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1

A Proposal of Evaluation of Frost Layer Thickness  

NASA Astrophysics Data System (ADS)

The frosting is an unsteady phenomenon occurs simultaneously with heat and mass transfer. Both the heat and water vapor in the humid air reach the surface of the frost layer and transfer to the cold surface. The frost surface plays an important role as an interface of heat and mass transfer between air-flow and ice-air composite solid layer. However, since the frost layer surface consists of ice and air, and is rough and unsteady, any specific definition of the frost layer thickness is not found. This paper tried to give the definition. The frost layer thickness was measured by using a micro photo-sensing device combined with a light emitter and receiver traversing normal to the frost surface. During traversing the device, a peak response from the device indicates the vertical position corresponding to the maximum frost area exposed to the emitted light i.e. air around the frost inside the frost layer. This position is defined as the frost layer position and it could give an effective frost layer.

Yotsumoto, Hiroyuki; Ishihara, Isao; Tanio, Kenichi; Matsumoto, Ryosuke

2

Robert Frost on Writing.  

ERIC Educational Resources Information Center

|This book is a collection of Frost's letters, reviews, introductions, lectures, and interviews on writing dating back to 1913. It provides Frost's view of literature, and its relation to language and social order. Part one, "Frost as a Literary Critic," discusses the scope of Frost's criticism and Frost as both critical theorist and practical…

Barry, Elaine

3

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

Microsoft Academic Search

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

Zhongliang Liu; Yunjun Gou; Jieteng Wang; Shuiyuan Cheng

2008-01-01

4

The Driving Force of Frost Boils and Hummocks Formation  

Microsoft Academic Search

Formation of frost boils has several aspects to be explained, including the bowl shape of boils, the formation of an organic layer at the periphery of the frost boils, the elevated center of the boils, and resistance of the soil surface to vegetation colonization. Genesis of frost boils and hummocks have been widely attributed to cryoturbation-a complex of seasonally interchanging

Y. Shur; C. Ping

2003-01-01

5

Influence of Several Parameters on Frost Growth in Low Temperature Environments  

NASA Astrophysics Data System (ADS)

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

Yamashita, Koji; Ohkubo, Hidetoshi

6

Depletion Forces in the Presence of Electrostatic Double Layer Repulsion  

NASA Astrophysics Data System (ADS)

We report direct measurements of the repulsive force-distance profiles between submicronic colloidal droplets stabilized by an ionic surfactant in the presence of the same surfactant micelles. We establish that the repulsive force profile may be described by a sum of two contributions. One is repulsive and arises from the presence of the droplets' double layers. The other originates in the depletion of charged micelles and is attractive. We conclude that the electrostatic repulsion between the micelles and the droplets enhances the depletion force. This effect is simply accounted for by considering an effective larger droplet diameter. We present the empirical relation between this extra thickness and the Debye length.

Mondain-Monval, O.; Leal-Calderon, F.; Phillip, J.; Bibette, J.

1995-10-01

7

Laboratory experiments concerning the growth and properties of frost flowers  

Microsoft Academic Search

Recently, frost flowers attracted a lot of scientific interest due to their specific properties. They constitute highly delicate structures, which grow on newly formed sea ice in both polar regions under certain meteorological conditions like a stable atmospheric boundary layer and low air temperatures. Frost flowers exhibit high specific surface areas and also contain high concentrations of sea salt components

H. Jacobi; S. Lehmann

2005-01-01

8

Remote Sensing of Boundary layer Trace Gases in the Presence of dynamic boundary layer events  

NASA Astrophysics Data System (ADS)

With the suite of instruments located at UMBC we are able to analyze how low level jets and convective rolls affect boundary layer carbon monoxide and ozone. Low level jets are an excellent transport mechanism for boundary layer air. These jets alter the nominal nocturnal ozone cycle and inhibit the total depletion of ozone during night time. Using BBAERI (Baltimore Bomem Atmospheric Emitted Radiance Interferometer) we retrieve boundary layer CO and total column ozone during both day and night. Comparing inactive to active nights we can better understand the effect jets have on the ozone cycle. The WRF regional model is used to simulate nocturnal jet events to elucidate source regions for the BBAERI retrievals of trace gas abundances. Previous studies using the AERI at the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Program Southern Great Plains (SGP) site near Lamont, Oklahoma have demonstrated the impact of horizontal convective rolls on boundary layer water vapor profiles. We will present results of CO retrievals from BBAERI and AERI in the presence of convective rolls to better understand how they mix CO. These observations demonstrate the utility of BBAERI and other AERIs for remotely monitoring boundary layer composition and dynamics.

Wilson, R. C.; McMillan, W. W.; Delgado, R.; Hoff, R.; Weldegabar, M.

2008-12-01

9

Tints, Shades and Frost  

ERIC Educational Resources Information Center

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

Sterling, Joan

2009-01-01

10

Ultrasonic Frost Suppression  

NASA Astrophysics Data System (ADS)

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

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

2003-02-01

11

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

Microsoft Academic Search

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

R. A. Peterson; W. B. Krantz

2008-01-01

12

Bacterial Presence in Layered Rock Varnish-Possible Mars Analog?  

NASA Astrophysics Data System (ADS)

Rock varnish from locations in Death Valley, California; Peru; Antarctica; and Hawaii reveal nanometer scale layering (less than 1 nm to about 75 nm) when studied with transmission electron microscopy (TEM). Parallel layers of clay minerals containing evidence of presumed bacteria were present in all samples. Samples range in age from a few thousand years to perhaps a million years. Diagenesis is relatively limited, as chemical composition is variable, both from top to bottom and along layers in these varnish samples. Also, occasional exotic minerals occur randomly in most varnish sections, and vary in size and hardness, again suggesting relative lack of diagenetic alteration. Additional information can be found in the original extended abstract.

Krinsley, D.; Rusk, B. G.

2000-08-01

13

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

14

Frost Insulating Materials in Roads.  

National Technical Information Service (NTIS)

A survey of the research and development work on frost insulating materials is presented. Different insulating materials such as bark, mineral wool, cellular plastics, and lightweight expanded clay were tested in situ for some years. Certain materials wer...

R. Gandahl

1974-01-01

15

Frost formation mechanism analysis and frost growth prediction on ground aircraft  

NASA Astrophysics Data System (ADS)

Frost predictions are needed to help the deicing operation decide. The mechanism of frost formation on aircraft surface under icing conditions has been analyzed. A simple theoretical frost growth prediction model by heat and mass transfer analysis has been presented. It produces a method to forecast the frost growth tendency. An experimental system for atmospheric frost reproduction is also presented. Effects of aircraft surface temperatures, air temperature on the frost growth is evaluated by this model.

Xu, Dandan; Wang, Liwen

2013-10-01

16

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

17

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

NASA Astrophysics Data System (ADS)

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.

2012-05-01

18

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

19

Heat pump frost control system  

Microsoft Academic Search

The invention relates to a self-contained air conditioning unit including a reversible refrigeration system and more particularly to a control system having a plurality of sensing means that are effective in maintaining operation of the unit in a heat pump mode when the ambient and the surface temperature of selected refrigeration components are above a preselected frosting temperature.

McCarty

1977-01-01

20

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

NASA Astrophysics Data System (ADS)

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

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

1981-10-01

21

Liquid layer flow over convex corners in the presence of an electric field  

NASA Astrophysics Data System (ADS)

The behaviour of a thin layer of liquid when it flows over a convex corner and in the presence of an electric field, is studied in the context of triple-deck theory. It is assumed that the Reynolds number is large. The same problem without the presence of the electric field and surface tension effects was studied by [1]. The governing equations lead to a novel triple-deck problem and linear and nonlinear numerical solutions are obtained for various limiting cases of the Weber number and capillary number.

Farid, Saadia; Gajjar, Jitesh S. B.

2013-10-01

22

Iterative method for supersonic flow laminar boundary layer interaction in the presence of separation  

NASA Astrophysics Data System (ADS)

The classical two-dimensional compressible boundary-layer equations supplemented by a relation describing the interaction of boundary layer with external inviscid flow (see, e.g., [1]) are treated as the governing equations in one of the methods to study the viscous-inviscid interaction. It is then necessary in the case of supersonic flow to specify certain downstream boundary conditions for the closure of the governing system, i.e., it is a boundary-value problem (e.g., [2]). The “shooting” technique for parameters at the beginning of the computational region to obtain the solution satisfying such a condition usually requires large computer time since the integral curves are highly sensitive to small changes in upstream boundary conditions. A more effective method is the algorithm of global relaxations of pressure distribution along the entire computational region [1]. A numerical method to compute supersonic interacting boundary layer in the presence of separation is presented in this paper.

Lyzhin, D. O.

1984-01-01

23

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

NSDL National Science Digital Library

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

Inouye, David

2012-01-04

24

Frost Heave Dynamics at a Single Crystal Interface  

NASA Astrophysics Data System (ADS)

We study flow in a surface-melted layer of a single crystal of ice at a plane solid interface. The flow, which is induced by a temperature gradient in the melted layer, causes the ice to grow normal to the interface. The process is the basis for frost heave in frozen soils. Flow is observed in a limited range of temperatures near the melting point, implying that surface melting is absent below this range. The data are analyzed in terms of a model which allows estimates of the fluid layer thickness. The results are not consistent with interfacial melting due to purely van der Waals forces.

Wilen, L. A.; Dash, J. G.

1995-06-01

25

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

26

Lactobacilli isolated from kefir grains: evidence of the presence of S-layer proteins.  

PubMed

In the present study we report for the first time the presence of S-layer proteins in Lactobacillus kefir and Lactobacillus parakefir isolated from kefir grains. Soluble whole-cell protein profile obtained either by mechanical disruption (X-press) or by a combined treatment with lysozyme and SDS on whole cells, showed a significant band of apparent molecular mass of 66-71 kDa as measured by SDS-PAGE. The intensity of this band was considerably reduced when cells were treated with 5 M-LiCl. The above mentioned proteins were recovered in the LiCl extracts. After dialysis and concentration, the proteins extracted were able to reassemble in a regular array. Negative staining of these protein preparations were analysed by transmission electron microscopy and a paracrystalline arrangement was seen. Thin sections of bacteria analysed by transmission electron micrographs showed an outermost layer over the bacterial cell wall, that was lost after the LiCl treatment. The production of this surface structure under different culture conditions was also evaluated. Finally, the relationship between the presence of S-layer proteins and surface properties (e.g. adhesion to Caco-2 cells, autoaggregation, and hemagglutination) was investigated. PMID:15190952

Garrote, Graciela Liliana; Delfederico, Lucrecia; Bibiloni, Rodrigo; Abraham, Analia Graciela; Pérez, Pablo Fernando; Semorile, Liliana; De Antoni, Graciela Liliana

2004-05-01

27

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

PubMed

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

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

2010-10-29

28

Aircraft Observations of Marine Aerosol Properties in the Presence of Boundary Layer Rolls  

NASA Astrophysics Data System (ADS)

The Hawaii Group for Environmental Aerosol Research deployed a wide range of airborne aerosol instrumentation as part of MILAGRO/INTEX (2006) and PASE (2007) experiments. These were designed to provide rapid information on aerosol composition, state of mixing (internal or external), spectral optical properties (scattering and absorption), the humidity dependence of light scattering - f(RH). The measurements revealed frequently observed presence of numerous periodic structures related both to horizontal convective rolls (HCRs) and Kelvin-Helmholtz instability (KHI). HCRs, commonly formed when some vertical wind shear is present, are significant to the vertical transport of momentum, heat, moisture, and air pollutant including aerosols within the boundary layer. KHIs, occurred in areas of enhanced velocity shear and/or a local minimum of static stability, contribute strongly to the dissipation of large-scale motions into turbulence. This presentation focused on the direct in-situ marine aerosol properties in the presence of BL rolls by providing evidence that the observed variations are caused by rolls. We also studied whether the presence of rolls leads to the enhancement of aerosol fluxes. We have investigated roll structures in diverse MBL settings and have demonstrated that these can play an active role in the redistribution of aerosol, gas and water vapor in the MBL. Depending upon the thermodynamic profiles and the roll size, altitude, temporal duration these rolls can have a marked effect on the exchange of air masses between the buffer layer, the surface mixed layer and the free troposphere. This will lead to changes in the horizontal extinction in these layers relative to regions not influenced by the rolls. Hence, the evolution of aerosol optical properties in the near-surface mixed layer will be affected by rolls and the conditions that stimulate them. These can occur with or without associated cloud features. Some ongoing studies include the following: what are the aerosol optics differences in rolls updraft and downdraft caused by RH, aerosol concentration and entrainment? what are implications of roll structure for extinction measurements and remote sensing? what are implications of rolls on the redistributions of aerosol and gases during transport?

Kapustin, V.; Clarke, A.; Howell, S.; Conley, S.; Faloona, I.; Brekhovskikh, V.; McNaughton, C.

2008-12-01

29

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

30

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

31

INTERACTION OF VEGETATION AND SOIL FROST PHENOMENA?  

Microsoft Academic Search

N northern lands special problems presented by frost in soils are receiving more and more attention as the pace of construction and settlement increases. Investigations aimed primarily at these problems, notably that of permafrost, have partially revealed the composition and mechanisms of the severe frost climate1 environment. Parts of this environment owe their nature to the influence of vegetation and

William S. Benninghoff

32

Measurement of Frost Heave Forces on H-Piles and Pipe Piles,  

National Technical Information Service (NTIS)

The magnitude and variation of forces and shear stresses, caused by frost heaving in Fairbanks silt and the adfreeze effects of a surface ice layer and a gravel layer, were determined as a function of depth by using electric strain gauges along the upper ...

J. B. Johnson J. S. Buska

1988-01-01

33

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

PubMed Central

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

Reif, Jochen C.

2013-01-01

34

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

2013-09-04

35

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

36

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

SciTech Connect

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

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

1995-10-01

37

Epitaxial growth of MnSi 1.7 layers in the presence of an Sb flux  

Microsoft Academic Search

Semiconducting MnSi1.7 layers were grown on Si(111) substrates by reactive deposition epitaxy in the presence of an Sb flux. The defect microstructure and epitaxial relationship of the layers were examined by X-ray diffraction and transmission electron microscopy. It was found that epitaxial MnSi1.7 layers with continuous and relatively smooth interfaces could be grown. The predominant epitaxial relationship adopts the (332),

Yoshinaga Souno; Yoshihito Maeda; Hirokazu Tatsuoka; Hiroshi Kuwabara

2001-01-01

38

Frosting and defrosting on rigid superhydrohobic surface  

NASA Astrophysics Data System (ADS)

Lotus leaves, which have superhydrophobic surfaces, have been extensively studied as a result of their extreme water repellency. Lotus leaves are liable to lose their superhydrophobicity when water condenses or frost forms and then melts on their surfaces. We have performed experiments to investigate the frosting and defrosting phenomena on various surfaces having differing wetting properties, ranging from superhydrophobicity to superhydrophilicity and including two kinds of superhydrophobic surface. Both flexible and rigid superhydrophobic surface have advantage of anti-frosting. However, only on the rigid superhydrophobic surface is defrosting effective without any water droplets. Therefore, the rigid superhydrophobic surface is most effective in defrosting and against frosting. Our results widen the potential applications of superhydrophobic surfaces and increase our understanding of water behavior at surfaces.

Jing, Tengyue; Kim, Yeongae; Lee, Sangmin; Kim, Dongseob; Kim, Jinyul; Hwang, Woonbong

2013-07-01

39

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

SciTech Connect

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

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

2011-07-15

40

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

SciTech Connect

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

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

2006-08-15

41

High-Quality Epitaxial MnSi(111) Layers Grown in the Presence of an Sb Flux  

Microsoft Academic Search

MnSi epitaxial layers have been grown on (111) and (001)-oriented Si substrates by Mn deposition and reaction with Si in the presence of an Sb flux. Characterization using transmission electron microscopy (TEM) confirmed the formation of high-quality epitaxial layers with smooth interfaces between the MnSi and the Si(111) substrate, when grown under optimal conditions, without the deposition of elemental Sb

Koji Matsuda; Hirokazu Tatsuoka; Kazuharu Matsunaga; Koji Isaji; Hiroshi Kuwabara; Paul D. Brown; Yan Xin; Rafal Dunin-Borkowski; Colin J. Humphreys

1998-01-01

42

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

NASA Astrophysics Data System (ADS)

We determine the optical losses in gate-induced charge accumulation/inversion layers at a Si/SiO2 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.; Sürgers, C.; Koos, C.; Freude, W.; Leuthold, J.

2013-07-01

43

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

44

Variation in frost-boil morphology and associated vegetation characteristics along a climatic gradient  

NASA Astrophysics Data System (ADS)

A team of researchers from the US and Canada has been conducting a series of investigations of the interactions of climate, vegetation, and permafrost in the study Biocomplexity of Arctic Frost-Boil Ecosystems. Frost-boils are small-scale patterned ground features formed by the seasonal expansion of ice lenses and the upward movement of soil during annual freeze thaw cycles in permafrost landscapes. The displacement of soils disrupts the vegetation layer, creating a mosaic of barren circular patches and vegetated interboil areas. The morphology of these features and the extent to which vegetation patterns are affected by the displacement varies with climate. We have been working at a network of 11 study sites along a transect from Happy Valley, Alaska to Ellef Ringnes Island, Canada. The project has five major components: Climate and Permafrost, Soils and Biogeochemical Cycling, Vegetation, Ecosystem Modeling, and Education. As part of the education component, students in the class Arctic Field Ecology have been addressing the question of how biodiversity patterns vary between boil and interboil areas within a given site and along the climatic gradient. In order to develop an understanding of variation in frost-boil morphology we analyzed boil and interboil differences in thaw depth, frost-boil width, micro relief, and vegetation cover from a series of 42 transects at six of the Biocomplexity study sites in Alaska and Canada. We present this variation in series of diagrams representing morphology typical of frost-boil patterning along a gradient from low to high arctic and of patterns in vegetation associated with frost boil morphology.

Gould, W. A.; Quijano, A.; González, G.; Walker, D. A.

2003-12-01

45

Transition of the boundary layer on a circular cylinder in the presence of a trip  

NASA Astrophysics Data System (ADS)

The instabilities in the flow past a cylinder are reviewed. The transition of the boundary layer on the cylinder is investigated numerically. In order to promote early transition, the boundary layer on the upper half is tripped by placing a roughness element of height, 0.5% of the cylinder diameter, at 55° to the freestream direction. Large eddy simulation (LES) is utilized to simulate the turbulent flow in three dimensions. A comparison is made between the characteristics of the flow past a smooth cylinder and the cylinder with roughness element for 1×104?Re?1×106. As Re is increased beyond 5×104, the boundary layer on the upper half of the cylinder with a trip experiences transition to a turbulent state. The transition is facilitated by the instability of the shear layer that rolls up into small vortices. As a result, the time-averaged drag coefficient, CD\\OverBar, decreases rapidly with Re leading to drag-crisis. On the smooth cylinder drag decreases in a single stage, while a two-stage staggered drag-crisis is observed for the cylinder with a trip. The flow becomes asymmetric due to the tripping of the boundary layer on only one half. This leads the cylinder to experience a net lift in a time-averaged sense. In the first stage of the drag-crisis positive lift is observed and during the second stage lift reversal takes place.

Behara, Suresh; Mittal, Sanjay

2011-07-01

46

Io: longitudinal distribution of sulfur dioxide frost.  

PubMed

Twenty spectra of Io (0.26 to 0.33 micrometer), acquired with the International Ultraviolet Explorer spacecraft, have been studied. There is a strong ultraviolet absorption shortward of 0.33 micrometer that is consistent with earlier ground-based spectrophotometry; its strength is strongly dependent on Io's rotational phase angle at the time of observation. This spectral feature and its variation are interpreted as indicative of a longitudinal variation in the distribution of sulfur dioxide frost on Io. The frost is most abundant at orbital longitudes 72 degrees to 137 degrees and least abundant at longitudes 250 degrees to 323 degrees . Variations in spectral reflectivity between 0.4 and 0.5 micrometer, reported in earlier ground-based spectral studies, correlate inversely with variations in reflectivity between 0.26 and 0.33 micrometer. It is concluded that this is because the Io surface component with the highest visible reflectivity (sulfur dioxide frost) has the lowest ultraviolet reflectivity. At least one other component is present and may be sulfur allotropes or alkali sulfides. This model is consistent with ground-based ultraviolet, visible, and infrared spectrophotometry. Comparison with Voyager color photographs indicates that the sulfur dioxide frost is in greatest concentration in the "white" areas on Io and the other sulfurous components are in greatest concentration in the "red" areas. PMID:17739547

1980-11-14

47

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

48

Insulator (Heat and Frost). Occupational Analyses Series.  

ERIC Educational Resources Information Center

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

McRory, Aline; Ally, Mohamed

49

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

50

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

51

Radiation from bending waves in the presence of a boundary layer  

Microsoft Academic Search

The effect of refraction by a flow boundary layer on the radiation of sound from a bending wave on a plate is investigated. Based on the relative velocities of the bending wave and the flow, four qualitatively different regimes are identified and results of numerical studies of radiation impedance and power emission are presented and discussed. For comparison, the role

A. Akay; K. Uno Ingard

1993-01-01

52

Nisin adsorption to polyethylene oxide layers and its resistance to elution in the presence of fibrinogen  

PubMed Central

The adsorption and elution of the antimicrobial peptide nisin at silanized silica surfaces coated to present pendant polyethylene oxide chains was detected in situ by zeta potential measurements. Silica microspheres were treated with trichlorovinylsilane to introduce hydrophobic vinyl groups, followed by self assembly of the polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) triblock surfactant Pluronic® F108, or an F108 derivative with nitrilotriacetic acid endgroups. Triblock-coated microspheres were ?-irradiated to covalently stabilize the PPO-surface association. PEO layer stability was evaluated by triblock resistance to elution by SDS, and layer uniformity was evaluated by fibrinogen repulsion. Introduction of nisin to uncoated or triblock-coated microspheres produced a significant positive change in surface charge (zeta potential) as a result of adsorption of the cationic peptide. In sequential adsorption experiments, the introduction of fibrinogen to nisin-loaded triblock layers caused a decrease in zeta potential that was consistent with partial elution of nisin and/or preferential location of fibrinogen at the interface. This change was substantially more pronounced for uncoated than triblock-coated silica, indicating that the PEO layer offers enhanced resistance to nisin elution.

Ryder, Matthew P.; Schilke, Karl F.; Auxier, Julie A.; McGuire, Joseph; Neff, Jennifer A.

2010-01-01

53

Turbulent Boundary Layer in the Presence of Chemical Reactions on the Surface (Applied to Carbon Surfaces).  

National Technical Information Service (NTIS)

Formulas are obtained for the limiting heat exchange law when chemical reactions occur on an entrainable surface, as well as within the boundary layer. Formulas are constructed to determine the heat content of walls for the complex heat exchange case taki...

E. G. Zaulichnyi S. S. Kutateladze A. N. Leontev

1967-01-01

54

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

55

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

56

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

57

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

58

Rapid frost weathering and its potential role as a periglacial buzzsaw  

NASA Astrophysics Data System (ADS)

Icy Bay, in the Chugach-St.Elias mountains of southern Alaska, provides an excellent opportunity to 1) document exceptionally rapid breakdown of cobbles on surfaces recently exposed by glacial retreat, 2) examine frost-induced breakdown in light of recent advances in theory, and 3) explore the potential role of periglacial processes in limiting the height of mountain ranges. The latter adds to the current interest in the interactions between topography, tectonics and climate, and in particular, the so-called glacial buzzsaw (Egholm, et al. 2009. Nature, 460, p 884; doi:10.1038/nature08263). This is the notion that the growth of mountains is curtailed by erosion and related effects of glaciers with little or no dependence on the factors that are generally thought to control the height of mountains; height increases with the elevation of the snow line, with little or no influence of uplift and exhumation rates, rock type, and precipitation. A well-documented retreat of tidewater glaciers in Icy Bay has resulted in a succession of outwash surfaces on which cobbles of diverse lithology were exposed to atmospheric conditions sequentially. Following deposition, initial breakdown rates were determined for each of four distinct lithologies: siltstone, sandstone, greenschist, and granite/gneiss. These rates decrease to negligible values after 10-15 years of exposure. Breakdown is significantly enhanced adjacent to the current shoreline with the fraction of surface cobbles fractured after 30 years ranging from 20% for granite/gneiss to 90% for siltstone. Theoretical considerations suggest that the susceptibility of a rock type to frost weathering is dictated by its specific surface area and resistance to fracture. These parameters define a threshold zone for frost weathering specific to ambient thermal and moisture conditions in Icy Bay, a conclusion substantiated by independent experimental evidence. This result, coupled with the fact that this and other studies have shown enhanced rock breakdown under relatively mild climatic conditions, suggests the importance of unfrozen water migration in frost weathering under natural conditions and a significantly greater spatial importance of frost weathering than previously recognized. The rate of frost weathering should be maximized for temperatures between -3 to -10°C and in the presence of abundant moisture. These conditions ought to define an elevation interval in mountainous landscapes most conducive to frost weathering. Climatic fluctuations ought to drive large altitudinal changes in this interval causing variations in affected land area. Frost weathering appears to be significantly faster than other subaerial weathering mechanisms, and probably contributes significantly to the rapid exhumation documented in the Icy Bay region (Berger, A.L., et al. 2008. Nature Geoscience,1, 793-802.)

Hallet, Bernard; Roche, James

2010-05-01

59

Aircraft Observations of Marine Aerosol Properties in the Presence of Boundary Layer Rolls  

Microsoft Academic Search

The Hawaii Group for Environmental Aerosol Research deployed a wide range of airborne aerosol instrumentation as part of MILAGRO\\/INTEX (2006) and PASE (2007) experiments. These were designed to provide rapid information on aerosol composition, state of mixing (internal or external), spectral optical properties (scattering and absorption), the humidity dependence of light scattering - f(RH). The measurements revealed frequently observed presence

V. Kapustin; A. Clarke; S. Howell; S. Conley; I. Faloona; V. Brekhovskikh; C. McNaughton

2008-01-01

60

Study of oblique particle-wall collisions in the presence of a thin viscous oil layer  

NASA Astrophysics Data System (ADS)

Collisions between wetted particles and between particles and the walls of containers occur in industrial processes such as filtration, coagulation, fluidization, sedimentation and slurry transport. To understand and model these collisions, the physical interactions occurring during contact should be known. In this work, we present the experimental results of oblique particle-wall collisions along with a brief model used to explain the observed results. Collisions of spheres with a quartz target covered with a thin oil layer at different angles of impact were observed to determine the coefficient of restitution (ratio of the rebound velocity to the approach velocity) for both normal and tangential components of motion. High-velocity impacts were performed by dropping spheres from various heights onto an oil-laden target. Low-velocity impacts were performed by suspending spheres with a light and long string to form a simple pendulum. The swinging sphere was impacted with a wet target at different angles. Low-velocity collisions were also performed in the low-gravity environment afforded in KC-135 parabolic flights of NASA. The results show that, for smooth spheres (e.g., steel), the normal coefficient of restitution of the spheres is unaffected by the tangential velocity or the angle of impact. However, for plastic spheres (e.g., teflon, nylon) that have significant surface roughness, it is seen that the normal restitution observed is slightly higher for oblique collisions than it is for head-on collisions. The normal restitution coefficient is adequately described by the theory for head-on collisions [Davis et. al. (2002) J. Fluid Mech. 468, 107-119] extended to oblique collisions. In particular, the spheres stick at low impact velocities due to lubrication forces and viscous dissipation in the thin oil layer. Above a critical impact velocity, however, a sufficient fraction of the initial kinetic energy becomes stored in elastic deformation, and rebound is observed. The tangential velocity of the spheres does not change significantly during wet or dry collisions except at very small impact velocities. As a first approximation, the normal and tangential components of motion of the sphere are considered decoupled and a scaling approximation for the tangential viscous force exerted by the fluid layer is developed. Scaling estimates show that the change in tangential velocity is small, as is seen in the experimental results. A rotational velocity is imparted to the sphere by the tangential viscous force exerted by the oil layer and/or solid-solid contact.

Kantak, Advait; Davis, Robert

2003-11-01

61

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

62

Estimates of vertical eddy diffusivity in the upper mesosphere in the presence of a mesospheric inversion layer  

NASA Astrophysics Data System (ADS)

Rayleigh and resonance lidar observations were made during the Turbopause experiment at Poker Flat Research Range, Chatanika Alaska (65° N, 147° W) over a 10 h period on the night of 17-18 February 2009. The lidar observations revealed the presence of a strong mesospheric inversion layer (MIL) at 74 km that formed during the observations and was present for over 6 h. The MIL had a maximum temperature of 251 K, amplitude of 27 ± 7 K, a depth of 3.0 km, and overlying lapse rate of 9.4 ± 0.3 K km-1. The MIL was located at the lower edge of the mesospheric sodium layer. During this coincidence the lower edge of the sodium layer was lowered by 2 km to 74 km and the bottomside scale height of the sodium increased from 1 km to 15 km. The structure of the MIL and sodium are analyzed in terms of vertical diffusive transport. The analysis yields a lower bound for the eddy diffusion coefficient of 430 m2 s-1 and the energy dissipation rate of 2.2 mW kg-1 at 76-77 km. This value of the eddy diffusion coefficient, determined from naturally occurring variations in mesospheric temperatures and the sodium layer, is significantly larger than those reported for mean winter values in the Arctic but similar to individual values reported in regions of convective instability by other techniques.

Collins, R. L.; Lehmacher, G. A.; Larsen, M. F.; Mizutani, K.

2011-11-01

63

Electrostatic double layer force between a sphere and a planar substrate in the presence of previously deposited spherical particles.  

PubMed

A finite element model of the electrostatic double layer interaction between an approaching colloidal particle and a small region of a charged planar surface containing four previously deposited particles is presented. The electrostatic interaction force experienced by the approaching particle is obtained by solving the Poisson-Boltzmann equation with appropriate boundary conditions representing this complex geometry. The interaction forces obtained from the detailed three-dimensional finite element simulations suggest that for the many-body scenario addressed here, the electrostatic double layer repulsion experienced by the approaching particle is less than the corresponding sphere-plate interaction due to the presence of the previously deposited particles. The reduction in force is quite significant when the screening length of the electric double layer becomes comparable to the particle radius (kappaa approximately 1). The results also suggest that the commonly used technique of pairwise addition of binary interactions can grossly overestimate the net electrostatic double layer interaction forces in such situations. The simulation methodology presented here can form a basis for investigating the influence of several previously deposited particles on the electrostatic repulsion experienced by a particle during deposition onto a substrate. PMID:16032900

Das, Prodip K; Bhattacharjee, Subir

2005-05-10

64

Long-time growth kinetics of first order phase transitions in the presence of a boundary layer.  

PubMed

The late stage growth mechanism for a first order phase transition, either through nucleation growth or spinodal decomposition, is well understood to be an Ostwald ripening or coarsening process, in which larger domains grow at the expense of smaller ones. The growth kinetics in this regime was shown by Lifshitz and Slyozov to follow at(1/3) law. However, the kinetics is altered if there exists a barrier ahead of the growth front, irrespective of the physical origin of the boundary layer. We present an analytic calculation for the growth kinetics in the presence of a boundary layer, showing that in the limit of barrier-dominated growth, the domains grow with at(1/2) law. This result holds true in the dilute regime independent of whether the growing nuclei are spherical or cylindrical. PMID:21280792

Mitra, Mithun K; Muthukumar, M

2011-01-28

65

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

SciTech Connect

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

Ishikawa, Tatsuo [School of Chemistry, Osaka University of Education, 4-698-1 Asahigaoka, Kashiwara, Osaka 582-8582 (Japan)]. E-mail: ishikawa@cc.osaka-kyoiku.ac.jp; Matsumoto, Kumi [School of Chemistry, Osaka University of Education, 4-698-1 Asahigaoka, Kashiwara, Osaka 582-8582 (Japan); Kandori, Kazuhiko [School of Chemistry, Osaka University of Education, 4-698-1 Asahigaoka, Kashiwara, Osaka 582-8582 (Japan); Nakayama, Takenori [Materials Research Laboratory, Kobe Steel, Ltd., 5-5 Takatsukadai 1-Chome, Nishi-ku, Kobe, Hyogo 615-2271 (Japan)

2006-04-15

66

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

67

An Intercomparison of a Two-Pressure\\/Two-Temperature Frost Point Generator and Chilled Mirror Condensation Hygrometer  

Microsoft Academic Search

Dew point sensors are used in industry to detect the presence of small levels of water vapor. Critical measurements in compressed air, breathing air, metals processing, battery making, plastics processing, natural gas and petrochemical production require water vapor levels to remain in the 1- 6000 PPMv (parts per million by volume) or equivalent -76 to 0ºC Td (frost point temperature)

Ken Soleyn

68

Frosting and Defrosting of Air Coils: A Literature Survey.  

National Technical Information Service (NTIS)

Frosting of air-coils is a well-known phenomenon in the fields of refrigeration and heat pump technology. The effects of a frosted coil will influence both the capacity, the efficiency, the availability, and the reliability of the refrigeration system. He...

P. Fahlen

1996-01-01

69

Uncertainty of the Kriss Low Frost-Point Humidity Generator  

NASA Astrophysics Data System (ADS)

The KRISS low frost-point humidity generator (LFPG), was developed in 2006 for the frost-point range (-95 to -40)° C in order to extend calibration capabilities. In this paper, the evaluation of the generator's uncertainty budget is reported for which each uncertainty component was categorized and estimated by experiment and calculation. The uncertainty of the LFPG depends on the generated frost point, gas flow rate, and change of moisture concentration in transportation. The standard uncertainty of LFPG is less than 32 mK in the frost-point range from -70 ° C to -40 ° C. However, in the lower frost-point range, the uncertainty increases to 137 mK at -90 ° C, and this is mainly due to water adsorption or desorption in the transportation tubing from saturator to hygrometer.

Choi, B. I.; Kim, J. C.; Woo, S. B.

2012-09-01

70

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

71

Experimental study of a turbulent boundary layer in presence of external manipulators of NACA 0009 profile in the transonic regime  

NASA Astrophysics Data System (ADS)

An experimental study was conducted to determine the effectiveness of manipulators of external-type turbulence on the reduction of wall drag in a turbulent boundary layer in the transonic regime. The manipulators used, NACA 0009 thin profile type, have an aerodynamic behavior inappropriate for this type of application. Flow visualizations show that the flow on the manipulator is complex, with regions of separation, as well as recirculation, and that the wake of the manipulator is sometimes very unstable. Some of such behavior may be the origin of the high levels of drag encountered and adversely affects the effectiveness of this method in the sense of net balance. The analysis of the average velocity profiles, downstream of the single manipulator, does not permit reaching definitive quantitative conclusions since it leads to abnormally high reductions of the coefficient of wall drag, due apparently to the presence of a longitudinal pressure gradient which was not considered in the equation of motion.

Poirier, Diane

1990-05-01

72

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

NASA Astrophysics Data System (ADS)

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

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

2001-01-01

73

Argon frost continuous cryopump for fusion applications  

SciTech Connect

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

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

1993-12-01

74

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

SciTech Connect

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

Eluszkiewicz, J.B.

1993-01-01

75

Frosts During the Growing Season. Frequency of Occurrence and Effects on Current Energy Forestry.  

National Technical Information Service (NTIS)

Frost during the summer is very common in Sweden. Two kinds of summer frosts exists; one is called advection frost which is caused by cold air coming down over the country from the north and the other is an inversion frost caused by long-wave radiation fr...

L. Christersson H. Fircks K. Perttu

1984-01-01

76

Frost monitoring of fruit tree with satellite data  

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

77

[Infrared spectroscopic analysis of Guilin watermelon frost products].  

PubMed

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

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

2012-08-01

78

Enhanced crystallinity of silicon films deposited by CVD on liquid layers (CVDOLL process): Silicon on tin layers in the presence of hydrogen chloride  

Microsoft Academic Search

Chemical vapor deposition of silicon on a graphite substrate coated with a 5-mum-thick fluid tin layer provides a possibility for the production of large grained polycrystalline silicon layers. Using silane as a source material, crystallites can be produced with a mean grain size of about 20 mum, compared with 5 mum on a substrate without fluid layer. The grain size

M. W. M. Graef; L. J. Giling; J. Bloem

1977-01-01

79

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

NASA Astrophysics Data System (ADS)

We present model studies with the one-dimensional model MISTRA to investigate the potential role of frost flowers, recycling on snow, and open leads in the depletion of tropospheric ozone in the Arctic spring. In our model, we assumed frost flower aerosols to be the major source of bromine. We show that a major ozone depletion event can be satisfactorily reproduced only if the recycling on snow of deposited bromine into gas phase bromine is assumed. In the model, this cycling is more efficient than the bromine explosion process and maintains sufficiently high levels of bromine to deplete ozone down to few nmol mol-1 within four days. We assessed the influence of different surface combinations (open lead/frost flowers) on the chemistry in the model. Results showed noticeable modifications affecting the composition of aerosols and the deposition velocities. A model run with a series of coupled frost flower fields and open leads, separated by large areas of snow, showed results comparable with field observations. In addition, we studied the effects of modified temperature of either the frost flower field or the ambient airmass. A warmer frost flower field increases the relative humidity and the aerosol deposition rate. The deposition/re-emission process gains in importance, inducing more reactive bromine in the gas phase, and a stronger ozone depletion. A decrease of 1K in airmass temperature shows in our model that the aerosol uptake capacities of all gas phase species substantially increases, leading to enhanced uptake of acids from the gas phase. Consequently, the so-called bromine explosion accelerated and O3 mixing ratios decreased. In our model representation, variations in wind speed affected the aerosol source function and influenced the amount of bromine in the atmosphere and thus the ozone depletion strength. Recent studies have suggested the important role of the precipitation of calcium carbonate (CaCO3) out of the brine layer for the possible acidification of the liquid phase by acid uptake. Our investigation showed that this precipitation is a crucial process for the timing of the bromine explosion in aerosols. Nevertheless, model runs with either 50% precipitation or complete precipitation displayed a relatively weak difference in ozone mixing ratios after four simulated days. By considering conditions typical for "Arctic Haze" pollution events at the start of the run we obtained a low pH in frost flower aerosols due to a greater mixing ratio of SO2, and a strong recycling efficiency via large aerosol number concentration. The aerosol acidification during a haze event most likely intensifies the ozone depletion strength and occurrence. The comparison between our modeled deposition on snow and sampled snow at Barrow (Alaska) shows that approximately 75% of deposited bromine may be re-emitted into the gas phase as Br2/BrCl. Among several non-halogen fluxes from the snow, model simulations showed that only HONO affects the chemistry. Finally, we investigated the release of Br2 potentially produced by heterogeneous reactions directly on frost flowers. In this case, we obtained unrealistic results of aerosol compositions and deposition rates on snow compared to observations in the Arctic.

Piot, M.; von Glasow, R.

2008-05-01

80

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

NASA Astrophysics Data System (ADS)

We present model studies with the one-dimensional model MISTRA to investigate the potential role of frost flowers, recycling on snow, and open leads in the depletion of tropospheric ozone in the Arctic spring. In our model, we assumed frost flower aerosols to be the major source of bromine. We show that a major ozone depletion event can be satisfactorily reproduced only if the recycling on snow of deposited bromine into gas phase bromine is assumed. In the model, this cycling is more efficient than the bromine explosion process and maintains sufficiently high levels of bromine to deplete ozone down to few nmol mol-1 within four days. We assessed the influence of different surface combinations (open lead/frost flowers) on the chemistry in the model. Results showed noticeable modifications affecting the composition of aerosols and the deposition velocities. A model run with a series of coupled frost flower fields and open leads, separated by large areas of snow, showed results comparable with field observations. In addition, we studied the effects of modified temperature of either the frost flower field or the ambient airmass. A warmer frost flower field increases the relative humidity and the aerosol deposition rate. The deposition/re-emission process gains in importance, inducing more reactive bromine in the gas phase, and a stronger ozone depletion. A decrease of 1 K in airmass temperature shows in our model that the aerosol uptake capacities of all gas phase species substantially increases, leading to enhanced uptake of acids from the gas phase. Consequently, the so-called bromine explosion accelerated and O3 mixing ratios decreased. In our model representation, variations in wind speed affected the aerosol source function and influenced the amount of bromine in the atmosphere and thus the ozone depletion strength. Recent studies have suggested the important role of the precipitation of calcium carbonate (CaCO3) out of the brine layer for the possible acidification of the liquid phase by acid uptake. Our investigation showed that this precipitation is a crucial process for the timing of the bromine explosion in aerosols. Nevertheless, model runs with either 50% precipitation or complete precipitation displayed a relatively weak difference in ozone mixing ratios after four simulated days. By considering conditions typical for "Arctic Haze" pollution events at the start of the run we obtained a low pH in frost flower aerosols due to a greater mixing ratio of SO2, and a strong recycling efficiency via large aerosol number concentration. The aerosol acidification during a haze event most likely intensifies the ozone depletion strength and occurrence. The comparison between our modeled deposition on snow and sampled snow at Barrow (Alaska) shows that approximately 75% of deposited bromine may be re-emitted into the gas phase as Br2/BrCl. Among several non-halogen fluxes from the snow, model simulations showed that only HONO affects the chemistry. Finally, we investigated the release of Br2 potentially produced by heterogeneous reactions directly on frost flowers. In this case, we obtained unrealistic results of aerosol compositions and deposition rates on snow compared to observations in the Arctic.

Piot, M.; von Glasow, R.

2007-04-01

81

Design Guide for Frost-Protected Shallow Foundations.  

National Technical Information Service (NTIS)

Frost-protected shallow foundations (FPSFs) offer a proven technology designed to substantially lower construction costs in colder climates, enhancing housing affordability for families in many parts of the United States. This document provides step-by-st...

1994-01-01

82

Frost-Protected Shallow Foundations. Phase 2. Final Report.  

National Technical Information Service (NTIS)

Frost-protected shallow foundations (FPSFs) offer a proven technology designed to substantially lower construction costs in colder climates, enhancing housing affordability for families in many parts of the United States. This document provides step-by-st...

J. H. Crandell E. M. Lund M. G. Bruen M. S. Nowak

1994-01-01

83

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

84

Synoptic analysis of frost days in Zanjan Province of Iran  

NASA Astrophysics Data System (ADS)

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

Alijani, B.; Tagiloo, M.

2010-09-01

85

Far field radiation from an arbitrarily oriented Hertzian dipole in the presence of a layered anisotropic medium  

Microsoft Academic Search

Far field radiation from an arbitrarily oriented Hertzian dipole for two-layered uniaxially anisotropic medium with a tilted optic axis is treated analytically by using the dyadic Green's function of the problem when the dipole is placed over or embedded in a two-layered uniaxially anisotropic medium. The radiation fields are evaluated using the steepest descent method. Parameter studies including anisotropy, layer

Abdullah Eroglu; Jay Kyoon Lee

2005-01-01

86

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

Microsoft Academic Search

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

Jon Ågren

1988-01-01

87

Stability Analysis and Numerical Simulation of Differential Frost Heave  

Microsoft Academic Search

Differential frost heave is often implicated in the formation of patterned ground in regions subject to recurrent freezing\\u000a and thawing. A linear stability analysis (LSA) indicates that a continuum model of frost heave is linearly unstable under\\u000a typical natural freezing conditions of silty-clay soils. A two-dimensional non-linear numerical analysis corroborates the\\u000a frozen time LSA results, and also indicates the importance

Rorik A. Peterson

2008-01-01

88

Residual Strength of the Frost-Damaged Reinforced Concrete Beams  

Microsoft Academic Search

The most severe types of destruction mechanisms are those causing internal cracking and thereby loss of cohesion of the concrete,\\u000a i.e. internal expansive attacks. The internal frost damage belongs to this category of destructive mechanisms. The frost attack\\u000a causes a random system of cracks in the heart of the concrete together with cracks parallel to the surface of the concrete.

Manouchehr Hassanzadeh; Göran Fagerlund

89

Frost risk for overwintering crops in a changing climate  

NASA Astrophysics Data System (ADS)

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

Vico, Giulia; Weih, Martin

2013-04-01

90

Delayed Frost Growth on Jumping-Drop Superhydrophobic Surfaces  

SciTech Connect

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

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

2013-01-01

91

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

92

Forecast of Frost Days Based on Monthly Temperatures  

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

93

Boundary layers for the nonlinear discrete Boltzmann equation: Condensing vapor flow in the presence of a non-condensable gas  

NASA Astrophysics Data System (ADS)

Half-space problems for the Boltzmann equation are of great importance in the study of the asymptotic behavior of the solutions of boundary value problems of the Boltzmann equation for small Knudsen numbers. Half-space problems provide the boundary conditions for the fluid-dynamic-type equations and Knudsen-layer corrections to the solution of the fluid-dynamic-type equations in a neighborhood of the boundary. Here we consider a half-space problem of condensation for a pure vapor in the presence of a non-condensable gas by using discrete velocity models (DVMs) of the Boltzmann equation. The Boltzmann equation can be approximated by DVMs up to any order, and these DVMs can be applied for numerical methods, but also for mathematical studies to bring deeper understanding and new ideas. For one-dimensional half-space problems, the discrete Boltzmann equation (the general DVM) reduces to a system of ODEs. We obtain that the number of parameters to be specified in the boundary conditions depends on whether the condensing vapor flow is subsonic or supersonic. This behavior has earlier been found numerically. We want to stress that our results are valid for any finite number of velocities. This is an extension of known results for single-component gases (and for binary mixtures of two vapors) to the case when a non-condensable gas is present. The vapor is assumed to tend to an assigned Maxwellian, with a flow velocity towards the condensed phase, at infinity, while the non-condensable gas tends to zero at infinity. Steady condensation of the vapor takes place at the condensed phase, which is held at a constant temperature. We assume that the vapor is completely absorbed, that the non-condensable gas is diffusively reflected at the condensed phase, and that vapor molecules leaving the condensed phase are distributed according to a given distribution. The conditions, on the given distribution at the condensed phase, needed for the existence of a unique solution of the problem are investigated, assuming that the given distribution at the condensed phase is sufficiently close to the Maxwellian at infinity and that the total mass of the non-condensable gas is sufficiently small. Exact solutions and solvability conditions are found for a specific simplified discrete velocity model (with few velocities).

Bernhoff, N.

2012-11-01

94

Adsorption of ions in the diffuse part of an electrical double layer at ionic surfactant solution-air interfaces in the presence of background electrolytes  

Microsoft Academic Search

The equations are derived for the calculation of adsorption values ?±d of coions and counterions in the diffuse part of an electrical double layer characterized by ?d potential in the presence of a background electrolyte. The case of arbitrary |?d| values is considered. Based on the known experimental data, the contributions of adsorption values ?±d to the surface excesses of

G. S. Aleiner; O. G. Us’yarov

2008-01-01

95

The influence of multi-layer ground on the electromagnetic field of an overhead power transmission line in the presence of buried conductors  

Microsoft Academic Search

Contents The present work investigates the two dimensional, quasi stationary, electromagnetic field of a faulted power transmission line in the presence of a buried pipeline, of mitigation wires and of a multi-layer ground. The related diffusion equation has been numerically solved by using the Finite Element Method (FEM). Using FEM results and Faraday's law, magnetic vector potential, as well as

K. J. Satsios; D. P. Labridis; P. S. Dokopoulos

1997-01-01

96

Dentinal wall adaptation of thermoplasticized gutta-percha in the absence or presence of smear layer: a scanning electron microscopic study.  

PubMed

The dentinal adaptation of injected thermoplasticized gutta-percha and thermoplasticized gutta-percha resulting from Ultrafil and Thermafil systems was evaluated by scanning electron microscopy and compared with adaptation obtained with the lateral condensation of gutta-percha. Each method was evaluated with and without the smear layer removed. Scanning electron microscopic observations showed the thermoplasticized gutta-percha resulting from either system to have better dentinal wall adaptation than lateral condensation of gutta-percha in either the absence or presence of the smear layer. In the absence of smear layer, the adaptation of gutta-percha was improved in all groups. Although sealer was used, removing the smear layer was found to enhance the ability of the thermoplasticized gutta-percha to enter the patent tubules. PMID:8151244

Genço?lu, N; Samani, S; Günday, M

1993-11-01

97

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

PubMed

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

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

2013-02-04

98

Inversion of multimode Rayleigh waves in the presence of a low-velocity layer: numerical and laboratory study  

NASA Astrophysics Data System (ADS)

The dispersion and the surface displacement as a function of frequency of multiple modes guided waves in stratified media including a low-velocity layer are studied by numerical simulation and experiment. A method is developed to determine the thickness and the shear wave velocity of individual layers. First, the modal analysis of Rayleigh wave is investigated numerically for three layered media. Then, ultrasonic surface measurements are performed for three specimens: Steel half-space, Lucite/Steel half-space and Aluminum/Lucite/Steel half-space. The Characteristics of the dispersion curves are analyzed using the frequency-wavenumber method. The non-dispersive Rayleigh wave is obtained for the first simple specimen. The dispersion curves for two modes are obtained for the second specimen with a low-velocity layer on a fast substrate. The dispersion curves for the third specimen containing a low-velocity layer are apparently discontinuous and correspond to different mode branches. Further analysis demonstrates that the apparent discontinuity is caused by a rapid change of mode excitation with frequency at the surface. While one mode vanishes from the recorded wavefield, the other appears. This indicates that the surface displacements of the modes should be also accounted for in the inverse problem, especially in stratified media with a low-velocity layer. Finally, shear wave velocity profiles are inverted based on the experimental (maybe discontinuous) dispersion curves of fundamental or/and higher modes using a Genetic Algorithm(GA). Besides the dispersion characteristics of each mode, the surface displacement distribution is also taken into account for the case of a low-velocity layer, and as a result, the mode-misidentification is avoided.

Lu, Laiyu; Wang, Chenghao; Zhang, Bixing

2007-03-01

99

Design guide for frost-protected shallow foundations  

SciTech Connect

Frost-protected shallow foundations (FPSFs) offer a proven technology designed to substantially lower construction costs in colder climates, enhancing housing affordability for families in many parts of the United States. This document provides step-by-step procedures to assist building professionals in designing and laying a slab- on-grade FPSF. FPSFs save money over conventional designs by requiring less excavation to construct a frost-proof foundation. It is specially insulated along its perimeter to raise the temperature of the surrounding ground and decrease frost penetration, thus allowing for the construction of a substantially shallower foundation. The FPSF is considered standard practice for homes in Scandinavia, where 40 years of field testing has proven it to be economical to construct, durable, and energy efficient. HUD strongly encourages wide spread adoption of FPSF technology in the United States and its incorporation into major model building codes.

NONE

1994-10-01

100

Frost sensor for use in defrost controls for refrigeration  

SciTech Connect

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

101

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

102

Lessons in the Conversation That We Are: Robert Frost's "Death of the Hired Man."  

ERIC Educational Resources Information Center

|Looks at Robert Frost's "The Death of the Hired Man" as a "representative anecdote" for Frost's work, which, taken as a whole, shows readers how to lose themselves among the overlooked places and turnings, the topics and tropes, that make up Frost's rhetorical home, the place of everyday human talk and gossip. (TB)|

Jost, Walter

1996-01-01

103

Frost-weathering on Mars: Experimental evidence for peroxide formation  

Microsoft Academic Search

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

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

1979-01-01

104

layer  

Microsoft Academic Search

This paper analyzes the propagation of a cohesive crack through a reinforcement layer and gives a solution that can be used for any specimen and loading condition. Here it faces the case of a reinforced prismatic beam loaded at three points. Reinforcement is represented by means of a free-slip bar bridging the cracked section, anchored at both sides of the

Gonzalo Ruiz

105

Spatiotemporal Interaction of Near-Surface Soil Moisture Content and Frost Table Depth in a Discontinuous Permafrost Environment  

NASA Astrophysics Data System (ADS)

The ubiquitous presence of frozen ground in cold regions creates a unique dynamic boundary issue for subsurface water movement and storage. We examined the relationship between ground thaw and spatiotemporal soil moisture patterns at three sites (peatland, wetland and valley) near Yellowknife NT. Thaw depth and near-surface soil moisture were measured along a systematic grid at each site. Energy and water budgets were computed for each site to explain the soil moisture patterns. At the peatland, overall soil moisture decreased through the summer and became more spatially homogeneous with deepened thaw, increased subsurface storage capacity, and drying from evapotranspiration. In the peatland and wetland, accumulated water in depressions maintained soils at higher soil moistures for a longer duration than the hummock tops. The depressions had deeper frost tables than the drier hummock tops because the organic mats covering the hummocks insulated the ground and retarded ground thaw. The wettest soils were often locations of deepest thaw depth due to surface ponding and the transfer of latent heat accompanying surface runoff from upslopes. For example, the 3.3 ha wetland received 3.08x105 m3 of surface inflow from a lake with 2.32 kJm-2 of convective heat available to be transferred into the frozen ground over the study period. Soil moisture patterns also revealed preferential surface and subsurface flow routes. The findings indicate that the presence of frozen ground and differential thawing have a diverse and dynamic relationship with near-surface soil moisture content. When the impermeable boundary is dynamic, and controlled by water and energy fluxes, thicker soil layers are associated with higher moisture. This contrasts findings from temperate regions with a fixed impermeable boundary which show that surface soil moisture content can be lower in areas with thick soil.

Guan, X.; Spence, C.; Westbrook, C. J.

2009-05-01

106

Reversed-phase thin-layer chromatography of various pesticides in the presence of water-soluble beta-cyclodextrin polymer  

Microsoft Academic Search

The modification of the hydrophobicity of 28 commercial pesticides with a water-soluble ?-cyclodextrin polymer (SCDP) in the presence of aqueous NaCl has been studied by reversed-phase thin-layer chromatography. The pesticides formed inclusion complexes with SCDP and these complexes are less lipophilic than the parent pesticides. The sodium chloride exerted a typical saltingout effect, the retention of each pesticide increased with

Y. Darwish; T. Cserháti; E. Forgács

1994-01-01

107

Frost-protected shallow foundations. Phase 2. Final report  

SciTech Connect

Frost-protected shallow foundations (FPSFs) offer a proven technology designed to substantially lower construction costs in colder climates, enhancing housing affordability for families in many parts of the United States. This document provides step-by-step procedures to assist building professionals in designing and laying a slab-on-grade FPSF.

Crandell, J.H.; Lund, E.M.; Bruen, M.G.; Nowak, M.S.

1994-06-01

108

BREEDING FOR IMPROVED FROST-SEEDED RED CLOVER SEEDLING ESTABLISHMENT  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

109

Heritability of frost-seeded red clover establishment  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

110

Remnant Fermi Surface in the Presence of an Underlying Instability in Layered 1T-TaS2  

NASA Astrophysics Data System (ADS)

We report high resolution angle-scanned photoemission and Fermi surface (FS) mapping experiments on the layered transition-metal dichalcogenide 1T-TaS2 in the quasicommensurate (metallic) and the commensurate (insulating) charge-density-wave (CDW) phase. Instead of a nesting induced partially removed FS in the CDW phase we find a pseudogap over large portions of the FS. This remnant FS exhibits the symmetry of the one-particle normal state FS. Possibly, this Mott localization induced transition represents the underlying instability responsible for the pseudogapped FS.

Pillo, Th.; Hayoz, J.; Berger, H.; Grioni, M.; Schlapbach, L.; Aebi, P.

1999-10-01

111

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

112

Effects of partial slip on boundary layer flow past a permeable exponential stretching sheet in presence of thermal radiation  

NASA Astrophysics Data System (ADS)

An analysis is presented to describe the boundary layer flow and heat transfer towards a porous exponential stretching sheet. Velocity and thermal slips are considered instead of no-slip conditions at the boundary. Thermal radiation term is incorporated in the temperature equation. Similarity transformations are used to convert the partial differential equations corresponding to the momentum and heat equations into highly non-linear ordinary differential equations. Numerical solutions of these equations are obtained by shooting method. It is found that the fluid velocity and temperature decrease with increasing slip parameter. Temperature is found to decrease with an increase of thermal slip parameter. Thermal radiation enhances the effective thermal diffusivity and the temperature rises.

Mukhopadhyay, Swati; Gorla, Rama Subba Reddy

2012-10-01

113

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

SciTech Connect

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

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

1990-08-30

114

H2O frost point detection on Mars  

NASA Astrophysics Data System (ADS)

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

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

1981-01-01

115

Nondestructive evaluation of frost heave effects on a runway  

NASA Astrophysics Data System (ADS)

An Airport located inland central Sweden is susceptible to frost heave. The runway is uneven especially at the end of each winter. The Swedish Road and Transportation Institute Laser Profiler was brought to the site in the spring of 1997 in order to study this seasonal effect. Several longitudinal profiles were sampled along the entire length of the runway. The test was then repeated in the fall when the runway had settled. The profiles were then investigated to see if certain criteria were fulfilled, like the International Civil Aviation Organization straightedge guideline. Several different wavelength intervals of unevenness were also examined. It was found that the frost heave affected certain wavelength bands more than others. It was also possible to determine exactly where the most troublesome spots were located and if they would adversely interfere with an expansion of the runway. Data from the profile could also serve as help in preparing guidelines for safety rules related to roughness.

Lenngren, Carl A.

1998-03-01

116

Do stratospheric aerosol droplets freeze above the ice frost point?  

Microsoft Academic Search

Laboratory experiments are presented which show that liquid stratospheric aerosol droplets under polar winter conditions do not freeze for temperatures higher than the water ice saturation temperature (frost point). Calorimetric measurements of the freezing of supercooled H2SO4\\/HNO3\\/H2O bulk solutions with concentrations typical of the polar stratospheric aerosol exhibit very small freezing rates, which exclude the possibility of homogeneous freezing of

T. Koop; U. M. Biermann; W. Raber; B. P. Luo; P. J. Crutzen; Th. Peter

1995-01-01

117

Climate Change Shifts Frost Seasons and Plant Growth  

NSDL National Science Digital Library

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

118

Bacterial ice nucleation: a factor in frost injury to plants.  

PubMed

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 degrees 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 degrees 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 degrees C are always active as ice nuclei at -5 degrees C. INA bacteria incited frost injury to all of the species of sensitive plants tested. PMID:16662618

Lindow, S E; Arny, D C; Upper, C D

1982-10-01

119

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

SciTech Connect

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

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

1989-08-01

120

Frost hardiness in the juvenile and adult life phase of ivy ( Hedera helix L.)  

Microsoft Academic Search

The common ivy (Hedera helix L.) remains juvenileat its northern, eastern and altitudinal distribution limits although juvenileparts are largely killed by severe frost spells. In order to explain thisdiscrepancy we investigated the seasonal course of frost resistance in variousorgans of juvenile and adult parts of the same H. helixplants. Maximum frost resistance of leaves (LT50-25?°C) and axis (xylem parenchyma:LT50 -29?°C;

Sigrid Andergassen; Helmut Bauer

2002-01-01

121

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

NSDL National Science Digital Library

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

Inouye, David

2012-01-04

122

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

Microsoft Academic Search

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

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

1982-01-01

123

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

124

Presence of all Three Allotropes of Impact-Diamonds in the Younger Dryas Onset Layer (YDB) Across N America and NW Europe  

NASA Astrophysics Data System (ADS)

We report the discovery of all three diamond allotropes (cubic diamond, lonsdaleite, and n-diamond) in an extraterrestrial (ET) impact layer (the YDB), dating to the Younger Dryas onset at 12.9 ka. YDB diamonds are distributed broadly across N America and NW Europe at 15 sites spanning 9,000 km or 23 percent of Earth's circumference. N-diamonds and lonsdaleite, or hexagonal diamond, do not co-occur with terrestrial diamonds, but are found in meteorites. Lonsdaleite is found on Earth only in association with known ET impacts, and thus, is a definitive impact indicator. The diamonds were identified by transmission electron microscopy (TEM) using selected area diffraction (SAED), which display reflections corresponding to the following lattice planar spacings definitive of diamond: (1) cubic: 2.06, 1.26, 1.07, and 0.89 A; (2) lonsdaleite: 2.184, 1.261, 1.092, and 0.826 A; and (3) n-diamond: 2.06, 1.26, 1.07, and 0.89 A, plus "forbidden" reflections of 1.78, 1.04, and 0.796 A. Nanodiamonds are rounded to highly angular, and range in size from 1 to 1700 nm with most between 1 and 50 nm. Concentrations are up to 3700 ppb, equaling more than 1 billion diamonds per cm3 of sediment (comparable to K/T levels of 3600 ppb). No diamonds were detected above or below the YDB layer at any site tested. These diamonds could not have formed from volcanic activity, because they combust at temperatures above 500° C in the presence of atmospheric levels of oxygen, and micrometeoritic diamonds are similarly destroyed. Also, the diamonds could not have accumulated from the constant rain of micrometeoritic debris, because multi-billions occur in YDB layer samples, but yet none have been found in non-YDB strata dating from 55,000 RCYBP to present. YDB diamonds are associated with abundance peaks in magnetic spherules, carbon spherules, soot, and iridium, which can peak in impact layers of known ET events, such as the K/T and the 1908 airburst at Tunguska, Siberia. Furthermore, a high proportion of the nanodiamonds are found deeply embedded within spherical particles of melted plant resins, a fact inexplicable by any normal terrestrial process. Altogether, this evidence strongly suggests that the widespread and abundant nanodiamonds constrained to the thin YDB layer resulted from a major ET impact/airburst at 12.9 ka.

West, A.; Kennett, J. P.; Kennett, D. J.; Que Hee, S. S.; Wolbach, W. S.; Stich, A.; Bunch, T. E.; Wittke, J. H.; Mercer, C.; Sellers, M.; Culleton, B. J.; Erlandson, J. M.; Johnson, J. R.; Stafford, T. W.; Weaver, J. C.; West, G.

2008-12-01

125

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

2013-07-22

126

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

Microsoft Academic Search

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

Anne Tolvanen

1997-01-01

127

The application of photo-coupler for frost detecting in an air-source heat pump  

Microsoft Academic Search

This experimental study is carried out to investigate reliability and effectiveness of a new method of using photo-coupler for detecting frost formation in an air source heat pump, and further to determine the most efficient initiation point of the defrost cycle. This new method of using photo-coupler as a frost sensing device is evaluated by comparing its performance with conventional

Ju-Suk Byun; Chang-Duk Jeon; Ji-Hoon Jung; Jinho Lee

2006-01-01

128

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

National Technical Information Service (NTIS)

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-...

M. Kandula

2010-01-01

129

WINTER RUNOFF PREDICTION BY WEPP WITH AN ENERGY BUDGET APPROACH TO SIMULATING SNOW AND SOIL FROST  

Technology Transfer Automated Retrieval System (TEKTRAN)

In cold regions, the occurrence of snow and soil frost influences hydrology and, in turn, the mechanisms of soil erosion processes. For these regions, modeling the dynamics of snow and soil frost is necessary to estimate runoff and erosion accurately under different management practices. With bett...

130

Simulating Snowmelt and Soil Frost Depth by an Energy Budget Approach  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

131

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

NASA Astrophysics Data System (ADS)

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

Haei, M.; Öquist, M.; Laudon, H.

2011-12-01

132

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

Microsoft Academic Search

Climate change is likely to alter soil frost depth and duration in the boreal zone in the future. Soil frost can influence biogeochemical soil processes directly, for instance by altering rates of microbial decomposition of soil organic matter (SOM) and by increasing root mortality. In addition, soil frost controls hydrologic flow paths, which in turn determines export of carbon from

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

2008-01-01

133

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

2013-08-28

134

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

135

Dew and frost chemistry at a midcontinent site, United States  

SciTech Connect

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

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

1992-12-20

136

FROST: a filter-based fold recognition method.  

PubMed

To assess the reliability of fold assignments to protein sequences, we developed a fold recognition method called FROST (Fold Recognition-Oriented Search Tool) based on a series of filters and a database specifically designed as a benchmark for this new method under realistic conditions. This benchmark database consists of proteins for which there exists, at least, another protein with an extensively similar 3D structure in a database of representative 3D structures (i.e., more than 65% of the residues in both proteins can be structurally aligned). Because the testing of our method must be carried out under conditions similar to those of real fold recognition experiments, no protein pair with sequence similarity detectable using standard sequence comparison methods such as FASTA is included in the benchmark database. While using FROST, we achieved a coverage of 60% for a rate of error of 1%. To obtain a baseline for our method, we used PSI-BLAST and 3D-PSSM. Under the same conditions, for a 1% error rate, coverages for PSI-BLAST and 3D-PSSM were 33 and 56%, respectively. PMID:12402359

Marin, Antoine; Pothier, Joël; Zimmermann, Karel; Gibrat, Jean-François

2002-12-01

137

Relationship between Ice Nucleation Frequency of Bacteria and Frost Injury.  

PubMed

Not every cell of a given bacterial isolate that has ice-nucleating properties can serve as an ice nucleus at any given time and temperature. The ratio between the number of ice nuclei and number of bacterial cells in a culture (i.e. nucleation frequency) was found to vary with incubation temperature, growth medium composition, culture age, and genotype. Optimal conditions for ice nucleus production in vitro included incubation of the bacterial cells at 20 to 24 degrees C on nutrient agar containing glycerol. The relationship between nucleation frequency and frost injury was examined by subjecting corn seedlings to -4 degrees C immediately after they were sprayed with bacterial suspensions with different nucleation frequencies and by following both ice nucleus concentration and bacterial population size on leaves of corn seedlings as a function of time after bacterial application. The amount of frost injury to growth chamber-grown corn seedlings at -4 degrees C was a function of the number of ice nuclei active at that temperature on the leaves. The number of ice nuclei, in turn, is the product of the nucleation frequency and population size of ice-nucleation-active bacteria present on the leaves. PMID:16662619

Lindow, S E; Hirano, S S; Barchet, W R; Arny, D C; Upper, C D

1982-10-01

138

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

USGS Publications Warehouse

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

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

2007-01-01

139

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

SciTech Connect

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

Not Available

1982-03-01

140

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

NASA Astrophysics Data System (ADS)

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

Strauch, Steffen; CLAS Collaboration

2012-04-01

141

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; Kløve, Bjørn

2013-04-01

142

Fundamentals of Frost Forecasting in Geological Engineering Investigations (Osnovy Merzlotnogo Prognoza pri Inzhenerno-Geologicheskikh Issledovaniyakh).  

National Technical Information Service (NTIS)

The textbook 'Fundamentals of Frost Forecasting in Geological Engineering Investigations' in regions of seasonally and permanently frozen rocks is the first and still the only contemporary textbook in the Soviet and foreign literature which embraces the m...

K. A. Kondrat yeva L. S. Garagulya V. A. Kudryavtsev V. G. Melamed

1977-01-01

143

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

144

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

145

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

Microsoft Academic Search

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

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

2009-01-01

146

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

Microsoft Academic Search

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

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

2009-01-01

147

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

Microsoft Academic Search

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

Elliroma Gardiner; Chris J. Jackson

2010-01-01

148

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

149

An inverse geometry problem in estimating frost growth on an evaporating tube  

NASA Astrophysics Data System (ADS)

When humid air comes into contact with a surface whose temperature is below the dew point of water vapor in air and also below the freezing point, frost deposition takes place over the surface. The phenomena of the frost growth are very complicated and therefore it is very difficult to model mathematically the behavior of frost growth and predict it. In the present study a transient inverse geometry heat conduction problem (shape identification problem) is solved using the conjugate gradient method (CGM) and boundary element method (BEM)-based inverse algorithm to estimate the unknown irregular frost thickness and shape. Results obtained by using the CGM to estimate the frost growth are justified based on the numerical experiments. It is concluded that the accurate frost shape can be estimated by the CGM except for the initial and final time. The reason and improvement of this singularity are addressed. Finally the effects of reducing the number of sensors and increasing the measurement errors on the inverse solutions are discussed.

Huang, C.-H.

150

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

151

Magnetization dynamics in the presence of pure spin currents in magnetic single and double layers in spin ballistic and diffusive regimes.  

SciTech Connect

In this paper we study the spin transport by using the spin-pumping effect in epitaxial magnetic single and double layer film structures. For the magnetic single layer sample we show the spin-pumping-induced interface damping increases and saturates with the Au capping layer thickness. In addition magnetic double layer structures allowed us to investigate both the spin-pump and spin-sink effects. Coupling of pure spin currents to the magnetization via spin-sink effect is studied using time-resolved magneto-optical Kerr effect. These measurements were used to study the propagation of pure spin currents across a Au spacer layer between the two ferromagnets. The propagation of spin momentum density through the Au spacer layer was well described by spin-diffusion equation, which takes into account electron momentum and spin-flip scattering. The spin-diffusion theory was integrated into modified Landau-Lifshitz equations accounting in self-consistent manner for spin-pump/sink mechanism and spin momentum density propagation. Good agreement between theory and experimental data was found.

Mosendz, O.; Woltersdorf, G.; Kardasz, B.; Heinrich, B.; Back, C. H.; Materials Science Division; Univ. Regensburg; Simon Fraser Univ.

2009-01-01

152

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

Microsoft Academic Search

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

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

2008-01-01

153

Study of frost melting on a heat pump heat exchanger  

SciTech Connect

This experimental work was carried out to obtain basic information on frost melting on a heat exchanger used as a heat pump air conditioner. The heat exchanger working fluid used in this experiment was a 50 wt% propylene glycol aqueous solution. The flow amount G and the temperature T{sub b} of the working fluid were 0.1 {lt} G m{sup 3}/hour {lt} 0.2 and 10 {lt} T{sub b}0{degrees}C {lt} 34, respectively. A melting thermal efficiency {eta} is defined in this paper as the ratio of the net heat for melting to the heat supplied to the heat exchanger until the critical time for melting t{sub c}. {eta} strongly depends on t{sub c}, and t{sub c} is strongly affected by G and T{sub b}. In conclusion, it was found that the heat supplied to the heat exchanger can be utilized with a high {eta} when t{sub c} becomes small.

Sugawara, M.; Kirihoshi, C.; Fujita, T. (Dept. of Mechanical Engineering, Akita Univ. (JP)); Uemura, S.; Yajima, R. (Daikin Industries, Ltd. (JP))

1990-01-01

154

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

155

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 ...

156

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

157

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

158

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

PubMed

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. PMID:24116022

Hoffmann, Holger; Rath, Thomas

2013-10-08

159

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

2013-09-19

160

EXPERIMENTAL STUDIES OF DEPOSITION RATES IN THE PRESENCE OF ALKALI SULFATE VAPOR SCAVENGING BY SUBMICRON PARTICLES IN COMBUSTION GAS BOUNDARY LAYERS  

Microsoft Academic Search

We examine the mass transfer consequences of the nonequilibrium scavenging of condensible vapor (Na2SO4) by suspended solid particles (MgO) within combustion gas boundary layers (BLs) using an extension of our 'flash-evaporation' technique (Rosner and Liang, 1986) and laser light scattering methods. In contrast to the result of introducing additives which form miscible condensates with the primary alkali sulfate on a

DANIEL E. ROSNER; BAISHEN LIANG

1988-01-01

161

Instability of a flat horizontal interface between a thin layer of a ferrofluid and a thin layer of a nonmagnetic liquid in the presence of a vertical magnetic field  

NASA Astrophysics Data System (ADS)

An asymptotic analysis of the equations and boundary conditions of fluid dynamics is performed, and a nonlinear model is constructed for the onset of the development of Rosensweig instability in a thin horizontal ferrofluid layer at rest covered with a thin layer of a lighter nonmagnetic liquid. The surface of a nonmagnetized slab is the lower boundary of the ferrofluid, and the interface with a gas is the upper boundary of the nonmagnetic liquid. The pressure in the gas is constant. The instability being considered arises upon the application of a rather strong uniform vertical magnetic field. The proposed model involves five dimensionless parameters. The critical magnetization of the initial ferrofluid layer with a flat upper boundary and the threshold wave number are found. The effect of the governing parameters on the instability region and on the wavelength of the fastest growing mode is studied in the linear formulation of the problem.

Korovin, V. M.

2012-10-01

162

Frost Growth CFD Model of an Integrated Active Desiccant Rooftop Unit  

SciTech Connect

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

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

2008-01-01

163

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

164

Evaluation fo frost damage in seed corn (Zea mays): with special emphasis on seed composition and moisture content  

Microsoft Academic Search

Fall frost is a serious concern to seed corn (Zea mays L.) producers in the Midwest. A frost event that happens prior to seed maturity can cause physical, biochemical, and physiological changes in the seed. These changes lead to decreased vigor and viability resulting in revenue loss for seed corn producers. Genetics and seed maturity greatly influence seed tolerance to

Heather Ann Hall

2009-01-01

165

Plant damage after freezing, and the frost resistance of varieties from the facultative and winter wheat observation nurseries  

Microsoft Academic Search

In the first experiments, studies were made on the survival % of fourwinter wheat varieties with good frost resistance and two with poor frostresistance, and on the degree of plant damage after freezing at –14 °C and -16 °C under phytotron conditions. In the secondexperiment the frost resistance of the varieties included in the 9thFacultative and Winter Wheat Observation Nurseries

O. Veisz; H.-J. Braun; Z. Bed?

2001-01-01

166

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

167

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

NASA Astrophysics Data System (ADS)

Frost flowers play a role in air-ice exchange in polar regions, contribute to tropospheric halogen chemistry, and affect ice core interpretation. Frost flowers were observed and collected on the Hudson Bay in March 2008. Their specific surface area (SSA) was measured using CH4 adsorption at 77 K. The Brunauer-Emmett-Teller analysis produced SSA values between 63 and 299 cm2 g-1 (mean 162 cm2 g-1, accuracy and reproducibility 5%). This range is very similar to that of Dominé et al. (2005) but our correlation of results with growth time and chemistry reveals the factors responsible for the wide range of SSA values. Longer growth time leads to higher SSA at low temperatures, so frost flowers are more likely to affect total surface area during colder periods. Chemical analysis was performed on frost flower melt and on local seawater and brine. We examined salinity and sulfate and bromide enrichment. The relationship between growth time and salinity varied spatially because of a freshwater plume from a nearby river and of tidal effects at the coast. Enrichment of certain ions in frost flowers, which affects their contribution to atmospheric chemistry, depends heavily on location, growth time, and temperature. No significant enrichment or depletion of bromide was detected. The low surface area index of frost flowers plus their lack of destruction in wind suggest their direct effect on sea salt mobilization and halogen chemistry may be less than previously thought, but their ability to salinate wind-blown snow may increase their indirect importance.

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

2009-10-01

168

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

PubMed

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

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

2011-09-01

169

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

Microsoft Academic Search

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

R. N. Clark

1981-01-01

170

A study on the performance enhancement of heat pump using electric heater under the frosting condition: Heat pump under frosting condition  

Microsoft Academic Search

The purpose of the present study is to enhance the heating capacity and increase COP under the frosting condition during heating operation of small capacity air-to-air heat pump. We applied an electric heater in front of outdoor unit of heat pump instead of indoor unit as usual. When the outdoor temperature is 2°C\\/1°C (DB\\/WB), the present heat pump turns on

Kyungmin Kwak; Cheolho Bai

2010-01-01

171

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

172

Provisional Prescriptions for Work during Frost. Commentary Notes on Specifications N 800 1967.  

National Technical Information Service (NTIS)

The report contains specific standardized rules to be followed in order to establish the continuation of construction work during frost. These rules are provisional and will be followed for a certain amount of time after which an evaluation will be made a...

1971-01-01

173

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

174

The frost heave program of the Alaskan natural gas transportation system  

Microsoft Academic Search

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

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

1982-01-01

175

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

Microsoft Academic Search

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.

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

2008-01-01

176

Evaluation of Frost Heave on Waste Transfer Lines with Shallow Depths in DST Farms.  

National Technical Information Service (NTIS)

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, and well compacted sandy material around waste transfer lines, the type of sandy and gravel soil, an...

M. A. Haq

2009-01-01

177

Effects of frost on wildflowers: an unexpected consequence of climate change--image 15 of 22  

NSDL National Science Digital Library

Photo of an early-stage inflorescence of tall larkspur (Delphinium barbeyi) after a mid-June snowstorm at the Rocky Mountain Biological Laboratory. The buds were killed by the cold temperature. Like Helianthella quinquenervis, D. barbeyi is a frost-sensitive species.

Inouye, David

2012-01-04

178

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

179

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

180

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

NSDL National Science Digital Library

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

Inouye, David

2012-01-04

181

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

Microsoft Academic Search

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.

Heikki Kukko

1992-01-01

182

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

SciTech Connect

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

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

1990-08-01

183

Variation among highbush blueberry cultivars for frost tolerance of open flowers  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

184

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

185

Study of the thermal behavior of a latent heat cold storage unit operating under frosting conditions  

Microsoft Academic Search

A study is performed of the thermal behavior of a latent heat cold storage unit operating under frosting conditions. This unit is employed to maintain the temperature inside the refrigerated compartment of a truck below 265 K. The system consists of parallel plates filled with a phase change material (PCM) that absorbs heat from the flow of warm moist air.

A. P. Simard; M. Lacroix

2003-01-01

186

Method for preventing damage to a refrigerated gas pipeline due to excessive frost heaving  

Microsoft Academic Search

Heat pipes are installed in the soil directly beneath a buried refrigerated gas pipeline and operate continuously in conjunction with operation of the pipeline to beneficially alter the heat and water flow patterns thereby substantially preventing frost heaving without regard to the season.

Hopke

1981-01-01

187

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

Microsoft Academic Search

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 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

J. H. Kamperschroer; M. B. Cropper; H. F. Dylla; V. Garzotto; L. E. Dudek; L. R. Grisham; G. D. Martin; T. E. OConnor; T. N. Stevenson; A. von Halle

1989-01-01

188

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

Microsoft Academic Search

Helium pumping on argon frost has been investigated on Tokamak Fusion Test Reactor (TFTR) neutral beam injectors and shown to be viable for limited helium beam operation. Maximum pumping speeds are {similar to}25% less than those measured for pumping of deuterium. Helium pumping efficiency is low, <20 argon atoms are required to pump each helium atom. Adsorption isotherms are exponential

J. H. Kamperschroer; M. B. Cropper; H. F. Dylla; V. Garzotto; L. E. Dudek; L. R. Grisham; G. D. Martin; T. E. O'Connor; T. N. Stevenson; A. von Halle; M. D. Williams; J. Kim

1990-01-01

189

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

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

190

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

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

191

Health Hazard Evaluation Report, Technical Assistance Report No. TA-80-059-851, Robert Frost Junior High School, Rockville, Maryland.  

National Technical Information Service (NTIS)

Carbon-monoxide (630080), hydrogen-chloride (7647010), hydrogen-fluoride (7664393), hydrogen-sulfide (7783064), nitrogen-dioxide (10102440), nitric-acid (7697372), and phenol (108952) exposures in the industrial arts area at Robert Frost Junior High Schoo...

R. L. Stephenson

1981-01-01

192

Frost resistance and ice nucleation in leaves of five woody timberline species measured in situ during shoot expansion.  

PubMed

Frost resistance and ice nucleation temperatures of leaves, from bud swelling until after full expansion, were measured in situ for five major woody timberline species with recently developed field freezing equipment. Frost resistance determined in situ on leaves of attached twigs was significantly higher than values determined on detached leaves in laboratory tests (e.g., the temperature at which incipient frost damage was observed (LTi) was 1.2 degrees C higher for detached leaves than for attached leaves of Picea abies (L.) Karst.). Frost resistance of leaves of all species changed significantly during shoot expansion (e.g., changes of 7.2 and 11 degrees C for Rhododendron ferrugineum L. and Larix decidua Mill., respectively). Expanding leaves (between 0 and 60% of full expansion) were the most sensitive to frost, with LTi values ranging from -3.4 degrees C in R. ferrugineum to -6.3 degrees C in L. decidua. Among the studied species, P. abies and R. ferrugineum were the most frost sensitive throughout the shoot elongation period. In situ freezing patterns of leaves of attached twigs also differed from those of leaves of excised twigs. During leaf expansion, two distinct freezing exotherms were always registered in situ. The first freezing event (E1, high-temperature exotherm) was recorded at -1.5 +/- 0.2 degrees C and reflected extracellular ice formation. Exposure of leaves to temperatures at which E1 occurred was, in all cases, noninjurious. The low-temperature exotherm (E2) mostly coincided with frost damage, except for some stages of leaf expansion in R. ferrugineum and P. abies, indicating that in situ freezing exotherms were not accurate estimators of frost damage in these species. PMID:14704142

Taschler, D; Beikircher, B; Neuner, G

2004-03-01

193

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

194

Frosted Branch Angiitis Diagnosed as Neuro-Beh?et: A Diagnostic and Etiologic Dilemma  

PubMed Central

Purpose To report a case of frosted branch angiitis (FBA) secondary to neuro-Behçet. Methods Description, diagnosis, angiogram imaging and follow-up of a 28-year-old female with FBA. Results ‘Frosted branch angiitis’ is a clinical term applied to three conditions: infiltration of vessels by malignant cells, and sheathing of vessels either secondary to an active disorder or subsequently to a previous inflammatory disease. Our patient's history of two optic neuropathies and the lack of demyelinating signs in neuroimaging made us consider FBA in the context of neuro-Behçet. Conclusion Recognition of the category of FBA from the clinical signs is essential to establish the correct diagnosis and prescribe the appropriate treatment.

Portero, Alejandro; Herreras, J.M.

2011-01-01

195

Heat and Moisture Exchange in a Permafrost Active Layer, Churchill, Manitoba  

Microsoft Academic Search

This thesis examines heat and moisture exchanges in the active layer of wet tundra soils during freeze-back and thaw. Measurements of rainfall, snow depth, air and soil temperature, soil moisture, and frost heave were recorded daily. Net radiation, soil heat exchange from soil solids and soil moisture, and soil latent heat exchange were calculated. It was determined that soil moisture

Linda Carol Jordan

1980-01-01

196

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

Microsoft Academic Search

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

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

1989-01-01

197

Balloon borne observations of PSCs, frost point, ozone and nitric acid in the North Polar vortex  

Microsoft Academic Search

A new balloon-borne instrument called a backscattersonde has been used to study polar stratospheric clouds (PSCs) at Alert, NWT during January and February of 1989. These measurements were supplemented with frost-point, ozone, and nitric-acid-vapor soundings. Type I PSCs were observed at temperatures and pressures generally consistent with present vapor-pressure models of NHO3\\/H2O condensate, but some noticeable inconsistencies exist. It is

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

1989-01-01

198

Balloon borne observations of PSCs, frost point, ozone and nitric acid in the North Polar Vortex  

Microsoft Academic Search

A new balloon borne instrument called a backscattersonde has been used to study Polar Stratospheric Clouds (PSCs) at Alert, NWT (82°N, 61.5°W) during January and February of 1989. These measurements were supplemented with frost point, ozone and nitric acid vapor soundings. Type I PSCs were observed at temperatures and pressures generally consistent with present vapor pressure models of HNO3\\/H2O condensate,

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

1989-01-01

199

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

Microsoft Academic Search

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

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

2001-01-01

200

Frost retardation of an air-source heat pump by the hot gas bypass method  

Microsoft Academic Search

This study is concerned with a hot gas (refrigerant) bypass method to retard the formation and propagation of frost in an air-source heat pump. The feasibility of the hot gas bypass method was investigated experimentally and the method's performance is compared with that of a normal, 1.12kW capacity air-source heat pump system with no defrost equipment such as an electric

Ju-Suk Byun; Jinho Lee; Chang-Duk Jeon

2008-01-01

201

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

202

Effects of frost on wildflowers: an unexpected consequence of climate change--image 11 of 22  

NSDL National Science Digital Library

Results of a demographic study of Helianthella quinquenervis (aspen sunflower, Asteraceae) within plots at 2,900m at the Rocky Mountain Biological Laboratory. Note that seedlings are not common in most years, and the overall population seems to be declining. The lack of seedlings in most years is a consequence of frost damage to flower buds the previous year (so no seeds were produced). The population decline is an apparent consequence of reduced seed production.

Inouye, David

2012-01-04

203

A case report of frosted branch angiitis and its visual electrophysiology  

Microsoft Academic Search

We reported a 5-years old boy with frosted branch angiitis in both eyes. The visual acuities of the two eyes were suddenly\\u000a lost to 5\\/50. The fluorescein angiography, electroretinograms (ERGs) and pattern evoked potentials (PVEPs) had been tested\\u000a at the acute and the recovery stage of the disease. At the onset of the disease, fluorescein angiography showed obvious dye\\u000a leakage

Guangwei Luo; Peizeng Yang; Shizhou Huang; Futian Jiang; Feng Wen

1998-01-01

204

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

NASA Astrophysics Data System (ADS)

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

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

2009-05-01

205

Coffee shade with Mimosa scabrella Benth. for frost protection in southern Brazil  

Microsoft Academic Search

Damage by radiative frosts is a major limiting factor for coffee cultivation in southern Brazil (south of 20 S latitude).\\u000a The use of Mimosa scabrella (bracatinga) as a shade tree, to modify the local energy balance and thus prevent damage to the coffee plants, has been evaluated\\u000a from 1986 to 1994. The study was carried out near Londrina, Parana State

P. H. Caramori; A. Androcioli Filho; A. C. Leal

1996-01-01

206

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

207

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

208

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

209

Seasonal to decadal variations of water vapor in the tropical lower stratosphere observed with balloon-borne cryogenic frost point hygrometers  

NASA Astrophysics Data System (ADS)

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 (10°N) 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.; VöMel, H.; Hasebe, F.; Shiotani, M.; Ogino, S.-Y.; Iwasaki, S.; Nishi, N.; Shibata, T.; Shimizu, K.; Nishimoto, E.; Valverde Canossa, J. M.; Selkirk, H. B.; Oltmans, S. J.

2010-09-01

210

Interaction between cold night skies, frost occurrence and seasonal growth: A coupling between atmospheric temperature and plant ecology  

SciTech Connect

The occurrence of nighttime frost is important to the ecophysiology and seasonal growth of alpine/subalpine plants. Frost episodes can be the direct result of the net loss of longwave energy from the leaf to the cold night sky, even when ambient air temperatures are above freezing. This microclimate scenario may be particularly characteristic of the last spring frosts and the first fall frosts, a primary determinant of the length of the seasonal growth period. Using a leaf energy-balance approach, we found that low upper-hemisphere infrared radiation can reduce nighttime leaf temperature (T[sub L]) up to 6[degrees]C below air temperature. Furthermore, this depression in T[sub L] resulted in a substantial increase in the frequency and duration of frost events, and an ultimate shortening of the seasonal growth period of over 30%. However, the seasonal effect on vegetative growth and reproductive effort depends greatly on such plant properties as leaf size, microsite selection, and plant height. A direct and sensitive coupling between atmospheric thermal radiation and plant ecology is apparent, along with corresponding implications associated with atmospheric warming.

Jordan, D.N.; Smith, W.K. (Univ. of Wyoming, Laramie (United States))

1993-06-01

211

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

2012-06-15

212

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

SciTech Connect

The Hapke (1986) equation is presently fit to ascertain the single-scattering albedo of the icy satellites of Uranus and Neptune and the one-term Henyey-Greenstein particle-phase function g for each of the Middleton and Mungall (1952) goniophotometric data samples. There emerge both very high single-scattering albedos and strongly forward-scattering particle phase functions; while these are in keeping with Mie theory-based theoretical considerations, they contrast with the observed backscattering behavior of icy satellites. It is suggested the icy satellite frost grains are aggregated into particles of complex texture, which produce the unusual backscattering behavior. 26 refs.

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

1990-12-01

213

Solar Reflectance Measurements of Calibration Targets and Martian South Polar Frosts  

NASA Astrophysics Data System (ADS)

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

Ono, Adrienne Momilani

214

Construction of the underground structures of a hydroelectric station under perrenial frost conditions  

Microsoft Academic Search

Conclusions  \\u000a \\u000a \\u000a \\u000a 1. \\u000a \\u000a The perennial frost condition of the rock has both a favorable and unfavorable effect on carrying out underground work. The\\u000a facilitating conditions are: greater bearing capacity and stability of the frozen rock in the absence of water inflow within\\u000a the frozen zone. Conditions impeding underground work are: the sharp drop in bearing capacity and stability of the rock

G. Ya. Gevirts; V. L. Chelnokov; É. E. Khdoshoyants

1968-01-01

215

Significance of Frost Action and Surface Soil Characteristics to Wind Erosion at Rocky Flats, Colorado. Second Progress Report, October 1, 1975--May 30, 1976.  

National Technical Information Service (NTIS)

This report summarizes information on soil frost effects collected on Rocky Flats during the 1975-1976 winter. On a broad scale, work on soil textures at and just below the ground surface corroborates the conclusion reached earlier that the general frost ...

N. Caine P. Morin

1976-01-01

216

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

217

Frosted branch angiitis as a result of immune recovery uveitis in a patient with cytomegalovirus retinitis  

PubMed Central

Background Since the introduction of Highly Active Antiretroviral Therapy (HAART), AIDs related morbidity and mortality have declined. However, the advent of HAART brought the new problem of immune recovery inflammatory syndrome. Cytomegalovirus retinitis remains the most common cause of visual loss in AIDs patients. Some patients with cytomegalovirus retinitis who experienced immune recovery as a consequence of HAART develop worsening of visual symptoms from immune recovery uveitis (IRU). Findings We report a case of cytomegalovirus retinitis and AIDs who developed an unusual presentation of IRU after the initiation of HAART. A 40-year-old woman presented with a history of blurry vision in the right eye. She was diagnosed with human immunodeficiency virus infection and cytomegalovirus retinitis, treated with intravitreal injections of ganciclovir. The retinitis improved. One week after HAART initiation, she developed IRU, characterized by increased intraocular inflammation, extensive frosted branch angiitis and cystoid macular edema. The CD4+ T lymphocyte count increased from 53 to 107 cells/mm3. Systemic prednisolone with continuation of HAART and intravitreal injections of ganciclovir were given with significant improvement. Conclusion Atypical presentation of IRU, characterized by extensive frosted branch angiitis and increased intraocular inflammation may occur in immunocompromised patients with cytomegalovirus retinitis who experienced immune recovery. The time from HAART initiation to develop IRU may vary from days to months. This case demonstrated a very rapidly developed IRU which should be recognized and appropriately managed to avoid permanent damage of the eye.

2013-01-01

218

Glazed Frost  

Microsoft Academic Search

REFERRING to the letters of Mr. Charles Harding and Prof. Meldola on the phenomenon of freezing rain, I remember the occasion referred to; it was on January 11, 1868, when trees were covered with ice by rain which froze instantly on touching a solid object. In driving through Richmond Park I noticed the branches bending under a weight of clear

ROLLO RUSSELL R

1912-01-01

219

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

PubMed Central

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

Feldman, Laurie Beth; Martin, Fermin Moscoso del Prado

2013-01-01

220

Wind Tunnel Investigation of Simulated Hoar Frost on a 2 Dimensional Wing Section with and Without High Lift Devices.  

National Technical Information Service (NTIS)

The effect of simulated hoar frost on the lift and drag characteristics of a two-dimensional wing section with and without high lift devices was investigated in a wind tunnel. Three wing configurations were tested. Three different grain size grinding pape...

B. L. Ljungstroem

1972-01-01

221

Studies of the Depth and Duration of Ground Frost of Peat Production Areas in Sweden and Finland.  

National Technical Information Service (NTIS)

A careful registration of the depth of the ground frost, snow, water level, and soil temperature, was done during the winter 1985/86, at eight different peat production areas in Sweden. At one of the places, Traeskmyran, a larger registration was carried ...

K. Dryler P. Frilander H. Niittylae A. Leinonen

1988-01-01

222

Cassini Measurements Show Seasonal O_2 — CO_2 Exospheres and Possible Seasonal CO_2 Frosts at Rhea and Dione  

NASA Astrophysics Data System (ADS)

We will present the recent finding of an O_2-CO_2 Dione exosphere by Cassini, and discuss modeling of the different north-south CO_2 density at Rhea, and the CO_2 abundance at Dione, indicating strongly seasonal CO_2 exospheres and polar frosts.

Teolis, B. D.; Waite, J. H.

2012-03-01

223

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

224

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

PubMed

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

Dumont, Estelle; Fontaine, Véronique; Vuylsteker, Christophe; Sellier, Hélène; Bodèle, Sylvie; Voedts, Najia; Devaux, Rosemonde; Frise, Marlène; Avia, Komlan; Hilbert, Jean-Louis; Bahrman, Nasser; Hanocq, Eric; Lejeune-Hénaut, Isabelle; Delbreil, Bruno

2009-03-26

225

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

226

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

227

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

228

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

Microsoft Academic Search

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

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

2007-01-01

229

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

Microsoft Academic Search

We compare coincident, balloon-borne, in situ measurements of temperature and pressure by two radiosondes (Vaisala RS92, Intermet iMet-1-RSB) and measurements of relative humidity (RH) by Vaisala RS92 sondes and frost point hygrometers. Data from a total of 28 balloon flights with mixed payloads are analyzed in 1-km altitude bins to quantify measurement biases between sensors and how they vary with

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

2011-01-01

230

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 Brandsæter; Thomas Smeby; Anne Marte Tronsmo; Jan Netland

231

Using Synchrotron Radiation-Based Infrared Microspectroscopy to Reveal Microchemical Structure Characterization: Frost Damaged Wheat vs. Normal Wheat  

PubMed Central

This study was conducted to compare: (1) protein chemical characteristics, including the amide I and II region, as well as protein secondary structure; and (2) carbohydrate internal structure and functional groups spectral intensities between the frost damaged wheat and normal wheat using synchrotron radiation-based Fourier transform infrared microspectroscopy (SR-FTIRM). Fingerprint regions of specific interest in our study involved protein and carbohydrate functional group band assignments, including protein amide I and II (ca. 1774–1475 cm?1), structural carbohydrates (SCHO, ca. 1498–1176 cm?1), cellulosic compounds (CELC, ca. 1295–1176 cm?1), total carbohydrates (CHO, ca. 1191–906 cm?1) and non-structural carbohydrates (NSCHO, ca. 954–809 cm?1). The results showed that frost did cause variations in spectral profiles in wheat grains. Compared with healthy wheat grains, frost damaged wheat had significantly lower (p < 0.05) spectral intensities in height and area ratios of amide I to II and almost all the spectral parameters of carbohydrate-related functional groups, including SCHO, CHO and NSCHO. Furthermore, the height ratio of protein amide I to the third peak of CHO and the area ratios of protein amide (amide I + II) to carbohydrate compounds (CHO and SCHO) were also changed (p < 0.05) in damaged wheat grains. It was concluded that the SR-FTIR microspectroscopic technique was able to examine inherent molecular structure features at an ultra-spatial resolution (10 × 10 ?m) between different wheat grains samples. The structural characterization of wheat was influenced by climate conditions, such as frost damage, and these structural variations might be a major reason for the decreases in nutritive values, nutrients availability and milling and baking quality in wheat grains.

Xin, Hangshu; Zhang, Xuewei; Yu, Peiqiang

2013-01-01

232

Dynamic simulation and performance investigation of no-frost refrigerator: Part II system simulation and performance analysis  

Microsoft Academic Search

The methodology for modeling no-frost refrigerator is described based on the component models developed in Part I, and then,\\u000a system simulation is applied to a BCD-235W refrigerator-freezer (RF). Experiments are carried out to study “pull-down” and\\u000a steady-state performance of the RF, and to determine how the experiment and simulation temperature stack up against each other.\\u000a Good match is found between

Xiu-ping Su; Jiang-ping Chen; Zhi-jiu Chen; Xiao-tian Zhou

2009-01-01

233

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

Microsoft Academic Search

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

Gunnar Öquist; Gunilla Malmberg

1989-01-01

234

Frost tolerance of two-year-old Picea glauca seedlings grown under different irrigation regimes in a forest nursery  

Microsoft Academic Search

This study examined the impact of increased irrigation efficiency on the hardening and frost tolerance of 2-year-old containerized white spruce seedlings in the context of groundwater protection, irrigation management and the maintenance of seedling quality in northern climates. The seedlings were grown under three different irrigation regimes (IR ? 30%, 40% and 55% v\\/v; cm3 H2O\\/cm 3 substrate) and were

Sylvie Carles; MOHAMMED S. LAMHAMEDI; DEBRA C. STOWE; HANK A. MARGOLIS; PIERRE Y. BERNIER; Linda Veilleux; Bertrand Fecteau

2008-01-01

235

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

Microsoft Academic Search

Here we present extensive observations of stratospheric and upper tropospheric water vapor using the balloon-borne Cryogenic Frost point Hygrometer (CFH) in support of the Aura Microwave Limb Sounder (MLS) satellite instrument. Coincident measurements were used for the validation of MLS version 1.5 and for a limited validation of MLS version 2.2 water vapor. The sensitivity of MLS is on average

H. Vömel; J. E. Barnes; R. N. Forno; M. Fujiwara; F. Hasebe; S. Iwasaki; R. Kivi; N. Komala; E. Kyrö; T. Leblanc; B. Morel; S.-Y. Ogino; W. G. Read; S. C. Ryan; S. Saraspriya; H. Selkirk; M. Shiotani; J. Valverde Canossa; D. N. Whiteman

2007-01-01

236

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

Microsoft Academic Search

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

H. Vömel; V. Yushkov; S. Khaykin; L. Korshunov; E. Kyrö; R. Kivi

2007-01-01

237

Predicting minimum temperature (especially frost) by the evening wet-bulb at Blue Hill, Mass. in spring  

Microsoft Academic Search

The observations of ten Aprils (1941 50) at Blue Hill have been analyzed, and it has been found that frost (night minimum temperature ≦32° F) ( T) can be predicted on the basis of the 19h wet-bulb temperature ( ti) by the formula: T=ti-k, in which k is found to be 1.8 F deg. in clear weather and 2.1 F

Photios P. Karapiperis

1953-01-01

238

Predicting minimum temperature (especially frost) by the evening wet-bulb at Blue Hill, Mass. in spring  

Microsoft Academic Search

Summary The observations of ten Aprils (1941–50) at Blue Hill have been analyzed, and it has been found that frost (night minimum temperature ?32° F) (T) can be predicted on the basis of the 19h wet-bulb temperature (ti) by the formula:T=ti?k, in whichk is found to be 1.8 F deg. in clear weather and 2.1 F deg. in cloudy. The

PHOTIOS P. KARAPIPEIIIS

1953-01-01

239

Numerical investigation of the stable nocturnal boundary layer  

NASA Astrophysics Data System (ADS)

The governing equations for the wind field and temperature field within the flat nocturnal atmospheric boundary layer (FNABL, (30)) are a highly nonlinear system of parabolic PDEs. This system is discretized into a crude two-layer numerical model via the finite difference approximation and the Monin-Obukhov similarity theory ( (22)), and analyzed as a set of ODEs. The steady state problem is also transformed into an equivalent system of first order ODEs and then discretized into a very accurate 'multi-layer' model using the orthogonal collocation method ( (12)). Some numerical techniques for nonlinear problems such as numerical continuation and bifurcation analysis are used to study the steady state solutions as some physical parameters vary. The resulting bifurcation diagrams from the two layer and multilayer models have qualitatively similar behavior. This implies that the two-layer model, though mathematically crude, does capture some essential features of the original system. Time dependent solutions of the two layer model are computed via the fourth-order Runge-Kutta technique, for various combinations of parameters, and they match and support related bifurcation diagrams. Physically realistic wind and temperature profiles over the boundary layer are computed from the 'multi-layer' model. Our results imply that operational application of this type of model of frost or pollution dispersion may not be made with confidence for certain parameter regimes, and they have important implications for the predictability of the nocturnal boundary layer for frost prediction or pollution dispersion. Space discretization for simple parabolic PDEs from an AUTO demo via pseudospectral method with Chebyshev basis functions is very accurate, and seems promising for future application to our problem.

Shi, Xingzhong

1997-10-01

240

Peripheral capillary nonperfusion and full-field electroretinographic changes in eyes with frosted branch-like appearance retinal vasculitis  

PubMed Central

We report a patient with frosted branch-like appearance retinal vasculitis associated with peripheral capillary nonperfusion and full-field electroretinographic changes. A 62-year-old man presented with sudden bilateral decreased vision accompanied by headaches. His best-corrected visual acuity was 0.01 in both eyes. Fundus examination and fluorescein angiography showed bilateral frosted branch-like appearance retinal vasculitis, and spectral-domain optical coherence tomography showed severe macular edema in both eyes. The cerebrospinal fluid analyses showed an increased lymphocyte count and protein levels. He was treated with systemic corticosteroid therapy, and his best-corrected visual acuity improved to 0.8 OD and 1.0 OS at 6 months after onset. However, fluorescein angiography showed a lack of capillary perfusion in the periphery, and the oscillatory potentials on full-field electroretinography were severely reduced in both eyes. These findings indicated extensive retinal ischemia and inner retinal dysfunction, and that fluorescein angiography and full-field electroretinograms can be useful during follow-up of eyes with frosted branch-like appearance retinal vasculitis.

Matsui, Yoshitsugu; Tsukitome, Hideyuki; Uchiyama, Eriko; Wada, Yuko; Yagi, Tatsuya; Matsubara, Hisashi; Kondo, Mineo

2013-01-01

241

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

242

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

243

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

2012-05-23

244

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

245

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

246

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

2013-04-05

247

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

2013-01-14

248

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

NASA Astrophysics Data System (ADS)

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

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

2011-07-01

249

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

250

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

PubMed

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

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

2013-04-12

251

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

2013-08-11

252

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

SciTech Connect

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

Cwirzen, Andrzej; Penttala, Vesa

2005-04-01

253

The rice Osmyb4 gene enhances tolerance to frost and improves germination under unfavourable conditions in transgenic barley plants.  

PubMed

The Osmyb4 rice gene, coding for a transcription factor, proved to be efficient against different abiotic stresses as a trans(cis)gene in several plant species, although the effectiveness was dependent on the host genomic background. Eight barley transgenic lines carrying the rice Osmyb4 gene under the control of the Arabidopsis cold inducible promoter cor15a were produced to test the efficiency of this gene in barley. After a preliminary test, the best performing lines were subjected to freezing at -11°C and -12°C. Frost tolerance was assessed measured the F(v)/F(m) parameter widely used to indicate the maximum quantum yield of photosystem II photochemistry in the dark adapted state. Three transgenic lines showed significantly increased tolerance. These selected lines were further studied under a complex stress applying cold and hypoxia at germinating stage. In these conditions the three selected transgenic lines outperformed the wild type barley in terms of germination vigour. The transgenic plants also showed a significant modification of their metabolism under cold/hypoxia conditions as demonstrated through the assessment of the activity of key enzymes involved in anoxic stress response. None of the transgenic lines showed dwarfism, just a slight retarded growth. These results provide evidence that the cold dependent expression of Osmyb4 can efficiently improved frost tolerance and germination vigour at low temperature without deleterious effect on plant growth. PMID:22246661

Soltész, Alexandra; Vágújfalvi, Attila; Rizza, Fulvia; Kerepesi, Ildikó; Galiba, Gábor; Cattivelli, Luigi; Coraggio, Immacolata; Crosatti, Cristina

2012-01-14

254

Synergistic effect of vegetation and air temperature changes on soil water content in alpine frost meadow soil in the permafrost region of Qinghai-Tibet  

Microsoft Academic Search

Seasonal changes over 2 years (2004-2006) in soil moisture content (? v) of frozen alpine frost meadow soils of the Qinghai- Tibet plateau permafrost region under three different levels of vegetation cover were investigated. Vegetation cover and air temperature changes had significant effects (synergistic effect) onv and its distribution in the soil profile. During periods of soil freezing or thawing,

Genxu Wang; Yuanshou Li; Hongchang Hu; Yibo Wang

2008-01-01

255

The temperature dependence of frost flower growth on laboratory sea ice and the effect of the flowers on infrared observations of the surface  

Microsoft Academic Search

This paper describes a laboratory study of frost flower growth on young sea ice at different temperatures and the effect of these flowers on the surface temperature observed with an infrared radiometer. The flowers grew on sea ice which formed in a salt water tank at room temperatures of -20, -24, and -30°C, with an additional experiment at -16°C, where

Seelye Martin; Yanling Yu; Robert Drucker

1996-01-01

256

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

257

Seasonal to decadal variations of water vapor in the tropical lower stratosphere observed with balloon-borne cryogenic frost point hygrometers  

Microsoft Academic Search

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

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

2010-01-01

258

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  

Microsoft Academic Search

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)

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

2010-01-01

259

Effects of three plant growth regulators on growth, morphology, water relations, and frost resistance in lemonwood (Pittosporum eugenioides A.Cunn)  

Microsoft Academic Search

Pittosporum eugenioides is a native ornamental species with a wide distribution throughout New Zealand. The effects of the application of two plant hormones (gibberellic acid and abscisic acid) and a gibberellin biosynthesis inhibitor (paclobutrazol) on the growth and development, frost resistance, and water loss on two-year old seedlings of P. eugenioides were studied.Gibberellic acid increased plant growth, stem diameter, and

Patrick J. Dwyer; Peter Bannister; Paula E. Jameson

1995-01-01

260

An Experiment on the Electrification and Growth of Frost Needles on the Surface of Frozen Water Drops in an Electric Field.  

National Technical Information Service (NTIS)

The paper describes an experiment on the electrification of frost needles during their processes of growth on the surface of frozen water drops in an electric field. The intensity of electrification is found to vary between 0.10 and .01 e.s.u., which is o...

C. Xiao-ping C. Qian X. Yu-ren

1967-01-01

261

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

262

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

ERIC Educational Resources Information Center

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

Carr, John C.

263

Homogenization of Thin Isotropic Layers.  

National Technical Information Service (NTIS)

Homogenization of extremely thin dielectric layers is considered. Special attention is focused on the fact that the permittivity near the surface of the slab is affected by the presence of the boundary. This makes the effective permittivity inhomogeneous,...

S. A. Tretyakov A. H. Sihvola

1998-01-01

264

Frost-cracking control on catchment denudation rates: Insights from in situ produced 10Be concentrations in stream sediments (Ecrins-Pelvoux massif, French Western Alps)  

NASA Astrophysics Data System (ADS)

The potential tectonic and climatic controls on erosion rates in the European Alps and other mountain belts remain strongly debated. We have quantified denudation rates at catchment scales using in situ produced cosmogenic nuclides ( 10Be) in stream sediments, sampled at the outlets of twelve variously sized (27-1072 km 2) catchments of the Ecrins-Pelvoux massif (French Western Alps), with average elevations ranging from 1700 to 2800 m. Spatially-averaged denudation rates, corrected for potential shielding by Little Ice Age glaciers, vary from 0.27 ± 0.05 to 1.07 ± 0.20 mm/yr on millennial timescales. Our results exhibit a correlation ( ?2 = 0.56) between denudation rate and mean catchment elevation, in the absence of significant correlation with any other morphometric parameters (relief, slope, catchment size, hypsometry, etc). Although such variations in erosion rates have been previously linked to variations in tectonic uplift rate, the relatively small size and tectonic homogeneity of our study area exclude a strongly variable tectonic control. We interpret the increase in erosion rate with elevation as the effect of frost-controlled processes, which are strongly temperature-dependent. We use a one-dimensional heat-flow model driven by high-resolution instrumental temperature records from the study area to correlate the variability in denudation rates with the integral of the absolute temperature gradient within the frost-cracking window (- 3 to - 8 °C), a proxy of the frost-cracking intensity, for each catchment. The results imply that the efficiency of frost cracking constitutes a major control on catchment-wide denudation rates in the study area, explaining more than half the measured variability in these rates. Our study shows that present-day denudation of the Ecrins-Pelvoux massif is controlled by a climatically driven factor and suggests that frost-cracking processes impose an important control on the post-glacial topographic evolution of mid-latitude mountain belts.

Delunel, Romain; van der Beek, Peter A.; Carcaillet, Julien; Bourlès, Didier L.; Valla, Pierre G.

2010-04-01

265

Embodied Social Presence Theory  

Microsoft Academic Search

We discuss and reflect on the importance of embodiment, context, and spatial proximity as they pertain to the sense of presence obtained by individuals in virtual environments. We propose Embodied Social Presence (ESP) Theory, a theoretical framework that focuses on the embodied virtual representation (i.e., the avatar) as the nexus of activity in social interaction within virtual worlds. We review

Brian E. Mennecke; Janea L. Triplett; Lesya M. Hassall; Zayira Jordan Conde

2010-01-01

266

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

Microsoft Academic Search

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

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

2002-01-01

267

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

2013-09-10

268

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

2013-01-11

269

Stratospheric water vapor measurement in the tropical zone by means of a frost point hygrometer on board long-duration balloons  

Microsoft Academic Search

Two long-duration balloon flights were performed during austral summer in the southern hemisphere tropical zone, between 23°S and 10°S, for stratospheric water vapor measurement by means of a frost point hygrometer. The observations show a mixing ratio minimum of about 3.5 ppmv near 50 hPa that corroborates the existence of the hygropause in low-latitude areas. Also observed was the approach

Joëlle Ovarlez

1991-01-01

270

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

271

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

Microsoft Academic Search

The first experiments demonstrating exhaust of thermal helium in a diverted, H-mode deuterium plasma have been performed on the DIII-D tokamak. The helium, introduced via gas puffing, is observed to reach the plasma core, and then is readily removed form the plasma with a time constant of ~10-20 energy-confinzement times by an in-vessel cryopump conditioned with argon frosting. Detailed analysis

M. R. Wade; D. L. Hillis; J. T. Hogan; M. A. Mahdavi; R. Maingi; W. P. West; N. H. Brooks; K. H. Burrell; R. J. Groebner; G. L. Jackson; C. C. Klepper; G. Laughon; M. M. Menon; P. K. Mioduszewski

1995-01-01

272

Minimal response in watershed nitrate export to severe soil frost raises questions about nutrient dynamics in the Hubbard Brook experimental forest  

Microsoft Academic Search

Experimental and theoretical work emphasize the role of plant nutrient uptake in regulating ecosystem nutrient losses and\\u000a predict that forest succession, ecosystem disturbance, and continued inputs of atmospheric nitrogen (N) will increase watershed\\u000a N export. In ecosystems where snowpack insulates soils, soil-frost disturbances resulting from low or absent snowpack are\\u000a thought to increase watershed N export and may become more

Kristin E. Judd; Gene E. Likens; Donald C. Buso; Amey S. Bailey

273

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

274

Simulation of spring snowmelt runoff by considering micro-topography and phase changes in soil layer  

NASA Astrophysics Data System (ADS)

The NICE model was extended to include the effect of the micro-topography in slope and shading characteristics and the phase changes in soil moisture on snow/frost depths and snowmelt runoff by combining the land-surface, the multi-layer runoff, and the groundwater flow models (NICE-SNOW). The model was applied to the upstream regions of shrinking Kushiro Mire in the invasion of alder, where the spring runoff affects greatly the annual sediment and nutrient transports because the spring flood continues in longer time than that in typhoon seasons. The simulation reproduced excellently the observed values of annual river discharge including snowmelt runoff with the greater time-to-peak of runoff than in snow-free period, in addition to snow depth, frost depth, soil temperature, soil moisture, and groundwater level, by conducting the quantitative assessment of goodness-of-fit and parameter sensitivity analysis. We quantified that the mechanism of spring snowmelt runoff is related to changes in micro-topography, soil structure, soil temperature, soil moisture, and groundwater flow. The model shows that the local effect of snow depth and the frost depth disappears in the snowmelt runoff discharge of catchment in the same way as some previous researches though they are very important as water resources of catchment. After the frozen soil restricts the infiltration in the coldest part of winter, the thawed soil increases the pore size in the early spring. The NICE-SNOW could explain the snowmelt flood continues a longer time than that in the typhoon period because some part of meltwater flows as an intermediate flow in the partially-thawed hillslope soil layer. This is also related to the simulation result that more than half of total soil moisture stays unfrozen at some places even in winter periods, which indicates that there is a high degree of spatial heterogeneity of frozen ground.

Nakayama, T.; Watanabe, M.

2006-08-01

275

Layer-by-layer doping of few-layer graphene film.  

PubMed

We propose a new method of layer-by-layer (LbL) doping of thin graphene films. Large area monolayer graphene was synthesized on Cu foil by using the chemical vapor deposition method. Each layer was transferred on a polyethylene terephthalate substrate followed by a salt-solution casting, where the whole process was repeated several times to get LbL-doped thin layers. With this method, sheet resistance was significantly decreased up to approximately 80% with little sacrifice in transmittance. Unlike samples fabricated by topmost layer doping, our sample shows better environmental stability due to the presence of dominant neutral Au atoms on the surface which was confirmed by angle-resolved X-ray photoelectron spectroscopy. The sheet resistance of the LbL-doped four-layer graphene (11 x 11 cm(2)) was 54 Omega/sq at 85% transmittance, which meets the technical target for industrial applications. PMID:20731442

Güne?, Fethullah; Shin, Hyeon-Jin; Biswas, Chandan; Han, Gang Hee; Kim, Eun Sung; Chae, Seung Jin; Choi, Jae-Young; Lee, Young Hee

2010-08-24

276

The male presence  

Microsoft Academic Search

Male domination of the news media begins, very simply, with numerical superiority. The male presence in the news industry is immense and far?reaching. Ninety?four percent of top management positions in U.S. news media are occupied by men. The top five executives at Capital Cities, ABC, Times Mirror, CBS, Knight?Ridder, the New York Times, and Turner Broadcasting System are all men.

David Croteau; William Hoynes

1993-01-01

277

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

278

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

279

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

NASA Astrophysics Data System (ADS)

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

Inouye, D. W.

2004-12-01

280

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

PubMed

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

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

2011-06-03

281

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

282

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

283

Lava Layering  

NSDL National Science Digital Library

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

284

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

USGS Publications Warehouse

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

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

2007-01-01

285

Engineering Presence: an Experimental Strategy  

Microsoft Academic Search

Over the centuries artists have developed a range of techniques for inducing a sense of presence in an audience. The goals of these are however essentially open-ended. The presence engineer, on the other hand aims to use presence for practical applications. After summarizing ways in which presence can be detected and measured this paper places 21 st century presence techniques

Fabrizio DAVIDE; Richard WALKER

286

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 what questionswhat are the causes and effects of presence?rather than the why question. The current paper tries

Kwan Min Lee

2004-01-01

287

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

NASA Astrophysics Data System (ADS)

Here we present extensive observations of stratospheric and upper tropospheric water vapor using the balloon-borne Cryogenic Frost point Hygrometer (CFH) in support of the Aura Microwave Limb Sounder (MLS) satellite instrument. Coincident measurements were used for the validation of MLS version 1.5 and for a limited validation of MLS version 2.2 water vapor. The sensitivity of MLS is on average 30% lower than that of CFH, which is fully compensated by a constant offset at stratospheric levels but only partially compensated at tropospheric levels, leading to an upper tropospheric dry bias. The sensitivity of MLS observations may be adjusted using the correlation parameters provided here. For version 1.5 stratospheric observations at pressures of 68 hPa and smaller MLS retrievals and CFH in situ observations agree on average to within 2.3% ± 11.8%. At 100 hPa the agreement is to within 6.4% ± 22% and at upper tropospheric pressures to within 23% ± 37%. In the tropical stratosphere during the boreal winter the agreement is not as good. The "tape recorder" amplitude in MLS observations depends on the vertical profile of water vapor mixing ratio and shows a significant interannual variation. The agreement between stratospheric observations by MLS version 2.2 and CFH is comparable to the agreement using MLS version 1.5. The variability in the difference between observations by MLS version 2.2 and CFH at tropospheric levels is significantly reduced, but a tropospheric dry bias and a reduced sensitivity remain in this version. In the validation data set a dry bias at 177.8 hPa of -24.1% ± 16.0% is statistically significant.

VöMel, H.; Barnes, J. E.; Forno, R. N.; Fujiwara, M.; Hasebe, F.; Iwasaki, S.; Kivi, R.; Komala, N.; Kyrö, E.; Leblanc, T.; Morel, B.; Ogino, S.-Y.; Read, W. G.; Ryan, S. C.; Saraspriya, S.; Selkirk, H.; Shiotani, M.; Valverde Canossa, J.; Whiteman, D. N.

2007-12-01

288

Ice nucleation temperature of individual leaves in relation to population sizes of ice nucleation active bacteria and frost injury.  

PubMed

Ice nucleation temperatures of individual leaves were determined by a tube nucleation test. With this assay, a direct quantitative relationship was obtained between the temperatures at which ice nucleation occurred on individual oat (Avena sativa L.) leaves and the population sizes of ice nucleation active (INA) bacteria present on those leaves. In the absence of INA bacteria, nucleation of supercooled growth-chamber grown oat leaves did not occur until temperatures were below approximately -5 degrees C. Both nucleation temperature and population size of INA bacteria were determined on the same individual, field-grown oat leaves. Leaves with higher ice nucleation temperatures harbored larger populations of INA bacteria than did leaves with lower nucleation temperatures. Log(10) mean populations of INA bacteria per leaf were 5.14 and 3.51 for leaves with nucleation temperatures of -2.5 degrees C and -3.0 degrees C, respectively. Nucleation frequencies (the ratio of ice nuclei to viable cells) of INA bacteria on leaves were lognormally distributed. Strains from two very different collections of Pseudomonas syringae and one of Erwinia herbicola were cultured on nutrient glycerol agar and tested for nucleation frequency at -5 degrees C. Nucleation frequencies of these bacterial strains were also lognormally distributed within each of the three sets. The tube nucleation test was used to determine the frequency with which individual leaves in an oat canopy harbored large populations of INA bacteria throughout the growing season. This test also predicted relative frost hazard to tomato (Lycopersicon esculentum Mill) plants. PMID:16664039

Hirano, S S; Baker, L S; Upper, C D

1985-02-01

289

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

SciTech Connect

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

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

1995-04-03

290

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

291

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

292

Enrichment in Specific Soluble Sugars of Two Eucalyptus Cell-Suspension Cultures by Various Treatments Enhances Their Frost Tolerance via a Noncolligative Mechanism.  

PubMed Central

A cell-suspension culture obtained from the hybrid Eucalyptus gunnii/Eucalyptus globulus was hardened by exposure to lower temperatures, whereas in the same conditions cells from a hybrid with a more frost-sensitive genotype, Eucalyptus cypellocarpa/Eucalyptus globulus, were not able to acclimate. During the cold exposure the resistant cells accumulated soluble sugars, in particular fructose and sucrose, with a limited increase in cell osmolality. In contrast, the cell suspension that was unable to acclimate did not accumulate soluble sugars in response to the same cold treatment. To an extent similar to that induced after a cold acclimation, frost-hardiness of the cells increased after a 14-h incubation with specific soluble sugars such as sucrose, raffinose, fructose, and mannitol. Such hardening was also observed for long-term cultures in mannitol-enriched medium. This cryoprotective effect of sugars without exposure to lower temperatures was observed in both the resistant and the sensitive genotypes. Mannitol was one of the most efficient carbohydrates for the cryoprotection of eucalyptus. The best hardiness (a 2.7-fold increase in relative freezing tolerance) was obtained for the resistant cells by the cumulative effect of cold-induced acclimation and mannitol treatment. This positive effect of certain sugars on eucalyptus freezing tolerance was not colligative, since it was independent of osmolality and total sugar content.

Travert, S.; Valerio, L.; Fouraste, I.; Boudet, A. M.; Teulieres, C.

1997-01-01

293

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, Akos; Vágújfalvi, Attila; Burke, Adrienne; Garland-Campbell, Kimberley; Galiba, Gábor; Dubcovsky, Jorge

2013-07-25

294

Turbulent boundary layer on a moving surface  

Microsoft Academic Search

An integral and a numerical method are proposed for calculating the turbulent boundary layer on a moving surface (flap) in the presence of a longitudinal pressure gradient under conditions of monotonic velocity profiles. The integral method is a modification of Fediaevskii's et al. (1973) integral method (for calculating turbulent boundary layers in an incompressible fluid) to include an airfoil moving

A. S. Ginevskii; G. N. Emalianova; A. V. Kolesnikov

1976-01-01

295

Boundary layers on a rotating disk  

Microsoft Academic Search

A numerical method is proposed for predicting the three-dimensional boundary layer that develops on a rotating disk in the presence of a steady incompressible axisymmetric flow. The method employs the eddy viscosity concept to model the Reynolds shear stress terms in the boundary layer equations. The governing nonlinear difference equations are solved by Newton's method using an efficient block-tridiagonal factorization

Tuncer Cebeci; D. E. Abbott

1975-01-01

296

Problems of matter-antimatter boundary layers  

Microsoft Academic Search

This paper outlines the problems of the quasi-steady matter-antimatter boundary layers discussed in Klein-Alfvén's cosmological theory, and a crude model of the corresponding ambiplasma balance is presented:(i)At interstellar particle densities, no well-defined boundary layer can exist in presence of neutral gas, nor can such a layer be sustained in an unmagnetized fully ionized ambiplasma.(ii)Within the limits of applicability of the

B. Lehnert

1977-01-01

297

Presence: concept, determinants, and measurement  

NASA Astrophysics Data System (ADS)

The concept of presence, i.e. the sensation of 'being there' in a mediated environment, has received substantial attention from the virtual reality community, and is becoming increasingly relevant both to broadcasters and display developers. Although research into presence is still at an early stage of development, there is a consensus that presence has multiple determinants. To identify and test which parameters affect presence, a reliable, robust and valid means of measuring presence is required. In this paper, we describe the categories of factors thought to have an impact on presence. Furthermore, we present an overview of various approaches taken to measuring presence, which can be divided into two general categories: subjective measures and objective corroborative measures. Since presence is a subjective experience, the most direct way of assessment is through users' subjective report. This approach has serious limitations however, and should be used judiciously. Objective measures, such as postural, physiological or social responses to media, can be used to corroborate subjective measures, thereby overcoming some of their limitations. At present, the most promising direction for presence measurement is to develop and use an aggregate measure of presence that is comprised of both subjective and objective components, tailored to the specific medium under study.

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

2000-06-01

298

Achieving Presence through Evoked Reality  

PubMed Central

The sense of “Presence” (evolving from “telepresence”) has always been associated with virtual reality research and is still an exceptionally mystifying constituent. Now the study of presence clearly spans over various disciplines associated with cognition. This paper attempts to put forth a concept that argues that it’s an experience of an “Evoked Reality (ER)” (illusion of reality) that triggers an “Evoked Presence (EP)” (sense of presence) in our minds. A Three Pole Reality Model is proposed to explain this phenomenon. The poles range from Dream Reality to Simulated Reality with Primary (Physical) Reality at the center. To demonstrate the relationship between ER and EP, a Reality-Presence Map is developed. We believe that this concept of ER and the proposed model may have significant applications in the study of presence, and in exploring the possibilities of not just virtual reality but also what we call “reality.”

Pillai, Jayesh S.; Schmidt, Colin; Richir, Simon

2013-01-01

299

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

Microsoft Academic Search

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

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

300

Layer rigidity, anharmonicity and the layered perovskites  

Microsoft Academic Search

We have measured the normalized basal-spacing of the layered perovskites Cs_xRb_1-xCa_2Nb_3O_10 over the range, 0 <= x <= 1 using high resolution x-ray diffraction. The results have been compared with previous measurements on other layered solids.(S. Lee et al., Phys. Rev. Letters 62), 3066 (1989). The host layers of the studied perovskites consist of three sheets of interconnected NbO6 octahedra.

S. A. Solin; D. R. Hines; Allan J. Jacobson; S. D. Mahanti

1996-01-01

301

MAC Layer and Coloring  

Microsoft Academic Search

The Medium Access Layer is part of the Data Link Layer (layer 2 of the OSI model) and sits directly on top of the Physical Layer (layer 1). Its purpose is to manage access to the\\u000a shared wireless medium. If transmissions from two different nodes arrive simultaneously at a receiver, neither of them is\\u000a received due to interference.\\u000a \\u000a In this

Steffen Mecke

2007-01-01

302

Display and Presence Disparity in Mixed Presence Groupware  

Microsoft Academic Search

Mixed Presence Groupware (MPG) supports both co- located and distributed participants working over a shared visual workspace. It does this by connecting multiple single-display groupware workspaces together through a shared data structure. Our implementation and observations of MPG systems exposes two problems. The first is display disparity, where connecting heterogeneous tabletop and vertical displays introduces issues in how one seats

Anthony Tang; Michael Boyle; Saul Greenberg

1996-01-01

303

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

2007-08-31

304

Discharge rate measurements for Micromegas detectors in the presence of a longitudinal magnetic field  

SciTech Connect

We present first discharge rate measurements for Micromegas detectors in the presence of a high longitudinal magnetic field in the GeV kinematical region. Measurements were performed by using two Micromegas detectors and a photon beam impinging a CH{sub 2} target in the Hall B of the Jefferson Laboratory. One detector was equipped with an additional GEM foil, and a reduction of the discharge probability by two orders of magnitude compared to the stand-alone Micromegas was observed. The detectors were p laced in the FROST solenoid providing a longitudinal magnetic field up to 5T. It allowed for precise measurements of the discharge probability dependence with a diffusion-reducing magnetic field. Between 0 and 5T, the discharge probability increased by a factor of 10 for polar angles between 19{degrees} and 34{degrees}. A GEANT4-based simulation developed for sparking rate calculation was calibrated against these data in order to predict the sparking rate in a high longitudinal magnetic field environment. This simulati on is then used to investigate the possible use of Micromegas in the Forward Vertex Tracker (FVT) of the future CLAS12 spectrometer. In the case of the FVT a sparking rate of 1Hz per detector was obtained at the anticipated CLAS12 luminosity.

B. Moreno, S. Aune, J. Ball, G. Charles, A. Giganon, P. Konczykowski, C. Lahonde-Hamdoun, H. Moutarde, S. Procureur, F. Sabatie

2011-10-01

305

Intimate Visual Co-Presence  

Microsoft Academic Search

Photo sharing via handheld devices has unique limitations and affordances that differ from paper-based sharing and PC-based archive and moblog sites. Based on studies of camphone use in Japan, this paper suggests an emergent visual sharing modality that is uniquely suited to the handheld space. Intimate visual co- presence involves the sharing of an ongoing stream of viewpoint- specific photos

Mizuko Ito

2005-01-01

306

Using Presence Questionnaires in Reality  

Microsoft Academic Search

A between-group experiment was carried out to assess whether two different presence question- naires can distinguish between real and virtual experiences. One group of 10 subjects searched for a box in a real office environment. A second group of 10 subjects carried out the same task in a vir- tual environment simulating the same office. Immediately after their experience subjects

Martin Usoh; Ernest Catena; Sima Arman; Mel Slater

2000-01-01

307

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

308

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

NASA Astrophysics Data System (ADS)

A three-dimensional model (GEM-AQ/Arctic) was developed to study the chemistry and processes involved in the ozone depletion events (ODEs) in the Arctic boundary layer (ABL), which included a comprehensive mechanism of multiphase halogen chemistry in the ABL and our current understanding of the ODEs. Assuming that frost flower-derived aerosols were the primary halogen source, the areas potentially covered by frost flowers were determined. The carbonate precipitation scheme was taken into account for triggering the bromine explosions in the model. A comparison of the simulations with GOME satellite measurements in springs of 2000 and 2001 showed that the spatial structure and temporal evolution of tropospheric BrO clouds were well predicted by the model. The majority of the springtime ODEs observed at three arctic stations was reasonably reproduced. An analysis on the model results indicated that most periods of simulated ozone depletion (O3 < 1 nmol mol-1) occurred in a layer 300 to 400 m deep at the Arctic sites. It is found that the halogen chemistry in the marine boundary layer (MBL) contributed substantially to the spring time ODEs, but atmospheric temperature and circulations as well as the transported air pollution in the ABL were also responsible for the ODEs. For springs of 2000 and 2001, two source regions with low surface O3 levels were identified: the Siberian/Beaufort Arctic and the Canadian Arctic, broadly corresponding to areas of enhanced BrO levels and accompanied by the Arctic anticyclones. Dominant trans-Arctic transport pathways were also investigated for the ODEs at Alert, Barrow and Zeppelinfjellet.

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

2008-12-01

309

Boundary Layer Simulator Improvement.  

National Technical Information Service (NTIS)

Boundary Layer Integral Matrix Procedure (BLIMPJ) has been identified by the propulsion community as the rigorous boundary layer program in connection with the existing JANNAF reference programs. The improvements made to BLIMPJ and described herein have p...

S. C. Praharaj C. P. Schmitz J. A. Nouri

1989-01-01

310

Layer-by-layer cell membrane assembly.  

PubMed

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

Matosevic, Sandro; Paegel, Brian M

2013-09-29

311

Transportlaag (Transport Layer).  

National Technical Information Service (NTIS)

The ISO-OSI (International Organization for Standardization-Open Systems Interconnection) transport layer standards are discussed. The transport layer (i.e., layer 4 of the OSI reference model) contains the functions of the OSI network dealing with an eff...

J. Vandelagemaat

1990-01-01

312

Boundary layer transition studies  

Microsoft Academic Search

A small-scale wind tunnel previously used for turbulent boundary layer experiments was modified for two sets of boundary layer transition studies. The first study concerns a laminar separation\\/turbulent reattachment. The pressure gradient and unit Reynolds number are the same as the fully turbulent flow of Spalart and Watmuff. Without the trip wire, a laminar layer asymptotes to a Falkner &

Jonathan H. Watmuff

1995-01-01

313

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

314

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

2008-04-08

315

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

2013-09-18

316

Increased abundance of Frost mRNA during recovery from cold stress is not essential for cold tolerance in adult Drosophila melanogaster.  

PubMed

Frost (Fst) is a candidate gene associated with the response to cold in Drosophila melanogaster because Fst mRNA accumulation increases during recovery from low temperature exposure. We investigated the contribution of Fst expression to chill-coma recovery time, acute cold tolerance and rapid cold hardening (RCH) in adult D.?melanogaster by knocking down Fst?mRNA expression using GAL4/UAS-mediated RNA interference. In this experiment, four UAS-Fst and one tubulin-GAL4 lines were used. We predicted that if Fst is essential for cold tolerance phenotypes, flies with low Fst?mRNA levels should be less cold tolerant than flies with normal levels of cold-induced Fst?mRNA. Cold-induced Fst abundance and recovery time from chill-coma were not negatively correlated in male or female flies. Survival of 2?h exposures to sub-zero temperatures in Fst knockdown lines was not lower than that in a control line. Moreover, a low temperature pretreatment increased survival of severe cold exposure in flies regardless of Fst abundance level during recovery from cold stress, suggesting that Fst expression is not essential for RCH. Thus, cold-induced Fst accumulation is not essential for cold tolerance measured as chill-coma recovery time, survival to acute cold stress and RCH response in adult D.?melanogaster. PMID:23901849

Udaka, H; Percival-Smith, A; Sinclair, B J

2013-07-31

317

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

PubMed Central

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

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

2013-01-01

318

Compressible Ekman–Hartmann boundary layers  

Microsoft Academic Search

We consider the effect of compressibility on mixed Ekman–Hartmann boundary layers on an infinite plane (z = 0), in the presence of an external magnetic field oblique to the boundary. The aim is to investigate the influence of the magnetic pressure on the fluid density, and hence, via mass conservation, on the mass flow into or out of the boundary

Krzysztof A. Mizerski; David W. Hughes

2010-01-01

319

Spectroscopic Characterization of Gapped Graphene in the Presence of Circularly Polarized Light  

Microsoft Academic Search

We present a description of the energy loss of a charged particle moving parallel to a graphene layer and graphene double layers. Specifically, we compare the stopping power of the plasma oscillations for these two configurations in the absence as well as the presence of circularly polarized light whose frequency and intensity can be varied to yield an energy gap

Godfrey Gumbs; O. Roslyak; Danhong Huang; Antonios Balassis

2011-01-01

320

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

321

Integral Scales for the Nocturnal Boundary Layer. Part 1: Empirical Depth Relationships.  

NASA Astrophysics Data System (ADS)

The stable-layer thickness h and near-surface potential temperature strength s, of the nocturnal boundary layer (NBL) are shown to have a `background' square-root of time dependence. Superimposed upon this background are other time variations caused by changes in bulk turbulence parameter B and average surface heat flux H: h = 5(HtB) 1/2 and s = (HtB1) 1/2 ). As an intentionally different approach to the NBL problem B is modeled in terms of forcings external to the NBL rather than in terms of internal variables such as friction velocity or Obukhov length. Nocturnal boundary layer observations from the Wangara and Koorin field experiments in Australia are used to guide some dimensional arguments to yield B (GUG1)(|fUG|Zs)3/2/(QHg), where UG is the geostrophic wind vector, f the Coriolis parameter, g the acceleration due to gravity, Zs is a site and wind-direction-dependent empirical parameter and the overbear indicates time-average since transition (near sunset). Apparently, Zs is a measure of the influence of terrain features such as roughness and slope on NBL development. The resulting model is shown to be adaptable to frost-warning and air-quality applications.

Stull, Roland B.

1983-04-01

322

Ozone Layer Protection Glossary  

EPA Pesticide Factsheets

Ozone:  A gas composed of three atoms of oxygen. Ozone is a bluish gas that is harmful to breathe. Nearly 90% of the Earth's ozone is in the stratosphere and is referred to as the ozone layer. Ozone absorbs a band of ultraviolet radiation called UVB that is particularly harmful to living organisms. The ozone layer prevents most UVB from reaching the ground.   From Ozone Layer Protection Glossary  -  Search all glossaries for terms containing "ozone"

2012-04-06

323

Layer Cake Geology  

NSDL National Science Digital Library

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

Wagner, John

324

Layered plasma polymer composite membranes  

DOEpatents

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

Babcock, W.C.

1994-10-11

325

Layered plasma polymer composite membranes  

DOEpatents

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

Babcock, Walter C. (Bend, OR)

1994-01-01

326

The Boundary Layer on a Flat Plate in Anisotropic Magnetohydrodynamics.  

National Technical Information Service (NTIS)

It is demonstrated that when calculating the boundary layer, despite the presence of thermal flow due to Larmor precession of electrons, it is possible to consider the temperature at the limit of the boundary layer as fixed. For this purpose the problem o...

V. B. Varanov A. G. Kukilovskii G. A. Lyubimov

1965-01-01

327

EVAPORATION FROM SHALLOW WATER TABLE THROUGH LAYERED SOIL PROFILES  

Microsoft Academic Search

The purpose of this study is to estimate the steady state evaporation rates from layered soils in the presence of high water table under isothermal conditions. A finite difference numerical scheme based upon the one-dimensional Richards equation has been employed to estimate the evaporation rates from a two-layered soil profile overlying a shallow water for appropriate initial and boundary conditions.

C. P. Kumar

1999-01-01

328

Properties of optical resonator with a layered metamaterial  

Microsoft Academic Search

The properties of longitudinal and transverse modes of an open optical resonator containing layers of a metamaterial with negative refractive index are studied. Due to the presence of these layers, the metaresonator acquires unique properties compared to a conventional open resonator. Eigenmodes of the metaresonator are studied in which the properties depend on the average dispersion and the average diffraction,

D. O. Saparina; A. P. Sukhorukov

2009-01-01

329

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

330

Buoyant Ekman Layer.  

National Technical Information Service (NTIS)

The solution of a steady-state, baroclinic boundary layer over a two-dimensional terrain in an f plane is obtained. The boundary-layer thickness is found to be dependent on both the stability S = (alpha sub m)g((T sub m/H) + (g/C sub p))/(4(omega squared)...

Y. Hsueh

1969-01-01

331

Background stratospheric aerosol layer  

Microsoft Academic Search

Balloonborne aerosol particle counter measurements are used in studying the stratospheric sulfate layer at Laramie, Wyoming, during 1978 and 1979, a 2-year volcanically quiescent period in which the layer appears to have been in a near equilibrium background state. Subtracting the background aerosol concentration from data obtained during an earlier volcanically active period indicates that the actual decay rate of

D. J. Hofmann; J. M. Rosen

1981-01-01

332

The atmospheric boundary layer  

Microsoft Academic Search

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

J. R. Garratt

1992-01-01

333

Layers of the Atmosphere  

NSDL National Science Digital Library

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

Fearing, Jack

334

The Atmospheric Boundary Layer  

ERIC Educational Resources Information Center

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

Tennekes, Hendrik

1974-01-01

335

Layered Depth Panoramas  

Microsoft Academic Search

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

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

2007-01-01

336

Daytime F Layer Trough.  

National Technical Information Service (NTIS)

The trough in the daytime winter F layer ionization is a fundamental feature of ionospheric-magnetospheric convection causing depletions of an order of magnitude in the electron density at the F layer maximum near midday. As observed by a world-wide array...

J. A. Whalen

1988-01-01

337

Multiple density layered insulator  

DOEpatents

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

Alger, T.W.

1994-09-06

338

Boundary layer transition  

Microsoft Academic Search

The boundary layer stability, its active control by sound and surface heating and the effect of curvature are studied numerically and experimentally for subsonic flow. In addition, the experimental and flight test data are correlated using the stability theory for supersonic Mach numbers. Active transition fixing and feedback control of boundary layer by sound interactions are experimentally investigated at low

L. Maestrello; A. Bayliss; S. M. Mangalam; M. R. Malik

1986-01-01

339

The Atmospheric Boundary Layer  

ERIC Educational Resources Information Center

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

Tennekes, Hendrik

1974-01-01

340

Geomorphic signatures of glacial activity in the Alba Patera volcanic province: Implications for recent frost accumulation on Mars  

NASA Astrophysics Data System (ADS)

landforms lying within impact craters on Mars have led to the identification of two mechanisms for their formation: (1) intermittent deposition of atmospherically emplaced snow/ice during past spin-axis/orbital conditions and (2) flow of debris-covered ice-rich deposits. The maximum presence of the young ice/snow-rich features (thermal contraction crack polygons, gullies, arcuate ridges, and lobate debris tongues) was observed on the pole-facing slope, indicating that this slope was the preferred site for ice/snow accumulation (during the last 10 Ma). In this study, we investigated 30 craters lying in the Alba Patera volcanic province in the latitudinal bands between 45°N and 32.4°N. Morphological comparison of the younger ice/snow-rich features in these craters led us to conclude that glacial/periglacial features in Alba Patera are mainly present within pole-facing slopes of craters lying within 45°N-39°N. The craters lying within 40.2°N-40°N did not show any glacial/periglacial features. We suggest that the formation of these young ice/snow-rich features follows the same orientation trends as those of other older (>10 Ma) glacial features (debris-covered ice/snow-rich large deposits at the base of the crater wall) in the region. The present work has revealed that the onset of physical processes that result in the formation of glacial/periglacial landforms is also dependent on the changes in elevation ranges of the investigated craters in Alba Patera. Our results confirm past inferences for accumulation of ice/snow on Mars and suggest that the period of ice/snow accumulation activity in Alba Patera occurred throughout the Amazonian and lasted until the recent past, i.e., 2.1-0.4 Ma.

Sinha, Rishitosh K.; Murty, Sripada V. S.

2013-08-01

341

Intermolecular dimerization with pillared layered clay templates.  

SciTech Connect

Solutions of pyrene in the presence of a pillared, layered montmorillonite clay produce hybrid organic-inorganic materials with substantial molecular loading in the gallery regions between the clay layers. The results are in sharp contrast to other aromatics, such as benzene, naphthalene, or perylene, which show minimal incorporation of the molecules into the gallery regions of the clay. We present evidence that the unusual affinity for pyrene to form intermolecular dimers is the reason for the high loading. Pyrene monomers are easily introduced to the layers. Through steric hindrance, subsequent intermolecular dimer formation is allowed, and they are captured by the pillared, layered structure. CW and time-resolved emission spectra strongly indicate the presence of face-to-face intermolecular dimers (excimers) within the clay galleries. The combination of the ease of high molecular loading into an inorganic, high aspect ratio template and the collective optical properties of the organic layer may be useful as a new means to create hybrid structures.

Wiederrecht, G. P.; Sandi, G.; Carrado, K. A.; Seifert, S.; Chemistry

2001-11-19

342

Electrochemical atomic layer processing  

NASA Astrophysics Data System (ADS)

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 method is referred to as electrochemical atomic layer epitaxy (ECALE). A number of II-VI compounds have been formed using this method, including: CdTe, CdSe, CdS, ZnTe, ZnSe, ZnS, and HgSe. Initial studies of GaAs and PbSe have also been pursued. A computer-controlled electrochemical flow deposition system is described. The system has been constructed to form thin films of the compounds listed above using the ECALE methodology. In addition, an analogous digital electrochemical etching procedure has been developed and used to etch CdTe substrates. The etching cycle consists of oxidizing off the top atomic layer of Cd atoms at a relatively positive potential, followed by reducing off the top layer of Te atoms at a relatively negative potential. Atomic force microscopy (AFM) has been used to image the resulting features. ECALE and the digital electrochemical etching process are both based on selecting potentials where an atomic layer of an element is deposited, or removed, in a surface limited reaction. The potentials used are referred to as underpotentials in the electrochemical literature. The atomic layer deposition process is referred to as underpotential deposition (UPD).

Rhee, Choong K.; Huang, Baoming M.; Wilmer, Elvin M.; Thomas, Sajan; Stickney, John L.

1994-06-01

343

Optical property measurement from layered biological media  

NASA Astrophysics Data System (ADS)

Near infrared (NIR) photon reflectance spectroscopy is applied to measurement of blood concentration and its oxygen saturation within biological tissue. The measurement relies upon the changes in photon absorption of hemoglobin in the tissue as changes occur in the hemoglobin concentration and oxygen content. In the present study, NIR light is introduced at the skin surface and the optical properties (absorption and scattering) within the underlying tissue are determined from the resulting surface reflectance. Typically the tissue is modeled as a homogeneous mixture of bloodless tissue and blood, and the model incorporates the physical relationship between the surface reflectance and the optical properties of the tissue. The skin and underlying tissue, although heterogeneous, have a characteristic layered structure. These layers can be differentiated optically. The modeling and the inverse problem of measuring the optical properties in each of the tissue layers from the surface reflectance have been the subject of much attention by a number of investigators. Nonetheless, quantification of the relationship between surface reflectance and the optical properties of layered tissue has not been well understood nor well described. In the forward problem, tissue optical properties yield surface reflectance profiles (SRPs). Surface reflectance profiles, or SRPs, from diffusive media consisting of two layers are calculated using numerical solutions to the Boltzmann equation. Experimental SRPs are also measured in vitro from a test medium and in vivo from the calf of human subjects. This study provides a new approach to solving the inverse problem of determining optical properties from SRPs. To solve the inverse problem, an effective diffusion constant (Ke) is determined for the layered media. The Ke is the diffusion constant of an equivalent homogeneous medium which best fits the SRP of the layered medium. The departure from Ke of the SRP for a layered media is captured concisely, and Ke becomes a tool in describing the layered optical properties. This approach is applied clinically to measure changes in the blood concentration and oxygenation measured in vivo from normals and patients with peripheral vascular disease. A significant finding from the modeling was to identify the functional relationship of Ke to the top and lower layer diffusion constants, and the top layer thickness. When applied to in vitro measurements from media containing homogeneous layers with known optical properties, this functional relationship predicted Ke within the 95% confidence interval of the measured Ke. For the in vivo measurements, changes in K e with exercise are consistent with expected exercise physiology. With the incorporation of the known optical absorbance of hemoglobin in the presence of oxygen, the SRPs provide a means to measure the oxygen saturation of a deep tissue layer from the surface light reflectance.

Muller, Matthew R.

1998-12-01

344

Concentric layer ramjet fuel  

SciTech Connect

This patent describes a solid fuel ramjet grain comprising concentric layers of solid ramjet fuel having a perforation therethrough along the center axis of the grain. The performation is connected to a combustion after-chamber. The solid ramjet fuel layers comprises a pure hydroxyl-terminated polybutadiene hydrocarbon fuel or a mixture of a hydroxyl-terminated polybutadiene hydrocarbon fuel and from about 5 to about 60 percent by weight of an additive to increase the fuel regression rate selected from the group consisting of magnesium, boron carbide, aluminum, and zirconium such that, when buried in the operation of the ramjet, each fuel layer produces a different level of thrust.

Burdette, G.W.; Francis, J.P.

1988-03-08

345

Inclined layer Soret instabilities.  

PubMed

Linear stability of a binary mixture buoyant return flow in a differentially heated inclined infinite layer is investigated by asymptotic long-wave analysis and pseudospectral Chebyshev numerical solutions. The Soret coefficient is negative so that thermodiffusion separates the species with the heavier component migrating to the hot wall, thus, promoting unstable stratification except in the classical Rayleigh-Benard arrangement. It is shown that longitudinal instabilities with small wave numbers are triggered at any finite temperature difference at all angles of inclination except very close to the horizontal heated from the above or below arrangements. Numerical results are given for a specific water-ethanol mixture and are in excellent agreement with the asymptotic results. As is well known the heated from below horizontal layer is overstable while that heated from above is doubly-diffusive unstable. Transition from the longitudinal stationary instabilities in inclined layers to these instabilities in horizontal layers is also given for this mixture. PMID:19518560

Zebib, A; Bou-Ali, M M

2009-05-08

346

Layer-Cake Earth  

NSDL National Science Digital Library

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

Tedford, Rebecca; Warny, Sophie

2006-12-01

347

The Effect of Freezing on Thylakoid Membranes in the Presence of Organic Acids  

PubMed Central

The effect of salts of organic acids on washed and non-washed chloroplast membranes during freezing was investigated. Thylakoids were isolated from spinach leaves (Spinacia oleracea L.) and, prior to freezing, salts of various organic acids or inorganic salts or both were added. Freezing occurred for 3 to 4 hours at ?25 C. After thawing membrane integrity was investigated by measuring the activity of cyclic photophosphorylation. At very low NaCl levels (1 to 3 mm, washed thylakoids) salts of organic acids either could not prevent membrane inactivation in the course of freezing (succinate) or were effective only at relatively high concentrations (0.1 m or more of acetate, pyruvate, malate, tartrate, citrate). If NaCl was present at higher concentrations (e.g., 0.1 m) some organic acids, e.g. succinate, malate, tartrate, and citrate, were able to protect frost-sensitive thylakoids at surprisingly low concentrations (10 to 20 mm). Other inorganic salts such as KCl, MgCl2, NaNO3 could also induce protection by organic acids which otherwise were ineffective or poorly effective. For effective protection, a more or less constant ratio between inorganic salt and organic acid or between two or more organic acids had to be maintained. Departure to either side from the optimal ratio led to progressive inactivation. The unspecificity of the protective effect of organic acids suggests that these compounds protect colligatively. There are also indications that, in addition, more specific interaction with the membranes contributes to protection. At temperatures above the freezing point, the presence of salts of organic acids decreased the rate of membrane inactivation by high electrolyte concentrations.

Santarius, Kurt A.

1971-01-01

348

Buoyant Ekman Layer  

Microsoft Academic Search

The solution of a steady-state, baroclinic boundary layer over a two-dimensional terrain in an f plane is obtained. The boundary-layer thickness is found to be dependent on both the stability S = ?mg[(Tm?H) + (g?cp)] (4?2L)?1 and the terrain slope. For a given terrain slope ? and Prandtl number ? = ??k, a critical value of the stability parameter S

Y. Hsueh

1969-01-01

349

Layers of the Sun  

NSDL National Science Digital Library

Students will explore the layers of the sun through interactive media and reading. Print off the following worksheet: layers of the sun worksheet Click on the electronmagnetic spectrum above the picture of the sun. On your own paper, describe what the sun looks like at the different wave lengths. At which two wavelengths does the sun look the same? Examine the sun at different wavelengths Now click on this website and read more about ...

Brown, Mrs.

2010-09-28

350

Earth Layers and Volcanoes  

NSDL National Science Digital Library

Why do we have volcanoes? Use the information on the websites to answer the questions on the worksheet. Worksheet First, review the layers of the earth. Labeling the layers game Next, go through the maze and read the information given. Magic School Bus volcano game Now, study the different shapes of volcanoes. Click enter, then volcano types in the menu. Read about the 3 types of volcanoes. Discovery Kids Games Finally, watch ...

Brookeshallow

2011-04-13

351

Bioactivity of polycrystalline silicon layers.  

PubMed

After oxygen, silicon is the second most abundant element in the environment and is present as an impurity in most materials. The widespread occurrence of siliceous biominerals as structural elements in lower plants and animals suggests that Si plays a role in the production and maintenance of connective tissue in higher organisms. It has been shown that the presence of Si is necessary in bones, cartilage and in the formation of connective tissue, as well as in some important metabolic processes. In this work, polycrystalline silicon layers are tested in terms of bioactivity, i.e., their ability to induce hydroxyapatite formation from simulated body fluid. Hydroxyapatite is a biologically compatible material with chemical similarity to the inorganic part of bones and teeth. Polycrystalline silicon layers are obtained by aluminum induced crystallization of Al and amorphous Si thin films deposited sequentially on glass substrates by radio-frequency magnetron sputtering and subsequently annealed in different atmospheres. The hydroxyapatite formation is induced by applying a method of laser-liquid-solid interaction. The method consists of irradiating the samples with laser light while immersed in a solution that is supersaturated with respect to Ca and P. As a result, heterogeneous porous sponge-like carbonate-containing hydroxyapatite is grown on the polysilicon surfaces. Crystals that are spherical in shape, containing Ca, P and O, Na, Cl, Mg, Al, Si and S, as well as well-faceted NaCl crystals are embedded in the hydroxyapatite layer. Enhancement of the hydroxyapatite growth and increased crystallinity is observed due to the applied laser-liquid-solid interaction. PMID:18464428

Pramatarova, Lilyana; Pecheva, Emilia; Montgomery, Paul; Dimova-Malinovska, Doriana; Petrov, Todor; Toth, Attila L; Dimitrova, Magdalena

2008-02-01

352

Undulating vortices in layered superconductors  

SciTech Connect

We present the detailed structure of vortices normal to the layers in layered superconductors, assuming only that the order parameter varies continuously between the layers. The magnetic field along the {ital c} axis undulates due to the reduced screening between the layers. The radial magnetic field also undulates, becoming zero on the layers, as well as midway between them.

Theodorakis, S. [Department of Natural Sciences, University of Cyprus, P.O. Box 537, Nicosia, Cyprus (??); Ettouhami, A.M. [Laboratoire d` Etudes des Proprietes Electroniques des Solides, Centre National de la Recherche Scientifique, B.P. 166, 38042 Grenoble Cedex 9 (France)

1995-05-01

353

Diffusion in the presence of periodically spaced permeable membranes  

NASA Astrophysics Data System (ADS)

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).

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

2004-12-01

354

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

355

The stability of the mesospheric plasma layer  

SciTech Connect

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

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

2011-12-15

356

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

357

Boundary layer processes in the Martian magnetosphere  

NASA Astrophysics Data System (ADS)

At Mars, in the absence of a global magnetic field, the flowing solar wind interacts directly with ionized atmospheric constituents, forming an induced magnetosphere. Turbulent boundary layer processes provide one means by which solar wind and atmospheric plasma can mix and exchange momentum, potentially leading to atmospheric escape. In this presentation, we describe MGS MAG/ER observations of Martian boundary layer oscillations, identified using a combination of magnetic field and electron data. We analyze electron distributions to identify interaction regions, and utilize magnetic field data to determine wave properties and boundary position and morphology. Our observations suggest several modes of interaction, including large-scale pulsations of a relatively smooth boundary, and corrugated boundary layer structures possibly indicative of the presence of boundary instabilities. We discuss each of these modes, and the implications for atmospheric escape process.

Halekas, J. S.; Brain, D. A.; Eastwood, J. P.

2010-12-01

358

Lithospheric layering in the North American craton.  

PubMed

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

Yuan, Huaiyu; Romanowicz, Barbara

2010-08-26

359

Perturbation Formula for the Natural Frequencies of an Object in the Presence of a Layered Medium  

Microsoft Academic Search

It is well known that the natural frequencies of an object are important distinguishing features which can be used in target detection and discrimination schemes. These natural frequencies are governed by the size, shape, and material composition of the object, as well as the environment in which the object resides. Since a given object of interest may reside in many

George W. Hanson; Carl E. Baum

1998-01-01

360

Momentum transfer in boundary layers  

Microsoft Academic Search

The continuity and momentum equations of fluid flow are considered along with thin-shear-layer equations, the analysis of laminar shear layers, the analysis of turbulent shear layers, numerical methods for thin shear layers, numerical solutions of laminar and turbulent boundary layers, aspects of stability and transition, and complex shear layers and viscous\\/inviscid interactions. Three-dimensional and unsteady flows are discussed, taking into

T. Cebeci; P. Bradshaw

1977-01-01

361

Origin of the polygons and underground structures in Southern layered deposits and Utopia Planitia on Mars  

NASA Astrophysics Data System (ADS)

Patterned ground is a common feature in the cold and/or arid regions of Earth, but similar features are also found on Mars. Polygons on the Martian surface have been classified into three different size classes: big (giant polygons, 1-20 km diameter), middle size (100-200 m diameter) and small size (5-20 m diameter). Many of small-scale polygons on the southern layered deposits near the South Pole possibly originated through thermal contraction as predicted by image analysis and statistical analysis, but many of the middle and small size polygons from Utopia Planitia may not be caused by thermal contraction. Polygons from southern layered deposits display characteristic shape factors, such as form factor, roundness, and aspect ratio, which are very similar to terrestrial frost polygons. Nearest-neighbor analyses of polygonal network distributions also yield comparable results with terrestrial polygonal networks. However, one significant difference is the spacing of the cracks, which is on the order of 5 - 10 times bigger than those on Earth. Polygon size provides some hints on the surface materials of the southern layered deposits. The polygonal patterns in Utopia Planitia have frequently been associated with collapsed features such as ancient subsurface channels (the width of the underground channel is estimated to be approximately 400-500 m) or a talik (unfrozen layer in the permafrost). These features also display linear structure, associated with lower surface albedo. The area of lower albedo has a higher density of polygonal patterns. These patterns potentially suggest that 1) the polygonal pattern is caused primarily by ground heaving and collapsing, 2) darker albedo materials had higher tensile strength and 3) liquid water or melt water (from ice rich materials) was running through the talik or near surface channel.

Yoshikawa, K.; Laderach, S.; Hinzman, L.

2001-12-01

362

Improvement of hot-dip zinc coating by enriching the inner layers with iron oxide  

Microsoft Academic Search

The performance of hot-dip galvanic coating formed on steel not only depends on the alloy composition of the superficial layer but also significantly, on the composition of the inner alloy layers at the coating\\/substrate interface. Further, the presence of barrier oxide layers, if any can also improve the performance of galvanic coating. In the present work, the effect of inner

S. M. A. Shibli; R. Manu

2006-01-01

363

Boundary layer receptivity - Theory  

NASA Astrophysics Data System (ADS)

The receptivity mechanisms by which free-stream disturbances generate instability waves in laminar boundary layers are discussed. Free-stream disturbances have wavelengths which are generally much longer than those of instability waves. Hence, the transfer of energy from the free-stream disturbance to the instability wave requires a wavelength conversion mechanism. Recent analyses using asymptotic methods have shown that the wavelength conversion takes place in regions of the boundary layer where the mean flow adjusts on a short streamwise length scale. This paper reviews recent progress in the theoretical understanding of these phenomena.

Kerschen, E. J.

364

Magnetohydrodynamic natural convection flow on a sphere with uniform heat flux in presence of heat generation  

Microsoft Academic Search

Summary  Magnetohydrodynamic natural convection boundary layer flow on a sphere with uniform heat flux in presence of heat generation\\u000a has been investigated in this paper. The governing boundary layer equations are transformed into a non-dimensional form and\\u000a the resulting nonlinear system of partial differential equations is then solved numerically by two distinct efficient methods,\\u000a namely (i) implicit finite difference method together

M. M. Molla; M. A. Hossain; M. A. Taher

2006-01-01

365

Silk layering as studied with neutron reflectivity.  

PubMed

Neutron reflectivity (NR) measurements of ultrathin surface films (below 30 nm) composed of Bombyx mori silk fibroin protein in combination with atomic force microscopy and ellipsometry were used to reveal the internal structural organization in both dry and swollen states. Reconstituted aqueous silk solution deposited on a silicon substrate using the spin-assisted layer-by-layer (SA-LbL) technique resulted in a monolayer silk film composed of random nanofibrils with constant scattering length density (SLD). However, a vertically segregated ordering with two different regions has been observed in dry, thicker, seven-layer SA-LbL silk films. The vertical segregation of silk multilayer films indicates the presence of a different secondary structure of silk in direct contact with the silicon oxide surface (first 6 nm). The layered structure can be attributed to interfacial ?-sheet crystallization and the formation of well-developed nanofibrillar nanoporous morphology for the initially deposited silk surface layers with the preservation of less dense, random coil secondary structure for the layers that follow. This segregated structure of solid silk films defines their complex nonuniform behavior in the D(2)O environment with thicker silk films undergoing delamination during swelling. For a silk monolayer with an initial thickness of 6 nm, we observed the increase in the effective thickness by 60% combined with surprising decrease in density. Considering the nanoporous morphology of the hydrophobic silk layer, we suggested that the apparent increase in its thickness in liquid environment is caused by the air nanobubble trapping phenomenon at the liquid-solid interface. PMID:22697306

Wallet, Brett; Kharlampieva, Eugenia; Campbell-Proszowska, Katie; Kozlovskaya, Veronika; Malak, Sidney; Ankner, John F; Kaplan, David L; Tsukruk, Vladimir V

2012-07-26

366

Layer-by-Layer Assembly of Enzymes on Carbon Nanotubes  

Microsoft Academic Search

The use of Layer-by-layer techniques for immobilizing several types of enzymes, e.g. glucose oxidase (GOx), horse radish oxidases(HRP), and choline oxidase(CHO) on carbon nanotubes and their applications for biosenseing are presented. The enzyme is immobilized on the negatively charged CNT surface by alternatively assembling a cationic polydiallyldimethyl-ammonium chloride (PDDA) layer and a enzyme layer. The sandwich-like layer structure (PDDA\\/enzyme\\/PDDA\\/CNT) formed

Jun Wang; Guodong Liu; Yuehe Lin

2008-01-01

367

Fiber optic device for sensing the presence of a gas  

DOEpatents

A fiber-optic device for sensing the presence of a gas in an environment is provided. The device comprises a light source for directing a light beam to a layer system having a first surface and a second surface opposite the first surface. The first surface is exposable to the light beam and the second surface is exposable to the environment. A first light portion encounters and reflects from the first surface at an angle of incidence free from optical wave guide resonance phenomenon and the second light portion encounters and reflects from the first surface at an angle of incidence enabling an optical wave guide resonance phenomenon. The layer system is selected to reversibly react with the gas to be detected. The reaction between the gas and the material changes the material`s optical properties and the wavelength at which the optical wave guide resonance occurs. Furthermore, a mechanism for measuring the intensity of the reflected first light portion relative to the reflected second light portion is provided with the ratio of the first and second light portions indicating the concentration of the gas presence in the environment. 5 figs.

Benson, D.K.; Bechinger, C.S.; Tracy, C.E.

1998-01-13

368

Fiber optic device for sensing the presence of a gas  

DOEpatents

A fiber-optic device for sensing the presence of a gas in an environment is provided. The device comprises a light source for directing a light beam to a layer system having a first surface and a second surface opposite the first surface. The first surface is exposable to the light beam and the second surface is exposable to the environment. A first light portion encounters and reflects from the first surface at an angle of incidence free from optical wave guide resonance phenomenon and the second light portion encounters and reflects from the first surface at an angle of incidence enabling an optical wave guide resonance phenomenon. The layer system is selected to reversibly react with the gas to be detected. The reaction between the gas and the material changes the material's optical properties and the wavelength at which the optical wave guide resonance occurs. Furthermore, a mechanism for measuring the intensity of the reflected first light portion relative to the reflected second light portion is provided with the ratio of the first and second light portions indicating the concentration of the gas presence in the environment.

Benson, David K. (14154 W. First Dr., Golden, CO 80401); Bechinger, Clemens S. (35 S. Holman Way, # 3D, Golden, CO 80401); Tracy, C. Edwin (19012 W. 60th Dr., Golden, CO 80403)

1998-01-01

369

Fiber optic device for sensing the presence of a gas  

SciTech Connect

A fiber-optic device for sensing the presence of a gas in an environment is provided. The device comprises a light source for directing a light beam to a layer system having a first surface and a second surface opposite the first surface. The first surface is exposable to the light beam and the second surface is exposable to the environment. A first light portion encounters and reflects from the first surface at an angle of incidence free from optical wave guide resonance phenomenon and the second light portion encounters and reflects from the first surface at an angle of incidence enabling an optical wave guide resonance phenomenon. The layer system is selected to reversibly react with the gas to be detected. The reaction between the gas and the material changes the material's optical properties and the wavelength at which the optical wave guide resonance occurs. Furthermore, a mechanism for measuring the intensity of the reflected first light portion relative to the reflected second light portion is provided with the ratio of the first and second light portions indicating the concentration of the gas presence in the environment.

Benson, David K. (14154 W. First Dr., Golden, CO 80401); Bechinger, Clemens S. (35 S. Holman Way, # 3D, Golden, CO 80401); Tracy, C. Edwin (19012 W. 60th Dr., Golden, CO 80403)

1998-01-01

370

Application-Layer Anycasting  

Microsoft Academic Search

The anycasting communication paradigm is designedto support server replication by allowing applicationsto easily select and communicate with the"best" server, according to some performance or policycriteria, in a group of content-equivalent servers. Weexamine the definition and support of the anycastingparadigm at the application layer, providing a servicethat maps anycast domain names into one or more IPaddresses using anycast resolvers. In addition

Samrat Bhattacharjee; Mostafa H. Ammar; Ellen W. Zegura; Viren Shah; Zongming Fei

1997-01-01

371

Cratering in Layered Media.  

National Technical Information Service (NTIS)

To study the cratering phenomena in a two-layered medium, a total of 32 model tests were performed. In all these tests the compressible stratum was simulated by dense sand while the stiff stratum was simulated by an artificial sandstone (cemented dense sa...

A. S. Vesic K. Bhushan N. M. F. Ismael

1971-01-01

372

Layer-Cake Earth  

ERIC Educational Resources Information Center

|In this article, the authors offer a safe, fun, effective way to introduce geology concepts to elementary school children of all ages: "coring" layer cakes. This activity introduces the concepts and challenges that geologists face and at the same time strengthens students' inferential, observational, and problem-solving skills. It also addresses…

Tedford, Rebecca; Warny, Sophie

2006-01-01

373

Layer Cake Geology  

NSDL National Science Digital Library

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

Wagner, John

374

MITRE sensor layer prototype  

Microsoft Academic Search

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

Francis Duff; Donald McGarry; David Zasada; Scott Foote

2009-01-01

375

Layer-Cake Earth  

ERIC Educational Resources Information Center

In this article, the authors offer a safe, fun, effective way to introduce geology concepts to elementary school children of all ages: "coring" layer cakes. This activity introduces the concepts and challenges that geologists face and at the same time strengthens students' inferential, observational, and problem-solving skills. It also addresses…

Tedford, Rebecca; Warny, Sophie

2006-01-01

376

Plasma sheet boundary layer  

Microsoft Academic Search

The plasma sheet boundary layer is a temporally variable transition region located between the magnetotail lobes and the central plasma sheet. We have made a survey of these regions by using particle spectra and three-dimensional velocity-space distributions sampled by the ISEE 1 LEPEDEA. Ion composition measurements obtained by the Lockhead ion mass spectrometers indicate that ionospheric ions play a crucial

T. E. Eastman; L. A. Frank; W.K. Peterson; W. Lennartsson

1984-01-01

377

Origins of Igneous Layering  

Microsoft Academic Search

Anyone who has ever seen a photo of a layered intrusion, let alone visited one first hand, or even seen a thin section from one, cannot help but be impressed by the stunning record of crystal growth and deposition. Such bodies stand as majestic monuments of undeniable evidence that intricate magmatic processes exist, processes that couple crystallization, convection, and crystal

Bruce Marsh

1988-01-01

378

Layers of the Earth  

NSDL National Science Digital Library

Students use graphs of seismic wave travel times, and value for the diameter of Earth obtained in the Size of the Earth activity, to investigate the internal structure of the Earth and determine that it is layered. Click here to view the full activity on the Kéyah Math Project website.

Semken, Steven; Perkins, Tracy

379

Magnetoplasmons in layered graphene structures  

Microsoft Academic Search

We calculate the dispersion equations for magnetoplasmons in a single layer, a pair of parallel layers, a graphite bilayer, and a superlattice of graphene layers in a perpendicular magnetic field. We demonstrate the feasibility of a drift-induced instability of magnetoplasmons. The magnetoplasmon instability in a superlattice is enhanced compared to a single graphene layer. The energies of the unstable magnetoplasmons

Oleg L. Berman; Godfrey Gumbs; Yurii E. Lozovik

2008-01-01

380

Layer Formation in Convective Magma Chambers  

NASA Astrophysics Data System (ADS)

The dynamics of a convective magma chamber is crucially influenced by the competetion between sedimentation and convective suspension of crystals. Crystal settling combined with the crystal's density contribution is a possible mechanism leading to differentiation and layer formation. Here we address the question whether crystals can remain suspended or whether they are able to dynamically form a layered structure within the convective lifetime of a magma chamber. We employ an existing numerical method that, by means of a finite volume scheme, discretizes the equations for thermally driven convection in an infinite Prandtl-number Boussinesq fluid in Cartesian geometry. We implement a newly developed settling algorithm for the numerical study of finite-sized-particle settling in a non-dilute convective suspension. Our approach considers a consistent settling velocity and the density contribution due to particle mass. The buoyancy ratio B, which is the ratio of the density variation due to crystal mass to the thermal density variation, is varied for five different Rayleigh numbers, covering a range of four orders of magnitude. We find B to be a critical parameter and its critical value to depend on the Rayleigh number. For subcritical values we observe that the presence of a crystal phase reduces convective vigor and most crystals stay suspended. When a critical buoyancy ratio is exceeded, the presence of crystals can significantly alter convective motion. For all investigated Rayleigh numbers we find a critical buoyancy ratio, above which layering can be achieved from an initially unstratified fluid. Most of the crystal mass collects in the dynamically created bottom layer, even for cases where the average settling velocity is three orders of magnitude smaller than the root mean square convective velocity. The time it takes a crystal to travel across the height of the cell with the full settling velocity in the absence of a thermal gradient defines the settling timescale. Layer formation in all observed layering cases occurs on this time scale, even though the average settling velocity is reduced by at least one order of magnitude due to hindered settling. In many cases (e.g. basaltic magma chambers) the settling time is short compared to the time that magma chambers take to solidify. We conclude that dynamical layer formation that is connected to crystal settling and the crystals' density contribution is a likely mechanism for creating layered structures within the convective lifetime of a magma chamber.

Höink, T.; Schmalzl, J.; Hansen, U.

2004-12-01

381

Nonlinear, electrocatalytic swimming in the presence of salt  

NASA Astrophysics Data System (ADS)

A small, bimetallic particle in a hydrogen peroxide solution can propel itself by means of an electrocatalytic reaction. The swimming is driven by a flux of ions around the particle. We model this process for the presence of a monovalent salt, where reaction-driven proton currents induce salt ion currents. A theory for thin diffuse layers is employed, which yields nonlinear, coupled transport equations. The boundary conditions include a compact Stern layer of adsorbed ions. Electrochemical processes on the particle surface are modeled with a first order reaction of the Butler-Volmer type. The equations are solved numerically for the swimming speed. An analytical approximation is derived under the assumption that the decomposition of hydrogen peroxide occurs mainly without inducing an electric current. We find that the swimming speed increases linearly with hydrogen peroxide concentration for small concentrations. The influence of ion diffusion on the reaction rate can lead to a concave shape of the function of speed vs. hydrogen peroxide concentration. The compact layer of ions on the particle diminishes the reaction rate and consequently reduces the speed. Our results are consistent with published experimental data.

Sabass, Benedikt; Seifert, Udo

2012-06-01

382

Nonlinear, electrocatalytic swimming in the presence of salt.  

PubMed

A small, bimetallic particle in a hydrogen peroxide solution can propel itself by means of an electrocatalytic reaction. The swimming is driven by a flux of ions around the particle. We model this process for the presence of a monovalent salt, where reaction-driven proton currents induce salt ion currents. A theory for thin diffuse layers is employed, which yields nonlinear, coupled transport equations. The boundary conditions include a compact Stern layer of adsorbed ions. Electrochemical processes on the particle surface are modeled with a first order reaction of the Butler-Volmer type. The equations are solved numerically for the swimming speed. An analytical approximation is derived under the assumption that the decomposition of hydrogen peroxide occurs mainly without inducing an electric current. We find that the swimming speed increases linearly with hydrogen peroxide concentration for small concentrations. The influence of ion diffusion on the reaction rate can lead to a concave shape of the function of speed vs. hydrogen peroxide concentration. The compact layer of ions on the particle diminishes the reaction rate and consequently reduces the speed. Our results are consistent with published experimental data. PMID:22697558

Sabass, Benedikt; Seifert, Udo

2012-06-01

383

Subsurface damage from oblique impacts into low-impedance layers  

NASA Astrophysics Data System (ADS)

Layered planetary surfaces occur ubiquitously in the solar system, where sedimentary sequences or icy layers overlay crystalline bedrock. Previous experimental studies investigated how the presence of weak layer overlying a strong basement affects crater morphology, subsurface damage and soft-sediment compression. Numerical studies generally focus on the final morphology as a function of thicknesses and burial depths of weak layers. In field studies of impact craters, the shock state of minerals is a key metric. Here, we evaluate the effect of a surficial low-impedance layer on peak pressure magnitudes and consequent damage extent in the competent substrate. Laboratory experiments coupled with 3D CTH models of oblique (30° from horizontal) hypervelocity impacts at laboratory and planetary scales show that surface layers with a thickness on the order of the projectile diameter shield the underlying surface and absorb/scatter ˜70% of the impact energy. Numerical simulations reveal that surficial layers reduce peak pressure magnitudes within the subsurface by ˜60-70%, while damage in the substrate is due to shear failure. Sedimentary layers are more efficient shields than icy layers, but both reduce the extent of subsurface damage and the resulting shock levels recorded by minerals. These results indicate that a thin surficial low impedance layer mitigates the expression of shocked minerals in the substrate even when a structural response is still observed.

Stickle, A. M.; Schultz, P. H.

2012-07-01

384

Unsteady flow on a porous plate in the presence of blowing /suction/  

NASA Astrophysics Data System (ADS)

A theoretical analysis is presented of an unsteady boundary layer formed in a viscous incompressible homogeneous fluid about a infinite porous plate in the presence of uniform blowing or suction. The problem is a generalization of Gupta's analysis (1972) of Ekman layers on a porous plate. The plate and fluid are in rigid-body rotation, and the unsteady flow is induced by nontorsional vibrations of the plate. The structure of the unsteady velocity field and the associated boundary layers is determined; an exact solution is obtained for the unsteady three-dimensional Naiver-Stokes equations.

Gurchenkov, A. A.; Ialamov, Iu. I.

1980-08-01

385

Application of HRSC Data to North Polar Layered Deposit Stratigraphy  

NASA Astrophysics Data System (ADS)

HRSC imaging data from Mars Express provide coverage of the north polar cap at resolutions suitable for regional analysis of the polar layered deposits (PLD) and trough systems. In order to analyze the interior structure of the PLD and address the role of troughs in layer formation and evolution, the orientation of the layers in three dimensions was examined using HRSC polar images (50 m/pxl) co-registered with MOLA gridded topography data. The stereo data from the HRSC camera was unavailable at the time of this study. As the polar MOLA data set is of comparable resolution to the data set that will be derived from HRSC stereo images (114 m/pxl and 100 m/pxl, respectively), utilizing the MOLA data was considered to be an excellent first step in this type of analysis. Layers exposed in local topographic variations such as a hill or depression within a trough were selected for analysis. To measure the orientation of an individual layer, the position of the layer was identified by locating at least eight specific points along the layer. The spatial information for each point in three dimensions was then extracted from the spacecraft data. Next, a trend plane was fitted to the points using a least-squares fit. Finally, the slope and aspect of the trend plane was calculated, providing the dip and strike of the layer. Measurement of 38 layers located around the cap and at different depths in the PLD stratigraphy reveals several trends in layer orientation. A majority of layers have strikes trending parallel to the orientation of the trough in which they are exposed; rather than following a circular pattern as might be expected of layers in a simple dome they follow the spiraling pattern of the troughs. A slight majority (21 out of 38) of layers dip away from the pole. The remaining (17 out of 38) layers dip toward the pole. The magnitude of the dip of an individual layer does not tend to reflect the surface slope of the portion of the cap surface immediately surrounding the trough within which the layer is exposed. These observations of PLD strike and dip are consistent with both 1) models of layer behavior in the presence of polar ice flow and 2) models of static ice accumulation in the presence of preexisting troughs. Further assessments of the potential existence and magnitude of flow of ice and ice-dust mixtures in the polar cap are required before we can successfully distinguish between these two possibilities or propose new interpretations that might involve combinations of these processes.

Milkovich, S. M.

2005-12-01

386

Boundary layer transition studies  

NASA Astrophysics Data System (ADS)

A small-scale wind tunnel previously used for turbulent boundary layer experiments was modified for two sets of boundary layer transition studies. The first study concerns a laminar separation/turbulent reattachment. The pressure gradient and unit Reynolds number are the same as the fully turbulent flow of Spalart and Watmuff. Without the trip wire, a laminar layer asymptotes to a Falkner & Skan similarity solution in the FPG. Application of the APG causes the layer to separate and a highly turbulent and approximately 2D mean flow reattachment occurs downstream. In an effort to gain some physical insight into the flow processes a small impulsive disturbance was introduced at the C(sub p) minimum. The facility is totally automated and phase-averaged data are measured on a point-by-point basis using unprecedently large grids. The evolution of the disturbance has been tracked all the way into the reattachment region and beyond into the fully turbulent boundary layer. At first, the amplitude decays exponentially with streamwise distance in the APG region, where the layer remains attached, i.e. the layer is viscously stable. After separation, the rate of decay slows, and a point of minimum amplitude is reached where the contours of the wave packet exhibit dispersive characteristics. From this point, exponential growth of the amplitude of the disturbance is observed in the detached shear layer, i.e. the dominant instability mechanism is inviscid. A group of large-scale 3D vortex loops emerges in the vicinity of the reattachment. Remarkably, the second loop retains its identify far downstream in the turbulent boundary layer. The results provide a level of detail usually associated with CFD. Substantial modifications were made to the facility for the second study concerning disturbances generated by Suction Holes for laminar flow Control (LFC). The test section incorporates suction through interchangeable porous test surfaces. Detailed studies have been made using isolated holes in the impervious test plate that used to establish the Blasius base flow. The suction is perturbed harmonically and data are averaged on the basis of the phase of the disturbance, for conditions corresponding to strong suction and without suction.

Watmuff, Jonathan H.

1995-02-01

387

Characteristics of acoustic scattering from a double-layered micro shell for encapsulated drug delivery  

Microsoft Academic Search

This work examines the characteristic differences in acoustic scattering between air-filled double-layered encapsulating (DLE) shells and air-filled single-layered encapsulating (SLE) shells. The analysis shows that the presence of an outer layer softer than the inner layer results in a shift of the first monopole of the reflectivity-frequency response to a higher frequency and a reduction in the monopole peak; and

Yuantai Hu; Shengping Qin; Qing Jiang

2004-01-01

388

Magnetoresistance studies of multilayers including hard magnetic CoSm layers  

Microsoft Academic Search

Cobalt-samarium alloy films were prepared by alternate deposition of Co and Sm in the presence of an external magnetic field to obtain thin magnetic layers with large in-plane coercive fields. These anisotropic CoSm layers were used as hard magnetic layers of noncoupled-type magnetoresistance multilayers or as pinning layers of spin-valve structures. Large magnetoresistance changes up to 4.6% were attained in

K. Mibu; T. Nagahama; T. Shinjo

1996-01-01

389

Renewable nanocomposite layer-by-layer assembled catalytic interfaces for biosensing applications.  

PubMed

A novel, easily renewable nanocomposite interface based on layer-by-layer (LbL) assembled cationic/anionic layers of carbon nanotubes customized with biopolymers is reported. A simple approach is proposed to fabricate a nanoscale structure composed of alternating layers of oxidized multiwalled carbon nanotubes upon which is immobilized either the cationic enzyme organophosphorus hydrolase (OPH; MWNT-OPH) or the anionic DNA (MWNT-DNA). The presence of carbon nanotubes with large surface area, high aspect ratio and excellent conductivity provides reliable immobilization of enzyme at the interface and promotes better electron transfer rates. The oxidized MWNTs were characterized by thermogravimetric analysis and Raman spectroscopy. Fourier transform infrared spectroscopy showed the surface functionalization of the MWNTs and successful immobilization of OPH on the MWNTs. Scanning electron microscopy images revealed that MWNTs were shortened during sonication and that LbL of the MWNT/biopolymer conjugates resulted in a continuous surface with a layered structure. The catalytic activity of the biopolymer layers was characterized using absorption spectroscopy and electrochemical analysis. Experimental results show that this approach yields an easily fabricated catalytic multilayer with well-defined structures and properties for biosensing applications whose interface can be reactivated via a simple procedure. In addition, this approach results in a biosensor with excellent sensitivity, a reliable calibration profile, and stable electrochemical response. PMID:21090581

Mantha, Saroja; Pedrosa, Valber A; Olsen, Eric V; Davis, Virginia A; Simonian, Aleksandr L

2010-11-19

390

Polymer\\/layered silicate nanocomposites as high performance ablative materials  

Microsoft Academic Search

The ablative performance of poly(caprolactam) (nylon 6) nanocomposites is examined. A relatively tough, inorganic char forms during the ablation of these nanocomposites resulting in at least an order-of-magnitude decrease in the mass loss (erosion) rate relative to the neat polymer. This occurs for as little as 2 wt.% (?0.8 vol.%) exfoliated mica-type layered silicate. The presence of the layers does

Richard A Vaia; Gary Price; Patrick N Ruth; Hieu T Nguyen; Joseph Lichtenhan

1999-01-01

391

Properties of optical resonator with a layered metamaterial  

Microsoft Academic Search

The properties of longitudinal and transverse modes of an open optical resonator containing layers of a metamaterial with\\u000a negative refractive index are studied. Due to the presence of these layers, the metaresonator acquires unique properties compared\\u000a to a conventional open resonator. Eigenmodes of the metaresonator are studied in which the properties depend on the average\\u000a dispersion and the average diffraction,

D. O. Saparina; A. P. Sukhorukov

2009-01-01

392

Monte Carlo Simulation of SiOx Layers Annealing  

Microsoft Academic Search

Monte Carlo model of SiOx layers annealing and growth was developed. Model layers of stoichiometric SiO2 with initially randomly distributed components on partially filled diamond-like lattice tends to SiO4 tetrahedron formation during high-temperature annealing. Chains of tetrahedrons are found to be connected by oxygen atom. Portion of properly coordinated atoms was up to 70%. Presence of excess silicon in SiOx

N. A. GIadkih; Nataliya L. Shwartz; ZoyaSh. Yanovitskaja; A. V. Zverev

2007-01-01

393

Electrodeposition and thermal treatment of nickel layers containing titanium  

Microsoft Academic Search

Composite Ni+Ti layers were prepared by simultaneous electrodeposition of nickel and titanium on a steel substrate from a nickel bath in which 40 g dm?3 of Ti powder was suspended by stirring. The presence of NaH2PO2 in the bath allows to obtain the Ni–P+Ti layers. The electrodeposition was carried out under galvanostatic conditions at a temperature of 343 K and

A. Serek; A. Budniok

2003-01-01

394

31 CFR 407.3 - Recording presence.  

Code of Federal Regulations, 2013 CFR

...Treasury 2 2013-07-01 2013-07-01 false Recording presence. 407.3 Section 407.3 Money and Finance...THE TREASURY BUILDING AND THE TREASURY ANNEX § 407.3 Recording presence. Except as otherwise ordered, the property...

2013-07-01

395

31 CFR 91.3 - Recording presence.  

Code of Federal Regulations, 2013 CFR

...Treasury 1 2013-07-01 2013-07-01 false Recording presence. 91.3 Section 91.3 Money and Finance...ON THE BUREAU OF THE MINT BUILDINGS AND GROUNDS § 91.3 Recording presence. Except as otherwise ordered, the property...

2013-07-01

396

Towards a neuropsychological basis of presence  

Microsoft Academic Search

Presence research studies the experience of being in a place or being with someone as it is mediated through technology. The experience of presence appears to be a complex perception, formed through an interplay of raw multisensory data, spatial perception, attention, cognition, and motor action, all coupled through a constant dynamic loop of sensorimotor correspondence. The fact that technology can

Wijnand IJsselsteijn

2005-01-01

397

Individual Differences in the Sense of Presence  

Microsoft Academic Search

There is a lack in the literature of studies that investigate the human factors involved in the engagement of presence. The present study is addressed to investigate the influence of five user's characteristics (spatial intelligence, personality, cognitive style, computer experience and test anxiety) on the sense of presence. This study is the first one to investigate the relationship between spatial

Ivan Alsina Jurnet; Cristina Carvallo Beciu; José Gutiérrez Maldonado

2005-01-01

398

Spatial Presence and Disney's Oswald Comedies  

Microsoft Academic Search

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

J. P. Telotte

2011-01-01

399

Behavioral Presence Test in Threatening Virtual Environments  

Microsoft Academic Search

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

Eric Malbos; Ronald M. Rapee; Manolya Kavakli

2012-01-01

400

Particle presence and indoor air quality  

Microsoft Academic Search

Indoor air quality problems (sick building syndrome) have been attempted to be explained by the presence of gaseous contaminants but no conclusive evidences have been found. This project has studied the presence of airborne particles in indoor air environments as well as perceived air quality with regard to problems of irritation of the mucous membranes in the upper respiratory tract

Anders Jansson; Bengt Christensson; Johan Johansson; Jüri Waher

401

High performance presence-accelerated ray casting  

Microsoft Academic Search

We present a novel presence acceleration for volumetric ray casting. A highly accurate estimation for object presence is obtained by projecting all grid cells associated with the object boundary on the image plane. Memory space and access time are reduced by run-length encoding of the boundary cells, while boundary cell projection time is reduced by exploiting projection templates and multiresolution

Ming Wan; Arie E. Kaufman; Steve Bryson

1999-01-01

402

Sharing and Analysing Presence Experiments Data  

Microsoft Academic Search

Presence research heavily relies on empirical experiments involving subjects in mediated environments. Such experiments can be extremely resource intensive and produce very large amounts of data. As the presence community matures, we would like to suggest that data collected in experiments will be publicly available to the community. This will allow the verification of experimental results, comparing results of experiments

Doron Friedman; Andrea Brogni; Angus Antley; Christoph Guger; Mel Slater

2005-01-01

403

Ethereal presences in holography and photography  

Microsoft Academic Search

This paper examines the concept of the 'Presence of Absence' in post-mortem photography and holography, drawing upon both historical and lesser-known images as reference. To create a photographic negative one needs the presence of light to expose the light sensitive surface, be it glass, a polished plate or plastic. A hologram may also be created when a coherent light source,

M. Richardson; Kay Byrne

2007-01-01

404

Our shrinking ozone layer  

Microsoft Academic Search

Depletion of the Earth’s ozone layer is one of the major environmental concerns for the new millennium having serious implications\\u000a on human health, agriculture and climate. In the past decades, research by the international scientific community has been\\u000a directed towards understanding the impact of human interference on the Earth’s atmosphere. The importance of ozone radiation\\u000a absorption in the atmosphere and

Shashi K. Pathak; Nigel J. Mason

2002-01-01

405

Density of Earth's Layers  

NSDL National Science Digital Library

In this activity, students measure the densities of samples of granite, basalt, peridotite/dunite, and an iron meteorite, which are used as representatives of the various layers of the Earth (crust, mantle, core). The samples are weighed to determine their mass, and the Archimedes Principle is used to determine volume. From these two properties, they calculate density, compare it to accepted values presented in the discussion, and answer questions about their observations.

Klosko, Eryn

406

Origins of Igneous Layering  

NASA Astrophysics Data System (ADS)

Anyone who has ever seen a photo of a layered intrusion, let alone visited one first hand, or even seen a thin section from one, cannot help but be impressed by the stunning record of crystal growth and deposition. Such bodies stand as majestic monuments of undeniable evidence that intricate magmatic processes exist, processes that couple crystallization, convection, and crystal sorting to form rocks so highly ordered and beautiful that they are a wonder to behold. These are the altars to which petrologists must carry their conceived petrologic processes for approval.Although significant in number, the best layered intrusions seem to be found almost always in remote places. Their names, Bushveld, Muskox, Kiglapait, Stillwater, Duke Island, Skaergaard, Rhum, ring through igneous petrology almost as historic military battles (Saratoga, Antietam, Bull Run, Manassas, Gettysburg) do through American history. People who have worked on such bodies are almost folk heros: Wager, Deer, Brown, Jackson, Hess, Irvine, McBirney, Morse; these names are petrologic household words. Yet with all this fanfare and reverence, layered instrusions are nearly thought of as period pieces, extreme examples of what can happen, but not generally what does. This is now all changing with the increasing realization that these bodies are perhaps highly representative of all magmatic bodies. They are simply more dynamically complete, containing more of the full range of interactions, and of course, exposing a more complete record. They are one end of a spectrum containing lava flows, lava lakes, large sills, plutons, and layered intrusions. This book uniquely covers this range with an abundance of first-hand field observations and a good dose of process conceptualization, magma physics, and crystal growth kinetics.

Marsh, Bruce

407

Laminar vortex boundary layers  

NASA Astrophysics Data System (ADS)

The interaction of a Burgers--Rott vortex with a rigid no-slip normal wall is investigated via direct numerical simulations of the unsteady axisymmetric Navier--Stokes equations. The flows in the boundary layer and away from the vortex core have a self-similar structure, i.e. the solutions at time t, radius r, height z, and Reynolds number Re can be reduced to single profiles for the angular momentum and the azimuthal vorticity dependent on a single similarity variable. The similarity variable is the direction normal to the wall scaled by Re^1/2 and a function of r and t. The boundary layer flow near the axis for low-Re consists of a matching between a Bödewadt-like flow near r=0, where the vortex flow is near solid-body rotation, and a potential vortex boundary layer flow. For medium Re, waves form within the core radius resulting from the inflection points in the Bödewadt-like profiles. At large Re, there are also waves that travel vertically along the interface between the rotational core and the irrotational flow outside the core at r? 1.

Arrese, Juan C.; Lopez, John M.

1996-11-01

408

Mapping Active-Layer Thickness in an Urban Area Using the Modified Berggren Solution  

NASA Astrophysics Data System (ADS)

Active-layer thickness (ALT) is typically mapped at coarse resolution. For engineering projects, individual structures are often assumed to be situated in relatively homogeneous environments. As urbanization increases, however, it becomes increasingly important to understand complex interactions between the built and natural components of the local environment. In this study, the modified Berggren solution was used to map ALT at a resolution of 30x30 m over a 150 km2 area. Special attention was given to analyzing differences in accuracy obtained in urbanized and relatively undisturbed tundra. Barrow, Alaska (71.3°N, 156.5°W) is the northernmost community in the USA, and the largest native settlement in the circum-Arctic region (~4600 residents in 2000). It has a long history of scientific research and is the location of the Barrow Environmental Observatory. Modern buildings are elevated 1-2 m on piles and the road network is comprised almost exclusively of 2 m thick, graded sand and gravel pads. Although the modified Berggren solution is known to provide much more accurate estimates of frost and thaw depth than the Stefan solution, it has not been used previously for mapping applications. For the thawing case, Berggren uses thermal conductivity of thawed soil, summer n-factors, seasonal air temperatures, soil density, soil water content, and the latent heat of fusion, as used in the Stefan solution. The Berggren solution introduces a dimensionless coefficient that accounts for heat required to raise the temperature of the soil, thereby improving the accuracy of predicted frost/thaw depths. Calculation of the Berggren coefficient requires information about mean seasonal and annual soil-surface temperature, thermal conductivity of the frozen soil, and frozen and thawed volumetric heat capacity of the soil. As part of the larger Barrow Urban Heat Island Study, 34 miniature data loggers were used to obtain records of air and soil temperature in the area. These data facilitated calculation of air and surface temperature fields, as well as summer n-factors based on nine urban and rural land-cover classes. Recent regional soils and land-cover maps were used to obtain additional input data. Soil and vegetation properties were based on classifications used on the maps and reference properties for soil classes. Validation was performed by comparing ALT probe measurements at the study sites with predicted pixel values. The Berggren solution provided considerable improvement in estimated ALT in comparison to the Stefan solution. It performed well for estimating mean values for land-cover classes in the rural and urban areas and shows promise as a tool for mapping ALT in other applications.

Klene, A.; Nelson, F. E.

2010-12-01

409

The Extratropical Tropopause Inversion Layer  

NASA Astrophysics Data System (ADS)

The extratropical tropopause inversion layer (TIL) is studied by analyzing numerical simulations with a dry idealized global circulation model. The model temperature field is relaxed towards different restoration profiles. We demonstrate that in simulations with the Held and Suarez restoration profile, a TIL is present in the steady state, whereas for a different restoration profile no TIL arises. Neither restoration profile includes a TIL-like structure and if an enhancement in the static stability occurs, it is a result of the model dynamics. We consider the mechanisms by which the TIL forms following previous work in attributing the formation to the structure of the residual circulation, but by further examining the relation of the residual circulation to the structure of the Eliassen-Palm flux convergence using the downward control principle. The presence of two separate regions of convergence of the Eliassen-Palm flux, one in the troposphere and the other in the stratosphere, is found to be necessary to the formation of the TIL. We also discuss the relations to other theories that emphasize the role of vertical gradients in radiatively active species.

Ming, Alison; Haynes, Peter

2013-04-01

410

MAGNETIC BRAIDING AND QUASI-SEPARATRIX LAYERS  

SciTech Connect

The squashing factor Q, a property of the magnetic field line mapping, has been suggested as an indicator for the formation of current sheets, and subsequently magnetic reconnection, in astrophysical plasmas. Here, we test this hypothesis for a particular class of braided magnetic fields which serve as a model for solar coronal loops. We explore the relationship between quasi-separatrix layers (QSLs), that is, layer-like structures with high Q value, electric currents, and integrated parallel currents; the latter being a quantity closely related to the reconnection rate. It is found that as the degree of braiding of the magnetic field is increased, the maximum values of Q increase exponentially. At the same time, the distribution of Q becomes increasingly filamentary, with the width of the high-Q layers exponentially decreasing. This is accompanied by an increase in the number of layers so that as the field is increasingly braided the volume becomes occupied by a myriad of thin QSLs. QSLs are not found to be good predictors of current features in this class of braided fields. Indeed, despite the presence of multiple QSLs, the current associated with the field remains smooth and large scale under ideal relaxation; the field dynamically adjusts to a smooth equilibrium. Regions of high Q are found to be better related to regions of high integrated parallel current than to actual current sheets.

Wilmot-Smith, A. L.; Hornig, G.; Pontin, D. I., E-mail: antonia@maths.dundee.ac.u [Division of Mathematics, University of Dundee, Dundee, DD1 4HN (United Kingdom)

2009-10-20

411

Layer-preference policies in multi-layer GMPLS networks  

Microsoft Academic Search

We address the problem of routing Label Switched Paths (LSPs) in multi-layer networks based on the Generalized MultiProtocol\\u000a Label Switching (GMPLS) paradigm. In particular, we pursue policies for choosing the appropriate layer to host a new LSP request,\\u000a as we find that such layer-preference policies have significant impact on network performance. We discuss several simple layer-preference\\u000a policies and we reveal

Péter Fodor; Gábor Enyedi; Gábor Rétvári; Tibor Cinkler

2009-01-01

412

Intercalation of an oxalatooxoniobate complex into layered double hydroxide and layered zinc hydroxide nitrate.  

PubMed

A Zn/Al layered double hydroxide with molar ratio of 3 was prepared by coprecipitation in alkaline pH and used as a matrix to intercalate the ionic complex diaquadioxalatooxoniobate(V) (DDON), derived from NH(4)[NbO(C(2)O(4))(2)(H(2)O)(2)]2H(2)O. In a similar way, the layered zinc hydroxide nitrate, Zn(5)(OH)(8)(NO(3))(2)2H(2)O, was synthesized, preexpanded with azelate ions ((-)OOC(CH(2))(7)COO(-)), and then intercalated with the niobium complex. For both layered matrices, the results from X-ray powder diffractometry, Fourier transform infrared spectroscopy, and thermal analysis (TG/s-DTA) indicate the presence of the oxalate ion. In addition, results from X-ray photoelectron and Raman spectroscopy indicate the presence of the niobium center bonded to oxygen atoms. Finally, diffuse reflectance UV-vis spectroscopy suggests that the niobium centers are coordinated to oxalate ions. This is the first report of the intercalation of niobium into a layered matrix. PMID:19022456

Arizaga, Gregorio Guadalupe Carbajal; Gardolinski, José Eduardo Ferreira da Costa; Schreiner, Wido Herwig; Wypych, Fernando

2008-11-20

413

Electrically Driven Vortices in Shallow Fluid Layers  

NASA Astrophysics Data System (ADS)

A theoretical and experimental investigation on the flow generated by electromagnetic forces in a thin layer of an electrolyte is presented. The experiment was performed by injecting a uniform steady electric current in a 4 mm layer of a sodium bicarbonate solution, exposed to the magnetic field produced by one or several permanent dipole magnets. The electromagnetic forces created by the interaction of the current and the applied magnetic field stir the fluid and originate different laminar flow patterns. Particle Image Velocimetry results were obtained in both the plane of motion parallel to the bottom wall and the plane transversal to this wall. Experimental results are compared with an analytic linear model as well as a numerical model that solves the two-dimensional non-linear magnetohydrodynamic equations with terms that take into account the Hartmann-Rayleigh friction due to the presence of the bottom wall.

Salas, H.; Cuevas, S.; Ramos, E.; Demiaux, F.

2004-11-01

414

Evaluation of the Presence of Mutagenic Dyes in Sediments from Cristais River  

Microsoft Academic Search

Azo dyes are largely used by coloring textiles and can contaminate the aquatic environment, including the sediment, through their release through effluent discharges. In this work the presence of mutagenic azo dyes was evaluated using Thin Layer Chromatography in sediment samples of the Cristais River upstream and downstream of an azo dye processing plant discharge area. Mutagenicity of the sediment

Danielle Palma De Oliveira; Mônica Luisa Kuhlmann; Gisela De Aragão Umbuzeiro

2006-01-01

415

Optimum Linear Estimation of Stochastic Signals in the Presence of Multiplicative Noise  

Microsoft Academic Search

This paper considers optimum (MMSE) linear recursive estimation of stochastic signals in the presence of multiplicative noise in addition to measurement noise. Often problems associated with phenomena such as fading or reflection of the transmitted signal at an ionospheric layer, and also situations involving sampling, gating, or amplitude modulation, can be cast into such formulation. The different kinds of estimation

P. K. Rajasekaran; N. Satyanarayana; M. D. Srinath

1971-01-01

416

Synthesis of phenol–formaldehyde resole resins in the presence of tetraalkylammonium hydroxides as catalysts  

Microsoft Academic Search

We synthesised phenol–formaldehyde resole resins in the presence of tetraalkylammonium hydroxides as catalysts. The activity of these catalysts was compared with the activity of sodium hydroxide. Gas chromatography, thin layer chromatography, 13C NMR spectrometry, potentiometric titration and a few simple physicochemical methods were used to estimate the composition of the obtained resins and their properties. It was concluded from these

B. Ka??dkowski; J. Hetper

2000-01-01

417

Transient Gravity Wave Critical Layer.  

National Technical Information Service (NTIS)

Numerical simulations of gravity wave, critical layer interactions are presented, which confirm theoretical predictions of critical layer behavior and explain important features of gravity wave observations in the atmosphere, including momentum deposition...

T. J. Dunkerton

1984-01-01

418

Cuckoo: Layered Clustering for NFS.  

National Technical Information Service (NTIS)

Layered clustering allows unmodified distributed file systems to enjoy many of the benefits of cluster-based file services. By interposing between clients and servers, layered clustering requires no changes to clients, servers, or the client-server protoc...

A. J. Klosterman G. Ganger

2002-01-01

419

Multiple layer thermal insulation device  

SciTech Connect

A thermal insulation device is described comprising a modular or block insulation composed of at least two layers of serpentine folded fibrous insulating blankets with the layers of blankets being secured by means of extended folds of the hot face layer being interengaged with folds of the cold face layer, with the cold face layer then being separately secured to attachment means for mounting the block on the wall, ceiling, door or other surface of a furnace, kiln or like structure. The layers of fiber are commonly composed of fibers of different compositions, with the more thermally resistant fiber comprising the outer or hot face layer and the less thermally resistant composition comprising the inner or cold face layer.

Cimochowski, A.E.; Heffelmire, B.A.

1982-07-20

420

Thin Layer Chromatography  

NSDL National Science Digital Library

Developed by the University of Southern Maine for college level chemistry students, this website offers instructive modules dealing with topics related to thin layer chromatography. Using Macromedia Shockwave, these interactive modules incorporate questions within the informative materials to advance users in their problem solving abilities. Topics covered at the website include RF Factor, hydrogen binding, visualization, and stationary phase. With the extensive use of diagrams and figures and the inclusion of a helpful glossary, students seeking assistance in chemistry can learn a great deal at this educational web site.

421

Simplifying presence - a survey and a proposal  

Microsoft Academic Search

As ubiquitous or near-ubiquitous connectivity becomes available for more and more people, instant messaging tech- nologies become even more pervasive in the society. At the same time, there is a growing need for exchanging presence and other real-world state information between users of con- nected devices. This paper evaluates current solutions for presence infor- mation. Based on the evaluation, a

Samuli Sorvakko

422

Chaotic motion in an oscillatory boundary layer.  

PubMed

The chaotic time oscillations in an incompressible fluid driven into motion by a harmonic time-varying pressure gradient is examined. Special attention is given to centrifugal destabilization of the viscous boundary layer. The basic flow is shown to be linearly unstable. For increasing modulation amplitude, the flow exhibits chaotic oscillations. The energy exchange between subharmonics and superharmonics of the least-stable spanwise wave number is considered. The presence of subharmonic Fourier modes are shown to accelerate the transition to temporally chaotic motion. (c) 1996 American Institute of Physics. PMID:12780290

Mehta, V.; Thompson, C.; Mulpur, A.; Chandra, K.

1996-12-01

423

Liquefaction mechanism for layered soils  

Microsoft Academic Search

Results from four centrifuge model tests are presented. Three of the model tests involve layered soil deposits subject to base shaking; one model test involves a uniform soil deposit of sand subject to base shaking. The layered soil models consisted of fine sand overlain by a layer of relatively impermeable silica flour (silt). Pore-water pressures, accelerations, and settlements were measured

Gregg L. Fiegel; Bruce L. Kutter

1994-01-01

424

Control of Turbulent Mixing Layers.  

National Technical Information Service (NTIS)

Study of the open-loop forcing of the shear layer by a pitching airfoil led to the following results: it is possible to induce very large changes in the shear layer growth rate downstream of the disturbance location, while leaving the portion of the layer...

P. E. Dimotakis M. M. Koochesfahani

1989-01-01

425

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

Microsoft Academic Search

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

Eva-lotta Sallnäs

2005-01-01

426

Local properties of the surface layer(s) of BiFeO3 single crystals  

NASA Astrophysics Data System (ADS)

The surface of BiFeO3 single crystals has been characterized at the local level using several AFM-based techniques. We have observed the presence of two different epilayers showing electrical and mechanical properties different from those of the bulk: a ferroelectrically ``dead'' outer skin of 5 nm sitting upon a subsurface layer that displays an extremely fine pattern of hierarchical self-ordered nanodomains. Based on the size of the nanodomains and applying a Kittel-like analysis, we argue that the nanotwinned region should be confined in a layer less than a micron deep. The superficial phase transition at T* = 275 °C is restricted to the outer skin layer (the ``dead'' layer), while the nanotwinned layer is insensitive to this transition. In view of the photovoltaic properties and spin-dependent transport of domain walls in BiFeO3, the existence of nanodomains (and thus a high density of domain walls) in bulk single crystals is likely to be relevant for understanding their functional properties.

Domingo, Neus; Narvaez, Jackeline; Alexe, Marin; Catalan, Gustau

2013-05-01

427

PRESENCE OF WAX ESTERS AND SQUALENE IN HUMAN SALIVA  

PubMed Central

Objective The purpose of this study was to determine the presence and relative composition of neutral lipids in human saliva. Design Whole unstimulated saliva was collected from 12 subjects ranging from 21 to 29 years old. Samples were lyophilized, and lipids were extracted using chloroform-methanol. Lipids were analyzed by thin-layer chromatography. Results Human saliva contains cholesterol, fatty acids, triglycerides, wax esters, cholesterol esters and squalene. The mean total neutral lipid content was 12.1 +/? 6.3 µg/ml. Conclusions This lipids in human saliva closely resemble the lipids found on the skin surface. These salivary lipids are most likely produced by the sebaceous follicles in the oral mucosa and sebaceous glands associated with major salivary glands.

Brasser, Andrew J; Barwacz, Christopher A; Dawson, Deborah V; Brogden, Kim A; Drake, David R; Wertz, Philip W

2011-01-01

428

Flexible, layered biofuel cells.  

PubMed

Similar to conventional electrolyte batteries, biofuel cells often need to be stacked in order to boost their single cell voltage (<1 V) up to a practical level. Here, we report a laminated stack of biofuel cells that is composed of bioanode fabrics for fructose oxidation, hydrogel sheets containing electrolyte and fuel (fructose), and O(2)-diffusion biocathode fabrics. The anode and cathode fabrics were prepared by modifying fructose dehydrogenase and bilirubin oxidase, respectively, on carbon nanotubes-decorated carbon fiber fabrics. The total thickness of the single set of anode/gel/cathode sheets is just 1.1mm. The laminated triple-layer stack produces an open-circuit voltage of 2.09 V, which is a 2.8-fold increase over that of a single set cell (0.74 V). The present layered cell (5 mm × 5 mm) produces a maximum power of 0.64 mW at 1.21 V, a level that is sufficient to drive light-emitting diodes. PMID:22704841

Miyake, Takeo; Haneda, Keigo; Yoshino, Syuhei; Nishizawa, Matsuhiko

2012-06-07

429

A Cross-Media Presence Questionnaire: The ITC-Sense of Presence Inventory  

Microsoft Academic Search

The presence research community would benefit from a reliable and valid cross- media presence measure that allows results from different laboratories to be com- pared and a more comprehensive knowledge base to be developed. The ITC-Sense of Presence Inventory (ITC-SOPI) is a new state questionnaire measure whose de- velopment has been informed by previous research on the determinants of pres-

Jane Lessiter; Jonathan Freeman; Edmund Keogh; Jules Davidoff

2001-01-01

430

Do stable atmospheric layers exist?  

NASA Astrophysics Data System (ADS)

The notion of stable atmospheric layers is a classical idealization used for understanding atmospheric dynamics and thermodynamics. Using state of the art drop sonde data and using conditional, dynamical and convective stability criteria we show that apparently stable layers are typically composed of a hierarchy of unstable layers themselves with embedded stable sublayers, and unstable sub-sub layers etc. i.e. in a Russian Matryoshka doll-like fractal hierarchy. We therefore argue that the notion of stable atmospheric layers is untenable and must be replaced by modern scaling notions.

Lovejoy, S.; Tuck, A. F.; Hovde, S. J.; Schertzer, D.

2008-01-01

431

Buried oxide layer in silicon  

DOEpatents

A process for forming Silicon-On-Insulator is described incorporating the steps of ion implantation of oxygen into a silicon substrate at elevated temperature, ion implanting oxygen at a temperature below 200.degree. C. at a lower dose to form an amorphous silicon layer, and annealing steps to form a mixture of defective single crystal silicon and polycrystalline silicon or polycrystalline silicon alone and then silicon oxide from the amorphous silicon layer to form a continuous silicon oxide layer below the surface of the silicon substrate to provide an isolated superficial layer of silicon. The invention overcomes the problem of buried isolated islands of silicon oxide forming a discontinuous buried oxide layer.

Sadana, Devendra Kumar (Pleasantville, NY); Holland, Orin Wayne (Lenoir, TN)

2001-01-01

432

Instabilities of a compressible mixing layer  

NASA Astrophysics Data System (ADS)

Instability waves in a free shear layer formed by two parallel compressible streams are analyzed using the linear spatial stability theory. The effects of viscosity, Mach number, the velocity, and temperature ratios on the growth rate are determined. Increasing the temperature ratio produces a strong stabilizing effect on the growth of the mixing flow; this stabilization does not, however, persist at higher Mach numbers. Whereas the maximum growth rate of the incompressible mixing layer varies linearly with the velocity ratio, the maximum growth rate of the compressible mixing flow varies nonlinearly with the velocity ratio. The convective Mach number is found to be the appropriate parameter for correlating the compressibility effects on the spreading rate of the mixing layer. Linear subharmonic instabilities of a compressible mixing layer are analyzed by using Floquet theory. The basic state is obtained by the linear superposition of a steady mean flow and the neutral primary wave of that mean flow. The growth rates of two-dimensional subharmonic instabilities are shown to increase with increasing amplitude of the periodicity but decrease with increasing convective Mach number. For subsonic convective Mach numbers, the presence of the periodicity enhances the growth rates of three-dimensional subharmonic waves over a wide range of spanwise wavenumber. However, when the convective Mach number is greater than one, the interaction between the subharmonic wave and the primary wave marginally increases the maximum growth rate of the subharmonic, which dramatically increases the range of amplified spanwise wave numbers. Fourth-order compact finite-difference codes are developed for solving the compressible boundary-layer equations and investigating their primary and subharmonic instabilities.

Wu, Jeun-Len

433

Effect of Boundary Layer Thickness and Entropy Layer on Boundary Layer Combustion  

Microsoft Academic Search

This project investigates the possibilities of scramjet combustor performance enhancement by reducing the skin friction through boundary layer combustion. Experiments were conducted in the T4 Stalker tube to investigate the influence of boundary layer thickness and entropy layers on the ignition of a hydrogen air mixture near the wall of a constant area duct. The hydrogen was injected tangentially from

R. M. Kirchhartz; D. J. Mee; R. J. Stalker

434

Liquefaction mechanism for layered soils  

SciTech Connect

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

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

1994-04-01

435

Plasma excitations of dressed Dirac electrons in graphene layers  

Microsoft Academic Search

Collective plasma excitations of optically dressed Dirac electrons in single and double graphene layers are calculated in the RPA. The presence of circularly polarized light gives rise to an energy gap Eg between the conduction and valence energy bands. Its value may be adjusted by varying the frequency and intensity of the light, and may reach values of the gap

Oleksiy Roslyak; Godfrey Gumbs; Danhong Huang

2011-01-01

436

Nonequilibrium shock layer radiation in a simulated Titan atmosphere  

Microsoft Academic Search

This work is a combined experimental and numerical study to assess the effect of nonequilibrium flow on the shock layer radiation surrounding the Huygens probe which will enter the atmosphere of the Saturnian Moon Titan at a speed somewhat under 6 km\\/sec in the year 2003. The radiation is especially enhanced due to the presence of a few per cent

D. Bershder; C. S. Park

1992-01-01

437

Drag reduction by microbubbles in a turbulent boundary layer  

Microsoft Academic Search

An experimental characterization of the turbulent boundary layer over a flat plate in the presence of small amounts of microbubbles is performed. The average diameter of the injected bubbles is comparable with the local Kolmogorov lengthscale, and the bulk void fraction C is approximately 0.1%. The velocity field of the liquid phase, as well as the bubble characteristics, is acquired

Boris Jacob; Angelo Olivieri; Massimo Miozzi; Emilio F. Campana; Renzo Piva

2010-01-01

438

Adhesion of Staphylococcus aureus to horny layer: role of fibrinogen  

Microsoft Academic Search

Staphylococcus aureus cells attach to and invade the epidermis more easily under conditions of abrasion or occlusion or in the presence of irritant dermatitis than when the epidermis is intact. This fact strongly suggests that exuded plasma components may play an important role in the adherence of S. aureus cells to the horny layer. S. aureus cells (Cowan 1 strain,

Hiroko Kanzaki; Yoshiko Morishita; Hisanori Akiyama; Jiro Arata

1996-01-01

439

Being there : the experience of presence in mediated environments  

Microsoft Academic Search

Presence, the experience of 'being there' in a mediated environment, has become closely associated with VR and other advanced media. Different types of presence are discussed, including physical presence, social presence, and co-presence. Fidelity-based approaches to presence research emphasize the fact that as media become increasingly interactive, perceptually realistic, and immersive, the experience of presence becomes more convincing. In addition,

Wijnand IJSSELSTEIJN; Giuseppe RIVA

2003-01-01

440

Mixed Layer Restratification: Early Results from the AESOP Program  

NASA Astrophysics Data System (ADS)

As part of the Office of Naval Research-sponsored AESOP program, an observational effort employed acoustically-tracked Lagrangian floats and a towed, undulating profiler (Triaxus) to investigate the relative importance of vertical and horizontal mixing in governing boundary layer structure in the presence of O(1 km) scale horizontal variability. Remotely sensed sea surface temperature and ocean color directed sampling to regions characterized by strong lateral gradients. Lagrangian floats deployed near frontal interfaces defined a drifting reference frame and characterized vertical mixing, while the towed profiler executed synoptic, high-resolution surveys to map three-dimensional variability following the drifting float. Sampling encompassed a variety of conditions, including an illustration of mixed layer restratification in the presence of strong lateral density gradients. Sampling began during a period of 20 - 30 kt winds and 30-m deep mixed layers, focusing on a region of strong horizontal denstiy contrast associated with an upper ocean front. Winds weakened to 5 - 10 knots over a 12-hour period, during which observations captured a continuous sequence of sections around a drifting float. The mixed layer rapidly slumped as winds weakened, with lighter waters overriding waters from the front's dense side to produce a fully stratified boundary layer within a 20-hour inertial period. Strong intrusions, visible in temperature, salinity and chlorophyll fluorescence, also contributed to stratification changes, especially in the region beneath the 24.5 kg/m3 isopycnal that initially defined the mixed layer base.

Lee, C. M.; D'Asaro, E. A.; Harcourt, R.

2006-12-01

441

Slow-wave resonance in periodic stacks of anisotropic layers  

NASA Astrophysics Data System (ADS)

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

Figotin, Alex; Vitebskiy, Ilya

2007-11-01

442

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

NASA Astrophysics Data System (ADS)

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

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

1998-04-01

443

Low temperature electrodeposition of zinc oxide layers as transparent conducting oxide window layers for CIGS solar cells  

Microsoft Academic Search

Electrodeposition of zinc oxide layers has been carried out in simple aqueous solutions at 80°C in presence of zinc ions and dissolved oxygen. Extrinsic n type doping has been proven to be effective by anionic substitution of oxygen by chlorine, using chloride containing electrolytes. Doping level upper values up to 9.1019 cm-3 have been obtained, associated with lateral resistivies in

Jean ROUSSET; Daniel LINCOT

2009-01-01

444

Technology and true presence in nursing.  

PubMed

If there is to be a future for nursing in the next millenium, it must be dictated not by technologic advances directly but by the manner in which technology relates with persons in health and illness. Technology enables nurses to care for persons in a more efficient and cost-effective manner. True presence, as articulated in the human becoming theory, affords members of the profession opportunities to be with persons in ways that make a difference to their quality of life. The article illustrates the recognition of the link between technology and true presence through the use of a nurse-person encounter. PMID:9849207

Bernardo, A

1998-07-01

445

Particle diffusion in the presence of trapping  

SciTech Connect

The diffusion of particles in the presence of randomly distributed trapping centres is examined. An analytical approach is developed for three simple models of the trap-release processes. It is shown that the particle motion remains diffusive on the average, but the diffusion coefficient can have large fluctuations. The results of the numerical simulations confirm the main qualitative trends found in the analytical study. Although they are very simple, the models can be useful for the examination of the diffusion in tokamak plasma in the presence of quasi-coherent structures which act as trapping centres. {copyright} {ital 1997 American Institute of Physics.}

Spineanu, F.; Vlad, M. [Association Euratom-Commissariat a lEnergie Atomique pour la Fusion, Departement de Recherche sur la Fusion Controlee, Centre dEtudes de Cadarache, 13108 Saint-Paul-lez-Durance (France)

1997-06-01

446

Turbulent boundary layer manipulation by outer-layer devices  

Microsoft Academic Search

A turbulent boundary layer manipulated by outer-layer devices has been studied. Experiments have been conducted in the 0.70 by 0.50 m2 low speed wind tunnel of the ‘Modesto Panetti’ Aeronautical Laboratory of the Politecnico di Torino. Mean values and turbulent quantities measured in the natural and manipulated boundary layers are shown for comparison. The mechanisms to explain the observed skin

G. Iuso; M. Onorato

1995-01-01

447

Layered SAW hydrogen sensor with modified tungsten trioxide selective layer  

Microsoft Academic Search

Layered surface acoustic wave (SAW) devices are investigated for sensing hydrogen (H2) concentrations less than 1% in air. Platinum (Pt) and gold (Au) catalyst activated tungsten trioxide (WO3) selective layers are investigated. The SAW sensors consist of two thin film metal interdigital transducers (IDTs) on a 36°Y-cut, X-propagating LiTaO3 substrate. A ZnO guiding layer is used to confine the acoustic

S. J. Ippolito; S. Kandasamy; K. Kalantar-Zadeh; W. Wlodarski

2005-01-01

448

Carrier Density Profiling of Ultra-Shallow Junction Layers Through Corrected C-V Plotting  

SciTech Connect

The aim of this report is to present and justify a new approach for carrier density profiling in ultra-shallow junction (USJ) layer. This new approach is based on a capacitance measurement model, which takes series impedance, shunt resistance and the presence of a boron skin on the USJ layer into account. It allows us to extract the depletion layer capacitances in the USJ layer from C-V plotting more accurately and hence to obtain better carrier density profiles. Based on this new approach the carrier density profiles of different USJ layers with and without halo-style implants are obtained and discussed.

Chen, James; Dimitrov, Dimitar; Dimitrova, Tatiana [Four Dimensions, Inc., 3140 Diablo Ave, Hayward, California, 94545 (United States); Timans, Paul [Mattson Technology, Inc. Fremont, California (United States); Gelpey, Jeff; McCoy, Steve [Mattson Technology Canada, Inc., Vancouver (Canada); Lerch, Wilfried; Paul, Silke [Mattson Thermal Products GmbH, Dornstadt (Germany); Bolze, Detlef [IHP, Frankfurt (Oder) (Germany)

2008-11-03

449

Could the presence of a Carhart notch predict the presence of glue at myringotomy?  

PubMed

The Carhart notch is a dip in the bone conduction at 2000 Hz without a corresponding dip in the air conduction. The main objective of this study was to establish how reliable is the presence of the Carhart notch in a preoperative audiogram in predicting the presence of glue at myringotomy. A prospective study has been carried out in 50 children presenting with glue ear to find out the association between the Carhart notch and the presence of glue at myringotomy. Children were seen before the operation and an audiogram and tympanogram were carried out. Myringotomy was carried out in 95 ears and the presence or absence of glue was recorded. The significance of the air-bone gap and the type of tympanogram in predicting a middle ear effusion were also examined. The audiograms of 37 ears showed a Carhart notch; of these, 36 ears were noted to have glue ear. The correlation between the presence of a Carhart notch in the preoperative audiogram and the presence of glue at myringotomy was found to be significant (P < 0.001) (chi-square test). Using the decision rule that the presence of a Carhart notch predicts the presence of glue, the following operating characteristics were determined: correct, 83 ears (87.4%); false positive, one ear (1.1%); false negative, 11 ears (11.6%). The presence of a Carhart notch was found to be a strong predictor of the presence of glue at myringotomy. PMID:12755752

Kumar, M; Maheshwar, A; Mahendran, S; Oluwasamni, A; Clayton, M I

2003-06-01

450

Pluralistic media ignorance: Presence and causes  

Microsoft Academic Search

This study examines the presence and causes of pluralistic media ignorance – incorrect estimation of media content in a way that creates the impression that popular broadcasting is overabundant with morally controversial material. Using the appearance of sexual content in television advertising in Israel as a case study, we compare survey estimates (N=305) of the prevalence of this material with

Amir Hetsroni

2011-01-01

451

Particularity, Presence, Art Teaching, and Learning  

ERIC Educational Resources Information Center

|This manuscript explores the interplay of the concepts of "thisness" and singularity with art making. It explores the particularity of the individual--person, object, animal, plant, place, event; the clarity and joyousness of "thisness" or specificity; the exquisite presence of now; and the relationship of these qualities to contemplation and art…

Kellman, Julia

2007-01-01

452

Teaching and Learning Immersion and Presence  

Microsoft Academic Search

It is known since Socrates that people learn better by experiencing a problem by themselves and by finding a (the) solution(s) by their own. It is however not always possible to offer such freedom to students when teaching the concepts of immersion and presence in virtual environments due to the technological complexity and the intrinsically subjective nature of these concepts.

Bruno Herbelin; Jan Cíger

2008-01-01