone of this local SIS was about 500 m.

  15. Frosted Granular Flow as an Analog for Recent Gully Activity on Mars

    NASA Astrophysics Data System (ADS)

    Hugenholtz, C. H.

    2008-03-01

    In this paper frosted granular flow (FGF) is presented as a new hypothesis for recent mass wasting in martian gullies. FGF is a rare type of terrestrial granular flow that has been observed on a maritime talus slope in the Province of Québec, Canada.

  16. A Basic Thermodynamic Derivation of the Maximum Overburden Pressure Generated in Frost Heave

    E-print Network

    Libbrecht, Kenneth G.

    Heave Engine Frost heave is a common environmental process in which the freezing of water into ice can heave is not the result of the simple expansion that takes place when water freezes. Rather, it results when water migrates through a porous soil, forming ice "lenses" within the soil. This migration tends

  17. Old World Monkeys Stephen R Frost, University of Oregon, Eugene, Oregon, USA

    E-print Network

    Rosenberger, Alfred H.

    Old World Monkeys Stephen R Frost, University of Oregon, Eugene, Oregon, USA Alfred L Rosenberger) article, Old World Monkeys by Walter Carl Hartwig and Alfred L Rosenberger. Old World monkeys that allows them to digest leaves and which include langurs, proboscis mon- keys, doucs and snub-nosed monkeys

  18. Morning Frost in Trench Dug by Phoenix, Sol 113 (False Color)

    NASA Technical Reports Server (NTRS)

    2008-01-01

    This image from the Surface Stereo Imager on NASA's Phoenix Mars Lander shows morning frost inside the 'Snow White' trench dug by the lander, in addition to subsurface ice exposed by use of a rasp on the floor of the trench.

    The camera took this image at about 9 a.m. local solar time during the 113th Martian day of the mission (Sept. 18, 2008). Bright material near and below the four-by-four set of rasp holes in the upper half of the image is water-ice exposed by rasping and scraping in the trench earlier the same morning. Other bright material especially around the edges of the trench, is frost. Earlier in the mission, when the sun stayed above the horizon all night, morning frost was not evident in the trench.

    This image is presented in false color that enhances the visibility of the frost.

    The trench is 4 to 5 centimeters (about 2 inches) deep, about 23 centimeters (9 inches) wide.

    Phoenix landed on a Martian arctic plain on May 25, 2008. The mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is led by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development was by Lockheed Martin Space Systems, Denver.

  19. Application of Satellite Frost Forecast Technology to Other Parts of the United States

    NASA Technical Reports Server (NTRS)

    Martsolf, J. D.; Chen, E. (principal investigators)

    1981-01-01

    Thermal infrared data taken from the GOES satellite over a period of several hours was color enhanced by computer according to temperature. The varying temperatures were then used to assist in frost forecasting. Input from Michigan and Pennsylvania to the cold climate mapping project is emphasized in the report of the second year's activities of a two year effort.

  20. A nano-frost array technique to prepare nanoporous PVDF membranes.

    PubMed

    Lee, Min Kyung; Lee, Jonghwi

    2014-08-01

    Frost, the solid deposition of water vapor from humid air, forms on the surface of a solid substrate when its temperature drops below the freezing point of water. In this study, we demonstrate how this natural phenomenon can be applied to develop novel nanoporous materials. The solvent annealing of polyvinylidene fluoride (PVDF) infiltrated into nanopores induced template-directed dewetting thus preparing nanoembossing films. Then, water nanodroplets formed on the cold polymer nanopatterned surfaces following the embossing patterns, similar to dew formation on the ground. Subsequently, the nanodroplets were frozen and then removed by freeze-drying. This nano-frost array technique produced nanoporous PVDF membranes with an average thickness of 250 (± 48) nm. It was revealed that the nanopatterned surface formed by solvent annealing played an important role in achieving a nano-frost array with an adjustable size. Additionally, the freezing process led to significant changes of the PVDF crystallinity and polymorphism. Our results prove that the nano-frost array technique can be broadly used to design ordered nanoporous structures and provide new prospects in nanomaterial fields. PMID:24865989

  1. Observations of backscatter, particle concentration and frost point in north polar vortex stratospheric clouds

    SciTech Connect

    Rosen, J.M.; Kjome, N.T. ); Oltmans, S.J. )

    1990-08-01

    Near-simultaneous soundings of backscatter, particle size distribution and frost point were obtained in north polar stratospheric clouds (PSCs) near the center of the vortex. The measured particle sizes and concentration in type I PSCs tend to confirm earlier predictions based on remotely sensed properties.

  2. NUCLEOSYNTHESIS IN INTERMEDIATE MASS STARS JOHN C. LATTANZIO AND CHERYL A. FROST

    E-print Network

    Lattanzio, John

    NUCLEOSYNTHESIS IN INTERMEDIATE MASS STARS JOHN C. LATTANZIO AND CHERYL A. FROST Department AND PETER R. WOOD Mount Stromlo and Siding Springs Observatories, ANU Abstract. We discuss nucleosynthesis lagging somewhat behind. Studies are desperately needed of the nucleosynthesis which occurs during

  3. What's Wrong with America's Playgrounds and How to Fix Them: An Interview with Joe L. Frost

    ERIC Educational Resources Information Center

    American Journal of Play, 2008

    2008-01-01

    Joe L. Frost is Parker Centennial Professor Emeritus at the University of Texas, Austin, and one of America's leading experts on play and playgrounds. In addition to having taught child development and early childhood education at Texas and several other universities, he has written or edited fifteen university-level textbooks and more than one…

  4. University of Alberta Adaptation of trembling aspen and hybrid poplars to frost

    E-print Network

    Hamann, Andreas

    be an essential adaptive trait to ensure frost tolerance and long-term productivity of hybrid poplar plantations were tested in a series of reciprocal transplant experiments across western Canada. The analysis found reported trade-offs between freezing tolerance and growth rate were not found in this study. Seed

  5. Frost Damage Detection in Sugarcane Crop Using Modis Images and Srtm Data

    NASA Astrophysics Data System (ADS)

    Rudorff, B.; Alves de Aguiar, D.; Adami, M.

    2011-12-01

    Brazil is the largest world producer of sugarcane which is used to produce almost equal proportions of either sugar (food) or ethanol (biofuel). In recent years sugarcane crop production has increased fast to meet the growing market demand for sugar and ethanol. This increase has been mainly due to expansion in crop area, but sugarcane production is also subjected to several factors that influence both the agricultural crop yield (tons of stalks/ha) and the industrial yield (kg of sugar/ton of stalks). Sugarcane is a semi-perennial crop that experiences major growth during spring and summer seasons with large demands for water and high temperatures to produce good stalk formation (crop yield). The harvest is performed mainly during fall and winter seasons when water availability and temperature should be low in order to accumulate sucrose in the stalks (industrial yield). These favorable climatic conditions for sugarcane crop are found in several regions in Brazil, particularly in São Paulo state, which is the major sugarcane producer in Brazil being responsible for almost 60% of its production. Despite the favorable climate in São Paulo state there is a certain probability of frost occurrence from time to time that has a negative impact on sugarcane crop, particularly on industrial yield, reducing the amount of sugar in the stalks; having consequences on price increase and product shortage. To evaluate the impact of frost on sugarcane crop, in the field, on a state level, is not a trivial task; however, this information is relevant due to its direct impact on the consumer market. Remote sensing images allow a synoptic view and present great potential to monitor large sugarcane plantations as has been done since 2003 in São Paulo state by the Canasat Project with Landsat type images (http://www.dsr.inpe.br/laf/canasat/en/). Images acquired from sensors with high temporal resolution such as MODIS (Moderate-Resolution Imaging Spectroradiometer) present the potential to detect the impact of climatic effects, such as frost, on crop growth, which is relevant information to evaluate the negative impact on sugarcane production. Thus, the objective of the present study is to detect the impact of the frost occurred on 28 June 2011 in the sugarcane production region of São Paulo state, using MODIS images acquired on board of Terra and Aqua satellites before and after the frost event. Also, Landsat type images were used to map the harvested sugarcane fields up to the frost event based on a sugarcane crop map for year 2011. The remaining sugarcane fields available for harvest in 2011 were monitored with the MODIS images acquired on 17, 19, 27, 28 June and 8 and 9 July, to detect frost damage. Field work was conducted shortly after frost occurrence to identify sugarcane fields with frost damage for training and validation purposes. MODIS images transformed to vegetation indices and morphometric variables extracted from SRTM (Shuttle Radar Topography Mission) data are being analyzed to detect and quantify the damage of the frost from 28 July 2011 on sugarcane crop.

  6. Climate change and the effect of temperature backlashes causing frost damage in Picea abies

    NASA Astrophysics Data System (ADS)

    Jönsson, Anna Maria; Linderson, Maj-Lena; Stjernquist, Ingrid; Schlyter, Peter; Bärring, Lars

    2004-12-01

    In boreal and nemoboreal forests, tree frost hardiness is modified in reaction to cues from day length and temperature. The dehardening processes in Norway spruce, Picea abies, could be estimated to start when the daily mean temperature is above 5 °C for 5 days. Bud burst will occur approximately after 120-170 degree-days above 5 °C, dependent on genetic differences among provenances. A reduced cold hardiness level during autumn and spring and an advanced onset of bud burst are expected impacts of projected future global warming. The aim of this study was to test if this will increase the risk for frost damage caused by temperature backlashes. This was tested for Sweden by comparing output from the Hadley Centre regional climate model, HadRM3H, for the period 1961-1990 with future IPCC scenario SRES A2 and B2 for 2070-2099. Different indices for calculating the susceptibility to frost damage were used to assess changes in frost damage risk. The indices were based on: (1) the start of dehardening; (2) the severity of the temperature backlash; (3) the timing of bud burst; and (4) the cold hardiness level. The start of dehardening and bud burst were calculated to occur earlier all over the country, which is in line with the overall warming in both climate change scenarios. The frequency of temperature backlashes that may cause frost damage was calculated to increase in the southern part, an effect that became gradually less pronounced towards the north. The different timing of the onset of dehardening mainly caused this systematic latitudinal pattern. In the south, it occurs early in the year when the seasonal temperature progression is slow and large temperature variations occur. In the north, dehardening will occur closer to the spring equinox when the temperature progression is faster.

  7. Cement mortar-degraded spinney waste composite as a matrix for immobilizing some low and intermediate level radioactive wastes: Consistency under frost attack

    NASA Astrophysics Data System (ADS)

    Eskander, S. B.; Saleh, H. M.

    2012-01-01

    The increasing amounts of spinning waste fibers generated from cotton fabrication are problematic subject. Simultaneous shortage in the landfill disposal space is also the most problem associated with dumping of these wastes. Cement mortar composite was developed by hydrating mortar components using the waste slurry obtained from wet oxidative degradation of these spinney wastes. The consistency of obtained composite was determined under freeze-thaw events. Frost resistance was assessed for the mortar composite specimens by evaluating its compressive strength, apparent porosity and mass loss at the end of each period of freeze-thaw up to 45 cycles. Scanning electron microscopy, infrared spectroscopy and X-ray diffraction analyses were performed for samples subjected to frost attack aiming at evaluating the cement mortar in the presence of degraded spinney waste. The cement mortar composite exhibits acceptable resistance and durability against the freeze-thaw treatment that could be chosen in radioactive waste management as immobilizing agent for some low and intermediate level radioactive wastes.

  8. FROST - FReezing Of coated and uncoated duST particles

    NASA Astrophysics Data System (ADS)

    Wex, H.

    2009-04-01

    In April 2008, the measurement campaign FROST (FReezing Of coated and uncoated duST particles) was conducted at the ACCENT (Atmospheric Composition Change - the European NeTwork of excellence) infrastructure site LACIS (Leipzig Aerosol Cloud Interaction Simulator). During the campaign, size selected coated and uncoated Arizona Test Dust (ATD) particles were characterized with respect to shape, chemical composition, hygroscopic growth and activation, and their ability to act as IN (Ice Nuclei). The ATD particles were dispersed by means of a fluidized bed generator. Coatings were applied in different furnaces, operated at different temperatures. The coatings were either succinic acid, sulphuric acid, or ammonium sulphate. A DMA (Differential Mobility Analyzer) was used for selecting particles with a mobility diameter of 300 nm. The following measurements were done: Three AMS (Aerosol Mass Spectrometers, e.g. Schneider et al. (2005) and references therein) were used to determine particle composition. Particles were collected on grids for subsequent TEM (Transmission Electron Micoscropy) analysis. Hygroscopic growth factors were determined by means of a HH-TDMA (High Humidity Tandem Differential Mobility Analyzer) that measured up to relative humidities (RH) of 98% (Hennig et al. (2005)). The critical super-saturations needed for the activation of the investigated particles into cloud droplets were measured with a continuous flow CCNc (Cloud Condensation Nucleus counter) from DMT (Droplet Measurement Technologies, Roberts and Nenes (2005)). The LACIS flow tube was extended to a length of 8 m, so LACIS could be used to examine the immersion freezing behaviour of the coated and uncoated ATD particles. By a bulk analysis and by the AMS measurements, the ATD particles were found to contain water soluble material, however in small quantities. By means of the online AMS measurements, it was possible to distinguish between thin and thick H2SO4 coatings. For the thin coatings, the H2SO4 was found to have reacted with material contained in the ATD, so that almost no free H2SO4 was found. For the thick coatings, obtained at higher coating temperatures, H2SO4 was detected. In general, uncoated particles and those coated with thin coatings of H2SO4 or of succinic acid, showed almost no hygroscopic growth. Particles coated with thicker coatings of H2SO4 and of ammonium sulphate grew noticeably above 95% RH (growth factors of about 1.1 at 98% RH). Both, coated and uncoated ATD particles, were found to activate at atmospherically relevant super-saturations (0.35% for pure ATD, 0.2% for succinic acid and thin H2SO4 coatings, 0.15% for thick H2SO4 and for ammonium sulphate coatings). Combining measured hygroscopic growth with activation data, a dynamic shape factor of the ATD particles of about 1.8 was derived, corroborating the deviation of the particle shape from that of a sphere. Uncoated ATD particles and particles coated with succinic acid or thin coatings of H2SO4 nucleated ice at higher temperatures, i.e. were more efficient IN, than particles with thick H2SO4 or ammonium sulphate coatings. Although the latter two were similar in hygroscopic growth and activation behaviour, they differed in their ability to act as IN, with ATD particles coated with ammonium sulphate being the most ineffective IN. This finding suggests that the investigated particle's ability to act as IN might not be related to water activity for the immersion freezing processes investigated in this study. References: Hennig, T., A. Massling, F. Brechtel, and A. Wiedensohler (2005), A tandem DMA for highly temperature-stabilized hygroscopic particle growth measurements between 90% and 98% relative humidity, J. Aerosol Sci., 36, 10, 1210-1223. Roberts, G., and A. Nenes (2005), A continuous-flow streamwise thermal-gradient CCN chamber for atmospheric measurements, Aerosol Sci. Technol., 39, 206-221. Schneider, J., N. Hock, S. Weimer, S. Borrmann, U. Kirchner, R. Vogt, and V. Scheer (2005), Nucleation particles in Diesel exhaust: Composition inferred from in situ mass sp

  9. Frost Monitoring and Forecasting Using MODIS Land Surface Temperature Data and a Numerical Weather Prediction Model Forecasts for Eastern Africa

    NASA Technical Reports Server (NTRS)

    Kabuchanga, Eric; Flores, Africa; Malaso, Susan; Mungai, John; Sakwa, Vincent; Shaka, Ayub; Limaye, Ashutosh

    2014-01-01

    Frost is a major challenge across Eastern Africa, severely impacting agricultural farms. Frost damages have wide ranging economic implications on tea and coffee farms, which represent a major economic sector. Early monitoring and forecasting will enable farmers to take preventive actions to minimize the losses. Although clearly important, timely information on when to protect crops from freezing is relatively limited. MODIS Land Surface Temperature (LST) data, derived from NASA's Terra and Aqua satellites, and 72-hr weather forecasts from the Kenya Meteorological Service's operational Weather Research Forecast model are enabling the Regional Center for Mapping of Resources for Development (RCMRD) and the Tea Research Foundation of Kenya to provide timely information to farmers in the region. This presentation will highlight an ongoing collaboration among the Kenya Meteorological Service, RCMRD, and the Tea Research Foundation of Kenya to identify frost events and provide farmers with potential frost forecasts in Eastern Africa.

  10. Frost monitoring and forecasting using MODIS Land Surface Temperature data and a Numerical Weather Prediction model forecasts for Eastern Africa

    NASA Astrophysics Data System (ADS)

    Limaye, A. S.; Kabuchanga, E. S.; Flores, A.; Mungai, J.; Sakwa, V. N.; Shaka, A.; Malaso, S.; Irwin, D.

    2014-12-01

    Frost is a major challenge across Eastern Africa, severely impacting agriculture. Frost damages have wide ranging economic implications on tea and coffee farms, which represent a major economic sector. Early monitoring and forecasting will enable farmers to take preventive actions to minimize the losses. Although clearly important, timely information on when to protect crops from freezing is relatively limited. MODIS Land Surface Temperature (LST) data, derived from NASA's Terra and Aqua satellites, and 72-hr weather forecasts from the Kenya Meteorological Service's operational Weather Research Forecast model are enabling the Regional Center for Mapping of Resources for Development (RCMRD) and the Tea Research Foundation of Kenya to provide timely information to farmers in the region. This presentation will highlight an ongoing collaboration among the Kenya Meteorological Service, RCMRD, and the Tea Research Foundation of Kenya to identify frost events and provide farmers with potential frost forecasts in Eastern Africa.

  11. Hydrochemical dynamics of stream water during snowmelt under differing soil frost regimes in a northern hardwood forest

    NASA Astrophysics Data System (ADS)

    Fuss, C. B.; Driscoll, C. T.; Green, M. B.; Groffman, P. M.

    2012-12-01

    Winter climate change is expected to alter the snowpack accumulation as well as the timing and magnitude of snowmelt events in northern hardwood forests. Additionally, lower snowpacks associated with climate change have been hypothesized to increase soil freezing events. Soil freezing has been associated with increases in acidity and the leaching of nitrate, but the observed effects are inconsistent, especially when comparing the plot and watershed scales. Snowmelt is a large portion of the annual hydrologic flux in northern hardwood forest catchments and characterized by acidic conditions, which can be deleterious for downstream water quality. The objectives of our study were to characterize the hydrochemical dynamics longitudinally within watersheds under differing climatic conditions and to determine if inconsistencies in observed responses to soil freezing can be explained by changes in hydrologic flowpaths associated with soil frost. We measured major solute chemistry in daily stream water samples collected throughout the snowmelt periods of 2010, 2011, and 2012 at the Hubbard Brook Experimental Forest, NH, USA. Samples were collected at the gauging station of three different watersheds (two south-facing and one north-facing) and at a higher elevation site (approximately 100 m higher than the gauging station) in one south-facing and one north-facing watershed). This sampling scheme was designed to take advantage natural differences in snow depth and soil freezing between and within watersheds. We found generally more acidic drainage water with greater flushing of nitrate (NO3-) and dissolved organic carbon (DOC) in the higher elevation sampling sites of the watersheds. Changes in solute chemistry with flow rate were more pronounced at the base of the watershed where the deeper soil profile at lower elevation allowed for more variation in hydrologic flowpaths compared to the shallow higher elevation soils. For example, changes in stream NO3- concentration associated with increases in flow during snowmelt were as much as 200% greater at the base of the watersheds compared to changes at higher elevation. Using data from soil water, shallow ground water, and snowpack, we are performing end-member mixing analysis (EMMA) to quantify the relative contribution of each source to stream water in order to characterize the hydrologic flowpaths throughout the course of snowmelt. We expect the results of the EMMA to show that the presence of soil frost attenuates lateral flow through shallow soil horizons during peak snowmelt. Our study indicates that the chemistry of snowmelt is the result of a complex set of biogeochemical and hydrological processes and that knowledge of the climatic and physical differences among subcatchments is important to understand how the northern hardwood forest is responding to winter climate change. We demonstrate that understanding the influence of soil frost on hydrology is necessary to interpret plot study soil freezing results and how they are used for larger scale predictions.

  12. Development and Sensitivity Analysis of a Frost Risk model based primarily on freely distributed Earth Observation data

    NASA Astrophysics Data System (ADS)

    Louka, Panagiota; Petropoulos, George; Papanikolaou, Ioannis

    2015-04-01

    The ability to map the spatiotemporal distribution of extreme climatic conditions, such as frost, is a significant tool in successful agricultural management and decision making. Nowadays, with the development of Earth Observation (EO) technology, it is possible to obtain accurately, timely and in a cost-effective way information on the spatiotemporal distribution of frost conditions, particularly over large and otherwise inaccessible areas. The present study aimed at developing and evaluating a frost risk prediction model, exploiting primarily EO data from MODIS and ASTER sensors and ancillary ground observation data. For the evaluation of our model, a region in north-western Greece was selected as test site and a detailed sensitivity analysis was implemented. The agreement between the model predictions and the observed (remotely sensed) frost frequency obtained by MODIS sensor was evaluated thoroughly. Also, detailed comparisons of the model predictions were performed against reference frost ground observations acquired from the Greek Agricultural Insurance Organization (ELGA) over a period of 10-years (2000-2010). Overall, results evidenced the ability of the model to produce reasonably well the frost conditions, following largely explainable patterns in respect to the study site and local weather conditions characteristics. Implementation of our proposed frost risk model is based primarily on satellite imagery analysis provided nowadays globally at no cost. It is also straightforward and computationally inexpensive, requiring much less effort in comparison for example to field surveying. Finally, the method is adjustable to be potentially integrated with other high resolution data available from both commercial and non-commercial vendors. Keywords: Sensitivity analysis, frost risk mapping, GIS, remote sensing, MODIS, Greece

  13. EVALUATION OF FROST HEAVE ON WASTE TRANSFER LINES WITH SHALLOW DEPTHS IN DST (DOUBLE SHELL TANK) FARMS

    SciTech Connect

    HAQ MA

    2009-05-12

    The purpose of this document is to evaluate the effect of frost heave on waste transfer lines with shallow depths in DST farms. Because of the insulation, well compacted sandy material around waste transfer lines, the type of sandy and gravel soil, and relatively low precipitation at Hanford site, it is concluded that waste transfer lines with one foot of soil covers (sandy cushion material and insulation) are not expected to undergo frost heave damaging effects.

  14. Two-dimensional model of coupled heat and moisture transport in frost-heaving soils

    SciTech Connect

    Guymon, G.L.; Berg, R.L.; Hromadka, T.V.

    1984-09-01

    A two-dimensional model of coupled heat and moisture flow in frost-heaving soils is developed based upon well known equations of heat and moisture flow in soils. Numerical solution is by the nodal domain integration method which includes the integrated finite difference and the Galerkin finite element methods. Solution of the phase change process is approximated by an isothermal approach and phenomenological equations are assumed for processes occurring in freezing or thawing zones. The model has been verified against experimental one-dimensional freezing soil column data and experimental two-dimensional soil thawing tank data as well as two-dimensional soil seepage data. The model has been applied to several simple but useful field problems such as roadway embankment freezing and frost heaving.

  15. Laboratory determination of frosting and defrosting losses for a high efficiency air-source heat pump

    NASA Astrophysics Data System (ADS)

    Miller, W. A.; Ellison, R. D.

    Tests to detail system and component performance data, to quantify the dynamic losses, and to seek and evaluate methods for reducing these losses were performed. A high efficiency split-system heat pump was installed in two separate air loops, with one loop housing the indoor and the other housing the outdoor unit. Calculations of the heat pump's performance based on air-side measurements were within 3% of that based on refrigerant side measurements. Performance of the heat pump was measured under steady-state, dehumidification, and frosting-defrosting conditions with major emphasis placed on the dynamic frosting operation of the system. The system and component performance was evaluated for ambient temperature levels of 8.3, 4.4, 1.7, -1.1 and -8.3 C, and for discrete humidity levels ranging from 50 to 90%.

  16. Frosted granular flow: A new hypothesis for mass wasting in martian gullies

    NASA Astrophysics Data System (ADS)

    Hugenholtz, Chris H.

    2008-09-01

    Recent gully deposits on Mars have been attributed to both wet and dry mass wasting processes. In this paper frosted granular flow (FGF) is presented as a new hypothesis for recent mass wasting activity in martian gullies. FGF is a rare type of granular flow observed on a talus slope in the Province of Québec, Canada [Hétu, B., van Steijn, H., Vandelac, P., 1994. Géogr. Phys. Quat. 48, 3-22]. Frost reduces dynamic inter-particle friction, enabling flows to mobilize onto relatively low slope gradients (25-30°) compared to those involving dry granular flow of the same material (35-41°). Resulting erosional and depositional features include straight to sinuous channels, levees and digitate to branching arrangements of terminal deposits. Similar features are commonly found in association with geologically-young gully systems on Mars. Based on terrestrial observations of FGF processes the minimum criteria required for their occurrence on Mars include: (i) readily mobilized, unconsolidated sediment at the surface; (ii) an upper slope gradient at or near the angle of repose; (iii) frost accumulation at the surface; and (iv) triggering by rock fall. All four conditions appear to be met in many areas on present-day Mars though triggering mechanisms may vary. Compared to terrestrial FGFs, which are lubricated by thin liquid films at inter-particle contacts, those occurring on Mars are more likely lubricated by vaporization of CO 2 and small amounts of H 2O frost that becomes incorporated in the translating mass. Some recent mass wasting activity in martian gullies, therefore, could be interpreted as the product of FGF.

  17. Frost damage in citric and olive production as the result of climate degradation

    NASA Astrophysics Data System (ADS)

    Saa Requejo, A.; Díaz Alvarez, M. C.; Tarquis, A. M.; Burgaz Moreno, F.; Garcia Moreno, R.

    2009-04-01

    Low temperature is one of the chief limiting factors in plant distribution. Freezing temperature shortens the growing season and may lower the yield and quality of any number of fruit crops. Minimum temperatures records for the Spanish region of Murcia were studied as limiting factor in fruit production. An analysis of temperature series since 1935 showed that the range of the absolute minimum temperatures (Tmin) on frost days in the target year, namely -0.5 °C to -4.0°C, was statistically similar to the range recorded in 1993, while the mean minimum temperatures (tmin) were found to have risen. The historical series also showed the mean minimum temperatures (tmin) to have increased, however. Through 1985, tmin ranged from 4.0 to -2.0 °C, depending on the area, while these limits shifted in more recent years to 7.0 - 0.5 °C. This increase in mean temperature produced that the frost episodes in March 2004 was considered by lemon, mandarin and olive producers as the worst in many years for frost damage since the minimum temperature was reached in a more sensitive phenological stage, despite the statistical evidence that similar freezing temperatures had been reached on similar dates in other years.

  18. Performance of a hypersonic hot fuselage structure with a carbon dioxide frost projected, nonintegral cryogenic tank

    NASA Technical Reports Server (NTRS)

    Sharpe, E. L.; Jackson, L. R.

    1975-01-01

    A model which consisted of a hot structure and a nonintegral tank protected by a carbon dioxide frost thermal protection system was tested under the following conditions: (1) room temperature loading and (2) heating and loading corresponding to the Mach 8 flight of an air-breathing launch vehicle. In the simulated flight tests, liquid nitrogen inside the tank was withdrawn at the rate fuel would be consumed. Prior to each simulated flight test, carbon dioxide was cryodeposited in the insulation surrounding the tank; during the tests, subliming CO2 frost absorbed heat and provided a purge gas for the space between the tank and the structure. A method of flame spraying the joints between panels with a nickel-aluminum material was developed to prevent excessive leakage of the purge gas through the outer structure. The tests indicated that the hot structure (with a joint repaired by riveting), the nonintegral tank and suspension system, and the carbon dioxide frost thermal protection system provide a workable concept with predictable performance.

  19. Frost for the trees: Did climate increase erosion in unglaciated landscapes during the late Pleistocene?

    PubMed Central

    Marshall, Jill A.; Roering, Joshua J.; Bartlein, Patrick J.; Gavin, Daniel G.; Granger, Darryl E.; Rempel, Alan W.; Praskievicz, Sarah J.; Hales, Tristram C.

    2015-01-01

    Understanding climatic influences on the rates and mechanisms of landscape erosion is an unresolved problem in Earth science that is important for quantifying soil formation rates, sediment and solute fluxes to oceans, and atmospheric CO2 regulation by silicate weathering. Glaciated landscapes record the erosional legacy of glacial intervals through moraine deposits and U-shaped valleys, whereas more widespread unglaciated hillslopes and rivers lack obvious climate signatures, hampering mechanistic theory for how climate sets fluxes and form. Today, periglacial processes in high-elevation settings promote vigorous bedrock-to-regolith conversion and regolith transport, but the extent to which frost processes shaped vast swaths of low- to moderate-elevation terrain during past climate regimes is not well established. By combining a mechanistic frost weathering model with a regional Last Glacial Maximum (LGM) climate reconstruction derived from a paleo-Earth System Model, paleovegetation data, and a paleoerosion archive, we propose that frost-driven sediment production was pervasive during the LGM in our unglaciated Pacific Northwest study site, coincident with a 2.5 times increase in erosion relative to modern rates. Our findings provide a novel framework to quantify how climate modulates sediment production over glacial-interglacial cycles in mid-latitude unglaciated terrain. PMID:26702434

  20. Numerical Simulation of Plain Fin-and-Round Tube Heat Exchanger under Frost Condition

    NASA Astrophysics Data System (ADS)

    Hussein, Amar Ali; Talib, A. R. Abu; Adam, N. M.

    2010-06-01

    Three-dimensional numerical simulations are carried out to investigate the amount of heat transfer of a plain fin-and-four staggered layout and round tube rows for different fin pitch namely 25.4, 12.7, 6.35 and 4.23 mm. The simulations were conducted for two different frost thermal conductivity of 0.1 and 0.3 W/m-1K-1 using FLUENT 6.3 CFD code. The amount of heat transfer of the plain fin-and-round tube heat exchanger under frost condition (0, 1, 2, and 3 mm frost thickness) was investigated. Fluid flow and heat transfer are simulated and results calculated using two turbulence models (k-epsilon, and Transitional SST k-omega), with steady-state solver. Model validation was carried out by comparing the pressure drop of simulated case to experimental results from the literature. Reasonable agreement was found between the present simulations compared to existing numerical study and experimental data.

  1. Proteomic and metabolomic profiling of Valencia orange fruit after natural frost exposure.

    PubMed

    Perotti, Valeria E; Moreno, Alejandra S; Trípodi, Karina E J; Meier, Guillermo; Bello, Fernando; Cocco, Mariángeles; Vázquez, Daniel; Anderson, Catalina; Podestá, Florencio E

    2015-03-01

    The aim of this study was to evaluate the response of orange fruit (Citrus sinensis var. Valencia Late) to freezing stress in planta, both immediately after the natural event and after a week, in order to understand the biochemical and molecular basis of the changes that later derive in internal and external damage symptoms. Using two-dimensional differential gel electrophoresis to analyze exposed and non-exposed fruit, 27 differential protein spots were detected in juice sacs and flavedo, among all comparisons made. Also, primary and secondary metabolites relative contents were analyzed in both tissues by gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry, respectively. Proteins and compounds involved in regulatory functions, iron metabolism, oxidative damage and carbohydrate metabolism were the most affected. Interestingly, three glycolytic enzymes were induced by cold, and there was an increase in fermentation products (volatiles); all of that suggests that more energy generation might be required from glycolysis to counter the cold stress. Moreover, a notable increase in sugar levels was observed after frost, but it was not at the expense of organic acids utilization. Consequently, these results suggest a probable redistribution of photoassimilates in the frost-exposed plants, tending to restore the homeostasis altered by that severe type of stress. Isosinensetin was the most cold-sensitive secondary metabolite because it could not be detected at all after the frost, constituting a possible tool to early diagnose freezing damage. PMID:25132553

  2. Mechanism of delayed frost growth on superhydrophobic surfaces with jumping condensates: more than interdrop freezing.

    PubMed

    Hao, Quanyong; Pang, Yichuan; Zhao, Ying; Zhang, Jing; Feng, Jie; Yao, Shuhuai

    2014-12-30

    Delayed frost growth on superhydrophobic surfaces (SHSs) with jumping condensates has been found by many researchers recently. However, the mechanism of this phenomenon has not been elucidated clearly. In this study, copper SHSs with or without jumping condensates were selected as the substrates for observing condensation icing at a relative humidity (RH) of 60%. The results showed that only SHS with jumping condensates showed delayed condensation icing. Moreover, when such SHSs were placed upward and the surface temperature was held at -10 °C, some discrete frozen drops first appeared on the SHSs. The following icing mainly occurred on these discrete global crystals and then expanded around them until covering the entire surface. Little macroscopic interdrop freezing phenomenon was found. The growth of the frost front is mainly dominated by jumping freezing (the condensed droplets jumped onto the ice crystals and were frozen) or direct vapor-ice deposition. Using microscopy, we found interdrop freezing occurred, in addition to the two mechanisms mentioned above. By placing the SHS downward at -10 °C and intentionally introducing or eliminating tiny dusts, we confirmed that there were no superhydrophobic defects on our SHSs. The discrete frozen drops first appearing on the SHSs were triggered by tiny dusts falling on the surface before or during condensation icing. The key approach in delaying or resisting frost growth on SHSs with jumping condensates is to retard initial ice crystal formation, e.g., eliminating the edge effect and keeping the SHSs clean. PMID:25466489

  3. Reliability of predicting the number of frost days in the MiKlip decadal prediction system

    NASA Astrophysics Data System (ADS)

    Kröner, Igor; Rust, Henning; Kruschke, Tim; Ulbrich, Uwe

    2015-04-01

    As decadal predictions are gaining more and more attention among for decision makers, it is essential that these predictions are reliable, i.e. that they 'mean what they say'. A popular prediction setting for the decadal scale is the probability of exceedances of threshold, e.g. the probability for the number of frost days (days with minimum temperature below 0°C) in a certain region exceeding the climatological median or the 2nd tercile. These probabilistic forecasts of dichotomous events (e.g., the probability of exceeding a threshold) are typically verified with the Brier Score. Its decomposition leads to the attributes diagram, an elegant graphical representation of the essential information needed for verification, such as the reliability. Within the frame of Germany's national initative for decadal predictions (MiKlip), we analyze the reliability of ensemble hindcasts for the number of frost days. The ensemble hindcasts stem from the Max-Planck-Institute's Earth System Model in a low-resolution configuration (MPI-ESM-LR). Hindcast verification is carried out for different setups of the model initialisation. Apart from investigating various spatial and temporal aggregation scales for the number of frost days, we compare different ways to quantify and communicate reliability to stakeholders using a discrete set of categories (e.g., reliable, skillful, potential useful, etc.)

  4. Climate Change and Crop Exposure to Adverse Weather: Changes to Frost Risk and Grapevine Flowering Conditions

    PubMed Central

    Mosedale, Jonathan R.; Wilson, Robert J.; Maclean, Ilya M. D.

    2015-01-01

    The cultivation of grapevines in the UK and many other cool climate regions is expected to benefit from the higher growing season temperatures predicted under future climate scenarios. Yet the effects of climate change on the risk of adverse weather conditions or events at key stages of crop development are not always captured by aggregated measures of seasonal or yearly climates, or by downscaling techniques that assume climate variability will remain unchanged under future scenarios. Using fine resolution projections of future climate scenarios for south-west England and grapevine phenology models we explore how risks to cool-climate vineyard harvests vary under future climate conditions. Results indicate that the risk of adverse conditions during flowering declines under all future climate scenarios. In contrast, the risk of late spring frosts increases under many future climate projections due to advancement in the timing of budbreak. Estimates of frost risk, however, were highly sensitive to the choice of phenology model, and future frost exposure declined when budbreak was calculated using models that included a winter chill requirement for dormancy break. The lack of robust phenological models is a major source of uncertainty concerning the impacts of future climate change on the development of cool-climate viticulture in historically marginal climatic regions. PMID:26496127

  5. Frost for the trees: Did climate increase erosion in unglaciated landscapes during the late Pleistocene?

    PubMed

    Marshall, Jill A; Roering, Joshua J; Bartlein, Patrick J; Gavin, Daniel G; Granger, Darryl E; Rempel, Alan W; Praskievicz, Sarah J; Hales, Tristram C

    2015-11-01

    Understanding climatic influences on the rates and mechanisms of landscape erosion is an unresolved problem in Earth science that is important for quantifying soil formation rates, sediment and solute fluxes to oceans, and atmospheric CO2 regulation by silicate weathering. Glaciated landscapes record the erosional legacy of glacial intervals through moraine deposits and U-shaped valleys, whereas more widespread unglaciated hillslopes and rivers lack obvious climate signatures, hampering mechanistic theory for how climate sets fluxes and form. Today, periglacial processes in high-elevation settings promote vigorous bedrock-to-regolith conversion and regolith transport, but the extent to which frost processes shaped vast swaths of low- to moderate-elevation terrain during past climate regimes is not well established. By combining a mechanistic frost weathering model with a regional Last Glacial Maximum (LGM) climate reconstruction derived from a paleo-Earth System Model, paleovegetation data, and a paleoerosion archive, we propose that frost-driven sediment production was pervasive during the LGM in our unglaciated Pacific Northwest study site, coincident with a 2.5 times increase in erosion relative to modern rates. Our findings provide a novel framework to quantify how climate modulates sediment production over glacial-interglacial cycles in mid-latitude unglaciated terrain. PMID:26702434

  6. High-Density Amorphous Ice, the Frost on Interstellar Grains

    NASA Technical Reports Server (NTRS)

    Jenniskens, P.; Blake, D. F.; Wilson, M. A.; Pohorille, A.

    1995-01-01

    Most water ice in the universe is in a form which does not occur naturally on Earth and of which only minimal amounts have been made in the laboratory. We have encountered this 'high-density amorphous ice' in electron diffraction experiments of low-temperature (T less than 30 K) vapor-deposited water and have subsequently modeled its structure using molecular dynamics simulations. The characteristic feature of high-density amorphous ice is the presence of 'interstitial' oxygen pair distances between 3 and 4 A. However, we find that the structure is best described as a collapsed lattice of the more familiar low-density amorphous form. These distortions are frozen in at temperatures below 38 K because, we propose, it requires the breaking of one hydrogen bond, on average, per molecule to relieve the strain and to restructure the lattice to that of low-density amorphous ice. Several features of astrophysical ice analogs studied in laboratory experiments are readily explained by the structural transition from high-density amorphous ice into low-density amorphous ice. Changes in the shape of the 3.07 gm water band, trapping efficiency of CO, CO loss, changes in the CO band structure, and the recombination of radicals induced by low-temperature UV photolysis all covary with structural changes that occur in the ice during this amorphous to amorphous transition. While the 3.07 micrometers ice band in various astronomical environments can be modeled with spectra of simple mixtures of amorphous and crystalline forms, the contribution of the high-density amorphous form nearly always dominates.

  7. Stabilization of Leidenfrost vapour layer by textured superhydrophobic surfaces.

    PubMed

    Vakarelski, Ivan U; Patankar, Neelesh A; Marston, Jeremy O; Chan, Derek Y C; Thoroddsen, Sigurdur T

    2012-09-13

    In 1756, Leidenfrost observed that water drops skittered on a sufficiently hot skillet, owing to levitation by an evaporative vapour film. Such films are stable only when the hot surface is above a critical temperature, and are a central phenomenon in boiling. In this so-called Leidenfrost regime, the low thermal conductivity of the vapour layer inhibits heat transfer between the hot surface and the liquid. When the temperature of the cooling surface drops below the critical temperature, the vapour film collapses and the system enters a nucleate-boiling regime, which can result in vapour explosions that are particularly detrimental in certain contexts, such as in nuclear power plants. The presence of these vapour films can also reduce liquid-solid drag. Here we show how vapour film collapse can be completely suppressed at textured superhydrophobic surfaces. At a smooth hydrophobic surface, the vapour film still collapses on cooling, albeit at a reduced critical temperature, and the system switches explosively to nucleate boiling. In contrast, at textured, superhydrophobic surfaces, the vapour layer gradually relaxes until the surface is completely cooled, without exhibiting a nucleate-boiling phase. This result demonstrates that topological texture on superhydrophobic materials is critical in stabilizing the vapour layer and thus in controlling--by heat transfer--the liquid-gas phase transition at hot surfaces. This concept can potentially be applied to control other phase transitions, such as ice or frost formation, and to the design of low-drag surfaces at which the vapour phase is stabilized in the grooves of textures without heating. PMID:22972299

  8. Seasonal to Decadal Variations of Water Vapor in the Tropical Lower Stratosphere Observed with Balloon-Borne Cryogenic Frost Point Hygrometers

    NASA Technical Reports Server (NTRS)

    Fujiwara, M.; Voemel, H.; Hasebe, F.; Shiotani, M.; Ogino, S.-Y.; Iwasaki, S.; Nishi, N.; Shibata, T.; Shimizu, K.; Nishimoto, E.; ValverdeCanossa, J. M.; Selkirk, H. B.; Oltmans, S. J.

    2010-01-01

    We investigated water vapor variations in the tropical lower stratosphere on seasonal, quasi-biennial oscillation (QBO), and decadal time scales using balloon-borne cryogenic frost point hygrometer data taken between 1993 and 2009 during various campaigns including the Central Equatorial Pacific Experiment (March 1993), campaigns once or twice annually during the Soundings of Ozone and Water in the Equatorial Region (SOWER) project in the eastern Pacific (1998-2003) and in the western Pacific and Southeast Asia (2001-2009), and the Ticosonde campaigns and regular sounding at Costa Rica (2005-2009). Quasi-regular sounding data taken at Costa Rica clearly show the tape recorder signal. The observed ascent rates agree well with the ones from the Halogen Occultation Experiment (HALOE) satellite sensor. Average profiles from the recent five SOWER campaigns in the equatorial western, Pacific in northern winter and from the three Ticosonde campaigns at Costa Rica (10degN) in northern summer clearly show two effects of the QBO. One is the vertical displacement of water vapor profiles associated with the QBO meridional circulation anomalies, and the other is the concentration variations associated with the QBO tropopause temperature variations. Time series of cryogenic frost point hygrometer data averaged in a lower stratospheric layer together with HALOE and Aura Microwave Limb Sounder data show the existence of decadal variations: The mixing ratios were higher and increasing in the 1990s, lower in the early 2000s, and probably slightly higher again or recovering after 2004. Thus linear trend analysis is not appropriate to investigate the behavior of the tropical lower stratospheric water vapor.

  9. Measuring the Size of a Small, Frost World

    NASA Astrophysics Data System (ADS)

    2006-01-01

    Observing a very rare occultation of a star by Pluto's satellite Charon from three different sites, including Paranal, home of the VLT, astronomers were able to determine with great accuracy the radius and density of the satellite to the farthest planet. The density, 1.71 that of water, is indicative of an icy body with about slightly more than half of rocks. The observations also put strong constraints on the existence of an atmosphere around Charon. ESO PR Photo 02a/06 ESO PR Photo 02a/06 Artist's Impression of the Pluto-Charon system Since its discovery in 1978, Charon and Pluto have appeared to form a double planet, rather than a planet-satellite couple. Actually, Charon is about twice as small as Pluto in size, and about eight times less massive. However, there have been considerable discussions concerning the precise radii of Pluto and Charon, as well as about the presence of a tenuous atmosphere around Charon. In August 2004, Australian amateur astronomer Dave Herald predicted that the 15-magnitude star UCAC2 26257135 should be occulted by Charon on 11 July 2005. The occultation would be observable from some parts of South America, including Cerro Paranal, in the northern Atacama Desert, the location of ESO's Very Large Telescope (VLT). Stellar occultations have proved to be powerful tools to both measure sizes - at km-level accuracy, i.e. a factor ten better than what is feasible with other techniques - and detect very tenuous atmosphere - at microbar levels or less. Unfortunately, in the case of Charon, such occultations are extremely rare, owing to the very small angular diameter of the satellite on the sky: 55 milli-arcsec, i.e. the size of a one Euro coin observed from 100 km away! This explains why only one occultation by Charon was ever observed before 2005, namely on 7 April 1980 by Alistair Walker, from the South Africa Astronomical Observatory. Similarly, only in 1985, 1988 and 2002 could astronomers observe stellar occultations by Pluto. Quite surprisingly, the 2002 event showed that Pluto's atmospheric pressure had increased by a factor of two in four years (ESO PHOT 21/02). "Several factors, however, have boosted our odds for witnessing occultations of Charon," said Bruno Sicardy, from Paris Observatory (France) and lead author of the paper reporting the results. "First, larger telescopes now give access to fainter stars, thus multiplying the candidates for occultations. Secondly, stellar catalogues have become much more precise, allowing us to do better predictions. And, finally, the Pluto-Charon system is presently crossing the Milky Way, thereby increasing the likelihood of an occultation." ESO PR Photo 02b/06 ESO PR Photo 02b/06 The Pluto-Charon System (NACO/VLT) The July 2005 event was eventually observed from Paranal with Yepun, the fourth Unit Telescope of the VLT, equipped with the adaptive optics instrument NACO, as well as with the 0.5m "Campo Catino Austral Telescope" at San Pedro de Atacama (Chile), and with the 2.15m "Jorge Sahade" telescope at Cerro El Leoncito (Argentina). An accurate timing of the occultation seen at the three sites provides the most accurate measurement of Charon's size: its radius is found to be 603.6 km, with an error of the order of 5 km. This accuracy now allows astronomers to pin Charon's density down to 1.71 that of water, indicative of an icy body with about slightly more than half of rocks. Quite remarkably, Charon's density is now measured with much more precision than Pluto's. ESO PR Photo 02c/06 ESO PR Photo 02c/06 Charon's Occultation on July 11, 2005 Thanks to these observations, Sicardy and his collaborators could determine that if an tenuous atmosphere exists on Charon, linking it to the freezing ­-220­ degrees centigrade or so surface, its pressure has to be less than one tenth of a millionth that at the surface of the Earth, or 0.1 microbar, assuming that it is constituted entirely of nitrogen. A similar upper limit is derived for a gas like carbon monoxide. This is more than a factor one hundred smaller than

  10. Recent changes in frost days events characteristics in Uruguay-Southeastern South America.

    NASA Astrophysics Data System (ADS)

    Renom, Madeleine; De Mello, Santiago

    2015-04-01

    There are few studies about extreme temperature events in Southeastern South America as is it mentioned in the SREX report (2009), although these events generate human health impacts and big economical looses. Southeastern South America is one of the major agricultural production regions worldwide. Particularly in Uruguay, agricultural production represents a high percentage of the GDP and, in the last 15 years there has been a significant increase in the area used for that economic activity. Although frost is not always is considered as an extreme event it causes, in the case of Uruguay, an impact on society, energy consumption and agricultural losses. Previous studies have shown a negative trend in the occurrence of cold nights (TN10) during winter (June-July-August) and autumn (March-April-May) in Uruguay. This work try to determine if these trends affects the occurrences and characteristics of frost days (Tmin< 0°C). Based on a high-quality daily minimum temperature for 11 meteorological stations that cover the period 1950-2009, we analyzed different features of frost days. Long term trends do not present a clear spatial behaviour suggesting that there is a not clear relationship between the percentile based index (TN10) and a fixed index (FD). At monthly scale, May and September show a negative trend, although these months present a low number of cases that difficult the statistical treatment. It is noticeable that from a decadal point of view the last decade (2000-2009) was the decade with fewer occurrences comparing with the rest, while the 90's is the decade that presents more cases. We also analyzed changes in frost period (FP) which commonly extends from May to September. In general all the stations present a decrease in the FP in accordance with the negative trend detected at monthly scale, suggesting a warming in autumn and spring time. Although we detected different behaviour in two stations, one located inner land and the other located on the Atlantic coast of the country. The former presents a linear trend in the FP, while the other shows a decadal variability. Regarding the frost intensity we analysed the consecutive frost days (CFD) index, which shows that the usual length is around 2-4 days. The decadal analysis shows that during the first decades events lasting 4-5 days were common, while in the last decades isolated events were detected. We also study the intensity considering the occurrence of events in different ranges of temperature: [0,-1], [-1,-2] and below -2°C. Overall, during the 90's there are more events below -2 °C, while during the 2000s although there were fewer events in the coastal stations they are more intense. Relationships with large scale anomalies circulations were also studied.

  11. Vertical movements of frost mounds in subarctic permafrost regions analyzed using geodetic survey and satellite interferometry

    NASA Astrophysics Data System (ADS)

    Beck, I.; Ludwig, R.; Bernier, M.; Strozzi, T.; Boike, J.

    2015-08-01

    Permafrost-affected soils cover about 40-45 % of Canada. The environment in such areas, especially those located within the discontinuous permafrost zone, has been impacted more than any other by recorded climatic changes. A number of changes, such as surface subsidence and the degradation of frost mounds due to permafrost thawing, have already been observed at many locations. We surveyed three frost mounds (lithalsas) in the subarctic, close to Umiujaq in northern Quebec, using high-precision differential global positioning system (d-GPS) technology during field visits in 2009, 2010 and 2011, thus obtaining detailed information on their responses to the freezing and thawing that occur during the course of the annual temperature cycle. Seasonal pulsations were detected in the frost mounds, and these responses were shown to vary with their state of degradation and the land cover. The most degraded lithalsa showed a maximum amplitude of vertical movement (either up or down) between winter (freezing) and summer (thawing) of 0.19 ± 0.09 m over the study period, while for the least degraded lithalsa this figure was far greater (1.24 ± 0.47 m). Records from areas with little or no vegetation showed far less average vertical movement over the study period (0.17 ± 0.03 m) than those with prostrate shrubs (0.56 ± 0.02 m), suggesting an influence from the land cover. A differential interferometric synthetic aperture radar (D-InSAR) analysis was also completed over the lithalsas using selected TerraSAR-X images acquired from April to October 2009 and from March to October 2010, with a repeat cycle of 11 days. Interferograms with baselines shorter than 200 m were computed revealing a generally very low interferometric coherence, restricting the quantification of vertical movements of the lithalsas. Vertical surface movements of the order of a few centimeters were recorded in the vicinity of Umiujaq.

  12. Liquid-infused nanostructured surfaces with extreme anti-ice and anti-frost performance.

    PubMed

    Kim, Philseok; Wong, Tak-Sing; Alvarenga, Jack; Kreder, Michael J; Adorno-Martinez, Wilmer E; Aizenberg, Joanna

    2012-08-28

    Ice-repellent coatings can have significant impact on global energy savings and improving safety in many infrastructures, transportation, and cooling systems. Recent efforts for developing ice-phobic surfaces have been mostly devoted to utilizing lotus-leaf-inspired superhydrophobic surfaces, yet these surfaces fail in high-humidity conditions due to water condensation and frost formation and even lead to increased ice adhesion due to a large surface area. We report a radically different type of ice-repellent material based on slippery, liquid-infused porous surfaces (SLIPS), where a stable, ultrasmooth, low-hysteresis lubricant overlayer is maintained by infusing a water-immiscible liquid into a nanostructured surface chemically functionalized to have a high affinity to the infiltrated liquid and lock it in place. We develop a direct fabrication method of SLIPS on industrially relevant metals, particularly aluminum, one of the most widely used lightweight structural materials. We demonstrate that SLIPS-coated Al surfaces not only suppress ice/frost accretion by effectively removing condensed moisture but also exhibit at least an order of magnitude lower ice adhesion than state-of-the-art materials. On the basis of a theoretical analysis followed by extensive icing/deicing experiments, we discuss special advantages of SLIPS as ice-repellent surfaces: highly reduced sliding droplet sizes resulting from the extremely low contact angle hysteresis. We show that our surfaces remain essentially frost-free in which any conventional materials accumulate ice. These results indicate that SLIPS is a promising candidate for developing robust anti-icing materials for broad applications, such as refrigeration, aviation, roofs, wires, outdoor signs, railings, and wind turbines. PMID:22680067

  13. New BEV/E+E Elektronik Low-Frost-Point/High-Pressure Generator

    NASA Astrophysics Data System (ADS)

    Mitter, H.

    2015-08-01

    Currently, the humidity standard at BEV/E+E is limited in the lower frost-point range to at pressures up to 1 MPa and to at ambient pressure. The system is also mainly designed for use with pure nitrogen as the carrier gas. In recent years, there has been a demand for humidity measurements in non-air gases (NAG) in contrast to "air gases" such as nitrogen, synthetic air, and -free standard air, even at pressures up to 10 MPa and in the frost-point range down to . NAGs can be gases such as , , and gas mixtures such as natural gas. To fulfill the requirements for humidity standards—especially in the high-pressure range—and to give the opportunity to determine thermodynamic properties such as enhancement factors in different carrier gases, a new "low-frost-point/high-pressure humidity generator" has been designed and verified at BEV/E+E Elektronik. The new humidity generator is designed as a single-pass generator with a maximum standard flow of and can be operated in the two-pressure mode as well as in the single-pressure mode at pressures up to 10 MPa. The design of the saturator focussed on reliability at high pressures and on achieving sufficient saturation efficiency at temperatures down to at least . First results of verification are presented in the range of saturator temperatures from to and at pressures up to 10 MPa. High-pressure data are presented for nitrogen and methane as carrier gases.

  14. Prediction of Frost Risks and Plagues using WRF model: a Port Wine region case study

    NASA Astrophysics Data System (ADS)

    Rodrigues, M. A.; Rocha, A.; Monteiro, A.; Quénol, H.; de Freitas, J. R.

    2012-04-01

    In viticulture where the quality of the wine, the selection of the grapevines or even the characteristics of the farming soil, also depending from local soil features like topography, proximity of a river or water body, will act locally on the weather. Frosts are of significant concern to growers of many cultures crops such as winegrapes. Because of their high latitude and some altitude, the vineyards of the Demarcated Douro Region (DDR) are subjected to the frost, which cause serious damages. But the hazards of vineyard don't confine to the incidents of the fortuitous and meteorological character. The illnesses and plagues affect frequently the vineyards of Demarcated Douro Region due, namely to the weather, to the high power of the regional stocks, to the dense vegetation badly drained and favourable to the setting of numberless fungi, viruses and/or poisonous insects. In the case of DDR it is worth noticing the meteorological conditions due to the weather characteristics. Although there are several illnesses and plagues the most important enemies for the vine in the DDR are the mildew, oidium, grey rottenness, grape moth,. . . , if the climatic conditions favour their appearance and development. For this study, we selected some months for different periods, at the 16 weather stations of the Region of Douro. We use the Weather Research and Forecast Model (WRF) to study and possibly predict the occurrence of risk and plagues (mildew) episodes. The model is first validated with the meteorological data obtained at the weather stations. The knowledge of frost and plagues occurrence allows one to decrease its risks not only by selecting the cultural species and varieties but also the places of growth and the planting and sowing dates.

  15. A laboratory study of the diffuse reflectance spectra of frosts occurring on astronomical objects

    NASA Technical Reports Server (NTRS)

    Glaser, F. M.

    1975-01-01

    Mechanical, optical, and operating properties of an experiment chamber are examined and possible sample contamination difficulty is explained. The mechanical and operational characteristics of this apparatus are well suited for the study of the reflectance spectra of frosts. The infrared energy available at the detector is low and steps to increase the energy and the responsivity of the detector were taken. The problem of a standard diffuse reflector which is useful in the far ultraviolet region is considered and it is suggested that bright gold be used as the standard.

  16. Further laboratory study of the diffuse reflectance spectra of frosts occurring on astronomical objects

    NASA Technical Reports Server (NTRS)

    Glaser, F. M.

    1976-01-01

    Oligoclase and bloedite, two mined samples, have been investigated, and the diffuse reflectance spectra are presented. These data are for powdered material, 50 microns to 5 microns size mixture, cooled to 160 K. The reflectivity of the oligoclase sample was also measured at room temperature, about 290 K, and the results at these two temperatures do indicate some tentative differences. A frost of ordinary water was prepared and its spectral reflectance is presented. This result compares reasonably well with measurements made by other investigators.

  17. Microbial Analysis of Arctic Snow and Frost Flowers: What Next Generation Sequencing Method Can Reveal

    NASA Astrophysics Data System (ADS)

    Mortazavi, R.; Attiya, S.; Ariya, P. A.

    2014-12-01

    We herein examined and identified the population of the microbial communities of Arctic snow types and frost flower during the spring 2009 campaign of the Ocean-Atmosphere-Sea Ice-Snowpack (OASIS) program in Barrow, Alaska, USA. In addition to conventional microbial identification techniques (culture-isolation-PCR amplification-sequencing) we deployed a state-of-the-art genomic Next Generation Sequencing (NGS) technique to examine the true bacterial communities in Arctic samples. Our results have indicated that diverse community of microbial exists in Arctic with many originating from distinct ecological environment. The alterations observed in the texture of Arctic samples by microbial has further signified their importance in ecosystem.

  18. Determination of E and G Observables in n Photoproduction on the CLAS Frozen Spin Target (FROST)

    SciTech Connect

    Senderovich, Igor; Morrison, Brian T.; Dugger, Michael R.; Ritchie, Barry G.; Tucker, Ross J.

    2014-01-01

    Polarization observables are vital for disentangling overlapping resonances in the baryon spectrum. Extensive data have been collected at Jefferson Lab in Hall B with circularly and linearly polarized tagged photon beam incident on longitudinally polarized protons provided by the Frozen Spin Target (FROST). The focus of the described work is on ? photoproduction, which acts as an "isospin filter", isolating the N*(I = 1/2) resonances. Preliminary results for the double-polarization observables E and G are presented. There are currently no data on these in the world database for ? photoproduction.

  19. Development of a Frost Risk Assessment Tool in Agriculture for a Mediterranean ecosystem Utilizing MODIS satellite observations Geomatics and Surface Data

    NASA Astrophysics Data System (ADS)

    Louka, Panagiota; Papanikolaou, Ioannis; Petropoulos, George; Migiros, George; Tsiros, Ioannis

    2014-05-01

    Frost risk in Mediterranean countries is a critical factor in agricultural planning and management. Nowadays, the rapid technological developments in Earth Observation (EO) technology have improved dramatically our ability to map the spatiotemporal distribution of frost conditions over a given area and evaluate its impacts on the environment and society. In this study, a frost risk model for agricultural crops cultivated in a Mediterranean environment has been developed, based primarily on Earth Observation (EO) data from MODIS sensor and ancillary spatial and point data. The ability of the model to predict frost conditions has been validated for selected days on which frost conditions had been observed for a region in Northwestern Greece according to ground observations obtained by the Agricultural Insurance Organization (ELGA). An extensive evaluation of the frost risk model predictions has been performed herein to evaluate objectively its ability to predict the spatio-temporal distribution of frost risk in the studied region, including comparisons against physiographical factors of the study area. The topographical characteristics that were taken under consideration were latitude, altitude, slope steepness, topographic convergence and the extend of the areas influenced by water bodies (such as lake and sea) existing in the study area. Additional data were also used concerning land use data and vegetation classification (type and density). Our results showed that the model was able to produce reasonably the spatio-temporal distribution of the frost conditions in our study area, following largely explainable patterns in respect to the study site and local weather conditions characteristics. All in all, the methodology implemented herein proved capable in obtaining rapidly and cost-effectively cartography of the frost risk in a Mediterranean environment, making it potentially a very useful tool for agricultural management and planning. The model presented here has also a potential to enhance conventional field-based surveying for monitoring frost changes over long timescales. KEYWORDS: Earth Observation, MODIS, frost, risk assessment, Greece

  20. Improving Freezing Tolerance of Cultivated Potatoes: Moving Frost Hardy Genes From Wild Potatoes and Making Real Progress Using Precise Screening Tools

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The common cultivated species Solanum tubrosum is frost sensitive and is killed at temperatures below -2.5°C. It has been estimated that by increasing frost hardiness by 1–2 C one can expect an increase in potato yield by 26 to 40% in the Altiplano (Peru and Bolivia) covering 63,000 ha. of potatoes....

  1. Comparison of stem damage and carbohydrate composition in the stem juice between sugarcane and sweet sorghum harvested before and after late fall frost

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A late fall frost may significantly affect sugar crops’ stem sugar composition, yield and juice quality for biofuel and bioproduct manufacture. Research on the effects of late fall frost in sugarcane is well documented, but information is lacking for sweet sorghum. Three and six commercial cultivars...

  2. THE EFFECT OF FROST/FREEZE EVENTS ON MOPANE TREES Prepared by Melissa Whitecross, Honours student, at the University of the Witwatersrand

    E-print Network

    THE EFFECT OF FROST/FREEZE EVENTS ON MOPANE TREES Prepared by Melissa Whitecross, Honours student that Colophospermum mopane (Mopane Tree) is affected by frost/freeze events and this could be related to the unique in temperatures falling below the freezing point (0°C). A freeze event, however, describes a severe cooling event

  3. Robert Frost's Chicken Feathers and Other Lectures from the 1968 Augustana College NDEA English Institute. Augustana College Press Monograph Series No. 1.

    ERIC Educational Resources Information Center

    Huseboe, Arthur R., Ed.

    The four lectures in this publication were composed with the common concern for making the study of high school English more effective and more delightful. Papers are (1) "Robert Frost's Chicken Feathers" by C. W. Geyer (discusses the influence of oral folklore and humor on Frost's poetry); (2) "Nature in Literature" by Gerhard T. Alexis; (3)…

  4. Copy number and haplotype variation at the VRN-A1 and central FR-A2 loci are associated with frost tolerance in hexaploid wheat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Frost tolerance is a key trait to ensure winter wheat survival. Natural variation for this trait is mainly associated with allelic differences at the VERNALIZATION 1 (VRN1) and FROST RESISTANCE 2 (FR2) loci. VRN1 regulates the transition between vegetative and reproductive stages and FR2, a locus in...

  5. Frost Growth and Densification on a Flat Surface in Laminar Flow with Variable Humidity

    NASA Technical Reports Server (NTRS)

    Kandula, M.

    2012-01-01

    Experiments are performed concerning frost growth and densification in laminar flow over a flat surface under conditions of constant and variable humidity. The flat plate test specimen is made of aluminum-6031, and has dimensions of 0.3 mx0.3 mx6.35 mm. Results for the first variable humidity case are obtained for a plate temperature of 255.4 K, air velocity of 1.77 m/s, air temperature of 295.1 K, and a relative humidity continuously ranging from 81 to 54%. The second variable humidity test case corresponds to plate temperature of 255.4 K, air velocity of 2.44 m/s, air temperature of 291.8 K, and a relative humidity ranging from 66 to 59%. Results for the constant humidity case are obtained for a plate temperature of 263.7 K, air velocity of 1.7 m/s, air temperature of 295 K, and a relative humidity of 71.6 %. Comparisons of the data with the author's frost model extended to accommodate variable humidity suggest satisfactory agreement between the theory and the data for both constant and variable humidity.

  6. The "Mechanostat Theory" of Frost and the OPG/RANKL/RANK System.

    PubMed

    Tyrovola, Joanna B; Odont, X X

    2015-12-01

    Frost's great interest to elucidate the principles of action underlying skeletal deformities, during, and after growth, urged him to undertake an extensive study of the mammalian skeleton. He suggested that survival of the skeleton (but also of other tissues, such as fibrous tissue, hyaline cartilage, fibrocartilage, cementum, or dentin) requires the functional coordination of modeling and remodeling. Modeling adapts bone to overloads, by enhancing additions of new bone and by changing bone architecture, and remodeling adapts bone to underloads by removing bone next to marrow and conserving normally used bone. There exists a mechanism that monitors bone metabolism (longitudinal growth, bone modeling, and remodeling activities) in relation to mechanical usage, the "mechanostat." Recent literature has presented new information regarding the physiological procedure of osteoclast and osteoblast activation. It has been understood that the OPG/RANKL/RANK proteinic system regulates bone metabolism by exerting biological effects on osteoblasts or osteoclasts. The same proteinic network, also regulates alveolar remodeling during tooth movement, as well as physiological root resorption and root resorption during orthodontic tooth movement. The aim of the present review is the presentation and evaluation of recent information in the field of osteoclast and osteoblast biology, as regards to the "mechanostat theory" of Frost. An attempt will be made to elucidate, whether recent data can support this remarkable theory and reveal the biological mechanisms behind it. J. Cell. Biochem. 116: 2724-2729, 2015. © 2015 Wiley Periodicals, Inc. PMID:26096594

  7. Combined effects of copper, desiccation, and frost on the viability of earthworm cocoons

    SciTech Connect

    Holmstrup, M.; Petersen, B.F. |; Larsen, M.M.

    1998-01-01

    The effects of heavy metal pollution on earthworms have been extensively studied, but no studies have examined how earthworms react if they are simultaneously exposed to metal pollution and climatic stress. This question has been addressed in a laboratory study where cocoons of Aporrectodea caliginosa and Dendrobaena octaedra were initially exposed to copper in aqueous solutions of copper chloride and thereafter exposed to realistic degrees of either desiccation or frost. Earthworm embryos absorbed copper in amounts comparable to concentrations found in various tissues of earthworms from metal-polluted soils. Desiccation and copper exposure in combination had synergistic effects on survival rates for both species. For example, at full saturation, the NOEC (the highest tested concentration with no statistically significant effect) for copper of A. caliginosa was 12 mg/L, whereas at 97% relative humidity it was only 6 mg/L. Frost and copper exposure in combination also showed synergistic effects in some experiments. No cocoons of A. caliginosa exposed to 20 mg copper/L were viable after exposure to {minus}3 C but at 0 C viability was as high as 95%. The same tendency was seen in D. octaedra but not as clearly as in A/. caliginosa. A change of the environmental conditions (moisture, temperature) to increasing severity caused a shift in the statistically derived NOEC toward lower critical values of copper. The involvement of combination effects in ecotoxicological tests could therefore improve risk assessment of soil-polluting compounds.

  8. Facile fabrication of biomimetic superhydrophobic surface with anti-frosting on stainless steel substrate

    NASA Astrophysics Data System (ADS)

    Liu, Yan; Bai, Yuan; Jin, Jingfu; Tian, Limei; Han, Zhiwu; Ren, Luquan

    2015-11-01

    Inspired by typical plant surfaces with super-hydrophobic character such as lotus leaves and rose petals, a superhydrophobic surface was achieved successfully by a chemical immersion process. Here, 304 SS (stainless steel) was used as substrates and a micro-nano hierarchical structure was obtained by chemical etching with a mixed solution containing ferric chloride. The results showed that the water contact angle (WAC) decreased obviously due to surface morphology changing after chemical etching process. However, we obtained a superhydrophobic surface with a WAC of 158.3 ± 2.8° after modification by DTS (CH3(CH2)11Si(OCH3)3). Furthermore, the superhydrophobic surface showed an excellent anti-frosting character compared to pure staining steel. The surface morphology, chemical composition and wettability are characterized by means of SEM, XPS and water contact angle measurements. This method could provide a facile, low-cost and stable route to fabricate a large-area superhydrophobic surface with anti-frosting for application in various environments including in humid condition.

  9. Nitrogen split dose fertilization, plant age and frost effects on phytochemical content and sensory properties of curly kale (Brassica oleracea L. var. sabellica).

    PubMed

    Groenbaek, Marie; Jensen, Sidsel; Neugart, Susanne; Schreiner, Monika; Kidmose, Ulla; Kristensen, Hanne L

    2016-04-15

    We investigated how concentrations of sensory relevant compounds: glucosinolates (GLSs), flavonoid glycosides, hydroxycinnamic acid derivatives and sugars in kale responded to split dose and reduced nitrogen (N) fertilization, plant age and controlled frost exposure. In addition, frost effects on sensory properties combined with N supply were assessed. Seventeen week old kale plants showed decreased aliphatic GLSs at split dose N fertilization; whereas reduced N increased aliphatic and total GLSs. Ontogenetic effects were demonstrated for all compounds: sugars, aliphatic and total GLSs increased throughout plant development, whereas kaempferol and total flavonoid glycosides showed higher concentrations in 13week old plants. Controlled frost exposure altered sugar composition slightly, but not GLSs or flavonoid glycosides. Reduced N supply resulted in less bitterness, astringency and pungent aroma, whereas frost exposure mainly influenced aroma and texture. N treatment explained most of the sensory variation. Producers should not rely on frost only to obtain altered sensory properties. PMID:26616985

  10. Polarimetric scattering from layered media with multiple species of scatterers

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Kwok, R.; Yueh, S. H.; Kong, J. A.; Hsu, C. C.; Tassoudji, M. A.; Shin, R. T.

    1995-01-01

    Geophysical media are usually heterogeneous and contain multiple species of scatterers. In this paper a model is presented to calculate effective permittivities and polarimetric backscattering coefficients of multispecies-layered media. The same physical description is consistently used in the derivation of both permittivities and scattering coefficients. The strong permittivity fluctuation theory is extended to account for the multiple species of scatterers with a general ellipsoidal shape whose orientations are randomly distributed. Under the distorted Born approximation, polarimetric scattering coefficients are obtained. These calculations are applicable to the special cases of spheroidal and spherical scatterers. The model is used to study effects of scatterer shapes and multispecies mixtures on polarimetric signatures of heterogeneous media. The multispecies model accounts for moisture content in scattering media such as snowpack in an ice sheet. The results indicate a high sensitivity of backscatter to moisture with a stronger dependence for drier snow and ice grain size is important to the backscatter. For frost-covered saline ice, model results for bare ice are compared with measured data at C band and then the frost flower formation is simulated with a layer of fanlike ice crystals including brine infiltration over a rough interface. The results with the frost cover suggest a significant increase in scattering coefficients and a polarimetric signature closer to isotropic characteristics compared to the thin saline ice case.

  11. Enceladus' CO2 Frost comes from Near-Surface Gas Pockets

    NASA Astrophysics Data System (ADS)

    Matson, Dennis L.; Johnson, Torrence; Castillo-Rogez, Julie; Davies, Ashley; Lunine, Jonathan; Radebaugh, Jani

    CO2 frost has been detected on the surface of Enceladus [1]. It was noted by Brown et al. [1] that the frost deposits are not likely permanent and that an active replenishment processes for the gas might be necessary. We suggest that the CO2 that forms the frost originates in shallow gas pockets below the surface. These pockets are a consequence of the ocean water circulation hypothesis [2]. They differ from the plume chambers [3] and are a previously unrecognized structure in the near-surface ice. Enceladus’ oceanic circulation is driven by gas bubbles that make seawater buoyant and bring up water, chemicals, and heat from the depths of a warm ocean [2]. The ocean water ascends through the icy crust and, near the surface, it spreads out laterally beneath a relatively thin ice cap, following the pattern of the thermal anomalies identified in Cassini data [4,5]. Topographic recesses on the bottom of the ice cap act as pockets that collect gas. As the ocean water flows horizontally, the gas bubbles in it continue to rise vertically. Rising bubbles reach the pockets and, over time, pop and release gas. The gas pockets can be ruptured by the regular tidally-controlled fissuring of ice in the South Polar Region (Hurford et al. [6]), forming rifts. If a rift reaches a gas pocket, CO2 gas may escape to the surface. The tortuosity and other properties along the escape route will determine if the gas vents as a seep or a jet. If enough gas is vented to form a cloud, some of the gas will freeze on the surface. This work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. 2006. [2] Matson D. L. et al., Icarus 221, 53-62, 2012. (also see Matson et al. LPS 44 Abstract 1371, 2013). [3] Schmidt J. et al., Nature 451, 685-688, 2008. [4] Spencer J. R. et al., Science 311, 1401-1405, 2006. [5] Howett C. et al., JGR 116, E03003, 2011. [6] Hurford T. A. et al., Nature 447, 292-294, 2007.

  12. Psychometric Properties of the Frost Multidimensional Perfectionism Scale with Australian Adolescent Girls: Clarification of Multidimensionality and Perfectionist Typology

    ERIC Educational Resources Information Center

    Hawkins, Colleen C.; Watt, Helen M. G.; Sinclair, Kenneth E.

    2006-01-01

    The psychometric properties of the Frost, Marten, Lahart, and Rosenblate Multidimensional Perfectionism Scale (1990) are investigated to determine its usefulness as a measurement of perfectionism with Australian secondary school girls and to find empirical support for the existence of both healthy and unhealthy types of perfectionist students.…

  13. Potential gradients produced by pore-space heterogeneities: Application to isothermal frost damage and submarine hydrate anomalies

    E-print Network

    Rempel, Alan W.

    Potential gradients produced by pore-space heterogeneities: Application to isothermal frost damage@gmail.com ABSTRACT Deformation that results from crystallization in material pores commonly re- quires temperature and pressure fields. Here, we show that under nearly isothermal and isobaric conditions, changes

  14. A Taxonomy of Sensor Network Architectures D.T. Fokum, V.S. Frost, P. Mani, G.J. Minden,

    E-print Network

    Kansas, University of

    A Taxonomy of Sensor Network Architectures D.T. Fokum, V.S. Frost, P. Mani, G.J. Minden, J.B. Evans Laboratory TechnicalReport The University of Kansas #12;A Taxonomy of Sensor Network Architectures D.T. Fokum share several invariants. Key words: Sensor Networks; Taxonomy; Sensor network architecture; Invariant

  15. Investigations Concerning Cavitation and Frost Fatigue in Clonal 84K Poplar Using High-Resolution Cavitron Measurements1[OPEN

    PubMed Central

    Feng, Feng; Ding, Fei; Tyree, Melvin T.

    2015-01-01

    Both drought and freezing-thawing of stems induce a loss of hydraulic conductivity (percentage loss of conductivity [PLC]) in woody plants. Drought-induced PLC is often accompanied by physical damage to pit membranes, causing a shift in vulnerability curves (cavitation fatigue). Hence, if cavitated stems are flushed to remove embolisms, the next vulnerability curve is different (shifted to lower tensions). The 84K poplar (Populus alba × Populus glandulosa) clone has small vessels that should be immune from frost-induced PLC, but results demonstrated that freezing-thawing in combination with tension synergistically increased PLC. Frost fatigue has already been defined, which is similar to cavitation fatigue but induced by freezing. Frost fatigue caused a transition from a single to a dual Weibull curve, but drought-fatigued stems had single Weibull curves shifted to lower tensions. Studying the combined impact of tension plus freezing on fatigue provided evidence that the mechanism of frost fatigue may be the extra water tension induced by freezing or thawing while spinning stems in a centrifuge rather than direct ice damage. A hypothesis is advanced that tension is enhanced as ice crystals grow or melt during the freeze or thaw event, respectively, causing a nearly identical fatigue event to that induced by drought. PMID:25786827

  16. Dimensionality and Typology of Perfectionism: The Use of the Frost Multidimensional Perfectionism Scale with Chinese Gifted Students in Hong Kong

    ERIC Educational Resources Information Center

    Chan, David W.

    2009-01-01

    This study investigated the dimensionality and typology of perfectionism based on the Frost Multidimensional Perfectionism Scale with a sample of 380 Chinese gifted students in Hong Kong. Confirmatory factor analyses supported a five-dimensional model that includes constructs of personal standards, parental expectations, parental criticism,…

  17. Patterns of late spring frost leaf damage and recovery in a European beech (Fagus sylvatica L.) stand in south-eastern Germany based on repeated digital photographs

    NASA Astrophysics Data System (ADS)

    Menzel, Annette; Helm, Raimund; Zang, Christian

    2015-04-01

    The seasonality of woody plants in cold and temperate climates is adapted to the annual course of temperature and photoperiod in order to maximise the length of the active growing season and, at the same time, avoid damages by frost events, especially by late spring frosts. Winter chilling, spring warming and finally photoperiod trigger the timely bud burst of European beech (Fagus sylvatica L.) which as a climax species is quite sensitive to winter frost and also as seedling to late spring frosts. However, due to relatively late and less varying dates of leaf unfolding, damages by late spring frosts should not occur each year. In case of a total loss due to a late frost event, F. sylvatica trees produce a new set of leaves which guarantees survival, but diminishes carbon reserves. With a phenological camera we observed the phenological course of such an extreme event in the Nationalpark Bayerischer Wald in May 2011: Spring leaf unfolding, an almost complete loss of fresh green leaves after the frost event in the night 3rd to 4th May, a subsequent leafless period followed by re-sprouting. We modeled this special leaf development from day 80 to 210, observed as green% from the repeated digital camera pictures, using the Bayesian multiple change point approach recently introduced by Henneken et al. (2013). The results for more than 30 trees predominantly suggested a model with five change points: firstly, start of the season, abrupt ending before the frost event, the loss by the frost event and after a longer period of recovery the second leaf unfolding (St. John's sprout) ending in full leaf maturity. Analyzing the results of these models the following questions were answered (1) how long is the period of recovery till the second green-up? (2) does the temporal course of the second leafing differ from the first one? (3) what are the individual factors influencing damage and recovery? (4) are individuals with early or late bud burst more prone to damage? The five change points of the model almost perfectly matched the expected break points: i) start of the first greening between DOY (day of the year) 108 to 119 (mean 113), ii) end of greening and iii) visible frost damage after the frost on the night of May 3rd/4th (DOY 123/124), iv) re-sprouting 19 to 38 days after the frost, and v) full maturity around DOY 178 (166 to 184) when all beech crowns had fully recovered. Since frost damage was nearly 100%, individual susceptibility did not depend on the timing of first spring leaf unfolding. However, we could identify significant patterns in fitness linked to an earlier start of leaf unfolding.

  18. Climatic significance of the bristlecone pine latewood frost-ring record at Almagre Mountain, Colorado, U.S.A.

    USGS Publications Warehouse

    Craig, Brunstein F.

    1996-01-01

    From 1900 to 1993, latewood frost rings occurred in 1903, 1912, 1941, 1961, and 1965 in 10 to 21% of the sampled bristlecone pines at Almagre Mountain, Colorado. In early to mid September in each of those years, a severe outbreak of unseasonably cold air from higher latitudes produced a memorable or historic late-summer snowstorm in the western United States. Record subfreezing temperatures during these snowstorms probably caused the latewood frost rings, shortened (by about 1 mo in 1912) already colder than normal growing seasons, and caused crop damage in parts of the Western United States. Latewood frost rings recorded in relatively high percentages of the sampled trees (such as the 1805 event in 61% of sampled trees) were probably caused by multiple severe outbreaks of unseasonably cold air from higher latitudes that occurred from early September (possibly as early as mid- or late August) to mid-September. Analyses of 1900-1992 temperature data for two widely separated Colorado stations, Fort Collins and Colorado Springs, show that average summer (June-September) temperatures during latewood frost-ring years in this century were 1.5 and 2.0??C cooler than normal, respectively. Mountain snowpack probably persisted through these cool summers and was subsequently buried by the earlier than normal snowfall in September. Latewood frost-ring, ring-width, historical, and other data suggest that severe to cataclysmic volcanic eruptions from 1812 to 1835 triggered (1) an extended period of climatic cooling from as early as 1816 or 1817 through the early 1850s in the Southern Rocky Mountains, (2) catastrophic winters in Colorado and Wyoming in 1842-43 and 1844-45, and in the Great Salt Lake Basin in 1836-37, that caused large-scale destruction of bison and other large plains animals, and (3) Little Ice Age alpine glacial advances in about 1850-60 in the western United States.

  19. Climatic significance of the bristlecone pine latewood frost-ring record at Almagre Mountain, Colorado, U.S.A.

    SciTech Connect

    Brunstein, F.C.

    1996-02-01

    From 1900 to 1993, latewood frost rings occurred in 1903, 1912, 1941, 1961, and 1965 in 10 to 21% of the sampled bristlecone pines at Almagre Mountain, Colorado. In early to mid September in each of those years, a severe outbreak of unseasonably cold air from higher latitudes produced a memorable or historic late-summer snowstorm in the western United States. Record subfreezing temperatures during these snowstorms probably caused the latewood frost rings, shortened (by about 1 mo in 1912) already colder than normal growing seasons, and caused crop damage in parts of the Western United States. Latewood frost rings recorded in relatively high percentages of the sampled trees were probably caused by multiple severe outbreaks of unseasonably cold air from higher latitudes that occurred from early September to mid-September. Analyses of 1900-1992 temperature data for two widely separated Colorado stations, Fort Collins and Colorado Springs, show that average summer (June-September) temperatures during latewood frost-ring years in this century were 1.5 and 2.0{degrees}C cooler than normal, respectively. Mountain snowpack probably persisted through these cool summers and was subsequently buried by the earlier than normal snowfall in September. Latewood frost-ring, ring-width, historical, and other data suggest that severe to cataclysmic volcanic eruptions from 1812 to 1835 triggered (1) an extended period of climatic cooling from as early as 1816 or 1817 through the early 1850s in the Southern Rocky Mountains, (2) catastrophic winters in Colorado and Wyoming in 1842-43 and 1844 45, and in the Great Salt Lake Basin in 1836-37, that caused large-scale destruction of bison and other large plains animals, and (3) Little Ice Age alpine glacial advances in about 1850-60 in the western United States.

  20. Results of the radiological survey at 5 Frost Place, Albany, New York (AL184)

    SciTech Connect

    Espegren, M.L.; Marley, J.L.

    1988-02-01

    A number of properties in the Albany/Colonie area have been identified as being potentially contaminated with uranium originating from the former National Lead Company's uranium forming plant in Colonie, New York. The property at 5 Frost Place in Albany, New York (AL184) was the subject of a radiological investigation initiated July 24, 1986. The residential property consists of a two-story frame house located on a rectangular lot. An asphalt driveway connects the house to the street. A diagram of the property showing the approximate boundaries and the 5-m grid network established for measurements outside the house is shown. The lot included in the radiological survey was /approximately/15 m wide by 31 m deep. A front view of the property is shown. 13 refs., 4 figs., 5 tabs.

  1. Physical Properties of CO2 Frost Formed by Radiative Cooling in a Mars Simulation Chamber

    NASA Astrophysics Data System (ADS)

    Wood, Stephen; Bruckner, A.; Hansen, G.; Cornwall, C.; Kimber, N.; Alvarez, F.

    2013-10-01

    We have performed realistic laboratory simulations of the thermal and radiative environment at the surface of Mars to produce the first samples of carbon dioxide ice formed as it does on Mars, by radiative cooling from a near-pure CO2 gas. It is important to determine the physical characteristics of Mars' seasonal CO2 polar ice caps because these determine their radiative properties which, in turn, control the polar energy balance and the seasonal variation in global surface pressure. It is not known whether they form as fluffy fine-grained deposits, dense solid ice, or something in between. Previous simulations have used conductive cooling, condensing CO2 onto a substrate cooled by liquid nitrogen (Kieffer 1968, Ditteon and Kieffer 1979). This technique favors the growth of grains having the best thermal contact with the surface, resulting in large grain sizes and a coarse texture. On Mars, however, the latent heat released by condensation must be lost radiatively to space. For this experiment, we have constructed a Mars simulation chamber containing low thermal conductivity analog regolith and low pressure CO2 gas. To grow radiation frost in the laboratory requires simultaneous containment of the atmosphere/vapor while allowing infrared radiation to escape (to balance the latent heat of condensation). Planets accomplish this using gravity to hold down the atmosphere. The key to our simulation is the use of a thin polypropylene film that is largely transparent in the thermal infrared yet strong enough to maintain the required pressure differential between our Mars-like "atmosphere" and the vacuum-enclosed space simulator (a liquid-nitrogen cooled plate). We use internal and external light sources to briefly illuminate the frost and obtain high resolution images of its physical morphology and texture using an in situ fiberscope with an articulated tip. Initial results will be presented.

  2. Chilling and frost tolerance in Miscanthus and Saccharum genotypes bred for cool temperate climates.

    PubMed

    Friesen, Patrick C; Peixoto, Murilo M; Busch, Florian A; Johnson, Daniel C; Sage, Rowan F

    2014-07-01

    Miscanthus hybrids are leading candidates for bioenergy feedstocks in mid to high latitudes of North America and Eurasia, due to high productivity associated with the C4 photosynthetic pathway and their tolerance of cooler conditions. However, as C4 plants, they may lack tolerance of chilling conditions (0-10 °C) and frost, particularly when compared with candidate C3 crops at high latitudes. In higher latitudes, cold tolerance is particularly important if the feedstock is to utilize fully the long, early-season days of May and June. Here, leaf gas exchange and fluorescence are used to assess chilling tolerance of photosynthesis in five Miscanthus hybrids bred for cold tolerance, a complex Saccharum hybrid (energycane), and an upland sugarcane variety with some chilling tolerance. The chilling treatment consisted of transferring warm-grown plants (25/20 °C day/night growth temperatures) to chilling (12/5 °C) conditions for 1 week, followed by assessing recovery after return to warm temperatures. Chilling tolerance was also evaluated in outdoor, spring-grown Miscanthus genotypes before and after a cold front that was punctuated by a frost event. Miscanthus×giganteus was found to be the most chilling-tolerant genotype based on its ability to maintain a high net CO2 assimilation rate (A) during chilling, and recover A to a greater degree following a return to warm conditions. This was associated with increasing its capacity for short-term dark-reversible photoprotective processes (?REG) and the proportion of open photosystem II reaction centres (qL) while minimizing photoinactivation (?NF). Similarly, in the field, M.×giganteus exhibited a significantly greater A and pre-dawn F v/F m after the cold front compared with the other chilling-sensitive Miscanthus hybrids. PMID:24642848

  3. Is Shade Beneficial for Mediterranean Shrubs Experiencing Periods of Extreme Drought and Late-winter Frosts?

    PubMed Central

    Valladares, Fernando; Zaragoza-Castells, Joana; Sánchez-Gómez, David; Matesanz, Silvia; Alonso, Beatriz; Portsmuth, Angelika; Delgado, Antonio; Atkin, Owen K.

    2008-01-01

    Background and Aims Plants are naturally exposed to multiple, frequently interactive stress factors, most of which are becoming more severe due to global change. Established plants have been reported to facilitate the establishment of juvenile plants, but net effects of plant–plant interactions are difficult to assess due to complex interactions among environmental factors. An investigation was carried out in order to determine how two dominant evergreen shrubs (Quercus ilex and Arctostaphylos uva-ursi) co-occurring in continental, Mediterranean habitats respond to multiple abiotic stresses and whether the shaded understorey conditions ameliorate the negative effects of drought and winter frosts on the physiology of leaves. Methods Microclimate and ecophysiology of sun and shade plants were studied at a continental plateau in central Spain during 2004–2005, with 2005 being one of the driest and hottest years on record; several late-winter frosts also occurred in 2005. Key Results Daytime air temperature and vapour pressure deficit were lower in the shade than in the sun, but soil moisture was also lower in the shade during the spring and summer of 2005, and night-time temperatures were higher in the shade. Water potential, photochemical efficiency, light-saturated photosynthesis, stomatal conductance and leaf 13C composition differed between sun and shade individuals throughout the seasons, but differences were species specific. Shade was beneficial for leaf-level physiology in Q. ilex during winter, detrimental during spring for both species, and of little consequence in summer. Conclusions The results suggest that beneficial effects of shade can be eclipsed by reduced soil moisture during dry years, which are expected to be more frequent in the most likely climate change scenarios for the Mediterranean region. PMID:18819947

  4. Chilling and frost tolerance in Miscanthus and Saccharum genotypes bred for cool temperate climates

    PubMed Central

    Friesen, Patrick C.; Peixoto, Murilo M.; Busch, Florian A.; Johnson, Daniel C.; Sage, Rowan F.

    2014-01-01

    Miscanthus hybrids are leading candidates for bioenergy feedstocks in mid to high latitudes of North America and Eurasia, due to high productivity associated with the C4 photosynthetic pathway and their tolerance of cooler conditions. However, as C4 plants, they may lack tolerance of chilling conditions (0–10 °C) and frost, particularly when compared with candidate C3 crops at high latitudes. In higher latitudes, cold tolerance is particularly important if the feedstock is to utilize fully the long, early-season days of May and June. Here, leaf gas exchange and fluorescence are used to assess chilling tolerance of photosynthesis in five Miscanthus hybrids bred for cold tolerance, a complex Saccharum hybrid (energycane), and an upland sugarcane variety with some chilling tolerance. The chilling treatment consisted of transferring warm-grown plants (25/20 °C day/night growth temperatures) to chilling (12/5 °C) conditions for 1 week, followed by assessing recovery after return to warm temperatures. Chilling tolerance was also evaluated in outdoor, spring-grown Miscanthus genotypes before and after a cold front that was punctuated by a frost event. Miscanthus×giganteus was found to be the most chilling-tolerant genotype based on its ability to maintain a high net CO2 assimilation rate (A) during chilling, and recover A to a greater degree following a return to warm conditions. This was associated with increasing its capacity for short-term dark-reversible photoprotective processes (?REG) and the proportion of open photosystem II reaction centres (qL) while minimizing photoinactivation (?NF). Similarly, in the field, M.×giganteus exhibited a significantly greater A and pre-dawn F v/F m after the cold front compared with the other chilling-sensitive Miscanthus hybrids. PMID:24642848

  5. EVIDENCE FOR FRESH FROST LAYER ON THE BARE NUCLEUS OF COMET HALE-BOPP AT 32 AU DISTANCE

    SciTech Connect

    Szabo, Gyula M.; Kiss, Laszlo L.; Pal, Andras; Kiss, Csaba; Sarneczky, Krisztian; Juhasz, Attila; Hogerheijde, Michiel R.

    2012-12-10

    Here, we report that the activity of comet Hale-Bopp ceased between late 2007 and 2009 March, at about 28 AU distance from the Sun. At that time, the comet resided at a distance from the Sun that exceeded the freeze-out distance of regular comets by an order of magnitude. A Herschel Space Observatory PACS scan was taken in mid-2010, in the already inactive state of the nucleus. The albedo has been found to be surprisingly large (8.1% {+-} 0.9%), which exceeds the value known for any other comets. With re-reduction of archive Hubble Space Telescope images from 1995 and 1996, we confirm that the pre-perihelion albedo resembled that of an ordinary comet and was smaller by a factor of two than the post-activity albedo. Our further observations with the Very Large Telescope also confirmed that the albedo increased significantly by the end of the activity. We explain these observations by proposing gravitational redeposition of icy grains toward the end of the activity. This is plausible for such a massive body in a cold environment, where gas velocity is lowered to the range of the escape velocity. These observations also show that giant comets are not just the upscaled versions of the comets we know but can be affected by processes that are yet to be fully identified.

  6. The daily and annual effects of dew, frost, and snow on a non-ventilated net radiometer

    NASA Astrophysics Data System (ADS)

    Malek, Esmaiel

    2008-08-01

    The formation of dew, deposition of frost and accumulation of snow mainly on the upper domes of a non-ventilated net radiometer seriously affect the measurement of available energy (net radiation). Net radiometers measure radiation, and energy balances and are widely used for estimation of evapotranspiration throughout the world. To study the effects of dew, frost, and snow on a non-ventilated net radiometer, a radiation station was set up which uses 2 CM21 Kipp & Zonen pyranometers (one inverted), 2 CG1 Kipp & Zonen pyrgeometers (one inverted), along with a Q*7.1 net radiometer (Radiation & Energy Balance Systems, Inc.; REBS) in a semi-arid mountainous valley in Logan, Utah, U.S.A. The pyranometers and pyrgeometers were ventilated using 4 CV2 Kipp & Zonen ventilation systems. The net radiometer was not ventilated. The ventilation of pyranometers and pyrgeometers prevents dew and frost deposition and snow accumulation which otherwise would disturb measurements. All sensors were installed at about 3.0 m above the ground, which was covered with natural vegetation during the growing season (May-September). The incoming and outgoing solar or shortwave radiation, the incoming (atmospheric) and outgoing (terrestrial) longwave radiation, and the net radiation have been continuously measured by pyranometers, pyrgeometers and a net radiometer, respectively, since 1995. These parameters have been measured every 2 s and averaged into 20 min. To evaluate the effects of dew, frost, and snow, three days were chosen: 26 April 2004 with early morning dew, 6 January 2005 with an early morning frost, and the snowy day of 24 February 2005. Dew formation, frost deposition, and snow accumulation occurred mainly on the upper dome of the non-ventilated Q*7.1 net radiometer on the related days, while the ventilated Kipp & Zonen system was free of dew, frost and snow. Net radiation measured by the non-ventilated net radiometer Rn,unvent. during dew and frost periods of the above-mentioned days was greater than ventilated ones Rn,vent. (- 0.2 MJ m - 2 vs. - 0.8 MJ m - 2 during almost 4 h on 26 April 2004, and - 0.2 MJ m - 2 vs. - 0.7 MJ m - 2 during almost 6.5 h on 6 January 2005). The reason for higher reading by the non-ventilated net radiometer during dew and frost periods was due to emission of additional longwave radiation from water and ice crystals formed mainly on the upper dome of the Q*7.1 net radiometer. In contrast, during the snowy day of 24 February 2005, the Rn,unvent. was less than Rn,vent. (- 4.00 MJ m - 2 vs. 0.77 MJ m - 2 , mainly from sunrise to sunset). The extremely low Rn,unvent. measured by the non-ventilated net radiometer on 24 February 2005 is due to blocking of the incoming solar radiation (mainly diffuse radiation) by the snow-covered upper dome.

  7. Local adaptations to frost in marginal and central populations of the dominant forest tree Fagus sylvatica L. as affected by temperature and extreme drought in common garden experiments

    PubMed Central

    Kreyling, Juergen; Buhk, Constanze; Backhaus, Sabrina; Hallinger, Martin; Huber, Gerhard; Huber, Lukas; Jentsch, Anke; Konnert, Monika; Thiel, Daniel; Wilmking, Martin; Beierkuhnlein, Carl

    2014-01-01

    Local adaptations to environmental conditions are of high ecological importance as they determine distribution ranges and likely affect species responses to climate change. Increased environmental stress (warming, extreme drought) due to climate change in combination with decreased genetic mixing due to isolation may lead to stronger local adaptations of geographically marginal than central populations. We experimentally observed local adaptations of three marginal and four central populations of Fagus sylvaticaL., the dominant native forest tree, to frost over winter and in spring (late frost). We determined frost hardiness of buds and roots by the relative electrolyte leakage in two common garden experiments. The experiment at the cold site included a continuous warming treatment; the experiment at the warm site included a preceding summer drought manipulation. In both experiments, we found evidence for local adaptation to frost, with stronger signs of local adaptation in marginal populations. Winter frost killed many of the potted individuals at the cold site, with higher survival in the warming treatment and in those populations originating from colder environments. However, we found no difference in winter frost tolerance of buds among populations, implying that bud survival was not the main cue for mortality. Bud late frost tolerance in April differed between populations at the warm site, mainly because of phenological differences in bud break. Increased spring frost tolerance of plants which had experienced drought stress in the preceding summer could also be explained by shifts in phenology. Stronger local adaptations to climate in geographically marginal than central populations imply the potential for adaptation to climate at range edges. In times of climate change, however, it needs to be tested whether locally adapted populations at range margins can successfully adapt further to changing conditions. PMID:25035801

  8. Autumn frost hardiness in Norway spruce plus tree progeny and trees of the local and transferred provenances in central Sweden.

    PubMed

    Hannerz, Mats; Westin, Johan

    2005-09-01

    Reforestation with provenances from locations remote from the planting site (transferred provenances) or the progeny of trees of local provenances selected for superior form and vigor (plus trees) offer alternative means to increase yield over that obtained by the use of seed from unselected trees of the local provenance. Under Swedish conditions, Norway spruce (Picea abies (L.) Karst.) of certain transferred provenances generally has an advantage in productivity relative to the local provenance comparable to that of progeny of plus trees. The aim of this study was to explore the extent to which productivity gains achieved by provenance transfer or the use of plus tree progeny are associated with reductions in autumn frost hardiness, relative to that of trees of the local provenance. In a field trial with 19-year-old trees in central Sweden, bud hardiness was tested on four occasions during the autumn of 2002. Trees of the local provenance were compared with trees of a south Swedish provenance originating 3 degrees of latitude to the south, a Belarusian provenance and the progeny of plus trees of local origin. The Belarusian provenance was the least hardy and the local provenance the most hardy, with plus tree progeny and the south Swedish provenance being intermediate in hardiness. Both the Belarusian provenance and the plus tree progeny were significantly taller than trees of the other populations. Within provenances, tree height was negatively correlated with autumn frost hardiness. Among the plus tree progeny, however, no such correlation between tree height and autumn frost hardiness was found. It is concluded that although the gain in productivity achieved by provenance transfer from Belarus was comparable to that achieved by using the progeny of plus trees of the local provenance, the use of trees of the Belarus provenance involved an increased risk of autumn frost damage because of later hardening. PMID:15996961

  9. Psychometric properties of the Spanish version of the Frost Multidimensional Perfectionism Scale in women.

    PubMed

    Gelabert, Estel; García-Esteve, Lluïsa; Martín-Santos, Rocío; Gutiérrez, Fernando; Torres, Anna; Subirà, Susana

    2011-02-01

    This instrumental study was designed to analyze the psychometric properties of the Spanish version of the Frost Multidimensional Perfectionism Scale (FMPS). The total sample was made up of 582 female college students, with a mean age of 21.68 (SD= 4.45). The results of confirmatory factor analysis identified the six-factor solution proposed by the original authors as the best factor structure, with acceptable fit indices. Cronbach's alpha coefficient was .93 for the FMPS total score and ranged from .74 to .91 for the subscales. Test-retest reliability suggested a good temporal stability of the FMPS total score [ICC= .89 (95% CI= .80-.94)] and its subscales. Results showed moderate to high associations between the Spanish version of the FMPS and other measures of perfectionism. The Spanish version of FMPS has shown satisfactory psychometric properties to be used in women. Future research should replicate these findings in broader samples, in clinical populations, and use longitudinal designs to determine whether perfectionism is a risk factor for psychopathology in women. PMID:21266154

  10. Thermodynamic and fracture mechanical processes in the context of frost wedging in ice shelves

    NASA Astrophysics Data System (ADS)

    Plate, Carolin; Müller, Ralf; Humbert, Angelika; Gross, Dietmar

    2015-04-01

    Ice shelves, the link between ice shields or glaciers and the ocean are sensitive elements of the polar environment. The ongoing break up and disintegration of huge ice shelf parts or entire ice shelf demands for an explication of the underlying processes. The first analyses of crack growth and break up events in ice shelves date back to more than half a century. Nevertheless, the mechanisms that trigger and influence the collapse of whole ice shelf parts are not yet fully understood. Popular presumptions link ice shelf disintegration to surface meltwater and hydro fracturing, explaining break up events in warm polar seasons. Fracture events during colder seasons are possibly triggered by more complex mechanisms. A well-documented break up event at the Wilkins Ice Shelf bridge inspires the possibility of frost wedging as disintegration cause. The present study shows a two-dimensional thermo-dynamical model simulating the growth of an ice lid in a water-filled crevasse for measured surface temperatures. The influence of the crevasse geometry and the ice shelf temperature are shown. The resulting lid thickness is then used for the linear elastic fracture mechanical analysis. The maximum crack depth is estimated by comparing the computed stress intensity factors to critical values KIc obtained from literature. The thermodynamic as well as the fracture mechanical simulation are performed using the commercial finite element code COMSOL. The computation of KI follows in post processing routines in MATLAB exploiting the benefits of the concept of configurational forces.

  11. Growth of C02 frost thickness near Chasma Borealis during northern winter and spring.

    SciTech Connect

    Feldman, W. C.; Boynton, W. V.; Prettyman, T. H.; Kelly, N.; Maurice, S.

    2003-01-01

    Epithermal neutron fluxes measured using the Neutron Spectrometer component of the Mars OdysscNGamma-Ray Spectrometer suite of instruments were studied to determ i ne the spatial and temporal dependence of CO2 frost cover of the nor t h polar cap for L, between 329 and 99 arcoccntric longitude. This time period spans the la t e northern xvinter through summer solstice . In the absence of a CO, cuvcr, the entire basement terrain p o l eward of about +55 latitude is vm, rich in I1 :0 . The consequent enhanced abundance of hydrogen in near-surface soils leads to an anomaluusly low flux of oumardly leaking cpithcrmal ncutrons, wh i ch is a prominent signatu r e of epi t hermal neutron maps measured after about L, = 90 . Because the epithermal neutron flux rises monotonically w i t h increasing thickness of t h e CO . fros t cover, it provides a robust measure of the CO2 thickness in space and time .

  12. Shaping a dune with wind and frost in Matara crater, Mars

    NASA Astrophysics Data System (ADS)

    Diniega, S.

    2013-12-01

    Matara crater dune field exhibits a complex and fascinating geologic history. It first gained scientific attention when dune gullies (of alcove-channel-apron morphology, a few hundred meters to 3 km in length) were observed in MOC and HiRISE images to be actively evolving during the last Mars decade. Additionally, aeolian processes are clearly active within this field as the dune brinks are quite crisp in appearance, ripples on the surfaces of these dunes have been observed to migrate, and ripples have formed within sediment recently remobilized by dune-gully activity. This study seeks to understand how sediment has been redistributed/mobilized through both aeolian processes and seasonal processes leading to gully and ripple evolution. In particular, we focus on how ripples form and grow due to the wind, and are sometimes erased due to new deposition within the gully apron. We primarily focus on one very large dune-gully apron in Matara crater, where we have observed both dune-gully activity and new ripple formation over the last few Mars years. By mapping out regions with different ripple wavelengths - indicative of different ripple ages, we will examine how seasonal frost and aeolian processes have interacted over the last few decades to centuries.

  13. Predicting the behavior of asphalt concrete pavements in seasonal frost areas using nondestructive techniques

    NASA Astrophysics Data System (ADS)

    Janoo, Vincent C.; Berg, Richard L.

    1990-11-01

    Four different pavement test sections were subjected to freeze-thaw cycling in the Frost Effects Research Facility (FERF). The test sections, each 610 cm in length, consisted of 15.2 cm of asphalt concrete pavement over a clay subgrade; 15.2 cm of asphalt concrete over 10.2 cm of crushed gravel over a clay subgrade; 5.1 cm of asphalt over 17.8 cm of crushed gravel over 20.3 cm of clean sand over a clay subgrade; and 5.1 cm of asphalt concrete over 25.4 cm of crushed gravel over 12.7 cm of clean sand over clay subgrade. Thermocouples were imbedded throughout the pavement structure and subgrade. During the thawing periods, deflection measurements were made at four locations in each test section using a Dynatest Falling Weight Deflectometer (FWD). The results of the deflection measurement are presented here. An analysis was done to qualify the subgrade strength based solely on FDW measurements. It was also shown that a relationship existed between thaw depth and FWD measurement in the subgrade.

  14. FrOsT: A new generation of normal mode seismology

    NASA Astrophysics Data System (ADS)

    Valentine, Andrew; Al-Attar, David; Trampert, Jeannot; Woodhouse, John

    2015-04-01

    Normal mode seismology provides important constraints on earth structure, particularly at the largest spatial scales, and enables the imaging of density heterogeneities within the Earth. In addition, computational approaches built upon normal modes offer an efficient route towards obtaining synthetic seismograms and their sensitivity kernels (partial derivatives of the seismograms with respect to source or structural model parameters). At present, it is difficult to compute normal modes at frequencies higher than around 100 mHz, and'as far as we are aware'no publicly-released codes can perform complete calculations in 3D earth models. However, these are software limitations, rather than inherent problems with the normal modes framework. We are therefore developing the Free Oscillation Toolkit (FrOsT), a suite of software for normal mode seismology designed to enable calculations for arbitrary 3D earth models, and to arbitrarily high frequencies. All codes will be released on an open-source basis in due course. We demonstrate that improved radial integration and mode-counting techniques enable stable calculations at high frequency, and present initial benchmarks in 1D earth models. Through the use of the generalised spherical harmonic formalism, we show that it is straightforward to obtain strain and rotation seismograms, in addition to displacement fields, enabling a full range of data to be handled simultaneously. Finally, we provide an overview of expected future developments, including software to compute complete seismograms in 3D models through full mode coupling.

  15. Influence of the female flowering environment on autumn frost-hardiness of Picea abies progenies.

    PubMed

    Johnsen, O; Skrøppa, T; Junttila, O; Dæhlen, O G

    1996-05-01

    Two experiments were designed to test possible effects of photoperiod and temperature during microsporogensis to anthesis on early autumn frost-hardiness of Picea abies progenies. Pollen lots were produced in phytotron rooms and used in crosses in a seed orchard. No biologically important differences in progeny performance were evident either between high and low temperature or between long and short-day treatments, and no significant interaction between photoperiod and temperature was found. In a third experiment, however, an effect of the environment during female flowering was obtained. Crosses performed in early spring (March) inside a heated greenhouse (short day, high temperature) produced progenies which were less hardy than their full-sibs reproduced from crosses indoors (long day, high temperature) and outdoors (long day, low temperature) in May. The most hardy siblings originated from the late-spring outdoor crosses. These results indicate that some stages in reproduction during female flowering, such as female meiosis, pollen tube growth, syngamy, early embryogenesis and embryo competition, may be sensitive to temperature and/or photoperiodic signals which can be transmitted to the progeny. We suspect that the altered performance of the progenies could be due to an activation of a regulatory mechanism affecting the expression of genes controlling adaptive traits. Both the present and earlier results have implications for the genetic interpretation of provenance differences in Norway spruce. PMID:24166543

  16. Patterns of late spring frost leaf damage and recovery in a European beech (Fagus sylvatica L.) stand in south-eastern Germany based on repeated digital photographs

    PubMed Central

    Menzel, Annette; Helm, Raimund; Zang, Christian

    2015-01-01

    Damage by late spring frost is a risk deciduous trees have to cope with in order to optimize the length of their growing season. The timing of spring phenological development plays a crucial role, not only at the species level, but also at the population and individual level, since fresh new leaves are especially vulnerable. For the pronounced late spring frost in May 2011 in Germany, we studied the individual leaf development of 35 deciduous trees (mainly European beech Fagus sylvatica L.) at a mountainous forest site in the Bayerischer Wald National Park using repeated digital photographs. Analyses of the time series of greenness by a novel Bayesian multiple change point approach mostly revealed five change points which almost perfectly matched the expected break points in leaf development: (i) start of the first greening between day of the year (DOY) 108–119 (mean 113), (ii) end of greening, and (iii) visible frost damage after the frost on the night of May 3rd/4th (DOY 123/124), (iv) re-sprouting 19–38 days after the frost, and (v) full maturity around DOY 178 (166–184) when all beech crowns had fully recovered. Since frost damage was nearly 100%, individual susceptibility did not depend on the timing of first spring leaf unfolding. However, we could identify significant patterns in fitness linked to an earlier start of leaf unfolding. Those individuals that had an earlier start of greening during the first flushing period had a shorter period of recovery and started the second greening earlier. Thus, phenological timing triggered the speed of recovery from such an extreme event. The maximum greenness achieved, however, did not vary with leaf unfolding dates. Two mountain ashes (Sorbus aucuparia L.) were not affected by the low temperatures of -5°C. Time series analysis of webcam pictures can thus improve process-based knowledge and provide valuable insights into the link between phenological variation, late spring frost damage, and recovery within one stand. PMID:25759707

  17. Validation of Aura Microwave Limb Sounder stratospheric water vapor measurements by the NOAA frost point hygrometer

    NASA Astrophysics Data System (ADS)

    Hurst, Dale F.; Lambert, Alyn; Read, William G.; Davis, Sean M.; Rosenlof, Karen H.; Hall, Emrys G.; Jordan, Allen F.; Oltmans, Samuel J.

    2014-02-01

    Differences between stratospheric water vapor measurements by NOAA frost point hygrometers (FPHs) and the Aura Microwave Limb Sounder (MLS) are evaluated for the period August 2004 through December 2012 at Boulder, Colorado, Hilo, Hawaii, and Lauder, New Zealand. Two groups of MLS profiles coincident with the FPH soundings at each site are identified using unique sets of spatiotemporal criteria. Before evaluating the differences between coincident FPH and MLS profiles, each FPH profile is convolved with the MLS averaging kernels for eight pressure levels from 100 to 26 hPa (~16 to 25 km) to reduce its vertical resolution to that of the MLS water vapor retrievals. The mean FPH - MLS differences at every pressure level (100 to 26 hPa) are well within the combined measurement uncertainties of the two instruments. However, the mean differences at 100 and 83 hPa are statistically significant and negative, ranging from -0.46 ± 0.22 ppmv (-10.3 ± 4.8%) to -0.10 ± 0.05 ppmv (-2.2 ± 1.2%). Mean differences at the six pressure levels from 68 to 26 hPa are on average 0.8% (0.04 ppmv), and only a few are statistically significant. The FPH - MLS differences at each site are examined for temporal trends using weighted linear regression analyses. The vast majority of trends determined here are not statistically significant, and most are smaller than the minimum trends detectable in this analysis. Except at 100 and 83 hPa, the average agreement between MLS retrievals and FPH measurements of stratospheric water vapor is better than 1%.

  18. Frost Injury and Heterogeneous Ice Nucleation in Leaves of Tuber-Bearing Solanum Species 1

    PubMed Central

    Rajashekar, Channa B.; Li, Paul H.; Carter, John V.

    1983-01-01

    The heterogeneous ice nucleation characteristics and frost injury in supercooled leaves upon ice formation were studied in nonhardened and cold-hardened species and crosses of tuber-bearing Solanum. The ice nucleation activity of the leaves was low at temperatures just below 0°C and further decreased as a result of cold acclimation. In the absence of supercooling, the nonhardened and cold-hardened leaves tolerated extracellular freezing between ?3.5° and ?8.5°C. However, if ice initiation in the supercooled leaves occurred at any temperature below ?2.6°C, the leaves were lethally injured. To prevent supercooling in these leaves, various nucleants were tested for their ice nucleating ability. One% aqueous suspensions of fluorophlogopite and acetoacetanilide were found to be effective in ice nucleation of the Solanum leaves above ?1°C. They had threshold temperatures of ?0.7° and ?0.8°C, respectively, for freezing in distilled H2O. Although freezing could be initiated in the Solanum leaves above ?1°C with both the nucleants, 1% aqueous fluorophlogopite suspension showed overall higher ice nucleation activity than acetoacetanilide and was nontoxic to the leaves. The cold-hardened leaves survived between ?2.5° and ?6.5° using 1% aqueous fluorophlogopite suspension as a nucleant. The killing temperatures in the cold-hardened leaves were similar to those determined using ice as a nucleant. However, in the nonhardened leaves, use of fluorophlogopite as a nucleant resulted in lethal injury at higher temperatures than those estimated using ice as a nucleant. PMID:16662901

  19. Carbon-Dioxide Frost Settling from Seasonal Outbursts on Mars (Movie)

    NASA Technical Reports Server (NTRS)

    2007-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] Frame #1 FRT00004959, Ls 195 Frame #2 FRT000049C2, Ls 196 [figure removed for brevity, see original site] [figure removed for brevity, see original site] Frame #3 FRT00004B45, Ls 199 Frame #4 FRT000059E2, Ls 226

    Mars' seasonal caps consist of frozen carbon dioxide mixed with smaller amounts of water ice frost and dust. The different composition of Mars' seasonal caps than Earth's seasonal caps (water-ice snow), plus the lower pressure of the Martian atmosphere, inevitably make springtime recession of the seasonal cap different than the snowmelt that characterizes retreat of Earth's seasonal cap. To monitor Mars' seasonal changes, CRISM repeatedly targets specific regions as Mars' seasons change. Results shown here are evidence that as warming carbon-dioxide ice vaporizes, some is trapped under the ice slab from which pressurized outbursts occur. The released gas expands, cools, and some of it refreezes and falls back to the surface as bright fans.

    The region shown in this movie, known informally as Manhattan, is located at 86.3 degrees south latitude, 99 degrees east longitude. To represent the content of the spectral images, two versions of the data are shown side-by-side. The left image was constructed from extended visible wavelengths, to look similar to color images from the High Resolution Imaging Science Experiment (HiRISE) camera. The right image is infrared false-color, with red being the reflectance at 1.30 micrometers, green being depth of the water ice absorption centered at 1.5 micrometers, and blue being depth of the carbon dioxide ice absorption centered at 1.435 micrometers. In this color scheme, surfaces with higher water ice content will appear greenish, while bright carbon dioxide ice will appear magenta. Areas covered by dust will appear dark. In both images, north is to the right. The four time steps in the movie were taken at solar longitudes (Ls) ranging from 195 through 226. (Solar longitude is a measure of seasons, where 180 is southern spring equinox and 270 is southern summer solstice.)

    The first frame (image FRT00004959, Ls 195) shows a number of spots and dark fan-shaped features, with a higher concentration of spots on a slope in the middle of the scene. The dark fans show multiple directions, generally indicating wind coming out of the east. The second frame (image FRT000049C2, Ls 196) was taken just a few days after the prior one and starts to show color variations in the fans.

    The third frame (image FRT00004B45, Ls 199) records appearance of bright (bluish) fans in addition to the dark fans. The bright fans are slightly more bluish in the false-color image at right, indicating enrichment in carbon dioxide ice. The tails of the dark fans are more greenish, indicated a slight enhancement of water ice. The fourth and final frame (image FRT000059E2, Ls 226) shows distinct bright fans that appear magenta in the false-color image, indicating carbon dioxide ice with little evidence of water ice. However the surrounding surface is greenish, suggesting small amounts of water ice contamination. The tails of the dark fans appear to be more greenish in the infrared than the surrounding ice, suggesting a slight enhancement of the water ice contamination. The difference between the directions of dark and bright fans suggests changes in the wind direction, perhaps as part of a diurnal cycle or pattern.

    CRISM science team members working with these data believe that they are seeing evidence for a process first proposed based on data from the Thermal Imaging System (THEMIS) instrument on Mars Odyssey. In this hypothesis, sunlight penetrating the ice warms the underling soil and causes carbon dioxide frost to vaporize at its base. At first the gas is trapped under the frost; when it is released, the e

  20. Agricultural losses related to frost events: use of the 850 hPa level temperature as an explanatory variable of the damage cost

    NASA Astrophysics Data System (ADS)

    Papagiannaki, K.; Lagouvardos, K.; Kotroni, V.; Papagiannakis, G.

    2014-09-01

    The objective of this study is the analysis of damaging frost events in agriculture, by examining the relationship between the daily minimum temperature in the lower atmosphere (at an isobaric level of 850 hPa) and crop production losses. Furthermore, the study suggests a methodological approach for estimating agriculture risk due to frost events, with the aim of estimating the short-term probability and magnitude of frost-related financial losses for different levels of 850 hPa temperature. Compared with near-surface temperature forecasts, temperature forecasts at the level of 850 hPa are less influenced by varying weather conditions or by local topographical features; thus, they constitute a more consistent indicator of the forthcoming weather conditions. The analysis of the daily monetary compensations for insured crop losses caused by weather events in Greece shows that, during the period 1999-2011, frost caused more damage to crop production than any other meteorological phenomenon. Two regions of different geographical latitudes are examined further, to account for the differences in the temperature ranges developed within their ecological environment. Using a series of linear and logistic regressions, we found that minimum temperature (at an 850 hPa level), grouped into three categories according to its magnitude, and seasonality, are significant variables when trying to explain crop damage costs, as well as to predict and quantify the likelihood and magnitude of damaging frost events.

  1. Agricultural losses related to frost events: use of the 850 hPa level temperature as an explanatory variable of the damage cost

    NASA Astrophysics Data System (ADS)

    Papagiannaki, K.; Lagouvardos, K.; Kotroni, V.; Papagiannakis, G.

    2014-01-01

    The objective of this study is to analyze frost damaging events in agriculture, by examining the relationship between the daily minimum temperature at the lower atmosphere (at the pressure level of 850 hPa) and crop production losses. Furthermore, the study suggests a methodological approach for estimating agriculture risk due to frost events, with the aim to estimate the short-term probability and magnitude of frost-related financial losses for different levels of 850 hPa temperature. Compared with near surface temperature forecasts, temperature forecast at the level of 850 hPa is less influenced by varying weather conditions, as well as by local topographical features, thus it constitutes a more consistent indicator of the forthcoming weather conditions. The analysis of the daily monetary compensations for insured crop losses caused by weather events in Greece, during the period 1999-2011, shows that frost is the major meteorological phenomenon with adverse effects on crop productivity in the largest part of the country. Two regions of different geographical latitude are further examined, to account for the differences in the temperature ranges developed within their ecological environment. Using a series of linear and logistic regressions, we found that minimum temperature (at 850 hPa level), grouped in three categories according to its magnitude, and seasonality are significant variables when trying to explain crop damage costs, as well as to predict and quantify the likelihood and magnitude of frost damaging events.

  2. Vertical movements of frost mounds in sub-Arctic permafrost regions analyzed using geodetic survey and satellite interferometry

    NASA Astrophysics Data System (ADS)

    Beck, I.; Ludwig, R.; Bernier, M.; Strozzi, T.; Boike, J.

    2015-04-01

    Permafrost-affected soils cover about 45% of Canada. The environment in such areas, especially those located within the discontinuous permafrost zone, has been impacted more than any other by recorded climatic changes. A number of changes, such as surface subsidence and the degradation of frost mounds due to permafrost thawing have already been observed at many locations. We surveyed three frost mounds (lithalsas) close to Umiujaq, northern Quebec, sub-Arctic, using a high-precision differential Global Positioning System (d-GPS) during field visits in 2009, 2010 and 2011, thus obtaining detailed information on their responses to the freezing and thawing that occurs during the course of the annual temperature cycle. Seasonal pulsations were detected in the frost mounds and these responses were shown to vary with the state of degradation and the land cover. The most degraded lithalsa showed a maximum amplitude of vertical movement (either up or down) between winter and summer (thawing) of 0.19 ± 0.09 m over the study period, while for the least degraded lithalsa this figure was far greater (1.24 ± 0.47 m). Records from patches with little or no vegetation showed far less average vertical movement over the study period (0.17 ± 0.03 m) than those with prostrate shrubs (0.56 ± 0.02 m), suggesting an influence from the land-cover. A differential Interferometric Synthetic Aperature Radar (D-InSAR) analysis was also completed over the lithalsas using selected TerraSAR-X images acquired from April to October 2009 and from March to October 2010, with a repeat cycle of 11 days. Interferograms with baselines shorter than 200 m were computed revealing a generally very low interferometric coherence, restricting the quantification of vertical movements of the lithalsas. Vertical surface movements in the centimeter range were recorded in the near vicinity of Umiujaq.

  3. Dehydration and osmotic adjustment in apple stem tissue during winter as it relates to the frost resistance of buds.

    PubMed

    Pramsohler, Manuel; Neuner, Gilbert

    2013-08-01

    In deciduous trees, measurement of stem water potential can be difficult during the leafless period in winter. By using thermocouple psychrometry, osmotic water potentials (?o; actual ?o: ?o(act); ?o at full saturation: ?o(sat)) of expressed sap of bark and bud tissue were measured in order to test if the severity of winter desiccation in apple stems could be sufficiently assessed with ?o. Water potentials were related to frost resistance and freezing behaviour of buds. The determination of ?o reliably allowed winter desiccation and osmotic adjustments in apple stem tissue to be assessed. In winter in bark tissue, a pronounced decrease in ?o(act) and ?o(sat) was found. Decreased ?o(sat) indicates active osmotic adjustment in the bark as observed earlier in the leaves of evergreen woody plants. In terminal bud meristems, no significant osmotic adjustments occurred and dehydration during winter was much less. Osmotic water potentials, ?o(act) and ?o(sat), of bud tissue were always less negative than in the bark. To prevent water movement and dehydration of the bud tissue via this osmotic gradient, it must be compensated for either by a sufficiently high turgor pressure (?p) in bark tissue or by the isolation of the bud tissue from the bark during midwinter. During freezing of apple buds, freeze dehydration and extra-organ freezing could be demonstrated by significantly reduced ?o(act) values of bud meristems that had been excised in the frozen state. Infrared video thermography was used to monitor freezing patterns in apple twigs. During extracellular freezing of intact and longitudinally dissected stems, infrared differential thermal analysis (IDTA) images showed that the bud meristem remains ice free. Even if cooled to temperatures below the frost-killing temperature, no freezing event could be detected in bud meristems during winter. In contrast, after bud break, terminal buds showed a second freezing at the frost-killing temperature that indicates deep supercooling. Our results demonstrate the applicability of thermocouple psychrometry for the assessment of winter desiccation in stem tissues of deciduous trees and corroborate the finding that dormant apple buds survive by extra-organ freezing and do not deep supercool. In addition, they indicate that significant changes of the frost-survival mechanism can occur during the apple bud development in spring. PMID:23939553

  4. Fluorescence-dip infrared spectroscopy of the tropolone-H2O complex Rex K. Frost, Fredrick C. Hagemeister, Caleb A. Arrington, David Schleppenbach,

    E-print Network

    Zwier, Timothy S.

    Fluorescence-dip infrared spectroscopy of the tropolone-H2O complex Rex K. Frost, Fredrick C to a combination band with the in-plane bending mode of the tropolone-H2O hydrogen bond, while the latter, but broadened to over 100 cm 1 in TrOH­H2O. Distinct substructure in the band is present, with spacings

  5. John Steinbeck: "The Pearl," Adapted by Warren Frost and Dramatized for the Kennedy Center by Nick Olcott. Cue Sheet for Students.

    ERIC Educational Resources Information Center

    Carr, John C.

    This performance guide is designed for teachers to use with students before and after a performance of "The Pearl" by John Steinbeck, adapted by Warren Frost and dramatized for the Kennedy Center by Nick Olcott. It is in the form of a Director's Notebook--a scrapbook/journal of clippings, memos, lists, illustrations, notes, and other items--to…

  6. Frost Grape Polysaccharide (FGP), an emulsion-forming arabinogalactan gum from the stems of native North American grape species Vitis riparia Michx

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A new arabinogalactan is described that is produced in large quantity from the cut stems of the North American grape species Vitis riparia (Frost grape). The sugar composition consists of L-arabinofuranose (L-Araf, 55.2 %) and D-galactopyranose (D-Galp 30.1%), with smaller components of D-xylose (11...

  7. Association mapping for frost tolerance using multi-parent advanced generation inter-cross (MAGIC) population in faba bean (Vicia faba L.).

    PubMed

    Sallam, Ahmed; Martsch, Regina

    2015-08-01

    A multi-parent advanced generation inter-cross (MAGIC) derived from 11 founder lines in faba bean was used in this study to identify quantitative trait loci (QTL) for frost tolerance traits using the association mapping method with 156 SNP markers. This MAGIC population consists of a set of 189 genotypes from the Göttingen Winter Bean Population. The association panel was tested in two different experiments, i.e. a frost and a hardening experiment. Six morphological traits, leaf fatty acid composition, relative water content in shoots were scored in this study. The genotypes presented a large genetic variation for all traits that were highly heritable after frost and after hardening. High phenotypic significant correlations were established between traits. The principal coordinates analysis resulted in no clear structure in the current population. Association mapping was performed using a general linear model and mixed linear model with kinship. A False discovery rate of 0.20 (and 0.05) was used to test the significance of marker-trait association. As a result, many putative QTLs for 13 morphological and physiological traits were detected using both models. The results reveal that QTL mapping by association analysis is a powerful method of detecting the alleles associated with frost tolerance in the winter faba bean which can be used in accelerating breeding programs. PMID:26041397

  8. Land Use and Energy: Connecting the Dots to Enhance Communities Chris Keeley, University of New Hampshire Cooperative Extension and Benjamin D. Frost, New Hampshire Housing

    E-print Network

    Land Use and Energy: Connecting the Dots to Enhance Communities Chris Keeley, University of New Hampshire Cooperative Extension and Benjamin D. Frost, New Hampshire Housing Why Do Land Use and Energy Matter? Local decisions about energy and land use affect everything from municipal and personal budgets

  9. Books on "Plant Respiration"(1932-1960): From Walter Stiles to Felix Frost Blackman to W.O. James to Harry Beevers

    E-print Network

    Govindjee "Gov"

    1 Books on "Plant Respiration"(1932-1960): From Walter Stiles to Felix Frost Blackman to W.O. James. Leach (1932) Respiration in Plants. Methuen's Monographs on Biological Subjects. Chemical Publication of their 124 page small (6 7/8 inch x 4 3/8 inch) book "Respiration in Plants": "The supreme importance

  10. An Approximate Method of Calculation of Relative Humidity Required to Prevent Frosting on Inside of Aircraft Pressure Cabin Windows, Special Report

    NASA Technical Reports Server (NTRS)

    Jones, Alun R.

    1940-01-01

    This report has been prepare in response to a request for information from an aircraft company. A typical example was selected for the presentation of an approximate method of calculation of the relative humidity required to prevent frosting on the inside of a plastic window in a pressure type cabin on a high speed airplane. The results of the study are reviewed.

  11. Hot Bottom Burning Nucleosynthesis in 6 M fi Stellar Models J. C. Lattanzio and C. A. Frost a , R. C. Cannon b , and P. R. Wood c .

    E-print Network

    Lattanzio, John

    1 Hot Bottom Burning Nucleosynthesis in 6 M fi Stellar Models J. C. Lattanzio and C. A. Frost a , R. C. Cannon b , and P. R. Wood c . a Mathematics Department, Monash University, Clayton, Victoria 3168 with metallicity Z = 0:02; 0:008; and 0:004. The calculations include Hot Bottom Burning. Our main results

  12. HOT BOTTOM BURNING IN INTERMEDIATE MASS STARS JOHN LATTANZIO 1;2 , CHERYL FROST 1;2 , ROBERT CANNON 2;3 , PETER WOOD 4

    E-print Network

    Lattanzio, John

    HOT BOTTOM BURNING IN INTERMEDIATE MASS STARS JOHN LATTANZIO 1;2 , CHERYL FROST 1;2 , ROBERT CANNON 2;3 , PETER WOOD 4 1 Monash University, Melbourne, Australia 2 Institute of Astronomy, Cambridge burning in the bottom of the convective envelope. We find strong CN cycling, with substantial Al

  13. Hot Bottom Burning in Red Giants Robert C. Cannon 2;3 , Cheryl A. Frost 1;3 , John C. Lattanzio 1;3 ,

    E-print Network

    Lattanzio, John

    Hot Bottom Burning in Red Giants Robert C. Cannon 2;3 , Cheryl A. Frost 1;3 , John C. Lattanzio 1;3 , and Peter R. Wood 4 1 Department of Mathematics, Monash University, Clayton, Victoria 3168, Australia 2 Creek P.O., A.C.T.2611, Australia Abstract. We present results of hot­bottom burning calculations

  14. Transgenic barley lines prove the involvement of TaCBF14 and TaCBF15 in the cold acclimation process and in frost tolerance

    PubMed Central

    Soltész, Alexandra; Smedley, Mark; Vashegyi, Ildikó; Galiba, Gábor; Harwood, Wendy; Vágújfalvi, Attila

    2013-01-01

    The enhancement of winter hardiness is one of the most important tasks facing breeders of winter cereals. For this reason, the examination of those regulatory genes involved in the cold acclimation processes is of central importance. The aim of the present work was the functional analysis of two wheat CBF transcription factors, namely TaCBF14 and TaCBF15, shown by previous experiments to play a role in the development of frost tolerance. These genes were isolated from winter wheat and then transformed into spring barley, after which the effect of the transgenes on low temperature stress tolerance was examined. Two different types of frost tests were applied; plants were hardened at low temperature before freezing, or plants were subjected to frost without a hardening period. The analysis showed that TaCBF14 and TaCBF15 transgenes improve the frost tolerance to such an extent that the transgenic lines were able to survive freezing temperatures several degrees lower than that which proved lethal for the wild-type spring barley. After freezing, lower ion leakage was measured in transgenic leaves, showing that these plants were less damaged by the frost. Additionally, a higher Fv/Fm parameter was determined, indicating that photosystem II worked more efficiently in the transgenics. Gene expression studies showed that HvCOR14b, HvDHN5, and HvDHN8 genes were up-regulated by TaCBF14 and TaCBF15. Beyond that, transgenic lines exhibited moderate retarded development, slower growth, and minor late flowering compared with the wild type, with enhanced transcript level of the gibberellin catabolic HvGA2ox5 gene. PMID:23567863

  15. A next generation sequencing of Arctic bacteria in snow and frost flowers: identification, abundance and freezing nucleation

    NASA Astrophysics Data System (ADS)

    Mortazavi, R.; Attiya, S.; Ariya, P. A.

    2014-12-01

    During the spring of 2009, as part of the Ocean-Atmosphere-Sea Ice-Snowpack (OASIS) campaign in Barrow, Alaska, USA, we examined the identity, population, freezing nucleation ability of the microbial communities of five different snow types and frost flowers. In addition to the conventional culture-based PCR identification approach, we deployed a state-of-the-art genomic Next Generation Sequencing (NGS) technique to examine diverse bacterial communities in Arctic samples. 11-18 known phyla or candidate divisions were identified with the great majority of sequences (12.3-83.1%) belonging to one of the five major phyla: Proteobacteria, Actinobacteria, Bacteroidetes, Firmicutes and Cyanobacteria. At the genus level, 101-245 different genera were detected. The highest number of cultivable bacteria in cultured samples was observed in frost flowers (FF) and accumulated snow (AS) with 325 ± 35 and 314 ± 142 CFU mL-1, respectively; and for cultivable fungi 5 ± 1 CFU mL-1 in windpack (WP) and blowing snow (BS). Complementary morphology and ice-nucleating abilities of the identified taxa were obtained using high resolution electron microscopy and ice nucleation cold-plate, respectively. Freezing point temperatures for bacterial isolate ranged from -20.3 ± 1.5 to -15.7 ± 5.6 °C, and for melted samples from 9.5 ± 1.0 to 18.4 ± 0.1 °C. An isolate belonging to the Bacillus species (96% similarity) had ice nucleation activity of -6.8 ± 0.2 °C. Comparison with Montreal urban snow, revealed a seemingly diverse community of bacteria exists in the Arctic with many originating from distinct ecological environments, and we discuss the potential impact of microbial snow in the freezing and melting process of the snowpack in the Arctic.

  16. Boundary layer simulator improvement

    NASA Technical Reports Server (NTRS)

    Praharaj, S. C.; Schmitz, C.; Frost, C.; Engel, C. D.; Fuller, C. E.; Bender, R. L.; Pond, J.

    1984-01-01

    High chamber pressure expander cycles proposed for orbit transfer vehicles depend primarily on the heat energy transmitted from the combustion products through the thrust wall chamber wall. The heat transfer to the nozzle wall is affected by such variables as wall roughness, relamarization, and the presence of particles in the flow. Motor performance loss for these nozzles with thick boundary layers is inaccurate using the existing procedure coded BLIMPJ. Modifications and innovations to the code are examined. Updated routines are listed.

  17. Spallanzani Layers

    NASA Technical Reports Server (NTRS)

    2006-01-01

    31 March 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a layered, light-toned mesa among other layered materials exposed in a mound that covers much of the floor of Spallanzani Crater.

    Location near: 58.3oS, 273.9oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

  18. Application of Satellite SAR Imagery in Mapping the Active Layer of Arctic Permafrost

    NASA Technical Reports Server (NTRS)

    Li, Shu-Sun; Romanovsky, V.; Lovick, Joe; Wang, Z.; Peterson, Rorik

    2003-01-01

    A method of mapping the active layer of Arctic permafrost using a combination of conventional synthetic aperture radar (SAR) backscatter and more sophisticated interferometric SAR (INSAR) techniques is proposed. The proposed research is based on the sensitivity of radar backscatter to the freeze and thaw status of the surface soil, and the sensitivity of INSAR techniques to centimeter- to sub-centimeter-level surface differential deformation. The former capability of SAR is investigated for deriving the timing and duration of the thaw period for surface soil of the active layer over permafrost. The latter is investigated for the feasibility of quantitative measurement of frost heaving and thaw settlement of the active layer during the freezing and thawing processes. The resulting knowledge contributes to remote sensing mapping of the active layer dynamics and Arctic land surface hydrology.

  19. Using Presence Questionnaires in Reality Using Presence Questionnaires in Reality

    E-print Network

    Slater, Mel

    compared to immersive virtual. #12;Using Presence Questionnaires in Reality 2 1. Introduction The concept1 Using Presence Questionnaires in Reality Using Presence Questionnaires in Reality Martin Usoh different presence question- naires can distinguish between real and virtual experiences. One group of 10

  20. A GIS analysis of the relationship between sinkholes, dry-well complaints and groundwater pumping for frost-freeze protection of winter strawberry production in Florida.

    PubMed

    Aurit, Mark D; Peterson, Robert O; Blanford, Justine I

    2013-01-01

    Florida is riddled with sinkholes due to its karst topography. Sometimes these sinkholes can cause extensive damage to infrastructure and homes. It has been suggested that agricultural practices, such as sprinkler irrigation methods used to protect crops, can increase the development of sinkholes, particularly when temperatures drop below freezing, causing groundwater levels to drop quickly during groundwater pumping. In the strawberry growing region, Dover/Plant City, Florida, the effects have caused water shortages resulting in dry-wells and ground subsidence through the development of sinkholes that can be costly to maintain and repair. In this study, we look at how frost-freeze events have affected West Central Florida over the past 25 years with detailed comparisons made between two cold-years (with severe frost-freeze events) and a warm year (no frost-freeze events). We analyzed the spatial and temporal correlation between strawberry farming freeze protection practices and the development of sinkholes/dry well complaints, and assessed the economic impact of such events from a water management perspective by evaluating the cost of repairing and drilling new wells and how these compared with using alternative crop-protection methods. We found that the spatial distribution of sinkholes was non-random during both frost-freeze events. A strong correlation between sinkhole occurrence and water extraction and minimum temperatures was found. Furthermore as temperatures fall below 41°F and water levels decrease by more than 20 ft, the number of sinkholes increase greatly (N >10). At this time alternative protection methods such as freeze-cloth are cost prohibitive in comparison to repairing dry wells. In conclusion, the findings from this study are applicable in other agricultural areas and can be used to develop comprehensive water management plans in areas where the abstraction of large quantities of water occur. PMID:23326518

  1. A GIS Analysis of the Relationship between Sinkholes, Dry-Well Complaints and Groundwater Pumping for Frost-Freeze Protection of Winter Strawberry Production in Florida

    PubMed Central

    Aurit, Mark D.; Peterson, Robert O.; Blanford, Justine I.

    2013-01-01

    Florida is riddled with sinkholes due to its karst topography. Sometimes these sinkholes can cause extensive damage to infrastructure and homes. It has been suggested that agricultural practices, such as sprinkler irrigation methods used to protect crops, can increase the development of sinkholes, particularly when temperatures drop below freezing, causing groundwater levels to drop quickly during groundwater pumping. In the strawberry growing region, Dover/Plant City, Florida, the effects have caused water shortages resulting in dry- wells and ground subsidence through the development of sinkholes that can be costly to maintain and repair. In this study, we look at how frost-freeze events have affected West Central Florida over the past 25 years with detailed comparisons made between two cold-years (with severe frost-freeze events) and a warm year (no frost-freeze events). We analyzed the spatial and temporal correlation between strawberry farming freeze protection practices and the development of sinkholes/dry well complaints, and assessed the economic impact of such events from a water management perspective by evaluating the cost of repairing and drilling new wells and how these compared with using alternative crop-protection methods. We found that the spatial distribution of sinkholes was non-random during both frost-freeze events. A strong correlation between sinkhole occurrence and water extraction and minimum temperatures was found. Furthermore as temperatures fall below 41°F and water levels decrease by more than 20 ft, the number of sinkholes increase greatly (N >10). At this time alternative protection methods such as freeze-cloth are cost prohibitive in comparison to repairing dry wells. In conclusion, the findings from this study are applicable in other agricultural areas and can be used to develop comprehensive water management plans in areas where the abstraction of large quantities of water occur. PMID:23326518

  2. On Multiple-Layered Vortices

    NASA Technical Reports Server (NTRS)

    Rossow, Vernon J.

    2011-01-01

    As part of an ongoing effort to find ways to make vortex flow fields decompose more quickly, photographs and observations are presented of vortex flow fields that indicate the presence of multiple layers of fluid rotating about a common axis. A survey of the literature indicates that multiple-layered vortices form in waterspouts, tornadoes and lift-generated vortices of aircraft. An explanation for the appearance of multiple-layered structures in vortices is suggested. The observations and data presented are intended to improve the understanding of the formation and persistence of vortex flow fields.

  3. Far-UV, visible, and near-IR reflectance spectra of frosts of H2O, CO2, NH3 and SO2

    NASA Technical Reports Server (NTRS)

    Hapke, B.; Wells, E.; Wagner, J.; Partlow, W.

    1981-01-01

    Measurements in the 0.1-2.5 micron range are presented for the reflectance spectra of the frosts of several volatiles pertinent to the study of comet nuclei. The frost spectra have distinctive features permitting their identification by spectroscopic reflectance remote sensing, notably in the far UV. It is found that: (1) H2O has a minimum at 0.16 microns and a maximum at 0.13 microns; (2) CO2 has minima near 0.21, 0.18 and 0.125 microns, with maxima at 0.19, 0.135 and 0.120 microns; (3) NH3 is bright at wavelengths longer than 0.21 microns, where reflectance drops to a value of only a few per cent at shorter wavelengths; (4) SO2 has a sharp drop at 0.32 microns, with a minimum at 0.18 microns and a maximum at 0.13 microns. The features in the frost spectra largely correspond to absorption line bands in the gas phase.

  4. Impacts of a water stress followed by an early frost event on beech (Fagus sylvatica L.) susceptibility to Scolytine ambrosia beetles - Research strategy and first results

    NASA Astrophysics Data System (ADS)

    La Spina, Sylvie; de Cannière, Charles; Molenberg, Jean-Marc; Vincke, Caroline; Deman, Déborah; Grégoire, Jean-Claude

    2010-05-01

    Climate change tends to induce more frequent abiotic and biotic extreme events, having large impacts on tree vitality. Weakened trees are then more susceptible to secondary insect outbreaks, as it happened in Belgium in the early 2000s: after an early frost event, secondary Scolytine ambrosia beetles attacks were observed on beech trees. In this study, we test if a combination of stress, i.e. a soil water deficit preceding an early frost, could render trees more attractive to beetles. An experimental study was set in autumn 2008. Two parcels of a beech forest were covered with plastic tents to induce a water stress by rain interception. The parcels were surrounded by 2-meters depth trenches to avoid water supply by streaming. Soil water content and different indicators of tree water use (sap flow, predawn leaf water potential, tree radial growth) were followed. In autumn 2010, artificial frost injuries will be inflicted to trees using dry ice. Trees attractivity for Scolytine insects, and the success of insect colonization will then be studied. The poster will focus on experiment setting and first results (impacts of soil water deficit on trees).

  5. Larval feeding behavior and ant association in frosted elfin, Callophrys irus (Lycaenidae)

    USGS Publications Warehouse

    Albanese, G.; Nelson, M.W.; Vickery, P.D.; Sievert, P.R.

    2007-01-01

    Callophrys irus is a rare and declining lycaenid found in the eastern U.S., inhabiting xeric and open habitats maintained by disturbance. Populations are localized and monophagous. We document a previously undescribed larval feeding behavior in both field and lab reared larvae in which late instar larvae girdled the main stem of the host plant. Girdled stems provide a unique feeding sign that was useful in detecting the presence of larvae in the field. We also observed frequent association of field larvae with several species of ants and provide a list of ant species. We suggest two hypotheses on the potential benefits of stem-girdling to C. irus larvae: 1) Stem girdling provides phloem sap as a larval food source and increases the leaf nutrient concentration, increasing larval growth rates and providing high quality honeydew for attending ants; 2) Stem girdling reduces stem toxicity by inhibiting transport of toxins from roots to the stem.

  6. statistical physics statistics of radiation Earth's Ozone Layer

    E-print Network

    statistical physics statistics of radiation Earth's Ozone Layer In this problem, we will show how the presence of the ozone layer could have a cooling effect on the Earth. For simplicity, let us consider layer, and TE the temperature of the Earth with the ozone layer. (a) Show that TE TE 4 = 1 + 1 - 2 2 - 1

  7. CFD Assessment of Forward Booster Separation Motor Ignition Overpressure on ET XT 718 Ice/Frost Ramp

    NASA Technical Reports Server (NTRS)

    Tejnil, Edward; Rogers, Stuart E.

    2012-01-01

    Computational fluid dynamics assessment of the forward booster separation motor ignition over-pressure was performed on the space shuttle external tank X(sub T) 718 ice/frost ramp using the flow solver OVERFLOW. The main objective of this study was the investigation of the over-pressure during solid rocket booster separation and its affect on the local pressure and air-load environments. Delta pressure and plume impingement were investigated as a possible contributing factor to the cause of the debris loss on shuttle missions STS-125 and STS-127. A simplified computational model of the Space Shuttle Launch Vehicle was developed consisting of just the external tank and the solid rocket boosters with separation motor nozzles and plumes. The simplified model was validated by comparison to full fidelity computational model of the Space Shuttle without the separation motors. Quasi steady-state plume solutions were used to calibrate the thrust of the separation motors. Time-accurate simulations of the firing of the booster-separation motors were performed. Parametric studies of the time-step size and the number of sub-iterations were used to find the best converged solution. The computed solutions were compared to previous OVERFLOW steady-state runs of the separation motors with reaction control system jets and to ground test data. The results indicated that delta pressure from the overpressure was small and within design limits, and thus was unlikely to have contributed to the foam losses.

  8. Ice Nucleation Temperature of Individual Leaves in Relation to Population Sizes of Ice Nucleation Active Bacteria and Frost Injury

    PubMed Central

    Hirano, Susan S.; Baker, L. Stuart; Upper, Christen D.

    1985-01-01

    Ice nucleation temperatures of individual leaves were determined by a tube nucleation test. With this assay, a direct quantitative relationship was obtained between the temperatures at which ice nucleation occurred on individual oat (Avena sativa L.) leaves and the population sizes of ice nucleation active (INA) bacteria present on those leaves. In the absence of INA bacteria, nucleation of supercooled growth-chamber grown oat leaves did not occur until temperatures were below approximately ?5°C. Both nucleation temperature and population size of INA bacteria were determined on the same individual, field-grown oat leaves. Leaves with higher ice nucleation temperatures harbored larger populations of INA bacteria than did leaves with lower nucleation temperatures. Log10 mean populations of INA bacteria per leaf were 5.14 and 3.51 for leaves with nucleation temperatures of ?2.5°C and ?3.0°C, respectively. Nucleation frequencies (the ratio of ice nuclei to viable cells) of INA bacteria on leaves were lognormally distributed. Strains from two very different collections of Pseudomonas syringae and one of Erwinia herbicola were cultured on nutrient glycerol agar and tested for nucleation frequency at ?5°C. Nucleation frequencies of these bacterial strains were also lognormally distributed within each of the three sets. The tube nucleation test was used to determine the frequency with which individual leaves in an oat canopy harbored large populations of INA bacteria throughout the growing season. This test also predicted relative frost hazard to tomato (Lycopersicon esculentum Mill) plants. PMID:16664039

  9. Evidence of frost-cracking inferred from acoustic emissions in a high-alpine rock-wall

    NASA Astrophysics Data System (ADS)

    Amitrano, D.; Gruber, S.; Girard, L.

    2012-08-01

    Ice formation within rock is known to be an important driver of near-surface frost weathering as well as of rock damage at the depth of several meters, which may play a crucial role for the slow preconditioning of rock fall in steep permafrost areas. This letter reports results from an experiment where acoustic emission monitoring was used to investigate rock damage in a high-alpine rock-wall induced by natural thermal cycling and freezing/thawing. The analysis of the large catalog of events obtained shows (i) robust power-law distributions in the time and energy domains, a footprint of rock micro-fracturing activity induced by stresses arising from thermal variations and associated freezing/thawing of rock; (ii) an increase in AE activity under sub-zero rock-temperatures, suggesting the importance of freezing-induced stresses. AE activity further increases in locations of the rock-wall that are prone to receiving melt water. These results suggest that the framework of further modeling studies (theoretical and numerical) should include damage, elastic interaction and poro-mechanics in order to describe freezing-related stresses.

  10. Layered materials

    NASA Astrophysics Data System (ADS)

    Johnson, David; Clarke, Simon; Wiley, John; Koumoto, Kunihito

    2014-06-01

    Layered compounds, materials with a large anisotropy to their bonding, electrical and/or magnetic properties, have been important in the development of solid state chemistry, physics and engineering applications. Layered materials were the initial test bed where chemists developed intercalation chemistry that evolved into the field of topochemical reactions where researchers are able to perform sequential steps to arrive at kinetically stable products that cannot be directly prepared by other approaches. Physicists have used layered compounds to discover and understand novel phenomena made more apparent through reduced dimensionality. The discovery of charge and spin density waves and more recently the remarkable discovery in condensed matter physics of the two-dimensional topological insulating state were discovered in two-dimensional materials. The understanding developed in two-dimensional materials enabled subsequent extension of these and other phenomena into three-dimensional materials. Layered compounds have also been used in many technologies as engineers and scientists used their unique properties to solve challenging technical problems (low temperature ion conduction for batteries, easy shear planes for lubrication in vacuum, edge decorated catalyst sites for catalytic removal of sulfur from oil, etc). The articles that are published in this issue provide an excellent overview of the spectrum of activities that are being pursued, as well as an introduction to some of the most established achievements in the field. Clusters of papers discussing thermoelectric properties, electronic structure and transport properties, growth of single two-dimensional layers, intercalation and more extensive topochemical reactions and the interleaving of two structures to form new materials highlight the breadth of current research in this area. These papers will hopefully serve as a useful guideline for the interested reader to different important aspects in this field and an overview of current areas of research interest.

  11. Regional Climate Change Influences Frequency of Frost Damage via Changes in Phenology: Effects of the North Pacific Oscillation (Pacific Decadal Oscillation) on Rocky Mountain Wildflowers

    NASA Astrophysics Data System (ADS)

    Inouye, D. W.

    2004-12-01

    There is a significant correlation (P = .049) between the state of the North Pacific Oscillation (Pacific Decadal Oscillation) and the amount of winter snowfall at the Rocky Mountain Biological Laboratory (2,800m in the Colorado Rocky Mountains). The 1998 change of this inter-decadal mode of variability of the north Pacific atmosphere system to a dry phase has resulted in decreased snowpack, reversing a trend for increasing snowfall since the previous phase change in 1976. The seasonal timing (phenology) of plant growth and flowering at high altitudes is determined almost entirely by the timing of spring snowmelt, even for species that flower at the end of the season, and the decreased snowpack since 1998 combined with warming air temperatures has resulted in significantly earlier initiation of the growing season and subsequent flowering. Flowering in 2002, for example, was the earliest recorded during my 31-year study, and probably the earliest since at least 1935. Frost (with temperatures as low as -6 or -7ºC) is still likely to occur as late as mid-June, however, and a consequence of the earlier beginning of the growing season is that many species have developed sensitive flower buds or other tissues by mid-June that are likely to be killed by frost. From 1994-1998 the average percentage of flower buds of Helianthella quinquenervis (Asteraceae; aspen sunflower) killed by frost was 26 percent(range 0-81), but since the 1998 NPO phase change a mean of 75 percent of flower buds have been killed (range 0-100; over 90 percent for each of the past four years). The loss of flowers from these frosts has consequences for plant demography (fewer seeds results in fewer seedlings), pollinators (which have fewer floral resources), seed predators (e.g., tephritid flies), and parasitoids (e.g., wasps, which have fewer seed predators to parasitize). A suite of wildflower species whose flowering abundance is positively correlated with the amount of winter snowfall has also produced fewer flowers since 1998, potentially exacerbating the effects of frost. Thus this regional climate event appears to be having ecosystem-wide consequences in the Colorado Rocky Mountains. Given the 50-75 year cycle length of the NPO, this area may be at the beginning of a decades-long change in snowfall that will reinforce the effects of global climate warming and result in significant ecosystem responses.

  12. Ice Lens Formation and Frost Heave at the Phoenix Landing Site

    NASA Astrophysics Data System (ADS)

    Zent, A.; Sizemore, H. G.; Rempel, A. W.

    2010-12-01

    Several lines of evidence indicate that the volume of shallow ground ice in the Martian high latitudes exceeds the pore volume of the host regolith. Boynton et al. (2002) found an optimal fit to the Mars Odyssey Gamma Ray Spectrometer (GRS) data at the Phoenix landing site by modeling a buried layer of 50-75% ice by mass (up to 90% by volume). Thermal and optical observations of recent impact craters in the northern hemisphere have revealed nearly pure ice. Ice deposits containing only 1-2% soil by volume were excavated by Phoenix. The leading hypothesis for the origin of this excess, or segregated, ice is that it developed in situ by a mechanism analogous to the formation of terrestrial ice lenses and needle ice. Problematically, terrestrial soil-ice segregation is driven by freeze/thaw cycling and the movement of bulk water, which are not expected to have occurred in the geologically recent past on Mars. We have developed a numerical model that applies the physics of pre-melting to track phase partitioning in soil pore spaces and test for conditions under which ice lenses could initiate. Our results indicate that diurnal cycling in the ice-cemented regolith and resultant pressure gradients in thin films at grain-ice interfaces can cause interparticle forces to unload, initiating an ice lens at temperatures as low as 245 K. These results indicate that in situ ice segregation may have occurred on Mars in the recent past, and that geologically young ice lenses may account for much of observed excess ice.

  13. Greenhouse gas fluxes in a drained peatland forest during spring frost-thaw event

    NASA Astrophysics Data System (ADS)

    Pihlatie, M. K.; Kiese, R.; Brüggemann, N.; Butterbach-Bahl, K.; Kieloaho, A.-J.; Laurila, T.; Lohila, A.; Mammarella, I.; Minkkinen, K.; Penttilä, T.; Schönborn, J.; Vesala, T.

    2009-06-01

    Fluxes of greenhouse gases (GHG) carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) were measured during a two month campaign at a drained peatland forest in Finland by the eddy covariance (EC) technique (CO2 and N2O), and automatic and manual chambers (CO2, CH4 and N2O). In addition, GHG concentrations and soil parameters (mineral nitrogen, temperature, moisture content) in the peat profile were measured. The aim of the measurement campaign was to quantify the GHG fluxes before, during and after thawing of the peat soil, a time period with potentially high GHG fluxes, and to compare different flux measurement methods. The forest was a net CO2 sink during the two months and the fluxes of CO2 dominated the GHG exchange. The peat soil was a small sink of atmospheric CH4 but a small source of N2O. Both CH4 oxidation and N2O production took place in the top-soil whereas CH4 was produced in the deeper layers of the peat. During the thawing of the peat distinct peaks in CO2 and N2O emissions were observed. The CO2 peak followed tightly the increase in soil temperature, whereas the N2O peak occurred with an approx. one week delay after soil thawing. CH4 fluxes did not respond to the thawing of the peat soil. The CO2 and N2O emission peaks were not captured by the manual chambers and hence we conclude that automatic chamber measurements or EC are necessary to quantify fluxes during peak emission periods. Sub-canopy EC measurements and chamber-based fluxes of CO2 and N2O were comparable, although the fluxes of N2O measured by EC were close to the detection limit of the EC system. We conclude that if fluxes are high enough, i.e. greater than 5-10 ?g N m-2 h-1, the EC method is a good alternative to measure N2O and CO2 fluxes at ecosystem scale, thereby minimizing problems with chamber enclosures and spatial representativeness of the measurements.

  14. The Presence of a Symbol 

    E-print Network

    Clark, Andy

    1992-01-01

    The image of the presence of symbols in an inner code pervades recent debates in cognitive science. Classicists worship in the presence. Connectionists revel in the absence. However, the very ideas of code and symbol are ...

  15. The frequency of growing season frost in the subalpine environment (Medicine Bow Mountains, southeastern Wyoming), the interaction of leaf morphology and infrared radiational cooling and the effects of freezing on native vegetation

    SciTech Connect

    Jordan, D.N.

    1995-05-01

    The subalpine environment is characterized by the possibility of frost throughout the summer. The frequency and severity of summertime frost episodes appeared particularly dependent on net losses of infrared energy to a cold night sky (radiation frost), as well as air temperature and wind speed. Longwave radiation minima from the night sky were strongly correlated with the occurrence of leaf temperature minima. Leaf temperatures were modeled using an energy balance simulation that quantified the specific effects of ambient air temperature, wind speed, sky infrared radiation, and sky exposure characteristic of this high-elevation environment. Plants growing in exposed and sheltered habitats have characteristic leaf structures (smaller, thicker leaves in more exposed locations) that have been traditionally associated with the total amount of incident sunlight. However, smaller leaves also appear adaptive for reducing the susceptibility to radiation frosts. Larger, more exposed leaves resulted in colder nocturnal leaf temperatures and greater frost frequencies. Microsite sky radiation, microtopography, plant habit and leaf structure all have important implications for estimating growing season length and plant distribution patterns, especially at higher elevations where summer frosts are common. Radiational frosts at night are typically followed by clear skies and full-sun exposure the next morning. The combination of low temperature stress followed by high light exposure can result in strong photoinhibition of photosynthesis. The morphology of a variety of conifer needles as well as of a broadleaf was modeled to evaluate the effect on incident sunlight intensity. Conifer leaf morphology was found to be particularly adaptive for avoiding high incident light conditions compared to broadleaves.

  16. Arctic organic aerosol measurements show particles from mixed combustion in spring haze and from frost flowers in winter

    NASA Astrophysics Data System (ADS)

    Shaw, P. M.; Russell, L. M.; Jefferson, A.; Quinn, P. K.

    2010-05-01

    Submicron atmospheric aerosol particles were collected between 1 March 2008 and 1 March 2009 at Barrow, Alaska, to characterize the organic mass (OM) in the Arctic aerosol. Organic functional group concentrations and trace metals were measured with FTIR on submicron particles collected on Teflon filters. The OM varied from 0.07 ?g m-3 in summer to 0.43 ?g m-3 in winter, and 0.35 ?g m-3 in spring, showing a transition in OM composition between spring and winter. Most of the OM in spring could be attributed to anthropogenic sources, consisting primarily of alkane and carboxylic acid functional groups and correlated to elemental tracers of industrial pollution, biomass burning, and shipping emissions. PMF analysis associated OM with two factors, a Mixed Combustion factor (MCF) and an Ocean-derived factor (ODF). Back trajectory analysis revealed that the highest fractions of the MCF were associated with air masses that had originated from northeastern Asia and the shipping lanes south of the Bering Straits. The ODF consisted of organic hydroxyl groups and correlated with organic and inorganic seawater components. The ODF accounted for more than 55% of OM in winter when the sampled air masses originated along the coastal and lake regions of the Northwest Territories of Canada. Frost flowers with organic-salt coatings that arise by brine rejection during sea ice formation may account for this large source of carbohydrate-like OM during the ice-covered winter season. While the anthropogenic sources contributed more than 0.3 ?g m-3 of the springtime haze OM, ocean-derived particles provided comparable OM sources in winter.

  17. Double Layers in Astrophysics

    NASA Technical Reports Server (NTRS)

    Williams, Alton C. (editor); Moorehead, Tauna W. (editor)

    1987-01-01

    Topics addressed include: laboratory double layers; ion-acoustic double layers; pumping potential wells; ion phase-space vortices; weak double layers; electric fields and double layers in plasmas; auroral double layers; double layer formation in a plasma; beamed emission from gamma-ray burst source; double layers and extragalactic jets; and electric potential between plasma sheet clouds.

  18. Transport Layer Cornell University

    E-print Network

    Low, Steven H.

    directions for the future evolution of the transport layer and suggest some further reading in sections VITransport Layer Ao Tang Cornell University Ithaca, NY 14853 Lachlan L. H. Andrew California of the physical layer, the link layer, the network layer, the transport layer and the application layer1 . See

  19. Multifunctional layered magnetic composites.

    PubMed

    Siglreitmeier, Maria; Wu, Baohu; Kollmann, Tina; Neubauer, Martin; Nagy, Gergely; Schwahn, Dietmar; Pipich, Vitaliy; Faivre, Damien; Zahn, Dirk; Fery, Andreas; Cölfen, Helmut

    2015-01-01

    A fabrication method of a multifunctional hybrid material is achieved by using the insoluble organic nacre matrix of the Haliotis laevigata shell infiltrated with gelatin as a confined reaction environment. Inside this organic scaffold magnetite nanoparticles (MNPs) are synthesized. The amount of MNPs can be controlled through the synthesis protocol therefore mineral loadings starting from 15 wt % up to 65 wt % can be realized. The demineralized organic nacre matrix is characterized by small-angle and very-small-angle neutron scattering (SANS and VSANS) showing an unchanged organic matrix structure after demineralization compared to the original mineralized nacre reference. Light microscopy and confocal laser scanning microscopy studies of stained samples show the presence of insoluble proteins at the chitin surface but not between the chitin layers. Successful and homogeneous gelatin infiltration in between the chitin layers can be shown. The hybrid material is characterized by TEM and shows a layered structure filled with MNPs with a size of around 10 nm. Magnetic analysis of the material demonstrates superparamagnetic behavior as characteristic for the particle size. Simulation studies show the potential of collagen and chitin to act as nucleators, where there is a slight preference of chitin over collagen as a nucleator for magnetite. Colloidal-probe AFM measurements demonstrate that introduction of a ferrogel into the chitin matrix leads to a certain increase in the stiffness of the composite material. PMID:25671158

  20. Multifunctional layered magnetic composites

    PubMed Central

    Siglreitmeier, Maria; Wu, Baohu; Kollmann, Tina; Neubauer, Martin; Nagy, Gergely; Schwahn, Dietmar; Pipich, Vitaliy; Faivre, Damien; Zahn, Dirk; Fery, Andreas

    2015-01-01

    Summary A fabrication method of a multifunctional hybrid material is achieved by using the insoluble organic nacre matrix of the Haliotis laevigata shell infiltrated with gelatin as a confined reaction environment. Inside this organic scaffold magnetite nanoparticles (MNPs) are synthesized. The amount of MNPs can be controlled through the synthesis protocol therefore mineral loadings starting from 15 wt % up to 65 wt % can be realized. The demineralized organic nacre matrix is characterized by small-angle and very-small-angle neutron scattering (SANS and VSANS) showing an unchanged organic matrix structure after demineralization compared to the original mineralized nacre reference. Light microscopy and confocal laser scanning microscopy studies of stained samples show the presence of insoluble proteins at the chitin surface but not between the chitin layers. Successful and homogeneous gelatin infiltration in between the chitin layers can be shown. The hybrid material is characterized by TEM and shows a layered structure filled with MNPs with a size of around 10 nm. Magnetic analysis of the material demonstrates superparamagnetic behavior as characteristic for the particle size. Simulation studies show the potential of collagen and chitin to act as nucleators, where there is a slight preference of chitin over collagen as a nucleator for magnetite. Colloidal-probe AFM measurements demonstrate that introduction of a ferrogel into the chitin matrix leads to a certain increase in the stiffness of the composite material. PMID:25671158

  1. The expression of CBF genes at Fr-2 locus is associated with the level of frost tolerance in Bulgarian winter wheat cultivars

    PubMed Central

    Todorovska, Elena Georgieva; Kolev, Stanislav; Christov, Nikolai Kirilov; Balint, Andras; Kocsy, Gabor; Vágújfalvi, Attila; Galiba, Gabor

    2014-01-01

    The regulation of the majority of cold-regulated genes in plants is mediated by CBF (C-repeat binding factors) transcription factor family. Natural differences in frost tolerance (FT) of wheat have been mapped to the Fr-2 (Frost Resistance-2) locus on chromosome group 5 and are associated with variation in threshold induction temperatures and/or transcript levels of CBF genes. This study used real-time reverse-transcription polymerase chain reaction (qRT-PCR) to compare the relative expression levels of four T. aestivum CBF genes (TaCBF15.2, TaCBFA19, TaCBFA2 and TaCBFD21) in crown tissue of two Bulgarian hexaploid winter wheat cultivars (Milena and Russalka) with distinct levels of low-temperature (LT) tolerance but same vernalization requirement, and the spring cultivar Chinese Spring. The transcription profiles of the selected TaCBF genes showed that they are induced by cold treatment at 2 °C. Analysis of transcript abundance revealed that the four TaCBF genes were expressed at higher levels in the frost tolerant Milena than in the susceptible Russalka. Largest differences (fivefold and fourfold) in expression levels between both winter cultivars were observed in two of the analysed genes, TaCBF15.2 and TaCBFA19, respectively. The higher steady-state expression levels of TaCBF genes before the onset of the LT treatment in Milena, combined with stronger induction by cold treatment, suggest that these molecular responses to LT are associated with superior FT development capacity. The results expand our understanding of the molecular mechanisms underlying LT acclimation in Bulgarian wheat and can be used for development of functional markers for improvement of FT wheat-breeding programmes.

  2. Achieving Presence through Evoked Reality

    PubMed Central

    Pillai, Jayesh S.; Schmidt, Colin; Richir, Simon

    2013-01-01

    The sense of “Presence” (evolving from “telepresence”) has always been associated with virtual reality research and is still an exceptionally mystifying constituent. Now the study of presence clearly spans over various disciplines associated with cognition. This paper attempts to put forth a concept that argues that it’s an experience of an “Evoked Reality (ER)” (illusion of reality) that triggers an “Evoked Presence (EP)” (sense of presence) in our minds. A Three Pole Reality Model is proposed to explain this phenomenon. The poles range from Dream Reality to Simulated Reality with Primary (Physical) Reality at the center. To demonstrate the relationship between ER and EP, a Reality-Presence Map is developed. We believe that this concept of ER and the proposed model may have significant applications in the study of presence, and in exploring the possibilities of not just virtual reality but also what we call “reality.” PMID:23550234

  3. Detecting the presence of microorganisms

    NASA Technical Reports Server (NTRS)

    Wilkins, Judd R. (Inventor); Stoner, Glenn E. (Inventor)

    1977-01-01

    The presence of microorganisms in a sample is determined by culturing microorganisms in a growth medium which is in contact with a measuring electrode and a reference electrode and detecting a change in potential between the electrodes caused by the presence of the microorganisms in the medium with a high impedance potentiometer.

  4. Predicting the presence and cover of management relevant invasive plant species on protected areas.

    PubMed

    Iacona, Gwenllian; Price, Franklin D; Armsworth, Paul R

    2016-01-15

    Invasive species are a management concern on protected areas worldwide. Conservation managers need to predict infestations of invasive plants they aim to treat if they want to plan for long term management. Many studies predict the presence of invasive species, but predictions of cover are more relevant for management. Here we examined how predictors of invasive plant presence and cover differ across species that vary in their management priority. To do so, we used data on management effort and cover of invasive plant species on central Florida protected areas. Using a zero-inflated multiple regression framework, we showed that protected area features can predict the presence and cover of the focal species but the same features rarely explain both. There were several predictors of either presence or cover that were important across multiple species. Protected areas with three days of frost per year or fewer were more likely to have occurrences of four of the six focal species. When invasive plants were present, their proportional cover was greater on small preserves for all species, and varied with surrounding household density for three species. None of the predictive features were clearly related to whether species were prioritized for management or not. Our results suggest that predictors of cover and presence can differ both within and across species but do not covary with management priority. We conclude that conservation managers need to select predictors of invasion with care as species identity can determine the relationship between predictors of presence and the more management relevant predictors of cover. PMID:26599567

  5. CHRISTINE FROST STRUCTURAL DYNAMICS

    E-print Network

    Ervin, Elizabeth K.

    Pine Wood 2 ­ 4x5x1/8 slats 2 ­ 8x1x3/4 columns 1 ­ 3x1x1/4 beam Terrarium 12x10x6 Gorilla Glue secured between the two wall panels using Gorilla Glue. The beam spanned the gap between the two columns

  6. Frost tolerance in plants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    When conducting studies to characterize and determine the underlying mechanisms for freezing tolerance, it is essential to take into account that the type and form of freezing injury varies with the species and its degree of freezing tolerance. There are at least seven different patterns of freezin...

  7. Perceptual presence without counterfactual richness.

    PubMed

    Madary, Michael

    2014-01-01

    In this commentary, I suggest that non-visual perceptual modalities provide counterexamples to Seth's claim that perceptual presence depends on counterfactual richness. Then I suggest a modification to Seth's view that is not vulnerable to these counterexamples. PMID:24739124

  8. Family presence during cardiopulmonary resuscitation.

    PubMed

    Clark, Angela P; Aldridge, Michael D; Guzzetta, Cathie E; Nyquist-Heise, Patty; Reverend Mike Norris; Loper, Patti; Meyers, Theresa A; Voelmeck, Wayne

    2005-03-01

    A recent phenomenon in emergency and critical care settings is the presence of family members during resuscitation events. It remains controversial in most institutions, but evidence is increasing that the experience has positive benefits for family members. In this article, the origin of family presence is described and research evidence about the experience is presented. Three case studies are presented to illustrate typical events, including the potential role of the hospital chaplain. Recommendations for implementation are included. PMID:15749398

  9. The Martian surface layer

    NASA Technical Reports Server (NTRS)

    Christensen, Philip R.; Moore, Henry J.

    1992-01-01

    The global characteristics of the Martian surface layer are discussed on the basis of thermal, albedo, color, and radar data for the region between approximately 60 deg S and 60 deg N. Thermal data reveal the presence of large low- and high-inertia regions of the northern hemisphere, with much of the south covered by material of moderate inertia. There is a strong anticorrelation between inertia and albedo, a correlation between inertia and rock abundance, and, over much of the planet, a correlation of radar-derived density with inertia. Viking Orbiter color data indicate the presence of three major surface materials: low-inertia, bright-red material that is presumably dust; high-inertia, dark-grey material interpreted to be lithic material mixed with palagonitelike dust; and moderate-inertia, dark-red material that is rough at subpixel scales and interpreted to be indurated. Observations from the Viking landing sites show rocks, fines of varying cohesion and crusts. These sites have indications of aeolian erosion and deposition in the recent past.

  10. Building biomedical materials layer-by-layer

    E-print Network

    Hammond, Paula T.

    In this materials perspective, the promise of water based layer-by-layer (LbL) assembly as a means of generating drug-releasing surfaces for biomedical applications, from small molecule therapeutics to biologic drugs and ...

  11. Diffraction by glasses with a layer structure

    SciTech Connect

    Wright, A.C.; Price, D.L.; Clare, A.G.; Etherington, G.; Sinclair, R.N.

    1987-06-01

    An outline is presented of the expected form of the diffraction pattern and the real space correlation function for a glass with a layer structure. The diffraction evidence for and against the presence of layers in the structure of the vitreous arsenic and germanium chalcogenides is briefly reviewed with special reference to the outrigger raft model for vitreous GeSe/sub 2/. 14 refs., 5 figs.

  12. On Active Layer Environments and Processes in Western Dronning Maud Land, Antarctica

    NASA Astrophysics Data System (ADS)

    Hansen, C. D.; Meiklejohn, I.; Nel, W.

    2012-12-01

    The current understanding of Antarctic permafrost is poor, particularly regarding its evolution, the current thermal characteristics, and relationships with pedogenesis, hydrology, geomorphic, dynamics, biotic activity and response to global changes. Results from borehole temperature measurements over a four-year period in Western Dronning Maud Land suggest that the active layer depth is dependent on the substrate, latitude, altitude and the volume of ground exposed; the latter alludes to the potential impact of surrounding ice on the ground thermal regime. The active layer depths at the monitoring sites, varied between 16 cm at Vesleskarvet, a small nunatak at 850 masl to 28 cm in granitic till at Jutulsessen (1 270 masl). The mean near surface (1.5 cm depth) ground temperatures from 2009 to 2012 in the region have a narrow range from -16.4°C at 850m to -17.5°C at 1270 masl. Permafrost temperatures for the same locations vary between -16.3°C and -18.3°C. While little variability exists between the mean temperatures at the study locations, each site is distinct and seasonal and shorter-term frost cycles have produced landforms that are characteristic of both permafrost and diurnal frost environments. One of the key aspects of investigation is the control that the active layer has on autochthonous blockfield development in the region. The, thus far, exploratory research is being used to understand controls on the landscape and the relationship between distribution and abundance of biota. Given the rapidly changing climates in the region, improving knowledge of what drives patterns of biodiversity at a local and regional scale is vital to assess consequences of environmental change.

  13. Interpretation of Stratified Fill, Frost Depths, Water Tables, and Massive Ice within Multi-Frequency Ground-Penetrating Radar Profiles Recorded Beneath Highways in Interior Alaska

    NASA Astrophysics Data System (ADS)

    Arcone, S. A.

    2014-12-01

    Road Radar generally refers to ground-penetrating radar (GPR) surveys intended to investigate pavement construction using pulses centered above 1 GHz. In interior Alaska thick sand and gravel grading and its frozen state by late winter generally afford up to 10 m of signal penetration at lower frequencies. Consequently, this penetration potentially allows identification of pavement issues involving frost heave and thaw settlement, while the smooth surface allows assessment of GPR performance in permafrost areas under ideal survey conditions. Here I discuss profiles using pulse center frequencies from 50 to 360 MHz, recorded over sections of the Steese and Elliott Highways within and just north of Fairbanks, respectively, and of the Tok Highway near Glennallen. Construction fill is easily recognized by its stratification; where marginally present along the Elliott it is replaced by steeply dipping horizons from the underlying schist. The frost depth and water table horizons are recognized by phase attributes of the reflected pulse, as dictated by the contrasts present in dielectric permittivity, their relative depths, and their continuity. Undulating stratification in the sand and gravel fill indicates thaw settlement, as caused by the melting of buried massive ice. The Tok section reveals the top and likely the bottom of massive ice. Generally, signal penetration is greatly reduced beneath the water table and so the highest resolution, at 360 MHz, covers all horizons. There is rare evidence of a permafrost table because it is most likely masked or nearly coincident with the water table. Permafrost penetration in frozen silts is a long-standing problem for GPR, for which I discuss a possible cause related to Maxwell-Wagner dielectric relaxation losses associated with unfrozen water.

  14. Arctic microbial and next-generation sequencing approach for bacteria in snow and frost flowers: selected identification, abundance and freezing nucleation

    NASA Astrophysics Data System (ADS)

    Mortazavi, R.; Attiya, S.; Ariya, P. A.

    2015-06-01

    During the spring of 2009, as part of the Ocean-Atmosphere-Sea Ice-Snowpack (OASIS) campaign in Barrow, Alaska, USA, we examined the identity, population diversity, freezing nucleation ability of the microbial communities of five different snow types and frost flowers. In addition to the culturing and gene-sequence-based identification approach, we utilized a state-of-the-art genomic next-generation sequencing (NGS) technique to examine the diversity of bacterial communities in Arctic samples. Known phyla or candidate divisions were detected (11-18) with the majority of sequences (12.3-83.1%) belonging to one of the five major phyla: Proteobacteria, Actinobacteria, Bacteroidetes, Firmicutes, and Cyanobacteria. The number of genera detected ranged from, 101-245. The highest number of cultivable bacteria was observed in frost flowers (FFs) and accumulated snow (AS) with 325 ± 35 and 314 ± 142 CFU m L-1, respectively; and for cultivable fungi 5 ± 1 CFU m L-1 in windpack (WP) and blowing snow (BS). Morphology/elemental composition and ice-nucleating abilities of the identified taxa were obtained using high resolution electron microscopy with energy-dispersive X-ray spectroscopy and ice nucleation cold-plate, respectively. Freezing point temperatures for bacterial isolates ranged from -20.3 ± 1.5 to -15.7 ± 5.6 °C, and for melted snow samples from -9.5 ± 1.0 to -18.4 ± 0.1 °C. An isolate belonging to the genus Bacillus (96% similarity) had ice nucleation activity of -6.8 ± 0.2 °C. Comparison with Montreal urban snow, revealed that a seemingly diverse community of bacteria exists in the Arctic with some taxa possibly originating from distinct ecological environments. We discuss the potential impact of snow microorganisms in the freezing and melting process of the snowpack in the Arctic.

  15. Multi-layer carbon-based coatings for field emission

    DOEpatents

    Sullivan, John P. (Albuquerque, NM); Friedmann, Thomas A. (Albuquerque, NM)

    1998-01-01

    A multi-layer resistive carbon film field emitter device for cold cathode field emission applications. The multi-layered film of the present invention consists of at least two layers of a conductive carbon material, preferably amorphous-tetrahedrally coordinated carbon, where the resistivities of adjacent layers differ. For electron emission from the surface, the preferred structure can be a top layer having a lower resistivity than the bottom layer. For edge emitting structures, the preferred structure of the film can be a plurality of carbon layers, where adjacent layers have different resistivities. Through selection of deposition conditions, including the energy of the depositing carbon species, the presence or absence of certain elements such as H, N, inert gases or boron, carbon layers having desired resistivities can be produced.

  16. Multi-layer carbon-based coatings for field emission

    DOEpatents

    Sullivan, J.P.; Friedmann, T.A.

    1998-10-13

    A multi-layer resistive carbon film field emitter device for cold cathode field emission applications is disclosed. The multi-layered film of the present invention consists of at least two layers of a conductive carbon material, preferably amorphous-tetrahedrally coordinated carbon, where the resistivities of adjacent layers differ. For electron emission from the surface, the preferred structure can be a top layer having a lower resistivity than the bottom layer. For edge emitting structures, the preferred structure of the film can be a plurality of carbon layers, where adjacent layers have different resistivities. Through selection of deposition conditions, including the energy of the depositing carbon species, the presence or absence of certain elements such as H, N, inert gases or boron, carbon layers having desired resistivities can be produced. 8 figs.

  17. Link Layer Modeling

    NASA Astrophysics Data System (ADS)

    Mühleisen, M.; Bültmann, D.; Klagges, K.; Schinnenburg, M.

    The Data Link Layer (DLL) is located above the PHY layer described in the previous chapter and below the network layer described in Chapter 16. All data received from these layers is digital. Today most parts of the DLL are implemented in software, either as device drivers running on general purpose Central Processing Units (CPUs) or as firmware running on dedicated network interface hardware.

  18. Layer Stripping John Sylvester

    E-print Network

    Sylvester, John

    Layer Stripping John Sylvester Dept. of Mathematics, Box 354350 University of Washington Seattle a rigorous layer stripping approach to inverse scattering for the Helmholtz equation in one dimension the Born approximation in each thin layer. 1 Introduction The layer stripping approach to inverse

  19. Impact of the vertical mixing induced by low-level jets on boundary layer ozone concentration

    E-print Network

    Xue, Ming

    Impact of the vertical mixing induced by low-level jets on boundary layer ozone concentration Xiao: Ozonesonde Low-level jet Atmospheric boundary layer Ozone WRF/Chem Residual layer a b s t r a c t After at multiple sites along the corridor. layer (RL) is leaky in the presence of a strong low

  20. Performance of a boundary layer ingesting propulsion system

    E-print Network

    Plas, Angélique (Angélique Pascale)

    2006-01-01

    This thesis presents an assessment of the aerodynamic performance of an aircraft propulsion system, with embedded engines, in the presence of aircraft fuselage boundary layer ingestion (BLI). The emphasis is on defining ...

  1. Discharge rate measurements for Micromegas detectors in the presence of a longitudinal magnetic field

    SciTech Connect

    B. Moreno, S. Aune, J. Ball, G. Charles, A. Giganon, P. Konczykowski, C. Lahonde-Hamdoun, H. Moutarde, S. Procureur, F. Sabatie

    2011-10-01

    We present first discharge rate measurements for Micromegas detectors in the presence of a high longitudinal magnetic field in the GeV kinematical region. Measurements were performed by using two Micromegas detectors and a photon beam impinging a CH{sub 2} target in the Hall B of the Jefferson Laboratory. One detector was equipped with an additional GEM foil, and a reduction of the discharge probability by two orders of magnitude compared to the stand-alone Micromegas was observed. The detectors were p laced in the FROST solenoid providing a longitudinal magnetic field up to 5T. It allowed for precise measurements of the discharge probability dependence with a diffusion-reducing magnetic field. Between 0 and 5T, the discharge probability increased by a factor of 10 for polar angles between 19{degrees} and 34{degrees}. A GEANT4-based simulation developed for sparking rate calculation was calibrated against these data in order to predict the sparking rate in a high longitudinal magnetic field environment. This simulati on is then used to investigate the possible use of Micromegas in the Forward Vertex Tracker (FVT) of the future CLAS12 spectrometer. In the case of the FVT a sparking rate of 1Hz per detector was obtained at the anticipated CLAS12 luminosity.

  2. Layers of the South Polar Layered Deposits

    NASA Technical Reports Server (NTRS)

    1999-01-01

    On December 3, 1999, the Mars Polar Lander will touch down on the upper surface of a thick accumulation of layered material known as the 'South Polar Layered Deposits.' The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) has been providing stunning new pictures of the south polar layered deposits that, in conjunction with Mars Polar Lander observations, will eventually help answer many questions about this terrain.

    Both the north and south polar regions are blanketed by thick accumulations of layered material. This has been known since the 1971-1972 mission of Mariner 9. Based upon data from the Mariner and Viking projects in the 1970s, the polar layered deposits have long been considered to be accumulations of dust and ice. The layering is thought to indicate changes in how ice and dust accumulate at the poles over the course of millenia. Changes in climate might affect the thickness and composition of polar layers in a way that is analogous to how years of drought and years of plentiful rain change the width of rings in a tree trunk on Earth.

    The pictures shown here provide new details of what the south polar layered deposits look like at extremely high resolution from the MGS MOC. The picture on the left is a context frame taken at the same time as the high resolution view on the right. The context image covers an area about 115 km (71 mi) across and shows a thick, smooth blanket of material covering the upper 2/3 of the frame. This thick blanket is the south polar layered deposit material. The circular features at the lower left in the context image are craters occurring outside the polar layered deposit. More craters occur underneath the polar layered deposits. The small white box indicates the location of the MOC high resolution image (right) along the edge of the polar layered deposits. The picture is illuminated from the lower right.

    The picture on the right shows one of the clearest and highest-resolution images of south polar layered material ever obtained. Located at 73.0oS, 224.5oW, this picture covers an area approximately 550 km (340 miles) northwest of where the Mars Polar Lander will touch down in December. Illuminated from the lower right, this scene covers an area 1.5 km (0.9 mi) wide and 4.6 km (1.9 mi) long. The smallest objects that can be seen are about the sizes of automobiles. Small dark streaks in the upper right are formed from winds that have blown small patches of sediment across the surface of the layered material. Layers of only a few meters thickness are exposed along the edge of the polar layered deposits. The amount of dust versus ice in these layers is unknown. It is hoped that the Mars Polar Lander will be able to help determine--at least for the upper layers of the deposit--how much ice is present.

  3. Burning Graphene Layer-by-Layer.

    PubMed

    Ermakov, Victor A; Alaferdov, Andrei V; Vaz, Alfredo R; Perim, Eric; Autreto, Pedro A S; Paupitz, Ricardo; Galvao, Douglas S; Moshkalev, Stanislav A

    2015-01-01

    Graphene, in single layer or multi-layer forms, holds great promise for future electronics and high-temperature applications. Resistance to oxidation, an important property for high-temperature applications, has not yet been extensively investigated. Controlled thinning of multi-layer graphene (MLG), e.g., by plasma or laser processing is another challenge, since the existing methods produce non-uniform thinning or introduce undesirable defects in the basal plane. We report here that heating to extremely high temperatures (exceeding 2000 K) and controllable layer-by-layer burning (thinning) can be achieved by low-power laser processing of suspended high-quality MLG in air in "cold-wall" reactor configuration. In contrast, localized laser heating of supported samples results in non-uniform graphene burning at much higher rates. Fully atomistic molecular dynamics simulations were also performed to reveal details of oxidation mechanisms leading to uniform layer-by-layer graphene gasification. The extraordinary resistance of MLG to oxidation paves the way to novel high-temperature applications as continuum light source or scaffolding material. PMID:26100466

  4. Burning Graphene Layer-by-Layer

    NASA Astrophysics Data System (ADS)

    Ermakov, Victor A.; Alaferdov, Andrei V.; Vaz, Alfredo R.; Perim, Eric; Autreto, Pedro A. S.; Paupitz, Ricardo; Galvao, Douglas S.; Moshkalev, Stanislav A.

    2015-06-01

    Graphene, in single layer or multi-layer forms, holds great promise for future electronics and high-temperature applications. Resistance to oxidation, an important property for high-temperature applications, has not yet been extensively investigated. Controlled thinning of multi-layer graphene (MLG), e.g., by plasma or laser processing is another challenge, since the existing methods produce non-uniform thinning or introduce undesirable defects in the basal plane. We report here that heating to extremely high temperatures (exceeding 2000?K) and controllable layer-by-layer burning (thinning) can be achieved by low-power laser processing of suspended high-quality MLG in air in “cold-wall” reactor configuration. In contrast, localized laser heating of supported samples results in non-uniform graphene burning at much higher rates. Fully atomistic molecular dynamics simulations were also performed to reveal details of oxidation mechanisms leading to uniform layer-by-layer graphene gasification. The extraordinary resistance of MLG to oxidation paves the way to novel high-temperature applications as continuum light source or scaffolding material.

  5. Burning Graphene Layer-by-Layer

    PubMed Central

    Ermakov, Victor A.; Alaferdov, Andrei V.; Vaz, Alfredo R.; Perim, Eric; Autreto, Pedro A. S.; Paupitz, Ricardo; Galvao, Douglas S.; Moshkalev, Stanislav A.

    2015-01-01

    Graphene, in single layer or multi-layer forms, holds great promise for future electronics and high-temperature applications. Resistance to oxidation, an important property for high-temperature applications, has not yet been extensively investigated. Controlled thinning of multi-layer graphene (MLG), e.g., by plasma or laser processing is another challenge, since the existing methods produce non-uniform thinning or introduce undesirable defects in the basal plane. We report here that heating to extremely high temperatures (exceeding 2000?K) and controllable layer-by-layer burning (thinning) can be achieved by low-power laser processing of suspended high-quality MLG in air in “cold-wall” reactor configuration. In contrast, localized laser heating of supported samples results in non-uniform graphene burning at much higher rates. Fully atomistic molecular dynamics simulations were also performed to reveal details of oxidation mechanisms leading to uniform layer-by-layer graphene gasification. The extraordinary resistance of MLG to oxidation paves the way to novel high-temperature applications as continuum light source or scaffolding material. PMID:26100466

  6. VOLUME 85, NUMBER 23 P H Y S I C A L R E V I E W L E T T E R S 4 DECEMBER 2000 Frost Heave in Argon

    E-print Network

    Wettlaufer, John S.

    VOLUME 85, NUMBER 23 P H Y S I C A L R E V I E W L E T T E R S 4 DECEMBER 2000 Frost Heave in Argon of Washington, Seattle, Washington 98105-55640 (Received 21 June 2000) The freezing of argon in silica powder is observed to generate bands of pure solid argon in the same manner as in the phenomenon of ice lens

  7. Photonic layered media

    DOEpatents

    Fleming, James G. (Albuquerque, NM); Lin, Shawn-Yu (Albuquerque, NM)

    2002-01-01

    A new class of structured dielectric media which exhibit significant photonic bandstructure has been invented. The new structures, called photonic layered media, are easy to fabricate using existing layer-by-layer growth techniques, and offer the ability to significantly extend our practical ability to tailor the properties of such optical materials.

  8. Layer-by-layer cell membrane assembly

    NASA Astrophysics Data System (ADS)

    Matosevic, Sandro; Paegel, Brian M.

    2013-11-01

    Eukaryotic subcellular membrane systems, such as the nuclear envelope or endoplasmic reticulum, present a rich array of architecturally and compositionally complex supramolecular targets that are as yet inaccessible. Here we describe layer-by-layer phospholipid membrane assembly on microfluidic droplets, a route to structures with defined compositional asymmetry and lamellarity. Starting with phospholipid-stabilized water-in-oil droplets trapped in a static droplet array, lipid monolayer deposition proceeds as oil/water-phase boundaries pass over the droplets. Unilamellar vesicles assembled layer-by-layer support functional insertion both of purified and of in situ expressed membrane proteins. Synthesis and chemical probing of asymmetric unilamellar and double-bilayer vesicles demonstrate the programmability of both membrane lamellarity and lipid-leaflet composition during assembly. The immobilized vesicle arrays are a pragmatic experimental platform for biophysical studies of membranes and their associated proteins, particularly complexes that assemble and function in multilamellar contexts in vivo.

  9. 22 Layer Chocolate Raspberry Cake

    E-print Network

    Alpay, S. Pamir

    Desserts 22 Layer Chocolate Raspberry Cake #12;22 Layer Chocolate Raspberry Cake $9 6 layers of cake, 5 layers of chocolate, 5 layers of raspberry jam 5 layers of chocolate mousse, 1 layer in an Oreo crust topped with whipped cream & chopped peanuts drizzled with chocolate. Brownie Sundae Supreme

  10. Scintillator reflective layer coextrusion

    DOEpatents

    Yun, Jae-Chul (Naperville, IL); Para, Adam (St. Charles, IL)

    2001-01-01

    A polymeric scintillator has a reflective layer adhered to the exterior surface thereof. The reflective layer comprises a reflective pigment and an adhesive binder. The adhesive binder includes polymeric material from which the scintillator is formed. A method of forming the polymeric scintillator having a reflective layer adhered to the exterior surface thereof is also provided. The method includes the steps of (a) extruding an inner core member from a first amount of polymeric scintillator material, and (b) coextruding an outer reflective layer on the exterior surface of the inner core member. The outer reflective layer comprises a reflective pigment and a second amount of the polymeric scintillator material.

  11. Significant relationships among frost tolerance and net photosynthetic rate, water use efficiency and dehydrin accumulation in cold-treated winter oilseed rapes.

    PubMed

    Urban, Milan Old?ich; Klíma, Miroslav; Vítámvás, Pavel; Vašek, Jakub; Hilgert-Delgado, Alois Albert; Ku?era, Vratislav

    2013-12-15

    Five winter oilseed rape cultivars (Benefit, Californium, Cortes, Ladoga, Navajo) were subjected to 30 days of cold treatment (4 °C) to examine the effect of cold on acquired frost tolerance (FT), dehydrin (DHN) content, and photosynthesis-related parameters. The main aim of this study was to determine whether there are relationships between FT (expressed as LT50 values) and the other parameters measured in the cultivars. While the cultivar Benefit accumulated two types of DHNs (D45 and D35), the other cultivars accumulated three additional DHNs (D97, D47, and D37). The similar-sized DHNs (D45 and D47) were the most abundant; the others exhibited significantly lower accumulations. The highest correlations were detected between LT50 and DHN accumulation (r=-0.815), intrinsic water use efficiency (WUEi; r=-0.643), net photosynthetic rate (r=-0.628), stomatal conductance (r=0.511), and intracellular/intercellular CO2 concentration (r=0.505). Those cultivars that exhibited higher Pn rate in cold (and further a significant increase in WUEi) had higher levels of DHNs and also higher FT. No significant correlation was observed between LT50 and E, PRI, or NDVI. Overall, we have shown the selected physiological parameters to be able to distinguish different FT cultivars of winter oilseed rape. PMID:24054752

  12. Frost Grape Polysaccharide (FGP), an Emulsion-Forming Arabinogalactan Gum from the Stems of Native North American Grape Species Vitis riparia Michx.

    PubMed

    Price, Neil P J; Vermillion, Karl E; Eller, Fred J; Vaughn, Steven F

    2015-08-19

    A new arabinogalactan is described that is produced in large quantity from the cut stems of the North American grape species Vitis riparia (Frost grape). The sugar composition consists of l-arabinofuranose (l-Araf, 55.2%) and d-galactopyranose (d-Galp 30.1%), with smaller components of d-xylose (11.2%), d-mannose (3.5%), and glucuronic acid (GlcA, ?2%), the latter linked via a galactosyl residue. Permethylation identified 3-linked Galp residues, some substituted at the 2-position with Galp or Manp, terminal Araf and Xylp, and an internal 3-substituted Araf. NMR (HSQC, TOCSY, HMBC, DOSY) identified ?Galp and three ?Araf spin systems, in an Araf-?1,3-Araf-?1,2-Araf-?1,2-Galp structural motif. Diffusion-ordered NMR showed that the FGP has a molecular weight of 1-10 MDa. Unlike gum arabic, the FGP does not contain a hydroxyproline-rich protein (HPRP). FGP forms stable gels at >15% w/v and at 1-12% solutions are viscous and are excellent emulsifiers of flavoring oils (grapefruit, clove, and lemongrass), giving stable emulsions for ?72 h. Lower concentrations (0.1% w/v) were less viscous, yet still gave stable grapefruit oil/water emulsions. Hence, FGP is a ?1,3-linked arabinogalactan with potential as a gum arabic replacement in the food and beverage industries. PMID:26234618

  13. Ice Lens Formation, Frost Heave, Thin Films, and the Importance of the Polar H2O Reservoir at High Obliquity

    NASA Technical Reports Server (NTRS)

    Zent, A. P.; Sizemore, H. G.; Rempel, A. W.

    2011-01-01

    Several lines of evidence indicate that the volume of shallow ground ice in the martian high latitudes exceeds the pore volume of the host regolith. Boynton et al. found an optimal fit to the Mars Odyssey Gamma Ray Spectrometer (GRS) data at the Phoenix landing site by modeling a buried layer of 50-75% ice by mass (up to 90% ice by volume). Thermal and optical observations of recent impact craters in the northern hemisphere have revealed nearly pure ice. Ice deposits containing only 1-2% soil by volume were excavaged by Phoenix. One hypothesis for the origin of this excess ice is that it developed in situ by a mechanism analogous to the formation of terrestrial ice lenses and needle ice. Problematically, terrestrial soil-ice segregation is driven by freeze/thaw cycling and the movement of bulk water, neither of which are expected to have occurred in the geologically recent past on Mars. If however ice lens formation is possible at temperatures less than 273 K, there are possible implications for the habitability of Mars permafrost, since the same thin films of unfrozen water that lead to ice segregation are used by terrestrial psychrophiles to metaboluze and grow down to temperatures of at least 258 K.

  14. Piezoelectric Resonator with Two Layers

    NASA Technical Reports Server (NTRS)

    Stephanou, Philip J. (Inventor); Black, Justin P. (Inventor)

    2013-01-01

    A piezoelectric resonator device includes: a top electrode layer with a patterned structure, a top piezoelectric layer adjacent to the top layer, a middle metal layer adjacent to the top piezoelectric layer opposite the top layer, a bottom piezoelectric layer adjacent to the middle layer opposite the top piezoelectric layer, and a bottom electrode layer with a patterned structure and adjacent to the bottom piezoelectric layer opposite the middle layer. The top layer includes a first plurality of electrodes inter-digitated with a second plurality of electrodes. A first one of the electrodes in the top layer and a first one of the electrodes in the bottom layer are coupled to a first contact, and a second one of the electrodes in the top layer and a second one of the electrodes in the bottom layer are coupled to a second contact.

  15. Oxygen inhibition layer of composite resins: effects of layer thickness and surface layer treatment on the interlayer bond strength.

    PubMed

    Bijelic-Donova, Jasmina; Garoushi, Sufyan; Lassila, Lippo V J; Vallittu, Pekka K

    2015-02-01

    An oxygen inhibition layer develops on surfaces exposed to air during polymerization of particulate filling composite. This study assessed the thickness of the oxygen inhibition layer of short-fiber-reinforced composite in comparison with conventional particulate filling composites. The effect of an oxygen inhibition layer on the shear bond strength of incrementally placed particulate filling composite layers was also evaluated. Four different restorative composites were selected: everX Posterior (a short-fiber-reinforced composite), Z250, SupremeXT, and Silorane. All composites were evaluated regarding the thickness of the oxygen inhibition layer and for shear bond strength. An equal amount of each composite was polymerized in air between two glass plates and the thickness of the oxygen inhibition layer was measured using a stereomicroscope. Cylindrical-shaped specimens were prepared for measurement of shear bond strength by placing incrementally two layers of the same composite material. Before applying the second composite layer, the first increment's bonding site was treated as follows: grinding with 1,000-grit silicon-carbide (SiC) abrasive paper, or treatment with ethanol or with water-spray. The inhibition depth was lowest (11.6 ?m) for water-sprayed Silorane and greatest (22.9 ?m) for the water-sprayed short-fiber-reinforced composite. The shear bond strength ranged from 5.8 MPa (ground Silorane) to 36.4 MPa (water-sprayed SupremeXT). The presence of an oxygen inhibition layer enhanced the interlayer shear bond strength of all investigated materials, but its absence resulted in cohesive and mixed failures only with the short-fiber-reinforced composite. Thus, more durable adhesion with short-fiber-reinforced composite is expected. PMID:25556290

  16. Layered plasma polymer composite membranes

    DOEpatents

    Babcock, W.C.

    1994-10-11

    Layered plasma polymer composite fluid separation membranes are disclosed, which comprise alternating selective and permeable layers for a total of at least 2n layers, where n is [>=]2 and is the number of selective layers. 2 figs.

  17. BIODIVERSITY Presence-only versus presenceabsence

    E-print Network

    BIODIVERSITY RESEARCH Presence-only versus presence­absence data in species composition determinant in the study. Sampling locations were based on true observations from the Global Biodiversity Information of species composition. Keywords Biodiversity, canonical correspondence analysis, environmental determinants

  18. Reflection of presence: toward more natural and responsive telecollaboration

    NASA Astrophysics Data System (ADS)

    Agamanolis, Stefan; Westner, Alex; Bove, V. Michael, Jr.

    1998-02-01

    THe purpose of reflection of presence is to create a framework for a telepresence environment that intelligently responds and adapts itself to its inhabitants in order to enhance interpersonal communication or also reflections of the other remotely-located participants, just as if every one is standing in the same room looking at each other through a real mirror. Using visual and auditory cues, segmented images of participants are dynamically layered into a single display using varying transparency, position and scale to reflect center of attention and degree of presence. Wireless tangible interfaces allow participants to customize their shared space and collaboratively manipulate and annotate media objects in the background. The system is novel in that it is implemented totally as a set of cooperating scripts instead of through a low-level programming language, enabling rapid experimental changes in the behavior of the prototype.

  19. Theoretical and experimental studies of the atmospheric sodium layer

    NASA Technical Reports Server (NTRS)

    Richter, E. S.; Sechrist, C. F., Jr.

    1978-01-01

    Atmospheric atomic sodium was studied with a laser radar system. Photocount data were processed using a digital filter to obtain continuous estimates of the sodium concentration versus altitude. Wave-like structures in the sodium layer were observed, and there was evidence for the presence of a standing wave in the layer. The bottomside of the layer was observed to undulate with a period of about 2 1/2 hours, and the layer was observed to broaden through the night. A meteor ablation-cluster ion theory of sodium was developed. The theory shows good agreement with existing atmospheric observations as well as laboratory measurements of rate constants.

  20. Community Matters: Social Presence and Learning Outcomes

    ERIC Educational Resources Information Center

    Hostetter, Carol

    2013-01-01

    The study examines the relationship between social presence and students' learning outcomes. An emerging body of research connects social presence with learning outcomes in online coursework. Social presence is the "degree to which a person is perceived as a 'real person' in mediated communication" (Gunwardena &…

  1. Layers and Erosion and more Layers

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 4 November 2003

    This image is located within a set of eroded layered rocks known as the Medusae Fossae Formation. Careful inspection of this image reveals four separate layers. Starting at the bottom of the image, as well as the bottom of the sequence of layers, is a somewhat hilly, cratered plain. Above that is a mud or lava flow with a lobate edge that is characteristic of fluid flow. Above that is a layer with a spectacular rayed crater. This layer shows linear erosional patterns that are probably caused by persistent wind abrasion, typical of rocks in this area. And finally, a more blocky unit lies on top, mostly eroded away.

    Image information: VIS instrument. Latitude 3.6, Longitude 218.6 East (141.4 West). 19 meter/pixel resolution.

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

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

  2. A case study of boundary layer ventilation by convection and coastal processes

    E-print Network

    Dacre, Helen

    by the presence of the Earth's surface. The depth of this layer is variable, changing with location, time of day air that is not affected by the Earth's surface, known as the free troposphere. This stable layer canA case study of boundary layer ventilation by convection and coastal processes H. F. Dacre,1 S. L

  3. The continuous spectrum for a boundary layer in a streamwise pressure gradient

    E-print Network

    Spiteri, Raymond J.

    The continuous spectrum for a boundary layer in a streamwise pressure gradient S. A. Maslowe spectrum are presented for boundary layers developing in the presence of a streamwise pressure gradient of the boundary layer can be much larger than it is for Blasius flow. This is particularly true when the pressure

  4. The stability of the mesospheric plasma layer

    SciTech Connect

    Pandey, B. P.; Vladimirov, S. V.

    2011-12-15

    The presence of micron and sub-micron size dust in the Earth's summer mesopause are a possible cause of electron density depletion. Whereas electrons in this weakly ionized and weakly magnetized layer are frozen in the magnetic field, the ions and dust are highly diffusive. This relative drift between the plasma particles will cause a current in the medium. The presence of such a current can destabilize the plasma layer with a growth rate of the order of Alfven frequency. Since required current density for the onset of this instability is on the order of J > or approx. 0.03A/m{sup 2}, it is quite unlikely that such a strong current is present in the mesosphere. However, owing to the prevailing ambiguity of measurements, the existence of such a current is not completely ruled out.

  5. Layered metal matrix composites

    SciTech Connect

    Lu, L.; Li, G.; Lai, M.O.

    1996-10-01

    Metal matrix composite (MMC) with composition of Al-4.5 wt.%Cu reinforced by 10wt.%TiB{sub 2} or 15wt.%SiC particulate has been successfully fabricated using powder metallurgy technique. Disk, compression and beam specimens were prepared with (a) layered structure containing ductile Al-4.5wt.%Cu with brittle Al-4.5wt.%Cu/TiB{sub 2} or Al-4.5wt.%Cu/SiC layers, and (b) homogeneous constituent with composition of Al-4.5wt.%Cu/10wt.%TiB{sub 2}. The specimens for the fracture toughness measurement were built through three ductile-brittle-ductile alternating layers. For the beam specimens, the layers were built through brittle-ductile-brittle sequence. The brittle layer consisted of Al-4.5%Cu with fixed amount of reinforcement. Fracture toughness testing revealed an increase for layered composites although the total amount of the reinforcement was the same for all disk specimens. The increase in fracture toughness is due to the existence of ductile layers which manifests a strong influence on delaying the occurrence of fracture. It acts as a barrier to resist the propagation of crack and hence increases the fracture toughness of the layered MMC specimens. Delamination in the beam specimens was observed to be due to shear stresses. Fracture surfaces of both disk, compress and beam specimens were characterized using the SEM.

  6. Multiple density layered insulator

    DOEpatents

    Alger, Terry W. (Tracy, CA)

    1994-01-01

    A multiple density layered insulator for use with a laser is disclosed wh provides at least two different insulation materials for a laser discharge tube, where the two insulation materials have different thermoconductivities. The multiple layer insulation materials provide for improved thermoconductivity capability for improved laser operation.

  7. Multiple density layered insulator

    DOEpatents

    Alger, T.W.

    1994-09-06

    A multiple density layered insulator for use with a laser is disclosed which provides at least two different insulation materials for a laser discharge tube, where the two insulation materials have different thermoconductivities. The multiple layer insulation materials provide for improved thermoconductivity capability for improved laser operation. 4 figs.

  8. The Atmospheric Boundary Layer

    ERIC Educational Resources Information Center

    Tennekes, Hendrik

    1974-01-01

    Discusses some important parameters of the boundary layer and effects of turbulence on the circulation and energy dissipation of the atmosphere. Indicates that boundary-layer research plays an important role in long-term forecasting and the study of air-pollution meteorology. (CC)

  9. Layer-by-layer nanoencapsulation of camptothecin with improved activity

    PubMed Central

    Parekh, Gaurav; Pattekari, Pravin; Joshi, Chaitanya; Shutava, Tatsiana; DeCoster, Mark; Levchenko, Tatyana; Torchilin, Vladimir; Lvov, Yuri

    2014-01-01

    160 nm nanocapsules containing up to 60% of camptothecin in the core and 7–8 polyelectrolyte bilayers in the shell were produced by washless layer-by-layer assembly of heparin and block-copolymer of poly-L-lysine and polyethylene glycol. The outer surface of the nanocapsules was additionally modified with polyethylene glycol of 5 kDa or 20 kDa molecular weight to attain protein resistant properties, colloidal stability in serum and prolonged release of the drug from the capsules. An advantage of the LbL coated capsules is the preservation of camptothecin lactone form with the shell assembly starting at acidic pH and improved chemical stability of encapsulated drug at neutral and basic pH, especially in the presence of albumin that makes such formulation more active than free camptothecin. LbL nanocapsules preserve the camptothecin lactone form at pH 7.4 resulting in triple activity of the drug toward CRL2303 glioblastoma cell. PMID:24508806

  10. Multiple layer insulation cover

    DOEpatents

    Farrell, James J. (Livingston Manor, NY); Donohoe, Anthony J. (Ovid, NY)

    1981-11-03

    A multiple layer insulation cover for preventing heat loss in, for example, a greenhouse, is disclosed. The cover is comprised of spaced layers of thin foil covered fabric separated from each other by air spaces. The spacing is accomplished by the inflation of spaced air bladders which are integrally formed in the cover and to which the layers of the cover are secured. The bladders are inflated after the cover has been deployed in its intended use to separate the layers of the foil material. The sizes of the material layers are selected to compensate for sagging across the width of the cover so that the desired spacing is uniformly maintained when the cover has been deployed. The bladders are deflated as the cover is stored thereby expediting the storage process and reducing the amount of storage space required.

  11. Fiber optic device for sensing the presence of a gas

    DOEpatents

    Benson, David K. (14154 W. First Dr., Golden, CO 80401); Bechinger, Clemens S. (35 S. Holman Way, # 3D, Golden, CO 80401); Tracy, C. Edwin (19012 W. 60th Dr., Golden, CO 80403)

    1998-01-01

    A fiber-optic device for sensing the presence of a gas in an environment is provided. The device comprises a light source for directing a light beam to a layer system having a first surface and a second surface opposite the first surface. The first surface is exposable to the light beam and the second surface is exposable to the environment. A first light portion encounters and reflects from the first surface at an angle of incidence free from optical wave guide resonance phenomenon and the second light portion encounters and reflects from the first surface at an angle of incidence enabling an optical wave guide resonance phenomenon. The layer system is selected to reversibly react with the gas to be detected. The reaction between the gas and the material changes the material's optical properties and the wavelength at which the optical wave guide resonance occurs. Furthermore, a mechanism for measuring the intensity of the reflected first light portion relative to the reflected second light portion is provided with the ratio of the first and second light portions indicating the concentration of the gas presence in the environment.

  12. Fiber optic device for sensing the presence of a gas

    DOEpatents

    Benson, D.K.; Bechinger, C.S.; Tracy, C.E.

    1998-01-13

    A fiber-optic device for sensing the presence of a gas in an environment is provided. The device comprises a light source for directing a light beam to a layer system having a first surface and a second surface opposite the first surface. The first surface is exposable to the light beam and the second surface is exposable to the environment. A first light portion encounters and reflects from the first surface at an angle of incidence free from optical wave guide resonance phenomenon and the second light portion encounters and reflects from the first surface at an angle of incidence enabling an optical wave guide resonance phenomenon. The layer system is selected to reversibly react with the gas to be detected. The reaction between the gas and the material changes the material`s optical properties and the wavelength at which the optical wave guide resonance occurs. Furthermore, a mechanism for measuring the intensity of the reflected first light portion relative to the reflected second light portion is provided with the ratio of the first and second light portions indicating the concentration of the gas presence in the environment. 5 figs.

  13. Lithospheric layering in the North American craton.

    PubMed

    Yuan, Huaiyu; Romanowicz, Barbara

    2010-08-26

    How cratons-extremely stable continental areas of the Earth's crust-formed and remained largely unchanged for more than 2,500 million years is much debated. Recent studies of seismic-wave receiver function data have detected a structural boundary under continental cratons at depths too shallow to be consistent with the lithosphere-asthenosphere boundary, as inferred from seismic tomography and other geophysical studies. Here we show that changes in the direction of azimuthal anisotropy with depth reveal the presence of two distinct lithospheric layers throughout the stable part of the North American continent. The top layer is thick ( approximately 150 km) under the Archaean core and tapers out on the surrounding Palaeozoic borders. Its thickness variations follow those of a highly depleted layer inferred from thermo-barometric analysis of xenoliths. The lithosphere-asthenosphere boundary is relatively flat (ranging from 180 to 240 km in depth), in agreement with the presence of a thermal conductive root that subsequently formed around the depleted chemical layer. Our findings tie together seismological, geochemical and geodynamical studies of the cratonic lithosphere in North America. They also suggest that the horizon detected in receiver function studies probably corresponds to the sharp mid-lithospheric boundary rather than to the more gradual lithosphere-asthenosphere boundary. PMID:20740006

  14. Water Uptake in PEMFC Catalyst Layers

    SciTech Connect

    Gunterman, Haluna P.; Kwong, Anthony H.; Gostick, Jeffrey T.; Kusoglu, Ahmet; Weber, Adam Z.

    2011-07-01

    Water uptake profiles of proton-exchange-membrane fuel-cell catalyst layers are characterized in the form of capillary-pressure saturation (Pc-S) curves. The curves indicate that the catalyst layers tested are highly hydrophilic and require capillary pressures as low as -80 kPa to eject imbibed water. Comparison of materials made with and without Pt indicates a difference in water ejection and uptake phenomena due to the presence of Pt. The addition of Pt increases the tendency of the catalyst layer to retain water. Dynamic vapor sorption (DVS) is used to characterize the water-vapor sorption onto Nafion, Pt/C, and C surfaces. The DVS results align with the trends found from the Pc-S curves and show an increased propensity for water uptake in the presence of Pt. The effect of the ion in Nafion, sodium or protonated form, is also compared and demonstrates that although the protonation of the Nafion in the catalyst layer also increases hydrophilicity, the effect is not as great as that caused by Pt.

  15. Layer Formation in Semiconvection

    E-print Network

    Joseph A. Biello

    2001-02-20

    Layer formation in a thermally destabilized fluid with stable density gradient has been observed in laboratory experiments and has been proposed as a mechanism for mixing molecular weight in late stages of stellar evolution in regions which are unstable to semiconvection. It is not yet known whether such layers can exist in a very low viscosity fluid: this work undertakes to address that question. Layering is simulated numerically both at high Prandtl number (relevant to the laboratory) in order to describe the onset of layering intability, and the astrophysically important case of low Prandtl number. It is argued that the critical stability parameter for interfaces between layers, the Richardson number, increases with decreasing Prandtl number. Throughout the simulations the fluid has a tendency to form large scale flows in the first convecting layer, but only at low Prandtl number do such structures have dramatic consequences for layering. These flows are shown to drive large interfacial waves whose breaking contributes to significant mixing across the interface. An effective diffusion coefficient is determined from the simulation and is shown to be much greater than the predictions of both an enhanced diffusion model and one which specifically incorporates wave breaking. The results further suggest that molecular weight gradient interfaces are ineffective barriers to mixing even when specified as initial conditions, such as would arise when a compositional gradient is redistributed by another mechanism than buoyancy, such as rotation or internal waves.

  16. Linear baroclinic instability in the presence of large scale topography

    NASA Technical Reports Server (NTRS)

    Reynolds, Nathaniel Dunton

    1987-01-01

    The effect of a planetary-scale, wavenumber 2 topography on baroclinically active disturbances is investigated for a channel domain in a two-layer, quasi-geostrophic context. When the lower-layer zonal velocity is nonzero, the topography influences the disturbances by forcing a stationary wave, and the topography and the forced wave influence the growth rates and the spatial structures of the time-dependent solutions. The case of zero zonal velocity in the lower layer was also investigated, for which no forced wave exists. Asymptotic forms of the equations, valid when the topographic effect (governed by the ratio of the nondimensional topographic height to the rotational Froude number) is small, are used to obtain both the stationary and time-dependent solutions. The latter are also obtained using a numerical approach, in which is determined the eigenvalues and eigenfunctions of a matrix representing the dynamical equations. Agreement is good between the two approaches. Recent laboratory experiments with a baroclinic annulus in which there is a false bottom with wavenumber 2 topography, are used to select governing parameters. The simultaneous presence of a stationary forced wave of wavenumber 2 and a time-dependent baroclinic wave of wavenumber 4, which has wavenumber 2 and 6 sidebands due to the topography, yields a flow field that exhibits some principal features of the laboratory experiments. The position of the forced wave and the location of an excursion in latitude of the storm track show qualitative resemblance to those features observed in the atmosphere.

  17. Nonlinear, electrocatalytic swimming in the presence of salt

    E-print Network

    Benedikt Sabass; Udo Seifert

    2012-02-16

    A small, bimetallic particle in a hydrogen peroxide solution can propel itself by means of an electrocatalytic reaction. The swimming is driven by a flux of ions around the particle. We model this process for the presence of a monovalent salt, where reaction-driven proton currents induce salt ion currents. A theory for thin diffuse layers is employed, which yields nonlinear, coupled transport equations. The boundary conditions include a compact Stern layer of adsorbed ions. Electrochemical processes on the particle surface are modeled with a first order reaction of the Butler-Volmer type. The equations are solved numerically for the swimming speed. An analytical approximation is derived under the assumption that the decomposition of hydrogen peroxide occurs mainly without inducing an electric current. We find that the swimming speed increases linearly with hydrogen peroxide concentration for small concentrations. The influence of ion diffusion on the reaction rate can lead to a concave shape of the function of speed vs. hydrogen peroxide concentration. The compact layer of ions on the particle diminishes the reaction rate and consequently reduces the speed. Our results are consistent with published experimental data.

  18. Functionalization of layered titanates.

    PubMed

    Ide, Yusuke; Sadakane, Masahiro; Sano, Tsuneji; Ogawa, Makoto

    2014-03-01

    This review article describes the synthesis, modification, and function of lepidocrocite-type layered titanate (A(x)Ti(2-y)M(y)O4, A: A, interlayer cation; M, metal or vacancy). Due to the compositional variation, which affects cation exchange, semiconducting and swelling properties, lepidocrocite-type layered titanates have attracted increasing attention in solid-state materials chemistry. The immobilization of functional units has been done to improve the properties as well as to impart additional functions. Here, we highlight recent developments of hybrid materials derived from the intercalation of inorganic and organic cations, organic functional groups, and nanoparticles into lepidocrocite-type layered titanates. PMID:24745207

  19. Physical Layer Modeling

    NASA Astrophysics Data System (ADS)

    de Baynast, A.; Bohge, M.; Willkomm, D.; Gross, J.

    The Physical Layer (PHY) is serving as the interface between the Data Link Layer (DLL) and the environment. Accordingly, it defines the relation between the device and the physical medium. In wireless systems, the general task of the PHY is to convert bit streams into radio waves and vice versa. Though the transmitter and the receiver are dual, they are comprised of different components in the physical layer. The transmitter takes digital input in form of (payload) bits and converts them into an analog signal, generally around a given carrier frequency which is then radiated via the antenna.

  20. Compliant layer chucking surface

    DOEpatents

    Blaedel, Kenneth L. (Dublin, CA); Spence, Paul A. (Pleasanton, CA); Thompson, Samuel L. (Pleasanton, CA)

    2004-12-28

    A method and apparatus are described wherein a thin layer of complaint material is deposited on the surface of a chuck to mitigate the deformation that an entrapped particle might cause in the part, such as a mask or a wafer, that is clamped to the chuck. The harder particle will embed into the softer layer as the clamping pressure is applied. The material composing the thin layer could be a metal or a polymer for vacuum or electrostatic chucks. It may be deposited in various patterns to affect an interrupted surface, such as that of a "pin" chuck, thereby reducing the probability of entrapping a particle.

  1. Meteoric layers in planetary ionospheres

    E-print Network

    Withers, Paul

    ;Sporadic E layer at Earth Sporadic E = Dense layers of plasma at E-region altitudes that aren't related) #12;Making narrow layers on Earth Mechanism for producing narrow layers of metal ion plasma by windMeteoric layers in planetary ionospheres Paul Withers Boston University Abstract SA11B-1919 withers

  2. Topography of the South Polar Cap and Layered Deposits of Mars: Viking Stereo Grametry at Regional and Local Scales

    NASA Technical Reports Server (NTRS)

    Schenk, P.; Moore, J.; Stoker, C.

    1998-01-01

    Layered deposits and residual polar caps on Mars may record the deposition of ice and sediment modulated by periodic climate change. Topographic information relating to layer thicknesses, erosional processes, and formation of dark spirals within these deposits has been sparce or unreliable until the arrival of MOLA in orbit in September 1997. To assist in evaluating these terrains prior to launch and to assess formation and erosion processes in the polar deposits, we have assembled Viking stereo mosaics of the region and have produced the first reliable DEM models of the south polar deposits using automated stereogrammetry tools. Here we report our preliminary topographic results, pending final image pointing updates. The maximum total thickness of the layered deposits in the south polar region is 2.5 km. The thick layered deposits consist of a series of megaterraces. Each terrace is several tens of kilometers wide and is flat or slopes very gently toward the pole. These terraces step downward from a central plateau near the south pole. Terraces are bounded by relatively steep scarps 100-500 meters high that face toward the equator. These scarps correspond to the pattern of dark spirals observed within the residual cap in southern summer, and are interpreted as ice or frost-free surfaces warmed by solar insolation. Several tongue-shaped troughs, with rounded cirquelike heads, are observed near the margins of the deposit. These troughs are 300-600 meters in deep and may be similar to troughs observed in the northern polar deposit.

  3. Membranes having aligned 1-D nanoparticles in a matrix layer for improved fluid separation

    DOEpatents

    Revanur, Ravindra; Lulevich, Valentin; Roh, Il Juhn; Klare, Jennifer E.; Kim, Sangil; Noy, Aleksandr; Bakajin, Olgica

    2015-12-22

    Membranes for fluid separation are disclosed. These membranes have a matrix layer sandwiched between an active layer and a porous support layer. The matrix layer includes 1-D nanoparticles that are vertically aligned in a porous polymer matrix, and which substantially extend through the matrix layer. The active layer provides species-specific transport, while the support layer provides mechanical support. A matrix layer of this type has favorable surface morphology for forming the active layer. Furthermore, the pores that form in the matrix layer tend to be smaller and more evenly distributed as a result of the presence of aligned 1-D nanoparticles. Improved performance of separation membranes of this type is attributed to these effects.

  4. Terby's Layered Rocks

    NASA Technical Reports Server (NTRS)

    2004-01-01

    14 March 2004 Layered rock outcrops are common all across Mars, and the Mars rover, Opportunity, has recently investigated some layered rocks in Meridiani Planum. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows layered sedimentary rocks in northern Terby Crater, located just north of the giant Hellas Basin near 27.5oS, 285.8oW. Hundreds of layers are exposed in a deposit several kilometers thick within Terby. A history of events that shaped the northern Hellas region is recorded in these rocks, just waiting for a person or robot to investigate. The picture covers an area 3 km (1.9 mi) across. Sunlight illuminates the scene from the left.

  5. The Abstract MAC Layer

    E-print Network

    Newport, Calvin

    2009-02-21

    A diversity of possible communication assumptions complicates the study of algorithms and lower bounds for radio networks. We address this problem by defining an Abstract MAC Layer. This service provides reliable local ...

  6. The Abstract MAC Layer

    E-print Network

    Kuhn, Fabian

    2009-05-11

    A diversity of possible communication assumptions complicates the study of algorithms and lower bounds for radio networks. We address this problem by defining an Abstract MAC Layer. This service provides reliable local ...

  7. The Abstract MAC Layer

    E-print Network

    Kuhn, Fabian

    2010-08-26

    A diversity of possible communication assumptions complicates the study of algorithms and lower bounds for radio networks. We address this problem by defining an abstract MAC layer. This service provides reliable local ...

  8. The abstract MAC layer

    E-print Network

    Kuhn, Fabian

    A diversity of possible communication assumptions complicates the study of algorithms and lower bounds for radio networks. We address this problem by defining an Abstract MAC Layer. This service provides reliable local ...

  9. Structured luminescence conversion layer

    DOEpatents

    Berben, Dirk; Antoniadis, Homer; Jermann, Frank; Krummacher, Benjamin Claus; Von Malm, Norwin; Zachau, Martin

    2012-12-11

    An apparatus device such as a light source is disclosed which has an OLED device and a structured luminescence conversion layer deposited on the substrate or transparent electrode of said OLED device and on the exterior of said OLED device. The structured luminescence conversion layer contains regions such as color-changing and non-color-changing regions with particular shapes arranged in a particular pattern.

  10. Wilson's DiseaseWilson's Disease Rett FrostRett Frost

    E-print Network

    Brutlag, Doug

    )incorporates into ceruloplasmin (Cu protein) · Copper builds up in the liver, brain, eyes, causesCopper builds up in the liver, manyCopper is necessary for bodily functions, many proteins require copper as a cofactorproteins gram of liver tissuetissue · Ceruloplasmin (protein that carries copper and binds iron

  11. Layers in the Presence of Conservation Laws Alin Pogan and Arnd Scheel

    E-print Network

    Scheel, Arnd

    been normalized to one and d is the diffusion rate of the chemical species E. Making the change u with suitable decay conditions at x = ±. Such systems arise in a number of physical, biological, and chemical applications; [1, 3, 4, 10, 11, 15, 16, 27]. A fairly simple model arises in the theory

  12. Frictional properties of the end-grafted polymer layer in presence of salt solution

    NASA Astrophysics Data System (ADS)

    Raftari, Maryam; Zhang, Zhenyu; Leggett, Graham J.; Geoghegan, Mark

    2012-02-01

    We have studied the frictional behaviour of grafted poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) films using friction force microscopy (FFM). The films were prepared on native oxide-terminated silicon substrates using the technique of atom transfer radical polymerization (ATRP). These brushes had constant grafting density (1.18 nm2), and of a thickness of ˜66 nm, as measured by ellipsometry. We show that single asperity contact mechanics (Johnson-Kendall-Roberts (JKR) and Derjaguin-M"uller-Toporov (DMT) models) as well as a linear (Amontons) relation between applied load and frictional load all apply to these systems depending on the concentration of salt and the nature of the FFM probe. Measurements were made using gold-coating and polymer functionalized silicon nitride triangular probes. Polymer functionalized probe included growth the PDMAEMA with same method on tips. The frictional behaviour are investigated between PDMAEMA and gold coated and PDMAEMA tips immersed in different concentrations of KCl, KBr and KI.

  13. High voltage switches having one or more floating conductor layers

    DOEpatents

    Werne, Roger W.; Sampayan, Stephen; Harris, John Richardson

    2015-11-24

    This patent document discloses high voltage switches that include one or more electrically floating conductor layers that are isolated from one another in the dielectric medium between the top and bottom switch electrodes. The presence of the one or more electrically floating conductor layers between the top and bottom switch electrodes allow the dielectric medium between the top and bottom switch electrodes to exhibit a higher breakdown voltage than the breakdown voltage when the one or more electrically floating conductor layers are not present between the top and bottom switch electrodes. This increased breakdown voltage in the presence of one or more electrically floating conductor layers in a dielectric medium enables the switch to supply a higher voltage for various high voltage circuits and electric systems.

  14. Under consideration for publication in J. Fluid Mech. 1 Localised convection cells in the presence of

    E-print Network

    Dawes, Jon

    Under consideration for publication in J. Fluid Mech. 1 Localised convection cells in the presence. (Received 16 June 2006) Thermal convection in a horizontal fluid layer heated uniformly from below usually magnetic field, convection may instead occur in vigorous isolated cells separated by regions of strong

  15. Reflection as an Indicator of Cognitive Presence

    ERIC Educational Resources Information Center

    Redmond, Petrea

    2014-01-01

    In the Community of Inquiry (CoI) model, cognitive presence indicators can be used to evaluate the quality of inquiry in a discussion forum. Engagement in critical thinking and deep knowledge can occur through reflective processes. When learners move through the four phases of cognitive presence (triggering, exploration, integration, resolution),…

  16. 36 CFR 520.2 - Recording presence.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 36 Parks, Forests, and Public Property 3 2011-07-01 2011-07-01 false Recording presence. 520.2 Section 520.2 Parks, Forests, and Public Property SMITHSONIAN INSTITUTION RULES AND REGULATIONS GOVERNING THE BUILDINGS AND GROUNDS OF THE NATIONAL ZOOLOGICAL PARK OF THE SMITHSONIAN INSTITUTION § 520.2 Recording presence. Except as otherwise...

  17. 36 CFR 504.2 - Recording presence.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 36 Parks, Forests, and Public Property 3 2011-07-01 2011-07-01 false Recording presence. 504.2 Section 504.2 Parks, Forests, and Public Property SMITHSONIAN INSTITUTION RULES AND REGULATIONS GOVERNING SMITHSONIAN INSTITUTION BUILDINGS AND GROUNDS § 504.2 Recording presence. Except as otherwise ordered, Smithsonian buildings shall be closed to...

  18. Immersion and Presence Daniel R Mestre

    E-print Network

    Immersion and Presence Daniel R Mestre Movement & Perception, CNRS & University.laps.univ-mrs.fr/~mestre/mestre.htm Abstract: In a Virtual Environment (VE), Immersion, defined in technical terms, is capable of producing of skills or knowledge learned in a VE to the real world. 1- Immersion and Presence Virtual reality

  19. Presence, Analogy, and "Earth in the Balance."

    ERIC Educational Resources Information Center

    Murphy, John M.

    1994-01-01

    Uses vice president Albert Gore Jr.'s book "Earth in the Balance" as a case study to examine the relationship between analogy and "presence." Argues that presence is a flexible critical construct allowing for examination of the relationship between the style, substance, and structure of arguments. Explores relationships between C. Perelman and the…

  20. Community of Inquiry: Social Presence Revisited

    ERIC Educational Resources Information Center

    Kreijns, Karel; Van Acker, Frederick; Vermeulen, Marjan; Van Buuren, Hans

    2014-01-01

    Social presence is a construct that has attracted the attention of many educational scholars involved in online collaborative learning settings wherein all the dialogue is happening through text-based asynchronous and synchronous communication channels. The social presence of the learning group members is associated with the degree of…

  1. Social presence and the composite face effect.

    PubMed

    Garcia-Marques, Teresa; Fernandes, Alexandre; Fonseca, Ricardo; Prada, Marilia

    2015-06-01

    A robust finding in social psychology research is that performance is modulated by the social nature of a given context, promoting social inhibition or facilitation effects. In the present experiment, we examined if and how social presence impacts holistic face perception processes by asking participants, in the presence of others and alone, to perform the composite face task. Results suggest that completing the task in the presence of others (i.e., mere co-action) is associated with better performance in face recognition (less bias and higher discrimination between presented and non-presented targets) and with a reduction in the composite face effect. These results make clear that social presence impact on the composite face effect does not occur because presence increases reliance on holistic processing as a "dominant" well-learned response, but instead, because it increases monitoring of the interference produced by automatic response. PMID:25939138

  2. Layered electrode for electrochemical cells

    DOEpatents

    Swathirajan, Swathy (West Bloomfield, MI); Mikhail, Youssef M. (Sterling Heights, MI)

    2001-01-01

    There is provided an electrode structure comprising a current collector sheet and first and second layers of electrode material. Together, the layers improve catalyst utilization and water management.

  3. The Mars water cycle at other epochs: Recent history of the polar caps and layered terrain

    NASA Technical Reports Server (NTRS)

    Jakosky, Bruce M.; Henderson, Bradley G.; Mellon, Michael T.

    1992-01-01

    The Martian polar caps and layered terrain presumably evolves by the deposition and removal of small amounts of water and dust each year, the current cap attributes therefore represent the incremental transport during a single year as integrated over long periods of time. The role was studied of condensation and sublimation of water ice in this process by examining the seasonal water cycle during the last 10(exp 7) yr. In the model, axial obliquity, eccentricity, and L sub s of perihelion vary according to dynamical models. At each epoch, the seasonal variations in temperature are calculated at the two poles, keeping track of the seasonal CO2 cap and the summertime sublimation of water vapor into the atmosphere; net exchange of water between the two caps is calculated based on the difference in the summertime sublimation between the two caps (or on the sublimation from one cap if the other is covered with CO2 frost all year). Results from the model can help to explain (1) the apparent inconsistency between the timescales inferred for layer formation and the much older crater retention age of the cap and (2) the difference in sizes of the two residual caps, with the south being smaller than the north.

  4. Final report: Bilateral key comparison SIM.T-K6.3 on humidity standards in the dew/frost-point temperature range from -30°C to 20°C

    NASA Astrophysics Data System (ADS)

    Huang, Peter; Meyer, Christopher; Brionizio, Julio D.

    2015-01-01

    A Regional Metrology Organization (RMO) Key Comparison of dew/frost point temperatures was carried out by the National Institute of Standards and Technology (NIST, USA) and the Instituto Nacional de Metrologia, Qualidade e Tecnologia (INMETRO, Brazil) between October 2009 and March 2010. The results of this comparison are reported here, along with descriptions of the humidity laboratory standards for NIST and INMETRO and the uncertainty budget for these standards. This report also describes the protocol for the comparison and presents the data acquired. The results are analyzed, determining degree of equivalence between the dew/frost-point standards of NIST and INMETRO. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  5. A combined analysis of the Frost Multidimensional Perfectionism Scale (FMPS), Child and Adolescent Perfectionism Scale (CAPS), and Almost Perfect Scale-Revised (APS-R): Different perfectionist profiles in adolescent high school students.

    PubMed

    Sironic, Amanda; Reeve, Robert A

    2015-12-01

    To investigate differences and similarities in the dimensional constructs of the Frost Multidimensional Perfectionism Scale (FMPS; Frost, Marten, Lahart, & Rosenblate, 1990), Child and Adolescent Perfectionism Scale (CAPS; Flett, Hewitt, Boucher, Davidson, & Munro, 2000), and Almost Perfect Scale-Revised (APS-R; Slaney, Rice, Mobley, Trippi, & Ashby, 2001), 938 high school students completed the 3 perfectionism questionnaires, as well as the Depression Anxiety Stress Scales (DASS; Lovibond & Lovibond, 1995). Preliminary analyses revealed commonly observed factor structures for each perfectionism questionnaire. Exploratory factor analysis of item responses from the questionnaires (combined) yielded a 4-factor solution (factors were labeled High Personal Standards, Concerns, Doubts and Discrepancy, Externally Motivated Perfectionism, and Organization and Order). A latent class analysis of individuals' mean ratings on each of the 4 factors yielded a 6-class solution. Three of the 6 classes represented perfectionist subgroups (labeled adaptive perfectionist, externally motivated maladaptive perfectionist, and mixed maladaptive perfectionist), and 3 represented nonperfectionist subgroups (labeled nonperfectionist A, nonperfectionist B, and order and organization nonperfectionist). Each of the 6 subgroups was meaningfully associated with the DASS. Findings showed that 3 out of 10 students were classified as maladaptive perfectionists, and maladaptive perfectionists were more prevalent than adaptive perfectionists. In sum, it is evident that combined ratings from the FMPS, CAPS, and APS-R offer a meaningful characterization of perfectionism. (PsycINFO Database Record PMID:25984636

  6. Ice Layer Cross-Section In False Color

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    The theme for the weeks of 1/17 and 1/24 is the north polar region of Mars as seen in false color THEMIS images. Ice/frost will typically appear as bright blue in color; dust mantled ice will appear in tones of red/orange.

    This image of shows a cross sectional view of the ice layers. Note the subtle peach banding on the left side of the image. The time variation that the bands represent is not yet understood.

    Image information: VIS instrument. Latitude 83.5, Longitude 118.2 East (241.8 West). 19 meter/pixel resolution.

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

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

  7. Predicting Tick Presence by Environmental Risk Mapping

    PubMed Central

    Swart, Arno; Ibañez-Justicia, Adolfo; Buijs, Jan; van Wieren, Sip E.; Hofmeester, Tim R.; Sprong, Hein; Takumi, Katsuhisa

    2014-01-01

    Public health statistics recorded an increasing trend in the incidence of tick bites and erythema migrans (EM) in the Netherlands. We investigated whether the disease incidence could be predicted by a spatially explicit categorization model, based on environmental factors and a training set of tick absence–presence data. Presence and absence of Ixodes ricinus were determined by the blanket-dragging method at numerous sites spread over the Netherlands. The probability of tick presence on a 1?km by 1?km square grid was estimated from the field data using a satellite-based methodology. Expert elicitation was conducted to provide a Bayesian prior per landscape type. We applied a linear model to test for a linear relationship between incidence of EM consultations by general practitioners in the Netherlands and the estimated probability of tick presence. Ticks were present at 252 distinct sampling coordinates and absent at 425. Tick presence was estimated for 54% of the total land cover. Our model has predictive power for tick presence in the Netherlands, tick-bite incidence per municipality correlated significantly with the average probability of tick presence per grid. The estimated intercept of the linear model was positive and significant. This indicates that a significant fraction of the tick-bite consultations could be attributed to the I. ricinus population outside the resident municipality. PMID:25505781

  8. Biocorrosion behavior of biodegradable nanocomposite fibers coated layer-by-layer on AM50 magnesium implant.

    PubMed

    Abdal-Hay, Abdalla; Hasan, Anwarul; Yu-Kyoung; Lee, Min-Ho; Hamdy, Abdel Salam; Khalil, Khalil Abdelrazek

    2016-01-01

    This article demonstrates the use of hybrid nanofibers to improve the biodegradation rate and biocompatibility of AM50 magnesium alloy. Biodegradable hybrid membrane fiber layers containing nano-hydroxyapatite (nHA) particles and poly(lactide)(PLA) nanofibers were coated layer-by-layer (LbL) on AM50 coupons using a facile single-step air jet spinning (AJS) approach. The corrosion performance of coated and uncoated coupon samples was investigated by means of electrochemical measurements. The results showed that the AJS 3D membrane fiber layers, particularly the hybrid membrane layers containing a small amount of nHA (3wt.%), induce a higher biocorrosion resistance and effectively decrease the initial degradation rate compared with the neat AM50 coupon samples. The adhesion strength improved highly due to the presence of nHA particles in the AJS layer. Furthermore, the long biodegradation rates of AM50 alloy in Hank's balanced salt solution (HBSS) were significantly controlled by the AJS-coatings. The results showed a higher cytocompatibility for AJS-coatings compared to that for neat Mg alloys. The nanostructured nHA embedded hybrid PLA nanofiber coating can therefore be a suitable coating material for Mg alloy as a potential material for biodegradable metallic orthopedic implants. PMID:26478426

  9. EDITORIAL: Atomic layer deposition Atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Godlewski, Marek

    2012-07-01

    The growth method of atomic layer deposition (ALD) was introduced in Finland by Suntola under the name of atomic layer epitaxy (ALE). The method was originally used for deposition of thin films of sulphides (ZnS, CaS, SrS) activated with manganese or rare-earth ions. Such films were grown for applications in thin-film electroluminescence (TFEL) displays. The ALE mode of growth was also tested in the case of molecular beam epitaxy. Films grown by ALD are commonly polycrystalline or even amorphous. Thus, the name ALE has been replaced by ALD. In the 80s ALD was developed mostly in Finland and neighboring Baltic countries. Deposition of a range of different materials was demonstrated at that time, including II-VI semiconductors (e.g. CdTe, CdS) and III-V (e.g. GaAs, GaN), with possible applications in e.g. photovoltaics. The number of publications on ALD was slowly increasing, approaching about 100 each year. A real boom in interest came with the development of deposition methods of thin films of high-k dielectrics. This research was motivated by a high leakage current in field-effect transistors with SiO2-based gate dielectrics. In 2007 Intel introduced a new generation of integrated circuits (ICs) with thin films of HfO2 used as gate isolating layers. In these and subsequent ICs, films of HfO2 are deposited by the ALD method. This is due to their unique properties. The introduction of ALD to the electronics industry led to a booming interest in the ALD growth method, with the number of publications increasing rapidly to well above 1000 each year. A number of new applications were proposed, as reflected in this special issue of Semiconductor Science and Technology. The included articles cover a wide range of possible applications—in microelectronics, transparent electronics, optoelectronics, photovoltaics and spintronics. Research papers and reviews on the basics of ALD growth are also included, reflecting a growing interest in precursor chemistry and growth processes. Summarizing, this special issue of Semiconductor Science and Technology reflects the rapidly growing interest in the ALD growth method and demonstrates the wide range of possible practical applications of ALD-grown materials, not only of high-k dielectrics, but also of a range of different materials (e.g. ZnO). Finally, I would like to thank the IOP editorial staff, in particular Alice Malhador, for their support and efforts in making this special issue possible.

  10. Layered Topological Crystalline Insulators.

    PubMed

    Kim, Youngkuk; Kane, C L; Mele, E J; Rappe, Andrew M

    2015-08-21

    Topological crystalline insulators (TCIs) are insulating materials whose topological property relies on generic crystalline symmetries. Based on first-principles calculations, we study a three-dimensional (3D) crystal constructed by stacking two-dimensional TCI layers. Depending on the interlayer interaction, the layered crystal can realize diverse 3D topological phases characterized by two mirror Chern numbers (MCNs) (?1,?2) defined on inequivalent mirror-invariant planes in the Brillouin zone. As an example, we demonstrate that new TCI phases can be realized in layered materials such as a PbSe (001) monolayer/h-BN heterostructure and can be tuned by mechanical strain. Our results shed light on the role of the MCNs on inequivalent mirror-symmetric planes in reciprocal space and open new possibilities for finding new topological materials. PMID:26340198

  11. Layered Systems Engineering Engines

    NASA Technical Reports Server (NTRS)

    Breidenthal, Julian C.; Overman, Marvin J.

    2009-01-01

    A notation is described for depicting the relationships between multiple, contemporaneous systems engineering efforts undertaken within a multi-layer system-of-systems hierarchy. We combined the concepts of remoteness of activity from the end customer, depiction of activity on a timeline, and data flow to create a new kind of diagram which we call a "Layered Vee Diagram." This notation is an advance over previous notations because it is able to be simultaneously precise about activity, level of granularity, product exchanges, and timing; these advances provide systems engineering managers a significantly improved ability to express and understand the relationships between many systems engineering efforts. Using the new notation, we obtain a key insight into the relationship between project duration and the strategy selected for chaining the systems engineering effort between layers, as well as insights into the costs, opportunities, and risks associated with alternate chaining strategies.

  12. Layered Topological Crystalline Insulators

    NASA Astrophysics Data System (ADS)

    Kim, Youngkuk; Kane, C. L.; Mele, E. J.; Rappe, Andrew M.

    2015-08-01

    Topological crystalline insulators (TCIs) are insulating materials whose topological property relies on generic crystalline symmetries. Based on first-principles calculations, we study a three-dimensional (3D) crystal constructed by stacking two-dimensional TCI layers. Depending on the interlayer interaction, the layered crystal can realize diverse 3D topological phases characterized by two mirror Chern numbers (MCNs) (?1,?2 ) defined on inequivalent mirror-invariant planes in the Brillouin zone. As an example, we demonstrate that new TCI phases can be realized in layered materials such as a PbSe (001) monolayer/h -BN heterostructure and can be tuned by mechanical strain. Our results shed light on the role of the MCNs on inequivalent mirror-symmetric planes in reciprocal space and open new possibilities for finding new topological materials.

  13. Stratospheric aerosol layer detection.

    NASA Technical Reports Server (NTRS)

    Cunnold, D. M.; Gray, C. R.; Merritt, D. C.

    1973-01-01

    The earth's daytime horizon was scanned on several occasions between 1963 and 1968. The limb was observed at six wavelengths in the ultraviolet and visible spectrum with a narrow field of view instrument on the X-15 aircraft. The inversion of such horizon observations to yield atmospheric density and the concentrations of ozone and aerosol extinctions is discussed. The most significant features of the X-15 data are effects attributed to stratospheric aerosols. Observations of both the 20-km aerosol layer and a layer at approximately 50 km are inferred from the data. Both layers apparently possess considerable variability. It is pointed out that the existence of substantial aerosol concentrations above 30 km is an important limitation of the nadir technique of determining ozone concentrations in which the earth's radiance is observed at ultraviolet wavelengths from a satellite.

  14. Boundary layer simulator improvement

    NASA Technical Reports Server (NTRS)

    Praharaj, Sarat C.; Schmitz, Craig P.; Nouri, Joseph A.

    1989-01-01

    Boundary Layer Integral Matrix Procedure (BLIMPJ) has been identified by the propulsion community as the rigorous boundary layer program in connection with the existing JANNAF reference programs. The improvements made to BLIMPJ and described herein have potential applications in the design of the future Orbit Transfer Vehicle engines. The turbulence model is validated to include the effects of wall roughness and a way is devised to treat multiple smooth-rough surfaces. A prediction of relaminarization regions is examined as is the combined effects of wall cooling and surface roughness on relaminarization. A turbulence model to represent the effects of constant condensed phase loading is given. A procedure is described for thrust decrement calculation in thick boundary layers by coupling the T-D Kinetics Program and BLIMPJ and a way is provided for thrust loss optimization. Potential experimental studies in rocket nozzles are identified along with the required instrumentation to provide accurate measurements in support of the presented new analytical models.

  15. East Candor Layers

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-507, 8 October 2003

    The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) experiment was designed to study the geology and geomorphology of Mars by providing images comparable in resolution to the aerial photographs used by terrestrial geologists in conducting their field work. For over six years, the MOC narrow angle camera has been returning pictures that underscore, time and again, the layered nature of the upper martian crust. It is from layered rock that geologists will one day be able to decipher the history of the red planet. This example of layered rock exposures occurs in eastern Candor Chasma, one of the troughs of the Valles Marineris system. The picture is located near 8.0oS, 67.0oW, and covers an area 3 km (1.9 mi) wide. The image is illuminated by sunlight from the lower left.

  16. Effects of the Spatial Extent of Multiple Harmonic Layers

    SciTech Connect

    Burby, J. W.; Kramer, G. J.; Phillips, C. K.; Valeo, E. J.

    2011-12-23

    An analytic model for single particle motion in the presence of a wave field and multiple cyclotron harmonics is developed and investigated. The model suggests that even in the absence of Doppler broadening, cyclotron harmonic layers have finite spatial extent. This allows for particles to interact with more than one harmonic layer simultaneously, provided the layers are tightly packed. The latter phenomenon is investigated in the context of the model using symplectic mapping techniques. Then the model behavior is compared with numerical simulations of neutral beam particle trajectories in NSTX using the full-orbit code SPIRAL.

  17. Method of depositing multi-layer carbon-based coatings for field emission

    DOEpatents

    Sullivan, John P. (Albuquerque, NM); Friedmann, Thomas A. (Albuquerque, NM)

    1999-01-01

    A novel field emitter device for cold cathode field emission applications, comprising a multi-layer resistive carbon film. The multi-layered film of the present invention is comprised of at least two layers of a resistive carbon material, preferably amorphous-tetrahedrally coordinated carbon, such that the resistivities of adjacent layers differ. For electron emission from the surface, the preferred structure comprises a top layer having a lower resistivity than the bottom layer. For edge emitting structures, the preferred structure of the film comprises a plurality of carbon layers, wherein adjacent layers have different resistivities. Through selection of deposition conditions, including the energy of the depositing carbon species, the presence or absence of certain elements such as H, N, inert gases or boron, carbon layers having desired resistivities can be produced. Field emitters made according the present invention display improved electron emission characteristics in comparison to conventional field emitter materials.

  18. Method of depositing multi-layer carbon-based coatings for field emission

    DOEpatents

    Sullivan, J.P.; Friedmann, T.A.

    1999-08-10

    A novel field emitter device is disclosed for cold cathode field emission applications, comprising a multi-layer resistive carbon film. The multi-layered film of the present invention is comprised of at least two layers of a resistive carbon material, preferably amorphous-tetrahedrally coordinated carbon, such that the resistivities of adjacent layers differ. For electron emission from the surface, the preferred structure comprises a top layer having a lower resistivity than the bottom layer. For edge emitting structures, the preferred structure of the film comprises a plurality of carbon layers, wherein adjacent layers have different resistivities. Through selection of deposition conditions, including the energy of the depositing carbon species, the presence or absence of certain elements such as H, N, inert gases or boron, carbon layers having desired resistivities can be produced. Field emitters made according the present invention display improved electron emission characteristics in comparison to conventional field emitter materials. 8 figs.

  19. Atomic-Layer-Deposited Transparent Electrodes for Silicon Heterojunction Solar Cells

    SciTech Connect

    Demaurex, Benedicte; Seif, Johannes P.; Smit, Sjoerd; Macco, Bart; Kessels, W. M.; Geissbuhler, Jonas; De Wolf, Stefaan; Ballif, Christophe

    2014-11-01

    We examine damage-free transparent-electrode deposition to fabricate high-efficiency amorphous silicon/crystalline silicon heterojunction solar cells. Such solar cells usually feature sputtered transparent electrodes, the deposition of which may damage the layers underneath. Using atomic layer deposition, we insert thin protective films between the amorphous silicon layers and sputtered contacts and investigate their effect on device operation. We find that a 20-nm-thick protective layer suffices to preserve, unchanged, the amorphous silicon layers beneath. Insertion of such protective atomic-layer-deposited layers yields slightly higher internal voltages at low carrier injection levels. However, we identify the presence of a silicon oxide layer, formed during processing, between the amorphous silicon and the atomic-layer-deposited transparent electrode that acts as a barrier, impeding hole and electron collection.

  20. Atomic-Layer-Deposited Transparent Electrodes for Silicon Heterojunction Solar Cells

    DOE PAGESBeta

    Demaurex, Benedicte; Seif, Johannes P.; Smit, Sjoerd; Macco, Bart; Kessels, W. M.; Geissbuhler, Jonas; De Wolf, Stefaan; Ballif, Christophe

    2014-11-01

    We examine damage-free transparent-electrode deposition to fabricate high-efficiency amorphous silicon/crystalline silicon heterojunction solar cells. Such solar cells usually feature sputtered transparent electrodes, the deposition of which may damage the layers underneath. Using atomic layer deposition, we insert thin protective films between the amorphous silicon layers and sputtered contacts and investigate their effect on device operation. We find that a 20-nm-thick protective layer suffices to preserve, unchanged, the amorphous silicon layers beneath. Insertion of such protective atomic-layer-deposited layers yields slightly higher internal voltages at low carrier injection levels. However, we identify the presence of a silicon oxide layer, formed during processing,more »between the amorphous silicon and the atomic-layer-deposited transparent electrode that acts as a barrier, impeding hole and electron collection.« less

  1. Titan's thick haze layer

    NASA Technical Reports Server (NTRS)

    1980-01-01

    Titan's thick haze layer is shown in this enhanced Voyager 1 image taken Nov. 12, 1980 at a distance of 435,000 kilometers (270,000 miles). Voyager images of Saturn's largest moon show Titan completely enveloped by haze that merges with a darker 'hood' or cloud layer over the north pole. Such a mantle is not present at the south pole. At Voyager's closest approach to Titan on Nov. 11, 1980, spacecraft instruments found that the moon has a substantial atmosphere, far denser than that of Mars and possibly denser than Earth's. The Voyager Project is managed for NASA by the Jet Propulsion Laboratory, Pasadena, Calif.

  2. Sedimentary Rock Layers

    NASA Technical Reports Server (NTRS)

    2004-01-01

    27 January 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows layers of sedimentary rock in a crater in western Arabia Terra. Layered rock records the history of a place, but an orbiter image alone cannot tell the entire story. These materials record some past episodes of deposition of fine-grained material in an impact crater that is much larger than the image shown here. The picture is located near 3.4oN, 358.7oW, and covers an area 3 km (1.9 mi.) wide. Sunlight illuminates the scene from the lower left.

  3. Layers Inside 'Endurance'

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This view of rock layers exposed in the upper portion of the inner slope of 'Endurance Crater' was captured by the navigation camera on NASA's Mars Exploration Rover Opportunity from the rover's position inside the crater during Opportunity's 134th sol on June 9, 2004. Scientists and engineers are assessing possible targets and routes among these rocks. The view is looking down into the crater, so the layers at the top of the image lie lower in the crater than the rocks in the foreground.

  4. Layered semiconductor neutron detectors

    DOEpatents

    Mao, Samuel S; Perry, Dale L

    2013-12-10

    Room temperature operating solid state hand held neutron detectors integrate one or more relatively thin layers of a high neutron interaction cross-section element or materials with semiconductor detectors. The high neutron interaction cross-section element (e.g., Gd, B or Li) or materials comprising at least one high neutron interaction cross-section element can be in the form of unstructured layers or micro- or nano-structured arrays. Such architecture provides high efficiency neutron detector devices by capturing substantially more carriers produced from high energy .alpha.-particles or .gamma.-photons generated by neutron interaction.

  5. Fig. 1 (a) inductive layer

    E-print Network

    Shinoda, Hiroyuki

    1 2 1) Fig. 1 (a) 2) inductive layer Fig. 1 (b) 2.4 GHz Fig. 2 Fig. 3 Fig. 4 1 m × 60 cm 400 mW Fig. 5 3 1) 2) 3.1 10 Daily 30 (a) Dielectric layer Conductive layer Inductive layer Sensor (b) Fig. 1: Cross-section of a 2DST

  6. 31 CFR 91.3 - Recording presence.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...TREASURY REGULATIONS GOVERNING CONDUCT IN OR ON THE BUREAU OF THE MINT BUILDINGS AND GROUNDS § 91.3 Recording presence...opinion of the senior supervising official of any Bureau of the Mint establishment covered by these regulations, or his...

  7. 31 CFR 91.3 - Recording presence.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...TREASURY REGULATIONS GOVERNING CONDUCT IN OR ON THE BUREAU OF THE MINT BUILDINGS AND GROUNDS § 91.3 Recording presence...opinion of the senior supervising official of any Bureau of the Mint establishment covered by these regulations, or his...

  8. 31 CFR 91.3 - Recording presence.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...Finance REGULATIONS GOVERNING CONDUCT IN OR ON THE BUREAU OF THE MINT BUILDINGS AND GROUNDS § 91.3 Recording presence...opinion of the senior supervising official of any Bureau of the Mint establishment covered by these regulations, or his...

  9. 31 CFR 91.3 - Recording presence.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...TREASURY REGULATIONS GOVERNING CONDUCT IN OR ON THE BUREAU OF THE MINT BUILDINGS AND GROUNDS § 91.3 Recording presence...opinion of the senior supervising official of any Bureau of the Mint establishment covered by these regulations, or his...

  10. 31 CFR 91.3 - Recording presence.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...TREASURY REGULATIONS GOVERNING CONDUCT IN OR ON THE BUREAU OF THE MINT BUILDINGS AND GROUNDS § 91.3 Recording presence...opinion of the senior supervising official of any Bureau of the Mint establishment covered by these regulations, or his...

  11. Presence within a mixed reality environment.

    PubMed

    van Schaik, Paul; Turnbull, Triece; van Wersch, Anna; Drummond, Sarah

    2004-10-01

    Mixed reality environments represent a new approach to creating technology-mediated experiences. However, there is a lack of empirical research investigating users' actual experience. The aim of the current exploratory, non-experimental study was to establish levels of and identify factors associated with presence, within the framework of Schubert et al.'s model of presence. Using questionnaire and interview methods, the experience of the final performance of the Desert Rain mixed reality environment was investigated. Levels of general and spatial presence were relatively high, but levels of involvement and realness were not. Overall, intrinsic motivation, confidence and intention to re-visit Desert Rain were high. However, age was negatively associated with both spatial presence and confidence to play. Furthermore, various problems in navigating the environment were identified. Results are discussed in terms of Schubert's model and other theoretical perspectives. Implications for system design are presented. PMID:15667049

  12. 31 CFR 407.3 - Recording presence.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...presence. 407.3 Section 407.3 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) SECRET SERVICE, DEPARTMENT OF THE TREASURY REGULATIONS GOVERNING CONDUCT IN THE TREASURY BUILDING AND THE TREASURY ANNEX §...

  13. 31 CFR 407.3 - Recording presence.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...presence. 407.3 Section 407.3 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) SECRET SERVICE, DEPARTMENT OF THE TREASURY REGULATIONS GOVERNING CONDUCT IN THE TREASURY BUILDING AND THE TREASURY ANNEX §...

  14. 31 CFR 407.3 - Recording presence.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...presence. 407.3 Section 407.3 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) SECRET SERVICE, DEPARTMENT OF THE TREASURY REGULATIONS GOVERNING CONDUCT IN THE TREASURY BUILDING AND THE TREASURY ANNEX §...

  15. 31 CFR 407.3 - Recording presence.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...presence. 407.3 Section 407.3 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) SECRET SERVICE, DEPARTMENT OF THE TREASURY REGULATIONS GOVERNING CONDUCT IN THE TREASURY BUILDING AND THE TREASURY ANNEX §...

  16. 31 CFR 407.3 - Recording presence.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...presence. 407.3 Section 407.3 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) SECRET SERVICE, DEPARTMENT OF THE TREASURY REGULATIONS GOVERNING CONDUCT IN THE TREASURY BUILDING AND THE TREASURY ANNEX §...

  17. Effect of spontaneous condensation on condensation heat transfer in the presence of non-condensable gases

    SciTech Connect

    Karl, J.; Hein, D.

    1999-07-01

    The presence of non condensable gases like nitrogen or air reduces the condensation heat transfer during condensation of binary steam mixtures. The non condensable gas accumulates in the vapor phase boundary layer and causes a high heat transfer resistance. Especially with high pressures and low water temperatures spontaneous condensation reduces heat transfer additionally. Fog forms within the steam-nitrogen boundary layer and the steam condenses on the water droplets of the fog layer. The convective mass transfer to the cooling water interface diminishes. Raman spectroscopy and film theory are used to quantify this effect locally. The calculation of overall condensation rates in large steam nitrogen systems requires to use three dimensional CFD codes. The paper presents equations to predict fog formation in the boundary layer which can be implemented in CFD codes.

  18. Teaching the Double Layer.

    ERIC Educational Resources Information Center

    Bockris, J. O'M.

    1983-01-01

    Suggests various methods for teaching the double layer in electrochemistry courses. Topics addressed include measuring change in absolute potential difference (PD) at interphase, conventional electrode potential scale, analyzing absolute PD, metal-metal and overlap electron PDs, accumulation of material at interphase, thermodynamics of electrified…

  19. Layer-Cake Earth

    ERIC Educational Resources Information Center

    Tedford, Rebecca; Warny, Sophie

    2006-01-01

    In this article, the authors offer a safe, fun, effective way to introduce geology concepts to elementary school children of all ages: "coring" layer cakes. This activity introduces the concepts and challenges that geologists face and at the same time strengthens students' inferential, observational, and problem-solving skills. It also addresses…

  20. Exposed Tsunami Sand Layers

    USGS Multimedia Gallery

    An outcrop composed of six tsunami deposits on the inland side of the lowland backing Stardust Bay over 0.5 miles from the sea. Brown soils developed into the top of each sand sheet and black tephra (air fall volcanic ash) layers between two of the sand deposits aided correlation of the six sand she...

  1. ACOUSTIC COMPACTION LAYER DETECTION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The depth and strength of compacted layers in fields have been determined traditionally using the ASAE standardized cone penetrometer method. However, an on-the-go method would be much faster and much less labor intensive. The soil measurement system described here attempts to locate the compacted...

  2. Thick diffusion limit boundary layer test problems

    SciTech Connect

    Bailey, T. S.; Warsa, J. S.; Chang, J. H.; Adams, M. L.

    2013-07-01

    We develop two simple test problems that quantify the behavior of computational transport solutions in the presence of boundary layers that are not resolved by the spatial grid. In particular we study the quantitative effects of 'contamination' terms that, according to previous asymptotic analyses, may have a detrimental effect on the solutions obtained by both discontinuous finite element (DFEM) and characteristic-method (CM) spatial discretizations, at least for boundary layers caused by azimuthally asymmetric incident intensities. Few numerical results have illustrated the effects of this contamination, and none have quantified it to our knowledge. Our test problems use leading-order analytic solutions that should be equal to zero in the problem interior, which means the observed interior solution is the error introduced by the contamination terms. Results from DFEM solutions demonstrate that the contamination terms can cause error propagation into the problem interior for both orthogonal and non-orthogonal grids, and that this error is much worse for non-orthogonal grids. This behavior is consistent with the predictions of previous analyses. We conclude that these boundary layer test problems and their variants are useful tools for the study of errors that are introduced by unresolved boundary layers in diffusive transport problems. (authors)

  3. Boundary layer transition studies

    NASA Technical Reports Server (NTRS)

    Watmuff, Jonathan H.

    1995-01-01

    A small-scale wind tunnel previously used for turbulent boundary layer experiments was modified for two sets of boundary layer transition studies. The first study concerns a laminar separation/turbulent reattachment. The pressure gradient and unit Reynolds number are the same as the fully turbulent flow of Spalart and Watmuff. Without the trip wire, a laminar layer asymptotes to a Falkner & Skan similarity solution in the FPG. Application of the APG causes the layer to separate and a highly turbulent and approximately 2D mean flow reattachment occurs downstream. In an effort to gain some physical insight into the flow processes a small impulsive disturbance was introduced at the C(sub p) minimum. The facility is totally automated and phase-averaged data are measured on a point-by-point basis using unprecedently large grids. The evolution of the disturbance has been tracked all the way into the reattachment region and beyond into the fully turbulent boundary layer. At first, the amplitude decays exponentially with streamwise distance in the APG region, where the layer remains attached, i.e. the layer is viscously stable. After separation, the rate of decay slows, and a point of minimum amplitude is reached where the contours of the wave packet exhibit dispersive characteristics. From this point, exponential growth of the amplitude of the disturbance is observed in the detached shear layer, i.e. the dominant instability mechanism is inviscid. A group of large-scale 3D vortex loops emerges in the vicinity of the reattachment. Remarkably, the second loop retains its identify far downstream in the turbulent boundary layer. The results provide a level of detail usually associated with CFD. Substantial modifications were made to the facility for the second study concerning disturbances generated by Suction Holes for laminar flow Control (LFC). The test section incorporates suction through interchangeable porous test surfaces. Detailed studies have been made using isolated holes in the impervious test plate that used to establish the Blasius base flow. The suction is perturbed harmonically and data are averaged on the basis of the phase of the disturbance, for conditions corresponding to strong suction and without suction. The technique was enhanced by using up to nine multiple probes to reduce the experimental run-time. In both cases, 3D contour surfaces in the vicinity of the hole show highly 3D TS waves which fan out in the spanwise direction forming bow-shaped waves downstream. The case without suction has proved useful for evaluating calculation methods. With suction, the perturbations on the centerline are much stronger and decay less rapidly, while the TS waves in the far field are similar to the case without suction. Downstream, the contour surfaces of the TS waves develop spanwise irregularities which eventually form into clumps. The spanwise clumping is evidence of a secondary instability that could be associated with suction vortices. Designers of porous surfaces use Goldsmith's Criterion to minimize cross-stream interactions. It is shown that partial TS wave cancellation is possible, depending on the hole spacing, disturbance frequency and free-stream velocity. New high-performance Constant Temperature Hot-Wire Anemometers were designed and built, based on a linear system theory analysis that can be extended to arbitrary order. The motivation was to achieve the highest possible frequency reponse while ensuring overall system stability. The performance is equal to or superior to commercially available instruments at about 10% of the cost. Details, such as fabrication drawings and a parts list, have been published to enable the instrument to be construced by others.

  4. Secondary three-dimensional instability in compressible boundary layers

    NASA Technical Reports Server (NTRS)

    El-Hady, Nabil M.

    1989-01-01

    Three dimensional linear secondary instability theory is extended for compressible boundary layers on a flat plate in the presence of finite amplitude Tollmien-Schlichting waves. The focus is on principal parametric resonance responsible for strong growth of subharmonics in low disturbance environment.

  5. Opacification of lenses cultured in the presence of Pb

    PubMed Central

    Lin, C.; Isom, R.; Vaishnav, K.; Zigler, J.S.

    2010-01-01

    Purpose Occupational and environmental Pb-exposure is associated with protein aggregation diseases which typically present in elderly populations (Parkinsons and cataract). Post-translational processing of crystallins, the major structural proteins of the lens, is altered with short-term Pb-exposure in Fisher 344 rats. In addition, lenses from aged rats become opaque upon long-term exposure to Pb in organ culture. To explore the route to lens opacification in the presence of Pb, cultured lenses from young rats which exhibit higher metabolic activity in lens culture and are more susceptible to experimental cataract in vivo and in vitro were exposed to Pb and evaluated for morphological and biochemical alterations. Methods Following culture in Pb (as lead nitrate) for four days (in the presence/absence of oxidative challenge), lenses were examined for clarity, integrity of epithelial layer, and molecular stability including crystallin post-translational modification and choline transport. Clarity of lenses cultured with/without Pb for up to 8 days was assessed to determine if Pb exposure would accelerate opacification. Results Lenses cultured in Pb for four days exhibited epithelial abnormalities including epithelial cell multilayering and nuclei abnormalities with extension of the nucleated epithelial cells past the bow region. Alterations in crystallin post-translational modifications and decreased membrane transport of choline were noted without corresponding lens opacification or altered ?-crystallin chaperone activity. Lenses treated with Pb according to the same exposure protocol with subsequent challenge by hydrogen peroxide became opaque while the contralateral control lenses did not. Lenses which were cultured in the presence of Pb for longer periods with no subsequent oxidative insult exhibited lens failure at earlier time points than did the controls. Conclusions These data indicate that Pb-exposure can accelerate the degradation of the cultured lens through induction of epithelial cell abnormalities, induce structural protein modifications before opacity, and predispose the lens to opacification with subsequent oxidant challenge. PMID:21139692

  6. Engineering electroresponsive layer-by-layer thin films

    E-print Network

    Schmidt, Daniel J., Ph. D. Massachusetts Institute of Technology

    2011-01-01

    Electroresponsive layer-by-layer (LbL) polymer films and polymer nanocomposite films were investigated as model systems for electrically triggered drug delivery applications and "mechanomutable" surface coating applications. ...

  7. Layer-by-layer assembly in confined geometries

    E-print Network

    DeRocher, Jonathan P

    2011-01-01

    The fundamental nature of layer-by-layer (LbL) assembly in confined geometries was investigated for a number of different chemical systems. The first part of this thesis concerns the modification of microfluidic and ...

  8. Ion transport and structure of layer-by-layer assemblies

    E-print Network

    Lutkenhaus, Jodie Lee

    2007-01-01

    Layer-by-layer (LbL) films of various architectures were examined as potential solid state electrolytes for electrochemical systems (e.g. batteries and fuel cells). The relationship between materials properties and ion ...

  9. Crack layer theory

    NASA Technical Reports Server (NTRS)

    Chudnovsky, A.

    1984-01-01

    A damage parameter is introduced in addition to conventional parameters of continuum mechanics and consider a crack surrounded by an array of microdefects within the continuum mechanics framework. A system consisting of the main crack and surrounding damage is called crack layer (CL). Crack layer propagation is an irreversible process. The general framework of the thermodynamics of irreversible processes are employed to identify the driving forces (causes) and to derive the constitutive equation of CL propagation, that is, the relationship between the rates of the crack growth and damage dissemination from one side and the conjugated thermodynamic forces from another. The proposed law of CL propagation is in good agreement with the experimental data on fatigue CL propagation in various materials. The theory also elaborates material toughness characterization.

  10. Layered seal for turbomachinery

    DOEpatents

    Sarawate, Neelesh Nandkumar; Morgan, Victor John; Weber, David Wayne

    2015-11-20

    The present application provides seal assemblies for reducing leakages between adjacent components of turbomachinery. The seal assemblies may include outer shims, and at least a portion of the outer shims may be substantially impervious. At least one of the outer shims may be configured for sealing engagement with seal slots of the adjacent components. The seal assemblies may also include at least one of an inner shim and a filler layer positioned between the outer shims. The at least one inner shim may be substantially solid and the at least one filler layer may be relatively porous. The seal assemblies may be sufficiently flexible to account for misalignment between the adjacent components, sufficiently stiff to meet assembly requirements, and sufficiently robust to operating meet requirements associated with turbomachinery.

  11. Dipping Rock Layers

    NASA Technical Reports Server (NTRS)

    2004-01-01

    23 May 2004 The central peak of Oudemans Crater, located at the edge of the Labyrinthus Noctis trough system, consists of steeply-dipping rock layers that were uplifted and tilted by the meteor impact that formed the crater. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an example. The banded features are layers of light-toned, possibly sedimentary, rock that were brought to the surface and uplifted by the impact process that formed the crater and its central peak. Oudemans Crater's central peak serves as a means for probing the nature of rock that lies beneath the plains cut by the Labyrinthus Noctis troughs, which are part of the vast Valles Marineris system. This March 2004 picture is located near 10.2oS, 92.0oW. The image covers an area about 3 km (1.9 mi) across and is illuminated by sunlight from the upper left.

  12. Layered Rock Ahead

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Now that solar conjunction is over so that communication between Earth and Mars is no longer blocked by the Sun, NASA's Mars Exploration Rover Spirit is continuing its trek through the 'Columbia Hills' in Gusev Crater. Straight ahead, in the foreground of this image, is a horizontally layered rock dubbed 'Tetl,' which scientists hope to investigate. Layering can be either volcanic or sedimentary in origin; researchers aim to determine which of these processes created this rock. If for some reason this particular rock is not favorably positioned for grinding and examination by the toolbox of instruments on the rover's robotic arm, Spirit will be within short reach of another similar rock, dubbed 'Coba,' just to the right, toward the middle of this image. Spirit took this image with its navigation camera on its 263rd martian day, or sol (Sept. 28, 2004).

  13. Sedimentary Rock Layers

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-348, 2 May 2003

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image acquired in March 2003 shows dozens of repeated layers of sedimentary rock in a western Arabia Terra crater at 8oN, 7oW. Wind has sculpted the layered forms into hills somewhat elongated toward the lower left (southwest). The dark patches at the bottom (south) end of the image are drifts of windblown sand. These sedimentary rocks might indicate that the crater was once the site of a lake--or they may result from deposition by wind in a completely dry, desert environment. Either way, these rocks have something important to say about the geologic history of Mars. The area shown is about 3 km (1.9 mi) wide. Sunlight illuminates the scene from the left.

  14. Layered Rocks in Crater

    NASA Technical Reports Server (NTRS)

    2004-01-01

    19 June 2004 Exposures of layered, sedimentary rock are common on Mars. From the rock outcrops examined by the Mars Exploration Rover, Opportunity, in Meridiani Planum to the sequence in Gale Crater's central mound that is twice the thickness of of the sedimentary rocks exposed by Arizona's Grand Canyon, Mars presents a world of sediment to study. This unusual example, imaged by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC), shows eroded layer outcrops in a crater in Terra Tyrrhena near 15.4oS, 270.5oW. Sedimentary rocks provide a record of past climates and events. Perhaps someday the story told by the rocks in this image will be known via careful field work. The image covers an area about 3 km (1.9 mi) wide and is illuminated by sunlight from the left.

  15. Avalanche mobility induced by the presence of an erodible bed and associated entrainment.

    SciTech Connect

    Mangeney, A.; Tsimring, L. S.; Volfson, D.; Aranson, I. S.; Bouchut, F.; Materials Science Division; Univ. of California at San Diego; Univ. Paris; Ecole Normale Superieure

    2007-11-20

    The partial fluidization model developed by Aranson and Tsimring (2002) is used to simulate the spreading of a 2D circular cap of granular material over an erodible bed made of the same material. Numerical results show that the presence of even a very thin layer of granular material lying on the solid bed strongly increases the mobility of granular flows. Furthermore, as the thickness of the granular layer increases, the dynamics of the flowing mass changes from a decelerating avalanche to a traveling wave. Numerical simulation suggest that surges are generated if enough mass is entrained, increasing the energy of the flowing material and balancing the energy lost by friction.

  16. Predictive processing, perceptual presence, and sensorimotor theory.

    PubMed

    O'Regan, J Kevin; Degenaar, Jan

    2014-01-01

    Mastery of sensorimotor contingencies can be viewed as attunement to potentialities. In our view, these potentialities have wider application than recognized in Seth's account of sensory presence, and should pertain to all of sensory experience. Instead of appealing only to a notion of counterfactual richness, we propose that the degree of sensory presence can be further specified in terms of bodiliness, insubordinateness, and grabbiness. While PPSMC can provide a possible implementation of a sensorimotor account of synesthesia, we suggest it should be rid of its representationalist interpretation. PMID:24742075

  17. Layers in Sulci Gordii

    NASA Technical Reports Server (NTRS)

    2005-01-01

    9 January 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows detailed layered rock features, mantled by fine dust, in the Sulci Gordii ridged region east of Olympus Mons. The scene is located near 21.9oN, 124.3oW. The picture covers an area about 3 km (1.9 mi) across, and is illuminated by sunlight from the left.

  18. Origins of Igneous Layering

    NASA Astrophysics Data System (ADS)

    Marsh, Bruce

    Anyone who has ever seen a photo of a layered intrusion, let alone visited one first hand, or even seen a thin section from one, cannot help but be impressed by the stunning record of crystal growth and deposition. Such bodies stand as majestic monuments of undeniable evidence that intricate magmatic processes exist, processes that couple crystallization, convection, and crystal sorting to form rocks so highly ordered and beautiful that they are a wonder to behold. These are the altars to which petrologists must carry their conceived petrologic processes for approval.Although significant in number, the best layered intrusions seem to be found almost always in remote places. Their names, Bushveld, Muskox, Kiglapait, Stillwater, Duke Island, Skaergaard, Rhum, ring through igneous petrology almost as historic military battles (Saratoga, Antietam, Bull Run, Manassas, Gettysburg) do through American history. People who have worked on such bodies are almost folk heros: Wager, Deer, Brown, Jackson, Hess, Irvine, McBirney, Morse; these names are petrologic household words. Yet with all this fanfare and reverence, layered instrusions are nearly thought of as period pieces, extreme examples of what can happen, but not generally what does. This is now all changing with the increasing realization that these bodies are perhaps highly representative of all magmatic bodies. They are simply more dynamically complete, containing more of the full range of interactions, and of course, exposing a more complete record. They are one end of a spectrum containing lava flows, lava lakes, large sills, plutons, and layered intrusions. This book uniquely covers this range with an abundance of first-hand field observations and a good dose of process conceptualization, magma physics, and crystal growth kinetics.

  19. Field recovery of layered tektites in northeast Thailand

    SciTech Connect

    Wasson, J.T.; Pitakpaivan, K.; Putthapiban, P.

    1995-07-25

    The authors recovered Australasian tektites in place throughout a 40 X 130 km region in northeast Thailand extending from the Laotian border westward to a line connecting Na Pho Klang in the northeast through Det Udom to Nam Yun in the south. With two exceptions, in sites near the western edge of this region, all fragments are layered (muong-Nong-type) tektites. It appears that large layered tektites are mainly found by rice farmers in fields that were forested until the recent past. The presence of layered tektites in this 40 X 130 km area implies that impact melt that fell in these areas was hot enough to flow if it was deposited on a sloping surface. The absence of splash-form tektites from the region indicates that the layer was still molten when masses having shapes (teardrops, dumbbells, etc.) produced by spinning reached the ground. To account for this and to allow time for the melt to flow a few tens of centimeters requires that the atmosphere remained hot (>2300 K) for a few minutes. Tektites that are in place are almost always associated with a widespread 10-cm to meter-thick layer of laterite. In two cases (one involving layered, one involving splash-form tektites), where accurate stratigraphic control demonstrated that the tektites were still in section, they were sited on top of the laterite layer just below a layer of aeolian sand. 27 refs., 1 fig., 1 tab.

  20. Field recovery of layered tektites in northeast Thailand

    NASA Astrophysics Data System (ADS)

    Wasson, John T.; Pitakpaivan, Kaset; Putthapiban, Prinya; Salyapongse, Sirot; Thapthimthong, Boonlom; McHone, John F.

    1995-07-01

    We recovered Australasian tektites in place throughout a 40×130 km region in northeast Thailand extending from the Laotian border westward to a line connecting Na Pho Klang in the northeast through Det Udom to Nam Yun in the south. With two exceptions, in sites near the western edge of this region, all fragments are layered (muong-Nong-type) tektites. It appears that large layered tektites are mainly found by rice farmers in fields that were forested until the recent past. The presence of layered tektites in this 40×130 km area implies that impact melt that fell in these areas was not enough to flow if it was deposited on a sloping surface. The absence of splash-form tektites from the region indicates that the layer was still molten when masses having shapes (teardrops, dumbbells, etc.) produced by spinning reached the ground. To account for this and to allow time for the melt to flow a few tens of centimeters requires that the atmosphere remained hot (>2300 K) for a few minutes. Tektites that are in place are almost always associated with a wide-spread 10-cm to meter-thick layer of laterite. In two cases (one involving layered, one involving splash-form tektites), where accurate stratigraphic control demonstrated that the tektites were still in section, they were sited on top of the laterite layer just below a layer of aeolian sand.

  1. Lifting potential of solar-heated aerosol layers

    NASA Astrophysics Data System (ADS)

    Boers, R.; de Laat, A. T.; Stein Zweers, D. C.; Dirksen, R. J.

    2010-12-01

    Absorption of shortwave solar radiation can potentially heat aerosol layers and create buoyancy that can result in the ascent of the aerosol layer over several kilometres altitude within 24-48 hours. Such heating is seasonally dependent with the summer pole region producing the largest lifting in solstice because aerosol layers are exposed to sunshine for close to 24 hours a day. The smaller the Angstrøm parameter, the larger the lifting potential. An important enhancement to lifting is the diffuse illumination of the base of the aerosol layer when it is located above highly reflective cloud layers. It is estimated that aerosol layers residing in the boundary layer with optical properties typical for biomass burning aerosols can reach the extra tropical tropopause within 3-4 day entirely due to diabatic heating as a result of solar shortwave absorption and cross-latitudinal transport. It is hypothesized that this mechanism can explain the presence and persistence of upper tropospheric/lower stratospheric aerosol layers.

  2. Image Annotation with Presence-vector Classifiers

    E-print Network

    Le Saux, Bertrand

    for scene description and the design of a classification scheme to separate data in the image- descriptor, such as for instance "politics" or "sport" (see Figure 1). The tools for automated image classification that we haveImage Annotation with Presence-vector Classifiers by Bertrand Le Saux and Giuseppe Amato

  3. 36 CFR 504.2 - Recording presence.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Section 504.2 Parks, Forests, and Public Property SMITHSONIAN INSTITUTION RULES AND REGULATIONS GOVERNING SMITHSONIAN INSTITUTION BUILDINGS AND GROUNDS § 504.2 Recording presence. Except as otherwise ordered, Smithsonian buildings shall be closed to the public after normal visiting hours. Such buildings, or...

  4. 36 CFR 504.2 - Recording presence.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Section 504.2 Parks, Forests, and Public Property SMITHSONIAN INSTITUTION RULES AND REGULATIONS GOVERNING SMITHSONIAN INSTITUTION BUILDINGS AND GROUNDS § 504.2 Recording presence. Except as otherwise ordered, Smithsonian buildings shall be closed to the public after normal visiting hours. Such buildings, or...

  5. 36 CFR 504.2 - Recording presence.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Section 504.2 Parks, Forests, and Public Property SMITHSONIAN INSTITUTION RULES AND REGULATIONS GOVERNING SMITHSONIAN INSTITUTION BUILDINGS AND GROUNDS § 504.2 Recording presence. Except as otherwise ordered, Smithsonian buildings shall be closed to the public after normal visiting hours. Such buildings, or...

  6. 36 CFR 520.2 - Recording presence.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 36 Parks, Forests, and Public Property 3 2012-07-01 2012-07-01 false Recording presence. 520.2 Section 520.2 Parks, Forests, and Public Property SMITHSONIAN INSTITUTION RULES AND REGULATIONS GOVERNING THE BUILDINGS AND GROUNDS OF THE NATIONAL ZOOLOGICAL PARK OF THE SMITHSONIAN INSTITUTION §...

  7. 36 CFR 504.2 - Recording presence.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Section 504.2 Parks, Forests, and Public Property SMITHSONIAN INSTITUTION RULES AND REGULATIONS GOVERNING SMITHSONIAN INSTITUTION BUILDINGS AND GROUNDS § 504.2 Recording presence. Except as otherwise ordered, Smithsonian buildings shall be closed to the public after normal visiting hours. Such buildings, or...

  8. 36 CFR 520.2 - Recording presence.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 36 Parks, Forests, and Public Property 3 2010-07-01 2010-07-01 false Recording presence. 520.2 Section 520.2 Parks, Forests, and Public Property SMITHSONIAN INSTITUTION RULES AND REGULATIONS GOVERNING THE BUILDINGS AND GROUNDS OF THE NATIONAL ZOOLOGICAL PARK OF THE SMITHSONIAN INSTITUTION §...

  9. 36 CFR 520.2 - Recording presence.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 36 Parks, Forests, and Public Property 3 2013-07-01 2012-07-01 true Recording presence. 520.2 Section 520.2 Parks, Forests, and Public Property SMITHSONIAN INSTITUTION RULES AND REGULATIONS GOVERNING THE BUILDINGS AND GROUNDS OF THE NATIONAL ZOOLOGICAL PARK OF THE SMITHSONIAN INSTITUTION §...

  10. 36 CFR 520.2 - Recording presence.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 36 Parks, Forests, and Public Property 3 2014-07-01 2014-07-01 false Recording presence. 520.2 Section 520.2 Parks, Forests, and Public Property SMITHSONIAN INSTITUTION RULES AND REGULATIONS GOVERNING THE BUILDINGS AND GROUNDS OF THE NATIONAL ZOOLOGICAL PARK OF THE SMITHSONIAN INSTITUTION §...

  11. Particularity, Presence, Art Teaching, and Learning

    ERIC Educational Resources Information Center

    Kellman, Julia

    2007-01-01

    This manuscript explores the interplay of the concepts of "thisness" and singularity with art making. It explores the particularity of the individual--person, object, animal, plant, place, event; the clarity and joyousness of "thisness" or specificity; the exquisite presence of now; and the relationship of these qualities to contemplation and art…

  12. Mercury Speciation in the Presence of Polysulfides

    E-print Network

    Morel, François M. M.

    Mercury Speciation in the Presence of Polysulfides J E N N Y A Y L A J A Y , * , F R A N C¸ O I Environmental mercury methylation appears modulated by sulfide concentrations, possibly via changes in mercury, there has been much recent interest in quantifying the chemical speciation and lipid solubility of mercury

  13. Stay the Course: Managing Online Presence

    ERIC Educational Resources Information Center

    Fredrick, Kathy

    2009-01-01

    How can a school librarian share instruction and information with students and colleagues in the virtual world? Library Web pages make resources available 24/7. New tools available to schools can also give new options in making a Web presence known. This article suggests a plan for school librarians on how they can manage their libraries' online…

  14. Magnetohydrodynamic three-dimensional flow of viscoelastic nanofluid in the presence of nonlinear thermal radiation

    NASA Astrophysics Data System (ADS)

    Hayat, T.; Muhammad, Taseer; Alsaedi, A.; Alhuthali, M. S.

    2015-07-01

    Magnetohydrodynamic (MHD) three-dimensional flow of couple stress nanofluid in the presence of thermophoresis and Brownian motion effects is analyzed. Energy equation subject to nonlinear thermal radiation is taken into account. The flow is generated by a bidirectional stretching surface. Fluid is electrically conducting in the presence of a constant applied magnetic field. The induced magnetic field is neglected for a small magnetic Reynolds number. Mathematical formulation is performed using boundary layer analysis. Newly proposed boundary condition requiring zero nanoparticle mass flux is employed. The governing nonlinear mathematical problems are first converted into dimensionless expressions and then solved for the series solutions of velocities, temperature and nanoparticles concentration. Convergence of the constructed solutions is verified. Effects of emerging parameters on the temperature and nanoparticles concentration are plotted and discussed. Skin friction coefficients and Nusselt number are also computed and analyzed. It is found that the thermal boundary layer thickness is an increasing function of radiative effect.

  15. The Influence of Social Presence and Teaching Presence on the Quality of Online Critical Inquiry

    ERIC Educational Resources Information Center

    Bangert, Arthur

    2008-01-01

    This study explored the use of Garrison, Anderson, and Archer's (2000) version of Dewey's (1933) practical inquiry model for assessing the influence of social presence and teaching presence on the quality of critical inquiry experienced by online learners. Students (N = 33) enrolled in an online version of a graduate-level, educational statistics…

  16. Protecting the ozone layer.

    PubMed

    Munasinghe, M; King, K

    1992-06-01

    Stratospheric ozone layer depletion has been recognized as a problem by the Vienna Convention for the Protection of the Ozone Layer and the 1987 Montreal Protocol (MP). The ozone layer shields the earth from harmful ultraviolet radiation (UV-B), which is more pronounced at the poles and around the equator. Industrialized countries have contributed significantly to the problem by releasing chlorofluorocarbons (CFCs) and halons into the atmosphere. The effect of these chemicals, which were known for their inertness, nonflammability, and nontoxicity, was discovered in 1874. Action to deal with the effects of CFCs and halons was initiated in 1985 in a 49-nation UN meeting. 21 nations signed a protocol limiting ozone depleting substances (ODS): CFCs and halons. Schedules were set based on each country's use in 1986; the target phaseout was set for the year 2000. The MP restricts trade in ODSs and weights the impact of substances to reflect the extent of damage; i.e., halons are 10 times more damaging than CFCs. ODS requirements for developing countries were eased to accommodate scarce resources and the small fraction of ODS emissions. An Interim Multilateral Fund under the Montreal Protocol (IMFMP) was established to provide loans to finance the costs to developing countries in meeting global environmental requirements. The IMFMP is administered by the World Bank, the UN Environmental Program, and the UN Development Program. Financing is available to eligible countries who use .3 kg of ODS/person/year. Rapid phaseout in developed countries has occurred due to strong support from industry and a lower than expected cost. Although there are clear advantages to rapid phaseout, there were no incentives included in the MP for rapid phaseout. Some of the difficulties occur because the schedules set minimum targets at the lowest possible cost. Also, costs cannot be minimized by a country-specific and ODS-specific process. The ways to improve implementation in scheduling and incremental costs are indicated. PMID:12285661

  17. Services Provides By DL Layer DLL Protocols

    E-print Network

    Ramkumar, Mahalingam

    Services Provides By DL Layer Framing DLL Protocols Other Layer 2 Components Data Link Layer Layer Framing DLL Protocols Other Layer 2 Components Outline 1 Services Provides By DL Layer Data Link Layer Issues 2 Framing 3 DLL Protocols PPP ADSL and Cable Internet Ethernet - IEEE 802.3 Wireless

  18. Cooperating systems: Layered MAS

    NASA Technical Reports Server (NTRS)

    Rochowiak, Daniel

    1990-01-01

    Distributed intelligent systems can be distinguished by the models that they use. The model developed focuses on layered multiagent system conceived of as a bureaucracy in which a distributed data base serves as a central means of communication. The various generic bureaus of such a system is described and a basic vocabulary for such systems is presented. In presenting the bureaus and vocabularies, special attention is given to the sorts of reasonings that are appropriate. A bureaucratic model has a hierarchy of master system and work group that organizes E agents and B agents. The master system provides the administrative services and support facilities for the work groups.

  19. The Keck keyword layer

    NASA Technical Reports Server (NTRS)

    Conrad, A. R.; Lupton, W. F.

    1992-01-01

    Each Keck instrument presents a consistent software view to the user interface programmer. The view consists of a small library of functions, which are identical for all instruments, and a large set of keywords, that vary from instrument to instrument. All knowledge of the underlying task structure is hidden from the application programmer by the keyword layer. Image capture software uses the same function library to collect data for the image header. Because the image capture software and the instrument control software are built on top of the same keyword layer, a given observation can be 'replayed' by extracting keyword-value pairs from the image header and passing them back to the control system. The keyword layer features non-blocking as well as blocking I/O. A non-blocking keyword write operation (such as setting a filter position) specifies a callback to be invoked when the operation is complete. A non-blocking keyword read operation specifies a callback to be invoked whenever the keyword changes state. The keyword-callback style meshes well with the widget-callback style commonly used in X window programs. The first keyword library was built for the two Keck optical instruments. More recently, keyword libraries have been developed for the infrared instruments and for telescope control. Although the underlying mechanisms used for inter-process communication by each of these systems vary widely (Lick MUSIC, Sun RPC, and direct socket I/O, respectively), a basic user interface has been written that can be used with any of these systems. Since the keyword libraries are bound to user interface programs dynamically at run time, only a single set of user interface executables is needed. For example, the same program, 'xshow', can be used to display continuously the telescope's position, the time left in an instrument's exposure, or both values simultaneously. Less generic tools that operate on specific keywords, for example an X display that controls optical instrument exposures, have also been written using the keyword layer.

  20. Layered Rocks in Ritchey

    NASA Technical Reports Server (NTRS)

    2004-01-01

    14 May 2004 This March 2004 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows light- and dark-toned layered rock outcrops on the floor of Ritchey Crater, located near 28.9oS, 50.8oW. Some or all of these rocks may be sedimentary in origin. Erosion has left a couple of buttes standing on a more erosion-resistant plain. This picture covers an area approximately 3 km (1.9 mi) across and is illuminated by sunlight from the upper left.

  1. Layered Rocks of Melas

    NASA Technical Reports Server (NTRS)

    2004-01-01

    04 August 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows layered sedimentary rock outcrops exposed by erosion in southern Melas Chasma, one of the major Valles Marineris troughs. Such outcrops are common in southern Melas; they resemble the rock outcrops seen in some of the chaotic terrains and other Valles Marineris chasms. This image is located near 11.9oS, 74.6oW, and is about 3 km (1.9 mi) wide. Sunlight illuminates the scene from the lower left.

  2. Remnant Layered Rocks

    NASA Technical Reports Server (NTRS)

    2004-01-01

    29 June 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a suite of small yardangs -- wind eroded hills -- on the plains immediately west of Meridiani Planum. These yardangs are the remains of layered, sedimentary rock that once covered this area. The few craters visible in this 3 km (1.9 mi) -wide scene are all exhumed from beneath the rocks that comprise the yardang hills. The image is located near 0.4oS, 7.2oW. Sunlight illuminates the picture from the lower left.

  3. Metal deposition using seed layers

    DOEpatents

    Feng, Hsein-Ping; Chen, Gang; Bo, Yu; Ren, Zhifeng; Chen, Shuo; Poudel, Bed

    2013-11-12

    Methods of forming a conductive metal layers on substrates are disclosed which employ a seed layer to enhance bonding, especially to smooth, low-roughness or hydrophobic substrates. In one aspect of the invention, the seed layer can be formed by applying nanoparticles onto a surface of the substrate; and the metallization is achieved by electroplating an electrically conducting metal onto the seed layer, whereby the nanoparticles serve as nucleation sites for metal deposition. In another approach, the seed layer can be formed by a self-assembling linker material, such as a sulfur-containing silane material.

  4. Do stable atmospheric layers exist?

    NASA Astrophysics Data System (ADS)

    Lovejoy, S.; Tuck, A. F.; Hovde, S. J.; Schertzer, D.

    2008-01-01

    The notion of stable atmospheric layers is a classical idealization used for understanding atmospheric dynamics and thermodynamics. Using state of the art drop sonde data and using conditional, dynamical and convective stability criteria we show that apparently stable layers are typically composed of a hierarchy of unstable layers themselves with embedded stable sublayers, and unstable sub-sub layers etc. i.e. in a Russian Matryoshka doll-like fractal hierarchy. We therefore argue that the notion of stable atmospheric layers is untenable and must be replaced by modern scaling notions.

  5. Buried oxide layer in silicon

    DOEpatents

    Sadana, Devendra Kumar (Pleasantville, NY); Holland, Orin Wayne (Lenoir, TN)

    2001-01-01

    A process for forming Silicon-On-Insulator is described incorporating the steps of ion implantation of oxygen into a silicon substrate at elevated temperature, ion implanting oxygen at a temperature below 200.degree. C. at a lower dose to form an amorphous silicon layer, and annealing steps to form a mixture of defective single crystal silicon and polycrystalline silicon or polycrystalline silicon alone and then silicon oxide from the amorphous silicon layer to form a continuous silicon oxide layer below the surface of the silicon substrate to provide an isolated superficial layer of silicon. The invention overcomes the problem of buried isolated islands of silicon oxide forming a discontinuous buried oxide layer.

  6. The Effects of Virtual Weather on Presence

    NASA Astrophysics Data System (ADS)

    Wissmath, Bartholomäus; Weibel, David; Mast, Fred W.

    In modern societies people tend to spend more time in front of computer screens than outdoors. Along with an increasing degree of realism displayed in digital environments, simulated weather appears more and more realistic and more often implemented in digital environments. Research has found that the actual weather influences behavior and mood. In this paper we experimentally examine the effects of virtual weather on the sense of presence. Thereby we found individuals (N=30) to immerse deeper in digital environments displaying fair weather conditions than in environments displaying bad weather. We also investigate whether virtual weather can influence behavior. The possible implications of theses findings for presence theory as well as digital environment designers will be discussed.

  7. Presence of Laminin Receptors in Staphylococcus aureus

    NASA Astrophysics Data System (ADS)

    Lopes, J. D.; Dos Reis, M.; Brentani, R. R.

    1985-07-01

    A characteristic feature of infection by Staphylococcus aureus is bloodstream invasion and widespread metastatic abscess formation. The ability to extravasate, which entails crossing the vascular basement membrane, appears to be critical for the organism's pathogenicity. Extravasation by normal and neoplastic mammalian cells has been correlated with the presence of specific cell surface receptors for the basement membrane glycoprotein laminin. Similar laminin receptors were found in Staphylococcus aureus but not in Staphylococcus epidermidis, a noninvasive pathogen. There were about 100 binding sites per cell, with an apparent binding affinity of 2.9 nanomolar. The molecular weight of the receptor was 50,000 and pI was 4.2. Eukaryotic laminin receptors were visualized by means of the binding of S. aureus in the presence of laminin. Prokaryotic and eukaryotic invasive cells might utilize similar, if not identical, mechanisms for invasion.

  8. Hyperautofluorescence in Outer Retinal Layers Thinning

    PubMed Central

    2014-01-01

    Purpose. To evaluate if paracentral hyperautofluorescence (HAF) retinal regions, which can be occasionally found and analyzed by optical coherence tomography (OCT), were related to retinal layer changes and to detect which layer was involved. Methods. This is a cross-sectional and retrospective study. 648 OCT files were revised. OCTs that showed a paracentral HAF area by using the fundus autofluorescence imaging in Heidelberg Spectralis (Heidelberg Engineering, Germany) were selected. Then retinal layer morphology was analyzed observing OCT scans and a retinal thickness was measured. Results. 31 patients were selected: 20 patients had chronic serous epitheliopathy (CSE), 8 patients had resolved central serous chorioretinopathy (CSC), and 3 patients wet age related macular degeneration (ARMD). The HAF zones corresponded to areas of thickness reduction of the external hyporeflective band. In all these areas the retinal pigment epithelium was not atrophic and the neuroepithelium was more or less dystrophic. In particular the retinal thickness was 264?um, 232?um, and 243?um in wet ARMD, CSE, and CSC, respectively; the reduction was significant (P < 0.01) compared to the same area of the other eye. Discussion. The presence of HAF imaging might be mostly due to a “window effect” rather than an accumulation of lipofuscin. PMID:25276816

  9. Modelling potential presence of metazoan endoparasites of bobcats (Lynx rufus) using verified records.

    PubMed

    Hiestand, Shelby J; Nielsen, Clayton K; Jiménez, F Agustín

    2014-10-01

    Helminth parasites of wild and domestic felines pose a direct or potential threat to human health. Since helminths depend on multiple environmental factors that make their transmission possible, it is imperative to predict the areas where these parasites may complete the transmission to potential hosts. Bobcats, Lynx rufus (Schreberer), are the most abundant and widely-distributed wild felid species in North America. The increase of population densities of bobcats raises concerns about their importance as reservoirs of pathogens and parasites that may affect wildlife, domestic animals and humans. Our objective was to predict the potential presence of the tapeworm Taenia rileyi Loewen, 1929, the fluke Alaria marcianae (La Rue, 1917) and the roundworm Toxocara cati (Schrank, 1788) in southern Illinois. The empirical presence of these parasites in localities across the region was analysed in combination with a sampling bias layer (i.e. bobcat presence) and with environmental data: layers of water, soil, land cover, human density and climate variables in MAXENT to create maps of potential presence for these three species in an area of 46436 km2. All climatic variables were low contributors (0.0-2.0% contribution to model creation) whereas land cover surfaced as an important variable for the presence of A. marcianae (7.6%) and T. cati (6.3%); human density (4.8%) was of secondary importance for T. rileyi. Variables of importance likely represent habitat requirements necessary for the completion of parasite life cycles. Larger areas of potential presence were found for the feline specialist T. rileyi (85%) while potential presence was less likely for A. marcianae (73%), a parasite that requires multiple aquatic intermediate hosts. This study provides information to wildlife biologists and health officials regarding the potential impacts of growing bobcat populations in combination with complex and changing environmental factors. PMID:25549497

  10. Constraints on the formation of layered tektites from the excavation and analysis of layered tektites from northeast Thailand

    NASA Astrophysics Data System (ADS)

    Fiske, Peter S.

    1996-01-01

    The size, shape, composition, and vesicle content of 6 kg of layered tektite fragments, excavated near the town of Huai Sai, Thailand, place some constraints on the formation of layered tektites. The mass, shape, and distribution of the fragments are not consistent with an origin as a "puddle" of impact melt but suggest that they were derived from a single equant block. The presence of vesicles up to 7 mm in mean diameter within the tektite fragments suggests that the material was too viscous to allow for significant gravity-driven flow. These results suggest that layered tektites may be analogous to lava bombs, which may have been stretched and deformed in flight but underwent little flow after landing. Rather than being a product of "unusual circumstances," such as multiple impacts, layered tektites may differ from splash-form tektites only in initial temperature of formation, speed of ejection, and small differences in initial composition.

  11. Flexible, layered biofuel cells.

    PubMed

    Miyake, Takeo; Haneda, Keigo; Yoshino, Syuhei; Nishizawa, Matsuhiko

    2013-02-15

    Similar to conventional electrolyte batteries, biofuel cells often need to be stacked in order to boost their single cell voltage (<1 V) up to a practical level. Here, we report a laminated stack of biofuel cells that is composed of bioanode fabrics for fructose oxidation, hydrogel sheets containing electrolyte and fuel (fructose), and O(2)-diffusion biocathode fabrics. The anode and cathode fabrics were prepared by modifying fructose dehydrogenase and bilirubin oxidase, respectively, on carbon nanotubes-decorated carbon fiber fabrics. The total thickness of the single set of anode/gel/cathode sheets is just 1.1mm. The laminated triple-layer stack produces an open-circuit voltage of 2.09 V, which is a 2.8-fold increase over that of a single set cell (0.74 V). The present layered cell (5 mm × 5 mm) produces a maximum power of 0.64 mW at 1.21 V, a level that is sufficient to drive light-emitting diodes. PMID:22704841

  12. Boundary-layer type classification and pollutant mixing

    NASA Astrophysics Data System (ADS)

    Harvey, N. J.

    For the first time, Doppler lidar and sonic anemometer data are used to objectively classify the observed boundary layer into nine different types based on the Met Office scheme. Examples of these types are decoupled stratocumulus cloud, cumulus capped and stable with no turbulent cloud. This method is applied to three years of data from the Chilbolton Observatory, UK, to create climatology of boundary-layer type. This climatology exhibits clear seasonal and diurnal cycles with the most common type over the three years being a cloud-free stable boundary layer. The decoupled stratocumulus type and the cumulus cloud under a stratocumulus layer type are diagnosed 10.3% and 1.0% of the period respectively. This new observationally based boundary layer classification is used to evaluate the boundary-layer type diagnosed by the 4 km and 12 km resolution versions of the Met Office Unified Model. The model is found to predict too many decoupled stratocumulus boundary layers by a factor of 1.8, in both the stable and unstable regime. Stratocumulus cloud is present in the morning in the model but it is underestimated in the afternoon. The skill of the model in predicting boundary-layer type at the correct time has also been assessed using the symmetric extremal, dependence index measure of skill. This analysis revealed that the skill of predicting the correct boundary-layer cloud type was much lower than the skill of predicting the presence of cloud. The skill of prediction is not affected by model resolution. Finally, a set of idealised single column modelling experiments have been conducted to investigate the impact of boundary-layer type diagnosis on the vertical distribution of pollutants.

  13. Topotactic condensation of layer silicates with ferrierite-type layers forming porous tectosilicates.

    PubMed

    Marler, B; Wang, Y; Song, J; Gies, H

    2014-07-21

    Five different hydrous layer silicates (HLSs) containing fer layers (ferrierite-type layers) were obtained by hydrothermal syntheses from mixtures of silicic acid, water and tetraalkylammonium/tetraalkylphosphonium hydroxides. The organic cations had been added as structure directing agents (SDA). A characteristic feature of the structures is the presence of strong to medium strong hydrogen bonds between the terminal silanol/siloxy groups of neighbouring layers. The five-layered silicates differ chemically only with respect to the organic cations. Structurally, they differ with respect to the arrangement of the fer layers relative to each other, which is distinct for every SDA-fer-layer system. RUB-20 (containing tetramethylammonium) and RUB-40 (tetramethylphosphonium) are monoclinic with stacking sequence AAA and shift vectors between successive layers 1a0 + 0b0 + 0.19c0 and 1a0 + 0b0 + 0.24c0, respectively. RUB-36 (diethyldimethylammonium), RUB-38 (methyltriethylammonium) and RUB-48 (trimethylisopropylammonium) are orthorhombic with stacking sequence ABAB and shift vectors 0.5a0 + 0b0± 0.36c0, 0.5a0 + 0b0 + 0.5c0 and 0.5a0 + 0b0± 0.39c0, respectively. Unprecedented among the HLSs, two monoclinic materials are made up of fer layers which possess a significant amount of ordered defects within the layer. The ordered defects involve one particular Si-O-Si bridge which is, to a fraction of ca. 50%, hydrolyzed to form nests of two ?Si-OH groups. When heated to 500-600 °C in air, the HLSs condense to form framework silicates. Although all layered precursors were moderately to well ordered, the resulting framework structures were of quite different crystallinity. The orthorhombic materials RUB-36, -38 and -48, general formula SDA4Si36O72(OH)4, which possess very strong hydrogen bonds (d[O···O] ? 2.4 Å), transform into a fairly or well ordered CDO-type silica zeolite RUB-37. The monoclinic materials RUB-20 and -40, general formula SDA2Si18O36(OH)2OH, possessing medium strong hydrogen bonds (d[O···O] ? 2.65 Å) are transformed into poorly ordered framework silicates. Some rules of thumb can be established concerning the successful zeolite synthesis via a topotactic condensation of layered precursors. Favourably, the precursor (i) possesses already a well ordered structure without defects, (ii) contains strong inter-layer hydrogen bonds and does not contain strong intra-layer hydrogen bonds and (iii) contains a suitable cation. The nature of the organic cation (size, geometry, flexibility, thermal stability) plays a key role in the formation of a microporous tectosilicate with well ordered structure. RUB-36 which meets these criteria yields a well ordered condensation product (RUB-37). PMID:24875843

  14. Antitumoral materials with regenerative function obtained using a layer-by-layer technique

    PubMed Central

    Ficai, Denisa; Sonmez, Maria; Albu, Madalina Georgiana; Mihaiescu, Dan Eduard; Ficai, Anton; Bleotu, Coralia

    2015-01-01

    A layer-by layer technique was successfully used to obtain collagen/hydroxyapatite-magnetite-cisplatin (COLL/HAn-Fe3O4-CisPt, n=1–7) composite materials with a variable content of hydroxyapatite intended for use in the treatment of bone cancer. The main advantages of this system are the possibility of controlling the rate of delivery of cytostatic agents, the presence of collagen and hydroxyapatite to ensure more rapid healing of the injured bone tissue, and the potential for magnetite to be a passive antitumoral component that can be activated when an appropriate external electromagnetic field is applied. In vitro cytotoxicity assays performed on the COLL/HAn-Fe3O4-CisPt materials obtained using a layer-by layer method confirmed their antitumoral activity. Samples with a higher content of hydroxyapatite had more antitumoral activity because of their better absorption of cisplatin and consequently a higher amount of cisplatin being present in the matrices. PMID:25767374

  15. Antitumoral materials with regenerative function obtained using a layer-by-layer technique.

    PubMed

    Ficai, Denisa; Sonmez, Maria; Albu, Madalina Georgiana; Mihaiescu, Dan Eduard; Ficai, Anton; Bleotu, Coralia

    2015-01-01

    A layer-by layer technique was successfully used to obtain collagen/hydroxyapatite-magnetite-cisplatin (COLL/HAn-Fe3O4-CisPt, n=1-7) composite materials with a variable content of hydroxyapatite intended for use in the treatment of bone cancer. The main advantages of this system are the possibility of controlling the rate of delivery of cytostatic agents, the presence of collagen and hydroxyapatite to ensure more rapid healing of the injured bone tissue, and the potential for magnetite to be a passive antitumoral component that can be activated when an appropriate external electromagnetic field is applied. In vitro cytotoxicity assays performed on the COLL/HAn-Fe3O4-CisPt materials obtained using a layer-by layer method confirmed their antitumoral activity. Samples with a higher content of hydroxyapatite had more antitumoral activity because of their better absorption of cisplatin and consequently a higher amount of cisplatin being present in the matrices. PMID:25767374

  16. Processes for multi-layer devices utilizing layer transfer

    DOEpatents

    Nielson, Gregory N; Sanchez, Carlos Anthony; Tauke-Pedretti, Anna; Kim, Bongsang; Cederberg, Jeffrey; Okandan, Murat; Cruz-Campa, Jose Luis; Resnick, Paul J

    2015-02-03

    A method includes forming a release layer over a donor substrate. A plurality of devices made of a first semiconductor material are formed over the release layer. A first dielectric layer is formed over the plurality of devices such that all exposed surfaces of the plurality of devices are covered by the first dielectric layer. The plurality of devices are chemically attached to a receiving device made of a second semiconductor material different than the first semiconductor material, the receiving device having a receiving substrate attached to a surface of the receiving device opposite the plurality of devices. The release layer is etched to release the donor substrate from the plurality of devices. A second dielectric layer is applied over the plurality of devices and the receiving device to mechanically attach the plurality of devices to the receiving device.

  17. Multicolor Layer-by-Layer films using weak polyelectrolyte assisted synthesis of silver nanoparticles

    PubMed Central

    2013-01-01

    In the present study, we show that silver nanoparticles (AgNPs) with different shape, aggregation state and color (violet, green, orange) have been successfully incorporated into polyelectrolyte multilayer thin films using the layer-by-layer (LbL) assembly. In order to obtain colored thin films based on AgNPs is necessary to maintain the aggregation state of the nanoparticles, a non-trivial aspect in which this work is focused on. The use of Poly(acrylic acid, sodium salt) (PAA) as a protective agent of the AgNPs is the key element to preserve the aggregation state and makes possible the presence of similar aggregates (shape and size) within the LbLcolored films. This approach based on electrostatic interactions of the polymeric chains and the immobilization of AgNPs with different shape and size into the thin films opens up a new interesting perspective to fabricate multicolornanocomposites based on AgNPs. PMID:24148227

  18. Ultrasonic Imaging Of Bond Layers Through Bond Layers

    NASA Technical Reports Server (NTRS)

    Chern, E. James

    1992-01-01

    Combination of hardware and software helps ultrasonic C-scan inspection system create images of bond layer in laminated composite material, even when obscured by another bond layer. Produces image of both layers in single scan. Includes ultrasonic transducer, pulser/receiver, mechanical scanner, personal computer as controller, and electronic circuitry that gates first and second peak signals, detects peaks, and feeds resulting amplitude data to computer.

  19. Templated, layered manganese phosphate

    DOEpatents

    Thoma, Steven G.; Bonhomme, Francois R.

    2004-08-17

    A new crystalline maganese phosphate composition having an empirical formula: O). The compound was determined to crystallize in the trigonal space group P-3c1 with a=8.8706(4) .ANG., c=26.1580(2) .ANG., and V (volume)=1783 .ANG..sup.3. The structure consists of sheets of corner sharing Mn(II)O.sub.4 and PO.sub.4 tetrahedra with layers of (H.sub.3 NCH.sub.2 CH.sub.2).sub.3 N and water molecules in-between. The pronated (H.sub.3 NCH.sub.2 CH.sub.2).sub.3 N molecules provide charge balancing for the inorganic sheets. A network of hydrogen bonds between water molecules and the inorganic sheets holds the structure together.

  20. Double layer secure sketch

    NASA Astrophysics Data System (ADS)

    Li, Cai

    2012-09-01

    Secure sketch has been applied successfully in a wide variety of applications like cryptography, biometric authentication systems and so on. All of these secure sketches have properties in common namely error-tolerance and small entropy loss. The former ensures an input set w' can unlock the system if w' is substantially overlapped with a template set w while the latter means it is hard for an adversary to get the information of w even with the knowledge of s, which is produced by w and stored in the system publicly. In their constructions, they all consider w as a set of atomic elements. However, in the real word, it is very likely the elements in the template set are sets as well. In this paper, we propose a double layer secure sketch to address this issue.