Sample records for frost layer presence

  1. Sublimation Behavior of Annular Frost Layer by Impinging Jet Flow

    NASA Astrophysics Data System (ADS)

    Inaba, Hideo; Horibe, Akihiko; Takamoto, Naoki; Kawakami, Yoshiaki; Imai, Seishi

    The present paper deals with a new method of defrosting using the frost sublimation phenomenon, which occurs below the triple point of water (273.16K, 610.5Pa). The present experimental study examines the mass transfer of the annular frost layer developed on a cooling pipe exposed to an impinging jet flow. The morphology of the frost layer during sublimation was observed using a digital video recorder. It was understood that the mass flux of the frost layer increased with increasing the jet flow velocity and the difference in the mass concentration of water vapor between the frost surface and the impinging jet flow. The non-dimensional correlation equations of mass transfer of defrosting were derived as functions of various parameters.

  2. Review Concerning Studies of Frost Deposition

    NASA Astrophysics Data System (ADS)

    Yamashita, Koji

    In order to increase the coefficient of performance of heat exchangers under frosting conditions such as in air conditioners, showcases, and unit coolers, it is necessary to elucidate the frost deposition mechanism. The previous studies about frost deposition were summarized in this study. The previous studies about observation of frost deposition, properties of the frost layer, simulation methods of the frost layer, frost detection, frost studies concerning heat exchangers and heat pumps, and defrost control methods were explained. There are many conditions that have not been measured yet, though the mechanism of frost deposition and properties of the frost layer have been elucidated from the previous studies. The study of frost deposition has been invigorated in Japan recently. The understanding of frosting phenomenon is expected to be deepened in the near future.

  3. Frost formation on a super-hydrophobic surface under natural convection conditions

    Microsoft Academic Search

    Zhongliang Liu; Yunjun Gou; Jieteng Wang; Shuiyuan Cheng

    2008-01-01

    In this paper, the frost deposition phenomena on a cold super-hydrophobic surface whose contact angle with water is 162° were observed of the formation of water droplets, the freezing process, the formation of initial frost crystals and the frost layer structure. The frost layer structure formed on the super-hydrophobic surface shows remarkable differences to that on a plain copper surface:

  4. Modeling of Frost Growth on Heat Exchanger Surfaces

    Microsoft Academic Search

    Katrin Prolss; Gerhard Schmitz

    2006-01-01

    A Modelica model to study the frost growth on paral- lel heat exchanger plates is developed. The coupled heat and mass transport phenomena involved in the process are described. A physical model which in- cludes the distributed densification of the frost layer is compared to a simple lumped model approach. The frost structure and thus the resulting properties such as

  5. 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.

  6. 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

  7. Influence of Several Parameters on Frost Growth in Low Temperature Environments

    NASA Astrophysics Data System (ADS)

    Yamashita, Koji; Ohkubo, Hidetoshi

    In order to increase the coefficient of performance of heat exchangers under frosting conditions such as in air conditioners, showcases, and unit coolers, it is necessary to elucidate the frost deposition mechanism in low temperature environments. Frost properties were measured at air temperature below 0°C. The experimental results were analyzed and a simulation model of frost growth in low temperature environments was developed. In the simulation model, frost growth during the crystal growth period was calculated by using the ice column model of Tao et al. and during the subsequent frost growth period, another model was used; the frost growth was calculated according to diffusion into the frost layer on the basis of Fick's law and the model of Le Gall et al. The simulations were performed to calculate the frost growth on a flat plate and the influences of several parameters on frosting phenomenon were elucidated at air temperature of about 0°C.

  8. 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.

  9. Frost tolerance of Trifolium species

    Microsoft Academic Search

    J. R. Caradus

    1995-01-01

    Thirteen Trifolium species were artificially frosted at ?4, ?8, ?12, and ?16°C in controlled environment rooms. This was carried out in such a way that soil freezing was avoided and only shoots were frosted. Frost tolerance was primarily assessed as the percentage of dead to total leaf dry weight present 1 week after frosting. Trifolium arvense, T. dubium, and T.

  10. Polygons in Martian Frost

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-428, 21 July 2003

    This June 2003 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a polygonal pattern developed in seasonal carbon dioxide frost in the martian southern hemisphere. The frost accumulated during the recent southern winter; it is now spring, and the carbon dioxide frost is subliming away. This image is located near 80.4oS, 200.2oW; it is illuminated by sunlight from the upper left, and covers an area 3 km (1.9 mi) across.

  11. Frosted Chasma Boreale Dunes

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-390, 13 June 2003

    This is a Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) view of frost-covered sand dunes in Chasma Boreale in the early northern spring season. Dark spots, some of them with bright halos of re-precipitated frost, have formed as the dunes begin to defrost. Most of the frost is carbon dioxide which freezes out of the atmosphere during the cold martian polar winters. This picture is located near 84.7oN, 358.8oW, and is illuminated from the lower left.

  12. Moisture performance analysis of EPS frost insulation

    SciTech Connect

    Ojanen, T.; Kokko, E.

    1997-11-01

    A horizontal layer of expanded polystyrene foam (EPS) is widely used as a frost insulation of building foundations in the Nordic countries. The performance properties of the insulation depend strongly on the moisture level of the material. Experimental methods are needed to produce samples for testing the material properties in realistic moisture conditions. The objective was to analyze the moisture loads and the wetting mechanisms of horizontal EPS frost insulation. Typical wetting tests, water immersion and diffusive water vapor absorption tests, were studied and the results were compared with the data from site investigations. Usually these tests give higher moisture contents of EPS than what are detected in drained frost insulation applications. Also the effect of different parameters, like the immersion depth and temperature gradient were studied. Special attention was paid to study the effect of diffusion on the wetting process. Numerical simulation showed that under real working conditions the long period diffusive moisture absorption in EPS frost insulation remained lower than 1% Vol. Moisture performance was determined experimentally as a function of the distance between the insulation and the free water level in the ground. The main moisture loads and the principles for good moisture performance of frost insulation are presented.

  13. A frost formation model and its validation under various experimental conditions

    NASA Technical Reports Server (NTRS)

    Dietenberger, M. A.

    1982-01-01

    A numerical model that was used to calculate the frost properties for all regimes of frost growth is described. In the first regime of frost growth, the initial frost density and thickness was modeled from the theories of crystal growth. The 'frost point' temperature was modeled as a linear interpolation between the dew point temperature and the fog point temperature, based upon the nucleating capability of the particular condensing surfaces. For a second regime of frost growth, the diffusion model was adopted with the following enhancements: the generalized correlation of the water frost thermal conductivity was applied to practically all water frost layers being careful to ensure that the calculated heat and mass transfer coefficients agreed with experimental measurements of the same coefficients.

  14. 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…

  15. Ultrasonic Frost Suppression

    NASA Astrophysics Data System (ADS)

    Adachi, Kazunari; Saiki, Kazushi; Sato, Hiroki; Ito, Takahiro

    2003-02-01

    The authors have observed the accumulation of frost on the surface of a rectangular aluminum alloy (duralumin) plate flexurally vibrating at approximately 37 kHz in an atmosphere of almost 100% relative humidity at 2°C. The plate surface, which had been prepolished with abrasive slurry for maintaining its average surface roughness of about 100 nm, was refrigerated at a temperature of -20°C with cold carbon-dioxide gas as coolant. Experiments have been conducted with and without fine silver oxide powder spread on the plate surface so as to examine the effect of artificial ice crystal nuclei. Ultrasonic vibrations with an amplitude of 3.4 ?m (rms) are found to suppress frost accumulation by approximately 60%. The phenomenon cannot be ascribed directly to the heat generation caused by high-amplitude vibration, but may have a complex mechanical and/or acoustical effect on small ice crystals.

  16. Water frost on Charon

    NASA Astrophysics Data System (ADS)

    Buie, M. W.; Cruikshank, D. P.; Lebofsky, L. A.; Tedesco, E. F.

    1987-10-01

    The authors present new spectra of the Pluto-Charon system taken just before and during a total eclipse of the satellite. From these data they have extracted the spectrum of the satellite, Charon, which reveals the spectral signature of water ice. There is no evidence for any methane or ammonia frost on the surface of Charon. This observation places important constraints on the composition and origin of this planetary system.

  17. Differential frost heave model for patterned ground formation: Corroboration with observations along a North American arctic transect

    Microsoft Academic Search

    R. A. Peterson; W. B. Krantz

    2008-01-01

    Frost boils in the Arctic are a manifestation of patterned ground in the form of nonsorted circles. Active frost boils involve convection of water through the soil that can bring basic salts from depth to the surface. As such, active frost boils can mitigate acidification and thereby strongly influence the type of vegetation supported by Arctic soils. The presence or

  18. Casimir force in presence of multi layer magnetodielectric slabs

    SciTech Connect

    Kheirandish, Fardin, E-mail: fardin_kh@phys.ui.ac.ir [Department of Physics, University of Isfahan, Isfahan 81746 (Iran, Islamic Republic of); Soltani, Morteza, E-mail: msoltani@Phys.ui.ac.ir [Department of Physics, University of Isfahan, Isfahan 81746 (Iran, Islamic Republic of); Sarabadani, Jalal, E-mail: j.sarabadani@phys.ui.ac.ir [Department of Physics, University of Isfahan, Isfahan 81746 (Iran, Islamic Republic of)

    2011-03-15

    Research Highlights: > The Casimir force has been obtained in the presence of some dielectrics. > The approach is based on a Lagrangian. > It can be generalized to include the rough surfaces. > Finite temperature correction can be easily obtained. - Abstract: By using the path-integral formalism, electromagnetic field in the presence of some linear, isotropic magnetodielectric slabs is quantized and related correlation functions are found. In the framework of path-integral techniques, Casimir force between two infinitely large, parallel and ideal conductors, with a different number of magnetodielectric slabs in between, is obtained by calculating the Green's function corresponding to each geometry.

  19. 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.

  20. 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. [Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas and Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

    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.

  1. 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

  2. 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.

  3. 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.

  4. Optical properties of insulator-excitonic-semiconductor superlattices in the presence of inert layers

    NASA Astrophysics Data System (ADS)

    Cocoletzi, G. H.; Ramrez Perucho, A.; Luis Mochán, W.

    1991-11-01

    We study the optical properties of an insulator-excitonic-semiconductor superlattice in the presence of exciton-free inert layers on both surfaces of each semiconducting region. Generalized boundary conditions are applied at the interface between the inert layer and the active region, and the dispersion relation of the collective normal modes of an infinite superlattice is calculated near an excitonic transition. We also obtain the optical reflectance of a semi-infinite superlattice for p polarization. We present results for CdS layers using two well-known additional boundary conditions. Increasing the inert-layer thickness induces a blueshift and modifies the structure in the complex spectra. This structure is interpreted in terms of guided transverse- and longitudinal-wave resonances in the active excitonic layers.

  5. The sodium layer in the presence of noctilucent clouds - Results from Odin's summer mesosphere mission

    Microsoft Academic Search

    J. Gumbel; J. Stegman; G. Witt; J. Plane; B. Murray; Z. Fan; E. J. Llewellyn

    2003-01-01

    It is known from in situ and lidar measurements that metal species can be depleted in the presence of noctilucent clouds (NLC). The OSIRIS optical spectrometer onboard the Odin satellite provides a unique opportunity to study the relationship between NLC and the mesospheric sodium layer on a \\

  6. 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

  7. Bottom boundary layer spectral dissipation estimates in the presence of wave motions

    NASA Astrophysics Data System (ADS)

    Gross, T. F.; Williams, A. J.; Terray, E. A.

    1994-08-01

    Turbulence measurements are an essential element of the Sediment TRansport Events on Shelves and Slopes experiment (STRESS). Sediment transport under waves is initiated within the wave boundary layer at the seabed, at most a few tens of centimeters deep. The suspended load is carried by turbulent diffusion above the wave boundary layer. Quantification of the turbulent diffusion active above the wave boundary layer requires estimates of shear stress or energy dissipation in the presence of oscillating flows. Measurements by Benthic Acoustic Stress Sensors of velocity fluctuations were used to derive the dissipation rate from the energy level of the spectral inertial range (the -5/3 spectrum). When the wave orbital velocity is of similar magnitude to the mean flow, kinematic effects on the estimation techniques of stress and dissipation must be included. Throughout the STRESS experiment there was always significant wave energy affecting the turbulent bottom boundary layer. LUMLEY and TERRAY [(1983) Journal of Physical Oceanography, 13, 2000-2007] presented a theory describing the effect of orbital motions on kinetic energy spectra. Their model is used here with observations of spectra taken within a turbulent boundary layer which is affected by wave motion. While their method was an explicit solution for circular wave orbits aligned with mean current we extrapolated it to the case of near bed horizontal motions, not aligned with the current. The necessity of accounting for wave orbital motion is demonstrated, but variability within the field setting limited our certainty of the improvement in accuracy the corrections afforded.

  8. Charge transfer in the presence of a layer of trapping centers in semiconductor SiC ionizing radiation detectors

    Microsoft Academic Search

    A. M. Ivanov; E. V. Kalinina; N. B. Strokan

    2008-01-01

    The formation of a response signal in the presence of a layer of trapping centers in semiconductor SiC ionizing radiation detectors is considered on the basis of a new model. Since the trapping layer is situated near the detector surface, nuclear particles that possess long tracks partly generate a charge behind this layer. Under certain conditions, the proposed model leads

  9. Unexpected presence of graminan- and levan-type fructans in the evergreen frost-hardy eudicot Pachysandra terminalis (Buxaceae): purification, cloning, and functional analysis of a 6-SST/6-SFT enzyme.

    PubMed

    Van den Ende, Wim; Coopman, Marlies; Clerens, Stefan; Vergauwen, Rudy; Le Roy, Katrien; Lammens, Willem; Van Laere, André

    2011-01-01

    About 15% of flowering plants accumulate fructans. Inulin-type fructans with ?(2,1) fructosyl linkages typically accumulate in the core eudicot families (e.g. Asteraceae), while levan-type fructans with ?(2,6) linkages and branched, graminan-type fructans with mixed linkages predominate in monocot families. Here, we describe the unexpected finding that graminan- and levan-type fructans, as typically occurring in wheat (Triticum aestivum) and barley (Hordeum vulgare), also accumulate in Pachysandra terminalis, an evergreen, frost-hardy basal eudicot species. Part of the complex graminan- and levan-type fructans as accumulating in vivo can be produced in vitro by a sucrose:fructan 6-fructosyltransferase (6-SFT) enzyme with inherent sucrose:sucrose 1-fructosyltransferase (1-SST) and fructan 6-exohydrolase side activities. This enzyme produces a series of cereal-like graminan- and levan-type fructans from sucrose as a single substrate. The 6-SST/6-SFT enzyme was fully purified by classic column chromatography. In-gel trypsin digestion led to reverse transcription-polymerase chain reaction-based cDNA cloning. The functionality of the 6-SST/6-SFT cDNA was demonstrated after heterologous expression in Pichia pastoris. Both the recombinant and native enzymes showed rather similar substrate specificity characteristics, including peculiar temperature-dependent inherent 1-SST and fructan 6-exohydrolase side activities. The finding that cereal-type fructans accumulate in a basal eudicot species further confirms the polyphyletic origin of fructan biosynthesis in nature. Our data suggest that the fructan syndrome in P. terminalis can be considered as a recent evolutionary event. Putative connections between abiotic stress and fructans are discussed. PMID:21037113

  10. Unexpected Presence of Graminan- and Levan-Type Fructans in the Evergreen Frost-Hardy Eudicot Pachysandra terminalis (Buxaceae): Purification, Cloning, and Functional Analysis of a 6-SST/6-SFT Enzyme1[W

    PubMed Central

    Van den Ende, Wim; Coopman, Marlies; Clerens, Stefan; Vergauwen, Rudy; Le Roy, Katrien; Lammens, Willem; Van Laere, André

    2011-01-01

    About 15% of flowering plants accumulate fructans. Inulin-type fructans with ?(2,1) fructosyl linkages typically accumulate in the core eudicot families (e.g. Asteraceae), while levan-type fructans with ?(2,6) linkages and branched, graminan-type fructans with mixed linkages predominate in monocot families. Here, we describe the unexpected finding that graminan- and levan-type fructans, as typically occurring in wheat (Triticum aestivum) and barley (Hordeum vulgare), also accumulate in Pachysandra terminalis, an evergreen, frost-hardy basal eudicot species. Part of the complex graminan- and levan-type fructans as accumulating in vivo can be produced in vitro by a sucrose:fructan 6-fructosyltransferase (6-SFT) enzyme with inherent sucrose:sucrose 1-fructosyltransferase (1-SST) and fructan 6-exohydrolase side activities. This enzyme produces a series of cereal-like graminan- and levan-type fructans from sucrose as a single substrate. The 6-SST/6-SFT enzyme was fully purified by classic column chromatography. In-gel trypsin digestion led to reverse transcription-polymerase chain reaction-based cDNA cloning. The functionality of the 6-SST/6-SFT cDNA was demonstrated after heterologous expression in Pichia pastoris. Both the recombinant and native enzymes showed rather similar substrate specificity characteristics, including peculiar temperature-dependent inherent 1-SST and fructan 6-exohydrolase side activities. The finding that cereal-type fructans accumulate in a basal eudicot species further confirms the polyphyletic origin of fructan biosynthesis in nature. Our data suggest that the fructan syndrome in P. terminalis can be considered as a recent evolutionary event. Putative connections between abiotic stress and fructans are discussed. PMID:21037113

  11. The physics of frost heave

    NASA Astrophysics Data System (ADS)

    Wettlaufer, J.; Rempel, A.

    2003-04-01

    Frost heave is a process during which the freezing of a water-saturated soil gives rise to the deformation and upward thrust of the ground surface. The phenomenon plays a central role in sculpting the landscape in regions subject to prolonged freezing and it is responsible for damage to engineered structures. Contrary to popular belief, this behaviour is completely unrelated to the density difference between ice and water, but instead is driven by intermolecular forces between ice and soil grains. The rate of heave is controlled by the flow of unfrozen water towards solidification fronts, which take the form of lenses that are parallel to isotherms. As such, the phenomenon of frost heave is common to the thermodynamic phase and fluid mechanical behaviour of most materials near their freezing temperatures. The process requires that the interface between the lens material (ice), and the porous material in which it sits, is wet by the liquid phase at temperatures below its bulk melting temperature. This behaviour is called ``premelting''. We demonstrate the essence of frost heave by examining the conservation conditions over the surface of an ice lens and show how the net effect of the intermolecular forces that promote lens formation and growth can be calculated explicitly. The rate of heave is determined by the water supply through premelted liquid that separates the ice and mineral surfaces --- both as a result of these same intermolecular interactions, and due to the more passive role played by the surface energy of curved interfaces in determining the geometry of the fluid pathways. By examining the physical interactions that take place on these microscopic length-scales we are able to construct predictive models for the initiation and growth of macroscopic ice lenses in consolidated porous media.

  12. Transition of boundary layer flows in the presence of Goertler vortices

    Microsoft Academic Search

    S. H. Winoto; H. T. Low

    1989-01-01

    Transition of boundary layer flows in the presence of longitudinal counter-rotating Goertler vortices was experimentally investigated\\u000a on a concave surface of 1.0 m radius of curvature in a perspex (plexiglass) curved rectangular duct connected to a low speed\\u000a wind tunnel for a free-stream velocity range of 5.7–11.8 m\\/s. Quantitative measurements were carried out using a single sensor\\u000a hot-wire anemometer, while

  13. Frost resistance of recycled aggregate concrete

    Microsoft Academic Search

    Roumiana Zaharieva; François Buyle-Bodin; Eric Wirquin

    2004-01-01

    The research presented in this paper deals with concrete containing building waste recycled as aggregates. The frost resistance is used as a durability indicator. The characteristics of recycled aggregates (RAs) and their impact on the characteristics of RA concrete are presented. Some basic factors concerning the frost resistance of RA concrete as RA content and degree of water saturation are

  14. 6, 1105111066, 2006 Sea ice, frost flowers

    E-print Network

    Paris-Sud XI, Université de

    ACPD 6, 11051­11066, 2006 Sea ice, frost flowers and halogen activation W. R. Simpson et al. Title Chemistry and Physics Discussions First-year sea-ice contact predicts bromine monoxide (BrO) levels better. Simpson (ffwrs@uaf.edu) 11051 #12;ACPD 6, 11051­11066, 2006 Sea ice, frost flowers and halogen activation

  15. 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.

  16. Frost heave induced mechanics of buried pipelines

    SciTech Connect

    Selvadurai, A.P.S. [McGill Univ., Montreal, Quebec (Canada). Dept. of Civil Engineering; Shinde, S.B. [Canada Ltd., Calgary, Alberta (Canada). Engineering Research and Technology Div.

    1993-12-01

    This paper examines the problem of the flexural interaction between a long-distance buried pipeline embedded in a soil medium that experiences differential frost heave. The modeling takes into consideration the interaction at a transition zone between a frozen region and a frost-susceptible region that experiences a time-dependent growth of a frost bulb around the buried pipeline. The heave that accompanies the development of a frost bulb induces the soil-pipeline interaction process. The analysis focuses on the development of a computational scheme that addresses the three-dimensional nature of the soil-pipeline interaction problem, the creep susceptibility of the frozen region, and a prescribed time- and stress-dependent heave in an evolving frost bulb zone. The numerical results presented in the paper illustrate the influence of the heave process and the creep behavior of the frozen soil on the displacements and stresses in the buried pipeline.

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

    SciTech Connect

    Schmit, P. F. [Sandia National Laboratories, MS 1186, P.O. Box 5800, Albuquerque, New Mexico 87185-1186 (United States)] [Sandia National Laboratories, MS 1186, P.O. Box 5800, Albuquerque, New Mexico 87185-1186 (United States); Molvig, Kim; Nakhleh, C. W. [Los Alamos National Laboratory, MS B259, P.O. Box 1663, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, MS B259, P.O. Box 1663, Los Alamos, New Mexico 87545 (United States)

    2013-11-15

    Knudsen layer losses of tail fuel ions could reduce significantly the fusion reactivity of highly compressed cylindrical and spherical targets in inertial confinement fusion (ICF). With the class of magnetized ICF targets in mind, the effect of embedded magnetic fields on Knudsen layer formation is investigated for the first time. The modified energy scaling of ion diffusivity in magnetized hot spots is found to suppress the preferential losses of tail-ions perpendicular to the magnetic field lines to a degree that the tail distribution can be at least partially, if not fully, restored. Two simple threshold conditions are identified leading to the restoration of fusion reactivity in magnetized hot spots. A kinetic equation for tail-ion transport in the presence of a magnetic field is derived, and solutions to the equation are obtained numerically in simulations. Numerical results confirm the validity of the threshold conditions for restored reactivity and identify two different asymptotic regimes of the fusion fuel. While Knudsen layer formation is shown to be suppressed entirely in strongly magnetized cylindrical hot spot cavities, uniformly magnetized spherical cavities demonstrate remnant, albeit reduced, levels of tail-ion depletion.

  18. 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.

  19. Charge transfer in the presence of a layer of trapping centers in semiconductor SiC ionizing radiation detectors

    Microsoft Academic Search

    A. M. Ivanov; E. V. Kalinina; N. B. Strokan

    2008-01-01

    The formation of a response signal in the presence of a layer of trapping centers in semiconductor SiC ionizing radiation\\u000a detectors is considered on the basis of a new model. Since the trapping layer is situated near the detector surface, nuclear\\u000a particles that possess long tracks partly generate a charge behind this layer. Under certain conditions, the proposed model\\u000a leads

  20. Frost flowers in the laboratory: Growth, characteristics, aerosol, and the underlying sea ice

    NASA Astrophysics Data System (ADS)

    Roscoe, H. K.; Brooks, B.; Jackson, A. V.; Smith, M. H.; Walker, S. J.; Obbard, R. W.; Wolff, E. W.

    2011-06-01

    In the laboratory, we have investigated the growth and composition of frost flowers. Their ionic composition has shown little difference from those of field measurements. Young frost flowers grown on sea ice are saline, leading us to speculate that wicking occurs continually during their growth on sea ice. The surface area of frost flowers is only a little larger than the area of ice underneath, consistent with recent field measurements from the Arctic. Time-lapse photography has allowed us to observe the extreme mobility of freshly forming sea ice, at the stage at which the mush has become rather solid, and continuing while the flowers grow. This mobility results in new brine being expelled to the surface, which therefore remains wet. During various stages of frost flower growth, we observed their freshly formed dendritic parts rapidly diminishing in size after contacting the surface, consistent with repeated wicking. Frost flowers proved to be very stable in the presence of wind, such that no aerosol was observed when wind was blown across them in the laboratory chamber. This is consistent with recent field observations of frost flowers coexisting with wind-blown snow.

  1. 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

  2. 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.

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

    SciTech Connect

    Lu Haoyu [Space Science Institute, School of Astronautics, Beihang University, Beijing 100191 (China); Sate Key Laboratory of Space Weather, Chinese Academy of Sciences, Beijing 100190 (China); Cao Jinbin [Space Science Institute, School of Astronautics, Beihang University, Beijing 100191 (China)

    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.

  4. Frost halos from supercooled water droplets.

    PubMed

    Jung, Stefan; Tiwari, Manish K; Poulikakos, Dimos

    2012-10-01

    Water freezing on solid surfaces is ubiquitous in nature. Even though icing/frosting impairs the performance and safety in many processes, its mechanism remains inadequately understood. Changing atmospheric conditions, surface properties, the complexity of icing physics, and the unorthodox behavior of water are the primary factors that make icing and frost formation intriguing and difficult to predict. In addition to its unquestioned scientific and practical importance, unraveling the frosting mechanism under different conditions is a prerequisite to develop "icephobic" surfaces, which may avoid ice formation and contamination. In this work we demonstrate that evaporation from a freezing supercooled sessile droplet, which starts explosively due to the sudden latent heat released upon recalescent freezing, generates a condensation halo around the droplet, which crystallizes and drastically affects the surface behavior. The process involves simultaneous multiple phase transitions and may also spread icing by initiating sequential freezing of neighboring droplets in the form of a domino effect and frost propagation. Experiments under controlled humidity conditions using substrates differing up to three orders of magnitude in thermal conductivity establish that a delicate balance between heat diffusion and vapor transport determines the final expanse of the frozen condensate halo, which, in turn, controls frost formation and propagation. PMID:23012410

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

    SciTech Connect

    Copuroglu, O. [Delft University of Technology, Faculty of CiTG, Micromechanics Laboratory (MICROLAB) (Netherlands)]. E-mail: o.copuroglu@citg.tudelft.nl; Fraaij, A.L.A. [Delft University of Technology, Faculty of CiTG, Materials Science and Sustainable Construction (Netherlands); Bijen, J.M.J.M. [Delft University of Technology, Faculty of CiTG, Materials Science and Sustainable Construction (Netherlands)

    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.

  6. 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-freeze climate zone. During winter a deicer-salt application is needed to melt snow on highways. Freezing in the presence of a deicer salt solution is considered a severe concrete exposure condition. Prolonged exposure

  7. Design of UMTRA covers to mitigate the effect of frost penetration

    SciTech Connect

    Banani, A.M.; Claire, R.F.

    1994-03-01

    The Uranium Mill Tailings Remedial Action (UMTRA) Project, contracted by the US Department of Energy (DOE), requires construction of disposal cells for residual radioactive materials from abandoned uranium mill tailings. A disposal cell consists of contaminated material placed within a stabilized embankment with a top cover. The embankment and cover should be effective for up to 1000 years, to the extent reasonably achievable, and in any case for at least 200 years. The embankment cover usually consists of a radon/infiltration barrier, a frost barrier and erosion protection layer consisting of bedding and riprap layers. The radon/infiltration barrier and frost barrier are two important elements of the cover systems. A radon/infiltration barrier is designed to reduce the radon emissions from the contaminated materials and to limit the surface water infiltration into the contaminated material. However, a radon/infiltration barrier has to be protected from repeated freeze-thaw cycles to prevent an increase in permeability. Frost penetration depth is site specific and depends on local climatic conditions and soil properties of the cover system. However, placing a frost barrier is not only very costly but also reduces the disposal capacity of the embankment. Recent laboratory test results indicate that freeze-thaw cycles do not significantly effect the permeability of compacted sand-bentonite mixtures. Therefore, radon/infiltration barriers using sand-bentonite mixtures may not require frost barriers for protection against the effects of freeze-thaw. In this paper the design of UMTRA covers is briefly explained; the criteria to determine a 200 year freeze event, and the frost penetration depth are discussed. The results of freeze-thaw permeability tests on compacted clay and sand-bentonite mixtures are also presented.

  8. How endangered is sexual reproduction of high-mountain plants by summer frosts? Frost resistance, frequency of frost events and risk assessment.

    PubMed

    Ladinig, Ursula; Hacker, Jürgen; Neuner, Gilbert; Wagner, Johanna

    2013-03-01

    In temperate-zone mountains, summer frosts usually occur during unpredictable cold spells with snow-falls. Earlier studies have shown that vegetative aboveground organs of most high-mountain plants tolerate extracellular ice in the active state. However, little is known about the impact of frost on reproductive development and reproductive success. In common plant species from the European Alps (Cerastium uniflorum, Loiseleuria procumbens, Ranunculus glacialis, Rhododendron ferrugineum, Saxifraga bryoides, S. moschata, S. caesia), differing in growth form, altitudinal distribution and phenology, frost resistance of reproductive and vegetative shoots was assessed in different reproductive stages. Intact plants were exposed to simulated night frosts between -2 and -14 °C in temperature-controlled freezers. Nucleation temperatures, freezing damage and subsequent reproductive success (fruit and seed set, seed germination) were determined. During all reproductive stages, reproductive shoots were significantly less frost resistant than vegetative shoots (mean difference for LT50 -4.2 ± 2.7 K). In most species, reproductive shoots were ice tolerant before bolting and during fruiting (mean LT50 -7 and -5.7 °C), but were ice sensitive during bolting and anthesis (mean LT50 around -4 °C). Only R. glacialis remained ice tolerant during all reproductive stages. Frost injury in reproductive shoots usually led to full fruit loss. Reproductive success of frost-treated but undamaged shoots did not differ significantly from control values. Assessing the frost damage risk on the basis of summer frost frequency and frost resistance shows that, in the alpine zone, low-statured species are rarely endangered as long as they are protected by snow. The situation is different in the subnival and nival zone, where frost-sensitive reproductive shoots may become frost damaged even when covered by snow. Unprotected individuals are at high risk of suffering from frost damage, particularly at higher elevations. It appears that ice tolerance in reproductive structures is an advantage but not an absolute precondition for colonizing high altitudes with frequent frost events. PMID:23386042

  9. 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...

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

    SciTech Connect

    Santos, Sergio [Laboratory of Energy and Nanosciences, Masdar Institute of Science and Technology, P.O. BOX 54224, Abu Dhabi (United Arab Emirates); Barcons, Victor [Departament de Disseny i Programacio de Sistemes Electronics, UPC - Universitat Politecnica de Catalunya Av. Bases, 61, 08242 Manresa (Spain); Verdaguer, Albert [Centre d' Investigacio en Nanociencia i Nanotecnologia (CIN2) (CSIC-ICN), Esfera UAB, Campus de la UAB, Edifici CM-7, 08193-Bellaterra, Catalunya (Spain); Chiesa, Matteo [Laboratory of Energy and Nanosciences, Masdar Institute of Science and Technology, P.O. BOX 54224, Abu Dhabi (United Arab Emirates); Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307 (United States)

    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.

  11. Optical absorption in silicon layers in the presence of charge inversion/accumulation or ion implantation

    SciTech Connect

    Alloatti, L.; Lauermann, M.; Koos, C.; Freude, W. [Institutes IPQ and IMT, Karlsruhe Institute of Technology (KIT), Karlsruhe 76131 (Germany)] [Institutes IPQ and IMT, Karlsruhe Institute of Technology (KIT), Karlsruhe 76131 (Germany); Sürgers, C. [Physikalisches Institut and DFG-Center for Functional Nanostructures, Karlsruhe Institute of Technology, P. O. Box 6980, Karlsruhe 76049 (Germany)] [Physikalisches Institut and DFG-Center for Functional Nanostructures, Karlsruhe Institute of Technology, P. O. Box 6980, Karlsruhe 76049 (Germany); Leuthold, J. [Institutes IPQ and IMT, Karlsruhe Institute of Technology (KIT), Karlsruhe 76131 (Germany) [Institutes IPQ and IMT, Karlsruhe Institute of Technology (KIT), Karlsruhe 76131 (Germany); Institute of Electromagnetic Fields (IFH), ETH Zurich, Zurich (Switzerland)

    2013-07-29

    We determine the optical losses in gate-induced charge accumulation/inversion layers at a Si/SiO{sub 2} interface. Comparison between gate-induced charge layers and ion-implanted thin silicon films having an identical sheet resistance shows that optical losses can be significantly lower for gate-induced layers. For a given sheet resistance, holes produce higher optical loss than electrons. Measurements have been performed at ? = 1550 nm.

  12. Role of growth temperature and the presence of dopants in layer-by-layer plasma deposition of thin microcrystalline silicon (muc-Si:H) doped layers

    Microsoft Academic Search

    A. Gordijn; J. K. Rath; R. E. I. Schropp

    2004-01-01

    Microcrystalline silicon (muc-Si:H) p- and n-type layers have been developed by Layer-by-Layer (LbL) deposition at high temperatures. The LbL deposition consists of alternating boron or phosphorus doped amorphous silicon depositions and hydrogen plasma treatments by Very High Frequency Chemical Vapor Deposition (VHF PECVD). The layers are developed to be resistant to the temperature and hydrogen flux of a micro- of

  13. Role of growth temperature and the presence of dopants in layer-by-layer plasma deposition of thin microcrystalline silicon (?c-Si:H) doped layers

    Microsoft Academic Search

    A. Gordijn; J. K. Rath; R. E. I. Schropp

    2004-01-01

    Microcrystalline silicon (?c-Si:H) p- and n-type layers have been developed by Layer-by-Layer (LbL) deposition at high temperatures. The LbL deposition consists of alternating boron or phosphorus doped amorphous silicon depositions and hydrogen plasma treatments by Very High Frequency Chemical Vapor Deposition (VHF PECVD). The layers are developed to be resistant to the temperature and hydrogen flux of a micro- of

  14. A Gentle Frost: Poet Helen Frost Talks about the Healing Power of Poetry and Her Latest Novel

    ERIC Educational Resources Information Center

    Margolis, Rick

    2006-01-01

    This article presents an interview with poet Helen Frost. Frost talked about how poetry can help at-risk children. She also related the challenges she faced when she wrote her latest book titled "The Braid."

  15. Frost resistance mechanisms in quinoa ( Chenopodium quinoa Willd.)

    Microsoft Academic Search

    S.-E. Jacobsen; C. Monteros; L. J. Corcuera; L. A. Bravo; J. L. Christiansen; A. Mujica

    2007-01-01

    Quinoa (Chenopodium quinoa Willd.) is traditionally grown in the mountain regions of the Andes where frost is common. However, the physiological mechanisms responsible for the frost resistance observed in quinoa are largely unknown. For this reason, a study on cultivars of quinoa originating from the Andean highlands and from the inter-Andean valleys was performed. Frost tolerance was determined by measuring

  16. Frost formation and ice adhesion on superhydrophobic surfaces

    Microsoft Academic Search

    Kripa K. Varanasi; Tao Deng; J. David Smith; Ming Hsu; Nitin Bhate

    2010-01-01

    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 textures without any particular spatial preference. Ice adhesion measurements on superhydrophobic surfaces susceptible to frost formation show increased adhesion over smooth surfaces with a strong linear trend with the total surface area.

  17. PROXIMITY TO CONIFERS MINIMIZES FROST EXPOSURE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In temperate climates, agricultural production is frequently damaged at both ends of the growing season due to episodic radiation frost. During these periods, air temperature is frequently adequate for forage and specialty crop growth. The effect of thermal radiation from conifer tree canopies on ...

  18. Modeling frost heave in freezing soils

    Microsoft Academic Search

    Leonid Bronfenbrener; Regina Bronfenbrener

    2010-01-01

    A generalized model for secondary frost heave in freezing fine-grained soils is presented. The cryostatic suction effect, which causes an increase in upward water permeation, ice-lens growth during freezing, and, as a consequence, the increase of soil heave, is considered to be the main mechanism of moisture transfer. Although the model in this paper has a number of approaches in

  19. 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,…

  20. Latest results from FROST at Jefferson Lab

    SciTech Connect

    Ritchie, Barry G. [Arizona State University

    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.

  1. 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

  2. Optical properties of polyimide layers prepared by vacuum deposition in the presence of gas

    NASA Astrophysics Data System (ADS)

    Strijkova, V.; Danev, G.

    2014-12-01

    Thin polyimide (PI) layers were prepared by simultaneous vacuum evaporation of the polyimide precursors pyromellitic dianhydride (PMDA) and 4,4'-oxydianiline (ODA). After deposition the layers were thermally treated 1 hour at 170°C followed by 1 hour at 250°C. Precursors were deposited in a residual atmosphere of different gases - argon, nitrogen, helium and air at a pressure 10?2 Pa. Conditions for fabrication of PI layers with reproducible composition, uniform and smooth surface, without mechanical and chemical defects have been established. It was found that the preparation conditions do not significantly affect the optical properties of the layers. The PI layers before and after thermal treatments are transparent over 85% in the studied spectral range (from 350 to 900 nm). The thermal treatment leads to a bathochromic shift, in a consequence of the transmission edge shift to the longer wavelengths, for all the samples, independently of the deposition conditions in the vacuum chamber. The average refractive indices at 633 nm varied from 1.67 towards 1.72 depending on the deposition conditions and thermal treatment.

  3. Role of growth temperature and the presence of dopants in layer-by-layer plasma deposition of thin microcrystalline silicon (?c-Si:H) doped layers

    NASA Astrophysics Data System (ADS)

    Gordijn, A.; Rath, J. K.; Schropp, R. E. I.

    2004-06-01

    Microcrystalline silicon (?c-Si:H) p- and n-type layers have been developed by Layer-by-Layer (LbL) deposition at high temperatures. The LbL deposition consists of alternating boron or phosphorus doped amorphous silicon depositions and hydrogen plasma treatments by Very High Frequency Chemical Vapor Deposition (VHF PECVD). The layers are developed to be resistant to the temperature and hydrogen flux of a micro- of polycrystalline intrinsic layer grown at a high deposition rate in a p-i-n or an n-i-p solar cell device. It is concluded that the LbL method is suitable to produce device quality ?c-Si:H p- and n-type doped layers in a temperature range from 250 to 400 °C. This is not possible with standard continuous PECVD employing high hydrogen dilution of silane, where the addition of dopants reduces the crystallinity. An optimum effective thickness per deposition cycle (total thickness divided by the number of cycles) of 1.5 nm/cycle is needed for the crystallization. This optimal effective sub layer thickness is independent of dopants and deposition temperature. However, a minimum thickness of the first layer is needed for a sustaining growth in the LbL process. The doped layers grown by LbL are smoother than reference samples grown by continuous wave (cw). The doping efficiencies in our LbL deposited layers are structurally higher than those in cw deposition (for p layers a doping efficiency of 39% in case of LbL, compared to 1% for cw). The properties of the best high-temperature doped layers are as follows: for LbL p-type ?c-Si:H (Ts=350 °C, 29 nm), activation energy=0.11 eV and dark conductivity=0.1 ?-1 cm-1; for LbL n-type ?c-Si:H (Ts=400 °C, 31 nm), activation energy=0.056 eV and dark conductivity=2.7 ?-1 cm-1. Test solar cells have been deposited using Hot-Wire CVD (HWCVD) and VHF PECVD deposited ?c-Si:H i-layers on top of the high-temperature LbL ?c-Si:H n-type doped layer in an n-i-p configuration on a stainless steel substrate without a back reflector. A high open circuit voltage of 0.56 V and a fill factor of 0.7 show the high doping efficiency and crystallinity of the n-type doped layer and the resistance to the impinging atomic hydrogen during the HWCVD deposition. The mechanism behind the LbL ?c-Si:H growth phenomenon is a controversial subject. We studied the LbL growth and nucleation mechanism as well as the incorporation of dopant atoms in the ?c-Si:H layers. Etching, abstraction, and hydrogen diffusion are analyzed and it is concluded that our observations support the nucleation model that is based on hydrogen diffusion, while chemical transport and epitaxial growth are excluded to be the mechanism behind the crystallization.

  4. The presence of two S-layer-protein-encoding genes is conserved among species related to Lactobacillus acidophilus.

    PubMed

    Boot, H J; Kolen, C P; Pot, B; Kersters, K; Pouwels, P H

    1996-09-01

    Previously we have shown that the type strain of Lactobacillus acidophilus possesses two S-protein-encoding genes, one of which is silent, on a chromosomal segment of 6 kb. The S-protein-encoding gene in the expression site can be exchanged for the silent S-protein-encoding gene by inversion of this slp segment. In this study the presence of S-protein and corresponding S-protein-encoding genes of strains belonging to species that are closely related to L. acidophilus was determined. All strains investigated were identified by numerical comparison of highly standardized one-dimensional SDS-PAGE whole-cellular-protein patterns. Western blot and Southern blot methods were used to identify the presence of, and homology between, S-proteins and S-protein-encoding genes. From these analyses we conclude that strains of L. acidophilus, L. crispatus, L. amylovorus and L. gallinarum possess an S-layer and contain two slp genes. Strains of L. helveticus possess an S-layer but have only one intact slp gene. Strains of L. gasseri, L. johnsonii and L. delbrueckii subsp. bulgaricus have neither an S-layer nor S-protein-encoding genes hybridizing with probes derived from the L. acidophilus slpA or slpB region. The presence of a highly conserved 5' region in the slp genes of strains of L. acidophilus, L. crispatus, L. amylovorus and L. gallinarum suggests that S-layer variation is a common feature for strains of these species. PMID:8828205

  5. Hypersonic boundary-layer transition in the presence of wind-tunnel noise.

    NASA Technical Reports Server (NTRS)

    Stainback, P. C.

    1971-01-01

    Description of additional results indicating that a unique relationship exists between rms sound pressure level and transition Reynolds number, provided all other parameters are held nearly invariant. The results illustrate the different levels of the transition Reynolds numbers obtained in six facilities with nearly invariant laminar boundary layers on the different models (at the same local unit Reynolds number) and indicate that some facility characteristic has a strong influence on the transition Reynolds numbers.

  6. 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.

  7. Epitaxial growth of high quality ?-FeSi 2 layers on Si(1 1 1) under the presence of an Sb flux

    Microsoft Academic Search

    Tsutomu Koga; Hirokazu Tatsuoka; Hiroshi Kuwabara

    2001-01-01

    ?-FeSi2 layers were grown on Si(111) substrates by Fe deposition and simultaneous reaction with Si under the presence of an Sb flux. High quality epitaxial layers were obtained at the substrate temperature of 650°C with smooth interface between the reactive resultant ?-FeSi2 layers and Si substrates, in comparison to the layers grown by conventional reactive deposition epitaxy (RDE). Sb\\/Fe flux

  8. 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.

  9. On the presence of giant particles downwind of ships in the marine boundary layer

    NASA Astrophysics Data System (ADS)

    Sorooshian, Armin; Prabhakar, Gouri; Jonsson, Haflidi; Woods, Roy K.; Flagan, Richard C.; Seinfeld, John H.

    2015-03-01

    This study examines large oceangoing ships as a source of giant cloud condensation nuclei (Dp > 2 µm) due to wake and stack emissions off the California coast. Observed particle number concentrations behind 10 ships exceeded those in "control" areas, exhibiting number concentration enhancement ratios (ERs) for minimum threshold diameters of ~2, ~10, and ~20 µm as high as 2.7, 5.5, and 7.5, respectively. ER decreases with increasing downwind distance and altitude. ER becomes better correlated with ship size variables (gross tonnage, length, and beam) as the minimum size threshold increases from 2 to 20 µm, whereas ship speed has a less distinct relationship with ER. One case study of a container ship shows that there are higher concentrations of sea-salt tracer species behind it relative to adjacent control areas. These results have implications for cloud properties and precipitation in marine boundary layers exposed to ship traffic.

  10. Frost formation and ice adhesion on superhydrophobic surfaces

    NASA Astrophysics Data System (ADS)

    Varanasi, Kripa K.; Deng, Tao; Smith, J. David; Hsu, Ming; Bhate, Nitin

    2010-12-01

    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 textures without any particular spatial preference. Ice adhesion measurements on superhydrophobic surfaces susceptible to frost formation show increased adhesion over smooth surfaces with a strong linear trend with the total surface area. These studies indicate that frost formation significantly compromises the icephobic properties of superhydrophobic surfaces and poses serious limitations to the use of superhydrophobic surfaces as icephobic surface treatments for both on-ground and in-flight applications.

  11. The fluid mechanics of frost heave

    NASA Astrophysics Data System (ADS)

    Rempel, Alan; Wettlaufer, John; Worster, Grae

    2002-11-01

    Frost heave is a process during which the freezing of a water-saturated soil gives rise to the deformation and upward thrust of the ground surface. The phenomenon plays a central role in sculpting the landscape in regions subject to prolonged freezing and it is responsible for damage to engineered structures. Contrary to popular belief, this behavior is completely unrelated to the density difference between ice and water, but instead is driven by intermolecular forces between ice and soil grains. The rate of heave is controlled by the flow of unfrozen water towards solidification fronts, which take the form of lenses that are parallel to isotherms. As such, the phenomenon of frost heave is common to the thermodynamic phase and fluid mechanical behavior of most materials near their freezing temperatures. The process requires that the interface between the lens material (ice), and the porous material in which it sits, is wet by the liquid phase at temperatures below its bulk melting temperature. This behavior is called ``premelting''. We demonstrate the essence of frost heave by examining the conservation conditions over the surface of an ice lens and show how the net effect of the intermolecular forces that promote lens formation and growth can be calculated explicitly. The rate of heave is determined by the water supply through premelted liquid that separates the ice and mineral surfaces --- both as a result of these same intermolecular interactions, and due to the more passive role played by the surface energy of curved interfaces in determining the geometry of the fluid pathways. By examining the physical interactions that take place on these microscopic length-scales we are able to construct predictive models for the initiation and growth of macroscopic ice lenses in consolidated porous media.

  12. 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.

  13. Argon frost continuous cryopump for fusion applications

    SciTech Connect

    Foster, C.A.; McCurdy, H.C.

    1993-12-01

    A cryopumping system based on the snail continuous cryopump concept is being developed for fusion applications under a DOE SBIR grant. The primary pump is a liquid helium cooled compound pump designed to continuously pump and fractionate deuterium/tritium and helium. The D/T pumping stage is a 500 mm bore cryocondensation pump with a nominal pumping speed of 45,000 L/s. It will be continuously regenerated by a snail regeneration by head every 12 minutes. Continuous regeneration will dramatically reduce the vulnerable tritium inventory in a fusion reactor. Operating at an inlet pressure of 1 millitorr, eight of these pumps could pump the projected D/T flow in the ITER CDA design while reducing the inventory of tritium in the pumping system from 630 to 43 grams. The helium fraction will be pumped in a compound argon frost stage. This stage will also operate continuously with a snail regeneration head. In addition the argon spray head will be enclosed inside the snail, thereby removing gaseous argon from the process chamber. Since the cryocondensation stage will intercept over 90% of the D/T/H steam, a purified stream from this stage could be directly reinjected into the plasma as gas or pellets, thereby bypassing the isotope separation system and further simplifying the fuel cycle. Experiments were undertaken in Phase I which demonstrated continuous cryosorption pumping of hydrogen on CO{sub 2} and argon frosts. The pumping system and its relevance to fusion reactor pumping will be discussed.

  14. 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.

  15. Frost formation on an airfoil: A mathematical model 1

    NASA Technical Reports Server (NTRS)

    Dietenberger, M.; Kumar, P.; Luers, J.

    1979-01-01

    A computer model to predict the frost formation process on a flat plate was developed for application to most environmental conditions under which frost occurs. The model was analytically based on a generalized frost thermal conductivity expression, on frost density and thickness rate equations, and on modified heat and mass transfer coefficients designed to fit the available experimental data. The broad experimental ranges reflected by the extremes in ambient humidities, wall temperatures, and convective flow properties in the various publications which were examined served to severely test the flexibility of the model. An efficient numerical integration scheme was developed to solve for the frost surface temperature, density, and thickness under the changing environmental conditions. The comparison of results with experimental data was very encouraging.

  16. 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

    NASA Astrophysics Data System (ADS)

    Eluszkiewicz, Janusz Bronistaw

    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. The projected lifetime of UARS should enable the present analysis to be extended to several SAO cycles.

  17. 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.

  18. Elephants, fire, and frost can determine community structure and composition in Kalahari Woodlands.

    PubMed

    Holdo, Ricardo M

    2007-03-01

    Fire, elephants, and frost are important disturbance factors in many African savannas, but the relative magnitude of their effects on vegetation and their interactions have not been quantified. Understanding how disturbance shapes savanna structure and composition is critical for predicting changes in tree cover and for formulating management and conservation policy. A simulation model was used to investigate how the disturbance regime determines vegetation structure and composition in a mixed Kalahari sand woodland savanna in western Zimbabwe. The model consisted of submodels for tree growth, tree damage caused by disturbance, mortality, and recruitment that were parameterized from field data collected over a two-year period. The model predicts that, under the current disturbance regime, tree basal area in the study area will decline by two-thirds over the next two decades and become dominated by species unpalatable to elephants. Changes in the disturbance regime are predicted to greatly modify vegetation structure and community composition. Elephants are the primary drivers of woodland change in this community at present-day population densities, and their impacts are exacerbated by the effects of fire and frost. Frost, in particular, does not play an important role when acting independently but appears to be a key secondary factor in the presence of elephants and/or fire. Unlike fire and frost, which cannot suppress the woodland phase on their own in this ecosystem, elephants can independently drive the vegetation to the scrub phase. The results suggest that elephant and fire management may be critical for the persistence of certain woodland communities within dry-season elephant habitats in the eastern Kalahari, particularly those dominated by Brachystegia spiciformis and other palatable species. PMID:17489259

  19. Calorimetric Study of Frost Attack During Cement Hardening

    Microsoft Academic Search

    A. Usherov-Marshak; O. Zlatkovski; V. Sopov

    2002-01-01

    This report deals with practical and experimental studies of the effects of frost attack on hardening cement stone and concrete.\\u000a The basic component of concrete, cement stone, is a typical capillary-porous material formed from solid, liquid and gaseous\\u000a phases. The level of knowledge on the effects of frost attack on cement stone and concrete hardening is insufficient, due\\u000a to the

  20. Delayed Frost Growth on Jumping-Drop Superhydrophobic Surfaces

    SciTech Connect

    Boreyko, Jonathan B [ORNL; Collier, Pat [ORNL

    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.

  1. Extension of Humidity Standards to -105° C Frost Point

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    The KRISS low frost-point humidity generator which has been operated by the two-temperature method in the frost-point range from -95° C to -40° C since 2006 is reformed to a two-temperature, two-pressure type, in order to extend the calibration capability to a frost point of -105° C. The temperature and pressure of the saturator were controlled to -95° C and 1 MPa, respectively. The water-vapor mole ratio generated by the upgraded humidity generator reached 4 nmol{\\cdot }mol^{-1} . 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 0.09° C at the frost point of -95° C and is increased to 0.19° C at the frost point of -105° C. The increase in uncertainty is mainly due to the water adsorption/desorption on the internal surface of tubing from the saturator to the hygrometer.

  2. Between-year variation in flowering and fruit set in frost-prone and frost-sheltered populations of dioecious Rubus chamaemorus

    Microsoft Academic Search

    Jon Ågren

    1988-01-01

    The flowering and fruiting patterns of the dioecious perennial herb Rubus chamaemorus L. were studied in frost-prone (open) and frost-sheltered (Shaded) habitats in northern Sweden over 6 years. The number of ramets with flower buds, the proportion of flower buds that opened, and fruit set varied markedly between years. In the frost-prone populations, the occurrence or absence of detrimental frosts

  3. 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.

  4. The material force acting on a screw dislocation in the presence of a multi-layered circular inclusion

    Microsoft Academic Search

    E. Honein; H. Rai; M. I. Najjar

    2006-01-01

    In this paper, we study the interaction of a screw dislocation with a multi-layered interphase between a circularly cylindrical inclusion and a matrix. The layers are coaxial cylinders of annular cross-sections with arbitrary radii and different shear moduli. The number of layers may also be arbitrary. Continuity of traction and displacement across all interfaces is assumed. We extend Honein et

  5. 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.

  6. 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.

  7. General frost growth mechanism on solid substrates with different stiffness.

    PubMed

    Petit, Julien; Bonaccurso, Elmar

    2014-02-01

    Preventing or delaying frost formation on surfaces is of significant importance in many aspects of our daily life. Despite many efforts and improvements recently achieved in the design of new icephobic materials and substrates, not all proposed solutions are universally applicable and frost formation still remains a problem in need of further flexible solutions. In this respect, we propose to take benefit from the tunable viscoelastic properties of soft polymer gel substrates, since they are known to strongly influence the dropwise condensation process of water, and to investigate condensation frosting on them. Using polymer gels with different stiffness and a hard substrate as a reference, we demonstrate their ability to delay frost formation compared to recent results reported in the literature on other solid substrates and in particular on superhydrophobic surfaces. By investigating the frost front propagation we singled out a general behavior of its dynamic evolution consisting of two processes presenting two different time scales. This general growth appears to be independent of experimental conditions as well as substrate stiffness. PMID:24456462

  8. Growth and photoluminescence study of low concentration InP layers grown by liquid-phase epitaxy in the presence of erbium

    SciTech Connect

    Mengchyi Wu; Chengming Chiu (National Tsing Hua Univ., Hsinchu (Taiwan, Province of China). Research Inst. of Electrical Engineering); Yuankuang Tu (Telecommunication Lab., Chung-Li (Taiwan, Province of China). Ministry of Communications)

    1993-10-01

    InP layers with electron concentrations as low as 7 [times] 10[sup 13] cm[sup [minus]3] were grown by liquid-phase epitaxy using rare-earth erbium as the donor-gettering source. The presence of Er during growth causes a decrease in electron concentration and the strong suppression of donor-related luminescence transitions due to the effective removal of residual donors in the growth solution. The exciton-related lines of the low concentration InP layers are observed by using Er as the gettering source.

  9. 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.

  10. Application of photoelectrochemical methods for the characterization of Cu(I) oxide layers modified in the presence of corrosion inhibitors

    Microsoft Academic Search

    F. Ammeloot; C. Fiaud; E. M. M. Sutter

    1997-01-01

    The influence of azole-type corrosion inhibitors (benzotriazole, mercaptobenzothiazole or mercaptobenzoxazole) on the photoelectrochemical behaviour of copper electrodes under open-circuit potential was investigated in a 0.5 M NaCl solution. A correlation between the inhibition efficiency of an inhibitor, the oxide layer thickness, the polarization resistance and the semiconducting properties of the Cu2O layer more or less stabilized by the inhibitor was

  11. 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.

  12. 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.

  13. 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.

  14. Two methods for assessing frost tolerance in flowers of highbush blueberry cultivars

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sensitivity of blueberry flowers to freezing temperatures differs among cultivars and stages of bud development. Also, the frost testing technique and the duration at lethal temperature can have a dramatic effect on bud injury. Artificial frost tests should duplicate the types of spring frosts in ...

  15. Plant responses of quinoa ( Chenopodium quinoa Willd.) to frost at various phenological stages

    Microsoft Academic Search

    S.-E. Jacobsen; C. Monteros; J. L. Christiansen; L. A. Bravo; L. J. Corcuera; A. Mujica

    2005-01-01

    Frost is one of the principal limiting factors for agricultural production in the high Andean region. One of the most important grain crops in that region, quinoa (Chenopodium quinoa Willd.), is generally less affected by frost than most other crop species, but little is known about its specific mechanisms for frost resistance. This study was undertaken to help understand quinoa’s

  16. Free flight determination of boundary layer transition on small scale cones in the presence of surface ablation

    NASA Technical Reports Server (NTRS)

    Wilkins, M. E.; Chapman, G. T.

    1972-01-01

    To assess the possibility of achieving extensive laminar flow on conical vehicles during hyperbolic entry, the Ames Research Center has had an ongoing program to study boundary-layer transition on ablating cones. Boundary layer transition results are presented from ballistic range experiments with models that ablated at dimensionless mass transfer rates comparable to those expected for full scale flight at speeds up to 17 km/sec. It was found possible to measure the surface recession and hence more accurately identify regions of laminar, transitional, and turbulent flow along generators of the recovered cones. Some preliminary results using this technique are presented.

  17. The presence of an iron oxide layer at the enamel\\/steel interface in one-coat porcelain enamelling

    Microsoft Academic Search

    D. Ritchie; H. A. Schaeffer; D. White

    1983-01-01

    The chemical measurement of the iron oxide present in the enamel was not in agreement with the iron oxide content calculated from diffusion profiles. This discrepancy could only be explained by assuming that a layer of iron oxide about 1 µm thick was present at the interface. An examination of the phenomena associated with this type of enamelling, the constant

  18. On Stabilization of Multi-Layer Hele-Shaw and Porous Media Flows in the Presence of Gravity

    E-print Network

    Daripa, Prabir

    of Rayleigh- Taylor instability in our earlier work [Daripa P, 2008, J. Stat. Mech. Article P12005, DOI: 10.1088/1742-5468/2008/12/P12005] on stabilization of multi-layer Saffman-Taylor instability. Fur- thermore, this article goes in comparison to pure Taylor instability; (iii) stabilization of disturbances on interior interfaces instead

  19. Interaction between an edge dislocation and a circular boundary in the presence of an alien surface layer

    Microsoft Academic Search

    Yu. Z. Povstenko

    1975-01-01

    tribution of stresses in the basic material has taken place, the latter being related to the removal of its portion. Then in the initial state the boundary layer remains unstressed and a change in its state is determined by the dislocation displacement from the initial point c 1 to the point c 2. This case simulates to some extent the

  20. 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

  1. RESEARCH ARTICLE Conservation and genetics of the frosted flatwoods salamander

    E-print Network

    Grether, Gregory

    RESEARCH ARTICLE Conservation and genetics of the frosted flatwoods salamander (Ambystoma, salamanders from the northern extent of the species range in South Carolina were not previously available of flatwoods salamanders. The mitochondrial and nuclear results are largely congruent, yielding strong sup

  2. BEST PRACTICES RESEARCH 2014 Frost & Sullivan 1 "We Accelerate Growth"

    E-print Network

    Fisher, Kathleen

    to AT&T. Key Industry Challenges Carrier Ethernet continues to gain acceptance among enterprises, due Business Metro Carrier Ethernet Services United States, 2014 Frost & Sullivan's Global Research Platform and consultants who monitor more than 300 industries and 250,000 companies. The company's research philosophy

  3. FROST-INDUCED CHANGES IN SPECTRAL CHARACTERISTICS OF GRAIN SORGHUM.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Visible and near-infrared spectral properties of grain sorghum (Sorghum bicolor) were observed using wideband and hyperspectral radiometers in Arizona. Field measurements that were taken before and after the later-planted, 1998 crop was damaged by frost, displayed temporal dynamics that were correl...

  4. 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

  5. Forest floor frost dynamics during spring snowmelt in a boreal forested basin

    NASA Astrophysics Data System (ADS)

    Stein, Jean; Proulx, Serge; LéVesque, Denis

    1994-04-01

    A previous study (Prévost et al., 1990) has shown that a lowering in the soil infiltrability index improves hydrograph snowmelt runoff peaks simulation of the Lac Laflamme basin. The hypothesis that explains this phenomenon is as follows: when the snowpack becomes discontinuous or thin during the spring, cold air temperatures during the night (<-10°C) freeze the water at the soil surface. To test this hypothesis, four plots were instrumented to follow the evolution of water table fluctuations, snow cover area, soil and air temperatures, and liquid and total water contents at different levels in the soil. Transect lines were also established to monitor snow depth, percentage of soil free of snow, and presence of basal ice and different types of soil frost (porous or concrete). Our results show that the minimum nightly air temperature of -5°C during snowmelt did not produce soil ice. It was not possible to validate or invalidate the hypothesis. The results of the survey at the basin scale show that concrete frost is prevalent throughout the basin, is associated with forest floors dominated by sphagnum or hypnobryale mosses, and originates from winter meteorological events.

  6. Ion acoustic double layers in the presence of positrons beam and q-nonextensive velocity distributed electrons

    NASA Astrophysics Data System (ADS)

    Ali Shan, S.; Mushtaq, A.; Akhtar, N.

    2013-12-01

    Linear and nonlinear studies are presented for an electron-ion plasma system which is being energized with an external beam of positrons. The electrons are assumed to follow the q-nonextensive velocity distribution. The growth rates of instability due to positron beam are analyzed numerically. The compressive and rarefactive double layers are studied in the system and it is found that by varying the entropic index parameter q, positron beam speed v po and concentration of positrons p, the dynamics of nonlinear profile is changing quite effectively. The relevance of the work regarding to astrophysical space plasma is pointed out.

  7. 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

  8. 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

  9. Selective presence of a giant saccular organelle in the axon initial segment of a subpopulation of layer V pyramidal neurons.

    PubMed

    Antón-Fernández, Alejandro; Rubio-Garrido, Pablo; DeFelipe, Javier; Muñoz, Alberto

    2015-03-01

    Recently it has been shown that a giant saccular organelle (GSO) of unknown function is present in the axon initial segment (AIS) of an uncharacterized population of pyramidal cells of the rodent neocortex. Using tract-tracing methods and immunocytochemistry, in the present study we show that in rodents this GSO is present in the AIS of subpopulations of layer V pyramidal neurons projecting to various subcortical, non-thalamic targets, including the spinal cord. GSO-containing neurons express SMI32 and some of them are under the control of the Thy-1 gene promoter. In addition, our results demonstrate that the GSO expresses the inositol 1,4,5-triphosphate receptor 1 (IP3R1) and the sarco (endo) plasmic reticulum Ca(2+) ATPase 2, both in rodent and human neocortex. These results indicate the involvement of the GSO in the regulation of Ca(2+) levels in the AIS in a particular subpopulation of layer V neurons that give rise to subcortical non-thalamic descending projections. PMID:24363122

  10. Blood-derived macrophage layers in the presence of hydrocortisone support myeloid progenitors in long-term cultures of CD34 + cord blood and bone marrow cells

    Microsoft Academic Search

    J. Clausen; M. Stockschläder; N. Fehse; H. T. Hassan; C. Gabl; A. R. Zander

    2000-01-01

    Monocytes\\/macrophages secrete various cytokines that induce proliferation of colony-forming unit granulocyte-macrophage (CFU-GM)\\u000a in short-term assays. To determine whether macrophages also support proliferation of more primitive progenitors, i.e., cells\\u000a that give rise to colony forming cells in a 5-week long-term culture (LTC), we established plastic-adherent macrophage layers\\u000a from human peripheral blood (PB) and filgrastim (G-CSF)-mobilized progenitor cell collections in the presence

  11. 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., E-mail: Denis.Goldobin@gmail.com; Lyubimov, D. V. [Perm State University (Russian Federation)

    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.

  12. 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.

  13. H2O frost point detection on Mars

    NASA Astrophysics Data System (ADS)

    Ryan, J. A.; Sharman, R. D.

    1981-01-01

    The Viking Mars landers contain meteorological instrumentation to measure wind, temperature, and pressure but not atmospheric water content. The landings occurred during local summer, and it was observed that the nocturnal temperature decrease at sensor height (1.6 m) did not exhibit a uniform behavior at either site. It was expected that the rate of decrease would gradually slow, leveling off near sunrise. Instead, a leveling occurred several hours earlier. Temperature subsequently began a more rapid decrease which slowed by sunrise. This suggested that the temperature sensors may be detecting the frost point of water vapor. Analysis of alternative hypotheses demonstrates that none of these are viable candidates. The frost point interpretation is consistent with other lander and orbiter observations, with terrestrial experience, and with modeling of Mars' atmospheric behavior. It thus appears that the meteorology experiment can help provide a basis toward understanding the distribution and dynamics of Martian water vapor.

  14. Stimulation of Phospholipid Biosynthesis during Frost Hardening of Winter Wheat.

    PubMed

    Willemot, C

    1975-02-01

    Lipids were labeled with (33)P during frost hardening of two varieties of winter wheat (Triticum aestivum), hardy Kharkov and much less hardy Champlein. The main labeled compounds were phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, and phosphatidylglycerol. With time of incorporation the proportion of the radioactivity incorporated into the lipids increased in phosphatidylcholine, especially in Kharkov and at 1 C. During hardening, phospholipid synthesis was greatly stimulated in Kharkov, but much less in Champlein. The proportion of the phospholipids synthesized changed only little with hardening, with a trend towards an increase in phosphatidylcholine. Increased phospholipid synthesis does not seem to be a prerequisite to hardening in winter wheat. However, a high rate of phospholipid synthesis may be required to maintain frost resistance. PMID:16659082

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

    PubMed

    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

  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. Climate Change Shifts Frost Seasons and Plant Growth

    NSDL National Science Digital Library

    This month's issue of Ecology Letters adds new evidence to the effect of climate change on ecosystems. In a paper by Professor of Biology Dr. David Inouye of the University of Maryland, global climate change appears to influence early and late frost events, which in turn, "inhibit growth and possibly damage many plants." This news brief from ScienceDaily.com describes the recent finding and comments on its wider significance.

  18. Developmental presence and disappearance of postsynaptically silent synapses on dendritic spines of rat layer 2/3 pyramidal neurons

    PubMed Central

    Busetto, Giuseppe; Higley, Michael J; Sabatini, Bernardo L

    2008-01-01

    Silent synapses are synapses whose activation evokes NMDA-type glutamate receptor (NMDAR) but not AMPA-type glutamate receptor (AMPAR) mediated currents. Silent synapses are prominent early in postnatal development and are thought to play a role in the activity- and sensory-dependent refinement of neuronal circuits. The mechanisms that account for their silent nature have been controversial, and both presynaptic and postsynaptic mechanisms have been proposed. Here, we use two-photon laser uncaging of glutamate to directly activate glutamate receptors and measure AMPAR- and NMDAR-dependent currents on individual dendritic spines of rat somatosensory cortical layer 2/3 pyramidal neurons. We find that dendritic spines lacking functional surface AMPARs are commonly found before postnatal day 12 (P12) but are absent in older animals. Furthermore, AMPAR-lacking spines are contacted by release-competent presynaptic terminals. After P12, the AMPAR/NMDAR current ratio at individual spines continues to increase, consistent with continued addition of AMPARs to postsynaptic terminals. Our results confirm the existence of postsynaptically silent synapses and demonstrate that the morphology of the spine is not strongly predictive of its AMPAR content. PMID:18202095

  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. 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.

  1. 3D stability analysis of Rayleigh-Bénard convection of a liquid metal layer in the presence of a magnetic field—effect of wall electrical conductivity

    NASA Astrophysics Data System (ADS)

    Dimopoulos, Dimitrios; Pelekasis, Nikos A.

    2014-10-01

    Rayleigh-Bénard stability of a liquid metal layer of rectangular cross section is examined in the presence of a strong magnetic field that is aligned with the horizontal direction of the cross section. The latter is much longer than the vertical direction and the cross section assumes a large aspect ratio. The side walls are treated as highly conducting. Linear stability analysis is performed allowing for three-dimensional instabilities that develop along the longitudinal direction. The finite element methodology is employed for the discretization of the stability analysis formulation while accounting for the electrical conductivity of the cavity walls. The Arnoldi method provides the dominant eigenvalues and eigenvectors of the problem. In order to facilitate parallel implementation of the numerical solution at large Hartmann numbers, Ha, domain decomposition is employed along the horizontal direction of the cross section. As the Hartmann number increases a real eigenvalue emerges as the dominant unstable eigenmode, signifying the onset of thermal convection, whose major vorticity component in the core of the layer is aligned with the direction of the magnetic field. Its wavelength along the longitudinal direction of the layer is on the order of twice its height and increases as Ha increases. The critical Grashof was obtained for large Ha and it was seen to scale like Ha 2 signifying the balance between buoyancy and Lorentz forces. For well conducting side walls, the nature of the emerging flow pattern is determined by the combined conductivity of Hartmann walls and Hartmann layers, cH + Ha -1. When poor conducting Hartmann walls are considered, cH ? 1, the critical eigensolution is characterized by well defined Hartmann and side layers. The side layers are characterized by fast fluid motion in the magnetic field direction as a result of the electromagnetic pumping in the vicinity of the Hartmann walls. Increasing the electrical conductivity of the Hartmann walls was seen to delay the onset of thermal convection, while retaining the above scaling at criticality. Furthermore, for both conducting and insulating Hartmann walls and the entire range of Ha numbers that was examined, there was no tendency for a well defined quasi two-dimensional structure to develop owing to the convective motion in the core. A connection is made between the above findings and previous experimental investigations indicating the onset of standing waves followed by travelling waves as Gr is further increased beyond its critical value.

  2. 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.

  3. Frost Formation Problem in the Development of a Hypersonic Turbojet Engine

    NASA Astrophysics Data System (ADS)

    Fukiba, Katsuyoshi; Sato, Tetsuya; Kobayashi, Hiroaki; Ohkubo, Hidetoshi

    The Japan Aerospace Exploration Agency has developed a hypersonic aircraft flying at Mach 5. A precooled turbojet engine is the candidate of the engine for the hypersonic aircraft. The precooled turbojet engine has a heat exchanger(precooler) which cools the breathed air by using cryogenic propellant, such as liquid hydrogen. The precooler has a problem that frost forms on the cooling tubes of the precooler, and the frost decrease the engine performance. Some approaches to deal with the frost formation problem have employed in the development. In this paper, those approaches are introduced and the results of some fundamental studies about frost are also shown.

  4. Layer-specific gene expression in epileptogenic type II focal cortical dysplasia: normal-looking neurons reveal the presence of a hidden laminar organization

    PubMed Central

    2014-01-01

    Background Type II focal cortical dysplasias (FCDs) are malformations of cortical development characterised by the disorganisation of the normal neocortical structure and the presence of dysmorphic neurons (DNs) and balloon cells (BCs). The pathogenesis of FCDs has not yet been clearly established, although a number of histopathological patterns and molecular findings suggest that they may be due to abnormal neuronal and glial proliferation and migration processes. In order to gain further insights into cortical layering disruption and investigate the origin of DNs and BCs, we used in situ RNA hybridisation of human surgical specimens with a neuropathologically definite diagnosis of Type IIa/b FCD and a panel of layer-specific genes (LSGs) whose expression covers all cortical layers. We also used anti-phospho-S6 ribosomal protein antibody to investigate mTOR pathway hyperactivation. Results LSGs were expressed in both normal and abnormal cells (BCs and DNs) but their distribution was different. Normal-looking neurons, which were visibly reduced in the core of the lesion, were apparently located in the appropriate cortical laminae thus indicating a partial laminar organisation. On the contrary, DNs and BCs, labelled with anti-phospho-S6 ribosomal protein antibody, were spread throughout the cortex without any apparent rule and showed a highly variable LSG expression pattern. Moreover, LSGs did not reveal any differences between Type IIa and IIb FCD. Conclusion These findings suggest the existence of hidden cortical lamination involving normal-looking neurons, which retain their ability to migrate correctly in the cortex, unlike DNs which, in addition to their morphological abnormalities and mTOR hyperactivation, show an altered migratory pattern. Taken together these data suggest that an external or environmental hit affecting selected precursor cells during the very early stages of cortical development may disrupt normal cortical development. PMID:24735483

  5. 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.

  6. Nowcasting in the FROST-2014 Sochi Olympic project

    NASA Astrophysics Data System (ADS)

    Bica, Benedikt; Wang, Yong; Joe, Paul; Isaac, George; Kiktev, Dmitry; Bocharnikov, Nikolai

    2013-04-01

    FROST (Forecast and Research: the Olympic Sochi Testbed) 2014 is a WMO WWRP international project aimed at development, implementation, and demonstration of capabilities of short-range numerical weather prediction and nowcasting technologies for mountainous terrain in winter season. Sharp weather contrasts and high spatial and temporal variability are typical for the region of the Sochi-2014 Olympics. Steep mountainous terrain and an intricate mixture of maritime sub-tropical and Alpine environments make weather forecasting in this region extremely challenging. Goals of the FROST-2014 project: • To develop a comprehensive information resource of Alpine winter weather observations; • To improve and exploit: o Nowcasting systems of high impact weather phenomena (precipitation type and intensity, snow levels, visibility, wind speed, direction and gusts) in complex terrain; o High-resolution deterministic and ensemble mesoscale forecasts in winter complex terrain environment; • To improve the understanding of physics of high impact weather phenomena in the region; • To deliver forecasts (Nowcasts) to Olympic weather forecasters and decision makers and assess benefits of forecast improvement. 46 Automatic Meteorological Stations (AMS) were installed in the Olympic region by Roshydromet, by owners of sport venues and by the Megafon corporation, provider of mobile communication services. The time resolution of AMS observations does not exceed 10 minutes. For a subset of the stations it is even equal to 1 min. Data flow from the new dual polarization Doppler weather radar WRM200 in Sochi was organized at the end of 2012. Temperature/humidity and wind profilers and two Micro Rain Radars (MRR) will supplement the network. Nowcasting potential of NWP models participating in the project (COSMO, GEM, WRF, AROME, HARMONIE) is to be assessed for direct and post-processed (e.g. Kalman filter, 1-D model, MOS) model forecasts. Besides the meso-scale models, the specialized nowcasting systems are expected to be used in the project - ABOM, CARDS, INCA, INTW, STEPS, MeteoExpert. FROST-2014 is intended as an 'end-to-end' project. Its products will be used by local forecasters for meteorological support of the Olympics and preceding test sport events. The project is open for new interested participants. Additional information is available at http://frost2014.meteoinfo.ru.

  7. A mechanism for dieren tial frost heave and its implications for patterned-ground formation

    Microsoft Academic Search

    Rorik A. Peterson; William B. Krantz

    The genesis of some types of patterned ground in- cluding hummocks, frost boils and sorted stone cir- cles has been attributed to dieren tial frost heave (DFH). However, a theoretical model that adequately describes DFH has yet to be developed and validated. In this paper we present a mathematical model for the initiation of DFH, and discuss how variations in

  8. Metal stress consequences on frost hardiness of plants at northern high latitudes: a review and hypothesis

    Microsoft Academic Search

    Kari Taulavuori; M. N. V. Prasad; Erja Taulavuori; Kari Laine

    2005-01-01

    This paper reviews the potential of trace\\/heavy metal-induced stress to reduce plant frost hardiness at northern high latitudes. The scientific questions are first outlined prior to a brief summary of heavy metal tolerance. The concepts of plant capacity and survival adaptation were used to formulate a hypothesis, according to which heavy metal stress may reduce plant frost hardiness for the

  9. 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...

  10. 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...

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

    SciTech Connect

    Wagner, G.H.; Steele, K.F. (Univ. of Arkansas, Fayetteville (United States)); Peden, M.E. (Illinois State Water Survey, Champaign (United States))

    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

  12. Studies on the Frost and Defrost Phenomena on the Surface with Micro Grooves

    NASA Astrophysics Data System (ADS)

    Yoshida, Kenji; Kataoka, Isao; Mizutani, Keiichi; Masuda, Tadashi

    In the present study, we employed the recent micron-order machining technology on the cooling surface and produced the artificial micro-ordered groove pattern. The frost and defrost phenomena on the artificial surface with micro-structure are experimentally investigated. The effects of the groove depth or pattern pitch between grooves on the frost phenomenon were focused. The direct observations of the frost and defrost phenomena on the surface were carried out by using the digital microscope with high spatial resolution. It is cleared that the grooves on the surface strongly affect the frost and defrost phenomena, especially the generation of the super-cooled droplets on the surface, which can be observed at the beginning of cooling. The water drainage after frost melting was also strongly affected by the micro grooves.

  13. 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

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

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

    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.

  15. Activating the microscale edge effect in a hierarchical surface for frosting suppression and defrosting promotion.

    PubMed

    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

  16. 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

  17. 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.

  18. Ecology of Dracophyllum subulatum-dominant heathland on frost flats at Rangitaiki and north Pureora, central North Island, New Zealand

    Microsoft Academic Search

    M. C. Smale

    1990-01-01

    The structure, composition, and dynamics of heathland dominated by Dracophyllum subulatum (monoao) on “frost flats” (plateaus and shallow basins supporting low vegetation and subject to year-round frosts) at proposed Te Papa Ecological Area, Rangitaiki and Waipapa Ecological Area, Pureora, were investigated. Systematic sampling and subsequent classification identified five frost flat and related communities at Rangitaiki, the three minor ones apparently

  19. 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.

  20. Frost-free greenhouse: design and operation considrations for commercial and community management

    SciTech Connect

    Not Available

    1982-03-01

    The following design topics are discussed: a frost-free greenhouse from a kit greenhouse, solving the energy problem, the greenhouse envelope, frost-free thermal analysis, no-cost energy conservation measures, standard insulating materials and techniques, thermal mass, ventilation and cooling systems, heat retention blankets for night insulation, and warm-air destratification. The following operation topics are included: inside the frost-free greenhouse, cost consideration, vegetable crops, ornamental crops, cut flowers, environment and layout, solar specific horticulture, potted plants, pest assault, suppliers of predators and parasites, case studies, and bibliographies. (MHR)

  1. 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.

  2. Ice/frost/debris assessment for space shuttle mission STS-27R, December 2, 1988

    NASA Technical Reports Server (NTRS)

    Katnik, Gregory N.; Higginbotham, Scott A.

    1989-01-01

    An Ice/Frost/Debris assessment was conducted for Space Shuttle Mission STS-27R. Debris inspections of the flight elements and launch pad are performed before and after launch. Ice/frost conditions 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 viewed after launch to identify ice/debris sources and evaluate potential vehicle damage. The Ice/Frost/Debris conditions of Mission STS-27R and their effect on the Space Shuttle Program are documented.

  3. 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.

  4. 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.

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

    E-print Network

    Yang, Jianxin

    2004-09-30

    This dissertation provides a detailed description of the research work completed on fin staged heat exchangers. The effects of staging fin on the frosting performance of heat pump evaporators and the whole heat pump system have been studied...

  6. Mariner 9 observations of the south polar CAP of Mars - Evidence for residual CO2 frost

    NASA Astrophysics Data System (ADS)

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

    1990-02-01

    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.

  7. Climate Change Impacts on Snow and Soil Frost Depth and Duration in Southern Wisconsin, USA

    NASA Astrophysics Data System (ADS)

    Murdock, E. A.; Potter, K. W.

    2013-12-01

    Soil frost plays a critical role in moderating the partitioning of precipitation in cold climates. Frozen soils show reduced infiltration and increased runoff and erosion, and frost can play a significant role in nutrient cycling. Frost formation, in turn, is strongly influenced by air temperature and by the depth of insulating snow cover. Understanding how the interactions between changes in temperature and precipitation impact frost and snow depth is therefore important to predictions of climate change impacts on water resources. We drove the one-dimensional Simultaneous Heat and Water (SHAW) model with a suite of four dynamically downscaled climate models based on the SRES A2 emissions scenario from the North American Climate Change Assessment Program (NARCCAP). Our modeling predicts that frost and snow cover depth and duration will decline in the future period (2041-2069) relative to the historical period (1971-1999) in southern Wisconsin, USA, despite an overall increase in winter precipitation. The magnitude of these declines varies significantly between climate models, however; with mean annual maximum snow depth change varying between -6.6 and -25.6cm, and mean annual maximum frost depth change in silt loam soils varying between -0.3 and -10cm. Frost duration is reduced in silt loam soils from 85-97 days to 44-69 days. Our modeling also shows significant reductions in runoff and increases in recharge during the winter and spring periods. These results are robust across a variety of soil types, and are attributable to the modeled changes in frost depth and duration.

  8. The seasonal course of frost resistance in some New Zealand pteridophytes

    Microsoft Academic Search

    Peter Bannister

    1984-01-01

    The frost resistance of fronds or pinnae of three native ferns (Blechnum penna-marina, Phymatosorus diversifolius, Polystichum vestitum), one introduced fern (Dryopteris filix-mas), and one introduced club-moss (Selaginella kraussiana), grown at low altitude in Dunedin, was examined over a 13-month period. Vegetative material of all species except Dryopteris showed similar patterns with little annual fluctuation and a maximum frost resistance of

  9. Ensemble analysis of frost damage on vegetation caused by spring backlashes in a warmer Europe

    NASA Astrophysics Data System (ADS)

    Jönsson, A. M.; Bärring, L.

    2011-02-01

    Tree dehardening and budburst will occur earlier in a warmer climate, and this could lead to an increased risk of frost damage caused by temperature backlashes. By using a spring backlash index and a cold hardiness model, we assessed different aspects of risk for frost damage in Norway spruce forests during the present climate and for one future emission scenario. Uncertainties associated with climate modelling were quantified by using temperature data from three climate data sets: (1) E-Obs gridded observed climate data, (2) an ensemble of data from eight regional climate models (RCM) forced by ERA-40 reanalysis data, (3) an ensemble of regional climate scenarios produced by the regional climate model RCA3 driven at the boundary conditions by seven global climate models (GCM), all representing the SRES A1B emission scenario. The frost risk was analysed for three periods, 1961-1990, 2011-2040 and 2070-2097. The RCA3_GCM ensemble indicated that the risk for spring frost damage may increase in the boreo-nemoral forest zone of southern Scandinavia and the Baltic states/Belarus. This is due to an increased frequency of backlashes, lower freezing temperatures after the onset of the vegetation period and the last spring frost occurring when the trees are closer to budburst. The changes could be transient due to the fine balance between an increased risk of frost damage caused by dehardening during a period when freezing temperatures are common and a decreased risk caused by warmer temperatures. In the nemoral zone, the zone with highest risk for spring backlashes during the reference period (1961-1990), the spring frost severity may increase due to frost events occurring when the trees are closer to budburst. However, the risk in terms of frequency of backlashes and freezing temperature were projected to become lower already in the beginning of this century.

  10. Preparation of frost atlas using different interpolation methods in a semiarid region of south of Iran

    NASA Astrophysics Data System (ADS)

    Didari, Shohre; Zand-Parsa, Shahrokh; Sepaskhah, Ali Reza; Kamgar-Haghighi, Ali Akbar; Khalili, Davar

    2012-04-01

    In this research, suitability of different kriging and inverse distance weighted ( IDW) methods in estimating occurrence date of frost was evaluated. Data included minimum daily air temperature values from 27 meteorological stations of Fars province in southern Iran from 18 to 45 years. Data ranges of 0 to -1.5, -1.5 to -3 and below -3°C were considered as mild, moderate and severe frost intensities, respectively. Starting with the first day of autumn, iso-occurrence days for the frost intensities and occurrence probabilities (25%, 50%, 75% and 90%) were estimated using ordinary kriging, cokriging, residual kriging type 1 ( RK1), residual kriging type 2 ( RK2), universal kriging and IDW methods. In these models, the errors of estimated frost intensities at different probabilities were lowest in the RK2 model, but lack of establishment of spatial structure due to long distance between stations caused the predictions not to be acceptable in some cases. In a proposed method (modified inverse distance weighted, MIDW), the trend between the first and last days of frost occurrence with earth elevation was removed, and the reminder values were estimated by ( IDW) method. Although, the errors for estimated frost dates by MIDW and RK2 methods were the same, but the MIDW method did not have the spatial establishment shortcoming. Furthermore, the simplicity and practicality of the MIDW method makes it a reasonable selection.

  11. 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

  12. Polar Layers

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Context image for PIA03083 Polar Layers

    This VIS image illlustrates how distinct polar layers appear with no frost cover. This image was collected during the height of summer at the south pole of Mars.

    Image information: VIS instrument. Latitude 80.7S, Longitude 295.6E. 17 meter/pixel resolution.

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

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

  13. Polar Layers

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Context image for PIA03288 Polar Layers

    Late in the summer season, the numerous polar layers are free of frost and easily visible.

    Image information: VIS instrument. Latitude -84.9N, Longitude 135.9E. 17 meter/pixel resolution.

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

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

  14. 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. 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.

  15. Germination and seedling frost tolerance differ between the native and invasive range in common ragweed.

    PubMed

    Leiblein-Wild, Marion Carmen; Kaviani, Rana; Tackenberg, Oliver

    2014-03-01

    Germination characteristics and frost tolerance of seedlings are crucial parameters for establishment and invasion success of plants. The characterization of differences between populations in native and invasive ranges may improve our understanding of range expansion and adaptation. Here, we investigated germination characteristics of Ambrosia artemisiifolia L., a successful invader in Europe, under a temperature gradient between 5 and 25 °C. Besides rate and speed of germination we determined optimal, minimal and maximal temperature for germination of ten North American and 17 European populations that were sampled along major latitudinal and longitudinal gradients. We furthermore investigated the frost tolerance of seedlings. Germination rate was highest at 15 °C and germination speed was highest at 25 °C. Germination rate, germination speed, frost tolerance of seedlings, and the temperature niche width for germination were significantly higher and broader, respectively, for European populations. This was partly due to a higher seed mass of these populations. Germination traits lacked evidence for adaptation to climatic variables at the point of origin for both provenances. Instead, in the native range, seedling frost tolerance was positively correlated with the risk of frosts which supports the assumption of local adaptation. The increased frost tolerance of European populations may allow germination earlier in the year which may subsequently lead to higher biomass allocation--due to a longer growing period--and result in higher pollen and seed production. The increase in germination rates, germination speed and seedling frost tolerance might result in a higher fitness of the European populations which may facilitate further successful invasion and enhance the existing public health problems associated with this species. PMID:24197990

  16. 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

  17. An exact solution of boundary layer flow over a moving surface embedded into a nanofluid in the presence of magnetic field and suction/injection

    NASA Astrophysics Data System (ADS)

    Elbashbeshy, E. M. A.; Emam, T. G.; Abdel-wahed, M. S.

    2014-01-01

    The effects of magnetic field, suction/injection, nanoparticles type, and nanoparticle volume fraction on heat transfer characteristics and mechanical properties of a moving surface embedded into cooling medium consists of water with Cu, Ag or Al2O3 particles are studied. The governing boundary layer equations are transformed to ordinary differential equations containing, suction/injection parameter, magnetic parameter, nanoparticle and volume fraction. These equations are solved analytically. The velocity and temperature profiles within the boundary layer are plotted and discussed in details for various values of the different parameters.

  18. Identification of candidate genes important for frost tolerance in Festuca pratensis Huds. by transcriptional profiling.

    PubMed

    Rudi, Heidi; Sandve, Simen R; Opseth, Lars M; Larsen, Arild; Rognli, Odd Arne

    2011-01-01

    Studies of differential gene expression between cold acclimated (CA) and non-cold acclimated (NA) plants yield insight into how plants prepare for cold stress at the transcriptional level. Furthermore genes involved in the cold acclimation process are good candidate loci for genetic variation in frost tolerance and winter survival. In this study we combine different approaches to try to decode the genetics of cold acclimation and frost tolerance in meadow fescue (Festuca pratensis Huds). An EST library of cold acclimation responsive genes was established by suppression subtractive hybridization (SSH), and a microarray experiment was used to identify gene expression differences between high and low frost tolerance genotypes in response to cold acclimation. Many genes known to be involved in CA in other species were confirmed to be involved in CA in F. pratensis, however, 18% of the ESTs did not show significant homology to any database proteins. Seven genes were found to be differentially expressed (>2-fold) between high and low frost tolerance genotypes. Two of these genes, FpQM and FpTPT, represent interesting candidate genes for frost tolerance in perennial forage grasses. PMID:21421350

  19. Micromechanics models and innovative sensor technologies to evaluate internal-frost damage of concrete

    NASA Astrophysics Data System (ADS)

    Dai, Qingli; Yu, Xiong; Ng, Kenny; Zhou, Jun

    2011-04-01

    Internal-frost damage is one of the major problems affecting the durability of concrete in cold regions. This paper presents micromechanics models and innovative sensor technologies to study the fundamental mechanisms of frost damage in concrete. The crystallization pressure due to ice nucleation with capillary pores is the primary cause of internal-frost damage of concrete. The crystallization pressure of a cylinder pore was formulated using interface energy balance with thermodynamics equations. The obtained crystallization pressure on the pore wall was input for the fracture simulation with the developed Extended Finite Element Model (XFEM). The XFEM fracture simulation on a homogeneous beam sample with a vertical cylinder pore leads to a straight line. The XFEM simulation was also conducted on the generated digital sample. The simulation results were favorable compared with the middle-notched single edge beam bending specimen due to the open-mode fracture behavior in both cases. An innovative Time-Domain Reflectometry (TDR) sensor was developed to nondestructively monitor the freezing process. The experimental data shows that the TDR sensor signals can detect the freezing degree, an important input parameter to micromechanics models. These studies indicate that the developed micromechanics models and TDR sensor techniques can be used by the practitioners to evaluate internal-frost damage of concrete. Future work will incorporate the TDR sensor measurements into micromechanics models to real-time predict the internal-frost damage process in concrete specimens. The predicted freeze-thaw damage process will be verified with acoustic emission detection.

  20. Evaluation of the impact of frost resistances on potential altitudinal limit of trees.

    PubMed

    Charrier, Guillaume; Cochard, Hervé; Améglio, Thierry

    2013-09-01

    Winter physiology of woody plants is a key issue in temperate biomes. Here, we investigated different frost resistance mechanisms on 1-year-old branches of 11 European tree species from November until budburst: (i) frost hardiness of living cells (by electrolyte leakage method), (ii) winter embolism sensitivity (by percentage loss of conductivity: PLC) and (iii) phenological variation of budburst (by thermal time to budburst). These ecophysiological traits were analyzed according to the potential altitudinal limit, which is highly related to frost exposure. Seasonal frost hardiness and PLC changes are relatively different across species. Maximal PLC observed in winter (PLCMax) was the factor most closely related to potential altitudinal limit. Moreover, PLCMax was related to the mean hydraulic diameter of vessels (indicating embolism sensitivity) and to osmotic compounds (indicating ability of living cells to refill xylem conducting elements). Winter embolism formation seems to be counterbalanced by active refilling from living cells. These results enabled us to model potential altitudinal limit according to three of the physiological/anatomical parameters studied. Monitoring different frost resistance strategies brings new insights to our understanding of the altitudinal limits of trees. PMID:24052567

  1. 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 ...

  2. Frost Growth CFD Model of an Integrated Active Desiccant Rooftop Unit

    SciTech Connect

    Geoghegan, Patrick J [ORNL; Petrov, Andrei Y [ORNL; Vineyard, Edward Allan [ORNL; Zaltash, Abdolreza [ORNL; Linkous, Randall Lee [ORNL

    2008-01-01

    A frost growth model is incorporated into a Computational Fluid Dynamics (CFD) simulation of a heat pump by means of a user-defined function in FLUENT, a commercial CFD code. The transient model is applied to the outdoor section of an Integrated Active Desiccant Rooftop (IADR) unit in heating mode. IADR is a hybrid vapor compression and active desiccant unit capable of handling 100% outdoor air (dedicated outdoor air system) or as a total conditioning system, handling both outdoor air and space cooling or heating loads. The predicted increase in flow resistance and loss in heat transfer capacity due to frost build-up are compared to experimental pressure drop readings and thermal imaging. The purpose of this work is to develop a CFD model that is capable of predicting frost growth, an invaluable tool in evaluating the effectiveness of defrost-on-demand cycles.

  3. Predicting Soil Frost and its Response to Climate Change in Northeastern U.S. Forests

    NASA Astrophysics Data System (ADS)

    Wicklein, H. F.; Ollinger, S. V.; Campbell, J.; Frolking, S.

    2007-12-01

    Depth and duration of seasonal snow cover has important effects on temperate forest ecosystems. In the northeastern U.S., recent predictions are that climate warming over the coming century will cause an increase in soil freezing as soils lose the insulation of continuous wintertime snow cover. These studies have also linked soil freezing to elevated nitrate export from soils and streams. In the present study, we used a physically based energy and water exchange model, SHAW (Simultaneous Heat and Water), to predict soil frost and snowpack dynamics at three forested sites in New England: Hubbard Brook (NH), Harvard Forest (MA), and Howland Forest (ME). Results indicate an inverse relationship across all three sites between the depth and duration of the snowpack and soil frost. Simulations were conducted for all three sites with historical weather data for the past 20-40 years, and for future projections (2000-2100) using two different IPCC climate scenarios (A1fi and BI) derived from statistically downscaled GCM simulations. Under both scenarios and at all three sites, SHAW predicted that both the amount of soil frost and the number of extreme soil freezing events will decrease during the 2000-2100 period. In addition, there was no relationship between predicted soil frost, 1966-2000, and observed stream nitrate concentration at Hubbard Brook. These results run counter to existing theories regarding both the impacts of soil frost and the changes that are expected to occur into the future. There was, however, a positive correlation between predicted soil frost and growing season CO2 uptake at Harvard Forest over the 1992-2002 period. This suggests that soil freezing does play an important role in forest biogeochemistry, albeit a different role than that which has been discussed in the literature.

  4. 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.

  5. On the improvement of the efficiency of organic photovoltaic cells by the presence of an ultra-thin metal layer at the interface organic\\/ITO

    Microsoft Academic Search

    Y. Berredjem; J. C. Bernède; S. Ouro Djobo; L. Cattin; M. Morsli; A. Boulmokh

    2008-01-01

    Organic photovoltaic cells based on the multilayers structure, indium tin oxide (ITO)\\/copper-phthalocyanine(CuPc)\\/fullerene(C{60})\\/aluminium tris(8-hydroxyquinoline) (Alq{3})\\/aluminium, have been studied. When an ultra-thin metal layer is deposited onto the surface of the ITO anode the power conversion efficiency of the cells is significantly improved. The improvement depends on the ITO used. These differences have been attributed to the difficulty to control the surface

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

    E-print Network

    Paris-Sud XI, Université de

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

  7. Accuracy of tropospheric and stratospheric water vapor measurements by the cryogenic frost point hygrometer: Instrumental details and observations

    Microsoft Academic Search

    H. Vömel; D. E. David; K. Smith

    2007-01-01

    The cryogenic frost point hygrometer (CFH), currently built at the University of Colorado, is a new balloon borne hygrometer, which is capable of continuously measuring water vapor between the surface and the middle stratosphere. The design is loosely based on the old NOAA\\/CMDL frost point hygrometer, with improved accuracy and a number of significant new features that overcome some limitations

  8. 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

  9. Water frost and ice - The near-infrared spectral reflectance 0.65-2.5 microns

    Microsoft Academic Search

    R. N. Clark

    1981-01-01

    The spectral reflectance of water frost and frost on ice as a function of temperature and grain size is presented with 1-1\\/2% spectral resolution in the 0.65- to 2.5-micron wavelength region. The well-known 2.0-, 1.65-, and 1.5-micron solid water absorption bands are precisely defined along with the little studied 1.25-micron band and the previously unidentified (in reflectance) 1.04-, 0.90-, and

  10. 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.

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

    NASA Astrophysics Data System (ADS)

    Ingersoll, A. P.

    1989-10-01

    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.

  12. Correlation between Cold- and Drought-Induced Frost Hardiness in Winter Wheat and Rye Varieties.

    PubMed

    Cloutier, Y; Siminovitch, D

    1982-01-01

    Exposure of six wheat (Triticum aestivum L.) and one rye (Secale cereale L.) cultivar to 40% relative humidity for 24 hours induced the same degree of freezing tolerance in seedling epicotyls as did cold conditioning for 4 weeks at 2 degrees C.Frost hardiness varietal relationships were the same in desiccation-stressed and cold-hardened seedlings. Drought stress could, therefore, be used as a rapid and simple method for inducing frost hardiness in seedling shoots in replacement of cold conditioning. PMID:16662170

  13. Study of frost growth on heat exchangers used as outdoor coils in air source heat pump systems

    NASA Astrophysics Data System (ADS)

    K P, Sankaranarayanan

    2011-12-01

    Scope and method of study. During winter heating operation, the outdoor coil of a heat pump acts as an evaporator and when the ambient temperature is near freezing, the moisture in the atmospheric air freezes on the coil surface. The frost growth affects the air flow and also adds resistance to heat transfer thus reducing the capacity and the efficiency of the heat pump. An experimental facility is designed and built to test a small scale heat exchanger working in frosting conditions. Tests are carried out using small scale fin-tube and microchannel heat exchanger over a range of glycol inlet temperatures, air velocities and ambient air RH. A semi-empirical frost model based on a scaling approach is developed and applied to both fin-tube heat and microchannel heat exchangers. The model is developed to handle non-uniformities in both refrigerant and air side. The frost model is integrated with a segment-by-segment heat exchanger calculation algorithm and is validated against experimental data. Frost growth model is also incorporated in a quasi-steady state system simulation algorithm. Findings and conclusions. From the experimental study it was observed that the temperature of the surface and air RH affected the rate of frost growth significantly while the air velocity did not have a great influence. It is demonstrated that a dry heat transfer correlation can be used during frost growth period by correctly accounting for frost thickness in the hydraulic diameter calculations. Ignoring the phenomenon of air redistribution was found to result in errors in the range of 20% to 50% in predicted frost thickness. Frost thickness predicted by the frost model is within 5% of the measured values for most of the cases. Frost mass accumulation predicted by the simple model is higher than the measured values due to a uniform thickness assumption in the model. An improved frost model based on 1-D finite volume discretization is also presented which improved the frost mass prediction to within 13% of measured values. The system simulation is validated against experimental results and found to match reasonable well. The discrepancy between simulation and experiments were due to the effects of system transience in the initial stages.

  14. 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.

  15. 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.

  16. Comparative study of direct and indirect evaluations of frost tolerance in barley

    Microsoft Academic Search

    I. T. Prášil; P. Prášilová; P. Ma?ík

    2007-01-01

    The aim of this paper was to compare different field, laboratory and physiological methods for the evaluation of frost tolerance in barley; as well as to show both the possibilities and limitations of these individual methods and approaches. The tolerances of 39 barley cultivars and breeding lines were evaluated by four direct methods (based on the exposure of plants to

  17. 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.

  18. Achieving optimized performance in frost heave protection systems for cryogenic storage vessels

    Microsoft Academic Search

    G. Gross; R. E. Barth; R. A. Hulett; H. Houghton

    2004-01-01

    The need to prevent frost heave and the resultant cracking in foundations of vessels containing natural gas and other cryogenically stored liquids is well known in industry. Most methods of preventing the underneath structure of the vessel from heaving due to freezing require the use of insulation and electric heating. This paper presents today's best practices regarding electric heating system

  19. Frost hardiness vs. growth performance in trembling aspen: an experimental test of assisted migration

    E-print Network

    Hamann, Andreas

    break in populations of trembling aspen, Populus tremuloides Michx., which were observed in a large break, frost risk, leaf senescence, phenology, Populus tremuloides, provenance trial, seed transfer, trembling aspen, Populus tremuloides Michx., is one of the most widespread and genetically diverse tree

  20. The transfer of heat and mass to a vertical plate under frosting conditions 

    E-print Network

    Poth, Louis Joseph

    1960-01-01

    , . 1 con~ veation, the results of several investig;;ti?. n into moisture condeneation md frost formation on a cold surf". ae by fox'oed eonveati. ?n are ~pplioable in p. ;rt to this invos+ig~ti:n, fe . sible ". etho?i f ?m"lysis to be folio???ed...

  1. Frost fatigue and spring recovery of xylem vessels in three diffuse-porous trees in situ.

    PubMed

    Christensen-Dalsgaard, Karen K; Tyree, Melvin T

    2014-05-01

    Frost has been shown to cause frost fatigue (reduced cavitation resistance) in branch segments in the lab. Here, we studied the change in cavitation resistance and percent loss of conductivity (PLC) from fall to spring over 2 consecutive years in three diffuse-porous species in situ. We used the cavitron technique to measure P25 , P50 and P90 (the xylem pressure causing a 25, 50 and 90% conductivity loss) and PLC and stained functioning vessels. Cavitation resistance was reduced by 64-87% (in terms of P50 ), depending on the species and year. P25 was impacted the most and P90 the least, changing the vulnerability curves from s- to r-shaped over the winter in all three species. The branches suffered an almost complete loss of conductivity, but frost fatigue did not necessarily occur concurrently with increases in PLC. In two species, there was a trade-off between conduit size and vulnerability. Spring recovery occurred by growth of new vessels, and in two species by partial refilling of embolized conduits. Although newly grown and functioning conduits appeared more vulnerable to cavitation than year-old vessels, cavitation resistance generally improved in spring, suggesting other mechanisms for partial frost fatigue repair. PMID:24117494

  2. Identification of frost-susceptible recycled concrete aggregates for durability of concrete

    Microsoft Academic Search

    A. Gokce; S. Nagataki; T. Saeki; M. Hisada

    2011-01-01

    Demolished concretes to be recycled show great diversity in property with regard to residual potential of resistance to the environmental effects such as frost action, when they are used in a new concrete as aggregate. There seems to exist no appropriate test method fitting specific characteristics of the recycled concrete aggregates with respect to the fair judgement of their unbound

  3. 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

  4. Frost weathering: Climate control of regolith production and critical zone evolution

    NASA Astrophysics Data System (ADS)

    Anderson, S. P.; Anderson, R. S.; Kelly, P. J.; Tucker, G. E.; Wickert, A.

    2012-04-01

    Rock generally displays greater fracture density and reduced strength near the surface than at depth. Relatively few processes can explain this profile of mechanical damage seen in rock. Motivated by weathered rock profiles measured in Gordon Gulch in the Boulder Creek Critical Zone Observatory (Colorado Front Range, USA), we focus on frost cracking as an important weathering process. We use our measurements to guide a model of frost cracking. Although the modern mean annual ground temperature is ~4°C, it was subzero during Pleistocene glacial times. Frost cracking is therefore a plausible mechanism of rock damage. Rock on north-facing slopes in this high elevation catchment (~2600 m a.s.l.) is more deeply weathered and displays lower tensile strength than rock on south-facing slopes. We present detailed subsurface temperature profile records at sites on both slopes, reaching depths up to 1.5 m, and therefore crossing the mobile regolith - saprolite interface. We augment existing frost cracking models by incorporating daily thermal cycles, snow cover, latent heat, variation in material properties with depth, and limitations imposed by long transport distances for water to the freezing front. The north- and south-facing hillslope asymmetries in critical zone architecture can be explained with differences in mean annual surface temperatures, although moisture differences may also play a role. A temperature-controlled model of rock weathering enables consideration of the effect of climate change on weathered profile development.

  5. 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…

  6. Sunlight penetration through the Martian polar caps - Effects on the thermal and frost budgets

    NASA Technical Reports Server (NTRS)

    Lindner, Bernhard L.

    1992-01-01

    An energy balance model of the seasonal polar caps on Mars is modified to include penetration of solar radiation into and through the ice. Penetration of solar radiation has no effect on subsurface temperature or total frost sublimation if seasonal ice overlies a dust surface. An effect is noted for seasonal ice which overlies the residual polar caps. For the case of an exposed water-ice residual polar cap, the temperature at depth is calculated to be up to several degrees warmer, and the calculated lifetime of seasonal CO2 frost is slightly lower when penetration of sunlight is properly treated in the model. For the case of a residual polar cap which is perennially covered by CO2 frost, the calculated lifetime of seasonal CO2 frost is very slightly increased as a result of sunlight penetration through the ice. Hence, penetration of sunlight into the ice helps to stabilize the observed dichotomy in the residual polar caps on Mars, although it is a small effect.

  7. Sunlight penetration through the Martian polar caps: Effects on the thermal and frost budgets

    NASA Technical Reports Server (NTRS)

    Lindner, Bernhard Lee

    1992-01-01

    An energy balance model of the seasonal polar caps on Mars is modified to include penetration of solar radiation into and through the ice. Penetration of solar radiation has no effect on subsurface temperature or total frost sublimation if seasonal ice overlies a dust surface. An effect is noted for seasonal ice which overlies the residual polar caps. For the case of an exposed water-ice residual polar cap, the temperature at depth is calculated to be up to several degrees warmer and the calculated lifetime of seasonal CO2 frost is slightly lower when penetration of sunlight is properly treated in the model. For the case of a residual polar cap which is perennially covered by CO2 frost, the calculated lifetime of seasonal CO2 frost is very slightly increased as a result of sunlight penetration through the ice. Hence, penetration of sunlight into the ice helps to stabilize the observed dichotomy in the residual polar caps on Mars, although it is a small effect.

  8. Regulatory genes involved in the determination of frost tolerance in temperate cereals

    Microsoft Academic Search

    Gábor Galiba; Attila Vágújfalvi; Chengxia Li; Alexandra Soltész; Jorge Dubcovsky

    2009-01-01

    Recent progress in the characterization of two groups of genes responsible for natural differences in frost tolerance in wheat and barley is reviewed here. The first group includes the vernalization genes that delay flowering until the end of the winter and protect sensitive floral primordia. This process is regulated mainly by differences in the regulatory regions of VRN1 and VRN3

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. Electric Field and Plasma Density Observations of Long Wavelength Structures and Localized Packets of Short Scale Waves Associated with Sporadic-E Layers in the Presence of QP Radar Echoes

    NASA Astrophysics Data System (ADS)

    Pfaff, R. F.; Freudenreich, H.; Kudeki, E.; Larsen, M.

    2006-05-01

    Electric field and plasma density data gathered on sounding rockets launched in the presence of sporadic-E layers and QP radar echoes reveal a complex electrodynamics including both DC parameters and plasma waves detected over a large range of scales. We present results from two different sounding rocket experiments equipped with similar instrumentation which were conducted in the presence of intense QP radar echoes: a NASA sporadic-E investigation launched from Wallops Island, Va., in 1999 and the Japanese "SEEK-2" rocket launched from Uchinoura, Japan in 2002. Electric field data from both experiments reveal the presence of km-scale waves as well as well-defined packets of broadband (10's of meters to meters) irregularities. What is surprising is that in both experiments, neither the large scale nor short scale waves appear to be distinctly organized by the sporadic-E density layer. Data from the NASA rocket revealed large scale structures with wavelengths of 2-4 km and amplitudes of 1-2 mV/m that were most intense in the region of 90-110 km during the downleg trajectory of this flight. The waves were oriented in the NE-SW quadrants. On the other hand, during the SEEK-2 experiment, the electric field data above the sporadic-E layer on the upleg, from 110 km to the rocket apogee of 151 km, revealed a continuous train of distinct, large scale, quasi-periodic structures with wavelengths of 10-15 km that also propagated between the NE-SW quadrants. The electric field structures had typical amplitudes of 3-5 mV/m with some excursions to 8-9 mV/m, and had associated perturbations in the plasma density. The electric field waveforms showed evidence for steepening and/or convergence effects and may have mapped upwards along the magnetic field from the sporadic-E region below. Candidate mechanisms to explain the origin of these structures include the Kelvin-Helmholtz instability and the Es Layer instability. In both cases, the same shear that formed the sporadic-E layer would presumably provide the energy to generate the km-scale structures. Other possibilities include a gravity wave explanation or a combination of these processes. The data suggest that these structures were associated with the lower altitude density striations that were the seat of the QP radar echoes observed simultaneously. The SEEK-2 structures may also have been associated with the mechanism responsible for a well-defined pattern of "whorls" in the neutral wind data that were revealed in a chemical trail released by a second sounding rocket launched 15 minutes later. Well-defined packets of higher frequency (shorter scales < 100 m) broadband waves were also observed in-situ on both rockets, consistent with the observations of intense radar backscatter during the times of each launch. The linear gradient drift instability involving the DC electric field and the vertical plasma gradient is shown to be incapable of driving most, although not all, of the short scale waves observed during each flight. The data suggest that other sources of free energy may have been important factors for wave growth, and we conclude that drift waves associated with winds and horizontal plasma density gradients, as well as thermal or other instabilities, are necessary to explain the short-scale wave generation observed during these sporadic-E encounters.

  14. Rapid induction of frost hardiness in spinach seedlings under salt stress

    Microsoft Academic Search

    Dirk K. Hincha

    1994-01-01

    The frost hardiness of many plant species can be increased by exposing plants to low, non-freezing temperatures. It has been shown that at least in some herbaceous mono- and dicotyledonous species, hardening can also be induced by treating plants with NaCl at otherwise non-hardening temperatures. In the present investigation, the roots of approximately six-week-old spinach (Spinacia oleracea L.) seedlings were

  15. 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.

  16. Spatial distribution and temporal variation of the winter wheat late frost disaster in Henan, China

    Microsoft Academic Search

    Xuefen Zhang; Youfei Zheng; Chunyi Wang; Huailiang Chen; Zhenhe Ren; Chunhui Zou

    2011-01-01

    The winter wheat late frost disaster (WFD) occurs mainly in the Yellow and Huaihe River area, of which Henan Province covers\\u000a the most part. Henan is the major area of wheat production in China, but it is severely hit by the WFD. In this study, we\\u000a construct a WFD index based on the minimum temperature and the winter wheat development

  17. An improved large area-type optical sensor using frosted glass

    Microsoft Academic Search

    Yuhki Kitazono; Shahera Hossain; Lifeng Zhang; Seiichi Serikawa; S. Nakashima

    2010-01-01

    A new area-type optical sensor with position detection function is developed. Area-type optical sensors are used widely today. However it is not cost-effective to develop a large sensor with semiconductor material. In our previous work, an optical sensor with a large sensing area using frosted glass has been developed for easy operating remote controller system. This sensor is low cost,

  18. Balloon borne observations of PSCs, Frost Point, ozone and nitric acid in the north polar vortex

    Microsoft Academic Search

    James M. Rosen; S. J. Oltmans; W. F. Evans

    1989-01-01

    A new balloon borne instrument called a backscattersonde has been used to study Polar Stratospheric Clouds (PSCs) at Alert, NWT (82°N, 61.5°W) during January and February of 1989. These measurements were supplemented with frost point, ozone and nitric acid vapor soundings. Type I PSCs were observed at temperatures and pressures generally consistent with present vapor pressure models of HNOâ\\/HâO condensate,

  19. Penetration of chlorides in hardened concrete during frost salt scaling cycles

    Microsoft Academic Search

    S. Bouteille; T. Fen Chong; M. Dierkens; P. Dangla; N. Moral; S. Boulanger

    2010-01-01

    Sixty samples from three concrete mixes (same components) were prepared and subjected to frost salt scaling cycles. A set of 20 samples from the same mix was tested according to the French standard XP P18-420. Another set was exposed to different chloride concentrations. Different numbers of freeze\\/thaw cycles were applied to the last set. The mass of scaled-off particles follows

  20. 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.

  1. 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.)

  2. Frosted branch angiitis in one eye and impending CRVO in the other: a diagnostic dilemma.

    PubMed

    Kumar, Abiraj; Yangzes, Sonam; Singh, Ramandeep

    2015-01-01

    We present a unique case of frosted branch angiitis in one eye and impending central retinal vein occlusion in other eye of a pregnant woman, which could be an initial manifestation of Behçet's disease. A 28-year-old, 33?weeks pregnant woman presented with sudden diminution of vision in her right eye. Her best-corrected visual acuity was light perception in the right eye and 20/20 in her left eye. The fundus examination revealed frosted branch angiitis in the right eye and impending central retinal vein occlusion in the left eye. After a thorough initial examination, she was administered intravenous methyl prednisolone 1?g once a day for 3?days followed by oral steroids. All extensive work up to find the cause of frosted branch angiitis was negative except for positive human leukocyte antigen B51. Systemic work up was normal. On last follow-up at 6?months, the patient had visual acuity of 20/60 in the right eye and 20/20 in the left eye. Her systemic work up was normal up to follow-up. She still remains a diagnostic dilemma, with Behçet's disease as the closest diagnosis. PMID:26055592

  3. 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.

  4. 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

  5. Frost effects on the microstructure of high strength concrete, and methods for their analysis

    NASA Astrophysics Data System (ADS)

    Kukko, Heikki

    1992-12-01

    The aims of the study are to identify and analyze the applicability of experimental methods through studies of the freeze thaw durability of high strength concretes with different binder compositions and to elucidate the microstructural changes that occur during freeze thaw degradation. The main features of concrete microstructure, existing analysis methods, and main theories of concrete frost resistance are surveyed. Pore and crack properties of concrete were measured by automatic analysis method. Five high strength concrete mixes with various binder compositions and one medium strength concrete were prepared. They were subjected to as many as 1000 freeze thaw cycles, and the defects were studied. Strength loss was used as the basic measure of degradation. Image analysis results can be used in mathematical modeling of strength changes of concrete. Visual optical analysis of thin sections was proved to be a reliable method. Mercury porosimetry results did not give a reliable basis for the estimation of frost crack increase due to ettringite formations in the cracks. Scanning electron microscopy is a valuable tool for detecting the causes of changes found in porosimetric analysis. The principle of critical degree of saturation applies to high strength concrete. The mathematical modeling of strength loss during frost tests can be based on a combined model including changes in total porosity and maximum crack length.

  6. The presence of an autologous marrow stromal cell layer increases glucocerebrosidase gene transduction of long-term culture initiating cells (LTCICs) from the bone marrow of a patient with Gaucher disease.

    PubMed

    Wells, S; Malik, P; Pensiero, M; Kohn, D B; Nolta, J A

    1995-10-01

    Gaucher disease is a lysosomal storage disorder resulting form deficiency of the acid beta-glucosidase, glucocerebrosidase (GC). Allogeneic bone marrow transplantation has been beneficial in the treatment of Gaucher patients. Therefore, this disorder may be an ideal candidate for gene therapy by GC gene transduction of hematopoietic stem cells. We sought to increase the extent of gene transfer into CD34+ cells from the marrow of a Gaucher patient using G1GC, a simple retroviral vector containing a normal human GC cDNA. The ability of autologous stromal support and recombinant cytokines to increase the extent of transduction of colony-forming-cells (CFCs) and long-term culture initiating cells (LTCICs) was assessed. The presence of a stromal layer significantly increased the extent of GC gene transfer into 14-day CFCs, as determined by polymerase chain reaction (PCR) of individual colonies (18.8% with stroma versus 5% without, P < 0.001). Stromal support also increased the extent of transduction of LTCICs (10% with stroma versus 0.83% without, P < 0.001). Non-adherent cells from long-term bone marrow cultures initiated with CD34+ progenitors transduced on autologous stroma had higher levels of GC enzyme activity than cultures initiated with cells transduced without stroma. The percentage of cells which were GC positive by immunohistochemistry was also increased (21.1% with stroma versus 2.7% without, P = 0.0003). The addition of cytokines (IL-3, IL-6 and Steel factor) to the transduction, in the presence of stroma, significantly increased the extent of gene transfer into CFCs but not LTCICs. These studies indicate that the GC gene can be effectively transduced into LTCICs by retroviral vectors in the presence of stroma at levels significant for clinical gene therapy trials in patients with Gaucher disease. PMID:8593601

  7. Genome-wide association mapping of frost tolerance in barley (Hordeum vulgare L.)

    PubMed Central

    2013-01-01

    Background Frost tolerance is a key trait with economic and agronomic importance in barley because it is a major component of winter hardiness, and therefore limits the geographical distribution of the crop and the effective transfer of quality traits between spring and winter crop types. Three main frost tolerance QTL (Fr-H1, Fr-H2 and Fr-H3) have been identified from bi-parental genetic mapping but it can be argued that those mapping populations only capture a portion of the genetic diversity of the species. A genetically broad dataset consisting of 184 genotypes, representative of the barley gene pool cultivated in the Mediterranean basin over an extended time period, was genotyped with 1536 SNP markers. Frost tolerance phenotype scores were collected from two trial sites, Foradada (Spain) and Fiorenzuola (Italy) and combined with the genotypic data in genome wide association analyses (GWAS) using Eigenstrat and kinship approaches to account for population structure. Results GWAS analyses identified twelve and seven positive SNP associations at Foradada and Fiorenzuola, respectively, using Eigenstrat and six and four, respectively, using kinship. Linkage disequilibrium analyses of the significant SNP associations showed they are genetically independent. In the kinship analysis, two of the significant SNP associations were tightly linked to the Fr-H2 and HvBmy loci on chromosomes 5H and 4HL, respectively. The other significant kinship associations were located in genomic regions that have not previously been associated with cold stress. Conclusions Haplotype analysis revealed that most of the significant SNP loci are fixed in the winter or facultative types, while they are freely segregating within the un-adapted spring barley genepool. Although there is a major interest in detecting new variation to improve frost tolerance of available winter and facultative types, from a GWAS perspective, working within the un-adapted spring germplasm pool is an attractive alternative strategy which would minimize statistical issues, simplify the interpretation of the data and identify phenology independent genetic determinants of frost tolerance. PMID:23802597

  8. 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.

  9. 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.

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

    E-print Network

    Yang, Jianxin

    2004-09-30

    the performance of fin-and-tube outdoor coils as well as the whole heat pump system. The objective of the experimental part of this study was to investigate the effects of the staging fin on the frost/defrost performance of heat pump outdoor coils under different... To My Wife vi ACKNOWLEDGEMENTS The research reported in this dissertation was funded by ASHRAE project 1002-TRP and an ASHRAE grant-in-aid for graduate students. The heat pump system and fin staged coils were donated by the Career Corporation. I am...

  11. 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.

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

    SciTech Connect

    Senderovich, Igor [University of Connecticut, Storrs, CT (United States); Morrison, Brian T. [Arizona State University, Tempe, AZ (United States); Dugger, Michael R. [Arizona State University, Tempe, AZ (United States); Ritchie, Barry G. [Arizona State University, Tempe, AZ (United States); Tucker, Ross J. [Arizona State University, Tempe, AZ (United States)

    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.

  13. Effects of chemical reaction, heat and mass transfer on an unsteady mixed convection boundary layer flow over a wedge with heat generation/absorption in the presence of suction or injection

    NASA Astrophysics Data System (ADS)

    Ganapathirao, M.; Ravindran, R.; Momoniat, E.

    2015-02-01

    The purpose of this work is to study the effects of chemical reaction, heat and mass transfer on an unsteady mixed convection boundary layer flow over a vertical wedge with heat generation/absorption in the presence of uniform suction or injection. The fluid is assumed to be viscous and incompressible. The unsteadiness is caused by the time dependent free stream velocity varying arbitrarily with time. Both accelerating and decelerating free stream flows are considered. Non-similar solutions are obtained numerically by using an implicit finite difference scheme in combination with the quasi-linearization technique. Numerical computations are carried out for different values of dimensionless parameters on velocity, temperature and concentration profiles graphically reported in the present study. Also, numerical results are presented for the local skin friction coefficient, the local Nusselt number and the local Sherwood number. Results indicate that the time effect is crucial on velocity, temperature and concentration profiles, and on the local skin friction coefficient, the local Nusselt and Sherwood numbers. The buoyancy assisting force causes overshoot in the velocity profile for lower Prandtl number fluids. Results are compared with previously published work and are found to be in an excellent agreement.

  14. Purafil-filtration prevents the development of ozone-induced frost injury: A potential role for nitric oxide

    NASA Astrophysics Data System (ADS)

    Neighbour, E. A.; Pearson, M.; Mehlhorn, H.

    The relationship between exposure to ozone in the summer and the subsequent development of frost hardiness in the autumn was evaluated in recent experiments with red spruce ( Picea rubens Sarg. Syn. P. rubra). When O 3 was added to air filtered only through charcoal (contaminated with nitric oxide (NO)), frost sensitivity in late autumn was increased as measured by conductivity from electrocyte leakage. However, when O 3 was added to air filtered through charcoal and Purafil (no NO), no enhancement of frost sensitivity was found. A possible explanation of this difference, involving the chain-propagating property of NO in the O 3-initiated oxidation of unsaturated hydrocarbons (HCs), is proposed and discussed. N 2O 5, which was found to be generated at approximately 0.02 moles per mole of O 3 in the first year's experiment, only marginally modified O 3 toxicity.

  15. 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....

  16. 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)…

  17. An investigation of the use of lime as a soil additive to modify the detrimental effects of frost action 

    E-print Network

    Earnest, Clyde Talley

    1959-01-01

    tures of -20 degrees F are recorded each winter causing frost, penetration to a depth of 30 inches. Similar good results were also obtained at the Donner Pass, California, Illinois, and ydssourl. According to a 1 April 1959 press release... with depth into the soil and that short term temperature variations have no effect on the rats of frost heave. ' Por these reasons it was decided to use the (121 freesing compartment of the Kelvinator refrigerator shown in Figure 5 as the cold chamber...

  18. 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.

  19. 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.

  20. Patterns of genetic variation in mountain hemlock ( Tsuga mertensiana (Bong.) Carr.) with respect to height growth and frost hardiness

    Microsoft Academic Search

    Andy Benowicz; Sylvia L’Hirondelle; Yousry A El-Kassaby

    2001-01-01

    Genetic structure (variance among and within populations) and geographic pattern of variations in growth and frost hardiness of mountain hemlock (Tsuga mertensiana (Bong.) Carr.) populations from coastal British Columbia (BC) were examined. Populations fell into two main groups — south coast (16 sources) and north coast (two sources). Height growth of greenhouse grown seedlings was measured during the first growing

  1. 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

  2. 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

  3. Investigations Concerning Cavitation and Frost Fatigue in Clonal 84K Poplar Using High-Resolution Cavitron Measurements.

    PubMed

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

    2015-05-01

    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

  4. 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.…

  5. Frost drought in conifers at the alpine timberline: xylem dysfunction and adaptations.

    PubMed

    Mayr, Stefan; Hacke, Uwe; Schmid, Peter; Schwienbacher, Franziska; Gruber, Andreas

    2006-12-01

    Drought stress can cause xylem embolism in trees when the water potential (psi) in the xylem falls below specific vulnerability thresholds. At the alpine timberline, frost drought is known to cause excessive winter embolism unless xylem vulnerability or transpiration is sufficiently reduced to avoid critical psi. We compared annual courses of psi and embolism in Picea abies, Pinus cembra, Pinus mugo, Larix decidua, and Juniperus communis growing at the timberline vs. low altitude. In addition, vulnerability properties and related anatomical parameters as well as wood density (D(t)) and wall reinforcement (wall thickness related to conduit diameter) were studied. This allowed an estimate of stress intensities as well as a detection of adaptations that reduce embolism formation. At the alpine timberline, psi was lowest during winter with corresponding embolism rates of up to 100% in three of the conifers studied. Only Pinus cembra and Larix decidua avoided winter embolism due to moderate psi. Minor embolism was observed at low altitude where the water potentials of all species remained within a narrow range throughout the year. Within species, differences in psi50 (psi at 50% loss of conductivity) at high vs. low altitude were less than 1 MPa. In Picea abies and Pinus cembra, psi50 was more negative at the timberline while, in the other conifer species, psi50 was more negative at low altitude. Juniperus communis exhibited the lowest (-6.4 +/- 0.04 MPa; mean +/- SE) and Pinus mugo the highest psi50 (-3.34 +/- 0.03 MPa). In some cases, D(t) and tracheid wall reinforcement were higher than in previously established relationships of these parameters with psi50, possibly because of mechanical demands associated with the specific growing conditions. Conifers growing at the alpine timberline were exposed to higher drought stress intensities than individuals at low altitude. Frost drought during winter caused high embolism rates which were probably amplified by freeze-thaw stress. Although frost drought had a large effect on plant water transport, adaptations in hydraulic safety and related anatomical parameters were observed in only a few of the conifer species studied. PMID:17249241

  6. Identification of leaf proteins differentially accumulated during cold acclimation between Festuca pratensis plants with distinct levels of frost tolerance.

    PubMed

    Kosmala, Arkadiusz; Bocian, Aleksandra; Rapacz, Marcin; Jurczyk, Barbara; Zwierzykowski, Zbigniew

    2009-01-01

    Festuca pratensis (meadow fescue) as the most frost-tolerant species within the Lolium-Festuca complex was used as a model for research aimed at identifying the cellular components involved in the cold acclimation (CA) of forage grasses. The work presented here also comprises the first comprehensive proteomic research on CA in a group of monocotyledonous species which are able to withstand winter conditions. Individual F. pratensis plants with contrasting levels of frost tolerance, high frost tolerant (HFT) and low frost tolerant (LFT) plants, were selected for comparative proteomic research. The work focused on the analysis of leaf protein accumulation before and after 2, 8, and 26 h, and 3, 5, 7, 14, and 21 d of CA, using high-throughput two-dimensional electrophoresis, and on the identification of proteins which were accumulated differentially between the selected plants by the application of mass spectrometry. The analyses of approximately 800 protein profiles revealed a total of 41 (5.1%) proteins that showed a minimum of a 1.5-fold difference in abundance, at a minimum of one time point of CA for HFT and LFT genotypes. It was shown that significant differences in profiles of protein accumulation between the analysed plants appeared relatively early during cold acclimation, most often after 26 h (on the 2nd day) of CA and one-half of the differentially accumulated proteins were all parts of the photosynthetic apparatus. Several proteins identified here have been reported to be differentially accumulated during cold conditions for the first time in this paper. The functions of the selected proteins in plant cells and their probable influence on the level of frost tolerance in F. pratensis, are discussed. PMID:19553368

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

    SciTech Connect

    Brunstein, F.C. [Geological Survey, Denver, CO (United States)

    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.

  8. 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.

  9. Results of the radiological survey at 15 Frost Place, Albany, New York

    SciTech Connect

    Espegren, M.L.; Marley, J.L.; Carrier, R.F.

    1987-12-01

    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 15 Frost Place in Albany, New York, was the subject of a radiological investigation initiated July 22, 1986. The residential property consists of a two-story frame house with a separate garage located on a rectangular lot. An asphalt driveway connects the garage 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/ 16 m wide by 33 m deep. Front and rear views of the property are shown. 13 refs., 5 figs., 5 tabs.

  10. Results of the radiological survey at 12 Frost Place, Albany, New York (AL178)

    SciTech Connect

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

    1987-12-01

    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. Radiological surveys were performed at 27 properties by members of the Radiological Survey Activities (RASA) group at Oak Ridge National Laboratory (ORNL) during the period July 13-July 26, 1986. The property at 12 Frost Place in Albany, New York was the subject of a radiological investigation initiated July 22, 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. The lot included in the radiological survey was /approximately/13 m wide by 29 m deep. 13 refs., 5 figs., 5 tabs.

  11. 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

  12. 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

  13. 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.

  14. 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

  15. The design, construction, and instrumentation of a chamber to study heat, mass, and momentum transfer from humid air to metal under conditions of frosting and free convection 

    E-print Network

    Hutchison, James P

    1961-01-01

    THE DESIGN? CONSTRUCTION? AND INSTRUMENTATION OF A CEAMSER TO STUDY HEAT, MASS? AND MOSNTUM TRANSFER FROM HUMID AIR TO METAL UNDER CONDITIONS OF FROSTING AND FREE CONVECTION A Thesis By James P. Hutchison Submitted to the Graduate School..., AND MOMENTUM TRANSFER FROM HUMID AIR TO METAL UNDER CONDITIONS OF FROSTING AND FREE CONVECTION A Thesis By James P. Hutchison Approved as to Style and Content: Chairman of Committee Head of Departm t + gkA4; August 1961 ACKNOWLEDGEMENT S The writer...

  16. Laboratory studies of charged particle erosion of SO2 ice and applications to the frosts of Io

    NASA Technical Reports Server (NTRS)

    Lanzerotti, L. J.; Brown, W. L.; Augustyniak, W. M.; Johnson, R. E.; Armstrong, T. P.

    1982-01-01

    The removal and/or redistribution of SO2 frosts on the surface of the first Galilean satellite, Io, can occur through the erosion of these frosts by the magnetosphere particle environment of the satellite. The energy, species, and temperature dependence of the erosion rates of SO2 ice films by charged particles have been studied in laboratory experiments. Rutherford backscattering and thin film techniques are used in the experiments. The ice temperature is varied between about 10 K and the sublimation temperature. The erosion rates are found to have a temperature-independent and a temperature-dependent regime and to be much greater, for 10-2000 keV ions, than those predicted by the usual sputtering process. The laboratory results are used together with measured magnetosphere particle fluxes in the vicinity of Io to estimate the erosion rates of SO2 ice films from the satellite and implications therefrom on an SO2 atmosphere on Io.

  17. Thaw-Subsidence Measurements in the Circumpolar Active Layer Monitoring (CALM) Program

    NASA Astrophysics Data System (ADS)

    Nelson, F. E.; Shiklomanov, N. I.; Streletskiy, D. A.; Little, J. D.; Maxhitova, G. G.; Hinkel, K. M.

    2007-12-01

    Vertical movement of the ground surface due to frost heave and thaw subsidence is a common phenomenon in permafrost regions. The magnitude of this movement varies both temporally and spatially, owing to interannual climatic variability at the ground surface and to local variations of soil moisture. Because measurements at point locations made using frost/thaw tubes at CALM sites during the 1990s indicated that penetration of thaw into the ice-rich transient layer may not be reflected in records of active-layer thickness, spatial sampling experiments were initiated early in this decade at several sites in Alaska and Russia. Differential Global Positioning Systems (DGPS) technology was employed at sites in the northern Brooks Range Foothills and on the Arctic Coastal Plain of northern Alaska. Traditional theodolite survey methods were used at sites in the European Russian Arctic. The resulting heave/subsidence records, in conjunction with temperature and active-layer measurements, were used to evaluate regional and site-specific factors affecting the spatial and temporal variability of frost heave and subsidence. Heave and settlement show patterns of spatial variation similar to those of active-layer thickness (ALT). Results from all locations indicate a monotonic increase in thaw penetration into the upper ice-rich permafrost during the period of observation. The CALM II (2004-09) measurement protocol accommodates long- term subsidence measurements, and instrumentation is being developed for deployment at most CALM observatories.

  18. Introgression mapping of genes for winter hardiness and frost tolerance transferred from Festuca arundinacea into Lolium multiflorum.

    PubMed

    Kosmala, A; Zwierzykowski, Z; Zwierzykowska, E; Luczak, M; Rapacz, M; Gasior, D; Humphreys, Mw

    2007-01-01

    Genes for winter hardiness and frost tolerance were introgressed from Festuca arundinacea into winter-sensitive Lolium multiflorum. Two partly fertile, pentaploid (2n = 5x = 35) F(1) hybrids F. arundinacea (2n = 6x = 42) x L. multiflorum (2n = 4x = 28) were generated and backcrossed twice onto L. multiflorum (2x). The backcross 1 (BC(1)) and backcross 2 (BC(2)) plants were preselected for high vigor and good fertility, and subsequently, a total of 83 BC(2) plants were selected for winter hardiness after 2 Polish winters and by simulated freezing tests. Genomic in situ hybridization (GISH) was performed on 6 winter-hardy plants selected after the first winter and shown to be significantly (P < 0.05) more frost tolerant than the L. multiflorum control. Among the analyzed BC(2) winter survivors, only diploid (2n = 2x = 14) plants were found. Five plants carried 13 intact L. multiflorum chromosomes and 1 L. multiflorum chromosome with a single introgressed F. arundinacea terminal chromosome segment. The sixth BC(2) winter survivor appeared to be Lolium without any Festuca introgression capable of detection by GISH. A combined GISH and fluorescence in situ hybridization analysis with rDNA probes of the most winter-hardy (after 2 winters) and frost-tolerant BC(2) plant revealed the location of an F. arundinacea introgression on the nonsatellite arm of L. multiflorum chromosome 2, the same chromosome location reported previously as a site for frost tolerance genes in the diploid and winter-hardy species Festuca pratensis. PMID:17621586

  19. Freezing damage and frost tolerance of the photosynthetic apparatus studied with isolated mesophyll protoplasts of Valerianella locusta L.

    PubMed

    Rumich-Bayer, S; Krause, G H

    1986-01-01

    Mesophyll protoplasts were isolated from unhardened and cold-acclimated leaves of Valerianella locusta L. and subjected to freeze-thaw treatment. To evaluate the extent and course of freezing injury, photosynthetic reactions of whole protoplasts and of free thylakoid membranes, liberated from protoplasts by osmotic lysis, were measured. In addition, the integrity of the protoplasts was determined by microscopy. The results reveal an increased frost tolerance of protoplasts isolated from acclimated leaves with respect to all parameters measured. CO2-dependent O2 evolution (representing net photosynthetic CO2 fixation of protoplasts) was the most freezing-sensitive reaction; its inhibition due to freeze-thaw treatment of protoplasts was neither correlated with disintegration of the plasma membrane, nor was it initiated by inactivation of the thylakoid membranes. The frost-induced decline of protoplast integrity was not closely correlated to thylakoid damage either. Freezing injury of the thylakoid membranes was manifested by inhibition of photosynthetic electron transport and photophosphorylation. Both photosystems were affected by freezing and thawing with strongest inhibition occurring in the water-oxidation system or at the oxidizing site of photosystem II. Photophosphorylation responded more sensitively to freezing stress than electron transport, although uncoupling (increased permeability of the thylakoid membranes to protons) was not a conspicuous effect. The data are discussed in relation to freezing injury in leaves and seem to indicate that frost damage in vivo is initiated at multiple sites. PMID:24443212

  20. Development of Fractal Ultra-Hydrophobic Coating Films to Prevent Water Vapor Dewing and to Delay Frosting

    NASA Astrophysics Data System (ADS)

    Quan, Yun-Yun; Jiang, Pei-Guo; Zhang, Li-Zhi

    2014-09-01

    Superhydrophobic films fabricated on copper and aluminum surfaces have potential applications to solve water condensation and frosting problems on chilled ceiling system. The rough surfaces of copper foils obtained by solution immersion method exhibit the existence of fractal structures. The hydrophobicity of copper surfaces is enhanced with fractal structures. The relationship between contact angles (CAs) and the fractal dimensions (FDs) for surface roughness of Cu samples with different etching time is investigated. Moisture condensation and frosting experiments on the two kinds of surfaces are conducted in natural environment under different chilling temperatures. During condensation, micro water condensate droplets drift down the surface like dust floating in the air. Several larger condensate droplets about 1-2 mm appear on the substrates after 3 h condensation. This continuous jumping motion of the condensate will be beneficial in delaying frosting. The results demonstrate that dense nanostructures on copper surfaces are superior to loose lattice-like microstructures on aluminum surfaces for preventing the formation of large droplets condensate and in delaying the icing. The large water droplets of 2-3 mm in diameter that would form on a common metal foil are sharply decreased to dozens of microns and small droplets are formed on a modified surface, which will then drift down like a fog.

  1. QTL analyses and comparative genetic mapping of frost tolerance, winter survival and drought tolerance in meadow fescue (Festuca pratensis Huds.).

    PubMed

    Alm, Vibeke; Busso, Carlos S; Ergon, Ashild; Rudi, Heidi; Larsen, Arild; Humphreys, Michael W; Rognli, Odd Arne

    2011-08-01

    Quantitative trait loci (QTLs) for frost and drought tolerance, and winter survival in the field, were mapped in meadow fescue (Festuca pratensis Huds.) and compared with corresponding traits in Triticeae and rice to study co-location with putatively orthologous QTLs and known abiotic stress tolerance genes. The genomes of grass species are highly macrosyntenic; however, the Festuca/Lolium and Triticeae homoeologous chromosomes 4 and 5 show major structural differences that is especially interesting in comparative genomics of frost tolerance. The locations of two frost tolerance/winter survival QTLs on Festuca chromosome 5F correspond most likely to the Fr-A1 and Fr-A2 loci on wheat homoeologous group 5A chromosomes. A QTL for long-term drought tolerance on chromosome 3F (syntenic with rice 1) support evidence from introgression of Festuca genome segments onto homoeologous Lolium chromosomes (3L) that this genome region is an excellent source of tolerance towards drought stress. The coincident location of several stress tolerance QTL in Festuca with QTL and genes in Triticeae species, notably dehydrins, CBF transcription factors and vernalisation response genes indicate the action of structural or regulatory genes conserved across evolutionarily distant species. PMID:21505831

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

    NASA Astrophysics Data System (ADS)

    VöMel, H.; David, D. E.; Smith, K.

    2007-04-01

    The cryogenic frost point hygrometer (CFH), currently built at the University of Colorado, is a new balloon borne hygrometer, which is capable of continuously measuring water vapor between the surface and the middle stratosphere. The design is loosely based on the old NOAA/CMDL frost point hygrometer, with improved accuracy and a number of significant new features that overcome some limitations of the older instrument. The measurement uncertainty of the new instrument depends on altitude and ranges between less than 4% in the tropical lower troposphere to no more than 10% in the middle stratosphere at 28 km. In the tropopause region the uncertainty is less than 9%. This instrument is used routinely at several sites for validation of satellite measurements and process studies in the upper troposphere and lower stratosphere region. It has proved to be particularly well suited for dehydration observations in the tropical upper troposphere, because the effects of cloud contamination have been significantly reduced. Results of this instrument are compared with the old NOAA/CMDL hygrometer, the Russian Fluorescent Lyman Alpha Stratospheric Hygrometer, the Vaisala RS92, the AURA/MLS satellite instrument, a cloud lidar, the NOAA/CSD frost point hygrometer and the Harvard Lyman-alpha hygrometer, both of the later instruments flown on board the NASA WB-57F high-altitude research aircraft. These comparisons demonstrate the level of accuracy of tropospheric and stratospheric water vapor measurements made by this instrument and point to areas where more research and development are needed.

  3. Frost decreases content of sugars, ascorbic acid and some quercetin glycosides but stimulates selected carotenes in Rosa canina hips.

    PubMed

    Cunja, Vlasta; Mikulic-Petkovsek, Maja; Zupan, Anka; Stampar, Franci; Schmitzer, Valentina

    2015-04-15

    Primary and secondary metabolites of Rosa canina hips were determined by HPLC/MS during ripening and after frost damage. Rose hips were harvested six times from the beginning of September until the beginning of December. Color parameters a*, b* and L* decreased during maturation. Glucose and fructose were the predominant sugars representing up to 92% total sugars, and citric acid was the major organic acid detected in rose hips (constituting up to 58% total organic acids). Total sugar and ascorbic acid content significantly decreased after frost damage; from 42.2 to 25.9g 100g(-1) DW for sugars and from 716.8 to 176.0mg 100g(-1) DW for ascorbic acid. Conversely, ?-carotene and lycopene levels increased in frostbitten rose hips to 22.1 and 113.2mg 100g(-1) DW, respectively. In addition to cyanidin-3-glucoside (highest level in hips was 125.7?g 100g(-1) DW), 45 different phenolic compounds have been identified. The most abundant were proanthocyanidins (their levels amounted up to 90% of total flavanol content) and their content showed no significant differences during maturation. The levels of catechin, phloridzin, flavanones and several quercetin glycosides were highest on the first three sampling dates and decreased after frost. Antioxidant capacity similarly decreased in frostbitten rose hips. Total phenolic content increased until the third sampling and decreased on later samplings. PMID:25768262

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

    SciTech Connect

    Feldman, W. C. (William C.); Boynton, W. V. (William V.); Prettyman, T. H. (Thomas H.); Kelly, N.; Maurice, S. (Sylvestre)

    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 .

  5. 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.

  6. 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.

  7. Penetration of chlorides in hardened concrete during frost salt scaling cycles

    NASA Astrophysics Data System (ADS)

    Bouteille, S.; Chong, T. Fen; Dierkens, M.; Dangla, P.; Moral, N.; Boulanger, S.

    2010-06-01

    Sixty samples from three concrete mixes (same components) were prepared and subjected to frost salt scaling cycles. A set of 20 samples from the same mix was tested according to the French standard XP P18-420. Another set was exposed to different chloride concentrations. Different numbers of freeze/thaw cycles were applied to the last set. The mass of scaled-off particles follows a lognormal distribution. Despite high standard deviation, this scaling test enables to separate high resistant from very low resistant concrete. A combined analysis reveals that the scaling and the chloride penetration front are independent from a phenomenological point of view and that the chloride concentration on the exposed surface directly influences the amount of scaled mass according to the typical pessimum effect. These results raise two main questions: is the amount of chloride on the surface solution a direct or indirect parameter and what happens to this pessimum effect if we take into account the scaling test dispersion?

  8. 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

  9. Fine-scale distribution of soil organic carbon associated with diapirs in the frost boils of a High Arctic polar desert.

    NASA Astrophysics Data System (ADS)

    Guy, Amanda; Lamb, Eric; Siciliano, Steven

    2014-05-01

    Polar deserts make up approximately a quarter of the ice-free Arctic region in Canada. Previous work on polar deserts suggests that carbon redistributed to depth via cryoturbation, leaching and root inputs may enrich subsurface soils with soil organic carbon (SOC). Given, arctic soils are sensitive to climate warming and contain nearly fifty percent of global terrestrial carbon stocks, understanding the SOC distribution in these landscapes is important. Diapirs are areas of uplifted parent material above the permafrost table that are associated with patterned ground such as frost boils. These diapirs might be an important feature in polar deserts as they are overlain with a Bhy soil horizon enriched in soil organic carbon (SOC) that may provide important resources for plants growing on the surface. We used a field-portable visible and near-infrared (vis-NIR) range spectrometer to detect SOC, indicative of the diapir Bhy horizon, in the subsurface soil profile of frost boils (n= 559). To better understand the fine-scale variability of SOC distribution, we collected spectra of the soil profile using a fine scale 3 x 3 sample grid on a subset of frost boils with (n= 12) and without (n= 12) diapirs detected. Profile spectra were analyzed for SOC using a calibration model developed in Unscrambler® X v.10.2 that was based on partial least squares regression and a calibration dataset for polar deserts. We found that SOC varied with depth between frost boils and enhanced SOC at depth indicative of diapirs occurred on approximately 17% of frost boils. The distribution of SOC within the fine scale grids was extremely variable and also differed between frost boils. These results provide a promising sign that better prediction of carbon distribution in frost boils can made using vis-NIR spectroscopy.

  10. 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

    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

  11. Frost hardiness in walnut trees (Juglans regia L.): how to link physiology and modelling?

    PubMed

    Charrier, Guillaume; Poirier, Magalie; Bonhomme, Marc; Lacointe, André; Améglio, Thierry

    2013-11-01

    In the literature, frost hardiness (FH) studies in trees have often been restricted to one organ (buds, leaves, needles or twigs). To extend our knowledge and gain a unified view, FH differences between organs and tissues or throughout the life of the tree have to be characterized in relation to physiological changes. In this study, different organs and tissues of young potted and mature orchard walnut trees (Juglans regia L.) were compared for seasonal changes in FH during different years. FH was assessed using the electrolyte leakage method. Physiological parameters were concomitantly monitored focusing on two significant traits: water content (WC) and carbohydrate content (glucose + fructose + sucrose, GFS). No seasonal variation in FH was observed in the root system, but acclimation and deacclimation were observed aboveground. Among organs and tissues, cold sensitivity levels were different in deep winter, with buds most sensitive and bark most resistant, but acclimation/deacclimation dynamics followed similar patterns. Physiological variation was also similar among organs: FH increased when WC decreased and/or soluble carbohydrates increased. Based on these results, relations between soluble carbohydrate content, WC and FH were calculated independently or in interaction. The key results were that: (i) the relationship between FH and physiological parameters (GFS and WC), which had previously been shown for branches only, could be generalized to all aboveground organs; (ii) lower WC increased the cryoprotective effect of GFS, showing a synergic effect of the two factors; (iii) the best fit was a non-linear function of WC and GFS, yielding a predictive model with an root mean square error of 5.07 °C on an independent dataset and 2.59 °C for the most sensitive stages; and (iv) the same parameters used for all organs yielded a unified model of FH depending on physiology, although the variability of GFS or WC was wide. The model should be of value for predicting FH in walnut independently of previous growing conditions (i.e., after sublethal stress accumulation). PMID:24271086

  12. 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

  13. 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.

  14. Comparisons of temperature, pressure and humidity measurements by balloon-borne radiosondes and frost point hygrometers during MOHAVE 2009

    NASA Astrophysics Data System (ADS)

    Hurst, D. F.; Hall, E. G.; Jordan, A. F.; Miloshevich, L. M.; Whiteman, D. N.; Leblanc, T.; Walsh, D.; Vömel, H.; Oltmans, S. J.

    2011-07-01

    We compare coincident, balloon-borne, in situ measurements of temperature and pressure by two radiosondes (Vaisala RS92, Intermet iMet-1-RSB) and measurements of relative humidity (RH) by Vaisala RS92 sondes and frost point hygrometers. Data from a total of 28 balloon flights with mixed payloads are analyzed in 1-km altitude bins to quantify measurement biases between sensors and how they vary with altitude. The disparities between sensors determined here are compared to measurement uncertainties quoted by the two radiosonde manufacturers. Our comparisons expose several flight profiles with anomalously large measurement differences. Excluding these anomalous profiles, 33 % of RS92-iMet median temperature differences exceed the uncertainty limits calculated from manufacturer-quoted uncertainties. A statistically significant, altitude-independent bias of about 0.5 ± 0.2 °C is revealed for the RS92-iMet temperature differences. Similarly, 23 % of RS92-iMet median pressure differences exceed the quoted uncertainty limits, with 83 % of these excessive differences above 16 km altitude. The pressure differences are altitude dependent, increasing from -0.6 ± 0.9 hPa at the surface to 0.7 ± 0.1 hPa above 15 km. Temperature and pressure differences between redundant RS92 sondes on the same balloon exceed manufacturer-quoted reproducibility limits 20 % and 2 % of the time, respectively, with most of the excessive differences belonging to anomalous difference profiles. Relative humidity measurements by RS92 sondes are compared to other RS92 sondes and to RH values calculated using frost point hygrometer measurements and coincident radiosonde temperature measurements. For some flights the RH differences are anomalously large, but in general are within the ±5 % RH measurement uncertainty limits quoted for the RS92. The quantitative effects of RS92 and iMet pressure and temperature differences on frost point-based water vapor mixing ratios and RH values, respectively, are also presented.

  15. Proteins Involved in Distinct Phases of Cold Hardening Process in Frost Resistant Winter Barley (Hordeum vulgare L.) cv Luxor

    PubMed Central

    Hlavá?ková, Iva; Vítámvás, Pavel; Šantr??ek, Ji?í; Kosová, Klára; Zelenková, Sylva; Prášil, Ilja Tom; Ovesná, Jaroslava; Hynek, Radovan; Kodí?ek, Milan

    2013-01-01

    Winter barley is an economically important cereal crop grown in higher latitudes and altitudes where low temperatures represent an important environmental constraint limiting crop productivity. In this study changes in proteome of leaves and crowns in a frost tolerant winter barley cv. Luxor in relation to short and long term periods of cold followed by a brief frost treatment were studied in order to disclose proteins responsible for the cold hardening process in distinct plant tissues. The mentioned changes have been monitored using two dimensional difference gel electrophoresis (2D-DIGE) with subsequent peptide-mapping protein identification. Regarding approximately 600–700 distinct protein spots detected on 2D gels, there has been found at least a two-fold change after exposure to low temperatures in about 10% of proteins in leaves and 13% of proteins in crowns. Protein and nitrogen metabolic processes have been influenced by low temperature to a similar extent in both tissues while catabolism, carbohydrate metabolism and proteins involved in stress response have been more affected in crowns than in leaves. The range of changes in protein abundance was generally higher in leaves and chloroplast proteins were frequently affected which suggests a priority to protect photosynthetic apparatus. Overall, our data proved existence of slightly different response strategies to low temperature stress in crowns and leaves, i.e., tissues with different biological role. Moreover, there have been found several proteins with large increase in accumulation, e.g., 33 kDa oxygen evolving protein of photosystem II in leaves and “enhanced disease susceptibility 1” in crowns; these proteins might have potential to indicate an enhanced level of frost tolerance in barley. PMID:23584021

  16. Ground Water and Frost Induced Seismic Velocity Changes in Ketzin (Germany)

    NASA Astrophysics Data System (ADS)

    Gassenmeier, Martina; Sens-Schönfelder, Christoph; Korn, Michael

    2014-05-01

    The principle of Seismic Interferometry (SI) is that the correlation of a random wave field like seismic noise recorded by distant receivers can be used to infer the Green function (or at least part of it) of the medium between the receivers. Beside tomographic inversion for the subsurface velocity it can also be used to detect small temporal changes in the propagation of the seismic wave field. As these changes can be related to changes of elastic properties in the propagation medium, SI can characterize dynamic processes in the earth's crust. This technique was successfully applied, inter alia, to monitor seasonal variations in response to environmental influences, shaking caused by earthquakes or material changes due to the eruption of volcanoes. We work with data acquired with a seismic network in Ketzin (Brandenburg, Germany), where CO2 is injected into a saline aquifer at a depth of about 650 m. We calculated daily cross-correlation functions (CCFs) of the ambient noise field for a time period of about 4 years from the beginning of the injection. Spectra showed that the frequency band between 1 and 3.5 Hz does neither show an annual periodicity (like for microseism) nor temporal shifts of peak frequencies. For this frequency band we estimated the noise propagation direction over two years and found a predominant direction from north-east. This direction matches with the location of a large wind park a few km away from the array. The direction of the noise wave field shows a good stability, which excludes variations of the noise source distribution as a cause of spurious velocity variations. To analyze possible velocity changes for each day, we computed stretched versions of a reference CCF and calculated correlation values between different time windows in the coda part of the stretched traces and the reference trace. We can observe velocity variations with a period of approx. one year that are not caused by the CO2 injection. Due to the almost continuous injection of CO2 we would expect a monotonic decrease of the seismic velocities if caused by the CO2. Based on an amplitude decrease when using time windows in the later part of the coda, we show that the variations must be generated in the shallow subsurface. A comparison to ground water level data reveals a direct correlation between the depth of the ground water level and the seismic velocity. The influence of ground frost on the seismic velocities is documented in a sharp increase of velocity when the maximum daily temperature does not exceed 0°C.

  17. Aggregate-cement paste transition zone properties affecting the salt-frost damage of high-performance concretes

    SciTech Connect

    Cwirzen, Andrzej; Penttala, Vesa

    2005-04-01

    The influence of the cement paste-aggregate interfacial transition zone (ITZ) on the frost durability of high-performance silica fume concrete (HPSFC) has been studied. Investigation was carried out on eight non-air-entrained concretes having water-to-binder (W/B) ratios of 0.3, 0.35 and 0.42 and different additions of condensed silica fume. Studies on the microstructure and composition of the cement paste have been made by means of environmental scanning electron microscope (ESEM)-BSE, ESEM-EDX and mercury intrusion porosimetry (MIP) analysis. The results showed that the transition zone initiates and accelerates damaging mechanisms by enhancing movement of the pore solution within the concrete during freezing and thawing cycles. Cracks filled with ettringite were primarily formed in the ITZ. The test concretes having good frost-deicing salt durability featured a narrow transition zone and a decreased Ca/Si atomic ratio in the transition zone compared to the bulk cement paste. Moderate additions of silica fume seemed to densify the microstructure of the ITZ.

  18. Color and albedo of the south polar layered deposits on Mars

    NASA Astrophysics Data System (ADS)

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

    1990-02-01

    Five color/albedo units, including polar frost, have been recognized and mapped in the southern layered deposits on Mars. Atmospheric dust scattering was measured in shadows and modeled in order to remove the component of brightness in Mars images due to the atmosphere and quantify the albedo and color of the surface. The layered deposits appear to be mantled by red dust, except where eolian stripping has exposed the underlying bedrock. Dark material has been deposited in topographic depressions in much of the south polar region, including the layered deposits. The available observational data suggest that the layered deposits are composed of bright dust, ice, and a small amount of dark material. If the dark material is sand, a periodic change in polar winds seems required in order to transport the sand poleward into the layered terrain. In any case, the observations are not consistent with the layered deposits being composed only of bright dust and ice.

  19. Frost-related dieback of willows. Comparison of epiphytically and endophytically isolated bacteria from different Salix clones , with emphasis on ice nucleation activity, pathogenic properties and seasonal variation

    Microsoft Academic Search

    M. A. Cambours; P. Nejad; U. Granhall; M. Ramstedt

    2005-01-01

    Swedish Salix plantations for biomass production have been suffering severe dieback during the past 10 years, possibly due to the combination of frost and bacterial disease. As opposed to summer and winter, spring and autumn are periods when epiphytic populations of ice nucleation active (INA) bacteria are generally high.The culturable bacterial floras from stems of diseased plants of four Salix

  20. 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

  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 .

    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, Australia We present a brief summary of some nucleosynthesis calculations for 6 M fi stellar models. Theoretical studies are desperately needed to quantify the nucleosynthesis which occurs in intermediate mass

  2. 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.

  3. Is the frosted elfin a fire evader? Pupa location and heat tolerance in fire prone habitats of the Southern Coastal Plain

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The imperiled frosted elfin butterfly, Callophrys irus Godart, is restricted to frequently disturbed habitats where its larval host plants, Lupinus perennis L. and Baptisia tinctoria (L.) R. Br. occur. C. irus pupae are noted to reside in both leaf litter and soil, which may allow them to escape dir...

  4. 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

  5. Differences in leaf proteome response to cold acclimation between Lolium perenne plants with distinct levels of frost tolerance.

    PubMed

    Bocian, Aleksandra; Kosmala, Arkadiusz; Rapacz, Marcin; Jurczyk, Barbara; Marczak, ?ukasz; Zwierzykowski, Zbigniew

    2011-07-15

    Perennial ryegrass (Lolium perenne) is a high quality forage and turf grass mainly due to its excellent nutritive values and rapid establishment rate. However, this species has limited ability to perform in harsh winter climates. Though winter hardiness is a complex trait, it is commonly agreed that frost tolerance (FT) is its main component. Species growing in temperate regions can acquire FT through exposure to low, non-lethal temperatures, a phenomenon known as cold acclimation (CA). The research on molecular basis of FT has been performed on the model plants, but they are not well adapted to extreme winter climates. Thus, the mechanisms of cell response to low temperature in winter crops and agronomically important perennial grasses have yet to be revealed. Here, two L. perenne plants with contrasting levels of FT, high frost tolerant (HFT) and low frost tolerant (LFT) plants, were selected for comparative proteomic research. The work focused on analyses of leaf protein accumulation before and after 2, 8, 26 h, and 3, 5, 7, 14 and 21 days of CA, using a high-throughput two-dimensional electrophoresis, and on the identification of proteins which were accumulated differentially between the selected plants by the application of mass spectrometry (MS). Analyses of 580 protein profiles revealed a total of 42 (7.2%) spots that showed at a minimum of 1.5-fold differences in protein abundance, at a minimum of at one time point of CA between HFT and LFT genotypes. It was shown that significant differences in profiles of protein accumulation between the analyzed plants appeared most often on the 5th (18 proteins) and the 7th (19 proteins) day of CA. The proteins derived from 35 (83.3%) spots were successfully identified by the use of MS and chloroplast proteins were shown to be the major group selected as differentially accumulated during CA. The functions of the identified proteins and their probable influence on the level of FT in L. perenne are discussed. PMID:21489653

  6. Earth's Layers

    NSDL National Science Digital Library

    Mrs. Walls

    2011-01-30

    Complete a poster all about Earth's Layers! Directions: Make a poster about Earth's Layers. (20 points) Include at least (1) large picture (15 points) on your poster complete with labels of every part (10 points). (15 points) Include at least three (3) facts about Earth's Layers. (5 points each) (15 points) Write at least a three sentence summary of your poster ...

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

    PubMed

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

    2013-04-01

    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

  8. Federal Government Presence in

    E-print Network

    deYoung, Brad

    Federal Government Presence in Newfoundland and Labrador November 2005 #12;I. Introduction. John's Government of Newfoundland and Labrador Local Media General Public #12;Our Focus The Federal in Federal involvement in the provinces over time Statistics Canada Newfoundland Statistics Agency

  9. Emerin presence in platelets.

    PubMed

    Squarzoni, S; Sabatelli, P; Capanni, C; Petrini, S; Ognibene, A; Toniolo, D; Cobianchi, F; Zauli, G; Bassini, A; Baracca, A; Guarnieri, C; Merlini, L; Maraldi, N M

    2000-09-01

    Emerin is an almost ubiquitous protein which is abnormal in X-linked Emery-Dreifuss muscular dystrophy (EMD), a syndrome characterized by muscle weakness, joint contractures and cardiac arrhythmia. Emerin is localized in the cells at the nuclear rim and its function is still unknown. In some models, emerin has also been described in the cytoplasm; however, its presence outside the nucleus is still matter of debate. We report the presence of emerin in circulating normal human platelets and its absence in platelets from X-linked EMD patients. Since platelets are cytoplasmic fragments derived from megakaryocytes, the presence of emerin in platelets confirms cytoplasmic localization of this protein, probably related to specific functions. We found also that emerin is present in the cytoplasm of megakaryocytes, while it is absent in circulating granulocytes. PMID:10965799

  10. 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.

  11. Seasonal frost tolerance of some ornamental, indigenous New Zealand plant species in the genera Astelia, Dicksonia, Leptospermum, Metrosideros, Phormium, Pittosporum, and Sophora

    Microsoft Academic Search

    I. J. Warrington; C. J. Stanley

    1987-01-01

    The frost hardiness temperature (i.e., the temperature that causes damage) and the lethal temperature (i.e., the temperature that causes death) were assessed in autumn (April-May), winter (July), spring (October), and summer (January) for 10 native plant species. The species in order of increasing winter hardiness\\/lethal temperature were Metrosideros kermadecensis and M. carminea ( — 3\\/ — 5°C), Sophora tetraptera and

  12. 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).

  13. 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.

  14. Sugar-free frosting, a homolog of SAD kinase, drives neural-specific glycan expression in the Drosophila embryo.

    PubMed

    Baas, Sarah; Sharrow, Mary; Kotu, Varshika; Middleton, Meg; Nguyen, Khoi; Flanagan-Steet, Heather; Aoki, Kazuhiro; Tiemeyer, Michael

    2011-02-01

    Precise glycan structures on specific glycoproteins impart functionalities essential for neural development. However, mechanisms controlling embryonic neural-specific glycosylation are unknown. A genetic screen for relevant mutations in Drosophila generated the sugar-free frosting (sff) mutant that reveals a new function for protein kinases in regulating substrate flux through specific Golgi processing pathways. Sff is the Drosophila homolog of SAD kinase, which regulates synaptic vesicle tethering and neuronal polarity in nematodes and vertebrates. Our Drosophila sff mutant phenotype has features in common with SAD kinase mutant phenotypes in these other organisms, but we detect altered neural glycosylation well before the initiation of embryonic synaptogenesis. Characterization of Golgi compartmentation markers indicates altered colocalization that is consistent with the detected shift in glycan complexity in sff mutant embryos. Therefore, in analogy to synaptic vesicle tethering, we propose that Sff regulates vesicle tethering at Golgi membranes in the developing Drosophila embryo. Furthermore, neuronal sff expression is dependent on transcellular signaling through a non-neural toll-like receptor, linking neural-specific glycan expression to a kinase activity that is induced in response to environmental cues. PMID:21205799

  15. Digital image sensor-based assessment of the status of oat (Avena sativa L.) crops after frost damage.

    PubMed

    Macedo-Cruz, Antonia; Pajares, Gonzalo; Santos, Matilde; Villegas-Romero, Isidro

    2011-01-01

    The aim of this paper is to classify the land covered with oat crops, and the quantification of frost damage on oats, while plants are still in the flowering stage. The images are taken by a digital colour camera CCD-based sensor. Unsupervised classification methods are applied because the plants present different spectral signatures, depending on two main factors: illumination and the affected state. The colour space used in this application is CIELab, based on the decomposition of the colour in three channels, because it is the closest to human colour perception. The histogram of each channel is successively split into regions by thresholding. The best threshold to be applied is automatically obtained as a combination of three thresholding strategies: (a) Otsu's method, (b) Isodata algorithm, and (c) Fuzzy thresholding. The fusion of these automatic thresholding techniques and the design of the classification strategy are some of the main findings of the paper, which allows an estimation of the damages and a prediction of the oat production. PMID:22163940

  16. Digital Image Sensor-Based Assessment of the Status of Oat (Avena sativa L.) Crops after Frost Damage

    PubMed Central

    Macedo-Cruz, Antonia; Pajares, Gonzalo; Santos, Matilde; Villegas-Romero, Isidro

    2011-01-01

    The aim of this paper is to classify the land covered with oat crops, and the quantification of frost damage on oats, while plants are still in the flowering stage. The images are taken by a digital colour camera CCD-based sensor. Unsupervised classification methods are applied because the plants present different spectral signatures, depending on two main factors: illumination and the affected state. The colour space used in this application is CIELab, based on the decomposition of the colour in three channels, because it is the closest to human colour perception. The histogram of each channel is successively split into regions by thresholding. The best threshold to be applied is automatically obtained as a combination of three thresholding strategies: (a) Otsu’s method, (b) Isodata algorithm, and (c) Fuzzy thresholding. The fusion of these automatic thresholding techniques and the design of the classification strategy are some of the main findings of the paper, which allows an estimation of the damages and a prediction of the oat production. PMID:22163940

  17. 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.

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

    NASA Technical Reports Server (NTRS)

    Zent, A. P.; Sizemore, H. G.; Remple, 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 excavated by Phoenix. The leading 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 metabolize and grow down to temperatures of at least 258 K.

  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. 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.

  1. 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.

  2. 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.

  3. Layered Liquids

    NSDL National Science Digital Library

    John Eichinger

    2009-05-30

    This activity involves an exploration of density. Why does oil float on water? How does drain cleaner sink down into the clogged pipe right through standing water? These questions will be answered as students make a layered "parfait" of colored liquids ba

  4. Photoelectrochemistry of strained-layer and lattice-matched superlattice electrodes: Effects due to buffer layers

    Microsoft Academic Search

    Arthur J. Nozik; B. R. Thacker; J. A. Turner; M. W. Peterson

    1988-01-01

    Strained-layer and lattice-matched superlattice electrodes have been studied and compared as photoelectrodes in photoelectrochemical cells, and the effects of the presence of buffer layers in the strained-layer systems have been established. Photocurrent spectroscopy and photomodulated reflectance spectroscopy of superlattice electrodes, etched superlattice electrodes, and buffer layer structures reveal that highly strained superlattices (1.8% mismatch) have poorly defined quantization effects in

  5. Measuring Presence in Virtual Environments: A Presence Questionnaire

    Microsoft Academic Search

    Bob G. Witmer; Michael J. Singer

    1998-01-01

    The effectiveness of virtual environments (VEs) has often been linked to the sense of presence reported by users of those VEs. (Presence is defined as the subjective experi- ence of being in one place or environment, even when one is physically situated in another.) We believe that presence is a normal awareness phenomenon that requires directed attention and is based

  6. An investigation of the heat and mass transfer by free convection from humid air to a horizontal metal plate under frosting conditions

    E-print Network

    Bell, Bobby

    1967-01-01

    doing student labor, 1s greatly appreciated. Others who have donated the1r own time and labor and. deserve thanks are Mr. Roy Gibson, Mr. A. M. Gaddis, Mr. A. B. Alter, and Dr. J. G. H. ~son. To all of those directly connected and to many others who... of refrigerant Diffusion coefficient of the condensing species Local acceleration due to gravity Grains of water vapor FL/MQ L/I I/f 2 Thermal convection coefi'icient oi' frost-air interface, defined by Newton's Iaw for Convective Cooling, h ~ q...

  7. An investigation of the heat and mass transfer by free convection from humid air to a horizontal metal plate under frosting conditions 

    E-print Network

    Bell, Bobby

    1967-01-01

    ~ 7 1. 00 . 727 0. 0 0. 0 0. 0 TOP BOTI'OM TEMPERATURE AND CONCENTRATION PROFILES FOR A FIAT HORIZONTAL PLATE UNUER FROSTING CONUITIONS TABLE 4 - RUN 3 SET No. T os F TEMPERATURE PROFI LES -36. 93 46. 49 5. 27 47. 85 -2. 96 40. 60 27. 40... 0. 488 . 068 Top . 089 Bot . 141 Top , 151 Bot . 215 Top . 154 Bot . 228 Top . 154 Bot 2. 222 1. 866 0 953 0. 578 119. 3 128. 8 114. 3 115. 5 . 64 . 51 ~ 35 ~ 25 1. 13 . 210 . 01 , 210 ? . 22 . 210 -. 18 . 210 GENERAL DATA...

  8. Polar Layers

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA02153 Polar Layers

    This image of the south polar region shows layered material. It is not known if the layers are formed yearly or if they form over the period of 10s to 100s of years or more.

    Image information: VIS instrument. Latitude -80.3N, Longitude 296.2E. 17 meter/pixel resolution.

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

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

  9. Computer Simulations of the Electric Double Layer

    Microsoft Academic Search

    André G. Moreira; Roland R. Netz

    2004-01-01

    We describe the Lekner-Sperb summation technique used to calculate the Coulomb interaction in 2D periodic systems, and discuss in detail the methods used to perform computer simulations of counterions close to charged objects (electric double layer). We focus on three situations where the double layer is formed: (1) when a wall with smeared out surface charge is in the presence

  10. Computer Simulations of the Electric Double Layer

    Microsoft Academic Search

    André Moreira; Roland Netz

    We describe the Lekner–Sperb summation technique used to calculate the Coulomb interaction in 2D periodic systems, and discuss in detail the methods used to perform computer simulations of counterions close to charged objects (electric double layer). We focus on three situations where the double layer is formed: (1) when a wall with smeared out surface charge is in the presence

  11. Stably stratified boundary layer over longitudinal ridges

    Microsoft Academic Search

    L. Falcomer; V. Armenio; G. C. Carnevale

    2003-01-01

    It is well known that a boundary layer (BL) developing over a topography behaves very differently from an analogous, plane BL. On the other hand, in geophysical applications topographic effects are often predominant. We analyze the turbulent boundary layer developing over a longitudinally-ridged wall in presence of stable stratification. The analysis is performed numerically, using large eddy simulation (LES). A

  12. 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.

  13. 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

  14. 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

  15. Fabrication and anti-frosting performance of super hydrophobic coating based on modified nano-sized calcium carbonate and ordinary polyacrylate

    NASA Astrophysics Data System (ADS)

    Wang, Hao; Tang, Liming; Wu, Xiaomin; Dai, Wantian; Qiu, Yipeng

    2007-09-01

    Nano-sized calcium carbonate (CaCO 3) particles were modified by heptadecafluorodecyl trimethoxysilane under acidic water condition. An ordinary polyacrylate prepared via radical copolymerization of methyl methacrylate, butyl acrylate, acrylic acid and ?-hydroxyethyl methacrylate was used as the binder to form hydrophobic coatings with the modified CaCO 3. Super hydrophobic coating with water contact angle of 155° was obtained from modified CaCO 3 and the polyacrylate at their weight ratio of 8/2 by a simple procedure. Based on surface analysis by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS), the super hydrophobicity can be attributed to both the surface microstructure and surface enrichment of fluoroalkyl chains. Due to a low water sliding angle, carbon black powder on super hydrophobic surface was easily removed by rolling water droplet. Furthermore, the anti-frosting performance of different surfaces was investigated, which indicated that the frost formed on superhydrophobic surface was greatly retarded compared with that on bare copper surface. The surface kept super hydrophobicity even after freezing-thawing treatment for 10 times.

  16. Presence Management and Merging Presence Information for NGN Services

    NASA Astrophysics Data System (ADS)

    Schumann, Sebastian; Mikoczy, Eugen; Podhradsky, Pavol; Muruchi, Feliciano; Maruschke, Michael

    This paper describes an approach for interworking scenarios between Session Initiation Protocol (SIP) based and non SIP based frameworks (e.g. web services) in case of the presence management service. The characteristics of the concept of a centralized presence management will be introduced.

  17. Inference of Polymer Adsorption from Electrical Double Layer Measurements : the Silver Iodide-Polyvinyl Alcohol System

    Microsoft Academic Search

    L. K. Koopal

    1978-01-01

    The purpose of this study was to investigate how the double layer properties of charged particles are modified by the presence of adsorbed polymer molecules and to obtain information on the conformation of the polymer layer from the observed alterations in the double layer properties.In chapter 1. the use of double layer investigations to obtain insight in the adsorbed layer

  18. Becquerel Layers

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-350, 4 May 2003

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows layered sedimentary rock outcrops in Becquerel Crater of western Arabia Terra. These materials were deposited in the crater some time in the distant past, and later eroded to their present form. They probably consist of fine-grained sediments; they could have been deposited directly from dust and/or volcanic ash settling out of the martian atmosphere, or silt and sand settling to the floor of an ancient lake. The image does not provide enough information to distinguish between the two possibilities. The picture is located near 21.5oN, 8.1oW. Sunlight illuminates the scene from the lower left.

  19. Polar Layers

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Context image for PIA03581 Polar Layers

    This image shows just one example of the bright and dark markings that appear during summer time. The marks are related to the polar layers. If you happen to see a wild-eyed guy sticking his tongue out at you, you'll know why this image qualifies for the old 'art' category of THEMIS releases.

    Image information: VIS instrument. Latitude 80.6S, Longitude 34.1E. 17 meter/pixel resolution.

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

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

  20. Titan's planetary boundary layer structure at the Huygens landing site

    Microsoft Academic Search

    Tetsuya Tokano; Francesca Ferri; Giacomo Colombatti; Teemu Mäkinen; Marcello Fulchignoni

    2006-01-01

    Huygens Atmospheric Structure Instrument (HASI) for the first time performed an in situ measurement of the thermal structure in Titan's atmosphere with a vertical resolution sufficient to analyze the planetary boundary layer (PBL). The vertical potential temperature profile reveals the presence of a weakly convective PBL, with a surface layer thickness of 10 m and an outer layer with a

  1. Long-term investigations on the water budget quantities predicted by the hydro-thermodynamic soil vegetation scheme (HTSVS) – Part I: Description of the model and impact of long-wave radiation, roots, snow, and soil frost

    Microsoft Academic Search

    N. Mölders; U. Haferkorn; J. Döring; G. Kramm

    2003-01-01

    Summary ¶An earlier version of HTSVS was further developed to numerically investigate the long-term evolution of water budget elements (water supply to the atmosphere, ground water recharge, change in storage) in climate studies. In doing so, parameterizations of root effects, infiltration, soil frost, and snow insulation were included into HTSVS to predict these water budget elements for a period of

  2. Descending Layer Variability Over Arecibo

    NASA Technical Reports Server (NTRS)

    Earle, G. D.; Bishop, R. L.; Collins, S. C.; Gonzalez, S. A.; Sulzer, M. P.

    2000-01-01

    Descending layers of ionization over Arecibo exhibit very diverse behavior from night to night that does not appear to be strongly correlated to geomagnetic activity, solar forcing, or average semidiurnal tidal winds. On some nights, three or more distinct layers are observed to form near 170 km over timescales of approx. 2 hours. Rather than descending smoothly over periods of several hours, these layers stall, abruptly disappear, or even reverse direction in the midst of their descent. The time scales for their disappearance are examined and compared to loss rates arising from diffusion and recombination. Diffusion alone is found to be too slow to account for the observations, but recombination is fast enough provided that the convergent wind shear that forms the layer is relatively weak coincident with their disappearance. The continuity equation is solved in conjunction with a time sequence of radar profiles to estimate the vertical drift and horizontal neutral wind consistent with the observed behavior. The resultant wind field is northward, has an average speed of approx. 80 m/ s, and varies significantly near the altitude where the layers are observed. These inferred winds are consistent with the presence of the observed layers, and their magnitudes as obtained from the classical continuity and momentum equations are reasonable for this altitude range.

  3. Layered Fan

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA03692 Layered Fan

    This beautiful fan deposit is located at the end of a mega-gully that empties into the southern trough of Coprates Chasma.

    Image information: VIS instrument. Latitude -14.9N, Longitude 299.8E. 17 meter/pixel resolution.

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

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

  4. 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.

  5. Incorporation of copper into indium gallium selenide layers from solution

    Microsoft Academic Search

    C. J. Hibberd; M. Ganchev; M. Kaelin; K. Ernits; A. N. Tiwari

    2008-01-01

    A chemical method for the incorporation of copper into indium gallium selenide (IGS) layers has been developed. The resulting copper-containing precursor layers have been annealed in the presence of selenium vapour with the goal of forming Cu(In, Ga)Se2 (CIGS) layers. It is found that copper ions in solution are incorporated into IGS layers during immersion, resulting in the formation of

  6. 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.

  7. Dynamic magnetization states of a spin valve in the presence of dc and ac currents: Synchronization, modification, and chaos

    E-print Network

    Li, Charles

    valve consists of a pinned layer whose magneti- zation is fixed at x axis and a single-domain free layerDynamic magnetization states of a spin valve in the presence of dc and ac currents: Synchronization and numerical calculations of dynamic magnetization states of a spin valve in the presence of dc and ac currents

  8. Connections Transport Layer

    E-print Network

    Ramkumar, Mahalingam

    layer Processes - application layer Could be connection oriented or connectionless Example - TCP, connection oriented UDP - connectionless Ramkumar TL #12;Services Connections TCP UDP Connection Oriented

  9. Federal Presence in Newfoundland and

    E-print Network

    deYoung, Brad

    Federal Presence in Newfoundland and Labrador Dr. James Feehan Professor of Economics September 14 Enterprises employment #12;Figure 7 Federal Government Employment Newfoundland and Labrador, 1981-2005 0 2 04 05 Year NumberofPeople #12;Figure 9 Federal Government Employment in Newfoundland & Labrador

  10. Receptivity of the compressible mixing layer.

    SciTech Connect

    Barone, Matthew Franklin; Lele, Sanjiva K. (Stanford University, Stanford, CA)

    2004-06-01

    Receptivity of compressible mixing layers to general source distributions is examined by a combined theoretical/computational approach. The properties of solutions to the adjoint Navier-Stokes equations are exploited to derive expressions for receptivity in terms of the local value of the adjoint solution. The result is a description of receptivity for arbitrary small-amplitude mass, momentum, and heat sources in the vicinity of a mixing-layer flow, including the edge-scattering effects due to the presence of a splitter plate of finite width. The adjoint solutions are examined in detail for a Mach 1.2 mixing-layer flow. The near field of the adjoint solution reveals regions of relatively high receptivity to direct forcing within the mixing layer, with receptivity to nearby acoustic sources depending on the source type and position. Receptivity 'nodes' are present at certain locations near the splitter plate edge where the flow is not sensitive to forcing. The presence of the nodes is explained by interpretation of the adjoint solution as the superposition of incident and scattered fields. The adjoint solution within the boundary layer upstream of the splitter-plate trailing edge reveals a mechanism for transfer of energy from boundary-layer stability modes to Kelvin-Helmholtz modes. Extension of the adjoint solution to the far field using a Kirchhoff surface gives the receptivity of the mixing layer to incident sound from distant sources.

  11. Connections Transport Layer

    E-print Network

    Ramkumar, Mahalingam

    to upper layer Processes - application layer Could be connection oriented pr connectionless Example - TCP, connection oriented UDP - connectionless More similar to DL layer than Network layer - why? Ramkumar TL #12;Services Connections TCP UDP Connection Oriented Service Reliable delivery of data In the right order

  12. Localised convection cells in the presence of a vertical magnetic field

    E-print Network

    Localised convection cells in the presence of a vertical magnetic field J. H. P. Dawes Department October 27, 2005 Abstract Thermal convection in a horizontal fluid layer heated uniformly from below usually produces an array of convection cells of roughly equal amplitudes. In the presence of a vertical

  13. Executive presence for strategic influence.

    PubMed

    Shirey, Maria R

    2013-01-01

    This department highlights change management strategies that may be successful in strategically planning and executing organizational change initiatives. With the goal of presenting practical approaches helpful to nurse leaders advancing organizational change, content includes evidence-based projects, tools, and resources that mobilize and sustain organizational change initiatives. In this article, the author discusses cultivating executive presence, a crucial component of great leadership, needed for strategic influence and to drive change. PMID:23892301

  14. 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 ...

  15. Microstructural investigations of light-emitting porous Si layers

    NASA Technical Reports Server (NTRS)

    George, T.; Anderson, M. S.; Pike, W. T.; Lin, T. L.; Fathauer, R. W.; Jung, K. H.; Kwong, D. L.

    1992-01-01

    The structural and morphological characteristics of visible-light-emitting porous Si layers produced by anodic and stain etching of single-crystal Si substrates are compared using transmission electron microscopy and atomic force microscopy (AFM). AFM of conventionally anodized, laterally anodized and stain-etched Si layers show that the layers have a fractal-type surface morphology. The anodized layers are rougher than the stain-etched films. At higher magnification 10 nm sized hillocks are visible on the surface. Transmission electron diffraction patterns indicate an amorphous structure with no evidence for the presence of crystalline Si in the near-surface regions of the porous Si layers.

  16. 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

  17. The effect of organic soil layer on simulated permafrost dynamics

    NASA Astrophysics Data System (ADS)

    Jafarov, E. E.; Schaefer, K. M.

    2014-12-01

    Soil organic layer controls energy exchange between the air and the ground in permafrost affected soils in the Northern Hemisphere. Organic soils contribute to an increase in soil moisture and provide a better insulation against summer heat. Better ground insulation is possible due to thermal conductivity of a thawed organic layer, which is about two times lower than thermal conductivity of a frozen organic layer. In this study, we implemented changing in time soil organic layer into the Simple Biosphere/Carnegie-Ames-Stanford Approach (SiBCASA) terrestrial ecosystem model to illustrate how the soil organic layer affects soil temperature dynamics and soil carbon dynamics. We used CRUNCEP reanalysis data to run the model for its equilibrium state with a stable climate. Our results indicate that the presence and dynamics of the organic layer allow us to better simulate active layer thickness. Moreover, dynamic carbon redistribution as a result of changing organic layer improves the simulated distribution of soil carbon with depth.

  18. 2-D airfoil tests including side wall boundary layer measurements

    Microsoft Academic Search

    W. Bartelheimer; K. H. Horstmann; W. Puffert-Meissner

    1994-01-01

    The data presented in this contribution were obtained in the DLR Transonic Wind Tunnel Braunschweig. The intent of the experiment was to provide data giving information on the development of the TWB-side wall boundary layer in the presence of a typical transonic airfoil model for further investigation of the influence of the side wall boundary layer on 2-D airfoil measurements.

  19. Magnetohydrodynamic Ekman and Stewartson Layers in a Rotating Spherical Shell

    Microsoft Academic Search

    Rainer Hollerbach

    1994-01-01

    I investigate numerically the flow of an electrically conducting fluid in a differentially rotating spherical shell, in the presence of an imposed magnetic field. For a very weak field the flow is seen to consist of an Ekman layer on the inner and outer spherical boundaries, and a Stewartson layer on the cylinder circumscribing the inner sphere and parallel to

  20. 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

  1. Multiple Freezing Points as a Test for Viability of Plant Stems in the Determination of Frost Hardiness 1

    PubMed Central

    McLeester, R. C.; Weiser, C. J.; Hall, T. C.

    1969-01-01

    A technique is presented for a simple, rapid, and reliable means of determining the viability of plant tissue subjected to freezing temperatures. Freezing curves of excised stems of Cornus stolonifera Michx., and several other genera were studied. Tissue temperature was recorded during freezing of plant stem sections. The heat of crystallization deflected the resultant freezing curves at points where tissue froze. Living stem sections of all genera studied revealed 2 freezing points, while dead tissue exhibited only 1. The influence of variables such as moisture content, sample size, thermocouple placement, and cooling rate on freezing curves was analyzed. Stem samples wrapped in moisture-proof film with a thermocouple inserted into the pith were frozen to a predetermined test temperature, thawed, and subjected to a second freezing cycle. The presence or absence of 2 freezing points in the second freezing cycle was used as a criterion for establishing viability. The results were immediately available and identical to results from regrowth tests which took about 20 days. PMID:16657031

  2. 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.

  3. Layered Spinach Salad Ingredients

    E-print Network

    Liskiewicz, Maciej

    Layered Spinach Salad Ingredients: 1 pound spinach leaves, torn 8 ounces mushrooms, whole 1 onion 2 dill weed 1 1/2 teaspoons lemon pepper 1 teaspoon onion powder Directions 1. Tear spinach into bite. Layer in bowl. 3. Cut the ends off of the onion, and peel off the brown layers. Run under water

  4. Connections Transport Layer

    E-print Network

    Ramkumar, Mahalingam

    Processes - application layer Could be connection oriented pr connectionless Example - TCP, connection Connections TCP UDP Connection Oriented Service Reliable delivery of data In the right order Acknowledged oriented UDP - connectionless More similar to DL layer than Network layer - why? Ramkumar TL Services

  5. The layers of artistic illusion

    Microsoft Academic Search

    Christopher Perricone

    1994-01-01

    Works of art consist of layers of illusion. Broadly, I see three. The first two layers I call the layers of tame illusion. I call the deepest layer wild illusion. On the first layer, psychology of perception examines how art is illusion. This is the phenomenological ~layer. An admirable example of inquiry into this layer is E.H. Gombrich's Art and

  6. Spectral changes in layered f -electron systems induced by Kondo hole substitution in the boundary layer

    NASA Astrophysics Data System (ADS)

    Sen, Sudeshna; Moreno, J.; Jarrell, M.; Vidhyadhiraja, N. S.

    2015-04-01

    We investigate the effect of disorder on the dynamical spectrum of layered f -electron systems. With random dilution of f sites in a single Kondo insulating layer, we explore the range and extent to which Kondo hole incoherence can penetrate into adjacent layers. We consider three cases of neighboring layers: band insulator, Kondo insulator, and simple metal. The disorder-induced spectral weight transfer, used here for quantification of the proximity effect, decays algebraically with distance from the boundary layer. Further, we show that the spectral weight transfer is highly dependent on the frequency range considered as well as the presence of interactions in the clean adjacent layers. The changes in the low-frequency spectrum are very similar when the adjacent layers are either metallic or Kondo insulating, and hence are independent of interactions. In stark contrast, a distinct picture emerges for the spectral weight transfers across large energy scales. The spectral weight transfer over all energy scales is much higher when the adjacent layers are noninteracting as compared to when they are strongly interacting Kondo insulators. Thus, over all scales, interactions screen the disorder effects significantly. We discuss the possibility of a crossover from non-Fermi-liquid to Fermi-liquid behavior upon increasing the ratio of clean to disordered layers in particle-hole asymmetric systems.

  7. 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.

  8. Sequential observations of the local neutral wind field structure associated with E region plasma layers

    Microsoft Academic Search

    R. L. Bishop; G. D. Earle; M. F. Larsen; C. M. Swenson; C. G. Carlson; P. A. Roddy; C. Fish; T. W. Bullett

    2005-01-01

    The first sequential rocket experiment to study intermediate layers in over 30 years was launched from Wallops Island, Virginia on the night of 29–30 June 2003. Using an onsite digisonde to determine the presence of sporadic E and conditions indicating the possible presence of an intermediate layer, four rockets were launched over a 4-hour period. Three of the rockets launched

  9. Geological Layer Detection and Candidate Science Target Identification

    NASA Astrophysics Data System (ADS)

    Castano, R.; Bornstein, B.; Thompson, D. R.; Wagstaff, K.; Estlin, T.; Anderson, R. C.

    2012-12-01

    Geologic layers provide valuable information about the history of a planetary region. We have developed an approach to identifying candidate science targets within layered geologic deposits onboard an in-situ spacecraft, such as the Mars Exploration Rover (MER) Mission or the Mars Science Laboratory (MSL) Mission. The approach includes automated detection of layers in a scene and an algorithm for selecting science targets for further study that sample across the span of identified layers. Identifying targets in representative observed layers enables rapid collection of targeted remote sensing data on valuable layer targets without requiring multiple ground communication cycles. This type of automated image processing and target selection could enable increasingly informed, onboard decisions about when and where to take follow-up measurements and could easily be integrated into existing flight software that prioritizes science targets for follow-up measurements. The approach is divided into two elements. First, the presence of layers in a scene is ascertained. To determine the presence and location of layers within the image, the statistical properties of image regions are used. A supervised (trained on known examples) and unsupervised method have been developed. Performance assessment criteria include detection and false alarm rates, as well as computational requirements and run time. Upon detecting the presence of layering, candidate science targets are efficiently selected and prioritized to enable surveying the layers. The approach involves estimating the slope of the layering, selecting a transect perpendicular to the direction of the layers and then determining relatively homogeneous regions along the transect. We show results on images collected by the MER Mission rovers using both Pancam and Navcam imagery as well as scenes from a field experiment in the Mojave Desert.

  10. 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.

  11. Modeling Transport Layer Protocols

    NASA Astrophysics Data System (ADS)

    Sasnauskas, Raimondas; Weingaertner, Elias

    In a layered communication architecture, transport layer protocols handle the data exchange between processes on different hosts over potentially lossy communication channels. Typically, transport layer protocols are either connection-oriented or are based on the transmission of individual datagrams. Well known transport protocols are the connection-oriented Transmission Control Protocol (TCP) [372] and the User Datagram Protocol (UDP) [370] as well as the Stream Control Transmission Protocol (SCTP) [340] and DCCP, the Datagram Congestion Control Protocol [259]. In this chapter, we focus on the modeling process of the transport layer. While we mostly use TCP and UDP as a base of comparison from this point, we emphasize that the methodologies discussed further on are conferrable to virtually any transport layer in any layered communication architecture.

  12. Layer breathing vibrations in AB-stacking few layer graphene and twisted bilayer graphene

    NASA Astrophysics Data System (ADS)

    He, Rui

    2015-03-01

    Interlayer interactions in few layer graphene can create a set of shear modes and layer breathing modes (LBMs) that involve lateral and vertical displacement of individual layers, respectively. LBMs are of importance because they can facilitate interlayer current conduction and are sensitive to external perturbations, such as the presence of substrate or surface adsorbates. We investigated low-frequency fundamental layer breathing vibrations in AB-stacking few layer graphene and twisted bilayer graphene using Raman spectroscopy. In AB-stacking few layer graphene we observed the Raman peaks from phonons at the Brillouin zone center for the lowest-frequency branch LBM vibration. The mode frequency depends strongly on the number of graphene layers. Notably, the LBM Raman response is unobservable at room temperature, and it is turned on at higher temperature (>600 K) with a steep increase of Raman intensity. The observation suggests that the LBM vibration is strongly suppressed by molecules adsorbed on the graphene surface but is activated as desorption occurs at high temperature. In twisted bilayer graphene, the fundamental LBM is observed in a small range of twisting angle at which the intensity of the G Raman peak is strongly enhanced. The dependence of this mode's frequency and linewidth on the rotational angle can be explained by the double resonance Raman process (LBM phonon with nonzero wavevector) mediated by the twisted bilayer graphene lattice which lacks long-range translational symmetry. The angle dependence also reveals the strong impact of electronic band overlaps of the two rotated graphene layers.

  13. 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.

  14. Family presence in the congenital catheterization laboratory.

    PubMed

    Heitschmidt, Mary

    2015-01-01

    Evidence suggests that family presence as an option during invasive procedures may provide a comforting presence to the patient and may not be notable disruptive to the health care team. Little research has explored family presence during cardiac procedures. This is the first documented report of family presence in the congenital cardiac catheterization lab (CCCL). The purpose of this article is to review the course for implementing a family presence program in the CCCL. The Iowa Model of Evidence-Based practice guided this process which included the development of a written policy of family presence in the CCCL at two academic medical centers. Successful family presence in the catheterization lab must include: written guidelines, involvement of all staff, family presence offered as an option, and preparation of the patient and family for the catheterization experience as well as emergency procedures. PMID:25766042

  15. 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

  16. 36 CFR 504.2 - Recording presence.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...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...

  17. 36 CFR 504.2 - Recording presence.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...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...

  18. 36 CFR 504.2 - Recording presence.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...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...

  19. 36 CFR 504.2 - Recording presence.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...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...

  20. 36 CFR 504.2 - Recording presence.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...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...

  1. Relationship between ocean velocity and motionally induced electrical signals: 2. In the presence of sloping topography

    Microsoft Academic Search

    Zoltan B. Szuts

    2010-01-01

    Motionally induced electric fields and electric currents in the ocean depend to first order solely on the vertical dimension. We investigate the significance of two-dimensional (2-D) perturbations that arise in the presence of sloping topography. The full electric response is calculated for a schematic geometry that contains a topographic slope, has a two-layer ocean with a layer of sediment beneath,

  2. Layers of Ice

    NSDL National Science Digital Library

    This is a lesson about the formation of glaciers, ice layering and stratigraphy, and the cryosphere and cryobotics. Learners will collect evidence of layering, explore the science story that layering tells, study snow and ice for insights into climate change, and learn about the tools used to explore ice layers on Earth and in the solar system. Connections between rings of a tree and rings in an ice core will be made. Activities include small group miming, speaking, drawing, and/or writing. This is lesson 7 of 12 in the unit, Exploring Ice in the Solar System.

  3. Instructor Presence in the Online Classroom

    ERIC Educational Resources Information Center

    Stone, Sophia J.; Chapman, Diane D.

    2006-01-01

    Presence in online classrooms has been linked to immediacy behaviors, instructor-student interaction, and participation. Research shows that presence can be managed and sustained, but little documentation exists about perceptions of the meaning of presence. An interview-based qualitative inquiry of three online instructors was conducted to…

  4. Immersion and Presence Daniel R Mestre

    E-print Network

    & Riva, 2003). Presence is indeed, historically, at the core of Virtual Reality (VR). Presence has often of skills or knowledge learned in a VE to the real world. 1- Immersion and Presence Virtual reality.laps.univ-mrs.fr/~mestre/mestre.htm Abstract: In a Virtual Environment (VE), Immersion, defined in technical terms, is capable of producing

  5. 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.

  6. Seabed Wave Boundary Layer Measurements and Analysis

    Microsoft Academic Search

    K. F. Lambrakos

    1982-01-01

    Velocity measurements made at two elevations off a rough sea floor in 18.3 m of water depth in the Strait of Juan de Fuca suggest the presence of a wave boundary layer. The wave velocities measured at 0.69 m off bottom are, overall, larger in magnitude and also shifted in time relative to the velocities measured at 1.85 m. These

  7. Regional climate modeling of heat stress, frost, and water stress events in the agricultural region of Southwest Western Australia under the current climate and future climate scenarios.

    NASA Astrophysics Data System (ADS)

    Kala, Jatin; Lyons, Tom J.; Abbs, Deborah J.; Foster, Ian J.

    2010-05-01

    Heat stress, frost, and water stress events have significant impacts on grain quality and production within the agricultural region (wheat-belt) of Southwest Western Australia (SWWA) (Cramb, 2000) and understanding how the frequency and intensity of these events will change in the future is crucial for management purposes. Hence, the Regional Atmospheric Modeling System (Pielke et al, 1992) (RAMS Version 6.0) is used to simulate the past 10 years of the climate of SWWA at a 20 km grid resolution by down-scaling the 6-hourly 1.0 by 1.0 degree National Center for Environmental Prediction Final Analyses from December 1999 to Present. Daily minimum and maximum temperatures, as well as daily rainfall are validated against observations. Simulations of future climate are carried out by down-scaling the Commonwealth Scientific and Industrial Research Organization (CSIRO) Mark 3.5 General Circulation Model (Gordon et al, 2002) for 10 years (2046-2055) under the SRES A2 scenario using the Cubic Conformal Atmospheric Model (CCAM) (McGregor and Dix, 2008). The 6-hourly CCAM output is then downscaled to a 20 km resolution using RAMS. Changes in extreme events are discussed within the context of the continued viability of agriculture in SWWA. Cramb, J. (2000) Climate in relation to agriculture in south-western Australia. In: The Wheat Book (Eds W. K. Anderson and J. R. Garlinge). Bulletin 4443. Department of Agriculture, Western Australia. Gordon, H. B., Rotstayn, L. D., McGregor, J. L., Dix, M. R., Kowalczyk, E. A., O'Farrell, S. P., Waterman, L. J., Hirst, A. C., Wilson, S. G., Collier, M. A., Watterson, I. G., and Elliott, T. I. (2002). The CSIRO Mk3 Climate System Model [Electronic publication]. Aspendale: CSIRO Atmospheric Research. (CSIRO Atmospheric Research technical paper; no. 60). 130 p McGregor, J. L., and Dix, M. R., (2008) An updated description of the conformal-cubic atmospheric model. High Resolution Simulation of the Atmosphere and Ocean, Hamilton, K. and Ohfuchi, W., Eds., Springer, 51-76. Pielke, R. A., Cotton, W. R., Walko, R. L., Tremback, C. J., Lyons, W. A., Grasso, L. D., Nicholls, M. E., Moran, M. D., Wesley, D. A., Lee, T. J., Copeland, J. H., (1992) A comprehensive meteorological modeling system - RAMS. Meteorol. Atmos. Phys., 49, 69-91.

  8. Logical Layers of Entrepreneurship

    Microsoft Academic Search

    Tadeusz Gospodarek

    2009-01-01

    Entrepreneurship is a logical consequence of the external economic situation and the internal necessity of human well being and freedom. Therefore it should be considered as a set of interacting logical layers, based on social, psychological, economical and technological aspects. Inside each layer which may be interpret as subsystems of entrepreneurship, there are defined internal relations and possible interactions similarly

  9. Layered Depth Panoramas

    Microsoft Academic Search

    Ke Colin Zheng; Sing Bing Kang; Michael F. Cohen; Richard Szeliski

    2007-01-01

    Representations for interactive photorealistic visualiz a- tion of scenes range from compact 2D panoramas to data- intensive 4D light fields. In this paper, we propose a tech- nique for creating a layered representation from a sparse se t of images taken with a hand-held camera. This representa- tion, which we call a layered depth panorama (LDP), al- lows the user

  10. STATE CONFIGURED LAYERED CONTROL

    Microsoft Academic Search

    James G. Bellingham; Thomas R. Consi

    1990-01-01

    A new implementation of layered control is described that is specifically tailored for a vehicle capable of complex missions. It can be configured by a user for a given mission in a relatively straightforward fashion. Results from layered control tests on a real vehicle were used to motivate the architecture. Survey-type missions were conducted in simulationto test the approach.

  11. Turbulent dispersion in cloud-topped boundary layers

    NASA Astrophysics Data System (ADS)

    Verzijlbergh, R. A.; Jonker, H. J. J.; Heus, T.; Vilöguerau de Arellano, J.

    2009-02-01

    Compared to dry boundary layers, dispersion in cloud-topped boundary layers has received less attention. In this LES based numerical study we investigate the dispersion of a passive tracer in the form of Lagrangian particles for four kinds of atmospheric boundary layers: 1) a dry convective boundary layer (for reference), 2) a "smoke" cloud boundary layer in which the turbulence is driven by radiative cooling, 3) a stratocumulus topped boundary layer and 4) a shallow cumulus topped boundary layer. We show that the dispersion characteristics of the smoke cloud boundary layer as well as the stratocumulus situation can be well understood by borrowing concepts from previous studies of dispersion in the dry convective boundary layer. A general result is that the presence of clouds enhances mixing and dispersion - a notion that is not always reflected well in traditional parameterization models, in which clouds usually suppress dispersion by diminishing solar irradiance. The dispersion characteristics of a cumulus cloud layer turn out to be markedly different from the other three cases and the results can not be explained by only considering the well-known top-hat velocity distribution. To understand the surprising characteristics in the shallow cumulus layer, this case has been examined in more detail by 1) determining the velocity distribution conditioned on the distance to the nearest cloud and 2) accounting for the wavelike behaviour associated with the stratified dry environment.

  12. Turbulent dispersion in cloud-topped boundary layers

    NASA Astrophysics Data System (ADS)

    Verzijlbergh, R. A.; Jonker, H. J. J.; Heus, T.; Vilöguerau de Arellano, J.

    2008-11-01

    Compared to dry boundary layers, dispersion in cloud-topped boundary layers has received less attention. In this LES based numerical study we investigate the dispersion of a passive tracer in the form of Lagrangian particles for four kinds of atmospheric boundary layers: 1) a dry convective boundary layer (for reference), 2) a "smoke" cloud boundary layer in which the turbulence is driven by radiative cooling, 3) a stratocumulus topped boundary layer and 4) a shallow cumulus topped boundary layer. We show that the dispersion characteristics of the smoke cloud boundary layer as well as the stratocumulus situation can be well understood by borrowing concepts from previous studies of dispersion in the dry convective boundary layer. A general result is that the presence of clouds enhances mixing and dispersion a notion that is not always reflected well in traditional parameterization models, in which clouds usually suppress dispersion by diminishing solar irradiance. The dispersion characteristics of a cumulus cloud layer turn out to be markedly different from the other three cases and the results can not be explained by only considering the well-known top-hat velocity distribution. To understand the surprising characteristics in the shallow cumulus layer, this case has been examined in more detail by 1) determining the velocity distribution conditioned on the distance to the nearest cloud and 2) accounting for the wavelike behaviour associated with the stratified dry environment.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Modelling the transitional boundary layer

    NASA Technical Reports Server (NTRS)

    Narasimha, R.

    1990-01-01

    Recent developments in the modelling of the transition zone in the boundary layer are reviewed (the zone being defined as extending from the station where intermittency begins to depart from zero to that where it is nearly unity). The value of using a new non-dimensional spot formation rate parameter, and the importance of allowing for so-called subtransitions within the transition zone, are both stressed. Models do reasonably well in constant pressure 2-dimensional flows, but in the presence of strong pressure gradients further improvements are needed. The linear combination approach works surprisingly well in most cases, but would not be so successful in situations where a purely laminar boundary layer would separate but a transitional one would not. Intermittency-weighted eddy viscosity methods do not predict peak surface parameters well without the introduction of an overshooting transition function whose connection with the spot theory of transition is obscure. Suggestions are made for further work that now appears necessary for developing improved models of the transition zone.

  18. Presence: four ways of being there.

    PubMed

    Osterman, P; Schwartz-Barcott, D

    1996-01-01

    Presence is an important but confusing concept in nursing. At times, it is used to simply characterize a nurse's physical presence, while, at other times, it is used in a highly metaphysical sense to depict a nurse's full physical, psychological, and spiritual presence. As a concept, presence has not been clearly defined. Its core characteristics need to be identified and separated from those characteristics that reflect its variability. The authors establish a definition of presence as "being there" based on the essence of the concept as it is used in the nursing literature; identifying four ways in which presence varies based on the quality of being there, the focus of the nurse's energy, and the nature of the nurse-patient interaction; and address possible outcomes of each type. PMID:8716883

  19. Accelerator Control Middle Layer

    SciTech Connect

    Corbett, J.

    2004-09-15

    This paper reviews an efficient implementation of the software ''middle layer'' that resides between high-level accelerator control applications and the low-level accelerator control system. The middle layer software is written in MATLAB and includes links to the EPICS Channel Access Library. Functionally, the middle layer syntax closely parallels the Family/Index naming scheme used in many accelerator simulation codes and uses the same convention to communicate with both the online machine and the accelerator model. Hence, machine control, machine simulation and data analysis tools are integrated into a single, easy-to-use software package.

  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. Wintertime Local Circulations in and around the Ulaanbaatar Metropolitan Area in the Presence of Temperature Inversion

    NASA Astrophysics Data System (ADS)

    Ganbat, Gantuya; Baik, Jong-Jin

    2015-04-01

    Temperature inversions are frequently observed in mountainous urban areas and can cause severe air pollution problems especially in wintertime. This study investigates wintertime local circulations in and around the Ulaanbaatar, the capital of Mongolia, metropolitan area in the presence of temperature inversion using the Weather Research and Forecasting (WRF) model coupled with the Seoul National University Urban Canopy Model (SNUUCM). Ulaanbaatar is located in complex terrain and in a nearly east-west oriented valley. A wintertime scenario with clear skies, weak synoptic winds, and temperature inversion under the influence of a Siberian high-pressure system is selected. It is found that the thickness and strength of temperature inversion layer are associated with the terrain. The temperature inversion layer is deeper and stronger in the valleys than the mountain slopes, and its top height is typically lower than the maximum ridge top height of the surrounding mountains but higher than the boundary layer height. Weak local circulations develop in the presence of temperature inversion. In the daytime, weak mountain upslope winds develop, up-valley winds appear to be stronger in the urban area, and channeling winds are produced in the narrow valleys. The bottom of temperature inversion layer rises up in the urban area, and winds below the bottom of temperature inversion layer strengthen. In the nighttime, mountain downslope winds and down-valley winds develop with a lifted daytime residual layer. Urban effects in the presence of temperature inversion are examined by comparing simulation cases with and without the city. It is shown that in the daytime the urban area acts to elevate the bottom of temperature inversion layer and weaken the strength of temperature inversion layer. Compared to the simulation case without the city, the simulation case with the city shows that winds east of the city weaken in the afternoon and that down-valley winds develop later. These result from the interactions of urban breezes with valley winds.

  2. Layer-Cake Earth

    NSDL National Science Digital Library

    Rebecca Tedford

    2006-12-01

    Though you can't tell just by looking at them, layers of sediments tell us much aboutEarth's history--when the ocean flooded continents, when mountains were formed, when climate was warmer or cooler, and so much more. Stratigraphy, the study of sediment layers and the relationships between rocks and fossils with time, has done much to help us understand Earth. While heading out to real-life dig sites with your students is not so realistic, there is a safe, fun, effective way to introduce geology concepts to elementary school children of all ages: "coring" layer cakes! All it takes is some simple baking to create a model of sediment layers and their fossil record. Exploring this topic in the classroom allows your students to learn about how geologists work while they explore Earth science.

  3. Transport Layer Cornell University

    E-print Network

    Andrew, Lachlan

    to another, such as by varying voltages on wires, or generating electromagnetic waves. The application layer and implementation, with an emphasis on the underlying ideas and fundamentals. We will also discuss possible

  4. Nanogranular Layered Magnetic Films

    Microsoft Academic Search

    G. N. Kakazei; Yu. G. Pogorelov; J. B. Sousa; J. M. Santos; S. Cardoso; P. P. Freitas

    Nanogranular layered magnetic films are a new class of magnetoresistive (MR) systems, consisting of well separated layers\\u000a of closely spaced ferromagnetic nanoparticles within an insulating matrix. Most commonly they are realized in the form of\\u000a discontinuous metal-insulator magnetic multilayers (DMIM), representing a general similarity with the formerly known magnetic\\u000a multilayered giant magnetoresistance (GMR) systems (Baibich et al., 1988). Compared to

  5. Tests on Double Layer Metalization

    NASA Technical Reports Server (NTRS)

    Woo, D. S.

    1983-01-01

    28 page report describes experiments in fabrication of integrated circuits with double-layer metalization. Double-layer metalization requires much less silicon "real estate" and allows more flexibility in placement of circuit elements than does single-layer metalization.

  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. Multilayer nanostructured porphyrin arrays constructed by layer-by-layer self-assembly.

    PubMed

    Smith, Arthur R G; Ruggles, Jeremy L; Yu, Aimin; Gentle, Ian R

    2009-09-01

    UV-vis absorption, atomic force microscopy (AFM), contact angle, and X-ray reflectivity experiments were performed on thin films deposited on crystalline silicon substrates as alternating layers of a porphyrin with anionic functionality, tetra-5,10,15,20-(4-sulfonatophenyl)porphine (TSPP) or the metalated version, Cu(II)TSPP, and the cationic polyelectrolyte, poly(diallyldimethylammonium chloride) (PDDA). The films were made by dipping in alternating aqueous solutions containing film components (layer-by-layer deposition). Modeling of the X-ray reflectivity data revealed differences in the films' thickness depending on the method of film deposition. An unusual decrease in film thickness after each polyelectrolyte dip was also observed for films using TSSP. UV-vis measurements revealed that a similar amount of TSSP was included within films despite the method of formation. UV-vis measurements also revealed the presence of free-base, H-aggregate, and J-aggregate forms of the porphyrin after TSPP dipping, and the subsequent disappearance of the J-aggregate after dipping in the PDDA solution. A model of film formation was proposed on the basis of the concept of two different types of porphyrin aggregates being present after dipping in porphyrin solution. A layer of porphyrin molecules initially attach to the Si surface such that the planar molecules are arranged side by side as H-aggregates with an excess of J-aggregated material on top. The J-aggregate is then removed and replaced by a layer of PDDA. A change in contact angle of 14 degrees was observed between porphyrin and polyelectrolyte layers due to the more hydrophobic nature of the polymer. The presence of the J-aggregate was confirmed in AFM images obtained from the porphyrin layer. Exposure of the films to solutions of alternating pHs of 10 and 1.8 resulted in reproducible switching of the UV-vis spectra, indicating a possible sensing application. PMID:19572527

  8. A lower limit on the top of Jupiter's haze layer

    NASA Technical Reports Server (NTRS)

    Cook, A. F., II; Duxbury, T. C.; Hunt, G. E.

    1979-01-01

    Remote sensing observations of the Jovian atmosphere at wavelengths ranging from UV to the IR are affected by the presence of haze layers above the visible clouds. These layers are difficult to detect as they generally contain submicron particles. In the present paper, a sequence of Voyager images of high-latitude haze, which extends through the Jovian stratosphere into the mesosphere is presented and discussed.

  9. 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.

  10. 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),…

  11. Behavioral Presence Test in Threatening Virtual Environments

    Microsoft Academic Search

    Eric Malbos; Ronald M. Rapee; Manolya Kavakli

    2012-01-01

    Presence, the impression of being existent in artificially created places, is an important factor for achieving maximum experience in virtual environments (VEs) and hence in their use for experiments or therapy. To date, most clinical studies have used self-report questionnaires or physiological measures to appraise the degree of presence. Some studies that have tested behavioral scales have used a single

  12. 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

  13. Analysis of modified MYJ and YSU boundary layer schemes in WRF-Chem with respect to simulated boundary layer heights and pollutant concentrations

    NASA Astrophysics Data System (ADS)

    Forkel, Renate; Foreman, Richard; Emeis, Stefan

    2014-05-01

    To improve the performance of boundary layer schemes currently applied within WRF-Chem (Grell et al., 2005), the Mellor-Yamada-Janjic (MYJ) model (Mellor and Yamada 1982) and the Yonsei University (YSU) PBL scheme (Hong et al. 2006) have been updated using data from a 100 m high offshore measurement tower called FINO1. The turbulence intensity in the Mellor-Yamada-Janjic model has been enhanced as described in Foreman and Emeis (2012). An alternative to the exchange coefficient for stable stratification in the YSU scheme is described in Foreman et al. (2014). These modifications to the two schemes have been applied and are compared with the existing schemes. For example, the updated MYJ scheme results in an improved representation of the turbulent kinetic energy throughout the boundary layer as compared with the measurements at FINO1. The modified MYJ and YSU schemes, which have been originally developed for wind energy applications, have been implemented into version 3.5 of the WRF model. Simulations with WRF-Chem were carried out for Europe and the region of Augsburg in order to evaluate the effect of the modified PBL schemes on simulated PBL heights, gas phase pollutant and aerosol concentrations. Foreman, R.J. and S. Emeis, 2012. A method for increasing the turbulent kinetic energy in the Mellor-Yamada-Janjic boundary layer parametrization. Boundary Layer Meteorology 145:329-349. Foreman, R.J. S. Emeis and B. Canadillas, 2014. Stable boundary layer parametrization without eddy viscosity or turbulent kinetic energy equation approaches. Submitted to Boundary Layer Meteorology 2014. Grell, G. A., Peckham, S. E., Schmitz, R., McKeen, S. A., Frost, G., Skamarock,W. C., and Eder, B., 2005. Fully Coupled Online Chemistry within the WRF Model. Atmospheric Environment 39, 6957-6975. Hong S, Noh Y, Dudhia J 2006. Nonlocal boundary layer vertical diffusion in a medium-range forecast model. Mon Wea Rev 124:2322-2339. Mellor GL, Yamada T 1982. Development of a turbulence closure model for geophysical fluid problems. Rev. Geophys. Space Phys 20:851-875.

  14. Layered Outcrops of Far West Candor Chasma

    NASA Technical Reports Server (NTRS)

    2000-01-01

    [figure removed for brevity, see original site]

    Images from Mariner 9 in 1972 revealed that some of the mesas and mounds found within the chasms of the martian 'Grand Canyon'--the Valles Marineris--have layers in them. Speculations as to the origin of these interior layered materials ranged from volcanic ash deposits to sediments laid down in lakes that could have partially filled the Vallis Marineris troughs, much as lakes now occupy portions of the rift valleys of eastern Africa. The proposal that the Valles Marineris once hosted deep martian lakes led to additional speculation as to the prospects for finding fossil evidence of martian life.

    Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images have ten or more times better resolution than the Mariner 9 and Viking orbiter images taken in the 1970s. MOC images have indeed confirmed the presence of layered outcrops within the Valles Marineris. They have also shown places previously not suspected to have layered rock, and they have shown that these materials might not have formed in the Valles Marineris, but were instead deposited in craters that were subsequently buried long before the chasms opened up (see discussion below). The layered rock is now visible because of faulting and erosion.

    The high resolution picture shown here (B, above right) was the first image received by MOC scientists that began to hint at a larger story of layered sedimentary rock on Mars. The picture shows a 1.5 km by 2.9 km (0.9 mi by 1.8 mi) area in far southwestern Candor Chasma (A, above left) that was--based on Mariner 9 and Viking orbiter images--not previously expected to exhibit layers. The MOC image reveals that the floor of western Candor Chasma at this location is indeed layered. What is most striking about the picture is the large number and uniformity of the layers, or beds. There are over 100 beds in this area, and each has about the same thickness (estimated to be about 10 meters (11 yards) thick). Each layer has a relatively smooth upper surface, and each is hard enough to form steep cliffs at its margins.

    Layers indicate change. The uniform pattern seen here--beds of similar properties and thickness repeated over a hundred times--suggest that the deposition of materials that made the layers was interrupted at regular or episodic intervals. Patterns like this, when found on Earth, usually indicate the presence of sediment deposited in dynamic, energetic, underwater environments. On Mars, these same patterns could very well indicate that the materials were deposited in a lake or shallow sea. Other MOC images suggest that these layers would not have formed in a lake in Candor Chasma, but instead were deposited in a crater or other basin that existed before Candor Chasma was cut (by faulting and erosion) into the surrounding terrain. However, it is not known for certain that these materials actually formed underwater, for it is possible that there were uniquely Martian processes occurring in the distant past that would mimic the pattern of sedimentation in water. For example, if the early Martian atmosphere was denser than it is today, and if the planet's atmospheric pressure changed on a cyclic basis (as it does today), then perhaps these materials are simply deposits of airborne dust that were later buried and cemented to create cliff-forming rock.

    Sunlight illuminates both the wide angle context view and the narrow angle high resolution image from the left/upper left. In both, north is toward the top and east to the right.

  15. 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

  16. Effects of the Spatial Extent of Multiple Harmonic Layers

    SciTech Connect

    Burby, J. W.; Kramer, G. J.; Phillips, C. K.; Valeo, E. J. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States)

    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. 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

  18. 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, between the amorphous silicon and the atomic-layer-deposited transparent electrode that acts as a barrier, impeding hole and electron collection.

  19. 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.

  20. Stability of mixing layers

    NASA Technical Reports Server (NTRS)

    Tam, Christopher; Krothapalli, A

    1993-01-01

    The research program for the first year of this project (see the original research proposal) consists of developing an explicit marching scheme for solving the parabolized stability equations (PSE). Performing mathematical analysis of the computational algorithm including numerical stability analysis and the determination of the proper boundary conditions needed at the boundary of the computation domain are implicit in the task. Before one can solve the parabolized stability equations for high-speed mixing layers, the mean flow must first be found. In the past, instability analysis of high-speed mixing layer has mostly been performed on mean flow profiles calculated by the boundary layer equations. In carrying out this project, it is believed that the boundary layer equations might not give an accurate enough nonparallel, nonlinear mean flow needed for parabolized stability analysis. A more accurate mean flow can, however, be found by solving the parabolized Navier-Stokes equations. The advantage of the parabolized Navier-Stokes equations is that its accuracy is consistent with the PSE method. Furthermore, the method of solution is similar. Hence, the major part of the effort of the work of this year has been devoted to the development of an explicit numerical marching scheme for the solution of the Parabolized Navier-Stokes equation as applied to the high-seed mixing layer problem.

  1. 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.

  2. Ridged Layer Outcrop

    NASA Technical Reports Server (NTRS)

    2004-01-01

    15 August 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a strange ridged pattern developed in an eroding layer of material on the floor of a Labyrinthus Noctis depression in the Valles Marineris system. The ridges bear some resemblance to ripple-like dunes seen elsewhere on Mars, but they are linked to the erosion of a specific layer of material--i.e., something in the rock record of Mars. Similar ridged textures are found in eroded dark-toned mantling layers in regions as far away as northern Sinus Meridiani and Mawrth Vallis. The explanation for these landforms is as elusive as this image is evocative. The image is located near 8.2oS, 93.6oW, and covers an area 3 km (1.9 mi) across. The scene is illuminated by sunlight from the upper left.

  3. Craters and Layers

    NASA Technical Reports Server (NTRS)

    2006-01-01

    11 March 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows some typical relations between impact craters and light-toned, layered rock on Mars. The larger circular feature at the north (top) end of the image marks the location of a filled, buried crater on intermountain terrain north of Hellas Planitia. The larger crater at the southeast (lower right) corner formed by meteor impact into the layered material in which the buried crater is encased. The layered rock, in this case, has a light tone similar to the sedimentary rocks being explored by the Mars Exploration Rover, Opportunity, thousands of kilometers away in Sinus Meridiani.

    Location near: 24.9oS, 299.3oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

  4. Ultrastructural observations reveal the presence of channels between cork cells.

    PubMed

    Teixeira, Rita Teresa; Pereira, Helena

    2009-12-01

    The ultrastructure of phellem cells of Quercus suber L. (cork oak) and Calotropis procera (Ait) R. Br. were analyzed using electron transmission microscopy to determine the presence or absence of plasmodesmata (PD). Different types of Q. suber cork samples were studied: one year shoots; virgin cork (first periderm), reproduction cork (traumatic periderm), and wet cork. The channel structures of PD were found in all the samples crossing adjacent cell walls through the suberin layer of the secondary wall. Calotropis phellem also showed PD crossing the cell walls of adjacent cells but in fewer numbers compared to Q. suber. In one year stems of cork oak, it was possible to follow the physiologically active PD with ribosomic accumulation next to the aperture of the channel seen in the phellogen cells to the completely obstructed channels in the dead cells that characterize the phellem tissue. PMID:19811698

  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. 36 CFR 520.2 - Recording presence.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...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....

  7. 36 CFR 520.2 - Recording presence.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...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....

  8. 36 CFR 520.2 - Recording presence.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...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....

  9. 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.

  10. Layers in Melas Chasma

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Click on image for larger annotated version

    This scene of layered deposits is from Melas Chasma, part of the Valles Marineris valley network. The area consists of a series of plateaus and cliffs that form a step-like terrain similar to the Grand Staircase-Escalante region of southwest Utah. The upper-right half of the image covers the highest plateau, and lower cliffs and plateaus step down in elevation toward the lower left of the image. Dunes of dark sand commonly cover the flat plateaus and distinct layers of bedrock are exposed in the cliffs. The orientations of these layers may help scientists to understand how the layers formed and the kind of environment that the layers formed in. Black rectangles on the left side of the image are areas where the image data was lost during transmission from Mars Reconnaissance Orbiter to Earth. This subscene [above] shows a series of boulder tracks on the left side of the image. The boulders fell from the cliffs above and left behind a series of small depressions. Each depression was made as the boulder bounced and rolled along the surface. In many cases, the tracks can be followed to the specific boulder that made them. Also visible in this subscene are cross-sections through the layered bedrock. This bedrock likely formed through settling of sand-sized particles out of the air or out of a body of water that has since drained away. These layers are 'cross-bedded', which means that subsequent layers are not parallel to each other but are instead oriented at an angle to other layers. The fact that these layers are cross-bedded indicates that the sand-sized particles were moved horizontally along the surface as they settled, just like sand dunes or ripples at the bottom of a stream. The size and shape of these cross-beds may help scientists to determine if the layers formed underwater or on land.

    Image PSP_001377_1685 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on November 11, 2006. The complete image is centered at -11.3 degrees latitude, 286.3 degrees East longitude. The range to the target site was 257.7 km (161.0 miles). At this distance the image scale ranges from 25.8 cm/pixel (with 1 x 1 binning) to 51.6 cm/pixel (with 2 x 2 binning). The image shown here [below] has been map-projected to 25 cm/pixel and north is up. The image was taken at a local Mars time of 3:32 PM and the scene is illuminated from the west with a solar incidence angle of 60 degrees, thus the sun was about 30 degrees above the horizon. At a solar longitude of 133.9 degrees, the season on Mars is Northern Summer.

    NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, is the prime contractor for the project and built the spacecraft. The High Resolution Imaging Science Experiment is operated by the University of Arizona, Tucson, and the instrument was built by Ball Aerospace and Technology Corp., Boulder, Colo.

  11. Signature of an overturning gravity wave in the mesospheric sodium layer: Comparison of a nonlinear photochemical-dynamical model

    E-print Network

    Signature of an overturning gravity wave in the mesospheric sodium layer: Comparison of a nonlinear. [1] In this paper we study the evolution of the sodium layer in the presence of an overturning (or and the associated evolution of the sodium layer. We use filtering methods to identify waves of similar scales

  12. Receptivity of Boundary Layers to Freestream Sound for 3-D Hypersonic Flows over Blunt Wedges and Cones

    Microsoft Academic Search

    Xiaolin Zhong; Haibo Dong

    1998-01-01

    The stability and transition of hypersonic boundary layers are altered considerably by the presence of bow shocks in hypersonic flows over blunt bodies. The bow-shock effects include the shock interaction with wave fields and the creation of entropy layers on the body surfaces. This paper studies by numerical simulation the receptivity of 3-D hypersonic boundary layers to freestream acoustic disturbances

  13. Accretion onto Neutron Stars in the Presence of Elemental Diffusion

    NASA Astrophysics Data System (ADS)

    Starrfield, S.; Truran, J. W.; MacDonald, J.; Sparks, W. M.

    2000-12-01

    We have begun a new series of calculations of accretion onto 10 km, 1.4Msun neutron stars. We are using our 1-D, implicit, Lagrangian hydro-code, NOVA (Starrfield et al. MNRAS, 296, 502, 1998; ApJS, 127, 485, 2000), which includes both a large nuclear reaction network and elemental diffusion (Iben and MacDonald ApJ, 296, 540). In our exploratory calculations, we have varied both the initial neutron star luminosity and mass accretion rate choosing similar values to those used by other investigators to successfully simulate X-ray bursts. We have found, however, for some previously successful sets of initial conditions, that accretion in the presence of diffusion causes the hydrogen to float to the surface. A thick layer of nuclear processed accreted material then grows under the proton rich surface layers and no X-ray burst occurs. Our simulations done with identical initial conditions but without the inclusion of diffusion do result in X-ray bursts. We gratefully acknowledge partial support from grants to our institutions from NASA, NSF, and the DOE.

  14. Reactivity and applications of layered silicates and layered double hydroxides.

    PubMed

    Selvam, Thangaraj; Inayat, Alexandra; Schwieger, Wilhelm

    2014-07-21

    Layered materials, such as layered sodium silicates and layered double hydroxides (LDHs), are well-known for their remarkable adsorption, intercalation and swelling properties. Their tunable interlayers offer an interesting avenue for the fabrication of pillared nanoporous materials, organic-inorganic hybrid materials and catalysts or catalyst supports. This perspective article provides a summary of the reactivity and applications of layered materials including aluminium-free layered sodium silicates (kanemite, ilerite (RUB-18 or octosilicate) and magadiite) and layered double hydroxides (LDHs). Recent developments in the use of layered sodium silicates as precursors for the preparation of various porous, functional and catalytic materials including zeolites, mesoporous materials, pillared layered silicates, organic-inorganic nanocomposites and synthesis of highly dispersed nanoparticles supported on silica are reviewed in detail. Along this perspective, we have attempted to illustrate the reactivity and transformational potential of LDHs in order to deduce the main differences and similarities between these two types of layered materials. PMID:24841986

  15. Earth Layers Webquest

    NSDL National Science Digital Library

    oregonstate,edu

    2011-10-30

    This asset is a webquest that guides students through the layers of the earth then asks them to answer a series of questions about their journey. The question page links back to the content for review. Students can then explore Volcano World magazine as an enrichment.

  16. Layered Depth Images

    Microsoft Academic Search

    Jonathan Shade; Steven J. Gortler; Li-wei He; Richard Szeliski

    1998-01-01

    In this paper we present a set of efficient image based rendering methods capable of rendering multiple frames per second on a PC.The first method warps Sprites with Depth representing smooth surfaces without the gaps found in other techniques. A second method for more general scenes performswarping from an intermediate representation called a Layered Depth Image (LDI). An LDI is

  17. Rendering Layered Depth Images

    Microsoft Academic Search

    Steven J. Gortler; Li-wei He; Michael F. Cohen

    1997-01-01

    In this paper we present an efficient image based rendering system that renders multipleframes per second on a PC. Our method performs warping from an intermediate representationcalled a layered depth image (LDI). An LDI is a view of the scene from a single inputcamera view, but with multiple pixels along each line of sight. When n input images arepreprocessed to

  18. TRANSPORT LAYER INTRODUCTION

    E-print Network

    Chiang, Mung

    and has changed many important aspects of our lives. Like any complex engineering system, the design, such as the hypertext transport protocol (HTTP) used to browse the Web, or the simple mail transfer protocol (SMTP) used sending e-mails. The net- work layer only cares about sending a stream of data out of the computer

  19. Outline o Layering

    E-print Network

    Biagioni, Edoardo S.

    Outline o Layering: - OSI - Internet o Ethernet) o Transport: reliability, end-to-end issues (TCP, UDP) o Network: basic end-to-end connectivity (IP, ATM AAL) o Data Link: hop-by-hop connectivity, framing (Ethernet, FDDI, ATM cells

  20. 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...

  1. Physical Layer CSC 343643

    E-print Network

    Fulp, Errin W.

    to electromagnetic (EM) waves (digital analog) · Receiver ­ Converts EM to bits (analog digital) · Communication·643 Fall 2013 3 #12;Sine Waves · Sine wave is the most fundamental form of a periodic analog signal · Three Physical Layer Concerned with moving information in the form of electromagnetic (EM) signals across

  2. Physical Layer CSC 343643

    E-print Network

    Fulp, Errin W.

    to electromagnetic (EM) waves (digital # analog) . Receiver -- Converts EM to bits (analog # digital) . Communication·643 Fall 2013 3 #12; Sine Waves . Sine wave is the most fundamental form of a periodic analog signal Physical Layer Concerned with moving information in the form of electromagnetic (EM) signals across

  3. Tapered acoustic matching layers

    Microsoft Academic Search

    M. I. Haller; B. T. Khuri-Yakub

    1993-01-01

    Typical ultrasonic transducers for immersion applications use one or more matching layers to increase their efficiency and bandwidth. In microwave circuits, it is common to use tapered impedance transformers to increase bandwidth. This has not been possible for acoustic transducers because of the difficulty of fabricating materials with a smoothly tapered acoustic impedance. We propose the use of silicon micromachining

  4. Layer Cake Geology

    NSDL National Science Digital Library

    John Wagner

    This classroom activity uses a cake to demonstrate geologic processes and introduce geologic terms. Students will learn how folds and faults occur, recognize the difference in behavior between brittle and ductile rocks, and attempt to predict structures likely to result from application of various forces to layered rocks. They will also attempt to interpret 'core samples' to determine subsurface rock structure.

  5. 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…

  6. 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…

  7. Influence of haze layers upon remotely-sensed surface properties

    NASA Technical Reports Server (NTRS)

    Jurica, G. M.; Murray, W. L.

    1972-01-01

    The possibility that the presence of hazy layers contributes to anomalous effects in airplane remote sensing data on corn blight distribution is studied. Computations of scattering angles along flightlines are used to estimate reflected intensity variations as observed in bright and dark sides along flightline of the aircraft.

  8. Langmuir probe measurements of double-layers in a pulsed discharge

    NASA Technical Reports Server (NTRS)

    Levine, J. S.; Crawford, F. W.

    1980-01-01

    Langmuir probe measurements were carried out which confirm the occurrence of double-layers in an argon positive column. Pulsing the discharge current permitted probe measurements to be performed in the presence of the double-layer. Supplementary evidence, obtained from DC and pulsed discharges, indicated that the double-layers formed in the two modes of operation were similar. The double-layers observed were weak and stable; their relation to other classes of double-layers are discussed, and directions for future work are suggested.

  9. 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.

  10. Numerical evaluation of electromagnetic fields due to dipole antennas in the presence of stratified media

    NASA Technical Reports Server (NTRS)

    Tsang, L.; Brown, R.; Kong, J. A.; Simmons, G.

    1974-01-01

    Two numerical methods are used to evaluate the integrals that express the em fields due to dipole antennas radiating in the presence of a stratified medium. The first method is a direct integration by means of Simpson's rule. The second method is indirect and approximates the kernel of the integral by means of the fast Fourier transform. In contrast to previous analytical methods that applied only to two-layer cases the numerical methods can be used for any arbitrary number of layers with general properties.

  11. Peeling Back the Layers

    NASA Technical Reports Server (NTRS)

    2004-01-01

    NASA's Mars Exploration Rover Spirit took this panoramic camera image of the rock target named 'Mazatzal' on sol 77 (March 22, 2004). It is a close-up look at the rock face and the targets that will be brushed and ground by the rock abrasion tool in upcoming sols.

    Mazatzal, like most rocks on Earth and Mars, has layers of material near its surface that provide clues about the history of the rock. Scientists believe that the top layer of Mazatzal is actually a coating of dust and possibly even salts. Under this light coating may be a more solid portion of the rock that has been chemically altered by weathering. Past this layer is the unaltered rock, which may give scientists the best information about how Mazatzal was formed.

    Because each layer reveals information about the formation and subsequent history of Mazatzal, it is important that scientists get a look at each of them. For this reason, they have developed a multi-part strategy to use the rock abrasion tool to systematically peel back Mazatzal's layers and analyze what's underneath with the rover's microscopic imager, and its Moessbauer and alpha particle X-ray spectrometers.

    The strategy began on sol 77 when scientists used the microscopic imager to get a closer look at targets on Mazatzal named 'New York,' 'Illinois' and 'Arizona.' These rock areas were targeted because they posed the best opportunity for successfully using the rock abrasion tool; Arizona also allowed for a close-up look at a range of tones. On sol 78, Spirit's rock abrasion tool will do a light brushing on the Illinois target to preserve some of the surface layers. Then, a brushing of the New York target should remove the top coating of any dust and salts and perhaps reveal the chemically altered rock underneath. Finally, on sol 79, the rock abrasion tool will be commanded to grind into the New York target, which will give scientists the best chance of observing Mazatzal's interior.

    The Mazatzal targets were named after the home states of some of the rock abrasion tool and science team members.

  12. Field recovery of layered tektites in northeast Thailand

    SciTech Connect

    Wasson, J.T. [Univ. of California, Los Angeles, CA (United States)] [Univ. of California, Los Angeles, CA (United States); Pitakpaivan, K.; Putthapiban, P. [Department of Mineral Resources, Bangkok (Taiwan, Province of China)] [and others] [Department of Mineral Resources, Bangkok (Taiwan, Province of China); and others

    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.

  13. 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 ...

  14. 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 ...

  15. Slow-wave resonance in periodic stacks of anisotropic layers

    NASA Astrophysics Data System (ADS)

    Figotin, Alex; Vitebskiy, Ilya

    2007-11-01

    We consider a Fabry-Perot resonance (a transmission band edge resonance) in periodic layered structures involving birefringent layers. In a previous publication [Phys. Rev. E 72, 036619 (2005)] we have shown that the presence of birefringent layers with misaligned in-plane anisotropy can dramatically enhance the performance of the photonic-crystal resonator. It allows us to reduce its size by an order of magnitude without compromising on its performance. The key characteristic of the enhanced slow-wave resonator is that the Bloch dispersion relation ?(k) of the periodic structure displays a degenerate photonic band edge, in the vicinity of which the dispersion curve can be approximated as ??˜(?k)4 , rather than ??˜(?k)2 . Such a situation can be realized in specially arranged stacks of misaligned anisotropic layers. On the down side, the presence of birefringent layers results in the slow-wave resonance being coupled only with one (elliptic) polarization component of the incident wave, while the other polarization component is reflected back to space. In this paper we show how a small modification of the periodic layered array can solve the above fundamental problem and provide a perfect impedance match regardless of the incident wave polarization, while preserving the giant slow-wave resonance characteristic of a degenerate photonic band edge. Both features are of critical importance for many practical applications, such as the enhancement of various light-matter interactions, light amplification and lasing, optical and microwave filters, antennas, etc.

  16. Slow wave resonance in periodic stacks of anisotropic layers

    E-print Network

    Alex Figotin; Ilya Vitebskiy

    2007-07-11

    We consider transmission band edge resonance in periodic layered structures involving birefringent layers. Previously we have shown that the presence of birefringent layers with misaligned in-plane anisotropy can dramatically enhance the performance of the photonic-crystal Fabry-Perot resonator. It allows to reduce its size by an order of magnitude without compromising on its performance. The key characteristic of the enhanced photonic-crystal cavity is that its Bloch dispersion relation displays a degenerate photonic band edge, rather than only regular ones. This can be realized in specially arranged stacks of misaligned anisotropic layers. On the down side, the presence of birefringent layers results in the Fabry-Perot resonance being coupled only with one (elliptic) polarization component of the incident wave, while the other polarization component is reflected back to space. In this paper we show how a small modification of the periodic layered array can solve the above fundamental problem and provide a perfect impedance match regardless of the incident wave polarization, while preserving the giant transmission resonance, characteristic of a degenerate photonic band edge. Both features are of critical importance for a variety of practical applications, including antennas, light amplification, optical and microwave filters, etc.

  17. Relationship between ocean velocity and motionally induced electrical signals: 1. In the presence of horizontal velocity gradients

    Microsoft Academic Search

    Zoltan B. Szuts

    2010-01-01

    Motionally induced electric fields and electric currents in the ocean depend to first order solely on the vertical dimension. We investigate the significance of two-dimensional (2-D) perturbations that arise in the presence of horizontal velocity gradients. The full electric response is calculated for two schematic geometries that contain horizontal velocity gradients, have a two-layer ocean with a layer of sediment

  18. Development of an etchant for selectively etching TiWNx in the presence of electroplated 95%Pb5%Sn solder

    Microsoft Academic Search

    L. N. Ramanathan; D. Mitchell

    2000-01-01

    Shrinking die sizes and increasing I\\/O density is motivating the push towards flip chip packages. A flip chip interconnection system with a under bump metallurgy stack containing sputtered TiWNx\\/sputtered Cu\\/electroplated Cu stud\\/electroplated 95%Pb-5%Sn was developed. An important step in the above process is the selective etching of the sputtered Cu bus layer and the TiWNx barrier layer, in the presence-of

  19. Development of an etchant for selectively etching TiWNx in the presence of electroplated 95%Pb5%Sn solder

    Microsoft Academic Search

    Lakshmi N. Ramanathan; Doug Mitchell

    2001-01-01

    Shrinking die sizes and increasing I\\/O density is motivating the push toward flip chip packages. A flip chip interconnection system with a under bump metallurgy stack containing sputtered TiWNX\\/sputtered Cu\\/electroplated Cu stud\\/electroplated 95%Pb-5%Sn was developed. An important step in the above process is the selective etching of the sputtered Cu bus layer and the TiWNX barrier layer, in the presence

  20. 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.

  1. Two-layered phantom experiments for characterizing the influence of a fat layer on measurement of muscle oxygenation using NIRS

    NASA Astrophysics Data System (ADS)

    Lin, Ling; Niwayama, Masatsugu; Shiga, Toshikazu; Kudo, Nobuki; Takahashi, Makoto; Yamamoto, Katsuyuki

    1998-04-01

    Two-layered phantom experiments were performed to examine the influence of a fat layer on measurement of muscle oxygenation using near-IR spectroscopy (NIRS). The phantom consisted of a fat-like layer and a muscle-like layer which were a mixture of agar and TiO2 powder and a suspension of washed bovine blood into 0.55 percent intralipid solution. An LED including 760 and 840 nm elements was used as the optical source, and the reflectance light was detected by photodiodes at source-detector distances of 20, 30 and 40 mm. Curves of optical density changes versus blood volume ratio were obtained with fat-like layer thickness of 0, 5, 10 and 15 mm. It was found that the change in optical density is significantly decreased and that the linearity of measurement characteristics clearly deteriorated by the presence of a fat layer. This strongly suggests that a new algorithm is needed for muscle oxygenation measurement to eliminate the influence of a fat layer. In addition to the phantom experiments, Monte Carlo simulations corresponding to the experiments were performed. Although the simulations showed similar results concerning the influence of a fat layer, it was noted that the changes in optical density obtained from simulations were lower than those of the phantom experiments. This discrepancy was though to be due to the light scattering caused by blood cells.

  2. 40 CFR 312.31 - The degree of obviousness of the presence or likely presence of contamination at the property...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...the presence or likely presence of contamination at the property, and the ability to detect the contamination by appropriate investigation. 312...the presence or likely presence of contamination at the property, and the...

  3. 40 CFR 312.31 - The degree of obviousness of the presence or likely presence of contamination at the property...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...the presence or likely presence of contamination at the property, and the ability to detect the contamination by appropriate investigation. 312...the presence or likely presence of contamination at the property, and the...

  4. Influence of wall suction on the organized motion in a turbulent boundary layer

    Microsoft Academic Search

    R. A. Antonia; L. V. Krishnamoorthy; L. Fulachier; T. Benabid; F. Anselmet

    1988-01-01

    Experimental wind tunnel and water tunnel studies have been performed in order to investigate the effect of wall suction on the organized motion of a turbulent boundary layer. Temperature traces in a wind-tunnel boundary layer developed over a slightly heated surface reveal the presence of two spatially coherent events which are characterized either by a sudden decrease or increase of

  5. Boundary-layer receptivity due to distributed surface imperfections of a deterministic or random nature

    Microsoft Academic Search

    Meelan Choudhari

    1992-01-01

    Acoustic receptivity of a Blasius boundary layer in the presence of distributed surface irregularities is investigated analytically. It is shown that, out of the entire spatial spectrum of the surface irregularities, only a small band of Fourier components can lead to an efficient conversion of the acoustic input at any given frequency to an unstable eigenmode of the boundary layer

  6. Experimental investigation of 3D acoustic receptivity of an airfoil boundary layer due to surface vibrations

    Microsoft Academic Search

    A. V. Ivanov; W. Wurz; S. Herr; S. Wagner; Y. S. Kachanov

    2005-01-01

    The three-dimensional acoustic receptivity of laminar boundary layers in presence of microscopic surface vibrations (the vibro-acoustic receptivity) is examined. The flow under investigation is the boundary layer on an airfoil at relatively high Reynolds numbers close to realistic ones for gliders. This flow has favourable and adverse pressure gradients and develops on a curved wall. The goal of the present

  7. Boundary-layer receptivity due to distributed surface imperfections of a deterministic or random nature

    Microsoft Academic Search

    Meelan Choudhari

    1993-01-01

    Acoustic receptivity of a Blasius boundary layer in the presence of distributed, two-dimensional surface irregularities is investigated analytically. It is shown that, out of the entire spatial spectrum of the surface irregularities, only a narrow band of Fourier components can lead to an efficient conversion of the acoustic input at any given frequency to an unstable eigenmode of the boundary-layer

  8. The detection and measurement of turbulent structures in the atmospheric surface layer

    Microsoft Academic Search

    J. L. J. Schols

    1984-01-01

    Turbulence data from the planetary boundary layer (PBL) indicate the presence of deterministic turbulent structures. These structures often show up as asymmetric ramp patterns in measurements of the turbulent fluctuations of a scalar quantity in the atmospheric surface layer (ASL). The sign of the slope of the sharp upstream edge of such a triangular pattern depends on the thermal stability

  9. Nitrate reduction catalyzed by nanocomposite layer of Ag and Pb Seongpil Hwang, Joohan Lee, Juhyoun Kwak *

    E-print Network

    Kwak, Juhyoun

    Nitrate reduction catalyzed by nanocomposite layer of Ag and Pb on Au(111) Seongpil Hwang, Joohan) of silver and lead on Au(111) was performed sequentially to produce a thin composite layer. Ag was deposited of the Ag adlayer in the Pb2+ electrolyte. In the presence of sodium nitrate, this composite system exhibits

  10. The Effects of Ground Plane and Parasitic Layer on Linearly Tapered Slot Antenna

    NASA Technical Reports Server (NTRS)

    Lee, Richard Q.; Simons, Rainee N.

    1996-01-01

    The effects of a large ground plane and an upper parasitic layer on a linearly tapered slot antenna has been experimentally investigated. Results indicate that the presence of a large ground plane causes the beam to steer by as much as 50 deg from the endfire direction in the H-plane. With the addition of a parasitic layer above the fed antenna, further beam scanning can be achieved when the spacing between the fed and parasitic layers is properly chosen.

  11. Traveling Salesmen in the Presence of Competition

    E-print Network

    Fleischer, Rudolf

    a (weighted) graph G = (V; E) and the task to #12;nd a shortest roundtrip that visits every vertex precisely the \\Competitive Salesmen problem" (CSP): We are given a (directed or undirected) road system, i.e., a graph G = (VTraveling Salesmen in the Presence of Competition S#19;andor P. Fekete Department of Mathematical

  12. Tensions in Rhetorics of Presence and Performance

    ERIC Educational Resources Information Center

    Watanabe, Sundy Louise

    2012-01-01

    This dissertation draws on theories of survivance and rhetorical sovereignty to document and interrogate interactional tensions in rhetorics of presence and performance occurring between selected American Indian students and non-Native faculty, staff, and graduate research assistants within a research-extensive university context. Tensions arise,…

  13. Synchronizing clocks in the presence of faults

    Microsoft Academic Search

    Leslie Lamport; P. M. Melliar-Smith

    1985-01-01

    Algorithms are described for maintaining clock synchrony in a distributed multiprocess system where each process has its own clock. These algorithms work in the presence of arbitrary clock or process failures, including “two-faced clocks” that present different values to different processes. Two of the algorithms require that fewer than one-third of the processes be faulty. A third algorithm works if

  14. Cisco TelePresence Movi for Windows

    E-print Network

    Derisi, Joseph

    Cisco TelePresence Movi for Windows User Guide 14409.07 April 2011 Software version 4.2.0.10318 #12;Movi for Windows User Guide (4.2) Page 2 of 21 Contents Getting started 4 Signing in 4 Show video window 4 Making a call 4 Receiving a call 4 Pop-up toolbar 6 Selfview and camera control 6 Controlling

  15. Controlling chaos in the presence of noise

    Microsoft Academic Search

    Dorning

    1991-01-01

    Although the presence of nonlinearity in real-world complex engineering systems is hardly a revelation, only recently has it been realized how ubiquitous and far-reaching its effects are. Important examples of oscillatory and chaotic behavior of complex, and even simple, nonlinear engineering systems abound. These are supplemented by an immense number of related scientific examples from pioneering laboratory experiments. Naturally, interest

  16. Acoustic levitation in the presence of gravity

    Microsoft Academic Search

    P. Collas; M. Barmatz; C. Shipley

    1989-01-01

    The method of Gor'kov (1961) has been applied to derive general expressions for the total potential and force on a small spherical object in a resonant chamber in the presence of both acoustic and gravitational force fields. The levitation position is also determined in rectangular resonators for the simultaneous excitation of up to three acoustic modes, and the results are

  17. Developing Presence in Online Undergraduate Courses

    ERIC Educational Resources Information Center

    Casey, Rae L.

    2013-01-01

    The purpose of this basic interpretive qualitative study (Merriam, 2009) was to understand the factors that excellent online faculty perceived as important to the development of presence in their online courses. Eight faculty members at two institutions in the northwest region of the United States participated in the study. Data were collected…

  18. Presence and interaction in mixed reality environments

    Microsoft Academic Search

    Arjan Egges; George Papagiannakis; Nadia Magnenat-thalmann

    2007-01-01

    In this paper, we present a simple and robust Mixed Reality (MR) framework that allows for real-time interaction with Virtual Humans in real and virtual en- vironments under consistent illumination. We will look at three crucial parts of this system: interaction, ani- mation and global illumination of virtual humans for an integrated and enhanced presence. The interaction system comprises of

  19. Extending Human Presence into the Solar System

    E-print Network

    Rathbun, Julie A.

    Extending Human Presence into the Solar System An Independent Study for The Planetary Society. Dependence on International Partners 14 3. Regulatory Concerns 15 Safety and Exploration Beyond LEO 15) and the smallest number of additional flights necessary to satisfy our international partners' ISS requirements

  20. Ultrasound attenuation measurement the presence scatterer variation

    E-print Network

    Drummond, Tom

    Ultrasound attenuation measurement the presence scatterer variation for reduction shadowing.cam.ac.uk #12; #12; Abstract Pulse­echo ultrasound display relies many assumptions which known incorrect. De­ parture these makes interpretation conventional ultrasound images di#cult, and visu­ alisations harder

  1. Providing presence cues to telephone users

    Microsoft Academic Search

    Allen E. Milewski; Thomas M. Smith

    2000-01-01

    A significant problem with telephone communication is that callers do not have enough awareness about the Personal Presence of people they want to call. The result can be unwanted, interrupting calls. Thelive addressbookis an application that helps users make more informed telephone calls and teleconferences, from anywhere, via their wireless PDA or desktop browser. Unlike other network-based address books, which

  2. Formation of sporadic sodium layers

    Microsoft Academic Search

    B. R. Clemesha; P. P. Batista; D. M. Simonich

    1996-01-01

    A study of sporadic sodium (Ns) layers observed at So Jos6 dos Campos (23øS, 46øW) shows that during their occurrence the form of the background sodium layer is differ- ent from that which it normally takes when Ns layers are absent. During Ns events, peak so- dium in the background layer typically occurs below 90 km, whereas the peak of

  3. Boundary layers in centrifugal compressors

    Microsoft Academic Search

    R. C. Dean Jr.

    1974-01-01

    The utility of boundary-layer theory in the design of centrifugal compressors is demonstrated. Boundary-layer development in the diffuser entry region is shown to be important to stage efficiency. The result of an earnest attempt to analyze this boundary layer with the best tools available is displayed. Acceptable prediction accuracy was not achieved. The inaccuracy of boundary-layer analysis in this case

  4. Reuse in the application layer

    Microsoft Academic Search

    Hirotomo Okuno; Hideki Matsumoto; Hironori Asai; Mikiko Sakurai; Takao Nakayama

    1996-01-01

    Today's advanced CASE tools, combining the building-block and generative approaches to software reuse, are effective for reuse of software components and procedures in the presentation layer and data layer of the three-layer model. There are no effective tools generally available, however, for reuse of application-layer components and procedures, which are usually too numerous and small for efficient reuse. Programmers therefore

  5. 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.

  6. Low-temperature formation of CoSi2 in the presence of Au

    NASA Astrophysics Data System (ADS)

    Detavernier, C.; Lavoie, C.; d'Heurle, F. M.; Bender, H.; Van Meirhaeghe, R. L.

    2004-05-01

    The formation of cobalt silicides was studied in the presence of interlayers and capping layers of Au, using both ex situ and in situ characterization techniques. The formation temperature of CoSi2 was found to be significantly lowered in the presence of Au. Two regimes can be discerned. For thin interlayers or capping layers, Au does not significantly affect the formation of Co2Si and CoSi, while it lowers the nucleation temperature of CoSi2. For thick interlayers, CoSi2 appears to form as the first phase at temperatures as low as 300 °C. The results are discussed within the context of classical nucleation theory and known models for phase selection during solid-state reactions.

  7. Electron energy-loss spectroscopy on the surface of conducting superlattices in the presence of plasma waves

    NASA Astrophysics Data System (ADS)

    Vázquez-Nava, R. A.; Cocoletzi, G. H.; Castillo-Mussot, M. Del; Mochán, W. Luis

    1998-06-01

    We present calculations for the inelastic scattering of electrons by the surface of binary conductor-conductor periodic superlattices described by local and nonlocal models. The conducting layers consist of metals or highly doped semiconductors and we include their spatial dispersion through the presence of longitudinal plasmons described by a hydrodynamic model. These modes manifest themselves as a series of peaks in the electron-energy-loss spectroscopy spectrum superimposed on the main structure due to the excitation of two coupled surface-plasmon bands. These peaks depend upon the nature of the first layer and are sensitive to the first few layers.

  8. Lidar observations of sodium density depletions in the presence of polar mesospheric clouds

    Microsoft Academic Search

    Jeffrey P. Thayer; Weilin Pan

    2006-01-01

    Since 1997, sodium resonance lidar and Rayleigh lidar measurements have been conducted simultaneously at the Sondrestrom upper atmosphere research facility near Kangerlussuaq, Greenland (67.0°N, 309.1°E) for studying the arctic mesosphere. The summertime lidar observations during the typical polar mesospheric cloud (PMC) season from June through August are used to investigate changes in the mesospheric sodium layer related to the presence

  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. An efficient CG method for layered problems with large contrasts in the coefficients

    E-print Network

    is confronted with when drilling for oil, is the presence of large excess pressures in underground layers \\Lambda Guus Segal \\Lambda Koos Meijerink y 1 Introduction One of the problems an oil company. Knowledge of the excess pressure may be of big help in the prediction of the presence of oil and gas

  11. Layered Crater Walls

    NASA Technical Reports Server (NTRS)

    2006-01-01

    16 September 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an impact crater that is approximately 3.5 kilometers (2.2 miles) in diameter. It is located to the northeast of Olympus Mons, in the Tharsis Region. Layered rock units are visible on the inside of the raised crater rim.

    Location near: 70.7oN, 271.0oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Spring

  12. Layered Trough Walls

    NASA Technical Reports Server (NTRS)

    2005-01-01

    2 May 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows layers of bedrock exposed in the walls on both sides of an east-west-trending trough in the Memnonia/Mangala Valles region. Large boulders released from these rocky trough walls are found on the slopes and on the trough floor.

    Location near: 18.4oS, 148.8oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Winter

  13. 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.

  14. 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.

  15. Capillary filling under electro-osmotic effects in the presence of electromagneto-hydrodynamic effects.

    PubMed

    Desai, Nikhil; Ghosh, Uddipta; Chakraborty, Suman

    2014-06-01

    We report various regimes of capillary filling dynamics under electromagneto-hydrodynamic interactions, in the presence of electrical double layer effects. Our chosen configuration considers an axial electric field and transverse magnetic field acting on an electrolyte. We demonstrate that for positive interfacial potential, the movement of the capillary front resembles capillary rise in a vertical channel under the action of gravity. We also evaluate the time taken by the capillary front to reach the final equilibrium position for positive interfacial potential and show that the presence of a transverse magnetic field delays the time of travel of the liquid front, thereby sustaining the capillary motion for a longer time. Our scaling estimates reveal that the initial linear regime starts, as well as ends, much earlier in the presence of electrical and magnetic body forces, as compared to the corresponding transients observed under pure surface tension driven flow. We further obtain a long time solution for the capillary imbibition for positive interfacial potential, and derive a scaling estimate of the capillary stopping time as a function of the applied magnetic field and an intrinsic length scale delineating electromechanical influences of the electrical double layer. Our findings are likely to offer alternative strategies of controlling dynamical features of capillary imbibition, by modulating the interplay between electromagnetic interactions, electrical double layer phenomena, and hydrodynamics over interfacial scales. PMID:25019889

  16. Capillary filling under electro-osmotic effects in the presence of electromagneto-hydrodynamic effects

    NASA Astrophysics Data System (ADS)

    Desai, Nikhil; Ghosh, Uddipta; Chakraborty, Suman

    2014-06-01

    We report various regimes of capillary filling dynamics under electromagneto-hydrodynamic interactions, in the presence of electrical double layer effects. Our chosen configuration considers an axial electric field and transverse magnetic field acting on an electrolyte. We demonstrate that for positive interfacial potential, the movement of the capillary front resembles capillary rise in a vertical channel under the action of gravity. We also evaluate the time taken by the capillary front to reach the final equilibrium position for positive interfacial potential and show that the presence of a transverse magnetic field delays the time of travel of the liquid front, thereby sustaining the capillary motion for a longer time. Our scaling estimates reveal that the initial linear regime starts, as well as ends, much earlier in the presence of electrical and magnetic body forces, as compared to the corresponding transients observed under pure surface tension driven flow. We further obtain a long time solution for the capillary imbibition for positive interfacial potential, and derive a scaling estimate of the capillary stopping time as a function of the applied magnetic field and an intrinsic length scale delineating electromechanical influences of the electrical double layer. Our findings are likely to offer alternative strategies of controlling dynamical features of capillary imbibition, by modulating the interplay between electromagnetic interactions, electrical double layer phenomena, and hydrodynamics over interfacial scales.

  17. QUANTIFICATION OF NUCLEOLAR CHANNEL SYSTEMS: UNIFORM PRESENCE THROUGHOUT THE UPPER ENDOMETRIAL CAVITY

    PubMed Central

    Szmyga, Michael J.; Rybak, Eli A.; Nejat, Edward J.; Banks, Erika H.; Whitney, Kathleen D.; Polotsky, Alex J.; Heller, Debra S.; Meier, U. Thomas

    2014-01-01

    Objective To determine the prevalence of nucleolar channel systems (NCSs) by uterine region applying continuous quantification. Design Prospective clinical study. Setting Tertiary care academic medical center. Patients 42 naturally cycling women who underwent hysterectomy for benign indications. Intervention NCS presence was quantified by a novel method in six uterine regions, fundus, left cornu, right cornu, anterior body, posterior body, and lower uterine segment (LUS), using indirect immunofluorescence. Main Outcome Measures Percent of endometrial epithelial cells (EECs) with NCSs per uterine region. Results NCS quantification was observer-independent (intraclass correlation coefficient [ICC] = 0.96) and its intra-sample variability low (coefficient of variability [CV] = 0.06). 11/42 hysterectomy specimens were midluteal, 10 of which were analyzable with 9 containing over 5% EECs with NCSs in at least one region. The percent of EECs with NCSs varied significantly between the lower uterine segment (6.1%; IQR = 3.0-9.9) and the upper five regions (16.9%; IQR = 12.7-23.4) with fewer NCSs in the basal layer of the endometrium (17% +/?6%) versus the middle (46% +/?9%) and luminal layers (38% +/?9%) of all six regions). Conclusions NCS quantification during the midluteal phase demonstrates uniform presence throughout the endometrial cavity, excluding the LUS, with a preference for the functional, luminal layers. Our quantitative NCS evaluation provides a benchmark for future studies and further supports NCS presence as a potential marker for the window of implantation. PMID:23137760

  18. Lactobacillus surface layer proteins: structure, function and applications.

    PubMed

    Hynönen, Ulla; Palva, Airi

    2013-06-01

    Bacterial surface (S) layers are the outermost proteinaceous cell envelope structures found on members of nearly all taxonomic groups of bacteria and Archaea. They are composed of numerous identical subunits forming a symmetric, porous, lattice-like layer that completely covers the cell surface. The subunits are held together and attached to cell wall carbohydrates by non-covalent interactions, and they spontaneously reassemble in vitro by an entropy-driven process. Due to the low amino acid sequence similarity among S-layer proteins in general, verification of the presence of an S-layer on the bacterial cell surface usually requires electron microscopy. In lactobacilli, S-layer proteins have been detected on many but not all species. Lactobacillus S-layer proteins differ from those of other bacteria in their smaller size and high predicted pI. The positive charge in Lactobacillus S-layer proteins is concentrated in the more conserved cell wall binding domain, which can be either N- or C-terminal depending on the species. The more variable domain is responsible for the self-assembly of the monomers to a periodic structure. The biological functions of Lactobacillus S-layer proteins are poorly understood, but in some species S-layer proteins mediate bacterial adherence to host cells or extracellular matrix proteins or have protective or enzymatic functions. Lactobacillus S-layer proteins show potential for use as antigen carriers in live oral vaccine design because of their adhesive and immunomodulatory properties and the general non-pathogenicity of the species. PMID:23677442

  19. Topological insulators in the presence of interactions

    NASA Astrophysics Data System (ADS)

    Rachel, Stephan; Le Hur, Karyn

    2010-03-01

    We study the behavior of topological insulators in the presence of interactions. As a paradigm, we consider the Haldane model subject to a standard Hubbard onsite term. The Haldane model consists of a nearest neighbor tight binding model on a honeycomb lattice plus second neighbor hopping accounting for intrinsic spin-orbit interaction. For strong interactions, the system develops a Mott gap and we derive an effective spin model by including the intrinsic spin-orbit interaction. In the weak-coupling limit, we thoroughly investigate the competition between the Dirac liquid phase and the topological insulator phase which is favored by the Haldane term. The stability of the topological insulator phase in the presence of the Hubbard term is discussed.

  20. Sedimentation stability and aging of aqueous dispersions of Laponite in the presence of cetyltrimethylammonium bromide

    NASA Astrophysics Data System (ADS)

    Savenko, V.; Bulavin, L.; Rawiso, M.; Loginov, M.; Vorobiev, E.; Lebovka, N. I.

    2013-11-01

    This work discusses the sedimentation stability and aging of aqueous suspensions of Laponite in the presence of cetyltrimethylammonium bromide (CTAB). The concentration of Laponite was fixed at a constant level Cl=2 %wt, which corresponds to the threshold between equilibrium gel IG1 and glass IG2 states. The concentration of CTAB Cs was within 0-0.3 %wt. In the presence of CTAB, the Laponite aqueous suspensions were unstable against sedimentation and separated into the upper and bottom layers (U and B layers, respectively). The dynamic light-scattering technique has revealed that addition of CTAB even at a rather small concentration, Cs=0.0164 %wt (0.03 cation exchange capacity), induced noticeable changes in the aging dynamics of the U layer. It was explained by equilibration of CTAB molecules that were initially nonuniformly distributed between different Laponite particles. Accelerated stability analysis by means of analytical centrifugation with rotor speed ?=500-4000 rpm revealed three sedimentation regimes: continuous (I, Cs<0.14 %wt), zonelike (II, 0.140.2 %wt). It was demonstrated that the B layer was “soft” in the zonelike regime. The increase of ? resulted in its supplementary compressing and collapse of “soft” sediment above certain critical centrifugal acceleration. The physical nature of the observed behavior, accounting for enhancement of hydrophobic interactions between Laponite particles, is discussed.

  1. The density and refractive index of adsorbing protein layers.

    PubMed

    Vörös, Janos

    2004-07-01

    The structure of the adsorbing layers of native and denatured proteins (fibrinogen, gamma-immunoglobulin, albumin, and lysozyme) was studied on hydrophilic TiO(2) and hydrophobic Teflon-AF surfaces using the quartz crystal microbalance with dissipation and optical waveguide lightmode spectroscopy techniques. The density and the refractive index of the adsorbing protein layers could be determined from the complementary information provided by the two in situ instruments. The observed density and refractive index changes during the protein-adsorption process indicated the presence of conformational changes (e.g., partial unfolding) in general, especially upon contact with the hydrophobic surface. The structure of the formed layers was found to depend on the size of the proteins and on the experimental conditions. On the TiO(2) surface smaller proteins formed a denser layer than larger ones and the layer of unfolded proteins was less dense than that adsorbed from the native conformation. The hydrophobic surface induced denaturation and resulted in the formation of thin compact protein films of albumin and lysozyme. A linear correlation was found between the quartz crystal microbalance measured dissipation factor and the total water content of the layer, suggesting the existence of a dissipative process that is related to the solvent molecules present inside the adsorbed protein layer. Our measurements indicated that water and solvent molecules not only influence the 3D structure of proteins in solution but also play a crucial role in their adsorption onto surfaces. PMID:15240488

  2. The Density and Refractive Index of Adsorbing Protein Layers

    PubMed Central

    Vörös, Janos

    2004-01-01

    The structure of the adsorbing layers of native and denatured proteins (fibrinogen, ?-immunoglobulin, albumin, and lysozyme) was studied on hydrophilic TiO2 and hydrophobic Teflon-AF surfaces using the quartz crystal microbalance with dissipation and optical waveguide lightmode spectroscopy techniques. The density and the refractive index of the adsorbing protein layers could be determined from the complementary information provided by the two in situ instruments. The observed density and refractive index changes during the protein-adsorption process indicated the presence of conformational changes (e.g., partial unfolding) in general, especially upon contact with the hydrophobic surface. The structure of the formed layers was found to depend on the size of the proteins and on the experimental conditions. On the TiO2 surface smaller proteins formed a denser layer than larger ones and the layer of unfolded proteins was less dense than that adsorbed from the native conformation. The hydrophobic surface induced denaturation and resulted in the formation of thin compact protein films of albumin and lysozyme. A linear correlation was found between the quartz crystal microbalance measured dissipation factor and the total water content of the layer, suggesting the existence of a dissipative process that is related to the solvent molecules present inside the adsorbed protein layer. Our measurements indicated that water and solvent molecules not only influence the 3D structure of proteins in solution but also play a crucial role in their adsorption onto surfaces. PMID:15240488

  3. Hydroxyapatite crystallization in the presence of acetaminophen

    NASA Astrophysics Data System (ADS)

    Mangood, A.; Malkaj, P.; Dalas, E.

    2006-05-01

    The effect of acetaminophen; a widely used analgesic and fever reducing medicine; in supersaturated solutions of calcium phosphate was investigated under plethostatic conditions, at 37 °C, 0.15 M NaCl, pH 7.40. The rates of crystal growth measured in the presence of acetaminophen 1.654×10 -4 mol dm -3 to 6.616×10 -4 mol dm -3 were reduced by 43% to 79%, respectively. The inhibition effect on the crystal growth rate may be explained through adsorption onto the active growth sites. Kinetic analysis suggested Langmuir-type adsorption of acetaminophen on the HAP surface with a affinity value of 2.4×10 -4 dm 3 mol -1, for the substrate in the concentration range investigated. The electrophoretic mobility measurements showed that in the presence of acetaminophen the charge of the acetaminophen covered HAP particles was shifted to more negative values as compared to bare HAP. In the presence of acetaminophen no changes observed in the HAP overgrown morphology or in the apparent order of crystallization.

  4. Siderite dissolution in the presence of chromate

    NASA Astrophysics Data System (ADS)

    Tang, Yuanzhi; Martin, Scot T.

    2011-09-01

    Siderite (FeCO 3) is an important reduced phase iron mineral and end product of bacteria anaerobic respiration. This study addresses its dissolution behavior in the presence of the oxidant chromate, which is a common environmental contaminant. Macroscopic dissolution experiments combined with microscopic observations by atomic force microscopy show that at pH < 4.5 the dissolution rate with chromate is slower than that in control solution without chromate. Isolated deep dissolution pits and clustered shallow pits occur simultaneously with surface precipitation. The implication is that the surface precipitate inhibits further dissolution. For 5 < pH < 9.5, the slowest dissolution and the fastest precipitation rates are observed, both at edge steps and on terraces. For pH > 10, the dissolution rate in the presence of chromate exceeds that of the control, plausibly due to electron transfer facilitated by Fe(OH)4-. Dissolution and re-precipitation of round hillocks are observed. X-ray photoelectron spectroscopy indicates the presence of Cr(III) as well as reaction products in a hydroxide form. Based on the redox reaction mechanism, macroscopic dissolution behavior, and previous studies on the reaction products of Fe(II) with Cr(VI), we propose the formation of a low solubility nano-sized Cr(III)-Fe(III)-hydroxide as the surface precipitate. Results from this study provide a basis for understanding and quantifying the interactions between reduced-iron minerals and aqueous-phase oxidants.

  5. Liquefaction mechanism for layered soils

    SciTech Connect

    Fiegel, G.L.; Kutter, B.L. (Univ. of California, Davis, CA (United States). Dept. of Civil and Environmental Engineering)

    1994-04-01

    Results from four centrifuge model tests are presented. Three of the model tests involve layered soil deposits subject to base shaking; one model test involves a uniform soil deposit of sand subject to base shaking. The layered soil models consisted of fine sand overlain by a layer of relatively impermeable silica flour (silt). Pore-water pressures, accelerations, and settlements were measured during all four tests. Results from the model tests involving layered soils suggest that during liquefaction a water interlayer or very loose zone of soil may develop at the sand-silt interface due to the difference in permeabilities. In each layered model test, boils were observed on the surface of the silt layer. These boils were concentrated in the thinnest zones of the overlying silt layer and provided a vent for the excess pore-water pressure generated in the fine sand.

  6. Layers for Novel Photovoltaic Materials

    NASA Astrophysics Data System (ADS)

    Uruno, Aya; Usui, Ayaka; Kobayashi, Masakazu

    2014-08-01

    AgGaTe2 and AgAlTe2 layers were grown on a-plane sapphire substrates by closed-space sublimation. These compounds replace Cd in CdTe with group I and III elements, and are, hence, expected to be ideal novel candidate materials for solar cells. The grown layers were confirmed to be stoichiometric AgGaTe2 and AgAlTe2 by x-ray diffraction (XRD). The AgAlTe2 layers had strong preference for the (112) orientation. The XRD spectrum of the AgGaTe2 layer was different from that of the AgAlTe2 layer, and strong peaks were observed for (103) and (110) diffraction. The variation in orientations of the grown layers was analyzed in detail by use of XRD pole figures, which revealed that the AgGaTe2 layers had an epitaxial relationship with the a-plane sapphire substrates.

  7. Thin layer chromatography.

    PubMed

    Santiago, Marina; Strobel, Scott

    2013-01-01

    In many experiments, it is important to be able to separate a mixture into its chemical components in order to isolate one compound or to assess the purity of the mixture. Thin layer chromatography (TLC) is one of the easiest and most versatile methods of doing this because of its low cost, simplicity, quick development time, high sensitivity, and good reproducibility. TLC is used by many industries and fields of research, including pharmaceutical production, clinical analysis, industrial chemistry, environmental toxicology, food chemistry, water, inorganic, and pesticide analysis, dye purity, cosmetics, plant materials, and herbal analysis. In its simplest form, glass plates are coated with a uniform layer of silica gel (SiO2). The dissolved sample is placed on the plate, and the plate is inserted into a screw-top jar containing the developing solvent and a piece of filter paper. When the solvent has risen to near the top of the plate, the plate is removed, dried, and visualized using UV light. Variations on this protocol are used for different purposes, including pretreating the sample, changing the sorbent, plate material, the solvent system, the development techniques, and method of detection and visualization or by coupling TLC to other techniques. PMID:24182936

  8. 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

  9. 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

  10. Layer-by-layer stereolithography of three-dimensional antennas

    Microsoft Academic Search

    Yilei Huang; Xun Gong; S. Hajela; W. J. Chappell

    2005-01-01

    Horn antennas are created using laser-based layer-by-layer stereolithography processing in which three-dimensional structures can be synthesized directly from three-dimensional CAD files. The horns are used as a simple demonstration of how to create three-dimensional objects using rapidly deposited two-dimensional layers of polymer. Two types of horns are created using the polymer fabrication and then metallized using a conductive ink seed

  11. 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.

  12. Interactive boundary-layer calculations of a transonic wing flow

    NASA Technical Reports Server (NTRS)

    Kaups, Kalle; Cebeci, Tuncer; Mehta, Unmeel

    1989-01-01

    Results obtained from iterative solutions of inviscid and boundary-layer equations are presented and compared with experimental values. The calculated results were obtained with an Euler code and a transonic potential code in order to furnish solutions for the inviscid flow; they were interacted with solutions of two-dimensional boundary-layer equations having a strip-theory approximation. Euler code results are found to be in better agreement with the experimental data than with the full potential code, especially in the presence of shock waves, (with the sole exception of the near-tip region).

  13. 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.

  14. Templated quasicrystalline molecular layers

    NASA Astrophysics Data System (ADS)

    Smerdon, Joe; Young, Kirsty; Lowe, Michael; Hars, Sanger; Yadav, Thakur; Hesp, David; Dhanak, Vinod; Tsai, An-Pang; Sharma, Hem Raj; McGrath, Ronan

    2014-03-01

    Quasicrystals are materials with long range ordering but no periodicity. We report scanning tunneling microscopy (STM) observations of quasicrystalline molecular layers on five-fold quasicrystal surfaces. The molecules adopt positions and orientations on the surface consistent with the quasicrystalline ordering of the substrate. Carbon-60 adsorbs atop sufficiently-separated Fe atoms on icosahedral Al-Cu-Fe to form a unique quasicrystalline lattice whereas further C60 molecules decorate remaining surface Fe atoms in a quasi-degenerate fashion. Pentacene (Pn) adsorbs at tenfold-symmetric points around surface-bisected rhombic triacontahedral clusters in icosahedral Ag-In-Yb. These systems constitute the first demonstrations of quasicrystalline molecular ordering on a template. EPSRC EP/D05253X/1, EP/D071828/1, UK BIS.

  15. Presence: the touch of the puppet.

    PubMed

    Zelevansky, Paul

    2006-09-01

    Using the ideal of the puppet as model and foil, this article looks at ideas about presence, play, animation, and belief. Puppetry's role as a vital, theatrical form has deep roots in universal, cultural experience, and the notion of an inhering spirit that acts for and through image, idol, toy, or fetish is perhaps the central thread running through all attempts to represent and simulate animate life. Through a discussion of the phenomenology of the puppet--the source of its sensory, aesthetic, and metaphysical power--questions are raised about the projection of desire and purpose onto other transitional things, real and imagined. PMID:17013678

  16. Six ways to establish a Web presence.

    PubMed

    Nagel, M

    2000-01-01

    Obtaining a Web presence may seem like a daunting task to many physicians. It's not, however. Because the Internet is quickly becoming the Yellow Pages of the 21st century, physicians without a Web site will not be able to be located by potential patients. This article provides information on six relatively simple and inexpensive methods that can be used to create a Web site, including: a personal Web page through Internet service providers; AMA Physicians Select; Medscape; a dot com biz card through Network Solutions; your own creation of a site; and a site created by a professional Web designer. PMID:14608769

  17. Adsorption of lanthanum to goethite in the presence of gluconate

    SciTech Connect

    Hull, Laurence C.; Sarah Pepper; Sue Clark

    2005-05-01

    Adsorption of Lanthanum to Goethite in the Presence of Gluconic Acid L. C. HULL,1 S. E. PEPPER2 AND S. B. CLARK2 1Idaho National Engineering and Environmental Laboratory, Idaho Falls, ID (hulllc@inel.gov) 2Washington State University, Pullman, WA (spepper@wsu.edu), (s_clark@wsu.edu) Lanthanide and trivalent-actinide elements in radioactive waste can pose risks to humans and ecological systems for many years. Organic complexing agents, from natural organic matter or the degradation of waste package components, can alter the mobility of these elements. We studied the effect of gluconic acid, as an analogue for cellulose degradation products, on the adsorption of lanthanum, representing lanthanide and trivalent-actinide elments, to goethite, representing natural iron minearals and degradation products of waste packages. Batch pH adsorption edge experiments were conducted with lanthanum alone, and with lanthanum and gluconate at a 1:1 mole ratio. Lanthanum concentrations studied were 0.1, 1, and 10 mM, covering a range from 10% to 1000% of the calculated available adsorption sites on goethite. In the absence of gluconate, lanthanum was primarily present in solution as free lanthanum ion. With gluconate present, free lanthanum concentration in solution decreased with increasing pH as step-wise deprotonation of the gluconate molecule increased the fraction lanthanum complexed with gluconate. Adsorption to the goethite surface was represented with the diffuse double-layer model. The number of adsorption sites and the intrinsic binding constants for the surface complexes were estimated from the pH adsorption edge data using the computer code FITEQL 4.0. Two surface reactions were used to fit the adsorption data in the absence of gluconate. A strong binding site with no proton release and a much higher concentration of weak binding sites with release of two protons per lanthanum adsorbed. The adsorption of lanthanum was not measurably affected by the presence of gluconate below pH 7. At pH values above 7, however, gluconate doubled the maximum amount of lanthanum adsorbed. This was modeled by including a ternary complex with a lanthanum-gluconate complex binding to a lanthanum bound on the surface. No spectroscopic data were obtained to verify the identify of the surface complexes. The presence of gluconate did not appear to affect the formation of solid lanthanum hydroxide at elevated pH and millimolar lanthanum concentrations. The effect of organic molecules on the mobility of lanthanides and trivalent-actinides cannot be simply described with equilibrium thermodynamic models based on currently available data.

  18. Artificial Neural Networks Single Layer Networks Multi Layer Networks Generalization Artificial Neural Networks

    E-print Network

    Kjellström, Hedvig

    Artificial Neural Networks Single Layer Networks Multi Layer Networks Generalization Artificial Neural Networks Artificial Neural Networks Single Layer Networks Multi Layer Networks Generalization 1 Artificial Neural Networks Properties Applications Classical Examples Biological Background 2 Single Layer

  19. Time dependent flexural gravity waves in the presence of current

    NASA Astrophysics Data System (ADS)

    Mohanty, S. K.; Mondal, R.; Sahoo, T.

    2014-02-01

    In the present study, a combined effect of current and compressive force on time dependent flexural gravity wave motion in both the cases of single and two-layer fluids is analyzed in finite and infinite water depths in two dimensions. The roots of the dispersion relation associated with the plane flexural gravity waves are analyzed via contour plots and by plotting various terms of the dispersion relation separately. The characteristic of plane flexural gravity waves is studied by analyzing the phase and group velocities along with the law of conservation of energy flux to understand the combined effect of current and compressive force on the wave motion. The integral form of the time dependent Green's function in the presence of current is obtained using the Laplace transform method and used in Green's identity to derive the time dependent velocity potential for the flexural gravity wavemaker problem. The time harmonic Green's function and velocity potentials are obtained as a special case from the time dependent problems. Numerical results are computed and analyzed in particular cases using the method of stationary phase to obtain the asymptotic results for Green's function and the deflection of ice sheet. The integral form of Green's function derived here will be suitable to deal with physical problem when the roots of the dispersion relation for the flexural gravity wave problem coalesces which were otherwise not possible in the eigenfunction expansion method used for time harmonic problems.

  20. Excited waves in shear layers

    NASA Technical Reports Server (NTRS)

    Bechert, D. W.

    1982-01-01

    The generation of instability waves in free shear layers is investigated. The model assumes an infinitesimally thin shear layer shed from a semi-infinite plate which is exposed to sound excitation. The acoustical shear layer excitation by a source further away from the plate edge in the downstream direction is very weak while upstream from the plate edge the excitation is relatively efficient. A special solution is given for the source at the plate edge. The theory is then extended to two streams on both sides of the shear layer having different velocities and densities. Furthermore, the excitation of a shear layer in a channel is calculated. A reference quantity is found for the magnitude of the excited instability waves. For a comparison with measurements, numerical computations of the velocity field outside the shear layer were carried out.

  1. Effects of mussel filtering activity on boundary layer structure

    NASA Astrophysics Data System (ADS)

    van Duren, Luca A.; Herman, Peter M. J.; Sandee, Adri J. J.; Heip, Carlo H. R.

    2006-01-01

    The structure of the benthic boundary layer over a bed of mussels ( Mytilus edulis) was investigated in a large racetrack flume. Flow was observed to be modified both by the physical roughness of the mussel bed and by the momentum input of the exhalent jets of the mussels. Particularly when the mussels were closed, and filtering activity was reduced to a minimum, we observed an internal boundary layer, around 4 cm thick, within the log layer. This internal boundary layer was often masked when the mussels were filtering actively. The presence of an internal boundary layer indicates that the boundary layer is not only structured by friction drag, but that form drag due to roughness elements also plays an important role. Consequently, estimates of bed shear stress based on velocity or Reynolds stress measurements carried out more than a few cm above the bed may be inaccurate. Over inactive mussels the shear velocity in the internal boundary layer (the roughness sub-layer) is smaller and bed shear stress is consequently reduced. Filtration activity of the mussels increased the velocity gradient in the lower layer at low and intermediate velocities, but at higher flow rates velocity profiles were not affected. Clear effects of the exhalent jets on absolute levels of TKE could be measured at all ambient velocities, while the effect on the Reynolds stress was limited. Velocity normalised TKE and Reynolds stress also indicated that the effect of the siphonal currents was limited at high velocities. Our results indicate that mussel filtration activity may have an important effect on exchange processes at the sediment-water interface, but that the extent of the effect is highly dependent on the ambient flow conditions.

  2. Oxygen-reducing catalyst layer

    DOEpatents

    O'Brien, Dennis P. (Maplewood, MN); Schmoeckel, Alison K. (Stillwater, MN); Vernstrom, George D. (Cottage Grove, MN); Atanasoski, Radoslav (Edina, MN); Wood, Thomas E. (Stillwater, MN); Yang, Ruizhi (Halifax, CA); Easton, E. Bradley (Halifax, CA); Dahn, Jeffrey R. (Hubley, CA); O'Neill, David G. (Lake Elmo, MN)

    2011-03-22

    An oxygen-reducing catalyst layer, and a method of making the oxygen-reducing catalyst layer, where the oxygen-reducing catalyst layer includes a catalytic material film disposed on a substrate with the use of physical vapor deposition and thermal treatment. The catalytic material film includes a transition metal that is substantially free of platinum. At least one of the physical vapor deposition and the thermal treatment is performed in a processing environment comprising a nitrogen-containing gas.

  3. Multiple-layer Radiation Absorber

    NASA Astrophysics Data System (ADS)

    Baker, Robert M. L.; Baker, Bonnie Sue

    A structure is discussed for absorbing incident radiation, either electromagnetic (EM) or sound. Such a surface structure is needed, for example, in a highly sensitive high-frequency gravitational wave or HFGW detector such as the Li-Baker. The multi-layer absorber, which is discussed, is constructed with metamaterial [MM] layer or layers on top. This MM is configured for a specific EM or sound radiation frequency band, which absorbs incident EM or sound radiation without reflection. Below these top MM layers is a substrate of conventional EM-radiation absorbing or acoustical absorbing reflective material, such as an array of pyramidal foam absorbers. Incident radiation is partially absorbed by the MM layer or layers, and then it is more absorbed by the lower absorbing and reflecting substrate. The remaining reflected radiation is even further absorbed by the MM layers on its "way out_ so that essentially all of the incident radiation is absorbed _ a nearly perfect black-body absorber. In a HFGW detector a substrate, such as foam absorbers, may outgas into a high vacuum and reduce the capability of the vacuum-producing equipment, however, the layers above this lowest substrate will seal the absorbing and reflecting substrate from any external vacuum. The layers also serve to seal the absorbing material against air or water flow past the surfaces of aircraft, watercraft or submarines. Other applications for such a multiple-level radiation absorber include stealth aircraft, missiles and submarines.

  4. Midlatitude sporadic-E layers

    NASA Technical Reports Server (NTRS)

    Smith, L. G.; Miller, K. L.

    1981-01-01

    Rocket borne probes and incoherent scatter radar were demonstrated to be effective methods of studying the structure of midlatitude sporadic E layers. Layers are formed when metal ions are converged vertically in a wind shear to produce a local enhancement of electron density. Rocket and radar observations show that the layers may occassionally have complex structure produced by an unstable wind shear. The partial transparency to radio waves of sporadic E layers is shown to be due to localized regions of high electron density.

  5. Secondary polymer layered impregnated tile

    NASA Technical Reports Server (NTRS)

    Tran, Huy K. (Inventor); Rasky, Daniel J. (Inventor); Szalai, Christine E. (Inventor); Carroll, Joseph A. (Inventor); Hsu, Ming-ta S. (Inventor)

    2005-01-01

    A low density organic polymer impregnated preformed fibrous ceramic article includes a plurality of layers. A front layer includes ceramic fibers or carbon fibers or combinations of ceramic fibers and carbon fibers, and is impregnated with an effective amount of at least one organic polymer. A middle layer includes polymer impregnated ceramic fibers. A back layer includes ceramic fibers or carbon fibers or combinations of ceramic fibers and carbon fibers, and is impregnated with an effective amount of at least one low temperature pyrolyzing organic polymer capable of decomposing without depositing residues.

  6. Seasonal variations of the Na and Fe layers at the South Pole and their implications for the chemistry and general circulation of the polar

    E-print Network

    Chu, Xinzhao

    [2] The presence of tenuous layers of neutral metal atoms in the upper atmosphere between about 75, and the metal layers too far below 85 km. They also show that an additional source of gas-phase metallic species] Until recently, only sporadic measurements of the mesospheric metal layers at high latitudes have been

  7. Layer-by-layer surface modification of lipid nanocapsules

    Microsoft Academic Search

    Samuli Hirsjärvi; Yan Qiao; Audrey Royere; Jérôme Bibette; Jean-Pierre Benoit

    2010-01-01

    Lipid nanocapsules (LNCs) were modified by adsorbing sequentially dextran sulfate (DS) and chitosan (CS) on their surface by the layer-by-layer (LBL) approach. Tangential flow filtration (TFF) was used in intermediate purifications of the LNC dispersion during the LBL process. The surface modification was based on electrostatic interactions between the coating polyelectrolytes (PEs) and the LNCs. Therefore, a cationic surfactant, lipochitosan

  8. Effect of ZnO seed layer on the morphology and optical properties of ZnO nanorods grown on GaN buffer layers

    SciTech Connect

    Nandi, R., E-mail: rajunandi@iitb.ac.in; Mohan, S., E-mail: rajunandi@iitb.ac.in; Major, S. S. [Department of Physics, Indian Institute of Technology Bombay, Mumbai - 400076 (India); Srinivasa, R. S. [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai - 400076 (India)

    2014-04-24

    ZnO nanorods were grown by chemical bath deposition on sputtered, polycrystalline GaN buffer layers with and without ZnO seed layer. Scanning electron microscopy and X-ray diffraction show that the ZnO nanorods on GaN buffer layers are not vertically well aligned. Photoluminescence spectrum of ZnO nanorods grown on GaN buffer layer, however exhibits a much stronger near-band-edge emission and negligible defect emission, compared to the nanorods grown on ZnO buffer layer. These features are attributed to gallium incorporation at the ZnO-GaN interface. The introduction of a thin (25 nm) ZnO seed layer on GaN buffer layer significantly improves the morphology and vertical alignment of ZnO-NRs without sacrificing the high optical quality of ZnO nanorods on GaN buffer layer. The presence of a thick (200 nm) ZnO seed layer completely masks the effect of the underlying GaN buffer layer on the morphology and optical properties of nanorods.

  9. Effect of ZnO seed layer on the morphology and optical properties of ZnO nanorods grown on GaN buffer layers

    NASA Astrophysics Data System (ADS)

    Nandi, R.; Mohan, S.; Srinivasa, R. S.; Major, S. S.

    2014-04-01

    ZnO nanorods were grown by chemical bath deposition on sputtered, polycrystalline GaN buffer layers with and without ZnO seed layer. Scanning electron microscopy and X-ray diffraction show that the ZnO nanorods on GaN buffer layers are not vertically well aligned. Photoluminescence spectrum of ZnO nanorods grown on GaN buffer layer, however exhibits a much stronger near-band-edge emission and negligible defect emission, compared to the nanorods grown on ZnO buffer layer. These features are attributed to gallium incorporation at the ZnO-GaN interface. The introduction of a thin (25 nm) ZnO seed layer on GaN buffer layer significantly improves the morphology and vertical alignment of ZnO-NRs without sacrificing the high optical quality of ZnO nanorods on GaN buffer layer. The presence of a thick (200 nm) ZnO seed layer completely masks the effect of the underlying GaN buffer layer on the morphology and optical properties of nanorods.

  10. Radar resonance reflection from sets of plane dielectric layers

    NASA Astrophysics Data System (ADS)

    Jackinsl, P. D.; Gaunaurd, G. C.

    1983-05-01

    The prediction of the Resonance Scattering Theory (RST) for the reflection coefficient from a set of two contiguous plane dielectric layers separating two semi-infinite dissimilar non-conducting media, is constructed and compared to the exact classical model solution. The comparsion serves to: (1) show the accuracy and simplicity of the RST prediction, and (2) to underline the usefulness of the RST to produce simple physical interpretations of generally complex phenomena. The analysis provides a systematic method for detecting the presence of a dielectric layer under another one covering it (possibly the situation caused by an oil spill in ice-covered Artic regions), by certain modulation effects present in the "response surface' of the returned echoes. This method also identifies the material composition of the lower or hidden layer in the bilaminar configuration. The process disentangles which resonance feature present in the radar reflection coefficient is caused by which of the two interacting layers. RST, therfore, solves the inverse scattering problem for the composition and thickness not only of the top visible (ice) layer, but also of the substance (oil) hidden under that upper layer.

  11. Natural melanin composites by layer-by-layer assembly

    NASA Astrophysics Data System (ADS)

    Eom, Taesik; Shim, Bong Sub

    2015-04-01

    Melanin is an electrically conductive and biocompatible material, because their conjugated backbone structures provide conducting pathways from human skin, eyes, brain, and beyond. So there is a potential of using as materials for the neural interfaces and the implantable devices. Extracted from Sepia officinalis ink, our natural melanin was uniformly dispersed in mostly polar solvents such as water and alcohols. Then, the dispersed melanin was further fabricated to nano-thin layered composites by the layer-by-layer (LBL) assembly technique. Combined with polyvinyl alcohol (PVA), the melanin nanoparticles behave as an LBL counterpart to from finely tuned nanostructured films. The LBL process can adjust the smart performances of the composites by varying the layering conditions and sandwich thickness. We further demonstrated the melanin loading degree of stacked layers, combination nanostructures, electrical properties, and biocompatibility of the resulting composites by UV-vis spectrophotometer, scanning electron microscope (SEM), multimeter, and in-vitro cell test of PC12, respectively.

  12. Boundary-Layer & health

    NASA Astrophysics Data System (ADS)

    Costigliola, V.

    2010-09-01

    It has long been known that specific atmospheric processes, such as weather and longer-term climatic fluctuations, affect human health. The biometeorological literature refers to this relationship as meteorotropism, defined as a change in an organism that is correlated with a change in atmospheric conditions. Plenty of (patho)physiological functions are affected by those conditions - like the respiratory diseases - and currently it is difficult to put any limits for pathologies developed in reply. Nowadays the importance of atmospheric boundary layer and health is increasingly recognised. A number of epidemiologic studies have reported associations between ambient concentrations of air pollution, specifically particulate pollution, and adverse health effects, even at the relatively low concentrations of pollution found. Since 1995 there have been over twenty-one studies from four continents that have explicitly examined the association between ambient air pollutant mixes and daily mortality. Statistically significant and positive associations have been reported in data from various locations around the world, all with varying air pollutant concentrations, weather conditions, population characteristics and public health policies. Particular role has been given to atmospheric boundary layer processes, the impact of which for specific patient-cohort is, however, not well understood till now. Assessing and monitoring air quality are thus fundamental to improve Europe's welfare. One of current projects run by the "European Medical Association" - PASODOBLE will develop and demonstrate user-driven downstream information services for the regional and local air quality sectors by combining space-based and in-situ data with models in 4 thematic service lines: - Health community support for hospitals, pharmacies, doctors and people at risk - Public information for regions, cities, tourist industry and sporting event organizers - Compliance monitoring support on particulate matter for regional environmental agencies - Local forecast model evaluation support for local authorities and city bodies. Giving value to the above listed aspects, PASODOBLE objectives are following: - Evolution of existing and development of new sustainable air quality services for Europe on regional and local scales - Development and testing of a generic service framework for coordinated input data acquisition and customizable user-friendly access to services - Utilization of multiple cycles of delivery, use and assessment versus requirements and market planning in cooperation with users - Promotion and harmonisation of best practise tools for air quality communities. Further European multidisciplinary projects should be created to better understand the most prevalent atmospheric factors to be impacted in predictive, preventive and personalised medicine considered as the central concept for future medicine.

  13. (STARC), (), (NEC), () 1st. Layer 2nd. Layer 3rd. Layer

    E-print Network

    Kasahara, Hironori

    , , , , , , (STARC), (), (NEC), () PG401 Program BPA RB SB BPA RB SB BPA RB SB BPA RB SB BPA RB SB BPA RB SB BPA RB SB 1st. Layer 2nd. Layer 3rd. Layer Total System BPA BPA 1 BPA 3 BPA2 BPA 4 BPA 5 BPA 6 RB 7 RB15 BPA 8 BPA 9 BPA 10 RB 11 BPA 12 BPA 13 RB 14 RB END RB RB BPA RB Data

  14. Historical aspects of human presence in Space

    NASA Astrophysics Data System (ADS)

    Harsch, V.

    2007-02-01

    Purpose: This paper presents the development of human presence in Space from its beginnings. Study hypotheses were based on historical findings on scientific, medical, cultural, and political aspects of manned Space flight due to the different attitudes of Space minded nations and organizations. Impacts of aerospace medicine on the advances of biomedical sciences will be touched upon, as well as the historical development of aviation and Space medical achievements which are described briefly and visions for future developments are given. Methods: An overview was gained by literature-study, archives research and oral history taking. Results: Aviation Medicine evolved parallel to Man's ability to fly. War-triggered advancements in aviation brought mankind to the edge of space-equivalent conditions within a few decades of the first motor-flight, which took place in the USA in 1903 [V. Harsch, Aerospace medicine in Germany: from the very beginnings, Aviation and Space Environment Medicine 71 (2000) 447-450 [1

  15. Acoustic levitation in the presence of gravity

    NASA Technical Reports Server (NTRS)

    Collas, P.; Barmatz, M.; Shipley, C.

    1989-01-01

    The method of Gor'kov (1961) has been applied to derive general expressions for the total potential and force on a small spherical object in a resonant chamber in the presence of both acoustic and gravitational force fields. The levitation position is also determined in rectangular resonators for the simultaneous excitation of up to three acoustic modes, and the results are applied to the triple-axis acoustic levitator. The analysis is applied to rectangular, spherical, and cylindrical single-mode levitators that are arbitrarily oriented relative to the gravitational force field. Criteria are determined for isotropic force fields in rectangular and cylindrical resonators. It is demonstrated that an object will be situated within a volume of possible levitation positions at a point determined by the relative strength of the acoustic and gravitational fields and the orientation of the chamber relative to gravity.

  16. Tailored Nanocomposites of Polypropylene with Layered Silicates

    SciTech Connect

    Xu, L.; Nakajima, H; Manias, E; Krishnamoorti, R

    2009-01-01

    The melt rheological properties of layered silicate nanocomposites with maleic anhydride (MA) functionalized polypropylene are contrasted to those based on ammonium-terminated polypropylene. While the MA functionalized PP based nanocomposites exhibit solid-like linear viscoelastic behavior, consistent with the formation of a long-lived percolated nanoparticle network, the single-end ammonium functionalized PP based nanocomposites demonstrated liquid-like behavior at comparable montmorillonite concentrations. The differences in the linear viscoelasticity are attributed to the presence of bridging interactions in MA functionalized nanocomposites. Further, the transient shear stress of the MA functionalized nanocomposites in start-up of steady shear is a function of the shear strain alone, and the steady shear response is consistent with that of non-Brownian systems. The weak dependence of the steady first normal stress difference on the steady shear stress suggests that the polymer chain mediated silicate network contributes to such unique flow behavior.

  17. A Process Model of the Formation of Spatial Presence Experiences

    Microsoft Academic Search

    Werner Wirth; Tilo Hartmann; Saskia Böcking; Peter Vorderer; Christoph Klimmt; Holger Schramm; Timo Saari; Jari Laarni; Niklas Ravaja; Feliz Ribeiro Gouveia; Frank Biocca; Ana Sacau; Lutz Jäncke; Thomas Baumgartner; Petra Jäncke

    2007-01-01

    In order to bridge interdisciplinary differences in Presence research and to establish connections between Presence and “older” concepts of psychology and communication, a theoretical model of the formation of Spatial Presence is proposed. It is applicable to the exposure to different media and intended to unify the existing efforts to develop a theory of Presence. The model includes assumptions about

  18. Social Presence: What Is It? How Do We Measure It?

    ERIC Educational Resources Information Center

    Lowenthal, Patrick Ryan

    2012-01-01

    Social presence theory is a central concept in online learning. Hundreds of studies have investigated social presence and online learning. However, despite the continued interest in social presence and online learning, many questions remain about the nature and development of social presence. Part of this might be due to the fact that the majority…

  19. Basic Telecommunications, The Physical Layer

    NSDL National Science Digital Library

    Mullett, Gary J.

    This page from Delmar Learning provides more information about the book "Basic Telecommunications, The Physical Layer" by Gary J. Mullet. The book includes information on wireline, wireless, and other fiber optic topics, focusing on physical layer implementation of system hardware. Users may order the book via this website. A link is also provided to request a review copy.

  20. MEMS Cantilevers - Sacrificial Layer Removal

    NSDL National Science Digital Library

    This animation, created by Southwest Center for Microsystems Education (SCME), "illustrates the removal or etch of the sacrificial layer of silicon dioxide. Removing this layer allows the micro-cantilevers to move. Such cantilevers are used as sensors for a variety of applications." The supporting MEMS Cantilever Learning Modules and activities can be downloaded from the SCME website under Educational Materials.