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1

Sublimation Behavior of Annular Frost Layer by Impinging Jet Flow  

NASA Astrophysics Data System (ADS)

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

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

2

Review Concerning Studies of Frost Deposition  

NASA Astrophysics Data System (ADS)

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

Yamashita, Koji

3

Frost-free North Polar Layers in the Good Old Summertime  

NASA Technical Reports Server (NTRS)

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

2006-01-01

4

Identifying and Mapping Seasonal Surface Water Frost with MGS TES  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

5

Frost Heave Patterns and Optimal Design of Insulated Culverts.  

National Technical Information Service (NTIS)

When a culvert is placed under a road, the presence of air at freezing temperatures in the culvert may induce differential frost conditions in pavements. Also, a differential frost heave pattern can appear when the culvert is placed in a frost-susceptible...

C. Duquennoi R. L. Sterling

1991-01-01

6

Dielectrophoretic interdigitated electrode arrays in the presence of double layer  

NASA Astrophysics Data System (ADS)

Uncharged particles in electrolytic solutions can be manipulated using a nonuniform AC electric field which generates a dielectrophoretic (DEP) force, acting on those particles. Nonuniform AC electric fields generated by coplanar microelectrodes also produce steady fluid flow in electrolytic solutions also called AC electroosmosis, ACEO. This fluid flow is explained by the presence of an electrode shielding or double layer where ions from the bulk fluid are distributed above electrodes when an electric field is applied. If the electric field is constant, the distribution of ions can be described by Debye and Huckel. If the electric field is alternating, as is the case in dielectrophoretic, the behavior of the double layer becomes more complex. The presence of this double layer is significant for microfluidic applications and combined use of ACEO and DEP have been used to manipulate micro and nano-particles. DEP force fields have been studied ignoring the presence of the double layer. We study the influence of the electrode shielding on the dielectrophoresis forces. We adopt the simple mathematical model used in previous simulations of ACEO pumps. Neglecting Faradaic reactions, the double layer on each electrode acts like a capacitor with a constant capacitance in the linear regime of small voltages. According to this approach, the DEP force field has interesting properties which could now give an understanding of some previously unexplained experimental observations.

Loire, Sophie; Mezic, Igor

2008-11-01

7

Frost-induced deformations and stresses in pipelines  

Microsoft Academic Search

Forst-induced soil-pipeline interaction is modelled using a time-dependent thermo-mechanical process. A simplified one-dimensional frost heave model is used to evaluate frost heave, and a beam on elastic foundation finite element is used to model the buried pipeline. The time-dependent creep displacements of frozen soil are determined based on the elastic theory for the multi-layer half space. The frost-related soil stiffness

A. G. Razaqpur; Daiyu Wang

1996-01-01

8

Frost Formation and Defrosting for Heat Pump Systems  

NASA Astrophysics Data System (ADS)

Recently, frost formation becomes an more important phenomenon not only in the cryogenic equipment but also in the air conditioner equipped with heat pump systems. When heat pump systems are used to supply thermal energy from air for the purpose of space heating in winter, the surface temperature of the evaporator often falls below 0°C and then frost deposition occurs there because it gains heat from the cold outdoor air. Frost formation cannot be treated easily as a growth of uniform substances such as ice because of the complicated nature of a frost layer. Accordingly, frost formation has been studied from the various points of view. This paper will give a review of studies on frost fomation and defrosting connected with heat pump systems.

Aoki, Kazuo

9

Frosted Chasma Boreale Dunes  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

10

Revised procedure for pavement design under seasonal frost conditions  

Microsoft Academic Search

This report presents engineering guidance and design criteria for pavements at Army and Air Force facilities in seasonal frost areas. Design methods for controlling surface roughness and loss of subgrade strength during thawing periods are provided. Criteria for using thermal insulating materials and membrane encapsulated soil layers in seasonal frost areas are presented. Six design examples are included.

R. L. Berg; T. C. Johnson

1983-01-01

11

Revised procedure for pavement design under seasonal frost conditions  

NASA Astrophysics Data System (ADS)

This report presents engineering guidance and design criteria for pavements at Army and Air Force facilities in seasonal frost areas. Design methods for controlling surface roughness and loss of subgrade strength during thawing periods are provided. Criteria for using thermal insulating materials and membrane encapsulated soil layers in seasonal frost areas are presented. Six design examples are included.

Berg, R. L.; Johnson, T. C.

1983-09-01

12

Microorganisms in Frost Scars.  

National Technical Information Service (NTIS)

A microbiological survey was carried out among different types of frost scars. Surface samples from soils supporting extensive vegetation contained significantly more mesophilic and psychrophilic bacteria than samples from bare, mineral soils. There were ...

W. L. Boyd J. W. Boyd

1971-01-01

13

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

14

A frost formation model and its validation under various experimental conditions  

NASA Technical Reports Server (NTRS)

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

Dietenberger, M. A.

1982-01-01

15

Predicting Pipeline Frost Load  

Microsoft Academic Search

A study was undertaken to fínd a formula for predicting the additional load imposed on underground pipelines by soil freezing. The authors conclude that a modified Boussinesq equation can be used to assess this load. Results also showed that frost affects the modulus of soil reaction and therefore the induced stress in flexible pipe. Se emprendió un estudio para hallar

Mellburne B. Fielding; Arieh Cohen

1988-01-01

16

Predicting pipeline frost load  

SciTech Connect

A study was undertaken to find a formula for predicting the additional load imposed on underground pipelines by soil freezing. The authors conclude that a modified Boussinesq equation can be used to assess this load. Results also showed that frost affects the modulus of soil reaction and therefore the induced stress in flexible pipe.

Fielding, M.B.; Cohen, A.

1988-11-01

17

Polygons in Seasonal Frost  

NASA Technical Reports Server (NTRS)

8 February 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a summertime scene in the south polar region of the red planet. A patch of bright frost--possibly water ice--is seen in the lower third of the image. Polygon patterns that have developed in the ice as it sublimes away can be seen; these are not evident in the defrosted surfaces, so they are thought to have formed in the frost. This image is located near 82.6oS, 352.5oW. Sunlight illuminates this scene from the upper left; the image covers an area 3 km (1.9 mi) wide.

2004-01-01

18

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

19

Winter Frost and Fog  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

20

Frost Action on Transportation Facilities.  

National Technical Information Service (NTIS)

The 7 papers in this report deal with the following areas: measurement and prediction of frost penetration in highways; a device for evaluation of thaw weakening of frost-susceptible soil; change in soil structure due to freeze-thaw and repeated loading; ...

R. A. Chisholm

1983-01-01

21

Seeing through Frost on Enceladus  

NASA Astrophysics Data System (ADS)

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

Helfenstein, P.

2012-12-01

22

Improved Drainage and Frost Action Criteria for New Jersey Pavement Design. Phase II. Data Analysis.  

National Technical Information Service (NTIS)

The feasibility of including open-graded drainage layers in their highway pavements was studied. Before constructing actual pavements with open-graded drainage layers, frost penetration depths and moisture content profiles beneath several pavements in New...

R. L. Berg

1979-01-01

23

Pluto - Evidence for methane frost  

NASA Technical Reports Server (NTRS)

Results are presented for infrared photometry of Pluto in the wavelength range from 1.2 to 2.2 microns, which includes the diagnostic absorption bands of water and methane frosts (designated as H1 and H2, respectively). Based on Pluto's observed J-H color and H1/H2 reflectance ratio as well as restrictions imposed by other observational and theoretical studies, it is concluded that methane frost is probably the dominant reflecting material on the planet's surface. It is suggested that this frost may be mixed with other materials, and some variation of the frost cover is indicated. Two plausible sources for the methane on Pluto are discussed, the average geometric albedo of the planet is assumed to be 0.4, and its diameter is estimated to be 3300 km.

Cruikshank, D. P.; Pilcher, C. B.; Morrison, D.

1976-01-01

24

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.

25

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

SciTech Connect

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

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

2012-03-20

26

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

SciTech Connect

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

Spence, E. J.; Roach, A. H.; Edlund, E. M.; Sloboda, P.; Ji, H. [Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas and Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

2012-05-15

27

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

28

Frost Susceptibility of Unbound Bases  

Microsoft Academic Search

The Mineral Criterion is an important part of the evaluation process of frost susceptibility concerning base materials for road construction in Austria. Dependent on grain size distribution, it defines mineralogical limiting values for the fraction < 0,02 mm. On the one hand the Mineral Criterion has proved successful, but on the other hand it turned out to be too strict.

H. Kugler; F. Ottner; B. Schwaighofer; W. Strasser

2005-01-01

29

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

30

Diffusion bonding of stainless steel to Zircaloy4 in the presence of a Ta intermediate layer  

Microsoft Academic Search

Diffusion bonding of stainless steel to Zircaloy-4 in the presence of Ta as interlayer has been investigated using diffusion couples heat treated at 1150 °C under vacuum for 3 h. Different types of regions have been observed in stainless steel, Zircaloy-4 and Ta foil. A Cr rich layer formed in stainless steel is found to act as a diffusion barrier.

M. Ahmad; J. I. Akhter; Q. Zaman; M. A Shaikh; M. Akhtar; M. Iqbal; E. Ahmed

2003-01-01

31

Winter frost at Viking Lander 2 site  

NASA Astrophysics Data System (ADS)

This paper presents quantitative evidence for cold trapping (frost redeposition) at the Viking Lander 2 site. This evidence consists of the frost surface coverage and color transition, the timing of this transition, and the limited vertical mixing and horizontal water transport. It is argued that cold trapping must be a general property of seasonal frost and, therefore, must be considered in order to understand the evolution of the surface environment of Mars.

Svitek, T.; Murray, B.

1990-02-01

32

Frost heave induced mechanics of buried pipelines  

Microsoft Academic Search

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

A. P. S. Selvadurai; S. B. Shinde

1993-01-01

33

Frost Growth and Densification in Laminar Flow Over Flat Surfaces.  

National Technical Information Service (NTIS)

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...

M. Kandula

2011-01-01

34

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

PubMed Central

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

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

2011-01-01

35

Study on Heat and Mass Transfer under Frosting Condition  

NASA Astrophysics Data System (ADS)

A set of boundary layer eqations - continuity, momentum, energy and diffusion equations - is solved numerically with satisfaction of a thermodynamic equilibrium between temperature and concentration of water vapor, when frost deposits on a flat plate under laminar forced convection. The effects of frost surface temperature and ambient air condition - temperature and humidity - on the coefficients of heat and mass transfers are investigated. The relationships between Nusselt number and Reynolds number, and between Sherwood number and Reynolds number are maintained the similar tendency respectively whether the thermodynamic equilibrium is satisfied or not. When the eqlli1ibrillm is satisfied, the mass transfer coefficients are lower and the heat transfer coefficients are higher than ones without satisfaction of the equilibrium.

Ishihara, Isao

36

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

37

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

38

Frost-ring chronologies as dendroclimatic proxies of boreal environments  

NASA Astrophysics Data System (ADS)

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

Payette, Serge; Delwaide, Ann; Simard, Martin

2010-01-01

39

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

40

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 Perú) 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

41

DIFFERENTIAL FROST HEAVE AT PIPELINE-ROAD CROSSINGS  

Microsoft Academic Search

Essentially all areas of Canada are affected by significant seasonal frost penetration. The effect of the frost penetration on roads and highways, especially the amount of total frost heave and the effect of the subsequent thaw, varies with soil type. Road design and construction must consider the effects of frost heave and subsequent spring thaw. The location and amounts of

Gerry Ferris

42

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

PubMed

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

Zhao, Yusheng; Gowda, Manje; Würschum, Tobias; Longin, C Friedrich H; Korzun, Viktor; Kollers, Sonja; Schachschneider, Ralf; Zeng, Jian; Fernando, Rohan; Dubcovsky, Jorge; Reif, Jochen C

2013-11-01

43

Modelling Frost Heaving and Frost Penetration in Soils at Some Observation Sites in Finland: The SSR Model.  

National Technical Information Service (NTIS)

The purpose of the study was to monitor frost heaving and frost penetration at six observation sites in Finland in 1982 - 1984. Frost heaving was also studied in the laboratory with frost-heave tests carried out on undisturbed specimens. A calculation mod...

S. Saarelainen

1992-01-01

44

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

NASA Astrophysics Data System (ADS)

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

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

1996-06-01

45

Diffusion bonding of stainless steel to Zircaloy-4 in the presence of a Ta intermediate layer  

NASA Astrophysics Data System (ADS)

Diffusion bonding of stainless steel to Zircaloy-4 in the presence of Ta as interlayer has been investigated using diffusion couples heat treated at 1150 °C under vacuum for 3 h. Different types of regions have been observed in stainless steel, Zircaloy-4 and Ta foil. A Cr rich layer formed in stainless steel is found to act as a diffusion barrier. A region observed with the Ta foil in Zircaloy-4 is rich in Cr, Ta, Fe and Zr while two zones are formed in Zircaoly-4 containing Zr, Ta, Cr, Fe and Ni. The zone rich in Zr gives black contrast and the other zone gives grey contrast and these are identified as eutectic phases of the type TaCr 2-Liq.-?-Zr and Ta(Cr,Fe) 2-Liq.-?-Zr.

Ahmad, M.; Akhter, J. I.; Zaman, Q.; Shaikh, M. A.; Akhtar, M.; Iqbal, M.; Ahmed, E.

2003-05-01

46

Enhancement of hydrolysis in alkali ultrathin layers on metal substrates in the presence of electron confinement  

NASA Astrophysics Data System (ADS)

Vibrational spectroscopy has been used to study the interaction at room temperature of H 2O with ultrathin alkali films grown on Cu(1 1 1), Ni(1 1 1) and Ag/Ni(1 1 1). We find strongly enhanced dissociation efficiency in the monolayer regime of Na/Cu(1 1 1), indicative of an active role of the existing Na-derived quantum wells in hydrolysis. No water adsorption has been observed for alkalis (Na, K) adsorbed on Ni(1 1 1), very likely due to the absence of electron confinement in these systems. On the other hand, partial water dissociation has been revealed in K-doped silver thin layers on Ni(1 1 1), in the presence of Ag 5sp-derived quantum wells.

Politano, Antonio; Chiarello, Gennaro

2010-07-01

47

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

2009-08-01

48

Boundary-layer variations due to orographic-wave breaking in the presence of rotation  

NASA Astrophysics Data System (ADS)

A mesoscale numerical model is used to study the atmospheric boundary-layer (ABL) response to nonlinear orographic forcing with Coriolis effect, f, over a mountain with length (the cross-wind component) comparable to the Rossby radius of deformation, LR. The orographic-wave breaking occurring for Froude number Fr < 1, affected by f > 0, intensifies on the northern flank for westerly flows, as also found in other recent studies. A cumulative effect occurs as the Coriolis force lifts the northern ABL top and generates a stronger low-level jet (LLJ) than on the southern side. A differential layering also appears, since the specific humidity is higher in the lower southern ABL than in the related northern ABL, and vice versa. By contrast, there are higher values of the turbulent kinetic energy and humidity in the upper northern ABL. The breaking of flow symmetry around the orography due to f changes both the vertical vorticity and horizontal divergence field, (, D), it modulates eddies and turbulence leading to the differential layering of the ABL. The stronger northern LLJ and its weaker southern counterpart, both meandering, together with the asymmetric wave breaking, induce strong lee-side fluctuations of the (zeta, D) field in the presence of f. The enhanced (zeta, D) production due to wave breaking over the distance apLR, the primary atmosphere-orography resonance occurs mainly in the vertical, while the 'f-enhancement' occurs in the horizontal plane. In this way, the initial mesoscale forcing may extend its effects over the synoptic scale.

Grisogono, B.; Enger, L.

2004-10-01

49

Design of Civil Airfield Pavements for Seasonal Frost and Permafrost Conditions.  

National Technical Information Service (NTIS)

A supply of water, freezing temperatures, and frost-susceptible soil is essential to cause frost action. The report describes the frost susceptibility of various FAA soil groups. The detrimental effects of the frost heaving of airfield pavements are contr...

R. L. Berg

1974-01-01

50

Frost halos from supercooled water droplets.  

PubMed

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

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

2012-10-01

51

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

52

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, Jürgen; Neuner, Gilbert; Wagner, Johanna

2013-03-01

53

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

SciTech Connect

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

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

2013-07-29

54

Frost Protection of Buried Water and Sewage Pipes. Three Articles.  

National Technical Information Service (NTIS)

Two of the articles in this report discuss frost prevention for privately owned water and sewage pipes laid shallow (above the frost penetration level) in bedrock type terrain. The third article contains frost load data in tabular form for all communities...

P. Gunderson

1978-01-01

55

Rapid Method for Determining the Frost Resistance of Bricks.  

National Technical Information Service (NTIS)

A rapid method for the determination of the frost resistance of bricks has been developed, based on the partial thawing of the test specimen between the frost cycles. The time required for each frost cycle can be reduced to 2-3 hours by using alcohol as t...

F. Sanford H. Fredholm

1969-01-01

56

Studies of dust acoustic double layers in the presence of trapped particles  

NASA Astrophysics Data System (ADS)

An analytical solution for time stationary weak double layers in an unmagnetized dusty plasma by using Sagdeev's pseudopotential method is studied considering dusts with constant charge and mass. Here, the plasma consists of electrons, ions and negatively-charged micron-sized dust particles. From the study, expressions for the potential and the dust acoustic velocity of the double layer is determined.

Mahanta, M. K.; Moulick, R.; Goswami, K. S.

2014-01-01

57

Frost Heave Control with Buried Insulation.  

National Technical Information Service (NTIS)

To investigate the effectiveness of extruded insulation panels in the mitigation of frost heave problems, two sites were selected: SH 40 at Rabbit Ears Pass with an elevation of 9,000 feet and I-70 east of Eisenhower Tunnel at an elevation of 10,000 feet....

A. Ardani

1989-01-01

58

Frost Heave Control with Buried Insulation.  

National Technical Information Service (NTIS)

To investigate the effectiveness of extruded insulation panels in the mitigation of frost heave problems, two sites were selected: SH 40 at Rabbit Ears Pass with an elevation of 9,000 feet and I-70 east of Eisenhower Tunnel at an elevation of 10,000 feet....

A. Ardani

1987-01-01

59

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

Microsoft Academic Search

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

Ronald W. P. King; Sheldon S. Sandler

1994-01-01

60

Distribution of Sulfur Dioxide Frost on Io  

NASA Technical Reports Server (NTRS)

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

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

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

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

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

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

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

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

1997-01-01

61

Bridge Frost Prediction by Heat and Mass Transfer Methods  

NASA Astrophysics Data System (ADS)

Frost on roadways and bridges can present hazardous conditions to motorists, particularly when it occurs in patches or on bridges when adjacent roadways are clear of frost. To minimize materials costs, vehicle corrosion, and negative environmental impacts, frost-suppression chemicals should be applied only when, where, and in the appropriate amounts needed to maintain roadways in a safe condition for motorists. Accurate forecasts of frost onset times, frost intensity, and frost disappearance (e.g., melting or sublimation) are needed to help roadway maintenance personnel decide when, where, and how much frost-suppression chemical to use. A finite-difference algorithm (BridgeT) has been developed that simulates vertical heat transfer in a bridge based on evolving meteorological conditions at its top and bottom as supplied by a weather forecast model. BridgeT simulates bridge temperatures at numerous points within the bridge (including its upper and lower surface) at each time step of the weather forecast model and calculates volume per unit area (i.e., depth) of deposited, melted, or sublimed frost. This model produces forecasts of bridge surface temperature, frost depth, and bridge condition (i.e., dry, wet, icy/snowy). Bridge frost predictions and bridge surface temperature are compared with observed and measured values to assess BridgeT's skill in forecasting bridge frost and associated conditions.

Greenfield, Tina M.; Takle, Eugene S.

2006-03-01

62

Study of Frost Properties in a Low Temperature Environment  

NASA Astrophysics Data System (ADS)

Performance of heat exchangers in appliances such as air-conditioners, showcase coolers and unit coolers can deteriorate under frosting conditions. To address this issue, the mechanism of frost deposition needs to be investigated. To achieve this goal, the frost formations process was observed and properties of frost were measured at air and cooling surface temperatures less than 0 °C using a refrigeration apparatus. Frost crystals formed on the cooling surface had a needle-like structure under the chilled condition, which represents an air temperature of 0 °C and cooling surface temperature of -10°C. On the other hand, frost crystals formed on cooling surface had a block shaped structure under the frozen condition, which represents an air temperature of -15°C and cooling surface temperature of -29°C. This work examined the relationship between density and thermal conductivity of frost, and calculated Nusselt number and Sherwood number.

Yamashita, Koji; Hamada, Mamoru; Ohkubo, Hidetoshi

63

Peculiarities of evaporation of a thin water layer in the presence of a solvable surfactant  

NASA Astrophysics Data System (ADS)

Evaporation of a thin layer of a polar liquid (water) having a free surface and located on a solid substrate is investigated. A solvable surfactant is placed on the free liquid-vapor interface. The surface tension is a linear function of the surface concentration of the surfactant. The surface energy of the solid-liquid contact line is a nonmonotonic function of the layer thickness and is the sum of the Van der Waals interaction and the specific interaction of the double electric layer on the interface. The effect of the solvable surfactant on the dynamics and stability of the propagation of the evaporation front in the thin liquid film is analyzed in the long-wave approximation in the system of Navier-Stokes equations.

Gordeeva, V. Yu.; Lyushnin, A. V.

2014-05-01

64

Aerosol Frost flower vs Sea Salt Concentrations with the use of ?34S at Alert, Nunavut, Canada  

NASA Astrophysics Data System (ADS)

Frost flowers have been determined to be of significant importance to the sodium content of snow pack and ice cores in costal polar regions. Frost flowers are characterised by a negative dependence of calculated non sea salt sulfate (NSS SO42-) with sodium concentrations in which the calculated NSS SO42- will be less than zero. This negative calculated concentration is because of the frost flower Na:SO42- ratio being larger than that of sea salt ratios. The use of only concentration analysis to determine the presence of frost flower in aerosols does have weaknesses. A negative NSS SO42- concentration will reveal that frost flowers are present but not necessarily how much. For instance, all sodium present may come from frost flowers or only a portion with the remainder coming from sea salt. Samples without negative NSS SO42- concentration may also have frost flower influence to a lesser degree due to excess sulfur coming from anthropogenic influences. This is especially true in the Arctic where Arctic haze from long range transport is prevalent in fall and winter. Unfortunately no clear way has been able to distinguish the amount of sea salt versus frost flower sulfate. A method using stable isotopes is introduced to set limits on the contributions from sea salt and frost flower sulfate. During the Fall of 2007 and 2008, size segregated aerosols were measured biweekly at Alert, Nunavut, Canada for sulfate sulfur isotopes values and major ion concentrations (including sodium and sulfate). Na:SO42- weight ratios ranged from 0 to 9.8. A ratio of 4 would indicate 100% sea salt, with values above 4 indicating frost flower influence and ratios less than 4 indicating other non sea salt sulfate sources (ie. anthropogenic or biogenic). ?34S values ranged between +4 and +15% during the same sampling time period. Explanation of the constraints imposed using ?34Snss are presented along with the calculation of the maximum and minimum frost flower contribution during the sampling period.

Seguin, A.; Rempillo, O. T.; Norman, A. L.

2011-12-01

65

Frost tolerance in wild potato species: Assessing the predictivity of taxonomic, geographic, and ecological factors  

Microsoft Academic Search

The use of genetic resources could be more effective and efficient if we were able to predict the presence or absence of useful\\u000a traits in different populations or accessions. We analyzed the extent to which taxonomic, geographic and ecological factors\\u000a can predict the presence of frost tolerance in wild potatoes. We used screening data for 1646 samples from 87 species

Robert J. Hijmans; Mirjam Jacobs; John B. Bamberg; David M. Spooner

2003-01-01

66

YSi2-x formation in the presence of interfacial SiO2 layer  

NASA Astrophysics Data System (ADS)

YSi2-x films were grown by ion-assisted evaporation in an ultrahigh vacuum (UHV) on Si(111) through a thin SiO2 layer. The films grown on the oxidized Si were changed from a polycrystalline structure with various phases of oxides and silicides into a single-crystalline silicide structure as the annealing temperature was increased in the UHV chamber. The structural change with the annealing temperature implied that various Y2O3 phases formed by the reaction between Y and SiO2 were decomposed and transformed into YSi2-x under the UHV environment. Rutherford backscattering spectroscopy/channeling showed that, although the interfacial crystallinity of the film grown on the SiO2 layer was poorer quality than the film grown on a clean Si surface, a single crystalline YSi2-x layer with high crystallinity (chimin)=8% was grown. These results showed that the difference of the thermal energy and the formation energy between the oxides of Y2O3-SiO2 and yttrium silicide determined the evolution of the silicide layer formation and its crystal structure.

Cho, M.-H.; Ko, D.-H.; Choi, Y. G.; Lyo, I. W.; Jeong, K.; Whang, C. N.

2002-11-01

67

Formation of walls in cylindrical smectic C layers in the presence of a tilted magnetic field  

Microsoft Academic Search

A theoretical study of the elastic properties of a smectic C liquid-crystalline system consisting of cylindrical smectic layers is presented. We show that the ground state configuration of the c-director for such a system depends on the signs of two combinations of the relevant elastic constants. With these configurations as a starting point, we describe how a set of walls

T. Carlsson; I. W. Stewart; F. M. Leslie

1992-01-01

68

Layer formation on metal surfaces in lead–bismuth at high temperatures in presence of zirconium  

Microsoft Academic Search

If the operating temperature lead–bismuth cooled fission reactor could be extended to 800 °C, they could produce hydrogen directly from water. A key issue for the deployment of this technology at these temperatures is the corrosion of the fuel cladding and structural materials by the lead–bismuth. Corrosion studies of several metals were performed to correlate the interaction layer formation rate

Eric P Loewen; Hannah J Yount; Kevin Volk; Arvind Kumar

2003-01-01

69

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

Microsoft Academic Search

We report new geochemical evidence from ten Cretaceous-Tertiary boundary sites in North America and Europe, indicating the presence of a material remnant of a large asteroid or comet that struck the Earth at 65.0 Ma. Mössbauer spectroscopic data reveals that a ubiquitous iron-rich nanophase material exists at the uppermost part of the K-T boundary layer in the Western Hemisphere and

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

2001-01-01

70

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

NASA Astrophysics Data System (ADS)

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

Rostami, Habib; Asgari, Reza

2013-07-01

71

Hydrodynamics of surface phenomena in the presence of an electric double layer  

SciTech Connect

The effects of an electric double layer at the interface of two electrically conducting fluids were examined within the framework of a single hydrodynamic scheme which considered electrocapillarity, mass exchange between the interface and the bulk phases, surface chemical (including electrochemical) reactions, surface diffusion of the components, energy exchange between the surface and bulk phases, and friction of the surface and bulk phases. The interphase layer was modeled from a macroscopic viewpoint by a surface of strong discontinuity endowed with mass, momentum, energy, and other variables. The surface equations were augmented with the equations of motion of bulk media. The study was limited to the approximation of a polarizing medium when there is no magnetization in the natural coordinate system.

Taktarov, N.G.

1988-01-01

72

Characteristics of light nonaqueous phase liquid recovery in the presence of fine-scale soil layering  

Microsoft Academic Search

The effects of fine-scale layering of soil properties on light nonaqueous phase liquid (LNAPL) recovery using pumped groundwater drawdown were investigated using a Monte Carlo approach. Three-dimensional simulations were performed to study the characteristics of a variety of measures describing LNAPL recovery in heterogeneous sandy aquifers. Heterogeneity models included both uncorrelated and correlated vertical permeability distributions, with both permeability-scaled and

C. D. Johnston; M. G. Trefry

2009-01-01

73

Pluto: evidence for methane frost.  

PubMed

Infrared photometry (1.2 to 2.2 micrometers) of Pluto provides evidence for frozen methane on the surface of the planet. This appears to be the first observational indication of this ice in the solar system. Its presence on Pluto suggests that the planet's albedo (reflectance) may be >/= 0.4 and that its diameter may be less than that of the moon. PMID:17744185

1976-11-19

74

Trichohyalin: presence in the granular layer and stratum corneum of normal human epidermis.  

PubMed

Trichohyalin, a protein contained in granules in the cells of the hair-follicle inner root sheath and in the medulla of the hair shaft, has been purified previously from sheep hair bulbs and is also a major protein of filiform papillae of tongue epithelium. Polyclonal affinity-purified antibodies and a monoclonal antibody raised to purified pig tongue trichohyalin both stained the inner root sheath of hair follicles and the medulla of hair fibers and identified human trichohyalin as a single 220-kDa band on immunoblots of human hair bulb proteins. These antibodies were used to examine human epidermis by immunofluorescence and immunoblotting. The antibodies decorate granules in cells in the granular layer and stratum corneum of non-hair-bearing human skin, and immunoblots identify a protein in epidermis comigrating with trichohyalin from human hair and human tongue epithelium. Absorption of antibody to trichohyalin on a trichohyalin affinity column abrogated staining of the epidermis and the bands on the immunoblots. Trypsin-separated epidermis contained 220 and 160 kDa bands identified as trichohyalin, but epidermis shaved from skin and quickly frozen showed only a single 220-kDa band, indicating that the 160-kDa protein was generated by proteolysis. Double immunofluorescence for trichohyalin and filaggrin showed that some cells containing filaggrin also contain trichohyalin. These studies show that trichohyalin is not limited to hair and tongue but is present in isolated cells in the granular layer and stratum corneum of normal epidermis. PMID:1708794

Hamilton, E H; Payne, R E; O'Keefe, E J

1991-05-01

75

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

76

Mathematical model of frost heave and thaw settlement in pavements  

NASA Astrophysics Data System (ADS)

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

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

1993-04-01

77

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

78

Thin layer chromatography-application in qualitative analysis on presence of coumarins and flavonoids in plant material.  

PubMed

Drugs, natural medicinal plant, animals and mineral materials, have a large and various application in official pharmacy and medicine. Carriers of multilateral pharmacological effects that those drugs shown, are chemically define as active components that are present in them. Methods of qualitative and quantitative analysis are used for the chemical investigation of components that drugs contain. Method of thin layer chromatography has been shown as very reliable. According to the chemical investigation of single drugs, it is possible to define a group of compound or single compound comparing them with standards. Relating to the usage of method of thin layer chromatography, it has been carried out investigation on presence of coumarins and flavonoids in domestic plant material that have wide everyday usage. Coumarins and flavonoids from the point of view of chemical belonging are phenol derivatives with important pharmacological effects. Applying method of thin layer chromatography, it is detected presence of coumarins and flavonoids substances in plant material that has been tested. Anethi graveolens fructus et folium (fruit and leaf of dill), Anethum graveolens L., Apiaceae, Avenae sativae fructus (fruit of oats), Avena sativa L., Poaceae and Asperulae odoratae herba (sweet woodruff), Asperula odorata L., Rubiaceae. Chromatograms are developed in systems cyclohexane-ethylacetat (13:7) and toluene-ether (1:1) saturated with 10% acetic acid, and visualisation by observing on UV lamp (254 and 366 nm), spraying with reagents KOH (10% ethanol solution) and diphenylboryloxyethylamine (1% methanol solution). PMID:16232145

Kovac-Besovi?, Elvira E; Duri?, Kemal

2003-07-01

79

The characteristics of frost growth on parallel plates  

NASA Astrophysics Data System (ADS)

An experimental investigation was undertaken to characterize the effect of environmental conditions on frost growth on a vertical plate in a parallel flow geometry. Humid air was conditioned to have a dew point below 0°C and laminar flow prevailed. The test section was fabricated by using three cooling plates with individual insulators to minimize longitudinal conduction. It is known that frost formation on the heat exchanger surfaces seriously affects the performance of the system. The frost is dominantly formed in the inlet region of a heat exchanger. In order to understand the characteristics of frost growth in the entrance region, several experiments were carried out. The experimental parameters were plate temperature, air humidity, air temperature, air Reynolds number, location, and uncooled inlet length. The frosting conditions were limited to air temperatures from 5 to 15°C, air Reynolds numbers from 1600 to 2270, air humidity ratios from 0.00275 to 0.0037 kg w /kg a , and plate temperatures from -10 to -20°C. Frost growth toward the front of the plate was thicker and denser than toward the rear. In the low humidity conditions below 0°C dew point frost growth increased with decreasing plate temperature and increasing humidity. For laminar flow, the dew point below 0°C and non-cyclic frosting period, the frost thickness increased with increasing air temperature. This behavior can be explained by an increase of the transfer rate and a non-cyclic frosting without melting in a sublimation-ablimation process. The average growth thickness at three locations showed little dependence on the Reynolds numbers. However, there were only small differences in the front and rear plates. Frost thickness decreased with increasing uncooled inlet length. This result could be used to suppress frost growth in the plate finned tube heat exchanger.

Han, Heung Do; Ro, Sung Tack

80

Frost resistance and pore size distribution in bricks  

Microsoft Academic Search

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

M. Maage

1984-01-01

81

Frost salt scaling resistance of concrete containing CFBC fly ash  

Microsoft Academic Search

The possibility for using coal combustion by-products in concrete exposed to frost-salt aggression was investigated. The research\\u000a was aimed to assess an influence addition of circulating fluidized bed combustion (CFBC) fly ash on frost-salt scaling of\\u000a air-entrained concrete. For evaluation of the resistance of concrete to frost salt scaling the test called “depth sensing\\u000a indentation” (DSI) was applied. The DSI

Michal A. Glinicki; Marek Zielinski

2009-01-01

82

Alaska Frostless, an inherently frost resistant potato variety  

Microsoft Academic Search

A potato clone with frost resistant foliage designated Alaska Frostless has been selected from the progeny of crosses involvingSolanum acaule and commercial varieties. Its chromosome number is (2N=5X=60). Nearly mature vines have withstood field frosting at?3 C for\\u000a 2 hours and have recovered from several frosts of?2 C. Yields in cwt per acre of tubers 2–3.5 inch in diameter have

C. H. Dearborn

1969-01-01

83

Utilizing the frost resistance of diploid solanum species  

Microsoft Academic Search

Introductions of 13 frost-resistant diploid (2n=2x=24)Solanum species (2 non-tuberous) were inter-crossed to produce F1 hybrids involving two frost resistance sources. Successful F1 combinations were: (i) inter-crossed to produce hybrids involving 3 to 4 frost resistance sources, (F1×F1); and (ii) crossed with haploids (2n=24) of frost-susceptible tetraploid (2n=4x=48)S. tuberosum subsp.tuberosum, (F1×tbr).\\u000a \\u000a Thirty-five of the 75 crosses between the 13 species produced

R. W. Ross; P. R. Rowe

1969-01-01

84

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

85

First-year sea-ice contact predicts bromine monoxide (BrO) levels better than potential frost flower contact  

NASA Astrophysics Data System (ADS)

Reactive halogens are responsible for boundary-layer ozone depletion and mercury deposition in Polar Regions during springtime. To investigate the source of reactive halogens in the air arriving at Barrow, Alaska, we measured BrO, a marker of reactive halogen chemistry, and correlated its abundance with airmass histories derived from meteorological back trajectories and remotely sensed sea ice properties. The BrO is found to be positively correlated to first-year sea-ice contact (R2=0.55), and weakly negatively correlated to potential frost flower (PFF) contact (R2=0.04). These data indicate that snow contaminated with sea salts on first-year sea ice is a more probable bromine source than are frost flowers. Recent climate-driven changes in Arctic sea ice are likely to alter frost flower and first year sea ice prevalence, suggesting a significant change in reactive halogen abundance, which will alter the chemistry of the overlying Arctic atmosphere.

Simpson, W. R.; Carlson, D.; Hoenninger, G.; Douglas, T. A.; Sturm, M.; Perovich, D.; Platt, U.

2006-11-01

86

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

87

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

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

88

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

89

Frost sensitivity of hybrids between wild and cultivated carrots  

Microsoft Academic Search

Frost could potentially limit the survival ofhybrids between cultivated and wild carrots innatural habitats, and thereby the likelihoodthat (trans)genes spread from the crop to wildplants. To test this, cultivated, wild carrotsand their hybrids were exposed to differentfrost treatments. Hybrids survivedsignificantly less than the wild carrots, butonly slightly better than the cultivars,indicating that frost will indeed limit theirsurvival.

Thure P. Hauser

2002-01-01

90

Thermal resistance of frost on a finned air cooler  

SciTech Connect

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

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

1987-09-01

91

A New Way to Mitigate Frost Heave Around Manholes  

Microsoft Academic Search

Frost heave of pavement around manholes in northern cities all over the world has been a costly problem ever since sanitary and storm sewers were installed. Freezing of frost-susceptible soil under the road structure can lead to substantial uplift, deformation and cracking of the pavement surface. This new technology is based on utilizing the heat in flowing water in sanitary

O. J. Svec

2001-01-01

92

Frost heaving of forest tree seedlings: a review  

Microsoft Academic Search

Soil frost heaving is the result of the formation of ice lenses in the soil caused by a segregation of the soil water. Ice lenses are growing from below and pushed upward. Seedlings heave when they are pushed out of the ground by the ice sheet formed at the surface of the soil. Frost heaving may greatly reduce growth and

France Goulet

1995-01-01

93

Frost formation on an airfoil: A mathematical model 1  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

94

Genetically engineered microorganisms to rescue plants from frost injury.  

PubMed

Ice nucleation active bacteria belonging to genera Pseudomonas, Xanthomonas and Erwinia contribute to frost damage to plants by initiating the formation of ice in plants that would otherwise supercool and avoid the damaging ice formation. The biological control of frost injury can be achieved by the application of non-ice nucleation active bacteria to the plant surfaces before they become colonized by Ice+ species. ice genes have been cloned from Pseudomonas and isogenic Ice- derivatives constructed via genetic manipulations. These genetically engineered microorganisms (GEMs) have been released into the environment to control the frost damage. The incidence of frost injury to the plants has, thereby, been reduced by 50-85% during natural frosts. These GEMs do not survive in soil and show no aerial dispersal in the environment. PMID:8213308

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

1993-01-01

95

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

96

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

97

The inheritance of frost resistance and flowering response in broccoli ( Brassica oleracea var. Italica )  

Microsoft Academic Search

Broccoli inbred lines derived from the cross, broccoli x (cabbage x kale) were observed to differ in flowering response and frost resistance. Analysis of the F2 population from the cross, slow-bolter, frost tolerant and bolter, frost susceptible suggested that two dominant epistatic genes conditioned frost resistance, whereas flowering was polygenically inherited.

J. C. Bouwkamp; S. Honma

1969-01-01

98

Characteristics of Frost in a Major Wheat-growing Region of Australia  

Microsoft Academic Search

Frost at anthesis of wheat reduces grain set. Characteristics of frost in a large section of the wheat belt of one Australian state (N.S.W.) are described. Using cluster analysis, the region can be divided into four homogeneous areas according to five general characteristics of frost. These characteristics are the mean Julian day of first and last frost, the mean number

Rizaldi Boer; A Lindsay

99

Energies of freezing and frost desiccation.  

PubMed

A stable cellulose paper system was studied to relate water distribution data, as obtained previously from plant tissues, to the analysis of freezing energy. Water distribution data for the cellulose system were obtained by several techniques and were coordinated with calorimetric data. The effect of the cellulose system on the latent heat of freezing was evaluated to estimate activation energies as functions of the amount of associated liquid water. Similar activation energies of water phase transitions in critical plant tissue systems may be heritable characteristics that affect freezing stress. Adhesion energy, that develops between ice and hydrophilic polymer systems as they compete for liquid water in a complex interface, was suggested as one possible source of freezing stress. This does not occur in frost desiccation. PMID:16658785

Olien, C R

1974-05-01

100

Frost flower formation on sea ice and lake ice  

NASA Astrophysics Data System (ADS)

Frost flowers are clusters of ice crystals found on freshly formed sea ice and occasionally on frozen lakes. They belong to a class of vapour-related phenomena that includes freezing fog, hoar frost and dew. It has hitherto been supposed that they form by condensation from a supersaturated atmosphere or from water wicked up through porous sea ice. Here we show that they can form on solid, pure ice sublimating into an unsaturated atmosphere. We derive a general regime diagram showing the atmospheric conditions under which the different vapour-related phenomena occur and confirm our predictions of frost-flower formation with a series of laboratory experiments. Our results can be used in climate models to predict occurrence of frost flowers, which significantly enhance albedo and provide the substrate for chemical production of ozone-depleting bromine monoxide, and in paleo-climate reconstructions by relating observations of sea-salt aerosols in ice cores to atmospheric conditions.

Style, Robert W.; Worster, M. Grae

2009-06-01

101

Revised Procedure for Pavement Design under Seasonal Frost Conditions.  

National Technical Information Service (NTIS)

This report presents engineering guidance and design criteria for pavements at Army and Air Force facilities in seasonal frost areas. Design methods for controlling surface roughness and loss of subgrade strength during thawing petiods are provided. Crite...

R. L. Berg T. C. Johnson

1983-01-01

102

Freezing Test for Evaluating Relative Frost Susceptibility of Various Soils.  

National Technical Information Service (NTIS)

The report presents a description of the equipment and procedures used in the laboratory test of the relative frost susceptibility of different soils on Corps of Engineers construction projects and includes typical results of freezing tests of natural soi...

C. W. Kaplar

1974-01-01

103

Characterisation of Phenolic Compounds in Oils Produced from Frosted Olives  

Microsoft Academic Search

Frost is one of the most important weather related hazards for the Australian olive industry and it has caused significant\\u000a economic losses during the last decade. Its impact on oil quality was significant in 2006 with more than 20% of Australian\\u000a oil of that year being affected to some degree. Early frosts will normally affect the fruit leading to significant

Claudia Guillaume; Leandro Ravetti; Sonja Gwyn

2010-01-01

104

Frost rings in trees as records of major volcanic eruptions  

Microsoft Academic Search

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

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

1984-01-01

105

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

106

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

107

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

NASA Astrophysics Data System (ADS)

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

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

1991-01-01

108

(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

109

Surface circulation associated with frost in the wet Pampas  

NASA Astrophysics Data System (ADS)

The aim of this paper is to make a synoptic-climatic classification of atmospheric circulation in order to obtain synoptic frost-related patterns in the wet Pampas. Both partial (recorded in 25 to 75% of the meteorological stations) and widespread (recorded in more than 75%) frost events that occurred during the winters (June-July-August) of 1972-83 are included in this study. Frost days are grouped into Neutral (G1), El Nińo (G2), and La Nińa (G3) years. In addition, the complete dataset, called the total group, is analysed for reference purposes. Each group is analysed using the unrotated and Varimax rotated principal component analysis using the T-mode approach. Six synoptic situations accounted for 94% of the variance associated with frosts in the area studied.In general, the principal component score patterns given by the unrotated and rotated components are similar. The biggest difference between unrotated and rotated solutions was in variance redistribution. After rotation, only one of the two possible situations (direct/inverse) of each pattern represented a real synoptic type associated with frost in the wet Pampas. Persistence and location cause temperature drops in the area studied. The most frequent patterns in rotated results are those termed A, B, C* (in G2) and D (in G1 and G3). They are connected with cold anticyclones, which cause advective and/or radiative frosts. The remaining patterns accounted for about 5% of the variance and represent real, though rare, situations, which are important because of their effect on the wet Pampas.The results obtained for the different groups show that inter-winter variability of the equatorial Pacific signal produces changes in the frequency of frost-connected patterns, rather than different patterns for cold events.

Müller, Gabriela V.; Compagnucci, Rosa; Nuńez, Mario N.; Salles, Alejandra

2003-06-01

110

Teoretiska och experimentella studier av frostbildning i luftspalt. (Theoretical and experimental studies of frost between two plates).  

National Technical Information Service (NTIS)

Frost has a complex structure and frost formation is influenced by several parameters, according to a literature study. A basic understanding of the frost formation process would be valuable in many situations, e.g. when optimizing equipment. A mathematic...

I. Andersson

1992-01-01

111

First-year sea-ice contact predicts bromine monoxide (BrO) levels at Barrow, Alaska better than potential frost flower contact  

NASA Astrophysics Data System (ADS)

Reactive halogens are responsible for boundary-layer ozone depletion and mercury deposition in Polar Regions during springtime. To investigate the source of reactive halogens in the air arriving at Barrow, Alaska, we measured BrO, an indicator of reactive halogen chemistry, and correlated its abundance with airmass histories derived from meteorological back trajectories and remotely sensed sea ice properties. The BrO abundance is found to be positively correlated to first-year sea-ice contact (R2=0.55), and essentially uncorrelated with potential frost flower (PFF) contact (R2=0.04). Assuming that PFF accurately predicts frost flowers, these data indicate that snow and ice contaminated with sea salts on first-year sea ice is a more probable bromine source than are frost flowers, for airmasses impacting Barrow, Alaska. Climate-driven changes in Arctic sea ice are likely to alter frost flower and first year sea ice prevalence. An accurate understanding of how these sea ice changes would affect the halogen chemistry of the overlying atmosphere depends upon understanding the relative roles of frost flowers and saline snow and ice surfaces as reactive bromine sources.

Simpson, W. R.; Carlson, D.; Hönninger, G.; Douglas, T. A.; Sturm, M.; Perovich, D.; Platt, U.

2007-02-01

112

Stability of evaporating two-layered liquid film in the presence of surfactant—I. The equations of lubrication approximation  

Microsoft Academic Search

In this study we consider the stability of horizontal two-layered liquid film attached to a heated solid substrate. The film can contain surfactant that is soluble in both liquid phases. The evaporation of solvent from the upper film is also taken into account. Thus, the two-layered film can exhibit both thermocapillary and Marangoni instabilities coupled with the effect of solvent

Krassimir D. Danov; Vesselin N. Paunov; Norbert Alleborn; Hans Raszillier; Franz Durst

1998-01-01

113

The New KRISS Low Frost-Point Humidity Generator  

NASA Astrophysics Data System (ADS)

A new low frost-point humidity generator (LFPG) has been designed, and its performance has been tested, in order to extend the calibration capabilities to the low frost-point range at KRISS. The water vapor gas mixture is generated by saturating air with water vapor over a surface of an ice-coated saturator under the conditions of constant temperature and pressure. This LFPG covers a range of frost point from - 99 °C to - 40 °C. The temperature of the saturator, which is controlled by thermoelectric devices and a two-stage mechanical refrigeration system, is stable within 5 mK, and the difference between the saturator temperature and the frost point generated at the saturator outlet is less than 20 mK. This stability is achieved by using oxygen-free high-conductivity copper materials as the saturator body, and applying a precision PID temperature control system. The performance of this new LFPG system is compared with the KRISS standard two-temperature generator in the frost-point range ( - 80 to - 40) °C, and its performance is tested with a quartz crystal microbalance (QCM), which was built at KRISS, to - 91 °C.

Choi, B. I.; Nham, H. S.; Woo, S. B.; Kim, J. C.; Kwon, S. Y.

2008-10-01

114

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

115

Frost Action Phenomena in Soils and Pavements. A Comprehensive Literature Survey on Theories and Design Practices.  

National Technical Information Service (NTIS)

The study is concerned with the influence of climatic variables on the depth of frost penetration beneath pavements. The report is separated into three parts. Part I is concerned with the main factors influencing frost action. It is primarily theoretical ...

R. J. Cominsky G. Cumberledge A. C. Bhajandas

1972-01-01

116

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

117

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

118

Frost-weathering on Mars - Experimental evidence for peroxide formation  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

119

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

120

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

121

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

122

Far-infrared spectra of CO2 clathrate hydrate frosts  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

123

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

Microsoft Academic Search

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

C. T. Sanders

1974-01-01

124

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

Microsoft Academic Search

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

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

2005-01-01

125

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

SciTech Connect

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

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

1993-10-01

126

Evaluation of the effect of discrete fluid injection on turbulent boundary layer skin friction in the presence of wall roughness  

Microsoft Academic Search

The purpose of the present experimental study was to determine if discrete mass injection into a turbulent boundary layer over a rough wall would effectively smooth the surface and reduce the skin friction drag. Accordingly, a test program was planned and a series of tests were conducted in the Free Surface Water Tunnel at the California Institute of Technology. In

W. W. Haigh; D. D. Mantrom; J. E. Lewis

1976-01-01

127

Investigation on the Formation of Needle Frost. II.  

National Technical Information Service (NTIS)

The report selects different types of easily-accessible colloids and tests to see whether they had any effect on the formation of needle frost. For example, about 20 different types including silicic anhydride gel, active carbon powder, dye, agar-agar, ge...

M. Fujita

1970-01-01

128

Genetic Architecture of Winter Hardiness and Frost Tolerance in Triticale  

PubMed Central

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.

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

2014-01-01

129

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

130

Mathematical model of frost heave and thaw settlement in pavements  

Microsoft Academic Search

Since 1975 the U.S. Army Corps of Engineers, the Federal Highway Administration and the Federal Aviation Administration have been working cooperatively to develop a mathematical model to estimate frost heave and thaw weakening under various environmental conditions and for various pavement designs. A model has been developed. It is a one-dimensional representation of vertical heat and moisture flux. It is

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

1993-01-01

131

High-Frequency Mutual Impedance Extraction of VLSI Interconnects In the Presence of a Multi-layer Conducting Substrate  

Microsoft Academic Search

We propose a computationally efficient method to calculate, with high accuracy, the mutual impedance between two wires in the presence of multilayer substrates, as needed for high frequency CAD applications. The resulting accuracy (errors smaller than 2%) and CPU time reduction (factors of seven) emerge from three different ingredients: a two dimensional Green's function approach with the correct quasi-static limit,

Navin Srivastava; Roberto Suaya; Kaustav Banerjee

2008-01-01

132

High-frequency mutual impedance extraction of VLSI interconnects in the presence of a multi-layer conducting substrate  

Microsoft Academic Search

We propose a computationally efficient method to calculate, with high accuracy, the mutual impedance between two wires in the presence of multilayer substrates, as needed for high frequency CAD applications. The resulting accuracy (errors smaller than 2%) and CPU time reduction (factors of seven) emerge from three different ingredients: a two dimensional Green's function approach with the correct quasi-static limit,

Navin Srivastava; Roberto Suaya; Kaustav Banerjee

2008-01-01

133

Wear resistance of heat treated and chemical-thermally treated steel parts in the presence of an abrasive layer  

Microsoft Academic Search

For the purpose of checking the effectiveness of heat treatment and chemical-thermal treatment for increasing the resistance of steel parts against abrasive wear we have made laboratory wear-resistance tests of samples with an abrasive layer (quartz sand) in the rubbing zone. The rubbing was done according to a sleeve-insert method (arrangement described in [7] ) with a unit load of

Vo M. Golubets; V. Vo Kozub; K. P. Tabinskii

1976-01-01

134

Impact of Device Layout and Annealing Process During the Passivation of Interface States in Presence of Silicon Nitride Layers  

Microsoft Academic Search

This paper reports the experimental evidence of anomalous electrical characteristics of large test structures for the characterization of both silicon-oxide-nitride-oxide-silicon (SONOS) and MOS gate stacks featuring nitride caps. The anomaly has been studied on devices featuring different layouts and it has been attributed to the property of silicon nitride layers to block the diffusion of hydrogen used for the passivation

Francesco Driussi; Luca Selmi; Nader Akil; Michiel J. van Duuren; Rob van Schaijk

2008-01-01

135

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

NASA Astrophysics Data System (ADS)

Frost flowers have been proposed to be the major source of sea-salt aerosol to the atmosphere during polar winter and a source of reactive bromine during polar springtime. However little is known about their bulk chemical composition or microstructure, two important factors that may affect their ability to produce aerosols and provide chemically reactive surfaces for exchange with the atmosphere. Therefore, we chemically analyzed 28 samples of frost flowers and parts of frost flowers collected from sea ice off of northern Alaska. Our results support the proposed mechanism for frost flower growth that suggests water vapor deposition forms an ice skeleton that wicks brine present on newly grown sea ice. We measured a high variability in sulfate enrichment factors (with respect to chloride) in frost flowers and seawater from the vicinity of freezing sea ice. The variability in sulfate indicates that mirabilite precipitation (Na2SO4 · 10 H2O) occurs during frost flower growth. Brine wicked up by frost flowers is typically sulfate depleted, in agreement with the theory that frost flowers are related to sulfate-depleted aerosol observed in Antarctica. The bromide enrichment factors we measured in frost flowers are within error of seawater composition, constraining the direct reactive losses of bromide from frost flowers. We combined the chemical composition measurements with temperature observations to create a conceptual model of possible scenarios for frost flower microstructure development.

Alvarez-Aviles, Laura; Simpson, William R.; Douglas, Thomas A.; Sturm, Matthew; Perovich, Donald; Domine, Florent

2008-11-01

136

Experimental Paved Shoulders on Frost Susceptible Soils.  

National Technical Information Service (NTIS)

Approximately 4 miles of I-80 east of Joliet, Illinois were constructed in 1967 with experimental shoulder sections. The mainline pavement is 8 in. CRCP on 4 in. of subbase which extends 18 in. into the shoulders. A 4 in. layer of open-graded shoulder sub...

L. J. McKenzie

1969-01-01

137

Instability of multi-layer fluid configurations in the presence of time-dependent accelerations in a microgravity environment  

NASA Technical Reports Server (NTRS)

The increasing number of research opportunities in a microgravity environment will benefit not only fundamental studies in fluid dynamics, but also technological applications such as those involving materials processing. In particular, fluid configurations which involve fluid-fluid interfaces would occur in a variety of experimental investigations. This work investigates the stability of a configuration involving fluid-fluid interfaces in the presence of a time-dependent forcing. Both periodic (g-jitter) and nonperiodic accelerations are considered. The fluid configuration is multilayered, and infinite in extent. The analysis is linear and inviscid, and the acceleration vector is oriented perpendicular to each interface. A Floquet analysis is employed in the case of the periodic forcing. In the problem of nonperiodic forcing, the resulting system of equations are integrated in time. Specific nondimensional parameters appear in each problem. The configuration behavior is investigated for a range of parameter values.

Lyell, M. J.; Roh, Michael

1991-01-01

138

Single kaolinite nanometer layers prepared by an in situ polymerization-exfoliation process in the presence of ionic liquids.  

PubMed

A simple chemical route for the exfoliation of kaolinite in the presence of polymerizable ionic liquids and the resulting obtainment of exfoliated nanocomposites is reported. The exfoliation was achieved using three different ionic liquids structurally bearing a vinyl group: 1-methyl-3-(4-vinylbenzyl)imidazolium chloride salt (IL_1), 1-methyl-1-(4-vinylbenzyl)pyrrolidinium chloride (IL_2), and 1-methyl-3-vinyl imidazolium iodide (IL_3) and a urea-kaolinite intercalate as precursor. The reaction was done in one step by an in situ polymerization-exfoliation process. (13)C CP/MAS NMR spectra confirmed the spontaneous polymerization of the ionic liquid during the exfoliation process to afford atactic polystyrene derivatives in the case of IL_1 and IL_2. The amount of organic material in the exfoliated nanocomposite was close to 30% as shown by thermal gravimetric analysis. This amount is small in comparison to the amount obtained when the exfoliation was done using sodium polyacrylate (Letaief and Detellier, Langmuir2009, 25, 10975). XRD as well as SEM analysis confirmed a total exfoliation of the kaolinite when the reaction was done using urea kaolinite, whereas a microcomposite, made predominantly of kaolinite platelet aggregates dispersed in the polymeric matrix, was formed when dimethylsulfoxide kaolinite was used as the precursor. PMID:22073925

Letaief, Sadok; Leclercq, Jérôme; Liu, Yun; Detellier, Christian

2011-12-20

139

Stimulation of Phospholipid Biosynthesis during Frost Hardening of Winter Wheat.  

PubMed

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

Willemot, C

1975-02-01

140

Chemical frost weathering of olivine: Experimental study and implications  

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

141

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 (50×50×35 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 10°C and -5°C 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

142

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

PubMed

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

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

1979-12-01

143

Critically reduced frost resistance of Picea abies during sprouting could be linked to cytological changes.  

PubMed

Frost resistance of sprouting Picea abies shoots is insufficient for survival of naturally occurring late frosts. The cellular changes during sprouting appeared to be responsible for frost damage as frost events that damaged sprouting shoots did not damage older needles and stems. Whilst resting buds showed initial frost damage at -15.0 degrees C, 20 days later, current year's growth was damaged at -5.6 degrees C. The decrease in frost resistance in sprouting shoots of P. abies was accompanied by a significant reduction of the cellular solute concentration, indicated by much less negative Psi(oSAT) values (increase from -2.8 to -1.2 MPa). psi(oSAT) decreased again after the final cell volume was reached and cell wall thickening began. After bud break, ice nucleation temperature increased from -4.7 degrees C to -1.5 degrees C. This increase was probably caused by the loss of bud scales, the onset of expansion growth of the central cylinder and the development of vascular tissue permitting the spread of ice from the stem into the growing needles. The onset of mesophyll cell wall thickening coincided with the lowest frost resistances. Cell wall thickening caused an increase in the modulus of elasticity, epsilon, indicating a decrease in tissue elasticity and after that frost resistance increased again. Metabolic and cytological changes that evidently leave little leeway for frost hardening are responsible for the low frost resistance in current year's growth of P. abies. This low frost resistance will be significant in the future as the risk of frost damage due to earlier bud break is anticipated to even further increase. PMID:19533300

Neuner, G; Beikircher, B

2010-07-01

144

The effects of frost formation on the thermal performance of finned tube heat exchangers  

NASA Astrophysics Data System (ADS)

An experimental investigation into the effects of frost growth on the thermal performance of wavy and corrugated plate finned tube heat exchangers has been conducted. Frost accumulation, pressure drop across the heat exchanger and an energy transfer coefficient based on a logarithmic mean enthalpy difference have been quantified under frosting conditions in terms of air humidity, air temperature, and fin geometry. It was found that higher air temperatures up to 4 C, air humidities, and fin density all led to an increase in frost accumulation, higher pressure drops, and increased energy transfer.

Kondepudi, Sekhar N.; O'Neal, Dennis L.

1989-06-01

145

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

146

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

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

147

Frost Formation Problem in the Development of a Hypersonic Turbojet Engine  

NASA Astrophysics Data System (ADS)

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

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

148

Effects of frost on wildflowers: an unexpected consequence of climate change--image 06 of 22  

NSDL National Science Digital Library

Ants (Formica obscuripes) searching for extrafloral nectar on the involucral bracts around a flower head in bud in the frost-sensitive herb Helianthella quinquenervis. The ants help to deter oviposition by flies (Tephritidae) that try to lay eggs on the flower heads. Because fly larvae eat developing seeds, the ants benefit the plants. Thus, the ant / herb interaction represents a mutualism. This mutualism can be disrupted if flower buds are killed by frost, as they won't secrete the extrafloral nectar. But frost also negatively impacts the flies, as frost-killed buds provide no food for the fly larvae.

Inouye, David

2012-01-04

149

Layers in the Martian polar deposits and the climate connection  

NASA Astrophysics Data System (ADS)

Abstract Since the polar layered deposits (PLD) likely contain the most complete record of relatively recent climate change on Mars, it is crucially important to obtain a realistic understanding of what a "layer" is and what its characteristics and stratigraphic position tell us about the contemporary martian climate. Using data from the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter, we reassess the methods by which layers within the NPLD could be defined and delineated. From these analyses, we find that the appearance of layers depends to a large degree on the distribution of younger, mantling deposits and on the shape and location of the particular outcrop. We have measured the thicknesses of several layers found to be similar to famous Marker Bed discovered by [1] using a high resolution DEM created from a HiRISE stereo pair. The thicknesses and separation distances of these layers and their observed morphologic characteristics hint at several possible but disparate climate connections. Defining "Layer" HiRISE has confirmed that apparent layer brightness is not necessarily indicative of the bulk composition of the layer [2]. Therefore, the bright and dark striping of the polar layers cannot be used alone to delineate layer boundaries. Additionally, there can exist several types of layers, defined by the means used to detect them: radar, visible images, thermal images, spectroscopic measurements, etc. Compositional layering, for example, will not necessarily exactly match visible layering. Different scales of layering also certainly exist. For example, Viking scale layers actually consist of packages of MOC scale layers, and annual layering cannot be observed from orbit. In this study, we define a "layer" as a stratum evident in images and topography that cannot be broken-up into thinner strata at the best data resolution available. As discussed below, we delineate the layers based on their morphologic appearance, topographic expression, and, to a lesser extent, on their apparent brightness. Controls on Layer Brightness Qualitatively, our observations indicate that apparent brightness depends largely on the presence of younger, mantling deposits of frost and dust. The distribution of this mantle in turn is controlled by trough shape (e.g., bends in the trough affecting wind direction), trough location (wind and illumination patterns), and roughness on the several meters scale. Fig. 1 illustrates that the small, meter-scale physical properties of the layers (aspect, roughness, and slope) have little effect on apparent brightness. The Marker Bed and other marker beds Malin and Edgett [1] easily traced a particular layer in three different images and thus named it the Marker Bed. Our observations of HiRISE images reveal other layers similar in appearance to the original Marker Bed; we suggest that these layers have a similar origin and name them "marker beds" as well. The marker beds are hummocky, exhibit linear erosional fluting on their upper edges, and, compared to the surrounding layers, are generally smoother, protrusive, and covered with less ice and frost. These beds correspond to layers previously identified by [3] in MOC images (but not recognized at the lower resolution to be marker beds) and correlated across the PLD. We have not, thus far, found any evidence of finer scale layering within the marker beds, indicating that they were either deposited quickly, as massive beds, or that the younger, mantling deposits are shrouding evidence of fine layering. Fig. 2 shows examples of the marker beds. We have also observed sets of thin (~1m and less) layers between the marker beds in all HiRISE images examined thus far, but erosion and the presence of the younger mantling deposits makes it difficult to count these layers and correlate them from place to place. Future work with more images to be taken during the upcoming northern summer season and with more DEMs should make that process easier and allow comparison with layering elsewhere on

Fishbaugh, K.; Byrne, S.; Herkenhoff, K.; Russell, P.; Kirk, R.; Fortezzo, C.; McEwen, A.

2008-09-01

150

Current density enhancement in ZnO/CdSe photoelectrochemical cells in the presence of a charge separating SnO2 nanoparticles interfacing-layer.  

PubMed

Photoelectrochemical cells (PECs) of ZnO/CdSe decorated with a charge separating SnO2 nanoparticles (NPs) layer of various thicknesses are prepared and characterized by using scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), UV-visible absorption, energy dispersive X-ray analysis spectroscopy (EDX) and incident photon-to-current conversion efficiency (IPCE) measurements. A uniform coverage of the SnO2 NPs layer over ZnO/CdSe electrode surface is evidenced. The EDX elemental mapping analysis of the ZnO/CdSe/SnO2 PECs demonstrates the presence of Sn and O over the surface. A remarkable improvement in the light harvesting efficiency confirmed from the IPCE measurement, supports an enhancement in current density in the current density-voltage measurement due to increased electron transport and smaller charge recombination. Moreover, these observations are corroborated with the EIS measurement as a cell with SnO2 reveals a reduced charge transfer resistance due to which the power conversion efficiency is increased from 2.20 to 3.41% i.e. 55% compared to the pristine ZnO/CdSe PEC. PMID:23873500

Patil, Supriya A; Shinde, Dipak V; Bhande, Sambhaji S; Jadhav, Vijaykumar V; Huan, Tran N; Mane, Rajaram S; Han, Sung-Hwan

2013-09-28

151

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

PubMed Central

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

2014-01-01

152

Nowcasting in the FROST-2014 Sochi Olympic project  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

153

GIVRE: A Protection Against Frost Deposit on Polar Instruments  

NASA Astrophysics Data System (ADS)

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

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

154

Spatial interpolation-based mapping of the spring frost hazard in the Champagne vineyards  

Microsoft Academic Search

The Champagne vineyards, famous worldwide, are located at the northern limit of viticulture. Consequently, they are very sensitive to spring frosts that can occur after bud burst. These spring frosts occur mainly in radiative atmospheric situations (low speed wind, clear sky) where spatial variations in minimum temperatures are very important. The latter depend on several factors at different scales: from

M. Madelin; G. Beltrando

2005-01-01

155

EFFECT OF TREE WRAP ON THE INCIDENCE OF FROST CRACK IN NORWAY MAPLE1  

Microsoft Academic Search

During the winters of 1970-1971 and 1971-1972, frost cracks developed on Norway maple cv. 'Emerald Queen' planted in a Michigan nursery. Trees in low areas or on poorly drained soils were more frequently injured than those planted on better drained soils. Wrapping trees in November, 1971, with bands of Kraft paper did not reduce the incidence of frost cracks during

John H. Hart; Gurdon K. Dennis

156

Verification of the Criteria for Evaluation of Water and Frost Resistance of Asphalt Concrete  

Microsoft Academic Search

The paper presents the results of field investigation—condition survey of existing pavements and the results of laboratory tests on water and frost resistance of samples cored from the these pavements. The purpose of testing was to verify the criteria for evaluation of the resistance of asphalt concrete to the action of water and frost by way of comparing the results

Piotr Jasku?a; Józef Judycki

2008-01-01

157

Effects of frost on wildflowers: an unexpected consequence of climate change--image 04 of 22  

NSDL National Science Digital Library

A graphical representation of a frost event at the Rocky Mountain Biological Laboratory (Colorado). The temperature dipped to 25.1 F on 11 June 2004. Winter snowpack melted at the monitoring location on 8 May that year. The late-spring frost killed flower buds that had developed in the four weeks following snowmelt.

Inouye, David

2012-01-04

158

Stresses and deformations in a buried oil pipeline subject to differential frost heave in permafrost regions  

Microsoft Academic Search

Differential frost heave of the buried oil pipelines in permafrost regions can have an adverse effect on the mechanical status of the pipeline, and seriously endanger the pipeline security. In order to reduce the damage to the pipeline during its designed lifetime, it is necessary to analyze the mechanical behavior of oil pipelines taking into consideration the differential frost heave

Yaping Wu; Yu Sheng; Yong Wang; Huijun Jin; Wu Chen

2010-01-01

159

Computations on frost damage to Scots pine under climatic warming in boreal conditions  

SciTech Connect

To investigate the risk of frost damage to Scots pine (Pinus sylvestris L.) in northern regions under climatic warming, a submodel for such damage to trees was included in a forest ecosystem model of the gap type. An annual growth multiplier describing the effects of frost was calculated with the help of simulated daily frost hardiness and daily minimum temperature. The annual growth multiplier was used in the main ecosystem model when simulating the development of a tree stand using a time step of one year. Simulations of the growth and development of Scots pine stands in southern Finland (61{degrees} N) under an elevating temperature indicated that climatic warming could increase the risk of frost damage due to premature onset of growth during warm spells in the late winter and early spring. Risk of frost damage implies uncertainty in yield expectations from boreal forest ecosystems in the event of climatic warming. 38 refs., 9 figs., 4 tabs.

Kellomaeki, S.; Haenninen, H.; Kolstroem, M. [Univ. of Joensuu (Finland)

1995-02-01

160

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.

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

2013-01-01

161

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

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

162

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

PubMed

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

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

2013-01-01

163

Numerical and experimental investigation on frosting of energy-recovery ventilator  

NASA Astrophysics Data System (ADS)

Frosting of energy-recovery ventilators results in two major problems: increase of pressure losses and reduction of heat transfer rates. Frost formation of heat and mass exchangers used in these ventilation systems is investigated both experimentally and numerically. A numerical model for the prediction of the thermal behavior of the exchanger is presented. The model is validated with experimental data and is then employed to conduct a parametric study. Results indicate that the absolute humidity is the prevailing parameter for characterizing the frosting phenomenon. A frost-mass-fraction chart is established in terms of the absolute humidity of the warm exhaust stream and of the temperature of the cold supply stream. The effect of time and mass flowrate is also evaluated. The transient three-dimensional model shows that the absolute humidity and the temperature of both air flows vary nonlinearly in the frosted zone.

Bilodeau, Stephane; Mercadier, Yves; Brousseau, Patrick

164

Nature and origin of layered deposits of the Martian polar regions  

NASA Technical Reports Server (NTRS)

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

Cutts, J. A.

1973-01-01

165

How the Enga cope with frost: Responses to climatic perturbations in the Central Highlands of New Guinea  

Microsoft Academic Search

The adaptive strategy of a population of New Guinea highland subsistence farmers is considered in the light of events surrounding a series of severe frosts experienced in 1972. Coping with frost is seen to be a critical preoccupation for all Enga, and agricultural mounding a universal response, adequate to deal with the mild frosts of Central Enga country below 2250

Eric Waddell

1975-01-01

166

Polar Dunes In Summer Exhibit Frost Patches, Wind Streaks  

NASA Technical Reports Server (NTRS)

Mars Global Surveyor passes over the north polar region of the red planet twelve times each day, offering many opportunities to observe how the polar cap frosts and dunes are changing as the days goby. Right now it is summer in the north. This picture, taken the second week of April 1999, shows darks and dunes and remnant patches of bright frost left over from the winter that ended in July 1998. Dark streaks indicate recent movement of sand. The picture covers an area only 1.4 kilometers (0.9 miles)across and is illuminated 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

167

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.

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

2014-01-01

168

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

169

Fast, nondestructive measurement of frost hardiness in conifer seedlings by VIS+NIR spectroscopy.  

PubMed

Frost hardiness development from mid-August to mid-November was evaluated in seedlings of three provenances of Norway spruce (Picea abies (L.) Karst.) and three provenances of Scots pine (Pinus sylvestris L.) raised at nurseries in north, central and south Sweden. Measurements of the visible + near infrared (VIS+NIR) spectra of shoots were made simultaneously with estimates of frost hardiness based on electrolyte leakage following artificial freezing. Nine physiological variables known to influence frost hardiness were measured throughout the experiment. Multivariate analysis showed that VIS+NIR spectra explained 69% and 72% of the variation in frost hardiness in Scots pine and Norway spruce, respectively. Stem lignification, dry weight fraction, and starch, glucose, fructose, galactose, sucrose, raffinose and stachyose concentrations together explained 80% and 85% of the variation in frost hardiness in Scots pine and Norway spruce, respectively when used as independent X variables in a partial least squares model. These physiological variables could be related to varying degrees with variation in the VIS+NIR spectra. We conclude that VIS+NIR spectroscopy provides a rapid nondestructive technique for measuring frost hardiness in conifer seedlings based on causal relationships between the spectra and the physiology of seedling frost hardiness. PMID:11470661

Sundblad, L G; Andersson, M; Geladi, P; Salomonson, A; Sjöström, M

2001-07-01

170

Toward a molecular scale understanding of frost heaving, phase 1  

NASA Astrophysics Data System (ADS)

A fundamental understanding of the physical and chemical basis for frost heaving is of utmost importance for improving the design of structures for use in cold regions. The research reported here represents a multidisciplinary effort to develop a molecular-scale understanding of this cold region phenomena. Propagation of the molecular-scale information to a field scale is also important and the scale-up problem has also been addressed. A multiphase, multicomponent hybrid theory of mixtures approach was used to scale up information. Equilibrium and nonequilibrium statistical mechanical tools were developed and employed to examine nonlocal diffusion and dispersion. Phase transitions were studied with MC and MD methods. New techniques were developed to compute the chemical potential of the vicinal phase. Interfacial tension was studied using GCEMC. Anomalous diffusion in monolayer films was analyzed via MD, scaling arguments and fractal Brown motion.

Cushman, John H.

1993-12-01

171

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

172

Experimental results on frost as a first wall shielding concept for inertial confinement fusion  

SciTech Connect

An experimental effort was undertaken at the Energy Technology Engineering Center in support of the design of the Laboratory Microfusion Facility (LMF) by Lawrence Livermore National Laboratory. The purpose of the experiments was to determine the ability of a frost-covered wall to act as a first wall in the LMF for the absorption of x-rays and debris. Certain aspects of the frost shielding concept were verified including growth rate, thermal conductivity, crush strength, ability to absorb shock waves and withstand vibration, and integrity after growth. The experimental results indicate that frost would function as a suitable first wall for the LMF. 87 figs.

Neely, H.H.; Hoffman, N.J.; Murray, K.A.

1990-03-01

173

The geochemical composition of frost flowers in the Alaskan Arctic and their role in mercury deposition  

NASA Astrophysics Data System (ADS)

Frost flowers are small (centimeters long) intricate crystals that form on newly formed sea ice. They grow from a combination of water vapor deposition and wicking of brine upward from the sea ice surface. Frost flowers are generally two to three times the salinity of seawater and they have a depleted sulfate to sodium ratio that is believed to be caused by the precipitation of mirabilite during their growth. They are a link between the lower atmosphere and sea ice and thus may play a role in the physical and chemical processes that deposit mercury to the Arctic. Reactive halogen radicals oxidize gaseous elemental mercury to reactive gaseous mercury in the lower atmosphere of the Arctic. The resulting reactive gaseous mercury is deposited to snow and ice during spring time Atmospheric Mercury Deposition events (AMDEs). Since frost flowers are halogen rich they are implicated in AMDE chemistry. We collected frost flowers, brine, snow and seawater from the Arctic Ocean north of Barrow, Alaska during three field seasons. Most recently, we participated in the sea ice component of the Ocean-Atmosphere-Sea Ice-Snow (OASIS) campaign in Barrow in 2009. All of our frost flowers yield sulfate to sodium ratios of less than 0.15 which is roughly half that of seawater (0.24). Brine collected from the sea ice surface yields sulfate to sodium ratios close to seawater values. Over an 11 day period all major elements but sulfate decreased in the frost flowers. This suggests that: 1) vapor phase deposition of ice to frost flowers continues long after they initially form, and 2) mirabilite precipitation continues after initial flower growth. Stable oxygen isotope values of the frost flowers became increasingly lower over time with ?18O values evolving from roughly -3‰ to -10‰ over the 11 day period. This further suggests vapor phase deposition onto exposed frost flower surfaces is a continual process following initial flower growth. Brine yielded ?18O values ranging between -0.1‰ and +4‰ suggesting oxygen-18 is preferentially fractionated out of the sea ice crystal lattice more than oxygen-16. Dissolved organic carbon concentrations were below 15 mg/L for all brine and frost flower samples but DOC was detected in seawater (10-11 mg/L). Mercury concentrations in frost flowers range between 25 and 200 ng/L. Some frost flowers were less than eight hours old which suggests that mercury deposition chemistry occurs on the timescale of hours. This geochemical information will be presented in reference to arctic atmospheric chemical processes that promote AMDEs.

Douglas, T. A.; Sturm, M.; Blum, J. D.; Sherman, L. S.; Steffen, A.; Simpson, W. R.

2009-12-01

174

Use of Frost sutures in an orbital trauma patient with extensive conjunctival oedema and pseudoproptosis.  

PubMed

Frost sutures are temporary suspension sutures conventionally used in oculoplastics. The case is presented here of a patient with multiple orbital fractures who developed worsening conjunctival chemosis and pseudoproptosis. This patient was managed successfully with Frost sutures. To the best of the authors' knowledge, there is no documented use of Frost sutures in this type of case. It is emphasized that this technique should only be considered following rigorous exclusion of retrobulbar pathology and careful attention towards early detection of raised intraocular pressure. PMID:17391921

Krishnan, R; Izadi, S; Morton, C E; Marsh, I B

2007-07-01

175

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

176

Effects of frost on wildflowers: an unexpected consequence of climate change--image 13 of 22  

NSDL National Science Digital Library

Delphinium barbeyi, or tall larkspur, flowering in a year with no frost damage. Photographed (by David Inouye) in front of Gothic Mountain, at the Rocky Mountain Biological Laboratory. Altitude about 9,500 ft (2,900m).

Inouye, David

2012-01-04

177

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

PubMed

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

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

2014-06-25

178

Effects of frost on wildflowers: an unexpected consequence of climate change--image 19 of 22  

NSDL National Science Digital Library

Example of a frost-killed ovary (on left) and a normally developing fruit (on right) of Erythonium grandiflorum, the glacier lily. The two plants were selected to show the difference, and weren't growing next to each other.

Inouye, David

2012-01-04

179

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

NASA Technical Reports Server (NTRS)

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

Glaser, F. M.

1978-01-01

180

THE RELATION BETWEEN THE RADIOACTIVE PHOSPHORUS ABSORPTION IN AGRICULTURAL CROPS AND THEIR FROST-RESISTANCE  

Microsoft Academic Search

An attempt was made to evaluate the frost resistance of winter wheat and ; several other agricultural crops by measuring the absorption of phosphorus-32 at ; various temperatures. Data are tabulated. (C.H.);

V. I. Razumov; N. D. Feofanova

1959-01-01

181

Effect of Soil Frost on Snow-melt runoff Generation: Stable Isotope Study in Drained Peatlands  

NASA Astrophysics Data System (ADS)

In this study, we analysed stable isotopes and water quality of runoff water collected daily from two different peatland drainage areas with automated samplers from March 2012 to October 2012, located in Northern Finland. In addition we collected weekly snow samples for stable isotope analysis. Our primary aim was to find out how different land use types, i) peat extraction area and ii) peatland forestry, are affecting the flow paths and runoff water quality during the snow melt period. Results show that there is a clear difference in ?O18 signal between these systems. The peatland forestry area is located at groundwater dominated area which can be seen as a flat line when ?O18 values of all samples are plotted. Samples taken at the peat extraction area show a clear response to the snowmelt event. Most likely this difference is caused by different soil frost conditions. Quantity of the groundwater at the forestry area prevents the soil from freezing during winter, therefore water originating from melting snow is able to infiltrate to the peat soil and push pre-event water into the drainage system. This observation is also visible in water quality of runoff water as high peak in colour during the snow melt period. Contrary, the peat extraction area behaves in opposite way. Melting water from snow is not able to infiltrate to ditches but instead will rapidly move on the frozen soil surface as a Hortonian overland flow. Because the soil is frozen, moving water is not able to leach humic substances from soil layers or erode particulate matter from the soil surface. These observations can be used to develop water quality protection policies for drained peatland areas. In Northern areas, where freezing of soil during winter is common it is not crucial to emphasize water protection during spring snowmelt, as frozen soil helps to maintain the runoff water quality at reasonable levels. In the areas where ground frost is rarer the impact of purifying runoff water in spring thaw will be more beneficial for the receiving water bodies.

Eskelinen, Riku; Ronkanen, Anna-Kaisa; Marttila, Hannu; Klřve, Bjřrn

2013-04-01

182

Trends of spring time frost events and phenological dates in Central Europe  

NASA Astrophysics Data System (ADS)

Over large parts of the Northern Hemisphere's continents temperature has been increasing during the last century. Particularly minimum temperatures show a more pronounced increase than maximum temperatures. Not only the phenological seasons, but also the potentially plant damaging late frost events are governed by the atmosphere. In case of a rise of minimum temperatures one would expect phenological phases and spring late frost events to occur earlier. In this work the question is elucidated whether plant phenology shifts at a higher or lower rate towards earlier occurrences than potential plant damaging events, like spring late frost events. Frost events based on the last occurrence of daily minimum temperatures below a certain threshold have been moving faster to earlier occurrence dates than phenological phases during the last decades at 50 climate stations in Central Europe. Trend values of frost time series range around -0.2 days/year and of phenological time series are between -0.2 and 0.0 days/year over the period from 1951-1997. `Corylus avellana beginning of pollination' is the only one of the 13 phases considered here with a lower trend value of -0.28 days/year. Early phases are more adapted to below zero temperatures and therefore follow more closely the temperature variability. Later phases seem to have more reason to be concerned about possible late frost events and react more cautiously towards higher spring temperatures and earlier last frost dates. The risk of late frost damage for plants should have been lower during the last decade as compared to the previous decades.

Scheifinger, H.; Menzel, A.; Koch, E.; Peter, Ch.

183

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

Microsoft Academic Search

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

S. A. Tassou; C. J. Marquand

1987-01-01

184

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

NASA Astrophysics Data System (ADS)

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

Jönsson, A. M.; Bärring, L.

2011-02-01

185

Two Cases of Frosted Branch Angiitis with Central Retinal Vein Occlusion  

Microsoft Academic Search

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

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

2001-01-01

186

Frost flowers growing in the Arctic ocean-atmosphere-sea ice-snow interface: 2. Mercury exchange between the atmosphere, snow, and frost flowers  

NASA Astrophysics Data System (ADS)

Frost flowers are ice crystals that grow on refreezing sea ice leads in Polar Regions by wicking brine from the sea ice surface and accumulating vapor phase condensate. These crystals contain high concentrations of mercury (Hg) and are believed to be a source of reactive halogens, but their role in Hg cycling and impact on the fate of Hg deposited during atmospheric mercury depletion events (AMDEs) are not well understood. We collected frost flowers growing on refreezing sea ice near Barrow, Alaska (U.S.A.) during an AMDE in March 2009 and measured Hg concentrations and Hg stable isotope ratios in these samples to determine the origin of Hg associated with the crystals. We observed decreasing ?199Hg values in the crystals as they grew from new wet frost flowers (mean ?199Hg = 0.77 ± 0.13‰, 1 s.d.) to older dry frost flowers (mean ?199Hg = 0.10 ± 0.05‰, 1 s.d.). Over the same time period, mean Hg concentrations in these samples increased from 131 ± 6 ng/L (1 s.d.) to 180 ± 28 ng/L (1 s.d.). Coupled with a previous study of Hg isotopic fractionation during AMDEs, these results suggest that Hg initially deposited to the local snowpack was subsequently reemitted during photochemical reduction reactions and ultimately accumulated on the frost flowers. As a result of this process, frost flowers may lead to enhanced local retention of Hg deposited during AMDEs and may increase Hg loading to the Arctic Ocean.

Sherman, Laura S.; Blum, Joel D.; Douglas, Thomas A.; Steffen, Alexandra

2012-07-01

187

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

PubMed

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

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

2012-08-01

188

Application of the phase equilibrium method for generation of -100 °C of humid gas frost-point temperature  

NASA Astrophysics Data System (ADS)

Realization of the phase equilibrium method for very low frost-point temperature generation of a humid gas is presented. A theoretical approach to the analysis of thermodynamic processes of the phase equilibrium achievement is suggested. On the basis of theoretical and experimental analyses, preliminary and main saturators, as parts of the standard low frost-point humidity generator, are designed, enabling us to generate down to -100 °C of frost-point temperature.

Mamontov, George

2000-06-01

189

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

190

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

NASA Astrophysics Data System (ADS)

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

Peterson, Rorik A.

191

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

192

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

2014-01-01

193

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

194

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

195

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

PubMed

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

Charrier, Guillaume; Cochard, Hervé; Améglio, Thierry

2013-09-01

196

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

NASA Astrophysics Data System (ADS)

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 condenses and sublimates in a seasonal exchange of CO2 between the ground and the atmosphere. Columnar thickness and mass results are discussed and plotted for latitudes including +/-60° and poleward. GRS observations are compared to predictions from the NASA Ames Research Center General Circulation Model and to similar experimental results from the Mars Odyssey High Energy Neutron Detector and Neutron Spectrometer. Models for north and south polar atmosphere and regolith distributions are incorporated, and our results indicate that the assumption of a 100% H2O-ice residual cap underlying the seasonal frost in the north is accurate. The GRS CO2 frost observations are in good agreement with the other studies mentioned, in particular for the timing of the beginning of frost deposition to the complete sublimation of surface CO2 back into the atmosphere. The total amount of condensed carbon dioxide mass seen by the GRS is on the order of 6.0 × 1015 kg and verifies previous reports that nearly 25% of the Martian CO2 reservoir participates in the ground-atmosphere exchange cycle.

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

2006-12-01

197

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 2021–2050 compared to 1971–2000, 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 2078–2087. 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.

Hoffmann, Holger; Rath, Thomas

2013-01-01

198

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

2011-03-01

199

Sexual reproduction in a greenhouse and reduced autumn frost hardiness of Picea abies progenies.  

PubMed

In 1989, identical crosses (2-3 females within males) were performed with Picea abies (L.) Karst. in a greenhouse seed orchard at Biri nursery and in an outdoor seed orchard at Huse, 32 km north of Biri. Pollination began 17 days earlier in the greenhouse than outdoors at Huse. The potted grafts in the greenhouse were moved outdoors when the seed cones were no longer receptive. Twelve full-sib family pairs (Biri and Huse) from these crosses were grown in a phytotron and tested for height and autumn frost hardiness during their first growing season. No significant difference was found between the indoor (Biri) and outdoor (Huse) progenies for height growth. However, the progenies from the greenhouse seed orchard were significantly more susceptible to frost than their full-sibs from the outdoor seed orchard. There was no significant interaction between males and the flowering environment, but a significant female x flowering environment interaction was present as a result of greater differences in frost hardiness between progenies from females in the greenhouse seed orchard than in the outdoor seed orchard. Although seeds from the outdoor seed orchard generally had a greater biomass than seeds from the greenhouse seed orchard, the difference in seed weight did not explain the difference in frost hardiness. We hypothesize that temperature and photoperiod during pollination and fertilization affect the frost hardiness of the progenies. PMID:14965942

Johnsen, ŘYstein; Skrřppa, Tore; Haug, Gunnar; Apeland, Inger; ŘStreng, Geir

1995-01-01

200

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; López-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

201

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

202

A Community Frost/Freeze Susceptibility Operational Guidance Tool  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

203

Observations of Chemical Composition in Frost Flower Growth Process and Their Implication in Aerosol Production and Bromine Activation Chemistry  

NASA Astrophysics Data System (ADS)

Frost flowers are believed to be responsible for most of the salt aerosol and possibly the bromine in the gas phase during springtime in Polar Regions. Frost flowers are vapor deposited ice crystals that form on new forming sea ice and wick brine from the sea-ice surface resulting in high salinities. We propose a conceptual model of frost flower growth and chemical fractionation using chemical analysis to support this model. We also consider how the chemical composition of frost flowers can tell us about the role of frost flowers in bromine activation and aerosol production. Our conceptual model is centered in two important events that occur when sea ice grows and the ice surface temperature gets colder. Brine on the sea-ice surface is drawn up the frost flower by capillary forces, therefore the high salinity values found. Secondarily salt hydrates begin to precipitate at certain temperatures. These precipitation reactions modify the chemical composition of the frost flowers and residual brine, and are the main topic of this research. We found variability and generally depletion of sulfate as compared to sea-water composition in most of the mature frost flowers. This result is in agreement with the literature, which proposes the depletion in sulfate occurs because mirabilite (Na2SO4 · 10H2O) precipitates before the brine is wicked. The observation of some slightly sulfate-enhanced samples in addition to depleted samples indicates that the brine/frost flower environment is the location where mirabilite precipitation and separation from residual brine occurs. Frost flowers bromide enhancement factors are all, within analytical limits, identical to sea water, although nearby snow is depleted in bromide. Because of the high salt concentrations in frost flowers, significant bromine activation could occur from frost flowers without being detected by this measurement. However, if all bromide activation occurred on frost flowers, and frost flowers are not depleted in bromide, no snow would be found that was depleted in bromide. Therefore, the observation of snow that is depleted in bromide shows there must be some activation of bromide subsequent to frost flowers formation.

Alvarez-Aviles, L.; Simpson, W. R.; Douglas, T. A.; Sturm, M.; Perovich, D. K.

2006-12-01

204

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 ...

205

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

PubMed

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

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

2013-12-01

206

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 (Löhnis) Dye are sufficient to incite frost injury to sensitive plants at ?5°C. 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 ?2°C, 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 ?5°C are always active as ice nuclei at ?5°C. INA bacteria incited frost injury to all of the species of sensitive plants tested.

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

1982-01-01

207

Reflectance spectra for sodium and potassium doped ammonia frosts - Implications for Io's surface  

NASA Technical Reports Server (NTRS)

This paper reports measurements of the reflection spectra of sodium- and potassium-doped ammonia frosts as a function of alkali metal concentration for the wavelength range 0.35-2.5 microns. The purpose of the measurements was to determine whether or not the reflection spectra for such a solid was compatible with the spectra albedo of Io. The data show that, with a sufficiently large alkali metal concentration, the reflection spectra of the doped ammonia frosts do not display the characteristic ammonia features at 2.0 and 2.25 micron. The high reflectance of the more concentrated samples and the character of the observed reflection spectrum make it difficult to rule out sodium-doped ammonia frost as a surface constituent on Io on the basis of existing data.

Rosen, M. D. A.; Pipkin, F. M.

1978-01-01

208

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 -15°C. 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

209

Lipase-based quantitation of triacylglycerols in cellular lipid extracts: Requirement for presence of detergent and prior separation by thin-layer chromatography  

Microsoft Academic Search

A protocol, based on the use of Pseudomonas lipase, is presented to measure quantitatively the amount of triacylglycerols in extracts from cultured cells or tissues.\\u000a Since the lipase also acts on di- and monoacylglycerols, separation of the extracts by thin-layer chromatography is recommended.\\u000a In order to allow the lipase-catalyzed hydrolysis to proceed efficiently, lipid extracts or eluates from silica scraping

Paul P. Van Veldhoven; Johannes V. Swinnen; Murielle Esquenet; Guido Verhoeven

1997-01-01

210

Assessing the protective effect of vertically heterogeneous canopies against radiative frost: The case of quinoa on the Andean Altiplano  

Microsoft Academic Search

Night radiative frost is a highly limiting factor for agriculture in Andean highlands. Nevertheless, a diversity of crop species have been domesticated there, commonly showing high heterogeneity in plant growth at the field level. The possible protective effect of crop canopy heterogeneity against nocturnal radiative frost is examined using a dual approach, combining a field experiment and a simplified energy

T. Winkel; J. P. Lhomme; J. P. Nina Laura; C. Mamani Alcón; C. del Castillo; A. Rocheteau

2009-01-01

211

Frost Prediction using a Combinational Model of Supervised and Unsupervised Neural Networks for Crop Management in Vineyards  

Microsoft Academic Search

Frost prediction models could contribute significantly towards the successful growth and production of quality crop yield in horticulture, especially in precision viticulture where the benefits are significant because frost damage is well-known for its potential leading to total harvest failure, with a follow-on regional or national economic impact outcome. This reality has increased interest among scientists and growers to advance

P. Sallis; M. Jarur; M. Trujillo

212

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

213

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

Microsoft Academic Search

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

H. Vömel; D. E. David; K. Smith

2007-01-01

214

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

215

Study on Heat and Mass Transfer under Frosting Condition-2nd Report  

NASA Astrophysics Data System (ADS)

The author and other investigators have reported experimental results that coefficients of mass transfer under frosting conditions decreased as the wall temperature decreased. On the other hand, in the previous paper,the theoretical analysis of heat and mass transfer under frosting conditions has been made with satisfaction of a thermodynamic equilibrium between temperature and concentration of water vapor in humid air. In this paper,the experimental results of Nusselt number Nu and Sherwood number Sh are compared with the analytical ones,and Sh/Nu is discussed and analyzed in consideration of phase change process of water vapor in humid air.

Ishihara, Isao

216

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

217

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

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

218

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

Microsoft Academic Search

Two reproducible stability indicating methods were developed for the determination of risperidone (RISP) in presence of its degradation products in pure form and in tablets. The first method was based on reversed phase high performance liquid chromatography (HPLC), on Lichrosorb RP C 18 column (250mm i.d., 4mm, 10?m), using methanol:0.05M potassium dihydrogen phosphate pH 7 (65:35 (v\\/v)) as the mobile

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

2005-01-01

219

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

PubMed

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

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

2005-01-01

220

Weak acid transport across bilayer lipid membrane in the presence of buffers. Theoretical and experimental pH profiles in the unstirred layers.  

PubMed Central

This paper presents a simple model to describe experimental data on weak acid transport across planar bilayer lipid membrane separating two buffered solutions. The model takes into account multiple proton-transfer reactions occurring in the unstirred layers (ULs) adjacent to the membrane. Differential equations of the model are shown to be reduced to a set of nonlinear algebraic equations. Since the latter equations depend monotonically on unknown variables, they can be easily solved numerically, using bisection method. For the particular system studied experimentally (with acetate as the weak acid and TRIS+MES as the buffer mixture) pH profiles in the ULs are calculated from the model. These results are compared with experimental data obtained using pH microelectrode. The agreement between theoretical and experimental pH profiles is found to be satisfactory. The most pronounced deviations are observed at the UL/bulk solution boundary. To obtain a better correlation between the theoretical and experimental results, two other, less idealized models are considered. They take into account, respectively, (a) the electric field arising in the ULs from ion diffusion and (b) finiteness of the rates of proton-transfer reactions. However, both acetate membrane fluxes and pH profiles in the ULs computed from these models are found to be close to those of the simple model. One can thus conclude that the difference between experimental and theoretical pH profiles is due to the inconsistency of the generally accepted model of the "unstirred layer", assuming the existence of a strict boundary between the regions of "pure diffusion" and "ideal stirring".

Antonenko, Y N; Denisov, G A; Pohl, P

1993-01-01

221

Possum browsing—the downside to a eucalypt hybrid developed for frost tolerance in plantation forestry  

Microsoft Academic Search

Eucalyptus hybrids are being investigated for use in plantation forestry to incorporate frost tolerance into marketable species. Five large field trials at four altitudes in Tasmania, southern Australia, were established to measure performance of E. gunnii, E. globulus, their F1 hybrids and E. nitens, the species currently used at higher altitudes. Four of these trials were browsed by brushtail possums

Sarah L. Scott; Clare McArthur; Brad M. Potts; Kelsey Joyce

2002-01-01

222

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

NSDL National Science Digital Library

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

Inouye, David

2012-01-04

223

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

Microsoft Academic Search

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

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

2009-01-01

224

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

Microsoft Academic Search

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

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

2001-01-01

225

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

226

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

227

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

228

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

2014-07-10

229

Mapping genes affecting flowering time and frost resistance on chromosome 5B of wheat  

Microsoft Academic Search

Two populations of single chromosome recombinant lines were used to map genes controlling flowering time on chromosome 5B of wheat, and one of the populations was also used to map a new frost resistance gene. Genetic maps were developed, mainly using microsatellite markers, and QTL analysis was applied to phenotypic data on the performance of each population collected from growth-room

B. Tóth; G. Galiba; E. Fehér; J. Sutka; J. W. Snape

2003-01-01

230

Acclimation to frost alters proteolytic response of wheat seedlings to drought  

Microsoft Academic Search

A comparative examination of cysteine proteinases in winter wheat (Triticum aestivum L.) seedlings differing in sensitivity to frost and drought revealed many similarities and differences in response to water deprivation. Azocaseinolytic activity was enhanced under water deficiency, but the enhancement was significantly lower in the tolerant genotype (Kobra cultivar). On the contrary, acclimation of wheat seedlings at low temperature had

Ma?gorzata Grudkowska; Barbara Zagda?ska

2010-01-01

231

SIMULATION OF FROST RESISTANCE OF WINTER WHEAT IN EUROPE BETWEEN 1975 AND 2005  

Microsoft Academic Search

Frost damage is very important especially for Eastern Europe, but in some winters this aspect is of interest also for larger areas of Europe. The effect of the temperature at the crown level (considered as a function of snow and air temperature, Aase and Siddoway, 1979) it is better estimated if the physiological condition of the plant (hardening index) is

232

Flavonoid composition in frost-resistant Rhododendron cultivars grown in Poland  

Microsoft Academic Search

A relationship was found between flavonoid concentration in rhododendron (Rhododendron L.) leaves and their frost resistance. The flavonoid content in various taxons of rhododendrons bred in Poland was compared with the extent of injury caused by the action of sub-zero temperatures. High performance liquid chromatography (HPLC) was used to analyze flavonoids and their glycosides. The results suggest that flavonoid concentrations

Adam Swiderski; Piotr Muras; Henryk Koloczek

2004-01-01

233

PENNDOT Portion of Research on the Project Fundamentals of Frost Action in Subgrade Soils.  

National Technical Information Service (NTIS)

The research report deals with the investigative work done to develop a routine test for soil frost susceptibility. The objectives of the test investigation were: (1) the refinement of a testing apparatus constructed by M.I.T. and similar in design to app...

G. Cumberledge G. L. Hoffman

1976-01-01

234

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 -25°C. 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.; Monzó, J.; Soriano, L.; Payá, J.

2014-03-01

235

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 Săo Paulo state, which is the major sugarcane producer in Brazil being responsible for almost 60% of its production. Despite the favorable climate in Săo 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 Săo 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 Săo 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

236

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

SciTech Connect

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

Miller, W.A.

1986-01-01

237

THE FROST EFFECTS RESEARCH FACILITY AND URBAN INFRASTRUCTURE  

Microsoft Academic Search

The design of urban pavements has unique requirements that are not found with highway pavements. Some characteristics that contribute to the overall performance of urban roads include slower vehicle speeds, heavy loading, numerous cycles of deceleration and acceleration, particularly at intersection locations, as well as the presence of buried utilities and building structures. Failure mechanisms for urban roads are different

Vincent Janoo; Robert Eaton; Lynette Barna

238

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

239

Interactive effects of elevated ozone and springtime frost on growth and physiology of birch ( Betula pendula ) in field conditions  

Microsoft Academic Search

We studied the impact of ozone enrichment and late frost, singly and interactively, on four birch (Betula pendula Roth) families selected from a naturally regenerated birch stand in southeastern Finland. Seedlings were exposed to 1.5×\\u000a ambient ozone over one and a half growing seasons using free-air ozone enrichment system. Simulated springtime frost was implemented\\u000a at the beginning of the second

Tarja Silfver; Elina Häikiö; Matti Rousi; Toini Holopainen; Elina Oksanen

2008-01-01

240

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

241

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.

242

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

NASA Astrophysics Data System (ADS)

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 the relevant actions and events (or outcomes), specifying the effect of taking protective action, and describing the relationships among temperature, bud loss, and yield loss. A bivariate normal distribution is used to model the relationship between forecast and observed temperatures, thereby characterizing the quality of different types of information. Since the orchardist wants to minimize expenses (or maximize payoffs) over the entire frost-protection season and since current actions and outcomes at any point in the season are related to both previous and future actions and outcomes, the decision-making problem is inherently dynamic in nature. As a result, a class of dynamic models known as Markov decision processes is considered. A computational technique called dynamic programming is used in conjunction with these models to determine the optimal actions and to estimate the value of meteorological information.Some results concerning the value of frost forecasts to orchardists in the Yakima Valley of central Washington are presented for the cases of red delicious apples, bartlett pears, and elberta peaches. Estimates of the parameter values in the Markov decision process are obtained from relevant physical and economic data. Twenty years of National Weather Service forecast and observed temperatures for the Yakima key station are used to estimate the quality of different types of information, including perfect forecasts, current forecasts, and climatological information. The orchardist's optimal actions over the frost-protection season and the expected expenses associated with the use of such information are determined using a dynamic programming algorithm. The value of meteorological information is defined as the difference between the expected expense for the information of interest and the expected expense for climatological information. Over the entire frost-protection season, the value estimates (in 1977 dollars) for current forecasts were $808 per acre for red delicious apples, $492 per acre for bartlett pears, and $270 per acre for elberta peaches. These amounts account for 66, 63, and 47%, respectively, of the economic value associated with decisions based on perfect forecasts. Varying the quality of the minimum temperature forecasts reveals that the relationship between the accuracy and value of such forecasts is nonlinear and that improvements in current forecasts would not be as significant in terms of economic value as were comparable improvements in the past.Several possible extensions of this study of the value of frost forecasts to orchardists are briefly described. Finally, the application of the dynamic model formulated in this paper to other decision-making problems involving the use of meteorological information is mentioned.

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

1982-04-01

243

Frost action of freezing ground surrounding underground storage of a cold liquid  

NASA Astrophysics Data System (ADS)

A small tank in the shape of a cylinder 80 cm in diameter and 50 cm in depth was placed in a basin, filled with a silty soil, of the frost test field in Tomakomai, Hokkaido Japan, with its top at the same level as the ground surface in the basin. The double wall (two steel sheets 10 cm apart) constituted the exterior of the side and bottom. As a cold liquid at temperature of -23 C was poured inside the gap of the double wall and circulated, the soil around the tank began to freeze sideways and downwards from the tank. Studies made are as follows: (1) the progress of the freezing front was measured and preestimated; (2) frost heaving characters of the tank and the ground surface around it were observed; (3) soil water migration was calculated by measuring moisture tensions at several points within the soil; (4) soil pressure acting on the tank was measured.

Kinosita, S.; Fukuda, M.; Ishizaki, T.; Yamamoto, H.

244

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

245

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.

Petras, David

2013-01-01

246

Rapid induction of frost hardiness in spinach seedlings under salt stress  

Microsoft Academic Search

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

Dirk K. Hincha

1994-01-01

247

Effects of frost on wildflowers: an unexpected consequence of climate change--image 17 of 22  

NSDL National Science Digital Library

The glacier lily (Erythronium grandiflorum) is one of the earliest wildflowers to bloom after snowmelt in the Rocky Mountains. Its ovaries and seeds are sensitive to late-season frosts. But because the species is a perennial, it can survive occasional years of reproductive failure by blooming the following year. By avoiding the cost of producing the relatively large fruit and seeds in one year, the plant may have better survivorship and be able to produce more flowers the next year.

Inouye, David

2012-01-04

248

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

249

Thermoluminescence (TL) and ESR study of ?-irradiated SO 2 frost for future dating in outer planets  

Microsoft Academic Search

Thermoluminescence (TL) and electron spin resonance (ESR) of SO2 frost were studied for future TL and ESR dating of materials from the outer planets. The solid SO2 gamma-ray-irradiated at 77 K shows five TL peaks at about 110, 125, 140, 150 and 180 K. TL curves were simulated to obtain the activation energy E and the frequency factor v0. The

K. Kanosue; H. Toda; M. Hirai; H. Kanamori; M. Ikeya

1997-01-01

250

Frost resistance among the Solanum species in the ir-1 potato collection  

Microsoft Academic Search

Summary  Five-hundred eighty-six wild and cultivated introductions representing 82Solanum species maintained in the IR-1 Potato Collection were evaluated in the field for frost resistance following freezing temperatures\\u000a down to 27 F (?2.8 C). The most resistant introductions were those ofS. acaule, S. chomatophilum, S. commersonii, S. xcurtilobum, S. demissum, andS. sanctae-rosae. Resistance comparable to the best in the tuberbearing species was

R. W. Ross; P. R. Rowe

1965-01-01

251

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 -4.0°C, was statistically similar to the range recorded in 1993, while the mean minimum temperatures (tmin) were found to have risen. The historical series also showed the mean minimum temperatures (tmin) to have increased, however. Through 1985, tmin ranged from 4.0 to -2.0 °C, depending on the area, while these limits shifted in more recent years to 7.0 - 0.5 °C. This increase in mean temperature produced that the frost episodes in March 2004 was considered by lemon, mandarin and olive producers as the worst in many years for frost damage since the minimum temperature was reached in a more sensitive phenological stage, despite the statistical evidence that similar freezing temperatures had been reached on similar dates in other years.

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

2009-04-01

252

WCS120 protein family and frost tolerance during cold acclimation, deacclimation and reacclimation of winter wheat.  

PubMed

We studied how long-term cold acclimation of winter wheat (variety Mironovskaya 808), interrupted by deacclimation and then followed by reacclimation, affected the levels of cold-induced WCS120 proteins, dry-weight content, and frost tolerance in leaves. Two experiments were performed: (1) plants undergoing long-term cold acclimation (up to 112days) were quickly deacclimated (for 5days), and then reacclimated again to cold; (2) plants vernalized for varying periods of time in an early stage of their development were, after a longer deacclimation of about 14days, exposed for the same time period to cold. Five members of the WCS120 protein family were detected and quantified by image analysis in protein gel blots (in the first experiment); as well as in two-dimensional electrophoresis gels (in the second experiment). In both experiments, partially vernalized plants, after reacclimation, re-established their frost tolerance to levels similar to plants having had the same duration of cold treatment, but without deacclimation. On the other hand, these partially and fully vernalized plants reaccumulated WCS120 proteins to lower levels than plants that were not deacclimated. Further, using a mathematical model (the peak four-parameter Weibull equation), the same type of response curve was observed during plant cold treatment not only for the level of frost tolerance, but also for dry-weight content and accumulation of WCS120 proteins, with the maximum values reached at about the same time as vernalization saturation. PMID:18676155

Vítámvás, Pavel; Prásil, Ilja Tom

2008-11-01

253

Effects of frost on wildflowers: an unexpected consequence of climate change--image 10 of 22  

NSDL National Science Digital Library

The number of flowers produced by the aspen sunflower (Helianthella quinquenervis) in a particular year is affected by the date of the start of the growing season, which is in turn influenced by the date that the winter snowpack melts. Years with low winter snowfall and warm springs have more rapid snowmelt and an earlier start to the growing season than years with a heavy snowpack or a cool spring. But each year, the last hard frost occurs in early - mid June, regardless of the snowmelt date.In years having an early start to the growing season (shown in blue), aspen sunflower plants had relatively few unfrosted flowers. In such years, the early snowmelt allows plants to start their growth early. They develop many buds that are filled by the late season frost. Thus, plants produce few flowers in those years.In years having a late start to the growing season (shown in red), aspen sunflower plants had many unfrosted flowers. In those years, the late snowmelt delayed the growth of plants. Thus, frost events in June had little impact on flower production because the plants had not produced buds by that time.As seen in Image 09, years of early snowmelt have been especially common in the past decade. Thus, plant populations have experienced poorer reproductive success than in previous decades.

Inouye, David

2012-01-04

254

Decadal predictability of frost days in the MPI-ESM-LR model  

NASA Astrophysics Data System (ADS)

The number of frost days (days with minimum temperature below 0°C) is a typical index for cold temperature extremes defined by the Joint CCl/CLIVAR/JCOMM Expert Team on Climate Change Detection and Indices (ETCCDI). It's predictability on inter-annual to decadal time scales bears economic and societal relevance, e.g. as basis for energy or agricultural policy planning. As part of the MiKlip initiative for decadal prediction, annually initialised ensemble hindcast experiments with the Max-Planck-Institute Earth System Model in a low resolution configuration (MPI-ESM-LR, T63L47) have been carried out. For a period of 35 years (1961-1995) we analyze the number of frost days per season and grid point on a 5° x 5° longitude-latitude grid for the northern hemisphere stemming from ten/three ensemble member hindcasts produced with two different initialisation strategies. The ensembles are interpreted as probabilistic predictions of historically equiprobable three-category events (below normal, normal, above normal) and as such are compared to frost day counts from HadEx2 and the 20th Century Reanalysis. Prediction skill over climatological forecasts and uninitialised climate projections is assessed for various lead times using the Ranked Probability Skill Score (RPSS).

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

2014-05-01

255

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

256

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

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

257

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

NASA Astrophysics Data System (ADS)

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

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

2006-05-01

258

Two loci on wheat chromosome 5A regulate the differential cold-dependent expression of the cor14b gene in frost-tolerant and frost-sensitive genotypes.  

PubMed

Although cold acclimation in cereals involves the expression of many cold-regulated genes, genetic studies have shown that only very few chromosomal regions carry loci that play an important role in frost tolerance. To investigate the genetic relationship between frost tolerance and the expression of cold-regulated genes, the expression and regulation of the wheat homolog of the barley cold-regulated gene cor14b was studied at various temperatures in frost-sensitive and frost-tolerant wheat genotypes. At 18/15 degrees C (day/night temperatures) frost-tolerant plants accumulated cor14b mRNAs and expressed COR14b proteins, whereas the sensitive plants did not. This result indicates that the threshold temperature for induction of the wheat cor14b homolog is higher in frost-resistant plants, and allowed us to use this polymorphism in a mapping approach. Studies made with chromosome substitution lines showed that the polymorphism for the threshold induction temperature of the wheat cor14b homolog is controlled by a locus(i) located on chromosome 5A of wheat, while the cor14b gene was mapped in Triticum monococcum on the long arm of chromosome 2Am. The analysis of single chromosome recombinant lines derived from a cross between Chinese Spring/Triticum spelta 5A and Chinese Spring/Cheyenne 5A identified two loci with additive effects that are involved in the genetic control of cor14b mRNA accumulation. The first locus was tightly linked to the marker psr911, while the second one was located between the marker Xpsr2021 and Frost resistance 1 (Fr1). PMID:10778737

Vágújfalvi, A; Crosatti, C; Galiba, G; Dubcovsky, J; Cattivelli, L

2000-03-01

259

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

PubMed Central

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

2013-01-01

260

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

261

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

262

High-Density Amorphous Ice, the Frost on Interstellar Grains  

NASA Astrophysics Data System (ADS)

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 < 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 Ĺ. 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 ?m 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

263

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

264

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

265

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

266

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

267

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

NASA Technical Reports Server (NTRS)

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

Glaser, F. M.

1976-01-01

268

Determination of E and G Observables in ? Photoproduction on the Clas Frozen Spin Target (frost)  

NASA Astrophysics Data System (ADS)

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

Senderovich, Igor; Morrison, B. T.; Dugger, M.; Ritchie, B.; Tucker, R.

2014-01-01

269

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

270

Frosted Branch Angiitis as Ocular Manifestation of Beh?et's Disease: Unusual Case Report and Literature Review  

PubMed Central

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

Kwon, Soon Jae; Park, Dong Ho

2013-01-01

271

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

272

Winter frost resistance of Pinus cembra measured in situ at the alpine timberline as affected by temperature conditions.  

PubMed

Winter frost resistance (WFR), midwinter frost hardening and frost dehardening potential of Pinus cembra L. were determined in situ by means of a novel low-temperature freezing system at the alpine timberline ecotone (1950 m a.s.l., Mt Patscherkofel, Innsbruck, Austria). In situ liquid nitrogen (LN?)-quenching experiments should check whether maximum WFR of P. cembra belonging to the frost hardiest conifer group, being classified in US Department of Agriculture climatic zone 1, suffices to survive dipping into LN? (-196 °C). Viability was assessed in a field re-growth test. Maximum in situ WFR (LT??) of leaves was <-?75 °C and that of buds was less (-70.3 °C), matching the lowest water contents. In midwinter, in situ freezing exotherms of leaves, buds and the xylem were often not detectable. Ice formed in the xylem at a mean of -2.8 °C and in leaves at -3.3 °C. In situ WFR of P. cembra was higher than that obtained on detached twigs, as reported earlier. In situ LN?-quenching experiments were lethal in all cases even when twigs of P. cembra were exposed to an in situ frost hardening treatment (12 days at -20 °C followed by 3 days at -50 °C) to induce maximum WFR. Temperature treatments applied in the field significantly affected the actual WFR. In January a frost hardening treatment (21 days at -20 °C) led to a significant increase of WFR (buds: -62 °C to <-?70 °C; leaves: -59.6 °C to -65.2 °C), showing that P. cembra was not at its specific maximum WFR. In contrast, simulated warm spells in late winter led to premature frost dehardening (buds: -32.6 °C to -10.2 °C; leaves: -32.7 to -16.4 °C) followed by significantly earlier bud swelling and burst in late winter. Strikingly, both temperature treatments, either increased air temperature (+10.1 °C) or increased soil temperature (+6.5 °C), were similarly effective. This high readiness to frost harden and deharden in winter in the field must be considered to be of great significance for future winter survival of P. cembra. Determination of WFR in field re-growth tests appears to be a valuable tool for critically judging estimates of WFR obtained on detached twigs in an ecological context. PMID:22011966

Buchner, Othmar; Neuner, Gilbert

2011-11-01

273

Stabilization of Leidenfrost vapour layer by textured superhydrophobic surfaces.  

PubMed

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

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

2012-09-13

274

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

275

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

276

Visible-light-induced water splitting based on two-step photoexcitation between dye-sensitized layered niobate and tungsten oxide photocatalysts in the presence of a triiodide/iodide shuttle redox mediator.  

PubMed

Water splitting into H2 and O2 under visible light was achieved using simple organic dyes such as coumarin and carbazole as photosensitizers on an n-type semiconductor for H2 evolution, a tungsten(VI) oxide (WO3) photocatalyst for O2 evolution, and a triiodide/iodide (I3(-)/I(-)) redox couple as a shuttle electron mediator between them. The results on electrochemical measurements revealed that the oxidized states of the dye molecules having an oligothiophene moiety (two or more thiophene rings) in their structures are relatively stable even in water and possess sufficiently long lifetimes to exhibit reversible oxidation-reduction cycles, while the carbazole system required more thiophene rings than the coumarin one to be substantially stabilized. The long lifetimes of the oxidized states enabled these dye molecules to be regenerated to the original states by accepting an electron from the I(-) electron donor even in an aqueous solution, achieving sustained H2 and I3(-) production from an aqueous KI solution under visible light irradiation when they were combined with an appropriate n-type semiconductor, ion-exchangeable layered niobate H4Nb6O17. The use of H4Nb6O17 loaded with Pt cocatalyst inside the interlayer allowed the water reduction to proceed preferentially with a steady rate even in the presence of a considerable amount of I3(-) in the solution, due to the inhibited access of I3(-) to the reduction site, Pt particles inside, by the electrostatic repulsion between the I3(-) anions and the negatively charged (Nb6O17)(4-) layers. It was also revealed that the WO3 particles coloaded with Pt and IrO2 catalysts exhibited higher rates of O2 evolution than the WO3 particles loaded only with Pt in aqueous solutions containing a considerable amount of I(-), which competitively consumes the holes and lowers the rate of O2 evolution on WO3 photocatalysts. The enhanced O2 evolution is certainly due to the improved selectivity of holes toward water oxidation on IrO2 cocatalyst, instead of undesirable oxidation of I(-). Simultaneous evolution of H2 and O2 under visible light was then achieved by combining the Pt/H4Nb6O17 semiconductor sensitized with the dye molecules having an oligothiophene moiety, which can stably generate H2 and I3(-) from an aqueous KI solution, with the IrO2-Pt-loaded WO3 photocatalyst that can reduce the I3(-) back to I(-) and oxidize water to O2. PMID:24128384

Abe, Ryu; Shinmei, Kenichi; Koumura, Nagatoshi; Hara, Kohjiro; Ohtani, Bunsho

2013-11-13

277

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

Microsoft Academic Search

This study investigated the dimensionality and typology of perfectionism based on the Frost Multidimensional Perfectionism Scale with a sample of 380 Chinese gifted students in Hong Kong. Confirmatory factor analyses supported a five-dimensional model that includes constructs of personal standards, parental expectations, parental criticism, concern over mistakes and doubts, and organization. Clustering procedures yielded three clusters of students interpreted as

David W. Chan

2009-01-01

278

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

Microsoft Academic Search

From 1900 to 1993, latewood frost rings occurred in 1903, 1912, 1941, 1961, and 1965 in 10 to 21% of the sampled bristlecone pines at Almagre Mountain, Colorado. In early to mid September in each of those years, a severe outbreak of unseasonably cold air from higher latitudes produced a memorable or historic late-summer snowstorm in the western United States.

Brunstein

1996-01-01

279

Elevated CO(sub 2) and development of frost hardiness in Norway spruce (picea abies (L.) Karst.).  

National Technical Information Service (NTIS)

This thesis discusses controlled laboratory experiments carried out to study the effects of CO(sub 2) pollution on Norwegian spruce. It was found that elevated CO(sub 2) increased height growth and biomass production. It slightly increased frost hardiness...

L. S. Dalen

1998-01-01

280

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

SciTech Connect

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

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

1984-11-01

281

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

SciTech Connect

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

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

1996-02-01

282

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

USGS Publications Warehouse

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

Craig, Brunstein, F.

1996-01-01

283

Layers and Layers  

NSDL National Science Digital Library

This lesson has students create their own rock layers by slowly adding and observing how different types of sediment interact when layered upon each other. This lesson is meant to illustrate how we can use these layers to discover the relative age of an object found in that layer by utilizing the Law of Superposition.

Tremarco, Cheri

2011-10-07

284

Polarimetric scattering from layered media with multiple species of scatterers  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

285

Mars south polar spring and summer temperatures - A residual CO2 frost  

NASA Technical Reports Server (NTRS)

Viking infrared thermal mapper (IRTM) energy measurements over the Mars south polar cap throughout the Martian spring and summer revealed complex spatial, spectral, and temporal variations. High albedos did not directly correspond with low temperatures, and as the cap shrank to its residual position, it maintained large differences in brightness temperature between the four IRTM surface-sensing bands at 7, 9, 11, and 20 microns. The late summer infrared spectral pattern can be matched by a surface consisting of CO2 frost with 20 micron emissivity of 0.8 and about 6% dark, warm soil under a dusty atmosphere of moderate infrared opacity and spectral properties similar to those measured for the Martian global dust storms. Low temperature, the absence of appreciable water vapor in the south polar atmosphere, and the absence of surface warming expected if H2O were to become exposed, all imply that the residual south polar cap was covered by solid CO2.

Kieffer, H. H.

1979-01-01

286

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. Miscanthus×giganteus was found to be the most chilling-tolerant genotype based on its ability to maintain a high net CO2 assimilation rate (A) during chilling, and recover A to a greater degree following a return to warm conditions. This was associated with increasing its capacity for short-term dark-reversible photoprotective processes (?REG) and the proportion of open photosystem II reaction centres (qL) while minimizing photoinactivation (?NF). Similarly, in the field, M.×giganteus exhibited a significantly greater A and pre-dawn F v/F m after the cold front compared with the other chilling-sensitive Miscanthus hybrids. PMID:24642848

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

2014-07-01

287

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

PubMed Central

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

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

2014-01-01

288

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

289

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

NASA Astrophysics Data System (ADS)

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

Malek, Esmaiel

2008-08-01

290

Presence disparity in mixed presence collaboration  

Microsoft Academic Search

We present the design of an experiment investigating presence disparity in mixed presence collaboration using digital tabletops. In an attempt to verify previous work and relate their results, we examined different presence representations of remote collaborators: audio, video, telepointers and video arms. Our early results show some interesting trends that we are currently investigating in more detail through further analysis

Anastasia Bezerianos; Gregor Mcewan

2008-01-01

291

Effect of hardening on frost tolerance and fatty acid composition of leaves and stems of a set of faba bean ( Vicia faba L.) genotypes  

Microsoft Academic Search

Frost tolerance is a main component of winter-hardiness and improving it would promote faba bean (Vicia faba L.) cropping in cool-temperate regions. In many species, leaf fatty acid composition was found to be related to frost tolerance.\\u000a The objective of this study was to determine, in a representative sample of genotypes, the effect of hardening on leaf and\\u000a stem (1)

Mustapha Arbaoui; Wolfgang Link

2008-01-01

292

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

PubMed Central

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

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

2014-01-01

293

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

294

ABA level, proline and phenolic concentration, and PAL activity induced during cold acclimation in androgenic Festulolium forms with contrasting resistance to frost and pink snow mould ( Microdochium nivale)  

Microsoft Academic Search

The metabolic changes in foliar abscisic acid, proline and phenolic concentration, and PAL activity induced during cold acclimation in androgenic forms of Festulolium contrasting in terms of their resistance to frost and Microdochium nivale were studied. The frost-resistant and snow mould-resistant (cross-tolerant) genotype (561) was characterized by a higher ABA amount and higher PAL activity compared to those of the

Ewa Pociecha; Agnieszka P?a?ek; Franciszek Janowiak; Zbigniew Zwierzykowski

2008-01-01

295

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

296

Frost damage of bricks composing a railway tunnel monument in Central Japan: field monitoring and laboratory simulation  

NASA Astrophysics Data System (ADS)

Bricks of tunnels and bridges of Usui Pass railway (Japan) exposed to north are subject to frost damage. Average depth of erosion due to detachment of angular blocks is around 1-1.5 cm. In order to assess this weathering and to understand its mechanism, an experimental study was carried out in the field and laboratory. Field monitoring showed the combination of seasonal and diurnal freezing with a maximum of heave when the freezing front reached 5 cm depth. Bricks taken from the site were submitted to unidirectional freezing at capillary and vacuum saturation in the laboratory. Results showed that frost damage of bricks was favoured by high saturation level and repetition of freeze-thaw cycles.

Thomachot, C.; Matsuoka, N.; Kuchitsu, N.; Morii, M.

2005-07-01

297

Evidence for Fresh Frost Layer on the Bare Nucleus of Comet Hale-Bopp at 32 AU Distance  

NASA Astrophysics Data System (ADS)

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.

Szabó, Gyula M.; Kiss, László L.; Pál, András; Kiss, Csaba; Sárneczky, Krisztián; Juhász, Attila; Hogerheijde, Michiel R.

2012-12-01

298

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

299

Frost-shattered debris facies of Younger Dryas age in the coastal sedimentary successions in western Norway: palaeoenvironmental implications  

Microsoft Academic Search

The occurrences of a characteristic facies of in situ frost-shattered debris have been studied in the late Quaternary (late and post-Weichselian) coastal deposits in the Mřre-Romsdal district of western Norway. The sedimentary successions represent gravelly beaches, coarse-grained glaciofluvial deltas and colluvial-fan deltas. The majority of these occurrences correspond to the Younger Dryas relative sea level, and the associated facies indicate

Lars Harald Blikra; Oddvar Longva

1995-01-01

300

The frost Gene of Neurospora crassa Is a Homolog of Yeast cdc1 and Affects Hyphal Branching via Manganese Homeostasis  

Microsoft Academic Search

The Neurospora crassa mutant frost has a hyperbranching phenotype that can be corrected by adding Ca2+, suggesting that characterization of this gene might clarify the mechanism of Ca2+-dependent tip growth. The wild-type allele was cloned by sib selection using protoplasts from arthroconidia. RFLP analysis revealed that the cloned DNA fragment mapped to the fr locus. The nucleotide sequence of genomic

Teruo Sone; Anthony J. F Griffiths

1999-01-01

301

Production of somatic hybrids between frost-tolerant Solanum commersonii and S. tuberosum : characterization of hybrid plants  

Microsoft Academic Search

Somatic fusion of mesophyll protoplasts was used to produce hybrids between the frost-tolerant species Solanum commersonii (2n=2x=24) and dihaploid S. tuberosum (2n=2x=24). This is a sexually incompatible combination due to the difference in EBN (Endosperm Balance Number, Johnston et al. 1980). Species with different EBNs as a rule are sexually incompatible. Fifty-seven hybrids were analysed for variation in chromosome number,

T. Cardi; E D'Ambrosio; D. Consoli; K. J. Puite; K. S. Ramulu

1993-01-01

302

Winter Annual Legumes for Use as Cover Crops in Row Crops in Northern Regions: II. Frost Resistance Study  

Microsoft Academic Search

including cultivars, age of subclover plants, and daylength treaments iments. The effects of freezing temperatures on sub- was carried out. The study showed that frost resistance of subclover was increased by short-day treatments both before and through the clover have rarely been considered, however (McGuire, hardening periods. The effect of short-day treatments was more pro- 1985). Studies related to the

Lars Olav Brandsćter; Thomas Smeby; Anne Marte Tronsmo; Jan Netland

303

Electrophysiological Investigation of Frost Resistance in Plants: 3. Critical Points Detected on the Freezing of Winter Wheat  

Microsoft Academic Search

Winter wheat (Triticum aestivum L.) seedlings of three cultivars differing in frost resistance were used to study cooling-induced changes in the bioelectric potential. Measurements were performed with nonfreezing graphite–glycerol electrodes in the regime of monitoring. Upon a gradual change in air temperature from 20 to –15°C at the rates of 20 and 2°C\\/h, the bioelectric potential underwent abrupt transitions at

A. I. Martynenko

2000-01-01

304

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

Microsoft Academic Search

Quantitative trait loci (QTLs) for frost and drought tolerance, and winter survival in the field, were mapped in meadow fescue\\u000a (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\\u000a species are highly macrosyntenic; however, the Festuca\\/Lolium and Triticeae homoeologous chromosomes

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

305

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

306

North Polar Layered Deposits in Summer  

NASA Technical Reports Server (NTRS)

The High Resolution Imaging Science Experiment (HiRISE) on NASA's Mars Reconnaissance Orbiter acquired this image during its first day of test imaging from the spacecraft's low-altitude mapping orbit, Sept. 29, 2006.

This image of Mars' north polar layered deposits was taken during the summer season (solar longitude of 113.6 degrees), when carbon dioxide frost had evaporated from the surface. The bright spots seen here are most likely patches of water frost, but the location of the frost patches does not appear to be controlled by topography. Layers are visible at the bottom of the image, mostly due to difference in slope between them. The variations in slope are probably caused by differences in the physical properties of the layers. Thinner layers that have previously been observed in these deposits are visible, and may represent annual deposition of water ice and dust that is thought to form the polar layered deposits. These deposits are thought to record global climate variations on Mars, similar to ice ages on Earth. HiRISE images such as this should allow Mars' climate record to be inferred and compared with climate changes on Earth.

Image TRA_000825_2665 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on September 29, 2006. Shown here is the full image, centered at 86.5 degree latitude, 172.0 degrees east longitude. The image is oriented such that north is to the top. The range to the target site was 298.9 kilometers (186.8 miles). At this distance the image scale is 59.8 centimeters (23.5 inches) per pixel (with two-by-two binning} so objects about 1.79 meters (70 inches) across are resolved. In total the original image was 12.2 kilometers 7.58 mile; 10024 pixels) wide and 6.1 kilometers (3.79 miles; 5000 pixels) long. The image was taken at a local Mars time of 3:30 PM and the scene is illuminated from the southwest with a solar incidence angle of 63.5 degrees, thus the sun was about 26.5 degrees above the horizon.

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace Corporation and is operated by the University of Arizona.

2006-01-01

307

TuBaFrost 6: virtual microscopy in virtual tumour banking.  

PubMed

Many systems have already been designed and successfully used for sharing histology images over large distances, without transfer of the original glass slides. Rapid evolution was seen when digital images could be transferred over the Internet. Nowadays, sophisticated Virtual Microscope systems can be acquired, with the capability to quickly scan large batches of glass slides at high magnification and compress and store the large images on disc, which subsequently can be consulted through the Internet. The images are stored on an image server, which can give simple, easy to transfer pictures to the user specifying a certain magnification on any position in the scan. This offers new opportunities in histology review, overcoming the necessity of the dynamic telepathology systems to have compatible software systems and microscopes and in addition, an adequate connection of sufficient bandwidth. Consulting the images now only requires an Internet connection and a computer with a high quality monitor. A system of complete pathology review supporting bio-repositories is described, based on the implementation of this technique in the European Human Frozen Tumor Tissue Bank (TuBaFrost). PMID:17027253

Teodorovic, I; Isabelle, M; Carbone, A; Passioukov, A; Lejeune, S; Jaminé, D; Therasse, P; Gloghini, A; Dinjens, W N M; Lam, K H; Oomen, M H A; 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; Lopez-Guerrero, J A; Llombart Bosch, A; van Veen, E-B; Oosterhuis, J W; Riegman, P H J

2006-12-01

308

Frost hardiness of mycorrhizal (Hebeloma sp.) and non-mycorrhizal Scots pine roots.  

PubMed

The frost hardiness (FH) of mycorrhizal [ectomycorrhizal (ECM)] and non-mycorrhizal (NM) Scots pine (Pinus sylvestris) seedlings was studied to assess whether mycorrhizal symbiosis affected the roots' tolerance of below-zero temperatures. ECM (Hebeloma sp.) and NM seedlings were cultivated in a growth chamber for 18 weeks. After 13 weeks' growth in long-day and high-temperature (LDHT) conditions, a half of the ECM and NM seedlings were moved into a chamber with short-day and low-temperature (SDLT) conditions to cold acclimate. After exposures to a range of below-zero temperatures, the FH of the roots was assessed by means of the relative electrolyte leakage test. The FH was determined as the inflection point of the temperature-response curve. No significant difference was found between the FH of mycorrhizal and non-mycorrhizal roots in LDHT (-8.9 and -9.8 °C) or SDLT (-7.5 and -6.8 °C). The mycorrhizal treatment had no significant effect on the total dry mass, the allocation of dry mass among the roots and needles or nutrient accumulation. The mycorrhizal treatment with Hebeloma sp. did not affect the FH of Scots pine in this experimental setup. More information is needed on the extent to which mycorrhizas tolerate low temperatures, especially with different nutrient contents and different mycorrhiza fungi. PMID:23558517

Korhonen, Anna; Lehto, Tarja; Repo, Tapani

2013-10-01

309

Snow depth, soil frost and nutrient loss in a northern hardwood forest  

NASA Astrophysics Data System (ADS)

We have initiated a long-term experiment to examine the consequences of decreases in snowpack accumulation at the Hubbard Brook Experimental Forest (HBEF), a northern hardwood dominated forest located in the White Mountains of New Hampshire. We are quantifying the effects of decreases in snowpack accumulation on root dynamics of two key tree species in this forest (sugar maple, yellow birch), microbial biomass and activity, NOcation loss, the acid-base chemistry of drainage water, and soil-atmosphere trace gas fluxes. We are calibrating an existing model (SNTHERM) to depict snow depth and soil frost dynamics given past or future climate scenarios for our site. In this paper, we describe the methods we are using for the manipulation studies that began in the winter of 1997/1998 and present preliminary results from our first full year of treatment. Results from our methods development efforts show that it is possible to keep plots snow free by shovelling without disturbing the forest floor. Preliminary test plot work showed that the SNTHERM model is capable of depicting snow depth and soil temperatures in both control and manipulated plots at our site. Results from our first full year of treatment showed that a relatively mild freezing event induced significant increases in nitrogen (N) mineralization and nitrification rates, solute leaching and soil nitrous oxide production and caused significant decreases in soil methane uptake. These results suggest that soil freezing events may be major regulators of soil biogeochemical processes and solute delivery to streams in forested watersheds.

Groffman, Peter M.; Hardy, Janet P.; Nolan, Scott; Fitzhugh, Ross D.; Driscoll, Charles T.; Fahey, Timothy J.

1999-10-01

310

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

SciTech Connect

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

Tantakitti, C.

1985-01-01

311

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

312

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

313

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

PubMed

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

Johnsen, O; Skrřppa, T; Junttila, O; Dćhlen, O G

1996-05-01

314

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

NASA Astrophysics Data System (ADS)

The exchange of carbon dioxide between the atmosphere and the polar caps on Mars creates a seasonal cycle of growth and retreat of the polar caps. As the major component of the Martian atmosphere, CO 2 condenses in the polar regions of the planet during the winter seasons and precipitates as CO 2 frost. It then sublimes during the spring and summer seasons in response to solar radiation. Through natural radioactivity or when exposed to cosmic rays, elements in the Martian near-subsurface (uppermost meter) emit gamma rays with distinct, characteristic energies. The Gamma Ray Spectrometer (GRS) onboard the 2001 Mars Odyssey satellite is used to measure the gamma rays coming from the Martian regolith to calculate elemental distributions, abundances, and temporal variations in the gamma ray flux. Changes in the CO 2 frost over time can be quantified by observing attenuation effects of H (2223 keV hydrogen) and 40K (1461 keV potassium) gamma ray signals transmitted through various depths of polar CO 2 overburden throughout the Martian seasons. Conclusions are drawn about the spatial extent, column density, and mass of Mars' seasonal polar caps as a function of time utilizing GRS data. Columnar thickness and mass results are discussed and plotted for latitudes including 60° and poleward. GRS observations are compared to predictions from the NASA Ames Research Center Mars General Circulation Model (ARC GCM) and to similar experimental results from the Mars Odyssey High Energy Neutron Detector (HEND) and the Neutron Spectrometer (NS). Models for north and south polar atmosphere and regolith distributions are incorporated, and the results indicate that the assumption of a 100%, H 2 O-ice residual cap underlying the seasonal frost in the north is accurate. The GRS CO 2 frost observations are in good agreement with the other studies mentioned, in particular for the timing of the beginning of frost deposition to the complete sublimation of surface CO 2 back into the atmosphere. The total amount of condensed CO 2 mass derived from GRS data is on the order of 6.0 × 10 15 kg and verifies previous reports that ~25% of the total Martian exchangeable-CO 2 reservoir participates in the ground-atmosphere cycle.

Kelly, Eleanor Jane

2006-06-01

315

Freezing pattern and frost killing temperature of apple (Malus domestica) wood under controlled conditions and in nature.  

PubMed

The freezing pattern and frost killing temperatures of apple (Malus domestica Borkh.) xylem were determined by differential thermal analysis and infrared differential thermal analysis (IDTA). Results from detached or attached twigs in controlled freezing experiments and during natural field freezing of trees were compared. Non-lethal freezing of apoplastic water in apple xylem as monitored during natural winter frosts in the field occurred at -1.9?±?0.4 °C and did not change seasonally. The pattern of whole tree freezing was variable and specific to the environmental conditions. On detached twigs high-temperature freezing exotherms (HTEs) occurred 2.8 K below the temperature observed under natural frosts in the field with a seasonal mean of -4.7?±?0.5 °C. Microporous apple xylem showed freezing without a specific pattern within a few seconds in IDTA images during HTEs, which is in contrast to macroporous xylem where a 2D freezing pattern mirrors anatomical structures. The pith tissue always remained unfrozen. Increasing twig length increased ice nucleation temperature; for increased twig diameter the effect was not significant. In attached twigs frozen in field portable freezing chambers, HTEs were recorded at a similar mean temperature (-4.6?±?1.0 °C) to those for detached twigs. Upon lethal intracellular freezing of apple xylem parenchyma cells (XPCs) low-temperature freezing exotherms (LTEs) can be recorded. Low-temperature freezing exotherms determined on detached twigs varied significantly between a winter minimum of -36.9 °C and a summer maximum -12.7 °C. Within the temperature range wherein LTEs were recorded by IDTA in summer (-12.7?±?0.5 to -20.3?±?1.1 °C) various tiny clearly separated discontinuous freezing events could be detected similar to that in other species with contrasting XPC anatomy. These freezing events appeared to be initially located in the primary and only later in the secondary xylem. During the LTE no freezing events in the bark and central pith tissue were recorded. Attached twigs were exposed to various freezing temperatures at which LTEs occur. Even if 60% of XPCs were frost-damaged twigs were able to recuperate and showed full re-growth indicating a high regeneration capacity even after severe frost damage to XPCs. PMID:22628198

Pramsohler, Manuel; Hacker, Jürgen; Neuner, Gilbert

2012-07-01

316

Global Effects of Double Layers.  

National Technical Information Service (NTIS)

The importance of the global response of a current carrying plasma to the presence of an electrostatic double layer is discussed. The double layer provides a means of localized energy conversion accelerating particles at the expense of energy sources pres...

M. A. Raadu

1984-01-01

317

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

Microsoft Academic Search

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

A. I. Leontiev; A. M. Pavlyuchenko

2008-01-01

318

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

319

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

320

Comparative ANNs with different input layers and GA-PLS study for simultaneous spectrofluorimetric determination of melatonin and pyridoxine HCl in the presence of melatonin’s 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

321

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

PubMed Central

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

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

2013-01-01

322

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

323

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

PubMed

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

Pramsohler, Manuel; Neuner, Gilbert

2013-08-01

324

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

325

Presence in Teaching  

ERIC Educational Resources Information Center

This article articulates a theory of "presence" in teaching and seeks to establish a theoretical foundation for presence that can serve as a platform for further research. It seeks to address the current educational climate that sees teaching as a check list of behaviors, dispositions, measures, and standards, and to articulate the essential but…

Rodgers, Carol R.; Raider-Roth, Miriam B.

2006-01-01

326

Identification and frequency of atmospheric circulation patterns causing spring frost in the northern French vineyards using the objective version of the Hess-Brezowsky classification  

Microsoft Academic Search

The possible impacts of climate change at small spatial scales are still very little known. The knowledge of the climate risks at small scales is yet essential for agricultural activities and productions like vine growing, because of their serious economic impacts. Because of their relatively high latitude, the vineyards of the northern Half of France are subjected to spring frost,

H. Quénol; O. Planchon; L. Wahl

2009-01-01

327

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

328

Influence of Wind Velocity Fluctuation on Air Temperature Difference between the Fan and Ground Levels and the Effect of Frost Protective Fan Operation  

NASA Astrophysics Data System (ADS)

We invested the influence of wind velocity fluctuation on air temperature difference between the fan (4.8 m) and ground levels (0.5 m) and the effect of frost protective fan operation in order to develop a new method to reduce electricity consumption due to frost protective fan operation. The results of the investigations are summarized as follows: (1) Air temperature difference between the fan (4.8 m) and ground levels (0.5 m) was decreased following an increase in wind velocity, and the difference was less than 1°C for a wind velocity more than 3.0 m/s at a height of 6.5 m. (2) When the wind velocity was more than 2-3 m/s, there was hardly any increase in the temperature of the leaves. In contrast, when the wind velocity was less than 2-3 m/s, an increase in the temperature of the leaves was observed. Based on these results, it is possible that when the wind velocity is greater than 2-3 m, it prevents thermal inversion. Therefore, there would be no warmer air for the frost protective fan to return to the tea plants and the air turbulence produced by the frost protective fan would not reach the plants under the windy condition.

Araki, Takuya; Matsuo, Kiyoshi; Miyama, Daisuke; Sumikawa, Osamu; Araki, Shinsuke

329

A new screening tool for diabetic retinopathy: the Canon CR5 45NM retinal camera with Frost Medical Software RIS-lite digital imaging system.  

PubMed

The introduction of the Canon CR5 45NM non-mydriatic retinal camera with the Frost Medical Software RIS-Lite digital imaging system provides a new screening tool for diabetic retinopathy with potential for remote diagnosis and telemedicine. This paper presents a description and early evaluation of the system. PMID:9282428

Young, S; George, L D; Lusty, J; Owens, D R

1997-03-01

330

Laboratory Evaluation of the Heating Capacity and Efficiency of a High-Efficiency, Air-to-Air Heat Pump with Emphasis on Frosting/Defrosting Operation.  

National Technical Information Service (NTIS)

A high-efficiency, air-to-air split-system residential heat pump of nominal 3-ton capacity was instrumented and tested in the heating mode under laboratory conditions. Performance of the system was measured during steady-state, dehumidifying, and frosting...

W. A. Miller

1982-01-01

331

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

Microsoft Academic Search

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

Yang Yao; Yiqiang Jiang; Shiming Deng; Zuiliang Ma

2004-01-01

332

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

NASA Technical Reports Server (NTRS)

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

Jones, Alun R.

1940-01-01

333

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

334

A quantitative and constraint-specific method to assess the potential impact of new agricultural technology: the case of frost resistant potato for the Altiplano (Peru and Bolivia)  

Microsoft Academic Search

A quantitative and constraint-specific approach to assess the potential impact of new agricultural technology is described and applied to frost resistant potato cultivars for the Altiplano (Peru and Bolivia). The approach uses geo-referenced databases and a simulation model. Calculations are made for small grid cells, and no arbitrary delimitation of agroecological zones is needed. The LINTUL potato growth simulation model

R. J. Hijmans; B. Condori; R. Carrillo; M. J. Kropff

2003-01-01

335

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

336

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

337

Aqueous Foams for Frost Protection of Plants: Stability and Protective Properties  

Microsoft Academic Search

Efficient technology has been developed for aqueous foam protection of plants against radiative night cooling. Experimental and mathematical simulations together with field tests were carried out in a search of foaming solutions and methods of application of the foam layer that provide optimal protection. A new parameter—insulation endurance—was developed for evaluating the thermal protective properties of unstable insulation materials such

Boris Krasovitski; Eitan Kirnmel; Michael Rozenfeld; Ilan Amir

1999-01-01

338

Formation of periodic layered pattern of tetrahydrofuran clathrate hydrates in porous media.  

PubMed

Directional growth of tetrahydrofuran (THF) clathrate hydrates was studied in a mixture of glass beads and a stoichiometric THF-water solution. Results showed that disseminated pore space type hydrates formed in a mixture containing 50-microm beads. However, a pure hydrate layer formed pushing the beads in a mixture containing 2-microm beads (frost heaving of hydrates). As the growth proceeded, new layers were formed repeatedly, leading to the eventual formation of a periodic layered pattern. It was found that as the growth rate increased, both the thickness of a hydrate layer and the interval between the neighboring layers decreased according to power laws. The effects of the applied temperature gradient and the weight ratio of the solution and glass beads were also systematically studied. Further, the possibility of applying our model experiments to the formation of natural methane hydrates was discussed. PMID:18642948

Nagashima, Kazushige; Suzuki, Takahiro; Nagamoto, Masaki; Shimizu, Tempei

2008-08-14

339

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 ...

Walls, Mrs.

2011-01-30

340

Snippets from the past: the evolution of Wade Hampton Frost's epidemiology as viewed from the American Journal of Hygiene/Epidemiology.  

PubMed

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

Morabia, Alfredo

2013-10-01

341

Tropical cirrus clouds near cold point tropopause under ice supersaturated conditions observed by lidar and balloon-borne cryogenic frost point hygrometer  

NASA Astrophysics Data System (ADS)

Simultaneous vertical profiles of cirrus cloud backscattering and frost point temperature were obtained for the first time in the tropopause region over Bandung, Indonesia, (6.9°S, 107.6°E). These profiles were measured by ground-based lidar and by balloon-borne Cryogenic Frost point Hygrometer (CFH) sondes. Supersaturation up to several ten percent was observed by the CFH just below the cold point tropopause at the altitude where a cirrus cloud was observed by lidar. The water vapor mixing ratio decreased slightly at the altitude of the cirrus cloud, suggesting that this decrease was caused by uptake in the cirrus cloud and that the water vapor reduction corresponds to the lower limit of the cloud water content of the observed cirrus cloud. Theoretical calculations of the scattering parameters for the observed cirrus cloud particles and estimations of the time constants for sedimentation and for condensational growth indicate that particles size range is between 4 ?m and 30 ?m.

Shibata, Takashi; VöMel, Holger; Hamdi, Saipul; Kaloka, Sri; Hasebe, Fumio; Fujiwara, Masatomo; Shiotani, Masato

2007-02-01

342

Simultaneous Inhibition of Linolenic Acid Synthesis in Winter Wheat Roots and Frost Hardening by BASF 13-338, a Derivative of Pyridazinone.  

PubMed

Treatment of 12-day-old winter wheat (Triticum aestivum) plants with BASF 13-338 {4-chloro-5 (dimethylamino)-2-phenyl-3(2H)-pyridazinone} 36 hours before frost hardening simultaneously and completely inhibits accumulation of linolenic acid in the roots during the hardening period and the acquisition of frost resistance. Increased unsaturation of fatty acids is therefore probably an important part of the mechanism of cold adaptation in winter wheat.BASF 13-338 also prevents the increase in per cent dry weight in roots and shoots during hardening and causes a decrease in root lipid phosphorus and total fatty acids.The concurrent increase in linoleic acid and decrease in linolenic acid in the treated plants, while the level of the other fatty acids is but little affected, suggest that BASF 13-338 specifically inhibits linoleic acid desaturase. PMID:16660018

Willemot, C

1977-07-01

343

Association analysis of frost tolerance in rye using candidate genes and phenotypic data from controlled, semi-controlled, and field phenotyping platforms  

PubMed Central

Background Frost is an important abiotic stress that limits cereal production in the temperate zone. As the most frost tolerant small grain cereal, rye (Secale cereale L.) is an ideal cereal model for investigating the genetic basis of frost tolerance (FT), a complex trait with polygenic inheritance. Using 201 genotypes from five Eastern and Middle European winter rye populations, this study reports a multi-platform candidate gene-based association analysis in rye using 161 single nucleotide polymorphisms (SNPs) and nine insertion-deletion (Indel) polymorphisms previously identified from twelve candidate genes with a putative role in the frost responsive network. Results Phenotypic data analyses of FT in three different phenotyping platforms, controlled, semi-controlled and field, revealed significant genetic variations in the plant material under study. Statistically significant (P < 0.05) associations between FT and SNPs/haplotypes of candidate genes were identified. Two SNPs in ScCbf15 and one in ScCbf12, all leading to amino acid exchanges, were significantly associated with FT over all three phenotyping platforms. Distribution of SNP effect sizes expressed as percentage of the genetic variance explained by individual SNPs was highly skewed towards zero with a few SNPs obtaining large effects. Two-way epistasis was found between 14 pairs of candidate genes. Relatively low to medium empirical correlations of SNP-FT associations were observed across the three platforms underlining the need for multi-level experimentation for dissecting complex associations between genotypes and FT in rye. Conclusions Candidate gene based-association studies are a powerful tool for investigating the genetic basis of FT in rye. Results of this study support the findings of bi-parental linkage mapping and expression studies that the Cbf gene family plays an essential role in FT.

2011-01-01

344

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 41°F and water levels decrease by more than 20 ft, the number of sinkholes increase greatly (N >10). At this time alternative protection methods such as freeze-cloth are cost prohibitive in comparison to repairing dry wells. In conclusion, the findings from this study are applicable in other agricultural areas and can be used to develop comprehensive water management plans in areas where the abstraction of large quantities of water occur. PMID:23326518

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

2013-01-01

345

CBF gene copy number variation at Frost Resistance - 2 is associated with levels of freezing tolerance in temperate-climate cereals  

Microsoft Academic Search

Frost Resistance-1 (FR-1) and FR-2 are two loci affecting freezing tolerance and winter hardiness of the temperate-climate cereals. FR-1 is hypothesized to be due to the pleiotropic effects of VRN-1. FR-2 spans a cluster of C-Repeat Binding Factor (CBF) genes. These loci are genetically and functionally linked. Recent studies indicate CBF transcripts are downregulated by the VRN-1 encoded MADS-box protein

Andrea K. Knox; Taniya Dhillon; Hongmei Cheng; Alessandro Tondelli; Nicola Pecchioni; Eric J. Stockinger

2010-01-01

346

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

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

347

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

348

The frost gene of Neurospora crassa is a homolog of yeast cdc1 and affects hyphal branching via manganese homeostasis.  

PubMed

The Neurospora crassa mutant frost has a hyperbranching phenotype that can be corrected by adding Ca(2+), suggesting that characterization of this gene might clarify the mechanism of Ca(2+)-dependent tip growth. The wild-type allele was cloned by sib selection using protoplasts from arthroconidia. RFLP analysis revealed that the cloned DNA fragment mapped to the fr locus. The nucleotide sequence of genomic and cDNA was determined. The deduced amino acid sequence showed homology to the Saccharomyces cerevisiae CDC1 protein, implicated in manganese homeostasis. The fr mutant was sensitive to Mn(2+), and a revertant allele whose product differs by one amino acid was tolerant to Mn(2+). Mn(2+) depletion induced the wild-type strain to hyperbranch, resulting in a morphology similar to that of fr. The fr mutant was also sensitive to calcineurin inhibitors. These results suggest that fr is involved in Mn(2+) homeostasis and point to a role for Mn(2+) in Neurospora branching. PMID:10669587

Sone, T; Griffiths, A J

1999-12-01

349

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

PubMed Central

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

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

2011-01-01

350

Effect of soil frost on growing season nitrogen uptake by fine roots of mature trees in northern hardwood forests of the United States  

NASA Astrophysics Data System (ADS)

Forests of the northeastern United States are predicted to experience a decrease in the depth and duration of the winter snowpack over the next 100 years. Even when coupled with warmer winter air temperatures, the absence of snow as insulation can increase soil frost during the winter months. Past research has determined that there are species-level effects of soil frost on dominant forest trees. For example, in stands dominated by sugar maple (Acer saccharum), induced soil frost led to increased fine root mortality and soil nitrate leaching. Soil frost also increased fine root mortality in stands dominated by yellow birch (Betula allegheniensis), but there was no significant change in leaching of soil nitrate. We hypothesized that greater nitrogen (N) losses from stands dominated by sugar maple may be due to reduced N uptake by fine roots of this tree species. To determine the impact of increased soil freezing on fine root uptake of N, we established a snow manipulation experiment in mixed sugar maple/American beech (Fagus grandifolia) forests at the Hubbard Brook Experimental Forest in New Hampshire (n=4 paired snow-removal and reference plots; each 13m X 13m). Snow removal occurred during the first six weeks of winter over two years. During each growing season following snow removal, we used the N depletion technique to measure in situ rates of uptake of ammonium and nitrate by fine roots of sugar maple during the early, peak and late growing season. Among all sampling dates and plots, we observed significantly lower uptake of N as nitrate compared to ammonium. During the first growing season, at moderate ammonium availability (35 ?M N) we observed significantly less uptake of ammonium by fine roots of sugar maple in the snow removal plots relative to the reference plots during the early growing season (April-May), with no significant differences in uptake of ammonium during the peak (July) and late (September) growing season. We observed no differences in uptake of ammonium among the snow removal and references plots at higher ammonium availability (200 ?M N), nor nitrate at either concentration throughout the growing season. Results of our study suggest that the observed increase in N losses following periods of soil frost could be due to a decrease in N uptake by fine roots of mature trees, especially in the early growing season. Our study shows the effects of vegetation responses to climate change on ecosystem nitrogen cycling.

Socci, A. M.; Templer, P. H.

2010-12-01

351

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

352

Layered Slopes  

NASA Technical Reports Server (NTRS)

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

2004-01-01

353

Presence-Exchanges: Toward Sustainable Presence-Sharing  

Microsoft Academic Search

Presence-sharing is a promising platform for cooperative location-aware applications, but applications must provide direct benefit to users for their presence information. If not, these services give users strong incentives to free-load to avoid privacy risks and administrative burden. Modeling presence-sharing as an iterated prisoner's dilemma shows that it is not sustainable under these conditions. Thus, to create sustainable presence-sharing, we

Landon P. Cox; Angela Dalton; Varun Marupadi

2006-01-01

354

Non-stationary temporal characterization of the temperature profile of a soil exposed to frost in south-eastern Canada  

NASA Astrophysics Data System (ADS)

The objective of this work was to compare time and frequency fluctuations of air and soil temperatures (2-, 5-, 10-, 20- and 50-cm below the soil surface) using the continuous wavelet transform, with a particular emphasis on the daily cycle. The analysis of wavelet power spectra and cross power spectra provided detailed non-stationary accounts with respect to frequencies (or periods) and to time of the structure of the data and also of the relationships that exist between time series. For this particular application to the temperature profile of a soil exposed to frost, both the air temperature and the 2-cm depth soil temperature time series exhibited a dominant power peak at 1-d periodicity, prominent from spring to autumn. This feature was gradually damped as it propagated deeper into the soil and was weak for the 20-cm depth. Influence of the incoming solar radiation was also revealed in the wavelet power spectra analysis by a weaker intensity of the 1-d peak. The principal divergence between air and soil temperatures, besides damping, occurred in winter from the latent heat release associated to the freezing of the soil water and the insulation effect of snowpack that cease the dependence of the soil temperature to the air temperature. Attenuation and phase-shifting of the 1-d periodicity could be quantified through scale-averaged power spectra and time-lag estimations. Air temperature variance was only partly transferred to the 2-cm soil temperature time series and much less so to the 20-cm soil depth.

Anctil, F.; Pratte, A.; Parent, L. E.; Bolinder, M. A.

2008-05-01

355

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

356

Why Presence Occurs: Evolutionary Psychology, Media Equation, and Presence  

Microsoft Academic Search

Despite the intense interest in the phenomena of presence, there have been limited attempts to explain the fundamental reason why human beings can feel presence when they use media and\\/or simulation technologies. This is mainly because previous studies on presence have focused on \\

Kwan Min Lee

2004-01-01

357

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

358

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

NASA Astrophysics Data System (ADS)

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

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

2009-06-01

359

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

360

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.

361

Leaky Layers  

NSDL National Science Digital Library

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

Tackley, Paul J.; Geoscience, Nature

362

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

Eichinger, John

2009-05-30

363

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

364

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

365

Examination of a Water-saving Type Sprinkler System with a Variable Time-step Temperature-based Controller for the Protection of Tea Shoots from Frost  

NASA Astrophysics Data System (ADS)

In order to reduce of the amount water used for protection of new shoots from frost,we examined a sprinkler system that could adjust the amount of water supply by choosing from several watering intervals depending on the surface temperature of tea plant canopy. When the temperature of new shoots was lower than the critical level, our sprinkler system continued to supply water, and when the temperature was higher than the critical level, our system reduced the amount of precipitation. In our study area, the temperature of new shoots was higher than the critical level,which was assumed to be -2.4°C during 3 examination seasons (from 2005 to 2007). Further,compared to a fixed interval sprinkler system, our system was found to be more effective in protecting the shoots from frost and in conserving water. During the examination periods, the amount of water used by our system was about 40% of that used by the ordinary continuative sprinkler system, and it was about 80% of that used by the fixed interval sprinkler system.

Tanaka, Toshihiro; Orita, Takaaki; Uezono, Yutaka; Kanno, Masamichi; Kato, Masaaki

366

Large deletions in the CBF gene cluster at the Fr-B2 locus are associated with reduced frost tolerance in wheat.  

PubMed

Wheat plants which are exposed to periods of low temperatures (cold acclimation) exhibit increased survival rates when they are subsequently exposed to freezing temperatures. This process is associated with large-scale changes in the transcriptome which are modulated by a set of tandemly duplicated C-repeat Binding Factor (CBF) transcription factors located at the Frost Resistance-2 (Fr-2) locus. While Arabidopsis has three tandemly duplicated CBF genes, the CBF family in wheat has undergone an expansion and at least 15 CBF genes have been identified, 11 of which are present at the Fr-2 loci on homeologous group 5 chromosomes. We report here the discovery of three large deletions which eliminate 6, 9, and all 11 CBF genes from the Fr-B2 locus in tetraploid and hexaploid wheat. In wild emmer wheat, the Fr-B2 deletions were found only among the accessions from the southern sub-populations. Among cultivated wheats, the Fr-B2 deletions were more common among varieties with a spring growth habit than among those with a winter growth habit. Replicated freezing tolerance experiments showed that both the deletion of nine CBF genes in tetraploid wheat and the complete Fr-B2 deletion in hexaploid wheat were associated with significant reductions in survival after exposure to freezing temperatures. Our results suggest that selection for the wild-type Fr-B2 allele may be beneficial for breeders selecting for varieties with improved frost tolerance. PMID:23884601

Pearce, Stephen; Zhu, Jie; Boldizsár, Ákos; Vágújfalvi, Attila; Burke, Adrienne; Garland-Campbell, Kimberley; Galiba, Gábor; Dubcovsky, Jorge

2013-11-01

367

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

368

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.

History, American M.

2008-01-01

369

Evidence of the Barrier Layer in the Surface Layer of the Tropics  

Microsoft Academic Search

Comparisons between isothermal depth to the top of the thermocline, and the mixed layer depth based on a sigmat criterion were undertaken for the tropical world oceans. In three equatorial regions, a shallower mixed layer than isothermal layer occurs, implying the presence of a strong halocline above the thermocline. This distance separating the top of the thermocline and the bottom

Janet Sprintall; Matthias Tomczak

1992-01-01

370

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

371

Interface conditions governing evaporation of stored liquids in presence of non-condensable gas  

Microsoft Academic Search

Experiments were conducted to determine the variation of interface temperatures during the storage and draining of liquid nitrogen from large containers in the presence of the non-condensable gas. A chilled layer was seen to be formed at the interface in the presence of the non-condensable gas and this layer advanced into the warm liquid at speeds higher than the characteristic

K. Ramamurthi; S. Sunil Kumar; B. S. Chaitanya

2006-01-01

372

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

373

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

374

Polar Layers  

NASA Technical Reports Server (NTRS)

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

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

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

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

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

2005-01-01

375

The protective effect of sugars on chloroplast membranes during temperature and water stress and its relationship to frost, desiccation and heat resistance.  

PubMed

Freezing, desiccation and high-temperature stress may under certain conditions result in inactivation of electron transport (DCIP reduction) and cyclic photophosphorylation of isolated chloroplast membranes of spinach (Spinacia oleracea L.). When sugars are present during temperature and water stress, the thylakoids may be partially or completely protected. This membrane stabilization depends on the concentration of sugars and their molecular size. The trisaccharide raffinose is, on a molar basis, more effective than the disaccharide sucrose and the latter more than the monosaccharide glucose. An uncoupling effect and a stimulation of electron transport can be observed during freezing, desiccation and heat treatment, e.g. electron transport reactions are less sensitive to temperature and water stress than is photophosphorylation. As sugars are known to accumulate in winter, unspecific membrane stabilization by sugars may help to explain the often reported parallel development of frost, drought and heat resistance in many plants during winter. PMID:24468903

Santarius, K A

1973-06-01

376

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.

2011-01-01

377

Regulation of frost resistance during cold de-acclimation and re-acclimation in oilseed rape. A possible role of PSII redox state.  

PubMed

A possible role of photosynthetic apparatus during cold de-acclimation was studied in oilseed rape (Brassica napus var. oleifera). Plants of spring (Star) and winter (Górczański) cultivars were cold acclimated at + 5 degrees C, and de-acclimated during 4 weeks at combinations of + 12 and + 20 degrees C operating in the light or/and dark, with a 12-h photoperiod. Evidence is presented that the photosynthetic apparatus may be involved in temperature perception during de-acclimation. De-acclimation was faster under a 20/12 degrees C (day/night) treatment than under the reverse 12/20 degrees C (day/night). De-acclimation rate was constant when the day temperature was constant, irrespective of the night temperature both under cold day temperature regimes (12/20, 12/12 degrees C (day/night) and warm-day treatments (20/12, 20/20 degrees C (day/night). The fast decrease in frost resistance observed under warm-day de-acclimation was always accompanied by an acceleration of elongation growth. In the spring cultivar, elongation growth increased starting from the second week of de-acclimation, regardless of temperature conditions. Once elongation growth had commenced during de-acclimation, it continued throughout the period necessary for re-acclimation to low temperature. Re-acclimation to the initial freezing tolerance level was only possible when plant elongation was reduced. In addition re-acclimation of the photosynthetic apparatus to low temperature was impossible in fast growing plants. A possible relationship between PSII, growth rate and frost resistance during cold acclimation and de-acclimation is discussed. PMID:12060241

Rapacz, Marcin

2002-06-01

378

Descending Layer Variability Over Arecibo  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

379

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

380

Ion-acoustic double layers  

Microsoft Academic Search

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

T. Sato; H. Okuda

1980-01-01

381

The Martian surface layer  

NASA Technical Reports Server (NTRS)

The global characteristics of the Martian surface layer are discussed on the basis of thermal, albedo, color, and radar data for the region between approximately 60 deg S and 60 deg N. Thermal data reveal the presence of large low- and high-inertia regions of the northern hemisphere, with much of the south covered by material of moderate inertia. There is a strong anticorrelation between inertia and albedo, a correlation between inertia and rock abundance, and, over much of the planet, a correlation of radar-derived density with inertia. Viking Orbiter color data indicate the presence of three major surface materials: low-inertia, bright-red material that is presumably dust; high-inertia, dark-grey material interpreted to be lithic material mixed with palagonitelike dust; and moderate-inertia, dark-red material that is rough at subpixel scales and interpreted to be indurated. Observations from the Viking landing sites show rocks, fines of varying cohesion and crusts. These sites have indications of aeolian erosion and deposition in the recent past.

Christensen, Philip R.; Moore, Henry J.

1992-01-01

382

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 Mäkinen; Marcello Fulchignoni

2006-01-01

383

The initiation of elongation growth during long-term low-temperature stay of spring-type oilseed rape may trigger loss of frost resistance and changes in photosynthetic apparatus.  

PubMed

The aim of the present investigation was to determine if the loss of frost resistance observed in spring-type oilseed rape during winter may be the effect of the tendency to start elongation growth during the prolonged low-temperature stay. Interactions between elongation growth rate, properties of photosynthetic apparatus and frost resistance were studied under these conditions in spring and winter cultivars of oilseed rape. Both spring and winter cultivars of oilseed rape reached the maximal frost resistance after 6 weeks at +5 degrees C. Photosynthetic apparatus of both cultivars acclimated to functioning in cold. The resistance of winter type plants remained unchanged at the end of the experiment (10 weeks) whereas spring-type plants lost the maximal resistance in subsequent weeks. It was preceded in the 7th week of low-temperature stay by acceleration of elongation growth without an increase in dry matter accumulation. A gradual loss of photosynthetic activity was also observed during this period. It was manifested as a decrease in antenna trapping efficiency, photochemical and non-photochemical fluorescence quenching and actual quantum yield of PSII without affecting apparent quantum yield of PSII. At the 70th day of the experiment, a decrease in CO(2) exchange and dry matter accumulation were even observed. The possible relationships between growth rate and functioning of photosynthetic apparatus are discussed. PMID:11448752

Rapacz, M; Tokarz, K; Janowiak, F

2001-07-01

384

Multicomponent Double Layers.  

National Technical Information Service (NTIS)

A model of a multicomponent double layer is considered. For the sake of simplicity it is assumed that the layer is steady, strong, and nonrelativistic. The multicomponent double layer is composed of several different kinds of positively and negatively cha...

P. Carlqvist

1992-01-01

385

Geophysical and GIS study of gravel layer on Gyöngyös 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 Rába, 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 Gyöngyös 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 Gyöngyös stream, the northern is the Répce'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 Acsád 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 Gyöngyös 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 toKozár-Borzó 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 TÁMOP 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.

Szabó, Vera; Kovács, Gabor

2014-05-01

386

Presence of calmodulin in Tetrahymena.  

PubMed Central

Ca-dependent affinity chromatography on phenothiazine-Sepharose 4B has been used to isolate a pure protein from the ciliate Tetrahymena pyriformis. This protein has been identified as calmodulin by demonstrating three of the Ca-dependent activities attributed to calmodulins. Tetrahymena calmodulin also has physicochemical properties similar to those of the previously characterized mammalian, coelenterate, and plant proteins, except for a lower molecular weight (15,000) and slightly different CNBr fragments compared to bovine brain calmodulin. Calmodulin is a constituent of demembranated Tetrahymena cilia from which it can be extracted with the crude dynein fraction. Sucrose density gradient fractionation indicated its presence in fractions containing the 14S dynein ATPase. It is concluded that the essential properties of calmodulin have been highly conserved during much of eukaryotic evolution, and it is suggested that calmodulin plays a role in the control of ciliary motility in Tetrahymena. Images

Jamieson, G A; Vanaman, T C; Blum, J J

1979-01-01

387

Topography and Stratigraphy of the Northern Martian Polar Layered Deposits Using Photoclinometry, Stereogrammetry, and MOLA Altimetry  

USGS Publications Warehouse

We present two photoclinometric profiles across a trough in the martian northern polar layered terrain. Complications caused by albedo variations were avoided by using an early springtime Viking image with a thin cover of seasonal CO2 frost. The topographic profiles were constrained with stereogrammetric elevations derived from summertime Viking images of the same region. We find that the photoclinometric profiles are consistent with a nearby MOLA (Mars Orbiter Laser Altimeter) track crossing the same polar trough. The trough is asymmetric, with higher relief and a steeper slope on the equatorward-facing wall. Individual layers are subdued and difficult to observe in the profiles. A decrease in both relief and elevation toward the eastern end of the trough suggests that layers become thinner to the east. Declining equatorward slopes in the eastern portion of the trough imply that erosion rates have varied along the trough. The variation in erosion rate may be linked to the change in layer thickness along the trough. Layers have an average thickness of 19??8 m in the center of the trough and 59??32 m on the northern wall. The northern wall is most likely composed of thinner layers that are obscured. To first order, we find that a 19-m layer requires 16,000 years of deposition to form. Although this timescale does not coincide with orbital variation periods of 105 and 106 years, deposition rates may not be constant and thus the 16,000-year layer formation time does not preclude layer formation during part of each orbital oscillation. ?? 2000 Academic Press.

Fenton, L. K.; Herkenhoff, K. E.

2000-01-01

388

Effect of frost hardening on lipid and Fatty Acid composition of chloroplast thylakoid membranes in two wheat varieties of contrasting hardiness.  

PubMed

Lipid and fatty acid composition of chloroplast thylakoid membranes was determined in two varieties of wheat (Triticum aestivum L.), the hardy Miranovskaja and the sensitive Penjamo. Plants were grown at room temperature or under frost hardening conditions (1.5 degrees C). Changes in lipid and fatty acid composition of the isolated thylakoids could be related to the temperature dependence of light-stimulated proton uptake. Changes in the thylakoid phospholipids upon hardening of the two varieties did not show any direct relation with low temperature tolerance of light-dependent H(+) uptake; neither did changes in phospholipid fatty acid chain lengthening to 20 and 22 C-atoms in combination with increased desaturation up to 6 double bonds. Increased low temperature tolerance of light-induced H(+) uptake by hardening was correlated with the following glycolipid changes: maintained glycolipid level, a proportionally increased digalactosyl diglyceride fraction, a decrease in thylakoid monogalactosyl diglyceride, increased sulfolipid fatty acid chain lengthening (20 and 22 C-atoms), and increased sulfolipid desaturation (4-6 double bonds). We suggest that the above mentioned changes in glycolipids have adaptive value for low temperature tolerance of light-dependent proton uptake. PMID:16664487

Vigh, L; Horvŕth, I; van Hasselt, P R; Kuiper, P J

1985-11-01

389

Effect of Frost Hardening on Lipid and Fatty Acid Composition of Chloroplast Thylakoid Membranes in Two Wheat Varieties of Contrasting Hardiness 1  

PubMed Central

Lipid and fatty acid composition of chloroplast thylakoid membranes was determined in two varieties of wheat (Triticum aestivum L.), the hardy Miranovskaja and the sensitive Penjamo. Plants were grown at room temperature or under frost hardening conditions (1.5°C). Changes in lipid and fatty acid composition of the isolated thylakoids could be related to the temperature dependence of light-stimulated proton uptake. Changes in the thylakoid phospholipids upon hardening of the two varieties did not show any direct relation with low temperature tolerance of light-dependent H+ uptake; neither did changes in phospholipid fatty acid chain lengthening to 20 and 22 C-atoms in combination with increased desaturation up to 6 double bonds. Increased low temperature tolerance of light-induced H+ uptake by hardening was correlated with the following glycolipid changes: maintained glycolipid level, a proportionally increased digalactosyl diglyceride fraction, a decrease in thylakoid monogalactosyl diglyceride, increased sulfolipid fatty acid chain lengthening (20 and 22 C-atoms), and increased sulfolipid desaturation (4-6 double bonds). We suggest that the above mentioned changes in glycolipids have adaptive value for low temperature tolerance of light-dependent proton uptake.

Vigh, Laslo; Horvath, Ibi; van Hasselt, Philip R.; Kuiper, Pieter J. C.

1985-01-01

390

Seasonal differences in photosynthesis between the C3 and C4 subspecies of Alloteropsis semialata are offset by frost and drought.  

PubMed

The regional abundance of C(4) grasses is strongly controlled by temperature, however, the role of precipitation is less clear. Progress in elucidating the direct effects of photosynthetic pathway on these climate relationships is hindered by the significant genetic divergence between major C(3) and C(4) grass lineages. We addressed this problem by examining seasonal climate responses of photosynthesis in Alloteropsis semialata, a unique grass species with both C(3) and C(4) subspecies. Experimental manipulation of rainfall in a common garden in South Africa tested the hypotheses that: (1) photosynthesis is greater in the C(4) than C(3) subspecies under high summer temperatures, but this pattern is reversed at low winter temperatures; and (2) the photosynthetic advantage of C(4) plants is enhanced during drought events. Measurements of leaf gas exchange over 2 years showed a significant photosynthetic advantage for the C(4) subspecies under irrigated conditions from spring through autumn. However, the C(4) leaves were killed by winter frost, while photosynthesis continued in the C(3) plants. Unexpectedly, the C(4) subspecies also lost its photosynthetic advantage during natural drought events, despite greater water-use efficiency under irrigated conditions. This study highlights previously unrecognized roles for climatic extremes in determining the ecological success of C(3) and C(4) grasses. PMID:18410490

Ibrahim, Douglas G; Gilbert, Matthew E; Ripley, Brad S; Osborne, Colin P

2008-07-01

391

Significant relationships among frost tolerance and net photosynthetic rate, water use efficiency and dehydrin accumulation in cold-treated winter oilseed rapes.  

PubMed

Five winter oilseed rape cultivars (Benefit, Californium, Cortes, Ladoga, Navajo) were subjected to 30 days of cold treatment (4 °C) to examine the effect of cold on acquired frost tolerance (FT), dehydrin (DHN) content, and photosynthesis-related parameters. The main aim of this study was to determine whether there are relationships between FT (expressed as LT50 values) and the other parameters measured in the cultivars. While the cultivar Benefit accumulated two types of DHNs (D45 and D35), the other cultivars accumulated three additional DHNs (D97, D47, and D37). The similar-sized DHNs (D45 and D47) were the most abundant; the others exhibited significantly lower accumulations. The highest correlations were detected between LT50 and DHN accumulation (r=-0.815), intrinsic water use efficiency (WUEi; r=-0.643), net photosynthetic rate (r=-0.628), stomatal conductance (r=0.511), and intracellular/intercellular CO2 concentration (r=0.505). Those cultivars that exhibited higher Pn rate in cold (and further a significant increase in WUEi) had higher levels of DHNs and also higher FT. No significant correlation was observed between LT50 and E, PRI, or NDVI. Overall, we have shown the selected physiological parameters to be able to distinguish different FT cultivars of winter oilseed rape. PMID:24054752

Urban, Milan Old?ich; Klíma, Miroslav; Vítámvás, Pavel; Vašek, Jakub; Hilgert-Delgado, Alois Albert; Ku?era, Vratislav

2013-12-15

392

Layered Dynamic Textures  

Microsoft Academic Search

A novel video representation, the layered dynamic texture (LDT), is proposed. The LDT is a generative model, which represents a video as a collection of stochastic layers of different appearance and dynamics. Each layer is modeled as a temporal texture sampled from a different linear dynamical system. The LDT model includes these systems, a collection of hidden layer assignment variables

Antoni B. Chan; Nuno Vasconcelos

2009-01-01

393

An Objective Surrogate for Presence: Physiological Response  

Microsoft Academic Search

This talk discusses our investigation into an objective presence measure. In our experiment, we investigated the correlation among a post-experiment presence questionnaire, human peripheral response (electrodermal activity and skin temperature), and a behavioral-presence questionnaire. Our findings show that the measures do correlate and have use as a potential objective surrogate for subjective presence measures. We also found a significant decrease

Michael Meehan

394

Multifunctional layer-by-layer coating of digitally encoded microparticles.  

PubMed

In the field of medical diagnostics there is a growing need for inexpensive, accurate, and quick "multiplexing" assays. By making use of encoded microparticles, such assays allow simultaneous determination of the presence of several analytes in a biological sample. The microparticles under investigation in this study are encoded by writing a digital dot or bar code in their central plane. This study evaluates to what extent a "multifunctional" coating can be applied around the digitally encoded microparticles by the layer-by-layer (LbL) technology. We show that a LbL coating containing CrO2 nanoparticles allows (a) an optimal (optical) readout of the dot and bar codes, (b) a perfect orientation of the microparticles, necessary to be able to read the code, and (c) an optimal coupling of capture probes to the surface of the microparticles. PMID:17760466

Derveaux, Stefaan; De Geest, Bruno G; Roelant, Chris; Braeckmans, Kevin; Demeester, Jo; De Smedt, Stefaan C

2007-09-25

395

Triplex molecular layers with nonlinear nanomechanical response  

NASA Astrophysics Data System (ADS)

The molecular design of surface structures with built-in mechanisms for mechanical energy dissipation under nanomechanical deformation and compression resistance provided superior nanoscale wear stability. We designed robust, well-defined trilayer surface nanostructures chemically grafted to a silicon oxide surface with an effective composite modulus of about 1 GPa. The total thickness was within 20-30 nm and included an 8 nm rubber layer sandwiched between two hard layers. The rubber layer provides an effective mechanism for energy dissipation, facilitated by nonlinear, giant, reversible elastic deformations of the rubber matrix, restoring the initial status due to the presence of an effective nanodomain network and chemical grafting within the rubber matrix.

Tsukruk, V. V.; Ahn, H.-S.; Kim, D.; Sidorenko, A.

2002-06-01

396

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

PubMed Central

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

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

1969-01-01

397

A Comparative Study of the Short Term Cold Resistance Response in Distantly Related Drosophila Species: The Role of regucalcin and Frost  

PubMed Central

The molecular basis of short term cold resistance (indexed as chill-coma recovery time) has been mostly addressed in D. melanogaster, where candidate genes (Dca (also known as smp-30) and Frost (Fst)) have been identified. Nevertheless, in Drosophila, the ability to tolerate short term exposure to low temperatures evolved several times independently. Therefore, it is unclear whether variation in the same candidate genes is also responsible for short term cold resistance in distantly related Drosophila species. It should be noted that Dca is a candidate gene for cold resistance in the Sophophora subgenus only, since there is no orthologous gene copy in the Drosophila subgenus. Here we show that, in D. americana (Drosophila subgenus), there is a north-south gradient for a variant at the 5? non-coding region of regucalcin (a Dca-like gene; in D. melanogaster the proteins encoded by the two genes share 71.9% amino acid identities) but in our D. americana F2 association experiment there is no association between this polymorphism and chill-coma recovery times. Moreover, we found no convincing evidence that this gene is up-regulated after cold shock in both D. americana and D. melanogaster. Size variation in the Fst PEST domain (putatively involved in rapid protein degradation) is observed when comparing distantly related Drosophila species, and is associated with short term cold resistance differences in D. americana. Nevertheless, this effect is likely through body size variation. Moreover, we show that, even at two hours after cold shock, when up-regulation of this gene is maximal in D. melanogaster (about 48 fold expression change), in D. americana this gene is only moderately up-regulated (about 3 fold expression change). Our work thus shows that there are important differences regarding the molecular basis of cold resistance in distantly related Drosophila species.

Reis, Micael; Vieira, Cristina P.; Morales-Hojas, Ramiro; Aguiar, Bruno; Rocha, Helder; Schlotterer, Christian; Vieira, Jorge

2011-01-01

398

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

399

A double layer review  

Microsoft Academic Search

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

Lars P. Block

1978-01-01

400

Electrochemical Atomic Layer Processing.  

National Technical Information Service (NTIS)

Atomic layer processing with electrochemical control is discussed. A method for the electrodeposition of compound semiconductors based on the principles of atomic layer epitaxy (ALE) is reported, with specific reference to the formation of ZnTe. This meth...

C. K. Rhee B. M. Huang E. M. Wilmer S. Thomas J. L. Stickney

1994-01-01

401

Layer-by-layer Cell Membrane Assembly  

PubMed Central

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 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 of both purified and 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.

2014-01-01

402

A Double Layer Review.  

National Technical Information Service (NTIS)

A review of the main results on electrostatic double layers (sometimes called space charge layers or sheaths) obtained from theory, and laboratory and space experiments up to the spring of 1977 is given. Double layers are defined in terms of potential dro...

L. P. Block

1977-01-01

403

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

404

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

405

Development of Technologies for Coastal Observing Systems and the Study of Benthic Boundary Layer Processes  

NSF Publications Database

... BBL - defined here as the portion of the water column and surface sediments impacted by the presence ... to comprise the bottom boundary layer of the water column and surface sediment layer. The dynamic ...

406

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

NASA Astrophysics Data System (ADS)

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

Hansen, Gary B.; Stephan, K.

2013-10-01

407

Boundary Layers in Strain-Gradient Theory of Linear Elasticity.  

National Technical Information Service (NTIS)

In a previous investigation based on couple-stress theory the presence of an elastic boundary layer of minute thickness was established in which the states of stress and displacement differ essentially and significantly from classical elasticity solutions...

M. A. Sadowsky S. L. Pu

1970-01-01

408

Diffusion in the presence of periodically spaced permeable membranes.  

PubMed

The diffusion of molecules in biological tissues and some other microheterogeneous systems is affected by the presence of permeable barriers. This leads to the slowdown of diffusion at long times as compared to barrier-free diffusion. At short times the effect of barriers is weak. In consequence, the diffusion coefficient D(t) decreases as a function of time. We derive an exact solution for the Laplace transform of D(t) for diffusion in a space separated into layers by equally spaced, parallel identical planes of arbitrary permeability. Additionally, we give an approximation to D(t) which is reasonably accurate over the whole range of the partition permeability from zero (the case of isolated layers) to infinity (the case of no barriers). PMID:15634083

Dudko, Olga K; Berezhkovskii, Alexander M; Weiss, George H

2004-12-01

409

Defrost improvement by heat pump refrigerant charge compensating  

Microsoft Academic Search

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

Wang Zhiyi; Wang Xinmin; Dong Zhiming

2008-01-01

410

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

411

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

1998-02-01

412

Acoustic double layers in multispecies plasma  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

413

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

414

Laboratory evidence for ion-acoustic-type double layers  

NASA Technical Reports Server (NTRS)

The formation of an ion-acoustic-type double layer was observed in the laboratory for the first time. The rarefactive part of a long-wavelength ion-acoustic wave grew in amplitude because of the presence of drifting electrons. The corresponding current limitation led to the formation of the double layer.

Chan, C.; Cho, M. H.; Hershkowitz, N.; Intrator, T.

1984-01-01

415

Internal Layers in The Turbulent Boundary Layer*  

NASA Astrophysics Data System (ADS)

Coherent structures in zero-pressure gradient turbulent boundary layers are investigated using particle image velocimetry (PIV). Instantaneous streamwise and normal velocity components were measured in a two-dimensional plane at Req = 1000 and 7000. The images have a wide field of view to capture over three d in the streamwise direction. Recent evidence1 suggests that growing, internal boundary layers exist close to the wall, and may be modulated by the large-scale bulges of the outer region. The investigation focuses on the existance and nature of these layer, the properties of outer region turbulent bulges, and the possible interaction of these two structures. 1 C. D. Meinhart and R. J. Adrian, Phys., Fluids 7 1995. * Work supported by ONR Grant No. N00014-93-1-0552

Tomkins, C. D.; Adrian, Ronald J.

1996-11-01

416

Combined electron-spin-resonance, X-ray-diffraction studies on phospholipid vesicles obtained from cold-hardened wheats : I. An attempt to correlate electron-spin-resonance spectral characteristics with frost resistance.  

PubMed

Phospholipid multibilayers, obtained from two cultivars of thermally acclimated wheats of different frost resistances (Triticum aestivum L. cv. Penjamo 62, the sensitive cultivar, and T. aestivum L. cv. Miranovskaja 808, the frost-resistant cultivar), were investigated using electron-spin-resonance and X-ray-diffraction techniques. The former technique revealed two breaks in the motion of the spin-labelled fatty acid 2-(14-carboxyte-tradecyl)-2-ethyl-4,4-dimethyl-3-oxazolidinyloxyl, for both cultivars (+3°C,-17° C and +5° C,-18° C, respectively) when grown at 22° C. T