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1

Crystal Ice  

Microsoft Academic Search

IN reference to the ``crystal ice'' proposed by Dr. Calantarients, of Scarborough, for skating upon with ordinary skates, it may not be generally known that more than thirty years ago a skating pond was constructed in Liverpool, consisting, I believe, entirely of crystallised Glauber's salt. I have a perfect recollection of this miniature lake with its grotto-like surroundings, of its

R. H

1880-01-01

2

Dependence of the single-scattering properties of small ice crystals on idealized shape models  

Microsoft Academic Search

Small ice crystals (with maximum dimension <50 mum) appear quasi-circular when imaged by probes on aircraft flying through cloud. Therefore, idealized models constructed to calculate their single-scattering properties have included quasi-spherical models such as Chebyshev particles, Gaussian random spheres, and droxtals. Recently, an ice analogue grown from sodium fluorosilicate solution on a glass substrate, with several columns emanating from a

J. Um; G. M. McFarquhar

2010-01-01

3

Dependence of the single-scattering properties of small ice crystals on idealized shape models  

Microsoft Academic Search

The projections of small ice crystals (with maximum dimension <50 mum) appear quasi-circular when imaged by probes on aircraft flying through cloud. Therefore, idealized models constructed to calculate their single-scattering properties have included quasi-spherical models such as Chebyshev particles, Gaussian random spheres, and droxtals. Recently, an ice analogue grown from sodium fluorosilicate solution on a glass substrate, with several columns

J. Um; G. M. McFarquhar

2011-01-01

4

Snow Ice Crystals  

NSDL National Science Digital Library

This article from Physics Today by Yoshinori Furukawa and John S. Wettlaufer and John S. Wettlaufer describes how ice crystals form on the earth. The resource includes graphics depicting how different shapes of ice crystals are formed.

Furukawa, Y.; Wettlaufer, John S., 1963-

2010-03-12

5

Biosynthesis of quasi-spherical Ag nanoparticle by Pseudomonas aeruginosa as a bioreducing agent  

NASA Astrophysics Data System (ADS)

Use of microorganism as a novel and eco-friendly strategy to production of nanomaterials is an important aspect of modern nanotechnology. Biosynthesis of quasi-spherical silver nanoparticles (Ag-NPs) has been investigated using Pseudomonas aeruginosa. We observe that silver (Ag+) ions when exposed to P. aeruginosa biomass are reduced in solution, thereby leading to the formation of Ag-NPs. Quasi-spherical shape and nearly well distribution and FCC crystal structure of Ag-NPs were confirmed by XRD pattern, STM and TEM micrographs. UV-Vis spectra show a surface plasmon resonance (SPR) band at ~ 435 nm.

Taheri Otaqsara, S. M.

2011-12-01

6

Quasi-spherical direct drive fusion.  

SciTech Connect

The authors present designs of quasi-spherical direction drive z-pinch loads for machines such as ZR at 28 MA load current with a 150 ns implosion time (QSDDI). A double shell system for ZR has produced a 2D simulated yield of 12 MJ, but the drive for this system on ZR has essentially no margin. A double shell system for a 56 MA driver at 150 ns implosion has produced a simulated yield of 130 MJ with considerable margin in attaining the necessary temperature and density-radius product for ignition. They also represent designs for a magnetically insulated current amplifier, (MICA), that modify the attainable ZR load current to 36 MA with a 28 ns rise time. The faster pulse provided by a MICA makes it possible to drive quasi-spherical single shell implosions (QSDD2). They present results from 1D LASNEX and 2D MACH2 simulations of promising low-adiabat cryogenic QSDD2 capsules and 1D LASNEX results of high-adiabat cryogenic QSDD2 capsules.

VanDevender, J. Pace; Abbott, Lucas M.; Langston, William L.; McDaniel, Dillon Heirman; Nash, Thomas J.; Roderick, Norman Frederick; Silva, M.

2007-01-01

7

Sublimation of Ice Crystals  

Microsoft Academic Search

Recent experiments on the sublimation of single crystals of ice in an atmosphere of air indicate that the sublimation rate is diffusion limited and initially solid prismatic crystals evolve into time-independent shapes similar to confocal ellipses rotated about their major or minor axis (prolate or oblate spheroids). Step formation at crystal edges and vapor diffusion easily explain these observations.

Jon Nelson

1998-01-01

8

The effect of ice crystal shape on aircraft contrails  

NASA Astrophysics Data System (ADS)

Aircraft contrails are a common phenomenon observed in the sky. They are formed mainly of water, from the ambient atmosphere and as a by-product of the combustion process, in the form of ice crystals. They have been identified as a potential contributor to global warming. Some contrails can be long-lived and create man-made cloud cover, thus possibly altering the radiative balance of the earth. There has been a great deal of research on various aspects of contrail development, but to date, little has been done on the influence of ice crystal shapes on the contrail evolution. In-situ studies have reported that young contrails are mainly quasi-spherical crystals while older contrails can have a much more diverse spectrum of possible shapes. The most common shapes found in contrails are quasi-spherical, hexagonal columns, hexagonal plates, and bullet rosettes. Numerical simulations of contrails to date typically have assumed "spherical" as the default ice shape. This work simulated contrail development with a large eddy simulation (LES) model that implemented both spherical and non-spherical shapes to examine the effects. The included shape effect parameters, such as capacitance coefficient, ventilation factor, Kelvin effect, fall velocity and ice crystal surface area, help to establish the shape difference in the results. This study also investigated initial sensitivities to an additional ice parameter, the ice deposition coefficient. The literature shows conflicting values for this coefficient over a wide range. In the course of this investigation a comparison of various ice metrics was made for simulations with different assumed crystal shapes (spheres, hexagonal columns, hexagonal plates, bullet rosettes and combination of shapes). The simulations were performed at early and late contrail time, with a range of ice crystal sizes, and with/without coupled radiation. In young and older contrails and without coupled radiation, the difference from the shape effect in ice crystal number, N(t), is not significant compared with the level of uncertainty. In young contrails, the difference between spherical and non-spherical shapes in N(t) is less than 7% for relatively large ice particles and 23% for relatively small ice particles. The ice mass, M(t), is not significantly affected by the crystal shapes, with less than 8% difference. However, the ice surface area, S(t), is the ice metric more sensitive to crystal shape, with a maximum difference of 68%. It increases at late time, though it is mainly governed by geometrical rather than dynamical effects. The small sensitivity to shape effects in the ice contrail metrics when radiation is not included suggests that the spherical shape will provide a reasonable representation for all shapes found in the in-situ studies. The radiation is included at late time, when the lasting effects of contrails are more critical. The inclusion of coupled radiation increases the level of dispersion in the results and hence increases slightly the differences due to shape effects. The small difference is also observed in the infrared heating rates of contrails.

Meza Castillo, Omar E.

9

Cluster self-organization of intermetallic systems: Quasi-spherical nanocluster precursors with internal Friauf polyhedra (A-172) and icosahedra (B-137) in the Li{sub 19}Na{sub 8}Ba{sub 15} (hP842) crystal structure  

SciTech Connect

A combinatorial and topological analysis of Li{sub 19}Na{sub 8}Ba{sub 15} (hP842, a = 20 A, c = 93 A, V = 33552 A{sup 3}, P3-bar) has been performed using computer methods (the TOPOS program package). Two types of crystal-forming quasi-spherical nanoclusters about 20 A in diameter with internal Friauf polyhedra (A-172) and icosahedra (B-137) have been established by the complete decomposition of the 3D factor graph of the structure into cluster substructures. Each type of nanoclusters forms close-packed 2D layers 3{sup 6}, which alternate along the c axis. The B-137 and A-172 nanoclusters are composed of three layers and have shell compositions (1 + 12 + 32 + 92) and (1 + 16 + 59 + 103) with local symmetries 3 and 3-bar, respectively; they were revealed for the first time in crystal structures as cluster precursors. The icosahedral B-137 nanocluster contains a 104-atom quasicrystal approximant (Samson cluster).

Ilyushin, G. D., E-mail: ilyushin@ns.crys.ras.ru [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Blatov, V. A. [Samara State University (Russian Federation)

2010-12-15

10

Dependence of the single-scattering properties of small ice crystals on idealized shape models  

NASA Astrophysics Data System (ADS)

Small ice crystals (with maximum dimension <50 ?m) appear quasi-circular when imaged by probes on aircraft flying through cloud. Therefore, idealized models constructed to calculate their single-scattering properties have included quasi-spherical models such as Chebyshev particles, Gaussian random spheres, and droxtals. Recently, an ice analogue grown from sodium fluorosilicate solution on a glass substrate, with several columns emanating from a common center of mass, was shown to be quasi-circular when imaged by state-of-the-art cloud probes. In this study, a new idealized model, called the budding Bucky ball (3B) that resembles the shape of the small ice analogue is developed. The corresponding single-scattering properties (scattering phase function P11 and asymmetry parameter g) are computed by a ray-tracing code. Compared with previosly used models, 3B scatters less light in the forward and more light in the lateral and backward directions. The Chebyshev particles and Gaussian random spheres show smooth and featureless P11, whereas droxtals and 3Bs, which have a faceted structure, show several peaks in P11 associated with angles of minimum deviation. Overall, the difference in the forward (lateral; backward) scattering between models are up to 22% (994%; 132%), 20% (510%; 101%), and 16% (146%; 156%) for small ice crystals with repective area ratios of 0.85, 0.77, and 0.69. The g for different models varies by up to 25%, 23%, and 19% for particles with area ratios of 0.85, 0.77, and 0.69, respectively. Becuase the single-scattering properties of small ice crystals depend both on the choice of the idealized model and the area ratios used to characterize the small ice crystals, higher resolution observations of small ice crystals or direct observations of their single-scattering properties are required.

Um, J.; McFarquhar, G. M.

2010-11-01

11

Dependence of the single-scattering properties of small ice crystals on idealized shape models  

NASA Astrophysics Data System (ADS)

The projections of small ice crystals (with maximum dimension <50 ?m) appear quasi-circular when imaged by probes on aircraft flying through cloud. Therefore, idealized models constructed to calculate their single-scattering properties have included quasi-spherical models such as Chebyshev particles, Gaussian random spheres, and droxtals. Recently, an ice analogue grown from sodium fluorosilicate solution on a glass substrate, with several columns emanating from a common center of mass, was shown to be quasi-circular when imaged by state-of-the-art cloud probes. In this study, a new idealized model, called the budding Bucky ball (3B) that resembles the shape of the small ice analogue is developed. The corresponding single-scattering properties (scattering phase function P11 and asymmetry parameter g) are computed by a ray-tracing code. Compared with previously used models, 3B scatters less light in the forward and more light in the lateral and backward directions. The Chebyshev particles and Gaussian random spheres show smooth and featureless P11, whereas droxtals and 3Bs, which have a faceted structure, show several peaks in P11 associated with angles of minimum deviation. Overall, the difference in the forward (lateral; backward) scattering between models are up to 22% (994%; 132%), 20% (510%; 101%), and 16% (146%; 156%) for small ice crystals with respective area ratios of 0.85, 0.77, and 0.69. The g for different models varies by up to 25%, 23%, and 19% for particles with area ratios of 0.85, 0.77, and 0.69, respectively. Because the single-scattering properties of small ice crystals depend both on the choice of the idealized model and the area ratios used to characterize the small ice crystals, higher resolution observations of small ice crystals or direct observations of their single-scattering properties are required.

Um, J.; McFarquhar, G. M.

2011-04-01

12

a Dynamical Symmetry of the Quasi-Spherical (or Spherical) Collapse  

Microsoft Academic Search

By linearly scaling the initial data set (mass and kinetic energy functions), it is found that the dynamics of quasi-spherical (or spherical) collapse remains invariant for dust or a general (Type I) matter field, provided the comoving radius is also appropriately scaled. This defines a symmetry of the quasi spherical (or spherical) collapse. That is, the linear transformation identifies an

Ujjal Debnath; Subenoy Chakraborty; Naresh Dadhich

2005-01-01

13

Fundamental Ice Crystal Accretion Physics Studies.  

National Technical Information Service (NTIS)

Due to numerous engine power-loss events associated with high-altitude convective weather, ice accretion within an engine due to ice-crystal ingestion is being investigated. The National Aeronautics and Space Administration (NASA) and the National Researc...

A. P. Broeren D. Fuleki D. Knezevici J. Tsao M. Vargas P. M. Struk T. Currie W. Wright

2011-01-01

14

Fundamental Ice Crystal Accretion Physics Studies.  

National Technical Information Service (NTIS)

Due to numerous engine power-loss events associated with high-altitude convective weather, ice accretion within an engine due to ice crystal ingestion is being investigated. The National Aeronautics and Space Administration (NASA) and the National Researc...

A. P. Broeren D. Fuleki D. Knezevici J. C. Tsao M. Vargas P. M. Struk T. Currie W. B. Wright

2012-01-01

15

Thermal undulations of quasi-spherical vesicles stabilized by gravity  

NASA Astrophysics Data System (ADS)

The classical treatment of quasi-spherical vesicle undulations has, in the present work, been reviewed and extended to systems, which are affected by a gravitational field caused by a density difference across the membrane. The effects have been studied by the use of perturbation theory leading to corrections to the mean shape and the fluctuation correlation matrix. These corrections have been included in an analytical expression for the flicker spectrum to probe how the experimentally accessible spectrum changes with gravity. The results are represented in terms of the gravitational parameter, g0=?? g R4/kappa. The contributions from gravity are in most experimental situations small and thus negligible, but for values of g0 above a certain limit, the perturbational corrections must be included. Expressions for the relative error on the flicker spectrum have been worked out, so that it is possible to define the regime where gravity is negligible. An upper limit of g0 has also been identified, where the error in all modes of the flicker spectrum is significant due to distortion of the mean shape.

Henriksen, J. R.; Ipsen, J. H.

2002-11-01

16

Structure of ice crystallized from supercooled water  

PubMed Central

The freezing of water to ice is fundamentally important to fields as diverse as cloud formation to cryopreservation. At ambient conditions, ice is considered to exist in two crystalline forms: stable hexagonal ice and metastable cubic ice. Using X-ray diffraction data and Monte Carlo simulations, we show that ice that crystallizes homogeneously from supercooled water is neither of these phases. The resulting ice is disordered in one dimension and therefore possesses neither cubic nor hexagonal symmetry and is instead composed of randomly stacked layers of cubic and hexagonal sequences. We refer to this ice as stacking-disordered ice I. Stacking disorder and stacking faults have been reported earlier for metastable ice I, but only for ice crystallizing in mesopores and in samples recrystallized from high-pressure ice phases rather than in water droplets. Review of the literature reveals that almost all ice that has been identified as cubic ice in previous diffraction studies and generated in a variety of ways was most likely stacking-disordered ice I with varying degrees of stacking disorder. These findings highlight the need to reevaluate the physical and thermodynamic properties of this metastable ice as a function of the nature and extent of stacking disorder using well-characterized samples.

Malkin, Tamsin L.; Murray, Benjamin J.; Brukhno, Andrey V.; Anwar, Jamshed; Salzmann, Christoph G.

2012-01-01

17

Structure of ice crystallized from supercooled water.  

PubMed

The freezing of water to ice is fundamentally important to fields as diverse as cloud formation to cryopreservation. At ambient conditions, ice is considered to exist in two crystalline forms: stable hexagonal ice and metastable cubic ice. Using X-ray diffraction data and Monte Carlo simulations, we show that ice that crystallizes homogeneously from supercooled water is neither of these phases. The resulting ice is disordered in one dimension and therefore possesses neither cubic nor hexagonal symmetry and is instead composed of randomly stacked layers of cubic and hexagonal sequences. We refer to this ice as stacking-disordered ice I. Stacking disorder and stacking faults have been reported earlier for metastable ice I, but only for ice crystallizing in mesopores and in samples recrystallized from high-pressure ice phases rather than in water droplets. Review of the literature reveals that almost all ice that has been identified as cubic ice in previous diffraction studies and generated in a variety of ways was most likely stacking-disordered ice I with varying degrees of stacking disorder. These findings highlight the need to reevaluate the physical and thermodynamic properties of this metastable ice as a function of the nature and extent of stacking disorder using well-characterized samples. PMID:22232652

Malkin, Tamsin L; Murray, Benjamin J; Brukhno, Andrey V; Anwar, Jamshed; Salzmann, Christoph G

2012-01-09

18

Impurities in Spin Ice Crystals  

NASA Astrophysics Data System (ADS)

Spin ice crystals (and pyrochlore oxides in general) have raised a lot of interest of late thanks to their exotic properties, including emergent gauge symmetries, possible spin liquid behavior, and magnetic monopole excitations. Theoretical and experimental efforts in the study of these materials have benefited from the relative ease of growth of large clean single crystals. Even in such clean systems, however, impurities can play a crucial role in determining the properties at very low temperatures (see e.g., C. Henley, http://arxiv.org/abs/1210.8137). Here we investigate this issue both experimentally and theoretically. We study how controlled non-magnetic Y-dilution in Dy2Ti2O7 gradually alters the effective monopole description and the thermodynamic properties of the system at low temperature (extending earlier work by other authors to regimes that have not been investigated so far). We also study how oxygen deficiency affects spin ice samples, and we discuss how the oxygen stoichiometry can be quantified and controlled experimentally.

Sala, Gabriele; Castelnovo, Claudio; Goff, Jon; Gutmann, Matthias; Dharmalingam, Prabhakaran

2013-03-01

19

Overview of NASA Engine Ice-Crystal Icing Research.  

National Technical Information Service (NTIS)

Ice accretions that have formed inside gas turbine engines as a result of flight in clouds of high concentrations of ice crystals in the atmosphere have recently been identified as an aviation safety hazard. NASA s Aviation Safety Program (AvSP) has made ...

H. E. Addy J. P. Veres

2011-01-01

20

Nucleation and Growth of Ice Crystals.  

National Technical Information Service (NTIS)

The basic information regarding nucleation in supercooled water was reviewed. Measurements were performed with water drops and water in bulk. Ice growth was measured as a function of crystal orientation, temperature, flow velocity of solution, salt concen...

J. Farrar W. S. Hamilton

1965-01-01

21

Evolution of crystal fabric: Ice-Age ice versus Holocene ice  

NASA Astrophysics Data System (ADS)

Ice-Age ice has smaller crystals and higher concentrations of impurities than Holocene ice; these properties cause it to develop a more strongly-aligned crystal-orientation fabric. In many regions of the Antarctic and Greenland ice sheets, the Ice-Age ice is now at depth and its flow properties may dominate the ice flow patterns, particularly where sliding is minimal. We use a fabric evolution model, based on that developed by Thorsteinsson (2002), to explore the evolution of Ice-Age ice fabric along particle paths for ice within Taylor Glacier, a cold-based outlet glacier of the East Antarctic Ice Sheet. The bulk of the ice within Taylor Glacier consists of Ice-Age and older ice because the Holocene ice has ablated away (there is no Holocene ice remaining within 25km of the terminus, Aciego, 2007). We initialize the evolving fabric based on fabric measurements from Taylor Dome where available (DiPrinzio, 2003) and other ice core records. We compare model results with thin-section data from shallow cores taken near the terminus. As expected, crystal alignment strengthens along the ice particle path. Due to lateral shearing along valley walls and the ice cliffs (terminal ice cliffs are cold in winter and present a resistance to flow), a tilted single maximum is common near the terminus. The highly-aligned fabric of Ice-Age ice is significantly softer than Holocene ice in simple shear parallel to the bed, this softness not only results in faster flow rates for glaciers and ice sheets such as Taylor, but creates a climate-flow-fabric feedback loop through concentrating ice-sheet flow within the Ice-Age ice. Thorsteinsson, T. (2002), Fabric development with nearest-neighbor interaction and dynamic recrystallization, J. Geophys. Res., 107(B1), 2014, doi:10.1029/2001JB000244. S.M. Aciego, K.M. Cuffey, J.L. Kavanaugh, D.L. Morse, J.P. Severinghaus, Pleistocene ice and paleo-strain rates at Taylor Glacier, Antarctica, Quaternary Research, Volume 68, Issue 3, November 2007, Pages 303-313, ISSN 0033-5894, DOI: 10.1016/j.yqres.2007.07.013. DiPrinzio, Eos Trans. AGU, 84(46), Fall Meet. Suppl., Abstract C11C-0834, 2003

Kennedy, J. H.; Pettit, E. C.

2009-12-01

22

Quasi-spherical direct drive fusion simulations for the Z machine and future accelerators  

Microsoft Academic Search

We explored the potential of Quasi-Spherical Direct Drive (QSDD) to reduce the cost and risk of a future fusion driver for Inertial Confinement Fusion (ICF) and to produce megajoule thermonuclear yield on the renovated Z Machine with a pulse shortening Magnetically Insulated Current Amplifier (MICA). Analytic relationships for constant implosion velocity and constant pusher stability have been derived and show

J. Pace VanDevender; Dillon Heirman McDaniel; Norman Frederick Roderick; Thomas J. Nash

2007-01-01

23

Quasi-spherical cavity resonators for metrology based on the relative dielectric permittivity of gases  

Microsoft Academic Search

frequencies. The frequency splittings are consistent with the cavity's shape, as determined from dimensional measurements. We deduced ersp, Td of helium and of argon at 289 K and up to 7 MPa from the resonance frequencies f ln s , the resonance half-widths gln s , and the compressibility of copper. Simultaneous measurements of ersp, Td with the quasi-spherical resonator

Eric F. May; Laurent Pitre; James B. Mehl; Michael R. Moldover; James W. Schmidt

24

Adiabatic Quasi-Spherical Compressions Driven by Magnetic Pressure for Inertial Confinement Fusion  

SciTech Connect

The magnetic implosion of a high-Z quasi-spherical shell filled with DT fuel by the 20-MA Z accelerator can heat the fuel to near-ignition temperature. The attainable implosion velocity on Z, 13-cm/{micro}s, is fast enough that thermal losses from the fuel to the shell are small. The high-Z shell traps radiation losses from the fuel, and the fuel reaches a high enough density to reabsorb the trapped radiation. The implosion is then nearly adiabatic. In this case the temperature of the fuel increases as the square of the convergence. The initial temperature of the fuel is set by the heating of an ion acoustic wave to be about 200-eV after a convergence of 4. To reach the ignition temperature of 5-keV an additional convergence of 5 is required. The implosion dynamics of the quasi-spherical implosion is modeled with the 2-D radiation hydrodynamic code LASNEX. LASNEX shows an 8-mm diameter quasi-spherical tungsten shell on Z driving 6-atmospheres of DT fuel nearly to ignition at 3.5-keV with a convergence of 20. The convergence is limited by mass flow along the surface of the quasi-spherical shell. With a convergence of 20 the final spot size is 400-{micro}m in diameter.

NASH,THOMAS J.

2000-11-01

25

Scattering of light by polyhedral ice crystals.  

PubMed

The single-scattering phase functions of polyhedral-shaped ice particles are calculated by means of geometric optics and the diffraction theory. Particle orientation is assumed to be random in space. Particle shapes are taken both from ice-crystal classifications and from in situ measurements. The effects of particle concavity on the scattering signature are discussed in detail. A common feature is the pronounced forward-scattering peak, as well as different halo peaks that are due to a minimum deviation at corresponding ice prisms. An unusual halo phenomena, which results from a minimum deviation in a double-prism configuration, is found and verified. The comparison of different particle types shows that backscattering is a sensitive indicator for the identification of types of ice-crystal. Aggregate particles, like bullet rosettes, basically show the scattering characteristics of their individual components. PMID:20820442

Macke, A

1993-05-20

26

Carbon dioxide enhances fragility of ice crystals  

NASA Astrophysics Data System (ADS)

Ice caps and glaciers cover 7% of the Earth, greater than the land area of Europe and North America combined, and play an important role in global climate. The small-scale failure mechanisms of ice fracture, however, remain largely elusive. In particular, little understanding exists about how the presence and concentration of carbon dioxide molecules, a significant component in the atmosphere, affects the propensity of ice to fracture. Here we use atomic simulations with the first-principles based ReaxFF force field capable of describing the details of chemical reactions at the tip of a crack, applied to investigate the effects of the presence of carbon dioxide molecules on ice fracture. Our result shows that increasing concentrations of carbon dioxide molecules significantly decrease the fracture toughness of the ice crystal, making it more fragile. Using enhanced molecular sampling with metadynamics we reconstruct the free energy landscape in varied chemical microenvironments and find that carbon dioxide molecules affect the bonds between water molecules at the crack tip and decrease their strength by altering the dissociation energy of hydrogen bonds. In the context of glacier dynamics our findings may provide a novel viewpoint that could aid in understanding the breakdown and melting of glaciers, suggesting that the chemical composition of the atmosphere can be critical to mediate the large-scale motion of large volumes of ice.

Qin, Zhao; Buehler, Markus J.

2012-11-01

27

Modeling, Simulation and Comparison Study of Cirrus Clouds' Ice Crystals  

Microsoft Academic Search

Various methods and techniques to estimate ice crystals radar response have been developed to study the structure of cirrus clouds. Most methods assume a spherical shape for the ice crystals. This assumption leads to mistakes on the parameter estimation related to the particles' size. In this work, we modeled the shape of ice particles found in cirrus cloud as measured

Jorge M. Villa; Sandra L. Cruz-Pol; José Colom-Ustáriz; Stephen M. Sekelsky

28

Modeling, simulation, and comparison study of cirrus cloud ice crystals  

Microsoft Academic Search

Various methods and techniques to estimate ice crystals radar response have been developed to study the structure of cirrus clouds. Most methods assume a spherical shape for the ice crystals. This assumption leads to mistakes on the parameter estimation related to the particles' size. In this work, we modeled the shape of ice particles found in cirrus cloud as measured

Jorge M. Villa; Sandra L. Cruz-Pol; Jose G. Colom-Ustariz; Stephen M. Sekelsky

2003-01-01

29

Impact of small ice crystal assumptions on ice sedimentation rates in cirrus clouds and GCM simulations  

Microsoft Academic Search

In the prediction of climate change, the greatest uncertainty lies in the representation of clouds. Ice clouds are particularly challenging, and to date there is no accepted method for measuring the smaller ice crystals (D < 60 ?m). This study examines the sensitivity of a global climate model to different assumptions regarding the number concentrations of small ice crystals when

David L. Mitchell; Philip Rasch; Dorothea Ivanova; Greg McFarquhar; Timo Nousiainen

2008-01-01

30

Properties of Columnar Ice Crystals Precipitating front Layer Clouds  

Microsoft Academic Search

Single unrimed columnar ice crystals (>200 µm in length) from shallow layer clouds were collected in silicone oil, photographed under a microscope, and melted to determine their mass. These ice crystals were representative of those growing in a water sub-saturated environment in the temperature range 4 to 10C. The axial lengths of the crystals were related by the expression D

K. O. L. F. Jayaweera; T. Ohtake

1974-01-01

31

Augmentation of Radiation Intensity in Quasi-Spherical Double Liner/Dynamic Hohlraum  

SciTech Connect

To increase the conversion efficiency of magnetic energy to radiation in Double Liner/Dynamic-Hohlraum and to approach closer to the ignition conditions we proposed the concept of implosion of a quasi-spherical double liner. The almost spherical implosion can be realized with a special mass distribution in liners. Axial cumulating of liner kinetic energy and more efficient radiation energy confinement allow augmentation of radiation intensity on the capsule with respect to cylindrical case under the same driver conditions. A controllable mass redistribution inside the nested external liner allows significant reduction and correction of distortions produced by the Rayleigh-Taylor instability. A phenomenon of energy confinement and enhancement of radiation intensity is considered and compared with the cylindrical case. On the basis of the developed physical model of non-LTE plasma using the RMHD code ZETA the dynamics of quasi-spherical Double Liner/Dynamic-Hohlraum and generation of radiation in two-dimensional geometry is examined and liner configuration is optimized.

Zakharov, S.V.; Smirnov, V.P. [RRC Kurchatov Institute, 123182 Moscow (Russian Federation)

2006-01-05

32

Aircraft Observations of Ice Crystal Evolution in an Altostratus Cloud  

Microsoft Academic Search

Observations from a Lagrangian spiral descent within altostratus cloud associated with a cold front were used to study the evolution of ice particle spectra by following populations of ice crystals as they fell through the cloud. The flight track was corrected for wind effects and was divided into distinct regions for spatial comparison of ice particle spectra. Analysis of size

Paul R. Field

1999-01-01

33

The structure of ice crystallized from supercooled water  

NASA Astrophysics Data System (ADS)

The freezing of water to ice is fundamentally important to fields as diverse as cloud formation to cryopreservation. Traditionally ice was thought to exist in two well-crystalline forms: stable hexagonal ice and metastable cubic ice. It has recently been shown, using X-ray diffraction data, that ice which crystallizes homogeneously and heterogeneously from supercooled water is neither of these phases. The resulting ice is disordered in one dimension and therefore possesses neither cubic nor hexagonal symmetry and is instead composed of randomly stacked layers of cubic and hexagonal sequences. We refer to this ice as stacking-disordered ice I (ice Isd). This result is consistent with a number of computational studies of the crystallization of water. Review of the literature reveals that almost all ice that has been identified as cubic ice in previous diffraction studies and generated in a variety of ways was most likely stacking-disordered ice I with varying degrees of stacking disorder, which raises the question of whether cubic ice exists. New data will be presented which shows significant stacking disorder (or stacking faults on the order of 1 in every 100 layers of ice Ih) in droplets which froze heterogeneously as warm as 257 K. The identification of stacking-disordered ice from heterogeneous ice nucleation supports the hypothesis that the structure of ice that initially crystallises from supercooled water is stacking-disordered ice I, independent of nucleation mechanism, but this ice can relax to the stable hexagonal phase subject to the kinetics of recrystallization. The formation and persistence of stacking disordered ice in the Earth's atmosphere will also be discussed.

Murray, Benjamin

2013-03-01

34

Radar Anisotropy of sea ice due to preferred Azimuthal orientation of the horizontal c axes of ice crystals  

Microsoft Academic Search

Results of impulse radar, ice crystal c axis, and subice current measurements on the fast ice near Narwhal Island, Alaska, are presented. The crystal structure of the ice was found to have a horizontal crystal c axis with a preferred azimuthal orientation. This orientation was found to align with the direction of the current at the ice-water interface. Impluse radar

Austin Kovacs; Rexford M. Morey

1978-01-01

35

Quasi-spherical direct drive fusion simulations for the Z machine and future accelerators.  

SciTech Connect

We explored the potential of Quasi-Spherical Direct Drive (QSDD) to reduce the cost and risk of a future fusion driver for Inertial Confinement Fusion (ICF) and to produce megajoule thermonuclear yield on the renovated Z Machine with a pulse shortening Magnetically Insulated Current Amplifier (MICA). Analytic relationships for constant implosion velocity and constant pusher stability have been derived and show that the required current scales as the implosion time. Therefore, a MICA is necessary to drive QSDD capsules with hot-spot ignition on Z. We have optimized the LASNEX parameters for QSDD with realistic walls and mitigated many of the risks. Although the mix-degraded 1D yield is computed to be {approx}30 MJ on Z, unmitigated wall expansion under the > 100 gigabar pressure just before burn prevents ignition in the 2D simulations. A squeezer system of adjacent implosions may mitigate the wall expansion and permit the plasma to burn.

VanDevender, J. Pace; McDaniel, Dillon Heirman; Roderick, Norman Frederick; Nash, Thomas J.

2007-11-01

36

Simulation of quasi spherical direct drive capsules for pulsed-power driven inertial fusion energy  

NASA Astrophysics Data System (ADS)

Magnetic pressure from 35-MA current in a 1-mm-radius liner is equivalent to the ablation pressure in the beryllium pusher of an inertial fusion capsule in a 300 eV hohlraum and can, in principle, drive a Quasi Spherical Direct Drive (QSDD) fusion capsule to yields of ˜600 MJ with a 45 MA, 40 ns pulsed power driver. Analytic theory and 1D and 2D simulations of QSDD capsules show insensitivity to magnetic Rayleigh-Taylor instability, internal pulse shaping, efficient compression of cryogenic fuel on a low (?=1.5) adiabat, hot spot heating, current diffusion into the hot spot with alpha trapping, and burn. However, practical QSDD capsules require a large rate of change of current dI/dt ˜1.5 MA/ns and are susceptible to a wall instability, which must be further mitigated.

Vandevender, J. P.; Slutz, S. A.; Vesey, R. A.; Herrmann, M. C.; Sinars, D. B.; Nash, T. J.; Roderick, N. F.; Sefkow, A. B.

2011-11-01

37

Acoustic detection of ice crystals in Antarctic waters  

NASA Astrophysics Data System (ADS)

During the voyage of the RSV Aurora Australis to the region of Prydz Bay, Antarctica in January-March 1991, ice crystals were encountered at depths from the surface to 125-m in the western area of the bay. On two occasions, crystals were retrieved by netting, and echo sounder records have been used to infer additional regions of occurrence. Acoustic target strength estimates made on the ice crystal assemblies encountered show significant spatial variation, which may relate to crystal size and/or aggregation. Data from a suite of conductivity-temperature-depth casts have been used to map regions of the study area where in situ water temperatures fell below the computed freezing point. Such regions correlate well with those selected on the basis of echogram type and imply that ice crystals occurred at depth over large areas of the bay during the cruise period. The ice crystal distribution described is consistent with that expected from a plume of supercooled water emerging from under the Amery Ice Shelf and forming part of the general circulation of the bay. The magnitude of the supercooled water plume is greater than those reported previously in the Prydz Bay region. If misinterpreted as biota on echo sounder records, ice crystals could significantly bias biomass estimates based on echo integration in this and potentially other areas.

Penrose, John D.; Conde, M.; Pauly, T. J.

1994-06-01

38

Secondary Ice Nucleation and Crystallizer-Performance Optimization.  

National Technical Information Service (NTIS)

A batch crystallizer was used to investigate the secondary nucleation of ice in NaCl and KCl solutions. The kinetics of nucleation were determined over a range of salt concentrations, agitation power inputs, and solution subcoolings. The nucleation kineti...

E. Woltz

1975-01-01

39

Determination of the Boltzmann constant using a quasi-spherical acoustic resonator.  

PubMed

The paper reports a new experiment to determine the value of the Boltzmann constant, k(B)=1.3806477(17)×10(-23) J K(-1), with a relative standard uncertainty of 1.2 parts in 10(6). k(B) was deduced from measurements of the velocity of sound in argon, inside a closed quasi-spherical cavity at a temperature of the triple point of water. The shape of the cavity was achieved using an extremely accurate diamond turning process. The traceability of temperature measurements was ensured at the highest level of accuracy. The volume of the resonator was calculated from measurements of the resonance frequencies of microwave modes. The molar mass of the gas was determined by chemical and isotopic composition measurements with a mass spectrometer. Within combined uncertainties, our new value of k(B) is consistent with the 2006 Committee on Data for Science and Technology (CODATA) value: (k(B)(new)/k(B_CODATA)-1)=-1.96×10(-6), where the relative uncertainties are u(r)(k(B)(new))=1.2×10(-6) and u(r)(k(B_CODATA))=1.7×10(-6). The new relative uncertainty approaches the target value of 1×10(-6) set by the Consultative Committee on Thermometry as a precondition for redefining the unit of the thermodynamic temperature, the kelvin. PMID:21930563

Pitre, Laurent; Sparasci, Fernando; Truong, Daniel; Guillou, Arnaud; Risegari, Lara; Himbert, Marc E

2011-10-28

40

An experimental study of crystallization and crystal growth of methane hydrates from melting ice  

Microsoft Academic Search

An experiment with well defined gas-water interfacial surface area was developed to study the crystallization and crystal growth of methane hydrates. Measurable formation rates were observed only when melting ice was involved. No hydrates nucleated from liquid water or from non-melting ice. It is concluded that melting ice, which like hydrate water is hydrogen-bonded, provides a template for hydrate nucleation

M. J. Hwang; D. A. Wright; A. Kapur; G. D. Holder

1990-01-01

41

The Backscattering Linear Depolarization Ratio of Ice Clouds Composed of Small Ice Crystals  

NASA Astrophysics Data System (ADS)

The importance of small ice crystals (< 50 µm) for cirrus cloud radiative properties is a matter of controversial debate, mainly because some measurements seemed to clearly overestimate the number concentrations of small ice particles due to particle shattering on the instrument inlets. On the other hand, there is no doubt that small micrometer-sized ice crystals dominate the particle size distributions of contrails and cirrus clouds emerging from contrails. Polarisation LIDAR is frequently used to investigate the microphysics of contrails and contrail cirrus remotely. These investigations reveal unusually high maximum linear depolarization ratios of 0.5 - 0.7. The knowledge of the link between ice crystal depolarization and their size and shape is a prerequisite for the interpretation of these LIDAR data. Since young contrails consist of relatively small ice crystals with sizes typically less than 10 µm, the scattering matrix of these non-spherical particles can be calculated by the T-matrix method. In order to investigate the relation between the linear backscattering depolarization ratio and the microphysical properties of small ice particles that closely resemble those found in contrails and young cirrus, we started to run dedicated ice crystal nucleation and growth experiments at the large cloud simulation chamber AIDA of Forschungszentrum Karlsruhe. Such studies became feasible after the installation of the new in situ laser scattering and depolarization set up SIMONE at the chamber in 2006. The light scattering measurements are analyzed in the context of the microphysical properties of the ice clouds measured by optical cloud particle spectrometers, single particle imaging, and in situ infrared extinction spectroscopy. We compare our experimental results with theoretical results generated by the T-matrix method for finite cylinders. The results give new insight into the scattering depolarisation properties of small ice crystals grown under simulated contrail and cirrus formation conditions.

Schnaiter, M.; Abdelmonem, A.; Benz, S.; Leisner, T.; Möhler, O.; Wagner, R.

2009-04-01

42

Zn2+-A?40 Complexes Form Metastable Quasi-spherical Oligomers That Are Cytotoxic to Cultured Hippocampal Neurons*  

PubMed Central

The roles of metal ions in promoting amyloid ?-protein (A?) oligomerization associated with Alzheimer disease are increasingly recognized. However, the detailed structures dictating toxicity remain elusive for A? oligomers stabilized by metal ions. Here, we show that small Zn2+-bound A?1–40 (Zn2+-A?40) oligomers formed in cell culture medium exhibit quasi-spherical structures similar to native amylospheroids isolated recently from Alzheimer disease patients. These quasi-spherical Zn2+-A?40 oligomers irreversibly inhibit spontaneous neuronal activity and cause massive cell death in primary hippocampal neurons. Spectroscopic and x-ray diffraction structural analyses indicate that despite their non-fibrillar morphology, the metastable Zn2+-A?40 oligomers are rich in ?-sheet and cross-? structures. Thus, Zn2+ promotes A?40 neurotoxicity by structural organization mechanisms mediated by coordination chemistry.

Solomonov, Inna; Korkotian, Eduard; Born, Benjamin; Feldman, Yishay; Bitler, Arkady; Rahimi, Farid; Li, Huiyuan; Bitan, Gal; Sagi, Irit

2012-01-01

43

Acoustic detection of ice crystals in Antarctic waters  

Microsoft Academic Search

During the voyage of the RSV Aurora Australis to the region of Prydz Bay, Antarctica in January-March 1991, ice crystals were encountered at depths from the surface to 125-m in the western area of the bay. On two occasions, crystals were retrieved by netting, and echo sounder records have been used to infer additional regions of occurrence. Acoustic target strength

John D. Penrose; M. Conde; T. J. Pauly

1994-01-01

44

Visual Simulation of Ice Crystal Growth  

Microsoft Academic Search

The beautiful, branching structure of ice is one of the most striking visual phenomena of the winter landscape. Yet there is little study about modeling this effect in computer graphics. In this paper, we present a novel approach for visual simulation of ice growth. We use a numerical simulation technique from computational physics, the \\

Theodore Kim; Ming C. Lin

2003-01-01

45

Superheating of ice crystals in antifreeze protein solutions.  

PubMed

It has been argued that for antifreeze proteins (AFPs) to stop ice crystal growth, they must irreversibly bind to the ice surface. Surface-adsorbed AFPs should also prevent ice from melting, but to date this has been demonstrated only in a qualitative manner. Here we present the first quantitative measurements of superheating of ice in AFP solutions. Superheated ice crystals were stable for hours above their equilibrium melting point, and the maximum superheating obtained was 0.44 degrees C. When melting commenced in this superheated regime, rapid melting of the crystals from a point on the surface was observed. This increase in melting temperature was more appreciable for hyperactive AFPs compared to the AFPs with moderate antifreeze activity. For each of the AFP solutions that exhibited superheating, the enhancement of the melting temperature was far smaller than the depression of the freezing temperature. The present findings clearly show that AFPs adsorb to ice surfaces as part of their mechanism of action, and this absorption leads to protection of ice against melting as well as freezing. PMID:20215465

Celik, Yeliz; Graham, Laurie A; Mok, Yee-Foong; Bar, Maya; Davies, Peter L; Braslavsky, Ido

2010-03-09

46

Ice Crystals Produced by Expansion: Experiments and Application to Aircraft-produced Ice  

Microsoft Academic Search

The production of ice crystals as a result of the expansion and cooling of moist air was investigated by laboratory experiment. In particular, the warmest expanded air temperature that produces crystals was sought as a function of the initial temperature. The results fit the standard theory of homogeneous nucleation of water droplets, as long as the droplets remain at a

T. C. Foster; J. Hallett

1993-01-01

47

Growth of ice discs from the vapor and the mechanism of habit change of ice crystals  

NASA Astrophysics Data System (ADS)

Ice crystals nucleated on a liquid nitrogen cooled glass fiber grow first as thin disks which subsequently transform to plates and columns as they thicken and extend to regions of higher supersaturation. Crystals are often found to be dislocation-free, which suggests that growth results from surface nucleation, the habit depending on preferential nucleation in an adsorbed multilayer on basal or prism face.

Keller, V. W.; McKnight, C. V.; Hallett, J.

1980-07-01

48

Theory of quasi-spherical accretion in X-ray pulsars  

NASA Astrophysics Data System (ADS)

A theoretical model for quasi-spherical subsonic accretion on to slowly rotating magnetized neutron stars is constructed. In this model, the accreting matter subsonically settles down on to the rotating magnetosphere forming an extended quasi-static shell. This shell mediates the angular momentum removal from the rotating neutron star magnetosphere during spin-down episodes by large-scale convective motions. The accretion rate through the shell is determined by the ability of the plasma to enter the magnetosphere. The settling regime of accretion can be realized for moderate accretion rates ? g s-1. At higher accretion rates, a free-fall gap above the neutron star magnetosphere appears due to rapid Compton cooling, and accretion becomes highly non-stationary. From observations of the spin-up/spin-down rates (the angular rotation frequency derivative ?, and ? near the torque reversal) of X-ray pulsars with known orbital periods, it is possible to determine the main dimensionless parameters of the model, as well as to estimate the magnetic field of the neutron star. We illustrate the model by determining these parameters for three wind-fed X-ray pulsars GX 301-2, Vela X-1 and GX 1+4. The model explains both the spin-up/spin-down of the pulsar frequency on large time-scales and the irregular short-term frequency fluctuations, which can correlate or anticorrelate with the X-ray flux fluctuations in different systems. It is shown that in real pulsars an almost iso-angular-momentum rotation law with ?˜ 1/R2, due to strongly anisotropic radial turbulent motions sustained by large-scale convection, is preferred.

Shakura, N.; Postnov, K.; Kochetkova, A.; Hjalmarsdotter, L.

2012-02-01

49

The characteristics of mid-latitude and low-latitude ice cloud crystals  

Microsoft Academic Search

An accurate understanding of the dimensional characteristics of atmospheric ice crystals is important for weather and climate models. Ice crystal fall speed which partially governs cloud lifetime is dependent on crystal mass and projected area. Ice cloud radiative properties are dependent on crystal shape as well as cloud optical thickness which can vary widely depending on local conditions and cloud

Carl George Schmitt

2009-01-01

50

Mechanism of Ice Crystal Growth Habit and Shape Instability Development Below Water Saturation.  

National Technical Information Service (NTIS)

Ice phase process in supercooled clouds play dominant roles in development of updrafts and downdrafts as well as various forms of precipitation. In a supercooled cloud, an ice phase process begins normally with vapor diffusional growth of ice crystals. Co...

G. D. Swoboda

1981-01-01

51

Modeling, simulation, and comparison study of cirrus cloud ice crystals  

NASA Astrophysics Data System (ADS)

Various methods and techniques to estimate ice crystals radar response have been developed to study the structure of cirrus clouds. Most methods assume a spherical shape for the ice crystals. This assumption leads to mistakes on the parameter estimation related to the particles' size. In this work, we modeled the shape of ice particles found in cirrus cloud as measured by airborne instruments, specifically ice bullets. These can be found depending on the temperature and cloud altitude, isolated or in groups of two or more bullets, called bullet rosettes. The model of the bullets was developed using the parameters obtained by airborne measurements from the National Center for Atmospheric Research (NCAR) Video Ice Particle Sampler (VIPS). This is an airborne instrument that takes samples of the cirrus cloud particles sizes. With these sample parameters we created a bullet function in DDSCAT with the actual shape of the bullets. This software allows us to create irregular models of particles using the Discrete Dipole Approximation method. With this model we can analyze the backscattering produced by the bullet and rosette model or reflectivity and compute the total volume backscattering coefficient from the cirrus clouds. Various models of ice crystal habits are compared.

Villa, Jorge M.; Cruz-Pol, Sandra L.; Colom-Ustariz, Jose G.; Sekelsky, Stephen M.

2003-04-01

52

Ice crystal properties retrieval using radar spectral polarimetric measurements within ice\\/mixed-phase clouds  

Microsoft Academic Search

In the field of atmospheric research, ground-based radar systems are often employed to study ice\\/mixed-phase cloud properties based on retrieval techniques. These techniques convert the radar signal backscattered by each bulk of ice crystals being probed within the same radar resolution volume to cloud’s microphysical characteristics. However, the size of a radar resolution volume is often too large compared to

Y. Dufournet

2010-01-01

53

Crystallization of CO2 ice and the absence of amorphous CO2 ice in space.  

PubMed

Carbon dioxide (CO2) is one of the most relevant and abundant species in astrophysical and atmospheric media. In particular, CO2 ice is present in several solar system bodies, as well as in interstellar and circumstellar ice mantles. The amount of CO2 in ice mantles and the presence of pure CO2 ice are significant indicators of the temperature history of dust in protostars. It is therefore important to know if CO2 is mixed with other molecules in the ice matrix or segregated and whether it is present in an amorphous or crystalline form. We apply a multidisciplinary approach involving IR spectroscopy in the laboratory, theoretical modeling of solid structures, and comparison with astronomical observations. We generate an unprecedented highly amorphous CO2 ice and study its crystallization both by thermal annealing and by slow accumulation of monolayers from the gas phase under an ultrahigh vacuum. Structural changes are followed by IR spectroscopy. We also devise theoretical models to reproduce different CO2 ice structures. We detect a preferential in-plane orientation of some vibrational modes of crystalline CO2. We identify the IR features of amorphous CO2 ice, and, in particular, we provide a theoretical explanation for a band at 2,328 cm(-1) that dominates the spectrum of the amorphous phase and disappears when the crystallization is complete. Our results allow us to rule out the presence of pure and amorphous CO2 ice in space based on the observations available so far, supporting our current view of the evolution of CO2 ice. PMID:23858474

Escribano, Rafael M; Muñoz Caro, Guillermo M; Cruz-Diaz, Gustavo A; Rodríguez-Lazcano, Yamilet; Maté, Belén

2013-07-15

54

Mixing antifreeze protein types changes ice crystal morphology without affecting antifreeze activity  

Microsoft Academic Search

All three fish antifreeze protein types (I, II and III) inhibit the growth of ice to form hexagonal bipyramidal ice crystals of characteristic morphology. Mixtures of these different antifreezes produced ice crystals of hybrid shapes and dimensions, consistent with the different antifreeze types binding to the same ice surfaces. The activity of the mixtures was independent of the proportions of

Chao Heman; Carl I. DeLuca; Peter L. Davies

1995-01-01

55

Atmospheric Ice Crystals over the Antarctic Plateau in Winter.  

NASA Astrophysics Data System (ADS)

Falling ice crystals were collected daily on a gridded glass slide at South Pole Station, Antarctica, during the Antarctic winter of 1992 and were photographed through a microscope. Nine types of ice crystals are identified, which fall into three main categories: `diamond dust,' blowing snow, and snow grains. The dimensions of about 20 000 crystals were measured on scanned images of the photomicrographs. The predominant crystal types are hexagonal columns and plates (diamond dust) and rounded particles of blowing snow. Diamond-dust crystals have a large range of lengths (2-1000 ?m) and aspect ratios (0.1-100). Diamond-dust crystals can usually be classified as either columns or plates; nearly equidimensional crystals are rare. `Long prism' crystals with aspect ratios greater than 5 were collected often, and very long prisms (`Shimizu' crystals), 1000 ?m long but only 10 ?m thick, were collected occasionally. The extreme Shimizu crystals were predominant on only one winter day, but the meteorological conditions on that day were not unusual. Some precipitation was observed on every day; even when the dominant crystal type was blowing snow, there were always, in addition, some snow grains or diamond dust. Blowing-snow particles dominate by number and contribute nearly one-half of the total surface area. Bullet clusters and blowing snow each contribute about one-third of the total volume of atmospheric ice. Size distributions of the equivalent spherical radius are obtained for each of the nine crystal types, as well as for the three main categories of crystals, using the volume-to-area ratio to specify the equivalent spheres. In addition, the effective radius for each day when crystals were sampled is computed. Many of the distributions are approximately lognormal. The effective radius (area-weighted mean radius) of the entire size distribution of diamond dust is 12 ?m in winter, somewhat smaller than in summer (15 ?m). The small size of wintertime blowing snow allows it to reach heights of tens of meters in winter, as compared with only a few meters in summer. The average effective radius was 11 ?m for blowing snow and 24 ?m for snow grains. The most probable effective radius for any given day in winter is about 11 ?m.

Walden, Von P.; Warren, Stephen G.; Tuttle, Elizabeth

2003-10-01

56

Artificial antifreeze polypeptides: ?-helical peptides with KAAK motifs have antifreeze and ice crystal morphology modifying properties  

Microsoft Academic Search

Antifreeze polypeptides from fish are generally thought to inhibit ice crystal growth by specific adsorption onto ice surfaces and preventing addition of water molecules to the ice lattice. Recent studies have suggested that this adsorption results from hydrogen bonding through the side chains of polar amino acids as well as hydrophobic interactions between the non-polar domains on the ice-binding side

Wei Zhang; Richard A. Laursen

1999-01-01

57

Nanoscale Ice: Spectroscopic Ellipsometry of Epitaxially-Grown Crystals  

NASA Astrophysics Data System (ADS)

A new laboratory technique has been developed to examine the surface characteristics and kinetics of ice crystals at the nanoscale. Uncertainties remain regarding the fundamental physics of nucleation and depositional growth in atmospheric ice crystals. These molecular-scale uncertainties propagate upward into modeling outcomes at all scales of atmospheric interest: particle models, cloud models, mesoscale models, and climate models. Molecular-scale growth mechanisms and kinetics have been mainly inferred from bulk and particle-scale experiments as well as crystal-growth theory. The precarious nature of the ice surface resisted the first generation of direct nanoscale probing technologies, but new in-situ techniques including ESEM, AFM, and ellipsometry promise to divulge a wealth of new knowledge. Spectroscopic ellipsometry measures changes in the polarization state of light as it reflects off the surface of a thin film. This non-destructive technique is capable of measuring layer thicknesses as small as a single monolayer (~1 Å) and up to thicknesses of ~10 ?m. Other physical parameters including index of refraction and surface roughness are also accessible. At the TCNJ Cloud Physics Laboratory, a Horiba Scientific Auto-SE ellipsometer (440 - 1000 nm spectral range) has been adapted for in-situ measurements of ice crystals. The ice crystals are grown epitaxially on various horizontal substrates in a custom-built static diffusion chamber. The diffusion chamber is housed within a vacuum chamber and an optical path is provided from the ellipsometer light source to sample stage and back to the ellipsometer analyzer at 75° from normal. The diffusion chamber is cooled in two stages, with initial cooling accomplished with a fluid-chilled block and final chilling controlled by two independent thermoelectric cells. A wide range of temperatures, pressures, and saturation ratios are accessible: from 0°C to -30°C, 50mb to atmospheric pressure, and from subsaturated to greater that 200% RHi. Temperature and moisture profiles are continuously determined by platinum resistance thermometers. Optimization of cooling efficiencies are under way and should permit extension of temperature range to -60°C. Ongoing efforts are targeted at kinetic measurements of thickness changes in order to identify growth thresholds as a function of ambient conditions and nucleation mechanism.

Cumiskey, A.; Grippaldi, J.; Magee, N. B.

2011-12-01

58

An uncoupled multiphase approach towards modeling ice crystals in jet engines  

NASA Astrophysics Data System (ADS)

A recent series of high altitude turbofan engine malfunctions, characterized by flameout and sudden power losses have been reported in recent years. The source of these incidents has been hypothesized to be due to the presence of ice crystals at high altitudes. Ice crystals have been shown to have ballistic trajectories and consequently enter the core engine flow, without getting centrifuged out towards the engine bypass as droplets do. The crystals may melt as they move downstream to higher temperatures in successive stages, or hit a heated surface. The wetted surface may then act as an interface for further crystal impingement, which locally reduces the temperature and could lead to an ice accretion on the components. Ice can accrete to dangerously high levels, causing compressor surge due to blockage of the primary flowpath, vibrational instabilities due to load imbalances of ice on rotating components, mechanical damage of components downstream due to large shed ice fragments, or performance losses if ice enters the combustor, causing a decreased burner efficiency and an eventual flame-out. In order to provide a numerical tool to analyze such situations, FENSAP-ICE has been extended to model mixed-phase flows that combine air, water and ice crystals, and the related ice accretion. DROP3D has been generalized to calculate particle impingement, concentration, and field velocities in an uncoupled approach that neglects any phase change by assuming both ice crystals and supercooled droplets are in thermodynamic equilibrium. ICE3D then accounts for the contribution of ice crystals that stick and melt on an existing water-film and promote ice accretion. The extended ice crystal impingement and ice accretion model has been validated against test data from Cox and Co. and National Research Council icing tests conducted on a NACA0012 airfoil and unheated non-rotating cylinder respectively. The tests show a consistent agreement with respect to experimental profiles in terms of capturing the overall shape, although some of the ice profiles were conservative since they over-predicted the amount of ice accreted. The experimental observations suggest that ice crystals cause splashing of an existing film, and erosion effects when they impact an iced surface, and cause an overall loss in the amount of ice, as well as a general streamlining of the ice profile. This has not been taken into account in the present numerical model. The overall predictions in comparison with other numerical models, however, have improved and are a promising step towards simulating ice-shedding characteristics in a turbomachine.

Nilamdeen, Mohamed Shezad

59

Optical detection and characterization of ice crystals in LACIS  

NASA Astrophysics Data System (ADS)

Tropospheric ice and mixed phase clouds are an integral part of the earth system and their microphysical and radiative properties are strongly coupled e.g. through the complexities of the ice nucleation process. Therefore the investigation of influences of different aerosol particles which act as ice nuclei (IN) on the freezing behaviour of cloud droplets is important and still poses unresolved questions. The Leipzig Aerosol and Cloud Interaction Simulator (LACIS) is used to investigate the IN activity of different natural and artificial aerosol particles (mineral dust, soot etc.) in heterogeneous freezing processes (immersion or deposition freezing). A critical part of LACIS is the particle detection system allowing for size-resolved counting of activated seed particles and discrimination between ice crystals and water droplets. Recently, two instruments have been developed to provide these measurements at the LACIS facility. The Thermally-stabilized Optical Particle Spectrometer (TOPS) is measuring the particle size based on the intensity of light scattered by individual particles into a near-forward (15° to 45°) direction. Two symmetrical forward scattering channels allow for optical determination of the sensing volume, thus reducing the coincidence counting error and the edge zone effect. The backscatter channel (162° to 176°) equipped with a rotatable cross polarizer allows for establishing the change in linear polarization state of the scattered light. The backscatter elevation angle is limited so that the linear depolarization of light scattered by spherical particles of arbitrary size is zero. Any detectable signal in the depolarization channel can be therefore attributed to non-spherical particles (ice crystals). With consideration of the signal in the backscatter channel the separate counting of water drops and ice particle is possible. The Leipzig Ice Scattering Apparatus (LISA) is a modified version of the Small Ice Detector (SID3), developed at the Science and Technology Research Institute at the University of Hertfordshire, UK. The SID instruments have been developed primarily as wing-mounted systems for airborne studies of cloud ice particles. SID3 records the forward scattered light pattern with high angular resolution using an intensified CCD (780 by 582 pixels) at a rate of 20 images per second. In addition to the SID3 capabilities, LISA is able to measure the circular depolarization ratio in the range of scattering angles from 166° to 172°. Whereas particle size, shape and orientation are characterized by the angular distribution of forward-scattered light, the measured value of the circular depolarization can be used to validate the existing theoretical models of light scattering by irregular particles (RTDF, GSVM, T-Matrix, DDA). The first measurements done at the LACIS facility have demonstrated a promising sensitivity of LISA's depolarization channel to the shape of ice crystals. Results showed an increase of the mean circular depolarization ratio from 1.5 (characteristic for the liquid water droplets above 3 µm) to 2.5 for the "just frozen" almost-spherical droplets in the same size range. The presentation will describe details of instruments set up and present some exemplary results from experiments carried out at LACIS and AIDA (KIT) facilities.

Kiselev, Alexei; Clauß, Tina; Niedermeier, Dennis; Hartmann, Susan; Wex, Heike; Stratmann, Frank

2010-05-01

60

Mitigation of ice crystallization fouling in stationary and circulating liquid–solid fluidized bed heat exchangers  

Microsoft Academic Search

Liquid–solid fluidized bed heat exchangers are attractive ice crystallizers since they are able to mitigate ice crystallization fouling and exhibit high heat transfer coefficients. Experiments show that the fouling removal ability of stationary fluidized beds increases with decreasing bed voidage (95–80%) and increasing particle size (2–4mm). The removal of ice crystallization fouling appears to be more effective in circulating fluidized

P. Pronk; C. A. Infante Ferreira; G. J. Witkamp

2010-01-01

61

Numerical Simulation of Three-Dimensional Unsteady Flow past Ice Crystals  

Microsoft Academic Search

The unsteady flow fields around falling columnar ice crystals, hexagonal ice plates, and broad-branch crystals are simulated by numerically solving the time-dependent Navier-Stokes equations appropriate for these geometries in the primitive equation form. A predictor-corrector method and a quadratic interpolation for convective kinematics (QUICK) scheme are applied on nonuniform grids to determine the velocity fields. The ice crystals are held

Pao K. Wang; Wusheng Ji

1997-01-01

62

Modeling the effects of frazil ice crystals on the dynamics and thermodynamics of Ice Shelf Water plumes  

NASA Astrophysics Data System (ADS)

The seawater that comes into contact with the base of a floating ice shelf is modified as a result of the phase changes that occur. Melting is prevalent in the deepest parts of the subice cavity, and this drives a buoyant flow of Ice Shelf Water (ISW) along the sloping ice shelf base. The ascent of the ISW toward the surface of the ocean causes supercooling, because the freezing point rises with the falling pressure, and this induces a change from melting to freezing. Assuming that seed crystals exist, the ISW now fulfills the condition for the rapid growth of disc-shaped frazil ice crystals, which may subsequently settle (upward) out of suspension under the action of gravity. A simple numerical model of these processes has been developed, based on the theory of inclined plumes. The ISW is treated as a turbulent, particle-laden gravity current ascending a reactive boundary and containing a suspended crystal load which evolves in response to the supercooling of the water and the inverted sedimentation of the crystals. The frazil ice has two important effects on the behavior of the ISW plume. Because the generation of crystals through-out the plume provides such a large area over which phase changes can occur, the conversion of supercooling into ice happens much more readily than is possible through turbulent transfer of heat and mass at the ice shelf base. A suspended crystal load reduces the bulk density of the ISW, so that a growing suspension causes the plume to accelerate, while deposition of crystals onto the ice shelf effects a deceleration. There are positive feedbacks in that an acceleration of the plume induces more rapid crystal growth, while a deceleration allows suspended crystals to settle out more easily.

Jenkins, Adrian; Bombosch, Andreas

1995-04-01

63

Study of Ice Crystal Formation in Tubes Under Steady Flow Conditions as Relating to Freeze Desalination.  

National Technical Information Service (NTIS)

A test loop was assembled to investigate several designs for indirect freeze crystallization of brine solutions. Various parameters were monitored to determine the conditions that allow successful production of ice crystals in the flowing brine. At certai...

W. S. Schoerner T. R. Carbery T. J. Nowak

1981-01-01

64

Growth Rates and Habits of Ice Crystals between -20° and -70°C  

Microsoft Academic Search

A laboratory study of ice crystal growth characteristics at temperatures between -20° and -70°C has been performed at ice supersaturations and pressures comparable with those in the atmosphere using a horizontal static diffusion chamber. Maximum dimension, projected area, and volume growth rates, in addition to habit frequency, have been measured for individual habit types as functions of temperature, ice supersaturation,

Matthew Bailey; John Hallett

2004-01-01

65

Fluidized bed heat exchangers to prevent fouling in ice slurry systems and industrial crystallizers  

Microsoft Academic Search

Ozon layer depletion and global warming by synthetic refrigerants forces refrigeration industries to switch over to natural but hazardous refrigerants like ammonia and hydrocarbons. A promising technology to safely use the latter refrigerants is the application of indirect refrigeration systems with ice slurry as heat transfer fluid. Ice slurry, a suspension of aqueous solution and small ice crystals, has a

P. Pronk

2006-01-01

66

Tropical tropopause ice clouds: a dynamic approach to the mystery of low crystal numbers  

NASA Astrophysics Data System (ADS)

The occurrence of high, persistent ice supersaturation inside and outside cold cirrus in the tropical tropopause layer (TTL) remains an enigma that is intensely debated as the "ice supersaturation puzzle". However, it was recently confirmed that observed supersaturations are consistent with very low ice crystal concentrations, which is incompatible with the idea that homogeneous freezing is the major method of ice formation in the TTL. Thus, the tropical tropopause "ice supersaturation puzzle" has become an "ice nucleation puzzle". To explain the low ice crystal concentrations, a number of mainly heterogeneous freezing methods have been proposed. Here, we reproduce in situ measurements of frequencies of occurrence of ice crystal concentrations by extensive model simulations, driven by the special dynamic conditions in the TTL, namely the superposition of slow large-scale updraughts with high-frequency short waves. From the simulations, it follows that the full range of observed ice crystal concentrations can be explained when the model results are composed from scenarios with consecutive heterogeneous and homogeneous ice formation and scenarios with pure homogeneous ice formation occurring in very slow (< 1 cm s-1) and faster (> 1 cm s-1) large-scale updraughts, respectively. This statistical analysis shows that about 80% of TTL cirrus can be explained by "classical" homogeneous ice nucleation, while the remaining 20% stem from heterogeneous and homogeneous freezing occurring within the same environment. The mechanism limiting ice crystal production via homogeneous freezing in an environment full of gravity waves is the shortness of the gravity waves, which stalls freezing events before a higher ice crystal concentration can be formed.

Spichtinger, P.; Krämer, M.

2013-10-01

67

Stable growth mechanisms of ice disk crystals in heavy water.  

PubMed

Ice crystal growth experiments in heavy water were carried out under microgravity to investigate the morphological transition from a disk crystal to a dendrite. Surprisingly, however, no transition was observed, namely, the disk crystal or dendrite maintained its shape throughout the experiments, unlike the results obtained on the ground. Therefore, we introduce a growth model to understand disk growth. The Gibbs-Thomson effect is taken into account as a stabilization mechanism. The model is numerically solved by varying both an interfacial tension of the prism plane and supercooling so that the final sizes of the crystals can become almost the same to determine the interfacial tension. The results are compared with the typical experimental ones and thus the interfacial tension is estimated to be 20 mJ/m(2). Next, the model is solved under two supercooling conditions by using the estimated interfacial tension to understand stable growth. Comparisons between the numerical and experimental results show that our model explains well the microgravity experiments. It is also found that the experimental setup has the capability of controlling temperature on the order of 1/100 K. PMID:22181428

Adachi, Satoshi; Yoshizaki, Izumi; Ishikawa, Takehiko; Yokoyama, Etsuro; Furukawa, Yoshinori; Shimaoka, Taro

2011-11-22

68

An uncoupled multiphase approach towards modeling ice crystals in jet engines  

Microsoft Academic Search

A recent series of high altitude turbofan engine malfunctions, characterized by flameout and sudden power losses have been reported in recent years. The source of these incidents has been hypothesized to be due to the presence of ice crystals at high altitudes. Ice crystals have been shown to have ballistic trajectories and consequently enter the core engine flow, without getting

Mohamed Shezad Nilamdeen

2010-01-01

69

75 FR 8116 - Notice Pursuant to the National Cooperative Research and Production Act of 1993-Ice Crystal...  

Federal Register 2010, 2011, 2012, 2013

...National Cooperative Research and Production Act of 1993--Ice Crystal Consortium Notice is hereby given that, on December 31, 2009...15 U.S.C. 4301 et seq. (``the Act''), the Ice Crystal Consortium (``ICC'') has filed written...

2010-02-23

70

On the correlation between ice water content and ice crystal size and its application to radiative transfer and general circulation models  

Microsoft Academic Search

We performed correlation analysis involving ice water content (IWC) and mean effective ice crystal size (De) intended for application to climate models. For this purpose, ice crystal size distributions obtained from in situ measurements conducted from numerous field campaigns in the tropics, midlatitude, and Arctic regions were used and we show that IWC and De are well-correlated in this regional

K. N. Liou; Y. Gu; Q. Yue; G. McFarguhar

2008-01-01

71

Microfluidic experiments reveal that antifreeze proteins bound to ice crystals suffice to prevent their growth.  

PubMed

Antifreeze proteins (AFPs) are a subset of ice-binding proteins that control ice crystal growth. They have potential for the cryopreservation of cells, tissues, and organs, as well as for production and storage of food and protection of crops from frost. However, the detailed mechanism of action of AFPs is still unclear. Specifically, there is controversy regarding reversibility of binding of AFPs to crystal surfaces. The experimentally observed dependence of activity of AFPs on their concentration in solution appears to indicate that the binding is reversible. Here, by a series of experiments in temperature-controlled microfluidic devices, where the medium surrounding ice crystals can be exchanged, we show that the binding of hyperactive Tenebrio molitor AFP to ice crystals is practically irreversible and that surface-bound AFPs are sufficient to inhibit ice crystal growth even in solutions depleted of AFPs. These findings rule out theories of AFP activity relying on the presence of unbound protein molecules. PMID:23300286

Celik, Yeliz; Drori, Ran; Pertaya-Braun, Natalya; Altan, Aysun; Barton, Tyler; Bar-Dolev, Maya; Groisman, Alex; Davies, Peter L; Braslavsky, Ido

2013-01-08

72

Microfluidic experiments reveal that antifreeze proteins bound to ice crystals suffice to prevent their growth  

PubMed Central

Antifreeze proteins (AFPs) are a subset of ice-binding proteins that control ice crystal growth. They have potential for the cryopreservation of cells, tissues, and organs, as well as for production and storage of food and protection of crops from frost. However, the detailed mechanism of action of AFPs is still unclear. Specifically, there is controversy regarding reversibility of binding of AFPs to crystal surfaces. The experimentally observed dependence of activity of AFPs on their concentration in solution appears to indicate that the binding is reversible. Here, by a series of experiments in temperature-controlled microfluidic devices, where the medium surrounding ice crystals can be exchanged, we show that the binding of hyperactive Tenebrio molitor AFP to ice crystals is practically irreversible and that surface-bound AFPs are sufficient to inhibit ice crystal growth even in solutions depleted of AFPs. These findings rule out theories of AFP activity relying on the presence of unbound protein molecules.

Celik, Yeliz; Drori, Ran; Pertaya-Braun, Natalya; Altan, Aysun; Barton, Tyler; Bar-Dolev, Maya; Groisman, Alex; Davies, Peter L.; Braslavsky, Ido

2013-01-01

73

Interaction of turbulence, ice crystals, and water vapour in cirrus clouds  

NASA Astrophysics Data System (ADS)

The EMERALD-1 airborne campaign to investigate cirrus clouds was conducted at Adelaide Australia during September 2001. This involved the Egrett aircraft flying within cirrus clouds for in situ measurements of ice crystal properties, water vapour, wind, temperature and pressure. A second aircraft, a King Air, flew directly below the Egrett with an upward viewing lidar that mapped the structure of the clouds. Results are presented here that show the interaction between turbulence, humidity, ice crystal nucleation, growth, and sublimation. The maximum intensity of turbulence was measured at the top and bottom edges of the cloud, where ice crystals were either forming or sublimating. At the cloud top the largest ice crystal concentrations were associated with the greatest turbulence intensity. The width of the statistical distribution of relative humidity over ice was inversely proportional to the crystal concentration. The RHi distributions were approximately Gaussian in form and did not exhibit skewing toward supersaturation.

Cook, C. R.; Whiteway, J.; Busen, R.; Connolly, P.; Choularton, T.; Gallagher, M.; Bower, K.; Flynn, M.; Hacker, J.

2006-12-01

74

Light scattering by absorbing hexagonal ice crystals in cirrus clouds.  

PubMed

An improved ray-optics theory for single scattering and polarization of hexagonal columns and plates randomly oriented in space has been developed by considering absorption and by using the Chebyshev solution for diffraction integrals. The vector-tracing method and statistics technique of random sampling are employed. The equivalent forms of Snell's law and Fresnel formulas for absorbing ice crystals are derived, and two equivalent optical constants, m' and m?, are obtained. Comparison is made of the computed results of our model and the Takano and Liou model for asymmetry factors, single-scattering albedos, and scattering phase matrix elements. Some characteristics of our model are discussed, and these analyses demonstrate that our ray-optics model is practical and much improved. PMID:21060422

Zhang, J; Xu, L

1995-09-01

75

Microscopic pattern of ice crystal growth in the presence of thermal hysteresis proteins  

SciTech Connect

This study examines the effect of thermal hysteresis proteins (THPs) from the winter flounder (Psuedopleuronectes americanus) on the ice-water interface morphology during freezing of aqueous solutions. Experiments were performed using a directional solidification stage, and the development of the two-phase interface was observed through a microscope and recorded by a video system. Unusual ice crystal morphologies were observed, including faceted ice crystal growth along the (1100) crystal plane; spicular or needlelike growth in the (1010) direction; and growth parallel to the c-axis, (0001), consisting of incorporated liquid inclusions bounded by hexagonal prism faces. The observed crystallographic structures can be explained as an effect of the interaction between the THPs and the primary prism faces of ice crystals. This results in an increase in the Gibbs free energy of these planes, followed by ice growth into the supercooled liquid adjacent to these faces.

Coger, R.; Rubinsky, B. (Univ. of California, Berkeley, CA (United States). Dept. of Mechanical Engineering); Fletcher, G. (Memorial Univ. of Newfoundland, St. John's, Newfoundland (Canada))

1994-08-01

76

Morphological investigations of disaccharide molecules for growth inhibition of ice crystals  

NASA Astrophysics Data System (ADS)

Freezing of solutions including disaccharides (trehalose, sucrose, and maltose) has been investigated by microscopic observations of freeze-fractured replicas using FE-TEM. Three typical features were observed: the smooth surface considered as the ice crystal, fine particles as the precipitated disaccharide molecules, and remaining part as the glass state of the solution. The expanded observations of fine particle and its distribution investigations suggested that it was larger than 10 nm in size and averaged approximately 20 30 nm in diameter. The smallest particle was estimated to include several hundred disaccharide molecules. Based on systematic observations of trehalose solutions regarding concentrations and freezing rates, we concluded that ice crystal growth was inhibited by trehalose molecules. Since the ice crystal size reduced exponentially with increase in trehalose concentration, we could control ice crystal size formed in the frozen material. The growth inhibition of ice crystals with trehalose resulted both from a reduction in the free water in the solution due to a significant hydration effect and from an enhancement of nucleation of the ice crystals. It was confirmed that trehalose was more effective than the other disaccharide solutions examined for inhibiting the growth of ice crystals.

Uchida, Tsutomu; Nagayama, Masafumi; Shibayama, Tamaki; Gohara, Kazutoshi

2007-02-01

77

Using polarimetric remote sensing measurements to estimate ice particle size, optical depth and ice water path during CRYSTAL-FACE  

NASA Astrophysics Data System (ADS)

In situ observations made during the CRYSTAL-FACE field experiment have indicated that ice crystals have smaller sizes and are more reflective than is commonly assumed in most current climate models. The size of the particles appears to be principally determined by temperature with the smallest particles being found at the coldest temperatures. Previous analyses of polarimetric measurements in non-absorbing bands have suggested that either bubble inclusions (inhomogeneous hexagonal mono-crystals) or distortions of the hexagonal crystal shape (distorted chain aggregates) are responsible for the observed general absence of haloes, smooth angular variation of reflectance and brightness of ice clouds. In this paper we use multi-angle measurements made by the Research Scanning Polarimeter (RSP) to examine the polarized and unpolarized reflectance of cirrus clouds in bands where ice is non-absorbing (670 and 865 nm) and absorbing (1590, 1880 and 2250 nm). During CRSYTAL-FACE the RSP scan was biased so that the view angle range was from 0 to 75 degrees to the rear of the Proteus aircraft and from 0 to 45 degrees to the front and was oriented to scan along the groundtrack of the aircraft. This allowed observations of a single target over a wide scattering angle range particularly when consecutive flight legs could be combined which allows for basic discrimination of crystal habit using the non-absorbing bands, similar to previous studies (at least in the gross sense of being able to separate columns from plates from distorted crystals from spheroidal shapes). However, compared with non-absorbing bands, the reflectance in absorbing bands is different depending on whether ice particles are geometrically distorted or contain air bubble inclusions because the path length of light inside an ice crystal is quite short which limits scattering off the bubble inclusions. Consequently the retrieved particle size is also sensitive to whether ice crystals are modeled as being distorted or containing air bubbles. We examine how the RSP size retrievals, with an appropriate vertical weighting determined by Green's function calculations, compare with in situ measurements and examine the angular and spectral polarized and unpolarized residuals from the retrievals. This allows us to identify the most appropriate crystal habit for use in the remote sensing of cirrus clouds formed by convection over land, such as those observed during CRYSTAL-FACE, and provide best estimates for the particle size, optical depth and ice water path determined using solar reflectance measurements.

Geogdzhayev, I.; Cairns, B.; Mishchenko, M. I.; Travis, L. D.

2006-12-01

78

Growth of epitaxial ice crystals on covellite (CuS) under reduced air pressure  

Microsoft Academic Search

The advance velocity of nonthickening crystals and basal steps were measured as a function of temperature, supersaturation, and air pressure, using an optical interference technique. Ice crystal growth at -7 C in a thermal diffusion chamber was also investigated as a function of supersaturation. The radial growth rates of nonthickening crystals and the advance velocity of a 0.08 micrometer step

N. K. Cho

1982-01-01

79

Importance of small ice crystals to cirrus properties: Observations from the Tropical Warm Pool International Cloud Experiment (TWP-ICE)  

NASA Astrophysics Data System (ADS)

During the Department of Energy Atmospheric Radiation Measurement Program (DOE ARM) sponsored Tropical Warm Pool International Cloud Experiment (TWP-ICE), ice crystals with maximum dimensions (D) < 50 ?m were measured in aged cirrus and fresh anvils by a Cloud and Aerosol Spectrometer (CAS) and a Cloud Droplet Probe (CDP). The CAS/CDP ratio of the number concentrations of droplets with 3 < D < 50 ?m, N3-50, averaged 0.98 +/- 0.69 in liquid clouds. However, N3-50, measured by the CAS averaged 91 +/- 127 times larger than N3-50 from the CDP in ice clouds. The CAS/CDP N3-50 ratio had a correlation coefficient of 0.387 with the concentration of particles with D > 100 ?m measured by the Cloud Imaging Probe, suggesting that ice crystals may have been shattering or bouncing on the CAS inlet or protruding airflow shroud enhancing N>3-50,CAS. During the Costa Rica Aura Validation Experiment N3-50,CAS measured by a CAS without an airflow shroud were an order of magnitude less than those observed during TWP-ICE. This, and estimates of the maximum shattering based on the inlet and shroud sizes, suggest that the airflow shroud used during TWP-ICE was responsible for much of the shattering or bouncing.

McFarquhar, Greg M.; Um, Junshik; Freer, Matt; Baumgardner, Darrel; Kok, Gregory L.; Mace, Gerald

2007-07-01

80

Growth–melt asymmetry in ice crystals under the influence of spruce budworm antifreeze protein  

Microsoft Academic Search

Here we describe studies of the crystallization behavior of ice in an aqueous solution of spruce budworm antifreeze protein (sbwAFP) at atmospheric pressure. SbwAFP is an ice binding protein with high thermal hysteresis activity, which helps protect Choristoneura fumiferana (spruce budworm) larvae from freezing as they overwinter in the spruce and fir forests of the north eastern United States and

Natalya Pertaya; Yeliz Celik; Carlos L DiPrinzio; J S Wettlaufer; Peter L Davies; Ido Braslavsky

2007-01-01

81

Radiative influences on ice crystal and droplet growth within mixed-phase stratus clouds  

Microsoft Academic Search

This study uses a box model and a Lagrangian microphysical parcel model to investigate the influences of radiative heating and cooling on the vapor diffusional growth of liquid drops and ice crystals within mixed-phase clouds. Without radiative effects, the combined influences of drop and ice vapor diffusion lead to slight supersaturations with respect to liquid despite the rapid growth of

Z. J. Lebo; N. C. Johnson; J. Y. Harrington

2008-01-01

82

Structural transformation in supercooled water controls the crystallization rate of ice  

Microsoft Academic Search

One of water's unsolved puzzles is the question of what determines the lowest temperature to which it can be cooled before freezing to ice. The supercooled liquid has been probed experimentally to near the homogeneous nucleation temperature TH{\\\\approx}232 K, yet the mechanism of ice crystallization - including the size and structure of critical nuclei - has not yet been resolved.

Emily B. Moore; Valeria Molinero

2011-01-01

83

The Conversion of Aircraft Ice Crystal Measurements into Terms of Liquid Water Using Simulated Data.  

National Technical Information Service (NTIS)

This investigation presents simulated environments of ice crystals to computer analysis as a means of imitating particle measurements made by electro-optical devices such as the Particle Measuring System's 1-D instrument. A mathematical model is developed...

R. O. Berthel

1981-01-01

84

Epitaxial Growth of Ice Crystals on the Muscovite Cleavage Plane and Their Relation to Partial Dislocations.  

National Technical Information Service (NTIS)

The arrangement of oxygen atoms in hexagonal rings in crystals of ice and muscovite gives two possible alternatives of epitaxial connection between these two structures. Which one of these two alternatives is favored depends entirely on the location of po...

J. L. Caslavsky K. Vedam

1970-01-01

85

Determination of the Combined Ventilation Factor and Capacitance for Ice Crystal Aggregates from Airborne Observations in a Tropical Anvil Cloud  

Microsoft Academic Search

The ventilation factor and capacitance used in numerical models to represent ice crystal aggregates directly affects the growth rate of the ice crystal aggregates, and consequently the sink of atmospheric water vapor. Currently, numerical models that prognose ice water content (IWC) and water vapor mixing ratio represent the capacitance and ventilation factor of precipitation-sized particles with simplified geometries, such as

Paul R. Field; J. Heymsfield; Aaron Bansemer; Cynthia H. Twohy

2008-01-01

86

Geometric-optics integral-equation method for light scattering by nonspherical ice crystals  

Microsoft Academic Search

A new geometric-optics model has been developed for the calculation of the single-scattering and polar- ization properties for arbitrarily oriented hexagonal ice crystals. The model uses the ray-tracing tech- nique to solve the near field on the ice crystal surface, which is then transformed to the far field on the basis of the electromagnetic equivalence theorem. From comparisons with the

Ping Yang; K. N. Liou

1996-01-01

87

The characteristics of mid-latitude and low-latitude ice cloud crystals  

NASA Astrophysics Data System (ADS)

An accurate understanding of the dimensional characteristics of atmospheric ice crystals is important for weather and climate models. Ice crystal fall speed which partially governs cloud lifetime is dependent on crystal mass and projected area. Ice cloud radiative properties are dependent on crystal shape as well as cloud optical thickness which can vary widely depending on local conditions and cloud formation mechanisms. These are some of the reasons that cirrus clouds are considered to be one of the most uncertain elements in the earth's climate system. This thesis addresses some of these uncertainties. Mid-latitude cirrus clouds are frequently composed of bullet rosette shaped ice crystals. Bullet rosettes can grow with hollow ends which affects their radiative properties. In chapter 2, the frequency of occurrence of bullet rosettes with hollows ends is investigated. The radiative properties of hollow crystals are investigated in Chapter 3. For a thin cloud (optical depth of unity) with hollow crystals would lead to a difference of 5 W/m2 in short wave radiation at the surface compared to solid crystals. The properties of low latitude sub-visible cirrus cloud particles have been poorly investigated due to the difficulty of reaching them with instrumented aircraft. The properties of sub-visible cirrus clouds are investigated through the analysis of a large dataset of aircraft observations in chapter 4. Parameterizations for particle area, mass, size distributions and mass weighted fall speeds are developed. Mass weighted fall speeds were found to be lower than predicted by previous parameterizations due to the lack of large particles compared to previous studies. Most atmospheric ice cloud particles are irregular in shape. The final two research topics addressed in this thesis investigate the dimensional characteristics of irregularly shaped ice particles. In chapter 5, the total surface area of irregular ice crystals is investigated. Knowledge of particle surface area is important for atmospheric chemistry applications. In Chapter 6, ice crystal projected area and mass are investigated using fractal geometry techniques. Ice crystal aggregation was simulated to investigate the structure of ice crystal aggregates. The fractal analysis allows the determination of mass dimensional relationships from particle projected area measurements.

Schmitt, Carl George

88

Tropical tropopause ice clouds: A new approach to answer the mystery of low crystal numbers  

NASA Astrophysics Data System (ADS)

Water vapour is the most important natural green house gas. However, in the stratosphere an increase in water vapour would possibly result in a net cooling of the earth-atmosphere system. The major entrance pathway of trace substances into the stratosphere is the tropical tropopause layer (TTL). The TTL water vapor budget, and thus the exchange between troposphere and stratosphere, depends crucially on the occurrence and properties of ice clouds in this cold region (T < 200 K). New observations indicate that very low ice crystal numbers frequently occur in the TTL. This phenomenon is not yet understood and is not compatible with the idea that homogeneous freezing of solution droplets is the major pathway of ice formation. These low ice number concentrations are consistent with observed persistent high ice supersaturations inside cold TTL cirrus clouds, which in turn control the exchange of water vapor with the stratosphere. Here, we reproduce in-situ measurements of frequencies of occurrence of ice crystal concentrations by extensive model simulations, driven by the special dynamical conditions in the TTL, namely the superposition of slow large-scale updrafts with high-frequency short waves. The simulations show that about 80% of the observed incidences of low ice crystal concentrations can be explained by 'classical' homogeneous ice nucleation in the very slow updrafts (< 1cm/s), about 19% stem from heterogeneous freezing, while the remaining of about 1% originates from homogeneous freezing in slightly faster updrafts (> 1cm/s). The mechanism limiting the ice crystal production from homogeneous freezing in an environment full of gravity waves is that freezing events are stalled -due to the shortness of the gravity waves- before a higher number concentration of ice crystals can be formed.

Spichtinger, Peter; Krämer, Martina

2013-04-01

89

On the effects of ice crystal porosity on the radiative characteristics of cirrus clouds  

NASA Astrophysics Data System (ADS)

This paper attempts to illustrate how the porous nature of ice crystals might influence the relationships between the radiative properties of ice clouds and the ice water path. Solutions of the electromagnetic wave equation were obtained for a simplified, hollow, infinitely long circular cylinder. On the basis of these solutions it was implied that the effects of ice crystal porosity on the particle-scattering parameters can be expected to be small and that the major influence of porosity on radiation-ice water path (IWP) relationships will be primarily on the definition of IWP. It is suggested that this effect probably accounts for the existing discrepancy noted in this paper between the theoretical and observed ?-IWP relationships.

Stephens, Graeme L.

1987-04-01

90

Critical Supersaturation for Ice Crystal Growth: Laboratory Measurements and Atmospheric Modeling Implications  

NASA Astrophysics Data System (ADS)

An improved understanding of ice crystal growth, particularly at low temperatures, is much in demand for the advancement of numerical modeling of atmospheric processes. Cirrus models must contend with the complexity of ice crystals growing in cold temperatures, low pressures, low supersaturations, and with multiple nucleation mechanisms. Recent observations have allowed increasingly realistic parameterizations of cirrus ice crystal microphysics, but these observations need to be supplemented by a fundamental understanding of growth processes affecting low-temperature crystals. Several experimental studies have demonstrated that certain ice crystals require a minimum "critical" supersaturation before exhibiting detectable growth. These crystals are presumed to be essentially defect-free, preventing vicinal hillock growth at the site of crystal dislocations. In the case of crystal growth by spiral dislocation, advancement of faces begins as soon as supersaturation is present. The finding of conditional critical supersaturations have analogies in other materials (metals, semiconductors, potassium dihydrogen phosphate) and are thermodynamically predicted given a two-dimensional nucleation growth mechanism. Previous measurements have determined the critical supersaturation for ice as a function of temperature and crystallographic face from 0 to --15° C with extrapolation to --30° C. For both basal and prism faces, critical supersaturation is seen to increase with decreasing temperature, suggesting that low-temperature, low-supersaturation processes are most likely to be affected by this critical contingency. We present laboratory results to verify and extend prior critical supersaturation measurements using a novel approach for supersaturation generation, control, and measurement. The crystals are grown on the tip of a fine glass fiber ( ˜10 microns in diameter) under varying conditions of temperature, pressure, and saturation. Supersaturation is generated when a pre-saturated airflow passes over a coil of ice warmed by electrical resistance upstream from the growing crystal. Supersaturation is determined by a system of differential thermocouples calibrated to sulfuric acid drop size measurements. Measurements follow those made in earlier studies, but also extend to temperatures of --45° C, mimicking conditions found in some high altitude clouds.

Magee, N.; Moyle, A.; Lamb, D.

2003-12-01

91

Experimental investigation of the interactions of hyperactive antifreeze proteins with ice crystals  

NASA Astrophysics Data System (ADS)

Antifreeze proteins (AFPs) evolved in cold-adapted organisms and serve to protect them against freezing cold conditions by arresting ice crystal growth and inhibiting ice recrystallization. The freezing point depression by AFPs is defined as thermal hysteresis (TH) and AFPs are classified as hyperactive (hypAFPs) and moderate according to their TH activities. The mechanism of action of AFPs is not well understood. In particular, it is not clear what determines the concentration dependence of TH and whether the binding of AFP to ice is irreversible. Additionally, it is not known why some types of AFP are hyperactive compared to others and it was suggested that hyperactivity might be related to basal plane affinity of hypAFP to ice. The present study utilizes the techniques of microfluidic devices and fluorescence microscopy to study the interaction of AFPs with ice crystals. With novel temperature controlled microfluidic devices, we showed the accumulation and affinity of hypAFPs on the basal plane of ice. This supports the view that hypAFPs adhere to the basal plane. Additionally, for the first time in literature, small ice crystals of 30-50 mum sizes covered with adsorbed GFP tagged hypAFPs were stabilized in supercooled non-AFP solutions for hours with no observed ice growth in temperature controlled microfluidic devices. Repeated TH experiments of ice crystals incubated in AFP solutions before and after the exchange of liquids in microfluidic devices gave the same TH activity. This finding clarifies our understanding of concentration dependence of TH. Furthermore, we found that hypAFPs protect ice against melting as well as freezing, resulting in superheated ice. Ice crystals were superheated up to 0.5°C above their equilibrium melting temperatures and remained stable in this superheated state for hours. Measurements of fast melting velocities added additional evidence to the observed superheating of ice in AFP solutions. The experimental results of the current study provide strong evidence that AFPs bind to ice surfaces via irreversible binding. We have demonstrated that the use of microfluidics in combination with fluorescence microscopy is a valuable technique to study the binding mechanisms of AFPs and the concentration dependence of AFP activity.

Celik, Yeliz

92

The capacitance of pristine ice crystals and aggregate snowflakes  

Microsoft Academic Search

A new method of accurately calculating the capacitance of realistic ice particles is described: such values are key to accurate estimates of sublimation rates in numerical weather models. We have directly simulated the trajectories of diffusing water molecules, using random `walkers'. By counting how many of these trajectories intersect the surface of the ice particle (which may be any shape)

C. D. Westbrook; R. J. Hogan; A. J. Illingworth

2006-01-01

93

Aircraft Measurements of Icing in Supercooled and Water Droplet\\/Ice Crystal Clouds  

Microsoft Academic Search

Icing measurements were carried out in Spain during the Precipitation Enhancement Project experiment in 1979, with an instrumented DC-7 aircraft.The energy balance at the riming surface of a cylinder allows the prediction of the ice growth regime (wet or dry) for the present measurements with 85% success.The mixed conditions encountered show that the ice phase plays an important role in

M. Bain; J. F. Gayet

1982-01-01

94

Measurements of the aerosol and ice crystal populations in tropical stratospheric cumulonimbus anvils  

NASA Astrophysics Data System (ADS)

A pair of particle size spectrometers was flown aboard the NASA U-2 operating from the Canal Zone to make measurements of the aerosol and ice crystal budgets in cirrus produced by thunderstorms in the tropics. Measurements indicate that fairly large crystals up to 1 mm in size are injected into the stratosphere during cumulonimbus activity. Ice water contents range from a few thousandths to a few hundredths of a gram per cubic meter. Because the ambient temperature is typically around -80°C the mass of the larger crystals largely returns to lower altitudes before evaporating. Aerosol size distributions indicate a curious narrow growth mode between 0.15 and 0.2 µm in cirrus anvils which is absent outside these clouds. The presence of this narrow mode is attributed to near water saturation produced at cloud top. Nucleation of new ice crystals as well as aerosol is hypothesized.

Knollenberg, R. G.; Dascher, A. J.; Huffman, D.

95

The Growth of Atmospheric Ice Crystals: A Summary of Findings in Vertical Supercooled Cloud Tunnel Studies  

Microsoft Academic Search

Measurements of ice crystal growth under free fall in a generation of vertical supercooled cloud tunnels and some static cloud chambers as well as the related theoretical works are summarized.Growth parameters, that is, mass (m), dimensions, apparent density, and fall velocity (w), show extrema at about 5°, 10°, and 15°C where crystals are predominantly column-needle, isometric, and plate-stellar-dendrite, respectively. Crystal

Norihiko Fukuta; Tsuneya Takahashi

1999-01-01

96

Progress in Computing the Scattering and Absorption Properties of Nonspherical Ice Crystals: A Review  

NASA Astrophysics Data System (ADS)

Cirrus clouds consist of ice crystals that are exclusively nonspherical with their common habits including hexagonal plate, solid and hollow hexagonal columns, bullet rosette, aggregate, and more irregular shapes with various degrees of surface roughness. An outstanding scientific problem in remote sensing and climate research involving cirrus clouds has been to correctly compute or measure the single-scattering properties of these nonspherical ice crystals. Significant advances and substantial progress have been made by the radiative transfer and optics communities in the last three decades to understand and determine the fundamental scattering and absorption properties of ice crystals. In this presentation, we will review these advances and progress in the studies of the single-scattering properties (i.e., extinction coefficient, single- scattering albedo, and phase matrix) of nonspherical ice crystals in the Earth's atmosphere from the theoretical and computational perspectives, but will focus on the geometric optics method (GOM) in terms of the ray-tracing technique, including its relevant improvements, and the finite-difference time domain (FDTD) method. The GOM and FDTD are applicable to the computation of the scattering and absorption properties of large and small particles compared with the incident wavelength, respectively. Furthermore, we will also briefly review application of the single-scattering properties of ice crystals to the remote sensing of cirrus cloud optical depth and compositions.

Yang, P.; Liou, K.

2006-12-01

97

Surface melting of ice Ih single crystals revealed by glancing angle x-ray scattering  

Microsoft Academic Search

We present glancing angle x-ray scattering experiments at [00.1], [10.0], and [11.0] surfaces of ice Ih single crystals. The temperature dependence of the evanescent Bragg scattering upon heating reveals a quasiliquid surface layer well below the melting point of each investigated ice surface. At [10.0] and [11.0] surfaces, thermal faceting is observed, which is briefly discussed. The ``oxygen-forbidden'' (00.4) Bragg

A. Lied; H. Dosch; J. H. Bilgram

1994-01-01

98

Cirrus Clouds Millimeter-Wave Reflectivity Comparison with In-Situ Ice Crystal Airborne Data  

Microsoft Academic Search

In an effort to evaluate scattering models for particle size distributions of ice crystals within cirrus clouds, simultaneous data was collected during the Department of Energy (DoE) Atmospheric Radiation Measurement (ARM) Cloud Intensive operational period (Cloud IOP) at the Cloud and Radiation Testbed (CART) site in Lamont, Oklahoma, from the NCAR Video Ice Particle Sampler (VIPS) and UMass 33GHz\\/95GHz Cloud

José Morales; Jorge Trabal; Sandra L. Cruz-Pol; Stephen M. Sekelsky

99

Mechanical interactions between ice crystals and red blood cells during directional solidification.  

PubMed

Experiments in which red blood cells were frozen on a directional solidification stage under a microscope show that there is a mechanical interaction between ice crystals and cells in which cells are pushed and deformed by the ice crystals. The mechanical interaction occurs during freezing of cells in physiological saline and is significantly inhibited by the addition of 20% v/v glycerol to the solution. The addition of osmotically insignificant quantities of antifreeze proteins from the winter flounder or ocean pout to the physiological saline with 20% v/v glycerol generates strong mechanical interactions between the ice and the cells. The cells were destroyed during freezing in physiological saline, survived freezing in physiological saline with glycerol, and were completely destroyed by the addition of antifreeze proteins to the solution with glycerol. The difference in cell survival through freezing and thawing appears to be related, in part, to the habit of ice crystal growing in the suspension of red blood cells and the nature of mechanical interaction between the ice crystal and the cells. This suggests that mechanical damage may be a factor during cryopreservation of cells. PMID:7988158

Ishiguro, H; Rubinsky, B

1994-10-01

100

Crystal alignments in the fast ice of Arctic Alaska  

SciTech Connect

Field observations at 60 sites located in the fast or near-fast ice along a 1200-km stretch of the north coast of Alaska between the Bering Strait and Barter Island have shown that the great majority of the ice samples (95%) exhibit striking c axis alignments within the horizontal plane. In all cases the degree of preferred orientation increased with depth in the ice. Representative standard deviations around a mean direction in the horizontal plane are commonly less than +- 10/sup 0/ for samples collected near the bottom of the ice. At a given site the mean c axis direction X-bar/sub 0/ may vary as much as 20/sup 0/ with vertical location in the ice sheet. The c axis allignments in the nearshore region generally parallel the coast, with strong alignments occurring in the lagoon systems between the barrier islands and the coast and seaward of the barrier islands. In passes between islands and in entrances such as the opening to Kotzebue Sound the alignment is parallel to the channel. Only limited observations are available farther seaward over the inner (10- to 50-m isobaths) and outer (50-m isobath to shelf break) shelf regions. These indicate Ne-SW and E-W alignments, respectively, in the Beaufort Sea north of Prudhoe Bay.

Weeks, W.F.; Gow, A.J.

1980-02-20

101

Crystal structure of an insect antifreeze protein and its implications for ice binding.  

PubMed

Antifreeze proteins (AFPs) help some organisms resist freezing by binding to ice crystals and inhibiting their growth. The molecular basis for how these proteins recognize and bind ice is not well understood. The longhorn beetle Rhagium inquisitor can supercool to below -25 °C, in part by synthesizing the most potent antifreeze protein studied thus far (RiAFP). We report the crystal structure of the 13-kDa RiAFP, determined at 1.21 ? resolution using direct methods. The structure, which contains 1,914 nonhydrogen protein atoms in the asymmetric unit, is the largest determined ab initio without heavy atoms. It reveals a compressed ?-solenoid fold in which the top and bottom sheets are held together by a silk-like interdigitation of short side chains. RiAFP is perhaps the most regular structure yet observed. It is a second independently evolved AFP type in beetles. The two beetle AFPs have in common an extremely flat ice-binding surface comprising regular outward-projecting parallel arrays of threonine residues. The more active, wider RiAFP has four (rather than two) of these arrays between which the crystal structure shows the presence of ice-like waters. Molecular dynamics simulations independently reproduce the locations of these ordered crystallographic waters and predict additional waters that together provide an extensive view of the AFP interaction with ice. By matching several planes of hexagonal ice, these waters may help freeze the AFP to the ice surface, thus providing the molecular basis of ice binding. PMID:23486477

Hakim, Aaron; Nguyen, Jennifer B; Basu, Koli; Zhu, Darren F; Thakral, Durga; Davies, Peter L; Isaacs, Farren J; Modis, Yorgo; Meng, Wuyi

2013-03-12

102

From the single-scattering properties of ice crystals to climate prediction: A way forward  

NASA Astrophysics Data System (ADS)

Cirrus is composed of non-spherical ice crystals, and against the blue background of the sky, they appear as tenuous wispy clouds, usually located at altitudes greater than about 6 km. Their spatial and temporal distribution about the Earth's atmosphere is significant. With such distributions, their contributions to the Earth's natural greenhouse effect and hydrological cycle are important. Therefore, it is important that climate models are able to predict the radiative effect of cirrus, as well as their contribution to the total amount of ice mass that occurs in the Earth's atmosphere. However, cirrus is composed of ice crystals that can take on a variety of geometrical shapes, from pristine habits such as hexagonal ice columns, hexagonal ice plates and bullet-rosettes, to highly randomized habits, which may have roughened surfaces and/or air cavities. These habits also aggregate together, to form chains of aggregates and compact aggregates. The sizes of these habits may also vary, from about less than 10 ?m, to several cm, with the smaller ice crystals usually existing toward cloud-top and the larger ice crystals existing toward the cloud-bottom. Due to this variability of geometrical complexity, size, and ice mass, predicting the magnitude of the cirrus greenhouse effect has proven problematic. To try to constrain these radiative and hydrological uncertainties, since about 2006 there is now available the A-train constellation of satellites, which attempt to quantify the radiative and hydrological contributions of cirrus to the Earth's atmosphere. The A-train obtains nearly simultaneous measurements of cirrus from across the electromagnetic spectrum. Such simultaneous measurements pose challenges for theoretical scattering models of cirrus, as these models must conserve ice mass and be physically consistent across the electromagnetic spectrum. In this review paper, the microphysical properties of cirrus are summarized. The current idealized habit mixture models that have been proposed to represent the observed variability in ice crystal shape, size and mass are discussed. The theoretical light scattering methods that are currently applied to the idealized habit mixture models to solve for their scattering and absorption properties are discussed. The physical inconsistency of the current approach to parameterize the bulk scattering and absorption properties of cirrus in climate models is highlighted. An alternative parameterization, which couples cloud physics more directly with radiation, is proposed. Such a coupling is required, if climate models are to be physically consistent and radiatively interactive.

Baran, Anthony J.

2012-08-01

103

Dynamic pressure-induced dendritic and shock crystal growth of ice VI  

PubMed Central

Crystal growth mechanisms are crucial to understanding the complexity of crystal morphologies in nature and advanced technological materials, such as the faceting and dendrites found in snowflakes and the microstructure and associated strength properties of structural and icy planetary materials. In this article, we present observations of pressure-induced ice VI crystal growth, which have been predicted theoretically, but had never been observed experimentally to our knowledge. Under modulated pressure conditions in a dynamic-diamond anvil cell, rough single ice VI crystal initially grows into well defined octahedral crystal facets. However, as the compression rate increases, the crystal surface dramatically changes from rough to facet, and from convex to concave because of a surface instability, and thereby the growth rate suddenly increases by an order of magnitude. Depending on the compression rate, this discontinuous jump in crystal growth rate or “shock crystal growth” eventually produces 2D carpet-type fractal morphology, and moreover dendrites form under sinusoidal compression, whose crystal morphologies are remarkably similar to those predicted in theoretical simulations under a temperature gradient field. The observed strong dependence of the growth mechanism on compression rate, therefore, suggests a different approach to developing a comprehensive understanding of crystal growth dynamics.

Lee, Geun Woo; Evans, William J.; Yoo, Choong-Shik

2007-01-01

104

Simplification for Fraunhofer diffracting pattern of various randomly oriented ice crystals in cirrus.  

PubMed

This paper deals with Fraunhofer diffraction by an ensemble of independent randomly oriented ice crystals of assorted shapes, like those of cirrus clouds. There is no restriction on the shape of each crystal. It is shown that light flux density in the Fourier plane is azimuth-invariant and varies as 1/sin(4)?, ? being the angle of diffraction. The analytical formula proposed is exact. The key point of this study is conservation of electromagnetic energy. PMID:23201960

Pujol, Olivier; Brogniez, Gérard; Labonnote, Laurent

2012-09-01

105

Elemental composition and morphology of ice-crystal residual particles in cirrus clouds and contrails  

Microsoft Academic Search

Aircraft sampling of residual particles from evaporated ice crystals was performed using a Counterflow Virtual Impactor. Samples of crystals taken in both contrails and cirrus clouds were compared with interstitial aerosols found in natural cirrus. The samples were analyzed with a scanning electron microscope which was equipped with a windowless energy-dispersive X-ray detector (SEM\\/EDX). In the contrail and cirrus cases

A Petzold; J Ström; S Ohlsson; F. P Schröder

1998-01-01

106

A renewed argument for crystal size control of ice sheet strain rates  

Microsoft Academic Search

At present, it is generally believed that crystal size has no direct influence on strain rate in the ice sheets and that the fraction of strain rate enhancement there which is not ascribable to c axis fabric is due to impurity content. Here we challenge this view because it is not consistent with recent results from analyses of deformation at

K. M. Cuffey; T. Thorsteinsson; E. D. Waddington

2000-01-01

107

Time-varying ice crystal orientation in thunderstorms observed with multiparameter radar  

Microsoft Academic Search

Repeated changes associated with lightning have been observed with multiparameter radar in the echoes from the tops of Florida thunderstorms. These lightning-related radar signatures are interpreted as changes in the orientation of ice crystals being preferentially aligned parallel to the in-cloud electric field. The changes occur at intervals on the order of 10 s and are easily observed in the

I. Jeff Caylor; V. Chandrasekar

1996-01-01

108

The Deposition of Ice Crystals on Cooling Surfaces in Low Temperature Plant  

Microsoft Academic Search

A study is made of the conditions governing the deposition of ice crystals from a moist air stream on to the inside surface of a cooled tube. The promoting effect of impurities such as oil vapour in the air stream is demonstrated. Series of experiments were made to establish the effect of air velocity, and of the temperature difference between

G. G. Haselden

1950-01-01

109

A global classification of snow crystals, ice crystals, and solid precipitation based on observations from middle latitudes to polar regions  

NASA Astrophysics Data System (ADS)

This paper presents an extensive revision of Magono and Lee's (1966) classification of natural snow crystals, which has been widely used in snow and ice studies to describe snow crystal shapes. The new classification catalogs snow crystals and other solid precipitation particles into 121 categories, in contrast to Magono and Lee's 80 categories. Of these, 28 categories were created to classify new types of snow crystals that have been discovered in polar regions since 1968, seven were created after reconsidering the original categories, and six categories were created to classify solid precipitation particles such as frozen cloud particles and small raindrops. Because our observational area extended from middle latitudes (Japan) to polar regions, we refer to our new classification scheme as 'global-scale classification' or 'global classification'. The global classification consists of three levels – general, intermediate, and elementary – which are composed of 8, 39, and 121 categories, respectively. This paper describes the characteristics of each type of snow crystal, ice crystal, and solid precipitation particle.

Kikuchi, Katsuhiro; Kameda, Takao; Higuchi, Keiji; Yamashita, Akira

2013-10-01

110

Ice crystal size estimation using multiple-wavelength radar  

Microsoft Academic Search

Measurements and simulations of multiple-wavelength radar scattering have demonstrated the feasibility of using multiple-wavelength systems to estimate effective hydrometeor size in ice-phase clouds, and in various forms of precipitation. Radar reflectivity differences occur when the higher frequency experiences non-Rayleigh scattering. For cloud particle sizing, the higher frequency must exhibit non-Rayleigh scattering from small hydrometeors. This occurs at mm-wavelengths where radar

Stephen M. Sekelsky; Robert E. McIntosh; Warner L. Ecklund; Kenneth S. Gage

1998-01-01

111

Lattice Boltzmann Simulation of Water Isotope Fractionation During Growth of Ice Crystals in Clouds  

NASA Astrophysics Data System (ADS)

The isotopic composition of precipitation, especially that of snow, plays a special role in the global hydrological cycle and in reconstruction of past climates using polar ice cores. The fractionation of the major water isotope species (HHO, HDO, HHO-18) during ice crystal formation is critical to understanding the global distribution of isotopes in precipitation. Ice crystal growth in clouds is traditionally treated with a spherically- symmetric steady state diffusion model, with semi-empirical modifications added to account for ventilation and for complex crystal morphology. Although it is known that crystal growth rate, which depends largely on the degree of vapor over-saturation, determines crystal morphology, there are no existing quantitative models that directly relate morphology to the vapor saturation factor. Since kinetic (vapor phase diffusion-controlled) isotopic fractionation also depends on growth rate, there should be a direct relationship between vapor saturation, crystal morphology, and crystal isotopic composition. We use a 2D Lattice-Boltzmann model to simulate diffusion-controlled ice crystal growth from vapor- oversaturated air. In the model, crystals grow solely according to the diffusive fluxes just above the crystal surfaces, and hence crystal morphology arises from the initial and boundary conditions in the model and does not need to be specified a priori. The input parameters needed are the isotope-dependent vapor deposition rate constant (k) and the water vapor diffusivity in air (D). The values of both k and D can be computed from kinetic theory, and there are also experimentally determined values of D. The deduced values of k are uncertain to the extent that the sticking coefficient (or accommodation coefficient) for ice is uncertain. The ratio D/k is a length that determines the minimum scale of dendritic growth features and allows us to scale the numerical calculations to atmospheric conditions using a dimensionless Damkohler number: Da = kh/D, where h is the width of the 2D calculation domain. Varying the nondimensional Da in the model is equivalent to varying the scale (h) in the model. Our calculations confirm that the crystal/vapor isotopic fractionation approaches the equilibrium value, and the crystals are compact (circular in 2D) as the saturation factor approaches unity (S= 1.0). At higher oversaturation (e.g. S = 1.2), dendritic crystals of millimeter size develop on timescales appropriate to cloud processes, the isotopic fractionations are dominated by kinetic effects, and similar to those predicted by the spherical diffusion model. Dendritic crystals are constrained to be relatively large, with dimension much greater than D/k. The most difficult aspect of the modeling is to account for the large density difference between air and ice, which requires us to use a fictitious higher density for the vapor-oversaturated air and scale the crystal growth time accordingly. A different approach, using a larger scale simulation to derive boundary conditions for a nested smaller scale calculation is in progress. The results to date clarify the controls on dendritic crystal growth, the relationships between saturation state, growth rate, crystal morphology and isotopic fractionation, and provide limits on the value of the accommodation coefficient.

Lu, G.; Depaolo, D.; Kang, Q.; Zhang, D.

2006-12-01

112

Elementary steps at the surface of ice crystals visualized by advanced optical microscopy  

PubMed Central

Due to the abundance of ice on earth, the phase transition of ice plays crucially important roles in various phenomena in nature. Hence, the molecular-level understanding of ice crystal surfaces holds the key to unlocking the secrets of a number of fields. In this study we demonstrate, by laser confocal microscopy combined with differential interference contrast microscopy, that elementary steps (the growing ends of ubiquitous molecular layers with the minimum height) of ice crystals and their dynamic behavior can be visualized directly at air-ice interfaces. We observed the appearance and lateral growth of two-dimensional islands on ice crystal surfaces. When the steps of neighboring two-dimensional islands coalesced, the contrast of the steps always disappeared completely. We were able to discount the occurrence of steps too small to detect directly because we never observed the associated phenomena that would indicate their presence. In addition, classical two-dimensional nucleation theory does not support the appearance of multilayered two-dimensional islands. Hence, we concluded that two-dimensional islands with elementary height (0.37 and 0.39 nm on basal and prism faces, respectively) were visualized by our optical microscopy. On basal and prism faces, we also observed the spiral growth steps generated by screw dislocations. The distance between adjacent spiral steps on a prism face was about 1/20 of that on a basal face. Hence, the step ledge energy of a prism face was 1/20 of that on a basal face, in accord with the known lower-temperature roughening transition of the prism face.

Sazaki, Gen; Zepeda, Salvador; Nakatsubo, Shunichi; Yokoyama, Etsuro; Furukawa, Yoshinori

2010-01-01

113

Sea Ice  

NSDL National Science Digital Library

In this resource, students will discover that there are notable differences between sea ice and fresh-water ice, such as density. In on segment, students learn that the first sign of freezing on the sea is an oily appearance of the water caused by the formation of needle-like crystals. The site explains the relationship between growth and the rate at which heat flows from the water and that the ice pack can alter its shape and dimension due to the movement of winds, currents, thermal expansion, and contraction of the ice. Types of ice described here include new ice, nilas, young ice, first-year ice, and old ice while the forms of ice covered include pancake ice, brash ice, ice cake, floe, and fast ice. The site also explains the meteorological and oceanographic factors that control the amount and movement of ice.

114

Characterizing Single-Scattering Properties of Non-Spherical Ice-Crystal Ensembles  

NASA Astrophysics Data System (ADS)

Retrievals of atmospheric particulate constituents using remote sensing means rely on the characterization of the single-scattering properties of these particulate matters. We are able to characterize with fairly high accuracies the single-scattering properties involving spherical particles, due to the symmetry of their shape. For example, it has been demonstrated that liquid water content, effective radius, and effective variance adequately characterize the single-scattering of an ensemble of spherical cloud water droplets in the visible and near-infrared wavelengths (Hansen and Travis 1974). Such is not the case, however, for non-spherical particles such as ice crystals. In order to characterize the scattering of these non-spherical particles we need to first find realistic representations of their shapes. The Snowfake (Gravner and Griffeath 2009) model is a numerical growth model for ice crystals based on diffusion and vapor deposition. It is capable of “growing” realistic ice crystals with the exquisite fine features observed in nature. Before the advent of Snowfake, single-scattering calculations are performed on shapes described by simplified mathematical formulae, which bear only a rough resemblance to the real ones. With crystals “grown” by the Snowfake model we can be more confident with the representativeness of the single-scattering properties obtained. Single-scattering properties of these particles are calculated using the open-source DDSCAT software developed by Draine and Flatau (2008), based on discrete dipole approximation (DDA). In this presentation we report early results obtained from the effort of characterizing the single-scattering of ensembles of pristine ice crystals using geometric parameters derived from the particle size distribution (PSD) of the ensembles at the wavelengths of current spaceborne radars.

Kuo, K.; Han, Q.; Smith, E. A.

2009-12-01

115

Ice  

NSDL National Science Digital Library

When a chunk of ice "twice the size of Manhattan" broke away from the northernmost part of the Antarctic Peninsula in February, ice was at the forefront of scientific news. Now, with the spectacular discovery of bacteria in Antarctic ice and with new evidence of slush beneath the frozen surface of Jupiter's moon Europa, water in its frozen form is once again in the news. The discovery of living organisms in the Antarctic ecosystem, described in the June 26, 1998 issue of Science, is significant because it presents a model for "how life may have arisen and persisted on other worlds." Scientists speculate that if organisms can thrive in the hard ice of Antarctica, they may possibly have done so on Europa and Mars. Galileo's closest approach to Europa occurred on July 21, 1998, offering new images of ice in space. The nine sites listed offer insights and details of the recent findings and discoveries related to ice.

Harris, Kathryn L.

116

Size and location of ice crystals in pork frozen by high-pressure-assisted freezing as compared to classical methods  

Microsoft Academic Search

In high-pressure-assisted freezing, samples are cooled under pressure (200 MPa) to ? 20 °C without ice formation then pressure is released (0.1 MPa) and the high super-cooling reached (approx. 20 °C), promotes uniform and rapid ice nucleation. The size and location of ice crystals in large meat pieces (Longissimus dorsi pork muscle) as a result of high-pressure-assisted freezing were compared

M. N. Martino; L. Otero; P. D. Sanz; N. E. Zaritzky

1998-01-01

117

Possible Evidence for Crystallization of Astrophysical Ice Analogs by Heavy and Energetic Cosmic Rays  

NASA Astrophysics Data System (ADS)

We present an experimental study about the alteration of the 3300 cm-1 band (?_1 vibration mode) in the infrared spectra of water-rich ices due to the bombardments with heavy, highly-charged, and energetic ions (15.7 MeV 16O5+; 46 MeV 58Ni13+). The experiments simulate the physical chemistry as well possible morphological changes induced by heavy-ion cosmic rays at water-rich astrophysical ices. The measurements were performed inside a high vacuum chamber at the heavy-ion accelerator GANIL (Grand Accelerateur National d'Ions Lourds) in Caen, France. The experiments employed pure amorphous water ice and mixed H_2O:CO_2 amorphous ices at 13 K. In-situ analysis was performed by a Fourier transform infrared spectrometer (FTIR) at different ion fluences. After the ion bombardment the center of this water band is shifted to lower frequencies (longer wavelength).We suggest this behavior may be attributed to the destruction of small water clusters (n=2,3), as well the production of larger clusters (n>5), both as a result of energy delivered by the fast ions (and its secondary electrons) along the neighborhood of the ion tracks inside the ices. The vibration of individual small water clusters are representative for the left wing of the ?_1 band in water ice while larger individual clusters are important for the right wing (lower energy). An experiment employing H_2O:CO_2 ice at 80 K, showing a small crystallization degree, does not show changes in the water ?_1 profile during the ion bombardment. The results suggest that a small degree of crystallization may be achieved in the amorphous astrophysical ices after the extensive bombardment with heavy and energetic ions. This may give us some clues about the crystalline water features observed at some cold regions in the interstellar medium such as the ices around young stellar objects, and also at some frozen surfaces of outer solar system bodies. Both regions are highly exposed to galactic cosmic rays.

Pilling, S.; Seperuelo Duarte, E.; da Silveira, E. F.; Rothard, H.; Domaracka, A.; Boduch, P.

2011-05-01

118

FAST TRACK COMMUNICATION: Growth melt asymmetry in ice crystals under the influence of spruce budworm antifreeze protein  

Microsoft Academic Search

Here we describe studies of the crystallization behavior of ice in an aqueous solution of spruce budworm antifreeze protein (sbwAFP) at atmospheric pressure. SbwAFP is an ice binding protein with high thermal hysteresis activity, which helps protect Choristoneura fumiferana (spruce budworm) larvae from freezing as they overwinter in the spruce and fir forests of the north eastern United States and

Natalya Pertaya; Yeliz Celik; Carlos L. Di Prinzio; J. S. Wettlaufer; Peter L. Davies; Ido Braslavsky

2007-01-01

119

Crystal structure, stable isotopes (delta O-18), and development of sea ice in the Ross, Amundsen, and Bellingshausen seas, Antarctica  

NASA Astrophysics Data System (ADS)

The crystal structure and oxygen isotopic composition of ice cores obtained from floes at the end of summer in the eastern Ross Sea, the Amundsen Sea, and the western Bellingshausen Sea were investigated to determine the ice growth processes and conditions that contribute to sea ice development in the eastern Pacific sector of the southern ocean. The isotope data indicate that a moderate amount of snow contributes to the development of the sea ice. However, even the combined use of isotopes and crystal structure analysis does not unambiguously explain the means by which all of the snow is entrained in the ice. Nevertheless, it seems clear that much of the snow is contained in granular snow-ice that results from seawater flooding of floes and the base of the snow cover. The snow cover in the Ross-Amundsen region was as much as 2 m deep and supported by 7- to 8-m-thick floes primarily composed of frazil ice. In the Bellingshausen region the snow cover and the floes were thinner than in the Ross-Amundsen region. The Bellingshausen cores were composed primarily of multiple layers of frazil and congelation ice. In addition, in both regions there were numerous tipped or inclined blocks of congelation ice and layers of rafted nilas in the cores. The data indicate that the sea ice develops by multiple mechanisms in a turbulent environment.

Jeffries, Martin O.; Shaw, Raymond A.; Morris, Kim; Veazey, Alice L.; Krouse, H. Roy

1994-01-01

120

Particle habit in tropical ice clouds during CRYSTAL-FACE: Comparison of two remote sensing techniques with in situ observations  

Microsoft Academic Search

Ice crystal shapes in tropical ice clouds are estimated with two different remote sensing methods and compared with measurements from an in situ cloud aerosol spectrometer (CAS) during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE) campaign conducted in Florida during July 2002. The remote sensing techniques use dual-satellite reflectances and lidar linear depolarization

H. Chepfer; V. Noel; P. Minnis; D. Baumgardner; L. Nguyen; G. Raga; M. J. McGill; P. Yang

2005-01-01

121

THE MECHANICAL PROPERTIES OF SINGLE CRYSTALS OF ICE AT LOW TEMPERATURES  

Microsoft Academic Search

The mechanical properties of single crystals of ice have been investigated at various temperatures down to — 90 °C. Two methods have been used: creep tests in tension and constant strain-rate tests in compression. Results show that the activation energy for creep varies with temperature from 0.41 -_t 0.03 eV between — 50 °C and — 90 °C to 0.68

S. J. JONES; J. W. GLEN

122

Geometric-optics-integral-equation method for light scattering by nonspherical ice crystals.  

PubMed

A new geometric-optics model has been developed for the calculation of the single-scattering and polarization properties for arbitrarily oriented hexagonal ice crystals. The model uses the ray-tracing technique to solve the near field on the ice crystal surface, which is then transformed to the far field on the basis of the electromagnetic equivalence theorem. From comparisons with the results computed by the finite-difference time domain method, we show that the novel geometric-optics method can be applied to the computation of the extinction cross section and single-scattering albedo for ice crystals with size parameters along the minimum dimension as small as ~6. Overall agreement has also been obtained for the phase function when size parameters along the minimum dimension are larger than ~20. We demonstrate that the present model converges to the conventional ray-tracing method for large size parameters and produces single-scattering results close to those computed by the finite-difference time domain method for size parameters along the minimum dimension smaller than ~20. The present geometric-optics method can therefore bridge the gap between the conventional ray-tracing and the exact numerical methods that are applicable to large and small size parameters, respectively. PMID:21127681

Yang, P; Liou, K N

1996-11-20

123

Geometric-optics{endash}integral-equation method for light scattering by nonspherical ice crystals  

SciTech Connect

A new geometric-optics model has been developed for the calculation of the single-scattering and polarization properties for arbitrarily oriented hexagonal ice crystals. The model uses the ray-tracing technique to solve the near field on the ice crystal surface, which is then transformed to the far field on the basis of the electromagnetic equivalence theorem. From comparisons with the results computed by the finite-difference time domain method, we show that the novel geometric-optics method can be applied to the computation of the extinction cross section and single-scattering albedo for ice crystals with size parameters along the minimum dimension as small as {approximately}6. Overall agreement has also been obtained for the phase function when size parameters along the minimum dimension are larger than {approximately}20. We demonstrate that the present model converges to the conventional ray-tracing method for large size parameters and produces single-scattering results close to those computed by the finite-difference time domain method for size parameters along the minimum dimension smaller than {approximately}20. The present geometric-optics method can therefore bridge the gap between the conventional ray-tracing and the exact numerical methods that are applicable to large and small size parameters, respectively. {copyright} {ital 1996 Optical Society of America.}

Yang, P.; Liou, K.N. [Center for Atmospheric and Remote Sounding Studies, University of Utah, 809 William C. Browning Building, Salt Lake City, Utah 84112 (United States)

1996-11-01

124

Laboratory Growth of Ice Crystals Under Simulated Polar Stratospheric Cloud and High Altitude Cirrus Conditions at Temperatures Below -70 C  

NASA Astrophysics Data System (ADS)

A static diffusion chamber has been used to grow ice crystals at temperatures below -70 C under controlled conditions of temperature, pressure, and ice supersaturation. Type 1 polar stratospheric cloud (PSC) particle growth was performed with frozen nitric acid solution drops in the presence of nitric acid and water vapor at temperatures between -75 C and -85 C. Type 2 PSC particle growth was performed with predominantly pure water at temperatures below -85 C. Ice crystals were also grown from pure water vapor over the same range of temperatures for comparison, nucleating on frozen sulfuric acid solution drops and on mineral dust particles. Linear, projected area, and volume growth rates are presented.

Bailey, M.; Hallett, J.; Peterson, H.; Petersen, D.

2006-12-01

125

A global view of horizontally oriented crystals in ice clouds from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO)  

Microsoft Academic Search

We analyze optical signatures in 18 months of CALIOP layer-integrated backscatter and depolarization ratio to investigate the geographical and seasonal distribution of oriented crystals in ice clouds on a global scale. Oriented crystals are found to be rare: they appear in ?6% of all ice cloud layers, and inside these layers the proportion of oriented crystals is estimated below 5%,

Vincent Noel; Helene Chepfer

2010-01-01

126

Crystallization of amorphous ice as the cause of comet P/Halley's outburst at 14 AU.  

PubMed

The post-perihelion eruption of comet P/Halley, detected in Feb. 1991 and believed to have started 3 months earlier, can be explained by crystallization of amorphous ice taking place in the interior of the porous nucleus, at depths a few tens of meters, accompanied by the release of trapped gases. Numerical calculations show that for a bulk density of 0.5 g cm-3 and a pore size of 1 millimicron crystallization occurs on the outbound leg of comet P/Halley's orbit, at heliocentric distances between 5 AU and 17 AU. The trapped gas is released and flows to the surface through the porous medium. It may also open wider channels, as the internal pressures obtained surpass the tensile strength of cometary ice. The outflowing gas carries with it grains of ice and dust, and thus can explain the large amounts of dust observed in the coma at 14.3 AU and beyond. The typical decline time of the process is found to be on the order of months, in agreement with observations. The rate of outgassing is two or three orders of magnitude higher than in quiescence. In an asymmetric, non-uniform nucleus--in contrast to the one-dimensional spherical model--the process should occur intermittently, such as was observed for comet P/Halley beyond 5 AU. PMID:11538062

Prialnik, D; Bar-Nun, A

1992-01-01

127

Microphysical and Optical Properties of Atmospheric Ice Crystals at South Pole Station  

NASA Astrophysics Data System (ADS)

In early February 2001 (during the austral summer), over 900 000 digital images of ice crystals were recorded at the South Pole using two ground-based cloud particle imagers (CPIs). Of these, 721 572 crystals >50 ?m were classified into crystal habits. When sorted by number, 30% of the crystals were rosette shaped (mixed-habit rosettes, platelike polycrystals, and rosette shapes with side planes), 45% were diamond dust (columns, thick plates, and plates), and 25% were irregular. When sorted by area, rosette shapes comprised 50%, diamond dust 30% and irregular 20%. By mass, the percentages were 57% rosette shapes, 23% diamond dust, and 20% irregular. Particle size distributions as a function of maximum dimension and equivalent radius are compared with previous studies. Particles are generally found to be slightly larger than previous austral wintertime studies. In 2002, a polar nephelometer (PN) that measures scattering phase function was incorporated with one of the CPIs. Correlated measurements between the two instruments showed that 22° and 46° peaks in the phase function were present when diamond dust was recorded by the CPI, but not when rosette shapes were present. Visual observations confirmed the presence of 22° and 46° atmospheric halos in some, but not all, of the diamond dust events. No visual halos were observed when rosette shapes were precipitating. Average PN phase functions are presented for diamond dust and rosette shapes. The diamond dust and rosette-shaped ice crystals appear to be very similar in shape to those observed by CPIs in cirrus clouds. Cloud conditions at the South Pole that were associated with various crystal types are discussed, as are some effects of blowing snow.

Lawson, R. Paul; Baker, Brad A.; Zmarzly, Patrick; O'Connor, Darren; Mo, Qixu; Gayet, Jean-Francois; Shcherbakov, Valery

2006-11-01

128

Using a quartz crystal microbalance to probe formation of Xe hydrate in thin ice films  

NASA Astrophysics Data System (ADS)

We have demonstrated the ability of the quartz crystal microbalance to successfully measure the formation and dissociation of thin films of Xe hydrate formed from ice films in the presence of Xe gas or from a cooled mixture of water vapor and Xe gas. By monitoring the uptake of mass, we have measured the formation of Xe hydrates on ice films in the temperature range 180

Chan, J.; Forrest, J. A.; Torrie, B. H.

2004-09-01

129

Accuracy of the Anomalous Diffraction approximation to light scattering by column-like ice crystals  

NASA Astrophysics Data System (ADS)

The wavelength and the particle size effects on the accuracy of ADA (Anomalous Diffraction Approximation) method are discussed by comparing the scattering results between ADA method and Mie theory for spherical particles, which indicates that the ADA accuracy depends mainly on the particle size parameter, and is not sensitive to the condition of | m - 1 | ? 1. The results comparison between ADA method and ray tracing method for hexagonal column-like ice crystal particles shows that within the visible wavelength range, results from both methods agree well, and within the infrared wavelength range, there is large discrepancy for co-albedo result due to different assumptions of the ray path inside the particle.

Liu, C.; Jonas, P. R.; Saunders, C. P. R.

130

Final Report for "Improved Representations of Cloud Microphysics for Model and Remote Sensing Evaluation using Data Collected during ISDAC, TWP-ICE and RACORO  

SciTech Connect

We were funded by ASR to use data collected during ISDAC and TWP-ICE to evaluate models with a variety of temporal and spatial scales, to evaluate ground-based remote sensing retrievals and to develop cloud parameterizations with the end goal of improving the modeling of cloud processes and properties and their impact on atmospheric radiation. In particular, we proposed to: 1) Calculate distributions of microphysical properties observed in arctic stratus during ISDAC for initializing and evaluating LES and GCMs, and for developing parameterizations of effective particle sizes, mean fall velocities, and mean single-scattering properties for such models; 2) Improve representations of particle sizes, fall velocities and scattering properties for tropical and arctic cirrus using TWP-ICE, ISDAC and M-PACE data, and to determine the contributions that small ice crystals, with maximum dimensions D less than 50 ?m, make to mass and radiative properties; 3) Study fundamental interactions between clouds and radiation by improving representations of small quasi-spherical particles and their scattering properties. We were additionally funded 1-year by ASR to use RACORO data to develop an integrated product of cloud microphysical properties. We accomplished all of our goals.

McFarquhar, Greg M. [University of Illinois] University of Illinois

2003-06-11

131

High crystalline quality of large single crystals of subglacial ice above Lake Vostok (Antarctica) revealed by hard X-ray diffraction  

Microsoft Academic Search

X-ray diffraction experiments carried out on large single crystals from accreted ice above Lake Vostok, a subglacial lake lying beneath the East Antarctic ice sheet, revealed a surprisingly very low lattice distortion. This crystalline quality does not seem to be affected by impurities. Chloride and sodium appear to be homogeneously distributed in the ice lattice in spite of their relatively

Maurine Montagnat; Paul Duval; P. Bastie; B. Hamelin; M. de Angelis; J. R. Petit; V. Ya Lipenkov

2003-01-01

132

Sensitivity of the Global Distribution of Cirrus Ice Crystal Concentration to Heterogeneous Freezing (Invited)  

NASA Astrophysics Data System (ADS)

This study presents the sensitivity of global ice crystal number concentration, Nc, to the parameterization of heterogeneous ice nuclei (IN). Simulations are carried out with the NASA Global Modeling Initiative (GMI) chemical and transport model coupled to an analytical ice microphysics parameterization. Heterogeneous freezing is described using nucleation spectra derived from theoretical and empirical considerations, considering dust, black carbon, ammonium sulfate, and glassy aerosol as IN precursors. When competition between homogeneous and heterogeneous freezing is considered, global mean Nc vary by up to a factor of twenty depending on the heterogeneous freezing spectrum used. IN effects on Nc strongly depend on dust and black carbon concentrations, and are strongest under conditions of weak updraft and high temperature. Regardless of the heterogeneous spectrum used, dust is an important contributor of IN over large regions of the northern hemisphere. Black carbon however exhibits appreciable effects on when the freezing fraction is greater than 1%. Compared to in situ observations, Nc is overpredicted at temperatures below 205 K, even if a fraction of liquid aerosol is allowed to act as glassy IN. Assuming that cirrus formation is forced by weak updraft addressed this overprediction but promoted heterogeneous freezing effects to the point where homogeneous freezing is inhibited even for IN concentrations as low as 1 L-1. Chemistry and dynamics must be considered to explain cirrus characteristics at low temperature. Only cloud formation scenarios where competition between homogeneous and heterogeneous freezing is the dominant feature would result in maximum supersaturation levels consistent with observations.

Nenes, A.; Barahona, D.; Rodriguez, J. M.

2010-12-01

133

Ice-crystal absorption: a comparison between theory and implications for remote sensing.  

PubMed

The problem of the disagreement between cirrus crystal sizes determined remotely and by in situ measurements is shown to be due to inappropriate application of Mie theory. We retrieved the absorption optical depth at 8.3 and 11.1 mum from 11 tropical anvil cirrus clouds, using data from the High Resolution Infrared Radiation Sounder (HIRS). We related the absorption optical depth ratio between the two wavelengths to crystal size (the size was defined in terms of the crystal median mass dimension) by assuming Mie theory applied to ice spheres and anomalous diffraction theory (ADT) applied to hexagonal columns, hexagonal plates, bullet rosettes, and aggregates (polycrystals). The application of Mie theory to retrievals yielded crystal sizes approximately one third those obtained with ADT. The retrievals of crystal size by use of HIRS data are compared with measurements of habit and crystal size obtained from in situ measurements of tropical anvil cirrus particles. The results of the comparison show that ADT provides the more realistic retrieval. Moreover, we demonstrate that at infrared wavelengths retrieval of crystal size depends on assumed habit. The reason why Mie theory predicts smaller sizes than ADT is shown to result from particle geometry and enhanced absorption owing to the capture of photons from above the edge of the particle (tunneling). The contribution of particle geometry to absorption is three times greater than from tunneling, but this process enhances absorption by a further 35%. The complex angular momentum and T-matrix methods are used to show that the contribution to absorption by tunneling is diminished as the asphericity of spheroidal particles is increased. At an aspect ratio of 6 the contribution to the absorption that is due to tunneling is substantially reduced for oblate particles, whereas for prolate particles the tunneling contribution is reduced by 50% relative to the sphere. PMID:18273143

Baran, A J; Foot, J S; Mitchell, D L

1998-04-20

134

Role of small ice crystals in radiative properties of cirrus: A case study, FIRE II, November 22, 1991  

NASA Astrophysics Data System (ADS)

Aircraft observations of cirrus cloud were made near Coffeyville, Kansas, during November 1991 as part of the FIRE II project. Cloud ice particle spectra measurements were made using both a PMS 2DC probe and an ice particle replicator. Particles larger than 200 ?m were column rosettes. The replicator shows the presence of large numbers of ice crystals smaller than 66 ?m (two PMS size bins) that are not recorded by the PMS 2DC probe. Calculations based on the replicator data of the geometrical blocked area and absorption cross section of the cloud per unit volume show that small particles can contribute significantly to and sometimes dominate both the solar extinction and the infrared emission. Intercomparison is made of the ice particle size, area, and mass distributions determined by these different instruments. Power law relationships for area occluded by a crystal as a function of crystal maximum dimension were computed from the PMS 2DC data. The wavelength-dependent infrared absorption cross section per volume was computed using a simple model based on anomalous diffraction and area and mass dimensional relationships for the ice crystals.

Arnott, W. Patrick; Dong, Ya Yi; Hallett, John; Poellot, Michael R.

1994-01-01

135

Sierra Nevada Winter Storms: a Study Using Microwave Radiometry, Ice Crystal and Isotopic Analysis Technique  

NASA Astrophysics Data System (ADS)

An observational study has been made of ice-phase winter storm clouds over the Sierra Nevada mountains. In Part I, two microwave radiometers, one designed with a spinning reflector to shed precipitation particles while the other radiometer's reflector was fixed, are compared. The absence/presence of contaminated periods in the data was attributed to difference in design. These apparent contaminated periods led to lower correlation coefficients between the radiometers. Comparison of radiometer and rawinsonde resulted in a correlation coefficient of 0.97 for the spinning reflector as opposed to 0.8 for the fixed reflector radiometer. In Part II, stable water isotopes were used to study mesoscale and microscale storm modifications by the Sierra Nevada. Initially, a low level warm front lay across the region and its elevation lowered with time from 2.5 km to 1.7 km. This decrease of frontal surface height was accompanied by a steady increase in the delta ^{18}O values. In the pre-cold frontal period, the delta^{18 }O values at the upwind site signified warmer origin ice crystals than the downwind site. This is explained by orographic effects and the production of supercooled liquid water at low elevations on the upslope side. The delta^{18}O value peaked around -13perthous which translates to an "equivalent temperature" of -10.7^circC for ice phase water capture at the upwind site. At the downwind site, this was some 5 to 6 centigrade degrees colder. During surface cold front passage, the differences in delta^{18}O at the two sites are small probably because, during frontal passage, the orography plays a less significant role in the precipitation production process. In Part III, observations of precipitation rates, ice crystals, wind and supercooled liquid water (SLW) upwind and downwind of the Sierra Nevada are presented. Observations show that the stage of development of the storms was important in the liquid and vapor development. High SLW, and increased riming were located before the frontal passage. Duration of SLW as observed by the radiometers, was always shorter over the downwind station. Heavy riming was associated with precipitation decrease while high precipitation rates were correlated with high number fraction of aggregate crystals. Aggregation was found to be an important process for precipitation development over the downwind station.

Demoz, Belay Berhane

136

Crystal growth investigations of ice?water interfaces from molecular dynamics simulations: Profile functions and average properties.  

PubMed

Attempts to simulate crystal growth of ice from liquid water and to provide a consistent microscopic description of this process have been challenging tasks. In this paper we have adapted our previously developed molecular dynamics simulation methodology to enable the investigation of steady-state directional crystal growth?melting of ice. Specifically, we examine ice?water systems of the (001), (110), and (111) faces of ice Ic and the (0001), (1010), and (1120) faces of ice Ih, where the TIP4P, TIP4P-Ew, and SPC?E water models have been utilized. The influence of different growth?melting conditions (temperature gradients and growth velocities) is investigated. Profile functions of properties of interest across the interface are obtained from nonequilibrium steady-state simulations and provide consistent descriptions of ice?water interfaces. The widths of the various crystallographic faces are found to increase in the apparent order Ic111, Ih0001 < Ih1010 < Ih1120 < Ic001 < Ic110. The observed growth rates were in agreement with experimental values and the possible dependence on the various faces is explored. The melting temperatures obtained with the present methodology for the different models are in good agreement with estimates from other work. PMID:21219023

Razul, M S Gulam; Kusalik, P G

2011-01-01

137

Parameterization of Photon Tunneling with Application to Ice Cloud Optical Properties at Terrestrial Wavelengths  

NASA Astrophysics Data System (ADS)

Sometimes deep physical insights can be gained through the comparison of two theories of light scattering. Comparing van de Hulst's anomalous diffraction approximation (ADA) with Mie theory yielded insights on the behavior of the photon tunneling process that resulted in the modified anomalous diffraction approximation (MADA). (Tunneling is the process by which radiation just beyond a particle's physical cross-section may undergo large angle diffraction or absorption, contributing up to 40% of the absorption when wavelength and particle size are comparable.) Although this provided a means of parameterizing the tunneling process in terms of the real index of refraction and size parameter, it did not predict the efficiency of the tunneling process, where an efficiency of 100% is predicted for spheres by Mie theory. This tunneling efficiency, Tf, depends on particle shape and ranges from 0 to 1.0, with 1.0 corresponding to spheres. Similarly, by comparing absorption efficiencies predicted by the Finite Difference Time Domain Method (FDTD) with efficiencies predicted by MADA, Tf was determined for nine different ice particle shapes, including aggregates. This comparison confirmed that Tf is a strong function of ice crystal shape, including the aspect ratio when applicable. Tf was lowest (< 0.36) for aggregates and plates, and largest (> 0.9) for quasi- spherical shapes. A parameterization of Tf was developed in terms of (1) ice particle shape and (2) mean particle size regarding the large mode (D > 70 mm) of the ice particle size distribution. For the small mode, Tf is only a function of ice particle shape. When this Tf parameterization is used in MADA, absorption and extinction efficiency differences between MADA and FDTD are within 14% over the terrestrial wavelength range 3-100 mm for all size distributions and most crystal shapes likely to be found in cirrus clouds. Using hyperspectral radiances, it is demonstrated that Tf can be retrieved from ice clouds. Since Tf is a function of ice particle shape, this may provide a means of retrieving qualitative information on ice particle shape.

Mitchell, D. L.

2006-12-01

138

A laboratory study on the uptake of HCl, HNO 3, and SO 2 gas by ice crystals and the effect of these gases on the evaporation rate of the crystals  

Microsoft Academic Search

The results of our new and earlier laboratory studies on the uptake of gases by ice crystals are summarized in terms of (1) the equilibrium phase diagram for a system gas\\/H2O, (2) the effect of these gases on the evaporation rate of ice crystals, and (3) in terms of the uptake of the gases by water drops. It is shown

K Diehl; S. K Mitra; H. R Pruppacher

1998-01-01

139

Retrieval of cirrus optical thickness and assessment of ice crystal shape from ground-based imaging spectrometry  

NASA Astrophysics Data System (ADS)

A ground-based hyperspectral imaging spectrometer (AisaEAGLE, manufactured by Specim Ltd., Finland) is applied to measure downward spectral radiance fields with high spatial (1024 spatial pixels within 36.7° field of view), spectral (488 spectral pixels, 400-970 nm, 1.25 nm full width at half maximum), and temporal (4-30 Hz) resolution. The calibration, measurement and data evaluation procedures are introduced. A new method is presented to retrieve the cirrus optical thickness (?ci) using the spectral radiance data collected by AisaEAGLE. The data were collected during the Cloud Aerosol Radiation and tuRbulence of trade wInd cumuli over BArbados (CARRIBA) project in 2011. The spatial inhomogeneity of the investigated cirrus is characterised by the standard deviation of the retrieved ?ci as well as the width of its frequency distribution. By comparing measured and simulated downward solar spectral radiance as a function of scattering angle, some evidence of the prevailing cirrus ice crystal shape can be obtained and subsequently used to substantiate the retrieval of ?ci. The sensitivity of the retrieval method with respect to surface albedo, effective radius (reff), cloud height and ice crystal shape is quantified. An enhanced sensitivity of the retrieved ?ci is found with respect to the surface albedo (up to 30%) and ice crystal shape (up to 90%). The sensitivity with regard to the effective ice crystal radius (≤ 5%) and the cloud height (≤ 0.5%) is rather small and can be neglected.

Schäfer, M.; Bierwirth, E.; Ehrlich, A.; Heyner, F.; Wendisch, M.

2013-08-01

140

Sensitivity of Cirrus Bidirectional Reflectance at MODIS Bands to Vertical Inhomogeneity of Ice Crystal Habits and Size Distribution.  

National Technical Information Service (NTIS)

A common assumption in satellite imager-based cirrus retrieval algorithms is that the radiative properties of a cirrus cloud may be represented by those associated with a specific ice crystal shape (or habit) and a single particle size distribution. Howev...

P. Yang B. C. Gao B. A. Baum W. Wiscombe Y. Hu S. L. Nasiri P. F. Soulen A. J. Heymsfield G. M. McFarquhar L. M. Miloshevich

2000-01-01

141

T-1020 NaI crystal test for DM-Ice  

SciTech Connect

This is a memorandum of understanding between the Fermi National Accelerator Laboratory (Fermilab) and the experiments of the NaI Crystal Test for DM-Ice from the University of Wisconsin who have committed to participate in detector tests to be carried out during the 2011-2012 Fermilab Neutrino program. The memorandum is intended primarily for the purpose of recording expectations for budget estimates and work allocations for Fermilab, the funding agencies and the participating institutions. It reflects an arrangement that currently is satisfactory to the parties; however, it is recognized and anticipated that changing circumstances of the evolving research program will necessitate revisions. The parties agree to modify this memorandum to reflect such required adjustments. Actual contractual obligations will be set forth in separate documents. The DM-Ice collaboration is designing a sodium-iodide (NaI) based detector for a direct dark matter search. The detectors should have low readout noise and background levels to carry out a sensitive search. A 17-kg version of the experiment is running at the South Pole, 2500 m deep in the Antarctic ice, and a large scale experiment is currently being designed. One of the keys to the success of the experiment is to have a good understanding of the background levels intrinsic in the NaI detectors. To measure the background level, the detectors have to be shielded against cosmic rays. The lead shielding used for DAMIC in the Minos Underground Areas is a well-suited location for this test since it offers enough overburden to shield against cosmic rays, lead shielding, and experimental infrastructure. The goal of the test is to assess the background levels in the detector and to assess the characteristics of phosphorescence induced by muons and 100 keV-3 MeV gamma rays.

Maruyama, Reina; Heeger, Karsten; Pierpoint, Zachary; Pettus, Walter; Broerman, Benjamin; Hilgenberg, Chris; Webber, David; /Wisconsin U., Madison

2011-11-03

142

Density and surface temperature of graupel and the charge separation during ice crystal interactions  

NASA Astrophysics Data System (ADS)

Significant amounts of charge are separated when vapor-grown ice crystals interact with riming graupel a mechanism widely believed to be responsible for the generation of electric charge in thunderstorms. This study shows that the density of graupel, by itself, is not an effective parameter in determining the sign of the separated charge. The well-known charge sign reversal temperature is found to be strongly influenced by the surface temperature of the rime at low cloud water content (CWC). At a cloud temperature of -10°C and a CWC of 0.4 g m-3 the charging current to the graupel reversed from positive to negative as the surface temperature of the graupel exceeded -6°C. The maximum CWC at which the sign could thus be reversed increased as the cloud temperature decreased, ranging from less than 0.7 g m-3 at -10°C to less than 0.9 g m-3 at -20°C. At higher cloud water contents the rime surface temperature had no effect on the charging sign. The observations are shown to be broadly explicable in terms of the hypothesis where, during an interaction between two ice particles, the particle that is growing faster from the vapor acquires the positive charge.

Jayaratne, E. R.

1998-06-01

143

The peculiarities of water crystallization and ice melting processes in the roots of one-year plants (Plantago major L.).  

PubMed

Results are presented of a water phase transition study in plantain (Plantago major L.) roots, which were used as a model system to research the peculiarities of water crystallization and ice melting processes in complex heterogeneous biological systems. It was confirmed that water in such systems is crystallized in two clearly distinguished temperature ranges: -10 to -25 degree capital ES, Cyrillic and -25 to -45 degree capital ES, Cyrillic. These water fractions are conditionally attributed to extracellular (-10 to -25 degree capital ES, Cyrillic) and intracellular (-25 to -45 degree capital ES, Cyrillic) solutions. A possible explanation is given for such significant supercooling of the intracellular solution. The values of osmotic pressures of extra- and intracellular solutions were determined according to ice melting curves. It is noted that the intracellular solution, which crystallized at lower temperatures, had a lower osmotic pressure. PMID:18754062

Bakradze, N; Kiziria, E; Sokhadze, V; Gogichaishvili, S

144

Crystal-field states of Pr3+ in the candidate quantum spin ice Pr2Sn2O7  

NASA Astrophysics Data System (ADS)

Neutron time-of-flight spectroscopy has been employed to study the crystal-field splitting of Pr3+ in the pyrochlore stannate Pr2Sn2O7. The crystal field has been parameterized from a profile fit to the observed neutron spectrum. The single-ion ground state is a well-isolated non-Kramers doublet of ?3+ symmetry with a large Ising-like anisotropy, ?zz/???60 at 10 K, but with a significant admixture of terms |MJ?±J>, which can give rise to quantum zero-point fluctuations. This magnetic state satisfies the requirements for quantum spin-ice behavior.

Princep, A. J.; Prabhakaran, D.; Boothroyd, A. T.; Adroja, D. T.

2013-09-01

145

Application of ground-based hyperspectral imaging to retrieve ice crystal shape and fields of cirrus optical thickness  

NASA Astrophysics Data System (ADS)

A ground-based hyperspectral imaging spectrometer (AisaEAGLE) is applied to measure downward spectral radiance fields with high spatial (1024 spatial pixels within 36.7° field of view), spectral (488 spectral pixels, 400-970 nm, 1.25 nm full width at half maximum) and temporal (4-30 Hz) resolution. The calibration, measurement, and data evaluation procedures are introduced. A method is presented to retrieve the cirrus optical thickness ?ci using ground-based spectral radiance data collected by AisaEAGLE. On the basis of four measurement cases during the second campaign of the Cloud Aerosol Radiation and tuRbulence of trade wInd cumuli over BArbados (CARRIBA) project in 2011 the spatial inhomogeneity of the investigated cirrus is characterized by the standard deviation of the retrieved ?ci, as well as the width of the frequency distribution of the retrieved ?ci. By comparing measured and simulated downward solar radiance as a function of scattering angle, a first estimation of the detected cirrus ice crystal shape is given and used in the retrieval of the ?ci. The sensitivity of the retrieval method with respect to surface albedo, effective radius reff, cloud height, and ice crystal shape was characterized. Significant sensitivities of the retrieval method were found for the assumed surface albedo (up to 30%) and ice crystal shape (up to 90%). The sensitivity with regard to the effective radius (≤ 5%) and the cloud height (≤ 0.5%) is rather small and can be neglected.

Schäfer, M.; Bierwirth, E.; Ehrlich, A.; Heyner, F.; Wendisch, M.

2013-02-01

146

The effects of small ice crystals on the infrared radiative properties of cirrus clouds. Semiannual status report, 1 October 1989-31 March 1990  

SciTech Connect

To be successful in the development of satellite retrieval methodologies for the determination of cirrus cloud properties, fundamental scattering and absorption data on nonspherical ice crystals that are found in cirrus clouds must be available. Recent aircraft observations (Platt et al.) reveal that there is a large amount of small ice particles, on the order of 10 micron, in cirrus clouds. Thus it is important to explore the potential differences in the scattering and absorption properties of ice crystals with respect to their sizes and shapes. In this study the effects of nonspherical small ice crystals on the infrared radiative properties of cirrus clouds are investigated using light scattering properties of spheroidal particles. In Section 2, using the anomalous diffraction theory for spheres and results from the exact spheroid scattering program, efficient parameterization equations are developed for calculations of the scattering and absorption properties for small ice crystals. Parameterization formulas are also developed for large ice crystals using results computed from the geometric ray-tracing technique and the Fraunhofer diffraction theory for spheroids and hexagonal crystals. This is presented in Section 3. Finally, applications to the satellite remote sensing are described in Section 4.

Takano, Y.; Liou, K.N.; Asano, S.; Heymsfield, A.; Minnis, P.

1990-04-01

147

Ice Cream  

NSDL National Science Digital Library

In this chemistry activity, learners use the lowered freezing point of water to chill another mixture (ice cream) to the solid state. Learners will record the temperature of the ice before and after mixing it with the ice cream ingredients and discover that adding a solute to a solvent lowers the freezing point of that solvent (also known as a colligative property). This activity can also be used to introduce learners to crystallization.

House, The S.

2013-05-15

148

Effects of ice-crystal structure on halo formation: cirrus cloud experimental and ray-tracing modeling studies.  

PubMed

During the 1986 Project FIRE (First International Satellite Cloud Climatology Project Regional Experiment) field campaign, four 22° halo-producing cirrus clouds were studied jointly from a groundbased polarization lidar and an instrumented aircraft. The lidar data show the vertical cloud structure and the relative position of the aircraft, which collected a total of 84 slides by impaction, preserving the ice crystals for later microscopic examination. Although many particles were too fragile to survive impaction intact, a large fraction of the identifiable crystals were columns and radial bullet rosettes, with both displaying internal cavitations, and radial plate-column combinations. Particles that were solid or displayed only a slight amount of internal structure were relatively rare, which shows that the usual model postulated by halo theorists, i.e., the randomly oriented, solid hexagonal crystal, is inappropriate for typical cirrus clouds. With the aid of new ray-tracing simulations for hexagonal hollow ended column and bullet-rosette models, we evaluate the effects of more realistic ice-crystal structures on halo formation and lidar depolarization and consider why the common halo is not more common in cirrus clouds. PMID:20935827

Sassen, K; Knight, N C; Takano, Y; Heymsfield, A J

1994-07-20

149

Nucleation and growth of ice crystals inside cultured hepatocytes during freezing in the presence of dimethyl sulfoxide.  

PubMed Central

A three-part, coupled model of cell dehydration, nucleation, and crystal growth was used to study intracellular ice formation (IIF) in cultured hepatocytes frozen in the presence of dimethyl sulfoxide (DMSO). Heterogeneous nucleation temperatures were predicted as a function of DMSO concentration and were in good agreement with experimental data. Simulated freezing protocols correctly predicted and explained experimentally observed effects of cooling rate, warming rate, and storage temperature on hepatocyte function. For cells cooled to -40 degrees C, no IIF occurred for cooling rates less than 10 degrees C/min. IIF did occur at faster cooling rates, and the predicted volume of intracellular ice increased with increasing cooling rate. Cells cooled at 5 degrees C/min to -80 degrees C were shown to undergo nucleation at -46.8 degrees C, with the consequence that storage temperatures above this value resulted in high viability independent of warming rate, whereas colder storage temperatures resulted in cell injury for slow warming rates. Cell damage correlated positively with predicted intracellular ice volume, and an upper limit for the critical ice content was estimated to be 3.7% of the isotonic water content. The power of the model was limited by difficulties in estimating the cytosol viscosity and membrane permeability as functions of DMSO concentration at low temperatures. Images FIGURE 1

Karlsson, J O; Cravalho, E G; Borel Rinkes, I H; Tompkins, R G; Yarmush, M L; Toner, M

1993-01-01

150

Polarimetric radar observation of ice crystals and aggregates: Backscattering modeling of signatures from C to Ka band  

NASA Astrophysics Data System (ADS)

Hydrometeor classification using polarimetric Doppler weather radar is based on the characteristic polarimetric signature for each hydrometeor class. This signature can be obtained by either experimental campaigns or by proper electromagnetic modelling. Both approaches have advantages and drawbacks: the experimental approach is not easy to conduct as it requires co-located measurements of a weather radar with in-situ sampler (usually installed aboard an aircraft); moreover, it is generally strictly related to the measurement configuration (e.g., frequency, range) it is performed. Of course, experimental campaigns are needed for definitive validation, but the modelling approach exhibits a high flexibility in terms of system and meteorological parameters very well suited for retrieval algorithm design. On the other hand, a model approach is heavily dependent on the model capability to represent hydrometeor volumes in a realistic way. Within the electromagnetic scattering modelling of hydrometeor radar response, a well known technique to simulate the radar backscattering from an ensemble of particle is based on the T-matrix algorithm (Kim, 2006). The T-matrix model is based on the equivalence principle and can ensure numerical convergence for a small set of canonical shapes such as ellipsoids. These shapes are useful to represent raindrops and vertically-oriented small crystals, but are largely unrealistic when dealing with ice aggregates and crystals. In this work we use a different approach to the scattering modelling that fits well for classes like ice crystals and aggregates of different shapes and sizes: the discrete dipole approximation (DDA). The DDA model lets us simulate almost any kind of particle under the hypothesis it can be approximated as a three dimensional array of dipoles that generate the scattering field (the wavelength should be large compared to the distance between dipoles). The DDA code used is DDSCAT, developed by Draine and Flatau (2004), which computes the scattering by a single randomly oriented particle. With this approach a variety of hydrometeor shapes have been simulated: cylindrical ice crystals, aggregates of ice cylinders, snow crystals, mixed-phase particles, etc. From DDA it has been possible to obtain the polarimetric signature for ground-based radars at C and X band for these hydrometeor classes after solving some heavy computational issues. An equivalent spheroid model has been also developed for the ice hydrometeor classes in order to use a T-matrix code, faster than DDA, to simulate ice crystals-equivalent spheroids (Weinman and Kim, 2007). Numerical results will be discussed analyzing the sensitivity of the DDA model to the particle shape, wavelength, size distribution and orientation. The accuracy of T-matrix approximation of the ensemble particle polarimetric signature will be also evaluated within the context of hydrometeor classification schemes based on either fuzzy-logic or Bayesian techniques.

Botta, G.; Montopoli, M.; Marzano, F. S.

2009-04-01

151

EFFECT OF LASER LIGHT ON MATTER. LASER PLASMAS: Effects of CO2 laser radiation on large orthophosphoric acid and water drops and on spherical ice crystals  

NASA Astrophysics Data System (ADS)

An experimental investigation is reported of the conditions present during evaporation of suspended orthophosphoric acid and water drops, and of spherical ice crystals with a radius of the order of 1 mm when the laser radiation power density was 20-104 W cm-2 at the wavelength of 10.6 ?m. The lower limit of explosive evaporation was determined for H3PO4 drops and ice crystals. Only one evaporation mechanism of H3PO4 drops was observed (this mechanism was explosive), but there were two mechanisms in the case of water drops (convective with vapour ejection and explosive) and spherical ice crystals (melting followed by evaporation of a water drop and explosive evaporation). Repeated explosions of H2O drops were observed for a power density w = 104 W cm-2 when the beam diameter was 10 mm.

Rudash, V. K.

1994-02-01

152

Effects of cirrus spatial heterogeneity and ice particle shape on remote sensing of cirrus optical thickness and effective crystal radius - A case study  

NASA Astrophysics Data System (ADS)

The relative importance of three-dimensional (3D) effects and ice crystal shape of spatially heterogeneous cirrus on the remote-sensing of optical thickness and effective crystal radius is evaluated. In current ice cloud retrievals, the single-scattering properties of ice crystals have to be assumed a-priori. Likewise, the effects of spatial cloud heterogeneity are ignored in current techniques. Both simplifications introduce errors in the retrievals. The study is based on 3D and independent pixel approximation (IPA) radiative transfer calculations. As model input a cloud case that was generated from data collected during the NASA Tropical Composition, Cloud, and Climate Coupling (TC4) experiment is used. First, spectral upwelling radiance fields from the input cloud as they would be sensed by airborne or spaceborne radiometers were determined with 3D radiative transfer simulations. Then the cirrus optical thickness and ice particle effective radius that would be obtained in standard satellite techniques under the IPA assumption were retrieved. The ratios between retrieved and original fields are used as a metric for cloud heterogeneity effects on retrievals. Second, in the retrieval single-scattering properties (crystal shapes) different from those in the radiance calculations were used. In order to isolate ice crystal habit effects, the net horizontal photon transport was disabled here. Thus, the ratios between retrieved and original values of optical thickness and effective radius serve as metric for ice crystal habit effects. When comparing the two metrics, it is found that locally both can be of the same magnitude (up to 50% over- and underestimation), with different dependencies on cirrus optical thickness, effective radius, and optical thickness variability. On domain average, shape effects bias the retrievals more strongly than 3D effects.

Eichler, Heike; Schmidt, Konrad Sebastian; Buras, Robert; Wendisch, Manfred; Mayer, Bernhard; Emde, Claudia; Pilewskie, Peter; King, Michael; Platnick, Steven

2010-05-01

153

On the observation of unusual high concentration of small chain-like aggregate ice crystals and large ice water contents near the top of a deep convective cloud during the CIRCLE-2 experiment  

NASA Astrophysics Data System (ADS)

During the CIRCLE-2 experiment carried out over Western Europe in May 2007, combined in situ and remote sensing observations allowed to describe microphysical and optical properties near-top of an overshooting convective cloud (11 080 m/-58 °C). The airborne measurements were performed with the DLR Falcon aircraft specially equipped with a unique set of instruments for the extensive in situ cloud measurements of microphysical and optical properties (Polar Nephelometer, FSSP-300, Cloud Particle Imager and PMS 2-D-C) and nadir looking remote sensing observations (DLR WALES Lidar). Quasi-simultaneous space observations from MSG/SEVIRI, CALIPSO/CALIOP-WFC-IIR and CloudSat/CPR combined with airborne RASTA radar reflectivity from the French Falcon aircraft flying above the DLR Falcon depict very well convective cells which overshoot by up to 600 m the tropopause level. Unusual high values of the concentration of small ice particles, extinction, ice water content (up to 70 cm-3, 30 km-1 and 0.5 g m-3, respectively) are experienced. The mean effective diameter and the maximum particle size are 43 ?m and about 300 ?m, respectively. This very dense cloud causes a strong attenuation of the WALES and CALIOP lidar returns. The SEVIRI retrieved parameters confirm the occurrence of small ice crystals at the top of the convective cell. Smooth and featureless phase functions with asymmetry factors of 0.776 indicate fairly uniform optical properties. Due to small ice crystals the power-law relationship between ice water content (IWC) and radar reflectivity appears to be very different from those usually found in cirrus and anvil clouds. For a given equivalent reflectivity factor, IWCs are significantly larger for the overshooting cell than for the cirrus. Assuming the same prevalent microphysical properties over the depth of the overshooting cell, RASTA reflectivity profiles scaled into ice water content show that retrieved IWC up to 1 g m-3 may be observed near the cloud top. Extrapolating the relationship for stronger convective clouds with similar ice particles, IWC up to 5 g m-3 could be experienced with reflectivity factors no larger than about 20 dBZ. This means that for similar situations, indication of rather weak radar echo does not necessarily warn the occurrence of high ice water content carried by small ice crystals. All along the cloud penetration the shape of the ice crystals is dominated by chain-like aggregates of frozen droplets. Our results confirm previous observations that the chains of ice crystals are found in a continental deep convective systems which are known generally to generate intense electric fields causing efficient ice particle aggregation processes. Vigorous updrafts could lift supercooled droplets which are frozen extremely rapidly by homogeneous nucleation near the -37 °C level, producing therefore high concentrations of very small ice particles at upper altitudes. They are sufficient to deplete the water vapour and suppress further nucleation as confirmed by humidity measurements. These observations address scientific issues related to the microphysical properties and structure of deep convective clouds and confirm that particles smaller than 50 ?m may control the radiative properties in convective-related clouds. These unusual observations may also provide some possible insights regarding engineering issues related to the failure of jet engines commonly used on commercial aircraft during flights through areas of high ice water content. However, large uncertainties of the measured and derived parameters limit our observations.

Gayet, J.-F.; Mioche, G.; Bugliaro, L.; Protat, A.; Minikin, A.; Wirth, M.; Dörnbrack, A.; Shcherbakov, V.; Mayer, B.; Garnier, A.; Gourbeyre, C.

2012-01-01

154

On the observation of unusual high concentration of small chain-like aggregate ice crystals and large ice water contents near the top of a deep convective cloud during the CIRCLE-2 experiment  

NASA Astrophysics Data System (ADS)

During the CIRCLE-2 experiment carried out over Western Europe in May 2007, combined in situ and remote sensing observations allowed to describe microphysical and optical properties near-top of an overshooting convective cloud (11 080 m/-58 °C). The airborne measurements were performed with the DLR Falcon aircraft specially equipped with a unique set of instruments for the extensive in situ cloud measurements of microphysical and optical properties (Polar Nephelometer, FSSP-300, Cloud Particle Imager and PMS 2D-C) and nadir looking remote sensing observations (DLR WALES Lidar). Quasi-simultaneous space observations from MSG/SEVIRI, CALIPSO/CALIOP-WFC-IIR and CloudSat/CPR combined with airborne RASTA radar reflectivity from the French Falcon aircraft flying above the DLR Falcon depict very well convective cells which overshoot by up to 600 m the tropopause level. Unusual high values of the concentration of small ice particles, extinction, ice water content (up to 70 cm-3, 30 km-1 and 0.5 g m-3, respectively) are experienced. This very dense cloud causes a strong attenuation of the WALES and CALIOP lidar returns. The mean effective diameter is of 43 ?m and the maximum particle size is about 300 ?m. The SEVIRI retrieved parameters confirm the occurrence of small ice crystals at the top of the convective cell. Smooth and featureless phase functions with asymmetry factors of 0.776 indicate fairly uniform optical properties. Due to small ice crystals the power-law relationship between ice water content (IWC) and radar reflectivity appears to be very different from those usually found in cirrus and anvil clouds. For a given equivalent reflectivity factor, IWCs are significantly larger for the overshooting cell than for the cirrus. Assuming the same prevalent microphysical properties over the depth of the overshooting cell, RASTA reflectivity profiles scaled into ice water content show that retrieved IWC up to 1 g m-3 may be observed near the cloud top. Extrapolating the relationship for stronger convective clouds with similar ice particles, IWC up to 5 g m-3 could be experienced with reflectivity factors no larger than about 20 dBZ. This means that for similar situations, indication of rather weak radar echo does not necessarily warn the occurrence of high ice water content carried by small ice crystals. All along the cloud penetration the shape of the ice crystals is dominated by chain-like aggregates of frozen droplets. Our results confirm previous observations that the chains of ice crystals are found in a continental deep convective systems which are known generally to generate intense electric fields causing efficient ice particle aggregation processes. Vigorous updrafts could lift supercooled droplets which are frozen extremely rapidly by homogeneous nucleation near the -37 °C level, producing therefore high concentrations of very small ice particles at upper altitudes. They are sufficient to deplete the water vapour and suppress further nucleation as confirmed by humidity measurements. These observations address scientific issues related to the microphysical properties and structure of deep convective clouds and confirm that particles smaller than 50 ?m may control the radiative properties in convective-related clouds. These unusual observations may also provide some possible insights regarding engineering issues related to the failure of jet engines commonly used on commercial aircraft during flights through areas of high ice water content.

Gayet, J.-F.; Mioche, G.; Bugliaro, L.; Protat, A.; Minikin, A.; Wirth, M.; Dörnbrack, A.; Shcherbakov, V.; Mayer, B.; Garnier, A.; Gourbeyre, C.

2011-08-01

155

Supercooled Droplets and Ice Crystals in Mixed-Phase Clouds: Numerical Simulations Considering Isotropic Turbulence of the Ambient Flow Field  

NASA Astrophysics Data System (ADS)

In midlatitudes the formation and evolution of precipitation is the result of a chain of processes taking place in mixed-phase clouds. Due to the coexistence of supercooled water drops and ice particles in such clouds mutual interactions by collisions, i.e. riming and aggregation, take place leading to ice hydrometeors of a large precipitation size. In the past these collision mechanisms have been investigated - besides laboratory measurements - by numerical simulations of the collision process where trajectories of the participating hydrometeors have been calculated as occurring in an environment at rest (Pruppacher and Klett, Kluwer Academic Publishers, Dordrecht, 1997). However, as it is well-known the flow field in clouds is almost always turbulent (Siebert et al., Atmos. Res. 97 (2010) 426-437) except in undiluted updrafts of single strong convective clouds. And it has been argued that turbulence may enhance precipitation formation. As a consequence turbulence effects on the collisional interaction of cloud and other heavy particles came into focus during the last decade and gave rise to the description in terms of radial distribution function, mean radial relative velocity and the collection efficiency all derived from numerical simulations. Up to now mostly the turbulence influence on cloud droplet/cloud droplet collisions has been investigated (Ayala et al., New J. Phys. 10 (2008) 075015), (Bec et al., J. Fluid Mech. 646 (2010) 527-536). Much less is known about the influence of turbulence on particles in mixed phase clouds. This is mainly due to the various and complex shapes of the ice particles depending on the temperature, the supersaturation, and their life time. Hence, our knowledge about the behavior of ice crystals in turbulence is based on wind tunnel experiments. In the early stage ice crystals often have the shape of hexagonal plates or needles. In theoretical and numerical studies these are commonly approximated by ellipsoids. However, except in (Pinsky and Khain, Atmos. Res. 47-48 (1998) 69-86) only laminar flows have been considered so far. Therefore we have developed a numerical experiment with a novel setup (Kunnen et al., under review in Atmos. Res. (2013)). Therein synthetic turbulence is generated at the inflow and is then advected by a mean flow through the domain. The full Navier-Stokes equations are solved using a DNS method on an Eulerian Cartesian grid. The evolving decaying turbulence shares similarities with the grid-generated turbulence of wind tunnels. In this flow several million particle spheres as well as ellipsoids are advanced in a Lagrangian manner in order to represent the supercooled droplets and ice crystals out of a small region of a mixed-phase cloud. Statistics will be gathered about the orientation, the sedimentation velocities, the clustering, and the relative velocities of these particles. From this basis collision kernels can be calculated. These are input parameters for cloud models estimating the evolution of precipitation.

Siewert, Christoph; Kunnen, Rudie; Meinke, Matthias; Schröder, Wolfgang; Beheng, Klaus

2013-04-01

156

Ice rule correlations in stuffed spin ice  

NASA Astrophysics Data System (ADS)

Stuffed spin ice is a chemical variation of a spin ice material like Ho2Ti2O7 in which extra magnetic ions are inserted into the crystal structure. Previous studies have shown that the degree of stuffing has very little effect on the residual entropy in the system, which takes a value very close to the spin ice entropy. We argue, however, that the observation of this entropy does not imply long range coherence of the ice rules, that determine the local spin configurations. We have characterized deviations from the ice rules by means of a polarized neutron diffraction study of a single crystal of Ho2+?Ti2-?O7-?/2 with ? = 0.3. Our results demonstrate that the ice rules in stuffed spin ice are strictly valid only over a relatively short range, and that at longer range stuffed spin ice exhibits some characteristics of a ‘cluster glass’, with a tendency to more conventional ferromagnetic correlations.

Aldus, R. J.; Fennell, T.; Deen, P. P.; Ressouche, E.; Lau, G. C.; Cava, R. J.; Bramwell, S. T.

2013-01-01

157

Cloud Resolving Simulations of Mixed-Phase Arctic Stratus Observed during BASE: Sensitivity to Concentration of Ice Crystals and Large-Scale Heat and Moisture Advection  

Microsoft Academic Search

The authors' previous idealized, two-dimensional cloud resolving model (CRM) simulations of Arctic stratus revealed a surprising sensitivity to the concentrations of ice crystals. In this paper, simulations of an actual case study observed during the Beaufort and Arctic Seas Experiment are performed and the results are compared to the observed data. It is again found in the CRM simulations that

Hongli Jiang; William R. Cotton; James O. Pinto; Judy A. Curry; Michael J. Weissbluth

2000-01-01

158

Isothermal Ice-Crystallization Kinetics in the Gas-Diffusion Layer of a Proton-Exchange-Membrane Fuel Cell  

SciTech Connect

Nucleation and growth of ice in the fibrous gas-diffusion layer (GDL) of a proton-exchange membrane fuel cell (PEMFC) are investigated using isothermal differential scanning calorimetry (DSC). Isothermal crystallization rates and pseudo-steady-state nucleation rates are obtained as a function of subcooling from heat-flow and induction-time measurements. Kinetics of ice nucleation and growth are studied at two polytetrafluoroethylene (PTFE) loadings (0 and 10 wt %) in a commercial GDL for temperatures between 240 and 273 K. A nonlinear icecrystallization rate expression is developed using Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory, in which the heat-transfer-limited growth rate is determined from the moving-boundary Stefan problem. Induction times follow a Poisson distribution and increase upon addition of PTFE, indicating that nucleation occurs more slowly on a hydrophobic fiber than on a hydrophilic fiber. The determined nucleation rates and induction times follow expected trends from classical nucleation theory. A validated rate expression is now available for predicting icecrystallization kinetics in GDLs.

Dursch, Thomas J.; Ciontea, Monica A.; Radke, Clayton J.; Weber, Adam Z.

2011-11-11

159

Remote Sounding of Cirrus Cloud Optical Depths and Ice Crystal Sizes from AVHRR Data: Verification Using FIRE II IFO Measurements.  

NASA Astrophysics Data System (ADS)

Using the data obtained from the Advanced Very High Resolution Radiometer (AVHRR) 3.7-µm and 10.9-µm channels, a retrieval scheme has been developed to simultaneously infer cirrus cloud optical depth and mean effective ice crystal size based on the theory of radiative transfer and parameterizations. A numerical scheme is further developed to remove the solar component in the 3.7-µm radiance for applications to daytime satellite data. This scheme is based on the correlation between the 3.7-µm (solar) and 0.63-µm reflectances. Validation of the algorithm has been performed by using various datasets that were collected during the FIRE-II IFO (Nov-Dec 1991) at Coffeyville, Kansas. We have focused on the 26 November and 5 December cases. The retrieval analysis over a 0.5°×1.0° area is performed around Coffeyville for each case based on AVHRR-HRPT data. For validation the authors analyze the photomicrograph data collected by the balloonborne replicator, determine the microphysical and optical properties of the sampled cirrus clouds, and derive their position at the satellite overpass based on sounding data. It is demonstrated that the retrieved cirrus cloud temperature, mean effective ice crystal size, and optical depth closely match the observed values. Further, the retrieved cirrus cloud properties are applied to the computation of surface radiative fluxes using a radiative transfer program that involves a consistent representation of cirrus cloud fields. The computed values are compared with the data measured from ground-based radiometers, and it is shown that the computed downward surface IR and solar fluxes are within 5 and 10 W m2 of the measured values, respectively, near the time of satellite overpass.

Ou, S. C.; Liou, K. N.; Takano, Y.; Rao, N. X.; Fu, Q.; Heymsfield, A. J.; Miloshevich, L. M.; Baum, B.; Kinne, S. A.

1995-12-01

160

Measurements of HNO3 and NOy on Cirrus Ice Particles and in Solution Aerosols During CRYSTAL-FACE  

NASA Astrophysics Data System (ADS)

NOx (NO + NO2) is central to tropospheric O3 production. The larger family of gases with which NOx interconverts, NOy, or total reactive nitrogen, includes HNO3. One potential mechanism for the removal and/or vertical transport of NOy is via uptake on ice particles and aerosols. NOx is unlikely to be subject to such uptake, and HNO3 is likely the most significant NOy species subject to uptake. Thus the uptake of HNO3 has the potential to affect indirectly the O3 budget of the atmospehre [Lawrence and Crutzen, Tellus, 1998; Meier and Hendricks, JGR, 2002]. To assess the degree of uptake, condensed-phase HNO3 and NOy were measured during CRYSTAL-FACE by instruments in adjacent pallets on the WB57. The instruments employed nearly identical inlets for the enhanced (anisokinetic) sampling of condensed-phase species. Each instrument employed a second inlet for the measurement of the gas-phase plus small-particle fraction. Differences in the small-particle sampling by these latter inlets has proven beneficial for the inference of condensed-phase HNO3 on particles with diameters of order 1 micron. This talk will emphasize the southern survey flight of 9 July 2002, for which we infer the presence of condensed-phase HNO3 in ternary solutions of H2O, H2SO4, and HNO3. Ice was found in greater and lesser amounts in the presence of the aerosols, but ice appears to have played little role in the uptake of HNO3 here, as the aerosols compete very effectively for the HNO3 in this particular case, due to the relatively large particle volume and the low temperatures. In addition, the condensed-phase NOy measurements are compared to the condensed-phase HNO3 measurements described in another presentation at this meeting (Popp et al.) Overall the condensed-phase HNO3 and NOy amounts are similar to one another and give no indication that other NOy species are taken up by cirrus ice particles.

Weinheimer, A. J.; Knapp, D. J.; Montzka, D. D.; Ridley, B. A.; Popp, P. J.; Gao, R. S.; Marcy, T. P.; Fahey, D. W.; Baumgardner, D.; Anderson, B. E.; Wilson, J. C.; Lee, S. H.; Reeves, J. M.; Lafleur, B. G.; Hilbert, H.; Schmit, O.; Herman, R. L.; Weinstock, E. M.; Smith, J. B.; Sayres, D. W.; Vellovic, J.; Anderson, J. G.; Bui, T. P.; Bowen, S. W.; Pfister, L.; Dean-Day, J.; Chang, C.

2003-12-01

161

Using MODIS data to detect the presence of ice crystals in and above super-cooled liquid water clouds over the Arctic  

NASA Astrophysics Data System (ADS)

Determining cloud properties from satellite data over the Arctic is difficult due to low solar elevation angles and the large extent of snow and ice cover. Although it is well established that ice clouds can be discriminated from those having a liquid phase, the mixed-phase clouds represent a problem since they appear nearly identical to liquid phase clouds in satellite data. This is due to the liquid-dominant top found in many mixed-phase stratus clouds. The Terra MODIS particle size ratio between 1.6 and 3.7 ?m for super-cooled liquid water (SLW) clouds is useful for determining ice crystal presence. Since the 1.6 ?m channel detects radiation from deeper inside the clouds, particle size retrievals using this channel are expected to be larger than 3.7 ?m retrievals if ice crystals are embedded inside the cloud. A technique utilizing the MODIS 6.7, 7.3, 8.5, 11 and 12 ?m channels is also used to determine ice crystal presence in SLW clouds. After determining the phase occurring at the cloud top, the internal cloud phase is parameterized in terms of the thermal and water vapor structure above the cloud. This method is useful since it can be applied to nighttime and twilight scenes in addition to daytime scenes. Although the focus of this study is on single layer cloud systems, a multilayer cloud algorithm, which discriminates thin, high ice crystal clouds from low level SLW clouds, is also run. Microwave radiometer, cloud radar and rawinsonde data collected at the Atmospheric Radiation Measurement DOE site in Barrow, Alaska and surface observations from the National Weather Service collected at the Barrow airport are used to evaluate MODIS cloud phase, and to determine whether MODIS can detect differences in the amount of ice embedded in SLW clouds. Accurately assigning cloud phase over large areas of the remote Arctic will benefit the aviation community for aircraft icing detection. Also, since mixed-phase clouds usually precipitate, the likely occurrence of snowfall can be determined remotely. The assignment of cloud phase is also critical in retrieving a cloud’s optical depth, height, particle size, and water path.

Spangenberg, D.; Minnis, P.; Palikonda, R.; Chang, F.; Shupe, M.

2010-12-01

162

Crystallization and preliminary X-ray crystallographic analysis of an ice-binding protein (FfIBP) from Flavobacterium frigoris PS1.  

PubMed

Ice growth in a cold environment is fatal for polar organisms, not only because of the physical destruction of inner cell organelles but also because of the resulting chemical damage owing to processes such as osmotic shock. The properties of ice-binding proteins (IBPs), which include antifreeze proteins (AFPs), have been characterized and IBPs exhibit the ability to inhibit ice growth by binding to specific ice planes and lowering the freezing point. An ice-binding protein (FfIBP) from the Gram-negative bacterium Flavobacterium frigoris PS1, which was isolated from the Antarctic, has recently been overexpressed. Interestingly, the thermal hysteresis activity of FfIBP was approximately 2.5?K at 50?µM, which is ten times higher than that of the moderately active IBP from Arctic yeast (LeIBP). Although FfIBP closely resembles LeIBP in its amino-acid sequence, the antifreeze activity of FfIBP appears to be much greater than that of LeIBP. In an effort to understand the reason for this difference, an attempt was made to solve the crystal structure of FfIBP. Here, the crystallization and X-ray diffraction data of FfIBP are reported. FfIBP was crystallized using the hanging-drop vapour-diffusion method with 0.1?M sodium acetate pH 4.4 and 3?M sodium chloride as precipitant. A complete diffraction data set was collected to a resolution of 2.9?Å. The crystal belonged to space group P4(1)22, with unit-cell parameters a = b = 69.4, c = 178.2?Å. The asymmetric unit contained one monomer. PMID:22750870

Do, Hackwon; Lee, Jun Hyuck; Lee, Sung Gu; Kim, Hak Jun

2012-06-28

163

Thermal Qpalescence in Crystals and the Colour of Ice in Glaciers  

Microsoft Academic Search

IN a previous communication to NATURE (vol. 109, page 42) it was pointed out that the thermal agitation of the atoms in crystals causes optical heterogeneity which should give rise to a noticeable scattering when a beam of light is sent through the substance, and that this effect may actually be observed with suitable arrangements in clear quartz or rock-salt.

C. V. Raman

1923-01-01

164

Ice-Crystal Absorption: A Comparison Between Theory and Implications for Remote Sensing  

Microsoft Academic Search

The problem of the disagreement between cirrus crystal sizes determined remotely and by in situ measurements is shown to be due to inappropriate application of Mie theory. We retrieved the absorption optical depth at 8.3 and 11.1 m from 11 tropical anvil cirrus clouds, using data from the High Resolution Infrared Radiation Sounder (HIRS). We related the absorption optical depth

Anthony J. Baran; John S. Foot; David L. Mitchell

1998-01-01

165

Frazil ice formation in an ice shelf water plume  

NASA Astrophysics Data System (ADS)

We present a model for the growth of frazil ice crystals and their accumulation as marine ice at the base of Antarctic ice shelves. The model describes the flow of buoyant water upward along the ice shelf base and includes the differential growth of a range of crystal sizes. Frazil ice formation starts when the rising plume becomes supercooled. Initially, the majority of crystals have a radius of ˜0.3 mm and concentrations are below 0.1 g/L. Depending on the ice shelf slope, which controls the plume speed, frazil crystals increase in size and number. Typically, crystals up to 1.0 mm in radius are kept in suspension, and concentrations reach a maximum of 0.4 g/L. The frazil ice in suspension decreases the plume density and thus increases the plume speed. Larger crystals precipitate upward onto the ice shelf base first, with smaller crystals following as the plume slows down. In this way, marine ice is formed at rates of up to 4 m/yr in some places, consistent with areas of observed basal accumulation on Filchner-Ronne Ice Shelf. The plume continues below the ice shelf as long as it is buoyant. If the plume reaches the ice front, its rapid rise produces high supercooling and the ice crystals attain a radius of several millimeters before reaching the surface. Similar ice crystals have been trawled at depth north of Antarctic ice shelves, but otherwise no observations exist to verify these first predictions of ice crystal sizes and volumes.

Smedsrud, Lars H.; Jenkins, Adrian

2004-03-01

166

Crystal shape-dependent magnetic susceptibility and Curie law crossover in the spin ices Dy2Ti2O7 and Ho2Ti2O7  

NASA Astrophysics Data System (ADS)

We present an experimental determination of the isothermal magnetic susceptibility of the spin ice materials Dy2Ti2O7 and Ho2Ti2O7 in the temperature range 1.8–300 K. The use of spherical crystals has allowed accurate correction for demagnetizing fields and allowed the true bulk isothermal susceptibility ?T(T) to be estimated. This has been compared against a theoretical expression based on a Husimi tree approximation to the spin ice model. Agreement between experiment and theory is excellent at T > 10 K, but systematic deviations occur below that temperature. Our results largely resolve an apparent disagreement between neutron scattering and bulk measurements that has been previously noted. They also show that the use of non-spherical crystals in magnetization studies of spin ice may introduce very significant systematic errors, although we note some interesting—and possibly new—systematics concerning the demagnetizing factor in cuboidal samples. Finally, our results show how experimental susceptibility measurements on spin ices may be used to extract the characteristic energy scale of the system and the corresponding chemical potential for emergent magnetic monopoles.

Bovo, L.; Jaubert, L. D. C.; Holdsworth, P. C. W.; Bramwell, S. T.

2013-09-01

167

Ice Tank Experiments Highlight Changes in Sea Ice Types  

NASA Astrophysics Data System (ADS)

With the current and likely continuing reduction of summer sea ice extent in the Arctic Ocean, the predominant mechanism of sea ice formation in the Arctic is likely to change in the future. Although substantial new ice formation occurred under preexisting ice in the past, the fraction of sea ice formation in open water likely will increase significantly. In open water, sea ice formation starts with the development of small ice crystals, called frazil ice, which are suspended in the water column [World Meteorological Organization, 1985]. Under quiescent conditions, these crystals accumulate at the surface to form an unbroken ice sheet known in its early stage as nilas. Under turbulent conditions, caused by wind and waves, frazil ice continues to grow and forms into a thick, soupy mixture called grease ice. Eventually the frazil ice will coalesce into small, rounded pieces known as pancake ice, which finally consolidate into an ice sheet with the return of calm conditions. This frazil/pancake/ice sheet cycle is currently frequently observed in the Antarctic [Lange et al., 1989]. The cycle normally occurs in regions that have a significant stretch of open water, because this allows for the formation of larger waves and hence increased turbulence. Given the increase of such open water in the Arctic Ocean caused by retreating summer sea ice, the frazil/pancake/ice sheet cycle may also become the dominant ice formation process during freezeup in the Arctic.

Wilkinson, Jeremy P.; DeCarolis, Giacomo; Ehlert, Iris; Notz, Dirk; Evers, Karl-Ulrich; Jochmann, Peter; Gerland, Sebastian; Nicolaus, Marcel; Hughes, Nick; Kern, Stefan; de la Rosa, Sara; Smedsrud, Lars; Sakai, Shigeki; Shen, Hayley; Wadhams, Peter

2009-03-01

168

Ice recrystallization inhibition in ice cream by propylene glycol monostearate.  

PubMed

The effectiveness of propylene glycol monostearate (PGMS) to inhibit ice recrystallization was evaluated in ice cream and frozen sucrose solutions. PGMS (0.3%) dramatically reduced ice crystal sizes in ice cream and in sucrose solutions frozen in a scraped-surface freezer before and after heat shock, but had no effect in quiescently frozen solutions. PGMS showed limited emulsifier properties by promoting smaller fat globule size distributions and enhanced partial coalescence in the mix and ice cream, respectively, but at a much lower level compared to conventional ice cream emulsifier. Low temperature scanning electron microscopy revealed highly irregular crystal morphology in both ice cream and sucrose solutions frozen in a scraped-surface freezer. There was strong evidence to suggest that PGMS directly interacts with ice crystals and interferes with normal surface propagation. Shear during freezing may be required for its distribution around the ice and sufficient surface coverage. PMID:19021802

Aleong, J M; Frochot, S; Goff, H D

2008-11-01

169

Frazil Ice Formation In An Ice Shelf Water Plume  

NASA Astrophysics Data System (ADS)

A major portion of floating Antarctic ice shelves is marine ice. Marine ice differs from meteoric ice in conductivity, stable isotopes, and grain size, and is mostly formed by mm sized frazil ice crystals that precipitate upwards from the ocean below. In this study a size spectrum for growth and precipitation of frazil ice crystals has been added to a plume model describing the flow of buoyant water upwards along the base of Antarctic ice shelves. Formation of frazil starts when the rising plume becomes supercooled in situ as a result of prior cooling by melting of the ice shelf at greater depths. Small frazil crystals grow quicker than larger crystals, so intitially the majority of the crystals have a radius of 0.3 mm, and concentrations are below 0.1 g/l. Depending on the ice shelf slope which controls the plume speed, frazil crystals increase in size and concentration. Typically crystals up to 0.8 mm in radius are kept in suspension, and concentrations reach a maximum of 0.4 g/l. The frazil ice in suspension decreases the plume density and give the buoyant plume an extra speed of up to 3 cm/s. As larger frazil crystals have a higher rise velocity, the 0.8 mm crystals precipitate upwards onto the ice shelf base first. When the plume slows down smaller crystals follow, and in this way marine ice is formed at rates of up to 4 m/year in some places. The plume leaves the ice shelf base when it is no longer buoyant, and at this stage the frazil remaining in suspension has usually started to melt. This is caused by the cessation of cooling as the plume no longer rises vertically and entrainment of warmer water from below. If the plume reaches the end of the ice shelf before it is neutrally buoyant, its rapid rise at the ice front produces a high supercooling and the crystals reach a radius of several mm before reaching the surface. The frazil ice size spectrum thus has a significant impact on the overall mass balance of the marine ice layer and the ice shelves, and may also explain some of the marine ice properties as grain size and isotopic values.

Smedsrud, L. H.; Jenkins, A.

170

Temperature dependence of fluorescence lifetime of 2-naphthol in ice (I(sub h)) crystal. A study of the proton motion in ice  

NASA Astrophysics Data System (ADS)

The lifetime of the fluorescence from 2-naphthol (CI0H8OH) doped in ice I(sub h)was measured from 27 to 300 K. The slow component tau(sub s) (5.3 ns at 27 K) shows a significant decrease in the temperature range 130-200 K, while the faster component (tau(sub f) approximately 0.7 ns) shows a slight decrease above 200 K. The relative intensity I(sub f)I(sub s) increases above 130 K. The results were interpreted in terms of a model involving the transfer between the two states, S(sub 1) and S'(sub 1), which correspond to the excited states of 2-naphthol with and without considering the trapping of proton with L defects in ice, respectively.

Qi, Ping; Okazaki, Katsuhiko; Akiyama, Tomoya; Abe, Kohji; Shigenari, Takeshi

1994-12-01

171

Diffusion-controlled metabolism for long-term survival of single isolated microorganisms trapped within ice crystals  

PubMed Central

Two known habitats for microbial metabolism in ice are surfaces of mineral grains and liquid veins along three-grain boundaries. We propose a third, more general, habitat in which a microbe frozen in ice can metabolize by redox reactions with dissolved small molecules such as CO2, O2, N2, CO, and CH4 diffusing through the ice lattice. We show that there is an adequate supply of diffusing molecules throughout deep glacial ice to sustain metabolism for >105 yr. Using scanning fluorimetry to map proteins (a proxy for cells) and F420 (a proxy for methanogens) in ice cores, we find isolated spikes of fluorescence with intensity consistent with as few as one microbial cell in a volume of 0.16 ?l with the protein mapper and in 1.9 ?l with the methanogen mapper. With such precise localization, it should be possible to extract single cells for molecular identification.

Rohde, Robert A.; Price, P. Buford

2007-01-01

172

Formation of Anvil Ice Particles in a Deep Cumulus Updraft of CRYSTAL-FACE Simulated with an Explicit Microphysics Model - The Influence of Various Nucleation Processes  

NASA Astrophysics Data System (ADS)

Simulations of a cumulonimbus cloud observed by the Citation aircraft in the Cirrus Regional Study of Tropical Anvils and Cirrus Layers - Florida Area Cirrus Experiment (CRYSTAL-FACE) with an advanced version of the Explicit Microphysics Model (EMM) are presented here. Observations of the concentration of cloud condensation nuclei (CCN) by the Twin Otter aircraft in the planetary boundary layer are utilized to provide inputs to the model, together with measurements by the ER-2 and Citation aircraft. The interconnected mechanisms of secondary droplet nucleation and the warm rain process both combine to regulate the supercooled droplet concentration in the mixed phase region of the updraft, which determines the anvil ice concentration aloft. Perturbations in the turbulence enhancement coefficients for coalescence and in the CCN concentration are found to alter the properties of the anvil updraft because of their effects on the warm rain process. Homogeneous aerosol freezing can occasionally occur if the anvil ice concentration in parcels becomes very low.

Phillips, V. T.; Sherwood, S.; Bansemer, A.; Conant, W. C.; Heymsfield, A.; Heymsfield, G.; Poellot, M.; Vanreken, T.

2003-12-01

173

Influence of particle size and shape on the backscattering linear depolarisation ratio of small ice crystals - cloud chamber measurements in the context of contrail and cirrus microphysics  

NASA Astrophysics Data System (ADS)

The article presents the laser scattering and depolarisation instrument SIMONE that is installed at the large aerosol and cloud chamber facility AIDA of the Karlsruhe Institute of Technology. SIMONE uses a 488 nm cw laser to probe simulated atmospheric clouds by measuring the scattered light from the 1.8° and 178.2° directions. At 178.2°, the scattered light is analysed for the linear polarisation state to deduce the linear depolarisation ratio ?l which is a common measurement parameter of atmospheric LIDAR applications. The optical setup and the mathematical formalism of the depolarisation detection concept are given. SIMONE depolarisation measurements in spheroidal hematite aerosol and supercooled liquid clouds are used to validate the instrument. SIMONE data from a series of AIDA ice nucleation experiments at temperatures between 195 and 225 K were analysed in terms of the impact of the ice particle microphysics on ?l. We found strong depolarisation values of up to 0.4 in case of small growing and sublimating ice particles with volume equivalent diameters of only a few micrometers. Modelling runs with the T-matrix method showed that the measured depolarisation ratios can be accurately reproduced assuming spheroidal and cylindrical particles with a size distribution that has been constrained by IR extinction spectroscopy. Based on the T-matrix modelling runs, we demonstrate that in case of small ice crystals the SIMONE depolarisation results are representative for the LIDAR depolarisation ratio which is measured at exact backscattering direction of 180°. The relevance of our results for the interpretation of recent LIDAR observations in cirrus and contrails is discussed. In view of our results, the high depolarisation ratios observed by the spaceborne LIDAR CALIOP in the tropical upper troposphere might be a hint for the presence of small (sublimating) ice particles in the outflows of deep convective systems.

Schnaiter, M.; Büttner, S.; Möhler, O.; Skrotzki, J.; Vragel, M.; Wagner, R.

2012-06-01

174

On the ice nucleation spectrum  

NASA Astrophysics Data System (ADS)

This work presents a novel formulation of the ice nucleation spectrum, i.e. the function relating the ice crystal concentration to cloud formation conditions and aerosol properties. The new formulation relies on a statistical view of the ice nucleation process and explicitly accounts for the dependency of the ice crystal concentration on temperature, supersaturation, cooling rate, and particle size, and, in the case of heterogeneous ice nucleation, on the distributions of particle area and surface composition. The new formulation is used to generate ice nucleation parameterizations for the homogeneous freezing of cloud droplets and the heterogeneous deposition ice nucleation on dust and soot ice nuclei. For homogeneous freezing, it was found that by increasing the dispersion in the droplet volume distribution the fraction of supercooled droplets in the population increases. For heterogeneous ice nucleation it was found that ice nucleation on efficient ice nuclei (IN) shows features consistent with the singular hypothesis (characterized by a lack of temporal dependency of the ice nucleation spectrum) whereas less efficient IN tend to display stochastic behavior. Analysis of empirical nucleation spectra suggested that inferring the aerosol heterogeneous ice nucleation properties from measurements of the onset supersaturation and temperature may carry significant error as the variability in ice nucleation properties within the aerosol population is not accounted for. This work provides a simple and rigorous ice nucleation framework were theoretical predictions, laboratory measurements and field campaign data can be reconciled, and that is suitable for application in atmospheric modeling studies.

Barahona, D.

2011-11-01

175

Relationship between Recrystallization Rate of Ice Crystals in Sugar Solutions and Water Mobility in Freeze-Concentrated Matrix  

Microsoft Academic Search

To better understand the relation between recrystallization rate and water mobility in freeze-concentrated matrix, isothermal ice recrystallization rates in several sugar aqueous solutions and self-diffusion coefficients of water component in corresponding freeze-concentrated matrix were measured. The sugars used were fructose, glucose, maltose, and sucrose. The sugar concentrations and temperature were varied so that ice contents for all samples were almost

Tomoaki Hagiwara; Richard W. Hartel; Shingo Matsukawa

2006-01-01

176

The Spectral Signature of Mixed-Phase Clouds Composed of Non-Spherical Ice Crystals and Spherical Liquid Droplets in the Terrestrial Window Region  

SciTech Connect

An outstanding problem facing the cloud modeling and remote sensing community is to improve satellite-derived cloud microphysical and macrophysical properties when a single cloud layer exists within a temperature range for which a combination of water and ice particles may be present. This is typically known as a ''mixed-phase'' cloud condition, and is prevalent when the cloud-top temperature lies between -40C and 0C. In this paper, we report on a sensitivity study of the spectral signature of mixed-phase clouds in the infrared terrestrial window (8-13 um). Mixed clouds are assumed to be a vertically uniform cloud layer composed of a mixture of pristine hexagonal crystals and spherical water droplets. Unlike the conventional approach that derives the bulk scattering properties of the mixed-phase clouds by a linear weighting of the contributions of ice and water components, the bulk single-scattering properties of mixed-phase clouds are formulated on the basis of fundamental physics. With the aid of a line-by-line radiative transfer model and a discrete ordinates radiative transfer (DISORT) computational program, we investigate the high-resolution spectral signature, expressed in terms of brightness temperature, of mixed-phase clouds with various effective sizes, ice fraction ratios, and optical thicknesses. Small particles are found to have a significant impact on the infrared spectral signature of mixed-phase clouds when the size discrepancy between the ice and water particles is large. Furthermore, the simulation results show that the infrared radiative spectrum associated with cirrus clouds can be quite different from their mixed-phase counterparts even if only a small amount of water droplets exist in the mixed-phase cloud layer.

Yang, P.; Wei, H.- L.; Bryan, B. A.; Huang, H.- L.; Heymsfield, Andrew J.; Hu, Yong X.; Gao, B.- C.; Turner, David D.

2003-06-01

177

Interpreting ancient ice in a shallow ice core from the South Yamato (Antarctica) blue ice area using flow modeling and compositional matching to deep ice cores  

Microsoft Academic Search

We explore methods of dating a 101 m ice core from a bare ice ablation area in the Yamato Mountains, Dronning Maud Land, East Antarctica. There are two unknowns, the age of the ice at the surface and the age spanned by the core. The ice crystal growth rate was used to estimate the age span of the core at

John C. Moore; Fumihiko Nishio; Shuji Fujita; Hideki Narita; Elizabeth Pasteur; Aslak Grinsted; Anna Sinisalo; Norikazu Maeno

2006-01-01

178

Aircraft Icing  

Microsoft Academic Search

Full-scale icing experiments and, therefore, certification time and cost can be significantly reduced by developing calculation methods to evaluate the aircraft and system performance for a wide range of icing conditions. This article summarizes calculation methods for icing that include ice accretion, ice system performance, and icing effects on aircraft.

Tuncer Cebeci; Fassi Kafyeke

2003-01-01

179

Crystals  

NSDL National Science Digital Library

In this earth science/math/art activity, learners use simple ingredients to grow crystals and examine the repeating geometric shapes and patterns. Learners compare the growth of crystals from four types of crystal-starters (table salt, Borax, sand, and Epsom salt) to see which starter grows the most crystals in 14 days. Learners report their results online and find out what other learners discovered. Afterward, learners can use the crystals they grew to create works of art.

Science, Lawrence H.

2009-01-01

180

Ice particle growth in the presence of nitric oxide  

NASA Astrophysics Data System (ADS)

An experimental study was undertaken to examine the effects of nitric oxide (NO) on ice crystal growth. This study focused on growth rates and ice crystal habit. A chamber was used to grow ice at controlled temperature and supersaturation, and images of ice crystals were obtained using a video camera. Ice crystals grow more quickly when NO concentrations are elevated above background to 370 and 710 ppb and lengthen (c-axis growth) more quickly than they thicken (a-axis growth). The results have implications for ice crystal growth in thunderstorms and may aid in determining whether an air parcel in a thunderstorm originated from an electrically active region.

Peterson, Harold; Hallett, John

2012-03-01

181

Determination of ice cloud models using MODIS and MISR data  

Microsoft Academic Search

Representation of ice clouds in radiative transfer simulations is subject to uncertainties associated with the shapes and sizes of ice crystals within cirrus clouds. In this study, we examined several ice cloud models consisting of smooth, roughened, homogeneous and inhomogeneous hexagonal ice crystals with various aspect ratios. The sensitivity of the bulk scattering properties and solar reflectances of cirrus clouds

Yu Xie; Ping Yang; George W. Kattawar; Patrick Minnis; Yongxiang Hu; Dong L. Wu

2012-01-01

182

Frazil Ice Formation in the Polar Oceans  

NASA Astrophysics Data System (ADS)

Cracks in the sea ice cover, known as leads, can form due to mechanical forcing and expose ocean water directly to the cold atmosphere. The formation of sea ice in these leads plays an important role in the mass balance of sea ice and the salt budget of the ocean. The formation of sea ice is a complex process, which initially involves the creation of frazil ice, then "grease ice", pancake ice and finally a layer of solid ice. This study concentrates solely on modelling the first stage, frazil ice formation. This initial stage is characterised by small millimetre-sized crystals of ice which are formed in turbulent waters. The crystals are first formed through a process of seeding. Once we have a seeded crystal the following processes occur: growth/melting, secondary nucleation and flocculation. The first is the effect the change in temperature has on the crystals either making them grow (supercooling) or melt (superheating). The last two are the effects turbulence has on the crystals. By creating collisions, we have new nucleus breaking off from larger crystals (secondary nucleation) or larger crystals breaking up into smaller crystals (flocculation). The mathematical model used will rely on the conservation of mass, momentum and thermodynamics, and will have as variables sea surface temperature, air temperature, ice concentration, air and ocean velocities.

Radia, N. V.; Feltham, D. L.

2009-12-01

183

Three-dimensional rocking curve imaging to measure the effective distortion in the neighbourhood of a defect within a crystal: an ice example  

PubMed Central

Rocking curve imaging (RCI) is a quantitative version of monochromatic beam diffraction topography that involves using a two-dimensional detector, each pixel of which records its own ‘local’ rocking curve. From these local rocking curves one can reconstruct maps of particularly relevant quantities (e.g. integrated intensity, angular position of the centre of gravity, FWHM). Up to now RCI images have been exploited in the reflection case, giving a quantitative picture of the features present in a several-micrometre-thick subsurface layer. Recently, a three-dimensional Bragg diffraction imaging technique, which combines RCI with ‘pinhole’ and ‘section’ diffraction topography in the transmission case, was implemented. It allows three-dimensional images of defects to be obtained and measurement of three-dimensional distortions within a 50?×?50?×?50?µm elementary volume inside the crystal with angular misorientations down to 10?5–10?6?rad. In the present paper, this three-dimensional-RCI (3D-RCI) technique is used to study one of the grains of a three-grained ice polycrystal. The inception of the deformation process is followed by reconstructing virtual slices in the crystal bulk. 3D-RCI capabilities allow the effective distortion in the bulk of the crystal to be investigated, and the predictions of diffraction theories to be checked, well beyond what has been possible up to now.

Philip, Armelle; Meyssonnier, Jacques; Kluender, Rafael T.; Baruchel, Jose

2013-01-01

184

The Antiferroelectric Phase Transition in the Slater-Takagi Model of Ammonium Dihydrogen Phosphate (NH4H2PO4) Type Crystals —Effect of the Removal of the Ice Condition—  

NASA Astrophysics Data System (ADS)

The antiferroelectric phase transition in ammonium dihydrogen phosphate NH4H2PO4 (ADP) type crystals is discussed in terms of the Slater-Takagi model with the ice condition completely removed. It is found that the transition can be of the second order if the energy level of the Takagi configuration is suitably chosen.

Ishibashi, Yoshihiro

1987-07-01

185

Recreating Engine Icing on the Ground  

NASA Video Gallery

NASA's finding the causes of and solutions to a phenomenon called ice crystal engine icing. The research includes flight tests but also tests on the ground that can safely simulate engine icing conditions. A test cell at the Propuslaion Systems Lab at NASA's Glenn Research Center has been modified with a series of spray bars that will emit the ice crystals. This animation shows what the eventual test sequence will look like. › Read More

Christopher O

2012-03-20

186

On the ice nucleation spectrum  

NASA Astrophysics Data System (ADS)

This work presents a novel formulation of the ice nucleation spectrum, i.e. the function relating the ice crystal concentration to cloud formation conditions and aerosol properties. The new formulation is physically-based and explicitly accounts for the dependency of the ice crystal concentration on temperature, supersaturation, cooling rate, and particle size, surface area and composition. This is achieved by introducing the concepts of ice nucleation coefficient (the number of ice germs present in a particle) and nucleation probability dispersion function (the distribution of ice nucleation coefficients within the aerosol population). The new formulation is used to generate ice nucleation parameterizations for the homogeneous freezing of cloud droplets and the heterogeneous deposition ice nucleation on dust and soot ice nuclei. For homogeneous freezing, it was found that by increasing the dispersion in the droplet volume distribution the fraction of supercooled droplets in the population increases. For heterogeneous ice nucleation the new formulation consistently describes singular and stochastic behavior within a single framework. Using a fundamentally stochastic approach, both cooling rate independence and constancy of the ice nucleation fraction over time, features typically associated with singular behavior, were reproduced. Analysis of the temporal dependency of the ice nucleation spectrum suggested that experimental methods that measure the ice nucleation fraction over few seconds would tend to underestimate the ice nuclei concentration. It is shown that inferring the aerosol heterogeneous ice nucleation properties from measurements of the onset supersaturation and temperature may carry significant error as the variability in ice nucleation properties within the aerosol population is not accounted for. This work provides a simple and rigorous ice nucleation framework where theoretical predictions, laboratory measurements and field campaign data can be reconciled, and that is suitable for application in atmospheric modeling studies.

Barahona, D.

2012-04-01

187

The Origin of Ice in Mountain Cap Clouds  

Microsoft Academic Search

Ice crystal development in relatively simple layer clouds was studied using airborne instrumentation. The patterns in the development of ice in those clouds suggest that the ice originates in association with the initial condensation process, near the upwind edge of the cloud. Since continued ice production does not occur beyond that region, the ice development can be attributed to nucleation.

William A. Cooper; Gabor Vali

1981-01-01

188

Measurements of growth rates of an ice crystal from supercooled heavy water under microgravity conditions: basal face growth rate and tip velocity of a dendrite.  

PubMed

The growth of single ice crystals from supercooled heavy water was studied under microgravity conditions in the Japanese Experiment Module ''KIBO'' of the International Space Station (ISS). The velocities of dendrite tips parallel to the a axis and the growth rates of basal faces parallel to the c axis were both analyzed under supercooling ranging from 0.03 to 2.0 K. The velocities of dendrite tips agree with the theory for larger amounts of supercooling when the growth on the basal faces are not zero. At very low supercooling there is no growth on the basal faces. With increasing supercooling the basal faces start to grow, the growth rate changing as a function of supercooling with a power law with an exponent of about 2, with the exponent approaching 1 as supercooling increases further. We interpret the growth on the basal faces as being controlled by two-dimensional nucleation under low supercooling, with a change in the growth kinetics to spiral growth with the aid of screw dislocations with increasing supercooling then to a linear growth law. We discuss the combined effect of tip velocity and basal face kinetics on pattern formation during the growth of ice. PMID:21631108

Yokoyama, Etsuro; Yoshizaki, Izumi; Shimaoka, Taro; Sone, Takehiko; Kiyota, Tatsuo; Furukawa, Yoshinori

2011-06-20

189

The viscoplastic behaviour of ice in polar ice sheets: experimental results and modelling  

Microsoft Academic Search

The slow motion of polar ice sheets is governed by the viscous deformation of anisotropic ices. Physical mechanisms controlling the deformation of ice crystal and polycrystal are reviewed. For the low stress conditions prevailing in ice sheets, the stress exponent of the flow law is lower than 2 and the deformation is dominated by the glide of dislocations on the

Maurine Montagnat; Paul Duval

2004-01-01

190

Ice, Ice, Baby!  

NASA Astrophysics Data System (ADS)

The Center for Remote Sensing of Ice Sheets (CReSIS) has developed an outreach program based on hands-on activities called "Ice, Ice, Baby". These lessons are designed to teach the science principles of displacement, forces of motion, density, and states of matter. These properties are easily taught through the interesting topics of glaciers, icebergs, and sea level rise in K-8 classrooms. The activities are fun, engaging, and simple enough to be used at science fairs and family science nights. Students who have participated in "Ice, Ice, Baby" have successfully taught these to adults and students at informal events. The lessons are based on education standards which are available on our website www.cresis.ku.edu. This presentation will provide information on the activities, survey results from teachers who have used the material, and other suggested material that can be used before and after the activities.

Hamilton, C.

2008-12-01

191

Ice formation in subglacial Lake Vostok, Central Antarctica  

NASA Astrophysics Data System (ADS)

The investigation of chemical and isotopic properties in the lake ice from the Vostok ice core gives clues to the mechanisms involved in ice formation within the lake. A small lake water salinity can be reasonably deduced from the chemical data. Possible implications for the water circulation of Lake Vostok are developed. The characteristics of the isotopic composition of the lake ice indicate that ice formation in Lake Vostok occurred by frazil ice crystal generation due to supercooling as a consequence of rising waters and a possible contrast in water salinity. Subsequent consolidation of the developed loose ice crystals results in the accretion of ice to the ceiling of the lake.

Souchez, R.; Petit, J. R.; Tison, J.-L.; Jouzel, J.; Verbe, V.

2000-09-01

192

Stability of ice XII relative to ice V and ice VI at high pressures  

NASA Astrophysics Data System (ADS)

The Gibbs energy difference between ice XII and ice V and between ice XII and ice VI at high pressures has been estimated in their fully orientationally disordered states from the available data. The Gibbs energy of ice XII is 183 J/mol higher than that of ice V at 0.5 GPa, and therefore ice XII is metastable with respect to ice V. The Gibbs energy of ice XII is 180-475 J/mol higher than that of ice VI at 1.1 GPa and 100 K. This is inconsistent with the recent deduction [T. Loerting, I. Kohl, C. Salzmann, E. Mayer, and A. Hallbrucker, J. Chem. Phys. 116, 3171 (2002)] that ice VI in the range 0.7-1.5 GPa and 158-212 K is metastable with respect to XII, and also with the speculation that proton (or orientationally)-ordered ice XII could have formed in Johari and Whalley's [J. Chem. Phys. 70, 2094 (1979)] search for orientationally ordered ice VI. An examination of the available dielectric data and Raman spectral features show no indication of ice VI to ice XII transformation at high pressures. Therefore, ice VI, not ice XII, is the stable phase at ~1 GPa and in the 158-212 K range. Ice polymorphs coexist in a thermoelastic equilibrium when the strain energy increase at the two-phase interface of the crystals growing in the parent phase becomes equal to the Gibbs energy decrease resulting from the growth. Hence a multiplicity of phases may coexist at high pressures.

Johari, G. P.

2003-01-01

193

Smokable ("ice", "crystal meth") and non smokable amphetamine-type stimulants: clinical pharmacological and epidemiological issues, with special reference to the UK.  

PubMed

"Ice", "crystal meth", is the smokable form of methamphetamine hydrochloride. This paper will comment on the pharmacological, epidemiological, clinical and social issues related to smoking the drug as opposed to either its injection or ingestion. Furthermore, some data related to amphetamines/methamphetamines consumption, request for treatment, seizures, related offences and deaths in the UK (1990-2002) will be offered here. Peak rates, for most indicators, were reached at the end of the '90s, to fall down in the following years. The only indicator which seemed not to show any declining rates is number of deaths, but this may be related to a more general increase in stimulant death rates recently observed in the UK. It is argued that methamphetamines, and particularly "crystal meth", could reach the same prevalence levels of use in the UK as it is already in the US but recent reclassification of the drug to Class A in the UK could help to better control this emerging issue. PMID:17536161

Schifano, Fabrizio; Corkery, John M; Cuffolo, Giulio

2007-01-01

194

Crystal Multiplication without Nucleation.  

PubMed

Disk-shaped ice crystals grow out from the surface of polycrystalline ice in undercooled water. The rupture of the neck of the attached disk is a means of multiplying the number of viable crystals in the surrounding undercooled water. This is a source of frazil ice in streams and a source of new crystals in metal castings which are grain-refined by stirring. PMID:17819420

Chalmers, B; Williamson, R B

1965-06-25

195

Slaughtering of gilthead seabream ( Sparus aurata ) in liquid ice: influence on fish quality  

Microsoft Academic Search

Liquid ice or binary ice is a new food chilling technique that requires less time to chill products and acts more uniformly than other types of ice. The practical advantage of binary ice is its pumpability. Moreover, on account of the microscopic size of the ice crystals, the main benefit of binary ice is its ability for rapid chilling of

A. Huidobro; R. Mendes; M. Nunes

2001-01-01

196

Ice/hydrohalite crystallization structures in sub-eutectic freezing experiments in the system NaCl-H20 and possible implications for the properties of frozen brines in Europa: A preliminary report  

NASA Astrophysics Data System (ADS)

Sulfates are likely to be the most abundant solutes in the subsurface Europan liquid ocean. NaCl may also be a significant component of such liquids based on the compositions of stony meteorites like those thought to be among the source materials for the silicates in Europa's interior. The system NaCl-H20 exhibits a eutectic at -20.8°C and 23.3 weight percent NaCl between ice Ih and hydrohalite (NaCl.2H20). This low eutectic temperature compared to Mg and Na sulfate hydrate/ice eutectics indicates that hydrohalite should be among the last salts to crystallize in brine upwellings along rifts and other places where resurfacing by melt extrusion occurs on Europa. We conducted a suite of freezing experiments on NaCl brines with 20.3, 23.3, and 26.6 (saturated) weight percent NaCl by holding these liquids at a few degrees below the eutectic temperature. These runs produced ice-rich, eutectic and hydrohalite-rich aggregates of both phases, respectively, as confirmed by cryogenic x-ray diffraction and x-ray fluorescence spectroscopy. Based on direct observations of crystals forming at the tops and bottoms of the sample chambers and on refractive index measurements of subsequently melted sample material, marked fractional crystallization and segregation by density of ice, hydrohalite, and residual liquids occurred in the 20.3 and 26.6% samples and less so in for the eutectic composition. Crystallization of very fine grained eutectic intergrowths was recognized in cryogenic SEM images of all these samples and they were especially prominent in samples frozen from saturated brine. These samples were very difficult to cleave compared to pure polycrystalline ice, and hence are likely to have high fracture toughness. Direct measurements of this property and also the effects of partial melting on ductile flow rates are planned on such samples. Refracturing of such regions of fine eutectoid ice/hydrohalite intergrowths is likely to be inhibited in refrozen rifts compared to more ice-rich regions on Europa.

Rieck, K.; Kirby, S. H.; Stern, L. A.

2005-12-01

197

Ice Sheets  

NSDL National Science Digital Library

This educational brief describes the nature and properties of the Greenland and Antarctica ice sheets. Topics include the thickness and aereal extent of the ice sheets, volume of water contained in them, mass balance, and the mechanisms by which ice is lost from or accumulated by the ice sheets.

198

Aircraft icing  

Microsoft Academic Search

This paper reviews the background to and the current status of analyses developed to address the problem of icing on aircraft. Methods for water droplet trajectory calculation, ice accretion prediction, aerodynamic performance degradation and an overview of ice protection system modelling are presented. The paper addresses the issues involved in the development of icing analyses including problem formulation and assumptions,

R. W. Gent; N. P. Dart; J. T. Cansdale

2000-01-01

199

Geomicrobiology of Vostok Ice: Implications for Life in Lake Vostok  

NSDL National Science Digital Library

This abstract introduces newly discovered microbe assemblages within Lake Vostok and the research it has inspired. Current studies hope to gain insight into the following areas: physical stresses in deep glacial and accretion ice; the role of clathrates on gas dynamics within the lake; the origin of microbes in accretion ice; the physiological state of ice-bound microbes; the geochemistry of the ice column; and living microbes in ice veins that form at triple junctions in the ice crystal matrix.

Priscu, John

2011-09-15

200

Validation and determination of ice water content-radar reflectivity relationships during CRYSTAL-FACE: Flight requirements for future comparisons  

NASA Astrophysics Data System (ADS)

In situ measurements of cirrus ice water content (IWC) by the Harvard water vapor and total water instruments during Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment are compared with remote sensing data made by the Cloud Radar System instrument in order to derive and validate an empirical IWC-radar relflectivity Ze relationship. The comparisons show that for measurements of in situ IWC and remotely measured radar reflectivity, collocated within 2 km of each other, a single IWC-Ze relationship can be found that fits the data with an uncertainty of ±20-30%. A cloud resolving model shows this level of uncertainty to be consistent with sampling errors associated with comparing two measurements that are not collocated. Uncertainties are quantified in the use of in situ data to validate the retrieval algorithms used to derive the IWC of clouds from remote sensing observations, such as radar reflectivity Ze. Uncertainties are classified into instrumental uncertainties, uncertainties related to sampling errors, and uncertainties in using a single IWC-Ze relationship to describe a cloud.

Sayres, D. S.; Smith, J. B.; Pittman, J. V.; Weinstock, E. M.; Anderson, J. G.; Heymsfield, G.; Li, L.; Fridlind, A. M.; Ackerman, A. S.

2008-03-01

201

Turbulence beneath sea ice and leads: A coupled sea ice/large-eddy simulation study  

NASA Astrophysics Data System (ADS)

The importance of leads, sea ice motion, and frazil ice on the wintertime ocean boundary layer was examined by using a large-eddy simulation turbulence model coupled to a thermodynamic slab ice model. Coupling was achieved through exchange coefficients that accounted for the differing diffusion rates of heat and salinity. Frazil ice concentrations were modeled by using an ice crystal parameterization with constant crystal size and shape. Stationary ice without leads produced cellular structures similar to atmospheric convection without winds. Ice motion caused this pattern to break down into a series of streaks aligned with the flow. Eddy fluxes were strongly affected by ice motion with relatively larger entrainment fluxes at the mixed layer base under moving ice, whereas stationary ice produced larger fluxes near the top of the boundary layer. Opening of leads caused significant changes in the turbulent structure of the boundary layer. Leads in stationary ice produced concentrated plumes of higher-salinity water beneath the lead. Ice motion caused the lead convection to follow preexisting convective rolls, enhancing the roll circulation salinity and vertical velocity under the lead. Comparison of model time series data with observations from the Arctic Leads Experiment showed general agreement for both pack ice and lead conditions. Simulated heat flux carried by frazil ice had a prominent role in the upper boundary layer, suggesting that frazil ice is important in the heat budget of ice-covered oceans.

Skyllingstad, Eric D.; Denbo, Donald W.

2001-02-01

202

Snow Crystals  

NSDL National Science Digital Library

This site describes snow crystals and snowflakes. Although a common meteorological phenomenon, snow crystal growth is a fascinating and poorly understood process, in which remarkably complex and beautifully symmetric structures appear, quite literally, out of thin air. The many facets of snow crystals are described here, along with the attempts to understand their formation. Site highlights include research on creating designer snow crystals in the laboratory, the history of early snow crystal observations, snow crystal photography, properties of frozen precipitation, and a snow crystal primer for a short course in snow crystal physics - what snow crystals are, how they form, and why they form the way they do. Information is offered on snow crystal classification, preservation, and unusual crystal forms. An extensive image gallery of lab-created crystal forms is available, with enlargeable thumbnail images. There are even instructions for users on how to create crystals. This could be made into a classroom activity, as the science of the growth is explained. Snowflake Physics discusses diffusion, dendrite growth, ice surface physics, electric growth, and ice properties. A vast list of related links is also provided.

Libbrecht, Kenneth

203

A model of grease ice growth in small leads  

Microsoft Academic Search

When a strong, cold wind belows over open polar leads, ice grows in the form of small crystals which are herded downwind by both wind waves and a wind-driven surface current to pile up at the downwind edge of the lead. As this process continues, the piled-up ice, called `grease ice,'' advances upwind until the entire lead is ice covered.

Jane Bauer; Seelye Martin

1983-01-01

204

Method of forming calthrate ice  

DOEpatents

A method of forming clathrate ice in a supercooled water-based liquid contained in a vessel is disclosed. Initially, an oscillator device is located in the liquid in the vessel. The oscillator device is then oscillated ultransonically so that small crystals are formed in the liquid. Thes small crystals serve as seed crystals for ice formation in the liquid and thereby prevent supercooling of the liquid. Preferably, the oscillating device is controlled by a thermostat which initiates operation of the oscillator device when the temperature of the liquid is lowered to the freezing point. Thereafter, the operation of the oscillator device is terminated when ice is sensed in the liquid by an ice sensor.

Hino, T.; Gorski, A.J.

1985-09-30

205

Icing Prevention by Ultrasonic Nucleation of Supercooled Water Droplets in Front of Subsonic Aircraft.  

National Technical Information Service (NTIS)

Experiments were performed in the NASA Lewis Research Center (LeRC) Icing Research Tunnel (IRT) to explore the possible application of a novel icing prevention technique. This technique is based on nucleation ice crystallization in supercooled cloud dropl...

D. R. Worsnop R. Miake-Lye Z. Hed

1992-01-01

206

Icing Prevention by Ultrasonic Nucleation of Supercooled Water Droplets in Front of Subsonic Aircraft.  

National Technical Information Service (NTIS)

Experiments were performed in the NASA Lewis Research Center (LeRC) Icing Research Tunnel (IRT) to explore the possible application of an icing prevention technique. This technique is based on nucleation ice crystallization in supercooled cloud droplets u...

D. R. Worsnop R. Miake-lye Z. Hed

1992-01-01

207

The Influence of Platelet Ice and Snow on Antarctic Land-fast Sea Ice  

NASA Astrophysics Data System (ADS)

Sea ice fastened to coasts, icebergs and ice shelves is of crucial importance for climate- and ecosystems. Near Antarctic ice shelves, this land-fast sea ice exhibits two unique characteristics that distinguish it from most other sea ice: a sub-ice layer of ice platelets and a highly stratified and thick snow cover. Ice platelets are flat, plate-like ice crystals forming and growing in a layer of super-cooled water which originates from ice shelf cavities. During growth, heat is lost to the super-cooled ocean rather than conducted to the atmosphere. The crystals accumulate beneath the solid sea-ice cover, forming a layer of loose platelets and eventually becoming incorporated into the sea-ice fabric as platelet ice. Considering the fact that the amount of platelet ice contributes between 10 and 60% to the mass of the land-fast sea ice around Antarctica, very little is known about its spatial and temporal variability. A thick and partly multi-year snow cover develops on top of the Antarctic fast ice, ultimately altering the sea-ice surface and affecting the sea-ice thermodynamics and mass balance. It typically leads to snow-ice formation, surface flooding, and the development of superimposed ice from snow melt water. In order to investigate the role of platelet ice and snow for Antarctic fast ice, we have initiated a regular observation program on the land-fast sea ice of Atka Bay as part of the international Antarctic Fast Ice Network (AFIN). We performed manual measurements of sea-ice and snow thicknesses from June to December 2010 and 2011. Additionally, a mass balance buoy and an automatic weather station were deployed in 2011 and ice cores were taken. Our measurements will reveal insight into the spatial and temporal variability of sea-ice and snow thickness distributions on Atka Bay fast ice. First results show that sea-ice thickness is lowest in the eastern part of the Bay, where a thick snow cover leads to extensive surface flooding. In the West, dynamic conditions lead to high thickness and high local variability. Ice platelets were observed regularly in the boreholes, but measurement techniques have to be improved to assess the thickness of the platelet layer.

Hoppmann, M.; Nicolaus, M.

2011-12-01

208

Modeling the formation and deposition of frazil ice beneath Filchner-Ronne Ice Shelf  

NASA Astrophysics Data System (ADS)

Large areas of the Filchner-Ronne Ice Shelf are underlain by layers of marine ice, which form when supercooled seawater circulating beneath the ice shelf freezes. The freezing process initially produces a suspension of disc-shaped frazil ice crystals, and these are subs quently deposited onto the ice shelf base in areas where the flow of water is slack enough. This has been modeled assuming that the freezing takes place within buoyant plumes of Ice Shelf Water ascending the ice shelf base from source regions near the grounding lines of the major inlet glaciers. The deposition of the majority of the suspended frazil ice is found to occur in spatially discrete bursts, where peak rates of accumulation at the ice shelf base exceed 1 m yr-1 of solid ice. There is a good correlation between the location of the zones of crystal deposition and the position of the upstream limits of the marine ice layers. The high rates of localized accumulation account for the rapid buildup observed in the layer thickness, which then gradually declines as the marine ice is carried downstream with the flow of the ice shelf. Model results also suggest an origin for the ice platelets observed at depth in the water column near the Filchner Ice Shelf.

Bombosch, Andreas; Jenkins, Adrian

1995-04-01

209

Crystals  

NSDL National Science Digital Library

This page contains four documents explaining crystals. The topic is covered at an advanced level in relation to nanotechnology and requires background knowledge in eight grade science. A powerpoint with illustrations and instructor guide containing activities are included to aid in teaching this subject. Additionally, links to related videos, a lab handout, and discussion questions are available.

2012-10-16

210

Airborne measurement of tropospheric ice nuclei aerosols using the Portable Ice Nucleation Chamber (PINC)  

Microsoft Academic Search

Ice clouds and mixed phase clouds have different microphysical and radiative properties that need to be assessed in order to understand their impact on the climate. Indeed, on one hand ice crystals found in the ice phase have the ability to scatter incoming solar radiation and absorb terrestrial radiation. On the other hand, about 70% of the tropical precipitation forms

C. Chou; O. Stetzer; B. Sierau; U. Lohmann

2009-01-01

211

Ancient ice  

NASA Astrophysics Data System (ADS)

Simon Belt, Guillaume Massé and colleagues rammed their way through sheets of ice, spotting some polar bears on the way, in their attempt to reconstruct Arctic sea-ice records covering thousands of years.

2009-11-01

212

Core drilling through the ross ice shelf (antarctica) confirmed Basal freezing.  

PubMed

New techniques that have been used to obtain a continuous ice core through the whole 416-meter thickness of the Ross Ice Shelf at Camp J-9 have demonstrated that the bottom 6 meters of the ice shelf consists of sea ice. The rate of basal freezing that is forming this ice is estimated by different methods to be 2 centimeters of ice per year. The sea ice is composed of large vertical crystals, which form the waffle-like lower boundary of the shelf. A distinct alignment of the crystals throughout the sea ice layer suggests the presence of persistent long-term currents beneath the ice shelf. PMID:17779616

Zotikov, I A; Zagorodnov, V S; Raikovsky, J V

1980-03-28

213

Studies in Ice Physics and Ice Engineering.  

National Technical Information Service (NTIS)

Contents: Static pressure of sea ice; Method for predicting strength characteristics of ice cover; Experimental studies in an ice-research laboratory; Scale effect as indication of ice-breaking mechanism; Division of the Arctic Marine ice cover into regio...

G. N. Yakovlev

1973-01-01

214

Cryoelectron microscopy of low density lipoprotein in vitreous ice.  

PubMed Central

In this report, images of low density lipoprotein (LDL) in vitreous ice at approximately 30 A resolution are presented. These images show that LDL is a quasi-spherical particle, approximately 220-240 A in diameter, with a region of low density (lipid) surrounded by a ring (in projection) of high density believed to represent apolipoprotein B-100. This ring is seen to be composed of four or five (depending on view) large regions of high density material that may represent protein superdomains. Analysis of LDL images obtained at slightly higher magnification reveals that areas of somewhat lower density connect these regions, in some cases crossing the projectional interiors of the LDL particles. Preliminary image analysis of LDL covalently labeled at Cys3734 and Cys4190 with 1.4-nm Nanogold clusters demonstrates that this methodology will provide an important site-specific marker in studies designed to map the organization of apoB at the surface of LDL. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 6

Spin, J M; Atkinson, D

1995-01-01

215

Spray Ice.  

National Technical Information Service (NTIS)

This was a Joint Industry Project (JIP) to review the state-of-the-art in spray ice developments. The development of spray ice technology is relatively new. No comprehensive source of information exists on designing and building with spray ice. Much of th...

E. G. Funegard J. P. Poplin J. S. Weaver R. Sisodiya W. St. Lawrence

1992-01-01

216

Extreme Ice  

NSDL National Science Digital Library

This activity students through the ways scientists monitor changes in Earth's glaciers, ice caps, and ice sheets. Students investigate about glacier locations, glacial movement, and impacts of climate change on glaciers depending on the depth of research. It is linked to 2009 PBS Nova program entitled Extreme Ice.

Kuntz, Margy; Teachers, Pbs

217

Melting Ice  

NSDL National Science Digital Library

Monitor the temperature of a melting ice cube and use temperature probes to electronically plot the data on graphs. Investigate what temperature the ice is as it melts in addition to monitoring the temperature of liquid the ice is submerged in.

Consortium, The C.

2011-12-13

218

Modelling Ice Shelf Water flow beneath Filchner-Ronne Ice Shelf  

NASA Astrophysics Data System (ADS)

A two-dimensional depth-averaged plume model that incorporates Coriolis forces is used to study the flow and thermodynamics of Ice Shelf Water (ISW) under Filchner-Ronne Ice Shelf (FRIS), Antarctica. Buoyant ISW plumes are generated when meltwater is released near the grounding line of large ice shelves. Due to the pressure variation of seawater's freezing temperature, they may become supercooled as they ascend along the underside of an ice shelf, causing frazil ice crystals to form and multiply within the plume. As these frazil crystals are buoyant, they can precipitate onto the ice shelf base to form marine ice (in conjunction with direct freezing). The primary aim of this study is to model the plumes responsible for the thick (>400m) deposits of marine ice observed at the base of FRIS. Results are presented which show both the general effect of Coriolis forces on ISW plumes and the particular importance of rotation on plume flow beneath FRIS.

Holland, P. R.; Feltham, D. L.; Jenkins, A.

2005-12-01

219

Ice Ages  

NSDL National Science Digital Library

During most of the last one billion years the globe had no permanent ice. However, sometimes large areas of the globe were covered with vast ice sheets. Users can read and view pictures which help explain what ice ages are, when they occurred, and why they occur. This site, sponsored by the Illinois State Museum, has links to web pages on paleontology of the midwestern United States during the last ice age and to an animation showing the advance and retreat of the ice sheet in North America 20,000 years ago.

220

Physical properties of sea ice relevant to remote sensing  

NASA Astrophysics Data System (ADS)

An understanding of the physical processes and properties of sea ice is critical in interpreting microwave signatures. The incorporation of salt in the form of brine inclusions in the ice makes sea ice a vastly different material than freshwater ice. The amount of brine incorporated is largely growth-rate dependent. In columnar ice brine is trapped in inclusions within ice crystals in a platelet substructure, while in frazil ice the inclusions are located between the crystal boundaries. Brine drainage begins immediately after ice formation, occurring slowly during the growth season, but increasing considerably during summer. In the Arctic, enhanced surface melting, coupled with increased interconnectivity of the brine inclusions, almost completely flushes the salt from the ice in the upper layers, leaving air voids and channels; a process that greatly increases the ice's porosity.

Tucker, W. B., III; Perovich, Donald K.; Gow, Anthony J.; Weeks, Wilford F.; Drinkwater, Mark R.

221

Effect of Sweetener, Stabilizer, and Storage Temperature on Ice Recrystallization in Ice Cream  

Microsoft Academic Search

ABSTRACT In ice cream manufacturing, control of ice crystal growth,through,proper formulation,and storage tem- perature is important,for stability during storage. The objective of this study was,to investigate the influence of sweetener (sucrose, 20 dextrose equivalent corn syrup, 42 dextrose equivalent corn syrup, and 42 high fructose corn syrup), with and without stabilizer, on ice recrystallization in ice cream,at three storage temperatures.

Tadashi Hagiwara; Richard W. Hartelt

1996-01-01

222

Inhibition of bacterial ice nucleators by fish antifreeze glycoproteins.  

PubMed

Certain bacteria promote the formation of ice in super-cooled water by means of ice nucleators which contain a unique protein associated with the cell membrane. Ice nucleators in general are believed to act by mimicking the structure of an ice crystal surface, thus imposing an ice-like arrangement on the water molecules in contact with the nucleating surface and lowering the energy necessary for the initiation of ice formation. Quantitative investigation of the bacterial ice-nucleating process has recently been made possible by the discovery of certain bacteria that shed stable membrane vesicles with ice nucleating activity. The opposite effect, inhibition of ice formation, has been described for a group of glycoproteins found in different fish and insect species. This group of substances, termed antifreeze glycoproteins (AFGPs), promotes the supercooling of water with no appreciable effect on the equilibrium freezing point or melting temperature. Substantial evidence now indicates that AFGPs act by binding to a growing ice crystal and slowing crystal growth. As the ice-nucleating protein surface is believed to have a structure similar to an embryonic ice crystal, AFGPs might be predicted to interact directly with a bacterial ice-nucleating site. We report here that AFGPs from the antarctic fish Dissostichus mawsoni inhibit the ice-nucleating activity of membrane vesicles from the bacterium Erwinia herbicola. The inhibition effect shows saturation at high concentration of AFGP and conforms to a simple binding reaction between the AFGP and the nucleation centre. PMID:3386720

Parody-Morreale, A; Murphy, K P; Di Cera, E; Fall, R; DeVries, A L; Gill, S J

1988-06-23

223

A first evaluation of the role of wave-ice interactions on the global sea ice volume  

NASA Astrophysics Data System (ADS)

Sea ice frequently forms in wavy waters. Wave motion packs forming ice crystals into small floes, while the ice attenuates the waves as the ice floes increase in diameter and thickness. Swell has been reported up to a few hundred kilometres inside the ice pack. Because of ocean waves, young ice floes take a rounded shape that led hungry early explorers to give them the name of pancake ice. Observations suggest that pancake ice thickness grows up to twice as fast as for ice forming in quiet seas. In this work we try to evaluate whether future large-scale sea ice models should include wave-ice interactions to properly simulate large-scale distributions of ice concentration and thickness. In the large-scale 3D ice-ocean modelling system NEMO-LIM, a representation of pancake ice formation is included. First, the ERA-40 ocean wave climatology is extrapolated in the sea ice zone as if the ocean was ice-free. After diagnosing the simulated ice edge, ocean waves are propagated from the ice edge further inside the ice pack assuming exponential decay of amplitude. Finally, the thickness of newly forming ice is computed as a function of wave amplitude, as given by the equilibrium pancake ice theory. Wavelength is prescribed. We will show how significantly pancake ice formation affects the ice production, ice concentration and thickness in both hemispheres. The role of key parameters (wave attenuation, equilibrium pancake thickness, ...) on the global sea ice statistics will be investigated through sensitivity experiments.

Vancoppenolle, M.; Fichefet, T.; Ackley, S. F.; Shen, H. H.; Massonnet, F.; Mathiot, P.; Lecomte, O.

2011-12-01

224

Physical states of astronomical ices  

NASA Astrophysics Data System (ADS)

The physical state of water ice at low temperatures is a subject of continuing research and debate. Particularly in astrophysics, the phases of water ice are an important indicator of the state, history and evolution of the icy astrophysical surfaces such as those found in the outer solar system (e.g., icy satellites and planetary surfaces, rings, trans-Neptunian objects), comets, or in the interstellar clouds. When deposited from the vapor phase, and depending on the substrate temperature, water ice can be found crystalline (hexagonal or cubic) or amorphous. In this work, we address the question of how the deposition rate (several orders of magnitude different between laboratory conditions and real astrophysical surfaces), the presence of contaminants (a likely scenario for astrophysical bodies) and the constantly exposure to radiation environments can affect the final state for the water ice phases.We also present a detailed study of the isothermal crystallization of thick ASW ice films grown at 100 K. These films are thick enough to ensure that the crystallization rate remains independent of substrate and influenced/initiated by surface nucleation. The phase transformation is studied as a function of annealing temperature and is monitored via infrared spectroscopy over a range of temperatures (130 - 140 K). Determination of the extent of crystalline during annealing is determined via the de-convolution of the partially crystallized infrared spectrum into amorphous and crystalline components. The present measurements aim to resolve some anomalies in the literature regarding the crystallization mechanism of ASW.

Fama, Marcelo A.; Burke, D.; Baragiola, R. A.

2009-09-01

225

Deformation and folds of the basal ice under the Greenland ice sheet  

NASA Astrophysics Data System (ADS)

Improvement of the depth sounding radio echo sounding over Greenland Ice Sheet has made it possible to map the near basal layers that have not been 'seen' earlier due to the very high demand of attenuation needed to reach through more than 3000m of ice. The basal 10% of the ice thickness reveals very disturbed layering in the central and north parts of the Greenland ice sheet. The onset of the disturbances very often seem to coincide with the ice from the climatic inception from the Eemian period to the Last Glacial period around 115.000 years before present. Studies of the ice rheology reveals big changes of ice crystal size and orientation at this boundary caused by big contrast of impurity concentrations in the ice from the warm and cold climatic periods. The warm ice from the Eemian (130.000 years - 115.000 years b2k) seems to behave as a big rather hard layer in the ice with the easier deformable glacial ice above and below. Examples of the ice folds from CReSIS radio echo images especially from the NASA ICEBRIDGE spring 2011 campaign over Greenland is shown together with ice rheology studies from the GRIP, NGRIP and NEEM ice cores.

Dahl-Jensen, D.; Gogineni, P.; Paden, J.; Leuschen, C.; Kipfstuhl, S.; Montagnat, M.; Waddington, E.

2012-04-01

226

Ice Fishing.  

National Technical Information Service (NTIS)

The booklet is written for the newcomer to ice fishing. It provides the basic information needed to take up the sport, safely and inexpensively. At first, perhaps, the novice may find ice fishing simply an intriguing pastime to occupy long winter weekends...

W. Downs

1973-01-01

227

Measuring Ice  

NSDL National Science Digital Library

To successfully model the climate, scientists need to know - among many things - how much ice there is at the poles. This radio broadcast reports on a new technique to measure the thickness of the ice by listening to it cracking and creaking. The clip is 2 minutes in length.

228

Medical ice slurry production device  

DOEpatents

The present invention relates to an apparatus for producing sterile ice slurries for medical cooling applications. The apparatus is capable of producing highly loaded slurries suitable for delivery to targeted internal organs of a patient, such as the brain, heart, lungs, stomach, kidneys, pancreas, and others, through medical size diameter tubing. The ice slurry production apparatus includes a slurry production reservoir adapted to contain a volume of a saline solution. A flexible membrane crystallization surface is provided within the slurry production reservoir. The crystallization surface is chilled to a temperature below a freezing point of the saline solution within the reservoir such that ice particles form on the crystallization surface. A deflector in the form of a reciprocating member is provided for periodically distorting the crystallization surface and dislodging the ice particles which form on the crystallization surface. Using reservoir mixing the slurry is conditioned for easy pumping directly out of the production reservoir via medical tubing or delivery through other means such as squeeze bottles, squeeze bags, hypodermic syringes, manual hand delivery, and the like.

Kasza, Kenneth E. (Palos Park, IL); Oras, John (Des Plaines, IL); Son, HyunJin (Naperville, IL)

2008-06-24

229

Creep Tests on Antarctic Glacier Ice  

Microsoft Academic Search

THE strain rate of polycrystalline ice is known to depend on the applied stress, the temperature and the orientation of crystals in the specimen. From laboratory creep tests on randomly oriented ice, Glen1 derived the simple flow law where epsidot is the strain rate, sigma is the stress, and k is constant for a given temperature. Other workers have confirmed

Malcolm Mellor

1959-01-01

230

Mars Water-Ice Clouds and Precipitation  

Microsoft Academic Search

The light detection and ranging instrument on the Phoenix mission observed water-ice clouds in the atmosphere of Mars that were similar to cirrus clouds on Earth. Fall streaks in the cloud structure traced the precipitation of ice crystals toward the ground. Measurements of atmospheric dust indicated that the planetary boundary layer (PBL) on Mars was well mixed, up to heights

J. A. Whiteway; L. Komguem; C. Dickinson; C. Cook; M. Illnicki; J. Seabrook; V. Popovici; T. J. Duck; R. Davy; P. A. Taylor; J. Pathak; D. Fisher; A. I. Carswell; M. Daly; V. Hipkin; A. P. Zent; M. H. Hecht; S. E. Wood; L. K. Tamppari; N. Renno; J. E. Moores; M. T. Lemmon; F. Daerden; P. H. Smith

2009-01-01

231

Frazil deposition under growing sea ice  

NASA Astrophysics Data System (ADS)

Platelet ice may be an important component of Antarctic landfast sea ice. Typically, it is found at depth in first-year landfast sea ice cover, near ice shelves. To explain why platelet ice is not commonly observed at shallower depths, we consider a new mechanism. Our hypothesis is that platelet ice eventually appears due to the sudden deposition of frazil ice against the fast ice-ocean interface, providing randomly oriented nucleation sites for crystal growth. Brine rejected in plumes from landfast ice generates stirring sufficient to prevent frazil ice from attaching to the interface, forcing some of it to remain in suspension until ice growth rate and brine rejection slow to the point that frazil can stick. We calculate a brine plume velocity and match this to frazil rise velocity. We consider both laminar and turbulent environments. We find that brine plume velocities are generally powerful enough to prevent a significant range of frazil sizes from sticking in the case of laminar flow and that, in the turbulent case, there may be a critical ice thickness at which most remaining circulating frazil suddenly settles.

McGuinness, M. J.; Williams, M. J. M.; Langhorne, P. J.; Purdie, C.; Crook, J.

2009-07-01

232

Ice Nucleation Mode and Kinetic Growth Inefficiency in Cirrus  

Microsoft Academic Search

Ice nucleation mechanisms and molecular surface kinetics for small ice crystals in cirrus remain areas of intense research in cloud physics. A theoretical relationship between ice nucleation mode and subsequent kinetic limits on depositional growth was investigated using the combined results of recent experiments, observations, and models. A variety of recent data suggest that under certain conditions, the growth of

N. B. Magee

2008-01-01

233

Flammable Ice  

NSDL National Science Digital Library

What's cooler than being cool? Setting ice on fire! In this demonstration, educators can amaze learners by setting ice on fire. Through this activity, learners can explore the properties of everyday materials and observe how these materials can change states to produce gas. Safety note: this activity is not suitable for learners to do themselves and should only be conducted by an experienced educator in a well ventilated lab area. Before doing this demonstration, educators should read the "Practicalities" section.

Museum, Science

2012-04-12

234

Laboratory study of frazil ice accumulation under wave conditions  

NASA Astrophysics Data System (ADS)

Ice growth in turbulent seawater is often accompanied by the accumulation of frazil ice crystals at its surface. The thickness and volume fraction of this ice layer play an important role in shaping the gradual transition from a loose to a solid ice cover, however, observations are very sparse. Here we analyse an extensive set of observations of frazil ice, grown in two parallel tanks with controlled wave conditions and thermal forcing, focusing on the first one to two days of grease ice accumulation. The following unresolved issues are addressed: (i) at which volume fraction the frazil crystal rising process starts and how densely they accumulate at the surface, (ii) how the grease ice solid fraction evolves with time until solid ice starts to form and (iii) how do these conditions affect, and are affected by, waves and heat loss from the ice. We obtained estimates of the initial frazil ice solid fraction (0.04-0.05), the maximum solid fraction to which it accumulates (0.24-0.28), as well as the time-scale of packing, at which 95 % of the frazil reaches the maximum solid fraction (12-18 h). Comparison of ice thickness and wave observations also indicates that grease ice first begins to affect the wave field significantly when its thickness exceeds the initial wave amplitude. These results are relevant for modelling frazil ice accumulation and freeze-up of leads, polynyas and the seasonal ice zone.

de La Rosa, S.; Maus, S.

2011-07-01

235

Rheological Studies of Side-Chain Liquid Crystal Polymers in Nematic Solvents  

NASA Astrophysics Data System (ADS)

Previous studies, which measured the electrorheological (ER) and shear stress transients (SST) of side-chain liquid crystal polymers (SCLCP) with end-attached mesogens, dissolved in low molar mass nematic solvents, led us to propose a modification of the Brochard hydrodynamic theory to include viscous dissipation due to an elastic coupling between polymer backbone configuration and director orientation. Here we report further ER and SST experiments on nematic solutions of an SCLCP with laterally-attached mesogens, which disagree with the modified Brochard theory. The earlier studies and theoretical analysis on end-attached SCLCP indicate that the chain conformation in that case is quasi-spherical, whereas the present data on laterally-attached SCLCP indicate a strongly prolate conformation. Thus the present results indicate that the theoretical model has to be further modified to account for the higher chain anisotropy.

Jamieson, Alex. M.; Chiang, Yen Ching; Zhao, Yiqiang

2003-03-01

236

Deformation and folds of the basal ice under the Greenland ice sheet  

NASA Astrophysics Data System (ADS)

Improvement of the depth sounding radio echo sounding over Greenland Ice Sheet has made it possible to map the near basal layers that have not been 'seen' earlier due to the very high demand of attenuation needed to reach through more than 3000m of ice. The basal 10% of the ice thickness reveals very disturbed layering in the central and north parts of the Greenland ice sheet. The onset of the disturbances very often seem to coincide with the ice from the climatic inception from the Eemian period to the Last Glacial period around 115.000 years before present. Studies of the ice rheology and deformation tests of the ice reveals big changes of ice crystal size and orientation at this boundary and very different deformation properties in the ice from the warm and cold climatic periods. Based on the different flow properties of the interglacial ice and the glacial ice models are used to simulate the formation of folds in ice.

Dahl-Jensen, Dorthe

2013-04-01

237

Operation IceBridge: Sea Ice Interlude  

NASA Video Gallery

Sea ice comes in an array of shapes and sizes and has its own ephemeral beauty. Operation IceBridge studies sea ice at both poles, and also runs across interesting formations en route to other targets.

Holly Zell

2012-11-05

238

Ultrafast superheating and melting of bulk ice  

NASA Astrophysics Data System (ADS)

The superheating of a solid to a temperature beyond its melting point, without the solid actually melting, is a well-known phenomenon. It occurs with many substances, particularly those that can readily be produced as high-quality crystals. In principle, ice should also be amenable to superheating. But the complex three-dimensional network of hydrogen bonds that holds water molecules together and gives rise to unusual solid and liquid properties strongly affects the melting behaviour of ice; in particular, ice usually contains many defects owing to the directionality of its hydrogen bonds. However, simulations are readily able to `create' defect-free ice that can be superheated. Here we show that by exciting the OH stretching mode of water, it is possible to superheat ice. When using an ice sample at an initial temperature of 270K, we observe an average temperature rise of 20 +/- 2K that persists over the monitored time interval of 250ps without melting.

Iglev, H.; Schmeisser, M.; Simeonidis, K.; Thaller, A.; Laubereau, A.

2006-01-01

239

Investigating the « ice mélange » in an ice-shelf coastal rift along the Princess Ragnhild Coast (Antarctica)  

NASA Astrophysics Data System (ADS)

This paper presents the first results of a glaciological investigation conducted in the vicinity of the new Belgian Antarctic research station "Princess Elisabeth" during the 2008-2009 Antarctic field season. The study is part of the BELISSIMA project which aim is to investigate the dynamics of transition zones at the grounding line and the interaction of the ice sheet and the ice-shelf with the ocean, with respect to the stability of the ice sheet. The studied site is a conspicuous rift zone developed in a short floating ice shelf, a few kilometres downstream from the grounding line associated with the presence of a coastal ice dome. The rift, very close to the location of the old Belgian Station "Base Roi Baudouin", is about 10 km long and between 0.5 and 4 km wide. A natural ramp on the eastern apex of the rift allowed access to the rift base, from where a series of five, 10-38 m-long cores were recovered. Visual observation of these cores indicates that they consist of heterogeneous ice types, which is typical of what is often referred to as the "ice mélange". Wind-blown snow, firn and ice dominate outside the rift and within the rift's apex ramp. However, within the base of the rift proper, where episodic tensional stresses dominate, the ice is correspondingly more heavily crevassed and shows clear surface albedo contrasts, suggesting material heterogeneity. Ice cores from these areas show an abrupt transition within a few metres of the surface from surface-derived firn and ice to a sharply contrasting ice type that is translucent, greenish, and bubble-free -interpreted as marine ice. Such ice results from the consolidation of frazil ice crystals which are known to be forming in Ice Shelf Water through ice-ocean interactions in other regions of Antarctica (e.g. Filchner-Ronne Ice Shelf, Amery ice Shelf, Nansen Ice Shelf). One of our drill sites was located in a surface outcrop of marine ice, yielding 13 m of solid translucent ice, overlying ~0.5 m of fragile and loosely consolidated ice before the sub-shelf interface was reached. Borehole images from below this interface reveal an additional thickness of at least 5 m of loose platelet ice crystals located below the shelf, suggesting an active thermohaline convection in the region. The paper presents textural, structural, bulk salinity, bulk density and stable isotopes (DeltaD, Delta18O) results from the five ice cores and discusses origin and transformation of the various ice types forming the "ice mélange" and their potential impact on the welding efficiency of the rift.

Depoorter, Mathieu; Samyn, Denis; Hubbard, Bryn; Pattyn, Frank; Matsuoka, Kenny; Dierckx, Marie; Tison, Jean-Louis

2010-05-01

240

Phase Relations and Properties of Salty ices VI and VII: Implications for Solar System Ices  

NASA Astrophysics Data System (ADS)

Ice VI and ice VII may be important in the interiors of Europa, Ganymede, Callisto and Titan. Oceans and interior pore waters in these bodies likely contain dissolved salts. To address the role of salt on ice VI and ice VII, we investigated phase equilibria in the system H2O -NaCl at 1 molal (5.5 wt%) NaCl in an externally heated diamond-anvil cell. Phase identifications were made by optical microscopy combined with Raman spectroscopy. Experiments were conducted at 22-150°C and up to 5 GPa by allowing the cell to thermally equilibrate at a given temperature and then varying pressure isothermally while observing phase changes. The liquidus curves of ice VI and ice VII in a 5.5 wt% NaCl solution were determined. Melting was observed from 22 to 80°C (ice VI) and from 35 to 150°C (ice VII). Both melting curves are steeper than the respective NaCl-free curves, indicating that the freezing-point depression at this bulk composition increases with pressure. The intersection of the two liquidus curves indicates that VI-VII-liquid triple point is shifted toward lower T and higher P relative to pure H2O. The 5.5 wt% NaCl bulk composition crystallizes into a single solid phase of NaCl-bearing ice VI or ice VII solid solution over the investigated T range (the subscript 'ss' indicates solid solution). Large single crystals of ice VIss or ice VIIss can also be grown by slow compression of the cell from near-liquidus conditions to the solidus. Raman spectra of these crystals clearly show zoning in these crystals. The zoning persists for days at 22°C, indicating relatively slow Na+ and Cl- diffusivity. The large depression of the freezing point in a 1 molal NaCl solution has important implications for the oceans and interiors of the icy satellites of Jupiter and Saturn. Salty fluids may remain stable to much greater depth than expected. This would promote extensive hydrothermal metamorphism of the silicate interiors. If not limited to ice VI and VII, this behavior may suppress formation of ices at the bottoms of deep oceans in Titan and the Galilean satellites. The observation that ices VI and VII form solid solutions with NaCl from 22 to 150°C is also important. The qualitative inference of low Na+ and Cl- diffusivity suggests that compositional gradients could persist over at least modest time scales in these ices. Moreover, the presence of NaCl in ice VI and VII will likely reduce their viscosity and increase electrical conductivity.

Daniel, I.; Manning, C. E.

2008-12-01

241

Cell Dimensions of Ordinary and `Heavy' Ice  

Microsoft Academic Search

I HAVE recently made accurate determinations of the cell dimensions of crystals of ordinary and `heavy' ice (D2O). Single crystals were used. The apparatus consisted of a small Dewar flask mounted on the arcs of a Bernal photogoniometer, and filled with a mixture of acetone and solid carbon dioxide. A holder of copper wire attached to the bottom of the

H. D. Megaw

1934-01-01

242

Quantum melting of spin ice  

NASA Astrophysics Data System (ADS)

A quantum melting of the spin ice is proposed for pyrochlore-lattice magnets Pr2TM2O7 (TM =Ir, Zr, and Sn). The quantum pseudospin-1/2 model is derived from the strong-coupling perturbation of the f-p electron transfer in the basis of atomic non-Kramers magnetic doublets. The ground states are characterized by a cooperative ferroquadrupole and pseudospin chirality in the cubic unit cell, forming a magnetic analog of smectic liquid crystals. Then, pinch points observed in spin correlations for dipolar spin-ice systems are replaced with the minima. The relevance to experiments is discussed.

Onoda, Shigeki; Tanaka, Yoichi

2010-03-01

243

High density amorphous ice at room temperature  

PubMed Central

The phase diagram of water is both unusual and complex, exhibiting a wide range of polymorphs including proton-ordered or disordered forms. In addition, a variety of stable and metastable forms are observed. The richness of H2O phases attests the versatility of hydrogen-bonded network structures that include kinetically stable amorphous ices. Information of the amorphous solids, however, is rarely available especially for the stability field and transformation dynamics—but all reported to exist below the crystallization temperature of approximately 150–170 K below 4–5 GPa. Here, we present the evidence of high density amorphous (HDA) ice formed well above the crystallization temperature at 1 GPa—well inside the so-called “no-man’s land.” It is formed from metastable ice VII in the stability field of ice VI under rapid compression using dynamic-diamond anvil cell (d-DAC) and results from structural similarities between HDA and ice VII. The formation follows an interfacial growth mechanism unlike the melting process. Nevertheless, the occurrence of HDA along the extrapolated melt line of ice VII resembles the ice Ih-to-HDA transition, indicating that structural instabilities of parent ice VII and Ih drive the pressure-induced amorphization.

Chen, Jing-Yin; Yoo, Choong-Shik

2011-01-01

244

Iced Tea  

NSDL National Science Digital Library

Dissolving things in the universal solvent water is an everyday experience for almost all of us. We don't have a lot of trouble dissolving honey in our hot tea, but when it comes to sweetening cold iced tea, it is quite a task, if not almost impossible. O

Konicek-Moran, Richard

2009-04-01

245

De-icing: recovery of diffraction intensities in the presence of ice rings  

SciTech Connect

Macromolecular structures are routinely determined at cryotemperatures using samples flash-cooled in the presence of cryoprotectants. However, sometimes the best diffraction is obtained under conditions where ice formation is not completely ablated, with the result that characteristic ice rings are superimposed on the macromolecular diffraction. In data processing, the reflections that are most affected by the ice rings are usually excluded. Here, an alternative approach of subtracting the ice diffraction is tested. High completeness can be retained with little adverse effect upon the quality of the integrated data. This offers an alternate strategy when high levels of cryoprotectant lead to loss of crystal quality.

Chapman, Michael S.; Somasundaram, Thayumanasamy (Oregon State U.); (FSU)

2010-11-03

246

Laboratory study of frazil ice accumulation under wave conditions  

NASA Astrophysics Data System (ADS)

Ice growth in turbulent seawater is often accompanied by the accumulation of frazil ice crystals at its surface, forming a grease ice layer. The thickness and volume fraction of this ice layer play an important role in shaping the gradual transition from a loose to a solid ice cover, however, observations are very sparse. Here we analyse an extensive set of observations of frazil ice, grown in two parallel tanks with controlled wave conditions and thermal forcing, focusing on the first one to two days of grease ice accumulation. The following unresolved issues are addressed: (i) at which volume fraction the frazil crystals' rising process starts and how densely they accumulate at the surface, (ii) how the grease ice solid fraction and salinity evolve with time until solid ice starts to form and (iii) how do these conditions affect, and are affected by, waves and heat loss from the ice. We obtained estimates of the minimum initial grease ice solid fraction (0.03-0.05) and the maximum solid fraction to which it accumulates before freezing into pancakes (0.23-0.31). The equivalent thickness of solid ice that needs to be accumulated until grease ice packs close to maximum (95% of the compaction accomplished), was estimated as 0.4 to 1.2 cm. Comparison of grease ice thickness and wave observations indicates that a grease ice layer first begins to affect the wave field significantly when its thickness exceeds the initial wave amplitude. These results are relevant for modelling frazil ice accumulation and freeze-up of leads, polynyas and along the seasonal ice zone.

de La Rosa, S.; Maus, S.

2012-02-01

247

Smart Icing Systems for Aircraft Icing Safety  

Microsoft Academic Search

Ice accretion affects the performance and control of an aircraft and in extreme situations can lead to incidents and accidents. However, changes in performance and control are difficult to sense. As a result, the icing sensors currently in use sense primarily ice accretion, not the effect of the ice. No processed aircraft performance degradation information is available to the pilot.

Michael B. Bragg; Tamer Basar; William R. Perkins; Michael S. Selig

2002-01-01

248

Sea Ice Index Monitors Polar Ice Extent  

Microsoft Academic Search

In September 2002, Arctic sea ice extent reached a minimum unprecedented in 24 years of satellite passive microwave observations, and almost certainly unmatched in 50 years of charting Arctic ice. Again, in September 2003, ice retreated to an unusually low extent, almost equaling the previous year's minimum. The Sea Ice Index (http:\\/\\/nsidc.org\\/data\\/seaice_index\\/), an easy-to-use source of information on sea ice

Florence Fetterer; Kenneth Knowles

2004-01-01

249

The physics of ice - Some fundamentals of planetary glaciology  

NASA Astrophysics Data System (ADS)

Selected properties of ice, particularly those that may be useful for remote sensing in the planetary system or understanding the behavior of ice there, or that will help to predict properties that planetary scientists need, are reviewed. Among them are the phase diagram, including a new easy transformation of ice Ih at 77 K near the extrapolated melting line, the microwave spectrum of ice Ih as determined from an extrapolation of the far-infrared spectrum and used to determine the thickness of ice in Saturn's rings, and the use of halos to detect crystals of hexagonal and cubic ice. Many properties of ice that are needed for planetary studies may need to be calculated from molecular potential functions. These can be tested by predicting the energies of the phases of ice at zero temperature, which can be evaluated from experimental measurements.

Whalley, E.

250

Effect of type III antifreeze protein dilution and mutation on the growth inhibition of ice.  

PubMed Central

Mutation of residues at the ice-binding site of type III antifreeze protein (AFP) not only reduced antifreeze activity as indicated by the failure to halt ice crystal growth, but also altered ice crystal morphology to produce elongated hexagonal bipyramids. In general, the c axis to a axis ratio of the ice crystal increased from approximately 2 to over 10 with the severity of the mutation. It also increased during ice crystal growth upon serial dilution of the wild-type AFP. This is in marked contrast to the behavior of the alpha-helical type I AFPs, where neither dilution nor mutation of ice-binding residues increases the c:a axial ratio of the ice crystal above the standard 3.3. We suggest that the ice crystal morphology produced by type III AFP and its mutants can be accounted for by the protein binding to the prism faces of ice and operating by step growth inhibition. In this model a decrease in the affinity of the AFP for ice leads to filling in of individual steps at the prism surfaces, causing the ice crystals to grow with a longer c:a axial ratio. Images FIGURE 3 FIGURE 4

DeLuca, C I; Chao, H; Sonnichsen, F D; Sykes, B D; Davies, P L

1996-01-01

251

Effect of type III antifreeze protein dilution and mutation on the growth inhibition of ice.  

PubMed

Mutation of residues at the ice-binding site of type III antifreeze protein (AFP) not only reduced antifreeze activity as indicated by the failure to halt ice crystal growth, but also altered ice crystal morphology to produce elongated hexagonal bipyramids. In general, the c axis to a axis ratio of the ice crystal increased from approximately 2 to over 10 with the severity of the mutation. It also increased during ice crystal growth upon serial dilution of the wild-type AFP. This is in marked contrast to the behavior of the alpha-helical type I AFPs, where neither dilution nor mutation of ice-binding residues increases the c:a axial ratio of the ice crystal above the standard 3.3. We suggest that the ice crystal morphology produced by type III AFP and its mutants can be accounted for by the protein binding to the prism faces of ice and operating by step growth inhibition. In this model a decrease in the affinity of the AFP for ice leads to filling in of individual steps at the prism surfaces, causing the ice crystals to grow with a longer c:a axial ratio. PMID:8913575

DeLuca, C I; Chao, H; Sönnichsen, F D; Sykes, B D; Davies, P L

1996-11-01

252

Modeling interfacial liquid layers on environmental ices  

NASA Astrophysics Data System (ADS)

Interfacial layers on ice significantly influence air-ice chemical interactions. In solute-containing aqueous systems, a liquid brine may form upon freezing due to the exclusion of impurities from the ice crystal lattice coupled with freezing point depression in the concentrated brine. The brine may be segregated to the air-ice interface where it creates a surface layer, in micropockets, or at grain boundaries or triple junctions. We present a model for brines and their associated liquid layers in environmental ice systems that is valid over a wide range of temperatures and solute concentrations. The model is derived from fundamental equlibrium thermodynamics and takes into account nonideal solution behavior in the brine, partitioning of the solute into the ice matrix, and equilibration between the brine and the gas phase for volatile solutes. We find that these phenomena are important to consider when modeling brines in environmental ices, especially at low temperatures. We demonstrate its application for environmentally important volatile and nonvolatile solutes including NaCl, HCl, and HNO3. The model is compared to existing models and experimental data from literature where available. We also identify environmentally relevant regimes where brine is not predicted to exist, but the QLL may significantly impact air-ice chemical interactions. This model can be used to improve the representation of air-ice chemical interactions in polar atmospheric chemistry models.

Kuo, M. H.; Moussa, S. G.; McNeill, V. F.

2011-09-01

253

Synthesis of hydroxyapatite crystals using amino acid-capped gold nanoparticles as a scaffold.  

PubMed

Inorganic composites are of special interest for biomedical applications such as in dental and bone implants wherein the ability to modulate the morphology and size of the inorganic crystals is important. One interesting possibility to control the size of inorganic crystals is to grow them on nanoparticles. We report here the use of surface-modified gold nanoparticles as templates for the growth of hydroxyapatite crystals. Crystal growth is promoted by a monolayer of aspartic acid bound to the surface of the gold nanoparticles; the carboxylate ions in aspartic acid are excellent binging sites for Ca(2+) ions. Isothermal titration calorimetry studies of Ca(2+) ion binding with aspartic acid-capped gold nanoparticles indicates that the process is entropically driven and that screening of the negative charge by the metal ions leads to their aggregation. The aggregates of gold nanoparticles are believed to be responsible for assembly of the platelike hydroxyapatite crystals into quasi-spherical superstructures. Control experiments using uncapped gold nanoparticles and pure aspartic acid indicate that the amino acid bound to the nanogold surface plays a key role in inducing and directing hydroxyapatite crystal growth. PMID:15896069

Rautaray, Debabrata; Mandal, Saikat; Sastry, Murali

2005-05-24

254

Mars water-ice clouds and precipitation.  

PubMed

The light detection and ranging instrument on the Phoenix mission observed water-ice clouds in the atmosphere of Mars that were similar to cirrus clouds on Earth. Fall streaks in the cloud structure traced the precipitation of ice crystals toward the ground. Measurements of atmospheric dust indicated that the planetary boundary layer (PBL) on Mars was well mixed, up to heights of around 4 kilometers, by the summer daytime turbulence and convection. The water-ice clouds were detected at the top of the PBL and near the ground each night in late summer after the air temperature started decreasing. The interpretation is that water vapor mixed upward by daytime turbulence and convection forms ice crystal clouds at night that precipitate back toward the surface. PMID:19574386

Whiteway, J A; Komguem, L; Dickinson, C; Cook, C; Illnicki, M; Seabrook, J; Popovici, V; Duck, T J; Davy, R; Taylor, P A; Pathak, J; Fisher, D; Carswell, A I; Daly, M; Hipkin, V; Zent, A P; Hecht, M H; Wood, S E; Tamppari, L K; Renno, N; Moores, J E; Lemmon, M T; Daerden, F; Smith, P H

2009-07-01

255

Coarsening of Crystals During Temperature Cycling in Magmas and Icy Materials  

NASA Astrophysics Data System (ADS)

Temperature cycling during crystal growth produces large crystals and coarse texture in magmas and ices by dissolution-crystallization. This has implications for crystal growth and texture development on the Moon, Mars, and comets.

Mills, R. D.; Glazner, A. F.

2012-03-01

256

Prevention of crystallization fouling during eutectic freeze crystallization in fluidized bed heat exchangers  

Microsoft Academic Search

Eutectic freeze crystallization is a promising separation technique to produce salt and ice crystals with very high purities and requires less energy than competitive evaporative crystallization techniques. A drawback of this technique is crystallization fouling, which seriously reduces heat transfer rates. Solid–liquid fluidized bed heat exchangers may be attractive crystallizers for this purpose, since they have demonstrated to prevent severe

P. Pronk; C. A. Infante Ferreira; G. J. Witkamp

2008-01-01

257

Characteristics of basal ice and subglacial water at Dome Fuji, Antarctica ice sheet  

NASA Astrophysics Data System (ADS)

(Introduction): The second deep ice coring project at Dome Fuji, Antarctica reached a depth of 3035.22 m during the austral summer season in 2006/2007. The recovered ice cores contain records of global environmental changes going back about 720,000 years. (Estimation of basal ice melt): The borehole measurement was carried out on January 2nd in 2007 when the temperature disturbance in the borehole calmed down by the rest of drilling for 2 days. Temperature measurement was performed after 0 C thermometer test was done in the ground. The temperature sensor of pt100 installed in the skate-like anti-torque was used. We did not have the enough time until the temperature of thermometer was matched with the temperature of ice sheet. Some error was included in ice temperature data. The resistance of pt100 sensor was converted to temperature in the borehole measurement machine. But we used only two electrical lines for pt100 sensor. Rate of heat flow in the ice sheet was calculated using the vertical temperature gradient of the ice sheet and rate of heat conductivity of ice. The deepest part of heat flux using temperatures at 3000m and 3030m was about 45mW/m2. We assumed that this value was the heat flux from the bedrock in the ice sheet. Heat flux to the bedrock surface in the ground was assumed 54.6mW/m2 adopted by ice sheet model (P. Huybrechts, 2006). Then the heat flux for basal ice melt was about 10mW/m2. This value was equaled to melting of 1.1mm of ice thickness per year. On the other hand, the annual layer thickness under 2500m was not changed so much and its average was 1.3mm of ice thickness. So the annual layer thickness and melting rate of basal ice was the same in ordering way. Or ice equivalent in annual layer is melting every year. The age of the deepest part of ice core is guessed at 720,000 years old and the ice older than basal ice has melted away. (The state of basal ice): When the ice core drilling depth passed 3031.44m, amount of ice chip more abundant than the cutting chips has been collected. When the drilling passed 3033.46m, the amount of ice chip was decreased. But the amount of ice chip collected increase again from 3034.59m and many large ices have taken the upper part of ice core. The temperature of ice sheet near the bedrock is the pressure melting point. So the liquid water can exist easy there. The water like groundwater infiltrated into the borehole and froze in drilling liquid from 3031.44m to 3033.46m. Under 3034.59m, the subglacial water infiltrated into the borehole and froze in drilling liquid. The existence of water channel in the ice core was found. We think that the liquid water has been flowing through the boundary of ice crystal. (Characteristics of chemical constituents): The melted ice was analyzed every 10cm per 50cm from 2400m to 3028m and continuously every 10cm from 3028m to 3034m. The analytical items were water isotopes (d18O and dD), micro particles (dust) and major ion components. The variations of water isotope and dust in ice near the bedrock have no conspicuous change. But, the concentrations of Cl- and Na+ ions had interesting behavior. The concentration of Cl- ion increased and Na+ ion was decreased deeper than 3020m. Further the concentrations of all ions were decreased suddenly deeper than 3034m. The concentration of ions will be decrease in turn according to the solubility of the ion. home/

Motoyama, H.; Uemura, R.; Hirabayashi, M.; Miyake, T.; Kuramoto, T.; Tanaka, Y.; Dome Fuji Ice Core Project, M.

2008-12-01

258

Temperature dependence of ice critical nucleus size.  

PubMed

We present a molecular dynamics study of ice growth from supercooled water. By performing a series of simulations with different initial conditions, we have quantitative established the relationship existing between the critical nucleus size and the temperature. The results show that ice embryos containing hundreds or thousands of molecules are needed for the system to crystallize macroscopically, even at high degrees of supercooling. Our findings explain the difficulty in observing spontaneous ice nucleation in atomistic simulations and the relative ease with which water droplets can be supercooled under controlled experiments. PMID:21787014

Pereyra, Rodolfo G; Szleifer, Igal; Carignano, Marcelo A

2011-07-21

259

Sea Ice Index Monitors Polar Ice Extent  

NASA Astrophysics Data System (ADS)

In September 2002, Arctic sea ice extent reached a minimum unprecedented in 24 years of satellite passive microwave observations, and almost certainly unmatched in 50 years of charting Arctic ice. Again, in September 2003, ice retreated to an unusually low extent, almost equaling the previous year's minimum. The Sea Ice Index (http://nsidc.org/data/seaice_index/), an easy-to-use source of information on sea ice trends and anomalies, assists in observing these minima. The Sea Ice Index is intended for both researchers and the scientifically inclined general public.

Fetterer, Florence; Knowles, Kenneth

2004-04-01

260

Ice Forces and Ship Response to Ice. Consolidation Report.  

National Technical Information Service (NTIS)

Conclusions from this study include: (1) Both peak force and peak pressures during an impact increase with ice severity (ice thickness and ice strength). (2) In arctic regions, operation at higher latitudes increases ice severity and therefore ice loads. ...

C. Daley I. Glen J. W. St John R. Brown

1990-01-01

261

Ice-surface adsorption enhanced colligative effect of antifreeze proteins in ice growth inhibition  

NASA Astrophysics Data System (ADS)

This Communication describes a mechanism to explain antifreeze protein's function to inhibit the growth of ice crystals. We propose that the adsorption of antifreeze protein (AFP) molecules on an ice surface induces a dense AFP-water layer, which can significantly decrease the mole fraction of the interfacial water and, thus, lower the temperature for a seed ice crystal to grow in a super-cooled AFP solution. This mechanism can also explain the nearly unchanged melting point for the ice crystal due to the AFP's ice-surface adsorption. A mathematical model combining the Langmuir theory of adsorption and the colligative effect of thermodynamics has been proposed to find the equilibrium constants of the ice-surface adsorptions, and the interfacial concentrations of AFPs through fitting the theoretical curves to the experimental thermal hysteresis data. This model has been demonstrated by using the experimental data of serial size-mutated beetle Tenebrio molitor (Tm) AFPs. It was found that the AFP's ice-surface adsorptions could increase the interfacial AFP's concentrations by 3 to 4 orders compared with those in the bulk AFP solutions.

Mao, Yougang; Ba, Yong

2006-09-01

262

Phase Transformation and Intense 2.7??m Emission from Er3+ Doped YF3/YOF Submicron-crystals  

NASA Astrophysics Data System (ADS)

Yttrium fluoride YF3:Er3+ and yttrium oxyfluoride YOF:Er3+ submicron-crystals with mid-infrared fluorescent emissions were synthesized for the first time. The rhombohedral phase YOF submicron-crystals were synthesized by the crystalline phase transformation from pure orthorhombic YF3 submicron-crystals, which were prepared by co-precipitation method. The composition and morphology were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM), which showed that submicron-crystals were quasi-spherical with the particle size of ~400 nm. A novel formation mechanism of YOF submicron-crystals was proposed. Photoluminescence (PL) spectra indicated the 2.7 ?m emission of Er3+ has remarkably enhanced with the increase of Er3+ doping concentration, and a novel dynamic circulatory energy transfer mechanism was proposed. Fourier transform infrared spectra (FTIR) were used to demonstrate the change of hydroxyl content. These oxyfluoride submicron-crystals provide a new material for nano/submicron-crystals-glass composites, and open a brand new field for the realization of mid-infrared micro/nano-lasers.

Chai, Guanqi; Dong, Guoping; Qiu, Jianrong; Zhang, Qinyuan; Yang, Zhongmin

2013-04-01

263

Ice storage receptacle light for ice maker  

SciTech Connect

In a refrigeration apparatus having a cabinet defining an access opening, a bin in the cabinet for storage of ice bodies therein, and closure means for providing a selective access to the bin through the opening for removal of a desired quantity of ice bodies therefrom, improved illuminating means for illuminating the ice bodies in the bin for observation thereof through the opening, the illuminating means is described comprising: ice forming means for forming an ice slab; a lamp; means for mounting the lamp in the cabinet spaced above the bin; grid means for receiving the ice slab from the ice forming means, the grid means being spaced below the lamp and above the bin, the grid means defining means for diffusing light shining from the lamp onto the ice bodies in the bin, the grid means comprising heating wire means; and means for energizing the heating wire means for cutting an ice slab received thereon into a plurality of ice bodies and permit the ice bodies to fall from the grid into the bin, the lamp providing sufficient light for diffusively illuminating the ice bodies in the bin through the grid means and an ice slab on the grid means.

Hooper, C.R.; Michael, L.W.

1988-01-19

264

Ice Core Secrets  

NSDL National Science Digital Library

In this activity, students will explore the characteristics of ice and explain the influencing factors by using Internet connections to polar field experiences, making their own ice cores and taking a field trip for obtaining a local ice core. The students will practice scientific journaling to document their observations. They will assemble their findings, develop a poster of their ice core and explain their observations. The 'ice is ice' misconception will be dispelled. Students will explain what scientists learn from ice cores and define basic vocabulary associated with ice cores.

Kolb, Sandra

265

Effect of biopolymers on structure and ice recrystallization in dynamically frozen ice cream model systems.  

PubMed

Ice crystal growth and microstructure of sugarsolutions prepared with stabilizers (carboxymethyl cellulose [CMC], xanthan gum, locust bean gum [LBG], and gelatin) with or without milk solids-nonfat (MSNF) after freezing in a scraped surface heat exchanger and temperature cycling (5 cycles from -6 degrees C to -20 degrees C) were studied. Ice crystal growth was calculated from brightfield microscopic images acquired from samples before and after cycling. Freeze-substitution and low-temperature embedding (LR-Gold resin) were sample preparation techniques utilized for structure analyses by light microscopy and transmission electron microscopy. Differential staining for carbohydrates and proteins allowed the identification of stabilizer gel-like structures in LBG, gelatin, and gelatin/MSNF solutions. In the absence of milk proteins, xanthan and LBG were the most effective at retarding recrystallization, while in their presence, only xanthan had an effect. Cryo-gelation of the LBG was observed but is not the only mechanism of stabilizer action. Thermodynamic incompatibility between biopolymers was observed to promote localized high concentrations of milk proteins located at the ice crystal interface, probably exerting a water-holding action that significantly enhanced the stabilizer effect. Qualitatively, solution heterogeneity (phase separation) was directly proportional to ice crystal growth inhibition. It is suggested that water-holding by stabilizer and proteins, and in some cases steric hindrance induced by a stabilizer gel-like network, caused a reduction in the kinetics of the ice recrystallization phenomena and promoted mechanisms of melt-regrow instead of melt-diffuse-grow recrystallization, thus resulting in the preservation of the ice crystal size and in a small span of the ice crystal size distribution. PMID:12487439

Regand, A; Goff, H D

2002-11-01

266

Subliming Ice Surfaces: Freeze-Etch Electron Microscopy  

Microsoft Academic Search

Vacuum sublimation of oriented single crystals of ice at temperatures from -110 to -60 degrees Celsius was studied by electron microscopy with the freeze-etch technique. Sublimation etches the ice surface to produce pits and asperities and above -85 degrees Celsius causes extreme surface roughening. The etch pits are ascribed to surface dislocations, and the extreme roughening is ascribed to the

J. Gordon Davy; Daniel Branton

1970-01-01

267

Ice Nucleation Mode and Kinetic Growth Inefficiency in Cirrus  

NASA Astrophysics Data System (ADS)

Ice nucleation mechanisms and molecular surface kinetics for small ice crystals in cirrus remain areas of intense research in cloud physics. A theoretical relationship between ice nucleation mode and subsequent kinetic limits on depositional growth was investigated using the combined results of recent experiments, observations, and models. A variety of recent data suggest that under certain conditions, the growth of small ice crystals, and in turn the macroscopic evolution of cirrus, are strongly modulated by very small deposition coefficients (?<0.01). Field data, modeling studies, and experimental results all highlight particular crystal sizes (<20? m) and ambient supersaturation regimes (S<0.2) where kinetic growth limitations are expected to be most important. Theoretical explanations of crystal growth suggest that deposition coefficient for ice is likely to be function of supersaturation, temperature, and facet dimension. At the instant of nucleation, all three of these variables differ with the mode of ice nucleation. In combining recent data and growth theory, it becomes apparent that the mode of ice nucleation plays an important role in determining the magnitude and importance of the overall kinetic inefficiency. Depositional growth of ice following homogeneous nucleation from liquid drops appears likely to be significantly less restricted by kinetic inefficiency as compared to heterogeneous nucleation occurring at lower supersaturation.

Magee, N. B.

2008-12-01

268

Cloud Liquid Water and Ice Content Retrieval by Multiwavelength Radar  

Microsoft Academic Search

Cloud liquid water and ice content retrieval in precipitating clouds by the differential attenuation method using a dual-wavelength radar, as a function of the wavelength pair, is first discussed. In the presence of non- Rayleigh scatterers, drizzle, or large ice crystals, an ambiguity appears between attenuation and non-Rayleigh scattering. The liquid water estimate is thus biased regardless of which pair

Nicolas Gaussiat; Henri Sauvageot; Anthony J. Illingworth

2003-01-01

269

Some ice nucleation characteristics of Asian and Saharan desert dust  

Microsoft Academic Search

The large (7 m×4 m cylinder) AIDA (Aerosol Interactions and Dynamics in the Atmosphere) cloud chamber facility at Forschungszentrum, Karlsruhe, Germany was used to test the ice nucleating ability of two desert dust samples from the Sahara and Asia. At temperatures warmer than -40°C droplets were formed before ice crystals formed, there was no deposition nucleation observed. At temperatures colder

P. R. Field; O. Möhler; P. Connolly; M. Krämer; R. Cotton; A. J. Heymsfield; H. Saathoff; M. Schnaiter

2006-01-01

270

Study on Permeability of Ice/Water Mixtures  

NASA Astrophysics Data System (ADS)

The purpose of the research was to study how the permeability of porous ice/water mixtures changes during storage under controlled conditions, and how those changes vary with difference in types of ice particles. Also, difference in stickiness between various kinds of ice particle was examined. Experiments were carried out on mixtures of water with sliced ice, semispherical ice particles and frazil ice, and the permeability of the samples were measured before and after storage in a tank where the samples were kept at 0°C. No channeling effect was observed. The permeability of the sliced ice and compressed frazil ice increased during 24 hours of storage. On the other hand, the semispherical ice had no change. Almost all types of ice particle stick to one another by storing. Exception was observed on frazil ice. Frazil ice tends to stick to one another with the same crystal direction at the early stage, but later on there was no distinguishable difference in sticking behavior with others. It was concluded that clustering of particles in the porous mixtures into bigger size, and transformation of sharp edges on the particles into smoother surfaces caused the increase in permeability.

Okawa, Seiji; Saito, Akio; Eiriksson, Ari; Maeda, Tasuku; Hozumi, Tsutomu; Kumano, Hiroyuki

271

Friction of ice on ice  

NASA Astrophysics Data System (ADS)

New measurements have been made of the friction coefficient of freshwater polycrystalline ice sliding slowly (5 × 10-8 to 1 × 10-3 m s-1) upon itself at temperatures from 98 to 263 K under low normal stresses (?98 kPa). Sliding obeys Coulomb's law: the shear stress is directly proportional to the normal stress across the interface, while cohesion offers little contribution to frictional resistance. The coefficient of kinetic friction of smooth surfaces varies from ?k = 0.15 to 0.76 and, at elevated temperatures (?223 K), exhibits both velocity strengthening at lower velocities (<10-5 to 10-4 m s-1) and velocity weakening at higher velocities. Strengthening and weakening are attributed to creep deformation of asperities and localized melting, respectively. At intermediate temperatures of 173 and 133 K, the kinetic coefficient appears to not exhibit significant dependence upon velocity. However, at the low temperature of 98 K the coefficient of kinetic friction exhibits moderate velocity strengthening at both the lowest and the highest velocities but velocity independence over the range of intermediate velocities. No effect was detected of either grain size or texture. Over the range of roughness 0.4 × 10-6 m ? Ra ? 12 × 10-6 m, a moderate effect was detected, where ?k ? Ra0.08. Slide-hold-slide experiments revealed that the coefficient of static friction increases by an amount that scales logarithmically with holding time. Implications of the results are discussed in relation to shearing across "tiger stripe" faults within the icy crust of Saturn's Enceladus, sliding of the arctic sea ice cover and brittle compressive failure of cold ice.

Schulson, Erland M.; Fortt, Andrew L.

2012-12-01

272

Ice Flora (Bottom Type): A Mechanism of Primary Production in Polar Seas and the Growth of Diatoms in Sea Ice.  

National Technical Information Service (NTIS)

A field survey off Barrow in the summer of 1964 revealed that sea ice in the Arctic develops a layered structure through the growth of diatoms. The diatoms increase in brine solutions which occur in the microfissures between fine crystals of sea ice and f...

H. Meguro K. Ito H. Fukushima

1967-01-01

273

Laboratory studies of deposition mode heterogeneous ice nucleation: Effects of ice nuclei composition, size and surface area  

Microsoft Academic Search

The indirect aerosol effect contributes to major uncertainties in determining the radiation budget of the earth. A large uncertainty is due to the formation of ice clouds onto natural or anthropogenic aerosols. Field studies have shown that mineral type particles are often associated with ice crystals in the mid-upper troposphere and given the long residence time in the atmosphere of

Zaminhussein Abdulali Kanji

2009-01-01

274

Evaluating the importance of grain size sensitive creep in terrestrial ice sheet rheology  

Microsoft Academic Search

The rheology of ice in terrestrial ice sheets is generally considered to be independent of the size of the grains (crystals), and appears well described by Glen's flow law. In recent years, however, new laboratory deformation experiments on ice as well as analysis of in situ measurements of deformation at glaciers suggested that grain size and variations therein should not

C. N. P. J. Maaijwee; J. H. P. de Bresser

2009-01-01

275

The Influence of Polysaccharides on the Glass Transition in Frozen Sucrose Solutions and Ice Cream  

Microsoft Academic Search

The objective of this study was to describe further the mechanism by which polysaccharide stabilizers contribute to stability of frozen dairy desserts. The influence of stabilizers on the thermal properties and viscosity of carbohydrate solutions at subzero temperatures, on the thermal properties of ice cream mix, and on ice crystallization and growth in ice cream were investigated. Polysaccharide stabilizers did

H. D. Goff; K. B. Caldwell; D. W. Stanley; T. J. Maurice

1993-01-01

276

Airborne measurements of tropospheric ice-nucleating aerosol particles in the Arctic spring  

Microsoft Academic Search

Instrumented aircraft flights were made during field experiments in the Arctic Ocean, the NASA FIRE Arctic Cloud Experiment and SHEBA (Surface Heat Budget of the Arctic). Airborne measurements of ice nucleating aerosol particles (IN) used a continuous flow diffusion (CFD) chamber, covering -10° to -30°C and humidities from ice saturation to water supersaturation. During selected time periods, ice crystals that

David C. Rogers; Paul J. DeMott; Sonia M. Kreidenweis

2001-01-01

277

Intragranular strain field in columnar ice during elasto-viscoplatic transient creep regime, and relation with the local microstructure  

Microsoft Academic Search

The viscoplastic behaviour of polycrystalline ice is strongly affected by the very strong anisotropy of ice crystals. Indeed, in the dislocations creep regime relevant e.g. for ice sheet flow, dislocation glide on the basal plane of ice single crystals leads to strain-rates ˜6 order of magnitude larger than strain-rates that might be obtain if only non-basal glide is activated. At

F. Grennerat; M. Montagnat; P. Duval; P. Vacher; O. Castelnau

2009-01-01

278

Make Ice Cream  

NSDL National Science Digital Library

Learners add salt to ice to chill it lower than its freezing point. This chilled ice can then be used to freeze milk and sugar into ice cream. Learners can experiment by adding different flavors such as fruit juices and candy to the ice cream mix.

Museum Of Science And Industry, Chicago

2012-01-01

279

Polarimetric radar studies of atmospheric ice particles  

SciTech Connect

Single scattering properties of ice crystals are described at microwave frequencies using discrete dipole approximations and Rayleigh scattering techniques. For a given shape, the average bulk densities of ice crystals can be estimated using the ratio of the copolarization basis. Reflectivity depends on the ice content (g [center dot] m[sup [minus]3]), and also on both size distribution parameters and average bulk density of the scatterers. Differential propagation phase is primarily a function of shape, ice water content, and is independent of size distribution parameters. Thus, by using a combination of polarimetric radar measurements, average ice content, bulk density, and shape of distributed scatterers can be inferred. These techniques become quite complex in the case of a winter storm where scatterers can exist with varying shape and bulk densities. Polarimetric radar properties of such complex distributed scatterers are modeled. Physical variations in the relation among ice water content, reflectivity, and differential propagation phase are considered with respect to change in the shape of size distribution, bulk density, and average shape of the scatterers. Also, simultaneous polarimetric radar observations and in situ aircraft measurements are shown to demonstrate practical applicability of the techniques.

Vivekanandan, J. (National Center for Atmospheric Research, Boulder, CO (United States)); Bringi, V.N. (Colorado State Univ., Fort Collins, CO (United States). Dept. of Electrical Engineering); Hagen, M.; Meischner, P. (DLR, Oberpfaffenhofen (Germany). Inst. fur Physik d. Atmosphaere)

1994-01-01

280

Freezing of Confined Water: A Bilayer Ice Phase in Hydrophobic Nanopores  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations were performed to study the phase behavior of a thin film of water confined to a slit nanopore with smooth walls. A first-order water-to-ice freezing transition has been observed. The resulting ice, which is a crystal of bilayer consisting of rows of distorted hexagons, does not resemble any ice crystals found so far. The confined water contracts upon freezing when the confinement load is low ( ~0.5 kbar) and expands when the load is high (10 kbar). The residual entropy of the bilayer ice can be calculated exactly, which is about half of the entropy of the bulk ice.

Koga, Kenichiro; Zeng, X. C.; Tanaka, Hideki

1997-12-01

281

Antifreeze proteins bind independently to ice.  

PubMed Central

It has been suggested that cooperative interactions between antifreeze proteins (AFPs) on the ice surfaces are required for complete inhibition of ice crystal growth. To test this hypothesis, a 7-kDa type III AFP was linked through its N-terminus to thioredoxin (12 kDa) or maltose-binding protein (42 kDa). The resultant 20-kDa and 50-kDa fusion proteins were larger in diameter than free AFP and thus precluded any extensive AFP-AFP contacts on the ice surface. Both fusion proteins were at least as active as free AFP at virtually all concentrations tested. By these criteria, AFPs function independently of each other and do not require specific intermolecular interactions to bind tightly to ice.

DeLuca, C I; Comley, R; Davies, P L

1998-01-01

282

Arctic ice islands  

SciTech Connect

The development of offshore oil and gas resources in the Arctic waters of Alaska requires offshore structures which successfully resist the lateral forces due to moving, drifting ice. Ice islands are floating, a tabular icebergs, up to 60 meters thick, of solid ice throughout their thickness. The ice islands are thus regarded as the strongest ice features in the Arctic; fixed offshore structures which can directly withstand the impact of ice islands are possible but in some locations may be so expensive as to make oilfield development uneconomic. The resolution of the ice island problem requires two research steps: (1) calculation of the probability of interaction between an ice island and an offshore structure in a given region; and (2) if the probability if sufficiently large, then the study of possible interactions between ice island and structure, to discover mitigative measures to deal with the moving ice island. The ice island research conducted during the 1983-1988 interval, which is summarized in this report, was concerned with the first step. Monte Carlo simulations of ice island generation and movement suggest that ice island lifetimes range from 0 to 70 years, and that 85% of the lifetimes are less then 35 years. The simulation shows a mean value of 18 ice islands present at any time in the Arctic Ocean, with a 90% probability of less than 30 ice islands. At this time, approximately 34 ice islands are known, from observations, to exist in the Arctic Ocean, not including the 10-meter thick class of ice islands. Return interval plots from the simulation show that coastal zones of the Beaufort and Chukchi Seas, already leased for oil development, have ice island recurrences of 10 to 100 years. This implies that the ice island hazard must be considered thoroughly, and appropriate safety measures adopted, when offshore oil production plans are formulated for the Alaskan Arctic offshore. 132 refs., 161 figs., 17 tabs.

Sackinger, W.M.; Jeffries, M.O.; Lu, M.C.; Li, F.C.

1988-01-01

283

Phase transitions in ice phase of clouds under influence of adsorbed ions electric field  

Microsoft Academic Search

New theoretical estimations of ice phase formation possible mechanisms in Earth's atmosphere clouds bounded with adsorbed ions have been carried out. Homogeneous mechanism of cloud droplets crystallization and heterogeneous ice nucleation by sublimation on an aerosol particle have been considered. The main principle of an electric field action on the phase transition is conserved. The electric field promotes crystallization if

V. V. Klingo

2000-01-01

284

Black carbon enrichment in atmospheric ice particle residuals observed in lower tropospheric mixed phase clouds  

Microsoft Academic Search

The enrichment of black carbon (BC) mass in residuals of small ice crystals was investigated during intensive experiments in winter 2004 and 2005 at the high alpine research station Jungfraujoch (3580 m asl, Switzerland). Two inlets were used to sample the bulk aerosol (residuals of cloud droplets and ice crystals and nonactivated aerosol particles) and the residual particles of small

J. Cozic; S. Mertes; B. Verheggen; D. J. Cziczo; S. J. Gallavardin; S. Walter; U. Baltensperger; E. Weingartner

2008-01-01

285

Internal Friction of H2O, D2O and Natural Glacier Ice.  

National Technical Information Service (NTIS)

The three parts of this report are entitled (1) internal friction of pure H2O, D2O and doped ice crystals, (2) internal friction at crystal boundaries, and (3) the internal friction of natural glacier ice. Part 1 uses the flexural vibration method and exp...

D. Kuroiwa

1965-01-01

286

Microphysical Parameterization of Arctic Diamond Dust, Ice Fog, and Thin Stratus for Climate Models  

Microsoft Academic Search

A parameterization is described for low-level clouds that are characteristic of the Arctic during winter. This parameterization simulates the activation of aerosols, the aggregation\\/coalescence, and the gravitational deposition of ice crystals\\/water droplets and the deposition\\/condensation of water vapor onto ice crystals\\/water droplets. The microphysics scheme uses four prognostic variables to characterize clouds: ice water content, liquid water content, and the

Eric Girard; Jean-Pierre Blanchet

2001-01-01

287

Dynamical conditions of ice supersaturation in the extratropical tropopause regions  

NASA Astrophysics Data System (ADS)

Cirrus clouds are one of the largest sources of uncertainties in predicting future climate. Ice nucleation and ice crystal growth inside cirrus clouds require ice supersaturation (ISS). However, the dynamical processes and conditions that control ISS are not well understood in the upper troposphere. In this work we present an analysis of ISS (T <= -40 °C) using the water vapor measurement by the Vertical Cavity Surface Emitting Laser (VCSEL) Hygrometer (Zondlo et al., 2010) on the NSF Gulf-stream V research airplane during the Stratosphere Troposphere Analyses of Regional Transport (START08) Campaign. START08 campaign sampled chemical and microphysical variables under various dynamical conditions near the extratropical tropopause and upper level jets. The data allow us to contrast ISS and ice crystals generated from the region of convective clouds versus those generated from the mixing of stratospheric and tropospheric air near the frontal zone during a stratospheric intrusion. We also compared the dynamical conditions of two different schemes for ISS: suppressed nucleation and suppressed growth schemes. To understand how mixing processes play a role in the formation of ISS and ice crystals, we analyzed how ISS and ice crystals are distributed relative to the jets streams and the extratropical tropopause transition layer based on O3-CO tracer-tracer correlations. The mixing lines represented by the tracer correlations help identify the dynamical processes that dominated the formation of the ISS parcels. Case studies identifying the specific dynamical conditions of observed ISS and ice particles will be presented.

Diao, M.; Zondlo, M. A.; Pan, L.; Jensen, E. J.

2011-12-01

288

Cirrus Uncinus Generating Cells and the Evolution of Cirrdorm Clouds. Part III: Numerical Computations of the Growth of the Ice Phase  

Microsoft Academic Search

Equations were developed to calculate the growth of the ice phase in cirrus clouds. Calculations indicated that nucleation of ice crystals in cirrus uncinus heads forming at temperatures lower than 35°C generally should occur near the upwind base of the head, and in cirrostratus clouds at the top of the cloud.The growth of ice crystals and the resulting shape of

Andrew Heymsneid

1975-01-01

289

Growth of Gray Tin Crystals  

Microsoft Academic Search

A method is proposed for growing large a-Sn single crystals without their disintegration as a result of the ß ? a phase transition. a-Sn crystals are prepared by freezing the closed system water–Sn–seed in such a way that the pressure exerted by the expanding ice minimizes the amount of a-Sn nuclei and reduces the growth rate.

A. D. Styrkas

2003-01-01

290

Fish antifreeze protein and the freezing and recrystallization of ice.  

PubMed

Antifreeze glycopeptide and peptides from the blood of polar fishes prevent the growth of ice crystals in water at temperatures down to approximately 1 degree C below freezing point, but do not appreciably influence the equilibrium freezing point. This freezing point hysteresis must be a disequilibrium effect, or it would violate Gibbs' phase rule, but the separate freezing and melting points are experimentally very definite: ice neither melts nor freezes perceptibly within the 'hysteresis gap', for periods of hours or days. We report here unusual crystal faces on ice crystals grown from solutions of very low concentrations of the anti-freeze glycopeptides and peptides. This is a clue to the mechanism of freezing inhibition, and it may be the basis of a simple, very sensitive test for antifreeze material. Very low concentrations of the antifreeze protein are also remarkably effective in preventing the recrystallization of ice. PMID:6700733

Knight, C A; DeVries, A L; Oolman, L D

291

Spectral properties of ice-particulate mixtures and implications for remote sensing. 1. Intimate mixtures.  

USGS Publications Warehouse

The spectral properties of water ice-partitioning mixtures are studied for the purpose of deriving the ice and particulate abundances from remotely obtained spectra (particulates referring to non-icy materials in the form of grains). Reflectance levels and ice absorption band depths are a complex function of the single scattering albedo of the particulates embedded in the ice. The ice absorption band depths are related to the mean optical path length of photons in ice through Beers law, Fresnel reflection from the ice-crystal faces on the surface, and ice absorption coefficient as a function of wavelength. Laboratory spectra of many ice- particulate mixtures are studied with high-, medium-, and low-albedo particulates.-from Authors

Clark, R. N.; Lucey, P. G.

1984-01-01

292

Assessing aerosol indirect effect through ice clouds in CAM5  

NASA Astrophysics Data System (ADS)

Ice clouds play an important role in regulating the Earth's radiative budget and influencing the hydrological cycle. Aerosols can act as solution droplets or ice nuclei for ice crystal formation, thus affecting the physical properties of ice clouds. Because the related dynamical and microphysical processes happen at very small spatial and temporal scales, it is a great challenge to accurately represent them in global climate models. Consequently, the aerosol indirect effect through ice clouds (ice AIE) estimated by global climate models is associated with large uncertainties. In order to better understand these processes and improve ice cloud parameterization in the Community Atmospheric Model, version 5 (CAM5), we analyze in-situ measurements from various research campaigns, and use the derived statistical information to evaluate and constrain the model [1]. We also make use of new model capabilities (prescribed aerosols and nudging) to estimate the aerosol indirect effect through ice clouds, and quantify the uncertainties associated with ice nucleation processes. In this study, a new approach is applied to separate the impact of aerosols on warm and cold clouds by using the prescribed-aerosol capability in CAM5 [2]. This capability allows a single simulation to simultaneously include up to three aerosol fields: online calculated, as well as prescribed pre-industrial (PI) and present-day conditions (PD). In a set of sensitivity simulations, we use the same aerosol fields to drive droplet activation in warm clouds, and different (PD and PI) conditions for different components of the ice nucleation parameterization in pure ice clouds, so as to investigate various ice nucleation mechanisms in an isolated manner. We also applied nudging in our simulations, which helps to increase the signal-to-noise ratio in much shorter simulation period [3] and isolate the impact of aerosols on ice clouds from other factors, such as temperature and relative humidity change. The results show that homogeneous ice nucleation is the main contributor that leads to strong longwave ice AIE in this model. The estimated PD-PI longwave cloud forcing (LWCF) change is strongly sensitive to the simulated sub-grid updraft velocity. Considering the effect of pre-existing ice crystals on ice nucleation can help to significantly reduce the LWCF change. In comparison, the effect of heterogeneous ice nuclei spectra is relatively small, although the perturbations in the LWCF and shortwave cloud forcing are still non-negligible.

Zhang, Kai; Liu, Xiaohong; Yoon, Jin-Ho; Wang, Minghuai; Comstock, Jennifer M.; Barahona, Donifan; Kooperman, Gabriel

2013-05-01

293

Slow wave dynamics stalls tropical tropopause ice clouds  

NASA Astrophysics Data System (ADS)

Water vapour is the most important natural green house gas. However, in the stratosphere an increase in water vapour would possibly result in a cooling. The major entrance of trace substances into the stratosphere is the tropical tropopause layer (TTL), localized between the main level of convective outflow, 150 hPa, and 70 hPa. The TTL water vapour budget, and thus the exchange with the stratosphere, depends crucially on the occurrence and properties of ice clouds in this cold region (T < 200 K). It is believed that homogeneous freezing of liquid solution particles, which predominate the particle population, is the preferred pathway of ice formation. High water vapour supersaturation with respect to ice is required to initiate homogeneous ice nucleation. The number of emerging ice crystals depends on temperature and the ambient relative humidity over ice (RHi). Strong increase in RHi due to rising vertical velocity will produce large amounts of ice crystals. In the TTL, very slow large-scale updraughts prevail (? 0.01 m/s), which would lead to low ice crystal concentrations (? 0.1cm-3). However, tropical deep convection initiates intrinsic gravity waves and consequently, we would expect much higher vertical velocities and therefore higher ice crystal number concentrations. Since the many ice crystals rapidly grow by water vapour diffusion it is also expected that the initially high ice supersaturation quickly reduces to saturation after ice formation. Contrarily, during the last years high and persistent ice supersaturations were observed in the cold TTL in several airborne field campaigns inside and outside of ice clouds (Peter et al., 2006), creating a discussion called the 'supersaturation puzzle'. A step forward in that discussion was made recently: Krämer et al. (2009) observed ice crystal concentrations much lower than expected (most often < 0.1cm-3), but consistent with the measured high supersaturations. These observations turned the 'supersaturation' into a 'nucleation puzzle'. The 'nucleation puzzle' is currently intensely discussed and other nucleation pathways suppressing, modifying or replacing homogeneous freezing are proposed. All these approaches to explain the TTL ice nucleation are of chemical or microphysical nature. Here, we present intense model studies of ice cloud formation under dynamical conditions typical for the TTL. From direct comparison of model simulations and observations we claim that the special TTL dynamics - namely a superposition of very slow large-scale updraughts with high-frequency short waves - can produce the observed low numbers of ice crystals solely by 'classical' homogeneous freezing. References: Krämer, M., Schiller, C., Afchine, A., Bauer, R., Gensch, I., Mangold, A., Schlicht, S., Spelten, N., Ebert, V., Möhler, O., Saathoff, H., Sitnikov, N., Borrman, S., de Reus, M. and P. Spichtinger, 2009: On Cirrus Cloud Supersaturations and Ice Crystal Numbers. Atmos. Chem. Phys., 9, 3505-3522. Peter T., Marcolli C., Spichtinger, P., Corti, T., Baker M.B., Koop, T., 2006: When dry air is too humid. Science 314 (5804), 1399-1402.

Spichtinger, Peter; Krämer, Martina; Borrmann, Stephan

2010-05-01

294

Sea Ice Rheology  

NASA Astrophysics Data System (ADS)

The polar oceans of Earth are covered by sea ice. On timescales much greater than a day, the motion and deformation of the sea ice cover (i.e., its dynamics) are primarily determined by atmospheric and oceanic tractions on its upper and lower surfaces and by internal ice forces that arise within the ice cover owing to its deformation. This review discusses the relationship between the internal ice forces and the deformation of the ice cover, focusing on representations suitable for inclusion within global climate models. I first draw attention to theories that treat the sea ice cover as an isotropic continuum and then to the recent development of anisotropic models that deal with the presence of oriented weaknesses in the ice cover, known as leads.

Feltham, Daniel L.

2008-01-01

295

Ice depolarization on low-angle 2 GHz satellite downlinks  

NASA Astrophysics Data System (ADS)

The impact of ice depolarization on the statistical performance of satellite downlinks were investigated. Propagation data recorded during 1979 and 1980 to see what impact of ice depolarization on link performance were analyzed. The effects on the cross polarization discrimination (XPD) statistics amounted to at most a 2 to 4 dB reduction in the XPD values which rain would have produced for a given percentage of time. Ice depolarization had no effect on the statistics of XPD values below the 0.01% level. Most of the severe ice depolarization events were associated with drops in barometric pressure and the passage of intense cold fronts through our area. Ice contents as the product of three individually undetermined quantities were defined: ice particle density, ice cloud thickness, and the average volume of the ice crystals. It is indicated that populations of ice particle with ice contents on the order of 0.002 m4/m3 are probably responsible for the lower values of measured XPD.

Stutzman, W. L.; Bostian, C. W.; Tsolakis, A.; Pratt, T.

1984-02-01

296

Food Crystals: the Role of Eggs  

Technology Transfer Automated Retrieval System (TEKTRAN)

Sugar, salt, lactose, tartaric acid and ice are examples of constituents than can crystallize in foods. Crystallization in a food product can be beneficial or detrimental and is of particular importance in candy and frozen desserts. The most common crystal in foods is sugar which affects the quali...

297

Ice electrode electrolytic cell  

DOEpatents

This invention relates to a method and apparatus for removing heavy metals from waste water, soils, or process streams by electrolytic cell means. The method includes cooling a cell cathode to form an ice layer over the cathode and then applying an electric current to deposit a layer of the heavy metal over the ice. The metal is then easily removed after melting the ice. In a second embodiment, the same ice-covered electrode can be employed to form powdered metals.

Glenn, D.F.; Suciu, D.F.; Harris, T.L.; Ingram, J.C.

1993-04-06

298

Ice sheet margins and ice shelves  

NASA Astrophysics Data System (ADS)

A possible consequence of climatic warming is an increase in ice sheet melting rates and, ultimately, a perceptible rise in sea level. This would occur very slowly unless thinning at the ice sheet margins triggered a major increase in ice drainage rates. The ice sheet in West Antarctica is the one most susceptible to this type of collapse because it rests on bedrock well below sea level. The most probable outlet for rapid ice discharge would be through the area covered today by the Ross Ice Shelf, which would have to be severely weakened first. Currently, the ice shelf appears to be either in equilibrium or actually growing thicker. Most of the wastage from the ice shelf is by occasional calving of large tabular icebergs. Weakening could be achieved most rapidly if summer temperatures were to rise to several degrees above the melting point for two or three months each year. Then, widespread surface meltwater would fill crevasses and force them to overdeepen. This would cause accelerated iceberg calving and explosive fragmentation of the resulting icebergs-conditions similar to those found in the Arctic today. Such accelerated iceberg calving could also threaten portions of the ice sheet in East Antarctica. Here, although bedrock is below sea level, the ice sheet appears to be protected by coastal bedrock sills which are too shallow for a tabular iceberg to pass over them, but would not prevent the discharge of small iceberg fragments. The most vulnerable portion of the ice sheet is probably that drained by Pine Island and Thwaites glaciers in West Antarctica. These glaciers are not protected by large ice shelves and, although there is no evidence for present day retreat, they may be the first glaciers to respond to climatic warming. However, even an order of magnitude increase in the activity of one of these glaciers would cause a sea level increase of less than 1 mm yr-l. The measurements necessary to monitor ice sheet extent and elevation, summer melt zones and sea ice cover can all be obtained from a satellite in near-polar orbit using well-proven techniques. The establishment of such a program should take highest priority in future research.

Thomas, Robert H.

299

Of Ice and Microbes  

Microsoft Academic Search

Inuit hunters of the North have long recognized ice as the natural state of water from which life flows on Earth. Although unaware of the microscopic world, they chart changes in properties of ice and water that derive from a succession of microbial inhabitants. Scientific hunters of the West have largely overlooked all but the warmest of ices as dynamic

Jody Deming

2006-01-01

300

Multi-year ice  

USGS Multimedia Gallery

ARCTIC OCEAN - A multi-year ice floe slides down the starboard side of the Coast Guard Cutter Healy Aug. 11, 2009, as the ship heads north into even thicker ice. "You can tell that this is a multi-year ice floe by the light blue melt ponds that have formed on top of the floe," said Pablo Clemente-Co...

2010-02-19

301

Ice Versus Rock  

ERIC Educational Resources Information Center

|During a snow bank exploration, students noticed "ice caves," or pockets, in some of the larger snow banks, usually below darker layers. Most of these caves had many icicles hanging inside. Students offered reasonable explanations of ice cave formation--squirrels, kids, snow blowers--and a few students came close to the true ice cave-formation…

Rule, Audrey C.; Olson, Eric A.; Dehm, Janet

2005-01-01

302

Experiments in Ice Physics.  

ERIC Educational Resources Information Center

|Describes experiments in ice physics that demonstrate the behavior and properties of ice. Show that ice behaves as an ionic conductor in which charge is transferred by the movement of protons, its electrical conductivity is highly temperature-dependent, and its dielectric properties show dramatic variation in the kilohertz range. (Author/GA)|

Martin, P. F.; And Others

1978-01-01

303

Frazil Ice Formation.  

National Technical Information Service (NTIS)

Frazil ice forms in flowing or turbulent water that has become supercooled by heat transfer to overlying air. This report investigates the influences of turbulence and water temperature on frazil ice formation. The rate and the quantity of frazil ice form...

R. Ettema M. F. Karim J. F. Kennedy

1984-01-01

304

Viscoelastic Properties of Ice  

Microsoft Academic Search

An apparatus has been constructed for the study of deformation under tension of single and polycrystalline ice. Deformations down to 10?5 cm could be measured. Deformation of single and polycrystals was investigated as a function of time, stress, and temperature. Whereas the strain rate for polycrystalline ice decreases with time, that for single glacier ice increases linearly with time. The

H. H. G. Jellinek; R. Brill

1956-01-01

305

Technology for Ice Rinks  

NASA Astrophysics Data System (ADS)

Ron Urban's International Ice Shows set up portable ice rinks for touring troupes performing on temporary rinks at amusement parks, sports arenas, dinner theaters, shopping malls and civic centers. Key to enhanced rink portability, fast freezing and maintaining ice consistency is a mat of flexible tubing called ICEMAT, an offshoot of a solar heating system developed by Calmac, Mfg. under contract with Marshall.

1983-01-01

306

Analysis of Iced Wings.  

National Technical Information Service (NTIS)

A method for computing ice shapes along the leading edge of a wing and a method for predicting its aerodynamic performance degradation due to icing is described. Ice shapes are computed using an extension of the LEWICE code which was developed for airfoil...

T. Cebeci H. H. Chen K. Kaups S. Schimke J. Shin

1992-01-01

307

Ice Jam Data Collection.  

National Technical Information Service (NTIS)

Ice jam data collection is necessary to gain information on ice jam events, which may occur rarely and are often short-lived, but can at the same time cause large damages. An ice jam data collection program involves field data collection, review of existi...

K. D. White J. E. Zufelt

1994-01-01

308

CRREL Ice Jam Database.  

National Technical Information Service (NTIS)

This report provides information on the CRREL Ice Jam Database and its potential use for analyzing ice-related flooding problems. Rivers in the northern United States are subject to ice jams that cause flooding; block hydropower and water supply intakes; ...

K. D. White H. J. Eames

1999-01-01

309

Arctic Sea Ice  

Microsoft Academic Search

Of all the recent observed changes in the Arctic environment, the reduction of sea ice cover stands out most prominantly. Several independent analysis have established a trend in Arctic ice extent of -3% per decade from the late 1970s to the late 1990s, with a more pronounced trend in summer. The overall downward trend in ice cover is characterized by

J. C. Stroeve; F. Fetterer; K. Knowles; W. Meier; M. Serreze; T. Arbetter

2004-01-01

310

A uniform stress, multi-grain model for migration recrystallization in polar ice  

NASA Astrophysics Data System (ADS)

A multi-grain model for a migration recrystallization process in polar ice is presented. The model is based on the Sachs-Reuss approximation of the stress homogeneity in a polycrystalline aggregate. An individual crystal of ice is treated as a transversely isotropic and incompressible medium which deforms by viscous creep. The highly anisotropic viscous behaviour of the ice crystal is described by a constitutive law expressing microscopic strain-rate in terms of the deviatoric stress and three fluidity parameters that define different viscous resistances of the crystal in different glide directions. It is assumed that the recrystallization occurs in those crystals in the aggregate which are most slowly deforming, and new crystals are nucleated at orientations which favour the crystal deformation by basal glide. The model predictions are illustrated by results of numerical simulations of simple flows, showing the evolution of the microscopic structure of ice and the variation of macroscopic viscosities with increasing deformations.

Staroszczyk, Ryszard

2011-10-01

311

Synchronizing ice cores from the Renland and Agassiz ice caps to the Greenland Ice Core Chronology  

Microsoft Academic Search

Four ice cores from the Agassiz ice cap in the Canadian high arctic and one ice core from the Renland ice cap in eastern Greenland have been synchronized to the Greenland Ice Core Chronology 2005 (GICC05) which is based on annual layer counts in the DYE-3, GRIP and NGRIP ice cores. Volcanic reference horizons, seen in electrical conductivity measurements (ECM)

B. M. Vinther; H. B. Clausen; D. A. Fisher; R. M. Koerner; S. J. Johnsen; K. K. Andersen; D. Dahl-Jensen; S. O. Rasmussen; J. P. Steffensen; A. M. Svensson

2008-01-01

312

Rapid switch-like sea ice growth and land ice–sea ice hysteresis  

Microsoft Academic Search

Rapid and extensive growth of sea ice cover was suggested to play a major role in the sea ice switch mechanism for the glacial cycles as well as on shorter millennial scales [Gildor and Tziperman, 2000]. This mechanism also predicts a hysteresis between sea ice and land ice, such that land ice grows when sea ice cover is small and

Roiy Sayag; Eli Tziperman; Michael Ghil

2004-01-01

313

Ice composition evidence of marine ice transfer along the bottom of small Antarctic ice shelf  

Microsoft Academic Search

The existence of marine ice transfer along the underside of the Hell's Gate Ice Shelf (Victoria Land), is indicated by an isotopic and chemical study of ice cores. Because of top surface ablation, the marine ice formed at the ice shelf-ocean interface, ultimately appears at shelf surface. A succession of congelation, platelet and frazil ice is shown to occur. The

R. Souchez; M. Meneghel; J.-L. Tison; R. Lorrain; D. Ronveaux; C. Baroni; A. Lozej; I. Tabacco; J. Jouzel

1991-01-01

314

In situ observations of a high-pressure phase of H2O ice  

USGS Publications Warehouse

A previously unknown solid phase of H2O has been identified by its peculiar growth patterns, distinct pressure-temperature melting relations, and vibrational Raman spectra. Morphologies of ice crystals and their pressure-temperature melting relations were directly observed in a hydrothermal diamond-anvil cell for H2O bulk densities between 1203 and 1257 kilograms per cubic meter at temperatures between -10??and 50??C. Under these conditions, four different ice forms were observed to melt: two stable phases, ice V and ice VI, and two metastable phases, ice IV and the new ice phase. The Raman spectra and crystal morphology are consistent with a disordered anisotropic structure with some similarities to ice VI.

Chou, I. -M.; Blank, J. G.; Goncharov, A. F.; Mao, H. -K.; Hemley, R. J.

1998-01-01

315

Black carbon enrichment in atmospheric ice particle residuals observed in lower trophospheric mixed phase clouds  

SciTech Connect

The enrichment of black carbon (BC) in residuals of small ice particles was investigated during intensive experiments in winter 2004 and 2005 at the high alpine research station Jungfraujoch (3580 m asl, Switzerland). Two inlets were used to sample the bulk aerosol (residuals of cloud droplets and ice crystals as well as non-activated aerosol particles) and the residual particles of small ice crystals (diameter 5 - 20 m). An enrichment of the BC mass fraction in the ice particle residuals was observed by investigating the measured BC mass concentration as a fraction of the bulk (submicrometer) aerosol mass concentration sampled by the two inlets. On average, the BC mass fraction was 5% for the bulk aerosol and 14% for the ice particle residuals. The observed enrichment of BC in ice particle residuals suggests that BC may act as ice nuclei, with important implications for the indirect aerosol effect via glaciation of clouds.

Cozic, J.; Mertes, S.; Verheggen, B.; Cziczo, Dan; Gallavardin, S. J.; Walter, S.; Baltensperger, Urs; Weingartner, E.

2008-08-15

316

Physical and structural properties of the Greenland Ice Sheet Project 2 ice core: A review  

NASA Astrophysics Data System (ADS)

Substantial data sets have been collected on the relaxation characteristics, density, grain size, c axis fabrics, and ultrasonic velocities of the Greenland Ice Sheet Project 2 (GISP2) core to its contact with bedrock at 3053.4 m. Changes in all these properties paralleled closely those found in cores from Byrd Station, Antarctica, and Dye 3, Greenland. Density increased progressively with depth to a maximum of 0.921 Mg/m3 at about 1400 m, at which depth the ice became bubble free. Below about 2000 m, in situ densities began to decrease in response to increasing ice sheet temperatures. Since drilling, much of the ice core has undergone significant volume expansion (relaxation) due to microcracking and the exsolving of enclathratized gases, especially in the brittle ice zone between 650 and 1400 m. Grain size increased linearly to about 1000 m, thereafter remaining fairly constant until the Younger Dryas event at 1678 m where a twofold to threefold decrease in grain size occurred. These grain size changes were accompanied by a progressive clustering of crystal c axes toward the vertical, including a small increase in c axis concentration across the Younger Dryas/Holocene boundary. Increased dust levels in the Wisconsin ice have contributed to the maintenance of a fine-grained texture which, with its strong vertical c axis fabric, persisted to nearly 3000 m. However, beginning at about 2800 m, layers of coarse-grained ice intermixed with the much finer-grained matrix ice are observed. Below 3000 m the ice became very coarse grained. This change, attributed to annealing recrystallization at elevated temperatures in the ice sheet, was accompanied by a dispersed or ring-like redistribution of the c axes about the vertical. Ultrasonic measurements of vertical and horizontal P wave velocities made at 10-m intervals along the entire length of the GISP2 core fully confirmed the results of the crystallo-optical observations. A return to fine-grained ice coincided with the first appearance of brown, silty ice 13 m above bedrock. Bedrock material consisted of 48 cm of till, including boulders and cobbles, overlying gray biotite granite comprising the true bedrock. There is evidence that disturbed structure in the GISP2 cores begins little more than 70% of the way through the ice sheet. This disturbance increases with depth until it becomes large enough to cast suspicion on features lasting centuries or more in the bottom 10% of the ice sheet.

Gow, A. J.; Meese, D. A.; Alley, R. B.; Fitzpatrick, J. J.; Anandakrishnan, S.; Woods, G. A.; Elder, B. C.

1997-11-01

317

Anchored clathrate waters bind antifreeze proteins to ice  

PubMed Central

The mechanism by which antifreeze proteins (AFPs) irreversibly bind to ice has not yet been resolved. The ice-binding site of an AFP is relatively hydrophobic, but also contains many potential hydrogen bond donors/acceptors. The extent to which hydrogen bonding and the hydrophobic effect contribute to ice binding has been debated for over 30 years. Here we have elucidated the ice-binding mechanism through solving the first crystal structure of an Antarctic bacterial AFP. This 34-kDa domain, the largest AFP structure determined to date, folds as a Ca2+-bound parallel beta-helix with an extensive array of ice-like surface waters that are anchored via hydrogen bonds directly to the polypeptide backbone and adjacent side chains. These bound waters make an excellent three-dimensional match to both the primary prism and basal planes of ice and in effect provide an extensive X-ray crystallographic picture of the AFP?ice interaction. This unobstructed view, free from crystal-packing artefacts, shows the contributions of both the hydrophobic effect and hydrogen bonding during AFP adsorption to ice. We term this mode of binding the “anchored clathrate” mechanism of AFP action.

Garnham, Christopher P.; Campbell, Robert L.; Davies, Peter L.

2011-01-01

318

The anomalously high melting temperature of bilayer ice  

NASA Astrophysics Data System (ADS)

Confinement of water usually depresses its melting temperature. Here we use molecular dynamics simulations to determine the liquid-crystal equilibrium temperature for water confined between parallel hydrophobic or mildly hydrophilic plates as a function of the distance between the surfaces. We find that bilayer ice, an ice polymorph in which the local environment of each water molecule strongly departs from the most stable tetrahedral structure, has the highest melting temperature (Tm) of the series of l-layer ices. The melting temperature of bilayer ice is not only unusually high compared to the other confined ices, but also above the melting point of bulk hexagonal ice. Recent force microscopy experiments of water confined between graphite and a tungsten tip reveal the formation of ice at room temperature [K. B. Jinesh and J. W. M. Frenken, Phys. Rev. Lett. 101, 036101 (2008)]. Our results suggest that bilayer ice, for which we compute a Tm as high as 310 K in hydrophobic confinement, is the crystal formed in those experiments.

Kastelowitz, Noah; Johnston, Jessica C.; Molinero, Valeria

2010-03-01

319

Physics of ice friction  

NASA Astrophysics Data System (ADS)

Although the study of friction has a long history, ice friction has only been investigated during the last century. The basic physical concepts underlying the different friction regimes, such as boundary, mixed, and hydrodynamic friction are also relevant to ice friction. However, these friction regimes must be described with respect to the thickness of the lubricating liquidlike layer on ice. In this review the state of knowledge on the physics of ice friction is discussed. Surface melting theories are introduced. These theories attempt to explain the existence and nature of the liquidlike surface layer on ice at any temperature and without any load applied. Pressure melting, as the long-time explanation for the ease of ice friction, is discussed, together with the prevailing theory of frictional heating. The various laboratory setups for ice friction measurements are presented as well as their advantages and disadvantages. The individual influence of the different parameters on the coefficient of ice friction is discussed; these include the effects of temperature, sliding velocity, normal force exerted by the sliding object, the contact area between ice and slider, relative humidity, and also properties of the slider material such as surface roughness, surface structure, wettability, and thermal conductivity. Finally, the most important ice friction models based on the frictional heating theory are briefly introduced and research directions on the subject of ice friction are discussed.

Kietzig, Anne-Marie; Hatzikiriakos, Savvas G.; Englezos, Peter

2010-04-01

320

GIA Ice Models  

NASA Astrophysics Data System (ADS)

Defining the ice load in a way that avoids circularity is perhaps the most difficult aspect of GIA modeling. At any instant of past time the global land-supported ice load must honor the meltwater curve and the known edges of the ice, but within these constraints the ice mass can be swapped to a considerable extent between the various glacial systems and parts of those systems. In our models, ice thickness is controlled by the effective basal shear stress (EBSS). This parameter incorporates the sub-ice lithology (e.g., whether the ice rests on sediment of crystalline rock), the relative local snow accumulation rate, and the local basal shear strength (which presumably depends most strongly on sub-ice temperature). The effective basal shear stress can be fairly easily modified to construct an ice model. The ice model is evaluated by the geological reasonability of its changes in EBSS in space and time, and by how well it matches measured GIA data. The risk that an incorrect earth model can be forced to fit the GIA data by manipulating the ice model (the circularity mentioned above) can be minimized by evaluating the longest wavelength deformations (peripheral bulge behavior) before proceeding to the shorter wavelength deformations (local emergence variations). The poster will describe how we have proceeded in this fashion to develop a framework for interpreting GIA data in Norway. The poster will be augmented by computer software that compares emergence data to models at specific sites in Norway.

Kachuck, Samuel; Cathles, Larry; Amantov, Aleksey

2013-04-01

321

ICE SLURRY APPLICATIONS.  

PubMed

The role of secondary refrigerants is expected to grow as the focus on the reduction of greenhouse gas emissions increases. The effectiveness of secondary refrigerants can be improved when phase changing media are introduced in place of single phase media. Operating at temperatures below the freezing point of water, ice slurry facilitates several efficiency improvements such as reductions in pumping energy consumption as well as lowering the required temperature difference in heat exchangers due to the beneficial thermo-physical properties of ice slurry. Research has shown that ice slurry can be engineered to have ideal ice particle characteristics so that it can be easily stored in tanks without agglomeration and then be extractable for pumping at very high ice fraction without plugging. In addition ice slurry can be used in many direct contact food and medical protective cooling applications. This paper provides an overview of the latest developments in ice slurry technology. PMID:21528014

Kauffeld, M; Wang, M J; Goldstein, V; Kasza, K E

2010-12-01

322

Heterogeneous ice nucleation ability of crystalline sodium chloride dihydrate particles  

NASA Astrophysics Data System (ADS)

The aerosol and cloud chamber AIDA (Aerosol Interactions and Dynamics in the Atmosphere) of the Karlsruhe Institute of Technology has been used to quantify the deposition mode ice nucleation ability of airborne crystalline sodium chloride dihydrate (NaCl • 2H2O) particles with median diameters between 0.06 and 1.1 µm. For this purpose, expansion cooling experiments with starting temperatures from 235 to 216 K were conducted. Recently, supermicron-sized NaCl • 2H2O particles deposited onto a surface have been observed to be ice-active in the deposition mode at temperatures below 238 K, requiring a median threshold ice saturation ratio of only 1.02 in the range from 238 to 221 K. In AIDA, heterogeneous ice nucleation by NaCl • 2H2O was first detected at a temperature of 227.1 K with a concomitant threshold ice saturation ratio of 1.25. Above that temperature, the crystallized salt particles underwent a deliquescence transition to form aqueous NaCl solution droplets upon increasing relative humidity. At nucleation temperatures below 225 K, the inferred threshold ice saturation ratios varied between 1.15 and 1.20. The number concentration of the nucleated ice crystals was related to the surface area of the seed aerosol particles to deduce the ice nucleation active surface site (INAS) density of the aerosol population as a function of the ice supersaturation. Maximum INAS densities of about 6 ? 1010 m-2 at an ice saturation ratio of 1.20 were found for temperatures below 225 K. These INAS densities are similar to those recently derived for deposition mode ice nucleation on mineral dust particles.

Wagner, Robert; MöHler, Ottmar

2013-05-01

323

Artic ice and drilling structures  

Microsoft Academic Search

The sea ice in the southern Beaufort Sea is examined and subdivided into three zones: the fast ice zone, the seasonal pack-ice zone, an the polar pack ice zone. Each zone requires its own type of system. Existing floating drilling systems include ice-strengthened drill ships, conical drilling systems, and floating ice platforms in deep-water land-fast ice. The development of hydrocarbon

Sodhl

1985-01-01

324

Numerical simulation of water transport and intracellular ice formation for freezing of endothelial cells.  

PubMed

Endothelial cell detachment may cause failure of blood vessel and corneal cryopreservation, and thus successful cryopreservation of endothelial cells is regarded to be the first step to optimize cryopreservation of endothelial cells containing tissues. In this study, the pre-determined biophysical parameters were incorporated into the model for intracellular ice formation (IIF) and the growth of intracellular ice crystals (ICG) to calculate cell water loss, supercooling of intracellular solution, intracellular ice formation and the growth of intracellular ice crystals. The optimal protocols were determined according to the combination effect of both solution injury and IIF injury. PMID:23435709

Zhao, G; Xu, Y; Ding, W P; Hu, M B

325

Ice-cloud particle habit classification using principal components  

NASA Astrophysics Data System (ADS)

A novel automatic classification method is proposed for identifying the habits of large ice-cloud particles and deriving the shape distribution of particle ensembles. This IC-PCA (Ice-crystal Classification with Principal Component Analysis) tool is based on a principal component analysis of selected physical and statistical features of ice-crystal perimeters. The method is developed and tested using image data obtained with a Cloud Particle Imager, but can be applied to other silhouette data as well. For three randomly selected test cases of 222, 200, and 201 crystals from tropical, midlatitude, and arctic ice clouds, the combined classification accuracy of the IC-PCA is 81.1%. Since previous, semiautomatic classification methods are more time-consuming and include a subjective phase, the automatic and objective IC-PCA offers a notable improvement in retrieving the shapes of the individual crystals. As the habit distributions of ice-cloud particles can be applied to computations of radiative impact of cirrus, it is also demonstrated how classification uncertainties propagate into the radiative transfer computations by using the arctic test case as an example. Computations of shortwave radiative fluxes show that the flux differences between clouds of manually and automatically classified crystals can be as large as 10 Wm-2 but also that two manual classifications of the same image data result in even larger differences, implying the need for a systematic and repeatable classification method.

Lindqvist, H.; Muinonen, K.; Nousiainen, T.; Um, J.; McFarquhar, G. M.; Haapanala, P.; Makkonen, R.; Hakkarainen, H.

2012-08-01

326

Effect of storage temperature on quality of light and full-fat ice cream.  

PubMed

Ice cream quality is dependent on many factors including storage temperature. Currently, the industry standard for ice cream storage is -28.9 °C. Ice cream production costs may be decreased by increasing the temperature of the storage freezer, thus lowering energy costs. The first objective of this research was to evaluate the effect of 4 storage temperatures on the quality of commercial vanilla-flavored light and full-fat ice cream. Storage temperatures used were -45.6, -26.1, and -23.3 °C for the 3 treatments and -28.9 °C as the control or industry standard. Ice crystal sizes were analyzed by a cold-stage microscope and image analysis at 1, 19.5, and 39 wk of storage. Ice crystal size did not differ among the storage temperatures of light and full-fat ice creams at 19.5 or 39 wk. An increase in ice crystal size was observed between 19.5 and 39 wk for all storage temperatures except -45.6 °C. Coldness intensity, iciness, creaminess, and storage/stale off-flavor of the light and full-fat ice creams were evaluated at 39 wk of storage. Sensory evaluation indicated no difference among the different storage temperatures for light and full-fat ice creams. In a second study, light and full-fat ice creams were heat shocked by storing at -28.9 °C for 35 wk and then alternating between -23.3 and -12.2 °C every 24h for 4 wk. Heat-shocked ice creams were analyzed at 2 and 4 wk of storage for ice crystal size and were evaluated by the sensory panel. A difference in ice crystal size was observed for light and full-fat ice creams during heat-shock storage; however, sensory results indicated no differences. In summary, storage of light or full-fat vanilla-flavored ice creams at the temperatures used within this research did not affect quality of the ice creams. Therefore, ice cream manufacturers could conserve energy by increasing the temperature of freezers from -28.9 to -26.1 °C. Because freezers will typically fluctuate from the set temperature, usage of -26.1 °C allows for a safety factor, even though storage at -23.3 °C did not affect ice cream quality. PMID:21524511

Buyck, J R; Baer, R J; Choi, J

2011-05-01

327

Description of Ice Cover in View of Ice Load Calculation.  

National Technical Information Service (NTIS)

In this report, we have described the ice cover from an ice load calculation point of view, by describing the different ice features and how they affect the calculation of ice loads. The report commences with a description of the constituents of an ice fi...

K. Englund P. Kujala R. Riska

1996-01-01

328

The role of acids in electrical conduction through ice  

NASA Astrophysics Data System (ADS)

Electrical conduction through meteoric polar ice is controlled by soluble impurities that originate mostly from sea salt, biomass burning, and volcanic eruptions. The strongest conductivity response is to acids, yet the mechanism causing this response has been unclear. Here we elucidate conduction mechanisms in ice using broadband dielectric spectroscopy of meteoric polar ice cores. We find that conduction through polycrystalline polar ice is consistent with Jaccard theory for migration of charged protonic point defects through single ice crystals, except that bulk DC conduction is impeded by grain boundaries. Neither our observations nor modeling using Archie's Law support the hypothesis that grain-boundary networks of unfrozen acids cause significant electrolytic conduction. Common electrical logs of ice cores (by electrical conductivity measurement [ECM] or dielectric profiling [DEP]) and the attenuation of radio waves in ice sheets thus respond to protonic point defects only. This response implies that joint interpretation of electrical and chemical logs can determine impurity partitioning between the lattice and grain boundaries or inclusions. For example, in the Greenland Ice Core Project (GRIP) ice core from central Greenland, on average more than half of the available lattice-soluble impurities (H+, Cl-, NH4+) create defects. Understanding this partitioning could help further resolve the nature of past changes in atmospheric chemistry.

Stillman, David E.; MacGregor, Joseph A.; Grimm, Robert E.

2013-03-01

329

Radio-wave depolarization and scattering within ice sheets: a matrix-based model to link radar and ice-core measurements and its application  

Microsoft Academic Search

Crystal-orientation fabric (COF) has a large influence on ice-sheet flow. Earlier radar studies have shown that COF-based birefringence occurs within ice sheets. Radio-wave scattering in polar ice results from changing physical properties of permittivity and conductivity that arise from differing values of density, acidity and COF. We present an improved mathematical model that can handle all these phenomena together. We

Shuji Fujita; Hideo Maeno; Kenichi Matsuoka

2006-01-01

330

Solid ammonium sulfate aerosols as ice nuclei: a pathway for cirrus cloud formation.  

PubMed

Laboratory measurements support a cirrus cloud formation pathway involving heterogeneous ice nucleation by solid ammonium sulfate aerosols. Ice formation occurs at low ice-saturation ratios consistent with the formation of continental cirrus and an interhemispheric asymmetry observed for cloud onset. In a climate model, this mechanism provides a widespread source of ice nuclei and leads to fewer but larger ice crystals as compared with a homogeneous freezing scenario. This reduces both the cloud albedo and the longwave heating by cirrus. With the global ammonia budget dominated by agricultural practices, this pathway might further couple anthropogenic activity to the climate system. PMID:16946035

Abbatt, J P D; Benz, S; Cziczo, D J; Kanji, Z; Lohmann, U; Möhler, O

2006-08-31

331

Multiwalled ice helixes and ice nanotubes  

PubMed Central

We report six phases of high-density nano-ice predicted to form within carbon nanotubes (CNTs) at high pressure. High-density nano-ice self-assembled within smaller-diameter CNT (17,0) exhibits a double-walled helical structure where the outer wall consists of four double-stranded helixes, which resemble a DNA double helix, and the inner wall is a quadruple-stranded helix. Four other double-walled nano-ices, self-assembled respectively in two larger-diameter CNTs (20,0 and 22,0), display tubular structure. Within CNT (24,0), the confined water can freeze spontaneously into a triple-walled helical nano-ice where the outer wall is an 18-stranded helix and the middle and inner walls are hextuple-stranded helixes.

Bai, Jaeil; Wang, Jun; Zeng, X. C.

2006-01-01

332

Point defects at the ice (0001) surface  

PubMed Central

Using density functional theory we investigate whether intrinsic defects in ice surface segregate. We predict that hydronium, hydroxide, and the Bjerrum L- and D-defects are all more stable at the surface. However, the energetic cost to create a D-defect at the surface and migrate it into the bulk crystal is smaller than its bulk formation energy. Absolute and relative segregation energies are sensitive to the surface structure of ice, especially the spatial distribution of protons associated with dangling hydrogen bonds. It is found that the basal plane surface of hexagonal ice increases the bulk concentration of Bjerrum defects, strongly favoring D-defects over L-defects. Dangling protons associated with undercoordinated water molecules are preferentially injected into the crystal bulk as Bjerrum D-defects, leading to a surface dipole that attracts hydronium ions. Aside from the disparity in segregation energies for the Bjerrum defects, we find the interactions between defect species to be very finely balanced; surface segregation energies for hydronium and hydroxide species and trapping energies of these ionic species with Bjerrum defects are equal within the accuracy of our calculations. The mobility of the ionic hydronium and hydroxide species is greatly reduced at the surface in comparison to the bulk due to surface sites with high trapping affinities. We suggest that, in pure ice samples, the surface of ice will have an acidic character due to the presence of hydronium ions. This may be important in understanding the reactivity of ice particulates in the upper atmosphere and at the boundary layer.

Watkins, Matthew; VandeVondele, Joost; Slater, Ben

2010-01-01

333

Sea Level: Ice Volume Changes  

NSDL National Science Digital Library

In this exercise, students observe simulations of melting sea ice and a melting continental ice sheet in order to investigate the relationship between the melting of the ice and the water level in the tank. The water tanks simulate the world oceans. In the first example, the ice is floating in water. This would be an example of icebergs or Arctic ice floating on the ocean. In the second example the ice lies on a wood structure. The structure simulates a continent. The block of ice on top of the structure simulates ice grounded on top of a continent. This would be an example of ice sheets in Greenland and Antarctica.

334

Elaboration and characterization of a KCl single crystal doped with nanocrystals of a Sb2O3 semiconductor  

NASA Astrophysics Data System (ADS)

Undoped and doped KCl single crystals have been successfully elaborated via the Czochralski (Cz) method. The effects of dopant Sb2O3 nanocrystals on structural and optical properties were investigated by a number of techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDAX) analysis, UV-visible and photoluminescence (PL) spectrophotometers. An XRD pattern of KCl:Sb2O3 reveals that the Sb2O3 nanocrystals are in the well-crystalline orthorhombic phase. The broadening of diffraction peaks indicated the presence of a Sb2O3 semiconductor in the nanometer size regime. The shift of absorption and PL peaks is observed near 334 nm and 360 nm respectively due to the quantum confinement effect in Sb2O3 nanocrystals. Particle sizes calculated from XRD studies agree fairly well with those estimated from optical studies. An SEM image of the surface KCl:Sb2O3 single crystal shows large quasi-spherical of Sb2O3 crystallites scattered on the surface. The elemental analysis from EDAX demonstrates that the KCl:Sb2O3 single crystal is slightly rich in oxygen and a source of excessive quantities of oxygen is discussed.

Bouhdjer, L.; Addala, S.; Chala, A.; Halimi, O.; Boudine, B.; Sebais, M.

2013-04-01

335

The seasonal appearance of ice shelf water in coastal Antarctica and its effect on sea ice growth  

NASA Astrophysics Data System (ADS)

In this paper we report measurements from the first year-round mooring underneath sea ice in McMurdo Sound, Antarctica, which we combine with full-depth ocean profiles to identify the incremental appearance of potentially supercooled ice shelf water (ISW). We investigate the effects of ISW on sea ice using observations of sea ice growth and crystal structure together with under-ice photography. We show that the appearance of ISW at the surface leads to a disruption in the columnar texture of the sea ice, but that persistent growth enhancement occurs only once the entire water column has cooled to the surface freezing point. In doing so, we demonstrate the possibility of inferring the presence of ISW beneath sea ice through crystallographic analysis of cores. These findings will be useful for both modeling and observing the extent of ISW-enhanced ice growth. In addition, we found that the local growth of first-year landfast sea ice only accounted for half of the observed increase in salinity over the water column, which indicates that polynyas are responsible for approximately half of the salt flux into McMurdo Sound.

Mahoney, Andrew R.; Gough, Alexander J.; Langhorne, Patricia J.; Robinson, Natalie J.; Stevens, Craig L.; Williams, Michael M. J.; Haskell, Timothy G.

2011-11-01

336

Study of the Structure and Electrical Properties of the Liquid-Like Layer on Ice/Air, Ice/Solid and Ice/Liquid Interfaces  

NASA Astrophysics Data System (ADS)

We have studied the thickness and electrical properties of the liquid-like layer (LLL) on the interfaces between single crystals of ice on the one side and air, hexane and solids on the other side. NanoScope III and Auto Probe SA scanning force microscopes were used in the SFM experiments. Force-versus-distance curves (FC) were used to determine the LLL thickness and the adhesion force between ice and microscope tips made of silicon and silicon nitride. These measurements were carried out in the temperature range from -1 dgr C to -30 dgrC on the basal and prismatic planes of pure ice and on ice doped with KOH and NaCl. Similar experiments were also directed on ice/hexane interface. We found that the LLL thickness depends strongly on temperature, doping level and an interface material type. The LLL thickness found in SFM experiments was then compared with the thickness of an ice subsurface layer characterized with high-density space charge. The thickness and density of this electric layer were calculated from data on the layer capacitance, C, and conductance, G. To measure the C and G we developed field effect transistors made of ice. The paper discusses the important role that this electrical layer plays in forming the LLL on the ice surface. Work supported by ARO

Petrenko, V. F.; Khusnatdinov, N. N.; Petrenko, V. V.; Nickolayev, O. V.

1996-03-01

337

Fluid dynamics of planetary ices  

Microsoft Academic Search

The role of water ice in the solar system is reviewed from a fluid-dynamical point of view. On Earth and Mars, water ice forms ice sheets, ice caps and glaciers at the surface, which show glacial flow under their own weight. By contrast, water ice is a major constituent of the bulk volume of the icy satellites in the outer

Ralf Greve

2009-01-01

338

Field demonstration of the ICE 250[trademark] Cleaning System  

SciTech Connect

The ICE 250[trademark] Cleaning System was engineered to convert water into small ice particles for use in cleaning and decontamination applications. Ice crystals are produced in a special icemaker and pressured through a hose-nozzle onto the surface to be cleaned. The Rocky Mountain Oilfield Testing Center and Ice Cleaning Systems, Inc., conducted a test of this system at Naval Petroleum Reserve No. 3 to evaluate the system's cleaning capabilities in an oil field environment. Equipment cleaned included an oil storage tank, a rod pumping unit, a road grader, and a wellhead. Contaminants were unrefined sour crude oil, hydraulic fluid, paraffin, and dirt, occurring separately and as mixtures. In all four demonstration cleaning tasks, the ICE 250 System effectively removed surface contaminant mixtures in a timely manner and left no oily residue. A minimal amount of waste moistur2048s generated, thereby reducing cleanup and disposal costs.

Johnston, J.L.; Jackson, L.M.

1999-10-05

339

Field demonstration of the ICE 250{trademark} Cleaning System  

SciTech Connect

The ICE 250{trademark} Cleaning System was engineered to convert water into small ice particles for use in cleaning and decontamination applications. Ice crystals are produced in a special icemaker and pressured through a hose-nozzle onto the surface to be cleaned. The Rocky Mountain Oilfield Testing Center and Ice Cleaning Systems, Inc., conducted a test of this system at Naval Petroleum Reserve No. 3 to evaluate the system's cleaning capabilities in an oil field environment. Equipment cleaned included an oil storage tank, a rod pumping unit, a road grader, and a wellhead. Contaminants were unrefined sour crude oil, hydraulic fluid, paraffin, and dirt, occurring separately and as mixtures. In all four demonstration cleaning tasks, the ICE 250 System effectively removed surface contaminant mixtures in a timely manner and left no oily residue. A minimal amount of waste moisture was generated, thereby reducing cleanup and disposal costs.

Johnston, J.L.; Jackson, L.M.

1999-10-05

340

Anomalous Proton Dynamics in Ice at Low Temperatures  

SciTech Connect

We present incoherent quasielastic neutron scattering measurements on ice Ih (ordinary ice) and Ic (cubic ice) which show the existence of nonharmonic motion of hydrogen at low temperatures, down to 5 K. We show that this dynamics is localized, nonvibrational, and related to the hydrogen disorder since it is absent in ordered ice VIII. A main jump distance of 0.75 A is identified, hence close to the distance between the two possible proton sites along the oxygen-oxygen bond. The dynamics is non-Arrhenius, has a large time rate of 2.7x10{sup 11} s{sup -1}, and affects only a few percent of the total number of hydrogen atoms in the crystal. These results give evidence for the existence of concerted proton tunneling in these ice phases.

Bove, L. E.; Klotz, S. [IMPMC, CNRS-UMR 7590, Universite P and M Curie, F-75252 Paris (France); Paciaroni, A.; Sacchetti, F. [CNR-INFM CRS-Soft, c/o Dipartimento di Fisica, Universita di Perugia, I-06123 Perugia (Italy)

2009-10-16

341

Arctic Sea Ice  

NASA Astrophysics Data System (ADS)

Of all the recent observed changes in the Arctic environment, the reduction of sea ice cover stands out most prominantly. Several independent analysis have established a trend in Arctic ice extent of -3% per decade from the late 1970s to the late 1990s, with a more pronounced trend in summer. The overall downward trend in ice cover is characterized by strong interannual variability, with a low September ice extent in one year typically followed by recovery the next September. Having two extreme minimum years, such as what was observed in 2002 and 2003 is unusual. 2004 marks the third year in a row of substantially below normal sea ice cover in the Arctic. Early summer 2004 appeared unusual in terms of ice extent, with May a record low for the satellite period (1979-present) and June also exhibiting below normal ice extent. August 2004 extent is below that of 2003 and large reductions in ice cover are observed once again off the coasts of Siberia and Alaska and the Greenland Sea. Neither the 2002 or 2003 anomaly appeared to be strongly linked to the positive phase of the Arctic Oscillation (AO) during the preceding winter. Similarly, the AO was negative during winter 2003/2004. In the previous AO framework of Rigor et al (2002), a positive winter AO implied preconditioning of the ice cover to extensive summer decay. In this hypothesis, the AO does not explain all aspects of the recent decline in Arctic ice cover, such as the extreme minima of 2002, 2003 and 2004. New analysis by Rigor and Wallace (2004) suggest that the very positive AO state from 1989-1995 can explain the recent sea ice minima in terms of changes in the Arctic surface wind field associated with the previous high AO state. However, it is also reasonable to expect that a general decrease in ice thickness accompanying warming would manifest itself as greater sensitivity of the ice pack to wind forcings and albedo feedbacks. The decrease in multiyear ice and attendant changes in ice thickness distribution could in turn precondition the Arctic ice cover to further reductions in the subsequent summer(s) regardless if the summer temperatures were anomalously warm. The NSIDC Sea Ice Index (http://nsidc.org/data/seaice_index/) can be used to view trends and anomalies from 1979 on.

Stroeve, J. C.; Fetterer, F.; Knowles, K.; Meier, W.; Serreze, M.; Arbetter, T.

2004-12-01

342

Analysis of polarization radar returns from ice clouds  

Microsoft Academic Search

Using a modified T-matrix code, some polarimetric single-scattering radar parameters (Zh,v, LDRh,v, ?hv, ZDR and ?hv) from populations of ice crystals in ice phase at 94 GHz, modeled with axisymmetric prolate and oblate spheroidal shapes for a ?-size distribution with different ? parameter (?=0, 1, 2) and characteristic dimension Lm varying from 0.1 to 1.8 mm, have been computed. Some

A. Battaglia; O. Sturniolo; F. Prodi

2001-01-01

343

Engine Icing Test Simulation  

NASA Video Gallery

This new engine icing ground test simulation, now with sound, uses cutaways to show what a future engine icing test would look like at NASA's Glenn Research Center. The ground tests will be done to safely observe and find design solutions to a type of ice that can build up on engine blades. The test starts with air flow at subsonic speeds; then a mist is sprayed from bars at the end of the tunnel. In the animation, one set of blades remains stationary to show how it's believed ice builds up on a blade. The ice could then break off, causing engine power loss or damage. › Read More About Fire and Ice Mission

Christopher O

2012-05-01

344

Ice-Nucleating Bacteria  

NASA Astrophysics Data System (ADS)

Since the discovery of ice-nucleating bacteria in 1974 by Maki et al., a large number of studies on the biological characteristics, ice-nucleating substance, ice nucleation gene and frost damage etc. of the bacteria have been carried out. Ice-nucleating bacteria can cause the freezing of water at relatively warm temperature (-2.3°C). Tween 20 was good substrates for ice-nucleating activity of Pseudomonas fluorescens KUIN-1. Major fatty acids of Isolate (Pseudomonas fluorescens) W-11 grown at 30°C were palmitic, cis-9-hexadecenoic and cis-11-octadecenoic which amounted to 90% of the total fatty acids. Sequence analysis shows that an ice nucleation gene from Pseudomonas fluorescens is related to the gene of Pseudomonas syringae.

Obata, Hitoshi

345

Incorporation of crude and fuel oil into salt-and freshwater ice  

SciTech Connect

North Slope Crude, no. 2 fuel oil, and vegetable oil were each released under columnar freshwater and saltwater ice grown in a laboratory coldroom. Because the thermal conductivity of all the oils is lower than that of water or ice, thinner ice grew under the oil and resulted in a concave ice/water interface. Both the fresh and saline ice encapsulated the oils, but the saline ice did so more slowly. Thin sections of the ice blocks containing the crude and fuel oils show how the columnar ice crystals bend around and under the oil patches. The movement of the vegetable oil during melting was photographed, and spectral reflectance measurements of the ice surface were made to determine if the oil could be detected remotely. Although we could detect the presence of oil under 10 cm of ice, under field conditions the optical detectability of oil will depend upon the depth of the oil within the ice, the type of ice, and the contrast between the under-ice oil and the background against which it is being viewed.

Taylor, S.; Perron, N.

1995-02-01

346

Kagome spin ice  

NASA Astrophysics Data System (ADS)

Spin ice in magnetic pyrochlore oxides is a peculiar magnetic state. Like ordinary water ice, these materials are in apparent violation with the third law of thermodynamics, which dictates that the entropy of a system in thermal equilibrium vanishes as its temperature approaches absolute zero. In ice, a "zero-point" entropy is retained down to low temperatures thanks to a high number of low-energy positions of hydrogen ions associated with the Bernal-Fowler ice-rules. Spins in pyrochlore oxides Ho2Ti 2O7 and Dy2Ti2O7 exhibit a similar degeneracy of ground states and thus also have a sizable zero-point entropy. A recent discovery of excitations carrying magnetic charges in pyrochlore spin ice adds another interesting dimension to these magnets. This thesis is devoted to a theoretical study of a two-dimensional version of spin ice whose spins reside on kagome, a lattice of corner-sharing triangles. It covers two aspects of this frustrated classical spin system: the dynamics of artificial spin ice in a network of magnetic nanowires and the thermodynamics of crystalline spin ice. Magnetization dynamics in artificial spin ice is mediated by the emission, propagation and absorption of domain walls in magnetic nanowires. The dynamics shows signs of self-organized behavior such as avalanches. The theoretical model compares favorably to recent experiments. The thermodynamics of the microscopic version of spin ice on kagome is examined through analytical calculations and numerical simulations. The results show that, in addition to the high-temperature paramagnetic phase and the low-temperature phase with magnetic order, spin ice on kagome may have an intermediate phase with fluctuating spins and ordered magnetic charges. This work is concluded with a calculation of the entropy of kagome spin ice at zero temperature when one of the sublattices is pinned by an applied magnetic field and the system breaks up into independent spin chains, a case of dimensional reduction.

Mellado, Paula

347

Laboratory studies of cometary ice analogues  

NASA Astrophysics Data System (ADS)

Laboratory studies were performed in order to simulate the physico-chemical processes that are likely to occur in the near surface layers of short and intermediate period comets. Pure H2O ice as well as CO:H2O, CO2:H2O, CH4:H2O, CO:CO2:H2O, and NH3:H2O ice mixtures were studied in the temperature range between 10 and 180 K. The evolution of the composition of ice mixtures, the crystallization of H2O ice as well as the formation and decompostion of clathrate hydrate by different processes were studied as a function of temperature and time. Using the results together with numerical modeling, predictions are made about the survival of amorphous ice, CO, CO2, CH4, and NH3 in the near surface layers of short period comets. The likeliness of finding clathrate and molecular hydrates is discussed. It is proposed that the analytical methods developed here could be fruitfully adapted to the analysis of returned comet samples.

Schmitt, B.; Espinasse, S.; Grim, R. J. A.; Greenberg, J. M.; Klinger, J.

1989-12-01

348

A van der Waals density functional study of ice Ih.  

PubMed

Density functional theory with the van der Waals density functional (vdW-DF) is used to calculate equilibrium crystal structure, binding energy, and bulk modulus of ice Ih. It is found that although it overestimates the equilibrium volume, vdW-DF predicts accurate binding energy of ice Ih, as compared with high level quantum chemistry calculations and experiment. Inclusion of the nonlocal correlation, i.e., van der Waals interaction, leads to an overall improvement over the standard generalized gradient approximation in describing water ice. PMID:21142304

Hamada, Ikutaro

2010-12-01

349

A van der Waals density functional study of ice Ih  

NASA Astrophysics Data System (ADS)

Density functional theory with the van der Waals density functional (vdW-DF) is used to calculate equilibrium crystal structure, binding energy, and bulk modulus of ice Ih. It is found that although it overestimates the equilibrium volume, vdW-DF predicts accurate binding energy of ice Ih, as compared with high level quantum chemistry calculations and experiment. Inclusion of the nonlocal correlation, i.e., van der Waals interaction, leads to an overall improvement over the standard generalized gradient approximation in describing water ice.

Hamada, Ikutaro

2010-12-01

350

INFORMATION NEEDS WHEN ESTIMATING ICE JAM FLOODS AND ICE RUNS  

Microsoft Academic Search

Ice jams are a major cause of floods in mid- to high-latitude regions. This paper discusses the information needs in estimating\\u000a ice jam floods and for forecasting major ice runs (sometimes called ice gorges) that may precede ice cover formation and jamming,\\u000a or be consequent to the sudden collapse of a jam. It outlines how ice-jam floods are influenced not

ROBERT ETTEMA

351

Simulation of the interaction of acetone with ice: (0001) surface, bulk ice and small-angle grain boundaries  

NASA Astrophysics Data System (ADS)

Local structures and energies are calculated for the interactions of acetone with ice Ih by force-field and ab-initio methods. Three interaction sites are investigated: 1) (0001) surface of ice 2) ice bulk (with the acetone substituting one or more water molecules as point defect) 3) small-angle grain boundaries in ice (2D-lattice defects) Ice Ih is the stable ice polymorph at atmospheric conditions.[1]When ice (snow/hail/graupel) begins to form in the troposphere, volatile organic compounds will be adsorbed at the surface or incorporated into the crystals. Acetone (CH3)2CO is one of the most prominent organic pollutants in the atmosphere. For the force-field calculations a modified Dreiding force field[2] was used. Results[3] 1) An acetone molecule adsorbed on the (0001) surface of ice forms two hydrogen bonds between the CO group and two dangling O-H bonds (i.e. bonds which stick out from the surface) of two water molecules. The calculated adsorption enthalpy corresponds well with experimentally determined values. This geometry was confirmed by ab-initio calculations. 2) In bulk ice, the acetone molecule replaces only one water molecule, and distorts the surrounding ice structure. 3) The position of an acetone molecule at a small-angle grain boundary or at a similar lattice defect is energetically more favourable than incorporation in bulk ice. [1] V. F. Petrenko and R. W. Whitworth, Physics of Ice, Oxford University Press Inc., New York, 1999. [2] S. L. Mayo, B. D. Olafson, W. A. Goddard III, J. Phys. Chem. 1990, 94, 8897-8909. [3] S. M. Hammer, R. Panisch, M. Kobus, J. Glinnemann, M. U. Schmidt, CrystEngComm 2009, accepted.

Hammer, S. M.; Panisch, R.; Kobus, M.; Glinnemann, J.; Schmidt, M. U.

2009-04-01

352

Expression and Characterization of an Ice Binding Protein from a Bacterium Isolated at a Depth of 3,519 Meters in the Vostok Ice Core, Antarctica  

NASA Astrophysics Data System (ADS)

The cryopreservation of microorganisms in ancient glacial ice is possible if lethal levels of macromolecular damage are not incurred and cellular integrity is not compromised via intracellular ice formation or recrystallization. There are numerous examples of cold-adapted species that prevent or limit ice crystal growth by producing ice-binding proteins (IBP). Previously, a bacterium (isolate 3519-10; Flavobacteriaceae family) recovered from a depth of 3,519 meters below the surface in the Vostok ice core was shown to produce and secrete an IBP that inhibits the recrystallization of ice. To explore the phenotypic advantage that IBPs confer to ice-entrapped cells, experiments were designed to examine the expression of 3519-10's IBP gene and protein at different temperatures, assess the effect of the IBP on bacterial viability in ice, and determine how the IBP influences the physical structure of the ice. Total RNA isolated from aerobic cultures grown at temperatures between 4C to 25C and analyzed by reverse transcription-PCR indicated constitutive expression of the IBP gene. Additionally, SDS-PAGE analysis of 3519-10's extracellular proteins revealed a polypeptide corresponding to the predicted size of the 54 kDa IBP at all temperatures tested. The total extracellular protein fraction was subsequently used in assays with Escherichia coli to examine the effect of the IBP on bacterial survival in warm ice (-5C) and after freeze-thaw cycling. In the presence of 100 ?g mL-1 of extracellular protein from 3519-10, the survival of E. coli was increased by greater than 100-fold; however, the survival of E. coli suspensions containing the same concentration of bovine serum albumin was not significantly different than controls (p<0.05). Microscopic analysis of ice formed in the presence of the IBP indicated that in a mm^2 field of view, there were 5 times as many crystals as in ice formed in the presence of washed 3519-10 cells and non-IBP producing bacteria, and 10 times as many crystals as in particle-free deionized water. Presumably, the effect that the IBP has on bacterial viability and ice crystal structure is due to its activity as an inhibitor of ice recrystallization. Although a myriad of molecular adaptations are likely to play a role in bacterial persistence under frozen conditions, the ability of 3519-10's IBP to control ice crystal structure may provide one explanation for its successful survival deep within the Antarctic ice sheet for thousands of years.

Christner, B. C.; Achberger, A.; Brox, T. I.; Skidmore, M. L.

2011-12-01

353

ICE-SHELF RESPONSE TO ICE-STREAM DISCHARGE FLUCTUATIONS: 11. IDEAL RECTANGULAR ICE SHELF  

Microsoft Academic Search

Ice-sh elf thick ness and velocity anomalies resulting from ice -stream discharge fluctu ations are calc ulated for an ideal ice shelf fed by a single ice stream and confined within a rectangular coastal geometry. Ice-sh elf response to perio dic forcing is found to be linear (thickness and velocity anomalies oscillate at the forcing frequency, and res ponse scales

MANFRED A. LANGE

1988-01-01

354

Ultrafast superheating and melting of bulk ice  

Microsoft Academic Search

The superheating of a solid to a temperature beyond its melting point, without the solid actually melting, is a well-known phenomenon. It occurs with many substances, particularly those that can readily be produced as high-quality crystals. In principle, ice should also be amenable to superheating. But the complex three-dimensional network of hydrogen bonds that holds water molecules together and gives

H. Iglev; M. Schmeisser; K. Simeonidis; A. Thaller; A. Laubereau

2006-01-01

355

Ice nucleation on BaF2(111).  

PubMed

The mechanism of heterogeneous ice nucleation on inorganic substrates is not well understood despite work on AgI and other materials over the past 50 years. We have selected BaF(2) as a model substrate for study since its (111) surface makes a near perfect match with the lattice of the basal face of I(h) ice and would appear to be an ideal nucleating agent. Two series of experiments were undertaken. In one, nucleation of thin film water formed from deposition of vapor on BaF(2)(111) faces was explored with the finding that supercooling to -30 degrees C was required before freezing occurred. In the other series, nucleation of liquid water on submerged BaF(2) crystals was studied. Here supercooling to -15 degrees C was needed before ice formed. The reason why BaF(2) is such a poor nucleating agent contains clues to realistic mechanisms of heterogeneous nucleation. Our explanation of these results follows the model of Fletcher [J. Chem. Phys. 29, 572 (1958)] who showed that heterogeneous ice nucleating ability depends on how well ice wets a substrate. In this view, a smooth BaF(2)(111) face is poor at nucleation because ice only partially wets its surface. In an extension of Fletcher's model, our calculations, consistent with the experimental results demonstrate that the pitting of a submerged BaF(2) crystal dramatically improves its ice nucleating ability. PMID:15740398

Conrad, Peter; Ewing, George E; Karlinsey, Robert L; Sadtchenko, Vlad

2005-02-01

356

Ice barrier construction  

SciTech Connect

A method is provided for constructing spray ice barriers to protect offshore structures in a frigid body of water from mobile ice, waves and currents. Water is withdrawn from the body of water and is sprayed through ambient air which is below the freezing temperature of the water so that a substantial amount of the water freezes as it passes through the air. The sprayed water is directed to build up a mass of ice having a size and shape adapted to protect the offshore structure. Spray ice barriers can also be constructed for the containment of pollutant spills.

Finucane, R. G.; Jahns, H. O.

1985-06-18

357

An ice lithography instrument  

NASA Astrophysics Data System (ADS)

We describe the design of an instrument that can fully implement a new nanopatterning method called ice lithography, where ice is used as the resist. Water vapor is introduced into a scanning electron microscope (SEM) vacuum chamber above a sample cooled down to 110 K. The vapor condenses, covering the sample with an amorphous layer of ice. To form a lift-off mask, ice is removed by the SEM electron beam (e-beam) guided by an e-beam lithography system. Without breaking vacuum, the sample with the ice mask is then transferred into a metal deposition chamber where metals are deposited by sputtering. The cold sample is then unloaded from the vacuum system and immersed in isopropanol at room temperature. As the ice melts, metal deposited on the ice disperses while the metals deposited on the sample where the ice had been removed by the e-beam remains. The instrument combines a high beam-current thermal field emission SEM fitted with an e-beam lithography system, cryogenic systems, and a high vacuum metal deposition system in a design that optimizes ice lithography for high throughput nanodevice fabrication. The nanoscale capability of the instrument is demonstrated with the fabrication of nanoscale metal lines.

Han, Anpan; Chervinsky, John; Branton, Daniel; Golovchenko, J. A.

2011-06-01

358

An ice lithography instrument  

PubMed Central

We describe the design of an instrument that can fully implement a new nanopatterning method called ice lithography, where ice is used as the resist. Water vapor is introduced into a scanning electron microscope (SEM) vacuum chamber above a sample cooled down to 110 K. The vapor condenses, covering the sample with an amorphous layer of ice. To form a lift-off mask, ice is removed by the SEM electron beam (e-beam) guided by an e-beam lithography system. Without breaking vacuum, the sample with the ice mask is then transferred into a metal deposition chamber where metals are deposited by sputtering. The cold sample is then unloaded from the vacuum system and immersed in isopropanol at room temperature. As the ice melts, metal deposited on the ice disperses while the metals deposited on the sample where the ice had been removed by the e-beam remains. The instrument combines a high beam-current thermal field emission SEM fitted with an e-beam lithography system, cryogenic systems, and a high vacuum metal deposition system in a design that optimizes ice lithography for high throughput nanodevice fabrication. The nanoscale capability of the instrument is demonstrated with the fabrication of nanoscale metal lines.

Han, Anpan; Chervinsky, John; Branton, Daniel; Golovchenko, J. A.

2011-01-01

359

An ice lithography instrument  

SciTech Connect

We describe the design of an instrument that can fully implement a new nanopatterning method called ice lithography, where ice is used as the resist. Water vapor is introduced into a scanning electron microscope (SEM) vacuum chamber above a sample cooled down to 110 K. The vapor condenses, covering the sample with an amorphous layer of ice. To form a lift-off mask, ice is removed by the SEM electron beam (e-beam) guided by an e-beam lithography system. Without breaking vacuum, the sample with the ice mask is then transferred into a metal deposition chamber where metals are deposited by sputtering. The cold sample is then unloaded from the vacuum system and immersed in isopropanol at room temperature. As the ice melts, metal deposited on the ice disperses while the metals deposited on the sample where the ice had been removed by the e-beam remains. The instrument combines a high beam-current thermal field emission SEM fitted with an e-beam lithography system, cryogenic systems, and a high vacuum metal deposition system in a design that optimizes ice lithography for high throughput nanodevice fabrication. The nanoscale capability of the instrument is demonstrated with the fabrication of nanoscale metal lines.

Han, Anpan [Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States); Chervinsky, John [School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States); Branton, Daniel [Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138 (United States); Golovchenko, J. A. [Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States); School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States)

2011-06-15

360

Ice age paleotopography  

SciTech Connect

A gravitationally self-consistent theory of postglacial relative sea level change is used to infer the variation of surface ice and water cover since the Last Glacial Maximum (LGM). The results show that LGM ice volume was approximately 35 percent lower than suggested by the CLIMAP reconstruction and the maximum heights of the main Laurentian and Fennoscandian ice complexes are inferred to have been commensurately lower with respect to sea level. Use of these Ice Age boundary conditions in atmospheric general circulation models will yield climates that differ significantly from those previously inferred on the basis of the CLIMAP data set.

Peltier, W.R. (Univ. of Toronto, Ontario (Canada))

1994-07-08

361

Nonequilibrium air clathrate hydrates in Antarctic ice: a paleopiezomdter for polar ice caps.  

PubMed

"Craigite," the mixed-air clathrate hydrate found in polar ice caps below the depth of air-bubble stability, is a clathrate mixed crystal of approximate composition (N2O2).6H2O. Recent observations on the Byrd Station Antarctic core show that the air hydrate is present at a depth of 727 m, well above the predicted depth for the onset of hydrate stability. We propose that the air hydrate occurs some 100 m above the equilibrium phase boundary at Byrd Station because of "piezometry"--i.e., that the anomalous depth of hydrate occurrence is a relic of a previous greater equilibrium depth along the flow trajectory, followed by vertical advection of ice through the local phase-boundary depth. Flowline trajectories in the ice based on numerical models show that the required vertical displacement does indeed occur just upstream of Byrd Station. Air-hydrate piezometry can thus be used as a general parameter to study the details of ice flow in polar ice caps and the metastable persistence of the clathrate phase in regions of upwelling blue ice. PMID:11607442

Craig, H; Shoji, H; Langway, C C

1993-12-01

362

Arctic Sea Ice Maximum 2011  

NASA Video Gallery

AMSR-E Arctic Sea Ice: September 2010 to March 2011: Scientists tracking the annual maximum extent of Arctic sea ice said that 2011 was among the lowest ice extents measured since satellites began collecting the data in 1979.

Holly Zell

2011-03-29

363

New insights into ice growth and melting modifications by antifreeze proteins  

PubMed Central

Antifreeze proteins (AFPs) evolved in many organisms, allowing them to survive in cold climates by controlling ice crystal growth. The specific interactions of AFPs with ice determine their potential applications in agriculture, food preservation and medicine. AFPs control the shapes of ice crystals in a manner characteristic of the particular AFP type. Moderately active AFPs cause the formation of elongated bipyramidal crystals, often with seemingly defined facets, while hyperactive AFPs produce more varied crystal shapes. These different morphologies are generally considered to be growth shapes. In a series of bright light and fluorescent microscopy observations of ice crystals in solutions containing different AFPs, we show that crystal shaping also occurs during melting. In particular, the characteristic ice shapes observed in solutions of most hyperactive AFPs are formed during melting. We relate these findings to the affinities of the hyperactive AFPs for the basal plane of ice. Our results demonstrate the relation between basal plane affinity and hyperactivity and show a clear difference in the ice-shaping mechanisms of most moderate and hyperactive AFPs. This study provides key aspects associated with the identification of hyperactive AFPs.

Bar-Dolev, Maya; Celik, Yeliz; Wettlaufer, J. S.; Davies, Peter L.; Braslavsky, Ido

2012-01-01

364

New insights into ice growth and melting modifications by antifreeze proteins.  

PubMed

Antifreeze proteins (AFPs) evolved in many organisms, allowing them to survive in cold climates by controlling ice crystal growth. The specific interactions of AFPs with ice determine their potential applications in agriculture, food preservation and medicine. AFPs control the shapes of ice crystals in a manner characteristic of the particular AFP type. Moderately active AFPs cause the formation of elongated bipyramidal crystals, often with seemingly defined facets, while hyperactive AFPs produce more varied crystal shapes. These different morphologies are generally considered to be growth shapes. In a series of bright light and fluorescent microscopy observations of ice crystals in solutions containing different AFPs, we show that crystal shaping also occurs during melting. In particular, the characteristic ice shapes observed in solutions of most hyperactive AFPs are formed during melting. We relate these findings to the affinities of the hyperactive AFPs for the basal plane of ice. Our results demonstrate the relation between basal plane affinity and hyperactivity and show a clear difference in the ice-shaping mechanisms of most moderate and hyperactive AFPs. This study provides key aspects associated with the identification of hyperactive AFPs. PMID:22787007

Bar-Dolev, Maya; Celik, Yeliz; Wettlaufer, J S; Davies, Peter L; Braslavsky, Ido

2012-07-11

365

Ice-binding structure and mechanism of an antifreeze protein from winter flounder.  

PubMed

Antifreeze proteins provide fish with protection against the freezing effect of polar environments by binding to ice surfaces and inhibiting growth of ice crystals. We present the X-ray crystal structure at 1.5 A resolution of a lone alpha-helical antifreeze protein from winter flounder, which provides a detailed look at its ice-binding features. These consist of four repeated ice-binding motifs, the side chains of which are inherently rigid or restrained by pair-wise side-chain interactions to form a flat binding surface. Elaborate amino- and carboxy-terminal cap structures are also present, which explain the protein's rich alpha-helical content in solution. We propose an ice-binding model that accounts for the binding specificity of the antifreeze protein along the <0112> axes of the (2021) ice planes. PMID:7760940

Sicheri, F; Yang, D S

1995-06-01

366

Theory of shallow ice shelves  

Microsoft Academic Search

   Ice shelves consist of two layers, an upper layer of meteoric ice nourished by the flow from the connected inland ice and\\u000a precipitation, and a lower layer of marine ice that is built by the melting and freezing processes at the ice-ocean interface\\u000a and the accretion of frazil ice from the underlying ocean. The governing thermomechanical equations in the

M. Weis; R. Greve; K. Hutter

1999-01-01

367

Artic ice and drilling structures  

SciTech Connect

The sea ice in the southern Beaufort Sea is examined and subdivided into three zones: the fast ice zone, the seasonal pack-ice zone, an the polar pack ice zone. Each zone requires its own type of system. Existing floating drilling systems include ice-strengthened drill ships, conical drilling systems, and floating ice platforms in deep-water land-fast ice. The development of hydrocarbon resources in the Arctic presents great challenges to engineers, since the structures are required to operate safely under various conditions. Significant progress has yet to be made in understanding the behavior of ice.

Sodhl, D.S.

1985-04-01

368

Elastic constants of phases III, V and VI of ice by Brillouin spectroscopy  

Microsoft Academic Search

Large (~0.3 cm3) high quality single crystal samples of H2O ice III, Ice V, and Ice VI have been produced in a high pressure cell. The cell was pressurized by means of hydraulic fluid and specifically designed so that the samples could be rotated about the vertical without having to reduce the pressure. Liquid water was initially placed inside the

Christopher Alexander Tulk

1997-01-01

369

Properties of sea ice and overlying snow in the Southern Sea of Okhotsk  

Microsoft Academic Search

The general properties of sea ice and overlying snow in the southern Sea of Okhotsk were examined during early February of\\u000a 2003 to 2005 with the P\\/V “Soya”. Thin section analysis of crystal structure revealed that frazil ice (48% of total core length)\\u000a was more prevalent than columnar ice (39%) and that stratigraphic layering was prominent with a mean layer

Takenobu Toyota; Shinya Takatsuji; Kazutaka Tateyama; Kazuhiro Naoki; Kay I. Ohshima

2007-01-01

370

X-Ray Diffraction Topographic Studies of Antarctic Deep Core Ice  

Microsoft Academic Search

X-ray diffraction topographs of Antarctic deep core ice revealed mosaic strctures in comparatively large single crystals near the bottom of a 2000 m ice sheet. Strain fields around thin cleavage cracks produced on the relaxation process of the ice exhibited characteristic ``Butterfly-wing'' contrasts on the topograph scanned on (0001) with {11\\\\bar{2}0} reflection. Three types of characteristic contrasts are well interpreted

Hitoshi Shoji; Akira Higashi

1978-01-01

371

Ice Core Investigations  

NSDL National Science Digital Library

What can glaciers tell us about volcanoes and atmospheric conditions? How does this information relate to our understanding of climate change? Ice Core Investigations is an original and innovative activity that explores these types of questions. It brings together popular science issues such as research, climate change, ice core drilling, and air pollution to create a meaningful science learning experience for students.

Krim, Jessica; Brody, Michael

2008-09-01

372

Antarctica: Sea Ice  

NSDL National Science Digital Library

This video segment, adapted from a NOVA broadcast, shows how sea ice forms in the Southern Ocean around Antarctica and how its seasonal fluctuation dramatically changes the continent. The segment, two minutes thirty-five seconds in length, includes rare footage of the destruction of the British ship 'Endurance', trapped and crushed by sea ice in 1914.

2010-09-30

373

Cleaning With Ice  

NSDL National Science Digital Library

Scattered nuclear laboratories around the country have left a legacy of toxic waste to seep into the ground. This radio broadcast discusses a way to clean up the soil, using simple ice. This can be done since water freezes pure, a property used to make ice beer. The clip is 2 minutes in length.

374

Antarctic Ice Velocity Data  

NSDL National Science Digital Library

The National Snow and Ice Data Center (NSIDC) (described in the October 2, 1998 Scout Report) provides the Antarctic Ice Velocity Data set. This set contains large satellite image maps along with latitude, longitude, speed, bearing, and error ranges data. Data for this set is available via FTP.

1999-01-01

375

Antarctica: Sea Ice  

NSDL National Science Digital Library

This video segment, adapted from a NOVA broadcast, shows how sea ice forms in the Southern Ocean around Antarctica and how its seasonal fluctuation dramatically changes the continent. The segment, two minutes thirty-five seconds in length, includes rare footage of the destruction of the British ship 'Endurance', trapped and crushed by sea ice in 1914.

376

Ice Core Investigations  

ERIC Educational Resources Information Center

|What can glaciers tell us about volcanoes and atmospheric conditions? How does this information relate to our understanding of climate change? Ice Core Investigations is an original and innovative activity that explores these types of questions. It brings together popular science issues such as research, climate change, ice core drilling, and air…

Krim, Jessica; Brody, Michael

2008-01-01

377

Making an Ice Core.  

ERIC Educational Resources Information Center

|Explains an activity in which students construct a simulated ice core. Materials required include only a freezer, food coloring, a bottle, and water. This hands-on exercise demonstrates how a glacier is formed, how ice cores are studied, and the nature of precision and accuracy in measurement. Suitable for grades three through eight. (Author/PVD)|

Kopaska-Merkel, David C.

1995-01-01

378

A Changing Ice Sheet  

NSDL National Science Digital Library

This animation shows the retreat of glacial ice, changes in the shoreline, and the disappearance of the land bridge across the Bering Sea which occurred at the end of the last ice age, beginning just over 21,000 years ago.

379

Ice under Pressure  

Microsoft Academic Search

THERE is a point in Dr. Carnelley's letter (NATURE, vol. xxii. p. 435) which I have been hoping to see cleared up by subsequent letters. He says, ``In order to convert a solid into a liquid the pressuremust be abovea certain point,'' and goes on to describe some experiments with ice, implying that ice is in this respect a typical

1880-01-01

380

Greenland Ice Sheet  

NSDL National Science Digital Library

A study of the Greenland ice sheet has shown it is melting faster than expected. This radio broadcast describes how the ice sheet thickness is measured and how this factors into the fight over whether pollution is raising global temperatures. The broadcast from 1999 is 3 minutes and 46 seconds in length.

381

Investigating Ice Worlds  

NSDL National Science Digital Library

In this activity about the solar system, learners use various light sources to examine ice with different components to understand how NASA studies planets and moons from space. This detailed lesson guide includes background information about distant ice worlds in the outer solar system, literature connections, instructions for a pre-activity demonstration, modified activities by age, tips, discussion questions, and resources.

Education, Carnegie I.

2011-01-01

382

Fire beneath the ice  

Microsoft Academic Search

A volcano discovered six years ago by researchers Blankenship and Bell under Antarctica poses questions about a potential climatic catastrophe. The researchers claim that the volcano is still active, erupting occasionally and growing. A circular depression on the surface of the ice sheet has ice flowing into it and is used to provide a portrait of the heat source. The

Monastersky

1993-01-01

383

Mountain of Ice: If the Ice Melts  

NSDL National Science Digital Library

This interactive resource portrays what might happen to world coastlines if entire sections of the Antarctic Ice Sheet were to melt. Viewers can see how much land area might be flooded by a relatively modest 17-foot rise in sea level (represented by the collapse of the Western Antarctic Ice Sheet), or a more severe 170-foot rise, represented by the collapse of the Eastern Antarctic Ice Sheet. By comparing present-day coastline positions with those from the peak glacial advance 20,000 years ago, it is possible to appreciate how much water is contained in glaciers, the importance of monitoring their condition, and the impact accelerated global warming could one day have on sea level. A background essay and list of discussion questions are also provided.

384

Optically thin ice clouds in Arctic : Formation processes  

NASA Astrophysics Data System (ADS)

Arctic ice cloud formation during winter is poorly understood mainly due to lack of observations and the remoteness of this region. Their influence on Northern Hemisphere weather and climate is of paramount importance, and the modification of their properties, linked to aerosol-cloud interaction processes, needs to be better understood. Large concentration of aerosols in the Arctic during winter is associated to long-range transport of anthropogenic aerosols from the mid-latitudes to the Arctic. Observations show that sulphuric acid coats most of these aerosols. Laboratory and in-situ measurements show that at cold temperature (<-30°C), acidic coating lowers the freezing point and deactivates ice nuclei (IN). Therefore, the IN concentration is reduced in these regions and there is less competition for the same available moisture. As a result, large ice crystals form in relatively small concentrations. It is hypothesized that the observed low concentration of large ice crystals in thin ice clouds is linked to the acidification of aerosols. Extensive measurements from ground-based sites and satellite remote sensing (CloudSat and CALIPSO) reveal the existence of two types of extended optically thin ice clouds (TICs) in the Arctic during the polar night and early spring. The first type (TIC-1) is seen only by the lidar, but not the radar, and is found in pristine environment whereas the second type (TIC-2) is detected by both sensors, and is associated with high concentration of aerosols, possibly anthropogenic. TIC-2 is characterized by a low concentration of ice crystals that are large enough to precipitate. To further investigate the interactions between TICs clouds and aerosols, in-situ, airborne and satellite measurements of specific cases observed during the POLARCAT and ISDAC field experiments are analyzed. These two field campaigns took place respectively over the North Slope of Alaska and Northern part of Sweden in April 2008. Analysis of cloud type can be done from these observations, and a first classification has been performed. Results are then compared to satellite data analysis. The new retrieval scheme of Delanoë and Hogan, which combines CloudSat radar and CALIPSO lidar measurements, is used to recover profiles of the properties of ice clouds such as the visible extinction coefficient, the ice water content and the effective radius of ice crystals. Comparisons with in situ airborne measurements allow to validate this retrieval method, and thus the clouds and aerosols properties, for selected cases whereflights are coordinated with the satellite overpasses. A comparison of combined CloudSat/CALIPSO microphysical properties retrievals with airborne ice clouds measurements will be presented. The Lagrangian Particle Dispersion Model FLEXPART is use to study the origin of observed air masses, to be linked with pollution sources.

Jouan, C.; Girard, E.; Pelon, J.; Blanchet, J.; Wobrock, W.; Gultepe, I.; Gayet, J.; Delanoë, J.; Mioche, G.; Adam de Villiers, R.

2010-12-01

385

Sea Ice 2000 - 2008  

NSDL National Science Digital Library

This site features a video that illustrates both seasonal patterns and long-term changes in sea ice distribution across the Arctic Ocean. It draws data from two satellite instruments that measure emitted microwave radiation, which helps distinguish open ocean from ice. It shows that during the winter months, a layer of ice forms across vast expanses of the Arctic Ocean and each summer, more than half of that ice vanishes. Students discover that this natural cycle of freezing and thawing is influenced both by seasonal temperature variations and long-term climate change and that scientists are using satellite images to measure the distribution of Arctic sea ice in order to gain a better understanding of how it is linked to Earth's climate system.

386

Eutectic freeze crystallization: Application to process streams and waste water purification  

Microsoft Academic Search

Two case studies are presented using eutectic freeze crystallization (EFC) as an alternative for evaporative crystallization: a 7.8 ton day?1 35 w% aqueous sodium nitrate and a 24 ton day?1 12 w% copper sulfate stream. The proposed crystallizer is a cooled disk column crystallizer (CDCC), using indirect cooling for heat transfer. In single stage operation, the formed ice crystals are

F. van der Ham; G. J. Witkamp; J. de Graauw; G. M. van Rosmalen

1998-01-01

387

Proton ordering in cubic ice and hexagonal ice; a potential new ice phase--XIc.  

PubMed

Ordinary water ice forms under ambient conditions and has two polytypes, hexagonal ice (Ih) and cubic ice (Ic). From a careful comparison of proton ordering arrangements in Ih and Ic using periodic density functional theory (DFT) and diffusion Monte Carlo (DMC) approaches, we find that the most stable arrangement of water molecules in cubic ice is isoenergetic with that of the proton ordered form of hexagonal ice (known as ice XI). We denote this potential new polytype of ice XI as XIc and discuss a possible route for preparing ice XIc. PMID:22009223

Raza, Zamaan; Alfè, Dario; Salzmann, Christoph G; Klimeš, Ji?í; Michaelides, Angelos; Slater, Ben

2011-10-19

388

The Effect of Underlying Substrate on the Crystallization Kinetics of Dense Amorphous Solid Water Films  

SciTech Connect

The crystallization kinetics of thin, dense amorphous solid water films deposited on crystalline ice and Pt(111) substrates are investigated. A dramatic acceleration of the crystallization rate is observed for amorphous films on crystalline ice substrates. The acceleration originates from the absence of the nucleation process on the crystalline ice substrate which serves as a 2-dimensional nucleus for the growth of the crystalline phase. This contrasts with the crystallization on a Pt(111) substrate which proceeds via bulk nucleation and 3-dimensional growth. Activation energies for growth and nucleation are determined to be 56 and 140 kJ/mol, respectively using the apparent activation energies measured on crystalline ice and Pt(111) substrates. For amorphous films deposited on crystalline ice substrates, the crystallization rate decreases rapidly with increasing distance from the crystalline ice substrate most probably due to crystallization induced cracking of the films.

Dohnalek, Zdenek; Kimmel, Gregory A.; Ciolli, Ryan L.; Stevenson, Kip P.; Smith, R. Scott; Kay, Bruce D.

2000-04-01

389

Einstein equations in the null quasi-spherical gauge III: numerical algorithms  

Microsoft Academic Search

We describe numerical techniques used in the construction of our 4th order\\u000aevolution for the full Einstein equations, and assess the accuracy of\\u000arepresentative solutions. The code is based on a null gauge with a\\u000aquasi-spherical radial coordinate, and simulates the interaction of a single\\u000ablack hole with gravitational radiation. Techniques used include spherical\\u000aharmonic representations, convolution spline interpolation and

Robert A. Bartnik; Andrew H. Norton

1999-01-01

390

Pequliarities of metal balls deformation by quasi-spherical shock waves  

NASA Astrophysics Data System (ADS)

The paper presents results of experimental researches of deformation of balls from Cu, Pb, Ó Ñ-type uranium, aluminum alloys AMg6 and D16, steels St.3, St.10, and stainless steel 12X18H10T with diameter from 55 to 42 mm by quasi-static waves. In the tests the shock waves converging to the ball center were caused by synchronous initiation of the detonation process in the great number of points of a thin spherical layer of heterogeneous solid explosive placed on the ball surface. The final result of shock-wave loading of balls is determined by the level of applied loading (HE layer thickness) and physical-mechanical properties of balls material, among which the yield strength is very important. For the all tested metals the average radius of a cavity, formed in the ball center, grows in progression as thickness of the spherical HE layer increases. With use of sequential increase of HE layer thickness for copper and lead balls continuous initially we recorded the loading regimes corresponding to various extent of damage: saving of material continuity, cavity formation, and ball fragmentation. In comparison with other metals, balls from Cu and Pb save their intactness having abnormally large sizes of cavity. These sizes reach in diameter a half of the same parameter of the ball due to high plastic properties of these metals. For aluminum alloys and steels one can observe influence of anisotropy of mechanical properties on the cavity geometry: the cavity shape is close to ellipsoidal. The paper presents discussion of results of metallographic analysis of the balls material after testing. The analysis results testify to irreversible structural changes in metals. The work was partially supported by RFFI funding (Grant #97-01-00344).

Glushak, B. L.; Novikov, S. A.; Sinitsyna, L. M.; Yukina, N. A.

1999-06-01

391

Pequliarities of metal balls deformation by quasi-spherical shock waves  

Microsoft Academic Search

The paper presents results of experimental researches of deformation of balls from Cu, Pb, Ó Ñ-type uranium, aluminum alloys AMg6 and D16, steels St.3, St.10, and stainless steel 12X18H10T with diameter from 55 to 42 mm by quasi-static waves. In the tests the shock waves converging to the ball center were caused by synchronous initiation of the detonation process in

B. L. Glushak; S. A. Novikov; L. M. Sinitsyna; N. A. Yukina

1999-01-01

392

In situ monitoring of growth of ice from supercooled water by a new electromagnetic method  

Microsoft Academic Search

The electromagnetic emission (EME) accompanying freezing of distilled water and dilute aqueous NaCl solutions is revealed and investigated. The EME signal is a sequence of discrete pulses of the electric field potential in the vicinity of the outward surface of ice–water system during the crystallization process. We found correlation between parameters of emission and kinetics and morphology of growing ice

A. A. Shibkov; Yu. I. Golovin; M. A. Zheltov; A. A. Korolev; A. A. Leonov

2002-01-01

393

An Intercomparison of Microphysical Retrieval Algorithms for Upper-Tropospheric Ice Clouds  

Microsoft Academic Search

The large horizontal extent, location in the cold upper troposphere, and ice composition make cirrus clouds important modulators of the earths radiation budget and climate. Cirrus cloud microphysical properties are difficult to measure and model because they are inhomogeneous in nature and their ice crystal size distribution and habit are not well characterized. Accurate retrievals of cloud properties are crucial

Jennifer M. Comstock; Robert D'Entremont; Daniel Deslover; Gerald G. Mace; Sergey Y. Matrosov; Sally A. McFarlane; Patrick Minnis; David Mitchell; Kenneth Sassen; Matthew D. Shupe; David D. Turner; Zhien Wang

2007-01-01

394

Impeded ice nucleation in glassy and highly viscous aerosol particles: the role of water diffusion  

Microsoft Academic Search

In situ and remote observations in the upper troposphere have disclosed the existence of water vapor pressures up to and even above water saturation. Under such conditions ice particle formation by homogeneous nucleation is expected to set in followed by ice crystal growth until the supersaturation is consumed. While the highest measured water vapor values might not withstand rigorous quality

C. Marcolli; T. Peter; B. Zobrist; U. K. Krieger; B. P. Luo; V. Soonsin; D. A. Pedernera; T. Koop

2010-01-01

395

Anisotropic elastocreep in glacial ice: A mechanism for intergranular melt and recrystallization  

Microsoft Academic Search

Bonded ice crystals under pressure are in a heterogeneous stress state because of the mechanical anisotropy of constituent grains. This condition plays a role in intergranular melt and recrystallization, which in turn influence properties such as permeability and biologic habitability. To examine this, we develop an anisotropic elastocreep model simulating subgrain-scale stresses in polycrystalline ice, choosing in particular the thermal

Steven M. Jepsen; Edward E. Adams

2008-01-01

396

Heterogeneous freezing of ice on atmospheric aerosols containing ash, soot, and soil  

Microsoft Academic Search

Nucleation of ice crystals in the atmosphere often occurs through heterogeneous freezing processes in which an atmospheric aerosol acts as the ice nuclei (IN). Depending on the ambient conditions and composition of the available IN, heterogeneous nucleation may occur through one of several freezing mechanisms, including contact and immersion. In this study, an optical microscope apparatus equipped with a cooling

Adam P. Fornea; Sarah D. Brooks; Jeffrey B. Dooley; Auromeet Saha

2009-01-01

397

Impact of heterogeneous ice nuclei on homogeneous freezing events in cirrus clouds  

Microsoft Academic Search

The influence of initial heterogeneous nucleation on subsequent homogeneous nucleation events in cirrus clouds is investigated using a box model which includes the explicit impact of aerosols on the nucleation of ice crystals and a new sedimentation scheme. Different effects are discussed, namely the impact of external versus internal mixtures of heterogeneous ice nuclei and the influence of size-dependent freezing

P. Spichtinger; D. J. Cziczo

2010-01-01

398

Modeling of Scattering and Absorption by Nonspherical Cirrus Ice Particles at Thermal Infrared Wavelengths  

Microsoft Academic Search

This paper examines a number of commonly used methods for the calculation of the scattering and absorption properties of nonspherical ice crystals at thermal infrared wavelengths. It is found that, for randomly oriented nonspherical particles, Mie theory using equivalent ice spheres tends to overestimate the absorption efficiency while the anomalous diffraction theory (ADT) and the geometric optics method (GOM) tend

Qiang Fu; W. B. Sun; Ping Yang

1999-01-01

399

Modeling of scattering and absorption by nonspherical cirrus ice particles at thermal infrared wavelengths  

Microsoft Academic Search

This paper examines a number of commonly used methods for the calculation of the scattering and absorption properties of nonspherical ice crystals at thermal infrared wavelengths. It is found that, for randomly oriented nonspherical particles, Mie theory using equivalent ice spheres tends to overestimate the absorption efficiency while the anomalous diffraction theory (ADT) and the geometric optics method (GOM) tend

Q. Fu; W. B. Sun; P. Yang

1999-01-01

400

Paleo-ice stream types  

NASA Astrophysics Data System (ADS)

During mapping of the Laurentide and Fennoscandian ice sheet beds we have observed and mapped a large number of paleo-ice streams, including apparently anomalous ice streams ocurring on high shear-stress bed materials, and with little or no topographic guidance. In addition, we have found evidence that in several places in the Canadian Arctic there developed a special category of small ephemeral ice streams during the deglaciation. They indicate flow patterns that are very different from older semi-stable ice streams in the respective areas. These observations of several types of "anomalous" ice streams lead us to think that scientific understanding of ice-stream behaviour has been hampered by an over-simplified terminology that presupposes that ice streams are one phenomenon, largely governed by one set of controls. Instead we hold the view that an understanding of ice-stream behaviour must start with a subdivision of the term "ice stream" into genetically distinct categories, with research focused at clarifying the controls for each category. A tentative classification scheme for paleo-ice streams should comprise at least five different types of ice streams, i/ Classical ice streams which occur on an excessively lubricated bed, i.e. preferably over fine-grained substrate with low permeability. Most of these ice streams terminated in lacustrine or marine water bodies. The numerous Baltic Ice Streams and the Cochrane surges into glacial lakes Agassis/Ojibway are examples of this type, ii/ Semi-stable ice streams which exist in locations where overall ice-sheet geometry favors the occurrence of long-lasting convergent flow, i.e. downstream of saddles in the ice-sheet surface. The Åre - Trondheim area in Scandinavia was likely a site for such an ice stream, iii/ Transient rigid-bed ice streams, which form without obvious topographical or substratum control when thawed spots start to develop under a largely cold-based ice sheet, which then finds itself with a steeper profile than the reduced bed traction can sustain. The unnamed Finnish ice streams that terminate in the Salpausselkä lobes are prime examples, and the Dubawnt ice stream in Keewatin may also be of this type, iiii/ Topographic ice streams, which are constrained by topography and fixed in space but variable in time. The Hudson Strait, Laurentian Channel, and Norwegian Channel ice streams are prime candidates for this type, and iiiii/ Re-equilibration ice streams, which probably develop as a response to rapid calving and breakup of ice in adjacent marine areas. Good examples are the east-trending ice stream on Prince of Wales Island, the small Cap Krusenstern ice stream and numerous ice streams on Baffin Island.

Kleman, J.; de Angelis, H.; Greenwood, S.

2010-12-01

401

Petrographic and Salinity Characteristics of Brackish Water Ice in the Bay of Bothnia.  

National Technical Information Service (NTIS)

Field observations made during the March 1988 BEPERS (Bothnian Experiment in Preparation for ERS-1) remote sensing experiment included measurements of the snow and ice thickness, temperature, salinity and crystal structure profiles of the different types ...

A. J. Gow W. F. Weeks P. Kosloff S. Carsey

1992-01-01

402

Does sea ice influence Greenland ice sheet surface-melt?  

Microsoft Academic Search

Recent decreases in Arctic sea ice and increases in Greenland ice sheet surface-melt may have global impacts, but the interactions between these two processes are unknown. Using microwave satellite data, we explore the spatial and temporal covariance of sea ice extent and ice sheet surface-melt around Greenland from 1979 to 2007. Significant covariance is discovered in several loci in the

Asa K Rennermalm; Laurence C Smith; Julienne C Stroeve; Vena W Chu

2009-01-01

403

Instant Ice Cream with a Dry Ice Bath  

NSDL National Science Digital Library

In this chemistry meets cooking activity, learners make carbonated, vanilla ice cream using dry ice and denatured ethanol, which are both inexpensive and accessible. This process to make ice cream is faster than using rock salt and water ice as the refrigerant. Use this activity to introduce learners to the process of sublimation and phase change and to provide a fun treat.

Ragan, Sean M.

2011-01-01

404

Distribution of marine ice beneath the Amery Ice Shelf  

Microsoft Academic Search

We present a map of the marine ice accreted to the base of the Amery Ice Shelf (AIS), East Antarctica. This map is obtained by converting a Digital Elevation Model (DEM) of the AIS generated from satellite radar altimeter data to an ice thickness map, assuming hydrostatic equilibrium, and subtracting from that a second ice thickness map, derived from airborne

Helen Amanda Fricker; Sergey Popov; Ian Allison; Neal Young

2001-01-01

405

Ice storm data base and ice severity maps  

Microsoft Academic Search

This paper describes the development of an ice storm data base and regional ice severity maps for the US using information from Storm Data, a National Climatic Data Center (NCDC) publication. This resource will provide convenient access to ice storm information for electric utility companies. Using this information, an engineer will be able to identify important characteristics of ice storms

L Shan; L Marr; R. M McCafferty

1998-01-01

406

Cryo-Microscopic Analysis of the Effects of Extra Cellular Proteins on Polycrystalline Ice Structure  

NASA Astrophysics Data System (ADS)

Recent work has demonstrated that microorganisms can occupy the liquid filled inter-crystalline veins in ice and maintain their metabolic activity under these conditions. While these discoveries have increased the extent of the biosphere to include the large continental ice sheets of Antarctica and Greenland as biomes, the habitat of the microorganisms within the inter-crystalline liquid veins is poorly understood. Certain cold tolerant organisms produce extra cellular proteins (i.e., ice-binding proteins) that have the ability to bind to the prism face of an ice crystal and inhibit recrystallization of ice. This phenotype affects the physical ice structure and the liquid vein network, potentially providing ice-inhabiting species a protective mechanism with which to control their habitat. One such microorganism is Chryseobacterium sp. V3519-10, a bacterium isolated from a depth of 3519 m in the Vostok Ice Core. Our investigation is examining the impact of extra cellular proteins from this ice-adapted bacterium on the formation of ice crystals and characterizing the inter-crystalline liquid filled vein network using cryo-microscopy.

Brox, T.; Skidmore, M. L.; Christner, B. C.; Achberger, A.

2010-12-01

407

Initiation of the ice phase by marine biogenic surfaces in supersaturated gas and supercooled aqueous phases.  

PubMed

Biogenic particles have the potential to affect the formation of ice crystals in the atmosphere with subsequent consequences for the hydrological cycle and climate. We present laboratory observations of heterogeneous ice nucleation in immersion and deposition modes under atmospherically relevant conditions initiated by Nannochloris atomus and Emiliania huxleyi, marine phytoplankton with structurally and chemically distinct cell walls. Temperatures at which freezing, melting, and water uptake occur are observed using optical microscopy. The intact and fragmented unarmoured cells of N. atomus in aqueous NaCl droplets enhance ice nucleation by 10-20 K over the homogeneous freezing limit and can be described by a modified water activity based ice nucleation approach. E. huxleyi cells covered by calcite plates do not enhance droplet freezing temperatures. Both species nucleate ice in the deposition mode at an ice saturation ratio, S(ice), as low as ~1.2 and below 240 K, however, for each, different nucleation modes occur at warmer temperatures. These observations show that markedly different biogenic surfaces have both comparable and contrasting effects on ice nucleation behaviour depending on the presence of the aqueous phase and the extent of supercooling and water vapour supersaturation. We derive heterogeneous ice nucleation rate coefficients, J(het), and cumulative ice nuclei spectra, K, for quantification and analysis using time-dependent and time-independent approaches, respectively. Contact angles, ?, derived from J(het)via immersion freezing depend on T, a(w), and S(ice). For deposition freezing, ? can be described as a function of S(ice) only. The different approaches yield different predictions of atmospheric ice crystal numbers primarily due to the time evolution allowed for the time-dependent approach with implications for the evolution of mixed-phase and ice clouds. PMID:21912788

Alpert, Peter A; Aller, Josephine Y; Knopf, Daniel A

2011-09-12

408

Incidence of rough and irregular atmospheric ice particles from Small Ice Detector 3 measurements  

NASA Astrophysics Data System (ADS)

The knowledge of properties of ice crystals such as size, shape, concavity and roughness is critical in the context of radiative properties of ice and mixed phase clouds. Limitations of current cloud probes to measure these properties can be circumvented by acquiring two-dimensional light scattering patterns instead of particle images. Such patterns were obtained in situ for the first time using the Small Ice Detector 3 (SID-3) probe during several flights in a variety of mid-latitude mixed phase and cirrus clouds. The patterns are analyzed using several measures of pattern texture, selected to reveal the magnitude of particle roughness or complexity. The retrieved roughness is compared to values obtained from a range of well-characterized test particles in the laboratory. It is found that typical in situ roughness corresponds to that found in the rougher subset of the test particles, and sometimes even extends beyond the most extreme values found in the laboratory. In this study we do not differentiate between small-scale, fine surface roughness and large-scale crystal complexity. Instead, we argue that both can have similar manifestations in terms of light scattering properties and also similar causes. Overall, the in situ data is consistent with ice particles with highly irregular or rough surfaces being dominant. Similar magnitudes of roughness were found in growth and sublimation zones of cirrus. The roughness was found to be negatively correlated with the halo ratio, but not with other thermodynamic or microphysical properties found in situ. Slightly higher roughness was observed in cirrus forming in clean oceanic airmasses than in a continental, polluted one. Overall, the roughness and complexity is expected to lead to increased shortwave cloud reflectivity, in comparison with cirrus composed of more regular, smooth ice crystal shapes. These findings put into question suggestions that climate could be modified through aerosol seeding to reduce cirrus cover and optical depth, as the seeding may result in decreased shortwave reflectivity.

Ulanowski, Z.; Kaye, P. H.; Hirst, E.; Greenaway, R. S.; Cotton, R. J.; Hesse, E.; Collier, C. T.

2013-09-01

409

Applied Sea Ice Research  

NASA Astrophysics Data System (ADS)

In the late 1960s oil and gas development became an issue in the northern coastal areas of Alaska and Canada. More lately this has also become an issue in the Euroasian Arctic with the Barents and Kara Seas as example on where offshore hydrocarbon production now is being planned. In such waters the key questions prior to a development are related to water depths at the site and in case of ice, how frequent and what type of ice features will be met. Especially the ice conditions and knowledge about them are very decisive for the field development solutions to be chosen. The paper will highlight examples on development solutions where the ice conditions have played a paramount role in the field development plans. An example is the consequences of iceberg threaten in an area and the effect sudden changes in ice drift directions may have on the exploration and drilling solutions chosen. The paper will also discuss how to derive design ice actions values for such waters including scaling from nature to model ice basins.

Løset, S.

2009-04-01

410

Ice sheets and nitrogen.  

PubMed

Snow and ice play their most important role in the nitrogen cycle as a barrier to land-atmosphere and ocean-atmosphere exchanges that would otherwise occur. The inventory of nitrogen compounds in the polar ice sheets is approximately 260 Tg N, dominated by nitrate in the much larger Antarctic ice sheet. Ice cores help to inform us about the natural variability of the nitrogen cycle at global and regional scale, and about the extent of disturbance in recent decades. Nitrous oxide concentrations have risen about 20 per cent in the last 200 years and are now almost certainly higher than at any time in the last 800 000 years. Nitrate concentrations recorded in Greenland ice rose by a factor of 2-3, particularly between the 1950s and 1980s, reflecting a major change in NOx emissions reaching the background atmosphere. Increases in ice cores drilled at lower latitudes can be used to validate or constrain regional emission inventories. Background ammonium concentrations in Greenland ice show no significant recent trend, although the record is very noisy, being dominated by spikes of input from biomass burning events. Neither nitrate nor ammonium shows significant recent trends in Antarctica, although their natural variations are of biogeochemical and atmospheric chemical interest. Finally, it has been found that photolysis of nitrate in the snowpack leads to significant re-emissions of NOx that can strongly impact the regional atmosphere in snow-covered areas. PMID:23713125

Wolff, Eric W

2013-05-27

411

Preventing Ice Before it Forms.  

National Technical Information Service (NTIS)

In the late 1990s, a team of engineers at Ames Research Center invented an anti-icing fluid to keep ice from building up on airplane wings. Ice on wings can be a serious safety hazard, especially during takeoff, when a sheet of ice the thickness of a comp...

2006-01-01

412

Overview of Ice Drilling Technology.  

National Technical Information Service (NTIS)

Significant advances in ice drilling technology since the Ice-Core Drilling technology since the Ice-Core Drilling Symposium at Lincoln, Neb., in August 1974 are reviewed. Three examples are: the flame jet and hot water drilling through the Ross Ice Shelf...

B. L. Hansen

1984-01-01

413

Inflight characterization of aircraft icing  

Microsoft Academic Search

This thesis advances the development of the Ice Management System (IMS), which has been previously proposed as an additional layer of safety against aircraft icing accidents, by presenting and validating a conceptual design for the icing characterization function of the IMS. This icing characterization function seeks to provide a near real-time estimate of the degradation of the aircraft flight dynamics

James William Melody

2004-01-01

414

Advances in ice mechanics - 1987  

SciTech Connect

This book presents the papers given at a symposium on the interaction of icebergs with offshore platforms. Topics considered at the symposium included advances in ice mechanics in the United Kingdom, ice mechanics in Finland, recent advances in ice mechanics in Canada, advances in sea ice mechanics in the USA, foundations, monitoring, hazards, risk assessment, and deformation.

Chung, J.S.; Hallam, S.D.; Maatanen, M.; Sinha, N.K.; Sodhi, D.S.

1987-01-01

415

Sea ice microbial communities (SIMCO)  

Microsoft Academic Search

Sea ice microbial communities (SIMCO) grow luxuriantly within several microhabitats of sea ice, indicating that the microorganisms comprising these communities are well adapted to the physicochemical gradients which characterize sea ice. We used SIMCO obtained from the bottom of congelation ice in McMurdo Sound, Antarctica, to test the hypothesis that low temperature limits microbial productivity in polar oceans and also

Steven T. Kottmeier; Cornelius W. Sullivan

1988-01-01

416

Ice storms and forest impacts  

Microsoft Academic Search

Ice storms, or icing events, are important meteorological disturbances affecting forests over a surprisingly large portion of the USA. A broad belt extending from east Texas to New England experiences major ice storms at least once a decade; and truly major events occur in the heart of this belt once or twice a century. In the areas most affected, icing

Lloyd C Irland

2000-01-01

417

Shokotsu River ice jam formation  

Microsoft Academic Search

A spring ice jam occurred in the Shokotsu River in March 1995. This has been the only known ice jam in this river since 1955. This paper discusses the ice jam processes and investigates the causes of the Shokotsu River ice jam by analyzing the available hydrometeorological data as well as hydraulic and geometric characteristics of the river. This analysis

Hung Tao Shen; Lianwu Liu

2003-01-01

418

Buried glacier ice in permafrost, a window to the past: examples from Bylot Island, Canadian Arctic  

NASA Astrophysics Data System (ADS)

Bylot Island is located north of Baffin Island (73°N, 80°W) and is extensively covered by an ice cap and its outlet glaciers flowing towards the arctic lowland of the Lancaster formation. During summers of 2009 and 2011 several active-layer detachment slides exposed large massive ice bodies and other types of debris-rich ice that were interpreted as buried glacier ice. The upper part of the massive ice and debris-rich ice were usually in contact with various types of ice-contact or glacio-fluvial sediments and in some cases they were covered by mass wasting/colluvial deposits. This suggests that their preservation was likely related to burial of the ice and refreezing of the overlying sediments following permafrost aggradation. A preliminary analysis of the ice facies and ice crystals revealed the presence of four distinct types of ice: 1) clear-ice bodies with very few sediment and no organic inclusions. The ice crystals were large (cm), randomly oriented and air bubbles were observed at the junction of crystals. These characteristics could potentially indicate an englacial (snow-neve metamorphism) origin for these clear ice bodies; 2) large, meter thick, clear ice layers with no sediment, nor organics. The ice crystals were large (cm), several cm long, oriented in the same direction, and vertically aligned. These characteristics could potentially point to water that refroze in a tunnel incised in englacial ice; 3) Successive, mm to cm thick, ice layers, separated by undulating sand and gravel bands also containing cobles to boulder size rock fragments. These characteristics could potentially represent regelation ice formed at the base of glaciers and incorporated to the glacier sole; 4) mm to cm suspended aggregate of fine-grained sediments in clear ice. These micro-suspended and suspended cryostructures were sometimes deformed and aligned in the form of thin (mm) undulating layers. These micro-structures were very similar to basal ice facies, presumably related to glacio-hydrologic supercooling, that we observed at the Matanuska Glacier in Alaska. Interestingly, the various types of ice contained in buried glacier ice permafrost date back to the englacial ice formation and its subsequent deformation by glacier flow and glacio-hydrological dynamics. It is thus older by several centuries to millennia than the permafrost aggradation itself (burial and active layer development) and we used the term antegenetic, in opposition to epigenetic or syngenetic, to characterize this type of permafrost. Buried glacier ice is a window to the past and a unique tool to reconstruct the paleogeography and paleoclimatology of Arctic regions. In a warming climate, as glaciers are receding, the burial of ice in the proglacial environment will offer opportunities to characterize antegenetic permafrost aggradation and its related cryofacies. In warming permafrost environments, as active layers on slope deepen and detachment slides are triggered, more buried Pleistocene glacier ice will likely be exposed.

Fortier, D.; Coulombe, S.; Kanevskiy, M. Z.; Paquette, M.; Shur, Y.; Stephani, E.

2011-12-01

419

Ice interaction with offshore structures  

SciTech Connect

Oil platforms and other offshore structures being built in the arctic regions must be able to withstand icebergs, ice islands, and pack ice. This reference explain the effect ice has on offshore structures and demonstrates design and construction methods that allow such structures to survive in harsh, ice-ridden environments. It analyzes the characteristics of sea ice as well as dynamic ice forces on structures. Techniques for ice modeling and field testing facilitate the design and construction of sturdy, offshore constructions. Computer programs included.

Cammaert, A.B.; Muggeridge, D.B.

1988-01-01

420