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1

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 48N 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 (68N) 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

2

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

3

Continuous property measurement techniques and physics based mathematical model for frost growth control  

Microsoft Academic Search

The development of a new set of frost property measurement techniques to be used in the control of frost growth and defrosting processes in refrigeration systems was investigated. Holographic interferometry and infrared thermometry were used to measure the temperature of the frost-air interface, while a beam element load sensor was used to obtain the weight of a deposited frost layer.

Jose Iragorry

2005-01-01

4

The control of carbon dioxide cryodeposits. [of frost for liquid hydrogen tankage thermal protection  

NASA Technical Reports Server (NTRS)

An experimental study has been conducted to investigate the parameters affecting the cryodeposition of carbon dioxide frost. In the investigation carbon dioxide frost was cryodeposited from a helium-carbon dioxide mixture into a layer of fibrous insulation surrounding a cylindrical cryogenic tank. Results of the study indicated that not only did deposition occur on the frost surface but also within the frost layer. Over the range of variables investigated both the frost density and the mass of frost deposited were most sensitive to the time of deposition, the percent of carbon dioxide in the purge-gas mixture, and the thickness of the insulation. Frost density and mass of frost deposition were found to increase with time and percent carbon dioxide, and to decrease with increasing insulation thickness.

Sharpe, E. L.

1973-01-01

5

Frost on Utopia Planitia  

NASA Technical Reports Server (NTRS)

This Viking Lander 2 picture from Utopia Planitia shows the first clear indication of frost accumulation on the Martian surface seen by lander cameras. The picture, looking due north, was obtained with a blue filter at 12:59 p.m. local lander time, Sept. 13, 1977. The season is late winter. Frost appears as a white accumulation around the bottom of rocks, in a trench dug by the lander sampler arm, and in scattered patches on the darker surface. The shadow of the lander, including the camera (center) and the meteorology boom (left), appears in foreground. As the sun moves, the shadow is moving from left to right, exposing areas covered by frost and previously protected from the sun by the lander shadow. (Another image taken one-half hour later suggests the frost patches have become smaller.) Apparently frost, formed during the Martian night, at least partially disappears during the warmer daytime. The composition of the frost, whether carbon dioxide or water or a mixture of the two (CO2 clathrate), is not known. Measurements from the meteorology instrument indicate minimum nighttime temperatures of 160 Kelvin (-171 Fahrenheit). At the time the image was taken, the temperature had risen to 175 Kelvin (-144 Fahrenheit). The atmospheric pressure was 8.835 millibars. This combination of pressure and temperature are inconsistent with carbon dioxide frost formation, but plausible near-surface mechanisms might have resulted in conditions favorable for CO2 frost formation. Viking orbiter thermal mapping and water vapor instruments indicate temperatures might have been slightly lower than measured by the lander, suggesting that the frost is more likely CO2 than H20. A remote, but possible, explanation is that the material is an extremely bright dust deposit. Color images to be taken will be able to discount this interpretation. The mechanism for frost deposition is unknown. Possibilities include formation directly on the surface, precipitation as snow, or material blown to the area around the lander from colder regions.

1977-01-01

6

Ubiquitous presence of laminae in altered layers of glass artefacts  

NASA Astrophysics Data System (ADS)

Whatever the chemical composition and the origin (natural or man-made) or the surrounding environment is, glass materials undergo alteration processes leading to the modification of their structure and chemical composition. Similar alteration patterns can be observed in different historical glass types, especially alteration layers characterized by a laminated structure. The study of medieval stained glass windows (14th century AD, from Northern France) and Roman glass blocks (2nd century AD, from a shipwreck in the Mediterranean Sea) with several centuries of exposure in atmospheric and marine conditions, respectively, show that laminated features, commonly described at micro-scale (e.g. lamination), can also be found at the nano-scale (laminae) using TEM analysis on FIB ultra-thin section. These features develop on different alteration layers - in the gel layer for medieval glass and in crystalline secondary phases (smectites) for Roman glass - showing that the formation mechanisms vary according to the exposure environment and the chemical composition of the glass.

Gentaz, L.; Lombardo, T.; Verney-Carron, A.; Chabas, A.; Loisel, C.; Neff, D.; Gin, S.; Leroy, E.

7

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

E-print Network

frost layer is entirely dependent on the interface temperaturebetween air and frost. 3. THE FROSTING SUB-MODEL The frost accumulation rate is determined by a loss of water vapor in the air, as water vapor condenses on the exit of outdoor waste... air surface of the channels wheel fresh air ventilator. It is expressed by: m fr = ( - ) (1) d1 outd1 Where: m fr ?frost accumulation rate (kg s ); 1? m ?mass flow?kg s ?; 1? ind1 ?moisture content of indoor waste air (kg water...

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

2006-01-01

8

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

9

Frost Forecasting for Fruitgrowers  

NASA Technical Reports Server (NTRS)

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

Martsolf, J. D.; Chen, E.

1983-01-01

10

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

11

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 9.1S, 83.0W is conspicuously darker than its surroundings, while an adjacent feature (P2) at 24.1S, 73.5W 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 273% at phase ?=124 to only 1.30.2% 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

12

Seasonal Frost in Terra Sirenum  

NASA Technical Reports Server (NTRS)

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

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

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

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

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

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

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

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

2006-01-01

13

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

14

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

15

Cross-Layer Measurements for a Comprehensive Characterization of Wireless Networks in the Presence of Interference  

Microsoft Academic Search

Assessing the overall performance of wireless communication networks is of key importance for optimal management and planning. With special regard to wireless networks operating in an unlicensed band, evaluating overall performance mainly implies facing the coexistence issues, which are associated with the contemporaneous presence of true and interfering signals at the physical layer. This task is difficult to fulfill only

Leopoldo Angrisani; Michele Vadursi

2007-01-01

16

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 27106. 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

17

Properties of ionospheric gyroechoes in the presence of a sporadic E-layer  

NASA Astrophysics Data System (ADS)

Generation and properties of ionospheric gyroechoes in the presence of a thin sporadic E-layer are investigated theoretically. Full wave analysis is used to calculate the transmission coefficients of model Es-layers. The intensification of the echo and the decrease in its virtual height at the onset of the Es-layer are explained in terms of mode coupling, the phenomena of which are shown to be more complicated than expected by Ellis (1960). A mechanism is also found of producing gyroechoes when an otherwise totally blanketing flat type Es-layer is present. When the maximum plasma frequency is so high that the whistler mode can propagate within the Es-layer at frequencies relevant to the gyroecho, the layer may be transparent for the extraordinary mode. Penetration of the ordinary wave becomes impossible, and the 0X0-reflection and ordinary F-trace can no longer be registered. Thus, the gyrotrace may be caused by the XXX-reflection only, and the resulting polarization on the ground is extraordinary.

Jalonen, L.; Nygren, T.; Turunen, T.

1981-10-01

18

Experimental strategies for frost analysis  

NASA Astrophysics Data System (ADS)

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

Janssen, Daniel D.

19

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

NASA Astrophysics Data System (ADS)

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

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

1994-08-01

20

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

21

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.; Gonzlez-Vias, W.; Beysens, D.

2013-01-01

22

Device for determining frost depth and density  

NASA Astrophysics Data System (ADS)

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

Huneidi, F.

1983-08-01

23

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, Universit de

24

Robert Frost's Major Themes Study  

Microsoft Academic Search

Interestingly, when it comes to the basic themes of human life there is shirking on his part, though he evades the universal experiences at the price of triviality. A point worthy to be stressed here is that the work of his contemporary writers who are characterized by topical labels became lusterless and outdated as the year passed. Meanwhile Frost's poems

M. M. Uma Maheswari

2008-01-01

25

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

26

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

27

Cave development by frost weathering  

NASA Astrophysics Data System (ADS)

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

Oberender, Pauline; Plan, Lukas

2015-01-01

28

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

29

Robert Frosts Hendecasyllabics and roman rebuttals  

Microsoft Academic Search

For Once, Then, Something (1920) is the only poem Robert Frost ever composed in a classical meter: it is written in phalaecean\\u000a hendecasyllabics. What led him to depart, in that single instance, from his declared commitment to native English meters?\\u000a So far no scholar or critic has ventured to say. This paper offers an explanation, and points to a greater

John Talbot

2004-01-01

30

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

31

Analysis of a Passive Circular Loop Antenna Radiating in the Presence of a Layered Chiral Sphere Using Method of Moments  

Microsoft Academic Search

In this paper, electromagnetic radiation due to a passive thin circular loop antenna when placed on the surface of a two-layered chiral sphere is analyzed and its far-zone radiation patterns are obtained. The method of moments is employed in this analysis to formulate the current distribution along the circular loop in the presence of the layered chiral sphere. The dyadic

L.-W. Li; M.-S. Leong; P.-N. Jiao; W.-X. Zhang

2002-01-01

32

Frost resistance in alpine woody plants  

PubMed Central

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

Neuner, Gilbert

2014-01-01

33

Frost resistance in alpine woody plants.  

PubMed

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

Neuner, Gilbert

2014-01-01

34

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

35

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

SciTech Connect

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

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

2011-07-15

36

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

37

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

1967-01-01

38

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

39

FROST CONTROL IN THE PACIFIC NORTHWEST  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

40

Genes for frost resistance in wheat  

Microsoft Academic Search

Wheat varieties differ in their responses to low temperatures. Geneticstudies on frost resistance in wheat are difficult because the effects arequantitative in nature and thus require precise genetic material andreproducible experimental conditions. The detailed diallel analyses indicatedthat the inheritance of frost resistance is polygenic and mostly additive.Nevertheless, studies using monosomic, ditelosomic and substitution lineshave identified specific chromosomes that carry genes

J. Sutka

2001-01-01

41

Frost heave induced mechanics of buried pipelines  

SciTech Connect

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

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

1993-12-01

42

Elevated Bacterial Abundance in Laboratory-Grown and Naturally Occurring Frost Flowers Under Late Winter Conditions  

NASA Astrophysics Data System (ADS)

Sea ice has been identified as an important microbial habitat, with bacteria and other microbes concentrated in the brine inclusions between ice crystals. Frost flowers, thought to draw brine from underlying sea ice, have not been characterized from a microbial standpoint. To test whether frost flowers serve as an upward vector of bacteria contained within sea ice brines we grew frost flowers in a freezer laboratory (air temperature of -21C) from saline water spiked with the mesophilic (and thus passive under experimental conditions) bacterium Halomonas pacifica. Salinity of melted samples was measured and bacterial abundance determined by epifluorescent microscopy. Bacterial counts scaled to ice-melt volume averaged 2.82 x 106 ml-1 for frost flowers, compared to 9.47 x 105 ml-1 for underlying ice (3 x higher). Bacterial counts also correlated significantly with salinity (maximum value of 62.5 psu) for frost flowers, brine skim, and ice (df = 17, r = 0.59, p < 0.0001). Segregation coefficients were calculated to describe the efficiency of transport of both cells and salt from the starting solution into frost flowers. From these coefficients an enrichment index was calculated to test for bacterial concentration into frost flowers at a different rate than salt. Analysis with a Students T-test (df = 24, t = 0.306, p = .76) indicated that cells and salt were not transported into frost flowers with a significantly different efficiency. To test these findings in the field we then collected frost flowers (and related samples) from new sea ice near Barrow, Alaska in April 2009. Bacterial counts were significantly elevated (again, a 3-fold increase) in natural frost flowers (mean = 2.73 x 105 ml-1) compared to underlying sea ice (mean = 8.46 x 104 cells ml-1). For all field samples collected (frost flowers, underlying brine skim and sea ice, as well as snow), bacterial abundance correlated significantly with salinity (maximum value 124 psu, df = 40, r = 0.60, p < 0.0001). The presence of elevated numbers of bacteria in frost flowers may have implications for the previously observed chemical reactions that take place in them, especially if microbial activity can be shown to occur in this unique low temperature, low water activity microbial habitat.

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

2009-12-01

43

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

44

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); Srgers, 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

45

Frost risks in the Mantaro river basin  

NASA Astrophysics Data System (ADS)

As part of the study on the Mantaro river basin's (central Andes of Per) current vulnerability to climate change, the temporal and spatial characteristics of frosts were analysed. These characteristics included intensity, frequency, duration, frost-free periods, area distribution and historical trends. Maps of frost risk were determined for the entire river basin, by means of mathematical algorithms and GIS (Geographic Information Systems) tools, using minimum temperature - 1960 to 2002 period, geomorphology, slope, land-use, types of soils, vegetation and life zones, emphasizing the rainy season (September to April), when the impacts of frost on agriculture are most severe. We recognized four categories of frost risks: low, moderate, high and critical. The critical risks (with a very high probability of occurrence) were related to high altitudes on the basin (altitudes higher than 3800 m a.s.l.), while the low (or null) probability of occurring risks were found in the lower zones (less than 2500 m a.s.l.). Because of the very intense agricultural activity and the high sensitivity of the main crops (Maize, potato, artichoke) in the Mantaro valley (altitudes between 3100 and 3300 m a.s.l.), moderate to high frost risks can be expected, with a low to moderate probability of occurrence. Another significant result was a positive trend of 8 days per decade in the number of frost days during the rainy season.

Trasmonte, G.; Chavez, R.; Segura, B.; Rosales, J. L.

2008-04-01

46

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

PubMed Central

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

Reif, Jochen C.

2013-01-01

47

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

E-print Network

used molecular imaging techniques for preclinical imaging. #12;BEST PRACTICES RESEARCH © 2010 FrostBEST 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

48

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; Brl-Babel, Anita; Leach, Richard; Baumann, Ute; Fincher, Geoffrey B; Collins, Nicholas C

2009-08-01

49

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

50

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

NASA Astrophysics Data System (ADS)

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

Strijkova, V.; Danev, G.

2014-12-01

51

A laboratory study of frost flower growth on the surface of young sea ice  

NASA Astrophysics Data System (ADS)

Frost flowers are fragile ice crystals containing salt which grow to a height of 10-30 mm on the surface of young sea ice. Such flowers are observed all over the Arctic. The importance of the flowers and their accompanying slush layer is that they provide a rapid way to change the surface albedo and increase the surface roughness of young sea ice. This paper describes a laboratory technique for growing frost flowers and the physical processes which accompany the growth. The study was carried out in a saltwater tank located in a cold room. To grow frost flowers, we alternately cool the surface of the growing sea ice with a fan, then supply it with water vapor from a vaporizer. For these conditions and a room temperature of -22C, the frost flowers begin to grow when the ice thickness reaches 5-8 mm. The flowers form at random locations on the ice and grow vertically to a height of 10-15 mm while spreading laterally from their original sites. Beneath the flowers, the surface is initially dry; then as the flowers spread laterally, a high-salinity slush layer forms beneath them. This layer, which forms only under the flowers, grows to a thickness of 5 mm in 48 hours and has a characteristic lateral scale of 100-200 mm. The salinity of the slush layer is about 80 psu, compared with a frost flower salinity of 100 psu. Within 24 hours of their appearance, the flowers grow to cover 75-90% of the surface. A surface water budget for the flowers and slush layer shows that most of the water in the flowers and slush layer comes from the ice interior, not from the vaporizer. This implies that an external vapor source may be important in determining the initial growth of the flowers but not in their subsequent development.

Martin, Seelye; Drucker, Robert; Fort, Meredith

1995-04-01

52

The manipulation of polar head group composition of phospholipids in the wheat Miranovskaja 808 affects frost tolerance  

Microsoft Academic Search

Caryopses of the frost-resistant cultivar of the wheat Triticum aestivum L., Miranovskaja 808, were germinated and grown in the presence of various concentrations of choline chloride. Changes in the composition of leaf total phospholipids and leaf total fatty acids at two extreme temperatures (25C and 2C) as well as changes in frost resistance were followed. A choline chloride concentration-dependent accumulation

I. Horvth; L. Vigh; T. Farkas

1981-01-01

53

Spin waves in exchange-coupled double layers in the presence of spin torques  

NASA Astrophysics Data System (ADS)

Spin-wave spectra of a double magnetic layer are calculated theoretically in the macroscopic limit. Magnetic dynamics is described in terms of the Landau-Lifshitz-Gilbert equation, and both static (of the Ruderman-Kittel-Kasuya-Yosida type) and dynamic (via spin pumping) interlayer couplings are taken into account. The influence of spin pumping and spin transfer torque on the spin-wave spectra (frequency and damping factor) has been studied for both parallel and antiparallel magnetic configurations. The spin-wave spectrum in the parallel magnetic state is reciprocal, while in the antiparallel configuration it is nonreciprocal. In both cases, a substantial reduction of the spin-wave lifetimes due to spin pumping to the nonmagnetic metallic layers has been found. In the parallel configuration, this reduction appears mainly for optical modes, while in the antiparallel configuration, it is remarkable for all modes. In turn, the spin torque due to spin current flowing from a metallic layer, created for instance by the spin Hall effect, gives rise to significant changes in the damping factors as well, but these modifications depend on the sign of spin current. For one spin current orientation, the spin-wave damping becomes reduced and may disappear for some modes at a specific threshold value of the spin current, indicating magnetic instability in the system due to spin transfer torque. For the opposite spin current, the damping is enhanced, which indicates stabilization of the corresponding magnetic state.

Bal, Pavel; Barna?, Jzef

2015-03-01

54

Numerical Study on Frost Profile over the Cooling Plate under Forced Convection  

NASA Astrophysics Data System (ADS)

This paper deals the numerical analysis on mass transfer under forced convection cooling. The transients of frost profiles on a cooling plat in a narrow channel were calculated by use of the packaged software with built in some original subroutines. In this paper, the architecture of these subroutines and this benchmark tests were showed. The calculation results exhibit local mass transfer rates and clarified following things. On the leading edge of the cooling plate, the frost accumulation accelerates locally. For the prediction on the cooling plate temperature distribution, to take into account latent heat of sublimation is necessary. In addition, the comparison between calculation and experimental results shows below issues. Both frost distribution profiles overlap in upstream; on the contrary, they do not overlap in the downstream. This comparison result indicates that the super saturation or mist flow is not negligible in the downstream. In terms of total frost weight, both results are roughly agreed and this weight increases proportionally with a run time despite increasing of the heat resistance caused by frost layer.

Kondou, Chieko; Senshu, Takao; Koyama, Shigeru; Kuwahara, Ken; Oguni, Kensaku

55

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

E-print Network

Doctoral Defense "Frost Deterioration in Concrete Due to Deicer Salt Exposure: Mechanism-freeze climate zone. During winter a deicer-salt application is needed to melt snow on highways. Freezing in the presence of a deicer salt solution is considered a severe concrete exposure condition. Prolonged exposure

Kamat, Vineet R.

56

Design of UMTRA covers to mitigate the effect of frost penetration  

SciTech Connect

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

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

1994-03-01

57

In situ sediment dispersion estimates in the presence of discrete layers and gradients.  

PubMed

One of the difficulties in validating sediment models has been the lack of reliable low frequency dispersion measurements. A reflection method is presented that yields in situ dispersion without sediment disturbance over a broad range of frequencies and can explicitly disentangle frequency-dependent effects of vertical structure, e.g., layers and gradients. Measurements on the outer shelf from 300 to 3000 Hz show that dispersion is a strong function of depth in the sediment column. The depth and frequency-dependent results generally agree well with independent measurements on core data. Cohesive sediments in the upper few meters exhibit a nearly frequency-independent sound speed and a nearly linear frequency dependence of attenuation. In the lower part of the sediment column the sediments are more granular: the lowest layer exhibits an attenuation with a peak frequency at 1100 Hz, where its dependence below and above trends to f(2) and f(1/2), respectively. While Biot theory predicts this dependence, its underlying physical explanation, fluid flow through interstitial pores, does not seem plausible for this sediment due to the unreasonable permeability value required. Viscous grain shearing theory also predicts this dependence, but it is not known whether the parameter values are reasonable. PMID:23297882

Holland, Charles W; Dettmer, Jan

2013-01-01

58

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

NASA Astrophysics Data System (ADS)

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

Yadav, Vandana; Mukherji, Sutapa

2015-02-01

59

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

PubMed

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

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

2013-03-01

60

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

61

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

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

62

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.

2001-01-01

63

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

DOEpatents

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

Malinowski, Michael E.

2005-01-25

64

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

65

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

66

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

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

67

Latest results from FROST at Jefferson Lab  

SciTech Connect

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, Barry G. [Arizona State University

2014-06-01

68

Insulator (Heat and Frost). Occupational Analyses Series.  

ERIC Educational Resources Information Center

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

McRory, Aline; Ally, Mohamed

69

A FrostLess Heat Pump  

Microsoft Academic Search

Frost accumulation on the outdoor coil of a heat pump is oneofthebasicconcernsaboutheatpumpoperation.Defrost- ing by cycle reversing is energy consuming, compromises indoor thermal comfort, and causes excessive and unneces- sary use of electric resistance heating. By adding a moderate amount of heat to the refrigerant stream in the accumulator, the evaporator coil temperature can be raised by several degrees. This concept

Viung C. Mei; Ronald E. Domitrovic; Fang C. Chen; Joe K. Kilpatrick

70

The fluid mechanics of frost heave  

Microsoft Academic Search

Frost heave is a process during which the freezing of a water-saturated soil gives rise to the deformation and upward thrust of the ground surface. The phenomenon plays a central role in sculpting the landscape in regions subject to prolonged freezing and it is responsible for damage to engineered structures. Contrary to popular belief, this behavior is completely unrelated to

Alan Rempel; John Wettlaufer; Grae Worster

2002-01-01

71

Electrode potential-dependent colorimetric response of fluorescein-modified layer-by-layer films in the presence of hydrogen peroxide.  

PubMed

Layer-by-layer (LbL) thin films composed of fluorescein-modified poly(allylamine) (F-PAH) and poly(styrenesulfonic acid) (PSS) were prepared on the surface of an indium-tin oxide (ITO) electrode and the electrode potential-dependent colorimetric response of the LbL films was studied in the presence of hydrogen peroxide (H(2)O(2)). The LbL films were prepared by an alternate deposition of F-PAH and PSS on the surface through an electrostatic force of attraction. The LbL films exhibited a UV-visible absorption band around 500 nm originating from fluorescein residues in the film and the intensity of the absorption band depended on the pH of the solution to which the LbL film is exposed. The absorbance of the film was higher at neutral pH than that in weakly acidic solutions. The intensity of the absorption band decreased when an electrode potential higher than 0.6 V was applied in the presence of H(2)O(2), while virtually no response was observed at lower electrode potential. The colorimetric response was suppressed in solutions with higher buffer capacity. The results were rationalized on the basis of the changes in local pH at the vicinity of the electrode surface, which in turn was induced by electrolysis of H(2)O(2) on the electrode surface. A possible application of the system for colorimetric sensing of H(2)O(2) was discussed. PMID:20621819

Nagasaka, Munenari; Yoshida, Kentaro; Sato, Katsuhiko; Hoshi, Tomonori; Anzai, Jun-ichi

2010-08-15

72

Beryllium oxide: a frost-preventing insulator.  

PubMed

A method is suggested of achieving low outdoor radiative losses by low spectral emittance in the atmospheric window of 8-13 microm, which will reduce dew and frost formation on surfaces exposed to the clear sky. The use of this selectively low emittance makes it feasible to use electrically insulating materials. It is argued that lattice-based reststrahlen bands can be exploited for this purpose. The observation is made that hexagonal beryllium oxide has a strong reststrahlen band that covers most of the primary atmospheric window. Results from experiments with polycrystalline samples demonstrate that bulk beryllium oxide is equally effective for dew and frost prevention as glass coated with conducting tin oxide. PMID:19770941

Ribbing, C G

1990-08-15

73

Biocomplexity of Frost-Boil Ecosystems  

NSDL National Science Digital Library

The NSF-funded project seeks to understand the complex linkages between biogeochemical cycles, vegetation, disturbance, and climate across the full summer temperature gradient in the Arctic. Researchers examine the complexity associated with self-organization in frost-boil, complexity associated with interactions between biogeochemical cycles, cryoturbation, and vegetation, and biocomplexity across spatial-temporal scales. The web site includes the project proposal, research objectives, preliminary results, maps, photographs, data sets, and publications.

2003-01-01

74

Genetic engineering: frost damage trial halted.  

PubMed

The University of California at Berkeley has announced the postponement of a planned experiment involving the field testing of bacteria genetically engineered to reduce frost damage to crops. The action came after Jeremy Rifkin, who had earlier filed suit against the National Institutes of Health after its Recombinant DNA Advisory Committee had approved the experiment, threatened to seek a temporary restraining order against the university to halt the experiment. PMID:6578420

Budiansky, S

75

Non-contact frost thickness measurement by using a micro-camera and image processing technology  

Microsoft Academic Search

Frost thickness is a key parameter to examine the effect of frosting or defrosting in refrigeration field, but frost thickness is not easy to measure through traditional methods, for frost is soft and easily to be damaged by heat or pressure. Aim at the problem of frost thickness measurement, a measurement method based on a microscopic image system and image

Dingyuan Wang; Tangfei Tao; Shaoying Kang; Guanghua Xu

2010-01-01

76

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

77

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

PubMed Central

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

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

2015-01-01

78

Laboratory evaluation of the effect of nitric acid uptake on frost point hygrometer performance  

NASA Astrophysics Data System (ADS)

Chilled mirror hygrometers (CMH) are widely used to measure water vapour in the troposphere and lower stratosphere from balloon-borne sondes. Systematic discrepancies among in situ water vapour instruments have been observed at low water vapour mixing ratios (<5 ppm) in the upper troposphere and lower stratosphere (UT/LS). Understanding the source of the measurement discrepancies is important for a more accurate and reliable determination of water vapour abundance in this region. We have conducted a laboratory study to investigate the potential interference of gas-phase nitric acid (HNO3) with the measurement of frost point temperature, and consequently the water vapour mixing ratio, determined by CMH under conditions representative of operation in the UT/LS. No detectable interference in the measured frost point temperature was found for HNO3 mixing ratios of up to 4 ppb for exposure times up to 150 min. HNO3 was observed to co-condense on the mirror frost, with the adsorbed mass increasing linearly with time at constant exposure levels. Over the duration of a typical balloon sonde ascent (90-120 min), the maximum accumulated HNO3 amounts were comparable to monolayer coverage of the geometric mirror surface area, which corresponds to only a small fraction of the actual frost layer surface area. This small amount of co-condensed HNO3 is consistent with the observed lack of HNO3 interference in the frost point measurement because the CMH utilizes significant reductions (>10%) in surface reflectivity by the condensate to determine H2O.

Thornberry, T.; Gierczak, T.; Gao, R. S.; Vmel, H.; Watts, L. A.; Burkholder, J. B.; Fahey, D. W.

2011-02-01

79

Laboratory evaluation of the effect of nitric acid uptake on frost point hygrometer performance  

NASA Astrophysics Data System (ADS)

Chilled mirror hygrometers (CMH) are widely used to measure water vapour in the troposphere and lower stratosphere from balloon-borne sondes. Systematic discrepancies among in situ water vapour instruments have been observed at low water vapour mixing ratios (<5 ppm) in the upper troposphere and lower stratosphere (UT/LS). Understanding the source of the measurement discrepancies is important for a more accurate and reliable determination of water vapour abundance in this region. We have conducted a laboratory study to investigate the potential interference of gas-phase nitric acid (HNO3) with the measurement of frost point temperature, and consequently the water vapour mixing ratio, determined by CMH under conditions representative of operation in the UT/LS. No detectable interference in the measured frost point temperature was found for HNO3 mixing ratios of up to 4 ppb for exposure times up to 150 min. HNO3 was observed to co-condense on the mirror frost, with the adsorbed mass increasing linearly with time at constant exposure levels. Over the duration of a typical balloon sonde ascent (90-120 min), the maximum accumulated HNO3 amounts were comparable to monolayer coverage of the geometric mirror surface area, which corresponds to only a small fraction of the actual frost layer surface area. This small amount of co-condensed HNO3 is consistent with the observed lack of HNO3 interference in the frost point measurement because the CMH utilizes significant reductions (>10%) in surface reflectivity by the condensate to determine H2O.

Thornberry, T.; Gierczak, T.; Gao, R. S.; Vmel, H.; Watts, L. A.; Burkholder, J. B.; Fahey, D. W.

2010-08-01

80

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.

81

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

82

Geophysical Implications of Enceladus' CO2 Frost  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

83

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

84

Risk analysis of first and last frost occurrences in the Central Alborz region, Iran  

NASA Astrophysics Data System (ADS)

Central Alborz is one of the important agricultural regions of Iran. Occurrence of the first frost in fall and the last frost in spring causes damage to the crops in this region every year. Information about the probable dates of frost occurrence helps farmers in preventing or reducing the damages caused by frost. Six stations, with 34 years of daily minimum temperature data, were selected at various elevations. Dates of frost occurrences in three degrees of severity (mild, moderate, and severe) and frost-free periods were obtained for each year. Appropriate distributions were determined for each frost series (dates of frosts and frost-free periods) on the basis of relevant statistical methods. It was found that the Pearson type III distribution was most appropriate. Probability distribution was constructed for each frost series. Frost occurrences up to a given date and maximum lengths of frost-free periods, with their probabilities, were determined. Correlations between the dates of frost occurrence and elevation, and between the maximum lengths of frost-free periods and elevation were identified in some probability levels. Our results show a positive correlation between the frequency of frost and elevation, and a significant negative correlation between the duration of frost-free period and elevation. Frost is more frequent in higher areas. The shortest and the longest frost-free periods occur on top of high mountains and on low altitude areas, respectively.

Rahimi, M.; Hajjam, S.; Khalili, A.; Kamali, G. A.; Stigter, C. J.

2007-03-01

85

Simulated frost effects on cool-season grass carbohydrate levels  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

86

Grammatical Categories in Robert Frost's Blank Verse: A Quantitative Analysis.  

ERIC Educational Resources Information Center

Structural linguistic techniques were utilized to categorize the grammatical elements employed by Robert Frost in 46 blank-verse poems. Nineteen main grammatical categories and 26 verb sub-categories based on distinctive selection criteria were devised to examine the range and distribution of Frost's grammatical patterns. Five control poems by E.

Lyford, Roland Hazen

87

Frost Collection Presented to University of the Incarnate Word  

ERIC Educational Resources Information Center

On April 21, 2004, the Joe L. Frost Children's Play and Play Environments Research Collection was dedicated at the J.E. and L.E. Mabee Library at the University of the Incarnate Word, San Antonio, Texas. This brief article describes the collection and Frost's plans for the future.

Childhood Education, 2004

2004-01-01

88

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

SciTech Connect

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

Eluszkiewicz, J.B.

1993-01-01

89

Mechanism of frost damage to concrete  

NASA Astrophysics Data System (ADS)

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 the contributions of thermal expansion, pore pressure, and crystallization pressure of ice to the strain observed in a mortar during freezing/thawing cycles. Air-entrained mortars contract upon freezing due to the cryo-suction effect, while non-air-entrained mortars expand primarily due to hydraulic pressure. Based on the theory originally proposed by Powers and Helmuth, we show that the poromechanical calculations account quantitatively for the contraction of samples with air entrainment, which is shown to quantitatively account for a reduction of salt scaling damage based on the glue-spall theory. The method of thermoporometry (TPM) that we used to study the pore structure of concrete is also discussed. In a study of ice propagation inside concrete, we re-examined experiments by Helmuth [Proc. 4th Int. Cong. Chem. Cement, NBS Monog. 43, Vol. II (National Bureau of Standards, Washington, D.C., 1962) pp. 855--869] from which he concluded that ice grows in the pores of cement paste under heat-flow control, and that the internal temperature rises to the melting point given by the Gibbs-Thomson equation. Using experimental and computational methods, we find that his conclusions are correct, but the growth rates he reports are misleading. Our experiment reveals the true growth rate, which is about three times smaller than found by Helmuth. The dendritic morphology explains how fast constant growth rates can occur when the interior temperature of the sample is very near the melting point: the temperature at the tip of the dendrite is a few degrees below the melting point, but the liquid behind the tip (between adjacent dendrites) is at the melting point. The implications of this type of growth for frost damage are discussed.

Sun, Zhenhua

90

Comparison of Projection Method in Frost Growth under Natural Convection  

NASA Astrophysics Data System (ADS)

The purpose of this study is to grasp the applicable extent and the general tendency of one dimensional frost growth model. The time change of frost height was calculated numerically using a prediction model with homogeneous and non-homogeneous properties in order to examine the effect of temperature and humidity in the atmosphere on frost phenomenon under the natural convection, and is was compared with the experimental result. The frost height calculated from the homogeneous model was high a little, on the other hand the value evaluated from the non-homogeneous model appeared low. Both models showed approximately a tendency equal to experimental result. Judging from the quantitative evaluation by RMS, the non-homogeneous model was closer to the experimental value, and was undoubtedly predominant. However, the problems are shown. It is necessary to grasp experimentally under the natural convection the distribution of properties in the frost growth direction, which are represented by the frost density, also, it is necessary to confirm the consistency with the calculation result. As for the frost height and density given as an initial value for the calculation, it is necessary to clarify that the value in the natural convection differs from the value in the forced convection.

Shimomura, Nobuo; Seki, Mitsuo; Ohkubo, Hidetoshi

91

[Infrared spectroscopic analysis of Guilin watermelon frost products].  

PubMed

The objective of the present study is to analyze different products of Guilin watermelon frost by Fourier transform infrared spectroscopy (FTIR), second derivative infrared spectroscopy and two-dimensional correlation spectroscopy (2D-IR) under thermal perturbation. The structural information of the samples indicates that samples from the same factory but of different brands had some dissimilarities in the IR spectra, and the type and content of accessories of them were different compared with conventional IR spectra of samples, peaks at 638 and 616 cm(-1) all arise from anhydrous sodium sulfate in watermelon frost spray and watermelon frost capsule; the characteristic absorption peaks of the sucrose, dextrin or other accessories can be seen clearly in the spectra of watermelon frost throat-clearing buccal tablets, watermelon frost throat tablets and watermelon frost lozenge. And the IR spectra of watermelon frost lozenge is very similar to the IR spectra of sucrose, so it can be easily proved that the content of sucrose in watermelon frost lozenge is high. In the 2D-IR correlation spectra, the samples presented the differences in the position, number and relative intensity of autopeaks and correlation peak clusters. Consequently, the macroscopical fingerprint characters of FTIR, second derivative infrared spectra and 2D-IR spectra can not only provide the information about main chemical constituents in medical materials, but also analyze and identify the type and content of accessories in Guilin watermelon frost. In conclusion, the multi-steps IR macro-fingerprint method is rapid, effective, visual and accurate for pharmaceutical research. PMID:23156761

Huang, Dong-lan; Chen, Xiao-kang; Xu, Yong-qun; Sun, Su-qin; Zhou, Qun; Lu, Wen-guan

2012-08-01

92

Modeling and simulation study of the self-discharge in supercapacitors in presence of a blocking layer  

NASA Astrophysics Data System (ADS)

Supercapacitors are promising energy storage devices due to their high life cycle and high power density. However, supercapacitors also known as Electric Double Layer Capacitor (EDLCs) are affected by high leakage or self discharge. The leakage is mainly dominated by redox reactions at the electrode surface through which electrons cross the double layer. Experiments have shown that a very thin blocking layer coating on the electrodes improves the energy storage capability by reducing the leakage, but it reduces the specific capacitance. The detrimental effect of the blocking layer on the capacitance requires the study of the blocking layer thickness' impact on the performance of the supercapacitor. In this work we have developed a mathematical model to study such effects. The model is a combination of simple quantum mechanical and electrochemical phenomena that occur during the self-discharge process. Using the developed model, a computational method was applied to simulate the discharge profile and specific energy in devices with various thicknesses in the blocking layer. The simulation approach can be used to study supercapacitor performances for practical applications.

Tevi, Tete; Takshi, Arash

2015-01-01

93

Synoptic analysis of frost days in Zanjan Province of Iran  

NASA Astrophysics Data System (ADS)

As a general rule it is accepted that every change in the environment is controlled by the changes in the pressure patterns or varying synoptic systems. We are witnessing intensive floods, damaging cold waves, or highly polluted air every year, all of which are related to some extent to the pressure patterns such as intensive cyclones or subsiding anticyclones. The frost days are one of these environmental conditions that are caused by these pressure patterns especially in the case of synoptic frosts. The Zanjan province of Iran with mountainous nature and higher elevations is one of the frost prone regions in the country. Most of the years this region suffers from intensive and damaging frosts such as the one occurred in December 2006 and January 2007. In order to advise planners and users, and lower the damages of such frosts, this study tried to analyze the synoptic origin of the December 2006 frost. To achieve the objective of the study the frost days of the province during months December 2006 and January 2007 were selected. During these months all of the four stations of the Province ( Zanjan, Khorramdarreh, Khodabandeh, and Mahneshan) had experienced sub-zero temperatures. The daily zero GMT surface and 500 hPa. maps of the region were extracted from the National Center of Environmental Protection (NCEP) site for the selected days. The pressure patterns of both levels were analyzed and assigned into different groups. The results showed that the main synoptic patterns responsible for the frosts of the region are the Caspian trough, Siberian high pressure, moving western anticyclones, upper level blockings, and cut off lows. When the Caspian Sea trough deepens it brings the westerly anticyclones to the area. Under its eastward displacement, the Siberian High develops and sends its ridges towards the study region. Some times the upper level blocking of the Siberian area brings the cold air masses to the study region. In general, the development and displacement of both Mediterranean and Caspian troughs control the cold air masses invasion to the Zanjan Province. Therefore it is highly recommended that the users and planners should watch the behavior of these troughs carefully and prepare themselves in advance. Key words: frost days, widespread frosts of Zanjan Province, synoptic analysis of frost days, hazards, environmental hazards.

Alijani, B.; Tagiloo, M.

2010-09-01

94

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 20072009 for\\u000a the 355

Carol K. Augspurger

2011-01-01

95

Relative Humidity Uncertainty Analysis using Dew\\/Frost Point Measurements  

Microsoft Academic Search

analyzing the uncertainty of the individual components, then combining those uncertainties to obtain the total expanded uncertainty. As it applies here, we'll analyze the uncertainties associated with the dew\\/frost point measurement and the air temperature measurement, then combine them to obtain the total expanded uncertainty in RH. In this analysis, we assume manufacturers stated specifications of 0.1C dew\\/frost point accuracy,

Bob Hardy; Daniel Mutter

1998-01-01

96

Frost risk for overwintering crops in a changing climate  

NASA Astrophysics Data System (ADS)

Climate change scenarios predict a general increase in daily temperatures and a decline in snow cover duration. On the one hand, higher temperature in fall and spring may facilitate the development of overwintering crops and allow the expansion of winter cropping in locations where the growing season is currently too short. On the other hand, higher temperatures prior to winter crop dormancy slow down frost hardening, enhancing crop vulnerability to temperature fluctuation. Such vulnerability may be exacerbated by reduced snow cover, with potential further negative impacts on yields in extremely low temperatures. We propose a parsimonious probabilistic model to quantify the winter frost damage risk for overwintering crops, based on a coupled model of air temperature, snow cover, and crop minimum tolerable temperature. The latter is determined by crop features, previous history of temperature, and snow cover. The temperature-snow cover model is tested against meteorological data collected over 50 years in Sweden and applied to winter wheat varieties differing in their ability to acquire frost resistance. Hence, exploiting experimental results assessing crop frost damage under limited temperature and snow cover realizations, this probabilistic framework allows the quantification of frost risk for different crop varieties, including in full temperature and precipitation unpredictability. Climate change scenarios are explored to quantify the effects of changes in temperature mean and variance and precipitation regime over crops differing in winter frost resistance and response to temperature.

Vico, Giulia; Weih, Martin

2013-04-01

97

Delayed Frost Growth on Jumping-Drop Superhydrophobic Surfaces  

SciTech Connect

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

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

2013-01-01

98

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

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

99

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

100

Forecast of Frost Days Based on Monthly Temperatures  

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

101

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

SciTech Connect

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

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

2007-05-15

102

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

103

Influencing of covers (peat, snow mosses) on the frost heave by the example of Yamburg (the North of West Siberia)  

NASA Astrophysics Data System (ADS)

The frost heave is the one of the widespread and intensively influencing on the objects process. It's also one of the reasons of forming the cryogenic relief. Analytics methods and frost heave map composition, which connected with landscape, cryolithology and geology conditions - the most effective decision of this problem. Now a lot of considerable trends were found out in The Bolshezemelskaya tundra, Yamal and Tazovskiy peninsulas, and they have shown the increase of temperature on 0.02 - 0.06 C per one year and about 0,7C per one year in East Siberia. We have studied frost heave in different areas, and calculation of the general frost heave deformation has shown that in West Siberia it's about 40 cm, in East Siberia up to 2m. The Yamburg gas field characterized as the syngenetic type of continuous permafrost area with the sincryogenetic sandshale deposits which are found almost on the all geomorphological levels. This factors are determinates the widespread occurrence of cryolithology factors, especially frost heaving. The frost heave on the Yamburg in the singenetic permafrost happens because of deep seasonal thawing to 1,5m. We have had a set of experiments to determine influencing of peat cover on frost heave. In the laboratory we were modeling conditions of "closed system" with fragmentary freezing. The results have shown that the most influencing cover - peat, while the moss has no affects on the frost heave. The results could be comparing with calculating data which were received for this region, for example in the cold years the peat cover influencing will be lower than in warmer and in the future we could expected the enormous increasing of deformation. Sand deposits which are presents here in itself are not apply to heaving soils, but in case of widespread development of peat and with high dispersion of deposits they are also heaving every season. The maximum ice content was registered in peat or on the contact mineral ground - peat. For the appraisal of experimental data also were done calculations of seasonal frozen layer thickness, in the system sandy clay-clay 2,1m, on the boggy area with peat - 0, 95 m, and with the high thickness of peat on the sandy clay-sand 1m, corresponding to it the frost heaving value will be change, which is confirmed by experiment. These experiments have shown that peat is the most affecting cover on the frost heave and also peat is the most widespread cover in this region. In transition of landscapes including the human intervention most of the natural territorial complexes in tundra interchange to the peats with various thicknesses, therefore it's necessary to pay special attention for interaction peat cover and soils systems and to peat cover influencing for development of cryogenic process.

Ablyazina, D.; Yampolskiy, G.

2009-04-01

104

Frost hardiness of tree species is independent of phenology and macroclimatic niche.  

PubMed

The differences in timing in bud burst between species have been interpreted as an adaptation to late frost events in spring. Thus, it has been suggested that the degree of frost susceptibility of leaves is species-specific and depends on the species' phenology and geographic distribution range. To test for relationships between frost tolerance and phenology as well as between frost tolerance and distribution range across Central European tree species, we studied the frost hardiness of closed buds before bud burst and of freshly opened buds at the time of bud burst. We hypothesized that species with early bud burst and species distributed in eastern and northern areas were more frost tolerant than species with late bud burst and species distributed in western and southern areas. Frost hardiness was estimated by exposing twigs to 11 frost temperatures between -4 degrees Centigrade and -80 degrees Centigrade and by assessing tissue damage by the electrolyte leakage method. In contrast to our hypotheses, neither frost hardiness of closed buds nor frost hardiness of freshly opened buds were related to any variable describing species' macroclimatic niche. Furthermore, frost hardiness of freshly opened buds did not differ among species. Thus, the investigated species with early bud burst take higher risks of frost damage than the species with late bud bursts. These findings indicate that frost hardiness might not play the key role in limiting the geographic distribution ranges previously anticipated. PMID:25740149

Hofmann, M; Bruelheide, H

2015-03-01

105

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

106

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

107

Low frost-point humidity generator. [calibration facility  

NASA Technical Reports Server (NTRS)

A low frost-point humidity generator has been developed at NBS to provide a capability for calibration, testing, and research at very low levels of water vapor content in such gases as atmospheric air, carbon dioxide and nitrogen. The generator produces frost points from -30 to -100 C at ambient pressures from 500 to 200,000 pascals (0.005 to 2 atm.). This is equivalent to mixing ratios of 4 micrograms to 51 grams of water vapor per kilogram of dry air and to vapor pressures of .0014 to 38 pascals. The generated test gas can be fed to a test chamber with independent temperature control between +25 and -100 C. The uncertainty of the frost point in the test chamber is estimated not to exceed 0.05 deg C.

Greenspan, L.

1973-01-01

108

FROST - FREEDOM OPERATIONS SIMULATION TEST VERSION 1.0  

NASA Technical Reports Server (NTRS)

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

Deshpande, G. K.

1994-01-01

109

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

110

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

111

Layers  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

112

Seasonal frost hardiness of Nothofagus solandri seedlings from two altitudinally diverse sites in Canterbury, New Zealand  

Microsoft Academic Search

Seasonal variation in frost hardiness was evaluated in beech (Nothofagus solandri) seedlings from sites in North Canterbury at 460 m near the lower altitude limit, and at 1100 m near timberline. Both 1-. 2-year old seedlings were lifted on five occasions through the year and exposed to a range of controlled frosts. Visual frost damage was measured four weeks later

Dennis H. Greer; Peter Wardle; Rowan p Buxton

1989-01-01

113

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

114

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.

2011-01-01

115

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

116

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 vapour-related phenomena occur and confirm our predictions of frost-flower formation with a series

Worster, M. Grae

117

Microclimate factors influencing the frequency and duration of growth season frost for subalpine plants  

Microsoft Academic Search

The subalpine environment of the Medicine Bow Mountains, Wyoming (USA) is characterized by frost events throughout the summer. As a result, growing season length is difficult to define in terms of frost-free days. For example, such a definition would have limited the 1993 growing season for many plants to only 5 days. The frequency of summertime frost events appeared particularly

Dean N. Jordan; William K. Smith

1995-01-01

118

3D stability analysis of Rayleigh-Bnard convection of a liquid metal layer in the presence of a magnetic fieldeffect of wall electrical conductivity  

NASA Astrophysics Data System (ADS)

Rayleigh-Bnard 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

119

Water frost and ice - The near-infrared spectral reflectance 0.65-2.5 microns. [observed on natural satellites and other solar system objects  

NASA Technical Reports Server (NTRS)

The spectral reflectance of water frost and frost on ice as a function of temperature and grain size is presented with 1-1/2% spectral resolution in the 0.65- to 2.5-micron wavelength region. The well-known 2.0-, 1.65-, and 1.5-micron solid water absorption bands are precisely defined along with the little studied 1.25-micron band and the previously unidentified (in reflectance) 1.04-, 0.90-, and 0.81-micron absorption bands. The 1.5-microns band complex is quantitatively analyzed using a nonlinear least squares algorithm to resolve the band into four Gaussian components as a function of grain size and temperature. It is found that the 1.65-micron component, which was thought to be a good temperature sensor, is highly grain-size dependent and poorly suited to temperature sensing. Another Gaussian component appears to show a dependence of width on grain size while being independent of temperature. The relative apparent band depths are different for frost layers on ice than for thick layers of frost and may explain the apparent band depths seen in many planetary reflectance spectra.

Clark, R. N.

1981-01-01

120

ORIGINAL PAPER Growth and frost hardening of European aspen  

E-print Network

The native European aspen grew faster, whereas hybrid aspen ? aspen frost hardened faster and exhibited of native species, thus threatening their overall fitness (Vanden Broeck et al. 2005). European aspen). It has been demonstrated that hybrid aspen, a man-made cross between European aspen and North American

Paris-Sud XI, Université de

121

Salt Frost Deterioration in Concrete Pavement --Causes and Mitigation  

E-print Network

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

122

Heritability of frost-seeded red clover establishment  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

123

Genetic architecture of winter hardiness and frost tolerance in triticale.  

PubMed

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

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

2014-01-01

124

A Study on the Symbolic Poems of Robert Frost  

Microsoft Academic Search

Symbolism is one of the techniques of expression in poetry. This article makes a careful analysis on the two poems of Robert Frost. He is one of the best poets well-known for the symbolic poems. The poems are saturated with original symbols and deep thought.

Xiaoping Zhou

125

Frost & Sullivan Press Release Published: 14 Dec 2006  

E-print Network

in the Automotive Industry LONDON - December 14, 2006 ­ Frost & Sullivan confers the 2006 Entrepreneurial Company of the Year Award in the automotive industry on Mobileye N.V in recognition of its superior entrepreneurial warning, headway warning and LDW, as well as the video recording option." Market participants

Shashua, Amnon

126

BREEDING FOR IMPROVED FROST-SEEDED RED CLOVER SEEDLING ESTABLISHMENT  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

127

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

128

GIVRE: A Protection Against Frost Deposit on Polar Instruments  

Microsoft Academic Search

The CEA, in coordination with IPEV and LUAN, will prepare an experiment to study frost formation on surfaces in radiative cooling in the winter. This experiment has been shipped to be installed at Concordia before the 2007 winter period. It will be controlled from Concordia winterover personal, through PC server that will locally archive data from WEBcams and several local

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

2007-01-01

129

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 Schrdinger 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

130

Features of frost-affected areas from digital METEOSAT IR images  

NASA Astrophysics Data System (ADS)

Frost is a natural hazard, which may cause significant damage to agriculture depending also on the phenological stage of the affected crops. In this paper, several features of the frost-affected areas are examined by using digital data of METEOSAT IR images. In particular the areal extent of frost is delineated by using the estimated temperature from the raw satellite data. Moreover, since digital METEOSAT IR images are recorded every thirty (30) minutes, it is possible to monitor the changes in the size of the frost-affected areas as well as the fluctuations in frost intensity and severity. The phenomenon is investigated in several regions in Greece.

Dalezios, N. R.; Lavrediadou, E. E.

131

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

SciTech Connect

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

Herkenhoff, K.E.; Murray, B.C. (California Institute of Technology, Pasadena (USA))

1990-08-30

132

Mars south polar spring and summer behavior observed by TES: seasonal cap evolution controlled by frost grain size  

USGS Publications Warehouse

Thermal Emission Spectrometer (TES) observations of the recession phase of Mars' south polar cap are used to quantitatively map this recession in both thermal and visual appearance. Geographically nonuniform behavior interior to the cap is characterized by defining several small regions which exemplify the range of behavior. For most of the cap, while temperatures remain near the CO2 frost point, albedos slowly increase with the seasonal rise of the Sun, then drop rapidly as frost patches disappear over a period of ?20 days. A Cryptic region remains dark and mottled throughout its cold period. TES observations are compared with first-order theoretical spectra of solid CO2 frost with admixtures of dust and H2O. The TES spectra indicate that the Cryptic region has much larger grained solid CO2 than the rest of the cap and that the solid CO2 here may be in the form of a slab. The Mountains of Mitchel remain cold and bright well after other areas at comparable latitude, apparently as a result of unusually small size of the CO2 frost grains; we found little evidence for a significant presence of H2O. Although CO2 grain size may be the major difference between these regions, incorporated dust is also required to match the observations; a self-cleaning process carries away the smaller dust grains. Comparisons with Viking observations indicate little difference in the seasonal cycle 12 Martian years later. The observed radiation balance indicates CO2 sublimation budgets of up to 1250 kg m?2. Regional atmospheric dust is common; localized dust clouds are seen near the edge of the cap prior to the onset of a regional dust storm and interior to the cap during the storm.

Kieffer, Hugh H.; Titus, Timothy N.; Mullins, Kevin F.; Christensen, Philip R.

2000-01-01

133

Large quasi-circular features beneath frost on Triton  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

134

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.

135

Introduction Winter colds, spring frosts and summer droughts  

E-print Network

Introduction Winter colds, spring frosts and summer droughts have been acknowledged as important (Áèòâèíñêàñ 1974, Áèòâèíñêàñ 1984), while the impact of sum- mer droughts have acquired greater attention only was noticed later (Bukantis et al. 2001). These trends and frequent intensive droughts were established also

136

Feeding value of frost-damaged soybeans for lambs.  

PubMed

Three experiments were conducted to determine the relative feeding value of frost-damaged soybeans (FDS) for ruminants. Frost-damaged soybean ether-extract content was variable and differed (P less than .05) from mature soybeans. Isonitrogenous supplementation of corn silage diets with soybean meal (SBM), SBM+soybean oil (SBO), mature raw soybeans (MSB), and FDS was compared in sheep. Acid detergent fiber and apparent N digestion were lower (P less than .001) for supplements containing oil. Nitrogen retention was reduced (P less than .07) only for raw soybean supplements. Ruminal NH3 N and branched-chain VFA concentrations differed (P less than .01) between SBM and supplements containing oil. Maximum tolerable inclusion level of FDS in corn silage diets was tested in wethers using diets containing 0, 7, 14, or 21% FDS. Dry matter and ADF digestibility declined linearly (P less than .01) with increasing dietary FDS. Ether extract digestibility was unchanged due to treatment, but GE digestibility decreased quadratically (P less than .01). The most pronounced decline in GE digestibility occurred when FDS increased from 14 to 21% of the diet. The effects of FDS on corn silage utilization were similar to MSB effects. Oil content and antinutritional factors contributed to detrimental effects. Frost-damaged soybeans should not exceed 14% of corn silage diets fed to growing wethers. PMID:1322878

Loesche, J A; Pritchard, R H; Reecy, J M; Wicks, Z W

1992-07-01

137

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

SciTech Connect

A new balloon borne instrument called a backscattersonde has been used to study Polar Stratospheric Clouds (PSCs) at Alert, NWT (82{degree}N, 61.5{degree}W) during January and February of 1989. These measurements were supplemented with frost point, ozone and nitric acid vapor soundings. Type I PSCs were observed at temperatures and pressures generally consistent with present vapor pressure models of HNO{sub 3}/H{sub 2}O condensate, but some noticeable inconsistencies exist. It is suggested that these apparent problems, as well as some characteristic peculiarities in the PSC profiles, could be explained by the presence of two phases of the HNO{sub 3}/H{sub 2}O condensate.

Rosen, J.M. (Univ. of Wyoming, Laramie, (USA)); Oltmans, S.J. (NOAA, Boulder, CO (USA)); Evans, W.F.

1989-08-01

138

Laboratory-produced sorted patterned ground by repeated frost heaving  

NASA Astrophysics Data System (ADS)

Sorted patterned ground is ubiquitous where gravelly fine soils experience freeze-thaw cycles, but laboratory models have rarely been successful in reproducing such patterns. Here we report the first result of an attempt to reproduce miniature sorted patterns by repeating needle-ice formation, which simulates frost sorting in regions dominated by diurnal freeze-thaw cycles. The laboratory models (505035 cm) consist of near-saturated volcanic fine soil topped by small stones with varying sizes, SSG (~8 mm), SG (~16 mm), MG (~19 mm) and LG (~26.5 mm), and varying surface coverage (20, 40 and 60%). The stones were white-painted and placed in a grid on the surface. These models were subjected to 10-20 temperature excursions between 10C and -5C in 12 hours. The evolution of surface patterns were visually traced by vertical and oblique photogrammetry taken at intervals of 10 minutes. The time series of pictures were compiled to produce animations. In addition, a data logging system continuously monitored vertical soil displacements, soil temperatures and moistures at different depths. All experimental runs displayed needle ice formation (2-3 cm in height) and resulting displacement of stones. Differential frost heave took place between the soil domains and stones, such that the soils tend to heave faster and higher than the stones. The preferential and higher heaving led to outward movements of the soil domains after cycles of frost heave and thaw settlement, and subsequently to concentration of the stones. In plan view, smaller stones (SSG and SG) showed relatively fast (1-2 mm/cycle) and long-lasting (up to 20 cycles) movements. In contrast, larger stones (MG and LG) displaced rapidly (1-2 mm/cycle) in the first 5 cycles, but thereafter they were stabilized. The lowest stone coverage (20%) produced stone islands at horizontal intervals of about 12 cm, whereas higher coverage (40%) resulted in a stone circle-island complex with a mean diameter of 13 cm. The latter geometry appears to represent incipient sorted circles, dimensions of which are comparable to those observed in the field. The experiments imply that needle-ice activity induces frost sorting rapidly, which potentially allows the formation of stone islands and incipient sorted circles within one or a few years, but more regular circles may need hundreds of diurnal frost heave cycles (i.e., decade-to-century time scales).

Yamagishi, Chizuru; Matsuoka, Norikazu

2013-04-01

139

[Research on quality changes in ginseng stems and leaves before and after frost].  

PubMed

The present study is to investigate the quality changes of ginseng stems and leaves before and after frost. The contents changes of ginsenoside, free amino acid, and total phenolic compounds, as well as DPPH radical scavenging effect before and after frost were measured. The content of 9 ginsenoside monomer in ginseng stems was decreased except for Rg, and Re after frost, but in ginseng leaves was all decreased. The total content of amino acids was decreased in ginseng stems after frost, while increased in ginseng leaves. The content of phenolic compounds in ginseng stems and leaves were both decreased after frost while the ability of DPPH radical scavenging was improved. The factor of frost has great impact on the quality of ginseng stems and leaves. PMID:25509298

Zhao, Yan; Ma, Shuang; Cai, En-Bo; Liu, Shuang-Li; Yang, He; Zhang, Lian-Xue; Wang, Shi-Jie

2014-08-01

140

Assessing the Value of Frost Forecasts to Orchardists: A Dynamic Decision-Making Approach  

Microsoft Academic Search

The methodology of decision analysis is used to investigate the economic value of frost (i.e., minimum temperature) forecasts to orchardists. First, the fruit-frost situation and previous studies of the value of minimum temperature forecasts in this context are described. Then, after a brief overview of decision analysis, a decision-making model for the fruit-frost problem is presented. The model involves identifying

Richard W. Katz; Allan H. Murphy; Robert L. Winkler

1982-01-01

141

Laboratory Evaluation of the Effect of HNO3 Uptake on Frost Point Hygrometer Measurement of Water Vapor under UT/LS Conditions  

NASA Astrophysics Data System (ADS)

Chilled mirror hygrometers (CMH) are widely used to measure water vapor in the troposphere and lower stratosphere from balloon-borne sondes. Systematic discrepancies among in situ water vapor instruments have been observed at low water vapor mixing ratios (< 5 ppm) in the upper troposphere and lower stratosphere (UT/LS). Understanding the source of the measurement discrepancies is important for a more accurate and reliable determination of water vapor abundance in this region. We have conducted a laboratory study to investigate the potential interference of gas-phase nitric acid (HNO3) with the measurement of frost point temperature, and consequently the water vapor mixing ratio, determined by CMH under conditions representative of operation in the UT/LS. No detectable interference in the measured frost point temperature was found for HNO3 mixing ratios of up to 2 ppb for exposure times up to 150 minutes. HNO3 was observed to co-condense on the mirror frost, with the adsorbed mass increasing linearly with time at constant exposure levels. Over the duration of a typical balloon sonde ascent (90-120 min), the maximum accumulated HNO3 amounts were comparable to monolayer coverage of the geometric mirror surface area, which likely corresponds to small fractional coverage of the actual frost layer surface area. This small amount of co-condensed HNO3 is consistent with the observed lack of HNO3 interference in the frost point measurement because the CMH utilizes significant reductions (>10%) in surface reflectivity by the condensate for the determination of H2O.

Thornberry, T.; Gierczak, T.; Gao, R.; Voemel, H.; Watts, L.; Burkholder, J. B.; Fahey, D. W.

2010-12-01

142

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

143

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 ?5.8C. Reproductive shoots, however, remained supercooled and ice free down to a range of ?7.2 to ?18.2C or even below ?22C, 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 ?10C 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; Briceo, Vernica F.; Wagner, Johanna; Neuner, Gilbert

2014-01-01

144

Soils and frost boil ecosystems across the North American Arctic Transect  

Microsoft Academic Search

We studied soil properties of frost boils at nine zonal-vegetation locations across the North American Arctic Transect (NAAT) in order to better understand arctic soils and their interaction with other biogeophysical components of frost boil ecosystems. Soil genetic horizons were analyzed for particle size, pH, electrical conductivity, total organic carbon (OC) and nitrogen (N), bulk density and volumetric water content.

G. J. Michaelson; C. L. Ping; H. Epstein; J. M. Kimble; D. A. Walker

2008-01-01

145

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. 10N. The frost

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

2000-01-01

146

Sensitivity of frost occurrence to temperature variability in the European Alps  

Microsoft Academic Search

In this study, we set out to investigate the linkage of frost frequency to monthly mean temperature and its sensitivity to temperature changes. According to other related studies, the linkage between frost frequency and monthly mean temperature is approximated month per month via hyperbolic tangent functions. These models are validated using three validation experiments including split sample tests and temporal

Ingeborg Auer; Christoph Matulla; Reinhard Bhm; Markus Ungersbck; Maurizio Maugeri; Teresa Nanni; Rossella Pastorelli

2005-01-01

147

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

148

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

E-print Network

Heave Engine Frost heave is a common environmental process in which the freezing of water into ice can ABSTRACT I describe a simple "heat-engine" derivation of the maximum overburden pressure that can an idealized frost heave "engine," together with the maximum thermodynamic efficiency of any heat engine, one

Libbrecht, Kenneth G.

149

[Association of microsatellite loci alleles of the group-5 chromosomes with frost resistance of winter wheat].  

PubMed

Analysis of frost resistance and microsatellite analysis of the group-5 chromosomes were performed on parental varieties and recombinant-inbred lines F7 Luzanovka odesskaya/Odesskaya krasnokolosaya. Allelic differences for Xcfd7-5B Xwmc415-5B and Xgwm 182-5D microsatellite loci were associated with the level of frost resistance of the lines. PMID:24228492

Halaieva, M V; Fa?t, V I; Chebotar, S V; Halaiev, O V; Syvolap, Iu M

2013-01-01

150

Heat and mass transfer in frost and ice, packed beds, and environmental discharges  

Microsoft Academic Search

This volume covers issues related to heat and mass transfer in frost and ice packed beds, and environmental discharges. Topics include: measurements of the effects of frost on heat exchanger performance, a study of steam zone behavior in porous media, heat and mass transfer by natural convection, and a review of selected programs for atmospheric dispersion.

R. V. Arimilli; D. E. Beasley; S. Sengupta; S. A. Sherif; R. G. Watts

1990-01-01

151

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

E-print Network

9/7/2004 Penumadu, Prashant, and Frost. EM-2004 1 A VIRTUAL TRIAXIAL COMPRESSION TEST SIMULATOR Dayakar Penumadu: Department of Civil and Environmental Engineering, University of Tennessee, Knoxville. #12;9/7/2004 Penumadu, Prashant, and Frost. EM-2004 2 Presentation Outline Concept of Virtual

Prashant, Amit

152

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

153

The effects of design and operating factors on the frost growth and thermal performance of a flat plate fin-tube heat exchanger under the frosting condition  

Microsoft Academic Search

An experimental study of the effects of various factors (fin pitch, fin arrangement, air temperature, air humidity, and air\\u000a velocity) on the frost growth and thermal performance of a fin-tube heat exchanger has been conducted under the frosting condition.\\u000a It is found that the thermal performance of a heat exchanger is closely related to the blockage ratio of the air

Kwan-Soo Lee; Woo-Seung Kim

1999-01-01

154

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

155

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

156

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

157

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

158

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

PubMed Central

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

159

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

160

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

SciTech Connect

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

Rosen, J.M.; Kjome, N.T. (Univ. of Wyoming, Laramie (USA)); Oltmans, S.J. (NOAA CMDL, Boulder, CO (USA))

1991-02-01

161

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

162

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

163

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

164

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 ...

165

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

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

166

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

167

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

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

168

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

E-print Network

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

Orradottir, Berglind

2002-01-01

169

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

170

Eye color Predicts Disagreeableness in North Europeans: Support in Favor of Frost (2006)  

Microsoft Academic Search

The current study investigates whether eye color provides a marker of Agreeableness in North Europeans. Extrapolating from\\u000a Frosts (2006) research uncovering an unusually diverse range of hair and eye color in northern Europe, we tested the hypothesis that light\\u000a eyed individuals of North European descent would be less agreeable (a personality marker for competitiveness) when compared\\u000a to their dark eyed

Elliroma Gardiner; Chris J. Jackson

2010-01-01

171

The seasonal course of frost resistance in some New Zealand pteridophytes  

Microsoft Academic Search

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

Peter Bannister

1984-01-01

172

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

1960-01-01

173

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

174

Seasonal polar carbon dioxide frost on Mars: CO2 mass and columnar thickness distribution  

Microsoft Academic Search

Conclusions are drawn about the column density (g\\/cm2), spatial extent, and mass of the seasonal carbon dioxide frost on the poles of Mars as a function of time utilizing data from the 2001 Mars Odyssey Gamma Ray Spectrometer (GRS). Quantification of these CO2 values is achieved by observing attenuation effects of the surface-emitted hydrogen gamma ray flux as the frost

N. J. Kelly; W. V. Boynton; K. Kerry; D. Hamara; D. Janes; R. C. Reedy; K. J. Kim; R. M. Haberle

2006-01-01

175

Frost flower surface area and chemistry as a function of salinity and temperature  

Microsoft Academic Search

Frost flowers play a role in air-ice exchange in polar regions, contribute to tropospheric halogen chemistry, and affect ice core interpretation. Frost flowers were observed and collected on the Hudson Bay in March 2008. Their specific surface area (SSA) was measured using CH4 adsorption at 77 K. The Brunauer-Emmett-Teller analysis produced SSA values between 63 and 299 cm2 g?1 (mean

Rachel W. Obbard; Howard K. Roscoe; Eric W. Wolff; Helen M. Atkinson

2009-01-01

176

SOIL MOVEMENT BY FROST IN THE HEX RIVER MOUNTAINS, WESTERN CAPE, SOUTH AFRICA  

Microsoft Academic Search

Diurnal frost processes are known to be important agents of soil disturbance and sediment transport. In this paper the role of diurnal frost processes on sediment transport in two areas of the Western Cape mountains is investigated. Sites were established to monitor differential heave, vertical movement profiles and downslope movement rates of surface materials.The sandy soils at Waaihoek Peak (18001900m

J. C. BOELHOUWERS

1997-01-01

177

Observation of compensation effects during the thermal dissolution of aluminum oxide layers on tungsten and molybdenum <111> and on tungsten ?110? in the presence of electric fields  

NASA Astrophysics Data System (ADS)

Aluminum oxide layer dissolution was studied between 700 and 1200 K in the substrate areas of W<111>, Mo<111>, and on W{110} by means of FEM. Varying the electric field strength, F, between +45 and {+105 MV}/{cm}, two types of dissolution could be observed: dissolution by surface diffusion (low F's) and dissolution by ion desorption (high F's). It is assumed that aluminum suboxides preferentially AlO are involved in the dissolution processes. The preexponential factors, AF, of an Arrhenius-Frenkel type equation were measured as a function of F. The field dependence of AF is determined by the dissolution mechanism: (a) dissolution by diffusion: log A 0F = log A 00 - {??F}/{2.3k ?T } (? ? molecular dipole moment, ?T ? isokinetic for W<111>, log A00 = - 6.0 and ?T = 940 K; for Mo<111>, log A00 = - 3.1 and ?T = 860 K; and (b) dissolution by ion desorption: log A +F = log A +0 + {n {3}/{2}e {3}/{2}F {1}/{2}}/{2.3k ?T }; for A+0 = - 22 and ?T = 1200 K; for W<111>, log A+0 = - 21 and ?T = 1200 K. Using earlier proposed safeguards, isokinetic relationships (compensation effects) could be established for each of the two dissolution processes. The coordinates of the isokinetic points have the following average values: log?A 00 = 2.5 and ?T = 920 K for diffusion; log?A +0 = - 1 and ?T = 1240 K for ion desorption. The entropy changes (at T = ?T , zero field strength, and unit pressure) for the phase changes: solid layer ? diffusion layer and solid layer ? ion gas, are of the order of {30 cal}/{K} mol and {90 cal}/{K} mol, respectively. The two dissolution mechanisms can be described by the following Arrhenius-Frenkel type equations: ? 0F = ?A 00exp[ {- (E 00 + ??F) }/{k ?T }] exp[( {E 00 + ??F) }/{kT}] for diffusion and ? +F = ?A +0exp[ {- (E +0 - n {3}/{2}e {3}/{2}F {1}/{2}) }/{k ?T }] exp[( {E +0 - n {3}/{2}e {3}/{2}F {1}/{2}) }/{kT}] for ion desorption.

Vanselow, R.; Pederson, L. R.

1984-05-01

178

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

179

Frost features in soil thin sections as a tool for Holocene reconstruction: a study case from the Northern Apennines  

NASA Astrophysics Data System (ADS)

The study of Holocene paleosols can be difficult in many cases, since soil features are usually much less expressed than in older paleosols and the ability to detect single genetic phases is much impaired. Frost action, a key diagnostic feature in past climate reconstructions, is not exempt to this rule, and can sometimes remain undetected at the macroscopic scale. In such cases micromorphology can be one of great use, since it raises the resolution of our observations allowing us to identify some of the less visible features. The northern slope of Mt. Cusna (2121 m a.s.l.) in the Northern Apennines is characterized by the presence of a paleosurface formed since the end of the last glacial period. Four soil profiles related to a morphologically flat area inside the paleosurface (at around 1760 m a.s.l.) were described and sampled for bulk and micromorphological analyses. Field descriptions and bulk analyses indicated the presence of two main soil units. The upper unit showed the structure of a colluvial deposit interested by a weak pedogenesis. The lower unit was composed by a truncated paleosol with strong evidence of clay illuviation. At the top of the lower unit, a blackish organic horizon poor in coarse particles and without apparent structure was found. At the microscopic level the microstructure of this blackish horizon, composed by fine (40-80 ?m) rounded granules, was interested by a pattern of parallel-perpendicular planar voids, which can be interpreted as the result of frost action. Moreover, in one profile they were expressed enough to form a secondary angular blocky structure, and in another profile a series of vertical fissures a few millimeters wide was also found at the top of the blackish horizon. These features weren't identified in any of the other horizons of the four described profiles. The micromorphological characteristics of these buried organic levels, coupled with the paleoenvironmental context of the profiles, allowed to interpret these horizons as the results of an independent pedogenetic phase. In fact, in mountain environments accumulation of organic matter at the soil surface without significant development is a likely sign of a period of climatic recrudescence. The presence of frost features clearly confirms this hypothesis. The absence of frost features both in the deeper paleosol unit and in the colluvium above suggests two things: first, that this period can be viewed as a climatic recrudescence of the previous one, during which a temperate forest paleosol was formed. Second, that temperatures were probably also colder than present, which implies a successive warming. Radiocarbon dating from one of the profiles puts the formation of the blackish horizon, and thus the period of climatic recrudescence, somewhere between the boundary Middle-Late Holocene and the Little Ice Age. This is consistent with the Holocene climatic fluctuations attested for Northern Italy, which describe the Late Holocene as an unstable phase of colder periods.

Stefano Mariani, Guido; Compostella, Chiara; Trombino, Luca

2014-05-01

180

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

181

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

182

Current and emerging screening methods to identify post-head-emergence frost adaptation in wheat and barley.  

PubMed

Cereal crops can suffer substantial damage if frosts occur at heading. Identification of post-head-emergence frost (PHEF) resistance in cereals poses a number of unique and difficult challenges. Many decades of research have failed to identify genotypes with PHEF resistance that could offer economically significant benefit to growers. Research and breeding gains have been limited by the available screening systems. Using traditional frost screening systems, genotypes that escape frost injury in trials due to spatial temperature differences and/or small differences in phenology can be misidentified as resistant. We believe that by improving techniques to minimize frost escapes, such 'false-positive' results can be confidently identified and eliminated. Artificial freezing chambers or manipulated natural frost treatments offer many potential advantages but are not yet at the stage where they can be reliably used for frost screening in breeding programmes. Here we describe the development of a novel photoperiod gradient method (PGM) that facilitates screening of genotypes of different phenology under natural field frosts at matched developmental stages. By identifying frost escapes and increasing the efficiency of field screening, the PGM ensures that research effort can be focused on finding genotypes with improved PHEF resistance. To maximize the likelihood of identifying PHEF resistance, we propose that the PGM form part of an integrated strategy to (i) source germplasm;(ii) facilitate high throughput screening; and (iii) permit detailed validation. PGM may also be useful in other studies where either a range of developmental stages and/or synchronized development are desired. PMID:22888127

Frederiks, T M; Christopher, J T; Harvey, G L; Sutherland, M W; Borrell, A K

2012-09-01

183

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

184

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

PubMed

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

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

2014-10-01

185

TuBaFrost: European virtual tumor tissue banking.  

PubMed

TuBaFrost is a consortium responsible for the task to create a virtual European human frozen tumor tissue bank, composed of high quality frozen tumor tissue collections with corresponding accurate diagnosis stored in European cancer centers and universities, searchable on the Internet, providing rules for access and use and a code of conduct to comply with the various legal and ethical regulations in European countries. Such infrastructure would enlarge tissue availability and accessibility in large amounts of specified or even rare tumor samples. Design of an infrastructure for European residual tissue banking with the described characteristics, clear focus points emerge that can be broken down in dedicated subjects: (1) standardization and quality assurance (QA) to avoid inter-institute quality variation; (2) law and ethics enabling exchange of tissue samples possible between institutes in the different European countries, where law and ethics are characterized by a strong variability; (3) rules for access, with sufficient incentives for collectors; (4) central database application containing innovations on search and selection procedures; (5) support when needed with histology images; and (6) Internet access to search and upload, with in addition a solid website giving proper information on the procedures, intentions and activities not only to the scientific community, but also to the general public. One consortium decision, part of the incentives for collectors, had major impact on the infrastructure; custodianship over the tissues as well as the tissues stay with the collector institute. Resulting in specimens that are not given to an organization, taking decisions on participation of requests, but instead the local collected tissues stay very easy to access by the collector and allows autonomous negotiation between collector and requestor on cooperation, coauthorship in publication or compensation in costs. Thereby, improving availability of large amounts of high quality samples of a highly specified or rare tumor types and contact opportunities for cooperation with other institutes. PMID:17163156

Riegman, P H J; Oomen, M H A; Dinjens, W N M; Oosterhuis, J W; Lam, K H; Spatz, A; Ratcliffe, C; Knox, K; Mager, R; Kerr, D; Pezzella, F; Van Damme, B; Van De Vijver, M; Van Boven, H; Morente, M M; Alonso, S; Kerjaschki, D; Pammer, J; Lpez-Guerrero, J A; Llombart-Bosch, A; Carbone, A; Gloghini, A; Teodorovic, I; Isabelle, M; Passioukov, A; Lejeune, S; Therasse, P; Van Veen, E B

2006-01-01

186

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

187

The barley Frost resistance-H2 locus.  

PubMed

Frost resistance-H2 (Fr-H2) is a major QTL affecting freezing tolerance in barley, yet its molecular basis is still not clearly understood. To gain a better insight into the structural characterization of the locus, a high-resolution linkage map developed from the Nure Tremois cross was initially implemented to map 13 loci which divided the 0.602 cM total genetic distance into ten recombination segments. A PCR-based screening was then applied to identify positive bacterial artificial chromosome (BAC) clones from two genomic libraries of the reference genotype Morex. Twenty-six overlapping BACs from the integrated physical-genetic map were 454 sequenced. Reads assembled in contigs were subsequently ordered, aligned and manually curated in 42 scaffolds. In a total of 1.47 Mbp, 58 protein-coding sequences were identified, 33 of which classified according to similarity with sequences in public databases. As three complete barley C-repeat Binding Factors (HvCBF) genes were newly identified, the locus contained13 full-length HvCBFs, four Related to AP2 Triticeae (RAPT) genes, and at least five CBF pseudogenes. The final overall assembly of Fr-H2 includes more than 90 % of target region: all genes were identified along the locus, and a general survey of Repetitive Elements obtained. We believe that this gold-standard sequence for the Morex Fr-H2 will be a useful genomic tool for structural and evolutionary comparisons with Fr-H2 in winter-hardy cultivars along with Fr-2 of other Triticeae crops. PMID:24442711

Pasquariello, Marianna; Barabaschi, Delfina; Himmelbach, Axel; Steuernagel, Burkhard; Ariyadasa, Ruvini; Stein, Nils; Gandolfi, Francesco; Tenedini, Elena; Bernardis, Isabella; Tagliafico, Enrico; Pecchioni, Nicola; Francia, Enrico

2014-03-01

188

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

189

Community impacts of mid-May frost event during an anomalously warm spring  

NASA Astrophysics Data System (ADS)

Global land and ocean surface temperatures of 2010 have gone on record as one of the warmest of the last 131 years. In the northeastern US extraordinarily warm spring temperatures were recorded, averaging +3 C above the long term mean, causing very early leaf development. However, the entire northeastern US region was hit by a severe frost event. Leveraging the coincidence of an anomalously warm spring and a late spring frost event we assess species specific responses of these combined extremes for three northern hardwood species(sugar maple, American beech, yellow birch) across an elevational gradient. We integrated ground observations with satellite and near-surface remote sensing data to address the following questions: 1) How did different species respond to a gradient in altitude / freezing temperatures? 2) How does phenological strategy influence this response? 3) To what extent were regional effects measurable? 4) How did the late spring frost event alter the carbon balance of a northern hardwood forest? 5) Finally, what changes do we foresee in community ecology? Our results show an early onset for all species, triggered by the anomalously warm spring. However, the three species responded differently to a late spring frost event. Where both yellow birch and American beech remained largely unaffected by frost, by comparison, sugar maple showed severe frost damage with increasing altitude resulting in leaf loss and delayed canopy development. Conservative estimates of gross carbon exchange losses due to the frost event ranged from 63 g C m-2 to 156 g C m-2, or ~5% to ~13 % of the annual gross carbon exchange of a northern hardwood forest. Our results suggest that the additional pressure on forest succession at high altitude range margins due to late spring frost events may provide a competitive advantage for yellow birch and American beech, at the expense of sugar maple. Consequently, a late spring frost does not only affect the short term carbon balance but has the potential to alter forest composition, ecosystem function and long term biosphere-atmosphere interactions.

Hufkens, K.; Sonnentag, O.; Keenan, T. F.; Richardson, A. D.; Melaas, E. K.; Bailey, A.; O'Keefe, J.; Friedl, M. A.

2011-12-01

190

Future Bloom and Blossom Frost Risk for Malus domestica Considering Climate Model and Impact Model Uncertainties  

PubMed Central

The future bloom and risk of blossom frosts for Malus domestica were projected using regional climate realizations and phenological (?=?impact) models. As climate impact projections are susceptible to uncertainties of climate and impact models and model concatenation, the significant horizon of the climate impact signal was analyzed by applying 7 impact models, including two new developments, on 13 climate realizations of the IPCC emission scenario A1B. Advancement of phenophases and a decrease in blossom frost risk for Lower Saxony (Germany) for early and late ripeners was determined by six out of seven phenological models. Single model/single grid point time series of bloom showed significant trends by 20212050 compared to 19712000, whereas the joint signal of all climate and impact models did not stabilize until 2043. Regarding blossom frost risk, joint projection variability exceeded the projected signal. Thus, blossom frost risk cannot be stated to be lower by the end of the 21st century despite a negative trend. As a consequence it is however unlikely to increase. Uncertainty of temperature, blooming date and blossom frost risk projection reached a minimum at 20782087. The projected phenophases advanced by 5.5 d K?1, showing partial compensation of delayed fulfillment of the winter chill requirement and faster completion of the following forcing phase in spring. Finally, phenological model performance was improved by considering the length of day. PMID:24116022

Hoffmann, Holger; Rath, Thomas

2013-01-01

191

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

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

192

Environmental controls of frost cracking revealed through in situ acoustic emission measurements in steep bedrock  

NASA Astrophysics Data System (ADS)

Frost cracking, the breakdown of rock by freezing, is one of the most important mechanical weathering processes acting on Earth's surface. Insights on the mechanisms driving frost cracking stem mainly from laboratory and theoretical studies. Transferring insights from such studies to natural conditions, involving jointed bedrock and heterogeneous thermal and hydrological properties, is a major challenge. We address this problem with simultaneous in situ measurements of acoustic emissions, used as proxy of rock damage, and rock temperature/moisture content. The 1 year data set acquired in an Alpine rock wall shows that (1) liquid water content has an important impact on freezing-induced rock damage, (2) sustained freezing can yield much stronger damage than repeated freeze-thaw cycling, and (3) that frost cracking occurs over the full range of temperatures measured extending from 0 down to -15C. These new measurements yield a slightly different picture than previous field studies where ice segregation appears to play an important role.

Girard, Lucas; Gruber, Stephan; Weber, Samuel; Beutel, Jan

2013-05-01

193

Bacterial Ice Nucleation: A Factor in Frost Injury to Plants 1  

PubMed Central

Heterogeneous ice nuclei are necessary, and the common epiphytic ice nucleation active (INA) bacteria Pseudomonas syringae van Hall and Erwinia herbicola (Lhnis) Dye are sufficient to incite frost injury to sensitive plants at ?5C. The ice nucleation activity of the bacteria occurs at the same temperatures at which frost injury to sensitive plants occurs in nature. Bacterial ice nucleation on leaves can be detected at about ?2C, whereas the leaves themselves, i.e. without INA bacteria, contain nuclei active only at much lower temperatures. The temperature at which injury to plants occurs is predictable on the basis of the ice nucleation activity of leaf discs, which in turn depends on the number and ice nucleation activity of their resident bacteria. Bacterial isolates which are able to incite injury to corn at ?5C are always active as ice nuclei at ?5C. INA bacteria incited frost injury to all of the species of sensitive plants tested. PMID:16662618

Lindow, Steven E.; Arny, Deane C.; Upper, Christen D.

1982-01-01

194

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

195

Soils and frost boil ecosystems across the North American Arctic Transect  

NASA Astrophysics Data System (ADS)

We studied soil properties of frost boils at nine zonal-vegetation locations across the North American Arctic Transect (NAAT) in order to better understand arctic soils and their interaction with other biogeophysical components of frost boil ecosystems. Soil genetic horizons were analyzed for particle size, pH, electrical conductivity, total organic carbon (OC) and nitrogen (N), bulk density and volumetric water content. Surface soils (0-5 cm) across frost boil patterns were analyzed for of pH, OC, water content, extractable N and P, and exchangeable K, Ca and Na. Our results revealed that soil texture, pH, EC, P, Na and Ca contents are strongly influenced by local parent materials. Soil pH was acidic in the north going to alkaline in the midtransect and then again back to acidic in the south. Simple correlations between soil analytical data and observed frost boil properties across the NAAT support and are consistent with the laboratory and theoretical-conceptual models of pattern ground dynamics that have been developed by others. Soil water related well to texture. Soil horizon %OC and profile OC stocks under the pattern corresponded well to biomass and frost heave, respectively. Also soil water was closely related to biomass and heave. Nutrients in surface soils at sites corresponded to OC stocks. An interaction between soil water and segregation of Na and Ca between the pattern and interpattern was found for locations with high cation availability. At these sites, chemical as well as physical disruption of the pattern area could affect plant establishment. Overall there was a good linkage between properties relating to frost boil pattern dynamics and soil biogeochemical properties. Our study offers insight into the important process of cryoturbation for carbon sequestration in Gelisols across the Arctic.

Michaelson, G. J.; Ping, C. L.; Epstein, H.; Kimble, J. M.; Walker, D. A.

2008-09-01

196

Presence Service in IMS  

PubMed Central

This paper describes the presence service, which is located in the IP multimedia subsystem. This service allows making many applications for different groups of people. The paper describes differences between a network without the service and with the service. The biggest change is an increased number of transmitted messages. The presence uses some part of the IP multimedia subsystem control layer, which is shown in communication between the user and the server. The paper deals with the number of generated messages depending on the behaviour of the users. This is described by a mathematical model using discrete Markov chains. PMID:23970836

Petras, David

2013-01-01

197

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

198

Moving Frost Hardy Genes From Wild to Cultivated Potatoes. Use of Precise Screening Tools to Make Real Progress  

Technology Transfer Automated Retrieval System (TEKTRAN)

The common cultivated species Solanum tubrosum is frost sensitive and is killed at temperatures below -2.5C. It has been estimated that by increasing frost hardiness by 12 C one can expect an increase in potato yield by 26 to 40% in the Altiplano (Peru and Bolivia) covering 63,000 ha. of potatoes....

199

A nano-frost array technique to prepare nanoporous PVDF membranes  

NASA Astrophysics Data System (ADS)

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

Lee, Min Kyung; Lee, Jonghwi

2014-07-01

200

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

201

Satellite prediction of spring frost impacts on vegetation growth and productivity within the conterminous US  

NASA Astrophysics Data System (ADS)

Spring temperatures strongly influence land surface phenology, including budburst and growing season onset, flowering date, and crop planting period. Recent increases in spring temperatures coincide with earlier and longer non-frozen season trends over the conterminous US and coincide with generally earlier spring canopy onset and annual productivity increases. However, earlier spring onset increases risk of frost damage, with potential negative impacts to productivity. These effects are spatially and temporally heterogeneous, while the occurrence and regional impact of frost events are difficult to monitor from in situ station networks. To enhance regional risk assessment and monitoring capabilities we developed a satellite remote sensing based spring frost index (SFI) and spring frost damage index (SFDI) at moderate (~25-km) spatial resolution from 1980 to 2010. The indices were developed from satellite passive microwave retrievals of global daily landscape freeze-thaw (FT) status and optical-IR sensor derived vegetation start of season (SOS). The SFI is the proportion of the total number of classified frozen (AM and PM frozen) and transitional (AM thawed and PM frozen) frost days in spring (March to May), while the SFDI is the proportion of the total number of classified frozen and transitional frost days following the SOS. The SFI results are validated using surface air temperature records from regional weather stations and crop planting dates for corn and soybean. Our results show a decreasing SFI trend (-2% decade-1; p<0.1) coincident with regional spring warming trends, while the SFDI is generally increasing (2.9% decade-1; p<0.1) within the conterminous US and 1980-2010 period. Spring warming is leading to fewer spring frost events, but an earlier SOS is increasing risk of potentially damaging events. The ecological significance of the SFI and SFDI changes were evaluated using satellite annual GPP and NDVI anomalies within the conterminous US. We find that respective SFI and SFDI levels below 10% and 14% have little impact on annual GPP. Reduced SFI and SFDI coincide with enhanced spring vegetation growth, but only the SFDI shows significant correlation with NDVI summer growth anomalies. The SFDI generally provides a better predictor of seasonal NDVI anomalies than the SFI, while vegetation sensitivity to the frost indices varies according to regional biome types and elevation zones. An increasing SFDI trend indicates potentially larger negative impacts on regional vegetation growth with continued warming.

Kim, Y.; Kimball, J. S.; Didan, K.

2013-12-01

202

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

203

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

NASA Astrophysics Data System (ADS)

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

K P, Sankaranarayanan

2011-12-01

204

Induction of homologous low temperature and ABA-responsive genes in frost resistant (Solanum commersonii) and frost-sensitive (Solanum tuberosum cv. Bintje) potato species.  

PubMed

A DNA fragment corresponding to a low-temperature- and ABA-responsive gene (Scdhn1) was amplified by PCR from genomic DNA of a wild, frost-resistant potato species, Solanum commersonii. A homologous gene (Stdhn1) was identified in Solanum tuberosum cv. Bintje, a frost-sensitive domesticated potato cultivar. The expression of the gene was studied during low temperature and ABA treatments in both Solanum species. The analysis revealed that both low temperature and ABA lead to the accumulation of a 1 kb transcript that corresponded to the PCR fragment. The induction of the gene was relatively rapid and maximum amounts of the transcripts were detected already after 1 day and 7 h of treatment with low temperature and ABA, respectively. Previous results have shown that there is no increase in the amount of endogenous ABA in S. tuberosum during low-temperature treatment, which indicates that two independent signalling pathways lead to the induction of this gene. PMID:8616256

Baudo, M M; Meza-Zepeda, L A; Palva, E T; Heino, P

1996-01-01

205

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

206

Frost resistance and biochemical changes during cold acclimation in different annual legumes  

Microsoft Academic Search

In Mediterranean areas of southern Europe growth of forages is seriously limited by the ability of each species to growth during cold winter. Therefore, the objective of this work was to prove the capacity for cold acclimation and frost resistance in four annual legumes native of Mediterranean region under laboratory conditions. Plants from subterranean clover (Trifolium subterraneum L. ssp. brachycalycinum

Marta Hekneby; M. Carmen Antoln; Manuel Snchez-Daz

2006-01-01

207

Experimental study on frosting suppression for a finned-tube evaporator using ultrasonic vibration  

Microsoft Academic Search

An experimental study was conducted to investigate the possibility and the effect of frost release from a finned-tube evaporator by using ultrasonic vibrations in natural convection. A compressor was adopted as cold source, and a finned-tube evaporator was placed horizontal on the frames inside a chamber. The aluminum fins surface was covered with hydrophilic coatings whose contact angle of the

Dingyuan Wang; Tangfei Tao; Guanghua Xu; Ailing Luo; Shaoying Kang

208

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

SciTech Connect

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

Rosen, J.M.; Kjome, N.T. (Univ. of Wyoming, Laramie (USA)); Oltmans, S.J. (NOAA CMDL, Boulder, CO (USA))

1990-08-01

209

Functional Characterization of the Frost Gene in Drosophila melanogaster: Importance for Recovery from Chill Coma  

Microsoft Academic Search

BackgroundAlmost all animals, including insects, need to adapt to temperature fluctuations. The molecular basis of thermal adaptation is not well understood, although a number of candidate genes have been proposed. However, a functional link between candidate genes and thermal tolerance has rarely been established. The gene Frost (Fst) was first discovered when Drosophila flies were exposed to cold stress, but

Herv Colinet; Siu Fai Lee; Ary Hoffmann; Ian Dworkin

2010-01-01

210

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

211

The sweetest dreams that labor knows: Robert Frost and the poetics of work  

Microsoft Academic Search

Purpose The purpose of this paper is to use the work of Robert Frost to give insights into the diverse meanings that work holds in daily lived experience. It aims to use this analysis to discuss general ways in which the content and formal properties of poetry allow unique insights into the world of work. Design\\/methodology\\/approach The paper

Gazi Islam; Michael J. Zyphur

2006-01-01

212

Variation among highbush blueberry cultivars for frost tolerance of open flowers  

Technology Transfer Automated Retrieval System (TEKTRAN)

Injury of open flowers often occurs in fruit crops by late winter or early spring frosts and can result in significant reduction in yield. In this study, freezing tolerance of open flowers of five highbush blueberry cultivars, Bluecrop, Elliott, Hannahs Choice, Murphy, and Weymouth, was d...

213

Soluble chromophores in marine snow, seawater, sea ice and frost flowers near Barrow, Alaska  

NASA Astrophysics Data System (ADS)

We measured light absorption in 42 marine snow, sea ice, seawater, brine, and frost flower samples collected during the OASIS field campaign between February 27 and April 15, 2009. Samples represented multiple sites between landfast ice and open pack ice in coastal areas approximately 5 km west of Barrow, Alaska. The chromophores that are most commonly measured in snow, H2O2, NO3-, and NO2-, on average account for less than 1% of sunlight absorption in our samples. Instead, light absorption is dominated by unidentified "residual" species, likely organic compounds. Light absorption coefficients for the frost flowers on first-year sea ice are, on average, 40 times larger than values for terrestrial snow samples at Barrow, suggesting very large rates of photochemical reactions in frost flowers. For our marine samples the calculated rates of sunlight absorption and OH production from known chromophores are (0.1-1.4) 1014 (photons cm-3 s-1) and (5-70) 10-12 (mol L-1 s-1), respectively. Our residual spectra are similar to spectra of marine chromophoric dissolved organic matter (CDOM), suggesting that CDOM is the dominant chromophore in our samples. Based on our light absorption measurements we estimate dissolved organic carbon (DOC) concentrations in Barrow seawater and frost flowers as approximately 130 and 360 ?M C, respectively. We expect that CDOM is a major source of OH in our marine samples, and it is likely to have other significant photochemistry as well.

Beine, Harry; Anastasio, Cort; Domine, Florent; Douglas, Thomas; Barret, Manuel; France, James; King, Martin; Hall, Sam; Ullmann, Kirk

2012-07-01

214

Relationship between frost tolerance and sugar concentration of various bryophytes in summer and winter  

Microsoft Academic Search

Frost resistance, measured via the photosynthetic capacity after freeze-thaw treatment, and concentrations of sucrose, glucose and fructose of thalli of seven species of Bryidae and one species of Marchantiidae were determined from January to March and June to September, respectively. A distinct increase in cold tolerance from summer to winter was found in Polytrichum formosum Hedw., Atrichum undulatum (Hedw.) P.

Dorothea Riitten; Kurt A. Santarius

1992-01-01

215

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

PubMed

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

Lee, Min Kyung; Lee, Jonghwi

2014-08-01

216

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 ~4C, 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

217

Die Abhngigkeit der Bulbillenbildung bei Poa alpina vivipara von Photoperiodismus und Frost  

Microsoft Academic Search

Summary Culturing experiments with Greenland plants ofPoa alpina vivipara have shown that after the action of frost the mode of reproduction is determined by the photoperiodoc factor. The influence of short days produces blossoms and that of long days results in bulbillae.

F. H. Schwarzenbach

1953-01-01

218

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

E-print Network

(thankfully!). Fire Blight - Fire blight is still an issue for a lot of the region, especially with this recent wet weather, and the big question is whether we can still become infected from fire blight with so on frosted blossoms cannot support a population of Erwinia amilavora, the causal agent of fire blight; hence

219

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

220

Improving frost-simulation subroutines of the Water Erosion Prediction Project (WEPP) model  

Technology Transfer Automated Retrieval System (TEKTRAN)

Erosion models play an important role in assessing the influence of human activities on the environment. For cold areas, adequate frost simulation is crucial for predicting surface runoff and water erosion. The Water Erosion Prediction Project (WEPP) model, physically-based erosion-prediction softwa...

221

The frost heave program of the Alaskan natural gas transportation system  

Microsoft Academic Search

Frost heave plays a critical role in the design of a chilled natural gas pipeline buried in certain regions of Alaska and Canada. Current plans call for the design and construction of a natural gas transportation system to move gas from Prudhoe Bay, Alaska, through Alaska and Canada to the West and Midwest of the United States. The Northwest Alaskan

J. E. Myrick; R. M. Issacs; C. Y. Liv; R. G. Luce

1982-01-01

222

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

Microsoft Academic Search

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

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

2004-01-01

223

An Evaluation of the Factor Structure of the Frost Multidimensional Perfectionism Scale  

ERIC Educational Resources Information Center

The purpose of the study was to investigate whether the six-factor structure of the Frost Multidimensional Perfectionism Scale could be replicated in a community-based sample. A sample of 255 adult participants (55.7% female, 44.3% male) ranging in age from 18 to 78 (mean = 37.0) completed the questionnaire. Based on the screen test and parallel

Harvey, Bronwyn; Pallant, Julie; Harvey, David

2004-01-01

224

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

225

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 0.4C per 100 m with distance from the SIS. The minimum air temperature increased from 0.5 to 2.8C, 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

226

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

Microsoft Academic Search

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

James M. Rosen; Norman T. Kjome; Samuel J. Oltmans

1990-01-01

227

Evaluation of frost damage in cement-based materials by a nonlinear elastic wave technique  

NASA Astrophysics Data System (ADS)

Frost resistance of concrete is a major concern in cold regions. RILEM (International union of laboratories and experts in construction materials, systems and structures) recommendations provide two alternatives for evaluating frost damage by nondestructive evaluation methods for concrete like materials. The first method is based on the ultrasonic pulse velocity measurement, while the second alternative technique is based on the resonant vibration test. In this study, we monitor the frost damage in Portland cement mortar samples with water to cement ratio of 0.5 and aggregate to cement ratio of 3. The samples are completely saturated by water and are frozen for 24 hours at -25C. The frost damage is monitored after 0, 5, 10, 15 and 20 freezing-thawing cycles by nonlinear impact resonance acoustic spectroscopy (NIRAS). The results obtained are compared with those obtained by resonant vibration tests, the second alternative technique recommended by RILEM. The obtained results show that NIRAS is more sensitive to early stages of damage than the standard resonant vibration tests.

Eiras, J. N.; Kundu, T.; Popovics, J. S.; Monz, J.; Soriano, L.; Pay, J.

2014-03-01

228

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

229

Developing a phenological model for grapevine to assess future frost risk in Luxembourg  

NASA Astrophysics Data System (ADS)

Late frost damage represents a significant hazard to grape production in cool climate viticulture regions such as Luxembourg. The main aim of our study is to analyze the frequency of these events for the Luxembourg's winegrowing region in the future. Spring frost injuries on grape may occur when young green parts are exposed to air temperature below 0C. The potential risk is determined by: (i) minimum air temperature conditions and the (ii) the timing of bud burst. Therefore, we developed and validated a model for budburst of the grapevine (*Vitis vinifera)* cultivar Rivaner, the most grown local variety, based on multi-annual data from 7 different sites across Europe and the US. An advantage of this approach is, that it could be applied to a wide range of climate conditions. Higher spring temperatures were projected for the future and could lead to earlier dates of budburst as well as earlier dates of last frost events in the season. However, so far it is unknown if this will increase or decrease the risk of severe late frost damages for Luxembourg's winegrowing region. To address this question results of 10 regional climate change projections from the FP6 ENSEMBLES project (spatial resolution = 25km; A1B emission scenario) were combined with the new bud burst model. The use of a multi model ensemble of climate change projections allows for a better quantification of the uncertainties. A bias corrections scheme, based on local observations, was applied to the model output. Projected daily minimum air temperatures, up to 2098, were compared to the projected date of bud burst in order to quantify the future frost risk for Luxembourg.

Caffarra, A.; Molitor, D.; Pertot, I.; Sinigoy, P.; Junk, J.

2012-04-01

230

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

231

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

232

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

233

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

NASA Technical Reports Server (NTRS)

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

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

2014-01-01

234

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

SciTech Connect

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

HAQ MA

2009-05-12

235

The SO2 frost distribution on Io from a combined analysis of Keck/OSIRIS and NIMS observations  

NASA Astrophysics Data System (ADS)

The geographic distribution and physical properties of Io's SO2 frost deposits are the primary observables used to constrain models of the SO2 cycle. Latitudinal/Longitudinal variations in frost grain size and fractional coverage constrain the relative importance of direct volcanic deposition vs. atmospheric precipitation, sublimation, and transport. The near-IR (2-5um) surface reflectivity spectrum is a diagnostic of the frost, as it depends on both grain size and fractional surface coverage. We present Keck/OSIRIS observations near 2um of the global distribution of SO2 frost --- probed by a weak transition that may be sensitive to the largest grains. Since an individual absorption band cannot uniquely constrain the frost grain size and fractional coverage, we interpret these ground-based observations in the context of a re-analysis of Galileo/NIMS measurements. Global maps of the equivalent widths from NIMS spectra in 4 bands that are sensitive to SO2 frost properties are presented. These maps include input from the entire NIMS dataset, with contributing observations filtered by wavelength range, spectral resolution and imaging geometry. While the weak transition observed by Keck/OSIRIS is not detectable at the lower spectral resolution of NIMS, it is has global coverage compared to 2/3 of the surface that is observed by NIMS. Previous models of the SO2 frost distribution have derived grain size and fractional coverage using models that incorporate the entire NIMS spectral range, requiring the inclusion of a number of contributing compounds and typically involving unconstrained input parameters (e.g., porosity). Using a simple Hapke model, our goal is to determine the combination of the fewest SO2 bands that are diagnostic of the grain size and fractional coverage distribution. Preliminary results suggests that a linear combination of ~2 grain sizes can reproduce the spatial variation in the observed spectra of SO2 frost. Latitudinal and longitude trends in the grain sizes derived using this analysis will be discussed.

Adamkovics, M.; Hayes, A. G.; De Pater, I.

2012-12-01

236

In-situ study of frosting and defrosting processes in tube-fin evaporators of household refrigerating appliances  

Microsoft Academic Search

The present paper advances an in-situ study of frosting and defrosting processes in tube-fin evaporators of household refrigerators and freezers. Frost growth experiments were carried out using a purpose-built test facility comprised of a refrigerated cabinet placed inside a climatized chamber, and a vapor compression refrigeration loop that controls both the evaporating temperature and the evaporator superheating. A first-principles two-dimensional

Fernando T. Knabben; Christian J. L. Hermes; Cludio Melo

2011-01-01

237

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

238

Calculation and Analysis of Frost Duration Times by Using Delphi Programming: A Case Study in Lorestan, Iran  

NASA Astrophysics Data System (ADS)

The purpose of the present study is to calculate the duration times of frosts by Delphi programming. To do this, the data related to the daily minimum temperature of four meteorology stations of Lorestan Province, i.e., Khoram-Abad, Boroujerd, Doroud and Aligoudarz that enjoy a ten-year statistics (from 1993 to 2003) were obtained from the information bank of the National Meteorology Organization. After taking out the frost days in desired threshold (zero and less than zero) during the statistical period, frost duration times of each station were calculated and extracted, using algorithm of the afore-mentioned program. Then, the duration times were selectively divided into eight (three-hour) classes. Their frequency percent charts were drawn and all stations were compared to one another in three classes of 0 to 3 h, 9 to 12 h and 21 to 24 h. It was concluded that Boroujerd Station enjoys the most frost hours and, hence damages to crops were the highest in this station compared with other stations. It was further concluded that the vegetation is the most effective factor in frost duration times of the region and that the height factor has no effect on frost duration times.

Hejazizadeh, Z.; Naserzadeh, M. H.

239

Dynamics of low velocity collisions of ice particle, coated with frost  

NASA Technical Reports Server (NTRS)

We continued our investigations of low velocity collisions of ice particles for velocities in range 10(exp -3) - 2 cm/s. The work focused on two effects: (1) the sticking forces for ice particles coated with CO2 frost, and (2) the completion of a 2-D pendulum system for glancing collisions. A new computer software was also developed to control and monitor the position of the 2-D pendulum.

Bridges, F.; Lin, D.; Boone, L.; Darknell, D.

1991-01-01

240

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

Microsoft Academic Search

In this research, suitability of different kriging and inverse distance weighted (IDW) methods in estimating occurrence date of frost was evaluated. Data included minimum daily air temperature values from 27 meteorological stations of Fars province in southern Iran from 18 to 45 years. Data ranges of 0 to -1.5, -1.5 to -3 and below -3C were considered as mild, moderate

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

2011-01-01

241

Protection of plants from frost using hydrophobic particle film and acrylic polymer  

Microsoft Academic Search

Summary Frost damage to potatoes, grapevine and citrus plants was assessed following treatment with either an acrylic polymer (AntistressTM) or with a hydrophobic particle film (CM-96-018). In large freezing tests, the application of the hydrophobic particle film consistently led to less damage whilst the acrylic polymer led to the same amount or more damage when compared to control plants. Detailed

M P FULLER; F HAMED; M WISNIEWSKI; D M GLENN

2003-01-01

242

Mapping SO 2 Frost on Io by the Modeling of NIMS Hyperspectral Images  

Microsoft Academic Search

We analyze a collection of hyperspectral images of Io acquired by the near infrared mapping spectrometer (NIMS) of Galileo during the G2 to E16 orbits of Jupiter. This analysis leads to the geographical distribution and physical characterization of SO2 frost deposits over about three-fourths of Io's surface. These deposits are excellent tracers of various phenomena, including volcanic production and emission,

Sylvain Dout; Bernard Schmitt; Rosaly Lopes-Gautier; Robert Carlson; Laurence Soderblom; James Shirley

2001-01-01

243

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

244

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

245

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

Microsoft Academic Search

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

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

1989-01-01

246

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

247

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

NASA Astrophysics Data System (ADS)

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

Kukko, Heikki

1992-12-01

248

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

249

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

PubMed

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

Perotti, Valeria E; Moreno, Alejandra S; Trpodi, Karina E J; Meier, Guillermo; Bello, Fernando; Cocco, Maringeles; Vzquez, Daniel; Anderson, Catalina; Podest, Florencio E

2015-03-01

250

High-Density Amorphous Ice, the Frost on Interstellar Grains  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

251

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

252

Effect of Air Velocity, Surface Temperature, and Absolute Humidity on Frosting Phenomena under Condition of Electric Field  

NASA Astrophysics Data System (ADS)

The correlation of effect of electric field and environmental parameters on frosting phenomena was studied. The investigation was based on experiments with a forced air stream on the cold plate surface under several frosting conditions. The effect of electric field, defrosting phenomena, was evaluated from frost formation rate and mass transfer coefficient, which was derived from the amount of frost remained on the cold plate surface. The results obtained were as follows ; (1)Under large difference of absolute humidity, the reduction rate of frost formation rate obtained by forming the electric field appeared at nearly constant rate and was independent of the difference of absolute humidity, but it disappeared where the difference of absolute humidity was small. (2)The mass transfer coefficient under the electric field became small as temperature of the cold plate surface became lower. (3)The reduction rate of mass transfer coefficient occured by forming the electric field decreased as air velocity increased. (4)The mass transfer coefficient under the electric field decreased proportionally as the field strength were strength end from 0 k V /cm, but became not to vary beyond a field strength, which depended on temperature of the cold plate surface.

Kusumoto, Hiroshi; Shizuya, Mitsutaka; Itoo, Masaaki

253

Measuring the Size of a Small, Frost World  

NASA Astrophysics Data System (ADS)

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

2006-01-01

254

Patches of Remnant Frost/Snow on Crater Rim in Northern Summer  

NASA Technical Reports Server (NTRS)

March 1999--it is summer in the martian northern hemisphere, yet patches of frost or snow persist in some areas of the northern plains. Winter ended eight months earlier, in July 1998. Recently, the Mars Orbiter Camera (MOC) passed over a relatively small impact crater located at latitude 68oN (on the Vastitas Borealis plain, north of Utopia Planitia) and took the picture seen at the left, above. The curved crater rims are visible in the upper and lower quarters of the image, and the crater floor is visible at the center right.

The picture on the right is a magnified view of the crater rim area outlined by a white box in the image on the left. The bright patches are snow or frost left over from the martian winter. These snowfields are so small that a human could walk across one of them in a matter of minutes--or perhaps sled down the small, sloping patch that is seen in a shadowed area near the lower left.

In winter, the entire scene shown here would be covered by frost. The long strip at the left covers an area 3 km (1.9 mi) wide by 26 km (16 mi) long. The expanded view on the right covers an area 2.9 km (1.8 mi) by 5.3 km (3.3 mi). Illumination is from the upper right.

Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

1999-01-01

255

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

256

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

257

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

NASA Technical Reports Server (NTRS)

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

Glaser, F. M.

1975-01-01

258

Timing of frost deposition on Martian dunes: A clue to properties of dune particles?  

NASA Technical Reports Server (NTRS)

Scans were made across the Martian dunes found in images taken at several different times to determine the time history of the dune albedo. Atmospheric contributions were estimated using optical depth data and the brightness of shadows in some images. The data show that the dunes brighten very substantially between L(s) = 10 and 40 deg, depending on the latitude. Bright coverings on dunes form outliers 1 to 5 deg north of the cap edge. Formation of the general cap then sometimes reverses the contrast of the dune field with the surrounding area. Causes for the early deposition of frost on dunes relative to surroundings are discussed.

Thomas, P.

1987-01-01

259

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

SciTech Connect

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. 26 refs.

Verbiscer, A.J.; Veverka, J. (Cornell Univ., Ithaca, NY (USA))

1990-12-01

260

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

SciTech Connect

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

2009-12-01

261

Free convection oxygen vaporizer heat transfer as a function of relative humidity and frost buildup  

NASA Astrophysics Data System (ADS)

A series of free convection heat transfer tests were made to simulate oxygen vaporizer fintube performance as a function of controlled levels of relative humidity. Test runs were made for relative humidity values set at 20, 40, 60 and 80%. Each test started with a bare fintube and continued until approximately steady state conditions were reached. Frost buildup on the aluminum fintubes was tracked by a continuous video of each test. Plots of heat transfer rates measured in these tests provide data for designing the two-phase portions of liquid oxygen vaporizers for varying ambient humidity conditions.

McIntosh, G. E.; Haaf, K. L.; Moyers, J. A.

2014-01-01

262

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

ERIC Educational Resources Information Center

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

Huseboe, Arthur R., Ed.

263

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

Technology Transfer Automated Retrieval System (TEKTRAN)

The common cultivated species Solanum tubrosum is frost sensitive and is killed at temperatures below -2.5C. It has been estimated that by increasing frost hardiness by 12 C one can expect an increase in potato yield by 26 to 40% in the Altiplano (Peru and Bolivia) covering 63,000 ha. of potatoes....

264

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

265

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

E-print Network

AN INVESTIGATION OF THE USE OF LIME AS A SOIL ADDITIVE TO MODIFI THE DETfEMENTAL EFFECTS OF FROST ACTION GLIDE T. EARNEST~ JR. Captain~ Corps of Engineers Submitted to the Graduate School of the Agricultural and Mechanical College of Texas... in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE August 1959 Ma)or Sub)acts Civil Engineering AN INVESTIGATION OF THE USE OF LIME AS A SOIL ADDITIVE TO MODIFY THE DETRIMENTAL EFFECTS OF FROST ACTION A Thesis CLYDE T...

Earnest, Clyde Talley

1959-01-01

266

[Temperature conditions of the formation of frost damages in conifer trees in the high latitudes of Western Siberia].  

PubMed

Frost damage to the bottom of the stem at a height of 0.2 m and at the height of the position of the thermometer in the weather station (2 m) and higher in the Siberian spruce (Picea obovata Ledeb.) and Siberian larch (Larix sibirica Ledeb.) growing at the northern limits of their natural habitat were studied in order to reveal the upper threshold temperature conditions of their formation. Possible causes of differences in the distribution of frost damage in the stem of the spruce and larch are discussed. PMID:25735171

2014-01-01

267

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

268

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

269

Polytrichum Strictum as a Solution to Frost Heaving in Disturbed Ecosystems: A Case Study with Milled Peatlands  

Microsoft Academic Search

Substrate instability is a common problem in many dis- turbed ecosystems. In the case of milled harvested peatlands, the pioneer moss Polytrichum strictum is commonly found; it is well adapted to tolerate the harsh microclimatic conditions and peat instability of these sites. A field experiment was used to determine the effective- ness of P. strictum against frost heaving, a major

Elisabeth V. G. Groeneveld; Line Rochefort

2005-01-01

270

Experimental Research of Air Source Heat Pump Frosting and Defrosting in a Double Stage-Coupling Heat Pump  

E-print Network

. The most common method of air source heat pump frost removal is reverse-cycle defrost. During the defrosting operation, the heat pump runs in the cooling mode. The defrost process is accomplished by reversing the normal heating mode. In this paper...

Wang, Z.; Gu, J.; Lu, Z.

2006-01-01

271

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

E-print Network

A red clover stand that was frost seeded into wheat. Using red clover as a cover crop in wheat Dan Red clover (Trifolium pretense) is Michigan's most common cover crop. Its easy establishment and shade common red clover cultivars are Michigan mammoth, Canadian mammoth (also known as Altaswede clover

272

Evaluation of the occurence of agricultural frost in state of Parana, Brazil, generated by a regional forecast model  

NASA Astrophysics Data System (ADS)

This study evaluated the potential use of a regional atmospheric model to predict the occurrence of agricultural frost three days in advance, as based on the vulnerability to low temperatures of the main crops in eight locations in the state of Parana, Brazil, between 2000 and 2007. Based on the reported occurrence of frosts, the values of the air temperature observed at meteorological stations were compared with the 66 h advance predictions obtained by the model. In general, we observed a slight overestimation of the air temperature values for all of the locations during the frost events. However, regression analyses demonstrated a good quality of the prediction of the model despite the data grid being relatively coarse. The coefficients of determination (R2) were larger than 0.65, whereas the systematic errors varied between 0.26 and 0.69C, and the magnitude of error does not exceed 1.7C. The hit rates of the categorical forecasts showed that the temperature 66 hours in advance was adequate to detect the occurrence of frost because the accuracy of forecasting exceeded 0.80, the probability of detection reached 0.70, and the false alarm rate did not exceeded 0.3.

Giarolla, Angelica; Chou, Sin C.; Faria, Rogerio T.

2013-04-01

273

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

274

The use of genetically engineered bacteria to control frost on strawberries and potatoes. Whatever happened to all of that research?  

Microsoft Academic Search

The identification of biological ice nucleating agents and their importance in frost induction and prevention is discussed. The discussion also includes information about the researchers who did the work, their original investigations, and struggles with government agencies to introduce their products. The original research was initiated independently by a group of atmospheric scientists in Wyoming and a group of plant

R. M Skirvin; E Kohler; H Steiner; D Ayers; A Laughnan; M. A Norton; M Warmund

2000-01-01

275

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

Microsoft Academic Search

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

Andy Benowicz; Sylvia LHirondelle; Yousry A El-Kassaby

2001-01-01

276

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

ERIC Educational Resources Information Center

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

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

2006-01-01

277

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

278

Frost-susceptible protein in plasma membranes in tubers of Helianthus tuberosus L.  

PubMed

When plasma membranes were prepared from tubers of Helianthus tuberosus L. (Jerusalem artichoke) frozen at a sublethal temperature (-10 degrees C), the levels of some plasma membrane proteins, named frost-susceptible proteins (FSPs), decreased [Uemura, M., et al., Plant Physiol., 80, 187-195 (1986)]. The aim of this study was to characterize the response of FSP120, which is named FSP-3 in a previous report, to freezing treatment by immunoblotting. Levels of FSP120 in the plasma membranes of tubers decreased after sublethal freezing, whereas no degraded products were detected in the microsomes or the soluble fraction. The amount of FSP120 in the crude extract of frozen tubers remained at a comparable level to that of the unfrozen tubers. These results suggest that FSP120 might be released from plasma membranes during freezing treatment of the tubers of Jerusalem artichoke. PMID:14745181

Arakawa, Keita; Hanazaki, Mitsuru; Yoshida, Shizuo

2004-01-01

279

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 g/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 g/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

280

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

281

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

PubMed

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. Miscanthusgiganteus 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

2014-07-01

282

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 plantplant 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 20042005, 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; Snchez-Gmez, David; Matesanz, Silvia; Alonso, Beatriz; Portsmuth, Angelika; Delgado, Antonio; Atkin, Owen K.

2008-01-01

283

Association of sugar content QTL and PQL with physiological traits relevant to frost damage resistance in pea under field and controlled conditions.  

PubMed

To increase yield in pea (Pisum sativum L.), autumn sowing would be preferable. Hence, frost tolerance of pea became a major trait of interest for breeders. In order to better understand the cold acclimation in pea, Champagne a frost tolerant line and Terese, a frost sensitive line, and their recombinant inbred lines (RIL) were studied. RIL frost tolerance was evaluated by a frost damage scale under field as well as controlled conditions. A quantitative trait loci (QTL) approach was used to identify chromosomal regions linked to frost tolerance. The detected QTL explained from 6.5 to 46.5% of the phenotypic variance. Amongst them, those located on linkage groups 5 and 6 were consistent with over all experiments, in field as well as in controlled environments. In order to improve the understanding of the frost tolerance mechanisms, several cold acclimation key characters such as concentration of sugars, electrolyte leakage, osmotic pressure, and activity of RuBisCO were assessed. Some of these physiological QTL colocalised with QTL for frost damage, in particular two raffinose QTL on LG5 and LG6 and one RuBisCO activity QTL on LG6, explaining 8.8 to 27.0% of the phenotypic variance. In addition, protein quantitative loci were mapped; some of them colocalised with frost damage and physiological QTL on LG5 and LG6, explaining 16.0-43.6% of the phenotypic variance. Raffinose metabolism and RuBisCO activity and its effect on photosynthesis might play a major role in cold acclimation of pea. PMID:19322559

Dumont, Estelle; Fontaine, Vronique; Vuylsteker, Christophe; Sellier, Hlne; Bodle, Sylvie; Voedts, Najia; Devaux, Rosemonde; Frise, Marlne; Avia, Komlan; Hilbert, Jean-Louis; Bahrman, Nasser; Hanocq, Eric; Lejeune-Hnaut, Isabelle; Delbreil, Bruno

2009-05-01

284

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

285

Comparative ANNs with different input layers and GA-PLS study for simultaneous spectrofluorimetric determination of melatonin and pyridoxine HCl in the presence of melatonins main impurity.  

PubMed

Melatonin (MLT) has many health implications, therefore it is important to develop specific analytical methods for the determination of MLT in the presence of its main impurity, N-{2-[1-({3-[2-(acetylamino)ethyl]-5-methoxy-1H-indol-2-yl}methyl)-5-methoxy-1H-indol-3-yl]ethyl}acetamide (DMLT) and pyridoxine HCl (PNH) as a co-formulated drug. This work describes simple, sensitive, and reliable four multivariate calibration methods, namely artificial neural network preceded by genetic algorithm (GA-ANN), principal component analysis (PCA-ANN) and wavelet transform procedures (WT-ANN) as well as partial least squares preceded by genetic algorithm (GA-PLS) for the spectrofluorimetric determination of MLT and PNH in the presence of DMLT. Analytical performance of the proposed methods was statistically validated with respect to linearity, accuracy, precision and specificity. The proposed methods were successfully applied for the assay of MLT in laboratory prepared mixtures containing up to 15% of DMLT and in commercial MLT tablets with recoveries of no less than 99.00%. No interference was observed from common pharmaceutical additives and the results compared favorably with those obtained by a reference method. PMID:23344205

Darwish, Hany W; Attia, Mohamed I; Abdelhameed, Ali S; Alanazi, Amer M; Bakheit, Ahmed H

2013-01-01

286

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

E-print Network

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

Hutchison, James P

1961-01-01

287

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

288

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

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

289

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

Microsoft Academic Search

Studies of global climate rely critically on accurate water vapor measurements. In this paper, a compari- son of the NOAA\\/Climate Monitoring and Diagnostics Laboratory (CMDL) frost-point hygrometer and the Fluorescent Advanced Stratospheric Hygrometer for Balloon (FLASH-B) Lyman-alpha hygrometer is reported. Both instruments were part of a small balloon payload that was launched multiple times at Sodankyl, Finland. The comparison shows

H. Vmel; V. Yushkov; S. Khaykin; L. Korshunov; E. Kyr; R. Kivi

2007-01-01

290

Bourgeois Myth versus Media Poetry in Prime-time: Re-visiting Mark Frost and David Lynch's Twin Peaks  

Microsoft Academic Search

This article explores IVIark Frost and David Lynch's television series Twin Peaks from the perspective of the two dominant world-views it dramatized. The world-view based in bourgeois myth can be described as employing significations that are always present in naturally and mythically transcendent terms. The other world-view is generated by media poetry, which is a virtual mode of signification that

Tom OConnor

2004-01-01

291

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

PubMed

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

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

2007-01-01

292

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

PubMed

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

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

2011-08-01

293

Changes in pick beginning date and frost damage risk of tea tree in Longjing tea-producing area  

NASA Astrophysics Data System (ADS)

We analyze the pick beginning date and frost damage risk trends of Jiukeng, Longjing-43, and Wuniuzao tea trees with time, using meteorological data from 12 station pairs over the period 1971-2010 in the Longjing tea-producing area. The pick beginning date of Jiukeng, Longjing-43, and Wuniuzao varieties had no statistically significant trends before 1990. The pick beginning date of Jiukeng variety had statistically significant decreasing trends after 1990, and there were no statistically significant trends in the start date after 1990 for Longjing-43 and Wuniuzao varieties. The average pick beginning dates of Longjing-43 and Wuniuzao varieties before 1990 are later than those after 1990 by 3.8-4.8 and 2.0-3.1 days, respectively. We used the trend of difference between beginning date of tea plucking (BDTP) and 0 C terminal date to analyze frost damage risk trends. Eleven counties had no statistically significant frost damage risk trends for Jiukeng, Longjing-43, and Wuniuzao varieties, leaving only one county with statistically significant trends.

Lou, Weiping; Sun, Ke; Sun, Shanlei; Ma, Fenghua; Wang, Dongfang

2013-10-01

294

Cryosorption of helium on argon frost in Tokamak Fusion Test Reactor neutral beamlines  

SciTech Connect

Helium pumping on argon frost has been investigated on Tokamak Fusion Test Reactor (TFTR) neutral beam injectors and shown to be viable for limited helium beam operation. Maximum pumping speeds are {similar to}25% less than those measured for pumping of deuterium. Helium pumping efficiency is low, {gt}20 argon atoms are required to pump each helium atom. Adsorption isotherms are exponential and exhibit a twofold increase in adsorption capacity as the cryopanel temperature is reduced from 4.3 K to 3.7 K. Pumping speed was found to be independent of cryopanel temperature over the temperature range studied. After pumping a total of 2000 Torr l of helium, the beamline base pressure rose to 2{times}10{sup {minus}5} Torr from an initial value of 10{sup {minus}8} Torr. Accompanying this three order of magnitude increase in pressure was a modest 40% decrease in pumping speed. The introduction of 168 Torr l of deuterium prior to helium injection reduced the pumping speed by a factor of two with no decrease in adsorption capacity.

Kamperschroer, J.H.; Cropper, M.B.; Dylla, H.F.; Garzotto, V.; Dudek, L.E.; Grisham, L.R.; Martin, G.D.; O'Connor, T.E.; Stevenson, T.N.; von Halle, A.; Williams, M.D. (Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ (USA)); Kim, J. (General Atomics, San Diego, CA (USA))

1990-05-01

295

Cryosorption of helium on argon frost TFTR (Tokamak Fusion Test Reactor) neutral beamlines  

SciTech Connect

Helium pumping on argon frost has been investigated on TFTR neutral beam injectors and shown to be viable for limited helium beam operation. Maximum pumping speeds are {approximately} 25% less than those measured for pumping of deuterium. Helium pumping efficiency is low, > 20 argon atoms are required to pump each helium atom. Adsorption isotherms are exponential and exhibit a two-fold increase in adsorption capacity as the cryopanel temperature is reduced from 4.3 K to 3.7 K. Pumping speed was found to be independent of cryopanel temperature over the temperature range studied. After pumping a total of 2000 torr-l of helium, the beamline base pressure rose to 2{times}10{sup -5} torr from an initial value of 10{sup -8} torr. Accompanying this three order of magnitude increase in pressure was a modest 40% decrease in pumping speed. The introduction of 168 torr-l of deuterium prior to helium injection reduced the pumping speed by a factor of two with no decrease in adsorption capacity. 29 refs., 7 figs.

Kamperschroer, J.H.; Cropper, M.B.; Dylla, H.F.; Garzotto, V.; Dudek, L.E.; Grisham, L.R.; Martin, G.D.; O'Connor, T.E.; Stevenson, T.N.; von Halle, A. (Princeton Univ., NJ (USA). Plasma Physics Lab.)

1989-11-01

296

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

297

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

SciTech Connect

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

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

2003-01-01

298

Federal Government Presence in  

E-print Network

Federal Government Presence in Newfoundland and Labrador November 2005 #12;I. Introduction Motivation Our Focus Methodology #12;Motivation Many concerns expressed about the decline in Federal Presence. John's Government of Newfoundland and Labrador Local Media General Public #12;Our Focus The Federal

deYoung, Brad

299

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

NASA Astrophysics Data System (ADS)

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

Guy, Amanda; Lamb, Eric; Siciliano, Steven

2014-05-01

300

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

PubMed

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

Menzel, Annette; Helm, Raimund; Zang, Christian

2015-01-01

301

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

PubMed Central

Damage by late spring frost is a risk deciduous trees have to cope with in order to optimize the length of their growing season. The timing of spring phenological development plays a crucial role, not only at the species level, but also at the population and individual level, since fresh new leaves are especially vulnerable. For the pronounced late spring frost in May 2011 in Germany, we studied the individual leaf development of 35 deciduous trees (mainly European beech Fagus sylvatica L.) at a mountainous forest site in the Bayerischer Wald National Park using repeated digital photographs. Analyses of the time series of greenness by a novel Bayesian multiple change point approach mostly revealed five change points which almost perfectly matched the expected break points in leaf development: (i) start of the first greening between day of the year (DOY) 108119 (mean 113), (ii) end of greening, and (iii) visible frost damage after the frost on the night of May 3rd/4th (DOY 123/124), (iv) re-sprouting 1938 days after the frost, and (v) full maturity around DOY 178 (166184) when all beech crowns had fully recovered. Since frost damage was nearly 100%, individual susceptibility did not depend on the timing of first spring leaf unfolding. However, we could identify significant patterns in fitness linked to an earlier start of leaf unfolding. Those individuals that had an earlier start of greening during the first flushing period had a shorter period of recovery and started the second greening earlier. Thus, phenological timing triggered the speed of recovery from such an extreme event. The maximum greenness achieved, however, did not vary with leaf unfolding dates. Two mountain ashes (Sorbus aucuparia L.) were not affected by the low temperatures of -5C. Time series analysis of webcam pictures can thus improve process-based knowledge and provide valuable insights into the link between phenological variation, late spring frost damage, and recovery within one stand. PMID:25759707

Menzel, Annette; Helm, Raimund; Zang, Christian

2015-01-01

302

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

NASA Technical Reports Server (NTRS)

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

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

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

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

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

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

2007-01-01

303

Earth's Layers  

NSDL National Science Digital Library

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

Mrs. Walls

2011-01-30

304

Application of the Java Message Service in mobile monitoring environments Martin Kuehnhausen , Victor S. Frost  

E-print Network

Application of the Java Message Service in mobile monitoring environments Martin Kuehnhausen ? on trains. The Java Message Service (JMS) presents a flexible transport layer for asynchronous communication

Kansas, University of

305

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

306

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

307

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

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

2014-01-01

308

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

NASA Astrophysics Data System (ADS)

The winter wheat late frost disaster (WFD) occurs mainly in the Yellow and Huaihe River area, of which Henan Province covers 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 construct a WFD index based on the minimum temperature and the winter wheat development period (WDP). The WFD degrees and days at 30 agrometeorological stations in Henan Province during the period of 1981-2004 are calculated. For the large-scale temporal variation analysis of WFD, the 24-yr WDP observation series is relatively short, so it is expanded by using the relation between the turning green date of winter wheat and the 5-day running mean temperature and that between the stem elongation phase and the effective cumulative temperature above a critical value of 2.5C. The WFD data are also expanded for the last 50 years and are analyzed by using the empirical orthogonal function (EOF) and the Morlet wavelet methods. Characteristics in the spatial distribution and temporal variation of WFD are revealed. The results show that the frequency of WFD is generally high, exceeding 40% in parts of Henan, and exhibits a rising trend in the period of 1970-1990. The variation trend of WFD degrees is similar to that of WFD days, and the areas with higher WFD degrees coincide the areas with more WFD days. Moreover, the WFD degree has a greater impact on the winter wheat yield than the WFD days. The areas with high WFD degrees lie in the southeast and southwest of Henan, and the areas with low WFD degrees lie in the south of the Huaihe River and parts of western Henan. Temporal variations of the first and second EOF modes of the WFD degree display 16- and quasi-22-yr periodicities, respectively. The areas of high (low) WFD frequency are distributed in the northern Henan and the southwest border of Henan (the northeast Henan and the middle part of southwest Henan). The temporal variation of the first (second) EOF mode of WFD days exhibits a periodicity (periodicities) of quasi-4 yr (quasi-3 and quasi-6-7 yr).

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

2011-04-01

309

Sensing presence of fire  

Microsoft Academic Search

Both the spectral absorption characteristic of air to test for gaseous combustion products, and the dispersion characteristics of atmosphere, to test for particulate matter, aerosols, smoke, and the like therin, are analyzed, and if there is coincidence of presence of carbon monoxide, and\\/or carbon dioxide, as well as dispersion of light, an alarm signal is generated. The light source is

Z. Horvath; G. Purt

1975-01-01

310

Incorporating soil frost and thaw fronts dynamics into the community land surface model CLM 3.5  

NASA Astrophysics Data System (ADS)

Freeze-thaw processes in soils, including changes in frost and thaw fronts (FTFs) , are important physical processes. The movement of FTFs affects soil water and thermal characteristics, as well as energy and water exchanges between land surface and the atmosphere, and then the land surface hydrothermal process. In this study, we implemented a water and heat transfer model including the changes in soil FTFs into the community land surface model CLM3.5, which is called Clm3.5-FTF, and then investigated the effects of soil FTFs dynamics on global land surface hydrological process. A local adaptive variable grid method was used to discrete the model. The simulation is validated with observed soil temperature, soil FTF depth, soil unfrozen water content on typical sites and areas in the world. Numerical experiments show that the global spatial distribution of simulated maximum frost depth by CLM3.5-FTF has seasonal variation obviously. Simulations by CLM3.5-FTF compared well with the observed data at sites and are better than those by CLM3.5. CLM3.5-FTF can continuously track the position of FTF, overcome interpolation numerical oscillations.

Xie, Z.; Wang, A.; Feng, X.; Tian, X.; Qin, P.

2013-12-01

311

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

312

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

Microsoft Academic Search

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

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

2005-01-01

313

Bulletin of the Buffalo Society of Natural Sciences, Volume 39, 2010 11 CLINTON, PECK AND FROST THE DAWN OF NORTH AMERICAN BOLETOLOGY  

E-print Network

Bulletin of the Buffalo Society of Natural Sciences, Volume 39, 2010 11 CLINTON, PECK AND FROST ­ THE DAWN OF NORTH AMERICAN BOLETOLOGY Ernst E. Both Buffalo Museum of Science, 1020 Humbolt Parkway, Buffalo, New York 14211 eboth@sciencebuff.org and Beatriz Ortiz-Santana Center for Forest Mycology

314

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

E-print Network

1 Books on "Plant Respiration"(1932-1960): From Walter Stiles to Felix Frost Blackman to W.O. James In 1954, G. E. Briggs (of Cambridge University; who later was a host to Robert Emerson when he had worked October, 1937 (pp. 82-105); Chapter V (The analysis of respiratory metabolism by the intensive study

Govindjee "Gov"

315

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

316

Ability of winter wheat plants to become hardened against frost related to peculiarities of carbon dioxide exchange, biomass synthesis, and various forms of water-soluble carbohydrates  

Microsoft Academic Search

The source-sink relations (SSR) in a plant under cold exposure to frost was studied in the plants of winter wheat (Triticum aestivum L.) Mironovskaya 808 cultivar and its allocytoplasmic hybrid containing alien cytoplasm of goat grass (Aegilops ovata L.) and grown in a water culture until phas of two leaves. The alteration of SSR was processed by treatment of plant

S. V. Klimov; E. A. Burakhanova; G. P. Alieva; T. A. Suvorova

2010-01-01

317

The development of frost tolerance and DHN5 protein accumulation in barley ( Hordeum vulgare) doubled haploid lines derived from Atlas 68Igri 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 68Igri 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.

Klra Kosov; Ilja Tom Pril; Pavla Prilov; Pavel Vtmvs; Jana Chrpov

2010-01-01

318

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

PubMed

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

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

2011-07-15

319

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

PubMed Central

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

Soltsz, Alexandra

2013-01-01

320

Lidar observations of Arctic polar stratospheric clouds, 1988 - Signature of small, solid particles above the frost point  

NASA Technical Reports Server (NTRS)

The paper presents recent (January 1988) Arctic airborne lidar data which suggest that Type I polar stratospheric clouds (PSCs) are composed of small solid particles with radii on the order of 0.5 micron. PSCs were observed remotely in the 21-24 km altitude range north of Greenland during a round-trip flight from Andenes, Norway on January 29, 1988, aboard the NASA Wallops Flight Facility P-3 Orion aircraft. Synoptic analyses at the 30-mb level show local temperatures of 191-193 K, which are well above the estimated frost point temperature of 185 K; this suggests that the PSCs were probably of the binary HNO3-H2O (Type I) class.

Poole, L. R.; Osborn, M. T.; Hunt, W. H.

1988-01-01

321

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

322

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

323

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.

324

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

325

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.

Paul J. Tackley

326

Layered Liquids  

NSDL National Science Digital Library

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

John Eichinger

2009-05-30

327

Layered materials  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

328

Measuring Presence in Virtual Environments: A Presence Questionnaire  

Microsoft Academic Search

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

Bob G. Witmer; Michael J. Singer

1998-01-01

329

Lava Layering  

NSDL National Science Digital Library

The Planetary Geology Group at Arizona State University developed this online activity to teach elementary and middle school students "the stratigraphy (layers) of lava flows produced by multiple eruptions" on the moon. The first part of the website provides teachers with background information about the layers of basaltic lava flows that cover about sixteen percent of the Moon as well as how to prepare for the activity and what to expect. Visitors can use the second part of the website as an instruction sheet for the students. The website describes how users can examine the patterns of lava flows on the moon with the help of four simple ingredients: baking soda, vinegar, food coloring, and paper cups. The questions provided at the end will help students understand the process that is taking place in their experiments.

330

Lava Layers  

NSDL National Science Digital Library

In this activity (on pages 11-12 of PDF) learners create models of lava layers that have formed on the moon. The model is created by mixing a series of different colored vinegar with baking soda, then using colored play dough to cover wet areas where each color of "lava" erupted. Clear straws are pushed into the thickest part of the finished layers to get a "core sample." Groups can present their findings and a list of questions is provided to guide students to a deeper understanding. The activity is part of a larger curriculum based on a video on DVD, which you can request for free by emailing center@amnh.org.

American Museum of Natural History

2008-01-01

331

Vitrification in the presence of salts  

SciTech Connect

Glass is an advantageous material for the immobilization of nuclear wastes because of the simplicity of processing and its unique ability to accept a wide variety of waste elements into its network structure. Unfortunately, some anionic species which are present in the nuclear waste streams have only limited solubility in oxide glasses. This can result in either vitrification concerns or it can affect the integrity, of the final vitrified waste form. The presence of immiscible salts can also corrode metals and refractories in the vitrification unit as well as degrade components in the off-gas system. The presence of a molten salt layer on the melt may alter the batch melting rate and increase operational safety concerns. These safety concerns relate to the interaction of the molten salt and the melter cooling fluids. Some preliminary data from ongoing experimental efforts examining the solubility of molten salts in glasses and the interaction of salts with melter component materials is included.

Marra, J.C.; Andrews, M.K.; Schumacher, R.F.

1994-07-01

332

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 41F 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

333

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

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 41F 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

334

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

NASA Astrophysics Data System (ADS)

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

La Spina, Sylvie; de Cannire, Charles; Molenberg, Jean-Marc; Vincke, Caroline; Deman, Dborah; Grgoire, Jean-Claude

2010-05-01

335

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

336

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

337

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

338

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

PubMed

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

339

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

340

Estimating Active Layer Thickness from Remotely Sensed Surface Deformation  

NASA Astrophysics Data System (ADS)

We estimate active layer thickness (ALT) from remotely sensed surface subsidence during thawing seasons derived from interferometric synthetic aperture radar (InSAR) measurements. Ground ice takes up more volume than ground water, so as the soil thaws in summer and the active layer deepens, the ground subsides. The volume of melted ground water during the summer thaw determines seasonal subsidence. ALT is defined as the maximum thaw depth at the end of a thawing season. By using InSAR to measure surface subsidence between the start and end of summer season, one can estimate the depth of thaw over a large area (typically 100 km by 100 km). We developed an ALT retrieval algorithm integrating InSAR-derived surface subsidence, observed soil texture, organic matter content, and moisture content. We validated this algorithm in the continuous permafrost area on the North Slope of Alaska. Based on InSAR measurements using ERS-1/2 SAR data, our estimated values match in situ measurements of ALT within 1--10 cm at Circumpolar Active Layer Monitoring (CALM) sites within the study area. The active layer plays a key role in land surface processes in cold regions. Current measurements of ALT using mechanical probing, frost/thaw tubes, or inferred from temperature measurements are of high quality, but limited in spatial coverage. Using InSAR to estimate ALT greatly expands the spatial coverage of ALT observations.

Liu, L.; Schaefer, K. M.; Zhang, T.; Wahr, J. M.

2010-12-01

341

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

342

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 -7C) 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

343

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

344

MITRE sensor layer prototype  

NASA Astrophysics Data System (ADS)

The MITRE Sensor Layer Prototype is an initial design effort to enable every sensor to help create new capabilities through collaborative data sharing. By making both upstream (raw) and downstream (processed) sensor data visible, users can access the specific level, type, and quantities of data needed to create new data products that were never anticipated by the original designers of the individual sensors. The major characteristic that sets sensor data services apart from typical enterprise services is the volume (on the order of multiple terabytes) of raw data that can be generated by most sensors. Traditional tightly coupled processing approaches extract pre-determined information from the incoming raw sensor data, format it, and send it to predetermined users. The community is rapidly reaching the conclusion that tightly coupled sensor processing loses too much potentially critical information.1 Hence upstream (raw and partially processed) data must be extracted, rapidly archived, and advertised to the enterprise for unanticipated uses. The authors believe layered sensing net-centric integration can be achieved through a standardize-encapsulate-syndicateaggregate- manipulate-process paradigm. The Sensor Layer Prototype's technical approach focuses on implementing this proof of concept framework to make sensor data visible, accessible and useful to the enterprise. To achieve this, a "raw" data tap between physical transducers associated with sensor arrays and the embedded sensor signal processing hardware and software has been exploited. Second, we encapsulate and expose both raw and partially processed data to the enterprise within the context of a service-oriented architecture. Third, we advertise the presence of multiple types, and multiple layers of data through geographic-enabled Really Simple Syndication (GeoRSS) services. These GeoRSS feeds are aggregated, manipulated, and filtered by a feed aggregator. After filtering these feeds to bring just the type and location of data sought by multiple processes to the attention of each processing station, just that specifically sought data is downloaded to each process application. The Sensor Layer Prototype participated in a proof-of-concept demonstration in April 2008. This event allowed multiple MITRE innovation programs to interact among themselves to demonstrate the ability to couple value-adding but previously unanticipated users to the enterprise. For this event, the Sensor Layer Prototype was used to show data entering the environment in real time. Multiple data types were encapsulated and added to the database via the Sensor Layer Prototype, specifically National Imagery Transmission Format 2.1 (NITF), NATO Standardization Format 4607 (STANAG 4607), Cursor-on-Target (CoT), Joint Photographic Experts Group (JPEG), Hierarchical Data Format (HDF5) and several additional sensor file formats describing multiple sensors addressing a common scenario.

Duff, Francis; McGarry, Donald; Zasada, David; Foote, Scott

2009-05-01

345

Multifunctional layered magnetic composites.  

PubMed

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

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

2015-01-01

346

Using Presence Questionnaires in Reality Using Presence Questionnaires in Reality  

E-print Network

, Ernest Catena, Sima Arman, Mel Slater Department of Computer Science University College London Gower different presence question- naires can distinguish between real and virtual experiences. One group of 10 subjects were given two different presence questionnaires in randomised order: the Witmer and Singer

Slater, Mel

347

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

348

Detecting the presence of microorganisms  

NASA Technical Reports Server (NTRS)

The presence of microorganisms in a sample is determined by culturing microorganisms in a growth medium which is in contact with a measuring electrode and a reference electrode and detecting a change in potential between the electrodes caused by the presence of the microorganisms in the medium with a high impedance potentiometer.

Wilkins, Judd R. (Inventor); Stoner, Glenn E. (Inventor)

1977-01-01

349

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

350

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

Microsoft Academic Search

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

L. K. Koopal

1978-01-01

351

Temperature controls on sediment production in the Oregon Coast Range - abiotic frost-cracking processes vs. biotic-dominated processes over the last 40 ka  

NASA Astrophysics Data System (ADS)

The Oregon Coast Range (OCR) is a mid-latitude soil-mantled landscape wherein measured uplift rates are broadly consistent with long-term measured erosion rates. The OCR was unglaciated during the last glacial period (~ 26 to 13 ka) and therefore is considered an ideal steady-state landscape to study and model geomorphic processes. However, previously published paleoclimate data inferred from a 42 ka paleolake fossil archive in the OCR Little Lake watershed (3 km2) strongly suggest that temperatures in the OCR during the last glacial were well within the frost cracking temperature window of -3 to -8 C. Therefore, we suggest that while present-day OCR sediment production is dominated by biota, specifically trees, frost-driven abiotic processes may have played a significant role in modulating erosion rates and landscape evolution during the last glacial interval. A new sediment core from the Little Lake basin at the lake's edge, centered proximal to hillslopes, spans ~ 50 ka to 20 ka. We observe a fourfold increase in sediment accumulation rates from the non-glacial interval (~50 ka to ~ 26 ka) to the last glacial interval (~ 26 ka to ~ 20 ka), including > 12 m of sediment from the last glacial maximum, dated at 23,062 - 23,581 cal yr B.P. The decreased inferred temperatures and increased sedimentation rates suggest increased sediment production and transport via frost processes during the last glacial interval, in contrast to sediment production and erosion rates controlled by biotic processes in the non-glacial intervals. We present a climate-time series scenario of likely frost-cracking intensity across the entire Oregon Coast Range from the non-glacial interval (at least 3 C cooler than present-day temperatures) through the glacial interval (7 to 14 C cooler) and into the Holocene (January temperatures ~ 5 C). We use the PRISM dataset, which consists of monthly temperature and precipitation for the contiguous United States, to calculate local monthly topographic lapse rates for maximum and minimum temperature and precipitation for the Oregon Coast Range. The topographic lapse rate downscaling method used generates climatically reasonable patterns in mountainous terrain. Using macrofossil data collected from cores in the well-studied Little Lake watershed, we generate climate envelopes using modern climate-species relationships. These inferred paleoclimatic values are then adjusted to the elevations of the hillslopes using the local topographic lapse rates. To calculate frost cracking intensity and depth, (critical controls on sediment production) we use a numerical model, which depends on the mean annual air temperature, soil depth, and daily annual temperature variation over an annual cycle. Applying the model on a 10 m DEM using the inferred paleoclimate data allows us to calculate frost-cracking intensity across the OCR under different climatic conditions at millennial timescales. Climate-induced changes in soil production and transport mechanisms in the soil-mantled OCR likely control changes in erosion rates at millennial time scales, and contradict the widely held assumption that the OCR is an ideal steady state landscape.

Marshall, J. A.; Roering, J. J.; Praskievicz, S. J.; Hales, T. C.; Gavin, D. G.; Bartlein, P. J.

2012-12-01

352

Effects of mid-season frost and elevated growing season temperature on stomatal conductance and specific xylem conductivity of the arctic shrub, Salix pulchra.  

PubMed

An increased risk of frost is expected during the growing season, as climate warming increases spring temperatures in the Arctic. Because deciduous species have a growth season limited in length and also have generally larger conduit volumes, they are more likely than evergreens to be injured by freeze-thaw-induced cavitation during the growing season. To test whether growth at elevated temperature increases susceptibility to freeze-thaw damage, we grew a deciduous arctic shrub species (Salix pulchra Cham.) in simulated Alaskan summer temperatures and at 5 degrees C above the ambient simulation (+5 degrees C plants) in controlled environments. Stem specific hydraulic conductivity (k(s)) and leaf stomatal conductance (g(s)) were measured in plants grown at both temperatures before and after a freeze treatment simulating a mid-season frost. Before the freeze treatment, specific xylem conductivity was 2.5 times higher and stomatal conductances were 1.3 times higher in +5 degrees C plants than in ambient-grown plants. Reductions in hydraulic conductivity and stomatal conductance as a result of the freeze were 3.5 and 1.8 times greater respectively in +5 degrees C plants than in ambient-grown plants. Many of the +5 degrees C plants showed extensive leaf damage. Plants grown in the two treatments also differed in comparative xylem anatomy; +5 degrees C plants had larger vessel diameters (25.4 versus 22.6 micro m) and higher vessel densities (71 versus 67.4 vessels mm(-2)) than ambient-grown plants. Our results suggest that higher growing season temperatures will increase the susceptibility of arctic deciduous shrubs to frost damage, which may offset their competitive growth advantage. PMID:12359530

Gorsuch, Dennis M; Oberbauer, Steven F

2002-10-01

353

Federal Presence in Newfoundland and  

E-print Network

Federal Presence in Newfoundland and Labrador Dr. James Feehan Professor of Economics September 14 and elaborates on the results of Phase I and adds: Federal government business enterprises Federal offices Federal government capital expenditures Federal support for businesses Excludes personal

deYoung, Brad

354

NETWORK NUMERICAL SIMULATION OF HYDROMAGNETIC MARANGONI MIXED CONVECTION BOUNDARY LAYERS  

Microsoft Academic Search

The study of a steady coupled dissipative layer, known as the Mangaroni mixed convection boundary layer, in the presence of a magnetic field is presented. The mixed convection boundary layer is generated when in addition to Marangoni (thermocapillary) effects there are also buoyancy effects due to gravity and external pressure gradient effects. In the model considered the Marangoni coupling condition

J. Zueco; O. Anwar Bg

2010-01-01

355

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

Microsoft Academic Search

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

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

2006-01-01

356

Thin layer chromatography of gangliosides  

Microsoft Academic Search

Thin layer chromatography is the easiest way to analyze the total glycosphingolipid mixtures extracted, and, in some cases,\\u000a partially purified from tissues and cultured cells. Several solvent systems have been introduced to separate the complex mixtures\\u000a as a function of their composition, presence of contaminants and, in some cases, of their quantity. In addition, colorimetric,\\u000a enzymatic, immunological and radiochemical detection

Federica Scandroglio; Nicoletta Loberto; Manuela Valsecchi; Vanna Chigorno; Alessandro Prinetti; Sandro Sonnino

2009-01-01

357

Building biomedical materials layer-by-layer  

E-print Network

In this materials perspective, the promise of water based layer-by-layer (LbL) assembly as a means of generating drug-releasing surfaces for biomedical applications, from small molecule therapeutics to biologic drugs and ...

Hammond, Paula T.

358

Mitochondrial energy-dissipating systems (alternative oxidase, uncoupling proteins, and external NADH dehydrogenase) are involved in development of frost-resistance of winter wheat seedlings.  

PubMed

Gene expression, protein synthesis, and activities of alternative oxidase (AOX), uncoupling proteins (UCP), adenine nucleotide translocator (ANT), and non-coupled NAD(P)H dehydrogenases (NDex, NDPex, and NDin) were studied in shoots of etiolated winter wheat (Triticum aestivum L.) seedlings after exposure to hardening low positive (2C for 7 days) and freezing (-2C for 2 days) temperatures. The cold hardening efficiently increased frost-resistance of the seedlings and decreased the generation of reactive oxygen species (ROS) during further cold shock. Functioning of mitochondrial energy-dissipating systems can represent a mechanism responsible for the decrease in ROS under these conditions. These systems are different in their response to the action of the hardening low positive and freezing temperatures. The functioning of the first system causes induction of AOX and UCP synthesis associated with an increase in electron transfer via AOX in the mitochondrial respiratory chain and also with an increase in the sensitivity of mitochondrial non-phosphorylating respiration to linoleic and palmitic acids. The increase in electron transfer via AOX upon exposure of seedlings to hardening freezing temperature is associated with retention of a high activity of NDex. It seems that NDex but not the NDPex and NDin can play an important role in maintaining the functional state of mitochondria in heterotrophic tissues of plants under the influence of freezing temperatures. The involvement of the mitochondrial energy-dissipating systems and their possible physiological role in the adaptation of winter crops to cold and frost are discussed. PMID:25100008

Grabelnych, O I; Borovik, O A; Tauson, E L; Pobezhimova, T P; Katyshev, A I; Pavlovskaya, N S; Koroleva, N A; Lyubushkina, I V; Bashmakov, V Yu; Popov, V N; Borovskii, G B; Voinikov, V K

2014-06-01

359

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

NASA Astrophysics Data System (ADS)

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

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

2007-09-01

360

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

361

CHRISTINE FROST STRUCTURAL DYNAMICS  

E-print Network

Pine Wood 2 4x5x1/8 slats 2 8x1x3/4 columns 1 3x1x1/4 beam Terrarium 12x10x6 Gorilla Glue secured between the two wall panels using Gorilla Glue. The beam spanned the gap between the two columns

Ervin, Elizabeth K.

362

Ozone Chemistry in the High-Latitude Boundary Layer  

E-print Network

;Ozone Loss in the Arctic · Natural chemistry in the Arctic caused by bromine episodically removes O3 bromine come from? "leads" spray deposits salt on snowv surfaces frost flowers made of brine #12;AerosolO + HOX HOBr HOBr + Br- + H+ Br2 + H2O Atmosphere Snow PackFrost Flowers Br Br #12;"Bromine Explosion

Toohey, Darin W.

363

On Active Layer Environments and Processes in Western Dronning Maud Land, Antarctica  

NASA Astrophysics Data System (ADS)

The current understanding of Antarctic permafrost is poor, particularly regarding its evolution, the current thermal characteristics, and relationships with pedogenesis, hydrology, geomorphic, dynamics, biotic activity and response to global changes. Results from borehole temperature measurements over a four-year period in Western Dronning Maud Land suggest that the active layer depth is dependent on the substrate, latitude, altitude and the volume of ground exposed; the latter alludes to the potential impact of surrounding ice on the ground thermal regime. The active layer depths at the monitoring sites, varied between 16 cm at Vesleskarvet, a small nunatak at 850 masl to 28 cm in granitic till at Jutulsessen (1 270 masl). The mean near surface (1.5 cm depth) ground temperatures from 2009 to 2012 in the region have a narrow range from -16.4C at 850m to -17.5C at 1270 masl. Permafrost temperatures for the same locations vary between -16.3C and -18.3C. While little variability exists between the mean temperatures at the study locations, each site is distinct and seasonal and shorter-term frost cycles have produced landforms that are characteristic of both permafrost and diurnal frost environments. One of the key aspects of investigation is the control that the active layer has on autochthonous blockfield development in the region. The, thus far, exploratory research is being used to understand controls on the landscape and the relationship between distribution and abundance of biota. Given the rapidly changing climates in the region, improving knowledge of what drives patterns of biodiversity at a local and regional scale is vital to assess consequences of environmental change.

Hansen, C. D.; Meiklejohn, I.; Nel, W.

2012-12-01

364

Stratified Atmospheric Boundary Layers  

Microsoft Academic Search

Various features of different stability regimes of the stable boundary layer are discussed. Traditional layering is examined in terms of the roughness sublayer, surface layer, local similarity, z-less stratification and the region near the boundary-layer top. In the very stable case, the strongest turbulence may be detached from the surface and generated by shear associated with a low level jet,

L. Mahrt

1999-01-01

365

Chemical characterization, energy values, protein and carbohydrate fractions, degradation kinetics of frost damaged wheat (with severely overall weight loss) in ruminants.  

PubMed

In Canada, frost damage can result in millions of tonnes of wheat that is not suitable for human consumption (such wheat is referred to as 'frozen') each year. There is a need to systematically evaluate the nutritive value of frozen wheat for ruminants. So far, little research has been conducted to determine the magnitude of the differences in nutritive value between frozen and normal wheat. The objectives of this study were to compare frozen wheat and normal wheat (AC Barrie) in terms of (i) chemical characteristics; (ii) protein and carbohydrate fractions; (iii) energy value; and (iv) rumen degradation kinetics. The results showed that the overall yield losses of the frozen wheat were around 24%. The frozen wheat was significantly lower (P < 0.05) in starch (47 vs. 62%DM), non-structural carbohydrates (60 vs. 70%DM), and non-protein N (63 vs. 93%SCP); and higher (P < 0.05) in crude fat (3 vs. 2%DM), acid (6 vs. 2%DM), neutral detergent fiber (22 vs. 10%DM), lignin (2 vs. 1%DM), acid (3 vs. 1%CP) and neutral detergent insoluble CP (19 vs. 14%CP). The frozen wheat was also lower in (P < 0.05) energy (TDN, DE(3X), ME(3X,) NEL(3X), DE(4X), ME(4X,) NEL(4X) for dairy; ME, NE(m), and NE(g) beef cattle). After partitioning of protein and carbohydrate (CHO) subfractions, the results showed that the frozen wheat was lower (P < 0.05) in the intermediately degradable CP (PB2: 47 vs. 59%CP); and higher in rapidly degradable CP (PB1: 12 vs. 2%CP) and unavailable CP (PC: 3 vs. 1%CP). The frozen wheat was also lower (P < 0.05) in intermediately degradable CHO (CB1: 60 vs. 77%CHO); and higher (P < 0.05) in slowly degradable CHO (CB2: 20 vs. 8%CHO) and unavailable CHO (CC: 5 vs. 2%CHO). The in situ results showed that the frozen wheat had different patterns in rumen degradation kinetics of protein and starch. The extent of the changes varied according to the specific nutrient examined. In conclusion, the frozen wheat differed in chemical characteristics, TDN and energy values, protein and carbohydrate fractions and in situ degradation behavior from normal wheat. The chemical and nutritional characterization of wheat was highly associated with climate condition (frost damage). The frost damage to the wheat reduced nutrient content and availability and thus reduced nutrient supply to ruminants. PMID:20163583

Yu, Peiqiang; Racz, Vern

2009-04-01

366

Structurized surface layers of normal alkanes  

NASA Astrophysics Data System (ADS)

The elevated viscosity of micron interlayers of certain normal alkanes compared to their viscosity in the "volume" is determined experimentally in shear flow using a rotational viscometer. The observed difference is considered to be caused by the manifestation, in such interlayers, of structural inhomogeneity due to the presence of structurized polymolecular surface layers on the substrates bounding them. The structural parameters of such layers, i.e., their equilibrium initial thickness and "hydrodynamic strength," are calculated in the model of a constant-viscosity layer. The measured effective viscosity of the interlayers diminishes with growth in the shear-flow velocity, which is attributed to the "cutting" of the structurized layer. Surfactant doping of the liquids leads to an increase in the effective viscosity of the interlayers, which is produced by the strengthening of the layer structure.

Altoiz, B. A.; Kiriyan, S. V.

2010-07-01

367

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

368

Multi-layer carbon-based coatings for field emission  

DOEpatents

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

Sullivan, John P. (Albuquerque, NM); Friedmann, Thomas A. (Albuquerque, NM)

1998-01-01

369

Localised convection cells in the presence of a vertical magnetic field  

E-print Network

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

370

Geophysical and GIS study of gravel layer on Gyngys plain and K?szeghegyalja, W-Hungary  

NASA Astrophysics Data System (ADS)

The Western-Hungarian Gravel Cover (WHCG) is located between the Eastern Alps and the Danube Basin, surrounded by the Rba, Ikva, Pinka rivers, K?szeg-Rechnitz and Sopron Mountains. The extension of the gravelly sediment coverage is approximately 3000 km2, the volume is ~30 million cubicmeter. The layers thickness changes between 5-35 m. My research area is limited to the Gyngys Plain which northern side belongs to the K?szeghegyalja is also the part of the WHGC. The western boundary of this region is the wide, flat valley of the Gyngys stream, the northern is the Rpce's asimmetric, steep valley. The plain itself has a very low angle, even slope to southeastern direction. The elevation of the plain is 190-260 meter above sea level. The northern side is more fragmented, incised by asimmetric valleys. The hight of this area could form a contiguous flat tilted surface with a consistent slope. The slope conditions of the plain are changing nearby Acsd village, becoming slightly steeper and tilted to east immediately next to a narrow ridge extending northward. This ridge is the eastern boundary of a 2 km wide depression with a steeper northern side flattened to southward. The purpose of my study is to explore the geometry of gravel layer and to infer the processes that could create it. Firstly I made a database from borehole descriptions collected from the research area. This database as basis for interpolated GIS models, show the gravels material properties, extension, distribution of thickness in a large scale depend on a borehole density. I compared these surfaces with Digital Terrain Models with SRTM- and a more detailed model, created from Hungarian National Grid map sheets (1:10 000). Golden Software Surfer and Global Mapper were used to interpolate, represent and interpret these surfaces. The models with the detailed borehole data show a 1-3 meter thick unsorted, unstratified gravel layer with reddish brown coloured clay or brown loam matrix. The gravel material is poorly rounded, 0.5-7 cm quartz, often with red coloured surface. The layer covers the total research area, follows the recent topography. The young alluvial sediment of Gyngys can easily be separated, because it has different presence both in geometry and material. In further part of the study was a near-surface geoelectrical resistivity tomography with Wenner-Schlumberger array type. It was carried out on three survey region in order to find out the small-scale disturbances of the gravel layer. Two sections were measured on undisturbed field to compare the results with the borehole datas and the surface models. Based on resistivity the clayey gravel is clearly separated from its loam cover, even though it has relative low apparent resistivity (30-45 ohmm) caused by solid clayey matrix. Another two sections were located across and near the ridge was mentioned above. These sections show deformations affected by tectonic impacts or periglacial frost effects. The last survey region lies on the northern part of the area, the western side of V-shaped valley belongs toKozr-Borz stream. Three sections run from the top of the plateau level down towards the stream. The resistivity distribution shows cascading sediments mantled by redeposited gravelly material refers to usually periglacial mass-movement as solifluction. To sum the models, results of electrical tomograpy and compared with analogous formation environments, the studied gravel seems to be a periglacial pediment, affected by the freeze-thaw induced processes that produced a nearly flat surface, and the gravelly sediment with clay matrix. The study was supported by Hungarian Scientific Research Fund (OTKA NK83400) and was realized in the frames of TMOP 4.2.4.A/2-11-1-2012-0001 high priority "National Excellence Program - Elaborating and Operating an Inland Student and Researcher Personal Support System convergence program" project's scholarship support.

Szab, Vera; Kovcs, Gabor

2014-05-01

371

Ebenezer Hopkins Frost (1824-1866): William T.G. Morton's first identified patient and why he was invited to the Ether demonstration of October 16, 1846.  

PubMed

Although he was not the first to use ether as an anesthetic, it was not until William Thomas Green Morton's demonstration of the efficacy of ether anesthesia that its use spread rapidly throughout the world. Full identities of the first anesthetized patients of William Edward Clarke and Horace Wells are not known, but we are quite certain that Crawford Williamson Long correctly identified James Venable as his first patient to receive anesthesia. Using municipal records, historical accounts, and recent analyses of Morton's unsavory side, we undertook this study to explore three questions. First, we examine how Morton refined the technique of administering anesthesia based on Wells' failed attempt. Second, we describe the circumstances under which Morton encountered his first patient to receive anesthesia. Third, we offer an explanation as to why Morton insisted on bringing along this patient to attend the grand event we celebrate as Ether Day. This is an essay about William Thomas Green Morton and Ebenezer Hopkins Frost. PMID:22728779

LeVasseur, Ryan; Desai, Sukumar P

2012-08-01

372

MGS MOC Extended Mission View of North Polar Layers  

NASA Technical Reports Server (NTRS)

The north polar cap of Mars is the only place on the surface of the planet that is known to have water. Of course, the water there is frozen. Unfortunately, the martian north polar cap has been a difficult place for the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) to view. Each winter, the pole spends approximately 6 months in darkness. Each spring, everything is covered with frost. In summer and through autumn, the cap is often obscured by clouds--sometimes clouds of dust from raging dust storms, and sometimes clouds of water ice crystals. However, a period of excellent viewing conditions occurred early in the MGS Extended Mission (from February through April 2001). This image, taken by MOC in April 2001, shows the layers comprising the north polar cap exposed in an arcuate scarp that occurs at one end of Chasma Boreale. MOC images acquired in 1999 showed that the polar cap has two types of layers: there is a stack of light-toned, nearly uniformly-bedded layers at the top, and a stack of darker-toned beds that form shelves and benches at the bottom. The darker, lower beds are older. Dozens of MOC images were targeted during the clear-atmosphere period in 2001 to test the MOC team's hypotheses about the polar cap layers and these images have helped in documenting the nature of these layers. The lower, dark layers of the polar cap appear to include considerable amounts of sand, while the upper layers lack sand and instead may be a mixture of ice and dust. The lower layers appear to contributes and to the dune fields that surround the polar cap, though no dunes are present in the image shown here. This image is illuminated from the lower right and covers an area 14.5 km (9 mi.) across. The scarp slopes toward the bottom of the scene.

Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

2002-01-01

373

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

374

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, Anglique (Anglique Pascale)

2006-01-01

375

Microstructural investigations of light-emitting porous Si layers  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

376

Layers of the South Polar Layered Deposits  

NASA Technical Reports Server (NTRS)

On December 3, 1999, the Mars Polar Lander will touch down on the upper surface of a thick accumulation of layered material known as the 'South Polar Layered Deposits.' The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) has been providing stunning new pictures of the south polar layered deposits that, in conjunction with Mars Polar Lander observations, will eventually help answer many questions about this terrain.

Both the north and south polar regions are blanketed by thick accumulations of layered material. This has been known since the 1971-1972 mission of Mariner 9. Based upon data from the Mariner and Viking projects in the 1970s, the polar layered deposits have long been considered to be accumulations of dust and ice. The layering is thought to indicate changes in how ice and dust accumulate at the poles over the course of millenia. Changes in climate might affect the thickness and composition of polar layers in a way that is analogous to how years of drought and years of plentiful rain change the width of rings in a tree trunk on Earth.

The pictures shown here provide new details of what the south polar layered deposits look like at extremely high resolution from the MGS MOC. The picture on the left is a context frame taken at the same time as the high resolution view on the right. The context image covers an area about 115 km (71 mi) across and shows a thick, smooth blanket of material covering the upper 2/3 of the frame. This thick blanket is the south polar layered deposit material. The circular features at the lower left in the context image are craters occurring outside the polar layered deposit. More craters occur underneath the polar layered deposits. The small white box indicates the location of the MOC high resolution image (right) along the edge of the polar layered deposits. The picture is illuminated from the lower right.

The picture on the right shows one of the clearest and highest-resolution images of south polar layered material ever obtained. Located at 73.0oS, 224.5oW, this picture covers an area approximately 550 km (340 miles) northwest of where the Mars Polar Lander will touch down in December. Illuminated from the lower right, this scene covers an area 1.5 km (0.9 mi) wide and 4.6 km (1.9 mi) long. The smallest objects that can be seen are about the sizes of automobiles. Small dark streaks in the upper right are formed from winds that have blown small patches of sediment across the surface of the layered material. Layers of only a few meters thickness are exposed along the edge of the polar layered deposits. The amount of dust versus ice in these layers is unknown. It is hoped that the Mars Polar Lander will be able to help determine--at least for the upper layers of the deposit--how much ice is present.

1999-01-01

377

Photonic layered media  

DOEpatents

A new class of structured dielectric media which exhibit significant photonic bandstructure has been invented. The new structures, called photonic layered media, are easy to fabricate using existing layer-by-layer growth techniques, and offer the ability to significantly extend our practical ability to tailor the properties of such optical materials.

Fleming, James G. (Albuquerque, NM); Lin, Shawn-Yu (Albuquerque, NM)

2002-01-01

378

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

379

Rendering with coherent layers  

Microsoft Academic Search

For decades, animated cartoons and movie special effects have factored the rendering of a scene into layers that are updated independently and composed in the final display. We apply layer factorization to real-time computer graphics. The layers allow targeting of resources, whether the ink and paint artists of cartoons or the graphics pipeline as described here, to those parts of

Jed Lengyel; John Snyder

1997-01-01

380

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

381

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

382

Modelling diffusivity in porous polymeric membranes with an intermediate layer containing microbial cells  

Microsoft Academic Search

Three-layer systems (membrane composite layer (cells+polymer) membrane) are important in different biochemical applications. Models of latex layered-membranes were evaluated and compared with experimental data in order to predict the diffusivity of substrates in the composite layer containing living E.coli microbial cells. Diffusivity predictions are dependent on the presence or the absence of a skin layer, on the degree

Manuel Mota; Alexander Yelshin; Marcello Fidaleo; Michael C. Flickinger

2007-01-01

383

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 of Washington, Seattle, Washington 98105-55640 (Received 21 June 2000) The freezing of argon in silica powder is observed to generate bands of pure solid argon in the same manner as in the phenomenon of ice lens

Wettlaufer, John S.

384

Layered plasma polymer composite membranes  

DOEpatents

Layered plasma polymer composite fluid separation membranes are disclosed, which comprise alternating selective and permeable layers for a total of at least 2n layers, where n is .gtoreq.2 and is the number of selective layers.

Babcock, Walter C. (Bend, OR)

1994-01-01

385

BIODIVERSITY Presence-only versus presenceabsence  

E-print Network

BIODIVERSITY RESEARCH Presence-only versus presence­absence data in species composition determinant in the study. Sampling locations were based on true observations from the Global Biodiversity Information of species composition. Keywords Biodiversity, canonical correspondence analysis, environmental determinants

386

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

387

Reflection of presence: toward more natural and responsive telecollaboration  

NASA Astrophysics Data System (ADS)

THe purpose of reflection of presence is to create a framework for a telepresence environment that intelligently responds and adapts itself to its inhabitants in order to enhance interpersonal communication or also reflections of the other remotely-located participants, just as if every one is standing in the same room looking at each other through a real mirror. Using visual and auditory cues, segmented images of participants are dynamically layered into a single display using varying transparency, position and scale to reflect center of attention and degree of presence. Wireless tangible interfaces allow participants to customize their shared space and collaboratively manipulate and annotate media objects in the background. The system is novel in that it is implemented totally as a set of cooperating scripts instead of through a low-level programming language, enabling rapid experimental changes in the behavior of the prototype.

Agamanolis, Stefan; Westner, Alex; Bove, V. Michael, Jr.

1998-02-01

388

Layers of Ice  

NSDL National Science Digital Library

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

389

Layer Cake Geology  

NSDL National Science Digital Library

In this activity a special layered cake is used to demonstrate folding and faulting of sedimentary layers. As a result of this activity students will understand the mechanisms by which folds and faults occur within the earth's crust, recognize the difference in behavior between brittle and ductile rocks, and be able to predict the structure likely to result from application of various forces to layered rocks. Students will also interpret "core samples" to determine rock structures beneath the land surface and learn the meaning of fracture as applied to rock layers.

John Wagner

390

Geological Layer Detection and Candidate Science Target Identification  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

391

Network Layer 4-1 Network Layer  

E-print Network

for mobile users who want to join network (more shortly) DHCP overview: host broadcasts "_________" msg [optional] DHCP server responds with "__________" msg [optional] host requests IP address: "___________" msg DHCP server sends address: "___________" msg #12;Network Layer 4-12 DHCP client-server scenario

Xing, Guoliang

392

A major quantitative trait locus for cold-responsive gene expression is linked to frost-resistance gene Fr-A2 in common wheat.  

PubMed

Low temperature induces expression of Cor (cold-responsive)/Lea (late embryogenesis-abundant) gene family members through C-repeat binding factor (CBF) transcription factors in common wheat. However, the relationship between the genetic loci controlling cold-responsive gene expression and freezing tolerance is unclear. In expression quantitative trait locus (eQTL) analysis, accumulated transcripts of Cor/Lea and CBF genes were quantified in recombinant inbred lines derived from a cross between two common wheat cultivars with different levels of freezing tolerance. Four eQTLs controlling five cold-responsive genes were found, and the major eQTL with the greatest effect was located on the long arm of chromosome 5A. At least the 1D and 5A eQTLs played important roles in development of freezing tolerance in common wheat. The chromosomal location of the 5A eQTL, controlling four cold-responsive genes, coincided with a region homoeologous to a frost-tolerance locus (Fr-A (m) 2) reported as a CBF cluster region in einkorn wheat. The 5A eQTL plays a significant role through Cor/Lea gene expression in cold acclimation of wheat. In addition, our results suggest that one or more CBF copies at the Fr-2 region positively regulate other copies, which might amplify the positive effects of the CBF cluster on downstream Cor/Lea gene activation. PMID:23641182

Motomura, Yoichi; Kobayashi, Fuminori; Iehisa, Julio C M; Takumi, Shigeo

2013-03-01

393

A major quantitative trait locus for cold-responsive gene expression is linked to frost-resistance gene Fr-A2 in common wheat  

PubMed Central

Low temperature induces expression of Cor (cold-responsive)/Lea (late embryogenesis-abundant) gene family members through C-repeat binding factor (CBF) transcription factors in common wheat. However, the relationship between the genetic loci controlling cold-responsive gene expression and freezing tolerance is unclear. In expression quantitative trait locus (eQTL) analysis, accumulated transcripts of Cor/Lea and CBF genes were quantified in recombinant inbred lines derived from a cross between two common wheat cultivars with different levels of freezing tolerance. Four eQTLs controlling five cold-responsive genes were found, and the major eQTL with the greatest effect was located on the long arm of chromosome 5A. At least the 1D and 5A eQTLs played important roles in development of freezing tolerance in common wheat. The chromosomal location of the 5A eQTL, controlling four cold-responsive genes, coincided with a region homoeologous to a frost-tolerance locus (Fr-Am2) reported as a CBF cluster region in einkorn wheat. The 5A eQTL plays a significant role through Cor/Lea gene expression in cold acclimation of wheat. In addition, our results suggest that one or more CBF copies at the Fr-2 region positively regulate other copies, which might amplify the positive effects of the CBF cluster on downstream Cor/Lea gene activation. PMID:23641182

Motomura, Yoichi; Kobayashi, Fuminori; Iehisa, Julio C. M.; Takumi, Shigeo

2013-01-01

394

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

Microsoft Academic Search

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

Zoltan B. Szuts

2010-01-01

395

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

396

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

397

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

398

Multiple density layered insulator  

DOEpatents

A multiple density layered insulator for use with a laser is disclosed wh provides at least two different insulation materials for a laser discharge tube, where the two insulation materials have different thermoconductivities. The multiple layer insulation materials provide for improved thermoconductivity capability for improved laser operation.

Alger, Terry W. (Tracy, CA)

1994-01-01

399

Layer Cake Geology  

NSDL National Science Digital Library

This activity provides young students with a relevant model (a layer cake) to help them understand concepts about sedimentary rock layers (such as the Law of Superposition), correlation of the rock record with geologic time and relative ages of rocks and fossils.

Molly Ward

400

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

401

Layers of the Atmosphere  

NSDL National Science Digital Library

In this activity, students learn that the atmosphere can be divided into layers based on temperature changes at different altitudes, by making a graph. They will read the background material, plot data points, and determine where layers begin and end from their comprehension of the reading material.

Jack Fearing

402

The Atmospheric Boundary Layer  

ERIC Educational Resources Information Center

Discusses some important parameters of the boundary layer and effects of turbulence on the circulation and energy dissipation of the atmosphere. Indicates that boundary-layer research plays an important role in long-term forecasting and the study of air-pollution meteorology. (CC)

Tennekes, Hendrik

1974-01-01

403

Multiple density layered insulator  

DOEpatents

A multiple density layered insulator for use with a laser is disclosed which provides at least two different insulation materials for a laser discharge tube, where the two insulation materials have different thermoconductivities. The multiple layer insulation materials provide for improved thermoconductivity capability for improved laser operation. 4 figs.

Alger, T.W.

1994-09-06

404

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-m frost over 20 m for the polar ice and about 1 monolayer of 1-m frost over 7 m 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 m, that the whole infrared spectrum 0.8-5.2 m 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 m base grain size with ~one monolayer of r=1 m ice. This grades gradually to r=20 or more m and a fractional 0.1) monolayer of r=2 m 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 m. 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

405

The stability of the mesospheric plasma layer  

SciTech Connect

The presence of micron and sub-micron size dust in the Earth's summer mesopause are a possible cause of electron density depletion. Whereas electrons in this weakly ionized and weakly magnetized layer are frozen in the magnetic field, the ions and dust are highly diffusive. This relative drift between the plasma particles will cause a current in the medium. The presence of such a current can destabilize the plasma layer with a growth rate of the order of Alfven frequency. Since required current density for the onset of this instability is on the order of J > or approx. 0.03A/m{sup 2}, it is quite unlikely that such a strong current is present in the mesosphere. However, owing to the prevailing ambiguity of measurements, the existence of such a current is not completely ruled out.

Pandey, B. P. [Department of Physics, Macquarie University, Sydney, NSW 2109 (Australia); Vladimirov, S. V. [School of Physics, University of Sydney, NSW 2006 (Australia)

2011-12-15

406

Layer-by-layer nanoencapsulation of camptothecin with improved activity.  

PubMed

160 nm nanocapsules containing up to 60% of camptothecin in the core and 7-8 polyelectrolyte bilayers in the shell were produced by washless layer-by-layer assembly of heparin and block-copolymer of poly-l-lysine and polyethylene glycol. The outer surface of the nanocapsules was additionally modified with polyethylene glycol of 5 kDa or 20 kDa molecular weight to attain protein resistant properties, colloidal stability in serum and prolonged release of the drug from the capsules. An advantage of the LbL coated capsules is the preservation of camptothecin lactone form with the shell assembly starting at acidic pH and improved chemical stability of encapsulated drug at neutral and basic pH, especially in the presence of albumin that makes such formulation more active than free camptothecin. LbL nanocapsules preserve the camptothecin lactone form at pH 7.4 resulting in triple activity of the drug toward CRL2303 glioblastoma cell. PMID:24508806

Parekh, Gaurav; Pattekari, Pravin; Joshi, Chaitanya; Shutava, Tatsiana; DeCoster, Mark; Levchenko, Tatyana; Torchilin, Vladimir; Lvov, Yuri

2014-04-25

407

Plate Tectonics: Layered Earth  

NSDL National Science Digital Library

This Science Object is the first of five Science Objects in the Plate Tectonics SciPack. It explores the characteristics of the various layers of the Earth, using the way waves travel through the different layers to illustrate the differences in each layer. The interior of the earth is hot, under high pressure from gravitational pull, and more dense than its rocky outer crust. The earth is layered with a relatively thin crust; hot, deformable mantle; liquid outer core; and solid, metallic, and dense inner core. Learning Outcomes:? Identify that Earth has layers (not necessarily name them), and that the interior is hotter and more dense than the crust.? Identify the crust as mechanically strong, and the underlying mantle as deformable and convecting.

National Science Teachers Association (NSTA)

2006-11-01

408

Multiple layer insulation cover  

DOEpatents

A multiple layer insulation cover for preventing heat loss in, for example, a greenhouse, is disclosed. The cover is comprised of spaced layers of thin foil covered fabric separated from each other by air spaces. The spacing is accomplished by the inflation of spaced air bladders which are integrally formed in the cover and to which the layers of the cover are secured. The bladders are inflated after the cover has been deployed in its intended use to separate the layers of the foil material. The sizes of the material layers are selected to compensate for sagging across the width of the cover so that the desired spacing is uniformly maintained when the cover has been deployed. The bladders are deflated as the cover is stored thereby expediting the storage process and reducing the amount of storage space required.

Farrell, James J. (Livingston Manor, NY); Donohoe, Anthony J. (Ovid, NY)

1981-11-03

409

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

410

Optical phenomena and antifrosting property on biomimetics slippery fluid-infused antireflective films via layer-by-layer comparison with superhydrophobic and antireflective films.  

PubMed

Sophisticated material interfaces generated by natural life forms such as lotus leaves and Nepenthes pitcher plants have exceptional abilities to resolve challenges in wide areas of industry and medicine. The nano- and microstructures inspired by these natural materials can repel various liquids and form self-cleaning coatings. In particular, slippery liquid-infused surfaces are receiving remarkable interest as transparent, nonfouling, and antifrosting synthetic surfaces for solar cells and optical devices. Here we focus on the transparency of lubricant-infused texture on antireflective films fabricated by layer-by-layer self-assembly that decrease light scattering, which is important to maintain device properties. A slippery fluid-infused antireflective film composed of chitin nanofibers less than 50 nm in diameter prevented light scattering at the long-wavelength side by Rayleigh scattering to achieve 97.2% transmittance. Moreover, films composed of the same materials demonstrated three different morphologies: superhydrophilicity with antireflection, superhydrophobicity, and omniphobicity, mimicking the biological structures of moth eyes, lotus leaves, and pitcher plants, respectively. The effect of thermal changes on the ability of each film to prevent frost formation was investigated. The slippery fluid-infused antireflective film showed effective antifrosting behavior. PMID:25093243

Manabe, Kengo; Nishizawa, Shingo; Kyung, Kyu-Hong; Shiratori, Seimei

2014-08-27

411

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

412

Lithospheric layering in the North American craton.  

PubMed

How cratons-extremely stable continental areas of the Earth's crust-formed and remained largely unchanged for more than 2,500 million years is much debated. Recent studies of seismic-wave receiver function data have detected a structural boundary under continental cratons at depths too shallow to be consistent with the lithosphere-asthenosphere boundary, as inferred from seismic tomography and other geophysical studies. Here we show that changes in the direction of azimuthal anisotropy with depth reveal the presence of two distinct lithospheric layers throughout the stable part of the North American continent. The top layer is thick ( approximately 150 km) under the Archaean core and tapers out on the surrounding Palaeozoic borders. Its thickness variations follow those of a highly depleted layer inferred from thermo-barometric analysis of xenoliths. The lithosphere-asthenosphere boundary is relatively flat (ranging from 180 to 240 km in depth), in agreement with the presence of a thermal conductive root that subsequently formed around the depleted chemical layer. Our findings tie together seismological, geochemical and geodynamical studies of the cratonic lithosphere in North America. They also suggest that the horizon detected in receiver function studies probably corresponds to the sharp mid-lithospheric boundary rather than to the more gradual lithosphere-asthenosphere boundary. PMID:20740006

Yuan, Huaiyu; Romanowicz, Barbara

2010-08-26

413

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

414

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

415

Electrohydrodynamics within the electrical double layer in the presence of finite temperature gradients  

NASA Astrophysics Data System (ADS)

A wide spectrum of electrokinetic studies is modeled as isothermal ones to expedite analysis even when such conditions may be extremely difficult to realize in practice. Going beyond the isothermal paradigm, we address here the case of flow induced electrohydrodynamics, commonly streaming potential flows, in a situation where finite temperature gradients do exist. By way of analyzing a model problem of flow through a narrow parallel-plate channel, we show that the temperature gradients applied at the channel walls may have a significant effect on the streaming potential, and, consequently, on the flow itself. Our model takes into consideration all the pertinent phenomenological aspects stemming from the imposed thermal gradients, such as the Soret effect, the thermoelectric effect, and the electrothermal effect, by a full-fledged coupling among the electric potential, the ionic species distribution, the fluid velocity and the local fluid temperature fields, without resorting to ad hoc simplifications. We expect this expository study to contribute significantly towards more sophisticated future endeavors in actual development of micro- and nano-devices for applications simultaneously involving thermal management and electrokinetic effects.

Ghonge, Tanmay; Chakraborty, Jeevanjyoti; Dey, Ranabir; Chakraborty, Suman

2013-11-01

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

Terby's Layered Rocks  

NASA Technical Reports Server (NTRS)

14 March 2004 Layered rock outcrops are common all across Mars, and the Mars rover, Opportunity, has recently investigated some layered rocks in Meridiani Planum. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows layered sedimentary rocks in northern Terby Crater, located just north of the giant Hellas Basin near 27.5oS, 285.8oW. Hundreds of layers are exposed in a deposit several kilometers thick within Terby. A history of events that shaped the northern Hellas region is recorded in these rocks, just waiting for a person or robot to investigate. The picture covers an area 3 km (1.9 mi) across. Sunlight illuminates the scene from the left.

2004-01-01

418

Layer-Cake Earth  

NSDL National Science Digital Library

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

Rebecca Tedford

2006-12-01

419

The Earth's Layers  

NSDL National Science Digital Library

What are the differences between the three layers of the Earth? (core, mantle, and crust) Look at each of these websites and be able to answer the question, what are the differences in the earth's core, mantle, and crust? Use this Graphic Organizer for Earth s Structure Go here to learn about the core. Write in words about the core in your chart. Info about Core with Quiz Visit this website and click on the three layers of the ...

Ms. Fields

2011-04-07

420

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

421

Ventilated oscillatory boundary layers  

NASA Astrophysics Data System (ADS)

A combination of field and laboratory experiments are made in order to expand our knowledge of naturally occurring oscillatory boundary layers. Chapter 1 describes field observations of the development of wave driven boundary layers at the fluid sediment interface. Under the crest of the wave, this development can be idealized as an identifiable sequence of three parts. The latter parts of this development are never observed to occur under the trough of the wave despite similarities in wave orbital velocity and acceleration. It is proposed that wave induced boundary ventilation, the oscillatory flow through the surface of a permeable bed, may be responsible for this apparent developmental asymmetry. In chapter 2, a laboratory study is presented of ventilated oscillatory boundary layers. These are boundary layers arising from a flow which oscillates parallel to a permeable bed which is subject to oscillating percolation of the same frequency as the bed parallel flow. Measurements of boundary layer velocities, bed stress and turbulent flow properties are presented. It is observed that suction (flow into the bed) enhances the near bed velocities and bed stress while injection (flow out of the bed) leads to a reduction in these quantities. As the ventilated oscillatory boundary layer experiences both these phenomena in one full cycle, the result is a net stress and a net boundary layer velocity in an otherwise symmetric flow. While production of turbulence attributable to injection is enhanced, the finite time required for this to occur leads to greater vertically averaged turbulence in the suction half cycle. Turbulence generated in the suction half cycle is maintained in a compact layer much closer to the bed. These effects appear to hold for Re ranging from 10(exp 5) to 10(exp 6) and for oscillations other than sinusoidal.

Conley, Daniel C.; Inman, Douglas L.

1993-02-01

422

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

423

Genes and traits associated with chromosome 2H and 5H regions controlling sensitivity of reproductive tissues to frost in barley.  

PubMed

Frost at flowering can cause significant damage to cereal crops. QTL for low temperature tolerance in reproductive tissues (LTR tolerance) were previously described on barley 2HL and 5HL chromosome arms. With the aim of identifying potential LTR tolerance mechanisms, barley Amagi Nijo x WI2585 and Haruna Nijo x Galleon populations were examined for flowering time and spike morphology traits associated with the LTR tolerance loci. In spring-type progeny of both crosses, winter alleles at the Vrn-H1 vernalization response locus on 5H were linked in coupling with LTR tolerance and were unexpectedly associated with earlier flowering. In contrast, tolerance on 2HL was coupled with late flowering alleles at a locus we named Flt-2L. Both chromosome regions influenced chasmogamy/cleistogamy (open/closed florets), although tolerance was associated with cleistogamy at the 2HL locus and chasmogamy at the 5HL locus. LTR tolerance controlled by both loci was accompanied by shorter spikes, which were due to fewer florets per spike on 5HL, but shorter rachis internodes on 2HL. The Eps-2S locus also segregated in both crosses and influenced spike length and flowering time but not LTR tolerance. Thus, none of the traits was consistently correlated with LTR tolerance, suggesting that the tolerance may be due to some other visible trait or an intrinsic (biochemical) property. Winter alleles at the Vrn-H1 locus and short rachis internodes may be of potential use in barley breeding, as markers for selection of LTR tolerance at 5HL and 2HL loci, respectively. PMID:19277599

Chen, Andrew; Reinheimer, Jason; Brl-Babel, Anita; Baumann, Ute; Pallotta, Margaret; Fincher, Geoffrey B; Collins, Nicholas C

2009-05-01

424

Reflection as an Indicator of Cognitive Presence  

ERIC Educational Resources Information Center

In the Community of Inquiry (CoI) model, cognitive presence indicators can be used to evaluate the quality of inquiry in a discussion forum. Engagement in critical thinking and deep knowledge can occur through reflective processes. When learners move through the four phases of cognitive presence (triggering, exploration, integration, resolution),

Redmond, Petrea

2014-01-01

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

High enthalpy hypersonic boundary layer flow  

NASA Technical Reports Server (NTRS)

A theoretical and experimental study of an ionizing laminar boundary layer formed by a very high enthalpy flow (in excess of 12 eV per atom or 7000 cal/gm) with allowance for the presence of helium driver gas is described. The theoretical investigation has shown that the use of variable transport properties and their respective derivatives is very important in the solution of equilibrium boundary layer equations of high enthalpy flow. The effect of low level helium contamination on the surface heat transfer rate is minimal. The variation of ionization is much smaller in a chemically frozen boundary layer solution than in an equilibrium boundary layer calculation and consequently, the variation of the transport properties in the case of the former was not essential in the integration. The experiments have been conducted in a free piston shock tunnel, and a detailed study of its nozzle operation, including the effects of low levels of helium driver gas contamination has been made. Neither the extreme solutions of an equilibrium nor of a frozen boundary layer will adequately predict surface heat transfer rate in very high enthalpy flows.

Yanow, G.

1972-01-01