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1

Sublimation Behavior of Annular Frost Layer by Impinging Jet Flow  

NASA Astrophysics Data System (ADS)

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.

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

2

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

E-print Network

1D Transient Model for Frost Heave in PEFCs III. Heat Transfer, Microporous Layer, and Cycling 446-912, Korea A computational model based on a frost heave mechanism has been developed to simulate-5,11-16 To determine the root cause of freeze/thaw dam- age, a frost heave thermal model has been developed

Mench, Matthew M.

3

Optimization of parameters of an artificial aerosol layer for radiation frost protection  

Microsoft Academic Search

Data are presented on losses from frosts in the Southern Federal Region of Russia. Problems are considered of optimization\\u000a for radiation frost protection, based on production of artificial smoke layers and fogs. Studies of infrared radiation attenuation\\u000a by aerosol of different dispersion and simulation of aerosol turbulent diffusion show that, within the atmospheric transmittance\\u000a window, a sufficient greenhouse effect can

A. M. Abshaev; Kh. Zh. Malkarov

2009-01-01

4

Review Concerning Studies of Frost Deposition  

NASA Astrophysics Data System (ADS)

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.

Yamashita, Koji

5

Frost-free North Polar Layers in the Good Old Summertime  

NASA Technical Reports Server (NTRS)

17 October 2006 The middle portion of the northern summer season is the ideal time of year to capture relatively dust- and haze-free views of martian north polar terrain. This year, much more of the north polar cap has sublimed away than has been evident in previous northern summers going back to 1999, when Mars Global Surveyor (MGS) began the Mapping Phase of the mission. This MGS Mars Orbiter Camera (MOC) image shows a nearly ice-free view of layers exposed by erosion in the north polar region. The light-toned patches are remnants of water ice frost. The layers are generally considered by the Mars scientific community to be record of past depositions of ice and dust. This picture is located near 82.5oN, 118.6oW, and covers an area about 3 km by 10 km (1.9 by 6.2 miles). Sunlight illuminates the scene from the upper left; the image was acquired on 22 September 2006.

2006-01-01

6

Identifying and Mapping Seasonal Surface Water Frost with MGS TES  

NASA Astrophysics Data System (ADS)

The Thermal Emission Spectrometer (TES) visible/near-infrared and thermal infrared bolometers measured surface broadband albedo and temperature for more than three Mars years. As seasons progress on Mars, surface temperatures may fall below the frost point of volatiles in the atmosphere (namely, carbon dioxide and water). Systematic mapping of the spatial and temporal occurrence of these volatiles in the martian atmosphere, on the surface, and in the subsurface has shown their importance in understanding the climate of Mars. However, few studies have investigated seasonal surface water frost and its role in the global water cycle. We examine zonally-averaged TES daytime albedo, temperature, and water vapor abundance data [after Smith, 2004] to map the presence of surface water frost on Mars. Surface water frost occurs in the polar and mid latitudes, in regions with surface temperatures less than 220 K and above 150 K, and can significantly increase albedo relative to the bare surface. In the northern hemisphere water frost is most apparent in late fall/early winter, before the onset of carbon dioxide frost. Dust storms occurring near northern winter solstice affect albedo data and prevent us from putting a latitudinal lower limit on the water frost in the northern hemisphere. Regardless, seasonal water frost occurs at least as low as 48°N in Utopia Planitia, beginning at Ls=~230°, as observed by Viking Lander 2 [Svitek and Murray, 1990]. Daytime surface water frost was also observed at the Phoenix Lander site (68°N) beginning at Ls=~160° [Cull et al., 2010]. The timing of albedo variations observed by TES agree relatively well with lander observations of seasonal frost. Seasonal water frost is not detected during fall in the southern hemisphere. A potential explanation for this discrepancy, compared with frost detections in the north, is the disparity in atmospheric water vapor abundance between the two hemispheres. The frost point temperatures for water vapor in the southern hemisphere are ~5-10 K lower for the corresponding season and latitude in the north [Smith, 2004]. This inhibits the stability of water frost on the surface in the southern hemisphere and also lowers the maximum thickness of a water frost layer, potentially limiting its effect on surface albedo. Our work here shows that the seasonal progression in the northern hemisphere of Mars involves extensive deposition of water frost, similar in progression to the carbon dioxide seasonal ice cap. This behavior results in variation of surface albedo and therefore affects surface and subsurface temperatures, which could impact the distribution of ground ice. Surface frost and subsequent mixing of vapor back into the atmosphere likely plays an important role in the global water cycle. Mapping of water frost's geographical extent, timing, and impact on surface albedo can provide insight into the processes controlling the present Martian climate. References: Cull, S. et al. (2010) JGR, 115, E00E19. Smith, M. D. (2004) Icarus, 167, 148-165. Svitek, T. and Murray, B. (1990) JGR, 95(B2), 1495-1510.

Bapst, J.; Bandfield, J. L.; Wood, S. E.

2013-12-01

7

Frost Growth and Densification in Laminar Flow Over Flat Surfaces  

NASA Technical Reports Server (NTRS)

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.

Kandula, Max

2011-01-01

8

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

NASA Astrophysics Data System (ADS)

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 absence of active frost boils is thought to play a pivotal role in establishing the sharp demarcation between moist nonacidic tundra (MNT) and moist acidic tundra (MAT) in the Arctic. The focus of this paper is to corroborate the predictions of a mathematical model that relates observable patterned ground features to ecosystem parameters with observations at the field sites along the North American Arctic Transect (NAAT) established by the Biocomplexity of Patterned-Ground Ecosystems Project. Model predictions indicate that recurrent one-dimensional frost heave can become unstable and evolve into multidimensional differential frost heave (DFH). A laboratory frost heave simulation produced a 28-cm pattern in an active layer of 10 cm, which agrees with linear stability theory predictions. A finite element solution predicts three-dimensional patterns with approximately 3-m spacing develop in a 1.0-m active layer with a surface n factor of 0.35, which agrees well with field observations from the NAAT. The lack of significant frost boil activity in the MAT is a result of suppression of DFH owing to denser surface vegetation characterized by low n factors. Prominent active frost boils are observed in the MNT at higher latitudes with more sparse vegetation characterized by higher n factors that promote DFH. However, at the northernmost field sites frost boils cannot be generated even though the n factors are relatively high owing to very rapid freezing conditions that mitigate DFH.

Peterson, R. A.; Krantz, W. B.

2008-09-01

9

Influence of Several Parameters on Frost Growth in Low Temperature Environments  

NASA Astrophysics Data System (ADS)

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.

Yamashita, Koji; Ohkubo, Hidetoshi

10

Frosted Chasma Boreale Dunes  

NASA Technical Reports Server (NTRS)

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.

2003-01-01

11

Frost tolerance of Trifolium species  

Microsoft Academic Search

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.

J. R. Caradus

1995-01-01

12

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

NASA Technical Reports Server (NTRS)

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.

Dietenberger, M. A.

1983-01-01

13

Dynamic Measurements of Laser Light Attenuation by Cryogen Film and Frost Formation  

E-print Network

Dynamic Measurements of Laser Light Attenuation by Cryogen Film and Frost Formation Bernard Choi1 surface. The cryogen pool eventually evaporates as frost forms on the skin surface due to condensation. The purpose of this study was to investigate laser light attenuation by the cryogen film/frost layer. Medical

Aguilar, Guillermo

14

Moisture performance analysis of EPS frost insulation  

SciTech Connect

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.

Ojanen, T.; Kokko, E.

1997-11-01

15

Heat transfer from a tube immersed in a fluidized bed with frosting  

SciTech Connect

Heat-transfer and flow-visualization experiments were performed for a single cooled tube immersed horizontally in a fluidized bed under frosting conditions. Measurements were made from local and average heat-transfer coefficients around the cooled tube surface. Glass beads having nominal diameters of 0.43 mm, 0.89 mm, and 1.6 mm were employed as the bed material. The 30 mm diameter tube was located 100 mm above the distributor. All the results obtained under frosting conditions were for an air temperature of about 5{degrees}C and an air relative humidity of about 80 percent. The heat-transfer coefficient with frosting evaluated in this investigation includes the heat-transfer coefficient from the frost surface to the bed and the thermal resistance of the frost layer. Comparisons are made to heat-transfer data without frosting. The heat transfer is found to be larger with frosting than without frosting under the fluidization state.

Torikoshi, K.; Kawabata, K.; Yamashita, H. (Mechanical Engineering Lab., Daikein Industries, Ltd. (JP))

1990-01-01

16

A frost formation model and its validation under various experimental conditions  

NASA Technical Reports Server (NTRS)

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.

Dietenberger, M. A.

1982-01-01

17

Frost heave Alan W. REMPEL  

E-print Network

Frost heave Alan W. REMPEL Department of Geological Science, University of Oregon, Eugene, Oregon that is produced by frost heave has motivated almost a century of concerted laboratory, field and theoretical predictive models for the macroscopic frost-heave characteristics that are seen in the field

Rempel, Alan W.

18

A transient analysis of frost formation on a parallel plate evaporator  

SciTech Connect

This paper presents the development of a transient model for evaluating frost formation on a parallel plate evaporator for heat pump applications. The model treats the frost layer as a porous substance, and applies the equations of conservation of mass, momentum and energy to calculate the growth and densification of the frost layer. Empirical correlations for thermal conductivity and tortuosity as a function of density are incorporated from previous studies. Frost growth is calculated as a function of time, Reynolds number, longitudinal location, plate temperature, and ambient air temperature and humidity. The main assumptions are: ideal gas behavior for air and water vapor, uniform frost density and thermal conductivity across the thickness of the frost layer; and quasi-steady conditions during the whole process. The mathematical model is validated by comparing the predicted values of frost thickness and frost density with results obtained in recent experimental studies. A good agreement was obtained in the comparison. The frost formation model calculates pressure drop and heat transfer resistance that result from the existence of the frost layer, and it can therefore be incorporated into a heat pump model to evaluate performance losses due to frosting as a function of weather conditions and time of operation since the last evaporator defrost.

Martinez-Frias, J.; Aceves, S.M.; Hernandez-Guerrero, A. [Univ. of Guanajuato (Mexico). Dept. of Mechanical Engineering

1996-12-31

19

Listening three frost poems  

Microsoft Academic Search

Joseph Brodsky (1995a) has referred to poetry as “a great disciplinarian”; (p. 100) to prose. I would add that poetry is a great disciplinarian to analytic listening. In this paper I look at the way language is used in the making of poetry in three Frost poems. My interest is not so much in what a poem is “about,”; but

Thomas H. Ogden

1997-01-01

20

Jack's Frost: Controllable Magic Frost Simulations for 'Rise of the Guardians' David Lipton*  

E-print Network

Jack's Frost: Controllable Magic Frost Simulations for 'Rise of the Guardians' David Lipton* Ken Jack Frost has the ability to cover objects in swirling, magical frost. The frost is an extension. To achieve this, we built a Houdini based system that allowed for precise control over the frost's animation

21

Influences of surface hydrophilicity on frost formation on a vertical cold plate under natural convection conditions  

SciTech Connect

Surface hydrophilicity has a strong influence on frost nucleation according to phase transition theory. To study this effect, a close observation of frost formation and deposition processes on a vertical plate was made under free convection conditions. The formation and shape variation of frost crystals during the initial period are described and the frost thickness variation with time on both hydrophobic and plain copper cold surfaces are presented. The various influencing factors are discussed in depth. The mechanism of surface hydrophilicity influence on frost formation was analyzed theoretically. This revealed that increasing the contact angle can increase the potential barrier and restrain crystal nucleation and growth and thus frost deposition. The experimental results show that the initial water drops formed on a hydrophobic surface are smaller and remain in the liquid state for a longer time compared with ones formed on a plain copper surface. It is also observed that the frost layer deposited on a hydrophobic surface is loose and weak. Though the hydrophobic surface can retard frost formation to a certain extent and causes a looser frost layer, our experimental results show that it does not depress the growth of the frost layer. (author)

Liu, Zhongliang; Zhang, Xinghua; Wang, Hongyan; Meng, Sheng; Cheng, Shuiyuan [Key Laboratory of Enhanced Heat Transfer and Energy Conservation, Ministry of Education and Key Laboratory of Heat Transfer and Energy Conversion, Beijing Education Commission, College of Environmental and Energy Engineering, Beijing University of Technology, Pingleyuan 100, Beijing 100022 (China)

2007-07-15

22

Seasonal Frost Changes on Mars  

NASA Technical Reports Server (NTRS)

Observations by NASA's 2001 Mars Odyssey spacecraft show a comparison of wintertime (left) and summertime (right) views of the north polar region of Mars in intermediate-energy, or epithermal, neutrons. The maps are based on data from the high-energy neutron detector, an instrument in Odyssey's gamma-ray spectrometer suite. Soil enriched by hydrogen is indicated by the purple and deep blue colors on the maps. Progressively smaller amounts of hydrogen are shown in the colors light blue, green, yellow and red. The hydrogen is believed to be in the form of water ice. In some areas, the abundance of water ice is estimated to be up to 90% by volume. In winter, much of the hydrogen is hidden beneath a layer of carbon dioxide frost (dry ice). In the summer, the hydrogen is revealed because the carbon dioxide frost has dissipated. A shaded-relief rendition of topography is superimposed on these maps for geographic reference.

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. Investigators at Arizona State University in Tempe, the University of Arizona in Tucson, and NASA's Johnson Space Center, Houston, operate the science instruments. The gamma-ray spectrometer was provided by the University of Arizona in collaboration with the Russian Aviation and Space Agency and Institute for Space Research (IKI), which provided the high-energy neutron detector, and the Los Alamos National Laboratories, New Mexico, which provided the neutron spectrometer. Lockheed Martin Astronautics, Denver, is the prime contractor for the 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.

2003-01-01

23

Winter Frost and Fog  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

24

Seeing through Frost on Enceladus  

NASA Astrophysics Data System (ADS)

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

Helfenstein, P.

2012-12-01

25

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

E-print Network

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

Ji, Hantao

26

Presence of a layered lithosphere beneath the Zagros collision zone  

NASA Astrophysics Data System (ADS)

The continental collision between the Arabian and Eurasian plates following the subduction of the Neo-Tethys ocean beneath Eurasia resulted in a complex deformation across the Zagros Mountains. We used more than 700 S receiver functions obtained from 61 permanent stations to provide a detailed image of the lithospheric interaction between the Eurasian and Arabian plates. Our results suggest the existence of two different lithospheric blocks. A 200 km thick lithosphere was observed beneath the Zagros collision zone and most likely represents the Arabian lithosphere, which has been strongly deformed, thickened and depleted. Based on our results, shortening due to the collisional process is differently accommodated by the crust and mantle lithosphere of the Zagros collision zone. We localized the thick Arabian lithosphere beneath the Zagros, Sanandaj-Sirjan Zone (SSZ) and Urumieh-Dokhtar Magmatic Assemblage (UDMA), whereas the crustal thickening (~ 70 km) seems to be concentrated just beneath the SSZ. Furthermore, we found a thin lithosphere of about 80-90 km that we interpret here as the Iranian lithosphere, beneath Central Iran and Alborz. Additionally, our results suggest the presence of remnants of the fossil Neo-Tethys subduction at depths ranging between 80 and 150 km within the Arabian lithosphere. This dipping structure can be seen beneath the Zagros, SSZ and UDMA and seems to disappear towards the northeast beneath Central Iran and Alborz. These findings may support the idea of a breakoff of the oceanic Neo-Tethyan slab beneath Central Iran, which results in an asthenospheric upwelling and thinning of the Iranian lithosphere beneath Central Iran and Alborz. The boundary between the Arabian and Iranian plates seems to be located northeast of the UDMA in the northwest of Zagros and southwest of the UDMA in the Central Zagros region.

Mohammadi, Elham; Sodoudi, Forough; Kind, Rainer; Rezapour, Mehdi

2013-11-01

27

Micropropagation of Frost-Resistant Eucalyptus1  

E-print Network

Micropropagation of Frost-Resistant Eucalyptus1 Michel Boulay2 For 10 years now, AFOCEL has, AFOCEL, Nangis, France. 102 Abstract: A method for the in vitro propagation of frost resistant eucalyptus entities of eucalypts which can resist to frost to minus 18°C or 20°C or to late spring frost in France

Standiford, Richard B.

28

Topological whisker bundles of amphibole and frost column of quartz  

NASA Astrophysics Data System (ADS)

Amphibole whiskers showing topological forms and frost column of quartz were found in association with hedenbergite crystals in a druse of skarn at Kakino mine, Gifu Prefecture, Japan. Both selectively grow from thin layers formed on the surfaces of Fe-rich portion of early formed hedenbergite crystals. Most whiskers occur in bundles of straight, helical, coil, curl, ribbon and rope forms. Single whiskers constituting these bundles are sub-micron size in thickness and millimeter to centimeter size in length, with aspect ratio attaining more than 1000, and are twisted. Micro-area XRD analyses indicate that the whiskers are crystalline, and not in amorphous state, in spite of their topological forms. Quartz layers showing fibrous texture, closely resembling frost column in form and texture, also occur in association with hedenbergite crystals and amphibole whiskers. Both amphibole whiskers and quartz frost columns nucleated and grew in layers formed on Fe-rich portions of hedenbergite, which was selectively reacted with S, H 2O and SiO 2 containing vapor phase. Based on these observations, the growth mechanism and the genesis of such unusual morphology are discussed. Essentially similar mechanism as vapor-liquid-solid (VLS) mechanism is suggested for amphibole whiskers. The same mechanism as for the formation of ice frost column is applicable to the formation of quartz frost column.

Sunagawa, Ichiro; Takahashi, Yasushi; Imai, Hiroyuki; Yamada, Shigeo

2005-04-01

29

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

SciTech Connect

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.

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

2012-03-20

30

Percolation-induced frost formation  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

31

Spatiotemporal change in China's frost days and frost-free season, 1955–2000  

Microsoft Academic Search

From 1955 to 2000, China has experienced a decrease in the number of frost days, while the length of the frost-free season between the last spring freeze and the first fall frost has increased. Three distinct regimes can be detected in the time series: up to about 1973, the annual number of frost days was about 2 d higher than

Binhui Liu; Mark Henderson; Ming Xu

2008-01-01

32

6, 1105111066, 2006 Sea ice, frost flowers  

E-print Network

ACPD 6, 11051­11066, 2006 Sea ice, frost flowers and halogen activation W. R. Simpson et al. Title than potential frost flower contact W. R. Simpson 1 , D. Carlson 1 , G. Hoenninger 1,2, , T. A. Douglas. Simpson (ffwrs@uaf.edu) 11051 #12;ACPD 6, 11051­11066, 2006 Sea ice, frost flowers and halogen activation

Paris-Sud XI, Université de

33

FROST: Revisited and Distributed Vincent Poirriez  

E-print Network

FROST: Revisited and Distributed Vincent Poirriez LAMIH UVHC,UMR CNRS 8530 59313 Valenciennes de la Recherche FROST: Revisited and Distributed Vincent Poirriez HICOMB'05:April 04, 2005 #12;Protein Threading Problem Associate a protein sequence to an already known 3D structure. FROST: Revisited

Singer, Daniel

34

Frost as a first wall for the ICF Laboratory Microfusion Facility  

SciTech Connect

We introduce the concept of using frost as the first wall of the ICF Laboratory Microfusion Facility being designed to produce 200--1000 MJ of thermonuclear yield. We present one design incorporating 2 cm of frost deposited at 0.1 g/cm/sup 3/ on an LN-cooled fiber-reinforced polymer substrate. We calculate that such a frost layer will protect the substrate from ablation by target x rays and debris, and from shock-induced spallation. Postshot washdown with water should permit low-activation operation, and should preserve the original wall properties. We expect the impact of the frost on laser optics to be minimal, and expect the preshot lifetime of thermally unprotected cryogenic targets to be extended by operating the wall at 100-150 K. Moreover, we believe that such a frost first wall will involve little technical risk, and will be inexpensive to construct and operate. 4 refs., 1 fig.

Orth, C.D.

1988-11-15

35

Accretion onto neutron stars with the presence of a double layer  

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

36

Accretion onto neutron stars with the presence of a double layer  

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

37

With Robert Frost in Tesolonia.  

ERIC Educational Resources Information Center

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

Welninski, Virginia

38

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

39

Rossby wave resonance in the presence of a nonlinear critical layer  

NASA Astrophysics Data System (ADS)

The behavior of Rossby waves on a shear flow in the presence of a nonlinear critical layer is studied, with particular emphasis on the role played by the critical layer in a Rossby wave resonance mechanism. Previous steady analyses are extended to the resonant case and it is found that the forced wave dominates the solution, provided the flow configuration is not resonant for the higher harmonics induced by the critical layer. Numerical simulations for the forced initial value problem show that the solution evolves towards the analysed steady state when conditions are resonant for the forced wave, and demonstrate some of the complications that arise when they are resonant for higher harmonics. In relating the initial value and steady problems, it is argued that the time dependent solution does not require the large mean flow distortion that Haberman (1972) found to be necessary outside the critical layer in the steady case.

Ritchie, Harold

1985-01-01

40

Mapping Statistical Characteristics of Frosts in Iran  

NASA Astrophysics Data System (ADS)

To model and map the statistical characteristics of frost in Iran, the data related to the minimum daily temperature for a 15-year period (1990-2005) was obtained from Iran Meteorological Organization. Then using multivariate regression models, the relationship among five statistical characteristics, i.e. the mean Julian day of the first frost, mean Julian day of the last frost, mean number of frost days per year, mean length of the frost period and mean length of growing season were modeled by three geo - climate factors: elevation, longitude and latitude. The precision of each model was explored using four hypotheses: linearity of the relationship between independent variables and the dependent variable, normality of errors, constancy of error variance and lake of correlation of errors were tested, and their precisions were confirmed. At the second stage, contour lines resulting from STRM were converted to the point features class. Altogether, 661 474 points were gathered from all over Iran. Then, the studied five frost characteristics were generalized to 661 474 points; then, the regionalization maps of statistical characteristics of frost were obtained for Iran using Kriging interpolation method. The results showed that the temperature of highland areas above 4200 m above sea level always was at least zero and below zero during the year, and also the coastal strip of southern Iran had no frost. Elevation was the most effective factor in the spatial arrangement for the frequency of occurrence of Julian day of the first frost. The most effective factors in spatial arrangement for the frequency of occurrence of Julian day of the last frost, length of frost period and length of growing season were elevation and latitude. Finally, spatial arrangement for the frequency of occurrence of the frost days was also a function of three factors of elevation, longitude and latitude. The dominant role of elevation in spatial arrangement for the occurrence of the first frost day in Iran showed that the occurrence of the first frost day in Iran could be of the type of radiation frosts and the dominant role of elevation and latitude demonstrated that late-winter frosts can be mostly of the type of advection frosts. Therefore, arrangement of statistical features of frost in Iran is both a function of geo - climate factors and the synoptic systems which have entered the country.

Mahmoudi, P.

2014-10-01

41

A red clover stand that was frost seeded into wheat. Using red clover as a cover crop in wheat  

E-print Network

wheat, but works well when seeded with oats. Michigan mammoth and June clover have been shown to perform and to germinate. Frost-seeding red clover "Frost seeding" red clover is the practice of broadcasting red clover with the urea after layering the urea and clover seed in a fertilizer spreader, although the risk of having

42

Heavy metal frost on Venus  

NASA Astrophysics Data System (ADS)

Chemical equilibrium calculations of volatile metal geochemistry on Venus show that high dielectric constant compounds of lead and bismuth such as PbS (galena), Bi 2S 3 (bismuthite) or Pb-Bi sulfosalts condense in the venusian highlands and may be responsible for the low radar emissivities observed by Magellan and Pioneer Venus. Our calculations also show that elemental tellurium is unstable on Venus' surface and will not condense below 46.6 km. This is over 30 km higher than Maxwell Montes, the highest point on Venus' surface. Elemental analyses of Venus' highlands surface by laser induced breakdown spectroscopy (LIBS) and/or X-ray fluorescence (XRF) can verify the identity of the heavy metal frost on Venus. The Pb-Pb age of Venus could be determined by mass spectrometric measurements of the Pb 207/Pb 204 and Pb 206/Pb 204 isotopic ratios in Pb-bearing frosts. All of these measurements are technologically feasible now.

Schaefer, Laura; Fegley, Bruce

2004-03-01

43

Effects of frost on wildflowers: an unexpected consequence of climate change--image 07 of 22  

NSDL National Science Digital Library

A meadow with thousands of plants of Helianthella quinquenervis (aspen sunflower, Asteraceae) at peak bloom. This species is a common long-lived perennial plant in meadows near the Rocky Mountain Biological Laboratory. This photo was taken during a year without frost damage. Compare the presence and density of sunflowers with the photograph of the same meadow in a year when frost damage killed all but a few flower buds.

Inouye, David

2012-01-04

44

Ion-acoustic double layers in the presence of plasma source  

SciTech Connect

Steady-state plasma turbulence and formation of negative potential spikes and double layers in the presence of ion acoustic instabilities have been studied by means of one-dimensional particle simulations in which velocities of a small fraction of electrons are replaced by the initial drifting Maxwellian at a constant rate. A steady state is found where negative potential spikes appear randomly in space and time giving rise to an anomalous resistivity much greater than previously found. Comparisons of the simulation results with laboratory and space plasmas are discussed.

Okuda, H.; Ashour-Abdalla, M.

1981-11-01

45

Frost resistance ln Eucalyptus nitens (deane & maiden). maiden.  

E-print Network

??Genetic and physiological aspects of variation in frost resistance were investigated in Eucalyptus nitens seedlings. Frost resistance was primarily determined by measuring the relative leakage… (more)

Tibbits, WN

1986-01-01

46

Frost formation and ice adhesion on superhydrophobic surfaces  

E-print Network

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 ...

Varanasi, Kripa K.

47

Mechanism of frost damage to concrete  

Microsoft Academic Search

We studied several topics that are important to explain the mechanisms of frost damage to concrete, including the volume change of concrete during freezing, the role of air voids in protecting concrete from frost damage, the pore structure of concrete, and the nucleation and propagation of ice in concrete. By combining calorimetric measurements with dilatometry, we were able to calculate

Zhenhua Sun

2010-01-01

48

Robert Frost and the Poetry of Physics.  

ERIC Educational Resources Information Center

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

Coletta, W. John; Tamres, David H.

1992-01-01

49

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

fulfillment of the requirements for the degree of MASTER OF SCIENCE January, 1967 Fh)or Sub)ect: Mechanical Engineering AN INVESTIGATION OF THE HEAT AND MASS TRANSFER BY FREE CONVECTION FROM HUMID AIR TO A HORIZONTAL METAL PIATE UNDER FROSTING... Sketch ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 16 Photographs of Frost Formation e ~ ~ ~ i ~ i i ~ 23 - 26 LIST OF CURVES 13 - 14 Temperature and Concentration Boundary Layer Profile ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 58 59 15 ? 16 Accumulation of Frost Grosth vs. Time...

Bell, Bobby

2012-06-07

50

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

SciTech Connect

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.

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

51

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

NASA Astrophysics Data System (ADS)

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.

Schmit, P. F.; Molvig, Kim; Nakhleh, C. W.

2013-11-01

52

Frost-ring chronologies as dendroclimatic proxies of boreal environments  

NASA Astrophysics Data System (ADS)

Frost rings are formed in tree stems when growing-season frosts affect immature wood cells, producing collapsed cells within annual tree rings. Open boreal forests are most susceptible to record growing-season frost because they lack the greenhouse effect commonly observed in closed forests. Here we present a novel method to construct regional frost-ring chronologies in lichen-black spruce woodlands of the boreal forest zone. Because the ability of trees to form frost rings depends on several factors (including bark thickness and ring width), we used two models to produce a Frost Composite Index based on a frost susceptibility window of cambial age <30 years. The frost-ring chronology showed alternating periods of high and low frost activity that were highly consistent within and among sites. Reconstruction of growing-season frost activity may be used as dendroclimatic proxies of climate variability and may give insights into future risks of frost damage in a warming climate.

Payette, Serge; Delwaide, Ann; Simard, Martin

2010-01-01

53

Mars' Dynamic Albedo: Evidence for Widespread Seasonal Water Frost in the Northern Hemisphere from TES, HiRISE and THEMIS  

NASA Astrophysics Data System (ADS)

Using multi-year TES bolometric albedo and temperature data, we identify the presence of seasonal water frost on Mars. Our findings show a stark hemispherical asymmetry, consistent with our understanding of atmospheric water transport.

Bapst, J.; Bandfield, J. L.; Wood, S. E.

2014-07-01

54

Io - Longtudinal distribution of sulfur dioxide frost  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

55

Frost & Sullivan Press Release Published: 14 Dec 2006  

E-print Network

Frost & Sullivan Press Release Published: 14 Dec 2006 https://www.frost.com/prod/servlet/press-release.pag?mode=open&docid=89716687 Frost & Sullivan Honours Mobileye N.V. with the 2006 Entrepreneurial Company of the Year Award in the Automotive Industry LONDON - December 14, 2006 ­ Frost & Sullivan confers the 2006 Entrepreneurial Company

Shashua, Amnon

56

BEST PRACTICES RESEARCH 2010 Frost & Sullivan 1 "We Accelerate Growth"  

E-print Network

BEST PRACTICES RESEARCH © 2010 Frost & Sullivan 1 "We Accelerate Growth" New Product Innovation, Medical Diagnostics and Imaging Technology EU, 2010 Frost & Sullivan's Global Research Platform Frost manage growth, innovation and leadership. Based on the findings of this Best Practices research, Frost

57

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

E-print Network

the effect of individually unstable interfaces on the overall stability of the flow, and the second studiesOn Stabilization of Multi-Layer Hele-Shaw and Porous Media Flows in the Presence of Gravity Prabir the cumulative effect of unstable interfaces as well as unstable internal viscous layers. In each case, modal

Daripa, Prabir

58

Varietal and chromosome 2H locus-specific frost tolerance in reproductive tissues of barley (Hordeum vulgare L.) detected using a frost simulation chamber.  

PubMed

Exposure of flowering cereal crops to frost can cause sterility and grain damage, resulting in significant losses. However, efforts to breed for improved low temperature tolerance in reproductive tissues (LTR tolerance) has been hampered by the variable nature of natural frost events and the confounding effects of heading time on frost-induced damage in these tissues. Here, we establish conditions for detection of LTR tolerance in barley under reproducible simulated frost conditions in a custom-built frost chamber. An ice nucleator spray was used to minimize potential effects arising from variation in naturally occurring extrinsic nucleation factors. Barley genotypes differing in their field tolerance could be distinguished. Additionally, an LTR tolerance quantitative trait locus (QTL) on the long arm of barley chromosome 2H could be detected in segregating families. In a recombinant family, the QTL was shown to be separable from the effects of the nearby flowering time locus Flt-2L. At a minimum temperature of -3.5 degrees C for 2 h, detection of the LTR tolerance locus was dependent on the presence of the nucleator spray, suggesting that the tolerance relates to freezing rather than chilling, and that it is not the result of plant-encoded variation in ice-nucleating properties of the tiller surface. PMID:19484216

Chen, Andrew; Gusta, Lawrence V; Brûlé-Babel, Anita; Leach, Richard; Baumann, Ute; Fincher, Geoffrey B; Collins, Nicholas C

2009-08-01

59

Five second helium neutral beam injection using argon-frost cryopumping techniques  

SciTech Connect

High power helium neutral beams for the heating of tokamak discharges can now be provided for 5 s by using argon cryopumping (of the helium gas) in the beamlines. A system has now been installed to deposit a layer of argon frost on the DIII-D neutral beam cryopanels, between tokamak injection pulses. The layer serves to trap helium on the cryopanels providing sufficient pumping speed for 5 s helium beam extraction. The argon frosting hardware is now present on two of four DIII-D neutral beamlines, allowing injection of up to 6 MW of helium neutral beams per discharge, with pulse lengths of up to 5 s. The argon frosting system is described, along with experimental results demonstrating its effectiveness as a method of economically extending the capabilities of cryogenic pumping panels to allow multi-second helium neutral beam injection.

Phillips, J.C.; Kellman, D.H.; Hong, R.; Kim, J.; Laughon, G.M.

1995-10-01

60

Boundary layer flow of air past solid surfaces in the presence of rainfall  

NASA Astrophysics Data System (ADS)

The steady two-dimensional laminar flow of an air stream, flowing past a solid surface at high Reynolds number, is examined in the presence of rainfall. As raindrops sediment on the surface they coalesce and form a continuous water film that flows due to shear, pressure drop and gravity, in general. In the limit as the boundary layer and film thickness remain smaller than the radius of curvature of the surface a simplified lubrication-type formulation describes the flow field in the film, whereas the usual boundary layer formulation is applied in the gas phase. In the case of a flat plate and close to the leading edge, x [rightward arrow] 0, a piecewise-self-similar solution is obtained, according to which creeping flow conditions prevail in the film and its thickness grows like x3/4, whereas the Blasius solution is recovered in the air stream. Numerical solution of the governing equations in the two phases and for the entire range of distances from the leading edge, x = O(1), shows that the film thickness increases as the rainfall rate, r[dot above], increases or as the free-stream velocity, U[infty infinity], decreases and that the region of validity of the asymptotic result covers a wide range of the relevant problem parameters. In the case of flow past a NACA-0008 airfoil at zero angle of attack a Goldstein singularity may appear far downstream on the airfoil surface due to adverse pressure gradients, indicating flow reversal and eddy formation inside the liquid film, and, possibly, flow separation. However, when the effect of gravity becomes evident in the film flow, as the Froude number decreases, and provided gravity acts in such a way as to negate the effect of the adverse pressure gradient, the location of the singularity is displaced towards the trailing edge of the airfoil and the flow pattern resembles that for flow past a flat plate. The opposite happens when gravity is aligned with the adverse pressure gradient. In addition it was found that there exists a critical water film thickness beyond which the film has a lubricating effect delaying the appearance of the singularity. Below this threshold the presence of the liquid film actually enhances the formation of the singularity.

Smyrnaios, Dimitris N.; Pelekasis, Nikolaos A.; Tsamopoulos, John A.

2000-12-01

61

Frost streaks in the south polar cap of Mars  

NASA Technical Reports Server (NTRS)

Viking Orbiter images of the annual south polar cap on Mars exhibit elongated bright features that are associated with craters and resemble wind streaks observed elsewhere on Mars. The study focuses on the well-documented frost streaks. The discussion covers the morphology of frost streaks, occurrence, seasonal behavior, thickness of frost in streak deposits, wind patterns inferred from frost streaks and other eolian features in the south polar region, formation of frost streaks, and other locales of preferential frost accumulation. The form and seasonal behavior of the bright elongated albedo markings which extend from the rims of many craters in the south polar cap suggest that they are accumulations of CO2 frost in the lee of craters. The frost streaks appear in the fall, increasing in length but not changing in direction during fall and winter. The frost streaks indicate a prograde circulation pattern of near-surface winds around the pole. Other details are also presented.

Thomas, P.; Veverka, J.; Campos-Marquetti, R.

1979-01-01

62

Frost halos from supercooled water droplets.  

PubMed

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

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

2012-10-01

63

Frost halos from supercooled water droplets  

PubMed Central

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

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

2012-01-01

64

Use of a phase change material to prevent frosting in a compact crossflow air exchanger  

Microsoft Academic Search

A mathematical model is presented for simulating the thermal behaviour of a cross-flow air exchanger with layers of phase change material (PCM) sandwiched between the hot and cold air streams to prevent frosting. The exchanger operates under winter conditions and uses electric power for storing heat in the PCM. The model is validated with experimental data, and the effects of

H. El Qarnia; M. Lacroix; Y. Mercadier

2001-01-01

65

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

SciTech Connect

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.

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

66

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

SciTech Connect

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.

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

67

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

SciTech Connect

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.

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

68

Modeling soil frost and snow for BALTEX: Module development, data  

E-print Network

Modeling soil frost and snow for BALTEX: Module development, data assimilation, and evaluation We ­ soil frost and snow metamorphism processes have to be treated in detail and the distributions of soil

Moelders, Nicole

69

Evaluation of fin staging methods for minimizing coil frost accumulation  

E-print Network

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...

Watters, Richard J.

2012-06-07

70

Experimental study on frost growth and dynamic performance of air source heat pump system  

Microsoft Academic Search

The effect of the frost growth and frost morphology on the performance of an air source heat pump was investigated experimentally. The frost thickness, frost accumulation and the dynamic performance of the heat pump were measured. It is found that the frost growth can be divided into three stages according to the frost morphology. In the initial stage, condensed water

Xian-Min Guo; Yi-Guang Chen; Wei-Hua Wang; Chun-Zheng Chen

2008-01-01

71

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

ERIC Educational Resources Information Center

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."

Margolis, Rick

2006-01-01

72

Original article Growth-chamber trial on frost hardiness  

E-print Network

Original article Growth-chamber trial on frost hardiness and field trial on flushing of sessile oak frost on 1-year-old seedlings of 10 European sessile oak provenances at different stages of development for frost injuries was between -4 and -8 °C. Terminal buds, lammas shoots and secondary buds dehardened

Paris-Sud XI, Université de

73

ORIGINAL PAPER Relationships between frost hardiness, root growth potential,  

E-print Network

ORIGINAL PAPER Relationships between frost hardiness, root growth potential, and photosynthesis in the mass of photosynthetically active foliage as a result of early frost may negatively affect the seedling photosynthesis varied with frost intensity and degree of needle hardening. The mass of new roots formed over a 21

Paris-Sud XI, Université de

74

Robert Frost Trailhead Acquisition Stella and Carroll Strysko Conservation Area  

E-print Network

Robert Frost Trailhead Acquisition Stella and Carroll Strysko Conservation Area The Rattlesnake,500. Such acquisition will protect the natural habitat and the Robert Frost Trail where it crosses Route 63 near will: · Protect trailhead access and a portion of the Robert Frost Trail ­ part of the Amherst Literary

Schweik, Charles M.

75

RESEARCH ARTICLE Conservation and genetics of the frosted flatwoods salamander  

E-print Network

RESEARCH ARTICLE Conservation and genetics of the frosted flatwoods salamander (Ambystoma Science+Business Media B.V. 2011 Abstract The federally threatened frosted flatwoods sal- amander been lost to land conversion for development, agricul- ture, or silviculture (Frost 1993; Ware et al

Grether, Gregory

76

Nr. 25 / 2013 // 8. Februar 2013 Antrittsvorlesung Professor Frost  

E-print Network

S. 1 / 2 Nr. 25 / 2013 // 8. Februar 2013 Antrittsvorlesung Professor Frost: Die Entstehung von vor. Professor Dan Frost, Lehrstuhl für experimentelle Geowissenschaften am Bayerischen Geoinstut, hat, Pflanzen, Ozeanen und der Atmosphäre. Dan Frost ist allerdings am Kohlenstoffkreislauf, der innerhalb des

Ullmann, G. Matthias

77

Original article Impact of late frost on height growth  

E-print Network

Original article Impact of late frost on height growth in young sessile oak regenerations Hatem 16 June 1998) Abstract - The damage due to late frost during the 1995 and 1996 growing seasons at the beginning of the 1995 growing season. In 1995, frost occurred after the complete elongation of the growth

Paris-Sud XI, Université de

78

ORIGINAL PAPER Growth and frost hardening of European aspen  

E-print Network

ORIGINAL PAPER Growth and frost hardening of European aspen and backcross hybrid aspen.V. 2011 Abstract & Introduction The interactive effects of water and nitrogen (N) on frost hardiness) supply influence the growth, bud phenology and frost hardening of seven young European aspen (Populus

Paris-Sud XI, Université de

79

Original article Modelling the influence of winter frosts  

E-print Network

Original article Modelling the influence of winter frosts on the development of the stem canker on the disease development. A model describing the influence of winter frost on the evolution of the cankers for which the model predicted poor survival of the fungus. Quercus rubra / Phytophthora cinnamomi / frost

Boyer, Edmond

80

SPECIALSPECIALREPORTREPORT97-197-1 Frost Shielding Protection of a  

E-print Network

SPECIALSPECIALREPORTREPORT97-197-1 Frost Shielding Protection of a Water Line, Berlin, New lines beneath the frost line in cold regions can be expensive when ledge or other difficult mate- rial was developed to predict frost penetration depth around buried utility pipelines. The program was How to get

Horvath, John S.

81

CRRELREPORT98-4 Frost-Shielding Methodology and  

E-print Network

CRRELREPORT98-4 Frost-Shielding Methodology and Demonstration for Shallow Burial of Water and Sewer the maximum frost penetration depth can be expensive when difficult digging conditions are encountered-element program was devel- oped to model various subterranean heat-flow situa- tions. It was used to design frost

Horvath, John S.

82

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

E-print Network

BEST PRACTICES RESEARCH � 2014 Frost & Sullivan 1 "We Accelerate Growth" INSERT COMPANY LOGO HERE #12;BEST PRACTICES RESEARCH � 2014 Frost & Sullivan 2 "We Accelerate Growth" Market Leadership Award Business Metro Carrier Ethernet Services United States, 2014 Frost & Sullivan's Global Research Platform

Fisher, Kathleen

83

Spatial and Temporal Patterns of Soil Frost in the  

E-print Network

1 Spatial and Temporal Patterns of Soil Frost in the Northern Midwest United States Tushar Sinha · Why is soil frost important ? · Objectives · Study area · Methodology · Results · Conclusions #12;3 Why is soil frost important ? · Soil ice reduces infiltration, cohesion and soil strength · Increases

Cherkauer, Keith

84

BEST PRACTICES RESEARCH 2013 Frost & Sullivan 1 "We Accelerate Growth"  

E-print Network

BEST PRACTICES RESEARCH © 2013 Frost & Sullivan 1 "We Accelerate Growth" Market Share Leadership Award Video Conferencing Hosted and Managed Services North America, 2013 Frost & Sullivan's Global Research Platform Frost & Sullivan is in its 50th year in business with a global research organization of 1

Fisher, Kathleen

85

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 not be accommodated within the pore system. Thus, a net expansion occurs. Joint Deterioration Frost Deterioration Model ·The cryogenic suction pump is a major factor in salt frost damage as it provides additional pore

86

Bioinformatics Computational Journal: Victor Frost, Terry Clark, Susan Gauch,  

E-print Network

Bioinformatics Computational Journal: User Guide Victor Frost, Terry Clark, Susan Gauch, Gerald: User Guide Investigators Victor Frost Terry Clark Susan Gauch Gerald Lushington Gary Minden Staff, Kansas 66045 Phone: (785) 864-4833 FAX:(785) 864-7789 e-mail: frost@eecs.ku.edu http

Kansas, University of

87

ORIGINAL PAPER Drought and frost resistance of trees: a comparison  

E-print Network

ORIGINAL PAPER Drought and frost resistance of trees: a comparison of four species at different /Published online: 1 December 2011 # INRA / Springer-Verlag France 2011 Abstract & Context Drought and frost, the vulnerability to drought-induced embolism and frost resistance of four species were analysed, whereby different

Paris-Sud XI, Université de

88

Electromagnetic field of a vertical electric dipole in the presence of a three-layered region  

Microsoft Academic Search

The electromagnetic field generated by a vertical electric dipole in the air over the surface of a two-layered region is determined for continuous-wave excitation. The region of interest consists of a conductor or dielectric with high permittivity, coated with an electrically thin layer of a dielectric under a half-space of air. Simple explicit formulas are derived for the field at

Ronald W. P. King; Sheldon S. Sandler

1994-01-01

89

Latest results from FROST at Jefferson Lab  

NASA Astrophysics Data System (ADS)

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.

Ritchie, B. G.

2014-06-01

90

Factors Modifying Frost Tolerance of Legume Species  

Microsoft Academic Search

temperature makes it more difficult to decide how much damage occurs from low temperature alone. Factors Variability in seedling death of legumes because of spring frost in such as crop species, growth stage, duration of freezing the USA and Canada is associated with several factors. Experiments up to 40% over unhardened seedlings across growth stages and species. pared with those

M. Badaruddin; D. W. Meyer

2001-01-01

91

Performance of organic photovoltaic devices in the presence of buffer layers  

NASA Astrophysics Data System (ADS)

We have investigated the dependence of the efficiency improvement of organic photovoltaic devices on the buffer layer. A device with a three-layer structure of ITO/CuPc/C60/BCP/Al was made as a reference through a thermal evaporation method. Characteristic parameters of the photovoltaic devices were measured and analyzed. The obtained open-circuit voltage V OC , short-circuit current density J SC , fill factor (FF), and energy-conversion efficiency (ECE) for the reference device were 0.25 V, 1.05 mA/cm2, 0.45, and 0.12%, respectively. Also, devices with five-layer structures of ITO/PEDOT:PSS/CuPc/C60/BCP/(LiF or Cs2CO3)/Al were fabricated, and their electrical characteristics were measured. The V OC , J SC , FF, and ECE for the device with the LiF buffer layer were 0.47 V, 3.31 mA/cm2, 0.51, and 0.81%, and those obtained for the device with the Cs2CO3 buffer layer were 0.49 V, 3.52 mA/cm2, 0.53, and 0.92%, respectively. The photovoltaic performance of the device with the Cs2CO3 layer was found to be better than those of the others. The V OC , J SC , FF, and ECE for the device with the Cs2CO3 layer were higher than those of the reference device by factors of 1.88, 3.35, 1.18, and 7.67, respectively.

Kim, Tae-Wan; Shin, Jong-Yeol; Kang, Yong-Gil; Kim, Seung-Tae; Choi, Hyun-Min; Kim, Gwi-Yeol; Hong, Jin-Woong

2014-08-01

92

Distribution of Sulfur Dioxide Frost on Io  

NASA Technical Reports Server (NTRS)

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

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

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

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

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

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

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

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

1997-01-01

93

Motion layer extraction in the presence of occlusion using graph cuts.  

PubMed

Extracting layers from video is very important for video representation, analysis, compression, and synthesis. Assuming that a scene can be approximately described by multiple planar regions, this paper describes a robust and novel approach to automatically extract a set of affine or projective transformations induced by these regions, detect the occlusion pixels over multiple consecutive frames, and segment the scene into several motion layers. First, after determining a number of seed regions using correspondences in two frames, we expand the seed regions and reject the outliers employing the graph cuts method integrated with level set representation. Next, these initial regions are merged into several initial layers according to the motion similarity. Third, an occlusion order constraint on multiple frames is explored, which enforces that the occlusion area increases with the temporal order in a short period and effectively maintains segmentation consistency over multiple consecutive frames. Then, the correct layer segmentation is obtained by using a graph cuts algorithm and the occlusions between the overlapping layers are explicitly determined. Several experimental results are demonstrated to show that our approach is effective and robust. PMID:16237998

Xiao, Jiangjian; Shah, Mubarak

2005-10-01

94

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

PubMed Central

• 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

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

2004-01-01

95

Nonlinear unsteady contact heat conduction of two-layer shells in the presence of thermal radiation  

NASA Technical Reports Server (NTRS)

A technique is proposed for calculating the complex heat transfer of mated shells with the surrounding medium which also takes into account the temperature dependence of the contact thermal resistance between the shells. This technique can be used for thermal calculations and for calculations of the temperature stresses in two-layer space structure shells.

Novikov, V. S.; Chumakov, V. L.

1974-01-01

96

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)

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.

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

2004-06-01

97

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

PubMed

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

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

2014-02-01

98

Winter Frosted Dunes in Kaiser Crater  

NASA Technical Reports Server (NTRS)

As the Mars Global Surveyor Primary Mission draws to an end, the southern hemisphere of Mars is in the depths of winter. At high latitudes, it is dark most, if not all, of the day. Even at middle latitudes, the sun shines only thinly through a veil of water and carbon dioxide ice clouds, and the ground is so cold that carbon dioxide frosts have formed. Kaiser Crater (47oS, 340oW) is one such place. At a latitude comparable to Seattle, Washington, Duluth, Minnesota, or Helena, Montana, Kaiser Crater is studied primarily because of the sand dune field found within the confines of its walls (lower center of the Mars Orbiter Camera image, above). The normally dark-gray or blue-black sand can be seen in this image to be shaded with light-toned frost. Other parts of the crater are also frosted. Kaiser Crater and its dunes were the subject of an earlier presentation of results. Close-up pictures of these and other dunes in the region show details of their snow-cover, including small avalanches. The two Mars Global Surveyor Mars Orbiter Camera images that comprise this color view (M23-01751 and M23-01752) were acquired on January 26, 2001.

2001-01-01

99

An aerosol climatology for the Jungfraujoch, Part 1: Criteria for cloud presence and boundary layer influence  

NASA Astrophysics Data System (ADS)

The high alpine research station at the Jungfraujoch in Switzerland is located at 3580 m asl. Depending on meteorological conditions, the station is in the planetary boundary layer or in the free troposphere; and often it is inside clouds. In one location, it is thus possible to study aerosols under very different conditions. These possibilities have been recognized early on, with aerosol measurements starting in 1995. Over the years, the instrumentation has been extended significantly, today including various measurements of aerosol optical properties (nephelometer, aethalometer, MAAP) as well as aerosol size distribution (SMPS, OPC, APS). Additionally, the station regularly hosts campaigns (e.g. CLACE) with a multitude of additional devices, mostly focusing on new particle formation, cloud condensation nuclei, and ice nuclei. However, there are no continuously operated direct measurements to determine whether the station is in the clouds or not, whether it is in the PBL or the free troposphere. As these are essential parameters to describe the aerosol observed at the station, we present approaches to describe them based on the observations available to us. The intuitive choices to look at in terms of clouds are relative humidity and dew point. When comparing dew point and ambient temperature, a clear criterion to identify clouds can be easily deducted. However, the determination of "no clouds" is more ambiguous. Based on longwave radiation measurements performed routinely at the site, it is possible to calculate the sky temperature, i.e. the temperature at the point of origin of the radiation. When within a cloud, the sky temperature should be identical or at least close to ambient temperature. The comparison of sky and ambient temperature shows two clear clusters which can be interpreted as "cloud" and "no cloud". One has to note that in case of inversion or clouds shortly above the research station, this approach will produce false positives. However, combining this method and the dew point criterion for clouds should allow for a clear distinction between "cloud" and "no cloud" conditions. To determine in which atmospheric layer the research station is Conen et al. (2011) have developed a method based on radon concentration measurements. Comparing radon concentrations at the Jungfraujoch with concentrations in Bern, one finds that the probability distribution of the difference is the sum of two log-normal modes. Essentially, one mode means that both sites are in the same layer, the second means the sites are in different layers. With this approach it is possible to determine a lower limit for the radon concentration difference: When the difference is larger than this limit, the JFJ site can be considered to be in the free troposphere. Based on these new and various traditional parameters (synoptic weather, meteorological conditions, etc) we have analyzed size distributions collected at the JFJ in the years 2008-2013, mainly focusing on SMPS data but including additional measurements when called for. The objective is to determine which factors shape the aerosol observed at the Jungfraujoch. References Conen, F., Zahorowski, W., & Zimmermann, L.: Defining a criterion for free tropospheric air at Jungfraujoch. From "International Foundation HFSJG Activity Report 2011". Bern, Switzerland, 2011.

Herrmann, Erik; Weingartner, Ernest; Gysel, Martin; Bukowiecki, Nicolas; Hammer, Emanuel; Collaud Coen, Martine; Conen, Franz; Vuilleumier, Laurent; Baltensperger, Urs

2014-05-01

100

www.frost.com US Machine-to-Machine (M2M) Communications  

E-print Network

www.frost.com US Machine-to-Machine (M2M) Communications Markets NC5E-65 #12;#NC5E-65 ©2013 Frost & Sullivan www.frost.com Frost & Sullivan takes no responsibility for any incorrect information supplied and therefore is subject to fluctuation. Frost & Sullivan reports are limited publications con- taining valuable

Fisher, Kathleen

101

Evolution of plant resistance and tolerance to frost Anurag A. Agrawal,1  

E-print Network

REPORT Evolution of plant resistance and tolerance to frost damage Anurag A. Agrawal,1 * Jeffrey K-season frost enabled us to estimate natural selection and genetic constraints on the evolution of frost found strong selection favouring plant resistance to frost, but selection against tolerance to frost

Stinchcombe, John

102

Frost resistance and pore size distribution in bricks  

Microsoft Academic Search

Correlation between frost resistance, porosity and pore size distribution was examined. Different test methods were used to\\u000a evaluate the frost resistance. Porosity and pore size distribution were examined in mercury intrusion porosimeter (MIP). Scanning\\u000a electron microscopy gave a visual view of the pore geometry, pore size and porosity. A linear correlation was found between\\u000a frost resistance and the inverse value

M. Maage

1984-01-01

103

Frost growth and melting characteristics on glass fibers  

SciTech Connect

Frost growth over glass fibers of uniform diameter is observed using a microscope to investigate the cyclic effect of frosting and melting on the moisture accumulation in fiber-glass insulation, typically encountered in cold climate applications. A simple-three-dimensional conduction model is presented to demonstrate the temperature and local heat flux variation in the accumulated frost/water and attaching fibers. The numerical results show that the subcooling period for frost growth on fibers strongly depends on the fiber sizes and weakly depends on droplet sizes. For fiber diameters of greater than 0.23 mm, the local thermal equilibrium is no longer a good assumption.

Tao, Y.X. [Tennessee State Univ., Nashville, TN (United States). Dept. of Mechanical Engineering; Mao, Y.; Besant, R.W. [Univ. of Saskatchewan, Saskatoon, Saskatchewan (Canada). Dept. of Mechanical Engineering

1995-12-31

104

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

E-print Network

Habitat characteristics of adult frosted elfins (Callophrys irus) in sandplain communities 2006 Keywords: Frosted elfin Callophrys irus Butterfly conservation Sandplain communities Invasive-dependent Lepidop- tera within sandplain habitats of the northeastern United States. The frosted elfin (Calloph- rys

Schweik, Charles M.

105

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

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

106

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

ERIC Educational Resources Information Center

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

Mosso, Janet L.

107

Thermal resistance of frost on a finned air cooler  

SciTech Connect

This paper presents a method for measuring the thermal conductivity of frost accumulated on the fins of air conditioners and estimating the subsequent losses in thermal efficiency to the conditioner. The method is intended for use in optimizing the configuration of the fin design and working conditions of the conditioner for minimum frost accumulation and maximum defrost capacity.

Chepurnoi, M.N.; Shnaider, V.E.; Lomakin, V.N.; Sinyuk, N.I.

1987-09-01

108

BEST PRACTICES RESEARCH 2013 Frost & Sullivan 1 "We Accelerate Growth"  

E-print Network

, 2013 Frost & Sullivan's Global Research Platform Frost & Sullivan is in its 50th year in businessTM, which serves as the foundation of its TEAM ResearchTM methodology. This unique approach enables us, it also continues to face key challenges. Current barriers to growth include: 1) A still

Fisher, Kathleen

109

Genetically engineered microorganisms to rescue plants from frost injury  

Microsoft Academic Search

Ice nucleation active bacteria belonging to genera Pseudomonas, Xanthomonas and Erwinia contribute to frost damage to plants by initiating the formation of ice in plants that would otherwise supercool and avoid the damaging ice formation. The biological control of frost injury can be achieved by the application of non-ice nucleation active bacteria to the plant surfaces before they become colonized

G. H. Dar; R. C. Anand; P. K. Sharma

110

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

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

111

Argon frost continuous cryopump for fusion applications  

SciTech Connect

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.

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

1993-12-01

112

Frost formation on an airfoil: A mathematical model 1  

NASA Technical Reports Server (NTRS)

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.

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

1979-01-01

113

Five second helium neutral beam injection using argon-frost cryopumping techniques  

SciTech Connect

High power helium neutral beams for the heating of tokamak discharges can now be provided for 5 s by using argon cryopumping (of the helium gas) in the beamlines. The DIII-D neutral beam system has routinely provided up to 20 MW of deuterium neutral beam heating in support of experiments on the DIII-D tokamak. Operation of neutral beams with helium has historically presented a problem in that pulse lengths have been limited to 500 ms due to reliance solely on volume pumping of the helium gas. Helium is not condensed on the cryopanels. A system has now been installed to deposit a layer of argon frost on the DIII-D neutral beam cryopanels, between tokamak injection pulses. The layer serves to trap helium on the cryopanels providing sufficient pumping speed for 5 s helium beam extraction. The argon frosting hardware is now present on two of four DIII-D neutral beamlines, allowing injection of up to 6 MW of helium neutral beams per discharge, with pulse lengths of up to 5 s. The argon frosting system is described, along with experimental results demonstrating its effectiveness as a method of economically extending the capabilities of cryogenic pumping panels to allow multi-second helium neutral beam injection.

Phillips, J.C.; Kellman, D.H.; Hong, R.; Kim, J.; Laughon, G.M. [General Atomics, San Diego, CA (United States)

1995-12-31

114

Delayed frost growth on jumping-drop superhydrophobic surfaces.  

PubMed

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 interdrop frost wave. The growth of this interdrop frost front is shown to be up to 3 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 interdrop 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 interdrop phenomenon that is strongly coupled to the wettability and drop size distribution of the surface. A jumping-drop superhydrophobic condenser minimized frost formation relative to a conventional dropwise condenser in two respects: preventing heterogeneous ice nucleation by continuously removing subcooled condensate, and delaying frost growth by limiting the success of interdrop ice bridge formation. PMID:23286736

Boreyko, Jonathan B; Collier, C Patrick

2013-02-26

115

Avoiding heat pump evaporator frosting through the use of desiccants  

SciTech Connect

Frost formation and the required defrosting is a major problem affecting air-source heat pumps operating under high ambient humidity conditions. It is claimed that the impact of frost can lower the heating efficiency by as much as 20%. If the moisture contained in the air flowing across the evaporator of the heat pumps could be eliminated or reduced, frosting would not occur. This project was undertaken to determine whether frost formation can be reduced or avoided by reducing the moisture in the air-stream passing over the evaporator by means of desiccants. A special test facility was constructed and tests were conducted with saturated air at frost promoting temperatures. Desiccant matrices were placed ahead of the evaporator and the times for coil frosting with and without desiccants were compared. It was found that the use of desiccants prevents coil frosting but only for a limited time. A method for regenerating the desiccant must be developed to make this concept commercially viable. This is to be accomplished in a second phase of the project.

Kondepudi, S. [Electric Power Research Inst., Palo Alto, CA (United States); Murali, K.; Lorsch, H. [Drexel Univ., Philadelphia, PA (United States); Bhalerao, A. [S.R. Steel, Bombay (India)

1995-11-01

116

Frost monitoring of fruit tree with satellite data  

NASA Astrophysics Data System (ADS)

The orchards are developing very fast in the northern China in recent years with the increasing demands on fruits in China. In most parts of the northern China, the risk of frost damage to fruit tree in early spring is potentially high under the background of global warming. The growing season comes earlier than it does in normal year due to the warm weather in earlier spring and the risk will be higher in this case. According to the reports, frost event in spring happens almost every year in Ningxia Region, China. In bad cases, late frosts in spring can be devastating all fruit. So lots of attention has been given to the study in monitoring, evaluating, preventing and mitigating frost. Two orchards in Ningxia, Taole and Jiaozishan orchards were selected as the study areas. MODIS data were used to monitor frost events in combination with minimum air temperature recorded at weather station. The paper presents the findings. The very good correlation was found between MODIS LST and minimum air temperature in Ningxia. Light, middle and severe frosts were captured in the study area by MODIS LST. The MODIS LST shows the spatial differences of temperature in the orchards. 10 frost events in April from 2000 to 2010 were captured by the satellite data. The monitoring information may be hours ahead circulated to the fruit farmers to prevent the damage and loss of fruit trees.

Fan, Jinlong; Zhang, Mingwei; Cao, Guangzheng; Zhang, Xiaoyu; Liu, Chenchen; Niu, Xinzan; Xu, Wengbo

2012-09-01

117

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

NASA Technical Reports Server (NTRS)

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.

Zhang, Ting-Jun; Li, Shu-Sun

2003-01-01

118

Aust. J. Agric. Res., 1993, 44, 1731-43 Characteristics of Frost in a Major  

E-print Network

Aust. J. Agric. Res., 1993, 44, 1731-43 Characteristics of Frost in a Major Wheat-growing Region, New Zealand. Abstract Frost at anthesis of wheat reduces grain set. Characteristics of frost, the region can be divided into four homogeneous areas according to five general characteristics of frost

Fletcher, David

119

Frost flower chemical composition during growth and its implications for aerosol production  

E-print Network

Frost flower chemical composition during growth and its implications for aerosol production; published 5 November 2008. [1] Frost flowers have been proposed to be the major source of sea-salt aerosol. Therefore, we chemically analyzed 28 samples of frost flowers and parts of frost flowers collected from sea

Douglas, Thomas A.

120

Mechanism of frost formation on lubricant-impregnated surfaces.  

PubMed

Frost formation is a major problem affecting a variety of industries including transportation, power generation, construction, and agriculture. Currently used active chemical, thermal, and mechanical techniques of ice removal are time-consuming and costly. The use of nanotextured coatings infused with perfluorinated oil has recently been proposed as a simple passive antifrosting and anti-icing method. However, we demonstrate that the process of freezing subcooled condensate and frost formation on such lubricant-impregnated surfaces is accompanied by the migration of the lubricant from the wetting ridge and from within the textured substrate to the surface of frozen droplets. For practical applications, this mechanism can comprise the self-healing and frost-repelling characteristics of lubricant impregnated-surfaces, regardless of the underlying substrate's topography. Thus, further research is necessary to develop liquid-texture pairs that will provide a sustainable frost suppression method. PMID:23565857

Rykaczewski, Konrad; Anand, Sushant; Subramanyam, Srinivas Bengaluru; Varanasi, Kripa K

2013-04-30

121

Experimental investigation of the surface temperature and water retention effects on the frosting performance of a compact microchannel heat exchanger for heat pump systems  

Microsoft Academic Search

Frost formation on a louvered fin microchannel heat exchanger was experimentally investigated in this paper with the aim of determining the dominant factors affecting the time of frosting and frost growth rate. A novel methodology was developed to measure frost thickness and frost weight at intervals during the frosting period. Frost mass and thickness growth rates, corresponding coil heat transfer,

Ehsan Moallem; Sankar Padhmanabhan; Lorenzo Cremaschi; Daniel E. Fisher

122

Frost damage and its cascading negative effects on Aesculus glabra  

Microsoft Academic Search

Frost damage and re-foliation are seldom quantified for forest species, but are of ecological and evolutionary importance.\\u000a This study of Aesculus glabra (Ohio buckeye) in a deciduous forest remnant in Illinois, USA, quantified frost damage to leaves and flowers after sub-freezing\\u000a temperatures in April 2007. It also documented re-foliation and later growth, reproduction, and survival in 2007–2009 for\\u000a the 355

Carol K. Augspurger

2011-01-01

123

Experimental investigation of frost formation on a parallel flow evaporator  

Microsoft Academic Search

This paper experimentally studied the frosting process of a folded–louvered-fin, parallel flow microchannel evaporator in a heat pump central air-conditioning system under three conditions, in which three open states of two capillaries were adopted. Surface temperature distribution on evaporator was measured by 16 thermocouples buried on the leeward side. Mesoscale frost formation processes on its front view surface for three

Jianghong Wu; Guang Ouyang; Puxiu Hou; Haobin Xiao

2011-01-01

124

Frost rings in trees as records of major volcanic eruptions  

Microsoft Academic Search

New data about climatically-effective volcanic eruptions during the past several thousand years may be contained in frost-damage zones in the annual rings of trees. There is good agreement in the timing of frost events and recent eruptions, and the damage can be plausibly linked to climatic effects of stratospheric aerosol veils on hemispheric and global scales. The cataclysmic proto-historic eruption

V. C. Lamarche Jr.; Katherine K. Hirschboeck

1984-01-01

125

Radiant frost tolerance in pulse crops—a review  

Microsoft Academic Search

Radiant frost is a major abiotic stress, and one of the principal limiting factors for agricultural production worldwide,\\u000a including Australia. Legumes, including field pea, faba bean, lentil and chickpea, are very sensitive to chilling and freezing\\u000a temperatures, particularly at the flowering, early pod formation and seed filling stages. Radiant frost events occur when\\u000a plants and soil absorb the sunlight during

Ahmad Maqbool; Shaista Shafiq; Lachlan Lake

2010-01-01

126

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

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

127

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

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

128

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

NASA Technical Reports Server (NTRS)

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.

Kandula, Max

2010-01-01

129

General frost growth mechanism on solid substrates with different stiffness.  

PubMed

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

Petit, Julien; Bonaccurso, Elmar

2014-02-01

130

Study of a frost-less heat pump  

SciTech Connect

Heat pumps, used as primary residential space conditioning systems in many temperate climates, have inherent requirements for defrosting of the outdoor evaporator coil during the winter heating season when frost forms. This paper describes a new concept and the results of the new technology that minimizes evaporator coil frosting to ambient temperatures as low as 33 F, and that reduces or eliminates the need for reverse cycle defrosting at many conditions. By strategically adding controlled heat to the liquid stored in the accumulator, the evaporator temperature is increased. Depending on the amount of heat added, an evaporator temperature increase of 7 F can be realized. This increased coil temperature acts to decrease frosting in the ambient temperature range that has high frosting propensity, 33 F to 41 F. Proof-of-concept experiments were performed in both a baseline configuration and with the new frost-less technology on an of-the-shelf two-ton residential heat pump. Results are shown for outdoor air temperatures from 33 F to 41 F with relative humidity kept at 80%.

Domitrovic, R.E.; Chen, F.C.; Mei, V.C.; Murphy, R.W.; Kilpatrick, J.K.; Richardson, J.O.

1999-07-01

131

Frost sensor for use in defrost controls for refrigeration  

DOEpatents

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

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

2002-01-01

132

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

E-print Network

Old World Monkeys Stephen R Frost, University of Oregon, Eugene, Oregon, USA Alfred L Rosenberger; Jablonski and Frost, 2010). Basic Biology Old World monkeys are catarrhine primates, and as such share

Rosenberger, Alfred H.

133

A Case Study of Coinduction in Isabelle HOL \\Lambda Jacob Frost y  

E-print Network

A Case Study of Co­induction in Isabelle HOL \\Lambda Jacob Frost y Computer Laboratory University of Cambridge e­mail:Jacob.Frost@cl.cam.ac.uk August 1993 Abstract The consistency of the dynamic and static

Haddadi, Hamed

134

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

E-print Network

fruit feeders like apple maggot). However, growe1 Minimal Spray Strategy for Frosted Apple Trees Nikki Rothwell, District Fruit IPM Educator Amy morning frost of Saturday, May 6th , many apples in the northwest region were affected. Based on some

135

Correlation of Water Frost Porosity in Laminar Flow over Flat Surfaces  

NASA Technical Reports Server (NTRS)

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

Kandula, Max

2011-01-01

136

Generation and development of small-amplitude disturbances in a laminar boundary layer in the presence of an acoustic field  

NASA Astrophysics Data System (ADS)

A low-turbulence subsonic wind tunnel was used to study the influence of acoustic disturbances on the development of small sinusoidal oscillations (Tollmien-Schlichting waves) which constitute the initial phase of turbulent transition. It is found that acoustic waves propagating opposite to the flow generate vibrations of the model (plate) in the flow. Neither the plate vibrations nor the acoustic field itself have any appreciable influence on the stability of the laminar boundary layer. The influence of an acoustic field on laminar boundary layer disturbances is limited to the generation of Tollmien-Schlichting waves at the leading-edge of the plate.

Kachanov, Y. S.; Kozlov, V. V.; Levchenko, V. Y.

1985-04-01

137

Frost-weathering on Mars: Experimental evidence for peroxide formation  

Microsoft Academic Search

Summary A laboratory study of the interaction of H2O frost with samples of the minerals olivine (Mg,Fe)2SiO4 and pyroxene (Mg,Fe)SiO3 at -11°C to -22°C revealed that an acidic oxidant was produced. Exposure of the frost-treated minerals to liquid H2O produced a sudden drop in pH and resulted in the production of copious O2(g) (as much as ~ 1020 molecules g-1).

Robert L. Huguenin; Karen J. Miller; William S. Harwood

1979-01-01

138

Far-infrared spectra of CO2 clathrate hydrate frosts  

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

139

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

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

140

Lake and wetland variability in regions of seasonal and permanent soil frost  

NASA Astrophysics Data System (ADS)

Northern Eurasian plays an important role in global climate partially due to the potential for positive carbon-cycle feedbacks associated with the interaction between frozen soil, temperature, and moisture. In particular, this region is characterized by numerous wetlands and lakes in areas of both seasonal and permanent soil frost. Soil ice content has a large influence on the temporal and spatial variation of soil moisture in these wetlands, which have the potential to produce large amounts of methane under saturated conditions. As soil temperatures increase, ice melt may result in more drainage and less soil saturation in areas of seasonal frost and discontinuous permafrost. In permafrost areas, the ice layer may provide a barrier to restrict drainage and subsequently increase surface inundation. Simulation of such changes in wetland extent is limited by understanding of the spatial heterogeneity of surface saturation. The Variable Infiltration Capacity (VIC) macroscale hydrologic model was modified to represent sub-grid variability in wetland distribution by integrating a modified topographic wetness index approach. In addition, simulation of changes in the extent of lake and wetland systems is improved by allowing the exchange of moisture content between lakes and adjacent wetlands. The modified VIC model is evaluated with respect to observations of water table depth and runoff obtained over a period of three decades from the Valdai research station located south of St. Petersburg, Russia. The variability in simulated wetland extent is then evaluated between 1930 and 2000 in the Upper Volga and Zapadnaya Dvina watersheds (seasonal soil frost) and the Yeloguy and Syum watersheds (discontinuous permafrost). The average wetland area determined from simulated hydrology is compared to landcover classifications derived from L-band satellite synthetic aperture radar imagery. This work was carried out at Purdue University, at the University of Washington, and at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Chiu, C.; Sathulur, K.; Bowling, L. C.; Bohnpodest, E.; Bohn, T.; Lettenmaier, D. P.; McDonald, K.

2007-12-01

141

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

USGS Publications Warehouse

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.

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

142

The influence of frost formation and defrosting on the performance of air coolers  

Microsoft Academic Search

The effects of frost formation on refrigerating equipment are examined to show the influence on the design of the equipment. The fundamentals of the frost formation process are discussed to supply basic information for the effects of frost on cooler performance. The specific problems involve: (1) a decrease in cooling capacity, (2) a decrease of air flow rate, and (3)

C. T. Sanders

1974-01-01

143

THE ASYMPTOTIC GIANT BRANCH J. C. LATTANZIO AND C. A. FROST  

E-print Network

THE ASYMPTOTIC GIANT BRANCH J. C. LATTANZIO AND C. A. FROST Department of Mathematics, Monash. The reader is referred to Iben & Renzini (1983), Frost & Lattanzio (1996a) and Lattanzio et al.(1996 expands. This essentially extinguishes the H­shell, #12; 2 J. C. LATTANZIO AND C. A. FROST CO core He

Lattanzio, John

144

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

E-print Network

A Basic Thermodynamic Derivation of the Maximum Overburden Pressure Generated in Frost Heave be generated in frost heave. The method stems from the fact that useful work can, in principle, be extracted from the forces generated by an advancing solidification front via the frost heave mechanism. Using

Libbrecht, Kenneth G.

145

Hybridization techniques and frost tolerance studies in intraspecific hybrids of Eucalyptus globulus Labill  

E-print Network

Hybridization techniques and frost tolerance studies in intraspecific hybrids of Eucalyptus. In intra- specific hybrids, seed characteristics and growth were evaluated in the field and frost tolerance seed type. Some of these seeds were planted in the field and evaluated for growth. Frost folerance

Paris-Sud XI, Université de

146

Status of ASCE Standard on Design and Construction of Frost Protected Shallow Foundations1  

E-print Network

Status of ASCE Standard on Design and Construction of Frost Protected Shallow Foundations1- insulation materials that are the key component of a frost-protected shallow foundation (FPSF) system Subject to Freezing and Frost," C. K. Tan (ed.), Geotechnical Special Publication No. 73, ASCE, 1997. 2

Horvath, John S.

147

Biocomplexity associated with biogeochemical cycles in arctic frost-boil ecosystems  

E-print Network

i Biocomplexity associated with biogeochemical cycles in arctic frost-boil ecosystems Principal CYCLES IN ARCTIC FROST-BOIL ECOSYSTEMS A PROJECT SUMMARY The central goal of this project to changing climate. We focus on frost-boils because: (1) The processes that are involved in the self

Wagner, Diane

148

Climatic controls on frost cracking and implications for the evolution of bedrock landscapes  

E-print Network

Climatic controls on frost cracking and implications for the evolution of bedrock landscapes T. C, a process called segregation ice growth. The depth and intensity of frost cracking is primarily dependent meter of the rock mass and a maximum frost penetration of $4 m. In contrast, negative MAT areas have

Roering, Joshua J.

149

In Live Interaction, Does Familiarity Promote Attraction or Contempt? Reply to Norton, Frost, and Ariely (2011)  

E-print Network

REPLY In Live Interaction, Does Familiarity Promote Attraction or Contempt? Reply to Norton, Frost and refute each of Norton, Frost, and Ariely's (2011) specific objections to the conclusion that, ceteris concur with Norton et al.'s call for an integrative model that encompasses both Norton, Frost, and Ariely

Reber, Paul J.

150

The effect of excess nitrogen and of insect defoliation on the frost hardiness of bark tissue  

E-print Network

Short note The effect of excess nitrogen and of insect defoliation on the frost hardiness of bark winter frost, causing severe bark necroses, and insect defoliation are two of the causal factors on the frost hardiness of the bark of adult oaks was tested. At several dates dur- ing winter, samples from

Boyer, Edmond

151

Formation of ice lenses and frost heave A. W. Rempel1  

E-print Network

Formation of ice lenses and frost heave A. W. Rempel1 Received 13 April 2006; revised 26 January.g., lenses) and frost heave. I account for the net effect of these microscopic interactions in a homogenized. Citation: Rempel, A. W. (2007), Formation of ice lenses and frost heave, J. Geophys. Res., 112, F02S21, doi

Rempel, Alan W.

152

ICARUS 62, 344-347 (1985) Polar Frost Formation on Ganymede  

E-print Network

ICARUS 62, 344-347 (1985) NOTE Polar Frost Formation on Ganymede R. E. JOHNSON Department Received June 25, 1984: revised February 4, 1985 The suggested models of polar frost formation on Ganymede is proposed. 19s5 Academic Press, Inc. Introduction. The observation of a polar frost on Ganymede, which

Johnson, Robert E.

153

Frost flower formation on sea ice and lake ice Robert W. Style1  

E-print Network

Frost flower formation on sea ice and lake ice Robert W. Style1 and M. Grae Worster1 Received 22 January 2009; revised 20 April 2009; accepted 6 May 2009; published 10 June 2009. [1] Frost flowers to a class of vapour-related phenomena that includes freezing fog, hoar frost and dew. It has hitherto been

Worster, M. Grae

154

Evaluation of MM5 Simulations With HTSVS With and Without Inclusion of Soil-Frost Parameterization  

E-print Network

Evaluation of MM5 Simulations With HTSVS With and Without Inclusion of Soil-Frost Parameterization and seasonally frozen ground are important surface features in high- latitudes. Because of this, a soil-frost and observations of precipitation were used to evaluate the importance of the soil-frost parameterization

Moelders, Nicole

155

Historic climate change impacts on soil frost in the Mid-Western  

E-print Network

1 Historic climate change impacts on soil frost in the Mid-Western United States Tushar Sinha #12;2 Outline · Why do we care about soil frost? · Observations of climate change · Variable Infiltration Capacity (VIC) model · Model calibration · Results #12;3 Why do we care about soil frost ? · Soil

Cherkauer, Keith

156

Seasonal soil frost in response to future climate change in the  

E-print Network

1 Seasonal soil frost in response to future climate change in the Midwestern US Tushar Sinha, Keith #12;2 Outline · Why do we care about soil frost? · Climate change impacts · Variable Infiltration Capacity (VIC) model · Model calibration and evaluation · Results #12;3 Why do we care about soil frost

Cherkauer, Keith

157

Frost sensor for use in defrost controls for refrigeration  

Microsoft Academic Search

An apparatus and method for measuring the total thermal resistance to heat flow from the air to the evaporative cooler fins of a refrigeration system. The apparatus is a frost sensor that measures the reduction in heat flow due to the added thermal resistance of ice (reduced conduction) as well as the reduction in heat flow due to the blockage

Patrick D. French; James R. Butz; Bradley D. Veatch; Michael W. OConnor

2002-01-01

158

Observation into Insight: The Poetry of Carol Frost  

Microsoft Academic Search

Carol Frost has quietly established a reputation as one of the foremost lyric poets of her generation. Although her poems are typically characterized by an exquisite expression of ideas and images, her sense of phrasing extends beyond the instinct for choosing the right word or the right combination of words. In the same way that Frank Sinatra and Peggy Lee

Martin Kich

2008-01-01

159

Frost, Goldstein, and Korenaga Awarded 2006 James B. Macelwane Medal  

NASA Astrophysics Data System (ADS)

Daniel J. Frost, Jerry Goldstein, and Jun Korenaga received the James B. Macelwane Medal at the AGU Fall Meeting honors ceremony, which was held on 13 December 2006 in San Francisco, Calif. The medal is given for significant contributions to the geophysical sciences by an outstanding young scientist.

Burch, James L.; Goldstein, Jerry; Rubie, David; Frost, Daniel J.; Jordan, Thomas H.; Korenaga, Jun

2007-01-01

160

Frost hardiness of Philadelphus and Hydrangea clones during ecodormancy  

Microsoft Academic Search

The frost hardiness of clones of two ornamental shrubs, hydrangea (Hydrangea paniculata Sieb. ‘Grandiflora') and mock orange (Philadelphus lewisii Pursh. var. lewisii ’Waterton'), was measured after completion of endodormancy. In addition to actual hardiness, minimum and potential hardiness were examined with the aid of four artificial hardening and dehardening treatments. Logit models were used for determining the lethal temperature. Artificial

Terhi Suojala; Leena Lindén

1997-01-01

161

Theoretical analysis of fin efficiency with frost deposition on heat exchanger surface  

SciTech Connect

Frosting phenomena are encountered in numerous fields of industry. Frosting process under unsteady conditions involves simultaneous heat and mass transfer. Since the heat exchanger is indispensable, it is obviously necessary to obtain an accurate fin efficiency under frosting condition. Several frosted fin efficiency functions have been discussed in the past. Different hypotheses had been made by different researchers. On the basis of linear and quadratic function of the saturated air enthalpy, two new algorithms are presented in this paper to determine the frosted fin efficiency when simultaneous heat and mass transfer occurs. Temperature distribution over fin surface is calculated by solving a nonlinear second-order differential equation. New fin efficiency function is more accurate. Analysis shows that the frosted fin efficiency is independent from the relative humidity. By using this function in frosting simulation, the simulation fits experimental data better.

Yu, B.; Feng, Y.; Tong, L.; Que, X.; Chen, Z.

1999-07-01

162

Severe soil frost reduces losses of carbon and nitrogen from the forest floor during simulated snowmelt: A laboratory experiment  

E-print Network

Severe soil frost reduces losses of carbon and nitrogen from the forest floor during simulated in understanding the impacts of soil frost on carbon (C) and nitrogen (N) cycling, but the effects of soil frost to determine the effects of soil frost on C and N fluxes from forest floor soils during snowmelt. Soil cores

Templer, Pamela

163

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

E-print Network

STUDY OF FROST GROWTH ON HEAT EXCHANGERS USED AS OUTDOOR COILS IN AIR SOURCE HEAT PUMP SYSTEMS OF FROST GROWTH ON HEAT EXCHANGERS USED AS OUTDOOR COILS IN AIR SOURCE HEAT PUMP SYSTEMS Dissertation of Frost Growth . . . . . . . . . . . . . . . . . . . . . 7 2.2 Frost Growth on Simple Geometries

164

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.

165

Acrylic coatings with surprising antifogging and frost-resisting properties.  

PubMed

We report an unusually effective antifogging/frost-resisting coating based on conventional acrylic polymers. The intriguing antifogging property originated from the delicate balance between the hydrophilicity and hydrophobicity of the acrylic copolymers of 2-(dimethylamino)ethyl methacrylate and methyl methacrylate, as well as between the water-swellability of the copolymer and the cross-linked network due to ethylene glycol dimethacrylate. PMID:24201972

Zhao, Jie; Meyer, Anthony; Ma, Li; Ming, Weihua

2013-12-28

166

Morning Frost in Trench Dug by Phoenix, Sol 113  

NASA Technical Reports Server (NTRS)

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.

2008-01-01

167

Frost-weathering on Mars: experimental evidence for peroxide formation.  

PubMed

A laboratory study of the interaction of H2O frost with samples of the minerals olivine (Mg,Fe)2SiO4 and pyroxene (Mg,Fe)SiO3 at -11 degrees C to -22 degrees C revealed that an acidic oxidant was produced. Exposure of the frost-treated minerals to liquie H2O produced a sudden drop in pH and resulted in the production of copious O2(g) (as much as approximately 10(20) molecules g-1). Exposure of frost-treated samples to 5 ml of 0.1M HCOONa solution resulted in the rapid oxidation of up to 43% of the formate to CO2(g). These reactions were qualitatively similar to the chemical activity observed during the active cycles of the Viking lander Gas Exchange and Labeled Release Biology experiments. Attempts to identify the oxidant by chemical indicators were inconclusive, but they tentatively suggested that chemisorbed hydrogen peroxide may have formed. The formation of chemisorbed peroxide could be explained as a byproduct of the chemical reduction of the mineral. The following model was proposed. H+ was incorporated into the mineral from surface frost. This would have left behind a residual of excess OH-(ads) (relative to surface H+). Electrons were then stripped from the surface OH-(ads) (due to the large repulsive potential between neighboring OH-(ads)) and incorporated into the crystal to restore charge balance and produce a chemical reduction of the mineral. The resultant surface hydroxyl radicals could then have combined to form the more stable chemisorbed hydrogen peroxide species. While the chemisorbed peroxide should be relatively stable at low temperatures, it should tend to decay to O(ads)+ H2O(g) at higher temperatures with an activation energy of greater than or approximately 34 kcal mole-1. This is consistent with the long-term storage and sterilization behavior of the Viking soil oxidants. It is possible that as little as 0.1--1% frost-weathered material in the martian soil could have produced the unusual chemical activity that occurred during the Viking Gas Exchange and Labeled Release experiments. PMID:522148

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

1979-12-01

168

Heat and moisture transfer in energy wheels during sorption, condensation, and frosting conditions  

SciTech Connect

A numerical model for coupled heat and moisture transfer with sorption, condensation, and frosting in rotary energy exchangers is presented and validated with experimental data. The model is used to study condensation and frosting in energy wheels. Condensation/frosting increases with humidity and at some humidity level, water/frost will continually accumulate in the wheel. The sensitivity of condensation and frosting to wheel speed and desiccant type are studied. The energy wheel performance is also presented during both sorption and saturation conditions for a desiccant coating with a type I sorption isotherm (e.g., molecular sieve) and a linear sorption isotherm (e.g., silica gel). Simulation results show that the desiccant with a linear sorption curve is favorable for energy recovery because it has better performance characteristics and smaller amounts of condensation/frosting for extreme operating conditions.

Simonson, C.J.; Besant, R.W. [Univ. of Saskatchewan, Saskatoon, Saskatchewan (Canada). Dept. of Mechanical Engineering

1998-08-01

169

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)

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.

Dimopoulos, Dimitrios; Pelekasis, Nikos A.

2014-10-01

170

Effects of frost on wildflowers: an unexpected consequence of climate change--image 08 of 22  

NSDL National Science Digital Library

Photo of a meadow with thousands of Helianthella quinquenervis (aspen sunflower, Asteraceae) plants. In the year that this photo was taken, a springtime frost killed all but a few flower buds. Compare with the photo of the same meadow in a year without frost. The lack of flowers in years having springtime frost has ecological consequences. There is no pollen or nectar for pollinators (bees and flies), no seeds for seed predators (tephritid flies and caterpillars), and no seed predators for parasitoid wasps.

Inouye, David

2012-01-04

171

Frost Formation Problem in the Development of a Hypersonic Turbojet Engine  

NASA Astrophysics Data System (ADS)

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.

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

172

Study of the process of frost formation in finned air coolers  

SciTech Connect

This paper presents the results of an experimental study of frosting in finned air coolers with a different fin spacing. The results of the measurements and the visual observations showed that the intensity of frosting is higher during the initial period of operation of the air coolers and decreases with time. The thickness of the frost decreases along the apparatus. It should be noted that there are essentially no other formulas aside from the one presented for determining the instantaneous density of the frost during the operation of the air coolers.

Chepurnoi, M.N.; Chepurnoi, V.M.; Lomakin, V.N.; Shnaider, V.E.

1985-07-01

173

Carbon Nanofiber Based Films for Anti-icing/Anti-frosting Applications.  

E-print Network

??Superhydrophobic surfaces have been increasingly researched as a solution for the icing problem. Despite promising results, superhydrophobic surfaces eventually fail under condensation and frosting. All… (more)

Kapatral, Shreyas

2014-01-01

174

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

NASA Astrophysics Data System (ADS)

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

Estrella, Nicole; Menzel, Annette

2014-05-01

175

Linear and Nonlinear Tunable Optical Properties of Intersubband Transitions in GAN/ALN Quantum Dots in Presence and Absence of Wetting Layer  

NASA Astrophysics Data System (ADS)

In this study we have performed a numerical approach to investigate the optical properties of GaN/AlN quantum dots (QDs). We have used nice homemade finite element method (FEM) codes to solve the Schrödinger equation, in presence and absence of wetting layer. The optical properties of both well-known, truncated pyramids-shaped, wurtize (WZ) and zinc blande (ZB) QDs have been investigated. It is demonstrated, there is slight amount of difference between all orders of absorption coefficients and relative refractive index changes (RRIC) for both structures. The effect of relaxation rate studied as well. Overlay it is shown that the optical properties ZB/WZ QDs could be engineered in well-manner.

Khaledi-Nasab, A.; Sabaeian, M.; Rezaie, M.; Mohammad-Rezaee, M.

2014-02-01

176

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

PubMed Central

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

2014-01-01

177

Virulence markers of mesophilic aeromonads: association of the autoagglutination phenomenon with mouse pathogenicity and the presence of a peripheral cell-associated layer.  

PubMed Central

Autoagglutination (AA phenotype) of mesophilic aeromonads in broth was found to be a virulence-associated marker. There were two kinds of AA+ strains: those that spontaneously pelleted (SP+), and those that pelleted only after boiling (PAB+). Of 79 strains tested, 24 (30%) were AA+, and 18 of these were recovered from clinical specimens. Most of the AA+ strains (n = 21) were identified as either Aeromonas sobria or Aeromonas hydrophila. Of the well-documented clinical isolates of A. sobria and A. hydrophila available, 5 (46%) of 11 from invasive disease and 4 (14%) of 29 from noninvasive disease were SP- PAB+. The SP- PAB+ phenotype was significantly associated with invasive infections (e.g., bacteremia and peritonitis [chi 2, P less than 0.05]). All seven of the SP- PAB+ A. sobria and A. hydrophila strains tested killed mice within 48 h after intraperitoneal infection with 1 x 10(7) to 3 x 10(7) CFU, whereas only two of four SP+ PAB+ strains tested were lethal. All of the SP- PAB+ A. sobria and A. hydrophila isolates examined shared common O somatic antigens and possessed an external layer peripheral to the cell wall as determined by thin-section electron micrography. The LL1 strain of A. hydrophila used by Dooley et al. (J. S. G. Dooley, R. Lallier, and T. J. Trust, Vet. Immunol. Immunopathol. 12:339-344, 1986) to demonstrate an S membrane protein component in aeromonads virulent for fish also was SP- PAB+ and possessed the peripheral membrane, suggesting an association between these two components. Seven AA- and three SP+ strains tested lacked this layer; furthermore, 22 (71%) of 31 such isolates did not kill mice. The AA phenotype was a stable characteristic upon long-term passage of isolates in vitro. Study of SP+ and PAB+ aeromonads by surface charge and hydrophobicity analyses indicated that neither property correlated with either virulence or the presence of an external layer. Images PMID:3679544

Janda, J M; Oshiro, L S; Abbott, S L; Duffey, P S

1987-01-01

178

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

PubMed Central

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

Kuprian, Edith; Briceno, Veronica F.; Wagner, Johanna; Neuner, Gilbert

2014-01-01

179

Frosting and defrosting behaviour of outdoor coils of air-source heat pumps; condensed report  

SciTech Connect

In this report the results and conclusions are given of an investigation into the behaviour of outdoor coils of air-source heat pumps during frosting and defrosting. The aim of the investigation was to get an insight into the factors influencing coil behaviour and to make recommendations and give directives regarding design and operation of heat pump coils operating under frosting condition.

Bouma, J.W.J.

1981-02-01

180

Recovery of the bilberry (Vaccinium Myrtillus L.) from artificial spring and summer frost  

Microsoft Academic Search

Vegetative and sexual recovery of bilberry (Vaccinium myrtillus L.) was monitored in the field for three growing seasons after artificially applied spring and early summer frost. Bilberry recovered vegetatively (density and biomass) by vigorous production of new ramets and by production of large shoots in the damaged ramets. Recovery did not occur sexually (production of flowers), however. Summer frost was

Anne Tolvanen

1997-01-01

181

Multiple Randomised Reed-Frost Epidemics and Epidemics upon Random Graphs  

E-print Network

Multiple Randomised Reed-Frost Epidemics and Epidemics upon Random Graphs Peter Neal To appear;The Annals of Applied Probability MULTITYPE RANDOMISED REED-FROST EPIDEMICS AND EPIDEMICS UPON RANDOM GRAPHS By Peter Neal University of Manchester We consider a multitype epidemic model which is a natural

Sidorov, Nikita

182

The relation between growth cessation and frost hardening in Scots pines of different origins  

Microsoft Academic Search

The cessation of shoot elongation, diameter growth and needle elongation were compared with the initiation of frost hardening of the stems and needles in an 8-year-old provenance trial of Scots pine (Pinus sylvestris L.) established in central Finland. The saplings were of six different origins ranging from Estonia to northern Finland, forming a latitudinal gradient of ca. 10°N. The frost

Tapani Repo; Gang Zhang; Aija Ryyppö; Risto Rikala; Martti Vuorinen

2000-01-01

183

The Frost Multidimensional Perfectionism Scale revisited: More perfect with four (instead of six) dimensions  

Microsoft Academic Search

The Frost Multidimensional Perfectionism Scale (FMPS; Frost, Marten, Lahart & Rosenblate, 1990) provides six subscales for a multidimensional assessment of perfectionism: Concern over Mistakes (CM), Personal Standards (PS), Parental Expectations (PE), Parental Criticism (PC), Doubts about actions (D), and Organization (O). Despite its increasing popularity in personality and clinical research, the FMPS has also drawn some criticism for its factorial

Joachim Stöber

1998-01-01

184

Static and Fatigue Bond Characteristics of Interfaces between CFRP Sheets and Frost Damage Experienced Concrete  

Microsoft Academic Search

Synopsis: Synopsis: Synopsis: Synopsis: Synopsis: Both short and long-term performances of repaired or strengthened concrete structures using external FRP bonding are greatly affected by states of bonding substrates, which are covercrete and may have experienced various damages. One of them is frost damage in cold regions. This paper intends to investigate how the initial frost damages in concrete influence the

Byj. g. Dai; Y. Saito; T. Ueda; Y. Sato

185

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

Microsoft Academic Search

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

Rorik A. Peterson; William B. Krantz

186

The potential importance of frost flowers, recycling on snow, and open leads for Ozone Depletion Events  

Microsoft Academic Search

We present model studies with the one-dimensional model MISTRA to investigate the potential role of frost flowers, recycling on snow, and open leads in the depletion of tropospheric ozone in the Arctic spring. In our model, we assumed frost flower aerosols to be the major source of bromine. We show that a major ozone depletion event can be satisfactorily reproduced

M. Piot; R. von Glasow

2007-01-01

187

The potential importance of frost flowers, recycling on snow, and open leads for ozone depletion events  

Microsoft Academic Search

We present model studies with the one-dimensional model MISTRA to investigate the potential role of frost flowers, recycling on snow, and open leads in the depletion of tropospheric ozone in the Arctic spring. In our model, we assumed frost flower aerosols to be the major source of bromine. We show that a major ozone depletion event can be satisfactorily reproduced

M. Piot; R. von Glasow

2008-01-01

188

The Antarctic First Regional Observing Study of the Troposphere (FROST) Project  

Microsoft Academic Search

An account is given of the Antarctic First Regional Observing Study of the Troposphere (FROST) project, which has been organized by the Physics and Chemistry of the Atmosphere Group of the Scientific Committee on Antarctic Research. The goals of FROST are to study the meteorology of the Antarctic, to determine the strengths and weaknesses of operational analyses and forecasts over

John Turner; Steven Colwell; Steven Leonard; David Bromwich; Stephen Dixon; Hugh Hutchinson; Kieran Jacka; Lawrie Marsh; Stephen Pendlebury; Tim Gibson; Terry Hart; Günther Heinemann; Michael Lieder; Henry Phillpot; Mike Pook; Ian Simmonds

1996-01-01

189

Dew and frost chemistry at a midcontinent site, United States  

SciTech Connect

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

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

190

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

NASA Astrophysics Data System (ADS)

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

Haei, M.; Öquist, M.; Laudon, H.

2011-12-01

191

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

NASA Astrophysics Data System (ADS)

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.

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

192

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

PubMed

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

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

2013-01-01

193

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

PubMed Central

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

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

2013-01-01

194

Managing potato biodiversity to cope with frost risk in the high Andes: a modeling perspective.  

PubMed

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

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

2014-01-01

195

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

PubMed Central

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

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

2014-01-01

196

A frost "buzzsaw" mechanism for erosion of the eastern Southern Alps, New Zealand T.C. Hales a,  

E-print Network

A frost "buzzsaw" mechanism for erosion of the eastern Southern Alps, New Zealand T.C. Hales a, , J Available online 3 January 2009 Keywords: Southern Alps Periglacial processes Frost buzzsaw Scree of uplift and erosion across the Southern Alps. Here, we assess the efficacy of frost cracking

Roering, Joshua J.

197

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

E-print Network

Potential gradients produced by pore-space heterogeneities: Application to isothermal frost damage the supply of constituents through a fluid phase. With frost damage, the gradi- ents in chemical potential for constituent supply. We illustrate the consequences and character of isothermal frost damage using the results

Rempel, Alan W.

198

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

E-print Network

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, elastic interaction and poro-mechanics in order to describe freezing-related stresses. Keywords: frost

Paris-Sud XI, Université de

199

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

Microsoft Academic Search

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

M. C. Smale

1990-01-01

200

Can we use forecasts of El Niño and La Niña for frost management in the Eastern and Southern grains belt?  

Microsoft Academic Search

Frost damage on winter cereals in Australia is a low frequency but high consequence threshold event with losses up to 100%. In frost prone regions grain growers delay their planting time and adjust the variety maturity selection to minimise the risk of severe frost damage and in doing so they usually incur a yield penalty of 5% to 20%. This

Bronya Alexander; Peter Hayman

201

Nature and origin of layered deposits of the Martian polar regions  

NASA Technical Reports Server (NTRS)

Layered deposits in the Martian polar regions are interpreted as accumulations of dust derived from atmospheric suspensions. Depressed and eroded terrains of the equatorial region are considered to be the principal sources of dust. A depositional model based on polar precipitation of dust predicts the formation of a vast, dome-shaped, featureless plateau underlain by layered deposits and occupying most of the area of annual frost cover. The rates of accumulation of dust and water ice in the polar regions have been estimated on the basis of atmospheric conditions in the present era. The analysis indicates an accumulation time of about 500 x 1 million years for the layered deposits and the presence of significant quantities of water ice in the deposits beneath the perennial cap.

Cutts, J. A.

1973-01-01

202

Evaluation and improvement of frost durability of clay bricks  

NASA Astrophysics Data System (ADS)

In cold regions like Canada, frost action was reported to be the major cause of disintegration of brick veneer. Two approaches to ensure frost durability of clay bricks were studied in this research. One involved the evaluation of durability, while the other studied the improvement of durability through impregnation. In order to carry out these studies, three major objectives were set out for this research. They were: (1) to develop an index to evaluate frost durability, (2) to investigate the feasibility of using nondestructive methods to evaluate durability, and (3) to study the effect of impregnation with different materials on improving durability. It was intended in this research to develop a general durability index for clay bricks, irrespective of the manufacturing process adopted. The performance of the brick was studied using laboratory freeze-thaw test. As the time and facility requirements necessary for the unidirectional freezing test were beyond the constraints which existed in this research, an accelerated omnidirectional freeze-thaw test was used. This fact must be considered while interpreting the results from the freeze-thaw test. The study carried out to compare the performance of existing durability indices showed that they had limitations in reliably assessing durability. Therefore new durability indices were developed based on water absorption properties of bricks. These indices were found to overcome the limitations of existing indices. The feasibility study on nondestructive evaluation of durability was carried out using ultrasonic pulse velocity. New durability provisions were derived based on pulse velocity, using ASTM C216 specifications. At this stage it can be used only along with the ASTM method but it can avoid the time consuming ASTM procedure in many cases. Studies on impregnated bricks showed that there was a general shifting of pore sizes towards lower diameter region. Paraffin impregnated brick showed excellent freeze-thaw performance. The bond between brick and mortar was found to have been adversely affected due to impregnation. But more studies using brick wall component are recommended before final conclusions are drawn on brick-mortar bond strength. Paraffin was found to be the most cost effective among the impregnating materials studied.

Koroth, Surej Raghavan

203

Helicity Asymmetry in gamma p -> pi+ n with FROST  

E-print Network

The main objective of the FROST experiment at Jefferson Lab is the study of baryon resonances. The polarization observable E for the reaction gamma p to pi+n has been measured as part of this program. A circularly polarized tagged photon beam with energies from 0.35 to 2.35 GeV was incident on a longitudinally polarized frozen-spin butanol target. The final-state pions were detected with the CEBAF Large Acceptance Spectrometer. Preliminary polarization data agree fairly well with present SAID and MAID partial-wave analyses at low photon energies. In most of the covered energy range, however, significant deviations are observed. These discrepancies underline the crucial importance of polarization observables to further constrain these analyses.

Steffen Strauch; for the CLAS Collaboration

2011-08-15

204

Helicity Asymmetry in gamma p -> pi+ n with FROST  

SciTech Connect

The main objective of the FROST experiment at Jefferson Lab is the study of baryon resonances. The polarization observable E for the reaction gamma p to pi+n has been measured as part of this program. A circularly polarized tagged photon beam with energies from 0.35 to 2.35 GeV was incident on a longitudinally polarized frozen-spin butanol target. The final-state pions were detected with the CEBAF Large Acceptance Spectrometer. Preliminary polarization data agree fairly well with present SAID and MAID partial-wave analyses at low photon energies. In most of the covered energy range, however, significant deviations are observed. These discrepancies underline the crucial importance of polarization observables to further constrain these analyses.

Steffen Strauch

2012-04-01

205

Helicity asymmetry E in ?p-->?+n with FROST  

NASA Astrophysics Data System (ADS)

The main objective of the FROST experiment at Jefferson Lab is the study of baryon resonances. The polarization observable E for the reaction ?p-->?+n has been measured as part of this program. A circularly polarized tagged photon beam with energies from 0.35 to 2.35 GeV was incident on a longitudinally polarized frozen-spin butanol target. The final-state pions were detected with the CEBAF Large Acceptance Spectrometer. Preliminary polarization data agree fairly well with present SAID and MAID partial-wave analyses at low photon energies. In most of the covered energy range, however, significant deviations are observed. These discrepancies underline the crucial importance of polarization observables to further constrain these analyses.

Strauch, Steffen; CLAS Collaboration

2012-04-01

206

Mate-finding behaviour in Calanus marshallae Frost  

PubMed Central

Mate-finding behaviour by Calanus marshallae Frost, 1974, was observed and video recorded in a 1 m diameter kreisel. Newly moulted females signal to males by depositing vertical pheromone trails many tens of centimetres long. Males search for trails along primarily horizontal trajectories. The orthogonality of signal trace and search trail trajectory maximizes the chance of intersection. Males often initiate a dance of rapid, tight turns upon encountering a pheromone trail, then waggle down it (chase swimming) to the signalling female. She jumps away after initial contact, and the male follows. Many successive approach, bump and jump sequences follow, with mating eventually ensuing. The actual copulatory clasp and spermatophore transfer were not observed, although a few instances of brief attachment and tandem swimming were seen. Male dances occur at times when chase swimming does not follow, and the function of dances is not yet known.

Tsuda, A.

1998-01-01

207

Determination of the correlation between physical measurements of roughness, optical properties, and perception of frosted glass surfaces.  

PubMed

Chemical frosting is used as a surface decorating method by many glass package producers. After immersion in an acid frosting bath, glass items present the desired frosted effect. The perception of this particular effect is due to the formation of a microscopic crystalline pattern on the glass surface, which scatters light passing through the glass surface. The chemical composition of the frosting bath influences these properties by modifying the surface roughness, the depth, and the average slopes of the crystalline pattern. Perception of the final aspect can be modified according to the chemical composition of the frosting bath. Different correlations between all these parameters exist and have been quantified. PMID:18641764

Frayret, Jérôme; Eterradossi, Olivier; Castetbon, Alain; Potin-Gautier, Martine; Trouvé, Gérard; de Roulhac, Hugues

2008-07-20

208

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

PubMed

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

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

2014-01-01

209

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

USGS Publications Warehouse

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

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

2008-01-01

210

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

USGS Publications Warehouse

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.

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

2007-01-01

211

Relationships among Vernalization, Shoot Apex Development and Frost Tolerance in Wheat  

PubMed Central

• Background and Aims Frost tolerance of wheat depends primarily upon a strong vernalization requirement, delaying the transition to the reproductive phase. The aim of the present study was to learn how saturation of the vernalization requirement and apical development stage are related to frost tolerance in wheat. • Methods ‘Mironovskaya 808’, a winter variety with a long vernalization requirement, and ‘Leguan’, a spring variety without a vernalization requirement, were acclimated at 2 °C at different stages of development. Plant development (morphological stage of the shoot apex), vernalization requirement (days to heading) and frost tolerance (survival of the plants exposed to freezing conditions) were evaluated. • Key Results ‘Mironovskaya 808’ increased its frost tolerance more rapidly; it reached a higher level of tolerance and after a longer duration of acclimation at 2 °C than was found in ‘Leguan’. The frost tolerance of ‘Mironovskaya 808’ decreased and its ability to re-acclimate a high tolerance was lost after saturation of its vernalization requirement, but before its shoot apex had reached the double-ridge stage. The frost tolerance of ‘Leguan’ decreased after the plants had reached the floret initiation stage. • Conclusions The results support the hypothesis that genes for vernalization requirement act as a master switch regulating the duration of low temperature induced frost tolerance. In winter wheat, due to a longer vegetative phase, frost tolerance is maintained for a longer time and at a higher level than in spring wheat. After the saturation of vernalization requirement, winter wheat (as in spring wheat) established only a low level of frost tolerance. PMID:15277245

PRÁŠIL, ILJA TOM; PRÁŠILOVÁ, PAVLA; PÁNKOVÁ, KATE?INA

2004-01-01

212

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

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

213

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

NASA Technical Reports Server (NTRS)

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.

Katnik, Gregory N.; Higginbotham, Scott A.

1989-01-01

214

The genetic potential for key biogeochemical processes in Arctic frost flowers and young sea ice revealed by metagenomic analysis.  

PubMed

Newly formed sea ice is a vast and biogeochemically active environment. Recently, we reported an unusual microbial community dominated by members of the Rhizobiales in frost flowers at the surface of Arctic young sea ice based on the presence of 16S gene sequences related to these strains. Here, we use metagenomic analysis of two samples, from a field of frost flowers and the underlying young sea ice, to explore the metabolic potential of this surface ice community. The analysis links genes for key biogeochemical processes to the Rhizobiales, including dimethylsulfide uptake, betaine glycine turnover, and halocarbon production. Nodulation and nitrogen fixation genes characteristic of terrestrial root-nodulating Rhizobiales were generally lacking from these metagenomes. Non-Rhizobiales clades at the ice surface had genes that would enable additional biogeochemical processes, including mercury reduction and dimethylsulfoniopropionate catabolism. Although the ultimate source of the observed microbial community is not known, considerations of the possible role of eolian deposition or transport with particles entrained during ice formation favor a suspended particle source for this microbial community. PMID:24673287

Bowman, Jeff S; Berthiaume, Chris T; Armbrust, E Virginia; Deming, Jody W

2014-08-01

215

Production of high quality single- or few-layered graphene by solid exfoliation of graphite in the presence of ammonia borane.  

PubMed

A solid exfoliation method is developed for the synthesis of single- or few-layered (?5 layers) graphene by ball milling of graphite with ammonia borane. Nearly quantitative yield in which ca. 25% is single-layered graphene can be obtained. We believe that this highly efficient method will offer a facile approach for the preparation of high quality and large quantity graphene. PMID:23900550

Liu, Lin; Xiong, Zhitao; Hu, Daqiang; Wu, Guotao; Chen, Ping

2013-09-18

216

Energy-effective frost-free coatings based on superhydrophobic aligned nanocones.  

PubMed

We demonstrate the feasibility of superhydrophobic aligned nanocones as energy-effective frost-free coatings. Exemplified by Co(OH)2 nanocone films with condensed microdrop self-removal ability, their edge and whole-surface frosting time can be delayed to about 10 and 150 min, respectively. By using a Teflon gasket to shield edges, the samples can keep frost-free state over 90 min. Further, the lasting frost-free state can be realized by intermittent weak airflow heating, which is energy-effective in contrast to usual high-power heating for defrosting flat surfaces. These findings are significant to develop antifrosting nanotechnologies for energy-effective heat exchangers such as heat pumps and refrigerators. PMID:24912381

Xu, Qian; Li, Juan; Tian, Jian; Zhu, Jie; Gao, Xuefeng

2014-06-25

217

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

NASA Astrophysics Data System (ADS)

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.

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

1990-02-01

218

Effects of frost on wildflowers: an unexpected consequence of climate change--image 18 of 22  

NSDL National Science Digital Library

A queen bumble bee (Bombus bifarius) foraging for nectar on a flower of Erythronium grandiflorum (glacier lily). This flower has frost-sensitive ovaries. Bumble bee queens and hummingbirds are common pollinators of Erythronium grandiflorum flowers.

Inouye, David

2012-01-04

219

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

E-print Network

As new equipment, the channel wheel fresh air ventilator has become increasingly popular in recent years. However, when such equipment is operated under low ambient temperature in the freezing area in winter, the formation of frost on the outdoor...

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

2006-01-01

220

CO_2 Frost Halos on the South Polar Residual Cap of Mars  

NASA Astrophysics Data System (ADS)

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.

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

2012-03-01

221

Effects of evaporator frosting and defrosting on the performance of air-to-water heat pumps  

Microsoft Academic Search

The performance of an 8 kW air-to-water heat pump operating under frosting conditions was investigated over a wide range of ambient temperatures and humidities. The results showed that the rate of frost formation and degradation in the heat pump performance is dependent upon both temperature and humidity, the effects of which should be taken into consideration in the design of

S. A. Tassou; C. J. Marquand

1987-01-01

222

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

E-print Network

THE TRAESFPIR OF HEAT . 'ND NASH 10 A VERTICAL PLATE UNDER FROSTING CONDITIONS A Thesis Louis Joseph Poth, Jr. Submitted to the Graduate School of the Agricultural and Nechanioal College of Texas in partial fulfili ment of the requirements... of the Husselt-Grashof correlation for heat transfer. coefficient of saturation temper ture and concen- tration gradient correlation, for small temper- ature difference. ooefficient of frost specific gravity-thermal oonductivity correlation. coefficient...

Poth, Louis Joseph

2012-06-07

223

A study of heat pump fin staged evaporators under frosting conditions  

E-print Network

A STUDY OF HEAT PUMP FIN STAGED EVAPORATORS UNDER FROSTING CONDITIONS A Dissertation by JIANXIN YANG Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR... OF PHILOSOPHY May 2003 Major Subject: Mechanical Engineering A STUDY OF HEAT PUMP FIN STAGED EVAPORATORS UNDER FROSTING CONDITIONS A Dissertation by JIANXIN YANG Submitted to Texas A&M University in partial fulfillment of the requirements for the degree...

Yang, Jianxin

2004-09-30

224

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

Microsoft Academic Search

A so-called selective inverted sink (SIS) was validated in frost protection of a 20-ha almond orchard. Daily counts of flower\\u000a buds were made for two branches of some selected almond trees in every plot to determine frost damage percentage. Temperatures\\u000a increased due to the SIS system, but there was an average gradient of temperature decrease of about 0.4°C per 100 m

H. Yazdanpanah; C. J. Stigter

2011-01-01

225

Two Cases of Frosted Branch Angiitis with Central Retinal Vein Occlusion  

Microsoft Academic Search

Background: Frosted branch angiitis usually occurs in children, and has a good prognosis. We report two cases of unilateral frosted branch angiitis in adults. Both had poor visual outcomes because of associated central retinal vein occlusion and neovascular glaucoma.Cases: Case 1 was a 36-year-old woman. Almost all retinal veins and some retinal arteries showed vasculitis in her right eye, and

Toshikatsu Kaburaki; Makoto Nakamura; Kazuhiro Nagasawa; Miyuki Nagahara; Satoru Joko; Yujiro Fujino

2001-01-01

226

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

PubMed

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

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

2012-08-01

227

Growth Rate of Frost Heave in Helium and Mass Transport in Solid 4He  

NASA Astrophysics Data System (ADS)

Frost heave phenomena have been studied in 4He on porous vycor glass, in which 4He in the pores remained supercooled fluid below the bulk melting temperature, T m . When we cool a bulk solid at T below T m on the vycor, the bulk solid sucks the supercooled liquid in the pores and grows. We measured the maximum frost heave pressure over bulk melting pressure, P m , as a function of ? T= T m - T. When temperature was suddenly lowered, the frost heave pressure increased in time to a next equilibrium pressure and we measured the time constant and derived the frost heave rate. The frost heave rate was measured as a function of temperature and decreased very rapidly as temperature was lowered. We propose models to explain the mass transport in solid either by vacancy or by amorphous solid between bulk solid 4He and vycor. From measured temperature dependence of the rate in comparison with our model, we conclude the frost heave rate is determined by mass flow in solid 4He due to thermally-activated vacancy diffusion.

Mizusaki, Takao; Nomura, Ryuji; Hiroi, Masahiko

2007-11-01

228

Differential frost heave manifest as patterned ground: Modeling, laboratory and field studies  

NASA Astrophysics Data System (ADS)

Frost heave refers to an uplifting of the ground surface due to freezing of water within the soil. Differential frost heave (DFH) can occur when the freezing is laterally non-uniform. DFH can give rise to patterned ground: surface features made prominent by the segregation of stones, ordered variations in ground cover, or regular topography. Types of patterned ground caused by differential frost heave include earth (or mud) hummocks, frost (or mud) boils, sorted stone circles, and possibly other forms as well. These types of patterned ground could serve as climate-change indicators because DFH is sensitive to environmental changes including regional and global warming and acid rain. The overall objective of this thesis is to explore the conditions necessary for DFH and the implications they have for patterned ground. Multidimensional equations have previously been developed that describe the frost-heave process based on the Miller frost-heave model. A linear stability analysis (LSA) indicates whether one-dimensional frost heave has the propensity to evolve into differential or multidimensional frost heave. A LSA was completed that assesses the environmental conditions and soil properties necessary for the initiation of DFH. The conditions and parameters investigated include ground-surface-temperature conditions, surface load, freezing depth, frozen-soil elastic modulus, and soil type. Because frost heave is inherently a transient process, both a frozen-time and real-time LSA were carried out. Explanations of the discrepancies between previous LSA studies and this work are included. A preliminary, finite-amplitude, two-dimensional DFH model is presented. A finite-amplitude model (FAM) is necessary because multidimensional frost heave evolves at a rate that is the same order of magnitude as one-dimensional frost heave. Results from the FAM indicate that the LSA predictions accurately describe the initiation of DFH. The FAM was not wed for long-time simulations because of numerical difficulties. Field observations of hummocks were made near Inuvik, NWT, Canada in order to substantiate the model predictions. Various characteristics of the hummock including size, spacing, and vegetative ground cover were compared with the LSA predictions and found to agree fairly well. Limited soil properties precluded coroborating the LSA predictions with patterned-ground observations in the literature. A laboratory apparatus capable of simulating the frost-heave process was built and experiments were conducted using a frost-susceptible soil in an attempt to form patterned ground. Two successful experiments resulted in soil patterning after several freeze/thaw cycles. In one, a 2 x 2 pattern of bumps formed, and in the other, a 2 x 2 pattern of dimples formed. We believe these experiments are the first successful attempts at forming patterned ground due to differential frost heave in the laboratory.

Peterson, Rorik A.

229

Effect of surface treatments on the frosting\\/defrosting behavior of a fin-tube heat exchanger  

Microsoft Academic Search

The effects of the heat exchanger surface treatment on the frosting\\/defrosting behavior in a fin-tube heat exchanger are investigated experimentally. It is found that the hydrophilic surface mainly influences the frosting behavior, while the hydrophobic surface has some influence on the defrosting behavior. In view of the frosting, a surface-treated heat exchanger with either hydrophilic or hydrophobic characteristic shows little

Sung Jhee; Kwan-Soo Lee; Woo-Seung Kim

2002-01-01

230

1.8.2001 31.12.2004 SOIL-FROST AND SNOW METAMORPHISM SIMULATIONS FOR THE BALTEX-  

E-print Network

01 LD 0036 1.8.2001 ­ 31.12.2004 SOIL-FROST AND SNOW METAMORPHISM SIMULATIONS FOR THE BALTEX://www.gi.alaska.edu/~molders/deklim.htm; http://www.uni-koeln.de/math-nat-fak/geomet/eurad.html Key words: soil-frost, snow metamorphism, data assimilation, 4DVAR, water and energy fluxes, BALTEX 1. Summary Modules to consider soil-frost and snow

Moelders, Nicole

231

RFLP mapping of the vernalization ( Vrn1 ) and frost resistance ( Fr1 ) genes on chromosome 5A of wheat  

Microsoft Academic Search

A population of single chromosome recombinant lines was developed from the cross between a frost-sensitive, vernalization-insensitive substitution line, ‘Chinese Spring’ (Triticum spelta 5A) and a frost-tolerant, vernalization-sensitive line, ‘Chinese Spring’ (‘Cheyenne’ 5A), and used to map the genes Vrn1 and Fr1 controlling vernalization requirement and frost tolerance, respectively, relative to RFLP markers located on this chromosome. The Vrn1 and Fr1

G. Galiba; S. A. Quarrie; J. Sutka; A. Morgounov; J. W. Snape

1995-01-01

232

The flowering locus Hr colocalizes with a major QTL affecting winter frost tolerance in Pisum sativum L  

Microsoft Academic Search

An understanding of the genetic determinism of frost tolerance is a prerequisite for the development of frost tolerant cultivars\\u000a for cold northern areas. In legumes, it is not known to which extent vernalization requirement or photoperiod responsiveness\\u000a are necessary for the development of frost tolerance. In pea (Pisum sativum L.) however, the flowering locus Hr is suspected to influence winter

I. Lejeune-Hénaut; E. Hanocq; L. Béthencourt; V. Fontaine; B. Delbreil; J. Morin; A. Petit; R. Devaux; M. Boilleau; J.-J. Stempniak; M. Thomas; A.-L. Lainé; F. Foucher; A. Baranger; J. Burstin; C. Rameau; C. Giauffret

2008-01-01

233

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

E-print Network

the fluid does not wet part of the vertical wall of the step. The presence of dry zones in the vertical part dimensional dam-break problem on slope precisely conform to laboratory experiments. Interaction of the Tsunami

234

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

PubMed

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

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

2014-03-01

235

Frost-free season lengthening and its potential cause in the Tibetan Plateau from 1960 to 2010  

NASA Astrophysics Data System (ADS)

Frost-free season was an important index for extreme temperature, which was widely discussed in agriculture and applied meteorology research. The frost-free season changed, which was associated with global warming in the past few decades. In this study, the changes in three indices (the last frost day in spring, the first frost day in autumn, and the frost-free season length) of the frost-free season were investigated at 73 meteorological stations in the Tibetan Plateau from 1960 to 2010. Results showed that the last frost day in spring occurred earlier, significantly in 39 % of the 73 stations. For the regional average, the last frost day in spring occurred earlier, significantly at the rate of 1.9 days/decade during the last 50 years. The first frost day in autumn occurred later, significantly in 31 % of the stations, and the regional average rate was 1.5 days/decade from 1960 to 2010. The changing rate of the first frost day in autumn below 3,000 m was 1.8 times larger than the changing rate above 3,000 m. In addition, the first frost day in autumn above 3,000 m fluctuated dramatically before the early 1990s and then it was later sharply after the early 1990s. The frost-free season length increased significantly at almost all stations in the Tibetan Plateau from 1960 to 2010. For the regional average, the frost-free season lengthened at the rate of 3.1 days/decade. The changing rate of the frost-free season length below 3,000 m was more significant than the changing rate above 3,000 m. Eight indices of large-scale atmospheric circulation were employed to investigate the potential cause of the frost-free season length change in the Tibetan Plateau during the past 50 years. There was a significant relationship between the frost-free season length and the Northern Hemisphere Polar Vortex indices. The weakening cold atmospheric circulation might be an essential factor to the Tibetan Plateau warming since 1960.

Zhang, Dan; Xu, Wenhui; Li, Jiayun; Cai, Zhe; An, Di

2014-02-01

236

Frost-free season lengthening and its potential cause in the Tibetan Plateau from 1960 to 2010  

NASA Astrophysics Data System (ADS)

Frost-free season was an important index for extreme temperature, which was widely discussed in agriculture and applied meteorology research. The frost-free season changed, which was associated with global warming in the past few decades. In this study, the changes in three indices (the last frost day in spring, the first frost day in autumn, and the frost-free season length) of the frost-free season were investigated at 73 meteorological stations in the Tibetan Plateau from 1960 to 2010. Results showed that the last frost day in spring occurred earlier, significantly in 39 % of the 73 stations. For the regional average, the last frost day in spring occurred earlier, significantly at the rate of 1.9 days/decade during the last 50 years. The first frost day in autumn occurred later, significantly in 31 % of the stations, and the regional average rate was 1.5 days/decade from 1960 to 2010. The changing rate of the first frost day in autumn below 3,000 m was 1.8 times larger than the changing rate above 3,000 m. In addition, the first frost day in autumn above 3,000 m fluctuated dramatically before the early 1990s and then it was later sharply after the early 1990s. The frost-free season length increased significantly at almost all stations in the Tibetan Plateau from 1960 to 2010. For the regional average, the frost-free season lengthened at the rate of 3.1 days/decade. The changing rate of the frost-free season length below 3,000 m was more significant than the changing rate above 3,000 m. Eight indices of large-scale atmospheric circulation were employed to investigate the potential cause of the frost-free season length change in the Tibetan Plateau during the past 50 years. There was a significant relationship between the frost-free season length and the Northern Hemisphere Polar Vortex indices. The weakening cold atmospheric circulation might be an essential factor to the Tibetan Plateau warming since 1960.

Zhang, Dan; Xu, Wenhui; Li, Jiayun; Cai, Zhe; An, Di

2013-04-01

237

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

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

238

Structural Analysis of the Redesigned Ice/Frost Ramp Bracket  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

239

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 ...

240

Effects of climate change on phenology, frost damage, and floral abundance of montane wildflowers.  

PubMed

The timing of life history traits is central to lifetime fitness and nowhere is this more evident or well studied as in the phenology of flowering in governing plant reproductive success. Recent changes in the timing of environmental events attributable to climate change, such as the date of snowmelt at high altitudes, which initiates the growing season, have had important repercussions for some common perennial herbaceous wildflower species. The phenology of flowering at the Rocky Mountain Biological Laboratory (Colorado, USA) is strongly influenced by date of snowmelt, which makes this site ideal for examining phenological responses to climate change. Flower buds of Delphinium barbeyi, Erigeron speciosus, and Helianthella quinquenervis are sensitive to frost, and the earlier beginning of the growing season in recent years has exposed them to more frequent mid-June frost kills. From 1992 to 1998, on average 36.1% of Helianthella buds were frosted, but for 1999-2006 the mean is 73.9%; in only one year since 1998 have plants escaped all frost damage. For all three of these perennial species, there is a significant relationship between the date of snowmelt and the abundance of flowering that summer. Greater snowpack results in later snowmelt, later beginning of the growing season, and less frost mortality of buds. Microhabitat differences in snow accumulation, snowmelt patterns, and cold air drainage during frost events can be significant; an elevation difference of only 12 m between two plots resulted in a temperature difference of almost 2 degrees C in 2006 and a difference of 37% in frost damage to buds. The loss of flowers and therefore seeds can reduce recruitment in these plant populations, and affect pollinators, herbivores, and seed predators that previously relied on them. Other plant species in this environment are similarly susceptible to frost damage so the negative effects for recruitment and for consumers dependent on flowers and seeds could be widespread. These findings point out the paradox of increased frost damage in the face of global warming, provide important insights into the adaptive significance of phenology, and have general implications for flowering plants throughout the region and anywhere climate change is having similar impacts. PMID:18409425

Inouye, David W

2008-02-01

241

Frost Growth CFD Model of an Integrated Active Desiccant Rooftop Unit  

SciTech Connect

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.

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

2008-01-01

242

Influence of frost formation and defrosting on the performance of air coolers: standards and dimensionless coefficients for the system designer  

Microsoft Academic Search

Over a period of more than 10 years, fundamental research on frost formation and defrosting behaviour of lamel type air coolers has been pursued at the Delft University of Technology. Many experiments have been performed to support the Dutch Standard for testing air coolers, NEN 1876. This standard gives an Objective description of the performance of air coolers under frosting

C. H. M. Machielsen; H. G. Kerschbaumer

1989-01-01

243

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

Microsoft Academic Search

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

H. Vömel; D. E. David; K. Smith

2007-01-01

244

Effects of air flow maldistribution on refrigeration system dynamics of air source heat pump chiller under frosting conditions  

Microsoft Academic Search

The effects of air flow maldistribution on the performance of an air source heat pump chiller under frosting conditions were investigated experimentally. The results indicated that air flow maldistribution was the dominant factor leading to hunting of the thermostatic expansion valve for medium and\\/or large size finned tube evaporators. With air flow maldistribution degree (AMD) increasing, frost occurred earlier, and

Jianying Gong; Tieyu Gao; Xiuling Yuan; Dong Huang

2008-01-01

245

Winter moisture content and frost-crack occurrence in oak trees (Quercus petraea Liebl. and Q. robur L.)  

E-print Network

Winter moisture content and frost-crack occurrence in oak trees (Quercus petraea Liebl. and Q in oak trees, using non- destructive sampling by increment cores, and relate it to frost-crack occurrence. Materials and Methods Increment cores were taken from 90 oak trees from 3 different forests in central

Paris-Sud XI, Université de

246

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

NASA Technical Reports Server (NTRS)

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

Spencer, John R.; Moore, Jeffrey M.

1992-01-01

247

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

NASA Technical Reports Server (NTRS)

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.

Ingersoll, Andrew P.

1989-01-01

248

Balloon borne Antarctic frost point measurements and their impact on polar stratospheric cloud theories  

NASA Technical Reports Server (NTRS)

Balloon-borne frost point measurements were performed over Antarctica during September-October 1987 as part of the NOZE II effort at McMurdo. The results show water mixing ratios on the order of 2 ppmv in the 20 km region, suggesting that models of the springtime Antarctic stratosphere should be based on approximately 2 ppmv water vapor. Evidence indicating that some PSCs form at temperatures higher than the frost point in the 15 to 20 km region is discussed. This supports the binary HNO3-H2O theory of PSC composition.

Rosen, James M.; Hofmann, D. J.; Carpenter, J. R.; Harder, J. W.; Oltsmans, S. J.

1988-01-01

249

High performance liquid chromatographic and thin layer densitometric methods for the determination of risperidone in the presence of its degradation products in bulk powder and in tablets.  

PubMed

Two reproducible stability indicating methods were developed for the determination of risperidone (RISP) in presence of its degradation products in pure form and in tablets. The first method was based on reversed phase high performance liquid chromatography (HPLC), on Lichrosorb RP C 18 column (250 mm i.d., 4 mm, 10 microm), using methanol:0.05 M potassium dihydrogen phosphate pH 7 (65:35 (v/v)) as the mobile phase at a flow rate of 1 ml min(-1) at ambient temperature. Quantification was achieved with UV detection at 280 nm over a concentration range of 25-500 microg ml(-1) with mean percentage recovery of 99.87 +/- 1.049. The method retained its accuracy in the presence of up to 90% of RISP degradation products. The second method was based on TLC separation of RISP from its degradation products followed by densitometric measurement of the intact drug spot at 280 nm. The separation was carried out on aluminum sheet of silica gel 60F254 using acetonitrile:methanol:propanol:triethanolamine (8.5:1.2:0.6:0.2 (v/v/v/v)), as the mobile phase, over a concentration range of 2-10 microg per spot and mean percentage recovery of 100.1 +/- 1.18. The two methods were simple, precise, sensitive and could be successfully applied for the determination of pure, laboratory prepared mixtures and tablets. The results obtained were compared with the manufacturer's method. PMID:15620522

El-Sherif, Zeinab A; El-Zeany, Badr; El-Houssini, Ola M

2005-01-01

250

A three-dimensional model study on the production of BrO and Arctic boundary layer ozone depletion  

Microsoft Academic Search

A three-dimensional model (GEM-AQ\\/Arctic) was developed to study the chemistry and processes involved in the ozone depletion events (ODEs) in the Arctic boundary layer (ABL), which included a comprehensive mechanism of multiphase halogen chemistry in the ABL and our current understanding of the ODEs. Assuming that frost flower-derived aerosols were the primary halogen source, the areas potentially covered by frost

T. L. Zhao; S. L. Gong; J. W. Bottenheim; J. C. McConnell; R. Sander; L. Kaleschke; A. Richter; A. Kerkweg; K. Toyota; L. A. Barrie

2008-01-01

251

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

E-print Network

THE EFFECT OF FROST/FREEZE EVENTS ON MOPANE TREES Prepared by Melissa Whitecross, Honours student, at the University of the Witwatersrand There are many studies that suggest frost as a possible driver of savanna that Colophospermum mopane (Mopane Tree) is affected by frost/freeze events and this could be related to the unique

252

A Conceptual Model of H2O/CO2 Frost Sublimation and Condensation Caused Albedo Change in Crater Interiors, Martian Seasonal Polar Cap Regions H. Xie1  

E-print Network

A Conceptual Model of H2O/CO2 Frost Sublimation and Condensation Caused Albedo Change in Crater at the seasonal polar cap regions, especially those associated with high-albedo deposits of frost and/or ice of ice and frost and detected first by Viking Orbiter/MGS [10]. [11] used Mars Orbiter Laser Altimetry

Texas at San Antonio, University of

253

Application of satellite frost forecast technology to other parts of the United States  

NASA Technical Reports Server (NTRS)

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.

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

1981-01-01

254

Frosting and defrosting behaviour of outdoor coils of air-source heat pumps. Final report  

SciTech Connect

Improvement of the COP of an air-source heat-pump may be obtained by means of improved design and operation of the coils under frosting conditions. The aim of the investigation was to get an insight into the factors influencing coil behavior and to make recommendations regarding design and operation of the coils.

Bouma, J.W.J.

1981-01-01

255

Cryogen spray cooling in laser dermatology: Effects of ambient humidity and frost formation  

Microsoft Academic Search

Background and Objective: Dynamics of cryogen spray deposition, water condensation and frost formation is studied in relationship to cooling rate and efficiency of cryogen spray cooling (CSC) in combination with laser dermatologic surgery. Study Design\\/Materials and Methods: A high-speed video camera was used to image the surface of human skin during and after CSC using a commercial device. The influence

Boris Majaron; Sol Kimel; Wim Verkruysse; Guillermo Aguilar; Karl Pope; Lars O. Svaasand; Enrique J. Lavernia; J. Stuart Nelson

2001-01-01

256

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

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

257

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

NASA Astrophysics Data System (ADS)

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

Hugenholtz, C. H.

2008-03-01

258

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

Microsoft Academic Search

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

E. L. Sharpe; L. R. Jackson

1975-01-01

259

FrostWall: a Dual-Sided Situated Display for Informal Collaboration in the Corridor  

E-print Network

to support collegial communication and collaboration within a co-located work environment by facilitating and encouraging informal information exchange in the corridors of a workplace using large situated displays. Frost workspaces in combination with projectors to create a display area that is effectively dual- sided: readable

Thomas, Bruce

260

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

NASA Astrophysics Data System (ADS)

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

Yazdanpanah, H.; Stigter, C. J.

2011-08-01

261

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

ERIC Educational Resources Information Center

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…

Lee, Dong-gwi; Park, Hyun-joo

2011-01-01

262

Effects of frost on wildflowers: an unexpected consequence of climate change--image 14 of 22  

NSDL National Science Digital Library

A female broad-tailed hummingbird (Selasphorus platycercus) in Colorado visiting tall larkspur (Delphinium barbeyi). The hummingbirds migrate north from Mexico each spring. Larkspurs serve as an important food source for them and for bumble bees. But larkspurs are also susceptible to frost, impacting the species that feed on them.

Inouye, David

2012-01-04

263

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

NASA Technical Reports Server (NTRS)

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.

Lindner, Bernhard Lee

1992-01-01

264

Effects of frost on wildflowers: an unexpected consequence of climate change--Image 05 of 22  

NSDL National Science Digital Library

A flowering plant of Helianthella quinquenervis (aspen sunflower, Asteraceae) at the Rocky Mountain Biological Laboratory. This species has flower buds that are frost-sensitive. The plants have a mutualism with ants, which are attracted by extrafloral nectar secreted by the bracts that cover flower buds.

Inouye, David

2012-01-04

265

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

NASA Technical Reports Server (NTRS)

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

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

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

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

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

2008-01-01

266

Laboratory examination and seasonal analysis of frosting and defrosting losses for an air-to-air heat pump  

SciTech Connect

An air-to-air split-system residential heat pump of nominal 2 3/4-ton (9.7-kW) capacity was instrumented and tested in the laboratory. The coefficient of performance, system capacity, and component efficiencies were measured during steady-state and frosting-defrosting conditions in the heating mode (1) to gain better understanding of the physical processes that affect the performance of the test heat pump and (2) to quantify the frosting and defrosting losses. Cumulative frosting and defrosting loss coefficients were calculated from which empirical frosting and defrosting algorithms were developed for modeling of frosting and defrosting losses. Seasonal analyses indicate that the test heat pump with tube-and-wavy-fin outdoor coil had 1% to 5% energy loss due to frosting and demand defrosting accounted for only an additional 1% to 3% yearly energy loss. Demand defrost control can reduce yearly frosting-defrosting losses by 5% to 10% over 90- and 45-minute time-temperature controls.

Miller, W.A.

1986-01-01

267

Climate warming and the risk of frost damage to boreal forest trees: identification of critical ecophysiological traits.  

PubMed

According to a hypothesis presented in the mid-1980s, climate warming will, paradoxically, increase the risk of frost damage to trees in the boreal and temperate zones. Dehardening and even growth onset may occur in trees during mild spells in winter and early spring, resulting in damage during subsequent periods of frost. In the present study, ecophysiological traits critical to the occurrence of frost damage in trees in the boreal zone were identified. Diagnostic computer simulations were performed to examine why one simulation model of frost hardiness in an earlier study predicted heavy frost damage as a consequence of climate warming, whereas another closely related model did not. The modeling comparison revealed that the response of ontogenetic development to air temperature during quiescence is a critical factor determining the risk of frost damage. As the response can be readily determined in growth-chamber experiments, the findings of the present study can be used to guide experimental work on the environmental regulation of the annual cycle of frost hardiness in trees. PMID:16585034

Hänninen, Heikki

2006-07-01

268

FROST - FReezing Of coated and uncoated duST particles  

NASA Astrophysics Data System (ADS)

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

Wex, H.

2009-04-01

269

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

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

270

Performance comparison of air source heat pump with R407C and R22 under frosting and defrosting  

Microsoft Academic Search

The dynamic performance characteristics of the air source heat pump (ASHP) with refrigerants R22 and R407C during frosting and defrosting are studied. The results show that both refrigerant systems have similar performance characteristics, except that the performance of the R407C system deteriorated faster than that of the R22 system under frosting, and the performance of the R407C system attains its

Zhiqiang Liu; Xiaolin Li; Hanqing Wang; Wangming Peng

2008-01-01

271

Influence of supermarket environmental parameters on the frosting and defrosting of vertical multideck display cabinets  

SciTech Connect

This paper reports on results of investigations to identify and quantify the effect of in-store environmental conditions on frost accumulation on the evaporator coils of open multideck refrigerated display cabinets. Field and environmental chamber-based tests have shown that both ambient relative humidity and temperature of a store have a significant effect on the rate of frost formation on the evaporator coils, with the effect of relative humidity being much more pronounced than the effect of temperature. In supermarkets where a fixed-time defrost control strategy is employed, it is possible that cabinets are defrosted too infrequently at high relative humidities, resulting in high product temperatures, and too frequently at low relative humidities, resulting in excessive energy consumption. Considerable opportunity exists for the application of more sophisticated defrost control strategies, both to save energy and improve temperature control.

Tassou, S.A.; Datta, D.

1999-07-01

272

Dynamic characteristics of an air-to-water heat pump under frosting\\/defrosting conditions  

Microsoft Academic Search

The dynamic characteristics of a medium air-to-water heat pump with multi-circuit evaporator controlled by the thermostatic expansion valve (TEV) under the frosting\\/defrosting conditions were investigated experimentally. The airflow maldistribution often occurs if the fin-and-tube heat exchangers in a medium heat pump are arranged in V-type or W-type position with the fan at the top. The experimental results show that the

D. Huang; Z. L. He; X. L. Yuan

2007-01-01

273

Infiltration in Icelandic Andisols: the Role of Vegetation and Soil Frost  

Microsoft Academic Search

Soil frost formation, snow distribution, and winter\\/spring\\/summer terminal infiltration rates (TIRs) were quantified in Icelandic Andisols with contrasting vegetation cover types (grassland, spruce and birch woodland, lupine, and sparsely vegetated lava site). TIRs (mm h21; determined with double-ring infiltrometers) were generally higher in unfrozen than in frozen soils (102-369 vs. 9-306, respectively in sandy soils; 28-94 vs. 3-72 in finer-textured

B. Orradottir; S. R. Archer; O. Arnalds; L. P. Wilding; T. L. Thurow

2008-01-01

274

Effects of frost on wildflowers: an unexpected consequence of climate change--image 02 of 22  

NSDL National Science Digital Library

An example of a late spring frost and snow event at the Rocky Mountain Biological Laboratory, at 9,500 feet in the Colorado Rocky Mountains. This photograph was taken on 13 June 2001, when the temperature went down to 21.5 F, (-5.8 C). This cold period killed flower buds of several wildflower species that had already produced leaves and buds.

Inouye, David

2012-01-04

275

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

NASA Astrophysics Data System (ADS)

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.

Hugenholtz, Chris H.

2008-09-01

276

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

Microsoft Academic Search

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

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

2011-01-01

277

Risk of spring frost to apple production under future climate scenarios: the role of phenological acclimation  

NASA Astrophysics Data System (ADS)

In the context of global warming, the general trend towards earlier flowering dates of many temperate tree species is likely to result in an increased risk of damage from exposure to frost. To test this hypothesis, a phenological model of apple flowering was applied to a temperature series from two locations in an important area for apple production in Europe (Trentino, Italy). Two simulated 50-year climatic projections (A2 and B2 of the Intergovernmental Panel on Climate Change - Special Report on Emission Scenarios) from the HadCM3 general circulation model were statistically downscaled to the two sites. Hourly temperature records over a 40-year period were used as the reference for past climate. In the phenological model, the heat requirement (degree hours) for flowering was parameterized using two approaches; static (constant over time) and dynamic (climate dependent). Parameterisation took into account the trees’ adaptation to changing temperatures based on either past instrumental records or the downscaled outputs from the climatic simulations. Flowering dates for the past 40 years and simulated flowering dates for the next 50 years were used in the model. A significant trend towards earlier flowering was clearly detected in the past. This negative trend was also apparent in the simulated data. However, the significance was less apparent when the “dynamic” setting for the degree hours requirement was used in the model. The number of frost episodes and flowering dates, on an annual basis, were graphed to assess the risk of spring frost. Risk analysis confirmed a lower risk of exposure to frost at present than in the past, and probably either constant or a slightly lower risk in future, especially given that physiological processes are expected to acclimate to higher temperatures.

Eccel, Emanuele; Rea, Roberto; Caffarra, Amelia; Crisci, Alfonso

2009-05-01

278

The role of permafrost and seasonal frost in the hydrology of northern wetlands in North America  

USGS Publications Warehouse

Wetlands are a common landscape feature in the Arctic, Subarctic, and north Temperate zones of North America. In all three-zones, the occurrnce of seasonal frost results in similar surface-water processes in the early spring. For example, surface ice and snow generally melt before the soil frost thaws, causing melt water to flow into depressions, over the land surface and at times, across low topographic divides. However, evapotranspiration and ground-water movement differ among the three climatic zones because they are more affected by permafrost than seasonal frost. The water source for plants in the Arctic is restricted to the small volume of subsurface water lying above the permafrost. Although this is also true in the Subarctic where permafrost exists, where it does not, plants may receive and possibly reflect, more regional ground-water sources. Where permafrost exists, the interaction of wetlands with subsurface water is largely restricted to shallow local flow systems. But where permafrost is absent in parts of the Subarctic and all of the Temperature zone, wetlands may have a complex interaction with ground-water-flow systems of all magnitudes. ?? 1993.

Woo, M.-K.; Winter, T.C.

1993-01-01

279

Balloon borne Antarctic frost point measurements and their impact on polar stratospheric cloud theories  

NASA Technical Reports Server (NTRS)

The first balloon-borne frost point measurements over Antarctica were made during September and October, 1987 as part of the NOZE 2 effort at McMurdo. The results indicate water vapor mixing ratios on the order of 2 ppmv in the 15 to 20 km region which is somewhat smaller than the typical values currently being used significantly smaller than the typical values currently being used in polar stratospheric cloud (PSC) theories. The observed water vapor mixing ratio would correspond to saturated conditions for what is thought to be the lowest stratospheric temperatures encountered over the Antarctic. Through the use of available lidar observations there appears to be significant evidence that some PSCs form at temperatures higher than the local frost point (with respect to water) in the 10 to 20 km region thus supporting the nitric acid theory of PSC composition. Clouds near 15 km and below appear to form in regions saturated with respect to water and thus are probably mostly ice water clouds although they could contain relatively small amounts of other constituents. Photographic evidence suggests that the clouds forming above the frost point probably have an appearance quite different from the lower altitude iridescent, colored nacreous clouds.

Rosen, James M.; Hofmann, D. J.; Carpenter, J. R.; Harder, J. W.; Oltmans, S. J.

1988-01-01

280

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

PubMed Central

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

2013-01-01

281

Biochemical Changes in Tuber-bearing Solanum Species in Relation to Frost Hardiness during Cold Acclimation 1  

PubMed Central

Biochemical changes in potato leaves during cold acclimation have been examined and compared between a frost-tolerant S. acaule and a frost-susceptible S. tuberosum species. Changes were also examined in S. tuberosum, S. acaule, and S. commersonii species when they were hardened at different temperatures to varying hardiness levels. During three weeks of stepwise cold acclimation, S. acaule increased frost hardiness from ?6.0 C (killing temperature) to ?9.0 C, whereas frost hardiness of S. tuberosum remained unchanged at ?3.0 C. Decreases in DNA content on a dry weight basis in both species suggest that matured leaf cells accumulated more dry matter during acclimation. The advantage of using DNA as a reference for comparing metabolite changes during cold acclimation is discussed. Under the stepwise acclimating conditions, both species showed the same trends for increasing total sugar and starch with an insignificant decrease in leaf water content. High levels of total RNA, rRNA, and total and soluble protein were observed in treated S. acaule plants as compared with controls, but not in S. tuberosum. Levels of total lipid and phospholipid also were high in treated S. acaule plants as compared with controls but decreased in S. tuberosum during acclimation. When S. tuberosum, S. acaule, and S. commersonii potatoes were cold-treated at constant day/night temperatures of 10, 5, and 2 C with 14-hour daylength, each species responds differently in terms of frost hardiness increase upon subjecting plants to a low temperature. For instance, after 20 days at 2 C, a net frost hardiness of 3 and 7 C was observed in S. acaule and S. commersonii, respectively, whereas the frost hardiness in S. tuberosum remained unchanged. Also, various levels of frost hardiness can be achieved in a species by subjecting plants to different low temperature treatments. Under a warm regime of 20/15 C day/night temperatures (14-hour light), both S. acaule and S. commersonii can survive at ?4.5 C or colder, whereas S. tuberosum can survive only at ?2.5 C. Biochemical changes in the leaf tissue of these species were investigated at 5-day intervals during low temperature treatments. Increases in total sugar and starch were found in all three species during hardening, although S. tuberosum failed to harden. Soluble protein contents were increased in both S. acaule and S. commersonii but decreased in S. tuberosum. RNA contents change in a pattern similar to the soluble protein. Net increases of the soluble proteins were positively and significantly correlated with net increases of frost hardiness in S. acaule and S. commersonii. PMID:16661447

Chen, Hwei-Hwang; Li, Paul H.

1980-01-01

282

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

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

283

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

PubMed

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

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

2012-08-28

284

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

285

Helium pumping by argon frosting on a 4. 5 K surface  

SciTech Connect

Pumping of helium gas by means of argon frosting on a bare copper surface cooled to {approximately}4.5 K has been investigated in one of the neutral beamlines of the DIII-D tokamak. The beamline is designed to handle high power hydrogen and deuterium beams and corresponding high gas feed rates. By prefrosting the cryo panels with argon in an actual beamline, multi-second helium gas pulses have been handled at a background gas pressure low enough for formation and transport of helium beams. Appreciable pumping of helium gas was observed even at an argon-to-helium ratio as low as 20. 16 refs., 5 figs.

Kim, J.; Schaubel, K.M.; Colleraine, A.P.

1989-12-01

286

Helium pumping by argon frosting on a 4. 5 K surface  

SciTech Connect

Pumping of helium gas by means of argon frosting on a bare copper surface cooled to {similar to}4.5 K has been investigated in one of the neutral beamlines of the DIII-D tokamak. The beamline is designed to handle high power hydrogen and deuterium beams and corresponding high gas feed rates. By prefrosting the cryo panels with argon in an actual beamline, multisecond helium gas pulses have been handled at a background gas pressure low enough for formation and transport of helium beams. Appreciable pumping of helium gas was observed even at an argon-to-helium ratio as low as 20.

Kim, J.; Schaubel, K.M.; Colleraine, A.P. (General Atomics, San Diego, CA (USA))

1990-05-01

287

CLAS+FROST: new generation of photoproduction experiments at Jefferson Lab  

E-print Network

A large part of the experimental program in Hall B of the Jefferson Lab is dedicated to baryon spectroscopy. Photoproduction experiments are essential part of this program. CEBAF Large Acceptance Spectrometer (CLAS) and availability of circularly and linearly polarized tagged photon beams provide unique conditions for this type of experiments. Recent addition of the Frozen Spin Target (FROST) gives a remarkable opportunity to measure double and triple polarization observables for different pseudo-scalar meson photoproduction processes. For the first time, a complete or nearly complete experiment becomes possible and will allow model independent extraction of the reaction amplitude. An overview of the experiment and its current status is presented.

Eugene Pasyuk; for the CLAS Collaboration

2009-06-23

288

Solar Reflectance Measurements of Calibration Targets and Martian South Polar Frosts  

NASA Astrophysics Data System (ADS)

The Viking Infrared Thermal Mapper (IRTM) solar reflectance measurements revealed anomalous photometric properties of the martian polar frosts. For example, while most planetary surfaces exhibit marked brightening towards high illumination angles, the IRTM observations of the martian south polar cap (SPC) show the exactly opposite trend. Recently, several hypotheses have been proposed to explain this unusual behavior, such as the effects of dust contamination or the effects of frost texture and opacity. I have analyzed IRTM observations of the SPC in order to reveal basic physical properties of the frost and also to shed light upon the viability of these hypotheses. This thesis includes laboratory measurements along with the IRTM data analysis. The laboratory work consists of the design, fabrication and photometric characterization of calibration targets used by two space-borne instruments, the Pressure Modulator Infrared Radiometer (PMIRR) on the Mars Climate Orbiter mission and the SVET radiometer on the Russian Mars '96 mission. The data analysis portion consists of a thorough study of the Viking IRTM solar channel observations of the south polar cap. The full seasonal history of cap reflectance is shown here, along with analysis of reflectance as a function of photometric angles, local time, season, and other parameters. The hypotheses mentioned above, together with others, have all been reexamined in light of the new findings of this work. This study finds that no single hypothesis put forth to date can account for all the variability and phenomena found in the data. Alone, neither dust deposition nor removal, water contamination, geography, nor atmospheric circulation, does well at predicting the IRTM south polar observations. Each may play a role, and it appears clear now that a combination of several processes controls the cap reflectance. At this time, there is still no unambiguous answer to which processes dominate. Furthermore, the idea of unusual frost formations with strangely behaving reflectance functions has been examined and found to not play a major role in the reflectance of the SPC. Also, the idea of the formation of a semi-transparent ice sheet, its development with season, and the implications it would have on the reflectance of the SPC has also been studied.

Ono, Adrienne Momilani

289

Scattering properties of natural snow and frost - Comparison with icy satellite photometry  

NASA Technical Reports Server (NTRS)

The Hapke (1986) equation is presently fit to ascertain the single-scattering albedo of the icy satellites of Uranus and Neptune and the one-term Henyey-Greenstein particle-phase function g for each of the Middleton and Mungall (1952) goniophotometric data samples. There emerge both very high single-scattering albedos and strongly forward-scattering particle phase functions; while these are in keeping with Mie theory-based theoretical considerations, they contrast with the observed backscattering behavior of icy satellites. It is suggested the icy satellite frost grains are aggregated into particles of complex texture, which produce the unusual backscattering behavior.

Verbiscer, Anne J.; Veverka, Joseph

1990-01-01

290

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

NASA Technical Reports Server (NTRS)

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.

Glaser, F. M.

1976-01-01

291

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

SciTech Connect

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.

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

292

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

293

Type II fish antifreeze protein accumulation in transgenic tobacco does not confer frost resistance.  

PubMed

Type II fish antifreeze protein (AFP) is active in both freezing point depression and the inhibition of ice recrystallization. This extensively disulfide-bonded 14 kDa protein was targeted for accumulation in its pro- and mature forms in the cytosol and apoplast of transgenic tobacco plants. Type II AFP gene constructs under control of a duplicate cauliflower mosaic virus 35S promoter, both with and without a native plant transit peptide sequence, were introduced into tobacco by Agrobacterium tumefaciens-mediated transformation. AFP did not accumulate in the cytosol of transgenic plants, but active AFP was present as 2% the total protein present in the apoplast. Plant-produced AFP was the same size as mature Type II AFP isolated from fish, and was comparable to wild-type AFP in thermal hysteresis activity and its effect on ice crystal morphology. Field trials conducted in late summer on R1 generation transgenic plants showed similar AFP accumulation in plants under field conditions at levels suitable for large-scale production: but no difference in frost resistance was observed between transgenic and wild-type plants during the onset of early fall frosts. PMID:10481310

Kenward, K D; Brandle, J; McPherson, J; Davies, P L

1999-04-01

294

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

SciTech Connect

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

Holmstrup, M. [National Environmental Research Inst., Silkeborg (Denmark). Dept. of Terrestrial Ecology; Petersen, B.F. [National Environmental Research Inst., Silkeborg (Denmark). Dept. of Terrestrial Ecology]|[Univ. of Aarhus (Denmark); Larsen, M.M. [National Environmental Research Inst., Roskilde (Denmark). Dept. of Marine Ecology and Microbiology

1998-01-01

295

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

NASA Technical Reports Server (NTRS)

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.

Kandula, M.

2012-01-01

296

Stabilization of Leidenfrost vapour layer by textured superhydrophobic surfaces.  

PubMed

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

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

2012-09-13

297

Air-source heat pump: field measurement of cycling, frosting, and defrosting losses, 1981-1983  

SciTech Connect

An air-to-air heat pump was installed in a single-family residence near Knoxville, Tennessee, and was operated in a multiyear test to permit characterization of dynamic losses in capacity and efficiency due to cycling, frosting, and defrosting. The residence and heat pump were extensively instrumented, and a state-of-the-art data acquisition system logged data for each of the several system operating modes (start-up transient heating and cooling, normal-mode heating and cooling, and defrost with recovery) throughout the testing period. For the test heating seasons, defrosting was responsible for 10.1%, losses due to frosting for 3.6%, on-off cycling losses for 8.4%, and off-cycle parasitic for 4.3% of the total energy consumption (exclusive of supplemental electric resistance heater energy use as required by second-stage thermostat demand). An overall heating seasonal performance factor of 1.96 was realized, and the value of the cyclic degradation factor, C/sub d/, in heating was found to be 0.24. Both output loss per cycle and input energy increase per cycle were directly related to off-time per cycle, increasing strongly with off-times up to approximately 20 min and at a much lower rate thereafter. Defrost time per defrost cycle and the associated energy use penalty varied directly with frosting potential; the effect of ambient temperature on defrost time is not clear, and additional investigation is warranted. Use of a desuperheater for domestic water heating reduced the heat pump's space heating capacity but had no measurable effect on dynamic loss levels. The steady-state cooling capacity and coefficient of performance (COP) of the heat pump were degraded from the manufacturer's ratings and those which were measured in initial steady-state tests, precluding definitive evaluation of dynamic losses during cooling operation. The cyclic degradation factor, C/sub d/, in cooling was estimated to be between 0.20 and 0.25.

Baxter, V.D.; Moyers, J.C.

1984-11-01

298

Enceladus' CO2 Frost comes from Near-Surface Gas Pockets  

NASA Astrophysics Data System (ADS)

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

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

299

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

PubMed

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

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

2006-12-01

300

Comparison of heat pump performance using fin-and-tube and microchannel heat exchangers under frost conditions  

Microsoft Academic Search

Vapor compression heat pumps are drawing more attention in energy saving applications. Microchannel heat exchangers can provide higher performance via less core volume and reduce system refrigerant charge, but little is known about their performance in heat pump systems under frosting conditions. In this study, the system performance of a commercial heat pump using microchannel heat exchangers as evaporator is

Liang-Liang Shao; Liang Yang; Chun-Lu Zhang

2010-01-01

301

Application of ERS-1 wind scatterometer data to soil frost and soil moisture monitoring in boreal forest zone  

Microsoft Academic Search

The feasibility of the ERS-1 Wind Scatterometer (WS) for monitoring the boreal forest zone is investigated, concentrating on soil frost and soil moisture monitoring. The ERS-1 WS measures the target area with coarse spatial resolution (about 50 km) using three separate antenna beams and a wide angular range. The investigations are concerned with the boreal forest zone using data (1)

Jouni T. Pulliainen; T. Manninen; M. T. Hallikainen

1998-01-01

302

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

E-print Network

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

Kansas, University of

303

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

ERIC Educational Resources Information Center

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

Chan, David W.

2009-01-01

304

Metabolism of  -aminobutyric acid during cold acclimation and freezing and its relationship to frost tolerance in barley and wheat  

Microsoft Academic Search

Amino acid homeostasis was investigated in frost- resistant barley seedlings under either cold- or freezing- stress conditions. Total free amino acid content varied only slightly, but a substantial conversion of glutamate to c-aminobutyric acid (GABA) was found that was proportional to the severity of the stress. Cold acclimation caused a significant increase in amino acid pools, and induced the expression

Elisabetta Mazzucotelli; Alfredo Tartari; Luigi Cattivelli; Giuseppe Forlani

2006-01-01

305

Seasonal polar carbon dioxide frost on Mars: Spatiotemporal quantification of carbon dioxide utilizing 2001 Mars Odyssey gamma ray spectrometer data  

Microsoft Academic Search

The exchange of carbon dioxide between the atmosphere and the polar caps on Mars creates a seasonal cycle of growth and retreat of the polar caps. As the major component of the Martian atmosphere, CO 2 condenses in the polar regions of the planet during the winter seasons and precipitates as CO 2 frost. It then sublimes during the spring

Eleanor Jane Kelly

2006-01-01

306

Bacterial blight (Pseudomonas pisi Sackett) of peas in South Africa, with special reference to frost as a predisposing factor  

Microsoft Academic Search

In the beginning of the nineteen fifties bacterial blight caused much damage to pea crops in South Africa, particularly to those grown for seed production. A study has been made of the causal organism and the conditioning factors of the disease, special attention being paid to frost as a predisposing factor.The symptoms of the disease vary according to weather conditions

B. H. Boelema

1972-01-01

307

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

USGS Publications Warehouse

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

Craig, Brunstein F.

1996-01-01

308

Phase-change numerical heat transfer analysis with applications to frost shielding  

SciTech Connect

This paper reports on a computer package developed to solve heat transfer problems with phase change and predict the temperature distribution and phase-front location variation with time. The fixed-mesh package incorporates latent heat effects using O'Neill's method. The time-domain solution uses a central-difference procedure. Published results on freezing the slab-shaped foodstuffs, solidification in an internal corner, a solidification outside a 270{degrees} wedge, and solidification of cast steel are used to demonstrate the validity of the numerical technique and the capabilities of the program. Underground freezing of pipelines with and without frost shields is studied using our package, and the results are discussed.

Farag, I.H.; Virameteekul, N. (Chemical Engineering Dept., Univ. of New Hampshire, Durham, NH (US)); Phetteplace, G. (U.S. Army Cold Regions Research and Engineering Lab., Hanover, NH (US))

1991-01-01

309

Surface temperatures and retention of H2O frost on Ganymede and Callisto  

NASA Technical Reports Server (NTRS)

Surface temperatures and ice evaporation rates are calculated for Ganymede and Callisto as functions of latitude, time of day, and albedo, according to a model that uses surface thermal properties determined by eclipse radiometry and albedos determined from photometrically decalibrated Voyager images. The difference in temperature between Ganymede and Callisto is not great enough to account for the lack of bright polar caps on Callisto, which seems instead to reflect a real deficiency in the amount of available water frost relative to Ganymede. The temperature difference between Ganymede's grooved and cratered terrains also cannot account for the high concentration of bright ray craters in the former, suggesting that an internal geologic process has enriched the grooved terrain in ice content relative to the cratered terrain.

Squyres, S. W.

1980-01-01

310

Seasonal and interannual variability of active layer development in permafrost wetland systems C. M. Chiu and Laura C. Bowling  

E-print Network

Seasonal and interannual variability of active layer development in permafrost wetland systems C. M soil frost, discontinuous and continuous permafrost. Not only do such wetlands influence the regional temperatures in northern environments therefore may disrupt the thermal balance in permafrost wetland

Cherkauer, Keith

311

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

PubMed Central

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

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

2014-01-01

312

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

NASA Astrophysics Data System (ADS)

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.

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

2013-10-01

313

Pharmacological evaluation for anticancer and immune activities of a novel polysaccharide isolated from Boletus speciosus Frost.  

PubMed

The fungal polysaccharides have been revealed to exhibit a variety of biological activities, including antitumor, immune-stimulation and antioxidation activities. In the present study, the immune and anticancer activities of a novel polysaccharide, BSF-A, isolated from Boletus speciosus Frost was investigated. The inhibitory rate of S180 tumors in mice treated with 40 mg/kg BSF-A reached 62.449%, which was the highest rate from the three doses administered; this may be comparable to mannatide. The antitumor activity of BSF-A is commonly considered to be a consequence of the stimulation of the cell-mediated immune response, as it may significantly promote the macrophage cells in the dose range of 100-400 µg/ml in vitro. The levels of the cytokines, IL-6, IL-1? and TNF-?, and nitric oxide, induced by BSF-A treatment at varying concentrations in the macrophage cells were similar to the levels in the cells treated with lipopolysaccharide. There was weak expression of the TNF-?, IL-6, IL-1? and inducible nitric oxide synthase mRNA in the untreated macrophages, but this increased significantly in a dose-dependent manner in the BSF-A-treated cells. BSF-A also had a time- and dose-dependent effect on the growth inhibition of the Hep-2 cells, with the concentration of 400 µg/ml having the highest inhibitory rate. A quantitative PCR array analysis of the gene expression profiles indicated that BSF-A had anticancer activities that affected cell apoptosis in the Hep-2 cells. The results obtained in the present study indicated that the purified polysaccharide of Boletus speciosus Frost is a potential source of natural anticancer substances. PMID:24566673

Hou, Yiling; Ding, Xiang; Hou, Wanru; Song, Bo; Wang, Ting; Wang, Fang; Li, Jian; Zeng, Yichun; Zhong, Jie; Xu, Ting; Zhu, Hongqing

2014-04-01

314

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

PubMed Central

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

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

2008-01-01

315

Laboratory evaluation of the heating capacity and efficiency of a high-efficiency, air-to-air heat pump with emphasis on frosting/defrosting operation  

SciTech Connect

A high-efficiency, air-to-air split-system residential heat pump of nominal 3-ton capacity was instrumented and tested in the heating mode under laboratory conditions. Performance of the system was measured during steady-state, dehumidifying, and frosting-defrosting conditions, with major emphasis placed on the dynamic frosting operation of the system. The study encompassed an evaluation of system and component performance for ambient temperature levels betwen 8.3 and -8.3/sup 0/C (47 and 17/sup 0/F respectively) and for discrete humidity levels ranging from 50 to 90%. The heat pump coefficient of performance (COP) and capacity, measured at 4.4/sup 0/C (40/sup 0/F) as a function of time after system start-up, decreased with time because of frost accumulation on the outdoor heat exchanger but increased with increasing ambient relative humidity. At ambient temperatures less than 4.4/sup 0/C (40/sup 0/F), the COP and capacity degradations caused by frost formation increased with increasing relative humidity because of greater frost accumulation of the outdoor heat exchanger. Experimental results revealed that both unnecessary and late defrosting operations occur when a time-and-temperature defrosting control is used. Concepts of advanced defrosting controls that could feasibly reduce both frosting and defrosting losses were developed from experimental data. Frosting caused greater degradation of heating capacity than defrosting did. Cumulative frosting loss coefficients were calculated as a function of time, temperature, and relative humidity and are applicable to modeling of frosting losses calculated in a seasonal performance program.

Miller, W.A.

1982-12-01

316

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

SciTech Connect

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

Szabo, Gyula M.; Kiss, Laszlo L.; Pal, Andras; Kiss, Csaba; Sarneczky, Krisztian [MTA CSFK, Konkoly Observatory, Konkoly Thege Miklos ut 15-17, H-1121 Budapest (Hungary); Juhasz, Attila; Hogerheijde, Michiel R. [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands)

2012-12-10

317

Frost, defrost, and refrost and its impact on the air-side thermal-hydraulic performance of louvered-fin, flat-tube heat exchangers  

Microsoft Academic Search

The thermal-hydraulic performance under conditions of an initial frost growth on the air-side surface, and for subsequent ‘refrosting’ after a defrost period is experimentally studied for folded-louvered-fin, microchannel heat exchangers. In total, five heat exchangers are considered; the thermal performances during one frost-growth cycle for four different fin geometries are compared in terms of overall heat transfer coefficient, pressure drop,

Y. Xia; Y. Zhong; P. S. Hrnjak; A. M. Jacobi

2006-01-01

318

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

PubMed Central

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

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

2014-01-01

319

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

PubMed

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

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

2014-03-01

320

Anthocyanins and glutathione S-transferase activities in response to low temperature and frost hardening in Vaccinium myrtillus (L.)  

Microsoft Academic Search

Anthocyanin (Acy) contents and GST activities of bilberry (Vaccinium myrtillus L.) were investigated in two experiments conducted in June (Exp. I: active growth) and in August–September (Exp. II: beginning of frost hardening) in Northern Finland (65°N). Bilberry plants were subjected to +2°C and +18°C in Exp. I or +5\\/0°C (day\\/night) and +18\\/+13°C (day\\/night) in Exp. II. GST activities were assessed

Erja Taulavuori; Marjaana Tahkokorpi; Kari Taulavuori; Kari Laine

2004-01-01

321

The relationship between vernalization-and photoperiodically-regulated genes and the development of frost tolerance in wheat and barley  

Microsoft Academic Search

The review summarizes the level of current knowledge of impacts of vernalization and photoperiod on the induction and maintenance\\u000a of frost tolerance (FrT) in wheat and barley. The phenomenon of vernalization is briefly described and the major vernalization\\u000a (VRN) loci are characterised. Vernalization requirement and the three major growth habits of Triticeae (facultative, winter and spring) are defined on the

K. Kosová; I. T. Prášil; P. Vítámvás

2008-01-01

322

Experimental research on air flow performance at supply-air openings in frost-free refrigerator by DPIV  

Microsoft Academic Search

In household frost-free refrigerators, the air flow field is the most important factor that affects temperature distributions in chambers, while the performance of the supply-air openings for each chest determines the character of the flow field in the chest. Thus, it is necessary to perform experimental research on the air flow performance at the supply-air openings to improve the service

Xiangzhao Meng; Bingfeng Yu

2009-01-01

323

Does a focus on universals represent a new trend in word recognition? A Commentary on Frost's Universal Model of Reading  

PubMed Central

Comparisons across languages have long been a means to investigate universal properties of the cognitive system. Although differences between languages may be salient, it is the underlying similarities that have advanced our understanding of language processing. Frost is not unique in emphasizing that the interaction among linguistic codes reinforces the inadequacy of constructing a model of word recognition where orthographic processes operate in isolation. PMID:22931560

Feldman, Laurie Beth; Martin, Fermin Moscoso del Prado

2013-01-01

324

Light and temperature dependent inhibition of photosynthesis in frost-hardened and un-hardened seedlings of pine  

Microsoft Academic Search

Needles of un-hardened and frost-hardended seedlings of Pinus sylvestris and Pinus contorta were exposed to photoinhibitory photon flux densities at temperatures between 0 and 35°C under laboratory conditions. Photoinhibition of photosynthesis was assayed by measuring oxygen evolution under saturating CO2 in a leaf disc oxygen electrode or by recording of photosystem II fluorescence induction kinetics at 77 K. It was

Gunnar Öquist; Gunilla Malmberg

1989-01-01

325

Laboratory determination of frosting and defrosting losses for a high-efficiency air-source heat pump having a one-row spine fin outdoor heat exchanger  

SciTech Connect

A high-efficiency, air-to-air, split-system residential heat pump of nominal 3-ton capacity was instrumented and tested in the heating mode under laboratory conditions. The coefficient of performance (COP) and heating capacity of the system were measured during steady-state, dehumidifying, and frosting-defrosting conditions, with major emphasis placed on the dynamic frosting operation of the system. The study encompassed an evaluation of system and component performance for ambient temperature levels between 8.3 and -8.3/sup 0/C (47 and 17/sup 0/F) and for discrete relative humidity levels ranging from 50 to 90%. The heat pump COP and capacity, measured under frosting conditions, decreased with time because of frost accumulation on the outdoor heat exchanger. Frosting caused greater degradation of heating capacity than did defrosting. Algorithms were developed as functions of time, wet-bulb temperature, and moist air enthalpy and are applicable to modeling of frosting losses calculated in a seasonal performance program.

Miller, W.A.

1984-01-01

326

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

327

Simulation of air to air heat pumps operating under frosting conditions on the outdoor coil  

SciTech Connect

A computer simulation program was developed to investigate the effects of frost deposited on the outdoor soil of air-to-air heat pumps. Three methods of defrost initiation were investigated. These were based on (1) air pressure drop in coil, (2) air temperature and compressor run time, (3) evaporator temperature and compressor run time. The values of the set-points for defrost initiation were varied to determine their effects on the coefficient of performance, the heating season performance factor, and the total energy consumption of the heat pump system. The simulation was done on an hour by hour basis for a full year of operation for eleven cities in the United States. The ASHRAE TRY weather years were used for each city. A residence with typical quantities of insulation, glass, and roof area was used to generate heating and cooling loads for the heat pump. Appropriate sizes (1.67, 1.83, or 2.5 tons) of heat pumps were selected for this residence for each geographical location. Correlations which include the heat/cooling degree days, design heating/cooling loads, and design temperature differences were developed for designer utilization.

Tantakitti, C.

1985-01-01

328

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

NASA Astrophysics Data System (ADS)

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

Diniega, S.

2013-12-01

329

Acute retinal periphlebitis mimicking frosted branch angiitis associated with exudative retinal detachment after blunt eye trauma.  

PubMed

We report a case of a 14-year-old otherwise healthy patient who developed acute retinal periphlebitis mimicking frosted branch angiitis inferotemporally and associated exudative retinal detachment in the left eye following blunt trauma. Fluorescein angiography revealed delayed filling of inferotemporal branch retinal vein and late leakage of sheathed retinal venules, and late pooling in the area of exudative retinal detachment. Indocyanine green angiography showed a crescent-shaped hypofluorescent streak concentric to the optic disk inferiorly highly suggestive of choroidal rupture. The patient was treated with oral prednisone, with gradual tapering over a period of 15 days. One month after presentation, retinal vein sheathing and exudative retinal detachment had resolved, with the development of peripapillary subretinal fibrosis, macular atrophy, pseudomacular hole, and epiretinal membrane. The acute perivenular sheathing in our patient might be related to autoimmune-mediated reaction induced by retinal vascular damage caused by severe ocular trauma. Fluorescein angiography and indocyanine green angiography findings might suggest that the retinal detachment could be caused by leakage from choroid through Bruch's membrane and retinal pigment epithelium rupture or by transient dysfunction of the outer or inner blood-retinal barrier. PMID:24912935

Kahloun, Rim; Abroug, Nesrine; Ammari, Wafa; Mahmoud, Anis; Jelliti, Bechir; Ben Yahia, Salim; Khairallah, Moncef

2014-10-01

330

Investigation of laminar-turbulent transition in supersonic boundary layers in an axisymmetric aerophysical flight complex and in a model in a wind tunnel in the presence of heat transfer and suction of air  

Microsoft Academic Search

Analysis is made of the problems associated with laminar-turbulent transition in wall boundary layers, as well as of scale\\u000a effects observed in the investigation of laminar-turbulent transition in wind tunnels and laminarization of flow. Flight-performance\\u000a data are given on the Reynolds number and on the gradient criterion of stability at the beginning of transition on the nose\\u000a part of the

A. I. Leontiev; A. M. Pavlyuchenko

2008-01-01

331

VOLUME 85, NUMBER 23 P H Y S I C A L R E V I E W L E T T E R S 4 DECEMBER 2000 Frost Heave in Argon  

E-print Network

VOLUME 85, NUMBER 23 P H Y S I C A L R E V I E W L E T T E R S 4 DECEMBER 2000 Frost Heave in Argon-solid boundary. PACS numbers: 64.70.Dv, 68.15.+e, 68.45.Gd, 82.65.Dp Frost heave is an unwelcome but common structures. Studies of frost heave began in the early years of the twentieth century [2] and have continued

Wettlaufer, John S.

332

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

PubMed

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

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

2013-11-01

333

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

334

Mixed convection boundary layer flow at the lower stagnation point of a sphere embedded in a porous medium in presence of heat source/sink: Constant heat flux case  

NASA Astrophysics Data System (ADS)

The steady mixed convection flow of an incompressible viscous fluid over an isoflux sphere embedded in a porous medium with the existence of heat source/sink is theoretically considered for both the assisting and opposing flow cases with small Prandtl number. The transformed equations of the non-similar boundary layer at the lower stagnation point of the sphere are solved numerically using a finite-difference method known as the Keller-box scheme. Numerical results are presented for the skin friction coefficient and the local wall temperature, as well as the velocity and temperature profiles for different values of the porosity parameter, the heat source/sink parameter and the mixed convection parameter for air. It is noticed that the solution has two branches in a certain range of the mixed convection parameter.

Fauzi, Nur Fatihah; Ahmad, Syakila; Pop, Ioan

2014-07-01

335

MoO3/Ag/MoO3 anode in organic photovoltaic cells: Influence of the presence of a CuI buffer layer between the anode and the electron donor  

NASA Astrophysics Data System (ADS)

MoO3/Ag/MoO3 (MAM) multilayer structures (layers thickness 20 nm/10 nm/35 nm) are used as anode in CuPc/C60/Alq3/Al organic photovoltaic cells. The averaged transmittance (400 nm-800 nm) of these MoO3/Ag/MoO3 multilayer structures is 70% ± 2% and their sheet resistance is 3.5 ± 1.0 ?/sq. When these multilayer structures are used as anode, the power conversion efficiency of the MoO3/Ag/MoO3/CuPc/C60/Alq3/Al cells is around 1%, this efficiency is increased of 50% when a thin CuI film (3 nm) is introduced at the interface between the anode and the organic film. This improvement is attributed to the templating effect of CuI on the CuPc molecules.

Makha, M.; Cattin, L.; Lare, Y.; Barkat, L.; Morsli, M.; Addou, M.; Khelil, A.; Bernède, J. C.

2012-12-01

336

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)

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.

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

2014-09-01

337

Physico-Chemical Properties and CO2 fluxes at a frost-flower station in the Bellingshausen Sea, Antarctica (SIMBA)  

NASA Astrophysics Data System (ADS)

This study documents the physico-chemical properties of newly formed sea ice at a frost flower site of the Ice Station ‘Belgica’. in the Bellingshausen Sea, (Sept-Oct 2007). Frost flower formation on sea ice is of interest, both for paleoclimatic reconstructions in deep ice cores and for potential impacts on atmospheric chemistry. The site has been surveyed for thickness at 3 occasions and samples were collected for multiparametric analyses on days 277 and 290 of 2007. CO2 fluxes were measured on day 290 along a 15 meters transect across the rim of the recently ice covered lead (8-27 cm). Ice samples were collected at 5 regularly spaced locations. Snow cover regularly decreased from the rim (10 cm) to the inner part of the lead (0 cm) We will present texture, temperature, bulk salinity, brine volume, ?18O, chl a, major cations and anions data and accumulation chamber-type CO2 fluxes and discuss the effect of the varying snow cover on salt fractionation and CO2 fluxes. The large contrasts in the snow cover along the transect resulted in contrasting snow-ice interface temperatures and therefore permeability, which in turn was clearly driving the gas fluxes and processes of salt concentration at the ice surface. This study provides the first field evidence that newly forming ice temporarily acts as a source for CO2 to the atmosphere, thereby confirming recent results from experimental work. It also brings new insights to the role of ice texture in controlling CO2 fluxes and suggests the potential need for revisiting the validity domain of the “law of fives”. Finally, it demonstrates that the processes responsible for frost flower formation are clearly inhibited by the snow cover build up.

Tison, J.; Geilfus, N.; Brabant, F.; Ackley, S. F.; Golden, K. M.; Worby, A. P.; Fritsen, C. H.; Delille, B.

2009-12-01

338

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

PubMed Central

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

Hlavackova, Iva; Vitamvas, Pavel; Santrucek, Jiri; Kosova, Klara; Zelenkova, Sylva; Prasil, Ilja Tom; Ovesna, Jaroslava; Hynek, Radovan; Kodicek, Milan

2013-01-01

339

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

PubMed

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

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

2013-01-01

340

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

NASA Astrophysics Data System (ADS)

Differences between stratospheric water vapor measurements by NOAA frost point hygrometers (FPHs) and the Aura Microwave Limb Sounder (MLS) are evaluated for the period August 2004 through December 2012 at three locations: Boulder, Colorado (40.0°N, 105.2°W), Hilo, Hawaii (19.7°N, 155.1°W), and Lauder, New Zealand (45.0°S, 169.7°E). MLS profiles coincident with the FPH soundings at each site are identified using unique sets of temporal and spatial criteria. Each FPH profile is convolved with the MLS averaging kernels to reduce its vertical resolution to that of the MLS water vapor retrievals. No statistically significant biases are found between the convolved FPH profiles and coincident MLS profiles at 8 pressure levels from 100 to 26 hPa (~16 to 25 km) above the three sites. Mean FPH-MLS differences for the 6 MLS retrieval levels from 68 to 26 hPa (~19 to 25 km) range from -0.11×0.18 to 0.12×0.22 ppmv (-2.5×3.9 to 2.5×4.6%). For 68-26 hPa, averages of the mean differences range from -0.07×0.09 to 0.05×0.09 ppmv (-1.6×1.9 to 1.0×1.9%). Below 68 hPa the mean differences become negative and larger, ranging from -0.08×0.31 to -0.29×0.37 ppmv (-2.1×7.8 to -7.3×9.1%) at 83 hPa across Boulder and Hilo, and from -0.22×0.45 to -0.44×0.46 ppmv (-5.5×11.2% to -10.9×11.3%) at 100 hPa across all three sites. At every pressure level from 100 to 26 hPa the mean differences are well within the combined MLS and FPH measurement uncertainties. FPH-MLS differences at each site are analyzed for temporal trends but none are statistically significant.

Hurst, D. F.; Lambert, A.; Read, W. G.; Davis, S. M.; Rosenlof, K. H.; Hall, E. G.; Jordan, A. F.; Oltmans, S. J.

2013-12-01

341

1 CEB,TheFutureofCorporateIT2013-2017: FiveOpportunitiestoDriveProductivityandGrowthintheNewWorkEnvironment 2 Frost&Sullivan: UCCMarketPredictionsfor2013andBeyond,December2012 3 IDG Enterprise Unified Communications and Collaboration Survey, March 2012 4  

E-print Network

OpportunitiestoDriveProductivityandGrowthintheNewWorkEnvironment 2 Frost&Sullivan: UCCMarketPredictionsfor2013andBeyond,December2012 3 IDG Enterprise Unified collaboration: The New Business Reality, March 2012 5 Frost & Sullivan, North American Video Conferencing

Fisher, Kathleen

342

Copyright 2008 by the author(s). Published here under license by the Resilience Alliance. Wunder, S., B. Campbell, P. G. H. Frost, J. A. Sayer, R. Iwan, and L. Wollenberg. 2008. When donors get  

E-print Network

, S., B. Campbell, P. G. H. Frost, J. A. Sayer, R. Iwan, and L. Wollenberg. 2008. When donors get cold) that Never Happened Sven Wunder 1 , Bruce Campbell 2,3 , Peter GH Frost 1 , Jeffrey A. Sayer 4 , Ramses Iwan

Vermont, University of

343

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

SciTech Connect

Tests were performed to detail system and component performance data, to quantify the dynamic losses, and to seek and evaluate methods for reducing these losses. A high efficiency split-system heat pump was installed in two separate air loops, with one loop housing the indoor unit and the other housing the outdoor unit. Calculations of the heat pump's performance based on air-side measurements were within 3% of that based on refrigerant side measurements. Refrigerant flow rate was measured using a turbine flow meter. Refrigerant temperatures and pressures were measured with thermocouples and pressure transducers connected at various strategic locations in the refrigeration circuit. Electric power consumption for all motors was measured with Thermal-watt converters. Performance of the heat pump was measured under steady-state, dehumidification, and frosting-defrosting conditions with major emphasis placed on the dynamic frosting operation of the system. The study encompassed an evaluation of the system and component performance for ambient temperature levels of 8.3, 4.4, 1.7, -1.1 and -8.3/sup 0/C and for discrete humidity levels ranging from 50 to 90%.

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

1981-01-01

344

Field-measured cycling, frosting, and defrosting losses for a high-efficiency air-source heat pump  

SciTech Connect

An air-to-air heat pump was installed in an unoccupied single-family residence and operated in a two-year test to characterize dynamic losses in capacity and efficiency due to cycling, frosting, and defrosting. During the heating season, defrosting losses were responsible for 10.2% of the total energy consumption (excluding supplemental electric resistance heating), frosting losses for 3.7%, start-up transient losses for 8.5%, and off-cycle parasitics for 3.3%. The heating cyclic degradation factor, C/sub d/, was estimated to be 0.26. Cooling mode steady-state performance of the heat pump was degraded from the manufacturer's ratings due most likely to a small refrigerant leak resulting in a slight charge deficiency. However, using the site measured performance as the steady-state base, it was found that start-up transient losses accounted for 2.8% of the total energy use and off-cycle parasitics for 4.4%. The cooling C/sub d/ was estimated to be 0.11 on this basis.

Baxter, V.D.; Moyers, J.C.

1985-01-01

345

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

SciTech Connect

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.

Cwirzen, Andrzej; Penttala, Vesa

2005-04-01

346

Presence in Virtual Theater  

Microsoft Academic Search

Using empirical data, this research suggests that key features of a typical theatrical rehearsal process can significantly improve the sense of presence for participants within a shared virtual environment. Research of shared virtual environments (VEs) for the production of theater shows suggests that theater applications have specific requirements for presence. These can be summarized as characterization, repetition, and group dynamic,

Carlton Reeve

2000-01-01

347

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)

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.

Jones, Alun R.

1940-01-01

348

The development of frost tolerance and DHN5 protein accumulation in barley ( Hordeum vulgare) doubled haploid lines derived from Atlas 68×Igri cross during cold acclimation  

Microsoft Academic Search

The dynamics of a long-term cold acclimation (CA) was studied in spring barley cultivar Atlas 68, winter barley cultivar Igri and a set of doubled haploid (DH) lines derived from an Atlas 68×Igri cross. The aim was to evaluate the effect of plant development on the ability to induce frost tolerance (FT) and to accumulate dehydrin 5 (DHN5) during CA.

Klára Kosová; Ilja Tom Prášil; Pavla Prášilová; Pavel Vítámvás; Jana Chrpová

2010-01-01

349

Selective occurrence of Rhizobiales in frost flowers on the surface of young sea ice near Barrow, Alaska and distribution in the polar marine rare biosphere.  

PubMed

Frost flowers are highly saline ice structures that grow on the surface of young sea ice, a spatially extensive environment of increasing importance in the Arctic Ocean. In a previous study, we reported organic components of frost flowers in the form of elevated levels of bacteria and exopolymers relative to underlying ice. Here, DNA was extracted from frost flowers and young sea ice, collected in springtime from a frozen lead offshore of Barrow, Alaska, to identify bacteria in these understudied environments. Evaluation of the distribution of 16S rRNA genes via four methods (microarray analysis, T-RFLP, clone library and shotgun metagenomic sequencing) indicated distinctive bacterial assemblages between the two environments, with frost flowers appearing to select for Rhizobiales. A phylogenetic placement approach, used to evaluate the distribution of similar Rhizobiales sequences in other polar marine studies, indicated that some of the observed strains represent widely distributed members of the marine rare biosphere in both the Arctic and Antarctic. PMID:23864572

Bowman, J S; Larose, C; Vogel, T M; Deming, J W

2013-08-01

350

The effect of sowing date and rate on seed coat discolouration due to frost in field peas in the southern Mallee of Victoria  

Microsoft Academic Search

Frost occurring during the reproductive period of field peas can cause downgrading through seed coat discolouration and yield loss. During 2001, a field trial was conducted to determine the optimum sowing date (9 May, 17 June and 11 July) and sowing rate (15, 35, 55, 75 and 110 plants\\/m 2 ) of 4 field pea cultivars (Dundale, Parafield, Snowpeak and

Jason Brand; Roger Armstrong; Greg Antonoff

2003-01-01

351

tEknolo Giavd ElinGEn FRost i JoRd 2007 1 Remote sensing of permafrost hazards in mountains  

E-print Network

tEknolo Giavd ElinGEn FRost i JoRd 2007 1 Remote sensing of permafrost hazards in mountains Fjernmåling av faremomenter ved permafrost i høyfjellsområder Andreas Kääb, Universitetet i Oslo (UiO) (kaeaeb ice involved. Norway with its significant areas covered by glaciers and underlain by permafrost

Kääb, Andreas

352

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

ERIC Educational Resources Information Center

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

Carr, John C.

353

A study on the performance of the airside heat exchanger under frosting in an air source heat pump water heater\\/chiller unit  

Microsoft Academic Search

Air source heat pump water heater\\/chiller (ASHPWHC) units, a cooling and heating source for buildings becomes increasingly popular. However, when such a unit is operated as a heating source under low ambient temperature in winter, the formation of frost on the surface of its airside heat exchanger becomes problematic, leading to the degradation of the heat exchanger's performance or even

Yang Yao; Yiqiang Jiang; Shiming Deng; Zuiliang Ma

2004-01-01

354

Causal Links of Presence  

Microsoft Academic Search

The purpose of this paper is to examine antecedent variables and an outcome variable of presence. Presence has been used to\\u000a explain the extent to which technology users are immersed and involved in a technology-created experience. In video gaming,\\u000a gamers frequently don’t distinguish between reality and the game world, and they identify characters with themselves. This\\u000a comes from a high

Donghun Chung; Chae-hwan Kim

2009-01-01

355

Color and albedo of the south polar layered deposits on Mars  

NASA Astrophysics Data System (ADS)

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.

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

1990-02-01

356

[About the influence of frost periods upon the serological detection of Prunus ring spot viruses in cherries (author's transl)].  

PubMed

During three years serological tests (latex test) were run from Novemeber till April to detect Prunus ring spot viruses in forced buds of Prunus avium L., P. avium L. var. avium, and P. cerasus L. It was found that Prunus necrotic ring spot virus (NRV) could be detected reliably during the winter in all infected trees. In contrary the detection of Prune dwarf virus (PDV) was affected by temperatures below zero. In 1971 a low percentage of positive reacting trees was pointed out after the frost periods in January and March. This result was started after the low temperatures in January 1972. The mild winter 1972/73 hardly influenced the reliability of the PDV-test. PMID:910571

Schade, C

1977-01-01

357

Micrometeorological test of microsprinklers for frost protection of fruit orchards in Northern Italy  

Microsoft Academic Search

Microclimate modification induced by intermittent water sprinkling at ground level has proven to be suitable to enhance protection against spring hoarfrosts in orchards. This research investigates about the efficiency of different sprinkler types and water volumes in enhancing air temperature in the canopy layer and to optimise the amount and the cycling of the water applied. Tests have been done

Stefano Anconelli; Osvaldo Facini; Vittorio Marletto; Andrea Pitacco; Federica Rossi; Franco Zinoni

2002-01-01

358

Federal Government Presence in  

E-print Network

Sector Employment, Table 183-0004. #12;Average Wages & Salaries Source: Statistics Canada, Public Sector Employment Employment and Population Changes in Employment Executive Employment Military Presence Wages and Salaries Federal Expenditures Qualitative Evidence #12;Federal Employment Down 25% since 1981: Down 32

deYoung, Brad

359

Snippets From the Past: The Evolution of Wade Hampton Frost's Epidemiology as Viewed From the American Journal of Hygiene/Epidemiology  

PubMed Central

Wade Hampton Frost, who was a Professor of Epidemiology at Johns Hopkins University from 1919 to 1938, spurred the development of epidemiologic methods. His 6 publications in the American Journal of Hygiene, which later became the American Journal of Epidemiology, comprise a 1928 Cutter lecture on a theory of epidemics, a survey-based study of tonsillectomy and immunity to Corynebacterium diphtheriae (1931), 2 papers from a longitudinal study of the incidence of minor respiratory diseases (1933 and 1935), an attack rate ratio analysis of the decline of diphtheria in Baltimore (1936), and a 1936 lecture on the age, time, and cohort analysis of tuberculosis mortality. These 6 American Journal of Hygiene /American Journal of Epidemiology papers attest that Frost's personal evolution mirrored that of the emerging “early” epidemiology: The scope of epidemiology extended beyond the study of epidemics of acute infectious diseases, and rigorous comparative study designs and their associated quantitative methods came to light. PMID:24022889

Morabia, Alfredo

2013-01-01

360

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

PubMed Central

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

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

2013-01-01

361

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

PubMed Central

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

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

2011-01-01

362

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

PubMed

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

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

2011-02-01

363

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

NASA Technical Reports Server (NTRS)

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

Tejnil, Edward; Rogers, Stuart E.

2012-01-01

364

Elevated bacterial abundance and exopolymers in saline frost flowers and implications for atmospheric chemistry and microbial dispersal  

NASA Astrophysics Data System (ADS)

Frost flowers (FF) have been studied for their potential influence on ice-surface reflectivity and roles in atmospheric chemistry, but not as microbial habitats. We examined FF grown in a freezer laboratory from a bacteria-containing saline solution and FF formed naturally in the coastal (April) and central Arctic Ocean (September). All FF contained bacteria (up to 3.46 × 106 ml-1 in natural FF) with densities 3-6-fold higher than in underlying ice. Bacterial abundance correlated strongly with salinity in FF (p values ? 0.001), a correlation that held for all components of the surface-ice environment (p < 0.0001, coastal samples). Concentrations of extracellular polysaccharides were also elevated in FF and brine skim relative to underlying ice (up to 74-fold higher). Here we consider implications of finding microbes and exopolymers within the chemically reactive surface-ice environment to the photolytic production of oxidants and long-range transport of potential ice-nucleating particles in the atmosphere.

Bowman, J. S.; Deming, J. W.

2010-07-01

365

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

PubMed Central

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

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

1985-01-01

366

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

PubMed Central

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

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

2011-01-01

367

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

USGS Publications Warehouse

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.

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

2007-01-01

368

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)

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.

Inouye, D. W.

2004-12-01

369

Boundary layer simulator improvement  

NASA Technical Reports Server (NTRS)

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.

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

1984-01-01

370

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

371

Ice Lens Formation and Frost Heave at the Phoenix Landing Site  

NASA Technical Reports Server (NTRS)

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.

Zent, A. P.; Sizemore, H. G.; Remple, A. W.

2011-01-01

372

Layered Slopes  

NASA Technical Reports Server (NTRS)

4 June 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows exposures of layered material on slopes in the south polar region near 81.9oS, 72.2oW. Layers record the history of a place, but accessing the information contained in these layers may one day require a visit by a human or robotic explorer. The south polar layers, in general, are believed to be accumulations of dust and ice that were built up in the most recent billion years or so. However, they could just as easily be sedimentary rocks from much earlier in martian history. The picture covers an area about 3 km (1.9 mi) across. The scene is illuminated by sunlight from the upper left.

2004-01-01

373

Ice Lens Formation and Frost Heave at the Phoenix Landing Site  

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

374

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

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.

Jordan, D.N.

1995-05-01

375

Lava Layering  

NSDL National Science Digital Library

This is a lesson about geologic history. Learners will work together to create models of volcanic lava flows and analyze the layers that form on a planet's surface. They will sequence lava flows produced by multiple eruptions. Students will be asked to observe where the flows travel, make a model, and interpret the stratigraphy. Students will use their volcanic layering model to demonstrate the relative dating and geologic mapping principles to later be applied to satellite imagery. The lesson models scientific inquiry using the 5E instructional model and includes teacher notes and vocabulary.

376

Leaky Layers  

NSDL National Science Digital Library

Figure from the Nature Geoscience article, Geodynamics: Layer cake or plum pudding? by Paul Tackley (Nature Geoscience 1, 157 - 158 (2008)). The figure shows the current understanding of the interaction between the 660 km discontinuity, the core-mantle boundary, downgoing slabs, upwelling plumes.

Tackley, Paul J.; Geoscience, Nature

377

Presence: concept, determinants, and measurement  

Microsoft Academic Search

The concept of presence, i.e. the sensation of 'being there' in a mediated environment, has received substantial attention from the virtual reality community, and is becoming increasingly relevant both to broadcasters and display developers. Although research into presence is still at an early stage of development, there is a consensus that presence has multiple determinants. To identify and test which

Wijnand A. IJsselsteijn; Huib de Ridder; Jonathan Freeman; Steve E. Avons

2000-01-01

378

Helium Exhaust Studies in {ital H}-Mode Discharges in the DIII-D Tokamak Using an Argon-Frosted Divertor Cryopump  

SciTech Connect

The first experiments demonstrating exhaust of thermal helium in a diverted, {ital H}-mode deuterium plasma have been performed on the DIII-D tokamak. The helium, introduced via gas puffing, is observed to reach the plasma core, and then is readily removed from the plasma with a time constant of {similar_to}10--20 energy-confinement times by an in-vessel cryopump conditioned with argon frosting. Detailed analysis of the helium profile evolution suggests that the exhaust rate is limited by the exhaust efficiency of the pump ({similar_to}5%) and not by the intrinsic helium-transport properties of the plasma.

Wade, M.R.; Hillis, D.L.; Hogan, J.T.; Mahdavi, M.A.; Maingi, R.; West, W.P.; Brooks, N.H.; Burrell, K.H.; Groebner, R.J.; Jackson, G.L.; Klepper, C.C.; Laughon, G.; Menon, M.M.; Mioduszewski, P.K. [General Atomics, San Diego, California 92184 (United States)] [General Atomics, San Diego, California 92184 (United States); [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); DIII-D Team

1995-04-03

379

On Multiple-Layered Vortices  

NASA Technical Reports Server (NTRS)

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.

Rossow, Vernon J.

2011-01-01

380

PRESENCE 2006 Content knowledge and thematic inertia predict virtual presence  

E-print Network

PRESENCE 2006 38 Content knowledge and thematic inertia predict virtual presence David Nunez, Edwin by the user. Furthermore, a particular cognitive tendency (thematic inertia), should facilitate the effect inertia, as well as controls for age and immersion/display factors. The ITC-SOPI was the dependent

Blake, Edwin

381

Presence Management and Merging Presence Information for NGN Services  

NASA Astrophysics Data System (ADS)

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.

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

382

Sodium-1,2-14C Acetate Incorporation in Roots of Frost-hardy and Less Hardy Alfalfa Varieties under Hardening Conditions 1  

PubMed Central

When the temperature of incorporation of sodium acetate-1, 2-14C into lipids of alfalfa (Medicago media Pers. var. Rambler and Medicago sativa L. var. Caliverde) roots was lowered from 22 C to 1 C, elongation and desaturation of fatty acids and the labeling of phosphatidylcholine were strongly stimulated. Controlled hardening of alfalfa stimulated strongly the incorporation of sodium acetate-1, 2-14C into root lipids of the hardy variety Rambler, but only slightly in the case of the frost-sensitive variety Caliverde. When incorporation was done at 1 C at various times of hardening, labeling decreased significantly in linoleic acid with a corresponding increase in oleic acid. Hardening, therefore, repressed specifically the initial low temperature stimulation of oleic acid desaturation, without affecting the stimulation of elongation of palmitic acid and the desaturation of stearic acid at low temperature. The radioactivity in linoleic acid was slightly greater in hardy Rambler than in Caliverde throughout hardening. When feedings were done at 1 C at various times of hardening, labeling of phosphatidylcholine increased in Rambler while it decreased in Caliverde. Throughout the hardening period, when incorporation was done at 1 C, linoleic acid represented a higher percentage of the label in phosphatidylcholine than in phosphatidylethanolamine or triglycerides and its specific radioactivity was much greater in phosphatidylcholine than in phosphatidylethanolamine and triglycerides and in Rambler than in Caliverde. Phosphatidylcholine seems, therefore, to play a special part in linoleic acid synthesis and in its control during the acquisition of frost hardiness. PMID:16659189

Grenier, Gilles; Hope, Hugh J.; Willemot, Claude; Therrien, Henri-Paul

1975-01-01

383

Quantum Layer Conjecture Quantum Layer Conjecture  

E-print Network

Quantum Layer Conjecture Quantum Layer Conjecture Zhiqin Lu, UCI Last revised, March 21, 2014 #12;Quantum Layer Conjecture Introduction The concept of quantum layer was introduced in mesoscopic physics. A quantum layer is a kind of complete non-compact manifold with boundary. Figure : Picture of a quantum

Lu, Zhiqin

384

Double Layers in Astrophysics  

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

385

2 Media Presence and Inner Presence: The Sense of Presence in Virtual Reality Technologies  

Microsoft Academic Search

Presence is widely accepted as the key concept to be considered in any research involving human interaction with Virtual Reality (VR). Since its original description, the concept of presence has developed over the past decade to be considered by many researchers as the essence of any experience in a virtual environment. The VR generating systems comprise two main parts: a

Carlos COELHO; Jennifer TICHON; Trevor J. HINE; Guy WALLIS; Giuseppe RIVA

386

High levels of nucleotide diversity and fast decline of linkage disequilibrium in rye (Secale cereale L.) genes involved in frost response  

PubMed Central

Background Rye (Secale cereale L.) is the most frost tolerant cereal species. As an outcrossing species, rye exhibits high levels of intraspecific diversity, which makes it well-suited for allele mining in genes involved in the frost responsive network. For investigating genetic diversity and the extent of linkage disequilibrium (LD) we analyzed eleven candidate genes and 37 microsatellite markers in 201 lines from five Eastern and Middle European rye populations. Results A total of 147 single nucleotide polymorphisms (SNPs) and nine insertion-deletion polymorphisms were found within 7,639 bp of DNA sequence from eleven candidate genes, resulting in an average SNP frequency of 1 SNP/52 bp. Nucleotide and haplotype diversity of candidate genes were high with average values ? = 5.6 × 10-3 and Hd = 0.59, respectively. According to an analysis of molecular variance (AMOVA), most of the genetic variation was found between individuals within populations. Haplotype frequencies varied markedly between the candidate genes. ScCbf14, ScVrn1, and ScDhn1 were dominated by a single haplotype, while the other 8 genes (ScCbf2, ScCbf6, ScCbf9b, ScCbf11, ScCbf12, ScCbf15, ScIce2, and ScDhn3) had a more balanced haplotype frequency distribution. Intra-genic LD decayed rapidly, within approximately 520 bp on average. Genome-wide LD based on microsatellites was low. Conclusions The Middle European population did not differ substantially from the four Eastern European populations in terms of haplotype frequencies or in the level of nucleotide diversity. The low LD in rye compared to self-pollinating species promises a high resolution in genome-wide association mapping. SNPs discovered in the promoters or coding regions, which attribute to non-synonymous substitutions, are suitable candidates for association mapping. PMID:21219606

2011-01-01

387

Ion-acoustic double layers  

Microsoft Academic Search

The formation of plasma double layers in the presence of ion-acoustic instabilities is investigated. One-dimensional particle simulations were performed for system lengths 1024, 512, 256, and 128 times the initial electron Debye length and an electron drift speed equal to 0.6 times the electron thermal speed. Simulated electron and ion phase-space distributions, electron and ion density profiles, and potential profiles

T. Sato; H. Okuda

1980-01-01

388

Step like surface potential on few layered graphene oxide  

NASA Astrophysics Data System (ADS)

We report surface potential maps of few layered graphene oxide films on different substrates. Kelvin probe force microscopy images reveal that the surface potential decreases in steps with increasing number of layers on the substrate until five layers are reached, where it saturates to a constant value. This intrinsic behavior is smeared out in the presence of ambient humidity where the surface potential is shielded by the presence of a thin water layer on the surface. This effect can be exploited to quickly determine the number of layers of graphene oxide on a substrate.

Jaafar, M.; López-Polín, G.; Gómez-Navarro, C.; Gómez-Herrero, J.

2012-12-01

389

Survivability in layered networks  

E-print Network

In layered networks, a single failure at the lower (physical) layer may cause multiple failures at the upper (logical) layer. As a result, traditional schemes that protect against single failures may not be effective in ...

Lee, Kayi (Edmund Kayi), 1977-

2011-01-01

390

Green House Gases Flux Model in Boundary Layer  

NASA Astrophysics Data System (ADS)

Analytical dynamic model of the turbulent flux in the three-layer boundary system is presented. Turbulence is described as a presence of the non-zero vorticity. The generalized advection-diffusion-reaction equation is derived for an arbitrary number of components in the flux. The fluxes in the layers are objects for matching requirements on the boundaries between the layers. Different types of transport mechanisms are dominant on the different levels of the layers.

Nurgaliev, Ildus

391

Stable Layers in the Atmospheric Boundary Layer  

NASA Astrophysics Data System (ADS)

Field experimental studies on the establishment and growth of the nocturnal stable layer near the ground were made in January, 1998 using a tethered balloon at a site in Phoenix, Arizona. Days and nights with clear skies and light surface winds were of particular interest because small particle and carbon monoxide concentrations can be high during such times. Closest to the ground a shallow stable layer 20 meters deep with a buoyancy frequency (N) of 0.05 1/s rapidly developed before sundown. The height of this layer and N remained constant throughout the night. Above the 20-meter level, there was a transition layer which was also stable with N = 0.025 1/s. This transition layer grew throughout the night and reached 120 meters by dawn. Above the transition layer was a neutrally stable (residual) layer left over from the previous day. An unsteady layer 10 to 100 m thick with N = 0.025 1/s was also found at the top of the troposphere with the neutrally stable troposphere below and the stable stratosphere above. The growth and/or decay of turbulence in such stable layers will be discussed in light of recent theoretical developments.

Mahalov, A.; Berman, N. S.; Fernando, H. J. S.; Yu, F.; Pardyjak, E.

1998-11-01

392

Ice Lens Formation, Frost Heave, Thin Films, and the Importance of the Polar H2O Reservoir at High Obliquity  

NASA Technical Reports Server (NTRS)

Several lines of evidence indicate that the volume of shallow ground ice in the martian high latitudes exceeds the pore volume of the host regolith. Boynton et al. found an optimal fit to the Mars Odyssey Gamma Ray Spectrometer (GRS) data at the Phoenix landing site by modeling a buried layer of 50-75% ice by mass (up to 90% ice by volume). Thermal and optical observations of recent impact craters in the northern hemisphere have revealed nearly pure ice. Ice deposits containing only 1-2% soil by volume were excavaged by Phoenix. One hypothesis for the origin of this excess ice is that it developed in situ by a mechanism analogous to the formation of terrestrial ice lenses and needle ice. Problematically, terrestrial soil-ice segregation is driven by freeze/thaw cycling and the movement of bulk water, neither of which are expected to have occurred in the geologically recent past on Mars. If however ice lens formation is possible at temperatures less than 273 K, there are possible implications for the habitability of Mars permafrost, since the same thin films of unfrozen water that lead to ice segregation are used by terrestrial psychrophiles to metaboluze and grow down to temperatures of at least 258 K.

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

2011-01-01

393

Initial and Shock Layers for Boltzmann Equation  

NASA Astrophysics Data System (ADS)

We study an initial value problem of the Boltzmann equation with a Euler shock wave as initial data. Our analysis exhibits the presence of three singular layers, the initial layer, formation layer, and the shock layer. An approximate solution is constructed based on a solution of the Burgers-type equation for the formation layer time scale. The macroscopic conservation laws are preserved for the approximate solution. The Green's function of the linearized Boltzmann equation around the approximate solution is constructed by a modification of the scheme introduced by Yu (Nonlinear wave propagation over a Boltzmann shock profile, 2013). With the Green's function approach and a wave tracing method, one shows that the error of the approximate solution converges to zero with the convergent rate in pointwise norm around the shock profile for and with the rate outside the shock zone, where is the strength of the weak hyperbolic shock wave.

Yu, Shih-Hsien

2014-01-01

394

Multi-layer carbon-based coatings for field emission  

DOEpatents

A multi-layer resistive carbon film field emitter device for cold cathode field emission applications is disclosed. The multi-layered film of the present invention consists of at least two layers of a conductive carbon material, preferably amorphous-tetrahedrally coordinated carbon, where the resistivities of adjacent layers differ. For electron emission from the surface, the preferred structure can be a top layer having a lower resistivity than the bottom layer. For edge emitting structures, the preferred structure of the film can be a plurality of carbon layers, where adjacent layers have different resistivities. Through selection of deposition conditions, including the energy of the depositing carbon species, the presence or absence of certain elements such as H, N, inert gases or boron, carbon layers having desired resistivities can be produced. 8 figs.

Sullivan, J.P.; Friedmann, T.A.

1998-10-13

395

A double layer review  

Microsoft Academic Search

A review is given of the main results on electrostatic double layers (sometimes called ‘space charge layers’ or ‘sheaths’) obtained from theory and laboratory and space experiments up to the spring of 1977.

Lars P. Block

1978-01-01

396

A temperature-based variable for monitoring outdoor coil airflow in an air-source heat pump during frost-forming conditions  

SciTech Connect

Frost-buildup tests were conducted on a 3-ton (10.6kW) nominal cooling capacity air-source heat pump with an orifice expansion device. This study was conducted to determine if a simple temperature-based control variable could be used to determine the amount of degradation in the outdoor airflow (and heating capacity) of the unit. Refrigerant pressures and temperatures were monitored through-out the system in addition to power requirements and airflow rates. A temperature-based variable was developed that could be used to predict airflow degradation across the outdoor heat exchanger. This variable was defined using the difference between ambient air temperature and a measured refrigerant temperature. Eight refrigerant temperatures in the system were recorded and evaluated. Plots of airflow as a function of this temperature variable, along with plots of the absolute value percent changes of this temperature variable and airflow, were evaluated to determine which refrigerant temperatures could best be used in the variable to predict degradation in airflow. The best fit between the temperature-based variable and airflow degradation occurred with the inclusion of the refrigerant temperature at the outlet from the evaporator. Calculations of percent changes based on values sampled after a defrost showed a polynomial or linear relationship between airflow and the temperature-based variable. Data from two previously tested heat pumps were also used to compare changes in the outdoor airflow to changes in the temperature-based variable. The base-case heat pump and another heat pump both used an orifice as the expansion device in the heating mode. A third heat pump, which used a thermostatic expansion valve (TXV) as the expansion device in the heating mode, failed to show the same goodness of fit between airflow and the temperature-based variable.

Payne, W.V. II; O`Neal, D.L. [Texas A and M Univ., College Station, TX (United States). Energy Systems Lab.

1994-12-31

397

Layer-by-layer cell membrane assembly.  

PubMed

Eukaryotic subcellular membrane systems, such as the nuclear envelope or endoplasmic reticulum, present a rich array of architecturally and compositionally complex supramolecular targets that are as yet inaccessible. Here we describe layer-by-layer phospholipid membrane assembly on microfluidic droplets, a route to structures with defined compositional asymmetry and lamellarity. Starting with phospholipid-stabilized water-in-oil droplets trapped in a static droplet array, lipid monolayer deposition proceeds as oil/water-phase boundaries pass over the droplets. Unilamellar vesicles assembled layer-by-layer support functional insertion both of purified and of in situ expressed membrane proteins. Synthesis and chemical probing of asymmetric unilamellar and double-bilayer vesicles demonstrate the programmability of both membrane lamellarity and lipid-leaflet composition during assembly. The immobilized vesicle arrays are a pragmatic experimental platform for biophysical studies of membranes and their associated proteins, particularly complexes that assemble and function in multilamellar contexts in vivo. PMID:24153375

Matosevic, Sandro; Paegel, Brian M

2013-11-01

398

Layer-by-layer cell membrane assembly  

NASA Astrophysics Data System (ADS)

Eukaryotic subcellular membrane systems, such as the nuclear envelope or endoplasmic reticulum, present a rich array of architecturally and compositionally complex supramolecular targets that are as yet inaccessible. Here we describe layer-by-layer phospholipid membrane assembly on microfluidic droplets, a route to structures with defined compositional asymmetry and lamellarity. Starting with phospholipid-stabilized water-in-oil droplets trapped in a static droplet array, lipid monolayer deposition proceeds as oil/water-phase boundaries pass over the droplets. Unilamellar vesicles assembled layer-by-layer support functional insertion both of purified and of in situ expressed membrane proteins. Synthesis and chemical probing of asymmetric unilamellar and double-bilayer vesicles demonstrate the programmability of both membrane lamellarity and lipid-leaflet composition during assembly. The immobilized vesicle arrays are a pragmatic experimental platform for biophysical studies of membranes and their associated proteins, particularly complexes that assemble and function in multilamellar contexts in vivo.

Matosevic, Sandro; Paegel, Brian M.

2013-11-01

399

Transparent Layer Constancy  

Microsoft Academic Search

Perceived transparency was studied as a constancy problem. In the episcotister (E-) model of scission, luminances are partitioned into layer and background components; four luminances determine values of two layer parameters that specify constancy of a transparent layer on different backgrounds. The E-model was tested in an experiment in which 12 Ss matched 24 pairs of four-luminance patterns by adjusting

Walter Gerbino; Casimir I. F. H. J. Stultiens; Jim M. Troost; Charles M. M. de Weert

1990-01-01

400

Perturbed free shear layers  

Microsoft Academic Search

The development of free shear layers formed by the mixing of initially separated free streams is examined in a review of recent work. The mixing layer is viewed as a prototype for a class of inviscidly unstable free shear flows including jets and wakes, and the focus is on 2D homogeneous incompressible mixing layers. Major areas covered include dynamical processes

C.-M. Ho; P. Huerre

1984-01-01

401

Group 11 - Ozone Layer  

NSDL National Science Digital Library

BACKGROUND Investigate the issues of the ozone layer. TASK - What is the ozone layer and where is it found? What is happening to it? What is causing that? Where is the hole located? What is ozones chemical make up? Who is currently studying this? Where? What has already been done to preserve the ozone layer? ...

Mecham, Mrs.

2006-11-30

402

Performance of a boundary layer ingesting propulsion system  

E-print Network

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 ...

Plas, Angélique (Angélique Pascale)

2006-01-01

403

Scintillator reflective layer coextrusion  

DOEpatents

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.

Yun, Jae-Chul (Naperville, IL); Para, Adam (St. Charles, IL)

2001-01-01

404

Community Matters: Social Presence and Learning Outcomes  

ERIC Educational Resources Information Center

The study examines the relationship between social presence and students' learning outcomes. An emerging body of research connects social presence with learning outcomes in online coursework. Social presence is the "degree to which a person is perceived as a 'real person' in mediated communication" (Gunwardena &…

Hostetter, Carol

2013-01-01

405

Acoustic double layers in multispecies plasma  

NASA Technical Reports Server (NTRS)

The formation of acoustic double layers in the presence of two ion species is examined via a particle simulation in a 1D bounded system. The effect of having two ion components, an H(+) and an O(+) beam, on double-layer evolution from ion acoustic turbulence driven by an electron drift relative to the H(+) beam of about 0.5 u sub e, where u sub e is the electron thermal speed, is examined. It is found that acoustic double layers form in either ion species on a time scale of about 100 omega sub ps exp -1, where omega sub ps is the ion plasma frequency for species 's' and s = H or O, and for drifts relative to the electrons lower than that required for double layer formation in simulations of single ion component plasma.

Gray, Perry C.; Hudson, Mary K.; Lotko, William

1992-01-01

406

The atmospheric boundary layer  

SciTech Connect

In this book, the author successfully reviews the current state of affairs in boundary-layer meteorology research. The book is organized into nine chapters. The first chapter is an introduction to the topic of the atmospheric boundary layer. The second chapter is a survey of turbulence theory. The third chapter reviews the similarity relationships that have been formulated for the various scaling regimes in the boundary layer. Chapter 4 deals with the deviations of the homogeneous boundary layer. In chapter 5 the boundary conditions for the atmospheric boundary layers are considered, that is, the energy fluxes at the earth's surface. In chapter 6 the characteristics and dynamics are discussed for the various prototypes of the atmospheric boundary layer, such as the convective and the stable boundary layer. Boundary-layer clouds are the subject of chapter 7. The final chapters, 8 and 9, discuss the use of boundary-layer meteorology in formulating parameterization schemes. In the preface of the book, the author states that his goal is to provide a book for researchers in atmospheric and associated sciences. The book will be an asset to any scientist active in boundary-layer meteorology or a related field.

Garratt, J.R.

1992-01-01

407

2-D airfoil tests including side wall boundary layer measurements  

Microsoft Academic Search

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.

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

1994-01-01

408

Modeling a close-up observation of Enceladus by Cassin/VIIMS with layered water ice  

NASA Astrophysics Data System (ADS)

We have been working on layered water ice models that fit the measured spectra of Enceladus by the Cassini Visual and Infrared Mapping Spectrometer (VIMS). Our original inspection using two observations (equatorial and South Pole) showed that good fits could be made using fractional monolayers of 2-µm frost over 20 µm for the polar ice and about 1 monolayer of 1-µm frost over 7 µm for the equatorial ice. We then ran ~200 general models that could be used for any analysis. We found that with small misfits around 1.5 and 2.5 µm, that the whole infrared spectrum 0.8-5.2 µm could be adequately fit by single layer models. The mosaic studied was observed on 14 July 2006, and extended from just above the equator to the sunlit south pole, and from 140-150 W to 230 W longitudes, crossing the leading-trailing boundary. The observations are all in high resolution mode, with a finest resolution of 4 by 8 km, but more typically 6 by 12 km. The modeling shows that the trailing side observed is uniformly r=5-7 µm base grain size with ~one monolayer of r=1 µm ice. This grades gradually to r=20 or more µm and a fractional 0.1) monolayer of r=2 µm ice. The south polar terrains are similar to the leading side pattern, except in the center of the tiger stripes where there is no layering and unresolved (requiring mixing of two grain sizes) grain radii close to 500 µm. This layering is due to Enceladus orbit in the E-ring of micron sized water ice particles whose source is the geysers on Enceladus' south pole. The low latitude grain size patterns do not agree well with band-depth studies, which find the grain size related to geology (Jaumann et al., 2008, Icarus 193, 407). We do not observe the whole globe here, so the patterns could be semi-hemispherical similar to ring dynamics models show (Kempf et al., 2010, Icarus 206, 446).

Hansen, Gary B.; Stephan, K.

2013-10-01

409

Screening of selective radiation in a boundary layer  

Microsoft Academic Search

An analysis of numerous calculations of the flow and radiative-convective heat exchange in a hypersonic shock layer near a blunt body, both at an impermeable surface [1] and in the presence of ablation [1–4], made it possible to establish some relationships connected with the screening in the boundary layer of radiation from the high-temperature part of the shock layer. It

T. V. Kondranin; I. N. Kuz'minskii

1978-01-01

410

Curved branching crystals and differentiation in comb-layered rocks  

NASA Technical Reports Server (NTRS)

An investigation is conducted concerning two common features of comb layered rocks. Attention is given to the curvature of oriented, elongate, branching crystals and the tendency to form highly differentiated layers. Crystallization studies of plagioclase show that some degree of supercooling is necessary to produce the skeletal, curved, and branching plagioclase crystal morphologies found in comb-layered rocks and that curved crystals can be grown without the presence of a directed stress.

Lofgren, G. E.; Donaldson, C. H.

1975-01-01

411

Layers of the Earth  

NSDL National Science Digital Library

This is an introductory lesson that can be expanded into the areas of geology, volcanos, earthquakes, and archaeology. Students will be introduced to geology in its simplest form and learn how a rock is formed. They will be able to identify the layers of the earth and the approximate thicknesses of each, list the sciences that study the earth's layers and how the information is used, and identify the basic composition of each layer.

1998-01-01

412

Dual Layer CT  

Microsoft Academic Search

\\u000a Dual-energy CT enables improvement of material and possibly tissue separation when compared to regular CT. Philips Healthcare\\u000a has been successfully operating a dual-layer detector system in a modified Brilliance 64 CT scanner installed since 2005 in\\u000a Hadassah University Medical Center, Israel. The dual-layer detector acquires single x-ray source CT data using two scintillation\\u000a layers on top of each other with

Alain Vlassenbroek

413

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)

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.

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

2010-05-01

414

Layers and Erosion and more Layers  

NASA Technical Reports Server (NTRS)

[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.

2003-01-01

415

Presence management in next-generation networks  

NASA Astrophysics Data System (ADS)

The popularity of instant messaging highlights the power that the addition of presence information can bring to communications. Instant messaging systems combine multi-party communications with active presence notifications, allowing users to monitor the presence status of others. We describe several ways presence information can enhance next generation telephone communications and how integration can actually improve instant messaging as well. In addition, we will describe some of the issues associated with implementing and deploying such services, including privacy, data ambiguity and inter-system compatibility.

Wullert, John R., II; Shim, Hyong S.; Mouchtaris, Petros; Li, S. Peter; Chiang, Cho-Yu Jason

2001-07-01

416

Frictional properties of the end-grafted polymer layer in presence of salt solution  

NASA Astrophysics Data System (ADS)

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.

Raftari, Maryam; Zhang, Zhenyu; Leggett, Graham J.; Geoghegan, Mark

2012-02-01

417

Many-layered learning  

Microsoft Academic Search

We examine how a network of many knowledge layers can be constructed in an online manner such that the learned units represent building blocks of knowledge that serve to compress the overall representation. Our novel STL algorithm demonstrates a method for simultaneously acquiring and organizing a collection of concepts and functions as a many-layered network.

Paul E. Utgoff; David J. Stracuzzi

2002-01-01

418

Many-Layered Learning  

Microsoft Academic Search

We explore incremental assimilation of new knowledge by sequential learn- ing. Of particular interest is how a network of many knowledge layers can be con- structed in an on-line manner, such that the learned units represent building blocks of knowledge that serve to compress the overall representation and facilitate trans- fer. We motivate the need for many layers of knowledge,

Paul E. Utgoff; David J. Stracuzzi

2002-01-01

419

The atmospheric boundary layer  

Microsoft Academic Search

In this book, the author successfully reviews the current state of affairs in boundary-layer meteorology research. The book is organized into nine chapters. The first chapter is an introduction to the topic of the atmospheric boundary layer. The second chapter is a survey of turbulence theory. The third chapter reviews the similarity relationships that have been formulated for the various

J. R. Garratt

1992-01-01

420

Effects of Communication Mode on Social Presence, Virtual Presence, and Performance in Collaborative Virtual Environments  

Microsoft Academic Search

How does communication mode affect people's experience of social presence, presence, and performance, and how does it affect their actual collaboration in a virtual environment? In a first experiment, subjects communicated by text-chat, audio conference, or video conference in a desktop collaborative virtual environment (CVE). Both perceived social presence and presence were shown to be lower in the text-chat condition

Eva-Lotta Sallnäs

2005-01-01

421

Fiber optic device for sensing the presence of a gas  

DOEpatents

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.

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

422

The analysis of electrode impedances complicated by the presence of a constant phase element  

Microsoft Academic Search

The electrical double-layer at a solid electrode does not in general behave as a pure capacitance but rather as an impedance displaying a frequency-independent phase angle different from 90°. Ways are indicated how to analyse the interfacial impedance if such a complication arises in the presence of a faradaic process, both on the supposition that the double-layer behaviour is due

G. J. Brug; M. Sluyters-Rehbach; J. H. Sluyters

1984-01-01

423

Defrost improvement by heat pump refrigerant charge compensating  

Microsoft Academic Search

During winters, the air-source heat pump often operates with substantial frost formation on the outdoor heat exchanger, and the frost layer has to be melted away periodically to keep a high heat pump coefficient of performance (COP). Otherwise, the unmelted frost layer and water will become high density frost or ice layer in heating mode. However, it is difficult to

Wang Zhiyi; Wang Xinmin; Dong Zhiming

2008-01-01

424

Behavioral Presence Test in Threatening Virtual Environments  

Microsoft Academic Search

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

Eric Malbos; Ronald M. Rapee; Manolya Kavakli

2012-01-01

425

Presence, Analogy, and "Earth in the Balance."  

ERIC Educational Resources Information Center

Uses vice president Albert Gore Jr.'s book "Earth in the Balance" as a case study to examine the relationship between analogy and "presence." Argues that presence is a flexible critical construct allowing for examination of the relationship between the style, substance, and structure of arguments. Explores relationships between C. Perelman and the…

Murphy, John M.

1994-01-01

426

From presence to consciousness through virtual reality  

Microsoft Academic Search

Immersive virtual environments can break the deep, everyday connection between where our senses tell us we are and where we are actually located and whom we are with. The concept of 'presence' refers to the phenomenon of behaving and feeling as if we are in the virtual world created by computer displays. In this article, we argue that presence is

Maria V. Sanchez-Vives; Mel Slater

2005-01-01

427

Presence and Embodiment in Mobile Phone Communication  

Microsoft Academic Search

This paper explores the temporal and spatial characteristics of mobile phone communication, comparing the experience of presence in phone calls and in virtual reality environments. It is argued that in phone communication interactional affordances create an experience of presence and a degree of embodiment. The theoretical framework adopted combines Goffman's frame analysis with Gibson's affordance theory and a situated cognition

Ruth M. Rettie

2005-01-01

428

Personality-related differences in subjective presence  

Microsoft Academic Search

Even though user-related variables are important determinants of presence, quite little is known about their role. The main aim of the present study was to examine differences in presence experience as a function of personality. Participants navigated through a multimedia presentation on a desktop computer. Half of them had the opportunity to navigate through the stimulus without interruptions, the other

Jari Laarni; Niklas Ravaja; Timo Saari; Tilo Hartmann

2004-01-01

429

Spatial Presence and Disney's Oswald Comedies  

Microsoft Academic Search

Even prior to Mickey Mouse, Walt Disney was exploring new stylistic patterns in animation. His Oswald comedies, for example, demonstrate a new attitude towards filmic space emerging in this period—what Anthony Vidler terms spatial presence. This article examines how space assumes a “presence” that shapes the Oswald comedies' narratives.

J. P. Telotte

2011-01-01

430

Community of Inquiry: Social Presence Revisited  

ERIC Educational Resources Information Center

Social presence is a construct that has attracted the attention of many educational scholars involved in online collaborative learning settings wherein all the dialogue is happening through text-based asynchronous and synchronous communication channels. The social presence of the learning group members is associated with the degree of…

Kreijns, Karel; Van Acker, Frederick; Vermeulen, Marjan; Van Buuren, Hans

2014-01-01

431

Topography of the South Polar Cap and Layered Deposits of Mars: Viking Stereo Grametry at Regional and Local Scales  

NASA Technical Reports Server (NTRS)

Layered deposits and residual polar caps on Mars may record the deposition of ice and sediment modulated by periodic climate change. Topographic information relating to layer thicknesses, erosional processes, and formation of dark spirals within these deposits has been sparce or unreliable until the arrival of MOLA in orbit in September 1997. To assist in evaluating these terrains prior to launch and to assess formation and erosion processes in the polar deposits, we have assembled Viking stereo mosaics of the region and have produced the first reliable DEM models of the south polar deposits using automated stereogrammetry tools. Here we report our preliminary topographic results, pending final image pointing updates. The maximum total thickness of the layered deposits in the south polar region is 2.5 km. The thick layered deposits consist of a series of megaterraces. Each terrace is several tens of kilometers wide and is flat or slopes very gently toward the pole. These terraces step downward from a central plateau near the south pole. Terraces are bounded by relatively steep scarps 100-500 meters high that face toward the equator. These scarps correspond to the pattern of dark spirals observed within the residual cap in southern summer, and are interpreted as ice or frost-free surfaces warmed by solar insolation. Several tongue-shaped troughs, with rounded cirquelike heads, are observed near the margins of the deposit. These troughs are 300-600 meters in deep and may be similar to troughs observed in the northern polar deposit.

Schenk, P.; Moore, J.; Stoker, C.

1998-01-01

432

Wet adhesion between two soft layers.  

PubMed

Two solids can adhere to each other in the presence of a liquid bridge between them, which is called wet adhesion. When the solid is soft, the liquid bridge can cause deformation in the material, and in turn, the deformation may have dramatic effects on the wet adhesion. To investigate the effect, in this article, we calculate the deformation in two soft layers with different separations and connected by a liquid bridge. We illustrate the effect of deformation in the soft layers on the adhesive force. For a given liquid volume and separation between the two layers, the adhesive force increases dramatically by decreasing the elastic moduli of the soft layers. We also discuss the contact between the two soft layers due to the deformation caused by the liquid bridge. Depending on the volume of the liquid bridge, the two layers may be in contact with each other at the center of the wetting area or some other locations between the center and the contact line. The results may improve current understanding of wet adhesion between soft materials and have potential applications in designing and fabricating soft devices and structures. PMID:25178195

Li, Kai; Cai, Shengqiang

2014-11-01

433

Many-layered learning.  

PubMed

We explore incremental assimilation of new knowledge by sequential learning. Of particular interest is how a network of many knowledge layers can be constructed in an on-line manner, such that the learned units represent building blocks of knowledge that serve to compress the overall representation and facilitate transfer. We motivate the need for many layers of knowledge, and we advocate sequential learning as an avenue for promoting the construction of layered knowledge structures. Finally, our novel STL algorithm demonstrates a method for simultaneously acquiring and organizing a collection of concepts and functions as a network from a stream of unstructured information. PMID:12396572

Utgoff, Paul E; Stracuzzi, David J

2002-10-01

434

Compliant layer chucking surface  

DOEpatents

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.

Blaedel, Kenneth L. (Dublin, CA); Spence, Paul A. (Pleasanton, CA); Thompson, Samuel L. (Pleasanton, CA)

2004-12-28

435

Thermal insulation layer  

SciTech Connect

A thermal insulation layer, suitable for use in a duvet, comprises a convection inhibiting structure and at least one surface with a low thermal emissivity. The structure may be a flexible cellular foam sheet or a web of fibrous material, while the low emissivity surface may be a coating on the sheet or on a thin flexible thermally insulating film. Perforations are provided through the foam sheet or the film to permit diffusion of water vapour through the layer, and the layer may include an additional web of fibrous material or feathers adjacent to the low emissivity surface.

Pollock, J. F.

1985-06-25

436

Theoretical and experimental studies of the atmospheric sodium layer  

NASA Technical Reports Server (NTRS)

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.

Richter, E. S.; Sechrist, C. F., Jr.

1978-01-01

437

Modelling the transitional boundary layer  

NASA Technical Reports Server (NTRS)

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.

Narasimha, R.

1990-01-01

438

Asymmetric magnetic reconnection in the presence of a guide field  

NASA Astrophysics Data System (ADS)

The properties of asymmetric magnetic reconnection in the presence of a guide magnetic field are investigated using two-dimensional particle-in-cell simulations. The reconnection process is initiated by applying a spatially localized and temporally steady convection electric field at the high-density/low-magnetic-field (magnetosheath) side of the current layer. The in-plane Hall currents are dominated by the electron flows along the separatrices from the high-density to low-density side of the layer, and they strongly enhance the out-of-plane magnetic field in one hemisphere and decrease it in the other. On the enhanced magnetic field side are situated a bipolar pair of parallel electric fields and an electron velocity shear flow layer, both of which extend several ion inertia lengths (di) away from the X line. The shear flow layer is unstable to the generation of small-scale ($\\ll$di) electron vortices which propagate away from the X line and produce a reduction of the order of 30% in the magnitude of the By field. An example of such a large-amplitude, short-duration depression in By is identified in a magnetopause crossing by the THEMIS spacecraft. The Ohm's law (E + Ue × B/c)y = 0 is violated in this parallel field/velocity shear region, and the deviation arises predominantly from the divergence of the electron pressure tensor. Criteria based on the demagnetization of the electrons (large values of the electron agyrotropy and the Lorentz ratio) are found to characterize neither the immediate electron scale region around the X line nor the larger electron shear flow region.

Pritchett, P. L.; Mozer, F. S.

2009-11-01

439

The Abstract MAC Layer  

E-print Network

A diversity of possible communication assumptions complicates the study of algorithms and lower bounds for radio networks. We address this problem by defining an abstract MAC layer. This service provides reliable local ...

Kuhn, Fabian

2010-08-26

440

The Abstract MAC Layer  

E-print Network

A diversity of possible communication assumptions complicates the study of algorithms and lower bounds for radio networks. We address this problem by defining an Abstract MAC Layer. This service provides reliable local ...

Newport, Calvin

2009-02-21

441

The Abstract MAC Layer  

E-print Network

A diversity of possible communication assumptions complicates the study of algorithms and lower bounds for radio networks. We address this problem by defining an Abstract MAC Layer. This service provides reliable local ...

Kuhn, Fabian

2009-05-11

442

The abstract MAC layer  

E-print Network

A diversity of possible communication assumptions complicates the study of algorithms and lower bounds for radio networks. We address this problem by defining an Abstract MAC Layer. This service provides reliable local ...

Kuhn, Fabian

443

Layers of the Skin  

MedlinePLUS

... involved in the immune system in the skin), Merkel cells and sensory nerves. The epidermis layer itself is ... spots. Melanoma develops when melanocytes undergo malignant transformation. Merkel cells, which are tactile cells of neuroectodermal origin, are ...

444

Structured luminescence conversion layer  

DOEpatents

An apparatus device such as a light source is disclosed which has an OLED device and a structured luminescence conversion layer deposited on the substrate or transparent electrode of said OLED device and on the exterior of said OLED device. The structured luminescence conversion layer contains regions such as color-changing and non-color-changing regions with particular shapes arranged in a particular pattern.

Berben, Dirk; Antoniadis, Homer; Jermann, Frank; Krummacher, Benjamin Claus; Von Malm, Norwin; Zachau, Martin

2012-12-11

445

Layers of the Sun  

NSDL National Science Digital Library

Students will explore the layers of the sun through interactive media and reading. Print off the following worksheet: layers of the sun worksheet Click on the electronmagnetic spectrum above the picture of the sun. On your own paper, describe what the sun looks like at the different wave lengths. At which two wavelengths does the sun look the same? Examine the sun at different wavelengths Now click on this website and read more about ...

Brown, Mrs.

2010-09-28

446

Earth Layers and Volcanoes  

NSDL National Science Digital Library

Why do we have volcanoes? Use the information on the websites to answer the questions on the worksheet. Worksheet First, review the layers of the earth. Labeling the layers game Next, go through the maze and read the information given. Magic School Bus volcano game Now, study the different shapes of volcanoes. Click enter, then volcano types in the menu. Read about the 3 types of volcanoes. Discovery Kids Games Finally, watch ...

Brookeshallow

2011-04-13

447

Water Uptake in PEMFC Catalyst Layers  

SciTech Connect

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.

Gunterman, Haluna P.; Kwong, Anthony H.; Gostick, Jeffrey T.; Kusoglu, Ahmet; Weber, Adam Z.

2011-07-01

448

31 CFR 91.3 - Recording presence.  

Code of Federal Regulations, 2010 CFR

...Finance REGULATIONS GOVERNING CONDUCT IN OR ON THE BUREAU OF THE MINT BUILDINGS AND GROUNDS § 91.3 Recording presence...opinion of the senior supervising official of any Bureau of the Mint establishment covered by these regulations, or his...

2010-07-01

449

31 CFR 407.3 - Recording presence.  

Code of Federal Regulations, 2010 CFR

...presence. 407.3 Section 407.3 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) SECRET SERVICE, DEPARTMENT OF THE TREASURY REGULATIONS GOVERNING CONDUCT IN THE TREASURY BUILDING AND THE TREASURY ANNEX §...

2010-07-01

450

31 CFR 407.3 - Recording presence.  

Code of Federal Regulations, 2013 CFR

...presence. 407.3 Section 407.3 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) SECRET SERVICE, DEPARTMENT OF THE TREASURY REGULATIONS GOVERNING CONDUCT IN THE TREASURY BUILDING AND THE TREASURY ANNEX §...

2013-07-01

451

31 CFR 407.3 - Recording presence.  

Code of Federal Regulations, 2011 CFR

...presence. 407.3 Section 407.3 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) SECRET SERVICE, DEPARTMENT OF THE TREASURY REGULATIONS GOVERNING CONDUCT IN THE TREASURY BUILDING AND THE TREASURY ANNEX §...

2011-07-01

452

31 CFR 407.3 - Recording presence.  

Code of Federal Regulations, 2012 CFR

...presence. 407.3 Section 407.3 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) SECRET SERVICE, DEPARTMENT OF THE TREASURY REGULATIONS GOVERNING CONDUCT IN THE TREASURY BUILDING AND THE TREASURY ANNEX §...

2012-07-01

453

Some aspects of adaptive grid technology related to boundary and interior layers  

Microsoft Academic Search

We consider the use of adaptive mesh strategies for solution of problems exhibiting boundary and interior layer solutions. As the presence of these layer structures suggests, reliable and accurate solution of this class of problems using finite difference, finite volume or finite element schemes requires grading the mesh into the layers and due attention to the associated algorithms. When the

Graham F. Carey; M. Anderson; B. Carnes; B. Kirk

2004-01-01

454

Tests on Double Layer Metalization  

NASA Technical Reports Server (NTRS)

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.

Woo, D. S.

1983-01-01